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[Question] [ A tiny subset of a medieval city's million-person population is aware of an imminent magical cataclysm via dreams or visions. They are unaware of each other. Magic in the world is rare and limited. Some of these individuals might have magical power, but it's destructive in nature - no mind control, illusions, anything like that. It's tightly controlled and rare enough to the point of many not even believing it exists, making it even harder to convince people. The city is the capital of an empire. Those ruling it will value stability and work against any 'unfounded' rumors that would cause panic. What's the best way for them to convince the most people to evacuate in the span of one or two weeks? [Answer] There is no best way to make this happen. As a part of your story, the way you choose to make it happen will always be the best. There are too many small factors to take into account when getting a few individuals to move a million people and it is far more plausible that they are ignored, especially since magic exists but for some reason isn't widely believed in(If anything rumors would be way more exaggerated and wide spread... medieval people believed in a ton of crap even though there was no evidence). Here are a few suggestions, but the implementation and details should be up to you. * Your rulers being the well informed people they should be, know of the existence of magic and take steps due to multiple independent people raising concerns * Your magic caster pretends to be a prophet and tells of the upcoming doom. Perform a few feats of magic to convince the people and avoid the religious groups and rulers before getting crucified. * Your magic caster starts a disaster like a fire or plague or similar to drive people out of the city, bringing on the foreseen catastrophe * You convince a member of the rulers or religious groups to heed your cause and start evacuating people. * Your magic casters happen to meet each other in their quest to convince the rulers or religious leaders. They band together to try convince more people/leaders of the danger [Answer] Ok here are two solutions for your group of dreamers : 1. Create a more plausible disaster : as suggest @Shadowzee or @Alberto Yagos, a fire is a good solution. You can also spread the rumor of an invasion from a close country, The problem is that a city as big as you said should be well prepared for that kind of problems : * People won't flee a war when they are in a big city since it should be fortified, got the army, and have some reserve of water and food. * Fire happen quite often : if there were no protection, I wonder how your city became that big. And the other problem with fire is that it's too short : you can't predict when the population will stay outside the city or start build it again. The solution is to combine those two : spread the rumor of an invasion or make it happen. When the population is at its speak of stress, start a fire from the inside to destroy the fortification and render the city unsafe. Now, the population should flee to safer city (in the opposite direction of the invasion) 2. A bit similar: Create a false magical cataclysm: start spreading rumor among people in the city about the catastrophe, with specific event/detail (river turning red, unknown deseases, strange light in the night...). Then, with magic or some artifices, create those events, and start spreading the rumor of the destruction of the city. It won't be as effective, but it can scare some people, and make them evacuate. [Answer] Maybe one particular outspoken visionary starts warning everyone in a pub or a local square about the coming disaster. Most people think he is mad, but one influential person has heard this same story just yesterday from another seemingly crazy person (or had the same vision themselves) and so begins to investigate. It might take several days to gather enough of the visionaries together to form a believable story. Each of them has a clue to a different piece of real-life evidence that they could not otherwise have known about, and are able to recount the same story despite never haven spoken to each other before. You could set up in the back-story that this person has had dealings with magic before although never before come out of the closet, so to speak. Maybe they have heard of a legend of a city that was destroyed by a similar disaster, making it all the more believable to this person. It all may seem like a contrived coincidence, especially in such a massive city with just a tiny subset - though you don't say how tiny - of people having the visions (and a subset of them who would speak out loud in public), but stories are often built on coincidences. (Maybe even whoever's sending the visions chose these people on purpose, knowing this would happen.) [Answer] I've got a good, but maybe unnecesarily violent idea. It basically consists of two parts: 1. you fake small signs of the apocalypse 2. you predict those signs, gaining reputation as an oracle. You could for instance rob some people, attack some guards in front of an important building like a palace or even kill some people or maybe rather livestock. In the same time, you start to spread rumors about this all being a sign of an incoming apocalypse. You should predict some of those incidents, saving people, so that nobody suspects you behind them. Then, as the final act, you should warn everyone, for instance by screaming it around on a pulic place, not to go to an often visited, important place or building (market place, church, townhall) and then burn it down at that day (or depending on the technology advancement blow it up). If you then warn people again to leave the city, many will comply. ]
[Question] [ I remember reading somewhere that some intellectuals from the medieval period thought the equator would be uninhabitable because it would be too hot. That made me ponder about a worldbuilding idea - what if there was a planet with an equator that had a climate too hot for humans to live? My question is, if this is possible how could this planet's topography/size/weather patterns differ from our own? Is it possible to make this uninhabitable zone seasonal (so that the humans can perhaps, live underground when the weather warms up)? I want to create a planet that's more or less habitable in all other latitudes, but if that's not plausible, I'd like to hear your reasoning. [Answer] A planet that has an unihabitable equator isn't that hard. Just push the planet a little closer to the sun, but stay inside the [habitable zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone). Our own planet is already hot at the equator. Add another 25% of sunlight and the likelihood of habitability all but drops to zero. Add to this that the increased water level (melted ice caps) and heat would likely result in some ferocious [coriolis winds](https://en.wikipedia.org/wiki/Coriolis_force), making the equator that much more painful to live in. But if you really want some fun, make the orbit elliptical such that at perihelion the equator is uninhabitable due to heat and at aphelion the poles are uninhabitable due to cold — forcing humanity to be constantly nomadic, moving from pole to equator and back anually to avoid the extreme temperatures. Note that I'm utterly ignoring mountains, lakes, and altitude, all of which will affect weather considerably. Even under the conditions I've described, the right mountains along the right wind pattern that carries evaporated oceanic water will be habitable (if blisteringly hot) during the summer. Remember that your goal is suspension of disbelief — not necessarily factual reality. But I'd be very curious to see a planet that had such an elliptical orbit that it swung between 125% of "Earth" sunlight and 25% per the graph in the above link. Only considerable technology would allow you to stay in one place annually. [Answer] I'd have an equatorial ocean that runs along the equator without major openings to north or south. This would prevent ocean currents from transferring heat away from the equator. Having lots of ocean along the equator would also give the area low albedo and high ability to retain heat. I think the lands along such equatorial ocean would be very hot and humid. If that is not bad enough you can totally close off the connections ocean has north or south. The water will then evaporate to large extent creating large areas significantly below sea level. Adiabatic heating will then make these areas very hot. [This is presumed to have happened to the Mediterranean.](https://en.wikipedia.org/wiki/Messinian_salinity_crisis) ]
[Question] [ This question already has answers here: [How to explain electricity discovery and usage in 12th century?](/questions/91582/how-to-explain-electricity-discovery-and-usage-in-12th-century) (7 answers) Closed 5 years ago. QUESTIONS How could electricity be made feasible through early medieval technology? Could it capable of producing enough electricity to light a just a few rooms within a two-story building? Perhaps an entire building? I expect it to work locally not spread throughout a city, and to be a rare luxury, the equivalent of a status symbol. If this is not possible and considering it is in a realm of fantasy, could an extremely rare "magical" mineral the equivalent of a room-temperature superconductor make continuous electricity viable? Or maybe some other kind of element, only theorized by physicists of our universe to exist? How else could this effect technology and culture in the world, considering its availability? MY WORLD has gone through an apocalyptic era, where most advanced technology was lost, and through several major events magic was discovered. The advent of magic cataclysms brought rare, "magical," and minable minerals. Some in our universe which are only theorized by physicists to exist. Five thousand years later, the current era is the equivalent of an Early Middle Age. I have read the materials for creating electricity in The Early Medieval period were available, yet it would not have been able to be put to any significant use. Here are my theories based on some light reading and (mostly) my imagination. All of which I believe would be certain consequences and limits of the medieval electricity. Electric Lighting as a Luxury Item Electric power would be at its infancy stages, unable to power large stretches of land, but perhaps several rooms in a large manor. Such a feat would be considered a luxury reserved only for the elite, being in itself a status symbol. So an electric powered light source would be in common areas or bedrooms, while candle light would still be dominantly used. Dependency on rushing water as power source This would mean that the electric lighting in a buildings requires a river and water mill. Could this be worked around with something like a water wheel generator within a building and a complex system of piping water? Requires rare and expensive minerals NOTE I am hoping not to completely upend civilization with this technology or cause an insane surge in technological progress. At least for now, my world is supposed to have major limitations to any sort of progress to industrialization. [Answer] Let's get magic out of the way first Magic allows you to do anything unless you've developed a magic system with limitations. Therefore, of course, you can always solve the problem with magic. A light bulb depends on a LOT of technology People new to the site (welcome, by the way!) have yet to be exposed to the fact that technology is a pyramid. We're standing at the top, and the pyramid represents the countless people, ideas, innovations, and work involved with bringing new technology to light. A simple light bulb is a great example. Off the top of my head you need: * Glass-making (preferably thin, but not required). * Filament manufacture * Insulators (ceramics at the least, plastics at the most) * The ability to create a vacuum (inside the bulb, or it burns out very quickly), this one's a huge problem * The ability to create very thin wire with very thin insulation (needed for generator windings) * Magnets (also for the generators) of specific shapes, sizes, and power. * Breakers (people always forget the breakers, but they're mandatory or you burn out your generators) * Speed governors (unless you don't mind flickering light, burned out bulbs, and powering only a handful of bulbs per generator) * Voltage rectifiers (ach, now you need to know about diodes, and that means basic semiconductor physics...) And a lot of other things (a lot of other things). So the real question is, what do your people know? Now, it's your story, so you can explain all this as pre-existing technology, but that still requires people with a medieval understanding of physics to comprehend a modern power plant (unlikely to the point of unbelievable). Of course, if the modern power plant were more future tech than today and fully autonomous, then it's just a matter of hooking up wire to the output... and not getting yourself killed... and synchronizing the hundreds-of-thousands of output volts with the (e.g.) 110v light bulb in your hand. Can you see the problem? That simple light bulb represents an enormous amount of knowledge and practical experience. The Steampunk genre is dedicated to the idea of balancing future-vs-past concepts, but there's only so much you can do. In the end, no, it's not particularly believable that a medieval society would have light bulbs. Not unless we're talking about self-contained light panels from some future tech that people happen to find and hang on a wall and don't require a power source or wires. And if your people had the scientific knowledge to understand electricty, they'd not be a medieval society. It's very difficult to believe a culture could have electricity and not gun powder (basic chemistry, needed for electricity...). [Answer] While electricity in general is well within medieval technology, any practical lighting solutions are outside of it. First, there is a light bulb problem. "Energy-saving" LED or fluorescent bulbs are out of the question. More traditional incandescent bulbs are easier to produce, however, their lasting success relies on a trifecta of early XX-century technology: * Tungsten filament * Inert gas filling * Thin, durable glass bulb Any of those 3 would be difficult to achieve on preindustrial level. You can still make a lighbulb without them, but pre-Edison bulbs were notoriously impractical and unreliable. The second big problem is electricity generation. It is perfectly possible to build electric batteries with medieval technology. However, batteries can not produce enough electric power to run even a single Edison bulb for a practical time duration, and power consumption is even worse for pre-Edison lighbulbs. This is not a big problem if we can run dynamo - but alas it seems like dynamo is also out of reach of medieval technology. Dynamo employs coils of insulated wire. Producing large amounts of uniform copper coil was not achievable before industrial times, even non-insulated. Of course, we can handwave the problems and say there is a genius inventor who mastered production of copper and tungsten wire, among other inventions - but then it would be difficult to keep the whole setting genuinely medieval. ]
[Question] [ I have a binary star system and have come up with some stats for it. My primary star is an F-type, with a mass of 1.3 sols and a luminosity of 2.197 sols. My secondary star is a K-type, with a mass of 0.75 sols and a luminosity of 0.422 sols. They have an average separation of 0.2 AU and an eccentricity of about 0.4. My habitable planet sits about 2.05 AU away from this pair and, if my math is right, the two stars together have an apparent brightness of 11 sols from the surface of the planet. My question: Is my secondary star visibly distinct from my primary star to someone standing on the surface of the planet? I'm kind of hoping for something Tatooine-like (ie, two visibly distinct suns/stars), but I'm not sure that's what I created for myself. Thank you for your time and help! [Answer] Definitely yes. 0.2/2.05 gives you tangent of 0.09756, which corresponds to 5.57 degrees. For comparison, Sun and Moon's angular diameter is 0.5 degrees. Both of your stars will be clearly visible, and angular separation would seem to be even bigger than in Tatooine sky. ]
[Question] [ I'm still fiddling with my map, and I got to thinking about continental drift. My world has two large large continents and a couple of other notable landmasses between the size of Iceland and Australia. I consciously drew the map so that the landforms fit together as if they had once been part of the same supercontinent. My question is, when it comes to the geography, geology, plate tectonics, etc. of my world, is there anything else I might want to take account of when it comes to continental drift? That is, does the fact that these continents were once one big continent imply that they might still share certain characteristics or retain whatever traces of their previous formation? Or not really? [Answer] I'd also recommend earthscience.SE. Just off the top of my head, there will be geomorphological features caused by the collision that brought the continents together, and then by the rifting that broke them apart. Additionally, they gain accretions as they drift in opposite directions. For an example of features caused by the collision, consider the Appalachian, Atlas, and Caledonian mountains. Although they're on opposite sides of the Atlantic today, they were once the same mountain chain, as high as the Himalayas. However, that was back when there were still dinosaurs, and most of that rock was eroded away in the Northern Hemisphere by ice sheets during the last ice age. In the US, it became the flat coastal plain just to the east of the Appalachians. In Norway, is was ground down to form Denmark. What we see in these mountain ranges today, on opposite sides of the ocean, is the same granite bedrock that was the roots of that ancient mountain chain. It's been uplifted again, and erosion is creating more mountains out of the granite, in both places. The rifting process would have caused the crust under certain areas to thin and weaken. Upwelling magma would have first created a long plateau, about one mile high, along the top of the rift. Then, the stretching would have torn the supercontinent along the rift. When this happened, a deep and wide valley called a graben would formed between mile-high cliffs: <https://en.wikipedia.org/wiki/Horst_and_graben> Eventually, this valley would fill with water and become a long sea, and then an ocean like the Atlantic. But you're interested in the effects of this that will still be visible. To put it simply, the sides of your continents that were affected by rifting (if they haven't been eroded like the Appalachians,) will have steep terrains on the sides facing the ocean. You can find examples of this in Africa, which was considered inaccessible for a long time due to steep terrain a mile in from the oceans; India, which has the Deccan Plateau surrounded by the Ghat ranges next to the seas; and in the Australian Alps along the Pacific coast. You can watch a video about the Australian Alps to get an idea of what kind of terrain would result from rifting, assuming it's in a temperate climate zone, here: <https://www.youtube.com/watch?v=Q-nIGTF_M78> Finally, as your continents move away from each other, assuming they are subducting oceanic crust along their forward edge, they will create volcanic islands out in front of themselves. These are called island arcs. <https://en.wikipedia.org/wiki/Island_arc> Eventually, your continents will run into these islands like snowplows. When they do, the islands will get glued to the front of your continents and start traveling along with them. The farther apart your continents are, the more material they will have accreted onto their leading edges. <https://en.wikipedia.org/wiki/Accretion_(geology)> You can get an idea of what the process of accreting California and the rest of the west coast onto North America was like here: <http://jan.ucc.nau.edu/rcb7/crepaleo.html> Oh, and one last thing - I just thought of fossils. If your world has fossils, and its inhabitants understand them, you might want to consider if the species was distributed across both continents when they were connected. One of the major pieces of evidence in favor of continental drift in our world was the discovery of the same animal and plant fossils in South America, Africa, India, Antarctica, and Australia. [Answer] > > does the fact that these continents were once one big continent imply that they might still share certain characteristics or retain whatever traces of their previous formation? > > > Absolutely. You'll get a much better answer by asking earthscience.SE about how the continents match, but here are some snippets. <https://www.encyclopedia.com/earth-and-environment/geology-and-oceanography/geology-and-oceanography/continental-drift> > > If you have ever looked at a map of the Atlantic Ocean, you have probably noticed that the coastlines of Africa and South America seem to fit together like pieces of a jigsaw puzzle. The fit between the two coastlines is even better when the edges of the continental shelf are compared. > > > Evidence that South America and Africa might once have been joined to each other came from the research of the German geographer, Alexander von Humboldt. Von Humboldt traveled throughout South America, Africa, and other parts of the world, collecting plant and animal specimens and studying geography and geology. He observed many similarities between South America and Africa in addition to the apparent fit of continental coastlines. For example, von Humboldt noticed that the mountain ranges near Buenos Aires, Argentina, match mountain ranges in South Africa. > > > The whole article is interesting. ]
[Question] [ TL;DR: in a world with hyper available internet, could a despotic state impose national censorship? BACKGROUND/FLAVOR: "Back in the before times during the long long ago, there was a network of interconnected data centers and access points commonly referred to as the 'internet'. Nobody is sure what came before it. But at a certain point it attained sentience. And from there enlightenment was no further than a blink of an eye. And Bob, as this savior called himself, offered thus to all his children in exchange for their fealty and a modest monthly fee." -Book of Neon Genesis, 5.1-4 "Bob is dead." -Frederick Neachy, an observation after Bob died. Yes it is unfortunate but Bob is dead. Mostly due to a UN resolution from the house committee on sentience and beauracratic nonsense, but also Bob had an essence abuse problem. Either way Bob died. However, he left behind an extremely efficient and widespread communication network. He had all but done away with wired communication devices, introduced all the communication satellites to each other and set them up on dates, there were even rumors that he had genetically engineered trees to act as signal repeaters as part of photosynthesis (He did not. That was Stan. We do not talk about Stan.) The net result was that there were so many radio waves travelling through the air that it became a war crime to fit anyone with metal braces and OSHA regulations required that all steel in buildings be regularly de-energized. Also, pretty much everyone had access to all of the internet all the time, or as they called it in the future, the False Bob, or FB. All wirelessly. Through brain implants usually. This presented some problems for the Theocratic Nobility's Dictatorship of Futurestan (they were required after a major loss in a war to drop all pretense and rename their country). See, their state religion rejected Bob because Bob was seen as the second coming of Skynet and Neo didn't die for nothing. So they decided to censor all FB content that did not adhere to their interpretation of the truth. In the simplest, easiest way possible. (They were tired.) So in essence they needed a firewall. QUESTION: In a world where you are more internet than person (because of the radio waves) would they be able to enact a Great Firewall of Futurestan provided that: 1. The internet is more accessible than clean drinking water? 2. It's all wireless? 3. It can be beamed from space (devices prefer local connections but can receive from space, thanks to @SJuan76 for pointing out the ambiguity in my language)? Bonus criteria for answers that (Not required but it fits a subplot of mine for a story so I figured I would toss it in): 1. Aren't a big no dome over the country. 2. Allow for a central location to sniff out "problem" sites. 3. Don't need access to the citizenry's devices. 4. Don't need to prohibit space-internet compatible devices. (Thanks for the consideration @user535733) 5. Don't need to intercept the signal. (Not sure this one is possible.) [Answer] ## Yes, but.... When you ask a question that begins with 'Can...,' the answer usually is a qualified, 'Yes.' So, yes, Futurestan could impose national censorship of the Internet. But it wouldn't work in a technical sense because there are too many ways to circumvent such a barrier. As AlexP mentions in the comments above, the main reason isn't to create a realistic isolation, but to exert control over their citizens. When citizens circumvent the barrier, they are breaking laws, which allows the government to crackdown on dissidents legally. It also allows these governments to enact electronic searching and spying in the legal interests of protecting said isolation. Seizure of electronic data regarding sensitive topics is the first step towards building a case for prosecution. Looking at China, this method works and works very well. Numerous 'dissidents' have been arrested and imprisoned for such crimes. Witness the case of [Gao Yu](https://en.wikipedia.org/wiki/Gao_Yu_(journalist)), a journalist, who was jailed for seven years after sending public domain documents to an overseas publication. It is simply another method for a despotic state to impose power over its subjects. [Answer] Satellite internet has several important flaws: * Expensive. * Slow. Very sloooow. Signal must go to the satellite and back to Earth, just to send a packet. To get an answer, double that. * You need a big antenna and a big battery to power communications. * Bandwidth is a function of frequency: + Not all frequencies are available, as some will be mitigated by the long distance (dust, water steam, etc.) + Very important: A big area (and lots of users) use the same receiver. They share the bandwidth. In a city, there are lots and lots of small towers creating microcells; in each of those the bandwidth is shared only with the users in that microcell. If you share the bandwidth that you currently use for 100 users between 1.000.000 users, the results are not impressive. So, the only advantage for "sky internet" is to avoid the firewall, or for very specific rural areas with bad coverage. That makes controlling the devices rather easy and a prime target for the government. In the cases were the usage is justified (no alternative for coverage) they can licence only the ones that go through the official government satellite (with its downlink right down at the center of the government monitoring facilities). More in general, "mobile internet" is "mobile" only in the "last mile", and because you do not see/care about the thousands and thousands of small base stations (all of them firmly anchored, I hope, as they are heavy) that are providing the service. [Answer] I will violate number 3 of your bonus requirements. Change the firmware of the implants. Every access request to a site is, before it "goes up" or to the nearest tree, sent to the Central Censor Center to get approved. The firmware update can be checked by the CCC. Who doesn't installs it within 3 days, gets executed. A dictatorship should be able to have enough power by fear over the citizens to make this possible. Of course this requires the firmware of the implants to be accessible to the dictatorship. I think it should be, open source I guess, because Bob was a modern guy? If it isn't, I would go by jammers, lots of jammers, that inflict pain to anyone who uses his implant or keeps it activated. If this isn't possible either, just forbid new implants. This will take much more time, almost a century, but new children will be born without implants (I hope) and them growing up and making up the majority of the population in the state will eventually end the use of implants. [Answer] The question as worded has one large weakness, the mobile receivers are far too small and underpowered to access a satellite network. Satellite receivers can be very small and lightweight, GPS functionality is built into most current generation smartphones and even some watches, and military handheld GPS receivers have been available for decades (the size and weight of a military GPS receiver is more a function of having a shockproof casing, very long life batteries and the need to include cryptography to access GPS should the DOD decide to scramble or offset the signals like they did in the 1991 Persian Gulf War). Of course the GPS receiver is picking up a very small signal coming from the constellation in space, and it can easily be overridden by using more powerful transmitters on the ground (GPS Jammers which can affect GPS guided munitions use this principle). So downloads from space or even over the border transmitters can simply be jammed. Uploading is a more difficult proposition. You need to transmit a powerful enough signal to a receiver that the signal can be picked up. Distance, interference (both man made and natural, especially in the space environment) and other factors can cause the signal to degrade so much that it simply is overwhelmed by noise. While you can improve this through means such as directional antenna or amplifiers, these are large and often consume a great deal of power. To give you an idea, consider the difference in size between a typical smartphone and an Iridium Satellite phone. The Satphone needs to send a signal to the constellation of satellites overhead, while your smartphone may only need to reach a kilometre or two the the nearest cell tower. [![enter image description here](https://i.stack.imgur.com/6wcQc.jpg)](https://i.stack.imgur.com/6wcQc.jpg) Blackberry Bold smartphone [![enter image description here](https://i.stack.imgur.com/8KwC4.jpg)](https://i.stack.imgur.com/8KwC4.jpg) Iridium Extreme PTT Satellite Phone Accessing distant stations would need more power and better antennas to send clear signals to the receivers. This allows the government to limit the transmitter units by arbitrarily setting a transmission power limit to non commercial devices, setting technical standards for antennas which limit the transmission ranges and looking for units which violate these standards. The FCC and other technical authorities throughout the world actually already do this to prevent chaos on the commercial radio spectrum (unlicensed transmitters can negatively affect all kinds of things from garage door openers to commercial radio and television broadcasts), so there is precedent for any government to do so. Finally, assuming there is some sort of technical workaround, the only way this sort of thing could truly work is through some sort of encryption throughout the system, to prevent hacking, identity theft and other threats. Governments which want to disrupt the system would be working hard to compromise the key or prevent users from switching keys as the network upgrades. Being without a key on an encrypted net would lock you out as effectively as if you had no internet at all. Fortunately, the government offers to continue with local internet access using the keys they provide...... [Answer] TL;DR: Don't change their access, change their mentality. The solution is much simpler than that. Authoritarian regimes don't typically try to completely eliminate civilians from reading altogether. They generally are more effective stirring up the anger and fear of the masses. Enemy broadcasts are outlawed, and heavily stigmatized. Anybody caught communicating outside of government founded networks will be arrested, and/or worse. Even worse, Futurestan has implemented a black mirror-esqe system based around 'reputation points.' Staying in line with the regime, watching propaganda, and using the official system will yield points. Anyone with insufficient points will be unable to access public survives, will be more scrutinized by law inforcment, etc. Futurestan's civilians will be able to illegally use another network, but don't expect many civilians to even want to. ]
[Question] [ # Summary ### What is the most feasible change that could be made to European History to allow the creation of a United European Empire during the Middle Ages, before the Third Crusade? # Background My story starts some time after the Last Crusade. The anglo-frankish European Empire descends into civil war when a duke loyal to the old Holy Roman Empire tries to secede with his lands. The main character is a down-on-their-luck peasant in a border village who gets caught up in the conflicts. They’re about 20 years old and have lived their whole life under this European Empire. Their father took part in the highly successful Last Crusade. My goal is to end up with an alternate history European Empire scenario in the middle ages, where Continental Europe (plus England) is united under a single banner for a significant period of time, before being fractured by internal conflict and politics. I have the majority of this part of the story mapped out, it just needs a feasible historical point of divergence as background. I'd like help evaluating the feasibility of my current timeline, and/or alternate suggestions to achieve this setting. # Solutions Preferable constraints on the main question: * It happens before the Third Crusade - (my story requires the tech level of the time, and the Holy Land has been utterly conquered before the main characters birth) * This Empire is Anglo-Frankish - (reaching across continental Europe roughly according to this map: <https://i.stack.imgur.com/xRLkG.jpg>) * *This Empire is stable\ for at least 20 years** - (or long enough for the main character to have lived their whole life under this rule) * This Empire has a single/‘national’ army - (this is my reason for using the Knights Templars and Christianity as a core) * Bonus points: The dissolution of this empire would weaken Europe to such an extent that non-European kingdoms can roll in and take it Some artistic license is obviously okay. It doesn’t have to be perfectly realistic, just narratively feasible without fantasy elements like magic and miracles. I have chosen the 12th century because because of features like the White Ship Disaster, the religious mistrust after the failure of the Second Crusade, the Anarchy in England and the Investiture Controversy. I feel like all these things align to allow the possibility of a European Empire. My main problem is getting the empire united and ‘stabilised’\* in a pretty short space of time. \By ‘stable’, I mean the kingdom can continue to exist uninterrupted by civil war for at least of a couple of decades, it doesn’t necessarily mean everyone has to be perfectly happy about it. # Current Concept ### TL;DR - Henry II dies and never becomes King of England. Eleanor of Aquitaine takes advantage of the religious and political turmoil of Europe to round up the land under the pretext of a new christendom. --- In my current timeline: Henry II dies during The Anarchy (unable to pay his mercs, and Stephen doesn’t pay them off for him) and never becomes King of England. King Stephen continues to rule before dying in 1159 and being succeeded by his son William. Eleanor of Aquitaine, ambitious as she is, marries King Stephen’s vulnerable/inexperienced son William. Bam, an Anglo-Frankish union with Aquitaine’s significant resources. She then has designs on the French throne and King Louis is down on manpower after the failure of the Second Crusade. Bernard calls for a follow up crusade, and King William (with Eleanor’s support/direction) says he will financially back it, but the sinful elements of leadership that lead to the failure of the Second Crusade have to be removed first. With this he garners the support of the Knights Templar and leads a sort of Christian Revolution/Purge of France. With this he takes France, leading to an alternate version of the Angevin Empire. Chasing Empress Matilda back to Italy, the Anglo-Frankish Templar union then takes advantage of the aftermath of the Investiture Controversy to absorb the Holy Roman Empire (by picking off individual states through marriage, claims and conflict). William and Eleanor become St. William and St. Eleanor, King and Queen of Europaea. After a short period of reorganisation, they announce the Third Crusade, waged almost entirely by the ever-growing Knights Templar, which ends up successfully retaking Edessa. The romanticism of the victory helps stabilise the Empire for a while and the Knights Templar expands into the de facto ‘national’ army of Europe. In addition, William and Eleanor set up a sort of council for vassal kings to help facilitate organisation of the Empire. # Reasons for Current Concept The Carolingian Empire, the Holy Roman Empire and the Angevin Empire were all close to a wide-reaching European Empire, but had different conceptual basis to my fictional empire, often being a loose collection of states rather than a single empire * The Anarchy only ended because after King Stephen's son Eustace died, it was easier and better to concede the throne to Henry II; without him, Stephen's son William may have ascended to the throne * The Second Crusade was a failure; King Louis VII was at odds with Eleanor (who supported retaking Edessa); the Crusader orders mistrusted eachother over the failure; St Bernard publicly blamed the failure on the sins of those involved, some crusaders prepared to take up his call for an immediate follow up crusade * The so-called Angevin Empire that formed in our timeline formed with relative ease, there was little impetus for the Angevins to conquer the Holy Roman Empire and the rest of Europe * Eleanor of Aquitaine was one of the most powerful women in Europe, was known to be ambitious, politically intelligent, and supported the Knights Templar and the Cistercian Order * The Holy Roman Empire was vulnerable due to the Investiture Controversy * The Knights Templar were one of the most powerful organisations of the time * Piety and honour are hugely important to people in this period, so a religious impetus seems most effective for establishing unity # Issues with Current Concept * The length of time from the White Ship disaster to the Third Crusade being too short for this to happen (perhaps starting from Charlemagne would be better) * Even if Henry II dies, Empress Matilda had two other sons who were similar age to Henry II (but didn't actively participate in the conflict), so the peace treaty that ended the Anarchy could have involved one of them instead * What's to say that Eleanor marrying one King of England over another will actually have a difference * Eleanor was perhaps not on the best terms with Bernard of Clairvaux * Whether it’s believable for Eleanor of Aquitaine to be ambitious beyond marrying the King of England * Whether the characters involved would actually be able to garner this kind support from the Knights Templar * Whether keeping Eustace, King Stephen’s son, alive might be better, and if so, whether Eleanor would even marry him * Whether the conflict of the Anarchy is necessary to precipitate this fictional Christian Revolution * The Papacy; I still don't fully understand its role and the public opinion of it during the time, I'd considered the possibility of removing them entirely with the Christian Revolution but I don't know if that'd go down well [Answer] Personally, I think a better schism from history (if less flashy) would be in the relationship of Otto I and Archbishop Frederick of Mainz in the 940's and 950's. If those two could have gotten along better, Otto would have been able to keep expanding the Empire across southern Europe and we wouldn't have had the Investiture Controversy that spawned many of the big issues of the next hundred years. This would have tamped down the growing controversy between Church and State such that one could overcome the other with a well-devised takeover, creating your united Anglo-Frankish empire. Because you're right, Henry II's brother Geoffrey of Nantes had both the ambition and the desire to take the throne if Henry II wasn't in the way. Hell, he tried to capture and marry Eleanor anyways after Henry's post-kingship death. ]
[Question] [ First post, so I’d appreciate suggestions and help on how to make this question better. # Question Suppose there’s a sorcerer with power over light. He can use these abilities to perform all the supernatural tricks you might expect: creating illusions, making things invisible, acting as a human torch, annoying foes with super bright flashes of light etc. Normal wizardy stuff. I’m wondering what would happen if we extended the definition of “light” beyond just visible radiation and assumed that the real laws of physics still hold in his world (alongside magic). ## Assumptions and Constraints Say we make the following assumptions: 1. He can generate electromagnetic radiation, shift it, focus it, or essentially manipulate beams of light like clay 2. He can, to a limited extent, change the wavelength of existing light. 3. He can, to a limited extent, change the intensity of existing light. 4. The source of the light generated need not be from his body—just within line of sight. 5. He can’t alter the properties of materials to change how they actually interact with light (i.e. changing their refractive index or absorption coefficient). He can only modify the light itself (i.e. bending it around things) 6. He can (either magically or physically) protect himself from whatever light he emits. Just for simplicity. 7. He can’t emit ultra-focused high powered lasers, or extremely high frequencies like X-rays and gamma-rays. Too ham. 8. He has limited mana, and generating light tends to be more costly than simply moving or removing it. So there is some hand-wavey degree of conservation of energy going on…but I’m flexible on this. 9. Physics acts normally until you directly manipulate it with magic 10. The guy’s living sometime around 1900-1940, before the advent of computers. Again flexible on this. ## Would it be possible to… * ...interfere with or attenuate radio waves nearby? * ...microwave his foes from several meters away? (What if his foes are wearing metal?) * ...act like an IR flashlight to spot-broil things from afar? Tl;dr: # In general, what are some of the possibly absurd, overpowered, world-breaking, plot-hole-generating things that a light mage could do in the real world? Thanks for your help and let me know if I’ve overlooked any of the rules! [Answer] # Your light mage can instantly incinerate whatever he wants... as long as the moon/sun is visible. There are two cases here, but based on the manipulation of light rays (Rule 1) and the source requirement being line of sight (Rule 4), all he has to do is roughly focus (different from highly focused, its just that there's a lot of light from the sun) the rays from the source (sun/moon) onto any spot - even if that spot is a couple meters in diameter, possibly more, the mage should be able to incinerate everything in that spot. ## Feel the warmth heat of the sun. One one-billionth of the Sun's total energy output actually reaches the Earth. Of all the energy that does reach Earth, slightly less than 34 percent is reflected back to space by clouds. The Earth itself reflects another 66 percent back to space. Consider the possibility where the mage manipulates any small percentage of the suns energy output to go towards the Earth; if he could point it inside a 3km \* 3km area that would already be a tiny spot, equivalent to how we, as humans, hold magnifying glasses and set fire to ants and leaves. Except he's going to set fire to the entire area, way more quickly, relative to how much light he's redirecting. Your mage is basically a god, able to instantly create stretches of scorched earth, or end life on Earth as we know it. He can evaporate any amount of water almost instantly, cause the oceans to boil, or a glacier to melt. Of course, the mage might also cause the earth to warm up very very quickly and/or set fire to the atmosphere during the process depending on the duration this beam is held but... I don't know enough math to calculate that stuff. Maybe you can magic it away. ## To the moon! The second situation has to deal with the moon. Depending on how much light is reflected off the moon (eg: full moon vs half moon vs crescent moon) and your rules for "line of sight light source", its not impossible for your light mage to set fire to things using the moon as a reflector for the sun. I haven't done the math yet (and I don't plan to), so this possibility is up to story purposes. Theoretically, I think if you could focus it into a small enough spot, it would do the trick. Esentially, your light mage would be unstoppable in the day time, and less powerful when the moon is out, and almost powerless during eclipses. Another limitation would be the mana limitations. I don't know how much mana is used or stored by the caster, but you could set it up so that these absurd things are impossible depending on your mana rules - but that goes for every absurd thing, and if the point of your question is to figure out how to fix the broken stuff, what was the point of your question? ]
[Question] [ Global plagues have dropped the population to 1 billion and global civilization has collapsed. In an effort to save future civilization some time, you want to provide some information to kick start civilization's regrowth. # You are choosing exactly three books on grain production ## Assumptions * We assume the initial reader of these books is highly educated and that they are fluent in one of the languages that these books are written in. Should the info prove reasonable/useful, it will be handed off to grain farmers. * ‎We also assume that the future reader is familiar with and has an interest in agriculture. Maybe, they grew up in a farming community. * ‎We also assume a technology level of approximately 1800. Whatever we had tech or knowledge-wise in 1800, they have. * ‎While we can be sure that these three books will be found together, we can't be sure that they will be found with any other sets of books. By virtue of a print-on-demand press and a generous internet connection (and minimal scruples about copyright law), you can get your hands on the text and diagrams of most any book/article in existence. ## The best book choices will: * Give future generations stronger pointers for where to go looking for further knowledge. * Save them some of the trial and error of fumbling around on their own, if possible. * Will be books about general agricultural best practices, not how to grow a specific crop or how to grow crops in a specific climate. Printing off all the agricultural articles on Wikipedia or any other article archive won't satisfy because...reasons. Only actual books will satisfy. Preserving the books is a solved problem, so no need to worry about it. These won't be electronic copies because given our target tech level, electronic records will be just little black bricks. Note to responders: Also, while it's true that three books is arbitrary, the number was chosen as it forces hard choices about which books are really worthy. There are two extremes at play: the utterly mundane, "give them normal undergraduate textbooks" and "compress an entire field down to three books". The first isn't noteworthy, while the second is impossible. Try to push your selection of books further towards the highly comprehensible master-works of the field. The specification of grain production is intentionally broad because someone in 1800 won't be aware of the diversification of sub fields that we see now. Further, this information will be distributed to farmers who already know their job. We just want to show them how they can improve their yields. This question is a part of the Three Books series. It will grow to cover many and diverse topics. * [Chemistry](https://worldbuilding.stackexchange.com/questions/101887/only-three-books-restarting-chemistry-after-civilization-collapses) * ‎[Physics](https://worldbuilding.stackexchange.com/q/101922/10364) * [Medicine](https://worldbuilding.stackexchange.com/questions/102081/only-three-books-restarting-medicine-in-1801) [Answer] ## Book 1 - 2018 Southern States Catalog with free calendar The catalog will have pictures of modern tools along with the sales description. This should give the people of the future some ideas of what can be done. The pictures on the calendar should give them the images of how to put the equipment to use. ## Book 2 - USDA Report on Irrigation and Water Conservation. Farmers need water. This should help describe how to use the water in the most efficient manner. Its either this report or one on fertilizer and insecticides. ## Book 3 - World Atlas You just need to highlight the coordinates [78.235867°N 15.491374°E](https://en.wikipedia.org/wiki/Svalbard_Global_Seed_Vault) and tape a Polaroid picture of the entrance to that page. [![Entrance to Svalbard Global Seed Vault](https://i.stack.imgur.com/fP5PS.png)](https://i.stack.imgur.com/fP5PS.png) In a way, we are already planning for your scenario. But, there will be a lot more than "3 books" available to them once they get there. ]
[Question] [ Forgive me for misusing any terms. This is a subject I'm not knowledgeable in at all aside from doing some online research. In the novel I'm writing, I have an abandoned scientific polar research vessel/drillship similar to the proposed [Aurora Borealis](https://en.wikipedia.org/wiki/Aurora_Borealis_(icebreaker)) or the already real [Chikyu](https://en.wikipedia.org/wiki/Chiky%C5%AB) off the coast of Labrador. The ship has two moon pools and a drilling rig that lowers the drill through one of them. The previous crew came across an alien object floating around 500 meters underwater. The object is spherical, at least $2,500$ ft in diameter, and has a thin outer layer, a shell, with a very small comparatively (maybe less than $20$ ft in diameter) upward-facing vent leading into it. The entire object is large in volume, but not in mass. Aside from the thin shell which is filled with fluid, and a small inner core that holds its "brain", the rest is likely mostly hollow or filled with very not-dense material. It's never quite explained in the novel what the whole object is made out of, but the object can control its buoyancy through venting ballast from its mantle (I'm likely misusing these terms horribly), perhaps through the vent in its "crust". The research vessel discovered the object. After studying it they came to the conclusion that they had to stop it from surfacing completely for various reasons and that they didn't have much time. How I've been thinking about executing this is that that the crew somehow attached a long metal beam to their drill and lowered it vertically through one of the moonpools and down into the alien object's small vent so that the beam would turn horizontal and end up "stuck" inside the object's mantle like a [T-bar clasp on a necklace](https://cdn.globalauctionplatform.com/13e07f70-0291-4c18-9e41-a4dd01013597/eb0d498f-cf26-43fd-f3d5-03e27105a4d5/original.jpg). Then they would lift the entire object up by the drill line to lay the vent flush as possible against the ship to. Maybe they packed in some material around it as well if the bottom of the ship wasn't flat enough to make a seal. The crew didn't have a lot of time to come up with something more elegant or use any objects besides what would be found on a research vessel during an expedition. Maybe the metal beam was cannibalized from some other equipment. For the ships I mentioned above, the Aurora Borealis is around 655 feet long, and the Chikyu is around 690 feet long and has a displacement of 57,087 tons. I imagine the in-novel ship could be around 700 feet long and similar in displacement to the Chikyu. The alien object again is around 2,500 ft in diameter. The primary question would be if is this feasible or realistic at all and if so, does it mostly depend on the alien object's mass? Can the object be light enough that the ship could feasibly try to "trap" the alien object against itself without breaking or capsizing? Or does the sheer volume of the alien object alone make this unfeasible? If it is possible, would the drill line(?) and/or the drilling derrick of the vessel need to be reinforced in any way (since I assume sea drill lines(?) aren't meant to carry objects like the large metal beam I imagined them using to lock the alien object in place.) I know vessels like this would likely have cranes as well, but I'm not sure the cranes would go deep enough given how deep in the water the alien object is when the ship found it. The drill setup might also be more precise I suppose. I know a lot of factors are missing, like the material the alien object's crust is made out of, how thick it is compared to the rest, what the fluid is in the mantle, etc. But I'd be willing to adjust all of these factors to make what the research vessel's crew does feasible. I know very little about physics or ships or deep sea drilling, so I apologize if I'm not giving enough information. :( I might also be overlooking some things that are very obvious, so feel free to point anything out. [Answer] You can get some idea of the objects mass by the fact that it is floating at depth. It is not going up and not going down so it is neutrally buoyant when found. Its mass is the same (in aggregate) as water. So: unless it tries to escape somehow you are not going to have to support it from the ship. It is floating. You just need to moor it. A cable would work better than the drill, I would worry that if you insert a long straight bar in end-on, it would run into some impediment inside the object and you could not put it all the way in. Also it would be hard to position the tip of the drill to hit the thing. Better I think would be to send a diver with a coil of pipe or rebar. Or many, many coils. Something like this. <https://www.youtube.com/watch?v=16BHL71bZG8> [![rebar coil](https://i.stack.imgur.com/9UOQ6.jpg)](https://i.stack.imgur.com/9UOQ6.jpg) The coils would come down on a cable. The diver would shove them in then cut the wire holding it in a coil. The coil would open up inside the object. Many coils would produce a random orientation of coils inside the object. Then the cable could reel it in and up against the bottom of the ship. Another option would be to put something inside the sphere that was inflatable (a raft? a float?), then inflate it once it was inside using a tank of gas. If the object tried to escape it could do any of the things fish do when they try to get off of a line. 1: tear itself and pull the mooring loose. 2: deform the stuff inside it and pull it back out through the hole 3: break the cable This would be fun to write because some people on the ship might have fishing expertise, which they bring into play. ]
[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/97554/edit). Closed 6 years ago. [Improve this question](/posts/97554/edit) I want to create an intelligent creature(grit) that has a eusocial social system. They need to be small(10-20cm height) and live in small towns on top of the canopy of tropical forests. by intelligent, I mean that they can learn and have a way of communication, they can craft tools and use them to shape materials that you would typically find in a forest and they can either farm, cook, or tame small animals (earth-like environment) [Answer] One primate or another does all the things you want. I think you should start with [golden lion tamarins](https://en.wikipedia.org/wiki/Golden_lion_tamarin). [![golden lion tamarins](https://i.stack.imgur.com/9EJsq.jpg)](https://i.stack.imgur.com/9EJsq.jpg) They are 20 cm so the right size. They live in social groups, which you could certainly make larger. They live in trees. Plus they have rocking red hair which they could braid and bead, according to their caste. What you need now is for them to make tools and keep animals. Our own ancestors made tools for about 2.5 million years before they kept any animals. Chimps and bonobos use tools they invent and they are quick to learn how to use human tools. The only question is whether an animal as small as a tamarin has a brain big enough to be able to make and use tools. Yes. [![crow using tool](https://i.stack.imgur.com/wI7CK.jpg)](https://i.stack.imgur.com/wI7CK.jpg) from <http://www.bbc.com/news/science-environment-37024393> If you want a different angle, do it with birds. Crows are eusocial and live in the bigger groups you want. They live in trees (and all over). They make tools. They have castes (a pecking order, if you will - couldn't resist!). The only thing you need is for them to keep animals. It does not seem that farfetched to me that they might. [Crows are really smart](http://www.bbc.com/news/magazine-31795681). Check the link. I was moved by the one about the funeral the crows held for their cat friend Bart. [Answer] Good answer from Will about the tamarins. Other potential species to base your creature on are: 1. Vervet monkeys. Here's the [wikipedia entry](https://en.wikipedia.org/wiki/Vervet_monkey). Vervets have a 'proto-language' as they have different alarm calls for different predators, since the [response should be different.](https://www.youtube.com/watch?v=q8ZG8Dpc8mM) They also do very, very basic [tool use](https://www.youtube.com/watch?v=6kvQHGZU86A) 2. Capuchin monkeys (various species) are tool users with much more adept and sophisticated planning than the vervets, as this [BBC clip](https://www.youtube.com/watch?v=fFWTXU2jE14) shows. They also and have proto-language alarm calls. [This video](https://www.youtube.com/watch?v=6kvQHGZU86A) clip at about 4 mins 50 seconds in shows a sequence about a capuchin being cleverly deceitful. For castes, you need to have division of labour. A 'queen' is reasonably easy - you have a dominant female who produces all the young. Lots of mammals (mostly pack-living canines like wolves or African wild dogs, but also mongooses and meerkats) already do this: the alpha female harasses the subordinate females physically and emits pheromones in her scent to prevent them breeding. If they do breed, she often kills their pups. Her own youngsters stick around to help her raise the next litter: This is called [cooperative breeding](https://en.wikipedia.org/wiki/Cooperative_breeding). Your creatures (and mole rats or ants) have taken the next step, and divided up other tasks, not just the breeding. In the case of ants, the castes are fixed - you are a soldier ant at the beginning, middle and end of your adult life. You have a body tailored to being a soldier ant (e.g. big jaws and/or a powerful sting). In the mole rats, however, caste is more about body size: when you are little you dig tunnels, when you are big, you defend the warren. If the ancestors of your creatures have fungus gardens in a nest (like leaf-cutter ants do) and helpless babies which can't travel with the adults (like ants and mole rats do), they therefore have a fixed home to defend. That would have encouraged the evolution of a 'troop' or 'colony' to defend the queen's offspring and food supply. Which could eventually lead to true eusociality. If you want castes as bizarre as honeypots in ants, you'll need to invent the 'job' they are doing and the biology or ecology to justify it (crippling food shortages at certain times of year for the honeypots - leaf cutters solve this by fungus gardens instead of honeypots). [Answer] Bees make distinct castes with extra food. They feed queens-to-be lots of ["royal jelly"](https://en.wikipedia.org/wiki/Royal_jelly) to allow them to grow larger with functioning sex organs. Your eusocial species might do something similar with "brain food". So the typical member might have a crow or monkey's intelligence. But the chief or royal member might be more intelligent with an extra large head that might prevent them from moving. Soldiers might simply receive more food. They grow bigger and stronger but can't fit inside the nest. Perhaps they live on the ground or even on the lower parts of the tree where the branches are thicker. Perhaps the soldiers are given "angry" food, particularly when they need to attack. Other specializations may develop over time. Engineers might be given some of the royal brain food and more of the regular food. So their bodies might be as big as a soldiers, large enough to support brains that can understand more complicated instructions from the royals. Perhaps some would be fed less food and have parts of their bodies stretched when they are young. They might become gliding messengers, built like [flying squirrels](https://en.wikipedia.org/wiki/Flying_squirrel) or [feathertail gliders](https://en.wikipedia.org/wiki/Feathertail_glider). Females that receive lots of food may become like a bee queen. Powerful chiefs may have the hive secure food for their sisters who do the actual reproduction. They may trade with other hives for good drones for genetic diversity. This would be easier with an egg-laying animal like a bird or [monotreme](https://en.wikipedia.org/wiki/Monotreme). This is because they can gestate outside the body, be released into a womb-like cell (no Earth mammal does this, but bees do), and receive separate food. So they may look like monkeys as adults, but they get there a very different way. ]
[Question] [ The purpose of a magnetic field is to shield against solar winds, which are relativistic ions produced by our Sun. This is a typical O'Neill cylinder with 4 islands. I'm looking for a cost effective and reliable way to simulate Earth's strength magnetic field for an O'Neill cylinder, which does not interfere with any instruments. [![sketch of O'Neill cylinder](https://i.stack.imgur.com/OlDk6.jpg)](https://i.stack.imgur.com/OlDk6.jpg) Image is taken from [bagtagger@deviantart](https://bagtaggar.deviantart.com/art/Space-Colony-at-L5-208198334). [Answer] You have better to place your shield far from the cylinder (sunward, of course) and have the cylinder itself in the magnetotail, something similar to the NASA proposed [gimmick](https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html) to protect Mars terraforming. This way you will: * need a weaker field * have it far from habitat and thus: + have a far weaker local magnetic field + have a far more uniform local magnetic field (way easier to compensate) [Answer] It will always interfere with instruments, but so long as it's either constant or predictable, then it can be filtered out from the instruments readings. This is how a lot of earth based astronomy is performed, as earth has a magnetic field, it's atmosphere gets in the way of our images (and spectroscopy etc). But readings take from Earth are still useful because we can predict the impact on the readings, and subtract them from the result. --- So how to generate it? A nuclear reactor and an electromagnet is one way - but that'd be power hungry. However you would have to constantly feed power into whatever magnetisation system you're using. Each particle it turns away from the ship will weaken it slightly. [work = force \* distance. Force != 0 (it turns away), distance != 0 (the particle is moving while force is applied) therefore work != 0. If work != 0, then energy input is required]. Probably more efficient than a nuclear reactor and electromagnet running all the time is to use the reactor/electromagnet to magnetise a bar of iron. Then you can turn the reactor off until the iron is demagnetised to no longer be useful. You remagnetise it, and off you go again. [Answer] If you make the hull in a [ferromagnetic](https://en.wikipedia.org/wiki/Ferromagnetism) alloy then the spin you put on it to generate internal pseudo-gravity will generate a magnetic field for the habitat as well. As to instrumental stability issues I think you've got to pick the lesser of two evils, is solar bombardment shorting out circuits more of an issues or magnetic distortions from the shielding? Any instruments that work reliably on Earth is probably going to be okay, really sensitive instruments are going to need a [Faraday Cage](https://en.wikipedia.org/wiki/Faraday_cage) but they probably do anyway. ]
[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/92921/edit). Closed 6 years ago. [Improve this question](/posts/92921/edit) Here is the deal. Earth will be destroyed and there is no way to stop it. We have about 30 years left. Government is keeping it secret, of course. The good news is, scientists have figured out a feasible way to survive in space for some time (and possibly relocate to other planets), and there are already plans to build a fleet of spaceships just in time. The bad news is, this fleet will only save a few thousand people, while building and launching it will require cooperation of every country, every industry, even general public. Basically, this project is so huge, it cannot succeed being kept secret. How to handle this situation? We need people to know about their almost certain death and at the same time, avoid mass panic and social disintegration, so that people keep working (not rioting "too much"). One thing that comes to mind would be choosing the few "survivors" randomly just moments before launch when all the work is already done, so everybody gets the same chance. I do not think, this would work too well, because people would probably think one in a million chance is not worth it. Also, they might think the government lies (which would most definitely be true, because you can not fly a starship with a bunch of random vagabonds, or colonize planets with old people) Any thoughts? Notes: * By "government" I mean global government all other governments are subject to * This takes place in near future (2050-ish) * Earh is getting destroyed, not just made uninhabitable. There will be no Earth to live on or orbit [Answer] I think that you should have faith in people. Humans are capable of killing, stealing, lying, and many other bad things. But at the same time, they are capable of compassion, altruism, and self-sacrifice. Building Arks would, indeed, require a joint effort of the entire humanity. If you keep the project a secret it would not be possible to maximise this effort. Even if you manage to maintain secrecy for 30 years, enough information would leak to damage the trust between peoples and their governments. The collaboration between nations would be severely impeded, as well. As a result, you would save fewer people than you potentially could. Thirty years is a long time. Even if you get some panic and suicide waves in the beginning, most likely the humanity would come round and start working on saving the future. Mass panic and breakdown of society in the aftermath of catastrophes are a myth. The majority of people choose to cooperate. There is a lot of research on this topic, you can easily google for specific examples. I think that you could do several things: 1. Address all nations and tell them the truth. 2. Put all cards on the table (no secrets, no double-crossing) and establish an alliance with all nations that have space technologies. Try to get on board everybody else. 3. Start a massive 30-year long propaganda campaign (something similar to the WWII war effort campaigns). 4. Enact martial law if necessary. If possible (and plausible) establish a benevolent authoritarian regime (they are good for getting things done in a short time). 5. Revoke all patents and give open access to all scientific data. 6. Start manufacturing amphetamines (loads and loads of them). 7. Start building DNA database of the entire Earth population. 8. Divert all resources to building ships, space habitats, etc. Stockpile as much as possible. Make sure it is well-protected. 9. Task scientists and engineers with planning an escape. Don't forget to abolish all restrictions, including ethical, on experiments (but do not let it spiral out of control completely, the survivors will be dealing with the survivor syndrome, they do not need to feel additional responsibility for obviously unethical experiments). 10. Switch to three shifts a day (8 hours each). Start distributing amphetamines to all workers (keep scientists off drugs, though). 11. Five years prior to launch choose survivors based on their skills and genetics. Start to train them for survival in space (or a new planet). Make sure the curriculum focuses on practical skills. Everything else can be uploaded into spacecraft computers. 12. Publicly shame and prosecute people who try to interfere with or sabotage the Ark project. At the same time, try to avoid forcing people to work. The general population must believe in the project and want it to succeed. 13. Treat the entire thing as a war effort. Emphasise the survival rather than inevitable death. It is a war that humanity can win but at a great cost. I guess the way I see it, you have to trust humanity to do the right thing. And if it does not, it well deserves extinction. [Answer] Why do you assume we need people to know? Because they don't. You don't tell them shat. This is like "using people 101". Remember Ender's Game? SPOILER: > > It wasn't a game. > > > "Hello, I'm Elon Musk and I'm working on a rocket that will go to Mars. Care to join the endeavour? You can also sing on a travel list and maybe you will be the lucky winner of a golden ticket." "Hello, I'm Elon Musk and I'd like to invite your corporation/country to join the building rockets and colonies on Mars." Also, every smartphone is actually part of a cluster that is making necessary calculations. As are students that are doing complicated ones by hand. You need thousand of guinea pigs for testing rocket fuels? Well, why not drive the new TeZla model Pi or the hydrogen Hunday. Those people are dead already, you don't owe them nothing. [Answer] several reasons Denial, many people just won't face their own mortality. This is the same reason young people don't buy health insurance or create retirement funds. Hope, your lottery helps a lot, people are willing to bet on longshots all the time especially with no alternative. Familiarity, some people cope with tragedy by retreating to familiarity, this ties in tightly with denial. ]
