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I am writing up a system of wormhole-based gates to allow "fast travel" in a far-future setting. My description is an extrapolation of the way I understand a flatlander's experience of the following illustration of an [Ellis wormhole](https://en.wikipedia.org/wiki/Ellis_wormhole):
Right now, there are the following specific questions that I am not sure about whether my interpretation is correct:
1. Am I correct that there is a maximum "aperture" width at the throat of the wormhole? And that a ship that was too big yet forced itself through would essentially fill the entire throat up, thereby "looping around" in this non-Euclidean deformed space within the wormhole and bump into ITSELF, crushing itself?
2. Am I correct that objects of sufficient hardness (ie. lack of elasticity) would crack/pulverize when forced through a wormhole due to the curvature of the space?
3. If so, would they "resist" going into space with increased curvature before they do? As in, would a diamond inside a ship passing through a heavily curved wormhole (seem to) respond to some force that stopped it from moving further without cracking? Ie. the diamond would start moving towards the back of the ship as the curvature of space pushed back against it harder than it did against the softer materials of the ship.
For completeness' sake, here is the full description as I have it planned right now.
A network of gates spans the known parts of the galaxy. These gates come in various sizes, but are consistently ring-shaped. The rings consist of ancient, self-powering, self-repairing technology yet to be understood by modern civilizations. The area circumscribed by the ring holds a spherical field that appears very much like a soap bubble, with various colorful distortions slowly drifting and mingling. However, unlike a soap bubble, one cannot see through this field; instead the opaque bubble acts as a mirror, showing a reflection of the surrounding space.
What we know of them is that they come in pairs (the matching gate is always of identical size) and function like wormholes. The space between gates features high levels of geometric distortion, but is otherwise safe to traverse without any special equipment.
Because of this geometric distortion, there is a maximum to the size of the ships that can use a gate (which is smaller than the size of the gate sphere). Think of the gates as entrances to tunnels, with the width of the tunnel at the narrowest part being the limiting factor. Of course, within this distorted space there are no walls as such, the tunnel walls simply represent where space starts looping around on itself, and a ship that is too big risks bumping into or even crushing itself.
The geometric curvature of the space between the gates has been and still is an important field of study to ensure the safety of inter-gate travel. Conventional spaceships and most lifeforms are usually not in any danger using a gate, but materials with very high hardness (diamonds and harder) have spontaneously pulverized when transported through gates with relatively high curvature.
As a general rule, the minimum size of a gate is defined by the minimum width of the tunnel and the maximum amount of curvature; the bigger a gate is, the wider the tunnel can be at the same maximum curvature, or conversely, the bigger a gate is, the lower the curvature can be when not changing the tunnel aperture.
The bubbles are theorized to modulate the size and curvature of, and hold stable the wormholes connecting them. Perhaps the civilization that created these gates had ways of changing these parameters of existing gates, but as far as is currently known, gates are static in curvature and aperture width. Inactive and broken gates have been found, some of which had tiny regular wormholes - lacking the distinctive bubble - at their centre.
[Answer]
The wikipedia article already shows a modelled Ellis (traversable) wormhole:
[](https://i.stack.imgur.com/XNzSd.jpg)
I must admit I would have problems to use that thing. :)
But essentially wormholes only exist in dimensions one higher than the dimension in it was created. That means the entry is not a 2D hole, but a 3D sphere, you can enter it from each direction and move out from each direction. Essentially it also makes much more sense than Hollywood wormholes like Stargate:
[](https://i.stack.imgur.com/b1cQ8.jpg)
Because using a plane as separator forces a progression from one side to the other which asks the question how something which passes the barrier is not seperated immediately (one part is suddenly a world away). A correct wormhole **has no barrier**, you can enter and leave it continously at will.
It has boundaries which cannot be violated, so if something is too big, it won't get through (at least not without collapsing the hole). The tunnel itself consists of at least a 5-dimensional entity (yes, literally hyperspace) so if you are inside the tunnel, effects are unknown, but light and matter should pass through and also time is felt normally.
Forget only the thing with the space-time curvature. There is no effect on materials, remember the thing has one dimension more than normal (5-dimensional containing 4D space-time), so it does not restrict anything which is transported. Both ends could be on completely different sets of time and location.
While an Ellis wormhole does not show sign of gravitation because it was specifically constructed to do so, some other wormholes may not be so unforgiving. What a traveller may experience with the curved space-time in the transition zone which creates the dizzying effect is very strong gravitation. So once you get too near to other wormholes than the Ellis case, you will be sucked in literally. Depending on the size and dimensions it could lead to deadly spaghettification or only strong acceleration. The main problem of wormhole traversal will then to get out of the wormhole again.
[Answer]
From the comments on the excellent summary answer by Thorsten S., it appears you still have specific questions: I’ll address just that, without going over the rest again.
It’s generally OK to work in a *flatland* analogy so you can visualize it and make physical models, as with your picture.
There is some question about whether the items in the space perceive the same curvature and distortion that you see from your hyperspace model. The answer is that it doesn’t have to be the same.
Start with a rubber sheet model of a plane. Draw your X-Y grid on it, and this becomes your *metric*. Roll up the sheet and the citizens won’t know or care. Stretch and distort the sheet, and it looks funny to you; but [*the metric* is what controls the experience for those on the inside](http://www.gregegan.net/FOUNDATIONS/02/found02.html). Mr. A.Square’s rulers will stretch by the same amount, and he only cares about the passing tickmarks, *not* how they are seen by you. Picture looking at the plane through a funhouse mirror: it does not affect the plane itself.
Now if you made holes in the plane such that some gridlines were cut, they would notice that on the inside. If you distort the topology of the metric such that [it’s not Euclidian](https://en.wikipedia.org/wiki/Hyperbolic_geometry), they would notice.
In the case of a wormhole, you have a topological feature which restricts how you can draw your metric. Approaching the bridge, you have a choice of having abrupt boundries where gridlines just end, *or* a hyperbolic geometry where [parallel lines get squeezed together](https://en.wikipedia.org/wiki/Hyperbolic_geometry) (the case you illustrate).
Yes an object can be too large to pass and will wrap around so that the right edge bumps into its own left; you could reach out and take our own hand.
Because of parallel lines converge (or diverge coming out) a ship will be squeezed and stretched as the ship’s sides, initally taking parallel tracks, are forced together. A large ship must travel slowly enough to deal with the resulting stresses, and perhaps be built with joints to absorb this!
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**Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers.
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## Introduction
Many videogames and other fictional worlds portray mages or wizards casting personal shields around themselves or in defense of other party members. These are often alike from fictional work to fictional work, appearing as glowing domes or bubbles that wrap around the mage or the target of the spell. Less commonly, magic shields look like glowing shields that are either worn like a normal shield, or thrown up as a barrier against an incoming attack.
These shields act as defensive barriers, absorbing blows that would otherwise hit the target. They typically deplete after a while, and will fade faster under harder and more frequent blows.
## With the advent of more modern weaponry (firearms in particular), how will the shape of a shield effect its ability to deflect high-velocity kinetic projectiles?
**Q1)** Do domes, shield shapes and bubbles make the cut vs firearms based on their structure?
**Q2)** Can anyone tell me if there is a physics-based reason why these shapes/structures might be so popular in the first place?
**Q3)** Is there any way magical shields could be improved by altering their shape/structure alone?
**Please assume** for the purpose of these questions that, for any shield shape:
1. Shields are powered by a depletable resource (such as mana).
2. Shields are entirely defensive in nature.
3. Shields provide a thin, but entirely solid, barrier against physical objects.
[Answer]
Q1) Do domes, shield shapes and bubbles make the cut vs firearms based on their structure?
To examine this, it's pretty easy to look at [breastplate designs](http://cdn.shopify.com/s/files/1/0760/6691/products/823p_1024x1024.jpg?v=1426545523) after firearms became a popular weapon. You'll notice that the breastplate is *not* a simple curve, but has a central ridge. The reason is to try and divert a projectile *from its most probable trajectory*. You're much more likely to be attacked from the front, so having armor in a wedge shape was important to deflect the projectile from the center of the body to the side. This comes at a risk (shots coming from slightly to the side will hit more straight on), but *most* shots *most* the time will have their effectiveness reduced.
Q2) Can anyone tell me if there is a physics-based reason why these shapes/structures might be so popular in the first place?
No, of course not. It just looks cool, and it makes simple sense. Since magical force barriers have never been battle tested, those criteria will determine what's going to be most popular, even if different shapes would actually be more effective.
Q3) Is there any way magical shields could be improved by altering their shape/structure alone?
Absolutely. The problem with a sphere/bubble is that any attack hitting it dead on with have to be *stopped* instead of *deflected*, and deflecting an attack takes a *lot* less force than stopping it. Further, a sphere/bubble with it's center on the person is *most likely* to be head dead on a *lot*, since people will be aiming for... the person in the middle.
So, if the wizard knows where the attack is coming from, s/he can work to deflect it. If you've read any of the *Dresden Files* books, you'll notice Harry Dresden frequently uses his shields in a flat angle to deflect attacks coming from a specific direction. If you're getting attacked from absolutely every direction, a sphere can make *some* sense, but that is rarely the case. This means you can make shields designed to deflect attacks just enough to miss you from the direction you expect.
You can also look at how fortifications changed following the rise of cannons. Straight and curved walls were terrible at deflecting cannon blast, so people started building [star forts](https://en.wikipedia.org/wiki/Star_fort). This isn't a perfect transfer (much of the star fort design is to channel charging infantry into kill zones), but you can see how a modified star shape would be able to more effectively channel projectiles away from your body than a sphere, even when being attacked from every direction. The points of the stars can protect you from side shots that would threaten a simple wedge, and the shots that *do* hit a plane head-on aren't actually pointed at your body, so if they break through you still aren't dead.
The biggest danger with the star shape is the concave points. But, since you aren't actually worried about charging infantry, you can have deliberate gaps here that lead to another *interior* star barrier that still channels projectiles away from your body. That way, there's no point in the shield that needs to *stop* a projectile, just *redirect* it.
[](https://i.stack.imgur.com/U8SYg.png)
Seen here, the circle is the mage, and there are two nested six pointed stars. The best design would require some more design work and careful consideration of the angles (and, therefore, number of points), entry point size, and if projectiles that *entered* the first barrier could be redirected to exit again, instead of needing to be absolutely halted by the internal barrier. But this is a good place to start.
[Answer]
**Everything depends purely on your magical shield nature/properties. By your will it can just destroy high velocity projectiles upon impact or even bounce them back at the attacker.**
Following is written, assuming your magical shield has some properties of material object, otherwise the question of shape is mostly cosmetic.
**A2:**
Spherical shapes are used in armor welding to deflect slashing hits, making them to lose force due to slipping (less force from hit goes directly to armor = less chance to break armor). Also spherical shapes are good to contain crushing blows due to better force redistribution, when directly hit (in comparison with flat armor shapes).
I think this is one of the reasons, why magical shields are depicted spherical along with nature of different forcefields like magnetic or gravitational, which tend to be "spherical":
[](https://i.stack.imgur.com/0bTZl.png)
However even spherical shape can't make a bullet/arbalest bolt slip off a fragile armor due to a bullet's/bolt's high impact force. Making medieval armor, that could make a bolt slip was nearly impossible as there were no materials both hard and light enough to allow a soldier to fight efficiently, while wearing one.
*Here could've been some references about "perfectness" of spherical shape in geometrical sense and about spherical shape, met in nature (such as planets shape, shape of the falling waterdrop, etc.), however I'm unable to find good articles in English*
**A1:**
Yes, but only if the material has enough hardiness to stop the bullet. However I can't tell for sure if word material is appliable when talking about magical shields.
With enough hardiness shape will actually play a role: spherical shield should be used when you want shield user to avoid being hit at less cost (less direct force applied to shield), while flat should be used, when you actually want to stop the bullet (avoid ricochets).
**A3:**
No, the sphere is perfect in all cases, unless your magical shield has some "magical" restrictions (like bigger energy consumption per square inch of it or less shield "density" with bigger shield area).
P.S.: Sorry for bad English. Any help with grammatically improving this answer is highly appreciated.
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From 359 to 298 million years ago, the "Carboniferous Coal Swamps" dominated the continents.
[](https://i.stack.imgur.com/VmSZb.jpg)
It was the Carboniferous coal itself that sparked one of the greatest watersheds in human history--the Industrial Revolution, spanning from 1760 to either 1820 or 1840.
[](https://i.stack.imgur.com/wThND.gif)
60 million years of dead plants solidifying into coal had fed an age of revolution in Europe. It is surreal to comprehend...
In this alternate scenario, the Industrial Revolution began in China, around the 1330s CE, after the newly appointed emperor decreed an end to the old ways (Daoism, Buddhism, etc.) in favor of a future of progress. (Picture a medieval Mao Zedong.) It wouldn't be until the 15th century that China would decree expanding and updating trade by inventing rail transportation, starting with a railroad starting in Beijing, crossing through the wilds of Mongolia and Russia, then dividing Europe in half before bridging the Strait of Gibraltar to Africa, cutting off the rock of North Africa and the sands of Israel, Syria, Iraq and Iran before crossing through India and finally completing the circle right to where it began--Beijing. When the Asian and European migrants colonized the New World, they'd take the Industrial Revolution technology with them. This alternate Industrial Revolution would end sometime in the final legs of the 19th century.
It's not just the length of the Industrial Revolution that's being augmented. It's the **scope** as well.
[](https://i.stack.imgur.com/wuW05.jpg)
[](https://i.stack.imgur.com/bMv3X.jpg)
[](https://i.stack.imgur.com/eGhAC.jpg)
[](https://i.stack.imgur.com/FXrBg.jpg)
[](https://i.stack.imgur.com/7Jni0.jpg)
[](https://i.stack.imgur.com/SeOhL.jpg)
These paintings don't show any ordinary Victorian fantasy. This is steampunk, and one of its most popular features are larger, grander buildings and boatloads of airships. In steampunk, the sky really is the limit, but its scope can't be realistic if the coal swamps of deep time lasted only 60 million years.
So what geological point of departure would I need to give Planet Earth enough coal to feed an Industrial Revolution of the length and scope proposed above?
[Answer]
It's not that you need more coal. Hundreds of years after the start of the industrial revolution, and the world still isn't particularly close to running out of coal, even after long term increases in consumption. What you need instead is a lack of availability of other fuels-- no oil, no gas, no hydro, solar, etc as realistic options. Because oil and gas are produced mostly in the oceans, you could have a world with minimal tectonic plate action to move land to where the oceans used to be. Hydro power and wind will be developed as soon as the coal-fired generator/electricity itself, but these technologies, as in our world, could easily be too rare/expensive to develop on a large scale. Nuclear power of course can only be developed once atomic physics is well understood. All of this leaving a world dominated by coal.
There's only one problem. China and India are huge coal users in our world, but they don't have steam powered trains. They use coal for electricity generation. How are you going to prevent this from happening? Perhaps the coal in your world is very clean-burning, so there is no incentive to switch to electricity from the steam- powered model.
[Answer]
I'm thinking Money might be more important than Coal.
We make the changes we do primarily because it's either more successful monetarily, or more efficient in terms of labor. the later flows right into the former.
So if we got to some handwaving point where an external combustion, coal burning steam engine remained the cheapest and most efficient way to do things rather than processed petroleum, you would get a longer lasting steam age.
Maybe you could kill off a few key scientists like Otto, and drive Lenoir insane. While you are at it, make Edison not a jerk, and give Tesla more business sense. Have Wilbur Wright run over his brother in a tragic bicycle accident.
Make Helium more plentiful and available for airships. Or at least changing the doping method for a hydrogen gas bag. Zeppelins were expensive, but they would remain viable as long as fixed wing flight is delayed.
Finally, make the Babbage thinking engine work, and work well.
**In all of the above things, you would be retarding the growth of those technologies that displaced a lot of the stuff that we think of as Steampunk, while at the same time keeping the older tech economically viable**
Bonus points if you identify some prominent Art Deco architects, have them start their own influential schools, and make them even more successful. Them and the guy who designed all the wonderful radio cabinets from the 20's and 30's.
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Noting that
[this question](https://worldbuilding.stackexchange.com/q/56243/885)
is specific to *human* colonization, and Thucydides’s answer is explicit that driving concerns are *to support life*, and I notice that the story I’m working on turns this on its head because the [premise is different in a fundamental way](https://worldbuilding.stackexchange.com/questions/51078/why-build-a-datacenter-with-an-awsome-view), I thought I'd ask a new question with this difference:
As a **post-human** culture emerges and finds its need for resources potentially growing by orders of magnitude *and* it is freed from many of the issues of needing to support fragile flesh, it naturally expands into space. (See [this question](https://worldbuilding.stackexchange.com/questions/51746/when-will-uploaded-minds-be-a-reality) for timeline.)
My plot has development driven by a Great Goal of launching an interstellar mission on a deadline, but before that expansion into space has already started.
What order would they do things in?
Other than the quest for resources to eventually build a new civilization, and the general desire to get away from the politics and economy of Earth, one goal relevant to the early part of the plot is scientific knowledge: [build a series of telescope modules](https://worldbuilding.stackexchange.com/questions/45756/how-big-can-we-make-a-telescope) that will be farther out from the sun than Jupiter.
[Answer]
Currently I can’t picture the whole process, but I can tell you that one of the first objectives will be the moon colony.
The idea is that you can have frequent flies from Earth to the moon with technology A which is designed to enter and exit Earth atmosphere, and then have ships build technology B that is designed for longer space travel but not really for Earth reentry.
Here is where I’m unsure, because the question seems to suggest that resources are not really an issue: after the moon colony, you could try to use those ships to send robots ahead, not for exploration but for mining and building – mars and the asteroid belt seem to be good targets for prospection, there is a chance they’ll discard mars depending if the gravity well is worth the minerals.
Either way, future manned mission would be building and launched on space.
[Answer]
In terms of order, I am going to make the assumption that the development of post-humans and strong AI happen during the period when humans are colonizing the Solar System. This is plausible since we currently do know how to move and settle the Solar System with only small extensions of existing technology, while we still have no clear idea of how things like uploading, AI or biological post humanism would work.
In terms of "Where" and "When", I suspect the post human will choose Jupiter as the locus of their settlement and civilization. There are many factors which will drive this:
1. Energy. Regardless of how beings work, they will need energy for their life processes and technologies. Jupiter has both an immense amount of energy close at hand (the flux tube between Io and Jupiter is essentially an electrical circuit with 2 trillion amps of current) and more importantly a large number of heat sinks. The oceans and ice moons orbiting Jupiter can serve as vast heat sinks for factories devoted to building data centres, and the computers can be exposed to the cold of space. Mercury has much higher energy density, but is a very hot environment, while Uranus may be far colder, but energy production is limited by the need to build and operate fusion reactors "burning" 3He.
2. Building materials. The Jovian system has 67 moons in close proximity, and thousands of Trojan asteroids, providing a huge trove of materials to build communications infrastructure, computer matrix substrates, radiation shelters and all the other infrastructure needed for post human "life". There will most likely need to be a very complex technological "ecosystem" to support advanced post human life, much like a major city on Earth needs a complex market and infrastructure to allow so many people to live in close proximity.
3. Proximity. Since post humans, downloads and AI's will be thinking thousands to a million times faster than human brains, latency and proximity is an issue. The distance between the Earth and the Moon is only 1.25 light seconds, but for a 1,000,000x faster uploaded being, that might be a subjective week. Beaming information or uploads across the solar system would be incredibly painful for these beings, since they will be taking decades or centuries of subjective time during the trip. If physically flown across the solar system, where it might take years for any realistic spacecraft to cross the gulf, thousands of subjective years could pass. Dying of boredom could become an actual cause of death in these circumstances. The 67 moons of Jupiter, in contrast, are only light seconds apart, so a rich and incredibly diverse culture could arise with 67 or more distinct "worlds" only a few weeks apart from each other from the POV of the post humans.
So once post humanism becomes possible, I could see a movement by the post humans to bring their physical bodies to Jupiter and initially settle in existing infrastructure. Since they will be thinking and working much faster than the existing human population, they will rapidly "explode" across the Jovian system, initially claiming uninhabited moons and building space infrastructure until they are by far the majority in system. The Humans will probably be allowed to stay, since they pose no realistic threat, and are being massively outcompeted for resources anyway. If the humans choose to stay, they will be confined to radiation safe zones like bubble cities driven into the ice of Ganymede, otherwise the humans might gradually choose to move back to the Solar Zone between Earth and Mercury (where it is too hot for massive computer data bases to function effectively), or to deep space where the post humans might die of old age or boredom before being able to arrive.
[Answer]
It is reasonable to assume there will be a fair amount of technological infrastructure installed in the solar system prior to post-human colonization. What is often overlooked is that automated and cybernetic machines will be the vehicles and industry occupying space and objects in the solar system.
The post-humans may not colonize various bits of solar real estate, but they may exploit their resources via self-aware and self-directed machines. Once they created more than sufficient infrastructure, the post-humans will take up residence in the more desirable parts of the solar system.
Post-human colonization is likely to proceed in terms of accessing the mass and energy they need to further construct and expand their occupation of the solar system.
The Moon and near-earth objects (NEOs), basically asteroids, will be initially the sites of solar power arrays, automated mining machinery, and mass-drivers to ship out material. No post-humans need be on site. A combination of AIs and remote control can do the job.
Next go inwards for energy and more mass. Mercury is believed to be rich in minerals and metals. Close to the Sun there will be solar power to burn. (Apologies for the demotic turn of phrase!) Venus can be harvested for carbon-based material. Floating structures will be used both as infrastructure and possible habitats for post-humans. The view will be spectacular. Both planets are energetically easier to get to, than going further outwards.
The next phase of colonization will be the planets Jupiter and Saturn and their attendant moon systems. The first wave will always be AI controlled systems to establish the basis of later industrialization, habitats, and colonization.
Both planets and their moons are rich in valuable and usable resources. Water, deuterium, carbon, oxygen, nitrogen, aluminium, and silicon. Also, it's hard to imagine any colonization would ignore Titan as it has to be the most Earthlike world, outside of Earth itself, anywhere in the solar system.
One problem in deciding the order of a post-human colonization of the solar system would proceed is that much of it will happen simultaneously and there will be considerable overlap in their settlement. This could happen to such an extent that the colonization might not proceed in any specific order.
For example, the exploitation and utilization of asteroids will start early with NEOs and then gradually continue to embrace the asteroid belt proper. It may be continuing to expand while the gas giants are being colonized.
Also, there is a degree of undecidability in knowing the impact of the plot driver for the Great Goal of an interstellar mission. But yourself as the author will have to make that decidable.
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I'm trying to create a habitable planet but with a low atmospheric pressure, similar to Mars. But instead with 15 percent of Earth's atmospheric pressure, what traits can I give my animals so they have the best chances to survive? If the atmospheric composition is about the same as Earth and orbiting a star like the sun at the same distance, it also has only 51% of Earth's gravity. Also 60 percent of its surface is covered by water.
Some other details about the planet,
Distance from primary star - 1 AU
Star - Sunlike
Mass - 0.14949 (M⊕)
Diameter - 6881 km
Gravity - 0.51 g
Oceans - 60% surface coverage
Atmosphere - Earthlike
Density - 5.25 g/cm3, slightly higher than Venus.. Hopefully this unusually high density for a small terrestrial planet is enough to generate, at least, a weak magnetic field, similar to Mercury maybe!
[Answer]
Lower atmospheric pressure equals a lower boiling point for water. Possible lower night temperatures, though will still have to consider the thermal stability due to 60% water coverage, also cloud coverage too will have an influence.
Lower gravity will favour hopping animals like hopping mice, kangaroos & wallabies. Flying animals may be hampered by the lower air density, while the lower gravity will make it easier to get off the ground. Arboreal creatures will do well due to the low gravity. Gliders might have a tough time due to low air density. Swinging & springing critters should do well in the trees.
Expect more amphibians. The lower gravity will make the transition from water to land easier.
These are a few suggestions. You may find it worthwhile to do research into [biomechanics](https://en.wikipedia.org/wiki/Biomechanics) when designing your creatures. There is a good starting [text](http://www.sciencedirect.com/science/article/pii/S0960982205009012) by R. McNeill Alexander who is an expert in animal biomechanics.
## REFERENCES
Alexander, R.McN. (1983). Animal Mechanics 2nd Edition (Oxford:
Blackwell).
Alexander, R.McN. (2003). Locomotion of Animals (Princeton: Princeton
University Press).
[Answer]
* No birds or other large flying animals. At 15% of Earth's atmospheric density, there is no way Earthly or similar birds would have a chance. On our Earth, birds at least have a 1:2 ratio of body length : wingspan. On your planet, the ratio would perhaps be at least 1:10 or so, which is rather impractical to manage. However, you **may** have some small (sparrow-sized) birds with 1:4 body shape which can manage flight by extremely rapid wing flapping.
* Land living animals would probably have weaker/lighter skeletons as compared to Earthly animals, since they would not have to support themselves against such high gravity.
* Ears would be far less important for animals' survival as compared to Earthly animals. Sound travels in a medium and when the medium is 85% thinner than Earth's medium (atmosphere), sound would travel much slower and have much lesser amplitude, making ears less useful.
* The sense of smell would have greater emphasis. Odors also travel in the air and a very much thinner air would imply that odors would not fade out as quickly as they do on Earth, since the diffusing medium would be very much thinner.
* Similarly, vision would be very much enhanced. Forgoing the fact that the visual range would be very much reduced due to the smaller size of the planet, all things would be seen very clearly with virtually no haze effect at all, even for very long distances.
[Answer]
Lot's of great possibilities.
Locomotion:
Smaller animals could have small wings, or winglike structures (think flying squirrel). Floating animals (filled with gas) could use that gas for propulsion, like attitude jets on a space craft (and they would not have to be located only at front and rear, you could have a gill-vent for turning, etc.)
Considering your planet's 60% water you could reasonably have amphibians who could fly in the air and use the same wing/fin / propulsion combination to move about underwater.
Predators: would have to be fast and accurate - think moray eel, both in and out of water. So their prey would have to be faster and smarter and trained from birth (or have genetic memory) for evasion.
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Humanity is an advanced civilization, and has long, long since took to the stars. Their resources are seeming boundless, and their technology is fantastic. For some reason beyond our 21st century understanding, they have decided to perform a very odd experiment. They wish to create a world and strand a few ten thousand brainwashed members of their own race on it, and see how they evolve as a society. The members will have no memory of humanity's past, but will have basic skills (a common language, understanding of simple machines, agriculture, animal husbandry, basic construction, tool making, etc., placing them on par with barbarian Europe during the early medieval ages. They want to watch humanity develop on a planet of the following description:
* Earth like as possible (similar climates, weather patterns, resources, gravity, although it doesn't need earth-like geography, as in the shape, nature, and location of landmasses)
* Physically and structurally stable
* Hidden in its man-made nature enough that it will remain unknown that it was man-made until at least the society reaches early space faring technology (such as what humanity reached in the mid-to-late 20th century)
* **And as absolutely large as physically possible**
...And they're willing to build this world from scratch.
By no stretch of the imagination does this world need to be a planet in our traditional sense; it's perfectly acceptable for it to be an artificially created structure. The magnetic field this new planet possesses doesn't need to be created by a molten core. In fact there doesn't need to be a core at all! It's even been suggested that making the planet hollow (if such can be engineered, and complications like affected gravity can be dealt with) might allow for a much larger surface area.
In the end the planet just needs to seem like a natural Earth-like planet up until at least the predescribed point in the developing society's future. It's also worth noting that this developing society has no point of comparison as to what a *natural* planet actually looks like, so as long as it doesn't affect the development of the society they could stumble upon some (hidden) artifacts of the planet being hand-crafted.
Again, humanity has seemingly endless supplies to throw at this project, are in no particular rush to need it completed (a few generations' put towards this effort are perfectly fine), and have extremely advanced technology. However they are still constrained by the laws of physics as we know them.
What would this planet be like to achieve the predescribed goals as closely as possible? What solution might humanity use?
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A Shell World.
<https://www.youtube.com/watch?v=TfMr_XkWcEs>
As Isaac Arthur explains in his video, you can build it **as big as you want** and the amount of filler material is proportional to the surface area, so its density goes down as the size goes up. You use one megaton of matter per square foot of surface, for Earth-normal gravity.
You could have a thick crust with fake geology and places to mine things.
It's not until they develop advanced technology that they will detect that the world is hollow and has a dynamic support structure under the crust, just as we figured out the insides of Earth. They may be puzzled when developing theories about planet formation and long-term state, though.
On Earth, note that for most of history people thought the planet *was* “made”, and only started to admit natural processes as distinct from supernatural when they started figuring out the details of what makes it tick. So your postulated people will always assume that the gods made it or something like that.
So I think what you’re asking for is that naturalness is faked, and the equivalent of our geology and scientific inquiry [from the 17th](https://en.wikipedia.org/wiki/History_of_geology#17th_century) through early 20th centuries would point to a natural origin, and only more advanced technology reveal the deception.
I think making it unnaturally large would put a kink in that. The density is not what they would expect as they came to learn these things. The heat budget and [thermodynamics](https://en.wikipedia.org/wiki/Timeline_of_thermodynamics) would not make sense, and that’s the first science to [develop with the industrial revolution (19th century)](https://en.wikipedia.org/wiki/Steam_power_during_the_Industrial_Revolution).
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Assuming these brainwashed humans "don't know any better," there are plenty of options that wouldn't give away the nature of the experiment. It may even be useful to put them in varying conditions to see the effects of each environment. Here are a few:
# The Halo Ring
Anybody who's played Bungie's hit shooter can recognize the Halo rings: artificial ring-shaped structures with a living environment spanning the entire interior. As far as the transplanted humans know, "that's all there is."
# The Matrix
Why bother creating a whole new planet if you can just simulate one? This also has the added bonus of being able to change things more-or-less on the fly without any complicated engineering going on behind the scenes.
# The Terraformed Planet
The boring option: take a planet that already exists, throw in an atmosphere, some water, and a few other biologic basics and let 'er rip! After a while you should have a biosphere in homeostasis.
# The Galaxy Planet
This is a pretty absurd idea, but it would be interesting to see what happens when humans are on an artificial planet the size of a galaxy. Such a scale would eventually mean that humans would evolve quite distinctly, as there could eventually be enormous societies so far apart from each other that traversing between them would take generations. You could even go the Sid Meier's Civilization route and give one of the factions access to superior weapons and technology, and see how long (if ever) it takes to conquer the rest of what used to be humanity.
# The Flat World
It would be pretty funny to see people literally afraid of falling off the edge of the world so while you're padding the budget, why not?
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Is it possible that a large, multicellular, naturally evolved organism with an advanced intellect on the order of a human's could have evolved to pass on its knowledge and memories in a fashion that could be described as 'genetic'?
By 'genetic', I mean that a newly born/hatched/whatever organism would emerge with at least a reasonable subset of one or both/all of its parents' stock of knowledge at the time at which it was born or conceived (depending on the means of reproduction) without having to be taught in the manner that human children must be taught.
Obviously, this should not preclude such offspring learning naturally in the manner with which we are familiar *after* birth.
Should this be possible, by what mechanism might this take place?
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Why limit the knowledge transfer to the DNA/reproductive process itself? A reproductive system is designed and adapted to create new life and get it up and running. A brain is designed to handle knowledge and use it to do all kinds of cool stuff. If I wanted to create a species that did this, I wouldn't focus on messing around with how the reproductive system works. I would make a third system which transfers knowledge. Say, some kind of neural connector that latches onto the fetus in utero and establishes a connection to the mother's brain. Long term memory in the mother could be more or less reproduced if the fetus had a brain sufficiently developed to have somewhere to store it. Obviously, this species would have to develop their brains completely much earlier than humans, but if they had a neural transfer mechanism/organ, obviously, they would be adapted to do this.
The memories would be like a photocopy of long term memory from the mother, and would probably be accessible to the child in stages as their brain developed. Who knows, maybe the creatures could even learn to focus on particular areas that are important to pass on during pregnancy? There could be a pretty formalized corpus of species knowledge passed on every time with a lot of stuff that each generation had thought was very important to relate. Also, like a photocopy, you would have to figure that the accuracy of the transfer would probably degrade over time. How well would the transfer of a firsthand memory of your great, great, grandmother work?
It's an interesting mechanic, but that way you aren't mucking around with the actual reproductive system itself, which is already very complicated and absolutely must be reliable for the species to survive.
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## Reasons why this won't work by way of introduction
As a person with a degree in the life sciences you do realise this could involve one or both of its parents storing their knowledge and memories in their germ cells and that somehow these memories are expressed and translated into knowledge and memory in the brain of their offspring.
The density of information encoded into the spermatazoa and ovum would be massive. To say nothing of the potential harm caused by decryption errors into their offspring's brain. All of which would be prohibitive. So direct genetic transmission of knowledge and skills from one generation to the next is impossible. OK?
## A modest proposal for transmitting knowledge and skills reproductively
Now let's do it another way. Through the reproductive process itself, but it's not reproduction as we know it.
Assume the two parents do something when they reproduce that no respectable metazoan would ever consider doing, namely, their bodies fuse, soften and effectively liquefy as they and their organs form a single mass of living matter. Effectively this is a gigantic syncytium.
Their child will be formed out of this somatic fusion, probably in a womblike cavity at the centre of this fused body, and it will inherit the recombined genetic material from both its parents, as if was normal dioecious reproduction, and imprinted on its brain will be the knowledge and memories of both of its parents. And all that epigenetic stuff that is becoming so fashionable in biology these days too.
Once the child is sufficiently formed to be viable, the fused mass separates into the both of the two parents with their offspring between them. As a bonus offer, there's no reason why twins or other multiple births might not result from this from this reproduction by immersive fusion.
There you are one great big gooey reproductive mechanism for the direct inheritance of memories and knowledge from one generation to the next. Naturally this reproductive mechanism will be produced by evolution, but how and why it evolved in the first place that's something for you to figure out.
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I'm currently building a world centered around a city. This city's main export, currency, and source of power are little metal orbs containing energy. Basically, it's the only place in the world where those are produced, and everyone in the city needs some.
They're not only used as money would be (buying food, clothes, and other stuff, and being received as salary), but are also necessary for lights, ovens, means of transportation, etc... to function. Think of it like batteries being used as money. A working citizen usually earns enough for him to power his house, and buy what he needs to live with the rest.
I've established that producing those orbs require levels of heat unbearable for organic beings, so people living there built robots to work in the furnaces in their place. Those robots are obviously powered by those same orbs, and are humanoid in structure (a head, two arms with hands, two legs, bipedal stance).
Now I'd like to have those robots become sentient thanks to the energy inside the orbs: people know how to manufacture and use them, but don't quite know how they really work, deep down. For the sake of simplicity, assume those robots acquired conscience thanks to the orb's magic.
My question is, **how can those robots and ONLY those robots acquire sentience, but not the rest of the city's commodities** (lights, vehicles, advanced tools, etc) **since they're powered by the same orbs ?**
The fact is I'm building it for a game and those robots are meant to be playable. It would kinda be a mess (although a hilarious mess) if players were able to play as a walking, talking oven.
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Processing power and range of ability.
An oven is an oven, it heats stuff and that's pretty much it. Even advanced machines only do exactly what the humans make them do, so nothing complicated there.
The robots, however, are meant to replace human workers. This means they are capable of doing many different tasks, respond to unexpected problems, and handle complex tools. Even if they're not sentient, being able to do that requires quite a bit of processing power - enough to hold a consciousness.
The orbs might try to make other things sentient, but their processors and memories - their "brains" - are simply too small to hold all the necessary parts. It's like trying to bestow intelligence on a cockroach - there's simple not enough of a brain to work with. These machines might acquire some small quirks as a side-effect of the attempts though. Small things that doesn't really impact functionality, but each machine becomes somehow unique.
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# The question
How would a fortress built on a floating island look like? what kind of defensive emplacements and structures could be expected to be built for such a construction in order to defend it from attacks in the setting described below?
# Context
The world is a gas giant planet about twice the size of earth, it is covered with floating landmasses at different heights, some in places where life as we know it can and has developed.
**The fortress**
The fortress was built to secure a nation's control over a strategically important resource and to prevent enemy raids and attacks on the local infrastructure.
**The island**
The island on top of which the fortress sits is a floating rock of about 400 x 400 square meters of irregularly shaped and plateaued terrain on top (some parts of the island being at different heights than others) and a thickness of 200 meters at the center, decreasing towards the sides.
There is no ground below the island, only clouds (the planet being a gas giant). The island is also static, meaning it doesn't naturally drift or fall unless a huge force is applied to it.
The island's structural integrity is solid enough for a network of tunnels to be build without risk of collapse and there is no risk of the island toppling over due to unbalance because of the mechanism that makes the island float.
There *is*, however, a risk of the island beginning to fall, should more than 1/3 the island's weight were put on top of it (about 25.000 metric tons with some quick calculations).
**Technology**
The technology is all over the place.
The world is currently undergoing an industrial revolution thanks to the discovery of new sources of iron, copper, tin and other metals, before this, metallurgy was limited due to the difficulty of access and collection of these metals.
The steam engine was never invented, instead, people rely on the strong and constant winds that blow past the islands to power the booming industry. Magically powered engines are also used, but in a much smaller scale.
Despite all this, flying machines have existed for quite a while in the form of hot air balloons, canvas gliders and canvas airplanes (metal airplanes being only a recent invention).
Firearms also exist in this world in the form of semi automatic rifles and canons powered by magic instead of gunpowder.
There is precision engineering and manufacture, so mechanical computers are not out of the question.
**Magic**
The mechanism by which islands float is similar to flux pinning, but people don't harness its power as they don't really understand it.
There is another type of magic related to elemental spirits. People can trap these spirits using specially designed containers to use them as batteries and power different machines and devices, before the spirits are completely depleted they can be recharged with their respective elements. This is done to power devices for which it may be cumbersome to carry a power-source or generator, such as airplanes or guns, powered with fire spirits.
**Politics and warfare**
With the exception of a few uncommonly large islands, most islands are ruled in their entirety by a single political entity, meaning that ground based warfare is pretty uncommon. Instead, most battles are fought with airplanes and airships.
The extent of an infantryman's work is dropping from aircraft to an island to secure structures and assert control over the population. But it is rarely, if ever, that they have to actually push the enemy lines. Their role is similar to that of a marine.
Recently it was discovered that below the clouds (the nether) there are islands covered in soil rich in metals. This soon led to a huge political conflict between many nations over the control of these nether islands.
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If I were designing such a fortress, I would place ballista's around the island covering 360 degrees. As most of the transportation in your world relies on balloons, the easiest way to sink attacking air ships is to puncture their hulls. They could be modified to also fire ball-and-chains as well as spinning blades, designed to cut into and disable the canvas of gliders.
Depending on the mechanism for the air ships buoyancy (if they're filled with flammable gas), the arrows may contain oil and a fuse (similar idea to cannonballs). In this case, the arrows would be designed to latch onto the balloons rather than create the largest possible puncture, and wait for the fire to take the ship down.
Because the island is floating, defensive fortifications would have to account for attacks from anywhere around the fortress - including attacks from underneath the landmass. Ballistas could be in bubbles protruding from the floor of the island, with internal tunnels allowing access for soldiers to man them. I imagine them as similar to aircraft gunner ports, but with giant metal ballista and arrows instead of guns. It would also be useful to have simple rocks rigged to drop and the command of the fortress's defenders, ripping the canvas off unsuspecting gliders and popping air ships passing underneath.
All of the buildings should be mined into the island, with minimal entrances to the surface of the land. (In fact, it would be a good idea to place bombs all around the upward surface of the "ground.") The less that's visible to the air, the harder it is to take for an attacking force. It also creates choke points for troops attempting to breach the fortress. There would likely be minimal walls; as the real battle would happen in the air - not on the islands surface itself.
An airfield would likely be on the island, and it would make sense to booby trap it in the event that forces disabled the balista's and attempt to land on the fortress. Soaking the field in oil or utilizing your magic would make for a nice surprise.
Assuming the island doesn't lack resources, I'd also place tethered balloon scouting posts floating far above the island. The largest threat to such a fortress would be an air raid with bombs or massive amounts of weight intending to sink the land. As such, defenders manning said outposts could watch the skies above for possible attacks and signal defensive responses.
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On modern day Earth, a floating island used for military purposes is called an aircraft carrier. Prior to the development of reliable powered flight, floating military islands were called battleships or sometimes dreadnoughts. Before the ability to make large ships out of metal, wooden floating islands for military purposes were called "Line of Battle ships".
What I am getting at is the "floating island" part of the question is a McGuffin, what is important to consider is the dominant military technology of your setting. If it is a setting in the middle ages, then the floating island will be full of soldiers, catapults and probably fields to grow crops to feed everyone. Today it might only have some remote sensors because everyone can see the island and will target it with a nuclear weapon, so your military will not want to be sitting on a giant floating target.
An interesting middle ground might be a WWII era setting. A British "mad scientist" named Geoffrey Pyke developed a composite material consisting of @ 14% wood pulp mixed with water and frozen. His plan was to create a "pykrete" aircraft carrier the size of an iceberg which would be essentially unsinkable by any existing or projected German weapon, and could serve as a mobile airbase for 4 engined heavy bombers. Based on the description of your setting, a mobile "airbase" is what you are talking about, so we are looking at a giant aircraft carrier.
[](https://i.stack.imgur.com/UUbio.jpg)
There will be one or more flight decks to launch and recover aircraft, and depending opn your setting, a multitude of anti aircraft batteries to defend the airstrips and shoot down approaching enemy aircraft that slip past the combat air patrol. A modern aircraft carrier has missile launchers and the Close In Weapons System (CIWS) to deal with incoming missiles and aircraft, but you might have "flack" 88's or whatever fits your scenario best.
Oddly enough, the other possible inspiration might be the "Battlestar Galactica", since it is effectively an aircraft carrier in space, so there is a more 3 dimensional flavour to how they operate.
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It seems like this island is primarily a base for aircraft and is situated in/near an airstream utilized for travel and floats over another island mined for metal ore (but concealed within clouds). So the fortress needs to be able to control the airstream, deny the enemy from occupying the ground beneath it, and maintain a clear airspace above it to prevent bombardment.
Presumably the top of the island is mostly armored hangars and landing strips/pads for aircraft. All the people would live in bunkers. SO it would look less like a castle and more like a Japanese island from WW2. Everything critical is within the tunnels because it would easy to bombard the island from above. Below the islands "horizon", assuming it looks like an iceberg or something from Avatar, there would be tunnels leading to armored bunkers protruding from the sides like blisters.
If the island has the structural integrity to be heavily landscaped, the island may be carved into a shape that maximizes offensive capabilities (a giant octahedron with smooth upper contours to deflect falling bombs, reverse terraced lower portion so airframes can hang, ready to drop into action and allow for a clear field of fire straight down, big open hangers to allow for aircraft to land in enclosed bays, etc).
There has to be 360 degree (x, y, and Z axis) observation and anti-aircraft capability. If the enemy craft are relatively fragile dirigibles and the like, then high rate of fire/low penetration weapons should suffice. But if armored "sky battleships" are possible then there will have to be shielded bunkers containing heavier cannon. But the best defense is a good offense so constant "CAP" (combat air patrol) and multiple means of launching defensive aircraft would be the most effective means of accomplishing the mission.
Since the land below is concealed by clouds the only way to effectively target anything there would be to have predesignated target points that island based artillery could hit based on the directions from a ground based forward observer (this would require the island and the land below to be VERY static in position WRT each other, or the TPs would have to be constantly updated). A more fluid battle would require signaling like a flare launched up through the clouds to give the fortress something to aim at. Aircraft could obviously fly below the clouds and hit an invading army, so obviously this is why the fortress must be taken in the first place.
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To start off, I would suggest against the use of much metal in the construction as it is highly dense and would not go far with your weight limitations. You may look into whether there is any way that your civilization has the know-how to modify the island in order to give it more lift which could compensate for added weight.
Being an floating island, you will only be attacked from the sky which will require a based aerial combat team as well as a fast means of deployment. A runway may be necessary for landing, but your best bet for deployment of aerial units might be to have tunnels in the island itself with a 20 degree grade to them to allow units to pick up speed in a short distance before launching out into the air.
An aerial proximity mine field may also prove useful. Placing them on the edge of your boundary with a potentially hostile force will reduce their ability to strike with little notice as they would have to take their time to navigate through the field or go around. Ideally you would have scouts patrol the field and each would have a device onboard that would deactivate any mines within a certain range of them. This would allow your scouts to patrol with ease and safety and should they spot anything, they can get clear to send warnings leaving a trail of reactivating mines behind them (you would have to ensure these devices did not fall into the wrong hands though - or allow them to as a plot point).
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By now many of you have seen those apps and sites that predict the way you'll die, some of them even going as far as telling you the day and time. Well what if that were real....to an extent?
**Background**
Imagine every country had a public government office specifically for reading details about your future death. Appointments would need to be made several months in advance and once there the staff will sit you in a quiet room with a machine interface that reads out the details of your death. This prediction would be highly accurate but in the case of murders or accidents it doesn't imply who the offending party was, in fact all the system provides is a following in the template shown below:
* Name: Tom Smith
* Age: 47
* Date of Death: 11/08/2020
* Time of Death: 14:02
* Description of Death: Exsanguination (Sufficient blood loss to cause death)
The system would work by taking a blood sample from the user (possible during the booking period) and using some analytical quantum computation to reach an end state to the user's life. The technique or software used is highly classified and is unlikely to be leaked to the black market / public space.
**More Info**
1. You can only book an appointment once every 6 or so months.
2. Government agencies can formally request data for help in crimes investigations and intelligence gathering.
3. Information learnt during these sessions will be printed on a certified documented.
4. Trying to desperately change or follow the prediction has been documented to increase chances of said event happening.
5. Only a small percentage of people have seen a active change on their prediction (not all people would bother to check again).
**The Question**
As a consequence to the above one can imagine life insurance companies trying to exploit this to make the most out of their customers whilst the military might use it to select soldiers for certain operations and such. There'd also be other implications as a whole but what's the biggest change to our modern or rather daily lives?
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As stated in the comments, this is an incredibly broad question, but there are some specifics that can be called out.
* People would plan lives around death. People in American society mostly make decision as though they will die after 70; long-term career planning, family building, spending money on education and housing with expectation that the investment will pay off "in the long term". This is done couched with the possibility one would die immediately; regular vacations, life insurance, "cross off my bucket list", etc.
If people knew somehow when they would die their entire lives would be organized differently... they could calculate the exact amount of money they need to live their exact number of years and do the things they want to do. They wouldn't have to take vacations early, as there would be no need; there could be a "work phase" and an "enjoy phase".
* Entire industries would shift. The concept of insurance makes much less sense, as you said. The need for preventative medical care is likely also less relevant (depending on the definition of the question). There may be new industries as well; companies could loan out cash, in case you want to have your "enjoy phase" prior to your "work phase".
* Crime would be different. The technology may not be leaked, but the data it generates would be incredibly valuable, and data is hard to keep secret. Espionage/sabotage would be a huge issue.
* Privacy would be a huge issue. Leaking this data would have big implications. One huge issue would be discrimination... I only want people who will die young to do my physically-demanding, body-destroying task; I only want people who will die later for my long-term positions; I won't vote for someone who may die soon. Kids may be told they can't go into certain jobs because of their risk factors.
Probably lots of other implications as well related to culture and religion, these sprung to mind first.
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Life insurance would become more and more expensive as you got closer to your appointed death date. Life insurance companies would refuse to insure people who had not discovered there death date or refused to till them when it was. And would not sell insurance to those who where try to by insurance five years or less from there death date.
Because of this I think most of population would take the test. Political parties would most certainly have there members take the test.
companies would also require the their ceo to take the test.
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People would only use it I'd they were unhappy with their life. It would be considered the equivalent of smoking as far as social stigma.
The PREDICTOR will go through three phases...
1) Everybody wants to use it. The press is going crazy about how we can now tell the future. It is super popular.
2) Once people start using it they become obsessed with their death. A man told that he would die in a car crash will avoid all roads. This actually happens with people who believe in fortune tellers. Harvard and other prestigious IV league universities start coming out with studies about how knowing how you're going to die negatively effects your mental health. The media is actively calling to shut out down.
3) It becomes a dangerous thing to do. It's like doing drugs. Once you do it once you'll never be the same again. Those who are happy with their lives will not take it while those who are unhappy and have less to lose might.
In the end the government probably takes it down after phase two.
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There have been questions about [sizing giant animals](https://worldbuilding.stackexchange.com/questions/316/can-you-simply-scale-up-animals), [giant humanoids](https://worldbuilding.stackexchange.com/questions/8569/how-to-make-a-realistic-giant), [giant flying creatures](https://worldbuilding.stackexchange.com/questions/819/what-is-the-maximum-size-of-a-flying-creature) (also discussed [particularly for dragons](https://worldbuilding.stackexchange.com/questions/313/how-could-dragons-be-explained-without-magic) and [giant floating mammals](https://worldbuilding.stackexchange.com/questions/34892/evolution-of-giant-floating-mammals)), and [giant spiders, one type of invertebrate](https://worldbuilding.stackexchange.com/questions/36007/what-kind-of-world-changes-are-necessary-to-make-giant-spiders-feasible). The first link has some general applicability here, but I am particularly interested in the mechanics and feasibility of a different type of invertebrate, **giant worms**, similar to what [this question](https://worldbuilding.stackexchange.com/questions/12912/how-to-escape-a-horde-of-worms-using-magic-with-minimal-injury) mentions:
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> 60 feet in length and 20 feet in girth burrow up from under the mountain
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That question has the worms carnivorous, but I am more interested in a generally docile worm, much like a large [earthworm](https://en.wikipedia.org/wiki/Earthworm) (though obviously at that type of size, could *incidentally* seriously injure or kill a person).
Parameters for Feasibility:
* **Environment**: Lives on Earth-like world (gravity, atmosphere, etc.); essentially, if in question, pretend we are talking about Earth.
* **Ecosystem**: Land based (burrows like an earthworm, though [preferably] may be considered to in some way penetrate harder rock than just loose earth); may be able to swim as well; must dwell exclusively subterranean with possible deep ocean excursions (whether swimming or just poking itself out of the earth at deep ocean depths).
* **Size**: 10-15 feet in diameter at the most, but may be however long it is deemed necessary within reason; proportions of earthworms do not directly scale width/length according to the previous Wikipedia link that states:
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> 10 mm (0.39 in) long and 1 mm (0.039 in) wide to 3 m (9.8 ft) long and over 25 mm (0.98 in) wide [the larger size being the [Giant Gippsland earthworm](https://en.wikipedia.org/wiki/Giant_Gippsland_earthworm)]
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I would not desire my 10' diameter worm to be 1000' long! So they will be a wider, stouter variety (more like a [Goliath Beetle's larva](https://video.search.yahoo.com/video/play;_ylt=AwrTccHUXhFXizwAJjtjmolQ;_ylu=X3oDMTBsOXB2YTRjBHNlYwNzYwRjb2xvA2dxMQR2dGlkAw--?p=Goliathus%20goliatus%20larva&tnr=21&vid=B96D92C7EA4E4A19EEE7B96D92C7EA4E4A19EEE7&l=119&turl=http%3A%2F%2Fts1.mm.bing.net%2Fth%3Fid%3DOVP.Vf3afb104d1ffded6b3db95b30a512fb7%26pid%3D15.1&sigi=12bs1qoou&rurl=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DjoeEsZXC-uc&sigr=11b7u1183&tt=b&tit=Goliathus%20goliatus%20-%20Larva%20wandering&sigt=114dsssrl&back=https%3A%2F%2Fsearch.yahoo.com%2Fyhs%2Fsearch%3Fp%3DGoliathus%2Bgoliatus%2Blarva%26vm%3Dp%26type%3Dsearch_6%26param1%3D3312269%26param2%3D3202820%26param3%3D0%26param4%3D1195092205%26hsimp%3Dyhs-prodege_001%26hspart%3Dprodege%26fr%3Dyhs-prodege-prodege_001%26ei%3DUTF-8&sigb=16jg3hjcb&hspart=prodege&hsimp=yhs-prodege_001&vm=p) proportions, which "[are capable of growing up to 250 millimetres (9.8 in) in length](https://en.wikipedia.org/wiki/Goliathus#Life_cycle)" with a much thicker shape). Something in the 50'-150' range seems reasonable to consider.
* **Shape**: May have some type of small "leg-like" appendages either in the front or full length, but generally still a worm more than a centipede, so either very few, short stout legs (like the grub example above) or smaller, almost "hairlike" (in proportion to its size, anyway) legs the run the length.
* **Diet**: Not naturally carnivorous, though if they are "capable" of eating flesh, that is okay; ideally, while earthworms subsist not off earth itself, but plant matter in the earth, some consideration of how they might actually digest and subsist off earth/rock would be nice (acidic juices that "dissolve" the rock before ingestion, etc.), since they are purely subterranean.
* **Intelligence**: Nothing more than animal (or even that of an earthworm) needed.
What things need to be considered to have such a worm be "naturally" feasible? A small suspension of belief is acceptable, but generally what kind of systems (physiological, ecological, etc.) would it need to have in place to grow to that size and *possibly* live off "earth" (or if not, what would it need to survive)?
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First thing I would consider is gravity on the worm, you have, essentially, a giant sack of water. You need to consider how it holds itself up, things like whales tend to die out of water because they are unsupported.
Potentially it could use the walls of its tunnels to support itself, that could be an interesting limitation on the worm, if it exposes too much of itself it can die.
Next you have heat, living things need to dissipate heat, depending on how fast your worm is going the heat needs to:
a) get removed from the worm (conductive slime to transfer heat to walls? excrement?)
b) get moved far away from the worm so it can continue to produce and eject heat
Maybe your worm makes holes in the surface to shoot out piles of high-temperature fecal matter, maybe it needs certain chemicals to run endothermic reactions internally, maybe its just very very heat resistant (and has a high conductivity meaning the heat transfer through the worm is fast).
Food, urgh, this thing is going to be using a huge amount of energy to move. I think biological machines are about 30% efficient, so all that heat it made, it needs all that and more (i.e. only 30% of the energy it eats is food, the rest is heat). This is probably going to need some suspension of disbelief. It needs to either consume dirt that gives it more energy than it takes to move through the dirt, or eat something else.
Maybe you could get away with it eating coal or something, a high energy-density material like that. Otherwise its going to be biomass of some kind. Probably not flesh because theres probably no way to get enough flesh efficiently enough to sustain it (unless its a stationary trap worm). Meat tends to run away from things that try to eat it. Also it would need a very large prey population. This would have to maybe eat trees? Maybe it eats a tree and then just sits there and digests it. So you dont have the heat and the efficiency problem, since its only the minimum energy it needs. Then it goes on to the next tree, since this is a forest. I guess then it kind of rejuvenates the forest behind it. Maybe it serves as the forest fire of its planet?
Hope this helps.
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This started as a comment on Taha's answer, but grew in length.
The problem with giant animals is going to be how to fuel them and what sort of lifestyle they will need in oder to get enough food and extract enough energy from it to survive.
Monster earthworms will have to extract a lot of energy from the environment somehow, and will also be using a lot of energy to burrow through the ground. Their sheer size will also make significant impact on the local ecosystem, so the worms will be co evolving in some sort of environment where they "make sense".
Forest worms actually seem to fit the bill, since tree trunks represent a concentrated form of energy (as anyone with a fireplace or wood stove knows). A forest worm that rises up, eats through a root and then knocks over the tree to consume the trunk and foliage will be able to extract a fair bit of energy, but their biology will be very different from any conventional worm.
In order to consume a tree, the forest worm will need a mouth full of cutting teeth resembling a lamprey in order to cut through roots and the trunk of the tree. This wood chipper like mouth will not be enough to actually digest the tree, so internally there might be a gizzard full of rocks to grind the wood into a pulp, or a series of stomachs and intestines full of bacteria that digest the wood chips (somewhat like a termite), with the worm actually living off the byproducts of its microbiome.
Churning slowly through the earth will use up a lot of energy, so the worm's lifestyle will be to slowly burrow up to a tree, cut through the roots, then rise up and slowly consume the fallen trunk. Since the worm will be partially on the surface and exposed at that point, it will have an armoured skin to resist predation, and presumably retreat into the burrow after cutting through a part of the trunk, rising to take another "bite" later on. The worm's sense organs will have to be attuned to the presence of trees and roots, as well as sensing vibrations, electrical fields or other means of locating potential threats and being able to analyze the nature of the soil it is burrowing through to bypass large rocks and other underground hazards. Being able to locate other worms underground is also a bonus for finding a mate or defending it territory from other worms.
The forest will benefit through the deeply tilled soil filled with organic matter in the forest worm's castings, as well as the ability of the tunnels to absorb and hold water during rainstorms (this might be especially important if the climate is extreme like a rain forest or a monsoon environment.
The worms will have grown large not only to consume trees (presumably there are smaller sub species which live on the edge of forested areas which consume scrub and shrubs), but in response to predation. We already have an armoured skin, and a wood chipper like mouth, so a question you might ask is what sort of creature would feast on a massive forest worm? (presumably there is also a subset of parasites and symbionts which live in or off the worm). Working out the rest of the ecology of the giant forest worm should be interesting...
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This question
[How often must carnivorous grassland eat?](https://worldbuilding.stackexchange.com/questions/38354/how-often-must-carnivorous-grassland-eat)
was really interesting for me to read. However it made me wonder, how would the bone grass scientifically kill? (is there a way to really make paralytic pollen?)
Here are the criteria:
* as long as it looks like white grass it counts(you could have snakes hidden in the ground or something)
* it must kill via paralyzing its prey
* the more efficient it is at "hunting" the better
* solution must be scientifically plausible
* no need to explain the reasons it would evolve, I don't believe in that. Makes creature design easier. :)
If anyone has any suggestions I'd love to hear them.
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There certainly are toxins that will put people to sleep, paralyze them, etc. [Spider Wasps](https://en.wikipedia.org/wiki/Spider_wasp) for example paralyze their prey and then inject eggs into them.
One interesting idea though would be for the grass to take carbon dioxide out of the air and store it in inflatable bladders around the plant or maybe in its roots. When a trigger happens such as a herd of grazing animals getting into the center of the field they all release the CO2 at once. Being heavier than air it forms a pool and suffocates all life in the field silently and invisibly. The field would then be fertilized by the bodies but safe to enter for a few months while they rebuilt their CO2 reserves.
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In order to get a plan that look like white grass you could put the toxin in the leaves, much like the stinging hairs of nettles.
You could also combinable the poison with the substance used to digest the prey, for example: a sticky substance covering the plant. When someone step on the plant, the poison paralyse him while the leaves stick on him start to slowly dissolve the flesh. The plant keep produce poison while the prey is on the ground so it can't escape.
In order to attract animal, the paralysing substance could produce a sweet aroma. In order to attract human, the plant could adopt a pretty design or mimic a inoffensive or useful plant.
For the poison efficiency, the plant use theirs poison to deter animals from eating them but not to kill instantly a prey. Consequently, their effect are often delayed in time. But the [Dendrocnide moroides](https://en.wikipedia.org/wiki/Dendrocnide_moroides) is a stinging plant renowned for causing unbearable pain. The pain is so intense that there are report of horses jumping off cliffs after being stung and a man who commit suicide in order to stop the pain. So a more effective version of this toxin could nail to the ground due to the pain until slower toxin completely paralyse the prey.
