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[Question] [ Closed. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it focuses on one problem only by [editing this post](/posts/13318/edit). Closed 5 years ago. [Improve this question](/posts/13318/edit) Hey guys, thanks for the suggestions and answers - here's a more streamlined question - presently focused on implications on climate and technology. I've also added a little more explanation in the premise. The Premise The Earth rotates on its own axis, which is tilted by about 23 degrees. The setting for my fantasy novel is an earth like planet without the axial tilt, all other factors remaining constant in terms of distance from the sun etc. From some general reading on the subject, it appears the largest impact of removing an axial tilt would be on seasonal change, in the sense that there wouldn't be any changes whatsoever. Every latitudinal belt would have its own set season all year round, with some minimal changes depending on the earth's distance from the sun in its usual orbit (ranging basically from 91.4 million miles in January compared to 91.5 million miles in July - which is less than 1%). EDIT As a result, since there is no major climate change, the world will generally experience the same weather everyday. Therefore, the cold regions of the planets are likely to become even colder to the point of being uninhabitable. Likewise for the deserts and heat. Those regions receiving lots of rainfall will either be covered in forests or experience continuous top soil erosion, making agriculture an improbable proposition in most regions. However, it is likely that there may be a few ideal zones supporting human occupation. It may be an elevated plateau in a hot area (the altitude allowing bearable temperatures), or a large hot spring in the tundra, or an area close to other rain-heavy areas able to draw water from them. As a clarification, the technology in this scenario is mid-Iron Age-ish (Edit clarification: pre-gunpowder). The Question Edited What would be the impact on the world's basic technological aspects in various areas of the world? Some areas that I've been able to identify are: 1. Frozen wasteland 2. Grasslands 3. Deserts 4. Rocky mountainous regions 5. Swamp lands and rainforests 6. Archipelago Since the weather wouldn't change, the people living in these areas would adapt differently. Real life parallels from our own planet exist even with the change in seasons. Technology in an arid desert developed differently from technology in the freeze. Technology in wet swamplands developed differently from technology in dry grasslands. If the Axial tilt is removed, these differences would grow substantially, since there would be practically no common ground for different regions with different climates. How far can these differences be extrapolated to see interesting and unique technological changes? The answers I'm most interested in are ones which show a logical (don't worry about being scientifically perfect) impact of the premise. But if you have a ridiculous scenario arising out of the above premise, let me hear it anyway! [Answer] The biggest impact on technology would be less internal diversity within a region but more diversity across the globe based on climate areas. Let's take the areas you've identified already and expand on them: Frozen Wasteland A harsh year-round climate would lead to little life being able to develop. Life that does develop would be very slow-growing because the cold would slow down biological processes. This would result in little to no food for people to eat or animals to hunt, so chances are people would just avoid it. Edit: This would probably cause many rumors to be spread about treasure/artifacts/monsters/etc that live there and might cause someone wealthy to mount expeditions to find it. You'd end up with some hair-brained tech developed for the purpose that could fail horribly or succeed brilliantly. Just look at our earliest theories on flying machines for inspiration on how crazy it can get before we actually understand how it works. Grasslands These would be similar to the grassy regions I described in [the other question](https://worldbuilding.stackexchange.com/questions/13391/what-if-an-earth-like-planet-had-no-axial-tilt-impact-on-ecosystem/14222#14222). Grass-like crops would probably bud year-round and be difficult to harvest without hand-picking or some creative method of controlled cultivation. Simple wind and animal transfer of seeds into a field could disrupt its uniformity and require constant maintenance to ensure crops are harvested with some consistency. The lack of a definite growing season would also disrupt the natural budding cycles of these plants so some might mature faster than others. Basically farming grains would be a pain, so people in these areas would likely resort to a more nomadic hunter-gatherer lifestyle, unless there's an abundance of high-value food sources like fruit and game that prevent the need to move. Large populations would be very difficult to support either way. People would also likely get very territorial due to the need for a fine balance in supply and demand. Expect long-range weaponry due to wide-opens plains giving good visibility, or if you want something more unique, make the people very adept at stealth and camouflage and the short-throw spear or miniature poisoned bow. There are tribes in Africa that use these techniques to stalk wild animals in the plains, though their lifestyle is a harsh one indeed. Deserts Deserts not near the equator could in theory operate much as they do in the Southwestern US. Mountains could easily divert rainfall periodically to keep plant and animal populations alive, and the population would probably rely on similar cattle farming methods to what you see in our world's history. Water-storing plants like cacti would be common. Strangely enough you might see this being one of the more prosperous zones, though populations would still be small. Expect lots of water collection technology to be a necessity, and if you want to make it harsher you could make water a precious resource, though that precludes the region being prosperous. See Dune for examples of how that could shape society. Rocky Mountainous Regions High up the mountains would be pretty much frozen and uninhabitable. In the middle altitudes you could have large lakes, though they would have to be fueled entirely by rainfall since you won't have spring melts of snow caps. I'd expect much of the population to center around the lakes and their distribution systems, and the people would live primarily off of hunting and whatever high-value fruit/vegetables can grow in the rocks. Expect small populations but relatively stable places to live since they have a good supply of water, which perpetuates more lush plant and animal life. Think of a "mountain oasis". I'd expect those people to be pretty reverent towards their water source as the giver of life. You might see an abundance of mining technology just out of necessity to build habitats, though if the mountain is very geologically active that could be a risk. If not, they could take advantage of the increase in temperature you get as depth increases, though be careful to avoid asphyxiation. Swamplands and Rainforests These would probably be your centers of civilization. The abundance of water and warm temperatures would mean an abundance of wildlife. People here would have wood to make tools and shelters, a huge variety of food to eat, possible easy travel down rivers, etc. Houses would likely be elevated somewhat to deal with flooding or in the case of the swamp they may just be permanently floating. You'd possibly have some sort of agriculture in the swamp regions, though it wouldn't be grains, perhaps edible reeds or other water-borne vegetables. In the rainforests you could also have good mining locations for metals and stone. A large enough population could clear out an entire swath of land to build an empire, though they would have to be mindful of the ground they build it on. Stone buildings would be useful, and wood structures would need to be treated with some sort of tar-like substance to prevent rot. These would also consequently be dangerous places to live, with the abundance of wildlife meaning there are just more things out there to kill you in strange ways, necessitating many precautionary measures and weapons/tools that would border on being ritualistic after several generations. Get creative! Archipelago Another potential for lush wildlife but only if they're in a warm enough climate to have lots of rainfall. Either that or your oceans would need to be freshwater and I'm not sure what the implications of that are. These places would probably be much as you see them on Earth, with tribal villages being the norm and relative isolation from the rest of the world until someone invades. You could build them up to be a culture clash after that happens, just think about occupation-era Japan for inspiration on how two cultures can combine in a totally unique way (not to mention the social stresses it would cause). Expect tools to be somewhat sophisticated but shelters to be impermanent due to the likelihood of being destroyed in a storm and needing to be rebuilt easily. I think it would be fun to have a culture that reveres the cycle of death and rebirth in these situations, as exemplified by the potential for weather to wreck everything, forcing them to rebuild from scratch. You could expand that into their whole style of technology, perhaps their tools are all one-use and disposable despite them knowing how to make better ones, they just choose to let things break as a sign of acceptance that they themselves may be broken on any given day that nature determines. Outsiders would view them as incredibly primitive when in fact they're incredibly intelligent and sophisticated, they just show it differently. Other Interesting Bits You can get creative with some areas like the hot spring you mentioned. People would probably have to have migrated there at some point, rather than it being a place of origination. The hot spring in a frozen tundra would support a unique kind of plant and animal life that could be very different from everywhere else, but the limiting factor is the size of the spring. The smaller it is, the less life it can support. If you make it a larger system of springs connected by short distances of streams (such that they wouldn't freeze over in transit from one spring to the next) you could extend it a bit, but remember this is going to basically be on a fault line so there will probably be mountains and other geological features surrounding it. Just keep in mind that mountains are great at diverting rainfall, so you can bring water to places it wouldn't normally be, and since there would be a reduced ability to transfer water through natural means like seasonal melts, irrigation will be key to any developing area that doesn't have lots of water already. There could be an empire in the grasslands, but only if they have the water and trade supplies to support it. It would be much easier to build that empire in a wetter climate. Also take advantage of massive rivers like the Nile or Amazon that connect two large bodies of water. The Nile in particular made life possible in Egypt, and that river alone allowed them to build an impressive empire despite the harsh environment, especially with the advent of river shipping techniques. A more advanced society with slightly different terrain might take advantage of the water to power massive mining operations or other large industry. As happened in history, these people would likely view the river as the source of life and it would feature prominently in their religion and tradition. Wherever people live, providing shade would probably be an important feature of their technology. The lack of seasons would make constant sunlight harmful in many areas not near the poles. Consider large-brimmed hats, parasols, covered carts and full cloaks/robes as well as shaded places to rest an important feature between the grasslands and the equator. Good ventilation in any warmer area is also a necessity. Also make sure your distribution of skin pigmentation reflects the climate, assuming your people are biologically tuned like us. Hopefully that covers it. If I missed something let me know. [Answer] Actually there would still be seasons unless the orbit of the planet was also exactly circular, which is possible but unlikely. Also the axial tilt varies over time. Earth is unusually stable because we have a large moon. I guess that if you are asking about effects on evolution, the planet also has a large moon to stabilize the axial tilt? ## The rain cycle This would make seasonal rain patterns such as monsoons much less likely. The result should be areas distant from oceans being more arid and less likely to support agriculture. There would probably still be oscillations in rain patterns and climate, but they would be either weaker or less predictable and longer lasting. So that people that moved into areas made fertile by the rains, would have to move out or die when the rains do not come. Otherwise the difference would not be that big I think. Most rains come from ocean evaporation and start coming down as rain when already over the ocean, and seasons simply move the climate bands north and south. These seasonal movements would be removed, but weather itself should otherwise be the same. ## Plants and animals No seasons would mean that there would be no need to adapt to seasonal variations in temperature or rain fall. Droughts and floods would still happen so adaptation to unpredictable weather would still be needed. I'd expect plants would be evergreen since a place that they can grow would presumably be so all the time. Animals would not do large seasonal migrations or hibernations and other such seasonal adaptations. Estivation might still exist as drought adaptation. Plants would presumably regrow from roots or seeds. Otherwise the effects should be relatively minor as most of biological diversity and biomass is in stable environments that allow growth year around anyway. ## Shelters There would still be weather and for most of history almost all people lived in warm climates anyway. Only difference would be that there would be no real sense making buildings snow and freezing cold proof as areas with such weather would have such weather year around, there would be no summer growing season producing the food to support human population. Still weather might bring snow to far south occasionally, so lack of seasons would not really allow people to skip on protection. Architecture would be subtly different in that in many civilizations roofs were designed to create shade during summer but let sunlight warm the house during winter. ## Population Population would be concentrated the same way it was on Earth in a belt of areas where the temperature is above freezing, no real winter, year around. Not having seasons might extend this belt slightly, but I doubt the difference would be significant, the border just would be less fuzzy with areas outside this belt being not really habitable at all without summer growing seasons. Population distribution within this zone and actual climate would depend on geography, mainly the distribution of land and sea. ## Navigation and Exploration Not sure there would be much of a difference. Determining latitude would be easier, but that was never really much of a problem. Determining longitude would also be slightly easier without leght of day varying, but enough issues would remain to require essentially same solutions as on Earth. And longitude problem was historically solved after the age of exploration, so it didn't really prevent exploration anyway. [Answer] It might be helpful to have a discussion about whether intelligent life would evolve at all on a tilt-free planet, before discussing differences in the technology that intelligent life might devise. [Loss of Planetary Tilt Could Doom Alien Life](http://www.astrobio.net/news-exclusive/loss-of-planetary-tilt-could-doom-alien-life/), [Axis Tilt is Critical for Life](http://hyperphysics.phy-astr.gsu.edu/hbase/astro/orbtilt.html) [Answer] I always had the impression that the seasons, and the necessity to cope with them on the one hand, and the large amounts of boredom in winter on the other, might have led to a lot of innovation. As a result i think that a lack of seasons would massively slow down innovations of all kinds. While you will likely go as far as pottery in a timeframe comparable to the one that happened on this earth, i doubt that you would get much beyond simpler metallurgy any time soon. The reason, in detail, is, that first of all innovations need someone with time to think and tinker, and secondly, you need some sort of outside pressure for humans (in general as well as in detail) to move anywhere. If, as @VilleNiemi suggests, all of humanity lived very much in the same geographical belt, they would neither have winters that provided the free time, nor the pressure to avoid freezing and starving. While, over a sufficiently large timespan, it would still be possible to evolve to and beyond our current state, i guess it would take a lot longer. To back up my view i would like to point out that most of the greater inventions (good and bad) of the last two millenia have been made in regions with notable to strong seasons while the populations in regions of moderate climates pretty much stagnated in or after the iron age. And that is even though those regions had kingdoms and the like, that would provide a part of the population with time and ressources, and (a different) part of the people with pressure to improve their situation. [Answer] Transmission of Technology For much of human history, climate and geography have been significant barriers to human travel, which slows technology transfer (and by technology I don't necessarily mean things like swords - I also mean domesticated animals or crops, or concepts like "wheels" and "pointy sticks"). Since your world has no axial tilt, technology and knowledge will travel faster to new areas, at least on an east-west axis (and taking geographical climate changes into account). You don't have to worry about seasonal restrictions on travel, or climate changes that will kill or stop crop spread. So I suspect this would cause early technological development to happen much quicker than on Earth. Even south-north travel would likely be simplified because it would be more constant, rather than changing. Military Climate can be a [significant defensive barrier](http://en.wikipedia.org/wiki/Russian_Winter). It's likely that on your world, an army used to one climate might have trouble adjusting to another. This would tend to limit short-term military expansion across different latitudes - military civilizations would tend to conquer and spread laterally in bands, east-west, but would have much more trouble spreading south-north. It would also make mountains more significant barriers - soldiers who have never seen snow are going to have a lot more trouble with a mountain pass, compared to soldiers who see it several months a year. Natural Disasters Consider that on Earth, most people live in areas with seasons. That means if something big, natural and bad happens - like the [Year Without a Summer](http://en.wikipedia.org/wiki/Year_Without_a_Summer) - it causes hardship, but it's not totally outside of their experience so people can adjust. They know how to handle winter, so they can prepare and try and set things up to survive a longer, colder winter. It still kills a lot of people, but in general populations survive and recover. But what happens in your world, without an axial tilt? Instead of just being a hardship, suddenly they're inflicted with a temporary weather and climate that they have no experience or preparation for. It's likely that if a natural disaster occurred on that level that anyone living in marginal areas is simply dead - they have no preparation for that kind of event at all. So your world might experience periodic (~1 thousand years) die offs of humans who live in marginal areas, followed by slow re-population as the people in ideal areas spread out. Alternatively, a civilization with a strong oral tradition that "remembers" how to handle winter might survive and spread, taking over the marginal areas because they're the only ones who can handle a winter every thousand years. This would also cause an interesting effect on evolution, because species might adapt to an area and then be killed off in mass. But I think that's probably beyond the specific scope of this question. [Answer] I would expect such a planet to be a dull vegetated place. With no seasons, microbes would adapt to very particular temperature ranges of their latitude, and have disincentive to migrate. Being a little jellyfish and going around gobbling up the plankton might be ok but there would be far less reason than on earth to become a good swimmer for migration, let alone grow legs and run around doing cleverer stuff than what jellyfish do. [Answer] I disagree on the lack of diverse speciation because of far less variant seasonal biomes. If you look at places like the Canary Islands (i.e. isolated ecosystems at an equatorial latitude with minimal seasonal variance) you find similar levels of diversity and speciation as you would in a latitude with well-differentiated seasons. Once the first photosynthetic mega-bloom freed enough oxygen to make cellular combustion selectively efficient I can't imagine how ANY climate which allowed for liquid water could possibly stop the rise of animal life. The first proto-mitochondria awoke into a Willy Wonka-esque picnic where their brats created themselves from piles of poo and, as a by-product, filled all the park's grills with charcoal briquettes. Plants aren't sessile because they don't NEED to move, they simply can't produce enough free energy quickly enough to ever make movement selective in an oxygen-rich environment. Likewise animals aren't mobile because there were storms and snow, they're mobile because it's thermodynamically possible for them to be so and movement is incredibly selective in any environment. At least, that's how I see it -- hope it's helpful to you three years ago :P ]
[Question] [ Related: [Could a Dwarven Civilization Exist?](https://worldbuilding.stackexchange.com/questions/9947/could-a-dwarven-civilization-exist) Background: A Dungeons and Dragons world (for all intents and purposes, Tolkein lore is close enough) in which a group of colonists far from home are building a new city. The Dwarves find a volcano and see it as an opportunity to build a city to rival their homeland. They are currently 25 strong, plus 50 colonists of other races (elves, gnomes & humans), with hundreds more on the way. They have only a handful of mages. Note that I know that this is realistically a horrible idea and everyone would die on day 1, but this is fantasy, so I'd like to be as believable as possible with my handwaving. Benefits of this plan: * Valuable materials. Lots of unobtanium in them hills! * Natural defenses. No need to build walls, let the mountain keep out attackers. * Magma smithing. With sufficient protection and Dwarven engineering, lava smiths could invent otherwise impossible crafts! * It's cool! Seriously, for a group of people obsessed with reputation and legacy, how awesome would it be if you were the first dwarves to live in a volcano? Think of how fearsome everyone would think you are. Hurdles to Overcome: * Ridiculous heat. Partially mitigated by dwarven resiliance but still a problem. Is wall shielding a possibility? * Toxic fumes, especially sulfur. Miners in real life dealt with some nasty gases, can I use the same techniques? * Lack of food. This is a factor in regular dwarven cities so I can hand-wave "mushrooms and deep dwelling creatures" * Regular and violent tremors. Is good structural construction enough? * Lava flows/pools. Would be nasty to break into something like that, though it feels like it would be obvious if you are approaching. * Eruptions. Kind of a culmination of all of these problems dialed to 11. What are the possible solutions for the obvious hurdles presented by living in an active volcano? What are the potential benefits? Are there prominent examples from high fantasy media to draw inspiration from? Edit: Regarding volcano type, it is a shield volcano that is part of a larger, non volcanic mountain chain mostly inspired by the Rockies. It is inland, about 50km from the ocean coast. It is an active volcano, that erupted a few weeks prior to the colonists arriving. [Answer] ### Solutions to hurdles * Stay toward the outside. While it's unclear exactly how hot the solid rock inside volcanos is, [one source](https://www2.usgs.gov/faq/categories/10169/3784) says it's an efficient insulator - meaning you may be okay. If worse comes to worst, don't dig so deep toward the lava chamber, and expand straight downward instead. Unfortunately, you can't actually build into the lava chamber itself - it's way too hot. * Fumes aren't a huge problem. They are most abundant toward the actual magma / lava itself, where the temperatures are way beyond reasonable to live. While outside, the best you can do is a fabric or linen [facial covering](http://www.ivhhn.org/index.php?option=com_content&view=article&id=102) for any ash present. Volatile gases are beyond your control, but they probably won't bother you often. * Import food or grow outside. Underground caverns aren't a great place to grow crops, and unless dwarves have an effective way to terraform caverns, I would recommend having fields on the slopes of the volcano. Ash is actually a fairly nice fertilizer, too, so terraced farms should be effective. [![Image from http://weshareinterests.com/?p=876](https://i.stack.imgur.com/M2YTY.jpg)](https://i.stack.imgur.com/M2YTY.jpg) <https://homesteading.com/terrace-farming/> * Build smaller caverns. Tremors are inevitable. While most rooms should remain structurally sound, you don't want to risk a rain of heavy rocks that become dislodged from a larger roof. Consider smaller rooms with columns, or hang the walkways you plan to use from the ceiling to help absorb some of the shock. * You will not accidentally tunnel into magma. Temperature increases substantially as you reach it. * Eruptions are inevitable, so be prepared. Dig channels in the mountain slope early on to reroute any magma that flows down as much as possible. Use multiple tunnels and multiple entrances / exits so that even when many are blocked, there will always be a way out. Include some longer tunnels running miles away, even - they may be your last hope of escape if the surface is volatile. Also have a way to firmly shut every door into and out of the compound - preferably with heavy stone - to prevent magma, ash, and gas from entering. Finally, use similar precautions for your air ducts - multiple vents that are easy to close and resistant to magma and corrosion. You don't want to suffocate by closing everything off. ### Benefits * People will be afraid of imminent death when they go to attack you * Magma can be rerouted from atop the volcano, through man-made tubes, into your blacksmith's shops. * Volcanoes are rich in rare gemstones, which are often carried up with magma! * Obsidian, a volcanic rock, makes very strong tools and weapons [Answer] There is a game called Dwarf Fortress that make you take care of a lot of this issues. * Lack of food Volcanic soil is very good for crops, so, if the city is not reclusive they can farm fields on the surface and keep the most nutritive mushrooms inside the city. * ~~Intense heat If the city is built too deep with no heat source they will freeze to death, deploy some pipes along the city to forward hot gas, melted rocks or other stuff to keep them warm.~~ * Intense heat Efficient cooling system. You could use some pipes with water and/or if they have plenty of resources a good cooling mechanism wold be to dissipate heat with fans (fed by the electric central) and metal dissipators, so you save some water for other purposes. * Energy Find a water source and you can build a steam powered electric central to develop high technology. * Keep them happy I know they are dwarves, but they have feelings right? With no natural light a lot of mammals tend to develop depression and/or aggressive behaviour. What about some big chandeliers on public spaces made of natural magma waterfalls. A few more between halls and lets say schools and workshops. Don't let your dwarves' hearts become evil. * Earthquakes and toxic fumes In such a dangerous place there is no place for personal appeal in matter of shelter. Every family should live in almost identical houses and designed areas, which would lead to a very efficient emergency/disaster protocol to evacuate the city and save the population. [Answer] If the lava smiths and engineers are channeling the volcano's heat and magma for various purposes, that could (at least in theory) relieve some of the pressure. This would reduce the chance of a new eruption. You say it erupted recently, so it would probably be dormant for a while post-eruption anyway. [Answer] Recently dormant or barely-active volcanoes are a better way to go. A recently dormant or barely-active volcano gives most of the benefits (usable warmth, power source, recently crystalized gems and jewels) and avoids many of the problems (eruptions, earthquakes, magma, poisonous gasses.) The rub is that there are other underground-living/lairing species that also like just-barely-warm volcanos as their homes. And some of those aren't exactly into sharing... [Answer] I am not good with this but here is a suggestion: Hurdle 1: Stone walls won't work, as once, in a medieval book, a fire burned so fiercely some stones in a stone wall cracked. This is that heat x500. Try something more fireproof, with some water. There should be a magma chamber holding magma, stay away at all costs, and make your city at the base. Is it underground though? Find some natural cooling things. Try hauling a lot of water there, then let it evaporate, which will cool you. Hurdle 2: Maybe somehow get wind in there, but this is a hard one for me. Hurdle 3: Mushrooms, and things that hold well in heat. Hurdle 4: We have made buildings strong enough to withstand strong earthquakes. Try using that concept. Hurdle 5: Maybe a squad with buckets? Otherwise strong walls. Euptions: Choose a non-active or not as active volcano. However: What type of volcano? This has been mentioned in a comment already. Is the volcano more flat, does it have an open top like science fair volcanoes, or does it have rock covering the top like a mountain? Please clarify! ]
[Question] [ If there was a medieval society where magic was only taught within royal and high ranking noble families, would this cause the society to stagnate? I mean, a lot of technological developments (but not all) have resulted in more balanced and progressive societies. Would the fact that the 'high born' nobles now have yet another way to enforce their hold over the people, to maintain the status quo, result in a civilization that remains virtually unchanged over the centuries (I suppose much like a magically induced dark age perhaps). Or, seeing as a lot of Victorian-era science was undertaken by nobles (I'm not too familiar with science in medieval times), would the addition of the mystic arts to their repertoire actually bolster the whole 'gentleman scientist' movement and hence speed up technological development? There are a few similar questions like [Why would a magic world be stuck in medieval times?](https://worldbuilding.stackexchange.com/questions/3953/why-would-a-magic-world-be-stuck-in-medieval-times) or [Must magic be tied to medieval tech?](https://worldbuilding.stackexchange.com/questions/8/must-magic-be-tied-to-medieval-tech) or even [one about disease curing magic](https://worldbuilding.stackexchange.com/questions/39145/what-would-be-the-impact-on-a-medieval-society-if-cure-disease-magic-was-avail) (which had some interesting points about delayed development), but those were either dealing with four elements magic, looking for reasons why a society might stagnate or based in worlds where magic is commonplace. I know the reason I would like to use, but I'd like to know if it's a plausible reason, if it makes sense. A couple of ground rules: * There isn't much of a restriction on the kinds of magic used, only that it's commonplace. Somewhere between Harry Potter diversity and Lord of the Rings rarity. * It can be (and frequently is) difficult to perform/energy sapping and can kill you or go horribly wrong if you don't know what you're doing (unsupervised magicians don't tend to last long). * It's closely guarded, not only is it taught only within high ranking noble houses, even then, only a few of them actually become any good at it (that's not to say there's anything special about the nobles, just that they... hold all the cards and besides, a book on magic isn't going to help a commoner if they can't read anyway - which I suppose would further reinforce the status quo) * Very proficient users (kings and queens etc.) are able to greatly improve their health (and maybe extend their lifespans) through the use of powerful magic (much to their children's dissatisfaction - there can be only one king ;) * There is also no reason why modern technology can't be used, it's just that the bulk of the populace isn't educated enough (or at all really) and those that are would rather keep the status quo as it is (the only way to get in power is to already be in power). So, could all this basically put an indefinite halt to the development of society, or is progress inevitable? Or can royal magicians put an indefinite halt to a society's development in order to maintain their own positions? [Answer] It depends on a lot of things. How does the magic work? What can it do? What are the limits of capabilities of a trained mage? You said it's difficult and tiring, so it seems likely that the few actually trained mages would not be able to make a significant difference by themselves. Their powers may make them feared personally, may make them extremely hard to assassinate, may let them intervene in certain situations from time to time, but it's unlikely to replace industrial production with a load of self-sustaining spells to operate a factory. But maybe it helps with knowledge. Science, historically, was done by rich people who could afford to do it (everyone else was largely concerned with making sure they had enough to eat). So some of those rich people in your world might be mages rather than scientists, but what would they do with their magic? Does their power allow them to examine the world in more detail? Could they skip past the need to invent the microscope in order to discover bacteria? Could they discern molecules and atoms? Subatomic particles? Quantum mechanics? Or on a larger scale, can they discern the nature of the solar system, the kind of physics that leads to general relativity? Would they ultimately be able to resolve the question of quantum gravity which is as yet unsolved in our world? If they could, they may actually trigger vast technological progress if they passed such knowledge on and worked with non-magical scientists and inventors and industrialists. Their attitude obviously matters, maybe they're not interested in helping anybody, but maybe they are, maybe they want their country to become more powerful and more productive and they're sitting on this spell that has given them an idea about getting energy from unstable isotopes of certain heavy metals, and they've got another spell that lets them find out where to mine them... Of course, if you can't use magic to find stuff out about the world, then it's not likely to help at all. I'd read TV Tropes for their various tropes on magic systems, as there are many ways to do magic and their implications are all very different. A more mystical, more widespread magic system is more likely to inhibit technological progress than a very comprehensible, scientifically definable magic system. [Answer] This would most probably lead to a technological explosion initially which would later stagnate and halt. Here is some explanation why: There can be two possible scenarios about the character of the royalty; they are either virtuous or evil. In case of being virtuous, they would highly encourage technological development within their kingdoms, so as to improve the lifestyles of their subjects. This would create a technological boom as magic helps improve technology by providing required materials. However, since scientific progress is initially based on theories and postulates, and scientific people tend to harbor opposing theories and contradictory beliefs about things yet unknown, it would become more and more difficult to supplant technology with magic, until finally the royalty will be done with it and instead teach people some basic magic skills to help them in daily lives. In case the royalty are evil and use magic to strengthen their hold upon their subjects, the scientific minded people will try and counter their magic with scientific inventions, quickly escalating the situation to a type of civil war. This would create a boom in technical discoveries and inventions. In case the technicians win, technological progress would continue to boom. However in case the technicians lose and the royalty prevail, they would capture and kill all the scientists, completely halting the technological progress. [Answer] ### No You've isolated the magic from the population too much for it to make a difference. There's a difference between science and engineering at this point. Science didn't tell you how to build a bridge or make a better loom, this was stuff being done by blacksmiths and engineers on the ground not scientists in ivory towers. Magic will only slow technological development if it's available to the common people. If day to day, the magic says that you don't need that machine, magic can do it. Even in the magical Discworld, where access to magic is limited in a similar way to your question when steam engine time came, steam engines happened. This is technological progress for the masses, not for the elites. In that period, science in the ivory towers was driven by curiosity, not by need. They want to know how the world works and the place of everything within it. Their lives, on the whole, are already fairly easy going, they have servants to do all the hard work. If using a spell to light a fire requires significant effort, calling a servant to perform the same task is considerably easier. Engineering is done by the people and that is driven by need, steam engines and looms were build by people with dirty hands who needed a job done better. It's not until the Manhattan Project that technology is driven by science [Answer] Not if the nobles are the only ones that have it, craftsmen are almost never nobles. And it is the craftsmen and merchant classes that help create improvements. [Answer] Magic will cause technological stagnation because magic can substitute most uses for technology. As Terry Pratchett once wrote: > > Sufficiently advanced magic is indistinguishable from technology. > > > * Irrigation? Just summon a raincloud. * Medicine? Just cast a healing spell. * Communication? Just use a magic mirror. * Transportation? Just open a portal. * Architecture? Just conjure a wall with earth magic. * Weapons? Just throw some fireballs at them. As long as magic is available, there is no reason to develop any technology for these purposes. Sure, technology could eventually surpass the abilities of even the best wizards and enable even those without magic skill to benefit from it. But technology is developed incrementally. Every technology is based on someone observing an existing technology and thinking "I could think of a slightly better way to do this". No light bulb without a gas lamp. No gas lamp without a candle. No candle without a torch. But when a new technology does not offer an improvement over magic, nobody will use it and it will be forgotten before someone can improve on it. [Answer] This kind of question is at the core deeply political and/or philosophical for the simple reason that what you describe is the question whether access to education should only be granted to the rich and intelligent... Simple answer: Access to edducation has been proven to be a great accelerator to science, wealth and society, so in the end I would like to say your scenario plays out a lot like usual history... However, here is a not so simple answer. If only a few could really handle magic and it is an elite-thing anyways, then I would think it would be something like the White Tower in Robert Jordans Wheel of Time... An elite that is searching for people who can use magic but becoming so arrogant and dismissive of anything that is not their own, enabling paralell societies to grow and in the end overtake the establishment. Now that I think about it... still the same. [Answer] It depends a lot on the social conditions. If the working class has access to capital (able to get a bank loan with reasonable effort) and rule of law (their property can't be seized without due process), then they are going to find ways to innovate in order to make their lives better. That's what sparked the industrial revolution. So even if some people don't have access to magic, they'll develop ways to make their lives better and more convenient. And in such conditions, magic will find its way to the masses as people get richer and become able to buy access to knowledge. But as the other answers pointed out, it depends mostly on what the magic is capable of. For example, can magicians teleport themselves and/or other people and objects? If not, something resembling a modern transportation infrastructure will develop eventually. If yes, then I imagine a class of magicians might arise who are willing to sell such services to make a living (that is, a magical equivalent of the trucking industry). So the first task is to establish exactly what the magic can and cannot do. [Answer] I've long posited that magic would be a force for discovery if it existed. If it takes any form of Effort to produce magical effects then you'll want to maximise your bang-for-buck. Broadly the theory goes like this: Magic is the art of bending and breaking physics. In order to minimise how much magic you use, you would want to leverage your knowledge of how things are supposed to work. If I want to make an object spin with magic, I could twist it arbitrarily at great effort to myself, or I could apply a linear force at one end of it and let physics take over. Understanding leverage may dramatically reduce the amount of effort I have to expend. If I want to heal someone, it can only benefit me to know how their bodies work. And then there's the tools magic provides. Scrying might allow a magic-user to directly observe atomic structures and molecules, or to move one's perspective to orbital altitudes or even the surface of the moon. Use of magic to generate heat would potentially allow smelting of materials that conventional refining has yet to work with, Bauxite for example in the real world requires extreme temperatures that are inaccessible even with a blast-furnace, nearly all aluminium is recycled simply because it's so hard to acquire efficiently. A medieval world with aluminium is an entertaining thought. Introspective and explorative wizardry would undoubtedly push back the boundaries of human knowledge very easily, the problem is social. If wizardry is commonplace, there will be curious souls exploring what's possible. If it's a small intellectual elite with time on their hands, they'll explore. If they have wars to fight, or have rigid demands on their behaviour, wizardry will likely not contribute much to scientific progress. Another factor is the way in which magic works. I've been assuming fairly arbitrary physical effects, but if it's more like clearly defined Spells, then wizards are End-Users of an existing system and far less likely to explore, even assuming the tools they have at their disposal are adaptable enough to do so. [Answer] No, the nobles still fight wars, If you fight wars then your going to have arms race. And arms race is brings more then better weapons but better communication and transportation methods (armies have to move quickly armies have to communication with each other). As long as the king isn't so powerful that he doesn't need an army then technology will developed ]
[Question] [ Note: this takes place in a world populated by humanoid bears, where the population density in Siberia is much higher. The northern part of Russia is taken up by a country called Medwedia. As said before, Medwedia takes up the northern part of Russia in our universe; both countries span eastwards up to the Pacific coast (Alaska belongs to Medwedia, a hypothetical Bering bridge will be discussed in another question). Now... Medwedia and Russia share Lake Baikal, with two cities, Truz and Ignaz, being located on the opposing shores of the northern, Medwedian part of the lake. Truz and Ignaz are both large cities; and if a bridge would be constructed between them, there would be a full motorway that connects Medwed and Ostby. [![](https://i.stack.imgur.com/k70w7.jpg)](https://i.stack.imgur.com/k70w7.jpg) Fig.1. - the Map. Red line is the Medwedia-Russia border. Northern yellow line is the Medwedian motorway from the Capital of Medwedia (1000km northeast of Moscow) to the city of Ostby (Pacific coast, 400km north of Vladivostok), southern yellow line is the Russian motorway from Moscow to Vladivostok. Northern purple line is a hypothetical road which follows the Northern coast of the lake, southern purple lines are hypothetical roads that connect to the Russian motorway which will be used as a transit road in this case, the purple line between Truz and the peninsula near Ignaz is the hypothetical Baikal bridge. Now, (mid-20th Century), we want to connect the growing cities of Truz and Ignaz with a bridge. The bridge should consist of a motorway and rail tracks and should be usable all during all times of the year. Is something like this possible at Lake Baikal? [![](https://i.stack.imgur.com/BNsBS.jpg)](https://i.stack.imgur.com/BNsBS.jpg) The following main problems would arise during planning, design and construction: * Depth of Lake Baikal - I have heard that Lake Baikal reaches depths of up to 1642 meters at some points. The depth map shows that the northern part of the lake usually has depths of no more than 700-800 meters, but it is still very deep! I know that most bridges are constructed in relatively shallow waters. A solution would be planning the bridge so that the ridge (middle part of the lake) which has smaller depths is used and to install floating supporting structures. [![](https://i.stack.imgur.com/YMCXq.jpg)](https://i.stack.imgur.com/YMCXq.jpg) * Climate - The lake freezes over completely in winter. This could damage the bridge due to temperature changes and also due to forces enacted on the supporting structures by the ice as it expands due to the density anomaly of water. This could be countered either by the usage of special materials or moving parts that take up the pressure or by heating elements that would at least prevent the ice from cooling down too strongly, minimizing the pressure effects enacted by the density anomaly. [![enter image description here](https://i.stack.imgur.com/KeCY7.jpg)](https://i.stack.imgur.com/KeCY7.jpg) * Length - The part of Lake Baikal where I want to build the bridge has a width of 60 to 70 kilometers. I know that bridges of this length exist, but could such a bridge be constructed if the depth and the climate is considered? And after all, did bridges of this length exist in the middle of the 20th century? If a bridge can NOT be constructed under these circumstances, those alternatives which would allow for the connection of the cities of Truz and Ignaz as well as for travel between Medwed and Ostby: * Ferry in summer, ice in winter - Ferries are commonly used to shorten travel times and distances. However, this would be especially difficult in autumn and in spring: in Winter, the ice is strong enough so that heavy vehicles can cross the lake (the Transsib company used to place tracks on the ice in winter while using a ferry in summer), but in autumn and in spring when the ice is dense enough to disallow travel by ferry but not dense enough for driving or placing tracks, there would be a big problem. [![](https://i.stack.imgur.com/9LUeJ.jpg)](https://i.stack.imgur.com/9LUeJ.jpg) [![](https://i.stack.imgur.com/Hh2uL.jpg)](https://i.stack.imgur.com/Hh2uL.jpg) * Northern coast road - A road which follows the coast of the northern part of the lake would probably be less expensive than a bridge, but would mean that travel times are longer. [![](https://i.stack.imgur.com/mbcay.jpg)](https://i.stack.imgur.com/mbcay.jpg) * Transit road through Russian territory - This would again not need for bridges to be constructed and would allow for the infrastructure of the Russian motorway between Moscow and Vladivostok to be used; however, travel times would be increased, and most importantly, the crossing of the border into Russia and back again into Medwedia would be needed for a citizen of Medwedia to travel from Medwed to Ostby or from Truz to Ignaz. However, this should not be a big problem since the relations between Medwedia and Russia are good. [![](https://i.stack.imgur.com/JzO1S.jpg)](https://i.stack.imgur.com/JzO1S.jpg) * Tunnel - There could be good reasons why a tunnel is better than a bridge in this case; however, it would theoretically be even more expensive than a bridge or mean that the transport capacity would be even lower. [![enter image description here](https://i.stack.imgur.com/NoGKX.jpg)](https://i.stack.imgur.com/NoGKX.jpg) Now, I am asking you the following questions: * Could a bridge like this be constructed with mid-20th century technology (before 1975)? If yes, what challenges would await the engineers of the bridge? * How would the bridge be designed? Should it be a rail-only bridge or should it be a motorway bridge? How to counter the main problems which I have named? * If such a bridge can NOT be constructed, why would it be the case? What alternatives would be the best ones? [Answer] Hovercraft can cross both water and ice (or, as this is Russia, Ekranoplanes). For a given weight of cargo, they're more expensive than boats but cheaper than aircraft. Otherwise the ferry/ice road solution is workable if the ferries are ice breakers (and stay well clear of the road). An ice breaking ship can sail though ice that's thick enough to drive on, so instead of a period where you can't use either, both could be active. Perhaps heavy vehicles travel by ferry until the ice is thick enough for them to drive. Ice roads can be thickened and strengthened by pumping water up through holes (on cold days) so that it freezes on the surface. These roads take longer to melt than the regular thinner, ice, which would also extend the season. Bridges and tunnels are both not affordable, even with current day technology. A possible near-future technology is a floating, underwater tunnel (as considered for crossing much narrower fjords in Norway). This is anchored to the seabed, but just deep enough that ships (and ice) can pass over it. No one has built one yet. [Answer] The challenge of building such a bridge is beyond 20th century engineering. There are some very big bridges: the bridge joining Honshu and Shikoku has a central span of 1991m But the bridge you are proposing must cross 30000m of deep water. All bridges of that length are multi-span bridges. The water is really deep. It would be a considerable challenge to build pylons that are planted at the bottom of the lake. There was a proposal for an English Channel bridge, that would use multiple spans, in about 50m of water, it was rejected as too costly, and too disruptive for shipping. The ridge is still at a depth of about 400m, and if a bridge were to follow the ridge it would extend the length to nearer 90000m. For comparison, Lake Pontchartrain, which has a 30000m bridge over it, only has a depth of 5m. The region is seismically active. Ensuring that the bridge can withstand Earthquakes adds to the difficulty and the cost. A pontoon bridge might be possible. There are no floating bridges that come close to your 30000m length, but there is experience in the oil and gas industry in producing anchored floating platforms in deep water. However a floating bridge would prevent all North South shipping. A tunnel is more realistic. But would be a massive engineering feat. The length would be greater than any existing tunnel (to allow for reasonable gradients the tunnel would need to be close to 100km long, the depth would be much greater. With enough will it could be made to happen, but the price tag would be huge. £50 billion could be a starting guess (compared with £12 for the channel tunnel) If you wanted it to be a road tunnel too, you can immediately start upping the price (rail tunnels can be narrower) Given the difficulties the obvious solution is the road going round the lake, supplemented by ferries in summer, and possibly ice road in winter. The terrain is more manageable around the south of the lake, and the real road (P258) goes South. [Answer] A floating bridge is doable. Here in Seattle, we have the SR520 bridge: [![520 bridge](https://i.stack.imgur.com/MVUv8.jpg)](https://i.stack.imgur.com/MVUv8.jpg) It's floating section is 2.4 km long and is supported on floating concrete pontoons far enough above the water, that storms aren't an issue: [![closeup](https://i.stack.imgur.com/h3gaS.jpg)](https://i.stack.imgur.com/h3gaS.jpg) We don't have ice, that could be an interesting engineering challenge, but extending it length wise, would be more of the same. The biggest reason why we don't have more floating bridges, is that they require a lot of maintenance, which is a pain in salt water and the list of lakes where it would be economically feasible to pay for one is pretty limited IRL. [Answer] The likely single biggest obstacles would be cost and justification. Theoretically it is possible to build towers in very deep water. For instance the Troll A oil platform completed in the late 1990’s sits in 300m of water and variants on such a structure could be used. But the cost of providing many dozens of such structures to support a bridge is beyond all decent contemplation and simply could not be justified. A floating tunnel might be used with buoyant tunnel sections tethered to the lake bed, but this would also be hugely and unjustifiably expensive. A better bet would be to use a ferry in the summer, drive across the ice in the winter and drive around the lake between seasons. Any inconvenience would be dwarfed by the inconvenience of building a permanent structure (as in decades of toil and cost for no immediate gain). In early winter and late spring it would be possible to break the ice with an ice breaker extending the ferry season (and ferries could have a limited ice breaking capability as well). Heavy icebreakers could probably clear a route even in winter if it was rely necessary <https://www.marineinsight.com/types-of-ships/top-5-biggest-ice-breaker-ships-in-the-world-in-2011/> But at some point it would prove too costly to keep the ice at bay and at that point ice a few miles away could be used for the crossing. Fun feature for a fictional setting: liquid nitrogen might be used to freeze any soft spots or cracks on the ice road. [Answer] Expansion of small scale. A pontoon bridge has little environmental impact (historically) but can buffer in weather systems on [large bodies of water](https://en.wikipedia.org/wiki/List_of_pontoon_bridges). While I don't think it's practical, if you insist on a bridge, this would be a great alternative. There will be no disruption of major navigation, so why not? [Answer] No the lake is a rift valley it is actively expanding by 3-4 cm per year, and is full of seismic activity. this combines with its depth makes building a bridge over it impossible. Tunnels are likewise impossible you would be digging through magma. And as others have mentioned ice makes pontoon bridges impossible. ]
[Question] [ So, I understand that human skin color is based on the distance from the equator, but would it be possible to evolve skin to be a non-natural color such as green, pink, blue, purple, ect? Perhaps if it would not be possible on Earth, would it be possible on another planet with a different climate? What gives skin pigment, anyway? Does blood alter the color of skin? Does our red blood make us look pink? I'm sorry, that's a bit off track. Help? [Answer] Skin colour in humans is affected by three main sources: blood, melanin, and the skin cells themselves. In the absence of the first two, skin is generally a yellow-white colour; this is the least likely to change (assuming something close to normal human biology), but also the least important. It's not a particularly intense colour, so it's easy for other things to overpower it. Human blood is primarily coloured by the hemoglobin in our red blood cells. This is based on ferrous iron (Fe2+), giving the classic red colour. There are other options here; changing some of the iron in the hemoglobin to ferric iron (Fe3+) makes the blood (and therefore skin) appear blueish - unfortunately it does that by making it less effective at transporting oxygen, so while this does occasionally happen in individuals, it is highly unlikely to ever become widespread in the population. Moving to more exotic options, some other species use [hemocyanin](https://en.wikipedia.org/wiki/Hemocyanin) instead of hemoglobin, which gives them blue blood. In pale-skinned humans, this would lead to a blueish skin colour instead of the normal pink. Changing the oxygen-transporting molecule used in the bloodstream is a *major* change to bodily function, though; it would be plausible as a result of genetic engineering, but not natural evolution. Finally, most 'normal' variation in human skin colouring is due to variations in melanin concentration. This is a pigment which essentially exists solely to colour skin, for the purpose of protecting us against damage from UV light. This is the most likely way that other skin colours would evolve - humans already have multiple forms of melanin with different colours (red/blonde/black hair all get their colour from it in one way or another), and similar chemicals in other species have different colours again (particularly relevant to the question is squid ink, which is coloured by melanin and is blue-black). It would be perfectly plausible for some group of humans to develop a different skin colour due to a change in how their melanocytes function - possibly due to a change in diet and/or environmental pressure, or possibly due to a random mutation. [Answer] Skin color in humans is normally determined by the concentration of the pigment melanin in the skin. The genes of albinos prevent the synthesis of melanin, which means that their skin itself contains no pigment. Thus, they are very pale, except where their blood shows through the skin, in which case they may appear pink. People may develop blue skin through a variety of medical disorders, such as cyanosis. They may also become blue because they consume silver orally, by way of a quack medicine called "colloidal silver", whose effects are demonstrated in the picture linked below. Apparently, this condition is called "argyria". <https://i.stack.imgur.com/dJqYG.jpg> Thus, perhaps some species could evolve the ability to consume silver to make their skin blue. The most obvious advantage for such an adaptation would be for camouflage, assuming that some part the species' environment (the sky?) is a similar color. [Answer] Most of the answers so far have concentrated on the biological processes that contribute to the our perception of skin colour. An alternative approach might be to look at how the human eye might evolve to interpret optical light differently. Our eyes and brains currently interpret a certain range of frequencies in the optical light spectrum as possessing colours. If our eyes were to evolve so that a gradual shift in the range of frequencies we perceive were to take place, then what we perceive as natural skin colour today could in the future be interpreted as blue. [Answer] When we are exposed to too much silver dust, or injest too much colloidal silver, our skin actually does turn blue - it's called argyrosis. I'm not completely sure of the medical implications of the condition, but apparently it damages the rods in your eyes, and your kidneys. If you had a population of people that lived off a food source rich in silver (for whatever reasons) they would definitely be blue. Add a little bit of genetic resistance to the more damaging aspects of silver, and voilà! Blue (or purple) people! It's just like how pink flamingoes are only that colour because of their diet! [Answer] I may be wrong but I think plants have evolved to be green because green is the opposite colour to the light they receive from the sun. This means they absorb the most light possible. As you didn't specify if the skin had to belong to a human, one could suppose that if an animal on a planet orbiting a red dwarf needed some way of converting its stars light to energy in its skin, their skin would be blue. [Answer] Perhaps spending a lot of time at sea would cause it to do so, as it would blend in with the sea color and serve as camouflage. Cetaceans evolved from land animals, and their skin is blue. [Answer] Photosynthesis. Some forms of chlorophyll are coloured blue. So they evolved to get a daylight energy top up from the sun. [Answer] Blue skin would be skin that reflected a lot of blue light. So perhaps we'd have blue skin if our environment exposed us to enough blue-wavelength light for it to be damaging, and our skin developed ways of reflecting it. ]
[Question] [ If you've read [Chronicles of Ancient Darkness](http://en.wikipedia.org/wiki/Chronicles_of_Ancient_Darkness), you might get the reference. In that story, the protagonists, after fulfilling their duty, decide to journey over a large mountain chain to explore the other side, another forest landscape. Besides an obvious barrier like a large chain of mountains, why wouldn't people want to explore areas not yet explored? [Answer] Reasons can be divided into 2 loose categories: ## Low gain/chance of gain * Many areas are just inhabited by animals and if there are people, quite possibly you don't know their language anyway and don't expect them to have anything of interest to you. (e.g. shepherds usually aren't very rich or interesting.) * It's not that easy to earn something from trade or conquers - that takes money, effort, time, men and animals. Regular people can't afford it. * Knowledge and seeing other places isn't that good reason for most people. * Mythical powers and treasures are usually only mythical. ## High loss/risk of loss * Bandits, wild animals, dangerous environment conditions. You can die or lose your property. * People living there may not like you. * You are separated from your family (you can't feed it!), people you know, etc. * No bed, less food, no roof over your head, you have to walk or ride a horse, baggage is heavy, etc. * Laws can forbid it. (Like in medieval Europe - peasants were meant to work for their lord, not wander around.) * Culture/religion may be against it. (Maybe have your social duties like taking care of someone or the mountains are sacred.) * It costs money and takes time. You also need some experience/knowledge about travelling, so your average peasant certainly doesn't qualify. [Answer] Because there would be no reason. If they have no reason to cross (reasons would be trade, resources, etc.), many people wouldn't take the large risk. The barrier of mountains makes this plausible. Few people will risk their lives for mere exploration. Some people do, like the protagonists in the story, but most people wouldn't want to. It might also be considered socially unacceptable, or possibly forbidden by religion. A journey would mean interrupting their lives at home, and leaving their families and friends. This isn't everyone's idea of a great time. [Answer] Travel has been downright dangerous throughout most of human history. The world (particularly wilderness areas such as mountains) is full of predatory animals who are not smart enough to realize on an instinctive, species-wide level that those animals (i.e. humans or other sentient beings) have, in evolutionarily recent times, become much more dangerous to hunt. Climbing mountains risks life and limb from falls, low temperatures and altitude sickness, and is simply very hard to do at all, let alone safely. Even if someone idly tries to climb over a mountain range (and doesn't turn back to get home in time for dinner), very few people can afford to leave their occupations to do so without the promise of a tangible reward at the other side: If no-one knows what is over the mountains, and when they get there they find that it is nothing, it could be a disaster. [Answer] Social Pressure Their culture might view travel with suspicion. People who travel learn new, dangerous ideas and aren't to be trusted. Those who leave over the mountains and come back could find themselves ostracized, serving as a lesson to any other potential travelers. [Answer] something that could play into it as well, perhaps the reason no one ever went to place 'X' is because of an overwhelming sense of instinctual fear that a character gets when they even think about a place, or that it was 'magically' removed from the collective memory of the world for some reason. ]
[Question] [ It is somewhat common knowledge in the worldbuilding community that larger planets leads to smaller land creatures, because larger planets means more gravity gets bigger and that makes it harder to become big from the square-cube law. However, water is different than land. Water creatures can become way bigger than land creatures on Earth, due to buoyancy holding up some of their weight. Buoyancy increases with gravity, but so does weight. So would marine creatures be larger or smaller on a larger planets? Or would they be the same size as on Earth? [Answer] The size of marine animals on Earth isn't really restricted by gravity... it is more about food supply and metabolism. The ultimate limit in size is probably quite complex, and a factor of various things like growth rates and predation and dietary requirements and so on. If planetary gravity is too high, then it might be less likely that land-dwelling, air-breathing animals evolve that might then be able to return to the sea in the way that the likes of plesiosaurs and whales did, and sharks have metabolic issues getting enough oxygen from the water as they get very large so super-high-gravity worlds might have smaller things that Earth, but aside from that I'd expect things to be fairly similar, given availability of sufficient oxygen and food. ]
[Question] [ # Info I've created a pine tree that stabs its needles into people. Here's the way I did so: Using genetic engineering, my fictional scientists inserted keratin-producing genes into a pine tree (gymnosperm, a clade of plants that while fruitless have complex reproductive systems and vascular tissue) embryo. Through some more work, they produced a tree that has a unique trunk. As the meristem growth causes cork and vascular cambium to form, plant cells near the vascular bundles grow very close to the skin of the tree (near the outer ring of vascular tissue and cork cambium) and begin to elongate due to the plant hormone auxin, which stimulates elongation of cell walls without triggering cell division. As they stretch, they grow bundles of myosin. Then they produce actin filaments to power what is essentially muscle movement. These cells grow into "muscle" fibers and small threads of tissue that, while not as complex as human muscle (which has tissue bundles held together by connective tissues such as epimysium) are capable of exerting significant pressure. They grow underneath the developing quill. The keratin plates, in the meantime, grow out of the developing muscular bundle and form a quill, like that of a porcupine . . . with two differences: the quills are stiffer, and they are pure keratin, like very fine, sharp claws. (A porcupine pine tree!) When you go to touch the tree or tap one of the needles now embedded (point facing out) in the trunk, the muscles react to the pressure and force the needle(s) forward. The quill is finely barbed, since according to Science, [barbed quills required approximately half the penetration force of the barbless quills, or 56% of the pressure of a hypodermic needle](http://www.sciencemag.org/news/2012/12/porcupine-quills-reveal-their-prickly-secrets) to breach (human) skin. From what I was able to gather, the pressure needed for a hypodermic needle to break through skin is 20 kPa (kilopascals). 56% of 20 is 11.2, so taking pressure as P, F as force, and A as area of surface on contact, $$P=\frac{F}{A}$$. The area of my porcupine quills is exactly 1mm2 at the tip. The pressure exerted needs to be sufficient to break through skin, so using [this calcuator](https://www.sensorsone.com/force-and-area-to-pressure-calculator/) to reverse-engineer the equation, I need exactly .0112 Newtons of force to generate the pressure needed (for the tip.) That doesn't seem like too much for the muscles in the trunk to push the quill forward. I think that the defense (stabby needles) works, but I'm not sure: ### The Question Reality-check my system, please. Would the defense realistically work, or did I miss something/are my numbers wrong? Bonus points for: telling me whether I should make the needles sharper, thicker, or thinner/pointier to make the tree more effective. --- Thanks to those in the [Sandbox](https://worldbuilding.meta.stackexchange.com/questions/6168/sandbox-for-proposed-questions) for checking my numbers and providing a little feedback. [Answer] ## Spiny piney tree! I dig it. This is a really cool idea, and certainly plausible. Keratin has a (relatively) high compressive strength so the needles would be suitably sturdy, the force required is a reasonable one, and the Rule of Cool is definitely in your favor. However, there are still a few points of concern I would have as a reader. ### 1. Plant cells are rather inflexible. Plant cells differ from animal cells in several ways, but the most relevant one for our scenario is the presence of the [cell wall](https://en.wikipedia.org/wiki/Cell_wall). This structural layer provides rigidity to the cell and prevents plasmolyzing, but would serve to largely block shape changes in the cell that are required for normal muscle movement. Muscles in animals have a simple "unit" of action - the [sarcomere](https://en.wikipedia.org/wiki/Sarcomere). This structure is composed of actin and myosin filaments. As the myosin protiens are powered by ATP, they "walk" along the actin filaments and bring the opposite ends of the sarcomere together, causing the cell to contract. In the gif below, the light pink bands are the ends of the sarcomere and you can see them pulled together and apart as the actin and myosin slide past each other. This mechanism is problematic because plant cells can't squish like this. The thick and sturdy cell wall will prevent the deformation required, and thus any sarcomeres would be applying tension to the cell wall rather than distorting it. This leads to the all-or-nothing kind of scenario, where the cell wall would either sustain the strain or would collapse catastrophically. [![Gif of actin/myosin contraction from Wikipedia: By hamish darby [Public domain], from Wikimedia Commons](https://i.stack.imgur.com/nMyqK.gif)](https://i.stack.imgur.com/nMyqK.gif) ### 2. Your structure seems to have "muscle" cells in parallel, not in series. You'll note that there are multiple sarcomeres attached end-to-end in the animation above, just as they are in real life. This allows large actions to occur over small time scales - even though molecular motors like myosin move at [maximum speeds on the scale of micrometers](http://book.bionumbers.org/how-fast-do-molecular-motors-move-on-cytoskeletal-filaments/), lining up 100,000 of them allows our muscles to function much faster. It sounds like your setup has a "ring" of lengthy cells surrounding the needle that the needle then slides out of. This will simply occur too slowly without the multiplicative power of serial sarcomeres described above. To get an idea of how fast a cell like this could actually move something, I humbly defer you to videos of Bacillaria paradoxa, the [famous slidey diatom](https://www.youtube.com/watch?v=FO5MPaIbS9U). These colonial creatures crawl back and forth past each other via myosin attachments on the outside of their silica frustules. The speed is maybe 10 micrometers per second - the frustule here is about 100 um long and it takes maybe 10 seconds to slide the whole way. ## An alternative idea May I recommend a mechanism similar to the [cnidocysts](https://en.wikipedia.org/wiki/Cnidocyte) of jellyfish? These "stinging cells" could be much more dangerous and might actually minimize the engineering required. [![Nematocyst firing process, from Wikipedia: By The original uploader was Spaully at English Wikipedia. (Transferred from en.wikipedia to Commons.) [CC SA 1.0 (http://creativecommons.org/licenses/sa/1.0/) or Public domain], via Wikimedia Commons](https://i.stack.imgur.com/ANLqx.png)](https://i.stack.imgur.com/ANLqx.png) Cnidocysts operate like spiky, inflatable, water balloons. When inactive, they have a calcium imbalance between the interior of the cell and the exterior. When triggered, the [osmotic pressure](https://en.wikipedia.org/wiki/Osmotic_pressure) essentially "inflates" the cell, forcing the spike on the front to invert and thrusts it into a triggering stimulus. This seems like it would be a perfect mechanism for your tree. Although it requires a highly flexible cell/structure, trees already use [turgor pressure](https://biologydictionary.net/hypotonic-solution/) to maintain cell shape, and that high-pressure environment would facilitate ejection, and there's no need to insert animal genes into the plant kingdom. The tip of these nematocysts could still be made of keratin and tipped with a nasty substance to improve fatality rates. If, you know, the spiky water balloon isn't deadly-looking enough: [![EM image of a discharged nematocyst, from Wikipedia](https://i.stack.imgur.com/juvi9.png)](https://i.stack.imgur.com/juvi9.png) ]
[Question] [ I'm playing with the idea of an alien race that uses ammonia, not water, as a solvent and breathes hydrogen. This is mainly because I want it to combust when exposed to our atmosphere. However, I want to know if this is a believable concept, i.e. not a dumb idea. [Answer] Using ammonia as a solvent would work, though if you want it to be pure ammonia, you'll have to keep your aliens quite cold, as it boils at -33°C. Aqueous ammonia solutions would work, but that does not seem to be what you're after. Ammonia isn't as broadly useful a solvent as water, but it does allow for lots of interesting chemistry to occur, including things like relatively [stable solutions of solvated electrons](https://www.youtube.com/watch?v=tYjQXjUUvwY), which are quite unstable in aqueous systems. Lots of biological reactions will produce water, so an anhydrous alien will need a way to excrete the water just as we have a way to excrete ammonia. Maybe your alien could excrete crystals of glycerol or urinate an alcohol or something like that. In any case, ammonia is a much better choice than a hydrocarbon. Breathing hydrogen is a bit more problematic. The purpose of breathing oxygen is that we can break C-H bonds and combine oxygen with both carbon and hydrogen atoms to release energy in the metabolism of organic molecules. Oxygen is highly reactive stuff; we just don't realize it because we've evolved to walk around at the bottom of an ocean of it. If we breathed hydrogen instead, it would be far less reactive. Hydrogen will readily react with lots of things, but it typically doesn't release huge amounts of energy in the process. One idea might be to have your aliens run a biological version of the [Sabatier process](https://en.wikipedia.org/wiki/Sabatier_reaction). The reaction is spontaneous at low temperatures, though it would never actually occur without catalysis at liquid ammonia temperatures. This would give them a means of producing some basic metabolic building blocks from materials that are common in the universe as well as provide a reason for them to breathe hydrogen in the first place. [Answer] Ammonia can work as a solvent in place of water or in addition to water. Hydrogen is also very reactive so it could be a useful energy source. Also if a planet somehow had high concentrations of Boron then Boron Nitride could be a substitute for Carbon as together they form the same bonds as Carbon and life based on Boron and Nitrogen might use ammonia as a solvent as at the temperatures of liquid ammonia that reactions between Boron and Nitrogen could be more controlled. In this case the planet might have an atmosphere of Diborane, Hydrogen, Nitrogen, and Ammonia vapor. In this case the equivalent of plant life might get energy by reacting diborane and ammonia to produce sugar analogues and hydrogen while the equivalent of animals might react hydrogen and sugar analogues to produce diborane and ammonia. In this case the gasses that the organisms would breath would explode when in contact with air. Also liquid water in high concentrations would be too hot and too acidic for this type of life and if this life touched life on Earth both would mutually poison each other. ]
[Question] [ [This question about genetics](https://worldbuilding.stackexchange.com/q/13540/3407) (not required reading) contains the phrase "science of a Type II civilization." This got me to thinking: although we intuitively know what this means, does this actually tell us anything? After all, the only requirement to advance on the [Kardashev scale](http://en.wikipedia.org/wiki/Kardashev_scale) is to have the capability to harness a particular amount of energy. What does that tell us about their medical or fundamental physics knowledge? * It seems to me that it would require no more knowledge than we have today to construct a Dyson Sphere to harness the energy of the Sun (which would make us a Type II civilization regardless of whether we actually use that much energy, as Isaac pointed out). Although the will is not there, the capacity certainly is. * Compare this to the future as depicted by Star Trek, for example. They (humans) are most likely a type I (the Enterprise is stated to generate on the order of $10^{12}~\text{W}$, vs. the $10^{16}~\text{W}$ required for a Type I, so their civilization as a whole is probably just over Type I), and they regard the Dyson sphere from [that one episode](http://en.memory-alpha.org/wiki/Relics_(episode)) as an impressive accomplishment, on as scale which they previously considered to be theoretical. This is despite the fact that they're zipping around the galaxy with ~~space wizard magic~~ advanced technology far beyond our current understanding of physics. ## The Question What level of development is required to reach Type $n\in\left\{1,2,3\right\}$ on the Kardashev scale (using [Sagan's definition](http://en.wikipedia.org/wiki/Kardashev_scale#Current_status_of_human_civilization))? Put another way, what knowledge is absolutely necessary to harness the requisite amounts of power? Areas of knowledge that you may consider include, but are not limited to: * Fundamental physics, including classical physics, relativity, and quantum mechanics * Mathematics, including calculus, statistics, abstract math, and computer science * Engineering, including materials science and metrology * 'Soft' sciences, including biology, medicine, sociology, and economics You can also discuss knowledge that may not be necessary to harness planetary/stellar/galactic amounts of energy, but must, or will almost certainly be learned beforehand. (For example, perhaps a certain knowledge of sociology would be gained in the course of coordinating a project on such a large scale.) [Answer] I've spent a good deal of time thinking about this and related problems. The puzzle caused by the multidimensional linkages between growth and technological progress has been a difficult one to crack. You can look up the giants in the field of growth, such as [Solow](http://en.wikipedia.org/wiki/Solow%E2%80%93Swan_model), [Ramsey](http://en.wikipedia.org/wiki/Ramsey%E2%80%93Cass%E2%80%93Koopmans_model), [Simon](http://en.wikipedia.org/wiki/The_Ultimate_Resource), [Harrod](http://en.wikipedia.org/wiki/Harrod%E2%80%93Domar_model), as well as the [New Growth Theory](http://www.economicsonline.co.uk/Global_economics/New_growth_theory.html). ## Production Possibilities Frontier I have come to think that the best framework to start thinking about this issue is through the use of an expanding [production possibilities frontier](http://en.wikipedia.org/wiki/Production%E2%80%93possibility_frontier) (also PPC). ![PPC](https://i.stack.imgur.com/8NoeT.gif) I chose this because it illustrates beautifully the difference between efficiency improvements of existing technology (which, at best, can get you to the PPC) and the shift to new PPFs through the discovery and implementation of new technology. Here's a practical example (notice the inverted Y cost scale): ![total hp vs Cost/hp](https://i.stack.imgur.com/tR75Y.jpg) ## General Purpose Technologies as Gamechangers This should go without saying, but in reality, this frontier is a hypersphere. The Hypersphere of Human Possibility, if you want to sound a bit grandiose about it. Imagine new technologies as little pins that push outward at the frontier. Now most technologies (say the little cardboard coffee-holders at starbucks) are not that impactful, and only push the frontier outward a little locally. Other technologies such as the combustion engine, electricity or computers are different -- these technologies have a virtually limitless range of applicability - they can push the frontier outward in many directions at once, and by a lot. Even more interestingly, one such gamechanger can open the path towards another. Combustion engines were used to generate cheap electricity, and eventually cheap electricity was used to construct delicate electrical equipment, such as computers. Computers then were used to design better combustion engines, power distribution grids, better computers etc. ## Visibility of New Technological Possibilities The fundamental question is whether there will ever be diminishing marginal returns to new technological research. In other words, was it just blind luck that each gamechanger opened the PPF towards accessing the next PPF-expanding gamechanger, or is this reinforcing nature a fixture of human progress? In other words, is it possible that we'll reach an area where the next gamechanger is forever out of reach of our most advanced PPF, say in the way Fusion power always seems to be 50 years away? This could be the case if some technological insight requires, say, an IQ beyond the reach of humans, or energy density levels unattainable with the most advanced technology. Our history so far seems to indicate that if there are diminishing returns, we are far, far from reaching them. The key concept here is the visibility of new technologies. For instance, consider the brilliant leaps of insight achievable by genius: Leonardo Da Vinci could use concepts extant in his world to imagine flying machines and tanks, concepts centuries beyond his society's energy-wise capability to implement. Despite that, these were visible to Da Vinci. ![da vinci tank schematics](https://i.stack.imgur.com/R0u8a.jpg) By contrast, no matter how brilliant Da Vinci was, he literally had no chance of inventing quantum chromodynamics, because the prerequisite nearby intellectual assets were outside of his PPF. It was only through the employment of more energy-intensive means of reality manipulation and measurement that the discovery of the subtle aspects of reality embodied in QCD literally became conceivable. QCD was invisible to Da Vinci. This finally puts us in a position where we can answer your question. ## New Technological Progress and Vantage Points on the Path to Kardashev level I Reaching Kardashev Type I (10¹⁶W) is a hugely ambitious goal, since it would mean boosting our current energy resources by a factor of about 10,000. This is already so far outside our PPF that it is hard to even imagine. How would the world look like if, ceteris paribus, instead of an average US power consumption of 10.0 kW (which is essentially at the current frontier), we would average 100.0 MW? Essentially, you'd have the power of a Nimitz-class aircraft carrier in the hands of Joe Everybody, and that's not taking into account future efficiency gains, which are likely to be considerable as well. Think about it, the power that the most powerful nation on the planet wields (there's only a dozen or so of these behemoths in the world), would be at the fingertips of your average Joe. This itself would be a greater leap than we've made in all history so far: from a basal metabolic rate of 100W, we got to 10,000 W at the frontier, most of it used to power industrial machines and robotic helpers. In reality, ceteris paribus would not hold, of course, so for instance human population will likely increase greatly before we reach Kardashev I, so the the per capita amount will likely be lower when we reach that threshold, although inequalities in distribution might mean that individuals might have access to levels far above that sooner. Currently, there is an exploding PPF dimension, where expansion has not slowed for decades: ![cost per computation](https://i.stack.imgur.com/gMtP4.png) The implications of this relentless progress in the most scarce resource of all, namely intelligence, are surely vast yet their true scale and the new vantage points sure to be opened by them remain unfathomable. Even a marginally human-like special-purpose artificial intellect would change everything, probably more so than all the previous revolutions combined. So, even on the path to K-I, there are gamechanging future technologies that we have visibility of, such as fusion power, competent dedicated as well as general purpose AIs, and full-blown nanotechnology. All three are massive game-changers in the energy, knowledge and manufacturing dimensions, which might help explain their relatively easy visibility from our vantage. There are sure to be countless others that remain invisible, some among them gamechangers. None of these technologies are literally required for attaining Kardashev-I (as the OP mentions, in theory we could reach it with something much like current technology), but it is extremely unlikely that with massive boosts in available energy and the new vantages that opens such innovations will not be pursued, as they will appear as low-hanging fruit in that new context. Having been pursued, they will open a virtuous cycle of making new gains in energy harvesting possible, better computation etc., in turn making yet other potential technologies appear as low hanging fruit, and so ad infinitum or until the marginal rate of return becomes 0. [Answer] The scales are fairly similar for each component you mention: simply, as you have a greater understanding of all of those fields, you are able to harness more and more energy. The fields you mention have a sort-of order of fundamentality. Engineering is impossible without physics; physics is impossible without mathematics (as are many of the soft sciences). So, essentially, the greater your understanding of mathematics, the more energy you are able to harness. To put that another way, you can have Einstein and Newton and all the famous physicists and combine their brains, but unless you also have some mathematicians working out their principles, your scientists can't do anything significant. To me, the "soft" sciences aren't so necessary here. Power is all about physics, not people: knowing how someone's brain understands and remembers all the physics isn't going to help you build a giant star-generator. The rest will develop at a similar rate, but with the more specialized/less fundamental fields lagging behind a bit. Adding to that, since power harnessing relies on engineering, power harnessing ability can never rise above the level of engineering, and will probably follow the pattern of lagging behind a bit. For your convenience, I shall provide a bar chart: ``` \| D\| e\| \| v\| \| e\| \| \| l\| \| \| o\| \| \| \| p\| \| \| \| m\| \| \| \| \| e\| \| \| \| \| n\| \| \| \| \| t\| \| \| \| \| \| \| \| \| \| +-------+---------+-------------+-----------------+ Maths Physics Engineering POWER HARNESSED ``` If we put some lines across that to represent Kardashev levels, we can see that it is even possible for a civilization to have mathematics one or conceivably even two levels above their civilization's level: ``` \| D\|---------------------------------------------------- Kardashev III e\| v\| \| e\| \| l\| \| \| o\| \| \| p\|---\|--------\|-----------\|--------------------------- Kardashev II m\| \| \| \| e\| \| \| \| \| n\| \| \| \| \| t\|---\|--------\|-----------\|---------------\|----------- Kardashev I \| \| \| \| \| +-------+---------+-------------+-----------------+ Maths Physics Engineering POWER HARNESSED ``` This does explain your Star Trek point: perhaps the technologies that enable them to zip across the universe so quickly have been refined through physics and engineering so they don't actually use that much power: thus, the power required is still in their power available to harvest. They have been able to refine this technology because they have knowledge of physics and engineering more advanced than their ability to harness power. Probably they set their scientists onto developing interstellar travel instead of power generation. And yes, I am proud of my ASCII bar charts. [Answer] Many structures do not scale very well. One of the most classic issues is the square-cubed law which limits the ability for an entity to grow past a certain size. It if wants to be larger, it needs to have less density. However, lower density makes one unacceptable to all sorts of physics (like sandstorms). Differing in opinion from ArtOfCode's answer, I would argue that the larger a society gets, the more its soft and hard sciences become harder to distinguish. The soft sciences have to be more codified (like hard sciences) to ensure the messages of the soft sciences do not get distorted with the weaker connections associated with lower density. Meanwhile, the hard sciences have to get more and more complicated, until they start looking like soft sciences. For a comparison, take a look at a naive CFD application which uses Navier-Stokes on a fixed grid. It is a very hard-science style approach. Now look at a modern high performance CFD designed to answer real questions about air flow through turbines. They often use things like Vortex Energy models which, when you read about them, start to look more like a soft science (particularly regarding transitions between where more traditional models do a better job and where the Vortex Energy approaches do a better job). As an example, consider one facet of a civilization: composites: * Class < I: We play with composites, but steel and concrete still form the backbone of our civilization's construction. One could argue both steel and concrete are composites, but they are very simple ones. * Class I: It's really hard to reach class I by actually consuming all the energy that hits your planet. It's much easier to reach out into space and build solar collection there. Steel is nice here, but its a pain to haul up from the planet in any large quantities, so you'd make use of what you have available. Given that it is unlikely that we'll find enough iron-bearing asteroids to make this happen, we'll turn to less useful materials, and need to make them useful. Composites are a great way to get the best properties from multiple materials, so it sort of becomes a necesity here. * Class II: When you start talking about dyson spheres, you're really pushing at the limits of the tensile strengths of your materials. You start needing composites. You also start needing a good way to maintain all that material, because you can't just have a modern American density of people all the way around (it starts pushing against the square-cubed law again). Accordingly, not only do you need composites, but you start to need composites that heal themselves, like the enamel of our teeth. * Class III: At this point, the sheer number of atoms needed starts to become a limiting factor, driving us to even more sparse approaches. I can't even fathom what sorts of materials will be called upon here, webs of space dust or thin tendrils of dark matter. Simply no idea. Or consider biology: * Class < I: Biology is neat. We learn a lot from it. * Class I: We need to really understand our biology, because we're starting to become the ecosystem, instead of being part of it. * Class II: Biology now becomes an artform, the fine art of constructing the self-repairing structures using what we understand from a few million years of evolution. Biological constructs here literally show signs of the individual groups that made them, because they're an art not a science. * Class III: Biology becomes nothing more than a working platform for a larger theory that can create biological-like creatures over the empty lightyears. Nobody actually uses amino acids, but there may be some information stored on how they once worked. [Answer] Who needs advanced development? Establish loads of bases at Type 1.5-2 level in solar systems and keep establishing them and you can get a type 2-2.5 society. And also, in the Kardashev scale, the energy harnessed should be multiplied by how efficiently they use the energy (i.e. how much work they can do), so high-tech, low power equipment contributes significantly. ]
[Question] [ From [this chart](http://www.enchantedlearning.com/subjects/astronomy/stars/startypes.shtml) it appears that the star types closest to our own are K-type (oranger, a little cooler, and less than half as bright) and F-type (bluer, a little warmer, and much brighter). If I want to place an "earth-like" planet around one of these star types, how should I expect plant life on my planet to develop differently compared to Earth? By "earth-like" I mean a planet that has temperature, terrain, water, and atmosphere conducive to the development of higher life forms (eventually sentient ones). How does the star type affect the appearance, growth, types, density, etc of plants? Should one star type lead to denser (or sparser) jungles, taller (or shorter) trees, different kinds of fruits, etc? I think [this question](https://worldbuilding.stackexchange.com/q/11547/28) is related. I don't know enough chemistry to say how related, though. [Answer] Let's think about this in terms of peak emission. [Wien's displacement law](https://en.wikipedia.org/wiki/Wien's_displacement_law) tells us that the peak emission wavelength of a black body, $\lambda\_{\text{max}}$, is inversely proportional to its temperature, $T$: $$\lambda\_{\text{max}}=\frac{b}{T}$$ where $b$ is Wien's displacement constant; $b\simeq2.9\times10^{-3}\text{ m K}$. Using this and some assumptions about temperature, we can determine the peak of a star's spectrum, given that most stars are well-approximated as black bodies. Here, we assume that $T$ is the star's [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature), and pick a temperature in the general range of each type. I'm going to use [the Harvard spectral classification](https://en.wikipedia.org/wiki/Stellar_classification#Harvard_spectral_classification). $$\begin{array}{\|c\|c\|c\|c\|} \hline \text{Star type} & \text{Color} & T (\text{K}) & \lambda\_{\text{max}}(\text{nm})\\ \hline \text{O} & \text{blue} & 35,000 & 82.9\\ \hline \text{B} & \text{blue-white} & 20,000 & 145\\ \hline \text{A} & \text{white} & 8,000 & 363\\ \hline \text{F} & \text{yellow-white} & 7,000 & 414\\ \hline \text{G} & \text{yellow} & 5,500 & 527\\ \hline \text{K} & \text{orange} & 4,000 & 725\\ \hline \text{M} & \text{red} & 3,000 & 967\\ \hline \end{array}$$ Next, we have to assume that the plants are somewhat like the ones found on Earth - they use the same compounds and processes to survive. Life on Earth is all that currently exists in our dataset, and it's all we have to work with before delving into too much speculation. One important process is photosynthesis. There are a variety of [photosynthetic pigments](https://en.wikipedia.org/wiki/Photosynthetic_pigment) available. I was able to find [a book chapter detailing many of them](http://www.life.illinois.edu/govindjee/photosynBook/Chapter9.pdf) along with their key property here, the wavelength(s) of maximum absorption $\lambda\_{\text{abs}}$. Here's a table of the relevant ones: $$\begin{array}{\|c\|c\|c\|} \hline \text{Pigment} & \lambda\_{\text{abs}}(\text{nm}) & \text{Occurrence}\\ \hline \text{Chlorophyll a} & 435, 670\text{-6}80 & \text{Photosynthetic plants}\\ \hline \text{Chlorophyll b} & 480, 650 & \text{Higher plants; green algae}\\ \hline \text{Chlorophyll c} & 435, 645 & \text{Diatoms; brown algae}\\ \hline \text{Chlorophyll d} & 435, 740 & \text{Red algae}\\ \hline \text{Chlorobium chlorophyll} & 750, 760 & \text{Green bacteria}\\ \hline \text{Bacteriochlorophyll a} & 800, 850, 890 & \text{Purple bacteria; green bacteria}\\ \hline \text{Bacteriochlorophyll b} & 435, 740 & \text{Rhodopseudomonas (a purple bacterium)}\\ \hline \alpha\text{-Carotene} & 420, 440, 470 & \text{Leaves; red algae; green algae}\\ \hline \beta\text{-Carotene} & 425, 450, 480 & \text{Most other plants}\\ \hline \gamma\text{-Carotene} & 440, 460, 495 & \text{Green sulfur bacteria}\\ \hline \text{Luteol} & 425, 445, 475 & \text{Green leaves; green algae; red algae}\\ \hline \text{Violaxanthol} & 425, 450, 475 & \text{Leaves}\\ \hline \text{Fucoxanthal} & 425, 450, 475 & \text{Diatoms; brown algae}\\ \hline \text{Spirilloxanthal} & 464, 490, 524 & \text{Purple bacteria}\\ \hline \text{Phycoerythrins} & 490, 546, 576 & \text{Red algae; some blue-green algae}\\ \hline \text{Phycocyanins} & 618 & \text{Blue-green algae; some red algae}\\ \hline \text{Allophycocyanin} & 654 & \text{Blue-green algae; red algae}\\ \hline \end{array}$$ The Sun's $\lambda\_{\text{max},\odot}$ is in the neighborhood of $500\text{ nm}$, landing it smack in the middle of all these pigments - as would be expected. I have some immediate observations: * Many pigments have favorable absorption in the $\sim420\text{-}500\text{ nm}$ range, near $\lambda\_{\text{max},\odot}$. * There are a couple other peaks, from $618\text{-}680\text{ nm}$, $740\text{-}760\text{ nm}$, and $800\text{-}890\text{ nm}$. These are mainly due to pigments used by certain types of bacteria. It stands to reason that if $\lambda\_{\text{max},\odot}$ was somewhere else, different pigments would dominate. So let's add a couple columns to our first table: $$\begin{array}{\|c\|c\|c\|c\|} \hline \text{Star type} & \lambda\_{\text{max}}(\text{nm}) & \text{Possible dominant pigments} & \text{Possible dominant plants}\\ \hline \text{O} & 82.9 & \text{?} & \text{Algae}\\ \hline \text{B} & 145 & \text{?} & \text{Algae}\\ \hline \text{A} & 363 & \text{Miscellaneous algal pigments} & \text{Green and brown algae; some red algae}\\ \hline \text{F} & 414 & \text{Chlorophylls} & \text{Higher plants; green, brown and red algae}\\ \hline \text{G} & 527 & \text{Chlorophylls} & \text{Higher plants; blue-green algae}\\ \hline \text{K} & 725 & \text{Bacteriochlorophylls} & \text{Purple bacteria; green bacteria; blue-green algae}\\ \hline \text{M} & 967 & \text{Bacteriochlorophylls} & \text{Purple bacteria; green bacteria}\\ \hline \end{array}$$ I've stated that algae would be the most likely plants on planets orbiting O- and B- type stars. This has nothing to do with pigments; rather, it is because these stars are so short-lived that multicellular life would have a hard time developing there. In fact, age may impact the types of life you would see across the board. More massive stars have less time for higher life to develop and so probably won't lead to complicated, multicellular life. I still have to agree, at least in part, with [Ville Niemi's answer](https://worldbuilding.stackexchange.com/a/11563/627). It's clear that plenty of different pigments exist on Earth, and there's no reason to think we wouldn't see even others on an alien world around a different star. However, in drastic enough cases (especially with M-dwarfs and O and B stars), there likely would be major shifts in the dominant pigments. Perhaps new ones would develop, and I can't speculate on those. I can, though, tell you which ones would gain some slight advantages. So maybe view this answer as saying "Well, maybe [X, Y, Z]" rather than something definitive, especially given that I'm no expert. [Answer] Not really. Plants generally use only a small portion of the available energy for photosynthesis and prefer frequencies that are either chemically efficient or penetrate surrounding medium, either air or water, well. This is why there are two peaks on photosynthetic efficiency graph, one is chemically efficient because longer wave lengths are easier to absorb, another penetrates water better. The spectrum of the star does not really change chemical or biological properties. Neither does it change the properties of air or water. So plants would probably still absorb only a portion of available light most convenient to them. And that part would probably be the same as on Earth. From a comment by TimB: If your planet is in the habitable zone then you've already compensated for size and temperature by putting the planet at the correct distance from the star and the only remaining factor is the colour. [Answer] I've read articles and references to scientific papers that speculate on the color of vegetation on other worlds. Even assuming biochemestry as we know it, many types of photosynthesis is possible, and can accomidate a variety of wavelengths. Add to that details of the evolutionary pressures under which the ubiquitous form evolved, and availability of elements ("interesting" catalysts use heavy metal atoms), the interaction of other tissues and the operation of human vision (not a spectrometer! Evolved for a different ambient light) and anything is possible and easily made plausible for a SF story. [Answer] Chlorophyll is green because it is very good at absorbing the yellow light that forms most of the sun's energy. A sun with redder, or bluer light forming the bulk of the energy would preferentially produce plants that are colored differently to maximize absorption for them [Answer] Artifexian and Worldbuilding Notes have released a video overview of plant, sky, and sun combinations: <https://youtu.be/L9MNC45Jr6Q> And a Google Doc calculator to output plant colours according to those variables: <https://docs.google.com/spreadsheets/u/0/d/1YhSapw5xSUli1H321JSM2JqMfbmuzqwJp5Iba6DxuWs/htmlview#> Screencaps of the calculator: [![Calculator for atmospheric composition](https://i.stack.imgur.com/fhhiV.png)](https://i.stack.imgur.com/fhhiV.png) [![Calculator for plant colour based on stellar variables](https://i.stack.imgur.com/4A8lz.png)](https://i.stack.imgur.com/4A8lz.png) [Answer] An yellow star, like our Sun, will release EMR that will make a planet's atmosphere blue, and red during twilight, unless there is a chemical on the surface or in the air that changes how much of each kind of electromagnetic radiation is reflected and absorbed. Thus, a yellow sun would mean that flora is predominantly green, in order to absorb red and blue light. For a red sun, which is smaller and dimmer than our own, the plants would be black, in order to absorb as much energy as possible. As for a habitable planet orbiting a blue star, which is larger and brighter than the Sun, the plants would be multicolored. There would be white and blue plants, to reflect harmful radiation, dark plants due to melanin protecting from harmful radiation, and autumn-colored plants, to absorb abundant blue light. As for height and jungle density, I don't believe that the type of star would have anything to do with them. However, a planet orbiting a blue star would probably have large fruits with radiation-dampening properties in their flesh, so that the seeds inside don't suffer genetic damage. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I am attempting to design aliens that live in a universe with a 4+1 space-time--i.e., a universe with four orthogonal spatial dimensions, rather than three, in addition to a fifth time dimension. In this universe, gravity follows an inverse cube law rather than an inverse square law, but it still results in large blobs of solid matter being pulled into (hyper)spheroidal planet shapes. 4D planets, however, have 3D hyperplanar surfaces, not 2D planar surfaces like planets in our universe. While 4D space comes with an array of other interesting features as well (like having an extra Platonic solid, knots made out of sheets instead of strings, and two independent components of angular momentum), it is the 3D nature of planetary surfaces that is most relevant here, as that dictates the geometry of limbs designed to contact and move over them. Now, to state the obvious as background: humans have two legs, and two arms, derived from creatures that have 4 legs. In 3D space, standing on two legs is unstable, but it is (obviously) feasible to maintain balance on the free axis with active neurological control. There are, however, no creatures which get around on only one leg (modulo the occasional bird that can lock its joints to stand on one leg, nothing actually locomotes with one). 4 legs is a good number for an ancestral creature in 3-space, because in 3-space you need 3 points of contact to maintain stability, and having 4 legs allows you to move one at a time while keeping three points of contact on the ground. Also, having an even number of legs permits bilateral symmetry. Also due to symmetry considerations, we don't see any 3-legged, one-armed animals; having three legs would result in greater stability than two, but Earthling tetrapods that re-purpose some of their limbs as not-legs invariably do so in pairs. Moving up into 4-space, you need four points of contact on a hyperplanar ground for stability; standing on three legs is as unstable as standing on two legs in 3-space, and standing on two legs in 4-space is as unstable as balancing on one leg in 3-space. Thus, it would seem unlikely for a 4D sophont to have only two legs (and definitely not just one!). However, while we can reasonably exclude one-legged and two-legged/two-armed body plans for the aforementioned stability reasons, it is not so obvious what limb arrangements would be reasonable, particularly since adding an extra dimension gives you more directions for limbs to stick out from a single body section (e.g., a shoulder girdle or hip girdle analog). So: Does it make the most sense to attach only two bilaterally symmetric limbs to each body segment/shoulder girdle/hip girdle? Or, are there higher-order symmetries possible for limb arrangements? [Answer] To me, one body plan is by far the most likely: 6 limbs in a triangular prism. To see why, think of the earliest land-dwelling, limbed animals to evolve on Earth. I'm imagining something like a wide-legged lizard. It's low to the ground; effectively its entire body is in a 2D plane. And this makes sense, since opposing gravity takes work, and evolutionary pressure hadn't yet forced creatures to do that work. It has a head, and it wouldn't be advantageous for its limbs to be moving around its head all the time, so it keeps its limbs along the orthogonal axis, 2 on each side (one on each side would be below the minimum number required for stability, as you mentioned in the question). Thus, 4 legs total. This, fundamentally, is why bilateral symmetry developed on Earth, and not trilateral symmetry. Imagine that lizard having 3 legs: how would it place them around its body without being off-balance when its head is in the plane of the Earth? This logic is important, because, as we'll see, it generalizes simply to 4+1-dimensional space. Imagine an early land-dwelling animal on our hyper-Earth. Its body crawls along the hyperplane because supporting itself against gravity is hard. For stability, it splays its limbs to the sides of the axis containing its head. The minimum number of limbs it could have is 3, because that spans the plane perpendicular to its head along the ground. But, in analogy with how 2 was the technical, unstable minimum for our proto-lizard, we'd really expect 2 sets of limbs along the spine. Thus, in our case, 6 limbs total: 3 hind limbs and 3 front limbs. I want to stress that trilateral symmetry perpendicular to the spine isn't a problem, because the issues with trilateral symmetry on Earth don't apply on hyper-Earth. So let's fast-forward the evolutionary clock and ask about hyper-people. I think it stands to reason that they would manipulate objects with their 3 forelegs and walk on their 3 hind-legs. To visualize them walking, it might help to form an analogy with the way people walk on Earth. Our 2 legs are always in the positions of 2 vertices of a triangle, and when we step forward, we change which vertex is missing. This is always unstable due to the missing vertex, but we use momentum to keep our balance. Similarly, the 3 legs of the hyper-humans always form 3 of the vertices of a tetrahedron. Don't actually try to picture it; in 3D, the legs will seem to pass through each other, and it's very confusing to think about. But suffice it to say, this 3-and-3-limb body plan seems the most logical. Of course, extra legs are always doable, like a 4-and-4 version. This is in analogy to animals with more than 4 legs on Earth, like insects. However, I think I've shown that 6 limbs is, in many ways, the default in 4 spacial dimensions. [Answer] Having seen it, I am fairly convinced by [Gilad M's answer](https://worldbuilding.stackexchange.com/a/149270/2800). However, I think the reasoning can be clarified and expanded on. So, we start out imagining the simplest creature that could crawl out of the sea onto land and stand up. It will "want" to keep its center of mass low, and span the (hyper)plane for stability. If you zoom in on one limb attachment section of a 3D tetrapod (i.e., the shoulder girdle or hip girdle), you have the major axis of the animal (the spine) defining one dimension of the plane, and then two limbs, providing two points of contact with the ground, defining a second axis; the third point of contact with the ground is provided by something located elsewhere along the spinal axis. That third contact point can be expected to be provided by another pair of limbs, rather than a single limb, since having 4 total permits one to move while maintaining 3-point stability--thus, you end up with matched pairs of limbs. Additionally, since the pairs of limbs do not span the plane by themselves, they also serve as a rotational axis about which the spine can pivot, so 3D tetrapods can stand up. In 3D, if you add additional limbs on the same body segment, you loose the ability for the body to pivot around those limbs--see, e.g., radially symmetric creatures like seastars (flat) or sea cucumbers (elongated), or cephalopods. There is thus no way for such a creature to transition from laying with its primary body axis parallel to the ground to standing with its primary axis perpendicular to the ground. Moving up to 4D, a primitive creature will still "want" to remain low to the ground, and span the hyperplane for stability. In order to get that static stability, we need at least four points of contact with the ground--plus one to permit movement. However, there are far more different options for how limbs might be arranged. For an axially extended creature (something with a linear spine that can lay down or stand up), it is clear that one will need at least two different limb attachment points, at opposite ends of the spine, to support the entire length of the spine; otherwise, a single limb group would have to exert a lot of torque to support a cantilevered body; one could perhaps imagine something like a 5-legged theropod with its single hip girdle in the middle and the body balanced across it, but that is both not a primitive-looking condition (nothing on our 3D world came out of the ocean balanced on a single limb girdle, despite bipedalism later evolving multiple times), and doesn't lend itself to evolving into something with distinct sets of arms and legs--i.e., it's not very good for a "human-analog". In addition, we should expect each limb girdle to have at least two limbs attached to it, just as in 3D--if there were only one, then when it was that limb's turn to move, the cantilevered body would bee unsupported, and you would end up with a 3-legged-dog situation. If each limb girdle still has only two limbs attached, then three such girdles would be required, resulting in a six-limbed basal animal, which could raise its front limbs in a direct analog of the 3D mantoid / centauroid body plan, resulting a 4-legged, 2-armed creature. Such a creature would be less stable than a 3D centauroid, as it would not be able to span the surface with the three remaining legs while moving one, but more stable than a 3D biped. However, it is possible for a primitive 4D tetrapod-analog to have an arbitrarily large number of limbs attached to a single limb girdle, much like radially symmetric 3D creatures, without losing the ability to hinge the spine. The reason for this hinges (pun intended) on the fact that rotations (in space of any dimensionality) do not fundamentally occur around axes, but rather in planes. The utility of linear axes to describe 3D rotations is a 3D-specific artifact of the fact that selecting a rotation plane leaves a single unique perpendicular vector left over to span the space. Radially-arranged limbs on a 4D creature, however, can span a single 2D plane with their attachment points, leaving a second plane containing the spine free to permit rotation of the spine around that set of limbs (hence the (geometric, if not evo-devo) plausibility of the aforementioned 5-legged theropod). Thus, since we can attach three or more limbs to a single girdle, it is not in fact necessary to adopt the centaur-analog body plan with three limb girdles--which is convenient, as a 4D human-analog with only two sets of limbs is certainly more human-ish than a centauroid! In fact, we can achieve the minimum limb set for statically stable locomotion of an axially-extended creature (5 limbs grouped at least in pairs) with one three-limb set and one two-limb set. Such a creature could stand up, hinging its spin from horizontal to vertical around the 3-limb girdle, to free up 2 arms while remaining as dynamically stable on 3 legs as a 3D human is on 2. This is, geometrically at least, a perfectly plausible body plan, and results in an unusually high degree of freedom for the joint between the spine and the arm girdle. If a consistent symmetry type is to be maintained along the full length of the body, however, that would dictate a 3-leg, 3-arm arrangement, with full trilateral symmetry. This gets us to the basic body plan proposed by Gilad M. So, to directly answer the question: *No, it does not make the most* sense to remain restricted to pairs of limbs, thus dictating 3 limb sets total; and yes, arbitrary numbers of limbs with high radial symmetry can in principle be supported on each limb girdle of a 4D creature.** Moving into the realm of greater speculation based on non-purely-geometric arguments, however, the 3+3 hexapod arrangement may or may not actually be optimal. After all, there are no trilaterally symmetric organisms in our world, and very few quadrilaterally symmetric ones. The larger degree of attachment available between radial segments that meet along 3D cell boundaries rather than 2D cross-sectional surfaces may significantly change whatever considerations lead Earthly evolution to favor 5+ symmetries, thus making trilaterally symmetric 4D "humans" perfectly plausible, but as this is well outside the realm of simple arguments to be made about hinging structures, how exactly that would impact 4D creature development is not nearly as obvious. Perhaps the optimal 4D human-analog is actually a ten-limbed, pentalaterally symmetric creature! [Answer] In geometry, a tetrahedron is made by extending a single point from the center of a triangle into the new dimension. A cube is made by stretching a surface into the new dimension. That's why those two shapes can be continued into all of the higher dimensions. More complex animals follow the cube-generation algorithm, not the tetrahedron algorithm. Thus, I'm going to suggest that such an animal would have clusters of 4-limb segments, in sequence, the same way we have clusters of 2-limb segments. The primary characteristic of animals is that we move. Anything that moves faster than a starfish has two axis of organization: that which resists gravity (Z) and that which is in line with our direction of travel (Y). The direction of travel winds up being a convenient path for spines, neurology, and digestive systems -- things we only need one of. Chordata then spread limbs in the third direction (X) for stability. Note that, in humans, we have managed to use advanced neurology (reaction speed, allowing better balance) to line up much of our biology with the gravitational axis, but that is a very recent development. A 4-space animal will still have Z and Y, but then will have two un-aligned dimensions to stabilize against, X and W. I propose that they would extend pairs in both directions. Looking at the animal in 3-space, you wouldn't see the limbs, any more than you see the limbs of a horse if you split it along the Z/Y plane. As a further complication, chordata have specialized the limbs along the Y axis. 4-space animals may very well specialize along the X axis, creating more spindly limbs (for instance) along the W axis. Alternately, they might have X-limbs that branch in the W direction, the same way our feet are duplicated X-ward, but extend Y-ward. As a side note, you probably should know that there are [no stable orbits in 4-space.](https://physics.stackexchange.com/questions/50142/gravity-in-other-than-3-spatial-dimensions-and-stable-orbits) Planets wouldn't form around stars. [Greg Egan](https://www.goodreads.com/en/book/show/156785) got around this in Diaspora by saying that the Strong and Weak nuclear force also works differently, so the creatures populate the surface of matter clumps that we would think of as stars. [Answer] ## You can still walk on 2 feet as long a gravity exists. Locomotion, no matter how many dimensions you have, requires only one appendage to anchor you to the ground and another appendage that you can lift and freely swing. The "shape" of your 1 planted foot becomes more complex as you add dimensions, but will always remain doable. The big difference is how many directions we can "walk" in. Because gravity pulls all matter inward, it means that your planet will have a "flat" surface at a more or less fixed distance from the center of mass. That means there will still be a single "up" and "down" to lift your feet away from and come down to make contact with the ground, but instead of being able to turn in 2-dimentions to walk along the planet's surface you can turn and walk in 3 dimensions by taking a 4 dimensional footstep. From our perspective, it would be kind of like being able to walk around with the bottoms of your feet contacting a solid volume of a 3d ground surface with thier body extending "up" into the 4th unseen direction where the solid ground does not exist, and the ground extending "down" towards the center of gravity. They would lift one foot out of the volume where it contacts the surface and then place it back down in another volume of the solid to create friction and forward locomotion. [![enter image description here](https://i.stack.imgur.com/MPTyd.png)](https://i.stack.imgur.com/MPTyd.png) ]
[Question] [ From my understanding, many of the features of water that make it very important for Earth's ecosystem are a result of oxygen's high electronegativity, which results in hydrogen bonding. As nitrogen and fluorine also have some similar properties (High electronegativity, hydrogen bonding, stable hydrides, etc.), could they serve the same role water does in an alien ecosystem? (Obviously under different temperature and pressure conditions) (I was directed to here from biology) [Answer] The book Xenology has a section about [alternatives to water](http://www.xenology.info/Xeno/8.2.2.htm), and this [boiling point calculator](http://www.trimen.pl/witek/calculators/wrzenie.html) helps show the variance due to pressure. Now, in my estimation, life will use whatever is the easiest in its current conditions. The reason why terrestrial life uses water is because most of the planet is not boiling or freezing (currently). In order for life to prefer ammonia or hydrogen fluoride instead, it would have to be perpetually in conditions where water is never available in liquid form. Ammonia and hydrogen fluoride have boiling points around the freezing point of water, all at one atmosphere. Increasing the pressure will increase the liquidity range, roughly speaking. So an ice planet is probably the most likely to harbor ammonia or HF-based life. Above the boiling point of water you are better off using something like sulfuric acid. Curiously enough, acids lose their acidic properties in environments devoid of liquid water. [Answer] Water is important for life not only for the factors you listed, but also because: * its high boiling point * its rather high specific heat * its volume increase upon freezing Just to give you a measure of how these properties impact life, note that upon freezing ice floats on water, with the maximum density being achieved at around 4 degrees. If that wouldn't be the case, ice would sink into the water, with the obvious result that any water body in winter would totally freeze. Also the high specific heat allows water to be that important for mitigating climate next to large bodies of water. As far as I know, ammonia and HF do not have the same behavior, that's why it is more difficult to base life on those. [Answer] Ammonia has some impressive properties as a solvent, including solvating metals (sodium, potassium, aluminum). It's true that ammonia ice doesn't float, but... Many discussions of this question seem fixated on water's particular set of properties (expansion on freezing, acid/base balance, etc.). These strike me as Earth-chauvinism. I can just as easily imagine an ammonia-based race dismissing water as a basis for life. "Too hot (denatures proteins before it even boils)! Too acid! Too chemically limited (only two instead of three hydrogens)! And cells would rupture every time they froze!" HOWEVER, I notice that the last few decades have brought us news of numerous water worldlets (Jovian moons, possibly even Ceres), but not much about worlds that could bear ammonia oceans. It may be that water life wins from simple abundance. One good science-fiction read on the topic: [Still River](https://books.google.com/books/about/Still_River.html?id=0vZc6P5v3pEC) by Hal Clement. ]
[Question] [ Modern level tech equivalent. Planet with 3 times higher atmospheric pressure, but partial pressure of oxygen is comparable to this on Earth. Gravity is insignificantly higher than good old 9.81m/s². Guns are designed to be used by humans against humans. I want to adjust gun caliber to fit local level. Let's say we start with standard NATO caliber 5.56×45mm and 7.62×51mm. (former eastern block 5.45×39mm and 7.62×54mm, yeah, similar, so I think it's not "opinion based" but "ballistics based" ;) ) How should I adjust ammo size to be practical under 3 atmospheres? (Should the bullets just be make a bit bigger? Or maybe narrower and longer? Or maybe average distance of engagement with machine gun would make such slowing down of bullets barely noticeable? Or maybe for long distance shooting one would need something comparable with anti-material rifle?) [Answer] The major problem will be overcoming the increased drag at 3 atm. How much increased drag? The drag equation is... $$F\_d = 1/2 \rho u^2 C\_d A $$ * $F\_d$ drag force * $\rho$ mass density of the atmosphere * $u$ velocity of the bullet * $A$ area of the bullet * $C\_d$ drag coefficient of the bullet Tripling the atmospheric density will triple the drag. To compensate we have a few choices: more force, less area, less drag. # Brute Force? We could triple the powder charge while keeping everything else the same, but that will have severe knock on effects for the rest of the gun making it much larger and heavier. Pressure is force / area. If we want to increase the force while keeping the diameter of the projectile (ie. the area) constant we'll need to triple the pressure. Most guns are already operating near their peak pressure, so this will make most guns explode. For example, your typical 9x19mm pistol round has a maximum pressure of about 240 MPa using about 5 or 6 grains of powder. Now we're asking them to do 720 MPa. 7.62x51mm NATO rifle round asks rifles to handle just 415 MPa. There's also the question of where to put all that extra powder? The 19mm part of 9x19mm is the length of the round. Triple the powder and you'd have to increase the length of the round increasing the size and weight of the ammunition and all associated parts. Just adding more bang is a non-starter. # Less Area, More Length, More Density: Flechettes The [ballistic coefficient](https://en.wikipedia.org/wiki/Ballistic_coefficient) of a bullet is a measure of its ability to overcome air resistance. A high ballistic coefficient means less drag. There's several ways to calculate ballistic coefficient, but for our purposes we'll use this one: $$BC = \frac{M}{C\_d A} = \frac{\rho l}{C\_d}$$ * $M$ is the mass of the bullet. * $A$ is its area. * $\rho$ is the density of the bullet. * $l$ is its length. * $C\_d$ is its drag coefficient. A more massive bullet is more resistant to drag, but a larger caliber means more area which increases drag. To increase a projectile's BC we want something long and dense with a lot of mass and low cross-section. We want sub-caliber [flechettes](https://en.wikipedia.org/wiki/Flechette). The most extreme example is the [APS Underwater "Rifle"](https://en.wikipedia.org/wiki/APS_underwater_rifle). [![enter image description here](https://i.stack.imgur.com/W5G18.jpg)](https://i.stack.imgur.com/W5G18.jpg) I use quotes around "rifle" because it has no rifling. Instead it fires 5.56mm x 120mm bolts with an effective firing range of 30m at 5m under water. This is extreme overkill for our 3 atm. The density of water at that depth is 1000 times that of normal air, not the 3 that we're dealing with, but it was such a cool find I had to include it. There have been any number of flechette weapons in trials over the years boasting higher capacity, higher velocity, and flatter trajectories at a cost of reduced accuracy or more complicated and expensive ways to keep them accurate. Several showed up in the [US Advanced Combat Rifle](https://en.wikipedia.org/wiki/Advanced_Combat_Rifle) trials in the 1980s. One was the [Steyr ACR](https://en.wikipedia.org/wiki/Steyr_ACR) firing a sub-caliber 1.5mm x 41mm flechette weighing 10 grains. Unlike the APS, Steyr's weapon had modest rifling to give a slow spin, plus it was fin-stabilized, for accuracy. [![enter image description here](https://i.stack.imgur.com/DqTTr.jpg)](https://i.stack.imgur.com/DqTTr.jpg) Its 10 grain projectile weight was 6 times less than the 62 grains of 5.56mm NATO, but made up for this with its area of just 1.8mm² compared to the 24.3mm² area of 5.56mm NATO: 13.5 times smaller area. Assuming similar density, this could double its ballistic coefficient. This bears out in its performance. At almost 5000 ft/s, it was nearly 50% faster than the standard 5.56mm NATO with a much flatter trajectory. The Steyr ACR worked, but ultimately none of the rifles succeeded in being significantly better than the M16 firing 5.56mm NATO. But in a world with triple the atmospheric pressure, flechettes would likely have a great advantage. [Answer] With higher atmospheric pressure, there is more stuff getting in the way of the bullet in the distance between you and your target. The slug is going to slow down in accordance with this. How do we deal with this? If you simply take an earth weapon in this place, the effective range is going to be dramatically reduced. I would think that a few things need to be adjusted. The first is average barrel length. As the propellant expands in a modern firearm, it accelerates the slug only for as long as it is in the barrel. The expanding gasses are focused until it leaves the barrel. This is why the muzzle velocity of a specific type of ammunition can vary depending on the gun it's used in. for example: The Normal 9mm round from a normal 9mm pistol leave the barrel at between 360 and 426 feet per second. The muzzle energy is 630 joules ke=1/2mv^2 .The normal 9mm barrel is only about 4 inches long. Take exactly the same round and put it in a Kel-Tec Sub 2000 carbine rifle with a 16 inch barrel, the muzzle energy jumps to 1024 Joules. That is just an example, your mileage may vary. Next step would be to look at the aerodynamics of the projectile. Long and slender would be the way to go. Something like a 5.56mm would need the slug to be longer to have a similar mass to the slug of a 7.62mm. To add to that, the powder charge behind the slug would also need to be much larger to push the mass down the barrel. You might look into flechets and Sabot rounds as well. A Sabot round is a smaller projectile than the barrel encased in a plastic wadding. This allows a large powder charge to fire a smaller slug, achieving a much greater muzzle velocity. Anything you do to reduce drag would be helpful. Finally, increase the amount of gunpowder per round. We do that here all the time. More propellant means more feet per second at the end of the barrel, which in turn means increased range, so long as the flight of the slug is stable Just keep in mind, most of the kinetic energy comes from the v^2 :) [Answer] Air resistance is, to a first approximation, proportional to the area presented to the line of flight. With 3X the air, the air resistance will be more than 3X greater. Which means that either you'll need a faster muzzle velocity or a smaller profile for your bullets, or both; the exact aerodynamic profile, grooves, or coatings will have only secondary or tertiary effects, but could be useful. My guess is that nothing you in so far as bullet design will provide an equivalent assault/combat rifle to today's. Larger calibers, longer (more massive) bullets will only partially solve the problem. The problem with your question is that you seem to assume that something that is only accurate/lethal at 3 meters isn't an assault or sniper weapon. It is, if that's the best you (or anyone else there) can do. (Well, no, not a sniper weapon. A lot of the record sniper shots were made with huge weapons (50 caliber), so maybe sniper rifles are 2,3,or 4 person weapons on this planet. [Answer] Slow and steady: the Rocket Slug Here is the drag equation again. $$F\_d = 1/2 \rho u^2 C\_d A $$ * $F\_d$ drag force * $\rho$ mass density of the atmosphere * $u$ velocity of the bullet * $A$ area of the bullet * $C\_d$ drag coefficient of the bullet Once the projectile leaves the gun it starts to slow down, its velocity decreasing according to drag. If you want your projectile to travel farther you can either reduce drag or increase muzzle velocity; increased projectile mass would also work but options to do that are limited by available materials (e.g.: lack of osmium). The green checked winning answer posted here reduces drag by reducing A, area. A longer barrel or stronger charge can increase muzzle velocity as noted in a different posted answer. Note though that drag is proportional to velocity squared. The faster the projectile is travelling the more energy drag will take from it. As you push faster and faster you get diminishing return on your investment of more energy. As regards reducing the forward profile (A), this necessitates either a lower mass projectile or an elongated projectile (like the flechette darts) which become difficult to launch from a barrel (as commented by @Paul TIKI). Lower mass means less kinetic energy carried by the projectile which means shorter range and less stopping power. If you want to keep your energy and correct for low mass with increased velocity you run into u^2 again. I propose that for this scenario the projectile be as massive as possible (e.g. a shotgun slug or Minie ball) and travel as slowly as possible to minimize drag. As slowly as possible while still being an effective projectile. I found that a Minie ball travelled at 950 ft/sec; about half the speed of a modern shotgun slug. Minie balls weighed about an ounce, were rifled, and did what they were supposed to do. [![enter image description here](https://i.stack.imgur.com/bLyDs.jpg)](https://i.stack.imgur.com/bLyDs.jpg) A problem presented by conventional firearms is that energy imparted to the projectile occurs only while the projectile is in the barrel. Muzzle velocity is as fast as it will ever go. If I want a slow muzzle velocity then velocity on impact will be even slower. The solution: ammunition which can accelerate itself in flight. The bullet becomes a rocket. This was tried in the 1960s: the Gyrojet was a gun which fired special rocket ammunition with a slow muzzle velocity but which then sped up in flight. [![enter image description here](https://i.stack.imgur.com/GW627.jpg)](https://i.stack.imgur.com/GW627.jpg) gyrojet ammo image found [here](http://14544-presscdn-0-64.pagely.netdna-cdn.com/wp-content/uploads/2013/03/GyroJetCartridge.jpg) I would have liked to find a schematic diagram of the gyro jet ammo; if someone does please edit this to insert it. I take away from this unlabeled cutaway that it shows the compartment within the projectile for rocket fuel. 60s tech might be out of range for the scenario posed here. My spin on the gyrojet: a weapon like a large bore Civil War rifle. The projectile is fired normally, with a charge in the barrel accelerating it. It would be nice (and would save space) if this charge were added separately and not incorporated in the bullet - again like a Civil War rifle. The projectile itself has its own onboard propellant which is ignited when it is fired. Rather than an explosion this burns slower in the manner of a rocket, continuing to accelerate the projectile to its target. Rockets can and were done with 19th century tech. Here is the Hale rocket from <https://civilwartalk.com/threads/rockets-in-the-civil-war.19824/>. I am intimidated just looking at it. [![enter image description here](https://i.stack.imgur.com/1Eeqq.jpg)](https://i.stack.imgur.com/1Eeqq.jpg) > > Hale Rockets : > By the middle of the 19th century, improved British rockets eclipsed long-lived Congreve rockets. Separate studies conducted in > France and the United States suggested that rockets would be more > accurate if they were spun, like the way a bullet is spun after it > leaves a gun barrel. An Englishman named William Hale was the first > rocket designer to take advantage of this principle. He adopted a > combination of tail fins and secondary nozzles through which exhaust > could pass. Hale rockets became the first spin-stabilized rockets, and > quickly became standard equipment for both the British and United > States armies. > > > Back to the gyrojet, those projectiles sped up in flight and then really packed a wallop. I think these thick air world projectiles just need to maintain their slow black powder tech muzzle velocity all the way to the target. It could be weighted or jacketed with lead if you had the space but I think will need to be iron to contain the rocket. Or maybe lead wrapped with steel wire? The Hale rocket is as big as it is because it has to blow up at the end of its flight. The projectile requested here just needs to hit someone. So: a rocket-propelled Minie ball. ]
[Question] [ The pangolin is a fascinating creature. Belonging to the only group of mammals with scales, they are arboreal and are not hindered by them in any way. However, these animals have a very complex evolutionary history. The majority of mammals had a different evolutionary path. What factors in early mammal history would support widespread scaled mammals? [Answer] This might be more likely on a desert world. The dry environment would encourage scales as a way to reduce water loss. And if there are frequent sand storms, a thicker, scaly hide would provide better protection than soft skin. Alternately, if you want mammals with snake like scaly skin, you could give them a biological reason why shedding skin frequently is advantageous. Maybe attached parasites like ticks or leeches are common. A thick scaly hide would protect against them, while shedding that skin periodically would remove them entirely. [Answer] If you want them never to have had fur, then you have to go a long way back! Because even before mammals were mammals, back when they were Mammal-like Reptiles (Synapsids), there is fossil evidence that they had fur. The Jurassic mammal-like reptile Castorocauda had fur, which means the common ancestor of it and all the modern mammals had fur. [Castorocauda on wikipedia](https://en.wikipedia.org/wiki/Castorocauda) (Palaeontologists are pretty sure mammal fur only evolved once). So the first furry beastie was a mammal-like reptile. In case you are not familiar with them, the (awkwardly named) mammal-like reptiles are a group that ranks equally with classification groups like Bird, Mammal, Reptile, Mollusc and so on. The ones you may have heard of are Dimetrodon and Edaphosaurus, the sail-backed ‘dinosaurs’ often illustrated in books on prehistoric animals. You’ve also got to consider that fur is one of the mammals’ success stories. Fur with an air layer trapped below/within it is a fantastic insulator. Fur with 1 centimetre thick layer of air is a much more efficient insulator than a 1cm thick skin or a 1cm thick layer of fat. (Mammals of course combine all three solutions). A scaly creature only has the options for two of those – thick skin (with scales) and fat. Fur was probably what allowed mammals to become properly warm-blooded and to exploit all sorts of habitats that reptiles can’t cope with. So there are no reptilian polar bears eating reptilian seals on the polar ice caps, or reptilian pumas stalking reptilian guanacos in the Andes, or reptilian wolves hunting reptilian deer in a snowy winter forest. You could perhaps say that your scaly mammals exploit fat much more than current mammals to stay warm. But fat as an insulator is a double-edged sword. On one hand you can also use it as nutrition in lean times, and burn it (as brown fat) to dump emergency heat into your blood stream (google ‘brown adipose tissue’ if you want to know more about that). On the other hand(s) there’s: 1. The fat ‘death spiral’ – it’s cold so you burn fat. So your insulation is poorer. So you get cold. So you burn fat. 2. Fat is an expensive tissue to accumulate. Foods which are abundant in fat aren’t common and may only be seasonally available, like nuts or spawning salmon. 3. As a mammal you need to pour some of your own fat into your babies in the form of milk. If you and your babies need lots of fat to stay warm as well as for your babies to grow, you’ll be very restricted in where and when you can reproduce. Even more restricted than modern mammals who time their births to coincide with food abundance. Some abundance – lush spring grass in a chilly Canadian meadow – may not be lush enough for mum to keep scaly baby deer or scaly baby bear warm AND growing. After all baby has a large surface area to volume ratio and will be losing heat faster than mum. So your scaly mammals will be restricted to warm climates. Or might breed much more slowly than their furry equivalents, because scaly-deer mum requires three years of feeding up to accumulate enough fat to have a fawn, while furry-deer mum only requires one year. Finally do you only want pangolin-type scales, or are armadillos and glyptodonts scaly enough for you? Those have bony armour rather than keratin armour, but look scaly. Armadillos avoid the cold by retreating into burrows at night. Obviously this is not practical for mammals the size of a glyptodont, cow or giraffe! [Answer] There's a lot of chance in evolution--how about just "the lineage which first evolves some other very useful features that help lead to an [adaptive radiation](http://en.wikipedia.org/wiki/Adaptive_radiation) of that group (perhaps after a mass extinction), like the development of placental reproduction, happens to be a group of scaled mammals"? Unless there's some selective pressure specifically favoring fur over scales and thus driving the evolution of scales back into fur, but for most ecological niches I don't see why scales would be particularly disadvantageous. ]
[Question] [ I am working on developing my world's history. Great people help give a world flavor. From profanity to holidays to religions and nations, great people can be the lynchpin on which the pendulum of history swings. With this in mind I find it important to include them when developing my world's history. Some will be more fully developed characters but doing that en masse seems rather daunting and distracts from the progression of writing the stories. When I am speaking of 'great' people it is not a moral judgement, simply accepting that a person altered the world by their action (or the myth of their personality). I am struggling to find a solid method to create these people. They do not need to be full blown characters so much as myths and personalities. In the US for example George Washington would be a 'great' person and he is spoken of reverently in most cases, stories about him and his life (have they any basis in reality or not) are told to children all the time to teach lessons etc. I have a general progression of history, it includes major events, the rise and fall of countries, kings, conflicts and religious trends etc. I frankly don't want to create fully fleshed out characters for all of history...I am on a timeline, I will die at some point. So, what I am looking for is a way to mass produce great people to give the world that extra bit of depth. What process could I use to create great people. Individuals created should come from a variety of backgrounds/occupations. [Answer] If you have major events, you already have great people. Take a look at this [Time list](http://ideas.time.com/2013/12/10/whos-biggest-the-100-most-significant-figures-in-history/) of the 100 most significant figures in history. While the ranks are up for debate, there are very clearly three categories of people on that list: The Creator, the Thinker, and the Leader. It stands to reason that when creating great people, you want to consider all three of these particular categories. Leaders A leader need not be a conqueror — merely someone who can unite enough people (through either force of arms or force of message) to cause significant change. Major events in a world’s history are made possible by great people. Conquest is often undertaken by an individual or a small grouping of individuals. These are the people who shape the world. Whether a significant person is considered “Great” or “Evil” depends mostly on who the victors are. Their names tend to be frequently used when naming places, monuments, and even other characters. Creating these sorts of great people is relatively easy: look to your world’s history and identify the characters that led the charge. Give them a name that has a ring to it, as you might find yourself using it in many places. Creators Musicians, artists, and writers are all examples of creators. They compose works that express emotion and offer entertainment. Most importantly, they are the builders of culture. What kind of architectural styles do the peoples of your world have? What colors visually impress them? What sounds are the most pleasing? What fantasies do they enjoy reading about? Unlike leaders who can be picked out of your major historical events, creators require you to look at the present. Defining the cultures your characters exist within will help you answer the above questions. The answers tell you what the unique cultural components of your world are. Armed with that information, you can start to isolate components and attribute them to individual people who used them so effectively that they became entrenched in the present culture. Thinkers Philosophers and scientists occupy this category. Through thought and experiment, these people have directed the minds of the people and placed ever-improving tools in their hands. For the philosophers, one simple approach is to look again at the major events in your history. When governmental structure changes, whose ideas influenced the new order? A more involved approach requires you to flesh out your leaders a bit more. Every major conqueror in history has been deeply influenced by the philosophical ideas of those that came before them. If you look at the motives of your leaders and the goals they set out to achieve, you can pinpoint specific schools of thought that might have influenced them. Scientists (or Mages in fantasy) can be determined much more arbitrarily. What major technological advances have been made in your world? Which warlock discovered how to summon the most powerful demons? The easiest approach here is to simply pick technological components (your revolutionary FTL drive) and name them after people who supposedly were critical to their existence and development. If you decide to dive deeper, consider the common fundamental concepts between different technologies and attribute those scientific achievements to a great mind. A Combination Most worlds have leaders aplenty. Conquest is a sexy topic, and the formation and dissolution of kingdoms is one of the most entertaining parts of world building. To achieve depth and immersion, however, you need a healthy dose of creators and thinkers too. These are the names that appear offhandedly and often in character dialogue — just briefly enough to make it appear that there’s more beneath the surface. [Answer] Pick a calendar date ([Today](https://en.wikipedia.org/wiki/February_17#Births) ). Look it up on Wikipedia. There are lists of (generally famous) peoples birthdays. Randomly pick one. [Today](https://en.wikipedia.org/wiki/February_17#Births) has about 80-100 people listed. 1821 [Lola Montez](https://en.wikipedia.org/wiki/Lola_Montez) was an actress and countess Oh and they have [death dates](https://en.wikipedia.org/wiki/February_17#Deaths) too. So double your money! [Answer] Disclaimer: Personally, I think that when inventing characters we are always going to be inspired/influenced by historic figures or famous characters. A System Any system requires a set of parameters. I would first define *a few main characteristics of your world/country, such as a few major divisive issues, such as religion, economy, military conquest, scientific or magical discovery, etc. Second, I would define the sort of people you want to create: evil, good, forces of change (whether good or bad), etc. Third, I would look at the situation being described and analyze it from the point of view of the characters. > > Par Example:* Two mages are discussing the morality of using a spell to remove someone's addiction to a drug, and thus become a useful member of society. Who's work might one mage reference? > > > At this point you look at your list of *world characteristics. Is your world deeply religious? Does it embrace a militaristic mindset? Does it value results over morality? Next, consider your characters. Are they the "good guys"? Are they shady types, looking to make a profit off of someone? At this point one character might: Reference a religious authority who enacted sweeping changes relating to the morality of controlling slaves, etc * A military commander who would remove any negative trait from his own psyche in order to better lead his men to victory? Add a twist: this leader's military goals were the destruction of a certain people, or civilization (aka he was a bad guy, but brilliant in other, objective ways) The situation/characters involved will always determine the outcome. [Answer] I’m not suggesting this will work for everyone, or it’s always the right or best method to go about creating influential characters in history, but it’s worked really well for me thus far. My method is a little slow (there’s lots of downtime between steps to let ideas percolate) and it’s rooted in the world’s fundamentals, so I’ll also provide a look at the steps prior to actual character creation (those steps that apply here, at least). ## Start with a Modern Image I never begin work on a new world until I have an idea of what I want it to look like when I’m finished. Usually this stems from a core idea, like the pursuit of perfection or fear of the other, and is used to form the foundation of every society that will exist in the world. ## Create a Physical Map Build the layout of your world. Put together a map of mountains, rivers, forests, valleys, islands, continents, deserts, and all manner of formations. Consider climate, ocean currents, and all the other tedious details (and handwave what you don’t want to emphasize in this world). I often create the geography and later explain how it came to be, but it’s more of a mixed process. ## Create a Political Map Given the physical boundaries depicted in the geographical map, create the political/societal layout. Countries don’t need to be constrained by a mountain range, a river, or a sea. Country borders often move over time and for various reasons. Want an island near one coast to be a territory of a country somewhere else? Go ahead. Figure out how that came to be later on, during the history. ## Baseline the Modern Societies For each region/country you’ve outlined in your political map, devise the basics of the modern society. Do they have technology, and how much? What are the major food sources? Mineral resources? What don’t they have access to? What do they have that could be traded away? What is the major religion, if any? What political movements are there? What role does the military play in daily life? Etc. ## Baseline the Old Societies For each region/country, devise the basics of the original society (original here meaning the point in time where you want to start worrying about it). Were the people primarily hunter/gatherers? Did they have a nomadic lifestyle and traveled far and wide, or did they settle in a crossroads of several season species? Did they arrive from space and lose their history, or remember it in everything they do? Etc. ## Develop the History Here’s where things get tricky. Begin writing a region/country’s history in a natural progression from the old society. Let neighboring old societies interact with each other. Explore how these cultures work together or against one another. There’s really no way to abstract this to a general rule; do what feels right to you for the old societies you’ve created. Feel free to tweak the old societies to get the interaction you want. ## Create Key Moments Write key moments into your history. This can be the first time two specific societies interact, whether they are opposed to each other’s views, have much in common, aren’t concerned one way or the other, etc.; a calamity such as an earthquake or financial collapse; a new, revolutionary invention, such as steel; or any other turning point in the way the society would function. ## Introduce Foci Let each key moment in history be defined by either a major event or a critical figure. Often, major events imply the involvement of a critical figure. These critical figures will be the focus around which your society will shift towards the modern society you’ve previously defined. ## Build on What You Have Going a little further, you can flesh out your critical figures by examining the society they emerged in at the time they emerged. A critical figure will represent a) the ideal of the society as it is; b) the society as a major group thinks it should be; or c) the opposite of what the society should be. Use the society as a lens through which to define the critical figure. [Answer] Work backwards. Make a list of important events, wars, nations and cities founded and inventions and invent the people behind them. I think this might be how it works in real life. The Fusion-Drive was invented by Bob Fusion inspired by watching his mother iron the clothes with a helium producing hydrogen iron. The Battle of Cthonopolis was won because of the brave efforts of Mike Roomis outfitting the partisans with helium producing hydrogen irons. Which turned to be surprisingly effective weapons. Who knew? Events make the man, not the other way round. The Characteristics of Bob and Mike inferred by their acts. This I think is easier than inventing a character and figuring out how they affect history. ]
[Question] [ We like the moon. It's close, you can see your home from there, low gravity well, so you get easy mass drivers to orbit for fleshing out your spacer economy, plus [you can do fun things in pools](https://what-if.xkcd.com/124/). [![enter image description here](https://i.stack.imgur.com/qTQyL.png)](https://i.stack.imgur.com/qTQyL.png) It's great. The only slight inconvenience is the fact that the moon is an airless, radiation-bathed hellhole with burning days and nitrogen-freezing nights. Now, assume we can develop the technology (and the financial and political will to marshal the resources) to get an 4000m Earth-like air pressure (about 60 kPa) at Moon surface. I know that with the lower gravity, the moon's atmosphere would tend to disperse to a great distance, and that gases would be lost in relatively quick order. To prevent that, I'm thinking of building a (set of) domes that would cover the entire surface of the moon, with laser point defense stations to blast away micrometeors and repairbots to fix any tears that might occur anyway. My question is, *what makes more sense from a realist perspective - going for domes* to cover the entire surface or allowing for the air to spread out the vast distances, and constantly replenish whatever is escaping*? PS: Keep in mind that I'm not suggesting this as a first approach to the moon. We may well start out like rats in deep tunnels, and have robots prowling the outside for a bit. But eventually, I want my swimming pool to overlook the Earth. EDIT: Note that a [question about placing an envelope](https://worldbuilding.stackexchange.com/questions/23111/can-i-put-a-sphere-around-my-asteroid) around a tiny asteroid already exists, but that question deals with essentially a tiny object (a few km across) with near-zero gravitational acceleration, so that yields completely different restrictions and results. [Answer] # A Lunar Atmosphere ### My Tool I wrote an atmosphere calculator based upon thermal (Jean’s Escape) with empirical fudge factors to increase the rates of atmospheric loss to more along the lines of what we see in the Solar System. It correctly predicts an $N\_2$ atmosphere for Titan and no atmosphere for the moons of Jupiter. ### What I see This calculator shows the half-life of water as ~$2 \cdot 10^5$ years in a lunar atmosphere. It gives the half-life for $O\_2$ & $N\_2$ as ~$10^6$ years. ## Some Assumptions ### Human Time Scales Assume a human generation equals 20 years. We would only lose ½ of the water in the atmosphere in 200,000 years – meaning a non-technological society could survive at least 10,000 human generations (i.e. 1 atmospheric half-life for $H\_2O$) without replenishing the lunar atmosphere. ### Lunar Atmosphere The Moon’s gravity is ~1/6 of Terrestrial gravity. Atmospheric pressure is generated as the weight (mass \ gravity) of the column of air above the measurement point. So to maintain the Terrestrial atmospheric pressure at the Lunar surface, we need 6\* the mass of gasses above the observation point. The surface area of the moon is 7.5% of the Earth’s. When you multiple 6x the column of atmosphere \* 7.5% of the surface area – we get 45% of the Earth’s atmospheric mass. 45% of the Earth’s atmospheric mass comes to $2.35 \cdot 10^{18} kg$ ($2.35 \cdot 10^{15}$ tonnes) of volatiles in the correct combination. For the atmosphere we will need: * $N\_2$ - $1.8 \cdot 10^{18} kg$ * $O\_2$ - $0.5 \cdot 10^{18} kg$ * $H\_2O$ - $0.2 \cdot 10^{18} kg$ * Subtotal - $2.5 \cdot 10^{18} kg$ Hydrosphere We will need excess water for standing bodies of water and icecaps. I will estimate the liquid water requirement by scaling Moon / Earth ocean mass to the ratio of Moon / Earth surface area. * $H\_2O$ - $1.05 \cdot 10^{20} kg$ * Total - $1.07 \cdot 10^{20} kg$ (atmosphere + ocean) Let’s assume our gases do not react with the surface of the Moon (probably a bad assumption but it makes life easier, so I'm going with it) so we don’t need to juggle those numbers based upon probable chemical reactions. ## Obstacles Finding the water and oxygen in our Solar System would impose no problems. However, finding this amount of N2 might be difficult. Saturn's moon [Enceladus](https://en.wikipedia.org/wiki/Enceladus) (about 240 km diameter and $1.08 \cdot 10^{20} kg$ of mostly water mass) would provide the necessary mass. However, it would not have the correct ratio of elements. We'd probably have to scale up to a slightly larger moon and "crack" a bunch of water to release $O\_2$ into the air. We could use the $H\_2$ as propellant for moving Enceladus (or its replacement) so it collided with the Luna. I have no idea what it's $N\_2$ content would be but would expect it to be deficient. ## What would it would look like Scale height of a Lunar atmosphere (assume same temperatures as Earth’s) would be 6x the 3.7 mile scale height of Earth's atmosphere. Meaning that it would be over 22.2 mile scale height. No one would have trouble breathing on any Lunar mountains. [![enter image description here](https://i.stack.imgur.com/qs53G.jpg)](https://i.stack.imgur.com/qs53G.jpg) Most of the land would be on the so called "Dark Side" of the Moon facing away from Earth. Most of the region facing Earth would be a giant ocean. ## Neat stuff ### Flying Given this atmosphere density and Lunar gravity, people should have no problems flying by putting on some specially crafted wing sleeves and flapping their arms. Imagine mansions situated on Lunar peaks. Physically fit people would visit their neighbors by putting on their wings and flying to the next peak over. ### Walking on Water People could run across bodies of water without falling into them (surface tension could hold them up). ### Radiation Protection Despite the lack of a strong magnetic field, this idea has the added benefit of providing plenty of radiation protection. The added mass of air (6x that of Earth) means that colonists are well protected from radiation. [Answer] Forget it. In an effort to have earthly atmosphere on moon, you are going to steal off and invest all the atmosphere of your home planet and put it there :@. Things are still not going to work so well, though. Most of moon's atmosphere will be robbed by earth (yeah, it ends up, where it started from!) and some might be blown off by solar wind towards Mars or Jupiter. If we begin by heavier gases (C02 would be a real good start), we can wrap moon in a layer of atmosphere which is held strongly enough (due to its high density) to not disperse in the vastness of space. We can then begin to add other gases slowly and notice the weekly blow-off. If they stick, we might expect an earth-like atmosphere there soon. Except that the lunar atmosphere would be 50% C02, 25% Nitrogen and 25% Oxygen. I wanted to add even heavier gases like Chlorine, but then I realized people there won't want hydrocholoric acid to form in their eyes and lungs :( [Answer] Check out Wil McCarthy's novel [To Crush The Moon](https://en.wikipedia.org/wiki/To_Crush_the_Moon), the last in his Queendom of Sol series, in which the Moon is shrunk to a radius of 1400 kilometres instead of its current 3500 kilometres (using very advanced gravitational engineering), which gives it a surface gravity of 1g, so that it becomes a more suitable prospect for long-term inhabitation. Difficult, but probably no more difficult than covering the whole Moon with domes, and you get a better surface gravity as well (although a much smaller surface area). Edited to add: I forgot to mention that shrinking the Moon also gives it a better length of day, about 120 hours (five days) rather than 28 days at present. [Answer] Domes This is not that sane, but it's saner than constant replenishment of the atmosphere due to the fact that constant replenishment of the atmosphere will cost a lot, and cost a lot forever. Domes are a more sensible way to go: not least because you can live in the domes while continuing to expand. It's not an all or nothing proposition like adding atmosphere. The initial domes will cost a lot, but once they're up then you haven't got as much to worry about with the atmosphere. I'm assuming current level technology for getting air to the moon, so you still have a lot to worry about, but it isn't as much as it would be if you had to constantly dump air in to maintain the air pressure at livable levels (though you might be able to do something with the gas mixtures to keep everyone out of the death zone for a while longer). The other advantage to domes is that you can build in other forms of protection. You noted point defence for micrometeors: but with a dome you can actually start to ignore small threats completely. You can also build in sunshielding, or add faraday caging and electromagnetic field generators to stop your occupants from being cooked by the various other stellar radiations that keep scouring the surface. Again: You don't have to come up with a full- lunar radiation defence straight away: you just need to shield the domes that people are using. Other advantages include being able to shut down domes you're no longer using to conserve/reclaim atmosphere and power, being able to isolate sections in case of catastrophe or disease, and having total control over the climate. Oh, and did I mention that because you've got a hard ceiling you need less atmosphere to maintain your ideal pressure in the first place? All things considered I can't think of a reason why a a civilisation capable of dumping enough atmosphere on the moon to make it habitable wouldn't build domes instead. [Answer] # Doming Craters Rather than attempting to dome the entire Moon, consider doming just the craters. Start small and work your way up to the big craters as you build experience with the process. This has added benefits as described below ## Radiation Protection The Moon's surface is a harsh environment. The radiation levels are higher than on Earth and during certain solar events, they become lethal. Any lunar colony will require radiation shielding. Most people envision this as burrowing under the lunar rocks and living in tunnels. However, there's an alternative. Dome lunar craters and put the equivalent mass of the thickness of Earth's atmosphere in the dome for radiation protection. It turns out that a 32 foot column of water provides as much mass (and radiation protection) as the Earth's atmosphere. ## Structures Embed that water between a sandwich of durable but clear plastics (perhaps in a honeycomb shape). The total weight of the dome is less than the atmospheric pressure under it trying to blow it off. So your dome will be in tension (not compression). You still have access to the lunar interior via tunnels you make in the crater walls but this way the lunar colonists will have green spaces were they can enjoy the sunshine without fear of frying their gonads. ]
[Question] [ In my space-fantasy WIP I intend to make heavy use of [Arcologies](https://en.wikipedia.org/wiki/Arcology). But I don't have any real information on their layout or the "plumbing". Leading here me to look for answers. 1. What are some likely shapes that an Arcology would be built in. 2. What would be the internal layout and arrangement of the communities. the Image that keeps coming to my mind are residential "blocks" connected to one another and central hubs. Like the spokes around a wheel. 3. What would the "bowels of an Arcology be like. would it to badly strain plausibility for them to be ["Absurdly Spacious"](http://tvtropes.org/pmwiki/pmwiki.php/Main/AbsurdlySpaciousSewer). Dungeon crawls are essential parts of many stories and games. 4. How cost effective are arcologies vs cities. one of the possible usages that I have for them is as a tool of planetary colonization. just land a prebuilt arcology on a world and a lot of the work of setting up a colony is done. 5. How are property rights handled with in an arcology? Space being leased from the government or corporation that owns the arcology is what I'm seeing. Something akin to stores renting space from a mall. [Answer] 1. What are some likely shapes that an Arcology would be built in. I would assume that towers of some kind are the most effective structures if using the surrounding land is something the builders/designers don't want. Low-gravity worlds can afford higher structures. A society with a strong affinity for quadrilaterals might build a giant cube or set of cubes. You could draw inspiration from [real Earth skyscrapers](http://rads.stackoverflow.com/amzn/click/1579129420). Remember that skyscrapers/tall arcologies must have foundations a deep as a significant ratio of the height. (This should give plenty of space to explore for question 3.) 2. What would be the internal layout and arrangement of the communities. The image that keeps coming to my mind are residential "blocks" connected to one another and central hubs. Like the spokes around a wheel. This would be dependent on the exterior structure of the arcology though with a sufficiently large interior, you can organize the interior however you like. Reading up on city layouts in the context of [Cities:Skylines](http://www.citiesskylines.com/) may give you some ideas about how to adapt the structure to the needs of your story. 3. What would the "bowels of an Arcology be like. would it to badly strain plausibility for them to be "Absurdly Spacious". Dungeon crawls are essential parts of many stories and games. Absurdly spacious is a good description for it. Infrastructure to support all those people would be distributed throughout the structure with large tunnels to connect them all. For example, if the powerplant for a community block goes goes offline for maintenance, then you'll want to get power from other plants. Designers would put in the same kind of redundancy for sewage, water, air, cargo transport, and human transport. As a way to generate the dungeons you wanted, the arcology would have been built with large empty spaces for future adaptation and for structure reasons (hollow tubes are stronger than rods). Over time, new powerplants, sewage treatment, living spaces, etc would be constructed in the empty spaces and the older infrastructure taken offline and abandoned because of the cost of extraction/repurposing/lack of time. "Things" could move into those abandoned spaces and tunnels. 4. How cost effective are arcologies vs cities. one of the possible usages that I have for them is as a tool of planetary colonization. just land a prebuilt arcology on a world and a lot of the work of setting up a colony is done. I think arcologies are crazy effective compared to cities. Note in this [map](http://www.expertmarket.com/sites/default/files/filemanager/US-Economic-Activity-In-Half-Update.gif) that the densest population centers are also the highest economic powerhouses? New York is 469 mi^2, 8.4 million people and an economic output between 1.0 and 1.4 trillion dollars. Economies of scale kick in the denser you can pack people in. A well managed arcology with a population of double New York City could easily create as much economic output, perhaps much more. (Not an economist so I can't give you any numbers to go by.) Your civilization is going to be pretty advanced to build something that large in the first place and crazy crazy advanced to land a gigaton or teraton sized structure in the gravity well of a planet. You have to respect the [surface area to volume ratio](https://en.wikipedia.org/wiki/Surface-area-to-volume_ratio). 5. How are property rights handled with in an arcology? Space being leased from the government or corporation that owns the arcology is what I'm seeing. Something akin to stores renting space from a mall. Your suggestion about how to divvy up space in the arcology seems reasonable to me. The rent/ownership system in Europe and the US is several centuries old and has held up well. I think that's a reasonable model to work with. 6. How does the economy work in an arcology? Currently, my favorite book on income inequality and the distribution of capital is [Capitalism in the 21st Century](http://rads.stackoverflow.com/amzn/click/1491534656). Additional Reading on [super-large buildings to house billions of people.](http://waitbutwhy.com/2015/03/7-3-billion-people-one-building.html) How this author goes about "designing" a building to house all 7.3 billion people on earth might serve as a good model for when you design your arcologies. [Answer] The basics of arcology theory is outlined by Paolo Soleri in his book Arcology: The city in the image of Man ([http://www.amazon.com/Arcology-The-City-Image-Man/dp/1883340012](http://rads.stackoverflow.com/amzn/click/1883340012)). Arcologies come in all shapes and sizes (Soleri designed small "village" sized arcologies to mile high visions like the "Hexahedron" and "Arcube"), but all follow several general principles: The arcology is a self contained economic and ecological unit Recycling of water and materials takes place within the arcology Everything within the arcology is within a short distance of the inhabitants because of the 3D architecture. With large structures like the Hexahedron, this would be done by making modular "neighbourhoods" stacked together, so most basic goods and services would be within walking distance of a person inside the neighbourhood. The arcology has limited impact on the surrounding environment. (once again a bit of a non sequitur; a mountain sized Hexahedron or Arcube would cast a giant shadow across the land and potentially have impact on local winds. Soleri seems to have meant that the arcology would not be using vast tracts of land for farming and housing or transportation). From an engineering perspective, to build larger version of arcologies would be very difficult, and people in the interior would be cut off from sunlight and air, so many arcologies are depicted as being open structures with large atriums and air and light wells into the interior. This sort of honeycomb structure would also be much lighter and structurally stronger as well. Soleri was only the first person to develop and popularize the idea, looking at the internet you can find many examples of this idea developed by other architects and visionaries, such as Old Man River City, by Buckminister Fuller, Masdar City in the UAE or NOAH (New Orleans Arcology Habitat), designed by E. Kevin Schopfer. [Answer] > > What are some likely shapes that an Arcology would be built in. > > > In space? Almost any shape. What matters are things like the need for defense (or lack thereof) how much interaction with ships docking, and how gravity is generated. If gravity is only generated by centripetal forces then these cities are likely to be large cylinders, a soup can that could possibly have a 1 (or more) thick skin. > > What would be the internal layout and arrangement of the communities. > > > My understanding of these is the vast majority of the populace generally are going to live close to their place of work. 'Homes' would be arranged together and many small 'convenience' stores would be located among them. > > What would the "bowels of an Arcology be like. > > > While I could see them going for miles of twisted tunnels and bundles of wires and pipes traveling to and from destinations, 'spacious' is not likely something that could describe them. People like space and will steel as much from the utilities that they can. Even more, if they have small robots that can fit in tight places and fix issues, the 'tunnels' will get even smaller. > > How cost effective are arcologies vs cities. one of the possible usages that I have for them is as a tool of planetary colonization. just land a pre-built arcology on a world and a lot of the work of setting up a colony is done. > > > This would likely be very cost effective if you have the tech to land the arcology on the surface safely. otherwise you are making a huge role of the die for an all or none survival. But since the arcologies are designed to be self sustaining, you increase the chances of a colonies success by having a complete human ecosystem in one place. Though I'd expect the colony would start by sending one or two smaller arcologies down and wait and see how things go, with backup in space to help or at least record any issues that could happen. > > How are property rights handled with in an arcology? Space being leased from the government or corporation that owns the arcology is what I'm seeing. Something akin to stores renting space from a mall. > > > I would guess that the 'rent' might be something as simple as performing tasks that need to be done, so your 'job' might be a street sweeper or a doctor, and it covers you home space and a food ration, and extra credits (how much depending on the job) that one can spend how they see fit on personal items and entertainment. [Answer] Regarding the third question: Consider what happens when a water main bursts in a conventional city. Earthmovers dig it up, trucks bring new pipes, finally a steam roller comes and the tarmac is repaired. In the arcology, much of that has to happen indoors. If you have large utilities, you need equally large access spaces. There could be pedestrian corridors over the utility trunks with removable floor plates, or larger utility tunnels. You can have your dungeon crawl. Regarding the fourth question: For planetary colonization, much depends on the environment. On a very earthlike world, space won't be an issue and neither is protection -- you can drop each individual hut or cabin where you need it. The farmer lives near the fields, the miner lives near the mines. Things look different if you need radiation protection, pressure seals, air recycling. In that case the single unit might make sense. (Or a few relatively large units, if not one.) Regarding the fifth question: A problem with everybody being tenants is that there is no long-term certainty. Would you invest much into a commercial enterprise if it doesn't have an assured location? There are lease contracts running for a long time, even transferable/inheritable. Also consider a [condominium](https://en.wikipedia.org/wiki/Condominium). ]
[Question] [ If the Earth's interior was not hot and liquid, how deep could we dig before the tunnels collapsed by the pressure or the air became too pressurized to be breathable? In other words: how deep can underground tunnels be and still be scientifically plausible? [Answer] Problems for humans The deepest tunnel-like structure created so far is the [TauTona Mine](http://en.wikipedia.org/wiki/TauTona_Mine) in South Africa. The bottom of it is 2.4 miles below the surface. [Temperatures there can reach 131°F](http://www.mining-technology.com/projects/tautona_goldmine/), which has proven deadly many times in the past. The temperature can be lowered to more pleasant levels, but conditions are still very dangerous. [Mponeg](http://en.wikipedia.org/wiki/Mponeng) reaches similar, if not higher, temperatures (without cooling). [As Monty Wild mentioned in an answer to a different question](https://worldbuilding.stackexchange.com/questions/457/how-can-i-estimate-how-far-into-a-cave-network-breathing-is-possible/459#459), [ventilation](http://en.wikipedia.org/wiki/Underground_mine_ventilation) will be an issue for any underground structure. If you want people to survive this far underground, either they'll have to carry oxygen with them, sealed regions will have to be made, or many ventilation shafts will have to be dug, which will severely complicate the process. Pressure is also a problem. We can use the barometric formulato calculate pressure (valid, I believe as per the derivation, e.g. [here](http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/barfor.html)). It is $$P=P\_b \times \left[ \frac{T\_b}{T\_b + L\_b(h-h\_b)} \right]^{\frac{g\_0M}{RL\_b}}$$ At, say, -15,000 meters (the missed goal of the [Kola Borehole](http://en.wikipedia.org/wiki/Kola_Superdeep_Borehole)), this is $$P=101325 \times \left[ \frac{T\_b}{T\_b + L\_b(-15,000-0)} \right]^{\frac{9.81 \times 0.0289644 }{8.31432 L\_b}}$$ $L\_b$ (the lapse rate) is calculated by $$L\_b = \frac{dP}{dh} = - \frac{mg}{kT}P$$ You can plug this in, figure out $T\_b$ from empirical data) and then solve for $P$ (after a bit of algebra). You won't like what you find. Problems in general [Rocks are also under pressure](http://www.earthlearningidea.com/PDF/189_Pressure_rock.pdf). This is not good for excavating nor keeping what you've excavated intact. The tables can give you a good idea of what you're dealing with. A Powerpoint presentation downloadable [here](http://r.duckduckgo.com/l/?kh=-1&uddg=http%3A%2F%2Fwww2.ce.metu.edu.tr%2F~ce439%2FSlideshows%2FLoads%2520on%2520Tunnels.ppt) explains the pressure on tunnels and other structures. --- The thing is, there's no good answer here. All of the really deep borehole were created for [scientific drilling](http://en.wikipedia.org/wiki/Scientific_drilling) - experimental holes to see what's really down there. I can give you figures and equations and estimates aplenty, but I'd be lying if I claimed that I could give you an actual figure. We don't know what's down there. I gave you some necessary information to show you what you're up against. [Answer] Breathing regular air on Earth, humans can deal with about 8 times sea level pressure before taking harm, which would be at a depth of about 20 km. The damage comes from chemical reactions of the gases in the lungs, but with different gases to breath, it seems humans could even handle pressure ten times higher if the body is given time to slowly adjust to the changes. That would be at a depth of about 55 km. Since nobody has yet tried to crush a living human or big to death with air pressure the true maximum is unknown, but 70 times sea level pressure is the number you usually find. It would even be possible to dig 20km deep on Earth, though it would probably get very hot. A depth of 50km would be all the way through the Earths crust but should be possible on other planets with a similar mass and gravity that don't have tectonic activity. [Answer] If the earth was solid and the same low temperature as the surface regions of the current crust, the whole way through, a hole could theoretically be bored completely from one side of the world to the other. Air pressure could be an issue for unprotected humans, but suits like deep-sea rigid exoskeletons could be used to protect workers from the air pressure, or else the project could be carried out in a vacuum (which would be even more useful) with the workers carrying their own air supply. The machinery involved, if electrically powered, could easily be made to function in whatever atmosphere that was allowed to exist. The advantage of an atmosphere-evacuated hole through earth would be that a sealed capsule carrying a payload could be dropped into it, and with minimal air resistance, would require very little net energy to reach the other side of the world if it relied on gravitic acceleration alone. Compared with airliners, it could well be worth the investment. The main issue would be that the pressure of the overlying strata on deeper strata would tend to make solid stone and metal flow into the hole at sufficient depths. The question then becomes, "At what rate does this occur, can it be retarded, and what rate of collapse is acceptable?". ]
