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Is it feasible to modify a combustion engine to source fuel from air and oxidizer from a tank, in an atmosphere that has significant amount of flammable fluids, such as one found in Titan?
If so, can you also tell the necessary modifications in your answer? Is there any weak or strong points in such an engine, that does not exist in a normal heat engine?
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Yes. The combustion chamber only needs to receive the appropriate mix of fuel and oxidizer, it needn't know how it was put together.
Titan's atmosphere is about 97% inert nitrogen and 2.7% methane, which is below the [flammability limit](https://en.wikipedia.org/wiki/Flammability_limit) for this gas. So you would need a small distiller to separate and compress the methane, and a heater to mix it up with the oxygen. The heating part you can do on the cheap, using a radioisotope thermal generator. You can even go cheaper if your engine is not started and stopped frequently, providing the preheating energy using a condenser from excess heat that your engine naturally generates. In that case, you would need a battery/generator based heater only for starting until it gets warm to the point of self-sufficiency.
You want a "rich burn" to save on oxygen, so a FAR of 16:1; this means proportions of about 3.5 oxygen, 12.5 nitrogen, 1 methane. You need to enrich the methane proportion from 2.7% to 8% (1:12.5), i.e. about a factor of three. Then you add oxygen (1 L every 3.85 L of enriched Titan air).
This means that if we consider oxygen as the "fuel" ("what you have in your tank"), on Earth one engine cycle is 1/(16+1), on Titan it is 1/(1+3.85); your tankage efficiency is 4.85/17 = only 28% of whatever the same engine would have on Earth. **For the same mileage, you need three times as much tanks**.
My figures are probably a little off because I ran the calculations at STP, while Titan surface pressure is 1.45 atm. On the other hand, thermal cycle efficiency should be higher than Earth's since the ambient temperature is a good 200 K lower.
# on the possibility of "perpetual motion" on Titan
Combustion engines on Earth take fuel (let's say methane CH4) and the oxygen from the air (O2) and convert them into H2O and CO2. In the process, some nitrogen N2 gets sucked in and oxidised to NOx, subtracting useful energy and producing harmful nitroxides; which is why even hydrogen engines are not "clean", unless they burn pure, costly oxygen instead of nitrogen-containing, free air.
The final equation is that the chemical energy of H2O and CO2 added together is less than the chemical energy of CH4 and O2. The difference can be converted, with some efficiency loss, into heat and movement.
On Titan we have for free both N2 and CH4. If we add O2, the possible final compounds comprise CO2 and H2O, which have little energy (and less than N2 and CH4 combines, so we can operate conversion at a gain).
Actually, it is *because* we need lower-energy compounds that we need to bring along oxygen tanks for the engine.
But if there was some compound that needed no oxygen, say hydrogen cyanide HCN or (CN)2 cyanogen, or cyanamide, or anything else, **that also had less energy than N2 and CH4 combined**, *then* we could run the conversion and siphon off the energy difference to power our engine **for free**.
The "trick" would be that the conversion would need to be not spontaneous (otherwise Titan would have exploded long since); our "engine" would for example heat the CH4/N2 atmosphere in the presence of an appropriate catalyzer, expending some energy to supply heat, until the magic happened, then the expended mixture would be expelled, extracting useful work and heat to further the process, and the cycle would start again.
We would also need for the reaction *not* to be so strong as to be self-perpetuating, otherwise as soon as we started the engine, again Titan's atmosphere would explode.
It all depends on the availability of such an end product (I have done some math and unfortunately (CN)2 and HCN have too much energy to be useful; it would actually *cost* us to convert CH4 and N2 into those) and a suitably compact process. But it could be a workable idea, and after all, we needn't *name* this miraculous end compound.
(In Campbell's *Aarn Munro* series, the Teff-El people wage war using an unobtainium "atmospheric catalyzer" that has the effect of burning the atmospheric nitrogen, rendering the target planet scorched and effectively airless)
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The engine doesn't care what is the source of the mixture it is burning in its cylinders. As long as it burns, the engine is happy and running.
Therefore it is surely possible to have a tank of oxidizer providing the oxidizing agent to be mixed in the correct ratio with the combustible before reaching the combustion chamber and be burned.
If the oxidizer is stored in form of a liquid (i.e. liquid oxygen) you need the usual additional elements to evaporate the liquid preventing the cryogenic temperatures from negatively affecting your system. Maybe you can even use part of the waste heat for this scope.
You might also need additional protection on some engine parts from the pure oxidizing element, and don't forget that nitrogen in our atmosphere has a good role in mitigating the temperatures inside the combustion chamber. Burning pure mixture might overheat your engine if not properly taken into account during the design.
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It is a common trope that interstellar civilisations rise and fall, only to leave ruins behind. The origin of this idea seems to be a mismatch between empires and civilisations. Yet while (West)Rome fell, human civilisation hadn't disappeared from the Italian peninsula. And even when Homo Neanderthalis was replaced by Homo Sapiens, there still was a civilisation on Earth. Even an uninterrupted one.
We, as a species, are currently at a point where we could conceivably wipe ourselves out in a global war between superpowers. However this becomes ever more unlikely as a species spreads across the stars. Even though external hunters or internal wars could deal massive amounts of damage, nothing but an extremely systemetic approach to genocide will get everyone. I assume that there are groups of posthumans from this civilisation living as digital beings of nuclear reactors on icy rocks in the interstellar medium. This would only ever be a small group, only numbering in the billions, but if groups like them survive whatever kills 99.9999% of the civilisation, they will reestablish the civilisation in no time.
Even if they suffer from a maschine rebellion and every member of the original species is turned into biofuel, I don't care. **I'm looking at this from the perspective of the Fermi-paradoxon, so it doesn't matter if a maschine-civilisation replaces a biological or diverse one. I only care about utter and total annihilation of anything that could be called advanced.**
**So what**, apart from bathing the entire region of space a member of the civilisation could have reached with star powered gamma ray lasers for years, until every possible hiding hole has become uninhabitable, **can kill an interstellar civilisation of a million worlds?**
PS: This assume a no FTL hard-scifi universe.
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**Let's talk about your goal**
Historically, a "civilization" was defined in a one-world-centric and highly political way: if the ruling government, its supporters and military, were completely demolished — that civilization was considered destroyed. The Myans, the Easter Island peoples, Cahokia, the Olmec... Oh, for the most part their genetic code can be found lurking around today, but our history is littered with civilizations that once thrived and influenced our world — and yet are gone, leaving only ruins.
This is actually a good starting point for an answer. You want an entire species wiped out — but I posit that there's little to no difference between an entire species and an entire ethnic group. I watched during the 1990s as television brought horrific news about the Bosnian genocide. We're not talking about one empire destroying another — we're talking about peoples in Yugoslavia who had intermarried, done business with one another for decades (and generations), and yet (unbeknownst to the world) were harboring a hate that makes whatever nonsense is going on in the U.S. today look like a schoolroom spat. The result is known today as *ethnic cleansing,* which is simply a smaller scale of what you're looking for, "special cleansing\* (See [Merriam-Webster](https://www.merriam-webster.com/dictionary/special) definition 3b).
Whether the ethnicity is wiped off the face of the Earth or the species is wiped off the face of the galaxy — it's the same thing. What's left behind are the memories of a once vibrant people.
**Having got that out of the way... what can do this on a Grand Scale?**
*1. Disease*
We're living through that right now and the experience is directly relatable. All you need is a disease that's impossible/ultra-hard to eradicate, that has a very long incubation period (to meet the needs of a non-FTL universe), and is 80%-90% mortality rate and you have a believable condition to wipe out a civilization — especially if your disease does something gratefully rare among human-encountered diseases: make the carrier impotent. Whomever survives the disease can't propagate the species. The civilization is dead in one generation upon every planet it touches.
However, in a non-FTL universe where light can always deliver a message faster than the disease can travel, it becomes less believable that this method would work to completely wipe out a civilization. Not impossible, but unlikely. You could use the excuse that the disease killed quickly to keep the knowledge from spreading ... but then comms would go dark. It wouldn't take long for someone in those million worlds to figure out that something was spreading (would make for a really cool story, though).
*2. War*
This one is so obvious it's a trope all to itself — but having just discussed the Bosnian Genocide it's a very real and very viable solution to your problem. L. Ron Hubbard used a basic concept to set the stage for Psychlo ownership of Earth (and every other planet they were awarded): they gassed the planet.1 If you have access to interplanetary resources, it's beyond conceivable that you can release enough poison into any atmosphere to bring down a civilization. Yes, there's always the possibility that someone is quick enough to get into their bunker and survive — but your universe has no FTL, which means its inhabitants are conditioned to thinking in terms of decades and centuries. Send a fleet of drones to gas a planet and keep it gassed for 100 years. Then send your colonists to take over the planet.2
To be fair, "war" could be described as the most viable delivery mechanism for whatever destroys the civilization (in which case it kinda doesn't belong on this list) because it could deliver the disease as easily as it could a poison gas. However, war is likely the only mechanism that can bring about complete destruction of a species: an intentional, focused pogrom that would survive the test of time to complete its task.
*3. The collision of galaxies*
A million planets without FTL travel means millions of years were used to achieve this marvelous pinnacle of civilization! But millions of years actually count in terms of astronomical events. That's enough time for [galaxies to collide](https://www.space.com/hubble-telescope-galaxy-collision-photo.html). While this could lead to a suspension-of-disbelief solution (you didn't restrict how short the destructive period had to be), it does run up against a fundamental axiom of good science fiction:
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> Space is big. Really big. You just won’t believe how vastly hugely mindbogglingly big it is. I mean you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space. (Douglas Adams, *The Hitchhiker's Guide to the Galaxy*)
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Space is so big that it's conceivable for to galaxies to collide and not actually interrupt much of anything. Imagine the millions or billions of years required for the galaxies to actually collide and (let's say) pass through each other. "Whew!" some idiot might say, "[that was a near miss!](https://www.youtube.com/watch?v=zDKdvTecYAM)"
*4. Something's wrong with the black hole...*
If you need a natural phenomena that's not as slow as colliding galaxies but might not be as fast as war, consider something going wrong with the galaxy's central black hole. The easiest solution [is an explosion](https://www.nasa.gov/mission_pages/chandra/news/record-breaking-explosion-by-black-hole-spotted.html). However, if you want ruins left behind for someone to find, this might not be the best solution.
**Conclusion**
As a conclusion, I'd like to return to the Bosnian Genocide. Yugoslavia had successfully repressed the hate for a while, but once it was allowed to resurface, it came back with a breath-taking mind-alteringly scary vengeance (if you, the reader, were not alive to experience the 90s... you really have no idea just how deep hate can run). And this is important.
I find a million-planet utopia unbelievable. Completely unbelievable. Unless, like Yugoslavia, it's suppressing the hate. It's nice to believe that humans can outgrow hate (and maybe someday we can), but I simply don't see it.3 But for the sake of your story, let's assume that for the time it took to get to a million planets your civilization was able to suppress all the hate...
*5. Civil War*
Nobody gives enough credit to the civilization-destroying capacity of civil war. [Ancient civilizations were destroyed by it](https://historydaily.org/ancient-wars-that-destroyed-and-created-civilizations). Just because the U.S. survived its civil war doesn't mean it's improbable that others would be destroyed by it. Let the hate loose and and the doomsday machine tech that a million-world-spanning civilization will certainly have (we already have it here...) and you have the seeds to destroy any civilization no matter how large.
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1 *Battlefield Earth.*
2 *Kaiju are uber-cool, but a very inefficient way to take over a planet. I'm just sayin'.*
3 *This won't be a popular comment, but it's relevant to my statement. The "judgement free" generation is the most judgmental generation that's ever existed. Rather than judging ethnicity, race, sexual orientation, etc., it's judging ideas and philosophies - and the only right answer is the "judgement free" generation's answer - and anyone who disagrees is **hated**.*
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## Killing civilizations vs killing species.
When Ancient (Western) Rome fell, the Dark Age begin. It's mean that many things (art, technologies, knowledge) was lost and quality of life became low. That's why we call it *civilization fall* and that's the difference between another empire fall: when [British empire](https://en.wikipedia.org/wiki/British_Empire) fall, people still enjoy same level of tech and live in general.
## The end of interstellar civilization doesn't mean the end of civilization at all
In many apocalyptic scenarios people after global nuclear war still survive but population drops down and technologies degrade. When people lose access to rocket science, when flight become banned because of religion reasons - we say that human civilization is not space civilization anymore. Even if that civilization is great in biotech and achieved personal immortality.
## Transformation to something more
It's well known trick in many novels: *The Predecessors become somewhat more than space travelling civilization*. Some say they transform to energy form, some that they go away to higher dimensions, another argue that they recognized the Universe then they bored from life and then just fall asleep.
In fact, they never was destroyed but in fact they are not in our Universe now. And yes, when we say 'they' we suppose there are many civilizations before.
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Boredom, ennui, existential fatigue. A sudden breakthrough in logic overcoming its animal origins. A civilisation which ceases to care effectively ceases to exist as far as Fermi is concerned.
Put it another way: once a civilisation finally achieves the maturity to sit in a room and do nothing, it will never bother to make contact with any interstellar neighbours, having finally appreciated that there is no reason to do so.
The species involved would eventually die out, having no reason to breed.
Alternatively, you could invent video games, virtual reality or a religion promising an afterlife (or scientific proof of an afterlife) which would make IRL life not worth living.
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1. If the civilisation hasn’t spread to that many star systems it might be sufficiently unlucky to encounter a nearby Supernova. That could destroy civilisations for many light years in the vicinity. But OK this might not be appropriate for a million worlds.
2. There might exist a very technologically advanced civilisation that has some reason to destroy other civilisations. Perhaps the new spreading civilisation is seen as an exponentially expanding pest to the more technologically advanced one and they might systematically root them out and destroy them utterly.
3. Perhaps at a certain point in the development of most civilisations they make a discovery of some sort or have an encounter of some sort that changes them so utterly that they are transformed to such an extent that they no longer count as a civilisation as we would recognise it.
Case in point Arthur C Clarke's A Childhoods end where Mankind face a very unexpected “end”, although this only applied to Earth there is no reason why something similar shouldn’t happen to a much larger civilisation. A variation on this might be a breakthrough to another dimension of space or of mind offering so much more that they willingly abandon our universe / dimension entirely.
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Your number one goal is actually connectivity.
Think of it this way. If you wanted to destroy most of humanity without nuking the hole place, what would you do?
An airborne highly contagious virus who is engineered to infect and kill humans.
Also make it slow enough that it infects all of humanity before it starts killing people, I actually have a zombie idea similar to that, so before people can even go into bunkers they are hit.
So because air connects all humanity right now, and people were not warned.
This virus would destroy humanity.
And your added engineering would make it impossible for the immune system to
fight it.
Now imagine this virus was only spread through intercourse, or even like the corona virus.
It's still deadly. But if you stay at home or use complete protection, it just won't be able to infect you no matter how deadly it is.
So I'm leading to how in Mass Effect, and maybe a spoiler here so beware, how the evil robotic race of murderers actually designed and maintained something called mass relays.
Those relays enable faster than light speed travel and thus they connect the entire galaxy together.
Now this had the added benefit of making sure that every single civilization that ever appears would relay on those mass relays making sure that their advancement path is in line with the Reapers. So later when the Reaper emerge from deep space, they just follow the dotted lines set by the mass relays and wipe out all advanced life forms from the face of the galaxy.
Easy peasy
Now I think you just need to find a way to connect the entire civilization of that race together with a technology or a even magic, if you want.
Bonus points if the same tech is used in spaceships and even on far outposts.
And this would make the premise, imo at least, far more interesting.
As it would make the fall much much worse by the same tool they used for them advancement. Technology.
I know it's not exactly unique, but it works.
Once you connected them then unleash the doom virus or killer robots or angry demons or whatever you want.
I would offer other more "magical" concept but I don't think they will fit.
So I will just casually mention that they might be connected by "souls" and how dappling in this field caused their doom. But that's more of a science fantasy.
Anyway unless they are completely connected, you won't destroy them.
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Dual purpose Von Neumann probes.
Imagine early in the space exploration, Earthlings launch a few Von Neumann probes. After some troubles, either technical or political on Earth, contact with the probes is lost and they are forgotten. Over the millennia it takes humanity to spread over the nearby star systems, there is no sign of the first pioneers. But they are around, they keep colonising world unsuitable for humans, extracting resources and growing both faster than humans and with a significant head start.
Then when the humans and the machines meet again, an unpleasant truth comes out. The probes weren't just for exploration and colonisation. They had a military purpose as well. Maybe they were supposed to be a buffer against other species. Maybe they were supposed to limit spread of other nations or people with the other skin colour. Or maybe they were just trained to "recognise" criminals on a racist data set. Whatever is the case, machines consider the new human civilisation their designated enemy. And there is no pleading with them, no talking it out, the machines won't stop till all the undesirables are exterminated.
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As the title: I want to know what kind of organs or modifications need for plants like tree to gain energy from lightning or electricity (and still fine or safe or alive of course).
Since I have a region that constantly has thunderstorm in it, and just recently seeing a tree get struck by lightning make me wonder about it.
* the tree need to be organic so no machine or bionic thing.
* the tree may or may not have the usual photosynthesis, would help to know the impact or side effect though.