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I am interested in writing a survival-themed interactive fiction story (a sort of "what would you do" scenario game). Obviously, the zombie apocalypse might come to mind as the setting, but this has been done to death (pun intended), and I would like to avoid those tropes.
My alternative scenario is this: a dense, persistent gas/smog descends on a city. Visibility is extremely limited, and the gas does not blow away with the wind; it sits in the streets and open buildings of the city, and remains for the most part at the same density/thickness (i.e. so visibility remains constant, within some degree).
The important part is that the gas is problematic enough that the government is unable to reclaim the city; so it becomes a sort of Pripyat, or otherwise a 'besieged' city, where no one can leave easily. Hence limited visibility is an important obstacle.
The other effect of the gas is that when it was first deployed, it was lethal. A week later or so it is no longer immediately lethal, but is still potent; it is corrosive, and does hideous damage to exposed skin; it does damage to mucous membranes, upon contact; i.e. it will kill you if you are not protected. However, people need to be able to survive with amateur protection, such as scarves wrapped around their face/mouth, since gas masks won't be everywhere (though a month or so of this sort of exposure will kill you off).
I'm not sure whether the gas will suddenly be released onto the city, implying residents will need to survive, and will not be able to easily leave the city (nor will help be easily reached), or whether it is a known issue and the city was evacuated months before, and instead it becomes a hub of illegal activity, S.T.A.L.K.E.R like.
Basically; what sort of realistic 'gas' substance would I want to use here? Most importantly: What sort of gas/smog would persist in an urban environment and not get blown away/diffused by the wind? Secondly: what sort of gas of this type would have the health effects as listed above (mustard gas would seem obvious, but that doesn't meet criterion 1).
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The not being blown away by wind thing is unrealistic. Wind can get really powerful and horrific when it decides to. Remember tornadoes and hurricanes? And you think such winds would not be able to blow away some petty smog?
[Tungsten Hexafluoride (WF$\_6$)](https://en.wikipedia.org/wiki/Tungsten_hexafluoride) is the gas which comes to mind. It is extremely heavy, very corrosive and *extremely* deadly if a huge cloud tends to wrap a city. Upon reaction with water/fog, it forms deadly Hydrogen Fluoride ([HF](https://en.wikipedia.org/wiki/Hydrogen_fluoride)) which is worse than hydrochloric acid. The problem with tungsten hexafluoride is that it is not manufactured on large scale and it is not formed naturally.
You could simply use chlorine gas too. It is *much* heavier than air (70 grams per mole versus ~30 grams per mole). Besides being corrosive, it is also brightly colored and a city-wide cloud of chlorine would easily impair the vision of all inhabitants. However it is *very* lethal and a 2 minutes exposure to dense chlorine fumes is enough to seriously damage the eyes, create deadly amounts of hydrochloric acid in the lungs and burn the skin.
Goodluck with your search.
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You might want to consider an airborne organism rather than a non-living gas. Billions of tiny creatures filling the city streets like an airborne algae bloom. Cohesion among the organisms and extremely fast reproduction could explain why they can't just be cleaned off or blown away. Mutation could explain why symptoms of exposure to it changed over time.
Throw in a little bioluminescense and your entire city could be trapped in an eternal twilight. Great atmosphere for terror (pun intended).
I had a setting like this in one of my short stories, and the Vile (which is what residents called the living smog) was an artificial organism designed to feed off of air pollution. It was released over San Francisco as a test case, but quickly mutated and became a bigger problem than the original smog. City residents had to wear full biological containment suits whenever they went outside and those suits had to be replaced regularly because of the Vile's acidic secretions.
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# Make it hard to disperse because of the area's geography
Making the gas hard to disperse by wind could be due to geography of the area rather than the innate properties of the gas. All the gas would have to do is to be heavier than or equally as heavy as air in that case. Similar to question in [Deadly, Heavier than Air Gas](https://worldbuilding.stackexchange.com/questions/14792/deadly-heavier-than-air-gas), but you would have to make sure that you pick one of the opaque gases. Some good candidates I can see (but haven't checked throughly, sorry) are nitrogen dioxide, anhydrous ammonia or bromine. They may or may not meet your needs, as they may be too aggressive/mild or too slow acting for your needs.
One limitation of heavier-than-air gases I picked is that it would be pretty hard to see them in nature, either no natural occurrence at all or rare ingredients would be needed. Why not have a local refinery leak for example?
# Consider using *two* gases
Why not have two gases leak one after another to meet your first criterion: first, a really potent gas leaks out. It's instantly lethal but it's either lighter-than-air and floats away, or decomposes/reacts away chemically. Then, the weakened gas tanks of the refinery burst again, this time with the permanent gas. It's not instantly lethal, but still dangerous.
# *Example*
The city is located right in the middle of a "bowl" area, surrounded by hills/mountains or located within a crater. A terrorist attack bursts one of the gigantic Gas A tanks, which kills a lot of people. Gas A slowly disperses over the period of two days, but before it's gone, manages to corrode away one of the gigantic tanks of Gas B. The one corroded the worst explodes, triggering a chain reaction which bursts the remaining ones. The city is forever shrouded in the heavier-than-air gas cover which doesn't dissipate.
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The [Boötes Void](https://en.wikipedia.org/wiki/Bo%C3%B6tes_void), a.k.a the Great Void, is celebrated for having a comparatively(competitively) lower matter density than the rest of the universe. Imagine an intelligent species similar to our ancestors was to evolve (created, if you will) on a rogue super-Jupiter left for dead for millions of years in the vastness of space inside the Boötes Void.
The atmosphere is very thick and opaque; the heat produced by the sheer size of the planet helps to sustain life and also to produce some of the most complex weather systems no one could have imagined let alone conquering it.
**How could these Stone Age (Dust Age, to be exact) alien hunter gatherers navigate in the absent of constellations in perpetual darkness?**
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## Knowing the wind
I assume they do something along the lines of ballooning to get around. Without star, suns, or seasons they do not have an external reckoning of time. Assuming they have an internal one (heart beats or what not) and compasses Worked. They would just have to remember or record the currents and count them off. Altitude would be easy. Directions to a place would look like
up 1000 beats north into the wind count 10000 beats drop 2000 beats in east flowing wind. This is assuming the wind patterns are predictable chances are they would be in the short run on a gas giant. the longevity of Red spot attests to this.
## The planet has bands
[](https://i.stack.imgur.com/mKT32.jpg)
Latitude is knowable by what the air smells like. Your Jovial Mariners would have to develop a method of telling where they are by trace chemicals.
## Back to that compass
Jupiter's field is mostly a dipole but also has quadrupole, octupole and higher components. If our species could "hear" the magnetic fields with the same discernment we can discern sound they would have a lot of geolocation info to get around with.
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There's no land. Congregations of lower life forms might form around congregations of *materials* that form due to weather patterns. These might not have fixed locations at all relative to each other, and be transient in nature.
You may have an eternal great spot and patterns at the poles, and "places" around and within them that are impermanent but at least can be navigated because it forms a perimeter relative to a major feature.
Things that occur at boundaries of specific bands might have characteristic lattitudes but can be anywhere around the planet. [Hal Clement had a novel about a waterworld](https://www.goodreads.com/book/show/1528534.Noise) where the floating cities had to be located before they could be landed on. This would be similar: you have increasing constraints in searching for it, but nothing like a fixed location.
And we've only discussed a two-dimensional surface. The bulk of the planet may be interesting in *depth*. Phase changes occur with different pressures and temperatures, and this affects composition and can form membranes that attract their own features.
The aliens with implied technological artefacts might not live in the *sky* at all, since their stuff would just fall and where did they get *things* in the first place?
Perhaps a *much* deeper layer that is more like a liquid phase and dense enough that solid bits would stay within the media.
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There are no fixed locations in something like a gas giant, everything is going to be floating around inside the atmosphere. With that being the sense conventional navigation means nothing, it doesn't matter where you are - it matters where you are in relation to something else.
One possibility would be that large settlements would have huge drum towers in the center. People would beat on those drums at regular intervals sending out pulses of low frequency sound and each settlement would have their own rhythm or pattern. To find a settlement you just head towards that settlements tone.
Smaller settlements would advertise their position relative to the larger ones and may even have their own quieter beacons that lead people nearby to them. (i.e. we'll be near Artanis in a week, follow their beacon until you hear ours).
With no physical surfaces to absorb the sound it could spread a long way, especially if you can find channels in the atmosphere to guide it similar to those used by whales in the ocean.
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Is there any way to make a planet with a [corkscrew orbit](https://www.newscientist.com/article/dn27516-corkscrew-planets-spiral-back-and-forth-between-two-stars/) ([like this](https://theastroholic.files.wordpress.com/2015/05/spiral_04.jpg)) that could host a sci-fi civilisation? It'd be amazing if there was a way to make life arise naturally, but colonize-able works too. I realize that this is probably a rather stupid idea, but if it was possible, it could make for an extremely amazing world!
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**Unfortunately not.**
This is because a corkscrew orbit isn't a real thing. The author of the paper that New Scientist was reporting on is a molecular physicist, which doesn't bode well.
Greg Egan has a nice dissection of the idea [here](http://www.gregegan.net/SCIENCE/NoCorkscrews/NoCorkscrews.html).
If you want to skip all that, it's still probably a bust. He based it on the binary system Kepler-16. Those stars are 0.22 AU apart (about a quarter of the distance between the Earth and the Sun), getting a planet orbiting (oscillating?) between them will make it far too close to support Earth-like life.
Of course, if you want to colonize it and you've got a civilization capable of that, then perhaps they have the technology to make it livable.
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Turn the planet into a ship, in some sense it is this already, use electromagnetic manipulation to establish a basic control, and or propulsion mechanisms and their necessary master systems, locate these geoelectromagnetic propulsion "engines" in pre-computer modelled stategic locations on earth, use these engines to manipulate the natural geoelectromagnetic processes that control axis and orbital positions, this to give the ability to navigate the planet, thereby reestablishing a suitable orbit, while also retaining the system control abilities and the ability to counteract or constantly keep in check future orbital anomalies as the system capabilities either forecast or detect variance in positioning systems.
It may become necessary to do the same to the moon, or to neutralize the moon's gravitational effect on the earth's axis and orbit , as this is an ongoing significant contributing catalyst for the earth's axial and orbital deviations.
The two bodies and the geoelectromagnetic compensation system can be constantly kept in a feedback controlled condition, using the many earth geospatial technologies being previously computer modelled to establish a usable predictive analysis for use in the electromagnetic compensation engines control system,and being interlinked to these systems with automation employed to constantly use all available gps systems and the many and various interlinked geospatial systems networked together with all suitable smart technologies and neural net computing systems to make calculations and adjustments by measuring planet/moon orbital positions and/or computer modelling to maintain a constant stability of said axis and orbit.
Could be used to reposition another planet into a suitable orbit as well, noting this would require the abilities to construct and or build off-world the systems necessary on a removed planet at some distance from earth.
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I'm talking about ionized gas not the plasma in our blood. I have been reading science articles about plasma and they keep hinting at the idea of plasma based life.
[Here](https://www.newscientist.com/article/dn4174-plasma-blobs-hint-at-new-form-of-life/) is my first example and an added [second](http://science.howstuffworks.com/weird-life.htm). Apparently plasma can arrange itself into cell-like structures that even "transfer information."
I would like to create a plasma based life-form. What obstacles to staying alive would this lifeform experience? What would such a being look like?
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That article is very.........
I think it would be exciting to be in the laboratory when when a spherical blob of matter diverged into two spherical blobs of matter, sure. But, without being a scientist myself, I think that the scientist described in the article is jumping the gun if he actually claimed to have discovered something akin to a life form. It sounds more like a "bubble" than a "cell". Is a rain drop "reproducing" if it breaks into two rain drops? It hasn't replicated any information. If it doesn't replicate information, then how can it evolve?
In order for there to be life, there would need to be some kind of internal structure or information system that can reproduce itself. As far as I know, plasma cannot provide this because it does not allow for any chemical interactions or bonding. It is, and always will be, a homogeneous swirling mass of particles.
Edit:
If there were non-plasma dust particles inside of the plasma, then the plasma *might* be able to work as a catalyst for chemical reactions and organization. It could be like the cytoplasm inside of a cell, allowing for life without water. That is a far more interesting thought not mentioned in the referenced article.
Boiling the problem down to it's most basic premise... life is a system by which matter can be assembled into complex, self-replicating structures. You might think of it as a computer that runs on chemical reactions and molecular sized mechanics rather than circuits and transistors. It requires software (DNA) containing information on how to replicate those structures (including itself) and hardware that is able to read and follow those instructions.
Despite the stigma attached to any anti-evolutionary sentiment, it remains a legitimate philosophical question as to whether the hardware needed to synthesize DNA AND the DNA needed to synthesize the hardware can both simultaneously apparate out of exited particles. One of many mysteries of science.
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The problem with plasma is the high temperature needed to achieve ionization and the electrical repulsion of the charged particles within the plasma tend to cause plasmas to rapidly expand and dissipate. This is hardly conducive to anything resembling life, since information storage, reproduction or replication and other facets of life processes would also be impossible. (This is also why plasma would make a crappy weapon...)
The only ways we know to overcome this is through powerful magnetic fields, such as in Tokomaks or other experimental fusion reactors, or to pile on gravity, such as in a star. Trying to corral plasma with magnetic fields has proven to be frustratingly difficult, which is why fusion energy has been "20 years away" for about the last 50 years.
If self organizing plasmas can exist, then they will be confined to very extreme environments such as the photospheres of stars, accretion discs of black holes and perhaps the "atmosphere" of a neutron star. As you can imagine, locating and recognizing life in that sort of environment will be quite difficult, not to mention how would you interact with it?
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In an alternate universe there is a force known as the emotion force although the force has nothing to do with emotions. Anything that interacts through the emotion force has an emotion charge that is either positive or negative. Emotion charge is entirely independent of electric charge. Like emotion charges attract while opposite charges repel. The force between two emotion charges is equal to the square root of the product of their emotion charges divided by the distance between them squared multiplied by a constant. The force carrier for the emotion charge is massless and so the emotion force has an infinite range. The strength of the emotion force is about 1/100,000.
Could a universe have a force like this and what effects would this kind of force have on physics?
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Yes.
We can write out the force as
$$\mathbf{F}=-k\frac{\sqrt{e\_1e\_2}}{r^2}\mathbf{u}\_r$$
where $\mathbf{u}\_r$ is the unit vector in the direction of $\mathbf{r}$, defined as
$$\mathbf{u}\_r=\frac{\mathbf{r}}{r}$$
Is this possible? Well, it's an inverse-square law (i.e. $\mathbf{F}\propto r^{-2}\mathbf{u}\_r$), and we have two of those in our universe (gravity and the electric force, at least in classical approximations). The only problem is, [as Alex mention](https://worldbuilding.stackexchange.com/questions/28089/could-a-force-with-these-properties-exist-in-a-parallel-universe#comment73540_28089), the square root. If $\text{sgn}(e\_1)=-\text{sgn}(e\_2)$, then we have the square root of an imaginary number, and thus a vector of imaginary magnitude, which is not a good thing.
This can be fixed, though. Simply modify the equation to be
$$\mathbf{F}=-k\frac{\sqrt{|e\_1e\_2|}\text{sgn}(e\_1)\text{sgn}(e\_2)}{r^2}\mathbf{u}\_r$$
Here, $\text{sgn}(x)$ is the [sign function](https://en.wikipedia.org/wiki/Sign_function), defined as
$$\text{sgn}(x)=\frac{|x|}{x}=\frac{x}{|x|}$$
This gives us a force that is proportional to the square root of the product of the magnitudes of the charges, as intended, while preserving the property that opposites repel, while like charges attract.
On a different note, it's your universe. In many cases, you can do whatever the heck you want. There are some cases where this doesn't hold, but this isn't one of those exceptions.
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Note that we can actually reformulate the "emotion force" to discard the square roots. I'll call my formulation the clumping force (for reasons that will become clear later).
First I define a clumping charge $\chi$ in terms of your "emotion charge" $e$:
$$
\chi = \text{sign}(e)\sqrt{|e|}
$$
Then we can write the (attractive) clumping force between two particles (equal to the "emotion" force) to be:
$$
F\_e = F\_\chi \\ k\_e\frac{\text{sign}(e\_1)\text{sign}(e\_2)\sqrt{|e\_1| |e\_2|}}{r^2} = k\_\chi\frac{\chi\_1\chi\_2}{r^2}
$$
We can see that the clumping force (and therefore the "emotion" force) is an ordinary inverse-square force, and we can use all the tools we've developed for similar forces like gravity and the electrostatic force.
I just want to point out that the clumping force *is* the "emotion" force, just with a more mathematically convenient way of expressing the charge. If you're really set on this square-root thing, go ahead, but just remember that the "emotion charge" is not additive (i.e. $e\_\text{tot} = (\sqrt{e\_1}+\sqrt{e\_2})^2 \neq e\_1 + e\_2$). (By the way, if this force has "nothing to do with emotions" I would suggest picking a different name.)
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Now the effect of a force depends not only on its strength, but also how its charge is distributed through matter. For example, gravity is a stunningly weak force, but totally dominates the [behavior of matter on large scales](https://en.wikipedia.org/wiki/Orbital_mechanics). In fact, in our everyday lives the electromagnetic force only becomes dominant at microscopic scales.
This is due to the fact that most objects are almost exactly electrically neutral: they carry no net electrical charge. On the other hand, every object has nonzero [gravitational charge](https://en.wikipedia.org/wiki/Mass), and the mass of the Earth is *huge,* so the "weak" gravitational force is *relatively* strong on large scales.
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Why is there such an imbalance? The answer is the "opposites attract" behavior of the electric force. If you try to assemble two charged particles into a more charged object, the particles will naturally repel and dissipate. On the other hand, if you try to assemble a neutral object from two oppositely charged particles, the electric force assists you and the object tends to stay together. This results in a natural evening-out of the electric charge.
Gravity, on the other hand, is always attractive, and therefore tends to assemble particles into [larger objects](https://en.wikipedia.org/wiki/Planet) with more mass. This results in the distribution we see today, with a small number of [very massive objects](https://en.wikipedia.org/wiki/Star) surrounded by almost-empty space.
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The emotion/clumping force is like gravity: since like charges attract, charged particles will tend to assemble into larger, even more charged objects. (Now you see the reason for the name.) As [Michael Kjörling posits](https://worldbuilding.stackexchange.com/questions/28089/could-a-force-with-these-properties-exist-in-a-parallel-universe#comment73577_28089) this could very well result in the eventual segregation of of all particles into two oppositely-charged clumps speeding away from each other. Every particle not part of one of the clumps will accelerate towards the clump of the same charge and away from the clump of the opposite charge.
Gravity would seem to act in the same way (except that only one clump would form, since there is no [negative mass](https://en.wikipedia.org/wiki/Negative_mass)), and indeed it does tend to [clump matter together](https://en.wikipedia.org/wiki/Galaxy). The Universe temporarily avoids this fate because the strong force is so much stronger than gravity: it tends to result in the [explosion of clumps that grow too massive](https://en.wikipedia.org/wiki/Supernova).
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Thus you basically have three options for this force:
* If the "emotion force" is stronger than the strong force, this will lead to the fate I described above (collapse of all "emotionally charged" matter into two oppositely-charged black holes).
* If it is weaker than the strong force but stronger than gravity, then the universe will consist of "emotionally-bound" stars, which will be smaller and burn much faster than the gravitationally-bound stars of this universe.
* If it is weaker than gravity, then you will get gravitationally-bound objects that tend to segregate themselves into two oppositely-charged halves. Depending on what types of particles have "emotion charge," this segregation could be impeded or even eliminated by the formation of neutrally-charged atoms or molecules.
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**tl;dr:** No, it is not possible to have the force proportional to the product of the square roots of the charges.
>
> In an alternate universe there is a force known as the emotion force although the force has nothing to do with emotions. Anything that interacts through the emotion force has an emotion charge that is either positive or negative. Emotion charge is entirely independent of electric charge.
>
>
>
So far, no problem. There's nothing wrong with having different types of charges which are independent of each other. Indeed, already in our world, we have that.
>
> Like emotion charges attract while opposite charges repel.
>
>
>
I have a feeling that this already should give problems, but I can't pinpoint it, so possibly that's no problem either.
>
> The force between two emotion charges is equal to the square root of the product of their emotion charges divided by the distance between them squared multiplied by a constant.
>
>
>
Here is the problem. While the inverse square of the distance is good (indeed, for a long-range force it's the only reasonable choice), the square root of the emotion charge is not.
Consider the following:
You have two objects of equal emotion charge close to each other, and a third one far enough away that you can in good approximation consider them to be at the same place. Let's call the charge of the far-away particle $q\_0$, and the charges of the other two particles $q\_1$ and $q\_2$
Then you can calculate the force on the far-away particle in two different ways:
1. The force is the sum of the forces due to the attraction from each individual object:
$$F = C \frac{\sqrt{q\_0}\sqrt{q\_1}}{r^2} + C \frac{\sqrt{q\_0}\sqrt{q\_2}}{r^2}
= C\frac{\sqrt{q\_0}}{r^2}\left(\sqrt{q\_1}+\sqrt{q\_2}\right)$$
2. The close-together individual objects are considered a combined object, whose charge is then of course $q\_1+q\_2$. The force between the far-away object and the combined force is therefore
$$F = C\frac{\sqrt{q\_0}\sqrt{q\_1+q\_2}}{r^2}
= C\frac{\sqrt{q\_0}}{r^2}\left(\sqrt{q\_1+q\_2}\right)$$
Clearly it is not possible for both equations to be fulfilled at the same time, unless one of the charges is zero.
>
> The force carrier for the emotion charge is massless and so the emotion force has an infinite range. The strength of the emotion force is about 1/100,000.
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No problems with this (indeed, a massless force carrier is both necessary and sufficient for an $1/r^2$ force).
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Following the same geometry as [this question](https://worldbuilding.stackexchange.com/questions/25547/if-one-of-the-spatial-directions-wrapped-around-how-would-combat-be-different), how would architecture be different?
To review, when go east or west 5 feet, you end up back where you started.
Is there a way to make structures feel roomier, despite the fact the wrap around thing (say, by connecting rooms in a certain way).
How would this affect structural integrity? How would the building be built different to deal with and/or take advantage of this.
How would you attach structures to themselves ("wrapped around")?
Anything else of note?
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A nice way to think about this type of thing is to imagine a bunch of $\infty\times\infty \times 5$ ft blocks stacked next to each other, with the same stuff in each block. So if you were in one block, looking into another, you would see another copy of yourself and the room you are in, and another one beyond that, and so on, repeating infinitely. In math, this is called a *covering space*. I will refer to the strange space you describe as cylindrical space.
Something interesting about this space is that it is not *simply connected*. Imagine you had a string in normal space. You could tie the ends together, and then do whatever you wanted with it. You could wad it up and put it in your pocket, for instance. But in this space, you could tie one end of your string in one of the blocks to the other end in the next block, and you would suddenly have an infinite strand which you could not wad up without breaking! Moving down from the covering space to cylindrical space, it would look like a an infinitely long piece of string. This is a really weird concept which is not true in normal space.
**Disadvantages**
Everything, obviously, would have to fit in this very narrow space. There is really no way around this. Every room only has two walls (unless you want it to be even narrower), so all the electricity and plumbing has to run to these two walls, or through the floor. Also, all things we normally put on walls, like TVs, paintings, mirrors, etc,... would have to go on these two very narrow walls. An architect would have to take advantage of vertical space to make lots of rooms. Beds would have to lie in the infinite direction because nobody taller than $5$ ft could lie down in the $5$ ft direction. Nevertheless, skinny houses and buildings are possible. Something like this [narrow house](http://www.huffingtonpost.com/2013/09/27/narrow-house-new-york_n_4004418.html) might be what you get.
**Advantages**
It's not all bad. Even though the room is narrow, you don't have to worry about everybody seeing the TV; there are a whole array of TVs, one in each copy of the universe all stacked next to each other. Since you only need two walls, the building will be stronger. Also, you don't need so many mirrors in the bathroom because it is really easy to see the back of your head. There would be more advantages, I think if the universe were a little wider. Say, $30$ ft. Then you could take advantage of the cylindrical properties to have hallways that wrap around. Then, instead of two rooms being at opposite ends of the hall $30$ ft apart, the furthest apart they can be is $15$ ft. The same advantage applies to lots of application where minimizing distance is an issue.
Some things could seem infinite, like beds or bathtubs five feet wide. That would be pretty cool.
All in all, this would be a pretty weird place to live.
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You'd only need one side wall to support your structure. It would be pressed on from both east and west and therefore resist from both east and west. Of course, with a front and back wall, you could forego the side wall entirely.
Your world would have to build up and down a lot, but you'd still be constrained by gravity. I'm not sure how gravity would be affected, but it would change the density of stars and planets.
I'd imagine you'd have a lot of hobbit-type holes. People would live underground (or at least under roofs) and pathways would be built on top of them. You could build above the pathways, but since buildings are heavy and people are not it would make more sense to put the lightweight things on top.
If you came to a bridge that's out, there'd be no way to bypass it. But because water can't travel sideways particularly, there probably wouldn't be many wide chasms to begin with.
The world would have a lot less water, or there'd be no dry land. On the other hand, if there's less gravity (not sure that's true), the mountains would be much taller, so you could have really deep lakes and oceans and still have dry land.
Weather patterns would change dramatically. There would be no way for pressure to move sideways, so tall buildings might be out of the question, although there's still some limited room to build pipes between floors to allow air pressure to flow north to south.
Sideways momentum would be weird. If you came across other planetary systems, you'd have to add a sideways vector. I don't know that it's terribly complex, but it would be different since you can't orbit along that axis, just move.
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I seek a realistic method, either by genetic change or other scientific method that doesn't require magic or future tech, to obtain naturally occuring two tone hair for a race of humanoids.
My idea is simple, **as the hair grows in length, X happens that causes a natural change in color.** Basically the higher the "Age" of the hair, the more it changes, either by exposure to air or what have you.
The issue is, I can't solve for X.
I'm already using another race that has cyanophores in their hair naturally from consuming creatures that contain them on their planet over time. Their effect is simply when their hair gets wet it slowly changes to a bright blue.
But for two tone hair? I'm stumped.
Is such a thing possible?
**Please keep in mind their home planet doesn't need to be just like earth**, I will adjust it to meet this possible requirement.
**Also:** I seek to explore the possibilities of how the hair could change color quickly enough to make the switch from say, brown to blonde occur quickly enough to allow the gradient change to only appear in around half an inch of the hair itself.
[Answer]
There is another example in nature that hasn't been mentioned yet, "[Agouti banding"](https://en.wikipedia.org/wiki/Agouti_gene). My tabby cat's fur has bands of color like this, with grey then beige then a dark band and some have light tips.
[](https://i.stack.imgur.com/ncr9U.jpg)
Other animals also have this type of coloring (rabbits, dogs, horses and mice are also mentioned in the wikipedia link).
[Answer]
Human hair naturally bleaches in UV light from the sun; "beach-blonde" is a desirable change from mid-brown at the roots through a gradient to blonde; coupled with a deep tan, the look is someone who has enough leisure time to be outside playing on the beach all day. It's a switch from older historical preferences in many cultures for very pale skin, indicating someone who is wealthy enough to not have to work outdoors (now that most employment is indoors and sunlight exposure itself is the luxury, the preference is largely reversed). But I digress.
Given that this basic property holds for your aliens' hair, all you need is a base color that doesn't bleach out when the melanin (or whatever) does, and voila, you have hair that bleaches blue (or red or green) over time.
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It already happens a little bit on earth - it's called sun bleaching.
Have the hair created with two pigments, one of those pigments is sensitive to light and gradually gets damaged by it.
Now hair near the roots will be one colour, but then it will transition to the other colour as the first pigment is destroyed by sunlight.
This could have some interesting cultural effects as well, covering your hair and protecting it from the sun would keep it single colour.
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The hair could contain a combination of chemical substances that changes colour after a given time. If the time needed for that process is long enough to allow the hair to significantly grow, but smaller than the life time of the hair (say, about half as long), then you get two-tone hair.
See [Wikipedia](https://en.wikipedia.org/wiki/Chemical_clock) for such chemical reactions.
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The mechanism already exists on earth, and is seen in the different winter coats of Arctic and sub-Arctic mammals such as Arctic foxes, [stoats](https://books.google.com/books?id=5ae9c7GO_cUC&pg=PA63&lpg=PA63&dq=winter%20animal%20fur%20mechanism&source=bl&ots=M8qyemaBUs&sig=AuUhfxmBgCRRu8P6BZaETAwOM84&hl=en&sa=X&ved=0CDYQ6AEwBTgKahUKEwj_ho3YocXIAhUIFT4KHXwuC_c#v=onepage&q=winter%20animal%20fur%20mechanism&f=false) and rabbits and hares. Responding either to shortened days and/or dropping temperatures, the animals stop producing pigment in their brown fur, and it grows out white.
Similarly, you would have either a one-pigment or a two-pigment system. A one-pigment system would operate like earth animals, with a base color for the hair and an overriding pigment which is produced either only in early life or in later life. A two-pigment system would presumably occur with a relatively neutral base color for the hair, and one pigment produced early in life, while the other is produced later.
And for what it's worth, a restrained version of your desired change can occur in people. In my family, several males were redheads as children, then turned brown at puberty, then white when older.
[Answer]
**Sunbleaching or an aerosol in the environment could cause the color change.** Bleaching by the sun on earth breaks down the pigments causing the item to go white. However, a chemical reaction with an environmental aerosol would allow the hair follicle to turn to a color other than white. Depending on the interplay between reaction rate, aerosol availability, and follicle growth, the follicle may change color closer or farther from the root.
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In many series (Elder scrolls for example) they have a huge moon. It is rare though when they explain how it can be larger. There are only two choices both of which couldn't work;
One is to bring the moon closer, but that can get risky, how close can it get for example never mind the tides.
Two is to keep the distance but make it bigger but then how big can I make it?
Either way it seems impossible to make the moon very large (for your answers lets assume I want it to appear twice the size of the sun) But are there any ways I can make the moon appear that large without the world ending side effects
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> One is to bring the moon closer, but that can get risky, how close can
> it get for example never mind the tides.
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The answer to this is the Roche Limit. Closer than this and gravitational forces will rip it apart. The Roche Limit is about 2 1/2 times the radius of the central body. Just to make things easy, figure 3 times the radius of the earth to the center of the moon, or about 12,000 miles. Since the current average distance to the moon is about 240,000 miles, this is 1/20 the current value.
When the moon is directly overhead, the distance will be 2 radii, or 8,000 miles. Since the moon's radius is 0.237 earth, or 938 miles, the apparent size of the moon, in degrees, is $$\theta = 2 tan^{-1}(\frac{948}{2\times 3960}) = 13.7 degrees$$ Comparing this to the current size, about 0.23 degrees, the close moon will be about 60 times bigger (apparent diameter, not area) than is true now.
Something else to consider is that, as the distance to the moon changes, the orbital period changes, too, and the change goes as (Kepler's Third Law)$$T^2 = K\times R^3$$ Reducing the radius by a factor of 20 will reduce the length of a month by a factor of 90. So the moon will orbit the earth about every 7 1/2 hours.
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> Two is to keep the distance but make it bigger but then how big can I
> make it?
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That's pretty straightforward: you can make it as big as you like. Of course, if it gets much bigger than the earth, the earth will be the moon. Since the moon doesn't have an iron core it is less dense than earth, so if the makeup and densities are kept the same, the moon will have to get somewhat larger than earth before it becomes more massive, which is what counts in determining which is primary and which is satellite. Since the current diameter ratio of moon to earth is 0.237, the moon can get about 4 times bigger than it is now, and still be the moon. Of course, if it does get that big it will probably have an atmosphere and won't look at all like it does, but rather more like earth.
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The gravitational force between any two bodies, such as the Earth and the Moon, is proportional to their mass, but inversely proportional to the square of their distance. Apparent angular diameter, however, is roughly radius over distance. That is to say, $F\propto m/r^2$, $\theta\approx R/r$. What does this mean? Suppose we multiply the radius of the Moon by a factor of $a$. The mass is multiplied by a factor of $a^3$. If we multiply the distance from Earth by a factor of $a^{\frac{3}{2}}$, the gravitational force stays constant. The apparent size is multiplied by $a^{-\frac{1}{2}}$. What this implies is that if we shrink the Moon, decrease the mass, and move it closer, the apparent size could increase. For example, if we halve the radius of the Moon, and multiply the distance by 0.35 or so, then the gravitational force stays the same, but the apparent size is increased by about 40%. So to double the size of the Moon, make the radius 1/4 its current value, and cut the distance to an eighth of its current value.
Let me emphasize something: this does not change the gravitational force. That is, except for a somewhat more heterogeneous field, because the point mass approximation is somewhat less valid, the gravitational pull of this new smaller, closer Moon is the same.
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The moon could be much closer.
The closer it is the faster it needs to orbit to stay up.
If its orbital period was exactly 1 planetary day then it would be tidally locked. (ie: high tide would stay on the same side of the planet so that nobody experiences tides.) but it would only be visible form 1 side of the planet.
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This is a common trope in Scifi; Android armies. From Star Wars, to Battlestar Galactica, these mechanical beings have influenced the content of our movies and books in many ways.
**Android specs**
* roughly 10 times stronger than the average human
* possibility to reach maximum speeds of 64 kmph
* A breakthrough (possibly some form of [programmable matter](https://en.wikipedia.org/wiki/Programmable_matter)) has allowed us to quickly and efficiently mass produce them.
* My androids use advanced AI. They are capable of handling all basic battlefield tasks without human supervision, and the high command is comprised of cyborgs with increased mental capacities. Only human interference required is to give general orders (e.g. 5th Battalion should proceed to point xy of battlefield and hold position).
**Other details**
* This is sometime in 23rd century. While we have colonies on Mars and bases on various bodies in our solar system, they are mainly self reliant and do not fall under the jurisdiction of Earth governments. [The United Nations became inefficient in in late 21st century and ceased to exist during the mid 22nd century](https://worldbuilding.stackexchange.com/questions/26302/how-can-i-realistically-dissolve-the-united-nations).
* The richer nations, such as the (fictional) Black Sea Union, European Union, United States of North America, the New Japanese Empire, Russia, and the New Islamic Caliphate rely heavily on Androids. The Chinese use Cyborgs (humans with cybernetic implants) to take full advantage of their relatively massive populations. The poor third world (see present day third world) have primarily human militias augmented by cyborg mercenaries.
* Conflicts regularly occur in border regions, although full scale war has only happened twice so far, about once per century.
My question is this;
**How would the use of cyborg and android soldiers by major world powers affect weapons design.**
The use of these robotic contraptions would surely affect how weapons are designed. Weapons would be targeting the internal circuitry rather than the exterior shell since damage of the metal armor would do nothing but "piss them off."
If you need clarification of any kind, leave a comment.
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**Every state on the planet will be able to afford the sensor networks that only the US can afford now and guided munitions will be super cheap.** It's completely conceivable that in 200 years the fog of war won't exist anymore. Whether it be from drones, satellites, or boots on the ground the amount of information available to the common Third World army commander will surpass the wildest dreams of the most forward thinking technocrat general of today. The ability to process this information into actionable info will also far exceed anything we can imagine now.
**Android Mounted Weapons**
Androids *are* the weapons. They can take over the roles that lightly armored tanks fill now. They will have equivalent firepower though perhaps not as great survivability as a tank. (Though perhaps their smaller size will compensate for lack of armor. Difficult to tell without systems to test.)
At close range, they will have blade weapons backed up by muscles that don't tire and a nervous system that doesn't need to rest. Ultra-sharp vibro-blades or energy blades may be available.
At longer ranges, the below mentioned beam and hypervelocity weapons can be mounted to androids. Because of their computer controlled muscles and integration into the wider battlenet, they will be able to hit and kill targets at beyond visual ranges. If there's line of sight between an android and a target, regardless of range, an android should be able to kill it.
**Low Tech Weapons Still Effective**
In some respects, weapons design won't change much. Asymmetric warfare will still depend on IEDs and ambushes in whatever form the sensor packages of the day can't detect.
**Lasers and Railguns**
We have these in 2015 and will have them deployed on several US Navy ships by 2020. Miniaturization of power supplies, improved power storage of batteries will meet awesome power requirements of beam and hypervelocity weapons. With miniaturization, these weapons can be mounted on humans. The lethality of beam weapons and guided hypervelocity projectiles cannot be understated. Beam weapons can be set to maim.
Combat with these weapons will be brutally bloody at close range or not very bloody at long range. Armor will help with beam weapons though not much help with railguns.
**Orbital Bombardment**
Yeah, this will be a thing. There are treaties in place now that prevent this from happening right now but 200 years is a long time for treaties to live. Given the degree of political upheaval described by the OP, many treaties will have expired or are just ignored. Whether this is a "Rods from the Gods" or "Freaking Lasers in Space!" scenario will depend on launch costs. Probably lasers because those satellites are lighter than having to lift tons of tungsten carbide into orbit (although with the advent of superheavy lift rockets such SpaceX's BFR, or asteroid mining, getting lethal projectiles into orbit may be exceptionally easy.)
**Guided weapons**
Delivery of bombs via manned aircraft went out of style in the late 21st century. Drones now deliver mass launched stand-off missiles. Heck, the missiles themselves will qualify as drones (again, we already have munitions that guide themselves). The degree of automation and intelligence embedded in even common bullets (if bullets are even still used) will far surpass 2015 tech.
[Answer]
The androids are probably going to use something similar to anti-vehicle weapons. Things like armor-piercing rounds and explosives(RPGs, missiles, etc) will be much more common. Weapons will probably be much larger than they are these days, because not only do they have to deliver more of a punch, but they also have stronger operators to carry them.
Body armor may make a comeback, though history has shown that armor and the weapons to pierce them are constantly evolving to overcome each other, so it's hard to say which will be winning during the time of your story. Your androids may go naked into battle, relying on their metal skin to brush off small arms and schrapnel, or they trudge along decked out in inches-thick titanium chainmail; I think it's really up to you.
There is a case that I'd like to point out, where androids fighting in close proximity to humans will be limited by how much collateral damage they want to do to these humans. Anything they're firing is most likely capable of penetrating walls and/or destroying buildings. Human settlements will be like houses of cards; this will be a necessary consideration for the defending army. In cases where civilian casualties are not an option, I'd really like to think that the androids would resort to melee combat to deliver lethal force safely.
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In a word with mechanical soldiers, human-like androids would only be useful for cleaning up the urban area. In field combat, in desert or steppe automatic vehicles would be much more useful.
Moreover, even in urban areas I think, light-weight flying drones or microcopters would be much more useful.
So in general, androids well, would be the most useful for parades, and the majority of robots in the battlefield would be robotic vehicles and drones.
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For this answer I'm assuming there are reasons that Androids are the go-to soldier-type, rather than dropping nukes and rods from god from orbit or scattering micro-sattelites into the stratosphere and using their data to pinpoint perfectly hit things the size of ants with precision artillery/aircraft ammunition.
The current design of weapons, mainly the size of the ammunition and the power behind it, came to be because this was an effective size to power ratio. Even against someone wearing bodyarmor such weapons are going to be effective. But with very strong Androids these weapons will be insufficient and you'll need to use other weapons.
Beam weapons are an option, but they have the drawback of scatter whenever they hit reflective surfaces. No matter how reflective the surface, any laserbeam capable of being used as a weapon will be able to burn the reflective surface off with the energy that isn't reflected. But not before scattering the laserbeam in a great many directions. This is a great hazard for the eyes and sensors of anyone around it, mainly the people trying to shoot said target. This means people will equip a reflective surface on all armor to increase the chances that some of the attackers are reduced in effectiveness when their eyes/sensors are hit. So beam weapons would only really be used by low-level militia who can't handle the recoil forces of projectile type weapons.
Projectile weapons like railguns/coilguns would be another option, assuming you have a solution for the power requirements but considering the massive amounts of energy-sucking androids with super-strength and speed runnning around I guess that's not a problem. Railguns would be able to reach hypervelocity speeds, and by decreasing the projectile's weight but increasing it's speed you can keep the recoil as low as current weapons but with much more power behind the bullet (and much higher power requirement to fire it).
Lastly, melee would make a return. It is likely that the power requirements for the laser/railgun weapons is so massive that it's unfeasible to use them a lot against androids. So Androids would use their strength and speed to engage each other after the initial clash.
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NASA's Project Orion created the concept of a spacecraft that detonated nuclear bombs behind it, and rid the shockwaves as a form of propulsion, but the project was abandoned because nuclear bombs are dangerous and there is no need for something that powerful.
However, let's say that today, an apocalypse scenario was predicted in 5 years that would wide destroy all life on earth, maybe a meteor or a supernova or something.
With our current technology + 5 years of research and development, could we use Project Orion's concept to build city-sized spacecraft and evacuate the entirety of humanity from earth?
[Answer]
Given the very short timelines, I will say "no".
The largest Orion craft under serious study were 4000 ton behemoths for flights to Mars, Saturn or to create "Space Battleships" to dominate the Earth, and as we all know, no actual hardware was ever made for these. More "serious" studies were done for much smaller ships capable of being lofted into orbit on Saturn V boosters (i.e. much more detailed studies) but even than no metal was actually bent.
This means that the actual parameters of some of the most critical aspects of ORION, like the mechanisms of the shock absorbers are relatively unknown. The size of the shock absorbers for a 4000 ton ORION is the size of a building, and no one to my knowledge has ever built something like that, much less tested it under extreme conditions (nuclear shockwaves, the vacuum of space), so how they would perform is unknown. The secondary shock absorbers are also a bit of a mystery (I am a bit dubious of a stack of ring shaped airbags as the secondary unit), so much of the R&D will be to actually test these 50 year old concepts.
Now it is possible that there are new technologies that would work "better" (I am picturing something like a giant solenoid for the shock absorber unit), but now we are talking about adapting a *different* technology for very extreme conditions.
And of course no one ever built or tested the drive plate "for real". I think the only thing which was ever physically tested were concept models of the "physics package" which would power the ship, mostly to determine if such small devices would have other sorts of utility (nuclear artillery shells, the ignition units for very small thermonuclear weapons, nuclear shaped charges, etc.)
A five year crash program would probably be enough to build ORION ships of modest size, perhaps similar to the ones planned for liftoff to orbit via Saturn V booster (even if you launched them from the ground), since the size of the components would be reasonable to design, build and test with existing infrastructure. A 4000 ton ORION *might* be possible at the outside edge of possibility, but multi million ton vessels like the ones Freeman Dyson postulated as starships when calculating the "ultimate" possible ORIONs would be far beyond us even today.
[Answer]
**Short answer:** Yes, but I don't think you'd want to.
**Long answer:**
Nukes would be cheaper so it's feasible, but nukes can be significantly more dangerous.
Wikipedia actually has a calculation for something along these lines: (Paraphrasing)
>
> With the "Momentum Limited" Orion, a 50,000,000 kg payload could be
> brought from Earth to Alpha Centauri and would cost around \$367
> Billion USD. That's about **$7,340/kg.**
>
>
> Source: [Wikipedia: Project Orion](https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)#Interstellar_missions)
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The [SpaceX Falcon 9 rocket](https://en.wikipedia.org/wiki/Falcon_9_v1.1) can put 4,850 kg into Geosynchronous Transfer Orbit (it's a cakewalk after getting to GTO) for \$61.2 million. That's about **$12,618/kg**. Add an additional chunk to get us further into space and we're even more expensive (I can't give an exact figure).
The real problem is that nukes give off loads of radiation. And you can't really get much away from it. You could shield the effect with lead, but the more lead, the more it costs, and the less you could bring up with you. Traditional rockets don't have this issue.
Additionally, traditional rockets have to be made small just due to the cost of leaving Earth. The Orion craft mentioned above from Wikipedia, you'd be putting a lot of your eggs in a single basket. Specially 10,309 eggs for each traditional rocket into a single orion basket.
Most rockets have a 98%+ success rate. For the same weight in the orion ship, you'd have around 10,309 traditional ships. Around 206 would fail (around 1,000,000 kg). At an [average of ~80.7kg/person](https://www.google.ca/webhp?q=average%20weight%20of%20a%20human), at most **that's 12,391 lives lost** (likely less due to luggage)
If the orion craft breaks, you'd lose all 50,000,000 kg. At most, **that's 619,578 lives lost**. That's quite a lot of lives.
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In addition to the size problem that Thucydides brings up there's also the fact that the bigger something is the longer it takes to construct. Even if they were handed known-good plans for the city-sized craft that doesn't mean they would go that route.
Besides, this is the sort of problem where you try every approach and hope something works. You're not going to build one big craft, you're going to build a bunch of small craft. They may dock together during the freefall part of their voyage but they'll boost separately.
I don't think we have anything like the bombs to lift Earth's entire population anyway. At best you'll get enough off to form a colony.
Given either of the threats you name I don't think the right answer is evacuation, anyway.
1) Supernova. Looking at the sky we don't find any prospects for a star that could actually fry the surface of the Earth. The threat is frying the ozone layer and ending up with really brutal UV for some years. Survival consists of sunshades and greenhouses. Even if there is something that can fry the surface every 3' of dirt provides 1000x attenuation. There are houses today that provide that kind of shielding--not preppers but rather surrounding the house with enough thermal mass that you have basically no need of heat or AC.
2) Meteor. Here things get nastier. The area for hundreds of miles around the impact would have to be evacuated. Beyond that you need protection from the fires and the splash--the same houses I mentioned in the supernova case with some filters and bottled air would do the job.
If the impactor is **really** big (large asteroid size) evacuation would be the only option, though.
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In my world agriculture doesn't work, the day lasts many years so the people are always on the move. You can't farm if you won't be there for the next 8 or 9 years. Well, When I read this question it got me thinking. After reading [this question](https://worldbuilding.stackexchange.com/questions/22459/feeding-an-army-by-mobile-farming), it made me wonder, would an airship be able to carry a small plot of farm land?
The plot could be any size. And medieval as well as modern and future situations could have this. The largest Medieval villages would only contain at most 200 people. Modern towns would have more around 700-900. Future cities would contain up to 40,000
[Answer]
Density of loose earth = [1200](http://www.engineeringtoolbox.com/earth-soil-weight-d_1349.html) kg/m*3*
Weight a large, modern day zepplin can carry = [226,796 kg](http://www.dailymail.co.uk/news/article-2416809/Return-zeppelin-Firm-unveils-gigantic-airship-revolutionise-goods-carried-world.html)
Farmland required to feed 1 american = [1 acre](http://www.farmlandlp.com/2012/01/one-acre-feeds-a-person/) (4046.86 m*2*)
1 acre of loose soil weighs 4046.86 m*2* \* 0.5 m \* 1200 kg/m*3* = **2,428,116 kg**
Some really rough numbers to give a first guess... but a modern day large zeppelin apparently can't even come close to holding the mass required to hold enough farmland to feed even a single person (assuming a 50 cm soil depth).
We can make some assumptions to help the case like eating a vegetarian diet requires less land, using hydrogen like you suggest, as opposed to helium in the example I gave... but these are pretty small improvements compared to the order of magnitude weight difference that needs to be addressed.
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I would suspect that as long as the people are not staying to close to the morning side that they will be doing a LOT of gathering of plants and vegetables along the way. Plants will likely have to die or go dormant when they get past evening, and wake up in the morning and grow and reproduce. Long days make a huge difference in the growing capabilities of plants. Look at Alaska, their growing days can be 18+ hours long in places. They get huge produce and lots of it, in a relatively short time.
So it would also be possible for the city to float 'ahead' park and grow some crops for a few months, harvest and then leap frog ahead to another useful place to grow the next batch.
while some plants could be grown on the ship, it would likely mostly have to be a few fresh fruits and veggies to help supplement the traveling diet. Dirt is heavy and so are plants, they need a lot of water too. I think gathering food from the local plants below and or leap frogging to raise their own crops would be more likely.
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**My question regards mirroring**, specifically what you would expect from a universe that was mirrored from the perspective of our own, regarding its interactions with our own. The mirroring works exactly, well like a mirror, so handedness is going to be switched it seems on many things.
**The universe** in question is identical in all other respects, but is mirrored. I suspect there would be significant changes, but these wouldn't affect the world itself somewhat like a anti-matter universe, but if the two worlds interacted, say through a portal or something it would affect their interactions potentially violently.
**Certain things come to mind** right away: many organic compounds have a handedness, and as thus you can't consume them (differing handedness is how some fake sugars work), however more importantly I fear having opposite handedness on the subatomic level might mean any interactions between the two worlds would be very violent. I need to know the effects of interactions between "mirrored" universes for a future question, but if any interactions between the universes resulted in some catastrophic effect that would rule out this specific scenario.
**Other than** the potential for destructive interaction, merely having people not be able to eat the other universes food doesn't bother me, only results which rule out travel between universes bother me. Ultimately I ask this question, because I simply don't know enough to say how opposite handedness (or whatever you expect with mirroring) would affect the interactions between otherwise nearly identical universes. An ideal answer tackles the subatomic aspects, and if the interactions aren't to destructive then it also tackles some other effects at higher levels like chemistry.
**Clarification** The only difference between this universe and our own is is that it is flipped back to front *exactly* like a mirror, as thus the only difference effects will occur when you travel between them.
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Let me elaborate with some specific examples.
If you arrange copper, nickle, salt (sodium, chlorine) water (hydrogen, oxygen) according to plan and construct a device that produces electric current (dissimilar metals make a battery), make a coil of wire to form an electromagnet, coax more electrons out of the wire to fly across the magnet, *which way will the path of the electrons bend*?
If you reversed all, the directions when you built it: which way did you coil the wire, how are the components arranged on the bench, how did you label the ends; then the *entire experiment* will be a mirror image, including the resting path. Make a movie of the experiment, show it normal and show it mirrored, and both are correct in *this* universe.
So if you reverse left and right **everywhere** then nothing changes regarding gravity, electromagnetism, or the strong nuclear force. Only processes involving the weak "force" will make any difference.
So what's the point in your story? If everything is the same, why mention it? We presume it will be something people will notice. If you could travel with *your* apparatus, or at least a physical model that lets you say "this is left" along with the directions, and the electrons bent the *wrong way*, that would be consistent with the laws of physics if the *charge* of the electrons were reversed... oh, but the electromagnet would flip polarity also, so it still comes out the same!
You basically can't arbitrarily say some things are mirrored, since everything follows interrelated rules.
So you need to be more specific as to what is changed. If "everything" then it's nothing, which is pointless.
If you just pick things, without much knowledge of physics, you'll probably keep finding that it can't work.
So... look *only* at things that are conditions, not laws. Like, a planet with life based on mirror image molecules. But that doesn't need a different universe.
---
Your actual point is "everything the same... only notice a problem where they meet" and antimatter is a good way to go. Reversed time might amount to the identical thing if the time arrows line up across the portal.
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The combined CPT parity is fundimental. If you reverse P, you also reverse the combined CT. You can do that by reversing C, in which case you have antimatter. Actually, their antimatter is regular matter, since the things that caused the universe to produce matter rather than equal parts will have been reversed.
Or you can reverse T. The flow of time is the other way, but you are caught up in the flow so how can you tell? How do you compare the directions in different universes?
So someone who is transported there via a wormhole that lets a body move unchanged between them:
1. Will be made of antimatter relative to the surrounding material. Oops.
2. The mouth will discharge in the local time direction, so it is not obseevable that it's the other way around.
In the latter case, how can the *law* change but still allow a wormhole to connect the two spaces? You could not come through intact I would think. All the molecules would be messed up. If you did manage it, you would perceive that either the right-hand-rule is changed *or* all the particles innyour body have had their charges reversed.
Try looking at precession of a gyroscope... that doesn't make sense to reverse since it follows from Newton's laws which don't have directions mentioned in the laws.
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I'd say anything would be pretty much the same.
At a chemistry level, let's say in "normal world" you have "Sugar R", which is ok, and "Sugar L", which is toxic. In reverse world, everyone would go for "Sugar L", because your own molecules would also be the other way around, so you could consume it **[citation needed]**. Now, if you were a traveler from the "normal" world, you would keep away for their "normal sugar (R)" and go consume the toxic (for them) one, which is the appropiate for it.
At an artistic level could be some differences. Pick a painting, mirror it. Some won't change much. Some will be horrible. So the art (use of perspective and such) could change. How much does art influence the world? Well, that's up to you. I'd say *moderately*.
It could also be argued that mirrored brains made of mirrored molecules would perceive the mirrored version as more artistically pleasing so... who knows?
But yeah, apart from some quirks here and there (because of butterfly effect of little instances where the perspective DID matter), I'd say the world would be pretty much the same...
**Source:** *The Legend of Zelda: Twilight Princess.*
Its Wii version is a mirrored version of the Gamecube version because Link is left handed and people are most likely to be right handed and that's relevant when using a Wiimote and god forbid we only mirror the character f\*\*k we are mirroring THE ENTIRE WORLD and deal with it, walkthoughs. (Should be noted that, as stated before, some zones look/feel weird in the Wii version because they were designed to be seen and navigated the other way around)
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So in a setting I'm developing, a moon orbits a gas giant once every four days. It naturally is tidally locked to the parent body. Halfway through the day part of the cycle there is a two hour solar eclipse. If you assume hour zero is dawn, then the schedule looks somewhat like this for the part of the moon facing the gas giant (the part of the moon not facing the gas giant looks the same except it lacks the eclipse):
* 0-22.9: daylight
* 23-24.9: eclipse
* 25-47.9: daylight
* 48-95.9: night
Oh and I didn't specify it yet, but this moon is pretty Earth-like. Humans can easily survive on it; the gravity, atmosphere and temperature range is very similar.
A broad question anyone here can answer is: How would humans react to being placed on this moon?
However I'm looking for the answer to this question specifically: how would the day timetable specified above affect human sleeping patterns? What would happen?
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Using humans who live above the Arctic Circle as an example, they would do just fine by making their own night and day at the time intervals their circadian rhythms dictate. They would use blackout shades to cover the windows and artificial illumination to create daylight when they need it. Without the ability to create artificial day or night, things could get ugly fairly fast. There's a lot of [research](http://www.arcticfrontiers.com/arctic-frontiers/archive/2014-conference/side-events/178-the-dark-and-light-sides-of-arctic-sleep) floating around the Internet on what happens to Arctic inhabitants and research into modifying [sleep cycles](http://slumberwise.com/science/could-you-survive-an-endless-night/) using a process called [entrainment](https://en.wikipedia.org/wiki/Entrainment_(biomusicology)). Most subjects seemed to feel better on the 24-hour cycle though.
If the humans lived on that moon for thousands or tens of thousands of years then they would adapt to the longer days and nights (though perhaps with some residual memory of the 24-hour cycle?). If there is some kind of selection pressure that adapting to the long days somehow increases chances for survival, then I would expect the adaptation to happen a bit faster.
Given a wicked advanced set of genome engineering, then it may be possible for the humans to adjust their circadian rhythms without the resorting to the selection pressures of evolution. This is a mind boggling degree of power because those rhythms touch so very many systems.
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We don't sleep about 7-8 hours due to the night on our planet. We sleep that amount since our body needs that. Or, to be specific, our brains seem to need sleep. Our bodies outside our brains would be fine by simply lying around and rest. But without sleeping our brains will start to act weird, we cannot create memories, our level of consciousness changes. Based on animal tests after 18 days of being nonstop awake, we start to drop dead.
Thus regardless of the amount of day or night time some planet might have humans need that 8 hours of sleep to operate for the next 16+ hours. How much there are light or darkness may disturb some individuals ability to sleep well, but the overall need for sleep remains the same.
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As to your question, "how would humans react?" I think you have to remember that humans are intelligent, pattern seeking planners. If they have clocks, they are going to design a sleep schedule most similar to what they are familiar with, where they are awake for as much of the daylight as possible. Since 96 is divisible by 24, that shouldn't be hard. They'll probably get less sleep on nights where the sun is up, and sleep longer on days without sunlight.
Your moon would have time zones, in that the sun comes up and goes down at a different time all around the globe. The eclipse will happen at different times of day in every time zone. On half of the planet, the eclipse will happen at night and it will be like it isn't there at all. But, since everyone needs to sleep twice during each day and sleep twice during each night, a global society on this planet might agree to all wake and sleep on the same schedule, so the society might not use time zones.
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I am writing a book and have a species of invasive plants which secretes acid to turn plant and animal matter into a kind of fertilizer. Is this acid capable of causing a fire? Or are the countless other chemicals in plants and animals be enough to prevent a fire from starting?
Obviously the latter is the case when it comes to stomach acids, otherwise we would all combust into flames. But that would be an aspect of natural evolution. This is an invasive species and I have never known of a plant species to act in the matter that I am attempting to accomplish.
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The chemical term you are looking for is "hypergolic" and it means spontaneously causes ignition. There are all sorts of chemicals that are hypergolic with other specific chemicals but very few chemicals are hypergolic with most other chemicals.
I'm going to answer your specific question but follow it with a more general description and interesting articles (interesting if you like the topic that is).
**Short answer**
I didn't find much that was *directly* (meaning without other chemicals present) hypergolic with hydrochloric $ HCl $, however, there are some chemicals that are hypergolic with sulfuric acid ($ H\_2SO\_4 $).
This includes:
* Ether (burns vigorously)
* Nitric Acid (vigorous reaction but no flame)
* Potassium Perchlorate (explodes)
* Potassium Perchlorate + sugar/starch
* etc.
Here's some [discussion on a science board about what chemists have found react hypergolically or explosively](http://www.sciencemadness.org/talk/viewthread.php?tid=10776).
Here's a [list of videos which show the same](https://www.youtube.com/results?search_query=potassium+chlorate+sugar+sulfuric+acid&search_type=&aq=f).
**General discussion**
The problem with a plant carrying a digestive chemical which reacts so strongly with the chemistry of other living things is this: creatures evolved on the same planet, share the same chemistry. Meaning that plant contains chemicals which can cause itself to spontaneously burst into the flame if its reservoir of that chemical is ruptured.
Imagine an explore hacking his way through a jungle with a machette. He accidentally hits this *"flame bush"* and ruptures its digestive sack - **immediately causing the plant to burst into flame**. If any of that fluid sprayed out of the sack, say onto another plant or the explorer, **then adjacent plants and *even the explorer also burst into flame***.
**Fun stuff**
There are chemicals which are hypergolic with many other chemicals. You might find the discussion in **[Sand won't save you this time](http://pipeline.corante.com/archives/2008/02/26/sand_wont_save_you_this_time.php)** discussion amusing or interesting.
The chemical is called chlorine trifluoride ($ ClF\_3 $ ).
>
> There’s a report from the early 1950s (in this PDF) of a one-ton spill
> of the stuff. It burned its way through a foot of concrete floor and
> chewed up another meter of sand and gravel beneath, completing a day
> that I'm sure no one involved ever forgot. That process, I should add,
> would necessarily have been accompanied by copious amounts of horribly
> toxic and corrosive by-products: it’s bad enough when your reagent
> ignites wet sand, but the clouds of hot hydrofluoric acid are your
> special door prize if you’re foolhardy enough to hang around and watch
> the fireworks.