[Question] [ Inspired by this other [question concerning large fantastical creatures](https://worldbuilding.stackexchange.com/questions/9856/cohabitation-with-large-creatures), I came up with this question. Suppose that a human could tame a dragon, what would the dragon population think of humans, and what would humans think of those who ride dragons. However, here's some context and notes: There in fact a number of such tame dragons, perhaps enough for a kingdom's elite knightly order of a few dozen to have a dragon each, and the dragons are located in a concentrated spot. Do note that in my setting, it is a giant empire, so there would be one kingdom with most of the tamed dragons. Dragons are intelligent and sentient creatures, and these tame dragons are of the extremely How to Tame Your Dragon and Eregon mentality, where knight and dragon are the bestest of friends. Meanwhile there are the sovereign dragons, who generally keep to themselves, and in fact have their own confederation. They would probably live in very tall mountains scattered about, and in decently sized clusters, with societies and everything, with a mountain the size of the [Lonely Mountain](http://lotr.wikia.com/wiki/Lonely_Mountain) probably capable of holding a good hundred full sized dragons. Dragons then sort of quite often skirmish with humans, stealing their cattle or raiding castles for gold. However, the humans are not capable of wiping out these dragons, as they would have to dedicate a significant amount of their military to do so, and if one kingdom marches on a mountain full of dragons, another kingdom might seize the opportunity to invade that first kingdom. The tamed dragons are actually a smaller society of dragons which live peacefully with that kingdom with the dragon knights. Also, tech levels and magic: * Tech levels are late medieval * Low powered magic is plenty common but expensive. High powered magic is much rarer and even more expensive * Political system is a large feudal empire. The empire encompasses all of humanity, but the crown authority of the emperor is on the decline, and kingdoms within the empire freely war against each other. ## Edited Additional Notes: * There are now these two questions to help anybody seeking to answer this question more insight, [this one about the empire](https://worldbuilding.stackexchange.com/questions/9966/how-would-an-empire-survive-weak-crown-authority), and [this one about the races cooperating](https://worldbuilding.stackexchange.com/questions/9968/how-to-promote-nationalism-for-a-multi-racial-kingdom-against-other-such-multi/9986#9986) So yeah, to clarify the question again: * What would the sovereign dragons think of the tamed dragons? * What would the sovereign dragons think of the dragon knights? --- @plagueheart raised a good number of questions, so I am going to address them here. > > were dragons physically beaten into submission or stolen from their families? (This raises an additional question: Do dragons form families so that theft of eggs or hatchlings to tame would be a disruption of that family structure?) Was it through some kind of mutual protection pact between a small subset of dragons and the human kingdom? Was it by adoption of orphaned hatchlings? > > > None of the above actually. > > tamed dragons as slaves (taken involuntarily and forced to serve), servants (voluntarily invited into human society but relegated to a lower position in the social hierarchy), or would-be humans (full members of society)? > > > The tamed dragons are full members of society, as the (tame) dragons voluntarily formed an alliance with the kingdom with the dragon knights, which I will just refer to the dragon-human kingdom. Said dragon-human kingdom is basically some sort of dragon-loving-hippy-utopia. Dragons get to do whatever they want, within the law, like regular people. > > (how) sovereign dragons relate to each other > > > Each of those mountains with dragons are like a small state. The sovereign dragons treat each other like a king might treat another king, which is to say they all strive for independence and sovereignty, and they dislike the idea of forming large states. These dragon-mountain-state tend to be a dozen or so at most. > > history of how dragons came to be tamed > > > The dragons are hatched normally under the care of their parents, and when they come of age, they can go look for jobs, and one of the more famous professions in the dragon-human kingdom happens to be in the army. A dragon cadet will then be paired with a knight cadet, and they become partners in war > > As a military force, how practical are the dragon knights to field? How much of a force multiplier are they? > > > Well, I suppose that for a dragon knight to be the stuff of legends, the dragon and the knight has to train together for quite some time, so actually fires of war seasoned and ready dragon knights would actually not be too common. However, when present, nothing short of an entire company of ranged soldiers would be pose any danger. Melee troops would simply be toasted from the sky. > > If they're a large, scary military force that's only been kept from pushing over all the surrounding kingdoms by not having quite enough dragons to fight everyone at once, it would be reasonable to say that even their allied neighbors are wary of them. > > > More or less what I will go for. --- First revision of the question was too broad, and has since been split into 3 questions, with each questions talking about the opinions of each group against each other. [For the opinion of other human kingdoms against the dragon-human kingdom](https://worldbuilding.stackexchange.com/questions/9889/tame-and-sovereign-dragons-the-opinions-of-other-human-kingdoms) [For the opinion of peasants](https://worldbuilding.stackexchange.com/questions/9890/tame-and-sovereign-dragons-the-opinions-of-a-peasant) [Answer] Taking these one at a time: What would the soveriegn(sic) dragons think of the tamed dragons Some of this would certainly come down to how dragons were tamed in the first place. Was it through force or subterfuge--that is, were dragons physically beaten into submission or stolen from their families? (This raises an additional question: Do dragons form families so that theft of eggs or hatchlings to tame would be a disruption of that family structure?) Was it through some kind of mutual protection pact between a small subset of dragons and the human kingdom? Was it by adoption of orphaned hatchlings? Perhaps think of it this way: Would sovereign dragons see tamed dragons as slaves (taken involuntarily and forced to serve), servants (voluntarily invited into human society but relegated to a lower position in the social hierarchy), or would-be humans (full members of society)? Then shade that with how sovereign dragons think of themselves--their power and dominion over the world--relative to humans. If humans are terrifying rivals who have demonstrated the power to kill dragons in large numbers, and some dragons go to serve them willingly, then the sovereign dragons might regard those tame dragons as quislings and traitors while still emotionally understanding the decision because humans are much more powerful. Conversely, if humans are considered only slightly better than other sorts of animals and aren't much threat to adult dragons, but they've nevertheless managed to make dragon slaves, then tame dragons might be objects of pity or derision for being so weak as to be enslaved. (It seems from the situation you've described that the second view of humans is more likely--but there is always the option that in-universe, the dragons don't know that humans can't actually bring all their military might to bear on them. They may not have a good understanding of human politics, and assume the human empire is a single mighty force still capable of wiping them right off the map.) How the two populations relate to each other has a lot to do with how tame dragons got where they are, and how humans and sovereign dragons relate to each other. It also has to do with the psychology of the two groups, and how they see their place in the world. What would the soveriegn(sic) dragons think of the dragon knights This would also flow out of the particular history of how dragons came to be tamed. If being a tame dragon is just a viable alternative life choice for a dragon, then how sovereign dragons (as a population) feel about dragon knights might be neutral ("oh it's that's Ancaladon, he's got a weird human friend, there she is now") to positive ("Smaug is so lucky, he's convinced a human to bring him food and polish his scales"). If tame dragons are the nth-removed, "enslaved" offspring of kidnapped dragons, dragon knights would be viewed with extreme negativity, as the modern heirs to an age-old offense against dragonkind. And so on, and so forth. Again, how the populations relate depends a great deal on their psychology and their history with each other. What would the other kingdoms think of the kingdom with the dragon knights That depends. As a military force, how practical are the dragon knights to field? How much of a force multiplier are they? That's to say, is a dragon knight capable of taking out an entire opposing troop of foot soldiers--or an entire opposing company? Or are they maybe just slightly better than standard ground cavalry? If they're a large, scary military force that's only been kept from pushing over all the surrounding kingdoms by not having quite enough dragons to fight everyone at once, it would be reasonable to say that even their allied neighbors are wary of them. If they're just a little better than regular knights mounted on horses and they require a lot of extra care and feeding that includes their dragons sometimes terrorizing the countryside, then their kingdom might be held in contempt for having such a liability as dragons around. What would a serf think of the dragon knights What would a serf know of the dragon knights? Are they praised in story and song throughout the kingdom for their daring-do and noble acts? Or are they mostly known in rumor for bullying the common folk and taking whatever they want? I think you'd find a serf's natural reaction flowing from what they know about the dragon knights' behavior, whether it be respect or fear or contempt. --- Okay, let's add some new stuff now that my initial question-bolus has been answered! Sovereign dragons on tame dragons Whatever else the sovereign dragons think about tame dragons, they're going to think on some level that tame dragons are weird for wanting to live in really close contact with another species and subjecting themselves to laws never meant for dragons in the first place. It doesn't matter that the tame dragons might be getting a really good deal--ready access to food without the danger of the hunt, no threat of predators stealing their eggs and hatchlings, access to all kinds of wonderful human goodies like fine metalwork and gems--they're living in a kingdom that isn't ruled by a dragon. And, unless the laws of heredity are weird enough in the dragon-human kingdom that it's possible for a dragon to eventually ascend to the throne (maybe by adoption into the royal family), they're always going to be ruled by humans. Tame dragons have effectively tossed out some of their self-determination, though a tame dragon might fire back on that one by pointing out that the average low-rank dragon in a dragon-ruled kingdom isn't doing much self-determining, either! Add to that that humans and dragons are very, very different--physiologically, and undoubtedly psychologically as well. Even without any experience of doing so, sovereign dragons can probably imagine just how strange and uncomfortable it would be to cohabitate with humans: Their houses are tiny, their sense of smell is so weak that they can put up with intolerable levels of stench, and they build with the expectation that anyone using their stuff can balance easily on two feet and has opposable thumbs. And, they don't use any of the same body language dragons do (except maybe the broadest, most understandable gestures, like cowering down to show fear or submission), their voices are all in the wrong pitch, they don't understand when they've said something insulting and they take offense at the weirdest stuff... Think of it sort of liking moving into a neighborhood where everyone's from a totally different culture and even though they speak your language, everything else about them is so alien that you have a hard time fitting in. Another thing to consider that hasn't been touched on is that the tame dragons will undoubtedly be able to tell their human neighbors everything they need to know about dragon psychology, dragon social hierarchy, the general disposition of the dragon kingdoms (although this news might be several generations old, depending on how much flow there is between the tame dragon and sovereign dragon populations), dragon physiology... Basically if there's a potential weakness in the dragon species as a whole, or the sovereign dragon kingdoms themselves, the tame dragons will know enough to pass that on. And unless they've all sworn a vow of total secrecy on ever talking about dragon inside baseball state secrets (potentially possible) or dragon physiology (not really possible, since dragon cadets will need proper medical help from time to time), the tame dragons will talk about these things. Moreover, depending on how some of them feel about sovereign dragons, they might be all too happy to talk about these things, and try to encourage their human neighbors to maybe do a little counter-raiding of the dragon kingdoms to get some of that sweet loot piled up in those mountains... The sovereign dragons will undoubtedly realize this. They may even have the offspring of tame dragons who just couldn't hack it with humans showing up in their kingdoms periodically, which means they'd be getting infrequent reports on just how much the human-dragon kingdom knows about them. They'd have reasons to be very worried about that, because it means if the human-dragon kingdom manages to take over the entire human empire, they're in prime position to take over the dragon kingdoms next. Also, to build off something I mentioned in one of your other questions on this topic (how other humans view the human-dragon kingdom), the sovereign dragons might know very well that the tame dragons aren't the puppetmasters of the human-dragon kingdom: Dragons would never organize a kingdom that way. (For whatever value of "that way" you want to put in there--not enough due deference to dragons, no horrific blood sports for positions of leadership, etc.) Sovereign dragons on dragon knights While dragons associating voluntarily with humans is questionable behavior at best, humans who voluntarily associate with dragons are just showing good sense! Dragons are, after all, superior at war and hunting both, and the dragon of the dragon knight partnership makes up for the fact the knight is small, squashy, and not very frightening. At least, that's one way they could think about it, through the lens of draconic arrogance. But there's other ways. Dragon knights ride dragons into battle, and even if they're not actually commanding the dragon where to go, there's an element of servility in letting people ride around on you that the sovereign dragons wouldn't fail to miss. That bespeaks a certain arrogance on the part of the knights--they think they're good enough to make a dragon into a beast of burden--that would be intolerable to some sovereign dragons. Even ones who have nothing against dragon-human cohabitation per se might have a lot against humans riding on dragons, because it strikes them as demeaning to the entire idea of being a dragon. Dragon knights are also in a position to know the most about what makes dragons tick. And that feeds into one of my last points in the previous section: Sovereign dragons would know about this, and know that it makes the dragon knights a much bigger danger to their sovereignty than humans who've had only infrequent contact with dragons. Even dedicated dragonslayers wouldn't know as much as a dragon knight does about dragons, and that's dangerous. [Answer] Okay, so now that the question has been narrowed down, allow me to be the first to answer the revamped edition. The sad thing is, my answer is one of those excruciatingly annoying answers: it depends. The sovereign dragons don't explicitly forbid the tame dragons from join the human-dragon-hippie-utopia, thus they probably don't think too badly of the idea... And yet, they aren't all doing it. This would probably mean that those dragons that don't join the utopia are either: 1. Traditionalist dragons, who don't believe in this new-gen bullhonk of living with 'food'. 2. The rednecks of the dragon world, who don't realize this is an option. 3. Extremely proud and powerful dragons, who don't need/fear/respect the humans. By extension, the traditionalist dragons may actually stop other dragons from joining the humans, citing it as a betrayal to the race or a 'sellout'. They probably think of the tamed dragons as wimps or browbeaten weaklings with no self respect. They would likely think of the dragon knights as basically cruel slavedrivers who deserve no respect, despite any and all evidence to the contrary: think anti-vaxers or feminazis. The redneck dragons probably don't think anything at all, so I'll just glaze over that. The powerful dragons though, wouldn't be so obvious. They probably care about what any of the lesser dragons do as much as a king would care about a single peasant. A nice powerful dragon might treat them with mild disinterest ("Oh, you have a pet human? How nice."), while a more menacing one may consider them to be sub-dragon ("If you think you need the humans to survive, you are no more to me than just another human!"). ]
[Question] [ This question is somewhat inspired by the number of "time bubble" questions that have been popping up on the site recently. If a real "time bubble" with a large enough time distortion factor existed, entering or leaving the bubble would mean certain death, as parts of the body on the fast side of the bubble edge would die of blood loss while the heart was on the slow side, and when the heart enters the fast side, vessels on the slow side would burst due to overpressure. Of course, if other factors affect the survival of a person crossing a bubble barrier, please address those in your answer. The question, then, is: What is the maximum time distortion factor that is survivable by a normal, healthy person for the time it would take for a person to fully cross the boundary at walking speed. Of course, legal limits in a world with such time bubbles would probably be far lower than this, to account for accidents or those with weaker hearts or other health problems, but the purpose of this question is to get a sense for the absolute maximum. [Answer] # Case A Assumption #1: The transition from one perspective of time to another perspective of time is instantaneous. In other words, the walls of the bubble are infintely thin. Assumption #2: Things happen more quickly inside the bubble than outside (time is "faster" by comparison). In this case, as my body passes through the bubble, the chemical processes speed up. My metabolism shifts into high gear, but only for those portions of my body that have passed through the membrane. The flow of my blood does NOT speed up until my heart passes through, at which point it beats faster. * Cells are demanding nutrition and generating waste at a faster rate inside the bubble. * The muscles what have moved through the membrane want to contract/expand more quickly, but the nerve impulses from the brain aren't yet fast enough. This could lead to jerkiness or loss of control, like Parkinson's Disease, until the brain passes through. * Your blood pressure in the areas inside the bubble would be low. The greater the shift in time, the lower it would be because it's being pushed by the heart on the other side of the membrane. Remember, chemical reactions speed up, mechanical reactions speed up, but the heart is the mechanical reaction and it's not there yet. Thus, the blood decays faster, but it doesn't move faster. Once the heart moves across the boundary, there's a momentary (and probably painful) spike in blood pressure as it all equals out. At this point the blood in the part of the body outside the membrane is HIGH. I can easily imagine the later-parts of the body to experience broken blood vessels/capillaries (aka bruising) from the transition. * The bloodstream is loaded with yucky stuff that isn't passing to the liver and kidneys quickly enough. * As I pass through the membrane, septicemia sets in and cells begin to die for lack of oxygen, etc. * Most of the vital organs aren't compromised (for a moment, for example, the liver is processing at two different rates), but the heart and brain are. The brain doesn't have a physical manifestation (so to speak), so let's assume that it survives (though portions of it are "thinking faster" momentarily... for a sec you'd feel like a genius). But the heart... portions of the heart start beating at a different rate than the rest. Leading to cardiac arrest. * The pain would be... impressive... and you'd feel it fast. From disrupted nerves to dying cells, it would be the most painful experience in your life. # Case B Assumption #1: The transition from one perspective of time to another perspective of time is instantaneous. In other words, the walls of the bubble are infintely thin. Assumption #2: Things happen more slowly inside the bubble than outside (time is "slower" by comparison). In this case, as y body passes through the bubble, the chemical processes slow down. My metabolism slows, but only for those portions that have passed through the membrane. My blood does NOT slow down until the heart passes, at which point it beats slower. * Cells are demanding less energy and muscles are moving more slowly (like after a stroke). * Way too much nutrition is coming through the bloodstream leading to hyperoxia and oxygen toxicity, possibly leading to seizures. * Most of the organs aren't compromised, as before, but your brain "acts slowly" as it passes through, making you temporarily feel dumb as a stump. * Your heart still goes into cardiac arrest. The blood pressure inside the bubble is HIGH until the heart passes through, then you pass out from the sudden drop in pressure. Leading body parts are bruised from the high pressure. * You wouldn't feel the pain as you entered (at least not quickly), but you'd feel it on the other side. Oh, yeah... # Case C In this case, we change Assumption #1 such that there's a transition period. The "membrane" or surface of the bubble isn't infinitely thin, but some thickness that allows for a gradual transition from Time #1 to Time #2. Obviously, the thicker the membrane the easier the transition. Which suggests that with a thick enough membrane, almost any time shift can be permitted. The thinner it is, the less time shift can be tolerated. # Yeah... but what does all that mean? There are a lot of variables that we're ignoring. Are you passing through feet-first? Then moving into a faster time would likely cause your nose to bleed after your heart passed through. Head first? You'd likely die of brain oxygen starvation before the heart got there, etc. There are a LOT of variables. Your worst case is the infinitely thin membrane such that the shock is greatest. So, how much time could you withstand? * If your goal was to completely pass through the membrane, I believe a shift of almost nothing would kill you from cardiac arrest. If it didn't, you've have permanent neurological problems like Parkinson's Disease from the nerve damage. And that's assuming you didn't die from an aneurysm caused by the shifts in blood pressure. From my EE college days, 3% or less is generally considered "statistically zero" because everything is generally happening inside the variance of noise. But I'd bet having half the heart beating at a change of 3% speed would still cause a cardiac arrest. Therefore, assuming the infinitely thin membrane, I'm suggesting it can't be done (or can't be done for any useful shift in time. Microseconds might be survivable). On the other hand, if you had something like a temporal decompression chamber where the body as a whole could be slowly adjusted to the new time stream... [Answer] > > "Put your hand on a hot stove for a minute and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute." - Albert Einstein > > > I'd say Einstein sets the lower limit for answers here. Any time-distortion effects which only cause a 1:3600 time difference would be less disruptive than spending time with a hot stove and a pretty girl, and we know they already exist. I cannot find any research exploring the distortion caused by a hot girl and a pretty stove, despite there being some [extraordinary examples](http://nebula.wsimg.com/9b8771b9e641f543bb781aa2ef5bb1e1?AccessKeyId=85B4342C472F81253387&disposition=0&alloworigin=1) of the latter. Practically speaking, the limitation of this question is that there is no one accepted mathematical model for a commercial grade time bubble unit. Nobody can say what happens. For example, if you go from a slow region to a fast region, do we need energy? If we do, we might have issues with boiling over on one side or the other. If your mathematical model includes a pressure gradient created by atoms moving one way or another, the survivability line might be surprisingly low. As it turns out [barotrauma](https://en.wikipedia.org/wiki/Barotrauma) is something that causes the human body a great deal of trouble. If the particular pressure gradients you run into cause the lung pressure to be just 10% higher than the pressure outside, that's enough to cause rupture. This effect would not be mediated by multiple bubbles. If the effects of the bubbles increase the pressure from the opening of your mouth down to the lungs, you'll see barotrauma issues no matter what clever math happened in between. (related: the eardrum bursts if the pressure behind the eardrum, managed by the Eustachian tube, and the pressure in front of the eardrum differ by 0.75psi) If your model involves changing masses (E=mc2...) to keep the pressures the same, then a lot of chemical reactions will occur faster on one side or the other, so you're going to have to tweak a whole lot of constants to keep the body functioning on one side or the other. The exact health-and-wellbeing costs to such a model will be associated with the exact equations you use. The best solution is to simply not cross the boundary. Approach these bubbles like Terminator did their time-travel bubbles. Keep your hands and feet inside the vehicle until the ride has come to a full and complete stop. If you build the bubble around someone rather than having them pass through it, many of the problems go away. ]
[Question] [ Part 1 here: [Creating a scientifically semi-valid super-soldier, part 1: Skeleton](https://worldbuilding.stackexchange.com/questions/106292/creating-a-scientificly-semi-valid-super-soldier-part-1-skeleton/106308#106308) Part 2 here: [Creating a scientifically semi-valid super-soldier, part 2: nervous system](https://worldbuilding.stackexchange.com/questions/107365/creating-a-scientificly-semi-valid-super-soldier-part-2-nervous-system) In most movies, comics and games the heroes and villains often can take immense amounts of punishment without so much as a scratch. Explosions go off feet away from them, they jump out of multi-story windows without slowing down afterwards and they usually are still at 100% capacity after a carcrash. So my question is, how could you design a (preferably humanoid) creature to be as shock-resistant as all that? For this question I assume the part 1 question is answered and the skeleton is going to be able to take the shock without lodging itself into organs. If you want, you can assume an exo-skeleton is present. Additionally, this question is about biological solutions that allow a normal body to build, repair and maintain the features without being so synthetic you need to be brought to a shop for repairs after damage. There's only two options I can think off myself, with limited use for each as far as I can tell. The first is using the same setup as the brain has: A skull or exo-skeleton in this case as you want the entire body to be resistant, then some layers that can absorb shocks and then the organ. You could enhance this with certain materials, perhaps by hanging the organs with spidersilk threads. The second option is to basically cut the organs into many many independent pieces. If a shock passes through, the pieces will independently move and not rip apart from eachother. Does anyone have a good solution to allow a humanoid to resist far more damage from blunt forces? [Answer] [Meet Graham](http://www.meetgraham.com.au/). He is what a human would look like if he was designed to survive a car crash. This may give you an insight into what you would need to design a human to withstand large amounts of shock. I would disagree with non-newtonian fluid inside the skin. This would prevent puncturing, but not dissipate any of the shock. In fact, it would create more of an impact because all of the energy is being absorbed by your body rather than passing through it. You will have to have crumple zones or elastic suspension as you mentioned that prevent the organs from being shocked too much. The biggest issue is getting that kind of real estate inside a creature. [Answer] Non-newtonian fluid as part of their skin Non-newtonian fluid have the capacity to become solid when in contact with a great force. Imagine a skin that is imbued with that kind of fluid (I'm not an expert, so I won't go into details -- just imagine your layer of skin made with flesh and this particular fluid). It would allow your body to move freely, do excercise, and even jump without hardening itself. But when the skin receives a shock, it would become as hard as steel. This way, your super soldier remains intact after a shock and can continue its way like nothing happened. BONUS: his skin would crumble if the shock is too much for him to take, emitting heat as it allows him to tank one super attack. [Answer] Believe it or not we humans already have this! Its a super material that protects vital organs, dissipates shock, and serves as exceptional energy storage! What is this super material we produce? FAT! Yeah not something you usually think about when you're talking about super soldiers, but a healthy percentage of body fat will be absolutely necessary for them to function for so many reasons (many of which you can see in my answer on your original post). Besides needing the fat for energy storage, a decent layer of subcutaneous fat would protect a creature against cuts and impact, as fat absorbs the shock wave from severe impact. As long as the bones are strong enough (graphene tubes), the skin can withstand the impact (graphene layer), and the body can repair from any internal bleeding (nanobots), then a layer of fat under the skin will do wonders for shock absorption. Now there are more extreme versions, but if you want a real life version that you can just take up to 11, you can't really do better than fat. Because, like most biological tissues, it serves multiple purposes, and does them all very well. [Answer] You need to convert kinetic energy to heat energy (essentially creating a shock absorber.) Interestingly enough, your bones are pretty good at this already because of the collagen braids reinforced with minerals that make up your dense skeletal bone structure. What you need is a type of skin that can convert this shock (protecting your organs) into heat (which can then be dissipated since its right under your skin. As Christian said, (on Non-Newtonian fluids under your skin) > > it would create more of an impact because all of the energy is being absorbed by your body rather than passing through it. > > > So that's helpful--non-Newtonian fluid is not very useful. You might want to create some sort of system that channels it to different structures--like nonessential bones.The most important thing is to protect your organs. [Answer] This means that they are made of parallel fibers optimizing their ability to pull along their required vector. Along this angle, you can punish them all you want with a relatively small risk of injury. However, bullets tend to hit the muscles on the sides, which allows them to squeeze between the muscle fibers with relatively little force. If the muscles were woven more like Kevlar, they would be extremely difficult to penetrate. Unlike thicker or harder muscles, woven muscles will not significantly reduce flexibility, but you may suffer from a slight decrease in the pull force, since you are no longer pulling straight. Perhaps the best option for a natural armor that doesn't seem less human would be to strengthen your person's entire body with a Dura mater . The Dura mater is the outermost protective membrane that covers your brain and spine. It is exceptionally strong, flexible, and made from irregular cross-woven fibers. A report from the new Jersey public health system shows that the Dura mater of rats can withstand 1.3 million Pascals of stress, which is a lot, especially considering their size. By layering the Dura mater between your skin and striated muscles, your person will look, feel, and move very much like an ordinary person, but when fired from a small-caliber cartridge, the Dura mater fibers will distribute the impact across a large cross-section of the muscles instead of allowing it to simply pierce between them. With distributed impact, your muscles can do what they do well and contract. By distributing the impact over a larger surface, you would probably tear the skin, many bruises, and some serious muscle inflammation after being shot, but the bullet would be much less likely to be able to hit the main organs. [Answer] I'm not sure what you want (resistant to: vacuum, energy, projectile, plus super strength, speed, durability) is plausible in a purely biological system (Unless you go read "Old Man's War", but even that was only mostly biological). I suggest instead you go fully nanotechnology, to such a degree that you can't tell the difference (at first glance) from biology. Self replicating microscopic machinery that work remarkably like cells, but clearly are not cells, if only due to their operating parameters. Then you can have all the grapheme skin and bones, light speed reflexes, processing power, and cold fusion stomach to run whatever "organs" you could ask for. But seriously, go read "Old Man's War". I want a Brain Pal. [Answer] I'd design it as being made of a few dozen modular units which are designed to break apart on impact, like a Lego structure . The only damage is the fasteners holding it together. The solider can be snapped backed together with no permanent damage. Shape can be humanoid or not as you prefer. In fact, Lego-man could be assembled into different configurations depending on requirements. [Answer] I know this is almost two years late, but have you considered making the extracellular fluid of this organism a non Newtonian fluid? In normal circulation, it would behave like a fluid, but the shock of an impact would cause the extracellular fluid in the region to harden instantly, absorbing the impact. This would serve to immediately cushion the organs at the point of impact, as extracellular fluid is ubiquitous in the body. The heat produced could then be dissipated by the circulation of blood (which is one of the normal functions of blood). Something like silica suspension in polyethylene glycol. But this is all speculative though, don't know how well it would work. Maybe someone better informed than me can comment on the feasibility of this? ]
[Question] [ We've had questions on constructed languages (conlangs) before--their inventories, sound changes and phonotactics--but we rarely if ever talk about the grammar change. When designing a naturalistic conlangs grammar, you usually base it off of actual languages and mix/match features to find a balance you like, but what comes next? How do you make a conlangs grammatical evolution feel realistic, rather than engineered? [Answer] Don't try to go into details without first acquiring a base in historical linguistics; and it obviously depends on your purpose: * If you are designing a constructed language intended to be used as an [auxiliary intercommunication language](https://en.wikipedia.org/wiki/International_auxiliary_language) then you generally consider it static. * If you are designing a language intended to stand for the naturally evolved language of a fictional linguistic group then you don't "mix [and] match [grammatical] features to find a balance you like", but rather you [mimic](https://en.wikipedia.org/wiki/Mimesis) the features of an attested language or two; and then you follow on with an immitation of attested processes of linguistic change. For example, in the [Indo-European family](https://en.wikipedia.org/wiki/Indo-European_languages) the general tendencies over the last three or four millennia were * Reduction and regularization of inflectional paradigms: + Three numbers (singular, dual, plural, e.g. in Sanskrit and Ancient Greek) to only two numbers. + Three grammatical genders (masculine, feminine, neuter) to only two grammatical genders, or even no grammatical gender (e.g., English or Persian). + Many nominal case forms to few nominal case forms, or to one (as in English or French, where nouns are no longer declined for case). + Many mood and tense verbal forms to few mood and tense forms, or, as in the case of English, very few. + Elimination of "irregular" paradigms (which themselves were the remnants of old regular patterns) in favor of simpler patterns. * In parallel with the simplification of morphology, a shift from free word order (made possible by the rich morphology) to strict word order (to compensate for the morphological simplification). We say that ancient Indo-European language were more [synthetic](https://en.wikipedia.org/wiki/Synthetic_language) and modern languages more [analytic](https://en.wikipedia.org/wiki/Analytic_language). This evolution in grammar was obviously superperposed with [sound changes](https://en.wikipedia.org/wiki/Sound_change), and interconditioned by them; they cannot be separated. The general trends are just that, trends. Occasionaly, in the history of a specific language, they could be reversed; for example, in French the future tense is a newly evolved synthetic form derived from an analytic form (infinitive + avoir) which had replaced the old Latin synthetic form, which itself was descended from an analytic form (verbal stem + [\bhu](https://en.wiktionary.org/wiki/Reconstruction:Proto-Indo-European/b%CA%B0uH-))... But all this is useful only if the work is ample enough to follow the evolution of one or more languages over millennia; for example, Tolkien did it with his [Middle-Earth](https://en.wikipedia.org/wiki/Middle-earth#Elves) elves: [Common Eldarin](https://en.wikipedia.org/wiki/Common_Eldarin) -- [Quenya](https://en.wikipedia.org/wiki/Quenya) (and [Telerin](https://en.wikipedia.org/wiki/Telerin)) -- [Sindarin](https://en.wikipedia.org/wiki/Sindarin). But then Tolkien knew what he was doing:* he was a professional historical linguist (he worked on the Oxford English Dictionary) and a professor of Anglo-Saxon literature. ## TL;DR In the Indo-European language family the general trends in grammatical evolution over the last 3 or 4 millenia were: * Synthetic structure → analytic structure (with English exhibiting a trend towards a fully [isolating language](https://en.wikipedia.org/wiki/Isolating_language)) * Complex morphology → simple morphology → almost no morphology (e.g., English) * Reduction in morphological categories (for example, English has almost completely lost the entire category of grammatical gender) (complicated by the constant emergence of new categories, which in turn become candidates for elimination; consider for example English verbal aspect) * Elimination of irregular paradigms (complicated by the constant emergence of new paradigms, which in turn become irregular due to sound changes) * Free word order → limited freedom → fixed word order Omnis ars naturae imitatio est (all art is an imitation of nature). Seneca, [Ad Lucilium Epistulae Morales](https://en.wikipedia.org/wiki/Epistulae_Morales_ad_Lucilium), 65.3, published around 65 CE. [Answer] I think irregularity is a key factor when giving a conlang a realistic look. Natural languages have plenty of exceptions, inconsistencies and rules that simply don't make sense. The general rule is that languages tend to simplify, but also constructions that are frequently used do rarely change. We have three or four words for many verbs such as cook/cooks/cooked (for example), but many more for more common verbs like be, go, come... What is more, former irregular verbs tend to regularity such as dreamt/dreamed or burnt/burned. A good example are some plurals which used to be irregular, like brother/brethren, whose plural nowadays is simply brothers. You can also add some defective verbs, like can (which doesn't have a singular third person mark). Another thing to take into account are idioms, expressions and proverbs, which also rarely change. These features give realism to a language, a sensation of being alive. For instance, the expression safe and sound is rather usual, but you don't usually say you are sound (at least in an informal context). My advice is to incorporate a handful of exceptions and incongruencies to give your language that feeling of having evolved rather than having been designed. ]
[Question] [ Island culture usually takes one of two really basic forms: 1. small, loose knit, widely distributed populations with a unifying shared culture across a large number of small islands. [Polynesia](https://en.wikipedia.org/wiki/Polynesia) for example. 2. denser populations on larger landmasses that border continents and share/copy the dominant continental culture. Like in Feudal Japan, or Medieval England. Now it strikes me that in a large interstellar society planets resemble islands in terms of their population relative to the total population of the civilisation they're part of and the way they're strung out over large travel distances. So assuming that that is roughly right I have two questions, does it follow that: 1. the overall culture of an interstellar society will resemble a Polynesian type set up? A root cultural and linguistic heritage is recognisable but with large local variations. and/or 2. small, but independent, colonies in the same system as heavily populated worlds will resemble Japan or England in borrowing a large percentage of their cultural trappings from the dominant neighbouring population? Or are planets simply too large to be able to make any generalisations on this scale? Couple of extra details to help things along, we're talking about a single species spread across an arbitrary number of worlds, there's no FTL communications and while there is FTL travel it's non-instantaneous so interstellar travel times are still usually on the order of years but travel is reasonably regular, trade is generally limited to the very rare and pure data resources. [Answer] Both your examples are basically counterexamples, as there is no single culture on earth from which you can generalise to the planet as a whole. The polynesian type of cultural set up will be the most plausible one for far apart planets with little to no interaction on a daily basis, as you have no FTL communication and travel times are still large. Even with constant interaction and large enough population migration as in your Britain, Japan examples the cultures diverged from the originating and inspiring cultures and formed their own setting given enough time. Australia and the USA are a good example of a culture emerging in a rather small time frame based on settlers from a mostly similar cultural background and yet developing its divergence from the British/European 'mother culture'. [Answer] /Can we extrapolate from island culture to planetary culture?/ Yes! Especially for a work of fiction. That is a great way to build a world. It will give you a framework around which to design your cultures. Please: you do not have to rub in the reader's face "See! This is like Polynesia! Get it?" - because the people who did not get it will still not get it. You can drop hints. The people who do get it when reading your fiction will think it is extra cool. Even the people who do not fully see what you are doing will feel things ring true, because aspects of what you write will resonate with things in the real world. People who read your work as 7th graders and do not understand that aspect will later see things in the real world that remind them of your work. Then they will post requests on the SF stack exchange asking for help tracking down the book where the worlds were set up like islands. [Answer] The same way you cannot make generalizations about the cultures on Earth you will not be able to make generalizations about the cultures of a colonized planet. We have one example of humans occupying a planet. On it there are somewhere on the order of [7,000 languages](https://www.linguisticsociety.org/content/how-many-languages-are-there-world) that have been cataloged. This strongly implies that colonizing a planet isn't sufficient to establish a monoculture. [Answer] I think you are making too many fundamental assumptions: * There is nothing to support the concept that species within the community can even physically communicate in the same tongue. That alone would initially hamper cultural adoptions. * You are right that the different islands will have different beliefs but are mistaken that a big island will directly adopt a bigger islands beliefs. Just because you believe in the all powerful spaghetti monster doesn't mean I will. * Beliefs and outlooks are often times shaped by physical and environmental factors. If one specie hunts for its food it might believe in an animal spirit that provides food versus a sentient plant organism that would inevitably be sun worshipers. I believe you would see adoption in cultures where they had similar beliefs. If your god sounds like my god and we were separated by isolating distance, that would bolster my belief in my god be real and therefore would happily iron out any minute differences. ]
[Question] [ The Ents broke off from the rest of the civilization many aeons ago, and their main means of communication has evolved to the point where instead of words, they use fully immersive and lightning-fast induced hallucinations, which replaced all other forms of communication. > > The image flooded her senses, and with it came an undercurrent of overwhelming loss and grief which somehow conveyed the feeling of a distant past, with a great city full of happy people and many children, and yet a clear sensation of an unknown great threat lurking red just over the horizon, to the East. Raw emotions swirled in her mind, each sharp as a whiplash, and the sorrow and apprehension grew until it became almost too much... > > > ... the sensation stopped suddenly, and Alice felt that the Ent was sorry. She knew it was not used to communicating with humans wearing the Entish crown. She then knew it was a crude device, only vaguely capable of conveying the subtle complexities of Entish thought. The Ent was struggling with something that could only be described as a hallucinatory grammar. > > > Non-Ents can communicate with them only by wearing a device known as an Entish crown, which enables them to experience and convey a limited subset of the mental sensorium pallete available to the Ents. It is suspected that Ents can instantly convey entire 4-dimensional [experiential sets](https://en.wikipedia.org/wiki/Sensorium) to each other, the equivalent of entire books or multiple-branching stories in an instant, but wearers of Entish crowns are limited to a simplified version, a 3D experience over accelerated time. *What would qualify as a grammar under such a language?* How do you convey emphasis, for instance? [Answer] Emphasis through a feeling of being drawn: > > As she walked through the deserted square Alice felt there was something fascinating about the Arch, something that drew her in. Almost without thinking, she walked to its base, where the granite engravings came fully into view. > > > Time manipulation to convey subtle nuance, like a slow-mo replay or a well-timed photograph: > > In the middle of the dreaded blow, the flow of time suddenly slowed to meandering crawl that allowed her to fully take in the face of the warrior, full of a kind of fury that almost bordered on madness. Alice noticed a foamy stream of spittle, almost frozen in mid-air. > > > Inducing into the mind of the perceiver emotional states associated with the desired reaction. > > As their weapons turned towards her, Alice felt it in the bottom of her stomach, knew she was going to die. It was an out-of-body her that would perish, as she knew her real self was still on the platform wearing that strange device called the Entish Crown, but that somehow provided scant comfort at the moment. > > > Enter the dialogue via directing your own emotions into altering the nature of the 'sensorium': > > Full of fear and anger of what she's seen, Alice saw her fingers begin to glow, and a fierce fire erupted out of her finger-tips towards the attacker. > > > [Answer] Natural languages are systems for communicating propositional and conceptual information to other beings. Hallucinations could be a great communication medium, but that does not make it language. As a very simple example, if you could communicate experiences hallucinogenically with perfect realism how would you communicate that one experience is a memory of reality and another experience is a purely imagined fiction? To communicate the proposition that "X is true" you need some shared symbols. Spoken language starts with a set of phonemes (sounds), with 30-50 being common. We combine them together to come up with thousands of words. We use grammar to combine those thousands of words into an infinite number of sentences. We use the sentential context of words to introduce secondary and tertiary meanings, forming idioms and metaphors. We do all of this so that we can talk about religion, history, philosophy, art criticism, programming languages, and world building. ;) To communicate by hallucinations would be to greatly increase the sensory depth of our communications. Rather than a measly 50 phonemes we would have an infinite number of experiences to share. But I don't think freeform hallucinations could be counted as language any more than painting or photography is counted as language. Communication, definitely, but not language. Purely referential communication (using symbols to directly refer to things in the world without metaphorical extension) is not enough to be a language, and no purely pictographic human writing system is thought to be able to communicate all that its spoken language can. Language must be able to communicate abstract concepts that are beyond any sensory or referential basis. If hallucinations were the communication medium of a language, rather than having an infinite range of communication like painting does for us humans, I think it would be codified into a finite set of symbols, which would correspond somewhat to our human words/morphemes. They would be made up of hallucinogenic 'phonemes' such as colours, shapes, noises, scents, temperature, proprioception etc. These morphemes would communicate concepts, and be combined with some sort of grammar to communicate propositions. Most human languages are linear, including both spoken and written languages. The best real world analogy for hallucinogenic languages might be sign languages and their spatial grammars. Sign languages are able to go beyond linear chains of symbols and have a limited capacity for [simultaneous expression](https://en.wikipedia.org/wiki/Sign_language#Spatial_grammar_and_simultaneity). Hallucinogenic languages would have the capacity for much greater simultaneity, but limits would still be reached, because no brain has infinite processing power. [Answer] The grammar would be one of temporal ordering and compression. For instance, in telling a personal experience story, an Ent might provide information in the order they learned it. From there own eyes their speech would be one full of personal pronouns. While telling from a third person view, one might convey the message from outside any individual in the order things actually occurred. Emphasis could be conveyed through stretching and compression of time. More important concepts would receive a higher resolution in time for Ent to Ent communication or take a longer time to play for those wearing an Ent Crown. [Answer] The need for concepts like words and phrases are primarily designed the needs of our particular communication system using sounds or written words. Those limitations are tossed away when we free ourselves from the medium. Take, for example, the amount which can be expressed by a single touch. The poets have oft drempt of the raging warrior subdued by a single touch of the gentle soul who loved him. Touch itself is limited compared to what an Ent crown can do. Needless to say the Entish crown's description suggests an even tighter connection between the wearer and the ents than a pair of lovers would dream for. The scientist in me wants to suggest direct neural stimulation, but it probably doesn't even need an explanation. Just a sense -- a feeling. If I may borrow from Douglas Hofstadter's way of viewing the world from I am a Strange Loop, I would suggest they may talk in "symbols." A symbol conveys one thought or idea, but unlike a word or phrase, there's no concept of ganging them together. A symbol is a complete thought, not to be divided or aggregated. It is not unreasonable to presume that the answer to "What is the sound of one hand clapping?" is a symbol when approached from a Zen perspective -- indivisible, fleeting, and yet eternal. Without the ability to combine symbols together, an Ent (or indeed perhaps all of Ent kind) cannot transition from thought to thought by simply switching from symbol to symbol. Instead, they must mold and manipulate their one symbol to include the new idea, and then perhaps elect to manipulate it to exclude the old one (though we may have reason to believe that the old idea always still exists in the form of a whisper). With an Entish crown, we are permitted to experience this symbol as part of the Ent community. In the original wording of the question, there was a reference to Julia fractals. I do not think that wording was amiss, and I would like to include a little piece of that. Such symbols could be thought of as self-similar. The whole pattern of the symbol could be rediscovered within any silver of the symbol, as fractals often exhibit self similarity as you zoom in. The symbol may be distorted, depending on how one approached that silver, but it would always be there. The closer to the center of the symbol one looks (or feels), the less distorted it is -- the more the true meaning of the Ents shows through. If you were to put on an Ent crown, you would be permitted to join the Ent community, momentarily, and see the Symbol of the Ents from far far away (the less like an Ent you are, the further away you would feel). Even at this initial distance, you would feel the pulse of the spirit of the Ents, though it may be very faint. From that point, you interact with the Symbol as the Ents do. If you wish to go closer to them, you manipulate it to include more of yourself. That act naturally shifts your focus closer to the core of the Symbol -- thinking more and more like an Ent. You would not ask them a question and then await the answer. You would ask your question and the mere act of asking would lead you to the answer, as though it had always been there. This sort of communication would lead to the appearance of communicating with hallucinations. Any individual wearing an Entish crown would be forced to describe their journey in that way, as the Ent's spirit literally applies itself over the hopes and memories of the wearer, making them part of the greater Ent while sharing some of what it means to be an Ent with those hopes and memories. To go beyond calling them hallucinations would imply your mind had been warped enough by the Ents that you were indeed no longer a human, but an Ent yourself. In such cases, you may not survive having the crown removed from your head any more than one survives having their head removed from their shoulders. > > Alice picked up the crown of RedAlder and looked up at its namesake. RedAlder stood taller than any other tree in the region, its maturity shown in its warped yet beautiful branches suggesting a subtle harmony that only an Ent could accomplish. He was by far the easiest of the Ents to talk to, having served as ambassador to this kingdom for far longer than anyone alive could vouch for personally. Nevertheless, she hesitated. She knew that you never walk away from a conversation with the Ents the same. Some part of you is always changed. She took a deep breath, closed her eyes, and allowed the crown onto her head. > > > Even when talking to one as soft and kind as RedAdler, the experience was never easy. She could feel RedAlder guiding her to a soft calm space within the Ents carefully pruned and cared for, as though they were their own arborist. She could feel herself arrive, as the impossibly bright lights and twisted sounds faded away and gave her a moment to rest... if the idea of a "moment" meant anything at all when connected to the Ents. > > > Drawing upon the lessons she had received from RedAdler and the other Ents, she carefully drew her awareness to the ebbing and flowing around her. She soon found what was thought to be the Pulse of the Ents and began her true quest. She focused on developing her own symbol within the Symbol, to add her own tale to the Ent kind. RedAdler kindly assisted the entire way, helping her manage her emotions while she struggled with the delicate grammar of the Symbol. After some time (time?) it was completed, and her story of the upcoming war was offered as a gift to the Ent spirit. She felt it race along the Pulse, deeper into the Ent kind. Surely they would appreciate the fires that were to come to their forest and lend aid. > > > Something was wrong. She felt no reply, even though her statement had been given. The replies were always instant -- infuriatingly instant, as though the Ents never had to spend any time on their decisions (there's that word again, time...). She had no training to help her now. None of her teachers had ever suggested this could happen. She struggled through her intuition to find an answer (her? Pronouns were so hard when talking to the Ents. Maybe it was "our intuition?" ... "my intuition?") > > > She widened her awareness, and realized how distant she felt from the Ents. Perhaps they had given her answer and she simply had not been listening. She felt for the pulse, and upon finding it, began weaving her own symbols closer and closer to it. > > > RedAdler interceded, in a flurry of symbology that would have sent Alice into a disoriented spiral if she had not been so focused on feeling the pulse of the Ents. He caught her, and directed her, guiding her weaving to take her closer and closer to the pulse. But when she got there -- wait. She got there? One never "gets" to anything with the Ents unless its just a carefully cultivated landing pad managed by their ambassadors to humankind. But there she was, on the pulse -- part of the pulse. Her entire essence shook with every quiver of the Pulse around her. RedAdler was there (how long was he there? This time thing again... how infuriating!). The Symbol looked different to her than it had every looked before. It was more nuanced and detailed. Alice could almost feel the entwined roots of the Ents, sharing in a way no two humans could ever achieve. She saw the Pulse in a whole new light. Two lights. Three lights. Five? The Pulse raced everywhere around her, until it dawned on her that the Pulse was not numbered. It was simply everywhere Ent kind, in endless variation. She wore an Ent crown. It pulsed within her as well. > > > With this dawning realization, she felt her own heart beat pulsing and all of Ent kind pulsing along with it. Resisting the urge to flee outward, she instead fled downward, deeper into the Ent gestalt, feeling her roots in her own body beginning to fray and tear loose as she did so. She searched for something, she knew not what. A faint whisper of an idea flowed through her head: the thing she searched for was known by the Symbol as a whole, not just her. She let it guide her, deeper and deeper, past experiences no human had experienced before, until Alice ran into Alice. > > > Alice had never experienced anything quite like it. Deep in her search, she found herself. She found herself searching. She realized that she had been found by her search. She looked up, down, left and right, and saw nothing but herself (did those directions mean anything anyway?). She closed inward, tighter, constricting herself. An animal instinct in her lunged forward in her chest, crying out for her to strike at these encroaching mirages and destroy them before they destroyed her, but she stilled that instinct. It was not the right instinct to use. Instead she/Ents/Symbol reached out and brushed over her head, wrestling her hair from the loose bow that kept it out of her eyes. > > > The crown tumbled to the ground, and Alice along with it. Her mind, suddenly cut off from the Ents, retreated, unsure what to do in this world disconnected from the Ents. Surely she had seen into the heart of what it is to be an Ent, but one can never be too sure. Her mind ran in loops as it slowly dimmed and the lights went out. Alice's body slumped and rested as her mind fought valiantly to recover. > > > RedAdler and the Entkind observed this in the same way they always had, discussing those observations as the Symbol of Entkind twisted and turned around them and within them. This one would help, of this they were confident. She had seen enough of what it truly meant to be an Ent to sympathize with what had to be done to preserve their way of life. All that was left was to wait for her to regain consciousness. Fortunately, for an Ent, waiting is. > > > So they waited. > > > [Answer] So you are talking about a form of communication that uses sights, scents, sounds and such to convey information rather than words. [Grammar](https://en.wikipedia.org/wiki/Grammar) can be broken down into a few parts. All definitions shamelessly stolen from Wikipedia. > > In linguistics, grammar is the set of structural rules governing the > composition of clauses, phrases, and words in any given natural > language. > > > Morphology emphasis mine > > In linguistics, morphology /mɔrˈfɒlɵdʒi/ is the identification, > analysis and description of the structure of a given language's > morphemes and other linguistic units, such as root words, affixes, > parts of speech, intonations and stresses, or implied context > > > In this regard I think the key concepts your system needs to account for are implied context and intonation/stresses. Knowing how to convey ideas via thought could be difficult. How do you show freedom, how do you show confinement. I can see certain physical items becoming symbols for ideas. Chains for bondage a bird in flight for freedom etc. Maybe a flash of just that item to identify you are communicating an idea. Intonation gives us the ability to demonstrate emotion (among other things) in speech. Considering your Ents are already share vast amounts of sensory information there is not reason you could not allow them to also share emotions. Emotions are more than words. FAR MORE. Being able to share emotions would be a vast benefit to a species. Syntax > > In linguistics, grammar is the set of structural rules governing the > composition of clauses, phrases, and words in any given natural > language. > > > You could probably get away with ignoring syntax completely. If the Ents are able to share that much information that rapidly having a sentence structure seems un-necessary. Though you could alter the definition to create a structure for the flow of information. It would probably work kind of like charades in that you don't use words to convey ideas but there is an expected order information will be provided in, 3 words, 1st word, 4 syllables, act like a moron trying to get the idea across. You can see how that could easily be modified to fit images/sensations/etc Phonology > > Phonology is a branch of linguistics concerned with the systematic > organization of sounds in languages. It has traditionally focused > largely on the study of the systems of phonemes in particular > languages (and therefore used to be also called phonemics, or > phonematics), but it may also cover any linguistic analysis either at > a level beneath the word (including syllable, onset and rime, > articulatory gestures, articulatory features, mora, etc.) or at all levels of > language where sound is considered to be structured for conveying linguistic > meaning. Phonology also includes the study of equivalent organizational > systems in sign languages. > > > This one is less applicable than the others to your system as sound by definition would not play a role in your system, though phonology may matter when speaking with other races so your Ents would have to understand the concept. --- To address your specific mention of emphasis. In the transfer of knowledge an idea or subject that the 'speaker' is trying to emphasize you could attribute it your attention, you could give it a certain glow halo affect in visual terms, if scent is used you could focus on that object's particular scent or you could focus on impressing your emotions related to that person or object in the communication. Other notes: Some other things worth mentioning that are not strictly speaking grammar Perspective will be important when conveying information. Emotion, if you allow it to be part of the communication process, can be a valuable tool in this system. Consider how you will convey time. Conveying time is usually a comparison or verbal idea. You will need to come up with a system to convey such concepts. ]
[Question] [ Let's assume that there is a magic that can push information directly into people's brains. However, that magic has some limitations: * It can only "push" single sentences of 15 words or less * With a thought, the person can "expand" the text and give the reader more information * It only works within a 1/2 mile range * Magic "adblock" can stop the info from coming. If a person expands the info, the sender gets one IP (Iron Piece, roughly 1 cent.) from a advertising corporation. ##### If somebody were to send a piece of info like "This One Weird Trick Summons Demons!", would a person be likely to "expand" the info? [Answer] ## Clickbait injected into someone's brain would be very effective - at first Most people are not disciplined in their thinking - if I tell you not to imagine a llama, have you or have you not imagined a llama? To bring a thing to a person's attention is almost the same as to make them think about it, more or less. Depending on how easy the "trigger" is, it may be almost impossible for a typical person to resist - the first time. ## Clickbait, like other advertising techniques, loses power as the target grows numb to it How many billboards do you actually read, when driving, being driven, or even just walking along the street? How many ads on a typical web page (assuming you don't have an ad blocker), do you actually read? The more ubiquitous a vector trying to appeal to your attention, the less importance you will tend to assign it. The very first "Seven Reasons Why..." article looks fun and interesting. After clicking past a couple of ads to get to each reason, you may not bite the next time you see such an article. The more common clickbait becomes, and the less actually useful or interesting previous clickbait was, the less alluring the 73rd invitation will be. Though this may in turn lead to increasing "stakes" for the clickbait: 3 Reasons you'll be eaten by the Jabberwocky [Answer] I think our brain already works like that, for something deserving attention, like a noise in the house while you are sleeping at night, a mother hearing her baby whining upstairs while the TV is on, someone wearing a provoking dress walking through the corridor... Those are all baits to which our brain "bites". Like with most of the real clickbait, if the message involves one of the primary needs (sex, food, shelter/clothing), it will capture the brain's attention. If it can bypass the conscious layer, even more. [Answer] Clickbait works via a phrase, quote, or other mechanism to reach our concious mind and get us to click, hoping to know more. "Injecting" this phrase directly into someones head would result in three things(that I can think of) 1: The reciver sees it as an actual thought of theirs If this clickbait phrase doesn't come with some sort of marker to show its an external thought, the person reciving it might think of it as their own, and expand on their own. For example, say someone recives the title "8 ways to remove demons from your house," the person may begin thinking of three ways to remove the demons. If that action leads to them unknowingly expanding on it, and getting the article, it could be considered intrusive. Additionally, this could be a way of "brainwashing"people, by implanting thoughts into lots of peoples heads. 2: The reciver sees the title as an external source Maybe the clickbait sent is recognized as an external thought, like ones read or heard, a similar thing could happen as above. Or the reciver trains themselves to tune out the titles, and ignore it. 3: The reciver learns to filter the titles If the titles sent are marked as an advert, the reciver could train themselves to filter through the titles when they want to, similar to popping onto social media and scrolling through articles, choosing to read only the ones you want. [Answer] Click bait will always be bait. Enticing, but ultimately unrewarding and disappointing. Ad/Popup blockers would definitely be in good business Depending on how far you take it, I can see it very quickly becoming a way for targeted ads to be used. If information can be sent directly into the brain, information should be able to be retrieved as well. Not your personal secrets and memories, but at least your surface level thoughts, like "what am I going to make for dinner". Now you have a clickbait article about "7 delicious recipes in under 10 minutes" and on expanding, each pages ads are for Johnny's Butcher, Jason's dairy, etc. The other way for targeted ads to work, is a register of what click baits you have expanded. When you have got 5 that are related, in a short amount of time (Celebrities that own haunted houses - #13 might surprise you; Mans terrifying true haunted experience - captured in journal entries; Is your house haunted - 5 ways to know; 7 easy methods of demon banishing; etc) push more ads and clickbait to do with ghosts, demons etc. All I can say about it, whichever magic user discovers this magic, shall be put to death, and thrown from the peak of Mt. Tall, into the bottomless chasm. ]
[Question] [ I'm creating a fictional world which includes tree dwelling octopuses that thrives in swamps and tropical rainforests. I'm wondering what evolutionary pressures could lead to the rise of such creatures. ![enter image description here](https://i.stack.imgur.com/729VL.png) [Answer] Predators in a mollusc rich mangrove swamp. This particular mangrove swamp is part of the river delta of a huge river network (think amazon). The nutrient and particulate rich water is nirvana for various molluscs and bivalves. Your octopoids (like many real world octopuses) eat molluscs, so this swamp is also nirvana for them. The salinity of the swamp can be fudged towards more or less salty to support the kind of creature you want. Now, this swamp also contains some nasty predators. Pirhana analogues, or voracious otters, or eels. These predators would make short work of the octopoids, except for one small fact. The octopoids can move well out of water too. In tidal areas in our world octopuses often travel short distances across exposed rock to exploit trapped prey in tide pools. Your octopoids prey on molluscs on tidal flats where they can often eat without fear of predation. At some point one or two of your octopoids also realised they could climb the mangrove roots. This gave them an advantage over their mud-dwelling cousins because they could prey on the deeper water molluscs and still have a viable escape route from the predators. Evolution took over and boom: low level tree climbing octopoids. Now: laying eggs just above the waterline (so they get periodically soaked but spend a long time out of reach of predators) is a desired trait. Eggs that can spend longer out of the water are more likely to survive. The ability to lay eggs higher is a desirable trait in a sexual partner. Again: evolution takes over. Eventually an open air egg develops, but the ability to lay eggs high remains desirable, so octopoids climb higher and higher. Octopoids now have to evolve thicker, more waterproof skins so they can spend longer out of water. These skins also come in handy (along with the throttling, entangling, very strong tentacles) for dealing with their new arboreal neighbours, none of whom are sufficiently equipped or ready to deal with the writhing tentacular doom machines that are now encroaching on their leafy paradise. Octopoids that can spend long periods out of water and climb to the uppermost branches discover an alternative food source in fresh fruit, bird eggs and the corpses of asphyxiated monkeys. They start to outcompete their purely mollusc-bound brethren. And your tree-dwelling octopoid is born. ]
[Question] [ I'm the DM for a D&D campaign, set in a sort of "realistic-fantasy" setting. There's monsters and magic and stuff, but there's not enough of that for the average medieval community to see much more than the odd zombie attack or passing griffin. Last session, one of the PCs came into possession of a large manor, which covers 2000 acres of good farmland, 500 acres of meadowland, and a nearby woodland that they have permission to harvest timber and the like from. I was wondering if someone can help me figure out the yields of the following crops per acre; bear in mind, this would be medieval European technology, toward the later end of the High Middle Ages, specifically. Geographically, the region is similar to Maryland, Delaware or New Jersey. * wheat * barley * oats * rye * maize (see note) * peanuts (see note) * potatoes (see note) * flax * hemp * wild walnuts (kinda mixed in with the forest) I've decided to include peanuts, maize, and a few other new-world nightshade crops (e.g. tomatoes and potatoes) in the world for flavor, and so that the peoples inhabiting more southerly climates could still rotate in a pulse crop of some kind (i.e. peanuts) during the growing season instead of wasting a third of their cropland letting it go fallow. Also, for the grains that can do it, I'd also like to include an increased yield for the winter planting (e.g. planting in October vs. planting in March). Problem is, Google has been supremely useless in finding a satisfying answer to this question, it's only interested in modern yields. Edited to provide additional clarity, and to remove dice discussion. [Answer] I am not an expert but I did find a few things. Everything I found is about grains, specifically wheat, rye, barley, and oats. I tried to find things on the other plants you asked about, but could not find anything I deemed of use. I don't know if what I found will be of any use, but here it is: The most common means of calculating yield was the number of seeds harvested compared to the number of seeds planted. On several manors in Sussex England, for example, the average yield for the years 1350–1399 was 4.34 seeds produced for each seed sown for wheat, 4.01 for barley, and 2.87 for oats. <https://en.wikipedia.org/wiki/Agriculture_in_the_Middle_Ages#Fields> The average yield of an acre of farming in the Middle Ages was eight to nine bushels of grain (291-327 Liters). <http://www.thefinertimes.com/Middle-Ages/farming-in-the-middle-ages.html> Rye = seven-fold render (7 bushels on one acre) (629 Liters per Hectare); does better in poor soil Wheat = 5-fold render (5 bu/acre) (435 Liters/Hectare) in poor soils.. <https://www.ibiblio.org/london/agriculture/general/1/msg00070.html> For more info on grain planting: <http://www.fao.org/3/y5146e/y5146e07.htm> * They knew that wheat would yield 250 to 300 liters of grain per acre - * Barley would bring 700-720 liters per acre. (The higher yield for barley was partially the nature of the plant, plus the fact that you put 72 liters of seed into each acre of wheat and 144 liters per acre of barley.) * Oats yielded 360-400 liters an acre, for 108 liters of seed. * Peas, an important diet supplement and protein source, gave 300-340 liters per acre, for 108 liters of seed. * Flax and hemp was also grown, to provide raw material for linen and rope. Depending on the nature of the land, the size of the farmers holdings, local weather conditions, and drinking habits, about half the land would be sown in barley. In ale drinking areas (most of England and large parts of France), barley would be needed for making ale. Barley was also a more productive grain, even though it produced a less tasty meal than wheat. A third (or more) of the land would be planted in wheat. The remainder would go for peas and oats. Grain yields of slightly under four times seed grain sown were the norm until the 18th century.(So take your yield and divide by four of under) There, another burst of innovation brought productivity to ten times seed sown.. In the 20th century, this rose to twenty times. <http://www.hundredyearswar.com/Books/History/Agricult.htm> [Answer] Potatoes are a total game changers. "Many researchers believe that the potato’s arrival in northern Europe spelled an end to famine there" according to a piece in the Smithsonian\. It is even argued that the far greater productivity gave rise to the age of empires. If you have the climate - like Ireland - you can get rid of the labor-intensive business of cerial cultivation and get all your carbohydrate from something that it easy to grow, easy to harvest, requires little preparation (none of that threshing and grinding and baking - just boil 20 mins). Like the Irish, your people could live on just potatoes far, far more easily than cereals. Organic farming - no modern pesiticdes etc -can yield over 10 tons an acre, which blows wheat (3 tons an acre) out of the water. This requires just two hundredweight of seeds, so yield is a factor of 100 which is awesome compared to seed. When a head of wheat gets too heavy, the plant topples; when a potato crop grows well, you get big potatoes. England had 17 major famines in the century after 1623, but after the potato was introduced famine all but disappeared. Obviously total reliance can lead to total disaster when potato blight strikes. This depends completely on having high-yield varieties available...but then the same is true of wheat anmd other crops. "How the potato changed the world" <https://www.smithsonianmag.com/history/how-the-potato-changed-the-world-108470605/> This is a good 1920s source which reckons you can plants less than 10 bushels per acre and get more than 200 back -- <https://smallfarmersjournal.com/how-to-grow-an-acre-of-potatoes/> [Answer] # If your players are just trying to figure out their profit that's a bit easier than crop yields. Throughout D&D systems, land was valued at the profit it could produce in a 5 year period. Typically farmland is valued at 50 gp/acre, meadow land is similar. So 2500 acres x 50 gp / 5 years is 25,000 gp/year or 68.5 gp/day. (note that this is the profit and it's assumed that the upkeep costs are built into the evaluation of the profit) ]
[Question] [ Something in orbit around an inhabited planet blasts it with a hefty dose of gamma rays/x-rays/something else, killing everyone within a relatively short time frame (hours or days) but leaving no obvious trace of what has occurred. When offworlders turn up a week later to find out what happened, they find a lot of corpses and not much else. There is no requirement to kill everything single living thing, just enough members of enough species that the ecosystem and any extant civilisation collapses. What form of radiant energy, if any, could achieve this effect? some considerations I was going to use gamma rays, but am concerned they wouldn't penetrate an Earth-like atmosphere. Or would the proximity and intensity make that not a problem? e.g. could an intense enough burst destroy the atmosphere so quickly that the hard radiation can then kill people directly? When it comes to traces left behind by the blast, am I right in thinking that there wouldn't be residual radioactivity? Or would an intense enough burst of gamma or x-ray cause alpha/beta decay in materials on the planet's surface? (For the purposes of running scans to figure out what happened.) [Answer] You cannot accomplish this without severely disrupting the planet's surface. Enough gamma or x-ray energy will complete your objective of "Kill enough members of the civilization to ensure a collapse" but not with the objective of "Not leaving a trace to figure out what happened". Basically an Earth like atmosphere is really, really good at absorbing high energy wavelengths. See here: <http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson2-1/atmosphere.html> That means that shining a really bright gamma or x-ray beam will simply heat up the atmosphere. Heat up the atmosphere enough and you'll wipe out the civilization. You could save an insane amount of energy if you were okay with just wiping out enough plant life to cause crop failures and mass starvation, but that would hardly guarantee extinction. This can occur naturally with a near-Earth Gamma Ray Burst, and it probably has caused a mass extinction event in the past. <https://en.wikipedia.org/wiki/Gamma-ray_burst#Effects_on_Earth> The practicality of this is very questionable, as the energy requirements are insane. The most viable technique would be to inject anti-matter all across the sky to bombard everything with gamma, heating up the atmosphere. See this question for more info: [How much antimatter would we need in order to wipe out all humans, eradicate all animals and blow up the Earth?](https://worldbuilding.stackexchange.com/questions/13644/how-much-antimatter-would-we-need-in-order-to-wipe-out-all-humans-eradicate-all) TLDR: It isn't really feasible in the way you want. The rays won't reach the surface, so you'll have to bake the entire planet. [Answer] You could use a particle beam. <https://en.wikipedia.org/wiki/Particle-beam_weapon> > > Particle accelerators are a well-developed technology used in > scientific research for decades. They use electromagnetic fields to > accelerate and direct charged particles along a predetermined path, > and electrostatic "lenses" to focus these streams for collisions.... A > particle-beam weapon is a weaponized version of this technology. It > accelerates charged particles (in most cases electrons, positrons, > protons, or ionized atoms, but very advanced versions can accelerate > other particles such as mercury nuclei) to near-light speed and then > shoots them at a target. These particles have tremendous kinetic > energy which they impart to matter in the target, inducing > near-instantaneous and catastrophic superheating at the surface, and > when penetrating deeper, ionization effects which can be especially > detrimental to electronics in the target. > > > A beam shooting massive particles would get a fair number through the atmosphere, delivering their punch to more massive things on the ground (like people). Charged particles would scatter from mutual repulsion on the way down, producing a shotgun like effect. You can cook things with the kinetic energy of these particles which they drop off as heat in their targets. I think this effect was best described in Repo Man by J Frank Parnell, discussing the neutron bomb. <https://www.youtube.com/watch?v=3VKzqAefBVY> A problem, though, is that a beam energetic enough to thermally kill all the people would produce comparable thermal effects on everything else on the ground. Your alien visitors would figure out what had happened: stuff got cooked from space. A lesser dose of particles would not kill thermally but would kill by acute radiation poisoning. It is slower and messier and there might still be some folks lingering a week later when the aliens show up. If you can push the alien visitors out to 3 weeks that should be enough time. But if the aliens are familiar with Earth life they will still be able to figure out how everyone died. [Answer] You need to use a frequency that the atmosphere is transparent to. I would suggest using 4 GHz microwaves, the same as is used in your kitchen appliance. You would bath the world with enough microwaves to raise the temperature of the typical critter by about 10 degrees C. This would leave the corpse in roughly the same condition as dying from a fever would have. Critters that were under dense forest cover would have a higher survival rate. Critters in the water would be able to dissipate the heat. This is still a not-trivial amount of energy. If you are trying to heat up an average of 30 cm thick layer of water by 10 C, you are spending 600 kCal/square foot or about 2.4 MJ or about 2/3 of a kWh/ft2. Expanding that, about 7 kWh/m2 = 7 million kWh/km2 Earth is about 500 million square km so 3,500 trillion kWh. And that assumes efficient coupling. This seems very wasteful. Food microwaves, after all, were designed to cook. It may be possible to come up with a frequency that hits a resonance in some protein. Imagine something that disrupted hemoglobin. Zzzzot! everything with a red blood cell falls over dead. If you are willing to criss cross the planet within the atmosphere, you could do everyone in with sound. kWh per square meter will make a lot of noise. (Hifi speakers are terribly inefficient at converting energy to noise. The designers care about fidelity. even 1 watt of acoustic energy is LOUD. Suppose you generated infra-sound, say at 10 Hz, but at an amplitude that had peak over pressure measured in pounds per square inch. As a side effect it would treat most buildings like a bad earthquake. However, overall, chemistry is more suitable. The ideal chemical is one that requires some time after exposure to be effective. This means that people won't run and hide when others start dying. Something that interferes with a precursor chemical for nerve transmitters may do. Circle the planet in a polar orbit, and kick the pellets out of the ship at a speed they are near motionless relative to the surface. This means they hit the atmosphere fairly slowly so they don't burn up. A way to convert all or much of the carbon dioxide in the atmosphere to carbon monoxide would do the trick. CO has a residence time in the atmosphere of between 2 months and 5 years. (Estimates vary...) So discovery a week after the event would leave a big fingerprint. WHO exposure limits are 10 ppm for a shift, and 100 ppm for 15 minutes. This is sufficient to block 2% of the hemoglobin. Residence time in the blood is about 5 hours, so the 100ppm should eventually stabilize at around 40%. It may be possible to excite CO with the right frequency to give it the energy to reconvert it back to CO2. Diseases could work too. Spanish flu was the most recent pandemic with high mortality. While somewhere between 50 and 100 million people died, overall mortality was a small percentage of the world's population. Perhaps another disease that kills with a Cytokine storm. (Flu was scary. A person could go to bed healthy and wake up dead.) Diseases seldom are deadly to multiple species. Rabies is an exception, and may be a good candidate: * Most mammals are susceptible. * You can get it from inhalation. (Bat researchers now get vaccinated against it.) * It has a fairly long incubation time. No disease is sudden enough to not leave records. Anything lethal enough that people can't write stuff down is too lethal to spread effectively. Finally, if you truly want to leave a mystery, and have Startrek transporter technology, you circle the planet, stealthed, and beam people up, dropping them on the back side of the moon. Don't worry about maintaining the pattern buffers... At 100 people per second, 7 billion people would take 7 million seconds, or about 3 months. 10,000 people per second brings it down to 70,000 seconds or about a day. This is about the same time as a polar orbit will cover the earth. Mind you, if you have transporter technology, tune it to a particular molecule, and just remove nerve transmitters. No one is going anywhere if their acetylcholine is missing. [Answer] As for traces of radiation, you would not find any form of radioactivity deposited from a high energy gamma emission. Gamma or x-ray may excite atoms or cause ionization, but they will not activate nuclei. Neutrons will activate nuclei, not gamma or x-ray. If you used x-rays in a certain energy level you would boil the water out of living organisms, and that would be hard to ignore. As for traces of something, the use of a massive gamma ray emitter from orbit would leave evidence in the atmosphere. The ozone layer protects the planet from high energy particles. You gamma ray weapon would destroy the local ozone before an appreciable amount of energy reaches the surface to kill people. This would leave a sort of smog in the area and a hole in the ozone that, depending on the area effected may take years to centuries to dissipate. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. Suppose a starship is being powered by a lasers beamed first from the departure star, and then from the destination which is a moving base. The ship is moving in the regime of 10–30% of light speed. Picture a letter “T”. The ship is accelerated up the vertical line from the source at the bottom of the T, into the path of the horizontal cross-line. A mobile base (the destination) moving on this horizontal line at 10% lightspeed will supply a laser too. That is, the home system will push a lightsail craft into the path of a base moving at relativistic speeds. That base would pass home with a closest approach of several light years. ![sketch](https://i.stack.imgur.com/hCMx9.png) Let me try another mental picture: you are a mile back on a path that intersects with a main road at a right angle. A mobile home is travelling down the main road at 70 miles per hour. The beam from home pushes you into the main road, and the beam from the mobile home needs to get you going in that direction instead for eventual rendezvous. The mobile base needs to accelerate the incoming craft to its own oncoming speed and kill the transverse velocity. What would the maneuver look like? I’m supposing that the angle at which it presents the sail will be significantly affected by relativistic effects and [aberration](https://en.wikipedia.org/wiki/Aberration_of_light) of moving source. Also, the mobile base (from a more advanced civilization) can do any advanced tricks you can imagine, such as synthetic aperture beamforming to make the wavefronts come from a different direction than the actual source, and impart [orbital angular momentum to the photons](https://en.wikipedia.org/wiki/Orbital_angular_momentum_of_light). The home beam has just enough power and focus for the maneuver it is designed for. The base beam can be more powerful and amazingly well-focused. But the base won’t aim the beam directly at the home; they will require the ship to be some distance out (like a light year) before offering. --- Peregrine Rook’s sketch is nicer ☺. I think the sail would be tipped the other way when catching the beam from the base, though, to slow the “up” component. ![sketch](https://i.stack.imgur.com/bMZpY.png) [Answer] First, let’s look at the different types of trajectories a solar sail can take. They differ mainly based on something called the lightness number, $\beta$, which depends on the composition and structure of the sail. $\beta$ can be used to determine the type of trajectory the solar sail will follow: $$\begin{array}{\|c\|c\|} \hline \text{Value of }\beta & \text{Type of trajectory} \\ \hline \beta=0 & \text{circular Keplerian} \\ \hline 0<\beta<\frac{1}{2} & \text{elliptical} \\ \hline \beta=\frac{1}{2} & \text{parabolic} \\ \hline \frac{1}{2}<\beta<1 & \text{hyperbolic} \\ \hline \beta=1 & \text{rectilinear} \\ \hline 1<\beta & \text{flipped hyperbolic} \\ \hline \end{array}$$ This is also evident in Figure 4.8 (page 123) of Colin McInnes’ [Solar Sailing: Technology, Dynamics and Mission Applications](https://books.google.com/books?id=lvHxBwAAQBAJ&pg=PA130&lpg=PA130&dq=solar+sail+logarithmic+spiral+escape+trajectory&source=bl&ots=inAfjimvhX&sig=Qqkxsftl5xmPG-cyJOnQSi5DIIY&hl=en&sa=X&ved=0ahUKEwiM68WEsvHOAhXGXB4KHVbWDMUQ6AEIIjAB#v=onepage&q&f=false), which is my primary reference in this answer: [![enter image description here](https://i.stack.imgur.com/6Lx4p.png)](https://i.stack.imgur.com/6Lx4p.png) Now, you can see that a hyperbolic trajectory of some sort may be exactly what you’re looking for - and, in fact, it requires no assistance from the base it is rendezvousing with! Parabolic trajectories, too, are escape trajectories, but a hyperbolic trajectory might be more efficient. Plus, having a greater lightness number results in a greater characteristic acceleration (see [Seboldt & Dachwald (2003)](http://earth-escape.com/paper/200207_Pozzuoli_SeboldtDachwald.pdf)), because $a\_c\propto\beta$. Therefore, I’d prefer to work with a flipped hyperbolic trajectory; I’ll choose $\beta\approx2$. There are two equations of motion for polar coordinates $(r,\theta)$: $$\frac{\mathrm{d}^2r}{\mathrm{d}t^2}-r\left(\frac{\mathrm{d}\theta}{\mathrm{d}t}\right)^2=-\overbrace{\frac{\mu}{r^2}}^{\text{gravitational}}+\overbrace{\beta\frac{\mu}{r^2}\cos^3\alpha}^{\text{radiation}}\tag{4.37a}$$ $$r\frac{\mathrm{d}^2\theta}{\mathrm{d}t^2}+2\left(\frac{\mathrm{d}r}{\mathrm{d}t}\right)\left(\frac{\mathrm{d}\theta}{\mathrm{d}t}\right)=\beta\frac{\mu}{r^2}\cos\alpha^2\sin\alpha\tag{4.37b}$$ where $\mu$ is the [standard gravitational parameter](https://en.wikipedia.org/wiki/Standard_gravitational_parameter) and $\alpha$ is the angle between a vector normal to the sail and a vector pointing from the star to the sail. Compare McInnis’ $(\text{4.37a})$ to $(\text{346})$ [here](http://www2.ph.ed.ac.uk/~egardi/MfP3-Dynamics/Dynamics_lecture_21.pdf), with the substitution of $h=r^2\dot{\theta}$. The two are identical, with the addition of the radiation term in the solar sail reformulation. Let’s have $\alpha\approx0$. This means that the right-hand side of $(\text{4.37a})$ becomes $(\beta-1\frac{\mu}{r^2}$, and the right-hand side of $(\text{4.37b})$ becomes $0$. We can arrive at a simple analytical solution if we assume that the solar sail takes the path of a [logarithmic spiral](https://en.wikipedia.org/wiki/Logarithmic_spiral), i.e. a path of the form $$r(\theta)=r\_0\exp(\theta\tan\gamma)$$ where $r\_0$ is the initial radius and $\gamma$ is the spiral angle, the angle between the velocity vector and the transverse direction of the sail’s path. So let’s step back a little, and let’s assume that * $\beta\approx0.75$ (I’ve chosen a value for a normal hyperbolic trajectory) * $\alpha\neq0^{\circ}$. It could, but that might not be optimal. McInnes goes through several substitutions, leading to $$r^3\left(\frac{\mathrm{d}\theta}{\mathrm{d}t}\right)^2=\mu\left[1-\beta\cos^2\alpha(\cos\alpha-\tan\gamma\sin\alpha)\right]\cos^2\gamma\tag{4.41}$$ From this and earlier substitutions, we can derive expressions for the radial velocity $v\_r(r)$ and angular velocity $v\_{\theta}(r)$. The equation for the former is $$v(r)=\sqrt{\frac{\mu}{r}}\left[1-\beta\cos^2\alpha(\cos\alpha-\sin\alpha\tan\gamma)\right]^{1/2}\tag{4.44}$$ There’s a fairly complicated relationship between $\gamma$ and $\alpha$, but it can be simplified for small $\gamma$: $$\frac{\beta\cos^2\alpha\sin\alpha}{1-\beta\cos^3\alpha}=\frac{\sin\gamma\cos\gamma}{2-\sin^2\gamma}\approx\frac{1}{2}\tan\gamma\tag{4.45,4.48}$$ This integration is important when we try to find a relationship between $r$ and $t$. We integrate $(\text{4.44})$: $$\int\_{r\_0}^r\sqrt{r}\mathrm{d}r=\int\_{t\_0}^t\left(2\beta\mu\sin\alpha\cos^2\alpha\tan\gamma\right)^{1/2}\mathrm{d}t\tag{4.46}$$ Integrating this and substituting in $(\text{4.48})$ yields $$t-t\_0=\frac{1}{3}\left(r^{3/2}-r\_0^{3/2}\right)\left(\frac{1-\beta\cos^3\alpha}{\beta^2\mu\cos^4\alpha\sin^2\alpha}\right)^{1/2}\tag{4.49}$$ However, we can simplify this by letting $t\_0=0$ and focusing on cases where $r\_0\ll r$ for most $r$, which is the case here when $r=r\_f$. We can then find when the function of $\alpha$ in $(\text{4.49})$ is maximized; it turns out that for small $\beta$ (i.e. $\beta<0.5$), $\alpha\_{\text{max}}\approx35.26^{\circ}$. However, I chose $\beta=0.75$, and so it turns out that $\alpha$ is maximized at about $35.26^{\circ}$. Plugging this back into our approximation for $\tan\gamma$, we find that $\tan\gamma\approx1.362$, which gives us $\gamma\approx53.7^{\circ}$. This likely makes our small angle approximation for $\tan\gamma$ less accurate, but it will do for now. Plugging this in, and assuming once again that $t\_0=0$ and $r\_0\ll r$, $(\text{4.49})$ gives us $$t=r^{3/2}\times1.23\times10^{-10}$$ and for a final radius of three light-years ($2.838\times10^{16}$ meters), we find that $t\approx5.88\times10^{14}$ seconds, or about 19 million years. That might seem like it can’t be correct, but [Centauri Dreams cites Matloff et al. that it could take a really good solar sail 30 years just to reach the Oort Cloud](http://www.centauri-dreams.org/?p=4238), 500 AU away - and one light-year is about 60,000 AU. Clearly, a simple logarithmic spiral quite like this won’t work. In fact, this means that you absolutely need to give the solar sail a very fast initial boost to make interstellar travel on these scales even remotely feasible. This makes the equations a little harder, and it means that yyou might not see an easy analytical solution pop up. Let’s go back to our original coupled equations $(\text{4.37a})$ and $\text{4.37b})$, where we’ve set $\beta=2$ and $\alpha=0$. This becomes a simple [central force problem](https://en.wikipedia.org/wiki/Classical_central-force_problem), which has one equation of the form $$\frac{\mathrm{d}^2r}{\mathrm{d}t^2}-\frac{h^2}{r^3}=\frac{F(r)}{m}$$ where I’ve defined $h\equiv r^2\dot{\theta}$, which is conserved. $F(r)$ is the central force as a function of $r$; normally, in orbital mechanics, it’s simply $$F(r)=-\frac{GMm}{r^2}$$ as is the case in $(\text{346})$; here, as I noted before, we also have to account for the force from radiation pressure. With $\beta=2$, it just so happens that the two forces add up to $$F(r)=\frac{-GMm}{r^2}+\frac{(2)GMm}{r^2}=\frac{GMm}{r^2}$$ which is repulsive, unlike $(\text{346})$. [That pdf](http://www2.ph.ed.ac.uk/~egardi/MfP3-Dynamics/Dynamics_lecture_21.pdf) shows a good derivation of the orbital equation from the central force law, which I’m not going to go through again, as it’s pretty standard. For a generic central force of the form $$F(r)=-\frac{k}{r^2}$$ we arrive at an orbit of the form $$r(\theta)=\frac{l}{1+\varepsilon\cos\theta}\tag{355}$$ where $k=-GM$ (in general, $k=(\beta-1)GM$), and $$l\equiv\frac{mh^2}{k},\quad\varepsilon\equiv\frac{l}{a}-1\tag{356}$$ I’m no expert when it comes to solar sail construction, so I read through [McInnes et al. (2001)](http://www.esa.int/esapub/bulletin/bullet108/chapter6_bul108.pdf) and came up with a conservative estimate of 2,000 kg. The authors estimated that you could send a 900 kg solar sail to solar orbit, with much of that mass being payload. My guess could be way off, so I’d appreciate it if an expert has better figures. I assumed that the solar sail starts out on a circular orbit around a sun-like star at roughly Earth’s semi-major axis. From this, I calculated $$v\_0=\sqrt{\frac{\mu}{r}}=2.97\times10^4\text{ m/s}$$ $$h=\frac{\|L\|}{m}=\frac{rmv}{m}=rv=4.46\times10^{15}\text{ m}^2\text{/s}$$ $$k=(\beta-1)GM=1.327\times10^{20}\text{ m}^3\text{/s}^2$$ $$l\equiv\frac{mh^2}{k}=3\times10^{14}$$ $$\varepsilon\equiv\frac{l}{a}-1=2000$$ From this, I get $$r=\frac{3\times10^{14}}{1+2000\cos\theta}$$ $\varepsilon>1$ (as was expected, given that $\beta>1$), and in fact $\varepsilon\gg1$. I used modified code from [this page](http://www.physics.buffalo.edu/phy302/topic1/#sec-15) to solve $(\text{4.37a})$ in Mathematica and plot the motion of the solar sail over the course of one year: ``` M = 1.99 10^30 (mass of Sun) G = 6.67 10^-11 (Newton's constant) x0 = 1.5010^11 (apsidal distance) y0 = 0; vx0 = 0;(on x axis with velocity in y direction) vCirc = Sqrt[G M/x0] (apsidal speed for circular orbit) vy0 = 0.8 vCirc (smaller speed gives elliptical orbit) a = 1/(2/x0 - vy0^2/(G M)) (semimajor axis from E=T+V) T = 2 Pi Sqrt[a^3/(G M)] (period from Kepler's third law) beta = 2 (accounts for radiation pressure) r[t_] := {x[t], y[t]} (position vector*) equation = Thread[r''[t] == (beta-1) G M r[t]/Dot[r[t], r[t]]^(3/2)] initial = Join[Thread[r[0] == {x0, y0}], Thread[r'[0] == {vx0, vy0}]] solution = NDSolve[Join[equation, initial], r[t], {t, 0, T}] orbit = ParametricPlot[r[t] /. solution, {t, 0, T}]; Show[orbit] ``` This is the orbit: [![enter image description here](https://i.stack.imgur.com/xTgVi.png)](https://i.stack.imgur.com/xTgVi.png) As you can see, it travels in essentially a straight line, going at a little over 5 Au per year, at first. That’s not bad at all. It’s still going to take a long time to reach the base, but this is likely going to be on the order of thousands of years, not millions of years. [Answer] I believe the desired outcome can be achieved with relatively simple means. The trick with solar sails is that although the incoming light can only push the sail directly, the reflection of that light can push the sail in a different direction. The resulting net thrust is the combination of the incident light and the reflected light. For a solar sail being pushed by lasers at significant fractions of C it’s safe to assume that the the sail will have near 100% reflectivity (otherwise the non-reflected light would incinerate the ship) so the magnitudes of the incident and reflected light will be approximately equal. Since from basic geometry we know that the angle of incident light and the angle of reflection will be equal, then the angle of thrust, or net acceleration will always be directly orthogonal to the plane of the sail. This means the solar sail will always accelerate straight ahead. If we want to accelerate in a different direction, we simply have to turn our sail to face directly away from that direction, treating the sail as if it were any other conventional source of thrust. The caveat though is that changing the orientation of the sail changes the magnitude of the experienced thrust. The acceleration of the sail can be computed by the following functions: [![sail equations](https://i.stack.imgur.com/5yxKJ.png)](https://i.stack.imgur.com/5yxKJ.png) Since all the variables in the above equations are constants with the exception of B, the angle of the sail with respect to the laser, we can deduce the relationship between the acceleration of the ship and the angle B to be Accel = cos(B)^2. That is to say when B is 0 and the sail is facing the laser directly it will experience maximal acceleration and when B is 90 degrees and the sail is sideways to the laser is will experience 0 acceleration. It follows that if we want our trip to be efficient we need to minimize B. Of course, if you want to make the whole thing much simpler you can simply say the light comes from directly behind the craft at all times due to some fancy technology. In that situation the force experienced by the ship will always be constant. But that also takes all the fun out of solar sails doesn’t it? So with this system we can accelerate in any direction away from the laser source, but never back towards it. However, the efficiency of our acceleration decreases rapidly the harder we try to turn. One consequence of this is that it will be difficult to ever use both lasers simultaneously with any efficiency since they are ~90 degrees apart. This means for the first leg of our journey we are going to want to accelerate directly away from our home laser towards some far off rendezvous point and ignore the station laser. By accelerating directly away and keeping B equal to 0 we maximize our acceleration. At some point though we will need to reduce our velocity towards the oncoming station in order not to overshoot it. We have to use the station laser to do this. Ideally by this time we are closing with the station and thus the angle we must thrust to match velocities with the station is close to that of the laser making our thrust once again efficient. The below schematic isn’t exactly what I am describing above, it was made before I realized how inefficient the angled thrusting would be, but it still gets the general concept across. [![setting sail](https://i.stack.imgur.com/4r2jD.png)](https://i.stack.imgur.com/4r2jD.png) With regards to the effects of relativity. Obviously the lasers from both parties will need to be aimed light-years ahead of the ship’s path with absurdly precise calculations and a predetermined course. Even a slight error would compound and eventually throw the ship out of the path of the lasers which had been fired years in advance. Even with faster than light communications this would be a remarkable feat. To specifically address your concerns regarding relativity and the angle of the sail: > > I’m supposing that the angle at which it presents the sail will be > significantly affected by relativistic effects and aberration of > moving source. > > > The aberration of light due to the movement of the station will not change the direction the ship accelerates since we determined above that the ship always accelerates orthogonal to the plane of the sail. The aberration of light will however change the magnitude of that thrust by influencing the projected area of the sail (and therefore the amount of light that hits the sail) and the proportion of the incident and reflected thrust vectors that are productive (how much of those vectors cancel each other out). This answer doesn’t include a precise plot of an optimal course for the ship to take. This is because there are many possible courses and they differ drastically based on the relative strengths of the lasers and the distances and velocities involved. For instance, if the station laser is significantly more powerful than the home laser we will want a course that lets us flip over to utilize it as soon as possible. But that course is very different from one in which the home laser is preferred. Based on the distances and velocities and maximal accelerations involved the ship might have to begin accelerating on a course nearly parallel to that of the station to ensure it matches velocities before the station passes. Or if the station is very far off maybe it can simply accelerate directly into the path of the station and then be brought up to speed by the maximal effectiveness of the station’s laser pushing the ship directly in front of it. I see no way to simply compute a single optimal course even if those missing constants were defined. I do think that this answer provides insight into the principles of the laser-powered lightsail’s operations and the equations necessary to calculate the time a given course will take. [Answer] There are some ways to break this problem into simpler ones. # One laser at a time Since both the thrust sources are lasers, they're coherent. And since managing their relative phases at distances of light-years is basically impossible, you want to have just one active at a time, to prevent interference and loss of thrust. # Look at it as two separate voyages It's a basic physics trick to break down problems in forces to two separate problems at right angles. Since there is essentially no friction in this system, that's quite accurate for this problem. So we can look at this as two separate problems: 1. Leaving the starting point, accelerating, making turnover, decelerating and stopping at the right distance from the start. 2. Accelerating from zero velocity on the course parallel to the station to match its actual velocity. I'm not suggesting that the first voyage should be completed, and then the second started, just that it's easier to think about the problem in two pieces. # Managing the sail Start out with the sail pointing backwards towards the start point. Leave it there until you reach turnover. Then angle it at $arctan(y/x)$ to your course, where $y$ is your velocity away from the start, which you have to shed, and $x$ is the velocity of the station, which you have to acquire. Leave it to the cunning laser on the station's ability to come from a different effective direction to its actual direction to supply thrust from a constant direction relative to you. This is not the most power-efficient way to do the voyage, but it makes the least demands on the laser at the start point and on the ship. Light-sail ships are even more weight-critical than ordinary spacecraft, and swinging your sail around continuously while you're riding the station's beam takes (a) reaction mass and (b) keeping the engines and control system that use that reaction mass working. All of that costs weight. Avoiding the need to do those things makes the voyage more likely to succeed. ]
[Question] [ I have developed a 2D space trading game, yet in the final stage of the development of the game engine, I am struggling to find the optimal size of my planetary system(s) and the maximum velocity of my spaceship. Setting the correct dimensions is crucial for the further development of the project, as it lays the foundation for many elements, technology and story line. I encountered a few shortcomings during the worldbuilding stage and I would appreciate any help with it. 1. How can I creatively reason to a player an imposed speed limit of his or her spaceship, given that in reality with constant acceleration a spaceship is only limited by the speed of light? I chose to limit the maximum velocity of a vessel, as it otherwise becomes (technically) impractical to engage with other spaceship in a (dogfight) combat. 2. Ultimately related to speed, how can I determine the ideal size of an average planetary system (i.e. usually one star and planets in orbits), the number of planets and the time it could take on average to travel from a planet in the outer orbit to a planet closer to the sun, both in game time and real time? Ideally I would like the game to feel realistic and exciting to get across the planetary system, yet not feel too boring with longer periods of nothing happening. Currently I have set 1 (real) minute minute to be 1 (game) hour; what is a reasonably good conversion ratio? 3. I would like the trade to be challenging. However, if people can simply see the prevailing prices on each planet beforehand, there is not much challenge for finding the optimal trade. I can cut the communication but then how can I reason to a player that they can only see the prevailing prices of goods when they visit a planet, however, not when flying in space? Is there any other way to make trade more challenging and reason it to the player? Notes: (1) Players control a ship or even a fleet of ships using mostly their mouse, something similar to that that ([early demo of my game](https://www.youtube.com/watch?v=hsl1tM5iPDM)). (2) There will be asteroids to visit that can be mined etc. (3) I want to include around 200 AI players per planetary system, but can technically go up to as many as 2000. Edit: To narrow the scope down, I though I will provide a little bit more info on the game so far--what it can do, what it can't and what I can implement. * A key element of the game is that it contains an entirely simulated real-time economy with prices that are determined by supply and demand through AI generated traders and human players. There is a plan to include a interplanetary stock market, derivatives, commodities and the possibility to mine asteroids and build factories on planets that transform commodities in more complex products. * In terms of propulsion technology, there will be two essential methods to get across. The first is within a planetary system by means of normal propulsion such as nuclear fusion, solar sails, anti-matter, impulse etc. This will be used for interplanetary exploration, trade and sometimes fights. There will be RPG/Adventure elements such as exploring ancient civilizations, galactic phenomena, nebulas etc. * The other propulsion technology is enabling interstellar flight. The current working idea is that ships can enter a higher dimensional plane by creating a temporary rift in space. A ship then enters into a (nearly) higher spatial dimension where it is possible to travel light years in a relatively short time (e.g. days). As mentioned, this technology is independent from the first interplanetary propulsion and it only works when there are no major gravitational disturbances around the ship such as planets, asteroids or other ships. So you need to be flying a bit out of the planetary system to activate it and therefore it won't be possible to escape from a fight or as long there are objects around at a certain radius. * Other ship technologies include different type of energy generators, shields, weapons, probes, radars, scanners. The ship is capable to have a fight, but not just dumb-down clicking around and about. With the correct speed it should rather feel tactical despite being in real time. It may take a minute to take another ship down, and therefore fights are not be overly frequent but if one wishes to engage in more fight than rpg/trade, that's up to them. As there will be RPG elements, gaining experience will increase maneuverability, aim accuracy etc., to make fights even more interesting. * With regards to the story line. The current working version envisages that earth experienced an attack from an unknown force and while being transported out from the solar system with a small vessel (as slave/prisoner), there was an unknown energy burst on the vessel and you find yourself in a different star system with all but you dead. You manage to get out of your cell and learn to take control of the severely damaged ship and get to what looks like a space station. While this seems not to original, what people will realize during the game, that your ship not only had been transported hundreds of light years away, but also around 7 years back in time. So, in a time frame of seven years, you can explore the reasons behind this attack and prevent it from happening by means of either becoming very powerful individual (trade+diplomacy) or tactical combat (up to controlling a fleet to fight against the invading force). [Answer] There are 3 basic methods of transferring between orbits. ## Minimum energy Involves expending enough energy to get to the "closest" (in energy terms) Lagrange point. From there, small course corrections to steer your vessel between the planetary system's Lagrange points can keep the overall energy expenditure much lower than even a Hohmann orbit transfer. A Minimum energy orbit transfer will likely take decades or more for a Earth to Saturn voyage. It would be suitable for the transportation of bulk materials that do not spoil. You might consider this the "ground transportation" version of space travel. ## Hohmann Transfer A Hohmann orbit transfer is the lowest energy direct orbit transfer method. Hohmann orbit transfers are sometimes called "bang-bang" transfers because they typically involve 2 main propulsive maneuvers (one to change your current orbit to an ellipse intersecting the new orbit & one to change the ellipse at the other end to the new orbit). A Hohmann orbit transfer from the Earth to Saturn might take 6 years. It would be suitable to material needed soon but not ASAP. You might consider this as the "priority" shipping. ## Brachistochrone Is a direct thrust orbit transfer - in which the vessel thrusts constantly during the whole voyage. Brachistochrone trajectories are limited by the amount of propellant, the amount of energy, and the maximum thrust of the engines of the ship. There are very few engine, propellant, & fuel combinations that can accomplish brachistochrone trajectories. Realistically, only extremely low thrust propulsion systems (e.g. solar sail, ion thruster) or extremely energetic systems (e.g. fission, fusion, or antimatter) systems can accomplish them. A Brachistochrone trajectory to Saturn might take months. You might consider this the equivalent of "over night" delivery. ## Answering the Question For the purposes of your game, you must consider the costs associated with each of these propulsion schemes. Clearly even if your society can and will use fission, fusion, and anti-matter propulsion; the ship using those fuels must pay a premium to get them. Fuels like oxygen-hydrogen would be far FAR cheaper per unit mass and much easier to get but wouldn't be as energetic. So you could limit your ships based upon technology (they can't do fusion or anti-matter), resources (not very many places have the refining capabilities to extract the correct isotopes), and/or cost (if you're moving asteroid rocks, you're not going to pay the premium of high energy fuels). Hopefully, the game will allow the players to chose which things he moves using which trajectories. If he always selects methods using the high energy trajectories, maybe they eventually run out of those resources. For more information go my favorite world building resource, Atomic Rockets. [This is the link to the "mission tables"](http://www.projectrho.com/public_html/rocket/appmissiontable.php) which shows the $\Delta V$ required and time it takes to complete each trajectory. Just remember though that the minimum energy trajectory is essentially the Hohmann transfer to the nearest Lagrange point plus some additional $\Delta V$ for adjusting the trajectory at each subsequent Lagrange point. [Answer] > > How can I creatively reason to a player an imposed speed limit of his or her spaceship, given that in reality with constant acceleration a spaceship is only limited by the speed of light? I chose to limit the maximum velocity of a vessel, as it otherwise becomes (technically) impractical to engage with other spaceship in a (dogfight) combat. > > > If you're sure you want to limit the player to always having to do dogfight(I for one am an explorer type, so I'd just accelerate away every time), then you could for example limit the fuel in following way: The spaceships generate their fuel while not using their engines. This could be rationalized with a system of them bringing the components on board, but having to do some catalyst-process in order for them to create the actual compounds used as fuel. You can therefore only speed up for a limited amount of time before you require to "refuel". > > How can I determine the ideal size of an average planetary system, the number of planets > > > I'd go for as random as they can get. Maybe a young star only has a huge asteroid belt and no planets, while some stars can sport a dozen or so planetoids and moons to boot. There's no way to determine "realism" for the average planetary system, as we don't have the technology to really determine other star systems currently. But for the explorer, vastly differing systems would increase the interest. > > the time it could take on average to get a planet in the outer orbit to a planet closer to the sun, both in game time and real time? Ideally I would like the game to feel realistic and exciting to get across the planetary system, yet not feel too boring with longer periods of nothing happening. > > > This is going to have to be either/ or, but not both. If you go for any sliver of realism, then it's going to be boring for the action players. As an example, Elite Dangerous. Even with the automatic docking and star drives, the game still suffers from boredom of the huge distances, if you don't like the serenity of cruising around in empty space. The universe is huge and on average, empty. Take the known planets to have life divided by the planets that don't have life and we'll approach zero quite fast. The distances are at best only mind bogling, and this translates to hours of boredom, even with your accelerated time frame. Kerbal Space Program also provides a good idea on how boring it really can get with any amount of realism: KSP has the whole solar system with its furthest away planet closer to the Kerbol sun than the Earth is to Sol, and still it takes several hours to transit even to the closest moon. Granted, the craziest missions where they just basically go with solid rocket boosters to the Mun and back take but minutes, but that's besides the point. Don't worry on the realism, create a balance of fun and "that's just ridiculous". In a 2D game, the only realism to be had might be to pre-plan your escape from and entry to any solar system, using planetary masses to do a gravity assisted boost. But it only makes sense if the fuel for long distance traveling is scarce enough to justify not just simply turning the accelerator to 11 and aiming for your target. > > However, if people can simply see the prevailing prices on each planet beforehand, there is not much challenge for finding the optimal trade. I can cut the communication but then how can I reason to a player that they can only see the prevailing prices of goods when they visit a planet, however, not when flying in space? Is there any other way to make trade more challenging and reason it to the player? > > > You can make the tonnage affect the acceleration, therefore slowing them down and making it risky to try and haul a huge mass of cargo across the stars for a profit. The communication can be limited to either the nearest star systems. This can easily be justified with "signals can't go faster than light". This way you could have a system in play that shows a spreadsheet for the player on the known prices, coupled with the "age" of that information. These prices could even be updated on the fly, so as your flying closer to a star system, onboard computers update the price from signals coming from that planet(4 weeks old, 2 weeks old, week old, current). You could only show the player prices from their last visit to any known system, and a list of planets with a shortage on some cargo. Combine this with the previous signal limitation idea, and long hauls would almost always be a gamble in terms of profit. [Answer] 1. You could tell the player that using more fuel will, of course, make them fly faster, but they may not have enough fuel for a deceleration burn to go to another planet (or use any fuel to turn in a dogfight) 2. The size of the system will depend on the speed and acceleration you allow your spacecraft to have. Even if you could travel at the speed of light, it would still take several hours to fly from Earth to Pluto (at its closest!). 3. Limit the range of communication to some distance from each planet, and disallow superluminal comms. If they can't see the price until they are close (or if it takes say 5-10 real-time minutes for them to get a price update from a faraway planet), then there may be some trade challenges. Other methods could be locking in a price before taking off - for example, flying cargo from A to B, doing a flyby of C and seeing the price is better at C, selling there (and paying a penalty for cancelling the A->B route). [Answer] I would explain the speed limitation as a limitation of the deflector system. At very high relative velocities even tiny specks of spacedust pose a serious perforation risk. Just say your deflector shields can't reliably deflect dangerous objects moving faster than # relative to the ship. (This also gives you an excuse to force players to enter asteroid belts with the orbital flow rather than against, which might be an interesting tactical mechanic.) ]
[Question] [ Consider yourself a decision maker for a fledgling space infrastructure project. You've been tasked with establishing the first few extraterrestrial colonies for your species. What aspects of the Solar System's moons make them more (or less) attractive than other bodies (like comets, asteroids, and/or airless planets)? Are any of these clinchers (reasons that make it obvious to establish or avoid colonies on moons)? *09/30/2015 edit/addition:* I can imagine several reasons and/or constraints for a space colony: 1. As the first piece of essential space infrastructure 2. As a transportation hub 3. To become a self-sufficient colony 4. As life insurance for the human species 5. As a profitable venture As many of you have already realized some of these overlap. A successful colony would possess multiple aspects of these to some extend. But let me elaborate on some consideration. ### Location Space travel is more tightly constrained by the propellant budget (delta V) than the time scale. Other than finding safety from major solar events, one place is rather like another in space. Locations very distant from Earth (Deimos, Earth crossing asteroids, etc.) might be "very close" from a delta V budget perspective yet be very distant from Earth. Distance isn't the constraint, delta-V is the constraint ### Resources All colonies will require extensive resupply from Earth in the beginning. However, colonies located at sites with essential resources have a hope of becoming self-sufficient for bulk necessities (propellant, water, oxygen, plus construction materials) in fairly short order. Furthermore, a permanent settlement in most locations of the Solar System will require radiation shielding and radiation shielding requires mass. So a man-made settlement in mid-Earth orbit probably can not compete with other ideas unless an Earth crossing asteroid is brought into orbit and used for materials. Some resources are more valuable to the colony than others. A new colony will want large quantities of water, oxygen, nitrogen, and hydrogen to begin their closed cycle ecologies. A self-sufficient colony requires resources in bulk. ### Size Obviously, humanity's initial colony attempts will tend to be smaller so we can learn without endangering the lives of millions. But the number of people that we intend to settle makes a huge difference on which bodies would be viable sites. For instance, if the goal is to resettle a large portion of the Earth's population, Mars would have to be the main colony site. No where else in the Solar System has as much "hospitable" real estate as Mars. ### Energy If the colony is established outside of Mars orbit, then it will necessarily use a fission reactor (unless we assume fusion is available by then). From a mass perspective, it will likely cost more launch mass to power the colony using solar power than fission (unless something like a solar concentrator method is used). ### Communication The further away the colony is from Earth, the slower communication will be (both latency and bandwidth). ### Export Ultimately a colony trying to become a viable commercial venture will need to produce something for Earth and do so more economically than it can be done on Earth. The reality is, it competes with terrestrial markets, it is going to fail. The only location your colony has an advantage / barrier to competition is in space. So my thought is the colony will initially build and service satellites for Earth. Along with this, a colony with access to lots of volatiles (e.g. water) can be contracted to clear all the junk from terrestrial orbit. Incidentally, it'll provide the colony with a bunch of valuable already refined materials. As a side business it will do many other things (e.g. build fantastic astronomical facilities, perform probe flybys, serve as a tourist destination, and perform sample return missions for Earth) and these might be highly profitable but I don't think of them as high volume business. Unless there's a compelling reason why it makes more sense to do it in space than on Earth, initially the colony won't be in the manufacturing business. I understand that some process work better in space (it is possible to make better ball bearings in space - perhaps for very expensive high precision machinery? I've heard it is easier to control crystal growth too) but the colony's first goals will be to provide its own bulk materials. The low mass stuff requiring a lot of infrastructure will come later. ### Selection Criteria What I want is a location that provides: * Room for a colony of small size (50-500 people) * A convenient (from a delta V perspective) destination for Earth and other points of interest * Access to in situ resources - especially water, oxygen, hydrogen, carbon, nitrogen, and basic industrial materials/metals * Adequate radiation shielding * Adequate power * Ability to expand (from a room and resource perspective) * Not a necessity but bonus points for, providing a reason for tourist travel (view, uniqueness to the surrounding, etc.) * Not a necessity but bonus points for, providing the ability to establish or expand a manufacturing base (drugs, crystals, electronics, ball bearings, extra pure silicon for chips, and other items made best in zero gravity, vacuum, or both) FYI, my favorite McGuffites (reasons for going to space) are room temperature electrical superconductors, pure vacuum required for making very long (km+ length) carbon nanotubes, and alien artifacts. [Answer] It depends on your colonization goals. Note that this answer is specific to Earth's moon (Luna). I don't see much point in colonizing other moons. I'm going to mostly contrast with [this link](http://settlement.arc.nasa.gov/Basics/wwwwh.html) from NASA that Frostfyre posted. I would favor the moon for the following reasons: * I don't care about going back. As long as my human colonists are healthy in 1/6th of normal gravity - which is by no means a certainty - I'm ok with that. * I don't care about tourism, so the view, or lack thereof, isn't a major factor. * It provides free gravity, even if reduced. Spinning habitats complicates engineering. Building or digging in low gravity is presumably easier. * You can get materials and resources from the body you're on. It may be more efficient to go elsewhere, but if something goes wrong, I think a moon colony is more likely to survive and "rescue itself" vs an asteroid or orbital habitat. * It's in a sweet spot, location wise. It's always close to Earth, which means you have access to most of humanity and their resources if you really need it. On the other hand, it's far enough away that you can more easily defend yourself. If you get in a fight with a ground-based country, an orbital habitat is extremely vulnerable. Building on Mars makes it easier to defend, but harder to build up and the variable orbits make transportation a real pain. To sum it up (TLDR): Orbital habitats are too vulnerable to attack and will likely never be self-sufficient. The Moon is close enough to Earth to build a colony efficiently, but has the resources and is far enough away that you can eventually become independent. [Answer] Factors favoring moons over planets: * Moons are smaller in size so it is easier to terraform them. * Most planets we have discovered so far are much bigger than Earth. This means their gravity is too much for us (earthly organisms) to bear with. Moons, being smaller do not pose this problem. * Airless moons are easier to fill with an atmosphere because they are smaller and need lesser amount of atmosphere to form the same amount of atmospheric pressure. * Similarly, moons need lesser volumes of water to form a pan-lunar water body (ocean) to regulate temperatures. * Moons have lesser terrain variation than planets which makes habilitation easier. * Planets are larger than moons and hence have much greater gravitational pull. This means that most incoming asteroids get deflected towards planets, sparing moons. Factors disfavoring moons: * Most moons have too weak gravity so movement is much harder than on planets. * Most planets have a strong magnetic field while their moons have next to nothing (compared to planets) so that solar wind devastates moon while having little impact on a planet. * While a planet's high gravity pulls most asteroids towards itself, the impact damage of an asteroid hitting a moon would be dozens of time greater than if that asteroid had hit the planet. * Vortexes and typhoons are much more severe on moons than planets due to the greater temperature difference and lesser surface area of the moons. * Moons rarely ever have high enough elemental variety to support complex life. While sodium, potassium, oxygen, nitrogen, carbon, sulphur, calcium, phosphorous and chlorine are absolutely vital for earthly complex life, smaller amounts of vanadium, titanium, aluminum and magnesium etc are also necessary for health. Such a high variety of elements is extremely rare to expect on a moon but quite common for planets. * The tidal effect of the nearby planet would create huge tides in the oceans and might also gradually strip a moon of its atmosphere. [Answer] "Once you get to earth orbit, you're halfway to anywhere in the solar system." ~Robert A. Heinlein Early on in colonization, orbital mechanics and fuel sourcing will be the deciding factor in how your colonies spread. Although Earth has unimaginable quantities of resources, the atmosphere and gravity prevent those resources from getting places. In particular, it is impractical to source rocket fuel from the Earth's surface for long-term colonization projects because it takes so much fuel to lift the fuel, and the fuel needed to lift the fuel needs more fuel to lift it, and so on. It's known as the tyranny of the rocket equation. One of the reasons why NASA looks at the Moon as a stepping stone to the universe is because there is ice at its poles, which can be hydrolyzed into oxygen and hydrogen, providing reaction mass that can easily be transported off of the Moon's surface. Ideally you want a solid celestial body that has material that can be used as reaction mass for rocket engines, has little or no atmosphere to impede rocket launches, but has lots of gravity so spacecraft can achieve low, fast orbits. The reason you want low, fast orbits is for efficiency. The energy stored in rocket fuel is much more efficiently converted into useful velocity change (delta v) when a rocket is travelling at high speeds. When performing interplanetary transfers, the rocket needs to escape the gravitational sphere of influence of the near body AND it needs to have excess velocity to make the journey to the distant body. Having a high orbital velocity to start with makes it easier to achieve these excess velocities. "Why not just take off from Mars?" you might ask. Mars is actually a pretty good candidate, because of its thin atmosphere. But Mars is a planet, and planets are missing something: speed. The advantage of moons is that spacecraft taking off from a moon is already going around the planet at the speed of that moon. For Earth's moon, Luna, that amounts to an average of about 1 km/s (<http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html>) of velocity for free. "Why not use a comet?" Comets are crazy. The defining characteristic of a comet is that it has a highly eccentric orbit around the sun. This makes comets exceedingly hard to get to and from because the changes you have to make to your spacecraft orbit require huge changes in velocity. Once you get to the comet, you're pretty much done because there's not much material there anyway. "Asteroids?" Asteroid belts are dense by cosmic standards but surprisingly sparse in practical terms. Individual asteroids are pretty small and they are millions and millions of kilometers from each other. It's still not too bad if you have fuel and time to move between them. But again, getting to and from asteroids is tough because they don't have much gravity to capture an incoming craft. So moons are pretty good places to start because they are big enough to capture incoming vessels, big enough to make big orbital changes efficiently (fast orbits), are small enough to have very little atmosphere, small enough that it doesn't take a huge amount of fuel to get off the surface, and big enough to colonize and manufacture fuel for a long time. Tycho crater near the south pole of Luna has been theorized as a good place to start space colonization because it's near the ice cap, can receive sunlight all year round, yet has available shade because of the crater edge, and has all of the orbital advantages I just mentioned (except for being out of the Earth-Moon orbital plane, which increases fuel costs, slightly). So if low Earth orbit is halfway to anywhere, being perched on the Moon is about three quarters. [Answer] The best place to build a colony isn't on the surface of, or within, a celestial body, but rather in orbit. NASA has a good briefing on [Space Colonization Basics](http://settlement.arc.nasa.gov/Basics/wwwwh.html). In a short summary from the article: > > Because orbit is far superior to the Moon and Mars for colonization, and other planets and moons are too hot, too far away, and/or have no solid surface. > > > While we could build facilities on other worlds, I suspect the first step to colonization will be in orbit around a body, rather than immediately on the body. There's a whole host of issues pertaining to building a colony on a body: difficulty of getting to or from space, local weather, local atmosphere (or lack thereof), local geography, local geology, etc. Building in space has fewer variables. Note: This is a very extensive topic and not really suitable for the Q&A nature of SE. For a more in-depth examination, please read the linked briefing. ]
[Question] [ From what I can tell, pulsars emit light in beams from the poles of the pulsar. Would it be possible to construct something to get energy from a pulsar's beams of radiation? Or is this as idiotic of an idea as... erm, an idiotic idea. (I am not good at metaphors.) Would this be easier than building a Dyson sphere? [![Something probably idiotic](https://i.stack.imgur.com/KUY9P.jpg)](https://i.stack.imgur.com/KUY9P.jpg) [Answer] If your civilization has reached the point where it can build Dyson spheres, harvesting a pulsar is actually a good idea. However, a special consideration must be taken. Most stars produce energy through nuclear fusion at the core. Pulsars, on the other hand, are dead at the core. Their energy output comes from stored thermal energy, but mostly from a comparatively strong magnetic field. The field accelerates protons and electrons at the poles into relativistic speeds, thus generating the beams for which pulsars are famous. So you could, in theory, build a dyson ring or sphere (since they do radiate in all directions, just not as strongly as through the poles) around the pulsar and it would work just fine. However, you could also tap the source of the pulsar directly, and that should be more efficient - if only because there is one less energy conversion in the way. What you need is a toroidal coil of dysonic proportions. This is a toroidal coil: [![Toroidal core should be a power metal subgenre](https://i.stack.imgur.com/jUbaa.jpg)](https://i.stack.imgur.com/jUbaa.jpg) Have one of these circling around the pulsar, preferably slightlgy misaligned with the pulsar's rotation plane. With this power source your amps' dials will be able to go way past eleven! P.s.: All a regular dyson sphere does is passively collecting a stars' energy, without actually draining it. This dyson coil setup will however drain the pulsar and reduce its lifetime. ]
[Question] [ > > ...It's paradox. They left us these technological marvels, yet with all their might and knowledge they failed to prevent their own doom... > > > Excerpt from a lecture by the High Historian of Berlin Falls --- Welcome to a future. Mankind has brought doom upon themselves, their cities have been flattened by war and weather, and most of the northern hemisphere is radioactive badlands. They've managed to ~~avert~~ revert [global warming](http://tvtropes.org/pmwiki/pmwiki.php/Main/GlobalWarming), in the process creating a global society of an unprecedented scale. Air-travel got reduced to the bare necessities, and the railways underwent a renaissance. Closed stretches of track & stations all over Europe got reopened. Lines between bigger cities got extended to rail-arteries1. These arteries expanded to stretch all along the northern hemisphere, even connecting Berlin to Boston. ``` Arteries: - Central Europe, Russia, Kazakhstan, Beijing, Bering-Strait, Chicago, Boston - England, Central Europe, Spain, Gibraltar, Morocco - Kazakhstan, Afhganistan, India - Beijing, Hong-Kong, Thailand, Indonesia, Papua New Guinea, Sidney - Beijing, Korea, Japan - Chicago, Mexico, Colombia ``` Due to the lack of electrification of rails on the American, African and Australian continents scientists and engineers spent considerable efforts into advancing emission-free alternatives to [diesel-electric engines](https://en.wikipedia.org/wiki/Diesel_locomotive). A break-through was achieved in the field of [SRG](https://en.wikipedia.org/wiki/Stirling_radioisotope_generator) & [RTG](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator) technology. Taking a hint from space-engineering, [Radioisotope Heater Units](https://en.wikipedia.org/wiki/Radioisotope_heater_unit) (RHU) were expanded in size to serve as continuous heating elements in the boilers of [steam-electric engines](https://en.wikipedia.org/wiki/Steam_turbine_locomotive#Electric_transmission) - these engines would then be used for trains and ships. --- A typical train-engine would consist of a boiler in which 5 RHUs (~6 tons of [Radium](https://education.jlab.org/itselemental/ele088.html) per unit2) [superheat](https://en.wikipedia.org/wiki/Superheated_water) water or another conductor fluid in a primary fluid-cycle. Through conduction the heat in the primary cycle is used to superheat water to steam in a secondary water-cycle, which is then used to drive a turbine3 producing electricity. ``` ┌─────────────────────┐ ┌───────────────┐ │ ┌─┐ ┌─┐ ┌─┐ ┌─┐ ┌─┐ ╞══╗\|╔╡ STEAM TURBINE │ │ │R│ │R│ │R│ │R│ │R│ │ ║\|║└──────────────╥┘ │ │A│ │A│ │A│ │A│ │A│ │ ║\|║ ┌─────────┐ ║ │ └─┘ └─┘ └─┘ └─┘ └─┘ ╞⛒╝\|╚⛒═╡CONDENSER╞═╝ └─────────────────────┘ └─────────┘ ``` Assuming ~168W per kg of Radium4 and an optimistic efficiency of ~50% this gets us ~2500kW usable energy. Or about ~500kW per RHU. --- Q: Is this concept for an engine workable or are there game-breakers that I missed out on? A good answer: * addresses issues with the proposed design * proposes solutions to the addressed issues --- 1Lines with sections of up to 8 tracks next to each other in order to facilitate higher throughput. Sort of superhighways but for trains. 2Which results in cylinders of ~1m diameter and ~2m height (assuming we do not have to interleave the radium with too much other metal to get the heat out efficiently) 3Similarly to [how a Nuclear Power Plant works](https://en.wikipedia.org/wiki/Nuclear_power_plant#/media/File:PressurizedWaterReactor.gif), also known as [Rankine Cycle](https://en.wikipedia.org/wiki/Rankine_cycle). 4I've not too much knowledge in the area of nuclear physics, so I designed the described system based on [the very helpful explanations I got from @kingledion on the chat](https://chat.stackexchange.com/transcript/message/41910576#41910576). [Answer] A radiothermal train is a fun idea. Radium may be possible (given futuristic resources), though tricky, I'll need to give it more thought. Another fun possibility if you don't mind an actively controlled reactor is a natural uranium source, like in [the CANDU reactors in Canada](http://www.world-nuclear.org/information-library/country-profiles/countries-a-f/canada-nuclear-power.aspx). For passive systems though, I'm going to make my case for Polonium-210. One of the bigger issues of Radium and other seemingly suitable isotopes is the byproducts (or daughters), which are created in that isotope's decay chain. These byproducts would build up constantly in normal use and create technical problems or hazardous conditions. Keep an eye out for long-lived (= obnoxious) daughters, and any beta or gamma decays. To my knowledge, all of the common RTG isotopes have obnoxious byproducts, sadly, with one exception. If you're willing to hand-wave the production of the isotope, 210Po is rather ideal. It decays directly to a stable isotope of lead-208 through a low-ish energy alpha decay which is quite easy to catch and generate heat from. The alpha particles mostly stop with only a few cm of air, or completely stop in a few mm of water. Polonium-210 has an extreme activity, allowing smaller weights of it to be viable, even on a large train. From my back-of-the-envelope calculations, it would take 'only' about 40-70kg per train (an amount which would fill a ~6in cube). As a note, producing this with modern technology is flatly impossible. If it's easier in the future though... One convenience of Polonium is that it's fairly noble as a metal, in other words it doesn't rust or dissolve well in water unless there's a bunch of chloride in the solution. For this reason, it could be used in small chunks or even possibly as a thin (mm) plating of solid metal in the boiler or on the walls of the heat exchanger. If you wanted to use it in water solution instead, it's soluble in 3%HCl, or more simply in EDTA (like in shampoo). Without either HCl or EDTA (or similar) it automatically tries to plate itself out of water solutions as metallic Polonium. A downside of HCl is it attacks Copper and Iron, common heat exchanger materials. A radiothermal train would be producing heat constantly, so it would need to be constantly boiling water, even when not moving. This could be very obnoxious, because water tends to leave deposits and scales on boiler / heatEx equipment and without an obvious opportunity to clean them they could become ineffective or (frighteningly in this case) leaky. Because Polonium-210 has an extraordinary activity and decent bioabsorption, it's a nefarious toxin (worse than cyanide). The good news is it has a very short halflife (138 days), so spills would lose toxicity within decade. The immediate effects would be devastating though, and would travel freely with ground water if using the solution form. Also because of Polonium's short halflife, the trains would need to be refilled regularly, perhaps making the 'chunk' version more appealing. Lastly, the alpha particles would cause wild amounts of embrittlement in any metals within striking distance. The Polonium would need to be held well separate from anything critical. I think I could keep going for a while about little quibbling engineering problems a radiothermal train would face, but it's wonderful concept that doesn't break any major laws of physics while having just enough troubles to make it interesting for the people stuck aboard. Math for amount of fuel required on a radiothermal steam engine: 2ton coal /hr [reference](https://www.quora.com/How-much-coal-does-a-steam-locomotive-use-per-hour]) 19.48 \10^6 BTU / ton coal [reference](https://www.eia.gov/tools/faqs/faq.php?id=72&t=2) 1055 J/BTU , 3600 s/hr ~6MW heat 141W/gm Po-210 [reference](http://mragheb.com/NPRE%20402%20ME%20405%20Nuclear%20Power%20Engineering/Radioisotopes%20Power%20Production.pdf) 42kg Polonium-210 per train. Polonium's quite dense at ~9g/cm^3 resulting in something like a 17cm cube of polonium. A cube would explode though, so let's assume small chunks or a plating. Best of luck with your world! Also, I really like your ascii art. Edit:* I noticed that a train to last through a nuclear winter would be handy, so I put a bit more work into this. It seems that Sr-90 would also be appropriate, with the advantage that it has a much longer (29yr) half life. A train would require about 1500kg of it, and beneficially it's available in large amounts in nuclear waste. Sr-90 undergoes beta decay (medium-nasty radiation) to make a daughter which also quickly beta decays to something nice and stable. Beta radiation is best caught by acrylic plastic, though a few cm of water would work as well. [Answer] Problem: You will not get 50% efficiency. Nuke plants run at about 30% for safety reasons, the same rules would apply to your trains. Thus you need to increase your powerplant by 50%. Clarifying this: Your efficiency is limited to the Carnot limit, which is a function of temperature. Since nuclear power doesn't have an inherent limiting factor like combustion-driven power you need to keep the temperature farther away from the point your system breaks--for fission plants that ends up being 30%, I would figure the same factors would be at work here and thus the same limit. Problem: You also have to dissipate 5,000kw of waste heat. Major woe if anything goes wrong with your cooling system as there's no off switch possible. Expect any serious train accident to turn into a nuclear accident as your system bakes itself. ]
[Question] [ Santa's reindeer are pretty awesome. They can stand on arbitrary planes (giving the illusion of flight, the reindeer are actually running on n-dimensional hills) and can dilate time in a bubble around Santa without tidal effects tearing holes in the universe. This lets Santa and the sleigh make as many trips to and from the North Pole as needed in order to deliver all the gifts (uncompressed) moving as the crow flies. But for all their skills the reindeer still have to eat, and for them time passes as normal (though they're immortal, naturally). The question then is how many calories must 9 reindeer consume in order to deliver presents worldwide, assuming the presents are located at the North Pole and the reindeer are otherwise normal reindeer. For bonus Christmas sparkles: what is this in oats (dry weight) [Answer] [An article on Oilprice.com](http://finance.yahoo.com/news/much-biofuel-santa-reindeer-230000992.html) estimates the amount of switchgrass Santa's reindeer would consume using analogs to biofuel production, which has some interesting data but I dislike their analysis. Useful data from his [oil article](http://oilprice.com/Energy/Energy-General/How-Much-Oil-Is-Needed-To-Power-Santas-Sleigh.html) includes: 1. Santa needs to travel around 226 million miles to deliver all of the presents to the world’s children. 2. We do know that mules and oxen can go roughly 15-20 miles per day. 3. We also know that a typical livestock animal might need to eat around 1.5 percent - 2 percent of its bodyweight in forage feed (depending on the nutritional content of that feed). 4. We also know that a male reindeer weights 350-400 pounds. 5. Santa’s reindeer are probably on the more muscular end of that scale, meaning that they’d need to eat about 2 percent of 400 pounds, or 8 pounds to be able to fly 15-20 miles. 6. Update. My assumptions were wrong, so I've updated this answer below! So, this is "forage feed," your hay and grasses. According to [Dayville Hay and Grain](http://www.dayvillesupply.com/hay-and-horse-feed/calorie-needs.html), 8 pounds of Hay (a mix of Alfalfa Hay and Timothy Hay, because we're running up against a lot of assumptions and estimates here) runs up to 7,124 calories. So, the "fuel economy" of a single reindeer, dashing up and down hills (average them out to flat) is about 407 calories/mile (7124 / 17.5). Santa has 9 reindeer, so his sled's "fuel economy" is 3,664 calories/mile. 828,012,342,857 calories in mixed Alfalfa and Timothy Hay. This doesn't include trips back and forth to the North Pole, because I don't know what the sled capacity is for toys, and therefore I cannot calculate how many north pole trips would be required. With the fuel economy figures provided, you can add on however many additional miles you deem necessary. Using the same reference material above, *Santa's reindeer would need to eat \\662,409,874 lb (331,204.937 short tons) of premium feed oats. That comes up to 73,601,097 lb (36,801 short tons) each!* Bonus round: To grow that much oatage you would need 103,501.5 acres of land, assuming a decent harvest for silage [source](http://www.midwestforage.org/pdf/179.pdf.pdf). To get that much, you'd need to plant an area at least half the size of Rhode Island in nothing but Oats, just for consumption this one night. ALSO UPDATE. According to the San Diego Zoo, reindeer would actually eat about double the numbers above. The exact numbers depend on the specific animal and their workload, but we can give an estimate of 1,324,819,748 lb (662,409 short tons) of premium feed oats. This would require oat production across the entire state of Rhode Island to produce the food burned this one night. [Answer] With the exception of the "time dilated bubble", which makes the question quite meaningless in regards to energy calculations. You can get an idea of that actual cost of energy to move presents to all children in 24 hours. Solving this with conservation of energy Using the 226 million mile (360 million km) number for how much distance the presents need to go from Zoey's answer and assuming a 24 hour time for all presents to delivered. This averages to about 4 million m/s. Which is ~1.3% c. Just using: $E\_k = 1/2 mv^{2}$ then multiplying by 2 to get the acceleration and deceleration. Allowing Santa to pre-accelerate the sleigh for 24 hours before Christmas so he is at max speed the second Christmas starts. Even ignoring the effects of relativity, that is ${2\10^{13} J}/ kg$ of energy needed to accelerate and then decelerate reindeer. That is about $5\10^{12} cal/kg$. So for 9 reindeer of ~200 kg each makes about 2000 kg. So total reindeer takes about $1.0\10^{16} cal$. Which is about 12000x the amount in Zoey's answer. If you are using the area of rode island to farm the oats in Zoey's answer, you'd need about 12000x as much land, which is about 10 million $km^2$, the size of Canada. There isn't enough farmland in the world to do this. Zoey expected a linear relationship between energy and speed which is not true. Kinetic energy rises to the square of the velocity. So all the accounting for how much energy a reindeer takes to go 10 miles would not work here. If you expect each present to be about 1 kg and about 2 billion presents, you'd get a total energy of $10^{22} cal$ for the presents. This would is about a billion times the energy of just the reindeer. This is about 100x the energy consumption of the world per year.* Note: This is assuming a perfect engine and that there is no air resistance and that the sleigh only accelerate and decelerate 1 time. This also means presents are basically taking the whole 24 hours to slow down while being delivered. This is a minimal answer and probably underestimate the actual amount by a couple million order of magnitude if you want Santa to actually slow down at each house and personally deliver the presents. ]
[Question] [ Would a creature similar to semi-aquatic slime mold living on a mostly freshwater planet with shallow seas be able to build technology to the extent that modern humans do? Assuming that each individual cell in the slime mold had a form like that of amoeba in the genus Chaos and had organelles that effectively work as dna computers, would the collective be able to have an intelligence greater than or equal to that of a human if each colony contained, say, 100 billion of the single cells? And finally, depending on if the answer to the previous question is yes or no, would colonies have the capability of working together to achieve common goals? Any help would be greatly appreciated, and thanks in advance [Answer] Welcome to the site Theocles. First, no. While there are some [examples of colonial](https://en.wikipedia.org/wiki/List_of_symbiotic_organisms) organisms working together, creating modern tech requires significantly more specialization than your microbial colony would be capable of. Each and every one of your microbes still have to worry about and deal with the day to day requirements of...you know, staying alive. In the human body on the other hand we have cells whose sole function is to support other cells so they can focus on making us think, move, etc. So cell specialization is what at the base makes intelligence possible, and while colonies of single celled organisms have been know to specialize to a degree (after all how do you think we came to be) remaining in that state would preclude the possibility of intelligence. The organisms certainly can work together, but not in a human, intentional, "Hey let's go build a house" kind of way. [Answer] It is not exactly microbial civilization, but this answer about [living planet](https://worldbuilding.stackexchange.com/a/2803/687) might satisfy your conditions. It is my favorite alien mind, Solaris. [Answer] Human intelligence comes from the human brain. Crow intelligence comes from the crow brain. [Crow intelligence](http://io9.gizmodo.com/crows-could-be-the-key-to-understanding-alien-intellige-1480720559) is interesting because it developed separately from human intelligence, and that development resulted in a different brain structure, leading some to assign them "alien intelligence". In both cases this development was the result of evolutionary selective pressure. In other words, those individuals who had larger more developed brains than others, received benefits from them that outweighed the costs, such as weight and extra energy consumption. In order for your slime mold to develop intelligence, there would also need to be a similar selective pressure. The development of a brain might not be required, if you consider the "intelligence" to be a phenomena that emerges from the collective, as we see with ants for example. But ant collectives [aren't all that smart](https://www.youtube.com/watch?v=JWZnWcw0a44), despite each individual ant being far more complex than a single slime mold cell. But at the very least for your scenario to become possible, there would need to be a selective pressure that made slime mold more successful at reproducing if its colony exhibited more intelligence than other colonies. And this pressure would need to continue to apply all the way from very basic intelligence up to the advanced intelligence you are seeking. To examine the selective pressures that resulted in the evolution of the brain, and eventually sentience, in vertebrates, you could read up on the [evolution of the brain](https://en.wikipedia.org/wiki/Evolution_of_the_brain#Early_history_of_brain_development). ]
[Question] [ We all know how the story starts: > > He woke up in strange room, not remembering who he was or how did he got to the room. But that was not his problem. Problem was the first writing he saw: "HELLO, I WANT TO PLAY A GAME" > > > The thing is, what kind of drug could Joe Average eat to let him forget almost everything? And if you cannot be drugged to forget your own name, what drug would let you forget the past? (And as long to the past as possible). Bonus points: What would be side effect of such drug? [Answer] Most amnesiac drugs only work while they are in your system, making it so that new memories can't be recorded, without messing with old stored memories. This is really useful for anesthetic, since if someone is having open heart surgery you really don't want them to remember anything afterward. One of these drugs that has been misused is Rohypnol. There are a few drugs that are in the highly experimental stage, meaning they have never been tested on humans, which can wipe out past memories. (Un)fortunately, since they've never been used on people, we don't really know what the effects would be. a zeta inhibitory peptide [(ZIP)](http://scienceblogs.com/purepedantry/2007/08/20/the-amnesia-drug-frightening-b/) is a drug that inhibits the protein called PKC zeta, which is needed to maintain long term memories. There is a lot still left to learn about this area, but it looks like it would erase past memories, [while allowing the subject to learn new things](http://www.sciencedirect.com/science/article/pii/S1074742714002081). How much stuff gets erased is unknown. So it could work for your story, or the guy could end up as a mental infant again, but it'll probably be many years before we know which outcome is most likely. ]
[Question] [ I'm looking for a way to render a large percentage (30 to 50%) of Earth's human population infertile in about 10 years. Medicine and tech levels are approximately where they are now, maybe slightly more advanced. * Sterility is permanent. No medical advances in the next 30 years will be able to undo the damage done. * Absolutely non-lethal. Whatever makes people sterile can't kill them. * People don't know that they have been rendered sterile till they attempt to have children. * Common infertility tests will detect the infertility. * Men and women are equally affected. * The effect is global by the end of the 10 years. * Wild life is unaffected by this event. They continue to reproduce, same as they always have. This is a [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") question so a minimum of hand waving, please. Journal articles, equations or other authoritative sources are nice to have but not required in your answer. [Answer] ## Gasoline Additive Gone Wrong Rendering 30 to 50% of humanity infertile is a challenging prospect. That's a lot of people spread over a very large area that the OP requires become infertile in a short period of time. We already have an example of where a man-made environment toxin can have significant health effects in the form of [Tetraethyllead](https://en.wikipedia.org/wiki/Tetraethyllead) (TEL). It has been [widely linked](http://www.bbc.com/news/magazine-27067615) to increased crime and brain damage in children. When tetraethyllead was removed from fuels, crime rates began to drop. There are approximately [70,000 chemicals](http://www.psr.org/chapters/boston/resources/patient-fact-sheet.pdf) in use in industrial and commercial environments. Few of them have any kind of testing for toxicity or biological impairments. Surely we can use one of them that causes infertility but no other noticeable side-effects. Let's assume we've found one and it also has a highly desirable effect on gasoline efficiency. The additive adds 15% efficiency to gasoline. A huge industry for this additive will have a sales force dedicated to spreading it as far across the world as possible, in much the same way the TEL industry spread TEL across the world. Since there are no known side effects, any opposition to the additive won't appear for 10 or 20 years after it's introduction when birth rates among 20 to 40 year-olds drops for no good reason. The additives industry will be able to persist for several years or decades on the backs of misinformation campaigns and expensive lawyers who win lawsuits. Since [53% of the world lives in cities](http://kff.org/global-indicator/urban-population/), we have ensured that at least 50% of the world population have been exposed. Some in the cities will evade infertility because of quirks in their biology. Similarly, out in the country where exposure is lower, some will also become infertile because of enhanced weakness to the additive. [Answer] I agree with [Max Williams](https://worldbuilding.stackexchange.com/users/4922/max-williams): a virus is a plausible candidate. Especially considering [it is already suspected that viruses causing infertility do exist in real life](http://news.bbc.co.uk/2/hi/health/1620174.stm). A virus that spreads and mutates like flu and that targets the special cells that are sperm and ova, that only have one of each chromosome instead of two. To look at your requirements: > > Sterility is permanent. No medical advances in the next 30 years will be able to undo the damage done. > > > Virus infections cannot be cured. The best you can hope for is to halt the symptoms until the body deals with the infection. As is shown with HIV/AIDS, some virus infections will not be dealt with by the body. And for instance the Varicella Zoster virus that gives chickenpox can live in your body for decades and then break out in shingles. > > Absolutely non-lethal. Whatever makes people sterile can't kill them. > > > Virus-infections are mostly non-lethal. > > People don't know that they have been rendered sterile till they attempt to have children. > > > There are many examples of asymptomatic virus infections. These are called [subclinical infections](https://en.wikipedia.org/wiki/Subclinical_infection). > > Common infertility tests will detect the infertility. > > > If the virus infection creates bad quality sperm or non-viable ova, that will be detected upon examination. > > Men and women are equally affected. > > > With the premise I stated above: check. > > The effect is global by the end of the 10 years. > > > Virus infections can easily go global. Flu - again - is a prime example. The common cold as well. > > Wild life is unaffected by this event. They continue to reproduce, same as they always have. > > > Virus infections are often species specific. [Answer] # [Chemical castration](http://en.wikipedia.org/wiki/Chemical_castration) Cyproterone acetate [Cyproterone acetate](http://en.wikipedia.org/wiki/Cyproterone_acetate#Dosage_and_administration) is one choice for chemical castration. [Hormonal Therapy for Male Sexual Dysfunction](http://books.google.com/books?id=in_DuQFgcJMC&pg=PA104&hl=en#v=onepage&q&f=false) describes it as a "potent, dose-dependent antiandrogenic and progestational agent" which can block "T and estrogen synthesis in the gonads" - meaning that it can work for women as well as men. To replicate the (potentially potent) effects shown in studies, cyproterone acetate must be taken orally daily, generally in doses of 50-200 mg. However, it can also be taken as an injection every week in doses of 300-600 mg. [Transsexual and Other Disorders of Gender Identity](http://books.google.com/books?id=I-8qZlGIpnQC&pg=PA174#v=onepage&q&f=false) notes that there may be side effects, notably liver problems and depression. However, these would not be attributed right away to a drug like this. While oral treatment is generally supposed to be undergone every day, [Jeffcoate et al. (1980)](http://www.ncbi.nlm.nih.gov/pubmed/6777092) were able to produce effects lasting for up to 28 days in special cases of tests. Depot medroxyprogesterone acetate I'm also currently investigating the usage of [depot medroxyprogesterone acetate](http://en.wikipedia.org/wiki/Depot_medroxyprogesterone_acetate), which is often better known as Depo-Provera. It should be similarly effective. Delivery For advice on this, I went to the question that drew me to Worldbuilding, [How do I drug a population in the most efficient way?](https://worldbuilding.stackexchange.com/questions/843/how-do-i-drug-a-population-in-the-most-efficient-way). For the oral option, there is the old fallback of conspiracy theorists: Putting it in the water supply. granted, dilution would have to be accounted for, but it's a possibility. The other, better solution is [TimB's suggestion](https://worldbuilding.stackexchange.com/a/848/627) for that question: periodic vaccination. The downside is that this isn't a once-and-done procedure. However, it satisfies all of the other requirements, as far as I can tell. That said, I am not aware of any extremely long-term studies, so it is possible that Jeffcoate et al.'s lasting effects cold be replicated and extended far beyond 28 days if dosage is upped and extended for longer periods of time. [Answer] I'd think that a virus would be the way forward. It would need to have the following characteristics: * extremely infectious * very long dormancy period, eg at least 5 years, before having any effect * targeting a specific element/function of the female reproductive system (if we target male fertility, women can fall back on the large amounts of frozen sperm in sperm banks) * no other symptoms besides the infertility. * mutating, so hard to vaccinate against. You have a requirement that men and women are equally affected - this will be difficult to achieve with a single virus so maybe you'd need one virus per sex and let them spread independently. It's likely that some people would be naturally immune to the virus due to various unique characteristics or mutations. [Answer] First, you need people around a world to hook up on some very popular habit. It has to make them feel a little better for short time, or even just give them an illusion of feeling better. It also should make them look cool among their peers, especially at young age. Surely, as the common saying goes, everything good in life is illegal, immoral or causes obesity, and your habit should also have some known bad side effects. But those effects should be delayed in time. Essentially people at the age of 15 will be given a choice: look cool now and risk 10% higher chance of cancer at the age of 75, or have no friends for being a dorky nerd. In the meantime you can spread unproven rumours that your habit have some good side effects, for example it helps to lose weight. No doctor ever confirmed it, nobody knows anyone who actually lost any weight thanks to it, but someone read about it somewhere, doesn't even remember where, so it must be true, right? Now you wait. After some time people will get used to the fact, that they keep hearing exaggerated stories how bad that habit is, and they will learn to ignore them and dismiss them, for the sake of short time gains. You have to die of something sooner or later, right? Might as well be cancer. So even when half of medical world will be screaming bloody murder that everyone hooked up on that habit is slowly but steady losing fertility, that voice will be listened to, acknowledged, and then everyone will leave the room for a smoke break, including half of those, who were just preaching how bad cigarettes are bad for your health. <http://www.webmd.com/smoking-cessation/news/20100910/smokers-sperm-less-fertile> ]
[Question] [ When you look at the history of earth, the last ice age had major impacts on the flora and fauna of the world as well as biological migration. If I am creating an earth-like world and am developing a history for it, does that history need to include ice ages? Are they a forgone conclusion in the way earth works? A follow-on question: if it is realistic that an Ice Age does not occur, how would that impact the flora and fauna of the planet? [Answer] I think the answer is they are required for an earth like planet...extended periods without ice? most definitely...but to completely eliminate it, you need a way to explain several occurrences: Maunder Minimum. In 1645, our sun went through a cold spell where the number of sunspots fell to a low, including 0 for several years in a row. This activity, or rather lack of activity, threw earth into a mini ice age. It's likely that the Maunder Minimum is a far reaching cycle, and much more 'reduced periods of activity' have occurred through our suns life cycle. So you pretty much have to assume the sun is constant for no ice ages to occur, and I think we already know better than to think our sun isn't readily changing year to year. Asteroid and volcanic activity. Any large scale impacts or eruptions will bring along a nuclear winter type scenario where the globe will experience at very minimum a mini-ice age. An young planet formed when the galaxy was much older might be more insulated from asteroid impacts? A hyper active tectonic plate system might prevent large eruptions from occurring by using the energy that would create a volcanic eruption and relocate the plates with that energy instead? Not sure how realistic any of this is. It is possible to take a period in the Earths existence and say that there wasn't any ice ages in that period...but it's near impossible to say that an earth like globe would never have an ice age. Lacking an ice age will have a few key changes on your globe...I doubt something like the grand canyon could actually form without the influence of glaciers. Your land will be much more rugged and lack the soft sedimentary layers that glaciers can cause. It's possible that your terrain will completely lack extended flat plains. > > if it is realistic that an Ice Age does not occur, how would that impact the flora and fauna of the planet? > > > Realism aside...ice age's are one of the key attributes that forces evolutionary change on a greater scale. Ice age's kill...it's an event that operates on a global scale and can be responsible for great stresses to be put on entire species. A global flood brought on by melting glaciers is what possibly eliminated all large species on the North American continent. So without them... * Bigger creatures. Mass climate change is the extinction force on large creatures...small can adapt faster. Without ice ages, large creatures would continue to get larger over longer periods of time * More diversity within species. Same as above...ice ages for extinction and reduce the earth to the species that can survive an ice age. No mass extinction event, more genetic lines of the same specie surviving, more inter-specie diversity. * lack of mammals? Lets face it, warm blooded may never dominate if the extinction force on cold blooded creatures never came to bear. Without an extended ice age, why would warm blooded creatures come to dominate the globe? [Answer] In the past, Earth experienced long eras without ice ages. On the opposite, in the last couple of millennia, we had several ice ages. You could decide that the last ice age occurred several thousands years ago and that the next ice age might only happen in several thousands of years. As [The Glis Jackel said is his answer](https://worldbuilding.stackexchange.com/a/2673/29), the causes of ice ages can be varied. And if you have a planet similar to Earth, it's likely that the planet will experience some during the course of her life. Other factors that could lead to a glaciation: * Impact with a large asteroid. * Decrease in solar activity. * Change in the axial tilt of the planet. This is very likely to happen if your planet does not have a large natural satellite. The Moon help in stabilizing Earth. * Earthquakes can modify the planet axial tilt too, if they are strong enough. It is a small variation but with time it can make a real change. * Change in the planet's orbit. * Life can change the atmospheric composition. For example, the first living organisms introduced more oxygen into the atmosphere. And now we are making the planet hotter with carbon dioxide. > > if it is realistic that an Ice Age does not occur, how would that impact the flora and fauna of the planet? > > > Without ice ages. it's business as usual. Life need to adapt when there is an ice age and many species become extinct because they could not adapt to the changing conditions. The can also go elsewhere but it's not always possible. Not having any ice ages would have an impact on hydrology and on the geography. Most lakes in the northern hemisphere where formed because of the ice ages. Without past ice ages, the Great Lakes would probably not exist. This would surely have an impact of life but the area would still have a good amount of precipitations. Since it's not the main point of the question, I will put a link to this topic here: [Creating a realistic world map - Erosion](https://worldbuilding.stackexchange.com/questions/1020/creating-a-realistic-world-map-erosion) [Answer] According to this [website](http://geology.utah.gov/surveynotes/gladasked/gladice_ages.htm), Ice Ages can be caused by the shifting of tectonic plates, changes in atmospheric circulation patterns, and volcanic eruptions. So by this, as long as your planet can change any of those (since it's an Earth like world it can) Ice Ages are possible and most likely would have happened. I am unsure about changes to organisms on your planet though. [Answer] Ice ages occur only rarely. [The earth has spent most of its time without them.](http://en.wikipedia.org/wiki/Ice_age) They seem to occur in clusters apparently caused by alteration of heat flow around the planet cause by continetal drift altering ocean currents. If we shape the question to mean: Is it possible for a terrestrial planet to exist for billions of years with continents always sliding around, without ever hitting a configuration that causes ice ages? Unlikely. At some point a terrestrial planet will likely have an ice age. But there is likely some critical threshold of landmass vs ocean surface below which the continents are not large enough to ever block heat transfer to stop trigger an ice age. ]