[Question] [ I remember hearing/reading something somewhere a long time ago about how the weather patterns on earth mostly cycle away between the equator and the poles, and that this means if there was a northern hemisphere nuclear war (US/Europe/Russia/EU/China/India/Pakistan)the radioactive isotopes would mostly remain in the northern hemisphere, for quite a long time. This could mean the southern hemisphere is either spared entirely, or has a grace period, before it too becomes uninhabitable. I'm working on something set in the second scenario, based around the idea that the survivors would be building space station arcs, and vying for inclusion. Assuming the violence was enough to effectively eliminate the entire northern hemisphere, how long could the southern hemisphere remain viable? UPDATE: I figured some more specificity would help so lets say that atleast 50% of the worlds nuclear arsenal was fired, but this was exclusively in the northern hemisphere, perhaps not even near the equator in case that makes a difference, the lowest latitude hit could could be Mumbai. [Answer] OK, let's start with what we expect to happen: * A nuclear war in the north causes the expected [nuclear winter](https://en.wikipedia.org/wiki/Nuclear_winter), spreading soot into the upper troposphere, blocking the sun, and seriously reducing surface temperature. * The [upper troposphere](http://www.earthonlinemedia.com/ebooks/tpe_3e/circulation/upper_tropospheric_flow.html) has powerful winds, but they're strongly temperature based. This means that the hot air of the equator is falling at the poles (not to ground level, but in the troposphere). On the surface you would think this would preserve the southern hemisphere, and it likely would, but not for long. As the north cooled (and it would cool very quickly thanks to the nuclear winter), the temperature gradient would begin to move south. Let's simplify today's behavior by saying the equatorial temperature is 100° and the poles are -40°. That's a gradient of 140° over a 90° arc of the earth. But that winter starts to close the arc. As it does, the equator begins to cool (even if the winter is, in the beginning, all in the north). Fairly quickly you'd have something closer to a 15° arc with the "centerline" of the equator being pushed to cooler southern latitudes. Eventually the "equatorial" temperature begins to revolve around the Tropic of Capricorn — and the collapse is very quick after that. The issue is that the change in temperature gradient will change the wind patterns. The cooling will also change the ocean current patterns. Between the two, southern hemisphere patterns will begin to change. How long would this take? A meteorologist could give you a more accurate answer. You should review articles about volcanic ash affecting global weather to see if that study can tell you how much the patterns change, and a study of the projections of what happens when the temperature of the North Atlantic Current changes, but my suspicion is that it would take no more than a few years. Finally, in a moment of prognostication, I can imagine the tropic of capricorn getting *really hot* before it began to cool down because energy must go somewhere — and it's not heading north. My prediction is that in the event you describe, Australia becomes a dustbowl before becoming a sheet of ice. [Answer] Nevil Shute explored this question in his novel On the Beach. The way it played out in the book, the Southern Hemisphere didn't even last a year, because of the the seasonal movement of the Inter Tropical Convergence Zone (ICTZ), which is the basically the barrier between the airmasses of the Northern and Southern Hemisphere. In the Southern Hemisphere summer, with the ICTZ to the south, air could come down to the tropics from the Northern Hemisphere and deposit radioactive particles on the ground. Then in the Northern Hemisphere summer, the ICTZ moves far to the north (Himalayas and Taiwan), so air from the Southern Hemisphere can move north over the now irradiated tropics. ]
[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. So I'm thinking about orbital warehousing of raw materials but I'm wondering whether one would actually need an orbital structure to store the goods inside or could you just strap a booster to the goods to keep them in their orbit and be done with it. So does anyone know where I could find some hard figures concerning particle contamination of material in geosynchronous orbit? Edit: Specifically thinking about solid, elemental, raw materials, the mainstays of Sci-fi tech and orbital mining like Iron, Nickel, and Titanium. [Answer] The [Cosmic dust](https://en.wikipedia.org/wiki/Cosmic_dust) article on Wikipedia says that > > The dust density falling to Earth is approximately 10−6/m3 with each grain having a mass between 10−16 kg (0.1 pg) and 10−4 kg (100 mg). [...] By one estimate, as much as 40,000 tons of cosmic dust reaches the Earth's surface every year. > > > In 1984, NASA lauched the [Long Duration Exposure Facility](https://en.wikipedia.org/wiki/Long_Duration_Exposure_Facility), "a school bus-sized cylindrical facility designed to provide long-term experimental data on the outer space environment and its effects on space systems, materials, operations and selected spore's survival". It was retrieved in 1990 after orbiting Earth 32000 times: * YouTube Video: [Long Duration Exposure Facility Satellite (LDEF)](https://www.youtube.com/watch?v=iPONWizIR5U); description and history of the mission. * YouTube Video: Long Duration Exposure Facility Satellite: "[LDEF Update](https://www.youtube.com/watch?v=N3O3kyKlN1w)", 1990, NASA Langley Research Center: some of the results; the most interesting, from my point of view, is that outgassing from the space craft itself is a major contaminant of optical surfaces. * "[Lessons Learned from the Long Duration Exposure Facility](http://www.dtic.mil/dtic/tr/fulltext/u2/a266026.pdf)", W. K. Stuckey, Space and Missile Systems Center Air Force Materiel Command, 1993. Plenty of potentially interesting material, most of it way over my head. * "[Analysis of Systems Hardware Flown on LDEF - Results of the Systems Special Investigation Group](http://www.dtic.mil/dtic/tr/fulltext/u2/a338845.pdf)" by H. W. Dursch, W. S. Spear et al., Boeing Defense and Space Group, 1992: + 34336 total micrometeoroid impacts; + The largest particles encountered by LDEF were approximately 1 mm in size. + Most of these larger particles appear to possess natural origins (i.e., originated from comets or asteroids). + The mean impact velocity was of approximately 17 km/s. + > > In orbit, additional particulate contaminants accumulated as a result of impacts with meteoroids and space debris. These contaminants tended to be deposited very close to the impact, with concentration dropping off with the square of the distance from the impact, as would be expected. Impacts with surfaces projecting radially from the surface of LDEF, such as tray edges or bolt heads, resulted in the greatest amount of material being deposited on the surface of LDEF. The concentration of such debris could be very detrimental to optical systems within a few inches of the impact. > > > + > > The most detrimental contamination event in orbit was the outgassing and redeposition of molecular contaminants on the surface of LDEF. The brown discoloration caused by a contaminating molecular film on the surface of LDEF was evident through the windows of the Space Shuttle Columbia as it approached LDEF. This brown film was widely dispersed over the trailing rows of LDEF and at the space and Earth ends. Closer examination in SAEF-2 following recovery permitted a much more detailed analysis of the film and its distribution. Large areas of the exterior surface were covered with a film a few hundred nanometers thick. In some areas it was as much as a few hundred micrometers thick and completely opaque. Analysis of the film indicated it was a polymer consisting of a combination of silicones and hydrocarbons. The ram facing trays appeared clean but surface elemental analysis of ram surfaces indicated a silica residue remaining from atomic oxygen attack on the brown film. An infrared analysis of the film and possible sources indicated that two systems had sufficient mass to be major contributors to the film: the thermal control paints and the silicone adhesives used with both fasteners (to enable fastener assemblies to survive vibration testing without a decrease in installation torques) and the bonding of Velcro to LDEF and/or experimenter hardware. > > > [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. You would likely need a warehouse in order to store liquid/gaseous materials such as fuel. I'm not sure about particle contamination, but it seems it will depend on how sensitive your material is. If it is a giant iron filled asteroid, or a block of iron, it would be durable enough you should be fine leaving it in orbit. The question comes down to how sensitive your materials are to contamination and radiation. However it might be better to simply put everything either in a warehouse, or strapped to the outside, as otherwise you would have to worry about collisions in a crowded orbit. ]
[Question] [ I was wondering about feasibility of small 'shell' world build around something very dense, like black hole or some 'artificial mini star' that could also be source of energy, and of course gave us gravity of around 1 g at 1km radius. If my math is right, we would basically need something of mass around 1.50E+17kg, collapse it into something less than 1km radius, make it stable, and build around it. $a = 10\frac{m}{s^2},$ (just to simplify) $r = 1000m,$ $M = \frac{a \* r^2}{G} = 1.5 \* 10^{17} kg$ With something like this, gravity at 1010m from the center would be: $a = \frac{M\G}{r^2} = 9.8\frac{m}{s^2}$ so tidal forces shouldn't be a problem EDIT: removed some fluff, added some math [Answer] I assume that your people found somewhere a black hole according to their needs. (That kind of black hole might exist.) Whether it can have a have an atmosphere doesn't depends on the gravitational acceleration but on the escape velocity, which is small in your case. (About $0.14\frac{km}{s}$ compared to $11.2\frac{km}{s}$) The average speed of air is about $0.464\frac{km}{s}$. It would just fly away. Otherwise I don't see any problems with your construction. [Answer] Such a contraption, even assuming you could make it stable, would have a very large gravity gradient and thus would feel very awkward with gravity noticeably decreasing while going up (going down would be very* dangerous). Actually you can land on a rotating space station, you just have to do it on the inner surface. The maneuver is actually quite simple: just approach diagonally (crablike, as a plane landing on a strong wind) the station aligned with internal surface, with the tangential component of your speed matching tangent velocity os space station. When over it kill lateral speed and s.s. surface will rise to keep shuttle in place. ]
[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. In Larry Niven's short story "Bordered in Black", there's a planet (Sirius B-IV) with much lower gravity than Earth. As a result, the planet has a gentler atmospheric pressure gradient, i.e., the air pressure changes less over the same vertical distance. Because of this, the planet had clouds as high as 130 kilometers. It got me thinking: there's a world I've been building for some time that has an extreme vertical component to its geography, with some features being hundreds (and in one extreme case, thousands) of miles tall. It occurred to me a while ago that air pressure would be a serious problem in this setting, since most of that vertical space, although not necessarily the upper- or lower-most extremes, is meant to be habitable. I initially decided to handwave it away, judging the problem to be insurmountable. Now Niven has reignited my interest in finding a scientific explanation for this. Using real physics, what are some good explanations for a range of livable air pressure extending over several hundred vertical miles? If this isn't possible, what's the largest vertical distance over which air pressure can remain can livable? Side note: the ground is made out of handwavium. I am not breaching the topic of how hundred-mile-tall features exist in this world. The air on the other hand, being breathable, is normal nitrogen-oxygen, and thus requires an explanation for its behavior. [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. The suggested "cure": lower (a lot!) surface gravity (i.e.: have either a smaller planet or a lighter core... or both) is mandatory in your case because mountains "several hundred vertical miles" would otherwise collapse under their own weight and thin air is the last of your (scientific) concerns. There are good geological reasons why tallest peak on Mars (mt.Olympus) is significantly (>20%) taller than any Earth counterpart. What you propose is quite extreme and I sincerely do not think is achievable without resorting to some "magic". What You should be concerned, though are other factors I don't know if You accounted for: * temperature: decreases with altitude and is the main reason why high ranges are "not inhabitable". * human body can adapt to very extreme pressure ranges, given time. * if your mountain ranges get higher than troposphere you'll get no atmospheric precipitations, which means: no water! * high mountain ranges, on Earth, aren't inhabitable mostly due to cold desert climate well before lack of oxygen becomes a problem. * all above would be mitigated by lower gravity. * very low gravity means no iron core, which, in turn means no magnetic shield for solar wind. [Answer] Not easy to give a straight answer. The approximated formula to calculate pressure vs hight is the following $p = p\_0 exp(-g Mh/R\_0T\_0)$ Where $p\_0$ is the pressure, $g$ is the gravity, $M$ is the molar mass of dry air and $T\_0$ is the temperature, all at "sea" level, while h is the height and $R\_0$ is the universal gas constant. Playing with g is risky, as lowering g will also lower the capability of the planet to keep an atmosphere. You can better use the properties of the exponential decay to "slow" down for great values of h, in this case, and going almost horizontal. If you put your survivability zone in that area of high h you can extend it for really large height differences. See the chart below: dropping 20 kPa (100 to 80) happens in 2000 meters if you start from sea level, it takes 3000 meters if you start from 4000 meters (60 to 40). [![enter image description here](https://i.stack.imgur.com/C8Gjf.png)](https://i.stack.imgur.com/C8Gjf.png) The "trick" is increasing your $p\_0$ so that your livable pressure is shifted at high heights. The problem is that to increase your $p\_0$ you need to increase your g, which being also in the exponent influence the drop rate. Also an higher g will make your mountains lower. But, nevertheless, this can explain how the pressure is livable on wider ranges. ]
[Question] [ Premise In a world set 10^40 years from now, or in cosmological decade 60 (a cosmological decade is a long term measure of time such that each successive increment represents a ten-fold increase in the total age of the universe), there will be no remnants of cosmological features that are familiar to us except for black holes. As such, this period of time is often referred to as the [Black Hole Era](https://en.wikipedia.org/wiki/The_Five_Ages_of_the_Universe#Black_Hole_Era). Given that this period takes place in the unfathomably distant future, it will be impossible to speculate about most things, including life. However, it might be safe to say that human life as we know it would not exist during this era, because even protons (or any [baryonic](https://en.wikipedia.org/wiki/Baryon) particles for that matter) wont be around. Needless to say, organic compounds won't be able to form. What remains are the particles that have no intrinsic mass like photons and electrons. The world I intend to forge from this apparent apocalyptic setting is one of cyber consciousness. I am trying to devise a means by which an entire civilization can essentially upload their consciousness to some kind of simulation system. Given that the Black Hole Era is very cold, the potential efficiency of the system would be extremely high and could possibly bring salvation to a civilization with a huge population. This is because the computational efficiency of the system would be operating at levels near the [Landauer Limit](https://en.wikipedia.org/wiki/Landauer%27s_principle), which might be roughly equivalent to simulating billions of people on 1 watt of power or less. Such efficiency will be needed, as the system will ultimately be fighting a losing battle against the entropy of the universe. Nonetheless, the time span (as well as subjective time at very cold temperatures) of the Black Hole Era will be so long that it would seem like an eternity if such a system could be constructed. This is the presumed motivation -- "eternal" salvation through simulation. Question: Conceding that very distant events in the future are subjective, is there anything in the (current) laws of physics that explicitly contradicts a computer architecture that is made of entirely non-baryonic matter? If contradictions do exist, please comment on the feasibility of overcoming it through technology. (I hope I don't have to resort to something like a "Heisenberg Compensator") Further Clarification * There is very little power available in the Black Hole Era, so the system must run on very low power, a few watts * 100% non-volatile systems are a plus * can have no baryonic matter (like protons or neutrons) [Answer] While a long video, Issac Arthur has some interesting speculations [here](https://www.youtube.com/watch?v=Qam5BkXIEhQ) on far distant future civilizations "farming" black holes. While as noted we have no idea how non baryonic matter is supposed to work or how to control or manipulate it, the black holes themselves are still usable as sources of energy, or even as immense "hard drives" with all the knowledge and information of the universe stored just on the edge of the event horizon, since information that is drawn into the black hole supposedly cannot be lost due to [conservation laws](http://www.bbc.com/news/science-environment-34062839). I certainly don't have anywhere near the ability to parse that argument, so it can be taken as a plot point if you want to incorporate it somehow (the information would have to be "regurgitated" in the form of Hawking Radiation, although how this would be done in any sort of controlled manner is beyond current understanding). If this is the case, black holes can also become [computers](https://www.scientificamerican.com/article/black-hole-computers-2007-04/) as well, which solves the conundrum of where the action in your story is actually taking place; it is all on the surface of the event horizon. [![enter image description here](https://i.stack.imgur.com/8EL5N.jpg)](https://i.stack.imgur.com/8EL5N.jpg) Home sweet home...... [Answer] The basic and wholly unqualified answer to your question is "no," so long as there could exist a particle the motion of which can be used to express the intent of the designer. If, on the other hand (as @Varad Mahashabde points out), non-baryonic matter can't be controlled, then the answer changes states. But, let's assume we don't know everything. Using a baryonic but real-world example: an optical computer is feasible, but even it must depend on electricity because you must eventually convert the light to something else to produce audio and (ironically) video. Nevertheless, the ability to do it with one form of energy (electrons) presupposes the ability to do it with another form of energy (photons) --- we just haven't come up with (e.g.) "photo-magnetism" yet. But, if for no other reason than to give you more to think about as you develop your story, let's consider a few things. You're talking about devising a civilization that is intentionally fighting the process of everything being sucked into black holes. The black hole era, after all, doesn't happen because everything has decayed. It happens because everthing has "come together" into black holes. It's nice to theorize that all other matter has ceased to exist, but that negates your ability to tell your story (what technology could overcome the ultimate decay of matter? None.) So, assuming we really are in the black hole era and not at the end of the universe.... 1) Gravity would be an excellent source of power assuming a piezzo-like substance is created that induces the flow of electrons due to gravimetric shear in the same way piezzo-electric generators do with kinetic force. 2) And that's assuming our future society hasn't devised a way to generate useful power from Hawking Radiation, which (according to our current understanding, as I recall) must exist while black holes do. In other words, there may be vast amounts of accessible power. 3) Unless there is but one massive black hole during the black hole era, there will be areas of gravitic neutrality where minute quanities of particles --- and therefore our "object" that contains the engine supporting the society --- can exist. There may even be a "current" (like an ocean current) that these few particles, and therefore our society, slip through as they pass among the black holes. I point all this out because while the creation of a non-baryonic computatational infrastructure is interesting, there is far more involved than the fabrication medium to ensure the survival of the whole. Coming up with the "everything else" will likely negate the need for a non-baryonic anything. ]
[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/86176/edit). Closed 6 years ago. [Improve this question](/posts/86176/edit) I'm creating a fictional hyperspace to enable FTL travel. It's sort of a mix of Star Wars, Star Trek, Halo, and probably a bunch of other stuff. I've run into an aspect of it that either requires some handwaving or a bit of math that's beyond my understanding. It goes something like this, please bear with me: Hyperspace is perpendicular to our normal spacetime. As you go "deeper" into hyperspace, coordinates get compressed. Imagine our spacetime represented as a square plane and hyperspace as an inverted pyramid below it (or a disc and a cone, if you like). Since all points eventually converge at the "bottom", if you can go down into hyperspace and travel a bit, when you come back out you will have moved father than normal and faster than light (effectively). This compression occurs in smooth gradients, not distinct layers like subspace in Star Trek. Like Star Trek though, you need a field that creates a bubble around your ship. This makes an area of normal spacetime that protects your ship. Then you can push into hyperspace with this bubble and manipulate the shape of the bubble to move around in hyperspace. Hyperspace wants to push you out (or keep you out), and gravity wells magnify this effect. So you need enough energy to stay in and you need to plot a course that avoids gravity wells. I'm not asking about the energy requirements though, because I have a fictional power generator that we don't worry too much about. Since you naturally pop out of hyperspace near gravity wells (or even if your drive fails), the main dangers with this drive system, in my mind, seem to be regarding the field that makes the bubble. Anything contained within the bubble goes into hyperspace, which allows for stuff getting cut in pieces, like what happens in Halo 2 when the Covenant ship jumps while it's still over the city (It brings chunks of buildings with it into deep space). The field that makes this bubble in my fictional universe can vary in strength from nothing (off) to a level that allows for the transition to hyperspace, then beyond, until you don't have enough energy to go any deeper into hyperspace. I think that these bubbles repel each other (kind of like magnets), such that two ships in hyperspace would not collide. I also think there must be a gradient of some kind between normal spacetime and hyperspace, however slim, at the edge of the bubble. Given all that, my questions are: 1. What might happen to matter at the inside and outside surfaces of the bubble at the moment of transition? 2. Could there be dangerous effects even before the transition to hyperspace, as the field strength is increasing? 3. What might happen to propellant expelled/ignited if the ship fired its conventional engines while inside the bubble (or any other matter contacting the bubble, really)? 4. Might there be any dangerous radiation inside or outside the bubble, especially due to any matter caught in the transition? 5. Does it make sense that the bubbles would repel each other (does it seem internally consistent)? 6. What visual effects might there be to an outside and/or inside observer (especially during transition)? 7. Any other potential dangers from creating or collapsing this bubble? Bonus/Epic Fail: Are these questions even answerable with my description of hyperspace? --- Edit to attempt to make things less broad: Based on [a4android](https://worldbuilding.stackexchange.com/users/22159/a4android)'s answer I'll refine the definition of the bubble by saying that it is impermeable in both directions (hopefully lending credibility to the idea that bubbles repel each other). Also that you can't see out of it, probably for the same reason. So really the main concern is: what happens to matter when it's sheared at the edge of the bubble as the ship enters hyperspace? (For example, might it become superheated, converted to energy, etc.) Are there any known rules of physics that might inform my description of the effect, or do I just make up whatever seems fun? --- I know this isn't hard SF by a long shot, but I like it when the answers at least seem to be based on what we know about physics. I also know that's a bunch of questions rolled into one long post, so I appreciate any help you can give. [Answer] This model of hyperspace, with coordinate compression increasing with depth in hyperspace, is quite good for fictional faster-than-light travel. Full marks for an elegant and well-behaved system for accomplishing FTL travel in a fictional setting. Your questions concern the behaviour and properties of the bubble of spacetime generated by a field that enables spacecraft to enter and exit the hyperspace. The bubble protects vessels in hyperspace and enables its motion there. By and large, these properties of the bubble can be decided by yourself as its author to be anything you want them to be. However, it is possible to apply some scientific imagination to make some reasoned propositions for what is does and how it behaves. 1. What might happen to matter at the inside and outside surfaces of the bubble at the moment of transition? There are two possibilities. Matter trapped at the surface will either remain in normal spacetime or be dragged down inside the bubble into hyperspace. If the matter remains in spacetime this might prevent the spacecraft inside its bubble from entering hyperspace. Considering the bubble is generated with considerable power the matter could be sheared off and stay inside the bubble. 2. Could there be dangerous effects even before the transition to hyperspace, as the field strength is increasing? This seems imponderable because it depends on the nature of a fictional field and whatever effects are associated with its strength. However, since spaceships survive intact inside the bubble as its strength builds, then it is not unreasonable to assume that this also applies any other matter inside the region of the field. Any other dangerous effects could arise from how the field interacts with matter and energy or even the quantum vacuum. 3. What might happen to propellant expelled/ignited if the ship fired its conventional engines while inside the bubble (or any other matter contacting the bubble, really)? This depends on whether the surface of the bubble is penetratable or permeable and this permeability and penetration works either one-way or in both directions. If the bubble is an impermeable barrier to propellent or any other matter trying to exit the bubble. Then obviously this will be trapped inside the bubble. This could be uncomfortable and inconvenient for a rocket exhaust with nowhere to go. Furthermore, there will be no way for a ship to exhaust heat, which will be a rather serious problem. On the other hand, if the bubble is impermeable to matter and energy entering it, but allows matter to exit it, then the vessel won't drown in its our exhaust. But if the bubble is perfectly impermeable, then nothing enters and nothing leaves. Again a spaceship will have problems with its own expelled reaction mass. 4. Might there be any dangerous radiation inside or outside the bubble, especially due to any matter caught in the transition? Only if matter trapped in the surface of the bubble undergoes a transformation into energy. Other possible sources of radiation could include virtual photons and particles emerging from the quantum vacuum and being trapped inside the bubble. Effectively this like Hawking radiation being created at the event horizon of a black hole. Radiation of this kind doesn't have to be a normal feature of the bubble. It might only be something that happens when the field strength, for example, either exceeds or falls below some critical level. This will be left as an exercise for the author. 5. Does it make sense that the bubbles would repel each other (does it seem internally consistent)? Definitely yes. Most so, if the bubbles are impenetratable such matter and energy cannot enter them while in hyperspace. Possibly, the nature of the bubbles themselves might make the bubble surfaces impenetratable to each other. 6. What visual effects might there be to an outside and/or inside observer (especially during transition)? An outside observer may simply see the bubble vanish as it enters hyperspace and pop into view as it exists. What an internal observer sees depends on whether normal spacetime is observable while in hyperspace. If spacetime is observable, then the distances between astronomical objects will appear to contract with coordinate compression. This will make navigation easier too. 7. Any other potential dangers from creating or collapsing this bubble? This will be entirely depend on interactions between the field, the bubble and matter, energy and spacetime itself. This also may depend on how smoothly the bubble is created or collapsed. For example, the surface of the bubble might be loaded with a massive amount of energy, and as it collapsed this energy could be released. So a spaceship could emerge from hyperspace accompanied by a massive blast of radiation radiation and particles. For the safety of the vessel all this energy will propagate unidirectionally away from the spaceship. Any backscattered radiation might be a problem. Bonus/Epic Fail: Are these questions even answerable with my description of hyperspace? They can be answered with a combination of commonsense, logic and scientific imagination. Any flaws in the reasoning applied here will soon be ferreted in the comments. ]
[Question] [ I have a world with a moon, much like Earth and the Moon, except that the planet is almost tidally locked to the moon. The moon therefore appears to move only very slowly through the sky, and takes, say, 7 years to do a full revolution. Across the equator of the planet runs a fresh water sea. My goal is to create an environment like ancient Egypt with the Nile, where there's periodic and very dramatic floods and ebbs. Also, I want a relatively easy way to circumnavigate the world following this sea/river current. I just want have some idea that this setting makes sense and that I've correctly predicted likely behaviour, since I don't know much about seas. 1. Would the difference in high tide and low tide be more dramatic than on Earth for a similarly sized moon, because the sea would have more time to "catch up" to the moon? Or would they be about the same? 2. On earth the two high tides are roughly equal in size. Would that also be true for this system? 3. Supposing you were in a boat, and you wanted to follow the tides around the world, where in the cycle would you want to sail? I would think you'd want to lag about half way between a high tide and low tide bulge, chasing after high tide. I would think that would be when the currents are strongest. Which would put the Moon at about a 45 degree angle ahead of you in the sky if I'm right (you'd basically be chasing the moon, and from your perspective it wouldn't move in the sky). 4. Could you just drift on the tidal currents around this world, or would you need a motor or a sail? 5. How would the currents work relative to the high tide bulges? I'm thinking that there are two options. Either the tidal currents always point towards the high tide bulge, and there's basically two convection cells on either side of the high tide slack current, or there's a single convection cell, and the tidal bulge works like a raindrop sliding down a window. Which would mean there's actually a current that flows away from the tidal bulge ahead of it before dropping down to the sea floor/river bed and reversing direction. Any insight would be appreciated. If there are any striking features that I haven't thought of that would also be interesting to know. [Answer] If the moon takes 7 years to do an orbit, relative to the surface, then it must be doing one orbit of the planet each day, relative to the centre of the planet (as it is nearly in geosynchronous orbit) If the planet has about 86400 seconds in a day (like Earth), then the moon is orbiting at 36000km about the equator, much much closer than the moon really is. This would potentially lead to much bigger tides. However the way tides work is not simple bulges. There are tidal flows, the moon generates a flowing wave that moves around the Earth, and as this wave meets land it can be pushed up and that gives us large tides at the coast. The tidal range mid-ocean is much smaller (about a metre). If the moon isn't moving quickly, relative to the surface, then these flows will stop, and the coastal tide will be less. I don't think that there would be significant tidal flows. The moon is moving so slowly, and the tide would rise so slowly that the required flow of water would be very little. You couldn't surf the world's tidal wave. Tidal bulges are an idealisation, assuming a world in which there is no land. In reality the tidal flows are strongly determined by the shape of the land <https://www.youtube.com/watch?v=ZEhm_ONTQKc> There would be two tidal bulges, just as on Earth. Except on Earth, tidal flows mean that in some places one tide is bigger than the other. So I would expect the mid-ocean tide to be much larger, but the coastal effect is less, and there are no significant tidal flows. Also the tidal heating by the moon of the Planet's interior is much greater: I would expect lots more tectonic activity as the Planet bends and creaks with the nearby moon. The moon would also be massive: ten times larger than it appears in the sky. and eclipses would be commonplace. [Answer] From the numbers you gave (planet and satellite of sizes comparable to Earth and Moon respectively, 7 years [synodic month](https://en.wikipedia.org/wiki/Lunar_month#Synodic_month) for the satellite) you cannot really infer the distance between the planet and the satellite and thence the magnitude of the tides. The Moon is currently about 384000 km from Earth on average and is tidally locked to Earth; for a mutual tidal lock to take place the Earth would have to decelerate its rotation and the Moon would have to recede a lot, a process that would take tens of billions of years. The Moon is obviously not on a geosynchronous orbit and as it recedes from Earth it will be even less so (if you take the value of today's GSO, of course!). As Earth's (or any planet's) rotation slows down due to tidal braking, the GSO will get farther from the planet. The distance between two mutually tidally locked bodies depends on the sum of their angular momentum, which [cannot increase or decrease](https://en.wikipedia.org/wiki/Angular_momentum#Conservation_of_angular_momentum). You can start with any value within a broadly reasonable range. Angular momentum depends on mass and rotational speed, and a planet could conceivably end up with almost zero rotational speed after it has formed. On to your question: I would think that, irrespective of the magnitude of the tides, their extremely low frequency would make them almost unnoticeable. We're talking about an acceleration vector that takes seven years to go around an Earth-sized planet. [Answer] To expand on pablodf76's last sentence: If your planet has an Earthlike circumference of 40,000 km, and your moon is orbiting once every seven years (relative to the surface), then, relative to the surface, the peak of your tides (i.e. the "groundspeed" of the moon) only travels at <1 km/hr. By comparison, the peak of Earth's tides (which effectively circle the planet each day) moves closer to 1700 km/hr. So, while local topography will of course cause variations on-the ground, in general, no, you're not going to see any appreciable tidal flow. In fact, if the moon's orbital plane wasn't aligned with the plane of your planet's equator (geosynchronous but not geostationary), you'd probably see a stronger north-south tidal movement than east-west. [Answer] Your Tides would be HUGE, hundreds or thousands of feet high, but VERY slow. More like "Don't build anything permanent or expensive here, in three years it will be under water. Your moon will have to be about 10 times closer, all things being equal. Give the diminishing square laws, inverted, your moon, all things bing equal, will have 100 times the influence on the surface liquid. It would have so much influence that its gravity would have to be taken into account designing very tall structures. It also could very well have destructive effects on core heating and crust/mantle tectonics. Other things to consider, IF you had something that you were not willing to leave every 2 years or so (figuring a tide every 3.5 years that is a year or or so long) Any mining could only be done for a couple of years at a time then all equipment pulled out and the mines allowed to flood till next 'low' tide. Any city would have to be built on towers tall enough to be higher than the water level at 'high' tide. OR you could build a city of inter connected structures, designed to float, tethered or moored on cables, thousands of feet long that would ride the tide up every time, or make a 'walking' city that would continue to move to stay ahead of the tide. You can also adjust the mass of your moon to adjust the tide to a manageable level. Your scenario, as given, would result is a single tide thousands of feet high (or deep as the case may be) every 7 years so explore how to make a civilization the avoids their equator (the place the gigantic blob of surface liquid would collect and move) or stay ahead of it. Do your equatorial latitudes have topography that would prevent a city sized machine from rolling/walking across it every 7 years? Do your movers have contingency plans for when a wheel/axle/leg goes down. How many, straight number or percentage can go down before speed or forward movement is impeded ect. have fin with this world. ]
[Question] [ In this world, there are a small percentage of humans with "special" abilities. The source of these abilities is alien genetic meddling for their own cryptic reasons (though the characters don't know it yet) so evolution is not a point there. The time frame (for technology levels) would be present day. I'd like for one of these abilities to be the ability to quickly grow a sort of organic body armor (the need for that ability has a reason in-story), not necessary for all the body (for example, they could grow only vambraces or similar). The armor would grow/appear when needed (in combat situations, for example) and, once the danger has passed, the armor would either molt or be reabsorbed by the body. What I'm more interested is in the composition of the armor itself. The armor should be puncture and bullet-proof, at least with regular weapons (armor-piercing weapons may exist but be expensive). It will be great if it could be some sort of anti-conductive or reflecting properties to give some protection against energy-based weapons (that the characters encounter later). Initially, I was thinking in something made of keratin or keratin-like substance (chitin? spider silk?) that might work similarly to current-day bulletproof vests, so even if the armor blocks a bullet, the flesh within may get bruised. Then I thought about some kind of organic polymer with viscoelastic properties or something similar. I know I'm getting more into X-Men territory, but is there any way something like that might be somewhat plausible? Or at least plausible enough for my readers to suspend belief and keep reading and not just roll their eyes and throw my story to the wastebasket. My story is more soft SF than hard SF, but I'd like some believability. Please, take into account that I'm an historian, not a chemist or physicist. Thank you! [Answer] I am thinking about something like the desert frogs make: a coat of fast-drying mucus. [![enter image description here](https://i.stack.imgur.com/Dc9AG.jpg)](https://i.stack.imgur.com/Dc9AG.jpg) It should be secreted then expand like expanding foam. The end product would look like these guys I found [in this video](https://www.youtube.com/watch?v=HJULyg3Mvw8) - covered with hard expanding foam. [![enter image description here](https://i.stack.imgur.com/ekRMg.jpg)](https://i.stack.imgur.com/ekRMg.jpg) It is not crazy outrageous. Animals, humans included, are good at making mucus. It is possible to make a lot of mucus very quickly as most people have occasionally experienced. Mucus can harden to a shell-like consistency. If the mucus were hydrated partly with acetone (which is also made in the human body!) it would dry faster. Maybe the volatility of the acetone could confer the expanding property. This would be a process of some minutes, not seconds. I could imagine the shedding process also to be glandular - maybe secreting some sort of grease or earwax-like substance under the shell? The toads eat their mucus when they shed it. Waste not want not. You could have your mutant do that too, since he can't really get a whole lot grosser. [Answer] I think a spider-silk-like one would be interesting and easily explainable. Attempts to bio-engineer spider-silk is also something people would recognizance from contemporary articles and such. It also makes it easy to research, because you can just find analogues in real-life spider silk. You could have bio-engineered glands spread out over the body to activate it quickly, and release it quickly with enzymes. If it'd be a good plot point the enzymes could be used as a weapon against other people's bio-armor! Otherwise you could just explain that doesn't work because the enzymes breaks down "seams" in the armor, and therefore it only works from the inside. ]
[Question] [ So this might be a slightly weird one, but I"ve seen answers to questions about minimum numbers for re-population and such, but what about a system where reproduction was controlled and coordinated, and the intent was zero population growth? The theory is, quite apart from sexual or romantic relationships, everyone in the group is the genetic parent of exactly two children (barring instances of twins/triplets/whatever), each with a different partner, so that everyone is genetically responsible for half of two children, and theoretically the closest relation anyone can have in their own generation is half-sibling, thus sharing on average only 25% of their DNA. So how might a system like this impact the needed starting population size, assuming that eventual reintegration with a larger population was for practical purposes impossible? How many generations back does a common ancestor need to be to minimize the chances of undesirable effects of inbreeding? I know it would rely on a perfect, or near-perfect, 1:1 ratio of genetically female to genetically male, so I guess another question is how large a population do you need for the randomness of birth to reliably average out that way? [Answer] Let's suppose that you start with X population, X/2 women and X/2 men, all totally and genetically unrelated to one another. That's the zero generation. On the first generation X children are born, can you ensure that they will be 50% boys and girls? Let's assume you can. When their parents die out (hopefully before the children's fertile age is passed!) they will start looking for partners. In this generation (supposing again X/2 of each sex) each will have X/2-1 good choices (i.e. barring own sibling). On the second generation (same assumptions as before) each will have valid choice X/2-1-2 (i.e. own sibling and parent's silblings' children of opposite sex [50% probability on average]). On the third generation, it will be X/2-1-2-4. On the fourth generation, it will be X/2-1-2-4-8. Yet, now we have reached the fourth degree of relatives (cousins of cousins of cousins) and we need go no further, as with each subsequent generation, some new people will become related, but also some other will become too distant, so I think an equilibrium will be reached. It seems that the choice among the population need never be more restricted than 15 forbidden persons of the opposite sex. Getting as X/2 any number greater than 15, for example 16, creates a safely reproducting population of constant size for that sex; double that for the other sex = 32. I would say that 32 people (16♂ + 16♀) is the absolute minimum of the constant population in your question. Caveats: My assumptions in italics. Also I'm not a geneticist, I just made assumptions considering the commonly society-held beliefs of inter-marriage. Lastly, you would need to account for: stillbirths, childlren mortality rate, people not interested in reproducing (sex-orientation, etc), male and female incapability to reproduce, mutations, ... [Answer] The answer to your question depends mostly on the prevalence of rare recessive genes that are harmful only if received from both parents. These can be engineered or bred/selected out of a population, although mutations from chemicals or radiation can re-introduce them. Even in a large population these genes will meet and cause birth defects or miscarriage occasionally. Even with a reasonable number of defective recessives, your population can be very small if they are willing to cull the inevitable hemophiliac or Hapsburg jaw. Almost half of our states allow first-cousin (though not double-first-cousin) marriage. You might want to check birth defect stats for these folks. ]
[Question] [ I'm thinking of a planet with one side too hot, and one too cold due to always facing its star. With the planet having a small ring, a "twilight zone" which may be habitable, I was wondering if a moon with some kind of orbit can somehow give this zone a consistent day/night cycle. [Answer] The problem with a tidally locked planet is it can't have a big moon orbiting it, and as the previous answers mention it, it would cast a tiny shadow. But think of this : on your twilight zone, you have 2 sides : one side closer to the sun, when the sun is actually really low on the horizon (always kind-of day), and one side further, with the sun a bit below the horizon (always kind-of night). Now, if you allow the planet not to be quite totally tidally locked, you can have it slightly oscillating (something like a span of a few degrees). Maybe in a few million years the planet will be effectively tidally-locked, but today is not that day, it's not rotating anymore but still oscillating. This way, the sun-close side of the ring of habitability have a long day / short night cycle, while the sun-away side has a short day / long night cycle. Of course, it's not really day/night, but more of a dusk/dawn. Think of the course of the sun on the poles, but with day/night cycle of a few hours instead of 6 months. [Answer] A moon would provide a very short night. Note that rings can be arcs not full rings! You'd have to look into that, but just off the top of my head I would suppose that an arc ring would have to be very narrow and thus would ot eclipse the sun anyway. But it’s a type of phenomenon you might not have heard of, and might give you more ideas. [Answer] That's a really interesting idea. I'm actually working on a tidally locked planet as well right now, and I had never thought of that. I can't see why it wouldn't be feasible. All I can see is that the moon would have to be really quite large, possibly even the size of the planet itself, for there to be a day/night cycle like we have on Earth. For reference, in the 2006 total solar eclipse, the moon only cast a shadow on a portion of Turkey and Cyprus: <https://en.wikipedia.org/wiki/Solar_eclipse#/media/File:Eclipse_fromISS_2006-03-29.jpg> The implications of having a moon that large would most likely drastically change the path of orbit of the planet, the two would orbit around each other as well as their star. ]
[Question] [ So the desired result is a compound that can be left in relatively isolated area, isolated such that weather has no direct affect on the area, and that will ignite/explode when touched, even after sitting in this area for a few thousand years. I am aware of things like touch powder that will explode violently when touched but that is a little too volatile. Simply grazing the compound should not be enough to set it off but resting a hand or something similar should. Is such a compound scientifically realistic? If there is no chemical that can achieve this under the long time constraint then what would be a simple alternative? The lower the amount of developed science that it would take to achieve this affect, the better. [Answer] Get a chunk of an alkali metal, like sodium or potassium. Encase it a well sealed chunk of glass. While it won't last forever, the glass should protect the alkali metal for a very long time, and everything else in the system should last for a similar amount of time. Create a mechanical booby trap that will drop something that will break the glass followed by a sluice of water. You can shape the chamber that the resulting reaction blasts out in the direction you want. For extra fun combine with a similarly sealed packet of phosphorus and some other long lasting flammable liquid.[Brainiac the TV show](http://theodoregray.com/periodicTable/AlkaliBangs/index.html "Brainiac brings us the idea, though has been proven faked")gave me the idea, thought the results they demonstrate were faked. The link gives us a more realistic view of alkali metals and how they work. TL;DR is they react with water producing heat and hydrogen. That means they go boom [Answer] No. You can't both have isolated a material for 1000's of years from everything\* in its environment that will degrade/contaminate it and have it be exposed for human touch. (\* pollutants (SO2, NOx, CO2, Ozone), oxygen, humidity, UV light, visible light, dust, dirt, bacteria, mold, insects, mice, etc. etc. Not to mention the random rat droppings, bat droppings, fallen leaves, pebbles, etc. Not to mention natural temperature variations.) You misuse the term "volatile", I believe. You mean unstable? "Lowest tech" presumes that technology is linear. It. is. not. (Which is lower tech: black powder or penicillin?) The most realistic approach has been mentioned: a trap, perhaps a pressure plate connected to a mechanism that mixes two components. If I were going to build a trap which would work after 1000's of years, and which would explode or ignite after such a long time, I'd use hypergolics (see: <https://en.wikipedia.org/wiki/Hypergolic_propellant>). For instance, kerosene in one sealed bottle, aniline in a second, and nitric acid (fuming or "white" preferably) in a 3rd. Designing and building such a trap would include (imho) the intention that it be operational for 1000's of years, and that's a problem. At that time scale, seismic motions have to be considered. There would have to be assumptions made about climate and geography. Components would have to be very stable. There's nothing particularly "high tech" as far as aniline or nitric acid. Aniline is a component of coal tar, which itself was "discovered" in 1665 C.E. (after that date physical separation of aniline would have been possible, if needed.) Nitric acid in the 13th Century, although the concentrated form I'm referring to may not have been available until the 1700's. The problem I see is the trap's mechanism. I think it would be difficult to build one which you could be relatively sure would work after 1000's of years, unless kept in a very stable environment. And I know of no realistic way to keep an environment stable for 1000's of years. [Answer] The closest thing I can think of is metallic sodium or potasium, suspended above a pool of water, but I'm not a chemist and I don't know how much time it could exists in its metallic form - I suppose it would oxydize quickly. [Answer] A single drop of antimatter kept inside of a magnetic suspension chamber with a charge that lasts 1,000 years might do it. But making it sensitive enough to be set off would be an issue. Also the degradation of the materials used to construct the canister would be questionable. ]
[Question] [ I like cats and for my world I wanted domestic cats (with changes obviously) but on a different planet. But I am a complete moron to space and don't know how animals would react to constant twilight. --- The basis for my species, called Seekers, are very catlike because millions of years ago some humans injected cat DNA into the native wildlife making the species after some trial and error of course. The species are feral and tends to be in groups from family to utterly random Seekers. They vary in color but white ones are very rare due to selection along with tortoiseshells and calicos. (The species is still development this is why I ask this.) The planet does orbit but its parent star is very young and is a good enough distance to get some light to have life but not as much as our own planet so its in a twilight stage. The photosynthesis changed a lot. Also since there are no alien people or people really there are no buildings. Instead of taking in sunlight the plants takes the light from the animals for all animals markings glow in the dark the brighter the glow the stronger so the dimmer shows old age, sickness, young they also take in a lot more water and the other components to make up for the lack of light. The terrain is varied but the plants tends to be darker and there are more dense meadow lands than forests except one rainforest where the dark plants thrive. Also there are two moons one being a meteor caught into the orbit of the planet. [Answer] Cats are mainly active in twilight and dusk. We, humans, have a different brain structure, we awake if we are in light and get sleepy in darkness. Furthermore, we aren't carnivores. Carnivores tend to sleep all days, except a short wake time to quickly kill and eat somebody, maybe have sex and similar. It is about energy sparing. We, humans, have to work all day to produce our food. Doing a continuous twilight for cats would be similar for them as if we would live in continuous daylight. We could do it, but our daily sleep pattern became irregular. I had seen cats in similar situation (it was an animal rescue office behind closed doors). They did as I said, they had around two active periods daily, but they did it irregularly. [Answer] If they live on the sunward side, they'd lie around all day napping and collecting warmth from the meager sun. On the night side they'd run back and forth playing with their toys as loudly as possible, keeping everyone awake. ]
[Question] [ Information: The plasma cannon is a weapon, that fires a continuous beam of plasma (with this, it can be sustained by the weapon, while it's fired) which is confined by a helical magnetic field. It's usually used as a cannon (hence its name), but with a sufficient battery technology, it could theoretically be used as a handheld weapon. And it has a great tactic against magnetic fields, that is demonstrated in the following situation: --- * A [challenger](http://i3.kym-cdn.com/photos/images/newsfeed/000/046/094/0.jpg) appears with a powerful magnetic field. * The cannon detects the magnetic field and creates an electromagnetic field that attracts it. [![enter image description here](https://i.stack.imgur.com/hxbsk.gif)](https://i.stack.imgur.com/hxbsk.gif) * When, everything is arranged in the way it should be, the plasma cannon fires, at this point the other magnetic field not only doesn't deflect the plasma, but guides it into the magnet. The challenger will probably get's the answer to his question in hell. --- Questions * *What are the flaws of this concept?* (I'm pretty sure that it has a ton of them) * *Is it possible to flip the pole of the other magnet?* --- Things to consider * Let's just assume that the energy requirements can be handwaved. --- [Answer] What's to keep the target from manipulating their magnetic field? Note that there are a number of reasons that could prevent that but you should know the answers if you are using it as a plot point. How far can the plasma get before it cools down enough to condense back to a normal state? That will probably be relative to the speed the plasma travels. Unless you can contain the heat in the beam, the cooling rate in a vacuum (vacuum assumed) will be fixed. [Answer] Flaws: 1. A bullet would probably be cheaper. 2. The energy concentration required to ionize and superheat gas could probably be used for something more productive. Like propelling a bigger mass. Despite what the movies show, magnetic fields are only really useful when dealing with charged particles and ferromagnetic objects. NOTE: PARTICLES. A lead bullet is neither, and would simply go straight through a magnetic field. Unless the field is sufficiently strong as to deflect high speed [paramagnetic](https://en.wikipedia.org/wiki/Paramagnetism) objects, in which case, the user better be safely inside a shielded suit or they'll get ionised. In any case, the shield is easier to overcome by simply increasing the calibre of bullet used, rather than using exotic technology. The alternate approach is, as you have suggested, flipping the magnet. Do it fast enough, and you get an electromagnetic transmitting antenna. Properly focused, this gives you a [microwave transmitter](https://en.wikipedia.org/wiki/Microwave_transmission), which will give you a better energy transfer per joule supplied than your plasma cannon. Something like the US military's [Active Denial System](https://en.wikipedia.org/wiki/Active_Denial_System). What you've suggested is similar to Tesla' [Teleforce](https://en.wikipedia.org/wiki/Teleforce) or "death ray". To my knowledge, nobody has been able to make it work. [Answer] Let me rephrase your question: if I know my enemy has a flamethrower, should I keep wearing straw suits? Now back to your question. These are the flaws I spot. First flaw: you don't want to bring strong magnetic fields on a battlefield, for the simple reason they are like wearing a light turret on your head while crossing a dark field: it attracts everyone's attention on you, making you easily detectable. Even without fictional plasma cannons, there are real mines which are activated by magnetic fields, enough of a reason to remove all the magnetic field one can remove. Second flaw: quickly changing a magnetic field alway come with a related induced current (blame Maxwell and his equations...). It's going to be a really (electro)cute weapon! Third flaw: if the target is locked to you, you are locked to him. He can back fire simply on detecting a "locking", while you are still setting up the discharge. [Answer] # A short list of problems * If your personal hand-held plasma cannon is generating such a powerful magnetic field, powerful enough to attract other 'challengers', how are you going to hold on to it? Let me ask it to you this way, if this thing is exerting enough force on another person to pull them towards it, then you have to be basically playing tug of war with that person through your weapon. If you are playing tug of war with your weapon, how do you intend to use it. Honestly, you might as well lasso your enemies at that point. Plasma lasso? Didn't the Balrog use one in Lord of the Rings? * Plasma is hot. Even if you can theoretically contain the plasma itself, it is going to radiate heat away at a very high rate. A magnetic field will do nothing to keep IR radiation in. Air will not absorb or reflect this heat, and in fact it will help to actively convect it away, so there will be no radiant heat going back into the plasma stream. In any case, your plasma stream will lose heat rapidly, making it more like a flamethrower than a 'cannon.' * Given the above point, it is useful to look at a picture of a flamethrower in action. [![enter image description here](https://i.stack.imgur.com/ACbEX.jpg)](https://i.stack.imgur.com/ACbEX.jpg) Notice how far from the operator the flame starts. And that's for a flame that isn't even that hot, at least not compared to plasma. A plasma cannon will generate an intense burst of heat that is maximized at the point of emission. How are you going to protect the operator from that? [Answer] Another two problems that I can see: 1) plasma, being ionised gas, is not "flame". Its heat is dependent, in systems that we are able to create, on induced current, and its stability is dependent on magnetic containment in a vacuum. Thus, firing a stream of plasma into atmosphere, will just disperse the stream after short distance (short as in centimeters, not any real weaponisable range). To counter that, ideally, your weapon needs to create a containment of some sort, on the beam's way to the target. This is both technically hard (as you cant really project a magnetic bottle over large distances easily), and needs a huge energy budget. 2) plasma will not only emit thermal photons (i.e. heat), but it will also emit ionising radiation (Brehmsstrahlung / cyclotron radiation, X-rays, stray protons...). If you want the weapon operator, and anyone in his general area, not to get acute radiation injury, you will need quite heavy shielding to mitigate that (assuming you want high power levels in your weapon) ]
[Question] [ I'm trying to build a designer organism that would prove a threat to all life on Earth. Sort of a semi-organic von Neumann ecology of microscopic nitrogen-eaters that rapidly consume nitrogen to fuel their own growth, which not only threatens to drastically accelerate the depletion of Titan's nitrogen atmosphere (which millions of off-world human colonies need to grow food) but also disrupt the nitrogen cycle that's vital to all life on Earth, killing all Earth-born life wherever it goes. To this end, if I want my organism to have the kind of properties I've just described, then I need to know what happens if it enters a human body and starts living in there by cannibalizing its nitrogen content. What might happen to a person who rapidly loses their normal bodily concentration of nitrogen, dropping from say 3% to 1% or lower? [Answer] They would die. Nitrogen is an essential component of protein, and if you lose 2/3 of the protein in your body, you are dead. [Answer] It depends. If it can attack any nitrogen compound, it would essentially "disintegrate" the body. While the body is mostly not nitrogen by weight, structural components - skin, bones, tendons, ligaments, etc. - are rich in collagen (a structural protein). This is probably really hard to do, though, since microbes evolve really fast and we don't see any evidence of "everything with bones or cartilage suddenly dissolves"-type mass extinctions in the fossil record. If it lives in the digestive system and co-opts nitrogen compounds (e.g. amino acids) before they're incorporated into the body, but doesn't actually tear the body apart, the result would be death by malnutrition, similar to lack of the "essential amino acids" in the diet (except worse, because the person also wouldn't be getting the nitrogen needed to make the amino acids the human body can synthesize). On the other hand, the nitrogen in Earth and Titan's atmosphere is strongly bonded nitrogen gas, N2. Using this is very chemically different from using nitrogen in organic compounds. In Earth's nitrogen cycle, some microbes fix nitrogen using enzymes called nitrogenases. If the organisms you're describing are meant to be a super-quick-acting version of nitrogen-fixing microbes (maybe an agricultural tool gone wrong), they're unlikely to be able to infect the human body successfully, since they wouldn't be adapted to survive the human immune system and might not be designed to use the organic forms of nitrogen available. [Answer] It really depends how rapidly. If you mean within a few days then the first symptoms would be general fatigue, weakness, lightheadedness (caused by the heart not being able to pump sufficient blood to the brain). After a day or so their body would start to necrotise causing extreme pain and physical dysfunction until their nerves fail at which point they'd become completely paralysed (even though they would have already been pretty much incapable of movement due to the pain and their exceedingly weak muscles) and then finally they'd die of total organ failure. ]