>
>
> ”It is, of course, extremely toxic, but that's the least of the
> problem. It is hypergolic with every known fuel, and so rapidly
> hypergolic that no ignition delay has ever been measured. **It is also
> hypergolic with such things as cloth, wood, and test *engineers***, not to
> mention asbestos, sand, and water-with which it reacts explosively. It
> can be kept in some of the ordinary structural metals-steel, copper,
> aluminium, etc.-because of the formation of a thin film of insoluble
> metal fluoride which protects the bulk of the metal, just as the
> invisible coat of oxide on aluminium keeps it from burning up in the
> atmosphere. If, however, this coat is melted or scrubbed off, and has
> no chance to reform, the operator is confronted with the problem of
> coping with a metal-fluorine fire. **For dealing with this situation, I
> have always recommended a good pair of running shoes.**”
>
>
>
Put chemicals like these under the title "*if you discover someone messing with these, run away from them as fast as you can*".
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Plants which secrete acids or digestive chemicals actually do exist, in the form of Venus Flytraps, Pitcherplants and other sorts of plants which trap and digest insects. This is probably a bit slow for what you are looking for.
Other plants have various toxic chemicals circulating or stored in their various leaves, stems or fruit in order to deter herbivores from eating them. Advancing a bit from Jim2B's answer, some plants on your world may have evolved a way of storing a hypergolic chemical as a means of deterring predation by even the most aggressive and well armoured herbivores. One bite into the "flame pod" and the problem of being eaten is rapidly solved. As a bonus, the herbivore may be mortally wounded and die close by, providing some much needed bio-matter to the soil. The burst of fire might also clear out competing plants, providing more space for growth, clearings for new seedlings to sprout and a clear space for sunlight to filter in through the canopy.
Since most animals might eventually learn to avoid the flame plant, there would also be some sort of mechanism for the plant to open the flame pods so the plant can get the benefits of fire without waiting to be eaten. It would also be interesting to think through the implications on the rest of the ecological system if such a plant actually existed (what do the other plants use as countermeasures, for example?)
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What of the organism was purposfully engineered for that? It could be like Nivin's [stage trees](http://www.larryniven.net/knownspace.shtml). In a civilisation where all types of industrial chemestry is done this way, the only feedstocks produced would be things that can no longer be used in biological enzyme systems, so in addition to growing synthetic fiber, ordinary fuel, fertilizer, etc. **they would grow truely nasty stuff** that must then be put in a non-living vat for subsequent processing.
Consider that this is somehow approchable to them with a low tech level, due to the nature of life on their world and their species innate capabilities. Directed invented substances would emerge somewhat after agraculture, and maybe became signigicant in a time like our ancient Greek civilizations. Their equivalents of Heron and Archemedes produced synthetic materials.
Move forward a few thousand years, with civilizations falling and rising, and environments changing in an area. You might have some *very* interesting wildlife, with especially spectacular sterile hybrids. Their Archemedes analogue would have produced weapons...
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Yesterday I was driving at night on an unlit road (nothing nefarious, I swear), and there was a truck behind me with a ridiculous amount of headlamps on, and catching a glimpse of it in my mirror it looked a bit like an angry animal. It got me to thinking, if there was an animal that could switch on headlights in the jungle, it could scare off quite a lot of predators.
Now I know that there are fish, like the electric eel (whose scientific name is "Electrophorus Electricus", which I find rather hilarious) that can use electricity for hunting and communication and self-defence. But I'm wondering if an entire species (like all types of cats for example) could have evolved to use electricity for similar purposes.
And I'm not talking properly Pikachu style, just channel enough electrons to create a bright light source for a limited amount of time, to scare off predators or to startle prey for example.
I don't know if this would be through bio-luminescence, like an angler fish, or more like an actual light bulb, by running electrons through some sort of natural filament to create the light. Whichever one is possible to create a significant amount of light really.
This animal doesn't necessarily have to have evolved on the Earth we live in now, it could have any conditions to evolve.
So my main points of the question are:
1. Could an animal evolve to use electricity which could power, let's say as an example, two 85 watt bulbs for 5-10 seconds?
2. Could an animal use this electricity to produce things like light for their survival and that of their family, be it through hunting or protection?
3. **Bonus**: If such an animal/species were to exist in a habitat on land (like in the mighty jungle), would other animals that currently exist on our planet be able to coexist with this animal, as its predator or its prey? Or would they need to evolve to be able to catch/escape it?
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This doesn't sound too unreasonable except that organisms rarely use electricity to create light. Metal filaments are in short supply in nature.
1: Yes but you'd need a decent explanation. Perhaps a large decedent of something like an electric eel which evolved to prey on very large prey and needs to provide a large jolt. Though they're unlikely to produce a 5-10 second pulse since a shorter more powerful pulse is more likely to be useful as a weapon.
2: It tends to be vastly more efficient to make light with chemicals.Doing so with electricity wastes a lot of energy.
<http://www.washingtonpost.com/wp-dyn/content/article/2010/10/11/AR2010101104495.html>
>
> Some species glow as a warning that they're poisonous; others confuse
> or blind attackers by releasing clouds or jets of light-emitting
> chemicals while trying to escape.
>
>
> Some marine organisms, if attacked, produce what scientists call a
> burglar alarm - a visual 911 call designed to attract a larger fish
> that's only too happy to gobble up the flashy prey's assailant.
>
>
>
3:I don't see why not though out of water such an animal would probably need direct physical contact. If it was a major predator you can be sure other species would evolve many methods for counteracting electrical shocks.
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[Electric Eel](http://en.wikipedia.org/wiki/Electric_eel) produces enough electricity to light a LED bulb for half a second. Traditional filament bulb - not really.
>
> In the electric eel, some 5,000 to 6,000 stacked electroplaques are capable of producing a shock at up to 600 volts and 1 ampere of current (600 watts) for a duration of two milliseconds.
>
>
>
I'm not sure if it would manage 160 watt for 10-15 seconds, but it's well enough to seriously shock any animal (including humans) that threaten the eel.
Light bulbs are terribly lossy; they have light efficiency of order of 0.5%. Chemical-electric luminescence is far more efficient and quite a few species of the deep can "power" their glowing cells through neuroelectric impulses.
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[Jaswinder](http://www.behindthename.com/random/random.php?number=1&gender=u&surname=&all=yes) lives in a world much like ours except that there is magic, and he has suddenly manifest it. He is able to at will draw on up to (at any one time) the equivalent of 8.9876e+19 joules of magical power (being 1000 kilograms mass-energy conversion) and a completely non-logical effect happens, localized within 1km of Jaswinder (at first), though Jaswinder will always survive whatever it is that happens. Being non-logical, Jaswinder is unable to control what happens and no one studying it would be able to predict what would happen either; it can not be adequately explained by science.
Should Jaswinder ever use his powers? Is there a way to calculate the optimal strategy for Jaswinder to use his powers? What would the optimal power level and minimal safe distance be at that power level? Excluding just killing anyone who manifested powers, how could society cope, use, or incorporate individuals with magic?
Non-logical would seem to be true randomness; if it is following a distribution there aren't enough observations to determine what it is separate from being uniformly distributed among all possible outcomes that could ever happen with that amount of matter-energy. Assume no anti-matter is produced.
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The limits of Jaswinder's powers are, as I understand it:
* 1000 kilograms worth of energy, though not antimatter (spoilsport!)
* effects within 1 km radius (though the effect could be a point or a 1km sphere)
* the effect is not logical
The key is how one interprets "not logical;" here are three possibilities:
## "Doesn't follow the logical rules of the universe"
Picture, if you will, a circular target with three rings. The center of the target is a stable object. It will probably be a lump, or dust, or something else with no recognizable shape, but at least it will exist. The second, much larger ring is radioactive matter; if Jaswinder makes anything with some sort of mass, it's probably going to be radioactive, because none of the atoms will have the right number of protons, neutrons, or electrons to be stable. The outside ring is energy; whatever Jaswinder's magic produces, it either decays quickly, or was simply energy to begin with. Finally, if the target is missed completely, the thing that is created can't exist in our universe, to the point of not actually interacting with the universe.
When Jaswinder uses his powers, it is equivalent to standing at the opposite end of the universe and throwing a dart at random. While it's possible that he creates something, or makes a burst of raw energy, the overwhelming chances are that whatever he creates will never interact with the universe at all. In other words, if Jaswinder used his ability all day, every day, by the end of his life, he will probably not have more than a single observable effect to his name.
## "Completely random"
This one is much more exciting, as it actually makes Jaswinder into a bomb, though not a reusable one. Given any configuration of sub-atomic matter or energy, most of the time the "matter" Jaswinder creates will be nothing more than stray electrons, protons, neutrons, or raw energy. The energy and matter would be scattered around Jaswinder in a 1 km sphere. The random matter would mostly be free sub-atomic particles, which will wreak havoc on matter.
The fact that Jaswinder survives the explosion would be great, except there's a pretty good chance that the ground Jaswinder was standing on would be vaporized or otherwise destroyed, leaving him to plummet into a hole that will be as deep as 1 km.
If Jaswinder wants to survive, he would have to calculate how much energy he should draw to be able to fry the area around him without damaging the ground he is standing on. Of course, he doesn't know if the energy will be evenly spread around the 1 km sphere, or piled in a tiny point just under his feet.
## "Random, but recognizable"
Unlike the previous two answers, here Jaswinder's power creates something that not only can exist, but is recognizable. When he uses his powers, he creates an object somewhere in a 1 km sphere that weighs between 0 and 1000 kg. The object could be anything: a bubble of hydrogen, a 1000 kg gold statue of his grandmother, 100 dead mice, an exact living duplicate of Elvis, or a two-story-tall supercomputer; what it is shaped like, what it is made of, and whether it is organic, inorganic, living, dead, or somewhere in between is completely at random. Oh, and it appears anywhere within 1 kg of our "hero".
At first, that ability would be really cool; he would summon a gold statue nearby, and a wind-up robot that can talk. Of course, it wouldn't be long before he also calls up a perfect copy of his grandmother 1 km above his head, a cute puppy embedded in his bedroom door, 500 kg of raw sewage into his house, and 100 kg of spiders in his own bed.
Jaswinder would not want to use his power. Random is bad.
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Well, I can see two different uses right off the bat.
The first, send him into the enemy lines and let him blow off steam over there, it would be a terrible blow to anyone trying to attack. But he would need to have a secret Identity or he would be assassinated pretty quickly, maybe only get one chance...
The other would be to crate some kind of containment to convert the released energy into power to be used for other things. Beyond that?
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This is a great start, but you can't leave it at that. If you can get any material thing within a mass range with equal probability (mass-wise, atom-wise?) you're getting either:
* A bunch of hydrogen, with a few atoms of heavier elements (if atom-wise probabily distro reflects that of [the universe](http://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Abundance_of_elements_in_the_Universe))
* A (most likely supercritical) radioactive pile (if uniformly distributed across all [possible nuclear isotopes](http://en.wikipedia.org/wiki/Table_of_nuclides_%28complete%29))
Neither is particularly plot friendly, unless you like fizzle or pop. What you need is what I'll call a **probability scaffold**. This is a tool that, when provided the first atom-equivalent electron-Volts of energy, uses it or discards it (returning it to the magical fount, hopefully) if unsuitable, then moves on to the next, and the next and the next. Depending on the abilities of the magical probablity scaffolder, you can generate simple objects like a **bar of solid gold** or if you're good, **complex and otherwise impossible to build three dimensional structures**.
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I recently re-watched an awesome show - [Diebuster](http://en.wikipedia.org/wiki/Diebuster). At one point in the show, one of the characters uses Jupiter as a projectile, slamming it into one of the aliens, but to no avail.
I can't find a good picture of that scene for some strange reason.
Anyway, this question is not about how such a feat would be achievable, or even about whether or not it is possible, rather it is about just how powerful such a projectile would be. How much damage would Jupiter do as a projectile, assuming it is travelling at a speed fast enough to be perceivable by the human eye or to be at least considered projectile speeds (I'm not sure the exact numbers)?
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You are going to do a ***lot*** of damage. To restate the calculations PipperChip has done:
$$ E\_k = \frac{1}{2}mv^2 $$
$$ E\_k = \frac{1}{2} \times 1.89 \times 10^{27} \times 13000^2 $$
$$ = 1.6 \times 10^{35} \text{J} $$
That's quite a lot of energy - enough to [destroy 665 Earths](https://worldbuilding.stackexchange.com/questions/4679/the-opposite-to-worldbuilding-world-destruction). And that's just the energy Jupiter has at its orbit velocity.
However, if you're going to *move* it, you also need a lot of energy. Most likely this energy is also pretty significant: not only is Jupiter incredibly heavy, it's a gas giant, so you can't just hire a rocket to give it a push - it'll go right through. With that kind of technology and energy to throw around, it would be a foolish alien to mess with you.
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There are, at least, a few ways to measure the damage a weapon can do. Perhaps the simplest, and most easily transferred between varying weapon types, is the energy behind the blast. This is often normalized per kg because you can often get bigger explosions by simply adding more explosives. [Another good way](http://en.wikipedia.org/wiki/TNT_equivalent) is to measure the energy in terms of how much TNT you would need to produce that energy.
[TNT](http://en.wikipedia.org/wiki/Trinitrotoluene) (the explosive) has an energy of 2.8 megajoules per kg. Dynamite is at 7.5 megajoules per kg, or about 2.67 times as explosive as TNT. Let's talk about kinetic rounds.
[Kinetic rounds](http://en.wikipedia.org/wiki/Kinetic_energy_penetrator) do not use explosive force, but they do carry the common currency of energy. Obviously, kinetic rounds use kinetic energy, not "explosive" energy like TNT. Since both objects are often measured in how much energy they hit the target with, you can make the comparison.
To determine the kinetic energy of something, you use can use:
$$E\_{k}=\frac{1}{2}mv^2$$
Where m is the mass of the object and v is it's velocity.
For Jupiter, going at the speed of a bullet from a high-powered rifle (mach 1), gives you about $1.09899149 × 10^{32} J$. That is $3.925 \* 10^{25}$ kg of TNT. However, Jupiter is so big that this speed is *really* slow. Jupiter orbits at $13\frac{km}{s}$, whereas the speed of sound is a measly $.340 \frac{km}{s}$.
If you shot jupiter at .1c, one-tenth the speed of light ($2.998\*10^{7} \frac{m}{s}$), you get $8.530 \* 10^{41} J$. That is $3.046 \* 10^{41}$ kg of TNT.
For reference, the [Tsar Bomba](http://en.wikipedia.org/wiki/Tsar_Bomba), considered the most powerful man-made explosion in the world, was 50 megatons of TNT. That is 209.2 PJ ($209.2 \* 10^{15}$ J). That also assumes that nothing else blows up when Jupiter hits, as it's mostly (~89%) $H\_2$. (Oxygen is not naturally present in large amounts in Jupiter, so it would not explode like the [Hindenburg](http://en.wikipedia.org/wiki/Hindenburg_disaster) did.)
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The story I'm writing has characters that speak a different language from the protagonists.
I'm thinking about building them a conlang (constructed language) but I don't know the best way to go about.
The world they inhabit is culturally and technologically and geographically similar to our own. That said I've struggled with naming and languages.
Should I create a conlang completely from scratch OR should I modify an existing language?
By modify and existing language I mean is their language how for example French would have evolved on this planet and in this culture in this time period?
OR
how, for example, Vulgar Latin would have evolved in their region/culture/time into a brother/sister language to French/Spanish/Portuguese/Italian/Romanian etc?
[Answer]
# Modifying a Language
Some perks:
1. The grammatical structures used already exist, whether you are aware of them or not.
2. People who speak that language may get tickled if they can understand the modified one.
3. You can quickly get a different language by applying some [vowel](http://en.wikipedia.org/wiki/Vowel_shift) or [consonant](http://en.wikipedia.org/wiki/High_German_consonant_shift) shift to one language (but be careful not to reverse some previous sound shift. You may start with Dutch and end up with German!)
Some Downsides:
1. People who speak that language could get seriously insulted.
2. You need to learn a language to modify it. Otherwise, you run the risk of breaking rules in the unmodified language, which can then ruin the modified language's authenticity.
# Building Your Own
Some Perks:
1. It will be foreign to everyone! You'd need a linguist or a dedicated fan to figure out the language. Even so, your sample size may be small enough that NO ONE WILL GET IT! They'd need a ["rosetta stone"](http://en.wikipedia.org/wiki/Rosetta_Stone) to translate it.
2. You will be able to define your own grammars, words, and ideas in this language
3. You can use whatever sounds the [human voice can produce](http://en.wikipedia.org/wiki/International_Phonetic_Alphabet). This is also a downside.
4. Conlangs can be super sweet. After all, J. R. R. Tolkein had a [deep linguistic background](http://en.wikipedia.org/wiki/J._R._R._Tolkien#Languages_and_philology). They can also serve to build your world.
Some Downsides:
1. It can be too mechanical. [Irregular verbs](http://en.wikipedia.org/wiki/Regular_and_irregular_verbs), for instance, are a common hallmark of actual, spoken languages. Real languages tend to have such quirks and exceptions. (English is a prime example: English has [exceptions which have exceptions](https://www.youtube.com/watch?v=1edPxKqiptw)!)
2. It can be [too irregular](http://en.wikipedia.org/wiki/Regular_and_irregular_verbs). If a language is totally irregular, it becomes very unusable. Many Indo-European Languages have a mixture of both.
3. Languages do not exist in a vacuum. They arrive in [families](http://en.wikipedia.org/wiki/Language_family), bump into each other, swap words, and morph over time. If a conlang exists in world, what do the other people speak?
4. You can use whatever sounds the human voice can produce. Good luck trying to use the roman alphabet to approximate those sounds! If you use IPA, you can get the sounds down, but only a select group of people can read it. Editors may not like you very much.
5. You likely need a good grounding in linguistics to have a complete enough conlang. Does it follow the [SVO grammar](http://en.wikipedia.org/wiki/Subject%E2%80%93verb%E2%80%93object) structure? What tenses and cases does it have?
[Answer]
I've usually been far more entertained by the idioms and turns of phrase that writers create for another race/culture than simply a cool new language.
Best example is from the new Mass Effect game, Andromeda. The game takes place in the Andromeda galaxy, and it rather goes without saying that the alien races there are speaking different languages. But they bypass them entirely by having universal translators. So instead of learning how to say "laser gun" in Angaran, we learn a few of their proverbs.
Example - "Ocean of fish, one will have gems in its mouth." That's perfect example of a proverb about optimism.
I'd rather hear what an alien race's analogue is to "let's flip a coin" than to know simply what their term for "coin" is.
] |
[Question]
[
I am creating a fantasy world where a given race is mystically tied to the planet. Predominately this race will be earth-dwellers, quite happy and content to burrow underground, but I'd like some of the race to be happier in the sea. The world is very Earth-like, so it works as a good model.
I know that the Earth's surface is covered by 71% water and roughly 10% by ice. And I know the Earth is about 0.023% water by mass, but that's a comparison against the total mass of the Earth. Neither of those figures however are what I'm after; surface area gives too large a percentage and the total percent by mass is probably too low.
So, the question is how much of the Earth's crust water by mass? As in what is the mass of the oceans, seas, rivers, and so on, compared just to the stones and rocks that make up the surface of the planet: the continents, sea-floors, and everything down to the mantle? I'm not even sure I'd know where to begin on that calculation, so even a rough ballpark would be helpful.
[Answer]
The Earth's crust [has a mass of $1.913\*10^{22}$ kilograms](http://loki.stockton.edu/~hozikm/geol/Courses/The%20Earth/Content%20Web%20Pages/Kim/crust.htm) and its [oceans have a mass of $1.35\*10^{21}$ kilograms](http://www.universetoday.com/65588/what-percent-of-earth-is-water/).
If you want to include all the mass from the mantle up to the surface as "the surface of the Earth" then simply add the two together: $2.048\*10^{22}$ kilograms of crust and ocean riding on the mantle.
**The oceans are about 6.6% of the mass from the mantle to the surface of the Earth.**
] |
[Question]
[
I have a certain vision for a post-apocalyptic cyberpunk world in which civilization itself is collapsed, but technology and structures are still existant. 98% of human population is wiped out by a viral mutagen, of the remaining 2% a part that is immune against the mutagen, a part is sentinent mutant and a part are mentally degenerated mutants with more animal-like behaviour.
So far so good, buildings are mostly intact, so is existing technology. But for roleplaying reasons I want most ways of communication, e.g. internet, telephone, cellphone to be broken down as well as the electricitry grid. Level of the technology would be similar to what we have today, a bit more advanced in some areas like robotics and medicine.
[Answer]
EDT: [Sorry I missed pointing out how this was relevant! Losing %98 of the human population would be cause enough all by itself for these things to happen. All those things need people doing a lot of work to keep it all running smoothly.]
Well most telecommunications and major electricity grids would be down pretty quickly. Maybe as little as a few days. (the internet would go down with the telecommunications gird) Coal plants need a constant influx of material, nuclear power plants need monitoring. Hydro-electric would be the best bet, they should be able to go a few years with minimal maintenance before they break.
However, making and maintaining small power generation systems, wind mills, vegetable oil power generating engines, etc could still be used for a host of things.
HAM radio would likely be the first way to get long distance communications. If you had smart enough robots to help generate more technology, then it is possible, because most people wouldn't know how to build a mother board, much less create RAM or processors.
[Answer]
# [Coronal Mass Ejections](http://en.wikipedia.org/wiki/Coronal_mass_ejection#Impact_on_Earth)
That's when the sun basically makes a really big burp, and the ensuing particles don't do enough damage to harm plants or animals, but has the potential to knock down power grids, satellites, and all that depends on those. It's enough to trigger an apocalypse.
# Malicious Use of EMPS
An [EMP](http://en.wikipedia.org/wiki/Electromagnetic_pulse) could knock out the electrons from your circuitboards which are not shielded. This is actually considered a national security threat. A well placed EMP could knock down a power grid, wipe cell phones, and generally be devastating to modern life in general.
To be specific, you need to read about the [Starfish Prime](http://en.wikipedia.org/wiki/Starfish_Prime) and the [Soviet Project K nuclear tests](http://en.wikipedia.org/wiki/Soviet_Project_K_nuclear_tests). We learned from those that there are three main pulses; E1, E2, and E3. The E1 pulse of an EMP can and will destroy most electronics. An E1 pulse induces *huge* amounts of voltage in conductors, so your electronics will *literally* fry. In the Soviet Project K tests, an EMP actually caused fire in a nearby power plant.
That being said, uses of EMP may be too devastating for your world. Also, it's super easy to shield some things from EMPs, but you just need to prepared for it. It should also be noted that [vacuum tube electronics are not affected much by EMPs](http://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse#Vacuum_tube_versus_solid_state_electronics). Old TVs and WWII era technology would survive rather well.
EMPs are considered an actual threat, and nations are taking precautions to help their power grids and communication systems handle such attacks.
[Answer]
What you need is to work on one alternative reality or counter-history
If you want internet working strongly and steadily after the apocalypse, then you'll need to move all the internet infrastructure to space, then, you need something that damages almost all the electronics on earth but leave satellites mostly untouched and satellite servers storing websites & stuff untouched, so, to say, all the internet was moved up to be fully satellite communication, nothing ever exist on earth physically of it after and after that, in some point of history the cataclysm happened, but for that moment the internet was already safe there.
Then is the electricity stuff, if you want to make something like electricity still exist, you can make something like kinetic generators or somewhat improvised and modified water generators/windmills, using brute animal force is a way to go too... but you must say than the power is keeped in some batteries or something, we don't have the same demand than today now, because just the 2% of the population survive.
But then again, how will you have the knowledge to do that?
Well there are two choices here who are both compatible between them two...
1) The survivors are mostly returning from somewhere/something from where they survive the effects of the plague, when they return they'll be vaccinated from the virus by the few survivors who made it.
so that way you can justify have a bunch of experts to rebuild something like a safe perimeter, like a safe-city or something who actually have internet and generates enough power to itself but without saving themselves from the apocalypse.
2) The survivors find and study the Safebox of knowledge kept to restore civilization, that thing actually exist, so they learn the knowledge to make them own safe haven and you take them from there.
What can make that apocalypse happen?
Zombies? Human-Bots Wars? But bots are controlled by a super-computer and using biological weapons, or something like that?
In fact a Big Brother computer use the virus to attack humanity, but the mutants just go too fast out of control.. so the mutants harrass humanity but also the big brother computer, leaving humanity and that computer almost utterly destroyed (or just utterly destroyed saving some humans).
That should explain your problems.
[Answer]
Remember, the internet etc rely on very, very long cables. Lose 90% of the grid and what's left is worthless. Lose 90% of the examples of technology and your 2% survivors will have plenty to go around. (Note, though, that the society you describe will not be able to create new items--when the existing stuff wears out there will be no replacements.)
] |
[Question]
[
Exactly as asked on the title, is there a way that a human, or at least, a species that appears outwardly human, could survive being pincushioned by arrows, at least for a suitably dramatic length of time (several minutes, the length of one pre-death monologue, maybe.)?
I would rather if the answer came from a more biological standpoint rather than a technological one (e.g. tough leathery hide, redundant organs instead of "nanomachines, son!")
[Answer]
Well you pretty much covered it. There are a number of issues, and solutions for them.
**Vital Organ Damage**
To stop them dying due to a strike to vital organs you need some combination of:
1. Redundant organs
2. The ability to function without certain organs for a while as the organ repairs itself (or just in a last frenzied burst/monologue before they die if that's your intention).
3. Thick hide, bone, scales, fur, etc shielding the organs.
**Blood Loss**
To stop death due to blood loss you need some combination of:
1. Super-clotting
2. Self-sealing blood vessels
3. Rapid healing
Large size helps in general too, the larger you are the more arrow strikes will not penetrate to dangerous depths or can hit you but fail to strike vital organs.
[Answer]
**Shoot them at an American human.**
But really, a thick layer of adipose tissue (fat) covering the body will provide protection from immediate death by all but the highest velocity arrows. This can be seen in bears, whales, and over [6% of american humans](http://www.ncbi.nlm.nih.gov/pubmed/22986681). They're difficult to bring down with arrows alone, unless they're very well placed or shot with a very nice bow.
The layer of fat simply provides more material that has to be penetrated before vital organs are reached. They will likely still die from bleeding out, but that will take a while, especially considering the avascularity of adipose tissue (not many blood vessels).
[Answer]
There are already two conditions that we recognize as being disease states, that would facilitate this type of resistance.
Scleroderma - This is a chronic, rheumatoid autoimmune disease that causes thickening and hardening of the skin. (There are a number of other nasty effects as well, depending on the type, but this will just focus on the skin effects). If you have a population that is predisposed to this, or if your population develops just the skin portion, it would make it harder for arrows to penetrate, and would decrease the depth that they penetrate.
Factor V Leiden Thrombophilia - This is basically the opposite of hemophilia, in that instead of uncontrolled bleeding, the blood has an overactive tendency to clot. In "normal" biology, this presents a danger in the form of free floating blood clots (Which in turn can cause strokes and pulmonary emboli), however if it was task adapted to be faster/hyperactive clotting when exposed to air, it would also have the same effect.
So if you have a race that is predisposed to scleroderma and Factor V, then these could eventually mutate to be beneficial adaptations rather than debilitating disease states.
[Answer]
Perhaps a biological adaptation or mutation that causes skin to act like a Non-Newtonian fluid?
These are structures that are fluid or free to move normally but sharp impacts cause the surface to harden as the molecules bind under the force of the impacting object.
Silly putty is one example as is [D3o](http://en.wikipedia.org/wiki/D3o)
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[Question]
[
I posed a similar question earlier but was told maybe I should ask another one. I hope I am doing the right thing, so here goes.
The setting is a post-catastrophe Earth that is entirely or almost entirely covered in water, so naturally people live exclusively on big oil/tanker ships. For safety and community people usually develop fleets of ships that travel together, let's say that during a particularly strong storm, unnaturally strong that is, one of the ship's engines become damaged beyond repair and that ship is now adrift. Just to clarify the engines got damaged during the storm and the storm is still ongoing and the ship is adrift, the situation must be addressed *during* the storm.
* The technology level is today's commercially available technology
* The ship has lifeboats
* Is near the rest of the fleet, uncomfortably near
* It is otherwise in normal functioning condition - no fire, hull intact, only the engines are gone, the only risk is of ramming into the other ships
* The fleet has lifeboats and a couple of helicopters
How can the people on the ship be saved?
Can the ship itself be saved?
[Answer]
That doesn't sound too bad at all.
There's no threat to either the ship or the lives of the people on board (other than possible collision with another vessel), if I understand correctly. This is therefore a situation of '[urgency](http://en.wikipedia.org/wiki/Pan-pan)' rather than distress.
So the obvious thing to do is:
* Ship communicates "[vessel not under command](http://navruleshandbook.com/Rule27.html)" to nearby vessels (using radio, lights, etc). Crew and passengers remain on board (much safer than evacuation in bad weather).
* Other vessels manoeuvre to avoid collision.
* All parties wait for the storm to die down and then think about next steps: repair, towing, etc.
Lights and shapes:
[International Collision Regulations > Part C - Lights and shapes >
Rule 27 - Vessels not under command or restricted in their ability to manoeuvre](http://www.otenmaritime.com/international-collision-regulations/part-c---lights-and-shapes/rule-27---vessels-not-under-command-or-restricted-in-their-ability-to-manoeuvre)
>
> (a) A vessel not under command shall exhibit:
>
> (i) two all-round red lights in a vertical line where they can best be seen;
>
> (ii) two balls or similar shapes in a vertical line where they can best be seen;
>
> (iii) when making way through the water, in addition to the lights prescribed in this paragraph, sidelights and a sternlight.
>
>
>
>
[Radio transmission of urgency message](http://www.portreath-harbour.org/distress-proceedures/pan-pan/):
>
> The format of the urgent message is as follows:
>
> PAN PAN (repeated three times) Your vessels name (repeated three times).
>
> Your International call sign and MMSI.
>
> PAN PAN (once) your vessels name (once).
>
> Your Position (in Lat and Long) or compass bearings if you have no way of working out your position. Or position unknown.
>
> Contents of urgent message
>
> Over.
>
>
>
> for example:-
>
>
>
```
PAN PAN, PAN PAN, PAN PAN
This is fishing vessel LL307 Early Dawn Early Dawn Early Dawn call sign 2CSG2 MMSI 235075333
PAN PAN fishing Vessel LL307 Early Dawn call sign 2CSG2 MMSI 235075333
My position is Five Zero degrees, Four Six minutes, North: Zero Zero Five degrees, One Seven minutes, West
I have a crewman who has passed out, breathing and pulse steady, I require medical advice.
Over.
```
<http://www.portreath-harbour.org/distress-proceedures/pan-pan/>
[Answer]
If ship is only way to survive (no land), you would NOT want to abandon the ship if it is afloat and not sinking. Other boats would stay in safe distance and crew would do everything to repair the engines and make her sea-worthy before next storm hits.
But you have problem: with no safe harbor, no dry docks, your civilization will last few decades max. Unless you build floating factories, oil refineries and steel producing facilities.
Your ships doesn't have to float all the time - you can use things like stationary oil platforms, place them in shallow areas/reefs, and start mining iron.
If situation is extremely dire, only the rescue crew will try to save ship, and non-required crew and resources would be evacuated. But with no land, situation is pretty desperate and you will risk a lot to save ship. Without ship, you cannot support the population, so other ships might be reluctant to get more mouths to feed. They may select some of rescued crew which skills are important, but others - tough bad luck but we cannot feed you.
[Answer]
You can quite easily do both.
Rescuing the ship's people is the easier task. Deploy the lifeboats of the stricken ship with as many crew as possible in them (with current regulations, there should be enough for all crew but in a post apocalyptic society there may not be). Any remaining crew can be evacuated with helicopters equipped with winches. Sea Kings and Merlin helicopters often come with this equipment already on board.
You can recover the ship in one of two ways.
**1. Take it under tow**
You can come reasonably close in another ship, throw a catching line across to a remaining crew member, who can then pull a steel tow hawser across from the tow ship. Once fastened, this line should be made as long as possible to reduce the collision risk, but you would at lease have some control.
**2. Side-along tow or Sandwich Ships**
This solution is better suited for calm weather. A ship comes alongside the stricken ship, fixes lines bow and stern, and moves away taking the unfortunate with it. However, given that the stricken ship has no power, the tow ship needs to use its side thrusters for movement to avoid going round in circles.
This problem can also be solved with "sandwich ships", where a ship comes alongside on both sides and fixes on. Although this requires two ships, it does solve the problem of going round in circles.
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[Question]
[
Is there a theory, model, technique that could help when placing cities on a map, instead of placing them randomly?
I have an estimate of the population for a given territory so I know more or less how many cities I'm supposed to have but I'm not sure how I should place them.
[Answer]
## Central Place Theory
As an Urban Planner, I could not help but put out there, the age-old [Central Place Theory](http://en.wikipedia.org/wiki/Central_place_theory). It describes a hexagonal layout, and all other things are equal. It describes a generic urban settlement, that appears as a hexagonal assembly, and its relationships with other larger or smaller settlements.
It's generally well-accepted as a very high level conceptual diagram of *trends* in urbanism.
Other factors will include accessibility (your settlements should be on economically-accessible areas: trade routes or where there is economic opportunity) and it will do even better if there is an attractive climate - although that's not as strong a pull as the former.
[Answer]
I'm basing this in part on my *meh* answer to [another one of your questions](https://worldbuilding.stackexchange.com/questions/2475/how-can-i-estimate-how-many-people-are-living-in-a-specific-territory). I think I can make this one better, though. By the way, I hope you didn't use my data for your estimates here; I seriously doubt it would produce accurate large-scale results.
Here are some places you could put cities:
* **Rivers:** London, Paris, etc. Rivers mean transportation; transportation means trade; trade means a strong economy. Rivers also mean source of fresh water, as well as fish. Although I think we'd all get sick of flounder after a few days.
* **Ports:** Boston, New York, Rome (indirectly), Hong Kong, etc. Ports mean long-distance trade, and long-distance travel. Until your species can travel via the air, water is going to be important (this hearkens back to my section on rivers). Jason Patterson also raised an excellent point: Settlements will spring up *wherever* roads meet water. This can include points by a river where two sides are the closest, or the narrowest part of a lake.
* **Mountain Passes:** Strange but possibly true. Let's say you have a city at point $A$ (done in LaTeX for dramatic effect) and a city at point $B$. Point $C$ is in the middle of a mountain pass, right in between the two. I can assure you that people from both cities will want to build a settlement there to control travel and trade between the two. Think a land-based version of the Bosphorus and the Dardanelles.
* **Lakes:** Back to the water. You've got water, you've got fresh food, you've got some land - who could ask for anything more? (Corny, I know.)
* **[Wherever there are roads](https://worldbuilding.stackexchange.com/questions/3135/a-realistic-road-network/3169):** You aren't going to have a city where there aren't any roads. Try spots that are in places where roads meet open fields or flat ground. These junctions may also provide arable land.
[Answer]
Unless you are working with a planned nation, i.e. leaders started it from scratch kind of like a planned city, distance is not particularly relevant when assigning locations.
I think it important to define a city...which may seem ludicrous but stick with me.
* City: A collection of people and structures with socials services, and defenses in a contained, contiguous geographic area.
Why bother defining it? Well if you look at some situations, for example Minneapolis/St Paul, its pretty easy, with the exception of politics to call that one city and for the sake of map building you can consider it one city, even if you later break it apart for political or localized geographic reasons.
**So, moving on to your question.**
>
> Is there a theory, model, technique that could help when placing
> cities on a map, instead of placing them randomly?
>
>
>
Not that I am aware of, but luckily we don't need one.
* Start with a map. If you have your map you can get a solid idea of where cities should be placed. This map needs to be fairly detailed, you need to know the terrain, the major bodies of water, the local climate...is it arid, or temperate, how much rainfall etc etc etc.
* The first cities: Once you have your map find good geographic locations for settlements, as HDE mentions water is huge. The first (and oldest) settlements you place are simply going to be locations that have all humans need to settle and grow a town.
* Non agrarian cites: These will develop along trade routes, or at strategic points. (cross roads, passes, river crossings, holy sites) This question may help you as well: [How can I ensure my cities don't all look the same?](https://worldbuilding.stackexchange.com/questions/2838/how-can-i-ensure-my-cities-dont-all-all-look-the-same/2900#2900)
* Keep resources in mind. As mentioned in step 1, you have to know your map. Your question is right in assuming that you can only have population centers so close together. This is why. Only so many people can live so close together...though perhaps the population of two nearby large cities are overwhelming local resources...which leads to conflict, which leads to a good story setting...
You are better off applying logic here rather than a mathematical formula. Just try to consider how things developed. First you had mainly nomadic peoples, hunters and gatherers. They wandered and perhaps picked and ate corn, maybe eventually they noticed it grew in the same place every year. You start a settlement where food and water are plentiful and shelter is available. Rather than being nomads you now have a small village and hunters that range out from the center. Agriculture develops. This happens all over the area with splinter or other totally isolated groups. Eventually as things grow people interact and trade. Common paths develop. Pull the thread. Its a fun trip.
[Answer]
I couldn't find a reference online, but I vaguely remember that they did a study and if you take a fairly featureless landscape and assume most travel is done by foot, then settlements tend to be about 6 miles apart.
Terrain will affect this, mountains, and hills, valleys, rivers and lakes etc. Roads connecting them will follow the easiest routes.
Better transport, roads, rivers etc. will increase the interconnectedness of communities and trade will follow the easiest paths, or connect the most desirable commodities to their markets.
[Answer]
The settlements would be focused around resources or crossroads for the most part.
Start with the landscape, and built up. Think about the resources required, easy access to wood, farming, water, etc.
] |
[Question]
[
In a science-based futuristic world, individuals (soldiers) are able to become invisible **to the human eye** while keeping a decent amount of agility. What could be the different possible technologies behind such ability and what would be their downfalls?
For example, I'm thinking solutions could be:
* they are wearing a suit that displays in the front what it films in the back. An issue with this would be a possible lag in the display.
* they are wearing a suit made of material that distorts the light so that it goes around them. A downfall of this method would probably be that you see a distortion in the shape of a person, like looking at someone's eyes through correction glasses.
No solution is too crazy as long as it is scientifically sound.
Again, I'm trying to fool **humans** only, not cameras, dogs, sensors and whatnot.
[Answer]
## Metamaterial Cloaking
Light (all electromagnetic radiation) is based on the electromagnetic force [2]. This means it has an electric and a magnetic component. Normal matter only interacts with the electrical component. Yet optical metamaterials [3] interact with the magnetic component to prevent material from interacting with the electrical component.
This can be used to design cloaking materials [4]. The picture below shows a normal object on the Left. It changes the pattern representing the electrical component of the light. Thus it is visible. On the Right, we see an object using metamaterial cloaking. The magnetic component of light is used to prevent interaction with the electrical one. The object does not disturb the electrical pattern. Thus it is invisible.
[](https://upload.wikimedia.org/wikipedia/commons/7/73/Circular_EM_cloak_using_transformation_optics.svg)
Picture and description from Wikipedia: "Left: The cross-section of a PEC cylinder subject to a plane wave (only the electric field component of the wave is shown). The field is scattered. Right: a circular cloak, designed using transformation optics methods, is used to cloak the cylinder. In this case, the field remains unchanged outside the cloak and the cylinder is invisible electromagnetically. Note that the special distortion pattern of the field inside the cloak."
[](https://www.ft.com/__origami/service/image/v2/images/raw/http%3A%2F%2Fcom.ft.imagepublish.upp-prod-eu.s3.amazonaws.com%2Fd723b070-31eb-11e8-b5bf-23cb17fd1498?source=next&fit=scale-down&quality=highest&width=1260)
This graphic from this recent article [6] illustrates the phenomenon somewhat more graphically.
Now it is easier to manipulate lower wavelengths than higher ones. Radio, Microwave, and Infrared can be manipulated this way. Scientists are currently working successfully on Visible Spectrum cloaking and some very small object have already been cloaked this way. Ultraviolet seems plausible, but X-Ray and Gamma seem improbable, as the manipulation of their wavelengths would require molecular and atom scale structures respectively. Although those would make one hell of a nice radiation shield...
**So how do we build you an invisibility cloak?** That's easy enough. We put you under a flexible version of the Visible light metamaterial and for good measure, we equip the inside of your suit with a Thermal Infrared invisible metamaterial. Now you are invisible in the Visual and Thermal Infrared. Anyone using a Near Infrared or UV camera, seismic detection, echolocation, electric detection a Thermal Infrared laser and a billion other members of the cast of *Utility Belt: The Movie* could still detect you. But that's beyond the scope of your question, thus not my problem.
Be aware that this technology brings more than Harry Potters cloak. This video [7] is a good summary of its implications.
[2] <https://en.wikipedia.org/wiki/Electromagnetism>
[3] <https://en.wikipedia.org/wiki/Metamaterial#Electromagnetic_metamaterials>
[4] <https://en.wikipedia.org/wiki/Metamaterial_cloaking>
[6] <https://www.ft.com/content/c6864c76-de7d-11e7-a0d4-0944c5f49e46>
[7] <https://www.youtube.com/watch?v=s0UZ6-oeiIE>
[Answer]
Douglas Adams describes an unique cloaking technology known as the [SEP field](https://en.wikipedia.org/wiki/Somebody_Else%27s_Problem#Fiction) in his novel *Life, the Universe and Everything*. This technology persuades the observer that the object under the field is Somebody Else's Problem and doesn't concern them, so they just ignore it.
The Hitchhiker series is of course not hard Science Fiction but rather a parody thereof, but this particular concept isn't actually that strange. When we extrapolate hard sciences like Physics or Biology, then why not also extrapolate soft sciences like Psychology?
A technology which manipulates people psychologically to ignore and forget the subject might not actually be that implausible. It could employ some kind of hypnosis or other neuropsychological effect.
Possible drawbacks could be:
1. Its effectiveness might depend on the emotional state of the observer. It could be more or less reliable depending on the observers current level of certain neurotransmitters like adrenaline (stress) or endorphine (happiness). Psychoactive drugs which alter the emotional state of the observer might counter the effect reliably. The observer actively looking for the subject and expecting it might also affect the reliably (in any direction).
2. It might not work on everyone. People with certain mental conditions might be immune to the effect.
3. It might not work under any condition. When it works visually, a completely unobstructed view and certain light conditions might be required for it to work. When it works through sound, it might not work well when there are other noises around.
4. It is unlikely to work on animals, except when designed for that specific species.
5. It will not work on any automatic detection systems which recognize threats automatically without human input (although there might be a chance that advanced neural networks could be vulnerable).
[Answer]
I cannot comment on the possible scientific approaches, but their downfalls would be all the same: individual invisibility is great for spying, criminal activity and *maybe* small special operations teams.
# Warfare
Any scale of warfare needs a very detailed picture of where the friendlies are. You need to coordinate the troops. You need to evacuate the wounded. You need to make sure there is no friendly in the explosion radius or line of fire of your weapon. You do not want to miss on the morale boost that the feeling of *"the man next to me"* gives to the troops. In short, what you *really don't want* is an individual soldier, seemingly all alone, in danger of getting hit by the enemy as well as getting hit by any weapon his buddies may fire, fully aware that he cannot be evacuated and any wound will be his death. So what you need is a way to identify those invisible soldiers. And if that technology *exist*, it's only a matter of who wins the encryption race. Will the enemy be able to decrypt (or maybe just trace the signal to a specific point in 3D to fire on, that would be enough) the signal in real time and kill the invaders or not. Kind of the [Enigma](http://en.wikipedia.org/wiki/Enigma_machine) in WWII.
# Technology
Generally speaking, technology can come in two variants:
* Fooling the individual viewer
* Actually sending a different image
Fooling the viewer by for example somehow manipulating his brain can easily cicurmvented by technology available today. Cameras. If you cannot fool an optical recording device, things like night vision or modern day tank optics will already invalidate the whole concept, because it's short time recording and replay.
So what you need is a device that actually changes the rays of light and transmit a different image to any image processing device, technical or biological. The obvious countermeasure is to emply a different sense for detection. Guard dogs are not exactly the pinnacle of technology, but they *work*. Ok, lets assume with the invisibility kit came a "smell transmutor". We could still detect moving bodies by air pressure. And radar. And maybe Infrared or Ultraviolet. Or maybe ultrasonic sound. So this invisibility kit needs to be a full blown scientific wonder, or the technology to detect invisible people will be cheaper than the invisibility itself.
Assuming the invisibility is perfect in any way, it would still be vulnerable to things that normally *obscure* visibility or hinder our senses. Invisible people moving through smoke or rain will be visible by their surroundings. The rain not hitting spots, the smoke moving around columns of "nothingness". Any kind of muddy ground can make technology worth a few millions totally meaningless. Comic-style even in the case of muddy footprints. People will need to be very skilled and specially trained even if they have perfect technology.
# Society
And still, if the guy employing such a kit is absolutely not detectable, the world is in danger of failing. How do you prevent crimes with such technology available. For a believable world, you will need a way to *control* such technology. If this technology is widely available in wartime, what would the civilization look like in peacetime? With all the guys that know that *nothing* can stop them? Maybe the *real* drawback of the technology will be, that after war all the veterans able to use that technology will need to *vanish without trace* because society would fail if they were actually coming back alive.
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In my world, I have a type of plant with a two-stage life cycle. The first stage grows into a structure that functions like a greenhouse that allows in most of the Sun's light but insulates against temperature. It does this to support the second stage, an extremely delicate type of flower which can only grow in the exact conditions fostered by the first stage's greenhouse.
The first stage constructs the greenhouse by growing a ring of stalks that eventually meet at a point above the center of the ring; after meeting in the center the stalks [build? excrete? weave?] the greenhouse from meeting-point down to the ground. Edit: L.Dutch's answer made me realize size may be important here. I would like for these structures to be about a foot in diameter in the wild.
Is there any biological structure or nonbiological material that a plant could use as described to build greenhouse walls that permit a significant amount of light but shield against temperature fluctuations? This is a world that has some effects percieved by humans as "magic", and these effects are the reason a plant with such a tenuous life-cycle came into existence, but I would prefer the plant to operate on nonmagical principles aside from its magical start hence the science-based tag.
Thanks in advance for your advice!
Edit: @Alex P.'s comment pointed out that the original title sounded like I was asking for a list of materials. The actual intent behind the question is "is there at least one way for a plant to make this work", so I have updated the title to match.
[Answer]
The plant can produce [biogenic silica](https://en.wikipedia.org/wiki/Biogenic_silica) and have it act like the glass in a greenhouse.
>
> Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants.
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However consider that in order to be a proper greenhouse, the size of the envelope should be on the larger side: something along the shape of a coconut, probably. Too small envelopes might have a too high surface to volume ratio, resulting in too high heat losses.
[Answer]
## Plants with their own little greenhouse
AlexP already mentioned Haworthia cooperi, but the pictures in Wikipedia do not present the more [strange-looking varieties](https://succulentalley.com/clear-succulent-plants/):
These are tiny, but larger ones could probably form in some circumstances, especially if they are cultivated and bred.
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**Setting**
This question is about a human culture, with conditions essentially the same as Earth's with technology roughly comparable to early middle ages. The climate is roughly Alpine, although the mountain is taller than any on Earth.
**Society**
I've been playing around with a culture that values elevation (for essentially religious reasons). The people live on the slopes of a mountain and base their social standing on the height at which they live\*. This leads them to live as high up the mountain as possible, even at a cost to their health or life expectancy.
The general social structure is therefore that the lower class (those living further down the mountain) farm the lower, more arable land while the upper class struggles to survive in smaller settlements on the less hospitable land higher up, relying at least partially on 'tithes' from those beneath them.
These people do have contact with civilisation beyond the mountain, so have ways to trade the mountain's goods (metals, gemstones) for exotic materials they can't obtain themselves.
**Question**
What technologies would this society develop in order to attain as much elevation as possible?
**Note**
Whether this society is feasible isn't part of the question. I'm aware that there are issues I haven't addressed that would cause this society to break down, but for the purpose of this question just assume everyone goes along with it.
---
\*More accurately social standing is a function of average and maximum elevation. Someone who frequently makes trips up and down the mountain would be considered more important than someone with the same average elevation who doesn't travel. This means it is valuable to find ways to get higher even if it isn't permanent.
[Answer]
Let me suggest that you aren't going to get an exact match for "middle ages" technology. You're describing a society of engineers who mine for a living, so I suspect they would develop a rail system comparatively early. When adjusting technology levels, I always identify something that's equivalently reduced. In this case, I suggest that they would have excellent stone carving but a lower level of woodworking and hydraulic systems.
The first railways don't show up in our history until 1600 or so. Previous to that, they used wooden wagons. Let's say your people considered their elevators to have the same importance as Roman highways or aqueducts. You'd have chains pulling iron-shod carts up stone railways, with counterweights. They would have something similar in their mines. If they advanced their metallurgy, they might even develop iron rails maybe a century before the outside world would.
Reliable elevators is actually the thing that prevented humans from making taller structures in most cultures. We could build twelve story masonry structures, but who wants to climb that many stairs? You have a similar issue distributing food and water to those places. If you have elevators, then you need something to power them. Water wheels will only get you so far.
At a higher level, you have to ask what activities are going on "higher up." Is this where people live and throw parties? Is it where they have business offices? Is this the seat of government, or just the monastic few? That will define the volume of traffic, and will specify the effort that they would go to for their transport system.
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My thinking would be something along the lines of hot-air balloons. One of the core jobs of the peasants below could be building a maintaining of such devices in order to get goods quickly to the top of the mountain.
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I would expect the elites to take the highest comfortable zone and just deny it and anything higher to everyone else as sacred ground or out of reach due to expense.
Similar strategies are in place everywhere already.
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New here, so forgive me if I commit a faux pas or two
So I wrote a society that, never being wealthy or organized enough to invest in rail and road networks, stuck with beasts of burden, even as the rest of the world developed. I had the idea of camels or donkeys having piezoelectric shoes that generate power as they walk; maybe merchants would invest in some as the technology got cheaper. I figured that these might power mechanical exoskeletons that the animals wear, allowing them to carry greater loads, or even chain them in a kind of a giant mechanical centipede type device that would allow them to sleep in shifts, feed them, take care of waste, etc while on the move; I suppose there might be a market for swapping spent batteries for charged ones, but there are a lot more efficient ways to charge a battery. How much power could these caravans realistically generate? Could they even power anything helpful with the energy that livestock would generate just carrying their cargo from one place to another?
[Answer]
Mechanical exoskeleton for camels powered by muscle power of the same camels doesn't make sense, there is a law of conservation of energy. You have two processes - power generation and power usage, both have efficiency significantly below 100%. You would be wasting most of the energy to heat the environment. The camels would be much better off without this extra weight.
Power derived from beasts of burden is very expensive - they eat, and not just grass. They were used not because they were good, there was nothing better. Transporting stuff over rivers and seas was many times cheaper than over the roads.
If your people had batteries, they would charge them using rivers and wind "for free".
"never being wealthy or organized enough to invest in rail and road networks" - they would still have roads. They can't walk over the fields and any place traveled well enough becomes a trail.
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The island of Malta has [4000-year old railway tracks](https://www.amusingplanet.com/2014/02/the-mysterious-cart-tracks-of-malta.html). The amusing factoid that Roman chariots determined the railway gauge, and that determined the dimensions of the Space Shuttle is largely myth, but people have increased the carrying power of horses by having tracked cars or sledges. Mines used horse-drawn railways. The first Stockton to Darlington run was horse-drawn, with a stationary steam engine to run pulleys to help the carts up a particular hill. If you are not going far, then the solution seems to have always been to make the track as level and as smooth as you can. This has been re-invented lots of times.
The Silk Road probably was a collection of routes, and a particular item might change hands many times. The route itself was too long to turn into a proper road, and probably had to be re-routed whenever rocks fell, or sands shifted. So, camel trans of the sort you describe did most of the ferrying. I can also imagine people such as those in the Middle East with a nomadic tradition treasuring the ways of their forefathers. So, an oil sheikh on holiday might travel by camel, or by Lambourghini. But they probably won't want to invent a bicycle that camels can pedal, so they can go faster.
The nearest I can suggest is some generator that uses the ambient shaking when you are on a camel to power your laptop or mobile phone. This might be safer and more reliable than wires going down to the animal's hooves.
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The idea is old already. But rather than each animal wearing special tools, we can just pave the tracks with piezoelectric tiles and any foot traffic including humans will generate electricity. Each won't generate much but they all add up.
[You can even make them at home fairly easily.](https://www.instructables.com/Electricity-from-walking/)
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Piezoelectric generators don't generate much energy and might be bulky on a horse. You could use dynamos instead, a solutiin employed in some bicycles to power things like lights.
Ever seen one of thode flashlights that is powered by someone jerking it? That's a dynamo at work.
The TL;DR of how it works is that you have a magnet going in and out of a looped wire. Everytime a magnet moved through a loop, it makes current flow in the wire.
Put some dynamos over parts of a horse that shake and you have a power source.
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In the isekai genre of anime, it is a common trope for a person to be reborn into a baby's body while retaining their full cognitive abilities. Assuming they maintain full control of their coordination (balance and limb control), how long would it take for such a person to develop enough muscle strength to begin walking for a sustained period of at least a few minutes? with regular babies, the largest limiting factor is the amount of time it takes to learn to balance and walk, as far as I am aware.
While it would likely take some time for a person to recalibrate to their new body, for this question you can assume that time to be negligible. I am only asking after the stage of development/age at which their muscle strength would be sufficient.
How such a person would maintain their cognitive abilities while having the underdeveloped brain of a baby is not relevant. You can assume that to be magic.
[Answer]
### Between 9 and 18 months
Typically, the milestones for normal babies are creeping around 6 months, pulling up to stand around 9, taking steps around 11 and walking around 12 or 13. Much of this learning is instinctual. We don't learn how to creep by reading a book or consciously ruminating on what muscles are involves and what steps might be required to accomplish the task.
You're positing something that is lies within a triangular continuum between a *new* baby freshly learning to walk (as above), an injured adult relearning to walk, and a normal adult considering the processes of both.
Assuming that these sort of reincarnated *old* babies are born with the old non-corporeal mind & consciousness properly seated within the physical brain & body, I would argue that this person would have a time advantage. Not much, really. The *old* baby would be born already self-aware, already pre-loaded with the knowledge of how to walk, already having the self-determination and conscious desire to walk.
This person would only have to wait for the muscles and nerves to sufficiently develop and strengthen. Therefore I'd argue that a person with a strong will and desire to walk as soon as possible and gets the support she'd need would probably be able to walk by nine months after birth. A person with less determination and less support would probably take a little longer.
[Answer]
By the time a baby is 7-8 months old, they've developed sufficient strength to theoretically be able to walk, which is why this is when babies normally start standing on their own.
That said, I don't know if having pre-existing coordination helps. Remember that coordination isn't simply software that's loaded in, it's based on automatic reflexes, practice, and conscious thought developed by a system where the software is an intrinsic part of the hardware that has been in development for however old the person is. Putting aside "magically adapted to the body" exceptions, you've got someone in a body that, prior to meeting Truck-kun's front bumper, is hugely different in proportions, weight distribution, and basic size from what they're in now.
It's well known that children undergoing rapid growth spurts can sometimes be a bit uncoordinated because they're unused to their new proportions. Now imagine that magnitudes *worse*.
Again, magic aside, I don't think someone would actually have that much of an advantage over a normal baby. They could, given the premise, have an advantage in learned skills; something like playing an instrument, or touch typing, or something, but I suspect they'll have no great advantage, at least not one noticeably greater, when it comes to basic body movements than that of any physically precocious child not inhabited by someone who couldn't look both ways.
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In a short story I'm writing, a non-tropical island nation has an economy centered around selling an oil made from a particular animal. The oil is special because it produces a light purple flame when burned. How would such an oil and animal be possible?
For extra clarification, the animal is a species that occurred naturally, not by some science experiment or accident. My idea for the animal is probably one that lives in the ocean since whales used to be hunted for their oil.
I know that certain chemicals, such as potassium chloride and potassium permanganate, do burn violet, but I don't know how an animal would naturally have these chemicals in a large enough concentration that the oil would burn purple or what end affect these chemicals would have on the biology of the animal.
So my question is this: how can a naturally occurring animal get enough potassium chloride or another chemical in order for its body fat to burn purple?
[Answer]
You're on the right track in identifying that the Potassium ion is the most common ion that flame-tests something that might be described as purple; and Potassium is abundant in sea water, and biologically compatible. The question, then, is what biochemical pathways lead to high concentrations (1000+ ppm, I'd imagine, is needed) of Ka+ in fat deposits.
Really, you can choose any non-soluble Potassium salt, posit a reason for it to form in your creature, and then safely assume (a) a transport mechanism to move the precipitate or preferentially precipitate the salt in fatty tissues (since the absence of such a mechanism would put the creature at risk of e.g. kidney stones and other obstructive diseases, this would be evolutionarily favored) and (b) a mechanism to extract sufficient potassium (in the form of potassium chloride) from seawater (which already exists, but would have to be more active due to the loss of potassium from precipitation in this case).
One challenge is that very few potassium salts are particularly insoluble, so you're going to have a hard time getting the concentrations high enough (without other biological consequences) for precipitation. Ideally you want to precipitation to occur at blood / body fluid concentrations low enough to not really effect osmotic pressure or anything. Still, options exist, including just running a somewhat-insoluble salt at super-high concentrations -- perhaps as a biological antifreeze -- and solving the osmotic pressure issue another way.
If you want something more fun, and that may guide plot, one salt that comes to mind is Potassium hexachloroplatinate. Suppose a whale-type creature that is able to go to deep depths, beyond what is accessible to your humans. Suppose also that something -- most likely an ancient meteorite -- has deposited a huge mass of relatively pure platinum on the sea bottom in the midst of this creature's habitat. Suppose that the creature is ingesting so much platinum that its actually at risk for metal poisoning -- for example, it's a filter feeder evolutionarily, a delicious type of brine shrimp has decided that the rubble of this meteor is its home, and your filter feeder has started to get excellent meals by scooping piles of platinum-rich rubble into its mouth and filtering out the good stuff -- but also an uncomfortable amount of platinum. (The major problem with this is that metallic platinum is really, really not bio-reactive, so the amount needed to be poisonous is absurd -- but hey, due to evolutionary chance your creature is sensitive to it.)
A technique of removing platinum is needed, and given the abundance of biologically available chlorine, coordinating that platinum into PtCl6(2-) is a perfectly reasonable pathway to take. This will form Sodium hexachloroplatinate in the (sodium ion rich) blood stream, which is soluble and fine; but the creature needs to not just coordinate the platinum but also eliminate it from the blood stream to avoid accumulative poisoning. Fortunately, it's trivial (evolutionarily speaking) to transfer selective ions across cell walls; and the fat cells specifically evolve to do so. When the Sodium hexachloroplatinate enters the potassium-rich cytoplasm of a cell, some Potassium hexachloroplatinate will form, precipitate out, and the reaction will continue until the platinum is eliminated, or reduced to a low level, in the blood stream
In this way, over time members of this species that filter-feed on the platinum-rich detritus of the meteorite will concentrate Potassium hexachloroplatinate in their fat tissues. When purified and burned, this oil will burn a violet/purple. Like most oils, this will burn with very little ash (solid residue)... but what ash there is will be very rich in platinum that can then be purified. So the purple oil is valuable not only for its beauty, but because it gives a source of a rare and valuable metal.
And of course if one were to try to raise these creatures in captivity, their oil would not burn purple, and there would be no platinum to be found...
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I'm writing a fictional story where someone from our time (the present), travels back to 1896. He has a lot of knownledge about science and electronics, so he can easily built some basic circuits, as long as the components needed have been already created or could be created with the technology of the time.
In this case, the first thing he built is a tube amplifier to boost the signal from a microphone and be able to use the boosted signal to impulse the needle of a vinyl recorder to record the audio.