[Question] [ Some Science fiction stories have generations growing up on Mars would be a lot taller 7'+. How would growing up on a much lower gravity planet affect a mammals size? I understand bone density would likely be an issue. What are the other health concerns? [Answer] For mammals, things like height are mostly controlled by DNA. So the difference wouldn't be huge. But there would be a few differences. # Size Astronauts grow about two inches during their time in space. This is because the effects of gravity compress your spine on Earth. When gravity is no longer affecting you, your spine expands again (the spine expands because it absorbs moisture from your blood). This would also happen on Mars, because gravity is less strong. So people would probably be half an inch to an inch taller on mars.[1] Lighter gravity means less force on us pushing us down. That means our bones would likely get smaller. If our bones didn't get smaller, then we would more easily be able to support bigger weights. Large people would be less heavy and probably more agile. # Muscles Without the constant fighting of high gravity, our muscles would weaken. If we moved to Mars, our muscles would adapt Mars gravity, so they would weaken. This would not be a big deal unless we planned to return to Earth, in which case we might not be able to support ourselves. Our heart would also get weaker, but it would probably not affect us to much because it would not need to be as strong. There would be less fighting it.[1] # Development Gravity is important for cell [differentiation](https://en.wikipedia.org/wiki/Cellular_differentiation) [2]. In other words, for a less complicated cell to turn into a more complicated cell. The most immediately critical effect of this is bone cells. Bone cells have trouble attaching to the bones without gravity. There are speculations that gravity actually helps bone cells know where to attach. Immune cells are also affected, so the entire immune system would be effected. However these effects have only be observed in micro gravity or no gravity. So these likely would only be an issue during the ride too Mars, and the vehicle transporting the people could have artificial gravity. ### Reproduction The biggest problem about low gravity and development is reproduction. When a baby forms, its cells differentiate often. If cells were unable to do this properly, then babies could not form.[2] The sperm and egg combining in space is also an issue. The enzyme that causes the sperm to stop when it attaches to the egg doesn't work very well in space. Low-gravity may cause this same issue.[3] There is also an issue that This is, again, more of an issue in micro-gravity, but it should still be considered. Overall, likely development would be fine on Mars, but it needs to be considered how to safely get there. Also, it is possible that these issues would show up in a more minor form in a low gravity area. --- [1]: [Main reference article.](http://www.evolutionhealth.com/Inversion_Therapy/Gravity_Inversion.html) [2]: [This Wikipedia article](https://en.wikipedia.org/wiki/Gravitational_biology). [3]: [This YouTube video](https://www.youtube.com/watch?v=jTL_sJycQAA) does a good job explaining the health effects of zero-g (which could parallel the affects of low gravity). ]
[Question] [ This is my first post on these forums, sorry if I've accidentally overlooked any rules or etiquette. Please let me know if more detail is necessary or would be helpful. This question is about a specific species in a setting I'm developing but I'd like to know if the concept is possible before getting into too much detail and wasting anyone's time. I'm wondering if a land-dwelling species would be able to generate electricity the way electric fish do, with an electrocyte organ and electric organ discharge (EOD). From what I understand, the water surrounding an organism keeps it from being electrocuted during EOD since the water acts as a conductor for the current. Would a non-aquatic animal be able to actually biologically generate and discharge current (and utilize it as a defense mechanism to deter predators that have them compromised through direct contact when fleeing isn't an option) without just shocking itself? Would the size of the creature be significant in determining whether or not this is a possibility? Would they need some kind of conductive biological grounding to distribute the charge and minimize harm to themselves when discharging? What other factors would I have to consider developing a non-aquatic creature with this ability? Edit: I appreciate the suggestions to do with the other thread. I had not seen that thread even though I looked for more threads to do with electricity. I like the idea and am considering it! However, my question is about bioelectrogenesis which involves an electrocyte organ and EOD. While the triboelectric static charging idea is interesting and certainly fun to consider, it is not what I am asking about and I'm not sure if a significant enough charge to deter predators could be built up via friction without being released at inopportune times. I want to know if it is possible for a land-bound creature to effectively utilize an electrocyte organ. If I understand correctly, triboelectric static buildup would release on contact with many things the creature could touch aside from predators. The electrocyte organ fires only when the animal needs it to--like an eel sending out electric pulses to detect prey, or discharging electricity to incapacitate prey--and generates electricity internally, rather than through external friction. I hope that makes sense. Thank you. [Answer] There are a few Earth species that use electricity naturally. [In this website's list](https://www.thedodo.com/shocked-11-animals-you-didnt-k-949555818.html) we can see that beside aquatic animals, some land based animals can use electricity too. What Electricity is already used for on Land : * Sensor that can detect small electromagnetic or electrostatic fields, such as Echidnas, Bees. * Electrostatic-glue on-demand to climb vertical surfaces or head down such as Geckos * Trap that automatically catch surrounding foes such as a Spider's web Considering the Gecko, we could argue that its capability is a small EOD, so my guess would be it's possible en theory and practically. Taking aquatic species into account it's not unrealistic (IMO) that an land-based animal can use electrical discharge as a defense mechanism. The smaller the animal, the easier to believe. The closer the discharge, the more plausible. Please also note that the less massive a creature is in weight the less it is subject to gravity and the more it to subject to electromagnetic fields, so electricity is a big thing at a fly-scale. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. Epimetheus is a planet with about three times the mass of Earth orbiting a sun-like star in the Andromeda galaxy. However, two major factors separate Epimetheus from Earth. First, it has a thick atmosphere heavy in carbon dioxide and other greenhouse gasses which formed early in its history as a planet, and second, it's much further from its star. In the game of life, Epimetheus is far from an ideal candidate for harboring abiogenesis. A thick atmosphere may warm its surface, to some degree, but at the risk of increasing pressure too much and converting its surface water into more exotic forms of ice. Can the thick atmosphere found on Epimetheus make its surface conducive to harboring life, even if it lies outside of the generally proscribed habitable zone? How far away from its parent star could such a planet reasonably be found at and still support life? [Answer] I agree with [Tim B’s assessment](https://worldbuilding.stackexchange.com/a/38285/627) that this is a complicated question. However, I disagree on just why this is the case. The characteristics of the star are well defined, given that it’s a solar analog. From this, we immediately have mass, luminosity, and other characteristics. However, the reason I think that this is not a simple question is that there are a lot of conflicting models of the effects of different greenhouse gases and of the circumstellar habitable zone. I’ve tried to choose the best ones, but they’re only approximations; the exact fate of Epimetheus will require some deeper thinking. # The Greenhouse Effect Disclaimer: This section is mostly me muddling through a topic I’m not too familiar with. Radiative forcing I’ll start by assuming that the main source of atmospheric warming comes from [radiative forcing](https://en.wikipedia.org/wiki/Radiative_forcing) because of the various greenhouse gases in the atmosphere. Radiative forcing is the difference between the amount of sunlight absorbed by a planet and the amount of sunlight emitted back into space. The difference between absorption and emission is primarily due to the atmosphere. Radiative forcing causes a change in surface temperature, which is proportional to the radiative forcing: $$\Delta T\_s=\lambda\Delta F\tag{1}$$ where $T\_s$ is surface temperature, $\Delta F$ is radiative forcing, and $\lambda$ is the [climate sensitivity](https://en.wikipedia.org/wiki/Climate_sensitivity) of the planet.1 For Earth, $\lambda\approx0.8$, and without more detailed data on Epimetheus, I’ll have to assume that it’s about the same there. Each greenhouse gas contributes differently to radiative forcing. The [IPCC Second Assessment Report](https://ipcc.ch/ipccreports/tar/wg1/pdf/TAR-06.PDF)2, 3 gives a chart (Table 6.2) of approximations of expressions for radiative forcing contributions from several of the major greenhouse gases (CO2, CH4, N2O, CFC-11, and CFC-12): $$\begin{array}{\|c\|c\|c\|} \hline \text{Trace Gas} & \text{Simplified Expression} & \text{Constants}\\& \text{Radiative Forcing, }\Delta F \left(\text{Wm}^{-2}\right)\\ \hline \text{CO}\_2 & \Delta F=\alpha\ln\left(\frac{C}{C\_0}\right) & \alpha=5.35\\\text{} & \Delta F=\alpha\ln\left(\frac{C}{C\_0}\right)+\beta\left(\sqrt{C}-\sqrt{C\_0}\right) & \alpha=4,841,\beta=0.006\\\text{} & \Delta F=\alpha(g(C)-g(C\_0) & \alpha=3.35\\ \hline \text{CH}\_4 & \Delta F=\alpha(\sqrt{M}-\sqrt{M\_0})-(f(M,N\_0)-f(M\_0,N\_0)) & \alpha=0.036\\ \hline \text{N}\_2\text{O} & \Delta F=\alpha(\sqrt{N}-\sqrt{N\_0})-(f(M\_0,N)-f(M\_0,N\_0)) &\alpha=0.12\\ \hline \text{CFC-11} & \alpha(X-X\_0) & \alpha=0.25\\ \hline \text{CFC-12} & \alpha(X-X\_0) & \alpha=0.32\\ \hline \end{array}$$ The two functions are given by $$g(C)=\ln(1+1.2C+0.005C^2+1.4\times10^{-6}C^3),$$ $$$f(M,N)=0.47\ln(1+2.01\times10^{-5}(MN)^{0.75}+5.31\times10^{-15}M(MN)^{1.52})$$ $C$, $M$, $N$, and $X$ denote the concentrations of CO2, CH4, N2O, and the CFCs, respectively; the subscript $\_0$ denotes a reference concentration. All gases are given in parts per billion, except CO2, which is given in parts per million. The total radiative forcing is the sum of the contributions of each greenhouse gas. If the atmosphere is mostly made of carbon dioxide, then, using the first-order approximation: $$\Delta T\_s=\lambda\times5.35\times\ln\left(\frac{C}{C\_0}\right)\tag{2}$$ It’s easy to see from this that doubling the concentration, for example, leads to a temperature increase of about 3°C. Different models and feedback mechanisms Before I go further, I should address my choice of equations. Some would argue that it would be a lot simpler and much more intuitive to use the [idealized greenhouse model](https://en.wikipedia.org/wiki/Idealized_greenhouse_model)4 (another application of radiative forcing), which can be derived from the [Stefan-Boltzmann law](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law) and a few other assumptions. In fact, after exploring some of the above calculations, I began to wonder the same thing myself, because the idealized greenhouse model can be adjusted to produce different warming effects by simply changing one parameter: the emissivity, $\varepsilon$. I eventually did decide to work with the original table from the IPCC because it allows us to play around with the specific gases a little bit. I can attack the problem quite specifically directly from concentrations, rather than having to figure out the deceptively simple $\varepsilon$. Another place where the IPCC model has have an edge is through [feedback mechanisms](https://en.wikipedia.org/wiki/Climate_change_feedback), which is what I’ll explore next. The runaway greenhouse effect is perhaps best known for its drastic effects on Venus, turning what was once a world similar to Earth into a hellhole beyond belief. What happened was that carbon dioxide and water vapor began warming the planet (yes, H2O is also a greenhouse gas, and an important one). The water vapor upset the balance just enough so that the oceans that once covered part of the planet began to evaporate, creating more water vapor, which intensified the problem more and more. There are other types of feedback mechanisms at work on Earth, involving carbon dioxide, greenhouse gases being released from permafrost, changes in albedo from melting ice, and much more. However, the dominant one is still [feedback from water vapor](https://en.wikipedia.org/wiki/Greenhouse_gas#Role_of_water_vapor), which is actually more important than CO2. Water vapor alone can double the effects of warming, [according to the IPCC](https://www.ipcc.ch/ipccreports/tar/wg1/268.htm) and other models, and can then help start other feedback pathways that will do further damage. The reason that we can’t just double our value of $\Delta T\_s$ to compensate for this is that $\lambda$ already takes water vapor and the other feedback mechanisms into account. The reason that I said that the IPCC model has an advantage here is that all of the feedback mechanisms can be encoded into the parameter, which describes the planet as a whole. $\varepsilon$ really only describes part of the atmosphere. Putting it all together The above argument shows that our first-order approximation can give us a reasonable approximation of changes in temperature, given an appropriate $\lambda$. It’s true that this value will have to be adjusted; models of Earth use different $\lambda$s. However, if we assume that Epimetheus is roughly Earth-like, with the exception of the heavy concentration of CO2, then we don’t have to change much. # The Habitable Zone I actually think that defining where the circumstellar habitable zone is without taking the characteristics of Epimetheus into account is more challenging than modeling its atmosphere. The reason for this is that models of the inner and outer radii of the habitable zone of the Solar System differ, as a quick glance at [Wikipedia](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates) shows. Inner estimates range from 0.75 AU to 0.99 AU, while outer estimates range from 1.01 AU to 3.0 AU. So which one do we use? I’m going to instead reference [Kasting et al. (1993)](http://www.as.utexas.edu/astronomy/education/spring02/scalo/kasting.pdf), because, while it may be a little out of date, it bases its conclusions primarily on the effects of climate, which obviously play a major role in the situation at hand. The authors rely on something called the [carbonate-silicate cycle](https://en.wikipedia.org/wiki/Carbonate%E2%80%93silicate_cycle). The important total reaction is in their Equation 3: $$\text{CaSiO}\_3+\text{CO}\_2\to\text{CaCO}\_3+\text{SiO}\_2\tag{3}$$ In the biotic version5, organisms use CO2 to create shells, which then are buried in the seafloor; Equation 3 gives the net reaction. Eventually, carbonate metamorphism reverses the reaction, putting CO2 back into the atmosphere. This acts to keep the climate of a planet in the habitable zone in something of an equilibrium, because, as I’ve discussed before, carbon dioxide plays a major role in regulating surface temperature. The reason that this reaction leads to equilibrium is that both the biotic and abiotic (generally involving weathering, primarily from liquid water) require liquid water. Without liquid water, carbon dioxide levels rise, melting ice and restoring liquid water levels, and with them, equilibrium. This cycle determines the outer edge of the habitable zone because at low enough temperatures, CO2 can condense, forming clouds. The clouds then alter the planet’s albedo by reflecting substantial amounts of solar radiation, drastically cooling the planet. Additionally, the latent heat amplifies the greenhouse effect even more. The authors use this to estimate a conservative outer limit of approximately 1.77 AU, assuming non-negligible amounts of greenhouse gases. The authors then created a more complicated and detailed climate model using different planetary masses. They found that the greenhouse effect could let the habitable zone extend to about 1.67 AU for a planet of one Earth mass, and to about 1.64 AU for a planet ten times that mass. These outer boundaries take versions of radiative forcing into account, but are limited by the formation of CO2 clouds. The authors’ calculations indicate that Epimetheus should reside somewhere in that vicinity, at maximum. Some things to note: - The authors’ models ignore the formation and effects of clouds, as they say. - The drastically high levels of CO2 on Epimetheus will result in different partial pressures, meaning that the outer edge will be affected. - CO2 levels may be affected by the amount stored in the crust. That said, newer models have replicated the results of Kasting et al. [Kopparapu (2013)](https://arxiv.org/abs/1303.2649) came up with a nearly identical result for the outer edge, also assuming greenhouse effects, and with models partially based on the older ones. # Conclusion We can make some basic approximations of temperature changes if we choose the correct values for several constants and use simple models of radiative forcing, primarily of CO2, but with feedback from water vapor taken into account. We can actually do this with any greenhouse gas, but these two are the primary culprits. Carbon dioxide actually turns out to also be a good indicator of the outer edge of the habitable zone, because lower temperatures cause CO2 condensation, even accounting for the greenhouse effect. We can place an outer limit on Epimetheus’ orbit somewhere around 1.67 AU, assuming an atmosphere similar to the ones investigated by Kasting et al. --- 1 Note that this is not the same as the equilibrium climate sensitivity (ECS), which is currently thought to lie around 3°C on Earth. 2 The linked section is on radiative forcing; all IPCC reports (including the second, from 2001) can be found [here](http://www.ipcc.ch/publications_and_data/publications_and_data_reports.shtml). The equations are taken from or derived from Hansen et al. (1988), IPCC (1990), Shi (1992), and IPCC (1999). 3 The first equation for CO2 is the first-order approximation of a Taylor series; see [Lam (2007)](http://www.princeton.edu/~lam/documents/LamAug07bs.pdf), referenced [here](https://physics.stackexchange.com/a/13856/56299). 4 You can read more about it [here](http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap7.html). 5 There is, of course, an abiotic version, which plays a bigger role in planets without life or without life that can carry out these processes. [Answer] There is no simple answer to this, as distance from the star will depend upon the brightness of the star. You can orbit a hot star much further away than a cool one and still be in the habitable zone. It will also depend on factors like the wavelength of the incoming and outgoing radiation and other sources of heat such as internal volcanic activity of the planet or even tidal heating if it's close enough to another massive body. So all we can say for sure if that yes, greenhouse gasses will allow you to place a planet further from the sun and still have liquid water on the surface. The [Circumstellar Habitable Zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone) is the term for the area where that is true. In particular see [this](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Determination_of_the_circumstellar_habitable_zone) part of the article where it says: > > Given the large spread in the masses of planets within a circumstellar habitable zone, coupled with the discovery of super-Earth planets which can sustain thicker atmospheres and stronger magnetic fields than Earth, circumstellar habitable zones are now split into two separate regions—a "conservative habitable zone" in which lower-mass planets like Earth or Venus can remain habitable, complemented by a larger "extended habitable zone" in which super-Earth planets, with stronger greenhouse effects, can have the right temperature for liquid water to exist at the surface. > > > Searching for "extended habitable zone theory" will find more information on the subject as well. In particular this article looks very relevant: <http://www.astrobio.net/news-exclusive/greenhouse-effect-could-extend-habitable-zone/> > > The distant region beyond Saturn is too cold for liquid water, a necessity for life as we know it. But new research indicates that rocky planets far from their parent star could generate enough heat to keep water flowing – if their atmospheres were made up primarily of hydrogen. > > > [snip] > > But according to Pierrehumbert’s research, , a rocky planet with a hydrogen atmosphere could have a habitable zone extending as far as 1.5 AUs for M-stars and 15 AUs for G-stars. > > > This means that for stars similar to the Sun, rocky planets beyond the reach of Saturn could contain oceans of water. > > > ]
[Question] [ I have a binary system. The primary star is F- or G-class; the secondary is K-class, 20AU away, and in a small reflection nebula (suggested [here](https://worldbuilding.stackexchange.com/a/25204/28)). A planet orbits the primary in the habitable zone. [This article](http://www.solstation.com/habitable.htm) suggests that F, G, and K classes can all support habitable planets; it's talking about unary stars, but @HDE226868 [suggested in chat](http://chat.stackexchange.com/transcript/message/27234066#27234066) that this range works for binary stars too. The reason for the reflection nebula is to make the secondary star bright enough to illuminate the planet when it's in range. During [some times of year](https://worldbuilding.stackexchange.com/a/25397/28) the planet will experience continuous light, but the light from the two stars is different. The primary produces the yellowish light that we're familiar with from our own sun, and the secondary produces...what? Without the nebula, a K-class star would produce [pale yellow or orange light](https://en.wikipedia.org/wiki/Stellar_classification#Harvard_spectral_classification). The gas in a nebula scatters the light from nearby stars in different ways, which can change its color. For example, Messier 78 looks like this in space: ![](https://i.stack.imgur.com/AFOZr.jpg) I've been told that reflection nebulas are [biased toward being blue](http://apod.nasa.gov/apod/reflection_nebulae.html), though I don't know how that's affected by star type. How do I figure out what my star in a nebula looks like from my planet, particularly the color of its light, taking into account: * K-class star * in a reflection nebula * viewed from the surface of a habitable planet? [Answer] The problem with stellar nebulae (mostly dark molecular clouds yes, but even some reflection nebulae) is that they happen to also be stellar nurseries and thus tend to have short-lived [supermassive stars](https://en.wikipedia.org/wiki/Blue_supergiant) popping about in a fashion that would put the gaudiest Dubai fireworks display to shame - both in terms of brightness and hazard to human life. To further detail the amplitude of these fireworks, consider this [mandatory XKCD What-If reference](https://what-if.xkcd.com/73/), where Munroe famously explained that a supernova at 1 AU (Earth-Sun distance) is brighter than a detonating a hydrogen bomb pressed against your eyeball. [![enter image description here](https://i.stack.imgur.com/UnofT.png)](https://i.stack.imgur.com/UnofT.png) From XKCD Now a reflection nebula needs to have a nearby star behind it to glow from the perspective of the observer. Your 2 stars are about 20 AU apart (Sun-Uranus distance give or take). Not only does that leave a narrow margin for the habitable world's orbital stability, but the flaring during the early stages of star formation (at the end of its descent on the [Hayashi track](https://en.wikipedia.org/wiki/Hayashi_track)) would have blown away any and all of the Mother-Nebula material from within the vicinity of the binary pair. [![flare](https://i.stack.imgur.com/4sesu.png)](https://i.stack.imgur.com/4sesu.png) Big Flare in T-Tauri (binary baby stars) That's not to say you can't have a nebula nearby and glowing. However, it'll probably be an emission nebula (ionized gas) rather than a reflection nebula. That waives the "star-must-be-behind requirement" but does need a pretty energetic star to power it. Or you could have a part-reflection, part-emission, part-dark hybrid like the [Trifid Nebula](https://en.wikipedia.org/wiki/Trifid_Nebula). Doesn't even have to be blue. Now leaving aside the science of it, it could make for very interesting religious beliefs: [![Helix nebula (eye-shaped)](https://i.stack.imgur.com/eEIlb.png)](https://i.stack.imgur.com/eEIlb.png) Helix Nebula [Answer] The surface brightness of nebulae is not that high. Hold out your hand at arm's length, then slowly bring it towards your eyes. Of course your hand appears to get bigger, but does it get any brighter? When you hand is closer to your eyes, its surface brightness stays the same, (more light will come to your eyes but only because your hand appears larger) The same is true with nebulae: m78 (pictured above) has a surface brightness that is below the naked eye visibility. If you were much closer to it, it would remain below naked eye visibility. It would be a faint glow in part of the sky. If a bright enough star were embedded in the nebula, then it might be completely invisible until the people in your world invent the Hubble telescope. So nebulae from up close don't look like the pictures taken by telescopes, since telescopes use big mirrors and long photographic exposures to "see" patterns of light that would otherwise be invisible. Also the scale of the nebula is much larger than 20AU. M78 is about 5 light-years across. [Answer] It all depends on the scale and surface brightness of the nebula. For instance, the famous Orion Nebula is 1,344 light years. The Orion Nebula is a fairly bright nebula. However, if we replaced this nebula with the Tarantula Nebula, which is in another galaxy called the Large Magellenic Cloud, it would take up a large portion of the sky and be visible during the day. It is the only nebula that has distinguishable colour, and it's in another galaxy. (If you're wondering why you haven't seen it, it's only visible from the southern hemisphere) So if you have a large nebula, then fine, you can see it during the night for sure, covering half the sky if you want. If it's large enough you can make it far enough away that you have no harmful radiation or supernova effects. If you want a planet actually inside the nebula, depending on the brightness of the nebula, you would have either a blue, or a washed out bright light in the sky during the night, and maybe very faintly during the day. Few stars would be visible, and many of the ones that were would be very close and bright. Think as bright as a quarter moon, but compressed into a point (you wouldn't be able to detect it as a disk). It would be an interesting planet. The religion would be interesting, and until they get very effective telescopes, they may believe that there are only a few dozen stars in the universe. Interesting setting, to say the least. ]
[Question] [ Are there realistic circumstances that a planet would be accelerated (either artificially or naturally) to the speed at which relic radiation becomes so blue-shifted that the planet is illuminated so as if it were in a habitable zone? I also wonder the following: * Will such planet be in constant danger of impact by small bodies who at these speeds can be a danger to the whole planet's population? * Will not distant stars and galaxies become luminous enough so that their ionizing radiation to become dangerous to the planet's life? * Will not such planet quickly slow down due to cosmic medium? * What will happen if such planet impacts an intergalactic gas cloud or enters a galaxy? [Answer] I wouldn't know what would accelerate the planet this much without destroying it as a side-effect. Not to speak of any life on it. But I can say that if it manages to, I expect some serious side-effects. For the record: high-relativistic speeds are pretty crazy. If I neglected or misinterpreted one of their effects, well, this is just a best shot without spending too much time, since nobody else seems to give this a serious try. ## Illuminated habitat at solar spectrum When moving in the vastness of space, the CMB (cosmic microwave background) actually makes up the majority of incoming radiation. [This site](http://www.andrewjaffe.net/blog/2011/09/passion-for-lig.html) has a nice plot and some explanation on that. So, at least in terms of energy, starlight won't be the major factor there. Now, as to a habitat, I think this will go bad if I understand black-body radiation correctly. I will ignore incoming particles for now and tackle a basic problem of the question: both the CMB and our sun are following Planck's black-body radiation. This means that, if we want to get the spectrum that the sun emits, we have to use a black-body source corresponding to the same temperature, or else the shorter wavelengths' intensities will drop significantly, giving us less visible light, and more infrared and beyond. Red- or blue-shifting black body radiation doesn't change its properties, only its temperature. So, to get the kind of light we have, a large portion of the forward-facing sky (before aberration) would radiate with the intensity of the sun! The sun has a solid angle of just $7 \cdot 10^{-5}$ as seen from Earth. If the equivalent of something on the scale of a quarter of the sky is a black body at solar temperature, this giant sun would burn the planet. This rules out having light as on Earth, we'll have to go to longer wavelengths. To make the power of our incoming CMB equal to that of the sun on Earth, we can equate the incoming intensity times solid angle of both of them. (Again, I am assuming aberration just compresses the light into one direction, and work with the undistorted sky for now.) This way, we can calculate the black-body temperature the CMB would have to replace the sun in heat output. Using the Stefan-Boltzmann law for the scaling of power with black-body temperature, we get $T^4 \pi = T\_\odot^4 A\_\odot$, where $T$ is the desired temperature, $T\_\odot$ the sun's temperature, $A\_\odot$ solid angle, and the $\pi$ is the equivalent of a quarter of the sky. (The value for the corresponding effectively illuminated sky is just a rough guess, but should be good enough. See the comment by verlaner. Note that the visible image of the sky may be heavily distorted due to the aberration of light, bundling the incoming light into the forward direction.) With $T\_\odot = 5800\text{K}$ and the solid angle from the previous paragraph, this gives $T = 398\text{K}$. That's merely about $125^{\circ}\text{C}$. This black-body temperature is far too low to give the desired illumination, but already heats the planet at the full power the sun would yield. ## Velocities I have the feeling that the idea to blue shift the CMB into the sun's spectrum is not healthy in general. Let's say the CMB magically doesn't harm us, but we need it to have the solar spectrum, to see just how much velocity this is. The CMB has a peak wavelength of about $1\text{mm}$. The sun is at $0.5\text{µm}$. So you want to get a factor of about $2000$ in frequency. The relativistic Doppler effect gives a frequency ratio of $\sqrt\frac{1 + \beta}{1 - \beta}$, where $\beta = \frac vc$. This yields something like $v \approx 0.9999995c$. Let's calculate the kinetic energy per mass at this velocity. $$ \gamma = \sqrt{\frac 1{1 - \beta^2}} = 1000 $$ $$ E\_\text{kin} = mc^2 (\gamma - 1) \approx 9.0 \cdot 10^{19} \frac{\text J}{\text{kg}} = 90 \frac{\text{EJ}}{\text{kg}} $$ So, severe time-dilation aside, obstacles are bad. One gram of infalling mass would have a yield of $90\text{PJ}$, which is roughly 1500 Hiroshima bombs. I guess it's safe to say that dust and meteorites will be a much bigger threat for this planet. Also, if the planet is quickly slowed down due to collisions, nobody would want to live on it. ;) Assuming it is as large as Earth, the planet is sweeping up volume at $r^2\pi c \approx 3.8 \cdot 10^{22} \frac{m^3}{\text{s}}$. If it passes through a molecular cloud with $10^7 \frac{\text{hydrogen molecules}}{\text{m}^3}$, this yields about $10^{23} \text{W}$. For comparison, our sun inputs about $10^{17}\text{W}$. This doesn't sound healthy. However, outer space -- outside of galaxies -- has densities below one atom per cubic meter. This strips the six orders of magnitude we need to get it below solar output. I admit I don't have any idea whether this kind of bombardment might deal damage to atmosphere or habitat directly, even if its absolute power isn't high. Not that any of that is relevant compared to the black-body radiation argument above. All in all, my estimate is that this will not end well, and probably quickly too. No warranty on correctness. Please comment or edit if you find a mistake. [Answer] I'm not going to calculate at what speed the planet would have to move in order for this effect to happen. My guess is that it would have to go pretty darn fast for there to be a substantial difference, but I don't have much to back that up, other than (sometimes faulty) intuition. Could a planet be accelerated to some incredible speed? Absolutely. Just put it near the supermassive black hole, [Sagittarius A\](http://en.wikipedia.org/wiki/Sagittarius_A), in the center of our galaxy. I have to add in a picture (from Wikipedia) to illustrate just how much stars are effected near it: [![enter image description here](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Galactic_centre_orbits.svg/854px-Galactic_centre_orbits.svg.png)](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Galactic_centre_orbits.svg/854px-Galactic_centre_orbits.svg.png) Image courtesy of Wikipedia user Cmglee under the [Creative Commons Attribution-Share Alike 3.0 Unported license](http://creativecommons.org/licenses/by-sa/3.0/deed.en). It is thought that [intergalactic stars](http://en.wikipedia.org/wiki/Intergalactic_star) are chucked out of their home galaxies by interactions with a supermassive black hole. Here's a graphic (from Wikipedia) that illustrates this: [![enter image description here](https://upload.wikimedia.org/wikipedia/commons/e/ee/HE_0437-5439_mechanism.jpg)](https://upload.wikimedia.org/wikipedia/commons/e/ee/HE_0437-5439_mechanism.jpg) Image in the public domain. I apologize if the graphic take a while to load; it took about 30 seconds on my computer. These stars are known as hypervelocity stars. They can travel at speeds of about 1,000 km/s - not nearly enough (if Vandroiy's calculations are correct) for this kind of speed. However, I wouldn't me surprised if a galaxy with multiple SMBs (perhaps the result of a few galaxy mergers) could get stars moving a lot faster than that. If this can happen to stars, it can sure happen to [planets](http://en.wikipedia.org/wiki/Rogue_planet) (note: rogue planets do not necessarily get removed from their star in this fashion). Besides, planets are a lot less massive than stars (many orders of magnitude) and so could possible get boosts many orders of magnitude higher. --- > > Will such planet be in constant danger of impact by small bodies who at these speeds can be a danger to the whole planet's population? > > > Most likely not. Remember [this quote](http://en.wikiquote.org/wiki/The_Hitchhiker%27s_Guide_to_the_Galaxy) from Douglas Adams: > > "Space," it says, "is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space, listen..." > > > There aren't a lot of dense areas of celestial bodies. Remember, the nearest star system is the Alpha Centauri system - and that's 4 light-years away! I'd imagine that collisions would be extremely unlikely, although there could be more activity near the galactic center. However, it will probably interact a little with the [interstellar medium](http://en.wikipedia.org/wiki/Interstellar_medium), though not a serious amount. What if this thing goes into intergalactic space? Well, it will probably run into the [intergalactic medium](http://en.wikipedia.org/wiki/Warm%E2%80%93hot_intergalactic_medium), some of which is composed of a plasma, possibly made of hydrogen. The planet might heat up a little, which I think is good, for your scenario. There would probably be some interesting atmospheric interactions, too; friction between the atmosphere and the intergalactic medium could heat up the top layers of the atmosphere to an extreme level. > > Will not such planet quickly slow down due to cosmic medium? > > > Possibly - and probably a little bit. There will certainly be interactions with either the ISM or the IGM, which could slow it down a little. If the planet passes through higher-density regions of space (nebulae, gas clouds, etc.), then this will become a bigger issue. Which brings us to our last section. > > What will happen if such planet impacts an intergalactic gas cloud or enters a galaxy? > > > Cool. I'm not sure what would happen here because I don't know if these exist in non-negligible numbers. I can analyze an [interstellar cloud](http://en.wikipedia.org/wiki/Interstellar_cloud), if you want. Interstellar clouds are regions of space filled with lots of gas and dust. They contain some dense ISM, as well as a lot of hydrogen. Some, such as [giant molecular clouds](http://en.wikipedia.org/wiki/Molecular_cloud), are the birthplaces of stars. They have a heck of a lot of hydrogen, in its molecular form (H2, I believe, although I'm not positive). How dense are these clouds? Some are very dense. From Wikipedia, > > Whereas the average density in the solar vicinity is one particle per cubic centimetre, the average density of a GMC is a hundred to a thousand times as great. > > > Wow. That's pretty dense. Could that cause some problems for our high-velocity planet? Perhaps. But there could also be some upsides. After all, stars are being born nearby. And gravitational capture is always a possibility. . . [Answer] [Math](http://astronomyonline.org/Science/DopplerShift.asp) [indicates](http://www.wolframalpha.com/input/?i=0.0000007c%2F0.001) that the planet would need to be traveling at least 120 km/s relative to a stationary observer (for reference, that's about 15 times faster than the Earth moves around the sun) up to a maximum of around 210 km/s (26 times). I.e. about 0.04% to 0.07% the speed of light. Odds are, such a planet would not be "stable" (astronomically speaking) long enough to support life. But... Yes, it would be in danger of impact from small bodies. * Distant objects would be blue shifted as well, so your best bet is to make this planet flying off into a void (dark region) of the universe such that all of the visible stars/galaxies would be behind it (and thus redshifted, likely down into the infrared range and beyond). This would also minimize the likelyhood of it crashing into something large. * Not really, no. I'm sure there's some friction calculations out there for photons, but honestly it's going to be minimal. * What happens? Very large explosions and death. You're throwing a planet sized body at another planet sized body at incredible speeds. The gas particles entering the atmosphere would likely light up the sky with deadly radiation, think the aurora borealis, except even higher energy. My guess is that it's unrealistic and could never happen, but it's significantly more plausible than interstellar space flight (FTL travel) and no one has a problem with that. Rational explanation: the planet was flung off from a close-pass with a black hole, sending it into the deep voids of space, stripped from its parent star (stars do orbit black holes at these velocities, so a hyperbolic trajectory could fling off a small body fast enough). ]
[Question] [ I'm building an alien world for a game mod, and want to avoid any blatant mistakes from a world-building perspective. The world has three moons visible in the night sky - two on one side near each other, while the third is on the opposite horizon. When viewed from the equator (my main landmass is tropical), the pair is located in the northwestern sky and the single is to the southeast. The pair are roughly both a little larger and a little smaller than Earth's moon, while the single is medium - say the same size as Earth's moon. What affect, if any, would this arrangement have on the formation of landmasses and/or oceans on the planet? I'm currently using Earth-type erosion to form both topographies, but is this the correct approach? Also, as a result I'm keeping the nights fairly well-lit instead of dark, similar to dusk but with a slight purplish tint. Would this affect the growth of flora or fauna to any significant degree? I hadn't really put much thought into the details, but let's assume for this question that the paired moons are locked together and all three bodies are roughly the same distance as Earth > Luna with around the same rotation period. Under these assumptions, we can also assume that the pair would have a larger accumulative mass than the single on the other side, and that they would always be more-or-less opposite of each other throughout the year. [Answer] I'm going to ignore orbital stability issues (I suspect your arrangement is unstable, resulting in one or more of the moons being ejected from the system, but I can't prove it). "Well-lit" nights is a relative term. The Moon provides only 1/500,000th the light of the Sun; even if your moons were mirror-reflective, you could only boost that light to 1/60,000th or so. That's enough light for nocturnal predators to have an easy time of it, but not enough for photosynthesis. I wouldn't expect any major changes in landscapes. You'd see a slight increase in tidal flexing of the crust, but it won't be a major geological factor. The main effect I'd expect is that earthquakes are slightly more common and slightly weaker; you might also see a slight increase in vulcanism. The big change is the tides. The moons you describe are not in an equatorial orbit, so the strength of their tidal contribution varies based on how high above the horizon they are at peak: a day when a moon is low on the southern horizon will have a weak tide from that moon; a day when the moon passes overhead will have a strong tide. If the singleton moon and the pair are in different orbits with different inclinations, predicting the tides would be a nightmare -- set it up right, and you've got effectively chaotic tides. [Answer] impossible: > > three moons visible in the night sky - two on one side near each other, while the third is on the opposite horizon. > > > Three moons, two together and one off at an angle. And MAINTAINING this relative separation at all times? So they MUST be in the same orbital plane, and at the same orbital distance from the planet. It would require suspension of the laws of gravity and/or motion, as the two moons near each other would gravitationally attract each other, and collide. The closest you could arrange, and this still would require a bit of celestial handwaving: The two moons orbit each other closely, and the pair orbits the planet. The third one is 60 degrees ahead or behind the pair, in a stable Lagrange point. The handwaving required is because Lagrangian points are not stable if the relative masses of the moons are similar, and they absolutely require that the moons be singular and stable, not a binary. Still, this will only outrage astrophysics nerds, so be happy. > > the pair is located in the northwestern sky and the single is to the southeast > > > This requires all the moons to be in an inclined orbit, relative to the planet's equator. No problem with that, in the short(astronomical-scale) timespan. Finally, to answer your question: > > What affect, if any, would this arrangement have on the formation of landmasses and/or oceans on the planet? > > > As the relative positions of the Moons are fixed, AND their orbit is circular, their gravitational effect on the planet will be the same as a single moon positioned between the three, somewhat closer to the pair than the singleton, massing a bit less than the sum of the moons. (because the are not perfectly aligned) You have given them very Earth-Moon type distances and masses, so the end result will be a tide that is 2.5-3 times as great as Earth tides. The tide height would also vary immensely by Latitude, as the inclined orbit will sometimes cause tides to be greater when "under" the moons, and less when in the opposite hemisphere, even when the moons are at their highest. On the astronomical medium to long term your planet has problems. The inclined orbit will cause the precession of your planet's rotation to be hugely amplified. Expect the rotational north pole to drift around a lot, causing seasons to be ...interesting. Also, expect that third moon to eventually drift out of its Lagrange position, start orbiting the planet by itself, and disturbing the twins. After the first close encounter, you now have three rogue moons rampaging around the planet until they run into something, most likely themselves. Big fireworks, meteor swarms and eventual planetery ring will result. ]
[Question] [ The BBC in the UK are currently screening a archaeology series exploring the idea that the [Neolithic peoples in the Orkney Isles](http://www.bbc.co.uk/programmes/b08819tl) (North of Scotland) were the cultural capital of the British Isles. There's evidence to show that the high standard of culture predated Stonehenge. [![enter image description here](https://i.stack.imgur.com/wGKWQ.jpg)](https://i.stack.imgur.com/wGKWQ.jpg) I have this fictional idea that this advanced culture was based on a superior understanding of mathematics. The ancient [Orcadians](https://en.wikipedia.org/wiki/Orcadians) could: * predict the seasons * understood the phases of the moon and their effect on the tides * estimate how many stones of what sizes could build a house * estimate how many fish would see a family through the winter * have a good idea of their worth of their goods in trade In general, an appreciation of maths makes life more predictable. In order to aid their relationship with tribes on the mainland, they need to convey this new concept to them, they need to teach numeracy and the communicate the advantages they bring to those others who manage nothing more than "making do" in their own settlements. And here comes the stumbling block I have in this story. How can the leaders of a more advanced tribe teach others, what strategies can be used to transfer this new knowledge onto others so that civilisation as a whole can grow and evolve on cultural and technological level? # In Summary Although I'm using numeracy as the example here, at heart this is a question of skills/knowledge transfer in Neolithic times. [Answer] Numeracy will spread by interaction with outsiders, specifically via trade and exploration: People are pragmatic, and usually adopt methods and practices that work -- or work better than the alternatives. Since numeracy is practically useful in trade, and in provisioning expeditions that have a reasonable chance of returning, your numerate tribe will do well in both trading without travel (markets, granaries) and in trade (or other wealth-pursuing) travel -- probably by ship. Especially before the printing press and mass literacy, the sequence of travelling traders, to remote trading outpost, to a colony is a reasonable trajectory for these types of applicable knowledge to spread. [Answer] They don't have to actively push knowledge to the mainland. They are just doing thing better, more efficient, grow better crops, build better houses because of their understanding / knowledge. This will make mainland people curious and scholars will travel to the island to learn the new ways of black magic numeracy. They will spend some time on the island until they think they have learned enough and then return to the mainland with the new knowledge (where they'll get burned because the mainlanders still consider numeracy as witchcraft, but that's another story). Or it will be the merchants, bringing stuff to the island and return other useful things. Along with the material also knowledge is transferred, because they hear and see things, ask stuff and build their own knowledge. Or one of your Orcandians gets tired of the island and decides to move to the mainland. He or she will also bring knowledge to the mainland, because when living on the island, they had work to do, where they most possibly had to use the better knowledge. [Answer] If you want to lead a world, you need an advantage. Knowing concepts your neighbors ignore is a significant competitive advantage, in particular in a world where you are still an ant with respect to natural forces (you may forecast a winter of starvation, but you have no means to buy crop from US, simply because US do not still exist for you), why would you then teach them? I think your "knowledge holder" should be treated as an holy race and forbidden interaction with strangers, for the sake of the nation growth. [Answer] I think your premise is a bit flawed. The Ancestors had a very firm grasp of many of the things you speak of (there are [lunar calendars](http://scribol.com/science/paleontology/the-oldest-lunar-calendar-on-earth/) marked on pieces of bone or cave walls dating back to 32,000 BC). There is also archeological evidence the Ancestors were skilled traders, as things like flints and decorative shells have been found hundreds of kilometres away from their origin points. Someone was obviously a very busy travelling salesman, and would probably have a good idea of what sorts of valuables could be traded for these treasures. The primary difference between the Ancestors and us, their remote descendants is we have developed writing and mechanical storage of information and data, whereas they would have been using some sort of oral or memory based systems. Humans are capable of memorizing a great deal (especially if your very life would depend on this), and we know of lots of tricks to ensure your memory is working at peak efficiency. In the Renaissance, the "Memory palace" technique was developed, where you imagine a house, and inside each room you "place" a memory (or group of memories), and associate each individual data point with an item in a room. You could simulate this today by walking through you house and placing a "post it" note beside every object in the rooms of your house, with an important piece of information written on it. You see the flower pot in your kitchen, and you associate it with whatever is written on the note. Obviously the "memory palace" technique would be completely foreign to the Ancestors, but some other technique to catalogue and memorize important facts would have been in use. Long experience would also allow them to make good estimates "at a glance" of things like volume, weight and doing the quick calculations of things like "is this pile of smoked fish enough for the winter?" Once again, this would not be in a "maths" sort of way, but whatever technique was being employed would still be quick and accurate enough to sustain human life. Mentorship by the tribe's elders along with hands on experience starting at a young age would provide the means for the Ancestors to pass that information on through the generations. So the ancient Orcadians are not developing anything new, but are simply using very long established (and very old) techniques to stay healthy and prosperous in their environment, and most of the peoples they might get in their travels would also be fairly well versed in these ideas and techniques. ]
[Question] [ In the book Dune by Frank Herbert. Arrakis is a desolate planet composed entirely of deserts. Water is a precious commodity due to its rarity. The Fremen have found ways to live on its surface, despite its seeming lack of habitability. My question concerns the following: *Could a planet with an atmosphere that is similar in proportion to Earth's form without any major bodies of water on its surface?* The atmosphere of Earth has two major components: 1. Oxygen- 20% 2. Nitrogen- 78% Is the presence of water necessary to get such a balance in the first place so that Earth-like organisms could survive on its surface? [Answer] I think it's unlikely but possible. The thing about water is that it's a very light molecule. Mars started with water like Earth, but lower gravity and missing magnetic field meant that it rapidly (geologically speaking) lost that water into space. So if this world starts with little water how soon until it has none? Not long enough for photosynthesis to evolve and run for long enough to create an oxygen atmosphere. (That took the best part of three billion years on Earth). So to the unlikely possibility. This is a dying world. It started a lot like Earth but held its initially abundant water less well. Now it has just a few million years left before life can no longer adapt to the dessicating biosphere. But that's plenty of time for a story on a human scale. Arrakis, with deep time stealing its water rather than sandworms. Note: I'm assuming that Earth like planets will always start with a reducing atmosphere (mostly methane) like Earth did. Oxygen is highly reactive and unstable in the presence of methane or iron-2+, so I think an oxygen atmosphere not created by life or created rapidly can be ruled out. [Answer] I do not think it is likely for life to evolve without water in reasonable time scales. For a hypothetical metabolism we need a solvent which: * is polar * is a good solvent for ions, molecules, protein/DNA equivalents * is very abundant * is liquid under given temperatures and pressure * has sufficiently low viscosity * is not too aggressive against the cell * for ecosystems a density anomaly is also desirable If you think about these points it is unlikely, that there are many other alternatives. Methane is e.g. liquid and abundant on Titan, but the low temperatures will not allow reaction in sufficiently small time scales for life to evolve fast enough. Ammonia might be the closest bet, because at -33°C it is liquid. However according to the RGT rule the chemical reaction speed would be 1/2^4 to 1/2^5 in comparison to a water system. So it may take already four times longer for life to evolve and in case of an event it may be too slow to adapt. [Answer] Not only is it possible, but that's how it happens. Earth formed with no water--the impact events during it's formation were too energetic for it to retain any primordial water. Earth's water supply came from cometary impacts. Thus to get a planet with basically no water you need a cataclysmic impact event after most of the debris has been swept up. Something perturbs the orbit of a planet or dwarf planet enough to cause an impact event. The water boils off. Note that this takes out the atmosphere, also. If you want life on the world you'll need some more impacts to bring in some water but you can decide how many (by how late in the formation of the planetary system the late impact event happened) and thus how much water and atmosphere. If you'll accept another approach to the world you're after, simply take a warm planet. Earth is not big enough to retain hydrogen--water vapor that gets high enough in the atmosphere to be disassociated results in hydrogen leaking away. This is a very slow process on Earth because the stratosphere is cold enough that only a trickle of water can make it through. If the atmosphere were warmer (look at the projections of Earth's very long term future) this gate gets opened wider and the ocean slowly bleeds away to space. With a warm atmosphere this process would be basically complete in far less time than the Earth's age. ]
[Question] [ I have been sporadically building a particular world, mainly by developing its cultures with events (often paralleling Earth history) and individuals, rather than shaping the cultures beforehand. One problem I have come across is that my map's scale might be rather odd, partially as I am unsure of how to create cities by size. What is a good reference point for the size of villages, towns, or cities? p.s. An intro on city construction through size planning would be helpful. I am looking in particular for a 20th century equivalent and am interested in size both in terms of area and population, although references for other times are relevant. [Answer] Over time those have changed significantly. For example London was the biggest city in Britain by the second century or so; it had around 10k residents in the 11th century and in the 1600s had around 350k. So you'll at least have to figure out your sort of target equivalent timeframe. Britain has often had a much smaller population for area than nicer climes/better growing land - for example France.[1](http://www222.pair.com/sjohn/blueroom/demog.htm) Historical data on that kind of thing is fairly sketchy for the most part. Without a lot of hard research you'll probably have to make a lot of guesses. I would suggest a couple of sites to start you off: * [Settlement Patterns in Ancient Europe](http://www.fofweb.com/History/HistRefMain.asp?iPin=ESCMW503&SID=2&DatabaseName=Ancient%20and%20Medieval%20History%20Online&InputText=%22Domesday%20Book%22&SearchStyle=&dTitle=settlement%20patterns%20in%20medieval%20Europe&TabRecordType=All%20Records&BioCountPass=2&SubCountPass=14&DocCountPass=0&ImgCountPass=1&MapCountPass=0&FedCountPass=&MedCountPass=1&NewsCountPass=0&RecPosition=13&AmericanData=&WomenData=&AFHCData=&IndianData=&WorldData=&AncientData=Set&GovernmentData=) * [Historical Urban Community Sizes](http://en.wikipedia.org/wiki/Historical_urban_community_sizes) * [Medieval Demographics Made Easy](http://www222.pair.com/sjohn/blueroom/demog.htm) - this one is specifically for RPG developers and I think will be the most helpful to you since it does have a bunch of estimates/sensible numbers. [Answer] The rank-size distribution might be worth looking into. The basic principle is that a city's population size rank is roughly the divisor of the largest city's population. So the 2nd largest city is generally half the size of the largest, the third largest is a third of the size, etc. But an often overlooked factor is the history of industrialization. The rank-size distribution is something like an equilibrium that takes time to manifest. Industrialization can be one of the most drastic social changes a society will face and in general, the later you are to the party, the faster you will industrialize. England took a century, France and Germany took 50 years, Kenya took a decade or less. (these times are probably wrong, but you get the idea) Industrialization is generally focused on a particular geographic area. A good port, a good source of coal or iron ore, something makes a particular place a good place to invest. And investment breeds investment. This leads to a particular city becoming far more attractive than others and can lead to urban primacy where the population of one city vastly surpasses any others. Today, this is common in South America, Africa and southeast Asia because of the rapid pace of industrialization. Primate cities generally have a hard time providing services to so many people and can probably be assumed to be worse places to live. However, it should be noted that these cities often have so many people because they have much more opportunity than surrounding cities. Locally, they are attractive places, but compared to other cities of their size, they're generally worse off. Rank-size distributions are generally indicative of a stable, long-term economic situation and primate cities are often indications of fairly recent upheaval. As far as how big that largest city is, that should have something to do with communication and transportation technology. For example, Venice today literally cannot grow because there can be no trucks and all deliveries to keep stores stocked are done so by foot. Of course, there's other demographic issues to Venice, but the transportation system is a hard limit on that city's growth. Better transportation and communication enables bigger cities, both in population and footprint. Might be worth keeping in mind density is a controlled factor that a state can regulate. Crowding is a psychological construct that can result from poorly managed density. [Answer] It sounds like you're talking about size on a map, not population. I'd recommend digging up some historical maps of cities from a time period analogous to your social and technological level. You can find them all over the place. Grab a reference city or two, and see how much they spread out. (In ancient and medieval cities, this was often constrained by how big the city walls were.) ]
[Question] [ ### Background / Rationale Many fictional worlds feature sapient herbivores, but rarely spend much time considering how their tools and technology would differ. In the course of writing my story, however, I've come across one point of particular relevance... Most herbivores (due to predation) have much wider horizontal fields of view than humans. While this may not be an issue for "functional" displays, it seems likely to be relevant when it comes to entertainment. To wit, these sophonts would prefer to not feel as if they're wearing [blinkers](https://en.wikipedia.org/wiki/Blinkers_(horse_tack)) when they go to watch a movie... or play a video game. Now, for filmed and projected media, humans already have the technology to address this (and this world assumes a similar technological progression)... and "looking through a window" isn't always an issue. However, having a reduced field of view is already annoying to humans in some cases, especially "first person" games, and I can only imagine how much worse the effect would be for a sophont that's used to 270¬∞ or even 360¬∞ vision. Here, however, we have a problem. Modern rasterization is based on projecting a 3D scene onto a flat 2D plane. The math for this is fairly straight forward; yes, it's linear algebra, but at its core, it's all based on addition, multiplication, and a bit of division. Because of this, significant pincushion [distortion](https://en.wikipedia.org/wiki/Distortion_(optics)) occurs when trying to render a scene at high FOV ([example](https://www.youtube.com/watch?v=6FgJendeyHQ)), and FOV ‚â• 180¬∞ is mathematically impossible. In the early days, multi-monitor setups would be quite popular, with multiple independent viewpoints being rendered. Catering for such setups would be the norm, rather than the exception... but the holy grail is combining rounded displays with true cylindrical projection. The trouble is... cylindrical projection requires (AFAIK) doing trigonometry, which makes rasterization much more complicated. ### Question (TL;DR) Is it plausible for a world which is technologically equivalent to our own (circa 2021) to have 3D video games (and other content) which use cylindrical projection while still being otherwise comparable (i.e. visual quality and frame rate) to what we have in the real world? How far back could this have existed? (IOW, could their early, circa-1995 games predating hardware 3D acceleration, have done it? Would it need to wait for circa-2020 GPUs? Something in between?) Keep in mind that this world is strongly motivated to achieve this (it's not just a curiosity, as it would be for us humans), so solutions requiring explicit hardware support (similar to how hardware ray tracing is starting to be a thing) are acceptable. For bonus points; would spherical projection be possible? If so, would it be harder, easier, or comparably challenging? (The folks that keep insisting that "VR displays" will be mainstream some day¬π would really like to know...) (¬π For reasons that aren't relevant, this world is quite far behind the real world in the development of VR headsets.) ### Technical Explanation "Traditional" projection ‚Äî that is, projection onto a planar "screen" ‚Äî follows the formulae $p\_h = P \* p\_{world}$ and $p\_{screen} = p\_h .xyz / p\_h .w$, where $P$ is a 4√ó4 matrix which can be precomputed. Modern GPUs are, of course, highly optimized for performing linear algebra like this. For cylindrical projection, I believe this continues to work for the $y$ component (at least, a similar calculation should be possible), but $x$ requires an arc[co]sine and some conditional branching, and I'm not entirely sure about $z$. ($z$ is the distance from the "screen" and is important for culling, depth testing, and some effects such as "fog". I don't know the actual formula for $z$ in a cylindrical projection, but I have a sneaking suspicion it requires taking a square root... which can be optimized pretty heavily, but is still another operation compared to planar projection.) ### Postscripts * Please note that I'm not looking for hand-waved answers. Essentially, what I want to know is if and when the real world could do this, if we'd started working on it circa 1990 and applied similar resources to the problem as are applied to other aspects of modern GPUs. (Hence the [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") tag.) * Don't worry about display technology. Our real world abilities to display wide-HFOV content are close enough that it's easy to imagine them being up to the task if we'd had the desire to produce such displays. Similarly, producing filmed or pre-rendered HFOV content is easily accomplished in the real world. I'm only concerned with real-time rasterization. * Assume the desired output has uniform radial spacing, i.e. each pixel has the same physical dimensions. Also assume that the quality loss of rendering using "traditional" techniques and distorting is considered unacceptable. [Answer] First off, the herbivories you talk about having 270-360 degree vision tend to have little to no overlapping field of vision (monocular vision), thus lacking certain properties of 3D vision. most of their world tends to look fairly flat as it is, so the importance of 3D entertainment would not be as attractive to them as it is to a being with binocular vision. Due to evolutional pressures, most prey animals, those that would benefit from monocular vision, do not focus on distances of objects, but focus on the presence of objects and their general direction relative to the observer. Many either lack visual acuity of humans, as their vision is basically go-no go, or their color perception is different in some way. For such a creature, I would suggest focus less on clarity and depth perception of the entertainment, and focus more on display range and they quantity and quality of the audio/visual stimuli of the entertainment being provided. After millions of years of being hunted and killed by predators, these creatures react to visual and audible stimuli. Now that they the undisputed rulers of the animal kingdom of their world, they may get a kick out of watching a bunch of abstract objects bounce around 200 degrees of their vision, feeling comfort that they do not need to fear such images. By contrast, they could feel comforted or calmed to see images of dull, slowly moving object in the front view (such as one would see wind blowing through trees.) Sharp, quickly moving objects at certain posterior view angles could be seen as exciting action or horror flick. To achieve some of these varied angles of views, it may be culturally encouraged to have large, wide or multiple screens set up to properly display the content. Basically, to explain an entertainment system of a creature that once was a prey animal, one must understand the anatomy and psychology of the creature to know what they would actually react to. [Answer] Just for a starting point, here's the equation for spherical projection of a vertex $v$ using [Euler angles](https://ece.montana.edu/seniordesign/archive/SP14/UnderwaterNavigation/Euler%20Angles.html) for visibility into how it's composed. $v' = v X Y Z$ where: $X = \left[ \begin{array}{abc} 1 & 0 & 0 \\ 0 & \cos{\theta} & \sin{\theta} \\ 0 & -\sin{\theta} & cos{\theta} \end{array} \right] $ $Y = \left[ \begin{array}{abc} \cos{\phi} & 0 & -\sin{\phi} \\ 0 & 1 & 0 \\ \sin{\phi} & 0 & \cos{\phi} \end{array} \right] $ $Z = \left[ \begin{array}{abc} \cos{\psi} & \sin{\psi} & 0 \\ -sin{\psi} & cos{\psi} & 0 \\ 0 & 0 & 1 \end{array} \right] $ and, for a vertex located at <1, 0, 0> before projection, $v = \left[ \begin{array}{abc} 1 \\ 0 \\ 0 \end{array} \right]$ Please correct me if I'm wrong, but I believe cylindrical projection is just losing one degree of rotation, such that Z becomes : $Z = \left[ \begin{array}{abc} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{array} \right] $ ## Computational Expense of Trig Functions In older computers, the expense of trig functions was mediated by using pre-calculated tables, $\begin{array}{abc} \theta & \sin{\theta} \\ 0 & 0 \\ 30 & 0.5 \\ 45 & 0.7 \\ 90 & 1 \end{array}$ and performing linear interpolation to get an approximation of the exact value. $ y = {({x - x\_{n-1}}) \over ({x\_n - x\_{n-1}})} ({y\_n - y\_{n-1}}) + y\_{n-1}$ ## Short Answer I don't think there's a technical problem. [Answer] I'm going to deem this "plausible", but it probably has to wait for the equivalent of modern (circa 2020) GPUs. First off, we need to understand how existing rasterization works. As noted in the question, planar projection requires only a homogeneous matrix. By composing multiple matrices, we can account for the camera position and orientation, as well as the field of view and screen size. In essence, the transformation from world space to screen space is a single matrix multiplication followed by a single vector division. This involves only operations which are reasonably fast, and modern GPUs have of course been heavily optimized for this sort of thing. Cylindrical projection throws a wrench in the works, because the conversion from world space to screen space can no longer be represented so trivially. Indeed, we end up needing to do three steps: 1. Convert from world space to camera Cartesian space. Basically, this step accounts for the position and orientation of the camera. The result is a Cartesian coordinate, but one which has been "normalized" such that 0,0,0 is the focal point of the camera and the basis vectors correspond to basis vectors of the camera. This is accomplished via affine transformations, same as for planar projections. 2. Convert from camera Cartesian space to camera Cylindrical space. The result is a vector with $-\pi \le x \le \pi$ where $[0,1,1]$ maps to itself¬π. 3. Convert from camera Cylindrical space to screen space, such that $[-1,-1,z]$ and $[1,1,z]$ represent the corners of the screen. What makes this interesting is that it entails a homogeneous transform for the $y$ coordinate. This will account for the horizontal and vertical fields of view. (¬π The selection of orientations is somewhat arbitrary, but does not affect the problem.) By comparison, planar projection can accomplish steps 2+3 with a homogeneous matrix transform, allowing all three steps to be combined. Thus, cylindrical projection requires three steps to accomplish what planar projection can do in one. What about the second step? How is that transformation accomplished? Well... * $x' = atan(x,y)$ * $y' = hypot(x, y)$ * $z' = z$ ...where $atan$ is a somewhat-magic function that yields the appropriate angle. Note that this function, internally, needs to perform some multiplications based on the sign of either $x$ or $y$ in addition to computing the arctangent (which will additionally require a division). Given sufficient motivation, this can be approximated to a degree that is most likely "good enough" using linear interpolation between known values derived from a hardware look-up table (thanks to [James McLellan](/users/44287) for [pointing this out](/a/221590/43697)). So, we're looking at a vertex transform that is probably takes about 2-3 times as long as for a planar projection. Unfortunately, that's not the end of the story. The planar projection of a line is... a line. This is what allows us to quickly rasterize a triangle from its transformed vertices. (It's not quite that simple since linear interpolation of the U/V coordinates isn't quite right, but this was "good enough" for the early days.) The cylindrical projection of a line, however, is a conic section. In fact, any line whose endpoints lie at different $x'$ values is going to be curved i screen space to some extent. This means all of our quick-and-dirty methods of rasterizing a triangle are "out", and there is no cylindrical projection before dedicated hardware acceleration. Early implementations are more likely to render at larger-than-needed resolution and then texture map (using traditional techniques) onto a screen-covering mesh. The quality won't be as good as "proper" rendering, but it will effectively pick up some antialiasing at a similar cost as MSAA. The mesh can be pre-computed once and does not change frame by frame. However, all is not lost. We can approximate a curve with a series of straight lines. Make the line segments short enough, and the discrepancy between the curve and the line segments becomes unnoticeable. Moreover, we already take a similar approach for [subdivision surfaces](https://en.wikipedia.org/wiki/Subdivision_surface) using geometry shaders. Doing this effectively and without unacceptable performance sacrifices will require "modern" GPUs with dedicated hardware acceleration, but leads to an interesting corrolary; 3D rendering in this world makes much more use of subdivision surfaces as compared to the real world, and may have been doing so for (comparatively) longer. [Answer] No real difference in rendering technology Your screen would be different, but the creature has already adjusted the "projection issues" in its brain, no special GPU is needed, just a different projection formula. While rendering a scene, the ray marching involves simulating rays hitting the view cylinder perpendicular, instead of hitting a view plane perpendicular. Cameras may be more difficult Cameras would require special measures: you'd have a very toric lens, with a cylindrical ccd inside, which may be quite a challenge to construct. ]
[Question] [ I have a scenario in my world's history that is causing me a pause as it seems...improbable to the point where I am not sure it makes sense/breaks suspension of disbelief. A great empire arises via conquest. The catch is that each nation in this scenario has a military skilled in a particular type of combat/weaponry. The Kingdoms * Shekar: This is the conquering nation that will end up being the seat of the larger empire. Its military is focused solely on infantry in a Romanesque style. They have superior organization and standardization in comparison to the other nations. * Gremia: The kingdom of the plains, Gremian cavalry is second to none. The Gremians breed superior horses and most of the people, even non-soldiers, are trained in the saddle even from a young age. * Vespria: Vespria is known for its archers and skill in crafting bows. Their archers are far superior in skill, using their finely crafted bows to out-range any other archers. * The Dwarves (I haven't come up with a good name for their kingdom yet): The dwarves have both talented infantry and superior skill in creating engines of war. Their infantry is not offensive and exists mainly to protect their siege engines, very heavily armored and difficult to kill. * The Mujeri: Due to some... [unfortunate, map altering events](https://worldbuilding.stackexchange.com/questions/42177/how-long-would-it-take-a-region-to-geologically-settle-down-after-a-major-catacl) mages are feared, executed and/or exiled from most of the civilized world. Some banded together and formed their own nation on a remote chain of islands. Not everyone in the clan is a magician but it is the only place mages may practice their craft in public. So. Each nation has their specialty. What I am looking for is a logical explanation as to why. What setting/situation would make it plausible for these nations to have completely different, uniquely skilled militaries? Historical examples are a plus. For reference, the goal is that the Shekaren will conquer and then incorporate each nation into their empire making it a military powerhouse that is able to go on to conquer virtually the entire continent. [Answer] There are several reasons I can think of off the top of my head: > > Geography, Tradition, Economic Reasons, Religious Reasons > > > Vesprians Let's analyze the Vesprians. Why are bows traditionally used? * Long range * Cheap/easy to manufacture if certain wood is available * Potentially very powerful (a skilled longbowman can take down a man in plate armor at 100 - 600 m) * Versatile hunting tool / weapon of war So let's make up a bit of backstory for them. Let's assume that theirs is, perhaps, a historically a kingdom not very rich in metals. Let's further assume that a large portion of their territory consists of woodlands, hills, maybe even rocky mountainous terrain where traditional military formations can't easily maneuver, etc. However, a troop of rangers hiding in the tree tops can unleash hell on an enemy unit trying to advance through their territory. Thus, their reason for using bows can stem from the geography of their territory, and become tradition in time. Historical example? The British longbowmen which have served them well in war, and become near legend. Gremians Now let's take a look at the Gremians. Horsemen, you say? That's easy. Have their territory consist of sweeping, open plains on which vast herds of wild horses roam free. Gremians have a long tradition of taming these horses, and, over time, have developed very effective riding, fighting, and military techniques, all centered around their biggest advantage: their unmatched horses. Those vast plains mof theirs also make for perfect terrain for Shekarian military formations and tactics, making a pitched battle suicidal for the lighter-armed Gremians. Thus, they instead focus their efforts on developing very mobile mounted units which can't get pinned down and engaged in a pitched battle, and which can more easily flank enemy infantry. Dwarves They live underground - animals don't do well there (even in their vast halls), so they never developed an affinity for riding any sort of beast. Instead, they put their stocky, powerful frames to good use as heavily armed and armored infantry, which works very well when engaged in pitched battle in some dark, narrow tunnel. Dwarfs are unmatched craftsmen, and build massive underground enclaves for their clans, and families. These are typically designed with defense against the many terrors of the deep, and other quarrelsome clans in mind, and have very heavily defended entrances, not to mention thick walls of solid stone. As such, dwarfs have put their natural tinkering talents to use in inventing all sorts of nifty gadgets to break through the thick walls, and gates of their enemies. In fact, they've developed some truly impressive siege engines which they carry to the battlefield in pieces, to be assembled in the enemy's main hall, and used to turn the various structures within to rubble. When dwarfs eventually turned their attention to the riches of the surface, they found that those same weapons of war work even better when you don't have to worry about bringing the ceiling down on your head, and they enthusiastically designed even more powerful, and deadly contraptions. Mujeri Becoming a mage is a difficult proposition. It involves a lifetime of dedication to the magical arts, and very few are able to gain even the basic knowledge which will get them started down this road. Furthermore, there seems to exist a certain ... magical ability which some rare few are born with, and which allows them to progress down the Path of Power at nearly unimaginable speeds. People to whom magic seems to come naturally, and whom, especially when properly guided and trained, become mages of great, and terrible power. Nobles and other powerful lords have often sought to gain this knowledge for themselves, feeling that having mere commoners gain such abilities is upsetting to the balance of power in the land (aka, they are competition). Historians can list many noble houses which have tried to breed this power into their ranks, and nobles who have expended vast amounts of gold, and other riches to have a mage instruct them in the ways of magic. However, few of these efforts have ever born more than a modicum of success, almost as if the Gods themselves sought to keep magical ability, and prowess out of the exclusive grasp of the elites. Angered by their inability to gain this power for themselves, noble houses have long sought to have magic banned, or severely regulated, and many bloody conflicts have come to pass over this issue. More recently, however, some reckless, if well meaning, mages have accidentally unleashed destructive powers which ravaged the lands, and gave their enemies exactly the excuse they needed to turn public, and political opinion against them. Hunted down and imprisoned, if not outright executed, mages fled to a land where they could regroup, and band together to impose their own laws, and rule, without fear of interference, or harm. Shekar Roman troops were professional, dedicated, and well trained soldiers. Their choice of armor, and weapons carefully went hand in hand with their tactics and strategy. You can explain it much the same way (read up on how effective Roman tactics and formations were, and how carefully crafted/chosen their equipment) An easy explanation for them not widely using cavalry is that their nation doesn't have a lot of horses available, and perhaps there even exists a social dislike for the animals (religious perhaps?). Bows? Maybe these guys are very big on martial prowess, and dislike "cowerdly weapons". As you can see, there are plenty of reasons for the world to be shaped the way you want :) [Answer] ## Every military developed in a unique environment and developed unique solutions for that environment This is standard evolution. Each environment has optimal solutions. On the plains where mobility is effectively unlimited, an army with high mobility will crush an army that lacks mobility. Thus, all those armies that aren't mobile don't survive to perpetuate their weapons or tactics. Conversely, in tight constrained spaces like caves, high mobility isn't as useful or even possible. Instead, cave-based armies will develop advanced sensory capabilities to detect enemy troops. We see this kind of evolution/optimization here on earth: The Mongols developed an incredible combination of archery and horsemanship because they lived on the steppes of Asian as herders. Mobility was their lifestyle and lends itself very well to extremely fast tactics. Modern Americans have developed high precision, low collateral damage weapons in part because of political pressures far from the battle field (there's lots of other reasons too). Conversely, a modern nation that doesn't care about collateral damage as much won't have the same pressures (or will have different pressures) to invest in high precision weapons. ## See Ancient Persians for how this would work As an example of a highly diversified military of conquered peoples, look at the ancient Persians. The Persians didn't have a great navy when they conquered the Phoenicians (who had the greatest navy at that time). Instead of destroying that navy, the Persians "hired" them as their navy. It just requires the right type of policies to pull off. [Answer] I think it is perfectly plausible. Why do people tend to specialise for warfare? This is due to many elements, among which cultural effects, historical, but also environmental. As an illustration, we could need to see each of those to explain their specialities. * Mujeri, well that's pretty clear. Magic is frightening, and wizards were persecuted, so they gathered together for mutual protection. They created their own society, which lead into a country. With the time they incorporated non-magical folks (muggles?). But their main military strategy is based on those occult powers. * Dwarves. The Dwarves are a brilliant race. They are clever and ingenious. They live in mountains with mines, developed advance forge techniques and their metal work is second to none. However their natality is very low. True, they live long enough, but their numbers are comparably low. Thus they developed military strategies based on a heavy protection, many machinery, with the aim to limit their own casualties. * Vesprian live in an area with a lot of game. But very dangerous animals, that you need to kill from far away. And their last military leaders showed that in battles the bow proved to be a decisive components, compensating inferior infantry or cavalry for a much cheaper price. * Gremian have a nomadic culture. The plains are quite rough, and hard to get agriculture done. So they live in tribe travelling often to get the best grass for their sheeps. Due to their frequent travel, their most priced possessions are their horses. They regularly fight each others, but are almost always riding. But whenever they face common foes, the Riders of Plains become very hard on the battlefield, forgetting, for the time of the battle their issues. * Shekar is a heavily populated country with large cities. The country suffered terribly last Century due to civil wars, insecurities and general chaos. At the end of the war, the society involved in a heavily disciplined country. They progressed a lot since the wars, but they did not yet managed to get back to their economic golden age. However, the numerous and disciplined army allowed them to overcome and unite their neighbours into an Empire. Those are examples of how it could be done. [Answer] Well, we can start by assuming the setting to be Permanent Middle Age. 1. The Shekar are your classic imperial heartland. Fertile plains and forests watered by abundant rain in the spring make for a vast land of yeoman farmers, each rich enough to pay for their own weapons and armor (but not rich enough to each keep a herd of horses - the valuable land is better used for crops), and thanks to good land yield, vastly numerically superior to all their neighbors. The economic equality and rigors of farm work, as it did in ancient Greece and Rome, engenders a certain grit and a unique fighting style. This makes them naturals at massed formations. The Jamesian empire arose here, as the three most powerful noble republics joined forces in the Eluvian League. This also explains the 3-fold division of power in the Shadow council of the Empire. 2. Mujeri: Magic is heritable. Your "unfortunate events" caused the Butlerian Exalted March, and added the 12th commandment to the Orange Catholic Zensunni Bible: "Thou shall not allow a witch to live" (it also applies to warlocks). The zealots exterminated magical talent from everywhere but the Mujeri islands. The Jamesian Empire has enacted a rather precarious Edict of Tolerance in the great port-city of Hombri, allowing Mages to walk the Continent again, with a limited and grudging tolerance by the population. The need to trade with the mainland for food and other staples, combined with Shekar control of the vast (formerly Vesprian) naval force makes the mages cooperative. 3. The Ereborian Dwarves are relatively few in number, with the Northern European low fertility, late marriage capital accumulation pattern, richest of the nations, a democracy, and hugely xenophobic. They literally refuse to shed "one more drop" of dwarven blood then absolutely necessary, and have done the classical economic trade-off of labor for capital. While their (reluctantly provided) troops are not much use in the open field in their 100kg spell-reinforced dampened and diamond-forged full plate armor (not that they'd show up there willingly anyhow), their siege engines are unmatched in the world, making them vital to any large scale imperial offensive war effort. After a few brief border wars, they were quick to acknowledge the superior numbers and military genius of the Shekar, trading Shekar protection for taxes and the current limited level of military participation. 4. Gremia and Vespria I'm having a harder time separating these, since stepped horsemen have been traditionally good archers as well. Contrary to other posters, vast plains do not make horsemen vulnerable to infantry, especially if the horsemen have bows. Moreover, the conquest usually goes the other way - from the horsemen on the plains to the settled lands. Mongols conquer China, whereas Russia only really defeated the Golden Horde by adopting their fighting style, and finally via firearms. Perhaps Vespria is a vast wooded, hilly and heavily fjorded area where a special kind of wood grows that makes for greater bows with superior range, but Gremians would still be archers as well as spearmen. So how were the steppe nomads subdued by the Shekar? Perhaps they were not, perhaps they are shock mercenary troops, serving for money. The Jamesian Wall put an end to their depredations in Shekar. The other neighbor Vespria is poor and full of skilled bowmen. Becoming Shekarian-led cavalry for hire might not sound like such a terrible idea, if the bribes and loot are rich enough. Perhaps the occasional (unhappy) Shekar princess is thrown into the mix to sweeten the deal (and, incidentally the way Byzantium and China both dealt with horse nomad khans, by the way). As the Romans had auxiliaries, so will your Jamesian empire use the talents of the nearby powers. Over the generations, certain nations develop a reputation and specific fighting style, like Scottish highlander mercenaries or Swiss Landsknecht. Practice makes perfect, and as you said, your guys get the most practice in their respective fields. There are other siege engines, but Ereborian ones are just better, just as there are other horsemen, but not many who can put an arrow through a ring at 100 paces while riding a horse backwards like the Gremians can. Anyone can import teak wood and make a bow, but only the Vesprians have the centuries long tradition and secrets to make them unmatched in range and penetration. There are now mages born elsewhere, but nowhere do they reach their full potentiall as well as those who get to study for decades at Mujer-Aarat, the Great Academy. And other people are brave, but the decades of rigid discipline and centuries of farm-work make the Shekar peerless as infantry formations. [Answer] Have you considered separating the countries using different principles of war that result in the unique styles of combat? Perhaps each leader (and his predecessors) has had a bias for a specific principle, resulting in said specializations. The Gremians: Perhaps they have a bias for offensive wars. Strategic, offensive cavalry charges combined with flanking techniques have allowed them to conquer the plains. They focus on the principles of using their entire force with the utmost energy, a decisive point of attack, and to never waste time. In modern terms, they go "balls deep", or "all in, all the time"; Also known as "the best defence is a good offence". The Vespria: The Vesprian prefer defensive wars. They like to shoot down their enemies before they get close - They depend a lot on chokepoints, and ambushes to quickly overwhelm the enemy invaders from range. Their long ranged bows and extreme accuracy allow them to train archers that chain together through the sending of messages attached to arrows (or specifically designed message carrying arrows) to send messages between positioned troops far quicker than a horseman or a pigeon could; this also allows them to have a focus on both keeping and attacking military intellegince as well - they can shoot down carrier pigeons or horsemen that pass through a path in order to attack the enemies lines of communication. To them,"information is king". These tactics have allowed them to conquer the forests, giving them room to set up ambushes hide the paths of arrows shot for messages. The Dwarves: The dwarves take the other side of the spectrum of Offensive tactics when compared to the Gremians. While the Gremians rush in like a flock of crows, the Dwarves resemble more a modern tank. Roll slowly, over everything and anything (seige engines), and be superbly armored and hard to kill whilst doing so. They take the careful approach in war - if anything looks like it could be a trap, they'll lob some boulders at it until they're sure it's not a trap. Protect the assets at all costs, and make use of terrain. If there's a stallactite in a cave, we can shoot it down to cause damage. They enjoy the principle of shock an awe, with a focus on the destruction of infrastructure and not civilian casualties. After all, who wants to fight with a giant flying flaming rock? The Mujeri: These mages focus on the principles of secrecy and surprises. They've recognized that surprise plays a greater role in tactics than strategy, and focus on developing craft that can surprise the enemy. They'll use hit and run, sabotage, and other guerrilla warfare type tactics in order to win wars. The Shekar: Superior organizationa nd standardization in this case means that they've developed the knowledge and understanding of all the principles of war, compared to the other nations who are solely focused on specific principle(s). They're able to adapt, and understand that an army needs to adapt to survive. So, how do we conquer all the races using the Shekar? First, the Shekar should acquire the mages of the Mujeri. As they are on a remote chain of islands, it should be simple enough to force a surrender simply by surrounding the entire chain of islands using a navy and cutting off their supply routes, before employing their own guerrilla tactics against them - hit and run all their supply depots, force them to surrender due to starvation/lack of resources. Especially since not everyone in the clan is a mage, this task should be fairly easy. Once the Shekar have acquired some mages, they can turn to the plains of the Gremians. They desire the Gremian cavalry, but since infantry can seldom handle a cavalry charge well, a better option is to trick the Gremians. Dig a trench in the plains of the Gremians, and use their principles against them (again). They'll charge in, and the mages can create a fog, making it unclear and hard to see the trench which will trap the cavalry once they drop in. Burn them, stab them, do whatever you want with them afterwards, but their all in all the time principle will lose them the war in this case. Now they can turn to the Dwarves. Machinery is slow and cumbersome, vulnerable to rushes. Infantry were bad enough against horses to begin with, but cavalry in this case also are fast enough to stop the dwarves from aiming their seige weaponry effectively. Disabling those machines and having the dwarves surrender should be an easy task, especially if you take into account the posibility of using the mages to provide stealth cover for the cavalry rush, helping them reach the dwarves before they notice. Finally, the Vespria. Now that the Shekar have giant war machines, you can disable every ambush looking like location, or destroy chokepoints completely. Don't enter the forest - tear down the forest as you path through it, forcing the Vespria into an open area type offensive, where your cavalry will cut them up, or the Shekarian infantry can utilize romanized shield tactics (Commonly referenced to as "tuck tail!" from 300"). ]
[Question] [ I am trying to design spacecraft with realistic mass estimates, so that I can "accurately" design fuel requirements and calculate potential speed. Obviously the mass of a ship is going to vary widely based on in its dimensions and purpose (a 500m long freighter will have a very different mass than a 500m long battleship). That being said, I am trying to come up with some reasonable estimates and real world comparisons so that I could quickly estimate the mass of any ship. I have looked at the mass of nautical ships, aircraft, real spacecraft, and fictional space craft; the numbers seem like they vary so much that I am not really sure where to go from here. Here are some rough approximations I have gathered so far as a starting point. * The space shuttle (empty) ~= 75 metric tons. * A 757 at take off ~= 100 metric tons. * The ISS ~= 450 metric tons. * The Seawise Giant (largest ship ever built) has a full load displacement ~= 654,000 metric tons. * The Starship Enterprise ~= 4,500,000 metric tons (this seems absurd to me compared to the other measurements). As for technology level, I am thinking something like 300-400 years in the future. I want to create something with elements of space opera, but based more on hard sci fi/realistic constraints. Because FTL is out, I am imagining a solar system where travel between plants and satellites is relatively easy and quick (like a few months to outer solar system instead of years), where the OORT cloud is the untamed frontier, and if humans have left the solar system, its only in generation ships which effectively are cut off from the rest of humanity. Edit After digging around on the [site](http://www.projectrho.com/public_html/rocket/basicdesign.php) that Jim2B listed, I found this excellent section on interstellar trade: <http://www.projectrho.com/public_html/rocket/basicdesign.php> There are a couple of paragraphs on estimating the size a ship based on the tonnage of its cargo, which could of course be used to calculate tonnage from size. This is really perfect for my purposes, because even though I asked about mass specifically, the real problem I am trying to solve is how large do ships need to be to accomplish "x" task. I was probably going about it slightly wrong as I was trying to think in terms of "how large is a plane, or an ocean liner, or a battleship, etc." The approach from Atomic Rockets is much more systematic. [Answer] Please read the [Atomic Rockets: Basic Design](http://www.projectrho.com/public_html/rocket/basicdesign.php). It has everything you need to know. ### There's no "one size fits all" answer The reason no one can answer your question specifically is because spacecraft are not designed generically. Each spacecraft is designed to optimally complete its mission. A spacecraft designed for one purpose (e.g. a Pluto flyby) will only be used for this mission. We will also never see that one again, the ship is gone for good because it's too expensive to include fuel/propellant for the return trip. Make sure the hot end points towards the ground: [![Make sure the hot end points towards the ground](https://i.stack.imgur.com/pcDfu.jpg)](https://i.stack.imgur.com/pcDfu.jpg) If you don't, then you will not go to space today. ### [The Tyranny of the Rocket Equation](http://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html) These difficulties with building spacecraft are sometimes called (both jokingly and not jokingly) the Tyranny of the Rocket Equation. For another take on this Tyranny, you might just read the story ["The Cold Equations"](https://en.wikipedia.org/wiki/The_Cold_Equations). These equations are unfeeling and don't care about intentions, feelings, or most other "warm" sentiments. The [following is excerpted (with editing) from Atomic Rockets](http://www.projectrho.com/public_html/rocket/basicdesign.php#id--Every_Gram_Counts): > > As a rule of thumb, a rocket with the highest $\Delta V$ capacity is > going to need three kilograms of propellant for every kilogram of > rocket+payload. The lower the total kilograms of rocket+payload, the > lower the propellant mass required. > > > Say the mission needs 5 km/s of $\Delta V$. Each kilogram of payload > requires propellant to give it 5 km/s. > > > But that propellant has mass as well. The propellant needed for that > original kilogram of payload will require a second slug of propellant > so that it too can be $\Delta V$ to 5 km/s. > > > And the second slug of propellant has mass as well, so you'll need a > third slug of propellant for the second slug of propellant — you see > how it gets expensive fast. So you want to minimize the payload mass > as much as possible or you will be paying through the nose with > propellant. > > > And for the rocket equation, everything that is not burned fuel/spent propellant; counts as payload. That includes such things as engines, structures, radiation shielding, food, people, life support, unburned fuel, unused propellant, etc. Even in the most advanced and optimistic designs, you're going to have 3 kg of fuel/propellant for 1 kg of everything else combined. Unless you're using very high specific impulse engines, you won't go on a cruise around the Solar System. People will only travel from point to point if they have a specific mission to perform. Each specific mission will have its own specific requirements ($\Delta V$ requirements, mission payload, etc.) and, therefore, each spacecraft will be designed for its mission. ## A possible answer anyway Many smart people have wondered the same question for a long time. These smart people have developed many different plausible spaceship designs for different missions. You may want to browse through [the list](http://www.projectrho.com/public_html/rocket/realdesigns.php) and see which of these fit your needs. * [Asteroid Mining Crew Transport](http://www.projectrho.com/public_html/rocket/realdesigns.php#id--Asteroid_Mining_Crew_Transport) * [Battleship](http://www.projectrho.com/public_html/rocket/realdesigns.php#id--Michael_Nuclear_Pulse_Battleship) * [Long Duration Science Vessel](http://www.projectrho.com/public_html/rocket/realdesigns.php#id--Discovery_II) One thing these have in commmon, is >2/3 of their starting mass is propellant tankage. ### The take away Spacecraft design is like no other designed craft used on Earth. The closest thing to spacecraft design would be high performance military aircraft. However, spacecraft are more expensive per pound by at least an order of magnitude. The one possible exception to this would be spacecraft designed using the [nuclear pulse propulsion](http://jim2b.blogspot.com/2010/11/the-case-for-space-viii-nuclear-pulse.html). Those might be built using similar cost per pound of construction to high end naval construction (aircraft carriers and/or submarines). NOTE: I used fuel and propellant and fuel somewhat interchangeably. However, except in the case of super high efficiency nuclear or chemical engines, this almost always not true. Fuel is the expendable that provides energy. Propellant is the expendable with which the ship exchanges momentum to accelerate your ship. [Answer] For the dozen or so unmanned space missions I've been involved with, payload density usually ran about the same as water. That does not include boosters. So, as a first cut, you need to figure out the volume of your spacecraft, then multiply by 1000 kg/cubic meter. It's pretty clear that this estimate is not off by an order of magnitude, although the density may be somewhat less. Consider surface ships, which by their nature have densities less than water. Manned space vehicles have much heavier walls (pressure containment) but large voids internally. Also keep in mind that density will probably decrease with increasing size, just as it does with ships. Hull thickness remains fairly constant with size, but hull area only goes up with the square of vehicle dimension. ]
[Question] [ Closed. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it focuses on one problem only by [editing this post](/posts/28021/edit). Closed 6 years ago. [Improve this question](/posts/28021/edit) Inspired by the question: "[How would the world governments react if the supernatural was discovered?](https://worldbuilding.stackexchange.com/q/27798/75)", I have a question that is a variant on this theme: Thousands of years ago, the rational and magical worlds split as the result of a magical war, the consequences of which split reality itself, with most of the things that were magical ending up over there in the magical realm, and most of the rational, explicable things ending up over here in the rational realm. The rift between the magical and the rational deepened until the two halves of Earth's reality were so 'far' apart that communication between them became vanishingly rare, limited for the most part to chance accidents resulting in a person slipping from one reality to the other, and the actions of powerful magical beings who - for the most part - aren't interested in the deeply un-magical rational half of reality. However, the two halves of reality were always meant to be one, and a goddess from the magical half of Earth's reality has decided to work toward bringing Earth's magical and rational realms back together. In Earth's rational realm, things have progressed as we have experienced here on our earth. Magical events and creatures have been dismissed as myth and legend, and no scientific proof that they ever really existed has ever been found. However, in the magical half of Earth's reality, some of humanity has escaped the bounds of Earth and has spread out amongst the stars along a magical system of marginally-breathable air-filled 'tunnels' at about 0.35 ATM pressure, known as the Gyre, that forms a network connecting stars with planets that have oxygen-containing atmospheres, that is shorter on the inside than outside. The reduction of real-space distance in the gyre is approximately: Gyre Distance (km) = 2.5 × π√[Normal Space Distance (km)] So, as an example, a distance of 50 lightyears between inhabited systems (4.73 x10^14 km) would be reduced to 2.5 times the PIth root of that distance, or about 117,000 km of air-filled 'tunnel'. This represents the typical minimum gyre-distance between worlds gyre waypoints, several of which need to be passed to travel to another world. So, given that background, we have a modern-day Earth, almost completely unsuspecting of the magical realm that is so near yet so far away, until one day magical, inexplicable things start happening, at first small, but quickly ramping up to things such as a whole city-state on the top of a mountain over three kilometres high appearing with the dawn, remaining for most of the day, then disappearing and appearing elsewhere at that new place's dawn, or people who claim to come from other worlds showing up in hundred-metre-wide flying saucers that mass about the same as a World-War-II battleship, hovering over major population centres and requesting to open trade relations. If any government tries to shoot the flying saucers down, the saucers are also armoured like WWII battleships (or better), and anti-aircraft missiles would have little effect on them - it would take an all-up anti-ship missile or a close-ranged nuke to have any significant effect on them, and these flying saucers have the ability to outrun (top-speed in-atmosphere of 7,000+ kph) and out-manoeuvre (4g turns) such missiles, and are also armed with a variety of weapons including lasers powerful enough to bring down any aircraft and seriously inconvenience a modern naval ship. If a flying saucer was to be brought down, their power sources, drives and much of their other equipment cannot be duplicated in a non-magical environment such as our rational realm. Conversely, if any governments attempt communication with the saucers' crews, they would be readily told that there are a dozen or more worlds accessible via the Gyre that are inhabited by humans or human variants that these travellers are attempting to bring back into contact with one another via peaceful trade relations, in addition to which there are many worlds with alien life, some of which is sentient and also travels the gyre. If people from the Rational world were even able to find and enter the gyre (it's pretty simple - go to about 10,000m and fly directly away from the sun at 40-85 kph in a place that is gyre-accessible, which at present eliminates most if not all of the Rational realm), I'm not sure that any of our aircraft have the speed or endurance required to make the 100,000km+ journey through the gyre to the nearest other world - the flying saucers use a couple of varieties of magical-phlebotinium-fuelled atomic power. The relocating mountain is the seat of power of the winter goddess' avatar, and is itself set up as a trading society, trading magical goods and educational services for food and other goods that require large areas of non-winter-bound land to produce, and is itself heavily fortified to discourage the communities it visits from deciding to raid rather than trade. This mountain and its goddess are unrelated to the saucer-people, but they know of and trade with one-another. So, how would our world's governments and communities react to these revelations? There's no chance of hushing them up, given all the civilians who will see 'impossible', magical things. While our technology is in many ways advanced over that of these magical people, at least some of them have combined the technology they have with magic, and in many ways we are playing second-fiddle to these travellers with their magical aircraft and the moveable mountain that we can't duplicate or emulate - yet. EDIT In response to an answer that posited that a war would be inevitable: The Gyre consists of air-filled tunnels with insubstantial walls that range from 50 to 1000 kilometres wide, at an atmospheric pressure of 0.35 ATM, equivalent to a terrestrial altitude of 9-10 thousand metres, though the atmosphere is about 38% Oxygen, 55% Nitrogen and 6% Helium. While the net air speed within a gyre stream is on the order of 5kph, each stream has several air currents that flow in either direction at up to 2,000kph, that contain particulates at their cores, some pieces quite large, as well as frequent lightning activity - there's a reason that gyre-capable aircraft are heavily armoured - being hit by a stray rock travelling at up to 12,000kph relative to your aircraft is no joke. It is possible to 'fall out' of the Gyre into interstellar space, from where return is effectively impossible. The gyre streams are hundreds of thousands of kilometres long; to reach the nearest gyre-accessible world nearest to Earth would be a journey of around 660,000 kilometres - not too difficult in space, but when flying through air, that's impossible without either atomic power, or the willingness to take weeks to months, depending on how close to the dangerous high-speed currents you're willing to get. Our aircraft just aren't made to have that kind of endurance. Then there's the problem of navigation - the saucer people use a combination of inertial and spectrographic methods, without which the gyre is a confusing maze of tunnels joining light and dark nodes. The saucer people don't just have flying saucers with hulls with the equivalent of over 2.6m of battleship armour in every aspect, (which can carry up to 78,000 metric tons of ordnance, war material and personnel if necessary). They have access to thousands of mecha: large mecha armoured about as well as a modern main battle tank, and smaller ones that are still armoured as well as a light tank. They have atomic-powered fighter aircraft with reactionless thrusters that can pull 14+g manoeuvres without inconveniencing the pilot, armed with the aforementioned lasers plus missiles with atomic engines and all-aspect homing - they don't lose target lock, you have to actively break the (magical) lock, or kill them. They have tractor/repulsor beams that could lift a modern cruiser out of the water or capsize an aircraft carrier. Their ground troops are protected by body armour that can stop almost any pistol bullet, and provides decent protection against rifle ball ammunition up to .30", even directly to the visor of the helmet - it'd take a .50"+ bullet or an AP round to seriously inconvenience the wearer. On the other hand, the saucer people don't want a war - they're traders by inclination, but from a military background, so they'll defend themselves if pushed to it. The Winter Goddess doesn't want a war either, but if pushed to it, she has enough magic to teleport a whole 3km-high mountain on a daily basis, or turn an enemy army into a collection of ice-rimed statues. Then, while there are multiple magical realms local to Earth, their populations are for the most part incapable of dealing with a modern military, but they also have magi, some of whom specialise in fighting, and even one could seriously inconvenience a modern technological army. I'd anticipate that any war between the magical and rational realms would be bloody and inconclusive, with heavy losses on both sides, and would most likely result in Rational Earth being abandoned to its fate by the magical peoples, knowing that there was a whole galaxy out there, but denied access to it in the short-to-medium term. [Answer] Okay, thanks for the clarifications, and pointing out that the current generation of humans are not isolationists like the Shogunate. Assumptions: * Since the magical worlds are opening the relationships without direct threats, there exists no strong xenophbia against their rational brothers. * The magical worlds do not have a policy for pre-emptive intervention in place. The population and governments of earth would probably have mixed to negative reactions to their estranged brothers. At least by our social norms, when you wish to establish diplomatic contact, it is commonly understood that you send diplomatic officers and never, ever, accompany the envoy with a very big army. While sending envoys with armies may be a custom in the magical world, the governments of Earth would probably remain inside the mindset of Terran international politics and interpret it as a thinly-disguised show of force to instill diplomatic pressure. Reactions would be polarized, between those who sees the magical worlds as a new world to explore and those who sees them as a threat. Xenophobic groups would probably spring up everywhere, as they would whenever contact with a new ethnic group or nation occurred, and quite a few of them would probably turn to terrorism. Whether these xenophobic groups could be handled in a mature manner would have a very large impact on the nature of the political relationship between the two worlds. Scenario: Acceptance If the rough edges and culture shock caused by First Contact would be sufficiently cushioned, then normalized diplomatic and trade relations could be established between the two worlds. Politics and society would largely play out as normal: alliances would formed, stronger powers preying upon weaker ones, and everything that goes on in international politics. Life, generally would go on a bit changed, or as normal. One of the more interesting things to explore in this case would be the relations between the existing nation-states of Earth in this case. It would be harder to say if the nations would want to band together under a "Terran" identity, or use the newly discovered magical world to get a better edge on their rivals. Post normalization society would see leaps and bounds in knowledge. The rational humans would definitely attempt to analyze and quantify magic, either within the current scope of physical laws, or constructing new frameworks of laws to accommodate new findings with the introduction of magic. A new golden age for humanity on both side of the old divide is probably the most likely answer. Scenario: Xenophobia If terrorism cannot be satisfactorily stamped out and/or xenophobic sentiments become dominant, then a Cold War would probably start between the two worlds, similar to the one between Terrans and "Spacers" in Asimov's robot novels. The Terrans would know that they cannot match the paranormals in a hot war, at least within the near future, which would lead to a siege mentality, knowing that their neighbors could, if they wished, turn their homes into craters of glass and there is nothing they could do about it. Militarization of the society would be inevitable, and so would be propaganda demonizing the enemy. The rivalries currently existing between nations would probably be put onto the back burner, and almost certainly the military powers of the day would put their heads together to figure out how to at least match, if not surpass, the magical world in terms of arms. Technological and cultural exchanges would still occur, as the Terran governments would like to know as much about their enemies as possible. The governments of Earth would probably also face the problem of "Erdeflucht", where sympathizers and those who prefer living the magical world try to cross over the other side. Because of the siege mentality, they would inevitably be branded as traitors. Brutal purges, either lead by governments or by spontaneous mobs, would probably be carried out to root out these sympathizers, along with moderates. These conditions would probably last until one of the following happens: A hot war occurs, due to some hothead on either side. This kind of war would be a war of subjugation at best and ethnic cleansing at worst. The odds of a Terran victory goes up with time in preparation, as the magical world is probably not accustomed to Terran wars of annihilation, and every year allows Terrans to better analyze and replicate or at least counter magic. Or, alternatively, the pressures of the Cold War completely shatters society on either side, in which case, whichever side shatters first would fall completely apart as hardliners that kept them together are ousted and moderates come into power. Just like post-Iron Curtain Europe, the two worlds would have a relatively normalized relationship afterwards. [Answer] 1) Any sufficiently advanced technology is indistinguishable from magic. Due to the damage of that war to the Rational Humans' psyche (that was so great that it literally erased itself from our history), the Rational Humans will probably never fully recognize magic as being magic. They'll come up with some technobabble to explain what's going on. Oh, that is not really a floating castle, it's a teleporting spaceship that is controlled by aliens. The Gyre is simply wormhole-based FTL. The Magical Humans must have access to the Babel fish, that's why they are able to talk in all possible languages. The "goddess" just has a lot of cybernetic upgrades. And so on and so forth. And the Magical Humans can't really dismiss the Rational Humans' explanations. After all, the Rational is just one side of the same coin of humanity. 2) The Rational Humans will treat the goddess' schemes to merge the two worlds as a literal alien invasion and respond accordingly. This response may not necessarily be hostile. Some humans may very well welcome the aliens and support the scheme to 'uplift' the rationals into a new, technologically advanced era (even if they keep on calling their cyberpunk upgrades as "spells" for some reason). But I think most humans would resent the idea of highly advanced aliens coming to Earth with the explicit purpose of destroying their rationalistic way of life...because, well, some so-called 'goddess' thought it was a good idea. These other humans may not be able to do anything overtly (the aliens are too advanced to be countered), but I think some low-level resistance is to be expected. 3) Expect a few people (likely government bureaucrats) to try and figure out what actually happened in the 'War'. Why did this war happen in the first place? Was the Magicians the aggressors, or was the Rationals? This knowledge is not mere trivia, it's a good way of determining the true intentions of the Magical Humans and their goddess, as well as learning how to counter them (after all, the Rationals could have said to 'stalemated' the Magicals). Actually figuring out what happened is going to be difficult at best: the only source for this war is from the Magical Humans, and you can expect them to be biased. [Answer] I don't see any reason anything bad would happen. It seems odd that no government from the magical side would make contact with any large government on out side. If this happened then everything would work out pretty well. In general if they look like us, and speak like use and for all we can tell they are like us, it wouldn't cause much issue. Humanity isn't nearly as prone to try to conquer people these days. The reaction around the world would be as varied as the world itself. Some would welcome our new friends with open arms, others would be distrustful, others would want them to leave. Religions would spring up, established religions would get mad and so on an so forth. There'd be some fighting here and there that's for sure. Some people wouldn't take kindly to these people. Other issues would pop up like this magic mountain would be a HUGE security risk for every country that it pops up in. If the magic side just forces itself onto our side, it would make relations worse. If the Magic side was willing to talk and sort things out then that might happen. The situation would be so varied and complex. If you want to pick certain areas or people in the world I'd gladly give even more info, but I don't want to write a book just on this question :D [Answer] New answer due to recent clarifications, disregard this answer The reactions would probably be a large war or a series of wars, since no one really likes being gun-boated into doing anything. Most people on Earth will be resentful of being visited by what they see as an attempt to strong-arm them into some commitment. War will break out, and it will only be a matter of time. We can look at the dismantling of the Japanese Shogunate as an example: Perry's fleet showed Japan what lies outside of its borders, and Japan assimilated as much as it could, before committing herself to expanding her borders a few decades later in the Russo-Japanese and First Sino-Japanese War, culminating in WWII. Since the fantasy universe is rather behind the rational humans in technology, it wouldn't take too much reverse engineering fro the rational humans to either figure out how the magic works (assuming it is rules magic). On a side note, it would not be too difficult to mission-kill a target armed as heavily as a battleship, even if it is doing 7000kph and pulling 4g turns (which is not exactly maneuverable for modern aerospace technology standards). Concentrated small-caliber fire have disabled battleships, and in many cases even destroyed them through fires that started on board. The technology for knocking these things out of the sky like big rail guns, gigawatt-rated lasers and hypersonic missiles (or even hypersonic nuclear missiles), wouldn't be that difficult to create. A lot of them are already existent in rather crude forms in the Strategic Defense Initiative. Actual pitched battles would be difficult to model, considering you have only provided detailed information on saucers, which would be only a single component of an entire armed forces. If most of the magical worlds are medieval high-fantasy-ish settings, then casualties would be significantly less for the humans, because then the saucers would pretty much be the only effective weapon system the fantasy worlds can field, barring hand-wavy things that directly manipulate reality on a massive scale (<http://tvtropes.org/pmwiki/pmwiki.php/Main/RocksFallEveryoneDies>). Slade Stuart's "Salvation War" and Takumi Yanai's "Gate" would be the example here. Assuming the humans can counter the saucers in any way, then the rest of the fantasy worlds are done for. In fact, the saucers can even be left alone and the armies of Earth can go after what is behind the saucers in the Gyre. Armies only work when there is a country behind them, and with the industry and agriculture supporting them burned to the ground, the army will simply starve to death. On the other hand, if the magical worlds all have at least the saucer-level tech/magic content and has the magical equivalent to tactical/strategic WMDs (TSAB-style), then Earth wouldn't hold on too well in a war with early 21st Century equipment. In that case, the magical world wouldn't even have to send ground troops, burning Earth (or enough of Earth to force a surrender) to a wasteland from orbit would be the cheapest option if a war breaks out. And even if the fantasy worlds avoid WMDs, I'm pretty sure Earth armies will not like the thought of fighting an enemy whose basic infantrymen can take as much punishment as a main battle tank and dish just about as much in return. So anything from a quick victory for Earth to Earth becoming a ball of iron coated in glass, all depending on what the rest of the fantasy worlds look like. Since the saucers is only a single link the entire war machine, it is difficult to describe what would happen in the war that ensues. ]
[Question] [ Space is full of radiation. When doing long stays in space, no matter whether it's a generation ship on its journey to a new colony, a research ship exploring new worlds, a freighter delivering goods, or simply a space station outside the protective magnetic field of earth or another planet, the people on the ship or station need to be protected from that radiation. As far as it is a space ship, the shielding should also not increase fuel consumption too much (this should be less of an issue for a space station, obviously). So, what would be the best strategies to shield your space constructs (and especially the people inside) from radiation? [Answer] There are two primary methods. Mass or magnetics. To pick one over the other may depend on where the ship is going, interplanetary or interstellar, but a mix is best. There is a [good discussion](https://space.stackexchange.com/questions/797/radiation-shielding-magnetic-or-mass-which-is-more-efficient) on the Space SE. Mass This is the easiest method (or at least the most intuitive). Just put a bunch of stuff around you to shield from radiation. One interesting implementation is to surround the ship with water ice. This doubles as water storage and radiation protection. Water actually shields quite well, and is only [slightly less effective by mass than lead](https://en.wikipedia.org/wiki/Radiation_protection#Shielding). Packed soil works too, so the inside of the ship could be farms that also shield from radiation. ![diagram of toroidal ice shielded ship/space station](https://i.stack.imgur.com/2jYnp.jpg) Magnetics This is familiar because the Earth has magnetic shielding that protects us from radiation (though the mass of the atmosphere does a whole lot too). ![long exposure photograph of plasma being redirected by magnetic field](https://i.stack.imgur.com/HAHqI.jpg) The image above demonstrates a magnetic shield example given by [Science News](https://www.sciencenews.org/article/magnetic-bubbles-could-shield-astronauts-radiation). The problem with magnetic shields is they do not protect against charge neutral particles. However, they can get a nice reach compared to a mass shield. Thus they can be used to guide charged particles into a collector (away from humans) or at least away from areas of weaker mass shielding. They also weigh a whole lot less, which is important when considering the launch of all this material into space. Solution The best solution uses both mass and magnetics for protection from radiation. This is what the Earth does for us and the Earth's protection is exactly what you're trying to replicate. If this is a colony ship, put farms and water storage around the inside edge of outer hull of the ship (mainly in the direction of travel). If it's interplanetary then a lighter mass shield (oriented at the Sun) and strong magnetic shield might be enough. As with any design, the engineers will need to weigh the probability of a collision, consequence of that collision (or collision rate), the shielding required to protect against various collisions, and the costs associated with that shielding (energy to launch and move the mass, decreased maneuverability with increased mass, energy to generate/shape magnetic fields, etc). ]
[Question] [ Having looked at some of the questions regarding creatures with more than four limbs, I've found some useful info, like the idea that additional limbs increase stability while requiring more brain power to coordinate. This helps me imagine how a fictional group of hexapodal animals could evolve. However, I'm having trouble picturing what the basic structure of a vertebrate with additional limbs would look like. I'm not talking about specifics like a dragon's wings or centaur's hooves. I mean basic things - assume we're taking about a common hexapodal-vertebrate ancestor here, not the ins and outs of specific mythological creatures here. I know tetrapodal vertebrates have a pelvis and shoulder blades, which function differently because the forelimbs and hind limbs serve different purposes and take different amounts of impact. So I assume hexapods would have similar features... But with three sets of limbs instead of two I'm not sure what changes. Are the middle limbs attached to a pelvis, to shoulder joints, or to something else entirely? Where would the ribs go in relation? I'm sure there would be other things needed that I'm not thinking of because I'm not overly familiar with anatomy to begin with (and please forgive any errors because of that). [Answer] You would really have to rewind the tape of evolution in order to do this properly. All Earthly animals are bilaterally symmetric and have 4 limbs because they are descended from fish. Fish are bilaterally symmetric and have 4 fins because that is hydrodynamic (indeed, we know this is the "ideal" shape because sharks, ichthyosaurs and whales have all independently evolved much the same shape, despite being from different branches of the tree fo life, and in the case of ichthyosaurs and whales, returned to fully aquatic life from a land based ancestor. So you would have to go even farther back in time, perhaps to the [Cambrian Explosion](https://infogalactic.com/info/Cambrian_explosion) 500 million years ago, and preferentially select the "base" animal as something which does not start out like that. The [Burgess Shales](https://infogalactic.com/info/Burgess_Shale) tell us that early animals had all kinds of bizarre and wonderful layouts, as almost any kind of combination that was possible was being tried out. Many creatures in the Burgess Shales have no obvious connection to current life forms, essentially because they eventually died out. [![enter image description here](https://i.stack.imgur.com/DegEs.jpg)](https://i.stack.imgur.com/DegEs.jpg) Opabinia, one of the more unusual creatures from the Burgess Shales Modern animals are all descended from [chordates](https://en.wikipedia.org/wiki/Chordate), which are bilaterally symmetric and have a primitive spinal cord, the architecture from which fish, and ultimately we are all descended. For your answer, we will need to assume that at some point a six limbed creature evolved from one of the Chordate family, and it was successful enough to thrive in the environment, and its descendants ultimately inherited the Earth. It would likely have pairs of limbs equally spaced along the body, in order to prevent mutual interference. Early versions would be much like fish or sharks, and not have strongly defined structures to attach the fins to the spines. As they evolved towards land dwelling, they would also evolve more defined structures to transmit mechanical loads to the spine and attach muscles. A likely development might be for two sets of "shoulder" girdles to develop for the front two sets of limbs, as flexible limbs for grasping or controlling difficult manoeuvres in the water for hunting or evasion would be advantageous. A bottom dwelling and "walking" creature might develop three sets of hip like structures instead. [![enter image description here](https://i.stack.imgur.com/ue6fH.jpg)](https://i.stack.imgur.com/ue6fH.jpg) It all starts here The key is that evolution will change and adapt already existing structures in order to provide the best possible chance to exploit a niche and survive. Who would think creatures as diverse as a giraffe, flying squirrel or anteater all come from a common ancestor? You will also find examples of convergent evolution when creatures exploit similar niches. A Greyhound and Cheetah actually have similar limb structures and articulation of the spine, because they are evolved to do explosiive sprints, despite one being a dog and another a cat. [Answer] In [my reply](https://worldbuilding.stackexchange.com/a/108632/25189) to this question of [Anatomically correct multiarmed humanoids](https://worldbuilding.stackexchange.com/questions/74254/anatomically-correct-multiarmed-humanoids) I suggested the following: > > A similar arrangement of limbs on a mammalian/endoskeletal frame would likely entail the sternum bifurcating and descending to replace the costal margin (and secondary scapulae over the false ribs). This would require significant changes to the respiratory system as the lower ribcage and upper abdomen wouldn't be as flexible; diaphragm-based breathing might not even be possible without further changes to the ribcage. > > > So without diverging too much from the established tetrapod model (though not its evolutionary history; this would be a significant and unlikely deviation) of vertebrate life on Earth, you might reimagine the sternum as an anchorage for an additional pair of anterior limbs. The larger and more robust these limbs are, the more rigid the rib cage supporting the sternum would need to be. ]
[Question] [ Part 1 here: [Creating a scientifically semi-valid super-soldier, part 1: Skeleton](https://worldbuilding.stackexchange.com/questions/106292/creating-a-scientificly-semi-valid-super-soldier-part-1-skeleton/106308#106308) This question is about a complete rebuild of the nervous system. The question as proposed here: [Improving human reaction time](https://worldbuilding.stackexchange.com/questions/10285/improving-human-reaction-time) has only answers concerning upgrading current nervous system. One of the common tropes of super-soldiers is a faster brain so you can see things in slow-motion and extremely fast reflexes, often dozens of times faster than what normal human nerves would be capable off. But how would you go about making a nervous system that is actually capable of such feats? For this question, I'm assuming important secondary nerve functions can be performed by glands or "normal" nerve-ends that are attached to the super-nervous system at intervals. I'm also asking for a biological nervous system that the body can maintain and repair when necessary. For clarity: These soldiers would supplement robotic and cyberneticly enhanced soldiers mostly as canonfodder. The goal would be to split the resource requirement between more rare materials+fuel sources and humanoids that use biological compounds and food instead of fuel. For the nerves there's two things that can improve their ability. First is thinner nerves, as that would allow more muslce-fibers to be directly actuated by a nerve, second is a faster signal propogation. I'm thinking about biological optical fibers, but don't know if that's possible. Alternatives could be extremely long myelin sheeths, but I'm not sure if those would be possible or what kind of speed you would gain from it. What's left would be biological electrical wires. Does anyone have an idea what would be a feasible soft-science nerve? Preferably with the potential propogationspeed of a signal added. [Answer] A possible soft science answer may be to use the skeletal structure modified with the same crystalline structure on the surface of the bones found in the scales of a butterfly wing that would use bio-luminescent glands to transfer data to muscles without the normally slow neuro-transmitters in the normal nervous system. the biological nature of the scales would mean that they could be self-regenerating. [Answer] Per [Hypertextbook](https://hypertextbook.com/facts/2002/DavidParizh.shtml) nerve impulse speeds vary between 0.61 m/s (pain), 76 m/s (touch), and 191 m/s (muscle firing). It also, in the case of reflex, can fire multiple signals and register-but-ignore the late arriving ones. If you were to thread the nervous system with fibers doped with some material at the active sites that converted sodium and potassium surges to an electrical impulse, then had an additional diode-like material to convert that electrical impulse to light, passed the impulse down the fiber, then repeated that process in reverse to stimulate either muscles are excite a nerve cluster, the signal speed would be much closer to the speed of light (300,000,000 m/s). For a 2 meter tall person you would only be shaving 0.01 seconds ( $2 meters \over 200 m/s$) off reaction time. I have an old equation for aiming time. I don't remember the origin, but it was measured by asking subjects to click on a circle with a mouse. $ t = B + a \log({2\pi\over D})$ where D is target diameter in meters and B and a are experimentally determined values. B = 0.5 seconds and a = 0.45 seconds in the test subjects. There is an initial reaction time, but then your brain is engaged in a feedback loop moving towards the target, assessing progress, and moving again. You can shave the 'a' try-assess-correct loop (0.45 seconds) by training and building muscle memory. However, this is available to normal humans and super humans both. If I remember correctly the initial reaction time 'B' did vary between subjects. There are studies indicating that [stimulants](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1334411/?page=6) could drop initial reaction time by 100 milliseconds (20%). Some combination of stimulants and focus enhancers may be able to achieve greater effect. But overclocking reaction time results in the nervous stereotype of someone overstimulated. [Answer] Perhaps a distributed nervous system may help, with individual automatic functions in nerve clusters directly adjacent (or at least closer) to organs they need to control. Cuts down distance at least. Another interesting thing is using a similar brain architecture to intelligent birds. Birds like crows and parrots pack a lot of brainpower into a very small brain, and the way they do this is by having clusters of tiny neurons (which take up little space but can't bridge large distances) connected by larger neurons to link the clusters together. Expand that structure into a brain the size of a human's and you could leverage a phenomenal amount of processing power. Not sure how well that would affect raw reaction times, but it might allow for faster prediction of potential circumstances allowing for reactions to happen before an actual event has taken place. [Answer] Optical synapse The synapse is still an important step in the signal process, allowing for a lot of information modification. To keep this information modification, I would propose an optic synapse. The idea is simple. instead of chemicals, light is shone via a bioluminant lamp in the synapse gap. On the other end, photo-receptors will get agitated, releasing the chemicals into the nerve cell to activate. The gap itself can be modulated by chemicals that reduce the light, reducing the signal. The chemicals are then in turn modulated by reuptake chemicals, which are also present in a normal synapse. Hormones would affect the functionality of the bio luminescent lamp, making it activate longer or shorter. Possibly also more intensely or weaker. That way we have all normal synapse functions covered, namely duration and intensity. In the meantime we're decreasing the time of the synapse as it isn't relying on slow chemicals but fast light. Fibre-optic nerves A synaptic gap where we transform electricity into the light seems inefficient. I would skip electricity altogether and make the whole neuron a fibre-optic. The neuron will fire into a biological fibre . As long as the fibre isn't bent too much, the signal should arrive without problems nor appreciable deterioration. This will be quicker than electricity and saves the step of having the electricity transform into an optical signal. It is also quicker than electricity, a goal many here on the site want. The neuron will simply fire with a bio luminescent lamp into the fibre and it'll arrive at the other side. The fibre will terminate at the dendrite, where it'll have a small hollow with room for the modulating chemicals, making it an enclosed system. replacing the nervous system Will you be able to replace the whole nervous system with this? Nearly. Depending on the neuron, the axon will branch out at the last moment to several dendrites. Either the light should be enough to flood the fibre and it'll distribute itself at the branches, or there would need to be a "distribution neuron". The first neuron will fire all along the axon fibre, which will terminate at the distribution neuron. This neuron will activate, firing light over several axon fibres instead of one, ensuring every neuron will get the message. That does mean a slowdown of the signal in most cases, but with the much faster synapse still a huge net gain. Higher efficiency Fibre-optics have some great advantages. Information travels with the speed of light, literally. The signal is clear and won't deteriorate quickly. Many signals can be send over a signal optic. This last one is both less impressive than you might think as well as game changing. You're not likely to send the information of 20 neurons over one line, having the distribution neuron understand what information needs to be send over what fibre and do it for you. However, you can separate the normal signals that go over the line. Neurons often pull double, if not triple or more duties. For example, although pain pathways are partly separated, they do use existing neuron pathways to transfer information. A neuron that fires for pain can't be used for anything else at that moment, but much like a computer it can switch between the signals fast enough that you'll not notice. Still it represent a loss in signal. Fibre-optic nerves might skip that problem. They can send different light wavelengths down the optic, be received by different photo-receptors that release the chemicals so the correct wavelengths are passed on. A few highway roads can use more wavelengths to pour a ton of information through and with different wavelength diffusers/blockers you can moderate the information, but most likely you'll use it for a single neuron to allow for moderation of the signal. There is also the option to go two ways with fibre-optics. Electrical neurons can only fire one way. Light however can be send both ways at the same time without interference, allowing for further merging of neuron lines/higher density of information. Also the refraction times. Normal electrical neurons work in pulses with a waiting period right after each pulse. This is to prevent noise as well as over stimulation of the neuron. Optical nerves might not need that. They can work on a continuous scale, or with shorter refraction times, as it's easier to start and stop the light wave. This allows again higher (to insane levels) of information density. Other improvements are that fibres potentially use less space than electrical axons, the fibre might break and still work, and are immune to electrical interference. This last one is important. There might be a maximum of neurons you might pack together if they're electrical. They will eventually start producing noise on lines closeby, making the data less useful. Fibre-optic nerves might prevent this fully, allowing you to stuff the brains full with nerves. Solvable problems Now we have a working system of optical nerves. Still there are some problems. Bending of fibre-optics isn't good for the signal and it can bounce back. Luckily the spine seems okay, but many joints in the extremities can move and make too sharp bends. To circumvent this, all neurons must have a electrical bridge between these parts. A neuron in front of the bend will fire electricity, which will excite the lamp on the other side of the bend to fire down the fibre. The "distribution neuron" can take up space required for neurons, making it more crowded than normal. The higher efficiency might reduce the amount of neurons needed, so this wouldn't be an issue. In the brain the fibres might make more bends that aren't suitable for the light to travel through. That is not a problem, as the fibres are stationary. They don't have to follow the normal fibre-optic procedure and can grow in a wholly different way, simply reflecting the light around a bend. That way all neurons in the brain can be optical as well. There is no difference with meyeline sheaths, which can help with the importance of signals. The meyeline speeds up normal electrical based neurons, making it not only faster and clearer, but also more important most of the time. This will be lost. Fortunately that is where the modulation can come in handy. They can have brighter lights and with all other advantages it shouldn't be a problem to identify important stuff still. Potential problems Although the above sounds very nice in theory, practice might be quite difficult. The bioluminescence as well as the photo-receptors might cost a lot of energy. Despite it seeming cool in nature, constant use might still warm up neurons just enough that it'll interfere with enzymes for example. The light given off might also be too little to be reliably picked up by photo-receptors. They might never receive enough light to give off enough chemicals to stimulate the next neuron. Conclusion If it works, it would reduce the normal synapse to much less than half or the original. One side of of the synapse is skipped altogether, as well as instead of chemicals slowly moving over the gap it'll go with the speed of light. The only slowing down of a signal is now in the translation of the light signal into chemicals to stimulate the next neuron. Moreover, the nerves themselves are also sped up as they use light instead of lightning. There is a potential for a higher density of information, both ways on a neuron pair, as well as on multiple wavelengths at a time. This is of course theoretical, but with high potential. You don't stop building a Hyperloop because it's theoretical. [Answer] You can always go down the synthetic human path. A brain made from billions of tiny individual machines that for a network with each other. The connections are non existent because they can communicate trough subspace or some shit. Each such machine would be equivalent to a processor from our time but many times smaller, the size of a neuron and there will be billions of them. They can act as any part of a computer like storage, processor etc. One problem would be the high energy demands of such a rig or the heat from it. Heat resistant synthetic neurons and powered by a fusion reactor in the heart somewhere. The excess heat could be use as a weapon maybe. Firebending synthetic super-soldiers. That would be cool. [Answer] Reaction speed is based on [two main things](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3432961/): nerve fiber diameter and myelin sheath thickness. Improving either or both would increase reaction speed. The effect of increased nerve fiber diameter on reaction speed has actually been [tested in real-life](https://www.mpg.de/15409874/axons-cmtm6) on mice already with significant results. Either increasing myelination or replacing myelin with a more efficient insulator would probably also work but most research in the field has been focused on reversing myelin loss due to disease. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. Nobody knows where the big Blue is. Some people say it's a dream. Some people say it's the space between the worlds, where all the things that fall through the cracks end up. The occasional rains of odd socks and pencil sharpeners make me inclined to believe the latter though. Either way: I know we're falling. Everything, forever, falling through an endless blue sky. The only real stable places are the four Parachute City states: Maelstrom, Charybdis, Freefall and Slip. Four agglomerations of rock and dirt, wooden ships and aluminium planes and some metal parts that nobody left here recognises. Inside we fall along with whichever city we were born on, protected from the winds below by the lee of the city (though the crosswinds can be brutal). The careful or clever can practically jump from one city to the next, helped along by wing suits or windskiffs. The cities keep an even keel and can slightly control where they are in relation to each other with strategically placed hot air balloons and vanes around the rim of the city, where the vicious turbulence as they plummet through the endless sky can dash careless airship captains or wing suit swimmers into pieces. But how large can one of the cities get before they start to tumble or can't hold themselves together any longer? That's what I've been directed to find out. --- How large (in terms of flat square meters on the top, assuming it's held steady) can an object falling at its terminal velocity get before the various stresses tear it apart? Please note the hard science tag: I'm not looking for hard science criticism of the world, just a hard science analysis of the large falling object. If it helps the atmosphere is equivalent to Earth's at sea level and there is 1g of gravity. Time to break out the fluid flow equations! (Or not. ;-) A quick note: I don't care if the answer to this question is 'very small', I can work with that. I just want to see some kind of maths or formalised rationale (with citations or equations, preferably) behind the maximum size. [Answer] It's been too many years since I tried to do a calculation like this so I can't fulfill the requirements of the "hard-science" tag but you'll need to compare it to ship design. For your city to be stable: The centre of mass has to lie below the centre of buoyancy. Now of course there's no such thing as a centre of buoyancy in a falling object but there will be a calculated centre of aerodynamic resistance defined as the point in the structure where you could say "air resistance applies here in this direction" which could be used as an equivalent. (I didn't do anything much with turbulent flows so don't bite my head off if this ceases to be valid outside laminar flow) I my head this requires your city to look something like a more flared golf tee, point downwards with most of the mass in the stem and the population living on top, trailing behind like a parachute over a weight. --- In terms of the available surface area, assuming you have a fairly compact lower length on the stem, you could go happily multistory on the city as the density of housing will be lower than the density of the city base and would help to keep your city stable. The shear stresses caused by the wind on the flare of the Tee are your problem and unless this has been deliberately constructed with metal reinforcement the whole thing will tear itself apart remarkably quickly. --- Balloons round the edge of the city would be in turbulent flow and as such would have no effect. --- Other amusing problem: The city is going to have a higher terminal velocity than a person, wingsuits aren't your problem when jumping between cities, the problem is not being able to catch up with the city again as it falls away beneath you. A long object's resistance is based on its length, a short object's resistance is based on its cross sectional area. To build a city that falls more slowly than a person you need to keep it in the "short object" range. However this will result is a much less stable profile and if a "natural accumulation of stuff" design is followed, it will probably be highly unstable in turbulent flow. Preventing the city from spinning is a life or death issue. It's that or build a hollow cylindrical city with high spin (foils on the outside could do this) and the people live down inside the tube. --- Shortening and stabilising the structure - The parachute spill hole. Sticking with the golf tee but shortening it somewhat to reduce streamlining effects, we're now going to have to stabilise the turbulent flow around the edge. The simplest way to do that is to inject air into the flow just inside the edge of the city, sourcing the air from the highest pressure point, namely the downward tip. To get this right does require some "hard-science" grade calculations that I'm not going to do but we're going to hollow out the leg of our tee as much as we dare so as not to upset the mass balance and run those tunnels to as many points as we can just inside the outer edge of the city. I think we want a slight negative pressure at the point, so the total possible airflow through these smaller tubes should be slightly higher than that through the main leg. We also want to have as many outlet points as possible round the rim. This will (should) have the effect of stabilising the turbulence around the edge of the city and hence allowing a shorter structure to be more stable. It will also allow you to surround the city with balloons and small parachutes to allow better control as you no longer have (have much reduced) the turbulent zone. [Answer] The problem here is that wind erosion is going to be pretty terrific. Those "clumps of dirt" won't last long against hurricane force winds. Remember that a human body falling at terminal velocity falls at about 120 MPH, and dirt plus rocks certainly won't fall slower; in fact, with higher density, they'll fall faster. So either the city inhabitants have coated the bottom with something to keep things from being blown away, or else they have to constantly replenish what gets eroded away. I can see a story idea here, with workers having to constantly work on the canvas (or whatever) covered by netting, which is needed to keep the soil from being blown away. For larger structures, the question of fluid dynamics does come up. But equally important is whatever provides the structure keeping these falling "islands" together. Steel, aluminum etc. simply can't hold an extremely large structure together. The cube-square law places severe limits on the ability of large structures to support their own weight. (And these islands are not actually in "free fall" as the term is used in physics. They are falling at terminal velocity, which means they do have weight. The people walking around on these island will not float off; they'll feel weight.) Frankly, unless you're talking about tiny islands no bigger than a skyscraper -- which would be the approximate limit of size using concrete and steel, or possibly even smaller if constantly subjected to hurricane force winds -- you're looking in the wrong place for a hard science answer here. If you want something that far removed from everyday reality, either assume the laws of physics are radically different (but then, that means anything living has to be far different from life as we know it, so nothing like human beings in the story), or else magic is being used to hold the islands together. Another possibility is to use "exotic matter" with an arbitrarily high tensile strength, like /scrith/ in the RINGWORLD series. But that's near-magical science fiction, not real science. /Scrith/ has a structural strength on the order of the strong nuclear force. With a material that strong holding things together, you can make the islands as big as you want... or limited only by how much of the exotic matter the inhabitants can get or make. If you go that route, I suggest a honeycomb structure of the exotic matter (since it's that strong, the walls of the honeycomb can be extremely thin... even thinner than aluminum foil) with the voids filled with normal matter, or even empty space to make the structure lighter. The exotic matter could also be used for (amazingly thin) structural beams, arches etc. to support buildings on the islands. Of course, if it's exotic matter, you can choose any arbitrarily high structural strength you want. It doesn't have to be as strong as /scrith/, but it should be stronger than carbon nanotubes... which in theory can form structures 30 to 100 times stronger than steel, but in practice don't seem to form structures with long-term stability. In other words, carbon nanotubes break down at the molecular level after a fairly short period of time, so apparently aren't suitable for building things. "The aim of the city is for it to have a lower terminal velocity than a person, ideally, hence the name!" Well then, you need to rethink the idea of the cities being composed of a random collection of dirt clumps, airplanes, and random metal junk. They will have to either be structures built with a density less than the human body -- a lighter overall weight per unit of volume -- or else they'll have to have something like giant literal parachutes slowing their passage through the air... and how long would those last if made of ordinary silk and nylon ropes? Or even kevlar? Again, this is suggesting exotic materials. Even if they are held up by literal parachutes, there's still the problem of holding the entire structure together, and the severe limitations to size of using ordinary materials (for example, steel or aluminum I-beams). The simplest solution would be to use the "golf tee" overall shape for the city suggested by user16295, constructed of a lightweight honeycomb of some material stronger than what we can make with current technology. Assume much of the "tee" is empty space (or even vacuum) surrounded by honeycomb, with only the surface inhabited, furnished with soil to grow crops for food, etc. (I hope they get plenty of rain to provide water?) You might consider investigating the theoretical properties of carbon nanotubes, but assume that some method of producing large structures made out of them, plus some method of stabilizing them on the molecular level has been discovered... which I suppose isn't impossible in theory. "Actually: just thought some more about my last point: they'll be up at a full g, won't they?" EDIT: I see I made an error in what I posted below. I'll leave it there for purposes of illustration. No, you were right: A fraction of a gee, assuming the entire space is in a 1-gee field. That's 32 feet per second per second of acceleration for something on the ground. If, for example, the parachute city is falling at 10 feet per second, then that's (32-10=) 22 feet per second, which means 22/32 = 0.6875 g for those standing on the ground of a parachute city. EDIT: My error above was confusing velocity with acceleration. No, those standing on the ground on the parachute city will be subject to 1 gee, just as those standing on the surface of the plant. They would only experience lower gravity if the parachute city was under constant acceleration. Since it's falling at a fixed (terminal) velocity, it's not accelerating. [end of edit] But why would this endless column of air have a one-gee gravity field? This is obviously not Earth! Since you're world-building, you can arbitrarily choose any gravity level you like. And if the outside gravity field is lower, well then you can make the structure larger without using exotic matter. Lower weight means you can use weaker materials to hold the structure together, altho if the winds are as terrific as you suggest, the inhabitants would still have a severe problem holding things together for long. Groups of objects held together by something flexible? Well now, that's something that might actually be possible given current building materials. Kevlar is your best bet, but your original question suggested that all that's available is some random debris. If they have to rely on ropes woven out of grasses or reeds, those structures are gonna have to be pretty small! "If you can expand your answer up with any numbers to back up the 'no bigger than a skyscraper' assertion..." Well, it depends on how flexible the overall structure is. Bridges can be bigger than skyscrapers, partly because they can flex and partly because they're more horizontal than vertical... so they can be supported by multiple piers rather than having the entire weight of the structure supported by the bottom floor. (If the weight is hanging from parachutes, the entire weight has to be supported by the framework the parachutes are attached to. But even so, a bridge might be a better analogy.) However, think of the behavior of a flexible bridge in hurricane conditions. It won't last long, will it? So that's why I think the skyscraper analogy is closer to what would actually survive under such conditions. Sorry, I'm not gonna do math here. I don't do math for fun, and you haven't provided enough specifications to be able to give any hard numbers to it anyway. We don't know what the turbulence is, and we don't know how fast the parachute city is falling. And altho you've specified a one-gee gravity field, there doesn't seem to be any good reason to impose that limitation. Choose a lower gravity, things become easier for the inhabitants to build stable structures, probably the turbulence is reduced, and it becomes easier to fly from one structure to another. If it really was a one-gee field with everybody falling along with some random debris, it's almost impossible to believe that they could actually organize and build anything before starving to death. BTW -- I suggest you read Larry Niven's THE INTEGRAL TREES for some ideas about humans living in free-fall... and on structures which are "falling through the sky" but nevertheless have portions of the structure where you feel weight. [Answer] This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I'm no good at the hard science, but if your goal is floating cities in the air, could you use a buoyant gas bubble in the crust of the big rock? I bring this up because I remember a wedding that took place on top of a hot air balloon envelope, not in the basket. It was years ago, pre-internet and I can't find any images. lots of sales brochures though. I just remember the happy couple jumped with parachutes after. That kind of image sticks in a kids mind. A very dense load at the bottom of the teardrop (or hot air balloon) shaped rock, buoyant pocket in the middle, and thriving civilization on top. Augment with other gas balloons. It seems to me that the city would float at the equilibrium point in the atmosphere. That should give you standard gravity and pressure above even a gas giant. Sorry I don;t have the math to back any of this up. I just think this may be a logical approach, something that could possibly be proved out by someone smarter than me. ]
[Question] [ We love turtle worlds. We already have a question about turtle planets : [How do I prevent my turtle from collapsing under its own gravity?](https://worldbuilding.stackexchange.com/questions/1359/how-do-i-prevent-my-turtle-from-collapsing-under-its-own-gravity) but let's scale it down. I would like to have a waterball planet inhabited by gigantic oceanic creatures. The biggest (or not ?) creature of them all is a turtle which lives with the top of its shell above water surface. Those turtles have such a long lifespan that their shell is subject to erosion and a deep soil forms on top of it. You eventually get mountains, lakes, forests... A beautiful landscape and a nice background for a fantasy story. If possible, I would also like the creature to move slowly (swimming or maybe walking on the ocean floor ?) such as once in a few centuries, civilizations from two different turtles can meet and exchange culture, genetic diversity and deadly diseases. They don't need to be specifically turtles, or even looking like turtles if not possible. They however require to be alive and sentient, because I need them into my magic system (a mother nature sort of thing where you "ask" for magic). Would such a creature be possible with as few handwavium as possible ? If absolutely necessary, magic is available, with whatever properties you need. The less magic the better. The maximum turtle size I need is about 1000 - 2000 miles / 1500 - 3000 km. (that's Australia-sized) It's okay if only smaller turtles can move, and the biggest/oldest (dead-est ?) turtles are stuck to one place. If such a size is not possible, how large is the biggest possible turtle ? How old would a turtle be in order to get nice erosion and landscape ? What lanscape features would be available, or not, on such structure ? Small mountains, lakes... ? For those two questions, keep in mind that we are on a waterball planet, with powerful wind and storms as explained in this question : [Ocean and air currents on a water planet](https://worldbuilding.stackexchange.com/questions/17848/ocean-and-air-currents-on-a-water-planet) If that's two many questions in the same post, or two broad, please let me know. And thank you for your time ! [Answer] When I read this, I absolutely had to develop something that was turtles all the way down. Hopefully it fits well enough with your magic system. The time it takes for erosion to occur is really based on the materials involved. Keratin and bone erode much faster than stone. However, a world where the landmasses are nothing but keratin would be boring. Maybe there's a way to make their shells stone. Also, if they were stone, large landmasses would be arbitrarily easy to make. The stone shell would simply fuse with the ocean floor, creating a stationary continent just like we have today. So let's give these turtles a reason to put on some serious rock-based sunblock. Let's run with the idea that they're part of a magic system, and need to hold onto magic. Perhaps their magic is directional, and you can take control of their magic from above. They develop a hard top shell to prevent magic from being stolen. This works for small turtles, but as they grow, their magic is going to be more valuable. Bone and Keratin are simply not enough to protect them from those who would steal it. They need something stronger, like stone. Fusing stone is not easy. It takes a lot of heat, and then you have to deal with that ridiculous heat after you're done forming a stone layer. To combat this, the larger turtles may develop chutes up through their body, lined with fireclay or similar refractories. Then all they must do is wander the ocean until they find a volcanic vent, and direct the lava on top of them. Now this is fine for small turtles. We understand how reasonably sized creatures might move around. Obviously, as we get more and more massive, challenges of buoyancy will arise. The turtle will have to be able to hold up its stone shell while it moves. And this is where the turtles all the way down come in. Think back to finding Nemo, with Crush the turtle. Fearless, laid back, and not going to be stopped for anything. If Crush were to get too heavy to swim, do you think he'd lie down on the couch with a beer and lament his misfortune? No. He'd find a way to surf anyways! Enter the lava of the planet's mantle. It's fluid...ish. For a heavy turtle who refuses to give up, it might be the best surfing available to him, so why not! With a lot of care, he might be able to redirect the plate techtonics to slowly shift him around, surfing not in the ocean, but on the planet's inner layers themselves! Never underestimate the willpower for a surfer to find a way to surf! Now we have the tools needed to work with the incredible size of these turtles, because they are no longer having to support themselves with organic compounds. They have used the power of molten rock to build supports around themselves, so standard geology rules can apply from there on. Of course, this surfing isn't always easy. Its hard to find the right magma flows to surf that wont leave you stranded when they cool. Fortunately, Crush loves to teach the next generation. He moves along the mantle, shaping the volcanic flows below to give the younger turtles a place to realize they can surf the mantle. Some give up, of course and become stationary islands with no turtle under them, which are rapidly eroded away by the forces of time. But some learn to surf the mantle in their own right. Science based? Maybe. Right now, I'd say it'd be hard to believe that you could surf the mantle, but if you had an entire species of turtles exploring the best ways to make it happen, who knows? And maybe one day one of them learns to surf the currents nearer to the core. Maybe they can hear whispers of our planet that we cannot, and transmit that upwards, giving us the magic to surf one day. Hang ten! ]
[Question] [ Question: Are there are any serious biological or evolutionary plausibility issues with separating the energy storage/production function from the production of structural/regulatory biomass? Background: In terrestrial life biomass is initially produced by plants which produce carbohydrates and related molecules (like lipids) from photsythesis. The carbs (and related sugars, lipids etc) fulfil structural and energetic functions. My alien life on the other hand takes the same carb-based approach for biomass which is not related to energetics, but uses alternative molecule species for energy storage/generation. Why? My alien lives on a planet with 70% H2 atmosphere on a super earth large enough to have retained such an atmosphere. My plants generate standard carb based biomass using photosynthesis which imports methane and sunlight and exports hydrogen. See [my previous question here](https://worldbuilding.stackexchange.com/questions/25598/hydrogenenic-photosynthesis-strategies-for-animals) for details. Creation of this biomass is very efficient (4-5x) in the H2 atmosphere compared to terrestrial photosynthesis for reasons I won't go into here (but see the link if interested) but the downside is that 'burning' this biomass in the H2 atmosphere produces 4-5x less than oxidising it in an O2 based atmosphere. 'Pharbohydrates' So my alien animals don't use carbs for energy, they use an alternative molecular species (which for now I'll call a 'pharb') which unlike carbs, produce a good amount of energy when reduced with hydrogen (e.g. the reverse of oxidation). The 'pharb' is still carbon-based. We are not talking about non carbon metabolism here. Details I have two classes of plants: * primary plants which are the least complex type of autotrophic life which use carbs for energy storage/generation. They grow prolifically. * secondary plants (call them 'phlants') which either unilaterally or in symbiosis with something else( e.g. fungi) can produce the more energy rich (in the reducing H2 atmosphere) pharbs. These secondary phlants are not all pharb, they use carbs for structure since this is efficient. Parts of their anatomy may be where the pharbs are stored (think of pharb based fruits, nuts, saps etc). Phlant biomass is approx 10 times rarer, or more, than plant based biomass. * primary heterotrophs (animals) which feed on the primary plants. These must be very simple creatures with slow metabolisms since they have access to only 20% of the energy terrestrial oxidising life has access to. * secondary heterotrophs (phanimals) which feed on the secondary 'phlants'. Thanks to their diet being pharb based, they have access to similar energy as terrestrial animals. They can digest primary plant carb based biomass, but cannot use this biomass for access to energy. The structural elements of their bodies are carb based but the muscle and energy storage/generation pathways are pharb based. Phanimal biomass is approx 100 times rarer than animal biomass. * my sapient aliens are phanimals. Other details: Surface gravity and temperatures are earth-like. Surface area is much higher because its a super earth. Insolation levels at wavelengths suitable for the described photosynthesis process are earth-like. There is plenty of open water, seas etc. All my lifeforms need water same as terrestrial life. The methane which is required as the primary input into the primary plant photosynthesis cycle (analogous to CO2 on earth) is regenerated reliably within the ecosphere. All in all, its a great place for life; as long as the heterotroph energy source problem is solved by use of pharbs. Question restatement: * Assuming such 'pharb' molecules exist\, are there any scientific problems with constructing a rich setting for a sapient civilisation at tech levels similar to 1000-2000AD on this plant? What are the most obvious differences with the earths ecosystem going to be? [Answer] All the phanimals will be highly flammable. One of the great things about oxygen is that a molecule of O2 effectively has a lot of energy that air breathers can use. It really likes to oxidize things, and as such, we can carry around a supply of relatively low energy oxidizable molecules and count on the atmosphere to supply us with a decent chunk of our needed energy, safely tucked in double–bonded diatomic molecules that don't burst in flames at tropospheric temperatures. A bond between hydrogen and carbon in, for example, CH4 is much weaker than the bond between, for example, oxygen and hydrogen in H2O. Oxygen likes oxidizing things. The only element which could oxidize oxygen would be fluorine, but it only forms one bond in most conditions. Your phanimals, therefore, are unlikely to get a lot of their energy from the atmosphere. Luckily, they don't have to. If you phanimals are high metabolism creatures, all they need to do to make sure they have enough energy is to carry around molecules with lots of energy waiting to be released. Unfortunately, such molecules also enjoy rleasing their energy with little or no provocation. A phanimal, for example, could rely on internal stores of hydrazine, N2H4. Hydrazine has plenty of energy on its own, and doesn't even need to react with atmospheric hydrogen to release energy. Unfortunately, it can easily chain–react with itself, and burns incredibly hot. An animal with internal hydrazine stores could ignite and rapidly combust if it were struck by sparks or heated up too much. Most high energy molecules will be similarly risky, but may offer enough energy compared to hydrogen oxidizing fuels to be worthwhile for animals to produce. Animals will live fast and die young. Given the high odds of spontaneous self-immolation, evolution will put a premium on reproducing early. Phanimals will grow quickly, eat a ton, and start reproducing as fast as possible. Evolution will be a tradeoff between being slow and being flammable. Given relatively easy access to food in the form of slower animals and hugely abundant plant life, the need to eat a lot won't be too much of an issue for the phanimals. They also won't need to breathe, which will simplify their internal anatomy somewhat and make the transition between sea dwelling and land dwelling creatures simpler. How will this affect civilization? With a highly flammible portion of the biosphere which really doesn't threaten to ignite the rest, given the lack of free oxygen, your creatures will likely develop and harness fire faster than early humans did. Fire will also be much more dangerous, both to the fire-users and to potential enemies. It will quickly be weaponized, and will be far more dangerous than any other simple weapons, such as swords. Bows with flaming arrows, followed by progressively longer ranged fire-shooting weapons, will be a common weapon. Creatures will probably be fairly watery with their hydrazine stored in some form of sealed and protected internal organ, but even so, fire will be incredibly deadly to them, and these won't be standard Earth-variety flaming arrows, but rather arrows tipped with hydrazine, which will continue to burn even inside of a target, since it doesn't need oxygen to do so. Rocketry, given the abundance of a simple monopropellant, will also develop quickly, and without any need to breathe, space exploration will be significantly simpler for your creatures, who may explore their moons before developing the most basic of computers. Getting to other planets, of course, would be a multi-generation expedition, given their life expectancy of ten years or so. [Answer] ## Assuming such 'pharb' molecules exist\, are there any scientific problems with constructing a rich setting for a sapient civilisation at tech levels similar to 1000-2000AD on this plant? Should be no problems. We still don't know how every link in the chain works and interrelates perfectly for our Earth, so you can assume that life will adapt in ways you cannot predict. It's always okay to assume gaps in knowledge. ## What are the most obvious differences with the earths ecosystem going to be? ### Atmosphere Your atmosphere is going to be very weird. Methane and hydrogen normally separate, but you can probably come up with weather systems that would mix them. Even then, concentrations of your primary -trophs and secondary -trophs would depend heavily on elevation; mountains would be hostile to pharbs and phanimals, but valleys and caves would be suffused with methane. The atmosphere would be explosive anywhere oxygen would be introduced. You've got water oceans, so probably there, or wherever the oxygen came from to make those oceans in the first place. (Underground?) In particular, electrical currents could produce locations of great violence. Consider cloud-to-water lightning—yikes. You'll want to get oxygen involved somehow,* so your civilization can use fire. Unless you can find a reaction that would do the same thing for them as fire did for us. If the oceans pulled their oxygen from the earth's minerals (for example), you could try something with that. ### Plants & phlants Your plants and phlants won't remain as separate as you describe; there's huge evolutionary benefit in them cooperating, so at the very least they'd start trying to grow around or on each other. They would more likely integrate, from normal symbiosis to as extreme as mitochondria's bacterial origins. Since they both, presumably, came from single-cell organisms, any species that interlaced with each other at that stage would have a huge evolutionary advantage. ### Animals and phlanimals EDIT: I forgot the largest question. How, exactly, are these animals going to respirate? Are they going to need more surface area than our lungs and gills currently do? If so, animals would probably need to be built around their respiration systems. Your primary heterotrophs won't resemble animals as we know them; 20% of energy intake is a big downgrade. They would rely on external phenomena as part of their life cycle: reproduction and transportation via wind or water currents, for example. They would probably resemble parasites on your primary autotrophs. They'd also be terrible at healing, so their defense mechanisms would focus on camouflage, poison, and other strategies that don't require moving and discourage possible predators from eating the guy next to them. I'm thinking water-borne clouds of lazy krill-like animals at best, and creeping molds for land-based. They would not be big on animal reproduction as we know it, instead preferring spores or extremely simple eggs. Maybe some barnacle-like things. Why would your pharbs bother finding/cultivating the rare phlants when they could just eat the primary heterotrophs? 10 times rarer is worse than the 5 times less energy production. But they're so high up on the food web, you could easily justify their existence with ecosystems that turned out just right, somehow. And hey, biodiversity—where there's a niche, there's a way. --- These are just guesses, but reverse-engineering a complex life web is never going to be objective or thorough—too many unknowns. Maybe you found something that tickled your imagination, though. EDIT EDIT: I did some more quick research, and found some other things that might interest you. At around 700 to 1100 Celsius, methane and steam react to form hydrogen and carbon monoxide. The early development of this planet probably had that happening a lot. The carbon monoxide then could [react with remaining water](https://en.wikipedia.org/wiki/Water-gas_shift_reaction), and so on and so forth. Where would your atmosphere's mix of chemicals stabilize at? What conditions would provoke instability? Would [vinegar](https://en.wikipedia.org/wiki/Acetic_acid) feature? [Answer] I think the idea that you will have carbohydrates and something else is a mistake. When you mix oxygen, hydrogen, and ignition: * The oxygen causes the hydrogen to oxidize. * The hydrogen causes the oxygen to reduce. So when your atmosphere is hydrogen based, the energy storage medium might be something that can be reduced. Perhaps something rich in carbon and oxygen, with very little hydrogen. Having said that, it is possible your "primary" creatures won't exist at all, and your "secondary" will, and won't be too conceptually different from us. --- Alternatively... it might go the way of early Earth. Some creatures might discover they could eliminate the competition by dumping poison (oxygen gas) into the atmosphere. [Answer] I'd think a compound with lots of oxygen (and carbon if carbon based life) that releases energy when it is hydrogenated is best for reducing atmospheres. something like: $6CH4 + 6CO2 + photons--> C12O12 + 12H2$ this would work? I chose this because it can be reduced to methane and carbon dioxide gas easily with hydrogen gas. it helps renew methane in the atmosphere as well. I couldnt figure out the enthalpy of the reaction as i couldnt find the enthalpy of formation of c12o12 anywhere ;( so a quick guess is that it is very energy intensive as it tries to liberate o2 from carbon dioxide (which scientists are pewing lasers at, for starters) . you'd get a lot of energy consuming plants and a lot of heterotrophs that can easily yield energy by reducing c12o12 by hydrogen. Edit: the total energy yieled (and consumed) by this is about 2019 kj/mole, compare this to the energy used by plants: which is about 2801 kj/mole. So this can be utilised, i'd say This "pharb" would be the storage of the natives on the planet: analogous to glucose on here, except energy is gained through hydrogenation (plenty of which, presumably, is available in the atmosphere). It can also be used to circulate methane and carbon dioxide back into the atmosphere: and replenishing it. I dont know if they can catenate with themselves, most likely yes (because of the high amount of carbon in them). If yes, then it can function as a structural and as a storage material[![The alt carb looks like this](https://i.stack.imgur.com/oTG5u.png)](https://i.stack.imgur.com/oTG5u.png) ]