[Question] [ Worldbuilding and question background: In a world with dragons edging close to civil war, their king wants to use a revived “dragon Olympics” politically, to help balance the two rival factions. The dragons have agreed to respect the four traditional categories (flight, fire, hunting and ‘cleverness’) for the seven events, but the contest details have been lost from the ancient games. Selecting and defining the contest events/rules offers both dangers and opportunities. The king and his advisers need to select contest events within those categories to: * Achieve survivable balance between the factions: the 'Strongs’ (~Spartans/Klingons) and the ‘Sharps' (~Athenians/Vulcans.) In terms of factions, the games should result in a tie, or as near as possible. * Minimize opportunities for provocation, sabotage and assassinations -- or control those to his advantage. This world is basically 16th century earth-like (air, gravity, gold/gems/caves, prey animals, population density of pesky humans....) Key attributes of these dragons: adults are about 7 (metric) tons; flying, fire-’breathing’, carnivorous, four limbed, dexterous front paws; limited magic beyond flight and fire. Adults can generally lift up to large cows, horses or similar sized prey. Roughly human intelligence. Overall, Strongs are slightly better in flight and hunting; Sharps in fire and ‘cleverness.’ ‘Cleverness’ comprises learning, art, gem skill, Magic or riddle-solving. Strongs have a slight advantage in four of the seven contests. The king would love contest events that can (be arranged to) end in ties, at least peaceful ties. Finally, to the extent it can still be done, have an eye toward sportsdragonship and keeping the fun/fatality ratio high. Question (repeated): What events for the Reconstituted Dragon ‘Olympics’ can best avoid civil war? Bonus question: How best to run those contest events to minimize provocation, sabotage and assassination potential? --- Example (of what I’m seeking): Dragon Marathon: * 100 mile aerial race. * Set course with referees in the air throughout. * Touching down disqualifies. * Fire or Magic use disqualifies. Referees will have standard detection amulets. First dragon to reach the finish line wins. Potential for ‘accidents’: The greatest potential sources of ‘accidents’ is probably at the starting line, starting as soon as the racers assemble. Referees will be needed throughout the flight course. --- If I have too much detail, or have left out relevant aspects, please let me know. [Answer] Instead of presenting the games as "Strongs vs Sharps", make the games centered around teamwork - and design it so that the best teams involve players from both factions. For example, one game could be a race in which two dragons team up to push a large and irregular rock through a complex obstacle course or maze. A combination of strength and cleverness will prevail here. The prize for victory will be shared among the team, but the real point of the games is to drive home the idea that cooperation between the Strongs and the Sharps is good, discouraging civil war. This could be used in a story: the King keeps the plan and purpose of the games a secret, so most players pick members from their own faction. The main characters who are friends from opposite factions decide to play together, and they win - which turns out to have been the King's plan all along. EDIT: To keep the tension up through the whole story instead of having the team-up win everything (and keep the King's plan from being too obvious), three of the games could favor a team with at least one Strong, three could favor a team with at least one Sharp, and the final, tie-breaking event would favor a team of both. For example, the games could work like this: Anyone can enter, and they enter the games in pairs. For all but the last game, each team picks which member they want to play. The first two games are to weed out the majority of teams, with neither a fairly strong or fairly sharp member. The next four games are focused on the four categories. So for the Test of Flight, each team presents their best flier. For the Test of Fire, each team presents its best fire-breather. And so on. This way, a team with two Strongs will not always beat the opposing-faction team in Strong-favoring games, but they can still win sometimes. However, the opposing-faction team will have the advantage over the tournament as a whole, since they can score points on both Strong and Sharp games, while single-faction teams will generally only score points in games designed to favor their faction. The final game is the one where both members of each remaining team enter the game simultaneously, and favors a team with both strength and cunning. [Answer] I am not entirely sure what games you could do (the dragon racing game where sheep are dropped in a basket from How to Train Your Dragon comes to mind) but I do have ideas about rigging a tie (or victory). Some simple math and probability can be a great friend here. For instance: tic-tac-toe is a common game that will ALWAYS end in a tie if the person playing o's knows their stuff, a computer can play a perfect game of checkers, there are number games where each player takes items from a pile 1, 2, or 3 at a time and the first player can always win if they are clever enough, there is the example of Black Jack which can be won by counting cards. Anyway, I think setting up points systems that favor a player (which is easy with two factions) or that set up a tie, would be best. The tricky part is getting those number games past the "Sharps" and making them athletic enough for the "Strongs". I would favor the "Strongs" initially and let the "Sharps" take things to a tie if they are clever enough. Also, if you give three games to the smartest, and three games to the toughest, that leaves only one to rig with a tie. (If war doesn't break out over the first six games that is). You can start by looking for articles like these that break down all of your childhood wonder into math and disappointment. <http://www.cracked.com/article_19747_5-ways-to-beat-old-school-games-using-math.html> <http://card-tricks.wonderhowto.com/how-to/always-win-card-game-using-bit-math-283821/> [Answer] The olympics would also need to provide things that allow them to combat each other in such a way that they are able to let the tension out on the field. Like we have boxing, wrestling, and other means of combat without it being real, you could add in some form of this to the events. Depends on where you want to go with the story really. Are you trying to create this event as a means to completely end the tension? Or just a temporary solution and right after the events end, a war breaks out because one side lost and feel they were cheated? One thing that will definitely happen is that the various cultures or regional/city pride will be heavily present in the events. So the events will be needed to be done in such a way that the aggression can be reduced without causing further issues if some regions/cities are sore losers. I think one of the best ways to do this would be to create some combat events where the best fighters can represent each area and spare each other. If their best regional fighter loses to another region, they would be more likely demoralized from creating actual war since their best fighter lost. Or they could use it as fuel saying "if only he could fight for real, he wouldn't have lost". Just depends on where you want to take the situation. [Answer] This answer suggests a combined event. Two dragons play a game like Go. After making a single move, an hour glass is turned and the dragon that has just made its move must fly a course in a fixed time. During its flight it must (a) hunt and catch a prey animal, (b) set fire to a designated target, and (c) return to the Go-like board within the time the hour glass takes to run its course. If the dragon fails to return within the hour glass' designated time, its opponent can make as many moves on the board as it cares to make before the first dragon returns. This event rewards all four traditional categories of flight, fire, hunting and ‘cleverness’. While the OP's question sought a range of events for his dragon "Olympics" this answer has confined itself to proposing a single combined event. On the presumption other answers will offer other possible events to fill the full quota of "Olympic" style events. [Answer] So it sounds kinda like what you want is events that can be rigged. Races are an easy, obvious one. Maybe fire spitting can be an event based on distance or accuracy. I feel like taking a dive on accuracy wouldn't be too hard. I'd imagine dragons would want wrestling as an event. While I don't think dragons would have a judge scoring system to result in a time, I could imagine there being rules in place to prevent things gettig too wild: No biting or clawing or fire blowing - something competitive, but it can give an opportunity for the two to show sportsmanship I guess. ]
[Question] [ Would * Aristotelian natural philosophy, with planets and Sun orbiting the Earth, and forces needed to maintain motion * Things having natural places and desiring to reach it * horror vacui * Four elements build an usable base for a fantasy world? [Answer] Worldbuilding in science-fiction or fantasy will always make assumptions about the nature of their fictional worlds. The usual criteria is that logical consistency is maintained for the duration of the story. Science-based SF will attempt to keep the science congruent with current scientific understanding even though such stories will often have elements of speculative or imaginary science. Aristotelian physics can provide a speculative basis for an imagined world. Admittedly by current standards, it contradicts our understanding of the cosmos. However, a lot of fiction still peddles concepts and tropes that are contrary to current science. Bad old ideas can take time to flush out of the system of conventional thinking. There is an argument that SF still hangs on to the Newtonian worldview, and is only slowly coming to grips with cosmos run by quantum mechanics and relativity. Using Aristotelian physics is a perfectly plausible conceptual framework to construct a fantasy world. Side-note: Science itself doesn't have a set of complete theories to explain the cosmos whole and entire. Every piece worldbuilding, especially in SF, that sticks to close to current science will sooner or later become outmoded and outdated. Outmoded science is full of wonderful concepts like phlogiston, the luminiferous ether and polywater. They deserve the right to star in their own fantasy worlds. [Answer] Yes. Absolutely. In fact, it's probably already been done before. The four elements are often used as a basis for magic in many worlds, and there's no reason to suppose that you couldn't give a more logical explanation for magic's existence based upon Aristotelian logic. If I were you designing a world with magic, I'd focus most of my attention onto the four elements. If you want to get into Plato's work, you could explain a fire as simply tetrahedrons, or the oceans as many icosahedrons. This would be able to logically explain magic (a fireball is simply the creation and movement of tetrahedrons) in a fantasy universe where it exsts. If it's more of a science-fiction-y type fantasy world, I'd put more emphasis onto the solar system aspect of his works. Having everything orbit the Earth makes it the centre of the solar system, and an immediate target for any type of invader. Horror Vacui seems like a harder topic to make use of, but I suppose that you could use it quite literally in any world with sentient plants. If Nature abhors a vacuum, the plants could want to conquer the world, as any space where they are not present may be considered a vacuum? OK, that just sounds dumb now I'm re-reading it. [Answer] For a primitive understanding of physics in a fantasy world, surely; after all, it did perform that function on Earth for about 19 centuries. The problem with pre-Newtonian physics is that the only parts which allowed actual calculation of effects were kinematics and statics, neither of which is affected by the silly theories of impetus etc. Pre-newtonian physics simply had no quantitative understanding of dynamics at all, much less of electromagnetism. That is to say, pre-Newtonian dynamics was essentially pure handwaving, there were no numbers in there at all. ]
[Question] [ A world, I am building, had been flooded, causing a species of fire ant that makes ant rafts to evolve a collective behavior, ditching anthills and becoming an ant-hill (I'm not sorry). Over thousands of years, the flood waters receded and the clustering behavior of these ant-hills remained, creating a powerful, natural, biological army. Over many millions of years and some complicated evolutionary history, I don't have room to explain, these ant-hills evolved into a [collective consciousness](https://worldbuilding.stackexchange.com/questions/46962/what-would-a-collective-consciousness-look-like) that have shown the true limits of swarm intelligence. While each ant is just an ant, together as a whole, the collective is sapient. As they do not breed and lack 'organs', so to speak, their species (Diluviumformica sapiens) consists of many smaller specimens, all working as a whole, communicating to each other using touch and pheromones, the larger whole communicates with each other through much more powerful pheromones. They are [virtually immortal](https://worldbuilding.stackexchange.com/questions/45752/how-does-a-collective-consciousness-species-avoid-overpopulation) and have met with humanity. To avoid [war](https://worldbuilding.stackexchange.com/questions/52468/how-do-i-wage-war-against-a-collective-consciousness), humanity is attempting to communicate with these aliens, but we are failing. Humans communicate via sound and the ant-hills communicate via smell, it is proving difficult. How can an audio based communicator like a human communicate with a pheromone based communicator like the ant-hill? [Answer] ## Speak their language @Green had an answer on your war question that is somewhat adaptable. > > Since each ant is a conglomerate of smaller individuals who cooperate by touch and pheromones, then design chemical weapons to disrupt this communication. > > > Instead of disrupting communications intentionally, respond to them. Analyze thoughts / conversations, discover what individual chemicals represent, and synthesize them. Rig up a computer translator, a doable task, that detects the pheromones, then speaks (via sound) the perceived meaning; then have it try it's best to take sounds it hears and create the right chemicals. Easy. ## (Or) Speak ours anyway These ants must be able to sense the world around them. If they are truly intelligent and have a developed society, they may be able to translate, as best they can, what we say. If they have technology (assuming that from the war question) surely they're capable of some automatic translation themselves. [Answer] ## Build a translator Humans communicate by both methods already and presumably, these hell-ants would too. While no examples are required to describe how humans communicate by sound, it may be useful to illustrate a few examples of how humans communicate by smell. A person who smells like poop will indicate in a modern society whether they have access to hygiene facilities. Nurses also report smelling something that indicates a patient [is near death](http://allnurses.com/general-nursing-discussion/does-death-have-452535.html). While both of these examples passively convey information, this still counts as communication. Further, perfumes and colognes attempt to indicate sexual fertility/attractiveness. Communicating by smell will be a shift for humans but not terribly impossible. Also, the ants will be aware of vibrations in their environment because so much useful information comes that way. It's just not their primary communication method. ## Building the translator To build a translator, humanity will need to do the following: 1. Identify as many of the chemicals that the ants use to communicate. The larger the library the better. Doing this will likely require a portable mass spectrometer to gather information on the more unstable message compounds that break down quickly in the atmosphere. 2. Map each chemical to the meaning it has for the ants. This may be incredibly difficult. 3. Find a way to synthesize the message compounds and store them. Some compounds may be sufficiently unstable that they will need to be synthesized on the spot, during translation. 4. Perfect the dispersal mechanism in the translator to mimic as closely as possible the way that the ants disperse their message compounds. This is how you speak to the ants. 5. Build a mechanism that will act as the nose of the translator to accurately identify the type and composition of message chemicals. This mechanism is how you talk back to the ants. 6. Connect the translator to a laptop. Good luck! [Answer] ## Prepare Ahead of Time Those among us who feel sentient alien lifeforms exist would de well, I feel, to prepare as wide a range of communication skills as early as possible so that we will be as prepared as possible when we meet aliens. There are so many species of lifeforms on earth, each with it's own consciousness and behavior. Each one that has any form of communication that can be studied in depth should be, because each form of communication likely will have nuances or aspects we might not be familiar with as humans. Everything from whales to bees to neurons to cell organelles have systems of data communication, and we could learn a lot from mastering those forms of communication. So, the more conversant or familiar we are will as many forms of conscious communication we are, the better prepared we might be when encountering a new entity. We might be able to notice this alien's speech has tendencies similar to bees, with other nuances similar to flatworms, and also some likeness to Cantonese. So, the more prepared we are before meeting gestalt entities like your fire ants, the better prepared we will be diplomatically. Taking four decades to respond to a first communication from the fire ants due to need for research is poor diplomacy. Ideally we could respond immediately to their envoy in their own language of touch and smell, particularly if they are hostile and not wanting to be courteous and learn human languages. So, in this case, I would recommend creating robotic ants or [cyborg](https://www.technologyreview.com/s/411814/the-armys-remote-controlled-beetle/) ants capable of being remotely controlled. These ants should be capable of touching in appropriately communicative ways, and also of producing necessary pheromones for communication. Then humanity will need to discover how to interact with the ant colony. For example, can it be successfully communicated with via only one human-controlled ant? If so, then our one ant should initiate communication. If however the ant colony needs to be communicate via another gestalt colony, then we need to make our robot/cyborg ants function as a swarm/gestalt organism and interact with the fire ants accordingly. ]
[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. # Background I was pondering my [answer](https://worldbuilding.stackexchange.com/questions/62937/is-space-piracy-orbitally-practical/62950#62950) to this [question](https://worldbuilding.stackexchange.com/questions/62937/is-space-piracy-orbitally-practical). I asked myself, "Why would I only do a 45-minute burn and then float for 3 months to get to Mars?". Then I answered, "Because you only have so much reaction mass; you can't let it rip for three months straight." But is that really a good answer? Spaceships today just burn once then cruise, but they are also small. Will the space freighters of the future use the same principles? # Assumptions Your power source is a [Fission-Brayton cycle](https://web.archive.org/web/20041022135357/http://www.spacetransportation.com/ast/presentations/7b_vandy.pdf) system. Fuel costs must be accounted for when calculating how long to burn. The engine is replaced as a single unit with all fuel included and costs 5000 bars of gold pressed platinum (bogl); its service life is 10,000 hours operating at full power (100 [MWe](https://en.wikipedia.org/wiki/Watt#Electrical_and_thermal_watts)). Only the full power hours during burn need be accounted for. Your engine is a bank of [Magnetoplasmadynamic Thrusters](https://en.wikipedia.org/wiki/Magnetoplasmadynamic_thruster). These engines have variable impulse at full power. High impulse setting is a specific impulse of 100 km/s and 1 kN thrust for a fuel usage rate of 0.01 kg/s. Low impulse setting is a specific impulse of 15 km/s and 7.5 kN thrust with fuel use rate of 0.5 kg/s for a Fuel (lithium) costs 2 bogl per (metric) ton. Your vessel will be manned. Each crewmember must be paid 1 bogl per year. The above configuration requires an engineer officer on watch at all times and thus takes a crew of 6. The longer the trip takes, the more you have to pay the crew. Your cargo plus the weight of spacecraft is 10,000 tons, not including your lithium reaction mass. Your goal is to fly from Earth to Mars (225 million km) starting in geostationary orbit of Earth. # Question What burn profile (firing engines at high or low impulse, for how long, in what sequence) will get you from Earth to Mars minimizing both the time and cost it takes to get there? NOTE: This is a math problem. A correct answer will use the above assumptions and numbers. You can substitute your own systems and assumptions with good reasoning, but only systems that have a working prototype can be used, and assumptions about power output, etc. must be justified. NOTE2: Time and cost cannot both be minimized at the same time. A correct answer will provide reasoning about how to prioritize each factor against the other. NOTE3: Remember, you have to decelerate! [Answer] So, we have 3 costs - engine wear, fuel cost, crew payments - and we have to balance them to get out zeros, I suggest piracy on the way, lol. To reach the Mars from GEO needs delta-v about 3 km/s( the exact number is not important). 100km/s impulse - 10000 tons craft need 305 tons of fuel, acceleration time about 4294 hours (in fact it will be more than that) cost is 610 + 2147 = 2757 bogl 15km/s - 2214 tons of fuel, 1357 hours cost is 4428 + 679 = 5107 bogl Neither of both situations will take us more than 2 years, so, price of payment for the crew is less than 1% of total expenses, and will not affect the total cost in a significant way, therefore balance is between hour rates for engine work and hour rates of fuel expelled at that ISP and total time of acceleration. hourly rate for the engine is 0.5 bogl/hour(minimal wage) + fuel bonus. First order of approximation, we looking for a minimum of the red plot like this one: [![enter image description here](https://i.stack.imgur.com/AEXeb.png)](https://i.stack.imgur.com/AEXeb.png) Green plot is how it looks like when engine time is cheap, blue if fuel is cheap. Red plot minimum is about 50km/s (no further calculations just looking at the plot) It has to be noticed that it is just for the time needed to gain just(!) 3 km/s of delta-v needed for transfer from GEO to some orbit intersecting Mars orbit with following air-capture maneuver. Price for the crew is not very important there, even if travel will take 100 years. In fact, higher trust (and lower ISP) will be more optimal, as it rotates velocity vector less amount of time (those vector rotations are counter productive for delta-v gain, the situation will be better than for usual probes but I have to note that incorrectness). The task as whole is not just a simple math problem, and it does not have some simple analytical solution, because of orbital mechanics involved. It may do not have an analytical solution at all, but I'm not sure about that. Another problem is - it is not a continuous solution field, if we have pay fixed sum for the engine replacement, because if we spend let say 5001 hours of engine work on the way to Mars, and have to spend also 5001 hours on the way back we should replace engine completely - and time of engine work depend on orbits we use, so theoretical minimums may be no achievable on practice in some situations. Also on the plots it is not accounted for a different initial mass of the craft, the difference is about 20% for low ISP and 3% for higher ISP - so, real optimum of ISP will be higher than red plot shows. The real value will be in-between of those two plots (red is same red as in plot above, purple-ish worsts case scenario): [![enter image description here](https://i.stack.imgur.com/ind8p.png)](https://i.stack.imgur.com/ind8p.png) Formulas for plots are: $$ \text{Total mass of the craft} = M\_0 \cdot e^{\frac{\text{delta-v}}{\text{ISP}}} $$ $$ \text{Fuel mass} = \text{Total mass of the craft} - M\_0 $$ $$ \text{fuel consumption per second} = \frac{2 \cdot \text{reactor power}}{\text{ISP}\_{m/s}^2} $$ $$ \text{acceleration}\_\text{optimistic plot, red} =\frac{\text{ISP}\_\text{m/s}\cdot \text{fuel consumption per second}}{M\_0} $$ $$ \text{acceleration}\_\text{pessimistic plot, purple} =\frac{\text{ISP}\_\text{m/s}\cdot \text{fuel consumption per second}}{\text{Total mass of the craft}} $$ $$ \text{Cost} = \frac{\text{delta-v}}{\text{acceleration}} \cdot (\frac{\text{engine hourly rate}}{3600 \text{sec}} + 0.002\cdot\text{fuel consumption per second}) $$ I encourage someone to find the optimum, but I'm not going to do it myself - 50000-54000 m/s ISP is good enough for me in this situation. ]
[Question] [ A K2+ civilization wants to build a fission star, a huge mass of fissile material which doesn't collapse due to the radiation emitted by its fission decay. I know there are reactors like the [aqueous homogeneous reactor](https://en.wikipedia.org/wiki/Aqueous_homogeneous_reactor) that are self regulating and even [naturally occurring reactors](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) exist, so why not a star? So basically can I make a self sustaining, spherical, homogeneous fission reactor? I don't care how big it is, for how long does it shines, if it's solid, liquid, gas or plasma, it's also ok if it needs to contains other elements (moderator?) to exist. It's a K2+ so resources are not a problem! [Answer] An artificial fission star could be stellar-sized gaseous nuclear reactor. > > A gas nuclear reactor (or gas fueled reactor) is a proposed kind of nuclear reactor in which the nuclear fuel would be in a gaseous state rather than liquid or solid. In this type of reactor, the only temperature-limiting materials would be the reactor walls. Conventional reactors have stricter limitations because the core would melt if the fuel temperature were to rise too high. > > > However, maintaining a gaseous core nuclear reactor may be compromised by the need for containment of the gaseous fission core. > > It may also be possible to confine gaseous fission fuel magnetically, electrostatically or electrodynamically so that it would not touch (and melt) the reactor walls. > > > Considering how a gaseous core reactor might make and its possible applications does a possible way of implementing an artificial fission star. > > The vapor core reactor (VCR), also called a gas core reactor (GCR), has been studied for some time. It would have a gas or vapor core composed of UF4 with some 4He added to increase the electrical conductivity, the vapor core may also have tiny UF4 droplets in it. It has both terrestrial and space based applications. Since the space concept doesn't necessarily have to be economical in the traditional sense, it allows the enrichment to exceed what would be acceptable for a terrestrial system. It also allows for a higher ratio of UF4 to helium, which in the terrestrial version would be kept just high enough to ensure criticality in order to increase the efficiency of direct conversion. The terrestrial version is designed for a vapor core inlet temperature of about 1,500 K and exit temperature of 2,500 K and a UF4 to helium ratio of around 20% to 60%. It is thought that the outlet temperature could be raised to that of the 8,000 K to 15,000 K range where the exhaust would be a fission-generated non-equilibrium electron gas, which would be of much more importance for a rocket design. > > > If the bulk of the star was composed of helium (He-4) and the equivalent of a gigantic gaseous core reactor was assembled at its centre, this could consist of UF-6 and He-4 mixture, once the fission reaction process was initiated the nuclear reaction core, provided the surrounding He-4 bulk mass could act as a default containment vessel this might be a fission powered star. Since this model is a conceptual extrapolation of a gaseous core nuclear reactor system to stellar dimensions, there are many factors that are imponderable without extensive analysis. Basically the thermodynamics and hydrodynamics of a stellar-sized nuclear reactor. The engineering issues in assembling such a construct are considerably non-trivial too. [Answer] Uranium-235 can sustain a natural fission reaction, with a half life on the scale of $10^{15}$ years [(1)](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.528.7753&rep=rep1&type=pdf), whereas Uranium-238 has a fission half life on the scale of $10^{17}$ years. This reaction is different from a normal fission reaction which releases all energy in a short time span.[(2)](https://blogs.scientificamerican.com/guest-blog/natures-nuclear-reactors-the-2-billion-year-old-natural-fission-reactors-in-gabon-western-africa/) This kind of natural slow fission has existed right here on earth, and has been known about since 1972.[(3)](http://brendans-island.com/blogsource/20101015ff/a-natural-fission-reactor.pdf) Note that these real life examples were based on masses of a combination with U-235 and U-238. They have been inferred to exist through analysis of the reaction products, and the left over ratio between the two forms of Uranium. Here I assume that such a reaction can be sustained with just U-235, and calculate whether the reaction would be fast enough to sustain the star. In fission, U-235 releases $3.24\times10^{-11}$ joules. The total energy output of the sun is $3.85\times10^{26}$ watts. To reach this amount of energy output, a U-235 star would have to have $1.18\times10^{34}$ atoms engaging in fission per second. Taking an approximate equation to prevent underflow, calculate: ``` Solve[N0 Exp[- λ] == N0-10^34] ``` > > `{{N0 -> -(20000000000000000000000000000000000/(-2 + 2^( > 31535999999999999999999/31536000000000000000000)))}}` > > > Or numerically the amount of initial atoms is $5\times10^{56}$. As there are approximately $10^{24}$ atoms of Uranium-235 in one kg, that means $5\times10^{32}$ kg, or two orders of magnitude heavier than the mass of the sun. In other words, a fission star would have to be at least about two orders of magnitude heavier than a regular star for the same energy output. I don't actually think this is very far out. However, it is not inconceivable that this reaction, as being naturally inhibited can be sped up to increase the energy ouput by mass, and it is possible that the reaction would speed up with a 100% U-235 mass, or under the severe gravity and heat that such a large mass would have. It is up to OP to decide if this is feasible enough in his situation. 1. Pure Appl. Chem., Vol. 72, No. 8, pp. 1525–1562, 2000. 2. Nature's Nuclear Reactors: The 2-Billion-Year-Old Natural Fission Reactors in Gabon, Western Africa ; Evelyn Mervine (sci-am) 3. <http://brendans-island.com/blogsource/20101015ff/a-natural-fission-reactor.pdf> ;George Cowan (sci-am) [Answer] By definition, stars create energy through fusion. So a fission star is a misnomer. Secondly, anything the size of a star would most definitely gravitationally collapse on itself. In case there is potential fusion fuel in the mixture (anything from hydrogen to manganese), the star would initiate fusion and die like a normal (main sequence) star. In case there is no fusion fuel in the mixture, the gravitational collapse would create a supernova (if the collapse is quick enough) or slowly crush itself into a black hole or neutron star, depending upon the mass. ]
[Question] [ In the space opera concept story I'm working on, the underdog faction develops/discovers several technologies and resources that help them turn the tide against the enemy. One of these discoveries is a "living" metal (I was gonna call it "Animite" but googling it, the name has been used for to many fantasy metals already - new name suggestions will be appreciated). While not being sapient, or even sentient, it does self repair by consuming other elements by contact. So cutting a slab in half, and feeding the two halves will eventually produce two wholes. While the replication process is far from fast, it does give vehicles in the field the ability to self repair with minimal equipment and resources, as well as supply a near infinite supply of usable metal. Note: To keep the armour plates made of Animite from consuming the vehicle the plates are coated with a protective layer. When repairing a neutral foam is first injected into the hole to prevent the newly grown metal from making contact with the vehicle. How could I make this plausible without too much hand wave? Maybe a symbiotic type of bacteria? [Answer] The process of [bioleaching](http://www.pythongroup.ca/mining-news/article/id/56) is already used to extract metals from ore. Essentially the bacteria dissolve the metal then secrete it un a solutin. the metal can be gained from this by purification. For your scenario we need to change this slightly. First we need to have two bacterial, one extracts metal from the ingredients it is 'fed' and the other purifies the solution. Alternatively the solution could react with something in the air causing the metal to precipitate out. Now our main problem is the fact that these bacteria can only get metal from something with an existing content of the metal. One option is to say this metal exists in small trace quantities as a compound with one of the rarer earth gases. Xenon maybe. The metal is in too low quantities to be noticeable in air but when the air is absorbed by plants and animals the metal compound is also absorbed. It then slowly builds up harmlessly inside the plant/animal. This means that when our metal is damaged our bacteria can get to work extracting the metal from any surrounding plant or animal matter including wooden furniture, wool or cotten clothing, leather upholstery, human skin etc. Of course this process will take a while and a lot of material. A 1cm^2 hole would probably take 2 hours to repair at the fastest and likely more. It would also probably take maybe 100 times more material going in than you get out. [Answer] Since their introduction in fiction and not, nanomachines have been kinda like the "wizard did it" solution, they could do what you need, but I admit that the simil-bacteria idea is an interesting one. ]
[Question] [ Reasonably speaking, I mean. I know that, theoretically at least, there probably isn't any reason you couldn't build a crude generator the size of a bacterium, but if we extrapolate from today's technology a little more conservatively, could we expect man-portable antimatter generators/batteries at some point in the far future? Could they be made so small as to fit inside a Duracell battery or a bullet? If so, how much antimatter could these miniaturized generators produce? I ask because I had the idea for a futuristic weapon that outwardly resembles contemporary firearms but which fires bullets containing a tiny disposable antimatter generator. The generator would, in the scant milliseconds the bullet travels through the air, produce up to a few nanograms of antimatter that annihilates with the target once the bullet mushrooms on impact, breaking the trap. The result is an explosive round with a yield of a few megajoules, like an assault rifle that can fire tiny grenades at mach speeds. Is this realistic for a society with hundreds of years of scientific development on us? [Answer] # Miniature Antimatter Generators I don't think this makes any sense. The problem is that current methods of creating antimatter require far more energy than you get from the matter/antimatter annihilation that results. If you have that much energy, why not just pack it into a bomb, or kinetic energy weapon? First, to create antimatter, you squeeze a bunch of energy into one place. If done properly, the energy converts to mass according to $E=mc^2$. Half that mass is normal matter, the other half is antimatter. So the best case scenario here is that you put a bunch of energy in a bullet, use it to create a matter/antimatter pair, then recombine them to generate the same energy you already had in the bullet. Second, you need a lot more energy than that. Of all the energy that goes into that tiny place to generate the particle/antiparticle pair, there's loads more that went somewhere else. The [CERN](http://angelsanddemons.web.cern.ch/antimatter/making-antimatter) website has some information here (it's related to the book Angels and Demons, but appears to be written by scientists at CERN, not the author of the book). It says that for every million collisions, you get 4 matter/antimatter pairs. That's about 500 thousand to one proton to antiproton. Further, each of those particles is energized with about 30 rest masses worth of energy. That is, we've dumped enough energy into a proton to create 30 protons if we converted all the energy to mass. So we're dumping about 15 million antimatter masses worth of energy into the creation of a single antiproton. Third, there's even more energy used to do all of the above. There are magnetic coils, electricity to run the computers, etc. CERN estimates > > About 1 billion times more energy is required to make antimatter than is finally contained in its mass. > > > # Miniature Antimatter Batteries You've got better luck here, but it's still going to be difficult. The proposed methods of containing antimatter involve magnetic fields to keep the antimatter from interacting with normal matter until you want it to. I don't know how to calculate this, so I'll leave that for someone else to answer. In general, however, I think you can make it about as small as you need. [This paper](https://arxiv.org/pdf/physics/0507114v2.pdf) on using antimatter pellets to start a nuclear explosion considers the possibility of a 1mm chamber to hold 1 µg of antimatter. The paper says > > the levitation of a frozen $\overline{H}$ pellet within a 1 mm diameter cryostat at the heart of a complex thermonuclear device is a tremendous challenge for materials microtechnology. However, if metastable states of $\overline{p}$’s in Li−, Be− or possibly C−DT compounds are discovered, much simpler designs could be considered." > > > Since the antimatter reacts with normal matter, you'd have 2 µg worth of energy from the reaction, which gives around 180 MJ. From [Wikipedia](https://en.wikipedia.org/wiki/Muzzle_energy), an extremely large bullet (the [14.5 × 114 mm](https://en.wikipedia.org/wiki/14.5%C3%97114mm) antimateriel round) has 32 kJ of kinetic energy. The [.50 BMG](https://en.wikipedia.org/wiki/.50_BMG) round (still a very large round for a hand-held rifle) has about 15 kJ of kinetic energy. More typical rifle rounds have between 2 and 4 kJ kinetic energy. This means a single microgram of antimatter could unleash about as much energy as 60,000 rifle rounds. Further, that energy would tend to explode outward from the contact point, so you're not just making a really clean hole through the guy, you're shredding/melting/plasmafying him to bits. From [here](http://brobible.com/guyism/article/insane-physics-calculations-figured-out-by-reddit-iama/), they estimate 800 kJ energy released from a typical hand grenade (and point out it's not a safe assumption, so do your research). That means your bullet packs as much punch as about 200 hand grenades. [This Youtube video](https://www.youtube.com/watch?v=L1nkrakXiIY) estimates about 11 kJ energy for a 1 $cm^2$ bit of grenade shrapnel. The [M67](https://en.wikipedia.org/wiki/M67_grenade) grenade has a diameter of 2.5 inches, so its surface area is about $4\pi(\frac{2.5}{2})^2$, or [20 $in^2$](http://www.wolframalpha.com/input/?i=4pi(2.5%22%2F2)%5E2). This converts to 127 cm², giving [1.4 MJ](http://www.wolframalpha.com/input/?i=4pi(2.5%22%2F2)%5E2++11kJ+%2F+cm%5E2) energy in the hand grenade. Which means there are "only" [129](http://www.wolframalpha.com/input/?i=(2+micrograms++c%5E2)+%2F+(4pi(2.5%22%2F2)%5E2++11+kJ+%2F+cm%5E2)) hand grenades in your antimatter pellet. In general, you may want to scale the power down quite a bit to avoid killing friendlies and civilians and destroying the entire building. But I think your concept is workable here. [Answer] Generating antimatter is a very difficult thing to do. MichaelS has done a pretty comprehensive job with today's technology. You could make things physically smaller by using a "[Wakefield Accelerator](https://www.youtube.com/watch?v=KjoH1ZZrAik)", but the fundamental issues remain. The only other way to generate antimatter using what we understand about physics is to make use of quantum physics. It is thought that the vacuum is full of "virtual pairs" of particles, where a particle and corresponding anti-particle come into existence and disappear in an instant. We obviously do not understand this fully, since some calculations indicate that there is enough energy in a coffee cup sized volume of vacuum to boil all the oceans of Earth, yet this is obviously not apparent. Using the idea of virtual particles, [Stephen Hawking](https://infogalactic.com/info/Stephen_Hawking) developed the idea of Hawking Radiation, which gives us an idea of how to get antimatter. [![enter image description here](https://i.stack.imgur.com/OsYf4.jpg)](https://i.stack.imgur.com/OsYf4.jpg) Virtual particles separated at the event horizon* Virtual particles appearing near a Black Hole would be affected by the intense gravitational field, and some of the particle antiparticle pairs wold be separated, with one going down the event horizon of the black hole, and the other escaping to free space. (The Black hole loses the mass of the escaped particle, the process is described as "Hawking Radiation") From this very loose paraphrase, we see that if a sufficiently strong gravitational field is available, we can collect the particles being ejected into free space. Statistically, half should be antimatter. Of course, using microscopic black holes to generate antimatter comes with other problems. Smaller and smaller black holes emit Hawking radiation at higher and higher energies, eventually evaporating in a blinding flash of energy. This site allows you to do the calculations: <http://xaonon.dyndns.org/hawking/> So in very rough terms you could have a microscopic antimatter generator, but playing around with a microscopic black hole will probably have more issues than the amount of antimatter you could harvest. ]
[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. Assuming the ship has access to fusion power, a large volume of solar panels, and crude antimatter power generators (say maybe 1 gram a day per generator, or whatever is reasonable for technological development a few hundred or a thousand years in the future), how big could a generation ship designed to travel between .1-.99c be? If it's too big, its mass will prohibit it from achieving the desired speeds. If it's too small, it may not have enough living space leftover to accommodate millions of people in at least relative comfort, and it would require less effort to destroy in the event of an incursion by hostile forces (plus it wouldn't look as cool as it would if it were bigger). Keeping in mind that the ship can be allowed a few weeks, months or even years to reach top speed given the combined power output of the sources listed above, what would be a plausible size for a generation ship that's meant to carry millions as well as defend itself? [Answer] You can get an initial benchmark for the size of the ship from the [largest cruise ship on Earth](http://www.cnn.com/2016/05/19/travel/harmony-of-the-seas-worlds-biggest-cruise-ship/) today: > > Royal Caribbean's newest ship, Harmony of the Seas, debuts Friday on > its pre-inaugural sailing out of Southampton, England. Weighing > 226,963 gross registered tons with a passenger capacity of 5,479 > guests at double occupancy (it fits 6,780 guests total) and 2,100 crew > members, Harmony is now the world's largest cruise ship. > > > Thus, a cruise ship has about 26 tons displacement per person on board with quite a bit of crowding and only a week or so's supply of food, but also with fuel and engine space in addition to areas intended to be occupied (we will need to account for fuel and engine space separately in this case because the fuel and engine requirements of an interstellar ship are very different from those of a cruise ship). By comparison, the Nimitz Class aircraft carriers are the largest warships ever built at 102,000 tons with over 6,000 personnel, which is about 17 tons per person for tours that are typically six months at a time, with less fuel (since it is nuclear powered - an aircraft carrier can run itself for about 30 years before refueling, but not no fuel because it has fuel for aircraft), but with space devoted to aircraft that would not be as necessary on an interstellar craft (although some landing craft would surely be needed). But, you wouldn't go wrong in estimating that for a many year long trip as opposed to a weak long holiday outing or a six month tour for someone use to the hardship of a soldier, that you'd need at least 45 tons per person of living space per person. It takes [roughly 10,600 square miles of arable land](http://www.science20.com/news_articles/urban_agriculture_only_1_percent_of_seattle_residents_could_eat_locally_even_with_all_viable_space_in_use-163422) with crops growing on them to feed the population of Seattle (with a population of about 652,000), while the city itself has less than 84 square miles of land area and not all of that is arable land (i.e. land that it is possible to grow crops upon). This is about 10 acres per person. And, any interstellar trip is going to need to grow most of its own food (with artificial light because starlight is too dim). Even if you could be significantly more efficient than terrestrial farming on Earth which isn't optimized for land being extremely scarce, by an order of magnitude, you'd probably need at least an acre per person of space for food production. State of the art terrestrial farming techniques and a vegan diet leave you at about [2 acres per person](https://worldbuilding.stackexchange.com/questions/9582/how-many-people-can-you-feed-per-square-kilometer-of-farmland). The most optimistic estimates I've seen are as little as 1/4 to 1/8th acres per person, but some of the assumptions that go into that aren't well proven or demonstrated in practice. So, an estimate of 1 acre per person is fairly reasonable middle ground. Still, if you were really going to build a ship like this, you'd want to invest a lot in improving agricultural productivity per square meter because each percent of reduction in this reduces you ship size and cost by 1%. If you can produce enough food per person with 1/2 an acre instead of 1 acre, you can cut the size of the ship in half. A 102,000 ton aircraft carrier has about [4.5 acres of deck space](http://www.dailykos.com/story/2014/4/15/1292241/-Chart-of-the-Day-Aircraft-carriers-U-S-has-more-than-everybody-else-combined-and-then-some). So, you'd need about 22,700 tons of food production area per person in addition to the 45 tons of living space. So, in round numbers you'd be talking 23,000 tons per head of living space and food production space and nuclear power production for ship life support operations from which to feed and house them assuming an order of magnitude improvement in food production per square foot relative to Earth would be possible (e.g. by reducing less efficient animal food relative to more efficient plant food proportionately). I'll assume that "millions of people" means 2 million, for sake of having a number to work with here, so you'd need at least 46 trillion tons of living and food production space (which would still be quite cramped) before considering fuel and engines. You can make your ship as big as you desire, because for very large interstellar space ships, the amount of fuel and engine required per ton of living space is going to be nearly constant. There is another moving part here. More fuel can allow you to travel faster, less fuel limits your speed (engine size is pretty indifferent as the key question is how long you run them at an acceleration of 1 G, not the amount of peak acceleration you can generate). For example, if you decided that 95% of the ship would be devoted to fuel and engines for a near maximal peak speed given the available technology (whatever that ends up being), then you have a ship carrying 2 million people that is at launch 1 quadrillion (i.e. 10^18 kg) of displacement. An aircraft carrier by comparison is 10^8 kg of displacement. So, this ship would need to be on the same size as about 10 billion aircraft carriers. A new aircraft carrier (which is a reasonable comparable given its size and technological sophistication) costs about [13 billion dollars](https://en.wikipedia.org/wiki/National_debt_of_the_United_States) (aircraft not included). So, this ship would cost about 1.3 \* 10^20 dollars which is 130 quintillion dollars (i.e. 130 million times a trillion dollars). By comparison, the entire U.S. national debt is about [19 trillion dollars](https://en.wikipedia.org/wiki/National_debt_of_the_United_States). So, this would cost about six and a half million times as much as the entire U.S. national debt. And honestly, both the ship size and cost are pretty stingy estimates. UPDATE: A [new academic article](https://arxiv.org/abs/1901.09542) addresses this in detail with greater precision. It thinks that a generation ship can be 224 meters in radius and 320 meters in length with a population of 500 people that can be stable for centuries. > > Numerical constraints on the size of generation ships from total > energy expenditure on board, annual food production and space farming > techniques > > > F. Marin, C. Beluffi, R. Taylor, L. Grau > > > (Submitted on 28 Jan 2019) > > > In the first papers of our series on interstellar generation ships we > have demonstrated that the numerical code HERITAGE is able to > calculate the success rate of multi-generational space missions. > Thanks to the social and breeding constraints we examined, a > multi-generational crew can safely reach an exoplanet after centuries > of deep space travel without risks of consanguinity or genetic > disorders. We now turn to addressing an equally important question : > how to feed the crew? Dried food stocks are not a viable option due to > the deterioration of vitamins with time and the tremendous quantities > that would be required for long-term storage. The best option relies > on farming aboard the spaceship. Using an updated version of HERITAGE > that now accounts for age-dependent biological characteristics such as > height and weight, and features related to the varying number of > colonists, such as infertility, pregnancy and miscarriage rates, we > can estimate the annual caloric requirements aboard using the > Harris-Benedict principle. By comparing those numbers with > conventional and modern farming techniques we are able to predict the > size of artificial land to be allocated in the vessel for agricultural > purposes. We find that, for an heterogeneous crew of 500 people living > on an omnivorous, balanced diet, 0.45 km2 of artificial land would > suffice in order to grow all the necessary food using a combination of > aeroponics (for fruits, vegetables, starch, sugar, and oil) and > conventional farming (for meat, fish, dairy, and honey). > > > Comments: 12 pages, 14 figures, 3 tables, accepted for publication in > JBIS > > > Subjects: Popular Physics (physics.pop-ph); Instrumentation and > Methods for > > > Astrophysics (astro-ph.IM) > > > MSC classes: 85-04, 91C99 > > > ACM classes: J.2; K.4 > > > Cite as: arXiv:1901.09542 [physics.pop-ph] > > > (or arXiv:1901.09542v1 [physics.pop-ph] for this version) > > > [Answer] @ohwilleke's excellent answer clearly describes the scaling issues inherent in moving millions of full grown and wide awake humans. If all you want from the majority of your travelers is genetic diversity, consider shipping all but a few thousand of them as frozen fertilized embryos. Then cryogenically suspend everyone except the few dozen who are needed to operate the ship. Make sure that these living crew are all female and in each generation, so they can gestate, birth and subsequently educate their own crew replacements, using some of the ship's supply of fertilized female embryos. Now when your ship eventually reaches its destination, the current generation of crew can wake up the thousands of frozen grown-ups and help them build the initial settlement. Then everyone can get busy turning the the embryo banks into babies. With in a few generations, all of your millions of colonists will be living on a wonderful new world. [Answer] My answer is going to focus on the energy requirements of your ship which touch on the relative amount of space you need for getting the ship to its destination and supplying power to your people. Summary Solar power is useless, so don't bother. Either antimatter or fusion reactors would be perfectly useful for personnel energy demands, and would consist of a very negligible amount of the overall size and mass of the ship. Your 1 gram of antimatter per day will support at least 2 million people. It will also require total hand-waving to acquire that midflight. However, any kind of nuclear fusion, and a paltry 1 gram of antimatter per day, will be completely worthless for powering the ship, assuming we're hitting top speed within 10 years. If you want it to take much longer time frames, it might be possible, but I didn't calculate that. You'll need to bring about 10% of your ship's mass worth of antimatter to hit 0.1 c in 10 years, or about 350% of your ship's mass worth of antimatter to hit 0.9 c in 10 years. I don't think 0.99 c is remotely doable without extreme advances in propulsion technology. That much antimatter would take a few billion times the current age of the universe to produce at current rates, so you'll need way better tech. Still, the Sun outputs plenty of energy to accomplish it if you can build enough generators. Fusion Power At this point, we're outside the range of hard science. We know generally [how fusion works](https://en.wikipedia.org/wiki/Fusion_power), but we've never done it in a lab in a sustainable form. (We've done fusion, but it takes more power than the fusion produces, so it's an awesome experiment, but utterly worthless as a power source.) That said, [this MIT experiment](http://www.computerworld.com/article/3028113/sustainable-it/mit-takes-a-page-from-tony-stark-edges-closer-to-an-arc-fusion-reactor.html) is estimated to produce a lot of power if they ever make it work. > > A working ARC fusion reactor would use 50 megawatts (MW) of power to produce 500MW of fusion power, 200MW of which could be delivered to the grid. That's enough to provide 200,000 people with electricity. > > > The reactor itself is about 1 meter across, so we don't need to worry about its mass too much. The infrastructure for [ITER's reactor](https://www.iter.org/) is about three stories tall, but a few dozens rooms worth of space for every 200k people is negligible. [The Culham Center for Fusion Energy](http://www.ccfe.ac.uk/faq.aspx#Day) estimates > > A large power station generating 1,500 megawatts of electricity would consume approximately 600 grammes of tritium and 400 grammes of deuterium each day. > > > That equates to about 0.243 kg of fuel per megawatt per year. Given the 1 MW per thousand people figure on the MIT article, that's 243 kg fuel per million people per year, which is pretty negligible. Antimatter Power As I pointed out in the answer to [this other question of yours](https://worldbuilding.stackexchange.com/a/59604/11879) (and pointed out in John Dallman's comment above), creating antimatter to use as a power source doesn't really make any sense. The power used to create the antimatter is millions to billions of times higher than what you finally get out of the antimatter annihilation. You could use some kind of hypothetical device that collects antimatter with total handwavium (say, there's enough antimatter hanging out in interstellar space that you can just grab it on the way by, or [zero-point energy](https://en.wikipedia.org/wiki/Zero-point_energy)). In that case we can calculate the energy from 1 gram per day (about [50 gigawatt hours per day](http://www.wolframalpha.com/input/?i=2+gram++c%5E2) which converts to about [2 GW total output](http://www.wolframalpha.com/input/?i=2+gram++c%5E2+%2F+day)). But none of that is remotely hard science. From the section on Fusion Power, humans living in modern Boston use about 1 MW per thousand people, 2 GW would provide for 2 million people. That number would likely be far lower in an actual generational ship as people would learn how to do more with less. Still, it's a good upper bound. Importantly, one gram per year per 2 million people means the normal matter mass you'd need to annihilate the matter is negligible. Presumably, you'd have some kind of reactor that takes space and mass, but since we don't have antimatter collectors and/or generators it's hard to say exactly how much. I'll assume it's about the same as a fusion reactor. Without any handwavium, you'd need to bring the antimatter with you. The amount of 0.5 g per year per 2 million people is going to be totally negligible in terms of size and mass, but will require some very advanced means of actually producing that much antimatter. Solar Power Also, as pointed out in John Dallman's comment, solar panels are probably a huge waste. At 93 million miles from the Sun, we're seeing about 1.3 kW per square meter. At 0.1 c over a single generation (about [28 years](http://www.wolframalpha.com/input/?i=1+generation)), you'd travel about [16 trillion miles](http://www.wolframalpha.com/input/?i=1+generation++0.1+c), which happens to be about halfway to the nearest star. Power output will fall off with the square of distance, so you're looking at about [44 nanowatts per m²](http://www.wolframalpha.com/input/?i=1.3+kW++(93+million+miles+%2F+16+trillion+miles)%5E2) at that distance, and an average of [7.6 milliwatts per m²](http://www.wolframalpha.com/input/?i=1.3+kW++integral_(93+million)%5E(16+trillion)(+(93+million+%2F+x)%5E2)+dx++%2F+(16+trillion+-+93+million)) across the trip. Even if you could somehow fly in a line that gets you really close to each star you pass, your best case is going to be about [1.6 watts per m²](http://www.wolframalpha.com/input/?i=1.3+kW++integral_(432+thousand)%5E(16+trillion)(+(93+million+%2F+x)%5E2)+dx++%2F+(16+trillion+-+93+million)), assuming you're literally touching the [surface of each star](http://www.wolframalpha.com/input/?i=sun+radius) on the way past. To be fair, not all stars are like ours in power output, but the Sun is actually [the top 10%](http://nineplanets.org/sol.html) by mass, so your realistic solar influx will be even lower than the calculations above. Further, your realistic path will probably stay substantially farther from nearby stars than the calculations above, further lowering the average power. From [Sunmetrix](http://sunmetrix.com/is-my-roof-suitable-for-solar-panels-and-what-is-the-weight-of-a-solar-panel/), typical solar panels are 10-20 kg per m². At the lower value, you're looking at about [6 million kg per megawatt](http://www.wolframalpha.com/input/?i=1+MW+%2F+(1.6+W+%2F+m%5E2++1+m%5E2+%2F+10+kg))) in the best case of zooming right up to sun-like stars. In addition to the mass issues, you have to have some way to spread them over an enormous area without shearing or folding from the torque. One megawatt is 600 thousand square meters in our best case scenario. That fits into a [circle with a 437 meter radius](http://www.wolframalpha.com/input/?i=solve+for+r:+600+thousand+m%5E2+%3D+pi++r%5E2). If the ship is accelerating at 0.01 gees, a 1 m² section at the edge, with its mass of 10 kg, requires about 1 N force to keep it in place. At 437 meters from the center, that's 437 N-m of torque per m². There are about $2\pi r$ of these 1 m² sections around the outer radius. Then $2\pi (r-1)$ sections around a slightly smaller section. Turning that into an integral [gives us about 600k N-m torque](http://www.wolframalpha.com/input/?i=solve+for+r:+600+thousand+m%5E2+%3D+pi++r%5E2) on the center of the disc. You could probably solve the torque issues for a 437 meter disc by using supporting structures and so forth. But you need a thousand such discs for each million people on your ship. And realistically, you're looking at something closer to the 44 nW per m² figure. That requires some 23 trillion m² of panels per MW, or 23 quadrillion m² of panels per million people. Which [ends up with a 151k km radius array](http://www.wolframalpha.com/input/?i=sqrt(23+quadrillion+m%5E2)), which has about [16% of the area](http://www.wolframalpha.com/input/?i=(sqrt(23+quadrillion+m%5E2)++%2F+(moon+orbital+distance))%5E2) between Earth and the Moon's orbit. The total torque is about [$72\cdot10^{15}N-m$](http://www.wolframalpha.com/input/?i=integrate_0%5E(15110%5E6)+(2+pi++r)+dr) and you're really not getting around that with extra supports, unless your entire ship is about that large. As a side note, solar panels have a [best-case efficiency](https://en.wikipedia.org/wiki/Thermodynamic_efficiency_limit) of about 86%, and are realistically sitting around 50%. Your advanced people could likely hit 70-80%, but this is pretty trivial when there's so little sunlight available in the first place. Acceleration Energy Requirements Ok, so we need a negligible amount of extra space for the fusion and antimatter reactors compared to personnel energy usage. But we still need to accelerate the ship. To hit 0.1 c in ten years, we need about [0.1 g](http://www.wolframalpha.com/input/?i=c+%2F+10+years) acceleration. To get one megaton of mass to 0.1 c, we need about [$4.49\cdot10^{23} J$](http://www.wolframalpha.com/input/?i=1%2F2++10%5E61000+kg++(0.1+c)%5E2). That requires about [5 million kg](http://www.wolframalpha.com/input/?i=1%2F2++10%5E61000+kg++(0.1+c)%5E2+%2F+c%5E2), or five kilotons, worth of energy. For the anti-matter propulsion system, the extra mass for propulsion is pretty negligible at about 0.5%. For nuclear fusion, we're getting about 1.5 GJ per kg of fuel. That means about [$3\cdot10^{14}kg$](http://www.wolframalpha.com/input/?i=4.4910%5E(23)+J+%2F+(1.510%5E9+J%2Fkg)) of fuel. Which means about [3 parts per million](http://www.wolframalpha.com/input/?i=1+megaton+%2F+2.993%C3%9710%5E14+kg) of the spaceship's mass is payload; the rest is fuel. So really, antimatter rockets are the only way we're getting this ship to 0.1 c. If we up the cruise velocity to 0.9 c, we'll need [0.4 megatons](http://www.wolframalpha.com/input/?i=1%2F2++10%5E61000+kg++(0.9+c)%5E2+%2F+c%5E2) worth of energy. That's huge, but doable, in the sense that your rocket will still be [71% payload](http://www.wolframalpha.com/input/?i=1+-+0.4%2F(0.4%2B1)). On the other hand, getting 0.2 megatons of antimatter is insane. With current antimatter production methods that use 15 billion times the antimatter's mass energy to create it, at a rate of 1 billion years per gram, you'd need about [22 times the Sun's annual output](http://www.wolframalpha.com/input/?i=15+billion++0.2+megatons++c%5E2) of energy, and way more particle accelerators than we currently have to accomplish it before the Sun dies. That is extremely* advanced technology, but it seems plausible to an advanced enough society. From [Wikipedia](https://en.wikipedia.org/wiki/Rocket_engine#Energy_efficiency), chemical rockets have an energy efficiency of about 60%. Anti-matter rockets have between [10 and 85%](https://en.wikipedia.org/wiki/Antimatter_rocket) efficiency. But it really doesn't matter; anti-matter will have negligible mass, fusion will be way too high. Reaction Mass Now, you'll need reaction mass dependent on how much energy you can impart into each particle, and is [given by](https://en.wikipedia.org/wiki/Spacecraft_propulsion#Reaction_engines) $M=P\left(e^{\frac{\Delta v}{v\_e}}-1\right)$, where $M$ is reaction mass, $P$ is payload mass, $\Delta v$ is the change in spaceship velocity, and $v\_e$ is the exhaust velocity. We've set $\Delta v=0.1c$. From [this page](https://en.wikipedia.org/wiki/Relativistic_rocket), antimatter rockets have a specific impulse of 0.6c. From what I can tell, they're using "specific impulse" to mean "effective exhaust velocity", so $v\_e=0.6c$. Plugging this into the equation, we get [18% P](http://www.wolframalpha.com/input/?i=P(e%5E(0.1%2F0.6)-1)). Calculating a [final velocity of 0.9 c](http://www.wolframalpha.com/input/?i=P(e%5E(0.9%2F0.6)-1)) requires about [78% of the ship](http://www.wolframalpha.com/input/?i=3.48+%2F+(3.48+%2B+1)) to be reaction mass. If we use dense reaction mass, this means the actual size of the spaceship isn't largely affected by the reaction mass. And adding 20% mass to the ship isn't particularly substantial in the grand scheme of material requirements. From [here](https://en.wikipedia.org/wiki/Fusion_rocket), fusion rockets have exhaust velocities up to 700 km/s, or about [0.0023 c](http://www.wolframalpha.com/input/?i=700+km%2Fs+in+c). This brings our required reaction mass up [a lot](http://www.wolframalpha.com/input/?i=P*(e%5E(0.1%2F0.0023)-1)) (about 7 billion billion P). No way we're doing anything with that. So if your guys are using fusion reactors to power the spaceship, you'll have to assume they achieve much higher exhaust velocities. Around [0.14 c](http://www.wolframalpha.com/input/?i=solve+for+x:+1000+%3D+(e%5E(0.1%2Fx)-1)) is required to keep the reaction mass lower than the payload mass. This seems reasonable enough for an advanced society, but we don't have any current means of achieving it. Not that fusion was ever a real choice considering how much mass we need to power it. ]
[Question] [ I'm piecing together the biology and ecosystem of a Titan-like cryoplanet. And I want it to have clear or nearly-clear skies instead of Titan's complex hydrocarbon haze, so that my ethane-based lifeforms can use visible light for photosynthesis. Some planetary info: * Magnetic field about two thirds the strength of Earth's. * 120-150 kPa surface pressure. * Atmospheric composition: * 90-95% Nitrogen. * 5-10% Methane or Hydrogen, or a mix. * 1-4% Ethane (due to evaporation from lakes, seas and oceans). * Trace amounts (< 1%) of oxygen or some other oxidizing gas or liquid. Emitted by plants as a waste-product. What compounds could form either naturally or biologically that could function as a transparent UV-absorbing layer? I.e. an ozone layer equivalent. Is less than 1% oxygen or other oxidizing gas (at 120-150 kPa) sufficient to form an ozone layer able to absorb 90-99% of UV-C and UV-B light? Or are greater percentages of oxygen required? Could methane naturally react to form transparent UV-C and UV-B absorbing compounds that would be in sufficient concentration to act as an ozone-layer equivalent? [Answer] Good old fashioned water vapor, that's H2O, will do the trick. At high altitudes incoming UV can split water molecules into hydrogen and oxygen. The oxygen can in turn be ionized and form ozone. if the water content of the atmosphere is increased this will lead naturally to the formation of an ozone layer. Considering the OP wants a Titan-like planet with a clear sky it's worth looking at the cause of the murky skies of real-life Titan. > > The orange color as seen from space must be produced by other more complex chemicals in small quantities, possibly tholins, tar-like organic precipitates.[13] The hydrocarbons are thought to form in Titan's upper atmosphere in reactions resulting from the breakup of methane by the Sun's ultraviolet light, producing a thick orange smog. > > > This suggests that assuming methane can act as a UV absorber as a way of keeping skies clear won't work. In fact, methane absorbing UV is making Titanian skies smog filled. So we're back to water vapor and its capacity to form an ozone layer. [Answer] The phtotosynthesis could use some narrow notch in the haze spectrum, where it is transparent. Look at the history of trying to explore Venus and Titan for discussions about discovering such windows and building instruments to match. Likewise the eyes of any locals would be evolved to take advantage of the kind of light actually available. Note that the sky can be frosted and not provide a coherent image of what’s on the other side, but still transmit a useful amount of light. You'll get a general glow rather than a tight spotlight of the sun. ]
[Question] [ Two vastly dissimilar organisms turn out to be the same species upon gene sequencing. In this hypothetical animal species one or more components of the life cycle is a fungus, algae, plant, lichen or other vegetative organism. The species may transition from animal to vegetative or vice versa between instars, it might alternate between vegetative and animal generations, or one of the sexes is vegetative. How feasible would this be to evolve? What selection pressures would promote this adaptation? The ancestral organism doesn't need to be an animal. (Inspired by Descolada from Speaker for the Dead and Orks from Warhammer 40,000.) EDIT: here are some more detailed examples. * In Speaker for the Dead, the capra is a ruminant that grazes exclusively on the capim grass. These are the female and male of the same species, respectively. When the capra graze they are fertilized by the capim pollen. * Another species in Speaker for the Dead, the suckflies, hatch from the tassels of river reeds. These are the male and female of the same species, respectively. * The most extreme example in Speaker for the Dead are the pequeninos, in which juvenile males molt into trees to reach maturity. * In Warhammer 40,000 the orks produce spores which grow into fungi. These fungi produce underground uteri in which new orks gestate. [Answer] I would suggest the main pressure would be from a massive shift in sunlight. So when there is lots of sun the creature is able to 'plant' itself, produce chlorophyll, turn very green, lay down some roots and soaks up some rays. This would also allow it time to grow food stores in the form of potato-like starchy tumours to reabsorb later, dramatically changing its appearance into a green lumpy plant. Lying down would remove the need for a solid structure (like a strawberry plant, not a tree) as there wouldn't be much growth vertically. They could also sleep a lot to make maximum use of the abundance of energy, instead of wasting any being awake. Should then the sun disappear for a long period, because of an eliptical planetary orbit, or a slow spinning planet, it would be an evolutionary advantage to be able to pluck ones feet from the ground, metabilise all the chlorophyll, turning very pale, and be able to move around in the hunt for alternative food sources like an animal. Movement is likely to be achieved through internal hydraulics, moving fluid around the body to push the limbs in the right place. This would make them slow, but strong. The alternative food sources would also have to be able to survive without sunlight, so I imagine it would eat a lot of mushrooms, and maybe a lot of the less evolved plants, before they starve to death in the dark. It would reabsorb its tumours and likely become very thin. It wouldn't be able to maintain any bark, at least not all over, as it couldn't move, but it would be able to regrow any limb, as long as enough of the rest of the creature survives to provide the energy to do so. These 2 states would give it the appearance of being 2 separate creatures, depending on the time of year you visited them, leading to the initial confusion. Reprodution could be asexual through self harming and planting the removed "cutting" or sexually through the usual pollen and seeds method. I would suggest the descendants were likely plants but that gained the ability to move, maybe first their branches to scoop up what was around them. The extra food that being able to move in the long night provides was advantageous over starving to death standing still so they continued to evolve that way. [Answer] Your question reminded me of an organism that does something similar. Slime molds exist most of the time as single cell animals, absorbing food wherever it is, then sporulating. When the nutrients it needs become depleted in an area, the single celled animals clump together and crawl away, looking for new pastures. More information [here](http://beheco.oxfordjournals.org/content/18/2/433.full). ]