* not necessarily for the tree to use the electricity as self defense especially not on purpose or accidental or due to the side effect, but would be nice to know though, assuming the tree manage to contain such electricity in its body or organs somehow.
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A lightning has on [average](https://it.wikipedia.org/wiki/Fulmine#Descrizione) a voltage drop in the range of $10^9$ to $10^{10}$ V and a current in the range of 2 to 200 kA. This means that to store it for future usage, anything would need to handle between $2 \cdot 10^{12}$ and $2 \cdot 10^{15}$ W, as calculated by multiplying the voltage drop by the current.
I hope you realize those numbers are gargantuan, they are not too far from the solar power hitting our entire planet ($50 \cdot 10^{15}$ W). The lightning happens because the few kilometers of air between the cloud and the place where the lightning hits prefer to let that energy free instead of holding it.
Moreover the mechanism to store that insane amount of energy would need to act with the same time constant of the lightning discharge, which is from 5 to 500 milliseconds, and would need to be able to store it without releasing it back (see the atmosphere).
I don't think it is possible for a living organism based on life as we know it to be able to handle that amount of power while coming out of it alive.
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As L.Dutch said, lightning is super energetic and any plant probably wouldn't survive it's strike. What I can imagine is the forest benefiting from some of its trees *taking the hit for the team* and burning down. Here are some ideas (which might not be realistic):
* A tree could burn in a way that radiates lots of UV rays which would help the surrounding trees grow.
* Roots could burn into charcoal which would nurture the surrounding trees.
* Lightning strikes could in some way rid the forest of some tree-eating bugs that would otherwise pose a big problem for the trees. If there weren't such bugs, the trees could be more vulnerable to them in a way where they could have more of what those bugs are after.
Roots could have some special conductivity. If a tree got it, it would still burn down, but also send a *healthy amount* of electricity to other trees. This by itself wouldn't be a benefit, but could be used as a way to transform the enormous voltage into levels that other trees would survive.
* Tree bark could be covered in a layer that would harden itself upon electrification.
* Thees could be luminiscent a bit, one tree getting hit could *charge up* surrounding trees by charging up rechargable chemistry-based batteries.
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Rather than focusing on the dynamics of the actual lightning bolt, perhaps you could consider the mechanisms that occur before to discharge and breakdown of the air. Lighting forms from cloud to cloud, within clouds, and from cloud to ground, but also from ground to cloud.
[](https://i.stack.imgur.com/9QxxE.png)
The Feynman Lectures have some discussion of electric fields in the atmosphere. <https://www.feynmanlectures.caltech.edu/II_09.html>
and point out that we are walking around in a potential gradient most of the time anyway, so for your world you could look out how to have extremes of that. I think people have tried to come up with ways to capture the charge carried by rain drops, but it wasn't very successful.
In your case with the vegetation, as the previous posts mention, protective mechanisms to help discharge the actual strike might be more likely to evolve first, or might still be needed to protect the plant.
Anyway, the build up charge doesn't occur instantly, so perhaps there could be mechanisms that occur on biological time scale.
Electric eels have specialized cells each of which can have a voltage of about 100 millivolts, and then have several thousand of those cells stacked together to produce voltages of 800-1000 volts with substantial amperage that can discharge fairly quickly.
So perhaps there could be a similar like cellular structure where some form of rectification occurs when the charge build up is occurring, allowing a cellular battery like structure to charge up either chemically, or by polarizing a material. Or perhaps a super capacitor like structure could also be formed by the plant structure this would be a very high surface area organ within the plant where a conductive nanostructure is coated by an insulator. Although in our world on earth super capacitors tend to be low voltage devices. Or perhaps some genetic engineering is involved.
In writing this, I am mainly thinking of a non-earth like environment. However, even on earth trees can be viewed as electrical circuits and there are people who try to power electrical circuits from trees. (They don't produce much power)
[](https://i.stack.imgur.com/h1s21.png)
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If a tree some how manged to create bark that acts like a wire or a lightning rod (such as encrusting is with large amounts of iron or copper) then there may be a way.
If the tree picked up the sighs of a lightning storm, such as the affects to pressure and humidity, then they could begin to store large amounts of carbon dioxide and water just below the bark. Then they would protect the leaves somehow (lots of options). When the lightning strikes the tree the energy will be used as a stand-in for light in the photosynthetic process and produce massive amounts of glucose from the carbon dioxide and oxygen it stored beneath it's bark.
Ideally this tree would actually be part of a massive network of trees to spread the energy but still most of the energy will likely be sent to the ground to avoid frying the tree. Being part of a network would make the whole process more lucrative as the chances of getting hit would increase exponentially.
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I think there's a problem in terms of evolutionary timeframes, in that conditions that cause persistent thunderstorms are very rare, and are very contingent on broader climactic systems, which change on what are, on an evolutionary scale, very short periods of time, so it's doubtful that any organism similar to a tree will be able to evolve in the time available.
I think an organism like this, an electrosynthetic rather than photosynthetic organism, could only really exist on a planet where lightning strikes are a more reliable source of energy than sunshine, which I think points to something like a rogue planet (i.e. a planet that has been flung out of its home star system), with a thick, energy-retaining atmosphere(1). I don't think these organisms, overall, would be particularly tree-like. I imagine what we would see is some sort of above-ground rod structure, to attract electric discharge, and below ground, quite extensive structures for dispersing the energy into usable quantities and converting the electrical energy into chemical energy, which can then be cached and used over time to maintain the biological functions of the organism.
(1) I used to assume that rogue planets would always be icy, frozen planets, seeing as they have no sun to warm them, but according to recent models, because these planets don't suffer from the atmosphere-stripping effects of stellar radiation, they are more able than you would think to retain thick, hot atmospheres over time.
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It needs an Internal battery, batteries aren't too complex and one could imagine one biological version existing
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A group of English-speaking settlers travel to the Earth-like exoplanet of Rataan, which is 5 light years away. They board the generation ship *Genesis* that will reach Rataan in 200 years (0.25% of the speed of light). However, transmissions between *Genesis* and Earth are limited to text-only communications because of power costs. A new ship is built 150 years after reaching Rataan and reaches Earth in 50 years. Although the written form of English will likely remain the same over the 400 intermediate years, will sound shifts impair communication when the delegates from Rataan reach Earth 400 years later?
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Absolutely. Look at how different American English and British English are after only 300 years, and that was with continual contact. Same with Australian English. A real, back woods Aussie is barely intelligible by the rest of the English speaking world. And just look at Scottish twitter. Unless your ship has some grammar nazis or English majors on it, the dialect will most certainly shift drastically in that amount of time. I'm sure they'd even come up with their own words and idioms and whatnot within 100 years. The dialect on Earth would have also changed drastically in that amount of time as well. Two diverging groups of the same language with no audible contact and written contact of status reports only? That'd be like taking a peasant from 1600s England and putting them in today's Louisiana Bayou. Communication would be difficult, but not impossible if the two groups cooperate to use words and an accent that they both can understand.
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It can be an impediment if you want it to be. 400 years of linguistic drift within English is enough that linguists begin to treat it as a distinct language (Of course what is and isn't a distinct language is a fuzzy and ill defined distinction amongst linguists).
We can use this as a marker as a ballpark estimate for how much drift you can get in a 400 year span. It's enough that you can read documents and make some sense of them but not with the ease that you read the well written posts of this site.
Given that this is the amount of drift among one population and you have two to work with you have enough drift to have the populations as mutually intelligible as you like. One easy way to get the result you want is your decision about how effective their efforts to counteract this drift over the course of their voyage.
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Yes, 100%, no verbal contact for 400 years is definitely enough for a language to cease being intelligible to those who speak the original (pre-isolation) form.
Look at Old French and Old Spanish, noir and negro respectively for the colour Black, and that is with linguistic contact. Being isolated would speed up the divergence. So yes, the span of four hundred years with no verbal contact would indeed leave them as classifiable as different languages from the verbal changes over time.
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Another example to consider is the differences between Dutch and [Afrikaans](https://en.wikipedia.org/wiki/Afrikaans).
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The Dutch East India Company established a [colony](https://en.wikipedia.org/wiki/Dutch_Cape_Colony) in what is now Cape Town in the mid 1600s.
Until the early 20th Century Afrikaans was considered a dialect of Dutch but was later declared a distinct language.
Over time, different colonies of a language develop different terminologies based on what is important to them in their locality.
Pronunciations develop fashions, some die out and some continue, which can increase the divergence.
Some interesting books are *[Mother Tongue](https://en.wikipedia.org/wiki/The_Mother_Tongue)* and *[Made in America](https://en.wikipedia.org/wiki/Made_in_America_(book))*, both by Bill Bryson.
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I have this idea of a character capable of manipulating heat (more than just controlling fire, really controlling the heat of stuff around him). Let's now say that this character digs a tunnel. Would it be possible to harden the sides of the tunnel (and even create kind of pillars) simply by heating the dirt around ? Like turning it into a kind of magma and then cooling it down into something solid ?
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Depends on the dirt.
The best farming soil wouldn't work for this, as it's mostly organic substances, with mineral material as a substrate. Clays wouldn't work well, either, because by the time rock has weathered into clay, most of what might be seen as "rock" material has been converted to something that forms microscopic flakes that make up the clay -- they won't actually melt in a fire, they just sinter even at kiln temperatures, so you get something more like fired ceramic.
What would work, at least to some extent, is sandy soil. The sand is largely quartz (which melts at similar temperature to glass), feldspars (which melt at similar temperatures) and micas (which don't really melt, but will dissolve in the melt). The end result will likely resemble obsidian more than, say, granite -- but it'll pretty clearly be a rock of some kind.
This does require a fire much hotter than a campfire -- an air-blast coal fire could get hot enough, and surely a gas-oxygen torch flame could.
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It depends on where he is digging.
Some grounds can be "easily" turned by heat into a glassy material, some require more attention.
The higher the organic fraction, the more difficult it is.
The higher the clay content, the more difficult it is. (as a kid I tried to bake some clay which I dug from the ground. It became hard, but crumbled directly in the oven)
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**Unlikely**
Dirt contains a lot of organic compounds that would simply burn if you tried to melt it (at least if the environment contains any kind of oxidizer). You could however try to harden the dirt akin to clay by removing the water with heat, but then again, it would most likely become brittle.
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While I'm working on the *Magical Artillery*, let's look at another common spell.
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***Mage Light*** is a very handy invention. When cast, the spell creates an orb, 13 cm in diameter. The orb radiates white light, usually between 30-50 candelas in luminous intensity, though it can be decreased or increased at the mage's convenience, but brighter lights dim sooner.
The orb is very lightweight and lukewarm or warm to the touch. While it can last quite long, if its light begins to dim, a special fluid has to be poured into the orb to slowly restore its brightness to the preferred level.
Also, the orb can hover around people. It usually has an orbit (preset by the caster) that it tries to follow. However, it’s easy to detach or stop them; you can do it with one to three fingers.
The spell requires a very tiny amount of material components (not counting the fluid that it uses).
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Magic is actually ancient technology in this world. **Given that and the info above, how can my *Mage Light* actually work?**
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Tiny luminous nanobots in a utility swarm. ‘Light’ gathers them together in one spot and they start to glow, providing a strong point light source. The nanobots require fuel to glow, fuel which they usually passively harvest, but which needs actively supplying in times of high usage.
Also can be used to create ‘fairy lights’ to distract foes, if you just need low level all-encompassing illumination, ‘dispel darkness’, or outline foes in blue-green ‘faerie-fire’
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> the orb can hover around people.
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The orb is nothing more than a small, gasoline or alcohol propelled drone.
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> The orb is very lightweight and lukewarm or warm to the touch. While it can last quite long, if its light begins to dim, a special fluid has to be poured into the orb to slowly restore its brightness to the preferred level.
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Inside the orb there is a catalytic membrane where a small amount of the fuel (which you call special fluid) is burned to give off light and heat. Pouring the liquid is actually a mere refueling.
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**The orb is the mage.**
The orb is driven by autonomic functions of the mage, like the heartbeat or peristalsis of the gut. This autonomic function of following is contingent on the mage being alive - if a mage dies the orb drops to the ground.
It might not go out. The orb is powered by the mage as well, tapping energy reserves of fat or glycogen. Making an orb glow and move requires caloric expenditure on the part of the mage. Many mages cultivate an onboard caloric reserve, putatively for this reason. A mage who was physically going all out (example, running at top speed) might have his orb dim in brightness.
The fluid poured on the orb to restore it is of a high caloric value and is actually being poured into the mage. The fluid should restore his energy level and so improve the brightness of the orb. Mead is a favorite but distilled spirits work very well also. Many mages carry a flask containing orb restorative, putatively for this purpose.
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It is magic. It does not need real world explication. Look at Harry Potter: absolutily nothing "magic" makes sense, but we love it. May be casting the spells in a dead language like latin makes the trick. I dont Know. Avoid things like "3 cm in diameter" "between 30-50 candelas", this is scientific/technical talk. Magic is not scientific. It could tell: "a orange sized light orb", "so bright as five bee-wax candles".
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But if you insist on a scientific expanation (sort of) Static electricity is your friend. Will-o'-the-wisp and St Elmo's fire are just plain gas and electricity.
<https://en.wikipedia.org/wiki/Will-o%27-the-wisp>
<https://en.wikipedia.org/wiki/St._Elmo%27s_fire>
How do the Magic controls them? Electricity! Human brain works based upon electricity. It is all just a matter of electricity.
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I'm talking about place similar to the Jordan desert, where the biggest prey is similar to wild donkeys and antelopes like oryx and gazelles. My creature is 1.92 meters tall and 4 meters long, looks like a monitor lizard but its limbs are located under its body and has a tail that doesn't touch the floor, making it more quick and agile. Being a large animal and living in a place without trees or dense vegetation, how would it ambush his prey? Would it be enough to put big rocks or another thing where it can hide? How would it be its camouflage? Would it hunt in packs? Or would it be better another hunt technique?
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You are actually depicting [Megalania](https://en.wikipedia.org/wiki/Megalania) - a gaint monitor lizards , varan. It's biggest (and deadliest) alive relative is [Perentie](https://en.wikipedia.org/wiki/Perentie) - only 2 times smaller of what you need. Like any other of it's relative spices it was ambush predator. Megalania were living in desert and near it. There are some videos on youtube how varans hunting.
They do not actually need cover: they rely mostly on camouflage, tactics and, suprisely, speed. Yes, they can just chase their prey at a speed of a dog.
When they ambush, they slowly move toward their prey, preferaby from the back, from the low places. Prey in most cases do not run away even if it sees the lizard - varan is quite smart and uses special pattern of movement, so pray just thinks it passing by or laying in the sun (they learn and adjust it's behavior for each type of pray - to smart for a lizard).Then, when target is several meters apart - they quickly attack and bite legs using their sharp teeth and venom (yes they are smart fast poisonus lizard). This venom is not that deadly by itself, but it makes lizard's bite fatal even if prey gets away. So varan can just follow it and eat it when it drops.
So you don't need to invent what was already "invented in nature" - there were and and are gaint lizards with legs under body and tail above ground, leaving in the desert and hunting on any pray - from rats to cows.
P.S. I would never go to Australia wild lands. I am not that brave!
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**Ambush, sidewinder style.**
[](https://i.stack.imgur.com/zbKqt.jpg)
<https://www.naturepl.com/stock-photo-peringuey-s-sidewinding-adder-bitis-peringueyi-hiding-in-shallow-sand-image01561641.html>
Your great lizards will wriggle down into sandy spots chosen for their proximity to game trails, salt licks, or other places prey will visit. Maybe they hurl some sand and dirt up atop themselves. When the time is right they burst out and capture the prey. That is what this sidewinder is doing and that is pretty much the strategy of crocodile and alligators.
Hiding out under the sand is also good because it is cooler in there. Also, if you take a leak no-one will know.
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## At night
Probably the simplest possible answer you can think of. For this, your lizard will need a sensible advantage over its prey: better night vision (like lions), echolocation (like bats) or sense of smell (like copperhead).
The lizard can ambush (leopards) or actively pursue (wolfs) its prey, hunt alone or in packs. Pursuing behavior is a little bit harder to implement with a cold-blooded creature at night, but not impossible.
As far as I can tell, [Arabian wolf](https://en.wikipedia.org/wiki/Arabian_wolf) is the only predator close to this size in Jordan. Wolves are mainly nocturnal predators.
## With traps
If you want to create a scarier ambush predator then your lizard can take an example from spiders:
* bury itself in the sand, like a [six-eyed sand spider](https://en.wikipedia.org/wiki/Sicarius_(spider));
* dig a burrow and ambush its prey from it, like multiple species of [trapdoor spiders](https://en.wikipedia.org/wiki/List_of_trapdoor_spiders);
* build a giant web near the water source to trap antelopes, like any other spider.
For the last two options, the lizard should be able to produce silk.
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it could have very slow metabolism, meaning one catch could last long, and it should be able to hunt at night, plus, if it has super accurate thermal vision/echolocation/sense of smell/vibrations it would more likely be able to track prey succesfully, this dragon would not likely fly, for the energy consumption would be great, it could borrow itself into sand for a trap and give of a scent so animals come closer, then eat, also camouflage, could be actuall sand which is stuck by a mucose like substance that is sweated when they are prepared for the catch, the sand could help with temperature for the breath, which would probably not be fire but something poisonous, so if prey gets away, it wont be much longer till it dies
also: chlorophyl could be an alternative
P.S. I have a spanish keyboard setting, so it tries to correct words to spanish, so sorry if there are any misspelled words
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Sidewinder-style ambush.