However, the writer (me), doesn't know much about electronics, and the best I could do until now was setting up this simple circuit design:
[](https://i.stack.imgur.com/LZn3I.png)
But I have a lot of questions about this design:
* Are the resistances and capacitor values realistic for the time?
* How could I connect a simple AC to DC rectifier to the circuit
(since, for that time, it's the only way to get that voltage from
DC)?
* Is it possible to design a rectifier in that time? (Silicon free!!)
* The output voltage is about 12V, would it that be enough to move a
needle to record in a vinyl?
[Answer]
The most basic of vacuum tubes was discovered, rather than invented, by observation of the Edison effect, whereby carbon particles boiled off an early lamp filament showed a shadow of the other end of the filament where they adhered to the glass envelope.
This was first observed by Edison himself in 1875 and refined in 1883, and led to hypotheses of "thermions" that are emitted from a hot filament. These in turn led to assembling diodes, which used these "thermions" to conduct current across the vacuum between a filament and a plate, and from there insertion of a grid to create the first triode by Lee de Forest in 1906.
The glass blowing technique and materials to do this, however, existed from the earliest days of hermetically sealing glass vacuum lamps, which followed close on the first metallic filaments to replace the carbon threads of the first Edison lampts.
All this to say that, had the knowledge existed, triodes at least (equivalent to those used in early radio receivers and CW transmitters as well as for audio amplification) could have been made well before 1900, possibly as early as 1885 to 1890 time frame (I couldn't quickly find a good reference on when hermetically sealed vacuum lamps first appeared; they have have been from the first days of Edison's lamps).
A simple triode (filament, grid, and plate) can be made to provide good gain for audio (though you may need multiple stages, meaning multiple tubes, to get and audible signal or enough output power to operate a record cutting machine). Some were also suitable for longwave radio (lower frequency than modern AM broadcast band). There are several YouTube videos by Glasslinger that show the construction, not just of diodes and triodes, but even pentodes, replicas of commercial tubes from the 1900s to 1930s.
In respect to the voltage question, it was well known long before 1890 that battery cells could be added in series (the actual word "battery" derives from the way multiple primitive cells could resemble a "battery" of artillery, multiple cannons side by side). There is a Volta pile still in existence at a university (I've forgotten which one) built by Allesandro Volta himself that produces more than 200 volts, and the earliest radio sets typically ran on anywhere from 45 to 90 volts on the plates, supplied by dry cell batteries (of up to 60 cells), while the filaments were lit by one to six cell (2V to 12V) lead acid batteries that would be exchanged for charged ones for a small fee when exhausted.
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If a planet, lets call her Shiloh, had no oceans or liquid water on the surface; Could it still have deep, vast ocean basins? Or would a dry ocean basin level out over time?
[Answer]
## Yes
Let's expand on @L.Dutch's answer. Without water, what we have to work with is flora, wind, volcanism, and tectonic movement.
**Tectonic movement** has the ability to create trenches similar (in fact, identical to...) the [Mariana Trench](https://www.ncei.noaa.gov/news/planet-postcard-mariana-trench). An not only trenches, but also [mountains](https://www.youtube.com/watch?v=d9bKXY0OMxc). Both of these are important as they create difficult-to-erode high and low points on your world.
**Volcanism** also creates mountains, but more importantly for your world, it seals lighter soils underneath heavier magma flows and erupted ash. This is important as wind has the capacity to move material around like sandpaper, eroding everything theoretically smooth — except that we have high and low points that on your world can be made of basalt (much harder to erode) and the lighter soils the wind moves around are periodically sealed away by volcanism.
*If you get down to the science of that statement, it would depend on how much volcanism your planet experiences... but that really depends on just how "perfect" according to our current understanding of science you want your world to be. Often it's not valuable to get caught up in that much detail.*
**Wind** is the primary shape-causing function on your world. If we simplify this, both water and wind should flatten out whatever they erode. Water carries lighter soils just as wind does, so you'd think the Mariana Trench would eventually be filled by soils carried by ocean currents. The truth is that carried soil isn't that deep or that erosive such that the harder geology of the trenches and mountains disappear before they are expanded through tectonics. Consequently, wind is hollowing out soft spots and leaving alone hard spots. What this does mean is that you'll see more formations like those found in [Goblin Valley State Park](https://en.wikipedia.org/wiki/Goblin_Valley_State_Park) than you do here on Earth because your world has more space for the wind to work.
[](https://i.stack.imgur.com/Ke1Dm.jpg)
*Hoodoos at Goblin Valley State Park. Brian W. Schaller via [Wikipedia](https://en.wikipedia.org/wiki/Goblin_Valley_State_Park#/media/File:A078,_Goblin_Valley_State_Park,_Utah,_USA,_2002.jpg).*
The amazing thing about Goblin Valley State Park and the many low water and desert regions of Earth is that they all prove you can have a wondrously varied environment, even in terms of altitude, without water. You can have what people might believe are ocean basins, even though they aren't. You'll also have seas of sand... but that's another issue.
**Flora** Finally, we need to consider the value of flora on your world. You say there's no surface water, so I'm going to assume there's subsurface water. That means [deep rooted plants](https://www.gardeningdream.com/examples-of-deep-rooted-plants/) ranging from trees to alfalfa can still flourish on your world, at least in protected areas, and [desert plants, especially grasses](https://www.wildflower.org/expert/show.php?id=3360) for additional erosion control will compliment the slower but more permanent solution of volcanism. Flora, like (and in some ways better) than volcanism, will also keep the lighter soils at bay, allowing them to be scooped up in wind-sensitive areas and deposited and then retained in wind-insensitive areas, which will allow your planet to have "ocean" basins.
**Conclusion**
Frankly, let's look at the [surface of Mars](https://www.jpl.nasa.gov/images/pia02820-mars-topography), which isn't a perfect fit, but is nevertheless an excellent example of what you're trying to achieve. The map below shows "ocean" basins, mountains and plateaus... basically everything you want. The world doesn't have active volcanism and, yes, it is believed that once it might have had enough water for erosion. But after how ever many eons of time the winds and sandstorms of Mars (and here's the point) *have not smoothed the planet.*
[](https://i.stack.imgur.com/Uvi9y.jpg)
*Mars topography courtesy NASA/JPL.*
So I believe what you're looking for far surpasses the baseline of suspension-of-disbelief. In fact, I believe it's entirely plausible to have a world as you describe.
[Answer]
If there are no oceans there is hardly any water cycle, and with the lack of water comes the lack of a substantial erosion agent which speeds up closing the surface asperities.
There might be wind, but considering that a gas is about 1/1000 less dense than water, in the same ratio is also its erosion power. Therefore (ballpark estimate) what water erodes in 1 year, wind will erode in 1000 years.
On the other hand, having an active tectonic without water might be hardly possible.
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The vampires in my setting have the ability to control human minds when looking them right in the eyes. While lots of them generally only use this ability to make humans forget masquerade-breaking things they saw or non-violently resolve physical encounters with humans, there are very few limits to what a talented vampire can do to a human's mind with this ability, and the more a vampire messes with a human's mind, the less physically capable that human is of feeling negative emotions like fear, anger, sadness and stress, and the more that human's baseline emotional state becomes a dreamy (bordering on high) glow of contentment. This state is, as it turns out, incredibly addictive, and humans who are snapped out of it after spending too long in this state will find themselves dealing with depression and drastically reduced emotional stability that some never recover from.
One character my heroine encounters has been, and still is, in a heavily-brainwashed state for more than a decade, something that isn't unheard of for vampires to do to humans. When thinking of how to describe this character, it occurred to me that this kind of perpetual emotional state would undoubtedly have drastic effects, positive and/or negative, on this character's health. I know there are various negative impacts stress has on the human body that this character obviously wouldn't be dealing with, but for all I know that might not even be the half of it. For all I know that emotional state, long term, would have horrific consequences on the health of a human being, and this character would look positively ghastly.
**If someone were to be heavily brainwashed to not feel any negative emotions, and kept that way for a decade or more, what effects, positive and/or negative, would that decade have on their health?**
[Answer]
**Opiate Withdrawal**
>
> the more a vampire messes with a human's mind, the less physically capable that human is of feeling negative emotions. . . . and the more that human's baseline emotional state becomes a dreamy (bordering on high) glow of contentment. This state is, as it turns out, incredibly addictive, and humans who are snapped out of it after spending too long in this state will find themselves dealing with depression and drastically reduced emotional stability that some never recover from.
>
>
>
The closest real thing to the above is the state of euphoria induced by your favorite opiate. If we assume the mind control uses a similar physiological mechanism then the withdrawal mechanism will be similar.
I won't go into opiate addiction withdrawal here. I am sure there are a lot of first-hand accounts available. I hear it's bad.
[Answer]
**She rocks hard.**
[](https://i.stack.imgur.com/YrN46.png)
She is in fabulous physical condition because the vampire had her work out a lot. She has 2 grammies from a while back and more recent popular songs as well; the vampire had a good ear and she was blessed with gifts that the vampire made her hone to perfecton. She has several businesses because thanks to the mind control she was a canny and unemotional operator, willing to take risks and cut losses. She is very wealthy.
Now the vampire is gone. He had his own issues that caught up to him. No-one is surprised if your character now wants to coast a little, write some poetry, produce some songs by young artists. Her people notice the workouts have slacked off. They offer her yoga and tai chi which is easier on the knees.
It feels weird to no longer be the person that everyone around her thinks she is. But it feels ok.
[Answer]
Depending on how deep you want to sink into this, I recommend Antonio Damasio's "Descarte's Error." It's all about how emotion, especially negative emotion, has more to do with decision making than we give it credit. People tend to think of emotion and rationality as a polar spectrum, but the book discusses the case of a man with brain damage who couldn't feel negative emotion.
Despite being a competent businessman prior to the injury, his work and finances began falling apart because of bad decisions he was making. He could analyze things on a rational level just fine, but when let loose to make decisions he'd have enormous trouble.
A neuroscientist highlighted the problem using the following game: You have two decks of cards, Deck A and Deck B. You can choose to draw from one or the other, and you will then gain or lose some amount of money.
Unknown to you, the decks are set up in the following way (I'm paraphrasing, I haven't read it in a while): Deck A has a few high, positive cards, but generally lower negative cards, and works out to a net negative. Deck B has a few high negative cards, but is net positive.
Ordinary people try out both decks, and within 10-15 cards begin to draw entirely from deck B (again, don't quote me on numbers, just the concept). The man with brain damage who couldn't feel negative emotions (it may have been all emotion) kept drawing from A however.
Why? They think it's like this: Because discovering the pattern requires more data than most people can keep in working memory, people start lending the decks a "feeling" or "impression" that tracks the total overall good and bad emotion associated with each deck. It's an imperfect mechanism, of course, but slowly lots of small positive stimuli and the net positive of deck B start to make deck B feel good, while despite a few big winners, Deck A starts to generally look bad.
Without emotion, in other words, the man was only able to consider the small number of examples he kept in working memory, and couldn't develop a "feel" for each deck that would manifest in what we'd call a hunch or gut feeling.
Now, there's tons of reasons this would actually get more complicated, for one thing because the emotional measurement device is imperfect it can be gamed to fool people (read: gambling), but generally speaking I think it's fair to say your character would exist very much in the moment, and have trouble telling the difference between good and bad ideas/people/choices when those judgments would normally come from built up emotional prejudices. They'd have intelligence, but very little wisdom, and despite being able to remember the past, without it emotionally influencing the future they'd probably live almost entirely in the moment, disconnected from anchors or impressions that link them to long-term goals.
At least, that's one theory. *Shrug* It might make a good RP challenge, playing a character that's trying to rediscover their ability to feel, and to understand why it's necessary that people feel negative things sometimes despite it being unpleasant (and after being blissed out for ten years, I'm guessing anything negative would feel like it HURT!).
[Answer]
Compare such a person with a psycho who's on neuroleptics. Essentially a person that you describe has lived for ten years in constant euphoria, ignoring any and every negative happening to its body or mind. In case your vampire would not care for its target's health, that person could well be **DEAD** after ten years of random issues like festering wounds, broken teeth, sepsis, heart attack from extreme obesity that would develop because of no need to do fitness, etc etc etc. (Some of this might happen without the vampire noticing, especially with teeth)
In case the target receives enough health care like a modern day's dog handler gives to their pet, the person would still likely fall into neglect of its mind, resulting in **retardation**. Why should such a person bother with anything, if they don't really feel negative? They are already in a condition where everything is ideal, for their mind! Such a mind would degrade due to lack of practice, this lasting ten years could turn a human into a real vegetable. Lack of exercise would result in obesity, and forcing that target into doing exercise would be quite hard, if the human plain *doesn't want to* do anything. This also would result in gradual weakness of limbs, eventually leading to the human becoming immobile and unable to stand up. Then they would sh\*t self, requiring extra care like a paralyzed person requires, then they would probably shut down into vegetable state. And, I expect all this to happen quite a lot faster than ten years. So my answer is, the human would be either incapacitated and with no intelligence left, or dead.
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[Question]
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An 18th century coachman, who really loves their horses and won't allow any harm to come to them, needs a mechanism to instantly disengage their four-wheeled carriage from the horses midride, setting the animals free (perhaps with the pole and parts of tack still attached), in case they spook, or the cart tips over or catches fire, or something. However, they only have basic handyman tools available, and not a lot of time to set it up.
How much work would be involved in rigging such a mechanism?
Would it be something as simple as replacing the pin that holds the pole, so that pulling on a strap or kicking it hard enough disengages the pole? And maybe tying the breechings in a way so that a pull on an extra strap undoes the knots?
Or would it be a much more complex endeavour, requiring a blacksmith, a carpenter, and a few good hours of hammering and sawing and whatnot, way beyond a handy coachman's abilities?
Note: I have only basic knowledge how a horse and a carriage looks, and have googled a bit, and that's it.
Note 2: I don't need an exact solution, with specific knots and actual carriage types. I just need to know if I can handwave it or not. A rough "yeah, it could be done more or less like this" versus a "nope, it's way more complicated" will be just fine.
[Answer]
**Quick release knot**
<https://www.horsejournals.com/life-horses/how-tie-quick-release-knot>
[](https://i.stack.imgur.com/8NVohm.png)
>
> It’s fast and easy to tie, but the true value of the quick release
> knot lies in its ability to be quickly and easily untied in the event
> of an emergency. If a tied horse panics and pulls back on the rope, a
> single tug on the end of the lead will free him.
>
>
> The quick release knot’s ability to provide an “emergency exit” is the
> reason it is valued as the knot of choice for safely tying horses.
>
>
>
The link walks you thru how to tie it. It is basically a slipknot. If you pull on one end of the knot the thing comes untied. I like the part of the article that discusses "Houdini Horses" who lean to pull the loose end themselves to get away and go do their free horse thing.
[Answer]
**Why not a simple seat belt buckle ?**
If the seat belt buckle invention is posterior to XVIII century (1946?), this is tipicaly the type of thing Leonardo da Vinci could have invented : In case of energency, press the button and release your horses. You can found many patens of seat belt buckle: here is [one](https://data.epo.org/publication-server/document?iDocId=1614933&iFormat=2). Of course it require some blacksmith work but maybe a simpliest design exist.
[](https://i.stack.imgur.com/C4b6W.png)
[Answer]
If you look at horse carriages, many of them involve some wooden beams attaches to the horse by rope and leather strips. You won't be able to undo those really quick.
A very crafty woodsmith could make a mechanism to disengage the beams, but you ruled out having that professional.
Without resorting to professional tinkering with the carriage, your best option might be the a technique that is used to free stuck animals called the [Murica Maneuver](https://www.dailymail.co.uk/news/article-3671801/Army-veteran-rescues-bald-eagle-dangling-upside-rope-75-foot-tree.html). Basically have a really high caliber shotgun on you and shoot the beams. The horse(s) will run while still pulling beam pieces around, but they will be otherwise disconnected from the carriage.
Fun historical fact: the expression "riding shotgun" comes from the old west, when the carriage coach would usually be accompanied by an armed person sitting by their side. That was to disencourage robbers. So it is actually pretty accurate to have a shotgun available during your horse emergency.
[Answer]
The quick release knot is probably a good solution but also know that [panic snaps](https://www.horsetraileraccessorystore.com/Panic-Snap-with-Swivel-in-ChromeNickel-or-Brass_p_729.html) exist for this exact reason. I don't know when they were invented but they're fairly simple mechanisms so it's not unreasonable to say your character used or created one if they're clever.
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I am considering how to implement faster-than-light (FTL) travel in a sci-fi setting without the attendant problems with causality. One of the ways I've been thinking about for this is establishing a **preferred frame of reference**.
[Per Wikipedia](https://en.wikipedia.org/wiki/Preferred_frame):
>
> In theoretical physics, a **preferred frame** or **privileged frame** is usually a special hypothetical frame of reference in which the laws of physics might appear to be identifiably different (simpler) from those in other frames.
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My idea is that going FTL involves a point-to-point jump where both ends of the trip must be at rest in the preferred frame, which itself is approximately at rest relative to the cosmic microwave background (CMB) (that is, in the preferred frame the observed [CMB dipole](https://en.wikipedia.org/wiki/Cosmic_microwave_background#CMBR_dipole_anisotropy_(%E2%84%93_=_1)) is effectively eliminated). Thus to make an FTL jump from one star system to another, you must first decelerate your ship to rest relative to the CMB (which is approximately 370 km/s relative to Sol), and then after the jump you must accelerate to match velocities with your target star. Importantly, **causality is always maintained relative to the preferred rest** frame, though there may be other reference frames where it *appears* to have been violated due to Lorentz transformations. Crucially, even if you contrive a situation where someone observes an apparent causality violation (e.g. they are moving at a high fraction of lightspeed relative to the preferred frame and see a starship arrive at its destination before leaving its origin), they cannot send information about what they have observed in a way that violates causality (e.g. they cannot observe the arrival and then send a message to the starship's origin telling it not to depart in such a way that the message arrives before the departure occurs) because sending anything FTL requires being at rest in the preferred frame (e.g. they have to decelerate, *rotating their space and time axes such that their message does not go backwards in time*).
My question is: how would our understanding of physics need to be modified to account for such a preferred frame while also fitting the real-life experimental data we have regarding general relativity and special relativity? The theories of relativity specifically say that there is no preferred frame, so in my universe there must be something they're missing. I want it to be something that we could plausibly have missed, for instance something that is only apparent when you get close to being at rest within the preferred frame. I also do want it to be consistent with the experiments we've performed and observations we've made that have so far agreed with relativity.
[Answer]
There's really nothing needed to make a privileged frame consistent with what we currently know - you just have to make it so that the privileged frame is *empirically undetectable* with any experiment based on our *current* understanding of physics. (But it could, and probably should, be detectable via whatever new physics allows for the FTL jumps in your setting.)
In fact, there's a pretty strong argument from quantum mechanics that we should be considering the possibility of a privileged frame even from our current understanding of physics: [Bell's theorem](http://scholarpedia.org/article/Bell%27s_theorem) shows that our universe doesn't actually respect relativistic local causality.
(There is one thing you should be aware of, which is that in general relativistic contexts a *preferred frame* needs to be replaced by a *preferred foliation* of spacetime. You can think of a preferred frame in special relativity as a slicing of spacetime into parallel flat 3D hypersurfaces; a preferred foliation is the same thing but the hypersurfaces can be curved.)
[Answer]
There aren't any adjustments needed in order to implement a preferred reference frame. However, there is a problem. You see, our Milky Way is moving towards the Great Attractor (constellation Norma) at 627 km/s, relative to the CMB, and our Solar System is orbiting the center of our galaxy thus moving towards Cygnus at som 250 km/s. As Cygnus and Norma is almost 180 degrees apart in the sky, this gives us a net speed of 368 km/s relative to the CMB. The motion of the Earth around the sun doesn't matter as our orbit is almost perpendicular to the galactic plane. All you need to do is to accelerate towards the Cygnus constellation at 368 km/s until you cancel out your relative velocity with the CMB.
Problem is, you're never going to match the CMB perfectly. Everything is in motion. If the temperature inside your ship is 290 Kelvin, then the air molecules will be vibrating at 500 m/s. The molecules in your body will be vibrating even faster, and not to mention various things inside your body is constantly moving. As you can never match the CMB perfectly, there has to be some range of error allowed. This would cause various things inside the ship to arrive at the destination at different times. Even a tiny difference in time of arrival of different atoms of your ship (I'm talking nanoseconds) would cause your ship to arrive as a jumbled mess.
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I'm using as a means of "long-distance travel" the generation and exploitation of Einstein-Rosen bridges, through quantum entanglement of black matter in different points of the galaxy, as a way to control entry and exit points of travel.
I know I'm stretching a lot of theory by connecting quantum entanglement and wormholes, but, in theory, would it be possible, and, if it were, how fast and what would be the consequences for travelling through said Einstein-Rosen bridges?
[Answer]
I think there's a NOVA special that talks about this.
IIRC, the main problems are:
* these wormholes are microscopically small, so far too small to be of any practical use
* there's intense radiation, so anyone that goes through would be cooked to death
* the wormholes only exist for fractions of a second, something like the Planck time
Furthermore, I think quantum entanglement doesn't have anything to do with this.
It's thought that wormholes -- if they exist at all -- occur naturally at super-microscopic scales, at the level of quantum foam. They pop into existence and then pop back out of it, all on their own:
>
> The quantum foam hypothesis is sometimes used to suggest that tiny wormholes might appear and disappear spontaneously at the Planck scale, and stable versions of such wormholes have been suggested as dark matter candidates. -- [Wikipedia](https://en.wikipedia.org/wiki/Wormhole)
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>
---
But in direct answer to your question:
>
> Theoretically, a wormhole might connect extremely long distances such as a billion light years, or short distances such as a few meters, or different points in time, or even different universes. -- [Wikipedia](https://en.wikipedia.org/wiki/Wormhole)
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There is currently no even semi-plausible way to accomplish this, or anything like it. Doing so probably requires discovering matter than has negative mass (aka "exotic matter"), and then almost literally fighting and defeating a black hole.
None of this has ever stopped a sci-fi author from using wormholes in a story. Don't let it stop you, either.
[Answer]
[](https://i.stack.imgur.com/35MwF.png)
Prof. Lenny Len Len Junior Susskind suspects Einstein Rosen Bridges are formed by entangling black holes. He talks about it either [here](https://www.youtube.com/watch?v=pY5D7ZgWuXc) or in one of his many other online lectures. It's part of a wider idea that entanglement is exactly the stuff that makes one region of space be adjacent to another.
I believe the concensus among physicists is this MIGHT be true. If so then two (maximally) entangled black holes have a shared interior. Meaning you can jump into yours on Earth and I can jump into mine on Andromeda and we can shake hands. But we cannot then jump outside the shared interior because of black hole stuff.
These pairs of black holes can be made for example by entangling two particles with each other, and sending one to the left and one to the right. Then entangle another pair and send them in either direction. Repeat until you get enough particles on each side to form black holes.
This does not allow sending information faster than lightspeed because we have to push the black holes apart in the first place. This takes at least 2.5 million years.
[Answer]
"Einstein-Rosen bridge" specifically refers to the connection between the two exterior regions in the maximally extended Schwarzschild spacetime, which is shaped like this:
The two diamonds are the exterior regions. Nothing (except a tachyon) can have a worldline inclined by more than 45° to the vertical in that diagram, so nothing can get from one diamond to the other, even though the manifold is connected.
So the straight answer to the question is no. Writers who care about these niceties opt for other kinds of wormholes, usually the exotic-matter-stabilized kind, but those aren't Einstein-Rosen bridges.
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[Question]
[
I invented a fantasy world which primarily consists of 7 Realms, six based on the six colors of the rainbow (the consensus is that indigo isn't really a color), red yellow green blue orange violet, with a 'Realm of the Light' in the center.
Each morning, the inhabitants of the six outer Realms raise their colored crystals to the sun, the rays of the sun bend and shine towards the center, where the Citadel of the Light is located. There is a prism atop the Citadel, it combines the colored rays into a shaft of pure light that extends to an even higher world, a world that is not discussed much in my novel.
The purpose of this Light is to provide hope, joy, and optimism to Mankind, back on Earth.
Now, the Colors must remain in balance for the Light to form, if one Color were to dominate and overpower the rest, the Light will fail to emanate from the Prism, mankind will become depressed, and they will stop making art and wearing colors.
Every time a human chooses a color, to paint their house, to paint their car, to tattoo themselves, or to wear an item of clothing, the corresponding Realm in the Color Realms expands physically and its ruler gains more power.
The first book deals with a conflict between the King of the Realm of Blue and the King of the Realm of Green. In short, Blue wants to destroy the rainforests on Earth, causing the oceans to rise, and the entire world will be painted in Blue. Whereas Green will use all the water to grow new forests and spread green over the lands.
A human male and female are transported from Earth to the Color Realms to become Champions of the Light and unite the Realms of Blue and Green once more, in peace and harmony. They are part of an ultimately larger group of 14 young characters from 14 different countries and cultures who unite as a force for peace and healing.
**The Philosophies of the Rulers of the Realms**: So far, I've decided that none of the Kings and Queens are truly evil.
*Vallidius Blue* wants to cover the Earth in ocean. But this will cause a revolution of our entire ecosystem. Sure it will probably take millions of years, but we've been through this before, at one time everything was covered in ocean and then land rose into what we walk on today. He believes that the environment is so damaged that the only way forward now is a complete transformation of the whole system. Sure, the humans will likely die, but he doesn't care about them at all. He's looking big picture, at the Earth and life on Earth as a whole. When there is only blue ocean the Light won't form, and Vallidius is okay with that.
*Red* is fiery, seeks renewal & regeneration through flame, like a forest fire.
*Yellow* is nurturing like the sun, but too much of a good thing scorches everything!
*Yionaffe Green* prefers forests and greenery, even at the expense of water.
*Violet and Orange*: I am less clear about these; they are "in progress". Orange might be ferocious like a tiger, perhaps? Violet is perhaps an alien color?
*The Citadel of Light*: unaddressed as of yet.
**The Fatal Flaw** I believe there is a major flaw in all this, as follows: *if the Colors need to be in equal balance, I'm afraid that the Light can not be formed when Red, Violet, and Orange are so underrepresented both in nature and in fashion*.
As a reality check: **Does this world seem consistent or make internal sense?**
[Answer]
Frame challenge - the so-called "seven colors of the rainbow" are, for the most part, completely arbitrary. The only reason we think of the rainbow as having seven colors is because Isaac Newton had an obsession with making everything fit into sevens. As anyone who has looked at a rainbow will tell you, the colors blend into each other seamlessly, and you can divide them up however you feel like.
So the idea that each color must be "in balance" is kind of silly - do you need to find an equal number of objects in nature that are precisely chartreuse or puce? If you're having a problem finding a function for orange or violet, just leave them out.
If you want to connect something to human vision, you can use red, green, and blue as your primaries - the three kinds of color receptors in the human eye - and yellow, cyan, and magenta as your secondaries. Magenta can be an odd one out since it isn't part of the rainbow anyway (it's a color that is created within the brain when we perceive red and blue light simultaneously).
(Worth noting that Newton's "indigo" was probably just what we call "blue" and what he called "blue" was what we call "cyan". Again though, this just underscores how easily you can change the system to suit your needs.)
[Answer]
There were a lot of questions in there so I am just gonna respond to your first two...
>
> My first question is... ...if the Colors need to be in equal balance,
> then how can the Light be formed, when Red, Violet, and Orange are so
> underrepresented both in nature and in fashion?
>
>
>
Things can be in balance without being equal. Is there any rule in your world that says the colour pie of the prism must be totally equal - or could the whole thing stay balanced with, say, a bit less red and violet if only they had a bit more orange?
EG > Look at this old zodiac clock from Lund - the inner circle is off-centre which makes some constellations closer for longer. They don't all share equal time in the sky.
[](https://i.stack.imgur.com/921bQ.jpg)<https://thumbs.dreamstime.com/z/lund-sweden-november-horologium-mirabile-lundense-fifteenth-century-astronomical-clock-cathedral-131334210.jpg>\*
What if there could be different combinations of amounts of colours that harmonize and form a stable structure? As the author you could decide these stable recipes for yourself and allow the colours to change but to also represent both the quality and structure of your world.
This doesn't stop things from going out of balance. Like the world only needs a little bit of red - but what if they don't get it? Does everyone go mad spilling each other's blood to make red?
>
> Is Kylie Jenner really supporting the entire Orange way with her
> collection of super luxury Orange sports cars?
>
>
>
Maybe.
If you need more orange, what about including a sun? They last longer.
[Answer]
There is a lot to unpack in this "question", probably enough for more than one question, but anyway...
Problem 1:
>
> ...the Colors need to be in equal balance, then how can the Light be formed, when Red, Violet, and Orange are so underrepresented both in nature and in fashion?
>
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There is **another world** with different color distributions. On our world plants primarily use chlorophyll to make energy, which is green, but many plants have a purplelish pigment on their leaves too. In Otherworld the balance leans more toward purple leaves. Other "coin flips" in the evolution of the natural world went differently there too. Except they weren't random coin flips, it was nature enforcing the Law of Conservation of Chroma.
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Problem 2:
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> Violet and orange are the hard ones, perhaps someone can assist me in developing a philosophy for them. Orange ferocious like a tiger, perhaps? Violet is an alien color? Idk.
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I don't actually have an answer here, but it reminds me of the [color pie in Magic the Gathering](https://mtg.fandom.com/wiki/Color), which divides all spells/motivations/effects into the jurisdiction of 1 (or more) of the 5 colors. The color pie is a huge part of the game's balance and philosophy. One interesting aspect is with 5 colors, each has 2 "friendly" colors whose motivations overlap and 2 "enemy" colors whose motivations conflict But because each color contains so much (1/5 of the universe), even enemy colors have some commonality, and friends have some conflict. For example green has the power of life/regrowth/plants/beasts/nature, while black (one of its enemies) has death/greed/necromancy/ambition. Life/nature and necromancy are opposing, but life/death are part of the same process/cycle.
With 6 colors (an even number) the friend/enemy dynamics would have to work a little differently. Maybe this could serve as inspiration though
[Answer]
Frame challenge for red and orange: autumn in higher latitudes. Also remember that brown is mostly red, also include so many furry creatures. And as long as there are prey and predators in nature, there will be blood being spilled.
As for violet, there are many plants and bacteria of that colour. If they are not present in abundance in your world, just say they are denser in power, so a few special orchids here and there have as much power as oceans and forrests. That makes it even easier to throw the world off-balance because a few more or a few less of violet will either hurt or empower every other colour, respectively.
[Answer]
**(R,G,B) model**
Make (R,G,B) model where white light in (R,G,B) terms is (255,255,255). Then you will not worry about yellow, orange, violet, indigo etc. The model will be 6 colors (R,G,B) as primary + (C,Y,M) as secondary around and white in the middle. (C,Y,M) are just combinations or overlapping of (R,G,B).
[](https://i.stack.imgur.com/2Gs5n.jpg)
Yellow is overlap of Red and Green but Complimentary of Blue
and same for Cyan and Magenta
White = R+G+B OR B+Y OR G+M OR R+C
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[Question]
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I have a story where the setup is that, ~600 years prior to the story's beginning, there was an apocalypse of a magical nature that rendered most of the world uninhabitable. A few survivors from various places managed to escape to the one inhabitable landmass, an island roughly the size of Greenland. The island has a latitude, climate and environment similar to New Zealand. It had no prior inhabitants. The survivors are coming from a world that was approaching an Industrial Revolution, but their technological prowess will probably be set back because of the disaster.
So, say the starting population was ~10,000 people, after which there were no newcomers because, well, everyone else is dead. At least some of the surviving groups would've brought animals and plants, since they knew they would essentially have to restart civilization. What would the population of this island be 600 years later?
[Answer]
Your question is asking for a calculation of the biotic potential. The biotic potential combines growth factors, i.e. reproduction, and survival factors to reach an estimate of the unconstrained growth of an organism. Countering that is environmental resistance, such as food availability. In principle a population will grow until it reaches the environmental carrying capacity.
[Wikipedia](https://en.wikipedia.org/wiki/Biotic_potential)
There are different models available. The [Malthusian model](http://Malthusian%20growth%20model) assumes exponential growth. A probably better model, especially given your time span, would be the [logistic growth model](https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_modeling_population_growth) which explicitly caters for the carrying capacity.
The carrying capacity varies over time, as agricultural methods improve, and there are also models which cater for this.
An estimate of the upper bound of the carrying capacity of your island could be the biomass of New Zealand. This would assume that the entire biomass is made up of humans and their foodstuffs, which could be vat-grown produce. Not as nice to live in as New Zealand. Isaac Asimov wrote a short story about the Earth being in this state (actually, he wrote [two](https://en.wikipedia.org/wiki/The_Greatest_Asset)).
To calculate the reproductive potential, you need to consider the number of humans surviving to reproductive age, the number of years they reproduce and the average number of children per birth. These statistics are readily available, as is the average reproductive rate for various societies.
[Calculator for various growth models](https://www.vcalc.com/wiki/Logistic+Growth)
[Answer]
## Impossible to say for sure, due to many factors
How well picked are the colonists? Do they have the skills to rapidly re-establish modernity? Do the seeds/animals they have suit the environment? How much of the land is good arable land? How much can have, e.g. sheep grazed on it? Do they rapidly establish a single polity, or several friendly polities, or engage in repeated, destructive wars, etc.
### However, we can give a fair estimate by comparison to other countries
Given that length of time, and with modern agricultural technology, and medical science, they should be able to achieve levels similar to modern nations. If New Zealand had the same population density as Europe, it'd hit 31.3 million people; if it was as populous as England that would boost to 75 million. These numbers may seem high but both require population growth of less than 1.5%/year, substantially less than current growth levels in Nigeria or Ethiopia (~2.5%/year) that growth level would punt the population to an eye-watering 2.7 billion, and a population density of 101,000/km2 which is surely not realistic.
[Answer]
I agree with the logarithmic model, but wanted to explore this topic a bit more. Specifically, I wanted to try applying something like a sales funnel.
### Edit: 2-23-2022
Wanted to amend this answer to correct a very bad oversimplification. It's easy to concentrate on women, as the only producer of children. You might be tempted to assume, in this example, that for your 10,000 people, the best chances of survival would be if 9,999 of them are women + 1 man. But, on further study, the best ratio is 1 man per woman (or very close to it), for the following reasons
## Genetic Diversity
If you have a 1:1 ratio of men to women, then --
* In the first generation you have 5,000 sufficiently different lineages.
* In the second generation, and carrying forward you have 2,500 families that are not at high risk of defects because they are siblings or first cousins.
If the ratio is adjusted as little as 1:2 (a man, a wife, and an ex-wife) --
* 1st generation, 2,500 sufficiently different lines to avoid inbreeding problems
* 2nd generation, only 625 unique families far enough apart.
In a 1:$\infty$, everyone in the first generation of children in a sibling.
How important is genetic diversity? [This study](https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2656.12878) attempts to put some numbers to the situation. They found, roughly a 4-fold increase in negative traits (such as expression of proteins showing a susceptibility to tuburculosis infection) being expressed among the most inbred populations.
[This study](https://www.discovermagazine.com/the-sciences/inbreeding-and-the-downfall-of-the-spanish-hapsburgs), has generously attempted to develop criteria we can plug in to the survivability ($P\_s$) and fertility ($P\_f$) model below.
Whatever your base survivability ($P\_s$) is, reduce it by roughly double your inbreeding factor (F) -- 25% for siblings, 3% to 6% for first cousins, negligible for more distant. So, a $P\_s$ of 0.999 drops to about 0.949 for a society that's just a twinge inbred... which doesn't seem like much, but that has a pretty dramatic effect.
The fertility rate ($P\_f$) drops by about four times the inbreeding factor (F). So, our base $P\_f$ of 0.84 would drop to 0.72 for the same barely inbred society of F = 0.03 (first cousins). A very dramatic effect.
## Disease
This might also be easy to overlook, but 1:1 pairing is a firewall against contracted disease. With anything like a 1:$\infty$ one male for everyone relationship, every member of the community has everyone's illnesses, including many fatal ones that might wipe out the population.
### Back to statistics
Let's say our population of survivors $n$ can be broken into demographic buckets by gender $n\_w$, $n\_m$ and age $n\_{w,20}$, $n\_{w,21}$, ...
Now, concentrating only on the part of the population pipeline that can give birth $n\_w$ :
* Pf : percentage of the population that is able to have children is 0.84 (84%) -- you can dive deeper by age, if you like. [Reference](https://www.cdc.gov/nchs/fastats/infertility.htm).
* Pb : percentage of pregnancies that will end in live birth is 0.1857 (18.75%) -- with 75% of pregnancies ending in miscarriage before week 5, and other ~25% ending in miscarriage after week 5. [Source](https://www.medicalnewstoday.com/articles/322634)
* The youngest pregnancy ever recorded is at 5 years of age, and the oldest at 74 years of age; although most agree that, physically, this is most likely between the ages of 13 and 40.
Each "turn of the crank" in time, there are new people created in the $n\_{m,0}$ and $n\_{w,0}$ buckets at the front of our population funnel. The number of people created $n\_{i,0}$ is equal to the ${\sum\_{i=13}^{40}}Pf \times Pb \times n\_{w,i}$
Half this number is new baby boys $n\_{m,0}$ and half is new baby girls $n\_{w,0}$.
Also, each "turn of the rank" every demographic group moves a level down the age part of the funnel. The chance of surviving the year Ps varies by age group. According to [Unicef](https://data.unicef.org/topic/child-survival/under-five-mortality/) $P\_{s,0}$ is 0.995 (99.5%) and $P\_{s,1..5}$ is a sad 0.9 (90%) And then, according to actuarial tables I've looked at, survivability improves to $P\_s$ 0.999 (99.9%).
The survivability for new mothers is a little lower. Using a source from memory of the mortality statistics for hospitalized mothers when Ignaz Semmelweis was trying to convince doctors to wash their hands between studying cadavers and working with living patients, the survivability of new mothers $P\_s$ was 0.7 (70%). So, $P\_{s\_{w,13..40}}$ is $[n\_{w,i} - (n\_{w,i} P\_f P\_b 0.7)] P\_s$
Putting that all together, you get a funnel like this :
$\begin{array}{aaaa}
& a & 0 & 1-5 & ... & 13 - 40 & ... \\
& P\_s & 0.995 & 0.9 & 0.999 & 0.999 & ... \\
& P\_f & 0 & 0 & 0.16 & ... \\
t = 0 & n\_{w,a} & 0 & 0 & 0 & 10,000 & ... \\
1 & & 787 & 0 & 0 & 9,527 & ...
\end{array}$
Iterating this for five years gives me a population of 14,086. Figuring out the logarithmic exponent is $\ln{{n\_5} \over {n\_0}} = \ln{1.4} = 0.336 \div 5 = 0.067$ .. or about doubling $e^{0.067t} = e^1$ every ten years
Which is a really long and hard way of re-deriving the rule of thumb that "a population roughly doubles every ten years".
But we learned some new things from this long slog :
* the rule of thumb assumes only biological (not social) limits. If half the eligible women choose to opt-out, or wait until they can afford a child, or wait until they find the right man, this number of years "per doubling" can very easily dramatically increase
* in fact, the rule of thumb assumption that ALL of the available women are doing nothing with their time but trying to have babies seems a bit extreme
* also, the assumptions on generally surviving in the environment : having enough food, dealing with disease, are so optimistic that a model that doesn't include those risks at all produces very similar results.
* we've also assumed that the men don't have an impact. As a social limit, if women decide to only have children with a partner, then the man's fertility (Pf = 0.6 or 0.8, depending on source) affects the fertility of matched couples $P\_{f, total} = 0.6 \times 0.84 \approx 0.48$
* also deaths among the men (whatever $P\_{s,m}$ is), would result in widows, or just not enough men for every woman to have one. $P\_{f, total(2)} = P\_{f, total} \times P\_{s,m}$
## Making this Algebraic
Working with a spreadsheet with 100 columns and 600 rows isn't fun.
To simplify the math, we can see that if $P\_s$ doesn't change, then the compounded $P\_s$ over $t$ iterations is $(P\_{s,m})^t$ or $0.999^t$for men, and also for women not having children.
Note: $t$ is being used incorrectly as both "9 months" and "1 year". This mistake will effect the outcome, but I can think of a few ways to correct it later, and I think it only makes things murkier right now.
* $P\_{s,base} = 0.999^t$
* $P\_{s,w,13..40} = [(0.16 + (0.84 \times 0.81) + (0.84 \times 0.18 \times 0.7))\times 0.999]^t = (0.946 \times 0.999)^t = 0.945^t$
Against the number of children being born :
* $n\_{i,0} = {\sum\_{i=13}^{40}(n\_{w,i}) P\_f P\_b}
$
* where $n\_{w,i} = n\_{w,i-1} P\_{s,w,i-1} = n\_w (0.945)^t$
* so, $n\_{i,0} = {\sum\_{i=13}^{40}(0.945^t) P\_f P\_b}$
We can integrate this :
* $\int P\_f P\_b (0.945^t) = P\_f P\_b \int(0.945^t)$
* $\int (0.945^t) = { {(0.945^t)} \over {\ln{0.945} } } + C = { {(0.945^t)} \over {-0.0565 } } + C $
* $\int P\_f P\_b (0.945^t) = P\_f P\_b { {(0.945^t)} \over {-0.0565 } } + C$
* C, working it out by solving at t=0 is 28,302
This algorithm seems produce errors < 4% for the 4 t-values that I've manually calculated.
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Imagine a sci-fi scenario where there is, in effect, an arms race between countries in terms of investing in SETI-style efforts, each country wanting to make sure that if there is any intelligent life out there to find, they will be the first to find it. A country like the US invests a trillion dollars in the effort - what might this trillion buy them? Would there be economies of scale to be realized, or would there instead be huge diminishing returns?
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They could start imaging exoplanets. The [FOCAL](https://en.wikipedia.org/wiki/FOCAL_(spacecraft)) telescope is a proposed design where a telescope is sent to a distance of *at least* 550 AU (82 billion km) and uses the [gravitational lens of the sun](https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_I_Phase_II/Direct_Multipixel_Imaging_and_Spectroscopy_of_an_Exoplanet/) to image an exoplanet enough to get detailed images of the surface including continents, oceans, determine levels of atmospheric gases and even see if there are cities that light up at night like we have on earth.
[](https://i.stack.imgur.com/rblrl.png)
Source: <https://www.hou.usra.edu/meetings/V2050/pdf/8203.pdf>
The downside is that each telescope can only look in one direction, so NASA would have to send *fleets* of these telescopes. The furthest we've ever done so far is [Voyager 1](https://en.wikipedia.org/wiki/Voyager_1), which is only at [155 AU after 44 years of travel](https://voyager.jpl.nasa.gov/mission/status/), so it will require new methods of spaceflight to get there. This video explains the idea of using solar sails, so a spacecraft could buzz close to the sun and then get blown out to 550 AU very quickly: <https://www.youtube.com/watch?v=NQFqDKRAROI>
Side Note: If they wanted to test this idea, they don't have to spend a trillion and wait a decades to get out to 550 AU. There's an idea for a [Terrascope](https://www.scientificamerican.com/article/earth-could-be-a-lens-for-a-revolutionary-space-telescope/) which uses the Earth's gravitational field and a much closer detector.
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Considering that the Apollo program cost around $300bn adjusted for inflation, a trillion dollars being spent would be quite the sight to behold. It's also so much money, that even spread out over a long time-span, there will be difficulties spending it. Because of that, a multi-pronged approach would be likely, where any half-decent and remotely feasible idea gets basically infinite funding.
Here are some of those ideas:
* **Space is full of transmissions we just don't understand.** Due to our limited understanding of encryption and radio technology, what we interpret as "white noise" using our radio telescopes is actually internet traffic that carries alien memes or whatever. To attempt decryption, we build a vast supercomputer and create an AI to analyze this noise and search for patterns.
* **There is life on Mars/in our solar system.** The current scientific consensus agrees that there was liquid water on Mars, and most think there still is to some degree (in slush or underground lakes). The idea that microbe-analogue life exists on Mars right now has a decent chance of being true. With this huge infusion of money, and the advanced technologies available to us today, unmanned missions to all solar bodies will become near routine, and manned missions will likely stretch past the asteroid belt to investigate Jovian moons for signs of life.
* **We just haven't looked close enough yet.** When Hubble started sending back good science data, it revolutionized physics in many ways--all from only having a mirror less than three meters in size. JWST will doubtlessly do the same with its 6.5m mirror. With a functionally infinite budget, we can start considering truly ridiculously big telescope concepts, including gravitational ones that use the sun as a lens or converting a crater on the far side of the Moon into a massive radio telescope. Really, imagination is the limit here.
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**DNA cryptography.**
Assuming life was planted in our solar system by external intelligences, these intelligences might have left messages for us. The rational place to leave such messages would be in the DNA as this would be replicated and so maintained, where as a note in a bottle will probably not persist 4 billion years. Cryptographic analyses of conserved DNA across a range of organisms with an eye towards reconstructing the basal state of life will look for a message beyond the function of that DNA.
But 4 billion years is a while. Maybe it would be good to look someplace that evolution and mutation had not been going on for so long. Mars was nice 4 billion years ago and would probably have been seeded with life too. Maybe Venus as well. Perhaps DNA in the life from those days might still be preserved there. Search for remains of that life will ensue, with the idea that the message as preserved in that DNA will be cleaner than what exists here.
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I am trying to think of what sort of message I would send to my descendants 4 billion years in the future. I think it would be a joke.
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Could an animal realistically move around if it lacked knees in some legs?
For specifics, the animal for my world would be a tetrapod-analogue, having 2 large legs (with knees) at the back, and a smaller pair of knee-less legs near the front. The forelegs have a foot at the distal end, with a ball-and-socket joint at the ankle and shoulder. The creature has a complete and rigid endoskeleton, which extends throughout the torso, legs, and feet
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### Sure
You've pretty much reinvented the kangaroo. Your tetrapod has big hind limbs with hip, knee, ankle and toe joint; and smaller forelimbs with some kind of shoulder, wrist and finger joints.
Mostly they hop or leap along without recourse to their forelimbs. Only when moving slowly do they rest their forelimbs on the ground. When they do this, they simply use the forearms as pillars that pivot at the shoulder. Forward motion is accomplished by a short bump of the hind legs, sending the rump airborne, and then quickly curling the spine & hind legs forward to place them on the ground for the next short hop. To hop again, the beastie slightly lifts is front end, swings its forelegs a little bit forward and then rests them again on the ground, ready for their characteristic little rump bump.
[](https://i.stack.imgur.com/PLwkv.png)
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**The idea perished long ago**
Sometimes nature decides to mess around with funny designs. Some 500-600 million years ago during the Cambrian Explosion, we have had Hallucigenia, 8cm, shallow waters
[](https://i.stack.imgur.com/sUUmP.png)
<https://www.google.com/search?q=Hallucigenia+species&source=lnms&tbm=isch&sa=X>
Failed design, I'm afraid.. it looks funny, but these rigid legs.. not handy. e.g. it won't be easy to free yourself, when these legs gets stuck for some reason. And also notice Halucigenia needed flexible legs (or tentacles) up front, so it could bend over the head to graze for food. With rigid forelegs, it is far more difficult to reach for food.
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# They could move, but not very well.
Joints provide improved flexibility in movement. You can test this by tying up your arms and walking on your knees. You can move, but it's a lot harder to navigate around obstacles, or deal with anything complicated.
# Creatures with exoskeletons have knees.
[](https://i.stack.imgur.com/NcJyB.jpg)
It's useful to be able to twist your limbs, so your modification would be weird. It would be possible, but not very fluid.
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Winged jetpack comes with 2 set of fixed thrusters and a pair of foldable wings with adjustable aileron. (You put on the jetpack like a schoolbag)
Palm repulsors are heavy duty gloves each is equipped with a powerful plasma ejector that can deliver a constant force of max 100Kg of TNT up to 2 hours. (Both repulsors work independently)
I am wondering which of these offer more versatility and dexterity in flight? Both equipment can stay levitated in-situ for a long time but I think repulsors are more tiring and maybe one setback for the repulsors is that you cannot aim your weapon and fly at the same time.
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Palm repulsors, requiring the hands to be constantly busy with keeping the right attitude, effectively hamper the bearer from using their most versatile body part: if your hands are busy keeping you in the right direction, you can't use them to hold a gun, a sandwich, not even to scratch your nose when it itches.
If you are looking for versatility, palm repulsors totally kill it.
Moreover, having the force applied away from the center of mass makes them a nightmare to control, like you can see from any slapstick movie where someone is struggling to control a hose.
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Edited: I suppose the setting doesn't really matter.
Scenario: An earth-like planet in size and material and atmospheric composition experiences a phenomenon of purple light being the visible light at night when its two moons, one with a red surface and the other blue, both shine with equal luminosity, usually during a dual full moon. Both moons are the same size as Luna(ours) at a similar distance to ours, with the blue one being slightly closer to the planet than the red one but the difference in distance isn't enough to make the blue look too significantly larger than the red. The how and why of them each being different enough in material composition to so drastically reflect such different wavelengths doesn't matter, just whether or not that they do would actually lead to a combined hue on the local planet's surface.
**Would the light of two moons, one with a red surface and the other with a blue surface, lead to a purple light shining on the surface of the local planet at night?**
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Yes. If you've ever spent a lot of time in a place with no electricity, you'll know that it gets very dark at night when there's no moon. And when the moon is full, there's only just enough light to make out colors (when our eyes adjust to light little darker than that, everything is grayscale).
Now, you can check whether reflecting light changes the color of a thing by shining a bright light on something colorful and letting it reflect onto white paper. The resulting light is the color of the thing it was reflecting off of. Your moons would definitely reflect light of their own color.
So, when the moons are full enough for there to be substantial light, so that you can make out color, it would be blue and red light, and the combination would give a slight purple tint to the landscape.
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Yes, with both moons full in the sky, their combined light will appear [purple](https://en.wikipedia.org/wiki/Purple) to human eyes, and should give the landscape illuminated by them a purplish tint.
However, in practice the effect may not be as noticeable as you might expect, for two reasons:
1. Human [color vision](https://en.wikipedia.org/wiki/Color_vision) is most effective in bright light. In dim light, our eyes gradually switch to [scotopic vision](https://en.wikipedia.org/wiki/Scotopic_vision), which is more sensitive at low light levels but cannot distinguish color. The result of this is that in dim light, such as moonlight, we perceive colors only faintly, if at all.
2. Even in bright light, human eyes adapt to the color of ambient light and compensate for it to provide perceptual [color constancy](https://en.wikipedia.org/wiki/Color_constancy). This is why we're able to, for example, look at a piece of white cloth or paper under a bright blue sky, in dim reddish-yellow candlelight or in a forest under a canopy of green leaves, and in all cases agree that it is indeed white.
When deliberately tricked, or simply lacking the correct cues, this adaptation can also produce some pretty weird color illusions, like [the famous dress](https://en.wikipedia.org/wiki/The_dress) or [this Rubik's cube illusion](https://prosetech.com/blue-dress-is-nothing/). It can even synthesize perceived colors out of nothing, merely based on the lack of other colors, as in [this landscape drawn entirely with red and white pixels](https://en.wikipedia.org/wiki/Color_constancy#/media/File:Mountain-spring-redwhite.png).
Anyway, here's a quick way to test what the night might look like in your world:
1. Turn up your screen's brightness as far up as it will go.
2. Turn off all the lights in the room and cover any windows etc. that might let stray light in. (This is easiest to do at night, or in a windowless room. If you're on a laptop, you can just take it with out into a closet or something.)
3. Click the image below to open it in full size and switch your browser to full screen mode. You should now see nothing on your screen except a red and a blue circle.
[](https://i.stack.imgur.com/cml84.png)
(If you can't get the image to cover the full screen without some title bars etc. visible, try [this Google presentation link](https://docs.google.com/presentation/d/1l7BPjI6dzZ4q-iPuK1oCIkY9r5HVAOvr5Nk45Cdjeec) and press `Ctrl`+`Enter` to switch to presentation mode.)
4. Look around you.
I tried this myself, and honestly, the purple tint itself is kind of underwhelming. Yes, I can tell it's there, but my eyes adapt to it quickly and it becomes barely noticeable.
The colored shadows from the two separate light sources, however, look really cool.
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Ps. [Since the issue was raised in the comments](https://worldbuilding.stackexchange.com/posts/comments/674336), let me briefly discuss whether it's possible to actually have two moderately large moons visible in the sky at the same time.
The short answer, FWIW, is yes. The tricky part is actually having two large moons in stable orbits in the first place (and getting them to somehow [have the colors you want](https://worldbuilding.stackexchange.com/questions/218562/what-would-be-the-most-likely-compositions-of-the-red-and-blue-moons-to-so-almos)) — if you can manage that, there's no way to keep them from at least sometimes appearing in the sky together.
Anyway, as far as we know, there are basically three ways two have a pair of similarly sized moons in stable orbits around a planet:
1. They can orbit **at different distances** from the planet, meaning that their [orbital periods](https://en.wikipedia.org/wiki/Orbital_period) will be different. This is by far the most likely scenario, as it's what most moons in the solar system do.
In some cases the moons might end up in a stable [orbital resonance](https://en.wikipedia.org/wiki/Orbital_resonance), like the Laplace resonance between Jupiter's moons Io, Europa and Ganymede, where Ganymede's orbital period is exactly twice that of Europa and four times that of Io. This can stabilize the system and allow the moons to stay in stable orbits closer to each other than would otherwise be possible.
Note that it's also not strictly necessary for the moons to orbit the planet in the same direction, and in fact simulations show that having one of the moons in a [retrograde orbit](https://en.wikipedia.org/wiki/Retrograde_and_prograde_motion) can sometimes help stabilize the system. However, it's unlikely for a moon to form in a retrograde orbit, so it's thought that all such [irregular moons](https://en.wikipedia.org/wiki/Irregular_moon) in the solar system (which, except for Neptune's moon [Triton](https://en.wikipedia.org/wiki/Triton_(moon)), are all small and far from their planets) have been captured into their current orbits from elsewhere.
2. It's also possible for two moons of similar size to **share approximately the same orbit**. There's exactly one known pair of such [co-orbital](https://en.wikipedia.org/wiki/Co-orbital_configuration) moons in the solar system: Saturn's moons [Janus](https://en.wikipedia.org/wiki/Janus_(moon)) and [Epimetheus](https://en.wikipedia.org/wiki/Epimetheus_(moon)).
However, such moons will *not* stay a fixed distance apart — that would be an unstable arrangement. Rather, whichever moon happens to be slightly closer to the planet will orbit faster and gradually catch up to the other one. But once the moons get close enough to each other, gravitational interaction between them will cause them to *swap orbits*, with the outer, slower one getting pulled into a closer, faster orbit and vice versa. This makes the moons start moving slowly apart again, until eventually the now faster moon will complete a (nearly) full extra orbit and catch up to the other one from behind, at which point another orbit swap will happen and the cycle repeats.
3. Finally, it's of course also possible for the two moons to **orbit one another** as a "double moon". Obviously, this would make the moons always stay close to each other in the sky, although they can also regularly pass in front of each other.
There are no known examples of such double moons in the solar system, although several [double planets](https://en.wikipedia.org/wiki/Double_planet) (including, by some definitions, the Earth–Moon system) and [double asteroids](https://en.wikipedia.org/wiki/Binary_asteroid) are known. One reason for this is believed to be that, for moons close to their parent planet, the same tidal interactions that drive [tidal locking](https://en.wikipedia.org/wiki/Tidal_locking) will also destabilize double moons, as they cannot simultaneously lock to each other and to the planet. That said, you could probably handwave that issue away somehow.
If one of the moons was significantly smaller than (i.e. less than ~4% of the mass of) the other, it could also orbit stably at or near the other moon's 4th or 5th [**Lagrange point**](https://en.wikipedia.org/wiki/Lagrange_point), i.e. 60° ahead or behind it on the same orbit. No such "[trojan](https://en.wikipedia.org/wiki/Trojan_(celestial_body)) moons" are known in the solar system, but several planets have small asteroids orbiting at their L4 and/or L5 points, including the several thousands of [Jupiter trojans](https://en.wikipedia.org/wiki/Jupiter_trojan). However, if you want your moons to look roughly equally big and bright in the sky, this is unlikely to be what you want.
In general, however, note that your moons do *not* have to be anywhere near the same size in order to look roughly equally large in the sky, as long as the smaller one orbits closer in. For example, Mars's inner moon [Phobos](https://en.wikipedia.org/wiki/Phobos_(moon)), despite having only 0.00001% of the mass of the Earth's moon, looks [fairly comparable in size](https://en.wikipedia.org/wiki/Phobos_(moon)#/media/File:PIA17351-ApparentSizes-MarsDeimosPhobos-EarthMoon.jpg) as seen from the surface of Mars due to its much lower orbit.
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This is advice to Rubrikon and a reply to Goodies's comment that:
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> +1 wonderful scenario but I'm glad there isn't any "reality check" involved. I think the two large moons would eventually stabilize their orbits in eternal opposition. I'm afraid your two large moons won't have a common full moon. That would mean they are on the same side of the planet. Considering the large relative weight of our moon, a second one, forming a binary moon system with an Earth-like planet, will probably stabilize with the moons in orbit on either side of the planet, with no common full moon.
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That would not happen in real life.
There are many examples of multiple moon systems in our solar system. There are no examples of 2 moons orbiting at the same distance from the planet and always opposite to each other. And moons in different obits will always change their relative positions as they orbit.
Part One: Moons in different orbits.
If there are two moons, They will (almost always) orbit the planet at different distances. And so the moon with the inner orbit will orbit faster and pull ahead of the outer moon until it is 180 degrees ahead, on the opposite side of the planet, and then catch up with the outer moon until it eventually passes it, over and over again. Sometimes the two moons will appear close together, sometimes only one will be seen at a time.
Sometimes one moon will be seen in the day, and the other moon will be seen in the night. Sometimes both moons will be seen in the day. Sometimes both moons will be seen in the night, making the night purple as requested.
With different red and blue moons, there will be constant changes in the color of the night.
Part Two: Moons in Exchange Orbits.
It is commonly said that the moons Epimetheus and Janus of Saturn share an orbit, but that is not exactly true. They have very similar orbits, but one orbits slightly closer to Saturn than the other. Because of the very similar orbits and orbital speeds, it takes many orbits round the planet for the inner one to pull ahead of and then catch up with the outer one, and they orbit so close that every time the inner one catches up their gravitational interactions make them switch obits.
<https://en.wikipedia.org/wiki/Janus_(moon)>
>
> Epimetheus's orbit is co-orbital with that of Janus. Janus's mean orbital radius from Saturn is, as of 2006 (as shown by green color in the adjacent picture), only 50 km less than that of Epimetheus, a distance smaller than either moon's mean radius. In accordance with Kepler's laws of planetary motion, the closer orbit is completed more quickly. Because of the small difference it is completed in only about 30 seconds less. Each day, the inner moon is an additional 0.25° farther around Saturn than the outer moon. As the inner moon catches up to the outer moon, their mutual gravitational attraction increases the inner moon's momentum and decreases that of the outer moon. This added momentum means that the inner moon's distance from Saturn and orbital period are increased, and the outer moon's are decreased. The timing and magnitude of the momentum exchange is such that the moons effectively swap orbits, never approaching closer than about 10,000 km. At each encounter Janus's orbital radius changes by ~20 km and Epimetheus's by ~80 km: Janus's orbit is less affected because it is four times more massive than Epimetheus. The exchange takes place close to every four years; the last close approaches occurred in January 2006,[14] 2010, 2014 and 2018. This is the only such orbital configuration of moons known in the Solar System[15] (although, 3753 Cruithne is an asteroid which is co-orbital with Earth).