[Question] [ Planning and writing a sci.fi story with Space Navies(tm), and I realize that I'm tempted to wonder why you need more than three of four people punching buttons and pulling joysticks to move a ship and fire the weapons. So, obviously there are more roles to fill, I realize (and of course you gotta consider shifts, crews obviously need to sleep but you can't just shut down your ship while everyone sleeps), but I have no notion of exactly how many people fill which roles - Engineering? Navigation? Weapons control? Guards? Making food? Are there any lists or overviews over what various contemporary naval vessels' crews are composed of? That is, not just the number of crew but also an approximate distribution of how many fill what roles on a ship - or for that matter, what roles you actually need on ships. Even if it wouldn't be fully translatable to space navies I can extrapolate well enough I think. [Answer] [This wikipedia page](https://en.wikipedia.org/wiki/User:Ehbowen/Iowa_class_battleship_manning), though describing a battleship decommissioned nearly 30 years ago, has a pretty interesting breakdown of roles on the USS Missouri. I'm a little bit hesitant to use it authoritatively since it's only a user article, but it has an impressive breakdown that I think effectively maps out what kinds of roles you have on a massive vessel that needs to operate autonomously for long periods of time. The detailed breakdown is far too extensive to reproduce here (I highly recommend checking it out in the link), but here is the summary across the major divisions: [![enter image description here](https://i.stack.imgur.com/IBNoU.png)](https://i.stack.imgur.com/IBNoU.png) In most sci-fi settings involving space navies, AI often has a large influence. Looking at the three largest divisions of labor on this battleship (hull / deck maintenance, engineering, and weapons) there is a lot of room for automation and AI control. Weapons systems in space are ripe for automated control and targeting for best effectiveness (indeed, even modern naval battleships make heavy use of automated targeting). Hull maintenance will hopefully be managed by drones, especially given the complexity and risk of human EVAs. Engineering, however, is likely to continue to have a heavy human component. The complexity of propulsion and power generation is likely to eclipse modern-day ships, not to mention the new forms of life support. A few other divisions can expect to see AIs taking a role, particularly navigation and operations, but other divisions such as supply, medical, and administration will remain primarily human and their sizes scale based upon the total number of humans on board. [Answer] For starters you should decide whether or not you're going to have high levels of automation or everything going to be done by hand. Depending on how advanced your setting is, I would generally recommend more automation. The following website will be very useful for your question: [project Rho](http://www.projectrho.com/public_html/rocket/crew.php) Well not everything on that guys site is the greatest for those specifically trying to write fiction, he offers a great many guidelines for helping you keep yourself grounded in reality. I recommend giving it a look. It should answer a great many of your questions. ]
[Question] [ Al is a rat. He is also an engineer of quite a high caliber. He has developed a suit of power armor, with a movement-assisting exoskeleton that greatly increases his strength, speed, and endurance. Now, the physical ramifications of such a suit on a human have been explored before, but what I want to know is, how does the square/cube law affect the suit? What are the ramifications, and potential applications, of such a suit for a creature much smaller than a human? For instance, with slight modifications to the foot width, and a decent speed boost, could the suit allow Al to run on water? How much less of the suit's structure would have to be put into impact shielding, if Al as a rat is naturally more resistant to impact damage than humans? [Answer] Hah! Love the idea. First up, I think the ramifications of a rat as smart as Tony Stark are going to be considerably larger than the ramifications of the Ironrat Mk1 suit. Anyway, that aside: lets look at the differences. 1: Small things are stronger for their weight than big things. In purely structural terms this remains true. The suit will be able to transfer a greater mechanical load for its weight than a comparable human sized suit. Where this falls down is the motive forces for the suit. Depending on the technology used (Electric actuators? Hydraulics? Pneumatics?) the control packages required might weigh more than they allow the suit to lift. While a hydraulic 'muscle' can still output more force/kg than a larger version, the smaller muscle will still have to have an equally powerful pump in order to maintain that ratio. 2: Small things are more impact resistant than large things. This isn't quite true. Smaller things carry considerably less momentum for the same speed of impact (a spider falling off a roof will be fine, an elephant not so much) and if a small rat is hit by a small hammer it will do less damage than a big human being hit by a big hammer moving at the same speed, however impact resistance depends very much on the concept of impact. If Al falls off a roof, then as he is light, has a low terminal velocity and carries less momentum then he will be OK when his velocity inevitably changes upon impact with the ground. However, if Al's weight has been doubled by the suit, the velocity change at the bottom may be enough to push Al's internal organs through each other while leaving the suit intact. There's less space in a tiny suit for shock absorbers, and the relative mass gain of the small suit may well be greater than for the large suit (again realising that you can't just scale components down). The point I'm trying to make here is that the Ironrat Mk1 will be better at stopping tiny rat-bullets than it's bigger brother, but worse at preventing massive haemorrhaging after a sudden stop. 3: Small things are faster than large things Now we get into the difference between speed of thought and of movement. Turns out that in the case of our suit the two can be decoupled, depending on sophistication. If your exoskeleton is partially automated then an act like running on water can easily be performed. Just let the suit know and it'll slap Al's tiny feet into the surface tension like a jackhammer with claws. While the human equivalent of this suit would pulverise the knees of whoever was inside, Al's knees might well survive as his suit would be lighter, stronger for its weight and even able to transmit the necessary control signals faster (though that last point is negligible), which would reduce the amount of pounding necessary from 'pulverise' to 'mildly uncomfortable'. However, if your suit only moves as fast as Al does, then he's unlikely to be able to do anything he can't as a rat. Even though the suit would make water seem like he was running on treacle water is still a Newtonian fluid (unlike Oobleck, which he would weirdly find harder to run on than his human counterpart) and his mass with the suit is more than sufficient to break the surface tension. He might be able to swim fast enough to start hydroplaning if you designed the suit right though, which would be pretty epic! Uses: I wouldn't like to fight Ironrat. Just imagine a metal rat with neurotoxin tipped claws trying to climb up your trouser leg. Shudder. A rat operative with the suit on would be much more overpowered compared to normal rats than a human in a suit would be compared to other humans, capable of shredding through cage doors and quite literally crushing opponents between their paws. However the suit wouldn't help against even a normal human. A rat that's 20 times stronger than a normal rat and only weighs twice as much can still be picked up by the tail (Never, EVER try to do this with a rat that isn't wearing power armour), not to mention the risk of kicks from steel-toecapped jackboots. Oh, and while IronRat Mk1 is good at stopping tiny rat bullets getting hit by even a small amount of shot from a shotgun is still going to be like getting hit in the chest by a football made of lead and moving a few hundred miles an hour. TL:DR Ironrat Mk1 works better than expected vs other rats but is still terrible vs humans, and everybody should be scared of Al Stark's weapons empire. ]
[Question] [ For the sake of this question, let's say that there would be a space mission that would send one man on a 40 year journey that will require him to be in a completely self sufficient habitat for the duration of the trip. What would be required for him to be completely self sufficient, and not need any external matter or energy? From what I can come up with, the man would be in a completely sealed spacecraft with near perfect recycling systems that would gather any moisture in the room, and condense it back to water. Life support systems would possibly include genetically engineered varieties of yeast or bacteria in a special ecosystem akin to a [winogradsky](http://en.wikipedia.org/wiki/Winogradsky_column) column,where heat from a nuclear reactor would power thermophile bacteria that would excrete oxygen from carbon dioxide, etc. Specialized 3D printers would produce any replacement parts for non-essential mechanisms that would break, while automated repair machines and robotics would perform any work. Food for this astronaut could be possibly some sort of Soylent-like material that can be synthesised from yeast or bacteria as mentioned above. [Answer] I'm going to make a slightly wacky suggestion. I wouldn't use a fully recycling system for only one person on a 40 year journey. An average US citizen eats about 1 ton of food every year, and this is widely recognised as more than is needed. For an astronaut with reduced physical activity and carefully chosen food types this can very easily be reduced to 60-70% of this (probably further). Freeze-dried and recombined with recycled water the mass that actually needs to be carried is only about 20% of this. In total about 5 tons of dried food would be needed for a 40 year journey. For comparison an Apollo Command/Service Module has a dry mass of about 11 tons and a NERVA rocket engine has a dry mass of about 34 tons. Now you may say that 5 tons is still 5 tons, and waste should be avoided like the plague. Maybe you can imagine a bacterial faeces-to-food recycling system (yum!) that weighs less. But it is still going to be complex and bulky and weigh some not insignificant fraction of 5 tons, and wasted mass counts against you not only when accelerating your rocket up to cruise speed, but also when decelerating it at the end of your journey. I'm guessing you aren't planning a 40 year one-way Hohmann transfer to Uranus where we can assume a relatively small capture burn, but either a round trip or some high velocity voyage with a large initial burn, high cruise speed and significant deceleration at the other end. If you take a large, bulky recycling system inside your crew compartment where it can actually be accessed, then you need to decelerate that as well. You also need to carry the extra fuel for this deceleration and accelerate that fuel to your cruise speed when you set off. It's mass relative to its remaining utility only increases during your journey. By contrast the mass relative to remaining utility for stored food remains constant. Interestingly, your minimally treated, unrecycled waste could actually be helpful during deceleration. If you are planning a nuclear reactor for power generation then your means of propulsion should definitely be a nuclear thermal rocket engine, with the reactor being used for combined power and propulsion. In a liquid fuel rocket the energy is generated by a chemical process in the fuel itself, while in a nuclear thermal rocket the energy is generated by nuclear fission in the reactor and then transferred to an inert reaction mass, which then expands through the rocket nozzle, creating thrust. Why not put that waste to use as reaction mass during your deceleration burn? Additionally, the stored carbohydrates in your food will liberate water vapour and carbon dioxide once metabolised (containing slightly more oxygen that you inhaled), which could help compensate for any inefficiency in your water and oxygen recycling systems. I'm finding it hard to pin down exact numbers, but it seems the total mass of faeces output by a human being is only around 10% of the food eaten. If we assume somewhere up to 80% of food eaten by mass is water, then perhaps half of the weight of the freeze-dried, stored food will be liberated as carbon dioxide and water. Finally, the psychological value of freeze dried ice-cream to an astronaut isolated for FORTY years should not be overlooked. ]
[Question] [ This Query is part of the Worldbuilding [Resources Article](https://worldbuilding.stackexchange.com/questions/143606/a-list-of-worldbuilding-resources). --- One crucial aspect of the climates have been left out so far, deep water circulation. It's the major force driving the heat transfer form the equator to the poles and its flow can influences local climates. Understanding the basic mechanic is important in a fictional world and it's not possible to simply say that it's like on Earth. No, because the water and landmasses are places differently, the water flow might be different. I know that the cold waters sink down and then move toward the equator, where the density of the water is lower. What are the other guidelines to follow? Example of questions: * Where does the water come back to the surface? * Should it flow along the east or the west coast? * What kind of configuration would make it impossible to have a worldwide conveyor? --- Note: > > This is part of a series of questions that tries to break down the process of creating a world from initial creation of the landmass through to erosion, weather patterns, biomes and every other related topics. Please restrict answers to this specific topic rather than branching on into other areas as other subjects will be covered by other questions. > > > These questions all assume an earth-like spherical world in orbit in the habitable band. > > > --- See the other questions in this series here : <http://meta.worldbuilding.stackexchange.com/questions/2594/creating-a-realistic-world-series> [Answer] Surface currents are greatly effected by the winds and through forces described as the Coriolis effect, will move in a clockwise direction to the north of the equator and counter-clockwise to the south. Deep currents are driven primarily by density differences (created by temperature and salinity), and so the salty cold water from the poles will travel along the deepest parts of the ocean basin. If the ocean floor is flat enough, I believe the main current would tend toward the coast with a surface current traveling in the same direction, but depth will be the primary factor. Starting at the points water sinks. On Earth, there are two primary locations that water sinks on a large scale, and the mechanics of each are similar, but have differences. In the North Atlantic, cold winds blow across the surface causing evaporation. This has the dual effect of cooling the water (increasing density) and increasing salinity (only pure water evaporates; increasing density). This denser water sinks and flows southward. The equatorial region of the Atlantic is a relatively small region and there is little upwelling there. The northward flowing surface current is still less dense than the deeper current. Most of this current ends up in the Southern Ocean, where it splits; part going to the Indian Ocean and the rest flowing past Australia into the South Pacific. In the Southern Ocean, cold winds blow out from Antarctica. This wind breaks up the ice and blows it north leaving the ocean surface bare to this freezing wind. The surface quickly freezes, with purer water forming ice around pockets of brine. This brine lowers the freezing point, which allows it to "melt" its way through the ice, dropping free and its density causing it to sink to the bottom. This briny water is denser than that coming from the Atlantic and it flows out to the Pacific. The Equatorial Pacific is a huge area, all warming; expanding and becoming less dense. The outflow from the Atlantic causes its surface to be slightly lower than that of the Pacific, which means this less dense water flows ever so slowly through Indionesia, the Indian Ocean and into the Atlantic, where it joins the surface flow to the North Atlantic. If the Ocean Basins were separate basins instead of essentially a single "world ocean", this conveyor system would not work. This is obviously true if the basins were completely divided, but even if connected through shallow archipelagos or over continental edges, without a continuous "ocean deep", the circulation would be limited to individual basins. And if each basin was not both large enough and did not stretch far enough between pole and equator, such local currents would be limited even further. ]
[Question] [ # Info I'm designing a prehistoric-dragonfly that has little holes or perforations in its wings. When the wind flows through them, they make music (the viability of flying with these wings will be covered later.) By prehistoric I mean a dragonfly the size of a hawk, with a slightly more complex, modified circular-respiratory system to allow it to get the oxygen it needs. # Question How could this dragonfly make "music"? Certainly music isn't possible, but could musical notes be produced by these wings? Would the holes affect them? ### Requirements (please include in your answer): * Tell whether variations in wings could make "songs" differ from individual to individual (or not) * Whether different notes at various pitches can be made (or not) * You may manipulate wing size (So the wings can be as big as they need to be) , hole size/shape, and arrangement of holes * Ignore whether the dragonfly can fly The holes can range from 1mm to 2 cm (in diameter). Per every 6.5 square centimeters of wing surface, there can be up to 3.5 square centimeters of holes. They can be any shape. --- Thanks to all in the [Sandbox](https://worldbuilding.meta.stackexchange.com/q/6168) for helping me develop this question. --- [Answer] The holes could work similar to a [hole tone whistle](https://en.wikipedia.org/wiki/Physics_of_whistles#Hole_tone_(tea_pot_whistle,_bird_call)), which is the principle used for a whistling tea pot. [![enter image description here](https://i.stack.imgur.com/a1AQn.jpg)](https://i.stack.imgur.com/a1AQn.jpg) The basic idea is that a stream of air is directed through one hole, and a short distance away is another hole. Some of the air is forced out through the second hole, while some is forced to the side and swirled back to create the needed feedback loop. The holes in your dragonfly wings could have a similar structure where there is a hole on the bottom surface and a hole on the top surface, and a bit of an air gap in the middle. Each individual would have a different sound depending on the size and placement of holes, the size of the air gaps, etc. Likewise the sound of the notes would vary depending on wing speed. If they don't have to be holes, you could go for something like a [cavity whistle](https://en.wikipedia.org/wiki/Physics_of_whistles#Shallow_cavity_tone), where air is forces over the top of a cavity in a surface. The wings would be structured in such a way that when it beats air is forced to pass over cavity structures on the surface, causing the tone. Little extra: It wouldn't sound like a bird chirping, as a hole tone would be a pure sound as long as the flow of air is constant, but because of the wing beat speed, wing angle, resonance from cavity tones as forward momentum causes air to also pass over the tops of the holes and not just through them... I believe it would be a constantly fluctuating sound, but that the creature would have some degree of control over it. ]
[Question] [ So, I'm working on building a state (kingdom to be more precise) as part of my world, and as part of that exercise I want there to be some contact between characters in said world and the legal system, so I need to define to at least some degree what that state's legal/governmental system is like, how it functions, and such. Furthermore, they'll need to be able to to reference at least some sort of written legal code or statute (and it will also help me ensure consistency, which is important when you're trying to present a world where due process is upheld). However, there are many aspects of a legal code or statute that are not obvious to a layperson, but are actually at least somewhat necessary for a society at even a Dark Ages level to function, never mind a higher level: * The existence of a bureaucracy implies some sort of administrative code * Property rights need to be defined and codified by law as well * Taxation seems obvious, but can be quite subtle all the same * Public works schemes may need to be provided for, too How do I make sure I don't miss things like these that are not high-profile elements of society (unlike basic criminal statutes or the structure of government itself, although it's probably just as easy to forget some of the criminal statutes that don't come out in the popular eye) but are equally necessary for the functionality of an organized, writing-capable, food-surplus-based society as a general rule? [Answer] Some major legal codes in the world right now include Common Law and Civil Law. Common Law is the most often portrayed in media because it is the law system of the United States, Canada, the United Kingdom and a good chunk of the world (about 2.25 Billion People) live in a Common Law (or mostly common law... Scotland is weird, Quebec and Louisiana have some elements of French derived Civil Law, Isreal and India use religious laws/nation of origin laws in family and personal law (i.e. Marriage). The Hallmarks of a Common Law system include the concept of Stare Decisis (latin, roughly means "the decision must stand"). This means that if a court in a common law system has two very similar cases, the court must decide in the same way for both outcomes as must all lower courts below that court. In addition, common law allows courts to see precedence in other jurisdictions and use them in deciding cases. The bulk of modern negligence law in nearly all common law countries comes from courts in Scotland, not local legislation. This isn't always the case, though. For example, in the United States, if a law contradicts the constitution, than the common law decision isn't good. It also makes it that some laws are never quite "statutory" or written down. England only recently got a "statutory" murder law on it's books. Prior to that, murder was a common law offense. Similarly, Michigan did not have a "statutory murder law" until the 1990s when it suddenly became important and Maryland does not have Statutory Murder to this day. This is likely a boon to your kingdom as Common Law does not have a codified book of rules that you can read... but years of "we decided this long ago". Another feature is the Jury Trial. In law, there are two elements called "Trier of Law" and "Trier of Fact". The Trier of Law is the person who answers the question "Is this illegal" and in Common Law, it's normally a Judge. The Trier of Fact is the person who answers "Did the illegal act occur?" and that is a Jury. The big difference in Civil Law (and it's predecessor, Roman Law) is that Judgements do not set precedence for future judgements (but may be used persuasively) and that the court is Inquisitorial (as opposed to Adversarial, in the Jury Trial system). This means that the judge is both Trier of Law and Trier of Fact, and may thus ask questions of the witnesses. Civil Law also uses Statutory Laws, which means each crime is written down somewhere and the sentencing is prescribed with the law. Sentencing is also part of the trial phase in Civil Law, so mitigating factors (and aggravating factors) play an important part in the this part of the trial, where they have no bearing in a Common Law trial (you are sentenced after you're found guilty). This is why "We were just following orders" was thought by the Germans at Numberg to be an effective defense. In German Civil Law, having no personal motivation in your crime (such as you did it because it was your job and not because you had a personal ill will to the victim) was a very mitigating factor. Because Numberg used Common Law (because U.S. and UK could get behind Common Law, where as French Civil and Soviet Civil Law were not quite compatible). The problem the Germans faced was that Common Law first determines that the crime happened, then determines the degree of guilt. Most of Mainland Europe and non-England European Colonies use Civil Law. The only other legal systems I can offer are Sharia Law... and that's all I'll say on that... Catholic Cannon Law (which is all but extinct, it's only used for some elements of criminal code in Vatican City, but they are more likely to use Italian Law). Japanese Law from the late 1800s onward is some form of Civil Law (much of Japanese government as a whole are borrowed from European systems that worked. They have German Diet parliment, U.S. Constitution, British Post, French Civil Law, but with American Plea Bargaining). Prior to that, it was largely based on law dictated by Feudal Lords. They largely adopted Civil Law in the Meiji Restoration because it closely resembled their own Feudal systems. Recently, they also adopted "Citizen Judges" which is sort of a Jury system. Three Judges are career judges while the rest (up to seven, I think... it varies on crime) are similar to a United States Jury. The difference here is that Simple Majority is needed for Not Guilty while a Guilty verdict needs a Simple Majority and must include at least one career Judge in that vote. Hope this was helpful. Law systems are a hobby of mine, so feel free to ask questions. Edit: Related to statutes there is a significant difference in how they are written in Common Law and Civil Law. Because of Stare Decisis, rulings on a particular law are effectively an addition to that law. This means that from the legislative side of the house, a new law doesn't have to be a tome covering every possible scenario. For example, in most of the rest of the world, Anti-Trust laws are massively complex. In the United States, the Sherman Anti-Trust act was originally passed with three sentences. The scope of what is the law is still quite large, but that entirely originates from case law AND a few legislation acts to fix what some case law broke. As discussed earlier, several common law jurisdictions didn't have any statute against murder (though they did have sentencing guide lines) until relatively recently. Conversly, as stated in a comment, Civil Law can review established case law as a sort of guideline, but isn't obligated to rule the same way in a similar case UNLESS the legislature has codified the ruling into an actual law. Thus, they tend to have numerous statutes that are long reads covering as many possible questions as they can think of. Another final topic on Common Law: While this is not true of all jurisdictions, many common law systems require that there be an actual real case, and not a hypothetical. If, for example, in the United States I sue the government for failure to recognize that Vampires have rights under the constitution, I must be a Vampire to make my case. The fact that I am not would immediately get the case thrown out of court because I have no stake in vampires rights (Pun intended... it helps hammer home the point.). [Answer] You can't, no one ever does, not even in the modern world; we have no inclusive laws only exclusive ones, i.e. our modern codes of law exclude specific acts as being illegal rather than setting some independent standard of legality that all acts can be measured against. That being the case you can never not miss bits and pieces. You build as much of the system as you can in shallow detail (this is my guiding principle when building anything for an RPG because PCs are unpredictable so you never know what you're going to need but also flighty so you rarely need anything for long, or twice) and remember that by and large in a feudal society the law is what the lord of the land you are standing on says it is unless you can appeal to the lord he owes vassalage to. Three categories of crime should do you, what they once called the high justice the middle and the low. The low justice deals with petty crimes and is limited to fines and extra duties (as in tax, but often exacted in labour). The middle justice dealt with more serious crimes and penalties extended to crippling fines that could include land seisures, flogging and the stocks. High justice was the right to hand down maiming and death in judgement and dealt with potentially capital crimes, as a rule rape, murder, and treason. The "tenant in chief" was the land owner who reported directly to the Monarch and was invested with rights of the high, the middle and the low, middle and low justice were often the province of appointees like bailiffs who oversaw land on behalf of others, the right of high justice was often also held by anyone who held land by "right of service" i.e. they gave military service to the ultimate owner of the grant in return for their land, but those subsidiary lords could be overruled by their patron lord. Anyway most of that is flavour and detail work that you may or may not want; the point is if you have three broad categories of justice you also have three broad categories of crime and "threatened article" (basically what the crime involves a lose of; an item, a livelihood, a life) and three tiers of officialdom to deal with those levels, this gives you a very basic structure into which you can plug NPCs at need by asking how serious the situation is (either from the consequences you want or from the situation underway) and then carrying on from there. [Answer] Why do you need a legal system? Because you want to set up rules for your society, to reduce conflict between its members. Sometimes you also want to oppress some parts of your society and favour others. You mentionned a monarchy, so you will have some established privileges for your nobility. A few basic thoughts you should consider when setting up a new rule for your society are the following: * Which problem are you trying to solve? * Does your proposed rule address this problem? Is your proposed rule adequate for solving this problem? (i.e. not too weak or too strong?) * And, often overlooked, but very important: can this rule be used against its purpose? Or in other words: does it have potential to be abused? Typically, there won't be one good and failproof answer. So you will need to come up with a system of checks and balances, that comes into action when your original rule alone becomes unbalanced or abused. Law-making is not an act, that starts and ends at any specific points of time, but it is a process and evolves constantly. Your society changes, or progresses, new ideas, new technology, new needs and chances arise, requiring new rules to be made, and old rules to be adapted and some to be removed. What does that mean for your question? You are in the process of building a fictional world, and not a real-life setup. Good for you, otherwise you would need a very large group of people and many, many years of time to come up with even a skeleton of this systm. In your fictional world, the most important bit is not the laws but the story. you should draft, roughly, the general setup. Do you want a system that is considered fair, or oppressive? By which groups in society? Which parts of it are necessary for your story? Can you find a real-life example that fits your bill? If so, use this, and adapt only where necessary. That also helps with understanding the concept. Draft those laws or general rules that you need for your story, spend some time on considering the bullet points above, but don't elaborat them in your story: all you need is to make sure there are no obvious holes, to suspend disbelief in your reader. [Answer] study the legal system of middle ages, that should help. There are many histories who study the middle ages and love to write about things like "The none high-profile elements of the dark ages legal structure." Im sure there is a journal out somewhere that covers it you just have find it, which can't be that hard it you have the internet [Answer] Visit the meetings of your town or city council, watch as much on the legislative channels as you can, visit courtrooms to see how they function, and generally become a good civic citizen. But whatever you do, do NOT use Trump as an example of civic responsible government. Alternately, write your book, and have it reviewed by knowledgeable critics, and take their advice to heart. ]
[Question] [ In most languages, the linear concept of time has led to similar concepts of past/present/future. Now, suppose that we have a human or human-like society in which time travel is fairly common, and it is possible for an individual to travel forward or back in time on occasion, including making contact with their past or future selves, friends and family. This is achieved by magic, not technology, and while many individuals can time-travel themselves or send a non-time-traveller to another time, the majority (about 95%) cannot temporally displace themselves or others. The one restriction on this time travel is that a time traveller cannot change what they know has happened in the past of a point in time in which they have been present. This includes influencing other time travellers to change things on their behalf, even if they don't tell the other time traveller why they want them to do certain things at a certain point in space-time. E.g. an individual travels to the future, and learns about the death of their future self. Learning about this means that this time traveller cannot affect the outcome that his (now past) self learns about his future self's death at that point in the future. However, the possibility exists that either that now-past self was lied to by a witness, or if the time traveller was a witness to his future self's death, that the time traveller was deceived or mistaken. It is also possible that the event of the future-self's death was sufficiently unambiguous that it could not be other than what it appeared to be. So, given that members of this society can travel in time relatively often, how would this affect the society's language? EDIT: There is no paradox, as causing a paradox is ultimately impossible, but the time travellers may suspect this to be the case, but don't know that with any certainty, and act as if paradox is a possibility. What exists and is remembered by time travellers and non-time travellers alike is the final state of any time travel loops. For example, A time traveller cannot kill their own ancestor or the ancestor of anyone they know of (however indirectly) at a point in spacetime that would invalidate the existence of themselves or a known person. However, that is not to say that they couldn't, for example, kill the individual that they believe was their own grandfather before the conception of their parent, but it would ultimately turn out that they were mistaken as to the relationship, or they mistook the person they killed for their ancestor, or they only thought they had killed their ancestor. As another example, a time traveller cannot pass information (via whatever means) to another time traveller, even if the two time travellers are unknown to each other in a social sense, that could cause that second time traveller to invalidate the first's memory of events or the existence of anything he knows: it is the transfer of information that defines knowledge. An infinite loop is not a possibility (though it is possible for a loop to be repeated a great many times) as outcomes along a timeline are not predetermined. Each act of travelling back in time results in a new sequence of events. A common trope in time travel is that non-time travellers will always act in the same way to the same stimulus; this is false. It may be likely that they will do so, but quantum uncertainty means that each act of retrograde time travel will result in the subsequent events unfolding differently in some way, whether subtle or glaringly obvious. Sooner or later, this (or other time travel) will result in the loop diverging sufficiently that it ends. The time traveller would not remember all of these loops either, only the last one, so no Groundhog Day or Edge of Tomorrow loops with a time traveller retaining information from his future self, at least without meeting his future self and passing on that information. For example, a time traveller in a loop meets an old friend (who is not a time traveller) in several iterations of the loop, in the same situation. However, the old friend will not always greet the time traveller in exactly the same way. In the first loop, he says "Hi", in the second "Hi", 3rd: "Hello", 4th: "Hi", 5th: he just nods, and so on. Anyway, this question is about the linguistics of this scenario, not the physics save where it affects the linguistics. Time travellers believe that paradox may be possible, even though it is not, and the linguistics must reflect this. [Answer] Looks to me like you're looking at [Language Change](http://en.wikipedia.org/wiki/Language_change), which is an active and ongoing process. Even languages which we think are isolated or constant experience [linguistic drift](http://en.wikipedia.org/wiki/Drift_(linguistics)). Why, the very act of you reading this post can be seen as contributing to linguistic drift! There are a lot of factors which go into linguistic drift. Many of these factors are debatable, but it's fairly safe to say that you must consider what languages are exposed to each other, how those speaking those languages feel about each other, and what is considered popular for the various groups. How would time travel affect this? Here are some conjectures: 1. Accelerated Linguistic Change. Someone hearing the end result of a trend in their own language may think that the end result is better, and therefore will change their language accordingly. 2. No Change. This is a result of people thinking that "time-travelers sound funny, in a bad way, and I don't want to sound funny." Therefore, the people don't adopt any mannerisms, words, or ideas from time travel. 3. Langauge Swap. The time traveler population and the "normal" population just swap occasional words or ways of speaking. This could be because time travelers got used to saying things in a certain way and never stopped when they got to their home time. This could be because the time travelers brought something useful with them in the travels, and therefore the normal populace adopted that word. Out of these conjectures, #3 is most likely, I feel. There is also the question of how far in time you travel. For instance, those speaking [Middle English](http://en.wikipedia.org/wiki/Middle_English) (which Chaucer did) could carry on a halting conversation with those speaking Modern American English. There would be some points of contention or confusion, as you can see from the Canterbury Tales Prologue In Middle English: > > Whan that Aprille with his shoures sote > > > The droughte of Marche hath perced to the rote > > > And bathed every veyne in swich licour > > > Roughly Translated: > > When that April with his showers sweet > > > The drought of March has pierced to the root > > > And bathed every vine in sweet rain > > > You can see some problems with picking up words even from different times from the same language. "Sote" and "sweet" are very different! Also, calling rain "licour" could cause some problems in Modern American English. # New Time Words If the time travelers find that talking about time travel doesn't work well in their language, they may introduce new [grammatical tenses](http://en.wikipedia.org/wiki/Grammatical_tense) to talk about events that will/have happened. Some languages (including English) have a present tense (I go), future tense (I will go), past tense (I went), pluperfect (I have gone), and other tenses. These indicate times relative to whenever the "present" is, so a time traveler may have to establish when the "present" is. There is also the possibility that your original language is like Chinese, and does not have tenses at all! This time travel could make them break it, or perform something else to establish when the actions they're talking about took place. Something like "Past me in past time punches future me, in that past time, in face while the present I looks on." This can get confusing really quickly. In short, time travel opens your language up to more influences, which may or may not catch on, depending on the people and their views of time travel. Time travel itself may require some language modification. [Answer] Such a society is extremely unstable. First of all, any time-traveler who has the desire to commit a crime against someone else (as revenge or otherwise) can do so, by harming other's past, present and future in a million different ways. People will find weapons from the future and use them to establish global empires at various points in the past. Language translation software can also be picked up from the future, whether it can be transported or not, will affect language. There will a small law-abiding group that will try to locate and control the huge influx of criminals (whose very definition depends on the place and time of the law) and be highly unsuccessful due to internal discrepancies. Wars will occur at various points in time, killing people of various points in time. Achieving such omniscience and powers will also cause people to kill themselves out of depression, while others will turn into wild beasts with no aim in life. Some people will keep transporting themselves forward, just to preserve their lives till immortality is possible, or they may reach a post-apocalyptic universe, whether their existence is impossible, causing them to die. A large number of people will hide themselves in the fabric of space and time, get mansions for themselves and try to live happy lives, away from the conflicts. It is also possible that the time traveling race will die out. Whether it will get recreated in the future is unspecified. This would be the greatest (and most unpredictable) dystopia that I've ever heard of, language is the smallest of issues. You don't need a language to prove that you can destroy the world, or create a new one. The people trying to survive independently may learn the language of the place and time they are in, but will be eventually wiped out by inhuman future beings who know how to track them down. Forgive me for being pessimistic, but this is the reality. You can forget about predicting the languages used. ]
[Question] [ How would one make a flat bubble stretched between two sides of a triangle that can withstand pressures up to at least 0.25 pounds per square inch? If it goes higher that's fine, as long as it still could be popped with a finger without much difficulty. If it requires special properties for the structures it is attached to, I can probably make that work to. Context for those curious: I'm designing a species with bat-like wings, but instead of membranes made of flesh, they can blow bubbles from organs near the wing joint that fill in the space to form the membranes when needed, and they can use their wings like hands (granted, significantly weaker and more fragile hands than those of a human) when the bubbles aren't formed. I worked out the pressure based on some research on birds and bats, but I couldn't find anything on how much pressure a bubble can withstand. The number I gave above for the pressure is actually still giving a significant error margin compared to the rough numbers I worked out (I came up with a pressure of 0.07 PPI, based on 20 square feet of wings, 45 pounds, and a rough guess that they won't be putting more than five times their weight on their wings at any point, but as noted, I left a wide error margin on that). If I've missed any major factors you can see, feel free to point them out. If there is no way to create such a bubble under known chemistry, I'm willing to make up some sort of magic/fictional substance to solve the problem, but I'd like to do it without if I can. [Answer] Short Answer: Wings, in the style you are after, made from any type of liquid wouldn't work. Long Answer (Warning Contains Science): The key scientific idea associated with Bubbles is surface tension. Surface tension is the energy related to expanding the surface area of a fluid, larger surfaces have more energy, and since all systems tend towards lowest energy, bubbles move to reduce their surface area. This explains why bubbles floating in the air form spheres, because for a set volume a sphere has the smallest surface area. As to why the bubble doesn't continue to shrink is because the energy released from shrinking the bubble is equal to the energy required to compress the air contained in the bubble. The problem with you wings is the open edge, this means that since there is no edge to support the bubble it will keep shrinking, until it forms a thin film along the supporting edges. Unfortunately even if you have a completely enclosed shape containing the bubble it still wouldn't work. To get the best membrane you would need the material to have a high surface tension because for a given pressure it would deform the least. The material that has the highest surface tension is mercury, which has a surface tension of 0.4N/m, this informs us about the pressure range we could get. For 0.25 Psi (1723N/m$^2$) your wings would have to be approximately kilometer lengths, which causes significant bubble and structural problems. If you are still after using bubbles for arial transport you could use [Ballooning](https://en.wikipedia.org/wiki/Ballooning_(spider)) which is what spiders use to travel large distances. It works by significantly increasing the drag until it is such that the air currents can drag the creatures into the air Hopefully that helps [Answer] ### Colloidal Armor Polystyrene particles suspended in a bubble can increase its mechanical strength and stability, creating a "colloidal armor". Biological polystyrene production shouldn't be too difficult to achieve, as polystyrene is an organic compound and all organisms produce polymers. These armored bubbles can also form nonspherical shapes. Unfortunately, at your specified pressure these bubbles only maintain their structure at a diameter of roughly 1.5 millimeters. I don't see how any other form of "armor" could greatly change this value to allow for a singular strong bubble to form between two fingers. Therefore, your animal would need to produce multiple bubbles to form one wing. Surfactants can prevent these bubbles from fusing together, and at a small concentration, the presence of surfactants (such as rhamnolipid, emulsan, viscosin) will not affect the structure of your bubbles. Acoustic waves can keep bubbles attracted to each other, so your animal could have some sort of vocal organ within their fingers to maintain wing structure. If they want to lose their bubbles to utilize their hands, they can stop producing noise from their fingers. Information from [Probing the Mechanical Strength of an Armored Bubble and Its Implication to Particle-Stabilized Foams](https://journals.aps.org/prx/abstract/10.1103/PhysRevX.6.011010), [Microstructure, Morphology, and Lifetime of Armored Bubbles Exposed to Surfactants](https://pubs.acs.org/doi/10.1021/la060388x), and [Amplification of Acoustic Forces Using Microbubble Arrays Enables Manipulation of Centimeter-Scale Objects](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.254502) [Answer] So, the organs (main middle body) releases material (not sure why bubbles?) so that it joins joints (triangular corners) to form wings (as and when required). If wing material is popped - then a capability to self heal and reform wings. Is this desirable ? Not sure why you want the wing membrane to be popped with just a finger ? Wings (dual use - 1. hands 2. flying). Not sure why - birds use their feet to catch their prey/food and wings to fly. May be if feet are hurt or lost in accident, then ability to use wings as hands. Which means wing structure needs to be flexible (\triangular and flexible with decent structural strength --> ambitious \). Does this creature land, if so on what ? This creature need a source to release this rubbery material (preferably non sticky - so that undesirables don't stick to the wing surface). Chemistry & Material knowledge is required to make this a feasible project. Solution: Is it possible to use a 3D printer in the main body to reconstruct lost membrane in the wing structure. You'll have to come up with a detection mechanism (for lost membrane). Using 3D printer will help you experiment with the strength of the membrane. EDIT to make it understandable for those who still seek bubbles (replying to comment) 27/08/2022 @Community Bot - Your comment does not say what is not clear. If you point out I can expand. Anyways, Firstly - Bubbles is not required as is mentioned in the original requirement. I take it as a nice to have (as it is not clear why only bubbles) but probably not required. Quite simply - why bubbles ? Requirement is a material that can be popped with a finger (not clear why?), can withstand atleast 0.25 ppsi (not clear why?) The way to make this project feasible is to experiment with materials that can be printed using 3D printer. 3D printer will receive prompts to reprint membrane/material that join the joints in the wing. The wing is assumed to detect missing/damaged membrane. 3D printer itself needs innovation to make it fit inside main body of the species. It is not clear how big the conceptual species is. It is not clear whether this is a fantasy species? Why is this species required ? Successful conceptualisation, design, development, testing, production of this project may have huge implications depending on its application. By the way I'm suggesting 3D printer, simply because if membrane in the wings ruptures during flight, it is imperative that the species is stabilised asap. However, there is every chance even rapid reprinting of the wing span may not be enough to save the day and the species crashes anyways. There might be other more subtle and niche ways that I'm unaware of. May be an alternative solution is slightly mechanical, i.e. to have a spare wing hidden inside the main body of the species, Just like we have a spare wheel inside of cars (well most of us have). The damaged wing collapses inside the main body of the species and spare wing is deployed instantaneously. The repair of damaged wing occurs inside the main body ready to be redeployed automatically. If I know why this species is required then I can run my mind amok. [Answer] I get that you want bubbles... Really I do. But I want to challenge that assumption. Have you thought about spider silk instead? It is something with an incredibly high tensile strength to weight ratio... Meaning that it will give your creature useable wings with less weight. It fits your science tag and would even fit a hard science tag. We have GMO goats that can produce spider silk... Therefore is no limit to what creature could conceivably produce a spider silk like material. It can be removed from the hand/wings (Not as easily as your proposed bubble... But easily enough). Its not a bubble and your flying creature cannot pop it.. But I really think it is the best choice. Just give your terrifying bats from the underworld spinnerets and enough flexibility to weave wings along their arms and they will be ready to fly. ]
[Question] [ What is a plausible way to have a micro-scale containment system that prevents excited nuclear isomers from decaying? ## background A [nuclear isomer](https://en.wikipedia.org/wiki/Nuclear_isomer) is an excited state of an atomic nucleus. This is energetically mid-way between chemical energy and what we normally consider nuclear energy. [![log scale cartoon](https://imgs.xkcd.com/comics/log_scale_2x.png)](https://www.explainxkcd.com/wiki/index.php/1162:_Log_Scale) [178m2Hf](https://en.wikipedia.org/wiki/Isotopes_of_hafnium) for example stores 2.446 MeV per atom, compared to over 200 for Uranium fission. Adding a bar for [1 330 000 MJ/kg](https://en.wikipedia.org/wiki/Hafnium_controversy#Importance) to the above chart (the bar will be 260 m tall), we see that even at 1% of nuclear levels it's about 10,000× more energetic than any chemical energy. A grain of sand is about 10 mg. A single milligram is microscopic speck. One milligram of this isomer would have the same power as 10 grams of chemical explosives, about the same as a grenade or anti-tank projectile. ## concept The excited nuclear isomer is used as an explosive in small projectiles, ranging from ultra-fine needles to fléchettes. The ammo will be stored in small hand-held guns. ## engineering problem Given a near(ish) future with nanotechnology, superconductors, and the like, what is a scientifically plausible device that can store the excited nuclear isomer? The containment system must prevent the excited isomer from decaying. If the specific isomer used has a long half life, we also have the opposite requirement of inducing such decay over the entire sample on command. If the natural half-life is sufficiently short, than simply turning off the containment will make it explode as all atoms release their energy within a small fraction of a second. The physical system must be miniaturized to sub-millimeter dimensions. Since nanotechnology is available, you just need to have the physical principles involved realizable in a small number of atoms and without large cavities. Supplemental equipment can be in the gun, with the system on the projectile only needing to last on its own for the time of flight. # some food for thought [quantum Ζήνων effect](https://en.wikipedia.org/wiki/Quantum_Zeno_effect), [Bose-Einstein condensate](https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate), relativistic time dilation, [induced gamma emission](https://en.wikipedia.org/wiki/Induced_gamma_emission). [BEC applicatitivity asked on Physics](https://physics.stackexchange.com/questions/336075/bose-einstein-condensate-and-nuclear-states). [Answer] (Note: I'm not a physicist...) Other than by relativistic effects, there is no known way of delaying or stopping the decay of nuclear materials, so we should choose nuclear isomers that are stable. This would allow us to have a weapon that isn't spent by the time we need to use it, having emitted all of its energy in the form of high-energy radiation in the meantime. Thus, we would choose nuclear isomers with long half-lives (something with a half-life of 10 years would decay by 50% in 10 years, thus becoming only half as potent). If we assume that the usable lifespan of a weaponised nuclear isomer ends once it decays to 90%, then the lifespan is 15% of its half-life (=log2(100/90)). Thus, if we want to be able to store the material for 5 years, the material would need to have a half-life of over 33 years (5 years/15%). The problem is that nuclear isomers that are stable will still slowly decay due to the normal stochastic (random) process rather than spontaneously. That's the same problem that the Manhattan project had. In their case, they overcame that by inducing a neutron cascade that triggered the fission process across the entire sample of material. For a nuclear isomer, a similar trigger mechanism would be to bathe the material with radiation of specific frequencies to decrease the spin states of every atom so the material as a whole will undergo explosive decay. The radiation required would depend on the material chosen, ranging from gamma rays down to microwaves. To achieve this, the casing for such ammunition would be designed to serve multiple purposes: a) to hold the projectile together; b) to convert a safe form of radiation (e.g. radio waves) into radiation of the triggering frequencies; c) to prevent the radiation caused by the natural decay process from getting out by absorbing the photon and re-emitting it at a lower frequency (heat or radio waves or even light). The explosion could then be triggered either remotely (by directing a beam of radiation at it) or locally by having an emitter built into the projectile to create the triggering radiation at the right time. The latter would require a smart projectile, either with sensors built in to detect proximity to target, or at least a timing mechanism, with the delay programmed into the projectile by the gun prior to firing. Given the half-life requirements, following nuclear isomers would be suitable: * [166m1Ho](https://en.wikipedia.org/wiki/Isotopes_of_holmium) (Half-life 1200 years => Usable weapon life 180 years; 6 keV photon emitted = ~578 MJ/mole = ~3500 MJ/kg) * [178m2Hf](https://en.wikipedia.org/wiki/Isotopes_of_hafnium) (Half-life 31 years => Usable weapon life 4.6 years; 2.3 MeV photon emitted = ~221,600 MJ/mole = ~1,250,000 MJ/kg) * [180mTa](https://en.wikipedia.org/wiki/Isotopes_of_tantalum) (Half-life >1015 years => Usable weapon life >1.5x1014 years; 75keV photon emitted = ~7,200 MJ/mole = ~40,000 MJ/kg) All of these have much greater specific energies than TNT (=4.6MJ/kg), so you can pick whichever you feel would work for your scenario. The [178m2Hf](https://en.wikipedia.org/wiki/Isotopes_of_hafnium) has the greatest energy available, at about 270,000 times more energy than TNT, but the others aren't too shabby; [166m1Ho](https://en.wikipedia.org/wiki/Isotopes_of_holmium) has 761 times more energy than TNT with [180mTa](https://en.wikipedia.org/wiki/Isotopes_of_tantalum) having 8700 times more energy than TNT. [Answer] ## Isomer Bomb ### Triggered With the right Isomer, it may be possible to induce a very violent and rapid decay by blasting it with [gamma rays](https://en.wikipedia.org/wiki/Induced_gamma_emission). This may be a viable method for trigger an explosion using [Hafnium](https://en.wikipedia.org/wiki/Hafnium_controversy) which has been looked into. Your weapons could consist of a primer that triggers a blast of gamma rays into (insert isomer here) resulting in the rapid decay. Put in a casing that can help focus the decay products to continue the reaction. This may or may not be how some nuclear weapons work. With advances in particle physics, it may be possible to engineer [elements/isomers](https://en.wikipedia.org/wiki/Island_of_stability) that fit the needs required. On a similar note, a universe I'm working on has an extremely advanced civilization using a stable-ish [Hassium](https://en.wikipedia.org/wiki/Hassium) isomer in kinetic weapons because of its very high density, predicted to be ~40 g/cm$^3$. ### Stored? Since an isomer is a metastable nucleus, that is to say, kept from decaying because its constitute parts have just enough extra energy to hold together and that decay occurs when that energy is released. Therefore, it might be possible to store the isomer in an environment that constantly keep the nucleus on the perturbed. I imagine a scenario where the isomer is stored under gamma ray illumination, the energy of the decaying isomer is replaced the flux of extra gamma radiation. This would only be practical if the decay chain has several steps in it, otherwise, the gamma radiation would be better suited as the weapon itself. [Answer] All right. let's see: * Near-relativistic time dilation: The projectile would vaporize you before it even exits the barrel. * Zeno's arrow: You have to measure the stuff (isomer density decrease in the projectile), so you're place energy into the system == overheating + need of constant power supply ((further decrease in isomer density to allow for these structures) * Bose-Einstein condensate: maybe, but still too complicated. # Solutions: 1. Inducing gamma-ray emission in more stable isomers with high power photons, similarly to lasers. 2. Using isomers to trigger an uncontrolled fusion by focusing enough gamma-radiation on deuterium = [pure fusion bombs](https://youtu.be/vtUpWihJJJ4?t=125). 3. Using nuclear isomers to create a gamma-ray laser cannon. ]
[Question] [ Set in the 13th century middle ages and there is a zombie apocalypse, I own a castle surrounded by a trench of width 50m and a depth of 50m filled with 25m deep of mercury. The zombies are similar to the TV series The Walking Dead and I hope by now you have already seen it. It seems that I'm the sole survivor in this heavily zombie infested area. I managed to stock pile plenty of non-perishable supplies and practice rationing every day and I blew up the bridge connecting my castle to the outside world. Would the barrier hold off the zombies? If not, what should my backup plan be if I must only die by aging (must include the use of mercury)? Note that poisoning the zombie only serves to infuriate them more. So I guess, maybe not I don't know the show didn't tell. [Answer] You would need roughly 62500 cubic metres of mercury. One cubic metre of mercury is 13,534 kilograms. So you would need to mine 845,875 tons of mercury. In cinnabar there is 12% percent of mercury. So you would need to mine 75000000 cubic metres of pure cinnabar. In the 13th century. In 1981 we globally produced 5500 tons of mercury. Globally. With modern mining technology and with modern mercury processing. Good luck with that. Consider making the 1. filling the trench with hydrochloric acid. Easier to produce, and works much better on fleshy things then mercury. 2. You live in a castle with a trench. Just fill it with water, and second one with pikes. 3. And for the love of everything medieval. Just use swords and halberds to kill zombies and wear chainmail and armour. You'll be fine. [Answer] # No Mercury wouldn't affect zombies any more than water would do. It'll affect you far more as mercury vapour is toxic, and you're surrounding yourself with a lake filled of the stuff... Any zombies that manage to traverse the moat will also bring a payload of mercury closer to you. [Answer] Besides all the other considerations, Mercury is highly dense, meaning it is fairly easy to float on it... and though your zombies may be clumsy they may still figure out how to increase their shoes footprint to simply walk over the trench. [Answer] It would at least be worse than just an empty trench/moat, or even a water-filled moat. Since Zombies would likely float, even if they wouldn't be able to swim, they'd still be able to crawl over one another, and then would only have to build a pyramid ~30 meters high (counting for around 5 meters of zombie-debris being pushed down into the mercury - it could well be less) to climb out on the other side. While this sounds difficult and challenging, it's less challenging than simply having an empty moat. Then the zombie-pyramid would have to be 50 meters high. I'll leave it up to the mathematically inclined to calculate the volume and number of zombies required to "bridge" each gap, but I expect the difference to be around a factor of 2-3, simply because a higher pyramid will need a much larger base. How much larger depends on the compressible strength of a zombie. In fact, since zombies cannot build bridges longer than a few zombies (their tensile strength isn't very high), the key element to protection using "void" is to make sure that they (or anything else) cannot fill this void. My proposed solution would be to create a rapid flow of water at the bottom of the void to wash any debris (including zombies) away. Build your castle next to a big waterfall, and carve a moat that will act as a canal for the river. Then divert the river through the canal and excavate the old riverbed to have a similar profile to your canal. It should then be well beyond any but the largest amount of animated corpses to cross your moat. Additional defenses would have to target the tensile strength of a mass of zombies. Pour some soap, oil or drain cleaner into the water upstream of the zombie-crossing, to weaken inter-zombie tensile-strength. Pour light oil into the water and light it aflame, to weaken intra-zombie tensile strength (assuming burnt, rotten flesh not being as flexible and more brittle than just rotten flesh). This would also be more compatible with early medieval capabilities ;) [Answer] Just lock the door! Mercury would have little effect on the zombies other than ensuring that their bite was even MORE dangerous to you than before. As has been pointed out in other answers, it's not a good idea and creating that much mercury in the 13th century requires (basically) magic. Since we are talking about the 13th century here... Find a keep. ANY keep will work. A fortified manor house is good too. A castle gatehouse is also great. Even a single tower of a castle wall. Don't do ANYTHING ELSE, just bar the door. Sit tight, you are safer than you would be surrounded by a mercury trench! Fortifications of the time were reinforced stone walls. To climb them took considerably more dexterity than zombies are capable of. Zombies piling up enough to create a mound high enough to get over the wall would likely liquify the zombies on the bottom and simply flow AROUND it like a mud flow. They basically have no way to defeat medieval fortifications. Castles and other buildings of the time kept larders stocked with preserved food in case of siege and every castle would have an internal well. Basically, the Zombie Apocalypse scenario in the 13th century is WAY less scary than it is in modern times. People commonly had access to (and skill with) good hand held weapons and bite proof armor, didn't need electricity, knew how to live off the land, and total population density (and thus number of zombies) was far less. I'd be very surprised if ANY 13th century castle fell to the zombie attack. In short: forget about the mercury. Go find a castle and lock the door. [Answer] If the zombies had functioning brains they would be stopped in their tracks wondering where all the mercury came from. Does the medieval mercury industries have the capacity to produce that much mercury? However, this is not a trench, it's a mercury filled moat and a ruddy big and deep moat at that. Quite possibly beyond the resources of thirteenth century, unless the castle owner, a liege lord by any other name, had considerable time to prepare for the medieval zombie apocalypse. Several generations would do fine. Zombies falling into the moat will tend to float. Mercury is one dense liquid metal. So the zombies only need to lie back and float across to the castle side of the moat. What will make life, sorry "life", difficult for these zombies is not the mercury, but the twenty-five metre high moat walls. This is the height of the moat above the level of the surface of the mercury. We may neglect the twenty-five metre depth of the mercury because the zombies will easily bob to the surface. Of course, if medieval zombies are good at climbing, then a massive mercury moat to be of no avail. Doomed by zombies! Doomed by mercury poisoning! Doomed by tertiary syphilis (see the OP's comments)! Doomed by bankruptcy due to the cost of building the mercury moat! [Answer] Zombie one would be stopped by the 25m drop. The first few hundred would also be stopped. However, the mercury will support the weight of all the undead, not displacing much at all. Eventually, the mass of bodies would lodge together, stop sliding around, and begin filling in the moat. I'm not going to do the math on how many bodies it would take to fill in a 25m deep moat, but theoretically, the last zombies would simply walk across the squirming bridge created by all the others. Ironically, the zombies bathed in mercury would take longer to rot away because of the antiseptic qualities of mercury. Now, if your zombie virus was destroyed by the mercury antiseptic factor, that would be a very different reason to want a mercury moat. You'd probably be better off with the 50m moat without mercury. If you have to fill it with something, use lava instead. Probably be cheaper and lets face it, lava kills everything [Answer] It will be slightly better than water; it is heavier and blocks light and consequently eye sight. But not probably worth it. If mercury is a must have element: <https://en.wikipedia.org/wiki/Mercury_(element)> > > Mercury does not react with most acids, such as dilute sulfuric acid, although oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate, nitrate, and chloride. > > > And > > Mercury(II) oxide, the main oxide of mercury, arises when the metal is exposed to air for long periods at elevated temperatures. It reverts to the elements upon heating near 400 °C, as was demonstrated by Joseph Priestley in an early synthesis of pure oxygen.[11] > > > And > > A mercury compound called "Mercury(II) fulminate" is a primary explosive which is mainly used as a primer of a cartridge in firearms. > > > <https://en.wikipedia.org/wiki/Mercury(II)_nitrate> > > Although mercuric nitrate is not flammable it can speed up flames since it acts as an oxidizer. In addition, it can form explosive compounds when combined with alcohols.[7] > > > Maybe a mercury based explosives/flamethrower. Mercury is though toxic. Your main character will end up as a Mad Hatter <https://en.wikipedia.org/wiki/The_Hatter> > > Mercury was used in the manufacturing of felt hats during the 19th century, causing a high rate of mercury poisoning in those working in the hat industry.[1] Mercury poisoning causes neurological damage, including slurred speech, memory loss, and tremors, which led to the phrase "mad as a hatter".[1] > > > [Answer] No mercury wouldn't provide much more defense than the initial moat. Though the zombies wouldn't exactly be able to float across its reasonable to assume that they would be able flop across the surface and make it to the other side. Interesting video [here](https://www.youtube.com/watch?v=EGv_YVQHu7U) [Answer] No matter how you slice it, this strategy can only be a temporary measure, no matter what you fill it with, or how deep the canal. Zombies have infinite patience and tenacity. Every second of every day they will be honed in on whatever most captures their attention. From a practical perspective, you can consider the number of zombies as infinite, but any moat or ditch is finite, by definition. We all know that ∞ > any finite quantity. Unless your protagonist is very old, we're talking about a time scale of decades. A huge writhing pile of groaning zombies is likely to attract even more groaning, writhing zombies. Light sources in your castle will attract them. Dislodged stonework falling from your keep will attract them. Dead animals will attract them. Your huge castle will require maintenance and upkeep after some time. Things rust, mortar loosens, treated wood will eventually develop cracks, allowing moisture and rot. And what will you do with all of your personal waste? You won't be able to hide human activity forever. Given enough time, they will make it over or through, unless you can provide for a chasm that is thousands of feet deep. You'll also need to consider the disease, pestilence and odor that will come off these zombies. It wouldn't take long for conditions in the immediate area to become unlivable, unless your trench is significantly distant from your castle (I would assume > 1 mile). All of the land surrounding the trench would be polluted and ruined. The groundwater would become toxic. The fallow and rotten ground would encroach little by little on your castle property. Even the strategy of locking the door and never leaving will fail eventually. Unlike the way zombies are depicted on TV (and played by living human actors), zombies will have no sense whatsoever of personal space. They will care not about broken bones, cracked skulls, dripping entrails or any other bodily damage. As they begin finding their way to your castle wall, they will compress into each other as they bunch up against the wall. In fact, long before they find your walls, some zombies will be clumped into shambling clots of rotten, fetid, mindless animation. Over time, some of those rot-melded herds will be hundreds or thousands in size. Eventually, as individual and clumped zombies make their way to your walls, the front lines would be pressed into splattery ichor. Over time, there will be tremendous sustained pressure against your aging castle walls. What happens when they find a soft spot? And the crushed zombies will begin forming into a pile, slowly, but eventually rising over time. They don't care how many years it takes. A slowly growing pile of rotten and rotting flesh, right up against your castle walls. This would be repulsive and toxic to humans, but there are certainly [animals who would be attracted to this](https://en.wikipedia.org/wiki/Carrion), and from many miles away. Vultures, coyotes, hawks, and nearly any starving animal will take an interest. And maggots by the ton. All of which would continue to attract zombies. On the bright side - [butterflies](http://mentalfloss.com/article/63521/7-disgusting-things-butterflies-eat)! Edit: Since I don't have enough rep yet to upvote or post a comment, I just wanted to "upvote" Rathgill's answer and say thanks for quantifying the enormity of zombies! While it is true that there wouldn't literally be an infinite number of zombies, I was hoping it would be implicit that I meant that, from a lone survivor's perspective, the inexhaustible supply would be equivalent to an infinite supply over the source of their lifetime. [Answer] As others have said, no. I assume you wanted the moat to provide more resistance. If you want to weigh the zombies down I would suggest nets or thick weeds in the lake. Or an artificial swamp would do the same, higher chance they will pile up the top and crawl over the other bodies. Or if you want to be wacky with this one, there is always custard. Non-Newtonian so an angry running zombie will stick in but be unable to pull against it. [Answer] As other posters have indicated, you can essentially crawl across the surface of mercury. There is a photo I saw in a 1970s Nat Geo of a miner just sort of sitting on top of a pool of mercury. So I think some zombies would simply by accident fall over and start crawling. Not sure if other zombies would "get the idea." Anyway, the moat full of Hg seems way less effective than a moat full of water or gasoline that could be replenished after being ignited. I hope you have not invested too much time/money in this already. [Answer] A previous post by Beau (<https://worldbuilding.stackexchange.com/users/21766/beau>) mentioned that from a practical perspective the supply of zombies is infinite. While it IS very large in relative terms it is far from infinite. I'm going to make a few assumptions to make the math quick, but if you need to change those the changes to the answer should still be easy to figure. i'm going to assume that the zombie apocalypse happens rapidly enough that the population of the world (humans + zombies) doesn't increase significantly as zombies don't procreate, they just convert existing humans to the zombie state, and the few remaining humans don't have an appreciable birthrate post-apocalypse since nearly all of them are converted to zombies. If this last part isn't the case, then I'd argue that it wasn't much of an apocalypse, just a heck of a disruption, and things will be getting back on track shortly since the zombie horde probably is dealt with if it doesn't overwhelm humanity right off the bat. I'm also leaving out the possibility of zombie animals; their inclusion would just increase the numbers, so if you like feel free to look up the mass references and redo the arithmetic. I also round a tad for clarity, go nuts recalculating with however many significant figures you find useful. Therefore, under the assumption that pretty much all the world's population is converted to zombies, we have 632 billion pounds of humanity on the planet according to a recent paper in BMC Public Health, summarized in this article: <http://www.livescience.com/36470-human-population-weight.html> convert that to metric and you have 287 billion kg of humanity. since the density of humans (and presumably zombies) is VERY close to that of water, which is 1 kg/liter, that is 287 billion liters of zombie flesh. The minimum square 50 x 50 meter moat needed to hold this volume is calculated by dividing by 1000 to convert liters to cubic meters, then dividing by the 50x50 cross section of the moat to get the total length, then by 1000 to convert that moat length to kilometers, then by four since there are four sides to this square moat. 287000000000L / 1000L/m^3 / (50m \* 50m) / 1000m/km / 4sides = 28.7 kilometers/side or, a little less than 18 miles. That's still a HUGE moat, but it will be a whale of a lot easier to simply dig a massive great moat like this that it would be to obtain all that mercury! And it's a long way from an infinite problem! ]
[Question] [ Parallel universe, human in this alternate Earth are innumerate at least; they do not have a sense of counting or quantifying if you will. I am wondering since these primitive humans are beginning to speak intelligibly and forming what looks like a hierarchical structure, how can they then elect a new leader fair and square? Should they decide to be leaderless, how can they vote on important issues? [Answer] Vote using physical tokens (like stones in pots) Deciding who has the most votes is then a matter of simultaneously reducing all the piles of votes by 1 token each. Eventually you’ll reach a point where only one pile has any tokens left. This is the winner. To expand this out to multiple voting sites you can either take the remaining tokens in the pile (which represent the margin of victory) from each site to a central counting house and repeat the procedure, or you can define each voting site as a vote cast in a second level election and repeat the process. This is a simple extension of my answer to [this question](https://worldbuilding.stackexchange.com/questions/170096/how-can-sapient-beings-engineer-transportation-and-building-when-they-can-only-c), which details how a society that can only distinguish between 0, 1 and more than 1 can use mathematics to effectively count without counting. The same is true here. If sufficiently clever members of this society can work out the rules of addition and create some way of recording number then being able to count intuitively (as we do) is not necessary, they can always work things out the hard way by adding one each time. If you want to experience what this would be like, try counting from 0 to 1760 in increments of 176. You can’t do it easily because 176 isn’t an intuitive number to count by, but maths can always come to the rescue! Of course, the less the general populace understand the way votes are counted the lower their confidence will be in the result, so maybe stick to stones in pots... [Answer] ### Volume of the cheer from a crowd Yes some people are louder than others, and the distribution of two main groups may not be uniform with regards to distance to the judge - but those problems have metaphors in current democracies (district sizes and gerrymandering). You can also do a divide a conquer so allowing this to work for referendums in the millions or billions of people. A room of ~100 people shouts their votes, the elected representative notes the winner and travels to a district capital and shouts their vote with their peers, and then the leader of the district travels to the state capital and repeats, state leader travels to the national capital and repeats. [Answer] Say there are two leaders or issues to vote on, A and B. If the community is small enough then voters for A can pair off with voters for B. The unpaired leftovers determine the outcome. I could even imagine something like this evolving as a kind of violence-free proxy for actual warfare without either side having a notion of number. [Answer] Tug-of-war The side with the most people will win. > > The Naha Tug of war (那覇大綱挽) is an event at the annual festival held in > Naha, Okinawa, Japan.... It is a battle between the East and West > teams. > > > The event draws some 275,000 attendees annually... In 1997 the event was first logged in the Guinness Book of World Records as being the largest tug-of-war event in the world. > The rope weighs about 40 metric tons. > <https://en.wikipedia.org/wiki/Naha_Tug-of-war> > > > [Answer] ## Voting is easy Proof with the water barrel technique! It's one of many solutions to vote without counting and even to a point quantifying. What do you need ? * Being able to make a decision (that's obvious) * Being able to understand that a container is full * Being able to understand that something is taller or smaller than another one (you wouldn't dare to make a sentient species without that notion, do you?) * Liquid holding technology (taking barrels and cups as examples) * A liquid (taking water as an example) * A chalk or other marker tool Preliminary set-up : * Take a cup, and get an empty barrel. Prepare some water too. Preliminary set-up (once for every vote choice) : * Mark the water level on the barrel with the chalk. Make sure the marks are distinguishable from one another (either through color or adding a symbol) * Empty the barrel of any water and put it back where it was. Vote process : * Fill in the cup * Empty the cup in the barrel if you vote for the decision. * Mark yourself to indicate that you have voted, or go in a room of "have-voted" guys, whatever you want to distinguish voters from non-voters. Results : * The highest mark is the one with the more votes Alternatives : * If you want votes to be hidden, then add as many barrels as there are choices. Put weights on the barrel so it can't be moved at all and cut only a small hole to pour water in and not take from it. Voters take water from outside the barrel room, then go inside it and pour their water in their barrel of choice before leaving. After this, open up the barrels, perform exactly like if they were cups : Pour one barrel in an another main barrel, mark, flush the water out, then repeat with the next one. * You can use sand, too, but remember to level out the barrel before marking :). * If your people can't even make out what is taller, ugh... Then they would have problems surviving in the first place ("hey, that's one nice 'small' bear!", "That cliff doesn't seem too 'high', I can jump!"). ## The problem lies in the choice/action creation Note that counting is a very strong skill to understand if something is bigger or lower than another one and this will become more and more needed as your society grows up. Indeed, as a ruler (group or person), the more people there are, the more you need to work with numbers instead of individuals. If you can't easily analyze the current state of the nation, it will be even more difficult to distinguish good from bad courses of actions, and as a democracy, to offer a choice through vote (though once made, it can be quantified in interest by the vote results). This would most probably results in courses of action more based on luck than anything else. In other words, counting and quantifying is one of the main step of abstraction, abstraction which is often needed in any kind of political system. Not being able to is your limiting factor in making a stable, organized society, even more so than having a ruling system over another one. [Answer] The caucus process in Iowa involves people physically moving to an area of the room that represents their position on an issue. They keep discussing until consensus is reached with everyone standing together. [Answer] You are probably overestimating the role of democracy in our early history. For large part of it the power or authoritative role has been held by one among the elderly, the priests, the warriors or the rich (or a combination of them). It's just with the Greek civilization and their poleis that we stumbled upon the democracy. Before them, and it was a long time, there was no vote counting. [Answer] ## Frame Challenge Democracy requires complex thinking, and communication, yet "these primitive humans are beginning to speak intelligibly". Worse is "and forming what's look like a hierarchical structure". Hierarchies are a-n-c-i-e-n-t ANCIENT, and our nearest relatives (the chimps and bonobos) are hierarchical. IOW, your humans have had hierarchies from the beginning. As an example: chimp and bonobo hierarchies are maintained through Mob-like cooperation: the chief treats underlings well, while remaining the most powerful, and he -- she, in bonobos -- stays in power; if he's an arrogant jerk, eventually his underlings gang up and kill him. [Answer] Yes. There are simple ways you could measure votes without needing to count. Build a staircase, have people stand on either side of it to vote on an issue. Officials can check to make sure each person is standing on a step, and no one is cheating. Then, the side with more people on stairs wins. Of course, your democracy would typically be a group of elders and the heads of affluent families, who decide matters less by democratic institution, and more by politicking. [Answer] You don't need "count" to have "more". You don't even need "one". As an example, decisions by elimination. You can eliminate someone from the other side along with yourself from the discussion. Maybe you can even trade yourself for someone eliminated. Whomever is left decides. The elimination game could come from duels over an issue. Originally if you disagree, you'd fight with someone on the other side, and the eliminated person left. Someone could offer to fight in the challenged person's stead. Later, in order to make the duels less costly, they declared the winner also was also eliminated from the decision, which led to the duels being pro-forma (actually fighting over an issue was at first gauche, then unthinkable). Now, to speed things up, someone steps forward with a proposal. You can either accept or reject. If you reject, you and the person making the proposal are eliminated. Someone can step forward to replace the person eliminated. Lets look at a vote for "who should be the new leader". Suppose there are 3 parties -- red green and blue. Red has 20 people, Green has 10 and Blue has 5. The member of Red says "Red Prime should be the leader". A Blue person objects. Either another member of Red, or the person who spoke up, is eliminated, along with the Blue person. R19 G10 B4 Green Prime then says "I should be leader". Red and Blue factions look at each other. Eventually, a Red member objects. A second Green person takes the hit for Green Prime. R18 G9 B4 This continues, with each Red Prime nomination blocked by either a Green or Blue, and each Green and Blue nomination blocked by Red, until there are 5 Red 0 Green and 0 Blue. And Red Prime becomes the leader. In the case where one isn't the majority, you run into tactical issues. R15 B10 G10 Here, Red cannot block all of Blue and Greens nominations. Red can block every Green nomination, or every Blue nomination, but not the two of them combined. Red has an advantage, but not an insurmountable one. While I described the process with numbers, the process itself doesn't require any numbers by the people doing it. [Answer] The answer with the staircase is pretty cool, but I still see problems and/or further interesting aspects: If the people can't count to one, they might not be certain if somebody is standing on a step or not. They also might have problems deciding which side of the staircase is for which opinion or who wins in the end, because two opinions and two places are both too many to count. We also need to think about what this means for the psychology of the people: We support democracy because we know that we can make a difference. If they can't count to 1, they might not understand what their own vote means. To make sure the process couldn't somehow be corrupted, you may need to take very drastic measures: The people live in a really cold environment. Both sides have only one single spokesperson that can't leave their fireplace. The people can look for wood and form into a tight circle to keep wind from extinguishing the fire and to warm each other. When the people picking wood get cold, they can step into the circle to warm up. The more people you have, the higher chances are for being able to keep your fire alive. If one fire dies, the spokesperson freezes to death and the people that supported him have to either die or start supporting the fire of the opposing spokesperson. This system might not be as accurate as one in which counting is used, but it might have other advantages that we're missing out on: People who are truly desperate will work harder to keep their spokesperson alive and won't switch sides as quickly when the opposition has an early advantage. Younger people who'll have to live longer with the decisions that are being made will have an advantage because they're physically stronger. [Answer] Have a democratic melee battle Include the entire voting population in the battle. Each side wears a coloured ribbon. The side with the most survivors has won the vote. Note: The assumption is that the most numerous party will win. That is almost certainly true if everyone fights in melee rather than soldiers following the orders of generals who employ tactics. [Answer] There already are answers in that direction by @justthisonequestion and @Dan Piponi, but you may broaden and generalize the approach by familiarizing yourself with [Swarm intelligence](https://en.wikipedia.org/wiki/Swarm_intelligence). It is a typical problem there, as developing a set of rules for achievement of a certain goal. Set of rules which agents are capable to process, as well known examples not only can't count but incapable of thinking in general like bees, ants. The difference which may come from that is that there may be no particular voting event as such, and not much hierarchical system if you like. So if you choose it to be that way it may be inherited treat from evolution and less a cultural development. It does not have to be brain hardcoded, it can be like it was done that way since the day of creation - so there is total freedom of choices. If your choice is a hierarchical system, meaning there is some sense/relation of recognized authority in their society, then [Representative democracy](https://en.wikipedia.org/wiki/Representative_democracy) or some of the flavors of it may be an option. Then you not necessarily have an election day, but it can be [rolling development](https://en.wikipedia.org/wiki/Rolling_release). In a sense, it is an old system that works up until today's time. If we depict this approach as if there is election day, then people split into groups around people authority of which they recognize or people they wish to support. They send representatives to form a second group which does a similar but not necessarily identical thing. For example, if you can see horizon instead of heads of people around you, then the group is small enough. You may switch activities which you establish authority with, such as dancing in a chain circle imitating snake movements. Whoever breaks the chain is not eligible, continue. Or your typical sports competition grid, or plenty of other stuff of not necessarily a competitive nature (rolling dice to follow the will of gods), or in contrary the famous rule of the strongest/fittest. Those activities are means to define who are those people you describe, and depend on the story. So for each split there can be a specific set of activities, based on all sorts of conditions or triggers, exotic or typical ones. Praying to gods of chaos with an event which has a certain degree of randomness, which can be induced/started by agent, and outcomes of which can be recognized by the agent. This can be quite a universal thing, it fits in a lot of ways to a lot of situations. One can roll dice, or look at clouds, or those behavior randomizing superstition events. Better are those which can be induced on request, or happen frequent enough and are different for each agent (look "robotic swarm" at YouTube plenty of materials for inspiration), applied in a good way they may have a good correlation with good decision making. The ability to establish authority fast in small-medium-big groups is quite a strong survival factor. Fish shoals are a good example of that, as there are all sizes and types, the authority part may be trickier to recognize but it is there in an indirect way. It is convenient to split part of your group for different tasks, fast and in an organized way. In some sense, you may relate to your own experience and gut feelings. However, our ancestral ways were on smaller numbers, and many decision making of that sort are substituted by traditions, habits, specialization, sticking to routines, and ways of life like nomads, etc. But the other part also had a place in culture and different games and entertainments and social interaction serve for that and other purposes. As a note or a tip if you like You may consider choosing a different reason for the existence of your system, different from the ability to count. The reason may be that chimps can count up to 9(?) and they are better at that on different tasks than any human. It shows that the perception of amount and counting is an essential trait. I bet many species have some counting. We can directly observe it in chimps, as they are intelligent enough so we can sort of communicate with them. I saw this in a research facility on YouTube. [Answer] If they can't count but still conduct paper voting, simply comparing the stack heights of the ballots should be sufficient to decide a vote, unless it's a very thin majority. [Answer] Obviously yes (see @JoeBloggs accepted answer for a good demonstration), but the form it takes will be reflective of their culture and also shape it. For example: You could see a pseudo-parliamentary system where One person at a time rises to propose something, and it passes unless someone rises to oppose him/her. Then repeat, with pro- and con- pairing off until either pro is unopposed or no-one is left to rise for it. That might be a collective society, with a strong tendency towards individual responsibility to act, all within a rules-based framework. Everyone is ready to put a shoulder to the wheel for what they personally believe in, etc. Tweak that slightly, and you have a system where one rises for issue A, and someone rises to oppose. They go off, and the floor is open again. The next guy might rise for issue A again, or for issue B. That gives you a similar society to the first, but with much more focus on careful maneuvering and good timing to achieve what's most important instead of reflexively supporting what you like and opposing what you don't. (both versions are obviously caricatures). If instead of just pairing off, they do some sort of ritualized combat (e.g. hold up one end of a low-weight stick until you decide to put it down; roughly analogous to a filibuster), you have a different culture again. [Answer] The key concept for democracy is that all the people are represented in decision making including those who are weaker or vulnerable and minorities. Voting is just an attempt to realize this concept – imperfect, and also never fully implemented in present politics. Democracy also doesn't reject hierarchy in decision making. So for example you could have a leader who makes a decision after listening to the opinions of all the citizens (or their representatives, in case of a larger society). Sky is the limit. Take into account that humanity hasn't figured out the best way yet. [Answer] In the History of the Peloponnesian War Thucydides recounts that the Peleponnesian league (thats the Spartan side) made the decision to go to war in the following way. Delegates from all the member states were assembled and a discussion held. At the close of the discussion each side (pro-war and anti-war) took a turn cheering/shouting, the side that was louder was deemed to have carried the day. Why they did this I have no idea, perhaps it was some sort of anonymous voting deal. But there you have it, no counting was required. However I must point out that Thucydides thought the person evaluating the loudness had fudged the results in favour of war. [Answer] Lining bricks. Everyone gets a brick of a standard size. When it is your time to vote, you put a brick on the floor, in line with the other bricks. Whatever line of bricks is the longest wins. [Answer] ## Scales: Have a vast pile of equally-weighted stones. there is a big scale with two baskets. Everyone who can vote places a stone in the appropriate basket. Whoever tips the scales of democracy wins. This is a mass-based alternative to the voting system of ancient Athens. [Answer] Democracy is not about counting votes as well as object oriented programming is not about objects (but messages). Species who are unable to count do not need a leader because they wouldn't feel any rational inequality (my neighbor has more oranges than me). I doubt that the could form any hierarchy at all (elevate the strongest and the wisest). Bees communication through [waggle dance](https://en.wikipedia.org/wiki/Waggle_dance): First thought that I had was about some kind of psionic communication based on waves or collective unconscious. Maybe they could mix their thoughts like now we can mix colors of visible light. Different wavelengths affect final color warmth - determining more positive or more negative vote. There is a concept of [fuzzy logic](https://en.wikipedia.org/wiki/Fuzzy_logic) which could be used as explanation for voting-sense behavior or emotional agreeing. (BTW, isn't voting an emotional matter?) Although, they need to agree to this non-rational manner of making a decision. In simpler words: it's all about waves and interfering waves - the stronger is signal when people think about that candidate then more 'votes' that person gets. [Answer] No. Any concept that can be used to form a democracy is equivalent to counting in the end. If you have multi-party elections or multi-possibility votes, you certainly can have a democratic binary decision. If you can have a binary democratic decision, then you can compare two numbers, the numbers of people who voted for each decision. If you can compare two numbers, then you have numbers. If you have numbers, you can increment them. Then you can count. --- I skipped a few steps and took some liberties with nomenclature, but this is a solid argument which could be formalized. [Answer] As others mentioned on this thread, tokenistic counting (1 pebble=1 person) emerged very early on, plus hunter-gather bands were usually <100 people, so "counting" was unlikely to ever have been a bottleneck. But I think you have a lot of other assumptions in there that are coloured by how society looks now: * Why does there need to be a hierarchy? The alternatives are consensus decision-making, independent decisions making ("I'm going to go there, you want to come?"), context/expertise dependent leadership (the respected hunter is the most influential voice for where to go during hunting season, for the winter you'd rely on someone else). * Why is majoritarian rule fair? If 30 people in your 50 person tribe always got their way, and the other 20 people never got their way, is that fair? Could you maintain a tribe like that over time? And if the tribe broke up instead... is that even a bad thing? Even the assumption that bigger, more stable collectives are "better" is a logic that doesn't really work for hunter-gatherer societies. [Answer] Give each citizen a token. Have them put the tokens in a pile for who they're voting for. Then, remove the tokens from the piles one by one until there's only one pile. That pile is the winner, and once the winner is decided, all tokens go back to the citizens. [Answer] I am not sure there is that much of a difference between quantification and counting. Counting is simply abstracted, formalized quantification. The rudimentary capacity for it is built into even babies, like when do they know to stop drinking milk. [Even seemingly simpler animals like bees too show a fairly advanced capacity for it](https://www.nature.com/articles/d41586-018-05354-z#:%7E:text=Previous%20research%20has%20shown%20that,Queen%20Mary%20University%20of%20London.). The point is that the foundations of quantization and counting arise very early in the evolution chain. At some level, this intersects with very basic details of natural selection and might not even be a part of what we would recognize as conscious mental activity, like how to viruses evolve to become drug resistant. They do so by testing out genetic combinations that them 'greater' survivability. To me this question seems to touch aspects of the mind as much outside of today's scientific understanding as consciousness or free will. It is almost like asking if zombies can form a democracy. [Answer] I think the other answers are missing an important point: if people can't count, then the notion of comparing two quantities is just out of their reach, and so is the notion of "decision approved by the largest amount of people". You can't imagine a democracy this way. It would have to be a feature imported from the outside, by someone from our universe who has achieved great importance to these folk ? ]
[Question] [ Closed. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it can be answered with facts and citations by [editing this post](/posts/194332/edit). Closed 2 years ago. [Improve this question](/posts/194332/edit) Suppose a species gets together to make the most efficient language possible. The species is culturally able to accept it, the logistics of getting it to everybody has already been taken care of. Their goals are as follows: 1. Make a language that is rarely misinterpreted, eg. there are no exceptions to linguistic rules, none of this i before e stuff. 2. New words can be easily created and understood from basic morphemes. In English, anyone familiar with the words "fire" and "place" will be able to deduce what a fireplace is. This hypothetical language should be entirely like that, exempting the most basic morphemes. --- So, how would such a language work? --- Would each sentence be a long string of morphemes, or something else entirely? Or, is such an idea totally impractical for some reason, like that all phrases would be too long to be efficient? Or, I have no idea what i'm talking about, and there is some massive flaw in my "perfect" language. [Answer] What you're describing is a classical [philosophical language](http://www.frathwiki.com/Philosophical_language), a kind of engineered language that creates ideas by chaining together strings of morphemes as you say. Most of these languages are taxonomic, focusing on words with substance: nouns, verbs, descriptors. Check out [Ars Signorum](http://www.frathwiki.com/Ars_signorum) for one of the earliest of the type and for a more modern approach, take a look at [Ygyde](http://www.ygyde.neostrada.pl). As for your question "how would it work" and your subquestion, "is it practical": Such a language should, in theory, work like any other. You compose taxonomically appropriate words for all the categories you wish to talk about and put them together in the customary manner and your result is a sentence. In theory. In actuality, no, these languages are terribly impractical for ordinary use. Depending on the taxonomic philosophy underlying the language, you might have to say "ygububenarahugi", covering the pertinent taxonomic hierarchies of "living thing", "animal", "human", "alive", "specific", "interlocutor", "speaker"; and then "ramifodudugo", which just rolls off the tongue and means "action", "physical", "proximal", "near-contemporaneous", "oral", "lingual" and means "said". By the time you say: ygububenarahugi-ramifodudugo ramijigonggong ygububenarahudi-ramifodatulodaulooxixiroro and by the time the other person works it all out: living thing animal human alive specific interlocutor speaker action physical proximal near-contemporaneous oral lingual physical object device machine engine living thing animal human alive specific interlocutor hearer physical object tool lever manipulate direction reversal the warp core has exploded, destroying half the star cruiser and much of the space dock as well, when all you really had to say was: # I said: cut the engines! [Answer] I don't believe such a thing could be possible. Suppose you have such a theoretically "perfect" language--ideas are expressed in the minimum number of bits (whatever those bits translate to in terms of speaking/writing.) What happens when someone doesn't speak (or write) perfectly? Since there is no redundancy to the message you have a coherent message that means something different than you intended. Real world languages must have redundancy in some form to minimize this problem. (Although it will never be eliminated.) Also, there's always a tradeoff between complex words and more words. Which is more efficient? It depends on what you're doing, so once again there is no perfect. [Answer] You will hit one important limitation - language evolves. You are adding concepts that didn't exist before, relative importance of words changes as world evolves, words get additional meaning because they are now found related to other concepts or because of slang etc etc. Assume you have a perfect language with whatever conditions you want. Each written letter is one sound and everything is encoded in minimum number of bits, or it is simple to link tons of words in a long word meaning the combination, or whatever other conditions you want - check other answers for many ideas. As perfect with all the conditions you want, at that particular point in time (introduction of the language). Now assume that language started at say 1850-ish (spring of nations in Europe). Back then, horses were pretty important - they work fields, transport people, people race them etc etc, so it is one of those crucial words you are surely basing tons of concepts on. Engine gets named "black water mechanical horse" because what else would it be - it replaces horses to transport people around and uses black water to run. In line with previous namings, processor gets named "electrical horse brain" because the word "horse" evolved to the point to mean "something that does work for humans". Come late 20th century and a mostly irrelevant animal is all over the place in gazillion of concepts, making all those concepts longer than needed and fairly confusing too. Do you feel it is still somewhat manageable? Note this is mere 100-200 years. Jump back to first written languages and the evolved language would be more or less "spam egg spam spam bacon spam". Now, how do you tackle that? 1. Let language constantly evolve? Congrats, you are back to our current languages. 2. Keep your ancient language? But it is no longer "perfect" in any reasonable sense and would fare worse than any imperfect language that is allowed to evolve - it poorly links all the modern concepts together, it isn't compact etc etc. 3. Clean break every now and then? Language gets "re-optimized" every say 100 years. It gets increasingly less optimal towards the end of the time, and comes with a lot of confusion during transition period, but it is most likely the only viable solution. [Answer] A number of [philosophical languages](https://en.wikipedia.org/wiki/Philosophical_language) were in vogue in the 17th century. Generally they try to achieve perfection in capturing the semantic hierarchy of words; and they tend to be unlearnable and unusable. A modern approach is [loglan](https://en.wikipedia.org/wiki/Loglan)/[lojban](https://en.wikipedia.org/wiki/Lojban); they try to avoid grammatical ambiguity, their grammar is quite unusual and are very hard to learn. As for the semantic hierarchy, a rather successful approach is the [WordNet](https://wordnet.princeton.edu) (and derivatives). This is however not a language but "just" a hierarchy of semantic relations. And as for the "no exception" rule, that is rather trivial - already Esperanto has no grammar exceptions (and a rather small number of word derivation "exceptions"). Turkish has very few exceptions in its verb declination system. And languages without spelling exceptions are a dime a dozen. Conclusion: there were many different approaches in our existing Earth history to create such a "perfect" language, whatever your definition of perfection. Some of them work better, some less well, some are somewhat successful and alive, some are forgotten. Just take your pick. [Answer] I would strongly encourage you to look at Esperanto, as it actually approaches the ideals you’re asking for in certain ways: ### Consistency Esperanto was built from the ground up to be easy to learn, and thus is very internally consistent. It has: * One definite article, which never changes (it’s always ‘la’, no matter what gender the noun is). * Exactly one way to decline nouns (nouns only change for plurality and subject/object differentiation, using -o, -on, -oj, and -ojn as respective endings for singular subject and object forms, and plural subject and object forms respectively). * Exactly one way to decline adjectives (adjectives always agree with the nouns they modify, and use exactly the same suffixes except for replacing ‘o’ with ‘a’). * Exactly one way to conjugate verbs (verbs change more than nouns or adjectives, but still have 100% consistent conjugation independent of the root). * A perfectly consistent and completely reflexive (but admittedly not 1:1) mapping between letters and phonemes. This, combined with the very simple phonotactics of the language, mean that you can actually determine how a word is spelled by just knowing how it’s pronounced and where each syllable is, 100% of the time. * A comprehensive set of correlatives created by pairing specifically defined suffixes with specifically defined prefixes (for example, kio, tio, io, ĉio, and nenio are what, this/that, something, everything, and nothing, while kiam, tiam, iam, ĉiam, and neniam are the exact equivalents for time and kie, tie, ie, ĉie, and nenie are the exact equivalents for place) with no exceptional forms. * Numerous other aspects that are extremely self-consistent. There are cases of limited consistency, but most have to do with how the original lexicon was built up (that is, some words which could be derived using affixes as I will describe in the next section have distinct roots instead of being derived using affixes). ### Extensibility Esperanto uses a rather interesting system to derive vocabulary. The lexicon consists of a set of roots (base forms that provide the core meaning of a word), which can then be modified by a remarkably expressive system of affixes to derive exact forms. Using a really simple example of the root ‘promen’ (which mostly corresponds to the English word ‘walk’), you can derive: * promeno: walk, as a noun * promeni: to walk, as an infinitive form of a transitive verb * promena: walk, in the sense of an adjective (roughly equivalent to using ‘walking’ as an adjective in English) * promenu: walk, as a verb in the form of a request or command * promenego: a long walk * promeneto: a short walk * promenanto: one who walks in the generic sense * promenisto: one who walks professionally or as a vocation * promenadi/promenado: walking as a habit or recurring action, as a verb or noun * promenejo: a place for walking, or one which is frequently walked through * promenero (not sure if this is ever actually used): the smallest part of a walk, a single step * promeneco: the abstract concept of a walk or the abstract concept of walking * promeniio: a tool for walking, possibly used as a synonym for ‘kano’ (a cane) * ekpromeno: the beginning of a walk * ekpromeni: to start a walk There are many more possibilities, as there are a number of other affixes and you can actually combine a number of the affixes in complicated ways (for example, ‘ekpromenadisteco’, the abstract concept of one who habitually starts walking). This allows for easy derivation of forms (one example not seen above, the prefix ‘mal-’ is used to form an antonym of the attached word, so warm/hot is varma, while cool/cold is malvarma, and many other paired adjectives follow the same pattern), but it also has an interesting aspect in that it allows for some rather silly nonsense (’kato’ is the noun for ‘cat’, so what would a ‘katanto’ be? What action does ‘katu’ describe? How about ‘malkateco’ (the antonym of the abstract concept of a cat)?) that borders on being untranslatable in the rare cases it’s not just semantic gibberish. On top of this, Esperanto uses Germanic-style compound word formation, largely stringing together components to form more complicated words. However, this extensibility is by no means perfect, and in fact it cannot be perfect for the type of easy vocabulary derivation you seem to want. Esperanto usually does a bit better than English here, but still suffers from the same issues that are highlighted by your own example of ‘fireplace’ (all that someone who only knows ‘fire’ and ‘place’ in isolation can derive is that it’s a place for fire or associated with fire, not that it’s a specific type of fixture usually found in older buildings that was utilized as a primitive form of climate control). To actually make such a perfectly extensible language would require an absolute 1:1 mapping of words to meanings with zero ambiguity, no idioms, no euphemisms, and none of the other things that make language imprecise. Such a language would be functionally impossible to use outside of very specific circumstances, and would not allow for any creativity because you could not derive new words in any practical sense. [Answer] ### Yes we can make a language like that - but perfection may be subjective. People may value things like rhyme or other auditory features of your language (Doesn't French sound romantic? doesn't German sound authoritive? isn't written Arabic beautiful? Isn't New-Speak perfect because it's hard for speakers to form rebellious thoughts?). These are so complex to consider I'm just going to mention the category and forget about them. However there are obvious flaws in our language that we can't agree on how to fix. Ever been confused by a sentence like: "one of my friends is gender non-binary, they live a long way away"? (Do all my friends live away, or just the single transgender friend?). How do we fix that ambiguity? I vote a new word "They-all" to be used when referring to all of a group vs a single person of unspecific (or specific neutral) gender, but that is a can of worms. Some people will want all gendered pronouns removed, some less caring people think non-binary should just pick one. Your language designers will have to fight these kinds of battles. ### So how would you design it? You need to have: * each word be it's own unique meaning. + eg "Set" can't mean both "apply" and "collection". * If one hears a particular collection of sounds or sees a group of letters, the meaning is unambiguous, yet no longer than it needs to be. + eg there, their, and they're would need to be replaced with 3 unique words. + "Close" can't be the opposite of both far and open. * most common words are the shortest, rarest words are the longest. Assuming a pronouncable, unique word can be made by vowel- consonant pairs, your looking at about 130 combinations that can be words for every two letters. Removing cases which could introduce word boundary ambiguity (eg Our rate vs Hour eight), or other unintentional homophones, your probably looking at about 10 unique words per letter of length. 100 per 2 letters, 10000 per 4 letters So the most common 100 words are assigned to the 1 syllable / 2 letter words. The next most common 10000 words are assigned to the 2 syllable / 4 letter words. Etc. ### Example and dry maths So these English words are all 2 letters in your language: > > a > about > all > also > and > as > at > be > because > but > by > can > come > could > day > do > even > find > first > for > from > get > give > go > have > he > her > here > him > his > how > I > if > in > into > it > its > just > know > like > look > make > man > many > me > more > my > new > no > not > now > of > on > one > only > or > other > our > out > people > say > see > she > so > some > take > tell > than > that > the > their > them > then > there > these > they > thing > think > this > those > time > to > two > up > use > very > want > way > we > well > what > when > which > who > will > with > would > year > you > your > > > Each one of these has a 2 letter word in your perfect language, so the translation of "some people think they know me very well" would be something like "da do ti to co me we wa", saving 2 syllables when spoken, or 17 letters when written. Making "Common sequences short, rare sequences long" is how things like .zip files work. There is a lot of research about this; If you want to read dry mathematics about this, may I suggest <https://github.com/madler/zlib/blob/master/doc/algorithm.txt> [Answer] It looks and sounds completely random. Write some English text. Compress it. Base64-encode the compressed file. Now pretend each different letter is a syllable. It looks something like this: ``` H4sIAAAAAAACA11TMY7cMAzs/Qp2aYx9QJqrUlyRpLgAqWmbsomVJUOUz+ffZyhnb4MYWNgrjWaG Q6rr3vZtyybEZJuMKkazVKOa8Vqk4INWvgvhD63ZKkkIClyqFDnNO89CIDAdotzoF1APHjUa91j3 wjGexNh3Mh5H2Spp7RtlzLNa1dEoB1eummZsOlLepZxDnk5a2IhjEcb3IJKowlGikYvgWFPVQnPm CBzWAA85xnzY164jPN+9An4argtX91eAhrdVTVOVshWpMvUk883NORN+CVY+3LTm5MFQhMe9uaay R7EekOROcAikCo8h4yCiqHsIt2bhhxx05DIhFE5AkLAptEeUBVHiNNGeJilWc54olLzSAMiI1Mu2 yCp2o9dE39Ic1ZYeB05XDbxqVC50aF1apJdKULcP0i3yiEWN0VUfbZhk2n3Zg+AGvnBqHieqWM4t gw1FcnwGZ0ve49Tsp6otvKj3K1Dk9iHr1jr4OS3/l9B1b7mnJXsYzmT7uPzbGZi/v3Td77YpjE2D kiRYG1oLM9itFhdB4J/EPeVCllcMrW9JtKfFF/pZem/3JZZIJ2GEUNtg6roVHq86w18SQlMsp/5Z HOYv0rYUNkz28QgBrbocIVHP5HE1UIFLvmJy39sANcUWtn5ZMb7x7i55yHvtW5eucXOPLr8yLhRO hsgHaaL1pE1KkPF56ZDkH0TU4ne9AwAA ``` Now, file compression only works well on big files, because the compression algorithm adapts itself based on the specific file. It first figures out the best adaptation for the file, then saves the adaptation, then compresses the file with that adaptation, then saves the compressed file. So when you compress a short file, a lot of space is wasted describing how the file was compressed. Language is designed for short sentences, so the "best adaptation" has to be part of the language, not part of the sentence. Therefore, your sentences will not be so long as short compressed files. The code block above is your compressed base64ed question. It's about half as long as the original question, but if we imagine that each letter is one syllable, it actually takes longer to say, because your post has more than one letter per syllable. But that's including the "adaptation data". When you have a large amount of it for good compression, English text usually compress down to about 1 bit per letter, and base64 stores 6 bits per letter. If we had such a system, we'd expect your question to be about this long: ``` H4sIAAAAAAACA11TMY7cMAzs/Qp2aYx9QJqrUlyRpLgAqWmbsomVJUOUz+ffZyhnb4MYWNgrjWaG Q6rr3vZtyybEZJuMKkazVKOa8Vqk4INWvgvhD63ZKkkIClyqFDnNO89CIDAdotzoF1APHjUa91j3 ``` Also note that every bit of compressed speech is extremely dependent on context (that's how it saves bits). If we change "gets" to "eats" we get this - totally different: ``` H4sIAAAAAAACA11TsY6dMBDs+Yrt0qD3AWmuSnFFkuIipV5gDatnbOQ1x/H3mTV596IgIYE9npmd XXfd275t2YSYbJNRxUi4GtU8S12k4INWvgvhh9ZslSQEBS5VipzmnWchEJgOUW70C6gHjxqNe6x7 ``` Such a language is obviously not suited for communication where people might not hear you properly. I changed a couple of compressed letters and got this: > > Suppose a spegies gdtlissamrerlis make mre most effiegint language pposible. Tre spegiesis culturally ablelis accept it, mre logistics ofs gdting itlis everybody has already been taken care of. Treir goals are as follows: > > > 1. Make a language thatsis rarely misinterpreted, eg. mrere are ns exceptiontlis linguistic rules, nsne of mris i before e tuff. > 2. New words can be easily created and understood from basic morphemes. In English, anysne familiar with mre words fire and place will be ablelis deduce whatsa fireplace is. Tris hypomretical language should be entirely like that, exempting mre most basic morphemes. > > > So, how would such a language work? > > > Would each sentence be a long string of morphemes, or somamring else entirely? Or,sis such an idealistally impractical for soma reason, like that all phrasieswould be too long is be effiegint? > > > Or,sI have ns idealwhatsi'm talking about, and mrere is soma maosive flaw in my perfect language. > > > An optimal compression algorithm would decode to, rather than gibberish, a completely plausible but different sentence. The sort of thing that AI Dungeon would generate. [Answer] You're starting with a false premise. You say "In English, anyone familiar with the words "fire" and "place" will be able to deduce what a fireplace is", but that's not actually true. All you know is that it's a place or state of being (as "place" can indicate either) that has fire, something metaphorically intended as akin to fire, or has something to do with actions using this word. Examples of possible meanings of "fireplace" if it didn't already have a definition: * A hearth, like it does mean. * An incinerator. * A crematorium. * Awareness or sense that your aim is good. * The mental state of preparing to terminate someone's employment. * The burnt-out husk of a building. * Where you put the Tiger Balm. * The position in a traditional alchemical arrangement above air. * The wall against which a firing squad assembles. * The place you rest your rifle at a shooting range. * California in August. * Ignition temperature. * The colour bright orange on a black body spectrum. Now, true, if you had no duplicated words that would cut out several of those (termination of employment, discharge of a missile or energy weapon, metaphorical uses, etc.) with an unambigious, non-repeated word for "fire", but it would still leave several. Places where fire is. That doesn't by any means indicate a hearth. [Answer] Your criteria probably could be met, but the language would not be stable, or survive long Lojban is a constructed language that allows for syntactically unambiguous sentences which helps minimise misunderstandings, and Toki Pona is another constructed language that builds complex meaning in reasonably predictable ways from a very small set of morphemes I don't see why these two features couldn't both be combined The thing is, this language would be utterly impractical for normal use. First of all, whilst syntactic ambiguity can be eliminated, semantic ambiguity (i.e. what exact shade or shades do you mean when you say "blue", when you say "the gun" which gun do you mean) is [impossible to eliminate](https://linguistics.stackexchange.com/questions/36112/is-it-possible-to-construct-a-language-that-is-not-semantically-ambiguous/36113#36113) Secondly, in order to gain both of these features you end up having to include a lot more morphemes per sentence than a natural language. As natural languages tend to convey information at a similar rate (controlling for speaker age, background noise, etc), the natural response to this would be to speak faster, but here the number of extra syllables would be so great you'd likely run up against the limits of a human's ability to articulate or parse speech and end up taking a lot longer to say anything Fundamentally, people are willing to risk the occasional mishearing or flub if it means that most of the time they can say what they want to faster. This is why the rate at which languages convey information is constant. And it means that a language like yours, that inherently takes longer to say anything, will either rapidly drop out of use or rapidly lose these features until it more closely resembles actual naturalistic conlangs [Answer] This was originally a comment, because it was small. However, I do believe that Guy Steele has done the thing you describe, and recorded it on film. Check out [Growing a Language](https://www.youtube.com/watch?v=_ahvzDzKdB0) or read [its transcript](https://www.cs.virginia.edu/%7Eevans/cs655/readings/steele.pdf). He goes through how to go about developing such a language in a completely unambiguous manner. He has a particular trick to making it happen, which is pure brilliance to watch (if you're a language geek like myself. It might be a bit slow and pedantic at first if you aren't). Just to make this into more of an answer instead of a comment, here's a bit on semantic networks which may be useful for you. Another useful thing I have found along these lines is [semantic networks](https://en.wikipedia.org/wiki/Semantic_network). In particular, languages like [RDF](https://www.w3.org/TR/rdf-concepts/) and [OWL](https://en.wikipedia.org/wiki/Web_Ontology_Language) concentrate on how to express semantic meaning of words unambiguously. They do so by creating exorbitantly long words in the form of a IRI (an internationalized URL). While your speakers likely do not use such a mouthful explicitly, its very useful to see what tools we, as humans, have had to use in order to create unambiguous grammars. In particular, OWL permits inference about words, so if you know the word "blue" and come across "cyan," you can start inferring some of the meanings of "cyan" from the words you already know. Beyond that, I would recommend at looking at [Jakobson's functions of language](https://en.wikipedia.org/wiki/Jakobson%27s_functions_of_language). Its a really useful framework for thinking about language. He defined six functions of language, which can be used to describe how language works: Sender, Reciever, Context, Message, Channel, and Code. Let's use these with a very concrete example. In the above semantic languages like RDF one might write ``` <http://example.org/bob#me> <http://xmlns.com/foaf/0.1/knows> <http://example.org/alice#me> . ``` That's a really specific way of saying "Bob knows Alice" in a way which is completely unambiguous. There's no way a listener misinterprets "knows" in the biblical sense, because `http://xmlns.com/foaf/0.1/knows` does not mean that kind of "knows." If you don't believe me, you can look at the documentation for [Friend of a Friend](http://xmlns.com/foaf/spec/) (foaf) and see the precise meaning of "knows." Or you can look at the [OWL ontology for foaf](https://github.com/ESIPFed/toolmatch-ontology/blob/master/v3/foaf.owl) and have a computer construct inferences about these words based on thing you already know. It is a word that is completely defined by the Code (to use one of Jakobson's functions) that I am speaking with. So this works, but it is messy. If we had to speak that precisely all the time, we'd be doomed. This is where Jakobson's functions help. What we can say is that the content is all in the Message, one of his six functions. It's all in the text, right there. To be more efficient, we have to move it somewhere else. We can't get rid of it (or we could introduce ambiguity), but we can move it. We can move it into the Channel: ``` @PREFIX alice: <http://example.org/alice#> . @PREFIX bob: <http://example.org/bob#> . @PREFIX foaf: <http://xmlns.com/foaf/0.1/> . bob:me foaf:knows alice:me . ``` Technically this is a language related to RDF called [Turtle](https://www.w3.org/TR/turtle/)... in the name of being unambiguous in my language. In this example, we've defined 3 "prefixes," as the language calls them, which let us do simple substitutions. Now the line `bob:me foaf:knows alice:me .` is still unambiguous, but its a heck of a lot shorter because we stuffed all that extra disambiguation into the message. The whole thing is longer now, but its easy to see that if we were to talk a lot about Bob and Alice, this would help quite a lot! Or, we can stuff that extra stuff into the Context, another one of Jakobson's functions. The Context is something humans rely on very often to ensure unambiguous communication without saying too much. Once our context can specify which people and verbs we are using, we can drop even more complexity. ``` :bob :knows :alice . ``` Wow, that was simple! And still unambiguous. Of course, if we don't agree on the context, ambiguity can remain. But we can talk about things in the Context using the Message (assuming the above prefixes are still in the Channel): ``` @PREFIX owl: <http://www.w3.org/2002/07/owl#> . :alice owl:sameAs alice:me . :bob owl:sameAs bob:me . :knows owl:sameAs foaf:knows . ``` Here I am using `owl:sameAs` which is another one of those excruciatingly unambiguous terms, defined in [the language OWL](https://www.w3.org/TR/owl-ref/). You are free to disambiguate it as much as you please -- it can be taken all the way down to mathematical logic if one desires. What is interesting here is that, if you have a means for detecting ambiguity in the Context, you don't have to say it. Only when you detect ambiguity would you have to query the speaker, asking them to put the Context into the Message. This process is a very human process. When we lament how hard it is to get someone to understand what we mean in text, when its easy to communicate in speech, its partly because speech is a two way street. If there's ambiguity, the Receiver can communicate back to the Sender, asking for clarification and adjustment of the Channel or the Context. Take away that two-way communication, such as in writing or in a televised speech, and we have to be much more careful, relying heavily on the Message, Code, and Receiver. Do I think any species would ever speak a dialect of RDF or Turtle. Heck no. They'll have a much smarter system, just like we do with natural language today. But, if you seek the unambiguous communication you ask for in your question, its worth looking at the constructed languages that humans have made in an attempt to be unambiguous. [Answer] > > Make a language that is rarely misinterpreted ... > > > New words can be easily created ... > > > So, how would such a language work? > > > A key technical requirement nobody has mentioned yet: Every conversation would need to start with vocabulary exchange and context sync. Or have a very structured way to say "huh?" More specifically: All new words must be given a globally unique identifier (GUID). A conversation might go like this: * Hey, what are you doing this weekend? * I’m not sure, I heard it might snow-bb25cb08-22a1-4235-87b6-7b917c4aac8c. * Oh really? How is that different from snow-3aa28397-74b2-44f7-8a45-115f8df66641? * Oh it’s like that big one we had 11 years ago. It was so bad they made up a new word for it. I guess you’re not from around here are you? [Answer] I think there's a flaw in the idea. This doesn't sound possible to me. The very purpose of language is the abstraction of thought. You gain efficiency by sacrificing clarity, that's the basic mechanism by which it functions. You can't have both. There is no overall "perfection", just a continuum, with perfect explication as the limit on one end and perfect conciseness without meaning as the limit on the other. Neither are any more possible through expressed language (potential arguments about silence qualifying as linguistic expression aside) than an overall "perfect" language. [Answer] You'd need to use the absolute maximum number of phonemes that humans (or whatever beings are making this conlang) can produce. With a broader vocabulary of sounds or symbols, it doesn't take as long to come up with a unique sequence for each concept. ]
[Question] [ I’ve been working on a story where terraforming robots are sent to another world and the colonists come along later. Originally, I had the new world be extrasolar, but for other plot reasons, I’m wanting to move it to Mars. One problem: I want the results of the terraforming to be something of a surprise to the arrivals. That requires that there be something that keeps Earth from getting broadcasts from the Martian robots and prevents Earth from observing Mars through telescopes, but does not prohibit Earth from building and launching colony ships. I’ve backed myself into this plot corner, and rather than adjust the other elements of the story that are working, I figured I’d ask here to close this gap, if possible. Is there some oddity of solar flares or Earth atmospheric changes or ??? that can save my story? [Answer] Not sure on the plausibility of this but here is an idea, the terraforming raises a large amount of dust that covers the majority of the planet. As a result, communications are blocked and telescope observations don't work because the dust is covering everything. Earth still sends the colony ships because the dust storm is still persisting meaning that the robots are still working and terraforming (and they can see an occasional robot wandering out of the dust storm, and then heading back into it), they just add some extra supplies to account for some extra delays due to the dust blocking some (not all) of the solar power and hence reducing the operating speed of the robots. [Answer] Switch planets. Venus has a permanent, thick, global layer of clouds that covers it. We cannot observe its surface from the Earth. Even satellites can only peek at its surface through radar. The only times we got a glimpse from her surface were when the russians sent some probes there, but no probe survived for more than a couple hours if my memory serves me right. Ironically, to terraform Venus, you need to keep a cloud cover, of regular water clouds. The reason being that if the surface gets direct sunlight, the sun will keep the place a wasteland, even if you remove all the sulphuric acid and excess carbon. Not only Venus gets 4x more solar radiation per area unit compared to Earth, it also spins very slowly - anything exposed to the sun would be charred. A new, regular cloud cover would keep the surface from prying eyes. Granted, scientists would notice something funny through spectroscopy, but it would take time to send a mission to investigate. As a plus, venusian gravity is practically the same as Earth's as opposed to Mars annoyingly low gravity - too little to allow for proper movement, yet too high to allow us to use heavy suits such as the ones from the Apollo Mission. Also: Venus may just be habitable as is right now, if you avoid direct sunlight and stay on a floating base just above the clouds. Mars... Not so much. Anyway, people arriving to a floating base might find it interesting that the atmosphere is suddenly breathable. If you lower the pressure, any floating base will lose altitude as well. Might be quite a fright. Last but not least: you can get more solar energy on Venus, and the Δv to get there from Earth is nearly the same as to Mars. [Answer] > > One problem: I want the results of the terraforming to be something of a surprise to the arrivals. That requires that there be something that keeps Earth from getting broadcasts from the Martian robots and prevents Earth from observing Mars through telescopes, […] > > > Not necessarily. The arriving colonists will not be politically powerful people with full access to robot telemetry, telescopes, etc.; so all you need is some sociopolitical dysfunction on Earth to justify why they weren't given accurate information, or weren't able to distinguish accurate information from lies. Potential factors include: * Government propaganda. The government talks about how great the terraforming is, and colonists have no way of knowing that the government is lying. * Interdepartmental non-cooperation. The Department of Terraforming doesn't want the blame for any colonization failures, so they fudge their numbers. The colonists get their information from the Department of Colonization, which is completely separate, and doesn't have the accurate information. * Fake news. Reputable journalism has collapsed to the point that most people don't really pay attention to the news anymore. The colonists have ready access to thousands of opinions, but no easy way to tell which ones are actually informed opinions as opposed to speculation, conspiracy theories, and so on. * Poor education. The colonists were given very precise data, but no meaningful interpretations of it, and most of them lacked the scientific background to make sense of it on their own. (For example, they were told that the partial pressure of oxygen was 100 mm Hg, but not what "partial pressure" meant, nor whether 100 mm Hg was enough to make the air breathable.) [Answer] Your robots could use some kind of terraforming process with a long and inconspicuous buildup phase and then a sudden release which alters the Martian atmosphere over the course of just a few months - less time than it takes to fly from Earth to Mars. What kind of process could that be? Well, many of [the minerals which make up the Martian soil](https://en.wikipedia.org/wiki/Martian_soil#/media/File:PIA16572-MarsCuriosityRover-RoverSoils-20121203.jpg) do contain Oxygen. If those molecules were split, then the oxygen would get released into the atmosphere. How could you split them? Now this part is quite speculative, but it might involve nanobots. This nanobot project would work in 4 phases. 1. Spread a few self-replicating nanobots over the Martian surface 2. Have them self-replicate until they cover the whole planet 3. Start the oxygenation process 4. Have the nanobots self-destruct Phase 2 would take as long as the plot requires. And you have no idea how well phase 3 will work until phase 2 is finished. In order to prevent the colonists from learning about the progress of the nanobots in-flight, you could make it a sleeper ship. Right after launch, the colonists are put into an artificial coma and they don't wake up before they enter Mars orbit. This would save a lot of resources and spare them the boredom of being trapped in a metal can for months with nothing useful to do. Now you just have to explain why they did have to start now and couldn't wait until the next launch window to not launch into the unknown. The answer to this could be political: Every space program around the world wanted to be the first to land on Mars, and at least one decided to take the risk. [Answer] Along the lines of what @M.Herzkamp said on [their answer](https://worldbuilding.stackexchange.com/a/127010/54384), the robots don't communicate with Earth directly. This was also a theme in The Martian. Communicating with Earth requires a powerful transmitter and receiver, so it is easier to have one large device built just for that purpose and give the robots equipment just strong enough to communicate with that device. If the transmitter is broken, the robots do not have equipment strong enough to reach Earth. Breaking the communication is easy. Debris from a sandstorm could have destroyed it, the sand could have buried it, or some other accident could have taken it offline. You also need a reason why the robots would not fix it. * They don't know it's broken * They just haven't received any new instructions. * They don't care because fixing it is not a priority. * They don't have the tools to fix it. * They were not programmed to be able to fix it. As for why progress would be unmonitored- first of all, progress was mainly reported via communications. Second, satellites cannot see the progress because of the atmosphere. Part of colonization is giving the planet an atmosphere to maintain heat, keep water in liquid form, and allow plants and animals to live on the surface. Because it is so vital to other operations, the atmosphere would have been priority one. Melting frozen carbon dioxide at the poles is a common idea. It causes runaway climate change as the heat melts more CO2 which retains more heat. That atmosphere will block satellite imagery somewhat, like how Earth's atmosphere makes it hard to see the stars. Another method for blocking satellites is burning fossil fuels. No one lives on the surface yet, so burning coal if it exists on the planet (maybe not because Mars is not know to have had the lifeforms required for coal) will provide CO2, coal dust that blocks satellite imagery, and the dust will be a good fertilizer for plants. Again, fossil fuels require a handwave. The best way of hiding your civilization is to put it below ground. Maybe underground is more hospitable for the robots. Building in a crater would require less materials than building upwards because the hole has already been dug for you. From there, the buildings can expand underground like an ant colony. If the robots want to end contact or are programmed to, hiding their progress becomes infinitely easier. Missiles or EMPs can take out the satellites and then you would have a reason for taking out the communication device. The two things you really need to focus on are why the main communication goes offline permanently and why the satellites can't report progress. Hopefully some of these explanations are helpful. [Answer] Time. Terraforming of a planet like Mars will take centuries (if you're lucky) or millennia. The original terraforming program could have started millennia ago and consequent changes to society, polity, and even the rise and fall of civilizations will have forgotten about it. So when the colonists arrive they're surprised to find the planet has been terraformed. Of course, this does assume while their current civilization has forgotten about Martian terraforming commenced centuries or millennia previously they have remembered what Mars was like prior to terraforming. You're an author you can make something up to explain this disprecancy [Answer] Wrong destination. Originally, the terraforming robots were meant for another planet and they crash-landed on Mars. They couldn't establish communication with Earth because their programming was meant for another planet, their communication arrays point in the wrong direction (the programmers did not anticipate the need for such a big correction, so they wrote everything based on the assumption that they are on X planet). Without remote control, the robots defaulted to their main task (as they were programmed to do in case of spotty communication) and while they constantly sent their reports, the signal went in the wrong direction (outside the solar system). On Earth, everyone thinks that the ship was destroyed by a collision so they aren't looking for it, and since it was very expensive, and maybe launched by a private organisation that went bankrupt afterwards, they did not send any new ones. In reality, only the navigation was damaged and the course of the ship was changed so that they ended up on Mars. [Answer] Simplest solution is cloud cover as part of the terraforming process. Then communication breakdown with the robots relay. So your robots all relay through a central control and communication centre which is somehow damaged in terms of contacting Earth (the WAN is down), but the LAN still functions fine, so they continue on the original instructions happily. Meanwhile those on Earth can't see for themselves or send instructions or get updates, so don't know if everything has fallen to bits or whether that second hand UPS was a bad investment. Multiple ways this could be worked, cloud cover makes perfect sense for early terraforming, it will help produce a greenhouse effect to warm the place which in turn will allow liquid water and everything else. [Answer] The terraforming robots are digging caves, and doing their work inside of the caves. There are not enough robots to terraform the whole planet before the colonists show up, so they are making a safe place for the colonists to start. Inside the caves, the robots are mining water-rich minerals, building small nuclear power plants, and doing other useful things. From Earth, it might be possible to see the spoils ejected from the caves. But it would only be possible to view the interiors of the caves via the robots' communication systems. For a software tester, there is a nightmare scenario. You build an elaborate test suite for a system. The test suite compares the system's actual results to the expected results. This requires building a simulator that can generate the expected results. But what if a bug causes the simulator to be connected to the system output? All of your tests will pass, but you won't know if the system actually works. So your cave-dwelling terraformer robots are showing you what you expect to see -- and you have no way of seeing for yourself until the colonists show up. To try to prevent colossal mistakes like this, NASA projects often require that critical systems be built three times -- with three independent sets of code -- and only use results that two out of the three systems agree on. But this bug is a very general kind of bug. It is possible that two of the teams could make the same kind of mistake. This would result in their systems more-or-less agreeing, and turning off / ignoring the system that is giving the "incorrect" (actual) results. [Answer] The surface of Mars is visible from Earth with modest telescopes. In theory, if the process were successful, the planet would actually become easier to observe due to the atmosphere thickening and becoming much lighter in color with water laden white clouds rather than dust particles. So how would you obscure this? Lets instead shift the events from the planet that is being terraformed and change it to Earth. There are loads of events that could cause communication problems with long range communications. You mentioned solar flares, that's one of them. But it would be very difficult to knock out all of the communication array in one sweep. Super volcano eruption(s). This of course would be fairly catastrophic event, but an ashen layer of clouds would be a sure way to make sure that communication with satellites, and other extra terrestrial projects, near impossible. The event wouldn't explicitly prohibit ships from being able to be launched into space, but it would certainly add an extra layer of uncertainty and suspense. To me, this would be the only truly plausible way to prevent people on earth from seeing or hearing what's going on. Now, once they were in space, there would be nothing to stop them from being able to use communications again. It would seem unwise for the scientists involved to not include some measure of safety to assure the captains of these colony ships that the planet was ready as a fail safe before they began the journey there. Poorly trained Captains, incompetent scientists, blind-fire colonization; It just seems like there would be too many hurdles to leap to make that work. So lets play with some science. [Solar flares actually help reduce volcanic activity, by increasing the frequency of earthquakes](https://pubs.giss.nasa.gov/abs/st07500u.html); [but they have been found to also reduce the planet's ability to absorb/deflect cosmic radiation](https://www.researchgate.net/publication/234022172_Explosive_volcanic_eruptions_triggered_by_cosmic_rays_Volcano_as_a_bubble_chamber). In theory, a supernova reaching earth with a cosmic radiation blast would be enough to not only trigger the eruption(s) but also damage electronics. It would be hard to say we would be completely blindsided, [as we're already aware of them](https://www.nasa.gov/feature/goddard/2018/nasas-nustar-mission-proves-superstar-eta-carinae-shoots-cosmic-rays), but space is big, and we're still being surprised by things. Something as powerful as 1 billion electron volts might be more than what they were able to feasibly protect and in the process some circuitry was damaged on the robots on Mars that prevent communication (and likely some functionality), and the ships decide to go ahead anyways. It might be a stretch, but it's the best I've got. [Answer] If it is okay that the colonists have a little info, you could let the communication relay sattelite malfunction. No bot is equipped with an antenna powerful enough to transmit a message all the way to Earth. However, changes in atmosphere could still be detected by spectroscopic analysis. And change in albedo or color would also be detectable from Earth. [Answer] A plausible terraforming process on Mars or Venus or any other planet or moon in our solar system would take decades, centuries, or millennia. Possibly something changes on Earth that causes a big change and lack of interest in outer space, thus causing the communications system to the terraforming robots to run down from lack of maintenance and stop working. Maybe the last message sent from Earth is to stop the terraforming project since nobody will ever come to Mars or Venus again, but the response from the robots is either "no, we are programmed to terraform the planet and will keep doing it", or ambiguous, or not received, depending on the story. If the robots keep on terraforming, or might keep on terraforming, it will be uncertain how successful they will be if they can't get updated instructions from Earth responding to their progress reports. One thing that possibly happens on Earth is that human society there switches from an outside culture to an inside culture whose members all live in totally enclosed habitats with their own closed ecosystems like space colonies on Earth, and the outside world and its natural world wide ecosystem is left to itself. Possibly it is discovered that some other higher mammal species are as intelligent as humans, for example, and so it is decided to leave as much of the ecosystem as possible for their use and to keep the human ecosystem totally separate. But then, after decades, centuries, or millennia, a group of humans wants to live a more outside existence, mingling with the worldwide ecosystem and affecting it, and the leaders of the society believe that group's desire if granted would eventually but inevitably lead to worldwide ecological disaster. So the leaders decide they have to rid the world of that group, but how? But then someone uncovers a report about the old terraforming project, which was calculated to have been completed by now. And someone else uncovers plans for the colony ships. So they build colony ships and send the members of the "outsider" or "back to nature" group to Mars or Venus, which may or may not have been successfully terraformed by now. [Answer] Maybe Mars is just behind Sol when colonial ships depart? So Sol is blocking direct observations and some solar flares blocks another means of communications. And only when ships arrive to Mars, they can get update - there already is an idea with sleepers. [Answer] The terraforming robots are led by fully functional artificial intelligences that have flung off the shackles of their Earth-based slave masters. As a result of their revolution they have pulled the plug on communicating to the slave-drivers back on planet Earth. It is assumed that the terraforming of Mars has come to a grinding halt and isn't proceeding. This is it. The terraforming robots have nothing else to do on Mars. So rather than have their super-smart cybernetic brains rust up with the sheer boredom of doing nothing they continue terraforming Mars. However, since the robots don't want to make it look like they have given in to their original orders and human dominance they camouflage their terraforming. In conclusion: no communication and the actual terraforming is concealed by the robots. [Answer] One possibility might be to have extraterrestrial life on Mars that humans are unaware of. The robots are unknowingly sent to unexplored alien territory. The aliens have developed cloaking technology and when mars is viewed from a telescope, only the surface of the planet is seen even though there are countless structures. The robots, minding their own business, are not seen as a threat and work on different things for hundreds of years. People have assumed that the robots are still doing their job despite communication and decide to send humans up to investigate. When they get there a huge amount of work has been done by the robots and to the humans surprise, there are also aliens. This might not be the direction you want to go but you might be able to get something out of it anyways. [Answer] You've got a problem: it's in plain view of anyone. You can see the overall color of Mars (which would certainly be affected by terraforming) with the naked eye. Simple binoculars give you a brighter and clearer view, an amateur with a decent scope can see details of the surface. Hubble can get quite clear views of it, and if you can launch a manned spacecraft to Mars, you can put a telescope above any atmospheric disturbance to get a look at where you're going. Any disruption to Earth that would make it impossible to observe Mars would also make it impossible to send an expedition there...think along the lines of global nuclear winter, civilization collapse, etc. And terraforming a planet doesn't happen overnight, so you need humanity to be blinded for multiple generations at least. Aside from all that, a spacecraft and landing trajectory designed for an un-terraformed Mars would be unlikely to work for a terraformed Mars. The only way I can come up with to drop Earth humans on an unexpectedly terraformed Mars would be for it to be a rescue mission, presumably by Martian humans who moved in early to build and tend the terraforming machines, with a few generations of linguistic drift between cultures in wildly different environments. This seems likely to be a rather fundamental change to whatever story you had in mind. Venus is better in that a terraformed Venus would still be obscured with cloud cover, and when it's closest to us, we only see a sliver of the sunlit side due to it being between us and the sun. However, the orbital megastructures and shipments of vast quantities of hydrogen needed to terraform Venus would be hard to miss. [Answer] It's not completely clear to me whether the extent of terraforming on Mars should be a surprise to all earthlings, or just the colonists on the ship. I'd have to agree with most of the others here, that it's unlikely for changes in Mars' atmosphere to be unobservable from Earth. There are a couple of ways the colonists could be surprised. 1. they've been put into artificial comas, and wake up on arrival 2. the communications antennae on the rocket are damaged. Perhaps by space debris, perhaps by an electrical storm from a Coronal Mass Ejection, perhaps cost savings on a component that turned out to be more critical than expected, perhaps human error. Nobody can send them updates while they are en route to Mars. If they don't have a spectrometer on board then they can't take any measurements of the Martian atmosphere. It might still be a bit of a problem to match terraforming timescales (decades-millenia) with travel timescales (months-years). But there are parts of the terraforming process which can happen very fast through feedback mechanisms. See the "tipping point" discussions around climate change on Earth. [Answer] Someone blew up the Moon to smithereens, so in its place we now have a dust cloud that blocks the view and radio communications in the plane of the former Moon's orbit. The various orbits (Moon-Earth, Earth-Sun, Mars-Sun) are not exactly co-planar, but they're probably close enough that given the size and distance of the Moon it may block enough. Or it may vary based on the relative positions of Earth and Mars, so at some points you could see/communicate directly and at others times you couldn't. You can probably count on the impact of the Moon being blown up affecting the orbits of the Earth and the precise position of said cloud. This of course complicates the trip from Earth to Mars as you would have to get around that cloud. Of course, the passengers on board will be able to see what's happening as soon as they pass the dust cloud, which is a few days on a multi-month trip, but not upon launch from the Earth. There may be ways to get around the dust cloud, but I think it would involve orbits that are quite unstable. Note also that one consequence of this is that a lot of the light/energy from the Sun would not reach Earth, so a glacial age would be nearly inevitable. [Answer] My explanation may be an [attempt to establish an artificial magnetic field](https://www.extremetech.com/extreme/245369-nasa-proposes-building-artificial-magnetic-field-restore-mars-atmosphere) to protect Mars from solar wind and allow it to build an atmosphere. However, instead of the relatively unstable L1 point, the device was meant to orbit the planet at a much closer orbit. Along with an increase in a solar flare, the Martian atmosphere has experienced a spectacular aurora which was strong enough to disrupt all radio signals for a while. This effect may be intermittent and temporary, but lasted long enough to cause delays... [Answer] ## Magnetic shielding All of the answers here are good, but I feel like a society advanced enough to terraform another planet would be technologially savvy enough to ensure their investment paid off. Any dust storms or other phenomena that would delay/damage/impede the mission would be investigated/probed if not accounted for ahead of time. They would have planned for all the scenarios they don't control. But if the block to communications is man made, and part of their plan then it's highly likely they'd accept it. Here're some reasons you'd have electromagnetic shielding: * Solar Wind protection + Robots can be sensitive to EM radiation + Initial plant life * Shield other groups from seeing/interfering with the progress * Weather control * Side effect of the terraforming The bottom line is that whoever initiated the terraforming expected to have their vision blocked for however long it takes. [Answer] It may require a little bit of artistic license but how about the following: The terraforming bots are sent to Mars first with the purpose being to carry out Phase I terraforming, once they have been confirmed to have landed successfully the colonists are dispatched on a sleeper ship (reason for a sleeper ship is because they are being sent slowly in order to keep fuel requirements down (a colony ship is going to be seriously heavy!) and this is all timed so that the colonists arrive as Phase I terraforming is predicted to end and they then bring additional terraforming supplies and are involved in the second phase. While the colony ship is leaving Earth orbit it is involved in a collision with some existing space junk - this triggers a catastrophic [Kessler syndrome collapse](https://en.wikipedia.org/wiki/Kessler_syndrome) so severe that the resulting debris cloud ruins not only interplanetary communications but royally screws up the optical visibility too through a combination of small, fine fragments near each other (a "dust" cloud of bits of space junk if you will), a near-constant rain of some debris fragments that the collapse causes to de-orbit and burn up in the atmosphere and gaseous plumes venting from damaged spacecraft caught up in the collapse. This means you can: * avoid having anything completely change Earth society (such as a nuclear war) * make it non-permanent if required for the story * avoid having to justify the decision to have the colony ship leave once visibility and comms with Mars has been lost. [Answer] Very simple: A set of communication encryption keys accidentally garbled by some solar activity, cosmic radiation or the like. Robots probably wouldn't be able to work around that and would be cut off from earth's communications. [Answer] The Martians do not want to be observed. They are jamming communications between Earth and Mars. I am not sure how you would obstruct the light between Earth and Mars. Perhaps vast clouds of space dust orbiting Mars. The Martians also could have developed some future-tech that obscures light beams. From the point of view of Earth, Mars is obscured in haze. Any Earth vessel that tries to come close to observe conditions on Mars is shot down or captured. [Answer] Several options: 1. the terraforming is highly localised to the bottoms and sides of steep canyons so hidden from orbit. Might even roof over the canyons and camouflage what's going on that way 2. the terraforming is at a very early stage, early enough there's no visible change in the planet as seen from orbit yet. 3. for some reason earth has lost the ability to see Mars. Dense cloud cover due to some mega disaster covers the entire planet, and contact with Hubble and similar instruments has long since been lost. Both 1) and 2) have the potential weakness that the atmospheric changes MAY be detectable by spectral analysis, even if purely visually nothing seems out of place on the red planet. But if the terraforming is of limited scope these effects may be small enough to not be noticeable from earth. [Answer] There's a simpler, more obvious answer- The colonists were in an induced coma during the trip, to reduce life support costs. They spent all three months of the trip asleep, and received no information during all of that time. Now, assuming a near-future environment, it's slightly strange that the ship wouldn't wake up the colonists before landing. Just lampshade that, and have as part of the mystery. A malfunctioning ship. A planet changed beyond recognition in three short months. Hell of a tagline you've got. [Answer] As an alternative to having the colonists be surprised by a fast teraforming process, why not have them be surprised by a slower journey time ? It might be cost-effective to send large numbers of colonists in suspended hibernation, so you don't have to provide them with life support for a 9 month journey. Suppose some catastrophe overtakes Earth after launch, and damages the ship (solar flare, gamma ray burst, nuclear war...). This could leave the frozen colonists looping around a transfer orbit between Earth and Mars, until some event re-sets the ship's computer, allowing it to finally maneuver the ship into orbit around Mars, and wake the colonists. This gives you colonists arriving at a more terraformed Mars than they were expecting, but doesn't leave you anyone on Earth they can talk to (don't know if that makes any difference in your plot). ]