Your lizards would bury themselves completely in the sand, only leaving out their eyes. When they see the prey, they burst out and eat it. That is what Mr. sidewinder and stargazer are doing. I highly recommend that your lizard be able to stun the prey with electric shocks. Also, I recommend that the lizard have a venomous bite, to kill the prey. The burying in sand strategy will protect your lizard from the heat and prevent any creature from being suspicious.( MLP reference here.) This is how your lizard would hunt in the desert.
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So, it's the future and society has long since became divided upon distinct lines of rich and poor. The rich upper-class living a life of luxury and the poor lower-classes living each day at a time, thousands of meters above the Earth in the sky, in massive balloons and the tops of skyscrapers, the ground reserved for the rich, but why?
What are the poor doing up there, what work is being done up there, where the air is thin?
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**Menial jobs are there everywhere - even up there**
There are plenty of menial jobs that may need to be done in the sky. Here is a selection:
* **Courier** - People still order stuff, and especially if they are wealthy they don't necessarily want to go get it. So convenience often trumps effort, and even today with the emergence of instant ordering with next-day delivery this has spawned a whole new couriering industry.
* **Garbage Collection** - Currently we have many trucks going around cities to both poor and affluent alike, however perhaps in your world garbage collection is too slow on the ground, or in fact the wealthy don't like 'seeing' them at all. And if collection occurs in the air, perhaps it's convenient to sort out recycling and process it up there too.
* **Servicing** - the wealthy have machines that break down, jewellery that requires resizing, fabric to be repaired. It is conceivable in the ultra-convenience future that the poor who do these menial tasks live a nomadic life and need to be ultra-accessible.
* **Communication** - if it is a high-tech world, perhaps equipment to communicate for the wealthy. We currently have towers and antennae to do this, but if they for some reason are not desirable, then it makes sense that these are located in the air. They need maintenance. If a low-tech world, flag signals and a network of postal / visual communication requires a whole echelon of people up there.
* **Entertainment** - contrary to belief, entertainers are often poor, living lives with no central base. Circus performers, theatre actors are all in this class, and easily could be up there. Prostitution perhaps could be in this category too.
In fact, think of what the poor in cities do now. They are often transient, unable to retain property, come from disadvantaged backgrounds so are unable to break the cycle of poverty. Their work tends to be menial as they do not usually have the education and connections commonly entitled to the wealthy middle-class. They generally then do menial labour, finding work where they can. A nomadic life in the air is actually quite likely if they can't break the cycle to own property on the ground, living off the scraps and outcomes of the more established.
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**[Aeroponics](https://en.wikipedia.org/wiki/Aeroponics).**
Jobs wouldn't differ that much from those on Earth. Manufacturing would still be common (though arguably mostly automated), and many goods and services will still need to be produced.
The one notable exception I can think of is agriculture. Without land for crops below, working people will have to grow crops up above. Luckily, aeroponics (and hydroponics) are far more efficient than traditional farming, so they make sense given spatial constraints.
**Mining**
Someone needs to harvest and refine all the minerals used to keep people up in the air in the first place. I imagine some surface land will be used as the entrances to deep mineshafts, in which some lower class citizens may work. This could evolve into a feudal system of wealthy landowners leasing land.
If you really want to keep them up in the air, though, asteroid mining is the next best thing. The problem is, the required rockets are too expensive for sky dwellers, unless they're owned and operated by the rich.
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In many fantasy stories humans are capable of inter-breeding with different fantasy races. There is a precedent for this happening with neanderthal and Denisovan DNA being found in people of Eurasian descent so we do know that humans inter-breed with other hominids. In my story I have many fantasy races such as Orcs, Goblins, elves, Giants, etc. So what I want to know is what is the furthest back two hominids could have shared a common ancestor and still be able to produce viable offspring(offspring doesn't have to be fertile it just needs to survive outside the womb and be somewhat healthy)?
NOTE: Magic does not exist in my story.
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There's probably no way of knowing properly without consulting with a team of genetic scientists as the DNA-level intricacies of speciation and viable offspring, but my (extreeemely) rudimentary understanding is that procreation involves the 'zipping up' of two DNA halves from the mother and father's egg and sperm cells respectively.
Problems, and eventually complete inability to concieve occur as the attempt to 'zip' these two sides of the DNA fail increasingly.
i.e. if you tried to patch-together two sides of a different outfit and have the zipper work, it would depend on just how different the zipper teeth are from one another - a small amount of difference would be fine, but the more drastic the difference between them the likeleyhood of the zip working in a way that is sustainable (i.e. you can keep zipping it up and down) lowers.
Obviously DNA is much, much more complicated than this, but that is to some degree my understanding of it.
**So for example, we share more than 50% of our DNA with a lion**, but the remaining percent we don't have in common is drastic enough to critically fail in zipping up completely, whereas a lion and tiger are much more similar, and while the dna will zip, it will do so with such a number of problems the creature (a liger) will be sterile and have a plethora of other genetic issues.
**However, if you look at the drastic differences between breeds of dog**, you'd be forgiven for thinking they're all different species, but most of those differences truly are quite superficial, and are changes along lines that can neatly zip into the expected 'teeth' of each side of the helix *(longer legs, snout length, fur colour, temperament tweaks)*
**To conclude:**
If then, you treat the various fantasy races as (to put it bluntly) 'different breeds of dog' in your story - to justify that really they are all pretty much the same base archetype with a few superficial differences accrued in a relatively short period of time (I'd say no more than 20-30,000 years, given we've domesticated dogs for around 10-15,000, and done so ususally with one single aim in mind with each new breed) your fantasy races could diverge quite drastically from one another to meet the classic archetypal appearences of orcs/dwarves/ogres and such, assuming the complex internal workings of their bodies are roughly doing the same stuff.
Which seems perfectly in line with most classic fantasy (most fantasy-races are capably omnivorous regardless of preference, most have the same sort of brain, with the only real differences being sizes of this sector or that (e.g. you could give elves a big prefrontal cortex to give them better foresight)).
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A good example of which species can produce fertile off spring and which ones cannot are penguins. There are a couple of different penguin species and if you order them by average size of an adult then neighboring species can produce fertile offspring but species farther apart cannot.
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**As you mention, this is something we have real-world evidence for**
There's some good real-world examples in our own evolutionary history. There are two known interbreeding 'events' between homo sapiens and other related hominins, and I've heard of evidence of at least one more interbreeding event with an unknown 'ghost population'.
**Homo neanderthalensis**
There's genetic evidence that sapiens interbred with neanderthals in Europe, enough to contribute nearly 1.5-2.1% of the DNA of all humans outside of Africa. Our common ancestor was Homo heidelbergensis, which we diverged from about 300,000 years ago and neanderthals did about 240,000 years ago. The earliest suspected interbreeding period was around 110,000 years ago, and the latest around 47,000 years ago. So we have a potential window of 190,000 years of divergence, after which interbreeding was evidently still possible.
However, there has been no evidence of neanderthal mitochondrial DNA found in sapiens population. This suggests that while male-neanderthal/female-sapiens parings produced fertile offspring, the offspring of female-neanderthal/male-sapiens parings were infertile. This could also be suggestive of a very low rate of interbreeding between the two (sub)species, but might indicate that sapiens and neanderthals were nearing the point at which they couldn't interbreed.
**Homo denisova**
There is also genetic evidence of an interbreeding event between sapiens and denisovans in Asia, which contributes between 3-6% of of the DNA of Melanesians and aboriginal Australians (and a lower percentage in Southeast Asians, including Tibetans). The ancestry of denisovans is less clear than sapiens or neanderthals due to the limited number of finds, but best guesses suggest they're more closely related to neanderthals and split from them around 160,000 years ago (possibly interbreeding with another, unknown archaic human population).
Current estimates put the interbreeding event between sapiens and denisovans at around 44000-54000 years ago. If denisovans are derived from neanderthals, that would put a window of around 246,000 years, after which interbreeding was still possible.
Similarly to neanderthals, there is evidence that sapiens-denisovan pairings weren't always fertile. There are large parts of modern human genomes that are devoid of any denisovan DNA, the location of which could be explained by male hybrids being infertile. This would also suggest that humans and denisovans were approaching the point at which they could no longer interbreed. However, due to the scarcity of denisovan finds there are a lot of questions still unanswered.
**Morphological differences**
To find out the level of morphological differences you're likely to be able to support via natural genetic divergence you can look at the comparisons between sapiens, neanderthals and denisovans. As a starter for ten the latter two were more robust than sapiens with more pronounced brow ridges, and denisovans had different dentition.
**Another approach: artificial breeding**
If you're looking for greater morphological differences, but retaining the ability to interbreed then you could look at dogs. It would take some creative circumstances, but perhaps all your various breeds of hominids were selectively bred by a historical (and now absent) population. This could conceivably allow for some very distinctive physical differences with minimal genetic divergence.
A cursory google indicates that there might be some concerns around the ability of some very isolated dog breeds to produce fertile offspring, but the general consensus is that even dachshunds and great danes can produce fertile offspring. From here, we're talking about purely mechanical problems with the ability to produce offspring (I wouldn't want to see a non-giant try to give birth to a giant-hybrid).
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[Question]
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# Background
I am trying to find a design for a cylindrical habitat that would allow the enclosed cylinder to radiate heat out to space as does the Earth *without* using mirrors and windows.
# Problem
In my design, I am not using the [mirrors and windows](https://en.wikipedia.org/wiki/O%27Neill_cylinder#Sunlight) of the classic O'Neill design, my habitat is also tidally locked to the Sun facing it with on of its caps. I'm also assuming that solar panels around the habitat are used to provide the internal living area with the same energy density as the Earth gets from the Sun. In other words, each square meter of the habitat will receive the same power (in the form of electricity that will eventually turn to heat) as each square meter of the Earth. My design looks something like [this](https://infinitysedge.weebly.com/uploads/6/4/2/2/6422828/oneill-cylinders2.png?681) with the cap always facing the Sun.
[](https://i.stack.imgur.com/uGgcz.png)
The obvious problem now is that there no where for the heat building up inside the habitat to radiate to. For the Earth, the surface and atmosphere is always facing towards empty space, and so the Earth radiates as much as energy as it receives from the Sun creating temperature equilibrium. This is not the case by default in this habitat design.
**EDIT**: I'm not using windows and I'm unable to use radiators on the outer lateral area of the cylinder because those habitats are part of a Dyson swarm in my design. Therefore, any radiation from this outer lateral area would be absorbed by the other habitats and not radiated to space. The only area possible to radiate directly to empty space would be the end cap not facing the Sun.
# Partial solution
To make the habitat achieve the temperature equilibrium at the same temperature as the Earth does, I first thought that the heat will just propagate through the habitat walls and radiate into space, but I then found that conduction is very slow and the interior would be boiling before the outer layer of the habitat wall became hot enough to radiate at the required rate.
This made me think that the solution lies with the atmosphere inside the habitat. I think this can be solved somehow by creating a cycle for the atmosphere to allow it to be outside the habitat for some time to radiate the heat without losing it to space and running this cycle indefinitely. I'm not sure how practical this is and I can't really imagine a design for it.
**EDIT #2**: I think radiators must be used at the other end cap. The problem now is that the end cap area is 1/20 of the living area inside the habitat. Therefore, I need at least 20 times the area of the end cap to radiate the energy. 20 times the area means 4.5 the radius. If this radiator is rotating, the stresses will most probably break it apart. So, is there a way to use non-rotating radiator with a rotating habitat?
# Question
What are some designs for the above mentioned habitat that would allow it to regulate its heat radiation to space to keep it from overheating?
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A perfect circle 1AU in radius has a circumference of nearly a billion kilometres. A McKendree cylinder is about 1000km across. If separated from each other by 1000km, you'd be able to fit in ~470000 habitats, giving you a total internal surface area of ~6x1012km, which is ~12000 times the surface area of the Earth. Russia is one of the most sparsely populated regions on Earth, with a mere 8.4 people per square kilometre, which you give you plenty of space for fifty trillion people. Each habitat would have an almost entirely clear sky around it, so radiating in all directions would be absolutely fine and only a small fraction of the radiated heat would be re-absorbed.
This is just a single ring around the star... you could have an order of magnitude more habitats spread out in a sphere around the star and they'd be even more widely separated.
I'm not sure what you need your dense swarm for, or how you'd find enough mass to build it, or how you'd be able to fill it with people, for that matter. But anyway, rant over: lets move on.
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[](https://i.stack.imgur.com/JRAyK.png)
Behold, the cross-section of a cylinder with modified external geometry to support a) greater external surface area and b) a means of radiating heat without directing any laterally at all. Even if you don't use the sunward-side panels (and they'd be shaded from teh sun by the panel in front of them) you've still got a greater surface area than the cylinder itself.
Note also how you can increase the area of the spaceward endcap substantially, if that's what you felt you had to do.
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Water is an excellent material for particle radiation shielding, is useful for the occupants of the habitat, and has a very high heat capacity. Circulate it through the outer shell of your habitat to both shield and cool the interior. Pipe it out through external radiators to cool it again.
Ideally you'd use a heat pump system, possibly as a second cooling loop, to chill the water shield and run your external radiators at a higher temperature... [the power radiated by a black body](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law) is proportional to the fourth power of its temperature, so running your radiators hot is desirable to keep them small. If you're in a dyson swarm, you clearly have power to spare to run such equipment, so the inefficiencies won't be a problem
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Are you sure that you're already at the edge of the envelope for your materials? You haven't specified habitat radius or rotation rate and I'm not about to hazard any guesses, but there's a good chance that a big rotating radiator array is entirely possible.
You could make the radiator non-rotating, and indeed the engineering required to do so is child's play compared to that required to dismantle a solar system and turn it into a dense habitat cloud. It shouldn't be necessary, though.
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Heat pipes are the answer:
These were used for the McKenzie Valley pipeline to keep the permafrost cold under the supports.
Thought experiment: Take a 30 foot long steel pipe, and put a few gallons of liquid propane in it. Let it boil, pushing the air out. Cap it. Propane liquifies at -40 under normal atmospheric pressure and temperature, and is a liquid at about 120 psi.
Set the pipe in ground with about 10 feet exposed.
When it's cold out (all winter) propane condenses in the top end, slides down the wall of the pipe, hits the part warmed by the ground, boils. This will happen as along as the top end is colder than the bottom end.
When the top end gets warm, you just have warm propane gas at whatever pressure is in equilibrium with the liquid at the bottom.
This doesn't help your habitat, as you want the inside end to get cold. So you put a material that wicks whatever your working liquid is, and each heat pipe has a pump that pulls liquid from the sump at the space end, and wets the wick in the inboard end.
You want to choose your working liquid to NOT freeze into a solid if a pipe isn't used for a while. (Solids don't pump well) but also to slurp up reasonable amounts of heat to boil. LOX? Liquid nitrogen?
Now for this you a LOT of radiator. One side of your habitat is receiving 1300 W/m2
This calculator <https://www.spectralcalc.com/blackbody_calculator/blackbody.php> says that at 0 C (273K) a black body radiates 300 W into space. So you need between 4 and 5 square meters of radiator for each square meter of absorber.
However. No windows. For plant growth you don't need anything like full strength sunlight. And at present we don't use close to the full power of sunlight striking the earth.
So calculate your power needs on a per person basis, not on an area basis, paint most of the habitat white.
The sides are covered in dimples to shade the radiators.
Make your cylinder ~5 times as long as it is wide. This gives you a radiation surface of Pi \* r\* 10r, while the absorbing surface is Pi r^2 The side radiators will only do about 75W (roughly 1/4) of the radiation of a radiator pointed at a hemisphere of empty space.
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Edit: User has a dyson swarm of habitats. Lateral radiation will still work: But the efficiency goes down. What is now required is that radiators are 'beamed' in the sense that each habitat is the tip of a cone of radiation. The cone has to be narrow enough to miss the neighboring habitats. This isn't an onerous requirement at low swarm densities, but becomes increasingly difficult with increasing density.
The nature of a swarm is that it has to be done in 'belts' Orbits by their nature are planar, and are coplanar with the center of mass of the central star. So you can have orbit at 1 A.U. that is 1 habitat wide. Presumably they have some separation, probably by several times their own size. So the radiators that are pointed vaguely at the adjacent habitat aren't effective until they swing by. But if the spacing is say, 10 times the habitat size, then this degrades your radiator system by a percent or so.
Ok. Belt 2 you put in at 1.01 A.U. at, say 60 degrees to the first one. It has an occasional shadow fall across it twice an orbit.
Belt 3 you put in at 1.02 A.U. Also at 60 degrees, but you advance the ascending node by 60 degrees too. It gets 4 chances at a shadow falling on it.
After a while suppose you have 50% of the star's radiation intercepted. The rule still remains: If you take 1300 W/m2 of sunlight in, you need 4.5 square meters of perfect black body at 273 degrees to radiate it out.
Now here's where my thermodynamics falls down. 273K falls into the high microwave/far infrared band. If you can dump your heat as a beam of microwave energy then you can win. But I suspect that this comes in the 'no free lunch' class. That to beam it takes more energy than the system dissipates.