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<https://en.wikipedia.org/wiki/Epimetheus_(moon)#Orbit>
If your planet had two moons in very similar orbits like Epimetheus and Janus, they would be close together in the sky for a long time, and be farther away in the sky for a long time, and would be far enough apart that only one was visible at a time for a long time. Years could pass when only one moon was visible at a time, when the red and blue moon alternated in visibility and when only one lights the night sky at a time. And then after that there could be years when the two moons were close enough that they usually were seen together and light the night sky together.
If you want such a sequence of lighting effects you should go with a Janus and Epimetheus type orbit. And naturally some characters would worry that maybe something will go wrong the next time the moons exchange orbits, and fear that one of the moons might crash onto the planet.
Part Three: Moons in a Trojan Orbit.
With 2 moons in a trojan type orbit, they will both be the same distance from the planet, and one will alwys be about 60 degrees from the other. Being separated that far will mean that sometimes they will be seen together and sometimes one will be below the horizon while the other is visible (and sometimes both will be below the horizon). More importantly, one of the moons would have to be tiny compared to the other for long term orbital stability, and so it will reflect only a tiny amount of the light that the other one does.
Part Four: A Ring of Moons.
You could have a ring of 7 to 42 moons of equal mass equally spaced in the same orbit and alternating red and blue in color of surface material.
<https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/>
<https://ui.adsabs.harvard.edu/abs/2010CeMDA.107..487S/abstract>
But if the moons were massive enough to reflect enough light, orbital stability would probably require that the planet be too massive to be habitable for humans.
Maybe the habitable world would be a giant moon orbiting around a giant planet, and the ring of alternately red and blue moons would orbit the planet outside the orbit of the habitable moon.
Part Five: Double Moon - Two Moons Orbiting Each Other as They Orbit the Planet.
In a comment Ilmari Karonen suggested a double moon, with the two moons orbiting each other as they orbited the planet.
That might be the best way to have moons visble together for the mos time. They would be two equal size moons orbiting around their center of gravity or barycenter as they orbit the planet. The orbital distance between the two moons would be a rather small fraction of the total circumference of their orbit around the planet. Both the moons would be visible almost half the time. Both the moons would be out of sight below the horizon almost half the time. The red moon would be seen alone low above the horizon a small percentage of the time, and The blue moon would be seen alone low above the horizon a small percentage of the time.
They don't have to be exactly the same size. If one had half the diameter of the other one it would have a quarter of the surface area to reflect light, and one eighth of the mass of the larger one. It might appear to be only one quarter as bright as the other moon which may be a problem mixing colors to make purple light.
But if the two moons have different surface materials which have different colors, those surface materials could have different albedos, reflecting different percentages of the light that hits them. The larger moon's surface could refect a relatively small percentage of the light that hit it and the smaller moon could reflect a higher percentage of the light that hit it.
The variation in the albedo of various objects in the solar system is great enough that a moon with only one quarter the surface area of another one could reflect much more light than the larger moon.
And of course the star of the system might not emit equal amounts of red and blue wavelengths of light for the moons to reflect back at the planet. In fact it would probably be almost impossible for a star with a habitable planet to do so.
Of course designing a stable planet-moon system with a double moon orbiting the planet might be tricky, but it should be possible.
] |
[Question]
[
TL;DR: I have solved aging and cancer with the power of handwaving and genetic science. All rejoice.
Yes, there is a question at the end of this all, but you have to read it for it to make sense.
In order to provide context for this question, I had to write a wall of text to explain the specific mechanism of how my version of biological immortality works, since that mechanism is relevant to the question. I think it's around a 5 on the **(WARNING: TVTROPES LINK)** [Mohs Scale Of Science Fiction Hardness](https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness) **(WARNING: TVTROPES LINK)**.
Living things age. This is a fact. A specific component of the process of a living thing aging is the shortening of the [telomeres](https://en.wikipedia.org/wiki/Telomere) in that thing's cells.
Telomeres are [non-coding DNA](https://en.wikipedia.org/wiki/Non-coding_DNA) - more commonly known as junk DNA. This type of DNA cannot code for proteins, meaning that it is functionally useless. The function of telomeres is to essentially act as an [ablative](https://en.wikipedia.org/wiki/Ablation) shield for the rest of the [chromosome](https://en.wikipedia.org/wiki/Chromosome) they're attached to; each time a cell replicates, a little bit of the telomere is worn away, because the replication process is not 100% accurate/efficient. However, as a telomere wears down, the organism it's a part of is unaffected, since it's not the coding DNA being damaged. Once the telomeres are all burned out, actual DNA stops being replicated effectively, and the cell soon fails to replicate.
[](https://i.stack.imgur.com/deayn.jpg)
Think of it this way: you have a magic copier capable of copying [an entire stack of papers](https://en.wikipedia.org/wiki/Chromosome) at once, and you have a lot of [papers](https://en.wikipedia.org/wiki/Gene) you need to copy - each one of them is vital for your job, and you'll [get fired](https://en.wikipedia.org/wiki/Death) if enough of them are lost. However, each time the copier copies, it [folds, spindles, and mutilates](https://en.wikipedia.org/wiki/Punched_card#Do_Not_Fold,_Spindle_or_Mutilate) the topmost paper and the bottommost paper in the stack. The solution to that is to put in [sacrificial papers on the top and bottom of the stack](https://en.wikipedia.org/wiki/Telomere); these don't actually carry any information. However, after repeated copying, they eventually run out, and then the copier starts destroying paper with information on it, and you [get fired](https://en.wikipedia.org/wiki/Death).
This means that cells have a set replication limit - once they replicate enough times, they run out of telomere, and then they crash and burn. Over time, this eventually leads to bodily structures failing as their cells break down. This is aging.
However, there's a reason your body has telomeres, other than to cause depressing funerals, and it's an ugly one - cancer, a self-replicating blob of cells. Telomeres stop cancer cells from replicating out of control; they're essentially an automated self-destruct switch, and many cancers are likely never noticed by humans, since they fizzle out and die before getting really big - the telomeres stop them from making more of themselves *ad infinitum*. Only the biggest and meanest cancers make it to the killing-you-horribly phase thanks to telomeres.
This means that, while [biological immortality](https://en.wikipedia.org/wiki/Biological_immortality) is certainly an exceptionally appealing target for lots of research, you're not going to get it by removing the ability of the telomeres to shrink. While that'd stop aging, it'd also allow even the smallest cancers to replicate end-over-end until you're some kind of disgusting, gristly blob straight out of Warhammer 40,000, which will probably kill you long before old age would have (and in a much more unpleasant fashion, to boot!).
But, y'see - and this is the thing for any self-respecting hard sci-fi writer, as well as any self-respecting seeker of immortality - as of currently, eternal telomeres are one of our best bets at biological immortality. You can't have old age without telomeres, because, without them, your cells break down and you die. But you can't have *invulnerable* telomeres - ones that never wear down - because then you get cancer-inated.
What's a person to do?
Well, y'see, here's the solution: **instead of making invulnerable telomeres, you constantly add onto them.** They regenerate. They never run out.
"But - *how?*" the StackExchangians ask.
Well, [this](https://en.wikipedia.org/wiki/CRISPR_gene_editing) is how. CRISPR-Cas9 genome editing is amazing - it deserves more than a Nobel prize. We can manipulate the fundamental building blocks of life. We are GODS. Well, not quite, but you get the point.
Thing is, CRISPR-Cas9 can add to strands of DNA. Telomeres are strands of DNA. It can probably add to telomeres forever, actually. **As the telomeres wear down, CRISPR-Cas9 slaps more DNA onto the end.** The cells never age, because they never run out of telomeres. Aging is dead, and humanity has killed it. Bwah-hah-hah.
Now, figuring out how to integrate the processes of CRISPR-Cas9 into the body is another story, but it's a story for later, and, frankly, is worthy of a handwave - albeit a believable one. But there's another problem.
"But - *cancer*!" the StackExchangians exclaim.
That's the trickier bit, but I'm a tricky-ass brain-piloting-a-muscle-and-bone-mecha, and so I concocted an even trickier solution.
[DNA repair](https://en.wikipedia.org/wiki/DNA_repair) is, as Wikipedia so succinctly puts it:
>
> a collection of processes by which a cell identifies and corrects
> damage to the DNA molecules that encode its genome
>
>
>
Key word: **identifies. The cell can tell between normal and abnormal.**
Let's backtrack a bit - back to cancer.
Cancer cells are so awfully successful because they're good at getting around your immune system - to your immune system, a set of cancer cells look just like yet another set of your body's cells. Nope, nothing to see here, [officer](https://en.wikipedia.org/wiki/T_cell). Move along. Ignore the fact that there are more of us than there were a minute ago.
But what if the body could tell the difference? It'd kill the little bastards dead if it could tell the difference. But, unfortunately, it can't.
But, with my idea, it can.
Y'see, that CRISPR-Cas9 thing - it constantly adds more DNA to telomeres. This happens each time a cell replicates, so that the telomeres never shorten. [It doesn't take long for cells to replicate.](https://sciencing.com/much-time-dna-molecule-replicate-21660.html) This means that, with CRISPR-Cas9 [fully armed and operational](https://www.youtube.com/watch?v=2mlza-sPdBg), what the telomeres are made out of is constantly changing, since what they're made out of changes each time they replicate. Moreover, that change doesn't repeat for a long time - this weird, integrated-into-the-body CRISPR-Cas9 system just grabs the piece of the telomere that breaks off during cell replication and slaps it back into the base of the telomere as replacement material. Eventually, it'll come back up again, but by that time, all the cells in the body will have already gone through that configuration of telomeres (more on that later).
In other words, **the makeup of the telomeres constantly changes.** Moreover, and this is critical: **this occurs as a body-wide process - i.e. every single telomere in the body goes through the same configuration eventually.** This is *not* a handwave - remember, CRISPR just takes the bit that broke off the end of the telomere and puts it back at where the telomere connects to the DNA. It's always the same telomere, and not a bit of it changes - it's just that CRISPR rearranges it every time the cell splits. It might change at a different rate, depending on the type of cell in question, but it changes regardless.
Now, there is a way for the body to find and exterminate cancer. How? **It looks for out-of-date telomeres.** After all, cells replicate quickly, meaning that the telomeres change in composition quickly - the telomeres of 8:00 at night are different from the telomeres of 8:00 in the morning. Certainly, some cells replicate more quickly than others, meaning that differences in what's "up to date" will form (i.e. brain cells are on a different telomere than bone cells, etc.), but the solution to that is for the cells of each bodily tissue's CRISPR-Cas9 process to use a different [adeno-associated virus](https://en.wikipedia.org/wiki/Adeno-associated_virus) (below) to repair its telomeres - one for the muscle cells, one for the brain cells, one for the bone cells, etc.
Basically, each type of bodily tissue runs on a different "clock", which is separate from all the "clocks" the other bodily tissues run on. This ensures that the immune system doesn't kill off cells that grow more slowly than others.
[](https://i.stack.imgur.com/Fk7SM.jpg)
However - and this is the second handwave, other than CRISPR-Cas9 being integrated into normal cellular biology - this CRISPR-Cas9 process refuses to work with cancer cells. Somehow, it identifies them and refuses to add onto their chromosomes. This means that cancer cells age like normal, while the body's cells are immortal. This, alone, resets the cancer rate to a normal human - while eliminating aging.
But there's more.
Remember that bit about how **the cell can tell between normal and abnormal**, and the bit about how the telomeres of 8:00 at night are different from the telomeres of 8:00 in the morning? Well, I bet you that the body can apply the ability to tell between normal and abnormal to telomeres. A third handwave, but still 100% plausible.
This means that the body can separate the telomeres of 8:00 in the morning from the telomeres of 8:00 at night. It'll do this by using the slowest-reproducing cells as a reference; after all, those are the last ones to "roll over" to the next telomere configuration, meaning that all the other cells do so beforehand, and, therefore, any cells drifting around with out-of-date telomere configurations *must* be cancerous, and not just ones that replicate slowly.
Let's say it's 8:00 *at night*. The skeletal muscle cells are running on the most recent, "up-to-date" generation of telomeres - except for a little clump of cancerous skeletal muscle cells, which went rogue at 8:00 *this morning* and aren't. They're still stuck with the morning's revision of telomeres, since the CRISPR-Cas9 refuses to update them.
And, with the body's ability to tell between the cells of 8:00 AM and 8:00 PM, those cancer cells stick out like a sore thumb. They are not like normal, real-life cancer cells, which blend in and grow and expand - they are very clearly out of date in comparison to the rest of the skeletal muscle cells, by 12 hours.
They are rapidly exterminated.
So, not only does this cure cancer - it cures aging, AFAIK. And all it needs is three handwaves.
With all of the above in mind, I finally present the question you've all, I'm sure, been dying to answer:
**How long will can a 100% cancer-immune person live if they no longer age via cell death?**
Assume that they have a healthy diet, plenty of access to sunlight, are at no risk of injury, etc.
Like, I'm sure they'll somehow die *eventually*, but the odds are that it'll take a heckin' long time.
Also, AlexP kindly pointed out that neurons do not replicate. However, that doesn't mean that the CRISPR-Cas9 process won't constantly shuffle the telomeres of neurons anyway in order to keep up with the rest of the cells and avoid deletion.
[Answer]
Honestly your humans' maximum lifespan will probably be around ~100 years, due to something called "[Thymic Involution](https://www.frontiersin.org/articles/10.3389/fimmu.2020.00897/full)". In short the organ that controls your immune system (your Thymus), which also handles cancer killing, cell recycling and several other critical processes begins losing capacity at age 10 and continues to degrade throughout your life, by age 100 it basically doesn't exist except for a few slivers surrounded by fatty tissue. Without the ability to recover critically damaged but not dead cells, they'll eventually build up and overwhelm your body's ability to compensate. This is in addition to the regular problems of not having an immune system.
In [experiments on mice](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3494070/), giving the cancer resistant mice a treatment that caused them to overexpress telomerase improved their lifespans by 40%, but they still aged to death.
You'll want to combine your telomere treatment with some kind of senescent cell clearance at least.
[Answer]
**Assuming that death is now only by misadventure...**
You've given your humans a half-life. Not metaphorically, but mathematically.
Suppose that in any given century, someone has a 50% chance of death by misadventure. The average lifespan is 200y (the mean of an exponential distribution).
With an assumed ~8 billion people on the planet when this is first mass-adopted, that means that you'd expect 4 billion to survive the first century, 2 billion to survive another, etc ... and expect (on average) one to survive the 33rd.
That assumes that everyone has the same chance of death-by-misadventure, which is probably false.
---
The other problem here is that **the human body does not retain the ability to replace structures**. If your adult teeth are removed or badly damaged, there is no biological mechanism in place to repair or replace them, for example. This will lead to another answer to your question, along the lines of "what life-critical part will wear out first"? Specifically in females who birth children, depleted-bone-calcium is a contender - if that's still a part of your future, population control will be a consideration.
---
A note on hand-waving: Biochemically identifying cancerous cells is a rather significant challenge to handwave, as is integrating a trustworthy retrovirus factory into your (post-)humans. What protects it from the accumulated errors that lead to cancers in normal cells? But if you can trust it, it can repair that same damage throughout the body, potentially conferring resistance to some forms of radiation poisoning.
[Answer]
If indeed the mechanism *"somehow identifies cancer cells"* ...
... In this case, the entire Rube Goldberg machinery is useless. If you have a working mechanism to identify cancerous cells then all you have to do is express a marker protein on their surface and let the plain ordinary immune system do its thing. No need to mess with telomeres, daily variants and so on.
] |
[Question]
[
In my world, creatures evolved in the twilight zone of a tidally locked planet. Naturally, because there is little light, creatures either increased their light sensitivity or turned to other senses, the most common being their auditory sense.
I have originally thought of just larger ears but thought they didn't quite fit with some of my reptile-looking creatures. So I thought of another method, but am not sure if this would work.
Basically, the creatures would have large "plates" on the top of their heads, like that of triceratops.
[](https://i.stack.imgur.com/mv2nc.jpg)
These "plates" will be structured so that they would be sensitive to vibrations, and there would be many nerves that would pass on these vibrations to the brain.
There are some animals that sense the vibrations of the ground, but I don't know if this would work out for vibrations in the air...
So, in biological terms, is this method of "hearing" possible? If not, could there be any modifications to make this possible?
[Answer]
I think it's possible but would be inferior by far to how animals handle it today. The best hearing in low light animals isn't achieved by having larger ears.
Owls and the record holder which is a moth don't have large ears. Owls have no real external ears yet they can hear the heartbeat of a mouse 25 feet away. This is largely done internally by ear drums and other mechanisms.
Lizards have sub par hearing but taste the air with their tongues to get very precise information.
The closest parallel would be fish with their lateral lines, but those are in a water medium where it's much better suited. Air is a whole other story, it just doesn't have the density and other properties of water.
[Answer]
The [lateral line](https://en.wikipedia.org/wiki/Lateral_line) in the fishes has a similar purpose
>
> The lateral line, also called lateral line system (LLS) or lateral line organ (LLO), is a system of sensory organs found in aquatic jawed vertebrates, used to detect movement, vibration, and pressure gradients in the surrounding water.
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The main difference is that, due to the higher mismatch in acoustic impedance between the air and the body, it might be less effective in catching the sound. But that can be mitigated with an appropriate design.
Considering that the side of the body has also a larger surface than plates around the head, it looks also like a better location.
] |
[Question]
[
I've been looking around the internet but I can't seem to find out how fluoride salts would form naturally. My end goal is for my planet to have a mildly high concentration of hydrofluoric acid pools, and my idea was to utilize the already-abundant amount of sulfuric acid to combine with fluoride salts. Villiaumite would work but it would be preferable if the salts would form on the surface and be more readily available.
Could I just handwave it and have it still sound mostly plausible that there's fluoride salts growing in abundance on the surface, or is there a simple reason that'll work instead? If not, is there an easier way to achieve high concentrations of hydrofluoric acid?
Potentially relevant info about the planet: It's surface temperature is an average of 461ºK (~187ºC), it's atmosphere is high in sulfur dioxide, hydrogen sulfide, and chlorine, and it's around 1.5 times as dense as earth (atmosphere is twice as dense).
[Answer]
Here is some sodium fluoride.
[](https://i.stack.imgur.com/JEnIB.jpg)
<https://en.wikipedia.org/wiki/Villiaumite>
It is rare.
Here is some calcium fluoride. It is less rare.
[](https://i.stack.imgur.com/XaZ2y.jpg%5C)
<https://en.wikipedia.org/wiki/Fluorite>
Both are concentrated via hydrothermal liquids and then crystallize out.
It sounds like geothermal pools would not be out of place on your world. The pools would probably not be pure hydrofluoric acid but a mix of hydrofluoric and other (sulfuric, hydrochloric) acids.
[Answer]
>
> Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative element, it is extremely reactive, as it reacts with all other elements, except for argon, neon, and helium.
>
>
>
[Fluorine](https://en.wikipedia.org/wiki/Fluorine), as said above, is an halogen element, halogen being a term of Greek origin, meaning "which form salts".
Therefore it is possible to have fluorine based salts.
>
> Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance.
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>
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In the solar system it's even the most abundant halogen, therefore I don't see any problem with having an abundance of fluorine based salts in your world.
] |
[Question]
[
I'm hoping that the following scenario is one of those "you'll never actually see that so don't bother looking for it" things Because Reasons™ but I want to look at whether, and how, it is *physically possible*:
The Larry Niven essay *[Bigger Than Worlds](https://en.wikipedia.org/wiki/Bigger_Than_Worlds)* has a lot of ideas for making artificial habitable environments in outer space. In the section titled Inside Outside Niven suggests that you can create one such environment with a chunk of iron/nickel asteroid shaped like a mile long cigar. One drills down the centre of it, fills it with water, reseals the ends, and then heats it by spinning it under the glare of a parabolic solar mirror. The body will be semi molten when the heat reaches the water and turns it to steam puffing the whole thing up into an ovoid bubble that can then be moved into. There are serious issues with the proposed technique but the form of the final product is sound.
What I want to know is: **How could it happen naturally?**
Not a smooth artificial bubble being spun for pseudo-gravity obviously but a rocky-iron asteroidal shell around a void with enough volatiles to create some sort of atmosphere, when it is warm enough, contained in it. Sorry let me be clearer I'm **not** asking for the blown spheroid of Niven's suggestion, I'm pretty sure it won't work as written anyway, *I* just want an asteroid with a bubble of internal atmosphere contained in it.
[Answer]
>
> a rocky-iron asteroidal shell around a void with enough volatiles to create some sort of atmosphere, when it is warm enough, contained in it.
>
>
>
It seems unlikely: once a body starts to have significant self gravity, so that it is bound by it and not by electrostatic forces, also buoyancy starts to be sensible, and that will result in denser materials sinking toward the center of mass, while the less dense materials will move toward the outer of the body, eventually being vented out.
What might happen is that, if the material is in a molten state, the outer shell can solidify first and then trap any degassing coming from the inside, which will then end up undergoing coalescence and forming localized bubbles.
[Answer]
1. Take Ceres *Europa* out of Jupiter's influence and throw it into space until it freezes to interstellar space temperature by radiation loss
2. send it for some billions of year wandering in an iron rich nebula - perhaps you can find a cluster of old supernovas somewhere
3. when you have a thick enough iron shell on top of some form of [metallic ice](https://en.wikipedia.org/wiki/Ice#Phases), send it at grazing incidence at high speed in the polar jets of a neutron star. With a bit of luck, the eddy currents will sinter the outer shell and give it a rotation high enough to create the inner void from the ice. You may be lucky enough to let some of the ice briefly breach the shell and be ejected outside
4. place it around a nice star to keep it warm.
I would never bet even an atom of iron against a planet size diamond you'll be that lucky to have your hollow dwarf planet. Maybe because I just love iron atoms so much I'd never part with one.
[Answer]
# forming
Well, you need a volatile (icy) core covered in a rock or metal shell. This is the opposite of what happens normally when a melted body differentiates.
There *are* bodies that are all ice. So let's start with that, and figure out how to make a hard crunchy shell like a cosmic [M&M](https://en.wikipedia.org/wiki/M%26M%27s).
Planets normally grow by accretion anyway. You just need to move it from the region where it accumulated ice particles and into a region where it accumulates rock or other heavy material. These regions are normally separated in the protoplanetary disk, on either side of the [frost line](https://en.wikipedia.org/wiki/Frost_line_(astrophysics)#Location).
So, at first glance, it seems we just need to have a body that grows large as it [tacks inward](https://en.wikipedia.org/wiki/Grand_tack_hypothesis) and eventually crosses the frost line. Planets do in fact move around as they influence each other and interact with the surrounding media.
The main issue is that accumulating material causes the body to heat up, both from the energy gained by consolidating the particles and from radioactive materials incorporated. Many asteroids show signs of separating out denser material, and Ceres and Vesta were warm enough to relax into spheres. This is exactly what we don't want to happen.
But... [giant supernucules comets](https://en.wikipedia.org/wiki/Comet_nucleus#Size) do exist; they grew to large size without boiling themselves off. So take that as a given.
So how about this: A "rubble pile" recently got blown apart from an impact, forming a cloud of debris that will mostly pull itself back together again. It formed well inside the frost line but was pushed outward. Meanwhile, out frozen chewy center is moving inward and they happen to cross orbits right when the rubble pile was existing as an extended cloud spread out around an arc of its orbit. The large mass of the center easily pulls it back together again, but the debris gathers around the solid frozen center.
Now these rubble piles normally get blown apart and re-aggregate and indeed stay as loose rubble, *not* melting from the heat of formation. Again, they exist, it happens. The pieces are mostly in the same orbit already and come back together reasonably gently, compared to random collisions of protoplanets.
Meanwhile, the ice serves as a heat sink: a crashing mountain will blow off a small part of the ice, rather than heating up the whole globe. It *stays cold*, though loses some mass.
Once it is covered in a protective shell of rock, it can continue migrating inward and collect additional material. The now thicker crust *does* melt were it is impacted by random arrivals (not part of the same co-moving debris), and starts to form a solid shell. We just have to add to it gradually enough that it doesn't melt through, and cools between collisions.
So, we can **quite plausibly** get our cosmic M&M!
# baking
Now, how do we get it to heat up?
Move it to the oven! It's tacking inward... towards the forming star. It seems most convenient to continue on this tack rather than introduce more bodies.
This region will naturally make rocky bodies, as ice melts and vaporizes, but rock does not. So, the crust will not melt into magma but the ices will melt and boil off.
Now we need to get the temperature *just right* so the shell becomes soft and plastic, but doesn't melt into magma and sink into the ice. Layering helps: the outer layers exposed to the sunlight will melt but under that is still solid and the solid part cracks and shifts but the melted surface plasters over any gaps that open up as it expands.
Eventually, the initial high-UV phase of the star settles down into normal main sequence, and the oven goes from broil to keep-warm.
You are left with a hollow shell filled with an ocean and a thick atmosphere. Magma from the shell *dripped* down in places, forming long spires that criss-cross through the interior. The ocean might touch once side of the shell due to density differences, but keeps clearance on the opposite side at the very least.
] |
[Question]
[
i mean, our firearms, in many ways, are depend on this fact - that we only have 2 hands. What would the weapon look like, its ergonomics and its qualities and properties and usage - if the use of 4 hands were envisaged? I'm more interested in firearms, not a melee weapon ...
1.How might look and be used the firearm hand weapon for four-handed humanoids ?
2. For these mentioned humanoids (4 arms).
3. No special criteria for weapons other than those generally known for these types of weapon - hand fire weapons with full ergonomic capability of current type of hands. .
The question may sound like this too: what are the unexplored possibilities of designing and using arm weapon (or expanding its capabilities) - if we had 4 arms?
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the image of the race : <https://gamedev.ru/files/images/peleng_wip_18x.jpg>
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only and exceptionally for example only(!)- for any such 4-handed weapon: I can imagine firearms in which, for example, the muzzle rotates to 180 degrees for aiming without turning the body :
[](https://i.stack.imgur.com/S9PBg.jpg)
[](https://i.stack.imgur.com/bGXIF.jpg) Additional
[](https://i.stack.imgur.com/mQMu4.jpg)
Also <https://i.ibb.co/DMZW84y/A2.jpg>
[Answer]
I’d imagine a lot of firearms wouldn’t change much. There’s no need to make a gun more complicated just because you have more arms. For example, a pump shotgun would probably work the same way, as the process of loading the shells and pumping the shotgun (as well as pulling the trigger) can be done easily with two hands. I would honestly think if I was going to war with four hands, I’d still carry a rifle I could fire with two. Maybe I could carry two of those rifles with double the hands, or use my extra hands to carry some sort of shield or grenade launcher or something. One modification I could think of for high-powered firearms (sniper rifles for example) is extra handles or grips so I could use my extra arms to keep the weapon steady as I fire it. In fact, maybe four-armed weapons could include much more powerful rifles, as you have extra arms to control the recoil (assuming each arm is similar strength to an arm on a normal human).
At the end of the day, you could just carry four pistols.
[Answer]
The main difference that I envision when it comes to firearms built for four hands instead of two is nothing to do with modern firearms. Four arms may or may not be able to greater recoil, four hands might speed up clip exchanges slightly, and four arms may or may not give greater stability for aiming etc... but while modern semi and fully automatic weapons for a four armed creature may change in layout, mainly to include more handgrips etc... they will change very little in mechanical operation. So any modern firearm, designed to be operated with two hands, is going to be substantially similar to it's "four hands" equivalent.
What would have changed drastically was the efficiency and rate of fire of earlier firearms, most particularly early breech-loading firearms had a far higher rate of fire with four, or more, hands to run through the loading process. In the time of flint- and match-lock firearms it was common to have two, or even three, dedicated loaders rotating three, or four, rifles for a single sharpshooter. Multiple people formed crews to handled cannons, [carronades](https://en.wikipedia.org/wiki/Carronade), and large [blunderbusses](https://en.wikipedia.org/wiki/Blunderbuss#:%7E:text=The%20blunderbuss%20is%20a%20firearm,of%20relevant%20quantity%20or%20caliber.) to accelerate loading and firing. With four arms, assuming a human level of co-ordination between them, you could halve the number of loaders and get the same effect on rate of fire, to a point. This effect becomes more marked the smaller the weapon in question, cannons require a set of sequential steps that cannot be reordered and each step requires quite a lot of movement around the cannon so has to be handled separately. When loading a rifle or pistol on the other hand one pair of hands can attend to the pan and flint while the other rams home the powder and shot halving loading time. The larger guns and smaller cannons are somewhere in between.
[Answer]
## Here is the full range of weapons that your 4 armed friends would reasonably have:
1. **Knifes**
[](https://i.stack.imgur.com/kxdkAm.jpg)
Better than your hands, but not by much. Easy to make, use and conceal. If each arm is less strong then lighter weapons for each hand might be better.
2. **Swords**
You will be able to have one handed, two handed, three handed, and four handed swords. Since each individual hand is less powerful, you are likely to not have swords much bigger than our swords. However, the hilts will be larger.
[](https://i.stack.imgur.com/An2yum.jpg)
3. **Shields**
Shields again will be used like normal in most cases. As I will show later, the shield might be modified to also handle simultaneous use of long arms in addition to pistols. However, pre guns shields will be bigger since the two handed sword can get around the shield better.
[](https://i.stack.imgur.com/IGHQ0m.jpg)
SWAT members might also use the load out below to get the most "tactical" load out. Shield, long arm and pistol. Shield for defense, long arm for long range attacks, pistol for reloading and close up attacks.
[](https://i.stack.imgur.com/j09kHm.jpg)
4. **Pistol**
If your creatures are less strong in each individual arm, their pistols will be weaker. While crazy things like Dessert Eagles might not be possible, nearly any other small arm would be reasonable. Revolvers and other weapons would also make sense. These weapons exist because they are easy to make, easy to smuggle, concealable, and good for hunting or self defense.
[](https://i.stack.imgur.com/ggljpm.jpg)
5. **One sided long arms**
Since two handed weapons don't have to be fired with a left and a right hand, there will be an opportunity to fire weapons with only one side of the body. This will let the user either carry a shield on one side or expose even less of their body when going around a corner. In the case of shield this means that your gun grip will have either a normal grip or a fixed canted grip to the user's dominant side, as seen below. In the case of the less exposure on corners, your grip will have a lock that can be adjusted on the fly to let the user go either left or right around a corner. These grips already exist in real life, but are uncommon, in your universe they will be very common.
Each of the examples below has a straight grip, and then the canted grip.
*Shotguns*
[](https://i.stack.imgur.com/Mwgeym.jpg)
[](https://i.stack.imgur.com/dUtMFm.jpg)
*rifles*
[](https://i.stack.imgur.com/6ULArm.jpg)
[](https://i.stack.imgur.com/ncDIWm.jpg)
6. **Long Range Rifles**
For long range rifles, bipods will be more stable than hands, so there will be no change. For bolt action rifles meant to be used in a standing position either extra grips or people will just grip in the appropriate positions. because Rifles are longer on average there will be plenty of space to grab the weapon. Bolt action rifles will be very common and well used by these aliens since they can keep one hand on the bolt while aiming and work it with out taking their hands off their gun.
[](https://i.stack.imgur.com/vf3dNm.jpg)
[](https://i.stack.imgur.com/CtaYxm.jpg)
7. **Shotguns**
Since shotguns are not accurate and rely on the shoulder to absorb recoil, shot guns will remain mostly unchanged if they are meant for all four hands.
[](https://i.stack.imgur.com/zavhUm.jpg)
8. **Various Heavy Weapons**
Anti tank weapons, large machine guns, grenade launchers, and mines will remain unchanged. These don't depend on the number of arms, but more arms can stabilize the weapon, or can brace themselves with two hands while firing.
[](https://i.stack.imgur.com/uMdDfm.jpg)
[](https://i.stack.imgur.com/7fu4Im.jpg)
[](https://i.stack.imgur.com/PnyGzm.jpg)
9. **Under Barrel Weapons**
The one really cool weapon that could be done is under barrel weapons, or other combination weapons. These are smaller weapons attached to larger weapons, these would be under barrel shotguns, or grenade launchers. Normally these are sub par because you can't reload your second weapon while you have two hands on your weapon, meaning you might as well put down your first weapon while reloading. but since you have four hands you can afford to use two hands to reload your second weapon, as you hold your first weapon.
[](https://i.stack.imgur.com/ogyW0.jpg)
10. **Two Weapons**
Since you can reload a weapon with two hands while you hold another with two hands this means you can shoot two guns. Not at the same time, but as you get close to running out of one gun you pick up another and aim that while reloading the first gun.
[](https://i.stack.imgur.com/6Mysz.jpg)
11. **Corner Shot**
The weapon you have described bears resemblance to a [corner shot](https://en.wikipedia.org/wiki/CornerShot) weapon. This isn't necessarily a two handed weapon, or a more than two handed weapon, but having two hands to steady, one to pull the trigger, and one to aim would help. This takes your ability to turn corners better than other species to a whole new level since you now don't even need to be around a corner to shoot them.
[](https://i.stack.imgur.com/DjWEa.jpg)
[Answer]
Probably the biggest change would be the reloading mechanisms. They'd still aim & fire the gun identically to how we aim & fire ours, but with adjusted ergonomics so that one could reload with their free hands. That way they can easily keep aim on their target.
[Answer]
The characteristics of your species' firearms will be, indeed, a consequence of the 4 arms.
Please note for the answer the following hypothesis:
* Each hand is as powerful as our hand
* The 4 hands could be used with similar coordination possibilites and limits: this means that only trained people could desynchronize their hands (such as drummers in our world)
First question is: what are the possibilities with 4 weapons compared to 2 weapons existing firearms?
* Stability of the weapon: this is the most important thing: our weapons are made of one stabilizing hand (usually forward) and one operating hand. With 4 arms, you could add an orthogonal handle that would allow to stabilize more and direct faster the aiming point of the weapon. Drawback comes with a larger weapon, which can be inconvenient in urban fight for example
* Aiming the weapon: If we consider a modern world, we can imagine that the last hand of the species is used to manipulate an aiming device, for example with laser, that triggers a mechanisme to turn the weapon exactly in the direction aimed. This is let to your creativity :)
* Double ammunition loader: Currently, in our weapon, you fire until the end of the loader and you have to stop for reloading. With your species however, two or three hands could handle the firing weapon, and one or two prepare a second loader while the first one is already in place. Thus, at the end of the first loader, only a small move on a mechanism could switch loaders and allow to fire again faster than our weapons. **This point could really change infantry tactics.**
* Heavy caliber: the species as 4 hands similar to ours, so they are twice as powerful as us with forelimbs. Thus, they can have heavier weapons and use two hands instead of one on the forward position, where the leverage effect makes carrying the weapon more difficult
So how would the weapon look like? Given those usecases, I think that compared to our current weapon, such a weapon would have at least:
* One more handle
* A more complex aiming device
* A longer weapon to allow to loaders to be placed
* Heavier caliber
[Answer]
# Mount a gun on your gun!
There are under-barrel weapons there are weapons that can bend around corners the only thing preventing us from combining the two is an insufficient number of arms to aim both barrels independently. This arrangement is more than the sum of its parts because you can aim at two different targets at the same time (which you can't do with a normal under-barrel or corner shot) on top of a potential combination gun (one barrel is rifled the other is smoothbore) and shooting around corners (which is something you can't do with dual-wielding). Another benefit over going guns akimbo is the whole set can be held in one hand allowing the other arms to be used for other tasks like reloading both cartridges at the same time, throwing a grenade, or grabbing on onto something. Even with a second set of hands, accurately aiming is an issue so the focus would be on properly aiming the primary gun and using the secondary gun for closer targets (this one will likely be smoothbore). Depending on practicality the secondary gun can be on a gimbal for more freedom of movement while mounted or even on some kind of telescoping mount like the periscope rifles of World War One. Overall, a swiveling mounted gun provides unique opportunities to a species with four arms that aren't provided by existing weapons.
[Answer]
An all-in-one, Swiss knife like, weapon. Extra lever to expel jammed cartridges. Extra magazine. Grenade launcher. Laser that can be tuned to be used as a gun sight or to blind the enemies. Quickly pluggable silencer to use when the fighter can manage the extra recoil. Plus any thing that could come from future technologies.
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[Question]
[
Would transport between settlements on Mars be similar to Transport between Cities on Earth?, well except no boats because no oceans.
so what would be the most practical mode of transport between these settlements, Railways?, Roads?, Overland Rovers?, Aircraft?, or Suborbital Spacecraft? What mode of transport would be most effective or efficient assuming resources to construct transport infrastructure.
**Assumptions**
Mars has not yet been terraformed so the surface conditions are the same as present day.
The settlements in question are mostly underground to protect from radiation, and most have been established for roughly 100 years. The average distance between settlements is about 2000 km,
we can also assume widespread ISRU,(In-Situ-Resource Use), for building materials and other resources. so there is enough resources for construction of transportation infrastructure. for interplanetary travel, Nuclear Thermal Rockets are the most commonly used form of propulsion, so travel times between earth and mars are roughly the same as with current technology albeit with greater fuel efficiency.
[Answer]
Railways are the ships of the land. They are the most efficient form of land transport over long distances, and the only form of transport for heavy cargo. You can't efficiently transport heavy cargo by truck 500km, let alone 2000km. It's still pretty much the only solution to haul heavy cargo like building materials and resources by land.
Roads and overland rovers can't haul that kind of cargo. They are more for casual transportation which isn't going to be happening if the average distance between colonies is 2000km, even if things were already terraformed, let alone not being terraformed. You also need to haul enough fuel and oxygen to keep both your vehicle and body alive all that time. A train can do that.
Transportation of actual people between colonies, being non-casual, resource intensive, and perilous, would have to be in the form of public transport which would probably occur on trains. Aircraft and suborbital spacecraft are kind of luxuries to be honest, and might be used for public transport between colonies later on just due to speed, but trains would still be the mainstay since trains can transport both people and heavy cargo.
In short: trains, for many of the reasons they were the first form powered of long-distance transport on Earth, even when we wouldn't suffocate.
[Answer]
# Frame challenge - Distances Unrealistic
Barring political conflict that would make trade unlikely, even on Earth, colonies tended to be clustered for mutual support. If you need space, a hundred km is more than enough. Two thousand km (on average! For a century!) is totally unreasonable.
# Short-Haul Trucking
If we reduce the distance between the colonies, basically "all of the above" becomes more reasonable. First, colonists would use overland rovers that came with the colonizing gear. Roads would come next (being cheaper to make and maintain), then railroads. If general terraforming isn't going on, cargo aircraft are going to be a non-starter, as your power-to-weight ratio will need to be much higher.
[Answer]
# Point-to-Point Rockets
If Mars is colonized to the point where there are many settlements, we will have very inexpensive reusable rockets, and we will have fuel production for them on Mars.
The challenges of building any sort of planet-spanning road or rail infrastructure on Mars are daunting. We would need smelters for steel, mining for raw materials, etc. Any work would be carried out in spacesuits, and unless you already had another transportation system, the workers would have to bring their own habs and live on the road. That's something we won't be doing on Mars for a very long time.
On the other hand, let's say Starship eventually flies to Mars. There is no reason at all why a Starship couldn't be loaded with 100 tons of cargo and people and flown to another point on the planet. With an ISRU (In-Situ Resource Utilization) facility at each base making rocket fuel, Rockets could travel back and forth. In Mars' thin atmosphere and low gravity, rockets would be much more efficient than they are on Earth.
The key is that they would leverage the same infrastructure used to fly people and goods to and from Earth. Worst case they might have to build additional ISRU capacity to handle local flying, but that's a lot cheaper than building a road or rail system across another planet.
[Answer]
## Hyperloop
Take advantage of the already low pressure of the atmosphere on Mars, as well as the lower gravity, and get high-velocity transportation mode.
A lower-tech alternative may be the railroads, but changes of temperature on Mars can be quite extreme with a day/night cycle ranging from -73C to +20C, so that's far from your typical earth railroad conditions.
With a cover or a tube, you may somewhat keep things more under constant conditions, without such swings. And if there are reasons to have such cover then why not.
It can be a combined solution, meaning it may have a railroad inside as an alternative, or some maintenance needs or inheritance of building process or backup.
For roads there are not that many materials available on Mars, meaning it not your typical tarmac, and to build them expenses aren't lower - so it then some stone road, or not cool ground road - the absence of water helps there, but. It may be reasonable to have them as a backup.
You need a backup of backups mentality on mars, because if something fails for too long, an asteroid hit, meteorite - things may get tense quite fast.
## Challenges
Any ground transportation system will require a lot of work to make it.
* and I mean it, a lot, even if it imagined just like ground road it will require tremendous efforts to fill all the potholes and get all the materials energy for moving all the ground around.
yes, there are factors that help, mostly mean water/rain absence, but instead of it, there is another factor dust storms and dust movement.
if one has an open, not covered track - be it railroad or just road with hard layer (be it stone, martial cement, sintered ground, etc) one needs some protection to prevent dust settling or maintain it regularly - so no solution is maintenance-free in mars conditions.
And lower gravity and fine dust work against good traction, it was a problem on the moon so it will be on the mars as well. And that means no high-speed highways.
* no matter the problems, you need to have usual roads as well, as they have certain advantages such as easy to make branches, side roads, to reach multiple destinations in some area. That is the case we have on earth, but as for the long haul, not so great.
Big cities or small ones - it needs a fast and reliable transportation network. with hyperloop - the pressure is about right, so lower gravity plays as an advantage factor.
* with small cities, they have to share some resources like medical centers for complex cases.
* you need water, recycling or not, and there aren't that many places where it can be found(?) - they have to deliver it
* resources aka minerals etc
So overall you build a road first and then build a city - transporting many many materials and equipment for it, home appliances, pipes, wires, chemicals, machines, replacement parts, food, water, oxygen, energy sources(or energy line with the road of any kind), people if they need to be present at the site, emergency evacuations(individuals or all the workers), there is no end of the list even long before you build that city.
And when a city gets big, there also a need for high throughput of the system.
Hyperloop kind of thing may be a good solution for a long time from a start, up until a moderate size city.
And it has the convenience of connecting cities in one big megapolis. one spends so much technological efforts to get there and to start the first city - so hold the bar high, get the most out of it. Have luxury to visit city garden - because it is looong looong way to home and before your city will have one.
## results
it is clear that all the results and options will depend on capacities and what one has for the job, technology-wise, so as tool-wise, so as energy-wise.
So as it will depend on Mars - what it actually means and feels to build something there.
we may dismiss that type of construction, but after it goes through evaluation in specific conditions and means available, as any other potential solution.
if we talk about the first city and the necessity to prospect and reach some ore/minerals/whatever deposits - then good old railroad is probably a good choice, so as low long-range rover laboratory.
But when that stage is passed, and we need to connect to a second city, then it has to be something fast and convenient.
overall you can't avoid having different kinds of roads, but if we talk in between cities connection - pick fast one, it will help to have a healthier psychological climate in all cities, besides everything else.
[Answer]
## Airships
Your colonists should use lighter-than-air travel because the surface of Mars is awful and you want to avoid it as much as possible. In particular, there are massive stretches of jagged terrain you want to avoid at all costs, and the omnipresent dust that will cause maintenance headaches for ground-based transportation. Why put up with all those hazards when you can sail serenely *over* them instead?
You want lighter-than-air flight because heavier-than-air flight is [a genuine pain the rear](https://www.x-plane.com/adventures/mars.html). Because of the lighter atmosphere, you need to go absurdly fast, which (in addition to not being very efficient) makes it very difficult to maneuver or land. Rotorcraft are less affected, because while you do need to spin the rotor faster, that's only an engineering challenge, not a problem when you're actually flying. A Mars-based helicopter drone is being tested [literally as we speak](https://www.nasa.gov/press-release/nasa-ingenuity-mars-helicopter-prepares-for-first-flight) and aerodynamically at least, it appears sound. However, helicopters are not generally known as long-distance haulers when there's an alternative.
Enter the alternative: [heavy-lift hybrid airships](https://en.wikipedia.org/wiki/Airship#Heavy_lifting), an emerging technology that aims to pair the long-distance, high-efficiency (albeit slow) flight of airships with heavy payloads for efficient shipping. On Earth, this technology works perfectly fine, but it has difficulties finding a niche in between ocean shipping and conventional airliners. On Mars, neither of those alternatives is workable, leaving the space wide open for heavy-duty lighter-than-air craft.
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[Question]
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I want to create a planet that has:
* Low gravity.
* Giant creatures (not quite Godzilla sized, but bigger than Dinosaurs).
* Human explorers should be able to jump incredibly high there, maybe even fly/float (with the aid of some sort of device?)
* Humans don’t have to be able to breathe there (I’ll give them air tanks), but the creatures do.
* The atmosphere can be made of anything that will make this more possible.
* (Optionally) the planet should be jungle like, or ocean like, if either of those allow for it to be more possible.
I'd like to minimize handwavium here, but I'm flexible.
Is this possible?
[Answer]
Well, Draft85 predicted the inevitable appearance of the atmospheric escape diagram, and as no-one else has been forthcoming I guess it falls to me.
[](https://i.stack.imgur.com/EeUXl.png)
The missing scale on the right for the gas lines should be "ten times [RMS thermal velocity](https://en.wikipedia.org/wiki/Thermal_velocity) at surface temperature". This isn't quite the right model of [atmospheric escape](https://en.wikipedia.org/wiki/Atmospheric_escape) but it'll do as a starting point.
You can see that the lower limit of water vapour retention in the atmosphere at Earthlike temperatures coincides with a surface escape velocity of ~7kms. If you actually work out what ten times the RMS thermal velocity of water is at 273K, you'll find that it is more like 6.15km/s, but a) I'll follow the rules of the chart because it looks pretty and b) you don't wanna be right on the edge because then climate fluctuations can cause your atmosphere to fall off. If you do choose this limit, you can knock about 10% of the surface gravity figures below, but I'll stick with 7km/s for now.
[Escape velocity](https://en.wikipedia.org/wiki/Escape_velocity) is $v\_e = \sqrt{\frac{2GM}{r}}$ where $G$ is the gravitational constant, $M$ is the planet's mass and $r$ is its radius. That's slightly too many unknowns, so lets narrow it down a little.
The mass of a planet is proportional to its volume and density, and so for a spherical world $M = \frac{4\pi\rho\_pr^3}{3}$ where $\rho\_p$ is the density of the planet. Rearranging the escape velocity formula from the wikipedia link above and substituting the equation for mass given density, we get $\sqrt{\frac{3v\_e^2}{8\pi G\rho\_p}} = r$.
The density of Earth is ~5500km/m3, and lets use that for your world, too. This means that the smallest world with Earthlike density that might hang on to an Earthlike atmosphere has a radius of ~4000km, a mass of ~1.5x1024kg. This is smaller than Earth and Venus, but bigger than Mars. Surface gravity is ~.63 of Earth.
If you used the density of a much less metallic world, like Titan (~1900 kg/m3, mostly rock and ice with little iron) you end up with a *larger* world... a radius of ~6800 km makes it bigger than Earth! The low density means that surface gravity is lower... a Mars-like .37 gravities. That helps make your people fly more easily and your animals grow much larger, but conversely the absense of a heavy metallic core means that your world will have no magnetosphere and so the atmosphere will probably be blown away by the solar wind (as happened to Mars) or would need to be so dense and thick that the surface would be uninhabitable (as happened to Venus). That's not to say that it is impossible, but it will be hard. You'll also have to deal with your planet being a water world, not at all jungle like!
A compromise Mars-like density of ~4000 kg/m3 gives you a radius of ~4700 km and a surface gravity of ~.52 gees. The surface would definitely be solid, but the lack of a strong magnetosphere may limit the longevity of the atmosphere.
So:
>
> * Low gravity.
>
>
>
Ish. I'll assume the conservative .63 gravities from here on.
>
> * Giant creatures (not quite Godzilla sized, but bigger than Dinosaurs).
>
>
>
I don't see why not... with two thirds of the gravity of Earth, structural engineering has become more forgiving. You still probably won't get anything Godzilla sized without magic, but you could certainly have things that would tower over the tallest sauropods.
Remember though that the lower gravity means that bones can be thinner and lighter and less muscle mass is needed to hold up bodyweight, so you will find that many of the animals here may seem quite spindly compared to those on Earth... tall, but thin.
>
> * Human explorers should be able to jump incredibly high there, maybe even fly/float (with the aid of some sort of device?)
>
>
>
Maybe. Humans will certainly be able to jump higher, but they'll have to work to keep their muscle mass in low G.
Humans can fly under their own muscle power on Earth with the aid of suitable mechanisms... under a two-thirds gravity that would become something that merely very fit people would be able to do instead of the worlds most elite endurance athletes.
A very dense atmosphere will help here, but having a dense atmosphere without risking runaway greenhouse effects is hard. *Keeping* a dense atmosphere on a small, warm world is unlikely. Titan's atmosphere is very thick, and it has quite low gravity, but the surface temperature is so low there's little risk of everything boiling away into space. You could probably handwave higher surface pressure if you wanted, and tweaked the atmospheric composition appropriately.
>
> * Humans don’t have to be able to breathe there (I’ll give them air tanks), but the creatures do.
> * The atmosphere can be made of anything that will make this more possible.
>
>
>
You could have an Earthlike oxygen-nitrogen mix, and then sprinkle in whatever you like for flavour. You could have 10% CO2, for example, which the local wildlife coudld have adapted to but would be unpleasant and swiftly fatal for unprotected animals from Earth, including humans. A fairly simple respirator with a CO2 scrubber would allow the native atmosphere to be breathed just fine without the need for gas bottle, but the scrubber material will need to be replaced after a few hours of use.
High CO2 implies additional greenhouse warming, which would require your world to be a little further away from its Sun than Earth is.
>
> * (Optionally) the planet should be jungle like, or ocean like, if either of those allow for it to be more possible.
>
>
>
Whole planets don't get to be just one biome. There will be hot bits, dry bits, cold bits, wet bits. Seas and mountains. There can be enough jungle for your needs, it just won't cover the whole planet.
[Answer]
*(Optionally) the planet should be jungle like, or ocean like, if either of those allow for it to be more possible.*
The whole planet having a single biome is pretty unlikely, so you could combine these- Earth certainly has plenty of both jungle and ocean biomes.
If you wanted to maximise the area of forests and oceans, a climate similar to Earth during the Cretaceous could work well- no ice caps, large areas of shallow seas, rainforests at the poles. (Said rainforests were more like the Pacific Northwest than the Amazon.) Hotter than the present day, but many regions would be comfortable for humans.
With lower gravity, taller trees would be viable- you could get plants bigger than redwoods without the correspondingly massive trunks. And with these incredibly tall trees, you'd most likely evolve some kind of terrestrial herbivore analogous to giraffes and sauropod dinosaurs- long necks and long legs to feed on leaves and fruit from the treetops.
[Answer]
Possibly you might want to turn your planet inside out and make it in a artificial space habitat, a hollow cylinder that spins to produced simulated gravity on the inner surface.
Since such a cylinder is sealed and airtight, atmosphere shoudl escape from it much slower than from a planet, even one with a higher escape velocity than Earth. Thus there is no need to worry about giving the habitat a fast enough spin to match Earth surface gravity to keep the atmosphere from escaping into space.
Thus the surface gravity on the inner surface of the cylinder could be 0.5 g, or 0.1 g, ir 0.01 g, or .001 g, or some other very low value, and the habitate could still keep it s breathable atmosphere.
In the low gravity enviroment one of the main factors restricting the sizes of the largest animals would be removed.
A natural planet with a very low surface gravity and escape velocity could be terraformed to have an Earthlike environment. The atmosphere would thin out very gradually with height, and if it was a least as dense at Earth's atmosphere is at the surface, the great depth of the atmosphere might protect the surface from cosmic radiation. The atmosphere would have to have a roof of some sort to hold it in and prevent it from escaping into space.
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[Question]
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Could a creature which lays amniote-like eggs evolve into a creature similar to modern amphibians? The creature would be amphibious, spending most of their time in freshwater, and coming onto land to lay eggs, which would hatch into terrestrial larvae, which, rather than eating a unique diet like real modern amphibians, would be mostly lecithotrophic, with their diet supplemented by their adult diet. The adults would have simpler organs, and moist skin to extract oxygen from water, like modern amphibians. However, they would have flippers instead of legs, as these creatures would be more aquatic
[Answer]
There are much easier ways to go about doing what you want. For one, moist skin allowing oxygen to be extracted from the water is a synapomorphy of Lissamphibia, not amphibians as a whole. Most extinct "amphibians" (temnospondyls, anthracosaurs, semouriamorphs, lepospondyls, stem stegocephalians, colosteids) had either keratinous scales or some form of warty or thickened skin that allowed them to spend a considerable amount of time out of the water (groups like colosteids and stegocephalians didn't, but that's more because they didn't have legs that worked on land). However, all of these species that could breathe water had either external gills like a mudpuppy, or internal gill arches inherited from a fish-like ancestor (e.g., stegocephalians like *Acanthostega*, colosteids like *Greerepeton*).
Perhaps most notable for your purposes are the semouriamorphs, which are known to have a terrestrial adult phase that appeared to have had some form of thickened skin but have aquatic forms with external gills (e.g., *Discosauriscus*). This is still "aquatic larva, terrestrial adult", but at least it's possible to have reptile-like and amphibian-like stages of one's lifecycle.
Notably, true gills have never been re-evolved in Amniota after being lost. No clue if that's because they can't be, because the gill arches are still present embryonically, or if they can't because they run into competition with lissamphibians. However, several species of reptiles have the ability to absorb oxygen from the surrounding water. Sea snakes can absorb oxygen directly through their skin that accounts for 25% of all their oxygen needs, and many turtles are able to respire through their cloaca when underwater hibernating in soil. These reptiles notably do this without losing their scaly skin, and in ways that make them less vulnerable to the downsides of having a cutaneous, mucous-coated skin (e.g., susceptibility to toxins).
More broadly, **there are severe ecological consequences to having a terrestrial offspring but aquatic adults**.
* Having near-obligately aquatic adults means that your adults cannot easily leave the bodies of water they live in if there is a drought, a red tide/eutrophication, or other disasters that make the body of water uninhabitable.
* Additionally, your reproductive-age adults cannot easily disperse to new populations, making them very vulnerable to reproductive isolation and inbreeding. A good example of this is how global lissamphibian diversity has been gradually shaved away over time (e.g., there used to be salamanders on every continental landmass (based on fossils), but today salamanders are absent from Africa, western Asia, most of South America, and all of Oceania), and most of *those* belong to a single family (Salamandridae, coincidentally the least water-dependent) due to being very environmentally isolated.
* The juveniles are able to disperse, but smaller organisms have a harder time dispersing to new environments because they have less fat reserves and the distance between habitats represents a longer distance relative to body length (big animals migrate easier).
* Having cutaneous skin comes with some big side effects. Notably an increased vulnerability to environmental toxins (there's a reason chytrid fungus kills frogs and not lizards), and the fact that at larger sizes your species would struggle to obtain enough oxygen due to the square-cubed law. This is why the giant salamanders *Andrias* and *Cryptobranchus* are so wrinkly looking and live such low-activity lifestyles. Having complex, highly-enfolded organs like gills or a complex rectum would work better.
* A better idea would be to have the adults retain the ability to stay on land for prolonged periods anyway. There's generally a reason why many littoral niches throughout history have been increasingly occupied by amniotes (e.g., crocodiles, aquatic lizards, turtles, aquatic snakes) instead of amphibians. A broader question would be this: what can your species do that an appropriately-sized crocodilian cannot accomplish already?
[Answer]
## It's turtles all the way down the list.
* Most of the time in freshwater: check. Bog turtle, say.
* Brief period on land for larvae that return to the water to feed: check.
* Flattened limbs: check.
* Moist skin to absorb oxygen: [check!](https://www.cuteness.com/article/do-turtles-breathe-under-water) [seriously!](https://nature-discovery.com/can-turtles-breathe-through-their-butts/) The caveat is that it's only during hibernation - their needs are too much when they're active. *For now*. Evolution hasn't stopped doing its thing!
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[Question]
[
My idea is to have organisms that use [molten salt](https://en.wikipedia.org/wiki/Sodium_chloride) as their solvent in the chemistry of the creature. So what I was thinking to have the cells consist of [tungsten](https://en.wikipedia.org/wiki/Tungsten#:%7E:text=Tungsten%2C%20or%20wolfram%2C%20is%20a,as%20a%20metal%20in%201783.) [polyoxometalates](https://en.wikipedia.org/wiki/Polyoxometalate) but my issue is the fact that I cannot find any information on analogous structures to cell membranes and DNA from tungsten polyoxometalates and how they can have a controlled energy source analogous to ATP while using a solvent that is made of ions as that stops the ion gradient.
So my question is what analogous structures can be formed from tungsten polyoxometalates(and/or what ever else will function in the 1,470 °F) that can form cell membranes, DNA, and ATP with a system of energy transfer and storage system that works with a creature using liquid sodium chloride as a solvent?
[Answer]
You might have some issues to make a properly functioning biological system based on polyoxometalates and sodium chloride as a solvent, for the [following reasons](https://en.wikipedia.org/wiki/Water#Effects_on_life):
>
> From a biological standpoint, water has many distinct properties that are critical for the proliferation of life. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g., starches, triglycerides, and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g., glucose, fatty acids, and amino acids to be used for fuels for energy use or other purposes). Without water, these particular metabolic processes could not exist.
>
>
> Water is fundamental to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO2 (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO2 in the process (cellular respiration).
>
>
> Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H+, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as a hydroxide ion (OH−) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acids have pH values less than 7 while bases have values greater than 7.
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While the above can be criticized with the argument that obviously life developed around water would rely on water properties, still lets you get an idea that any other solvent should have similar chemical flexibility.
On the other hand for a story or a world where you want to have polyoxometalates based life, I don't think you need to go into the details of the functioning of the genetic mechanism or biochemical functioning of the cells to use it. Just a superficial statement like "their biochemistry seems to be based on polyoxometalates and they use molten salt as solvent, thus cannot live at temperatures where the salt is solid" should be enough for a good majority of the readers.
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If analogous to our biology, your cell walls are a non-polar lipid layer (in this case could be a tungsten polyoxometalate, $WO\_3$) that doesn’t mix with salt which is surrounded on the inside and outside by your polar solvent (NaCl) and held together by a web of surfactants (not sure what you’d use) that has a sodium-phobic end and a sodium-loving opposite end that gives the cell membrane a distinct inside and outside.
For the sake of being able to produce “lipids” with biological processes, I might suggest changing the tungsten polyoxometalate $WO\_3$ to a tungsten chloride $WCl\_6$, so that you can pull the chlorine in from your salt. The different oxidation states of tungsten allow for some interesting shapes (look at tungsten iii chloride W6Cl18 or tungsten I chloride W6Cl12)
For DNA then, if it’s similar to our microbiology build-up, you are looking at tungsten chloride and sodium foundations for your bases, decorated with some other chemical with the same oxidation state as nitrogen (-3). These would fit on a “sugar” backbone of tungsten, sodium, and chlorine; and be held together with phosphate analogues that are your sodium-tungsten-chloride “sugar” and another new element, probably with the same oxidation state as phosphorus (-3).