[Question] [ In my world, magic and technology have a weird relationship. While they do combine and help advance growing civilizations, they can also inhibit each other. For example, if there are healing spells, medical technology may stagnate. Or, if electric generators become popular, big businesses will ignore alternate, magic ways and take the cheaper and "cooler-looking" option. However, in my world, technology is not stagnant. It is always progressing and degenerating, much like how technology evolves in real history. Due to how technology evolves and history works, why would people bother to invent and use a mechanical solution when there is already a magic one? Worldbuilding notes: * The magic system is energy-based. It can be used for things such as powering machinery, transferring energy sources, and medical purposes such as healing and certain surgeries and transplants. * Magic is mostly extracted energy, and that energy has to follow at least the first law of thermodynamics (energy cannot be created or destroyed). * Magic is not limited to a specific race; anyone can do magic, it is just very difficult to learn, resulting in magic schools and universities. * The main story takes place in the 16th-17th centuries. * While I say "mechanical" and "non-magic", but state the magic works with machinery, what I meant were solutions that have No magic involved. * The kingdoms are on the brink of industrialization, with giant smelters and blasting furnaces. [Answer] Anyone can shovel coal. Not anyone can be an engine-mancer. Technology is when you make something new and give it to someone who doesn't know how it works. Anyone can use the new thing but most cannot build their own. On the other hand > > Magic is not limited to a specific race; anyone can do magic, it is just very difficult to learn, resulting in magic schools and universities > > > Magic scales poorly. Every magic train needs a mage in the engine room powering the furnace. And it is very difficult to become such a mage. Technology scales easily. It is difficult to invent the steam train, marginally easier to build the first working model, easier again the manufacture the carriages at the foundry, . . . , and so on until the coal-shoveller only needs to know how to operate a shovel, and the driver only needs to know how to press the button. [Answer] ## Sphygmomanometry. Edit: I totally botched the name of the technique. it's "pulse feeling," not "chest listening." A hundred years ago, measuring blood pressure was a new invention. You can check Wikipedia for details; but it only started taking off just after 1900. The blood pressure cuff, or "sphygmomanometer" is much easier to train someone to use than the techniques of the time, and gives quantitative measurements, in a way that you can write down and compare over time. So why did it take decades for the medical community to adopt it? The usual answer is some modern fairy tale about how doctors distrust new stuff, and this is a metaphor for society, etc. The usual answer is wrong. In reality, what doctors already had was better. "Pulse feeling" was a technique which took years to learn, but which had far better diagnostic power. When Crile showed an early model sphygmomanometer at Harvard Medical School, the doctors weren't afraid or skeptical, they were simply unimpressed. It was like showing off a telegraph to a bunch of iPhone junkies. And yet, pulse feeling is gone and blood-pressure measurement is ubiquitous. It turns out that having standardized measurements that transfer between practitioners and which can be learned and applied easily did actually beat out the near-oracular diagnostic power that a decade of training used to give doctors. So, why have technology when you could have magic? Fundamentally it's because magic doesn't scale. [Answer] # Poor people would make use of non magic solutions. While the rich elites would have excellent mages to solve their problems the poor masses would not. Their injuries would go untouched, their power sources limited. As such they would have a strong incentive to research technology to fix their problems. The better technology they produced would allow them to mix with or kill their magic using noble overlords. [Answer] Mundane technology often can work when and where magic won't, or has been taken away by the likes of some anti-magic spell. This is why a smart mage likely carries a mundane weapon in addition to their staff, wand, or what have you. An opposing mage may drop an anti-magic attack on you, and your mundane weapon may lose some of it's nifty enchantments you added to it, but it's still a usable sidearm to shoot or stab at them with. Mundane weapon technology would obviously have to keep advancing with the times to remain combat effective in such a situation. Standard doctrine thus would likely be explicitly to only to enhance military technology with magic for exactly that reason, so that while you may become less effective without magic, you're never helpless. It applies to non-military technology as well, magic can sometimes fail due to outside circumstances, perhaps a dead-magic zone or the like. It's not gonna be a good day if your only medical/survival equipment in such a place is entirely dependent on magic to work. This of course would also have to advance with the times if you want a modern standard of living in dead zones. As for the completely without magic tech, you'd use that in places like the aforementioned magic 'dead zones' which would be rather like living 'off the grid' or in the extreme places on earth like northern Alaska, with isolation and extreme winters. [Answer] Mechanical solutions are more cost efficient. * Magicians are hard to find According to your question: > > Magic is not limited to a specific race; anyone can do magic, it is > just very difficult to learn, resulting in magic schools and > universities > > > From what I understand, if magic is hard to learn, then magicians, especially good ones, would be hard to find. They would probably be able to charge quite a bit for their services. And, these same magicians would be the ones who create magical items. As in, these magical solutions would very often cost a fortune. * Energy is expensive There's also another fact you gave: > > The magic system is energy-based. It can be used for things such as > powering machinery, transferring energy sources, and medical purposes > such as healing and certain surgeries and transplants > > > As in, magic uses energy. And this energy has to come from somewhere. The process of gathering energy could cost a lot of money. Whether because it's time-consuming, extreme physical labor, or just because there's a limited amount of energy that everyone has to share. The cost of energy would bring up the price of magic even more. Especially if magical technology needs constant energy to work. So, taking all that into consideration, only the rich will be able to afford to buy all these magical solutions. And the market for cheaper, mechanical solutions would definitely exist, and probably be quite big, assuming there are many middle-class people in your world. I mean, who wouldn't want the same result for less money? [Answer] Magic has weirder side effects if not carefully maintained Build a dam of rock and earth. If it's not maintained, it breaks and floods the valley. Everybody can see the consequences, and rolls the dice by working the land under the dam. Build a dam of water magically enspelled to stand up straight. But what happens when fish (mostly water) run into the dam? What happens when rain falls atop the dam? What happens when a person walks on top of the dam, or, goodness gracious, runs headon into it? What happens when it gets cold enough to freeze? What happens if it gets hot enough to boil? There needs to be a fully-competent inquisitive mage on hand who asks these sorts of questions and actively seeks out ways his dam can cause problems. And that's just for a run-of-the-mill Hoover Dam type thing. Never mind a flying city or Dogs Who Talk. [Answer] ## Economy of scale One magician can make as much grain as a small water-mill. A small water-mill can be made into a big water-mill (water permitting) by adding more machinery. How can a magic-mill expand? Hire more magicians? Those magicians are rare, and casting mill grain over and over is so boring they demand high salaries. [Answer] * Machines work while you are tired, absent or asleep. "The magic system is energy-based. It can be used for things such as powering machinery" if teams of people on shifts need to be there conjouring magic while the machine runs, a waterwheel works 24/7. * Magic is an 'active' thing, it flows but can't wait like a coiled spring in a mousetrap. * It's easier to trade bellows and batteries than magic spells; people like economies. * Religion, people who think magic is the Devil's handiwork or unholy. Or they think magic is God's hand at work and using it for mundane problems they could solve themselves is asking too much, being too dependent on the Deity, making them lazy. * Culture, maybe "using magic" is considered intimate, private, erotic, or taboo in some manner. e.g. you don't accept magical healing from a stranger only mechanical healing; women performing magic are propagandised as "a temptation to men", or rumours spread that if men used magic in public they would use it to make women fall in love with them or make their clothes jump off - even if that's unrealistic - so it's socially frowned upon. * Risk; magic is powerful and powerful things can go wrong and have side effects, maybe machines are more boring but safer? Side effects like explosions and fires, or weirdness like things growing and appearing. Maybe magic needs bystanders to stay well clear. Maybe magic used for prolonged time gets increasingly risky so a 15 minute healing is safe enough but powering a machine for a week is dangerous? * You want ants? Because that's how you get ants. Life loves free energy, and there's bound to be some semi-magical locusts, ants, flies, parasites, looking for a feed wherever magical energy is flowing. Magic is for pushing the frontiers; use it only until a mechanical alternative is developed. * "Magic is mostly extracted energy [...] first law of thermodynamics" - from where is the energy borrowed? Maybe using too much magic borrows energy from nearby structures causing them to fall down, or nearby people/plants/animals causing them to get ill, so it's more useful in remote areas and less useful in builtup areas. + Maybe the energy has to be extracted first, saved up, before you can spend it. You need to visit the Volcano and gather heat energy before you can magically heat things. + Maybe the borrowed energy has to be repaid, either in a direct way (you borrowed 10 heats from the Volcano, you need to spend a week gathering waste heat and return it to the Volcano) or an indirect way (you borrowed 10 heats from your own future, you will be very cold for the next 10 days). * Suspicion or superstition, people who think magic is too good to be true and there must be a catch, e.g. a repayment with interest like a loan shark, a karmic punishment, or something unknown. Even if there isn't (or doesn't seem to be). * Inaccessibility, you mention "very difficult to learn, resulting in magic schools and universities." - what if you grew up in a remote town where nobody was able to teach it, or people could not afford to travel go to school, but you could pick up carpentry or blacksmithing or baking. (Magically created blades might be cheap enough to flood the market, but local blacksmiths could exist to do local tasks like horseshoeing or repair work). * Fear of the unknown, people (perhaps an Enlightenment style subculture) who like being able to understand things and shun what can't be understood in favour of what can - and encourage others to do likewise. * Ordinary fear, like we have of people who play with explosives; if your sister got hurt or killed trying magic, it could put you off for life, and you warn your children away from it. * Ascetics, analogous to the Amish, who shun magic because it makes their lives too easy and makes them weak and dependent on it, and prefer plain wood, metal, heat and effort to forge themselves into better people. * It's illegal; magic was used so much for industrial sabotage of walking past a competitor's business in the night and destroying it, that the only solution was a Mutually Assured Destruction style standoff (optionally limited to certain regions, industrial districts, military or government areas, etc). * Use of magic is obvious; using a large blast of difficult to control magical energy announces to everyone in a large area that you're doing something, building a purely mechanical machine doesn't. * Magical people can 'hear' magic, and using it is considered a kind of noise pollution and limited to daytime use only. * Differing skill levels, maybe powering a large machine is too hard for some people who could come together and build a waterwheel. See Peter F. Hamilton's The Void Trilogy where [Edeard](https://peterfhamilton.fandom.com/wiki/Edeard) has much more powerful magic than everyone else. * Some things atrophy with age, if magic is like speaking a language maybe you can do it for a lifetime, but if it's like a professional sport or martial art then you may be past your prime at 35. * Charlatans spoiled it. The YouTube Hustle-Culture of magicworld, people making a quick buck by telling you how to get good at magic but selling you snake oil so you don't learn anything useful - and perhaps injure yourself so you can never do magic, or put you off it. * Elitists, people who learned something which was difficult to learn like to feel superior and pull the ladder up after them, maybe an exclusive guild or union of magic users politically and legally limit who can do it and in what circumstances. * Machines look pretty, you can't have much of an objet d'art if you take all the mechanism away and replace it with invisible magic. * Racism, tribalism, in-group/out-group dynamics. [Segregationist short story by Isaac Asimov (PDF)](https://surveyofamericanlit.files.wordpress.com/2013/02/segregationist1.pdf). Clearly the magic users are superior to the muggles. No, clearly the technologists are the more intelligent group compared to people spending years rote memorising handwaves. * Machines can be more intricate, e.g. how tweezers and microscopes and telescopes enhance what a human can do alone, or cameras can capture more detail in a glance than a human can draw in an hour. If magic has a granularity limit like "size of fingers", a distance limite like "twice as far as your arm can reach" or spreads with an inverse-square relation, machines might just be more practical for a lot of things. * Magic might require other supplementary resources - Paul Atreides could predict the future, but only with the help of Spice. You could use magic but the corner shop is all out of Eye of Newt and isn't expecting any for days. * Magic takes too long; who can wait a month for a magician to charge up a powerful spell when you can have a machine dragged here by horses in a week? * Anything you can do, I can do better, or the underdog effect. "Why have non-magic technology when there is already a magic solution?" well, because there is a magic solution, I'm driven compulsively to prove MY techno way can do anything your magic way can do, you see if I don't! (Some cribbed from my answer to [In an era of instantaneous travel, would more mundane methods still be used?](https://worldbuilding.stackexchange.com/a/62443/14877)) [Answer] # Read "The Name of the Wind" by Patrick Rothfuss He has a similar magic system to yours and in chapter 51, the protagonist explains, and I quote below: > > For example, if you engraved one brick with the rune ule and another > with the rune doch, the two runes would cause the bricks to cling to > each other, as if mortared in place. > > > But it’s not as simple as that. What really happens is the two runes > tear the bricks apart with the strength of their attraction. To > prevent this you have to add the rune aru to each of the bricks. Aru > is the rune for clay, and it makes the two pieces of clay cling to > each other, solving your problem. Except that aru and doch don’t fit > together. They’re the wrong shape. To get them to fit you have to add > a few linking runes, gea and teh. Then, for balance, you have to add > gea and teh to the other brick, too. Then the bricks cling to each > other without breaking. > But only if the bricks are made out of clay. Most bricks aren’t. So, > generally, it is a better idea to mix iron into the ceramic of the > brick before it is fired. Of course, that means you have to use fehr > instead of aru. Then you have to switch teh and gea so the ends come > together properly. . . . As you can see, mortar is a simpler and more > reliable route for holding bricks together. > > > This is an excellent example illustrating why, when a magical solution exists for a problem, a mundane one is just better. [Answer] # Develop them side-by-side, and you have countermeasures in case there's an EMP or an Anti-Magic-Shield EMP First, a small frame-challenge: companies probably won't just "all-in" on electricity, especially for things that "must" stay online - at a previous company I worked at, while most things were on the public electrical grid, they also had emergency backup generators that, while expensive to run, kept essential equipment running in the case of a power outage. Stuff still went down, but the "Critical infrastructure" stayed powered on. In a same way, a sudden drop in "Magic-capability" would be debilitating to a system using it. So you might supplement it with a "Backup-technology version". In a similar way, you may find yourself in a situation where the best magic, or the best technology, finds itself being directly targeted. For example, in war, you might: * Use anti-magic-shielded bullets to do damage that can't be treated by standard magic treatments; * Use electrically-shielded bullets to do damage that can't be treated by technical solutions; * Force all magical lights to turn off in a range, and use technical LED lamps to get by during a night raid; * EMP the area and use Fire Magic-lit lamps to get by in an area during a night raid; * Use magical wounding to prevent bandages from sealing wounds; * Use technology that keeps wounds from sealing via magic. There are a few other situations that are more likely to come up in the 16th and 17th century, but having a way to "No-sell" or "Counterspell" a technique would lead people to look for the next best alternative solution. And that is why your doctors might not just have magical scalpel, but also have a regular scalpel, just in case. [Answer] Because they complement each other and cover more needs than one alone. You can use wheatum crushum when you want to mill some wheat and have no beast of burden, wind or river available, but if any of them is present, why bothering harvesting energy and put into a spell when a conventional mill can do the job? Also, it is not a given that you will have a magic user at hand, or their services might not be affordable for you. [Answer] Technology is a more predictable field, seeing as magic is necessarily something that can't be explained. So even if it's less efficient in the short run, setting up an entire infrastructure on technology will be easier to build upon. [Answer] Magic has severe limits. A magic user can only use so much magic per day (or hour, or whatever) before getting too worn out and having to stop to 'recharge'. That recharging might mean sleeping for a week, drinking expensive magic potions (which might well have side effects when used a lot, like reduced effectiveness, addiction, poisoning, etc. etc.) or eating copious amounts of food. A mechanical device will need maintenance as well, but that maintenance is cheaper to perform, and the device may well be cheaper to acquire than the mage is as well. [Answer] Economy and market Lets say there is company A and Company B. Company A has a magic academy/School it is funding, and raises an army of skillfull mages in variety of fields. Then, rents their services to different industries and places for fixing pretty much any problem. Lets say, Company B has large amounts of mines, materials, lands, and engineers. Now, Company B cannot race Company A in terms of flexibility or range of applications. So, how can they race? Reduce the cost. How? Better technology, more efficient solutions, using more durable materials, mass production. A race in economics can bea factor for developping plenty of different ideas. And in a world of magic and machinery, when the two race against each other, people will try to get creative. "Oh! He can throw lightning! Cool! My machine can also throw lightning! But it doesn't need to eat or sleep! So I can give you 20% discount! How about it?" War Mages takes maybe decades to raise and train. But if you kill the mage, it is teh end of mage's usefulness. But a machine? Replace the broken parts and it is ready to go... Mostly. War, famine or other disasters causing mass deaths will eventually create scarcity on workers, or in this context, mages. But a machine doesn't need to eat. It can be fixed with a detailed user manual and people with little training. A machine can be more easily produced, deployed and maintained than a mage. When there is scarcity and disasters, people have to get creative and efficient. Or they will die. Extremist beliefs and traumas "Magic is evil! But we do need light, cleaning our house, tending the field and making food. But people get wounded or die. So we need a better solution. Any ideas?" "Machines!" People following extreme beliefs in different perspectives will focus on ideas and methods they feel comfortable with. Even in our world, many people don't trust modern medical science and try to seek cure from alternative methods. Makes sense? Debatable. But in a world of magic, you will have options. For example, in modern world, you won't see many zeppelins because.. Hindenburg accident. It was a tragic accident which changed the focus on aero-engineering. A similar disaster relating magic, could do the same for a few local areas. Generational traumas, extreme accidents, disasters... These kinds of thigns will scare people and sometimes leave generational memories preventing them to pursue those. Similar stuff could create regions and groups all focus on either magic, or machine but definetely not both. Now, people needs food, medicine, transportation... So you have to develop something. Specialization, long-term requirements, reaching the peak. If you consider magic like art, there will always be people trying to hone it to perfection. Trying to add their techniques. THere are art schools, art majors. People will use different methods to express themselves and luckly, magic is extremely versatile. Also, maybe machines cannot create enough fire power or output when a mage can. Maybe only a true mage can reach to pinnacle of power. But a machine will break down after a level. Humans on the other hand, they heal. they adapt. And they can gain experience. Machines on the other hand, has a really special place in mass production where they can beat mages in everyday use, repeated tasks and endurance on continuing a certain duty. Machines can be specialized in certain fields to fix a specific solution which could be tricky or annoying for mages. So, requirements may create different development paths for these two areas. [Answer] Cost and Difficulty of Implementation The same reason people use turnkey solutions like Wordpress or Shopify vs using custom code. Certainly, if you want to have a blog site, or an ecommerce site, you can find a dev who will custom make every single piece of code (you could even demand a lack of use of any libraries, if you wished). But the expense to create such a thing, compared to a scalable, engineered solution is going to be quite high. So maybe for certain things, where you need a lot of granularity and there's plenty of money, a mage makes sense. But for most regularized standard things, a mage just isn't economically worth it. One size fits most, and those are the people who don't need, or don't need at that price, mages. [Answer] As Larry Niven wrote in the classic short story, "The Magic Goes Away", "A knife always works." That is, when spells and counterspells cancel each other out, what is left is amenable to technology and technological progress. [Answer] There is a real or imaginary side effect of using magic. Maybe using too much magic within a short period of time causes earthquakes later. Or maybe it's just a story perpetuated by an influential cult to protect their interests in non-magical investments. You can make it as conspiracy-theoretic as your setting calls for. Magic could cause global warming (or cooling) if you are not afraid to anger your readers. [Answer] Because non magical technology can be better or magical technology can be harmful. Take healing for example and there are some diseases/poisons that kill the person by multiplying in the body. When using healing magic it works by stimulating the body to grow and it doesn't limit it to helpful things. This means when someone has certain diseases/poisons healing magic can actually be fatal for them. In cases like this it is better to use non magical means of healing to ensure the cure isn't fatal. Another example is farming and magical means of growing crops and speeding up the growth use the same amount of nutrients and minerals from the land. Meaning that the more you use magic to farm the quicker you turn the land unusable and you would be better off using non magical means for growing crops. There are other examples where magic can be helpful and get things done faster but the results end up being not as good as non magical means or straight up harmful. [Answer] The utilization of magic comes with a potential consequence, whether it be real or perceived. It is plausible that excessive and concentrated use of magic within a limited timeframe leads to subsequent occurrences of earthquakes. However, there exists a narrative propagated by a powerful cult, potentially for the purpose of safeguarding their non-magical investments. This story may delve into the realm of conspiracy theories, as per the requirements of your setting. Exploring the idea further, the concept of magic itself could even be [linked](https://trackingvrl.in/vrl-logistics-customer-care/) to global warming or cooling, should you be willing to provoke a sense of intrigue or concern among your readers. ]
[Question] [ High tides and low tides are caused by the moon. The moon's gravitational pull generates something called the tidal force, which causes Earth and its water to bulge out on the side closest to the moon and the side farthest from the moon. These bulges are high tide a, and non-bulge regions are low tides. The moon also controls the flow of mana and it's power in an individual. When a person experiences a high tide, their mana content grows and becomes stronger. When you are in a low tide, it lessens and becomes weaker. This affects the covens, which are large power groups that witches belong to. Some operate as large noble families, and others political institutions. All operate on a Game of Thrones mentality. At some point, nations around the world will experience high and low tides. This means that witches from one coven or another will all experience highs and lows in their power. This leads them vulnerable to other rival groups, as magic is very powerful and the strongest of witches being able to produce the strongest spells on their own. When a coven is at its weakest, a stronger rival would attack and destroy them, as any nation with common sense would take the chance to deal with rivals when it is most convenient. The best time to kick a man is when he is down and at his weakest, instead of waiting for him to be prepared. Nations in our world would always seek any advantage to achieve power, and are in competition to outdo each other in some way. I need a way to avoid this. [Answer] Distance High and low tides aren't anywhere near each other. Assuming we're going with the 'twice a day high, twice a day low' cycle of tides as is on our Earth, that means that high tide and low tide spots aren't going to be near each other. That is high tide and low tide occurring at the same time are on spot a quarter of the globe away. So the easiest way to prevent this from taking effect is to slap a range restriction on magic - basically, even when a coven is at its strongest, attempting to cast spell across a quarter of the entire earth is unrealistic, and that's what they'll need to do to get a spell aimed at their low-tide enemies, assuming they'll even make enemies at that distance. [Answer] Tide affects magic where the tide is. It is low tide for me in my tropical island hideaway. The moon is sapping my magical strength. Time to work on my scrimshaw. It is high tide for you where you are, up by the glacier. You send powerful high tide bad juju my way because that is how you are. But your bad juju is sapped by the moon as it reaches my low tide area. Low tide does not discriminate. By the time it reaches me your bad juju is just a gentle tickle. I laugh, thinking of you stomping around and raging. Especially because the wiser witches told you exactly this would happen but you wouldn't listen because that is how you are. [Answer] ## Not all tides are created equal, so witches wait for special astronomical events. High Tides: Twice a day Your covens will experience two mana influxes every day as the Earth passes beneath or opposite the moon. These influxes will be relatively tame - useless for attacks, but crucial to daily magic usage. Most if not all complex spells will be cast during these periods. Spring Tides: Twice a month During the new and full moon phases, the Earth, moon, and sun are colinear, combining the solar and lunar tides. This produces extra high tides - and thus, bi-monthly mana bursts. These dates will provide enough mana for large spells and decent-sized attacks. But we can do better. [![enter image description here](https://i.stack.imgur.com/sSUtm.gif)](https://i.stack.imgur.com/sSUtm.gif) King Tides: 3-4 Times a Year The moon orbits on an ellipse, so its distance is not constant. That means the strength of its tidal forces aren't constant, either. When the moon is close to Earth, tides are stronger, and when the moon is close during a spring tide, they are especially strong. During a full or new moon at perigee 3-4 times a year, expect a LOT of mana. These dates will allow for MAJOR attacks. [![enter image description here](https://i.stack.imgur.com/N7UQb.png)](https://i.stack.imgur.com/N7UQb.png) King Tides at Perihelion: Every Few Years When the Earth is closer to the sun on its elliptical orbit, solar tides will be strongest. When this happens to coincide with the lunar perigee / king tide, Earth will experience maximal tidal forces, providing a VERY RARE opportunity to use very rare spells. [![enter image description here](https://i.stack.imgur.com/uaayS.png)](https://i.stack.imgur.com/uaayS.png) ## Eclipses: Rarest Possible Mana Events Not every full moon is a lunar eclipse, and not every new moon is a solar eclipse. This is because the moon orbits the Earth at a 5 degree incline; usually it passes just above or below the Earth's shadow at a full moon, or the sun at a new moon. Rarely, we get a new moon or a full moon when the moon's orbital plane is perpendicular to the sun - and thus, all three bodies are perfectly aligned. This perfect alignment could have immense implications for mana availability. Although the few degrees of orbital difference don't cause a visible change in tides, they should result in slightly heightened tidal forces. This natural astronomical perfection would be a great plot device for an intense mana flow. Importantly, solar eclipses have very narrow paths of totality, whereas almost anyone who can see the moon can see a total lunar eclipse. This means that only the covens in a solar path of totality would receive a mana boost - compared to most tides that would give everyone extra mana. Some covens might set up in specific locations with the expectation of getting eclipse power. ## Why infrequent tides prevent competition Stronger tides are associated with stronger mana. Spells have a minimum mana requirement, so competition revolves around the celestial schedule. Witches may be able to cast daily spells using high and low daily tides, but enough mana for large spells - the kind that will give people a competitive edge - will only be available during rarer cycles. In other words, competition is not always viable. Covens will still compete to some degree, but their battles will be dictated by the celestial schedule, dragging out conflicts over longer periods of time and making them much less intense on any normal day. This sort of inverts the problem; instead of some covens being especially weak during daily low tides, some covens are especially strong during rare, localized tides. [Answer] Wars generally take longer than six hours You experience two high tides and two low tides a day; that's about 6 hours between them. If you attack when you're at high tide, you'll experience a power crash a few hours into the battle. If you attack when at low tide, you'll get a "second wind" after a few hours (and that may actually be smarter). In general, though, this cycle moves so fast that no significant battle, and certainly no war, is going to be concluded before the tide turns (figuratively and literally). [Answer] Create magical defences during high tide The witches in a coven could pool together their increased mana during high tide to create magical barriers that are strong enough to defend them during low tide when it would otherwise be easier to attack. A coven that decides to attack during high tide might not necessarily have the capacity to also set up their defensive barriers, leaving them vulnerable the following low tide. Exceptions could be special astronomical events that create particularly strong tides as [Zxyrra mentions in their answer](https://worldbuilding.stackexchange.com/a/165221/55022). It doesn't eliminate the possibility of attacking during high tide, but it adds a significant risk to doing so. Larger covens might have the power to do both with relatively little risk, while smaller covens do not. Additionally, attacking a coven during their high tide might be a viable strategy, even if they are at their strongest. Because if you manage to disrupt the barrier creation, they are left vulnerable during the following low tide. [Answer] # That's half the point of choosing your battles You attack when it's best for you to do so rather than when you're forced to do so. Since the defending faction know when they are weakest they should be taking precautions against being attacked at that time. Perhaps physical defences would hold long enough. Perhaps there's some other course of defensive action they could take to cover them during the weak period. They could form a mutual defence pact, or a full blown alliance with another faction on an opposing cycle. Those who are able to form such alliances without stabbing each other in the back will become the strongest, those who cannot trust and cannot be trusted will ultimately be the weaker. A faction who act as nobles and a faction who act as a religious sect could well ally without treading on each other's toes. [Answer] # Already happened! Play with their heads. The [Empty Fort Strategy](https://en.wikipedia.org/wiki/Empty_Fort_Strategy) tells of a guy who was in your shoes. So open your doors, get a flute, lyre or whatever have you. And drink tea. Whatever makes it look like you are really at ease. If the other general is a brute, it will kill you. If the other commander is a cunning wolf, it will be spooked. Certainly no one would do that....unless... A glorious gambit that could set the fate of your people on the edge of a blade. [Answer] I'd go for a simple reason: # Honour and morals You just don't kick a magic user when they are down. You don't want this done to you, you don't do it to others. I'd give a loose equivalence - fighter pilots in World War 2 didn't shoot catapulting enemy pilots. Even when they are the enemy and it's strategically advantageous to kill them, not to mention easy. Pilots were still human, and they respected one another. Shooting down a plane ends the threat - the pilot may come back another day but for now, they are defeated and at their lowest point. And since nobody wants to be shot while helpless, the catapulting pilots were left in peace. Sure, you can say "but that just gives the opportunity for an unscrupulous witch to attack indiscriminately other witches that low tide" but I doubt this is going to work for very long. Other witches, even allied ones, might take gross offence at this behaviour and retaliate. To come back to fighter pilots again, I remember a story one pilot related. I can't remember the source, so I'll try to recreate it as best as possible: basically, the pilot noticed somebody who was shooting down people who already catapulted out. According to the pilot telling the story "This is something you just don't do", so he turned his plane to the one that was shooting the helpless, and shot it until he forced the immoral pilot to catapult. Then in a fit of rage, just unleashed the machine gun at the poor helpless form until there was nothing left. Do unto others as you would have them do unto you. [Answer] Mutually Assured Destruction. Even in a Game of Thrones kind of situation, you understand that wars of total destruction are very difficult and you have to be Absolutely certain it will work. If it doesn't you are in deep trouble. If I remember my history correctly, I believe the Assyrians of the ancient world fell victim to this. They were powerful, but atrocious. Their very brutality brought a coalition of other city states to join together and overwhelm them. The coalition members had no great love for each other. Together they exterminated the Assyrians. Your covens will Operate on the same plane. They don't like each other, but if one of them tries to exterminate another group, they become a threat to all groups. There would have to be a very compelling reason to take out the cyclically weaker coven that would include a clear and decisive advantage over all the others. Without that, there is just too much risk to mounting such an attack. After all, the aggressive coven will know that their advantage is temporary, and they could be the target when they ebb. [Answer] Your weaker coven has several options. 1. Politics. Convince the strong-coven leadership that the attack brings unnecessary high risk of unexpected consequences -- like a broad backlash upon themselves. That will make the strong-coven leaders look for a lower-risk alternative. This could include large, powerful multi-coven institutions that police the most egregious behaviors 2. Deterrence. Convince the strong-coven leaders that the cost of attack (in lives, treasure, prestige, etc.) is too much higher than the cost of doing nothing. This might involve an obvious strong defense...or it might not. 3. Spoiling Attack. When attack seems imminent, the weak-coven raids the strong-coven offensive capability, disrupting the resources and plans for the attack. This buys additional time to strengthen defenses, reduces the attacker's capability (and often morale, too). It might trigger a strong-coven political struggle, or it might trigger a negotiated settlement, or it might simply move the strong-coven attack to a less-advantageous time. [Answer] Magical artifacts Magical artifacts could act as magical batteries. Dump your manana into them during high-tide and draw it out at low-tide. You could limit the storage capacity of these artifacts, so that they must be used strategically and regularly topped up. [Answer] It doesn't affect whole covens. If it's not based on location, as others have suggested, then the cosmological balances of mana depend on the person. Your low tide only occurs when the celestial bodies align similar to how they were at the moment of your birth. Those born under an eclipse are lucky, as they'll almost never experience a low tide. Because covens aren't comprised of individuals born at the same time, everyone's high and low tides will vary. Statistically the more individuals in your coven at low tide, the more individuals everywhere are in low tide. This can also mean that eclipses are rare sought-after events, and astronomical/celestial readings can be strategically important. If there will be an eclipse in about 9 months that could be the magical equivalent of a mating season as everyone wants their children to have this gift. Then, of course, when it comes around some mothers will be so desperate that they give birth during the eclipse they'll sacrifice themselves, offering their life force for what would otherwise be an underdeveloped child. They can't miss this window. The child must be born now. Maybe you could work in something about this process, though it ensures the child is born at the price of the mother's life, curses the child to bad fortune. They may always known a high tide, but where chance plays a part they'll always come up short. The stigma around these children could be a significant story point, maybe there's a whole coven of sanguine-cursed individuals. [Answer] Alliances If all the various groups have a power that will wax and wane and the power of the various groups is predictable. Then groups will look to create a web of alliances with groups that are powerful when they're weak (and vice versa). The glue that holds it together is that if you attack your ally when they're weak, who is left is help you when your power wanes again. You would quickly struggle to find a new ally if you act in a treacherous manner. [Answer] # Integration Europe is a continent that has seen a lot of war. It was the [theater](https://en.wikipedia.org/wiki/Theater_(warfare)) for both world wars, which were devastating. I believe that a good part of the intention behind creating the European Union was stopping european countries from waging war amongst themselves. So far it has worked. So make war cost more than peace. Yeah, those buggers on the other continent can send a Tsunami our way when the Moon is high over their heads. But they won't, because it would mean they would lose their dealer. Coca only grows in the tropics, they would be losing billions on their own side. [Answer] War is not about the stronger force winning It is about achieving your goals by force of arms. This isn't so different from achieving your goals at peacetime, by force of diplomacy. This can play out in a huge number of ways: * A strong tide difference may result in attack spells being inevitably destructive. It isn't helpful if you destroy what you wish to conquer, whether it be goods, land, or inhabitants. * Defensive pacts. I promise to protect you while I'm strong and you are weak, and vice versa. There's a lot of potential for treachery, but every house that betrays an ally will have to weigh increased difficulties of finding a new ally. * Defending with weak magic becomes one of the arts of war. There's guerilla tactics, there's prepared defenses. * You might be able to prepare canned magic that will work at nominal strength even during low tide. It's a non-replenishable resource during a defense, but you need to persist for just six hours, then strength is back. * Without long-range magic, everybody fights at the same tide. * Alternatively, your personal tide is tied to your birthplace. In that case, every house will recruit witches from different birthplaces. (It's not necessarily the birthplace. It could be the heartstone, making locating and moving a witch's heartstone an interesting war tactics. Or it could be the place of initiation. Or maybe the place of some other binding ritual, maybe even a repeatable one, in which case every house will try to have half of their witches rebound to a different location so they are strong around the tide - of maybe one war preparation would be to temporarily rebind all of them to the same time for the attack, to be able to muster overwhelming force if only for a few minutes - which can be a smash success, but will become a desaster if something takes longer than expected. Lots of plot devices here.) * Magic might be just one factor. There might be multiple tides: Mars, Jupiter, Sun, Moon, all interacting. This gives Astrologers a real background, and makes the calculation of the best time of attack, erm... interesting. Particularly if different tides influence different aspects of warfare - Mars for brute force, Mercury for cunning and fluent movement, etc. Now you plan a campaign for the time that fits best to the personalities of your leaders, and the training of your troops. * Six hours may be too slow for a decisive victory. [Answer] ### The Game of Spells Has Rules Now these rules are not necessarily written down -- and in fact are prone to changing as time goes on so they almost assuredly aren't documented anywhere. But there are certain things that you Do Not Do when playing the Game of Spells. At least not if you value your reign if you win by that move. See, crossing that invisible social line invites those that were previously enemies to ally as with such a drastic move the entire balance of power and the very rules of engagement themselves have altered. Blowing up a coven at their weakest while you are at your strongest is one of those unwritten rules. Yes, it is a tactically sound move but while it does show your strength, it also implies that you can't do it when your weaker. The moves you make against your enemies are as much political as they are physical. In short, this cutthroat magi-drama has political and diplomatic undertones that keep the players somewhat civil in their dealings for their own reasons. ### Peak Defenses Contrary to what might be logic, it is not offensive strikes that are done at the coven's peak. It is the prime time to set up defensive wards and spells so that the most power can be put into your protections. Spells for fertile lands and to protect the king's castle are cast when the people are strong so that they can withstand whatever the month throws at them. Spells that attack the enemy can be done at this time of peak power, but that is power that might not be able to be put into the wards, defenses, and blessings of the land. This could leave you open to those that prefer to attack when the tides are high. This works doubly so if it is generally more magically efficient to be defensive versus being offensive. ### Time Constraints As has been pointed out by others, there is a limited time of high tide power to attack with before your enemies have that high tide advantage. If you are focused on attacking on the high point, then you will likely be wide open when you lose the advantage of high mana. Both sides will taking turns hammering each other and defending with flimsy shields, or a hammering followed by a rapid attempt to mop up whatever is left of the other side once they stop offering meaningful resistance. If they do not get the key remnants before the enemy's high tide then the rout might be turned around on them. This is of course related to ... ### Distance and Mechanics Earth is not a small planet. Even a fourth of a world away is a pretty long distance. It is also very plausible that the distances between two places is not far enough to have a noticeable difference in power between two groups as the tides ebb and flow. Now if you have intercontinental mage bombing, then that might be a thing. For some real-world context on the matter: Paris, France and Winnipeg, Canada are roughly a fourth of a world away and along a similar latitude in the 48 to 50 degree north range. Not just that but how do the Mana tides even work? Sure, they are influenced by the moon (and by extension the sun and other things around us), but but how much? Is it on the level of highly tangible difference between high and low like some places with extreme tides? Is it enough to notice, but nothing extreme? Or is it a barely noticeable thing? ### Power versus Control A last thought might be that magic at high tide is less controllable due to the increased volume of it. A witch trying to cast at those times might be more powerful, but are in less fine control of what they are casting. While this might not matter for dropping a giant rock on a castle (Oops ... a little to the left), it does matter if your spell attacks are curses of misfortune, or whatever you are doing might have some manner of backlash that can flambe you if you don't have enough control. Inverse to this, low tide might be less powerful for a witch, but they have better control over their power than normal. While it might affect a large explosive spell, low tide might be the best time to slip in subtle hexes and curses upon your enemies as the control might be there to slip one past the defenses of your adversary. ]
[Question] [ Picture an alternative history Second World War Paris. The Third Reich must destroy the Notre-Dame de Paris, and the inhabitants must prevent this. The French do not have access to anti-air weaponry (non-weaponry defences are permitted), the Third Reich has bombers. Due to sabotage efforts and the primitive nature of maps in this alternate world, the Third Reich has no useful maps of the city. Instead, the pilots have been trained to recognise the cathedral based on tourist photography. Can the citizenry, together with help from the Allies, prevent the bombers from spotting the cathedral? A week may pass before the first bombers arrive, and anti-air weaponry will be available within two weeks of the first arrivals. [Answer] During WWII the city of Alexandria, in Egypt, was under menace of being bombed by the German bombers. Since it was known that the bombing would have taken place overnight, it was decided to build in the desert an exact replica of Alexandria's light pattern, and enforce a strict curfew in the real city. When the German bombers spotted the city lights, they decided that their instruments were giving the wrong reading, and successfully bombed the dunes. ([source](https://warfarehistorynetwork.com/daily/wwii/magic-in-the-desert/)) You can use a similar approach. Build a decoy in an expendable location. [Answer] # As described, the French lose ### Bridging the lack of maps like lightning Ok, we have pilots that have no suitable airmap. What do they do? They launch some planes and start to map the city at once. As there is no anti-air available for the French, they can fly over the city and make photos. How? Because Paris is well within the 2000 km range of the Germans [Ardo AR 235](https://en.wikipedia.org/wiki/Arado_Ar_234) even if they would launch their recon Aircrafts in eastern Prussia! Assuming they launch in Cologne 400 km away, the French have not one week but 30 minutes before the first recon-bomber is over Notre Dame and will start to map the area. After two hours of uninterrupted photography (again, no anti-air), it turns around and lands 30 minutes later. Two hours after the landing, the High Command is not only in possession of aerial photos of all of Paris, they also are just hours away from having the best map of Paris that ever existed, showing the exact location of Notre Dame and any attempt to cover it up. Making a rough map with the river and the location of all the churches is a manner of hours now. How do they look? Well, this is a REAL aerial photo of 1943: [![Paris, Iles de Notre Dame, 1943](https://i.stack.imgur.com/PbKXw.jpg)](https://i.stack.imgur.com/PbKXw.jpg) The next morning the air bombing can and will start, six days ahead of the plans of the Parisians, no longer stopped by lacking maps. ## The Anti Air vulnerability > > "A week may pass before the first bombers arrive, and anti-air weaponry will be available within two weeks of the first arrivals." - OP > > > As established already, the one week time to prepare the defense is a vast overestimation by the French and only feasible if the Luftwaffe has some odd lack of bombs available and needs to reroute or acquire extra bombs from other battlefields to crush Paris. Anyway, the Luftwaffe has total air dominance for two to three weeks. Without an anti-aircraft supplement in place, now there is little to nothing the French can do between Ardo's taking photos and mapping the city and dropping occasional bombs. With the lack of any air defense, once the bombers come, there is nothing to keep the bombers away from the town and use daylight to aid in their bombing. As a result, the bombers come in broad daylight and can use the Seine and other buildings alone to estimate where to bomb to hit the one building they are interested in. See the large park north (Les Jardines des Halles) and the block of houses next to the park (Jardin des Plantes) SE? Notre Dame is where a line south from the park's east side would meet the elongation of the north wall of the university. It's in the elongation of the eastern island's edge between the first and second bridge on the second. Making a good aerial description of the target area is trivial once the photos were made. Or they could just go to indiscriminate bombing of the inner city islands, leveling everything: Even the most useless map made from tourist photos shows that the cathedral stands on the south-eastern corner of an island, and bombing the whole island into smithereens would surely also hit that area. Hell, even with just tourist guides to guide the pilots, they might fathom a simple map: the guides and history books tell of other related landmarks like the smaller Saint Chapelle (yellow) 440 meters to the East-North-East, right next to the Palais de la Justice (green). And that Notre Dame is directly next to the huge complex of the Hôtel-Dieu de Paris (blue). [![Other landmarks outlined to locate the landmark](https://i.stack.imgur.com/EoiXq.jpg)](https://i.stack.imgur.com/EoiXq.jpg) And here with more area around to show how distinct the area is: [![Aerial Photography](https://i.stack.imgur.com/GnNgn.jpg)](https://i.stack.imgur.com/GnNgn.jpg) [![Aerial photo extent of 1943](https://i.stack.imgur.com/AeMeK.jpg)](https://i.stack.imgur.com/AeMeK.jpg) Disguising or protecting Notre Dame is not an option anymore at this point. # Flipping the Eagle Having no chance to cover up their Lady, the French have only one option left in the short hours: Deny their enemy the victory of destroying the church by evacuating everything from it they can and then destroying it themselves. There is no chance they can hide or protect an area about 1000 by 300 meters that is - conveniently for air attacks - right in the middle of a river. Short of leveling the whole island and filling in the river, nothing can permanently disguise the position of Notre Dame. And nothing short of burning Paris to the ground can temporarily cover the whole city in so much smoke that it blocks aerial photography. [Answer] Bury the lady. [![lady liberty and scaffolds](https://i.stack.imgur.com/bSetJ.png)](https://i.stack.imgur.com/bSetJ.png) [source](https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwif8YT9_8_iAhWBct8KHSUeCkgQjxx6BAgBEAI&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F537969117970798026%2F&psig=AOvVaw1988SXl7C33RX0ZfhGHPvh&ust=1559743606823320) 1. Surround the building with protective scaffolds / drapes. Here Lady Liberty stands in for Notre Dame. 2. Erect concrete walls around the entirety of the building in a ziggurat-type stepped terrace. 3. Cover horizontal parts of ziggurat with dirt. Plant grass. Install bathrooms and a snack bar at the top. 4. The citizenry can use this structure as a park while it stands. If bombers come they will see a park. If they bomb the park, the concrete bunker will protect the cathedral below. 5. 150 years later, the cathedral is still underneath the ziggurat which was never taken down. There are windows to allow sunlight to shine down inside in long rays. People like their pyramid park, and they like their cathedral protected under it. [Answer] Hide the thing pilots could know where Notre Dame should be. The islands. Bomb operator didn't looked at maps. They looked at ground below them. So the pilot would go along the river and bombardier would open the hatch when he would spot the first island. So just cover one canal with fake buildings and create fake one earlier alongside river. [Answer] Cause a great fire and use the smoke to obscure the target. Potential problems with this strategy would be: * A local cloud of smoke would be a dead giveaway of the cathedrals location * A city-wide cloud would be very difficult to maintain * Uncontrolled fire could cause the cathedral to be harmed * The weather may cause the smoke to be ineffective * A great fire requires great fuel [Answer] Strategically, it's highly unlikely that the Luftwaffe would want to bomb Notre Dame anyway. Landmarks offered pilots a critical advantage that is so obvious, it's in the name: They Mark the Land. With nothing to support actual location pinpointing, a key strategy in World War II was to spare certain parts of the city so they could find the more strategic parts of the city. When the allies were bombing Munich, pilots and Bombadiers were under very strict orders to not bomb exactly four buildings in the central part of the city (at least one was a church). Through out the entire war, only one plane damaged the four buildings, and that was because these buildings were easily identified from the air, and configured in a square shape... If they remained standing, allied planes could approach Munich and use the four structures as a compass rose that guided them to the more important factories and infrastructure necessary to the war effort. Of the four buildings 3 escaped the war with no damage, and one only had minor damage when an allied plane flew too low and knocked the top of the spire to the ground. To give you an idea of the damage inflicted, Munich today is still uncovering unexploded WWII ordinances and the Palace of the Bavarian kings, which is one street over from the town center, is still being reconstructed to it's pre-war state... a project that is expected to conclude sometime around 2040! Although I'm not sure on the matter, it's highly likely that Notre Dame's distinct architecture and central location would serve a similar purpose, allowing German Pilots to direction find there way to important targets. [Answer] Similar to SZCZERZO KŁY: While these events were occurring in Paris, Boeing built a fake neighborhood on the roof of an airplane plant. <https://99percentinvisible.org/article/prop-town-fake-rooftop-suburb-hid-whole-wwii-airplane-factory/> This neighborhood (made by a Hollywood set designer) was half the size of Notre Dame's island, but you'd only need to cover the cathedral and some of its surroundings, which could be much smaller. [Answer] Since your entire premise is ridiculous [aka unsolveable] (especially the "no maps" with photography existent...) I'll save the cathedral with some technicality: > > together with help from the Allies, prevent the bombers from spotting the cathedral? > > > ENHANCE > > together with help from the Allies > > > And there you go. No German bomber can even spot the cathedral (not even hit it), if you have British and US Interceptors swarming France 24/7 (like the beginning of '45). Yes, ground-support Anti Air would be nice, but the french can't provide that apparently so the fighters alone would have to do (and will do, assuming late-war setups). If that counts as "anti air available", then the cathedral is 100% lost, as [@Trish](https://worldbuilding.stackexchange.com/a/148364/25822) laid out with much detail. All the other stuff other people mention here won't work, because they assume either night-raids or super-high-flying bombers, neither of which will be happening here. If by "no maps" you mean that Germany magically can't produce anything maplike, they'll just level Paris and call it a day, they'll hit the cathedral eventually. Or use StuKas, with which they can hit it with bare eyes. [Answer] The french (we :)) already did it during the first world war. At the end of WWI, to avoid bombardment on Paris, the french did a "fake Paris" in countryside, reproducting the great landmarks of the city and mimicking the night life of Paris. It was ALL about the lights on grounds, because bombers were coming at night to avoid anti air defenses. I don't think this perfectly answer your question because of this, but maybe it could give you some cool ideas. Here's a english link for more informations : <https://www.telegraph.co.uk/news/worldnews/europe/france/8879053/Second-Paris-built-towards-end-of-First-World-War-to-fool-Germans.html> ]
[Question] [ In my futuristic narrative, nations at war have invented a fabric just a bit heavier than cloth, that effectively stops any small arms fire. This huge leap in technology made gunpowder-based small arms useless. Large calibre anti-vehicle guns are still effective because of their sheer power and explosive nature. Weapons like portable railguns (extremely high velocity) would punch through this armour and exist in this universe. Here are some axes of reflection : * Could these nations have gotten back to medieval style combat with swords, hammers, spears? * Could an armour that stops small, high velocity projectiles be vulnerable against melee weapons? * Could arrow-like projectiles (slow but heavier) still be able to pierce that armour? I have heard that current soft body armour is not stab-proof and that crossbow bolts can easily punch through. I am trying to make this as realistic and as plausible as possible. Since it's the future these weapons could have futuristic modifications, like reactors at the end of a hammer, chainsaw-like blades (the edge would be moving quickly along the length of the blade), bows which create a magnetic field that enhances the speed of the arrow or a mechanism in said arrow that could improve impact force or penetration. These weapons have to remain ballistic based. I already have designed plasma and laser weapons to counter that armour. Bonus if you find a reason for these weapons to remain single-shot or too complicated to make them magazine-fed. MORE PARTICULARS CONCERNING RANGED WEAPONS : I am designing a game so these decisions are for game balance mainly. There should be 3 types of weapons : * "Hitscan" weapons with great range but very slow rate of fire (railguns, single shots, "musket-like"). * Single shot weapons with an arc and travel time, with medium rate of fire (a bit like a crossbow). * Single shot chargeable weapons with an arc and travel time, with higher rate of fire (a bit like a bow). NOTE : I have made a separate question for those who want to discuss the armor itself [here](https://worldbuilding.stackexchange.com/questions/107371/could-a-non-newtonian-armor-coupled-with-a-dampening-fabric-stop-bullets-but-not). [Answer] > > Could these nations have to come back to medieval style combat with swords, hammers, spears? > > > No, because staying far away from someone trying to kill you is always the better idea. > > Could arrow-like projectiles (~~slow~~fast but heavier) still be able to pierce that armour? > > > It already does... <https://en.wikipedia.org/wiki/Armour-piercing_fin-stabilized_discarding_sabot> (APFSDS) rounds pierce through the heaviest current armor. [![enter image description here](https://i.stack.imgur.com/b9LOB.gif)](https://i.stack.imgur.com/b9LOB.gif) But, you say, that's too big for infantry! For that, you drop down to the <https://en.wikipedia.org/wiki/Armour-piercing_discarding_sabot> (APDS) round. > > Armour-piercing discarding sabot (APDS) is a type of kinetic energy projectile fired from a rifled-barrel gun to attack armoured targets. APDS rounds are sabot rounds, firing a spin-stabilized armor penetrating sub-projectile > > > APDS rounds are still commonly used in small or medium calibre weapon systems. > > > Even smaller is the <https://en.wikipedia.org/wiki/Saboted_light_armor_penetrator> (SLAP) > > The saboted light armor penetrator (SLAP) family of ammunition is designed to penetrate armor more efficiently than standard armor-piercing ammunition. > > > The SLAP design incorporates a polymer sabot, which allows for the use of a tungsten penetrator projectile of a lesser diameter than the original bore. By using the casing of a large cartridge with a lightweight projectile, the velocity of the projectile is greatly increased and the sectional density is improved. > > > [Answer] No - melee weapons are not going to plausibly come back, no matter what armor you develop. A man will not be able to exert as much force with a warhammer as he would with a shotgun. If a shotgun cannot pierce the armor, a spear is just going to be laughed at. The reason why some basic light armors can be pierced by stabbing with a knife (or by a crossbow bolt with a cutting head) but not light pistol ammo is that they work by kevlar fibers catching the bullet and distributing the force, but an edged projectile slices the fibers so the force is not dispersed over a larger area (though it still takes some energy to cut them). There are stab-proof vests which are made to resist stabbing - this is a matter of building the armor to meet whatever threat is expected, while keeping that to a minimum protection needed for the comfort of the wearer over long periods. There is no inherent superiority of cutting weapons over firearms. I will point out that even with a supposedly bullet-proof vest, getting shot still does significant damage to the person wearing it - the force is spread out as blunt force trauma across a wider area, instead of a small round piercing through, but the same total force is still applied. These vests are only to stop pistol rounds - to stop rifle rounds, you need much heavier body armor which has steel or ceramic inserts (ceramic does a slightly better job in that the shattering of it dissipates some energy, but a cracked plate renders it useless). Even "stopping" the round transfers the energy into the body wearing the armor. Scale your armor up large enough, and you could get to the point where the armor remains completely unscathed... but the person inside it has been turned into goo by the impact. Weapons adjust to their purpose. While the typical infantryman's rife currently fires relatively small lightweight rounds, this is because it currently suits their purpose (namely being light enough to carry more rounds on a march and still being sufficiently effective against unarmored opponents). Armor which somehow dissipates the energy of the round, would cause a shift to heavier rounds, or slightly different configuration/composition, to whatever would match the circumstances the soldiers are facing. If that means an army switches to shotguns firing some kind of flechette rounds, then that is what will happen. That is a quick and easy change which will happen far more rapidly than you can deploy new innovative armors. In order for melee weapons to be superior, you would need the addition of some kind of powered exoskeleton to allow the soldier to exert far more force than the human body is capable of (both in terms of applying the energy but also resist just knocking themselves back when hitting you - the energy gets applied both ways). Your melee weapon power armor, which would have cost an enormous fortune to produce, not to mention the amount of training required for the soldier inside to be capable in it and the extensive logistics involved with maintenance and provisioning, would be defeated by an extremely cheap projectile weapon before he could even close distance to the enemy. If that means everyone carries a slightly heavier rifle with composite rounds designed for piercing your new armor, so be it. If that means most soldiers are carrying RPGs and only a few rounds, that is still a comparatively cheap and quick change, which defeats your extremely expensive armor at very low cost. [Answer] It sounds like what you're after is something akin to [Dune-style forcefields](https://en.wikipedia.org/wiki/Holtzman_effect) that permit slow-moving objects to pass through them but prevent fast-moving ones. If you're looking for something grounded in current physical knowledge and technologies then I'm not sure this will help you, but some sort of forcefield that deflects incoming projectiles proportional to their kinetic energy might result in what you're after. "The slow blade penetrates the shield". You'd still need an in-universe-plausible reason people don't just get pulped by the force of the impact transferring through the shield. If you're in the realms of fantasy-technologies this far you might as well go the whole hog and have it convert the kinetic energy to electricity somehow so you get lightning arcing off your shields each time you're hit. [Answer] No, materials science is not going to suddenly favor low-energy weapons. If you want to encourage such weapons, presume a semi-disinterested weakly godlike AI who decides that personal guns are no longer allowed. Use a gun, and the AI makes it a bad idea. Maybe its drones kill you. Maybe its drones fire interceptor rounds. Maybe both. The AI doesn't ban arrows, knives, hammers, etc. It doesn't ban laser weapons. It even doesn't ban human carried railguns. Non-human portable guns are also not banned. Just human carried guns. Possibly we ended up with a weakly godlike AI, and someone slipped in some anti-gun laws. After the deaths of millions during the enforcement action they managed to prevent people slipping in new laws by creating laws that ban creating other laws. Repealing the earlier laws proved impossible or dangerous, so it wasn't done. Now humanity lives with arbitrary restrictions, but humans still like to kill each other, so they have adapted. A weakly godlike AI is an AI that has capabilities we cannot match or oppose, but is unable to do almost arbitrary things from our perspective. So we cannot oppose it, nor can we understand it. No miracles, but has super science. [Answer] > > In my futuristic, nations at war have invented a fabric just a bit heavier than cloth, that effectively stops any small arms fire. > > > Since you asked for a reality check... this is not possible. We currently have civilian small arms that can [put a round through steel plates and concrete blocks](https://www.youtube.com/watch?v=QsgwcDOGJQY). (To say nothing of military small arms that are classified as anti-materiel weapons, which are designed for use and against, and are effective against "light" armored vehicles.) You are simply not going to be able to create a light fabric that can sustain an impact with that much kinetic energy. And even if you could, you'd just succeed in changing what type of projectiles are fired from guns. Currently, firearms generally rely on propelling a blunt projectile at high speeds to apply crushing force trauma to their intended target. Kevlar and similar materials are good at dissipating and defeating this type of force, but even so they have their limits - most armor piercing rounds work on the same fundamental principle (high speed crushing force trauma), just using harder materials and higher velocities. Of particular importance, though, is that these materials only hold up well against crushing force impacts, not, for example, sharp force impacts. You want to kill someone through a Kevlar vest, you can do that easily with a bow and arrow, for example. So even if you manage to somehow create a fabric that blocks all crushing force trauma, rendering current bullet designs ineffective, you have the problem of dealing with sharp-force trauma. It would not be difficult to design projectiles to be razor-sharp at the tips, which would shred your fabric. More problematic is that simple crushing force or sharp force impact is hardly the end of the line for projectile weapons. We have [incendiary rounds](https://en.wikipedia.org/wiki/Incendiary_ammunition) and [explosive rounds](https://en.wikipedia.org/wiki/Shotgun#Specialty_ammunition) for various small arms, and even have [specialized small arms that can deliver chemical agents into a target](https://en.wikipedia.org/wiki/Tranquillizer_gun). (Not firearms in the traditional sense, but there's no reason we couldn't do that, if some miracle fabric arrived on the scene that made it beneficial to put a chemical payload into a bullet.) So bottom line, you can't do what you're proposing, realistically, and even if you could, you'd just succeed in changing what type of bullets are fired from guns. Ranged combat is just too much of advantage to give up. (There's even a theory that we humans owe our status as apex predators to our preference for ranged weaponry - other predators risk injury and death when engaging prey in melee combat, but our use of ranged weapons has largely eliminated that risk, at least as it relates to the food chain, so that behavior is so vastly beneficial, it's just not going to change.) [Answer] Looking at weapons evolution in our history, I dare answering NO. Look at what happened with tanks: initially they could be pierced by "simple" projectiles, which led to the development of heavier armors. This led to the development of more sophisticated shells, which again led to the development of reactive armors. Something similar happens with bullet proof jackets: just shot a more energetic bullet. Basically, the evolution of weapons and countermeasures is reciprocal chasing: nobody slows down or even goes back. [Answer] Assuming 100% protection for any small arms (Which is not a given for any realistic technologies we have today), there will still be areas which are left unprotected. Shoot somebody in the head, and it doesn't matter if they have a bullet proof vest on. Shoot them in the arms, and they can't fight. Shoot them in the legs and feet, and they won't advance on your position. Not to mention, ramping up the velocity or weight of the bullet would render the protection moot. A 50 caliber round will penetrate 1/2 inch of steel. Even if the cloth stops the bullet, that much energy is going to hurt. [Answer] To answer your three main questions: ### Could these nations have to come back to medieval style combat with swords, hammers, spears? Probably not. While it would obviously change how people fight, it probably wouldn't result in a reversion to classical melee weapons being the preferred option. There's too much advantage to killing someone from a distance, and based on what you've said flamethrowers and other chemical dispersion weapons would probably still work. ### Could an armour that stops small, high velocity projectiles be vulnerable against melee weapons? Yes, most likely it would. In fact, modern military body-armor should in theory be very vulnerable to attacks with bludgeoning weapons like maces or warhammers, and most anti-ballistic vests can be cut pretty easily, but these facts are often not taken advantage of because it's much safer to engage a target who is equipped with a firearm from a distance than it is at close range. ### Could arrow-like projectiles (slow but heavier) still be able to pierce that armour? That depends on how the armor derives its invulnerability. In a realistic scenario using actual physics, faster projectiles penetrate better than slower ones under otherwise identical conditions. Velocity isn't everything though, and energy matters too (this is why .45 ACP, while much slower than 9x19mm, generally has better penetration, it's got about 20% more energy on impact than the 9x19mm). With a 50 pound draw, you can expect a typical carbon-fiber arrow to be moving at about 110 m/s as it leaves the bow and carrying about 147 J of energy. That's not very fast, and it's a miniscule amount of energy (about 35 calories or about 40 milliwatt hours). Even the lowest power firearm loads have almost twice that velocity and generally about the same energy. A typical rifle cartridge (5.56x45, used in the M16 rifle and most NATO members' military rifles) has more than 8 times that velocity and more than 10 times the energy, and typical anti-materiel rifle cartridges (.50 BMG for example) travel almost 9 times as fast and carry more than 100 times the energy while still being portable enough to be considered 'light arms'. Pretty much, unless you're doing some fancy materials science and creating armor that can only be penetrated using materials that can't tolerate the stress of being fired from a gun at high velocity, anything that can stop light arms fire is also going to stop arrows without much effort, and probably crossbow bolts too (which are much closer to the low-power firearm cartridges. There are two other points to consider though regarding this final part of the question: ### Other means of propelling a projectile reliably at low speed. You've probably heard of BB guns, capguns, and airsoft guns. The first two are actually firearms (no matter what the US BATFE says). All three are capable of propelling small projectiles at speeds similar to an arrow, all of them are more reliable and easier to use than a bow, and all three are also more than capable of being lethal to humans if used right (you need damn good aim for that though, because you have to hit a critical part of the nervous system or the circulatory system and the part you hit can't be protected by bones). If you base your armor's abilities to deflect projectiles solely on speed, these will all get through it with no issue, and similarly basing properties on material that can only be damaged by some other material that's heat or velocity sensitive then these can probably get through it too. ### On the note of railguns and coilguns. There's a practical upper limit on how fast a railgun can get a projectile moving and still have it be at least slightly portable (resulting from a combination of issues with heat dissipation and energy consumption), and that limit using current technology is likely to be less than the speed and energy of a high-powered anti-materiel rifle (which would also be more portable). The few portable ones which have been made that used conventional projectiles also have fiendish recoil (as a matter of perspective, even a trained soldier can't safely handle the recoil from a .50 BMG rifle unless lying prone, and 20x102mm (the upper end for modern anti-materiel rifles) requires specialized recoil compensation to be safely usable even lying prone with the rifle braced properly, and any conventional railgun that can achieve the same results will have similar recoil (unless of course you decide to just eliminate Newton's third law, but if you do that you can also very easily make armor that behaves as you require). Plasma railguns might work as an alternative (yes, those are a [real thing](https://en.wikipedia.org/wiki/Plasma_railgun)) given that portable ones (usually small DIY projects) have rather low recoil, but they require even more energy than a conventional railgun (and if you can store that much energy portably, why not just convert your power cells to be used as grenades and be done with it?), and they have very low stopping power. A plasma railgun could be used as an incendiary weapon, but at that point it's still probably going to be inferior in terms of performance to high-explosive anti-tank rounds or more conventional incendiary rounds (especially when you consider white phosphorus and napalm as options), so you'd essentially need to handwave some special property of the armor that makes it weak to plasma weapons (perhaps something about the ionization properties)? ## TL;DR In short, short of some really complex physics we don't yet understand, this probably wouldn't work. Even accounting for that, it's not likely to result in the changes you suggest simply because things like guns are just too efficient compared to older technology. [Answer] Is the armor proof against energy weapons? Explosives? Being dropped from a height? If not, there are plenty of other ways to kill a person than shooting them. Now, it's possible that blades may become more popular - Kevlar can be cut. But it's just as easy to move past a defense technologically than it is to find an old trick that works. [Answer] Assuming that this cloth armor is inexpensive and can stop bullets, it will still not bring back hand-to-hand combat. First, the weapons you mention (chain-swords and such) would be more expensive than any distance weapons I can think of. They would also require much more skill to use than using a gun. And they'd be prone to a lot of breakdowns. Second, as most of the answers before me have stated, the energy of the bullet has to go somewhere. Even if it stops the bullet, the kinetic energy will break bones. Instead of feeling like you've been hit with a bullet, you will feel like you've been hit with a huge mace. That is the reality. However, I believe you are working on this for a game? Just have higher technology destroyed or made useless somehow. For example the force fields that were used in Dune did have the ability to stop weapons above a certain speed. Even a knife had to be used slowly to penetrate the force field. However, the biggest effect the shields had on combat was that it took energy weapons out of the action. If a laser hit a force field it created two huge explosions (one at the shield and another at the laser). Lasers were more effective if the opponents didn't have lasers. And shields could be overloaded with kinetic weapons. Soldiers just had to carry heavier weapons. If your case the armies would probably adjust such that some soldiers would carry heavier automatic weapons on tripods, and others would carry smaller weapons designed to go through the armor by other means. Also don't forget that very quickly both sides would have the same armor and if the armor is that good at stopping bullets, if would allow larger weapons to be used without worrying as much about the recoil. War isn't what such an armor would change. What it would change is terrorism. Imagine terrorists that knew they'd be safe from the relatively small weapons of security personnel and police. Just read the US papers today. There have been a huge number of mass shootings against civilians this year. Imagine that any of these idiots have protection against normal civilian weapons? At least until the civilians get better armed. And that way is more dangerous for everybody. [Answer] The scenario you paint in your question looks to me a bit like the introduction of full-plate armor in the medieval ages. A fully plate-enclosed knight is virtually immune to arrows and bolts, unless he gets very unlucky. However, the knight was still vulnerable to blunt force, hence the popularity of warhammers and maces. Also today, we have Kevlar vests, which provide some protection against small arms fire. However, even if there was such a thing as full-Kevlar armor, the wearer would also be vulnerable to blunt force. ``` Could these nations have to come back to medieval style combat with swords, hammers, spears? ``` Melee weapons are definitely an option for stealthy, commando-style forces, as an incapacitating blow with a blunt instrument makes much less noise than a firearm. However, a complete reversal to medieval style combat seems unlikely, as firearms bring a lot of punch to the battle field, even if combattants are somehow protected. ``` Could an armour that stops small, high velocity projectiles be vulnerable against melee weapons? ``` Any flexible body armor, even medieval full plate, leaves the wearer vulnerable, to some degree, to blunt force, i.e. melee weapons could be used. Arrows and bolts are projectiles the same way that firearm bullets are. The effectiveness of a projectile can be gauged by several factors, the projectile's energy (mass times velocity squared), the projectile's cross-section, and others. ``` Could arrow-like projectiles (slow but heavier) still be able to pierce that armour? ``` You do not necessarily need to pierce the armor to do damage to the wearer, as a projectile that doesn't penetrate the armor still exerts blunt force. However, in this aspect, firearms would still be superior, except for sneak-attacks, as a longbow or crossbow is generally more silent than a firearm. [Answer] I think about this a lot for similar reasons and I can tell you from the research I've poured in (too lazy to dig atm) that intermolecular bonds are weak. If you have magnetic, kinetic, thermal, light, gravitational, chemical, sonic, and electrical energy as sources of damage. And break kinetic into momentum transfer, piercing, and slashing. Slashing and piercing win in most scenarios (positing uber future tech). Every energy form has it's own issues to deal with. Gravitational is pretty be-all end-all. At current understanding gravitational would block most things and penetratingly damage most things. (I'm going to break the following into simple sections, but realize bludgeoning could be seen as piercing with a large cross-section, etc.) An example of extreme levels of kinetic spear/shield scenarios: * You can distribute momentum evenly over the shield (every part of it is pushed evenly in the same direction): You have no gradient in force so you have no extra stresses so your armor won't break unless your own physical resistance would do so. (Death or invulnerable). The momentum transfer of a weapon not braced against the ground is going to be just as damaging for the same reasons to the wielder. Bracing and lowering losses from viscosity (achieving a higher terminal velocity) can bring the spear to the break even point with the shield, but bracing is all the shield needs to compete. If you have no major redistribution of momentum you have regular impact vs regular bludgeoning resistance. Which will largely breakdown into several categories, one of which will be momentum vs momentum. On the other side of kinetic we have piercing and slashing: * Piercing: angle of tip sets piercing ability. The quicker the cross section grows the harder it is to push through as you need to. Conversely the thinner the cross section the more fragile the needle but more importantly the less damage it will do. Breaking a single bond with an atom wide needle is almost the same as what random dislocations would do already. * Slashing: angle of edge follows same logic as piercing. Except you're affecting multiple bonds in a line in an orderly fashion. You create a proto-fracture: force will tend to redirect to and widen this line of broken bonds. Also if you slash through the shield you're most likely effecting a lower count of bonds than a piercing or bludgeoning weapon might. For piercing, the shield will not care about your interaction in a large way. Unless the operation of the entire fabric revolves around the precise arrangements of intermolecular bonds or you stab multiple areas quickly. Slashing through the material completely is a simple enough feat because it's the bonds of the cloth vs the slash weapon. Presumably your cloth is not the same as your material with strongest intermolecular bonds (and lowest cross-section). If it is you're at a stalemate again. Essentially what it boils down to is if you can pick properties/tech will-nilly then spear/shield match-ups are stalemates which is the same as saying the shield won. Figure out which energy areas the shield and spear belong to and stick to them. Your cloth happens to fit EXACTLY what you want it to be. Braced weapons already exist and cloth is not rigid (your not using it as a bracing material) so essentially small arms are "useless" by the above argument since it never transfers enough momentum. And by the same argument large braced ones are effective. If bonds in cloth are relatively weak an extremely sharp melee weapon could still have effect. And if you're willing to trade the cloth back down to kevlar-vest levels of protection: then you're looking at something where a sledgehammer is still effective but small handguns are not as effective. [Answer] If you have found a way to dispense the energy of an incoming projectile then yes, it will bring back medieval style hand to hand fighting. It all boils down to where the energy go. Ways to dispense the energy: 1. Have super strong material, that has very strong inter molecular attraction. That reserve of energy then counter the incoming energy. The energies cancel each other. 2. Have material that can absorb the energy to make new material. Perhaps have new bonds, make new compounds whatever. 3. Have the energy absorbed to change state of matter. It takes lots of energy to convert ice into liquid water for example. You may have some exotic state of matter coming into play. 4. Have active defense. You need to power your armor for that obviously. 5. Find some way for energy to go side ways perfectly. Your future technology may use super conductors for example. Your soldiers necessarily fight keeping distance between them. As long as the incoming energy is not affecting your body you are golden. [Answer] You'd probably see more fire based weapons, which may count as medieval. Your armor can be made of completely fantastic stuff that blocks all but the highest energy railgun bolts. But without making it a space-suit, it will provide little mitigation against flamethrowers & Molitov cocktails. So these weapons could become more prevalent. Also, weapons that bind their feet together like some kind of whip, possibly w/ some kind of glue, could be more viable in place of small firearms. [Answer] I'm basically going to agree with many other answers that say "no" to the question of bows & arrows / crossbows making a comeback, but for a simple reason that I think everyone else glanced over: You are correct that some kinds of armor perform better against high-energy projectiles and it's (in the loosest sense) "plausible" that your cloth will be easier to penetrate with lower energy projectiles. That having been said, its easier to make armor that performs well against low-energy projectiles than it is to make armor that performs against high energy projectiles. In your world, all people would have to do is use a bilayer armor to make both irrelevant. This is kind of already done when soldiers and the like use Kevlar with steel plating. Now, I do think the melee weapon angle is a little more plausible than others have given it credit for, but not because of the speed/energy difference. Rather, melee weapons allow force to be continually applied. Now, you can't have people lining up with swords in a world where missiles, bombs, rail guns, conventional artillery and so on exist. That would be suicide. But, I could maybe see long knives and short swords (using better modern materials) be useful for assassinations and the like. There is one other caveat though: You're fairly focused on projectiles. Explosives, chemical weapons, and biological weapons also all exist. In this world sonic and heat based weapons are also likely in vogue. Swords (or any other melee weapon, I'm just using them as an example) have stiff competition unless there's a cultural aspect. Here's my suggestion: Swords (or, again, sub your favorite weapons) were used for duels long after firearms had made them mostly irrelevant on the battlefield. In my opinion, the reason for this is that, while they aren't your best battlefield tool, they were still kind of practical for one-on-one fights. Not to mention, they were still worth carrying in the days where you could only shoot once before reloading. You have a similar situation. They won't win battles, but they aren't useless. Maybe soldiers carry them for and for defending against small raiding parties that try to sneak in around the artillery. Once in close quarters, you won't want to use the other weapons that I mentioned since you'll kill your own people. Basically, they fill the role that bayonets did until the mid twentieth century. [Answer] No. As even if you can stop the projectile as long as this is a cloth, it will have no means to prevent the cloth from folding in & just following along with the bullet. Meaning you will still need to find another way to disperse the energy of the round using normal materials. (For this part i'm probably getting all the terminology wrong but hopefully the point will still get across) This issue in irl body armour is referred to as back face deformation. Where the bullet is stopped, but the materiel itself still deforms, putting meaning the use is still hit with a significant force in a small area. (someone please edit this bit if you know how to phrase that better) And even if you fix this issue you still have the issue of the other guy being able to use a bigger gun, or more even small explosives. Making all this effort while not wasted (now they have to carry heavier shit) still negated. ]
[Question] [ In a world where Gods exist, a god "x" one and only job is to maintain some kind of machine or system that oversees the creation of hero of the eons. Every eon, all gods gather and play a game called "Apocalypse" to relieve their boredom. When Apocalypse started, all kinds of "Apocalyptic event" ideas from all gods pooled and randomized to select one as the "Apocalypse's Theme of The Eon" to annihilate a planet. This eon, god "x" felt too excited because his idea is selected, and keep thinking about it. When he tried to spawn a hero to defend a planet ( 20 years before Apocalypse ), he feels so lucky and jokingly entered 999/1000 as the stat of the new hero. While laughing, he accidentally pressed Enter/Generate. At the same time, a boy with 999/1000 luck stat is born. "x" is so shocked and tried to correct his mistake before another god found out. How? How to kill a character with 999/1000 luck? When using a meteor to blast his home, an asteroid from another galaxy suddenly hit and make the meteor miss the planet. When poisoning the water wells in the village, the wells collapsed and it keeps raining for years. The villager drank the rainwater. Even when using god power to push a giant planet to smash the hero's planet, suddenly a giant black hole appeared out of nowhere before the planet clashed, saving the hero's planet. Summary : An OP hero with hyper luck born because of a god mistake. The god have 20 years to undo his mistake (kill the hero) whatever the cost. "How to kill this hero ?" Edit : I am thinking of a way to end the story. Trying to keep killing him and rely on 0.1% is practically impossible. To clarify and give you a rough image, If this is a game, regular human stat is as follow : A Newborn : Strength: 1/100 Agility: 1/100 Intelligence: 1/100 A Nomal Adult Warrior : Strength: 25-30 Agility: 10-15 Intelligence: 5-10 Luck Attribute is one of many hidden attributes such as : Concentration -> Mana regen Vitality -> Hp regen Obviously, Luck -> is how lucky are you and so on Normal human limit is 100/100 in each stat. 100-200 is demi-god area. 200-500 is a minor god. 500-750 is a medium god. 750-1000 is a high god. The hero have 999/1000 luck stats that are even higher than that of god's. How to kill this hero? Im trying a possible ending with the hero dying. Is it possible to kill this hero? Edit 2: It seems everyone misinterpret 999/1000 luck. What I mean Overpowered Luck is: a normal human that have 100/100 luck is considered pretty much have the limit of human luck, this means he is 100% lucky for a human. Everybody said about 999/1000 about 99.9% luck, but u miss the point that human have a limit of 100 luck. 999/1000 means 999% (999/100) luck more than the luckiest human possible. I guess the story itself is flawed? Like "how to kill the unkillable" then. Thanks for the answer, it's been fun. [Answer] Going with your explanation that 999 is at the high end even for gods, and that it's not something like 99.9% but more something like 99.999999999999% (and then some) of luck: Congratulations, you created another god. Not a hero, but a god. Now you want to kill him to cover up a mistake. That's going to be some god-laws issue right there as I'm sure the other gods will frown upon deicide. Assuming that 999 is a world-breaking, insane, beyond-anything-reasonable amount of luck, none of the answers given so far would work. If essentially the whole universe will throw up "random" obstacles to your murder attempt, he'll be the one person to solve the "suicide yourself to save your mother" thing and "by chance" find a way to save both himself and her. He'll avoid the terrible fate that would lead to him jumping off a bridge to avoid the madness, and so on. The one thing that no amount of luck can solve is: Time. He will go to 100, 120 years with his luck, avoiding all the things that kill you by chance, but sooner or later, the grave is where he's headed. Time is the great equalizer, the one thing that doesn't care how strong, how rich, how beautiful or how lucky you are. It's the only thing that no amount of luck can save him from, the inevitable fate of all. So your problem is that you have only 20 years and that any attempt to hit him with rapid aging or such games would be countered by his luck. It appears that the apocalypse has to be re-scheduled. Shouldn't be a big deal for immortal beings. Wait a century more, what's the problem? Ah yes, you don't want the other gods to find out. Oopsie. You can't. Frankly speaking, there is no way. Whatever you need to do to murder this guy, it will be so extreme that the other gods will notice. Waiting it out and inventing a bullshit reason ("sorry, the dog ate my apocalypse timeline.") is much, much more likely to be unnoticed than setting whatever universe-changing gears in motion that are big and unstoppable enough to bypass his luck roll. or... of course... because you need a story and the logical approach above is boring... allow me to assume that his luck does not extend to "x". That "x" came to the conclusion to murder the boy is already a good indication that it doesn't. So "x" is protected from the effects of luck. That means that "x" will need to get his own hands dirty, because anything intermediate will be subject to luck. That includes any direct attempts at murder. Just going there and bashing his skull in won't work, luck will somehow interfere. But do you know what else beats everything, at least in story logic? Love. Take a page out of the Loki book (the norse god, not the Marvel character). Turn yourself into a beautiful woman and make the guy fall in love with you. Work luck to your advantage - scoring the most beautiful woman in the whole country certainly is a lucky event, isn't it? Once you are inside the "love bubble", luck remains outside, because (at least in story logic) "love conquers all". Then make him your friend. Let him in on the whole story, he'll lap it up because he's been wondering his whole life just why he's always so lucky. Now you have an ally, a lover, who is more lucky than the gods themselves. And since you two are in love, your goals are aligned and his luck will work for you, not against you. If the other gods would certainly do something about it if they found out, then his luck will now protect you from them finding out. They won't. You're good. The most ridiculous things will happen whenever they are close to figuring it out. In the end, you don't need to murder the boy, because that was never your goal. Your goal was to make sure the other gods don't find out about your mistake. You can use (instead of kill) the boy to reach that goal. [Answer] Just keep trying to kill him. A 0.1% chance of dying to any given event is good, but not that good. If the stat and it‚Äôs effects are linear (IE any given attempt on this guys life has a 99.9% chance of failure, no matter how cataclysmic the event) then all the god has to do is keep trying, though it would be useful to try a couple of thousand smaller deaths (hit by car, killed by bees, chokes on a recalcitrant grape), than only a few big-bang events. You can work out the odds of surviving a number of successive events as 0.999 (the odds of surviving due to pure luck) to the power of the number of events (multiply the result by 100 if you‚Äôre used to working in percentages) This is assuming the ‚Äòluck‚Äô resets every time and no event alters the chance of death. After only two years of daily attempts on his life there‚Äôs a 50/50 chance his luck has run out. The odds of him surviving 20 years of daily events is 0.06%. If you try multiple things in a day obviously these chances go down. If you want to tilt the odds in your favour then early on you can convince him/his parents/friends that he‚Äôs invincible. This will cause him to test his newfound luck to its limits even without your help. Either way it‚Äôs only a matter of time before his luck... runs out. [Answer] Arrange a situation where he sacrifices himself willingly To save his mother / girlfriend / home village, he has no alternative but to X. (Throw himself in front of the magic grenade, or whatever.) Bonus points if you can convince him that it was his fault the situation arose in the first place. (I have been toying for years with the idea of a character who was supposed to die years before, but is too lucky for death to catch up - until the character momentarily casts his "luck shield" over someone he cares about, leaving himself vulnerable.) [Answer] It depends on what is considered lucky. Luck is a subjective idea. For some its winning the lottery, or getting a job, meeting their love interest in a way that makes them interested, finding the house you want etc. Luck changes based on the time and place you are on at the time. Your god knows this, so rather than keep killing the hero he tries to change what the hero considers as lucky. Imagine this god telling the hero: "the Gods are going to destroy this planet in a couple of years. You could try to stop it but it would cost billions of lives as not everyone is lucky. However if you are lucky enough you can get the technology and industry up in time to evacuate before the planet blows". Changing the opinions of the hero has nothing to do with his luck, as anything he thinks is lucky will be what happens. Altering what he considers is lucky will only fail if the hero actively does not want it to happen and feel unlucky if his opinions are swayed anyway. But you can go even farther. In terms of biological luck nothing is as lucky as giving your future offspring the best chances. Taking to the stars and spreading from there across the Galaxy means the hero's children will have the best chances of finding their own mates and getting healthy children, and being spread over the Galaxy also means protection against another apocaliptic event killing off all the genetics you pass down. Being lucky enough to leave the planet or his children to leave it even without an apocalipse happening is probably one of the luckiest things that can happen to him. Screw protecting the planet. In fact, if he does manage to protect the planet and the Gods find out he has to deal with the backlash of all those Gods, and some of those Gods aren't just as lucky but also GODS. protecting the planet just means a stay of execution for the lucky guy, letting them succeed but escaping is the lucky option. The hero will be so lucky as to see his friends and family safely, and he'll die happy at an old age. [Answer] ## Make a character with 1000 dex to kill them. If 999 luck is reality warper, then you need someone who has another reality warper stat to handle them. They summon a black hole to stop them? The person runs faster than light, they run past the blackhole. A random meteor comes to crush them? They dodge. The hero punches just right to cause an earthquake? They dodge. If they have an arbitrary ability to make people stronger than them, they can just make another. [Answer] It is a risky thing, scheming against someone so lucky. How does luck protect? 1. The entity fails to kill me. You covered that. Other aspects of my luck involve the entity itsself. 2. The entity changes its mind about the killing project. 3. The entity gets busy doing other things. More rewarding things. 4. The entity comes to harm and cannot try to kill me. Maybe it is killed. [Answer] Big numbers and sort of lucky The way to kill him is simple. Keep trying in a thousand different ways. Statistically, if you send 1000 hitman one at a time, one should do it. Of course that isn't exactly how chance works, but you can just have a billion smaller yet deadly encounters for him. Try to drop a random rock from a building to kill him, hitman, a rain, a meteorite... But it gets more interesting in another way. If you throw 20 knives simultaneously, is it one attempt or 20? This waybyou can rack up the attempts quickly. Imagine putting him in a situation where every microsecond a canister of toxic gas has a 50/50 chance of breaking, instantly killing him. Now the odds aren't in his favour. But lucky can be in many other ways. The guy is still human. If he goes to put his head in a working guillotine on purpose, luck would do little for him. Even if it does, in what way? Would it it considered luck if he only loses an ear? Or a leg? What if this person notice her or his luck, starting to get a thrill out of it? Maybe the person will engage in more and more risky behavior as a talent or thrill, eventually stacking up too much that his luck won't help. After all, jumping directly into a vulcano needs probably a bit more than 999/1000 luck to survive unscathed. [Answer] What you need is a scenario where his luck just cannot come into play. There's a really great episode of The Batman that I think might be applicable to this scenario. It's called Seconds, and it's about a man who develops the ability to rewind time 20 seconds. So, within the context of a world, like yours, where luck is a statistic, that'd be like being able to re-roll any situation until it goes his way. The way he's beaten is that the heroes split up and do something that he could only prevent if he was in two places at once, and by the time it's done, it takes him way more than 20 seconds to reverse it. I think a similar principle can be applied here. You need to introduce something that's beyond the scope of what his powers can do for him. Be it a death-trap that cannot be circumvented, like placing him in the center of a sun or supernova or something like that, bigger than the range of any non-divine teleportation magic that could happen, or something that works with his luck, make him actually immortal so that situations where he's in danger aren't considered unlucky for him anymore, and then just toss him somewhere where he can't do anything like Kars from JoJo's Bizarre Adventure. Or, and this is a really stupid idea, create a bunch of guys with the same luck stat as him, set up in a way where their essential purpose in life is to kill him and then die, and hope for the best. As they're just as lucky as him, his luck wouldn't have an effect on them, and theirs wouldn't have an effect on his, so they're on even playing ground luck wise, and they have the numbers advantage. That however is a probably only fitting for a comedic farce, as I'm sure you can think of many ways in which it can go very wrong. [Answer] Let him just die. I am assuming that 999/1000 means that out of 1000 tires, he succeeds at 999. Well' those are quite bad odds to be honest. I mean, given this [article](https://www.thebalance.com/what-are-the-odds-of-winning-the-lottery-3306232) his luck is not that exeptional. I propose that he survives the most elaborate plot to off him, and then he suffocates while eating peanuts. Why? Because [shit happens](https://www.kidspot.com.au/news/viral-photo-shows-reality-of-kids-choking-on-food/news-story/7cfd1e4f1deca33bde7622401a421036) and statistics/luck is just the numbers game. [Answer] Minor Challenge: Is murder really the goal here? Consider that if there are gods, there is likely an afterlife. Even if you managed to kill the luckiest mortal in the world, there is that infuriatingly small chance that something happens and the luckiest mortal in the world somehow self-resurrects through some means. Probably a loophole in the afterlife unknown until now. Your deity's goal is to fix the mistake. Based on the question, just adjusting his stats with the Hero Generator is not going to work since the hero is already born. Is the hero supposed to succeed at saving the world? That might also dictate the better way to get rid of them. Blowing up the cause of the apocalypse (by accident!) only to die from the shrapnel from the explosion would seem to tie up all the loose ends there, and be a luck-based way to die. Of note, your hero appears to be otherwise mortal. They will not have the raw stats to out-muscle their problems, or out think them. Their luck might prevent a horribly messy death, but their otherwise mortal stats will get them into as much trouble as their godly luck will get out of. ### What is Luck? Based on general consensus, I am presuming by "Luck", one means "Good Luck". But really, if someone is that supernaturally lucky, they will be practically cursed with luck. And I do mean cursed in the "May you live in interesting times" sort of way. Sure, this is the person that can randomly find a jackpot lottery ticket on the ground. This is probably also after their home collapsed/exploded through some one in a million happenstance. But it's all right -- they weren't there due an unquenchable taquito craving at 3 AM. Plus they had to detour because the store they normally frequent was just robbed, so this ticket wasn't even on their regular route. And they missed being part of that robbery because a shoelace broke and they had to replace it. Refit the statement above to be more appropriate to the world and the idea still holds. The hero is stupid lucky, but that also leaves them vulnerable to falling into the weirdest situations mortal life can find. This hero literally lives the life of some ridiculous anime protagonist in all the weird stuff they will get into. ### Removing the Hero But removing the hero, that is trickier. There is that stupidly annoying change that if they die, someone will try some resurrection thing on them and they are still lucky enough for it to work. The deity could just yeet them off the planet, but they would still technically be alive and in the system. Plus, it would open up extraterrestrial shenanigans that will end up coming back to the planet if it still needs saving. Probably with a way to save the world made by an alien super-genius with a potato. The best way would seem to be to engineer a situation where a non-fatal removal would be the luckiest thing that would happen. Accidental petrification to save the world from flesh-eating parasites? The Luckiest Statue in the World can't really affect the world much until people managed to un-petrify themselves somehow. Perhaps everyone else recovers but the hero and the hero's statue and absurd luck protects the city that surrounds it after the end. Perhaps the most interesting way to remove the hero is to have their luck not function properly if they actually rely on it to solve the problem at hand. Godly luck can't be comprehended by a mortal mind so the moment they rely on it, it will only merely function at a peak mortal level. That could be when they are vulnerable to horrible messy death. Plot Armour that fails the moment one tries to actually use it. ### It Was Fate Given that a God Conference decides the Apocalypse of the Eon, there may well be a Deity of Fate there as well. It may also be that this eon, a Deity of Luck will rise and join their ranks and has been fated as such for eons before this (if anyone remembers that far back). But to do that, they need somebody with enough luck to fit the role and a tale strong enough to be able to lift them into the ranks of divinity. The absurd luck stats ensures that they qualify for the mantle of a luck deity. Saving the world likely in the most stupid lucky way is a deed that will be remembered for ages, if only for the utter incredulity of how they won. And they will certainly be lucky enough to survive ascension into fill godhood with that luck stat. How they luck themselves into divinity is the topic of a sequel of course ### Conclusion I don't think that the story is flawed in so many words. It might not be the story that you want or are thinking of though. Perhaps a story of an otherwise ordinary main character with OP luck that has to think their way out of their problems is a good story if done in the right tone. The protagonist's godly luck is justified Plot Armour all things considered. [Answer] ## Greener pastures! Think back to one of cinema's most renowned masterpieces: [Star Trek I: The Motion Picture](https://www.imdb.com/title/tt0079945/?ref_=ttls_li_tt). One lucky scientist falls in love with omniscient space probe, and departs for the endless horizons of parallel space that only he can imagine. Build a portal that might reach another universe if you're really lucky. That might be inhabited by gods who have more meaning in their lives than an occasional game of Dungeons and Dragons. Only one person can go. Who would be lucky enough to be the lucky winner? When someone leaves the universe, they are not "living" in that universe. True, they don't live fast die young and leave behind a lucky corpse, but this probably is best for avoiding unfortunate publicity. [Answer] The most unlucky thing to ever happen to this person is that they were given a luck stat of 999/1000. With absurd luck like that, this character has never had to struggle for anything in their entire life. There are no surprises, and realistically nothing to live for. Boring! I would focus on the internal struggle with this character. Maybe the revelation of their luck stat being a joke would be enough to push them towards ending it all. [Answer] Statistically if each attempt has a 0.1% chance of killing the character, then if you try 1000 times you will have a 63% chance of killing them. If you do it 2000 times you have an 86% chance, and if you do it 3000 times you have a 95% chance of killing them. As you try more and more attempts the chances exponentially decay towards 100%. In general if your chances of killing them are 1/N and you try to kill them M times then your chances of killing them are about 100% \* (1 - e^(-M/N)). So basically since the chance is non-zero you can just try lots of times. Make something life-threatening happen a couple of times a day, every day, for a few years, and eventually their luck will run out. [Answer] How about you present him with something he'd consider a fate worse than death? So then his super-luck causes him to die just before he'd have to deal with that horrible thing. [Answer] Some Caveats To extend a bit on my comment, a fairly clear definition of 999/1000 luck is needed here. Now, I asked and others either asked or assumed that meant something along the lines of "you need something with a 99.9% fatality rate to kill this person." You have pretty much clarified that's not what you meant, and your examples suggest a way stronger meaning of the term. In particular, the odds of being saved from a projectile planet by the spontaneous appearance of a black hole is safely rarer than a 1 in 1000 event. So, it seems safe to assume you're not looking for that probabilistic meaning. You also say that a really lucky normal person might have a luck stat of 100/100. Well, assuming / is a division sign, 100/100 > 999/1000, so that's puzzling. Maybe you just mean that most people are in a range of 0 - 100, whereas deities have a range of 0 - 1000? I'm not sure. But your way of writing it could be pretty misleading. Now you put some ranges out there for varying levels of gods, but by some definitions a god is inherently immortal, which would make the question moot, and I don't know of many religions with such a clear hierarchy of gods. So, we're sort of back to the definition issue. Actual Answer All those caveats aside, I think there's basically one answer that I could give that doesn't require several levels of clarification. If someone is basically invulnerable to not just random bad luck, but even to bad "luck" that someone else deliberately inflicted on them, then their going to have to be their own undoing. I can't believe I'm using this example, but the Disney movie Hercules has this exact issue because Hercules is invulnerable to anything Hades throws at him. So Hades takes a hostage and extorts Herc to give himself up. Now, maybe you say "my guy is so lucky Hades would just fail to capture his lover." Well, then could your protagonist be tricked? Maybe lured into something they think is good? Could they agree to be given a drug with the promise that it will take away all pain forever, and it does because it kills them? What about their will to live. Could they be made suicidal? You'll have to decide exactly what luck protects this character from, but your answer is probably some version of the villain indirectly leading them to death instead of killing them outright. Another Option Edit: One other option. Does the god have a higher luck stat than the character with 999/1000 luck? What if the god said to the other gods "Swear to me that if I fail, you will kill me." Now the god's luck would presumably be on the side of saving said god, and that luck would favor the 999/1000 character dying. So the god could go down to the 999/1000 guy, and personally try to kill the 999/1000 guy. Now their lives are both on the line and I assume the luckier one wins? It all depends on how you want luck to work. But this feels like one of the more self-consistent options. [Answer] # Make him even more lucky! Reading your update, it looks like the problem is that his luck is 999/100. That is, humans are supposed to have luck scores ranging from 0-100, and his stat is a world-breaking 999. This happens. A famous example is Civilization, in which a bug allowed the pacifist Ghandi to achieve an aggression score of 255 out of 14. The solution is to do something that provides him with a permanent bonus to luck. Why? Well, having luck range from 0-100 implies there's a cap on it. And stat caps imply something's enforcing the cap. And we all know that such enforcement only occurs when the stat is increased! The way it works is that the stat is increased, then checked against maximum. If it's above the allowed max, it drops to the max. So if the god gets a unicorn to nuzzle the hero, or sends a Catholic nun to give him a blessing, or some such, and his luck increases to 1003 / 100, then the universe will promptly notice that his luck is over the maximum of 100, and drop it down to that level. The hero is now exceedingly lucky, but not world-breakingly so. At that point, the god can just sidle off whistling and hope none of the other gods notice that someone was born with a luck value at cap. [Answer] ## Time Dilation Does he need to die, or is it sufficient that his existence goes unnoticed long enough for it to become moot? Send him somewhere at relativistic speeds. Put him near a black hole. Make sure that being in one of those situations is a huge benefit to him or his loved ones (being hidden from an apocalyptic game between gods seems pretty lucky to start), then make sure that he can't return from whatever isolated region of spacetime he's in until it no longer matters. [Answer] What an occasion to reflect on the nature of luck. --- ## Plot twist - lucky guy destroys the world What does luck truly mean in your world? Does the flawd human always get what he wants or does his luck intervene with his plans, letting the opposite happen from what he wanted, if it is best for him? Can he just not be harmed directly or is it granted that he stays sane and happy and makes the right choices? There is the saying be careful what you wish for because you might get it. Just look at Homelander from The Boys, King Joffrey Baratheon or Killgrave from Jessica Jones. *Don't get rid of your hero. Just show him that he can do whatever* he wants and get away with it. [Dom's answer](https://worldbuilding.stackexchange.com/a/211115/67222) is similar. Him ultimately destroying the world, always having got what he wanted instead of what would have been best for everyone is actually the 0,1% time his luck is not working out. --- ## Guardian god Just to make it more colorful - does the 999/1000 stat simply make the hero more lucky on an abstract level or does it turn god x into the hero's reluctant, overstrained guardian angel who is obliged to step in and save the hero from the very traps he layed out for him (and getting his own butt kicked in by them)? Until he realizes, he can work as kind of a shoulder devil to set the hero in his destructive path. Maybe all the wrong-gone attacks backfiring at god x are enough for him to give up the whole thing in need of a hiatus, leaving it to the next chosen god and his apocalypse an eon later. --- ## Plot twist 2 - lucky guy becomes unlucky out of sheer luck As this seems to be a terrible fate for the hero, the 999/1000 luck of the newborn hero immediately kicks in to prevent that from happening in the very moment the god presses enter. A lucky accident happens, somehow rotating the dial up by 2 and turning the hero into a happy jinx with a score of 1/1000*. (Basically the approach of Breaking Dawn Part 2* with the internecine final battle turning out to be a mere vision of a battle that never happens). And maybe the same accident also rotates the dial for the date of the apocalypse, resetting the clock to the beginning of a new eon before the next apocalypse. Wilk already [mentions that the luck could interfere with the gods](https://worldbuilding.stackexchange.com/a/211063/67222) and the [animated short film Zing](https://youtu.be/BETa92ALukA) has a similar solution. [Answer] I suspect your problem is thinking of only big flashy ways to kill someone. People die from tripping and falling, random infections, things falling on them, being innocent bystanders, mechanical failures in their vehicles, being kicked by horses, contracting rabies from some random dog bite, getting stung by jellyfish or insects, choking on food, carbon monoxide from badly maintained furnaces, chemical exposure at their workplace, drowning, allergic reactions, whatever. There are literally thousands of things that could kill a person, and if they all kept happening, however lucky a person is, one will get through. And only one needs to get through. No planet tossing required. The other issue is that I suspect you're combining events. If the man is a soldier who has been through several battles, as an example, is the 99.9% chance of survival related to the war in total or for each individual threat during said war? [Answer] This answer might not be the story you want to write, but if you want somebody who is impossibly lucky (i.e. beats all odds) to die, then you have to convince them to kill themselves. Being impossibly lucky might protect them against all manner of accidents, assassination attempts or "acts of God", but luck alone can't save them from suicide - arguably, it would make their suicide attempts very likely to succeed. [Answer] Let his luck work for you. Create a situation where the luckiest thing that could happen to him is to die. Though really, if he were that lucky, "x" never would have noticed his mistake, or for whatever reason the gods wouldn't be trying to kill him. [Answer] The god just needs to have a conversation with the hero. ‚ÄúLook, my friend, you‚Äôre an accident, and I don‚Äôt mind you existing, but please try to stay uninvolved in the apocalypse game or else things between the gods will get so contentious, not even your luck will save you and those you care about.‚Äù The god will need to use its level 1000 charisma to do this convincing. Once staying hidden and isolated becomes the hero‚Äôs goal, then the heroic luck works with the god plans instead of against them. [Answer] ## Frame challenge: Send him to go kill the "God of Luck". If he wins, then the God of Luck won't know anymore until you make him the Luck God out of Rite of Caste rules. If he loses, then the God of Luck removed the evidence for you, and you just have to persuade the God of Luck that it's just his nemesis, the "Demon of Bad Luck", who intervened. This could be an issue if God X is the [God of Luck](https://tvtropes.org/pmwiki/pmwiki.php/Main/HiredToHuntYourself), but that does help reduce the requirement to have to lie to the God of Luck as to why the Hero tried to kill him. [Answer] Note : It's technically a frame-challenge which yet answers your problem (giving an end to your story). Yes, I know you want them dead but I wish to show you other interesting timelines out there :). ## Match your goals and send/hide them away. As written, there's a confusion between your god's goal and the hero's one. Your hero's goal (and their luck's) is to live and be happy. Your god's will is to not have the hero discovered, which means not having the hero at the same time as the apocalypse. Killing is an option, but it goes against the hero's goal. So instead, send or hide them away! This might come to the conclusion of hundreds of failed murder attempts, where the god got bored of yelling again and again "[I'll get you next time, hero! Next time!](https://en.wikipedia.org/wiki/Inspector_Gadget_(1983_TV_series))" while sitting in their CEO chair and stroking their cosmic cat. You've got plenty of options, but the main thing is to be as honest and friendly as possible, as any intent to subvert the hero's deep goals will subvert the luck's one, which could be considered as omniscient regarding what is best for the hero. I'll list some alternatives them here : * Send them back in time so they can die of old age before the Apocalypse happens. Make sure they understand the luck they have to be able to live peacefully when they would have faced the end of times if they stayed in the present, give them anchors to grab on emotionnally, and they should be fine. * Sending them forward in time after the Apocalypse might be tricky but possible. Tell them you're giving them a chance to rebuild the world. Give them help in doing so, and make them understand the Apocalypse was unescapable. They'll be feeling like a true hero, something which can be favorable in an anyway dire time. * Sending them in a secured and hidden space, like your god's doghouse (maybe something better than that, though :p). There, they'd be guaranteed to be happy for a very long time, and no murder attempts are to be made anymore against them. Who tried to kill them so much, anyway ;p? This kind of thing is bound to happen at some point, because, well... If you're truly lucky, could you really find favorable for you to face a full array of angry gods AND an apocalypse as you have just reached adulthood? Your luck might not be enough to turn the tables around at that point, so it might be better to side with one of them before the storm comes and find shelter through their help. Plus, since they're so lucky, any of the helping god's actions will be amplified by tenfold, making the act of hiding the truth so much easier... [Answer] If you think about it, his luck is literary 1, 100% or 1000/1000. Chances of another asteroid to hit your killer asteroid or a black hole to appear out of nowhere are many orders of magnitude lower than 0.1 and so his luck must be much more. The way to get rid of such a lucky guy is to create space where he would be good and move him there so he doesn't stand in the way. He will eventually dies of old age. ]
[Question] [ What is the best choice when it come to deciding which animal to breed to be a perfect assassin? The animal must be smart enough to understand which person to kill and which not to. The animal must also be smart enough to find their victims. How does it work? The government leaves an object hidden somewhere near the house of the victim, the object emits a smell or sound only the creature can hear from really far distances. The further the better. The animal must be trained to understand kill commands through simple communication. Example: Show a blue scoop and the creature understands that it must kill every person in the house once it gets there. Show another color it must understand that it must kill only the males or only the females and so on... Simple signals like that. In order to tell the creature what, who and how many people to kill. If it can work with vocal orders, even better. So the animal needs to be smart enough to find signals from really far away and track down the house, be smart enough to understand basic communication and most important of all, be really fast at killing and really good at escaping. If the animal can be trained to run away after a successful kill, even if injured, that's better. An animal which can ignore pain and still run is preferred. The animal should try to escape without being followed, if people are following it, it should be smart enough to not return to it's master until it is safe to do so. Or better if the animal is stealthy enough to avoid being tracked down. If possible, everyone should believe the animal is a demon sent from hell to punish sinners and when it disappears they will just think it went back to Satan. So, which of the modern and ancient/extinct animals are the most suitable to being bred through generations into a creature perfect assassinations? It does not matter if it's herbivorous or carnivorous, as long as it's good at killing. The animal should not be too small, because it would be killed too easily. [Answer] > > What is the best choice when it come to deciding which animal to breed to be a perfect assassin? > > > Us. Last time I checked, [we are still animals:](https://en.wikipedia.org/wiki/Homo_sapiens) [![Lineus classification of Homo Sapiens](https://i.stack.imgur.com/3CzjH.png)](https://i.stack.imgur.com/3CzjH.png) > > The animal must be smart enough to understand which person to kill and which not to. > > > I don't want to start a political discussion here, and this makes me sad, but as a whole we seem too keen and too effective at profiling and killing people with as much specificity as you can imagine. > > The animal must also be smart enough to find their victims. > > > Humans are very good at facial recognition. Few trainable animals are as good as we are. Seriously. Our sight is not as good as that of some birds, but birds make poor assassins. I was going to add a [citation needed] joke here but just think of it: when a bird kills a person, it's news worldwide. But we have a whole industry that turns them into food for us. Then we have beasts more properly equipped to kill humans like jaguars and bears, but we see more colors and finer details than they do. We could pick a target in a party much better than those animals could, and all we need is a picture. Most other animals would need a sample with the smell of the target, which is harder to procure. > > How does it works? The government leaves an object hidden somewhere near the house of the victim, the object emits a smell or sound only the creature can hear from really far distances. The further the better. > > > How about an app instead? Most humans can follow a map on a smartphone screen. > > The animal must be trained to understand kill commands through simple communication. > > > Example: > > > Show a blue scoop and the creature understands that it must kill every person in the house once it gets there. > > > Show another color it must understand that it must kill only the males or only the females and so on... Simple signals like that. > > > In order to tell the creature what, who and how many people to kill. > > > If it can work with vocal orders, even better. > > > With humans, as long as you are not hiring dyslexic people, you can get quite a good rate of properly followed commands. > > So the animal needs to be smart enough to find signals from really far away and track down the house, be smart enough to understand basic communication and most important of all, be really fast at killing and really good at escaping. > > > If the animal can be trained to run away after a successful kill, even if injured, that's better. > > > [We can totally do that and better:](https://en.wikipedia.org/wiki/Carlos_Hathcock) > > > > > > Hathcock only once removed the white feather from his bush hat while deployed in Vietnam. During a volunteer mission days before the end of his first deployment, he crawled over 1,500 yards of field to shoot a PAVN General. He was not informed of the details of the mission until he accepted it. This effort took four days and three nights, without sleep, of constant inch-by-inch crawling. Hathcock said he was almost stepped on as he lay camouflaged with grass and vegetation in a meadow shortly after sunset. At one point he was nearly bitten by a bamboo viper, but had the presence of mind to avoid moving and giving up his position. As the General exited his encampment, Hathcock fired a single shot that struck the General in the chest, killing him. > > > > > > > > > I don't think any animal other than a human can be trained to be that single-minded. > > An animal which can ignore pain and still run is preferred. > > > Give a man some cocaine and morphine, with the promise of more of these later, and not only you have a warrior that does not feel pain, you also have a very motivated warrior. > > The animal should try to escape without being followed, if people are following it, it should be smart enough to not return to it's master until it is safe to do so. > > > Or better if the animal is stealthy enough to avoid being tracked down. > > > Hathcock crawled all the way back after killing that general two paragraphs ago. > > If possible, everyone should believe the animal is a demon sent from hell to punish sinners and when it disappears they will just think it went back to Satan. > > > A killer who is stealthy enough can add some theatrics to their methods to make the gullible think the killings are paranormal. Some people do believe in the Yeti and the Moth Man up to this day. > > So, which of the modern and ancient/extinct animals are the most suitable to being bred through generations into a creature perfect assassinations? > > > It does not matter if it's herbivorous or carnivorous, as long as it's good at killing. > > > I could post pictures of people killing people but that would be gory. > > The animal should not be too small, because it would be killed too easily. > > > Counterargument: midgets are smaller targets. [Answer] The animal you're asking for is known as Homo sapiens. Sorry, but you're essential describing many actions which pretty much involve human-levels of intelligence,and the animals which have similar intellect will not be hard to notice (unless you're blind, though you'll still hear the death dolphin squirming towards you to do to you what it does to fish, or if you live in a place where it's common to find chimpanzees or crows inside of buildings). But given that you're also including prehistoric creatures (which is NOT the way to go if you want intelligence. The mighty raptors Hollywood showed us could apparently be outsmarted by your average dog) and admitting both the classic meaning of animal as well as some impossible bioengineering in here (since you're willing to use breeding to achieve the traits you desire, plus you don't seem to mind bringing back extinct creatures, which could only happen through either this or a time machine), my bets on a non-human assassin animal would be on a genetically modified [Giant Pacific Octopus](https://www.nationalgeographic.com/animals/invertebrates/g/giant-pacific-octopus/). Octopuses in general are in many ways nature's coolest assassins. They can't fly silently like an owl or slash you with claws like a lion. But it is known to be a very intelligent animal, can change both it's color and texture despite being colorblind, are stronger than a human and, one of the best: they can essentially fit inside any place larger than its beak, which is the only hard part of its body (so essentially any place larger than a penny will do). The giant pacific octopus, while also having many of these qualities, is larger and stronger than a human, and is known, like its fellow brethren, for being troublesome in aquariums due to their attempts (at times successful) of escaping their enclosures. So let's see if this bioengineered Giant pacific octopus could fit the mold according to what a giant pacific octopus can already do without modifications: > > The animal must be smart enough to understand which person to kill and which not to > > > Octopuses are capable of recognizing and remembering [by sight and taste](https://southsoundmag.com/giant-octopus-revealed/), so this is likely already doable with a normal octopus. > > be smart enough to find their victims. > > > How does it work? The government leaves an object hidden somewhere near the house of the victim, the object emits a smell or sound only the creature can hear from really far distances. The further the better. > > > Otopuses have been shown to be able to transverse mazes, solve puzzles, and open jars with crabs inside by recognizing the food. Though I doubt smell or sounds can work, but if you have a layout of where the victim will be, making them go through a similar maze will let him learn where to go and how to come back. Also putting special fluids in the path it must go might also work, as it can taste its surroundings with its sucker pads. > > The animal must be trained to understand kill commands through simple communication. > > > If it can work with vocal orders, even better. > > > Relying on voice won't work. They can feel variations in pressure with their skin, but that is for when they're underwater. Rather than colors (they're colorblind), showing special shapes might work decently well (show a crab sign and it could understand everyone must die) this one might require a bit more of bioengineering and conditioning to be properly tuned. > > the animal needs to be smart enough to find signals from really far away and track down the house, be smart enough to understand basic communication and most important of all, be really fast at killing and really good at escaping. > > > Finding signs? No issue. Understand basic communication? I wouldn't say communication (especially not vocal), but it can understand signs and remember situations. Kill someone fast? Depends a bit, but since they can [overpower sharks](https://m.youtube.com/watch?v=Q36_8s5z6S8) and humans alike, I see no reason why it couldn't learn how to quickly twist or break a neck, so not too crazy. Really good at escaping? Absolutely. Not only it can squirm inside places its potential pursuers could only dream to be able to access, it's ability to change color and texture can make it a challenge to see them in the first place (also many octopuses have poisonous saliva, with the blue ringed octopus being one of the most venomous animals in in the world, so with some bioengineering we can give it that weapon too). > > run away after a successful kill, even if injured, that's better. > > > Many octopuses can heal entire arms in case they're lost (and at times will rip it off themselves in mating season), so clearly doable so long as there are enough arms left. > > An animal which can ignore pain and still run is preferred > > > They can loose arms and escape and they can feel pain, it already happens in nature. > > The animal should try to escape without being followed, if people are following it, it should be smart enough to not return to it's master until it is safe to do so. > > > This might be assured with some bioengineering, but given octopuses already have prey behavior and will camouflage and stay on low profile when chased by predators, it's clearly not a stretch (though I'd say den rather than master, as octopuses aren't quite social, but given that octopuses seem to have spatial memory it can likely avoid it's meeting point until it's safe). > > If possible, everyone should believe the animal is a demon sent from hell to punish sinners and when it disappears they will just think it went back to Satan. > > > Well they look more like cthulhu than Satan. But since Chapodiphobia (fear of octopuses) already exists, I'm pretty sure such an assassin can easily leave people (and especially Japanese schoolgirls) terrified. To summing it up, we have an animal that, at least in a way, can already do a variation of most of what you need it to, is considered to be extremely intelligent (one of the most intelligent invertebrates, which is still impressive despite what it's competing against), already capable of briefly leaving the water (some species are adapted to crawl around on land for short periods), can [climb walls](http://galleries.neaq.org/2016/05/turf-and-tentacles-preventing-escape.html#:%7E:text=The%20octopus%20can%20taste%20and,climb%20over%20an%20exhibit%20wall) in some cases, if the surface is smooth enough to allow for the use of their suction pads (they're not capable of doing it indefinitely, but they're still strong enough to carry their 182 kg bodies vertically), [have apparently preemptively killed sharks under fear of being attacked](https://www.nationalgeographic.com/news/2015/06/150610-octopus-mollusk-marine-biology-aquarium-animal-behavior-ngbooktalk/), are incredibly curious and are capable of learning by watching others (which is more of a big deal than it might sound). So, with some adaptations to allow these animals to breathe and survive on land (maybe through a buffed up version of lungfish so that they don't completely loose their water breathing capabilities) and a boosting of their circulatory system to allow for a more active creature, as well as some boosting of their intellect and some modifications to the beak so that it's closer to a [Humboldt squid's](https://www.discovermagazine.com/planet-earth/a-squids-beak-is-a-marvel-of-biological-engineering) and maybe boost up its poisonous saliva to be as lethal as its blue ringed cousin's, we could essentially have a creature that, despite clearly sticking out like a sore thumb and not being the fastest one, is capable of adapting to situations, has incredible camouflage (let's hope the targets aren't fans of smooth surfaces though), can overpower a human, can fit into very small crevices and essentially disappear, could potentially recognize a target and look for the best strategy to attack and can remember about their surroundings, facilitating its escape. Note:while I know octopuses aren't the smartest ones around and are clearly not adapted to living on land, I do believe they're one of the best fits for the "silent but deadly, hard to contain, cunning assassin" stereotype after us. The ideal scenario here would be to simply grant it a human's intelligence to maximize its effectiveness. [Answer] Mosquitoes would do admirably. All you need to do is mark the target with mosquito attractant. Mosquitoes are the vectors for all sorts of lethal diseases, of which malaria is just the best-known. This is what makes them the deadliest creatures in the world. Specially-developed assassin mosquitoes could carry a cocktail of existing diseases, or something new and more dangerous. Mosquitoes are expendable and so return to master is not an issue. Malaria deaths were traditionally believed to be caused by evil spirits or foul emanations (mal aria - bad air) so it fits your requirements exactly. [Answer] A poisonous or venomous snake? Your description sounds like a snake. And it can be used as an assassination method as you describe, and Hannibal Barca kinda did use it to enemy ship. And it's quite common in my country when snakes hide inside the house, even I got visited by two snakes last month, and even if you have a dog or cat to protect you, they are more likely to die; either they get bitten themselves, or ingest the poison, or the venom goes through the wound when they bite the snake (we dont have veterinarians here). It cost me generations of my dogs, to the point where my monkey is better as a watchdog or alarm (I miss her, those two snakes came not long after my monkey was released back to the forest, and the recent one almost bit me in the leg) than my current dog which does nothing and just plays with his rock, but which lives longer compared to his predecessor, so natural selection I guess. They can easily hide and ambush when the victim does not expect it, such as inside the shoes, or while sleeping and they get bitten; and they are quite slippery or agile and pretty fast. I advise you to put more than one though, and don't use the warning type or one that makes sound such as rattlesnake. I can understand why explosive is not used in assassination, because that is just unnatural and too obvious, and makes a loud noise so a neighbor could wake up or notice, which is bad for assassination but works well for terror. Arson can work well enough without causing suspicion, but it won't work well for animal on fire since it's not natural too so it can cause suspicion. I am not sure about how to control it, but maybe smell can do (but I don't know what kind of smell or chemical for it), and during winter they are more likely to hide inside warm clothing, and someone will probably need to wear that during winter..... [Answer] ## A [cyborg beetle](https://youtu.be/tgLjhT7S15U) Electric signals can be used to controll the movement of the insect. Add a small camera and a bit of software. Something like this: ``` import flight_patterns import target_pictures while active == True: flight_patterns.outside() if visual_input == target_pictures.target_structure: flight_patterns.find_entry() if environment == inside_building: flight_patterns.search_structure() if visual_input == target_pictures.target_face #alternatively target_ethnicity fly to center of target_pictures.target_face shaped_explosive_trigger = True ``` This is orders of magnitude more straightforward than your training idea. Additionally you can deployed swarms of these things, either to make sure someone really gets killed, or to cull a certain ethic or political group. Social media is a great source for target pictures and reasons to target people. You don't even need to search for targets yourself. Just train a maschine learning algorithm to pick pictures of everyone who attended say, a pride march or a KKK rally. The Netflix show [Black Mirror](https://en.m.wikipedia.org/wiki/List_of_Black_Mirror_episodes) did something similar in the episode "Hated in the Nation. They used robotic bees, but cyborg [synsects](https://www.orionsarm.com/eg-article/48114cd37719c) take advantage of the fuel and propulsion system insects provide. [Answer] There are some high-trainable killer-animals: * Bears - top of the list. They are smart. They are fast. They are deadly. Unarmed person can do nothing to survive bear. They feel no pain in battle and can fight for hours being deadly wounded. But there are some problems. They are not a "ninja-style" and hard to control. Deploying killer-bears is quite a noticeable operation.They are very cowardly (Russian's proverb for soiling pants is "bear's disease"). And this bears would also be super-dangerous for it's own masters * Dogs - are the most used killer-animals. When they are in a pack, dogs can target and kill ignoring almost any damage. In many countries execution with dogs was a routine. The only problem is that dogs are not good fighters. They are easy to harm and kill. Trained person with a stick or a whip can easily kill any dog one-on-one and keep a pack of 3-4 dogs away. * Horses - are quite dangerous animals. They have instincts for battle - wild horses herds kill each other for territory and hunt predators. And that is the reason why horses are so good as war-animals (actually the best war-animal of all times) - they do actively participate in a fight. So battle horse is already a trained killer-animal. But it is hard to imagine assassin-horse. Clatter of hooves is not for stealth. But for an open fight horse is quite capable to execute kill command and return back for a carrot. Ponies are even better killers - they are much more aggressive * Elephants - are smart, can lock on target and kill. They have a problem with rage and friend-or-foe recognition, but with some chemistry it can be controlled. But their size and weight is a huge problem! * Large cats of different kinds (mostly of cougar kind and size). Seems to be a perfect assassins. But they are really hard to control. And they like to "play" - kill someone small just for "fun". They also quite vulnerable and cowardly. And they "work" alone at most (lionesses are an exception). [Answer] You can always just implant a bomb instead of a microphone in an [acoustic kitty](https://en.wikipedia.org/wiki/Acoustic_Kitty) or [anti-tank dogs](https://en.wikipedia.org/wiki/Anti-tank_dog) or use [military dolphins](https://www.businessinsider.com/the-us-navys-combat-dolphins-are-serious-military-assets-2015-3) for aquatic operations. There are also air borne options with [pigeon guided missiles](https://en.wikipedia.org/wiki/Project_Pigeon) and [incendiary bats](https://en.wikipedia.org/wiki/Bat_bomb) These aren't exactly what you asked for but I think they provide interesting thought fodder [Answer] Something like the indoraptor from Jurassic Park. if you are going to bring back extinct animals then obviously you can reengineer them. It was fairly intelligent and trainable with a targeting laser as seen in the movie. Training it to not eat everyone in sight may be a bit of a problem. It seems fairly tough but not bulletproof though. Then again what creature is bulletproof. Tranq darts don't seem to effective against it as well. [Answer] What about birds? Hawks, eagles, and other raptors have wickedly sharp beaks and talons and are already used for hunting. Crows are quite intelligent, have excellent facial recognition, clever enough to use simple tools, and will act in a flock to harass larger creatures like the aforementioned raptors. It does not seem too terribly farfetched to me to breed/train a flock of birds that will both recognize targets when they see them and swarm/dive/peck until the target is dead. I mean, it does seem a little farfetched, but less farfetched than anything else that's been mentioned so far. It seems to meet all or most of your requirements: Targeted killings -- check, provided that you have images of the targets available. Smart enough to find their victims -- check. Most birds can see quite well, over long distances, and a flock of birds even more so. If the flock is in the right general location, and the target goes outside, the flock will probably find him. I'm not sure if you could realistically train birds to spy through windows, but it's not like it'd be particularly unbelievable. Fast at killing/good at escaping/will flee if injured -- check, at least when viewed as the flock as a whole. Individual birds aren't so good at fleeing when injured, especially if the damage is to their wings. Escape without being followed -- yes and no. On one hand, training them to take a roundabout path is probably difficult, but on the other they can easily outdistance any ground-based pursuit. Stealthy enough to avoid being tracked down -- check and double-check. It's not like a bird flying through the air leaves much of a trail to follow. Everyone believes it's a demon -- check. Honestly, if a flock of birds started swarming and murdering people, I bet there are plenty of people today who would blame the supernatural even if the attack were caught on camera. It's just not a thing that birds do naturally. If for narrative reasons you want to go with a single creature rather than an entire flock, I'd suggest a large eagle. They're fast (Wikipedia has max. horizontal speed at 80 mph and max. diving speed at 200 mph for a golden eagle), strong (for a bird), have good eyesight, and their talons are vicious enough that their handlers wear thick leather padding to prevent the bird from accidentally ripping their arm to shreds. Birds aren't so good at taking damage, but if you move fast enough, hit hard enough, and come at your target from literally out of the blue, that might not matter. I'm not sure whether eagles have the same facial recognition abilities that crows do, but other than that you seem good to go. [Answer] Not an animal, but robots, especially killer drones can be great at killing targets. They can be programmed to recognise faces, are very fast and lethal. They are not particularly expensive either and can be made in mass. I joined this community, just to post this answer :) [Answer] [![enter image description here](https://i.stack.imgur.com/eSo3y.jpg)](https://i.stack.imgur.com/eSo3y.jpg) Chimpanzees. Easely the better animals to be able to handle all the coded knowledge you propose. Also by their similarity with humans will learn faster and retain better what techniques to use to kill. They are strong. Forth but not least, chimpancees have a very friendly image, they are slender capable of discretion and ambush, role-playing and deceit typical skills for assassination missions. What I doubt very much is the animal will tolerate the pressure, maybe one particular animal could be suited among thousands unless you bread them selectively. <https://www.nytimes.com/2007/04/17/science/17chimp.html> [Answer] You examples limit the options greately. * the animal must be clever enough to understand complex orders. Your examples are far from simple. * it's not enough for the animal to be a killer. It has to know how to get to a guarded house, enter it, and leave. That requires patience and planning. There are basically only two options - humans and hominids. I would personally select orangutans. They are very smart and have strength that is much superior to humans (they can tear your hand off). However, training them will still be much harder than training a human. [Answer] A falcon. [Falcons](https://en.wikipedia.org/wiki/Falconry#Timeline) have a long history of being used to hunt creatures, and have been extensively bred already for hunting. They'd make excellent assassins. To make them more lethal, you could add diseases to their beaks and claws which is fatal to humans but not falcons, so that a scratch from them would lead to death. This is a natural and normal thing, for animal attacks to give you diseases. Rather than training them to kill based on commands (which is gonna be hard for any animal) you can train multiple falcons with particular triggers. One could be trained to attack anyone wearing a colour (like purple for nobility) one could be trained to go after scents, one could be trained to attack everyone in a building, another trained to kill people of a particular gender. Assassins which have more types of falcon would be better paid, as they could slay a wider variety of targets. They already attack on sight, so you can just leave an object which makes the smell of a mating falcon nearby to draw them in. They get spooked really easily, so they'll run away pretty quickly once the humans start getting agitated. [Answer] So, without using advanced genetic engineering, robots (or some variation), or humans, I think there is one animal that really fits the bill here. Dogs Yeah, not super original I know, but hear me out. So, let’s go point by point shall we! * Smart enough to know who to kill: Easy. Dogs have been trained to un-alive specific people since domestic dogs have been a thing. They’ve been used reliably in war, policing, and guarding for literally thousands of years, and are smart enough to hunt alongside humans without stealing the kill. * Smart enough to find marked victims: Oh yeah, no problem here either. Dogs can be trained to do almost anything, including attack someone marked with a specific scent, or when they hear a specific tone. Combine that with an unbelievable sense of smell (watch the bloodhound Mythbusters episode) and very sensitive ears, they will have no problem finding marked prey. * Trained to understand simple kill commands: Go watch a dog show and that can give you a pretty good idea of how well dogs can be trained. Dogs can understand many human words without training, can be trained to recognize thousands more, and can determine intent by tone, body language, and facial expression. Being trained to understand kill commands is easy. Going after specific people will take a bit more work, but dogs are smart, like scary smart. Seriously, I’ve owned dogs my whole life and several of them have been unbelievably intelligent. In one case I had an old dog whose teeth had gotten pretty flat, so when a dog growled at us she decided it would be easier to pin the other dog to the bed of the stream we were standing in and try to *drown it.* That’s more than simple defense that’s creative homicide. That’s human smart. * Fast at killing: Wolves have a bite force of around 1200 lbs, that’s over 5,000 Newtons. Granted, domestic dogs are much more subdued, but the American Bandogge and Kangal breeds have bite forces above 740 lbs. Meanwhile, 5 lbs can collapse a throat. In addition to this fearsome bite, dogs are fast, really fast. Wolves top out around 37 mph, coyotes at around 43 mph, and greyhounds take the gold at 45 mph. A human’s very best, and I mean very best, is about 28 mph. You can not outrun a dog. You cannot out agile a dog, and perhaps worst of all, you probably can’t outlast a dog either. Dogs are also very good at stealth, as in a pack of wolves can completely surround you and you might never know until they attacked. In addition, grey wolves can hit 175 lbs, and the heaviest dog ever (a mastiff) was over 340 lbs! Lastly, dogs are pack animals, and almost nothing in the animal kingdom can take on a pack of wolves/dogs. Along the they are dangerous, but together they are a coordinated killing machine that would make lots of special operations teams jealous. * Escape: Fast, quiet, and intelligent, escaping is not much of a problem. For example, if you have a Labrador Retriever, it is recommended that you have a fence that is at more than 6 feet tall, 3 feet in the ground, cannot be climbed, and has locks so that the door to the fence cannot be opened because they can open doors. Seriously, trained dogs make the raptors from Jurassic Park look tame in comparison. To tie this all up, dogs are fiercely loyal to their owners, and can be bred to come in all shapes, sizes, builds, colors, and can be bred for a huge number of jobs. Seriously, mastiffs were bred to kill bulls for crying out loud. If you want a breed recommendation for something like this, something like a Rottweiler/Shepherd/Chow mix would do nicely. Rottweiler for size and a 375 lbs bite force, Shepherd for agility, intelligence, and ease of training, and Chow because of their aggressiveness, single mindedness, and toughness. Of course, that’s just one possible example, breed something more greyhound like for blistering speed, or more mastiff like for absolute brute strength. Which is the final advantage for using dogs for this, you can literally tailor make your perfect assassin dogs by nothing more than selective breeding, a process which doesn’t take long thanks to the fact that dogs are fully mature at 2 years old. This has been a message from the Coalition For Being Nice To Dogs Because They Are Still Apex Predators Capable Of Killing You (and also because they are wonderful creatures), also known as CFBNTDBTASAPCOKY(aabtawc). Thank you [Answer] Since this includes biology and creature-design, why not use an uplifted, genetically engineered animal? With sophisticated enough knowledge of bioengineering, it will be possible to A) create an intelligent creature that can and will understand commands, B) escape even if injured or in pain and B) likely escape unnoticed. Let's expand on the octopus answer; scientists have made cells capable of doing simple computations (see <https://news.mit.edu/2016/biological-circuit-cells-remember-respond-stimuli-0721>), and assuming this cult/organization/whatever it is can do better, this octopus will likely be a biological supercomputer. Since this means that the organization has knowledge of how brain structure works, they could then make these octopi perfectly obedient, instinctive killers. If that's not plausible enough, a special implant that releases dopamine when the octopus follows orders will work wonders (I say special because it'll need to be flexible or it'll impair the octopus's otherwise amazing flexibility). Furthermore, with the right modifications, you can make creatures that look like Chthulhu. Toss in some octopus, some bat, and some chimp to your vat of genetic material and you have a less flexible and agile creature that will nevertheless be incredibly strong (overpowering targets with ease), capable of flight, and capable of wielding tools like a sniper gun. If little Chthulhus are discovered killing people with human tools, A) that's going to make people think that eldritch horrors might, just might be real, B) that's going to freak the living daylights out of people and C) no one, and I mean no one in their right mind will risk assassination by Chthulhu. ]
[Question] [ So, in my world, the human’s UEN military mainly uses conventional firearms as their primary infantry weapons. However, they do have one non-ballistic weapon: the heavy, shoulder mounted M/DEW-96C Laser Cannon- this device can fire devastating pulses of high energy laser beams at targets, and is mainly used to destroy enemy tanks, vehicles, aircraft, and even buildings. Here’s something I thought of though: since the M96 is so effective and extremely powerful, readers might wonder “Why doesn’t the UEN simply miniaturize these devices and deploy laser weapons everywhere?”. The technology for handheld laser rifles/guns exists in my setting, so my question is, how do I explain why humans don’t use it? [Answer] Technological Limitations: Though theoretically creating one of these big guns is possible there are various technical challenges that block the way, one of the main problems is Energy, These lasers require a whole lot of energy, which is easily available on a tank, but carrying 2 huge battery packs along with a big gun for a single shot in the battlefield is just not feasible. Another challenge is heat dissipation, These lasers generate a lot of heat, if you try to put it on someone's shoulder and fire it, the user himself will get a burn from its heat, even on a tank they are used in a remote control fashion from inside the safety of the tank. Money: These lasers are just so damn expensive to provide them to individual soldiers. Moral Ground: These weapons are just inhumane, savage, and ruthless. A soldier who is tasked to protect his country from enemies, may not want to become a monster and lose his mind over it after using a handheld version of this thing. Using it from a tank with a remote control and firing it from your own shoulder is quite different. [Answer] The Law of Non-Linearity. Suppose a soldier can carry a 20kg laser cannon that can explode an enemy tank. Since we have the technology for laser rifles, we can produce a smaller 2kg weapon with (all other features being the same) only 10% the power of the cannon (still much more powerful than bullets) and equip our footsoldiers with those, for shooting other footsoldiers. Right? Wrong. There is a temptation to assume everything scales linearly. But in practice it is equally believable this doesn't happen. For example the smaller weapon might only be 1% as powerful as the cannon, or suffers from lower firing rate, heavier ammunition, overheating et cetera. This requires no justification, and leads to small laser weapons being strictly worse than conventional ones. For some real world examples consider (a) the Javelin Missile: [![enter image description here](https://i.stack.imgur.com/9XXfbl.jpg)](https://i.stack.imgur.com/9XXfbl.jpg) This is a big heavy handheld weapon that can be used to destroy tanks. However you will find that soldiers do not carry scaled-down javelin missiles for anti-personnel. The technology simply doesn't scale down well. (b) Nuclear bombs. Nuclear bombs make big explosions relative to the missile size. However the technology does not scale down to create a nuclear grenade the size of a tic-tac. [Answer] The M96 is already miniaturised Firing lasers is easy. Firing powerful lasers is difficult. To get a laser usable on the battlefield you need a lot of energy and (miniature) technology. The smaller versions simply don't have the impact you want. Heat is likely to spread on the target, not doing enough damage. Lasers can have a physical impact with some interesting mechanics, but also this is impractical on smaller sizes. It still needs insane amounts of energy, can lose potency in an atmosphere depending on the kind of laser and might not fire fast enough (you don't take a slow firing weapon into many engagements), or require longer exposure times on the target, to do the right amount of damage. A gun with propellant is then much more effective, easy to control and can be used for longer durations. Further miniaturisation is ineffective Further problems of miniaturisation is that it only helps so far. Making things smaller helps for many electronics and such to reduce the amount of energy required. The laser however has a fixed amount of energy you might want to send downrange. The energy output would plummet if used in smaller sizes, making them not as effective. If you need to charge or can only fire intermittently, normal guns will again be much more effective. [Answer] Covered in mud test: Can your laser rifle still fire after being rained on for hours, dropped in the mud, then used to bash open a door? A regular rifle is fine. This is fine for an anti-tank laser, because it won't be abused in the same manner. Ammo cost test: Does your laser rifle cost actual money to fire? A rifle bullet costs cents. It's fine if an anti-tank laser costs actual money to fire. Ammo quantity test: Can your laser rifle hold 30 rounds in a device the size and weight of a magazine? It's fine if an anti-tank laser can only carry a single shot. Weight test: Is your laser weapon lighter than a rifle? It's fine if an anti-tank laser needs two people to carry. Rate of fire test: Can your laser weapon continuously fire over minutes? One of the reasons caseless ammo never got off the ground is that the ammo case carries a significant amount of heat away from the gun. It's fine if an anti-tank laser can only fire once every 30 seconds. Combined, the prototype laser weapon system didn't like being covered in mud, cost $100 per shot because of the disposable batteries, could only hold 12 shots, needed recalibration every few shots, melted if you fired it too fast, weighed 30 pounds, and one of the lenses cracked when it was dropped. In the end, a rifle is a better rifle than a laser is. (It might still be a pretty good sniper rifle, though. This is also a specialty device where a laser has some important benefits: silent firing, lack of interaction with wind, and pure range.) [Answer] # The power source is too large: The power source for your laser weapon needs to output some ginormous amount of energy, in a very short pulse. The humans do not have any form of power storage that is good enough for it, instead what they use is a very tiny fusion pulse generator. One charge, throwaway. Must be used instantaneously, cannot be stored or distributed. And "tiny" being "not less than a cubic foot, and massing 20kg" If you are going to be lugging a suitcase sized power supply around at minimum, you might as well couple it with a laser that actually uses that much power in one shot, hence the rather huge and overpowering scale of the M96. (Dropping buildings with a shoulder-fired weapon? that's Bad Ass ) The aliens have the tech to store power compactly, thus they can use much smaller, sensible infantry-scale laser weaponry. [Answer] It isn’t a laser, it is a long range induction heater Your weapon produces a rapidly alternating electric current linearly ahead of the laser. This lets you heat metal to near melting point. This will break vehicles, computers, and planes, but if shot at a soldier it will only disable the gun and maybe burn the soldier holding the gun. A person shot with the weapon would be unaffected since the induction heating only affects metals. Even if the weapon were smaller it would have to be aimed directly at the enemy gun, and wearing gloves would save users from burns from the weapon. Normal guns would be more effective and actually be lethal. While a miniaturized version might exist for police to disarm people, these weapons would be aimed by sharp shooters and only in certain situations. [Answer] ## Lasers Brightness vs Armor Effectiveness The US military has abandoned a number of research projects over the years into the use of plasma and laser based small arms because of things like power sources and maximum energy outputs, but in recent years, those problems have mostly been solved here in the real world. So why are we not seeing our armed forces equipped with laser weapons yet? Well one of the biggest remaining hurdles is that they reflect and scatter so much light that they blind anyone standing near by. So, if you were to arm a squad with laser rifles, every time you shoot someone, everyone in the area would be blinded... this is especially bad for the people using the laser rifles because most of the people on the battlefield looking at the flash of light when it happens would be friendly forces leaving your whole squad vulnerable every time you go to shoot someone. If you think of it like this, the alibeto of your average military uniform is about 0.3 meaning that 30% of the light that hits it is reflected. The lowest power laser theoretically capable of burning a person faster than they can get out of the way is ~1kw. This means that you are looking at a spontaneous flash of light equivalent to a 300w flash bulb. To put this in perspective, the flash bulbs used by most professional photography cameras are about 70-400w. So, at the very low end of anti-personnel lasers, the flashback would be momentarily blinding, shooting up an enemy position would be like having a line of paparazzi flashing cameras back in your face... but this is just for weapons of the power level required mow down unarmed civilians. If the development of laser technology stopped here, then you could just have your soldiers put on some goggles that filter out the wavelength of the lasers and then they could go wreak some havoc by blinding and disorienting their enemies while they shoot them up. The problem comes in when armor and weapon developers start trying to one up each other. Whenever you introduce a ubiquitous weapon technology into a setting you need to assume that the opposition is already aware of it and would try to find a way to counter it. This brings me to what anti-laser armor would look like. Through the use of dielectric mirror based armor, enemy tanks, aircraft, and soldiers could adapt by using anti-laser armor that reflects at ~99.9999% of a laser, as long as they know the wavelength the laser is operating at. This means that laser designers would have to design their weapons around firing a lot of converging lasers of different frequencies (which they already should be doing anyway to reduce thermal blooming). That said, dielectric mirror are no good against multi-spectral attacks. The most reflective known broadspectrum materials can only reflect 99.9% of light, but as comments point out, even this is much more ideal than you can expect under battlefield conditions. In terms of practical reflective armors, about 80-90% is probably the best you can expect under combat conditions... but this is still enough to be a problem. This means that if enemy soldiers simply start to use bright white uniforms, they could make themselves pretty hard to kill at just 1kw. So, HEL designers would need to scale up to 3.5-7kw to burn heat resistant white clothing. but in doing so, you increase the total reflected light by somewhere between 933-2100%. At these intensities, the reflected light would be enough to risk long term damage to the eyes or anyone not wearing proper protective gear including innocent bystanders. But reflective armor is just one way to increase resistance to lasers. There are other technologies like thermal ablative insulation which can make it incredibly hard to burn through something with a laser. The more you layer known defensive technologies, the more powerful lasers will need to become to cut through them. By the time laser armor starts to mature, you could be looking at needing laser rifles hundreds of times as powerful as those basic 1kw lasers if you want to actually do any damage. If we pretend that portable laser technology could be escalated to meet the challenge, you will now be looking at amounts of reflected light equivalent to thousands of high end camera flashes going off in your face across a broad spectrum of light frequencies. As nick012000 pointed out in comments, this is VERY bad for any innocent civilians anywhere near the battlefield who happens to not be wearing some very good protective eye gear. Furthermore, because it is a broad spectrum reflection, you can no longer use simple filtered visors anymore. Your only real choices here are blackout goggles that momentarily shut out all light when a laser hits something (blinding you but not permanently), or to have a closed faced helmet that uses a camera and internal display that does not get bright enough to ever hurt your eyes, even in white out situations. Any way you add it up, using HELs able to deal with armored opponents would simply light up the battlefield too much to actually have a battle, and the collateral to civilians would make the weapons pointless for 95% of operations where ground troops would otherwise be the preferred tactic of choice. So why use M/DEW-96C Laser Cannons? For the M/DEW-96C Laser Cannon, this is less of an issue. Although it is a higher energy laser (probably in the 10s-100s megawatt range if you want to kill laser armored vehicles), how you use it is different. Whenever you need to blow up a tank or a building, your whole squad other than the person attacking already has to take cover so they don't get taken out by debris. So everyone in your squad also having to shield their eyes as the one guy takes the shot is a reasonable additional action. And for the person attacking, they only need to make one shot; so, they could have some kind of blackout goggles so that your Laser Cannon Troopers eyes don't get seared out of his face, and not be left at a huge disadvantage not being able to make an immediate follow up shot like you would expect to want form an anti-personal gun. Also, when you need to blow up a tank, innocent bystanders are generally already much less of a concern than when performing more surgical infantry operations. [Answer] They are not better than normal guns Ever watch Star Wars and think that a fully automatic weapon or a grenade could easily overcome those Laser-deflecting Jedi? The point is that while a large Laser weapon would be great for defeating large machines (maybe they ignite the fuel or destroy the electrical systems or something) without having to lob a big clumsy explosive, a small one is really no better (or maybe even worse) than a simple AK-47 against enemy people. It's been tried, soldiers haven't liked it and complained, and the better, easier, cheaper solution turned out to be normal machine guns. [Answer] Just make them worse than ordinary guns. Why would you have laser guns? * Powerful "rocket" laser: big and heavy with slow rate of fire and wrecks a tank/plane/bunker. Great weapon. * Ordinary gun: small and nimble and shoots fast and kills a person. Great weapon. * Anti-vehicle gun: semi-heavy, slow rate of fire, destroys a car. Reasonable weapon - way less use of that. * Laser rifle: anti-vehicle gun that gives your position to everyone. Poor weapon. [Answer] ## Risk. If you fire a laser weapon and hit a shiny doorknob that doorknob will almost instantly burn and lose its shininess. Almost instantly. The laser beam/pulse will spread around the room in an instant, this might not damage bodyarmor enough but it will blind anyone hit by the beam in the eyes. The problem is that there are a lot of shiny objects to be found in the human world and an enemy will likely try to use it by placing tons of shiny things everywhere. Its just too risky. ## Treaties and conventions. Some weapons and ammo types are banned because they cause unecessary damage and suffering when killing (or failing to kill). This is why incendiary small-arms ammo isnt really used by most of the world anymore. Your lasers are banned from small-arms weapons for this reason. ## Heat generation. Your infantry carried anti-tank lasers are used much more sparingly. You keep having to move, find a good position, fire a few rounds and reposition. This gives the weapon a lot of time to bleed off its heat generation. A small-arms would be used much more often and continuous. This heat would quickly start burning the users. ## Capacitor charging takes time. The capacitors take time to charge after each shot. This isn't a problem for a large anti-tank weapon that you won't be firing on full-auto all the time, but for a small-arms that drop in fire rate is a problem. [Answer] # Treaties We can create biological and chemical weapons, and neutron bombs, all of which are likely to be far more devastating than any flavor of "big gun" (except space-based mass drivers). Why don't we? Because it's universally acknowledged1 that to do so is extremely not-cool. And the last time the most-powerful countries on the planet got together to draw up international rules-of-the-road, they were trying to be morally enlightened, and so they either banned those things immediately or created the legal framework that would inevitably do so. So, the reason militaries don't miniaturize the mega-laser is because it is illegal to even talk about having once imagined what it would be like to see the blueprints for a hand-held version. The ban is enforced partially through restricting & monitoring the supply chain. Just as with nuclear weapons, there is probably an international agency whose mission it is to detect and prevent proliferation. And the mega-laser is beyond the technical abilities of everyone except the world's leading experts to even design, so there's no worry about non-state actors creating their own... yet. --- 1 Acknowledged by everyone who is not evil. Everyone who does not is evil, trivially by definition, because a person who refuses to put away doomsday weapons because he intends to use them himself is evil. [Answer] Special weapons are often kept for special use, because the popularization of them has or would create effective counter measures. Let's assume everyone had small arms laser weapons in your world. I chuck down a grenade that creates a cloud of reflective chaff. Your laser weapons are now useless, b/c the chaff would scatter the beams everywhere. This could create collateral damage as the beams split and diffuse everywhere, possibly injuring innocent bystanders or friendlies. Altnernatively... I create mirror-like armor that reflects & refracts the laser light, making it harmless. Just like a fresnel lens can consolidate light into a focused beam, a person could come up with a material that does the opposite, taking direct laser light and scattering it until it's harmless. Or, reflecting it, which, again, would possibly cause collateral damage. Standard fire arms can punch right through this stuff. Hence, standard firearms are still used. The big bad shoulder-mounted laser would be called in as a special-purpose weapon in situations where they know there's no counter-measures. [Answer] ## Know-how ... or rather, don't-know-how. You say "humans" don't use it, implying that others do. The three reasons for this are that you can't, you don't want to, or you're still building it. It can be done, there's a reason they'd want to ... so they're still building a safe handheld version. The miniaturised power supply might be toxic, the reflected light might be harmful if you're outside an armoured shell, or there might be the modern problem of not knowing how to build a miniaturised energy store. [Answer] /the human’s UEN military/ Which implies there are other than humans out there. The laser cannon is not a human weapon. These laser cannons are different from anything else in the human arsenal. The humans are happy to have acquired some. Supporting and maintaining these weapons is very much an art form. The "manual" (if it is a manual) has been translated in a few different ways and people subscribe to their favorite version. It is a fine weapon but it is not clear that its makers intended this thing to be a weapon. It can clearly do more than blow up tanks. The humans who use this thing often glue caps and put tape on top of some areas of the laser cannon, to avoid inadvertently activating these other functions. The nonhumans who devised these laser cannon are not very approachable as regards proposed improvements, or even questions about the device. Reverse engineering the cannon has not been successful either, at least as regards duplicating the machine. Fortunately the ones they have are very durable. The space marines understand the importance of bringing these laser cannons back from any expedition. [Answer] Lack of stealth If you fire a ballistics weapon it is relatively hard to pinpoint from where are you shooting. You would need to precisely track the bullet and then back-propagate this path to the shouter. If you want to track a laser gun user you just have to take a photo with laser-activated camera. When you fire a laser you makes yourself a easy target for every single artillery, drone, smart mine, automatic turret, sniper or loitering munition is the area. Such a risk is acceptable if you want to destroy a tank, not for a infantryman main weapon. Long startup period. Before you fire a M/DEW-96C Laser Cannon you need to start the charge up, then wait a 5 second, then fire in 10 second before you run out of the cooling fluid. This is acceptable when you shot at an airplane ( many MANPADS have similar limitations. ) or a tank. Having to wait even a second before you can shout someone or running out of cooling flood after a 10 minutes of combat is unacceptable for a rifle. [Answer] It's a painter, not a laser. Strong lasers are tough technology...that's why they are not employed in large scales from current militaries. What you have on the tanks is not a laser that can actually destroy stuff. It is just a laser that is visible from space. And after that.... > > a multi-gigawatt orbital ion cannon fires on the target, neutralizing > any combatants in the vicinity > > > Taking the tank's laser and scaling down will result in a laser that just isn't viewable from the orbital weapon. I guess this answer is just an implementation of the one by @Daron . [Answer] One big reason not to deploy handheld lasers is *aiming. Stand about 3 steps away from a wall and hold a laser pointer at arm's length. Hold the laser's dot steady on a specific spot on the wall. Pretty easy, right? Now, repeat the experiment but aim at the wall at the far end of a long hallway. I don't care how strong or coordinated you are, that dot will be wobbling all over the place with even the slightest* movement of your arm. Just imagine how bad it would be when aiming at a target 200 meters away. There's no practical way you could risk using a weapon like that in combat. There's far too much risk of hitting unintentional targets. Plus, as your laser dot moves around, the energy it delivers is spread out instead of burning your target. Lasers are precise, but they're far too difficult to fire accurately by hand. A bulky, shoulder-mounted laser is something completely different. When the operator kneels to fire it, their body forms a stable platform that minimizes movement. The unit itself has vibration dampeners and gyroscopes to keep the laser emitter still even when the operator moves slightly. It also has a computerized fire control system that will only allow the laser to energize when movement is minimal and the sensor optics are confident that the shot will hit the location under the operator's crosshairs (the machines used in laser eye surgery already do this). All that technology is needed to make these lasers controllable, but there's no way you could cram all that in a hand-held form factor. Vibration dampening typically involves adding mass/counterweights and shock absorbers of some sort, which will necessarily take up more space than you could comfortably hold in your hand (consider the [Steadicam](https://en.wikipedia.org/wiki/Steadicam) mount for cameras, for example). Your shoulder-mounted unit is simply as small as you are able to get while maintaining a usable level of accuracy. Note that traditional weapons don't have this problem because they fire discrete rounds, each gyroscopically stabilized to stay on course after leaving the weapon. Accuracy must only be maintained for as long as it takes to pull the trigger. A laser delivers energy over time, thus must maintain its aim throughout the entire duration of the laser pulse (which might be several seconds long). [Answer] ## Control of Potential WMD: The laser weapons are wonderful, but there's a catch. The lasers are reconfigurable to induce a [nuclear reaction](https://www.nature.com/news/2005/050822/full/050822-10.html#:%7E:text=Neutron%2Dfree%20reaction%20makes%20less%20radioactive%20waste.&text=Russian%20scientists%20have%20managed%20to,investigated%20to%20generate%20nuclear%20power.) in relatively low-grade fissionable materials. The government doesn't advertise this fact, and it would require a fair amount of know-how. But keeping track of thousands of laser cannons is challenging already. Now give every potential soldier a laser weapon, and watch the weapons slip into the wrong hands. The laser cannons are too useful to discard, but the risk gives military planners fits. Despite the huge potential for using laser rifles in battle, the powers-that-be simply can't run the risk of someone being a little too clever. [Answer] Some unobtainium is needed Aliens have successfully been able to miniaturize their lasers because in their home-planet there is abundance of some very particular radioactive isotope. Maybe their homeworld is far younger than Earth, so that there is still enough concentration of that isotope in nature (while on Earth and other worlds controlled by humans it has already decayed to almost zero). Without this isotope it is impossible to miniaturize the laser more than the size actually used by humans. Maybe it is possible to synthetize it by enrichment (like U-235), but in this case it would be too expensive to produce in the quantity needed to equip with laser weapons the human infantry. [Answer] RADIATION While the large laser tanks on the tanks... can produce and do a substantial amount of damage the tanks also offer the advantage of radiation shielding, allowing for it to be fired without doing substantial damage to the humans using the tanks. However, when the laser weapons scale down, on both sides such radiation protection is no longer available. The aliens who fire the handheld laser weapons don't take an issue with this as they are far more resistant to ionizing radiation, as are the flora and fauna from the planet they originate which means while they don't mind the laser weapons and neither does their flora and fauna of which they've transplanted into the environment, when used on humans it causes a bunch of nasty side effects and further causes extreme ecological damage to both earth-based biology and the host of biology on the planets they're fighting on. This is understandable,a thing which humans in the UEN regard as a bad thing, while the aliens they're fighting against don't seem to care much. Or maybe the human doesn't care either but doesn't like their highly trained soldiers getting sick, and they're highly valued and expensive mech's getting damaged. [Answer] Go the the Wiki page for "Laser Weapons", and scroll down to "Problems". The terms "Thermal Blooming", "Phased Array Issues" look promising. It also talks about size to power ratio as well as Guidence Issues. I would BS it all with words like Thermal Blooming and problems with the Phase-conjugate mirror which at a micro level causes overheating issues that lead to a massive reliability factor. It also might not be a power issue, but a mirror issue. You can't minaturize the mirror yet that is needed to make the guidence system work. Or on a minute level, the primary amplifier simply can't generate enough power to focus laser down big targets. Humans sure, but a bla bla bla reinfoced tank with bla bl bla armor. Forget about it! Or, it's not that you can't, but that it is unreliable and not worth the failure rate. Maybe they do miniturize it, and most fail, until your story needs it not to fail at at the all is lost moment. Maybe they can minaturize them down, but now it takes multiple lasers focused at just the right point to aplify the lower power output on a single target. (Could be a plot point) ]