[Answer]
**Your Tidal Locking Dilema**
You are already pointing tidally locked solar panels at the sun, simply place the panels between the sun and your habitat. This puts your whole living space in their shadow. Then you just need to evenly distribute things inside of your habitat that generate heat (lighting, computer systems etc.) such that they are evenly distributed so that there is no major gradient of origin for heat sources. Then you simply create enough surface area on the outside of the habitat to radiate heat as fast as you make it.
Or if you want to keep your exact design, place things that produce more heat like machine shops, manufacturing, greenhouses, etc. at the back of the station, and lower power infrastructure near the front where it is more passively heated.
**Your Swarm Dilema**
When building a dyson swarm, there are factors at play that limit how densely your cloud can be built. If you put the habitats, too close together, gravity and tiny tiny little levels of asymmetry will cause a cascade of asymmetry which will result in accretion. (Just like all the dust did that formed the planets) This means you need your habitats really far apart from one another. Sure you can fit thousands, maybe even millions of them around a star, but nowhere near enough to create an even slightly solid shell.
Because of this, they will never be close enough together for lateral radiation to be a problem... unless something has gone terribly wrong in which case the people inside are about to be in for a much worse time than just some heat radiation issues.
Dyson spheres and Ring Worlds overcome this problem through their theoretical structural integrity, but swarms need their distance.
While you could try to overcome this with thrusters, that creates tons of problems as well. First off, you have a massive multi-body problem here. A course adjustment in one would cause a domino effect across the spacing of all stations. This would require ridiculous amounts of calculations and thrust over time to account for. Thrust takes a sacrifice of mass (unless you have a non-newtonian propulsion system); so, your swarm would need to consume a constant influx of matter from other places in the solar system which will lead to all sorts of long-term problems. Lastly, thrust fires highspeed mass out in a linear direction at the thing you are trying to get away from. This means your stations will get close enough to harm each other with maneuvering thrusters long before they get close enough to harm each other with radiant heat.
It is important to remember that heat radiates in spherical waves, not in straight lines; so, even if the structures are really close together as shown below, you'd still have most of the heat radiating out in angles facing deep space. In the graphic below, you'd have about 4/5ths of the radiant heat going off into space, on this axis, and more like 14/15ths along the other axis meaning even bodies this close together will only receive about 1/75th of the other body's radiant heat.
[](https://i.stack.imgur.com/xZLBV.png)
**Your End-Cap/Radiator Dilema**
I think my last point mostly solves this for you, but in case there is still any doubt: If your end caps have the same population density as your habitat ring, then the heat per area will be less than the rest of the cylinder because they have the extra wall. The exception to this in your current design is your sun-facing end cap which can be shielded if needed with solar panels as I mentioned.
In any case, you also don't need to worry about radiators making your ring less stable, properly designed they will in fact have the opposite effect. Scaffolding is stronger and lighter than a solid surface, and tubes are stronger and lighter than solid bars; so, you just need to build up a scaffold shaped radiator structure out of radiator tubes that has enough surface area to meet the requirements you need at any given area around the circumference of the structure. These shapes will not only radiate heat, but reinforce the station as a whole.
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Rearrange, and increase the size of, your solar panels so that they almost completely shade your entire cylinder from the sun. The only openings you need are an entrance to your mirror system for internal lighting.
Arrange any needed radiators on the external hull, which will still be shadowed, allowing for excellent cooling efficiency.
Note that a visibly rotating structure is not the likely appearance of any habitats using rotation to generate "gravity". Any rotating structures will likely be contained withing non-rotating shells.
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**Metal Iris Umbrella, or Slatted Umbrella**
Since your design always points the hub towards the Sun, the primary heat source, it makes designing a light shield really easy. Build a tower directly outward from the hub (it can have an offset if you want landings there). Build a sun-blocking structure that can be fine-tuned. There are many good shapes.
The simplest shape is just two radially-perforated disks, wider than the habitat. When you want it bright, rotate one disk so that the perforations line up and the maximum light comes in. When you want it dark, rotate the disk so that the perforations don't line up. If you can trust your motors and lubricants, merely set them spinning very slowly so that it's on a 24-hour cycle of brightening and darkening.
Your radiator can be at the other hub end. In the shadow of the habitat and its shade, it gives off heat into open space. Heat needs to be pumped into the radiator, perhaps with solid neopentylglycol refrigerants.
The problem with this design is that it doesn't fare well with torque. You need to have a very reliable and responsive and proactive set of thrusters, probably a ring around each hub, in order to keep the hab oriented and in the dark. If ships are docking, small impacts happening, the spin precessing, etc , then the habitat can swing out into the light.
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Heat on Earth spreads by convection, conduction and radiation. In space, convection and conduction almost entirely non-existent leaving radiation as the sole method to add or subtract heat.
In your station, anything facing the sun will absorb heat. Anything facing away from the sun will radiate heat. You only need balance the heat being absorbed, the heat required to keep a comfortable habitat and then radiate the remaining heat away from the station on shady surfaces that face away from the sun.
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The Doppish are a race of imp-like magical creatures. Their ancestors evolved venom glands in the liver, which over time further evolved into glands for mana, or magical energy.
They produce magical energy in these glands inside the liver, and it's stored throughout the body, with high concentrations in the liver, blood, and their tails.
How plausible is magic coming from the liver of this race? Should I choose a different organ to use?
Notes:
* The Doppish are mammal-like. They kind of look like a four way cross between a bat, a fox, a dragon, and a cartoon demon. They're humanoid, covered in fur, and have tails with spikes or spades on the end. They also have wings, usually membranous ones.
* I originally just picked the first organ that I thought of that made sense, but now I'm also somewhat influenced by the concept of the four humors, specifically blood, which was said to be produced in the liver and cause people to be excited and social, which I feel fits the Doppish pretty well, they're a highly social sapient species.
* I'm trying to be semi-realistic about things.
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Actually, after thinking about this, it actually MIGHT make a lot of sense to use the liver.
The principle here would be that magical energy infuses everything in the world, but it's not usable in this form. The function of the liver in your body is to help break down stuff you eat into forms your body can actually use. In this case, the Doppish have evolved so that their livers can actually distill the mana out of what they eat and turn it into a usable form.
Forget about the venom glands though, you don't need it here. You're just using the liver to do exactly what it's designed to do.
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Let's not say produced, let's say accumulates.
Everything is a little bit magical, things are eaten, the nutrients and the magic make their way through the digestive system and into the blood supply. The liver filters the blood and accumulates the magic, just as some creatures do with the toxins from their food to make themselves poisonous in turn.
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The liver is the chemical plant of an organism. If you want the venom to be dispatched outside, the liver makes no sense, as it can contribute to distribute it in the body.
For an outside delivery salivary glands, tear glans or kidneys are better suited.
That aside, magic can follow any path you like, since it's per definition not bound to science.
So, if you want it to be liver, let it be.
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**I'd suggest Bone Marrow.**
As it was stated, this is magic, so you can do whatever you like. But the liver is the body's source for removing impurities - it's not exactly the best place to *develop* poisonous organs. Most poisonous animals have their poison sacks somewhere else, even if they're immune to the poison.
Bone Marrow is the best place to put the source for a blood-based mana, as they're also the source for blood itself. They also could potentially be the source for the poison, so long the poison is for defense against predators, and not for hunting prey. (And the imps are immune to their own poison.)
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Given that the main ingredients for gunpowder(Charcoal, Saltpetre, and Sulphur) exist in varying quantities pretty much everywhere, I've been wondering how it wasn't discovered much sooner than the 9th century. I know there are some reasons for that but for the sake of the scenario let's assume that this society was roughly the size indicated by the Motza site in Israel(Roughly around three-thousand people). And was situated near a few hot springs vital for the collection of sulphur. With the surrounding countryside filled with large herding animals and dotted with Bat caves needed to supply the dung and/or guano needed to extract saltpetre. Given a small population and limited technological advancement, and given there's a limited amount of each ingredient to be realistically gathered in the local area, what could such a society make with this gunpowder?
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Without metallurgy you will be vastly limited in what you can do. Stone is strong in compression, but weak under tension. A cannon is essentially a gas pressure chamber that puts the walls under tension so it would not work.
Instead may I suggest using it to **startle and surprise** the enemy. A shallow trench filled with gunpowder placed around the perimeter of the camp could be ignited whenever the enemy attacks; blinding and disorienting them.
For other uses, I suggest looking at the history of [Gun Powder in Ancient China](https://en.wikipedia.org/wiki/History_of_gunpowder#Chinese_beginnings), which includes such excitement as **fire arrows, explosives, and naval bombs.**
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you can make [bamboo cannon](https://www.guaduabamboo.com/uses/lantaka-kerosene-bamboo-cannons) (but it prone to kill the user too and not as strong as metal cannon)
[](https://i.stack.imgur.com/QdQj1.png)
[](https://i.stack.imgur.com/Sk5oA.jpg)
even early [fire lance](https://en.wikipedia.org/wiki/Fire_lance) and fire arrow are made of bamboo too and theres plenty of type of it.
from:<https://slideplayer.com/slide/7694707/>
[](https://i.stack.imgur.com/OZq9p.jpg)
from :<https://sino-archives.tumblr.com/page/123>
[](https://i.stack.imgur.com/PaTPd.jpg)
early chinese use [trebuchet to throw explosive gunpowder contain inside ceramic/clay](https://en.wikipedia.org/wiki/Chinese_siege_weapons#Gunpowder) so for a primitive people, maybe they can make a sling or slingshot version for it or even just throw it barehand like ceramic grenade bellow
[](https://i.stack.imgur.com/xtLBC.jpg)
here the [clay/ceramic bomb](https://thumbs.dreamstime.com/z/yuan-dynasty-s-porcelain-bullet-china-cultural-relics-93808843.jpg)
another is [clay grenade](https://en.wikipedia.org/wiki/Type_4_grenade) (this one is from japanese ww1 but the early chinese have similar thing like this)
[](https://i.stack.imgur.com/vjI5B.jpg)
i think for use in stoneage society they can use it to [fish bombing](https://en.wikipedia.org/wiki/Blast_fishing) and raiding or defense against raid and even selfdefense against megafauna.
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I think the biggest advantage could be in firestarting. You ever try to start a fire by rubbing two sticks together? It sucks. It's tiring, it can take a very long time if you don't have the right tinder, it's impossible without dry wood, and depending on the technique it can be easy to give yourself splinters, which in a pre-antibiotic setting can be lifethreatening. Gunpowder doesn't totally eliminate this problem, but it will reduce it greatly. Gunpowder is pretty much the perfect tinder.
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Gunpowder can probably vastly speed up mining and other forms of dealing with rocks. Know how they dealt with hard stone before the advent of modern mining? They heated the rock, then cooled it with water until it cracked and broke, then finished the work with picks.
Gunpowder would be a godsend for this.
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In order to build a gunpowder-based engine, you will need advanced metallurgy. So I don't think that would happen in the Stone Age. However, an intuitive and easy-to-use use of gunpowder is to use it as an explosive for large-scale landscaping or to trap large prey (such as mamouth).
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# Very little impact, because gunpowder cannot be eaten.
Lots of questions about technological twists/advances in the stone age fail to appreciate just how undeveloped stone age man was. Never mind the lack of metallurgy for making guns: stone age man could not have survived in one place long enough to gather together the materials to make a useful quantity of gunpowder, because prior to the development of farming and animal husbandry humans were nomadic hunter-gatherers. Time spent chopping down trees for charcoal, collecting sulphur or mining potash is time not spent feeding themselves, and even assuming some group dynamics with some humans hunting while others worked the gunpowder, they would quickly exceed the carrying capacity of the local area. Even having made the gunpowder, they have only rudimentary leatherworking or pottery skills to make containers with which to store it, and it's complete dead weight for as long as they do carry it.
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The best thing to do would probably bei to use the black powder for mining flint. In warfare it could see use limited use in clay grenades, but I would Claim, that Stone Age armies are too scattered for it to be effective.
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Inspired by this [question](https://worldbuilding.stackexchange.com/questions/162055/how-much-would-we-learn-from-observing-an-ftl-starship-fly-by) about learning from FTL, I wonder
**Is it even possible for anything to happen, that, if observed by us using methods available to us, will unmistakably and absolutely certainly be the evidence that the object experiences FTL? If yes, what would it be?**
I.e. some event (chain of events) that if observed by us will have no other explanation but FTL?
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# Accurate predictions of the "future"
A spaceship arrives at Earth. The crew insists that they have FTL travel, but we don't believe them, so they propose an experiment. We (Earth) will build a "probe" that will broadcast some signal known to us but unknown to them. They will then take the probe and drop it off at some distance where we can a) receive the signal and b) determine how far distant the probe is. Then they drop the probe off and come back. When we receive the signal, we can calculate that the probe must have been moved faster than light.
(Variations on this are possible. My original idea was for them to "predict" some stellar event whose light hasn't reached us yet, but then maybe we'd only believe that they could *cause* such an event. Granted, if the event is something like a supernova, that would scare the <redacted> out of us...)
Of course, this requires that the folks with FTL are actively interacting with us to demonstrate their capability, but the question didn't exclude that...
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As the ship decelerates to a stop, it will appear to be in multiple places at once. First the light from the stopped ship (and any time it was moving slower than light) will reach us. Then after that, the light from its FTL travel will catch up to us, so the ship will appear in two places at once. From there, the "ghost" of the ship would travel *backwards* as the farther light reaches us and the previous light fades.
In short, the effects would be very unmistakable, not to mention the blueshift we would see (though that could be caused by sub-light speeds too).
**Edit**: Granted, *proving* that this is FTL would be tricky. However, based on analysis of the event (let's say it was all recorded in good quality) we could say with probably 95% certainty that it was indeed FTL, especially if we then see the ship take off again.
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The short answer is no there is nothing that unmistakably and with absolutely certainly would be evidence that a material object experiences FLT travel through space as we understand things today. This is because accelerating an object increases its mass and in the limit as light speed is approached the mass increases exponentially whilst the velocity tends towards c. So a material reference frame cannot accelerate across the light barrier.
There could be some very strange and unexplained events that puzzled people. Some might come up with theories that suggested these events were evidence of FTL travel. Such theories would be argued over and (hopefully) subject to scientific testing at which point either Einstein is proved right or the new theory holds up and our understanding of physics changes.
We can’t sensibly speculate on what happens if something beyond known physics happens and expect any kind of unmistakable certainty because we do not know how any such new physics would work. Extrapolating existing theories may not provide the correct answer and lots of assumptions would have to be made about the causality, and what we can expect under what conditions. Perhaps matter becomes invisible, perhaps it allows entry into hyperspace, perhaps matter is converted into anti matter who knows? Maybe our understanding of causality is flawed. The scope for new physics is very large.
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It depends on the nature of the FTL. For a best-case scenario, assume the ship has a Star Trek style use-anywhere in any direction FTL drive. To prove their case, you tell them you them to fly to some distant probe, get in front the probe's camera, display lights in a random pattern you give them, and come back to Earth.
Say the probe was one light-hour from Earth. If the image shows up in less than two hours after the ship leaves orbit, you know some form of FTL is needed.
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There seems to be a misconception that we do not have direct experimental evidence that FTL travel is possible. We do, and it is not in any dispute. What we don't know is how to reproduce the effect artificially and, most importantly, we have no idea how to mitigate the serious side-effects.
1. The universe is 14 billion years old or thereabouts, and the [observable universe](https://en.wikipedia.org/wiki/Observable_universe) is 93 billion light-years across or so. Since the newly born universe is known to have been very small, this directly implies that there *must* exist a means of travelling at least 47 billion light years in 14 billion years, with an average apparent speed not less than 3.3 times faster than light.
2. Astronomers can see distant objects which are at present much farther away than the distance light would have been able to travel since the time they were formed. For example, there is a galaxy far, far away, known as [GN-z11](https://en.wikipedia.org/wiki/GN-z11), which is 13.4 billion years old and yet it is 32 billion light-years away. It directly follows that in the distant past GN-z11 was only 13.4 billion light-years away and in the mean time its distance from us has increased by some 18.6 billion light years, for an average apparent speed 1.5 times faster than light.
The end result is that *we know* that FTL travel is possible; the example of the galaxy GN-z11 shows that we can even point to specific objects which *must have* travelled faster than light to be where they are.
What our physics says is not that FTL travel *as such* is impossible, but only that any means of FTL travel must use some method of doing something with the *space itself* between the origin and the destination. That is, what our physics says is that nothing can traverse more that 300 thousand kilometers per second; but it does not say that to go from A to B one must necessarily cross every single meter of space between A and B, or that every single meter of that space must have its usual length. If one could do something to the space between A and B so that every meter to be traversed by the vehicle is somehow reduced in size to 10 centimeters, then the vehicle could very well span the distance with an average apparent speed 10 times faster than light.
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In Game of Thrones the Targaryen family had special heritage allowing them to ride their iconic beasts of war. I want to ground this in reality. Is there a way for heritable trait to allow you to be more attractive by another specific organism?
I thought about the person having a gene that expresses chemicals in the skin that are much like those exhibited by dragons, making the dragons more receptive to the humans instead of auromatically assuming them to be prey (dragons are not usually cannibals).
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**Pheromones**.
These are chemical agents similar to hormones, but are excreted from the human body and used externally on other creatures of the same species, rather than internally. The thing is that humans have very weak pheromones, if at all, though numerous online retailers will do their best to convince you otherwise.