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This question relates the same world discussed in this post: [Horseback Travel in an Unpopulated Pacific Northwest](https://worldbuilding.stackexchange.com/questions/194912/horseback-travel-in-an-unpopulated-pacific-northwest)
Two mounted patrolmen are tasked with navigating and policing a reimagined Coastal PNW, the geography of this area is incredibly vertical and heavily forested. I understand this would naturally be unforgiving to signal transmission. That said, one of the patrolmen is a Field Radio Operator, he wears a pack much like the US Army had in the 80s and is able to send and receive transmissions from their support Airship, his partner, however, only has a *very* short-range communicator, (1-2 miles) only able to basically "walkie talkie" with his partner.
This short range communicator is written to where it cannot reach the airship due to its power, but the serviceman with the full pack is able to pass on the transmissions from the airship through the walkie talkie to his partner, is this realistic? Would this make sense given the physical setting and technological limitations of the universe? (No satellites, no well established supertall radio masts in the region, no smart tech) I understand that the Airship would act as an excellent semi-permanent radio transmitter/ signal repeater, but I am having trouble figuring out how to limit one of the servicemen's radio capability realistically.
As they move through the region, North from Vancouver Island towards Sitka, AK, they have semi-mobile radio towers airdropped to them, these cement a radio footprint and set up an emergency frequency for the denizens of the region to call for help. Please someone with radio transmitting knowledge help me out here.
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I believe communications range is a function of antenna size and power. (And that's without taking the geography into account). More of both means you can emit a stronger signal, which means people further away can receive it. That's because a radio signal is just an electromagnetic emission.
Think about the radio in your car or bedside alarm. It can pick up local radio stations just fine, but it can't transmit back to them. That's because receiving and transmitting are different.
So, the reason your two patrolmen have different communications abilities is because that backpack has a big antenna and a big signal amplifier. The reason both patrolmen can receive from the airship is because the airship has a huge antenna and amplifier. The reason one patrolman can only transmit to the other is because s/he has a smaller antenna and amplifier.
The particulars of the terrain then work as additional constraints on top of the basic facts about differing transmission power.
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I have worked in the region (PNW) with hand held radios in small teams. Some places had repeaters set up. Some places we worked with helicopters. So a range of scenarios.
For radios it really depends on topography. Do you have line of sight? If you have line of sight, most other factors like transmit power, antenna placement don't really matter. The other factors matter when you don't have line of sight. But not completely blocked by hills/mountains etc.
Scenarios that are similar to what you seem to be asking about that I have personally encountered. All using the same radio equipment unless noted.
Person A needs to talk to B and C. Both B, C are 1Km away from A. But B is separated from C by 200m. Due to topography(C has dropped elevation faster then B). A can talk to B. B can talk to C. But C and A can't hear each other. B relayed messages from A to C.
Person A, B are on a 60% slope. B is higher then A by 5m vertical. B can talk to C via radio. A and C can't talk to each other via radio. Once B walked up the slope they can communicate to C as well.
Person A has a second hand held radio with a whip that has extension wire that allows it to be elevated by 3 meters on the end of a stick. The radio with elevated antenna allows an additional 500m of range on flattish terrain.
A repeater was place on a mountain top. The team was 3KM further down a Valley from the repeater. Person A could hit the repeater while they are up one of the sides of the valley. Person B in the valley bottom directly below person A couldn't hit the repeater. Person A can talk via radio to person B as they are about 400m away from each other.
Persons A, B have are within 5m on level ground. A's radio picks up conversation clearly. B's radio only picks up one weak fragment. Probably partially broken hardware.
Person A is in fixed location using a 50W transmitter. All others can hear A clearly. A can only hear two out of five of the others.
If I understand your scenario, it is common. You can achieve your scenario even if both of your people have the same hardware so as long as they are separated by some distance or better yet, by elevation. You can even have situation where the person with the handheld can talk to your airship base, where the person with the better gear can't, just depends on where they are relative to each other.
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Note that I ask about the longest possible tree and not the tallest possible tree.
There have been a number of questions about the tallest possible tree, and I wrote a detailed answer to one: [https://worldbuilding.stackexchange.com/questions/191008/would-a-small-low-gravity-moon-be-able-to-harbor-complex-life/191115#191115[1]](https://worldbuilding.stackexchange.com/questions/191008/would-a-small-low-gravity-moon-be-able-to-harbor-complex-life/191115#191115%5B1%5D)
Where I used to live there was a steep slope, somewhat less than 45 degrees I think. And a small tree on that slope fell over in the downhill direction, so that its angle was only a little bit above vertical. Some of the tree roots remained buried in the soil and the tree continued to have green leves for years or decades.
So I wondered about a hypothetical species of trees, perhaps on an alien planet, which grows on slopes and has almost horizontal trunks, casting shade on trees below it and sticking out far from the slope to avoid the shadows cast by the trees higher up the slope.
What factors would limit the growth of those trees to their maximum length, and what would that maximum length be?
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I have once traversed over the branches of an horizontal tree that spans over 2 acres. Unlike [Pando](https://en.wikipedia.org/wiki/Pando_(tree)), which is a clonal forrest sprouting many trunks over the soil, [Pirangi's giant cashew tree](https://en.wikipedia.org/wiki/Cashew_of_Pirangi) sprouts new roots from its branches so it could hypothetically keep on growing forever, as long as the soil would be appropriate for it. It is constrained by sidewalks and pavement on its sides, though, so it won't be growing much in the future.
Here's an aerial view. The green woods in the middle are a single tree:
Some people from another city in Brazil claim to have a yet bigger one. I don't doubt that. A cousin of mine got a PhD studying genetic mutations on these trees that allow them to grow to such giant sizes.
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I don't think there's any limit beyond the fact that it isn't going to be able to grow beyond habitable terrain. A tree that goes along putting down roots and branches can do so until it either is killed by something or can't get enough nutrition. Think if it sort of as a colony organism.
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In the geological history of my planet, the plate tectonics resulted in the assembly of a kind of "ring supercontinent", that completely encircled a portion of the ocean and isolated it from the rest of the planet for a hundred million years or so.
It happened very shortly (geologically speaking) after the life on the planet discovered the joys of having vertebrae (Roughly analogous to the Silurian-Devonian or so in the Earth's history), and this configuration of continents lasted long enough that the species in the interior ocean and on the outside have been evolved separately, which had resulted in the rise of two distinctly different convergently evolved bony vertebrate lineages (Among the whole bunch of other parts of the biosphere), that have quite distinct anatomical structures that will in the future evolve into true bony skeletons, which in turn will result in the planet having two distinctly different types of land animals.
Sometime after that, the continents supposedly broke up and allowed the two biospheres to mix up. At the time of the continental break up the interior ocean had a surface area of about 3\5 of the Atlantic.
**Is there a way for them to do that in such a way that they both biospheres survive this mixing up, without one lineage out-competing the other into oblivion?**
Them coming out of mixing uneven is fine, my current worldbuilding states that descendant species from the inside of the continental circle consist only about 30% of all the vertebrates.
If you don't think so, please provide the next best thing that could result in drastically different skeletal structures of vertebrate animals (The kind I seek doesn't have a different amount of limbs or anything like that, but the shape of the bones and in particular the anatomy of the skull and jaws is entirely different to the point that I don't think that one could plausibly evolve out of the another, mostly the skull, since even 500 million years later, basically all vertebrate life on Earth still shares same general skull anatomy with those first 420 million-year-old jawed fishes, so I came to the conclusion that the point of divergence should be then or earlier).
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**One side will probably outcompete the other, with a few exceptions.**
The analogous real situation I can think of is the Great American Interchange, when North and South America became connected and allowed interchange of fauna.
<https://en.wikipedia.org/wiki/Great_American_Interchange>
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> In general, the initial net migration was symmetrical. Later on,
> however, the Neotropic species proved far less successful than the
> Nearctic. This difference in fortunes was manifested in several ways.
> Northwardly migrating animals often were not able to compete for
> resources as well as the North American species already occupying the
> same ecological niches; those that did become established were not
> able to diversify much, and in some cases did not survive for
> long.[78] Southwardly migrating Nearctic species established
> themselves in larger numbers and diversified considerably more,[78]
> and are thought to have caused the extinction of a large proportion of
> the South American fauna.[61][79][80] (No extinctions in North America
> are plainly linked to South American immigrants.[n 10]) Native South
> American ungulates did poorly, with only a handful of genera
> withstanding the northern onslaught.
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There are just a few successful South American natives in North America. The opossum is my favorite because marsupials take so much flak for being primitive and unworthy, but the opossums have been doing great. Shout out to the opossum! - and this hard to find little monograph which is a hidden gem. <http://www.wildlifeservices.org/PDFS/TheOpossum.pdf>
If this is for a fiction it will be more fun to have the losers represented as a few remaining species, their differences from the majority species being more interesting an d easier to convey because these species are exceptional and few in number - although (like the opossum!) represented by many individuals.
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**To make this possible, I think the easiest way is to make your two clades of animals occupy different niches.** At least to start with.
If a member X of Clade A specialises in something that no member of Clade B can do, perhaps because the niche simply doesn't exist in the domain of Clade B, the descendants of X could live on even if Clade A is otherwise out competed.
In the case of the Great American Interchange, you had two continents with forests and plains, large grazing animals, carnivores hunting these, and so on. When mixed, they competed on the same playing field, and one side lost.
Make up some circumstance that some inhabitants in one of your oceans cave conquered, let these survive and have the others extinct. This is easy to justify, and has the bonus effect of allowing all decedents to inherit some quirky adaptation to this circumstance.
With this special group in place, you could then let it slowly diversify and start entering other niches.
There are many ways to do this, and these are just a few suggestions:
* Let members of Clade A move up on land! Even if life in water end up dominated by Clade B, they can't out compete terrestrial animals. Nothing stops you from later having the terrestrial animals then reenter the oceans, like in the case of whales. Depending on how your rings are located, this could be facilitated by larger tides and large tidal planes on one side. You don't even have to make the transition to land complete, just make them somewhat amphibious.
* Ocean A has really really deep trenches, Ocean B doesn't. An ecosystem evolves down there which stays unaffected by the extinction of shallower A-life. There is then plenty of time for the deep life to have some animals slowly adopt to the shallows and the competition from B-life, and then spread to both oceans.
* Make a small but robust ecosystem that can spread without competing with the rest. In the tropics of Ocean A, you have small floating "islands" (composed of some fungus or the like), on which sit specially adopted barnacles, or maybe snails, which have incredibly hard shells. These islands are very sensitive to cold, and only survive very close to the equator. There are vertebrates in Ocean A which have co-evolved with these hardened suckers, and can gnaw through or maybe crush their shells. This would also explain the different heads! You could also have further fauna adapting to these islands, maybe become "terrestrial" and live on top of them? As the oceans mix, the islands spread to both oceans. Most animals in Ocean A is out competed, but the islands spread around the equator in the other ocean and the islanders along with them. Some B-life will no doubt eat the Gnawers, but if they can hide inside (or on top) the islands they have some chance of surviving long enough to have time to adopt and then maybe find other niches as well. They could transition to either other shelled things, and maybe end up more general predators?
These are just three suggestions; you could vary them or make up your own niches. You could also have "normal" animals survive on both sides, @Willk mentions the opossum, this is maybe even likely. It's harder to predict though, and not so spectacular. I also think having an isolated echo system survive betters your chances of not ending up with a single specialised species, but something that might actually evolve to make up a fair percentage of the fauna on a global scale.
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One simple solution:
The otherwise-inferior group developed flight, the otherwise-superior group did not.
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For my question I'm assuming that we're talking about colonies on the very biggest bodies that are 100s of kms in size. I'm assuming that by this point humans have become cyborgified/roboticized enough to run off electricity and not require a closed atmosphere or really care that there's low surface gravity and they can fly about. Nonetheless they need all forms of industry and production that we need today. These are colonies that don't really rely on trade from Earth or the planets very much. Do they need each other?
For example, if there were separate colonies on the minor planet/biggest asteroid Ceres, and others on Vesta, Pallas, and Hygiea, would it ever be worthwhile for these asteroids to trade with each other?
They have their own local resources and they could mine smaller uninhabited asteroids, but is there anything each of the major group could specialize in composition wise, or are they just too homogenous? Is it perhaps that everyone else would need Ceres but Ceres wouldn't need them?
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### Let's ignore all trading - what is the relationship between settlements?
Let's assume that the asteroids are perfectly heterogeneous and there is zero material reason for them to trade with each other, what does the ship traffic look like?
It is highly unlikely that a single asteroid colony would be self sufficient, even over long term. You need replacement parts and things not manufactured on each individual asteroid. These things would come from Earth (Or Mars or someone other massive settlement of humans).
If there are 10 settlements, does Earth send 10 rocket ships with each settlements order? or does it send one to a central hub, which then on forwards the other 9 orders. For the same reason container ships don't stop at every minor town, supply rockets will have a similar hub and spoke arrangement.
Combine with this the transit time and cost of getting replacement parts from Earth, and your settlements will be exchanging rockets with parts and tools simply because it's faster and cheaper than relying on Earth if your neighbours have spares.
This means you have rocket ships between the settlements **already**, before you even factor in differing resources around the belt.
### Now lets look at resources:
From Wikipedia's asteroid page:
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> The physical composition of asteroids is varied and in most cases poorly understood. Ceres appears to be composed of a rocky core covered by an icy mantle, where Vesta is thought to have a nickel-iron core, olivine mantle, and basaltic crust.[72] 10 Hygiea, however, which appears to have a uniformly primitive composition of carbonaceous chondrite, is thought to be the largest undifferentiated asteroid. Most of the smaller asteroids are thought to be piles of rubble held together loosely by gravity, though the largest are probably solid.
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So in short we don't know for sure, but it looks like composition is pretty varied. Your asteroid settlements will be probably trading raw materials.
However, look at more complex manufacturing. Does each colony need its own circuit board printing factory? Does each colony need its own IC manufacturing plant? Should each colony have its own chocolate factory? Trading allows for these specialist production facilities to be dispersed around settlements near each other in delta v costs, this is more efficient, and baring external factors like a war, is going to result in profitable trading for everyone.
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**Efficiency and resources**
Here on Earth it is commonplace that a lot of resources aren't close to each other. It can very easily take hundreds of kilometers to find the right kind. Your asteroids are less likely to have many kinds of resources. The heavier the elements, the more rare they are, the less likely they are on your asteroid or an asteroid in your vicinity. Trading is then a logical way to solve this. Some asteroids have more than they need from one resource, while lacking another.
The second is industry. Steel for example isn't a singular product. There are many kinds, fulfilling niches of usefulness. Having all kinds of production is difficult with both limited space and resources, and with some resources is short supply it makes more sense to trade them refined already instead of trading raw resources and producing them yourselves.
You might think to automate a lot of processes and mining also remote asteroids. This is of course possible, but only if there are enough asteroids and space between you and the next cyborg civilization this can be done without conflict.
So in all likelihood they would trade with each other to both benefit. Even if they both can supply themselves with everything that's needed, trading can be beneficial due to lower costs for a certain resource.
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There's 2 major sources for trade.
Staples and luxury items.
Luxury items will always be in demand because they're status identifiers.
Staples would probably be metals or machinery, these can be used to pay for the luxury items when possible or traded as necessities where they are not. But there will always be trade even in war time.
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I am toying for a while with the idea of an [hysteretic](https://en.wikipedia.org/wiki/Hysteresis) space-time.
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> Hysteresis is the dependence of the state of a system on its history.
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>
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Though it could make for some interesting twists in the world, I am not sure up to which point it could be made self-consistent.
Therefore my question is:
All the rest being the same, in a space-time that shows hysteresis, could elementary particles like bosons and fermions exist?
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# Yes, why not.
You could do that with some sort of extra particles or "hidden variables" (for example an electron, once removed from near a proton and brought back, would experience a slightly different electric force - its charge has become hysteretic).
There is something like this (but not so radical) in James P. Hogan's *Entoverse*.
But the hysteresis hypothesis has *tremendous* consequences, since you have, in effect, introduced a possibly nonzero [curl](https://math.wikia.org/wiki/Curl) everywhere - the electron above would experience its own hysteresis as a time variation of the local electric field. On a closed loop, this translates to total work being nonzero, i.e. energy can be destroyed or created from nothing. In a larger sense, no vector field can now satisfy the irrotationality criteria, *immediately doing away with any form of conservative field*.
No conservativeness for gravitational fields means *no stable orbits* (the consequences at the micro scale for the possibility of life are probably just as profound, but I haven't the knowledge to even begin *imagining* them).
A hysteretic space could *probably* exist just like some sort of dense quantum soup.
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I was looking over the conversation in the comments (which mentions things like "revision counters" and "reverse-hysteresis"), and then it struck me:
**Doesn't the universe work like that *anyway*?**
Think about causality. "Every action proceeds from another", as my high-school philosophy teacher used to say. Now, I get that philosophy is rather outdated, but the basic concept applies here: **Everything has a past, which has effected its current present.**
For example, consider the soot in a chimney. At one point that soot was some combination of wood, paper, and other flammable substances. If it had been left alone, it would stay exactly the way it was due to Newton's first law of motion.
However, that's not what happened. **At some point *in its history* the constituent components had excessive heat applied to them.** As a result, the carbon, tar, and a few other components sublimated, becoming the soot in that chimney.
**I argue that our universe does, in fact, work that way; the current state of each and every thing is derived from the events in its past.**
That being said, I don't have a physics degree, so I could be misunderstanding the question.
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One example that might be food for thought here is that of the [wave equation in even spatial dimensions](https://en.wikipedia.org/wiki/Wave_equation#Scalar_wave_equation_in_two_space_dimensions), which (unlike the cases of odd spatial dimensions such as the familiar one or three) exhibits a kind of hysteresis. Quoting Wikipedia (emphasis mine):
>
> … the solution at a given point $P$, given $(t, x, y, z)$ depends only on the data on the sphere of radius $ct$ that is intersected by the light cone drawn backwards from $P$. It does not depend upon data on the interior of this sphere. Thus the interior of the sphere is a **lacuna** for the solution. This phenomenon is called **Huygens' principle**. It is true for odd numbers of space dimension, where for one dimension the integration is performed over the boundary of an interval with respect to the Dirac measure. It is *not* satisfied in even space dimensions.
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Thus in even dimensions, provided the propagation of light and sound is still governed by the wave equation, one would in principle be seeing/hearing not only what is there "now" (really: the short moment of time ago that it took the wave to reach the observer) but also afterimages of what was there earlier. (It's possible this would lead to such blurring that sight and sound are rendered essentially useless as senses; I haven't checked how the math works out in that regard, but would expect interference to be important.) Since the [Klein–Gordon equation](https://en.wikipedia.org/wiki/Klein%E2%80%93Gordon_equation) is in a sense just a modification of the wave equation obtained by adding a term with just the function (rather than second partial derivatives thereof), one would expect something similar for that, and the [Dirac equation](https://en.wikipedia.org/wiki/Dirac_equation) is (to put it loosely) a square root of the Klein–Gordon equation, so again we have "waves" as solutions, and one would expect even/odd dimensionality to have an impact on what they look like.
Going to four spatial dimensions is probably too hard for just a story, but one could reasonably pull off a setting where there besides normal physics also are extra interactions (magic, [ley lines](https://en.wikipedia.org/wiki/Ley_line), maybe something like [axions](https://en.wikipedia.org/wiki/Axion), or whatever seems appropriate for the setting) that rather exhibits hysteresis — maybe because of obeying an even-dimensional wave equation analog, or maybe because there is a lasting imprint on materials as in magnetic hysteresis. One could argue that there for humans would be an evolutionary pressure against using the non-normal physics for senses (since such senses would report data that is no longer current), and hence these effects wouldn't be immediately apparent, but some animals could have other priorities; likewise genetics or proper training might give some individuals a certain sensitivity to it.
But as to your precise question, I too believe "**yes, why not**" to be a reasonable answer.
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To add to [The Daleks' answer](https://worldbuilding.stackexchange.com/a/188208/21222):
Let's consider electrons and quarks, which are elementary particles.
A neutron is composed of two down quarks and one up quark; a free neutron (i.e.: not associated to an atomic nucleus) decays in a little less than fifteen minutes, resulting in the appearance of a new electron in our universe. For that electron to exist, the neutron had to be freed from a nucleus; without that event, the electron would not be.
Besides that, one of the down quarks in the proton becomes an up quark in the process (converting the neutron into a proton). That quark changing flavor is also dependent on the system history; it would remain a down quark if nothing had happened.
I therefore extrapolate this to all particle physics and propose that any universe with at least one time-like dimension is hysteretic.
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I had an idea for a creature in my world: the enchanced canine.
Basically, they were dogs, mostly German shepherds, that were used by a police organization in the United States. These policemen, wanting better fighting dogs, made a contract with a bioengineering company that enchanced the dogs. The changes they made, in order, were-
* Increasing the dog’s muscle mass and strength.
* Increase their speed
* Increase the dog’s intelligence to make them more social, more obedient to train, and able to carry out basic tactics on their own.
* Better eyesight
Then, I planned on an apocalypse happening, and all these dogs being stranded in a new, more hostile world without their owners. And eventually, after a few generations, going wild. Mixing with gray wolves (who’s populations spread with the lack of humans), other dogs, and eventually forming packs that terrorize survivors, both human and animal alike.
My question is, is someone like this realistic, or plausible? Are all these changes within the realms of genetic engineering?
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This is quite realistic and plausible. In fact, humans have already been doing essentially this over thousands of years of selective breeding. Dogs have been bred selectively to enrich for certain qualities like size, strength, intelligence, and sociability. Adding genetic engineering into the mix will allow this process to happen even faster, as traits can be more reliably selected and purified, rather than selectively breeding animals over many generations.
Since all of these qualities are enriched versions of already-existing dog biology, this is very well within the realm of possibility. Adding wings or gills or something decidedly un-doglike would be more of a challenge, but selectively improving already-existing qualities should be relatively more straightforward.
Crossbreeding with a wolf is also completely plausible, as dogs and wolves are interfertile, meaning their offspring are themselves fertile. So long as your genetic engineering isn't so drastic as to create an entirely new species, it's totally plausible that one of these dogs could mate with a wolf and have lineage of multiple generations in the wild.
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There are two conflicting requirements in your list: more mass and more speed.
Compare a cheetah with any other big felids like lions, panthers, leopards and tigers: the cheetah excels in speed, being the fastest land animal on Earth, but to achieve that goal has been forced to sacrifice mass and robustness, being way more slender than the cousins.
Same applies for those dogs selected to be exceptional runners like the [sighthound](https://en.wikipedia.org/wiki/Sighthound),
[](https://i.stack.imgur.com/jBriW.jpg)
which cannot be compared in constitution to more robust breeds like a [rottweiler](https://en.wikipedia.org/wiki/Rottweiler).
[](https://i.stack.imgur.com/JCLK5.jpg)
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Domesticated dogs are basically small wolves.
Realistically however better eyesight ? Color sight would be a nice addition but would require them to completely rewire the visual cortex and conic cells in the eyes, making new eyes that were definitely more primate.
Dogs already have a pretty keen sense of smell as is and particulate matter REACHING the nose is really what determines that.
There is a limit as to what bipeds and quadrapeds can reach in size before their skeletal system could not possibly maintain their weight. Luckily for the storyline there are these things called big cats, which are ridiculously large and basically huge feral killing machines. So there is room to grow.
The problem is you'd also have to increase their fondness of their masters and social impulse to make sure they never turned on their masters or pack mates or well said masters are now lunch.
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I'm building a world, which takes place about 300 years in the future after an event in the near future, in which giant elemental monsters started to roam around the earth. These creatures are an average of 30 feet tall and have shapes of normal animals. They were resistant to conventional weapons and took the world by storm. After fighting humans and amongst themselves, these creatures have settled into large territories. The territories are large, like the size of New England region in the United States.
Humanity has been knocked back a bit to about industrial revolution technology and formed into city states inside the territory of the giant creatures. Humanity and these giant elemental creatures have learned to live with each other.
The giant creatures have learned to tolerate those within its territory but patrols their borders strictly. Any infrastructure between territories don't last long, except basic roads.
My question is how would the city states communicate with each other, if infrastructure can't cross the borders?
I was thinking something like radio. Would that infrastructure last 300 years or easy enough for industrial level people to build if they had the means?
[Answer]
Telegraph lines to the border. Theres a relay hut with a guy using Morse code that can communicate city-to-border at speed of light.
A relay operator then walks to his counterpart at the border and delivers the message directly (verbally or written down), the counterpart then forwards the message to his city.
No new infrastructure crossing the border is needed, the huts are a few hundred meters back allowing for both sides to patrol. Near Instant communications, and, crucially, it's hard for country C to listen to what A and B are saying. Radio wont have that advantage, unless your elemental warriors rediscover decent mathematics.
Morse code operators develop a "feel" for each others personalities based on minutiae of how they tap out messages, meaning an invading force cant kill the operator and then say "everything's fine" down the wire. There are also usually prearranged duress behaviours, eg a message with no misspellings means it was sent under duress.
[Answer]
Add a light based morse code at the border and you can signal from hut to hut without having to risk sending someone right down to the border. Semaphor flags would work too.
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[Question]
[
From puppetsock's reply to [Is it possible to build a black hole (kugelblitz) gun?](https://worldbuilding.stackexchange.com/questions/159244/is-it-possible-to-build-a-black-hole-kugelblitz-gun), it seems like a black hole of 228 tonnes evaporate after just 1 second. And the lifetime of a black hole in general is proportional to the cube of its mass.
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Edit: Clarifying my thought process:
* Step 1: The object barely surpasses the event horizon
* Step 2: The event horizon starts shrinking faster than the object is falling; catching up to/surpassing it.
[Answer]
No, this is unfortunately impossible.
The key here is that Hawking radiation bears no resemblance to the constituent matter that formed the black hole (this turns out to be a bit of a problem - see the [black hole information paradox for more details](https://en.wikipedia.org/wiki/Black_hole_information_paradox)). Black hole evaporation dramatically favors the production of lighter particles. For example, [a black hole of temperature $T=100\;\text{GeV}\approx10^{15}\;\text{K}$ emits less than 3%](https://physics.stackexchange.com/a/399749/56299) of its emitted energy in the form of protons and antiprotons (see [MacGibbon & Webber 1990](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.41.3052)). Over three quarters ends up as photons and neutrinos, with most of the remainder in the form of electrons and positrons.
As a rule of thumb, for a particle of mass $m$, a black hole needs to have a temperature $T$ such that its thermal energy $E\_T\approx k\_BT$ is on the order of $mc^2$ for that particle to be emitted significantly. Hence, hotter (read: less massive and closer to death) black holes may emit more massive particles, but the majority of their emission should still take the form of neutrinos and photons.
The upshot of all of this is that the mass of any object that travels inside the event horizon will reemerge in a form completely different from the original - dump a block of cheese into the black hole, and it won't emerge as anything like the original mixture of protons, neutrons and electrons, let alone a block of cheese.
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A black hole that explodes within the next second is of subatomic size. Anything that falls in must get atomized **before** it crosses the event horizon.
And anything that approaches will be ripped apart long before it reaches the event horizon due to the Hawking radiation that's coming out of the black hole. This radiation pressure makes feeding such a small black hole virtually impossible. It would even explode if it were embedded in the core of the sun. Once a black hole's radiation reaches a certain level, the only thing you can do is to flee if you don't want to be blown up with it. It's the perfect ticking time bomb, with a strength that dwarves all the nukes that we have built.
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**No**
An object doesn't quite 'fall' into a black hole, a more correct explanation would be that it forms an accretion on the hyper-dense mass which forms the black hole. It doesn't matter how little time an object spends in a black hole, once it's there, it's been compacted beyond all recognizable measure to the point where any object smaller than a human wouldn't even be able to be seen in its current state, assuming you could see the mass which makes up the black hole. Not to mention that when a black hole evaporates, it does so emitting radiation, like, a lot of it. Black holes aren't survivable.
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[Question]
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(Note: this is similar to [is Cryomancy scientifically possible?](https://worldbuilding.stackexchange.com/questions/44449/is-cryomancy-scientifically-possible), but not exactly the same.)
In my story, I have "magic" that amounts to telekinesis powered by the user's metabolism.
It seems that heating objects using this magic should be pretty plausible (although the amount of heat that can be generated is somewhat limited); the user metabolizes some energy, and that energy, instead of doing Work inside the user's body, causes a target object to heat up by that amount of energy. More specifically, the way I envision this working is something like the user's body produces energy via metabolism as normal ("using magic" can be though of as an additional way to trigger metabolic energy production), but the energy produced is magically teleported to a location of the user's choice and acts in a direction of the user's choice. (I think this is sufficient to blur the lines between "heat" energy and other, more useful forms of kinetic energy, thus explaining why a magic user can also do things like levitate small objects. This is playing pretty fast-and-loose with entropy, but it *is* magic, although the difference in entropy may factor in as a loss in efficiency.) There is also a range limit, with "lost" energy dissipating as heat between the magic user and the target. (Basically, at a distance $D$ from the target, the magic user must spend $2x$ energy to apply $x$ to the target, with the other $x$ getting lost somewhere en route, possibly as infrared radiation.)
To phrase this a little differently... magic is a lot like a combination of [Newton's Cradle](https://en.wikipedia.org/wiki/Newton%27s_cradle) — a moving ball strikes a stationary mass in an inelastic collision, and the energy is transferred through the mass (without the stationary mass moving itself) to another ball — and a "[super ball](https://en.wikipedia.org/wiki/Super_Ball)" — an object which, upon striking an "immovable" object, rebounds in a perfectly elastic collision such that its speed remains constant but the direction of its motion changes. All (my story's) magic brings to the party is that these effects are combined, i.e. it is like a Newton's Cradle where the stationary mass is immaterial (and can transfer energy/force through other matter occupying the same space as the immaterial "mass" with minimal effect on said matter), and can redirect the force in a different direction. (Propagation is presumably still subject to the speed of light, but for my purposes this is effectively negligible; magic only works over short distances.)
Now... it also seems like the reverse of heating things should be possible. After all, cooling is just applying an acceleration to atoms in opposition to those atoms' present velocity, and we certainly have technological means of cooling things (note the referenced question and answers thereto).
The problem is that this appears to violate thermodynamics; we can't just decrease the entropy of the universe. In particular, the "naïve" solution would be to postulate that the metabolic energy produced by the magic user perfectly counteracts the existing atomic motion of the target to be cooled, but this implies that the user's metabolism produces $k$ energy which doesn't *just* not affect the user directly, but effectively *vanishes* from the target. IOW, I just *removed* $2k$ energy from the universe (and incarnated [Maxwell's Demon](https://en.wikipedia.org/wiki/Maxwell%27s_demon) in the process).
How can I avoid violating thermodynamics in this manner, but still allow magic to cool things? I'm looking particularly for answers that can *quantify* how much heat needs to be dumped elsewhere (presumably into the magic user's body and/or surroundings).
[Answer]
You are basically asking for a [heat pump](https://en.wikipedia.org/wiki/Heat_pump). A lot of people learn that heat only flows from hot regions to cool regions. This is true, but isn't the whole story. You can make heat flow to a hotter region if you do work; this is what your refrigerator does.
The key to prevent this from violating the laws of thermodynamics is to make the telekinesis heat some reservoir more than it cools the target. Your refrigerator pumps the heat from inside to the rest of the room. This isn't 100% efficient either, so it also heats the room up a little extra. For example maybe it removes 1000 joules of heat from inside the fridge, but adds 1001 joules of heat to the rest of the kitchen.
You might still be violating other laws of physics, but this should be sufficient to not violate thermodynamics.
By the way, we actually do exactly what you're proposing in real life, but [with lasers](https://en.wikipedia.org/wiki/Laser_cooling) instead of magic.
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Without an established science on how telekinetic cooling works, we do not know how efficient it could be, but what we do know is refrigerators. According to <https://physics.stackexchange.com/questions/230465/heat-rejected-by-a-refrigerator>, a standard 25W refrigerator has an efficiency of about 17.4:1. Meaning one unit of energy is consumed for every 17.4 units of thermal energy you displace.
A good hard workout can typically burn up to 400 kCal; so, let's call this the cap on what you can safely do on a regular basis. This means that a common ice spell might displace somewhere around 29,140KJ of energy. It takes displacing about about 300KJ of energy to bring a gallon of water to freezing from room temperature; so, if your spell is as efficient as a refrigerator, you are looking at being able to freeze about 97 gallons of water with the same energy you would get from a light meal.
If you want to really go big, a lb of body fat contains about 3,500kCal of energy. A well fed cryomancer who just sits around all day playing video games and answering questions of stack-exchange might have a good 50lb of body fat he could tap into without emaciating himself. That would give him the power to create a 4" thick sheet of ice over an Olympic sized swimming pool turning the whole thing into a usable ice skating ring.
[Answer]
### Thought Experiment
[Ryan\_L](/users/51953) inspired me to try a thought experiment that I think might help.
So far, I haven't been able to poke any gaping holes in *heating* something... a magic user produces $x$ energy from metabolic processes which, instead of performing Work (e.g. contracting muscles) or heating the user's body, instead dumps $x$ of heat energy into the environment (mostly, but not entirely, into some target). This seems okay, but if not, someone please jump in and yell at me.
Okay, how about cooling? The thought experiment that made me realize I *definitely* have a problem is this: let's say that, instead of trying to cool some target, the magic user tries to cool *herself*¬π. Let's start by theorizing that this works in the manner of a perfectly efficient heat pump.
So, our hypothetical magic user produces (via metabolic processes) $x$ energy, which she uses to cool herself. Because that energy has to go *somewhere*, she dumps it *also* inter her own body... for a net change of zero.
However, there's a hitch. Her body temperature didn't change, but she *did* burn of some "biofuel"... and this energy just disappeared. This would be like lighting a bunch of gasoline, and seeing it undergo the usual chemical changes of combustion, but *without giving off any heat*.
Clearly, this won't work.
### More Rambling
Can we just move heat? The premise of magic is that it takes "metabolic energy" and applies it as force somewhere else. Again, if we want to *heat* something, this seems okay, but to *cool* something, I keep winding up back at Maxwell's Demon.
Okay, so what we're missing is the entropic cost of cooling versus heating. If we're *heating*, it's not unreasonable to postulate that the entropic cost is zero, or very close to zero; after all, the net entropy increase is still $x$, we've just changed *where* that increase happens. If we're to avoid running afoul of thermodynamics, our *best case scenario* is that converting $x$ of "biofuel" into magic results in no net change in entropy. Thus, our *best case* would be that a magic user can transfer heat energy between two points with 100% efficiency.
...But again, our magic doesn't work that way. Our magic says that to apply $x$ force requires *at least* $x$ of metabolic input. It stands to reason, therefore, that our magic user trying to "cool" herself has to spend $x$ energy in order to transfer $x$ energy from her body *to* her body. This works; effectively she made her body metabolize $x$ worth of biofuel and convert it directly to heat (might be good for keeping fit!). This puts our "best case" for cooling at being able to lower heat energy somewhere by $x$ while increasing it elsewhere by $2x$. (No danger of replacing refrigeration, there.)
### An Alternative
Maybe this isn't necessary. Maybe we can reframe magic as a transfer of energy in which the user is necessarily *one* of the end points. That would greatly simplify things; a magic user can cool something for no *direct* metabolic cost, but only by transferring the heat to themselves. This makes cooling in general really easy while putting a definite limit on how much a magic user can cool something without keeling over from heat stroke.
### Initial Conclusion
It seems likely that the best case is that cooling a target by $x$ heats the magic user by at least $x$, and possibly more than $2x$, depending on which model we use. A more likely model seems to be that she has to burn some of her own energy just to "do magic", but that cooling works "in reverse", by pulling heat from the target into her own body, rather than doing the reverse (as when heating or moving something), so we're sort-of back at the heat pump model.
### Refinement
Something I realized later is that transferring opposing forces from the magic user to a target to be cooled might not work. This is actually related to what happens when two atoms collide head-on; they lose their *kinetic* (heat) energy, but since that energy can't just vanish, it turns into photons instead; this is heat loss via radiation. If magic just makes this happen, then we can define it to work as follows: energy is produced via metabolism, which is "perfectly" paired up with the heat energy in the target in order to neutralize it, in a way that the resulting radiant energy all winds up elsewhere. This means that cooling something by $x$ produces $2x$ heat "somewhere", but presumably in the magic user's body, plus whatever inefficiency is inherent in doing magic in the first place.
I'd previously (and somewhat by accident) come up with numbers that would make magic 25% efficient ([comparable to muscles](https://en.wikipedia.org/wiki/Muscle)). In what may or may not be a coincidence, this is the same efficiency as if we throw out the idea of being able to change the direction of force and calculate how much energy we can extract along a given vector based on random input (i.e. heat). This is equivalent to magic being optimally efficient using only the portion of heat-energy along the vector of the force being magically exerted. It also means that magic (i.e. telekinesis) doesn't violate Newton's Third; levitating a book "weighs down" the magic user in *almost* the same way as carrying a book without magic (the difference being how the force is distributed). The corollary of this is that using magic requires leverage. However, it also suggests that a) *heating* something is 100% efficient, and b) *cooling* something can achieve our previously derived "best case" where cooling by $x$ heats the user by $2x$, or, more optimally, heats both the user *and something else* by $x$ (while requiring more mental effort).
### Takeaway
Our magic user won't be freezing any swimming pools (I knew that already, and I don't *want* that to be possible), but she can probably keep her beer cold (which *was* an objective).
I'd appreciate folks pointing out if I've done anything stupid here.
### Footnotes
1. The main magic user in my story is a female, so I'll use those pronouns.
2. At least, I haven't been able to come up with a plausible explanation that isn't overly complicated. It would have to be something like compressing a ball of air, waiting for it to cool, moving it, then letting it expand again.
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[Question]
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**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 far I've been using Artifexian's How To Build A Star YouTube video. The problem with this video is that it's quite old and thus outdated. The things I've noticed to be particularly weird are the equation for the star's diameter (doesn't take the star's age or consistency into consideration) and the usage of the MK Stellar Classification List. Are there any newer equations for starbuilding and what are they in that case?
Edit: I was not intending to imply that the MK Stellar Classification List is outdated, I was saying that the equations in the video rely heavily on it
[Answer]
In reality, if you want to build a star, you need to specify a mass and a chemical composition, and then use the [equations of stellar structure](https://www.astro.princeton.edu/%7Egk/A403/stellar.pdf). This requires some numerical integration, and it's far from simple. People have making careers out of it for generations. (One upshot of this, of course, is that there are plenty of existing stellar models out there, and you can essentially pick a star from a set of grids and find out all of its properties without having to do any calculations yourself!)
What we *can* do is make some analytical approximations that are valid in some specialized cases. The ones we'll use are valid for stars on the main sequence, where they'll spend the bulk of their lives. They also don't (for the most part) take into account the star's composition. These results depend solely on the mass of the star, which is arguably the single most important parameter you have to consider.
## Luminosity
By making some assumptions about energy transport, we can determine that [the luminosity should scale with mass](https://websites.pmc.ucsc.edu/%7Eglatz/astr_112/lectures/notes14.pdf) approximately like
$$\boxed{L\propto M^3}$$
Mass-luminosity relations are important topics of research which are actually take different forms depending on the mass of the star. The simplest are piecewise, of the form $L\propto M^{\alpha\_i}$, with different $\alpha\_i$ used in different mass ranges. $\alpha=3.5$ is usually a good rule of thumb for Sun-like stars, but let's work with $\alpha=3$ for now.
## Radius
Using the same assumptions, we can deduce that
$$\boxed{R\propto M^{(\nu-1)/(\nu+3)}}$$
where $\nu$ is a number that depends on the process by which the star produces energy. For the proton-proton chain reaction, used in stars of $M<1.3M\_{\odot}$, we have $\nu=4$. For the CNO cycle, used in stars of $M>1.3M\_{\odot}$, we have $\nu=20$. This gives us two different relations: $R\propto M^{3/7}$ and $R\propto M^{19/23}$.
## Surface temperature
Stars are, approximately, black bodies. This means that their luminosity, radii, and surface temperatures ($T\_{eff}$) are connected via the Stefan-Boltzmann law:
$$L=4\pi R^2\sigma T\_{eff}^4$$
We can rearrange this to get
$$T\_{eff}\propto\left(\frac{L}{R^2}\right)^{1/4}\implies \boxed{T\_{eff}\propto\frac{M^{3/4}}{M^{(\nu-1)/2(\nu-3)}}}$$
For low mass stars, we get $T\_{eff}\propto M^{15/28}\approx M^{1/2}$; for high-mass stars, we get $T\_{eff}\propto M^{31/92}\approx M^{1/3}$.
## Main sequence lifetime
The rate at which a star loses mass is proportional to its luminosity. We can then make a *very* rough guess at its main sequence lifetime by saying that $\dot{M}\propto L\propto M^3$. Integrating that differential equation gives us
$$\boxed{\tau\propto M^{-2}}$$
or, if you used $\alpha=3.5$, $\tau\propto M^{-2.5}$, which is the relationship you see tossed around a lot.
## Habitable zone
We can get some very, very basic bounds on the classical habitable zone by considering the temperatures at which water can exist in liquid form. This criterion is sometimes disputed, but it's what we've got to work with. Using the [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature#Surface_temperature_of_a_planet) of a planet - more black body models - we can see that the inner and outer boundaries are given by $R\_h\propto L^{1/2}$ or
$$\boxed{R\_h\propto M^{3/2}}$$
## Miscellaneous notes
* These mass scaling relations are applicable *only on the main sequence*. They won't tell you anything about post-main sequence evolution, which is arguably much harder - if not impossible - to reduce to analytical approximations. I think most folks don't bother, for worldbuilding purposes, with post-main sequence stars anyway.
* They neglect radiation pressure and convection and make some unrealistic assumptions about constant opacity. For some stars, we can ignore radiation pressure; for others, we can ignore convection. This is one reason why these scaling relations are best suited for Sun-like stars, rather than a broad range of masses.
* These are, I would say, order-of-magnitude results. In astronomy, I'm usually happy to get something right within a factor of 10, and I won't quibble with a factor of 2 or 3. To back that up: stars can differ by about a factor of 100 in mass, a factor of maybe 20 in temperature, and a factor of . . . well, quite a few orders of magnitude in luminosity.
---
Finally, a note on numerical grids: Your question ended with "Which [equations] do you use?" My personal answer is that I usually don't run the numbers myself; I find tables of stellar models and pick and choose the ones I want. Astronomers have already gone to the trouble of doing the detailed (and much more accurate) computations, and if the results are out there, hey, I might as well grab some.
Some quick Googling should turn up some helpful results. For a lot of answers on Worldbuilding, I've grabbed numbers from [a set of main sequence models by Eric Mamajek](http://www.pas.rochester.edu/%7Eemamajek/EEM_dwarf_UBVIJHK_colors_Teff.txt). They're finely spaced and contain some interesting quantities (e.g. color indices) that might be useful in niche situations. But there are really plenty of other grids out there (which [I've since written more about](https://worldbuilding.stackexchange.com/a/175698/627)). The [Geneva grids](https://www.unige.ch/sciences/astro/evolution/en/research/geneva-grids-stellar-evolution-models/) are excellent if I'm not feeling too lazy to sift through them.
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Giant dogs aren't uncommon in works of fantasy. Sif from Dark Souls comes to mind.
[](https://i.stack.imgur.com/qVCIx.png)
What I want to know is: what's the largest a canine could realistically get, what differences would they need compared to regular dogs in order to function, and what evolutionary pressures would lead a group of canids to evolve to such large sizes?
Note: Magic does not exist in my story.
[Answer]
The largest terrestrial mammalian predator by weight was Andrewsarchus:
[](https://i.stack.imgur.com/GGyyX.png)
You can get a little more height using a slighter build like Daeodon here:
[](https://i.stack.imgur.com/2XpIa.png)
But that is about your limit. Mammals are really poorly designed for large size, our bones, skeletal structure and respiratory system are just garbage if you are trying to be big. Dinosaurs get huge because they have hollow bones, a massively reinforced pelvic girdle, and no lumbar region.
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In some birds especially owls, we can observe a structure called [facial disk](https://en.m.wikipedia.org/wiki/Facial_disc), which is mainly composed of feathers and helps to direct sound to their ears. While being more common in owls, adding up to their asymmetrical ears to result in great hearing capabilities, this trait is also observed in harpy eagles, which can "retract" this structure as seen on the upper left and bottom right pictures below:
[](https://i.stack.imgur.com/Irn8E.jpg)
Now, my main issue in adapting this structure is the fact that it's composed of feathers. Could a 4 eared creature possibly develop a similar structure out of bones, skin and cartilage alone? The creature by default has smooth skin with a muscular layer below, high number of chromatophores and lacks hair, feathers or scales; much like a Cuttlefish. It relies on its sensitive hearing to hunt at night.
[Answer]
Make it evolve from the equivalent of [frilled lizard](https://en.wikipedia.org/wiki/Chlamydosaurus) and you may have your bird evolving a facial disk even before [evolving wings](https://www.youtube.com/watch?v=XAo09yYOpCU) (frilled lizards being able to climb on trees to escape predators, you may even have an evolutionary advantage pushing for wings)
If you don't need a bird, that's fine, the example shows that it is possible.
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[Question]
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In my world there is an engineered species of changeling-like shapeshifters. Their lifecycle is similar to that of cuckoos (and the fair folk) of replacing human children with their own, who then run away into the wilderness once they reach maturity.
The original changelings would have spoken the language of their creators. However, would we expect subsequent generations of changelings to switch over to the language of their victims as their childhood will have been spent among people?
Assumptions:
* Developmentally, language develops in shapeshifters in a similar manner to humans (in terms of age-related milestones in language development).
* The switch typically happens between early and late childhood. More ambitious shapeshifters would go for younger babies, whereas more cautious ones would go for children who are old enough to walk independently (to swap younger children would involve sneaking into dwellings, whereas older children could be lured away).
[Answer]
**Your assumption that they would adapt the language of their victims is correct.**
If the changeling babies spend their youth pretending to be human, the only language they will be taught, and subsequently know, would be that of their victims. They will not magically know the older languages of their species, nobody will have taught them. Advanced communications (beyond grunts and screams) does not come naturally to any species without being taught, magical or not.
Of course, they could learn the elder languages as a second language when they join their community later in life. The usefulness for this is debatable, as it would only be useful to communicate with their kin worldwide. They could communicate with their community in their youth language, as they will have grown up in the same area. But when international communications are needed, learning any common language could do, rather than the elder one.
Over the generations, the usefulness of the elder language will deteriorate, and eventually it will be forgotten. They will solely speak the language of their victims, and perhaps some second language(s) they choose to learn on top of that.
Note: This highly depends on the language of their creators to begin with. If this is any of the worlds most common languages, this could come in useful, and the language might stick around. Languages like Romanian, Greek, or Swedish for example are less universally known, and will not likely stick around for long.
[Answer]
I'd have thought they'd speak their adopted language only, unless their own was hardwired in as part of the changeling process.
Unless you are having clandestine "speak changeling" courses as they are growing up. Or once they "escape" to the wilderness, the 1st thing they do is learn their own language.
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[Question]
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The **Orion's Arm Universe Project** includes a description of what they call "**[To](https://www.orionsarm.com/eg-article/4802ab151e093)['](https://tvtropes.org/pmwiki/pmwiki.php/Main/PunctuationShaker)[ul](https://www.orionsarm.com/eg-article/4802ab151e093)['](https://tvtropes.org/pmwiki/pmwiki.php/Main/PunctuationShaker)[hian Worlds](https://www.orionsarm.com/eg-article/4802ab151e093)**", planets that are (in the simplest of terms) a cross between Earth and Venus.
**I'm working on designing a similar planet** for an unconnected story, and this OAUP page is the closest thing to a reference for my setting that I've found so far.
@galactic\_analyzer suggests that the OAUP world's CO₂ atmosphere is problematic, and I'd prefer an Earth-like nitrox atmosphere anyway, so for this question let's make that replacement.
**Could a planet like this exist in real life?** If not, what specifically causes problems with the concept?
The key points are:
* surface pressure of 10 to 100 bars
* surface temperature of 100 to 200 degrees Celsius
+ Note: at 10 bar, maximum temperature is 180°C; at 200°C, minimum pressure is 16 bar
* liquid water at the planet's surface
* an active carbon cycle
* develops oxygen-producing airborne life
* atmosphere includes thermosphere and ozone layer
* atmosphere consists primarily of ~~carbon dioxide~~ nitrox
[Answer]
Quite simply, it would not be possible. First of all, the **only** reason why the Earth does **not** have so much carbon dioxide is because of oxygen-producing life. If your planet has developed oxygen-producing life, it should already have converted most of the CO2 into oxygen. While oxygen-producing life may have evolved only recently on your planet, other aspects of your hypothetical planet prevent each other from forming.
The early Earth, although rich in CO2 with higher surface temperatures, did **not** have temperatures or pressures as high as Venus does today. Like Zxyrra said earlier, Venus’s current atmosphere was formed when greenhouse gases accumulated in its atmosphere, heating rocks to a higher temperature to form more greenhouse gases. This accumulated over time into its current atmosphere. The reason why this did not occur on Earth is because oxygen-producing life acted as a “brake” to halt the process. If oxygen-producing life evolved on your world, the planet would **not** have temperatures or pressures as high as they are mentioned in your question (10-100 bars, 100-200°C).
There is a great amount of difference between 10 and 100 bars of atmospheric pressure and 100 and 200 degrees Celsius. In **one** interpretation of your atmospheric pressure and temperature, liquid water **cannot** exist. A **different** interpretation would allow it to exist, but I do not know the exact values of your hypothetical planet's atmospheric pressure and temperature. A carbon cycle also could not exist on this world because oxygen-producing life is incompatible with higher surface temperatures and pressures. A thermosphere would also not exist on a planet with such high pressures; an ozone layer would similarly not exist because oxygen originating from photosynthetic organisms is a prerequisite for the formation of one.
In summary, your idea is an interesting thought experiment. However, there is either the toxic, hellish “Venus” type planet or the terrestrial, Earth-like planet with no “in-between.” So, your planet would not exist.
UPDATE: @Lawton edited his/her question to a nitrox (nitrogen-oxygen atmosphere similar to Earth) atmosphere. This is an entirely different scenario. If possible, I will answer his/her new scenario later when I have time.
[Answer]
# Life organisms
## Earth examples and liquid water
First of all within the ranges given, at temperatures lower than 150 °C and pressures greater than 10 bar water is [liquid](https://en.wikipedia.org/wiki/Water_(data_page)#Phase_diagram). Which also means that there is no runaway greenhouse effect under those conditions. Among the living organisms that live and reproduce in those conditions there are the following:
* [Methanopyrus kandleri](https://microbewiki.kenyon.edu/index.php/Methanopyrus_kandleri) lives optimally at 105 °C (up to 122°C) and it was found also underwater at 200 bar. It can consume CO2 and H2 to produce methane(CH4).
* [Pyrobaculum islandicum](https://microbewiki.kenyon.edu/index.php/Pyrobaculum_islandicum) lives best at 100 °C (up to 103°C). It can survive with only elemental sulfur, CO2 and H2 while acting as the producer of organic matter that the other living being may need.
* [Pyrolobus fumari](https://microbewiki.kenyon.edu/index.php/Pyrolobus_fumarii) lives best at 106°C (up to 113°C) and was also found underwater at 370 bar. Among the many ways, it can live by consuming O2 and H2.
* [Geogemma barossii aka. Strain 121](https://microbewiki.kenyon.edu/index.php/Geogemma_barossii) lives best at 103°C (up to 130°C) and it was found also underwater at 243 bar. It survives by using iron instead of oxygen.
* [Pyrococcus furiosus](https://microbewiki.kenyon.edu/index.php/Pyrococcus_furiosus) lives best at 100°C (up to 103°C-105°C). It can generate H2, but O2 is toxic to it. In its presence it tries to convert it into water.
## Carbon cycle and ozone
Assuming a way of producing O2 from water (which will be discussed later) the presence of O2 in the air would [transform the CH4](https://en.wikipedia.org/wiki/Atmospheric_methane#Removal_processes) produced by the Methanopyrus kandleri in formaldehyde(HCHO). This [would react with O2](https://en.wikipedia.org/wiki/Formaldehyde#Oxidation) to produce formic acid, which [readily decomposes](https://en.wikipedia.org/wiki/Formic_acid#Chemical_reactions) into H2O + CO in the presence of sulfuric acid, which is present in the [upper clouds of Venus](https://en.wikipedia.org/wiki/Sulfuric_acid#Venus).
For the ozone you mostly need only O2 due to the [ozone-oxygen cycle](https://en.wikipedia.org/wiki/Ozone%E2%80%93oxygen_cycle).
## Oxygen cycle
As per the missing production O2, this would be what plants usually do. [This wikipedia](https://en.wikipedia.org/wiki/Photosynthesis#Light_intensity_(irradiance),_wavelength_and_temperature) paragraph shows how increasing the temperature is either indifferent or improves the photosynthesis, but this may not apply to temperatures a bit over 100°C.
There are some like the [Chloroflexus aurantiacus](https://en.wikipedia.org/wiki/Chloroflexus_aurantiacus) that are able to do photosynthesis using bacteriochlorophyll instead of chlorophyll and grow at 70°C, but they don't produce O2 (this due to using bacteriochlorophyll). Others like [Cab. thermophilum](https://microbewiki.kenyon.edu/index.php/Candidatus_Chloracidobacterium_thermophilum) are able to use chlorophyll at 66°C, but they consumes O2 instead of producing it.
Even if I didn't found any O2 producing organism that lives at over 100°C, it's important to notice how such an environment is rather scarce on earth, which makes the few known cases have a rather low statistical relevance. There could be an alternative and possible evolution path where those exist, but it just didn't happen. From the data riported the existence of such a being seems plausible. On the other hand if there isn't such a being then the requested planet can't exist (no oxygen-producing airborne life at those temperatures).
# Environment planet-wise
## Required differences from Venus
First of all that planet should have a magnetic field like earth to reduce the loss of oxygen and hydrogen due to the solar wind, as they are both needed for life. Having a thermosphere is not a problem as both Earth and Venus have it.
Additionally a day duration more similar to the one on earth would allow for a more even temperature which helps (together with the CO2 that on the surface is a supercritical fluid with a good heat conduction) the organisms have the temperatures more near the mean of 100°C (131°C and they all die). This would have the effect of changing the wind circulation into one more earth-like.
## Consequences on sulfur
In a planet with an atmosphere composition like the one of Venus, the surface pressure would be around 90 bar, which is perfectly within range. As per the temperature, it'd surely be higher than the one of a planet like earth, but that would still depend on its distance from the sun. Just put it much further away and you'd get the desired surface temperature. This has also the effect of preventing the formation of the clouds as the sulfuric acid cycle needs a surface temperature of at least 300°C (which is not there) to [regenerate the clouds](https://en.wikipedia.org/wiki/Sulfuric_acid#Venus) from the acid rain like on Venus.
The result would make all the sulfuric acid stay mostly on the surface and a big reduction in SO2 content in the atmosphere, with clouds being created through evaporation like on earth. It's also worth notice how the surface temperature of 100°C is at 33% between the melting and boiling point of sulfuric acid, while the earth average of the surface sea is 16.1°C, roughly at 16% between the melting and boiling point of water. Being closer to the boiling point would create more clouds than on earth (it limits the photosynthesis), but still way less than the current situation on Venus.
## Life related atmospheric composition.
It's also important to consider that there would be a higher concentration of CH4 in the air due to the presence of the Methanopyrus kandleri. Additionally there would be two ways to consume O2: the atmospheric transformation of CH4 into CO2 and the Pyrolobus fumari that consumes H2 and O2. If the amount of CH4 produced is not enough to make the atmosphere fully consume the O2, the Pyrolobus fumari would help consuming the rest. This would result in an atmosphere with mostly CO2, and only in minor part of O2, CH4 and H2.
The low production of CH4 and consumption of CO2 could be attained by carefully choosing the surface temperature to control how fast each species reproduce. The amount of O2 present would probably be enough to kill the Pyrococcus furiosus needed to generate the H2, but I can't see why there couldn't exist a variation able to withstand a concentration of O2 a bit higher than that one.
This difference from Venus would help increasing the greenhouse effect due to the presence of CH4 instead of CO2, with the former having a greater [global warming potential](https://en.wikipedia.org/wiki/Global_warming_potential). Additionally it would reduce the pressure On the surface and depending on the variation, it may reduce the ability of the superfluid CO2 to conduct heat and keep the temperature uniform. This may complicate a bit the situation, but it wouldn't be a deal breaker
# other online resources used:
* <https://www.newscientist.com/article/dn14208-the-most-extreme-life-forms-in-the-universe/>
* <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4148896/#T1>
* <https://engineeringunits.com/pressure-at-depth-calculator/>
* <https://en.wikipedia.org/wiki/Atmosphere_of_Venus>
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With such temperatures you'd have another problem. At least, if your lifeforms are going to be anything like familiar biology.
Complex proteines break down at those temperature similar to how the proteine in meat changes its properties when subjected to high temperature, giving it its brown rather than pink or red coloration. The only thing coming remotely close to the kinds of lifeforms that could live in your environment are thermophiles with highly specialized enzymes. But that also has its limits, it doesn't allow for very complex and big proteine chains required for complex life. You'd have to deviate from carbon based since carbon based proteines simply won't hold up at such temperatures.
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As far as it is known, **Flywheels** are extremely efficient in energy storage, with the best even able to replace even the strongest batteries. They are accelerated by electricity to extremely high speeds, maintaining a sizeable amount of rotational kinetic energy.
[](https://i.stack.imgur.com/2vvRh.jpg)
So far, it is already possible to use Flywheels to power lasers:
<https://futurism.com/uk-laser-weapon-dragonfire-energy-flywheel>
In a forum, I came across an interesting idea to use a Flywheel's energy to propel bullets in guns and artillery. They said that with a flywheel made of an indestructible and frictionless material, say, Alexander Bolonkin's AB Matter, then you could store up to 10^11 joules in a 1 kg flywheel and fling things at .13 C.
By that idea, I believe that they were thinking of directly converting all of the flywheel's rotational energy to the bullet's kinetic energy.
I therefore ask if it is possible for this direct energy conversion. If that is possible, then the rest should be possible as well, for any flywheel power rating and subsequent bullet kinetic energy.
PS: Any size for the flywheels is fine.
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These kinds of weapons have been envisioned since the American Civil War, and likely before that
[](https://i.stack.imgur.com/oMYK0.jpg)
Demonstrations of these weapons showed they had a very high rate of fire and were extremely inaccurate. This is because the projectiles have no stabilizing spin orthogonal to the velocity vector.
Once the round leaves the centrifuge, it doesn't accelerate anymore, it travels at a fixed velocity in a straight line until turbulence from traveling through the air causes the round to veer off. I guess in outer space these weapons would be accurate but in worlds with atmospheres, the flight of the round is dominated by random forces.
If your weapon had a mechanism to impart spin on the projectile, then it would be more accurate. Modern rifling won't work since there isn't any force to push the projectile through the grooves of the barrel. The grooves would steal momentum from the round to impart spin, slowing it down considerably. Fins on the rear (or front) of the projectile could impart spin, but slowly, and at the cost of momentum. And the spin would take time to build up rotational velocity, so the first few moments out of the barrel the round would be dominated by random forces due to turbulence like an old-time cannonball.