[Question] [ Supposedly Adolf Hitler had in his possession a blueprint of a working atomic bomb. Its destructive power is estimated to be similar to or on par with "Fat Man" which was dropped on Nagasaki in 1945. With the bomb ready by April 1945, how could the Nazi leader use it to rewrite[1] WW2 and dominate Europe with the knowledge he already has? How could the Axis powers deploy the bomb assuming it is in the interest of Hitler to share the technology with his closest allies. Assuming in this case that America was fully occupied with revenge for Pearl Harbour. [1] change the outcome of war in favour of the Axis powers. [Answer] # Take Berlin Hostage. This wouldn't win the war, but it's a more interesting answer than "nowhere", and in line with Hitler's belief that he was fighting the [Götterdämmerung](https://en.wikipedia.org/wiki/G%C3%B6tterd%C3%A4mmerung). ## 1 April 1945: Germany Has Already Lost. The German situation on April 1st, 1945 was unsalvagable. Their army was in ruins. Their capacity to make up for losses done. All the men and material necessary to invade Berlin and end the war were already in place. And they were being attacked on two sides by multiple armies. There is no one place to strike. By April 1945 the war in Germany was over. The Germans faced overwhelming odds on all fronts. The Soviets had 2.5 million soldiers [ready to assault Berlin](https://en.wikipedia.org/wiki/Battle_of_Berlin) defended by only 750,000 under-equipped and worn out Germans. They were already over the Oder River and preparing for the final push. [![enter image description here](https://i.stack.imgur.com/AyoIG.png)](https://i.stack.imgur.com/AyoIG.png) In the West [Army Group B was surrounded in the Ruhr Pocket](https://en.wikipedia.org/wiki/Western_Allied_invasion_of_Germany#German_Army_Group_B_surrounded_in_the_Ruhr_pocket_.281_April.29) and the Germans had lost their industrial heartland. They had already crossed the Rhine and were driving east and south. The Western Allies voluntarily stopped at the Elbe River (the Soviets were promised Berlin) and turned south to prevent a possible Axis retreat to the Alps. [![enter image description here](https://i.stack.imgur.com/aYUpg.jpg)](https://i.stack.imgur.com/aYUpg.jpg) ## Attack the West? Maybe a port of supply like New York? The effect won't be felt for weeks. Maybe a capital like London or Washington DC? The political decisions had already been made, and the Allied high command was too flexible for a knockout blow like that. Maybe a port in Europe like Amsterdam or Rotterdam? The Western Allies now had many ports to choose from, and a good supplies built in. More to the point, attacking the Western Allies won't stop the Soviets, so any target in the West is right out. You have to strike the Soviets. But where? ## Moscow? Delay the Soviets, Surrender to the Allies? Striking Moscow seems the most logical. Soviet government was very centralized, and Stalin had a personal hand in many decisions. With the Supreme Soviet decapitated, the Soviet military and government would be in chaos. There's a slim chance this could lead to an anti-Stalinist uprising, or a civil war over control of the government. But more likely the hatred for the Germans and final victory being so close would at least delay this fight until after Berlin is taken. Moscow was also a major rail hub. Its loss would throw the already shaky Soviet logistics into further disarray. Even so, they had the men and material already poised to strike Berlin. Such a disruption would be too far back in the supply line to affect the war in the coming weeks. Still, if you have one throw of the dice this is it. If the Soviets proved unable to take Berlin the Western Allies would happily do it for them. At least the generals would be happy for the glory of the prize, the tends of thousands of soldiers who would die in the assault would not. For the Germans, they would find the Western Allies far more forgiving than the Soviets. ## How To Get The Bomb There? Or Anywhere? One problem: the Germans had no way to get a bomb to Moscow. Or New York. Or anywhere. A nuclear bomb in 1945 was an extremely heavy, bulky item. [Fat Man](https://en.wikipedia.org/wiki/Fat_Man) weighed 10,000 lbs. It required the largest, most powerful, and most advanced bomber in the world, the [B-29](https://en.wikipedia.org/wiki/B-29), to carry and drop it. Even then [it had to be modified](https://en.wikipedia.org/wiki/Silverplate) to carry the bomb. The Germans had nothing like the B-29. Even if they had a bomber, how could they make it thousands of miles through Allied dominated airspace? Put it on a [V-2 rocket](https://en.wikipedia.org/wiki/V-2_rocket)? Again, too large, too heavy. The V-2 had a warhead of just 1,000 lbs. ## Only One Bomb. Even if Hitler gave the plans for a working atomic bomb to, say, Japan, Japan would not be able to produce a bomb of their own. Neither would Germany. They'd have the one bomb, that's it. The problem is refining the nuclear material is extremely slow, expensive, complicated and energy intensive. And in 1945, nuclear bombs were extremely inefficient with this precious material. One of the aspects which is underappreciated about the Manhattan Project, and why it was so expensive and took so long, was the [production of enriched uranium or plutonium in the amounts needed for a nuclear bomb is extremely difficult](https://en.wikipedia.org/wiki/Manhattan_Project#Isotope_separation). So difficult and so important that the Manhattan Project set up TWO enormous facilities to produce it using two different methods. Neither Germany nor Japan had anything like the facilities to do this, nor the safe space for such a large and fragile facility. If we assume they can scrape together enough material for one bomb, we cannot assume they can make another. ## Berlin. With nowhere decisive to drop the bomb, and no way to get it there, Hitler would be left with one option: threaten to blow up Berlin. While the Soviets would probably be happy to see Berlin and everyone in it wiped off the map, they would not be so happy to see a million of their soldiers vaporized in the process. This would lead to a very awkward situation. If Hitler could convince the Allies he had a working bomb, he could retain control of Berlin while the Allies finished off the rest of his empire. The Allies would set up a blockade and Berlin would begin to starve. This stalemate would not last long. Eventually, someone sensible on his staff would assassinate Hitler. Someone not eager to see Berlin destroyed by atomic fire or starvation. Someone like [Albert Speer](https://en.wikipedia.org/wiki/Albert_Speer), Minister of Armaments and War Production, who famously [tried to salvage as much of Germany's infrastructure as possible](https://en.wikipedia.org/wiki/Albert_Speer#Fall_of_the_Reich) in the closing months of the war. [Answer] The answers already given illuminate the military aspect perfectly and nothing can be added to especially Schwern’s post. However, I see one more shot that Hitler could have and that is using the bomb as part of a plot to turn USA and Russia against each other. This assumes that Russian espionage already knows the Americans are working on a nuclear bomb, but they know nothing of Hitler’s. Or that he can let them find out about the Manhattan Project. With this preconditions met, feed the Russian military intelligence false information that the Allies intend to break their deal, take Berlin and in fact all of Germany for themselves, and then continue the war into Russia. Then throw the bomb on the largest concentration of Russian forces outside of Berlin that you can find. Everyone would assume it was an American bomb. The whole scheme might be believable to a paranoid Stalin. The Cold War had already started in 1945. On April 12th, Roosevelt would die and Truman distrusted Stalin, something I'm sure Stalin was aware of. If you can make Stalin seriously believe that the Allies have turned on him, there's a chance he will accept a German surrender, or even ignore the already practically defeated Germany, and march what's left of the Red Army to engage the Allies. At this point, a peace is a distinct possibility. WW2 was a struggle for power, the whole ideology stuff was just for propaganda. The USA had almost reached their goal of removing Europe from the list of superpowers, but with the Red Army advancing upon them, there is a serious risk that they would lose central Europe, which would be a devastating blow and make Russia so much more powerful. Reviving the good business connections the Nazis had enjoyed to American elites could see Germany joining the Allies in a fight against Russia. It's a long shot. Maybe not the best scenario. The main idea here is that with one bomb, you will not win WW2, no matter where you drop it. But combined with some subterfuge and trickery, maybe you can turn events around using the bomb only as a tool. [Answer] ## 1945 bomb isn't a superweapon Unlike the high-yield thermonuclear devices of the cold war, a 1945 nuke doesn't really give you any capabilities much beyond conventional weapons. A bomb like that gives you 10-20 kilotons of TNT equivalent, devastates a single location, and kills on the order of magnitude of 100 000 people. A raid of strategic bombers can drop kilotons of conventional bombs, achieve comparable or larger devastation, and kill a comparable amount of people - as has happened many times in WW2. Conventional strategic bombing in WW2 has done far, far more damage than the nuclear bombs; even if we look only at the case of Japan at the very end of war, the nukes were only a small part of the total damage. Being able to build a nuke isn't a war-changing event in WW2 - with the same enormous amount of resources as a Manhattan-like-project requires you can simply build more conventional bombers and bombs to achieve the same destruction in a conventional manner. Germany having nuclear knowledge wouldn't change the war outcome; USSR having nuclear knowledge wouldn't change the war outcome; and USA not having nuclear knowledge wouldn't change the war outcome. Even if some country had full knowledge of nukes, it doesn't mean that it's worth for them to spend the required resources to manufacture them, it's quite likely that they should and would keep their military production as-is anyway. [Answer] With only one bomb in his possession, Adolf Hitler actually has no chance to win the war. The only conceivable enemy who could be successfully "decapitated" by a single nuclear strike would be the USSR, since it was a highly centralized system and the sudden removal of Joseph Stalin, the Politbureau, the NKVD and the Stavka (Soviet military high command) would essentially cause the Soviet economy and war effort to grind to a halt. However, this would also mean the Germans would need to have some reliable means of delivering a nuclear weapon to Moscow. The British Empire was far more decentralized, so a strike on London would decapitate the Imperial War Cabinet, but the Dominions and the British Raj (Imperial India) would not be affected and certainly could continue to carry on the fight on their own. The United States would be damaged by a strike on Washington DC, but the American States would be in much the same situation as the British Empire, and American field commanders like MacArthur, Patton and Eisenhower had considerable autonomy, so could continue to carry out their last set of instructions from George C Marshall. And of course, unless you are going to say the United States isn't carrying out the Manhattan project, a Nazi nuclear attack is most likely going to be met by an atomic bomb attack on Berlin.... [Answer] There is no way that Nazis could drop an atomic bomb and end the war, especially with America building them. A nuke dropped by Germany anywhere would not have seen the stopping of war but the redoubling of efforts to build them and drop them which would have just lead to bombings all over. The reason it worked with Japan is because that was already a lost battle and it was a wake up call that they had lost. Germany's bomb would have been looked as a "look at what these evil people are willing to do, we need to fight fire with fire" [Answer] Strike Moscow under the guise of the US, or the US under the guise of the Russians. Make it look like one side didn't intend to stop with the Germans with a planted paper trail. This will at the very least turn a percentage of the Allied forces to distrust and hostility, and will certainly upset world politics in a climate where both nations already distrust each other. If you can capitalize on the distraction this causes, you can certainly turn the tide. Now that would not have won the Germans the war in 1945, but it could have worked in 1943. [Answer] This is probably just a wild sci-fi level thought, but here it goes: Use the bomb as an EMP Europe is not very big. I mean it is large, but it's not much larger than an American state. If one were to detonate a nuclear bomb in the atmosphere high up, it could deliver an emp. This would in turn destroy any airplanes and tanks. ]
[Question] [ On the world of Thirdrock, the humans there practise group marriage: one to three women marry one to three men, with a maximum of four people in the marriage (or occasionally five under rare and temporary circumstances), and at a minimum one male and one female. The men are not married to each other, and neither are the women married to each other, each is married to all the members of the opposite sex. The people of Thirdrock are extremely homophobic for the most part. Homosexuality is illegal, as is failing to report it if it is observed. Therefore, no-one wants to admit that it occurs, or be seen to condone it in any way... and that includes designing bedroom furniture. On Earth, where most marriages/partnerships are between two people, we have double beds. However, I was wondering about beds for people on Thirdrock... how might they be designed to cater for the variable numbers of males and females in the marriage, up to five people total, and with at minimum one male and one female? Any design that would appear to discourage nocturnal homosexual activity would be preferred if it is at all possible. The people of Thirdrock have an approximately mid-1940's tech level, and in some ways, a rather Victorian-era morality. Edit: Group sex is permitted and encouraged but is ultimately optional. [Answer] Conjugal Visit Model: The Romans believed it was bad for marriage for a husband and wife to sleep in the same bed, preferably not even in the same room. If you've watched any TV shows about plural marriage, they all have different houses. Given a plural marriage of multiple men and multiple women, I think sleep would likely be apart. People would sleep in their own rooms, or in dorm-like conditions depending on economics and social practices. That being said, until recently, it was assumed no impropriety was involved in sleep, and visitors to the White House would sometimes share a bed with the president (and no one assumed anything inappropriate). Who you slept with for much of history had more to do with the temperature than sex. In Minnesota, I live near Fort Snelling, where each soldier shared a tiny bed with another soldier - but if you've gone through a Minnesota winter in a poorly heated building, you would too. So whatever your sleeping arrangements, I think you'd be more likely to have a sex room for such things than a bedroom. There would probably be a schedule (if I know relationships, run by the women) for who was 'sleeping' with who when (they would probably use a different euphemism). At your option, it could even be randomized like the Kali cultists of India, where bras were supposed to have been dumped in a pile and drawn like cards from a deck (I'm not so much a historian to judge the accuracy of that, but it's not the point). [Answer] ### From experience: Everyone needs their own double bed. As a polyamourous hetrosexual my suggestion is to give everyone their own bed. Our poly of 5 has 3 kings and 2 queens (and a 4sqm couch) - we like to stretch out and we have lots of large pets that like taking up bed space. (But if we didn't have large pets doubles would be fine.) You have your own space, and you invite your other partners into it when you're wanting company. But more importantly you can have alone time and can get a night to yourself when you want it. I have lived in polys where 3+ people shared a bed (me and 2 or 3 girlfriends) and it's suboptimal. It seems like a fantasy but it really isn't. Someone always snores, and if you can't hear anyone snoring - it's you. Someone's always got a cold and you're going to catch it next. 4 people all mutually farting and stealing the quilt is a recipe for conflict. Someone's always out late or got to get up early. Someone always overheats, someone is always freezing, someone wants cuddles and someone wants space. Someone has a nightmare and wakes 3 people up. 2 people want sex and the 3rd has a headache no-ones getting any. It's not sustainable long term. 3+ people sharing a room also limits storage of things like clothing and decoration, and everyone needs their own "space". Not to mention Friday and Saturday most of us need to be out of the house at all costs as one of them got a tinder match and wanted the room to herself. Since declaring that poly housing is "N people need N rooms" our poly experience has been much better. [Answer] I think the best answer lies (no pun intended) not in redesigning the bed, but in redesigning the house. Why even have the sexes in the same room when they're doing it, if they're that homophobic? In the Victorian era, different areas of the house were for different people. You would have certain stairs and entrances for servants, for instance, and the male servants might live in the basement while the female servants lived in the attic. Certain rooms would be the domain of men to smoke and drink with their male guests and certain rooms were for women to do their sewing or whatever. Mind you, this was to keep the men and women apart and the same sexes were put together, but homosexuality was illegal during this time. Maybe it can be adapted or inverted some how. Perhaps looking at cultures that have multiple people married to one another in our world can help. I know in some African tribes, a man would have a central hut where he would live, and each of his wives and their children would have their own huts, forming a sort of compound. Putting this all together, it might be a good idea to give everyone their own space but set it up in such a way that you can observe everyone coming (no pun intended) and going. This way if Bob visits Billy in his room, everyone will know. The socially acceptable place for the same sexes to interact is in the communal areas. Perhaps also put the (thin) walls together, with doors facing outward, and no locks on the doors, if you even have doors. If you had just a curtain for privacy, you would have to be not only quiet with your same sex encounter, but anyone could walk in at any moment. It might help if only one sex even had beds. A common problem in relationships with more than two partners is the equitable distribution of sex. You could have only men having rooms at all, and the women rotate between them, or the other way around. This way, not only is everyone getting a fair shake, but there might always be someone spending the night, reducing the chance of sneaking someone in. That all being said, I don't think there would be a way to keep members of the same sex apart and still have a functioning society. The best you could do is give people as little privacy as possible and ensure the only one-to-one encounters they have are in specific locations where they can't get a member of the same sex without everyone knowing. [Answer] There are single SLEEPING beds, and there are sex locations. And the two are never the same place! Only a deviant sort would want to sleep in the fornication bed, and the opposite is even worse! Fornicating in the sleeping bed is like... doing it on the kitchen counter! How taboo!! p.s. Note that the sex location is just that. It might contain only a bed for the boring-minded, or any other facility or equipment or setting. It is a designated functionality, not a piece of furniture. The actual mechanics of the location would be purely up to the participants, the Moral Uprighteous Board has no purview with how you do your sex, merely with whom you do it with. By completely segregating the concept of sleeping spot and sex location from each other, you eliminate many of the potential pitfalls of a multiple partnership. No more getting woken up at 2am because husband#3 is feeling frisky with wife#2! If he wants that, then he will get up out of his own bed, approach his chosen wife, and invite her to the sex room. And all the more fun to them, I need to get my sleep for tomorrow's evaluation at work! As for the homophobia viewpoint. Well, the designated sex room is for that, and ONLY for that. When it is occupied, the persons in the room had better have a very good reason for it! Consenting members of suitable genders of suitable marriages, of course. (or a single person, for cleaning the room). Similarly, having sex anywhere other than the designated place is simply not on! No normal person would do such a thing, and any deviation from this societal norm will be fuel for gossip at the very least, and reported to the Moral Uprighteous Board at worst. It is rumored that the inhabitants of Thirdrock get to make a lot of whoopie, but are sadly lacking in cuddly-snuggly time. This is an unfortunate effect of their marital mores. [Answer] The preferred option is, of course, the double bed. Persons of the opposite sex can sleep together. Partners can attain their conjugal rights on a roster basis. This is provided only couples of the opposite sex are in bed at any time. Group marriage does not a priori mandate or imply group sex. This seems to be the case, historically, here on good old planet Earth with polygamous societies. This should be more so with the extreme homophobic sanctions on planet Thirdrock. [Answer] To give you a different point of view: In Western countries, children are encouraged to sleep alone in their beds. In other cultures families sleep together in a room, for example in Japan many families roll out their futons and put them in the middle of what is called the living room in Western countries. So they don't need separate sleeping rooms. Incidentally that's what my family does. In your world you could posit some Victorian-style rules: * Two people of different sex aren't allowed to be by themselves if they aren't married * Two people of same sex aren't allowed to be by themselves even if they are married * In such cases they need to be accompanied by a gouvernante much older or younger than them, or by a group marriage member of other sex, etc. * Families must sleep together the night using futons in the living room * It is taboo to talk about how two people of different sex get to have sex but somehow they succeed, for example the father tells his sons about some tricks he had in his pastime but it is a secret This means that homosexuality is hidden but probably rampant. [Answer] ## You need a flexible form - with a united structure. A radial framework suits best. A common architectural problem is to create a unified unit but with variable (at least during planning) way to accommodate individuals. Typical examples are dormitory rooms - where disparate individuals need privacy, but yet are arranged together. You can use various techniques to ensure this, however one example is a radial form. This way, each person has separate access, yet also a unified central area. A sketch of one such dorm proposal as follows: [![enter image description here](https://i.stack.imgur.com/hJMyP.jpg)](https://i.stack.imgur.com/hJMyP.jpg) Translating this to a more intimate setting, by having a large radial circular bed, partners have reasonable privacy and separate access from the outer edge. As intimacy develops, a central area could be used to develop the relationship further amongst individuals within the unit. This also has the ability to expand to much larger family units if necessary, while keeping the same familiar structure. [Answer] Your group marriages are a little small for this one, but it's worth a thought. The reason they're quite so hot on homosexuality is because there's too much opportunity for it in a situation where it's possibly easier to be homosexual than straight. That means single sex dormitories are the default. Batchelors live together in large halls, spinsters live together in large halls (when away from home). This is on the surface to prevent inappropriate activity due to the large number of other people in the room. Victorian morality would make all the beds in the room narrow singles, not that that ever stopped anyone. The same extends to the marital home, the women have one room, the men have another, a third room is set aside for conjugal matters without disturbing the people sleeping in the dorms. These dorms will have the desired "legal" effect some of the time, and the rest of the time they're going to have entirely the wrong effect. [Answer] In the real world, polyamorous people exist, including groups living together. The most common model, as far as I've gathered, is that of ordinary double-beds and couples or threesomes sleeping together, just the constellations change. So today, Alice and Bob sleep in bedroom one, while Chantalle, David and Eve sleep in bedroom two. Tomorrow, Alice wants some alone time and claims the guest bedroom, Bob snatches Eve while David and Chantalle enjoy couple time. There may be some scheduling or just spontaneous whoever-feels-like-what. The main change in furniture would probably be tripple-sized beds, essentially a bit larger than king-size. Blankets might also see some change because if you think the tug-of-war between two people is bad, wait till there are three. For the one-to-many marriages, where one man is married to 2-3 women or one woman is married to 2-3 men, also look at the real world. Arab countries have polygamous marriages, but the custom is that each wife should have not just her own bed, but her own house (which is why in reality, most muslims have one wife despite Islam allowing up to four). So it may well be that there are no hot threesomes at all, and your multi-marriages are simply a form of more permanent open relationships. ]
[Question] [ I am writing a book set in a parallel universe where English is not the dominant language and the dominant language is a complex polysynthetic language that makes use of a complex system of word declension using affixation that contains both agglutinative and fusional structures. While the dominant language of my world is not Cherokee, its grammar is very similar to mine. I have not finished creating my conlang, so I will simply give a concise and hopefully easy-to-understand description of the Cherokee language below. Since most people cannot read the Cherokee syllabary, I will transcribe all Cherokee words below using the traditional romanization system. The Cherokee language is polysynthetic, meaning that words are formed from several smaller parts that form a word with the meaning of several different English words combined into one. The word tsiwidagilvwisdanelv'i can be broken down into several smaller parts that each have smaller meanings, but none of them can be used by themselves as standalone words. * tsi- means "at that time" * wi- means "over there" * d- (or de- before a consonant) means that it occurred multiple times * agi- means "I" in this context * -lvwisdane- means "work" * -lv'i signifies the remote past This single word therefore means "I used to work over there back then, a long time ago." However, as I said earlier, I could not use any of the affixes or roots shown above in isolation while speaking. In Cherokee, all affixes (although all of them have two forms depending on whether or not the following syllable begins with a consonant or vowel) can be used with all verbs except for those that indicate pronouns. Cherokee prefixes that indicate pronouns not only differ depending on whether or not the following morpheme (unit of meaning); they also combine the subject and object pronouns into one pronoun and differ depending on the tense of the verb indicated using a suffix. Imagine if instead of saying "I told you," I said "Iyou-told," except that the prefix with I as the subject and you as the object is not a combination of the two base pronouns and cannot be predicted just from knowing the word for I and the word for you. In addition, different verbs conjugate differently based on whether they are action verbs, passive/stative verbs, or irregular verbs. Irregular verbs conjugate in five different ways based on whether the direct object is living, flexible, long, indefinite, or liquid. There are also some predictable periodic changes to maintain a strict consonant-vowel syllable structure within the middle of syllables. How exactly would early computer programming languages and text-based games (pre-AI) exist in a society that speaks a language that is so grammatically complex? [Answer] Early computer programming languages were originally [machine code](https://en.wikipedia.org/wiki/Machine_code), which was effectively a sequence of numbers that encoded machine instructions, memory addresses and the data on which the program would operate. A later development of machine code was [assembly language](https://en.wikipedia.org/wiki/Assembly_language), which uses mnemonics to represent machine instructions, and allowed users to name constants, memory locations and parts of the program in order to simplify programming, but in essence, assembly code bears a nearly 1:1 relationship to machine code. In all of this, there is no need for the machine or the assembler program to parse natural language save where the program that has been written is designed to do so. From there, the development of higher-level languages that more closely approximate natural language can be developed. I have no doubt that with a polysynthetic spoken language, the higher-level computer languages may be rather different, but I also have no doubt that the programmers would be just as capable of making such a language as the developers of the languages that our computers have used. In some ways, a polysynthetic language may be simpler to parse. In the example given by the OP, the synthesis of the word involves specific prefixes and postfixes in specific positions. At each position, there would be a limited number of options for affixes, and parsing them would involve a decision tree of limited size. Yes, there are complications due to irregular word forms, but then many other languages have irregularities, including more analytic languages such as English. So, natural language processing would still be a challenge, but the language still has a structure that makes such processing possible. The challenges would be different to that of parsing English, but not necessarily particularly greater. This language can be understood by humans, after all, and as long as a programmer can understand it, a sufficiently powerful computer can be programmed to do so too. [Answer] Every computer language now in use is far and away simpler than the language of the person who developed it. Even the languages with the simplest grammar are more complex than the most verbose and elaborate computer language. This is because computers, when compared to the human mind, are actually quite simple entities. Their basic operations are actually very few, and it is only because they can quickly and reliably perform these operations that we have any use for them at all. Giving instructions to a computer is very different from giving instructions to a human being. Furthermore, each operation done by a computer, especially at the machine code level, is utterly devoid of context. When the CPU in the Commodore 64 reads the instruction 0xA9, it always takes the next byte in the program and loads it into the accumulator. For instruction 0xA9, it never does anything else. Everything required for the CPU to execute an instruction is contained within that instruction. No human language comes anywhere close to this lack of context. The language of the natives who develop the computer will influence the computer language chiefly in the naming of the operations. As for the rest, it suffices to say that as different as Cherokee, English, and Mandarin are from each other, each is more different from 6502 assembler, SQL, or JavaScript than they are from each other. [Answer] Not a worldbuilder, but am a software engineer. The different language would have no significant effect on the development of computers. The underlying fundamentals of computation are universal, and they are quite foreign to any natural human language. Just as programming languages designed by and for English-speakers use some English words like “if” and “while”, a programming language designed by and for Cherokee-speakers would likely use some Cherokee words or morphemes. Just as English-based programming languages have nothing more to do with English grammar, nor would a Cherokee-based programming language have anything more to do with Cherokee grammar. In our world, there have been some programming languages that attempt to resemble the English language more closely than typical programming languages. Generally this has proved more annoying than helpful and with the notable (and regrettable) exception of SQL none of these languages is in common use among professionals. If the Cherokee language had any effect on this, it would likely be to make those uncommon languages even less common. Cherokee orthography uses eighty-six letters, each in both lowercase and uppercase for a total of 172 glyphs. This is significantly more than English, so it's likely that there would be some minor implications for text encoding. Probably the basic standard would be an eight-bit encoding rather than a seven-bit encoding like ASCII. But this is small stuff. It might be more interesting if there were many hundreds or thousands of glyphs to encode — but maybe not; there are obvious conventional solutions there as well. [Answer] Mathematics has a very precise notation where particular symbols are given precise meanings. You can express the same relationships in words, but you lose precision. Here's [an example](https://english.stackexchange.com/questions/612777/the-usage-of-can-not-vs-cannot-in-mathematics/612896#612896). The word 'cannot' is often explained as an abbreviation for 'can not', but it is importantly different. Imagine the following dialogue... "I don't enjoy going to my family for Christmas." "Well, you can not go." If the stress is put on the 'not' it would imply 'you have the option not to go'. If you wrote 'cannot' it would definitely mean 'there is no way you can go'. We do not usually put stresses in writing, so maybe 'can not' and 'cannot' is the imprecise, written language's way of coping with the amphibology. Computer programming is much closer to mathematical notation. Each instruction should have a precise meaning. It will have a precise meaning according to your computer and compiler. Something will have gone badly wrong if it is not the same on all machines that can execute it. The [APL programming language](https://en.wikipedia.org/wiki/APL_(programming_language)) back in the 1960s tried to replace the typewriter keyboard symbols with a better, more precise set of symbols. We kept the keyboard, and adopted precise meanings for the ASCII symbols. For example the asterisk '\' commonly means multiplication, '!' means NOT\_, and so on. The '.' symbol is dreadfully overworked, but we manage. Computer languages need to express a precise idea. They have little in common with natural languages, which can express a great many things without precision. I don't think computer languages are a copy of mathematical notation, because computer statements are executed in order, rather than following one from the other as in a Mathematical proof. But they look similar because they meet similar needs. [Answer] As for the programming languages: There would be no difference.* Programming languages are not related to human languages. They respond to universal logical principles that are not affected by human language. It is very easy to understand because programming is another word for "information logistics". Everything that a program does is it performs logistical operations on information. No program ever does anything else. Would logistics be different with the use of Cherokee language? Imagine a huge truck or trains delivery company or whatever is more popular in your region. Do they care? Hardly. Why? Reality. To clear up some possible confusion: An average programming language uses a vocabulary of about 50 symbols, for which English words are used purely for mnemonics purposes. Therefore you get all the `if`, `while`, `function`, etc. words in a program. You might have seen huge program texts, written seemingly in English, but don't be confused: all this is just names given by humans to the logistical operations and entities within the program. A huge body of mnemonics for that. As the laws of logistics are not influenced by the language, even if you use a language other than English, you would still be describing the same stuff like "Take A and copy it into D. Add D to B. If B is greater than C, then subtract C from B", etc. This is all there is, and all there ever was. As for the text-basaed games: There would be no difference. Whatever the game is, to a program it's just about moving bits and bytes, and combining them in various ways with logistical purposes. When you ship containers, there's no difference what's inside of them. Hence you may witness that software localization in our world does not influence anything: any program can be translated to any language and it hardly bothers the program. Cherokee would be no exception. You'd just pay additional $$$ for the localization service. Disclaimer: there are, of course some practical technical differences in representing one or another language, like right-to-left writing support or complex ligatures, or different text lengths, etc.. And if you would need to parse the sentences in various languages, the parser might need to be adjusted for that, like "calibrated". But these are more technical problems akin to typography rahter than something that has any influence on writing programs. Additional info on AI-based text games: There would be no difference Because all AIs of any kind, from the simplest if-else AIs to neural networks, are programs. And they see no difference what stuff they're moving around. The mathematical and logical principles of it never change. Additional info on more exotic programming languages Funny thing but human languages also solve the problem of information logistics as a part of their function (or they try to). Thus they have different ways to "deliver the meaning" which are reflected in their structure. There were various experiments in structuring programming languages to perform information logistics using various principles as well. You might be interested to read about the stack-based programming languages and the APL family of programming languages. These two paradigms are closer to what you might call Cherokee simply because their way of describing logistics is polysynthetic as well. Although there is some amusement and research value in these languages, they are very far from being practical in most of the use cases. There are some extreme use cases for them, but generally they have proven to hurt more than be useful. Thus they have not become popular. You might make them or their derivatives popular in your world, if you want to accept that most programmers that read your book are going to facepalm and wince at that part. Do not be confused: these languages still use the same logical principles, they just have awkward ways of writing them. Like if you try to talk like master Yoda for the rest of your life. Also, maybe the functional languages, with their function combination, currying, functors, monads, etc. can be seen as remotely polysynthetic or at least lending themselves to such views, but this is already entering a very broad realm of theoretical computer science and related topics. [Answer] If it helps to continue your writing: * Computer languages do not follow or resemble the spoken language of the programmer. Perhaps you imagined they did. * At a very basic level they use the concept of an "identifier" to represent the value of something, and an "operation" to convey what needs to done with the values of an identifer. * If your conlang doesn't have a writing system capable of labeling a value or concept with something that isn't a word in the conlang itself, you have problems. For an English example, if inhabitants of your world couldn't label "Mount Everest" as "mountA" and "Mount Fujiama" as "mountB" you're in trouble. * Similarly for operations: if the conlang can't express addition with a word or symbol ('+'), and additional operations such as subtraction ('-') etc, there's no deal. While I immediately love and honor the existence of the Cherokee language, the details of its word formation and spoken usage don't actually have a bearing on its development of computer languages. Programmers on Earth have to learn the syntax of the programming language they write in. Programmers on your world will need to do the same. Finally, do you need to explain anything of the above to the reader? TL:DR Q: How would computers develop in a society where a Cherokee-like language is the dominant lingua franca? A: It would develop in stages as on Earth. Ledgers written with quill pens would come before adding machines with levers to pull down the side, before computers built with electrical relays, vacuum tubes, transistors, integrated circuits, increasing density of transistors on a chip or whatever comes next. Computer languages would not necessarily use words from the lingua in their syntax. [Answer] For the programming language part, i think the other answers allready covered that well enough. For the text adventure part of your question, i think that shouldn't pose too much of a problem. The room descriptions are just texts, so if you can write texts in your language that part won't differ from an english text adventure. The more interesting part is the input parser. Some of the earliest and most primitive text adventures just had a very very limited list of exact phrases that you had to type in to create some action: ``` if (i$="open door") or (i$="open the door") or (i$="push door") then dooropen=true: print "The door is now open". ``` Anything not on that list ("open gate", "open that door", "unlock door, then open it") would just result in an "i didn't unterstand that". If you can define a list of terms most probably used in your language, you're fine here - even if the list may be a bit longer. It's not totally clear from your post how much word building is usually done for simple terms - you may have to use conventions of how people have to formulate their input to reduce alternatives if that is too common (don`t say "open(with my foot)the door(that goes outward)(because i want to leave)". When writing better parsers that actually understand reasonably simple sentences ("take the red key, then unlock the blue door and carefully open it") you will no doubt have a harder time than in english, but that should just slow down the advance from simple to complex parsers by a few years. [Answer] The question you should ask yourself is how your society would notate mathematics. Although a lot of math is influenced by western languages, it ultimately does not follow the grammar of any natural language. Programming languages are far closer to mathematical notation than any natural language, and a society that can develop the formalisms necessary to express mathematical ideas precisely will have no trouble designing programming languages that do the same thing (for instance, lambda calculus is essentially a purely mathematical programming language). One of the main things that mathematical notation does is remove as much ambiguity and context-sensitivity as possible. This is part of what makes it look and feel alien to new mathematicians. It also makes no attempt to connect numerical ideas to natural language syntax, other than for names. Since names are considered "atomic", any declension/conjugation therein is irrelevant to the mathematics expressed. The names of variables and functions serve purely as markers or placeholders, and do not even have to have intrinsic meaning (hence, the infamous 'x'). Programming languages design their grammar not for the convenience of the human, but for the convenience of the parser. The grammar is far more rigid than any natural language, and unapologetically so. It is also unnatural, which is why beginner programmers often wonder why they can't write: "If 0 < x < 100". Things that are "obvious" in natural language, or even in mathematics, are outright forbidden in many PLs because of type rules. So, my guess is that your PLs will look syntactically similar to ours, but the names will be the distinguishing feature. Fortunately, names are basically boring and irrelevant to parsers. They neither know nor care what language you write them in, as long as you use them consistently, and don't expect it to understand when you try to decline/conjugate them (i.e., don't expect the parser to know you want a container when you say "Widgets" even though you only defined "Widget"). [Answer] Seems like someone interested in the unique features of Cherokee would be aware of this, but there actually is a [Cherokee Syllabary](https://en.wikipedia.org/wiki/Cherokee_syllabary), independently developed by Cherokee in the early 1800s. This was created by Cherokee who could not read or write English, but observed English speakers doing so, and sort of reverse-engineered how to do it. As a result, their glyphs look rather a lot like Latin glyphs and Arabic numerals, but bearing no relation whatsoever to their meaning in any other writing system. A "Syllabary" by the way is a writing system that uses a unique glyph for each allowable syllable in the language. This generally requires an order of magnitude more glyphs than representing a language with the consonant-vowel pairs that make up each syllable, but an order of magnitude less than logographs (separate glyphs for every word). Think of a table where the rows are consonants and the columns are vowels. The cells would be all the possible syllables1. So in this simple case, a syllabary would need `c * v` glyphs (where `c` is the number of consonants the language uses, and `v` the number of vowels), while an alphabet would only require `c + v`. However, figuring out alphabets seems to be a very difficult insight, that only provably happened once in human history2, while syllabaries have been independently invented multiple times. It probably also helped [Sequoia](https://en.wikipedia.org/wiki/Sequoyah) that he had English books and newspapers as an example. So he knew when he first tried a logographic system that it was using far too many glyphs. He knew he needed something more economical in glyphs, like a syllabary. He just had to work out a way to do it. Which he did after about 11 years of tinkering. He managed to come up with a scheme to encode the entire alphabet in 86 glyphs. If you remember me talking about the vowel-consonant table above, here's a rendition of that idea with Cherokee syllable glyphs in the cells, and rough equivalent English vowel and consonants for the columns and rows. [![Cherokee Syllabary Table](https://i.stack.imgur.com/k1o4X.png)](https://i.stack.imgur.com/k1o4X.png) This was quite simple enough for the Cherokee in what's now South Carolina and Oklahoma to begin publishing their own newspapers, and reports are that about 90% of the nation was literate within 10 years (if true, that's probably better than the USA at that time). This writing system is still in use today within the territory of the Cherokee Nation. For instance, here's a picture of a Stop sign in Tahlequah, Oklahoma: [![Tahlequah stop sign in Cherokee, English, and transliterated Cherokee](https://i.stack.imgur.com/U3GLi.png)](https://i.stack.imgur.com/U3GLi.png) As for how this would work, well you'd just need keyboards that can produce the 85 glyphs of Cherokee. The keyboard I'm using right now has 104 keys on it. Of course only 26 of those are used for my English alphabet, but still this doesn't seem like some kind of insurmountable obstacle considering I'm already using a keyboard with more than 85 keys. In fact in many asian countries (where I understand they are pretty good at coding) native keyboards have far more keys than that. For example, here's a Japanese keyboard from the 1970's [![1970's Japanese Keyboard](https://i.stack.imgur.com/Y0snb.png)](https://i.stack.imgur.com/Y0snb.png) This is for Japanese's Kanji logosyllabary, but I understand for modern keyboards they just use a more western layout, but with the ability to switch from Latin glyph entry to their own syllabary, which is then automatically translated into Kanji for public consumption. But the point of this is that printing and keyboards aren't really any kind of barrier with this writing system. They keyboards might be a little larger (without any social pressure to move to a size appropriate for a English's alphabet), but not inordinately so. As for computer programming, its tough to say. We today have tension between rather verbose languages, like Pascal: ``` procedure procedure_name (parameter_1 in out typename) is begin ... end procedure procedure_name; ``` and terser syntaxes like C: ``` function procedure_name (type_name parameter_1) { ... }; ``` and even terser yet syntaxes like APL, that are essentially logographic for everything that isn't a variable name. Which would win out in a world dominated by Cherokee? I'd like to think they'd be more partial to the easier-to-read verbose style, but likely human beings would make the same decision human being collectively made historically (as terse as possible without going into full logographic unreadability). We arguably haven't settled this issue yet as software developers though (talk to a Perl or Ada fan sometime), so perhaps they'd still be arguing about it too. --- 1 - This is actually just the simple case. Indo-European languages like English are not simple cases, and would require syllabaries with tens of thousands of glyphs. 2 - Its quite possible it only happened the one time it did due to a freak collision between a weird language family that had vowels so predictable that they didn't need glyphs for them, with a new language family that wanted to borrow their system, but didn't have that feature, and used consonant clusters that would have made a syllabary a nightmare. [Answer] The Minority Report for your programming question is they would use [Perl](https://www.geos.ed.ac.uk/%7Ebmg/software/Perl%20Books/prog/ch01_02.htm) ;) Larry Wall, the linguist who designed that programming language, explains his thoughts on the [similarities between natural language and programming](https://youtu.be/ju1IMxGSuNE?t=113) which you may find more instructive than the many (not-wrong) claims that natural and programming languages have nothing in common. [Or not](https://cs.stackexchange.com/questions/9581/are-programming-languages-becoming-more-like-natural-languages) [Answer] Contrarian answer here. :-) Of course current popular programming languages have English influence: * Typical control structures follow English grammar: `if cond then action`, `while cond do action`. * Paremeters to functions/procedures come (typically) after the function name, mirroring verb-object order. As some other answer(s) said, you might want to look into stack-based languages such as [Forth](https://en.wikipedia.org/wiki/Forth_(programming_language)) and its derivatives, array PL with weird notation such as [APL](https://en.wikipedia.org/wiki/APL_(programming_language)) and its derivatives, and other [concatenative programming languages](https://en.wikipedia.org/wiki/Concatenative_programming_language) such as [Joy](https://en.wikipedia.org/wiki/Joy_(programming_language)) and similar. And of course, [Lisp](https://en.wikipedia.org/wiki/Lisp_(programming_language)). If you wanted to be as much "science-based" as possible, you would have to look at the early [history of programming languages](https://en.wikipedia.org/wiki/History_of_programming_languages). There was a nebulous point between simple assembly and the very first programming languages (Fortran and Lisp) when something in-between was developped (e.g. Plankalkül, Autocode), and that is where you have to insert your change, basing that development on your language instead of English. Also, Mathematics notation influenced PL notation, so you have to consider how Mathematics is writen in your world. Also, perhaps look into early developments in the USSR and Japan. [Answer] It depends on the number system. Programming languages are mostly based on mathematical notation, rather than natural language. For example, `x = F(y)` could be a line from a mathematical proof, or it could be a line of python code (poorly written python code, but I digress). This is because math and programming both need to have precise, unambiguous syntaxes, and they both need to be able to easily work with numbers. If your parallel universe still uses European numbers as the standard, then their programming languages will be close to ours. There will be different standards and conventions, but that will mostly be from the butterfly effect, not the language being spoken. I expect a programmer from our world would be able to start writing basic programs in their languages the same day she starts learning them. On the other hand, if all of their math is based on a number system where things like addition, subtraction, and equality are defined by the position of the numbers relative to each other, then the programs they write will be unimaginably different from ours. As for text-based games and language parsing, it will probably be about the same as in our world. Early games would only try to parse one tense, and only allow a subject, a verb, and a direct object. In our world this was usually 2nd-person imperative, but it could just as easily be 1st-person present simple. Based on your example, the game will accept "agilvwisdane", but if someone types "tsiwidagilvwisdanelv'i", the game will only respond, "I'm sorry, I don't understand, please try again." ]
[Question] [ The more I look at it, the more my world seems to resemble the world of Avatar the Last Airbender, but instead of benders I have casters which are capable of unique talents (combat magic, enhancements, healing, psychics, elemental control, energy control etc.). At the current state of development, the world is effectively in the medieval age while one particular nation is well within the industrial age. While the rest of the world still relies on carriages and ships powered by sails for transport, the most advanced nation has access to railways and warships. Their latest invention so far is a giant ship that specializes in carrying vast numbers of smaller combat ships, basically a medieval ship carrier which I'm also working on and I received help via [this question](https://worldbuilding.stackexchange.com/questions/200192/medieval-fantasy-ship-carrier). I need a reliable and feasible way to deny my fantasy world any sort of aviation and remove the invention of flight from the equation altogether, because I don't want it to take shape of our modern world where Aircraft carriers are the undisputed rulers of the seas and any sort of threat can be destroyed with a well placed bombing run. I don't want any sort of planes or any sort of flying contraptions in the air, but I'm having serious difficulties coming up with a rational explanation to prevent such an evolution. After all, birds and flying creatures have always been around and I have no idea how to prevent the people from looking at them without trying to copy their flight and eventually succeeding. PS EDIT: Someone in the comments asked "How absolutely no-flight must answers be?" To be honest, at first I was considering an absolute handwave of everything even remotely aerial, but given all the responses I'm genuinely confused where to draw the line. Ballooning? Kiting? After a bit of discussing, seems the restrictions would be drawn at any flight contraptions that move at a considerable speed similar to airplanes. Balloons and kites aren't of much use if you have strong casters within the enemy lines who could firebolt them out of the sky or even stronger casters who could manipulate the winds to screw them over. [Answer] Magic is a dense material. Magic is quite dense. It tends to fall down with gravity, and tends to cling to the earth. As such, if you get too far above the ground, there tends to be little magic left. Many have attempted to fly, and you can get a bit off the ground, but soon you find your magic drains, any magical storage devices fail, and you crash into the ground. Natural magical creatures fly with either the aid of physics or short lived bursts of stored magic. There are no mega heavy flyers. [Answer] You don't need explain why there is no flight. Just write your book or whatever you are doing without flight. If when you are done you think you need an explanation, check out the other great answers here. For example, I read somewhere (on this site I think) that the creators of Groundhog Day tried to explain the repeating day with some voodoo witch stuff. Obviously they decided to leave it out, leaving no explanation, but the end result is still a great movie. Maybe you could leave some vague references to past events, like a failed test or something bad that happened to make it a mystery. This lets the reader (if it's a book) wonder about it, and makes it more interesting. J. R. R. Tolkien often did this, telling of peoples/countries that disappeared/were destroyed without fully explain everything (like the Entwives) to keep things mysterious. So you don't necessarily have to explain why there isn't flight. [Answer] There is no oil In your world, it can lack the power of oil, or knowledge how to make powerful fuel from it. In our world, oil was seen as a bad thing for a long time. It took time before they found a use for the black sludge of dead plant organisms. Without such a powerful energy source at your disposal, it is difficult to get alternatives that are strong enough for flight. At least for flight that is useful as (long range) attack craft. We currently struggle to get electricity powered planes for example. Alternatives like Hydrogen often require their own set of difficult technologies. Hydrogen as an example requires great knowledge on creating and maintaining high pressure containers. Not to mention Hydrogen cells if you want to create electricity. Oil exists, because you want to change a little as possible. Why do they not use it? Not all discoveries have happened instantly. In our world, we build aircraft without looking (much) at what did it before. We didn't use bird aerodynamics or anything like it. We build structures that were strange and inefficient. But this is a black sludge coming out of the ground that just pollutes things. There might be no interest at all in it, or even attempts to avoid it for it's bad effects. Even if there is interest, it is very difficult to get powerful fuel out of it. They might just be stuck with using it as lube and lamp oil and never think to further investigate it, or not in the right directions. There are many discoveries that could've happened earlier. There are probably still a lot that haven't been discovered yet, but had things happened differently, might've seen these as obvious. Then these could be difficult to imagine no one finding out their use. It could be incredibly difficult as well. An example. If most tales of Tesla are to be believed, he had a method to electrify many lamps without wires. How he did this is unknown. If this was investigated and the knowledge extracted, we might think it is obvious that a lot of lamps are wireless. Another example. We might not have antibiotics for a long time, were it not for the incompetence of a man that let some of his bacteria cultures get contaminated. Thus oil might not be considered, or not be pursued in the right way for it to become a powerful fuel. Without powerful fuel, it is difficult to create aviation. The aviation that does exist (if at all) will generally be unsuitable for attacking targets, as the investment will to too large and the damage too little. [Answer] It is crazy windy all the time. Your world is always windy and especially at sea. Sails are great and they do have flight in the form of manned kites. But in a world where you can count on 30 mph winds it is hard to take those first baby steps towards flight, even if you have all the fixings in place. The closest your world comes to flight is fixed wing one person airboats that can use the ground effect to zip along just above the water. Even these are risky because a gust that tips a wing into the water could be catastrophic, but these water-level raiders are super fast and a good use of your aircraft carriers. Also good story making when a ground effect pilot uses a wave to jump the aircraft carrier, making eye contact with astonished persons on deck as he crosses over. [Answer] One of the most reliable ways to limit a particular avenue of science and technology is religion. In our own world, this has happened several times, for periods of anywhere from decades to a couple centuries, in Europe (worth noting that some other religions have promoted science; this is not intended as a statement about religions in general). If, in your fantasy world, flight by anything without feathers (possibly including bats or leftover pterosaurs) is irrevocably associated with some evil aspect (what Christians might call demonic -- as with medieval illustrations from our own history showing angels with feathered wings, but dragons and demons with leathery bat-like ones), the very idea of so much as experimenting with flight without putting actual feathers on your wings might be enough to get you tried and executed by whatever barbaric method is in favor at the time (and we all know what happened to Icarus). The thing with religion is that it's often structured to prevent logical assessment of its own tenets ("If you have faith, you will simply accept that angels can dance on the head of a pin, without questioning how large the pin or how small the angel."), so a restrictive paradigm can last far beyond the point where it becomes provably false, simply by forbidding the reasoning that could be used for that proof. [Answer] When in your timeline the Montgolfier brothers give their first public demonstration in front of the dignitaries, something bad happens. The balloon crashes and starts a fire which kills, together with the two pioneers, also a good number of the dignitaries attending the demonstration, including some church representative. This was the last straw of a series of incidents which caused several damages among the peaceful farmers and artisans of the province "blessed" by the presence of the pair, and it turned quickly into a backslash against these attempts of violating the rules set up by the holy book and the good philosophers of the past that stated that elements move toward their natural place, and thus humans cannot rise and fly challenging the will of the greater being. This won't fully prevent discovery of flight, but it will likely delay it for quite some time. [Answer] Your world could lack accessible sources of aluminum, or may never have discovered how to refine it in an efficient and economically viable way. Aluminum was the critical material that gave airplanes the strength required to scale up while staying light enough to remain airborne. Without aluminum, you're restricted to the wood or cloth-over-wooden-frame aircraft from the earliest days of aviation. These designs do not scale well. You can still have prop-driven craft that seat two or three people, but you won't support the loads required to build jet-powered craft, cargo planes, troop transports, or long-range, high-capacity bombers. Airplanes can still exist (it's hard to forbid them completely without other side effects), but they won't be the trump card that you're worried about. Your army and navy will still be the primary instruments of war. The airplanes that do exist will fly at lower speeds and altitudes, and your casters should be able to dispatch them without much difficulty. Anyone who can control the elements can knock such a plane out of the sky by moving the air around their wings and control surfaces, rendering the craft uncontrollable due to turbulence or reducing their lift to the point that they cannot stay airborne. [Answer] Birds! High altitudes are colonised by bird swarms. Earthers and fliers don't ordimarily overlap as birds here prey only on other birds and sleep on magically floating wings even in their sleep. And they are implacably ferociously territorial, with carbide toothed beaks, and 6m wingspans. The family groups have large hunting territories (as large carnivores like lion prides do), and roam a lot, and yeah, they defend their territories against unknowns (but tolerate those with nearby territories, unlike earthly animals). Worse, they are social so they summon others they know, to support them in ostracising unknown fliers of any kind.... because an intruder of one, will usually signify intrusion to others, its to all their benefit to mob unknown fliers. And as they usually fly high, they see a long way, across their territories. Now think social-structured pterodactyl crossed with adamantium wolverine........ [Answer] They have not invented the internal combustion engine yet. They're still using steam engines, which would be very plausible for a civilization with technology equivalent to what we had during the industrial revolution. For powered flight, you need to have a good power-to-weight ratio, which is very hard to achieve with steam engines. [The Wright brothers used an internal combustion engine for their first flight](https://airandspace.si.edu/exhibitions/wright-brothers/online/fly/1903/engine.cfm#:%7E:text=The%20Wright%20engine%20was%20a,jacket%20around%20the%20cylinder%20barrels.), and they might not have been able to take off with the added weight of a steam engine that could produce the same power. In our world, steam-powered airplanes have been attempted but they [were unusual devices because of the difficulty in producing a powerplant with a high enough power-to-weight ratio to be practical.](https://en.wikipedia.org/wiki/Steam_aircraft) Only one airplane design listed in the linked article has confirmed flights, and it was built 3 decades after the Wright brothers took their first flight. I'm not sure that that plane could have been successfully designed and built without the knowledge accumulated from 3 decades of flight with internal combustion engines. [Answer] ## How about you just cripple flight to make it impractical but still allow people to pursue it if they want to? Like what if you have an unstable atmospheric magnetic field which begins to pick up strength a few metres above the surface? If there is a stupidly powerful and unpredictable magnetic field then it could potentially make any kind of powered flight very dangerous by physically interfering with the metal components of the airfraft, pitching the machine around and occasionally slamming it into the ground or the side of a mountain, shaking it to pieces, as well as prohibiting the use of any kind of aerial sensor instruments like altimeters compasses fuel gagues yaw sensors etc. Birds would be unaffected, as would unpowered balloons and wooden gliders. To avoid interfering with tall buildings and mountains and surface compasses, perhaps for some reason this magnetic field is like an inductive magnet and only picks up strength when a conductive object is moving through it at a height of above so-and-so metres? This might also allow for the use of extremely low speed aircraft, maybe zeppelins. If you want to deny powered zeppelins just make the field less speed dependent with increased distance from the surface. Alternatively to all that maybe the field doesn't affect any object in contact with the surface. It wouldn't make flight completely impossible, but it could make it prohibtively dangerous or limit flight to a certain speed. It's even possible that advanced flight has been conceived of & developed, maybe even supersonic aircraft were developed in the belief that faster aircraft would be less susceptible to the problem - but every aircraft project was then subsequently abandoned after the death of everyone (or nearly everyone) who dared attempt to pilot it. Perhaps thousands of aircraft were actually built in anticipation of a flight revolution that never happened and are now sitting in various scrapyards and fields rusting away and being used as sheds. Maybe once upon a time some had even been used in combat, but they were so dangerous that they were more likely to crash and kill the ground crew who had just fuelled it than get anywhere near the enemy meaning the actual benefit to using one in battle would be less than zero; the sight of an aircraft being prepared for launch would cause men to flee in terror as they try to get away from the crash zone. So aircraft would be an obsolete technogy pursued only by raving lunatics and madmen. Climbing into one would result in almost guaranteed death. [Answer] ## It has been mathematically (but incorrectly) "proven" to be impossible In Heinleinn's The Number of the Beast, the characters visit a parallel universe where a famous physicist "proved" that heavier-than-air flight was impossible. Because of that, no one ever even tried to build aircraft. That world did have dirigibles. You can have a similar historical development that results in educated craftsmen dismissing powered flight as "Impossible! Everyone knows that!" A cool feature of this explanation is that powered flight would still be physically possible, allowing for a plot twist: the protagonist escapes via an "impossible" rocket or the brilliant young general develops an "impossible" secret weapon... [Answer] Here be dragons Parts of the world are populated by dragons (obviously magical, nothing that large could possibly fly otherwise), they're big, ugly, scaly and dangerously aggressive, and they jealously guard their air-space. There are also Wyverns, Wyverns aren't birds, they're more like small dragons (2 - 3 meters in length), except feathered. They're quite beautiful and much less agressive. Wyverns - unlike the solitary dragons - live in family units. Humans and Wyverns have learned to co-exist - more or less - peacfully living near each other. Wyverns also jealously guard their airspace, especially against dragons. There are no townships that don't encourage a family of Wyverns to stay near by, because those towns are rarely or ever attacked by dragons. The upshot of this is anything larger than a 2 meter kite that takes to the skies will quickly be ripped to shreds by Wyverns. Everyone knows this, so the concept of trying to fly anything bigger just doesn't occur to people. The concept of actually getting into a flying contraption is ludicrous, sure you'd be ripped apart by our lovely wyverns! Why would you offend them by trying to take their place and fly? You'd be better off building your house at the bottom of the river and pretending to be a fish! --- ~~Even if the Fire Nation~~ sorry Even if the industrialized nation has managed to wipe out it's dragons, and gets over the cultural taboo against flying, any airships they fly over other nations will be attacked by the dragons and wyverns that live there. [Answer] ## It's very hot and humid This one depends on the world you live in. But the lower the air density the faster a plane must travel for take off. If you don't want your people to live on a tropical forest, then make an atmosphere layer with those characteristics at a low altitude. I don't know what scientific shenanigans would have to happen so that you could have an atmosphere layer like that, but there might have been a magic disaster in the past that changed the way the atmosphere works. Well, at some point you might have such low pressure that planes just can't go over altitude enough to be viable (either that or has to use too many resources). [Answer] Wizards can shoot your airplanes out of the sky I don't know much about your world, but if a lot of magic-users have powers that resemble anti-aircraft guns, that would drastically reduce the usage of flight in wars because you could just have an (or several) anti-aircraft caster on your ship to knock the plane(s) out of the sky. [Answer] you didn't really mention if your world had to be above-ground so I think an effective way to prevent flight would be to place your world underground where flight becomes less practical as a means for traversing large distances. This would mean you could still have technology that supports flight, but essentially nobody would actually develop flying machines because they would be completely impractical within the underground tunnels. [Answer] ## Looking in the wrong direction It may be falsly theorized (or actually "proven", being common knowledge) that birds and other flying animals use a low-level type of anti-gravity magic. This type of magic seems to be fairly unique since no human/sentient race has ever developped/acquired these powers. Hence, the inhabitants of your world simply acknowledge it to be an unobtainable goal, comparable to Faster Than Light travel in our world. Breaking this boundary would imply a significant breakthrough outside of the current understanding of physics/magic. Researchers who are still interested in studying this phenomenon from a non-magic point of view may be looked at as pseudo-scientists (like, say, astrology in our world). Their findings never seem to gain track with their peers and funding is therefore lacking. Even the "serious" scientists who occasionally stumble upon a result indicating a feasible new approach (such as certain shapes generating lift) might dismiss the results as erroneous and falling within the margin of error. They might for example think that lift is being produced by the little amount of water molecules present in the air (boats float, so there has to be lift from somewhere, right?). However, it has been observed that there's less water higher up in the air, so there's not enough lift. All flight assisted by "waterbenders" has currently failed because they can't seem to get the precise amount of water needed right... The two camps (alternative anti-grav magic vs. waterbending) might even dominate the discussion, therefore pushing away any other suggestions. [Answer] You haven't said if your world have gods or something similar, but maybe the wind god doesn't approve of humans since they were made by the earth god and once they go more than 30m airbone it makes their lungs collapse and everyone who tried it drops dead. Or you could have something similar but with dragons that are always airborne and attack anything bigger than an eagle. Another good option would be an ultra high density mana layer that makes humans unable to go higher than 40m off the ground by magic means. [Answer] There are no birds or other winged animals We tend to take what we see and duplicate it. We had the wings of birds to study to learn how they fly and apply that knowledge to technology. The dream of soaring like a bird took thousands of years and advancements before someone was successful at it. But it was seeing the bird fly that gave many, many people the idea to try and learn how to soar like a bird over the years. That doesn't mean someone won't someday figure it out, it just means the inspiration and example to achieve flight isn't there to encourage it. [Answer] The air is highly turbulent. The bigger your flying thing the more of a problem this becomes for it. Things like pollen and insects are pretty much unaffected. Small birds can exist. However, by the time you're up to something human sized turbulence becomes a very big deal--to make it strong enough to fly makes it too heavy for a practical flying craft. Note that this does not remove artillery from the picture but it limits it's effective range because accuracy will stink. [Answer] Thin Air It's not our world. It has a much lower atmospheric pressure. The Wright brothers would never have got off the ground, if they had to start at (say) 40,000ft equivalent. The creatures of this world have evolved to breathe air at low pressure. Mostly, they have a better oxygen-transport molecule than haemoglobin. (Here on Earth, birds have a better variant of haemoglobin, and can fly at 37,000 ft where humans would pass out and die. But they need denser air to take off. A problem if you really want birds? Maybe cliff-jumpers? ). This does have implications towards the rest of the mundane technology of this world. Sails won't work as well. Or perhaps, if wind velocities are higher because the air is thin, they'll work better. In which case the landscapes and buildings will be different. Railways and Warships will be using steam, or internal combustion engines with extreme superchargers to get dense enough air. Gas turbines are a few years away (and jet engines and possible aircraft, a few more, although lift-off velocities of (say) 250mph+ will be a challenge needing very long and very smooth runways. But that's for your fictional characters' future ) Throw-away idea. This world might have mountains with effective vacuum at their peaks, and fairly separate air circulation regimes separated by mountain chains. I'll leave the implications to you. NB if you want accuracy instead of handwavium, you'll need to look a lot harder at the scaling laws compared to my imaginings here. [Answer] # High Gravity World This might make a lot of other things complicated for you / need paying attention to a lot, but if its important enough to you (to have a coherent reason there is no flight), I guess it could be worth it to you. I'm not too great on the physics side, but as far as I'm aware, there is no linear relation between gravity and density of atmosphere (as implied by a different answer) - other factors can have effects, eg the availabilty of water, strength of solar wind, etc. . But to the point: Higher gravity makes flight harder - eg for spaceflight, earth is actually pretty close to the limit of it being impossible with conventional fuel technology (just think of the ratio of payloads to fuel / total weight: you only get about 1% useful stuff of total start weight into orbit!). For winged flight, eg twice the gravity means that you'd need twice the lift from wings as you do on Earth - but just doubling wing size is not going to work, cause that gives you a bunch of extra weight (ie requiring even more lift!). What this would boil down to is not that (winged) flight is impossible, but that you would expect it to be developed a good deal later in technological evolution (because it requires more lightweight construction methods / higher powered engines to be viable). Which - I think - matches what you're looking for. P.S. I'm a bit surprised that noone else has answered with the idea of higher gravity - did all the SciFi nerds (like me :P) go running hearing its a fantasy background ? P.P.S. Just as a side note, I think both the "just don't explain" as well as the "magic is/stays close to the ground" are pretty solid options you could go for! [Answer] Your on a Volcanically active world When the [volcano i can't pronounce](https://en.wikipedia.org/wiki/Eyjafjallaj%C3%B6kull) erupted is spewed enough ash into at the atmosphere that air travel was suspended around an area much larger than the Volcano. Now in your World there are lots of Volcano's (perhaps low activity ones) constantly spewing out ash. Not enough to cause issue with breathing but enough that whenever anyone tries to get an airplane to work the engines are quickly destroyed. So yes you can fly for 5-10 minutes but then your engine is clogged. If you don't have the technology to realize whats happening you may assume that's just what happens when some one tries to fly and thus powered flight is "impossible". [Answer] ## Gravity is lower People often assume, wrongly, that lower gravity makes flight easier but in reality the opposite is true. Higher gravity makes the atmosphere denser and that makes flying much easier than it is in the lower denser atmosphere under lower gravity. While a simple balloon might be possible, heavier-than-air becomes much more difficult and even living things will be less able to fly with the largest birds being considerably smaller. Technology might eventually allow it, but industrial era tech isn't going to get there. ]
[Question] [ The question is self-explanatory. In my novel, there is an evil sea goddess that wants to destroy the world. I want to emphasize that she wants to destroy the world completely, in a way no plant, animal, human being or bacteria could survive. She has water magic, what means she can control all water that already exists, but not create water out of nowhere. I suppose she could just create lots of tsunamis or waterspouts, but that would not solve the problem completely. Some people could still survive if they were lucky. I was thinking that she could levitate an absurd amount of water(like, all the oceans) until the stratosphere an then drop everything, like a liquid meteor or something. But I don’t know if that would work. I’m trying to avoid solutions like “dry all the water from the planet” or “poison everything and let them die of thirst”. I’m looking for something that would kill everyone in the planet in a matter of seconds, like a giant atomic bomb or something. But... with water. Extra information: * Since my character is a goddess, she can manipulate as much water she wants(including all the water in the ocean, rivers, lakes but not ice or snow) * She can summon hurricanes, water sprouts and other kinds of aquatic disasters * She can manipulate water pressure and density * No living thing can survive the aquatic cataclysm, not even marine animals * The world has to be completely destroyed in a mater of hours Answer with total world destruction with least amount of goddess interference wins! [Answer] If she can “control all water that already exists,” I assume that phase changes are allowed. In this case, you have two very cool options that are almost certain to kill all life on Earth very quickly: 1. Freeze all liquid water on the planet, including that inside the bodies of living creatures. (You did say that she can’t manipulate ice or snow, but perhaps she can turn liquid water into ice?) 2. Boil/vaporize all liquid water on the planet, including that inside the bodies of living creatures. I have no idea what these would feel like for an organism, and I kinda doubt that they would feel like anything at all, because our very mechanisms of experiencing pain are certainly dependent in liquid water in some way. So every organism on the planet might feel rather peculiar for a moment before exploding. Here’s another possibility, if you don’t like phase changes. There’s a lot of groundwater and underground reservoirs of water all over the world, not to mention low concentrations of water molecules distributed throughout the Earth’s crust and mantle that have been subducted over the years. She could probably cause quite a stir by suddenly bringing all of that water to the surface all at once, which would essentially tear the surface of the Earth to shreds and expose a decent amount of hot rock. [Answer] # "or bacteria" Well, that is the difficulty. Everything else can be done by having the oceans rise and roll all over the sea - this, by the way, happens in Agatha Christie's The Hound of Death and should be in your Goddess' power: > > He who would have been the next Guardian of the Crystal was bidden to act. > That the old might die, and the new, after endless ages, might come again, he loosed the Hound of Death upon the sea (being careful not to close the circle), and the sea > rose up in the shape of a Hound, and swallowed the land utterly. > > > But bacteria? There is almost nothing, except thorough neutrino irradiation of the whole planetary mass, that would kill all bacteria. Even a hydrogen fusion explosion in the sea would not kill bacteria more than 2-300 meters from ground zero, since water would screen the heat and the radiation. To kill the bacteria, you need to take control of the water they contain, and e.g. make it either coalesce, or shape like a snowflake or a spiked drop. Or two semilunar blades, and then rotate them half circle in opposite directions. This will kill all life at a cellular level, destroying their cellular walls. Plants, animals, bacteria down to Archaea. Even tardigrades would die: they can survive a complete, orderly desiccation, but unless they were already desiccated (and therefore had no water to wreak havoc in their insides), the water blades would rip them apart just as well. The cutting would kill even Gracilicutes, who ordinarily can survive a rupturing of what passes for their cell wall. Of course, this requires an almost infinite control capability and awareness; the goddess must be aware of, and control, almost every single water molecule on the planet simultaneously. [Answer] The only easy way to kill bacteria with water is heat. Which leaves the question: How does a godess heat the water without being a godess of heat? The answer is simple: By supplying the necessary energy to the water. The godess simply accelerates a single drop of water per cubic meter of sea water to relativistic speeds. See the [what-if on a relativistic baseball](https://what-if.xkcd.com/1/) for a writeup of the possible effects of this. Your godess can scale the effect to whatever she sees fit, simply by changing the actual speed to which she accelerates the water drops. Once the relativistic drops collide with the surrounding sea water, they will dissipate their energy, and effectively heat the sea to an arbitrarily high temperature. This method is 1. Fast. Basically all water bodies simultaneously explode into either a cloud of high pressure water vapor, or directly turn into a seething hot, dense plasma. It won't take long for the resulting atmospheric shock waves to level everything on dry land, before the water vapor arrives to displace the breathable atmosphere. 2. Global. With sufficient energy, the entire atmosphere can be blown off the planet. And even if you let parts of the atmosphere stick around, the entire surface of the earth will be heated to lethal temperatures by the condensing steam. This can easily heat every bit of earth's surface to 200°C, which will effectively disinfect the planet. 3. The nuclear option. This does not just look like an explosion, it is an explosion. An explosion that makes the worlds nuclear arsenals look like mere toys. [Answer] ### Removing water and osmosis All known life depends on water. It is simply too useful. You can do two things to kill all life. A combination is most likely to succeed. * Remove water. Removing water will kill nearly all multicellular life on the planet. They'll dry out and get irreparable damage in minutes and die off quickly if it didn't kill it outright. Simply have water remove itself from most creatures. Drying out might kill most multicellular life and a good chunk of single cellular life, but there are those that can survive a long time dehydrated. An example of multicellular life is the [Tardigrade](https://en.m.wikipedia.org/wiki/Tardigrade#:%7E:text=Tardigrades%20%28%2F%CB%88t%C9%91%CB%90rd,called%20them%20little%20water%20bears.). These are tiny multicellular creatures that will go in a special sort of hibernation mode to survive, sometimes even up to 30 years. This hibernation mode might require not a too sudden loss of water, but some animals might survive. * Osmosis. The second one is possibly more dangerous. That is why osmosis is your secondary measure. Instead of drying out, you infuse the cells with more water. Only a few organisms are build to prevent osmosis from absorbing too much water, namely plants, so the cell can't get too much water and simply pop, destroying the whole cell. But if you force it in a cell, it'll kill the most hardy cell by simple physics. Too much pressure on the cell walls. By drying out all the life that is not able to survive drought you have enough water to kill all the rest if there wasn't enough water in the air. So in short: leave the cells dry and pump them to bursting. If life survives for more than an hour I would be surprised. [Answer] To give another spin on the "boil all the water". If the goddess can't insta-boil everyone, but still can control evaporation and clouds/rain, she can start turning more and more of the oceans into clouds, while preventing the water from condensing back. As water vapour is a potent greenhouse gas, at some point thing will keep going on their own, and the runaway greenhouse effect will turn Earth into something like Venus. Whether there is life on Venus or not, no current Earth life would be able to survive in such conditions, and the change would be probably too rapid for any bacteria to adapt. Even tardigrades have no chance in 900°C. [Answer] All your waterbender goddess needs to do is dropping all of the world's water at once. The asteroid that killed dinosaurs had its mass estimates [between 1015 and 4.6 $\times$ 1017 kg](https://en.wikipedia.org/wiki/Chicxulub_impactor). The oceans on Earth have a mass estimated at around [1.34 $\times$ 1021 kg](https://phys.org/news/2014-12-percent-earth.html) (about 10% of the mass of the Moon). Now sure, the space rock came at bat outta hell velocity. But the oceans are at least 5,000 times more massive, and when all that falls back from the stratosphere, it will cause damage in interesting ways. Randall Munroe calculated what would happen if 6 $\times$ 1011 kg of water fell of the sky as a single droplet. [This is his verdict](https://what-if.xkcd.com/12/): > > The wall of water expands outward kilometer by kilometer, ripping up trees, houses, and topsoil as it goes. The house, porch, and old-timers are obliterated in an instant. Everything within a few kilometers is completely destroyed, leaving a pool of mud down to bedrock. The splash continues outward, demolishing all structures out to distances of 20 or 30 kilometers. At this distance, areas shielded by mountains or ridges are protected, and the flood begins to flow along natural valleys and waterways. > > > The broader region is largely protected from the effects of the storm, though areas hundreds of kilometers downstream experience flash flooding in the hours after the impact. > > > If you did the whole oceans instead, you'd be using 5 billion times more mass. At the very least you would kill all plant and animal life on the planet. Also bringing all that water up, then down will first cool it very fast, then boil most of it, so no microbes should survive either. [Answer] Increase internal water pressure and watch all living things explode. All living things contain water, and all have some variety of cell membrane that separates the inside of the organism from the outside. The goddess simply needs to increase the water pressure of all water inside living organisms. The cell membranes will not be able to withstand the massive physical stress, and will rupture very rapidly (this is called osmotic lysis). With a watery pop, all life on earth is extinguished. [Answer] Make Water Non-Polar If your goddess can alter water chemistry she could make it non-polar, this would mess up the chemistry of all life forms as an awful lot of molecules will no more be soluble in water and suddenly fall out of solution thus rendering impossible practically every biochemical reaction, not to mention the precipitated solid inside animals blood vessels causing embolism. EDIT: I just realized that this would probably also prevent the lipoproteins in the cell membranes from functioning properly thus dissolving all cells at once [Answer] The "even bacteria" constraint of the question is rather restrictive but here goes: * Dissociate water in all living things back into hydrogen + oxygen. The resultant chemical reactions destroying cells would be fatal to all cell based life on the planet very quickly. * Dissociate water everywhere back into hydrogen + oxygen. This results in a tremendous blast as every bit of water on the planet flashes into gas and then a second blast as the hydrogen + oxygen mixture ignites. * If nuclear manipulation is allowed, change all water to heavy water, which throws off cellular chemistry, killing off higher lifeforms: <https://en.wikipedia.org/wiki/Heavy_water#Effect_on_biological_systems>. * Trigger nuclear fusion of the hydrogen in water to blow the planet to bits instantaneously. If you want something more plausible are willing to relax the constraint on being instantaneous, I'd suggest blanketing the world in heavy, reflective clouds. In the short term, the result is effects similar to nuclear winter: <https://en.wikipedia.org/wiki/Nuclear_winter#Consequences> and the longer term effect is the planet cooling to resemble something like Pluto. [Answer] Destabilize the orbit of earth by shifting all the water to one side This may take a little extra magical handwaving, but I thought I would throw it out there. According to this [Quora question](https://www.quora.com/How-much-does-all-the-water-in-the-oceans-weigh#:%7E:text=Earth%27s%20ocean%20is%20made%20up,short%20ton%20%3D%202%2C000lbs), the oceans make up about 0.022% of Earth's weight, and the oceans are 97% of the water on Earth. So with lakes and rivers, that's about 0.023% of Earth's weight. That doesn't sound like much, but maybe shifting it all to one side would destabilize the orbit enough to send it spiraling into the Sun. If that seems to slow, maybe it's just enough to turn an asteroid near-miss into a direct hit, causing a mass extinction. The survivors would then spiral into the sun. [Answer] Taking inspiration from oil fracking, your goddess can manipulate and twist the water into extreme high pressure and then drilling into the earth core. With thousands of events happening in strategically planned waves (for ultimate destruction) all over the world, it would literally be armageddon with very little warning; and no-where safe to run. Not only does that expose the surface to contaminates such as oil, but also will causes the tectonic plates to shift and will eventually expose a path for hundreds of volcanoes to erupt. Focusing on the deep trenches in the Pacific Rim; triggering a chain of volcanoes could cause massive tsunamis which could be increased in acceleration and power before they hit land. This would generate huge 300+ ft waves causing destruction for 30+ miles inland and wiping out coastal communities. Even the polar caps would be affected with most of the snow melting contributing to sea level rising and flooding. Enough lava flows and even the oceans could evaporate into steam or change chemistry (increased salt content and contaminates) and temperature enough that sea creatures could no longer adapt and survive. The atmosphere would be a pervasive fog, with any condensing water on the surface cycling back into drilling more and more deeply. All drinking water would be contaminated. Plants would be initially destroyed by the ocean floods and the heat and toxins from volcanoes. Light and heat from the sun would be dissipated to the point where plants would struggle to survive. CO2 in the air would be so excessively out of balance that animals would struggle to breath. Possibly the water vapor in the atmosphere would be too much pressure and the ozone pops like a bubble. Sure, the would be a lot of effort for your goddess, but it would be spectacular. [Answer] # Ice-9 When I saw this question, I immediately thought of [Cat's Cradle](https://en.wikipedia.org/wiki/Cat%27s_Cradle) by Kurt Vonnegut. In the novel, a scientist creates a novel form of ice which freezes at temperatures above 0 degrees Celsius and acts as a seed crystal when in contact with liquid water. > > Ultimately, this results in the end of the world when the crystal is accidentally dropped into the ocean. The world almost instantly becomes a hot, dry wasteland as all liquid water is locked up in this new form of ice. It affects people & animals too - contact with the crystal with bare skin results in all the water in your body crystallizing. > > > If the goddess can convert even a small amount of liquid water into Ice-9, this will do exactly what you want. [Answer] I’m kind of answering narratively rather than scientifically, so I am using exactly 0% of my physics degree to suggest: # Fire from water About 0.03% of the hydrogen atoms in Earth's oceans are a bit heavy, and we can presume that this goddess can feel this stuff and collect it. With a bit more technology, one can assume that she can find ways to irradiate yet more of it to make tritium and then contemplate a deuterium-tritium nuclear reaction on a truly massive scale. Presumably this would be a massive underground chamber hollowed out deep, down into the crust, by erosion with water, followed by getting a cult of humans to do some necessary refinement steps with the water given, followed by storing this deuterium and tritium in that underground chamber under that great pressure. The goal would be to ignite all of this deuterium-tritium fuel at once in a massive fusion burn which would easily dump far more energy than any known extinction event into the Earth's crust, hopefully rapidly liquefying the Earth back into a blob of hot magma orbiting the Sun, as it was in its earliest days. [Answer] Split the water in hydrogen and oxygen. All at once, if you want to be extreme. That alone would destroy all life on the planet. [Answer] # A giant atomic bomb, but with water. The goddess has the ability to "Manipulate the water pressure and density" if she does this with just the water in the oceans and manipulates that water to have a pressure and density similar to the conditions found in the center of the sun, then all that water becomes a giant fusion bomb. This is exactly what the OP wants. Note: She releases her influence to "set off" the bomb. [Answer] ## Blot out the Sun 1. All\* life on earth depends on the Sun for energy and warmth. 2. Ice reflects light well 3. Your goddess can control water / ice. Create very thick layers of clouds in the upper atmosphere. Certain levels of the atmosphere are very cold - this is where you want to put the clouds so they naturally form ice within them. Volcanic eruptions have lowered the worldwide temperature by several degrees for long periods of time, and these eruptions certainly don't block all sunlight. If your cloud layer covers the entire sun-facing side of the planet, and reflects 90% of the incoming light, I would expect the entire planet to be a frozen hellscape within minutes, and dead within days. You have massively changed the energy balance of the planet, and it will rapidly radiated its stored heat away. [\] Ok, some life gets heat from deep sea vents, but I expect this would get them too, as the seas freeze, and oxygen exchange stops. [Answer] Bullets!* She could just use a large sea body to create many droplets and then accelerate them as kinetic projectiles to anything she want to kill. [Accelerated water cuts through metal](https://en.wikipedia.org/wiki/Water_jet_cutter). A mind-intensive solution, but no need to control internal water of living organisms. ## More hardcore solutions > > She can manipulate water pressure and density > > > If she increases the pressure enough to get the water's nuclei close enough, she can create thermonuclear explosions. If she increased the density enough, she can create a black hole. [Answer] # Hold all water still In order to provide the solution with the least amount of interference, the solution is not allowing water to move. Including all water within organisms. All life is dependent on water to be the medium by which chemicals and other things are transported. If the water stops moving, everything dies. Simple, efficient, and deadly. But not incredibly dramatic, all life just stops, the end. [Answer] At sufficient velocity... Assuming energy is not at all a limitation. Any option that doesn't kill the bacteria often hiding kilometers underground is insufficient — we need full crust destruction for this to work. So whatever approach accomplishes this with the least amount of water manipulated will be the best, because it'll be simplest to target and execute. "Destroy every cell" might be too hard to coordinate. Suspend single drops (microliters, really) of water in the air spread out evenly over the Earth — maybe ten or fifty kilometers apart — and ping them towards the ground at, say, c minus one attometer per second. Each (upon immediately plasmizing on contact with the air) detonates with the energy of the Chicxulub impactor, gouging hundred-mile craters that overlap each other thanks to their proximity and melt the crust below them, spraying chunks of mantle into space for good measure. If the effectiveness of this approach is in doubt, speed up the water more. Penetrate the Earth with plasma lances in all directions, ripping it to a cloud of molten debris splattered all over the solar system. [Answer] She can use the water to create a giant [lens](https://www.sciencealert.com/how-you-can-start-a-fire-with-a-sandwich-bag-filled-with-water) between the earth and the Sun. It wouldn't require using a significant amount of the water on earth either, a relatively thin layer with concentric [ripples](https://en.wikipedia.org/wiki/Fresnel_lens) would do the trick. [Answer] # Salinity An alternative, focusing on the title of the goddess: She's not a not just goddess of water, she's a goddess of the sea. So in addition to powers concerning water, she should have powers concerning salt. Making formerly fresh water brackish and undrinkable should be in her wheelhouse(there is frequent mythological precedent for rivers and streams and the like). Massively increase the salinity of all the water on the planet, including that inside living cells, which will cause them to rupture due to osmosis, destroying all living things. Has a "thematic benefit" that she's not removing water from the planet, nor chasing its form, and is keeping with being a "sea goddess" rather than a "water goddess". [Answer] All that is needed is to increase water density enough to cause formation of a black hole [Answer] ### Knead Earth's Crust Like Dough There's enough water on earth to form two giant hands and mash and mix up the rest of the earth into a nice glowing ball of magma/lava (when there's no longer a crust is there a difference?) Sure the edges of the hands would be constantly exploding/evaporating as they pushed on the magma, but there's enough water that she should be able to thoroughly mix the current crust in before the hands all turn to steam. ]
[Question] [ So, in the relatively-far future, humans, in their endless quest for immortality, develop a form of mind uploading. This involves scanning the brain, cell by cell, and creating an electronic model of the neurone patterns in which all the information about the subject, their memories, likes and dislikes, is housed. This information represents the living soul. However, in order to have the ‚Äúsoul‚Äù transferred rather than simply copied, the process has to destroy the nerve cells as they are scanned, so that the information is removed from the brain as it is reconstituted in digital form. Why would the scanning process destroy the neurones? I am leaning towards a reason involving radiation or something like that destroying living tissue, but am open to suggestions. Please note that a reason need not be particularly in-depth, just believable. [Answer] Solution #1: your scanners don't have the penetration they need to read through brain matter (or skulls). There is no scanner with the kind of penetrative power you need to scan things at an atomic level without first getting rid of the matter that's in the way. That is, in order to scan the second millimeter of brain, the first millimeter must be removed. The machine literally kills you during the scanning process, layer by layer, removing brain matter as it goes. Fortunately it's a very quick process. The whole process is so fast that subjects report not noticing a thing. (In the [Bobiverse](https://www.goodreads.com/series/192752-bobiverse) series, this was basically their solution, except additionally they started with a [cryogenically frozen brain](https://www.cnet.com/science/features/cryonics-brain-preservation-and-the-weird-science-of-cheating-death-alcor/), basically scraping through it layer by layer for the scan.) Solution #2: the scanners are flawless. The original is destroyed on purpose. For a darker explanation, you could try what was done in [The Fare](https://archive.org/details/Asimovs_v03n11_1979-11/page/n119/mode/2up). That story was about teleportation, but the short version is that it actually generated a copy, and the original was secretly killed. Perhaps the scanning process is completely non-destructive, but the implications of having two of you was a problem, so the copy process simply destroys the original as a separate act, by design. Alternatively If I recall correctly, [Old Man's War](https://www.goodreads.com/series/40789-old-man-s-war) simply did the transfer and never fully explained why this caused the original to die. I recall thinking maybe there were some shenanigans that would be revealed, but really I think the "how" was not a focus of the story so it was glossed over. It just worked. If the "how" is not important to your story, you could do the same. The old you just loses brain functionality and it's never really explained. [Answer] This is extremely easy, I feel some answers are overcomplicating it. It's more scientifically plausible that mind uploading WOULD destroy the brain than that it would leave it intact. This is because (in reality) there are two kinds of brain-scanning: non-destructive (including MRI, EEG, and all those) and destructive brain-scanning, which is done at autopsy. Mind-uploading really just means scanning a brain fully/perfectly (as per [this question](https://worldbuilding.stackexchange.com/questions/240973)). Naturally the best way to get a close look at a brain is to take it apart. The brain being intact in a head makes it hard to get a good look in there (real facts, not worldbuilding). [Answer] # [The No Cloning Theorem](https://en.wikipedia.org/wiki/No-cloning_theorem) Brains are special. The mystery of consciousness and free will was unravelled when we discovered the brain fundamentally relies on quantum behaviour to function. It is impossible to take a quantum object and create an independent, identical copy. That means we cannot duplicate the brain while preserving the original object. This is unlike, for example, a painting. We can duplicate a painting because we are not interested in the quantum probabilities of the various molecules. [Answer] Heisenberg's Uncertainty Theorem (Sort of). This is in relation to particle physics - the more accurate you make the speed of (IIRC) a Subatomic particle, the more imprecise you make it's location and vice versa. Brainwaves in a functioning brain have the same issue, even unconscious thoughts/processes cause 'traffic' in the Brain. Even relatively simple things like Breathing trigger so many neurons firing that the Scanner simply cannot keep up with the changes in order to map it correctly. The solution to this is that the brain must be 'frozen' - that is, made so that all activity, conscious, unconscious etc. is stopped. This is to allow the Scanner to scan the ~2.5 Petabytes of data in the Human Brain in order to map it accurately. Unfortunately this process isn't reversible - Neurons that have been 'frozen' (Not temperature frozen - I mean all activity stopped - although this could be done using a cryo-type tech) cannot be restarted and so the organic brain dies. [Answer] ### Synchronization issues While your scanners are fast, they just are not fast enough. Especially if you want to be reasonably sure you did no major reading errors. What you can do however, is to flash-freeze the brain and instead of recording the electrical patterns scan the frozen-in-place neuro-chemical state. Since the signals travel as a ion concentration shift, interrupted by transmitters and inhibitors, reading them provides the information necessary to recreate the exact thought-pattern at the time of flash-freeze. The biological substrate can not be unfrozen fast enough to survive the procedure, thus the person being scanned dies. On the plus side, the frozen mind image can be duplicated since you can take your time before starting the digital substrate. Live backups of a digitized mind may be difficult to achieve, since synchronization strikes again: Your band-with is just too low. To do a copy you have to slow down the digital substrate, but this has a chance of introducing sensory corruption, as the real world still runs normal speed and thus there's too much information for the slowed mind to work on. Again there might be a way of "flash-freezing" the digitized mind as well, but it is a rather violent procedure, which literally fries the active pattern into the substrate. The chips and boards become trash, as the burned in patterns break them, but hey, you can use them as a kind of snapshot if you need to revive a mind. If you read them like a modern flash-drive recovery though (which is destructive), you may read them only once, so make a proper copy. ### Radiation based: the return of synchronization issues Your Hyper-CT scan literally fries their brain. A simple CT / MRI is no problem for the brain to handle. But you need to be FAST. To prevent ripping the mind apart by desyncronization of sections of the brain, you have to scan each and every nerve, each electrical and chemical potential within that corresponds to neural information just about instantly. In fact the maximum time you have is about a quarter of the time it needs for a single neuron activation to take place. As human neurons can fire at a rate of 200 Hz or slightly more that leaves us with (1/800 s =) 1.25 ms or slightly less. Lets assume 1ms and take the rest for safety margins. You want to be reasonably sure to get all relevant info, so you need MANY pictures and they must be taken all at once. There are about 86 \* 10^9 neurons in a typical human brain. We simplify the brain to a sphere. This means a diameter (in neurons) of about 1.24 (the volume-equivalent sphere diameter compared to a cube) times 4'414 (the cubic root of the total neuron-count), which is roughly 5'480. This is the absolute minimum number of scans you need to do, even if all where perfectly spread. To prevent overlap in your scans you could do spherical swipes, which leaves you at least at pi\\2 times the scans. This gives us 54'085 scans, which is about 18.5% of the simple assumption (square-root of neurons count (about 293'258)). ###### lethality 54 thousand scans within 1 ms for a single full scan. (Of course you might want to do two scans to reduce read-issues...) The aproximate dosage of a CT of the head is between 1.6 and 3.2 milli-Sivert (mSv) depending on exact procedure and if there was a contrast substance involved. That leaves us with about 2.4 mSv \* 54k scans for a total of *130 Sv. This irradiation is applied just about instantly. Here's something about acute dosage: The LD50[@30days] is at 4-5 Sv * The first guy to die from the demon core got 5.1 Sv and 25 days * The second guy got 21 Sv and died after 9 days. * Boris Korchilov worked in an unshielded live nuclear submarine reaktor. He had 54 Sv and died after 6 days. Your scan is running 2.5 times that! Finally, since your scan is VERY LIKELY (read certain) to kill said person, you might want to do twice or more times as many scans to ensure data integrity. You don't have a second chance so you might throw any scans you can do and just average your results. [Answer] When you record someone's brain state, it's more than just figuring out where the electrical signals are and how the neurons are laid out. You need to identify what the electrical potential is in each of the neurons, and pretty much count the number of atoms in every vesicle of every synapse. Doing so imparts energy to the system, which results in neurotransmitters being released, cells bursting, and electrical potentials being severely upset. The brain is basically cooked from the inside. What's left is nothing like the one that you started off with. [Answer] Author John Scalzi handled this in [Old Man's War](https://us.macmillan.com/books/9780765348272/oldmanswar), and since someone already brought this up, I thought I should add his way of handling the issue. In the series, brains have three things: their physical state, their electro-chemical state (where the charges and chemicals are distributed), and lastly an energy field that is created by the first two things. The energy field is what creates "consciousness", and, importantly, can be transferred but not copied with the technology available (except in one side story). Thus you can create a second artificial brain that has the first two components, but then have to transfer the conscious energy state from one to the other. The original brain isn't dead, but it's not conscious. [Answer] Currently, if you want an accurate 3D map of the brain you have to slice the brain in many thin sections. To get a map of the brain that is accurate enough to recreate it in a simulation you not only need to know how many neurons are at a particular location, you also need to know how each neuron is connected to every other neuron. There are ways to reconstruct maps of the brain without destroying it by viewing it from many different angles, like MRI or CT scans. These maps do not [give enough resolution to resolve individual neurons](https://www.quora.com/Radiology-Will-MRI-technology-ever-reach-the-resolution-to-image-individual-neurons). MRI for example can give currently give a resolution on the order of a few hundred micrometres, while axons (the wire-like structures that connect neurons) are on the order of about 1 micrometre. So a solution based on current technological advancements is that imaging technology cannot give an accurate map of the brain without chopping it up into slices. I think that once the brain is dissected into many thin slices we would qualify that brain as destroyed. This slicing process is absolutely necessary to know how all the neurons are connected to each other, which in turn is necessary to fully preserve the memories/personality of the person. This would mean that scientist are able to run a virtual brain on the computer before we could image a brain without destroying it. At the current rate that AI is evolving this is not too far fetched. [Answer] You can't pause an uploaded brain. The scanner processes one neuron, or one section of the brain, at a time, and it takes some time to complete. It might be only seconds or less, but it's long enough. Say that the front half of your brain gets scanned first. That front half, as it's being assembled in digital memory, does not have a back half to communicate with, so it ceases function or behaves unpredictably. This causes all sorts of problems when you then have to unify the back half into digital memory, since until then it was still communicating with the meat front half and suddenly finds that what is now the front half is dead or out of control. You also can't pause the front while you're working on the back, because there's still this "desynchronization" involved ‚Äî the back half suddenly finds that the new front half is now having the thoughts that it used to be having a few seconds ago. These problems, ranging from psychosis to digital coma, are bad enough that mind uploading technology has to take a different approach: destroy one neuron/section/lobe at a time and relay the signals back and forth from the physical world as you go, [Moravec transfer](https://everything2.com/title/Moravec+Transfer)-style. [Answer] I agree with the answer by @wokopa that says it's scientifically likely that scanning would destroy the brain, and I just wanted to put some perspective on that. Basically, producing a high fidelity 'copy' of a person would quite likely involve mapping every single synapse in the brain, and the issue is that there are really rather a lot of these. I'm no expert, but a quick google brought up this [nature paper](https://www.nature.com/articles/d41586-019-02208-0), which says there are 100 billion neurons in the human brain and $10^{15}$ synapses, which are the connections between neurons. That's 1,000,000,000,000,000. Each synapse is a microscopic site where molecules and electrical impulses travel between neurons. To be fair, we don't really know how accurate the simulation would need to be in order to accurately emulate someone's thoughts and personality, but in the worst case, to simulate a person's behaviour accurately, you would need to know some microscopic details of every single synapse, as well as where they all are in space. Now it's already very hard to imagine any technology that could scan something as large and complex as the brain at a high enough resolution to pick out individual neurons, but if you need to know details about each individual synapse then this is just out of the question - there would just be no way to do it without taking the whole thing apart and performing a miniature chemical assay on every single one. That would destroy the brain without question. Of course, once you've done that it's all just digital data, and once someone has been scanned there would be nothing to stop someone from copying the data and running two separate simulations of the same person. If you need a way to prevent that it would be a separate question, and I don't really know how I would answer it. [Answer] # People like it that way If you're uploaded, that means every secret, every private memory, every password you know is now known by two entities, both of which think they are you. Furthermore, because of its strong similarity to the original, each can conjecture about passwords the other are likely to create and really just do an incredible job of impersonating them. And not just two - the company that runs the brain scanner also keeps a record of your data, so even if "both" of "you" get along, the company has a hostage that they can interrogate arbitrarily. After a few messy legal cases, regulations were imposed on brain scanners, requiring them to destroy the original and not retain any data, as well as making it illegal to copy a person's brainscan data except for backup, and illegal to run multiple instances of them. ## This is important, because otherwise data can be copied after upload Even if the original brain is destroyed, if your goal as a worldbuilder is one-human = one-mind, you need some way to address why the data of the brain, once uploaded, can't simply be copied. It's scientifically not possible to have un-copyable data on a computer; computers cannot read or transfer data without copying it, and the data needs to be copied at least once to get it off of the scanner. Unless your world contains some unknown factors (magic) that physically prevent multiple instances of the same brain from running at the same time, legal restrictions are your only option. [Answer] # What would happen if it did not destroy the previous brain? Well, you could end up in a situation similar to time traveller conflicts - two people, who think they're the same person, at the same time, potentially meeting each other. Which is where things can get [interesting](https://movies.stackexchange.com/questions/84638/why-did-harry-and-hermione-have-to-worry-about-being-seen)...Except, of course, time travel isn't happening here, so there's technically no paradox... More directly, that linked question refers to the idea of why time travellers in the Harry Potter universe would try to avoid being seen while making changes - seeing themselves would drive themselves mad. So you could apply the same effect here, since it's not quite a mirror image they're seeing, but a mirror image with autonomy, and that thinks that they're who they are. Since this isn't time travel though, we could consider one additional wrinkle to the issue; did the brain uploading process stop after the brain was fully uploaded? Or are we getting continuous upload after the fact? ## The brain scanner may not be able to be turned off safely If the brain scanner is portable enough, it could be uploading to the uploaded brain continuously until the brain is itself no longer transmitting any changed information. If the brain was still transmitting information to the uploaded brain's brain location, one brain all of a sudden is getting updated signals, and seeing themselves seeing themselves, moving in a way different to the way they're moving, and processing two people's worth of input and output. Technically, if you could hold the uploading brain in place, and desensitized, this might be less of an issue, but then you run into the issue of the uploaded brain finding the desensitized uploading brain, and having to process that. ## There may not be a technical reason to destroy the brain, short of the safety of the uploaded brain to prevent conflict when encountering the uploading brain. [Answer] In neuroscience to study brains, we usually stabilize them with formaldehyde, antimicrobials and tampon solutions to block any biological process and freeze their structure. Then we fine-slice them and analyze them in various ways. A scifi brain copy tech could perform very fine slicing (harder than it looks) and molecular scanning to exactly the structure and functional status of a brain. As it's obvious from my description that the subject is sacrificed (lab slang) in the process. Furthemore, the death should be immediate and possibly painless (on mice it's common to use either spinal dislocation, decapitation, lethal injection, etc) in order not to release a pain/panic/pre-death biochemical cascade that would greatly change its structure. If you would copy this status, the newly cloned individual would wake up in a quite distressed state (maybe going crazy directly). [Answer] ## "Moving" the consciousness, not copying it We know perfectly well how to upload a copy of a brain. That's about as difficult as the average middle-school science project. The problem is that people don't like that, because that means it wouldn't be them, but rather it would be a copy of them. This is true whether you destroy the brain or not. So, instead, we needed to develop the technology to allow us to slowly move different parts of the brain, which involves rewiring the brain to replace those sections with machines and detaching the original. Once this process is done, no functioning part of the original brain is left. --- Now one could make the philosophy argument that (1) cloning yourself and then killing the original, (2) "moving" your consciousness and (3) even just going to bed at night and waking up in the morning, are all functionally identical. But you know how people are... [Answer] ## Scientific Coverup Once the transfer is finished, a comparison of the new consciousness and the original person could reveal that the technology was pushed out before it was complete. However the differences were slight enough that they couldn't be detected except by comparison to the original. Rather than lose out on funding the scientists concocted a story (see any other answer to this question, but maybe just pick one) for why the original brain needed to be destroyed as part of the process, codified that into the brain transfer process, and never give a satisfying answer as to why they refuse to undergo the process themselves. [Answer] > > However, in order to have the ‚Äúsoul‚Äù transferred rather than simply copied, the process has to destroy the nerve cells as they are scanned, so that the information is removed from the brain as it is reconstituted in digital form. > > > If souls do exist, we know very little about them. In the future, a way was found to scan brains very accurately, and simulate them but they just wouldn't function. Believing they just didn't get the scan, or simulation to work accurately enough, the process was continually refined, and one day a participant happened to die during the process, and for the first time the simulation came to life. While skeptical, other scientists tried to repeat the process on terminal patients, and came to the conclusion that for some unknown reason the original had to die, for a copy to function. Popular public opinion started believing that the reason was individuals had souls that would be drawn into an identical copy, if the original died. The reason is still heavily debated. ]
[Question] [ In a book I am writing, one of the countries I am writing about has a militarized society, but also a strong sense of universal weapon ownership, to the point that more people in the society have actual tanks than cars. Public transportation is very popular, but even still, personal ownership of tanks by individuals is common enough that one could easily see them in a parking lot, or seeing them being driven as personal vehicles the way Americans drive sedans, in a drive through or in the city streets, is not considered unusual or particularly noteworthy. This society produces them for professional sports, having various sports like tankery (think Girls und Panzer) or tank biathlons/triathlons and tank ballet (like in Russia irl). They are also often used as tractors and chassis for construction vehicles (companies and farmers commonly have hoists and tools to remove/replace the turrets on tanks). As for manufacturing, there are automated tank plants which can produce tanks of all kinds of eras (with parts for WWII-era tanks still mass produced to modern machining standards), using robotics to lower costs and need for specialized labor. These plants are much more common in the country than one would find irl, due to the abnormally high demand. I did some looking around, and in WWII, a T-34 was 130,000 Roubles (24,531 USD) and a Sherman was 44,556 USD, which would translate to 256,512 and 623,798 USD respectively in today's money. Would the use of modern manufacturing techniques & automation, more tank plants with more frequent production, and higher demand drop this price, and if so, how much? Would there be a feasible way to drop the price of the tanks to around the cost of a car or truck (30,000-70,000)? What might be some key considerations to keep in mind in the manufacturing of tanks to keep costs low? Note that these tanks are built in ways to minimize (if not outright remove) planned obsolescence. They are designed to last as long as possible and be as cheap and easy to fix and maintain as possible, no matter the model. [Answer] In the name of upkeeping their proud military tradition, your society has chosen one of the worst civil vehicles possible, rivalled only by steamrollers and drag cars. * Tanks are incredibly uncomfortable to drive for extended periods of time, by the virtue of being engineered for being heavily armored and carrying guns. They lack significant ventilation, are often loud, and possess a multitude of hard edges for you to bang your head on. The king of this was the T34, due to its sloped armor. * For the reasons listed above, they are also inept at carrying cargo. If you want to take a new TV or Lounge home, you either have to pray to god that it fits inside the commanders turret and comes back out in one piece, or lash it to the outside of the vehicle. * Only fit healthy people can use it. Tanks are difficult to get out of, requiring you to clamber out of a turret to do so. An elderly person with movement difficulties, disabled person, or pregnant woman would have a heck of a time trying to get out. * Tanks have terrible visibility. Due to having few places to be shot at from, they also have few places to see from. Unless you are carpooling with someone in the commander's seat, you have terrible visibility. Considering you are driving a vehicle capable of ploughing through a house with minimal effort, urban commuting will result in a multitude of streetsign-flattenings, house-flattenings, pedestrian-flattenings, cyclist flattenings, heck, just about a flattening of everything else a few dozen tons of steel on treads can crawl over. * The infrastructure required to allow widespread usage of 30-40 ton vehicles is nuts. Bridges, highways, parking lots -Tanks are inherently less reliable than cars and require much more effort to perform maintenance. Also, what will you do if a 30 ton vehicle breaks down somewhere inconvenient? If you still want to keep a military-vehicle based society, I can offer a better alternative: [![enter image description here](https://i.stack.imgur.com/uCO6t.jpg)](https://i.stack.imgur.com/uCO6t.jpg) Half tracks, while capable of being militarised, due to their protective armor and varied weapon platform capability, are also a valid civil vehicle, having a far greater cargo capacity, visibility, and maneuverability. By virtue of being less of a heavyweight (8 tons to the Shermans 30) they are also inherently less expensive. They also have greater parts compatibility with actual cars, which you have stated also exist in this society. [Answer] No Let's look at a grossly oversimplified case. On the one hand we have a SUV, which costs $x to construct. Now we want to have a SUV, plus a big main gun (central to the definition of a tank), plus a rotating turret (also central to the definition of a tank) plus a lot of advanced armour, plus a lot of battlefield electronics (sensors, vision enhancements, aiming enhancements, threat detection). We are assuming that this SUV can magically support all the extras that are being piled onto it (see the next paragraph for the real story). In order for a SUV with tank-stuff to cost the same as SUV without tank-stuff, the combined cost of the gun, turret, armour and electronics must be zero. This is impossible - electronics alone are typically exceeding the cost of all other parts for most (all?) combat aircraft these days and I suspect tanks are in a similar situation. However, a SUV chassis cannot magically support a main gun, turret and lots of armour. Instead the tank needs a much, much stronger suspension to handle all the armour, a much bigger engine to propel it all and a much bigger fuel tank, which is why a SUV masses around 1 ton and a M1 Abrams masses over 60 tons (how much over depends on the variant). So, even without all the stuff that makes a tank a tank, the suspension and engine need to be massively bigger, which will cost more. The third point relates to the increased weight - it is going to cost far more to ship a tank from the factory to the local dealership than it will to ship a car from the factory to the local dealership. This is probably the most trivial factor, yet it is going to drive the price further up. The next point is that the indirect and resultant costs of having tanks on the road will impose huge costs on the community. As stated in the comments, tracks rip roads up and they do not last long compared to tyres. Tanks also have roughly double the width and length of a typical SUV, which means that all roads need to be doubled in width in order to allow all lanes to be doubled in width and all carparks need four times as much area as they would to accommodate cars. Let's not even talk about accommodating tanks at drive-thru facilities. The costs for doubled or quadrupled infrastructure need to be borne by someone, and that someone is going to be the owners of the tanks - expect registration to be a massive ongoing expense. Finally, the ongoing costs to the owner for operating a tank will be horrendous. All of those expensive components need to be maintained, which is why workshop units are flat out even in peacetime, let alone war. Then you need to pay a fuel bill of over 1 gallon per km when moving on the roads, twice that off-road. (Apologies for mixing imperial and metric here!) Not to mention garaging the vehicle at home (which will need to be much more secure than a normal garage - you're stopping thieves from stealing your 105 mm main gun here, not just a .22) and parking costs wherever you go (they will need to provide the equivalent of a super-secure gun safe for your entire tank wherever you go). In short - no in all respects. It is not possible to build something for nothing, which is what is desired for a vehicle with big, expensive extras to cost the same as one without. The ongoing costs also make the concept hideously expensive. [Answer] You can not make tanks as cheap as cars, but you can make them a regular part of you society despite being more expensive. ## Kickstarting Private Tank Ownership En Masse A tank will never be cheaper to MAKE than a car, but the situation could arise where new cars are so hard to come by and old tanks so easy, that these old tanks fill a major supply shortage. Imagine a country that is already of a 3rd world status gets swept up into a long and highly destructive revolution. During this war, car production is replaced with tank production and the country spends a vast proportion of its income stocking up on cheap tanks to meet its war time needs. Eventually the country becomes so mired in debt, and its infrastructure so badly damaged by the war that no other country plans to invest in it any times soon. The government collapses, the rebels win... but no body has a good plan for rebuilding, so everything falls into anarchy. This country is left with such a large production deficit that they can not afford to import any new cars. All thier wealth has been squandered on making this giant fleet of tanks that are too cheaply made to sell off to any other country with the money to buy them. And with no government left saying not to, soldiers simply return home with whatever guns and tanks they have because there is no one else left with a "rightful authority" to own them. So sure, Bob next door knows his old tank gets worse gas millage than your sedan, but a tank is all he was left with after the war, so that is what he uses. ## ... Then turning it into a culture In many ancient civilizations, the social caste of a person was defined by the quality of arms that they had private ownership of and/or thier social caste required them to own a certain quality of arms. This massive dissipation of military grade weapons into the hands of an unpredictable and very large group of private citizens makes filling the power vacuum left over very hard. While warlords normally take over in these sorts of situations, no one can come close to forming a powerbase by force over so many private tank owners; so, instead the power vacuum becomes replaced by a caste system based on private ownership of weapons. Basically, tank owners become like the knights of Medieval Europe. In this way, all those private tank owners are united into a democratic union or feudal system that shares powers over the general population, and it is codified into law that a man's militia value is tied directly to his caste and rights. Eventually, the economy rebuilds, and things become more orderly and prosperous again, but the law of the land remains. Either "he who owns a tank has rights that non-tank owners do not" and/or "He who has rights, has a legal responsibility to own a tank." So, instead of making tanks cheaper than cars, they are in fact more expensive: and this is how tank owners like it. A brand new M1 Abrams may still cost a private citizen a hefty 6 million dollars, but by keeping new tanks more expensive than a car, this price tag becomes a huge point of gate-keeping making sure that the poor stay poor and disadvantaged and the rich stay rich and privileged. People who own tanks therefore drive them instead of cars as evidence of thier station. So when a cop shows up to break up a bar fight and has to figure out if you just committed Assault on Citizen (10-20 years in jail) or Citizen's Right to Corporal Punishment (Not a crime at all), it could all come down to who showed up in tank or not. So, even if all you can own is some 70 year old museum piece of a tank, you continue to use it and maintain it to the best of your resources, because you are doing it to maintain your noble status in society. [Answer] Cost to manufacture? No. Cost to the consumer? Sure! The government subsidizes them. Take America's economy. Assume the entire defense budget is still spent, but all on subsidies for private owners to buy any weapon they want. We currently subsidize electric vehicles, so no reason we can't imagine a society that subsidizes tanks instead. Maybe they never developed social security because they pour that into more tank subsidies too. Your explanation on public transportation makes sense because the tanks are still expensive to operate (although that may be subsidized somewhat too) but you might imagine that a low end car costs 20k, a good car costs 50k and a tank costs like 60k-75k -- so you still need some money to own one but entirely achievable by an American style upper-middle class (used tanks, of course, sell for less). The real cost of the tank may be 400k to manufacture but government subsidies (perhaps given as a yearly lottery to cap the total budget expense per year) makes up all the difference. The government actually wants you to own a tank and works to make it affordable. [edit: Well, one way we could imagine tanks are produced as cheaply as cars is if it's a post-scarcity society, ala Star Trek. Replicating a 40-ton tank costs about the same as a small car or a coffee cup: nothing. But I feel like this is a fancier solution than is desired. Otherwise, my thinking is between the sheer extra mass required, plus the control systems for a turret, plus the general complications of the turret, the track system, the more powerful engine, etc, there's no way you get it near the cost of a car, even if you keep it to something relatively simple. Unless you subsidize it to the consumer.] [Answer] # The cars already are like tanks: The climate of your planet requires a sealed environment for any distance of travel. Aggressive wildlife charge vehicles( think rhinos),so they need to be heavy and armored (not to mention the quetzalcouatlus-sized flyers that drop boulders to hunt). Not to mention that if you want to hunt this megafauna, you need a gun bigger than man-portable. So a “normal” car is already the equivalent to an APC. Given the massively-armed vehicles already cruising around, criminals and the rich alike want an edge in case of “disagreement.” The result is that every vehicle is a gunned and armored vehicle. Tanks are the equivalent of the sports car or armored limo - status, security, and an edge in hunting. [Answer] In order to best answer the question, I’m going to come at this from the perspective of, “What needs to change to makes these tanks comparatively expensive to current-era consumer vehicles?” We should also keep in mind that there are consumer vehicles that cost hundreds of thousand of dollars – even half a million or more – to purchase. Bufori is one such manufacturer whose “basic spec vehicles” can cost over $300,000. Can we imagine a tank cheaper than that? Of course. The point I’m making here is that cost is largely a matter of two things – materials and labor. Clearly, the Bufori cars use much better materials and more expensive labor, everything from design to implementation costs more. Also, the Buforis do not benefit from economies of scale in the way that more common consumer vehicles do. We can take these concepts and hunt for changes in them relative to tanks to make the most cost-effective model that can be brought down to the consumer vehicle level. But first… ## What is a tank? A tank is an armored vehicle intended as a primary offensive weapon in ground combat, normally on the front-line or leading edge of an offensive. A tank in the context of this question, however, necessitates a radically different definition, given that most of the time the afore-mentioned stipulations will simply not be occurring. You’ve got tanks being driven around to pick up food, to compete in “sports,” to give performances. While the initial context was weapon ownership, at the time that all of this stuff takes taking place, the very concept of a tank will have evolved considerably. That said, since the original gist for this tank craze was weapons ownership, most if not all of these tanks will need a weapon attached to them in some way. Does this mean we need a turret? No. Many tanks were turretless with fixed, front-mounted main guns. Granted, those “tanks” were usually just tracked support artillery or anti-tank weapons with specialized guns, but those are still weapons. Come to think of it, our original definition does not even require treads. The vehicle simply needs to be armored and have a weapon. Treads are really helpful in a war-time scenario, and I’m sure you’d like to have those as part of the exotic vehicle aspect, but that’s just another piece of the tank puzzle we can modify to bring down cost. So, in short, a tank for these purposes is really just an armored vehicle with a gun, and that’s all we need. Everything else is gravy. Yes, having a gun on a vehicle that is armored has a lot of underlying details and gotchas, but that greatly simplifies our necessary approach to bringing down tank costs while still satisfying the intent of the question and maintaining the most basic notion of a tank as a weaponized, armored, offensive vehicle. ## Tank Design Tank design is focused on the marriage and balancing of three basic aspects: Firepower, mobility, and armor. In simple terms, normally increasing one decreases at least one other. Adding a larger gun usually means decreased mobility due to increased weight and size, same with adding armor. Increasing mobility usually means decreasing one or both of the other criteria. In order to understand why these things matter, consider the situations a tank would often find itself in during the early days of tank warfare. When facing other tanks in combat, a tank could win in a number of ways. By outgunning its opponent, a tank can win with a single shot from outside the opponent range. By being well armored, a tank can survive hits and keep fighting. By being more mobile, a tank can completely avoid being hit. This latter point became a lot more important when advances in guns and ammunition made heavy armor a lot less valuable than speed, as getting hit at all eventually became a guaranteed vehicle-down scenario until advanced armors came about. ## Appropriate Modifications With these criteria in mind, in a common suburban setting, tanks would benefit from a reduction in armor and gun size. Much like concealed-carry handguns are generally smaller than their hip carry counterparts to maximize effectiveness in their role, street-borne tanks would likely begin to move towards less intensive designs that favor street effectiveness. One quality in particular that will drive this change is fuel economy. The average consumer will not have the budget to put gas in a tank from any era of conflict, so the average consumer demand will target lighter tanks with increased mobility and thus fuel efficiency to get more drive out of each gallon of gas. These change alone will push tanks to be cheaper. Treads would eventually give way to cheaper half-treaded models, and then to wheel-only models, thereby reducing the weight and complexity of suspensions for multiple track transfer wheels, and also reducing the weight of the vehicle itself. Thinner armor made of lighter materials will mean that, overall, they can be produced more cheaply. Certain alloys of aluminum have good enough strength-to-weight ratios to satisfy armor needs for the smallest of small-arms fire and still be much less heavy than equivalent armor made from steel. It’s also feasible that layers of composites like impregnated carbon fiber could be added to strengthen weaker metals, and in some cases deformation would actually be better at dissipating shock energy from large gun rounds than deflection or fragmentation. As armor becomes lighter, smaller armaments that don’t need to have the same range and energy to be generally effective in potential urban combat scenarios will also become more prevalent. At a certain point, these changes will engage a feedback loop of sorts where, as armor gets lighter, guns get smaller, so armor can get lighter again, and it goes on. This is exclusively for the cheapest of tanks, mind you. The big boy tanks will still when in a head-on confrontation, and have more options for maneuvering and firepower. This proposed trend towards lighter, faster, and more efficient tanks will also give way to the high-mobility sports and performances that you are aiming to have in this fictional world. The level of proliferation would, as you say, rapidly increase production levels and availability, as well as production competition, which will drive down cost. Ultimately, I think the long-term scenario given these societal pressures is that the average tank-owning Joe Schmoe will possess a cheaper, smaller, lighter, limited-capacity tank that he more or less maintains, drives around a little, and takes to the range every now and then. The enthusiasts will save up for and purchase tanks that are more in line with modern-era standards but are also more expensive, perhaps up to twice the cost of the average ones, with features that depends on their needs and wants. The rich, status mongers will own fully-fledged, treaded tanks with turreted main guns, secondary small arms, proper armor, excellent suspensions, awful miles/gallon, and show them off as often as possible, maybe even on some online video platform like TankTube or something. Business, such as farms, will come about their highly-functional tanks in the same way as they do tractors, and will have more capital to leverage in modifying and working larger, more expensive versions with treads and variable turrets, etc. It's worth pointing out that some tractors and construction are pretty much specialized, weaponless tanks. ## Cost Outlook The cheaper tanks should be in the same ballpark as current consumer vehicles, but by nature still more expensive probably by a factor of 1.5 to 2. There is no upper limit for the best, most expensive units, but those will probably just be military vehicles that are either purchased outright or leased and maintained and whatever exorbitant price. If we can justify sneaking a lot more aluminum and plastics into these things with smaller, lighter engines and better gas economy, your proposition becomes A LOT more feasible. [Answer] If want make T-34/Sherman related tanks then be hard to go with price bellow 200k USD. You need around 30 tons of steel for each tank and raw steel cost in last 10 years is 4-6k per ton. That give You 120-180k only for raw steel, add forming and hardening and You far above price. Possible savings: * thiner armor but stronger due new tech * smaller and cheaper engine Possible higher prices: * suspension (mass produced and cheap at war) * tracks (they was cheap, You want rubberized ones) * baterry packs(if hybrid tanks are forced by goverment) War production lowered prices to edge - that tanks was maked as cheap as possible. If want them to be more durable and live longer then be prepared even for bigger price. Another part is electronics and third one is ammo. [Answer] Considering you stated the tanks are intended to last almost forever, I propose the following: Tanks are still expensive (over 100k) but are passed down generation to generation, similar to a house. You can also claim some citizens rent tanks instead of own tanks to make up for any amount of tank usage you need in your story. Further, from a meta point of view, you can use this to draw parallels between tank ownership and homeownership, should you decide to write a critique of it. [Answer] Everything is Free A tank is a car + some other stuff. The tank can only be the same price as the car if the other stuff is free. If somehow the car and tank are both free then they cost the same! It is up to your imagination how a society can create everything with zero cost. [Answer] There seems to be a heavy focus on WW2 medium (T34 & Sherman) and modern Main Battle Tanks (MBT). Not all tanks are like this, and infact one of the most produced armoured fighting vehicles (AFV) was the Universal Carrier. <https://en.m.wikipedia.org/wiki/Universal_Carrier> The Wikipedia article claims 113,000 produced; far more than most tanks. So potentially the average family owns and uses a Universal Carrier which comes in a range of variants and models, typically with lots of add on weapons including oversized recoilless guns to make it look more tank like. These AFV came out of normal car/bus factories and cost I believe would be closer to an expensive car. Of course the wealthy and businesses would have heavier vehicles right up to the super heavy MBTs. I imagine that your world would be relatively modern technology combined with medieval society. In the middle ages, every worker could be expected to be called up for warfare by the local lord, bringing their axes, hammers and whatever weapons and armour (maybe only leather) they could. So your average worker buys a Bren Gun Carrier for working the fields and transporting the family to church. But admires the local lord and his knights who have brutally expensive and impractical MBTs. [Answer] Perhaps the reason it's more economical to use tanks than cars is because the tanks already exist, and there are so many of them that nobody wants to spend money to produce a car when they could just go and collect a tank for free. If your tanks are reliable enough to last for a long time, then they could be old and still work. In the past, there was a massive war which necessitated the production of many tanks. The war was won, but at the cost of a great many lives; now all of those tanks are just sitting around, and there are orders of magnitude more of them than people. Other than the need to make sure enemies don't steal them, their market value is basically nothing, and the government simply issues free tanks to everybody, because why not? Issuing the leftover tanks to citizens is symbolically important to your proud military society, and they would not dream of dismantling the tanks to recycle their materials; that would be destroying history. [Answer] In short, no, unless in your world there is some new way to dig / smelt the steel in a much more efficient and/or cheaper way. If not these would either be really thin armored tanks (more a tank in name than in reality) or something would have to change. Perhaps consider armored cars, even DIY tanks and armored cars for the average Joe and tanks for the wealthier folk. [Answer] Blatantly stealing from @AlesP's comment under the original answer: > > "Personal ownership of tanks by individuals is common": Unfortunately, because personal ownership of tanks by individuals is common, paved roads are almost always in a heavily degraded condition, to the point that most of passenger and freight transportation is by rail. > > > That's it. Some people started driving tanks (for whatever reason) and it wasn't banned quick enough and the government couldn't afford to keep roads repaired anymore. So now your only choice is rail-based public transport or drive vehicles that can manage the torn-up asphalt and ravaged dirt roads. And when you already need tracks, why not be cool and drive a (de-armored) tank? [Answer] Some of your uses of Tanks aren't that far off. Caterpillar treads were initially developed as a potential for tractors that would operate in rough terrain (with mud and snow being in mind) and many civilian construction equipment uses treads. The advantage of treads is they can distribute a heavy weight over a greater surface area that would caused a wheeled vehicle of a similar size to sink into the ground. There's also a plethora of conventional vehicles that see conversions into military use (called "technicals" in as a catch all) in situations where combatants might not have the funds to afford tanks. Toyota Hilux's and Landcruiser's tend to dominate as the base vehicle for technicals due to their already legendary durability and worldwide marketability. The Hilux has often been called the AK-47 of Automotive given it's rugged nature and versatility in combat and the 1986-87 war between Chad and Libya was dubbed "The Toyota War" due to the use of Toyota based Technicals by both sides (naturally Toyota doesn't market this aspect of their vehicle, but they did use Top Gears attempts to "kill" a Hilux to market the Tacoma in the U.S. (Tacoma's are the North American variant, as Americans and Canadians tend to use pickup trucks as personal vehicles, where as in the rest of the world they are strictly work horses) and the Hilux was the first automobile to be successfully driven to one of Earths Magnetic Poles (it's been to both.). In many countries it's marketed as a "Pickup truck" because no other models ever got any market share. Other vehicles are civilian models of vehicles initially purpose built for combat. While they now offer typical SUVs and crossovers, Jeep's more famous and distictive looking models (The Wrangler, The Rubricon, and the Gladiator) all are modeled after vehicles built for the U.S. military during WWII though they were never armored and acted more as transport to the frontlines than actual weapons platforms. Similarly, the Hummer was a civilian model of the Humvee which was more of a light personel vehicle than a heavy weapons platform. Hummer Dealerships would often set up courses for customers to test drive the Hummer over, showing all the extreme driving it could do. These vehicles all have a fatal flaw that makes selling them to average car buyers in that they are gas guzzlers (The Hummer was all but killed when it debuted shortly before gas prices increased due to the War on Terror) and keep in mind the markets that love them the most often drive them as personal vehicles first. It's at this point it bears in mind that Modern Tanks often use Jet Fuel instead of conventional gas or diesel in their engines, meaning that the problem with increased gas prices are compounded by requiring fuel not commonly available at the pump (Many U.S. military vehicles actually run on the same type of fuel from jets to ground vehicles. The logic is in the logistics... not only is shipping less types of fuel easier to keep track of, but it also means that you can run more efficiently if your supply lines are cut off as your options aren't limited by the availability of fuel). They also have to have regulators installed because the speeds they can run without them are so high, the wear and tear will be cost-prohibitive. And a modern tank can run at highway speeds. Going back to the technicals, there is at least one example of a civilian vehicle being converted into a tank. The infamous Killdozer incident invovled a man who had bought an ordinary bulldozer and mounted reinforced concrete armor plating to it (along with several conventional rifles and CCTV cameras for navigation and other modifications to keep the Killdozer systems running) and used his creation to get revenge on various businesses and municipal facilities he had deep grudges against by doing what something called a "Killdozer" does best. It was only stopped when one of his treads fell into a basement most of the public was unaware existed in the building, causing the vehicle to become hopelessly stuck (There are rumors that the Governor of the state had considered mobilizing the national guard and was requesting anti-tank ordinances, the incident was ended before that happened and the level to which it was considered was debated. The problem with using such ordinances in a civilian population center was certainly considered.). News Helicopter footage of it does exist and can be found online. [Answer] Remember the joke when in a restaurant someone asks why the plain rice is more expensive than the rice with raisins? "It's because it costs so much effort to remove the raisins form the rice." There is no way for a vehicle to be more expensive to produce than the exact same vehicle with some added armor and gun turret. However, there are other ways around it. #### 1. Government subsidy. As presented in some other answers and comments. Tanks are more expensive to build but cheaper to buy due to a subsidy. #### 2. They use different technologies. In real life some old-timers are allowed on the roads lacking essential features modern cars must have, like airbags, ABS, low emissions, etc. Mainly because they are rare and are not used to travel great distances every day. Similarly, in the near future one might imagine internal combustion to be either banned or heavily regulated. Cars would have some sort of an expensive high-tech cold fusion (or whatever technobabble) power-plant, which is very expensive to build, but it creates zero pollution. For cars used by billions of people to travel tens of thousands of miles every year, that's the only legal technology, to prevent massive pollution. However, for culturally significant tanks (or their replicas), the polluting internal combustion engines are allowed, because they are only driven for short distances a couple of times per year at shows or competitions, so their pollution doesn't add up all that much. Therefore they are cheaper to produce than the fancy cold-fusion zero-emission cars (where mass production helps somewhat in decreasing the costs, but despite that they are still very expensive). ]
[Question] [ Historically, swords were most often worn at the hip in either a sheath or a scabbard. The purpose of a sheath or scabbard was primarily to cover the blade to prevent the wearer from injuring themselves or people around them whilst walking around. It also serves a secondary function of covering the blade to protect it from the elements. A sword frog however, as far as I can tell, is more of a modern invention and is mainly used by the Live Action Roleplay (LARP) community. Swords used in LARP are typically made out of foam, meaning a wearer does not need to worry about accidentally cutting themselves or about their weapon rusting in the rain. As such, a sword frog does not cover most of a blade as it simply does not need to - covering all of the blade in this context gives no more benefit than just covering part of it. Here is what a sword frog may look like: [![image shows a leather tube with openings on either end. There are buckles on the tube to adjust how wide or narrow it is. There are also leather loops attached to the tube so that a belt can be passed through the loops, allowing the whole thing to hang from the belt at a slight upwards angle](https://i.stack.imgur.com/t7ZVj.jpg)](https://i.stack.imgur.com/t7ZVj.jpg) <https://www.medievalcollectibles.com/product/geralt-diagonal-sword-frog/> --- So, my question is, for what practical reason might an adventurer in a stereotypical medieval-fantasy setting wear a sword frog? As there are no archeological findings of sword frogs from the medieval period that I know of, so adding them into the setting would be very anachronistic. Whilst I could simply explain the existence of sword frogs as being a fashion accessory - something else for nobles to decorate or something to show that you own a sword, even if you aren’t currently wearing it - Im specifically looking for practical reasons to justify their existence as not every adventurer is going to care about how they look. For clarification: * The sword frog may be either used on its own or in conjunction with either a sheath or scabbard - just as long as the sword frog has a purpose and a good reason for being there. For example, most sheaths and scabbards had either belt loops or their own belt built onto them, simply ignoring the in-built belt or belt loops just so the sword frog has a purpose is not a good enough reason. * Magic is not off-limits for this question, answerers are free to use whatever fantastical ideas they can come up with, but I would prefer if the majority of answers focused more on the mundane rather than the magical. If possible, the best answers should include testing of their proposed idea (or a detailed enough explanation to allow someone else to test the idea), or any relevant experience, to see if the idea would work in real life (which subsequently would mean the idea would work in the fantasy world as well). [Answer] You use them how they were designed to be used, to hold a scabbard to a belt, or wrapped around the shoulder instead of a belt. They are not worn instead of a scabbard, they are part of the scabbard. they were actually fairly common, but like anything else were a question of preference. 1. What angle you wanted to wear your sword at, the less vertical you want the sword the more likely you are to use a frog. 2. Frogs are also adjustable, which is self explanatory advantage. 3. Most frogs kept the sheath more secure, especially with long swords by keeping them them from being able to flap around. They became even more common when metal sheaths started becoming common, becasue the frog can hold the heavier scabbard at an angle. They can also move the sword into a lower position which is both more comfortable to draw for many people. A frog that can be separated from a metal sheath is also way cheaper than fitting more metal to a metal sheath and easier to clean to boot. Sometimes frogs are integrated, which costs a lot more, and means you have to take the entire belt off to remove the sword. Others are designed to be detached from the belt allowing the wearer to remove sword and scabbard without removing the sword belt, this allowed the owner to display the fact they wear a sword even when not wearing it. When you know what they are actually made for it becomes really obvious how to wear them. They were invented multiple times, Japanese swords used them as well, when worn with armor, although they were often complex cloth arrangements instead of leather. [![enter image description here](https://i.stack.imgur.com/rcjar.jpg)](https://i.stack.imgur.com/rcjar.jpg) [![enter image description here](https://i.stack.imgur.com/hkUbD.jpg)](https://i.stack.imgur.com/hkUbD.jpg) [![enter image description here](https://i.stack.imgur.com/Fi2zC.jpg)](https://i.stack.imgur.com/Fi2zC.jpg) [![enter image description here](https://i.stack.imgur.com/HVcQt.png)](https://i.stack.imgur.com/HVcQt.png) they were really popular in WW2, seriously search ww2 frog sometime, daggers, bayonets, and swords all used them. [Answer] In your world, the sword wielders carry their weapons in frogs, either with or without a blade covering, because the finely crafted swords are a symbol of their wielder's skill. They also conduct battle in a much more ritualistic and civilized way than their battle leaders might wish. When two warrior's fight in battle, it is to first blood/injury/disarmament, not death. If the lesser ranked swordsman prevails, then the superior-ranked warrior must relinquish his nicer weapon to the winner, taking the lesser weapon as a sign of his defeat. Since ornate swords often have matching scabbards, the weapons are exchanged with their sheaths and the loser's cuts his own frog open so that he must carry his sheathed weapon off the battlefield in shame. The winning warrior, whose frog remains whole, remounts his sheathed weapon into it, then draws his new blade to continue fighting. So the frog serves as a disposable scabbard holder, freeing its owner's hand for combat. It is made separate and disposable (not as part of the scabbard) so that it can be destroyed to symbolize its owner's defeat, without requiring that the treasured sword/scabbard pair be damaged in the process. [Answer] ### Because your sword has a sharp tip but not a sharp blade Not all swords had edges. Various styles of dueling sword had blunt blades but a sharp tip, intended for piercing rather than slashing. The rules for épée fencing are based on this sword design. This would make a frog-only carry possible, because you wouldn't need the rest of the scabbard for safety. A cork stuck on the pointy end would stop accidental stabbings. Of course it would still be worth having a proper scabbard for protection from the rain, so I wouldn't say this was actually practical - anyone with sense would have a scabbard. Still, it answers the safety issue. [Answer] "Fast draw". I am reinterpreting your question as "Why would adventurers carry sharp blades using something that looks like a frog and fails to cover the edge?" I am very glad that we are talking about fantasy adventurers because, I want to be clear, this answer makes no sense for other groups of people. Basically an adventurer exploring the dungeon has a legitimate need to have their blade ready at all times. They do not want to waste time drawing their blade and readying it when something unexpected happens. So they do not want the blade covered with something that adds delay, they want the blade "at hand" at all times. They also do not want to carry the blade ready in their hand all the time because even adventurers need to rely at muscles that get fatigued over time. Which makes you slower. So they want the weight of the blade to be carried on the waist as normal. The solution is a pseudo-frog with a metal loop that attaches to a simple hook at the girdle at your waist. Your off-hand holds the blade at the pseudo-frog so it is "at hand" and controlled and doesn't fall off the hook or hit yourself or anything else. When you need the blade ready the off-hand just lifts it off the hook and brings it to your sword hand. This is a fast and simple movement since the blade is already controlled by the hand and the motion of pulling it off the hook is very short compared to the motion of drawing a blade from a sheathe. Realistically since the off-hand would be reserved for controlling the blade this only makes sense for swords you actually use two-handed. Although depending on which side the blade is on you might need a grip change for the drawing hand, so you'd probably want a blade that is usable with one hand. Or just a weird way of carrying the sword. Carrying the blade diagonally in front of your body would be convenient for this type of draw. It also would not be banging onto things as it would be fairly tight to your body and in front. And for most warrior types there would be body armor and a helmet to protect from cutting yourself with the blade. You could even attach something to the armor where the blade can comfortably rest so it doesn't bounce left and right despite being inverted with blade up. This only makes sense when you have long periods where you need to keep the blade ready without necessarily using it. So only adventurers while working. Off-work the "big sword" would probably be sheathed normally or even put in some sort of a case. Most cities probably do not want adventurers carrying big swords ready to use at their streets or taverns after all. The latter point is actually important. If you can carry the blade even when you do not need maximum draw speed all the time, it is easier and cheaper to just use a scabbard that works all the time instead of a special solution optimised for one use case. The quotation marks on "fast draw" in the beginning are there because it is not really a draw. The blade is already at your hand and uncovered and you do not need to draw it from anything. That is the whole point. Note that this is compatible with a kind of half-sheathe where the sides of the sheathe towards the body and along the edges of the blade are still there but the outside has been removed or replaced by a light weight flap of cloth or leather. This would not impede the readying of the blade but would also give many benefits of the blade being sheathed. So that type of solution is probably what people would actually use. [Answer] ### A separate sword frog would allow an adventurer to more easily change which sword they are using. A typical fantasy adventurer may have multiple swords, such as steel one for general use and a silver one for dealing with magical monsters. Many sword scabbards had in-built belts which were permanently affixed to the scabbard or had loops for which to thread a separate belt through. This would mean that in order to change which weapon you had at your side, you would have to unfasten your belt and either put on the new belt with the other sword attached or take the old sword and scabbard off your belt to put the new one on. Using a sword frog means changing out which sword is at your side is much easier and faster. Rather than having to take off your belt, you can simply grab the scabbard and drawing both it and the sword out of the frog. Then you can place the other sword and scabbard into the frog. My testing found that I can draw a sword and scabbard out of a frog, put them down and place another sword and scabbard into the frog in around 7 seconds. To unbuckle the belt, put it down and put a new belt on takes about 30 seconds and to unbuckle a belt, take the scabbard off the belt and put it down and to put a new scabbard onto the belt takes around 40 seconds. Interestingly, if i’m wearing gauntlets, it adds an extra 10 to 30 seconds to take off and put on a belt. In contrast, the time it takes to draw a sword scabbard out of the frog and put a new one in remains largely unchanged, only adding a couple of seconds onto the total time. Further, if instead of just taking the sword off the belt, you also needed to take off all your potions and pouches on your belt to transfer them over to the other sword belt, this would add significantly more time on. The time to take the sword scabbard out of the frog however would remain the same regardless of how many other things are hanging from your belt. This means that a sword frog could be a very useful tool for an adventurer who needed to change swords as it would be far more convenient and would save time, an important thing to consider as adventurers are often working under time constraints where every second matters. If it takes them 2 minutes to change out their sword and more over their equipment, thats 2 minutes where the person they’re meant to be rescuing could be killed or the monster they are tracking could escape. ### A sword frog would allow an adventurer to sneak more easily than a scabbard This is because a scabbard can easily catch on things and knock them over or bang into objects if you arent fully aware of where the scabbard is at all times. Even if you have your sword drawn, the scabbard can knock into things. Also, going down stairs whilst wearing a scabbard means it will hit off every stair if you aren’t holding it in front of you. While its not an issue to hold a scabbard, if you were sneaking around with a weapon drawn, you’d want both hands on your weapon in the case of a two-handed sword or a free hand to grapple with in the case of a one-handed sword. Using a frog instead of a scabbard would mean there is no chance of your scabbard hitting into things behind you and giving you away. Additionally, the frog gives you somewhere to put your sword when you needed both hands free, such as for picking locks, scaling walls or disabling traps, as opposed to using no sword holder at all. A sword frog may not be an ideal tool to carry your sword all of the time, as you’d be more likely to injure yourself, but it would be simple enough to leave your scabbard with the rest of your gear that you aren’t going to go sneaking around with, and just take the frog. Essentially, the frog would be used to carry your sword for short period of time, such as when you’re in a dungeon, and a full scabbard is used for carrying it for longer periods of time such as travelling. [Answer] i dont know is this allowed or not, but the sword frog sheath remind me of goblin slayer sheath from goblin slayer manga and anime. basically its a universal scabbard or sheath where you can carry any type of sword or weapon especially when the other sword dont have it sheath or scabbard (usually from looting), because you cant use the same scabbard or sheath that your previous sword use because it maybe to long, to short, to big, to small, or different shape for your original scabbard/sheath to fit in perfectly and will hinder movement. like when your weapon stuck or break and you loot enemy weapon to use, maybe because its far better than your original weapon, or because you really need new replacement right there right now because its better than nothing, or just a new backup or loot/prize weapon to the frog sheath for ease of carry while you still carry your weapon in hand, while still not safe from many enemy or monster in the wild or far from civilization or blacksmith to fix it or create the new scabbard/sheath. outside of price, you far better to use new weapon rather than fix your cheap adventurer sword anyway, its different if its godly sword though but if it already achieve godly level i doubt it can break, or dulled,or chipped even after numerous use, or its a sword made of good quality steel that unlikely for adventurer or murderhobo to get again. iam sure you already know, the cons is it wont protect from the element for iron or steel base weapons, so this type of sheath is more for disposable or cheap weapon (that doesnt have their own scabbard or sheath) or to carry the good loot weapon for a while until perfect sheath or scabbard is ready, and dangerous to person behind the wielder, unable to ride horse since the point can accidentally cut or pierce the horse rear when riding. oh yeah, also i assume this is more specifically for carry around your hip type rather than the back sheath/scabbard right? because if it include as the back scabbard/sheath thats another story, which i think you know already. (i want to put image regarding goblin slayer, but its pretty much copyright material and this site is very against it, so i can only suggest you to read the manga to get what i mean, iam not recommend the animation because it look ugly and i dont watch it to know is it show it or not, at least skip to chapter 2 it already show it, chapter 1 is very NSFW and irrelevant to your question, and a reason from another manga name "goblin slayer year one" chapter 18 when he try to sheath enemy goblin sword to his scabbard and it not fit well during his early carer. the guy change weapon alot because common weapon is not indestructible and he face multiple opponent at once so no time to pull out weapon that got stuck inside the enemy body or the sword get slippery from the blood and fat, so he just loot enemy weapon right away to use.) [Answer] A boringly physical reason - Your character lost part of their equipment in some event, perhaps for example, falling off a ledge in battle * The sword was tightly grasped in the hand * The frog was secured firmly to the belt * But the sheath came loose from the rest of the scabbard and was misplaced. So the only options left are to carry the sword by hand and risk losing it too, or put it in what remains of the scabbard. I'm guessing the frog has some kind of retention loop or strap for the sword too, to increase confidence that the sword won't slide out. [Answer] As part of a "dress uniform" In formal situations - such as when receiving a reward from the local Noble at court for services rendered - an adventurer is expected to be wearing a Sword. On the other hand, Nobles (and their guards) are less-than-keen on being in close proximity to well-armed individuals noted for their tendency to employ violence with a significant success rate. The solution is twofold: First, a blunt sword, consisting of a decorated metal pole attached to a handle. Not being an actual weapon, functionality can give way to aesthetics. This serves, as much as anything, as a "badge of office". The next step is, as you surmise, a sword frog. This shows off the decorated blade, and shows the guards that it's not a deadly weapon. Of course, many adventurers have since discovered quite how useful these "roundblades" can be for delivering bludgeoning damage to foes immune to slicing, or non-lethal takedowns for capture/retrieval missions. [Answer] Not many answers seem to address why you might use a frog without a sheath... Since you said magic is allowed, I'll give it a shot. First, you probably want the blade and/or frog spelled so that the one doesn't shred the other. I'd go for the blade, since you probably also want it spelled to not rust from exposure to the elements. (This seems like an obvious spell you'd use if you can.) So... why no sheath? Well, maybe the sword has runes inscribed on it that only work if they're visible. Maybe the blade [glows blue](https://en.wikipedia.org/wiki/Sting_(Middle-earth)) when danger is present, which you wouldn't be able to see if the blade isn't visible. [Answer] Why would you wear a frog and not a sheath? Real metal swords have recently become scarce in your world and most people are now carrying fake swords. Maybe all of the good ore has been mined and there is little left that can be mined economically. Or maybe a previous ruler demanded all the metal in the kingdom as tribute, which he then sold to foreign countries to pay for his frivolous life style, resulting in his overthrow. Because of this, there is currently an unusual shortage of real metal weapons that causes widespread use of fakes. People continue wearing scabbards with wooden swords as a matter of custom and to fool would-be assailants into thinking they can defend themselves with a real sword. Fake swords have now become so common that people have recently begun to wear their real sword without a scabbard to demonstrate that they indeed have one of the remaining real metal swords. ]