That said, it's very easy to say that humans can produce a certain type of pheromone which is contained in sweat. So this royal line of yours possesses a dominant gene that grants its descendants the mutation to produce this pheromone, which makes dragons identify them as a friend. Not as a fellow dragon (as this would get your human *killed* when the adolescent dragons decide to play-wrestle with them), but as some sort of symbiosis.
The real question is how the gene is passed on. If it's on a normal chromosome, than that means that someone who has them on both chromosomes would pass it on to all their children. A hybrid, which would exhibit these symptoms because the gene is dominant, would have a fifty/fifty chance of passing it to any given child.
Or, alternatively, you could make it sex-linked. Linking it to the Y chromosome guarantees that all male offspring down the line would receive it from their father, however it wouldn't be possible for the female to receive it. On the flip side, you could link it to the X, which means a father who had it would pass it on to all his daughters, but none of his sons. If the mother had it, then it'd again be put to a fifty/fifty chance.
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Can I introduce you to the recognised concept of a [Highly Sensitive Person](https://en.m.wikipedia.org/wiki/Sensory_processing_sensitivity) who has:
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> "an increased sensitivity of the central nervous system and a deeper cognitive processing of physical, social and emotional stimuli". The trait is characterized by "a tendency to 'pause to check' in novel situations, greater sensitivity to subtle stimuli, and the engagement of deeper cognitive processing strategies for employing coping actions, all of which is driven by heightened emotional reactivity, both positive and negative".
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Your dragon riders could be so Highly Sensitive that they can perceive and understand the aura/electrical impulses/impulses/thoughts of the dragons and able to therefore communicate and control the dragons (if only subconsciously). The dragon can sense this receptivity in the rider and hence their recognition of the riders as 'family' and in need of protection from the rest of humanity.
A HSP can be determined at birth by testing reactions to stimuli, it is typically a genetic trait passed down from one or both parents. Your excessively HSP dragon riders could be an extremely rare subtype of this genetic trait and would require careful maintenance of the bloodlines. I recommend close familial bonds are maintained over countless generations to ensure the gene isn't lost forever!
Fyi. Be careful not to overstimulate your dragon riders as they have been known to lash out and burn a city or two!
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There's precedent for animals which can detect medical problems by scent, for [example dogs which are trained to identify the smell of malaria.](https://www.wired.com/story/the-science-of-the-sniff-why-dogs-are-great-disease-detectors/) There are also plenty of genetic mutations which could cause a difference in scent. For example, the [ABCC11](https://en.wikipedia.org/wiki/ABCC11) gene can differentiate if a person has underarm sweat or the consistency of their earwax. It wouldn't be impossible that a specific (inheritable) genetic mutation causes one's sweat to smell differently or something.
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There are many possibilities. The people might well excrete a chemical signal from their skin as you describe. This might take the form of a distinctive smell, an odourless pheromone or simply be a chemical that the “mutant” humans use for one purpose that the dragons use for another.
It is also possible that the people have mutant vocal cords and their voices contain specific low or high frequencies that the dragons are attracted to. These sounds might be voluntary or involuntary when speaking.
<https://www.youtube.com/watch?v=KvtT3UyhibQ>
Another possibility is that the mutation causes some aspect of physical appearance that the dragons have learned to associate with friend rather than lunch. This could be anything from skin/hair colouration to facial features such as distinctive eye, nose or mouth features and might be quite subtle.
Finally it is also possible that the mutation causes some form of behaviour in the humans that makes them less vulnerable. For example a gene that made them frightened of dragons might prevent them from looking dragons in the eye. Which might be a very good thing if the dragons interpreted that as a threat or challenge (obviously the fear would have to be not so great that they could not bear to approach a dragon!).
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I was wondering if a vacuum created within a particular material in the shape of sphere could be used to harvest anti-matter from virtual particles? Within the vacuum, theoretically, virtual particles would form; is there a material that could be used to draw the electron towards it while it repels the anti-matter and forces it to the center of the sphere where it cannot come in contact with matter and be annihilated.
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I might actually make a second answer, for the first time, ever.
It [has been theorised](https://arxiv.org/abs/1004.5398) (or this [New Scientist](https://www.newscientist.com/article/dn19327-lasers-could-make-virtual-particles-real/) article on the paper) that a suffiently power laser pulse will have a strong enough *electrical* field to separate virtual particle-antiparticle pairs in the quantum vacuum, similar to the way that a black hole has a strong enough *gravitational* field to perform the same trick.
The theory suggests that once your laser gets up to about 5\*1025W/cm2 (with an electrical field strength of ~1.32\*1014V/cm) the power of the pulse will be rapidly depleted and you'll get a spray of electron/positron pairs that will then be amenable to more conventional electromagnetic collection and storage. This also means that you probably won't be able to get anything larger than an electron or positron out of the system, because of the challenges of developing even more power without it all being depleted by electron-positron generation. Note also that you cannot create neutron-antineutron pairs this way either, unlike the black-hole way, but this isn't necessarily a bad thing.
Whilst the production of particles will be *technically* more efficient than more boring old school means of generating positrons, the sheer difficulties of making such an outrageously powerful laser and the inefficiency of operating that laser will likely make the process uneconomical.
So there you go. Turns out that you *may* be able to use electrical fields to separate particle/antiparticle pairs, but the field strengths are so incredibly high that it may just be too awkward and expensive and inefficient to be worthwhile. It will at least be easier and safer than creating a million tonne black hole.
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The only know mean to separate the components of virtual pairs forming everywhere is the event horizon of a black hole, according to the mechanism known as [Hawking radiation](https://en.wikipedia.org/wiki/Hawking_radiation)
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> Hawking radiation is black-body radiation that is predicted to be released by black holes, due to quantum effects near the event horizon. [...] Hawking showed that quantum effects allow black holes to emit exact black-body radiation. The electromagnetic radiation is produced as if emitted by a black body with a temperature inversely proportional to the mass of the black hole. Physical insight into the process may be gained by imagining that particle–antiparticle radiation is emitted from just beyond the event horizon. This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being "boosted" by the black hole's gravitation into becoming real particles.
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Black holes are quite unpractical, since they have been shown to destroy any observer venturing too close to them.
As an additional remark, stacking charged particles in a point is not feasible: electrostatic repulsion would quickly spread the particles around, with easily predictable consequences in the case of anti-matter.
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L.Dutch is basically right, but I'll expand on their answer as there are a few important details that anyone hoping to harvest antimatter this way should know. Note that this involves maths and physics, and I'm not great at either. Take the numbers below with a small pinch of salt.
**TL;DR**: you'll need to make your own black hole, you can't get more stuff out of the quantum vacuum than the total mass the black hole started with, you can only extract stuff as fast as the black hole evaporates (which is either very slowly, or very dangerously quick), and a lot of the stuff coming out will be in the form of gamma rays, unstable and neutral particles and the kinetic energy of the stuff you *do* want, making it harder to catch. All in all, very difficult.
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The energy (or temperature, if you like) of the Hawking radiation coming out of an evaporating black hole is related to its mass. The more massive the black hole, the cooler the radiation. This is important, because no particles can be spat out of a black hole that have a rest energy greater than the energy of the Hawking radiation.
This has a number of important knock-on effects.
The temperature of a black hole is related to its mass by this nice, simple equation (from the [wikipedia page](https://en.wikipedia.org/wiki/Hawking_radiation#Emission_process)):
$$T = \frac{\hbar\,c^3}{\,8\,\pi\,G\,k\_\text{B}\,M\,}$$
where $ħ$ is the reduced Planck constant, $c$ is the $k\_\text{B}$ is the Boltzmann constant, $G$ is the gravitational constant, and $M$ is the mass of the black hole. You can simplify it to $T \approx \frac{1.227\times10^{23}}{M}$.
The rest energy of an electron or positron is 510KeV and for a proton or antiproton about 932MeV with equivalent temperatures of 6\*109K (hotter than the centre of the sun and our hottest fusion reactor projects) and 1013K respectively. The equipment for grabbing escaping particles, which will come out in all directions, must fully englobe the black hole and survive this rather hostile environment.
Once your black hole reaches those temperatures it'll start spitting out lots of the appropriate kinds of matter and antimatter particles... you'll get some at lower temperatures, but they won't exactly *gush* out. So, a black hole with a mass of about 20 billion tonnes will spit out things no heavier than an electron, and a black hole with a mass of about 11 million tonnes will spit out things no heavier than an antiproton, but the stuff it *does* spit out will include electrons and positrons, as well as protons and antiprotons and a whole soup of other particles and EM radiation (lots of gamma rays), most of which you won't want. Many of those particles will be neutral, so you can't catch them. Fifty percent of the escaping neutral particles will be *antiparticles*, and antineutrons flying out will react violently with your capture mechanisms. Many of the other particles will be unstable and will decay into all sorts of stuff, but mostly gamma rays (which will further scorch your equipment) and neutrinos (which are wasted mass, from your point of view).
The next important fact is that black holes evaporate over time, as their mass-energy is carried away by this Hawking radiation. The evaporation time of a black hole with mass $M\_0$ is given by
$$t\_\mathrm{ev} \approx 8.41092 \times 10^{-17} \;M\_0^3$$
You don't actually have to worry about these electron or proton-emitting black holes evaporating any time soon... the lighter, hotter proton-emitting hole will take over a million years to evaporate. A black hole that spits out protons *now* would have been less than a stellar mass when the universe was born, which raises [interesting questions about how that hole formed in the first place](https://en.wikipedia.org/wiki/Primordial_black_hole). No-one has spotted such a thing... that doesn't mean that they don't exist, but the chances are you'll need to make it yourself with regular matter. Good luck!
But here's the important thing: you can't get more stuff *out* via Hawking radiation than you put *in*. Really, what you're doing is converting millions or billions of tonnes of regular matter into energy and a 50/50 mixtures of particles and antiparticles via the means of a black hole. Whilst you might *technically* be harvesting those particles from the quantum vacuum, you can't even get more out than the mass you put in to start with. So there you go. The answer to your question is therefore "yes, kinda."
There's one *final* (probably) thing to be gathered from all of the above... if you can't get out more than you put in, and you can't get it out faster than the hole evaporates, and an 11 million tonne black hole takes nearly 4 million years to evaporate, your average yield is going to be a few tonnes-equivalent of mass energy every year (less than a tenth of a gram per second). Lighter holes evaporate faster, so it'll be *lower* than this to start with. How low?
Well, initial power generated from a black hole of mass $M\_0$ is given by
$$P \approx 3.56345\times 10^{32}(1/M\_0)^2$$
which for the electron-producing hole is a mere 830kW, equivalent to about 1019 electrons per second. The proton producing hole has a rather more fierce initial output of 2.77TW, equivalent to about 1022 protons per second. That's about a *third* of the average yield... about 3 hundredths of a gram per second. Of a mixture of particles and antiparticles and things you don't want. Assuming 100% production of desired particles (which won't happen... you'll get all sorts of stuff in there, and lots of EM radiation). For an initial input of some tens of billions of tonnes, if you can create a black hole without wasting any mass. It starts to sound like making a dyson swarm is the *sensible and easy* alternative, and you don't get to say that very often.
If you crank up your black hole initial power output to a toasty petawatt (effective temperature, 2\*1014K), you'll get a tonne-equivalent of matter and energy out every day. A black hole a mere half-million tonnes in mass will provide this output. It'll evaporate in a little over 500 years, and every day it'll release a little more power and hence a little more matter. Eventually your equipment will melt and after a while the hole will go bang spectacularly, releasing about a million megatonnes equivalent as it finally evaporates. You might think you could forestall that by pushing mass and energy back into the hole... only a) there's a lot of radiation coming *out* of the hole that'll make it difficult to get anything in, and b) and 10-19m across, its a pretty small target to hit. Honestly, the whole plan seems like a big "don't do that".
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[Question]
[
For this question, the word 'metals' does not refer to elements [heavier than hydrogen and helium](https://en.wikipedia.org/wiki/Metallicity). It instead refers to metals [as defined by the periodic table of elements](https://en.wikipedia.org/wiki/Metal).
After researching the [abundance of chemical elements](https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements), it is very clear to me that hydrogen and helium (and occasionally oxygen) far outrank all of the other elements.
In terms of mass fraction in the Milky Way:
Hydrogen = 73.9%
Helium = 24.0%
Oxygen = 1.04%
**Which equals 98.94%**
The following table shows the cosmological origin of each element:
[](https://i.stack.imgur.com/AZ54h.jpg)
In the scope of the universe:
## Just how likely or unlikely to form is a planet composed almost entirely of metals?
For this question, let's define "composed almost entirely of metals" as:
* Elemental composition by *volume*, not mass: More than 90% total by volume.
* Metals are defined in this question as belonging to either the [transition metals](https://en.wikipedia.org/wiki/Transition_metal) or the [post-transition metals](https://en.wikipedia.org/wiki/Post-transition_metal) groups.
* All other elements are not considered metals for this question. This include the [alkali metals](https://en.wikipedia.org/wiki/Alkali_metal), the [alkaline earth metals](https://en.wikipedia.org/wiki/Alkaline_earth_metal), or the [metalloids](https://en.wikipedia.org/wiki/Metalloid) groups.
Now, iron is the biggest contender here in terms of metals due to its abundance. But let's not forget about all of the others! [(here's a question involving a planet made of iron)](https://worldbuilding.stackexchange.com/questions/27277/a-planet-made-of-iron).
I would love to further ask what the chance of life forming on such a planet would be, but of course that would make this question [too broad](https://worldbuilding.stackexchange.com/help/on-topic).
[Answer]
I was just reading this article about **metal asteroids.**
<https://www.sciencenews.org/article/metal-asteroids-may-have-once-had-iron-spewing-volcanoes>
>
> Metal asteroids are thought to be the exposed iron-rich cores of planetesimals >that suffered a catastrophic collision as the solar system was developing, before >they could grow into full-sized planets. The naked core would have been exposed to >cold space while still molten. And it would have cooled and solidified from the >outside in, forming a solid iron crust that would be denser than the underlying >molten iron, say Abrahams and planetary scientist Francis Nimmo, also of the >University of California, Santa Cruz.
>
>
>
Asteroid [Psyche](https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/16-psyche/in-depth/) is a metal asteroid. I was surprised to learn these are so unusual given a fair number of meteorites are metal.
You could have your metal planet be a stripped core. Alternatively you could make it be an amalgam of many metallic objects which had coalesced into a planet sized body - for example remnants of the metallic core of a supernova. An object like that would be expected to have not only iron, but heavier elements as well (which as I understand require a supernova for their creation). These heavier elements would be radioactive and heat from their decay would affect the character of the planet by giving it a molten core.
[Answer]
A planet composed of 90% or more of metals is not that unlikely. The planet [Mercury](https://en.wikipedia.org/wiki/Mercury_(planet)#Internal_structure) is composed of 70% metals with the majority of the lighter non-metals being concentrated in the relatively thin crust and the mantle.
The crust and a lot of the mantle could be removed by an energetic collision with another large planetary body which could disrupt the entire planet striping away crust and mantle material. A lot of these lighter materials might then escape and not recoalesce into a solid planet again.
Another possibility is if Mercury were to orbit even closer to the sun in which case the crust might be heated to such an extent that the crust and even some of the mantle were boiled off and stripped away by the solar wind.
I would suggest that the chance of life develoing on such a world would be remote.
[Answer]
The mechanism for forming such a planet would be... unusual, to say the least. My best stab at something like this would be to have the planet in a binary star system, where one star is initially a smaller than Sol star, and the other is a star that could go supernova at some point - a supergiant perhaps.
I picture that the planet started out as a massive, probably hot, semi gas giant (my own term - something that looks like a gas giant with a with a very large core of rocky / metallic material), primarily orbiting the smaller star.
When the second star went supernova, the total mass of the planet, and distance from the exploding star (picture it in a larger orbit on the other side of the host star) combined so that the metallic / semimetallic core of the planet remained, but all of the existing atmosphere, and the equivalent of the crust and mantle, were ablated away by the heat and force of the supernova.
The core, being primarily liquid under pressure, would have had its own explosion, capturing elements from the gasses of the exploding star, as well as possible molten fragments of the mantle. This would have mixed into whatever combination of elements are now part of the planet, with the possibility of rare, somewhat intact mantle chunks being concentrated ores of the lighter / rarer elements.
As for life... your guess is as good as mine. In your defined planet, there would be scant solvent materials to allow for the different elements to mix, meaning that almost any actual life would have to be radically different than what we have envisioned, seen, or contemplated.
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[Question]
[
I have a species of early primates (lemur-like but *not* lemurs) developing into an intelligent species like humans (and yes, there is some influence from an intelligent species, it's not 100% natural if you're thinking it's unlikely).
Now, since lemur catta (ring-tailed lemurs) are matriarchal I wanted the society to be too, especially since there is a high degree of difference in colour vision with most males colour blind and most female with trichromacy.
My question is: what would a species that evolves like this look like?
From the time they were hunter-gatherers I assumed females could be the band leaders, standing back and ordering a band of males either to trap larger herbivores while looking out for predators with their better vision
Or… well indicating to males which fruits to pick while they do the dirty work of actually carrying stuff. This would have led females to evolve to be taller so they'd see better and males to be lean and agile.