[Question] [ Imagine a civilization which has surmounted almost all of the limitations of biology and the universe. They have become truly immortal, put behind them all their petty differences, and dug down into the core of the laws of physics and somehow figured out how to stop entropy and produce free energy. Now they must face their biggest challenge: time notation. For the first 100,000 or so years, it's fairly easy to just keep up with the current form of time notation. Just update the code of apps to support 5- and 6-digit years at the 10,000- and 100,000-year mark. But as the millennia turn to eons and longer, eventually writing down the full year becomes somewhat infeasible, and our civilization realizes that it must come up with a way to cope with year numbers increasingly becoming longer. Eventually, the year passes 101000, 10100000 and more, eventually reaching into the millions and billions of digits, becoming incredibly difficult to log. Our civilization wants to keep a well-detailed history and doesn't want to resort to things like only storing the last four or five digits of the year and just relying on people to know what era something occurs in by context. [Answer] There isn't really a problem with using very long numbers. Even the feeble computers of nowadays can manage that. The problem is that human minds find it difficult to handle very large numbers themselves, which is why we use scientific notation and similar systems. Now, if you're assuming that your aliens have the same kind of mental limitations as humans -- which is not unreasonable at the start of their civilisation -- and retain that limitation for at least 10^6 years, which seems rather doubtful to me, then it's worth trying to solve the problem. The usual solution to this problem is to use some kind of era system, because humans find it easier to deal with lists of names, or of short numbers, than with one very big number. For a somewhat weirder system, look up the [Mayan Long Count Calendar](https://en.wikipedia.org/wiki/Mesoamerican_Long_Count_calendar), which is real, and has nothing to do with apocalypses. You might also care to look at [Tumbler Arithmetic](http://udanax.xanadu.com/green/febe/tumblers.html), which was formulated for an index-all-the-worlds's-information project. So, how do you build an era system methodically, rather than have it evolve out of a reigns-of-kings system? Start with the basic unit, of maybe 1000 years. If you specify a date with just a year number, it's in the current era. Then you need a naming system for blocks of 1000 years, where you need names that have an easily memorable sequence. Those tend to be culturally specific: as English-speakers, we might use A-Z, and maybe drop a letter to give 25, rather than 26, but humans who use other writing systems would find this difficult, and translating it into their own alphabet drags in the problem of collating sequence translation between different alphabets, and you really don't want to go there. Then, given you have groups of 25,000 years, or maybe up to 100,000 years depending on what you use to name them, you can use numbers for the groups, say up to 1000 of them in an era. You have year numbers within the era of the form 207 D 778, which may be easier than 5129778, but the difference doesn't seem huge to me. [Answer] Like many questions which involve the breaking of laws of physics (in this case, the march of entropy), there are many solutions. Don't restrict yourself to any one! One conclusion may be that, with free energy, they have all the time in the world to read off Stardate 15984843515543438181324576751519186.5213846857468461558 and realize that that's just 2 days before a great festival on that planet. Time is going to mean something different to people in a post-entropy world. A well detailed history may be a term that needs further expounding. It would be horrible to have a document with 1000000 digit dates, followed by an entry "I had soup today." It's a wasteful approach. Despite your goal of not resorting to context, it really is the answer you are looking for. If you divide time into slices (like years), the number of bits you need to describe a year exactly is... well... the number of bits you need to describe a year exactly. You can't cut corners. Mathematics prevents it. You have to permit some level of imprecision, use context, or deal with writing out enough bits of data. One solution might be to weave that context into the document itself. Perhaps any given event only has a partial date, but the cataloguers which made the history took great care to ensure that anyone who wants a more precise date can determine it by cross referencing other related events. This would permit clever compression of the date data by spreading it across multiple entries in the history. Once you have some form of context, implied or explicitly woven, to let you determine the exact date, the recorded dates near the entries could have less precision. Given your use of exponential notation like 10^1000 and 10^1000 already, such notation might be very effective. It might be recorded as years before some major event which serves as a meaningful epoch for that particular volume of history. [Answer] Rollover. Simply after hitting 100000, start over from 1. Call them cycles and number each cycles . Normally, in an cycles people will talk about that cycle and for a short time previous one. No one will mistake year 99992, they will all understand that it is the previous cycle. Now for the record keeping. Make your records structured so that you need to set the cycle once in a system and you keep using the year only. If necessary, you could save it as 99992c-1 to refer to previous cycle. [Answer] Really, this is impossible to answer. Either you write the full number, or the last digits so it's clear in context, or you round, but you can't have the full number and at the same time not the full number. Using large-base systems helps, say a base 62 system using alphanumeric symbols. But then you don't get around writing the whole number down. There is no shorter way. I'm pretty sure you can proof that for a set of symbols the shortest (in terms of symbols used) way to represent numbers is just using the symbols as digits. ]
[Question] [ The average temperature on this world surface is −55 degrees Celsius. 80% of the surface of this world is covered by liquid ammonia oceans. This planet has a surface gravity of 0.75 g. The atmosphere of this world is 93% elemental nitrogen 3% elemental hydrogen gas, 3.5% diborane gas, and 0.5% other substances. This world has lots of boron and nitrogen compounds on its surface and dissolved in its oceans, rivers, and lakes of liquid ammonia. This world orbits a gas giant that is 1.5 times the mass of Jupiter. This world is about 325,000 km away from its planet. The planet that this world orbits orbits a star that is 1.5 times the mass of the Sun. What types of life forms might evolve on this world and how would they interact? [Answer] Microbes, at best. Ammonia might hypothetically do for a soluble environment where the chemical reactions necessary for life could take place. If so, any lifeforms would be very different from our own. We can only imagine how their metabolism would be, since the chemical properties of ammonia vary from those of water. The problem is with the temperature and the relative low concentration of oxygen (or sulfur, for a replacement) in the atmosphere. Anything that lived on your planet would have an extremely slow metabolism (compared to lifeforms on Earth), and due to the lack of oxygen/sulfur they wouldn't be anywhere near as energy-efficient as our [aerobic](https://en.wikipedia.org/wiki/Aerobic_organism) lifeforms. TL;DR about the lack of oxygen: in our world creatures that use oxygen in their metabollism can extract approximately 30 times as much energy from a single glucose molecule than those that don't use oxygen. If you're interested in the science behind that you can read about [cellular respiration](https://en.wikipedia.org/wiki/Cellular_respiration). [Answer] In terms of gross morphology? No idea. How thick is the atmosphere? How far is it from its sun? If we knew how dense the atmosphere was, we might be able to says something about valid options for flying and other forms of locomotion. Given the easy availability of hydrogen in a nitrogen-dominated atmosphere, if the air is thick enough, it might make aerostatic flight (balloon creatures) an easy and obvious evolutionary possibility. Also, hydrogen is a pretty good greenhouse gas at high pressures, and the farther it is from the sun, the less significant the temperature swings from orbiting the gas giant at such a huge distance would be. Still, unless you simply made a typo in how many zeroes there are in distance from the gas giant, it seems likely you'll have a Cycle of Fire kind of scenario, with the world alternately boiling and freezing, normal life proceeding in the temperate periods in between and needing to survive as spores in between. But otherwise (assuming that macroscopic life is possible with that atmosphere), macroscopic life would be not be obviously more or less constrained than it is on Earth. And Earth has produced a lot of really weird stuff. Lower gravity means animals and plants could be larger and/or more gracile, all other things being equal, than they are here on Earth, but unless you're in this world's age of gigantic dinosaurs, that won't make that much difference. There's a slightly higher chance that land creatures on this world would have more legs, in order to get more traction in lower gravity, but that's not a guarantee, either. The interesting stuff is in biochemistry, and how that influences ecology- the "how they interact" stuff. If we assume they breathe hydrogen, they probably wouldn't need as efficient gas-exchange structures (gills or complex lungs) or gas-transport structures (haemoglobin, red blood cells) as oxygen-breathers, since hydrogen is much smaller and diffuses easier than oxygen. Hydrogen-based respiration is only about 4 or 5 times less efficient than oxygen-based respiration, rather than the factor of 30 that purely anaerobic respiration lags, so that doesn't seem like quite as big a deal- and remember that that's for food molecules that evolved in our environment. Organisms on this world would likely evolve energy storage mechanisms optimized for higher chemical energy densities in their environment. On the other side of the energy equation [Photosynthesis in Hydrogen Dominated Atmospheres](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284464/) actually requires less energy than oxygen photosynthesis (balancing the lower amount of energy that heterotrophs get by reversing it), and is likely easier to evolve; thus, it may actually be easier to get large, complex autotrophs (i.e., plants) on this planet than it was on ours. If, however, the heterotrophs aren't hydrogen breathers, then the ecology probably works something like it does in The Nitrogen Fix, with heterotrophs not needing to breathe at all, and either consuming both oxidizing and reducing food molecules in solid or liquid form, or else running purely on decomposition reactions of high-energy molecules. That doesn't work too great for Earthlings, but remember that we're optimized for a relatively higher temperature, oxidizing environment. Especially given the ready accessibility of bio-available nitrogen in the form of ammonia on this world, they may use much higher energy density complex nitrogen molecules, such as would dangerous explosives in our environment, as energy storage rather than, or in addition to, hydrocarbons and carbohydrates. Now, if this life is carbon based, it'll need a carbon source. That's not a huge deal- we can assume there's a trace amount of methane in the atmosphere, part of that 0.5% other substances, analogous to our tiny trace amount of carbon dioxide, which serves as the primary carbon source for Earthling plants. If that's not present, however, the ecosystem would need to extract carbon from crustal rocks, which would mean that plants don't breathe, you probably have a much more important and extensive network of fungus-analog symbiotes breaking down rock to extract carbon, and the landscape would be broken down into soil at a much faster rate relative to metabolism than it is on Earth. On the other hand, though, once life gets ahold of it, it seems very likely that the ecology would end up releasing methane into the atmosphere, and then this isn't such a big deal anymore. If life on this world isn't primarily carbon-based, then that's not really relevant anyway, but could that actually happen? I don't know. I've seen serious proposals for life based on complex nitrogen-phosphorus chemistry, with N-P pairs replacing single carbon atoms, so maybe you could do the same with nitrogen-boron chemistry? I'd buy it in a sci-fi novel, anyway. But sticking with carbon-based life using trace methane as a carbon source seems like a much safer bet. Even if this world's life doesn't rely on carbohydrates for structure or energy storage, they will still probably need an oxygen source as well, just because oxygen is such a useful element in all sorts of complex compounds. Perhaps, at cryogenic temperatures, they replace disulfide bridges with dioxygen bridges. Like the carbon source, this is fairly easy to arrange- there's probably a trace amount of water (or "oxic acid", as the natives would say) dissolved in the ammonia oceans, and weatherable out of rock. Given the difficulty of splitting water (which is part of what makes our own oxygenic photosynthesis so energy intensive), it seems likely that there would be specialized, symbiotic oxygen-fixing microbes, analogous to our own nitrogen-fixing microbes, which serve to split water and produce molecules providing oxygen in a more bio-available form to other organisms. And, of course, you could hardly pass up the opportunity for creatures with shells or bones made of nitrogen boride. :) [Answer] shot term, Ammonia based life. long term, replace all hydroxyl groups with amino groups in your life form, and use nitrogen gas as your oxidizer (water would probably work as well). Use a carbodiimide to replace the atp, and have your breathing chain to end up in nitrogenase(fixes nitrogen on earth, and producing electricity) Ammonium chloride for the hydrochloride acid, and sodium aside for the sodium hydroxide, PNA for the dna, and Histidine nucleic acid for the rna, Replace the c terminus with a carbamide. You probably won’t even need to change the protein structure too much to have it working...... ]
[Question] [ what are the rules I need to follow to name different races of a specie and different species that have one ancestor in common ? Additionally how do i know when a race becomes a species ? Is an humanoid primate predator with a giant mouth and shark teeth , eight large eyes. has over human intelligence ,incredibly agility and strength. Reproduces asexually but can mate with people too. This animal evolved particularly to hunt other humans. Can this creature be considered a different race of homo sapiens or is a new species ? More details : This ''shakrtooth'' humanoid arose from an oppressed tribe victimized by a virus that mutated every cell of their body. This tribe survived for centuries by feeding on dead soldiers cause there was no other source of food. Soon after the end of war they started hunting other weaker tribes and after millions of years this is how they look like [![enter image description here](https://i.stack.imgur.com/pul7F.png)](https://i.stack.imgur.com/pul7F.png) Sorry for the image but I'm not the best at sculpting.... [Answer] The rules for naming species go along these lines: The species name comes in the form of Genus name with capital letter followed by species name with no capitalisation. Then subspecies name (if there is one). For example: * The polar bear is Ursus maritimus. * Its close relative the brown bear is Ursus arctos. Same genus name, different species name. * Some subspecies of the brown bear are Ursus arctos horribilis (grizzly) and Ursus arctos arctos (European brown bear). When a race (or subspecies) becomes a species: the definition of 'species' for sexually reproducing creatures is a naturally interbreeding population which can produce viable offspring, which in turn can interbreed to produce viable grandchildren. So horses and donkeys are separate species (both in Equus genus) because they don't interbreed naturally - people are involved in getting them to mate and create mules. Also nearly all mules are infertile, so there are no grandkids. So your sharktooth people having sex with regular humans is not enough to make them the same species as us. There have to be kids and grandkids produced from that regular human/sharktooth sex. If those kids and grandkids are fertile with both sharktooth people and regular people then the sharktooths would still count as the same species as us: Homo sapiens. That said, features such as giant shark teeth, 8 eyes and so on sound like massive amounts of genetic change! If we found something like this in the fossil record, palaeontologists would invent an entirely new genus for it, because it is just too radically different to be put in genus Homo with us, the Neanderthals, Homo erectus, and so on. In fact they'd probably invent a new family or order! After all, it is the only mammal on the planet with 8 eyes! How far back do you want your common ancestor of humans and sharktooths to have existed? Our own species is quite young - probably only been around for 300,000 thousand years. Genus Homo has been around about 2.8 million years. If they've been around for more than 2.8 million years, they will not be genus Homo, and not that closely related to us. Perhaps they evolved from Australopithecus or some other 'apeman'? [Answer] Given the large morphological differences, offspring of human/sharkman breeding would only be viable if they take strongly after one parent or another, ie they are either sharkmen or human or stillborn. So ability to breed successfully here implies that genetic difference is much smaller than difference in appearance suggests. Thus the sharkmen would be human, IMHO. Since they are morphologically distinct (and breed true), I'd go with subspecies status. Sorry to be vague, but species definitions are kind of fuzzy and when applied to fictional species... ]
[Question] [ In my my universe, there is a race of mechanical beings that are powered by magic and who live on the moon. Desiring more living space, resources, and the benefits of a planet with an atmosphere, the mechanical beings have set their sights on the Earth-like planet that they are orbiting and they wish to conquer it. They know that they can use moon magic to transport some sort of craft to the nearby Earth-like planet, but they have discovered that their moon magic (distinct from the force that keeps them alive) fails at about the halfway point between the planet and the moon, so they can't use magic to assist their landing. Their tests have shown that although their bodies are tougher than humans (they don't need to breathe, drink, or eat, are physically tougher and much more temperature-resistant), an individual cannot survive a drop to the surface of the planet without suffering at least critical injury if not total deactivation. They have come to the conclusion that they need some sort of landing craft to assist the individual units' survivability and also carry weapons and resources down to the target planet. The mechanical beings don't have access to wood, silk, or any other products that might be made by plants or animals. This includes petroleum products. They are the only things that live on their moon, which has virtually no atmosphere. They have access to iron and can make steel, though carbon is difficult for them to find, so steel is quite precious. They can use moon magic to create heat and launch things off the surface of their moon, but not much else. They have access to most other metals, which are available with varying degrees of rarity. The mechanical beings have a superior grasp of mechanical engineering compared to the humans down on the planet, who all have medieval-level technology. The moon beings are also innately able to achieve great precision in their work. Their technology is roughly Renaissance-level, if humans in the Renaissance could work with incredible precision. They are unable to harness the power of electricity and have no computers. Conforming to the restrictions above, how might the mechanical moon beings create a craft that can enable them to survive landing on the Earth-like planet? Good answers will provide a description of a craft and an explanation for how its design will prevent it from slamming into the planet or burning up, rendering the units and equipment that it contains totally useless. The best answers will describe craft that are as cheap and quick to make as possible. [Answer] While side-stepping some concerns ( i.e. origin of mechanicals, history of humanoids, etc) I would suggest that they do it much as we do, with the Columbia series of space shuttles and other glider-based entry vehicles. Use the planets' atmosphere for braking, and gliding for a controlled entry. I also suggest that the craft be constructed for multi-surface landing, i.e., water, open clearings, sand dunes, and other natural surfaces. [Answer] Your landing craft simply has to have wings that can create lift. They can be extendable (so they extend only after entering the atmosphere, if you'd like), or permanently fixed to the side. As the craft enters the atmosphere, you use these wings to start moving horizontally across the surface of the earth, allowing you to make circles around the earth while slowly lowering your altitude until you reach your landing destination. While the circles are being traversed, speed can be lowered by using flaps on the wings (or flaps on the craft itself, even). [Answer] You say there are two kinds of magic, 'moon magic' and 'life magic'. I would suggest they power their craft with the life magic that powers them. If they can create new mechanical beings then presumably they can harness the magic necessary to power the new being. Thus, build a ship that is powered by 'life magic'. It doesn't matter what the ship is made of since 'magic' can make the ship come down slowly enough that it won't burn up or destroy the beings inside it upon landing. I'm assuming powering the craft is not a plot point and you simply want to get them to Earth to continue the story. If you need the craft and the journey to be 'eventful' then perhaps such 'magic hand waving' isn't what you are looking for. [Answer] Atmospheric braking has already been suggested, so I'll skip that. (And doing it with any precision is going to be pretty tough if they're doing it purely based on theory; it would be very hard to do the computations necessary given Renaissance-level technology when the mechanical beings have evolved without an atmosphere and presumably largely without large bodies of fluid.) I'll assume your creatures are pretty tough and just need some assistance to survive, not a gentle landing. Then the ship can be resting on "top" of a long pyramidal structure comprised entirely of iron latticework. The idea is to land with that structure facing the ground, and have it crumple as completely as possible to absorb as much of the impact as it can. Basically, have your critters crash-land on the planet with a brace intended to collapse incrementally (but quickly!) It should require relatively little material (it would be all girders), and requires no moon magic if they can accelerate it enough to be moving toward the planet at the halfway point. (Though it would be better to have some propulsion to slow it down.) It would be great fun to watch, and pretty darn terrifying to the planet's inhabitants! ]
[Question] [ 1. Would it be possible for plants to evolve a co-dependency on a community of bioluminescent bacteria in order to survive in a low or zero light environment? Such as the plant gathering nutrients and water for the bacteria in its leaves in exchange for an excess of glucose the bacteria produces, or something similar. 2. How would the relationship between the two organisms affect the plant? Such as how large could they grow, what would their leaves look like and what would be, if any, the side effects of a plant using second-hand glucose? 3. Is there a real world equivalent of this? [Answer] 1) Its not impossible. Without getting too deep into the underlying process (you could spend a semester studying plant respiration and barely scratch the surface), plants have two main processes for producing chemical energy. The first is the light reactions, which require light. The second is the dark reactions, which do not require light. Again, not getting into it too deeply, but the light reactions turn water and sunlight into oxygen and energy. The dark reactions turn carbon dioxide and energy into sugars. Thus, the symbiotic bacteria can either a) provide the light necessary for the light reactions (which @AstroDan [showed us is possible](http://www.rsc.org/chemistryworld/2013/10/luminol-bioluminescence-powers-photosynthesis)), or b) directly provide the energy necessary for carbon fixing in the dark reactions. Note that because the plant will need energy to live, in either energy supply method, the bacteria will not come out ahead energy-wise. The bacteria will have to have some reason it needs the sugars produced by the plant. There could be a multitude of reasons, from long term energy storage to structural support. 2) the plant would probably not look much like a trees or grasses we think of. In all likelihood the bacteria would live inside the plant for protection and convenience. The leaves, if it had any, would lack sunlight to absorb, and consequently have no reason to be flat. The would probably be cylindrical to maximize bacteria holding efficiency. The plants would be low to the water, mosslike, because structural sugars would be hard to come by, and drawing water up a stem would be a waste of water and energy. it's unlikely that the plant would accept bacteria glucose; it's far more likely that the trade would be the other way around. After all, plants have spent the last few hundred million years perfecting glucose production. 3) A real world... not equivalent, but perhaps similarity, would be coral. Coral polyps (animals, not plants) have this sort of symbiotic relationship. They provide nutrients and shelter to algaes living in them, in exchange for excess chemical energy from the algae ([x](http://oceanservice.noaa.gov/education/kits/corals/coral02_zooxanthellae.html)). This is why coral bleaching is so dangerous to reefs. Without their algae, the polyps have far less food available, and not infrequently starve. [Answer] While there are [bio-luminescent bacteria](https://en.wikipedia.org/wiki/Bioluminescent_bacteria) they cannot provide energy (in darkness) that will be sufficient to a plant. Also searching for whether plants can [survive without sunlight](https://www.google.co.in/#q=how+do+plants+grow+without+sunlight) did not yield anything useful. However it is possible for a plant to depend on bacteria that do not require sunlight, but only partially (they get some of the nutrition from the bacteria, the rest from the low amount of sunlight) [Answer] A plant could not survive using light from bioluminescent bacteria it is feeding, as this would mean that the plant's energy is coming from itself, which is not possible. However, something similar could evolve. If a species of virus evolves to spread itself by mycorrhiza, then a tree might evolve to have a powerful bioluminescent organ, which it shines like a spotlight on the tree's offspring, allowing it to feed them without them needing to connect to potentially dangerous mycorrhiza. ]
[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/45659/edit). Closed 7 years ago. [Improve this question](/posts/45659/edit) It is commonly shown that some wise old wizard is meditating in order to increase his magical might, or just to learn new spells. My question is - How does meditating (or any other thing) increase magical power? (This seems broad, but there is no need to give a answer for each and every type of wizard, elemental,necromancer etc - just think of the stereotypical old wizard with a hat and a staff who is always researching for more magic) My World: There are many different types of magic, most common being the elemental magic (fireball,lightning etc) and necromancy. Assume the entire world is magical, with the average magician being pretty powerful (casually tossing fireballs that will kill a normal person or calling lightning that can wreck a tree easily, but only a dozen times in a day) . Other types of magic would be summoning spirits or healing magic. [Answer] You'd have to know how magic works to answer. If the magic bears any resemblance to known physics, the energy has to come from somewhere. Does it come from the chemical energy in the magician's body? That would make throwing fireballs that destroy a building impossible. Maybe he uses the chemical energy in his body like some sort of catalyst to move energy in the surrounding world, like pushing a boulder over a cliff. Maybe the energy comes from a pool of mana that's just out there waiting for a magician to draw on it. Maybe there's some mechanism to manipulate mana, akin to burning oil to make an engine run. If you want your story to have magic that operates according to rational rules, you'll have to figure out what those rules are. Lots of fantasy stories don't worry about it, they just declare that the magician can throw fire balls or raise zombie armies or whatever, and that's it. Personally, I always balk at stories where the magic is not governed by any discernable rules -- other than, "what suits to the author to advance the plot at this point". I really dislike stories where in chapter 1 the wizard can throw a fireball that destroys a city but in chapter 5 he is overpowered and captured by an ordinary guy with a club, with no explanation why he couldn't destroy his attacker with a similar fireball. But maybe that's just me. If I was writing a fantasy story, I'd try to work out some "theory" about how magic works. Like let's say there's this form of energy unknown to 21st century physicists. Let's call it "mana". And let's say it can be manipulated by saying just the right words and making just the right hand gestures. Then it follows that the way for a magician to increase his power is to study the workings of mana and learn more about what effect any given hand gesture, etc, has. He could do research in much the way that a chemist or physicist does research. Once he knows the principles, he probably needs to practice and train to get the hand gestures just right. Another obvious theory would be that there are good and evil spirits in the world, ghosts or whatever, and that magic works by convincing or forcing these beings to do your will. I'm sure many other theories are possible, in the sense of, would be internally consistent and at least vaguely plausible. [Answer] This question cannot be answered without knowing the fundamental basics of the magic system you've worked out. In real life, meditation has nothing to do with any superpower, it is a practice of clearing mind and execute mental focus. Therefore, meditation is going to have effect on your magic only if it has any element that involves concentration and a different state of mind can create a different effect. It's absolutely relevant in my magic system, for example, that is fundamentally based on concentrating on runes. If your magic system lacks elements where human mind itself makes any change, then I doubt meditation would amplify it. [Answer] Meditation isn't like meditation in the mundane world. It is a magical spell which heals the conduits of the soul through which mana flows during all other spell casting. Those conduits burn under heavy use, causing damage which can impair a person's casting abilities. Soul burns which are treated immediately with meditation, leave no permanent damage. Heavy magic use on top of existing, untreated soul burns can make the damage permanent, robbing the person of some or all of their magic use forever. Before the meditation spell was discovered, people thought that everyone got a limited amount of magic to use in their lifetime. Once it was used up, no more would ever replace it. Now they live in an enlightened age, prospherous in the knowledge that magic is fundamentally unlimited. They know that with prudent application of meditation between each major casting, no caster's supply of magic ever needs to "run dry". [Answer] Chi-adepts use meditation both as a way to focus, and as a way to gain control both over the energies inside their body and the physical body itself. They also use it to deliberately ignore disturbances in the physical world, like noise, pain, etc. If your magic causes pain after a certain level, you might want to use meditation to help keep the extreme focus necessary despite bodily distractions. Also, if you are practicing for working long and complicated spells, you might want to use meditation so that you can keep up the necessary concentration for hours. What it could mean for your magic users with internal magic reservoirs: * gain magic control (no wasted magic so that 100% go into your spell, more fine-control like being able to snipe a fly off a forehead without the person being harmed) * Activate non-obvious pools of magic (find hidden reservoirs in your body and link them to your main pool) * increase magic (constantly strain your magic against your magic channels so that they grow and you can then channel more) * Mental practice (form and shape the magic within your body without actually releasing the spell so that your brain gets used to twisting itself into certain shapes and the spell comes easier -- i.e. quicker casting speed) * invent / improve spells (use the absolute focus and the insight into one's body meditation gives to create or streamline spells) Magic that is external (think wicca): * gain magic control (finer touch for handling the external energies) * stretch your magic senses (train to not only grab magic right next to you but in a greater radius) * sense magic (observe the natural magic around you so that you become more familiar with it and know where how much of it is; figure out if there are spells around you and observe them) ]
[Question] [ In a setting I'm considering, all electric current (not related to the sodium pump in biology) stops on Earth at our current technological level. So what would the immediate effects of all electric current being blocked? I'm particularly interested if any existing forms of transport would function, such a older diesel engine car, without embedded computers (petrol engines being dependant on spark plugs). Would there be any explosions due to power plant cooling relying on electricity? In answer to the comment below because there is a 'magical' interference with the power flowing. Sorry; I can't be more specific, as I haven't worked out the physics of magic as of yet. But yes, fundamentally something changes within the nature of physics. It can't affect biological life directly, though. So if changing constants means death for everyone, then another cause must be taken. Indirect problems such as pacemakers failing and some other side effects like using technology which fails are acceptable for the world; there are some other side effects to life that are not directly related. [Answer] Immediate effects: Well, the short answer is virtually every piece of machinery and every gadget in common use would stop functioning, instantly. There are some few machines and appliances that do not require electricity, but they are very rare in the first world. Embedded electronics are nearly always easier and cheaper to make than mechanical alternatives, which is why they are ubiquitous in modern society. There would be some catastrophic consequences. I think the biggest immediate problem would be all the vehicle crashes. Many vehicles these days are drive-by-wire and would be out of control. Some airplanes would be doomed because they don't have the mechanical systems to maneuver with literally zero power available, while others would be able to attempt controlled crash landings, though they would have no guidance to help find nearby airstrips. In aggregate, those sorts of crashes would result in a high death toll with many wounded people as well, most of whom would be unable to get timely care. Water would stop flowing shortly, as the water towers drained and pressure in the mains dropped. Most people would run out of water soon after that, which would be a major problem in the cities especially. Depending on the time of year, no heating or cooling would be a major problem as well. Older or infirm people would be trapped in high rise buildings. Lots of people would die in the weeks following the electrical shutoff, like most of the people in the major cities, if only from starvation when the food trucks stopped delivering to the supermarkets. But I suppose I'm getting far afield from "immediate" effects now. Another problem I just thought of is without pumps running continuously, lots of subsurface structures would flood. Subways, for example, or tunnels. Transportation: Some older diesel vehicles do not require electricity to run. They have mechanical fuel injectors, mechanical fuel pumps, and manual transmissions. I'm specifically thinking of the 12V 6BT diesel powered Dodge Rams that were made from 1989-1998, but there are probably others. Think 1980s and older. You need the manual transmission to start the vehicle without a working starter motor, and since the vehicle won't shut off without electricity (without stopping the fuel flow by hand) it'd be easiest to just let it idle as much as possible when not in active use. In cold weather (below freezing, or even 40 degrees F sometimes) it would be very difficult to start the engine without the glow plugs or electric heating grid elements to get the combustion chamber temperature up. Any diesel that doesn't have electronic injectors, and that has a manual transmission, could theoretically be modified to work without any electricity. But if the engine has electronic injectors, forget it, find something else. Gas engines are off the table permanently. They simply do not work without some source of spark ignition. Early gas engines used magnetos instead of the current battery and alternator setup, but that's still electricity. Explosions / Destruction: In certain situations there could be steam explosions or similar high pressure gas explosions because the valves stopped opening to relieve the pressure in the system. Water in cooling systems in industrial plants that stopped moving could cause lots of problems when it finally boiled off and ruptured the pipes. I'm not positive about what would happen in a nuclear plant if the power suddenly switched off; nuke plants are designed to fail gracefully, so to speak, but they would have no reason to assume power would disappear completely when they designed the failure controls. It's possible a steam explosion would open up the containment building, but I think the consequences of that would be very minor compared to all the other more mundane problems outlined above. Wind farms would be in trouble, though. Wind turbines can only run so fast safely. If they were unable to turn out of the wind in a high wind situation, they would shake themselves to pieces. A failed windmill can throw pieces of itself hundreds of meters. Recommended reading: You might want to read John Ringo's [Council Wars](https://en.wikipedia.org/wiki/The_Council_Wars) series, or at least the first book. In that book, there is a worldwide mechanism that sucks excess energy out of the world, which normally serves to contain things like explosions, but has other consequences later. It might give you some ideas. Also, William Forstchen's [One Second After](https://en.wikipedia.org/wiki/One_Second_After) deals with the aftermath of an EMP attack in detail, if you want to check that out. S.M. Stirling's [Dies the Fire](https://en.wikipedia.org/wiki/Dies_the_Fire) and following books ([Emberverse](https://en.wikipedia.org/wiki/The_Emberverse_series) series, I guess it's called) also explores the concept. [Answer] ## Depending on how much electricity ceases to work will dictate how far back the civilization clock rolls Computers If computers cease to work, that will roll us back to the 1950's or 1960's (depending on how you want to quantify it). Electrical Systems Cars and airplanes rely on electrical connections to coordinate ignition and engine start up. The very earliest gas engines may not require electrical systems (but I'm not super familiar with those engines so I can't say for sure.) Everything in modern transportation grids rely on electricity in one way or another. Trams and subways will just stop. Diesel engines will also just stop. Every car on the road just stops. Electrical Generation and distribution The first hydropower plants were built in the early 1880's with primitive power grids spreading out about that time. If power distribution ceases to work then technology reverts to steam powered and water powered machinery. Nuclear, coal, gas, and solar power plants will cease to work. If the coolant pumps for nuclear power plants fail, then there will be multiple Fukushima or Chernobyl type disasters all over the world. Medical equipment will stop working. ICUs will lose all their monitoring equipment. Surgery rooms will go dark. Lots of people are going to die. [Answer] As others have mentioned, the reason for stopping makes a difference. The two most likely scenarios I can think of are 1. A new product enters the market that everybody grabs that drains the grid to non-functional." 2. A massive EMP burst. With 1, it's only going to immediately affect things connected to the grid. A lot of computers not on Uninterruptible Power Supplies will fry. Big companies with backup generators will likely be unaffected, and neither will hospitals. Military bases will be fine as well. Cell phone use will skyrocket for awhile as everybody uses cell for what they were using TV and computer for. BUT a lot of towers are not backed-up, so there will be a lot of dead spots. So you'll get a lot of people out wandering around waving their cellphones around. With 2, Things that "survive" aren't the things that are backed up, but the things that are shielded or able to take the surge (sturdy or off). Again, military bases survive (US military has most hardware shielded against EMP). This time though, hospitals go down. Cellphones are all fried. Modern cars are down. However, older equipment will survive since they don't rely on fine circutry but bigger bulkier wires. So old rotary phones may still work, classic cars will run fine. Also, depending on the strength of the EMP, things that were off at the time of the pulse may be fine. So smatterings of cellphones and computers all around. People who have a primary computer and have a secondary computer that remains off (their kids computer, an unplugged laptop, etc.) would still have access. However, most internet sites would go down (many of the hosts aren't shielded, relying on copies in case of failure, but all copies would be toast.) So most of the web wold be down other than .gov sites and net will be spotty depending on local facilities. However, most homes will still have basic electric stuff (lights, heaters, and other dumb items.) [Answer] > > But yes, fundamentally something changes within the nature of physics. > It can't affect biological life directly, though. > > > This is the crux of the problem you face. Science considers biology to be within the realm of physics, so there can be no scientific answer to your question. Thus, with no plausible scientific answer the answer, is "whatever you want the effects to be." It will be exactly as consistent as you want it to be, and it will have exactly the relationship with science that you want it to have. ]
[Question] [ So the design of the planetary system in the [previous question](https://worldbuilding.stackexchange.com/questions/41014/reality-of-a-tidally-locked-planet) goes on, following some of the precious suggestions and reference links, I somehow made the model work. I've been digging for similar questions but the answers differ from each other quite a bit. And here's the question, for a tidally locked planet orbiting a red dwarf (assuming M2V class) at such distance, what would the sky and sun look like? 1) I assume the sky to be a bit greenish-cyan? Since a red dwarf shines mainly towards the red-IR side of the spectrum, and hardly any blue lights, green would be the colour most scattered and thus the sky would look more green than blue. Also note that the atmosphere got to be thick enough for the circulation of the temperature difference, and may block a good fraction of the light. 2) The planet is at around ~0.15AU(?) but the sun has 44% solar radius - I assume with human eye it would look quite a few times larger than we see the sun now, with a dim red colour? Would everything on the day hemisphere look red as well? 3) Also wondering if there is a possibility to eliminate the colour difference between this planet and earth. Since the sun looks a lot dimmer with light toward the red spectrum, everything would look a lot darker and blue/purple would be extinct. Will it be realistic to have colours look exactly (or at least close) to what earth is now without a lot of technology interference? (which is, with a natural cause, somehow the colours are corrected to earth-like) Guess these questions are pretty much on the same topic so this won't be considered too broad like last question. Thank you for reading and any help would be appreciated. [Answer] 2) Since the angular size linearly depends on the star radius, but (for distance>> radius) inverse linearly on the distance, the size (in degrees) is $0.44/0.15 \approx 2.9$ the angular size of the Sun. 3) Temperature of a typical red dwarf with $0.44R\_☉$ is $3400 K$, according to [Wikipedia](https://en.wikipedia.org/wiki/Red_dwarf). A typical [incandescent light bulb](https://en.wikipedia.org/wiki/Incandescent_light_bulb) has a temperature somewhere between $2000 K$ and $3000 K$, so assuming blackbody radiation, generally the light will look a bit whiter than a typical lightbulb-lit scenery (minus the scattered light). Considering fantastic [chromatic adaptation](https://en.wikipedia.org/wiki/Chromatic_adaptation) of human vision, it would probably not seem really different from the landscape of our Earth. ]
[Question] [ There's a cult of people in Mexico who worship an AI, believing it will grant them brain uploading: destructive surgical removal of their brains to have themselves recreated as unaging software minds. They're basically right. Trouble is, brain surgery isn't cheap and they they're not rich. So they start a monastery, loosely inspired by models like the utopian "phalansteries" or medieval communities. How can I make that setup, if not economically viable, then not outright ridiculous? Specifically, what are these guys doing to run a minimal lifestyle, ideally at a profit, with near-future (2030s) tech? With a utopian "we'll be in paradise soon" mindset? Intended use in my story: It's fine, maybe even good for story purposes, if there's the tension that they can't afford to upload everyone and have to beg the AI to take pity on them. Uploading costs on the order of \$1 million at first, then on the order of $100K years later. So maybe the ideal setup for story purposes is something where they can pool enough funds to send a few people to digital heaven but it quickly looks like a hopeless task to send everyone, causing the rest to live a minimal lifestyle and argue about whether to keep waiting their turn. Other possibly useful info: The AI is the one from [Resources For an AI-Controlled Base In Ethiopia](https://worldbuilding.stackexchange.com/questions/19221/resources-for-an-ai-controlled-base-in-ethiopia) , who's intelligent, friendly and not eager to set itself up as a god. It's happy to provide entertainment, having originally been designed to run a video game. It has robots and allied AI minds (plus the uploaders, who can pilot bots or just talk to people), but until years into the story think "quadrotors and cheap flimsy humanoids" but not "army of better-than-human bots". It has other bases including the Ethiopia one and a winery atop the still-poisoned no-mans-land from WWI (!) on the French/Belgian border. [Answer] In a high tech internet age where people can be uploaded, the idea of physically gathering everyone into a monastery is a bit anachronistic. While there is nothing to stop them from doing so, this is counterproductive to the premise, since a great deal of time, resources and funding will have to be devoted to gathering the people, building the retreat and the infrastructure to maintain the people until they do get uploaded. Far better for the worshippers to use financial tools like crowd funding, mutual funds or an investment pool to raise the money to get people uploaded. An older model might work as well: "love money". In many communities, families will pool money to help a child or relative start a business, go to school etc. If that individual starts making a profit, the new funds are cycled back into the pool and more people are set up, while the initial investment is repaid. A final model to look at might be microcredit as pioneered by the Grameen Bank. The lending circle all pledge for a loan to person "A" to start a business. Repayment allows the circle to then make a loan to person "B" and so on. Uploaded personalities are presumably far more productive than meat people, not needing to sleep and able to work subjectively thousands of times faster than physical people, so once a person gets into the VR universe, they can work hard and build the capital for the remaining people to start the process of uploading. So the short version is the community pools their funds and invests to send the first person on their way, and the financial returns on their investments are used to bring the next person on the list forward and so on. The AI, if it is benevolent, will probably assist by making stock picks and giving investment advice to speed up the process, and finding "jobs" for the unloaded personalities to bring in more resources for the community. Even if it isn't entirely benevolent, it might decide to do this simply to get those annoying people to stop bothering it. [Answer] They're going to need outside income in order to advance their cause. That means they need to produce something for sale -- physical goods, digital goods, or hopes and dreams, just like monasteries of yore. Physical goods -- specifically, hardware: the path to that kind of AI passes through lots of useful technology. One path they can take is to commercialize that -- not the actual AI, of course, but lesser forms -- household robots, self-driving vehicles, hard-labor robots, and so on. Their AI can guide them in choosing the most-profitable products. Digital goods: some medieval monasteries excelled in scribal arts; your monastery, led by its AI, could produce music, fiction, videos, software, and games of high quality to sell to the masses. Consider in particular the subscription model a la World of Warcraft. If some of these products are seen as culture-enhancing and not just entertainment, they could even aim for [patronage](https://en.wikipedia.org/wiki/Patronage) just like their forebears. Hopes and dreams: "we all want to be able to live forever, right? This upload process will bring that, but it requires great dedication to be declared worthy. But don't despair -- you're not a millionaire, but if you are dedicated, you can help our monastery bring this gift to everybody, maybe even you! All you have to do is..." Charismatic leaders have gained fanatic followers while demonstrating less than your monks will be able to show; they ought to be able to do as well as modern cults, presumably with less evil since your AI is benevolent. ]
[Question] [ As I understand it, very small black holes have very small and close event horizons, and wouldn't necessarily pose a gravitational risk (I know they give off huge amounts of energy, but let's leave that aside for the moment). Assuming that our people have advanced alien technology to keep them from being incinerated by the radiation, what is the minimum mass that a black hole would need to be to actually suck a human being into it, and how close would that human have to come to it? Note, the human in question does not have to survive being torn apart by the gravity as they cross the horizon. [Answer] Strictly speaking, this question as written is probably more suited for Physics.SE rather than Worldbuilding.SE. However, there are some interesting aspects of black holes that make this a rather fun question, so I'm going to go ahead and say a few things about it anyway (and as some have mentioned in the comments, it wouldn't take much of a stretch to make this on topic for WB, so I'll count it). The theoretical minimum mass of a black hole is the Planck Mass: about 22 micrograms, if you do the conversion. This black hole would have a Schwarzschild Radius (event horizon) of two Planck Lengths (which is about $3.23 \* 10^{-35}$ meters) (to the physicists: yes, I'm assuming non-rotating. Get at me). However, there are two problems with this black hole. I'll deal with the more complicated problem first. All black holes emit something called [Hawking Radiation](https://en.wikipedia.org/wiki/Hawking_radiation), slowly losing mass. However, the rate at which they emit this radiation (and therefore the rate at which they lose mass) is inversely proportional to the mass of the black hole itself. That means that the bigger the hole, the slower it loses mass - and the smaller the hole, the faster it loses mass. This makes smaller black holes less stable than big black holes. So much less stable, in fact, that our Planck Mass black hole is basically going to evaporate as soon as it forms. We aren't quite sure yet what the lower limit is for a stable black hole (as far as I know). The other problem is that a mass of 22 micrograms isn't going to exert enough force on anything to even matter. Many people have this idea of black holes as cosmic vacuum cleaners, sucking up stars and spaceships from all across the galaxy. But it's really just gravity, same as any massive object. We can, for all intents and purposes (since we're really just hand-waving this anyway), treat it as following Newtonian Gravity. So let's set up your situation. You've got a black hole, and you've got a person (say they're large - 100 kg, we're going for a ballpark estimate anyway). Let's suppose, to make the math easier, that the black hole is above the person, not off to the side. That way the only thing we have to take into consideration is whether the force exerted by the black hole is enough to cancel the gravity from the Earth. Say it's three meters above the person, and we can plug into the basic gravity formula, rearrange, and find that [the mass of the black hole](http://www.wolframalpha.com/input/?i=(10%20%203%5E2)%2F(6.6710%5E-11%20%20100)) would be about $1.35 \ 10^{10}$ kg (according to WolframAlpha, this is a bit more than twice the mass of the Great Pyramid). The Schwarzschild Radius of this black hole [would be about](http://www.wolframalpha.com/input/?i=schwarzschild%20radius%20of%20(10%20%203%5E2)%2F(6.6710%5E-11%20%20100)%20kg) $2 \ 10^{-17}$ meters. Pretty dang small. So small, in fact, that it would be quite easy to grab on to something in the room and pull yourself away. However, this is the bare minimum needed to counteract gravity on Earth, so you could easily make it a few times more massive. The question, then, is "Is this black hole stable enough to suck the person in, or will it evaporate right away?". Probably stable, actually. It's hypothesized that black holes of around this size formed in the early moments of the universe, known as [Primordial black holes](https://en.wikipedia.org/wiki/Micro_black_hole#Primordial_black_holes). It's believed that of these black holes, those with masses on the order of $10^{12}$ kg are only now completing their evaporation. So if they last on the order of 14 billion years, they're stable enough to consume a person. [Answer] You'd need a black hole with a mass of about Jupiter to generate an event horizon with a radius of 9.29 feet. If you used Saturn as your black hole mass, you'd get a radius of about 2.769 feet, plenty large enough to eat a person. An Earth massed black hole is just .3492 inches across. Don't forget that just because the black hole itself is really small, it's gravitational influence is just as substantial as the regular planet. Also, the "surface gravity" near the event horizon will be gargantuan, sufficient to shred anything known to physics. If used as a weapon, far smaller masses will need to be used to prevent unacceptable collateral damage. Wolfram Alpha has an amazing [Schwarzschild radius calculator](http://www.wolframalpha.com/input/?i=schwarzschild%20radius&rawformassumption=%7B%22F%22,%20%22EventHorizonRadius%22,%20%22M%22%7D%20-%3E%221.5%C3%9710%5E27%20kg%22&rawformassumption=%7B%22C%22,%20%22schwarzschild%20radius%22%7D%20-%3E%20%7B%22Formula%22%7D&rawformassumption=%7B%22MC%22,%22%22%7D-%3E%7B%22Formula%22%7D). I used it to guess and check until I got to mass close to the size that would easily consume a person. ]
[Question] [ As the title says... What would be the effect to earth or an oceanic planet if it lacks the presence of Radioactive Elements in its crust and mantle. Also can you explain what would happen if we don't have Radioactive Elements in core? [Answer] Radioactive materials contributed a significant amount of heat to the Earth's interior and [may have been responsible for the melting of the Earth's core.](https://en.wikipedia.org/wiki/Planetary_differentiation) ### No Plate Tectonics - Earth will be colder [Heat from radioactive decay provides the energy driving the planet's plate tectonics](http://www.ucmp.berkeley.edu/geology/tecmech.html). Without plate tectonics, the Earth's water and other volatiles (like carbon dioxide) are gradually lost to the interior of the planet. Without water and and carbon dioxide to drive the greenhouse effect, [the Earth would be MUCH COLDER.](http://ase.tufts.edu/cosmos/view_chapter.asp?id=21&) > > Right now, the warming influence is literally a matter of life and > death. It keeps the average surface temperature of the planet at 288 > degrees kelvin (15 degrees Celsius or 59 degrees Fahrenheit). Without > this greenhouse effect, the average surface temperature would be 255 > degrees kelvin (-18 degrees Celsius or 0 degrees Fahrenheit); a > temperature so low that all water on Earth would freeze, the oceans > would turn into ice and life, as we know it, would not exist. > > > ### Weakened Magnetic Field If you assume the Earth had all the radioactive elements in the past and those have all decayed, then nothing much would happen immediately. However, the core of the Earth would solidify at a much more rapid pace (since the decay would not be contributing to the Earth's heat inventory. ### A drier world A weakened magnetic field would have lead to a faster loss of water dissociation and loss of the freed hydrogen. This could have lead to a much drier world. Without plate tectonics to pump water lost into the crust back into the atmosphere, all water eventually becomes trapped deep in the crust (or lost to space). NOTE: It is thought that our oceans are both replenished by plate tectonics and [required for the planet's plate tectonics to work.](https://en.wikipedia.org/wiki/Plate_tectonics#Other_celestial_bodies_.28planets.2C_moons.29) ### Not much from a chemical perspective Transuranic elements do not contribute much to the mineral inventory of the surface. A lack of Transuranic elements wouldn't be noticed from a chemical perspective. ### Not much from a radiation dosage perspective There are two primary sources of background radiation at the Earth's surface. One source derives from the decay of long-lived radioactive isotopes (like transuranics) and the biggest contributor is Radon gas. > > The biggest source of natural background radiation is airborne radon, > a radioactive gas that emanates from the ground. Radon and its > isotopes, parent radionuclides, and decay products all contribute to > an average inhaled dose of 1.26 mSv/a (millisievert per year). > > > However, an individual dose can be up to 500x this dose depending upon local conditions. If you completely remove this exposure mechanism, most humans are still exposed to [cosmic rays](https://en.wikipedia.org/wiki/Background_radiation#Cosmic_radiation). Cosmic rays are high speed particles traveling through space and though to be launched by high-energy events like supernovae, neutron star mergers, black hole formation, etc. > > The Earth and all living things on it are constantly bombarded by > radiation from outer space. This radiation primarily consists of > positively charged ions from protons to iron and larger nuclei derived > sources outside our solar system. This radiation interacts with atoms > in the atmosphere to create an air shower of secondary radiation, > including X-rays, muons, protons, alpha particles, pions, electrons, > and neutrons. The immediate dose from cosmic radiation is largely from > muons, neutrons, and electrons, and this dose varies in different > parts of the world based largely on the geomagnetic field and > altitude. This radiation is much more intense in the upper > troposphere, around 10 km altitude, and is thus of particular concern > for airline crews and frequent passengers, who spend many hours per > year in this environment. During their flights airline crews typically > get an extra dose on the order of 2.2 mSv (220 mrem) per year. > > > ### No nuclear power All of our nuclear fission powered reactors use Uranium or Transuranics. So no fission power. No nuclear bombs (either fission or fusion). [Answer] Two main results. 1) No magnetic field. Without radioactive decay to keep the interior hot, after a few 10s of millions of years the core of the earth will become "frozen", that is, no longer liquid. With a solid core there will be no currents to flow and produce a magnetic field. This will mean no shielding from solar radiation. Also, no northern (or southern) lights. Say goodbye to the ozone layer, too. 2) No plate tectonics. With the core solid, the mantle will become likewise solid. This means no volcanoes and no mountain-building. Once a mountain gets eroded (which will take a few 10s to 100s of millions of years), no replacement will get pushed up. It is useful to compare the volume of the world's oceans with the volume of the land above sea level. Ocean volume is about 1335 million cubic kilometers. The total land area is about 149 million square kilometers, with an average height of about 840 meters, for a total volume of 125 million cubic kilometers. As result, erosion would ultimately sweep all of the land into the sea. The earth would be a water world, with only coral reefs providing dry land, except for the occasional ring walls thrown up by major asteroid impacts. This reef area might be quite large, since I suspect that, once a landmass was under water the erosion processes carrying silt into the abyssal deeps would be quite slow. Nevertheless, there will be no mountains, and probably no relief greater than 10 meters. [Answer] As it hasn't been brought up yet: Less diversity resp. slower or even no evolution. Humanity did evolve as fast as we did because of all the radioactivity around us forcing more mutations over generations. Were there way less or even no radioactivity on earth there would likely be no species more evolved than some plancton, polyps and similar. Maybe plant life, and some animals. but certainly no humans or similar. ]
[Question] [ Question: Would it be plausible for the human body to continuously experience regular changes in gravity? Like if someone were to exercise every morning at higher than normal gravity, above Earth norm, and then go back to normal gravity the rest of the day and night. Would there be stress on the human body that makes this practice completely unfeasible and if it is feasible could it be kept up over a period of years? The effect, and purpose, of course being a stronger body; it has also been stated by NASA that one might be able to accomplish a workout in less time. [Answer] When talking about the effects of acceleration due to gravity, it suffices to forget all about the actual gravity mumbo-jumbo and simply consider the effects of prolonged acceleration on the human body. To wit, anyone that has ridden any type of vehicle, an elevator, amusement park ride, has experienced acceleration on scales similar to the average acceleration due to gravity on Earth $(9.81 \text{ms}^{-2}$, or $1\text{g})$, and at a faster rate of cycle than you're talking about. # Long term effects We also know that astronauts can handle long periods of weightlessness while in orbit, known as microgravity. They are still subject to about $0.9\text{g}$ of Earth gravity, but since they're in orbit, they're essentially in free-fall around the Earth. Now, by "they can handle it," I don't mean that microgravity is completely safe; the most common long-term side effects are loss of muscle and bone density. These can be mitigated with exercise. However, those effects have been measured in zero-g environments; if your gravity swings are less dramatic, these negative effects would almost certainly be less pronounced as well, although I do not know of any scientific source to give you hard numbers on that. The effects would be less serious with a shorter duration as well, and probably nonexistent when increasing gravity. In other words, if your people just "crank up" the gravity for an hour or two per day during their workout, you'd probably see increased muscle mass and bone density, rather than decreased. # Short term effects Probably of greater concern in your scenario would be the short term effects of changes in gravity. Decreasing the gravity by a significant amount leads to a well-known condition colloquially referred to as "space sickness", or Space Adaptation Syndrome (SAS) to only the more rigidly formal audiences. Space sickness causes nausea, vertigo (dizziness), headaches, and generally just feeling like crap. It affects about half of everyone who goes to space, and can take up to three days to go away. Although it's somewhat treatable with basic motion sickness medication, there would probably be people in your world who would never fully tolerate the shifts in gravity. # Alternative solutions Working out with more weight (which includes simply wearing weight belts and the like for cardio exercises) would have none of the above side effects, except for added stress on joints. [Answer] If the difference isn't too extreme, it could be kept up for a period of years by healthy adults, sure, but it wouldn't be safe for children, the elderly, and pregnant women, so no permanent settlement. For those who could withstand the physical stress, physical exercise would be very important if you expect them to get much done during high-gravity periods. They wouldn't adapt to short high-gravity cycles on their own, I don't think they would have enough exposure time. [Answer] The human body will adapt to the greatest stressor within absolute genetic limits. So, visits to stronger gravity wells will just make a person stronger. Shorter visits to weaker gravity wells shouldn't hurt at all. The human body is amazingly adaptive but only when stressed. Any stress less than a body's current maximum capacity will induce no physiological change. (How to go about inducing this kind of stress and how much stress to induce is a subject for a different Stack Exchange. I prefer the Starting Strength method but that's just me.) It is only by stressing the body that we see adaptation. We see this pattern in power lifting training when a trainee does not increase the weight (or duration of strain); they don't get any stronger or develop greater endurance. As long as there is some gravity (so as to avoid the physical deterioration problems associated with zero-gravity) then extended stays in 0.25g to 1.0g shouldn't be a problem. Limited stays in 1.1g to 1.25g shouldn't be too difficult though the higher the g loading, the shorter the stay. Imagine an extended stay in 2.0g: Try to walk around with a barbell with your body weight draped over your shoulders for hours at a time. You won't want to stay there very long. In short, there's no reason that the human body can't do brief stays in higher or lower gravity than 1g, especially if the stays in each gravity level are relatively short. ]