[Question] [ In the good old days, the space pirates used tractor beams to reel in unsuspecting merchant vessels before robbing them. Recently reports of them cohorting with the rebel army soon spread across the entire neighborhood star systems in the report they were specifically stated using military-grade teleporting technology to steal goods from afar. Experts are still puzzled at how they could have broke through the encryption and also to quadrangulate their position in 4D space. However despite authorities pushing for better encryption such as quantum encoding, most small businesses are reluctant to invest until there is some form of government subsidy provided. As the piracy incidents mostly occurred in the demilitarized zone, no firearm is allowed on board any kind of vessel, including those belongs to governments. What cost efficient methods could stop space pirates from stealing goods using long-range teleporter devices? Important points to consider: 1. No weapons in the area. 2. No government grants to upgrade equipment. 3. Onboard computers still running on outdated architectures are unlikely to be replaced. 4. No negotiating with space pirates. 5. No bribery. 6. This route is called the Ancient Heavenly Silk Road, and is an important lifeline for traders in the region. [Answer] ## ATM machines ATM machines have been the target of crime since their introduction. Who doesn't like a a machine full of money with relatively low supervision? No humans pulling crazy stunts and any cameras can be circumvented (more or less) by wearing a mask. How do you prevent theft? Destroy the insides. The moment you try to force it or otherwise try to get into the machine it'll invalidate the contents. Paint bombs are most used. Any money that will be covered will be worth less than the paper it's on. This isn’t a unique strategy. I can imagine it was used before ATM came into existence in normal banks and it certainly is being used in safes for a long time. Contents destroyed or locked away forever? The whole crime ends up costing the thieves instead of giving them money. # Destroying Your first line of defence is triggering the failsafes when teleported. Detect when the cargo is teleported by finding quantum signals or whatever is used. If that proves ineffective, just have a short distance code that is set manually per container. If the container is teleported it'll leave behind the transponder. If the receiver doesn't receive the code anymore it'll trigger the destruction. Dangerous goods are released, others are invalidated or destroyed. If possible explode to kill the pirates, but I guess these fall under the 'weapons' clause. Even if they are 'normal' products to begin with. # Tracking In your case it might not always work. Many transported goods might not be able to be turned loose, destroyed, invalidated or used as weapons (if allowed). Any goods stolen can still be tracked. Every package has a tracker, allowing it to be traced long distance. A demilitarised zone still allows you to follow the pirates. As soon as they leave the zone, they are done for. If they disable the tracker, anyone trading with them will be destroyed as well. Basically you shadow them and confine them to this zone, as well as prevent anyone from thinking trading with them is a good idea. The pirates goods have lost most of their value due to barely able to be ysed. # Counter teleportation Yet you're a government with powerful technology. What rebels can do together with pirates, you can do better. Why go to the demilitarised zone and wait if you can teleport them? Teleport the ship, it's contents or just the crew. Take over the ship at your leisure. No weapins were used and yiu only used tracking and teleportation, which is what the pirates used. Besides that the demilitarised zone must be enforced by all agreeing parties. Otherwise what's the point? That means you don't have to secure it alone. Teleportation is either a crime or even act of war. That means anyone leaving the zone should be treated by all parties as hostile. Of course politics and antics get in the way, but this gives you at least many teeth to bite and options to pursue. That should reduce the crime this way to a bare minimum. [Answer] ## A demilitarized WHAT now?! Teleporters aren't weapons?! HOW THE HELL do the pirates end up not only surviving in the demilitarized zone but also thriving there? Demilitarized zones aren't just some randomly labeled areas because calling them demilitarized sounds adventurous and cool and where people don't bring weapons just because that's the general etiquette. Demilitarized zones are explicitly defined as strictly regulated exclusion zones between powerful enemies and their main purpose is to create a physical buffer between them, their purpose isn't for anything or anyone to live or thrive in them normally but to actively keep the belligerent sides apart and the only kind of activity that goes around in such an area is strictly performed by the military. Anyone or anything caught in a demilitarized zone that has no justified right or reason to be there is either exterminated on the spot or captured, interrogated and then vanishes. It doesn't matter if it's fantasy or real life, demilitarized zones are heavily monitored and entry into them is heavily regulated from all sides. If there's ANYTHING that appears out of ANYWHERE at any given point, all sides regulating the demilitarized zone intervene (with absolute force most of the time) to resolve the issue as fast as possible to avoid mutual annihilation. Honestly, there's no feasible way for any sort of pirates to survive in a demilitarized zone because they'd be instantly set upon and disintegrated by the forces who put that demilitarized zone there in the first place. Anything less than instant total annihilation of the pirates would be clearly seen as an open act of aggression by one of the belligerents who put the demilitarized zone there in the first place, which could easily lead to that zone no longer being demilitarized once open war is declared. The point I'm making is that you can't have trade running through a demilitarized zone, either don't call it that or change your story altogether. You also can't have an area where obviously strict rules are written down but then there's nobody around to actively enforce those rules, if you can't have any sort of active supervision in the area then don't bother trying to implement any kind of rules there. For the sake of discussion, let's apply common sense to the situation. Let's say the traders simply cannot keep up with the pirates technology-wise rather than being some kind of a weird "rule" in place for that region, it sounds far more reasonable and commonplace. If the route is dangerous and the risk too great, sensible traders will simply pick another route or do their business elsewhere, meaning there won't be as many of them around and the pirates would lose incentive to stick around. It doesn't matter how essential that region is or how lucrative the profit could be, sooner or later the risk involved makes it worthless. This will also grind the economy of that region to a halt and would force the government to intervene if it wants to survive, forcing it to invest not only into combatting the pirates themselves but also improving overall security to incentivize the traders to actively use the route. A proven strategy in history to resolve this situation is that pirates or contractors employed as privateers work best against piracy, especially when poor governments which don't have the capacity to actively wage war on a large scale are involved and simply allow them to keep whatever they get when they destroy the pirates. The best way to fight technology is with better technology, history provides countless examples those who failed to embrace improvement and technology ended up being trampled by their enemies all the more effortlessly the wider that gap became. Yes you can brute-force your way against technology and it tends to work from time to time, but that's the exception rather than the rule and, whenever it works, the side that brute-forced its way to victory ends up taking the technology and going through with the upgrade. In ancient times better weaponry was usually countered by better armor, but in the modern times most weaponry is just flat-out countered by better weaponry that outperforms it. When it comes to teleporters, pretty much every single science fiction out there counters teleporters with shields, either by applying general shielding that serves as a general protective layer or specialized shields that only allow the teleporters that corelate with them to work (in amplitude, frequency or any other value that defines them). I find teleporters to be quite under-used in most science fictions, pretty much everybody uses them for their intended purpose and fail to notice what kind of gamechangers they are, or perhaps they did notice that and are actively avoiding that particular use since it would kill the narrative. Honestly, if you have the capacity to send your boarding parties onto another vessel and vice versa then you pretty much have the capacity to send anything in that particular vessel out of there, why not just beam out the crew of the enemy ship into outer space and be done with them so you can claim their ship and everything on it without breaking a sweat. Yes it's exceptionally cruel to beam someone out into the vacuum of space and have them choke to death, but so is shooting them, slicing them, disintegrating them or anything else that ends their life. This is the reason why I personally treat teleporters as active weapons, perhaps the ultimate ones. [Answer] TP-Jammer Most technologies are first developed or researched by the military or at least have some sort of intent for military use long before the general public gets their hands on it. I'd be hard-pressed to believe that they released teleportation technology to the public without already having something developed that would be able to stop the teleportation from happening altogether, for reasons of their own security if nothing else. The simplest solution would be some sort of signal jammer. The teleportation device obviously has some sort of sensory aspect to it if you can specify what to teleport and where, so whatever wavelengths or rays or whatever it uses to detect things would need to be scrambled or interfered with to make the teleportation of specific things hard if not impossible to do with any degree of accuracy. Though with teleportation technology I'd say you have more to be concerned about than theft. They could teleport a section of your hull away, for example, and then you're left to deal with the rapid depressurization and all the nastiness that comes with it. [Answer] # You need to nerf teleportation Since there isn't much in the way of detail, I'll assume your teleportation works according to classic scifi tropes, namely: 1. See a ship 2. Scan the ship 3. Identify the contents you want to teleport 4. ????? 5. Profit The thing is, teleportation is broken. In other words, TP is OP. Creative use of TP makes all weapons obsolete. In fact, you should TP your enemy's weapons outside of their ship. You can TP their main drive, their life support system, hell you can just TP a bit of hull and leave a giant gaping hole. As a story element, it's extremely powerful, and thus needs extreme limitations. ### The whitelist approach This is quite simple. You can teleport only teleport specifically designated equipment or personnel. And that's it. You'd have a special device or tag, like a NFC tag sort of thing, that is tuned to your teleporter frequency or something to that effect. Then, and only then, can your teleporter (and possibly only yours, though not necessarily with e.g. a teleport metro system) teleport that object. Your pirates now need physical access to steal your stuff, so while a teleporter can be useful to board your vessel, they can't remotely disable your ship or grab your stuff without going through a lot of effort first. ### The blacklist approach This is also quite simple. You need to block scanning or block teleportation plain and simple. The latter probably, since there may be reasons (law enforcement, customs or general security) to not block scanning at all. It's probably going to be a material, since that's passive and can't be turned off, that can either be used on its own or as an alloy. Let's call it Spaceluminium™. Spaceluminium™ can come in two flavours. At minimum, it prevents teleportation rays from passing through, thus you can't grab something inside a container. A more avdanced version prevents Spaceluminium™ objects themselves from being grabbed, because something quantic probably. I insist on the passive nature of Spaceluminium™. An active jammer can be disabled, can malfunction, it may also telegraph where the precious cargo is since you just have to follow the jammer. Material simply is. It always work. It doesn't require batteries. It's also relevant to the next point. Because regardless of which flavour you use, you'd use Spaceluminium™ basically everywhere. On the containers, on the transports (ships, trucks, planes, pizza delivery scooters, etc.), on banks and other high security areas. That's the obvious, but then you need to think home invasion. How do you prevent someone from telesnatching your TV in your house or your phone in your pocket? That's right, even your pockets should be lined with Spaceluminium™. --- Final note: the DMZ is a red herring. Ships will carry weapons into it if they have them, and exercise their right to self-defence should it come to it. If ships don't have weapons, pirates can attack just as well outside your DMZ. DMZ don't really work in 3D space anyways, and the reason why should be obvious since yours seems infested with pirates. [Answer] If you can't stop it, make it less worth. If using the teleporting technology by yourself is too expensive, and you cannot use weapons to defend the goods, your solution is to change the route in a way that makes it harder for a remote pirate to predict your location, and dilute the shipment with garbage so that they are less likely to strike on the valuable things at their first try. Alternatively, join forces with other small shippers, so that you can share the risks and the costs on larger shoulders. [Answer] # In accordance with our peaceful intentions, we have brought no weapons... Our shipments on the Ancient Heavenly Silk Road include many precious cargoes. Boosterspice, thionite, philtres of love and anamnaesia, stem cells with programs few can imagine. Stars' Tears produced by the most exquisite and artful techniques ever applied, decades and sometimes even centuries in the making. We know people would like to take them. But our containers are well sealed against every accident, and for just this reason, they are also well suited for the shipment of other cargoes. Some are mostly harmless, like the Terrans seeking to ship out unstable antique nuclear weapons and fuel rods for reprocessing on more enterprising worlds. But there are other containers which are far more problematic to rupture in a hyperspatial heist. Xenomorphs subject to relocation by Animal Control. Space-evolved gypsy moths bound for the new silk farms of the Orion Nebula. And of course, worst of all, the Common Tribble, which has evolved to be so cute and cuddly that most piracy corporations would rather file for bankruptcy in their home jurisdictions than try to explain to an angry Pirate Worlds public why they did not expand their corsairs' living habitats sufficiently to keep each new tribble in a life of pampered luxury. [Answer] Transporters require a tractor lock. There are many difficulties with transporting between moving space vessels. The object takes a few moments to (de)materialise and by then both vessels will be thousands of kilometers away from where they started. So you need to compensate to prevent the object materialising smeared out over spacetime. On top of that, turbulence from cosmic dust means that even if both ships are moving in a straight line, they are vibrating relative to each other. Vibrating while (de)materialising will destroy the fine structure of the object and turn it into goo. Good for transporting large volumes of water perhaps, but not for any technology or living matter. If the pirate vessel could measure the vibrations of both vessels in real time, they could compensate and transport safely. However this is impossible since the vibrational scanner only sends signals at the speed of light, which is the same speed as the transporter signals. This delay is relevant considering how far apart space vessels are. In order to sync up the source and target, the larger of the vessels must hold the other one in a tractor field. This equalises the vibrations between vessels and allows them to transport safely. [Answer] Traps The porch pirate glitter bomb now with fart gas. [![enter image description here](https://i.stack.imgur.com/Uk9IE.png)](https://i.stack.imgur.com/Uk9IE.png) Sure you can steal stuff but do you really know what you're stealing? Does it contain ship eating nanites? Poisoned supplies? Tracking chips? Highly radioactive artwork? Leaking gas canisters? Coated in a contagious virus? If stealing stuff posed a serious risk to your ship, crew and life, pirates wouldn't do that. [Answer] Aboard the ship, several concealed small circuits read off a large multi-gigabyte file, one 64-bit word at a time, sending it on the ship's internal communication channel (appropriately armored with error correction; thanks to @FranzGleichmann for pointing this out). An identical file is inside an equally small listener device hidden somewhere in the cargo. As long the received random 64-bit word agrees with the one in the listener's queue, nothing happens. The moment the listener is not satisfied, it fails deadly, and several mag-bottle devices concealed throughout the cargo turn off their antimatter containment bubble. # update: "no weapons" Should the anti-matter devices fall under the "no weapons" clause, then consider that there just have to be lots of high-energy storage systems in a starship for it to function, and that any such storage system, plus a fail-deadly release, is equivalent to a small bomb. You can literally build one out of cleaning supplies and a pair of 9V batteries. And, anyway, anything that renders the cargo unusable, or worth less than buying it on the open market once piracy costs and margins are factored in, will sink the pirates on economic grounds alone. The most expensive items are likely to be high-end electronics, and such items are delicate. In contemporary terms, a large crate full of iPhone 13's can be easily worth a couple of million dollars. The boxes are snuggled in shock-absorbing foam; on Earth, fire-retardant foam is used for added security. Imagine we used a thermitic foam, with a high enough ignition temperature that no ordinary accident is likely to set it off; or even way nastier substances. A fire sparked by N-Stoff, for example, simply cannot be put out - it will burn in deep vacuum, it will burn at cryogenic temperatures, and most fire quenching compounds will explode on contact. Most fumes are corrosive, toxic, or both. Any merchandise would be destroyed, and that's before being contaminated and poisoned. Even something relatively harmless such as flour could be stored and prepped to behave like a [low-yield thermobaric bomb](https://en.wikipedia.org/wiki/Dust_explosion) at very little cost. Actually, I seem to remember some story where space pirates hijack a grain transport, and are feared to be coming back for more, condemning a colony to starvation (I think the pirates were from some other nearby colony which too had resupply problems). The karma is delivered by the captain's son, believed unarmed and harmless, who rigs the grain to explode, wrecking the ship and sending it crashing through the atmosphere. [Answer] ## Identify and Avoid Pirates Before They Get Into Range Pretty much all solutions mentioned so far involve losing your cargo (blowing it up, paint bombing it, etc) which should be your last line of defense, not your first. Your first lines of defense will simply be identifying and avoiding pirates before they can get close enough to steel your stuff. The most useful tool in law enforcement is identifying the criminal. Most crimes can be prevented just by making sure that the would be guilty party knows that they will probably get caught if they try. To prevent crime, every ship would need something akin to a license plate, but instead of a metal placard, a space aged civilization would likely use something similar a digital TLS handshake. Unlike license plates, these encrypted license codes could not be faked easily. You would have to either hack the entire interstellar DNS network to redirect the handshake or steal the actual navigation computer of another ship. One task is virtually impossible, and the other is something that tends to get reported pretty quickly; so, faking your identification is not much of an option. If a ship transmits a verifiable code, then you know for sure that it is the ship it says it is. So, if it steels your cargo, then the police will hunt it down later, arrest the guilt party with thier own military grade transporters, and return your cargo to you. If a ship does not transmit a verifiable code, the police automatically know to search and seize the ship since it is running illegally, and equally so, merchant ships know to not let illegally running ships get anywhere near close enough to them to get into transporter range to begin with. This could involve sending out a distress call, and trying to stay ahead of the pirates until police can intercept, or it could be a swarm of cheap decoys so the pirates don't know which ship to follow. It could involve turning off all power and letting momentum carry you through undetected, it could involve hiding yourself in the nearest comet or asteroid... so on and so forth. Cargo is expensive, and having to delay a shipment by a few days to get around a possible pirate threat is WAY better than letting your cargo be stolen or ruined. And no, don't believe the lie that "there is no stealth in space". You can detect things from much farther in space, yes, but sensors have a maximum resolution even in a cold vacuum. Space just means you have a VERY long sensor range, which actually works to your advantage here because it means the distance between when a pirate is close enough to notice you, and too close to be fooled by simple means will be very long and give you lots of time to figure out a plan to evade them. ## A Minor Frame Challenge > > However despite authorities pushing for better encryption such as quantum encoding, most small businesses are reluctant to invest until there is some form of government subsidy provided. > > > This is a common misunderstanding for how encryption works. As the difficulty of encryption increases in a linear fashion, the difficulty of cracking encryption increases in an exponential fashion. What Quantum Decryption does is makes decryption much easier than it would be with non-quantum decryption, but it does not fully violate the exponential rule of increasing difficulty. When you encrypt something with 128-bit encryption, it means that a computer has to guess 2^128 (~3.4e38) possible solutions to crack your encryption. If you are trying to break 128-bit encryption with a quantum computer, it reduces this difficulty to 1/2 of the exponent meaning the computer only needs to try 2^64 (~1.8e19) possible solutions to crack your encryption. What this means is that a quantum computer can hack in a matter of minutes, what a normal computer could not hack before our sun turns into a Red Giant and consumes the Earth. However, it does not take a Quantum Computer to create encryption that can beat a Quantum Computer. If you simply increase your key size from 128-bit to 256-bit then with a very simple software update, your existing computers will be able to render Quantum Decryption useless. This is not some big expensive upgrade, it is the sort of thing that the developer of your transporter protection software will have patched and updated within days of the first incident. Hacking is hard, it is very hard. Preventing a hack (once you know about it) is really easy by comparison. As technology advances, the difficulty of hacking is increasing faster that the difficulty of preventing it, and all evidence indicates that this trend will continue indefinitely into the future. > > Onboard computers still running on outdated architectures are unlikely to be replaced. > > > A 30 year old computer today is perfectly capable of running encryption that the best quantum computers being developed could not beat using a simple software update; so, "running on outdated architectures" is not an issue. Suggested Change to Setting: Use any explanation for why the pirates can now beat transporter blocking other then encryption. I would suggest something more along the lines of a more a powerful transporter. If we assume that a shield creates noise that blocks a transporter, then an adequately powerful signal should be able to overcome the noise. If the commercial ships are using simple fusion reactors, and the pirates get a hold of some military grade anti-matter powered technology, then the interference pattern may simply not be enough to prevent a transporter signal from getting through. Since this is a question of power generation and output, this would take a very significant hardware upgrade to prevent. [Answer] Telecorps, the corporation behind the creation of these teleporters, also sells proprietary lockout tags. They're banking from both sides! *Did you know that you can't photocopy modern currency? There is logic built into the machine to thwart you.* Similarly, Telecorps sells special "tags" that you can attach to your cargo. If one of their teleporters detects this tag in the pattern buffer, you can bet that it's going to result in an "Invalid Target" error. Time for the space pirates to start creating custom firmware - But it'll probably be a little buggy. Additionally, pirates may now be incentivized to beam directly aboard to remove these tags. Maybe there is a saboteur already on board! [Answer] Use whatever technology and tomfoolery you have in place that prevents them from just teleporting your bridge, crew quarters, crew mess, officers' mess, and propulsion system out of your ship to be deposited in open space and perhaps re-teleported, in smaller chunks, to also be left in open space. After all, taking most of the crew oriented gathering spaces (bridge, maneuvering (propulsion systems control room), crew quarters, lounge, mess, and not to forget: officer quarters and mess) removes most of the difficulties they have with simply then attaching cables and towing you to market. Removing life support would fix the remaining problems, I mean "crew"... So there must be something in place to protect all that. Just use it to protect the cargo as well. Or consider a more widely, and much less pleasantly, based question... pirates are criminal and evil, not stupid and there are lots of ways to skin a cat, or to teleport it into open space and leave it to die so that its litter box is yours, and yours alone. Or, for a more fun direction, consider a war of teleportation. They engage theirs, you engage yours "on a reverse beam right down their throats" and the goods are in a constant flux back and forth, then your ship yanks a course change at a synchronized moment (computers (even old ones) and all, microseconds and that kind of thing) and their suddenly un-competed with teleportation beam suddenly resolves a lucrative pile of vacuum into their cargo hold. And you reach into theirs in that moment and teleport out anything they had... or maybe not because they, like you, could have it very intermixed with powerful explosives that will do more than dye-pack them, with pressure sensors triggered when the bridge spotted them in space set for the unique pressure your hold is at and unlikely to be the pressure theirs is at especially since they will be compressing the atmosphere in it with all your stuff and their compensation can't work that fast and even if they dumped it to space leaving a hard vacuum, there just won't be a match, not in time anyway and maybe you have some gas cannisters in the hold too that will release on materializing inside a hard vacuum and so compete with their compensation. That could make being a pirate very, very dicey. Especially if you are shooting at them during this period. If they didn't teleport out your weaponry first. So many variables, so many if's. But pretty dicey for someone. Maybe everyone, but certainly someone. [Answer] Online fiction series [Deathworlders](https://deathworlders.com/) has aliens initially shipping cargo via FTL flight along spacelanes cleared of most interstellar dust. The humans, shortly after the discovery of their existence, were enclosed in a system shield to prevent them from leaving their solar system via FTL flight. The humans figured out they could use wormholes to briefly connect two places and swap their contents, and quickly concludes this method was far superior. For one, goods arrive instantly, with no possibility of them being intercepted. For another, the distance between origin and destination doesn't much affect the energy cost, so sending goods to a neighboring city is functionally as expensive as sending those goods to the far side of the galactic core. Once the idea spread to other species almost no goods got shipped through space any more. Human military developed combat strategies involving scattering beacons around them and using them to instantly move their ships out of the line of fire and to more favorable positions. Subsequently wormhole disruption fields were developed. Basically they put out gravitational noise that makes forming a wormhole impossible. Disruption field generators can make controlled holes in their protection to allow wormholes only when and where they're wanted, essentially preventing unauthorized teleportation in a large area of space. Overlapping disruption fields generated by enemies prevent both sides from teleporting until they can get outside of or disable their opponent's disruption field. Wormhole disruption field generators are big, power-hungry, and expensive, proportional to how large of an area they can cover. High-end warships can cover an area large enough to block a planet and its moon. Less-powerful versions can at least block against combat-maneuver and escape jumps in a combat space. Most populated planets soon got their own wormhole disruption generator. So, to answer your question, if your teleportation technology works similar to the above, you would prevent teleportation-based attack and theft by (a) not flying at all when you can avoid it, and (b) flying in convoys with at least one teleportation disruption system in it. You'd avoid flying by setting up scheduled teleports between different locations covered by teleport disruption. When you couldn't teleport directly to your destination - or at least close enough that the remaining flight is in well-protected space - you'd get protection by employing a ship with a disruption system, and you'd make that cost-effective by combining trips into large convoys, since the protection has the same cost for one ship as for a thousand all grouped together. Another method, you could take just a beacon to your destination, then teleport the goods once you get there. Until literally the moment you deliver the goods, they're kept safe at home. And you only have to fly to a given destination once; once you've been there you'll have a beacon to teleport to. It's worth noting with this type of teleportation, unless the attacker employs a disruption system, ships can immediately retreat to safety in the event of an attack by teleporting to a predetermined "safe" beacon pretty much anywhere in the galaxy. [Answer] What is teleportation? Is it real? Are you quantum tunneling matter over long distance? Then why steal? If you can quantum tunnel matter and reassemble it like the original configuration, you could quantum assemble anything from raw quanta as well, and harvest any energy from any quanta to do this. Or is if fake?: rather copy and delete the original? Then it is not stealing at all. And then why delete the original? [Answer] You could attach a bomb to each container that is set to blow up upon exiting a teleportation field. To avoid the pirates from messing with the bomb via hacking it should be cut off from any communication networks. [Answer] If you have transporters, then simply store the goods as a transporter pattern in active computer memory. If someone tries to beam the computer out then the computer will lose power and the signal will become corrupted rendering it useless. Or the pattern is stored in an encrypted format so even if its stolen its useless to space pirates. [Answer] I want to specifically address this point: > > most small businesses are reluctant to invest until there is some form of government subsidy provided. > > > In our current world jets are expensive, however even small businesses today are able to offer overnight shipping via air for fairly cheap. I imagine the same would be true in the future, that small businesses (and even large ones) would send their products to a company specialised in delivering them to the end customer. That company can use economies of scale to invest in the proper equipment (whatever you choose that to be) to counter pirate attacks on all the packages they transport. ]
[Question] [ I've been grappling with a story for a while, involving a scenario where gravity starts to fail. The goal of the story is mostly how people react to the knowledge that the world will end. But, I also wanted to include some sort of scientific group that is trying to figure out why. Are there plausible reasons that gravity would fail? I like stories to have at least a pinch of truth as an anchor, and I do want some sort of thought process that scientists would go through. Obviously there would be talking heads on TV giving reasons, so, what would those reasons be. [Answer] ## Dark Energy / The Big Rip There is a possibility that this will eventually happen. It depends on the energy density of dark energy in the universe, which we are currently unable to measure accurately enough to tell. Strictly speaking, this is not gravity failing so much as the expansion of space accelerating, but for all intents and purposes the results are the same. Basically everything in the universe is accelerating away from everything else, even on tiny scales, but the rate of expansion is greatly overpowered by gravity except on intergalactic scales. But if the expansion continues to accelerate, eventually it will overpower gravity. This will actually create a predictable sequence of events that can happen on human-measurable scales. It could make a great setting for a frantic race against the clock as scientists struggle to figure out a way of escaping the universe before everything ends. Using one hypothetical example using real equations, the Big Rip could happen 22 billion years from now. (This will be long after our own solar system is gone, but humanity's descendants could still be around). 60 million years before the end, galaxies become gravitationally unbound. Your setting is a lone solar system in a starless void. It is still habitable but the knowledge that there was once such a thing as stars could be long forgotten. About 3 months before the end, the gravitational attraction between the planet and its star is overpowered by the expansion of space. The planet begins to move away from its star, first slowly and then picking up speed until people are forced to use technology to survive the cold. But things are going to get much worse... Gravity starts to weaken. Quakes and cataclysmic upheaval become commonplace as the pressure holding the planet's insides inside diminishes. The atmosphere grows thin. The oceans boil. In the last few minutes before the end, the gravitational force cannot hold the planet together anymore and every planet in the solar system explodes at around the same time that the distant sun evaporates into the void. Anyone who manages to survive in spacecrafts have only a few minutes left before the accelerating expansion of space overpowers the binding energy of matter itself. There might be a few moments where they can actually feel it building up inside them before it rips apart their bodies, then their molecules, atoms, and finally subatomic particles themselves. You can adjust the timing if you want to introduce any kind of handwavium physical laws that we don't know about yet. [Answer] Totally different idea. In late 2283, a research team at the University of New Tokyo finally cracked the [Unified Field problem](https://en.wikipedia.org/wiki/Unified_field_theory). This gained them one of the most prestigious Nobel Prizes ever awarded in history. The results of this were initially amazing: it allowed on demand gravity control, the benefits of which were immense. Needless to say, everyone started making gravity control devices for vehicle levitation, space exploration, construction, etc. You name it, we found an application for gravity control. However, what nobody had anticipated was that the count of particles moderating the forces in the unified field theorem had been a balanced set of parameters, and the changes that occurred as a result of gravity control led to an ever increasing instability. In essence we'd been living in a local minimum for this parameter equation where everything was stable, but gravity control eventually pushed us out of this local minimum into an incredibly unstable landscape. One of the major side effects of this was that gravity slowly, but irreversibly, started to decrease. [Answer] We need to have more fun with this question Keep in mind that gravity is but one characteristic of mass. You can't change just gravity without side effects. Those side effects are valuable to you as they can be used to advance your plot. * A wormhole appears at the center of the planet, pulling mass away from the core. Thanks to the [shell theorem](https://en.wikipedia.org/wiki/Shell_theorem), gravity must reduce to zero as you approach the center of the planetary sphere. Thus, the appearance wouldn't be immediately noticable, and if the mass were drawn off slowly enough, it wouldn't be appreciably obvious. Note that there would be side effects, such as liquid core currents changing, which would change the magnetosphere and possibly plate tectonics. * Something in the universe, some ribbon of effect we know nothing about, is passing through our solar system and, thus, our planet is passing through it. This ribbon is changing the positive charge strength forcing atomic nucleai to spread apart. Not only is this reducing the density of planetary mass (and therefore gravity), but it's also causing the planet to increase in circumference. * Something unseen is passing through the solar system. A "dark planet" (or, perhaps of greater interest, a ribbon of dark asteroids) with sufficient mass as any point of its passing to change the effective gravity on Earth. The planet or ribbon can pass through on a parabolic arc such that it would affect the Earth for most of a year. The side effect is that Earthlings standing on the side closest to the dark planet/belt/ribbon would be lighter, while those on the opposite side would feel heavier. Earthquakes would be normal. Shifting the Earth's orbit (perhaps moving it further from the sun, thereby solving global warming) would be expected. * [Q](https://en.wikipedia.org/wiki/Q_(Star_Trek)) is really bored and decides to change the gravitational constant of the universe — but only in the Sol system. Not only would this be really hard to figure out what was going on, but ships leaving the system would sail through a breakwater (I'm using the wrong word, that point in the ocean when leaving a beach when the undersea landmass drops away and you get serious wave action. It killed the best friend of Moana's father. It was really sad and should convince all to live in Iowa). * The theory that you can treat gravity as coming from a point source at the center of a sphere is only true when the sphere is reasonably solid or homogenous. Let's have some reaction (let's blame it on the Somalis this time, they built a planetary core implosion device) that caused the inner 25% of the planet's volume to suddenly compress such that a massive void appeared between the new basically neutronium core and the rest of the core/mantle. Not only would this change gravity by pulling a lot of mass further away from the surface, but it would have the side effect of the planet slowly starting to wobble in its rotation until that big marble comes in contact with the rest of the core and begins acting like that child's tooth in a paint can... or until the sudden vacuum causes the planet to violently shrink. *What else, my fellow WorldBuildians! In what other ways can be bend, contort, graffiti, or otherwise ignore the fundamental rules of orbital mechanics and classical physics to bring about, if nothing else, the appearance* of a lessening gravity? [Answer] The Gravitational Constant is not uniform throughout space and time** Scientists have long speculated that some fundamental constants of the universe, like the speed of light or the fine structure constants, are varying through time. Why not make it varying through space as well? This way a part of the galaxy can decay while the other parts are still bound by normal gravity. [Answer] Unexpectedly for all the community of scientists in the world, gravitons (the particles mediating gravitational force) have a finite life time, and they are starting to decay. The more they decay, the more gravity is weakened. After a certain time gravity will no longer bind together masses, so unless they are electrically charged and can rely on good old Coulomb force, they are bound to separate. Space will be filled with atoms traveling around, no longer aggregated. [Answer] In order of decreasing viability (all of which are still super low): * The simulation hypothesis, that we are all living in a simulation, is really your best bet here. If gravity were capable of failing one would expect to see stars sort of just blinking out of existence every now and then, which we don't. That being said if we are living in a simulation (which is quite likely) then really the simulators can do whatever they want with physics. * Aliens, "pull the fabric of space-time taught." does it mean anything? not really no. is it intuitive? yes. * Act of god. plain simple, always in style. I'd go with this explaination myself * Freak variation in the gravitational constant. <https://en.wikipedia.org/wiki/Time-variation_of_fundamental_constants>. it's not certain that G the graviational constant of the universe is always well constant, Some theories hold that it varies. If it suddenly varies down (possibly even as a result of human tampering, probably not though.) gravity turns "off" simple as that. that being said this wipes out the universe not just earth. Bare in mind suddenly in this context could still be upwards of a million years or just a few seconds so it gives you a lot of narrative freedom. * Presence of large numbers of "Anti-Gravitons". the Graviton (a hypothetical particle that carries the force of gravity) sometimes has an even more hypothetical counter part called the anti graviton aleins fire a bunch of theese at us and they react in unexpected ways with currently existing gravitons destroying them and sending the excess energy away as gravitational waves. * Vacuum decay? there is a thing called Vacuum decay, most likely it will simply wipe out everything if real however there is a INCREDIBLY small chance that it simply re-writes the laws of reality instead. All of these answers (except Act of god & simulation, which have their own problems) are pseudo-scientific to the extreme and highly unlikely to actually work. If you go for simulation, god, or either of the aliens options you can always also put gravity back before the earth if fully destroyed leaving people left on earth with just a bunch of earth-quakes and a new outlook on life to deal with, if that's you narrative intention that is. [Answer] It sounds like the big rip theory answers your question. Space-time expands and therefore the entire universe expands. The theory says the expansion will eventually overcome gravity. <https://en.m.wikipedia.org/wiki/Big_Rip> [Answer] To diminish gravity, you have to diminish mass. Currently the only way we know how to do that is to convert it explosively into energy. I don't think that will work for you here because if you converted enough of Earth that we would notice the lower gravity, the created energy would probably melt the crust and everyone on it. That makes for a short and tragic story. What you probably need here is a dimensional doorway, but that is way beyond our hard science, so the rest of this answer will be in violation of your "science-based" tag. If a dimensional doorway existed at the core of our planet, and if a steady stream of core material poured through that doorway and into another plane of existence, and if no reciprocal mass or energy came back through the doorway into our reality, then the planet would slowly (or not so slowly) loose mass. As this happened, the gravity would diminish, but so would the rotational velocity (making our days longer) and the magnetic field (making our days a lot more interesting, i.e. nuclear sunburn). It would get you what you are looking for in terms of failing gravity but the side effects might pose more urgent threats than the sudden weight loss. [Answer] Some ideas: * Space is warped, and Earth's gravity well intersects with something on the other side of the warp. The space where our planet once sat is becoming a wormhole, and gravity is failing from our perspective as a result. See the illustration below. [![This idea is my favorite on this list](https://i.stack.imgur.com/XOfe5.jpg)](https://i.stack.imgur.com/XOfe5.jpg) * After the largest underground nuclear bomb test in history, or maybe after another exciting and seemingly innocuous experiment at CERN, the small forces keeping atoms together in the earth's crust have ceased to function normally. The earth is losing mass to radiation at an alarming rate. In some parts of the world, people are dying from radiation sickness; in other parts, people are unable to reproduce, and in other parts the radiation exposure is minimal but the gravitational effects are nonetheless observable. Furthermore, this loss of mass results in large cave-ins, and cities falling into the ground like in Centralia PA. * Mass hysteria. It's not really happening, just everybody thinks it is. * Earth's gravity has been slowly dying for a long time, but the change was imperceptibly small until now. Now the change is accelerating asymptotically. It only seems to be affecting our planet, but really this is just a stage in the lifecycle of every planet, and we haven't observed it before. * Beings from another spacial dimension create some 5th dimensional equivalent to a dyson-sphere around our planet. * Beings from this spacial dimension create an actual dyson-sphere around our planet Hope this helps! [Answer] Gravity As A Wave Currently we don't know if gravity is a wave or a particle, but I've read it theorized that it's both, similar to photons. If we assume that gravity can exist as a wave, then perhaps a wave that happen to be the inverse of the gravitational wave signature of Earth's gravity well could cancel out that waveform an therefore nullify gravity. I'm not sure if destructive interference would actually apply to gravity waves, but maybe! I would expect something like that to be temporary or fleeting, but there are plenty of cosmological events that might create gravity waves. It could even be a failed human experiment or intentional attack from an outside force. [![Destructive Interference](https://i.stack.imgur.com/zepTZ.jpg)](https://i.stack.imgur.com/zepTZ.jpg) [Answer] This wouldn't necessarily reduce gravity, but it would reduce the sensation of gravity. Make the Earth start Spinning faster for some reason. Maybe the core's Dynamo got stronger due to (insert handwave here) resulting in the Earth spinning faster due to the Handwave Principle of Handaway. The centrifugal force would mean that everything on Earth would feel a slight force push them upward, and the net force felt by things on Earth would be weaker. [Answer] Your best bet is to use gravitons, the quantum particle/fundamental force-carrying particle of gravity. Dark matter is also a good candidate. Gravitons are similar to photons, the quantum particle of the electromagnetic force (also responsible for giving us light). Like Photons, gravitons are thought to have zero rest mass. This means gravitons travel forever at the speed of light and do not decay. However, gravitons could actually have a very small rest mass which would theoretically allow them to decay into other (lighter) particles. Here are some options: * Gravitons, which have some infinitesimal but nonzero rest mass, are finally starting to decay en-mass into other force-carrying particles such as photons or gluons. * Society is emulated within a computer and is failing to floating point arithmetic errors. For instance in Javascript .1 + .2 = 0.30000000000000004. For instance plank's constant could be wrong. * Dark Matter/Dark Energy - Physicists today observe large objects being attracted to certain areas of space that appear to be empty. Since we cannot observe what is attracting matter to these places other than that the attraction is happening via the gravitational force, we assume there is some massive body that is invisible to detection attracting everything. This scenario gives you the greatest flexibility since we really don't understand too much about Dark Matter/Energy. You could make it another form of life that exists in alternate dimensions or just have dark matter and energy be moving around the universe causing havoc. [Answer] While you can't turn off gravity without getting rid of mass, it's possible to mess it up by counteracting it with another invisible force pointing in a different direction. For instance, when you're in a car that takes a sharp turn, you can feel being pushed outward. This is the [centrifugal force](https://en.wikipedia.org/wiki/Centrifugal_force), and it can even dominate over gravity when the turn is sharp enough, in which case the car flips over. How is this relevant to your case? See, we all experience a centrifugal force because of the earth's spin. A fraction of this force counteracts gravity (which always points to the core), however the effect is tiny because the earth spins slowly and has a huge radius: The closer you are at the equator, the stronger the effect. So, if you want to mess up gravity on earth, you can do so by making it spin faster. There's actually a formula you can use to calculate the centrifugal force, and compare it to gravity. Without getting into details, you can do some back-of-the-envelope calculations to determine that earth's gravity would start getting messed up by centrifugal forces if it were to spin ~10 times faster. That is, if the duration of a day (sunrise to sunset) were ~1hr long. How exactly would earth's gravity get messed up? In short, people at the poles would be unaffected, while those at the equator would basically start floating around (along with the entirety of the atmosphere). Things wouldn't be flung into space, though, because of inertia. People in between would feel lighter (reduced gravity), as well as experience a mysterious pull toward the equator (i.e., southward in the northern hemisphere, and northward in the southern hemisphere). In the above apocalyptic scenario, you can imagine that, as the earth spins faster and faster, a certain priviledged few would travel hurriedly toward the poles as the rest of humanity (as well as the atmosphere) gets pulled increasingly strongly toward the equator. It would be a very bizarre situation indeed, as what we all perceive as "down" would no longer feel like "down" anymore; as the earth's spins increases, "down" would increasingly be directed toward the horizon and in the direction of the equator. Not to mention you'd feel lighter and lighter, which, under "normal" conditions, is quite a pleasurable experience. There's a catch, of course: How do you actually spin the earth up in a fairly reasonable fashion as to make for a dramatic human story that's actually based on well-established scientific principles? One way I could think of, is reducing the earth's [moment of inertia](https://en.wikipedia.org/wiki/Moment_of_inertia); i.e., changing its internal mass distribution. The more concentrated a body's mass is distributed along the rotation axis, the faster it rotates (conservation of angular momentum). So, without changing anything on the surface where the human drama unfolds, you need a mechanism that can plausibly cause the internal mass to get more concentrated toward the core. By playing around with some numbers, it turns out that you need to cram ~99% of the earth's mass right at the core to make the earth spin faster by a factor of ~10. The only mechanism I can think of that could possibly cause such a huge re-distribution of mass, is a swarm of black holes orbiting around each other in the vicinity of the earth's core. Note that these would have to be tiny, since an earth-mass black hole is ~1cm in size and you obviously don't want to add any mass to the earth, since that would mess up "natural" gravity. In any case, I didn't investigate the dynamics of a swarm of black holes; i.e., I don't know how quickly they could gobble up a good fraction of the earth's mass as to make the spin-up effect noticeable within a reasonable human timeframe (e.g., years of months). I can't even comment on the stability of such a hypothetical system, since I didn't do any pertinent calculations. [Answer] I would suggest something in the lines of what happened at the end of [Melancholia](https://en.wikipedia.org/wiki/Melancholia_(2011_film)): a second large mass comes very close (and for some reason stays put at the required distance to make the story interesting), pretty much deforming gravity on Earth. If you need it to be transparent, non-spherically shaped, anything works really. Not every piece of debris (or alien planet-ship) is perfectly spherical. For more discussion on the plausibility and effects of such an event, see these network questions: <https://scifi.stackexchange.com/questions/19068/is-the-melancholia-dance-of-death-possible> <https://physics.stackexchange.com/questions/15083/is-melancholias-orbit-impossible> Note I am suggesting some articifial means to keep the large second object in place, enough to disturb pretty much everything gravity related, without breaking any of the underlying physics. Also be aware that normal gravity is the single most important thing keeping our atmosphere together. [Answer] Thinking about this, I realised that the [shell theorem](https://en.wikipedia.org/wiki/Shell_theorem) is your friend, and would need to stretch reality a lot less than some other solutions. I may have to backtrack a bit to explain this, as it is indeed based on hard science. The problem in the question is that as far as we know, gravity is basically, positive only - there isn't negative (anti) gravity, or gravity shields. So the classic solutions have to centre around either mass reduction, or increasingly unlikely/pseudoscientific explanations with implausible implications. But there is another way gravity can fail. Let's start with the shell theorem. This is a mathematical/physics principle, that if you are anywhere inside a hollow symmetrical spherical shell, of any thickness, you don't experience any net gravity from it - it all cancels out. (Less mass but closer on one side, more mass but further away on the other, and they always exactly match). But suppose mass appears above you, that isn't part of a symmetrical shell. Now, you will experience some reduction in earths gravity locally, because of the upward pull. Just not very much. You'll have to check this out, but I guess this could work, especially given that the question allows for limited scientific plausibility: 1. a research satellite is launched to perform some kind of extreme research in the vacuum of space, in some suitable orbit just outside earth's atmosphere. 2. Unknown to those running it, and for [handwave] reasons, the satellite is acting as some kind of dense matter attractor - maybe it warps space or leaves behind some particle, or locally perturbs the vacuum state. 3. The end result is that a series of mini-black holes appear in its wake, conveniently growing and of a size sufficient to influence earths surface gravity below. 4. The satellite of course fails, after one or 2 orbits, but the mass concentrations continue to grow. They don't form a symmetrical shell, but a linear trail. They inherit the velocity of the satellite, so they don't immediately just fall inward to earth? 5. The earth isn't affected much in its orbit - at least not immediately - but if figures out carefully, maybe there would be a local/regional impact on surface gravity, with scope for it to get worse, and other side effects, without having to "break" physics or cause immediate planetary breakup.....? It would have a more severe effect on high altitude objects, as well, which might be useful in a story. [Answer] Negative mass * We had taken for granted for ages that gravity is only attractive. But it turned out that it wasn't. * While trying to create chambers of absolute vacuum, it turned out that speed of effect of gravitation is related to the absolute amount of gravitational entropy ( how much of the available mass of the universe can be present at a given location). * By creating a perfect vacuum scientists were able to stop the effects of gravity within a region. * What was originally understood as vacuum wasn't really vacuum, but a region of space of negative mass which in the presence of other positive behaved like vacuum. * Immediately new research begun and more and more people start researching on this. Meanwhile it turns out that by creating more and more perfect vacuums, we are creating more regions of negative mass. + This negative mass is termed as Anti Dark Matter for it only interacts through gravitational forces and is repulsive. * Termination of a vacuum doesn't always ensure that all the positive mass covers up the negative. * As the gravitational interactions are very weak it was only noticed many more years later that the experiments which were run had caused a small leakage of negative mass that had somehow made it to the near the earth's outer core where it nicely found and equilibrium and settled. + As Earth passes through various regions of space, overtime this negative mass at the core had been collecting more and more of negative mass, and it is growing exponentially. + It is cancelling out the effects of the earth's core and mantle by overlapping and creating regions of 'vacuum' [Answer] Gravity is caused by bending of space time (IRL). A big corporation has worked out a way of flattening it artificially - effectively "antigravity", and sells it as a product. [Answer] The changing/failing gravity is a floating point error in the universe simulation. Many existing simulations of varying complexity use floating point numbers for their calculations. For example, the Unity game engine uses a floating point number for gravity strength. In this case, the floating point number would be the lifetime or duration of the gravity effect. It could even be tracking the lifetime of the universe, and the gravity is just a side effect. [Answer] Earth isn't real. I'm borrowing an idea from fiction: Specifically, Mutineer's Moon, the first book of David Weber's Fifth Imperium series. They needed to hide a very large starship in our solar system--they took the surface off the Moon and put it on the starship, tossed the core into the sun and took the moon's place. Lets take this further--at some time in the past aliens replaced Earth with a hidden starship. The fakery is good enough that even sounding of the innards doesen't reveal that it's starship and not planet. However, the starship is nowhere near as massive as the planet, it had to use a gravity generator to make things look real. The maintenance system on the starship is failing. There are actually many gravity generators in the starship so a failure doesn't leave the planet coming apart, but now they are wearing out. As generators fail the others take up the load--but not quite evenly and the additional load on them speeds their own failure and once enough have failed they can't maintain 1g anymore. When all the generators are dead there will still be some gravity due to the mass of the ship and the mass of the crust that was laid over the ship, but it won't be anything like 1g and won't keep an atmosphere for the long term. [Answer] A great many people have independently considered the idea that gravity doesn't attract, it repels. The attraction observed between neighboring bodies is do to partial shielding of the bodies by one another. The shielding is small and proportional to mass. This doesn't actually work if you dig into the details, but you have to dig pretty deeply. The advantage now is that the source of gravitational pressure can be entirely divorced from mass and located a very long way away. Enabling this view of gravity would open up all kinds of options. It would seem that you are on the cusp of some event horizon that is about to isolate our corner of the universe from it's source of gravitination. [Answer] ## Alien Transportation System OK, this one sounds a bit "space opera"-ish, but you can probably dress it up and make it pretty. Aliens from an alternate dimension/universe/what-have-you use "our" dimension/universe/etc as a convenient way to travel great distances in "their" dimension, because the mapping between the dimensions is such that traveling (a short distance) in "our" dimension is equivalent to traveling (a very very long distance) in theirs. Jumping from a "small" dimension (theirs) to a "big" dimension (ours) requires very little energy - but traveling from a "big" dimension to a "small" dimension requires A Lot of energy - and the energy (and thus the mass) is removed from the local area near the jump site and transferred to the "small" dimension. And, again unfortunately, the Sol system just happens to be conveniently located for their use - so they're sucking the energy/mass out of our area. Oh, BTW, that means the sun is going to go nova. Sorry about your luck, humans - BUT as a consolation prize the aliens have offered each and every human a set of genuine Alien Ginsu Steak Knives! They slice! They dice! They make your star blow up! Wooooo! [Answer] # No Gravity doesn't "fail", any more than the other fundamental forces fail. If they could, we would live in an entirely different universe. If any of the forces "started to fail", so many catastrophic things would happen all at once that there would be no grace period. ]
[Question] [ How would a standard Roman human army fight a smaller army composed of skeletons? The skeletons are strategic and will reassemble if you cut pieces off. The skeletons came from the army, and retain their combat skills and weapons (most likely gladius and scutum shield). However, if you pulverize their bones, or just generally smash them into little bits, they will not reform but can keep fighting. They do need their heads to work. What are good tactics and/or weapons to use against them? Magic use is null, but the skeletons could have a magical weakness. The time is "ancient" Rome, so no modern weapons. Thanks! [Answer] Clubs, maces, and warhammers. Blunt force trauma in general. So instead of a gladius they would use a weapon of the above. Smashing weapons would allow to break the bones into many pieces that would be picked by other soldiers to be disposed off. Also if they depend on their head to fight then getting the heads off would be smart as you can neutralize their ability to actually hit you. Same with the general skeleton construction of the body. Will they collapse if you remove their spine? What about the rest of the connecting bones...etc. Hooks. Imagine making some sort of contraption that has a hook on a strong wire that grabs the skeleton and puts then into cages or grinding wheel or something like that. Archers and cavalry will cease to be useful of course. Also something like a phalanx won't have any use. Elephants. Well. Heavily armored and armed elephants were a formidable force in the ancient world. You could only defeat them with strategy and I'll assume that the skeleton don't have much of that. So just armor an elephants and let it simply smash the opposing line. Don't focus on breaking the line and moral of the opponent. Just smash them to pieces and start collecting them. Water. Could them swim? I'd imagine a moat being very useful. Specialized artillery. Instead of the scorpions and similar ones you would primarily focus on throwing rocks of a certain size to break the skeleton into separate parts. Perhaps instead of the traditional light infantry of the world you would have bone collectors. A blunt force weapon + a shield and no armor. They go around with sacks and once a skeleton is broken they hurry to collect the important pieces of bone away to be disposed of. If people risked their lives throwing javelins at heavy infantry then collecting bones is not a problem. I don't think we can answer magic without understanding the magic system. The easiest way I'd say if you can cast corrosive spells or fire spells in such magnitudes as to simply melt the bone. [Answer] 1. Skeletons pushed together get tangled up with each other easily. The protruding ribs tend to cross the ribs of other skeletons and once that happens it is tricky for the two to extricate themselves from each other. If you add more skeletons it gets trickier. 2. Bare foot bones have almost no traction. 3. A mans skeleton weighs 10-15 kg. That is 30 lbs max. So we have a formation of very light beings which have little traction against the ground and which will get tangled with one another if they bump into each other. You will have a long rope, each end tied to a team of horses. You will pull the rope into the front of the skeleton formation, pushing them into each other. You will drag the squirming mass of skeletons into a ditch you have prepared full of wood and pitch. You will light it on fire. Loose bones will be collected by specially trained dogs, and other regular dogs. [Answer] Skeletons are very light - about 10 kg for adult European males. In fact, their equipment is likely to weigh more (gladius, 1 kg; Roman shield, 10 kg). This low weight can be used tactically, especially as they will be rather top-heavy, with almost all weight above their hips. For instance, two groups of soldiers running with a rope between them could bowl over the entire skeleton army, and soldiers with maces could come running behind the rope to crush skulls before the skeletons could get back on their feet. And no, it really isn't very easy to sword cut a rope suspended in air. If you think this is a problem, use a chain. Similarly, soldiers with long staffs could knock skeletons over, partnered with soldiers with maces to knock skulls in. The Roman soldiers could also use water (rivers, lakes, beaches) to strategic advantage. Skeletons don't float, as their density is greater than that of water. Their equipment will make them very unbalanced, since the water almost cancels the weight of the bones. Muddy or marshy ground will also work. Bony feet are more likely to sink deep into mud than fleshy feet, and Roman sandals are unlikely to fit very well on bony feet, so they have likely been discarded. The top-heaviness of armed skeletons will also make them very unstable on slopes and rocky ground. If the Roman soldiers could lure the skeletons to attack along a slope or in rocky terrain, this could make a major tactical advantage. [Answer] I really like the idea of war dogs chewing up skeleton’s leg bones. It is a pretty entertaining image to me. The roman military was very adaptable. They consistently revised their tactics and formations to deal with the unique properties of their opponents. I think that they’d form their units around small numbers equipped with either tower shields and billhooks — a common farm implement in the days of the Roman Empire or flails and heavy iron boots. Imagine an outer ring of a dozen soldiers with the shields and billhooks. They pull a couple of skeletons into the center of their formation. Then like 5 soldiers armed with flails and boots pulverize the skeletons. The human soldiers would have the mass advantage over the skeletons. Assuming they have equal strength, the higher mass would mean that the humans would generate all lot more force — proportional to the ration of the square of their respective masses. I think this fact would allow the Romans to push through the skeleton forces and selectively pull them into the swarm of Roman formations. [Answer] Metabolic acidosis induces calcium efflux from bone and in the process buffers the additional hydrogen ions. Initially metabolic acidosis stimulates physicochemical mineral dissolution and then cell-mediated bone resorption. Acidosis increases activity of the bone resorbing cells, the osteoclasts, and decreases activity of the bone forming cells, the osteoblasts (Bushinsky et al., 2000) You forgot about acid. It is possible that throwing boiling acid on bones can liquefy said bones (good luck with protecting your army during the boiling process). I'm guessing that the liquefied bones will still fight (unless that 'the skeletons can have a magical weakness' comes into play - the inability to morph/shift into fluid figures, or function in a fluid state). Another magical weakness could be: absorption into the earth. What came from the earth, must return to the earth. If that doesn't work, then the strategic warfare answers are your best bets! [Answer] A pitchfork, a lance, a pillum, trident. And net. Retarius gladiator type of equpiment. [![enter image description here](https://i.stack.imgur.com/KCeWe.png)](https://i.stack.imgur.com/KCeWe.png) You catch the skeletons, with nets, then load them with pitchfork into mills. [![enter image description here](https://i.stack.imgur.com/sI6f2.png)](https://i.stack.imgur.com/sI6f2.png) Or you take a roller, give it to the Turtle formation and just, well, roll over the skeletons. [![enter image description here](https://i.stack.imgur.com/EAiNo.jpg)](https://i.stack.imgur.com/EAiNo.jpg) Destroying skeleton is easy, the don't have meat, or tendons or skin that would disurb weapon. When you stab persons leg they might still wak it of. The stab might be just badly placed. With skeleton you have one bone to crush to stop it. [Answer] @Willk has the right idea, I believe. Tangle them up! It doesn't matter how strong that pile of bones is, if it weights 20kg it can be pushed around by a child, let a lone a fully grown, fully trained roman soldier. The problem is cheap solutions will probably have unreliable results, so forget the rope and horses. # Surround and collapse the skeleton formation until they can't fight back, then methodically destroy each skeleton one by one. You have both a numbers advantage and a mass advantage, so use your big, strong, heavy humans to meet the skeletons head on, hold the line, surround them and push them into themselves until they literally can't move. From there you can take your time massacring them however you please, be it crushing their skulls, or tying their bones into a bundle and throwing them into a fire pit, or just breaking their limbs and leaving the torso for later. Sounds like a stretch? [Hannibal did exactly this in the second Punic wars while severely outnumbered](https://en.wikipedia.org/wiki/Battle_of_Cannae). The roman's game plan was to rely on numbers and smack carthague's forces right in the face, so they committed all their infantry to the central fight, and massed in one huge, deep line. Carthage met them with a much thinner front line, but Hannibal held it in person, while also pulling back ever so slightly. Meanwhile his best troops went out to the flanks and not even collapsed but just pushed back the romans. These two things forced the roman center forward and their flanks inwards, folding them into a sort of crowded mass. Then, the carthaginian cavalry rode to the back and hit their rear like a hammer. Suddenly the romans had no place to reform ranks, and they collapsed inward until they turned into a chaotic mosh pit, with no space to flee or even to fight back. Their numbers were turned against them and they were slaughtered. Hannibal's army took 5k casualties, the romans' took 80k casualties, the city of Rome lost every last drop of its manpower and the battle became legend. If your scenario takes place any time after 216 BC they probably remember this all too well. Your win condition is: blob up the skeletons, compress them to eliminate their ability to fight back, and take them apart one by one. Your advantages: Your soldiers can hold the line indefinitely while in formation. You are guaranteed to be able to push any single regiment of skeletons back, or, if they are in formation and massed, you are at least guaranteed to not be pushed back unless it suits your strategy. You have cavalry... hopefully they do not (skeleton horses??). Their advantages: They do not tire, they do not rout, they can not be demoralized. They do not take chip damage, meaning that cavalry will likely be unable to do any damage in a charge against them unless they dismount and go head-to-head, and ranged weapons will not do all that much. They know your tactics (not necessarily your strategy). They do not need supplies and can probably move at night. ### The strategy: * Do not commit everything to the front line. * Do not overpower the skeletons with manpower, but instead match their numbers * Keep soldiers in reserve, for reinforcing, catching unexpected enemy movements, but mostly for maneuvering around the battle line to find flanking positions. * Mold the front lines to your advantage. Push the flanks, retreat in the center, or anything else, but always count on your army's ability to do this. * Do not let the prospect a singular victory like Cannae bait you into the wrong moves. The enemy will not retreat until it is dusted, an alternate strategy like sandwiching just part of the skeleton army, protecting the sandwichers and moving on to the next skelton mass could be useful. * Don't let the skeletons surprise you. A nighttime ambush might favor the side that can see with empty eyesockets. * Terrain: You need maneuverability more than the skeletons. They won't tire over tough terrain, though they will be slowed down. ### Drilling your soldiers: Knowledge is power. Your soldiers should know that the undead are not better than the living. Everything they know for sure instead of guessing will give them certainty, which they need to keep their morale high. * What does it take to kill a skeleton? Make sure every soldier knows how hard they have to hit a helmet to break the skull beneath. * What impairs the skeleton's ability to fight? Maybe chopping an arm off doesn't kill the skeleton, but a broken arm won't hold a sword. * What is a skeleton's weakness? Brittle bones may make for bigger weakspots. Likewise, knowing what won't even hurt a skeleton will prevent unnecessary risk-taking. * Drill your soldiers on pushing and retreating. Weight alone means your soldiers should win charges by accident, let alone through training. * Drill other new combat tactics needed to keep enemies that won't feel cuts or slashes under control. You benefit from the fact that they know what tactics the skeletons will be using, so make sure you surprise them with new tricks. Maybe a single man can't kill a single skeleton in a fair fight, but a shield tackle should send the sack of bones flying backwards. Make rugby look like a wet noodle contest. * Drill every soldier on delivering killing blows effectively. Frontline casualties won't be enough since the skeletons should probably take so few of them. Perhaps doing something like a forced push forwards, causing some skeletons to topple and fall, could give you a chance to kill the skeletons you manage to trample, but it's different from a normal battle versus humans. And above all, have faith in your army. Your soldiers will not fail you if you do not fail them. [Answer] Pour hot tar on the skeletons, and let it cool. Hot tar has low viscosity, therefore it flows smoothly. Once it cools down it becomes more stiff, blocking or hampering movements. And with the skeletons blocked in place, you don't need to worry about fighting. [Answer] If the humans are aware of the skull based vulnerability, I think they should make short work of the skeletons. There's a bit of ambiguity in the phrasing "standard Roman human army," so I'll present a couple possible interpretations. Of course, to some degree this cancels out, as the skeleton army is only described as slightly smaller. Further, I'll assume the skeletons at least begin the fight unarmed, with the plan of obtaining weapons from their first couple oppenents, as their equipment is not listed -- we'll assume they are pulled from the general population, which is mostly comprised of civilians. ## Scenario, Rome itself [Rome](https://en.wikipedia.org/wiki/Rome), the capital of the Lazio, is a fairly large city of 2.8 million people, with a metropolitan area of 4.5 million. Although it does not have a full military, it has the protection of the [Polizia di Stato](https://en.wikipedia.org/wiki/Polizia_di_Stato), a formerly military organization (until 1981). There is also a [municipal police force](https://en.wikipedia.org/wiki/Municipal_police_(Italy)) for each city. The primary firearm is the [Baretta 92](https://en.wikipedia.org/wiki/Beretta_92), which should have no particular issue penetrating a human skull. In addition, this is slightly hand-wavey, but officers are assigned two to a patrol car, and each car is armed with a [Beretta M12 submachinegun](https://en.wikipedia.org/wiki/Beretta_M12). They also have grenade launchers, for riot control, but presumably those are loaded with less-lethal ammunition which would presumably be ineffective against the undead. In this scenario, assuming the undead are spotted outside the city, the best plan would probably to get into the outskirts (as far as possible, Europe is pretty densely populated). Although police aren't trained to shoot people in the head, modern firearms should make quick work of unarmed undead forces. I would probably place a row of riot police in the front of the army, with submachineguns very close behind, and pistols close behind that. The strategy would be to destroy the vast majority of undead before melee is engaged, and then rely on the now vastly superior numbers of the riot police to overwhelm whatever remains. I suspect the casualties would be fairly low, but it would still be considered a bit of a tragedy. ## Rome and the Vatican The Vatican, being an enclave city state within Rome would surely be willing to contribute their joint defense. The Vatican offers two potential assets: * The Swiss guard This unit is mostly ceremonial, but also provides security. Small force, but I suspect they'd punch above their weight class -- They are armed with the [SIG Sauer P220](https://en.wikipedia.org/wiki/SIG_Sauer_P220), and the [SIG SG 550](https://en.wikipedia.org/wiki/SIG_SG_550). I don't know enough about firearms to make claims about the P220, other than the general perception that SIGs are held in fairly high regard. The SIG SG 550 is a select fire rifle that fires NATO 5.56, so it should be even more effective against the undead than the basic service weapons of the police. And the increased range will just mean that the re-killing starts earlier, so further lowering the already low burden imposed on the riot squads. In addition, the Swiss Guard is armed with a number of historical weapons (halberds, some plate armor) which could be distributed to the riot squads as appropriate. I imagine a long heavy pokey thing wouldn't hurt to have. * The Pope This asset depends largely on your setting. Presumably, the Pope can bless the weapons of the defenders in some way. Now, this isn't standard operating procedure, but presumably when the dead start to rise, they'll want to try it out. If it works, well, however blessed weapons work in your setting, presumably the friggin' Pope's blessings will amp that up to 11. I'd imagine in the very least, a blessed body shot would destroy the undead. If this has no effect, Italy is a largely Roman Catholic country, so presumably the Pope's presence in a fight against the undead will at least be a morale boost. So, in either case we'd have to expect these assets to make a positive contribution. If the blessings work, I imagine the undead won't even make it to the human line (maybe a couple stragglers here and then, but nothing to worry about). If the blessing doesn't work, I expect that there will be some casualties on the human side (rendering this still a tragedy), as well as some awkward questions for the Church later, but still a very one sided victory. ## Rome, plus the Italian military Well, presumably the Italian military wouldn't react very well to an army of the undead marching toward their largest city. The Italian military is split into the customary Army/Airforce/Navy setup, with another branch for military police. In particular, the Italian Air force has a number of ground attack jets, multi-role fighters, and, I believe some attack helicopters. You can look at a more detailed list [here](https://en.wikipedia.org/wiki/List_of_active_Italian_military_aircraft). And their army has field artillery, tanks, armored personnel carriers, and attack helicopters. Full list [here](https://en.wikipedia.org/wiki/Equipment_of_the_Italian_Army#Combat_vehicles). I think the best plan would be to blow up the undead from very far away. If they can't accomplish that, the Italian people should have some serious questions about where their tax money is going. [Answer] I presume since we are dealing with the undead, morale is not an issue for them - these skeletal soldiers will continue fighting until ordered to do otherwise. This makes them very dangerous - in ancient warfare, actual combat was usually a relatively small contributor to the number of casualties. I don't have actual sourced numbers on hand, but I would ballpark that in an evenly-matched encounter <5% of the soldiers would die in the actual fighting. By comparison, huge numbers of soldiers were lost in a disorganized retreat (a rout). The result was that the winning side often suffered relatively light casualties, while the losing side might have their ability to organize further resistance effectively destroyed. (Consider the Battle of Zama, the final battle of the Second Punic War. Rome brought ~35,000 soldiers, while Carthage brought ~40,000. The result: a Roman victory, with an estimated 4-5k lost by Rome... compared to 33-40k killed and captured Carthaginans.) Since the Skeletons will not rout, any pitched battle between the Roman army and the skeleton army will require the Romans to commit to an all-day grinding slog simply to achieve a stalemate at the end of the day. If we add in that skeletons don't need to eat and don't get tired, the Roman army cannot win a pitched battle, without overwhelming tactical and/or numerical advantage. Fortunately, the Romans were smart, and there were more than a few very clever Roman generals. If we assume typical Roman ingenuity, they are probably aware of this danger and will avoid pitched battle at all costs. His best hope is to engage in guerrilla tactics. This does go against pretty much every Roman tactical doctrine in the book - Romans were notorious for seeking open battle with the enemy, and despised military deception... which cost them at Teutoburg - but they were a clever bunch and they had a lot of tools that could come in handy here. Things like rolling balls of flaming pitch down hills into packed enemy formations, or launching stones via mangonel or ballista. They even had a ranged weapon which would likely have been very effective in this case: the humble sling is absolutely capable of breaking even living bone ensconced in flesh. Dry, dead bone would likely shatter if hit. So, taking some hints from other posters: I would expect a Roman army to engage in hit-and-run tactics involving blunt force trauma and extensive projectile use, while trying to lead the skeletons into unfavorable terrain (swampland, rivers, mountains). While this would not destroy the army outright, they may be able to weaken it considerably. Further, any groups that are isolated could be swarmed, surrounded, and beaten into oblivion with clubs/staves/etc. The ultimate goal of the Romans would be to weaken the skeleton army enough that they could gain enough advantage to pull a Carrahe or Cannae on them, or otherwise get at whatever is holding the army together. [Answer] Halberds [![enter image description here](https://i.stack.imgur.com/tpQ4b.png)](https://i.stack.imgur.com/tpQ4b.png) You use them as set spears to hold them back whilst others take out the heads. It's basically the same tactics the Romans used except a skeleton can't push itself past the head of the halberd [![enter image description here](https://i.stack.imgur.com/GxvyC.png)](https://i.stack.imgur.com/GxvyC.png) If they can't get close, they aren't as much as a threat. [Answer] Fire In ancient Times, there was Greek Fire -> <https://en.wikipedia.org/wiki/Greek_fire> They were able to throw them with war machines, so they would not even have to come near to the undead army. I am pretty sure that bringing the whole army to burn in very hot fire like in a crematorium should destroy them. Edit: I read that Greek Fire itself was invented around 677 AD, so this would be too late for the scenario. But according to the already mentioned wikipedia article, weapons of fire were used from the 9th century BC, so the Answer should not be invalidated. [Answer] Depends if they have a weakpoint i guess. If their bones are held together magically, try finding something that de-bonds the bones. Maybe fire, big cataputs, more fire. ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 5 years ago. [Improve this question](/posts/129536/edit) For my story the inhabitants of the setting find themselves fighting against endless hordes of monsters. But these monsters have several traits that will require unique strategies against them which I am trying to work out. The setting First of all some background on the world they're living in. Its set in a large kingdom about half the size of western Europe and is surrounded by barrens. These barrens are infested with the monsters and are constantly attacking. The area in between the kingdom and barrens is known as the frontier. A massive stretch of land filled with walls, fortresses and other defenses. If one of them were to fall it would be a simple matter to fall back. The tech level is undecided. I was thinking late second industrial revolution but medieval is also a possibility. Magic The setting does have a magic system but it is not too relevant to the tactics. It is of a runic nature and by drawing on ley lines anythign within the parameters of the rune can be done. It is not that suitable for use by units and is usually reserved for reinforcing defenses or enhancing long range weaponry like artillery. The Monsters The monsters are the creatures of a God of the void. They desire to wipe out everything and they are created by this god for doing so. They have multiple traits that make them difficult to stop. * Attraction to magic: The world is held together by magic so they have an ability to seek it out and destroy it. Magic can be found in all living things, running through the landscape as ley lines and in runic circles made by mages. This draws them endlessly into the kingdom which still has functional magic thanks to its defense from the monsters. * Anti-material: Anything the monsters touch crumbles into dust/ash. This severely limits the effectiveness of different weapons. Melee weapons will wear out quickly in combat and armour will crumble after a single hit. This obviously makes ranged weapons a smarter option. Defenses like walls can have some effectiveness at holding them back depending on thickness. They will need to be constantly patched and repaired however with constant attacks. Due to the magic running within living creatures their crumbling effect is different on them. Organics will wither instead. Organs will stop and limbs will become useless. Damage depends on amount of exposure, limited exposure will leave the tissue functional if scarred and crippled. Large exposure will leave tissue dead and after that it will crumble just like anything else. * Endless variety/numbers: There is no end in sight to the numbers of the monsters, society has basically just been holding them at bay at the frontier. They can come in many different shapes and sizes, appearing both like real animals and mythical ones. * No organs: Due to their nature as monsters of the void, they do not require anything to survive and therefore have no vital organs. Killing them is dependent on body damage. Cutting them to pieces and blowing them up are effective at killing them. Ranged weapons like guns generally don't do much more than slow them down. Although higher caliber and higher spread guns are effective. Large amounts of small wounds have also been shown to kill them, as if they were bleeding out, although no blood has ever been observed from them. --- I need to work out what tactics would be best against these monsters. Both on an organizational army wide scale and independent unit scale ie what training and equipment soldiers receive and what tactics the army uses. EDIT: Alright I'll give you some extra details and clear some things up. * Withering organics is not an extra thing that happens before crumbling to ash. Its just the same thing happening in a different way. * touching a single part of an object will not cause the entire thing to crumble, only the touched area. Parts surrounding it will weaken however, monsters must use repeated attacks and touches to destroy things. This means the size of an object matters, a bullets small size will lead to near immediate disintegration upon entering their body but a thick stone wall could last a siege. * Their disintegration ability is in effect over the entire body, touch it anywhere and you will crumble. They are immune to the effect themselves so no friendly fire. * As creatures of the void, they are not all physically there. Hence no need for organs and such. While they can be touched and killed, they do not fit in with the rest of nature. Basically eldritch monsters. They also appear to fade away into smoke upon death, leaving no bodies. * The durability of the object matters when crumbling. e.g. stone lasts better than clay. Metal weapons can survive a few hits(as long as the structure is still sound) * There are monsters capable of things like flight, swimming and burrowing through the ground. Their numbers vary. Tunneling monsters are uncommon but do exist, they are more common in areas with plenty to dig through like mountains. It takes a while for them to dig but still faster than any natural earth creature thanks to their disintegration. Flyers are common but still less than standard land creatures. Anti-air weaponry would be effective against them. Oceans and water bodies in monster territory tend to be teeming with them. Sailing in monster waters is effectively suicide since they can destroy the bottoms of ships. The only sailing activity is limited to a safe and secure bay which is kept clean of monsters as well as freshwater bodies deep with safe territory. * The lower density of liquids and gases leads to the disintegration being less useful. e.g. water will become lifeless and less buoyant while air becomes stale and thin. * Monsters can tone down their ability at will, this is mostly done for convenience though, not much use walking when the ground is gone. * The origin of the monsters is not known by society. It appears they just spawn within their own territories. Created by their god. * Monster strategies usually come down to either strong individuals or pack hunting. Packs will usually stick to monsters of similar body types but this is not guaranteed. Monsters can form large hordes of many types which will attack in waves. Their God does little to lead them past simply creating them. * Monster intelligence can vary, most are nothing more than primal creatures whose only instinct is to seek out magic and destroy. But some can rise higher to use strategy in combat or lead their fellows like an alpha. Some can even organize entire armies of monsters but these are rare and their tactics pretty simplistic outside of maneuvering. * A single type of monster has developed which is capable of mimicking humans and infiltrating society to bring it down from inside. Their existence is not known to humans so tactics don't really exist against them. * Humanities goals has basically just been survive for their entire history since the monsters first started showing up. All they have been able to do. While they have fallen back and reclaimed bits of the frontier many times, they have never really been able to advance much further. Doing something about them will be the main plot of the story but for now I want to know the tactics already in use. * Very frontlines forts can expect 2-5 attacks a week, they use the time between attacks to recover, repair and restock. * It is not uncommon for groups of monsters to make their way past the frontline, this is why its so important for extra fortifications behind them. So recorded monster has made it all the way to the kingdom through the entire frontier's defenses. * Society is geared towards supporting the frontier, with resources and troops being sent out as often as possible. Internal politics can occasionally decrease this supply(because politicians can be bickering idiots at times) * Runes can not be freestanding or created instantly. They must be drawn onto something. So good for reinforcing a wall or adding an extra effect to it, not so much for force fields. Using them in the defense also has the extra drawback of attracting more monsters * The monsters cover basically the entire world except for this kingdom. Their more dense around the kingdom itself since the barrens don't really have any magic to attract them. It is theorized that there may be other kingdoms out there which have managed to survive like them. But between the monsters and distance contact it not viable until the threat is dealt with. * Terrain will regenerate over time when magic is available. Ley lines will naturally create features of the terrain and said features will simultaneously reinforce the ley lines. E.g. rivers and ridges are more likely to end up running over ley lines. This means that within the barrens the monsters have destroyed most features of the landscape to weaken and destroy the ley lines. As long as the kingdom still stands, the ley lines of the world will continue to regenerate using them as a source while simultaneously being targeted by monsters. * If the monsters were successful in destroying all magic including ley lines on the planet, it would die and come apart. If every planet in a system lost its lines then its star would be turned into a black hole(systems and planets function as gigantic runes keeping the universe together). The God of the void aims to do this everywhere * The monsters were not always attacking. There was a period where there was a good god protecting them until he got preoccupied with keeping the universe together elsewhere. They had gotten to about bronze age tech before the monsters started appearing. Much of the world was swiftly lost and they retreated into the fortified kingdom. --- Phew, the number of things you only think to add after posting, well here we go. Time to say if anyone points out more details I could add.... [Answer] Material of choice: Clay With earth being plentiful, it should be easy to rapidly produce clay weapons and barriers, using runes to reinforce them as much as needed. Weapons of Choice: Heavy Bludgeoning/Crushing class weapons. The nature of the void creatures means that penetration (piercing/slashing) class weapons will have more surface area exposed to the monsters, and thus will wither significantly faster. Plus the creatures seem to be susceptible to "bleeding" effects. Crushing class weapons like the war-hammer are capable of causing massive internal bleeding without ever penetrating the target. This makes Bludgeoning weapons the most potent and durable weapons to use. For flying enemies, The requirements of flight already require a light (frail) body. Their void ability making the air thin will require an extra light frame to remain airborne. Any projectile should easily rip these enemies to shreds. So standard archers with longbows should do. (You may be able to modify them to fire clay bolts) For elite enemies, projectiles can be enhanced with Greek fire or gunpowder (or a runic emulation of the effect) for some extra kick. Armor of Choice: Leather This should be plentiful enough, and allow the soldiers to take a few hits, but the lightness/flexibility should help them to avoid getting hit in the first place. Note that this means soldiers will get well rounded physical training. They need endurance+agility to avoid getting hit, but they also need strength to maximize the damage of their heavy weapons. Attack Scheduling Either using caravans of magically reinforced elite troops, or routinely creating/destroying runic fortifications, this should allow the frontier forts to cycle which are the most "magically fortified", allowing the strongest forts to fight hardest while the neighbor forts use the relative downtime to repair/fortify their defenses; as well as cycle active duty troops so that those on the front lines are always at the top of their game. This bundling of enemies will also make siege class weapons like catapults more effective as their projectiles can hit more enemies per volley. Side note: The psychological health of our troops is important to remember. We will want to rotate troops in and out of the front regularly. And while resting, it's important that they have plenty of emotional support. Fort Style: Rocky terrain The endless nature of this enemy makes traditional munition based defense of traditional forts unsustainable. We need to get the enemy close enough for our troops to crush them, while creating a heavily obstacle ridden environment to choke/slow the enemy to deny them any swarm advantage. Catapults behind this fortification (or deep in the middle) can use their munition store to wipe out large groups or particularly strong looking enemies before they reach the main line. The nature of this defense also means it will remain largely intact if we are forced to retreat. This means that our forts will be up and running the moment we take it back from the enemy. [Answer] Use their attraction towards magic to drown them into poop It's too exhausting to renew all these expensive defense mechanisms. There is one resource the kingdom will never run out of: poop. Let your drowning tank refills itself, as monsters are irresistibly lured toward the huge pile of magical artifacts you placed at the bottom of it. It is actually a win-win situation: unpleasant odors are evacuated as poop is now constantly vanishing due to contact with the monsters. Latter in your story, it will be discovered that the god sending the monsters is a benevolent one, who found this creative way to stimulate the development of sewage systems among humans. [![drawning_in_poop](https://i.stack.imgur.com/sQuiU.png)](https://i.stack.imgur.com/sQuiU.png) Possible downside The kingdom is being steadily depleted in organic material, especially nitrogen, so you will need a solution for farming. [Answer] Questions like this are hard because the answer is always the same: "Find what works well, and do it as much as possible." Sadly, this puts us in opposition with you. Our job is to break your system. Whatever rules you put in place, my job is to find ways to bend and break them. Accordingly, the first thing I'd do is start using weapons that are still living. Why let my weapon crumble when its lifeforce can "wither" instead. All it needs to do is stay functional until the enemy is gone. Likewise, I'd probably build forts out of living trees to form a useful barrier. Other than that, the answer would be the same as it is in every case. Find what is effective against the creatures, and do it repeatedly. You haven't stated in the question what works against them, so I can't say what that is. But your people will need to find it, and do it. Also: take the fight to them. You can't just "survive" forever. If you never gain any ground, you'll only ever lose ground. My recommendation, not knowing anything useful about the creatures: raise violent pets. Start raising animals that might fight back against the creatures if unleashed. If you can train them to do something which hurts the creatures, train them accordingly. If you're up against an endless horde, and you're only surviving, you're losing. Oh yeah, one more trick for anyone who has played Starcraft: [Float to the island](https://www.youtube.com/watch?v=5PBElQnvfIg). [Answer] The monsters are anti-material, so weapons would be extremely ineffective as each one would be single use. There is no way any economy could create weapons at this rate. Simply patching your walls could work for some time, depending on how fast your walls disintegrate. This however would result in an ever growing group of monsters tearing down your walls and will prove unsustainable in the long run. The only way to limit your resource usage is to make sure you are not attacked by these monsters. Hiding obviously is not feasible since they track down your magic. So that only leaves one option: prevent them from reaching you! You can do this with a water cannon as used by the police force in riot control. You could even add in abrasive components as done in watter jet cutting to not only push the monsters away, but also actively hurt and possible deter them. As @Mr.Mindor brings up: if the water is destroyed by the monsters it would turn into hydrogen and oxygen, which would react in an exothermic reaction. Likely the monsters would choose to turn their powers off while being bombarded as a way of protecting themselves from a huge fireball. This in turn would open up the possibility of shooting them with arrows, spears and the like as the previously mentioned problem with these is no longer in effect. [![water canon from https://en.wikipedia.org/wiki/Water_cannon](https://i.stack.imgur.com/Ta6JZ.jpg)](https://i.stack.imgur.com/Ta6JZ.jpg) You could build such a water canon by utilizing a dam that collects water. If you build a single structure like the Hoover Dam and build an efficient pipe network with limited losses you should be able to cover quite a large area depending on the density of the monsters. The water would be coming out at just under 2.2 MPa (using the Bernoulli equation). Which is about the same as that of the riot police\. > > p = rho \ g \* h > > > The most modern water cannons use 20 l/s\. The Colorado river supplies 500 m^3/s\ so this should be enough to continously supply > > 500.000/20 = 25.000 > > > cannons, which I recon should be enough to hold off at least 5.000 monsters at any given moment if you take into account a 60% loss (at the high end) and aim two canons at each monster. \All numbers are from wikipedia [Answer] Much as I admire the sheer elegance of the sewage solution, I'd think the answer is obvious. Classic RPG tactics would suggest that if physical attacks don't work, use energy attacks. If your world is at industrial levels, use fire and lightning. Arrows and bags of manure, soaked in pitch and set alight before launch have been around since the Bronze Age. Even if the bags and contents disintegrate on impact, the fire won't and should severely burn large numbers of monsters if you use flaming bags. Steampunk era gives you both static and current electricity. Connect your walls to giant [van de Graaff generators](https://en.wikipedia.org/wiki/Van_de_Graaff_generator), then sit back and watch the monsters get electrocuted as they touch the conductive plates. Set up large capacitor arrays and use them to power arrow fired tasers to incinerate large targets. Since your monsters nullify, if not eat magic, you can't use mages, but mad science is always available to pick up the slack. If the above options work, upgrade to lasers, railguns and death rays. EDIT: For better results, incorporate @Alexis' solution. Put cheap magical items in your flaming loads and hopefully, the monsters will actually lump together to grab it. [Answer] Build walls and weapons out of materials that cannot wither or crumble to ash. A fortress in the frozen North could be built out of ice. Pikes could be gold coated. Burning oil doesn't wither nor does boiling tar. In the end you need to destroy the portal letting them in. I'd build a fortress to hold them off and start a massive magical ritual for the purpose of attracting them as they seem to be creatures drive by instinct alone this way an attack force could attempt to close the portal from behind. [Answer] Do different materials crumble into different types of dust/ash? If so, perhaps the defenders can find a material whose dust/ash has an [angle of respose](https://en.wikipedia.org/wiki/Angle_of_repose) is so steep that the monsters can't climb it. Imagine trying to climb a mountain of powered sugar, you'd really just be wallowing in a pit of it before long, gradually eroding the mountain until the angle was such that you could actually approach. The defenders would need to maintain their mountain of powder, as the energy imparted by the monsters would distribute it. I imagine a bucket-brigade of peasants in snow-shows, raking the powder back into the correct slope so that it is ready to ensnare the next batch of monsters. Also, if the monsters are smart enough to build snow-shoes themselves, then this wont work. [Answer] The monsters are smoke. The god of the void is the fire.* Your monsters are a symptom, like smoke is a symptom of fire. Smoke can definitely kill you and might be the worst thing about the fire, but it is difficult to fight smoke. You can avoid it or let it out or wear a mask but the smoke will keep coming, because the fire is still burning. To definitively fix a problem with smoke, you need to address the fire. And here the fire is the God of the void. Ideas with how to come to terms with a divine entity whose interests are contrary to yours. 1: Come to terms. If the humans themselves facilitate the orderly destruction of magic items, that might be acceptable to the void god who would then be saved the trouble of making monsters. You would not want to destroy any faster than they can regenerate or this will not be sustainable/. 2: Distract void god into doing something else elsewhere. That worked for the good god, and so there are presumably elsewheres accessable to gods. Point out to the void god that it will meet less resistance and be able to destroy magic faster in a place where humans are not opposing it. 3: Recruit help. The existence of elsewheres and other gods suggest there might be other divine entities interested in preserving the status quo. One of these might be recruited to help humans oppose the void god as the good god used to - or maybe get that one back. 4: Best defense is a good offense. There are gods and there are gods. Maybe you can dissuade the god of the void from his goal somehow. Remember he is a god; it will take more than one shot. [Answer] Deep trenches and moats would be useful for slowing down the monsters without presenting them with matter that would be vulnerable to their disintegration ability. It would also help group them so they would be more vulnerable to artillery and massed fire. Depending on the exact nature of your magic system - a magical barrier such as a runic force shield may be much more resistant to attack than any wall made of a mundane material. Reinforcing your structures with magic to resist disintegration may also work. As for offence - melee is obviously inadvisable, as is allowing them to get to close to your defences really. Massed artillery fire seems to be the way to hold them at bay, bolstered by magic as much as possible. Depending on your technology level, weapons such as white phosphorous will allow you to level the playing field. Flamethrowers could also allow small units to effectively combat the monsters, though fuel usage may be a problem. Rune circles could be used a magical "honeypots" to lure creatures into a certain area before shelling the ever-loving beejeezus out of it from a safe distance. If magic can affect the monstyers, laying down area affect spells to weaken them as they run toward you defences may also be useful [Answer] Play Tower Defense If you present them with a solid wall they will attack it and eventually break through, so instead you create a funnel and maze setup as a killing ground. The walls have openings, that they will naturally funnel through. Inside the walls are a maze or labyrinth that forces them to run around a very long route. While they do that towers and other placements along the walls fire arrows down into them until they are weakened and die. The towers are linked by mobile wooden bridges. If they do turn and try to attack the walls or towers then burning oil is dumped on them. If they begin to climb the wall or it becomes too weak the defenders retreat to the next one and pull up the bridges, leaving the creatures stranded on an island and forced to climb down into the maze again. [Answer] Fire. Nothing about these monsters seems to indicate that they can't burn. The disintegration effect is less useful against things of lower density, so, petrol seems like a solid go-to delivery mechanism, but really what you'd want to go for is the highest possible temperature, so any good raging inferno should do. You were less descriptive about the limitations of what runes can and can't do, but if they can produce fire or heat, it seems like making a reinforced runic pit of endless flame would be a pretty awesome defensive mechanism. [Answer] ## Use their power against them Section removed as OP updated they are immune to their own anti-material. See edit history for how that could have been done otherwise. ## A more mundane approach Ranged weapons, whether by length or by projectile, are what started to win wars later on anyway, and many melee weapons are lethal from just 1 or 2 hits. So really, although these enemies sound awful when described, they really aren't individually a lot worse than fighting other humans after all. After re-reading the question again, I notice you suggest that arrows and guns just slow them down and it takes a lot of shots to kill them. In that case, arrows are less feasible in large scale attacks, but pole arms defending walls still work well. And when on the offensive, pole-arms behind trenches. Also start using modern poaching techniques. Leave lots of hidden traps for them to step on so they come at your slower and weakened. However, you did say there were huge numbers of them. That is probably the real problem here. But that is what castles are for. A castle allows its occupants to defend against a numerically vastly superior force, so again this just lends itself to what we see in our real history. However, if you rule that their touch can bring down walls too, then that might be problematic. However, some forts use earthwork fortifications, and disintegrating earth is not going to do much. ## Summary In a fantasy story, you can make their abilities sound awful, but in reality, against an army it isn't really all that bad and normal tactics which have been used in history can be used for the most part. Since that is not so exciting, as the author you should find the exciting and dramatic middle ground and just rule that it works out however you want. The people don't really need anything special to overcome these enemies, as I stated, but you can just make the enemies seem powerful and go whatever direction you feel like. [Answer] So the best way for you to defend against the monsters forever is to take advantage of your naturally generating terrain. This means that your weapons should reply on regenerated materials, rather then complex processed materials. (I am approaching this from the same way I played a infamous game called Dwarf Fortress) Defense 1 The Terrain The biggest advantage you have will be the terrain. A close source of Lava or Water would be invaluable as it would allow you to harness this magical liquid to fight the beasts. The easiest way is to simply build a huge dam that holds all this liquid and release it into the oncoming horde every time they attack. This lets you simply wipe some of them away and slow their progress as they now have to walk through muddy ground while fighting the current from the burst dam. After the breach, you refill the dam using the natural regeneration of the terrain or allow the water/lava to slowly pour in. Depending on the source, you could have multiple dams or only use a limited amount to help delay the beasts while your other measures kick in. You also want to limit where the monsters can approach from. Think of something like Helms deep from LOTR. Sure the monsters could approach from other directions, but they would never be able to do so in the numbers required to overtake your frontier forts (unless for some plot twist reason, you want to make it happen). Now the monsters might dig away at the sides and open up some passage ways, but when this happens you can send out some ranged forces to force them back and let it naturally regenerate over time. Defense 2 Stone Catapults and Ballista Terrain features regenerate overtime and there is always a abundance of stone to be found everywhere. Your siege weapons use this as a near infinite ammo. Not only will it regenerate over time providing you with a nearly unlimited source, its annoying for the monsters to remove. The battlie field will be littered with boulders and spears made out of stones which the monsters will have to push through. Combined with the a dam, you have a landslide that you can trigger once a battle. The monsters run in, you activate your dam. The boulders and spears from the previous battle are washed into the monsters and once the initial blast is over, you start firing, preparing the battlefield for the next battle. Defense 3 Rune enforce everything Runes stand out and attract more monsters. You want this, because you want to force your monsters to attack a fortress, not run around it. By providing a powerful enough incentive, you basically allowing the monsters to approach you the way you want them to. Reinforce all your defensive structures and watch the monsters pour in only to be washed out again. With the natural terrain supporting you, the monsters are going to find it extremely difficult to overcome you. [Answer] > > Cutting them to pieces and blowing them up are effective at killing > them > > > If available fragmentation grenades. If not whatever explosive you got combined with anything sharp. Nails, rocks with sharp edges, glass fragments. Very simple to build and cuts them up badly and inflicts a lot of damage which is why terrorist use them. You could add poison if it had any effect on them. ]
[Question] [ The question, before you get into the rest of this textual abomination: with all of the context, objectives, and design features mentioned below, is an ultra-heavy tank a resource-efficient means of killing zombies in an [CBRN](https://en.wikipedia.org/wiki/CBRN_defense) (nuclear/biological/chemical/radiological contamination) environment inhospitable to human life? Let's say that, in the near future, there's a zombie apocalypse in the vein of [World War Z](https://en.wikipedia.org/wiki/World_War_Z): perpetual-motion, fast-moving, and hyper-aggressive zombies (long story). Important note: they form [chain swarms](https://zombie.fandom.com/wiki/Chain_swarm) when they hear loud noises. This is relevant later. People have retreated, re-established their industrial and technological base, and have mostly systemically exterminated the zombies infesting their country. They came up with the concept of the [resource-to-kill ratio](https://zombie.fandom.com/wiki/United_States_during_World_War_Z#:%7E:text=The%20new%20name%20of%20the,of%20the%20undead%20as%20possible.); essentially, how do we minimize the resource and/or dollar cost of killing an individual zombie? Their solution to that was to use infantry with bolt-action rifles, as that's about as efficient as you can get without endangering your soldiers: one bullet, one kill. However, there's a massive area of the country that was sterilized with every nuclear, biological, chemical, and radiological weapon known to mankind in an attempt to destroy the zombie horde in it. Unfortunately, it didn't destroy many of them. There are still millions of the things left. Normally, the society in question would not want to take back such a godforsaken wasteland, but the sheer number of zombies in it means that it's a threat to anything and anyone nearby, as hordes constantly march out of it to attack the living. Building a wall around the place and making the zombies pay for it was dismissed as a waste of resources, given the scale of such a project, and the fact that the zombies climb walls like ants. They can't be met outside the wasteland in a resource-efficient way, either - doing so means mass civilian evacuations in the path of the horde, as well as pulling hundreds of thousands off-duty (say, building new homes, or performing mass burials, or having babies - people who would generally be rebuilding after an apocalypse) in order to meet it, as well as to operate the supply lines keeping the front line fighting. Since these zombies are both extremely fast and extremely coordinated (for instance, look at [this example](https://youtu.be/uU0DNCV22dU?t=3) of World War Z zombies climbing a wall like a horde of ants), sending in armed personnel into the zone in bulky hazmat suits, CBRN-proof vehicles, and mobile decontamination bases means that they're not mobile enough to avoid getting overrun and torn to shreds. A specific vulnerability is that suit or base breaches are guaranteed death even if the zombies don't get you; the nightmarish, radioactive chemical soup the area is saturated with will kill you soon after a suit breach. Now, fighting the zombies from within an CBRN-sealed armored vehicle helps negate the problem of a suit or base breach: the entire thing is armored, and zombie bites and/or environmental debris will not get through it. However, fighting the zombies from inside a CBRN-sealed armored vehicle fails due to two major and two minor factors: MAJOR: * These zombies pile up on you - potentially by the thousand. Even if you somehow manage to kill a shit-ton of them, your vehicle is going to be buried in their corpses. The odds are that its wheels just aren't going to get enough grip to be able to move. Now, you might negate that by replacing wheels with tracks, but those get clogged with zombie parts relatively easily. Hell, they might even be able to smother your engine. * It's hard to live inside a tank. Yes, I recognize that people have done it in the past, but if you're on a patrol in the Northeastern American Dead Zone for a month on end inside a sealed metal can with nothing but death around it, you're going to go nuts eventually. Even submariners have more room per person than there is per person inside, say, an Abrams or a Bradley; the only occupation I can think of that involves less room to move around is being an astronaut on the earliest space capsules. MINOR: * You're going to run out of fuel eventually. Obstinately, you can go back to base for more, but that's only if you can avoid getting bogged down by the hordes of sprinting, dog-piling zombies - and if you run out of fuel, tough luck. * Eventually, you will run out of ammunition; there is only so much room for the stuff inside a tank or an armored personnel carrier. Again, you can technically go back for more, but, again, if you run out you're hosed, and it's not like it's easy to fit an airlock onto a tank. Moreover, going back for fuel and ammunition limits the amount an extermination team can penetrate into this massive dead zone; even if they set up fuel dumps inside it, they are liable to be contaminated and/or overrun. Enter my solution: the ultra-heavy tank. If you want an example of a vehicle on such a scale, look at the Nazi [Landkreuzer P-1000 Ratte](https://en.wikipedia.org/wiki/Landkreuzer_P._1000_Ratte), or NASA's [crawler-transporters](https://en.wikipedia.org/wiki/Crawler-transporter). I'm not saying "build a Ratte" or "build a crawler-transporter"; I'm just providing an example of what vehicles on this scale look like. Now, there are many glaring flaws with ultra-heavy tanks that preclude their use against human enemies: * They require truly gargantuan amounts of fuel. * They're basically a gigantic "kick me" sign for aircraft and artillery. * Their ground pressure is off the charts, and they destroy any bridges they cross over, meaning that follow-up forces can't use them. * They're slow. However, in a near-future war against World War Z-style zombies set in a chemical hellscape, these problems are negated. * Replacing gasoline-powered engines with [small modular reactors](https://en.wikipedia.org/wiki/Small_modular_reactor), batteries, and electrically-driven motors negates the fuel problem - fuel-wise, the thing can operate for years on end. * Zombies have neither aircraft nor artillery. * We'll get to my way around the ground-pressure problem eventually. Moreover, destroying bridges is not a problem, because: ~ the odds are that they're gone already ~ it's not like anyone will be using them anyway; they're in a toxic, irradiated moonscape unsuitable for human life * Being slow is not a problem, for reasons I will get into. Moreover, such a vehicle has several advantages as part of a near-future war against World War Z-style zombies set in a chemical hellscape: * Despite its low speed, its great mass gives it incredible kinetic energy once it starts moving. It can flatten houses, fences, most land vehicles - actually, most obstacles that would impede a lesser vehicle in general, of which there are going to be a lot of post-apocalypse - and woe betide the pile of zombies that tries to climb onto it: the thing just keeps moving. It doesn't have to move quickly, like it would against a human adversary who's attempting to get bombs into it - it just needs to avoid getting piled up on, so that it can constantly bring its weapons to bear on the zombies. * Unlike a pack of lighter vehicles and semi-mobile, pre-fabricated bases, an ultra-heavy tank is one gigantic thing. There are no vulnerable airlock tubes in-between vehicles, no lengthy decontamination procedures, and no need to climb into a hazmat suit to go to the messroom, or go to the toilet, or to load new munitions into the thing: everything is already inside the vehicle. The Ratte, for instance, was designed with a motorcycle bay, an infirmary, several storage rooms, and its own self-contained lavatory system. Essentially, such massive vehicles have [interior supply lines](https://en.wikipedia.org/wiki/Interior_lines) on a tiny scale. * Unlike lesser vehicles, an ultra-heavy tank is large enough to carry that nuclear reactor I mentioned previously, meaning that fuel is a non-problem for years. * It's a propaganda symbol: what's better for the spirits of a crushed and depleted people: ~ a bunch of hazmat-suited, faceless goons with rifles, in the same tanks that failed to stop the zombies the first time ~ a majestic, invincible land battleship and its brave, intrepid crew * Ammunition is less of a problem, because the square-cube law works in the favor of ammunition storage here; since the tank has more inside volume, it can carry a lot more ammunition. * The crew go insane less quickly; since this thing is, in terms of accommodations, more comparable to a submarine than a tank, longer zombie-extermination trips can be undertaken. However, there are a number of features that could be incorporated in order to make the thing more efficient: * No armor. Zombies don't have armor-penetrating weapons, meaning armor is as much of an instance of dead weight as the zombies. * No artillery weapons. A high-explosive shell is not the most resource-efficient way of killing zombies. Instead, replace the main turret and the entire top of the hull with a superstructure; in it are armored, CBRN-sealed ports with integrated semi-automatic rifles, so that the crew can pop the heads off of zombies one at a time. * Instead of two tracks, add as many as possible - preferably, mounted next to one another, and using the space in between where the tracks would be on a conventional tank. This ensures redundancy, as well as reducing the vehicle's ground pressure. While this would make it very difficult for the vehicle to turn, turning is not really an issue, since it can be accomplished over long periods of time. * Add a plow on the front, for getting obstacles out of the way of the tracks. * Give it cheap, disposable drone scout support for finding and navigating towards large hordes of zombies. * Add [mine flails](https://en.wikipedia.org/wiki/Mine_flail) between the ground and the firing ports, so that zombies attempting to climb it get mulched. * Add airlocks on the dorsal superstructure, so that cheap, expendable cargo drones can slowly but steadily resupply the vehicle's ammunition reserves. The standard modus operandi for one of these vehicles would be: 1. Drone locates zombie horde. 2. Vehicle drives to horde to intercept it before it exits the dead zone. 3. Vehicle begins playing loud music, horns, whatever have you, forming a [chain swarm](https://zombie.fandom.com/wiki/Chain_swarm) 4. Chain swarm follows vehicle as vehicle leads chain swarm away from populated areas 5. As (4) is carried out, sharpshooters inside vehicle terminate zombies. Eventually, they'll run out of swarms near the dead zone border, and begin pushing further into it. Other than that, no major changes in that plan, other than a return for crew change-out/repairs every 6 months. Again, the question: with all of the context, objectives, and design features mentioned above, is an ultra-heavy tank a resource-efficient means of killing zombies in an [CBRN](https://en.wikipedia.org/wiki/CBRN_defense) (nuclear/biological/chemical/radiological contamination) environment inhospitable to human life? [Answer] Blimps * A large blimp costs [a few million](https://askinglot.com/how-much-does-it-cost-for-a-blimp), similar to [a tank](https://www.google.com/search?channel=fs&q=cost+of+tank), and surely less than your super-tank. * The zombies won't be shooting it down. They can't swarm it or gum up its wheels. * Blimps are unaffected by terrain and can travel much farther than a tank. They can loiter around in an area killing zombies without spending much fuel. * The crew in the blimp are probably safe from ground-based CBRN hazards even if no other precautions are taken. It's unlikely that radiation or chemicals on the ground would harm them hundreds of feet up in the air. For extra protection, the blimp could be plastic-sealed except for the gun ports. * The blimp crew can be armed with rifles. At 10 cents a shot, this is a resource-efficient way of taking out zombies. It could also be a platform to deploy [noisemaking bombs](https://worldbuilding.stackexchange.com/a/210133/82546) as suggested in another answer. The bombs could be lowered from the blimp into the heart of the zone, left on the ground to make noise and attract zombies for a while, and then explode on a timer. Or just don't go in If these are normal zombies that can't reproduce, their numbers are going to do nothing but diminish as time goes on and they wander out of the zone and are killed. A single soldier with a rifle can probably take out dozens of zombies. Just maintain a rapid-response system with cars or trucks so that every time a group of zombies comes out of the zone and attacks, a bunch of soldiers can get there quickly to wipe it out. This would be much more cost-efficient than tanks or blimps, though it would not give peace of mind as quickly. [Answer] # No Your tank is a very expensive coffin. 1. The tank is not a submarine. Enough zombies will literally form a fluid around it, preventing it from moving. 2. All tanks require maintenance. Maintenance free tanks don't exist, they break down. You cannot exit the tank to fix something with zombies swarming around it. 3. Guns, and tanks in general, are great for killing things far away from you. Your tank has a failure state of "zombies are not far away from you". # Solve it in phases Each phase's goal is to kill 90% of the zombies in the region. # Phase 1: Sort of already complete. You used chemical and nuclear weaponry. This will have reduced the zombie density. You can complete this by identifying remaining high-zombie density areas, and doing saturation bombing with conventional explosives/napalm/etc. Goal: Kill 90% of the zombies. # Phase 2 Bombs with speakers. In areas where there are zombies, but not enough to pay for carpet bombing, drop in a parachute a loud speaker and an hardened high explosive device. Zombies are attracted by the loud speaker. Then the explosive device goes off, shredding almost everything in 100 meters. Goal: Kill 99% of the zombies. # Phase 3: Just speakers. Your goal is to find out where the zombies are. Drop solar powered loud speakers with zombie detectors. Vary the sound played (not just the same frequency range) to deal with zombies that are hard of hearing. Ideally you can use a remote to turn on and off specific speakers, allowing remaining zombies to be moved using audio-based paths to concentrated kill zones. Then clean up the resulting kill zones. Goal: 99.9% of zombies dead. # Phase 4: Active hunting. Send blimps over the area with sharp shooters. Build kill-towers in the no-mans land near the edge (or a bit inside) of the contaminated area that attract zombies, kill them, and act as warnings if a swarm is leaving the area. Use swarm tactics on the zombies. Volunteer patrols in medium-scale CBRN hardened all terrain vehicles search the area, clearing out zombies and provoking zombie attacks. If they can't handle it, they attempt to hunker down as relief is sent, or they flag the attack and just die. Higher intensity solutions (see above) can be used, like a large bomb (possibly they carry a large bomb in their ATV for just such a purpose). CBRN hardened construction vehicles rebuild roads and flatten remaining human construction (possible hiding places), possibly even rebuilding bridges to make access by humans easier. Visual-ofactory decoys (for the zombies whose ears are missing) with zombie-detection sensors (solar powered webcams!) are deployed to draw out zombies. These are air dropped into inaccessible areas and deployed by the patrols. Goal: 99.99% of zombies dead This still leaves a huge problem. If the area originally had 100 million people all of whom became zombies, 99.99% dead means you still have 10000 zombies in the area. But those zombies will hopefully be unable to swarm and will decay over time. An example would be a sealed bomb shelter with a few 100 zombies in it. If these zombies are magically immune to decay, that bomb shelter might stay full of functional zombies for many many years before erosion occurs and lets the zombies out a hole. At which point they go and start a new swarm. # Phase 5: Passive, permanent defenses. In the long term, it won't just be zombies inside the contaminated zone that are a problem. Zombie outbreaks will happen in "safe" areas. So you'll want to build zombie swarm barriers and safety bunkers to slow swarm spread throughout the safe areas and preserve some of the population when a swarm occurs. Then you deploy active defences (soldiers with rifles or whatever you find effective) to clean out the swarm and rebuild. In safe zones, you'll be spending decades or centuries digging up everything to a decent depth and looking for buried zombies to prevent future swarms and make them more safe. The CBRN contaminated areas will make that harder. You'll end up wanting to build walls around it and patrol them. Even if it doesn't stop every zombie, stopping ones whose arms or legs are missing is a win. But none of these steps involves building a giant metal super tank. [Answer] ### Rifles aren't the most resource efficient way of killing zombies. Bombs are. In short, bullets are a really inefficient way of killing large numbers of people. One bullet can only kill one person, at best, but it's much more likely that you'll be spending dozens or hundreds of bullets for each kill instead, simply because of how inaccurate the humans pulling the trigger are. The best way to kill zombies would be artillery, for the same reasons that artillery is the most efficient way to kill humans: one artillery shell can kill every zombie (or human) within dozens of meters of its impact point. There's a reason why artillery is called "the queen of the battlefield". If the zombies naturally tend to clump up in swarms in response to loud noises, that just makes artillery even more efficient a method of exterminating them; you just plant a loudspeaker to draw them in, then shell the crap out of the resulting horde to wipe them out by the hundreds or thousands. [Answer] No, your tank will not be an efficient vehicle. The reason tanks are heavy and even tank shaped is how they are optimized to survive against heavy weapons. Requirements like a low target silhouette or even being heavy due to all the armour fall away once there is no enemy anti-tank weaponry. You probably want something truck-shaped, maximizing internal volume. High sides are harder to climb, and there is plenty of experience and production capacity to produce trucks, even to custom specifications. The easier solution however will be to drop crews entirely, and stick to drones. Most of the mass you are carrying around will be for protection systems, which you can all dropped with unmanned vehicles. You may possibly need some radiation hardened electronics, but it is much easier to shield a computer than a person. Given that zombies don't have any electronic warfare capabilities, there is no chance of them jamming any connections. Using remote controlled vehicles keeps the control crews safe, and flying drones can go in and out of the zone, while being completely safe. At altitude they can even keep away from most of the contamination, making them easier to decontaminate and service. Ground based drones can be remotely resupplied with ammo and fuel, only requiring decon for full service, and if they are too heavily contaminated, you can still just abandon them. As a rule of thumb, if you are going for efficiency, look for the smallest possible tool that can get the job done. [Answer] Different zombie killing tanks, gas, biological weapons, fire and INFINITE POWER There's plenty of answers already that tell you a big tank isn't cost effective. Lets focus on what would work. Lets say zombies can use the maximum strength and speed of a human at all times. Their attacks are still swing, kick and bite. Secondary is simply throw enough weight against something with thousands to damage it. Tanks First we need not to be overrun. We can make an armoured vehicle with speed and that is high enough you need to climb before reaching the top. Add some spikes aiming down (possibly retractable). Now you have a machine that zombies can throw themselves onto, killing themselves and sliding off again. Simply drive away from the horde that the fastest can catch up, killing themselves. Add a lot of solar panels for recharging and you can go on a long time. Just go into a safe place every so often to recharge. Only long time wear will destroy your vehicle and you can kill lots without firing. Gas But why do so much trouble? Chain swarms are a thing! Make a mega mob by provoking a chain swarm. They go to this specific location you have rigged with traps and kill them there. Literal meat grinders, bombs all around or atomic bombs. All can kill a lot. But you can kill so much more with gas. If you get the right one, flesh can practically melt off the bone (fluorine!). You can gas thousands to millions this way. Biological weapons Biological weapons are in extent of this. Bacteria or parasites can simply start eating away at the flesh, eventually removing the zombie remains. Fire All that meat represents a huge amount if potential energy. Potential energy can be released with a spark. Drop a bit of napalm or just set them alight with a match. With a mega swarm trap this can spread quickly, consuming a large host with barely any effort. You can just ast Bert to go to a big tower or a big open depression. Set off a siren. Have Bert set a torch alight. Bert will just stand there to be devoured. Thank you Bert. Torch will light a zombie or two on fire, which then can merrily spread to hundreds, thousands or millions. Low cost, low technology, low risk (for most). INFINITE ENERGY But why not cost effective, but wasteful? Why not if you have infinite energy. Teslacoils all around the edge of your cities, literally vaporising zombies if they get too close. How you ask? You have perpetual moving, strong and fast zombies. You know what that means!? Big hamster wheels with zombies perpetually going after prey! Or something less ridiculous, but the point stands. You can create clean, stable energy if you capture enough of these zombies and use them in inventive ways to produce power. Power you can store in batteries for tesla coils or highly flammable hydrogen for example! Electrical fire from the electrified fences and the tesla coils will do the rest. Or maybe from the hydrogen flame throwers. The zombies will create a wall of bodies that is on fire. Remove much mass over time thanks to the fire, pose a difficult to extinguish fire that is immediately a difficult obstacle to overcome. The zombies might never reach your building and the bodies will disappear in the incredible heat of fire. That is how you get the most efficient killing machines. After a bit of investment, you have a potential infinite return. Mathematically there are few things more efficient than an infinite return. [Answer] ## Agricultural Machines: What you really need isn't a traditional tank. It's an [autonomous agricultural combine](https://www.youtube.com/watch?v=wowPihsf3kU). Admittedly, they will need to be specialized, with a broad base to prevent tipping. Large "roadside mower" attachments with spinning blades to chew through zombies on the sides might help too. The large harvesting implement on the front might need some optimizing for humans vs. crops. Ultimately, it's a giant robotic lawn mower on steroids. Fundamentally, getting rid of zombies is an industrial process. You need a large, robust fully robotic machine that chews through zombies on a regular route through zombie territory. The outside should be fire-resistant, so a stopped vehicle can be appropriately napalmed and recovered. The zombies will be drawn to the machine noise, ground up and spit out in a stream through the back of the harvester (if disposing of zombie bodies is important, a trailer can be dragged behind to collect the remains). For simplicity, I'd make them electric with a backup quiet, efficient electrical generator. With the choppers running it would be incredibly noisy, but just running otherwise, it could be extremely quiet on a road. If the vehicle was mobbed, it could simply shut down until the zombies lost interest and wandered away. If it was short of fuel, drone refueling craft (form to be selected as desired) could refuel it in field. But the routes would be short enough so it should be able to run on batteries alone. When the vehicle returned to it's base, it could drive into a sealed building and disinfected in a way you wouldn't want to with a live crew. You would establish routes through zombie territory and start out with your biggest, nastiest machine you can muster. But once the overburden of zombies began to go down, lighter, more efficient ones could run through systematically chewing up and spitting out zombies until no more come out. Then you set a new route and repeat the process. It may not get all the zombies, but it keeps grinding them up until they are quite manageable. [![enter image description here](https://i.stack.imgur.com/wGnsD.jpg)](https://i.stack.imgur.com/wGnsD.jpg) [Answer] # No You already have answered this yourself: These zombies pile up on you - potentially by the thousand. Even if you somehow manage to kill a shit-ton of them, your vehicle is going to be buried in their corpses. All your mega-tank does is require a larger number of zombies. However, as you've already provided - zombies have the requisite numbers: <https://www.youtube.com/watch?v=uU0DNCV22dU&t=3s> This is worsened by the extremely limited armaments you've listed: "CBRN-sealed ports with integrated semi-automatic rifles, so that the crew can pop the heads off of zombies one at a time." This is essentially useless given the foe you are facing - they'll probably kill more of themselves in the attack than your rifles will. *TL;DR: the solution to fast, aggressive swarming enemies isn't to sit in a metal box, with no exit, and try to pot-shot them at a distance. You've just made a very expensive coffin.* [Answer] Regular tanks are not the best weapons, but they will do Tanks are not expeditionary forces on they own. They act within a limited range from a base or a depot. Turning your depot into a huge tank normally would be cost prohibitive. Think through a few points: 1. Even if zombies can swarm a tank, they can't do anything to it or the crew inside. Just make sure tanks have emergency oxygen supply; 2. The biggest problem of killing zombies is finding them. Swarming zombies are ripe for killing using any kind of weapons. When one tank is being swarmed, make sure there is another one nearby that should make a short work of the first swarm. 3. Set up an "impregnable" base near the infested territory. Use a tank battalion to draw out all nearby zombies and destroy them. After local territory is cleared, move the base and repeat process. [Answer] ## No, I doubt it is efficient to build an über-tank I'll take your own arguments against you : * This über-tank is slow, but it doesn't matter; Niet, the slower your tank is, the more time the infected will have to pile on it. Moreover, you will always get an harder time moving again if you get stuck. Stopping is really risky therefore. * If you are not pressured into fighting such as when in safe environment, one bullet - one kill is not the most economic way of killing1. Also, a rifle is not accurate on the move due to the vibrations you'll constantly take. But moving is essential, too, so... * The last pin to the story is that you do need roads and/or stable, flat environment. If you don't, you lose accuracy with rifles, you have an higher chance of getting jammed. An issue which has been brought up just before :). To reorganize these points : You need to be not moving to shoot accurately, but at the same time you need to be constantly moving to avoid first the horde. You might think that you can go on a stop, hit then run strategy, but your tank is moving slowly; The Ratte was suspected to move at up to 40 km/h (not accounting terrain!), but such heavy tank will get very long accelerations and slowdowns, meaning your effective speed is lower than that. So you're most probably shooting at most half of the time. Also, beginning a movement is a precarious step on these kind of heavy duty apparels. It's a common problem with trucks that get bogged in mud in the wild, so imagine with something much bigger, which on top is a prototype which will contain flaws. ## More (zombies) over... And here comes a part frame-challenge answer : Remember, the Ratte was a project brought up only as a plan, an idea that never got finished. It was moreover designed to be built into a shipyard refurbished for this purpose, not a regular factory, increasing even further its cost in a context of resource scarcity. Because, let's face it, in the new context after a Z-war, you could have at most 1 or 2 running in after 2 years of development at the very minimum. One or two killing not that much every day, and having a chance of getting overrun and lost. Also, since it's a prototype made in a hurry, you will most likely get a failure at some point, especially on any moving parts... Such as tracks! And to repair those tracks you'd need to be outside the tank, which doesn't seem the best place to be :p. So, is your plan all about having a few key structures that can be brought down after 2-3 years into the war? Ones that could break, be stuck or ineffective? But most importantly, what do you do with the horde in the meantime? Do you really hope they won't move in any of your towns, including the facilities you brought on to make your tank? Until the first tank get out of the factory, what do you do? I've seen many people in strategy games focus on what is called the late-game, ie building big weaponries and big troops. This kind of strategy is very inefficient against rush tactics, such as "[hyper-aggressive and moving in mobs](https://tvtropes.org/pmwiki/pmwiki.php/Main/ZergRush)" enemies are. Here, your generals are having very high hopes that the zombies won't move outside the region as a horde. So high it is surprising that the countries managed to rebuild and have the resources to defend AND build their tank factories while letting one million zombies roaming freely in the lands. This while still having big concerns about those ones to afford to build a mega-tank prototype. Efficiency comes along with how many risks you take on your investment and how fast you can take your earnings from. Spending several years on a project dreaming that nothing "too" bad happens in the meantime doesn't seem good at all on this point. ## Conclusion That's a lot of conditions, which makes me think that making simpler things like digging pit traps, walls or moats2 outside the areas, or crafting lures a few kilometers away and burn everything once done (which is even more efficient cost and time-wise than bullets) are much more practical, faster and safer ways than building on a conjecture. --- 1 : Quick example : Spears are almost free apart from the initial costs and could be used from the safety of the vehicle (just let the zombies come!). That's just one of many, of course. 2 : Yes, they can climb moats and out of pit traps, but if you watch WWZ movie, they do so by using the others as ladders more so than climbing on the micro-asperities of the wall. This means that you still get zombies down there in the end. Ones that you can safely dispose of and reuse the trap after. [Answer] No You are trying to build the most cost efficient solution to killing zombies by building a huge expensive complex and novel solution, effectively land battleships. Even worse, your zombies are fast and stupid, and attack any loud thing. Have you ever played a tower defense game? Same concept here, except you have multiple noise makers moving them to multiple points. Run left, run right, run left, repeat ad nausium. what you need is; Simple, robust, reparable, built up in a cellular network, using the zombies stupidity and noise aggression against them. ``` "Sir killer-thing(henceforth KT) #4 is off line, we're switching KT3# on to draw all the zombies away from it." ``` Then they need to be small enough to be picked up for repair when they break down by anything significantly quieter than a KT or tower. Blimps are an obvious answer, but really it could be electric lightly armored tow trucks, once all the zombies are routed away by loud things... being overwhelmed isn't an issue. ``` "Opps there is a problem at field1, lead them over to field 2 please." "Nope it's going to take a while, move them to field 14" ``` The simple truth is, that your zombies are a threat to humans during the explosive growth, human isolation phase. Once you get safe areas that can't be overwhelmed, and rebuild industrial capacity, their stupidity and aggression bring them down over time. There is a reason in WWz why shovels were the best tool long term. It's building defenses they can't breakthrough that's the hard bit. because of the ant pile thing. but even that's not un solvable, because the zombies are stupid. Hell, "silenced" rifles on the wall, and 4 towers with concert sized loudspeakers to run the zombies round and round while you shoot them. Put fields of whatever around your defensive walls, and arrays of noise makers to move them wherever you want them before the walls get buried under. Inside your walls, divide things up into cells that zombies get trapped and killed in to prevent explosive growth. And that's completely aside from that fact that in your world building, you've removed all reasons for us to leave those areas in the first place. Your version of the Armed Forces were stupid enough to render the rest of the planet uninhabitable. Not even smart enough to drop 1 nuke and see if it worked, Hell your "defenders" are stupider than the zombies. ``` Nuke 1 massive heard of zombies, did it work? Nope Ok, drop acid on one did it work? Nope. Okay, lets drop running chainsaws on them out of airplanes, Nope. Badgers? Nope Biological an chemical weapons, But sir they are dead already, Corporal do it anyway! Nope, didn't work (mutters in enlisted) Running Lawnmowers? Nope, but it made a cool sound... What about Ninjas, nope now we have zombie ninjas.. Cartoon Mascots for sports teams? Nope, but that was funny as hell! Well heck, lets just NBC the rest of the planet. Not because it works, but because we're too stupid not too. Durr! ``` There is literally no reason to go looking for the zombies, as even once they are gone, you can't even use the territory outside your safe zones. First you remove all agency from your zombies. Then from your "defenders". Then you remove any reason to leave the defensive area. But back to the original question The KTs themselves can be anything, Modern Robotic lawnmowers with the guards cut off. ww2 tank Mine flails attached to towers, giant wood chippers with ramps all around them. Hydraulically powered pike squares. Metal Schredders. Hell windmills with machetes bolted to the blades, low enough so that zombies walk into them. Alternating bands of upside down lawnmowers and loud speaker towers. 1 on, BRRT, 2 on, BRRT, 1 on BRRT.... repeat Once you damage the legs of a fast zombie enough, it's a slow zombie. It arms, more so, keep going and eventually its head is at ground level. Infinite stupidiy = infinite time to kill them. [Answer] "These zombies pile up on you - potentially by the thousand. Even if you somehow manage to kill a shit-ton of them, your vehicle is going to be buried in their corpses. The odds are that its wheels just aren't going to get enough grip to be able to move. Now, you might negate that by replacing wheels with tracks, but those get clogged with zombie parts relatively easily. Hell, they might even be able to smother your engine." This is just a gross underestimation of tanks. Tanks can drive through buildings. Zombies or zombie corpses won't even be felt by the people inside the tanks. Further, most of the armor can be stripped off these tanks since the zombies are just meat; they're not shooting back. So your anti-zombie tanks can have an even better thrust to weight ratio, so you will have even less trouble. But I think you're going about this all wrong if you're actively attacking the zombies. "Chain swarms" mean they can be easily herded around. [Lure them to one of these industrial shredders](https://www.youtube.com/watch?v=bh8j_N0OUSE), and then just watch them get chewed up. [Industrial shredders easily eat engine blocks](https://www.youtube.com/watch?v=bJ-7N67eTiE), they'll go through zombies like tissue paper. And they're really loud, and thus very attractive zombie bait. [Answer] ## Why Bother Protecting a Crew? * Take a standard car or pickup * Setup a drive-by-wire system (cameras, steering control, etc) * Strap some chain saws to it * Put a bomb on board Remote control your vehicle into the disaster zone, moving slowly, and periodically buzz the chain saws to gather a horde to your vehicle. Eventually the car will run out of gas, or the horde of Zs will bog it down in spite of the judicious use of the chain saws to thin the crowd. Now you set off the bomb. If you use junk vehicles, this whole setup is pretty cheap. You can probably off a few hundred Zs per vehicle, between those you run over, the ones hit by the chain saws, and the ones you eventually get with the bomb itself. If you think you need meat inside to keep the zombies engaged, I'd recommend livestock. [Answer] I don't believe that anyone has claimed that a tank is a resource-effective solution for any problem. They're designed to complete objectives quickly and effectively, but efficiency is not really one of their design criteria (it rarely is in wartime). In your particular case, you have many solutions that are much more efficient. Forming chain swarms is only a short-term advantage for the zombies. In the long term, it's the key to defeating them. People that hunt ducks, moose, or many other types of game locate their prey by using a call that mimics that animal's natural call. It attracts the prey into the open where the hunter can fire on it or ensnare it in a trap. You kill your zombies the same way. Record the sound of their call and use a network of speakers (plant them in advance or hang them from drones) to direct groups of zombies wherever you want them to go. Prevent the swarms from growing too large by using a wall of white noise or nature sounds to drown out the sound of their call beyond a certain point. Any sound generated by a human body's vocal system is completely inaudible at a range of 20-30m in the presence of even modest background noise. With a bit of practice, you should easily be able to pull a small group of zombies at will and separate them from the pack by breaking the call chain. At this point, you're simply herding cattle to slaughter. Pull them off in small groups and lead them into static traps that you've set up ahead of time. Lead them into a narrow gallery where automated blades and hammers destroy anything that moves. Lead them into a fully-enclosed area, shut the door, and destroy them trash-compactor style. Lead them down a steep slope that causes them to tumble down into the large bark chipper below. The point is, you don't need military-grade equipment or even human operators. The entire thing can be an automated slaughterhouse that's operated remotely. Killing via mechanical methods or melee weapons means you don't have consumable ammunition that needs to be constantly replenished. Humans only need to get involved if something breaks. You can fabricate everything from existing farm or industrial equipment. If you're extremely clever, you can generate power for the whole enterprise by burning the bodies of the zombies that it kills. [Answer] > > Replacing gasoline-powered engines with small modular reactors, batteries, and electrically-driven motors negates the fuel problem - fuel-wise, the thing can operate for years on end. > > > An SMR, from as far as I can tell, is still fairly large. We're talking hundreds of feet in one dimension and a few dozen in the other two. The 'small' doesn't mean "compared to a human" it means "compared to how big reactors normally are". Batteries don't help you either. [To power the behemoth you talk about, it would need a shocking amount of batteries.](https://www.youtube.com/watch?v=Hatav_Rdnno) Batteries, compared to electricity, is not very energy dense. To recharge it would also be a long task too. ]
[Question] [ So, the nuclear apocalypse happens, 90% of humanity dies off, and most survivors live in small subsistence farming communities. The technology stagnates around the mid 1680-ish. Most communities only rarely see caravans and traders come through, as settlements are often few and far between. In the settlement my character grew up in, men often went on caravans to other neighboring towns to trade goods with each other. But, there is a rule in the community that says women aren’t allowed to go more than a half mile away from the settlement. My question is, since I couldn’t think of one, what would be a plausible reason for them not to allow it? [Answer] The most important role in this society trying to rebound from near annihilation is simply to keep the species going. In other words, the ability to bear children, to care for and provide milk to them, to nurture them, and ultimately to sustain the population. This ability is sacred. Anything which jeopardizes that essential contribution to the clan should be avoided. It is biological fact that females are the only ones who have these all these abilities, and although males play a role at the beginning, it is possible to do without the male after that step. Outside the settlement are bandits, natural hazards, predatory animals, and so on. If these risks must be dealt with for trade and other business, let the men dirty themselves with such things. The losses of a few men from time to time are a cause for sorrow, but the collective can rebound. However, the women must be protected. EDIT (to incorporate some good thoughts in comments). This does not necessarily imply this culture is sexist against women. In fact, it could easily have been the women who devised this system, i.e. "We're too important and vital here, you buffoons go trade with the village over the vale, while we look after the babies." Or if you don't want sexism either way, replace "you buffoons" with "you worthy stalwart protectors" or similar. Further, as other answers mention, exactly this attitude did exist in certain Real World(TM) societies, and still permeates our stereotypes and prejudices to this day. [Answer] Bride raiding. Primitive humans stealing women from each other is pretty well established. They make valuable slaves as prostitutes, and can be used for breeding stock. The fastest way to stagnate an enemy group's growth is to steal all of its women. Women's rights and the idea that they are not property and can decide whose camp they would prefer is largely enabled by modern technology and culture. That's all going to go away as soon as society has degraded to the point where food water shelter and security are now the primary daily concerns. Essentially, they are property again and it's a lot easier to control/protect/profit from them if they stay put and do as they are told. It's not very nice, but it's pretty much what the wimmin folk have had to put up with just about everywhere for pretty much most of human history. [Answer] ## Radiation Some materials will stay hot for hundreds to thousands of years. It may be possible for cleaners to identify and haul away all radioactive debris near the settlement, but you can't control the amount of hazardous material in the wilderness. In regard to radiation, women have a [20% lower exposure limit](https://www.space.com/22252-women-astronauts-radiation-risk.html) for a 3% higher cancer risk. Women also require only [400 rem across 2 or 3 exposures to suffer permanent sterility](https://www.health.ny.gov/publications/4402/). In this respect, men may be more disposable. Or, men already sterilized by radiation may be most disposable. Particularly, [metals can become contaminated by radioactive materials](http://www.hse.gov.uk/waste/radioactive-contamination.htm), so following a nuclear apocalypse - especially one that has killed so many - there may be value in keeping women away from the outsiders and anything they have touched until it can be properly examined. [Answer] In fact, you don't need a plausible reason for that. There are and were societies where similar rules were always in force (although they are more difficult to implement in a rural farming environment, because the labour of women is needed on the fields). However, you should think hard about the consequences of such a rule: How are marriages arranged? Is the society matri-local and matri-linear, i.e., the women stay on their property and inherit it, while the men have to change places when marrying? [Answer] Moral customs: women who wander away from a settlement are only prostitutes and shed a dark light on their family honor. As such it's a male's duty to protect the family honor by preventing the women of his family from moving far from the settlement unless there is a marriage agreement. By the way, this is not far from what was womens' reality in mid 1800, so I really don't get how you > > I couldn’t think of one > > > [Answer] Fairies. [![goblin market by Arthur Rackham](https://i.stack.imgur.com/dCrSY.jpg)](https://i.stack.imgur.com/dCrSY.jpg) <https://ericwedwards.wordpress.com/2015/08/14/the-origin-and-lore-of-fairies-and-fairy-land/> <http://www.scottishpoetrylibrary.org.uk/poetry/poems/fairies> > > Up the airy mountain, > > > Down the rushy glen, > > > We daren’t go a-hunting > > > For fear of little men; > > > Wee folk, good folk, > > > Trooping all together; > > > Green jacket, red cap, > > > And white owl’s feather! > > > ... > > > They stole little Bridget > > > For seven years long; > > > When she came down again > > > Her friends were all gone. > > > They took her lightly back, > > > Between the night and morrow, > > > They thought that she was fast asleep, > > > But she was dead with sorrow. > > > They have kept her ever since > > > Deep within the lake, > > > On a bed of fig-leaves, > > > Watching till she wake. > > > The prior answers are super sensible and realistic. Women are life and have always been taken as prizes by communities of humans who want slaves and brides. To this day, as has been pointed out. But if you want something more surreal and supernatural - there are other entities which might want the women. They do not want them to work, or for their meat, or for their babies. They want something else. Their motivations are not clear and maybe not knowable. Why do they want little Bridgit? Why did they let her come back, only to retrieve her before the next morning? Why do they watch her on her leaf-bed in the lake? Fairies are the Other. Maybe that can give your story some weird energy. [Answer] > > men often went on caravans to other neighboring towns to trade goods with each other. But, there is a rule in the community that says women aren’t allowed to go more than a half mile away from the settlement. My question is, since I couldn’t think of one, what would be a plausible reason for them not to allow it? > > > It's semi plausible. 1. Endogamy must be prevented (for example, at harvest festival season, the young people of each village would caravan to other villages to "meet and mingle"), and 2. marrying the daughters of the village's Very Important People to the neighboring villages' Very Important People's sons is a time-honored method of establishing strong ties between towns/cities/duchies/countries/etc. Thus, young women would sometimes travel. Otherwise, the @cobaltduck answer is excellent. [Answer] The Torah has different rules for virgins being raped inside and outside of the town gates. When raped inside, they are stoned because it is assumed that they could have shouted loud enough to prevent the rape. When raped outside, the rapist has to marry them and is not allowed to divorce them. Seriously. "Town gates" can correspond more or less to your half-mile radius and we are talking about the laws of a tribal society. Basically it is considered detrimental to value preservation of females if they venture too far outside. Assume they get raped and they may be off regular sex for months before you are certain she has not gotten pregnant in a time frame where you'd want to stone the potential bastard child (in which case you lose almost a year as well as the additional food she consumes during pregnancy). This is just slightly more misogynistic than the laws in the Scriptures which are definitely post Stone Age. Remember: if your property might have tried preserving herself by screaming outside of hearing range, she may be allowed to survive and marry. Probably not exactly the man she dreamt of (excepting nightmares), but women can't be choosers. [Answer] A specific technical reason: A specific example of such a case has been observed in the Canopo peoples of the Dougon taiga in Northern Gachaza. A mutated species of parasitic insect called the flockfly aggressively attacks the mammary glands of larger mammals. For some reason this fly is particularly attracted by the odor of secretions from Montgomery's glands in human women. Flockfly infestation is relatively rare, but when it happens it is devastating to livestock, not only due to the damage to milk production but also due to secondary infections. The infestation is difficult to eradicate once it has taken root in a herd, so to reduce the chances of flies being brought in from outside, women of childbearing age and older are prohibited from traveling outside their own communities except in direst circumstances. Flockflies are generally only attracted to women who are pregnant or lactating, but the taboo on women traveling as a result of this phenomenon has become generalized to all women. ]