This reflection started with beards but it's also about any secondary sexual characteristics I guess. Which is breasts, beard, etc… so would females grow beards? Or is it necessarily tied to testosterone? Could males do without those secondary characteristics, cause I read (<https://www.sbs.com.au/topics/science/humans/article/2016/07/25/ask-evolution-why-do-men-have-beards>) that it helped males appear more aggressive.
[Answer]
Getting rid of the lions. Lion males are jerks.
**The new matriarchal primates will have a system that is a mix of matrilineal elephants and showy bird males.**
Elephants have a totally matriarchal, matrilineal system.
<https://www.elephantsforever.co.za/social-order.html>
>
> Elephants are a matriarchal society; that is, one that is led by a
> head cow, who presides over her herd of females. Each herd is made up
> of mothers, daughters, sisters and aunts. They are guided by the
> oldest and largest female of the herd. This herd sticks closely
> together, rejoicing at the birth of a calf and mourning at the death
> of a member.
>
>
> The herd of females, although maintaining close bonds among
> themselves, also interacts well with other herds, families, and clans.
> An average herd of immediate family will comprise of 5 to 15 adult
> elephants as well as immature males and females...
>
>
> The male, on the other hand, lives apart from the matriarchal herd,
> and travels alone or with other males in a bachelor pod. The drift
> from the herd starts during adolescence, at which time the young bulls
> start to spend less and less time with the herd. Eventually, the break
> is made completely. After this distance is established, the bulls will
> live solitary lives, mingling with the females of the family only for
> mating purposes
>
>
>
But elephant males are big jerks too, so we will borrow from birds, where the females pick among males who are trying hard to impress them. At mating season, all members of the species get together at the [lek](https://en.wikipedia.org/wiki/Lek_mating). The males show up and compete for mates. They do not fight or bully each other. The males are amazing, colorful and beautiful. They can sing and they can dance and that is what they do. It is the best show ever; something like KCON but with all boys. Reproductive aged females pick the male they like best.
Then the males rest up and drift off, working on their dance moves and songs for next year. Side benefit: the females all get pregnant at once, so they can help each other nurse and raise babies of the same age (borrowed from lions, but it is a very cool thing).
---
How they look: Females would have a primate body type appropriate for their feeding style, social style and ecosystem. Ground dwelling lemurs and baboons are not so far apart. I would pick baboon-type females because they are durable tough creatures and good for a primate life style.
Male baboons fight a lot and so are robust and have big teeth. Your males are not like that. They do not look much like the females at all. Example: the widowbird.
[](https://i.stack.imgur.com/Sno2E.jpg)
<https://www.worldbirdphotos.com/photo/widowbird-red-collared-euplectes-ardens-male-female-uganda/>
Males are spectacular Kpop stars with huge eyes, perfect teeth, and shiny manes. They have sweet voices and fluid moves. Only the fittest can keep up such appearances while at the same time finding food and fighting off predators, which is why the birds do it that way. Occasionally a young male might not have his lyrics down, or an older one might be a little more stiff in his dance moves but that is how it goes.
[Answer]
Female hyenas have genitals that looks like they belongs to a male.
What humans are concerned, women have wider hips than males because of childbirth. The more narrow hips makes men faster runner than women, so if the hunting requires running, males would probably be the ones who does the running part. Assuming the females of intelligent lemurs have wide hips as well.
Also, babies needs to be breastfed, and so females with babies can be too far away from their children, and running around with them (and while pregnant) would slow them down. Unless the females in a group gives birth at the same time of year, so with several mothers, some could feed the babies of others while they are away.
(the male Dayak fruit bats can also produce milk, but is obviously not a primate)
Males are often stronger and bigger than females due to testosterone. Sexual frustration and the competition to mate leads males in many species to fight to get access to the females. And the strongest and angriest ones wins.
The bonobos, which have matriarchs, have solved this problem by allowing everyone to have sex with everyone. I think one of the few exceptions are sons and mothers. They no longer have to fight to get sex, and with one of more partners available all the time, there is very little if any sexual frustration in the group. So there is no longer the same selection pressure for the males to be large and strong.
What size are concerned, it depends on how they live. If the females don't have to go out and hunt for themselves, they could be larger and therefore give birth to more children (or at least twins). Maybe there could be dominating females that prevents less dominate females from reproduce through hormones. But to produce more children at once it is a good idea to be larger.
So access to sex all the time could make the males smaller, and females who produce more children could make them larger. It all depends on their way of life.
If they are nomads that moves fast and efficient from one location to the next or have to run to get away from predators, being big and heavy is no longer a good idea.
[Answer]
Many human cultures (<http://mentalfloss.com/article/31274/6-modern-societies-where-women-literally-rule>) are matriarchical, with no distinct biological difference from males and females of other cultures (may have physical differences of appearance).
So you can have the lemurs evolve like regular humans.
In fact polygenism (<https://en.m.wikipedia.org/wiki/Polygenism>) is the theory that humans evolved from different species (of apes), and yet we are all so similar. Similarly, in mythology, there are stories galore of multiple animals standing and convening like humans in good council's etc.
So lemurs can grow up to be like humans as well, as matriarchy is a social phenomenon, not a biological one.
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[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.
Assume a civilisation with futuristically advanced knowledge of biochemistry. Assume it wants to develop a cybernetic device meant to facilitate the organism's ability to perform high-power activities (anaerobic or borderline anaerobic) for longer than normal.
* Would it be plausible for such a device/implant to be made possible by way of artificial, externally- or battery-powered synthesis of adenosine triphosphate with the subsequent transportation thereof to the target cells by blood?
* If it's not normally doable, would some kind of ATP-transporter nanites (or equivalent, analogous to the cassette transporters, perhaps?) make it doable?
* What other obstacles I may be overlooking on the path to artificially boosted endurance of high-energy-cost activities, and which of them are so bad that they're unlikely to overcome by hard-science means?
[Answer]
**Battery-powered synthesis**
ATP is kind of already synthesized by battery power. In fact, ATP synthase is occasionally referred to by biochemists as 'the world's smallest motor', and is powered by positive H+ ions moving across a concentration gradient. Picture below, essentially the purple ring rotates as H+ moves past it and forms ATP in the green umbrella.
[](https://i.stack.imgur.com/IVWxQ.png)
Your idea, if I'm understanding correctly, is to create a store of ATP artificially, and then send it to the target cell(s). This runs into problems, because of all the ATP you're now *dumping* into the cell. The ATP cycle is tightly regulated by internal feedback. A large shock dump may trigger the gluconeogenesis cycle. Then it's a question of raw energy. One mole of ATP gives ~7.3 kcal, which sure, *sounds* great. Except one mole of glucose produces 2 moles of ATP during glycolysis, (produce in the sense of recycling) which is anaerobic respiration. And ATP has nearly three times the mass of glucose. So you might be better off just injecting raw sugar. (That was a joke, don't do that. Reason will be explained later.)
That did give me an idea, though. Accelerating aerobic respiration. If you use implanted mechanical means, you can simulate the Electron Transport System and overloading the H+ ions in the matrix, then you can speed up ATP synthesis, which functions on a concentration gradient of H+ ions, which would require quite a bit of energy. This *also* has two added benefits - one, it requires no oxygen, as oxygen is the final stage of the ETS and you are skipping it via mechanical means. Also, since you've decided to get all your ATP like this, hopefully your body will decide not to speed up glycolysis. And that leads to the second benefit - no lactic acid buildup.
**Lactic Acid**
This is the real kicker. When it comes to brief energy, there's a cost. In red muscle cells, they aren't equipped to handle all that pyruvic acid which comes from non stop glycolysis. So it gets turned to lactic acid. (Except in *really* rare case where it gets turned to alcohol.) And that stuff is nasty. Earlier I attributed it to muscle fatigue, which is false, (thanks to Demigan for pointing that out) but what it does do is give you lactic acidosis, as acid builds up. The muscles get more acidic and that makes the enzymes stop working and stopping your muscles from working well. It's also hard to whisk to away. So let's discuss you're second idea - ATP cassette analogues. Why don't you use that in reverse - instead of spending energy to put energy in, spend the energy to drain the lactic acid faster than normal diffusion can.
There is a problem with this all, namely, I have no idea how these devices will work. I know far more about biology than I do about robotics. So I know that these tricks - speeding up the ETS and draining lactic acid will really help for anaerobic respiration. I also can tell you the rough forms needed for the biological equivalent. But once these nanites run out of power, it's over and I've no idea how you'd go about recharging them, save for just swapping them out and replenish it with new ones. (Honestly, swapping them out is a waste of energy, just have them detach when they run dry and let the body's waste system handle them.)
**ETS Analogue:**
There are 4 cytochromes within the Electron Transport Stystem (I, II, III, and IV) that act as membrance proteins. Also Cyctochrome c, which acts as a messenger between them. What happens within them is that electrons gets dumped at the far end (I and II, depending on whether NADH or FADH2 is dumping), which is ferried along until that H+ eventually is drawn out by oxygen and forms H2O. This is why you inhale oxygen and exhale water vapor. The movement of electrons in turn allows for free H+ ions to cross the membrane. An analogue system would have a lot (and I mean *a lot*) of electrons, in storage. When activated, it'd release those along it's own chain built into the membrane and ending at it's own far side which, of course, is less negative than that end. When it reaches there, that would allow for transportation of H+ against the gradient. When it finishes, it detaches and no longer interferes and a fresh nano-ETS-analogue slots into place. Rinse. Repeat.
[Answer]
If you have sufficient knowledge then of course! It would likely not be a device but rather a bunch of cells integrated into your body to create ATP.
But it might be simpler, "simple" being relative here. Currently when our cells are working anaerobically they will dump the lactate and other waste into the bloodstream. This will then move through the body and be processed by the liver into usable energy that will be transported back to the muscles again. But due to the random nature and long process of being pumped around the body until it reaches the liver it can take a while. So instead of one liver, add a series of liver cells downstream muscles. These liver cells transform the lactate and waste which is then transported by a local [lymphatic system](https://en.m.wikipedia.org/wiki/Lymphatic_system) specific for them to dump the product upstream so it immediately flows back to the muscles that originally created it.
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[Question]
[
Ever since I watched *Star Wars* I have always been fascinated with the Bacta Tank: that tank with the funky blue liquid Luke Skywalker was submerged in.
But now I'm wondering could it become reality? The basic premise of a Bacta Tank is: a tank of liquid (Bacta) that when a patient is fully submerged causes rapid healing and regeneration (judging by the films it cant regenerate full limbs or organs so it probably just regenerates what it can and mends the rest) allowing some one with rather severe to be stabilized and fully healed in the time span of a few days to weeks.
Could modern or near future science be able to create a liquid similar to Bacta? The main requirements of the liquid would be: to induce rapid healing by cellular regeneration and mending to allow a severely injured patient to make a full recovery (full as in not dead. Depending on the injuries some body parts might not fully regenerate)
Note: not too worried about time. So if the liquid takes longer than a few weeks that's fine.
I'm going with the assumption that Bacta can heal injuries quickly it cannot regenerate full limbs.
[Answer]
I think the "near-future" future requirement hurts this possibility. We don't know how to treat a lot of the things the bacta tank addresses to begin with even using the full extent of modern medicine.
### Here are some techniques that at least have a basis in current research (ie no super nanobots):
* There are a few proteins that aid the body's natural tissue healing process in mammals: for instance [MG53](https://www.sciencedaily.com/releases/2016/03/160302135149.htm) and [thrombospondin 2](https://www.ncbi.nlm.nih.gov/pubmed/10571734). The tank could contain bacteria that produce versions of these proteins altered to be more effective, as well as a soup of simple sugars to fuel the bacteria's production. Proteins that require energized ATP to function could be supplied by a different strain of bacteria. These proteins have been shown to accelerate healing and remove scars in mice; there's probably a good analog in humans.
* The mixture could be programmed to the genotype of the person submerged in it by a medical technician. Engineered stem cells float in the fluid until they find a spot including inflammation. They then specialize to become skin cells or immune system T-cells, aiding in closing wounds and fighting infection.
* The mixture could contain topical antibiotics (if there are bacteria in it as well they need to have antibiotic resistance)
* The mixture contain cells that produce [bacteriophages](https://www.nature.com/scitable/definition/bacteriophage-phage-293) to target foreign bacteria that they find. This is more precise than antibiotics and has fewer side effects
* The temperature of the fluid can be controlled to help the body regulate internal temperature, and the fluid can be made to conduct heat very well to speed up this process.
* The fluid can contain [Chemical Permeation Enhancers](https://www.nature.com/articles/s41598-018-37900-0) to make the skin more permeable, allowing introduction of water and various anti-inflammatory or [analgesic](https://en.wikipedia.org/wiki/Analgesic) drugs.
* The fluid can contain topical antivenins to counteract snake/insect bites, poison ivy/nettle burns, or even biological/chemical weapons.
* You can breathe a higher concentration or pressure of oxygen through a tube, allowing for accelerated healing and reduction of pain, inflammation and headaches.
The main thing with these though is that they only target the outside of the body. What if you have internal bleeding or broken bones?
The fundamental problem here is that if you have a fluid that can fix internal damage, the ideal method of delivery for it is not "dunk the patient in a big vat full of medicine until they get better." The fluid would have to enter the body at some point in order to function, and I don't see how it's going to do that.
### You could probably treat a good number of conditions with a relatively near-future bacta tank:
* Burns
* Scarring
* Cuts & abrasions
* Topical infections
* Skin fungus
* Hypothermia
* Hyperthermia (overheating, usually due to fever)
* Rash or inflammation
* Snakebites/insect bites/poisonous space monster bites
* Dehydration
* Headaches
* Sleep deprivation (because hey, you're floating in a tank for hours)
### Things it won't treat (not a complete list for obvious reasons):
* Broken bones
* Ruptured organs
* Brain damage
* Cancer
* Pneumonia (if you're having lung trouble breathing through a tube could cause problems)
* Radiation poisoning
* Food poisoning
* Pretty much any other type of poisoning
* Genetic diseases
* Psychological conditions
* Claustrophobia (duh)
* Fear of drowning (duh)
* Anaphylactic shock
* Ordinary shock
* Blood loss (it won't treat this without some other equipment providing blood)
* Hair loss
* Heart disease
* Diabetes
* Obesity
* Bruises or internal bleeding
* Shrapnel damage
* Missing limbs
* Missing organs
* Blindness
* Deafness
...You get the picture. It's not a panacea, but it is a valuable piece of medical equipment.
[Answer]
We know that human healing can be accelerated by large doses of oxygen, this is usually achieved by high pressures as in [Hyperbaric Oxygen Treatment](https://en.wikipedia.org/wiki/Hyperbaric_medicine), but it could be delivered by extremely heavily oxygenated [breathing fluid](https://en.wikipedia.org/wiki/Liquid_breathing) of some form. Given the apparent limitations of Bacta I would suggest that is just such an oxygenated fluid, carrying several times as much oxygen as usual to the cells of a body suspended in it. This would explain the accelerated but not miraculous scope of the healing in such tanks.
[Answer]
**No**
Bacta, in Star Wars, is basically the equivalent of healing magic. And that's fine for Star Wars, because it's soft sci-fi anyways, and draws heavily on classic high fantasy for inspiration. But here's a few uses of bacta you left out: Regeneration of large tissue loss without scars (chucks of skin, internal organs, etc., as long as part of the organ is there), the ability to cure every disease (except for those which cause bacta allergies), the ability to flush every toxin, full stasis when necessary, and (this is the kicker) can be applied to literally every alien in the franchise. The stuff can cure cancer and regenerate nerve damage. Like I said, healing magic.
As for something which just induces accelerate healing with modern technology- that's a bit more possible. A combination of steroids and the right diet should do the job, but there'd be a cost involve. Generally, there's a reason why your body heals at it's own pace, artificially inducing rapid healing probably has a cost on the human lifespan.
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[Question]
[
**Background:**
An Elven nation that once thrived for thousands of years as a predominantly agricultural race was forced underground because of unexplainable occurrences of extreme weather conditions (tsunamis, volcanic eruptions, hurricanes, blizzards) threatening their existence. The majority of weather this continent has experienced is sunshine, with the occasion of thunderstorms and rain. Having no previous experience with other weather conditions, the Elven nation migrates underground to prevent themselves from becoming extinct.
**Factors to consider:**
* These are the first Elves to exist, so any other species of Elves came about as a result of reproduction.
* There are around 100,000 Elves belonging to this nation.
* The majority of their food is plant-based but they occasionally eat meat.
* Their sight and hearing are better than that of any human.
* They are typically 6 feet (1.8 metres) tall.
* They are born with green eyes or blue, light brown hair or blonde.
* Due to sun exposure, they are mostly tan-coloured.
* These Elves live for 300 years buy only reproduce until they are 100. In this time, they have between 2-5 children.
* The extreme weathers are frequent but not constant so they do make surface trips for resources.
* The nation survives underground for at least 5,000 years.
* Although they cannot cast magic, they have some magical attributes such as longer lives and are more immune to diseases than humans.
Although it is unrealistic to suggest it has no effect on their sight, I would prefer they didn't go totally blind.