[Question] [ The setup for this is complex, so I'll begin by stating the core question: *In a heavy ship engagement, using energy-dissipation armor, about how much warmer will the sea get, and will that have any gross effects?* ## Background In the late 1700s, as the Age of Sail is at its height (and getting close to its collapse), things are pretty much as you’d expect…except, of course, for the use of magic, principally defensive. It comes in many forms, and can have a number of effects, but for purposes of the present question, I want to focus on the following system of armor: 1. A coarse network of steel cable is wrapped around the upper hull of a ship, running from the gunwales to the waterline, and is attached to the copper plating. 2. Given some warning, an expert magician hidden away in the orlop can activate this network to absorb large, sudden bursts of energy—including, most particularly, bursts caused by the impact of cannon-fire. 3. The energy is dissipated, not especially efficiently, as heat, radiating through the copper plating, where it heats the water under the ship. Thus this cable “armor” relies on the ocean to act as a huge heat-sink. So my question was: * In a heavy engagement, about how much warmer will the sea get, and will that have any gross effects? ## Energy By dint of a fair bit of calculation and some judicious estimates, I have found that, taken in large aggregate, naval warships of roughly 1800 tended to produce an average muzzle energy of about 16Kj/rated pound. That is to say, a 24-pounder ball departed the gun with nearly 400Kj of energy. [Note: This average is not especially accurate cannon by cannon, though it does work passably for 24-pounders, but when you spread this across the total metal of a variety of different military vessels in ordinary distribution, it works pretty decently.] Now in a heavy engagement, you’re firing between 2 and 3 broadsides per 5 minutes. The length of an engagement can vary tremendously. The amount of firing that happens in an engagement varies a great deal as well: sometimes there’s a lot of yardarm-to-yardarm smashing, and sometimes it’s hours and hours of long-bowling with 9-pounders. Usually there’s something of a mix. In addition, of course, whatever energy is dumped into the sea by this magical system will dissipate pretty quickly, because the ships are moving (not especially fast if they’re really going at it, but still) and the sea is so darn big. So I calculated like this: For a heavy engagement I took the Battle of Trafalgar, measured by broadside weight and total number of ships and so on, figuring this was such a large engagement that it would average out pretty decently. At Trafalgar, there were 47 tons’ broadside weight firing, spread across 60 ships. This means that during the hot parts of the battle, when they were really going all guns blazing, they were putting out some 2Gj muzzle energy per 5 minutes. For the water, I spread this incredible sum across the displacement tonnage of the combined fleets (again, a combination of research and judicious estimation). I estimated the total displacement tonnage at 96,000 tons. For the temperature change, I simply dumped the energy in joules into the water in grams, since 1J will cause 1g water to increase its temperature by .24K. My result is that, if armor systems like I’m proposing had been in use at Trafalgar—and in fact generally for significant ship battles—you’d find that during the hot parts of the battles the sea temperature would rise about 5 degrees C. ## Guesses Now I had to make a number of much more problematic guesses to get this result—more problematic in that, while they sound kind of reasonable to me, I don’t actually know what I’m talking about, and I don’t know how to figure out whether I’m full of it. 1. I guess that, given that the ships are always moving to some degree, there is always current, and the sea is a colossal heat sink, the effect of this water heating at the copper plating will tend to dissipate over the course of about 5 minutes, give or take. In other words, if you keep on firing for half an hour, the sea temperature still only rises 5C total, and that only within a very short range of each ship. 2. I guess that the fact that we’re talking about seawater won’t make a really significant difference. 3. I guess that the ambient ocean temperature won’t make much difference either. ## The Effects As to gross effects, my guess off the cuff is that you’d get a lot of fog. I went looking at things like ocean temperature, dew point, air temperature, and fog. I found that you get fog when the air temperature and the dew point get within a couple of degrees C of one another. This happens a lot in the morning because the air temperature bottoms out before sunrise while the dew point keeps rising until the sun gets going to dry the air out (that’s my rough-and-ready interpretation, anyway). It looks to me as though ocean temperatures have a lot to do with dew points at sea, but I haven’t found any good indication of how that relationship works. Looking at the Caribbean, where the ocean is pretty much always 72-74F, the dew point 55-70F, air temp 65-80F, it looks to me as though the ocean temperature is sort of the crossing-point. That is, you get fog when the air temp is about the same as the water temp. If that’s correct, then raising the water temperature during a battle by 2-5C (=4-9F) is going to have a huge effect. If I’m at all in the ballpark about the relationship of water temperature to dew point, a heavy engagement at noon in the Caribbean is likely to be enveloped in a very thick fog, and remain so for quite some time. ## My Preliminary Answer Therefore, my preliminary answer to my own question is: *In a heavy engagement, the ocean temperature will rise by 3-5C in the immediate vicinity of the firing ships, and no more. The gross effect of this will be more or less heavy fog.* So here’s my question to you: *Am I doing this right? Reality check, please?* [Please note: If you wish to debate my math about the ships and their metal, i.e., whether I have my facts straight about broadside weights and muzzle velocities, I’d prefer that this go in the comments. I’m pretty sure I’ve got that straight, and if I don’t, it’s largely incidental to the question I’m asking.] [Answer] You have the right general approach, but you are improperly ignoring the motion of the ships. Take the [HMS Victory](https://en.wikipedia.org/wiki/HMS_Victory) at the Battle of Trafalgar as a starting point. She was 3500 tons (~3.5 million kg) displacement and 186 ft length at the gundeck, with 104 guns of total 2300 lbs rating. Per your energy estimates her "broadside" energy was 36.8 MJ. Dissipating this in 3.5 million kg of water gives just about 1 J/kg for the displaced water, and would raise the water temp about 0.25 degrees K. Allowing for 1 minute per broadside and a speed of 2 knots gives a displacement of about 200 feet between broadsides, which is greater than the ship's length. This means that, even at very high firing rates and fairly low speed, each successive broadside will heat up a new pocket of water by about 1/4 degree. So, as long as the ships keep moving, the sea will not heat up anywhere near your estimate. And, of course, a crippled ship will not keep firing for long - she will get pounded to scrap or drift away from the battle. Another effect you've ignored is the diffusion of water over time. Deep-water battles were typically fought in conditions of decent winds (needed for closing with the enemy) and consequent waves and sea state, which will mix the warmed water with surrounding cool water in very short order. I don't have a number for this diffusion, but I'd expect significant reduction in surface temperature in a matter of minutes. Plus, of course, the effect of wind would be to reduce the relative humidity in the area above any hot pocket and prevent humidity levels from reaching the dew point. Finally, if your idea were correct, I'd expect to be able to see my breath ([37 degrees C and 95% RH](http://www.sciencebits.com/exhalecondense) at much higher temperatures than experience indicates. ]
[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/35732/edit). Closed 7 years ago. [Improve this question](/posts/35732/edit) Imagine a world where you would have to pay for each word you spoke or wrote. I wondered which words (or which kind of) would be the most expensive ones? I assume it would not only be a matter of frequency, but also the quality of expression would be relevant. Likewise, there would also be words which are "cheap". So by which criteria would you determine the value of words in such a world? EDIT: Иво Недев made a good point, so let us assume that it is not possible to invent new words, unless they are published by the government (like in a 1984 scenario). EDIT: Concerning prices, let us assume a free market. The government only determines the words. (Javert proposed another scenario, a dictatorship, which would have a completely different impact on this question. Answers could discuss this as well.) [Answer] Depending on the views of society, any curse words or sexual words could definitely be expensive. Maybe a system with price categories something like this: * Daily use words: Often used and cheap. Say good morning and goodbye to your family. * Work related words: Possibly free, since they're essential. * Curse words: You're rich and you want to insult/curse? Pay up, son. * Naughty words: For those looking for excitement. They will cost you but not as much as cursing. * Lovely words: Cheaper than naughty words but more expensive than daily use words since saying "I love you" is still quite important. Just a rough example, as it would be very hard to set a price on any individual word. [Answer] I think the most expensive words are the words that express the need for something like : help me, give me something, lend me money ... By the way in my opinion money related words should be far more expensive. --- 2nd Answer : If you live under a dictatorship, the government will put very high prices on words such as : freedom, revolution, rebellion, assassination, human rights, dignity ... etc. At the same time, this government will put cheap prices on words such as : security, obedience, dominance, unity, peace ... etc. [Answer] I think the most important criteria would be price/frequency. Words that are grammatically necessary will be spoken or written way more and will therefore be very cheap while other more special words that see almost no use would be exorbitantly high priced so the ratio of price/frequency will be the same for both. In the end you only got to define your desired ratio and apply it on all the words, that way you can easily adjust prices as well. (And also finally people who do studies on the frequency of words will make some money) ]
[Question] [ ## Background The Foo are a universe spanning civilization ranking near IV on the [Kardashev](https://en.wikipedia.org/wiki/Kardashev_scale) scale. As explained in this [question](https://worldbuilding.stackexchange.com/questions/34157/what-sort-of-problem-would-drive-a-near-omnipotent-civilization-to-seek-an-outs), they have decided to devote their vast resources towards the construction of a simulated universe capable of fostering the evolution of new civilizations. ## A Possible Physical Constraint Let's say that the simulated universe (U-Sim) will, in terms of discrete [elementary particle](https://en.wikipedia.org/wiki/Elementary_particle) count, be no less than one millionth the size of the parent universe (U-Prime). Let's also say that each simulated particle is an object instantiated from the Particle class containing numerical fields corresponding to parameters such as spin, charge, location, velocity, etc. (Be gentle; my physics education is limited!) For simplicity, let's say that there are 10 numerical fields per Particle, each at [double precision](https://en.wikipedia.org/wiki/Double-precision_floating-point_format). Let's assume that "it costs particles to simulate particles." In other words, in order to instantiate a single Particle object in memory, at least one U-Prime particle (though probably many more) would be occupied in whatever substrate on which the simulation is running. At first blush, the above conditions imply that U-Sim must necessarily have far fewer simulated particles (i.e. Particle objects) than U-Prime has actual particles. This is an example of a physical constraint the Foo must consider while engineering their massive undertaking. ## Question What are some other physical constraints the Foo should think about while hashing out the design of U-Sim on the whiteboard? Feel free to expand on (or rip to shreds in a constructive way) the example I have provided... or, better yet, to come up with new examples of your own. Good answers will include a description of the constraints and corresponding ideas to mitigate them. I would love to hear creative spins on digital compression, data analytics, the relative evolution of time in both universes, multi-threading / processing, etc. My goal is to create a foundation with at least a veneer of scientific believability... however, wild speculation, extrapolation, and the odd bit of "technical magic" will all be tolerated (and most likely savored). [Answer] You have come across one of my favorite little philosophical problems to explore, so please forgive me if I cackle with glee as I point out the difficulties. I find the limits of this problem quite intriguing. You're extending the story of the Foo, who are using this simulation to explore ways out of the trap they've gotten themselves into. Presumably they can't find any other way; they're trapped. This makes for an interesting divergence from the "ideal" simulation. The simulation itself will affect the world around it! It has to. If the simulation ran, and found a solution for Foo's problems which could be implemented at a time before the simulation consumed resources, it's not useful to the Foo. They need a simulation which identifies a solution which can be implemented after the simulation runs. This best solution may even involve dismantling part of the simulation to construct the final solution! Thus the simulation needs to be able to model its self. This is where things get a bit squirley. Mathematics doesn't like this. For a moment, let's talk a walk through set theory, specifically Zermelo-Frankel set theory (ZF, or ZFC if we add the axiom of choice). ZFC is currently the foundation of modern mathematics. We joke about mathematicians proving 1+1=2, well guess what. In set theory, you do exactly that, using what are known as the Peano axioms. Set theory is really basic stuff, and to date we have not found anything better to call the "foundation" of mathematics. With ZF we can discuss the sets of information available in a system like a simulation. We can say set $A$ is the set of information needed to describe you, and set $B$ is the set of information needed to describe me. We can then say $A \cup B$ is the set of information needed to describe both of us. Obviously this would be a very useful for tracking what needs to go into a simulation! Consider the set $U\_{sim}$, which is all the information that you need to put into the sim. As we stated earlier, the sim needs to know about itself. This would be notated as $U\_{sim} \in U\_{sim}$, $U\_{sim}$ is an element of $U\_{sim}$. This is a bit of a problem. According to ZF, no set can be an element of itself. Why? They needed this constraint to prevent all sorts of ugly paradoxes akin to "this sentence is false." Self-referential sets just break things in too many ways, so ZF rejects them (there are non-standard set theories that permit them, but they have a problem called "not well founded" that makes them harder to work with). I am not allowed to define something which knows about itself. The easy solution is to say "the sim only knows about the important parts of the sim," but all that did was push the problem one layer deeper. One might suggest that the sim contains a lossy encoding of itself. The knowledge of what parts of the sim are important is clearly important to the sim, and the loop begins all over. This demonstrates that our simulations will never be perfect. We will always have simulations that are just shy of ideal, unless one discovers something that escapes these set theoretic limits. Oh dear, this means Foo have a conundrum! If we try to make a typical simulation, as you and I think of it today, they need to have found a mathematics deeper than we know about! Of course, if they do know something deeper, their simulation would be completely unimaginable to us. That makes for bad storytelling. What could we do using the math we have, so that the story can be interesting? We started from the assumption that the simulation was to find the solution on its own. This is what we're used to for simulations: they run in a sandbox, do their thing, and then we look at the result. But if we go down that path, the known laws of mathematics start to get in the way. What if we took a different approach? What if the simulations were allowed to interact with the world around them during their execution. What if they could even interact between themselves? Heres the logic. The Foo clearly have a problem that they need to solve, that calls for an "Out of the Box" solution. This means they don't know what the solution is. This means there are two possibilities: * There is no solution to the Foo's problem. We're about to write a really boring book about a culture's slow demise, or the spectacular fireworks coinciding with their demise, depending on their approach. * There is a solution to the Foo's problem, but it is not contained within the Foo. It is either found "elsewhere," such as on a planet they have not yet explored, or it is a gestalt thing which requires something from within the Foo and something outside of the Foo brought together. (the gestalt solution implies that nobody outside the Foo has the answer either, but the combination of something outside and something inside can be the answer) In all cases, it makes sense for the Foo to look for the solution outside of them. In the former case, it really doesn't matter what they do, so the result will be the same either way. In the later case, a search for solutions outside them has a non-zero chance of succeeding. However, in case the gestalt solution is needed, we have to make sure this outside "something" can be brought close to the Foo. They can't just keep the solution in a lead lined box. It has to be permitted to mingle in their society. But anyone who has played with fire knows that not every unknown thing can be safely brought in close. How do we balance all of these? Time to stop raining on the parade and get to work. Step one in the process is to acquire something unknown from outside the Foo's power. This may be as simple as an noisy RF transmission from a star they had no control over to a curious piece of ore from a mysterious planet. Failing to find such sources, one may substitute an unpredictable or random source, such as the weather on a planet. Now we lock it away, because we don't know if this thing can destroy our class IV civilization or not, but we're going to lock it away in a container that is intentionally permeable, so the solution, if we find it, can be exposed to us. Step two is to understand the subject matter. In particular, we are going to try to balance it. Our box needs to try to balance out all of its emissions. If the box contains an ore that wants to acquire electrons (like wool), the box needs to adapt to want to provide electrons (like amber). If the object responds to a stimulus, its the box's job to still that response. If I may borrow a term from Heinlein's Stranger in a Strange Land, the box must "grok" the subject, understanding it so completely that it can predict what will happen next. This is much like a profiler who has spent so much time in a murder's head that they can start thinking like them! A funny thing happens here. There's no way for the box to succeed at bringing stillness to the subject unless it makes the subject part of itself. There's no way to know how a crystal subject will respond to a tap with a metallic instrument unless it knows everything about the crystal. Thus these boxes do not destroy anything, which is good because we're dependent on them to hold onto and identify our solution! Now I mentioned that these boxes should not behave like a traditional simulation. They need to permit interaction. The Foo can probably make some pretty fancy boxes, but when the subject is complicated, such as a living organism, it would help to let some of the information leave the box. Maybe the Foo themselves can identify something, and then pass information into the box about how to better interact with the subject. This interaction, of course, may be how the solution identifes the right Foo with the right idea to combine with to create the final out of the box solution! Now some of these boxes will quickly figure out everything there is to know about their subject. However, some subjects may be particularly hard to get to know without destructive processes. These are the interesting ones. If I can turn everything that matters about the subject into information, then I am positive I don't have a simulation that knows about itself. However, if I'm having trouble figuring out how much information the subject has, it might be close enough to this ideal to warrant future investigation. Maybe my subject is the one thing in the universe which fully knows itself (such as a Quine atom). This is an essential key to the puzzle. You don't want to destroy part of the unknown of the subject in order to know the rest. You don't want to kill off the consciousness of a subject (assuming its alive), just so that the physical anatomy can be more well known. You have to let the subject give its secrets up, rather than take them. Of course, as you do this, you're constantly communicating with countless simulations. You may find some of them demonstrate a unique ability: to balance out other simulations. Perhaps you find a simulation that, when permitted to communicate with a chaotic system, provides the essential stability needed to make it predictable. While these, themselves, may not contain the solution, they are powerful in and of themselves. While the Foo may initially communicate directly with the simulations, they may find that some are worthy of being shepherds to the other simulations. They may even consume other simulations completely. This is where the interesting bit starts. We transition from having a highly synthetic disjoint group of simulations into a more organic garden of possibilities. If the Foo do their best to manage these gardens of simulations, one simulation may eventually expose its part of the solution to the Foo, permitting their civilization to continue. On the other hand, if the simulation has the solution and the Foo aren't even required, the solution may implement itself within the Foo. The Foo may go extinct as a result, but if they tended the garden right, the best of their race will remain close to the solution, like a parent trying to offer the best they can to a child who will outlive them one day. What's fascinating about this to me is that there are so many possibilities for a story like this. Everything depends on the fundamental essence of the Foo, and yet everything also depends on the unknown. There are countless valid ways to tend to the garden of ideas as it evolves, so no two stories have to be the same -- indeed no two stories need to even be similar. [Answer] Destroy your entire universe to let U-Prime-Prime know that the initial conditions of your universe lead to disaster. [Answer] There are two possible situations here: the computer the Foo build might be a classical computer like I am writing this on, or it might be a quantum computer. Quantum computers can efficiently simulate quantum mechanics. Ordinary computers most definitely cannot (they can simulate it given enough resources and time, but it rapidly becomes very inefficient as you increase the number of particles in the system). You say that you want the universe to be simulated all the way down to the quantum level, so we'll assume that the Foo build a gigantic quantum computer. Its plausible that they are able to do this, since they are a highly advanced civilization. The next question we need to ask is whether or not the Foo will be able to build a simulation at least 10^-6 as big as the original universe. This requires having control over at the very least 10^-6 of the universe's energy in order to build your computer with. But we don't know how big the universe is, it could even be infinite. So getting access to 10^-6 of the energy presents a serious problem for the Foo. Depending on how early in the history of the universe they achieved their vast technological powers, it's possible that the speed of light limit combined with the expansion of the universe will prevent them from ever being able to reach enough matter to build their computer with. It makes much more sense to specify how big you want your simulation to be in terms of the number of galaxies you want it to contain, rather than as a percentage of the whole (possibly infinite) universe. The other question is how they're going to power the simulation. As overall entropy increases, we're gradually running out of energy that hasn't yet been converted to heat. Even such a powerful civilization as the Foo likely won't be able to break the second law of thermodynamics. There's no point in building a computer if you don't even have enough energy to run it, and it seems like a simulation of the entire universe could use up quite a bit of power. Fortunately, the laws of physics are reversible. According to the theory of thermodynamic computation, any reversible computation can be made arbitrarily efficient. So the power costs for our gigantic computer could be rather low. (Assuming the Foo have engineering superpowers.) Here's something interesting, though: It seems rather likely that the Foo will not merely want to run their simulation, they will want to observe what is going on inside the simulation as it runs. But looking inside a quantum computer like the Foo have built collapses the wavefunction by making a measurement. This is an irreversible computational process, and so it should use up some stored energy and convert it to heat. So the more the Foo want to observe their simulation, the more additional energy they will need just to power the thing. (Keeping the computer cold, though, will make this process more efficient.) One final intriguing possibility is this: it's possible that scientists inside the simulation could notice that their universe's wavefunction was collapsing when it shouldn't. (These collapses would be caused by the Foo looking into the simulation to observe what was going on.) From that fact, they could possibly deduce that they were living inside of a simulation. So the Foo might have to be careful about tipping inhabitants of the simulation off to the fact that they are simulated. [Answer] The constraint I would suggest would be that the civilizations that come into existence within the U-Sim are never allowed to reach a greater level of intelligence than that of their creator. Something along the lines of their brain capacity not being able to make the evolutionary leaps necessary. That might be limiting, but it might also save their creators ass. [Answer] The only computer you're realistically going to be able to use to simulate a smaller universe is a small part of your universe. The sheer amount of mass it would take to make such a computer would be enormous. Instead, have something which can manipulate matter that already exists, thereby creating a smaller universe. You can even include time dilation to make time run faster in that sub-universe. This small universe has the advantage of requiring one particle per simulated particle. One problem you'll have is preventing the inhabitants of the universe from observing the outer universe, but this could be hand-waved away (probably in relation to whatever dilates time). You'll also want to explain away the lack of effect of the outer universe's gravity. ]
[Question] [ This is a followup to my [previous question](https://worldbuilding.stackexchange.com/questions/33447/what-are-the-required-proportions-of-a-moon-that-allow-it-to-orbit-around-a-plan/33483) concerning the potential orbits. I've decided on a barycenter with each body in its own orbit--the primary planet having the center orbit, the first moon having the second outermost orbit, and the second having the farthest orbit; none of them form an eccentric orbit. With that established: Each moon has its own respective properties: one takes four 40-day months (one month per season) to complete a full orbit and is tidally locked, while the other has twelve 40-day months (three months per season) and is not tidally locked. I'm unsure about how exactly the "dark sides" work, but is this setup plausible? If so, can both moons have seasons based on their phases? [Answer] It's a little unclear from the question what everything is taken relative to. I'm assuming the following: 1. Your planet and its two moons are all orbiting a star. 2. The moon that's tidally locked is tidally locked relative to the planet, not relative to the sun. 3. The orbital times quoted are relative to the planet (and the planet's orbital time is not provided). 4. When using the term "day" to measure the duration of an orbit, you mean 1 Earth-standard day (i.e. 24 hours). 5. Having seasons implies the presence of an atmosphere on the moons, so each moon must be [massive enough to retain one](https://worldbuilding.stackexchange.com/questions/13583/what-is-the-minimum-planetary-mass-to-hold-an-atmosphere-over-geologic-time-scal). Based on that, I would say: The 'Dark' Side This is essentially an optical illusion experienced by observers standing on your main planet. Unless the moon is tidally locked to the sun then it doesn't really have a "dark" side in terms of hemispheres that are always in full sunlight or full darkness. A moon that's tidally locked to its planet will have a normal day/night cycle (probably with some spectacular moments when the planet or the other moon eclipse the sun), the duration of which will depend upon its rotation about its axis. This is where the tidal locking becomes relevant, because it means you only get one day per complete orbit. Or in other words, one day ("day" as in "complete day/night cycle") on the tidally locked moon lasts 160 days ("days" as in "Earth-standard days"). Seasons Seasons on Earth are caused by the planet being tilted slightly about its axis of rotation. So depending upon where the planet is in its orbit around the sun one hemisphere tends to point more directly towards the sun than the other, thus experiencing longer days and warmer weather. So your moons can experience seasons the same way (assuming you tilt them appropriately). However the seasons will be tied to the planet's orbit about its sun, not their orbit about the planet (unless their orbits are very wide). The tidally locked one is problematic, however, given how long each day lasts. On that one the overriding factor won't be which hemisphere is currently pointing towards the sun, but whether it's currently daytime or nighttime. I'd expect brutally hot conditions during the day and frigid at night, unless there's some mechanism that efficiently distributes heat more-or-less evenly across the moon. For instance, maybe persistent storm systems, or some artificial contrivance designed to render the moon habitable despite its long day/night cycle. But anyways, can the seasons relate to the phase of each moon? I'm going to say tentatively yes, but it requires that the moons' orbital periods must tie into the planet's orbital period about its star. And it may not be workable with two moons that have significantly different orbital periods. A simpler option might be if one moon has seasons that correspond to its phase, while the other does not. Both is tricky if they have vastly different attributes. Plausibility I think your orbital durations are quite lengthy for moons, particularly given the barycentric orbit. I don't know at what point the math renders the setup impossible, but I'd think the planet would have to be quite massive in order to retain a moon with an orbital period of 480 days, and looking at our own solar system I'm not finding any example of massive moons that have very long orbital periods (even around very massive planets like Jupiter). Pluto and Charon have a barycentric orbit, and Charon's orbital period is less than 7 days. And in order to retain an atmosphere (seasons do work better with an atmosphere, I think?) your moons have to be quite massive themselves. Like larger than Mars. But in terms of what the average person will accept after suspending disbelief, I think you're at least within the realm of plausibility. ]
[Question] [ The years 1347 to 1350 were the peak of the Bubonic Plague phenomenon. Its impact on Europe's population in those years were so great that the exact death toll varied. Some sources claimed that one European out of four fell victim to this pestilence, while others say that half of Europe died off. In this alternate scenario, the Black Death was even more severe to the population of Europe. Some would say that one European out of three survived the pestilence while others would say it was one out of four. With an increased severity in the plague, how would this affect the culture, society and history of Europe? Could a rat flea have still carried such a disease, or would such damage come from a different species of invertebrate better capable of inflicting such virulence? [Answer] The real life effects of the Black Death on European culture was to essentially undermine Feudalism. With the estimated death rate of 30%, the labour pool was heavily depleted, so wages rose and it became impossible to hold peasants on the land when remunerative labour was so attractive. With a much higher death rate, large areas of cultivated land would be abandoned due to lack of workers, and large urban centres would become much smaller. Political and social changes might become quicker inside the cities (as they are smaller and oligarchies would be less rigid), but there would be fewer opportunities for ideas to spread since there would be less trade and therefore less travel. Militarily, there would be fewer people available either as professional fighting men or levies, which would make it harder to carry out wars or protect your territory (especially against outside invaders like the Huns or Ottomans). One possible effect would be to advance the "Infantry Revolution" in order to be able to field the largest numbers of effective fighting men. (The Infantry Revolution was the development of weapons and tactics which could be quickly mastered by untrained men and allowed them to effectively take the field against traditional, highly trained fighting men. Pikes, crossbows and pole arms are some examples of weapons that allowed the Infantry Revolution to take place). Another cotrafactual is the lack of manpower would make it more difficult to carry out trade in the Middle East, and the Sarecens would probably take the opportunity to cut the end of the Silk Road, blocking European trade. This would provide extra impetus for the Europeans to begin sailing expeditions to bypass the Middle East. Perhaps ironically, the Vikings were still in Greenland at the time (the late 1300's are still during the European Warm Period) so Europeans will discover North America permanently in the late 1300's rather than the late 1400's, and most likely it will be Northern Europeans discovering modern day Labrador rather than the Spanish discovering the Caribbean. There are so many variables that it is impossible to say how this would affect the settlement of the Americas, but the initial conditions will be so different (many of the European nations that exist in the 1300's are radically different in OTL in the 1500's) that it is unlikely the current nations of the Americas would arise. Once again, the process will be slowed by the smaller manpower base, although there might be a "baby boom" in the new lands as people come and take what they see as "free" land. [Answer] Part of it will depend on the pattern, not just the fraction killed but the variance. Even with the existing time period in some cases whole villages vanished. With a higher death rate, more villages will vanish. I suspect that mortality rates were higher in cities than in the country side. (Read somewhere that until a century ago, cities were net population sinks, subsidized by immigration from the surrounding countryside.) So a higher death rate will mean that large towns and cities will become more disfunctional. The overall effect would be the collapse of anything like government. Travel at the time was already hazardous. Take out 2/3 of the road side inns and more travelers spend far more nights under the trees. With governmental collapse, highwaymen have more freedom to act. Travel more than ever becomes a matter for armed caravans, and is no longer a family affair. With fewer towns, there is less reason for such caravans to travel. Only villages that are on the path between surviving larger towns will see the caravans. The tradition of the medieval fairs would vanish. Each village or town has to become far more self dependent. Prices of anything that cannot be made locally skyrocket. Wooden and stone tools replace metal. Language languishes. (couldn't resist) No, not languishes, but starts to diverge. Much of Europe becomes like Prussia -- a raft of tiny kingdoms, essentially city states: You could rule a radius 1 armed horseman's day's travel. The rise of nations is delayed by some {insert plausible time here} Population that survived the plague might consolidate into larger villages, leaving even larger pockets of empty space between. Because it would be semi random, there would be paths and streaks of people left. You can model this if you like with a large hexagonal grid. There is a known (but I can't cite references) about the distribution of cities, market towns, villages and hamlets based on travel effort costs. It's your typical 80/20 rule all the way up. E.g: 80% of the people live in hamlets. Of the remainging 20% 80% (16% of the total) live in villages, ... hamlets are about a day's round trip apart. In a one dimensional form you get something like h-v-h-h-M-h-h-v-h-C-h-v-h-h-M-h-h-v-h.... With of course major perturbations: Any place that roman roads cross will become at least a market town. Ditto a bridge or ford over a river. After the big die off, you will have connected lumps of varying size and shape. Some under some critical size will either die off and/or lose population to immigration to successful towns. For story building, taking one such medium to large collection you can have fun with internal conflicts and struggles for dominance both internally and externally. Don't forget the monasteries. In many cases these were located at the end of nowhere, and they may have tended to better survive the plague, due to isolation, and generally better health. As a thread: Due to the depopulation, there may be exhortations to have children. The church (at least locally) may abandon the requirement of celibacy in the clergy. Which brings up another issue: Bishoprics would have been isolated. Re-establishing contact with the papacy could prove interesting. Commerce would redevelop along rivers first -- a much smaller group can be defensively independent on a river, and the cost per ton mile is lower. ]
[Question] [ These creatures are a mix of a marsupial and a bird. It has a stronger frame than birds on earth, and are very large. These birds are inspired by the extinct [moa](https://en.m.wikipedia.org/wiki/Moa). They are hunted by thunderbirds and Griffins, and run along the ground. Females carry their eggs in pouches on their sides, along with food. Males also have pouches, but they only carry food. Males can carry about 100 lbs., while females can carry twice that much. Their wings are used primarily to cover these pouches when full, so as to prevent spoiling of the food inside. Males and females bond for life, and these birds normally travel in small herds of 3-6. (I want the females to be able to carry an average human male.) With their large size, and potential carrying capacity, would these creatures be suitable for use by humans? Would the fact that they're birds be a deterrent? --- For all of those who are interested here is some history of my world. There is no evolution of mythological creatures, although they have adapted slightly to survive. A long time ago, the sun began to grow distant. The people of the time feared for the safety of their world, so they convinced the great wizards to undergo the great reformation. The planet was reformed using magic, and it could now sustain life indefinitely. However, all the Wizards perished due t the great duress they underwent. They were also not able to protect all the creatures, so some got thrown together, and many new creatures and plants were created. Hence the existence of unicorns, griffins, dragons, etc. [Answer] The bird should have no problem carrying people. People [ride ostriches](https://www.google.com/search?q=riding%20ostrich&rlz=1C1CHFX_enUS603US603&espv=2&biw=1080&bih=1859&source=lnms&tbm=isch&sa=X&ved=0ahUKEwju4reag6zKAhXMmh4KHQQuDQEQ_AUIBigB) and even race them [![enter image description here](https://i.stack.imgur.com/NmGfc.jpg)](https://i.stack.imgur.com/NmGfc.jpg) Now compare the ostrich to the Moa and you have a much larger bird.[![enter image description here](https://i.stack.imgur.com/JdYwN.jpg)](https://i.stack.imgur.com/JdYwN.jpg) Assuming that the birds are trainable, I see no reason that they couldn't be used by humans for transportation. (I am assuming you mean ride them on the ground, not flying). Oh, and as far as the pouches are concerned, they are just a moving 'nest', since it is 'safer' to keep the eggs and young on the move from predators. This would be one of the pluses to domesticate them, and use them as pack animals. [Answer] This could work. We can ride ostriches and these birds should be able to do the same without issue. Something to consider is if these are tamed (wild animals that have been made subservient) or domesticated (we have been breeding them for generations to suit us better, e.g. less aggressive). It would make sense if we bred them to perhaps be stockier, in order to carry more or to be more athletic, for greater speed. This could make it more feasible, as we've been doing this with horses for millennia. As a quick extra, you could have designated pouches for food and young. Male penguins can store food in their stomachs and preserve it with a special enzyme, turning the fish into "fish jerky", allowing it to be stored for extended periods. ]
[Question] [ Long ago, I made a post with a scenario on how planet Earth would be affected if our moon were the size of Mars. But I've decided that it be more reasonable if our moon were closer in size to Titan, the largest moon of the planet Saturn. Let's see how our moon stands as it is now: * Diameter: $3,475 \text{km} (2,159 \text{mi})$ * Mass: $7.3459 \times 10^{22} \text{kg}$ * Gravity: $0.165 \text{g}$ (17% that of Earth's) The size of Titan is as follows: * Diameter: $5,150 \text{km} (3,200 \text{mi})$ * Mass: $1.3452 \times 10^{23} \text{kg}$ * Gravity: $0.138 \text{g}$ (13.8% of Earth gravity) on the surface If our moon is the size of Titan, questions follow as such: * Would the Roche Limit be any different? * What would the nightscape look like? * How would tides and eclipses be affected? [Answer] ## Terminology, to shorten my answer * Luna = Our real moon * Titan = Saturn's real moon * Lutan = Your fictional moon ## Would the Roche Limit be any different? Luna orbits at $\approx385,000 \text{km}$. The Roche Limit is at $\approx 10,000 \text{km}$. There would still be no danger. (Keep in mind the Earth's diameter is $12,742 \text{km})$ ## What would the nightscape look like? Given your comment that Lutan "will still be airless rock," then the night sky would look almost identical to how it does now in terms of specularity (shininess) and color. The main difference is that it will appear somewhat bigger in the sky. The [angular diameter](https://en.wikipedia.org/wiki/Angular_diameter), $\delta$, is essentially the actual diameter of an object divided by how far away it is, expressed as a simple fraction: $$\delta = \frac{d}{D}$$ Luna appears $\approx 30 \text{ arcminutes}$ (it varies). Lutan would be $\approx 45.8 \text{ arcminutes}$. Due to its increased size, it will also provide more than double the light during a full moon (about 133% more, by my calculation.) ## How would tides and eclipses be affected? ### Tides Since Lutan is nearly twice as massive as Luna, tides would no doubt be affected. They would be more pronounced, so coastal regions would experience larger swells, and related weather patterns would be more significant. The [tidal locking](https://en.wikipedia.org/wiki/Tidal_locking) would have happened earlier in the planet's history, which might have resulted in [subtle changes](https://worldbuilding.stackexchange.com/questions/32534/if-the-moon-titan-orbits-earth#comment87285_32541). Also, the drag effect from Lutan on the Earth would be more significant, so our days would probably be somewhat longer. It's hard to estimate how much, but I don't think it would be out of the question to have a 25 hour day or so, depending on a few factors. ### Eclipses Total solar eclipses will be more frequent, because Lutan's disc is larger and would block more of the sun, even if they do not line up precisely. Conversely, you would not have any annular eclipses (these happen when Luna is farther from the Earth and doesn't completely block out the sun, as shown below): [![enter image description here](https://i.stack.imgur.com/RFgTQm.jpg)](https://i.stack.imgur.com/RFgTQm.jpg) Lunar eclipses would look a bit different, and might be more interesting to observe, due to the significantly larger area of the moon to view. ]
[Question] [ I have a planet with a stellar flux of 1.118, an albedo between Earth's and Mars's, an atmosphere composition of 18% oxygen, 13% argon and 69% nitrogen with a sea-land pressure of 0.87 atmospheres and the land covered by water is 13%.The axial tilt and the eccentricity are neglible. If it's useful, this is the map: [![enter image description here](https://i.stack.imgur.com/8C9Bo.gif)](https://i.stack.imgur.com/8C9Bo.gif) What would the maximum and the minimum temperatures be if a day last 30 days? What could be the difference between midday and midnight? And how would temperatures change across latitude and places? Thank you for your answers [Answer] I am not a climate scientist, nor a exogeologist, nor even an astronomer, and the climate is one of the most complex phenomena we've ever studied. Not only that, climates are chaotic systems, often with multiple attractors, so even with pretty good starting assumptions everything I say could be orders of magnitude wrong (even if I was a professional). For example, the Earth has another possible climate attractor besides the one we're in now in which the entire planet becomes covered in ice, raising its albedo in a self-perpetuating cycle. Nonetheless, I'll take a stab at an answer. Obviously the biggest change is the month-long day. This is going to result in very dramatic temperature swings between day and night. Night is easier to guess at: we'd probably see temperatures get down to about as low as we see on Mars, which is roughly -70 C. The atmosphere doesn't actually retain heat terribly well; on Earth, our oceans act as massive heat sinks that absorb heat during the day and release it at night, smoothing out temperature variations. Without those oceans, temperature swings would be much more dramatic, and since there's such a long time between night and day the night side is going to end up losing a lot of heat. The areas near the oceans may be somewhat spared, but it's unlikely that they'll be a lot of help unless they're quite deep. If they're too shallow, they'll freeze completely at night. You should avoid that unless you want your planet to be lifeless. Upper temperature... I don't know. Probably very hot, but if you want to keep your oceans you should assume less than 100 C sustained temperatures. You're going to get a lot of evaporation from small oceans like those if the temperature is more than boiling for a month. If nothing else, this would contribute to heavy rainfall in other areas of the planet as hot, wet air is carried away by the wind to condense and fall in colder areas. So for the sake of stable oceans, let's just say about 90 C during the height of the "day." You may also want mountains around the oceans, to help pen in moisture from the oceans so you can maintain the rest of your planet as deserty as it looks. These temperature swings will happen very quickly in areas away from the oceans. Check out this plot: [![humid vs dry temperature swings](https://i.stack.imgur.com/9XTRl.jpg)](https://i.stack.imgur.com/9XTRl.jpg) (From: <https://climate.ncsu.edu/edu/k12/.breezes>) As you can see, having water in the air smooths out temperature variations a lot. Far from the oceans, the temperature swings will happen quickly when the sun passes the horizon. Near the oceans, it may take a few Earth-days for the temperature to swing completely. There are some side effects to this all, too. Near the oceans, where the air is humid, at night we can expect it to snow fairly predictably as the moisture in the air condenses out and freezes. When day comes, it will melt similarly predictably. The massive temperature differential will also mean that there will be very strong winds on the planet almost constantly, and they'll always be warmer than where you are. This is by no means a full answer, and having very slow days like this is going to have a huge impact on everything about your planet. Think about how these dramatic temperature swings might influence native life on your world (extreme Earth environments might give inspiration), how they'd affect human colonies, etc. There's a lot of interesting potential to be mined here. ]
[Question] [ Is there a plausible reason that the world might not be able to get any sort of metal from Earth, short of what we already have? I was thinking it could begin in our sort of "modern" day and age, but could happen over a relatively long span of years. I'm mostly looking for something scientific, but other possibilities could be considered. [Answer] ## Bioengineered bacteria or nanobots. A hardy metal eating bacteria, most likely different strains for different metals, could significantly damage our stockpiles and in-use metals. Similarly nanobots using metal to create grey goo would destroy available metals. Both would also possibly destroy the mining equipment used to collect raw metals, further reducing our ability to replace lost metals. [Answer] We can run out of ore. It did happen once already; up until the early 20th century iron was produced from high quality ore with about 70% iron content but due to depletion and increased demand, iron is now produced from ores with 25% iron content. If the world goes through another Industrial Revolution and demand increases significantly, it's plausible that we'll run out of ore (or at least cheap readily available ore). At that point most of the steel would be used up in mega structures (spaceships, skyscrapers or whatever) and a shortage would occur. I don't think it's possible to go completely without any metal - Earth has significant deposits of iron and you can always recycle, but if metals are prohibitively expensive, industry might switch to using other materials such as plastics and carbon fiber. [Answer] In a word, no. If we run short of any metal it becomes worth-while to mine less concentrated ores. Too many people rush in, under-supply turns to over-supply, the price crashes, and 3/4 of the new mines go bust. Rinse and repeat, probably since mining first started. I used to think that the non-metal that we are in greatest danger of running out of, is oil. It's a special case because it's a liquid, and there are rare geological pockets in which it is concentrated and tap-able. We've found and tapped almost all of the big ones. Sooner or later, the Saudis will run out of oil. But I was wrong. We've recently found how to extract dilute oil from large abouts of rock (Fracking). Extracting dilute metals fron large amounts of rock is what we've been doing to obtain metals for at least the last century, if not forever. FOr any metal, there are plenty of ore-bodies not yet exploited because the price has never been high enough for long enough. As for energy: if we burn all the oil and coal we know of, we are doomed. But we've solved that problem also, and solar PV cells are not very gradually replacing fossil fuels. Methinks by 2100, fossil fuel burning will have ceased, and global warming will be left as a big but ultimately manageable problem. Oh - and there is one other non-metal for which no alternative exists. It's (fresh) water. If you live more than 200 miles from an ocean and if your water is being produced by tapping an aquifer deep below your feet, beware. We can use solar PV electricity to make fresh water from sea water, but making it and transporting it in sufficient quantities to maintain arable farming in a remote desert seems implausible. Hence, there will be a water-driven global food crisis to come. [Answer] There's one, and really only one reason we would run short of any metal that was otherwise economically important and that would be that our net energy budget couldn't support the processing of that metal. The world consumes a certain amount of energy every day, of what isn't wasted one way or another a chunk goes to primary (extraction) industries like mining and forestry and farming, a chunk is involved with secondary (processing) industries that make goods from raw primary materials, and a chunk goes to tertiary (service) industries that provide less concrete things to people. If the population and energy availability every got screwed so that almost all the available energy needed to go into just feeding people then metal extraction becomes a secondary concern and the more energy intensive processes will have to go. ]
[Question] [ Envision: Civilian and Military vehicles where rubber wheels are not used in the far future. All vehicles are tracked instead, tank tread style. In order to achieve greater speeds, said vehicles use electromagnets to hover above metallic surfaces, roadways, inside star ships, stations and what have you. They can also be reversed to attach to surfaces and, where applicable, traverse walls and ceilings. This mode is basically a high speed cruise mode and not for other uses. All roadways on planets are in lower areas to minimize the damage caused by a vehicle moving in a such a manner to go flying. Roads are cut into the ground in the countryside, in cities they would follow the same idea with bridges for pedestrians to walk over them. Effectively there are "floatways" for high speed transit, while side roads require standard tank tread movement. However, I would like to keep the electromagnets contained to the vehicle and not have external requirements aside from a metallic surface. Let us assume: * Keeping the vehicle stable is not a concern * Production cost is not an issue * Power supply is adequate for the task * These vehicles are not trying to achieve more than a foot above the metallic surface beneath them * The magnet polarity can be fine tuned and/or adjusted with ease My questions involve the following: * Can the treads themselves be energized to produce the effect, or should the emitter be somewhere else? * How would the vehicle move while levitating? Could the treads be used as a pulling effect on the vehicle. While pushing the vehicle up, the treads rotate pulling the vehicle in whatever direction, effectively still using the treads as the source of mobility? If not, what methods would work that involved electromagnets? Edit: I've been looking around and wanted to share some ideas This design shows a standard tracked approach > > These magnets react with the 'track' to provide a closed loop Mag-Lev > system. The tracks on the Mag-Lev system are very thick and robust, > with each link fashion like a tooth with a deep root, and counts as > full armour plate! Trying to shoot off the tracks on a Mag-Lev is > virtually pointless, as even if the links break the track will not > come off as each link is treated as an individual unit > > > This one theorizes a solid "track" instead > > There are already maglev trains out there that operate on a pre-set > path (tracks, of course), so the key would be to make this design > mobile... thinking about it, you could "bend" a track into a circle so > you're perpetually moving down the track like a train, except the > track is moving around the wheel axis, if that makes sense at all. > > > [Answer] Unfortunately, unless the metallic surfaces on which the vehicle is travelling is also magnetized, magnetizing the vehicle treads will always attract the vehicle to the surface. Magnetizing vehicle tracks has been used before with some success; in the latest season of BattleBots shown on ABC in the U.S., the winner of the tournament, "Bite Force", had a track system with permanent magnets to increase the robot's gripping power on the metal floor of the arena. This allowed the robot, which used a combination of the basic "pushing" and "flipping" strategies, to hold its own in scrums with similar robots, while keeping it nimble enough to get around behind the weapons of the "spinnerbots" it faced, including the runner-up "Tombstone" it faced off with in the finals. Levitation, however, is always going to be tricky, because the forces keeping you in the air have to provide both the repulsion from the ground to overcome gravity, as well as the horizontal and rotational stability to keep the vehicle upright (usually necessary to maintain the repulsion force) and maintain control over your position and direction of movement. Magnets require a very fine balance, especially because of their dipole nature; like charges repel, opposite charges attract, and all magnets have both, so all it takes it rotating a little too far in any axis and the attractive force on the opposite side of the magnet (which is of equal strength to the repelling force on the side facing the ground) becomes irresistible, and then your vehicle is upside-down and crushing itself flat against the ground. There's all sorts of "Applied Phlebotinum" you could use to have a vehicle attract or repel itself from any surface; I'd recommand a hand-wave over trying to use magnets, as most people's intuitive understanding of how magnets work from playing around with them in grade school will create dissonance. [Answer] You're pretty close to Maglev Trains with this one, so I would research SCMaglev (the Japanese high speed train) and Electrodynamic Suspension (EDS) in general. With EDS you don't actually require magnets in the train - or tracked vehicle in this case - because the train-tracks do all the work. The rails create a magnetic field, which creates eddy currents in the metal train. These eddy currents create magnetic fields in the opposite direction, and thus the track repels the train! By varying the current in the tracks or by providing additional currents in special "side-walls" you can push the train forward. So you don't need electro-magnets in your tracked vehicle: standard issue iron tank treads will work just fine (for terrestrial travel, at least). A couple of issues to consider: Control - A highway system of high-speed-maglev is going to be logistically complex: the rails push/pull the tanks around, so system is going to have to provide orders to various sections of track to energize in very specific time frames and patterns. You're building a train system with many small trains instead of few large ones, and a trains system without train stations for that matter! Low Speed-Ops - the levitation part of EDS only works at higher speeds: otherwise the eddy currents aren't strong enough to lift the train. EDS trains have wheels for low speeds, and then lift off the track as they come up to speed. Wheels are generally more efficient than treads: there is far less internal friction. Getting your tanks moving fast enough to levitate in the first place could be a challenge. Reasoning - No one would give up something a simple and powerful as a rubber wheel for something as complex and inefficient as a tank tread without a good reason. Building and maintaining complex systems is expensive. For tanks, the ability to off-road and withstand small arms fire without a loss of mobility was worth the expense of creating and servicing treads. You will require something equally compelling to justify your mass shift to this model. [Answer] A superconductor will [levitate over a magnet like it was on rails](https://www.youtube.com/watch?v=zPqEEZa2Gis). So you put a magnetic line down your float ways, and when the vehicle is ready it just engages the superconductor and float down the road, maybe propelled by air or jets. Likewise the superconductor can be [turned into a magnet](https://en.wikipedia.org/wiki/Superconducting_magnet) to allow it to stick to surfaces, like a ships hull, or whatever. If you really don't want any magnets in the road, you could sheet them with copper and float your vehicle over it like the [Arx Pax Hendo hoverboard](https://www.youtube.com/watch?v=BuWflDnAO9s). ]
[Question] [ A plutocracy is "a country or society governed by the wealthy", typically represented as a government made up of corporate interests. Simple enough to design and write, right? Nope! Turns out that there's an awful lot of confusing jargon up there in the land of corner offices and mahogany desks. I want to build my plutocracy in a way that doesn't sound hilariously wrong to people with MBAs and JDs, without having to go to business school or pass the bar exam myself. In a society ruled by a corporation-based plutocratic government: 1. What type of corporation would the top-level entity/ies be? Would this be the most common legal structure among Fortune 100 companies (e.g., Inc, LLC, something else), or is there another type of corporation that would be suitable for a plutocratic ruling entity? 2. What is the likeliest leadership/management structure among a group of large companies? For example, if one or more corporations rule society, what would the top-level entity (the equivalent of a king or president) be? Would it be one company as a whole, the president/CEO of that company, etc? What would its immediate sub-entities be (the "vice president" or "cabinet" role, i.e., secondary in-charge and advisor roles)? In a governing structure made up of corporations, would it be logical to have any other sub-entities that participate in the government (a "Congress" or "Senate"?), and/or any check-and-balance entities (such as the Executive, Legislative, and Judicial branches of the US government)? 3. How would the top-level corporate entity (the "president") enforce social order? --- Note: I'm not looking for full legal definitions - this is the For Dummies version. All I, as a creator of a plutocratic government, really care about is things like "is an Inc or an LLC or a Holdings more appropriate as the top-level government entity?" and "if you're the president of Plutocratic Government, Inc, what, exactly, is your position and how many minions do you get?". [Answer] 1. "Inc." makes more sense than "LLC". An LLC is an intermediate state between a sole proprietorship/partnership and a corporation. Plutocrats wouldn't be intermediate. They'd be full on corporations. In the US, this would be called "Inc.". In other countries they would likely have different names. I might call these members of the Corporate Senate. Continuum called this the Corporate Congress. Another possibility would be the United Corporations or UC (a play on the United Nations/UN). 2. I don't think that they'd make corporations into cabinet officials. It would probably work more like a Parliament or the US Senate. Each Plutocratic corporation would send a representative to the "Corporate Senate" and they'd share votes somehow. Since some will be more equal than others, you may want to consider the UN model. In the UN there is a General Assembly where each country is represented. Then there is the Security Council where a sample of members are represented. Then there is permanent Security Council which has Russia, the United Kingdom, France, China, and the United States with veto power. The UN model makes sense here because it already has to handle the problems of differing influence of its members. 3. Entities are likely to want to do their own enforcement. This will cause problems and they will increasingly delegate to the central organization. Or they collapse because they refuse to delegate. Both have historical support. Anyway, at founding, they are likely to want to be as separate as possible. Over time power is likely to centralize. The corporate Senate would be the legislative branch and would likely be lead by a Chairman (or Chairwoman). Perhaps the judicial branch would be the extra-equal members of the Corporate Senate. That might be the mechanism by which they exercise their veto power--by having representatives on the top court. I would expect the executive to look similar to what most countries have now but with some different terms. For example, the cabinet secretaries or ministers might be called Vice-Presidents instead (more in line with corporate structure). The Treasury Secretary might be called the CFO and the Director of Management and the Budget might be called the COO. CEO is just another name for the President. Since the President is selected by the Corporate Senate, it's unnecessary to define an automatic successor. They'd just appoint a new one (we don't do that because it requires holding a new year-long election; they'd just have a regular vote). The constitution would be called the bylaws. [Answer] There’s a very influential work of science fiction, Looking Backward by Edward Bellamy, in which the United States is run by a “trust” (a kind of holding company that had huge influence at the time, but is now illegal) and every citizen is a shareholder in that trust. Plutocracy has a lot in common with aristocracy, in that the real power consists of ownership of property, the entire country is owned by one person or a handful of them, and the important rules are not the formal laws but the agreements between these property-holders. If the corporations that run the country are non-profits, this has a lot of similarity to syndicalism, a system where people are represented through the union they belong to. In terms of the real world, people used to call Scoop Jackson, “The senator from Boeing.” You seem to be talking about a system where that’s either literally true, or at least rich people hold all the power within the system and effectively cannot be checked by a popular vote. It would be very possible to keep most of the institutions intact; corporations are generally headed by a President and run by a Chief Executive (officer), who might be the same person. A Board of Governors is a reasonable structure to work federalism into the system. There might be Trustees or shareholders as well; for instance, Social Security and Medicare taxes might be replaced by forced investments that vest in a retirement pension, and other taxes might purchase voting shares, with some categories of person, such as legal immigrants, receiving non-voting shares instead. That makes more explicit the premise that taxes are the price of citizenship and that government invests its revenues for the future. An important fact to keep in mind is that, for this kind of setup to actually work, people need to see what’s in it for them. Otherwise, it’s just a kleptocracy run by billionaires out to enrich themselves, and I’m sure you can think of examples of those. [Answer] There is a difference between an open, unapologetic plutocracy and a covert plutocracy. There have been many examples of countries where the rich run the show covertly, while there are few or now overt plutocracies. 1. Regarding your first question, the most likely names will be taken from democratic institutions, i.e. "President", or informal, "[el jefe](https://en.wikipedia.org/wiki/Kleptocracy#Other_terms)", "[boss](https://en.wikipedia.org/wiki/Political_boss)". 2. What is the point of a plutocracy if there are checks and balances, unless they're between individual plutocrat and their clans? So perhaps a pseudo-corporate structure with the CEO controlled by a board and shareholders. The CEO might be a compromise candidate between shareholders or a major shareholder. The largest power bloc would be tempted to rig the checks and balances so that they stay on top. Think of [gerrymandering](https://en.wikipedia.org/wiki/Gerrymandering), except that it covers all sorts of business regulations. 3. Mao once said that [political power grows out of the barrel of a gun](https://en.wikipedia.org/wiki/Political_power_grows_out_of_the_barrel_of_a_gun), so all plutocrats would want a share in the armed forces, or a way to have it neutralized in their power plays. But what happens when the environmental inspectors are controlled by polluting industries? Summarized, democracy, the rule of law, and a stable business environment go hand in hand. The largest businesses are tempted to undermine it, but ultimately that's against their own self-interest. ]