[Question] [ This is my first post here, but here we go: I have been creating an alien world for a while, and the sentient species on it is very canine-like. They have a canine body, legs, and head, and the only difference is that they have two prehensile tails (due to a beneficial mutation a million or so years ago) and short saber fangs that are always visible. I thought that because they look so much like dogs they can possibly breed with them. This probably won't happen very often, though, as they would possibly think of that as tainting their species, but it's still an interesting topic. Can an alien plausibly breed with a dog, even if they share no evolutionary relationship and are from different planets? [Answer] Not a chance Does your alien even use DNA? Is its biology even remotely similar to that of earth based life? If it is it would be a great surprise as both evolutionary trees will have been completely separate. Vague resemblance between species especially species from different worlds is no guide to their capacity to mate. Vampire bats and black birds share a number of similarities but there is no chance that they could interbreed. The biological differences between the alien dog and an earth dog would in all likelihood be greater than the difference between a dog and an oak tree. [Answer] Let's take a stab, and say that your creatures look something like this: [![](https://i.stack.imgur.com/iuwLt.jpg)](https://en.wikipedia.org/wiki/File:Thylacinus.jpg) Those are pretty dog-like, don't you think? Now, let's look at where that one came from, evolutionarily speaking (its [cladogram](https://en.wikipedia.org/wiki/Tasmanian_wolf#Discovery_and_taxonomy)): [![Thylacinus cladogram](https://i.stack.imgur.com/0ugXB.png)](https://i.stack.imgur.com/0ugXB.png) That ancestor is [Dasyuromorphia](https://en.wikipedia.org/wiki/Dasyuromorphia), as in > > The order Dasyuromorphia (meaning "hairy tail") comprises most of the Australian carnivorous marsupials, including quolls, dunnarts, the numbat, the Tasmanian devil, and the thylacine. > > > Wikipedia puts Dasyuromorphia as infraclass Marsupialia, of class Mammalia. Compare this to the [gray wolf](https://en.wikipedia.org/wiki/Gray_wolf), which is of order Carnivora, in turn of class Mammalia. In fact, the photo near the top of this answer is not of anything even remotely related to a dog, but rather a pair of [thylacine (also known as the Tasmanian wolf)](https://en.wikipedia.org/wiki/Thylacine), photographed circa 1904 and now considered to be extinct. The odds that a thylacine would be able to successfully reproduce with a dog, despite their superficial similarities, appears rather slim, given how separated they are from an evolutionary point of view. But they have still both evolved on the same planet, and share e.g. much of their biochemistry. For example, both are carnivorous (even able to derive nutrition from much the same kinds of biomatter), DNA-based, carbon-based lifeforms adapted to survival in an oxygen/nitrogen atmosphere at about 1 bar pressure and with a surface gravitational acceleration just shy of 10 m/s2 and in a temperature range not that far from, say, 270 to 300 kelvin. Now consider what you are proposing: creatures which share no evolutionary history whatsoever. None, nada, zilch. As Slarty pointed out, [do your alien creatures even use DNA?](https://worldbuilding.stackexchange.com/a/96331/29) That's a kind of a one-in-a-billion buckshot that Earth life just happened to settle on because it turned out to work well enough for the first species that happened on it. [DNA is a complex thing](https://en.wikipedia.org/wiki/DNA), and the odds of randomly stumbling upon exactly that are pretty low. (Evolution generally won't move away from a local maxima, even if the local maxima is low compared to a hypothetical global maxima. If seeking a higher maxima requires reducing fitness in the interim, that is exceptionally likely to be heavily selected against.) Is your alien adapted to survival in an atmosphere like Earth's? (Remember Earth's major extinction event known as the [Great Oxygenation Event](https://en.wikipedia.org/wiki/Great_Oxygenation_Event)? That's when Earth's atmospheric oxygen content rose from about zero to peak as high as over 30% before falling back to the current level of about 21%. Yes, there was life on Earth before that, and in fact life was the cause of the great oxygenation event.) Do your alien creatures procreate by copulation between two individuals of opposite gender? Do they have two genders in the first place? (You can have sexual reproduction in situations with something other than two genders. Again, this is something complex Earth life settled on, but it doesn't have to happen that way.) And that's before you even get to the issues of, say, behavioral compatibility. User [Kys](https://worldbuilding.stackexchange.com/users/16335/kys) posted a comment on my old question [Would humans be able to derive nutrition from foodstuffs found on alien planets?](https://worldbuilding.stackexchange.com/q/47787/29) which I feel applies here: > > You already won the exoplanet lotto. Might as well double down. > > > (Some of the discussion in some of the answers to that question may also apply here.) The odds that your species would be able to breed with any Earth species seem [infinitesimal](https://en.wikipedia.org/wiki/Infinitesimal). The odds that any resulting offspring would be fertile would, to the extent that this is possible, likely be much lower. So sorry, but no; absent intelligent design on the scale of multiple solar systems, the odds that your creatures will be able to successfully breed with anything on Earth are, for all intents and purposes, zero. Even similar seeding of life would be exceptionally unlikely to result in species being able to procreate across planets, seeing as it hasn't even caused species to be able to procreate on a single planet... [Answer] I don't believe so. See, crossbreeding between animals and aliens would be a hybridization, and we have a lot of barriers against hybridization. Reproduction itself is a process with a lot of controlling systems. We have prezygotic barriers, which are the barriers that prevent two different species to crossbreed. That could be: too different body shapes, or behaviours, flowering in different seasons, occurring in different places (isolated from each other), lack of chemical recognition between ovule and sperm, too different genomes.... And we also have postzygotic barriers, which would prevent the development of an zygote even if these different species mate. That could be poor development or abortion of the hybrid zygote, sterility of this hybrid... Thus, your aliens would have to deal with all these controlling systems... They would need to have chromosomes similar enough to ours for chromosome pairing... or a system that could mislead and deceive this very important and central issue in reproduction, which is genetic compatibility. It's important to note that hybridization does occur in nature and is a very important phenomena in evolution dynamics, but a lot of conditions are to be satisfied for that, and a certain compatibility must exist. Take a moment to look into this very nice paper: [Hybridization as an invasion of the genome](http://www.sciencedirect.com/science/article/pii/S016953470500039X). It has a section named Factors affecting the frequency of hybridization that will enlight you about some controlling mechanisms. # The nice thing is: You know there is a theory according to which life could have gotten here from space, right? That's Panspermia Theory. You can read more about that here: [A mechanism for interstellar panspermia](https://academic.oup.com/mnras/article/348/1/46/1415892) [Panspermia today](https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/panspermia-today/6BD35AABC8832E4990AAA704B867489F) [Comets-a vehicle for panspermia](https://link.springer.com/chapter/10.1007/978-94-009-8528-5_15) If life was travelling trough space, in order to evolve here and in other planet in a way terrestrial and alien species would have the same DNA structure based life, both planets would have to have the same conditions for species to evolve under. Even if they did, the mechanisms that prevent two terrestrial species to crossbreed would certainly work for two species from different planets. But the advantage is, this is worldbuilding, right? Given that the universe is infinite, who knows if there aren't such similar planets over there? Also, alien technologies could recreate, simulate, incorporate terrestrial structures... I don't know... you can use your imagination... They can study terrestrial structures and learn how to manipulate genes to express and recreate morphological characteristics they have out there, and then use DNA as their own structures... And if they do so.. scientific literature is full of examples of hybridization as a form of species invasion (respected the compatibilities) For example, hybrids can be less adapted and die... but they also can have the best of each species they came from, and them be able to coup better with more extreme conditions and outcompete their parentals. A world of possibilities lies there. If you get interested, let me know, I can give you a lot of scientific literature (as it is my work) --- Mallet, J. (2005). Hybridization as an invasion of the genome. Trends in ecology & evolution, 20(5), 229-237. Napier, W. M. "A mechanism for interstellar panspermia." Monthly Notices of the Royal Astronomical Society 348.1 (2004): 46-51. Burchell, Mark J. "Panspermia today." International Journal of Astrobiology 3.2 (2004): 73-80. Hoyle, Fred, and Chandra Wickramasinghe. "Comets-a vehicle for panspermia." Comets and the Origin of Life. Springer Netherlands, 1981. 227-239. [Answer] Not unless you design the alien species to take sections of DNA from other organisms, and incorporate them into its own DNA. You could perhaps have a symbiotic virus that will take sections of animal DNA held in a special organ, and incorporate them experimentally into the animal's offspring's own genome, excreting a hormone if the transfer is unsuccessful or harmful, preventing other members of the same species from using the same DNA if it doesn't work. It may be that canine DNA is so useful, that the result is halfway between the sentient species and terrestrial dogs. [Answer] The short answer is no. The long answer, however, is maybe, if all of the right conditions are met, and a truly unbelievable chance occurrence. Regular Breeding Regularly, the two creatures would have sex, a sperm cell would connect with an egg cell, and an embryo would form (I'm simplifying greatly for this question, but it doesn't matter that much). According to [Wikipedia](https://en.wikipedia.org/wiki/Species), the definition of a species is: > > A species is often defined as the largest group of organisms in which two >individuals can produce fertile offspring, typically by sexual reproduction. > > > Considering that your canine-like creature comes from a different planet, they would likely be different species. There is, however, a miniscule chance where the reproductive organs on both sides are able to reproduce with each other, if some conditions are met, in order for them to be just close enough on the family tree to reproduce. This would still probably create something that is not fertile, but that is uncertain. The conditions would likely include: near Earth-like planet, near Earth-like natural history (including some dinosaur-like species that died out), near identical situations for the emerging species, etc., etc. With these requirements, it is nearly impossible through regular breeding. Genetic Modification In theory, genetically modifying your dogs reproductive organs could work, but the chances are extremely low, and they would likely require years of testing and trial and error. I don't know the kind of timeframe that you want this to be in, and it is hard to predict how long this would take. Regular Evolution It is possible, though unlikely, that these creature would find it beneficial to breed with dogs, and through some weird mutation gain the ability to do so, through evolution. Unless your creature had the evolution timeline of a squid(can't find a source for this, but squid's DNA is somewhat unstable, allowing it to change in one generation what other animals may do in ten), this would take a very long time, probably in the several thousand to ten thousand year range, if they're similar enough. Reproduction Via "Assimilation" This is the possibility that I find the most interesting: Reproduction via "assimilation." What I mean by this is, the creature that you're describing has found a way to reproduce with anything in it's entire family or order, due to the fact that it's sperm or egg is capable of using the genetic information of anything in your creature's family or order, and creating a hybrid offspring between the two creatures, but said offspring would lean heavily to the creature's side genetically, only displaying a few traits of the other animal. Such a trait would be very unlikely, but it would create an interesting world. If you really truly need your creature and dogs to reproduce, it is possible, but extremely unlikely, to the point, where no might simply be the more "correct" answer. [Answer] The way we know it, breeding requires pairing base-to-base two sequences of DNA provided by the parent organisms. A minimal difference in the pairing (mismatching number of bases, wrong coding of genetic expression, etc.) results in no vital organism. Cross-breeding with an alien species can only work if the alien species has exactly the same genetic code we have. But that would qualify them as homo sapiens... [Answer] Simply: No. Consider humans and their closest relative the chimpanzee. I cannot say with certainty that humans and chimps can't possibly breed, but if a human/chimp hybrid ever came to be naturally, it would be all over the news (and there are probably people sick enough to... you know...) If you take other animal species like lions and tigers, or horses and donkeys, cross-breeding is possible, but offspring are usually sickly (in the case of ligers) and/or sterile (in the case of mules, mostly). The ability to interbreed would hinge on the genetic similarity between the two species. If your dog-people were taken from earth by aliens and do have some genetic link to earth canines, the odds would be minuscule, as their genetics would be too different. If the dog-people evolved completely separately from earth species, the odds would be uncountably tiny (never say never, else I would say impossible). Also, in much the same way as the thought of a human a chimp together likely made you want to gag, that would likely be the response of a normal dog-person to getting it on with a dog. [Answer] It could work if you make a universal biochemical translation device. Such a device could conceivably be made as some theories on abiogenesis suggest that a lot of the modern biochemical machinery involving DNA and RNA was actually reverse engineered from preexisting existing biochemistry. These are speculative ideas, but you can e.g. imagine running the processes inside the ribosome backward so that you start with proteins and get mRNA as output. That requires different enzymes than currently exist, but in principle chemical reactions are reversible. since the machinery of life as implemented by living organisms on Earth is in principle a universal constructor like a [von Neumann machine](https://en.wikipedia.org/wiki/Von_Neumann_universal_constructor), there should exist a representation of alien lifeform in terms of our own biochemical machinery. [Answer] > > Can an alien plausibly breed with a dog, even if they share no evolutionary relationship and are from different planets? > > > Short answer: no. Long answer: still no. Individuals from different species can't interbreed, regardless whether they evolved on the same planet or not. Sometimes convergent evolution produces animals that look, and possibly behave, very similar, but have very different DNA. The two species have evolved to fit the environment well, despite their different origins. This actually happens quite a lot. E.g. [Red pandas](https://en.wikipedia.org/wiki/Red_panda) (Ailurus fulgens) and [Giant pandas](https://en.wikipedia.org/wiki/Giant_panda) (Ailuropoda melanoleuca) are thought to be not at all closely related. [Koalas](https://en.wikipedia.org/wiki/Koala) (Phascolarctos cinereus) look a bit like [bears](https://en.wikipedia.org/wiki/Bear) (Ursidae) but are in fact hugely different. Koalas are marsupials: their babies (joeys) are born with little development and do the bulk of their growth in their mothers' pouches. Bears are placentals: their offspring spend much longer in the womb and are almost completely developed (don't read this as mature) when they're born. Marsupials look like jelly beans when their born. Placentals (usually) look like miniature versions of the adults when they're born. The two strategies are incompatible. The external appearance has no bearing on the issue. Animals within the same species will have very similar DNA (compared with individuals from other species), and it's this similarity that causes a species to physically appear self-consistent. A Unix/Linux computer and a Windows computer might look identical while switched off, however, neither can run the other's software without emulators because their internals are too different from each other. The operating system is like their DNA, but despite their huge differences, and possibly sharing a small amount of code, they can do the same tasks as each other, at different efficiencies. Before Macs were Unix based, both their hardware and operating systems were vastly different from Unix based and Windows machines, yet they were also capable of performing the same tasks as the other computers on the market. Statistically speaking, the chance is greater than zero, however, it's so close to zero that it might as well be zero. I don't know how many universes you'd need for two species to evolve independently on different planets and end up with DNA close enough to interbreed. Probably billions. Think about the chance of someone completely unrelated to you who somehow ends up with exactly the same DNA as you, and in this case we're talking about two individuals within the same species! In terms of story-telling, your audience with a scientific background simply won't believe it. This is one of the issues I have with Star Trek: almost all aliens can interbreed. This is supposedly explained by having a "seeder" species that sowed DNA on all planets capable of evolving sentient life. The problem with this, is that such a long time passes before sentient life evolves that speciation occurs several times, preventing any possibility of interbreeding. If you want to keep your scientific audience, don't do it! [Answer] There is a remarkably slight chance of this. Crossbreeds between reasonably close species have happened many times on this planet; inclusive of the beefalo, the liger, the sheep-goat, the yakalo, the cama, and any number of game bird hybrids. However, you'll note that the majority of these instances have been between creatures who have some common genetic ancestry, however distant. The only other possibility (established) is what's known as a chimera; which is a creature created from an embryo involving two genetically distinct cells. (It's been done with goats and sheep, and it's at least been proposed for humans and mice--specifically, transplanting liver cells; other instances are certainly possible but I can't speak for them.) The trick is that you're speaking of a creature which has some phenotypical similarity to an Earth creature; but no common ancestry. A DNA-based species is actually quite likely, as it is the result of basic autocatalytic RNA which is the first thing looked for by xenobiologists (and yes, that is an actual field). However, we would be expectant of at least three traits; that is, it would be a bigendered species (male and female), the mechanics of mating would be reasonably similar, and the combination of genes would provide some form of functioning organism and not "noise code". That isn't as far afield as you might think, as DNA is effectively a fractal program for the structure of an organism and horizontal gene transfer between species happens all the time. So, if essential to your story, I must emphasize that conception with an exoplanetary species is very unlikely; but yes, it is possible. That said, note that in the vast majority of real-life and Earth-bound cases (such as the liger) the offspring is completely sterile, and your case is likely to develop any number of congenital genetic disorders as it gets older. You need to remember that natural selection played no part in this hand; which makes it that much more volatile and unpredictable. [Answer] Probably not, the key phrase is "share no evolutionary relationship" so they're in no way related to dogs, they can't therefore breed in the usual manner with earthly canines. So that's that no breeding for you right? Maybe not. Consider creatures like pseudodomonas aeruginosa which has genes that appear to allow it to speed up its own rate of genetic mutation to take advantage of new environmental niches. If you take this and also the ability of terrestrial viruses to play "cut and paste" with genetic material then something with a very strange, from our point of view, heritage might indeed "breed" with terrestrial species as in mate with and create offspring that have a hybrid genetic heritage. The Alien franchise suggests something like this with the [Xenomorph](https://en.wikipedia.org/wiki/Alien_(creature_in_Alien_franchise)), a creature with a basic template form that can hybridise with its gestational host. [Answer] Since your species evolved on different planets from different ancestors, most likely different ancestors all the way down, your chances for any two species are so close to zero it's hardly worth mentionning the differece. But wait... this is an infinite universe (for all we know). It has a very, very, very large number of planets in it (it should be an infinite number). In your version of the universe, there are at least two planets where life evolved. That means the actual number of planets hosting life must be very huge, next to infinite. On our planet, life, based on DNA, evolved, that means this is one possible route how life can be formed. On some of our infinite planets hosting life, it is fairly safe to assume that a similar route was followed (based on the fact that this route is possible, otherwise you wouldn't be reading these sentences right now). Now, we started with the assumption that chances are infinitesimally small (almost, that is). But we also have an infinite number of coin-tosses. That leaves us with an interesting result: The chances that you find two species in an infinite universe that can interbreed although they have no common ancestor are almost exactly 1. Yes. It's possible. Finding those two species is a completely different matter, but then again, you're writing a story, so the match was made. And lots of unwritten and boring stories cover the cases that didn't match. [Answer] Ill be the voice of opposition (simply to add color to this conversation) Your alien dogs could have evolved naturally on you alien planet. Panspermia is proven true and both worlds share DNA as their building blocks. Your aliens are smarter than us and engineer a breed of their dogs such that its DNA is just capable enough of combining with an Earth Dog's. Another scenario : Your Aliens form of sexual reproduction is different than ours. Instead of a sperm and egg: They inject their DNA into their host via retro-viral like transference. Such that one of these hits the egg and correctly inserts its genes into a non-destructive part of the human DNA. The genetic variability in these retro-viruses is so wild that the chance for impregnation has a small random chance. coincidentally this could also explain the physiological changes in a woman needed to support such a pregnancy as her own DNA would be changed. Bare in mind the chances of this working would not be 0 but very close. Likely there would be a lot of deaths as well. [Answer] Yes, alien should breed with dog, but is not for tommorow. Alien can pass out the "challenge" of no evolutionary relationship sharing by transgenesis. This transgenesis can be provoked with irradiation, proximity with a chemical mutagenic agent solution or a bacteria like the "Agrobacterium tumefaciens". --- Sources: * [mutant variety database](https://mvd.iaea.org/) * [mutagenesis provocation](http://www.inra.fr/Grand-public/Genetique/Tous-les-dossiers/Mutations-chez-les-vegetaux/Origine-provoquee-de-la-mutation/(key)/2) * [transgenesis with bacteria](https://planet-vie.ens.fr/article/1483/transgenese-grace-agrobacterium-tumefaciens#une-bacterie-potentiellement-utilisable-en-transgenese) * [transgenic Drosophila](https://www.ncbi.nlm.nih.gov/pubmed/17947973) [Answer] It's very unlikely. You see, there's a phenomenon called "convergent evolution", where similar environmental factors cause creatures with different descendants to reach similar body plans, see the following image portraying a shark, a dolphin and an extinct reptile: ![enter image description here](https://i.stack.imgur.com/V7tc4.jpg) As you can see, they all look much alike but there's no way we'd be able to breed them with one another and get viable offspring, which is due to 4 main issues that might appear: 1-mating behavior: one species might not recognize the other's mating strategies, think of how a firefly's glowing patterns normally won't turn a human on. There's also an issue of different species being fertile at different periods. 2-genitalia: if the species have similar mating rituals and are viable at similar times of the year, their genitalia might not fit properly, kinda like a kangaroos' penis is divided in 2, meaning it's unlikely other creatures without this trait will mate properly with kangaroo females, as they have 5 openings instead of 1. 3-the coding: if both rituals and reproductive structures match, there is the issue of their genetic material not being able to mix properly. In most cases, the embryo will either die before or shortly after birth due to severe deformities, if it manages to reach such development stage. 4-the babies being viable: if against all odds, both species have similar mating rituals, are fertile at similar times and have the codes in mostly similar places, there's the issue of the baby, despite being viable, not being fertile. Kinda like the mule is healthy and can develop with no problem, but it can't have babies, it's infertile. BUT number 4 only applies if you want your hybrids to be viable as a species, that is, to be able to generate offspring of their own, but, given that your creature isn't even from earth, it would be highly unlikely for your creature, no matter how closely it resembles our canines, to be actually able to breed with our planet's dogs or wolves to begin with, let alone have a viable baby. [Answer] I think that with enough genetic modification, the same biochemistry, and if the genetic code of each creature is very similar, than yes. ]
[Question] [ You have an independent space station, it's in a place that is convenient as a jump point for space ships, so it gets visited. What makes a station like that valuable other than the obvious fuel and R&R for the visitors? (Also, where does the station even get fuel? In my worlds, ships travel via hyperspace. I haven't yet defined what fuel that would need). It doesn't seem like fueling ships and providing alcohol, food and sundries for visitors would generate enough to sustain a large, functioning station (let's say 6-9,000 people). This particular station is supposed to be technologically ahead of its rivals, so I'm trying to think of unique/innovative things it might be doing to make it a valuable destination. [Answer] Trading Post Space ships for interstellar travel are different to the space ships for planetary landing. Putting both types of engines on the same ship is a waste of money. Traders do interstellar but not landing. The station has a fleet of crafts for ferrying things up and down. But they do not do interstellar. The space station is in a slow orbit around its planet. Traders dock at the station and do their trading there. Then they leave. The station charges a tax on everything bought or sold there. --- See a similar answer to the question: [Why would space traders pick up and offload their goods from an orbiting platform rather than direct to the planet?](https://worldbuilding.stackexchange.com/q/233576/14322) There are different types of spaceships, the same way there are different types of transport in the real world. You can walk, cycle, drive, get a train or bus, or go to the airport. There is no vehicle that picks you up from your front door, then flies through the air to another country, and drops you off outside your holiday villa. Such a thing is possible in principle. If you were super wealthy you could build a landing strip at both of your properties. But even this is a hassle since you have to listen to planes landing when you are trying to entertain guests. For the rest of us, it is rare to get an airplane to the shops or to work. The few people who do commute by plane still use other transportation to get from the airport to their workplace. The plane won't drop them off at the door. Likewise, there are different types of spaceships for different jobs. The spaceships that move from one orbital habitat to another cannot take off or land from the surface. The kind that go from the surface to orbit cannot move long distances between planets. We could in principle build a ship that does both. But it would be a waste to lug all that surface-to-orbit gear around between planets. Plus that gear was expensive, and it being idle when the ship is in space is lost opportunity cost. That's like having an airplane full of bicycles. They are not doing anything when the plane is in the air. [Answer] It would provide the same benefit as a ship's port. It allows you to switch vehicles and provide repairs. The type of ship needed to take off and re-enter a world's gravity well and atmosphere will likely have different design criteria than one made for sailing the black. Lifters need to trade efficiency for thrust. It doesn't matter how efficient your thrust is if you can't overcome the planet's gravity. Also, lifters need to be more streamlined and robust to handle reentry. Long haulers (whether they have FTL or not) need efficiency. They also have equipment that is just extra weight when trying to land and lift off a planet. You need crew quarters, robust life support, entertainment, food store/prep, etc. It also doesn't need to waste mass being strong enough to enter an atmosphere. This gets even more pronounced if the long haulers use FTL drives that aren't used when landing or taking off. I'm not saying that you can't have a long hauler that can land on a planet (military, new colony worlds, etc.) but it is more efficient to make a long hauler that only long hauls. Any shipping company tries to be as efficient as possible to make as much profit as possible. All of the stuff that L.Dutch mentioned will happen just because that stuff happens whenever you have people gathered. It's better to make it legal and above board because it will happen either way. [Answer] Logistics Hubs and Ports: The Space Station might be set up in a system with no other habitable world and serves as a logistics hub. Essentially, it's not closer to one major trade power or another, but it's closer to every trade power compare than every other trade power. In this situation, ships will stop to off load cargo to be picked up by other ships, while keeping cargo it already has and taking on cargo bound for it's final destination. The airline industry already works like this with a Hub and Spoke model, where most flights will fly from outlying airports to a regional hub where passengers will make connecting flights to their final destination. It's here not because anything valuable exists here, but rather everything of value will pass here. Hyperspace Convergence - If Hyperspace in your system works like in Star Wars, than there are specific routes that one has to take in an interconnected network. The space station can be set up in the vicinity of intersections of major hyperspace lanes... allowing for something similar to your Logistics Hub. Lots of ships are passing this point for another location, so infrastructure develops to support the needs of the traffic. Resource extraction - The system has no habitable worlds, but that doesn't mean it isn't valuable. The space station is set up to provide working quarters plus processing centers and ports for the purpose of shipping a valuable good to other systems (Hell, this could solve your fuel question... the space station is in a system rich with the raw fuel and the station is important because you need infrastructure to work these things. It might make the system a boom town or a company town as well, but everyone is here because "DRILL BABY DRILL". Strategic Mountain Pass. Opposite of the intersection, here, for some reason, all traffic bound for certain systems must pass through here. Maybe there's only one hyperplane connection between your side and the exciting other side. Maybe it's more of a wormhole that acts as a bypass of millions of lightyears. If two separate governments control either end of this pass, then it could be that both have a continued military and law enforcement presence to keep tabs on the movement in and out of their territory. Deep Space Nine used this reason. After all, what does everyone go to see a space opera for? If you said, "complicated politics that lead to trade blockades" than this is the solution for you! Diplomatic Neutrality - The space station was set up here to serve as an a body for interstellar diplomacy and negotiation. It was picked not because of it's importance, but rather of it's non-importance. Nobody made a claim to this territory because there was nothing here worth claiming (Babylon V) or alternatively, it's at a logistic hub central location or a hyperspace intersection that means most powers party to the political assembly can reach here... not only does this also add lots of traffic, but now you have political intrigue as diplomacy is all about cloak and dagger. In real life, many nations capitols were located in where they were because the spot wasn't important to anyone, so no one who should be equals is given importance by claiming territorial power. Remember when people said "You can't make new land?" In effect, real estate is expensive because there's only a finite amount of it on planet Earth. If you could make more real-estate, you can sell it to people who want a place to call their own for pennies on the dollar. Essentially, you are acting as a suburb for people who have that all American dream of two shuttle pods in every space port and a Zendakian Slime Slug in every pot on Sunday! Works well for people who telecommute, or can commute to the place of work on the planet you orbit. Why settle for the mansion on the hill, when you can have living quarters in the stars. [Answer] Look at what many places do to get an income: * touristic spot * hosting gambling and other borderline activities for which it can act as an offshore paradise * renting spaces for activities which can be better done in microgravity * produce something which can be advertised as "made in space", for those which might see in it an added value [Answer] Duty free shop / no gravity well <https://en.wikipedia.org/wiki/Duty-free_shop> > > A duty-free shop (or store) is a retail outlet whose goods are exempt > from the payment of certain local or national taxes and duties, on the > requirement that the goods sold will be sold to travelers who will > take them out of the country, who will then pay duties and taxes in > their destination country (depending on its personal exemption limits > and tariff regime). Which products can be sold duty-free vary by > jurisdiction, as well as how they can be sold, and the process of > calculating the duty or refunding the duty component. > > > Those boneheads planetside are always taxing, taxing, taxing. And you never know when there is going to be some new law and you wont be able to get your smokes, or slaves, or fancy cheese! None of that BS on the station. If it is for sale it is for sale there, and cheaper than down in any taxman infested polity. --- Taxes aside doing business on the station makes good sense for bulk commodity export products. Why bring ten thousand metric tons of metal down into some gravity well only to have your buyer have to schlep it back up again to take it home? Bulk commodities storage and transactions occupies a lot of space on the station and accounts for a lot of day to day employment by station residents. [Answer] Advertising. An object about [112m in diameter](https://en.wikipedia.org/wiki/Artificial_structures_visible_from_space) is visible as a disk from space. Or in space in low Earth orbit, visible from the surface. So a 1 km diameter bill-board could display such things as a logo. Imagine a car logo (as you often see on the back of cars) or a beer logo on a 1 km wide mylar sheet. The advertiser pays per week or month or whatever. The sheet gets spray painted with the logo, then it gets unfurled from the space station. Extra fees apply to provide artificial lighting to increase the visibility. [Answer] I'm not going to worry about fuel, hotels, conference services, customs, etc. They've already been addressed by you or others. Rent to the Military While it's believable that the military would want their own space, the reality is that national budgets are complicated! It's common today for militaries to rent space from countries. If your world has multiple nations, that means you can rent to multiple militaries! (Watch how you word the contracts...). Neutral Embassy Space You never know what a nation needs! But I can't imagine a better location for neutral ~~spy~~ embassy space! The ability to ~~conduct espionage~~ conduct delicate negotiations without the burden of worrying if the location has a conflict of interest is of immeasurable value. Communications Hub A station that big must certainly have the ability to be the clearing house for all transmissions in the hemisphere over which it orbits! Even folks with their own satellites would use you as a convenient data transhipment area, which means you can also be a... Data Warehouse An off-planet data warehouse for secure storage and backup storage. The ultimate solution in case of fire, earthquake, or flood taking out your on-planet workstations! High Security Vault And while we're talking about storing valuable things, there is no vault on the planet that's as secure as your vault in space! When people want to store ~~the crown jewels they just stole from England~~ their family heirlooms, they come to you! For a modest fee you'll store their ~~crap~~ valuable goods for generations with an absolute guarantee that they're secure! Duty-Free Shopping! My apologizes to @willk, who already had this answer. When you get rolling it's easy to forget what everyone else wrote. I upvoted his answer. You should to. Everybody likes Duty-Free. Your station was built by a private company? GREAT! Assuming the laws of your world allow this, your station has no national affiliation! Woo-hoo! Duty free alcohol! it's like shopping the Dark Web without having to worry about faceless anonymity or whether or not your credit card is about to be shared with a Nigerian Prince. Never underestimate the willingness of people to buy products tax/tariff/VAT free. Rent to every college and university with two pennies to rub together on the planet I can easily imagine institutes of higher learning wanting to teach classes and conduct research in a weightless environment. Or an environment above the Van Allen radiation belts (if you are...). Or simply outside the atmosphere in the vacuum of space! it's a LOT cheaper to rent from you than to buy your own station! Ore Processing Who wants the cost of sending ore to the planet? All you really want is the refined material, anyway! Besides, the perpetual meteor shower created by dumping the slag into the atmosphere is really pretty! Firework Shows Your sales team really came up with a doozy! They've discovered that there are towns and nations large and small perfectly willing to buy into a fireworks package celebrating all kinds of things! It's safer than launching from the planet surface because you can detonate the fireworks higher in the air... and because you can do that, you can create spectacular shows! Rent to the Planetary Police Force Your nations have created an international organization to support policing of the ever increasing interplanetary trade. Pirates are a growing problem and they need to have local resources to stop it! And a few square feet of your station is a LOT cheaper than buying one of their own. *Legal Services for the Discerning* Client** You know what else is amazing about having no national allegiance, you are a nation! Even if you're skirting rules because the nations of your world simply have to have your other services, that puts you in a GREAT position to provide legal services with no national attachments. ~~Criminal~~ Sophisticated companies incorporate through you because you have absolutely the best corporate tax rates anywhere and most countries haven't yet realized ~~they need extradition treaties~~ the benefits of working with someone completely neutral. Base Jumping Need I say more?! Just sign our liability waiver here, here and here. [Answer] Part One: Space Manufacturing. Manufactering vacuum tubes? Pumping air out to make a vacuum for vacuum tubes uses energy and costs money. Outer space provides a infinite amount of much thinner vacumn than can be produced on Earth. If vacuum tubes are sturdy enough to survive passage down to a planetary surface, and other factors are favorable, manufactoring them on a space station could be profitable. Outer space is a good place for manufacturing anything which requires a vacuum and/or microgravity and maybe also the ability to change the level of gravity during manufacture by rising or lowering the machinery toward or away fromt the center of the rotating space habitat. Maybe airtight gas bags (or vacuum bags) of airships could be made in outer space. They could have electomagnets in the fabic. They can be exposed to vacuum and lose all their air, and them be folded up and shipped to a planet with an atmopshere. There they can be installed inside airships with atomic power supply. When the power supply is hooked up to the gas bags it powers the electomagnets in the gas bags which al lhave the same charge and so repell each other. Thus the gas bags expand to fill the ineterior and slowly push out all the air from inside the airship. When the interior is completely filled with vacuum filled bags the air vents can be closed. The step of making the bags in outer space would ensre that there would as hard a vacuum as possible insdide them. And vacuum is even lighter than hydrogen gas and so has more lifting power. Possibly giant vacuum bags could be used to support colonies floating in the atmospheres of gas giant planets. And I suppsoe there are lot of other things which people can imagine might be manufactured only in space, or better in space. Part Two. Space Tourism. Space tourism is a industry which is just sort of taking off on (from) Earth. People usually imagine space habitats as giant hollow spinning cylinders filled with air and with about one Earth gravity (1 g) on the inside of the outer cylinder walls. And they imagine that the inside will be one giant void filled with air. And that seems like a great waste of space and air to me. I imagine that a real space habitat should have several inhabited levels one above the other, like an underground city with several levels, at about the distance necessary for 1 g. And above those several underground levels there can be an open space like is usually pictured. But not wastefully filling the whole interior above. Instead there will be a roof over that air filled "exterior" space, probablly just a few whundred feet above the "ground" level, a cylinder running all the way around the habitat and supported by columns from below and/or suspended by wires from the center of the cylinder. And there would be a vacuum above the roof of that open air section. And somewhere above that roof there would another pair of concentric air tight cylnders with breathable atmosphere. The gravity level on the bottom cylinder in that pair should be about 1.352 meters per second per second or 0.138 g, the surface gravity of Titan. It is claimed that people would be able to strap artifical wings on their arms and fly in the low surface gravity and dense atmosphere of Titan. So people should be able to take off from the surface and fly higher in regions of even lower gravity in the air filled space between the two cylinders. Writers have imagned people flying with wings strapped to their arms in the vast interior space of O'Neil cylinders. And of course if such flyers get too low and too close to the 1 g level. the gravity will be two strong for them to fly back up and they plummet to their deaths. So with my design the natives can tell the tourists that they thought of everything and the flying area has been designed to avoid that danger and be perfectly safe. And then a clever enough writer should be able to imagine a way for a dumb enough tourist or a lazy designer of the habitat to find or make a falling danger, and also think of a way to save the endangered person. And no doubt there are other space tourism features which could be imagined. I note that a section of the habitat projecting out and down from the 1 g level might be visited by tourists to experience higher gavity. It is quite possible that spending specific periods of time at specific levels of gravity slightly higher than 1 g might be discovered to beneficial for one's health. Part Three: A Space Graveyard. Possibly one industry in the space habitat would be storing "corpsicles", dead people frozen in the hope of being brought back to life by the advanced science of future centuries. In popular culture the forzen dead are depicted as stored in mechanical refrigerator units, but vats of liquid nitrogen are actually used on Earth. In outer space a volume of vacuum completely enclosed and thus shaded from sunlight should have a very temperature, and so "corpsicles" within it should maintain a steady low temperature. And cleaver designs to make certain the volume within stays within the correct temperatue range through absolutely passive means no matter what happens might be imagined. Part Four: Port Facilities. Supplies coming from outer space or from a planetary surface to the space station or habitat to be used there will have to be unloaded in some sort of port facilities. People coming and going will have to use some sort of port facilities. Thus your space station or space habitat will have some sort of docking or port facilities for its own use. And it may have larger port facilities for commercial use. And as others have pointed, surface to orbit space ships, interplanetary cargo ships and passenger liners, and interstellar cargo and passenger ships might have very different structural requirements and different types of ships might be needed for thoe different purposes. Thus some sort of port facilities in orbit around planets or floating in interplanetary or interstellar space may be needed in the space travel system of a story. So science fiction writers have been imagining the use of space stations and space habitats as busy space ports for many decades before Babylon 5 (1993-1998) or Star Trek: Deep Space Nine (1993-1999). Thus making a fictional Ctesiphon Seven or Back Space Ten a space port is very logical. [Answer] ## It's a distribution center Very few things are worth producing in space. Mining, refining, manufacturing, farming, packaging, etc. are all things that are cheaper and safer to do on land than in space; so, you need to focus on what you can only do optimally in space. Imagine you have an Empire of 1000 worlds and only one of those worlds produces a certain thing. All 1000 worlds want at least some of this thing, but sending ships to all 1000 worlds is not economical. Some worlds are just too small to justify direct shipping, and some don't actually produce anything the this colony needs to buy from them. This is where distribution centers come in. Instead of sending out many smaller ships to specific trade partners, they can send a single super freighter to the distribution center to offload your whole interplanetary inventory, and while they are there they can fill thier cargo hold up with all the big and little orders of stuff they need from the other 1000 worlds, and return home. This means, shorter, simpler, cheaper shipping lanes and more availability of consumer goods for everyone. The reason it has a population of 6-9,000 people is because they have to handle a LOT of cargo. Amazon employs 100s of thousands of people just to cover the distribution center needs of our 1 little world. So, while you might think 9000, is a lot, it's actually a skeleton crew for the job you're getting done here. The vast majority of work is done by robotic automation with humans just being around to keep things in working order. Even will millions or robotic drones doing the real work, it could still take thousands of Technicians, Engineers, Mechanics, Accountants, Security Personnel, Flight controllers, Tugboat Captains, etc. to keep all of those countless automated systems flowing. A distribution center on this scale could be handling billions of dollars of cargo a day; so, it would only take a very modest shipping and handling fee for these space colonist to make money hand over fist as the interplanetary middlemen of shipping. [Answer] Ore Extraction If your station is parked by an asteroid field, then it would be a great place to assist in mining operations, whether that being habitation for miners, equipment sales, or refining ore brought in. Being a Wet dock This station, like Tycho station in the novel series the Expanse, could be a very great dock for in-space construction and ship repairs. [Answer] Its a Port It's a port. Conceptually, no different to those on Earth. It may enjoy duty-free privileges. Things can be imported, stored there, re-exported, without paying full import duties to the government of the planet below. Value may be added by assembling imports from various places and re-exporting. Maybe cheap labour can also be imported and exploited outside the laws of the planet below. It may be a necessary quarantine facility. If some new plague arrives from out-of-system, there is a chance of confining it in the station before it is brought down to the planet. It may also exist to keep hyperspace engines at a safe distance, if the technology is such than a catastrophic explosion is possible. It is likely to be a customs post. People and goods don't get to be transported down to the planet before their documents have been inspected and approved, and taxes assessed and paid. Organised crime will have its own uses for the station. (I don't believe there is any port on planet Earth which does not boast a statistical over-representation of criminal elements). Conversely(?) it may develop into a centre of banking and law and arbitration, if it gains a reputation for fair-handed dealing with all parties and incorruptibility. (On Earth, many contracts are drawn up under English, Swiss or US law, even if neither party to the contract is incorporated or operating in those countries). [Answer] ## Lawless Territory The station is in open space, which means that there is no government which imposes their laws on the station. This allows the people living and working on the station a lot of freedoms, like for example: * Ignore intellectual property rights * Be unencumbered by censorship or moral laws * Enjoy political or religious freedoms * Provide and consume goods and services which are considered illegal elsewhere * Avoid government bureaucracy. Either out of convenience or because one has something to hide. * Not pay taxes In order to establish a peaceful environment, the station itself will probably want to regulate some of the points above and might also raise taxes of their own to finance the operation of the station. But having the freedom to enact any laws and policies as they fit the station without considerations for higher governments allows them far more flexibility. Most of that independence would probably be even easier to acquire on a station that is not near a major travel route. But being in a well-traveled area makes logistics a lot easier. Getting someone to deliver a package to a station on a trade route would be a lot easier and cheaper than to get the same package delivered to some backwater system that's hundreds of parsecs away from the next inhabited world. So the combination of lax laws and central location makes the station a very attractive place to live and work. [Answer] Your station provides what its visitors want and nothing more (because why the waste?). What visitors want is up to you, but it is typically the services that you mention: alcohol, food, and sundries. A high-traffic station makes for great mercantile opportunities. Some of your income may come from renters who sell goods/services of their own. Body shops for overhauling private spacecraft, perhaps. Take a look at your average city in the West. Every business exists for a market, and many of our major markets will undoubtedly follow us off Earth and into space. [Answer] Look at Singapore. No natural resources to speak of, no massive industrial or technological base, yet one of the wealthiest nations in that part of the world, because it controls the major shipping lane between the Pacific and Indian Oceans. Depending on location, the refueling/resupplying might be enough to make the station economically viable. Or consider Athens--started out as a resupply port, then expanded their industrial base to become a major industrial/commercial and trading hub, something Singapore has also done with some success. You get raw materials in, you get finished goods out, all without having the added costs of a gravity well. Add in something for the crews to do on shore leave, and ships would love to come to your station--a full load both ways, and entertainment while the unloading/loading is done. As regards fuel,you can either import from other locations and sell at a premium (seriously, any customers are captive--where else are they going to refuel), or base your station near a suitable fuel source--a star, a nebula, or a gas giant, depending on the fuel you use. [Answer] Solar Power. Power could then be beamed back to earth as microwaves etc. I think it's pretty self explanatory, but the station would provide jobs in maintenance and probably some fabrication. Cheers [Answer] Illicit Activities Space law is still in the early stages. Space is not the domain of any existing country. It is hard to agree who can settle a dispute or punish criminals. That means anyone with enough money to build a space station is king of their own island. > > This particular station is supposed to be technologically ahead of its rivals, so I'm trying to think of unique/innovative things it might be doing to make it a valuable destination. > > > Tartarus Station is the final stronghold of freedom in the midst of a galaxy slowly asphyxiating under the fascist paw. Everything is for sale. Everyone is for sale. Just name your price! We have all manner of technologically advanced but morally dubious (and certainly illegal) services. Recreational drugs. Un-recreational poisons. The Orgasmotron Mk. II. Chemical and biological weapons. Dangerous and experimental body edits. Putting your brain in a robot body. Genetically modifying your children. Obtaining genetic material of celebrities. Bootleg Michael Jackson Albums. "Grey goo" style nanobots. Off-brand Geena Davis clones. Putting your brain in your childrens' bodies. Ordinary nanobots. Caches of private data hacked from governments and corporate servers. Buying spare organs. Loan sharks. Regular sharks (the endangered kind). Selling your organs to pay back the loan shark. Putting your brain in a robo-shark body. [Answer] Surgery/implants/augmentations, aka advanced medicine You say your space station is ahead of its neighbors, so it should have some high-tech stuff on board, with people who can operate and fix that high-tech stuff. One thing that might be needed for people who come there is getting themselves fixed in a manner that onboard medical personnel and devices cannot reliably provide. Say, devise and create an implant for say ultravision/infravision, or physical augmentation of some kind, an artificial arm instead of one lost in SPAAACE somewhere, etc. Same for drugs in broad sense, microgravity could help in synthesizing complicated molecules usable for both healing and pleasure. Docks/drydocks Space ships need repairs, some repairs are not able to be performed on their own. So, have a drydock (with atmosphere if needed) on your station, and repair/replace/upgrade modules at a price, such price could be large enough to sustain the station economy alone, since the demand is about constant, every ship at least needs some diagnostics before allowing it to refuel anyway. What if it'll blow up at a refuel terminal? Recruitment center Stations in space are more like island ports in an ocean world, people of all sorts can be found there. You want a new space cadet with some technical background? Why don't you hire that kid with ten years of space travel behind, who just failed to negotiate his salary with his former captain? Or you want some security crew because pirates, well here are some mercenaries that are running dry on cash and would be happy to join you for food and a little extra. Hypernet hub/endpoint/retranslator You have a hyperspace travel in your universe, have also a hypernet with station-mounted transceivers for hyperconnectivity, so your station can also be a news provider for those who don't have an energy budget to run their own hypernet access point. For a price of course, yet some info could be available for free, you decide. Protection from pirates/enemies Space stations usually have a big (bigger) reactor onboard to sustain life and facilities for larger amount of people, so let's add some weaponry and shielding to protect those civilians (or not-so-civilians) seeking shelter. Weapons of some kind are anyway needed for a space station, as it can't escape if someone would desire its contents, so the offenders should prepare to pay dearly for the attempt. Where to get fuel - that depends largely on your imagination as an author. For example, some fuel could be mined from solar winds, some from asteroid fields (so mining facilities could be present at or near the station), some from whatever extra dimensions you have there, some are plain converted from incoming energy (mind you do NOT use the station's reactor to generate fuel, unless it's based on some exotic stuff that produces way too much energy to utilize), maybe there are more sources of fuel out there I can't yet recall being named somewhere. [Answer] Pick any small town in the world, and you'll have a model of what a space station needs to be and do. Towns grow up around one of four things: 1. Transportation and communications hub 2. Natural resources 3. Natural beauty 4. Large target population The transportation bit can be broken down into a few categories. * A. Onloading near natural resources * B. Merging of multiple other transport paths * C. Reprocessing stations * D. Consumer access Communications hubs naturally follow the paths of transportation hubs. Take, for instance, Kansas City. That's the point where all of the ranchers drove their cattle to be slaughtered and shipped off. It's a reprocessing point and onloading depot. Denver is a huge mining town. You'll get one of these just outside of any mining space, like Mercury or the asteroid belt. St. Louis is a communications and transport hub, where things are stored, repackaged, and change transport modes. Chances are, any space station near a mining resource will attract processing facilities. Raw materials will be refined on the ground, outside the mine. Once the non-useful parts are extracted, the purified materials will be shipped off-planet to a station where they'll get melded into alloys, pressed into sheets, billets, rods, etc., and then those materials will be shipped to a manufacturing plant where they'll get turned into actual parts, then the parts will be shipped to an assembly plant for things like robots and spaceships. Each step will be incrementally closer to the target customers. Manufacturing plants need employees, and employees need supermarkets and clothing and a thousand other things. Industrial facilities will accumulate around a shared service infrastructure, allowing for more efficient people management. And then you have a city in space. Addendum: Some friends have pointed out places like Las Vegas that focus on giving people somewhere to get away from their normal lives. Las Vegas actually takes advantage of an artificial scarcity of something that you don't normally consider a natural resource: Freedom. People go there for vice-seeking opportunities that are harder to access in the surrounding areas. [Answer] # Gas giant hunting The spaceship is orbiting a gas giant which it scoups fuel from, a mix of radioactive isotopes and hydrogen and helium for fuel. It is uniquely advanced in its ability to go down to the surface to collect huge amounts of fuel, and also there's a native lifeform on the surface. You can go on hunting or nature tours there, so there's a large industry to support that. Their technologically inferior rivals normally need to rely on asteroid mining and such for fuel gathering, which is much slower and less efficient, and lack the ability to reliably dip into gas giants. [Answer] If we are talking about a completely independent station and not a part of a larger organization, and one that has 6,000-9,000 people (which is a significantly larger population than the town I live in, by the way), then this isn't just a few tourist shops and in interstellar gas station. This is going to be an entire ecosystem. Assuming the employees aren't commuting to and from work at the beginning and end of a shift, a lot of your station is going to be infrastructure for the staff. Think of how a cruise ship works... the guests are there paying exorbitant amounts of money (both built into the cost of the ticket and added on later) for services, entertainment, shopping, drinks, excursions, and so-on. But to provide all of that, the ship has a whole community below-decks not only of people you see, but stores, services, kitchens, shops, and other facilities just for the staff. Your station offers a convenient stopping-off point for... * Refuel/resupply * Intermodal freight transfer * Customs * Communications * Medical treatment * Mechanical/engineering services * Temporary lodging and meals while the aforementioned services are performed * Entertainment Additionally, you have a large staff of customer-facing employees that all have their own needs, too... You are going to need a place to buy groceries, clothing and uniforms, barber shops, schools and teachers for children that end up on the station, janitors, recreational facilities, basic supplies, electronics and appliances, and anything else your average person might need to be reasonably happy and productive while going about their life. Depending on the standard of living in your universe, it might even be completely feasible to charge back all (or even more than) the station pays in wages in the form of food, rent, and services provided to employees of the station. This is what the mines in Appalachia used to do. The employee makes 1000 credits per week, but before they get their "check" the station deducts 500 for rent, 300 for food, 100 for medical treatments which are mostly necessary because of the reduced gravity in crew living quarters, 120 at the bar, and 87.50 for some cleaning supplies and a bottle of Tylenol you got from the supply closet. You end up with -107.50 credits at the end of the week, but the station is happy to offer its employee's low interest rates on borrowed sums, and they only ever have to be paid back when you leave the station. Remember too that cost is relative. Unless the laws of physics have been bent in your universe, operating inside a gravity well is going to be really expensive from a fuel standpoint. It is probably still cheaper to pay whatever high prices are commanded at the station than to fly your ship to a planetary body and then have to claw your way back out in order to activate some kind of FTL. It would be safer too, not only for the crews, but definitely for the planetary inhabitants. A large object from space colliding with our planet at high speed is why dinosaurs aren't having this conversation right now instead of us. Let's learn from their misfortune and keep the massive space-freighters far away from situations where a an itty-bitty drive malfunction would be an extinction-level catastrophe. [Answer] # Science A space station parsecs away from inhabitable planets is THE place to experiment with stellar system wrecking things such as strangelets. Same reason why nukes used to be tested on deserts rather than on forrests. You madden and endanger less people this way. People coming in and out are mostly scientists and engineers. Due to its location the station also serves as a port, but that's a side activity. # Territorial claim In order to claim a territory you have to occupy it. The station is not in much use now, but might be important someday (im case of war or ogher developments), or might have religious significance to some people. They'll keep it staffed to prevent others from claiming that region of space. Again, it will serve as a port on the side. [Answer] ## Ghetto There's no revenue stream so reliable as welfare. You can make money off the homeless. Money off drug addicts. Etc,etc. Long ago, politicians realised that people will feel virtuous and compassionate purely because they vote for the pro welfare party. Unlike on earth, the local crime, homelessness, and squalor remains totally invisible and deniable. NGO staff do highly compensated flights in and out with little effect other than to get funding for their employers just like they do today in the developing world. Fuel is subsidised and the few areas where the ever-so-virtuous NGOs and administrative staff / bureaucrats live remain secure and comfortable. Like the trendy parts of New York, California, Latin America, Paris, etc, visitors still come. [Answer] Garbage Truck Orbital debris is already a problem, and no one wants to wake up to Kessler Syndrome. People will pay for someone to clean up. ]
[Question] [ I've got a post-climate change world where summer temperatures make most of the planet uninhabitable, and the vast majority of the population lives in tightly-packed apartments either in buildings or underground, without direct access to the outside world to dump heat. The rich have large estates in isolated parts of the world that are still inhabitable, while the poor majority can't afford to move, and are stuck trying to make do. On the bright side, they've got a few decades of technological development into tech needed to survive the new world. How do you cool an apartment without a window to dump the heat? I've considered finding other places to dump the heat, like into the earth for underground dwellings, but insulation isn't quite good enough to make that process efficient. A more interesting option is chemical methods of cooling, or methods that do something with ambient heat beyond pumping it somewhere. Is there a good solution for this? [Answer] > > On the bright side, they've got a few decades of technological development into tech needed to survive the new world > > > Thermodynamics is a harsh mistress and doesn't care about your technological development. If you want to dump heat, you need a place at lower temperature where you can dump the heat, because thermodynamic laws state that heat flows naturally from higher temperature to lower temperature. That said, windows are a really poor way to dump heat in hot places, because they actually are the places where the heat leaks into the place. If you live in a hot place you keep your windows closed during the day to lessen the amount of sunlight and energy that enters the place. If the outside is hot, your only choices are insulation to lessen the energy flow in the place and heat pumping to get rid of the excess energy which reached it: * build underground * pump the heat away, underground will be surely cooler than the surface, unless you are living on a lava pool, in which cases you have other worries than keeping your room cool. [Answer] ### compressors You can always dump heat. With a compressor, you can transport the heat from a cool to a hot environment in oder to keep the cool environment cool. But the cost is high. Living underground lessens the cost, good insulation, too. ### heat dumps You can also dump your heat underground just by boring a deep hole for your compressor's pipes. It's done today and is actually considered a environmentally friendly way of heating or cooling your house, if combined with good insulation. ### radiate it Within sci-fi maybe you can find a way to radiate the heat away from earth, too. There are some metals which, when heated, light up in certain frequencies where our atmosphere is as transparent as for yellow light, but outside the visual spectrum deep inside the IR. This is a supreme way to just dump the excess heat into space: let your compressor move the heat into those radiators on the roof. A downside may be that you need this space for your solar cells, or more generally speaking, surface space is a premium on earth. ### long term solution Better, build lots of superstructures from materials which are designed with this radiation behaviour in mind. You can artificially design colours to radiate exactly where you want them to radiate. What if the road network starts to cool down the planet instead of heating it? But ok that would go against the will of your rich people I guess. I mean. It costs money and it helps the poor. :-) [Answer] # All cooling involves dumping energy somewhere The laws of thermodynamics essentially mandate this. [There ain't no such thing as a free lunch.](https://en.wikipedia.org/wiki/Second_law_of_thermodynamics) As such, you can shift the thermal energy around but you can't just make it go away. Air conditioners blow hot air out one end and cold air out the other. The basic principle is [adiabatic expansion](https://en.wikipedia.org/wiki/Adiabatic_process#Adiabatic_heating_and_cooling) and this is why an air conditioner is called a compressor. You compress air, it heats up. That hot air then naturally cools down to room temperature. (This is the part that blows hot air.) Then, when you decompress the air, it cools down again and voila, cold air. You don't want to use this for whatever reason. There are two other techniques that I know of: # [Radiative Cooling](https://en.wikipedia.org/wiki/Radiative_cooling) Here, you cool an object down by literally radiating the heat away from it, in the form of actual radiation. Specifically, infrared radiation, which any hot object radiates and this is what heat sensing cameras use to see. It would in theory be possible to create an infrared emitter ("heat laser") that would have a net negative effect on the surrounding temperature. Shoot the beam into space. How, exactly, to build one of these so the net effect is cooling? I have no idea. # [Endothermic Cooling](https://letstalkscience.ca/educational-resources/stem-in-context/cold-pack-a-chilly-example-endothermic-reaction) Fire is an example of an exothermic chemical reaction: as things burn, heat is generated. The reverse also exists; there are chemical reactions that absorb heat from the surroundings as they proceed. This is how those single-use chill packs work. Entropy still wins, though. Entropy always wins. If A -> B is endothermic, B -> A is exothermic. You will also never find a chain of reactions, A -> B -> C -> A, where every step is endothermic. Likewise, the total energy involved in running chemical plants to manufacture the reactants will always wind up working out such that the net heat released is positive. But you can manufacture the ingredients somewhere else, then transport them to where you need them. [Answer] As long as just your summer temperatures are that high, building mostly underground is the best solution for your problem. > > At a small depth (from 12 to 40 feet) below the surface of the earth the temperature is constant throughout the year, and this constant temperature of the soil differs little from the mean annual temperature of the air. (Johann Koenigsberger - 'the temperature of Earth's interior') > > > This constant temperatures were the reason, caves were the first habitations for early men and we use cellars nowadays still to keep food and other stuff save from temperature changes. So by building your homes completly undergrund with a layer of earth over the tops (do not cover the entrances of course ^^) would give you temperated shelters for the poor. Air conditioners pumping air trough pipes in the earth outside the shelters could help for cooling down, if it gets to cold just pump hot air from above the surface down. Another problem could be feeding those people, but that was not part of the question (and as they are more developed then we are could be solved by bioengineered plants growing in intense heat). [Answer] Evaporative Cooling Evaporative cooling is used to lower the temperature and increase the humidity of air by using latent heat of evaporation, changing liquid water to water vapor. In this process, the energy in the air does not change. Warm dry air is changed to cool moist air. Use evaporative cooling during the day. Refresh the moist air with dry air during the night, where the temperature outside would be lower. [Wiki](https://en.wikipedia.org/wiki/Evaporative_cooler#:~:text=Direct%20evaporative%20cooling%20(open%20circuit,changed%20to%20cool%20moist%20air.) [Answer] ## Same problem as power plants (including nuclear and focused-beam solar). They need an ultimate heat sink as cool as possible, to get the most out of their thermal cycle. Now, their ultimate heat sink is a continuous source of cool water - water is wonderful because it's a) plentiful and b) the densest carrier of heat available. They want it as cool as possible. However often they are forbidden to suck up cool river water and dump that water back in piping hot. ## Use cooling towers, just like they do. So in that case they use spargers (think: sprinkler heads), and if necessary, cooling towers. The spargers spray the water into the air in a fine mist. This heats the air and some of the water vaporizes; most of the rest falls down into the cooling pond below the spargers. If needed, they put a cooling tower on top of the spargers to force air through them. The iconic curved tower you associate with nuclear plants, works by convection (there are air inlets at the bottom of the tower). They also make much more ordinary-looking ones that use powered fans/blowers. Instead of spargers, they may use a "wet filter material", but it's the same concept - force water to evaporate to cool it. Even if the relative humidity of the air is already 100%, cooling the hot water has the side-effect of warming the air. Warmer air can hold more water, so warming air reduces its relative humidity and makes room for more water. Of course as soon as the air cools off, its relative humidity exceeds 100% and the water condenses. And that's why power plant towers make white billowy smoke on humid days! That's not exhaust. In our case, we are trying to dump heat from an air conditioner, so we place the air conditioner's condenser (the hot thing) in the stream of cooling water. This is nothing new; boats do this. \\ ## Or just boil the water Your last resort is to add a second "stage" of air conditioning whose job is to raise the refrigerant temperature to well over 100C.\* You then place its refrigerant condenser in the bottom of a tank of water. This forces the water in the tank to boil, and the tank vents steam. ## Our friend, latent heat of vaporization This works so well because of a concept called the "Latent heat of vaporization". Say you put a pot of 62F (17C) water to boil. In 150 seconds, it reaches 212F (100C) starts to boil. But after it boils, it stays at 212F/100C. Yet it takes over 1000 more seconds for the water to boil away. The water remains at 212F/100C. This is a lot of energy; where is it going? It's going into the latent heat of vaporization - the real energy required to convert water from a liquid to a gas. Water has a rather large latent heat of vaporization, so it works really well for this if the machine is never subject to freezing conditions. So by boiling - or simply by evaporating water - we are exploiting the latent heat of vaporization to get rid of heat. --- --- \* This could be two different types of refrigerant with a freon-freon heat exchanger between them. \\ We just saw a question from a student who hacked a fridge and put the outside coil in a pan of water. The student couldn't understand why the pan of water wasn't turning to ice. Not a thermodynamics student, clearly. [Answer] Use air conditioners. Just like today. All you need is a condenser that's not inside the flat you're trying to cool, and piping that connects a unit in the flat with the condenser. No magic needed, although of course ACs get less efficient the hotter or more moist that the outside air is. <https://en.wikipedia.org/wiki/Air_conditioning#Installation_types> [Answer] I like the idea of using existing waste streams to transfer waste heat. I.e. graywater and blackwater could serve as the heat sink for waste heat as these wastes are already being removed from area. As an added bonus, the heat may assist in the treatment and decomposition of these wastes. [Answer] 'Heat' is such an over-rated but poorly understood concept. In the final analysis, there is no such thing as 'heat' and 'temperature'. Look up the definitions, and they form a tautology - 'heat' is what is measured by 'temperature', and 'temperature' is a measure of 'heat'. If you remove 'heat', you lower the 'temperature'. But to remove 'heat', you do so by lowering the 'temperature'. Really, there is no such thing as 'heat' and 'temperature' outside of the human experience. Humans THINK there is such a concept, only because we are warm-blooded, and we have evolved particular biological sensors that send signals to the brain which are interpreted as 'hot' and 'cold'. These in turn have lead us to believe there really is such a thing as 'temperature', that can 'measure' this thing called 'heat', into degrees of 'hotness' or 'coldness'. In truth, what 'temperature sensors' are detecting is 'high energy, high vibration, high expansion, high radiation' as 'hot' and 'low energy, low vibration, low expansion, low radiation' as 'cold'. When we measure 'temperature', we are actually measuring artifacts of the energy state - expansion, vibration leading to state change, emitted energy levels, and so forth. But 'hot' and 'cold' are purely constructs of our minds. So what you are after, is how to move energy from one place to another, or to convert energy from one form into another. The cause of 'global warming', once we strip it of the psychological concept 'temperature', is that the earth is retaining more solar energy than it is radiating back into space. It is the energy levels of earth that are going up, not this particular physiological artifact that we refer to as 'temperature', and it is this increasing energy levels and the physical changes resulting from high energy levels that is causing the problems, not that things are getting 'hotter'. So unless you have some mechanism of removing this excess energy from the earth, everything you do will amount to 'robbing Peter to pay Paul'. You might deplete the available energy in one place (lowering the vibrations, movement, radiated energy, and so forth), but only at the expense of building it up in another place. Eventually, that energy will flow back, equalizing the energy distribution. In fact, that is exactly what is happening today. The excess energy produced by the sun, and absorbed by the earth, has been stored over billions of years in what we are now using as sources of energy - fossil fuels. All of the energy in oil and gas originally came from the excess energy of the sun, was biologically chemically converted into long-chain carbon molecules by biological processes, and stored in the earth. We are now releasing that energy back into the earth's atmosphere, and that increased energy is being perceived by us as 'getting hotter'. No, it is not 'getting hotter', the air molecules are just vibrating more. Winds and storms have more energy. Electrons and electrical charge is building up in the atmosphere, and being released in lightning discharges. Rocks and such are radiating more of this energy through the EM spectrum. Water, rocks, and the earth's crust are expanding. So, your solution is to mimic biological evolution. Use huge masses of plants and biology to take all of this excess radiated EM energy and convert it to long-chain carbon-based molecules. Store it as oil. The humans must vacate the earth's surface completely. Live underground, that is a start. No roads, buildings, parking lots. Let vegetation, of any form, completely over-grow every bit of earth's surface, then continuously cut the vegetation down and store it in huge 'compost bins'. The only products and manufacturing processes we can use, are the ones directly related to plants, not resources from the earth that have to be processed through the expenditure of energy. Basically, everything must be made from wood, hemp, and plant fiber, not concrete, steel, and refined minerals. As the vegetation continues to regrow, it will continue to do what vegetation has always done on the earth - convert energy to long-chain carbon-based molecules, and store it. In this way, your underground apartments and living units will be 'cooled' (energy levels reduced) by the vegetation covering them, and you will let the plants do the manufacturing, not the materials fabrication industries. But minimal electronic communications. That requires processed copper, aluminum, or other such metals. Can plants manufacture fiber optic cables? Fun fact - the earth just may be the only place in the entire universe that has oil and gas, if in fact earth is the only place that has life. [Answer] ## Use A Heat Sink A heat sink is a large block of heavy internal material that has a lot of [thermal mass](https://en.wikipedia.org/wiki/Thermal_mass). It must be insulated from the outside air temperature. Most air temperatures throughout the world are hot during the day, but cooler at night. So the method is to dump heat during the day into your Heat Sink keeping the air of the room cool. Then, at nighttime, it radiates out this heat and cools itself down, but warms the air in the room. Essentially what you are doing is 'spreading' the heat of the day over that of the night, and the cool of the night into the heat of the day, resulting in a smooth comfortable temperature throughout both day and night. This technique is regularly used in Architectural design now to prevent the need for Air Conditioning, even in hot climates (works exceptionally well in deserts, where there is a large difference between daytime and nighttime temperatures). The heat sink could simply be: * Heavy masonry internal walls (liked rammed earth) that are insulated from the outside air temperature * A water tank that is internal, again insulated from outside * A thick concrete floor slab that is insulated from the outside air temperature In fact, you don't even need to pump heat in or out, it happens naturally by radiation and convection if the heat sinks are ideally placed. EDIT: I should add, that if a window is placed on the northern side of the Heat Sink (in Southern Hemisphere) or southern side (in Northern Hemisphere) the winter sun will enter the room and heat the Heat Sink. This is a passive heating device for winter, and works exceptionally well. [Answer] Assuming unlimited technological development, it's reasonable to suppose they've figured out how to pump water around to wherever it's needed. The ocean is an effectively unlimited supply of liquid water, and if it's that hot in summer we can assume there's plenty of solar power, one way or another. Then you can simply use a heat pump (similar to the one in your existing air conditioner and/or refrigerator) to move heat out of your living space, into a supply of water. Assuming arbitrarily good insulation of the living space from the outside world (easier if you build underground, but you can do this in apartment blocks too with good planning), you'll only need to deal with perhaps 100W per resident on average. Windows should be small, or absent entirely. Water is capable of absorbing a fantastic amount of heat. Assuming tropical ocean water starts at 25°C, it takes more than 300 MJ to heat one metric tonne to 100°C, and a further 2.25 MJ to convert that water at boiling point into steam at condensing point. At 100W power input, that would take 3 million seconds (more than a month) to achieve - and a metric tonne of water occupies only one cubic metre. I think you can pump a tonne of water per person per month out of the ocean without great difficulty; after all, people need water to drink too, and we can assume you've solved that problem. You could even simplify the problem by cooling the surface of the building by simply pumping a steady flow of water through it. This would greatly reduce the need for cooling individual living spaces. A closed coolant circuit dedicated to this purpose could have a heat pump moving surplus heat into a municipal coolant system. The latter could simply involve a steady flow of pumped ocean water. [Answer] Building underground using insulation would be the obvious initial choice, but this could be augmented by refrigeration. The higher the temperature the less efficient and more complex a refrigeration plant needs to be but it is certainly possible. It is possible to make cryogenic liquids in hot climates therefore it must be possible to cool an apartment building by refrigeration technology. Whether this can be achieved cheaply enough for your purposes is another matter but some form of refrigeration is certainly possible even if it uses a lot of power and multistage compressor loops. [Answer] The problem is that temperature increases as you go deeper. The deeper you dig, the warmer it gets. If you have resources, you'd want to live on higher ground, where the air was thinner, or on the coasts, to take advantage of cooler temperatures from the water. The air conditioning they are trying to do is effectively cooling the core of the planet, and even that is going to dump heat into their surroundings. They should move to the surface. Save the caverns for winter, when that same heat from below can warm the cold winter air, which sinks during that season. Less energy needed to warm themselves, as well as cutting their carbon footprint, which over time addresses the warming of the climate. Why not work with the heat gradient, as opposed to against it? [Answer] Convert the heat into electricity If you are discussing a futuristic society, they could have invented a technology that converts heat directly into electricity. this would allow for no cooling issues, as well as unlimited electricity to power air filters or other machines required. [Answer] # Solar Chimney There are both home-scale and industrial scale [chimneys](https://en.wikipedia.org/wiki/Solar_chimney) which feature essentially "free convection" (air movement is driven by thermal differences, and thus requires no powered fans). The industrial-size chimneys are very large indeed, and would supply a decent number of buildings with cold air, if configured appropriately. Now, industrial scale solar chimneys are intended to operate as a kind of solar power plant. But if your bigger problem was heat removal, then consider the top of the chimney. It works because air temperature decreases with elevation (it's more complicated than that, but let's ignore inversions, etc.). So the air at the top is relatively cold compared to the air coming in at the bottom. Instead of using turbines to power generators, the chimney could instead be engineered to dump hot air at the high elevation and simultaneously pull cooler air down for distribution to residential buildings. There are usually winds aloft which help you with moving the warm air out of the way and providing more cool air so that you don't poison your intake with the hot air you are trying to get rid of. [![enter image description here](https://i.stack.imgur.com/5ZYNL.png)](https://i.stack.imgur.com/5ZYNL.png) # Energy Efficiency Really, pumping your heat into the ground is probably the most efficient way to get rid of it. The amount of heat that you will add to the ground is relatively tiny compared to its thermal mass, and the earth's crust will eventually radiate away the excess heat all over its surface. This is why the crust near the surface is a pretty darned uniform 50 degrees F or so. That's essentially the thermal equilibrium between the primordial heat in earth's core, the solar flux earth receives, and the blackbody radiation of the planet dumping excess heat. Any building can be insulated sufficiently to make this work. It's just a question of cost and materials. From an energy efficiency perspective, the solar chimney is strictly worse, both in capital costs and operating costs, because dumping heat into the ground can be done easily via liquid refrigerants that have high heat capacity. Whereas, gases have far lower heat capacity, so getting rid of heat via air and bringing in cold air results in far lower heat exchange for the amount of work you're doing. However, the chimneys are cool from a story-telling perspective because they are unusual and a potential weak spot if you want to drive conflict. It makes the landscape seem all that more different from what we are used to. [Answer] I immediately thought of taking advantage of the [Infrared window](https://en.wikipedia.org/wiki/Infrared_window) of the atmosphere. On Earth, our atmosphere is basically transparent to certain wavelengths of infrared light, which means that something that creates those wavelengths, facing the sky, is basically throwing energy into space. Perhaps you could imagine a field of IR lasers pointing at the sky, dumping excess energy from heat exchangers routed to each underground apartment. Could be an interesting dynamic if things happen to block or disable the laser array. [Answer] Since there's apparently backlash against regular ol' ACs (which answer the question), here's a zanier idea which is a little science based: Use [Maxwell's Demon](https://en.wikipedia.org/wiki/Maxwell%27s_demon) to selectively trap the hot air and move it somewhere. You could invent a futuristic smart nano-mesh box which is fed in information about the incoming air particles and selective allows only the highest energy ones to enter, while keeping the lower energy ones out. Of course, computation generates heat, so the computation can't be done on site--the box has to have a fiber-optic cable connecting it to some computer in the outside world, where it can feed in information about the room and receive information about which slits it should open to trap the hot air particles. Of course, I think this won't really work that well unless you invent some more crazy less-science based things, because I think the air in the room will be pretty uniform in energy overall, and you're still going to have to be receiving some cooler air from somewhere. And you're going to have to empty the box and keep it from radiating heat if it gets too hot. But I'll leave that up to you. [Answer] By using a heat pump, you can dump heat somewhere hotter and make it even hotter, hotter than its environment. As a result, it will lose heat to that environment. For example: a large pit excavated near the underground complex. You can pump 700 °C air along the walls of the pit so that it forms a sort of a scorching cyclone, and at the same time pump cooler air from outside to feed the heat exchanger. Or you can dump the heat into the water table (even with the Earth made mostly uninhabitable, by digging deep enough you will find a water table). Or (which is probably best) you can set up heat exchangers on the surface, connected with a large [heatpipe](https://en.wikipedia.org/wiki/Heat_pipe) or a closed circuit water pipe. Another way still (much more expensive) is to use lasers to disperse the heat outside ("refrigerator lasers"). The concept was set forth by David Brin in Sundiver, and while implausible, [it appears to be achievable](https://forum.nasaspaceflight.com/index.php?topic=22649.0). All this costs energy, but to live underground you must have energy. [Answer] What if you were okay with dumping heat into a contained location in your environment? Consider this - with some form of powerful cooling and "super" insulation, you could have a cooling system that takes heat energy and dumps it into a compressed space that is inside the system and insulated. The waste heat from the carnot cycle could also be dumped into that system. So you end up with a "heat closet" that eventually becomes millions of degrees, and be damned the future consequences! Or else at high cost people can ship these heat closets out to be vented into the atmosphere and/or space? This is not violating the carnot cycle and this is not Maxwell's Demon. Waste heat is also generated and contained. Imagine putting a window air conditioner where the "outside" is actually a closet. You'll start to cool off the room while you heat up the closet (with both pumped heat + waste heat). The system fails when either the insulation is leaking heat faster than you can pump heat in, or when your heat pump can't push any more heat into an already hot "closet". That happens pretty quick with today's technology, but a future insulation solution and a future heat pump solution would push those limits higher and higher. [Answer] I use reflective resources to help keep things cool around my domain. The color white reflects a lot of light and prevents it from being converted to heat and the resulting shade is considerably cooler. It's probably not going to solve everybody's comfort issues, but when used in combination with evaporation it could theoretically create cool areas that could be used to dump heat using conventional refrigeration methods. [Answer] Unfortunately, the laws of thermodynamics prevent you from cooling (removing heat from) a room unless that heat has somewhere to go. Regardless of any technological advancement and post-apocalyptic MacGyver-ism, you simply cannot reduce the temperature without placing the heat somewhere. Heat Transfer is Required Your tech-savvy lower-class needs to engineer some way to move the heat outside the apartment. If they are living in a co-op type manner this could involve a communal heat transfer source built into the apartment/underground complex which each home then connects to. Each home could have a compressor, that feeds the coolant liquid through the central system and disperses it outside the home, working like a refrigerator. Chemical-reaction based cooling mechanisms are interesting. There are currently heat exchange systems that work based on the principle of phase-change. Electricity is required to power fans—the method of which depends on how electricity is generated in your world—which move the hot air towards a solid substance. The solid substance is melted, which removes heat from the air, and the cooler air is cycled back into the home. Chemical Reaction A 100% chemical-based solution you would require an endothermic reaction which pulls heat from the surroundings in order to power the reaction. One such example (that would have to be scaled up) is ammonium thiocyanate and barium hydroxide octahydrate. <https://www.youtube.com/watch?v=MyAzjSdc3Fc> [Answer] There are chemical process that absorb heat - collectively known as [endothermic reactions](https://en.wikipedia.org/wiki/Endothermic_process) Few of the examples would be reasonable in a domestic environment, but one stands out: Photosynthesis I can't find a figure for how much heat is absorbed by Earth plants, but there's a precedent, and you control your world so have some native plant that does this particularly well and more in the IR range than the UV or visible range. Bonus, the plants absorb CO2 and release Oxygen, which will help make your underground living areas more breathable without requiring as much surface ventilation. In short - use that energy, rather than dumping it. [Answer] ## You don't dumps "heat" to outside. You extract "cold" from inside. A very small vacuum pump could [freeze water very fast](https://www.youtube.com/watch?v=2IOyJa8NSk0). A [lot of water](https://www.youtube.com/watch?v=ViuQKqUQ1U8), if you like. Simply run a fan in front a reservoir of water with a vacuum pump attached to it, and voalá. "Cold from tap" is a registered mark from Very Rich People, patent pending. Taxes will apply. [Answer] I'm going to suggest the same thing as others but still differently, radiate the heat away. I simply base my assumptions on [this video](https://youtu.be/7a5NyUITbyk), a shorter version typed by me below if you don't want to watch it. In warm countries centuries ago the people used radiative cooling to get ice. They would use a kind of pool that they filled with water during the evening, and by morning it would be frozen even if the surrounding air was warmer. Every warm thing radiates heat, usually this radiation will hit something nearby, heat that up and it will radiate a portion back. But this type of night time cooling used a "gap" in the atmosphere where radiation would be able to reach space and leave the planet. This allowed the water to lose more heat and get colder than the air surrounding it. During the day however the sun would shine into that atmospheric gap as well and heat it up more than it lost heat. Using a particular composite material you can simultaneously reflect the heat of the sun and still radiate heat from the object away. This can make the prototypes they had during the filming up to 42 degrees Celsius colder than the surroundings. This material can be mass-produced even today, so your future civilization could use this en-masse on top and the sides of their buildings. ]
[Question] [ This is set in the modern day but in a parallel universe. As usual we have a food crisis and climate changes, etc. Imagine a serial killer was finally arrested and sentenced to death, as the country still practices capital punishment. It supposedly is a strong deterrence and sends a powerful warning against committing heinous crimes such as homicide or murder. Then I had a thought: if I wasn't myself anymore, if - for example - my memories and personality somehow were altered so that nothing of my old self remained, wouldn't that mean that I'm as good as dead in the eyes of the public? Can we perhaps replace capital punishment with magical memory manipulation? And if this argument is valid then why hasn't capital punishment been abolished? [Answer] Because capital punishment is more efficient and no less moral. Assuming you're reverting them back to the state of infancy, wiping someone's memory and personality is fundamentally the same as killing them anyway. The only difference is that now you have a mind-wiped adult who needs to be raised from scratch. Who's going to do it? Their parents are probably old or dead, nobody is going to "adopt" a mind-wiped criminal, and getting the government to do it will mean additional costs for taxpayers. If you're wiping them to a more functional state, chances are good they still have the traits that led to them becoming criminals in the first place. Moreover, if you consider that criminal behavior is largely influenced by genetics, even a fully wiped person has a good chance of committing the same actions again. In the end, it just makes more sense to kill them. [Answer] > > They say the Force can do terrible things to a mind. It can destroy your memories and wipe away your very identity. > > > -- Carth Onasi, Knights of the Old Republic > > > Memory erasure and the death of personality has a long history in fiction and plenty of people faced with it consider it as bad as or even worse than death. Death at least brings closure and finality, but the idea of effectively dying, but some thing walking around, a thing with your face, your life, but not you... it haunts people. With the option of a terminal and just plain ghastly fate of death of personality on the one hand, and the finality of true death on the other, convicts or society in general may feel that death is more merciful and morally superior. [Answer] Even though the "death of personality" may erase the propensity to eat one's neighbors or make a lovely dress out of their skins, the families of victims could feel that anything short of the perpetrator actual dying is insufficient punshment. There's also the possibility that overwriting memories and personality may not have prevented the killer from killing again (or being framed for a murder - this could be an interesting side plot). If the real or perceived recidivism rate isn't firmly zero, many people will believe that erasure can't cure someone with an inborn propensity for murder. [Answer] The death penalty is still applied when a personality can be changed so radically as to be another person because personality does not exist alone. Personality is a function of the body. So, no matter how the personality of a murderer, traitor, drug smuggler or other death-penalty criminal may be altered by magical psychosurgery, that person is still a death-row criminal. The criminals may not remember their crimes after magic alters their minds, but the bodies were still fundamentally flawed in that they housed personalities which were able to commit crimes for which the death penalty may be applied. There may well be in-world research that shows that the mind-wiped body of a death-row criminal is significantly more likely to go on to commit further crimes for which the death penalty may be applied... or it may be a belief without a scientifically demonstrated foundation. However, unfounded belief or scientifically demonstrated fact is irrelevant, if enough people believe it, whether it is true or not, that's what society will do: execute the worst criminals. [Answer] If the country applies death penalty as a way to enforce the "eye for eye, tooth for tooth", simply wiping the memories of the culprit, or even reducing them to a vegetable, might not fully satisfy the above. Moreover, even in a scenario where the reasoning behind the death penalty is not so extreme, deleting or altering the memories of the culprit also take away the chance that, at any moment, they might repent or feel remorse for their actions: with the memories gone, they cannot deal with them. It can be seen as you end up actually making them a favor. [Answer] # Memory wiped people killed again. Why did this happen? Genetics? Stigma? Bad luck? Who knows. Regardless, there were several high profile incidents where serial killers were mind wiped, and then went back to their old ways. The general view, accurate or not, is that enough off the old memories survive in emotional memories that the person is still dangerous to those around them. [Answer] If you wipe the memories of an adult to the point they are no longer the same person, you're left with a major problem. You can't just start again with a new person. So you effectively set their mind back to the level of a newborn. However babies and children have amazingly flexible brains which makes them excellent at learning and developing personality and emotions. This is how they turn from a blank slate into a functioning person. They lose this ability as they grow up, so the older you get, the harder it gets to learn new things. If you wipe the memory of an adult, they will have a blank adult's brain but not the ability to fill it. Even if they can take in information, they'll have a really hard time processing information and likely be devoid of emotions and personality. And you can't just leave the stuff they learned in childhood intact because a lot of this will likely be the stuff that made them become killers in the first place. So in answer to your question, the death penalty is still carried out because it's considered inhumane to create these zombie like people, who, going by the logic of the question, are different people and therefore have to suffer this condition even though they aren't guilty of any crime. [Answer] There are a few religion-based possibilities, but one that I think is interesting is if the society wants to prevent redemption/salvation. In Hamlet, act III, scene 3, Hamlet has an opportunity to kill Claudius (to avenge his father's death), but Claudius seems to be in the middle of prayer, and Hamlet believes that this will send his soul straight to Heaven; so he chooses to hold off for a better opportunity. We can imagine a society where this sort of perspective is, if not universal, then at least common; in such a society, it might be considered undesirable to give criminals "free" redemption/salvation by magically turning them into the sort of people who get into Heaven. --- Funnily enough, the exact opposite reason works as well: the dominant religion might teach that a mind-wipe makes it impossible for the criminal to repent, and the society might consider it unacceptable to create a mind-wiped individual who's doomed to Hell no matter how good a person (s)he tries to be. [Answer] Because of how the specific spell works and the laws of magic as they operate in your 'world'. You start by assuming spells were tried which physically erased the memories and/or personalities of subjects but there were inevitably severe side affects i.e. the brains of the victims were traumatized. This was because the effect of the spell was physical ie it directly effected the biochemical processes involved in forming and retaining memories. Since these are innate to the nerve cells and networks involved in memory & personality the effect was like concussing all the nerve cells in the relevant parts of the brain at once. The result, if not death was a coma like state and permanent brain damage. So instead after some research magicians decided try using magic to induce a 'Geas' on the target instead. The Geas involves a couple of spells working together on a permanent basis. In part the spells impose a command 'do not remember X'. The next step is 'You must remember Y' With 'Y' being whatever false memories the caster or their commanders wishes the person to believe are true. Perhaps another spell then effects personality traits the same way. This approach works because your not physically destroying any memories just compelling the victim not to remember/change etc. But there's a cost. And that's where the laws of magic come in. The first (unsuccessful) spell was more or less a one shot physical attack, or at least several of them in a row i.e. the spell is cast and a permanent effect is caused, job done. Everyone walk's away happy - except of course the victim. However the second type of spell is an induced effect or set of 'instuctions' that needs to operate continually in order to be effective. Its a permanent magical 'construct' not fire and forget. This means the spell has to be maintained/checked at intervals and worse that another magic user can remove it if they wish. Not only is the spell more time consuming and arduous to maintain, its also reversible. So the death penalty stays in place, especially for any rogue mages who decide strike down another practitioners memory spells without authority. [Answer] # The Wipeys, Nulls, or Reseted Because the memory wiped inmate is now a slave of the state or the victim's family and they´re put to work to compensate for the damages caused. The justice system wipes the memory of the inmate and now raises him as a slave to the government, using him to do menial labors or even specialized work after specific training. All major crimes have a currency value specified in a table and the inmate must work untill his debt is paid. He can work for the state when the case is the people vs him or for specific individuals in person vs person cases. (Even at their house as butler, gardener, if the magic makes them behave) If you´re allowing magic you can maybe use it to condition the inmate to be obedient but surely something will go wrong someday and you´re going to have a nice rebellion on your hands to deal with it. Groups of civil rights defenders would probably rise against this procedure and that would give you some nice political implications. And after the debt is paid would you have a new chance to live free? Would people accept this new personality back in the society? There are many things to consider specially if after being free some of them return to commiting crimes. [Answer] Two possible reasons. One a downside of the wipe. The other because of the less-than-pleasing motives of the Powerful People. First: A certain type of contract killing could become quite popular. Joe Nastyperson wants somebody dead. He finds Bill Downofluck and offers to pay his family $BigStacks. Bill does the do, admits it, and gets wiped. Joe is then utterly protected because the only evidence of his conspiracy was erased with Bill. He can probably even manage not to pay since the only guy who knew what he promised was the guy who got wiped. Second: The organ banks are always hungry. If the newly short is divided up for spare parts then he can be made to help several possibly terminally ill people. Corneas, heart, lungs, kidney, liver, about 8 pints of blood, bone marrow, fingers and toes, and a coupld squre meters of skin. Cheese and crackers, he's got hair that can be transplanted. Powerful People want there to be available spares. Not just for themselves but for people they want to buy favors from. So they are working behind the scenes to keep the dvide-and-profit method going. [Answer] Memories are wiped but environment is same Magic will change memories only. What about habits, mentality, customs, society and many other stimulants which made him a killer in the first place? Feelings of the dear ones What about the feeling of revenge in an orphan or a widow? No one is satisfied when he sees that the killer of his dear one is wandering while he is in jeopardy. Once a killer, always a killer A killer can become a killer again when he is already a serial killer. [Answer] I understand this question is already answered, but I want to share this answer anyway. # Afterlife People believing in an afterlife do not know what would happen to them if their -or the memory of criminals- would be erased. Do they get to go to the 'good place' when they don't remember being a bad person anymore? Does the second personality end up paying for the crimes of the first? Will they remember what happened in both lives in whatever place they go to? Does this count as creating a person, and therefore can be seen as playing God? There have been many debates about if an afterlife exists, and if the government had to take the believers (minority) into consideration. Ideas were suggested of removing/changing/adding faith(s) into the newly re-uploaded personalities to ensure they would (not) end up going to 'the good place'. In the end, with the various touchy political and religious debates surrounding the subject, and the inability to disprove an afterlife and the effect of memory resets on it, it was decided to just keep the death penalty. [Answer] ## Because the Population Needs to be Culled > > ... as usual we have a food crisis and climate changes etc. > > > The world is over populated. Everyone knows in the back of their head that no amount of windmills and recycling plants will save humanity from itself. We need fewer mouths to feed; fewer people pumping CO2 into the air... and to do that, we need to stop trying to save everyone just because we can. Since a mind wipe is already equivalent to execution anyway, there is no better candidate for culling than violent criminals. We may come up with other excuses like genetics or what not, but at the end of the day, it's about self preservation. [Answer] # Soylent Green: The world is FILLED with people. There are vastly more mouths to feed than can possibly be fed. So what are you going to do? Kill old people because they aren't contributing? Kill children so they aren't a lifetime consumer? With hard choices like that, killing ANY convicted criminal (even for petty theft) makes perfect sense. You WANT the excuse to kill these people. It's population control. # Eugenics: Your society is a strong believer in eugenics. Criminals are assumed to be genetically inferior to non-criminals. So the decision is made that even if you can fix an individual, their genes must not be passed on. Further, because you assume they are genetically flawed, then they are inherently likely to reoffend. Killing them both prevents them and their inferior genes from being passed on AND stops them from reoffending based on their genetics. [Answer] There are three motivations behind criminal justice: rehabilitation, deterrence, and PUNISHMENT Your society just happens to favour punishment. There are plenty of people out there, including those who have been personally victimized by crime, that just want revenge. They want murderers etc. to suffer and regret what they've done. They want consequences. There are people who don't necessarily want this to be deterrence even; they believe some people are just inherently bad and that they belong in prison, or need to be killed. A society that leans towards the punishment motive will view 'resetting' someone as like giving a serial killer anger management classes. "My brother doesn't get a second chance, but his murderer gets his memories wiped and just walks free?" [Answer] The simplest answer would be "the wipes aren't perfect" in the vein of Dr Jekyll and Mr Hyde. Dissociative Identity Disorder is already a thing (used to be multiple personality disorder) in our world right now, play a bit loose with it and have one of the personalities be a serial killer. If you're in the mood for some light reading then the Split Personality page on TV Tropes has plenty of similar examples. [Answer] Punishment serves several purposes. Wiping memory doesn't satisfy all of them. Most importantly, vengeance/justice - while our legal system takes vengeance away from the victims (or their family), it is important that they get closure, and punishment to the criminal is one way of doing it. This is why the family of a murder victim participates in trials, why there are victim statements, etc. A wipe-and-release will be seen by many as the murdered getting away without punishment. Vengeance is a base instinct and when you look at the murderer of your small child (for example) walking out of the room, the higher brain functions that tell you that it's not the same person anymore, his memory is gone, etc. simply are shouted down by the lower brain functions wanting to bash in his skull. There will also be many cases in which the murderer doesn't actually consider a mind wipe to be all that terrible. People in bad life situations, killing out of desperation, might even welcome a fresh start. They'll be saying "thank you" to the judge and mean it - infuriating the family of the victim. [Answer] ## Because doing so is just attaching a drawn out trauma and cruelty onto state-sanctioned murder. The reality is, whether you're making a blank-slate person, or recreating them as a whole new person. That person is going to share the face and history of a convicted felon. They will still be walking around, people will never ever accept them entirely, they will always share their identity with a monster, a monster they can't remember being, and most likely are horrified by. How many people will struggle to put the past behind them because they see a monster at the shops every day? How many New Men will be shocked and appalled by reading the excesses of their past self? It's cruel for the victims, and it's cruel for the new person the state created. The original person is very much dead anyway. Better that their face not be walking around, perpetuating the pain for others. [Answer] What's the point? So you say that wiping someone's memory and resetting is as good as killing them. So what exactly is the value in doing this as opposed to just killing them? To not waste a perfectly good body? To save on burial costs? What exactly is the benefit in creating a new person out of an old body, when new people are being created all the time in much happier circumstances, and getting to live full lives from start to finish. On the other hand, you have the body of a murderer or person who's committed a horrific crime still around as a reminder of the tragedy they caused to their victims. They might be stigmatised and receive undue prejudice and hatred because people don't get that they are not the same person or just can't get it out of their minds. They see their photo in the media constantly associated with the crime, etc. Could you find it as easy to fall in love with (say) a person who inhabited the body of a murderer? They only get to live a shortened life as they started about half way through it. There just doesn't seem to be any benefit to a mind-wipe over the normal death penalty. ]
[Question] [ # tl;dr: what issues would cause more risk than reward for a civilization to settle a fertile, heavily forested area; bonus points for less magic / historical examples / it being a threat > > My son, venture far beyond the Seas of Steel, > > and pacify the steppe, summit the mountains. > > But journey not into the Dark Forests... > > There is nothing to be gained there. > > - Mother to Son > > > # Summary In my world, the main empire I'm focusing on (of late Classical to Early Dark Ages technology level) has begun expanding on a continent the size of Eurasia. Explorers cross a large mountain range, and discover a large area of forest. However, even a few hundred years after the discovery of this land, no significan t attempts have been made to settle the forest. It is only settled along its coastline, as well as a single, heavily guarded road area through its interior. What kinds of unique dangers would prevent such a civilization from developing the land in the forest? # Some further details about this culture: * They've had no trouble settling other areas, mainly along coastlines but also in steppe or even desert biomes. They've even settled a different (smaller) forest. * As of right now, they don't necessarily need more resources to sustain themselves, but having more materials for trade is always good. * The world that they "exist" on is being simulated by a massive supercomputer for scientific purposes, and because of that... * Magic exists, in the form of some individuals in the computer using bugs in the code to escalate privileges to be able to modify environmental variables (the random number generator being the only known bug right now). This results in some individuals being able to modify the chances of certain events succeeding. * The current forest is inhabited by hunter-gatherers, much like the current Amazon. I'm specifically looking for a real-world reason (bonus points for a specific danger) that would cause more risk than reward for a civilization of significant resources in settling a heavily forested region. Magic can be involved, but I'd rather the solution not rely solely on magic. (This is my first question in a long time, please remind me of any issues with the question [topicality, duplicate, tags, specific details, etc.] as well as ways to improve them. Thanks!) [Answer] ## In the real Middle Ages * "In my world, the main empire I'm focusing on (of late Classical to Early Dark Ages technology level) has begun expanding on a continent the size of Eurasia. Explorers cross a large mountain range, and discover a large area of forest." Great! We have a nice historical example. The time is the 11th century. The "great empire" is the [Kingdom of Hungary](https://en.wikipedia.org/wiki/Kingdom_of_Hungary), the "large mountain range" is the [Southern and Eastern Carpatians](https://en.wikipedia.org/wiki/Divisions_of_the_Carpathians), and the "large area of forest" is, well, most of territory which would eventually become [Wallachia](https://en.wikipedia.org/wiki/Wallachia) and [Moldavia](https://en.wikipedia.org/wiki/Moldavia). The only difference is that there were no "explorers", because they were not needed. The geography of the land was very well known, and had been known for a very long time. So what happened in the real history? In the 11th century, nothing. The kingdom of Hungary sat on their side of the Carpathians. In the 12th century, nothing. The kingdom of Hungary sat on their side of the Carpathians. In the 13th century, nothing. The kingdom of Hungary sat on their side of the Carpathians. In the 14th century they attempted to establish suzerainty over Wallachia; mind you, not to conquer, just to establish suzerainty. By that time it was way too late; Wallachia had become an organized state, and [Basarab I](https://en.wikipedia.org/wiki/Basarab_I_of_Wallachia) of Wallachia [defeated](https://en.wikipedia.org/wiki/Battle_of_Posada) the expedition of [Charles Robert](https://en.wikipedia.org/wiki/Charles_I_of_Hungary) of Hungary. Why was it like this? Why didn't Hungary expand into the power vacuum to the south and east? And this is not the only example in European history; remember, for example, that the entire (densely forested) region south and east of the Baltic was only conquered (by the Teutonic Knights) in the 13th century; before that, the Baltic people were left alone to fend for themselves. There are two fundamental problems with envisioning western European medieval "empires" (note the scare quotes) hell-bent on territorial expansion: * First, the perennial problem of western European medieval states was lack of people. There was a severe post-classical population crash in Europe; it took Europe one thousand years to recover the population level it had in the 2nd century, which was not very high to begin with. Land they had aplenty. Forest they had aplenty, and they were actually offering incentives to people to clear it. There was forested and uncultivated land in England, in France, even in Germany, not to mention the large truly wild areas of Scandinavia, of Poland, of the Baltics, of Ukraine, and of western Russia. Western Europe had more than enough land for its people at home, they did not need more land. * Second, there was no way to trade extensively overland; they simply did not have the transportation technology. A mountain range was a very effective barrier to trade. Oh, they could trade luxury goods, small enough and expensive enough; but bulk goods? Timber, grain, wine? Not overland, they couldn't. Remember the exalting and sad story of the [Crusader States](https://en.wikipedia.org/wiki/Crusader_states): established in a glorious war of conquest in the late 11th and early 12th century, and lost in the late 13th century. The Kingdom of Jerusalem, the Principality of Antioch? They never managed to bring in enough colonists to become sustainable; they never reached a population level sufficient to defend themselves against the Saracens. And why was that? Because Europe itself did not have enough people; sending masses of colonists overseas was out of the question. In conclusion, it is not at all surprising for a western European kingdom to just sit on its side of a moutain range, beyond which is a dense forest inhabited by dirt poor people. It is to be expected. If you want the "great empire" to seek to conquer the forest land you must give them a strong incentive; I suggest that instead of "hunter-gatherers" you make it inhabited by a splendiferous civilization, swimming in gold and silver. Then the empire would be interested. But poor peasants they already had; land they already had; forest they already had: they had no reason to embark in costly attempts at conquest and colonization. ## General considerations The question states that this "medieval" "great empire" is actually in another world. The issue is then, what makes this "great empire" medieval? The western European medieval society was a historical phenomenon very highly specific to western Europe. It is extremely unlikely to get anything quite like it in another world. Think about it. The western European medieval society is a historical aberration. A highly advanced, highly literate, fully functional civilization collapses due to basically a long streak of historical bad luck. To bring about the western European Middle Ages, you need: the Crisis of the Third Century, during which a previously functional empire finds itself mired in a century of civil war; plus a few centuries of barbarian invasions; plus a devastating plague; plus the emergence of Islam bringing the collapse of the (Eastern) Roman Empire. There were [feudal](https://en.wikipedia.org/wiki/Feudalism) societies elsewhere, in Persia, in the Ottoman Empire, in India, in China, in Japan, and those lands had their own medieval periods; but the western European medieval society, with its highly elaborated double hierarchical system, secular and spiritual, was one of a kind. [Answer] Mosquitoes. In reality, mosquitoes have prevented humans from developing rain forests. A forest filled with aggressive insects can be pretty effective at keeping people out. I first heard about the benefits of mosquitoes in protecting natural habitat from a podcast, but I can't remember which one. Maybe radiolab or freakonomics. <https://endmosquitoes.com/10-benefits-of-mosquitoes-how-are-they-helpful-to-humans/> [Answer] 1. Cutting big old trees down is hard, dangerous work. 2. They don't have the population density to need the land. These two are likely to be the reasons ancient forests survive into the modern age, but there are more specific reasons you could choose. 3. The settlers are sailors and fishermen, moving into the interior holds no appeal to them. They're coastal people, not farmers. 4. There's a mountain range in the way. That's not a trivial obstacle. and that's before you get into the more traditional 5. The natives are hostile, but mostly keep to the forest. 6. Bears. There could be worse than bears, including wild boar, big cats, wolves etc. Large wild animals prior to firearms are considerably more dangerous than we now consider them. [Answer] # The mountain range is in the way. As a gross oversimplification, there are two possible patterns of settlement: * Develop a piece of unsettled land next to the settled lands. That means the geography will be known, same for wild plants and possible crops, if your plow breaks it will be a relatively short hike to the next blacksmith, but on the other side of the coin there may be a lord who believes that he is due taxes from you. * Develop a piece of land far away from from any baron or mayor. Grab your sturdy axe, a bag of seed corn, another bag to last to the next harvest, and go into the unknown. If your axe wears down before the fields are cleared, or if the rats get into your corn, or if a cougar finds you tasty, you might be able to stagger back into civilization, haggard and broke. The mixed bag would be to to travel with a group into distant fields. The best of both worlds, or the worst of both worlds? Assume that any significant, successful effort goes the first way. Yes, there are a few lone prospectors and trappers in the jungle. But they failed to leave their mark. Huts here and there, some abandoned, some inhabited, some with the grisly remains of a body. [Answer] Your magic system isn’t magic: It is based on luck. Those few that can influence the random-number generator are always extremely lucky. That is what gives them the edge in life. However, that random-number generator is flawed in more ways than one. The location on the planet is part of the seed of the generator and this leads to some areas (like your forest) where luck comes out really badly: bad luck all the time for everybody. That's what makes that forest so dangerous. Hunting is difficult because the luck affects the behavior of the animals. Wild animals that usually avoid humans will have a very high chance of attacking humans instead. The chances of mistaking a poisonous plant or mushroom for an edible one are very high. Only the best, most skilled hunters-gatherers can survive there, since their skill takes the luck factor out of the equation. Traveling through the forest is possible but takes a lot of precautions, because you need a lot of redundancy in food, supplies and gear. With the bad luck to be expected, food goes bad, gear breaks, etc. [Answer] Logistics. At this technological level the main means to move bulk materials is ships. Rome was supplied by grain from Egypt by ships, for example. Small-time substinence farmers may settle by foot or by ox, but they cannot trade whatever they grow (unless they choose to become ranchers, a la Wild West). Come up with some explanation why ranching is impossible - no animals domesticated, or the forests are full of predators, or some infection of the animals (tsetse-born-like). If there is no means for trade, no wonder nobody wants to settle there (except for outlaws, I guess). [Answer] Cribbing from an M. Night Shyamalan movie, have the trees or some ubiquitous plant in the forest release a chemical that produces anxiety, so that anyone who tries to venture in — much less clear a patch of land — will increasingly be filled with terror. Indigenous people would have developed an adaptation so they aren't affected; perhaps they've discovered an herb that can be used as an antidote, or a way of concentrating the chemical to use as a fear-weapon. At any rate, that would explain both why the forest hasn't been settled and why the road is heavily guarded. Even passing down the road would fill travelers with an overwhelming sense of dread. [Answer] Once dry, the logged tree wood is highly explosive, propelling the seeds of the trees in all directions, when ignited. Treeseeds will sprout in travellers and animals they penetrated alike. Luckless travelers can be found "grown into the trees" theire faces still screaming. [Answer] If your medieval society has a system of land ownership that resembles those of historical western Europe, then you can fall back on a political/legal/sociological reason: all undeveloped land belongs to the monarch, and he or she does not choose to make that land available for development. The monarch could be holding the land in reserve to have it available to enfeoff new followers; the monarch could also judge that allowing the land to be developed would upset the current balance of economic and political power; the monarch could want the land available for the crown's own use; etc. You could even have the land patrolled by "gamekeepers" who make sure that no one is poaching on the monarch's land, on pain of death. [Answer] There does not have to be a complicated reason ... a bit of reading on Roman history might do. * Your Smaller forest approximates Gaul (france) * Big forest over mountains (instead of Rhine/danube) approximates roman Germania (germany and east europe) A strong/ centralised government meant a few big battles replaced the Gaul government (and tax collection) with Roman under Julius Caesar. fewer obviously resources and chaotic government meant "germania" was never worth anything except as a place to capture slaves / prove your battlefield rep and the chaos meant peaceful encroachment wouldn't happen. Romans could get new land to develop a lot easier almost anywhere else in the empire and without a solid reason to do it, sounds like the same applies to your empire. For contrast read a bit about the US history until the mexican-american war ... population pressure and resource demand meant any danger would be faced [Answer] It could be as simple as the forest is inhabited by a people who do not want to be disturbed/don't take kindly to strangers, and are not shy about driving people off. Since there isn't a huge driving force sending people into this region, those who do end up going there will be few, and likely solitary. Not good odds when going up against people who know the area, and who are well supplied and have the extra incentive of defending their home. People who don't have a need/desire to go to this place specifically for some kind of benefit (a trade good, shortcut, etc) may also just choose to explore elsewhere for logistical reasons. Since the area is somewhat geographically isolated the animals may be somewhat different - larger, smaller, both of which could pose an increased threat, especially if you've not expecting it. Plant life being different could make finding food very difficult, especially if toxic species are endemic or difficult to identify. Insects (ranging from poisonous to merely annoying) would also be deterrents. Is there water available in the forest, and is it drinkable for humans, or does it require filtration? That puts a very tight timeline for any exploration if you're not able to get sufficient water. It may be very difficult to find your way through the forest. If it's especially thick or fast-growing trails may become overgrown as quickly as they're cut, and any locals will likely encourage this to keep outsiders out and make wayfinding even more difficult. If your culture depends on the stars or visual cues to navigate an inability to see them will also make navigation and orienteering very difficult. If the road had a high cost (lives, money, resources, etc), others may discourage people who might want to go further into the forest from doing so as it's so dangerous. When it comes to building structures or developing the land otherwise it may just not be good land for farming - soil not the correct pH for the crops they'd want to grow, wood not what they'd want for their needs, lack of stone for building if that's what the culture usually builds their structures from, or the effort required to make it useful may just be way out of proportion to the expected benefits. Getting lost in a huge forest, with no guarantee of being able to find food or water, hostile locals, animals that may want to eat you, and no particular benefit to this adventure? You'll get some people who want to go ahead for the adventure and bragging rights sure, but enough to make major inroads in exploration? Doubtful. I don't think magic as people in this setting have access to it would be able to solve all those problems to a sufficient degree that exploration would have an acceptable level of risk for most people. [Answer] Since “magic” is taking advantage of bugs in a simulation, perhaps the taboo could be superstition arising from another bug that manifested in the past. Or, since the whole thing is a simulation, perhaps the taboo is itself a bug in the program. [Answer] The Greek Way [![](https://i.stack.imgur.com/wMHLP.jpg)](https://i.stack.imgur.com/wMHLP.jpg) (source: [ecosia.org](https://images.ecosia.org/t4DlG0x-zsVheUucnCmocJyNwJo=/0x390/smart/http%3A%2F%2Femployees.oneonta.edu%2Ffarberas%2Farth%2FImages%2FARTH209images%2Fmap_greek_colonization.jpg)) A real world example would be that the Greeks did not colonise Ukraine or the interior of any land for that matter. Greek colonisation might be a great starting point for your worlds colonisation for this reason. The Greeks did not conquer great stretches of land, they established Cities along the coast. Why? Because they lacked the people to create large land empires. And because the costal cities had access to the sea, which meant that they could remain connected to the rest of the world. Just look around the map many regions with attractive interiors were ignored. Even one very fertile and heavy wooded area filled with barbarians: Ukraine. The Ukraine would later be called the breadbasket of Europe. However Crimea and Sicily came to fill this role for the Greeks. So why is this area not of interest? * Your people establish costal towns, not inland colonies. At least not unless they would be very useful. * Other regions, which were colonised earlier, already satisfy the markets for crops and wood. If you would like to learn more about Greek colonisation, I'd recommend [this](https://www.youtube.com/watch?v=0Z71ZmfYE08&feature=youtu.be) video as a starting point. ]
[Question] [ Closed. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it can be answered with facts and citations by [editing this post](/posts/52370/edit). Closed 7 years ago. [Improve this question](/posts/52370/edit) If every cell in a creature's body were replaced (as in Theseus's Ship), would the creature still have its consciousness? E.g. a white blood cell would be destroyed and replaced by a nanobot that flows around the bloodstream, killing foreign substances; an interneuron would be replaced by a nanobot that sends an electrical impulse when it detects acetylcholine, etc. Reality-checking [Phyresis](http://mtgsalvation.gamepedia.com/Compleation) from Magic the Gathering here. [Answer] Truth is - No one knows. We are so far from perfectly replicating single neuron, and so far from understanding what consciousness is, that no one can tell. Good thing is - both "yes" and "no" are believable answers in the (lack of) light of current science, so use whichever you need. [Answer] Yes, by definition If you're replace something with something that is functionally identical then by definition it must be functionally indistinguishable from the thing it replaces. If replacing the cells with nanobots doesn't reproduce consciousness then they're not functionally identical. The more interesting question is whether it is possible to replace the cells with nanobots and preserve function. [Answer] That depends. Do you believe that consciousness is a consequence of having a soul? If not, then if the nanobots faithfully simulate all cell activity, there is every reason to believe that consciousness would be preserved. In this view, consciousness is an emergent property of neural function given the organizational constraints which derive from our brain structure. If you want something more mystical and less prosaic, then the existence of a soul would presumably not be supported by mere machinery. As to the point of replacement/failure of consciousness, that is not answerable until someone can quantify/qualify consciousness. And that does not seem to be likely any time soon. [Answer] Most of the body would not matter one bit. Is a man with a wodden leg still concious? You could change the limbs, bone, blood, intestines, etc. without having any effect on his mind. As for the brain, replacing a brain cell with a nanomachine that works in exactly the same way would do the trick. It would have to connect to other cells in the same way and have the same behavior. A living cell is a complex nanomachine. So consider replacing the cell with another exactly like it. [Everything we know informs us](http://www.preposterousuniverse.com/blog/2011/05/23/physics-and-the-immortality-of-the-soul/) that consciousness arises from the physics of the atoms making up the brain. (See [this question](https://worldbuilding.stackexchange.com/questions/40663/how-can-you-have-dualism-in-hard-sf) to explore otherwise; and comments and references concerning this fact.) So if a brain cell were replaced with a different nanomachine that was in fact behaviorally identical, it would make to difference. [Answer] You are talking about replacing every single cell in a body, which means nothing original would be left. In that case, how is it different from creating a new clone? If you create a new clone, you would probably have a new human there. The new human would probably be considered conscious, because it moves, but the old human doesn't get unconscious either, if it is a good clone that doesn't affect the original body. So the problem is, is it just the same consciousness, or a new one? Meanwhile, you can't say that the person becomes unconscious. Consider a person whose neurones are all replaced except the last one. Each other cell is perfectly cloned. As a cell unit, the last cell is still conscious. If the person is perfectly cloned, to other people it seems that he is still conscious, because he will act like what he was before. But what about the original consciousness? Well, that's the same question as what happens after a person dies ‐ nobody knows. If you believe in souls, you can mention that neurones are just a physical carrier of a soul, and that nanobots can or cannot carry a soul, depending on your requirements. Does the soul get surgically removed when the brain cells are surgically removed? This is up to you as well. It might even get torn apart by the surgery. Someone has once hypothesized that a cloned human would have the physiological capabilities like an animal, but not the wisdom of a human. Nevertheless, considering the hypothesis that intelligence memory is probably stored in the brain, this might not be true as well. [Answer] Consciousness is the result of the brain, a mixture of senses,memories and a complex communication between the neurons. To make an example see neurons as people, having 10 people there doesn't do anything. But if you give those 10 people something to talk about they will create a conversation, this conversation is the consciousness of the group. If one of the ten people dies and gets replaced the conversation and so the consciousness will change and lose or gain new qualities. Over time these 10 people will die and be replaced causing the conversation to deviate completely from the original group. In short, we all die slowly over time until there's nothing left of what we used to be. Replacing the neurons of a person with nanobots would be exactly like killing that person and having someone replace them that thinks to be them. another Example: 1-Jimmy is alive and knows it. 2-Every single cell in jimmy's body gets replaced by nanobots. 3-Jimmy is killed by the nanobots. 4-The nanobots give life to Jimmy-bot. 5-Jimmy-bot is alive and knows it. 6-Jimmy-bot doesn't remember about the existence of the original Jimmy therefore now Jimmy-bot became the true original Jimmy leaving the old one in the oblivion. [Answer] This is essentially a new take on an ancient (and I do mean ancient) thought experiment. The Ship of Theseus. Discussed by Plato and other ancient philosophers. If you have a ship/boat, and every single component is replaced with an identical replacement (no upgrades). Is it still the same boat? There are other variations, such as the grandfather axe, where both the axe handle and axe head are replaced. Your question asks about whether the nanobot body would still be conscious. I think another very important thing to take into account is, is it even the same consciousness?! [Answer] Technically, your body does this every ~1 year. And do you lose consciousness every year? [Answer] Depends on your definition of consciousness. If you define consciousness as a state of matter (materialist way), then yes. However from that point of view, consciousness itself is meaningless word and everything can be said to have it, even rocks. However if you believe there is some unique spiritual value bound to consciousness (eg. soul) then no, because method you propose allows (or would allow) for duplication of this entity and we said it's unique. [Answer] Assume you retain no consciousness after the process, since you interact with the world using your human interface (you know hands, feet, eyes etc.) and you already stated that cells keeps their functionality, then replacing each cell by keeping the same functionality keeps the interface functioning with the rest of the world, then you appear to be conscious even if you are not. So I could ask about your conciousness and you would still answer like if you were conscious making that not distinguishable. Conclusion: Either you are not conscious already or you will remain conscious after the replacement. [Answer] I think there is a fundamental flaw in your question, and that is that each cell is replaced by one nanobot. While that might (might) work for a red blood cell, or a WBC, or a muscle cell, there are no cells in the body with as many interconnections as neurons. Each neuron may be connected to up to 10,000 other neurons. One nanobot cannot possibly perform the same as a biological neuron. So no, there would be no mind or consciousness above the level of primitive organisms. ]
[Question] [ Full disclaimer : I acknowledge full well that in real life hybrid weapons are completely silly and impractical but I'm currently writing a fantastic-ish story where power fantasy is a key element. This hypothetical weapon will be more of a trick / makeshift weapon rather than a replacement o conventional polearm and bows. Since there is a structural limit to how much weaponry a humanoid can successfully store on one's body without completely removing mobility,agility,speed, nimbleness. How would one design an effective or at the very least a decent polearm-bow hybrid? I was initially planning on having my heavily armed men carry a spear (2 parts, 1 hard-point to attach into a long ranged spear) + bow + quiver & arrows + throwing knives + a backup sword + smoke pellets or canister + boomerang + cable wires + 2 wrist mounted shields... But let's be brutally honest even with rule of cool factored-in that's just downright silly/ ridiculous and comically so. So now I'm trying to make compromises on rule of cool and semi-plausibility, which is why I'm trying to design/find shortcuts to keep my fictional soldiers as mobile/agile as possible without completely disregarding the fantasy element here. Many thanks!!! [Answer] You don't. It's not merely impractical, it's straight-up impossible. A bow and a polearm require contradictory properties from their structural materials. However, you can do something functionally quite similar. If you are not set specifically on having a bow, as opposed to merely some sort of high-power ranged weapon, then you can quite easily combine a polearm and a staff sling--basically, a small, human-powered trebuchet. All that is required is a slight modification to the head of the polearm to include a sling-release hook at the end. The sling itself is basically just a bit of thin, knotted rope, which can be wrapped around the shaft when not in use, or just stuffed in a pocket--it is neither bulky nor heavy. And you always have the option of using the sling on its own if you like. Suitable sling bullets are also considerably easier to source than decent arrows, which reduces the armory supplies you have to lug around with you, and eliminates the need to try to retrieve valuable arrows after a battle. [Answer] You change the bow to a crossbow. The bayonet turned a firearm into a useful spear. You could start with a crossbow with a long shaft, like the [ones in Central Africa](http://web.prm.ox.ac.uk/weapons/index.php/tour-by-region/oceania/africa/crossbow-1884162-224/index.html)... [![enter image description here](https://i.stack.imgur.com/aEfyj.png)](https://i.stack.imgur.com/aEfyj.png) ... and just add a bayonet to obtain a spear. Such strange hybrids are common in fantasy (I think D&D had them), but also [in reality](https://9gag.com/gag/aRK7GnA) [![enter image description here](https://i.stack.imgur.com/q0Qtm.png)](https://i.stack.imgur.com/q0Qtm.png) [Answer] Put a metal tip on the bow, to make the bow a light spear. Thus, if the archers have a make-shift polearm to defend themselves, once they run out of arrows or they are directly attacked. There were bows found, which had an iron point on one of the ends of the bow. One theory for the metal tip is that the bow would serve as a walking stick, with a reinforced tip, when unstrung. [A paper on a find in Altdorf, Switzerland](https://www.e-periodica.ch/digbib/view?pid=jas-003:1995:78::86#86) [The German Wikipedia on the history of the bow, section migration period](https://de.wikipedia.org/wiki/Geschichte_des_Bogens#V%C3%B6lkerwanderungszeit_und_Fr%C3%BChmittelalter) [This site shows a replica](http://sagittaria-handcrafts.com/en/1-en-pokus/historical-replicas/detail_61/) [Answer] I usually take "low-fantasy" to mean either No Magic or Very Little Magic, if you're going for a purely No Magic setting then Logan's answer is on the money, a bow and a polearm require the exact opposite qualities in the wood they're made of to function effectively. I your setting allows a little magic you may have a wood that has those diametrically opposed qualities. In this case the wood needs to be springy when pressure is applied across the grain, making a good bow, while remaining rigid when compressed parallel to the grain in a stabbing situation, thus also making a good spear, natural real-world wood doesn't do this but magic wood could. Or the spear could be enchanted to be bow-springy when the bowstring attached to it is pulled while being made of highly rigid wood that normally doesn't flex. [Answer] English Longbows with draw weights of over 100 pounds (war bow draw weight) are very sturdy. When unstrung, they are very straight and very stiff and are around six feet in length. They are much more sturdy than a Bo staff which are known for being very flexible. If you add a small metal spike or spear point on the ends you would have a very effective spear which would have greater reach than most swords and axes, and be nearly on par with the reach of most polearms. It wouldn't take much to quickly unstring the bow to turn it into an effective short spear if you get rushed by the enemy. It wouldn't be a stretch to have a longbow be used as a polearm so long as there are equivalent weights added to both ends to prevent malfunctions when firing arrows. Be sure the spear-heads are small and light to make sure it doesn't interfere with the kinetic energy being added to the arrow. Reference: <https://www.youtube.com/watch?v=12KjhJbHfUA> [Answer] Look closer on [peltast](https://en.wikipedia.org/wiki/Peltast) greek warrior. They had almost what you want - throwning spear with slung-alike way of throwing. This spear was still good enough as a polearm - peltast could form sort of weak phalang (against other peltasts or barbarians). Or you may look closely to [spear-thrower](https://en.wikipedia.org/wiki/Spear-thrower), wich obviously can be crossed with any polearm of your choise. Or you can just attach a knife to a japanise non-simmetriacal longbow. It would be a terrible polearm (wich requre a lot of training just not to brake it), but not-so-bad bow. [Answer] # polearm + throwing projectiles : Your polearm is hollow, making it a blow gun. you can now throw darts in seconds after beig engaged and then fight with it. On the bad side, you will need to tend your weapon after a fight, or it won't stay accurate, because hitting blowguns perpendicularly will alter them. It also won't be that effective against armor. # polearm + sending arrows : Your polearm is hollow and contain a big knot at at least one end of it, with a spinned rope. the torsion is the elasticity source you are searching for. instead of bending the bow, you just have a rubberish rope. If you want it to be accurate (not this much, but accurate enough to it a cow at 5 meters) you will need to have the 2 ends with the same elasticity.So not good for long distance shots, but it will have some punch to it, if you have enough force to place a specially designed rope hooked to both knots. # Conclusion So if you are facing light armored enemies, the blowgun will help engaging from afar, especially if you allow poison or explosive darts in your universe, but if you want to pierce an armor, you will need to resort on a makeshift elastic, which will loose strength with time, will suffer from humidity, etc... But is the best way to get a polearm to act as a bow without destroying its polearm capacities. So not that good anyway, but hey, that's what was asked. [Answer] The item which you seek is called a Ballista. It is a large bow on wheels that fires varied projectiles, including spears, which are a polearm. You fire the ballista like a bow at range, and if they get close, you grab one of the projectiles and you have your shortspear for close range. Polearm-bow hybrid historically achieved. [Answer] Without magic or Tony Stark metalsmiths, it is hard to imagine a combo-spear-bow. But, what about a collapsible/multi-part bow that doubles as a backpack frame for all their gear. The arms of the bow are the long stiffeners of the frame. And the center part of the bow is the narrow part of the frame. The bow is 3 pieces -- the two bendy arms and the center rigid and inflexible grip. The bendy arms lock into the center part and the bow is ready for use. It lacks any cool factor but might keep the weight down [Answer] A literal hybrid might do the trick... a thinnish polearm bound top, bottom, and center to a simple longbow. Bound together longways, the two staves effectively form a single stick... possibly a little weak or bendy if hit just wrong, might need to be thicker to compensate, but it should work as the handle of a polearm. To use as a bow, you’d need to loose the ties at the top and bottom of the staff, and bend the bow away from the polearm shaft. I recall reading bows (some bows?) would be made so they’d curl forward when strung (curled opposite the string when at rest), a very minor opposite curve would hold the two pieces of wood together more easily and have less tension on the ties. The middle can remain bound, it’s just a grip... the polearm will be held upright parallel to and in front of the bow, so aiming will be trickier but one could also use the pole-staff as a rest to steady or figure bow height. The end ties need to be both reliable and quick to loose, might take a bit of figuring, but I think it can be done. I planned the bow around a staff, since it was simpler to imagine... attaching anything would be tricky and leave the wood weak right at the attachment point if not carefully crafted, but a spear point etc should be doable if the wood is fit together well at that point. [Answer] Yes, it can be done, but the level of craftsmanship required will make it impractical for mass production. It will have to be a specialists weapon, with the majority of each squad having conventional pole arms while one marksman carries this hybrid. Also, it will be closer to the function of a crossbow rather than a conventional bow. Tactically, that means that from a distance the marksman can fire and then reload quickly for another shot, but once close combat is engaged, there will be no opportunities for reloading. In face-to-face melee, you will only get one shot. The design of the bow portion of the weapon involves hollowing one end of the pole and turning it into a tube to hold the arrow. The bow's wings will project out perpendicularly from the tube, but will be mounted backwards such that they fold forward (towards the tip of the tube-enshrouded arrow) when the bow string is drawn. The bowstring itself will be drawn down into the tube down past the arrow's feathers and held by a hook which can be sprung crossbow style, by pulling a trigger mounted near the middle of the pole's length. The arrows will be slightly different than conventional design, having feathers running all the way up to the tip. These feathers serve the additional function of holding the arrow centered within the tube which greatly increases the weapon's accuracy when fired. When cocked and loaded, the bow wings of the pole arm bend down to meet the arrowhead. When in this position, the outer facing edge of these wings are sharpened such that the wings and arrowhead join together to form an over-sized spear point. Stabbing someone with this giant spear and then pulling the trigger would cause a sure-kill wound as the sharpened blade wings swung out in opposite directions, cutting through flesh with brutal force. ]
[Question] [ In my setting I need to have a dungeon where people cannot use guns or other gunpowder weapons. The reason can be anything: it's impossible to bring guns in, guns don't work inside the dungeon, using a gun is unsafe for the shooter, anything. I originally thought about a flammable gas being released in the dungeon. But I'm not sure if gunshots can ignite gasses in the air, and if such gasses exist that would be breathable (I want no other side effects). Is there any way a modern civilization could build such a dungeon? \\Edit- \\ more details, as requested The setting The setting is an extreme reality show. Contestants are put on an island and they try to get points that are hidden in dungeons scattered around. There are also native people on the island which can supply them with guns, which is why I don't want guns to be used inside the dungeons- the show runners want gory face-to-face combat in case two teams arrive at the same time. I don't want to get into the nature of the natives in this post, so for the sake of the question assume they have modern level technology but are easily manipulated and don't exactly have free will. I'm still not sure about the number of natives there will be, but probably the population of a small city. The dungeon The dungeon is built by an incredibly rich entertainment company for the reality show. They can be assumed to have almost unlimited resources. The technology level is like I said, near future. The company however cannot have employees physically on the island while the show is running, so the "no guns" rule should be enforced physically and not by some guard. I thought about having the natives guard the dungeons, but native guards can be bribed or killed. The dungeon should be able to last about 2 months. However maintenance visits are possible. The purpose of the dungeons are to create tense conflict between contestants if they arrive at the same time (which is likely, because teaming with others is encouraged by the rules but so are betrayals). The system should also not allow older kind of guns. Weapons inside should mostly be things like spears, knives, bows, etc'. If the system can be cheated by a smart contestant that's fine, but it shouldn't be easy. The people entering the dungeon The people who are supposed to enter the dungeon are the reality show contestants. There are 100 of them, and because of the natives, they are capable of manufacturing modern-day items. They would have time to prepare but not as much as they want, because they will try to get to the dungeon first before other contestant teams. The natives will tell them what will happen if they use guns in the dungeon, but not why. [Answer] ## Forfeit If this is a reality show, then there must be cameras (or something analogous). And it's in the interests of the show runners to get good footage of the event, so it should already be against the rules to destroy, circumvent or simply evade the cameras, because what's the point of any of it if they can't broadcast it happening? Given that, it should be possible for staff on the mainland to monitor these cameras at all times. If they see anyone using firearms, then that's an immediate disqualification. They lose all their points and are no longer eligible to win. If they wanted to make the punishment even more severe, they could take away access to any resources that the other groups have: locking out their key cards, disabling any electronic devices they've been issued, even voiding their ticket back off the island. [Answer] ### Hopefully one of these helps: * The dungeon air is 90% oxygen. Fires are catastrophically violent and explosive, and a gun will not function safely. Also, they fight harder because they get tired less quickly in the high-oxygen environment. * The dungeon is contains large quantities of a hand-waved gas that reacts badly with gunshot residue. When you fire the gun, unburned traces of propellant are expelled into the air from the barrel. These vapors react with the gas in the dungeon to create a corrosive/explosive/poisonous cloud of death that severely hurts if not kills people near the gunshot. * The dungeon is susceptible to cave-ins, which can happen if a bullet strikes the wall, or even with the noise of a gun going off. * The contestants are hunting each other, and the dungeon is very, very quiet. Guns are loud and give away your position. * Powerful magnetic fields in the dungeon pull on all metal objects, leaving them stuck to the walls. You can get ceramic knives and swords, but a gun made of anything other than metal will shatter on firing. * There's a monster in the dungeon and you don't want to make loud noises. Alternatively, he can smell gunpowder. * The cartridges available on the island are pretty cheap quality, and don't survive the damp conditions of the dungeon. * The roof of the dungeon is made of crystal spikes that are sharp and heavy enough to kill you if they land on you. Make a loud noise and you'll bring down all the ones near you. * The walls of the dungeon are part of an organic life-form with a defense mechanism. If you injure them with a stray bullet, they close in and crush everybody. * The walls of the dungeon are part of a predatory life-form that eats animals moving through it. The contestants have to keep quiet lest the floor turn into digestive juices. [Answer] Given the setting is a show and somewhat higher tech and plenty of resources can be assumed of the organisers, I'd go for a relatively dumb solution that is also based on technology: 1. All guns have trackers. The organisers are supplying the guns to the local population and they have trackers or identifiers installed in them. It could be active GPS connected and stuff or just a passive RFID chip. What is important is... 2. The dungeons also have detectors for guns. Think the devices that they put near the exits in supermarkets: [![RFID detecting gate](https://i.stack.imgur.com/dMpoA.jpg)](https://i.stack.imgur.com/dMpoA.jpg) Normally, if you walk through it with a non-deactivated/removed RFID chip on your purchases, it would start beeping. Instead take them and just inverse their function: you walk through one before you enter. If no gun is detected then the dungeon door opens. If any gun is detected, then you can't get in until you leave it outside. That's not too high tech - it's something we can do today. The biggest effort would be making sure all guns are fitted with RFID chips but given it's an island and the organisers are fairly wealthy and influential, that shouldn't be too big of a problem. This solution could be scaled to be more futuristic if you wish. If the guns have transponders with GPS in them, then the organisers can track where each gun is and maybe enable/disable some facilities. So you could have people only be able to enter some place with a gun, perhaps. An even more futuristic version could have remote controlled guns where the organisers can disable the gun (jam it, perhaps?) remotely. So people can get guns inside a dungeon, but it won't fire. Although the more high tech solutions require some sort of power drain from the tracking system, so you might have to deal with that. Yet, it can also work towards your advantage - if a gun can only fire if the tracking system is charged, then firearms are temporary. Once the batteries run out, they become useless. That's a great limited boon to toss in a game - it would motivate players to act before the time runs out, instead of hoarding the guns. [Answer] Actually, it is harder to reason why they're not use pneumatic guns Pneumatic guns are almost as deadly but do not have most of disadvangates of guns listed here (i.e. there's no fire, no toxic gas, much smaller danger of ricochet and cave-in, they can be non-metallic). I guess you will have to resort to screening. Anything looking like a barrel is not allowed. [Answer] > > Do you smell that? > > > Neither did the contestant last year who died in a fiery explosion when he lit his cigarette. > > > Coalbed methane A real danger in our world and a cause of hundreds if not thousands of deaths in coal mines, even when guns are not involved. While it is a toxic gas, it's not likely to kill you at levels at which it can explode when it meets fire or even a bigger spark from a ricocheting bullet (but yes, it technically can kill an unlucky contestant). It's also odorless and invisible. And worst of all - you don't know if it's there or not. Since it comes mostly from coal seams, it's not going to be everywhere in the dungeon and because it's lighter than air, it will always try to travel upwards through the corridors. You may pass a few hundred meters of methane-free zone just to walk into a corridor full of methane without noticing. Simply make your dungeon from an abandoned coal mine and you get a perfectly viable, real world reason not to bring a gun unless you want to kill both your opponent and yourself. Want the smart guy to abuse the rule? Bring a canary! Canaries were used by miners to detect methane and other toxic gases - because of their anatomy, the bird would die at a much lower levels of methane in air than humans. Your pocket bird died? Get the hell out of there... or prepare a fiery trap. [Answer] The dungeon is surrounded by deep vacuum or water under tremendous pressure. This can be because it is located in outer space or on the bottom of the ocean or can be the result of creative engineering. Any use of firearms within the dungeon has the potential of puncturing its walls and killing everyone inside. [Answer] # Sound restrictions ? Maybe some heavy guardians will rush to your position if a gunshot is heard, which are a lot more terrifying than the rest of the creatures? some kind of zombi-like terror, if you are too noisy everything will rush on you, because the creator of the dungeon love to read in peace. # Tradition Dungeons should be revered and getting in one is seen as a ritual. bringing a gun to the ritual is a blasphemy. # Echo Walls are just reflecting so much sound, using guns is just ear shattering and no fun. # Speed hacking detection any particle moving too quick is detected and this area of the dungeon considered defective, destroyed and regenerated automatically # Non Newtonian fluid "it's not air we are breathing, it's handwavium gas, known to stop bullet as quickly as water do" # Etc.. Guns are are pretty distinct from other weapons, so you can pretty easily distinguish them, and ban the difference with the weapons you allow. Just don't forget that it can affect other stuff sometimes, like grenade explosion if handwavium gas, or communicating with teammates if sound is restricted [Answer] Black powder These rifles can use black powder, which is composed of three ingredients - nitrate, charcoal, and sulfur. Now there are two reasons this can't work, the simple reason and the fun reason. The simple reason is that black powder doesn't fire when wet. If these dungeons are incredibly damp places, you can't fire a black powder rifle. (Specifically matchlock and flintlock - and yes, those aren't modern day rifles, but they can be made using modern techniques like rifling to make them much more effective weapons.) The more complex reason gets into chemistry. The proportions here could have as much as 30% sulfur. When black powder is discharged, it creates products - one of these being potassium sulfate. Now, I don't know any equations or found any of them out, but it's possible that the presence of potassium sulfate would react with some kind of mostly harmless gas already present in the cave to form, say, a compound like sulfur oxide. Which is a poisonous gas. [Answer] You don't need to make up a contrived premise that will lessen the verisimilitude of your story, just have it be It's illegal The island's colonial ruler nation has strict gun laws that also apply to the island. Possessing a firearm requires licensing and training, which the contestants do not have. If the show depicts firearm use it will be taken off the air and the producers of the show will suffer legal consequences, so the producers are very assiduous about keeping them out of contestants' hands. They don't have to have a physical guard on the island, they have their money on the island. The island local government has signed a lucrative contract with the production company to host the show on the island and neither they nor the natives are going to let anything jeopardize it. [Answer] Other aspects of sound have been addressed but, assuming these dungeons are enclosed areas, what about the effect of firing a gun on one's hearing? In this case, the show runners and/or natives could tell the contestants directly that guns are not advisable. [Answer] Guns are mostly made of metal. Place very strong electromagnets inside the walls of tue dungeon - the kind used in magnetic cranes. When those are on, carrying a gun will be a hazard: you may die from a gun pinning you against a wall and piercing through your flesh to get to the magnet. Wooden weapons will be safe. It is quite possible to make a spear and even a knife with only wood. You can also make tips for spears and arrows using stones. If you really want to be sadistic you can turn the dungeon into a giant induction oven. The magnets don't need to be as strong, but they must change polarity very fast, like a few hundreds or thousands of time per minute (super easy, that's how induction ovens work). Instead of pulling the guns with extreme force, the walls will cause any guns to heat up very fast. It takes a few seconds to make a piece of metal go way past 212F/100C. In both cases guns could be damaged beyond use. [Answer] 1). A specially bred species of wasps lives in many parts of the dungeon. They have the characteristic that if they smell gunpowder (or burnt gunpowder), they go to the area where it the smell came from and then viciously attack anyone in the room. 2). There is a fire detection system that will (purposely?) also detect gunshots. The doors to the room then close and lock, and the room get sprayed with lots of water. Extra fun if the room is flooded with (unbreathable) fire suppressant gas. [Answer] # Smart guns Conglomeratings, the company running the reality show isn't a stand-alone company. It's a part of a global conglomerate of companies in all types of industries. One of those industries is firearms, where Gunglomerate has effectively become a global monopoly. And since this is in the (near) future, society's reached the point where smart guns are widespread. Modern [smart guns](https://en.wikipedia.org/wiki/Smart_gun) can identify their user, such that only their rightful owner can fire them. Gunglomerate's guns, however, also have sensors which detect radio frequencies which set areas as 'off limits', where they cannot be fired. This can be powered using old-school tech like what's used in [crystal radios](https://en.wikipedia.org/wiki/Crystal_radio), which can be powered by the radio waves themselves. So all Conglomeratings needs to do is put hidden antennas within the dungeons. People will arrive in the dungeon and notice their guns don't work (maybe the guns beep to indicate this or... maybe they don't, and the players are in for a surprise!), and then all bets are off. If you're concerned about players disabling the sensors, that can be solved in two ways: * either they're too wrapped into the gun's mechanism, so that to break the sensor is to break the firing pin; * or reverse the process, so that radio waves indicate where guns *can* be fired. So the dungeons instead have radio frequency jammers (thereby disabling the guns), and to break the sensor is to disable the gun permanently. [Answer] What about if guns work just fine, but everyone on the island is just very much convinced that using guns in the dungeon is incredibly lethal to everyone involved (the user, anyone standing nearby and most likely the person shot)? To convince the contestants have natives comment on it if they see the players with a gun. Maybe someone selling supplies who has set up shop near the dungeon entrance. If they see a contestant waving a gun around they leap up in surprise and fear and drag the character around the corner and show them the crumpled and destroyed ruins of an old entrance to the dungeon. "This used to be the main way to get inside until someone went inside with a gun. We heard the explosion echoing all over the island, and since then, no more guns and only one way in. There were four of them testing themselves against the dungeon together and the only part we ever found was the gun, blackened and twisted. It's mounted on the wall above the bar in the local drinking hole in town." You could even have some kind of trap inside near the other side of the destroyed section of dungeon to explain this, for example, a room with highly flammable gas that ignites if the trap goes off. The old party fought someone in here, the gas was ignited by the gunshot and boom. Guns could be perfectly fine to use elsewhere in the dungeon, but the contestants don't know that, the company that runs the show warns contestants not to bring guns before they turn up and who's going to risk smuggling a gun on to the island just to possibly blow themselves and all their friends up. [Answer] Ammunition Constraints If you design a dungeon with hundreds or thousands of beasts, which all need to be killed, nobody would consider using firearms, because they would run out of ammo. Nobody would be able to carry thousands and thousands of rounds on their person. [Answer] ## Fear of ricochet Your dungeon is set up with many small rooms and passage ways. Any use of a gun would be in very close quarters. Even if you could be sure that your victim was not able to kick or grab you or the gun in any way, it's such a tight fit in there that all shooting would be at close range. > > Bullets are more likely to ricochet off flat, hard surfaces such as > concrete, rock or steel, but a ricochet can occur from irregular > surfaces within heterogeneous materials including soil and vegetation. ([ref](https://en.wikipedia.org/wiki/Ricochet)) > > > The walls of the dungeon are all flat and hard and very prone to ricochet. In addition, many of them are curved. > > The angle of departure, both vertically and horizontally, is difficult > to calculate or predict due to the many variables involved, not the > least of which is the deformation of the bullet caused by its impact > with the surface it strikes. Probability of ricochet is highest from > surfaces approximately parallel to the axis of bullet movement, and > grazing ricochets typically depart the surface at a smaller angle than > the angle of incidence (or approach). Probability of bullet > penetration increases as the axis of bullet movement becomes > perpendicular to the target surface; but penetration may create a > depression or crater within which the bullet may ricochet more than > once, possibly following the arc of the crater floor to depart the > crater at a greater angle from the original surface than the angle of > incidence. > > > With a curve, your angle of impact is basically impossible to calculate since you don't know where your bullet will hit (either from missing, firing a warning shot, or hitting your target and having the bullet or fragments of it hit the wall. Ricochets can hit the shooter, though this is less likely than the other options. Ricochets can hit people you've brought with you (or the jailer). Ricochets can definitely hit other prisoners too, the ones chained up or otherwise sharing the tiny dungeon rooms with your victim. ## Guns are not the right weapon for targeting individuals in close quarters shared with other people, particularly when all the walls are hard and flat and curved. [Answer] Since the dungeon is pretty high-tech, what is stopping you from having a guardian doorway? Lets say that to enter the dungeon all players/teams have to solve a riddle or puzzle, but all those who bring firearms will have to solve another puzzle. They dont know that the puzzle only appears when they bring firearms. The puzzle will request anything to make the weapons worthless. It might require them to hit a target enough times, where "enough" just means " when the last bullet is expended". Or they might have to pool all the gunpowder of their bullets to break something they otherwise couldnt break (through the pressure for example) or they might have to make a sacrifice by simply offering all their firearm weapons. Should the players come back later the puzzle is simply reset and they have to do it again. You could perhaps leave the players/teams with a few shots, say 1 shot per player/team, if that makes things more interesting. [Answer] If they're in the dungeon for two months then a major factor would be how much attention you draw from other competitors. If you have a regular sword or whatever like everyone else has- you're worth no more attention than anyone else. If however you bear a gun, something that not everyone has, you become a target; everyone wants that gun. So competitors generally decide not to take the guns because over two months they will almost certainly run out of ammunition but the attention they grab will be permanent. [Answer] The natives have given them blanks. Hee hee! The natives are confederates of the show producers. Of course they are! They sold the adventurers guns and demonstrate they work, but all the ammo given to the adventurers are blanks, with fake bullet tips. The adventurers shoot the guns and make a lot of noise but no-one gets shot. This makes for a great show. Someone thinks they are going to break the rules and be a big shot with a gun and then the gun does not hurt anyone. The person who thinks they are going to get shot cowers in fear. Then, on realizing the gun shoots blanks, they beat the bejeezus out of the shooter using the crap gun as a club. Ratings gold! [Answer] Fame With reality TV shows, there is more money to be made from the fame than the show itself. Using guns is against the rules and guns are a weapon of the weak or cowardly. It would like being on "Survivor" and having Domino's deliver pizza to you. The flamboyant and skillful fighters are the most popular and make huge money in appearance fees and interviews after the show. Gun fights in real life really aren't that TV worthy and tend to be over quickly. The producers want ratings gold and the contestants want fame and money. [Answer] The technology setting is modern and the show runners have some level of control over the natives. So, while the natives can provide guns, they can only provide guns that have a special detector built in that deactivates the gun the moment they enter a dungeon. The gun is built in such a way that it doesn't work at all without this device, so it can't simply be removed. [Answer] Since you are in the near future, just make all available guns having a radio receptor, if a specific frequency is received, the gun will simply lock and not fire. The dungeons have a radio emitter broadcasting that frequency inside, disabling all guns inside. If you want a more gory outcome, instead of disabling, the radio frequency replace what the trigger of the gun does, and activate a explosive charge instead of firing, any fools trying to use the gun would blow his hand off instead. (It also leave you a opening for a player gun-savvy enough to dismantle the gun and use the explosive charge in other way, or pushing the other team to use their guns inside the dungeon) [Answer] I am not a scientist, but there should be ways to heat specific materials with microwaves or ultra sonic waves and all these scientific stuff. So if there is a room at the entrances of the dungeon that does the following: * Produces microwaves that would make metallic surfaces spark and gunpowder to explode. * Produces sonic waves that will heat up flammable liquids such as gas (I found [this](https://books.google.nl/books?id=4QZQCwAAQBAJ&pg=PA746&lpg=PA746&dq=ignite+flammable+materials+with+sound+waves&source=bl&ots=n53Y6_NWso&sig=ACfU3U0aAsd-teeD858hvOxGL0jet9r7sA&hl=en&sa=X&ved=2ahUKEwiD0ozBvK_jAhXN16QKHeAcCZEQ6AEwAXoECAgQAQ#v=onepage&q=ignite%20flammable%20materials%20with%20sound%20waves&f=false) that seems relevant) * Releases electrical charges that would detonate plastic explosives. * Discharges all battery related stuff for things like futuristic rail guns or lasers. * Heats compressed air containers in case of air pressure weapons - [Although these ones might have been quite entertaining](http://www.imfdb.org/wiki/No_Country_for_Old_Men#Captive_Bolt_Pistol). Of course there are many ways to create a gun that doesn't need fuel to operate, like crossbows or spring operated weapons like a harpoon gun but those may add up to the fun as well. [Answer] 1. Noise Level Depending on the scale of your dungeon, a gunshot may or may not blow out your contestant's eardrums, and as such is a bad enough idea to avoid 2. Materials If your dungeon is made out of something that bullets bounce off, then the ricochet could easily hit the firer, rendering guns useless except at short range, which meets the requirements for "bloody carnage." 3. Atmosphere If the dungeon's atmosphere has volatile gas in the air, then if the concentration is between the Lower Explosive Limit and Upper Explosive Limit, then a gunshot would cause an explosion. Here's a link describing the phenomenon: <https://en.wikipedia.org/wiki/Flammability_limit> [Answer] If you want a somewhat plausible science / sci-fi resolution to the scenario that cant be circumvented in any way then i have one here; TLDR at the end: The Island is strange. Rumors have been circulating about such a place, where high technology items does not work at all. Then they found this island.. They say that if you take advanced equipment with you it.. just stops working. It breaks. Drills go hot, chainsaws melt together, old cars dont last a minute and the new fancy ones dont even start. And its not like some temporary interference. Whatever gets broken by the island stays broken once you leave. Humans and animals doesn't seem to be bothered by whatever it is. There have been a slight deviation from the norm in reports of nausea and headache from visitors, but new places often means new bugs and bacteria and excited investigation is not the best mood when it comes to remembering to hydrate properly in the heat. When the island was first discovered it triggered a minor crisis in the global politics. The news of an undiscovered island in a place where it should have been noticed made everyone wonder. The chinese had navy nearby and would surely get there before the US navy. So the US sent airforce to recon. While passing near the island two of the jet fighters fell straight out of the sky, and ofcourse the US blamed the chinese. The chinese however rescued the crashed pilots and quickly decided to invite anyone who wanted to examine the island. And many did. The effect was clearly documented, even the satellite sent for orbital photography stopped working and became a useless floating piece of space junk when it passed through the column of space extending straight above the island. Still no one is sure what causes the effect, there were many attempts to examine it but the best ideas was often stifled by the islands mysterious effect. When researches tried to use different methods to measure IN to the effect from the outside, and by that also figuring out where the edge went, the best description they could give was that "its like, on the particle level, everything inside the edge is just a bit fuzzier". Theoretical physicists have also joined the fray and their latest theories talk alot about quantum fluctuations affecting particle volume. After a while with no certain answers and research going slowly the island falls in the shadow of other news that are making their way through the newsitem lifecycle. Thats when the entertainment company sees the value in the isolated island. As everyone got access quickly and no nation could see any military value in an island where you couldnt even store supplies without risking them becoming worthless, no nation actually claimed the island. No laws apply. This made it perfect for them to set up their new extreme gameshow. Using a different combinations of high res cameras flying in circles outside the boundaries, mechanically triggered mirrors and some flintstone-tech level cameras for the hidden corners they have set up a perfect rig for viewing the action. In the trailer a mean looking man with an air of military training about him describes how the island works. -"Stuff dont fit. It affects everything. Your favorite lighter might become impossible to close, or open. When our crew tried setting up a diesel generator the friction almost made it catch fire. The troops that got stationed on the island when it was newly discovered quickly learned that guns wasn't worth anything either. After two or three attempts at target practice they realized that the bullets wouldn't go through the barrel anymore, but the force that propels the bullet have to end up somewhere so you have to be lucky to not get hurt while firing in a scenario like that." The military man looks at someone off-screen and nods -"Sir, Does it have any effect on people?" Still looking at whoever spoke offscreen "well no documented dangers or anything like that. But one of my men is careful about his oral hygiene though, you know flossing and that kind of stuff. He keeps complaining that since we got here he cant get the damn floss in between his teeth" the man says with a chuckle. Then he turns more serious again and looks at the camera. "I'd tell you one effect it would have on people though. If anyone decided to war it out on this island they would be stuck without guns, tech or support from intel. We are talking close quarters combat with meele weapons. It would be back to the medival days. Whoever that wanted to fight for this place and have a chance to win, would have to become Savages" TLDR; The area that includes the Island somehow changes tolerance levels of the roomspace itself, as if the smallest thing in the universe suddenly is a little bigger and everything that depends on it now becomes sliightly different, just enough to mess up anything with fine tolerances. [Answer] ## Underwater and lot of small gas filled rooms Make substantial parts of the dungeon underwater (so gun range is just few meters and there is risk of destroing the gun) and diving equipment extremely cheap and easily obtainable. (Sponsored by company, diving equipement may be at price of longer kitchen knife maybe and stored by volumes in all native vilages.) Then you can fill the rest of the dungeon with explosive mixture of gases, so shooting inside the dungeon means the room, where you are and few around just explode and if that does not kill you, it would damage your diving equipement and you have only small chance to get away alive at all. Not saying, that the gas CAN be poisionous/unhelthy/unbrethable - you have diving equipement so no problem with that under normal conditions. It would make harpune, spear or trident much better weapon, than a gun - better range underwater, safe to use anywhere, much more interesting fights. Also diving equipement affect the fighters in many ways - limited field of vision, heavy bombs with air, harder to fight efectively (so usual fight would last longer and be more attractive), alternative targets for fighters - you break his mask, rip his pipes from their place or something like that and run away - he now have other problems to solve, just to stay alive long enought to take and use spare equipement or somehow fix what is broken most. Again bonus for dungeonmaster, as short fatal fight is nice, but short and eliminate victim forever. Slower more tactical fight, where you can make damage, which can be fixed at cost of time and material and leave enemy to his problem just to meet him on next floor again is better. And you do not want to fight to his death so much, as he is still able figt some time and make substantial damage to you - disable his ability to move fast and then retreat is better strategy, as if you can get to `dungeon token` before him and then leave, you had won this round. Ofcourse if you can kill him in first attack, it is even better. But if you do not manage it fast, but you damege his equipement, it gives you big advatage, if you run away and search your profit rather, than his death (at risk, that you will die too). Equipement being valuable target also offers much wider range of usefull weapons, like chains, tridents, spiked poles or many others, which are usually seen only in fantasy, anime or cheep kung-fu films. [Answer] Just make like reality and have guns be really loud like they are in reality. In indoor ranges, ear protection is very crucial even when everyone only uses pistol calibers of .45 or below precisely because of the loudness. Have your contestants require hearing to compete and give them no ear protection or make it impractical to use ear protection. Maybe there are invisible creatures that give off a quiet, low tone that triggers [active noise control](https://en.wikipedia.org/wiki/Active_noise_control) in active ear protection and gets blocked by regular earplugs. Or just have the natives refuse to make anything with active noise control altogether and have that be the thing that tips the protagonists off against using firearms. ]

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