*(Edited to ask only one question, be more specific, and to fix errors. The question asking how they would survive now has its own post. See: [How would Elves survive underground without prior experience?](https://worldbuilding.stackexchange.com/questions/146042/how-would-elves-survive-underground-without-prior-experience))*
[Answer]
## Food production
The big hurdle you have to overcome for your scenario to work out is **food production**. Essentially all food production we know relies on sunlight as it's source of energy. Meaning either *plants* take up sunlight during photosynthesis and store it in various forms of starch, etc., or *animals* eat said plants, take up the suns energy "second hand" to be then themselves (or their eggs/milk) eaten by your population. And, by the way, mushrooms are not a get-out-of-jail-free-card, as they rely themselves on (the suns) energy being stored in other microorganisms they rely on (see [this question](https://biology.stackexchange.com/questions/55841/where-do-mushrooms-get-their-energy-from)).
You will essentially need some stable, sustainable food production, either plant or animal-based, that will allow your elf population to survive in the long term. This either means some magic/handwaving/unobtainium/etc. or some sort of production cycle that relies on plants/animals/fodder or some other biomass being **brought in from the outside world**. So unless you come up with a magical solution it is unlikely that your elf population will truly live without any ties to the surface world.
The only idea I can come up with is to mainly rely on *hunting* animals (fish, moles, snails, ...?) that live underground but themselves travel to the surface or rely on surface food/nutrients somehow reaching them (e.g. via underground streams). This could be supplemented with some *gathering* of e.g. mushrooms, snails, worms, mussels, ... leaving you with a **hunter-gatherer society**.
## Physiological change
The 500 year time span you mention is far too short for any kind of evolutionary changes, even more so if the elves are long-lived like most of their fantasy counterparts.
What you would see is reduced Melanin production, so your ground-dwelling elves would become rather pale. Their hair would not be bleached by the sunlight, so might be a tiny bit darker, but that would be it: overall **no big change would occur**.
If your elves rely on some vitamin that is only produced under the effect of sunlight (as we humans do) then they are out of luck: they'd have to either find a supplement vitamin source (maybe some animal they can hunt?) or will perish rather quickly.
## Societal change
The societal change will certainly be the largest, especially within the given time period of 500 years. The first one or two generations might still be in 'survival mode', fighting with resource shortages and trying to get accustomed to the new situation, the newly available (or no longer available) resources, adapting to their immediate surroundings, etc. This would certainly be a big **struggle**, and a fair number of your population might starve. It is also likely that the sudden shortage of resources would lead to the formation of strong families/clans with infighting between them, so complete splits and the formation of new 'nations' might be possible.
After that the society would probably slowly **settle** in and optimise their new hierarchies and organisational structures to work well with the new ecosystem. In the long rund I'd expect your 'nation' (actually, 10'000 individuals is rather the size of a small town) to disperse in smaller settlements that consist of maybe some dozens to a few hundred individuals: because they are largely based on hunting they will need to cover bigger territories/hunting grounds to sustain the population without completely decimating the hunted species - similar to how human population was organised in the pre-agricultural hunter-gatherer times.
In the long run this will necessarily also lead to the **tech-level of your society dropping** markedly: a society based on a base unit of dozens/hundreds of individuals is simply not able to sustain the additional burden of the technology, the supply chains, the passing of knowledge, etc. that bigger societies can.
As the number of generations since the migrations grows the memories and stories would slowly grow more and more distant... It is rather likely that the increasingly distant past of the elves' surface-origins would then fade over towards some sort of **origin-myth or religion**, maybe with some deities being responsible for the migration (weather, storm, ...), or some new ones being invented that now shelter the elven population (rock, earth, ...).
## Summary
So again, summarised, I would predict the following changes:
* Struggle for food during transformation to hunter-gatherer society
* Formation of strong family ties or clans
* Separation into small family/clan based settlements
* Marked drop of tech level
* Formation of new mythology based on the surface origin
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Extreme weather... What would it actually do? It would prevent agriculture. It would feasibly destroy houses and most public buildings. It would kill the vast majority of your elves, mainly via famine and disease. That last bit is important to remember for the social effects.
Effects on the ecosystem at large? Since we are talking about **extreme** we can probably say that trees will be gone. I mean, if the trees could survive, it would be fairly easy to create buildings from wood that would also survive. So the landscape would probably be something like prairies or savanna. Grasslands with occasional small trees or bushes.
We can also assume common flooding and extreme erosion. Grasses are actually good at dealing with erosion and lack of rain is a major issue with the Earth analogues I gave, so it would probably be very rich and productive ecosystem but with spectacularly deep canyons or gorges for the rivers.
For animals you'd have antelopes, horses (or zebras), and some sort of bison/wildebeest equivalent. These would be hunted by lions, leopards, wolves. You'd also need scavengers such as hyenas. Very rich ecosystem very similar to one we have all seen in various nature documentaries over the years.
The point I am trying to make is that even with agriculture being impossible there is going to be lots of food outside. Lots more than underground, certainly. Your elves will live in the caves and hunt the animals outside. Maybe ones that come to drink at the river valley their cave overlooks. In short, they will live almost exactly like our ancestors lived before the agricultural revolution.
It would be fairly easy to assume that the weather is worse than this and there won't be rich ecosystem outside but, let us be honest, if the weather is so extreme that grasses cannot survive it, everyone will die. And something will be hardy enough to survive to eat those grasses. Or elves certainly will not survive.
Your elves would start with iron working, large scale organization, and knowledge of architecture. They would gather survivors, maintain order, scavenge all the tools and valuables they can find. The drop in population would cause major social changes (no large kingdoms) but medieval technology should be sustainable, if the elves stay organized.
This works much better if there is a nearby cave system that can hold thousands of elves that they can withdraw into and indeed have withdrawn in the past during wars and such. The end result would be independent elven communities with sizes from a small village to a small town depending on the size of the cave system available.
The elves would have the ability to expand their caves for more space. They would also build small gardens protected from wind and flooding. Eventually they might develop mushroom farming but initially they wouldn't have the space to do it to an extent that makes a difference.
Fires would be an issue because the storms would destroy most trees, so after the initial windfall gets burned or swept away, they'd have to start burning compressed manure collected from outside. While some trees would survive due to protected locations, those would be the exact locations where you'd want to build a garden for fruits or vegetables, or even build a house on. Far too rare and valuable to grow fire wood on.
Given the size of the settlements they would probably be chiefdoms, they'd be run by a chief, probably a descendant of the leader who founded the settlement, but probably with the approval of "clan elders". Sometimes decisions or chiefs might be discussed publicly and even voted on.
Religion would probably be shamanism of sorts. people would probably mainly want good luck with hunting and avoid bad luck with weather, famine, disease, so a combined spirit talker, witch doctor, wise man like a shaman would be quite appealing. Specialized priest or organized religion would generally require larger societies. And more wealth and leisure time than shell shocked survivors could provide. Besides after the weather suddenly turned against them people would quite reasonably blame nobility and priest for angering the gods. They might be quite devout and religious but organized religion with priest and dogma would probably not be that appealing.
[Answer]
Go ahead and google up some eye candy Drow hotties. Out of your system? Good. Let us set aside magic and consider ecosystems and evolution. No magic.
Elves are long lived primates; cousins of humans. They are intelligent, cooperative, slight of build, with a well developed culture.
Evolution means selective advantage. Certain traits give some elves the ability to have more children. Elves without those traits have less children. Let us consider also that the shift to cave dwelling occurs over many generations to give evolution time to operate. As the surface becomes less hospitable, elves which can support themselves on the resources of the underworld are more likely to have children who themselves survive.
**Meet the Elf Olm-Sloth**.
[](https://i.stack.imgur.com/U6io8.jpg)
1. **Slowest possible metabolism.** The surface is resource rich thanks to the sun and rain. The underworld is resource poor. Calories are scarce. The olm is a subterranean salamander with a metabolic rate slow even by amphibian standards. Sloths have super slow metabolic rates too so it is possible for a mammal. Slow metabolism means your calories go farther and you are less likely to starve. Your underelves would slow... way... down. She may be capable of a burst of speed to snag a fish, and then she rests.
2. **Noncooperativity**. Hunting and farming are methods to exploit the caloric wealth of the surface. Cooperativity helps with both endeavors. Gathering fish and bugs would be the way of the underworld. Gathering is not helped by cooperativity and in fact the more you spread out the less likely you will deplete resources in any given place and starve. Your underelves are asocial loners. Their culture falls away.
3. **A corollary of 1 and 2: slow thought**. Things do not change much in the underworld. There are not complex spatial problems to be solved, or problems of complex interpersonal relations. Curiosity killed the cat. Your underelves are uncurious.
4. **Semiaquatic**. Concentrated food resources in the underworld are in places where water can carry down some of the bounty of the surface - nutrients at least. Your elves become semiaquatic, because the water is where the fish and bugs are.
5. **Small.** Related to #1 - the smaller you are the less food you need. Large physical size is a drawback in the underworld. You need more calories and have less access to small spaces. The generations will dwindle your elves to shriveled monkeylike miniatures. At this point you can go google up some more Drow babes if you need to.
6. You're back! The underelves don't care how homely they have become because they are **blind**. It is dark down there and the prima donna eyes demand a lot of brainpower that they cant use. Hearing, smell and especially tactile vibratory sense become the dominant senses.
7. **Smelly**. If you are a tiny blind loner who lives alone, how do you find a mate? Sniff him out. The underelves stink pretty bad. This scent marking serves to mark occupied territory against incursions of other underelves. The diffuse funk also cannot be used to specifically locate another elf individual, which is protective because the underelves are
8. **Cannibals.** Of course they are. Calories are calories and an elf individual represents years of caloric accumulation. It is evolutionarily disadvantageous to eat a potential mate, but nonmates are definitely fair game and a big score as regards calories.
I hope one of you will see fit to draw [Drizzt Do'Urden](https://en.wikipedia.org/wiki/Drizzt_Do%27Urden) as the blind stinky stupid cannibal water monkey.
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I want a way to enclose an area (building-sized and on Earth, let's say) in a field that warps spacetime so that time appears to pass 100x slower within it. **You don't need to explain how the field got there or what effect could produce it, only lay out a consistent framework that it operates under.** (i.e. I don't need explanations for what kinds of relativistic effects would result in a field like that - just assume it works by magic). It doesn't need to conserve energy or momentum (I suspect it'll be nearly guaranteed NOT to conserve them, since the barrier breaks Lorentz invariance). It just has to have 3 features:
1. Within the barrier, it feels just like being in normal space, except that if you emerge from the field after (what feels like) an hour, it will have been more than 4 days.
2. People can pass through the barrier without protective gear and without being crushed by their own skeletons, burned by a shell of captured photons, ripped apart by expanding space, etc.
3. Conditions inside the field are hospitable to humans as well (i.e. I'd rather toxic levels of CO2 didn't build up inside the field). This is what dooms the naive answer of just setting time to pass 100x slower in the field with no other changes.
Anything that fulfills those conditions is fair game - I just want to know if it's possible. The edge of the field can taper gradually if you want, with the speed of time smoothly changing from 1x to 100x normal. You can make it so that space inside the region becomes physically larger, as do the people who enter it, if that helps. Not saying it will, just that enlarging things 100x might offset the pressure at the barrier, though I personally haven't been quite able to get it to work.
Issues to address:
* The field is open to the air, which means that if the rate of time is just strictly different inside, atoms outside the field will be moving 100x faster, so they enter the field 100 times more often than they leave. By this logic, the air inside the field should be at lethal pressures, regardless of whether or not the barrier is a smooth gradient.
* How does light interact with the barrier? Assume that, other than any spacetime-warping effects, it's transparent. My first instinct is that, since much more light enters the field per second than leaves it, the outside seems bright to the people inside and everything inside appears dim to those outside. Not too problematic, but I can imagine fixes to the previous bullet point causing issues here.
* We need to find the limiting factor for what about being in a time gradient would kill a person first. Certainly, blood pressure differences could cause issues, but I imagine the brain's sensitivity to timing differences would kill at much gentler gradients. Hard to put numbers to that, though.
Creative answers are welcome! Maybe the whole inside area is spinning! You know, interesting angles like that, except that they actually solve the problems instead of making things worse.
[Answer]
**Stargate to a world near a black hole.**
That's how they did it on Stargate SG1. I cannot find a video which shows the excellent opening of episode 2-15 but you can watch the whole thing here for $1.99.
<https://www.youtube.com/watch?v=4n2xxesfLDw>
In short - team SG10 is exploring a planet when the binary star of that planet condenses into a black hole. The team sees bad stuff going down in the sky and starts running to the stargate, which for those unfamiliar with the show is a technologically enhanced wormhole. They are transmitting through the gate and their transmissions get slower, and slower. As time slows for SG10, they will never reach the gate to escape. I like to think they never realize this.
The rest of this episode deals with the ramifications of being connected to a spot near a black hole via a Stargate wormhole. The ability to connect to a black hole via Stargate is revisited in a later (so awesome!) episode.
For your purposes: slow land is an area near enough to a black hole that time is slow. Alternatively it could be a destination that is moving extremely fast as compared to the starting destination. The transition from normal time land to slow land must be some Stargate-like tech enhanced spacewarp thru special space that matches velocity etc.
checking...hard science tag? No! It's all good.
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## Entering the field
So you're worried about timing differences hurting or killing people. A solution is that the time gradient will always be constant on a solid object. So if your person's center of mass is halfway across the boundary layer, they run at 1/10 speed1 as seen by the outside world. Every bit of them. You can take electronics inside and they won't fail from transistors running at different speeds.
It will help for people to not notice if the boundary layer is very thick. (If you have a difference of 1% per meter, then the boundary layer should be ~463 meters thick.) People noticing something is off might violate requirement #1 (Seems like ordinary space) but the boundary layer being incredibly thick is not a requirement for this solution to keep someone alive.
This would cause interesting effects for mechanical devices made up many different solid parts moving across the boundary layer.
## Air problems
The pressure buildup inside the zone will require a separate system to fix. Making the air exempt from the time dilation will result in people being squished, while including it, as you already realized, is that people die under 100 atmospheres of pressure.
On the harder side of ideas, the area inside the time dilation zone is a pressure chamber. When the hatch is open, it can pump out the excess air.
On the softer side of things, consider something like Red Tornado's aerokinetic core, from Justice League Unlimited and Young Justice. The aerokinetic core is what allows Red Tornado, a robot, to create tornadoes and wind. A similar system of mechanical aerokinesis would allow an effective pressure gradient to be kept across the boundary layer.
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1: I'd actually assume that a time dilation's boundary layer would have an exponential curve, so to square the rate the boundary layer doubles in thickness.
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The only solution is handwaving. There is no realistic way for this to not be lethal. Fortunately, things like this show up all the time in tv/movies/books, so you don't even have to explain it. Just do it and treat it like it is perfectly natural. As for why this isn't possible, it boils down to the fact that a 100x time dilation is actually quite large, and this impacts *everything*. For reference, to experience a 100x time dilation due to special relativity, you would have to travel at roughly 99.995% of the speed of light. By comparison, [a baseball traveling at 0.9c is a city-ending event](https://what-if.xkcd.com/1/). This is a crazy high time dilation factor. Here's what it does:
1. **Air Pressure:** It's not just about CO2. Air on one side of your barrier will enter faster than air on the other side of your boundary. If the boundary were to suddenly turn "on", the air on the inside would effectively act as if it had a fraction of the pressure. You would end up with a gigantic vacuum sucking air into the time dilation zone until the "pressure" on both sides equalized. I'm not 100% certain on how the math would apply, but let's assume the [ideal gas law applies](https://en.wikipedia.org/wiki/Ideal_gas_law) and that air inside the barrier is effectively traveling at 1% of the speed of air outside. [Temperature is proportional to kinetic energy](http://physics.bu.edu/~redner/211-sp06/class23/class24_kinetic.html) and kinetic energy is proportional to `velocity^2`. Therefore air with 1% of the speed has 0.01% of the temperature and 0.01% of the pressure (`PV=nRT`). Naively, this means that the pressure inside your dome is effectively 1/10000 of that outside. Therefore our gigantic vacuum will continue until that large pressure difference equalizes, with some very large change in density or temperature inside the bubble. In the end though, the bubble must have an air pressure of 10000ATM (1 gigapascal) to equalize, which is unbelievably high. For reference, the compressive strength of concrete is measured in megapascals. The pressure in the core of the earth is around 360 gigapascals.
2. **Light Intensity:** Light of course has the same problem, although this may be survivable for the people inside. Inside your time bubble time travels at 100th the rate. That means the light is travelling 100 times slower. As with air, this creates a problem at the boundary: light enters much faster than it leaves. In fact, when the field first turns "on" it may appear to turn black for a brief moment as light which enters cannot immediately bounce back out for you to see it. Presumably, things inside the barrier would initially appear 100 times dimmer. The eye is a logarithmic detector, so this difference won't be *as* apparent as you might think, but it would be quite obvious. It would be about the difference between a bright star at night and the dimmest you can see. However, this effect would be temporary (I think). The "energy density" of light inside the zone would always be 100 times higher than outside, but once light has had a chance to make it to the center and bounce back out, it will become visible at normal "brightness" (for the same reason that your vacuum stops once the pressure on both sides equalizes).