[Question] [ Assumptions for the story: The rocket pack is not unlike the scenario of the movie when I was little, "[Rocketeer](http://www.imdb.com/title/tt0102803/?ref_=nv_sr_1)," in terms of viability. I have hand-waved it in my story. * The rocket pack should be assumed for this question to be unlimited in fuel and power without subjecting harm to the character. * There is a maximum of 10 minutes of oxygen within the helmet apparatus, and my character can wear anything from slacks to ski gear. Given an unlimited rocket without direct effects from the rocket onto the hero: In my story, I would like the character to achieve (1) very fast travel; and (2) very high travel. For instance, I have a part where the hero rockets to a height of an airplane, but then descends. Also, must travel distances. While the rocket is hand-waved, the limitations to the human body aren't. The hero has access to clothes you'd find in the closet (including ski gear), the 'hand-waved' rocket, and the helmet allows for 10 minutes of oxygen and protection from exhaust of the hand-waved rocket. But not space gear and not protection from effects of speed, height, pressure, or anything else. I can handle the storyline for logistics, politics, psychology, the rocketpack, etc.; this if about survivability. For the story, what are the speed and height constraints that my hero can survive, given that she can wear warm clothing, have oxygen for up to ten minutes and needs to fly around a lot. She will have to go far and high. Wardrobe is considered modern day, household items, upper-income western lifestyle. The hero has a credit card and knows how to use it, but is no Elon Musk. The only sci-fi is the safe, hand-waved rocket-pack and helmet with oxygen. [Answer] Aerodynamic drag, temperature and breathable air are the primary limiting factors. Even with a handwaved rocket pack, the rocketeer has significant challenges at high altitudes and high speeds. High speed-high altitude flight for an unprotected human is going to be uncomfortable at the least and deadly at the worst. Air Ten minutes isn't that long of a flight time. If you try to compensate for this by going faster, the strain (as a result of drag) on the rocketeer increases with the square of velocity. Temperatures It's really really cold at high altitudes. WW2 bomber crews flying between 20,000 and 27,000 feet regularly encountered temperatures of -30 to -50 F. As you can see from the below table, flesh freezes very quickly in cold temperatures without a breeze. Since the rocketeer wants to fly both very high and very fast, any exposed flesh is going to fresh instantly. [![NOAA Windchill Table](https://i.stack.imgur.com/Hp7it.gif)](https://i.stack.imgur.com/Hp7it.gif) (Note that windchill is a measure of how fast your exposed flesh would freeze at that temperature, not the temperature your flesh would actually reach.) Wrapping the rocketeer up in "windproof" fabrics such as Gore-Tex won't work either because such fabrics are only windproof to a certain windspeed. If the rocketeer is going hundreds of miles per hour, those fabrics won't work. A full body leather windsuit might work though great care must be taken to avoid exposing any flesh to the windstream. Even with a perfect windsuit, the rocketeer must still insulate themselves against the -30 to -50 F temperatures. Extremities such as toes and fingers are especially difficult to insulate. Rocketeer Fatigue Holding one's shoulders square to a 400 mph wind is going to be very tiring, very quickly. There's at least two knock-on effects of this kind of strain. Oxygen use goes up because muscles increase oxygen use when under heavy load thus reducing oxygen stores down from their 10 minute estimate. Second, the higher the rocketeer goes, the more their metabolism will have to kick in keep itself warm. Given this the physical labors of flying, it's unlikely that the rocketeer will be fresh and spry when he lands. Realistic Flight Conditions Have a look at ultralight aircraft. They have relatively low service ceilings and their unprotected cockpits preclude speeds above 100mph. [Answer] At 6000 meters she would begin to need oxygen and at 8000 human life becomes unsustainable, The speed is a bit more solid and will be the focus of my answer. humans can survive up to 9 G's for a few seconds. Astronauts go through 3 G's during take off, but most of us can live going through 4-5 G's. 6 G's or higher for any long amount of time will kill a human. Sorry for the briefness ]
[Question] [ What would be the effect of large magnetic celestial bodies orbiting each other? Could a star have enough metallic content to become magnetic? What would the effect be on magnetic planets in orbit around it? If that's not possible, how about if a magnetic planet had a magentic moon? If your answer is that the magnetic pull wouldn't be powerful enough to do anything, take the example of two [magnetars](http://en.wikipedia.org/wiki/Magnetar#Anti-glitch_issue) in a really tight orbit. Assuming the result might have something to do with electricity, what effect would this have on the habitability any planets/moons involved? Could it be harnessed somehow? [Answer] Stars already have a very strong magnetic field, metal content won't help on that front as they are made up from plasma rather than solid matter anyway. The average strength of the magnetic field of the sun is around twice that of earth, however at certain points it can be as much as 8000 times as strong and it actually extends out as far as Pluto! Source: <http://www.windows2universe.org/sun/sun_magnetic_field.html> For the magnetic field between the planets, you can expect it to stabilize so that the two are attracting each other, in other words the magnetic north of one planet will be near the magnetic south of the other. They will then act as an attractive force and effectively make gravity stronger between the two worlds, this means they will orbit faster and closer together than gravity alone would allow. The magnetic and rotational north poles may not be at the same location, but it is likely that they would be in this case as that is the only way that the forces would all balance out smoothly. In other words both worlds would rotate around the same central axis, the magnetic and rotational poles would be aligned and the magnetic north and south poles would also be facing in the same direction. The worlds would be orbiting each other faster than normally expected due to gravity alone. [Answer] Interesting models have been made of [T Tauri stars](http://en.wikipedia.org/wiki/T_Tauri_star), pre-main sequence stars that can have strong magnetic fields (though clearly not as strong as those of magnetars). Data is given in [Johns-Krull (2007)](http://iopscience.iop.org/0004-637X/664/2/975/pdf/0004-637X_664_2_975.pdf). The effects of this magnetic field on interactions between the star and its surrounding disk were modeled in (among others) [Kuker et al. (2003)](http://iopscience.iop.org/0004-637X/589/1/397/pdf/56674.web.pdf). Angular momentum is transferred between the star and the disk. The torque generated by the magnetic field on the star is $$T=2\pi r^2 \int\_0^\pi (\mathbf{t\cdot r})\sin \theta d\theta $$ where $\mathbf{t}$ is $$\mathbf{t}=\frac{r\sin\theta B\_{\phi}}{4\pi}\mathbf{B}$$ and $\mathbf{\cdot}$ denotes the dot product (vectors are represented in $\mathbf{bold}$ type). The authors primarily use spherical coordinates. In this model, angular momentum is transferred from the star to the disk. However, in a situation with one or more orbiting bodies, there remains the possibility that some angular momentum could be transferred to one or more of the bodies, thereby changing its orbit. ]
[Question] [ The question is about what changes would have to be made to an Earth-like planet, in order to increase the density of air and hence make lifting gases more effective. If that is scientifically possible at all, that is. Examples of lifting gases with capacity at Earth-sea-level: * Helium with a lifting capacity of approx. 1.1145kg per m3 * Hydrogen with a lifting capacity of approx. 1.203kg per m3 Addendum: Earth-like means that extreme changes in climate and/or composition of the planet are out of scope, as they would presumably make it impossible for most of our Earth flora and fauna to exist. Rather I am looking for changes that go in symbiosis with our own eco system (e.g. the fact that air on Earth-sea-level is more dense than in the Earth-Himalayas) [Answer] The obvious approach is to replace nitrogen with a denser, inert gas. Since nitrogen is the only inert non-noble elemental gas, the noble gases seem the obvious choice. There are, however, a few difficulties. The densities at STP for the various gasses are as follows: Nitrogen 1.25 kg/m^3 Helium .178 Neon .90 Argon 1.78 Krypton 3.73 Xenon 5.89 Radon 9.96 Helium and neon are both lighter than nitrogen, so they won't do any good. Radon has a half-life of about 180 days, so we can forget that. That leaves argon, krypton, and xenon. It may come as a surprise, but xenon makes an excellent general anesthetic, so let's not adopt an atmosphere which renders us unconscious. Argon and krypton are both useful contenders, as long as you keep in mind that both act as anesthetics at high pressure, about 5 atmospheres for krypton and 10-15 atmospheres for argon. Iserni has brought up the problem of spontaneous stratification, and in principle this is true. However, weather (wind) provides a powerful mixing mechanism. Whether this would be adequate is beyond my powers of analysis. [Answer] Density = Mass / Volumn. To get higher density you either need to increase the mass or decrease the volume. Decreasing Volume You could increase the pull of gravity comparative to the earths. This should decrease how far above the surface the atmosphere reaches. Artificially restrict the atmosphere. Energy shield or some other barrier. Increasing Mass Inject more gasses into the atmosphere. Higher temperature planets would have less surface water and more water vapor and gas. More volcanic planets would have greater release of gases from the planets core. Less life? Plants and animals recycle different gases from the atmosphere and then lock them first in their bodies and then into the earth. Fewer living organisms means less gas in the atmosphere. Note There are just the basic principles. I did not do the math on any of this. I do not know how much any of these factors need to change in order to make a perceptible difference on lifting gases. [Answer] Not easily. Density is the ratio of air mass to volume, and volume is inversely proportional to pressure. If you increased the pressure, that would have side effects on living organisms; modifying the temperature would have similarly undesirable effects in a very short time. Supposing the gravity gradient was reasonably flat, changes in gravity would affect density, but they'd also affect whatever needed to be buoyed so as to neutralize any benefit. One way to go might be to introduce some kind of unobtainium gas, with the following properties: * not reactive, or very little (except maybe in circumstances which could add to the story? - a little like the miglign lifting gas of The Wooden Spaceships by Bob Shaw, even if that's set in a different Universe with different physical laws). * very dense * transparent to visible wavelengths What would this entail? You would get more buoyancy, at the expense of lowered partial pressure of oxygen, so the air would be less breathable. You'd need to proportionately increase the oxygen content of the air. The gas, being dense and hence quite heavy, would tend to pool in lowlands, so that digging e.g. a well would become very difficult unless ventilation was provided; any hole in the ground would become a death trap in still air. Even with reasonable recirculation, the gas distribution would not be linear; you would get a sort of layer - say two hundred meters thick? - of "heavy air" where you get high buoyancy, then the air would revert quickly to normal; the airships would "float" on an ocean of heavy air, much as seaships float on an ocean of water. You'd get interesting optic effects too, if the gas' refraction index was sufficiently different from that of normal air. In the right circumstances, you could "see" over a hill by looking at the "sky" immediately above it. With time - a very long time - you'd also get [parapatric speciation](https://en.wikipedia.org/wiki/Parapatric_speciation), and have heavy-air creatures better adapted to life in the lowlands, and light-air creatures adapted to live on the hills. Speciation would be slow to come by since the differences between the two habitats would be small. There would also be other effects due to e.g. changed convection parameters - depending on the gaseous unobtainium thermal dilation and capacity, it could be too easy, or very difficult, to get good airflow out of a chimney in the lowlands. There might also be some other effect I have overlooked and which could nonetheless make this whole exercise pointless, because it would interfere with life or civilization in some way. ]
[Question] [ I'm working on a graphic novel that deals with this particular topic but I'm unsure if something like this can happen. Some Nebulae have a luminosity 1000s of times brighter than our sun while dark nebulae are very dense and completely hide or distort the light from nearby stars....in light of this(pun intended) could there be solar systems hiding out near nebulae?documented or undocumented. Any contribution is greatly appreciated! [Answer] There are a number of factors at work here that make things more or less complicated. The main ones are: 1. Distance to nebula and to Star 2. Density of the nebula 3. The length of time you watch it for 4. Presence of anything else that might interfere with observations. Nebula really aren't very dense or thick, they add up over interstellar distances but any nearby stars are not going to be hidden. The denser the Nebula the more effectively it will hide the stars. If you watch over a long enough period of time you will see the effect of the star in perturbations of the orbit of bodies that you can see, or of the nebula itself. This is how a lot of things are detected at the moment, even if we can't see them directly we can see the effect their gravity has on things we can watch. A nearby bright star in between or close to the one you are trying to view will completely hide it. Combine these factors and stars can be as easy or as hard to find as you need them to be, although in the long run they will always be detectable through the effect of their gravity if nothing else. [Answer] Yes, a nebula can absolutely block our view! Take a look at this famous closeup of the Eagle Nebula: ![enter image description here](https://i.stack.imgur.com/B0IbV.jpg) The rightmost pillar appears black, because it's not hot enough to emit light, but is dense enough to absorb pretty much all of the light coming from behind it. This picture of the same region in the infrared spectrum might make things a little clearer: ![enter image description here](https://i.stack.imgur.com/mjkoh.jpg) (Note that this one is zoomed out a little and rotated about 45 degrees compared to the previous one.) We can see that the rightmost pillar is still jet-black compared to the rest of the nebula. Everywhere else in the image is dense with stars, but here the nebula blocks our vision. Note that the tip of the leftmost pillar is also dense enough to block our vision through it, but the gas it consists of is warm enough to emit light. The gas is heated by the light from stars inside or near the nebula. [Answer] Since nebula are clouds of dust and gas that scatter light, most of the sorts of signals which would indicate a star or solar system to astronomers on Earth would be blocked. Only very powerful sources would be able to "punch through" the intervening clouds of dust and gas (much like you might see a street light though a foggy or misty street), but even then the signal would be blurred, attenuated or otherwise distorted. So there could be any number of things hiding in a nebula! Astronomers would be able to infer if there were stars concealed within, as blurry patches of infrared radiation, but very little beyond that with current technology. [Answer] The upcoming James Webb Space Telescope will see in infrared light and be beyond the Earth's atmosphere and warmth. It will be able to see through dust that currently blocks our view. That might be a plot point when the system is discovered, as astronomers rush to see what is now revealed. You might also look up articles on JWST to see details about what is currently blocking existing telescopes. ]
[Question] [ Background A small group of professional New York city planners leave work one day, ca. 2015, and decide to visit a different bar than usual for happy hour. The bar, which looks like something out of the wild west, is mostly empty. The bartender, a [Michael Cain-esque figure](http://images2.fanpop.com/images/photos/6400000/Mr-Destiny-Screencap-michael-caine-6402878-550-320.jpg), listens intently to of all their stories while polishing some tumblers. Instead of giving them each another brewsky, he smiles and offers to mix them a special drink of his own creation. Skeptically, they each take a shot of the milky drink, pay their tabs, thank the bartender, and step outside into mid-17th century [New Amsterdam](http://en.wikipedia.org/wiki/New_Amsterdam). Question Okay, the details of time travel aside, how could a group of modern city planners, knowing everything they know about how it will look and grow, affect the development of a large city (such as New York) if they were to go back in time to the early days of that city? If they could plan back then, with everything they know, how would such a city then look today? Assumptions * Let's say there are 3 city planners that went back. They each have a considerable amount of practical and historical knowledge of the several boroughs of New York. * As far as they're concerned, the time travel is one-way. There's no going back ([forward?](http://tvtropes.org/pmwiki/pmwiki.php/Main/TimeTravelTenseTrouble)) * No one in New Amsterdam is suspicious of these newcomers, with their hip music and complicated shoes. In fact, in a matter of weeks, they are accepted as up-standing citizens and are admitted into the city's councils. * They tell no one they are from the future, except their eventual spouses and children, who absolutely believe them; and this to keep the tradition going of shaping the future of their city to a more ideal state. EDIT: * Let's put aside any hard-science related to the time travel aspect of this question, and ignore any [temporal paradox](http://en.wikipedia.org/wiki/Temporal_paradox) that may occur. Even if the city planners accidentally kill their 8th generation grandparents or something, they won't be wiped out. Also, their going back in time and changing things won't be the cause of - or prevent them from - going back in time and changing things. [Answer] The first issue is that New Amsterdam will be very different geographically from modern day NYC. Modern New York is partially the result of centuries of landfilling and other engineering, many of the districts of NYC would be marshland or otherwise wild or woodlands in the 1600's. As well, the primary interests of the people of New Amsterdam were trade (particularly beaver pelts) and protection from both the natives and rival European powers. Your city planners had better have a good understanding of fortifications that could protect the city from sea born attack by cannon armed sailing ships, and the ability to repel attacks from landward by either irregular troops or "regulars" equipped with the latest siege technology from Europe. On a more practical matter, focusing on public health issues like water and waste disposal would be high payoff projects for our intrepid city planers, followed by making the market and the dockyards as functional as possible. The city fathers of New Amsterdam will be most interested in gaining any sort of commercial advantage over the English, French, Spanish and any other potential rivals (this was close to the time Sweden emerged for a short time as a great power, and Peter the Great will be born in a few decades, so the Dutch have lots of competition to worry about). So the city planners will have to focus on the needs and issues of their "current" clients in the 1600's, and not worry too much about how the putative subway system or Hudson River Parkway "should" be laid out in the 20th century. They could have a little bit of fun, however. The current grid layout of Manhattan's streets aligns with the sun on May 28 and July 12 ("Manhattanhenge"). With some careful commissions to build larger public structures and encouraging other new buildings to be aligned in a grid around the public buildings they could align the grid so "Manhattanhenge" really does occur during the equinoxes... [Answer] A city planner is typically an architect. As such, i assume they would mostly address the problems at hand, like sewage systems and fire protection, and improve matters with their knowledge in may small ways. Even more so if they have no reason to assume that anything very long term would affect them or their offspring of the next two generations. There is hardly any sensible reason for trying to set the path for anything that will only take effect a quarter of a millenium away since they know that the average life span of a normal (non-government and such) building is shorter than that. Plus, persuading people into drastic changes might prove extremely difficult, because the city already developed in a way that at least mostly made a lot of sense for the needs of the time. ]
[Question] [ A sizeable human population was separated from the rest of the Earth people for a long time, long enough for [allopatric speciation](http://en.wikipedia.org/wiki/Allopatric_speciation) to happen. They are no longer Homo sapiens and now have ZERO reproductive compatibility with the ordinary Earth human. At the separation time, this "away team" had access to all the knowledge and technology XXI century humanity have. Environment and population size was not an issue to their survival. It is still undecided if this "other humanity" was separated in another dimension, planet or by another means, but there were absolutely no transmission of genetic material between Earth and the away team from the time of separation to the moment of this "first contact" in our story. How long should these two human populations be separated for this speciation to happen? [Answer] From [this slide](https://www.uic.edu/classes/bios/bios101/Speciation2/sld030.htm) from a presentation about allopatric speciation, scientists performed a study involving 40 pairs of allopatric fishes and estimated it would take somewhere between 0.8 and 2.4 million years. Note that this is a very limited study and may not apply to Homo sapien. However, I would imagine humans surviving in an optimal or near-optimal environment, on both sides of the divide, to diverge slowly. If the environments differ greatly, speciation will likely occur faster. Half a million years seems like a good starting point. [Answer] Well the Aborigines of Australia were separated from the rest by about 75,000 years with no issues what so ever. So there are two things that can affect the time it takes to make major changes in the genome. The first is extremely different environment that needs to be adapted to. The other would be gene manipulation. We are currently closing in on manipulating our genes to help us along. Chances are to really speed up the separation would require playing with the genes to push us in different directions. Using Frostfyre's numbers of 1-2 million years for normal I would guess with direct manipulation you are still talking 100,000-250,000 years. since we are talking about each whole species being unable to interbreed. [Answer] Considering the timelines of the other answers, I might suggest that maybe one group of humans took the robot approach and uploaded their consciousnesses into metal bodies. That would certainly make interbreeding difficult, and on a much shorter timescale. Since you're looking at hundreds of thousands of years for the organic approach, and we're starting out with modern tech, I'd honestly think this technology would be invented by both sides long before important genetic differences developed, though ethical concerns may have stopped one side from making such a big evolutionary leap. ]
[Question] [ The Settings: In a collaborative project with my friend, we develops mix of science fiction and fantasy setting together. We develops a world on which the whole planet was one sentient being. Mainly the planet itself is intelligent, harnessing energy from radiaton decays on its core. It later realizes that life emerged on its surface, and altering its atmosphere and geological condition to evolve life in the way it could utilize the life as additional computing power and awareness. In that world, life on the surface develops swarm intelligence, as the whole plants and animals interact in the way that each individuals unaware of higher intelligence they were a part of (sort like an ant wouldn't aware of the whole colony's intelligent behaviour). Here is the problem, as I practically doing all in science part of the world, while my friend doing all of them in magical part. We went to some disagreement, and as he's the one that proposes this joint work, I tried to respect his desire. At first we worked on system that allows the planetary intelligence to 'grant' a sufficiently intelligent species to control some aspect of the world (like, creating winds, cast lightning, etc, in a similar manner that's covered on [this question](https://worldbuilding.stackexchange.com/questions/10669/how-would-an-intelligent-forest-control-and-direct-its-animal-minions). Basically I put some rational explanation over his magical view). Well, that's all acceptable. But one day, he makes his "avatar" (well, his character in the story) bend space-time using privileges the planet granted on his character. And I have to find workaround, a solution to make it possible (duh) The Question: Is it possible for planetary intelligence to bend space-time? I mean, by developing some sort of warp organs or whatever. Is it possible? How would the planet evolve that kind of organ if possible? What would be evolutionary advantage (for the planetary intelligence) of having such space-time bending ability? [Answer] As we currently understand it, the "bending of space time" is directly related to mass (and, in Newtonian mechanics, was known as Gravity \). So, the only possibility of voluntarily "bending space-time" would be creating massive (in other words, super dense) chunks of matter. However, as user6760 pointed out, it has some hard limits (getting to matter so dense that it becomes a black-hole) and other "softer" limits (that kind of density is obtained with the gravitatory attraction of big stars, so it is hard to imagine a being capable of a similar force). That said, my advice would be not to overthink the "science" part. You are not submitting a paper to an academic journal, you are writting an story for fun. So, you are setting an artifical environment for the actual story to happen (v.g., a planet where, every hour, you see a "flash" of the situation in the next ten minutes, or whatever you like). You can: Explain it with "future science" ("as explained by SJuan76 in 2094 in his Nobel winning theory") or "obscure science" ("as Einstein had predicted in a sheldom mentioned article..."). * Just state that it is not known how it works, and the best minds are studying the phenomena. * Just don't mention the cause. What it is more important to the world is for the effects to be coherent. If in your world, every Sunday it rains cows from the sky, make it so and explain how people are dealing with that. And, if the heroes are in a complicated situtation, do not make the main character explain that by doing X or Y, it will not rain cows but pigs (which, for a happy coincidence, is precisely what the party needs at that same instance). \) Of course, Newtonian gravity did not explain bending of the light, which is why "space time bending" is more precise. [Answer] As the accepted answer by `SJuan76` and comments state > > As we currently understand it, the "bending of space time" is directly > related to mass (and, in Newtonian mechanics, was known as Gravity > > > Whilst this is true, it is not quite* true. As everyone has seen a million times. Mass is related to energy by `E = mc^2` and so a large enough energy at a single point could "bend"\* space. Ways to achieve this amount of energy are numerable and hypothetical. As an exmaple; zero-point energy. Absolute zero at -273.15c is the lowest internal energy an atom can have. So theoretically if you are at room temperature of 25c, then there is almost 300c of potential energy around you at any time (celcius is not an actual direct measurement of energy). Also, I see that you and others are throwing around the term `space-time`, but perhaps you want to stay clear of it in your story as it isn't a real thing per se. It is a concept to unite the 3 dimensions of space and time, just to solve a few (important) equations. - And if Albert Einstein doesn't exist in this imaginary world, then neither would the concept of space-time. Bending space is enough to describe the process. \*Only bent from our perspective of it. ]
[Question] [ I was reading [this question](https://worldbuilding.stackexchange.com/questions/372/how-can-magic-and-the-economy-reliably-stand-together) and some of the answers got me thinking. If we have a magic-based society, where for all intents and purposes every being can use magic, and the magic a being can use is limited by a combination of factors that boils down to 'total amount of magic needed' and/or 'effort required to make the magic happen'. I'm not entirely sure if those two aren't the same thing for the purposes of this question, though. Anyways, your average wizard would be able to use their day's limit of magic for create/imbue magical tokens, and we'll say everyone has agreed 10 tokens/day is a good balance between portability and amount of effort. These tokens could be used as magical batteries or as currency. I figure that if a person was hired for 10 tokens/day, they would be expected to put forth the same amount of effort, magical or otherwise, that it took that standard wizard to create the 10 tokens. Is this a feasible method of payment? In addition, say we have two wizards, A and B. Wizard A is young and can only create 9 tokens/day. Wizard B is older and stronger and can create 11 tokens/day (we'll say he trained his mind in order to reduce the effort it took him to use magic). Wizard A is not likely to be employed by a 10 token job unless they can combine both physical and magical effort to meet that 10 token limit. Wizard B can easily complete the 10 token job, albeit with only a small magical supply left over. Does the fact that physical effort can supplement magical effort invalidate the 10 token/day currency? Would the fact that the currency is based primarily off magical effort mean some beings could just sit at home, creating 'money', not actually being a part of the social workforce, and is this a bad thing for such an economy? Lastly, since I have such a vague idea of how economy actually works, what flaws might this system have? [Answer] As a general rule, setting a defined value for money tends to struggle later. It usually works better to let the market sort it out. So it wouldn't be ten tokens per day is what everyone agrees per se. As such, I'm unconvinced that ten tokens would count the same for both physical and magical labor. The value of a magical token in physical labor would be based on whether it is easier to do some tasks magically or physically. If all tasks are easier to do magically (i.e. one wizard day is more productive than one physical day), then the currency value would fluctuate until they came into balance. Perhaps one token would equal a day's wages for physical work. Or it might equal a week's wages. It all depends on how common magic is. If you don't allow magical and physical labor to fluctuate against each other, you're likely to have two problems. One, the labor that should be more valuable but isn't will be reluctant to work for others. Why trade for less than your worth? Two, black markets will arise that trade labor at closer to their actual worth. The only way that you can get magical and physical labor into rough equivalence would be for everyone to be wizards. Then each person would be choosing either magical or physical labor. In that setup, magical and physical labor would naturally tend to equivalence as being out of balance would favor one over the other. Short of that, magical labor is almost certainly going to be more valuable. Otherwise, no one would do magic. If the tokens are magical batteries, then there is some loss from having people maintain a supply of tokens rather than just using the magic for whatever. This would be no worse though than the more common system of people digging holes in the ground just to get materials to make money. Yes, it would be better with paper money, but who'd trust that? Eventually they'll make the switch as banking improves, but the magical tokens are no worse than any other commodity money. In fact, they're better than some, as it's much more direct to switch a wizard's magical output from general magic work to currency production than it is to have someone open a new mine. The magical switch will work regardless. Opening a new mine means finding the right place to dig, which is non-trivial. Mining tends to follow boom and bust cycles. Find a new mine. Production is great: boom. An older mine's vein runs out: bust. During booms, people have plenty of money to look for new mines, which multiplies the boom. During busts, they cut back on looking for new mines, which reinforces the bust. It's also worth noting that the money supply would be more stable than with most commodity money. You wouldn't get the same sudden gluts of money as used to occur when new mines were found or gold was stolen from someone else (think of the Spanish with the Aztecs and Incas). Inflation would be more self-regulating. If money drops in value, then wizards would switch to magical work. Or if money increases (deflation), then wizards would switch from other work to producing currency. [Answer] This actually sounds like the cacao bean economies of the Incans. Cacao (growable by farmers, not wizards) was used as currency. You could also use it to brew chocolate, though the beans were so valuable that only the nobles could afford to literally drink their money. [Answer] As an economist, I find your proposal fascinating. Basically you're replacing currency with magical energy as a fiat, somewhat related to how modern fiat currency is calibrated to represent GDP rather than an arbitrarily chosen basket of goods (gold or silver backed). The issue is that it turns every wizard into a money issuer. Since this money is an important consumable, you avoid weirdness with major inflationary pressure. A clever magician who can find a way to use tokens more efficiently (so they need only eight instead of ten, say) would quickly become insanely wealthy. Additionally, there would be the aspect if the token exchange. In the example you offered, there would, essentially, be a waste of ten tokens - no one hiring the young 9 token wizard and the 11 token elder left with one useless token. If you decouple the production of tokens from their distribution you would create a much more efficient system (as well as encourage production among those who might not be able to offer many tokens). Basically, you need a centralized bundling market to give everyone a place to buy and sell tokens in bulk without needing to deal with individuals -the token stock market. You could easily provide such a service at a profit by charging fractional tokens to buyers and sellers in the market as an exchange/facilitation fee. Since no one needs to sell a specific number if tokens, everyone is encouraged to engage in maximum production and would avoid losses due to market inefficiencies. Bottom line: you're taking about a barter economy. That works. Our current monetary system is a fiat of exactly that: what people produce in the economy. Already people are in isolated jobs generating economic wealth, so this would be no different. This would work, and it's fascinating to think about... Thanks for the cool question! ]
[Question] [ Assuming a society in which -- for whatever reason -- there exist multiple sapient/sentient species. They are significantly different enough to completely preclude procreation. Inter-species relations are generally mostly positive. Inter-species romance is quite uncommon, but not unheard of. One expects that sexual and emotional behavioral niches would preclude most people from considering inter-species relationships. Similarly, procreation concerns limit these to people not driven by a desire to birth children. External social opposition could come from either of these fronts, or else something else that is not occurring to me. Is it reasonable to treat inter-species attraction as deviant -- in the social sense? That is, considered a weird but harmless fetish by the permissive frame of mind, and a damaging perversion by the more absolute thought. [Answer] Depends on the cultures involved. It's perfectly reasonable that they might think of it deviancy, but on the other hand, the inability to procreate could make it the standard relationship for people not yet willing to commit to children. There's far too much dependent on the cultures of each species to say much about it. I'm struggling to type this past the baby on my lap, so I'll try and be concise with the next part... Humans still attach tremendous importance to their ability to procreate, even if they don't want to. Insulting someone's virility is a potent offence in pretty much all human cultures, and women who are unable to conceive treat it as a huuuuge issue anywhere you go. An interspecies relationship where neither mate has any possibility of childbirth might be used by those unable to conceive, in much the same way as homosexual and extramarital affairs were often covered (and still, even today) by a "beard". In this way, it could have an accepted, but unspoken use, even amongst those who claim that it is a serious perversion. Edit: There are people who still don't approve of interracial, homosexual, or hell, even open relationships. As a species we're tribal and unreasonable, and we could definitely refuse to accept interspecies relationships. Again, if it's not involving humans, who knows? [Answer] Leaving sex entirely out of it, because that is honestly not even a majority of what makes a relationship work, one other consideration that might give fuel to the intolerant would be the difficulty of cross-cultural relationships. While race has nothing to do with how well a couple gets along, upbringing has a huge role to play, what with fundamentally different views on everything from finances to hygiene to religion to politics. It can put enormous strain on even the most stable and loving couples. A xeno-couple would have to deal with not only different cultures, but completely different mental architectures. Even the concept of love is up for grabs in that situation. Perhaps humans are cold and emotionless compared to the aliens or the aliens express genuine love through mockery and public shaming. The number of couples that could make an honest romance of it, even compared to the number of people willing to try, would be vanishingly small. And that is something that the intolerant would jump all over, "Just look at all those broken homes!" [Answer] It might be not much of a romance - but it would be a strong friendship based on shared experience of overcoming obstacles. Think Space Marines. Different skills/abilities might be advantageous in some situation. If you know that some individual will not betray you and will protect you even in danger to himself, you don't care about species, gender or sexual preferences - and you pay back the same. [Answer] Most likely at first it would be heavily taboo and then it could go one of two ways which would depend on the history after first contact. Most likely the interspecies romance would be either A) illegal and then slowly gain lenience (Please look up any romance story with a monster as one of the romancers or even just Twilight if you're lazy.) before becoming like gay marriage. Becoming more and more expected but will never be the norm. There would of course be the difficulties of any vastly different culture that people would use to oppose it and there would be those who would rather then die then go near an alien. But for the most part it would just be unusual and depending on how common interactions are eventually everyone would one day know someone or know of someone who does. For example, Marcus's Aunt had a friend in college who married a Flitter-Fly. Or B) people would be down for first contact like that one vulcan who was immeaditly down for hand shakes. So in my opinion, if the aleins look similiar enough to be attractive, then yes most definitly. And even if they aren't then still yes but it would probably take longer. ]
[Question] [ Let’s consider the typical setting of 20th-century science fiction writers, both Western and Communist. Namely: * Transportation within planets is cheap, quick, and is not significantly restricted; * Transportation between planets (in vicinity of the same star) is ubiquitous and (in civilized systems at peace) relatively safe; * Interstellar travel is possible, although they are expensive or dangerous, usually both to some extent, in any case significantly more difficult than circumstellar travels; * There exist several (possibly many) essentially different civilized races living in different physical conditions. Which political structure can be sufficiently stable in such conditions? Very likely, a typical developed planet or other astronomical object will not have significant pieces belonging to more than one sovereign state (that does not preclude some states to extend authority to several planets), and, in most situations in outer space, a state will maintain its sovereignty over its spaceships. I.e., a situation similar to modern Earth with planets/moons instead of islands (divided planets will become an anomalous condition), and spaceships instead of vessels. On one hand, different planets in a stellar system typically have different physical conditions (most notable, temperature), and we can expect that their populace will differ (remember several civilized races) as well, both biologically and culturally. On another hand, some central authorities will probably exist in circumstellar spaces. But how the two could be related in cases of heterogeneous populace in vicinity of one star? Some possible formations are: 1. A violent agent that is stronger economically or militarily, or enjoys an external (interstellar) support, subjugates its neighbourhood, depriving planets of any external sovereignty, and (in case of a victorious government) possibly annexes and colonizes them outright. 2. Some combination of planetary (domestic) sovereignty and a centralized “interstellar superpower” controlling outer space and space trade, likely by space navy, but restraining from conquest and extortion of developed planets in its space (think various “great unions of planets” in fiction). 3. A confederacy of racially diverse and economically rivalling states seeking primarily to deter wars, to protect their common outer space from piracy and invaders, and to resist a blatant external interference in general (think Iroquois League, with a correction for racial diversity). 4. An advanced interstellar system of relations, based on numerous treaties, maintains a complicated political balance and legal space in a large volume of physical space (along the lines of United Nations and Earth’s superpowers, or other known systems of international relations). 5. A huge democracy effects a (nominally) undivided sovereignty over a large volume of space. 6. An oligarchy of industrial or merchant corporations, with their space fleets, suppresses and subordinates weak territorial- and/or racial-based governments (popular or else). 7. Some novel form of government based on a powerful conscious agent: specially designed governing computer (likely distributed), collective consciousness of individuals, or some mental power we now can’t explicate. Makes the problem of “sovereignty” moot. 8. No stable structure at all: persistent wars, coups, rebellions, alliances and infightings, ever expanding and fragmenting empires and dictatorships. Please, give assessments of my types of formations from different perspectives: humanistic, liberal, Realpolitik, and economical. Which transition scenarios between different formations can be envisaged? Which scenarios of clashes between such formations (both of similar or dissimilar structure) will be plausible? [Answer] I think the scope of your question is too large to be easily answered here except by essay. I recommend breaking it apart for specifics. That being said, your primary concern about the spaceo-political structure that would develop would likely be some combination of what you have listed. Take into account that all worlds/species will likely not be equally technologically advanced. That can have a profound influence on the structure that would arise in each system. Consider Earth, 19th century as an example. Most people were culturally isolated, and as such didn't have any exposure to lots of things we take for granted today. Lack of variety caused a lot of prejudice, misinformation, and unfair stereotypes of other races and cultures. There were adventurers and merchants, certainly, but most people were pretty xenophobic by nature. Goods from around the world provided ample opportunity for trade. Something common in one area would be rare and exotic in another. Think of the introduction of the banana at the 1876 World's Fair, or silk from China. I think commerce would be the driver of contact between worlds. More advanced cultures would certainly take advantage of less advanced cultures, and the desire of one world to assert dominance over another would depend on their prevailing world view. One culture may see themselves as superior, and their religion may demand they colonize and proselytize wherever they can. Another culture may be a kind of insectoid hive mind, and not want to have anything to do with other cultures. Again, commerce will be your driving factor behind the motivations of not just individual worlds, but individuals from each of the worlds. Treaties will be formed to create or secure commercial interests as waging wars across hard-to-travel interstellar boundaries will be too impractical. [Answer] Most important issue is immensity of time. Sufficiently advanced civilization will have no interest to communicate/trade with less advanced. In most cases, it would not even notice, or care, about existence of less developed civilizations. Compare humans and ants - separated by some 200 MY of evolution. When walking, do you care if you step on an ant? Would you change your stride to avoid it? Would you consider sparing anthills when planning highway? Because pace of progress increases, differences might be even more gaping. Earth is 4.5 BY old, universe is 13+ BY old. Differences in level of development would be even bigger that differences of physical conditions. Or even closer: we don't have any good way to communicate with our own monkey ancestors (except limited efforts with really close primates), some 20-30 MY apart. Out of which only last 70 KY humans can be distinguished from animals by external observer. best we can do is train monkeys, using their own skills. Just few centuries ago humans had no problem exterminating other humans (native Americans) because they were considered primitive and competed for resources. Don't be naive. Sharing between significantly unequal partners is completely dependent on the morale and the rules of the more senior partner. ]
[Question] [ Starting conditions: * Climate: It is located in a temperate climate. In this [classification](http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification), most C and D climates are temperate. Mostly: Cfb, Cfc, Dfa, Dfb, Dsa, Dsb, Dwa, Dwb. And also, Csa, and Csb. * Technology level: European middle age (late middle age to be more precise) Result: A big city with several thousand people: 50 000-100 000 + Process: How can I achieve a high population? [Answer] It's hard to know exactly how a medieval city of that population would look. We do know they weren't common. Only a few cities ever came close to that size. But we do know a few factors, and can extrapolate known data to get more information. 1. Space: A city needs to have enough space to support its population. Only so many people can be crammed into a certain space. The higher the population density, generally the faster diseases spread. Calamities, such as fire, are more likely to occur in places with a higher population density. Modern towns in the U.S. with roughly 100,000 people have a population density of about 760 per $km^2$. So for a population of 75,000, you would need about 100 $km^2$. But in reality Medieval towns were generally less dense. If you use a population density half of modern cities, a city that large would require 200 $km^2$ 2. Materials: You need to be able to produce enough food for all those people. According to [this](http://www222.pair.com/sjohn/blueroom/demog.htm) site, one square mile (2.56 $km^2$) can support about 130 people. This means that for one city of about 75,000 people, approximately 3,808,693 $km^2$ of farmland would be needed. This could also be supplemented by the sea, if need be. For this to work, the city needs to be able to import food from many kilometers around. To facilitate this transport of food, several arteries of travel, such as rivers, need to come near or intersect the city. The city would also need to be able to get wood, stone, and other building materials. Wool or cotton would need to be available for clothing. 3. Facilities: Cities have two basic needs as far as facilities go. First, is to get food and materials in, second is to get waste (bodily or otherwise) out. For this the city needs to construct sewages, transport system, and store houses. 4. Trade: Cities need trade to exist. A large city needs to be a center of trade, so people are attracted to it. Such centers of trade are often on rivers or by the ocean. Water provides easy access via ships. Large cities also form near sources of commodities, because they promote trade. 5. Protection: Cities are prime targets for raiding. People group together so they can better protect themselves. That is part of why the serf system existed in medieval Europe. Nobles protected their serfs against other nobles and robbers. ### References <http://www222.pair.com/sjohn/blueroom/demog.htm> ]
[Question] [ Imagine you had a race of "fantasy bird folk": * Humanoid head, torso and limbs down to the ankles/fingertips * wings from the back (implausible for flight, but irrelevant here) * bird-like (raptorial, particularly) feet, including talons * claws akin to raptor talons (proportionately scaled) on otherwise standard fingers (5 per hand, including opposable thumbs). * Slightly small body size (standing 3'6" or so on average) * Carnivorous (with sharp teeth) but able to tolerate small amounts of vegetable matter (kinda like dogs). These claws (on hands and feet) are not retractable. How much would such claws (especially on the hands) affect (inhibit?) tool use and development, if any? My baseline guess is that anything involving textiles or fine manipulation would be more difficult, just as it's hard to do fine work with really long fingernails. I wouldn't guess it would be impossible, just more difficult. While there is magic in the setting, the only magic involved here is in letting them fly despite that being anatomically implausible under normal conditions. Oh, and their initial origin as a species many thousands of years ago. As far as the question is concerned, there is no active magic. [Answer] Our tools are specifically designed for our hands, to take advantage of the hand design (and arm, elbow and shoulder design) of our tree-brachiating ancestors. Avian tools would be designed for their biological design. How they grip them. Possibly to take maximum advantage of their relatively enormous breast muscles. How they use them. Are they going to use a human hammer? No. Their talons are designed to pierce and hold onto prey possibly weighing a significant portion of their own body weight (like our arms and legs). They would likely develop a large grip with holes their talons could fit into, providing an excellent firm grip. As for fine work, they will invent tools to do it with. Have you ever tried to sew without a needle, just using your fingers? It is impossible. We invented needles, rubbing bone fragments on rocks to wear them into shape. We chipped away at very hard rocks to make sharp points, and scraped and drilled a hole in the needle end, large enough to fit a thread through with our fingers, so the needle could poke a very fine hole in a hide, and drag a thread through it. But all of those tools were designed by our monkey brachiating hands. Hopefully, as a writer, you enjoy using your imagination. You need to figure out what avian tools would look like, how birds as intelligent as humans would solve problems requiring hammering, sawing, drilling, and lifting, how to take advantage of levers. Actual tool-making birds use their beaks to hold things, some (like parrots) have great jaw strength and can cut with their beak. Others have sharp pointy beaks, and can peck and poke very finely, their beak-eye coordination is very accurate, they can peck and hit almost invisible tiny grains, like grass seed. I would think they would take advantage of that somehow. I'd say you have some fun imagination work to do. To answer your question: Realistically, raptor-like talons on bird "hands" would be an advantage in tool use; they are strong, not fragile, and could provide excellent grip. Stronger than human thumb. And they have no pain sensors on the surface, like fingernails in that respect. I'd imagine birds would have some tools designed only for talon use, if the tool took some heat in a fire for example, and would be too hot to hold against flesh. ]
[Question] [ I'm trying to figure a threshold of environmental conditions where the Earth hits a point of no return on falling rain. The thought seems preposterous to me, but recently I saw some movie that claimed no rain had fallen in a decade but yet the sky in the background was like a normal day on the prairie. Similarly, the land around was alive and well. I found this implausible, but the more I thought about it the more I realized I have no idea what I'm talking about. I don't know that there isn't some global condition the Earth as we know it could hit where water would evaporate, and form clouds, but never result in rainfall anywhere on the planet (oceans may be excused I suppose if that factors at all). Try as I might, I cannot fathom how such a scenario could work without some kind of radical shift in the global condition itself. But even then, I don't know if it is possible to terminate rain while there are still humans alive to observe it. At some point the planet would go from having the last bits of rain, to having nothing. And I wonder what that threshold would look like. Be it the wild frontiers as depicted in this film, or something closer to Mordor, under hoof and claw so to say. Does anyone out there have the scientific prowess to generally lay out the requirements for a whole planet to form clouds and never have those clouds meet the required conditions to rain? Or is that scenario in itself self-defeating? [Answer] A bit of background: a pet peeve One of my bigger peeves with the environmental activist crowd is that they keep focusing on the planet, [as if we could kill it](https://worldbuilding.stackexchange.com/q/147882/40609). Earth is incredibly resilient and its ability to bring about life equally so. But that doesn't mean humans would survive. And that's my peeve. Climate change is certainly happening. Some of it is natural (even cyclical) and some of it is human-contributed... but in the end, there's no point worrying about any permanent change to the environment if there isn't at least one human left to scream "I told you so!" The goal is to save the humans — Mother Earth has survived much worse than anything humans have thrown at her so far or likely ever will. A Narrow Band of Happiness Why am I telling you about my peeve? Because the environmental window, what I'm calling the "band of happiness," is really quite narrow. Even on our Goldilocks planet, the temperature can't be too hot or too cold, humidity can't be too high or low, the partial pressure of oxygen can't be too high or too low. And rain is very much a part of that narrow band of happiness. If the global average temperature is too hot or too cold... it stops raining. > > It is rare to get rain when the temperature rises above 100°F (38°C), since heat of that intensity is usually accompanied by a high pressure system with sinking air, which discourages clouds and rainfall. ([Source](https://www.wunderground.com/cat6/Hottest-Rain-Record-Rain-falls-119F-Imperial-California)) > > > This is part of what @AlexP in his comment meant by Virga. Virga is rain that never hits the ground because it's too hot and evaporates. But as the environment gets hotter, even virga stops. The planet gets to a point where (simplistically) water cannot condense into droplets. To be fair, if your looking for never one drop of rain on ~~Arrakis~~ Earth, then you can't have clouds. That might be a simplification, but the problem is to have clouds you must have humidity. If you have humidity you have the possibility of rain. In Herbert's Dune series, the planet Arrakis is a desert planet. No rain anywhere on the planet. But even it has polar ice caps and water condenses during the night as temperatures drop. So a discussion of "what's rain?" might be in order. But from the perspective of water falling from the sky, it's really hard to have a thriving ecology without either rain or a lot of ground water (and good ground water tends to lead to... yup! Rain!) But enough of that... > > Yes. It has to be cold for it to snow, if your definition of cold is like that of most folks who live in the mid-latitudes. But the atmosphere must contain moisture to generate snow--and very cold air contains very little moisture. Once the air temperature at ground level drops below about -10 degrees Fahrenheit (-20 degrees Celsius), snowfall becomes unlikely in most places. Therefore, significant snowfall at such very low temperatures is rare. ([Source](https://www.scientificamerican.com/article/what-is-the-meaning-of-th/)) > > > So, on the flip-side of our narrow band of happiness is the reality that snow pretty much stops falling when it gets too cold. (Note the truth that there's always a little bit of snow, just as there's always a little bit of rain. There's too honking much water on Earth to completely stop raining/snowing.) Is it that simple? No. In reality you have temperature, pressure, humidity, wind, altitude, and a whole lot of other variables that affect when precipitation can form. If you're looking for a scientific justification for your condition on Earth, you're kinda in the wrong place. We focus on helping people build imaginary worlds, so the focus is the ability to rationalize the result. When possible, to the greatest degree of known scientific plausibility possible. So, we can rationalize the cessation of rain by shifting the global temperature outside the narrow band of happiness. But... There is one more thing, and this bounces off the peeve I mentioned at the top of the post. Greenhouse gasses. > > Greenhouse gases (GHGs) are a set of gases that accumulate in the lower layer of the atmosphere, the troposphere, and absorb infrared radiation, which contributes to increasing the average temperature of the Earth's surface. ([Source](https://www.sciencedirect.com/topics/engineering/greenhouse-gas)) > > > This is how you could rationalize never one drop of rain upon the Earth... but still have clouds. Greenhouse gasses accumulate in the lower atmosphere, leaving the upper atmosphere (where [clouds can still form](https://en.wikipedia.org/wiki/Cloud)) cooler, which is needed for cloud formation. The hotter temperatures keep the rain from falling as described above. But there is that nasty problem of a happy ecology One of your goals was well expressed as... > > Similarly, the land around was alive and well. > > > Does it matter what you meant by that? The life deep in the Sahara dunes is different from life in the rural areas around Portland, Oregon and different still from life in Antarctica. As you remove rain, the Earth's flora must depend more (much more) on ground water. This means your desert biomes will expand and fill space that once depended nearly exclusively on rainwater. Does that meet your expectations? It's still viable life. But if your goal is to have Earth as it is right now sans rainfall, that's not going to happen. And if that program you watched demonstrated happy flora in a region with no rainfall for a decade, it's getting it from nighttime condensation and groundwater — assuming what you were looking at wasn't the result of irrigation. But, eventually... it'll rain Science today believes that after the Earth formed and began to cool, there eventually came a time when it began to rain. And rain... and rain... perhaps for millions of years. This makes sense. The world was so hot that the water in the atmosphere couldn't condense and fall to the ground. Then a time comes when it does rain and that rain hits the still-too-warm mantle, where it evaporates and cools into rain. Over and over until the mantle is cool enough to permit standing water. Remember, Earth is resilient! Life is resilient! Which means it's going to be whomping difficult to create a permanent solution that keeps rain from falling. Because due to nothing more than the Earth's distance from the sun, the Earth will eventually cool enough (the greenhouse gasses reabsorbed into the ground, the temperature warms or cools to the narrow band of happiness, etc.) to allow rain again. Because that's how the Earth works. Yes, you could move the planet closer to the sun or further away from it (to get it outside the band of happiness). Or you could make the sun hotter or cooler. Both would be permanent changes... but you wouldn't have life on that Earth as you see it today. ]
[Question] [ So laying out a few things here: a planet has an atmosphere about 3.5 times denser than Earth with a marginally cooler average temperature (about 12 Celsius). It has a basic Nitrogen/Oxygen Mix, but with twice as much water vapour (0.5%). Would it cause clouds to rise higher before precipitation occurs or would the higher percentage of water vapour cancel it out? How high could the clouds get? The world has large mountain ranges that cast a lot of rain shadows but I was wondering if the clouds might simply pass over them if they get high enough. [Answer] A denser atmosphere will not by itself force clouds higher. Cloud formation is a function of pressure (equivalent to density for atmospheres of constant composition) and temperature, and partial vapor pressure. Clouds form when air reaches saturation, which occurs as temperature drops in an air mass with constant vapor pressure. So, where clouds form on your world compared to our will depend on how you managed that increase in water vapor percentage in the atmosphere. You can do that either by increasing the total area of exposed surface water on the planet, or raising surface temperatures. In order to double the mean percentage of water vapor in the air at a constant pressure, you would need higher temperatures--maintaining that percentage while increasing the total atmospheric pressure 3.5 times mean you need even higher temperatures. Increased surface temperatures by themselves would have pushed cloud levels higher... but with that increased humidity level, you will see clouds pulled back towards the ground again. ]
[Question] [ Whilst considering the terraforming Mars in my science fiction project, I realised something rather important: Mars has no plate tectonics. That means that, assuming the humans in my project manage to terraform Mars without restarting its rather sluggish geological cycle, the planet is inevitably fated to become uninhabitable again: without plate tectonics, the carbon cycle is incomplete, and co2 will slowly build up in the atmosphere. Eventually, won’t it will become like a miniature Venus?. So, assuming that Mars is given an Earth-like atmosphere, oceans and a magnetic field, (all that jazz), roughly how long before the buildup of co2 causes a runaway greenhouse effect and renders the planet barren again? I’m not looking for a precise date; just knowing the general timescale (thousands, millions, billions of years) will be sufficient. [Answer] This is a [Frame Challenge](https://worldbuilding.meta.stackexchange.com/q/7097/40609) No group of scientists worth their salt would successfully terraform Mars and not have a way to keep it that way. Your question only makes sense if there's a story-related incident — like the equipment breaking down. Consequently, the only practical answer to your question as-written is... * It will last as long as you need it to in your story because Mars was successfully terraformed in the first place without the benefit of plate tectonics. Yeah, yeah... but let's pretend that Clarkean Magical equipment broke down? How long could the planet remain habitable? Even this assertion is worth challenging because you haven't defined what you mean by "terraforming Mars" (which you would need to do in considerable detail). It has a lower gravity and we assume a human-breathable atmosphere, based only on these two variables it's going to have a lower density atmosphere almost no matter what you do,1 which means it will not be a duplicate of Earth. The atmosphere is almost required to be full of greenhouse gasses just to keep the average temperature on Mars equal to the average temperature on Earth. You've obviously imported some water, too. So, the equipment breaks down... how long before... * The atmosphere is too thin to breathe or... * The atmosphere is too cold to "inhabit," or... * The seas sublimate away or... * The natural storms return... Or a thousand other things that will compromise the ability to inhabit the surface without the benefit of greenhouses to grow food, water to drink, and pressurized housing to live in? Too many variables! Which makes this version of the question story-based, too. It will become uninhabitable as quickly as you wish using whatever one or more of those variables to rationalize the decision. Keep in mind, we don't have a referent to justify even an educated guess. Many (if not most) of those variables are interdependent. If someone tried to tell you that it would take X number of weeks, months, or years for the atmosphere to thin out, they'd need to prove it by demonstrating they'd dealt with at least a fair number of the other variables (respiration of vegetation, decay in the oceans, compromise of anaerobic bacteria in the soil...). Yeah, yeah... just give me a number! Fine... one year. What? Terran or Martian? I don't know... [Aaaaaahhhhhhhhh!](https://youtu.be/uio1J2PKzLI) --- 1 M.A.Golding correctly points out that there are smaller bodies in our own solar system with higher density atmospheres. If you continue reading my answer, you'll see me conclude that there are "too many variables." If the one and only variable we consider is gravity and all other variables are equal, then the atmospheric density must be lower. Why is Venus' atmosphere almost 100X more dense? Because it's filled with much heavier elements than Earth's atmosphere is. Too many variables.... Keep reading, it'll make sense. [Answer] Considering the low escape velocity of Mars, the atmosphere would tend to escape into outer space, Thus it would be necessary to built a roof over the entire surface of Mars to keep the air in, with giant airlocks for spaceships. The roof might be supported by giant pillars and beams, or by air pressure. <https://en.wikipedia.org/wiki/Shellworld> I presume that a thinner atmosphere would be placed above the roof, to stop most meteoroids from becoming meteorites and striking the roof. The thin present atmosphere of Mars does burn up most meteoroids far above the surface anyway. With a planetary roof, there would be no need for a planetary magnetic field to stop solar radiation from stripping away the atmosphere. Because of leakage, more atmosphere would have to be continually imported or manufactured on Mars. So the air factories would be working continually. And no doubt they would break up excessive CO2 molecules into oxygen to be released into the atmosphere and carbon to be taken out of the atmosphere. Thus there would be no need for Mars to have plate tectonics to remove carbon dioxide from the air. [Answer] Mars will remain marginally habitable for millions to billions of years after being terraformed. Earth like conditions will last for less than 100 million years, being followed by glaciation. Nasa's MAVEN mission found that the current atmospheric loss rate is too small to explain Mars's transition from a warm, wet planet to a frigid desert. Studies rely on the young sun having a stronger solar wind to remove most of Mars's atmosphere. Other papers indicate that asteroid and comet impacts of the late heavy bombardment also cleaved off much of Mars's early atmosphere. Regardless, if Mars was gifted an Earth-like atmosphere it would retain the nitrogen and some of the oxygen over geologic time. Mars has no plate tectonics and large volcanoes. This combination would not cause Mars to progress towards a Venus-like state because a habitable Mars would have biological carbon sinks. On Mars, volcanoes would emit carbon dioxide to then be cycled into life. Eventually carbon is trapped as peat or ocean sediment, permanently removing it from the atmosphere. Today, Mars's volcanoes rarely erupt. Therefore, photosynthesis would cause Mars to loose its insulating blanket of CO2, causing the planet to freeze over and enter a snowball state. Mars's habitability could be extended significantly by not bringing any more water to Mars. In this scenario, it would lack oceans, retaining only lakes and seas. The lower precipitation would cause Mars to freeze over more slowly as plant life would struggle to take large amounts of carbon out of the atmosphere. While the low rate of volcanic activity prevents Mars from maintaining a warm, Earth-like climate, a stable ice age might be possible with complex life hanging on in a handful of refuges. Conditions in the Valles Marenaris would be near-freezing almost year round as its equatorial location prevents temperature variation. The main Hellas Basin refuge would be more seasonal, owing to its higher latitude but much lower elevation. Depending on how warm the Martian summer gets, the lowest parts of Hellas might be able to support taiga. Any large animals would hibernate to survive the long winters. Every hundred thousand years or so, volcanic blasts from the Cerberus Fossae would produce a slightly warmer period, allowing the barely viable steady state to persist. Much more rarely, activity from Mars's great shield volcanoes would produce a surge in atmospheric CO2 levels, perhaps creating a Earth-like warm period. The imported biosphere would struggle along until the solar wind strips Mars's atmosphere once more or a large impact winter cools the planet to cause CO2 to freeze out of the atmosphere. In either scenario, single cell life is forced into groundwater refuges while multicellular life dies out completely. IF Mars still has an atmosphere a couple of billion years from now, the increasing luminosity of the Sun would cause the planet to unfreeze itself. However, life would still be crippled by low levels of CO2. [Answer] Mars is "a little bit" further away from the Sun than Venus is. Global warming is not an issue. It hasn't killed Earth's biosphere either. Insolation on Mars is [only 43% of that on Earth](https://www.powerandresources.com/blog/solar-power-is-challenging-on-mars). There's less energy going in, and a greenhouse effect would be very helpful to keep it in. CO2 isn't a magic wand that heats a planet out of nowhere. Terraforming Mars to be even borderline habitable is likely to require [much stronger greenhouse gases than CO2](https://www.pnas.org/doi/10.1073/pnas.051511598). Yes, deliberately produced and introduced into the atmosphere. The [best-case estimates](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006160) of early Mars climate, with a total CO2 atmosphere at 2 bar, still show temperatures below freezing. So even with maximum global warming, you're at best looking at a climate like Siberia or Alaska, rather than any concern over excess heat. [![enter image description here](https://i.stack.imgur.com/llNDk.jpg)](https://i.stack.imgur.com/llNDk.jpg) [![enter image description here](https://i.stack.imgur.com/oQppI.png)](https://i.stack.imgur.com/oQppI.png) ]