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As a massive Battlebots fan, I think I have a neat idea for how it could work. A few robots there have used a flywheel to power a flipping arm, able to launch a 250 pound robot several feet in the air. A perfect example is [Blip](https://www.youtube.com/watch?v=bzZufNCXaeE). Bullets don't weigh anywhere near 250 pounds, and would end up travelling incredibly fast.
How Blip's mechanism works is it has a flywheel spun by a motor. The flywheel is attached to one half of a clutch system, the other half of which is connected to a bunch of ropes. When the clutch is engaged, these ropes twist, and the bundle shortens. This shortening pulls a lever, which is the arm. If you used a similar setup, make it smack into a bullet, you could launch it at ridiculous velocities. Plus, the air pressure provided by the acceleration would allow rifling.
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The exoplanet in question is [Proxima Centauri b](https://en.wikipedia.org/wiki/Proxima_Centauri_b). How might the mid-to-upper-level atmosphere of that planet be dangerously radioactive and full of airborne nuclear reagents, **without** it being the doings of an intelligent species?
**Edit.** I am aware that Proxima b is subject to extremely powerful solar winds from its host star, which makes it unlikely to have an atmosphere. However, if it were to have an atmosphere, is it possible that the gases that make up that atmosphere could react with the protons, electrons, alpha particles, etc. that it's being constantly bombarded with to undergo nuclear reactions as a result?
[Answer]
**Your planet is kicking out huge quantities of radon gas.**
<https://en.wikipedia.org/wiki/Radon>
>
> Radon is a chemical element with the symbol Rn and atomic number 86.
> It is a radioactive, colorless, odorless, tasteless noble gas. It
> occurs naturally in minute quantities as an intermediate step in the
> normal radioactive decay chains through which thorium and uranium
> slowly decay into lead and various other short-lived radioactive
> elements; radon itself is the immediate decay product of radium.
>
>
>
Radon can be problematic here on earth, even with the very low qualities of thorium and uranium in the crust. On a planet with much more of these heavy elements in the crust there would a lot more radon generated. It is heavy and so it will not be lost. As on Earth it will preferentially accumulate in low areas because it is heavy, but wind could carry it upward.
---
**Airborne particulate heavy metals.**
[Potential Human Health Effects of Uranium Mining, Processing, and Reclamation](https://www.ncbi.nlm.nih.gov/books/NBK201047/)
>
> Radon and its alpha-emitting radioactive decay products are generally
> the most important, but are not the only radionuclides of health
> concern associated with uranium mining and processing. Workers are
> also at risk from exposure to other radionuclides, including uranium
> itself, which undergo radioactive decay by alpha, beta, or gamma
> emission. In particular, radium-226 and its decay products (e.g.,
> bismuth-214 and lead-214) present alpha and gamma radiation hazards to
> uranium miners and processors. Radiation exposures to the general
> population resulting from off-site releases of radionuclides (e.g.,
> airborne radon decay products, airborne thorium-230 (230Th) or
> radium-226 (226Ra) particles, 226Ra in water supplies) present some
> risk...
>
>
>
If your world had enough uranium in the crust to make radon problematic, you could make volcanoes that spew uranium-containing ash high into the air. These particulates are long lived and can lodge in the lungs, and so are potentially more dangerous than radon. Volcanic ash particles can remain airbone for long periods and travel great distances. You could assert that the mid to upper atmosphere was contaminated by such particles.
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**Natural Nuclear Reactors**
A planet with high concentrations of uranium or other suitable fissile materials could contain numerous natural fission reactors like the one in Oklo, Gambon.
[Natural fission reactors](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor)
Perhaps these fission reactions happen when radioactive materials bubble up in lava flows and concentrate to the point where chain reactions kick off and they create radioactive waste. Then when the volcano erupts in full, the radioactive materials are blown into the stratosphere.
So, a highly volcanic world with large percentages of concentrated fissile material welling up from underground could be in a near constant state of having radioactive dust in the high stratosphere. Also, the presence of large quantities of radioactive material in the crust and mantle could be the reason why there is so much vulcanism, as the radioactive materials would add extra heat to the planet.
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I'm working on a roleplaying game in a medieval fantasy setting with a focus on crafting and I am having trouble visualizing how armor made from scales of creatures would be assembled; both for art and material list purposes. I wasn't able to find any good examples as animal scale isn't generally used for armor (understandable.)
In a setting where creatures existed that had scales that would be suitable for making armor, such as dragons, what would be the best approach for using those scales to make armor?
My first thought would be to use them in a similar fashion to historical metal scale armor. Metal scales are bound together with metal rings or heavy cord. Scales would have small holes punched in them for fastening and be used in place of metal. Scales of different sizes could be arranged in the way to make them most ideal to the wearer in terms of flexibility, fitment and protection. Quite a labor intensive task, but then again so was scale armor if you didn't have an efficient process.
While I was thinking on what the armor would look like, another approach came to mind. The scales are already bound together on the creature's skin, why not use that? Would it be practical to cut sections of the creature's skin, cure it, and stitch it back together as armor? Would this offer any benefits over the other approach?
Would both of these be viable ways to make armor using scales with their own benefits? Or am I overlooking a simpler solution?
For clarification: By "suitable for making armor," I mean that either the scales are comparable to metal in strength or have other beneficial properties (weight, magical effects, magic resistance, etc.) For the sake of the question, I'm using dragons as the example, however I am intending for their to be other scaled mythical creatures that armor can be made from.
Solutions I'm trying to avoid:
* Using magic, or other processes, to significantly alter the scales visibly. I want them to be visible and intact on finished armor. Kind of a status symbol for dragonslayers and accomplished adventurers.
* Using magic to adhere the scales to each other, or other materials. I want this to be something that can be done by tools. I'm seeing this as something that will require some really high quality (possibly enchanted) tools, but the majority of the work will be done by hand.
[Answer]
**Remove suitable scales and reattach them in a durable way using links or cord.**
[](https://i.stack.imgur.com/PJEhU.jpg)
<https://upload.wikimedia.org/wikipedia/commons/4/47/Japanese_scale_armor.JPG>
Depicted: scale mail made of leather scales. These synthetic scales are good because of uniformity of size. Also, a synthetic method of attachment means the mail owner can repair the armor in the field by sewing or attaching spare scales to replace damaged ones.
The natural attachment of scales to skin might be via organic structures which do not weather as well as the scales do. The scales will get loose and tend to fall out, like teeth from a skull.
If the function of the mail were purely ceremonial you could use a whole skin, like this crocodile scale armor.
[](https://i.stack.imgur.com/j0lD0.jpg)
<https://io9.gizmodo.com/roman-crocodile-armor-is-the-closest-thing-reality-has-5940451>
The source article states this armor was used in rituals for the Roman/Egyptian crocodile cult.
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I don't think the second solution would be practical, though you can always just make it possible by saying "so dragon's skin has these properties and can be used in these ways."
First one was viable except for the fact that dragon scales are generally considered the strongest material and cannot be damaged. How can you make holes in them? You would need good explanation there.
My answer is to create a new crafting method. this is a fantasy world so the crafting should also have something different from normal. You can use special fire that can melt scales or even a magic system for this purpose. Or maybe a special glue that can attach the scales to a metal or leather surface. Or maybe inscribing the same rune on all of the runes will make them stick together.
It depends on the premises and restrictions you set.
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## This will depend on what kind of scales the dragon has.
An easy way to make it specials is to consider if they have steel that can cut dragon scales why are they using dragon scale instead of that steel. So make the dragon scales harder/tougher than steel. You may say only adamantine can cut dragon scales but dragonhide is easier to come by than enough adamantine to make a full set of armor. Your players may have to have a quest just to find adamantine tools or an armor make who has such tools. Alternatively you could require that they use diamond tipped tools, magic, or the dragons own teeth to drill the scales.
Consider also how you dragon scales work, if they work like most reptile scales they are just thickened skin, that is the scales and skin are one contiguous material. Crocodilians have bony core to their scutes although the covering is the same. Fish scales are often made of enamel like teeth and they grow out of the skin and can be individually pulled out and overlap naturally. Emulating fish scales may be your best bet, since they are made of the hardest material available in the body.
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First, find a dead dragon.
Finding a dragon that is already dead is much safer than trying to kill a dragon or trying to get scales from a living dragon against its will.
If finding a dead dragon isn't possible, the next best thing would be to try to scavenge any scales that might be shed by a living dragon. One might have to try to trade gold for dragon scales.
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Scales connected to each other with cord or rings is called Lamallar, if you are interested in that method, direct your research to that term. Standard scale armor is attached to a backing, cloth, leather, or rarely a shirt of mail. That likely makes more sense than leaving it on the original skin, the scales falling out sounds like a very realistic fear.
How to craft it in a way that seems cool without magic? Your tools need to be of an alloy that can maintain some strength at high temperatures, then you work the scale with glowing hot tools. The heat softens the scales enough to make the holes.
Another idea... If the dragon has large scales, like shield size, you could use one scale as a breastplate and one as a backplate, carving the edges to fit for mobility, and adding straps.
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Design for an Extendable Melee Weapon?
**Background**
I've been working on a RolePlay setting, for me and friends. The setting mostly uses energy weapons, and at the higher levels, anti-energy shields (Beam deflecting shields, or laser reflective materials). This comes with a trade off, leaving energy shielded targets vulnerable to material weapons, such as bullets and melee weapons.
Which are far, *far* less common. Since one cannot dodge a laser, but can move away from a projectile impact.
The setting has power armor, and is fairly high-tech. Advanced enough for 'heat sabers' and 'vibrating sabers' which make mince-meat out... Most things, and 'Thunderhammers' jack hammers that explain blunt force trauma, in detail, to the those ignorant of it.
Since the average battle involves *heavy* firepower, ammunition can easily run out, having a melee weapon is a fairly good back up. Ignoring major problems, such as closing the distance, we reach the issue I'm having.
Volume.
How, exactly, do you compact a melee weapon IE; a halberd. Into a form that does not expose your silhouette to targeting programs and the like. *Then* somehow, extend back to fighting form when needed.
**Basically**
How to design weapons that are compact, capable of extending back into normal form?
(Being compact and capable of extension, are not required traits. If the solution still saves of on volume while being practical.)
[Answer]
Mechanized melee weapons have been experimented with, and they are the exception, not the norm, for a few very good reasons.
[](https://i.stack.imgur.com/msoG3.png)[](https://i.stack.imgur.com/4bKuR.png)[](https://i.stack.imgur.com/Hxqvb.png)
Basically, the more complicated an item is, the less durable it is.
Let's say that a blade made of some fictitious metal we'll call Aresium can be expected to withstand a 1 million joule impact per cubic centimeter of material. Let's say that, in the shape of a medieval longsword, is enough to get through the gaps in Power Armor. Here comes the problem: if you want it in the form of a retractable item, then you run into the chain-link issue: a mechanism is only as strong as its weakest part.
[](https://i.stack.imgur.com/esMVV.png)
If the blade folds on an Aresium mechanism whose smallest part is only half a cubic centimeter, then the weapon will break under the expected combat stress. To get the weapon to a minimum impact-ready level of sturdiness you need to make the smallest part of the mechanism twice as thick, which means making every other piece thicker to compensate, which adds a lot of weight and bulk, which is exactly the kind of thing you're trying to avoid in the first place by making it retractable.
The other problem is that the more complicated something is, the harder it is for a person to intuitively use. Have you noticed that a game of chess goes way slower than checkers? Now I'm not saying everything *has to be* simplified to oblivion, but when you're under stress, the less things you need to think about the better. People who actually know what combat is like don't *want* complicated gimmicky weapons because it'll slow them down. And in battle, half a second is all you have to save your life.
**Solution: Don't bother with fancy gimmicks.** Just make your melee weapon incredibly sturdy and stout, if you want it to be carried around as a sidearm.
And as you've said, melee weapons are rare in this world because they're only used if you happen to run out of ammo while the fight is still on, so you shouldn't be looking to things like halberds for inspiration, but rather to swords and knives.
Of course, if strength-enhancing power armor is part of the equation, then it's worth considering that a melee weapon is kind of redundant. Just punch the guy if it gets to that point, and it'll probably be lethal. A melee weapon would be marginally better in the sense that the wielder is more likely to win if the opponent is also out of ammo, and less likely to hurt his hand, but that scenario would be rare enough that most soldiers don't bother to consider it.
[](https://i.stack.imgur.com/IRhTx.png)
By Ysmir, if it's simple and strong, I can forge it.
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Considering you are working with really hi-tech power armor, we can assume that these EM shielded suits will also be taking advantage of materials at least as good as we have at our disposal today. A simple layer of graphene thinner than a sheet of paper will make this armor impenetrable by any normal melee weapon; so, it stands to reason that your melee weapons would not kill any better by impact or cutting than a plasma cannon would by heat. Instead they will need to bypass this armor in a way those ranged weapons can not.
A second consideration is that melee weapons are very rarely needed in a modern battle field. Since WWII, many militaries have trained their troops to use the battlefield tools that they already need as melee weapons so they are not carrying any extra weight.
**Bring in the Nanobots:**
In this situation, the nanobots will be a "swarm" of tiny robots that can crawl over each other at the microscopic scale, then interlock to become a solid form. (Think T-1000 from Terminator 2). This nanobot swarm can take on any shape for transportation such as forming a bracer around your wrist, or a brick you keep in a cargo pocket, etc. Being able to take on any shape, it is the ultimate field survival tool, it can become a shovel, a pick axe, a machete, a screwdriver, a spool of razor wire, a wrench, etc. Even if you never get into melee, it is still something every soldier would need, making it a logical investment.
While it may be assumed that this swarm of robots with all their little legs and machine bits would be brittle, materials such as graphene, carbon nanofibers, and synthetic goethite are so strong that even used sparingly, an interlocked nanoswarm could easily become strong as steel and as hard as diamond... which should be strong enough for all of your field tool needs.
When you get into range of an enemy, this tool can "come to life" and attack the opponent like a living tentacle, it will seek out the most vulnerable part of the armor (such as a breathing vent), and force its way in shredding through air filters and crawling in through the victim's mouth and nose where it has free reign to rip apart the squishy internal human bits with ease.
If you specifically want it to look and feel like a melee weapon, this is doable to. It could form into a long mace or war hammer, and on impact the head detaches and begins spreading out over its victim looking for soft spots to get into.
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Some harebrained ideas for hi tech melee weapons...
* Force field sword. Shape the weapon in whatever way you "normally" shape your fields, only this time the goal is something sharp and/or pointy. Perhaps a plane of force? Hard to explain unless your suits already have force fields, at which point this is just shaping the field around your hand (for example) to extend it into something dangerous.
* Monomolecular whip (with a little weight on the end to give it some control, or gravity manipulation, or more force field mojo to shape it as you like). Easily extended or retracted, ridiculously sharp, can be dangerous to the wielder.
* Someone else mentioned "inflatable". It need not be inflated with a gas. How about a fluid? How about a [non-Newtonian fluid](https://en.wikipedia.org/wiki/Non-Newtonian_fluid)? One that becomes solid with sufficient impact? Something like corn starch in water will harden when exposed to low frequency, forming standing waves. Throw in "a sufficiently advanced technology", and you don't even need a flexible tube to hold the fluid, you can just vibrate it into the shape you want, and slurp it back up when you're done.
+ Bonus points if the end result is a fractal, because that sounds like something a series of vibrations would induce in the final shape. [Flamberge](https://en.wikipedia.org/wiki/Flame-bladed_sword#/media/File:Dresden-Zwinger-Armoury-Sword.04.JPG) + [Mandlebrot](https://en.wikipedia.org/wiki/Mandelbrot_set) = Mandleberge!
+ Bonus points if your armor is already using some of said fluid to make it's joints flexible but still harden on impact... at which point this is merely weaponizing your refill tube.
* I had this crazy idea for a magic world setting you could apply using Sufficiently Advanced Technology: The ability to change an object's mass based on the "frame of reference". As far as the grip is concerned, an object might weigh 1/N of its actual mass, while from the business end, it could weigh xN times its actual mass... so make N = 4... or 1000. Combine that with someone's idea of a memory metal belt/sword, and you have something that can apply a ridiculous amount of kinetic energy in a very small space, and is easy to carry. Or an Asp-like collapsing baton that hits like it weighs several tons (being swung by someone as though it had zero mass). This sort of thing would have to be parried by something similarly affected... or just huge.
* Non-traditional melee damage. Weapons that look like swords or spears or whatever, and are used that way...
+ ...but are actually hacking tools that need to be close enough to work on enemy armor/gear/whatever.
+ ...but are actually capable of doing something Really Unpleasant at the business end that doesn't involve impact. "de-bonds oxygen atoms", "cloud of unstable sub-dimensional pinholes", heat, vibrations, gravity, EMP. Give any of these effect the range of a few millimeters, and it makes for a convincing melee weapon. Not sure how to explain parrying. Hmmm
[Answer]
So I can think of a few ways to get weaponry that will extend.
1. As Nosajimiki mentioned in comments, nanotech should be able to do this, though I would assume that it would only hold it's form when you're providing it power.
2. Memory metal wouldn't expand per se, but could move from say a belt to a sword maybe? Again, you'd have to provide power of some form to make the change.
3. How about an inflatable weapon? Especially if you inflate via a foam that creates a (semi) solid interior to the weapon. Disadvantages to that would be it probably would take a couple of seconds to expand and solidify, and once it's expanded, it probably won't be able to be compressed again.
4. Finally, how about your standard expandable baton as lidar mentioned? Something like the denn'bok the Rangers used in Babylon 5 if you want a more high tech version - <https://babylon5.fandom.com/wiki/Denn%27bok>.
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I want to make my dragon spew/breathe an explosive mix with gizzard stone fragments/shrapnel, more like a shotgun than the common flamethrower-like fire breath.
So is there any explosive chemical that can be reproduced biologically and be safely contained in the creature's internal organs? (I mean something like a gunpowder explosion not a hot water jet like a bombardier beetle or from pure pressure or muscle contractions, although I don't want to exclude a liquid type of explosion.) If possible include the pros and cons/risk of such a chemical to the dragon.
What kind of organs would need to be developed or changed to achieve this?
Maybe the dragon teeth could be retracted so the teeth won't get knocked out.
Similar to [Toothless](https://howtotrainyourdragon.fandom.com/wiki/Toothless_(Franchise)) from [How to Train your Dragon](https://www.dreamworks.com/how-to-train-your-dragon)
[](https://i.stack.imgur.com/SNiCC.gif)
I'm also considering shark teeth like growth, so if retracting the teeth is impossible biologically, at least the teeth can be knocked into the other sharp shrapnel with the gizzard stones without fear of really becoming Toothless.
Or should I use the tongue like a cannon to spew or breath the explosive instead?
Or should I use a mouth shaped like a cannon or a seahorse mouth instead? If I need to modify the mouth, please also provide a likely food source or a way for them to eat. (They are pure carnivores by the way.)
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Such explosive shells are made, naturally enough, by shell glands. A peculiarity of evolution has caused the dragon to grow blind-ended oviducts in its larynx, which produce lumps of albumen that are then wrapped up in a hardened shell.
However, in this particular instance, the "albumen" is actually a collection of vesicles of ammonium nitrite (note the "i" - less stable). These are produced by pumping the two ions, ammonium and nitrite, into vesicles where they then precipitate at high concentration. The nitrite is produced by symbiotic intestinal bacteria; unfortunately, it means that dragon meat must formally be marked "Processed Meat" at the supermarket, even when fresh. But the oviducts remove it avidly from the blood, keeping the concentration relatively low in most tissues.. The vesicles accumulate at the tips of the cells of the upper oviducts which are lost by apocrine secretion.
Also the "shell" is much thicker. Perhaps it is only calcium, perhaps with protein filaments that help it to shatter in a jagged manner. This evolution - for shrapnel - has not been tested on Earth.
Residual cytoplasm of the secretory cells is able to respond to cues from the dragon, "arming" the vesicles by changing their pH (more acid, if I recall) to destabilize the nitrite. This process should be reversed quickly if they are not used. The instability should be such that a strong shock, transmitted via the shattering calcium shell, creates points of pressure sufficient to set off the vesicles ... of course, it is vital that they not be any more unstable than this!
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It should be possible for your dragon to pick up pebbles, which it stores in a small pouch near its throat. When it needs to attack, the pouch will contract and bring the pebbles to the back of its mouth. Muscles in the throat will block of the oesophagus and the nose, so that when the dragon forcefully exhales, the air from its lungs forces out the pebbles in an explosive manner. Surprisingly, most species can already do something similar, even humans. We call it...coughing.
[Answer]
## Sabot Rounds:
I think you can come up with a variety of biochemical explosives; these have been addressed many times in numerous variants in worldbuilding. But I think you need to address the larger problems with your technique, and come up with a solution to your dragon-on-dragon fighting.
First, internal explosions are very challenging for organic life. Lots of our parts are soft, mushy, and prone to tearing, crushing, and shock effects. I think that you can compensate for most of these with a tough, bone/shell tube with lots of muscle, but that barrel will still be rather elastic (to deal with recoil and shock) and tend to absorb much of the force of the blast. So your projectiles will tend to be underpowered.
Second, you are fighting dragons, who have presumably evolved to deal with this kind of attack. The likely have various layers of composite sandwiching to absorb shrapnel and relatively low-velocity piercing attacks. In other words, what they can't dodge probably can't penetrate.
What you need is a [sabot round](https://en.wikipedia.org/wiki/Sabot_(firearms)). Your dragon needs to apply more force to a small projectile than what an average dragon throat will probably be able to manage. Further, most tiny, armor-piercing aerodynamic projectiles won't conveniently fire out of a large cannon-barrel/dragon throat - the shape would be wrong.
So your dragon manages a relatively large but low pressure explosion using whatever flammable gas they can muster for a dragon breath. But the dragon has laid an internal egg. This can be a hard shell/calcium carbonate spike, or perhaps something heavy and thin it has swallowed and built up a pearly coating on like a clam (this might explain dragons attacking knights - they want to swallow swords and dense sharp metals).
The egg creates a sabot around the projectile, so the gasses are trapped and efficiently propel the missile out of whatever orifice the dragon is firing. The shell flies apart as soon as it leaves the dragon, and the small armor piercing projectile has lots of kinetic energy and possibly even aerodynamics to penetrate it's armored foe.
* As an alternative to the sabot design, an egg similar to what Mike Serfas was proposing could be internally manufactured but then laid and carried in a special armored pocket on the dragon. Accidental detonations would be carried away like a shaped charge or claymore. The dragon could use a prehensile tail to hurl these projectiles at their enemies, allowing the explosives to be safer for the thrower and not requiring so much internal modification of the dragon to work.
[](https://i.stack.imgur.com/Recpp.png)[](https://i.stack.imgur.com/G3IP6.png)
[](https://i.stack.imgur.com/isSEm.png)
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The planet is huge roughly four times the size of earth, with lots of hydrogen in its atmosphere (group A water in Hydrogen out, B water out.) it is also very humid. what do I do to have giant Storms in the sky with Fire instead of thunder? What would these storms look like?
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**Flame cloud deflagrations.**
1. The surface of your world is mostly reduced gases: hydrogen, water, maybe some ammonia, methane.
2. On the surface the humidity and fog shields life from most solar radiation. In the higher atmosphere, energetic rays from your sun cause [photodissociation](https://en.wikipedia.org/wiki/Photodissociation) of molecules. The main effect of this is to strip oxygen out of water, producing molecular oxygen (O2) and ozone (O3-). These are high enough in altitude to be low concentrations and it is cold up there, so these reactive oxygen species can accumulate without reacting away.
3: During your storms there is atmospheric mixing. Oxygen rich gases from the upper atmosphere are pulled down into denser regions. They come into contact with hydrogen gas. When concentrations are right and there is a spark, the oxygen and hydrogen combine energetically.
In these circumstances there would be an excess of hydrogen and a relatively small amount of oxygen. The result would be a slow moving wave of flame, or deflagration.
[](https://i.stack.imgur.com/81DHH.jpg)
<https://www.youtube.com/watch?v=6gkblppESHA&t=6s>
>
> A balloon filled with 100% hydrogen is ignited with a small flame. As
> the flame ignites the hydrogen gas, it combines with oxygen in the
> surrounding air. A large, but relatively slowly moving ball of fire is
> created. This is called a deflagration.
>
>
>
Depicted is the deflagration - the supersonic one is next and it is an explosion, not a sweet flame cloud.
**These are your clouds of fire.** Flame is hot gas and so would rise. An initial fireball would spread laterally according to air currents. In still conditions it could form a spreading, rising ring of fire as oxygen is exhausted in the center. Very big rings would just look like a wall of flame moving across the sky, curling and rising as it went.
H2+O2-> 2 H2O. The result of these flame clouds is water vapor. This would condense in the upper atmosphere and serve to nucleate raindrops. I could imaging that under conditions of atmospheric turnover, a storm begins with flame clouds of this sort which in turn start the rain. Once the rain starts in earnest few additional flame clouds form.
[Answer]
[Handwavium explanation]
Without Oxygen, you will have a hard time burning the hydrogen to create a fire.
Since you do not mention the composition of atmosphere, one possible way you can achieve the Firestorm could be via a sudden outburst of oxygen in the atmosphere leading to the right conditions, which are otherwise absent.
This could be due to geological events disturbing internal rock formations storing oxygen - which got formed in the first place due to microbial activity decomposing water into Hydrogen and oxygen. Now, you want this firestorm to take the place of thunder. The regular thunder is produced by interaction of clouds. Instead, you can use a cyclone - they can easily span 400-700kms. This gives you [something like a firenado](https://www.youtube.com/watch?v=9ua4L5CnIq0), which you can modify to support taking the oxygen to the upper reaches of the cyclone, where it interacts with hydrogen to lighten up
Another property you could utilize here is that oxygen is much heavier than hydrogen, so they both would be at different altitudes in the atmosphere. So, by using a geological/climatic phenomena that brings the two in contact - say via heating up of surface by sun's rays, variations of walker cycle etc, you can then lighten them up.
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Is it possible for an organism to evolve a capacitor if the conditions were right (carnivore that stuns fish, living in complete darkness, etc.)? What kind of challenges would there be to evolve something like this? What fluid would it most likely be present in? I was looking at Wikipedia's page on electric eels and was just wondering about this. I'm learning about electrical fields and voltages in my college classes right now.
[Answer]
A capacitor is, in its bare components, a dielectric separating two opposite charges.
An electric eel creates its discharge by separating ions via an energy pump and opening the channel on demand.
Therefore, in a way, living organisms have already evolved a capacitor. It doesn't come with the package we see in printed boards, it has no color coding, but it does its job.
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Think of a species (ONLY ONE SPECIES) the individuals all live in the same environment, share the same sentience level BUT are divided into "A", "B" and "C" races which have different number of limbs, eyes, natural weapons, etc.
For example A has tentacles, B has bird legs and feet, C has horse legs, this sort of different.
They are able to interbreed and have fertile hybrid offspring, but the hybridization would last only for one generation, like if A and B have an offspring, it will be an hybrid AB, now if AB has offspring with A, all their children will be pure A, if AB has offspring with B, their children will pure B.
If an AB breeds with C, their offspring will be AC or BC hybrids. (AB +AB = 25% chance of pure A 25% chance of pure B, 50% chance AB hybrid).
Are aliens that have this sort of genetics, crazy different appearances, and only 1 generation lasting hybrids, possible?
Can this be explained by epi-genetics?
Is this possible at all?
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The early hominid period on earth had many highly intelligent species of ape existing in a relatively narrow band of time and often overlapping with one another, so that part of this question isn't so far fetched. If things had gone different and modern humans had proven to be less successful than we were, it isn't so hard to believe that there would have been a period where humans co-existed on this planet with Neanderthals and the like. Hybridization between modern humans and Neanderthals has also long been theorized as having been possible, so that portion of your theory is also somewhat possible.
However, it gets more complicated when you talk about things like not inheriting the traits of one's grandparents. That's very unlikely, and I'm not even sure it's possible at all. Even we contain the genetic remnants of ancient retroviruses that ravaged animal populations in the distant past, so the idea that somehow the grandparent's genes just aren't inherited at all is difficult to accept.
Bringing epigenetics into is an interesting idea, but I'm not sure it would solve your problem, at least not to the vast extent you're looking for. The changes in gene expression from epigenetics, at least as my *very* limited knowledge on the subject indicates, tend to be much more subtle than, say, causing a chitinous exoskeleton to grow in place of normal body hair.
The idea of a number of closely related species with vastly different traits, however, is not as out of the question. For instance: coyotes, grey wolves, and domestic dogs can all reproduce with one another and produce viable fertile offspring, despite the vast difference between say a wolf and a basset hound. However, some of the differences you describe would almost require organisms that fit into completely different species, assuming these alien organisms play by the same rulebook as earth. Boneless tentacles are genetically far different from horse legs. Gills and bug wings are almost more closely related (bug wings having ostensibly evolved from modified gills).
[Answer]
This arrangement is very possible and we don't need anything like epigenetics to explain it either. Your idea can be explained by classical Mendelian genetics, all we have to do is say that your alien species has two copies of a single, large chromosome.
To explain how this will work let's first go over some basics. Most genomes of multicellular life on Earth are fragmented into many chromosomes which are all inherited randomly. You have two copies of any given chromosome, one from your father and one from your mother. Your parents each had two copies themselves and random chance dictated which of those two copies you happened to inherit. Since we have 23 unique chromosomes that means each new generation represents a shuffling of alleles and traits. Because there are so many chromosomes and because of other mechanisms like [crossing over](https://en.wikipedia.org/wiki/Chromosomal_crossover) that further shuffle alleles each subsequent generation is a mixture of its parents' genomes. So you have roughly one-half of the genes of your parents, and roughly one-quarter of the genes of your grandparents, etc. With each generation, the many alleles in our genomes continue to mix with nearly infinite possibilities.
But what if instead, we had two copies of only one large chromosome which never crossed over? Now you would have discrete genetic possibilities without the potential for further mixing. So when your hybrids reproduce they won't produce further hybrids, rather their offspring will be either be hybrids (heterozygous) or revert back to purebred (homozygous). This is almost exactly the system you described above with one minor change. An AB individual reproducing with a BB individual would result in half of the offspring being AB and half being BB.
Basically, your organisms function as if they have only a single monoallelic trait. We often examine these systems using simple [Punnett squares](https://en.wikipedia.org/wiki/Punnett_square). By forcing the entire genome to be inherited as a single unit the whole organism now only has one "allele" and so all of the crosses you can make will obey the laws of the simple Punnett square and classical Mendelian inheritance.
You aren't limited to just 2 or 3 of these chromosomes either. You could have dozens of unique [haplotypes](https://en.wikipedia.org/wiki/Haplotype) if you wanted.
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It is in theory possible for something *like* your arrangement to exist in a species. It wouldn't last long and has horrible consequences for a lot of things, though.
Your species will require its morphogenic (body-planning) genes to be on a single chromosome. This might work, but is obviously unnatural. This chromosome is the "race" chromosome, similar to the sex chromosomes in real animals.
This means that an AB "hybrid" (race chromosomes AB) breeding with a purebred B (race chromosomes BB) has a 50% chance of another AB hybrid, which violates your "no grandchild hybrids" rule. This system also requires genetic infrastructure to stop gene shuffling between different race chromosomes.
However, this idea is dumb. See, your critters are going to have different requirements depending on what niche in the ecology of their environment. Something like a squirrel that lives on nuts and berries will require a different digestive tract compared to a predator, and both have different systems compared to a cow. A burrower is going to require different senses as compared to an airborne predator or an airborne scavenger. You're going to have to move so much on to the race chromosome that you're going to put the entire genome on it.
And hybrids are going to be a dead end. What do you get when you cross a buffalo's body plan with a wolf's? Something too slow to hunt but too small to be a ruminant (and therefore graze.)
Hybrids aren't going to happen either. Herbivores aren't going to want to mate with predators, and predators would eat herbivores rather than breed with them. The most available mates would likely be that of the same race.
[Answer]
I can think of two mechanisms to keep your 'Crazy Genetics' model self-sustaining.
They both deal with the species RNA.
The first mechanism is to assert that the RNA encoding only supports replication of A, B, C and pure combinations of those genotypes. When RNA encounters a hybridize form that would result in a non-pure (1/2 A and 1/2 C genes, for example) the RNA function stops, jams in a way, or stops operation entirely. The consequence of this is that mitosis and cell division would be impossible, meaning that any offspring of an AB parent and C parent will only be viable is its genotype is AC and other possible combinations would be non-viable in utero.
The other mechanism is similar, but the RNA replications the missing fraction of the genetic code using an internal encoding inherited intact from the mother. This mechanism would only be invoked in the case of the offspring was potentially hybridized, then it would make offspring have the same genotype as the mother.
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Something similar is happening in nature through not as crazy as you implied, just look at ants or bees, their queens have more or less DNA with their workers, but look totally different.
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So, there are birdpeople/birdfolk in my setting. They're ~170 cm tall bipedal humanoids with a pair of functioning wings, slightly below the shoulders. They're covered with feathers, except for the hands and legs, both of which have talons, though smaller on the hands. Their necks are slightly longer than humans'. Birdpeople have a head and facial structure very similar to bald eagles in shape (same as humans' in size), as well as a beak (though the type of that can vary).
Now, just like dragons, they usually glide (assume patterns and speed similar to the andean condor) as flight is energy-intensive at this size, and daddy anon is yet to cook up a solution.
I was in the middle of designing the armor when the whole gliding thing hit me. That would effect armor design and in ways which I've never anticipated.
The armor is made of laminated linen plates and a thinner gambeson underneath.
*What design (i.e: armor plate shape and placement) would provide the most protection and mobility with the smallest extra weight to a gliding birdfolk?*
**Assume medieval weaponry as the threat, with altitudes within range for bows and crossbows.**
Note: Birdfolk don't have to worry about aerial attacks. The reasons are complicated, scaly and blue...
[Answer]
**Flying sled shield.**
[](https://i.stack.imgur.com/2nACA.jpg)
<https://dancingwithfools.wordpress.com/2008/12/28/sunny-sunday-37/flying-kid-on-sled/>
Like a sled one lies upon, the armor would be a thin shield, shaped in the outline of the bird person with outstretched wings. It would be thin and aerodynamic, affixed to chest and ankles. The good thing about gliding is that the shape of the bird (or bird person) is fairly static and so a shield can give good coverage. The aerodynamic sled / shield would actually help to stabilize the flyer by allowing it to use its arms as a second set of wings; in this role the shield might actually be considerably larger than the flyer, occluding its body completely with viewing holes to look through.
The shield can be painted according to sky conditions to offer a measure of camouflage against the sky. Or painted flat black with big eyes, to be scary.
[Answer]
Several problems present themselves.
First, as you alluded to, the weight of the armour could make it prohibitive to fly. since the creature is already a glider by nature, the extra mass will make it far more difficult to take off or do powered manouevres when necessary
The second major issue is aerodynamics. The shape and structure of the armour (or any other things like clothing, packs etc. must not disturb the airflow in any major way. Disturbing the airflow will radically reduce the glide ratio and possibly even make flight unstable in different regimes. The Boeing 737 Max design suffered from that defect when the placement of the new engines caused the aerodynamics of the plane to change in an undesirable manner, which the engineers attempted to overcome with an active control system. Your beings will not have a computer assisting their flight (and the record of Boeing's active assist isn't looking very good).
Related to aerodynamics is how the armour will affect the articulation of the being. If you play a sport like Hockey or American football, you play with layers of padding and hard protection surrounding you. Despite the best efforts of designers, you will never have 100% of the mobility of an unencumbered person. The same considerations apply for military armour, from ancient to medieval to modern times. If the creature is being encumbered by protective armour, this might affect the ability to make the subtle movements of the wings needed for complex flight.
Finally, there is the issue of what exactly you are protecting against? Are the bird people only subject to ground fire, or do they have to consider attacks from the air by other members of their species? What sort of weapons are being protected against? If most of the fighting is in the air, then weapons like light crossbows, bolas and nets might be the major threat. If they land on the ground to fight, then edged weapons like swords, spears and knives are the primary threat, as are smashing weapons like maces. Each different threat will require different sorts of armour protection, and a protective ensemble which works in one situation might only provide limited protection elsewhere.
So without these details, it is actually difficult to provide any sort of clear answer.
[Answer]
Your birds use a special leather armor which feathers are passed through via holes. The leather armor itself must be worn by the bird in question as they grow new feathers (or molt), to ensure that the armor doesn't effect their flying and remains hidden (feathers can be puffed up to help hide a birds body) against their skin (its worn on the skin, under the feathers, with holes for the feathers to pass-through). Small metal scales are then attached to this leather.
The armor covers your birds heart, one of their most vital organs. You position it so that when your bird is attacking with its talons extended, it will block the path of a shot straight to its chest. For the rest of their body, your birds rely on their feathers to disguise their figure as additional armor will make them far too heavy.
[Answer]
Weight will be the biggest concern for the armour as they need to maintain flight. Limiting the plating to only the anterior of their bodies will halve the material needed and if they maintain positioning where they are facing the ground the posterior need not be protected.
Laminated linen may be light, but it may not offer the protection required from arrow heads. Instead, bird bones could be fashioned into chain-mail like material with linen holding the pieces together.
[Answer]
Something hollow might do, and a few slabs of flat kevlar. If you want metal, it's going to be harder, but aluminium might do wonders here, depending on how large and wide the wings are. You want the bird to be able to fly while wearing it, I think.
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Earth's deepest point, the Challenger Deep, is almost seven miles below sea level. By contrast, Europa is smaller than even Earth's moon, yet its oceans are anywhere between 40-100 miles deep! So the basic question is--would it be tectonically feasible for Earth's oceans to be as deep as Europa's? Meaning, would it still have active plate tectonics and above-sea-level landmasses?
[Answer]
Europa has a surface gravity of about $13\%$ of Earth's. This means the force (weight) of the water in Europa's oceans is proportionately less than on Earth. If you divide Earth's deepest ocean depth (about $11\,km$) by $0.13$ you get a "Europa equivalent depth" of about $85\,km$, which is actually the ballpark for Europa's deepest ocean depth estimates.
Earth is much larger and because of this the gravitational pull hardly changes from the surface to a depth of only $11\,km$. Put simply water at the surface weighs about the same at the deepest point of our oceans.
This is not the same for Europa, which is much smaller. Gravity at the bottom of Europa's ocean has decreased by about $7\%$ from it's surface value, so water weighs *less* further down and hence has a reduced pressure. This makes it a bit easier for the internal structure of Europa to support the extra ocean depth.
There is more to this. Earth's interior structure is quite different from Europa's. Somewhere inside Europa there may be a metallic core (like Earth) but mostly it's an icy lump of water. The boundary between ocean and solid on Europa is likely to be a more like a transition between frozen and liquid states of water than the boundary between totally different materials as it is on Earth. On Earth what you see on the surface is essentially all the water their is to exist as an ocean, whereas on Europa what you have is the ocean being continuous, but freezing (or compressing) to a solid after some depth.
**Could Earth support deeper oceans.**
Short answer "yes", long answer "probably not a lot more".
You will hear a lot of talk about global warming melting the ice caps and increasing sea levels. So you know from this that Earth's surface can support deeper oceans, but we're not talking about a hundred kilometers more, but maybe a kilometer more at most.
As I said, Earth's gravity is far greater than Europa's and if we increased the depth of Earth's ocean by a factor of $8\times$ you would have a huge extra weight of water on Earth's surface. This would alter the balance of forces a lot and I'd be guessing but would say their their would quite a difference in the way the plate tectonics function. Landmasses above sea level seem unlikely. Earth's highest mountain ranges are limited by the ability of the material to be supported by the "sub-levels" of planet's outer layers. Adding an ocean as deep as Europa's would be like making a mountain two or three times higher - they would push into the sub-layers and sink - they'd never actually exist in the first place. An island is no different. A continent is no different either when you get down to it. So it seems unlikely we'd have much (if any) landmass about sea level.
Everest is $8\,km$ high, so adding more that $8,km$ of land (about the equivalent of $24,km$ of water) is the most weight we could expect to be supportable, but the land cannot raise that high (it's denser) so the most you can do is add about $8\,km$ of ocean depth and leave "Everest island" as practically the only land mass (with a few other tall peaks).
[Answer]
Plate tectonics has nothing to do with sea level; you can have plate tectonics with no water or tons of water.
Given Earth's actual landmasses, no, there would be no above-sea-level land. I am hesitant to say it is impossible on any Earth-like planet, but 40 miles seems insane to me. Mount Everest is only 5.5 miles tall. The issue is that the Earth's crust floats on the semi-liquid mantle. The higher a mountain gets, the more weight it has, and the more the crust beneath it sinks into the mantle. This causes two problems if you want really tall mountains. First, as crust under the mountain sinks, it'll drag the mountain down with it. So relative to the surrounding terrain, your mountain stops getting taller and just gets wider. It's a diminishing returns thing. One ton of rock might add a meter of height at first, but by 10km another ton might only add 20cm. Second, eventually the mountain weighs so much that the crust beneath it starts getting pushed too deeply into the mantle, and it melts. You just can't add any more material. For every ton you add to the top, a ton melts off the bottom.
But I don't think you can have 40 mile deep oceans on an Earth-like planet anyways. Water can't be a liquid below about 0.006atm of air pressure, which happens on Earth at about 12 miles. You need a much denser atmosphere, or a planet-wide sheet of ice like on Europa if you want a 40 mile deep ocean.
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Imagine a creature much like ourselves that can control the usage of their own mind.
For example, a dying ancestor may tell some parting words which are so important that the individual explicitly saves them in their mind, with no way of the memory fading unless it is consciously 'unremembered'.
Another example would be a life-threatening scenario that made the individuals purposefully increase the strength of their capabilities (e.g. less sensory filtering and more processing) at the cost of other memories and skills, which later would have to be re-learned.
Usually they have no need to take such drastic measures, and it may take a lot of learning and concentration to master (preventing children from accidentally damaging themselves).
**Could such a brain be**, at least in theory, **possible? What drawbacks might there be?**
[Answer]
This is basically what the brain already does, but ramped up to 11 and in control of the conscious mind.
The problem is that this requires a very specific mind. During development your brain makes millions of connections with other parts of the brains, then at some point it starts to purposefully remove many of these, leaving the most used neural pathways and optimizing those. This accelerates thoughts as less energy and time is spend on what the removed pathways send around. Unfortunately this also means that if you want to use a brain segment normally used for storing a skill or memory for something else that there are few neural pathways connecting them. You would skip the neural pathway pruning and end up with a specific disorder: Autism. Now unlike popular opinion most people with autism arent unsocial people who scream at everything, in fact most people with autism are so good at learning to fake social interactions that they arent discovered even when they get unspecific psychological tests.
Then there is your idea for less sensory filtering. A suggestion is not to include that but shift it to a more specific sensory filtering, something the body already does. Talk about lice in front of people and the brain starts letting signals about itches through to the brain, signals that were filtered before. Gate theory (<https://en.m.wikipedia.org/wiki/Gate_control_theory>) is a part of this system.
Funnily enough, less sensory filtering is also a part of autism. Due to the "unnecessary" neural pathways and less filtering the brain is more easily overloaded, stuck trying to sift through all the information its bombarded with and unable to process more. The classical screaming autist that is practically a meme nowadays is one way this overload can express itself, its a (partially successful) coping mechanism to reduce the amount of sensory input, if only by making said input move away. More common though is unresponsiveness to outward stimuli or getting stuck performing a repetitive task to engage the conscious until the subconscious has figured everything out again.
Tl, dr: yes this is possible if you change the "less sensory filtering" into "more specific sensory filtering" and are willing to accept a partially autistic mind. Since your brain development would not have autistic filtering it would only think like an autist and suffer less from the negatives.
<https://scholar.google.nl/scholar?q=advantages+of+autism+spectrum+disorder&hl=nl&as_sdt=0&as_vis=1&oi=scholart#d=gs_qabs&u=%23p%3DSC7pbf1B-WcJ>
<https://www.verywellhealth.com/top-terrific-traits-of-autistic-people-260321>
Ignore the first point of "autistic people rarely lie", autistic people have trouble learning how to properly lie and get caught when they do, so they will stop trying to lie and tell truths. Your person would be able to learn lies.
[Answer]
For what we know, reducing the sensory filtering just overloads the brain, leaving very few capacity left for any other task. It is more or less what happens in the [Savant syndrome](https://en.wikipedia.org/wiki/Savant_syndrome).
>
> Savant syndrome is a condition in which someone with significant mental disabilities demonstrates certain abilities far in excess of average. The skills at which savants excel are generally related to memory. This may include rapid calculation, artistic ability, map making, or musical ability. Usually just one special skill is present.
>
>
>
What usually happens in time of needs is that the brain discards additional information.
The savant syndrome cannot be voluntarily triggered, but I think you have seen that when people are deeply focused in something they might often miss other important information from the outside world (i.e. people hitting a pole while walking and looking at their smartphone).
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I have an idea for an extremely crackpot engine design for a future society I may incorporate into my story.
What would happen is individual antihydrogen molecules injected into the center of carbon fullerene molecules using the combined electron clouds of the atoms to repel the antimatter into the center of the fullerene spheres so they don't touch anything. This keeps the antimatter from annihilating anything until needed for use.
Now to ignite the engine an electric spark is used to ignite the fullerene, releasing the antimatter creating annihilation. The annihilation would create an explosion that drives a piston turning a crankshaft.
Assuming a plentiful antimatter supply and the manufacturing to make a chamber capable of absorbing the impact and produce this sort of fuel in large numbers is this at all feasible?
[Answer]
Antimatter reactions are quite awkward things to make use of on a small scale, or in the presense of delicate things like people or electronics.
About a third of the energy liberated by the reaction comes out in the form of gamma rays. These won't be absorbed well by the fuel you're burning, but will heat up the engine block pretty effectively.
Most of the rest of the two thirds of the energy released comes out in the form of charged pions. Some of these will do interesting things to your fuel and heat it up (which is good!) but more are likely to just heat up your engine block (which is quite bad) and depending on how much shielding you have plenty more will just sail out into the space around your engine and decay into gamma rays out there. You'll need a decent amount of radiation shielding, and a decent amount of cooling. This is all heavy and inconvenient.
Can I make an alternative suggestion?
I give you... the **antimatter train**.
The engine is basically a [solid core antimatter rocket](http://www.projectrho.com/public_html/rocket/enginelist.php#id--Antimatter--Solid_Core). A cylinder of some dense, high-melting point metal filled with holes for water to run through. You liberate your antimatter in the centre of the cylinder, and most of the energy of the reaction products will go to heating up the cylinder which will also do a reasonable job of shielding spectators from deadly radiation.
The antimatter rocket needs to operate at a couple of thousand kelvin to be worthwhile, but the train can get away with merely enough to generate superheated steam. Then you just use that to run a conventional piston engine, or if you're being boring, a steam turbine. Now all you need is a very small fuel tank and a generous supply of water and you're good to go.
(some inspiration from the nuclear fission trains in *Singularity Sky*)
[Answer]
A company by the name of [General Fusion](https://en.wikipedia.org/wiki/General_Fusion) has a somewhat similar design for a nuclear fusion reactor. It is possible that the matter/antimatter reaction will create a form of harmful radiation that would need to be dealt with, or at least contained inside the reaction chamber. I would argue that attempting to store antimatter is not the best approach, as a failure of the containment vessel would be catastrophic. A better approach would be to generate the antimatter on the fly, expose it to its matter counter part, and then use the resulting explosion to power your pistons. You could also use the heat generated by the annihilation process to boil water and create steam similar to nuclear reactors.
[Answer]
Fullerenes are not able to contain antimatter. They are electrically neutral, to contain antimatter you either need to have it charged and use a ion trap, or freeze it and levitate it, to keep it from interacting with matter.
] |
[Question]
[
Assume these homo super-dwarf aka fairy and homo sapiens come from a common ancestor, and somehow they evolved a pair of wings and can do vertical takeoff.
The average adult is approximately the size of a tennis ball and weights around 58g, they are mammal by the way so how can they hover at the same flower for up to thirty minutes?
I think they belong to specie Homo genus Nimis Parvus....
[Answer]
They are a branch of the homo tree, but they ended up on a converging path together with bats.
Actually, there are [bats which are known for eating nectar from flowers](https://blog.nwf.org/2014/06/not-just-the-birds-and-bees-6-fast-facts-about-pollinating-bats/), for which hovering is a necessary ability.
Your specimens grew a membrane between their arms and body, exactly like bats did, and use it as wings.
[Answer]
Fairies could develop flight along similar lines to bats. They would evolve patagia (membranous skin) stretched from their arms to their sides and use these as "parachutes", slowing their fall as they jumped from trees. Eventually, they'd learn to flap and cover distance as they fell, until they ended up with the ability of powered flight.
[](https://i.stack.imgur.com/cchNq.jpg)
Keeping with the bat idea, there are hovering bats - they're called nectar bats, genus *Lonchophylla*, and there are 8 species. They do this by continually twisting their wings backward as they bring them up, keeping a constant flow of air downward to keep them in place. Them and hummingbirds are the only vertebrates which can perform hovering.
---
Now, normally, a 58-gram placental mammal would only need to consume about 47 kilocalories a day, according to my calculations. However, hovering flight is so energy-expensive that - based on hummingbirds - your fairies would have to eat more like 85 kilocalories a day. The main consequence of this is that they probably wouldn't be able to fuel an intelligent brain.
To summarize; **your fairies would probably look a lot like [fruit bats](https://en.wikipedia.org/wiki/Megabat) more than anything else, and they probably wouldn't be as intelligent as humans. Maybe crow-level intelligence, tops.** Hope this answers your question satisfactorily.
] |
[Question]
[
Imagine a dictator who owns a massive prison. The tech level is 12th-15th century, and the dictator has very few guards at his disposal. The prison already has all necessary resources such as food and water dispensed from [vending machines](https://worldbuilding.stackexchange.com/questions/132381/with-12th-15th-century-technology-is-a-vending-machine-possible), which use coins. Coins are obtained by doing work, such as carrying stones or building things. Unfortunately, with so few guards, none can be spared for this prison as they all work somewhere else.
Now, I suspect there's a way that some sort of economy in the camp based on the population of prisoners would be able to make the prisoners guard themselves. If one of them runs away, they are somehow punished. You can handwave how the vending machines that provide resources work, but assume they can know how many prisoners there are and calculate things like cost.
So, what would be an effective method of accomplishing this? You can divide up the prisoners any way you wish, and assume the "prison" is a massive camp, taking up several dozen acres with a large building for sleeping/housing the vending machines. The walls can be set up however you wish.
[Answer]
For the design of the prison itself, I would use something similar to the Panopticon designed by Bentham ([link to the wiki article here](https://en.wikipedia.org/wiki/Panopticon)), but still in use in some prisons today, possibly with similar central towers in the work areas, as you could use minimal guards and even trusted prisoners to staff the towers.
You would also want to build up a fairly strong list of rules and a system of rewarding prisoners for reporting others misdoings, e.g. if you get one vending machine coin for a full day's work, then you maybe get three coins for reporting someone has contraband, and five or even ten for reporting an escape plan. Punishments for breaking the rules should be fairly severe but not result in death, as a prisoner may feel too guilty to report someone if they think it will result in that person's death. This will help build a level of fear and mistrust between the prisoners - it's harder to organise an escape plan if you can't work with anyone for fear of them reporting you.
If you are keeping them in fairly poor conditions then you could also institute systems of reward and rank, e.g. if you make ten reports that have been proven accurate (or whatever works in your system), you get a slightly nicer cell, and slightly more responsibility, e.g. overseeing the work camp duties. Prove yourself in that and the guard duty or punishment duty etc etc.
While this sounds very a harsh scenario, there are unfortunately quite a few real world parallels, particularly in South America, for example San Pedro prison. You may find [this article](https://blogs.lse.ac.uk/latamcaribbean/2017/05/25/when-inmates-make-the-rules-self-governing-prisons-in-latin-america-and-beyond/), which talks about San Pedro and other prisons staffed by relatively few guards and self governed by the prisoners, interesting!
[Answer]
People's greed for power is enough to accomplish what you want.
In prison, all prisoners become low in rank while even the lowest (external) guard ranks higher than any prisoner. If left to themselves, the prisoners will soon establish a new rank or hacking order by organizing themselves in gang-like structures. There are always people manipulating, intimidating or simply fighting their way through life. These will probably become the gang leaders and prisoners of highest rank.
Now *you* are still much higher in rank, so you can bestow previleges on certain prisoners. All it costs you is sewing 10 armbands or similar identification marks and a prison-wide announcement than anyone wearing such armband is officially considered a guard and gets a few extra coins per day if no prisoner escapes that day.
Now suddenly those prisoners with the most power anyways have an incentive to stay in prison (because their life gets more comfortable and they have the power they crave) and to keep anyone else in prison as well.
Lean back and watch them tyrannize themselves, as did the scientists supervising the [Stanford Prison Experiment](https://en.m.wikipedia.org/wiki/Stanford_prison_experiment).
>
> The Stanford Prison Experiment (SPE) was a 1971 social psychology experiment that attempted to investigate the psychologicaleffects of perceived power, focusing on the struggle between prisoners and prison officers.
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> Early reports on experimental results claimed that students quickly embraced their assigned roles, with some guards enforcing authoritarian measures and ultimately subjecting some prisoners to psychological torture, while many prisoners passively accepted psychological abuse and, by the officers' request, actively harassed other prisoners who tried to stop it.
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---
Nice addition by Cadence:
You could simplify things even further if you wanted. "Whoever shows up here at noon with X carts of [whatever this place produces; rock, I guess] gets Y carts of food. Otherwise, good luck." The people who manage to put themselves in charge of food deliveries are de facto your trustees.
[Answer]
A scenario like this was the premise for a movie
See [Wedlock](https://www.imdb.com/title/tt0103239/)
Prisoners wear explosive collars linked to another random unknown collar. If the two collars become separated by more than 100 yard, boom, both prisoners die. If a collar is removed without deactivation, both prisoners die.
Since you don't know who your match was, it's in your best interest to make sure nobody tries to escape.
[Answer]
Easy, put them in some islands. There are about 100 prisoners per island, and the escape of one means the death of all others because there are these lions which prowl the islands. Each prisoner has to take some of their time to defend against the lions, and take all other time to scavenge and sleep. If someone escapes, the lion they are supposed to defend against attacks someone else, killing them because they are attacked by two lions at once, so the escape of one prisoner means the death of all others, and they will organize themselves to prevent escape. The "lions" could be anything that poses harm and needs all prisoners to work together.
] |
[Question]
[
So, let’s imagine a force of about 500 people, armed with what we would consider modern weaponry (or, more so, 1960s weaponry), are facing up against a force that outnumbers them at a ratio of 34:1, but with weapons more akin to the 1890s-WW1 levels.
The other force is planning on an all-out siege against your base, and you cannot call in reinforcements of any kind. Your base is surrounded by a large metal wire fence, with a large underground area beneath it. How would you go about defending your base from these attackers?
To help, here is the basic layout of the base[](https://i.stack.imgur.com/yC5pT.jpg)
[Answer]
World War I saw the advent of chemical gas used against soldiers. Since your attackers are not quite in that era, they would not have gas to use against the base or masks to protect themselves.
Send everyone in the base underground aside from the soldiers needed to carry out the counter attack. Put them in full protective gear, including masks. Seal off the underground bunker, leaving an "air lock" for the outdoor soldiers.
Launch canisters that open on impact and release thick poison gas. You want something that clings close to the ground (meaning about 8-10') and doesn't dissipate easily (you want it to spread out but not go more than a 100 yards or couple hundred yards/meters or so if possible). It should be absolutely lethal when fresh but it breaks down quickly over the next 24-48 hours. Second choice is a gas that renders the attackers unconscious for a few hours so well-protected base soldiers can go in and finish them off. Machine guns would be a good choice here if there are many from the attackers' side who are just far enough away from the center of the gas to be dazed but not down.
Timed and aimed properly, the first attack should at least halve their numbers. Hopefully it would kill off more like 75%. It will be harder to reach them for subsequent attacks, but should still be possible, given that they are unfamiliar with chemical warfare (if their knowledge level matches their tech level).
I also suggest electrifying the wire fence. If you can keep the attackers separated from the base for longer, that allows you more poison gas attempts. Put a few grenades into the mix as well. Make sure those attackers have no idea what is going to hit them.
If available to you, you can also send contagious diseases via the launchers. If you have a few weeks of time due to the fence, this could decimate them as well. If they break through to the base and get to your forces, you're all dead anyway, so your soldiers being exposed to the diseases isn't going to make a difference.
[Answer]
Well, the first thing I'd do is get the defenders outside the fence. Then...
Oh, wait. Let's back up a bit. Let's get a LOT more detail. How much advance warning do you have?
Those 500 - are they just researchers and random security people? Or are they 500 soldiers of your choosing, flown in with the necessary equipment needed for the defense? Let's go with soldiers.
You've stated that the OPFOR is "the enemies actually lean more to the 1890s", and as I've pointed out in comment to the OP, this in no way rules out an enormous mass of indirect-fire artillery (say, 1000 guns), along with hundreds of machine guns.
In which case you are (99%) screwed. They can saturate the base with artillery, send a few thousand assault troops right up to the wire, lift fires and overrun the place.
The other 1% possibility is entertaining: using a 1960's observation helicopter, keep a watch out for the oncoming army. Then engage with Davy Crockett nukes (produced in 1958). Since the Bad Guys are operating at 1890's level, they don't understand dispersion the way more modern armies do.
So, let's pull the historical references back about a generation. 1870's vs 1940's. This is a bloodbath and the defenders win.
The defenders take down the fence and import about 100 WWII 105 mm howitzers and a whole bunch of ammo. The guns are emplaced so as to be protected from direct fire and have 360 degree fields of fire. This is going to take up a good deal of area, which is why it will be outside the wire. 3 men per tube, and another 100 or so as ammo bearers. About 30 M2 .50 cal machine guns round out the defenses. And for a last-ditch reserve, you can have up to 10 M4A3R3 "Zippo" flame thrower tanks. They will be impervious to anything the other side can throw at them, and the psychological effect will be devastating.
All of this presumes that you can clear the terrain out to several kilometers from the base. If you have a base which is nestled in a charming little valley surrounded by dense forest, you're back to being screwed. And if your personnel are just boffins and rent-a-cops, you're also hosed.
] |
[Question]
[
I'm trying to create a planet which environment is not immediately lethal to humans, (reasonable oxygen level) however after closer inspection turns out not to be specially Earth-like.
One issues is its hydrosphere. Over 90% of planet surface is water (or ice). It's rather cold tidally locked planet, so to have a reasonable excuse why the water is still liquid, I'd prefer to beef up salinity.
**Which is acceptable salinity level in which carbon based life as we know it could realistically thrive?** By thrive I don't mean local equivalent of toughest archaea and tiny brine shrimps, but existence of bigger organisms, which weight exceeds at least kilogram)
[Answer]
It depends on how complex life you want to have. For simplicity, I will refer to what we can observe on Earth.
The body of water with the [highest salinity](https://en.wikipedia.org/wiki/List_of_bodies_of_water_by_salinity) on Earth is [Gaet'ale Pond](https://en.wikipedia.org/wiki/Gaet%27ale_Pond)
>
> The water of Gaet'ale Pond has a salinity of 43%, making it the saltiest water body on Earth. The waters of the lake originate from a thermal spring located beneath it. For this reason its temperature (50–55 °C) is hotter than the environment.
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No life forms are mentioned to be living there, while in the [Don Juan Pond](https://en.wikipedia.org/wiki/Don_Juan_Pond) in Antartica, studies are equivocal.