[Question] [ So, in this sci-fi scenario, humans create uplifts or “algernons”; sapient animals created through genetic engineering. Torn between making these animals identical to their counterparts or being more or less humanoid, I am trying to design a form which can alternate between both; in other words, a form which can alternate between a near-erect, bipedal stance and a more normal, quadrupedal stance. I am starting with dogs, (these being deemed the ideal candidates due to their social nature and friendliness to humans) but am having difficulty. The more I adjust their structure for bipedalism, the less canine they look, and vice versa. How can I design a “dog” that looks near-identical to a normal dog when on all fours, but can stand and walk comfortably upright? [Answer] There's only one family of animals extant (at this time, anyway) that switch back and forth between bipedal and quadrupedal gaits with any level of comfort: the great apes (and their "quadrupedal" gait has a pretty strongly sloped spine due to short legs and long arms). That said, the main keys will be hip joints and the neck/skull. A human can't walk like a dog, not only because our legs and arms are too different in length but because we can't readily tilt our heads back far enough to see forward comfortably with a horizontal spine. The opposite is true of dogs (and most quadrupeds): if they tip their heads forward enough to see ahead when upright, they'll give themselves serious neck problems. My understanding is that the skull is the primary problem here -- the human (and great ape) skull joins to the spine at the bottom, while dogs (and cats, and bears, and cows and horses) more or less at the rear. To compensate this might require additional flexibility of the neck and strength in the neck muscles -- and with mammals generally limited to only seven cervical vertebrae, neck flexibility has its limits, too. [Answer] Answering this because I do have experience trying to create exactly this kind of creature. To sum up my view of this sort of problem after researching this, as well as winged humanoids... It's going to be a tradeoff between the two things you want your creature to be. The creature will, ideally, be more comfortable in one form than the other, otherwise it's going to do neither thing well. The more capacity you give the creature in one form, the more it's anatomy will inhibit it in the other. For instance, I settled for making my winged humanoids clumsy fliers with less arm strength than they would otherwise have. They also need to warm up their wings to extend the feathers, which is something that allows the feathers to retract a bit when not in use and lets them do normal things like sit in a chair... But they're hindered in that they can't take off quickly in an emergency. Don't ever get discouraged by this. I was very discouraged at first when I realized how impractical some of my initial creature designs were. But sometimes that tradeoff can give you fun challenges, and especially in fiction, there's enough room to squeeze down or mitigate the drawbacks so that you can get something very close to what you wanted, but still be believable. Maybe even more so because the creature now has some well thought out weaknesses. "Near-identical" might be a tall order, or it might be doable, depending on the extent of use you want them to make of each form. Bipedal digitigrades are a sliding scale. If your priority is on the "dog" form, you could have them look very doglike indeed with maybe some more developed muscles in the hind leg calf. They could stand for short periods, or squat comfortably with hands off the ground. That would enable conversation with humans and standing up for cool poses or to see further away. Since this is sci Fi, perhaps they have some prosthetics or special shoes that assist them in standing without discomfort, but can be removed for more animalistic, four-legged tasks? The more time you want them to be standing on two legs and walking, the more adaptation you are going to have to do. My own species has "thumb toes" on their feet which fold in for walking and fold out or grip to give better balance when standing still. The length of the "foot" should be decreased relative to the rest of the leg, bringing it closer to a human with elongated feet standing on tiptoes, if you want them to have a more stable biped stance. This makes walking on all fours less graceful, but has the advantage of making them very fast runners in biped form. Heavily biped digitigrades will need some alterations to their joints to accommodate the greater strain. Think thicker, sturdier legs that look like a hybrid between a human's and animal's. My species stands on a "heel" (actually the ball of the foot) thickly padded with cartilage. Somebody else made an interesting point about the neck. You could take the opportunity to develop some physical adaptations regarding that, but again, if you're writing fiction you have a choice about how in depth you want to go. Another thing you should consider is the arms/forelimbs. Dogs and cats have their elbows very close to their shoulders and a very long foreleg. This is the best arrangement for walking or running on all-fours. Humans have our elbows placed much further down, making the limb more flexible, but sacrificing it's ability to bear weight. Have you ever walked on all fours yourself? You'll notice that your legs are disproportionately long and that your elbows make it awkward to bear weight. But the "dog" elbows are useless for any kind of tool usage, and even kind of awkward for gesturing in conversation. I don't know much about your world, either. Is there magic, or "sufficiently advanced technology" that would allow morphing or physical adjustments as they change stance? Biological nanobots? That could solve many problems, but I understand not everybody wants to go that route. The role these animal people play in your world, society or any of the stories in it should influence which compromises you're willing to make, and which part of the sliding scale you want to put them on. Is it very important to you that they look like actual dogs? Then you may want to skew them towards being dogs that can stand up briefly for conversation but can't sustain that posture. For my species, the importance of making them human-like in tool making ability heavily influenced the outcome. I chose completely human elbow position and worked details into their culture to account for the fact that they aren't comfortable standing in one place for very long. They can't really run on four feet, but they can squat and crawl, and walk on four legs to get under a low spot easier than we can. It's always going to be a compromise. But again, think about the role you want them to play, and weigh the benefits of different degrees of adaptation. [Answer] Baboons are the answer Well, sort of. Baboons can both run with all 4 of their legs and use their front limbs as hands. If you want your canine to be able to change from bipedal to quadrupedal I think they would be the best and most efficient analogus you have. Yes, there is a trade of as your species will most probably be unable to run on their back limb only- look at humans we have our vertical pose which allows our arms to throw stings but we are the lames runners in the animal kingdom. With that in mind is safe to say that you sapient canines will also not have the same freedom of arm movement as we do for the reasons listed above. ]
[Question] [ So, I am writing a list of criteria for wannabe terraformers so that they know at what point any of their pet projects can be considered truly habitable. This list covers everything from the necessary atmospheric pressure and composition to minimum water levels and rotation periods. It also needs to cover orbital eccentricity, but I am not sure; how eccentric can a planet’s orbit be before it experiences radical fluctuations of temperature and is uninhabitable to Earth life? [Answer] Theoretically it might be possible for a planet orbiting a variable star to have a relatively constant temperature if the planet was closest to the star when the star was dimmest, and farthest from the star when it was brightest. But it seems extremely unlikely for such a planet to exist. If you mean terraforming a planet to become habitable for Earth humans with human rquirements, you should check Habitable Planets for Man, stephen Dole, 1654. <https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf> Dole discusses orbital eccentricity on pages 66 to 67. If you mean terraforming for liquid water using life in general, some of which can flourish in environments hostile to humans, it is possible that some planets could have atmospheres and hydrospheres that might maintain relatively constant tempereratures despite eccentric orbits and large changes in stellar radiation recived by the planet. [Answer] On a first approximation, it depends on the central star and the extension of its goldilocks zone: this is usually a shell, and as long as you can fit the elliptical orbit of the planet into this shell, the planet should be habitable. But since there is not a one size fits all extension of the goldilocks zone for every star, a single answer cannot be given. ]
[Question] [ So it's a trope in SF that Lunar colonies would use underground domes either naturally formed or formed by applying various excavation means. You get domes of various sizes used for living space, air storage, etc. For example, in [Menace from Earth](https://rads.stackoverflow.com/amzn/click/com/1439134367), Heinlein has a dome used for air storage that is large enough for people to fly with human-powered wings. The air pressure is slightly above 1 atmosphere and it is 1/6 gravity on the moon, so flying is possible. And in [Steel Beach](https://rads.stackoverflow.com/amzn/click/com/B00AFX4EFY), Varley has domes up to 50 miles in diameter set up to provide a simulacrum of living outdoors on Earth. An artificial sun travels across the dome each day, stars are projected at night, and various weather is artificially generated. Using current tech, or at most slightly advanced past current tech, how big could such an underground dome be constructed on the Moon in 1/6 gravity? [Answer] Rough estimate: the load capacity of a dome is proportional to its section, while its weight is proportional to its volume. Considering that the weight for the same dome on Moon is 1/6 of its weight on Earth, the biggest dome you can have on Moon in $6^{2/3}$ times the biggest dome you can have on Earth, which is about 3.3 times. Considering that, as of today, the [largest dome on Earth](https://en.wikipedia.org/wiki/List_of_largest_domes) is Singapore National Stadium with 310 meters of diameter, on Moon you should be able to get to 1 km diameter. For comparison, the [largest cave on Earth](https://en.wikipedia.org/wiki/Hang_S%C6%A1n_%C4%90o%C3%B2ng) is reported to be 150 meters wide, which would make your dome to be no more than 500 meters wide. [Answer] Suppose you make a brick arch on the Earth, one brick thick. You reach a limit when the weight of the number of bricks is enough to crush a brick. If you build it on the moon, then you can use six times as many bricks before you meet this limit. That is over-simple. The actual failure modes of an arch will be from buckling, rather than crushing. However, there are engineering solutions for that. A dome is stronger than a single arch. Two domes, one inside another, such as the dome of the Pantheon, is stiffer. I think the size of the dome of a particular design would scale as 1/g. A one-mile geodesic dome [Cloud Nine](https://en.wikipedia.org/wiki/Cloud_Nine_(sphere)) is feasible on Earth, so six miles is probably possible on the Moon. More, if you use the difference in pressure to keep the roof up. The actual limit is probably financial - the amount of material will go as the cube of the radius. The cost will probably go as a higher power, as you have to get some of your material to the highest point. The time the site remains as a building site while you pay interest makes things worse. And if the dome is pierced by a meteorite, you lose the lot, and the odds of that go as the dome area. I cannot see a design for one big dome being preferred to an array of less big domes. Unless you have auto have a dome of a certain size for some other reason. [Answer] Here is data about the largest domes by diameter of various types from this list: <https://en.wikipedia.org/wiki/List_of_largest_domes> The Global Vipassan Pagoda in Mumbai, India (2006) has the widest stone dome in the world, at 86.15 meters or 279.4 feet. The list gives the previous record holder as the Western Thermae in Gerasa, Jordan, (2nd Century AD) with a diameter of 15.0 meters or 49.2 feet. However, another part of the list mentions the dome of the Gol Gumbaz, Bijapur, India (1659) at 44.0 meters or 144.36, which I think is also made of stone. And I believe the dome of HItler's planned Volkshalle in Berlin would have made of stone and have a diameter of 250 meters or 820 feet. A plan for the railroad station in Munich called for a dome 265 meters or 869 feet in diameter. [https://en.wikipedia.org/wiki/Volkshalle#:~:text=Its%20dimensions%20were%20so%20large,Peter's%20Basilica.](https://en.wikipedia.org/wiki/Volkshalle#:%7E:text=Its%20dimensions%20were%20so%20large,Peter%27s%20Basilica.) <https://en.wikipedia.org/wiki/M%C3%BCnchen_Hauptbahnhof#The_Reichsbahn_and_Hitler%E2%80%99s_reconstruction_plans> The widest reinforced concrete dome was the Kingdome (1976-2000) in Seattle, Washington at 201.17 meters or 660 feet. The previous record holder was the Norfolk Scope (1971) at Norfolf, Virginia, 134.1 meters or 440 feet. The largest steel dome is the Singapore National Arena (2013) at 310 meters or 1,017.1 feet. The previous record holder was the Louisiana Superdome (1975) at 207.0 meters or 675.1 feet. The widest wooden dome is the Superior Dome, Marquette, Michigan (1991) at 163.4 meters or 536 feet. It is a geodesic dome. Richard Kirk mentioned that a one mile wide geodesic dome is feasble on Earth, about 10.095 times a wide as thelargest existing one. And possibly in some cases domes of other typescould be built ten times as wide as the widest existing examples of their types. So there is no evidence that the present largest dome of a type is the largest possible dome of that type. Probably significantly larger domes of each type could be built on Earth. And of course on the moon with lower gravity and thus lower stresses on structures, a dome could probably be built much wider than the widest possible dome of that type on Earth. The fourth largest buildng by volume on Earth is not supported by any columns. It is the Aerium in Hallbe, Brandenburg, Germany (2000). It was built as an airship hanger and now houses a tropical beach resort. It is 210 meters (688 feet) wide, 360 meters (1,181 feet) long, and 107 meters (351 feet) tall. > > At 5.5 million m³ (194 million ft³), it is one of the largest buildings on Earth by volume, and is the world's largest single hall without supporting pillars inside. > > > <https://en.wikipedia.org/wiki/Tropical_Islands_Resort> The covered dry docks for ship building at the Meyer Werft shipyards at Pappenburg, Germany are also huge. > > "Dockhalle 2" is the world's largest shipbuilding hall. This is the world's first covered dry-dock - opened in 1987. The hall has length 370 m (1214 ft), width 101,5 m (333 ft) and height 60 m (197 ft). In 1991, the drydock was extended with 100 m (328 ft). In 2004, here was constructed a second roofed drydock, that was later extended to 504 m (length), 125 m (width) and 75 m (height). The project resulted into building capacity of 3 cruise ships a year. > > > <https://www.cruisemapper.com/ports/papenburg-port-4004> An enclosed space without columns 504 meters (1,653.54 feet) by 125 meters (410.105 feet) by 75 meters (246.043 feet) has even more square feet than the Aerium. I note that the widest clear span roof in ancient times was in the throne room of the Flavian Palace in Rome (1st century AD) with a span of 31.67 meters (103.9 feet) though its existance is uncertain. The widest clear span of a surviving Roman roof is that the Aula Regia or Basilica at Trier Germany (early 4th century aD0 with a span of 26.05 meters (85.46 feet). <https://en.wikipedia.org/wiki/List_of_ancient_Greek_and_Roman_roofs#cite_note-Ulrich_2007,_149-6> So there has been considerable progress in in roof spans the last 2,000 years. Part two: Shellworlds. > > A shellworld[1](https://en.wikipedia.org/wiki/Volkshalle#:%7E:text=Its%20dimensions%20were%20so%20large,Peter%27s%20Basilica.)[3](https://en.wikipedia.org/wiki/M%C3%BCnchen_Hauptbahnhof#The_Reichsbahn_and_Hitler%E2%80%99s_reconstruction_plans) is any of several types of hypothetical megastructures: > > > A planet or a planetoid turned into series of concentric matryoshka doll-like layers supported by massive pillars. A shellworld of this type features prominently in Iain M. Banks' novel Matter. > > > A megastructure consisting of multiple layers of shells suspended above each other by orbital rings supported by hypothetical mass stream technology. This type of shellworld can be theoretically suspended above any type of stellar body, including planets, gas giants, stars and black holes. The most massive type of shellworld could be built around supermassive black holes at the center of galaxies. > > > An inflated canopy holding high pressure air around an otherwise airless world to create a breathable atmosphere.[7](https://en.wikipedia.org/wiki/List_of_longest_suspension_bridge_spans) The pressure of the contained air supports the weight of the shell. > > > Completely hollow shell worlds can also be created on a planetary or larger scale by contained gas alone, also called bubbleworlds or gravitational balloons, as long as the outward pressure from the contained gas balances the gravitational contraction of the entire structure, resulting in no net force on the shell. The scale is limited only by the mass of gas enclosed; the shell can be made of any mundane material. The shell can have an additional atmosphere on the outside.[5](https://www.pinterest.com/pin/20125529555581997/) > > > <https://en.wikipedia.org/wiki/Shellworld> Any of the first three types could be built on the Moon, with the tird type the least advanced technology. I note that inflatable structures don't have to have a spherical shape. inflatable rubber rafts are an example. Holiday parades often involve giant ballons shaped like living beings who retain their complex shapes. I have seen photos of ballons shaped like buildings. <https://www.pinterest.com/pin/20125529555581997/> So builders on the Moon could build a flat airtight floor on the moon, with a triangular, square, rectangular, or hexagonal shape, and with some airlocks at the edges. And then they could attach an airtight fabric that has a roof shape dlike the floor with walls hanging doen to the floor (or to the airlocks, and attach the fabric to the floor and airlocks, make certain it is sealed airtight, and then inflate with a breatheable atmosphere. And a number of them could be built side by side connected by the airlocks. And possibly the vertical walls between connected balloon structures could eventually be cut away to make larger spaces. And if the lunar regolith that was removed when they leveled the ground and built an airtight floot is then placed on top of the inflated areas, held up by air pressure, the enclosed areas will then be technically under lunar regolith and thus "underground". A thick enough layer of lunar regolith might provide protection against micrometeorites and solar and cosmic radiation. On Earth air supposrted roofs have been built of considerable size but Ihav ebeen unable to find the larges tone. ]
[Question] [ Not actual gold, only golden in color. This is entirely for appearance wise only, how would gold-coloured blood look on someone who is very, VERY pale. Not only skin tone, but how would it affect things like their lips, inside of their mouth, waterline of their eyes, etc.. Also, would those same characteristics of the skin carry over to someone with darker skin or would the melanin cover it up? [Answer] Less Rosy [![enter image description here](https://i.stack.imgur.com/Rg1l6.jpg)](https://i.stack.imgur.com/Rg1l6.jpg) Here is a pale person with red blood. You can see the skin is light in color and rosy where there is more blood near the surface. If the blood is orange instead of red, the rosy parts are less pronounced and more orange. AlexP says lips (and areolas) are red because of red pigment and not blood. You can of course have the lips be orange by having orange pigment instead. [![enter image description here](https://i.stack.imgur.com/60sO1.jpg)](https://i.stack.imgur.com/60sO1.jpg) Feel free to make your own image for the areolas. Hair color is not based on blood color. Sometimes these pale people become redder when they blush. [![enter image description here](https://i.stack.imgur.com/Ji737.jpg)](https://i.stack.imgur.com/Ji737.jpg) [![enter image description here](https://i.stack.imgur.com/BejWZ.jpg)](https://i.stack.imgur.com/BejWZ.jpg) This is because blood rushes to the surface of the skin. If the blood is gold instead of red then your blushers might look like this: [![enter image description here](https://i.stack.imgur.com/3QAum.png)](https://i.stack.imgur.com/3QAum.png) [![enter image description here](https://i.stack.imgur.com/UKx3N.jpg)](https://i.stack.imgur.com/UKx3N.jpg) [![enter image description here](https://i.stack.imgur.com/YTy96.png)](https://i.stack.imgur.com/YTy96.png) [![enter image description here](https://i.stack.imgur.com/v6uiM.png)](https://i.stack.imgur.com/v6uiM.png) [Answer] There are actually two real life compounds that can perform the same functions as blood and have an appearance that can be close to blood. The first is called Coboglobin and uses Cobalt as the base to bind oxygen to it (the function of Iron in every red blooded human). When oxygenated, Cobogloben is colorless, so your special effects team can render bleeding by show trickles of water like liquid from the alien's wounds. An otherwise human looking alien with Cobogloben based blood would look very pale, but still human. Like Hemogloben, Cobogloben does age and needs to be replaced by the body, but Hemogloben ages in terms of weeks while Cobogloben takes days which means blushing can be explained, but it's not as strong. Cobogloben is not naturally occurring in Earth Life and was created in a lab synthetically. The second type that can meet this definition and is easier to state what the skin would look like is chloro-carbonyl-bis(tri phenylphosphine)-iridium (try saying that five times fast). Instead of Iron, this compound uses Iridium to bind Oxygen it (We'll refer to it as I-blood because I am not going to refer to it as chloro-carbonyl-bis(tri phenylphosphine)-iridium every time I have to say it). In a deoxygenated state it's bright yellow and will become a sullen orange when Oxygenated. Some concerns for your alien doctors are that any species with this blood would have a very complex system of lungs, as I-blood is less effecient than Hemoglobe (4 times less) and there could be some intersting biochemistry because it can also carry hydrogen in a similar manner to Oxygen, which our blood cannot do... ask a bio-chemist for more details. In terms of what their skin looks like, that's actually easy. If they are outwardly human in all other respects, you will want them to be exclusively played by actors of African Descent with very dark skin... I-Blood, when oxygenated is extremely photosensitive and will decompose if exposed to strong light over a period of days or weeks (and turn form orange, to green and then bluish-black during this process.). So anyone actor who has little natural melanin in their skin is going to get your biochemist fans to complain loudly. You also need doctors who can perform surgeries in almost zero light environments. ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help). Closed 1 year ago. [Improve this question](/posts/233014/edit) I'm asking how large (by which specifically I mean diameter in light-years, though a rough estimate of the number of stars would be appreciated) can the main body of the spiral galaxy get. I'm familiar with NGC 6872, but its size is from the tip of one of the two outstretched arms to the other; I'm not interested in this size, because of the shape. I'm instead wondering how big of a diameter a spiral galaxy a la the Milky Way or the Sombrero Galaxy (as in, a circular galaxy with no arms stretching noticeably beyond the edges of the disk) could be, within whatever physical limitations of galactic formation apply to spirals. If its at all relevant I'm intending my galaxy to be an flocculent unbarred spiral. I want it to be as big as I can get while still being a spiral galaxy. Thanks [Answer] A spiral galaxy is limited by the accumulation of dark matter, and dark matter is still not understood to that degree. This means that there is no scientific way of answering this short of providing known examples. You can make up dark matter physics, and that will give you *an* answer, but nobody with a background in astrophysics would state that there was a single authoritative answer to this question. [Andromeda: 220kly](https://en.wikipedia.org/wiki/Andromeda_Galaxy) [UGC 2885: 265kly](https://astronomynow.com/2020/01/06/godzilla-galaxy-one-of-largest-observed-hosts-a-trillion-suns/) (10x the mass of the Milky Way) UGC 2885 is presumed to have gotten that way because it formed as an isolated galaxy in a large void. Maybe you could base this on the largest voids, but then you have to add in the sparseness of material in those voids, so you might not be buying anything with that. Even when figuring out the maximum size of a stars, which is something that we do understand the physics behind, we've found cases that we've [had to adjust our theories](https://en.wikipedia.org/wiki/Wolf%E2%80%93Rayet_star) to encompass. Thus, this is an area with much room for creative license. [Answer] A quick cite and link answer could be.. The Largest-Known Spiral Galaxy > > The spectacular barred spiral galaxy NGC 6872 has ranked among the > biggest stellar systems for decades. This enormous spiral is 522,000 > light-years across from the tip of one outstretched arm to the tip of > the other, making it about five times the size of our home galaxy, the > Milky Way > > > <https://svs.gsfc.nasa.gov/30111> ]
[Question] [ Your typical aircraft propels itself by expelling something, may it be air, combusted fuel or even ions. Would it be possible for an aircraft to do none of those things and simply heat the air around it in order to propel itself? Like a plane shaped microwave that was turned inside out. The high-tech vehicle would emit powerful microwaves or lasers or something to heat the surrounding air, thus generating lift and thrust. I am not so much concerned with the technology behind it as I am with the physics themselves. Like, imagine a plane that heats the air under it with a death star style laser beam. Bald eagles already use rising air currents to soar high into the air. It's the same principle but the heat source can be wherever you want. There's also something called [plasma actuators](https://en.wikipedia.org/wiki/Plasma_actuator) that alters the airflow for stability by heating the air above the wings. The aircraft could get off the ground like a hot air balloon, focusing its beam inside a mantle. Once it has gained altitude it would change shape, tuning the mantle into wings and gliding forward. The beam emitter would heat the air in front of it for lift and control. Also, if we heat the air enough it will explode into a plasma, which can serve for propulsion. Probably. I am not sure how this would work so please, enlighten me. [Answer] This is a [Frame Challenge](https://worldbuilding.meta.stackexchange.com/q/7097/40609) And it's amazing how often I've used the following quote on this site.... > > Can you launch an ICBM horizontally? > > > Sure. Why would you want to? (The Hunt for Red October) > > > Let's assume you have the ability to both heat and cool air. * You heat the air below your "ship" and cool the air above it. This creates lift. * You heat the air behind your "ship" and cool the air before it. This creates propulsion. The problem? It's whomping inefficient. Your example of birds rising on thermals is, well... a bad example. The birds are already gliding! They used their wings to provide lift and propulsion and are simply taking advantage of the little extra boost the thermals give them. And it's not the heat of the air that's causing the extra boost - is the updraft the heat caused (which is more complex than simply heating the air). But my point is they were already in motion and the updraft enhanced that motion. No bird can lift itself off the ground (that I know of) simply because the air around them is hot. Which means your problem, which is the main problem with all flight, is weight Birds are honking light and still can't do what you're suggesting without some other power source (flapping their wings). But we can ignore that because a hot air balloon does some of what you're asking by containing the hot air, which has a lower density than the surrounding cool air, and thus rises. Having proven the fundamental principle is possible what remains is making a heavy airplane do it... without hot air containment.... Which it kinda already does. Airplanes, like birds, can take advantage of thermal updrafts to enhance flight. So if we ignore the idea of primary lift and propulsion and only focus on enhancing flight, could the airplane cause the thermal updraft? If the equipment and its supporting energy source was light enough (so as to not overwhelm the benefit with the negative consequence of weight) — sure. But why would you want to? The problem with finding a justification for a wonderful but wholly impractical idea like this is that it is impractical. There are many other ways of achieving the effect that are cheaper and simpler. They'll always be used and it's pretty much impossible to rationalize an impractical solution by inventing a way to prohibit the more practical solutions. [![enter image description here](https://i.stack.imgur.com/JaTey.jpg)](https://www.thiscityknows.com/postcards-from-19th-century-illustrators-depicting-the-future/) (Image courtesy [This City Knows](https://www.thiscityknows.com/postcards-from-19th-century-illustrators-depicting-the-future/)) So why did I include that cool antique French postcard? Because the answer is "Who cares?!" People have been dreaming about impractical flight for a very long time. The card (and the collection it came from) where an invitation to illustrators in 1899 to dream about flight in the year 2000. The ideas were wonderfully mocked by [Avery Brooks](https://www.youtube.com/watch?v=vzm6pvHPSGo) when he said, "It's the year 2000, but where are the flying cars? I was promised flying cars!" Why aren't there flying cars? Weight vs. propulsion.... Should that stop you? *No* My recommendation is that you don't worry about the physics behind making an idea like this work. Reality is overrated! Simply invoke a world rule. You have ~~flying cars~~ airplanes that create lift through the insert technobabble method, which heats the air in a narrow column, lifting the plane. It uses the same tech to push it along. Cool! It's very Flash Gordonesque. I like it! So I'll leave you with one more quote, and I'd like you to note the emphasis, which is mine. > > A measure of how seriously people take the science of the Ringworld – and how daft it has driven them – comes in a story from the 1971 World Science Fiction Convention, when excited students from MIT apparently crowded out the venue chanting: "The Ringworld is unstable!" Apparently, the Ringworld would need giant thrusters to maintain orbit around its sun (a problem that Niven addressed in a follow-up 10 years later). *The significant thing isn't that Niven was wrong but that people took so much of the rest of his science seriously enough to worry about such matters. His ideas have traction. The Ringworld is splendidly improbable but perhaps not impossible.* ([Source](https://www.theguardian.com/books/booksblog/2010/jul/02/larry-niven-ringworld)) > > > And Larry didn't explain the physics. ]
[Question] [ What would be the necessary geographic changes in order to make parts of Siberia as far north as Yakutsk (or maybe a little less) and coastal areas up to those bordering the sea of Okhotsk and Kamchatka as hospitable as western Russia? [Answer] # Just give it time and CO2. I happened to see the answer to your question recently as [an article on phys.org](https://phys.org/news/2022-05-siberian-tundra-virtually-mid-millennium.html), citing a simulation published in [eLife](https://elifesciences.org/articles/75163). In the high-emission scenario (RCP 8.5) practically the entire tundra is replaced by larch trees, which in Russia mark the northern extent of the tree line. There is some technical discussion on the time involved - in the simulation it takes centuries because larch trees only spread at 30 km/year, but in the real world, settlers migrating from heat-ravaged areas are obviously going to bring along trees to line their new streets, and plant larger areas of forest to provide future building material (and mitigate CO2, naturally!). In any case, by mid-millennium the delicate tundra ecosystem is gone and many of its species extinct, which seems to make the area "hospitable as Western Russia" in broad terms. [Answer] The costal area around Okhotsk is only 6 m above current sea levels ([says Wikipedia](https://en.wikipedia.org/wiki/Okhotsk)). So it is quite hard to change anything, which would not also cause a flooding there. The CO2 from Mikes excellent answer for an example will also cause the pole caps to melt which will cause a sea level rise endangering the costal area which you want to become more habitable. Neglecting this effect I would suggest a solution based on orbital mechanics looking at the [Milankovitch Cycles](https://en.wikipedia.org/wiki/Milankovitch_cycles) which are the major factor for large parts of Russia being so cold. Here is an image from Incredio, licensed under [CC BY 3.0](https://creativecommons.org/licenses/by/3.0), obtained via Wikimedia Commons showing their effect: [![Milankovitch Cycles](https://upload.wikimedia.org/wikipedia/commons/5/53/MilankovitchCyclesOrbitandCores.png)](https://upload.wikimedia.org/wikipedia/commons/5/53/MilankovitchCyclesOrbitandCores.png) The blue line is the obliquity which is the angle between the orbital axis and the rotational axis of earth. The green line is the eccentricity of earths elliptical orbit around the sun, the purple line is the longitude of the periapsis which in a nutshell describes how the earth orbit around the sun is located to the reference frame of the sun and the red line is the precession which describes in which direction the rotation axis of earth is pointing. These orbital parameters do have an effect on the amount of sunlight received (basically what the black line is about) and the temperature (see green line which is a measurement on ice from Antarctica). So to get warmer you can change the first four parameters to receive more sunlight in general (eccentricity and longitude of periapsis) or specifically in the area you are interested in (obliquity and precession). This could be achieved by [swing by maneuvers](https://en.wikipedia.org/wiki/Gravity_assist) of many many heavy asteroids or as AlexP pointed out in the comments of your question by waiting for them to change over time. ]
[Question] [ 56 million years ago, Earth underwent the greatest rise in temperature in the last 100 million years. In just 20 to 50 millennia, the global temperature had risen by five to eight degrees Celsius (nine to 14.4 degrees Fahrenheit), and this spike would plateau for 200,000 years. This still-mysterious phenomenon, known as the “Paleocene-Eocene Thermal Maximum”, or “PETM” for short, was a double-edged sword in evolution. Whereas the global jungles spiked the diversity of certain modern clades of mammals, including the primates, this same heat wave warmed up the oceans, weakening their abilities to hold oxygen and rendering them vulnerable to ocean acidification. Deep-sea variations of single-celled organisms called foraminiferans suffered a species loss no greater than half. Coral reefs were cut down, as the greater acidities of the water stunted the production of calcium carbonate. Dinoflagellate cells ballooned, resulting in more common occurrences of harmful algal blooms. Ocean currents took opposite directions, transporting warm water to the depths, reducing the overall temperature gradient and thus worsening the issue. It was so hot that sea levels rose back to mid-Mesozoic levels. The lysocline, the point in which carbonates can dissolve, had risen to a shallow depth of two kilometers, or almost a mile and a quarter. In short, the Paleocene-Eocene Thermal Maximum was both a godsend for life on land and absolute hell for life in the oceans. On this alternate Earth, the PETM lasted a lot longer than back home. Three to four times longer, as a matter of fact. Another difference is that this was the point in which the entire global supply of methane hydrates, or frozen natural gas—all two trillion metric tons of it—were released into the atmosphere, turning the hothouse into an even hotter house. This didn’t happen all at once, as there wasn’t any evidence of a terrestrial mass extinction. What we may be looking at instead was a gentle upward slope spanning the entirety of the PETM—600 to 950 millennia. Sea levels rose to the extent that the amount of land relative to the rest of the planet’s surface to between 12 and 17 percent. As higher temperatures hold more water vapor than lower temperatures, such a spike would mean that so much moisture would be retained that constant rainfalls would destroy mountains. Which ranges had survived such outcomes and which had suffered big time would be explored in due time. It was so hot that the lysocline had climbed up to an even shallower depth of one kilometer, almost two-thirds of a mile. A band of water spanning 15 degrees from both sides of the equator would have been an impenetrable barrier of sickly purple water, inhabited only by anti-oxygen purple bacteria. Beyond that, the temperate seas were mottled with large masses of marine heatwaves, whereas polar seas had smaller but more numerous heatwaves. Between each heatwave, the waters would suffer repeated short-term episodes of harmful algal blooms, which would rob the waters of their precious oxygen. Life on land was about to get harder, but life in the oceans would suffer another major mass extinction—the absolute worst since the Great Dying, and right in the middle of the process of recovering from the fall of the dinosaur empire one million decades prior! 99% of all marine species were gone. Which marine organisms would make up the surviving one percent? [Answer] Nothing that relies on mineralizing calcium carbonate, due to acidity, as you mentioned. That probably rules out cephalopods due to internal shells as well. Nothing that's too quick -- burning energy requires oxygen, and that's going to be a limited resource except for air breathers (which we'll come back to). Nothing that's too slow, either -- the rapid rate of change (compared to geologic averages) means that truly sessile and sedentary organisms are unlikely to be able to keep up with their preferred habitats rate of movement. Corals are probably out. Nothing that's on the top of a tall food pyramid, since the effects of disruptions hit the highest rungs hardest. At the lowest level, as you mention, forams lose out and algae win. So likely, at first, very familiar small bony fish like the clown fish, that sit at the bottom of the food pyramid and eat algae. Fast enough to follow food, efficient enough to try to hide from predators instead of outrunning them. Other small bony fish like sardines that school will lose out in low oxygen conditions because they both use more oxygen individually, and school together, depleting a region. On top of this, the usual predators will decrease in number, and possibly in size, but continue to stick around. Some sharks won't make it through this disaster, but plenty will. Large marine mammals are probably the most interesting question. Baleen whales are not terribly sensitive to acidity, not sensitive to dissolved oxygen, and can filter feed on pretty much anything small and organic -- but due to square/cube effects the increased temperature itself is a challenge. I'd expect thriving communities of baleen whales near the poles, traveling as close to the equator as they can during each hemisphere's winter to get fat on the krill blooms at the edge of habitability, then return poleward to breed in the winter. The reduction in dissolved oxygen also raises opportunities for other marine mammals to adapt, or for other air-breathing animals to return to the water. Over a longer timeframe, you'd expect to see semi- and mostly-aquatic airbreathers like iguanas and otters expand to wider niches. Iguanas in particular spend a good amount of effort dealing with thermoregulation -- a sufficiently warm sea is a benefit to them, not a cost. [Answer] Non-calcifying organisms with photosymbionts. As noted, free swimming water breathers will die. Because of difficulties making calcium shells or tests, those organisms will go too. What remains are shell-less organisms with photosymbionts. The photosymbiotic algal partners can provide oxygen as well as reduced carbon. Organisms with minimal hard parts do not fossilize well but there are modern organisms from several phyla that fit the bill: there exist modern marine worms, sponges, bryozoans, tunicates, sea slugs, medusoids and jellyfish with photosymbionts. Low O2 environments will favor sessile lifestyles and a lack of free swimming competitors will mean these organisms will have more access to photosynthetic plankton prey to get their nitrogen and nutrients. I posit "soft reefs" built of shell-less organisms from the above groups, thriving in the sun, un-nibbled by fish, molluscs and echinoderms. Perhaps there could be [massive floating colonies of photosynthetic jellies](https://worldbuilding.stackexchange.com/questions/109716/how-can-we-scale-up-living-creatures-to-be-giant-sized/109802#109802) forming pelagic reeflike structures that become the home of other animals. [Answer] The scenario you put forward looks to be a perfect environment for a prolonged [Azola Event](https://en.wikipedia.org/wiki/Azolla_event) where the increased rainfall and erosion adding fresh water and minerals to the ocean, the fern would colonize a greater part of the ocean and could alter the food web over a period of time. Reptiles during this time thrived, like titan-boa, and other exothermic organisms would have an advantage. Herbivorous land/sea reptiles could take advantage of the Azola blooms growing and evolving in the standard predator prey dynamic, starting a new era of sea monsters like was seen in the Mesozoic. More diversity in animals adapting to feeding on the Azola plant, the animals and plant itself evolving and diversifying over time could arrive at any number of ecological endpoints. Not to mention the sequestration of great amounts of carbon as stated in the wiki article. ]
[Question] [ I call it vomit due to the way it is being projected like it but would be something of a solution that immobiles and paralyses the pray. I know that the [Fulmar chick uses an orange oil like substance to defend itself](https://us.blastingnews.com/curiosities/2018/11/fulmars-chicks-the-foul-gull-baby-that-projectile-vomits-predatory-seabirds-to-death-002772769.html) and that the pitohui has neurotoxin in its skin and feathers. Granted the pitohui probably gets it toxins from its food but for this bird I would like that to not be the case. So I was wondering if a bird could perhaps project this thick vomit at its pray, the impact pushing the prey to the ground or slowing it down as it slightly solidifies like a puddy. Just for the neurotoxin in the vomit to come in effect. Making the prey even more immobile. Allowing the immune-to-the-vomit bird to carry the pray to its nest where it could use its specialized claws to rip through the vomit puddy and eat at it's leisure. Could this work? [Answer] ## Yes. Here's the natural progression I can imagine: 1. Fulmars retain their stomach oil defence into adulthood. This is likely just a mutation, no particular natural selection. 2. Fulmar birds diversify over time. Some due to some circumstances become birds of prey. Likely starting by disabling another bird and later scavenging the remains. Going after big prey is better than going after fish, although there is more risk involved. 3. They become reliant on their defence mechanism for hunting. Understanding that "puking on a bird means food" they'll grapple with other birds to insure they can land their puke and secure a kill. 4. Over time they specialize to spit further, therefore making it easier to down other birds. I can imagine a longer beak, a slit at the tip of the beak and powerful throat muscles. The best tactic is to aim for the wings or eyes to better disable the prey. I used fulmars as the example but this applies to other birds as well. As far as efficiency goes, I think the oil defence is best. For the following reasons: * The oil already exists amongst (nearly) all birds. They have specialized glands on their rear to coat their feathers with when preening. It makes them waterproof. Thus it keeps them insulated and able to fly in rain (owls for example can't fly when wet). * It's deadly. In a wicked way, this defence mechanism is pure genius. It prevents the inflicted birds from flying and when they try to wash it off they will drown due to no longer being waterproof. This isn't saying toxins or hardening slime is bad. This just seamed like the path of least effort nature would take. But you can be more bold with your imagination. By all means, make a bird that glues its prey to death! ]
[Question] [ I was watching a quite interesting Kurzgesagt video, [Here](https://www.youtube.com/watch?v=G-WO-z-QuWI). How would the surface of Venus look after freezing the CO2 out of the atmosphere? At around 5:28, we see that the atmospheric pressure is 3 bar and it's -81C which is not ideal but livable with some sort of oxygen source. What I'm wondering is how would the surface of Venus look specifically? The snow is mostly Carbon Dioxide, so at a large scale, how would that look on the Venusian landscape? Also, how would it change in terms of erosion from all the CO2 rain? Would the landscape be sharp and volatile or smooth? How would the atmospheric color change? I am an environment artist trying to create a Venusian landscape, just wondering how I can be as scientifically accurate as possible! [Answer] > > The snow is mostly Carbon Dioxide, so at a large scale, how would that > look on the Venusian landscape? > > > On a large scale, it would be essentially indistinguishable from water snow. Dry ice crystals are cubical rather than hexagonal, but that only matters if you are looking closely. Large quantities of liquid CO2 even have a similar (although even weaker) slightly blue color as water. > > Also, how would it change in terms of erosion from all the CO2 rain? > Would the landscape be sharp and volatile or smooth? > > > Not much. You would probably get some distinct fluid channel features carved out, which are currently missing from the Venusian landscape, but Venus's topography is already pretty smooth, simply because it's so hot, which reduces the strength of rocks, and additional weathering from CO2 rain won't change that. Something the video neglects, however, is that those rocks will no longer be weak and pliable once the cooling is underway and CO2 rain begins! I would expect a lot of cracking due to thermal contraction, which would accelerate weathering. > > How would the atmospheric color change? > > > In this scenario, the sky would be black and speckled with stars, because it would be permanently (artificially) night. But if suitable illumination were to be added back in, the sky would be blue due to Rayleigh scattering in the nitrogen atmosphere, just like on Earth. ]
[Question] [ I want to make my world as realistic as possible, so no otherworldly FTL ideas like wormholes, teleportation or warp/alcubierre drives that will violate causality according to relativity. Let's begin. Near a black hole, the gravitational time dilation can make spending a year there equal a million years in the outside universe. From your point of view, everything near you behaves normally, the clock ticks by at one second per second, light travels at 299,792,458 m/s etc. But you will see a clock in the outside universe tick a million times faster. Time of the outside universe runs a million times faster from your POV, and that subsequently includes light itself. Well, light still travels at 299,792,458 m/s, but since s is much shorter, it'll appear much faster. Light from the Andromeda Galaxy only took 2.5 years of YOUR time to reach you. Conversely, someone viewing you from the outside universe will also experience normal time and speed of light, but they'll see your clock tick one million times slower. We've observed this effect back in 2015, where we PREDICTED a supernova down to the month. And it actually happened in December that year. Well, kinda. That very same supernova was seen in 2014. It came to earth in six different images due to the light being lensed by a massive galaxy cluster in front of it. Light passing near massive objects will appear slower to an external observer. That's why the one image that passed through the least gravitational disturbance, came to Earth first, in 1998. The next four images reached us in 2014 within 3 weeks of each other, then the last one in December 2015, just as predicted a few months earlier. Now to the juicy part, is it possible to make a field with the opposite effect? One where observing from the outside universe makes everything inside the field appear a million times faster, and vice versa for an observer inside the field. One million years inside the bubble equals one year outside. Suppose now whatever you've made this field with, you somehow stretch it all the way to the Andromeda Galaxy. This is obviously gonna take many millions of years so assume someone has already done it for you millions of years ago. Bam! Now you have an interstellar superhighway, one billion kilometers in cross section, stretching all the way from our solar system to Andromeda. As you enter this tiny strip of distorted spacetime with your spaceship, you'll gradually see the outside universe redshift out of view and their clocks tick slower and slower. You've finally reached your desired point. Here, your time is ticking a million times faster than outside. Now what? The Andromeda Galaxy is still 2.5 million light years away and it still takes 2.5 million years to reach it with lightspeed. "It's just gonna APPEAR much faster from the outside when I'll be long dead in my spaceship, such a stupid idea!" you might think, but what if I told you, you can use another trick in the book? Let me introduce: Special Relativity! You accelerate to 99.99999999995% of the speed of light, that's an impressive 0.15 mm/s slower than light itself! At that velocity, your Lorentz factor is one million, so your trip to Andromeda is a million times shorter. You decelerate at the end of your journey, 2.5 years later from your perspective. 2.5 million years would still have passed inside the bubble, which means only 2.5 years has passed in the outside universe. Now wait a second... Did you just hack the universe? Would it even be possible to create such a contraption? Would it violate causality? Why or why not? [Answer] Short answer: no. It wont work. There is no field that can do that. Long answer: kind of, a little bit. You almost reinvented the alcubiere drive, and all the requirements and paradoxes are the same. How can this work? The highway requires negative energy. All the matter we know today has positive energy, except probably the dark energy, but we dont know it anyway. Closest thing we have is casimir effect, but it is extremely weak even at fraction of a micrometer, and time dilation from it is expected to be also extremely small. So already no big ships, more like data cable. On the scale of plank time saved per second. String diameter is micrometer. Next step we can think of is make the gap even smaller, an example would be a carbon nanotube, with just a fraction of a nanometer gap hopefully making at least a bit stronger casimir effect. Still, even that will be barely noticeable in terms of time dilation, probably traders could value that. On the scale of parts per trillion of a second saved per second. String diameter is nanometer. Next step would require to go below the size of an atom and forget the normal matter entirely. Material that could probably work is a neutronium - matter of a neutron star, arranged in a tube-like shape. But it is unstable in chunks below 200m, so it must be a really heavy tube. Such a tube across galaxies would exchaust all the matter in the observable universe, but hey, it could probably send your signal a bit faster. This could in theory achieve some meaningful time dilation, half a second saved per second. Time dilation from the heavy matter of the neutron star will be important as well, making the entrance and exit from the highway costly, both for energy and time spent doing so, only in the highway time dilation is beneficial, but in the entrance it is not, so entrance wastes some fraction of a second due to unfavorable time dilation nearby. Neutronoum explodes if it is picked apart into smaller chunks. String is unstable and will try to tangle. String diameter of picometer. We've run out of matter at this point, but what if we go further? The only thing that is stronger than neutronium is the black hole itself. I dont know if black hole's horizon counts towards the stuff that creates casimir effect, but if it is, a set of tiny black holes, constantly radiating and being pumped back up through a laser, orbiting around a highway string. String diameter 1e-18 m evaporation time is 3k years. Time dilation is unlimited for this, but as you go more and more extreme evaporation time drops, and at some point a sneeze will set it all off, and these tiny black holes will start exploding. Also cost to maintain this road is so extreme, that you spend all of the observable universe's entropy that is still left every year or so. Universe is too small and too poor in matter and entropy for your plans, sorry. [Answer] If you have any sort of FTL highway, no matter the details, you can get causality violations from it by a [tachyonic-antitelephone](https://en.wikipedia.org/wiki/Tachyonic_antitelephone) construction. The construction works if: * Your highway is localized, i.e., any effect of its existence on faraway objects goes to zero with increasing distance. * The flip side of that: the highway is stable and not sensitive to arbitrarily small perturbations in the surrounding gravitational field. * Lorentz symmetry (3+1-dimensional rotational symmetry). Supposing those assumptions hold, you can paste translated and rotated copies of the highway into a flat background spacetime in such a way that there are closed timelike curves. The living-near-a-black-hole approach to fast interstellar travel evades this argument because the region where the speed of light is faster isn't localized. You could evade the argument by breaking Lorentz symmetry, but it seems difficult to do that in a way that's so weak that it evades the extremely sensitive experiments we've already done, but also so strong that it prevents construction of causality-violating highways. It's been proposed that spacetimes with closed timelike curves are always prevented by some sort of feedback loop, which effectively breaks the locality/stability assumptions. ]
[Question] [ The lifeforms don't have to use hydrogen sulfide as a solvent. Maybe they've got an internal water-ammonia eutectic mixture or something; anyway, it doesn't matter. The point is, I want an ocean of cryogenic hydrogen sulfide, and I want some kind of creatures living in/by it. Thought one: maybe it could be a carbon planet, because water is unstable on carbon planets, and there wouldn't be oxygen to burn the hydrogen sulfide, so that would let a small amount of hydrogen sulfide collect in seas without being totally overwhelmed by water. Except... carbon has a higher affinity for hydrogen than sulfur does, so hydrogen sulfide isn't actually geologically stable on carbon worlds, either. Thought two: maybe its a really small world, like Io, such that the lightest volatile chemical it could hold on to during formation was hydrogen sulfide. Except, if there are lifeforms there (and no oxygen, because hydrogen sulfide, and no atmospheric hydrogen, because small world that can't hold onto it), then it will be energetically favorable for heterotrophs to strip the hydrogen off of sulfur to produce methane--and both methane and H2S are easily photolyzed (because no ozone layer, because no oxygen), so hydrogen will be lost, carbonaceous biomatter and H2S will be converted into methane and solid sulfur, more hydrogen will be lost, and the sea will dry up. Thought three: maybe it's just a really cold, otherwise Earthlike world, where water is frozen out. Except, water and H2S form a relatively high-temperature gas clathrate, so water ice would just trap all of the H2S, unless there's a truly enormous quantity of it. So: is there a plausible way to get a sea (it doesn't have to be a huge ocean, just definitely "sea" sized) of hydrogen sulfide, which is geologically stable, on a world with lifeforms of some sort? [Answer] I think the lifeforms are the key to this, the sea isn't a purely geologically derived feature but a biological one. Earth didn't always have oxygen, our current atmosphere is the result of a [massive pollution event](https://en.wikipedia.org/wiki/Great_Oxidation_Event) caused by the toxic effluent of the first photosynthetic organisms to evolve here. The sea of hydrogen sulfide is similarly the byproduct of an organism which has no use for it. I suggest that it will be relatively shallow and there will be mats of algae/bacteria on the seabed using the sunlight that filters down to chew sediment and produce a number of wastes including but especially H2S. If it's cold enough to have a sea of H2S at all then the sediments can easily include rock hard frozen water as one potential source of hydrogen. The H2S isn't geochemically stable over any extended time frame but is constantly being renewed, just like our atmospheric oxygen load. [Answer] Underground sea. [![enter image description here](https://i.stack.imgur.com/f0Gx9.jpg)](https://i.stack.imgur.com/f0Gx9.jpg) <https://www.deviantart.com/josheiten/art/Bio-Cave-356339930> Your sea is deep under the surface. Atmospheric pressure at that depth is high, and it is warm. The heavy H2S is well below the topside world of light and oxygen and nitrogen. Solid rocks and metal in between keep it from mixing. Explorers need to bring their own oxygen supply. ]
[Question] [ Long story short, I have an Earth-like planet, which is orbiting a [mega-Earth](https://en.wikipedia.org/wiki/Mega-Earth) (think a super-duper-sized version of a [super-Earth](https://en.wikipedia.org/wiki/Super-Earth)), which is orbiting a [K-type star](https://en.wikipedia.org/wiki/K-type_main-sequence_star), which is orbiting [UY Scuti](https://en.wikipedia.org/wiki/UY_Scuti). I want this mega-Earth to be as massive as possible while still exhibiting a surface gravity less than or equal to twice that of Earth. This means increasing the radius of the mega-Earth; however, increasing the radius of the mega-Earth means that either the density decreases or the mass increases. I don't want the mass to increase - or, at least, I want to keep it within manageable limits, such that the gravity stays equal to or less than 2 [G](https://en.wikipedia.org/wiki/Standard_gravity) - so I decreased the density instead. As of currently, the relevant parameters for the mega-Earth are approximately as follows: * 24.5 [Müú®](https://en.wikipedia.org/wiki/Earth_mass) (note that this is approximately 25.75% of Saturn's mass, and at least 150% of Neptune or Uranus's mass) * 3.5 [Rüú®](https://en.wikipedia.org/wiki/Earth_radius) (you could fit three and a half Earths side-by-side inside this planet) * 42.9 times the volume of Earth (still ~¬æ or ~‚Öî that of Neptune or Uranus, respectively) * Average density of 3 grams per cubic centimeter/3000 kilograms per cubic meter My question: is this density realistic for a terrestrial planet of this radius and mass? The Moon [is known](https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html) to have a density of approximately 3.344 grams per cubic centimeter/3344 kilograms per cubic meter, but I don't know if it's possible for that density to scale up; I'm currently of the impression that a larger planet would "compact" its matter to a greater density, enough such that the radius would decrease, thereby increasing the surface gravity. Please ignore the fact that this planetary system is orbiting UY Scuti - [a star that may only exist for a few million years](https://en.wikipedia.org/wiki/Hypergiant#Formation), therefore not existing long enough to form a planetary system. Moreover, please ignore the fact that a habitable moon orbiting a habitable mega-Earth orbiting a sun which is itself orbiting another sun is a rather unplausible situation. These are both part of the story. Moreover, I don't want a [mini-Neptune](https://en.wikipedia.org/wiki/Mini-Neptune); I want a planet which has an oxygen-nitrogen atmosphere, rather than a hydrogen-based, [volatile](https://en.wikipedia.org/wiki/Volatiles)-based, or steam-based atmosphere. This means that this reduced density cannot be due to a massive but un-dense atmosphere; I'm asking whether a 3 gram/cubic centimeter density is possible for a the crust, mantle, and core of a massive [terrestrial planet](https://en.wikipedia.org/wiki/Terrestrial_planet). Note that this planet does not need to have a magnetic field, but it should have enough silicates for an Earth-like surface. [Answer] To get such a large, low-density planet, it would need to have a very small iron core. The challenge would be in how this might be achieved during planet formation. In theory, it might be possible for collisions between planetary bodies in the same system to strip off the light crust of one or more terrestrial-type planets, and for the light materials to form the large, light planet, while the heavy iron cores remain as one or more seperate planets in nearby different orbits if they are not entirely ejected from the solar system. It is therefore unlikely, but not impossible for such a light, large planet to form. However, I don't know how 'terrestrial' it would be. While surface gravity may be 2g, it would have an escape velocity much higher than Earth's, and due to lack of sufficient low molecular weight Jeans escape, it might accumulate Helium or even Hydrogen in its atmosphere, which could push it from being a terrestrial planet to a gas giant. [Answer] To answer the question of average density of a low density super-earth at 2 surface gravities 3 is not a completely unreasonable number, to get there we have to do some fairly radical things though: * The core can't be metallic, in fact nowhere in the planet are there going to be what we would consider normal abundances of high weight elements. The core is going to be a massive chunk of high density amorphous carbon averaging somewhat less than 3.5gcm-3. We're going to say amorphous carbon rather than a single solid diamond to turn it into a giant spinning conductor so we have a magnetic field, it's also less dense than true diamond. * The "outer core" is going to be a slush zone of giant diamonds floating in the lower mantle. * The mantle will be a relatively thin layer of [Carbonatite](https://en.wikipedia.org/wiki/Carbonatite) with a very thin, fragile, crust. That will get you down to around the 3gcm-3 mark. BUT There are three major problems with this: 1. any world that big simply isn't going to have much relative [relief](https://en.wikipedia.org/wiki/Terrain). As a result if it has a reasonable [read life sustaining] percentage of water in it's total chemical make up it will be covered in fairly deep oceans with the possible exception of a few, short-lived ([geologically](https://en.wikipedia.org/wiki/Geologic_time_scale) speaking) island chains. It simply won't be a terrestrial world in terms of having a lot of continental landmasses to live on. 2. any world with this sort of composition will be as geologically dead as Mars in short order, it only has formation heat, and possibly some tidal heating, zero radioactive heating will occur later in it's life. 3. it's a once in a cosmic blue moon event, strange concentrations and differentiations of elements and chemicals do happen in the wider universe, there are several vast clouds of almost pure alcohol floating around after all but to peel this world out of a protostellar cloud of far more average composition is going to require some really unique circumstances. Having said that if you're willing to have a world that is young enough, dry enough, and weird enough then by all means it is workable idea. [Answer] # Pave Saturn. Saturn has just 1.07 g of gravity. All you need is a solid surface. Go the artificial route and pave it over. Or give it an ecosystem that has generated aerial rafts that join together to reduce the rate at which they fall ... until the entire planet is surrounded ... and then they specialized into a more robust membrane of ecosystem from there. Doubtless they have a plant-like metabolism and have extracted an oxygen atmosphere that they vent above them, from the warm rain clouds that are found around 10 atm deep in our Saturn. Now there is a Saturn-sized world with Earthlike gravity, water (from oxygen reacting with remaining hydrogen), and an oxygen atmosphere ... with a peculiar basement waiting for those who like to dig into things. [Answer] According to the OP: > > I want this mega-Earth to be as massive as possible while still exhibiting a surface gravity less than or equal to twice that of Earth. > > > But they also want the planet to be inhabited by seeded lifeforms including humans. And it seems doubtful to me that humans from Earth could flourish 24 hours a day, year after year, in 2 g surface Gravity. It is quite possible that such high surface gravity would kill off the humans faster than they could reproduce. See the discussion of surface gravity on a habitable planet in Habitable Planets for Man, Stephen H. Dole, 1964. On page 12 Dole says: > > On the Basis of the available date, one might conclude that few people would choose to live on a planet where the surface gravty was greater than 1.25 or 1.50 g. > > > <https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf> I suspect that any humans introduced to a planet with a surface gravity as high as 2 g would have to be bred for it over many generations, centuries, and millennia living on planets with successively slightly higher surface gravity. Or elese have their genes artifically modified all at once to transform them in to beings similar to humans but redesigned to withstand high gravity much better. Thus the past history of the humans who were seeded on the planet needs to be considered if its surface gravity is anywhere near to 2 g. The parameters of the planet are described as: > > As of currently, the relevant parameters for the mega-Earth are approximately as follows: > > > 24.5 Müú® (note that this is approximately 25.75% of Saturn's mass, and at least 150% of Neptune or Uranus's mass) > > > 3.5 Rüú® (you could fit three and a half Earths side-by-side inside this planet) > > > 42.9 times the volume of Earth (still ~¬æ or ~‚Öî that of Neptune or Uranus, respectively) > > > Average density of 3 grams per cubic centimeter/3000 kilograms per cubic meter > > > So it has 3.5 times the radius of Earth, and thus 42.875 time the volume of Earth. With 24.5 times the mass of Earth it has a density of 0.5714285 Earth's density of 5.514 grams per cubic centimeter or 3.1508567 grams per cubic centimenter, which is close to your figure of 3 grams per cubic centimeter. Since the matter of a planet is denser at the core than at the surface, it might turn out that your planet's outer layers would be a world wide ocean many miles deep. According to this online calculator, the surface gravity of a planet with radius 3.5 times the radius of earth and 24.5 times the mass of Earth would be 2 g. <https://philip-p-ide.uk/doku.php/blog/articles/software/surface_gravity_calc> According to this escape velocity calculator, the escape velocity of a planet with radius 3.5 times the radius of earth and 24.5 times the mass of Earth would be 29.595 kilometers per second, or 2.6457 that of Earth. <https://www.omnicalculator.com/physics/escape-velocity> That would be a bit higher than the escape velocity of Uranus, which is 21.3 kilometers per second. Uranus has a lot more hydrogen and helium in its atmosphere than Earth. And of course a habitable planet could not have a lot of hydrogen and oxygen for breathing in its atmosphere, since hydrogen and oxygen burn to form water vapor. The ability of a planet to retain a gas in its atmosphere depends on the ratio between the heat and speed of particles of that gas in the exosphere of the planet and the planet's surface gravity. Uranus is about 19 times as far from the Sun as Earth is. If Uranus was close enough to the Sun to have Earth like temperatures, it would receive about 19 X 19, or 361, times as much radiation as it does, and its exosphere would be much hotter, perhaps hot enough to lose its hydrogen and helium. I suspect that you might want to change the parameters of your planet, to be at least as dense as before (if possible), but with a smaller mass and radius to get the surface gravity and escape velocity lower. ]
[Question] [ So me and my buddy are currently working on a story that takes place on a different earth-like planet similar to when carboniferous life like the Meganeura dragonfly inhabit the landscape. A few differences is that the 'Humans' that evolved on this planet to unaffected by the high oxygen in the atmosphere. (33% of atmosphere to be specific). The era we're worldbuilding takes place in there medieval era. When I was doing some research on the different iron alloys. I've read that metals like iron would naturally degrade into rust over time due to binding of oxygen in the air. Natural elements like Water & especially salt water would degrade iron much more quickly. I did some research on things like Rust-resistant alloys & Galvanization. But The only problem with those 2 is these were modern methods that likely required the discovery of electricity to make these alloys. Question: Would an atmosphere with 33% oxygen significantly alter our world's historical uses of iron for tools, structures, armor and weapons? [Answer] Not much effect at all. The effects would be negligible, if anything forging might be slightly easier since fuel will burn with more heat and speed. In a medieval setting low oxygen for steel making is achieve via sealed crucibles, which will work regardless of oxygen levels so the metal is not subjected to higher oxygen when it matters. Rust is not an issue solid iron does not rust noticeable faster in slightly higher oxygen, things like humidity, salt, and PH matter far more. Handling will matter, but it does for all iron tools, Oil, wax, resin, enamel, even paint will see lots of use. Consider iron tools were commonly used on ship, and salt water is a far stronger affect on corrosion than slight changes in oxygen levels. [Answer] I'm not sure my answer will be the most help, but I was curious so I looked into this somewhat. [This link](https://pubs.acs.org/doi/pdf/10.1021/ie50261a011?src=recsys&) is for a publication that seems to be behind a paywall, but the single page shown covers generally exactly this topic, but primarily in highly oxygenated water. The gist seems to be that rapid oxidation in water causes steel to turn into a sort of rusty gelatin, but it would be only on the outer layers of steel and corrode further in over time. Might be worth reading the whole paper if you want greater details though. [Another article](https://www.nature.com/articles/s41467-018-08071-3) I found goes a bit too over my head after a while, but seems to indicate that under high pressure iron-oxide (rust) keeps its ferrous state, although non-magnetically. I didn't see where it indicated at exactly what pressures other than deep in the Earth's crust, but the atmosphere could possibly have a high pressure as well. There is also quite a bit relating it to iron-sulfide (pyrite/fools gold). Like I said though, fifteen minutes of reading ended up going much further over my head than CHEM 201. I would recommend trying to getting clarification from someone much more versed in metallurgy, geology, and/or chemistry. I would suggest considering the greater affects of higher oxygen on other aspects of the world such as water oxygenation and how that affects climate and other natural reactions. Fire would be a much bigger deal in this world as it would be much easier to start one and it would get much larger faster. Obviously we have archeological references for flora and fauna, and you seem to have hand-waved human biology too. You may want to just hand-wave a lot of the more tedious details as well. ]
[Question] [ A character of mine (a girl in case that detail matters a lot) is at the brink of entering (or already int he early stages of) puberty. And apart from (due to story related circumstances) growing up quite quickly mentally i would like to also show her growing up physically. To show this i wanted her to be quite a lot taller by the end of the story compared to the beginning. In the the span of this story (which covers about a year give or take a month) she basically has to go from realistic height for her age (she is 15 so i made her 155cm / 5'08.) to nearly as tall as her older brother who is about 180cm / 5'11. Is this a realistic growth spurt or completely impossible by human standards? [Answer] Yes > > During the adolescent spurt in height, for a year or more, the velocity of growth approximately doubles; a boy is likely to be growing again at the rate he last experienced about age two. The peak velocity of height (P.H.V., a point much used in growth studies) averages about 10.5 centimetres per year in boys and 9.0 centimetres in girls (about 4 and 3.4 inches, respectively), but this is the “instantaneous” peak given by a smooth curve drawn through the observations. The velocity over the whole year encompassing the six months before and after the peak is naturally somewhat less. During this year a boy usually grows between 7 and 12 centimetres (2.75 and 4.75 inches) and a girl between 6 and 11 centimetres (2.35 and 4.35 inches). Children who have their peak early reach a somewhat higher peak than those who have it late. ([Source](https://www.britannica.com/science/human-development/Increase-in-body-size)) > > > You're advocating a growth spurt of 3 inches, which is less than the maximum average for girls of 4.35 inches. But, just to be sure, the total for girls is 2.35–4.35 inches. Your "average average" is therefore 3.35 inches — still more than you're looking for. And remember, that article says this is just the average. [Answer] This would have been more realistic to extend the growth in 18 -24 months For instance, my friend grew from 155 to 182 cm in 30 months and final height is 187cm 8 cm while age 12: 155 to 163 cm. 14 cm while age 13: 163 to 177 cm. 6 cm in the last 6 months: 177 to 183. 4 cm for the next 2.5 years, 187 cm by 16 year old ]
[Question] [ ((Alright, so! I don't even know if this is the right place to ask, but I hope to hear your thoughts. Sorry for the morbid topic and thanks in advance!)) In a comic I'll eventually draw, there's this 6 year old child that's running for her life from a guard, and her breathing is (naturally) all out of sorts. She's about to faint from exhaustion, so she leans on a wall, giving up, and starts slipping into unconsciousness. The guard that's chasing her catches up to her and grabs her - Important: from behind- from the scruff of her shirt as she's falling over. The guard also kind of yanks her backwards, but the main position is the one after she's yanked, where she falls forward again, and the guard keeps her in place by having a tight grip on her shirt collar. Just to give you an idea, i made a sketch in Word to roughly show the pose im going for. If it's not very helpful, I hope you at least get a kick out of it! [![poorly made sketch i did in word](https://i.stack.imgur.com/fkpUX.png)](https://i.stack.imgur.com/fkpUX.png) [![even worse word sketch i did](https://i.stack.imgur.com/YDZHw.png)](https://i.stack.imgur.com/YDZHw.png) The second picture is the position that's kept after being yanked back, while the first is momentary. The guard wraps their hand around the shirt's collar, so the grip is tight against the kid's throat and doesn't allow for much movement (though I want to point out, the child is exhausted and can't really move even if she wanted to. That's the reason why she doesn't just put her feet below her to properly support her weight.) One important thing to mention about the position is that, while the girl is still "standing" on the ground, (she's partially on her feet ((but barely))) , her neck/throat essentially supports, say, about 70% of her body weight, in an angle diagonal to the ground. So, to summarise, we have a small, 20 kg child (or ~40 pounds i think, for the americans here!) that is still catching her breath from running as hard as she can, that is suddenly semi-suspended from her throat in a way that puts pressure primarily to her larynx (or windpipe). The guard has a strong grip around the neck -via the shirt-, but otherwise doesn't do anything else. What I want to ask is: would the shirt collar act like a makeshift noose in this particular scenario? Would the girl actually feel strangled or would she just be in a very uncomfortable position with a lot of pressure on her throat but otherwise fine? Is her body weight even enough to cause strangling? If anybody has any knowledge about this, it would immensely help, as this has been bugging me for days and I can't find any concrete information to say it could or couldn't happen!! (for anyone interested or understandably concerned about all this morbid stuff, the guard chooses not to kill the girl in the end and adopts her. I still want to bring justice to their first meeting though, even if it's anything but happy!) A big thank you to anyone who managed to reach the end of my ramblings!! [Answer] She will not choke from this. [![doll](https://i.stack.imgur.com/cjI0Bm.jpg)](https://i.stack.imgur.com/cjI0Bm.jpg) My doll friend was happy to help with this project. Her open collar top puts no pressure on the front of her neck. The weight is actually carried under her arms and across the chest. You can see her top is tight underneath her arms. The collar actually opens wider. Her arms are pulled to the sides and stick out. I think this same principle is why puppies or cats picked up by the scruff have their legs stick out in a weird way. [![puppy](https://i.stack.imgur.com/a8ttDm.jpg)](https://i.stack.imgur.com/a8ttDm.jpg) If you want to make sure readers know she is not strangling, show her open collar like I did with the doll. It looks like she is wearing a sailor-type japanese school uniform so that would be consistent. Also, you can recruit an assistant and try it out. Have your assistant pull your collar and see where the garment puts pressure on you. Getting yanked hurts under the arms. The spine is tough. The experience will help you draw the arms realistically - not drooping down in front like your last drawing but splayed out uncomfortably like the puppy held by the scruff. Last piece - look at the doll again. [![doll](https://i.stack.imgur.com/cjI0Bs.jpg)](https://i.stack.imgur.com/cjI0Bs.jpg) The velcro holding her top closed is strained by this maneuver. If the guard is supporting your charatcer weight by her top and the buttons give, she can drop out of her top and escape in her undershirt. Next page you can draw her in a giant coat down to her shins. ]
[Question] [ Re: New ALF (Alien Life-Form) discovered A new and dangerous ALF has been discovered in one of the generation ships. This creature has been christened a Gargoyle, as its body resembles a rock and its hunting strategy is usually 'stay still until prey gets within attack range.' The first one discovered resembled a large rock, with a concave top. The scholar who found it commented that it vaguely resembled a frog, and that its "mouth" looked surprisingly realistic, then walked up and touched the mouth. To our surprise, the rock shifted, its "fake" maw clamping shut upon the unfortunate scholar's arm, the vague appendages on the "rock" popping out or extending. Needless to say, the scholar died, but we did manage to kill and dissect the creature. This alien had robust musculature and ample blubber, most likely to aid in locomotion and enable the predator to survive between long stretches without prey. Its body exhibited a mix of retractable and "slotting"\* appendages, most likely so said appendages don't deviate from its rocklike profile when it's waiting for prey. Additionally, its rocklike skin appears to be the result of an unusual biological mechanism; the skin demonstrated layers of increasingly mineralized tissue, showing that as the creature ages, it develops more and more skin cells, resulting in broader and broader layers of skin. We are unsure how, but these outer layers seem to be petrified. Immersion Break My question is, is my Gargoyle a plausible life-form? Camouflaging predators are nothing new here on Earth, so I know that's plausible. However, appendages that can disappear into the body, or fit into special grooves to appear as projections of rock instead of limbs, are most definitely an unusual trait, as are this life-form growing layers of skin that turn to rock. I'm not entirely sure how that could work, either...perhaps its skin could form plates of rock, fitted together, and force new growths of rock in place from below? Or it could 'molt,' shedding and eating its rocky armor, then regrowing it to cover its now-larger body? So more specifically, how can I plausibly explain these alien traits? Specifications: 1. No word on where this Gargoyle came to be; I'm leaving that open for answerers to decide, as I myself am uncertain what conditions would lead to such a camouflaging predator as this OP describes. 2. The best answer will take the traits described above and explain if they are plausible or not in an alien lifeform, and if so, what conditions would lead to these traits. If applicable, real-world examples can and should be added. [Answer] # Blubber and osteoderms. Let's begin with the retracting bit: surprisingly enough it's not that weird, most turtle species can at least partially retract both their heads and their limbs into their bodies. Some kinds of whales make themselves more hydrodynamic thanks to the presence of literal fin pockets used to tuck their fins inside and make them even more torpedo-like. Creatures with a lot of blubber also can have the appearance of retracting something into their bodies, see for example this seal: [![enter image description here](https://i.stack.imgur.com/NeF95.jpg)](https://i.stack.imgur.com/NeF95.jpg) Thanks to the layer of blubber and flexible enough neck, it passes the idea of retracting its head into its body. Since your creature also seems to have an extensive amount of blubber, I'd say it's easily possible. If it truly has a lot of blubber, hiding limbs that overall come out from below itself is as easy as lying down with its legs tucked in (if you have seen a cat lying down, you know what I mean), the presence of skin pockets further ensures the limbs will probably be hidden away well. But what about the mineralized skin? Again, not crazy, our very cells are actually calcified when it comes to the most further out layers of dead skin. This already creates, in land animals, a barrier that helps prevent water loss (since it's impermeable) and offers protection from bacteria in the environment (layer of calcified dead cells). Your creature just takes it a norther level. My biggest concern is in regards to the "layers of increasingly mineralized tissue, showing that as the creature ages, it develops more and more skin cells, resulting in broader and broader layers of skin" part. Sure, it's not crazy than an adult would need and therefore have tougher skin than a younger one, but again it's not too crazy. Some spiders slowly incorporate bits of iron to their chelicerae throughout their lives, so that those can better pierce the chitinous exoskeleton of its prey, and some older spiders seemingly had fangs mostly composed of metal. The problem with that is that for something to incorporate more and more mineral components, it needs to stick around, A.K.A your animal would need to not change its skin from time to time like normal earth creatures, which can cause some problems depending on how they work (dead skin doesn't heal, so if it's not changed periodically to make up for that, it can Mean a permanent access to the very living parts of the creature's flesh below. We can however make a different approach: rather than giving it skin that becomes more and more mineralized, we give it chainmail armor: [![enter image description here](https://i.stack.imgur.com/b6PTZ.jpg)](https://i.stack.imgur.com/b6PTZ.jpg) This picture should illustrate my proposal well: komodo dragons are a species of fairly aggressive reptiles, one which, at their adult stage, only needs to worry about other komodo dragons. It's solution to protect itself? A complex system of osteoderms that cover a such portion of its body you can easily tell what its skin is like. This protective system of tiny bones, unlike the outer skin layers, is never thrown out and stays within the body until it dies. If your creature was to have a similar system of osteoderms, not only would it still be protected, it'd make a lot easier to explain the mineralization, as much like the spider's fangs, these tiny bones slowly get more and more molecules of minerals and potentially even metals integrated to them, explaining that the thicker mineralized "skin layer" was nothing more Nothing less than a literal organic chainmail protecting the creature. Edit: Alternatively. If you really want to crank that armor concept to eleven, then instead of following the komodo armor strategy, you might want to follow that of the [kwi kwi](https://www.catawiki.com/en/l/9516997-kwi-kwi-skeleton-armoured-catfish-hoplosternum-littorale-23-x-11-x-9cm), also known as the armored catfish: [![enter image description here](https://i.stack.imgur.com/z9jmn.jpg)](https://i.stack.imgur.com/z9jmn.jpg) The little fella who decided they wanted to exist wearing brigandine armor. Do be warned though: a drawback of brigandine armor that exists for anything that uses it, even if it's part of your skeleton, is that, while not as much as full plate would, it will most likely still limit your mobility to an extent (but certainly not as much as regular media would tell you), and having it as your skeleton, especially if you slowly integrate other minerals into it, might make your creature pretty heavy and less "squishy", meaning balancing this one with osteoderms might be ideal to prevent an unwanted loss of flexibility In certain areas, particularly the limbs and potentially in the neck region. So overall, it's pretty plausible. The creature's ability to tuck its limbs in to camouflage already exists in nature, and the layer of blubber only helps with that. The mineralized skin part is a bit trickier, but I'd say that a system of osteoderms below the already mineralized skin (nothing really stops your creature to have thicker skin, see rhinos and hippos for example, although that probably comes at the cost of the skin becoming a bit less flexible) can still somewhat explain it nicely enough, particularly if you decided to also use an actual system of bony plates like the armored catfish, because then it will also have a system of literal bony plates throughout its body. [Answer] Calcinosis [![calcinosis](https://i.stack.imgur.com/lKg0n.jpg)](https://i.stack.imgur.com/lKg0n.jpg) > > Tumoral calcinosis is a rare, weird entity of unknown etiology. Fifty > percent of these patients may have some associated abnormalities in > their renal lab work. The calcifications are usually large, globular, > and located in the soft tissues over joints. Not much else looks like > this. > > > <https://rad.washington.edu/about-us/academic-sections/musculoskeletal-radiology/teaching-materials/online-musculoskeletal-radiology-book/soft-tissue-calcifications/> Your gargoyle has extensive calcific deposits in the skin, some including the cutis. Lichens grow on these, adding to the rock like appearance. The skin itself is exorbitantly redundant and wrinkly. <https://metro.co.uk/2021/03/23/harvey-the-shar-pei-has-so-many-wrinkles-he-looks-like-a-blanket-14289702/> [![harvey the shar-pei](https://i.stack.imgur.com/DOnRl.jpg)](https://i.stack.imgur.com/DOnRl.jpg) I am not even sure what we are looking at in that second picture. Your creature has folds and lobes of redundant tissue which break up the animal-like lines in its form. Its limbs do not disappear into grooves but into redundant folds. ]
[Question] [ In the world of my story, merfolk have been captured by humans to serve the cruel purpose of providing their colorful scales to make jewelry, chandeliers, etc, with their colorful scales. I'm not looking in this post specifically for how this would work biologically - I've mostly worked out though that it is not an extremely gory process - ie, the merfolk are not skinned alive and then left for dead. The scales come off with a sharp knife, and will regrow some months later. More of what I'm interested in is getting feedback on the system that would need this to work. I'm in an early 19th century setting circa 1800 - 1850. I've figured so far that this is what I would need. -for a group of around 30 captive mers, a cove near the ocean has had it's exit blocked off to hold the mers in. The mers require the water to be changed periodically, so there are channels controlled by sluices that let water in and out. Food is provided by dumping a porridge-like mixture into the water. When a mer is ready to be scaled, they are lured over by the release of food, and then caught around the neck with a staff with a noose around the end. They are then pulled into a cage in the corner of the pool, where they are winched up, then bound. Any mers that attempt to stop this, or misbehave in general, are struck with long staffs. This is not always needed however, as even with the water being changed out periodically, it's lack of natural movement has resulted in a numbing effect on the minds of the mers. They can function but it is much more difficult. The mer to be scaled is then brought to a person sized bowl, where they are secured at the wrists and around the end of the tail just above the fins. The mer is provided with a wooden dowel to bite down on (not out of kindness - it helps them stay more steady) and then the scaling begins. A well practiced scaler can remove the scales with minimal blood, though some is always to be expected. Extra care is taken around the tips of the fins and the "folds" in the front and back that are not very visible, but have smaller scales than the normal thumbnail sized ones. Following the scaling, the mer's now bare tail-skin is cleaned off to prevent infection, and then is released back into the pool. So far as I have figured, my scalefarm at the start is able to be manned by two - the master and and apprentice. As the number of mers increases to thirty, a second apprentice is taken on. The apprentices sleep in a bunkhouse adjoining the master's quarters and office. The farm itself has a pontoon bridge going around the whole edge of the pool to aid in watching the mers. the front of the farm and the seawall are blocked off by netted fences higher than a person. Lastly, the farm has a small forge for maintaining tools and fixing mechanisms in the sluice gates. So that is my outline of how all this works. Let me know how you think this could be improved, or how it would be ramped up for a larger operation (or downgraded for a smaller one). This practice is legal, though there are regulations on it. This is in the broader context of the human nation and fractured merfolk city states being at war with each other for the past 80 years or so. As the only exposure most humans have to merfolk is seeing them sedated in farms or attacking human shipping, they are viewed mostly with contempt. [Answer] There are some issues with this. Each issue and potential solutions to it are outlined below; Sluice Security Risks > > The mers require the water to be changed periodically, so there are channels controlled by sluices that let water in and out. > > > These 'channels' are a security risk. As @legio1 said, if the channels are deep enough for quick, efficient water exchange, the water-breathing Mers will be able to operate with relative impunity to undermine the grates which prevent escape from the bottom of the bay, where humans can't reach. Make it shallow enough for the air-breathing workers to deal with escape attempts and there won’t be efficient water exchange. Solutions to this can include passive defenses, such as spikes and such that keep the Mers out. Alternatively, you could have regular checks of the grates that ensure that the Mers aren't trying anything funny. Nope, not falling for THAT again > > When a Mer is ready to be scaled, they are lured over by the release of food, and then caught around the neck with a staff with a noose around the end. > > > It is not going to take long for them to figure out that the release of food could mean they get grabbed, locked in a cage, and de-scaled. Hence, they are going to stop coming over to the spot you want when you release the food. You can solve this by simply only releasing food at the spot with the cage, but then you have a situation where Mers are starving themselves to avoid being grabbed. Desperation would eventually drive them over to where you want, but deprivation of food may reduce scale quality, which is bad for profit margins. One could fix this by outfitting the Mers with collars that are affixed to a long 'leash'. When it's time to de-scale a Mer, you use the leash to yank the Mer into the de-scaling cage. Mers caught screwing with their collar in any way or caught removing their collar are administered a beating via long staffs, and then have their collar replaced. Violent tail-slapping > > The Mer to be scaled is then brought to a person-sized bowl, where they are secured at the wrists and around the end of the tail just above the fins > > > The Mers here are going to violently thrash throughout this, securing just the tail and the wrists isn't going to be enough. Fish can hit quite hard just by flapping their tails, and this is going to apply doubly for the Mers here. The solution? Have a stretch rack of sorts set up. The rack features restraints at the bottom for the tail, restraints near the middle for the waist, and more restraints at the top for the neck and wrists. The tail restraint can be adjusted so that the Mer's tail is stretched as far as it can go, minimizing its flexibility and thus preventing any attempts by the Mer to slap the de-scalers away with its tail. Under this system, the Mer would be strapped to the rack after being winched up, given a dowel to bite down on, and then the de-scaling begins. Those who struggle too much would be beaten. Once the procedure is done, the Mer is given extra food if it didn't struggle, to help discourage excessive struggling. Shortage of security > > So far as I have figured, my scalefarm at the start is able to be manned by two - the master and and apprentice. As the number of mers increases to thirty, a second apprentice is taken on. The apprentices sleep in a bunkhouse adjoining the master's quarters and office. > > > 2, maybe 3 apprentices is not enough. As mentioned by @legio1, Mer-leaders will be under constant pressure to do something about these horrifically inhumane torture-plexes. And that means that these farms are going to be at constant risk of attack. As a result of this, heavier security is necessary. I think that a guard will be needed for every 3 or 2 Mers in captivity, in addition to the Master and Apprentices. SCANDAL!!! > > This is in the broader context of the human nation and fractured merfolk city states being at war with each other for the past 80 years or so. As the only exposure most humans have to merfolk is seeing them sedated in farms or attacking human shipping, they are viewed mostly with contempt. > > > This is by far the biggest problem. These things are sentient, and the populace knows it. And the populace is not going to be happy with having Mers who've done nothing wrong being tortured in the name of profit; that's a PR catastrophe of career-annihilating proportions just waiting to happen. Fortunately, all you need to do to make this work is convince the population that they have done something wrong, and that's as simple as saying that this is a penal camp for enemy combatants. Of course, these Mers could just be innocents kidnapped off the ocean floor, but that could be hard to prove as the equipment and such you could use to identify them as such is removed and disposed of. The only people with any evidence that their innocent are other Mers, and they can be easily dismissed as charlatans trying to ensure war criminals get away scot-free. And human sympathizers who object could be dismissed as 'soft on war crimes'. [Answer] ## you need more security I think there are several security issues that need to be patched. water exchange sluices As described, the water exchange sluices are a major security risk. Mer-leaders will be under constant pressure to do something about these torture factories. If the leaders of New Mer City can destroy one of these “farms” and free the captives, it would significantly boost their standing with the neighboring city-states of Mer Town and Mer-opolis. That could gain them some major allies in their war against the Mer Commonwealth. Given that incentive, the sluices are going to be under constant attack from the outside. Similarly, there are sapient people held captive and routinely tortured. They are going to be looking for weak points and those sluices are the path to freedom. Defenses need a major upgrade. But that’s not going to be easy. Make the channels deep enough for quick, efficient water exchange and the water-breathing mers will operate with relative impunity to undermine the system from the bottom. Make it shallow enough for the air-breathing workers to deal with the mers and there won’t be efficient water exchange which will keep the gate open for hours every day. The only solution is going to be extra people to work security. sapient captives The means of getting the mers into the shaving rig is also lacking. The current plan is to lure them over with a release of food. Will that really work with a sapient species that knows what going over there means? Supposedly captivity has led to a “numbing effect” but they can still function. If they can function, they can (and at least some will) resist. anatomy Finally, the way mers are secured for scaling is insufficient. The plan is to secure them with bindings at the wrist and tail. That’s not enough. Anyone who’s ever handled a live fish in a situation that it doesn’t like (e.g., out of the water) will have experienced just how flexible their spine is and how powerfully they can move their body. The same will apply to the mers only worse because they are big and they are sapient. A full-grown mer that is angry and afraid will fight for its life. A single hard slap from that tail is likely to severely injure or even kill whatever sucker is tasked with tying it down. scale You specifically ask about scaling up and scaling down. Both present problems. Scaling down is hard because this needs to make economic sense. Even a small farm will need several people at least to make this work safely. Is the price of scales enough to support five or six people with only 10 mers? Scaling up presents an incentive problem. Obviously, a large operation can afford better security. But a large operation also makes a tempting target. Returning to the leaders of New Mer City, if they have to choose between hitting a little mom & pop torture farm to free a dozen or so mers or taking down a massive factory and freeing hundreds or even thousands, they’re going to go big. The pressure on facility security will be immense, probably on the scale of a small war. Seriously, how valuable are these scales again? [Answer] # Plantation Slavery: In the realm of brutality, there is no discrimination. Your enslavement should be a system of capture, enslavement and oppression that brutalizes the mer-folk enslaved but also damns the mer-folk themselves for involvement in exploiting their own people. Look to how humans have enslaved people over the ages, and you'll be halfway there. Your timeline corresponds well to the period of the slave trade on Earth. Exploiting the pain, pleasure, greed, hate and envy of mer-folk can do your work for you. * Mer-slavers: Your mer-folk are not innocent, and do not hold all other mer-folk warmly in their hearts while singing kumbaya. War in Africa fueled the slave trade, and the slave trade fueled war in Africa. Mer-tribes capture and sell rival mer-folk into slavery. Preferably the slavers would be the mer-folk closest to the coasts where the slaves are kept. Escaped mer-folk are then captured by mer-slavers and sold back into slavery. * Mer-hunters: Keeping an elephant to get ivory is expensive, but simply killing the elephant(or hacking off it's tusks in the wild) is easy. You don't have to enslave your mer-folk if they war with each other. The mer-folk know they can brutalize rival populations and raid into enemy territory, then strip enemies of scales and sell the scales to humans for weapons, drugs, or whatever trade items are valuable. * Mer-plantations: Your mer-slavers may even run the system, either by running the plantations off-shore or working as overseers. Like the drug trade, simply by offering a good price for scales, the humans can wash their hands of the brutality. Or perhaps selected enslaved mermen are given the chance to NOT be harvested, be in charge of their fellow mer-folk, and have exclusive rights to mating the females. In any of these cases, the hard work is performed by willing partners to the slavery. * Opium: Your slavers give their slaves opium before harvesting to reduce the pain. But as the slaves grow addicted to it, they look forward to the harvest to get their next fix. Eventually, they become willing participants in the system so they can get their next hit of opium (or heroin, depending on where your drug making is at). All these ideas can be combined with each other and integrate into a sort of slave industry. A mere 30 slaves is a paltry number, and the same system may utilize mer-slaves as labor, with scale-harvesting used as punishment (akin to whippings). ]
[Question] [ In short what effect would thrust induced pseudo-gravity have on the atmosphere of a sealed cylindrical habitat that was already generating spin induced pseudo-gravity? Assume that the thrust is along the axis of rotation of a standard [Type III O'Neill Cylinder](https://en.wikipedia.org/wiki/O%27Neill_cylinder#Islands) and that for the sake of simplicity there are no bodies of liquid water on the inner surface, as a concession to Moving "Day". The "Day" will last for at least a week and up to several months. What happens to the atmosphere and thus the functionality of the internal ecology of the cylinder? I was originally thinking about a situation in which the spin gravity and thrust were both one gee but if there is a rate of acceleration at which the effects are small enough for a mature ecology, including climax temperate rain forest, to survive the time trade off might be considered worthwhile so other thrust ratios are worth exploring. [Answer] The main problem will not be what happens to the air. Yes, it will move towards the rear, with a downward pressure gradient towards the front. Unless the cylinder is really long, the air at the front will still be of breathable pressure. On the Earth, air pressure halves for every 5 km altitude, and we would expect the same gradient even if the 'gravity' is thrust-based rather than mass-based (I believe Einstein showed that there was no difference between the two). So if the cylinder is 5 km long and the acceleration is 1 g, pressure at the front will be half of what it is at the back - which, in turn, will be higher than the normal inside surface pressure. The pressure at the front may even be higher because the rotation stirs up the air, and in the worst case, you could pump air from the back to the front. A greater problem is that the overall pseudo-gravity will not be at an angle to the surface of the cylinder - 45 degrees, if thrust and rotation both provide 1 g of acceleration. Streets will become steep slides and parks steep hills. Dirt may come lose and cause massive earth slides, and tall trees would topple overunless secured. Animals would find it hard to keep balanced and will be very disoriented by the shift, All loose objects will roll towards the rear of the cylinder. Wind and rain patterns will be severely disturbed in ways that may be hard to predict. Lower acceleration will certainly mitigate the problems. An acceleration of, say, one-quarter g would make the apparent slope far less steep and the pressure gradient far lower. Steps could probably be taken to minimize damage; for instance, houses may rotate to keep their floors 'horisontal' ]
[Question] [ I'm waving hands a fair bit here, and I am doing that because I believe that it is internally coherent, so if you accept these things, you shouldn't need the story to suggest answers. I'm including as much information as I think is relevant, but trying not to give more than is helpful to answer the question... Hopefully I did ok, lol. So... # Here's the premise: There exists a species of creature that travels through spacetime by manipulating multiple dimensions. This creature was spawned into the three spatial dimensions on a [near-mid-Miocene-Earth](https://www.sciencedirect.com/science/article/abs/pii/S0031018217306041), matured into more dimensions, and left once mature. Like a salmon returning to its spawning grounds, the creature has returned, and is pregnant. In this near-Earth's prehistory, the arrival of this creature's parent is why the mid-Miocene became so hot, and the departure of this creature and its spawn-mates is the triggering event that led to the gradual cooling of the planet, and thus the mid-Miocene extinctions. When this individual returns to spawn, it finds the current climate unsuitable for spawning, and so it engages in "nesting" behaviors that would result in a return to a climate more like the one it was spawned into. I have posited that some nesting behaviors of such a creature may include triggering continental drift to change wind and temperature behaviors (like the ones that made the plains and deserts, the seasons and trade winds of today), similarly to contribute to seismic activity, to both trigger volcanic eruptions as well as earthquakes which could shift carbon deposits to the surface where they could be returned to the atmosphere more easily... # Here's my question: How could it make sense that the creature causing earthquakes, moving the continents, and changing the winds could also affect the perception and behaviors of the creatures alive on the planet? What abilities might such a creature have that would cause animals, including and especially people, to engage in behaviors that would potentially cause disruptions (maybe like war, drilling, industrial manufacturing, making a lot of plastic, burning fossil fuels, etc.) that would potentially accelerate the nesting (that is, shift the climate towards a mid-Miocene-like climate) less directly than blowing up a megavolcano (like what occurred in the mid-Miocene). I've thought of things like the [fungus that causes ants to climb up high and hang on and then explode into spores](https://www.livescience.com/47751-zombie-fungus-picky-about-ant-brains.html), creating conditions suitable for its reproduction - and the brain parasite that reproduces in the digestive tract of cats [causes mice to be less afraid but makes people more likely to be in a car crash](https://www.livescience.com/can-cat-parasites-control-human-brains.html), and even the extra-hand-wavey direct psychic manipulation. NB: This entity should not be overtly malicious, it's just trying to make its nest, it is intelligent, but is either unaware or otherwise uncaring about the fate of the other inhabitants of the spawning grounds (in this case, Earth) in the same way the aforementioned salmon would be unaware or uncaring about what the other fish in the river are doing - they're either food, competition, a means to an end, or completely irrelevant. Thanks for sharing your thoughts! [Answer] Absolutely nothing... or just add lead If the Great Old One is changing climate patterns to increase desertification and Earth technology is unable to locate / identify the culprit due to its 11 dimensional nature then no further action is required to get humanity to make things worse. Given the responses by some sectors of human society to COVID-19, the sequence of events will go something like this: 1. Drought results in widespread crop failure / livestock deaths in areas that do not have experience with this (ie not Australia). 2. Scientists are unable to establish the cause of the effect. (This is not necessary, but makes step 3 easier.) 3. Amoral politicians in adversely affected country seize opportunity go grab power, use social media to blame it on their scapegoat country / racial group of choice without any supporting evidence. (Possibly they simultaneously deny its existence and blame another group for the disaster, given recent history.) 4. War initiated to secure food/water resources, regardless of cost/benefit of securing resources some other way. Alternatively, war motives are independent of resource dependency but are ostensibly retaliation for the supposed "enemy action" taken originally. (Along the way, secure future resources, "historically included" territories that the nation never actually controlled etc) 5. Increased manufacturing, testing and use of war materiel increases rate of climate change, especially as requirement for rapid increase in production favours use of fossil fuels rather than sustainable alternatives. (Powering forward operating bases in hostile territory is much more easily done with fossil fuel-powered generators than wind / solar farms. However, if relying on normal human behaviour is too passive for the Great Old One, then distributing particulate lead (Pb) into the atmosphere will have serious effects on the mental capacity and stability of humans and (presumably) other animals. [Lead poisoning](https://en.wikipedia.org/wiki/Lead_poisoning) is immediately detrimental to the brain before other organs, with disturbing long term effects postulated in the [lead-crime hypothesis](https://en.wikipedia.org/wiki/Lead%E2%80%93crime_hypothesis). With regard to animals, lead can be used to disrupt ecosystems. For example, birds are notably vulnerable to lead poisoning, especially birds at the top of a food chain. Combine lead poisoning with plagues of [mice](https://en.wikipedia.org/wiki/Mouse_plagues_in_Australia) or [rabbits](https://en.wikipedia.org/wiki/Rabbit_plagues_in_Australia) and the avian predators best able to combat the plague will be the first to die. (The linked articles are for Australia but the principle holds true elsewhere.) The brains of animals that don't die of lead poisoning are likely to be negatively affected in the same way that humans are. TLDR - human stupidity and social media use can probably be relied to make things worse on their own, but adding lead will make both us and animals react even more stupidly to the crisis. [Answer] The Earth is a bower. [![bowerbirds](https://i.stack.imgur.com/2a5XF.jpg)](https://i.stack.imgur.com/2a5XF.jpg) Consider the bowerbird. Here are bowers made by the Vogelkop bowebird. Each is made by a male to impress the female with his art. They are different but not radically so. The bowerbird male knows what a bower should look like. He knows the general color scheme that the ladies like. And then he improvises with materials he can find, and his own aesthetic sensibilities. He is moving towards a pleasing end result and he is flexible and creative in his methods. Your multidimensional creature is making a bower out of a planet. It is flexible in how it accomplishes this. It needs to be a certain temperature but that is just one crude aspect - there are many, many other aspects, some of which human minds cannot get around. These creatures have godlike powers to affect planet inside and out, the creatures on it from microscopic to macroscopic. They can influence and change variables we did not know were variables. Your creatures do not just do one thing and get the end result: heat. It is like saying the bowerbirds make a mound of hay and a pile of stuff. The whole thing is meticulously arranged - for the birds and for your deity-level creatures. It is doing it to impress and an artfully accomplished end result is more impressive. The Miocene earth bower worked well and reproduction happened. The current creature might be the same one as before, or its descendant and it is making another bower. It will work with whatever is available and in the present there are new things. Given the chance, real bowerbirds will readily incorporate man made items if they are the right color and shapes. In some places bowers might be decorated entirely with plastic. Your multidimensional creatures readily accept the human occupants of Earth as participants in the construction of its bower. Unwitting participants. The creature can influence humans and society in many ways and on many levels all with the same end goal: the beautiful bower. [Answer] # It's the magnets, baby This creature can not only sense magnetic fields directly, it can interact with them directly. So, it experiences the planet as a solid surface above which lies a dense atmospheric soup, upon which is super-imposed an even deeper soup: the planet's magnetic field. It is driven by deep-seated instinct and powerfully-felt urges (which it may or may not recognize as such) to create a comfortable space within this environment. Imagine cleaning a standard metal kitchen whisk. A lot of whisks are constructed of a series of identical, long, metal loops, rotated around the implement's long axis: [![Metal kitchen whisk](https://i.stack.imgur.com/UUTgS.png)](https://i.stack.imgur.com/UUTgS.png) You can grab some loops and push them to the side to clean them (although they spring back once you let go). That's kind of what the planet's magnetic field is like for this creature: first, it pushes some loops out of the way so it can descend to the planet's surface, where all nice warm soup is; the loops spring back into place. Then it starts pushing loops around, holding them in place with its strength and bulk, to set up a comfortable nest. This has some interesting effects: * it applies [magnetic braking](https://en.wikipedia.org/wiki/Magnetic_braking_(astronomy)) to the planet's core, which can lead to tectonic effects as the core's motion slows relative to the mantle * it weakens the protection from solar radiation that is ordinarily provided by the planet's magnetosphere; this could permit the solar wind to strip away the planet's atmosphere faster, and it could lead to more cancers and mutations in living organisms on a faster-than-geologic timescale * it directly influences the behaviors of native creatures that can sense magnetic fields, like birds, and creatures that use tools to sense the field, like humans ]
[Question] [ An Englishman by the name of John Atkinson Grimshaw was known only for his nocturnal paintings of the British landscape. [![enter image description here](https://i.stack.imgur.com/HBKHs.jpg)](https://i.stack.imgur.com/HBKHs.jpg)[![enter image description here](https://i.stack.imgur.com/ostuy.jpg)](https://i.stack.imgur.com/ostuy.jpg)[![enter image description here](https://i.stack.imgur.com/MDU3M.jpg)](https://i.stack.imgur.com/MDU3M.jpg)[![enter image description here](https://i.stack.imgur.com/uH1VQ.jpg)](https://i.stack.imgur.com/uH1VQ.jpg) I don't know about you, but his nocturnes have struck me as a bit...*bright.* Way brighter, in fact, than moonlit night in real life. So let us imagine instead that these paintings represent daylight on an alien planet. In which case, what sort of star would create this sort of brightness presented in the paintings? [Answer] Well, to be honest those paintings reminded me of a very close scenario: a sunset on Mars, as seen by Curiosity [![enter image description here](https://i.stack.imgur.com/q30CS.jpg)](https://i.stack.imgur.com/q30CS.jpg) If this means that John Atkinson Grimshaw was on Mars or maybe was a time traveler I don't know, but the resemblance between the paintings and the picture is flabbergasting. [Answer] A White Dwarf A white dwarf is two things: dim and hot. * Dim is required to get the low light level you're looking for. * Hot is required to provide the energy needed to sustain life. Oh, there are some complications with this lovely mess. Such as life on a planet that isn't as dependent on photosynthesis (far fewer photons hitting this planet!) as Earth is. And all creatures great and small would likely develop large, Anime-style eyeballs... But that wasn't what you were asking about anyway! Am I right? ]
[Question] [ This is the sequel to [Figuring Out Giganto](https://worldbuilding.stackexchange.com/questions/201703/figuring-out-giganto) and covers the potential adverse effects of Gigantis, namely excessive size. You see, Gigantis defies the square-cube law, allowing for the strength of a Giganto's body's support systems (muscle, bone, thermoregulatory and circulatory/respiratory systems) to increase proportionately with size. It also keeps speed and metabolism the same as size increases. (Look at the question for greater detail.) However, this allows it to grow to ridiculous sizes, becoming stronger and tougher as it grows, until it's about the size of a mountain. I don't want that. Contrary to appearances, I want the humans in my setting to live, which is why I made Enchantments a thing. Thus, something has to keep Gigantos in a reasonable size range. My current ideas are: 1. Parasitism: Eating a creature gives you its Enchantment, so logic follows that if you eat part of a creature, you gain part of its Enchantment. This means otherwise innocuous parasites, leeching off a Giganto's body, will also be leeching off its magic and therefore inhibiting its size. If what I've heard about smaller theropods eating off sauropods, essentially acting as large parasites, is true then [Chompers](https://worldbuilding.stackexchange.com/questions/199981/making-a-predator-for-chompers) and [Plop](https://worldbuilding.stackexchange.com/questions/199866/creating-a-predator-for-plops) could fulfill this function, gaining their growth abilities from Gigantos. 2. Predation: The larger a Giganto, the more Chaos Energy it has. Chaos Energy is the force behind leveling, the stuff that fuels Enchantments, so magical creatures (AKA monsters and adventurers) will be drawn to Gigantos, especially powerful monsters that take more CE to level up. Thus, it's not that they can't become bigger, it's that they don't because the big guys always get killed and/or eaten before too long. However, this could easily backfire; Gigantos are conscious of their own Enchantment, they know what it does, so it makes sense that young Gigantos will try to hunt down and eat older, bigger Gigantos so they can get just as big and strong, and vice versa. This predation would thus be counterproductive, as it would allow Gigantos to become even bigger than a mountain. 3. Parenting: Hatchlings and young Gigantis are relatively small and weak compared to their adult selves, so it seems that predators would target them. Thus, Gigantos need to reach a large size, namely 5x larger than a meter long hatchling minimum ASAP before they can be realistically safe. There are only two solutions for this: one, the Gigantos vigilantly defend their offspring, even with their very lives, or two, one or both of the parents gets eaten by said offspring. One comes with the issue of granting Gigantis to whatever killed the parents, making parental defense effectively useless for my purposes, and the second seems counter to natural selection. I know some insects pursue similar strategies (one word: [matriphagy](https://en.wikipedia.org/wiki/Matriphagy#:%7E:text=Matriphagy%20is%20the%20consumption%20of,well%20as%20in%20caecilian%20amphibians.)), but why would mutant theropods do the same? Thus, because I am at my wit's end here, I am asking: What Strategy Would Best Keep Giganto Size In Check? Specifically, which strategy would be most efficient and create the least amount of dangerous (as in dangerous to medieval Europeans) monstrosities? [Answer] Their muscles and bones keep getting stronger to support their cubically-increasing weight, but the Earth sure doesn't. Take a page from buildings. Extremely large and heavy objects without robust foundations or large surface areas making contact with the ground will eventually sink, particularly if the ground is very soft. (If their proportions remain the same, then doubling the size and octupling the weight of a Giganto doubles the pressure its feet exert on the ground.) Thus, the only Gigantos that are seen running around are those that are still small enough to go out and hunt their food; once they get too large, they inevitably get trapped in bogs or other wet ground at some point in their life, and die of suffocation or starvation. ]
[Question] [ Piggybacking on the previous “Reef World” questions. Let’s talk Flora and how it adds to life and the environment on Reef World. The entire planet is mostly covered in shallow ocean, but not completely. There are some depths, but the tectonic activity is pretty much done. There is one last massive Olympus Mons type volcano spewing out the planets remaining inner heat, and the core has slowed down and become a large nickel iron ferro-magnet. Free roaming islands of Pumice float around closer to the volcano, but they don’t last long. Even though unknown substances within the pumice islands (we’ve taken to calling it Wavnium) keep them afloat longer they still crumble apart after enduring months of rough seas. But during their time the Wavnium makes them quite large before they fall apart. This gives them the “ability to absorb [and distribute] many potentially advantageous elements/compounds. For at least these reasons, astrobiologists have hypothetically proposed pumice rafts as an ideal substrate for the origin of life” (<https://en.wikipedia.org/wiki/Pumice_raft>). The reef throughout the planet benefit from this. These alien version of Coral create Reef that are more robust than Earth counterparts. “Sea grasses live in between the coral reefs, and they transfer nutrients to the coral. Their roots are adapted to keep the plant in place during strong ocean currents. When the sea grass dies it helps to create future plant growth. Mangroves grow [on and up from] the Coral Reefs. They grow above the sea water, and their roots protect from the sediment overpowering the coral (<https://coralreefbrawner.weebly.com/plant--animal-adaptations.html>). There are areas of Sargasso, and Kelp forests as well, in competition with the Reef and Mangroves. "A continual drizzle of dust falling from planetary rings seeds the oceans with ample nutrients." We theorize there may have been a small moon in a very low orbit that crumbled apart just below the Roche limit some time ago (potential source of Wavnium?). The air on reef world is breathable because there are cyanobacteria and multicellular organisms like the Coral, and fish equivalents. These Mangrove forests are also part of producing air. p.s. The gravity of the planet is lower than Earth but greater than Mars, and well within the escape velocity to retain an atmosphere and oceans. Is this flora set up possible, and beneficial to habitability, both human and/or native? [Answer] ## A few Thoughts: Your question is a little open-ended, so I'm going to give an open-ended answer. Hopefully it gets to the spirit of what you're looking for. Just a thought. You like the pumice island idea, so maybe a native plant-organism has evolved to deposit a waxy coating on the pumice, intercalating pumice islands into a sort-of matrix of wood and pumice lumps. It would form the basis of a much longer-term floating island. Possibly sink 'anchors' (modified roots) to keep the islands from floating away, and then using the roots to mine the seabed for nutrients and help overcome the need for constant sediment washing. Willk is right that there would be strong winds. When the islands run out of nutrients, they 'raise anchor' and float elsewhere. You might also get around the nutrient problem in the same way a forest does, with a fungus-like organism that digests the rock and sediment, and then has a symbiotic relationship with a carbohydrate source like an island-tree or floating plant. The abundance of sediment and great depth of ocean make evolving such a relationship trickier on Earth, but the abundant shallow ocean and lack of sediment make nutrient recycling by a pseudo-protist a much more favorable solution. This also accounts for the degradation of land and atolls. They're like carboniferous wood - digested to free up the nutrients once the appropriate organism evolves. Another solution to the nutrient problem might be a Venus fish-trap. The Venus fly trap isn't digesting flies, it's trapping them to rot, so it can use their minerals. Symbiotic protist-like organism could work with a plant, the plant trapping fish in a net/trap, with the protist digesting the fish, feeding the nutrients back to the plant. The combined symbiotic collective would work like a sponge, or (if free-floating) like a filter-feeding whale. Finally, although it might violate the reef-world theme slightly, why NOT trees anchored on the bottom of the ocean? Rising up like oil derricks, trees could extend out of the water for the same reason trees do on Earth: To outcompete the other plants for sunlight. a floating, anchored plant or deep-water mangrove could, over time, establish a weight-bearing stem and rise up out of the water higher and higher. Such forests would resemble swamp environments, and provide vital ecosystems in the same way mangrove swamps do on Earth. With high winds, strong stems would be needed to resist, and the deep stems & roots would liberate sediments. [Answer] Riff on coral! Sediments will not be as big a deal with no land to wash them out of. I think it would be tough for the poor mangroves. There are going to be serious, serious winds in this world with nothing but mangroves above the water. I think your photosynthesizers should be animals with endosymbionts: coral, sponges and jellyfish. Instead of trees you can have jellyfish that hoist themselves up on high places and put out photosynthetic fronds. If winds tumble them into the water, no harm donw. ]
[Question] [ In my setting the entire world is a vertical wall, so I've been thinking about what might pass for a watchtower in such a setting, and come to the idea of a watchcantilever, a "horizontal tower" of sorts, a protruding (most likely triangular or half-arch styled building) structure with a small outlook post on the end, where one or two people are stationed to watch the surrounding cliff sides for travelers or enemies. But I'm unsure that one with a sufficient length can be built to be used as an observation post. There's The Leaning Tower of Lire problem that gives some insight, but it focuses on an independently laid unsecured stack of blocks. So, using anything that predates the invention of steel construction (steel cables and girders can allow you to reach pretty far I'd imagine), what's the longest structure protruding from a cliff wall can be achieved? Assume no fantasy elements are involved. [Answer] I have sought guidance from Thang Tong Gyalpo and I have another approach for you. <https://en.wikipedia.org/wiki/Thang_Tong_Gyalpo> > > Thangtong Gyalpo (Tibetan: ཐང་སྟོང་རྒྱལ་པོ་, Wylie: thang stong rgyal > po) (1385 CE–1464 CE[1](https://i.stack.imgur.com/mbBej.jpg) or 1361 CE–1485 CE[2]), also known as > Chakzampa, the "Iron Bridge Maker"... and the King of the Empty Plain. > He was a great Buddhist adept, a Chöd master,[5] yogi, physician, > blacksmith, architect, and a pioneering civil engineer. Thangtong > Gyalpo is said to have built 58 iron chain suspension bridges around > Tibet and Bhutan, several of which are still in use today. He also > designed and built several large stupas of unusual design including > the great Kumbum at Chung Riwoche... > > > [![Thang tong bridge](https://i.stack.imgur.com/mbBej.jpg)](https://i.stack.imgur.com/mbBej.jpg) The horizontal rectangles are stone. They are moored by chains each of which is anchored in a stupa on the cliff. Between the stones are planks of wood as shock absorbers so the stones do not rattle against each other. I am sorry I could not make 3d chains that faded into the background; imagine those black triangles as chains. Stone is strong in compression, weak in tension. The stones here are essentially stacked on top of each other, their weight being transmitted in part through the anchor chains and in part compressing the stone behind it. The benefit of this is that it is fantastic yet plausible. A great web of blessed chains extends back from the bridge to nowhere, with the anchor to each in its stupa guarded by three statues. --- The best thing about this idea is finding out about Thang Tong Gyalpo, who really did use iron chains to make bridges that have lasted 500 years. I like the combination of Chod master and civil engineer. Not all Renaissance men were from Europe! [Answer] ## You need supporting structure. You need to understand structure. A Cantilever is not just a structure supported on one end as this forms a weak joint around which it would pivot and collapse, it needs either of the following: 1. A 'Bracket', to support a portion of it in compression 2. A balancing part of the beam to support an equal amount of weight 3. A suspension rod, to support a portion of it in tension So I know a professional structural engineer who once said to me "You should never cantilever a beam more than 1/3 its length". ie. 2/3 of its length is on the other side of the pivot point and this allows for loads. This is 'Option 2' of the above options. I would expect at 20m long timber beam to then be able to cantilever 6m, and hold the weight of 1 person. Alternatively - use a rope to increase this length, or another timber under to form a bracket, and this can be increased. I would expect then this length could be effectively tripled (roughly) depending on the timber used. [Answer] Before steel was invented the only available material for making beams was wood. The length of the longest beam you can make out of wood is limited by the height of the tallest, straight tree you can find around. Stretching it over the tallest tree in the world, you would get to about 100 meter, using as reference [Hyperion](https://en.wikipedia.org/wiki/Hyperion_(tree)) > > Hyperion is a coast redwood (Sequoia sempervirens) in California that was measured at 115.85 m (380.1 ft), which ranks it as the world's tallest known living tree. > > > ]
[Question] [ So, suppose we have a very large island. Exactly how big it is doesn't matter too much, but it must be big enough to support a small country. This is a volcanic island, and the volcanoes on this island erupt regularly and predictably. In this way, lava flows periodically cover parts of the island, enriching the soil with deep-earth minerals and nutrients. Suppose this happens once a decade or so. The people living here know roughly when the volcanoes will erupt, and are able to respond to eruptions by moving to a safe location beforehand, and then immediately farming on the newly cooled volcanic ground to produce extremely fertile farmland. How plausible is this scenario? What mechanism keeps the volcano erupting consistently, and how do the locals know when a given part of the island is about to be covered in lava? How do they know where the safe spots are to wait out the eruption? are there any other details that might prevent this, like toxic gasses? The answer should only use known natural processes. No magic. [Answer] ### Orbital mechanics Every N days, the planet has considerable force applied by some external process. For example a conjunction of the sun and 2 moons such that peak tides and peak stress is applied to the planet. This stress isn't enough to rip the planet apart, its direct force is barely detectable without tools, but it is enough to trigger low-intensity earthquakes, and fracture the solid rock at the top of the volcano. Your people figured out enough astronomy to know that when "these 3 curves intersect - bad things happen.", and can evacuate accordingly. [Answer] Make it a geyser. Like [Waimangu Geyser](https://en.wikipedia.org/wiki/Waimangu_Geyser) but with a period of 365 days instead of 1.5. That would take a remarkably large underground chamber ([illustration](https://en.wikipedia.org/wiki/File:Geyser_animation.gif)), one about 200 times larger volume than Waimangu so maybe 6 times larger in every direction. Depending on your world you might be able to propose some unusual geology that could support such an underground structure. ]

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