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> Salinity varies over time from 200 to 474 g/L, dominated by calcium chloride, and is over 18 times the ocean's salinity and 1.3 times that of the Dead Sea. It is the only Antarctic hypersaline lake that almost never freezes with a salinity of 338 ‰ = 33.8%. It has been described as a groundwater discharge zone.
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[Lake Rebta](https://en.wikipedia.org/wiki/Lake_Retba), the third in the ranking, hosts complex life forms like fishes:
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> The lake is known for its high salt content, up to 40% in some areas, [...] Fish in the lake have adapted to its high salt content by evolving ways to pump out extra salt and keep their water levels balanced. The fish are approximately four times smaller than those living in a normal environment, as a result of salt water fish dwarfism.
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Based on the above it seems reasonable that you can have some life forms at around 35% salinity.
[Answer]
Well look at what you have on earth; salinity is usually measured in parts per thousand (ppt or ). The average ocean salinity is 35ppt and the average river water salinity is 0.5ppt or less. This means that in every kilogram (1000 grams) of seawater, 35 grams is salt.
According to Cotruvo, humans can tolerate limited amounts of salts in water “for reasons of health and palatability,” but cannot tolerate excess salt intake. He notes in the article that there are also indications of positive benefits of minerals like magnesium and calcium in drinking water.
"When it comes to treating salt in water, “The universal treatment for salinity is membrane treatment related to desalination. Nanofiltration membranes are capable of removing multivalent ions more efficiently than monovalent ions, so they can be somewhat effective especially in non-seawaters,” says Cotruvo in the article. “Reverse osmosis achieves removal in the [98 to 99] percent range in thousands of high-pressure seawater desalination applications that can operate at rates as high as multimillion gallons per day.”
for more information check this out:
<https://www.watertechonline.com/understanding-salinity-in-drinking-water/>
] |
[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.
Prior to the Cambrian, there have been three separate ice ages--the Huronian, from 2.4 to 2.1 billion years ago; and the two Cryogenian ice ages, from 720 to 635 million years ago, split in such by a ten-million-year lull.
Post-Huronian came the first eukaryotes, cells with a nucleus concealed within membranes. The first of some of the multicellular eukaryotes, the animals, first appeared 665 million years ago, near the last legs of the Cryogenian... or did they? I ask that because one of the evidence questioning the occurrence of the Cambrian "Explosion" is the fact that trilobites, the most iconic organisms of the Palaeozoic Era, were already diverse by the time it allegedly happened, which would indicate that they evolved much earlier, at least 700 million years ago.
The fact that eukaryotes evolved in the wake of the Huronian was no problem. [As this BBC site may indicate](http://www.bbc.com/earth/story/20150112-did-snowball-earth-make-animals), isolation by ice may force the cells to be more specialized. But what does not make sense for me was that melting such a global snowball, as the Huronian essentially was, meant an increase not just of nutrients dumped into the oceans, but also free oxygen rising into the atmosphere, yet animals did not come into the stage until the Late Cryogenian, in which the melting did the exact same thing the melting of the Huronian did.
So my question was - **Could multicellular life evolve with just the Huronian glaciations and not the two Cryogenian glaciations?**
[Answer]
The earliest Metazoa originate between [800mya and 750mya](https://royalsocietypublishing.org/doi/full/10.1098/rstb.2015.0036), so anywhere from 80my to 30my prior to the beginning of the [Cryogenian](http://www.stratigraphy.org/index.php/ics-chart-timescale).
The occurrence of snowball periods is likely not a factor in their appearance. In fact, [it has been suggested](https://www.infona.pl/resource/bwmeta1.element.elsevier-4fe3b2c5-792b-3e6c-91a4-196da1a0c099) that the Cryogenian caused a loss of diverity in the Earth's oceans. This loss was not recovered until the glaciation ended, and the evolution of the Ediacaran fauna occurred.
My conclusion, therefore, is that the Cryogenian was not required for the evolution of animal life on Earth, and may have in fact inhibited it.
[Answer]
It is proposed that the Precambrian ice ages stalled evolution because the cold stalled photosynthesis. This is demonstrably not so.
On land, photosynthesis by algae proceeds fine in the snow.
[](https://i.stack.imgur.com/AUean.jpg)
<https://www.naturepl.com/stock-photo-green-snow-algae-petermann-island-antarctic-penninsula-antarctica-image01021676.html>
In sea ice, photosynthesis also proceeds fine in subzero temperatures.
[](https://i.stack.imgur.com/blk9q.png)
<https://askabiologist.asu.edu/explore/frozen-life>
During the Precambrian ice ages, sunlight would still be harvested and still be used to make oxygen. Evolving animal life would have access to the oxygen needed by multicellular life as we know it.
The animals were there after the Huronian. Trilobite ancestors for one, but also strange ones, the likes of which are hinted at in the Edicaran fossils. Probably there were predators too,, capitalizing on the resources stored by their sessile cousins,
But we do not know their shapes. A billion years elapsed between; time enough for the first stirrings of a maiden Earth to be lost. The thawing of the Cryogenian is the dawn of life not because life did not exist before, but time and change has obscured its traces in the darkness before dawn.
[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.
According to this link, <http://www.astrobio.net/origin-and-evolution-of-life/multicellular-life-evolve/amp/>, multicellular life first appeared 3.5 billion years ago, about a billion years after the Earth was formed.
Multi cellular animals began to appear in the fossil record about 600 million years ago, right in the middle of the cryogenian. As you noted, they are already very diverse, confirming what we already know, that the fossil record is incomplete.
As you note, the diversity of animal life in the mid cryogenian period suggests that multicellular animal life may have been abundant pre-cryogenian.
] |
[Question]
[
Atmospheric composition:
* | 2% Trace gases | 58% Nitrogen | 26% Oxygen | 11% Argon | 3% Carbon dioxide |
Average surface temperature:
* 36 degrees Celsius
Surface gravity:
* 1.36x Earth gravity
Info regarding of altitude, pressure, and atmospheric density:
```
altitude pressure density
(meters) (atm) (kg/m^3)
0 17 10
1000 15.3 9
2000 13.8 8.1
3000 12.5 7.3
4000 11.3 6.6
5000 10.1 6
10000 6 3.6
15000 3.6 2.1
20000 2.2 1.3
30000 0.8 0.5
40000 0.3 0.2
50000 0.1 0.06
```
What adaptations would creatures normally have on this world based on the high pressures of the atmosphere given? Would they have looser bones? Pressurized gas within the bones? Etc? **If possible, give detailed hypothetical answers, I'll be glad if examples are given in the answers for the question I'm asking**
[Answer]
# TL; DR:
Skip the Partial Pressures section and go directly to Adaptation; you don't need to read the sub-titles.
# Partial Pressures
First, we will calculate the partial pressures of your atmosphere:
Note that I don't know the $\text{gr/mol}$ of $\text{Trace Gases}$ so I tried to make an average with your actual gases.
In addition, I don't like atmospheres so I added a column for partial pressure in kilopascals. Remember:
$$\text{atm} = 101.325\text{ kPa}$$
$$ \left|
\begin{array}{cc|ccc|c|cc}
\text{Gas}&\text{%}&\text{gr/mol}&\text{Mols}&\text{Fractal Mol}&\text{Partial Pressure (Atm)}&\text{P.P (kPa)}\\
\text{N}\_{2}&\text{58%}&28.014&2.0703&\text{62.91%}&10.69&1,083\\
\text{O}\_{2}&\text{26%}&31.998&0.8125&\text{24.69%}&4.19&425\\
\text{CO}\_{2}&\text{3%}&44.01&0.0681&\text{2.07}&0.35&35\\
\text{Ar}&\text{11%}&39.948&0.2753&\text{8.37%}&1.42&144\\
\text{Others}&\text{2%}&30.900&0.0647&\text{1.97%}&0.33&33\\
\text{Total}&\text{100%}&174.87&3.2911&\text{100%}&17&17,222\\
\end{array}
\right| $$
* **Nitrogen (N2): 1,083 kPa (10.69 atm)**
+ **[Nitrogen narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis):** Nitrogen narcosis is developed under pressures above **240 kPa** and **354 kPa**. Values above **400 kPa** will produce serious nitrogen narcosis. Nitrogen narcosis is similar to drunkenness but worse. If you want to find more information [in this answer](https://worldbuilding.stackexchange.com/a/118921/35041) I wrote about its symptoms.
* **Oxygen (O2): 425 kPa (4.19 atm)**
+ **[Oxygen Toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity):** Values of oxygen higher than **50 kPa** are lethal for a terrestrial organism. That amount of oxygen burns our skin, eyes, lungs and even cells. Anyone would die in a few hours. In [this](https://worldbuilding.stackexchange.com/a/85096/35041), [this](https://worldbuilding.stackexchange.com/a/85100/35041) and [this](https://worldbuilding.stackexchange.com/a/85096/35041) answers I describe in detail their effects. The last link has a cute diagram with the effects.
* **Carbon Dioxide (CO2): 35 kPa (0.35 atm)**
+ **[Hypercapnia](https://en.wikipedia.org/wiki/Hypercapnia):** Hypercapnia is the production of carbonic acid in our body due to the elevated amount of CO2 because the body wasn't able to dispatch it (due to the elevated partial pressure outside). That is lethal and will kill animals very quickly. In [this](https://worldbuilding.stackexchange.com/a/118921/35041) and [this](https://worldbuilding.stackexchange.com/a/84125/35041) answers you will find additional information and a graphic with the common symptoms. The last link has a table which shows the "lethality" of different values. That table shows percentages based on Earth atmospheric pressure. Talking about your world, death arrives in a matter of minutes.
* **Argon (Ar): 144 kPa (1.42 atm)**
+ **[Argon Asphyxia](https://en.wikipedia.org/wiki/Argon#Safety):** Although argon is non-toxic, it is 38% denser than air and therefore considered a dangerous [asphyxiant gas](https://en.wikipedia.org/wiki/Asphyxiant_gas) in closed areas. It is difficult to detect because it is colourless, odourless, and tasteless. This gas may decant into zones without wind.
+ **[Argon Narcosis](https://en.wikipedia.org/wiki/Argox):** I don't know much about it, but it's hypothesized that argon can produce the same effects as nitrogen narcosis but only at higher pressures.
# Adaptations
I have done the analysis of the atmosphere but your question wasn't about if humans could survive, so we must think now which adaptations will need your creatures.
* Faster metabolism due to the increase in oxygen.
* Faster ageing, short lifespan, a lot of offspring (due to oxidative stress and stuff).
* Bigger insects (again, oxygen).
* Smaller lungs and possibly moister eyes and skin (oxygen and a bit of nitrogen). Insect respiratory system for smaller animals.
* Maybe some tweaks to the brain to avoid narcosis.
* Maybe the ability to smell argon.
* Stronger muscles and bones to counteract gravity. Shorter creatures.
* Increased sweating and ectothermic animals for the elevated temperature.
### Oxygen
Your oxygen levels are too high; that will hurt their eyes, skin and lungs.
Your species will need very small lungs because they will be able to collect a lot more oxygen with the same amount of space due the elevated oxygen pressure. I wouldn't be surprised to find "poorly evolved" lungs since efficiency isn't necessary here.
This oxygen will make metals rust faster due the increased oxidation speed. Flammable things will be even more dangerous. Oxygen has a lot of [ROS](https://en.wikipedia.org/wiki/Reactive_oxygen_species), molecules that break DNA, proteins or organelles in cells (for more information see [this answer](https://worldbuilding.stackexchange.com/a/118921/35041)). These damages accelerate ageing (also explained in the link above). Your creatures will have a very short lifespan but a lot of offspring to compensate.
Some ways to reduce this effect are the implementation of [active transport](https://en.wikipedia.org/wiki/Active_transport) (which consumes huge amounts of energy) or [semipermeables membranes](https://en.wikipedia.org/wiki/Semipermeable_membrane). Both are explained on the link for the paragraph above.
Furthermore, (**also** explained in *that* link), your insects will be **HUGE**. (Short-long-answer, insects don't have lungs; they breathe through the skin. More oxygen compensates for the lack of surface-volume relation, which lets them grow more). Because your vast oxygen partial pressure, I'm quite sure this technique will also be possible for smaller animals.
Finally, they may need wet skin and wetter eyes to counteract oxygen oxidation.
### Nitrogen
No idea how to fight that, maybe smaller lungs will fix that. Some modification to the brain (not sure how) may reduce nitrogen narcosis. If they evolve there, they must be used to being "drunken".
### Argon
Your creatures will need a way to smell argon, or they will accidentally die in an argon well because it's heavier and can get sunk in valleys or plains.
### Gravity
An increase of only 36% isn't very bad. A healthy human can survive that fine. They will evolve with slightly stronger bones and muscles to counteract that. I will suggest hollow bones like birds to compensate for the additional weight. Also, creatures will have a shorter height.
### Temperature Control
This is one of your lesser problems. Sweating more, having a lower metabolism and being cold-blooded animals will fix that. You can learn about [thermoregulation](https://en.wikipedia.org/wiki/Thermoregulation) in Wikipedia.
Basically, animals are divided into two big categories: [endotherm](https://en.wikipedia.org/wiki/Endotherm) and [ectotherm](https://en.wikipedia.org/wiki/Ectotherm). While the first ones produce their own heat to maintain their desired body temperature, the second category takes advantage of the environment's heat, using that as their body temperature.
I strongly advise to make your animals ectothermic, because they don't spend energy on warming up since the environment is enough to keep them warm, maybe even too much... (if 36 ºC is the average I don't dare to be there during summer...).
Anyway, we can still take some useful cooling traits from warm creatures (endotherms) before we get deep into the other. Endothermic creatures have [a few](https://en.wikipedia.org/wiki/Endotherm#Avoiding_overheating) mechanisms to avoid overheating:
* **Panting:** By panting with the tongue, they are able to lose temperature by increasing water evaporation in the breath. As you say in comments, birds' respiratory systems might be useful due to their fast breathing. I would add blood vessels which flow blood in the opposite flow direction to make [countercurrent heat exchange](https://en.wikipedia.org/wiki/Countercurrent_exchange).
[](https://i.stack.imgur.com/IqRos.jpg)
* **Flushing:** Increasing the blood flow to the skin transfers the heat from the inner body to the skin, place where it can be [radiated](https://en.wikipedia.org/wiki/Radiant_energy) into the environment. I encourage your creatures to have a large surface-volume ratio to avoid [gigantothermy](https://en.wikipedia.org/wiki/Gigantothermy) (big animals produce too much heat that they can't remove). For example, the usage of huge ears like car radiators (blood vessels) is very useful.
* **Sweating:** If the creature is hairless or short-haired, it can cool itself by sweating water. Take note that this method consumes water and minerals from the body.
Just for curiosity's sake, I'll tell you that endothermic creatures are more resistant to fungal infections due their own heath production. Sadly, you can't handle that. (Maybe the environmental heat is enough?). Also, your animals won't have [brown adipose tissure](https://en.wikipedia.org/wiki/Brown_adipose_tissue) because that is to produce heat, and you don't need more.
Now we must discuss ectotherms in more depth. As an advantage, ectotherms creatures eat a lot less (like 5 or 10 times less) because their slowed metabolism saves a lot of energy (lack of internal heating process); they are very economical! But they are only active during the day (due to the need to bask under warm sunlight), but your planet is quite hot so...
This requires cold-blooded animals to work with the fluctuations of ambient temperatures because they directly affect their body temperature. Ectothermic creatures are divided into even more categories based on how they "control" or "help" their temperature. Usually animals are very focused on one technique, but is possible to have trait of several, like reptiles. The main techniques are being poikilothermic and homeothermic.
The homeotherm is very known by everybody. These creatures try to always maintain the same body temperature, even if the temperature is only produced by the environment. Instead, poikilothermic creatures have between 4 and 10 enzyme systems (instead of 1 specialized but effective enzyme) in their bodies to survive and operate at different ranges of temperatures without problems. However, these enzymes are difficult to develop [Quotation need.] and make longer DNA (not sure if that is necessarily bad, but cool).
I don't know how your creatures are, but take note that poikilothermic creatures don't have sustained high-energy activities like powered flight (in large animals) or large brains. These creatures usually wait patiently for their prey rather than hunting actively, because they require between 10 to 20 times less energy than homeothermic animals (usually warm-blooded). And they usually seek shelter at noon but bask in the sun and takes advantage of gigantothermy to lose less heat, but luckily, on your planet there is plenty of heat! So I think they could have homeothermy, since there is enough heat to maintain a stable temperature.
Remember that even without a warm sunny day, some cold-blooded animals can still work. Some ectothermic animals have evolved to vibrate their muscles in order to generate a bit of heat when it's very necessary (this is usually done by insects, but I don't see it being difficult for other animals), a technique common in endothermic creature (like when you are cold and you begin to shiver).
For both cooling and heating, these creatures take advantage of [heat exchange techniques](https://en.wikipedia.org/wiki/Heat_exchanger#In_nature) (like countercurrent exchange). By using blood vessels, they can effectively move heat from outside to inside or from inside to outside for cooling and warming purposes. Also, the secretion of mucus is usually used to increase evaporation, and if the environment is very cold, they can enter into [torpor](https://en.wikipedia.org/wiki/Torpor) (decreased activity)
Finally, there is a third category after endothermy and ectothermy: mesothermy. They are hybrids between both techniques, basically adapting for the environment. They usually have poor metabolic control in their bodies (like ectotherms), but if it is necessary they will metabolize brown fat to produce heat (like endotherms) or increase in size (gigantothermy).
So, to summarize, your animals must pant and sweat. Being hairless, they will retain less heat, and by sweating through their skin and panting (with a large tongue), they will be able to lose heat by evaporating water. Passive techniques that don't require water will be flushing hot blood to the skin to radiate heat. It will be very advisable to increase the surface-volume ratio to avoid [gigantothermy](https://en.wikipedia.org/wiki/Gigantothermy), like having big ears like elephants, many blood vessels, and the ability to move at will. In this way, they will be able to radiate heat and flap to increase the airflow.
[Answer]
Pressure is a funny thing in biology
Note what i am about to say does not apply to vaccum because i am generalizing somethings.
In many ways pressure is irrelevant to physiology. What is critical is pressure difference because that is what kills. It would be possible for a human like body to survive (if created there) in the marianas trench only to explode when brought to sea level. There are plenty of fish that are great examples of this being able to exist in both places.
This obviously isnt the whole story. Those same fish have adaptations and simpler physiology to handle rapid yet gradual changes in pressure. For instance, gases acrue in their swim bladder which must then be expelled.
Now to put your question into a little more perspective:
The highest atmospheric pressure humans have survived in is ~14.7atm which is pretty close to the 17atm listed objective. This begins to show you that not a whole lot is needed for life to survive at that pressure.
Now one thing that id like to touch on is gas exchange. The key for organisms to respire in their environment is their ability to take in the abundant environmental chemistry to use in their metabolic processes. These constructs can have a lot of dependence on pressure. Gills dont function so well in air. Matter of fact we humans have a diaphram specifically to ensure a constant circulating supply of atmosphere. In higher pressures its reported that breathing requires less exertion.
So to answer your question, there MAY be no visible outward difference in adaptations at this pressure. There may be differences in respiratory organs. Its really however your alien nature decides to solve the problem of gas exchange, which there is no universal answer for and can be beyond our immagination.
<https://www.quora.com/What-is-the-maximum-atmospheric-pressure-a-human-can-survive>
[Answer]
If I'm assuming that your life forms are based on Earth life forms in the first instance, the biggest problem they'll face in the environment you've designed isn't the pressure; it's the mix of gases.
When designing hypothetical atmospheres for earth based life forms, the important thing to remember is that it's all about Partial Pressure. That is to say, that it's about the volume of each gas that gets absorbed, not the pressure of the overall mix. Let's look at the obvious example first, then look at the specific ratio described.
Everyone knows that you can't breathe pure O2; it burns out your eyes, lungs, etc. and over a given period is lethal. That said, the Apollo Astronauts spent over a week on a return trip in pure O2 without those effects. Why? Because their capsule was only pressurised to about 0.3 ATM. In effect, if you take 1 bar (sea level pressure) as the norm, then humans regularly breathe in around 0.2 ATM of O2 with each breath, and the Apollo Astronauts weren't breathing in much more than that in their capsules. So, it wasn't a problem.
Deep sea divers on the other hand require a special mix of air to dive deeply, because once you get below around 60m, you're in 7 Bar of pressure, meaning that every breath you take of normal air at that pressure is around 1.4 ATM of O2, which is toxic to humans.
The deepest humans can dive in SCUBA gear where their bodies are subjected to the full pressure of the ocean is around 140m, or 15 ATM of pressure. Let's assume though that we can make the leap to 17 ATM at sea level of your chosen planet; what are the gases going to do?
Well for a start, the O2 is definitely toxic at those levels. So is the Nitrogen, but long before it becomes toxic it'll become narcotic. At the percentages you've described, Nitrogen Narcosis would set in at around 4 ATM, and at 17 ATM I'm pretty sure it becomes toxic.
CO2 is your real worry, though. CO2 is toxic in very small doses, and should never be considered safe above 5% at 1 ATM. But, in your atmosphere, you've got a PP of CO2 of around 51% (17 x 3%) meaning that animals are really going to suffer in this environment.
The Argon is fine, but the trace gasses comprise a PP of around 34% (which if it was O2 alone would be too high) meaning that if some of that is (say) fluorine, any earth based animals in that environment are dead, end of story. At these levels, trace gasses aren't really 'trace' - the amounts breathed in by a normal earth based life form are enough to cause serious damage if any of them are dangerous because their presence is now material because of the atmospheric pressure.
So, what adaptations could we see to cater for living in such an environment? Well, obviously you no longer need an efficient gas exchange model like lungs. This is because at these pressures, pretty much everything you have in the atmosphere is a problem. So, the best solution is not to take too much of it in.
As I see it, this means 3 possibilities.
The first is smaller lungs. Lungs are still a good idea because they have the potential to be more efficient if the environment changes in some way. But, lungs will have to reduce in size as a percentage of body mass because to do otherwise will kill your subject. Chest muscles will have to be stronger to work in the higher pressure, and the bronchial tubes will no doubt be shorter and wider as well, to more effectively move the higher pressures in and out of the lungs, smaller though they may be.
The second is gills. At those pressures, you're probably better off doing what fish do and just letting the pressure and density of the gas run over a gas exchange system that's semi-external. It won't be as efficient, but then you don't want it to be, especially with the high concentrations of CO2.
Finally, there's osmosis. Insects are likely to thrive in your environment because they don't have lungs at all; they absorb O2 through their carapaces until it saturates their body, and waste CO2 is then expelled through the carapaces. On Earth, this limits the size insects can grow to because if they get too big, the oxygen can't reach the innermost areas of the insect's body. We believe there were periods in Earth's past where oxygen levels were much higher than now, allowing insects to grow to much larger sizes.
In your world, this is very likely to be the case because the partial pressure will allow more O2 to be absorbed into the insect's body, allowing for deeper saturation.
Of course, oxygen isn't the only consideration in insect size; being exoskeletal means that their carapaces can only get so big before they can't support the creature (square cube law) but certainly they would have an advantage on your world regardless.
Personally, I would expect land based creatures in your world to potentially have gills as if they formed in the ocean first (as we believe life did on Earth), it's one less change evolution would have to implement for survival.
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[Question]
[
Obviously, current oxygen levels should last us years, so we are talking about a long-term solution.
Also, in this hypothetical scenario, plants have stopped releasing oxygen but haven't stop producing organics, so the food is not a problem. I understand it's a far-fetched scenario, but I don't know how else to focus the question on oxygen production specifically.
Question:
If plants stopped releasing oxygen, how could we produce oxygen for breathing, and how sustainable and effective would these methods be?
[Answer]
Simple electrolysis of water would be the first step, as simply adding an electric current to water starts breaking the water down into free hydrogen and oxygen.
Of course, free hydrogen is very dangerous. Without proper care, one spark and your electrolysis facilities will go up in flames. By capturing carbon dioxide from the atmosphere, you could free up even more oxygen, and safely store both the carbon and the hydrogen to be later reused as fuel.
These chemical reactions take extra energy to perform. Water and carbon dioxide are the lowest energy forms that molecules that are made up of oxygen, hydrogen, and carbon can take. Since human life now depends on extra oxygen in the air, burning anything will be strictly regulated, so our energy will have to come from renewable sources, such as geothermal, dams, wind, and solar.
[Answer]
>
> Obviously, current oxygen levels should last us years...
>
>
>
Yes. A few hundred millions, give or take, supposing Earth's orbit does not change much across the eons. But I am not taking leap seconds into account.
[The atmosphere has a mass of about 5.15×1018 kg](https://en.wikipedia.org/wiki/Atmosphere_of_Earth). That is an expletive lot. ~21% is O2, approximately 1018 kg.
[According to NASA:](https://settlement.arc.nasa.gov/Contest/Results/96/winner/seis.html)
>
> A man needs 0.63 kg of oxygen per day.
>
>
>
So for 7 billion pairs of human lungs, we should need something in the vicinity of ~4.2×109 kg of oxygen per day.
If we off every other oxygen breathing creature, stop burning stuff, and keep the population level constant, we could keep breathing for maybe five hundred million years. Even if we didn't care and didn't change anything else we could still live long enough to colonize the galaxy and import working, alien plants from some other planet.
You see, we take oxygen from the atmosphere, and the plants and bacteria put oxygen back into it, but both sides only ever handle a very tiny fraction of the O2 present in it. If plants went on strike, we would have more than enough time to find another free, green source. Meanwhile we could use the process from [Ghedipunk's answer](https://worldbuilding.stackexchange.com/a/127144/21222) - electrolyse water to make some oxygen and get some nice rocket fuel on the side.
We could also find a way to turn silicon dioxide into metallic silicon and free oxygen - effectively using sand and quartz crystals as extra sources. [The crust of the Earth is 46% oxygen by mass](http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/elabund.html) - enough to knock ourselves out and blow the atmosphere into space, should we ever get tired of living here. [We might need a lot of acid though](https://chemistry.stackexchange.com/a/5036/31035) (this links to a question in [chemistry.stackexhange.com](https://chemistry.dtackexchange.com), and the method in the accepted answer can separate oxygen from materials other than iron too).
[Answer]
There seems to be two themes in the answers.
First, the current levels of oxygen would last a very long time.
Second, the problem of what to do with the oxygen from photosynthesis, if it is not released as oxygen.
I submit that there is a work-around plot mechanism for both issues.
Instead of releasing O2, the plants develop a mechanism to produce ozone, O3. Conceptually, I would suggest handwaving a new enzyme, spread by a virus, that infects all plants. It gets into the organelles, that allow photosynthesis. This enzyme modifies the photosynthesis equation enough for O3 to be formed.
Don't ask about the details of how, but given that biologists have had to resort to [quantum tunneling to explain photosynthesis](https://www.scientificamerican.com/article/when-it-comes-to-photosynthesis-plants-perform-quantum-computation/), I suggest that quantum tunneling would be a good mechanism to hand wave away the small details. It could plausibly explain how the electrons get from where they are in O2 to where they need to be in O3.
Once plants start to give off O3 instead of O2, we humans have a very big problem.
You see, O3 is toxic to us. Our lungs cannot use it. If we breathe pure O3, [we suffocate](https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners).
Except that, for the purposes of the plot, we have solved the two issues.
Plants get rid of the oxygen, and the atmosphere becomes non-breathable to humans.
In which case, the solution is to convert O3 back to O2. This process occurs naturally in the upper atmosphere. Humans just need to speed it up, perhaps commercially.
[Answer]
"in this hypothetical scenario, plants have stopped releasing oxygen but haven't stop producing organics" -- okay, so they're now fixating carbon dioxide.
The big problem is that this produces extra oxygen and there aren't many places where it can go if we don't vent it into the atmosphere:
- hyperoxygenated carbohydrates would wreck the plant's metabolism, and are poisonous. Plus they're flammable, explosive, or both.
- compressed oxygen can be stored in lignin bubbles but not for very long - then it enters equilibrium and nothing has really changed
- the soil contains phyllosilicates and hydrated silicates, and both are very near the maximum oxygen saturation possible.
However, the most obvious way of dealing with the oxygen scarcity would be
* try and kill off all the non-venting plants and replace them with the old versions,
* go live in arcologies, and supply oxygen from closed-cycle photosynthesis supplemented with chemical manipulation of whatever material the oxygen from outside gets stored into
* extract oxygen from silicates (simple dehydration plus electrolysis would suffice).
[Answer]
So the oxygen just vanishes, this is the basis of this answer. No weird biochemistry to account for it, just gone. Plants still use oxygen for their own breathing, and capture CO2 like normal, thus also thriving and bearing fruit for the ecosystem to carry on as normal.
Currently, about 21% of the atmosphere is oxygen. 19.5% is deemed the lowest acceptable content, so let's say that this is with a little safety margin, and say it's 18%. So 3%-points, or about 15% of the current oxygen could be used up before bad stuff starts happening (this is excluding the ecosystem-wrecking (and by the power of decaying stuff oxygen-depletion-accelerating) side effects of a dropping O2 content). 1.16x10E18 kg of oxgen in the atmosphere total come to about 1.6x10E17 kg of depletable oxygen. User AlexP gave 3x10E14kg global biological oxygen consumption per year, and i'm going with that figure as it roughly fits to humanities part in total global biomass (1x10E-4) and human consumption as given by Shadowzee. The biosphere would consume the usable oxygen in about 5000years. Humans produce about 1x10E13 kg of CO2 per year, about 75% of that being oxygen, so burning uses 7.5x10E12kg - meaning about 1/50th of the amount used for breathing - we would not even need to stop burning stuff.
As mentioned, the above does 'The Martian'-like naive calculations. No positive or negative feedback was taken into acount, no buffering, nothing. 5000 years still is such a huge timespan compared to human life expectancy that i dare say it would give humanity enough time to die on it's own accord...
To remedy the magically disappearing oxygen, we would need to produce some ourselves to offset the 3x10E14kg O2 life on Earth needs yearly. Usually, splitting H2O would come to mind, but unless the resulting H2 can be sent into the same magic vortex the plant-O2 went, this would be a zero-sum game. Better get the O2 off something where the reduced product can be stored without immediately beginning to oxygenate again. Sand? Store the resulting Si as slag? You need about 8x10E3Wh to produce 1kg of O2 from sand, so 2.4x10E18Wh annually to even out the missing plant-output. That is about 20 times the global human energy consumption... Might take a while to scale up to these levels, though the circumstance that the other part of the equation, pure Si, can also be used in energy production through solar cells might help a bit. And us having 5 millennia to get up to speed. - The ~10 000 square kilometers of real estate to build on could be found.
[Answer]
We would all die, there is no way for us as a species to replace oxygen as fast as we use it with out current level of technology and reliance on fossil fuels.
Think about it like this... we have roughly 80% of the worlds energy as fossil fuels and generated via burning. Coal, Gas and Oil account for basically the entire 80%. Renewables only form around 10% with the large majority being hydro... not solar or wind.. HYDRO. The rest of renewables is roughly 2%. (<https://en.wikipedia.org/wiki/World_energy_consumption>) (I leave out nuclear because as always, fear mongering has basically put it into the trash can and the plants take way too long to build).
So not only are we going to need to basically increase our current renewable production, we need to do it by 5000% in a single year because we run out of oxygen. (We need this energy production because without it, we dont have the power to convert Carbon dioxide into oxygen or water into oxygen.) (I also ignore hydro because that is very dependent on the terrain, water availability and requires the construction of huge dams to properly harness)
The problem with renewables and current renewable production and placement is that we have no way of doing anything significant in so short a time frame. We are ramping up production right now, but when that 1 year ticks by, oxygen levels start to drop, everything relying on power stops working because all our energy production methods rely on oxygen. What ever oxygen production plants we do have quickly become over crowded and people starve to death, because there is no way for them to get food (cars run on combustion, your kidding yourself if you think we can increase ALL current renewables by 5000% while converting all cars into electric and building oxygen conversion centers in a single year). Its not about renewables not being able to replace fossil fuels, its just we can't physically produce the numbers necessary to replace fossil fuels and our reliance on them.
Edit: just realised you put years.. I doubt we would have enough production capabilities even after 10 years. Not with our population still growing and the amount of time it takes for governments to understand the consequences that scientists have been telling us for over a decade and a clear lack of funding and push. Heck we probably won't even realize plants stop producing oxygen until a year later.
Edit2: I know 10 years is short, and I might be underestimating our supply (But seriously, its not going to be millions of years, maths below). The bigger issue wouldn't be the oxygen we breath but the lack of CO2 absorption by plants (since you take CO2 and create glucose and O2). That combined with all the algae in the world suddenly not producing oxygen would kill off sea life.
**Okay and here is the maths I did with the non google sources (I got lazy okay).**
So wikipedia says the atmosphere is 5.15\*10^18 and 20.95% is oxygen which is 10^18 Kg of oxygen. (plenty)
NASA says we need 0.84Kg per person and with 7 billion people it doesn't even get close to the ball park of being a worry (Another answer did this). <https://www.nasa.gov/pdf/146558main_RecyclingEDA%28final%29%204_10_06.pdf>
This article <https://www.sciencedirect.com/science/article/pii/S209592731830375X> is a bit better and goes into oxygen consumption in different industries. Basically they estimate a 0.1% drop by 2100, so I assume 0.1% per 100 years. Still plenty of time
The issue is we can't go to 0% oxygen. We breath in 20%, breath out 15% so we need 5%. Americas OSHA <https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=25743&p_table=INTERPRETATIONS> says an environment is oxygen deficient at 19.5%
so instead of having hunders of thousands of years for oxygen to drop to 0 we can only drop a single 1% before we are affected by it. Basically 1000 years. (16% and your out of breath while sitting, we if you want to push it, we can do the 5% drop). Still, thats plenty of oxygen, but no where near the figure that you guys have been saying. (To go on, 10% oxygen causes vomiting and 6% causes convolutions so 16% is probably the final limit we can hit before we need to recover).
The final pressing issue is that there is no oxygen renewal. Every single plant stops photosynthesizing. I assume they keep growing magically, but no oxygen comes out (and no oxygen goes in at night). Google said a tree produces 260 pounds of oxygen a year or 120Kg. Thats 120Kg per tree per year that isn't being produced anymore. Google also gives an estimate of 3 trillion trees, and that ends with roughly 2\*10^14 Kgs of oxygen that doesn't get renewed per year and is removed from the cycle (I'm not sure if the science article references this or not). So we effectively lose 2\*10^14 Kgs of oxygen as well as what we spend (I could be wrong in adding these... I didn't read the article in depth, only browsed through it).
And the final nail in the coffin is that algae, which produces 50%-85% of all oxygen (google again) stops. So at best, we lose 4\*10^14 Kg of oxygen or 10^15 Kg of oxygen per year (Which is 25 to 10 years due to the 1% drop requirement). Algae also replenishes a lot of the oxygen in the sea, which is going to experience a sharp drop in oxygen levels and a huge increase in CO2 levels which will kill off that ecosystem (Algae wont be using that CO2 for the same reason plants don't. They get to absorb some to grow, but I assume the exact reaction to make oxygen no longer occurs).
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[Question]
[
I am working on creating a fantasy race called the Aemani. As they are part deer they are [unguligrade](https://en.wiktionary.org/wiki/unguligrade) bipeds (like a faun or satyr).
I am in the midst of creating their culture however I don't know how they would ride a horse, or even if they could.
Would I need to consider another form of transport? It is set in a post-modern but medieval style world. Modern-day technology as we know it today (such as cars) is not available to them.
I would like to have my story as scientifically feasible as possible, even though I understand unguligrade bipeds are quite unrealistic to start with.
[Answer]
Typically in modern fantasy settings, [an unguligrade biped is depicted either with the ankle higher up than a normal human's ankle](https://www.youtube.com/watch?v=VJmQrULRins#t=03m53s), *or* with an [extra joint](http://animal-dream.com/data_images/satyr/satyr21.jpg) as a [reversed knee](https://vignette.wikia.nocookie.net/cassandra-palmer-world/images/d/df/Satyr_2.jpg/revision/latest/scale-to-width-down/300?cb=20150727011048) while still having [an ankle at the hoof area that faces the normal human knee direction](https://previews.123rf.com/images/bokononist/bokononist1507/bokononist150700003/43758091-satyr-with-pitcher-and-horn.jpg) again. So while the leg may be structured somewhat different, those differences ought not affect riding too much. NOTE: If one researches [more classical Greek depictions of satyrs](https://en.wikipedia.org/wiki/Satyr), the legs are either normal, or fairly normal to a human's, but I believe you are thinking more the later fantastical version.
### Prior Renditions
Artists have depicted satyrs riding other animals (I did not find an example of a horse, but the last one is pretty close):
**Riding a Goat**
If I read the info right, this is a 19th-20th century sculpture done in the "Manner of Andrea Briosco, called Riccio," who was a 16th century artist (from <https://metmuseum.org/art/collection/search/198377?rpp=30&pg=125&rndkey=20150309>, accessed 9/30/2018)
[](https://i.stack.imgur.com/Dfwgum.jpg)
**Riding a Bull**
Figure based on sculpture by Barthélemy Prieur, ca. 16th century (from <https://www.mutualart.com/Artwork/A-bronze-group-of-a-young-satyr-riding-a/DAF62B4FA05DC944>, accessed 9/30/2018)
[](https://i.stack.imgur.com/E7Gyym.jpg)
**Riding a Unicorn**
I don't speak or read Russian, it just happens to be the site where the image was found, but Google translates the page (so if the information is accurate) as having the statue itself located in Cambridge, United Kingdom, created in 1905 by Georg Wrba (from [https://www.diary.ru/~yukatan/p195188584.htm](https://www.diary.ru/%7Eyukatan/p195188584.htm), accessed 9/30/2018)
[](https://i.stack.imgur.com/cjhIym.jpg)
### Logically
There are examples of humans [riding backwards](https://www.google.com/search?biw=1280&bih=579&tbm=isch&sa=1&ei=vdSwW_6vJdPa9AOq5qOQBQ&q=riding%20a%20horse%20seated%20backwards&oq=riding%20a%20horse%20seated%20backwards&gs_l=img.3...202103.210134..210282...4.0..0.88.2261.35......1....1..gws-wiz-img.......0j0i67j0i8i30j0i24j0i30j0i5i30.k3zDnPmNsHk), which would probably be far harder than a satyr-type creature riding forwards, and some even supposedly in combat, such as this 4th century sculpted plate housed in the Iran Bastan Museum, Tehran, Iran (from <http://warfare.tk/6-10/Sassanid-Plate-Bastan-1275.htm>, accessed 9/30/2018):
[](https://i.stack.imgur.com/uLR24m.jpg)
Further, normally such satyr and faun like people are conceived of being able to jump rather well, so it seems that mounting up on a horse might be easier even than for most humans. Though the size of the people may matter (if they are quite a bit smaller than the average human, then they could still sit a horse, [much as a child *can*](https://good-horse.com/health-management/children-learn-ride-horses-ponies/), but might have a harder time controlling it).
## Conclusion
So conceptually, I believe there is no problem with the idea, though working out a few details related to your particular unguligrade biped people's size, anatomy, and skills may or may not need to be attended to.
[Answer]
[Stirrups](https://en.wikipedia.org/wiki/Stirrup) greatly increase the rider's ability to stay in the saddle and control the mount, increasing the animal's usefulness to humans in areas such as communication, transportation and warfare.
For an unguligrade to be able to use the same concept, you would need some sort of pouch, where the foot could be fully lodged to allow proper balancing.
On the other hand, for a bare back ride, being unguligrade or plantigrade doesn't make big differences, as the foot will hang loose in both cases.
[Answer]
When a normal - ok, me, so maybe not that normal :-) - human rides a horse, the feet are enclosed in boots. The front part of the boot goes in the stirrup, with most of the weight\* being carried on the ball of the foot. This isn't much different from the hoof shown in the unguligrade link. At most, a minor redesign of the stirrup would be needed.
\*Depending on what you're doing, various amounts of your weight are carried by your seat, inner thighs, or feet in stirrups.
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[Question]
[
[](https://i.stack.imgur.com/RXe8y.jpg)
### Context
This creature right here is one of the decedents of placoderms that that transitioned from rivers to land. The got onto land during the Middle Devonian and remained isolated from all other land animals. The only non-placoderm descended creatures are arthropods, amphibians, and a few species of birds.
### Anatomy
They have and spine, skull, a few ribs, flexible stringy organ support structures, and ball and socket joints for their exoskeleton. The exoskeleton is all over the outside except for in the joints and supports most of the creature. The joints are all endoskeletal and ball and socket joints covered with muscle and leathery skin. They have six legs and walk similarly to insects buy having three legs on the ground while walking. They don't molt their exoskeleton expands like sea urchins do and they don't even develop the exoskeleton until they at least halfway don't with growing to their full size. They are about 30% larger than a [Paraceratherium](https://en.wikipedia.org/wiki/Paraceratherium) ans weigh in at 45-57 tons.
### Question
Based on how this creatures anatomy works could it physically sustain the weight and height it is at, and if not what are the minimal changes I can make to allow it to be at this size and weight?
[Answer]
**Looking at Other Massive Animals**
The one of the largest land animals to ever live was the Argentinosaurus which could weigh in at a maximum of about 90 to 100 tons (though sizes of about 60 to 70 tons was probably more common.) Paleontologists utilized digital reconstruction of musculature and joints and estimated such an animal probably had a viable top speed of about 5 miles per hour. Bigger generally means slower. With extremely large animals joints and ligaments tend to be major structural weak points.
Additionally, titanic sized dinosaurs actually didn't have very big young, the massive Argentinosaurus laid eggs which were only about 22cm in diameter. Many such larger dinosaur species had to grow 10,000 to 20,000 times their birth weight to reach adulthood, predation was heavy and it is theorized that not many of the titanic dinosaurs ever reached adulthood. It is estimated that animals like the Argentinosaurus took 15 to 20 years to grow to the size they did. Something else you might include could be gastroliths, which are stones which the animal has swallowed to assist in grinding its food for more efficient digestion.
As far as your 6 leg design, there is a reason the only animals we see with limb configurations like that only tend to be very small like insects. An extra set of redundant legs burns a lot of extra calories without really adding much to the creatures ability to move. I understand that basic common sense makes it seem like 6 legs would be more stable and powerful than 4, but actually adding in an extra pelvis, spine, then another pelvis creates structural weak points as well. When dealing with moving weight in the tens of tons it is always better to minimize points of failure, and evolution seems to show us this. Across hundreds of millions of years no creature has ever evolved to have two pelvic bones and two spines. Its just too much complication and added points of failure when a stronger standard body layout is much more efficient.
[Answer]
Given the ancestral creature is actually a fish, and that fish are the ancestors of all modern animals from frogs to elephants and beyond, the question is actually moot: they can evolve to whatever size is required to successfully fill an environmental niche.
[](https://i.stack.imgur.com/Tshdm.gif)
*placoderm skeleton*
Like other animals, their skeletons will change and adapt, they may evolve structures analogous to hips or shoulders to deal with the weight and other adaptations might take place as well (large sauropod dinosaurs had many ligaments "strung" through their spinal columns and tails, creating a sort of composite structure using tension to provide a great deal of strength without a lot of weight.
Of course, the reason you chose this ancestral fish was likely the "cool" factor of the armoured head and jaws, but over the millions of years of evolution on land, you will need to explain what advantages this has in their current ecological niche. The picture seems to indicate a herbivore, so an armoured head and jaws don't seem to add much, and indeed might be an impediment, extra mass for little or no gain. Real creatures will either drop that adaptation if not needed, or shrink it to vestigial size.
So the short answer is this is an animal descended from fish, so like any self respecting fish (or animal) it will have a fully formed internal skeleton, not an exoskeleton, and thus have all the necessary adaptations and parts to successfully fill a niche on land.
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[Question]
[
Essentially, I'm designing a solar system for form of alien life. For the sake of ease, the star is roughly similar to the Sun, and the habitable planet follows an orbit anywhere between Earth and Mars.
However, from what I've been able to research, it seems that a large amount of extrasolar planets discovered so far are Hot Jupiters. Whether or not this means that this kind of planet is actually common or simply the easiest to detect is debated, but regardless, I've decided to include a Hot Jupiter in my solar system. However, that's raised a question for me -
**If a solar system contains a Hot Jupiter, what effect would it have on a nearby habitable planet?**
Quick note - I have yet to determine how close to the star my Hot Jupiter orbits, if that helps in anyway.
Any answers would be greatly appreciated.
[Answer]
# Orbits
Conventional wisdom says that terrestrial planets and hot Jupiters are not likely companions. These gas giants in close orbits aren't thought to form *in situ*, but rather to form further away from their stars and then migrate inwards. Two main mechanisms have been proposed:
* **[Type II gas disk migration](http://www.scholarpedia.org/article/Planetary_formation_and_migration#Gas_disk_migration)**, where a giant planet exchanges angular momentum with a protoplanetary disk, moving inwards. This usually happens early in the life of a planetary system, well before planets finish forming.
* **Scattering**, where a giant planet interacts with smaller planets or planetesimals, ejecting them to more distant orbits while moving inwards. This should happen later than type II migration.
It's clear that if hot Jupiters mainly migrate via scattering, the inner portion of a planetary system will be severely disrupted (see [Mustill et al. 2015](https://arxiv.org/abs/1502.06971)); any terrestrial planets would have to be much further out. However, it's possible that only the so-called *warm Jupiters*, which orbit 0.1 to 1.0 AU, use this method, while true hot Jupiters use type II migration to go even closer, according to [Levison et al](http://w.astro.berkeley.edu/%7Ekalas/disksite/library/levison06a.pdf).
Whether gas disk migration would be just as problematic for terrestrial planets is up for debate. Some simulations (e.g. [Fogg & Nelson 2008](http://adsabs.harvard.edu/abs/2008ASPC..398..525F)) imply that in such a scenario, material from the inner protoplanetary disk would be expelled into orbits outside the hot Jupiter's. Terrestrial planets could then form here, in a gentler region of the system.
# Composition
The simulations by Fogg & Nelson indicate that volatiles from beyond the snow line would be mixed with the inner disk debris, leading to terrestrial planets with heavy elements and water. This seems to show some good prospects for habitability. [Mandell et al. 2007](https://arxiv.org/abs/astro-ph/0701048) found that these planets would likely accrete icy planetesimals, leading to even more water; indeed, they could readily become worlds with oceans covering their entire surfaces. Some, in fact, could even end up in the habitable zone, with surface temperatures suitable for this water to stay liquid.
[](https://i.stack.imgur.com/yZNOi.png)
Fig. 2, Mandell et al. One of the authors' simulations. While most scattered protoplanets end up beyond the snow line, there's a chance for one or two to have stable orbits in the habitable zone.
# Atmosphere loss
Hot Jupiters often have their atmospheres ablated by the winds of their parent stars. This can result in atmosphere loss, forming a plume that trails behind the planet. [My order-of-magnitude estimates](https://worldbuilding.stackexchange.com/a/79943/627) indicate that this shouldn't be a problem for planets orbiting further out - and it certainly won't cause the ablation of *their* atmospheres, or some sort of mass transfer.
# Does this happen?
We do have a couple examples of systems with hot Jupiters and terrestrial planets coexisting. [WASP-47](https://en.wikipedia.org/wiki/WASP-47) is an interesting case. It contains two planets with masses slightly above Jupiter's - one close in, and one further out. There are also two terrestrial planets: one inside the hot Jupiter, and one between the two giant planets. This is a setup similar to some of the results of Mandell et al. In simulations with two giant planets, this sort of result was not unlikely. One giant could stay where it was, while the other migrated inwards. However, the furthest giant planet has an unusually high eccentricity relative to the other bodies, and so a more complicated mechanism may be at work.
[Answer]
The effects would vary
Gravitationally, hot Jupiters are known for their very low density, but their overall mass can go from roughly a third that of Jupiter, to ten times as big. While their distance to the habitable zone (HZ) in a Sol-like star is large (over ~0.5AU), a planet with 11 Jupiter masses would cause strong gravitational disturbances even at that distance. Possibly strong enough to push a planet in said HZ into an eccentric orbit that dips outside of it.
Brightness-wise, a low density, massive hot Jupiter may be able to block a significant portion of the sun with every orbit, meaning that every ten days or less (by the definition of hot Jupiter) your planet would suffer large dips in sunlight which may strongly affect habitability.
Essentially, a small hot Jupiter would have little effect upon a planet in the HZ, while a large one may even make the planet non-habitable, regardless of orbit.
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[Question]
[
So, bit of an unusual question, but here goes...
As I've read on other questions on the site, a creature gaining sapience would not automatically translate to a society equal to ours, and I believe it's safe to say that this isn't exactly a novice idea. Multiple films and TV shows show aliens, for one example, having an ant colony-style structure.
So, one thing is imagining forms of intelligent life, but another figuring out what kind of society has spawned from that intelligence. A species with a eusocial caste structure -again, like ants- could be envisioned as a communist-like society. On the other hand, giving intelligence to a solitary creature, such as an anteater, would probably spawn no society that can transcend the death of the individual, for it wouldn't be in their nature to come together.
So, after a somewhat lengthy prelude, my question is this -
**If a species of herd animal gained intelligence, what form of society would most likely develop, given the difference in their hard-wired behavior compared to us troop-descended humans?**
Any answers would be greatly appreciated.
[Answer]
**Herd animals have social structure. Use that.**
Most herbivorous animals live in matrilineal groups of old females and their descendants and pre sexual young. The dominant male of the day might reside with these groups (like horses and hippos do) or it might reside separately (like elephants). Sexually mature non dominant males are kicked out of the birth group by the dominant male when they come of age. These nondominant males are solitary or live together as equals.
That is a fine system for intelligent creatures too. A problem with intelligence: it is at root an arms race with intelligent conspecifics, who want to kill you and take your resources. A problem with intelligence and the social structure of herd animals is that a lot of the energy of the males is devoted to either ousting / killing the dominant male or maintaining dominant status. I suspect that entities as intelligent as humans (or chimps) will need to find some way for males to cooperate on some terms, or their intelligence will wipe them out.
[Answer]
**The only *technical* intelligence we know is Human - have a close look.**
If you look at dolphins, they have complex social structures, as well as many other mammals too. Normally this revolves around a dominant (male or female) group or individual surrounded by subservient others, in a competitive group vs group environment.
If you look at us, or rather the genus homo, we have been around for over two million years. You could argue the first evidence of cities, a major hallmark of intelligence, was 9000 - 10000 years ago.
So there is a difference between intelligence and technical intelligence. It begs the question of: Why didn't dinosaurs, in their 250 million years, develop technical intelligence? Why don't dolphins now?
There is a theory that a solution to the Fermi Paradox may be that life might be abundant- indeed, it may be intelligent - however technical intelligence is so rare that it hasn't happened in the universe before we developed it. Looking at the only evidence, us, developing technical abilities after such a long time of being around lends credence to this theory.
So the chance of developing *technical* intelligence is almost zero if this postulate is true, and the only gauge of this is our own society. Thus there may be a few factors to develop such intelligence which is rare and not inevitable:
* Fire: although other species developed stone tools, only the homo genus developed fire. It was developed independently around a dozen times amongst 1,200,000 years, and only caught on relatively recently, around 400,000 years ago when it became mainstream. Without this development humans cannot disperse from its native environment, and it has been argued cannot create home groups.
* Inadequacies: Humans are not very physiologically adaptable. We can only withstand a limited temperature range, uncomfortable in the rain, eat only a minority of foods of certain types and texture, can't run fast, not particularly strong, can't fly and so on. Security is a major problem. These deficiencies have been argued to spur on intelligence by virtue we need to find ways to overcome them.
* Farming and Cities - We need farming to free up labour and thought to develop technical abilities, and cities are concurrent with complex social structures.
In your herd society, using the above one of the main problems is already you have a large group. Individuals in herds act in accordance with established rules, and distance themselves from others in the group according to these rules. They are not usually intelligent, and only react to their immediate surroundings which usually include others in the herd.
The herd 'reacts' to the environment usually by those at the outer edge, and migrates across environments to suit the best and ideal temperature, food and other requirements.
Therefore a key ingredient to the above definition of intelligence is removed - that of fire, it is not needed. Another ingredient - insecurity - is already dealt with by the protection of the herd, and the formation of cities is not necessary too, and therefore the development of farming.
For technical intelligence to occur in your herd society, according to the above definition, the herd needs to have a need for fire (perhaps for food), a need for farming (same) and a need for security (perhaps other herds that roam and conflict with these herds). A command structure is needed to retain knowledge and pass it down. It could be old to young, perhaps the older individuals are in the centre, which hold the knowledge, and younger more fit are at the edge.
Yet there also needs to be adversity - not just other conflicting herds, but where technical intelligence needs to be required. Ie- perhaps if there was acid rain, the only way a herd can survive is to erect structures to accommodate the herd, or fit in caves. The knowledge for this needs to be passed to subsequent generations.
Again, as herd mentality is simply following those around you, you need to constantly fight this complacency with learned knowledge transferred from individuals. Eventually the herd mentality will likely break, with a centre group of individuals (likely hereditary) will develop, as this is the most efficient form of knowledge transference from generation to generation. It is inevitable then that it may actually be a monarchistic society eventually (perhaps with varying degrees of size of aristocracy).
[Answer]
In *[Surface Detail](https://en.wikipedia.org/wiki/Surface_Detail)*, Banks introduced the [Pavuleans](https://en.wikipedia.org/wiki/List_of_civilisations_in_the_Culture_series#Pavuleans), an alien society evolved from a hoofed herd species. Their civilization is described as conservative and slow to change, and valuing "Collective Wisdom" over individual exceptionality. They are also distressed by heights and being alone; their buildings are gently sloped ziggurats and they sleep communally.
That's just one possible take on the stereotypical herd mentality, of course. There are numerous human social structures all derived from that same aforemented "troop" so I would suggest taking one aspect of one sort of herd species and build upon it.
A more *flock*-like herd might value individualism as much as we (tend to) do, but each individual would be highly aware of everyone around them and it would produce a sort of dynamic conformity that ripples across society like the change of direction in a flock of starlings. Imagine a society changing as rapidly as fashion; belief systems and values might rise and fall on a seasonal time scale, distinct language and nationstates might be inherently precarious concepts.
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[Question]
[
So I am in a sci-fi world where I am trying to figure out a system of super-national and multi-national organizations that would retain the independence of nations while also defining how colonization, trade, international relations and war can be performed and also how it can have the power to enforce its rules while still allowing the nations to be independent. Basically what I want these organizations to do is to control the common resources shared by men of all nations: the air, the ocean, space and colonizable worlds, this organization is totally committed to the preservation and exploitation of these resources and attempts to prevent the tragedy of the commons from taking place with common resources, they also ensure that nations trade, perform diplomacy and other such things according to certain guidelines, and the most important thing is that they have the power to enforce their rules.
So there are many bodies with this inherent structure within the solar system, the ones that govern worlds are planetary governates, the ones that govern planetary systems are orbital councils and the one that governs the colonization of the solar system as a whole is the orbital council, these nations are multi-national in origin but most of them are super-national in practice, so let me explain what that means.
Multi-national organizations are organizations that are created by multiple nations to facilitate co-operation between nations to achieve certain, agreed upon, goals.
Super-national organizations are organizations that may be created by multiple nations but it has the property that it doesn't require the co-operation of nations to enforce its goals, it attempts to achieve certain goals that it decides independently from the nations and forces them to comply and it has the power of force to do so.
Now I want these governates to be super-national organizations that can tell nations what they can and cannot do to a certain extent, but I still want total national sovereignty to exist, ie. the right to declare war, the right to colonize other worlds, the right to claim territory, the right to independently exploit resources and so on.
To simplify
The organizations must be able to make rules independently from nations and they must be able to enforce those rules against un-co-operative nations using military force, however a nation must retain almost all of its rights including how it governs its citizens and the management of exclusive resources (exclusive resources are resources that can be exploited by one group without affecting the ability of another group to exploit their own) as-well as the right to declare war. The organizations won't always be as benevolent as they should be and sometimes they will become less independent then they are designed to be but what's important is that they are able to do the things I want them to do (manage and preserve common resources and controlling trade, war and diplomacy as far as it relates to the management of common resources) while also not having to infringe upon the independence of nations.
Edit: Governates are a term used inside the story, do not edit it out.
[Answer]
What you're describing is a more complex, multi-tiered version of a [federation](https://en.wikipedia.org/wiki/Federation).
Federations are effectively a collective of states that hand over *some* of their powers to a central body for the collective good. In Australia for instance, states can't raise a military as that is seen as the responsibility of the Federal government, but the Federal Government has its powers over the state limited to a set number of areas as defined in the Australian Constitution.
In the USA, the states seem to have more power than they do in Australia but in essence the same rule applies; states give over some of their power to a central authority that is there to provide for the common good of the states.
In your model, there are a number of other entity types, which sit between the states and federal authority whereas in Australia (and the USA) the third tier of government sits below the state at the local government or municipal level. That said, studying up on various federal government designs across the world would be where I would start my research into this.
As a special note on the EU; the EU may one day become a federal government for many European 'states' but at present that is not strictly the case. The recent political discussions over there about not being reliant on the USA for defence and building their own collective military capabilities / organisation is however a reasonable starting place for it one day becoming a federal government in its own right, however. Time will one day tell.
Another case you might want to look at is the UK, where you have England, Wales, Scotland and Northern Ireland all under a single rule, but with each 'nation' still having a some measure of their own self-determination.
Ultimately, what you suggest is entirely possible, and really only requires you shifting the dial of power within a federation back towards the states for this model to become a reality.
[Answer]
>
> super-national organizations that can tell nations what they can and
> cannot do to a certain extent, but I still want total national
> sovereignty to exist.
>
>
>
I'm afraid that it's blatant self-contradicton. Full-blown national sovereignty means that a nation in any moment can say "F\*ck you all, I'll do what I want". Even if it means breaking international laws/agreements or performing acts of genocide.
The best that you can get, while keeping national sovereighty intact, is some form of gentlemen agreement between all states involved. "I promise that I will try my best to follow the rules of our multinational organisation, but such behaviour will be completely voluntary". And of course, membership will be voluntary too. But such "gentlemen club" is anything but the world government, even if all countries in the world are its members.
[Answer]
I think your best option would be to have a semi-feudal system, kind of like what the Earth Kingdom does in Avatar: The Last Airbender. Make it so that the federal government controls things like the operation of the military and allocation of resources, but the states or whatever this universe's version of states are control everything else. For example, the federal government controls what to DO with troops, but each state is responsible for raising its own army that is subordinate to the federal government. I'm not suggesting you recycle this point-for-point, but incorporating elements of it could prove useful in your scenario. If you're still confused, check out this video on the topic. The guy explains it very well and I highly recommend it: <https://www.youtube.com/watch?v=I-FNPuIM9jg>
[Answer]
I think it would be better to make tiers of government, not nations, more like in the way that the US works. You have a federal government, multiple tiers of councils, and then the local governments. That way you make it clear that if any country secedes, the full weight of the nation will come crashing down upon it.
That also makes governing easier- all local governments (nations) can make their own rules, but anything anyone higher up says becomes law. Then you have less levels of redundant laws. Instead of everyone having laws about pollution, they have a page that says "See your local orbital council for other regulations imposed by the state" or they have a law that says "Regulations for pollution imposed by this country are x times as harsh as the statements outlined in orbital council rule 134432b. This rule allows local government rules to be equal to or harsher than this rule".
Wow, I meant this as a comment but I passed the length limit by 301 characters.
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