3. **Light Frequency:** Of course it isn't just the intensity of light that will change - also its frequency. This is more or less the same as what happens with the [doppler effect](https://en.wikipedia.org/wiki/Doppler_effect). Light entering the bubble would be "blueshifted" by a factor of 100, turning visible light into high energy ultraviolet light. Conversely light leaving the bubble would be redshifted, moving visible light into the near infrared. This means that if you were inside looking out you would see not visible light but infrared (you'd be able to see everyone glowing!), and if you were outside looking in you wouldn't be able to see any light sources inside. Technically you'd be able to see any ultraviolet light sources, but we don't actually use a lot of those, so you won't see anything unless it is illuminated from light first coming from the outside.
4. **Impulses:** Force exchange from the outside to inside of the barrier becomes interesting. I assume energy is still conserved. If you imagine being inside the barrier and hitting an object just outside the barrier with a hammer, the amount of energy you impart will presumably remain the same. However, from the perspective of the thing outside, that energy is imparted over a time period 100 times smaller. Same energy, less time = larger impulse, more force. I'm guessing wildly here, but this might mean (for instance) if the field is in the middle of a high rise, people walking inside the bubble may end up cracking and breaking the floor just outside of the bubble without meaning too. I'm not sure what other impacts this might have.
The unfortunate part is that a gradient doesn't help any of this. A gradient might turn your vacuum down to a small wind, but in the end the atmosphere inside won't stabilize until the pressure at the center is 10000x higher than outside. I just don't think there is anyway to cancel out all the effects of such an extreme time dilation without completely violating the laws of physics. At that point in time, the answer is really just "magic", so just own it and come up with your own fun explanation.
Again though, I don't personally think it's a big deal, even as someone with degrees in physics who excessively criticizes movies/books for bad physics. This time dilation zone works and doesn't kill people inside because you say that it doesn't (or more specifically, you don't say anything and people in it don't die). See [this clip](https://www.youtube.com/watch?v=xT7F0eKfctg), especially starting at 1:10.
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On the atmospheric point, unless I'm missing something, CO2 isn't going to enter the time dilation zone at any different rate than any other component of the atmosphere? So CO2 poisoning shouldn't be a problem, but runaway pressure build-up could still be, but you could remedy this with just a big air pump shifting the surplus air back out of the dilation zone. This would take a lot of energy to power, but luckily you could generate a lot of that power by setting up a ring of wind turbines around the circumference of the dilation zone to take advantage of the super-sped-up air (these would also have the advantage of slowing that air down somewhat).
[Answer]
## Problems & Solutions
**Safely entering the area**
The extreme sudden difference from a sharp change would likely damage most hints to enter the field. Because of this, you should likely use one of the following methods.
The field has a gradient barrier, or objects that enter partially get a similar field around their body as they enter. These allow for less harm from the sharp change between 2 body parts by either making the change slower over a distance, or too fast to be harmed by it.
**Air pressure**
Luckily, this isn’t going to be a major problem. As the gas approaches the battier/enters it, the particles will retain the energy from before. As the time is slower, they appear to slow down if looking in on the outside. The pressure differentials do not exist due to the barrier not involving slowing particles down, but rather time. Gases should appropriately diffuse normally for the most part. One way to imagine it is by thinking of throwing a bowling ball at the barrier. One ball rests just inside the barrier. If both have the same mass, the bowling balls will impact and will both have half of the velocity of the first moving ball.
**Light**
Light passing into and then out will appear as though it was normal wavelength to those outside. Light reflected from objects inside will appear redshifted. To those inside, the outside is blueshifted by a factor of 100: inverse to the view of those outside. The light is going to have a increase in amplitude as well. Due to this, energy from light and sound becomes stronger as it enters. As it leaves, though, it weakens. These effects could likely balance out. In this case, it is similar to how cosmic voids and clusters affect wavelengths of light.
**Conservation of energy**
It takes more energy to move an object partially inside of the region as the difference would lead to 100 times the energy to cause objects inside to appear to move at the same speed. (For example, rolling a ball at 1 cm/s on the outside, and another rolling at 1 m/s inside.) Acceleration is easier to apply to the outside by anything inside for the same reason, but in reverse.
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I see that @Willk has already meantioned a black hole, which is what i was thinking of.
>
> *To a distant observer, clocks near a black hole would appear to tick more slowly than those further away from the black hole.[78] Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow as it approaches the event horizon, taking an infinite time to reach it.[79] At the same time, all processes on this object slow down, from the view point of a fixed outside observer, causing any light emitted by the object to appear redder and dimmer, an effect known as gravitational redshift.[80] Eventually, the falling object fades away until it can no longer be seen. Typically this process happens very rapidly with an object disappearing from view within less than a second.[81]*
>
>
> Via <https://en.wikipedia.org/wiki/Black_hole#Event_horizon>
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We know that it is impossible for life to exist within a black hole, however its your story, so you could possible have something like a very small, spontaneous black hole forming on a planet, and if someone enters it, there is the time gradient like above, and because its your story, life is possible but we dont know because the time difference makes it that anyone who enters and then leaves, even a couple of minutes later, are a few days ahead of an observers timeframe.
Dont know if that helps or would fit in for you?
hope the link works
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Well according to Einstein's Theory of Relativity (Time Dilation-- a video on it is linked below), time is relative, but the faster something moves the less time it takes (i.e. Walking a mile will take 30 minutes, running a mile takes 15). So this field of time could make people/life move exponentially faster which would make time inside the field feel short and the time outside long. And because it is its own field, this transition could potentially feel normal to those inside it.
[Video on Einstein's Theory of Relativity](https://www.youtube.com/watch?v=yuD34tEpRFw)
There is one other scientific possibility. Passage of time on Earth is mostly dictated by the sun (i.e. One revolution= 1 year, 12 months in a year, 1 turn of earth= 1 day, 24 hours a day, 60 minutes an hour, 60 seconds a minute). So if our planet's time is based on the sun in our solar system, that can easily be done with other solar systems (considering there are at least 200 billion stars in our galaxy alone). Yet that is from Earth. If we colonized Pluto, one year on Pluto would be 248 Earth years.
So if you have a star in a solar system that is used for relativity, you could create a sort of planet-to-planet time field. So four days on one planet could equal an hour on another planet.
Though travel through this planetary time relativity field would require high-tech space traveling technology.
But if it didn't need to be explained...bubbles and trees seemingly came to mind. I don't know why. But maybe you just have this weird flat plain made of trees made of bubbles. Bubbles that last super long and don't pop very often (unless touched), which became the deciding factor of time. So when the bubbles pop an hour has passed or something (and the bubbles just regenerate themselves).
[Answer]
Most answers focused on air pressure. The reasoning looks like *speed should be increased* **->** *molecules of air should move faster* **->** *air pressure is different* **->** *air would leak from field border*. But I suppose it's incorrect in many ways.
## Air pressure difference is not necessary.
Not only air molecules would move faster. Anything and anybody. What about human speed? Is people moving 100x faster too?
Also, in general relativity theory time could be slow down not because of fast moving but because of high gravity. In that case air pressure inside should be *increased*.
Since *barrier breaks Lorentz invariance* we could easily say it **breaks *continuity* of speed** (or **continuity of gravity**). Just because **speed is component of momentum** which you suppose don't conserve.
## (Magic) Gateways
What if border consist of many something like airlock gateways?[](https://i.stack.imgur.com/aeNJq.png)
Each gateway isn't so big, just 1m size. It could be constructed by ~~magic~~ handwaving technology from fields, not from steel. So when human travel through the border it passes dozens small gateways. Probably he even doesn't noticed that gateways.
If human traffic is low then remember animals, birds and insects would traveling through similar gateways. So we could say there is **enough air traffic** between inside and outside areas to allow **CO2 to be ventilated**.
## Building ventilation system
If we talk about building size let's see how same problem are solving in buildings. Most of them have **ventilation system** (with propellers or just passive one). Let's say that inputs and outputs of this system are **passes through barrier**. Somehow.
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Your field has a gel like skin that prevents anything from traveling through it without effort. How it would work is any object attempting to travel through would push a bubble out and when the entire object is over the threshold of the field the field reforms behind them and the bubble they pushed out pops effectively instantly making them a part of the new time on whichever side they are on.
For most other effects (eg the sunlight is entering the field 100x slower than normal making the light from outside seem dim) The gel compensates for as much as you want, increasing the intensity of light, being selectively air permeable to let gas exchange with the outside at what would seem to be a normal rate from inside, correcting gravity because I'm not sure how time dilation effects that.
One interesting side effect of this is from the view of people in the bubble anyone pushing in would enter almost instantly, where as people exiting could be watched pushing through for hours by people outside (and maybe pushed back inside).
[Answer]
**It takes a long time to enter or exit the field**
This particularly dense area of spacetime offers a *resistance* to anything entering or exiting. The border is only a metre or so thick. But walking through it is like pushing against cornstarch slime (time gel). The barrier is not made up of solid matter but some sort of handwavey space-time gradient. You cannot force your way through. You just have to move really slowly over the course of about ten minutes until you get past the barrier.
This makes it safe for people to cross over since the worst that can happen is you get tired pushing and have to rest halfway through the barrier, then proceed more slowly.
Fast-moving objects have problems though. A missile fired through the barrier would be torn up as the gradient suddenly slows it down. Fast-moving light and air particles have difficulty passing through but statistically some proportion of them still make it.
By some miraculous coincidence this proportion is about 98%. This just about cancels out the fact that there is 100 times as much light/air trying to enter as leave.
Visually I expect most of the light to be refracted and/or reflected off the barrier. So from the outside it looks like an extremely foggy mirror.
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In my world, the government has prohibited owning your own military-like force. So what is a filthy rich person supposed to do to get back at the one who has given them a deadly insult? Hire mercenaries!
There is a well-established and respected mercenary guild, with few (if any) mercenaries operating outside of the guild. If you hire mercenaries from them, you'll be guaranteed professionals who won't give you anything less than their best. If your adversary also hires from the mercenary guild the mercenaries will use non-lethal tactics against each other, but with the reputation of the guild at stake you are still guaranteed that the mercenaries won't give you less than their best.
**What regulations from the government and/or self-regulations from the guild can prevent this system from being abused?** I want to avoid situations where a richer person could force a less wealthy rival into a fight in order to have the rival spend money they can't afford to (or kill them off if that's allowed as an outcome). However, the system also needs to be able to provide satisfaction - leaving a deadly insult unpunished could lead the insultee to attempt more drastic measures. In any case, the mercenary guild does want to ensure its own profits, but it definitely doesn't want the government to feel the need to step in.
[Answer]
Set up a system resembling insurance or mutual assistance funds.
Whoever wants to be protected by the service of the "honor guild" has to pay a monthly fee. In exchange, he can use the guilds in the cases you mentioned above. However, if he is the one to challenge, his fee will increase, so that one is discouraged from being excessively litigious.
In this way the costs for the individual will be lower, as it will be spread over a larger base, while still serving the purpose of protecting one's honor.
[Answer]
**The dead don't get paid**
Those mercs who get "killed" (in a laser tag kinda way) don't get paid. Those who survive get paid an awful lot.
Suddenly it's not in the rich guy's best interest to have an overwhelming victory because he has to pay the survivors and the poor guy pays very little as his soldiers are likely to be wiped out.
The mercs will treat it as life and death and fight hard because they want to be paid. The winner will want to win but want to only just win to keep the costs down and the loser will spend only a little as his team died.
The end result will be a close battle with neither side wanting an overkill. The guild charges a booking fee and a cut of the survivor's pay.
This would lead to some interesting tactics where a poor guy might hire a handful when he knows the enemy hired hundreds and use them to flee to minimise his losses leaving the winner with no casualties and a massive bill.
[Answer]
The Guild may only allow you to hire a certain fixed amount of mercanaries at any one time. This prevents one person hiring significantly more mercenaries than another, making the fights more balanced.
As L.Dutch stated, there also may be a challenger’s fee where a significantly richer challenger may be charged more, discouraging over-hiring of mercs. There may also be a “victor’s fee” for the challenger where, if they win the battle using the guild’s mercs, the challenger has to pay an extra fee to the guild (almost like a forced tip, which seems like something a guild of mercenaries might enforce).
Alternatively, you might have a loan-based system where, even if you can’t currently afford to hire these mercenaries, you take out a ‘loan’ with the guild where they supply you with however many mercs you agree upon and you agree to repay a fixed amount to the guild every month (or, if you can’t, the guild will seize any assests you own to repay the loan). This prevents one richer person out-buying a poorer opponent. Again, you could also charge richer people a higher interest fee to discourage over-hiring.
(Over-hiring could be a problem for the guild because, if all their mercs are being rented out, they won’t be able to offer more people loans and make more money)
[Answer]
Since the guild has the last word, the fighting sides could be chosen by a random (weighted) draft. Of course the mechanism shouldn't be too unfair toward the bigger payer, otherwise the richest ones would be prompted to hire mercenaries out of the guild.
So:
* A rich merchant decides to pay 100 thalers to hire a mercenary to fight against a less rich rival
* The rival can't afford to pay as much, so he pays only 50 thalers to the guild
The guild will then receive 150 thalers in total and will publish a list of available mercenaries: the one who pays more will have the first, third, fifth... choice, the other the second, fourth, sixth... choice.
The mercenaries will be paid by the guild, withdrawing from the 150 thalers (the first chosen will earn 50 thalers, the second one 40 thalers and so on)
This way:
* He who spends more will have a small advantage (which is in the interest of the guild), but not decisive
* In order to avoid situations where somebody pays 100 thalers and the other one pays only half thaler, if the ratio between the prices exceeds a certain threshold, the richer one receive an extra choice (for instance, first and second choice, then fourth, sixth...)
* It could be also a good idea to keep the paid prices secret until the draft, so that noone knows who will have the best choices; in case both offer the same price, the guild will auction the right of first choice
* Mercenaries will give their best to increase their fame and be the first ones to be called for the next challenges
* If both sides are scrooge (both offering 1 thaler), they won't find any good mercenaries available, but only the weakest ones
[Answer]
A possible alternative solution could be that your mercenaries will not take that fight to any location they wish to, but instead you have an **arena** of sorts where the fights between mercenaries take place. Your **mercenaries** will act like **gladiators** without being slaves in the first place - professional fighters with no intention of actually killing each other, but fighting to the best of their abilities in single combat or in groups in order to improve their standing in the guild or arena rankings and thus their payment.
This has the added bonus from the *government perspective* that the chance of **innocents getting injured or killed as collateral damage will be reduced or eliminated** completely depending on the arena safety.
In addition, it has the added bonus from the *rich person's perspective* that everyone will be aware and able to watch, how their honour is being avenged and give a clear **show** case of "**do not cross me**".
In order to prevent abuse of the system you could make it a lottery which gladiators will be assigned to which rival and make payment ot the guild dependent on social rank and income. In this way, anyone can afford the system, the mercenaries have a high intrinsic motivation independent of who hires them and the public receives their constant amuesment in the form of arena fights.
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We all know Pikachu, fuzzy, small rodent, with the ability to discharge electrical energy as an attack. But could Pikachu ever evolve in our world, and how would it do so?
What's required:
* Rodent-like bodyshape, and
* The ability to generate enough electricity that the Pikachu can discharge it to deal damage to other creatures.
Bonus points:
* Small body,
* The ability to say it's own name, and
* Vibrant yellow and black fur.
This is part of the Anatomically Correct Series, a list of questions may be found here:
[Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
[Answer]
Electric eel. Well, not an eel but knifefish and not fish really but actually a lizard (in it's evolved state).
Make electricy? Check.
Yellow? look at that dewlap, look yellow to me.
[](https://i.stack.imgur.com/snfIs.jpg)
Rodent-like bodyshape? Depend on what you put emphasis on. If hairs then something like hairy viper of bearded dragon (who have yellowish tint on itself). If the snot and legs ratio then Geckos are very "rodent" like.
The ability to say it's own name? It's the easiest. It name would be "Kshhhh" or "Ssssss" or "Kheee". Name the animals from the sound they make not the other way around.
[Answer]
I am going to reuse [my answer](https://worldbuilding.stackexchange.com/a/109202/30492) to the question on [electric unicorns](https://worldbuilding.stackexchange.com/q/109199/30492):
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> The unicorns are symbiotic with a jumping spider species, residing on the horn.
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> The horn is kept at (or can be quickly charged to) a sufficient high potential, and the jumping spiders can be directed to jump on the target while threading a thin wire of cobweb attached to the horn.
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> As the spider or a group of spiders land on the target the circuit is closed and the target is zapped.
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> Alternative to the spiders: the unicorn can blow mucus covered particles to the target, with the particles keeping a thin slimy rope of mucus attached to the horn. Zap as above.
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> Pick the one more suited for your story and stomach.
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In this case you don't have a horn, but simply an appendix which can be dielectrically insulated from the rodent size body, where the spiders reside and from where they jump toward the target.
The yellow and black fur is a consequence of the same mechanism used by wasps and friends: it's an alert to inform the potential attacker that "I can hurt you badly, but doing so will cost me quite a lot. For each other's sake, stay away".
The ability to say its name is simply explained with an omophonia: we ear a sound that resemble Pee-ka-chu, and we think the beast is saying its name.
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A portal to another Earth in a parallel universe is open at the bottom of the Ocean and all the water is moving to the new Earth in the form of a waterfall in the middle of the Atlantic. The form of new Earth is exactly like ours.
* Is there still land available? If yes, how much?
I'm focusing on this new Earth.
[Answer]
The average depth of the ocean is about [3,7 km](https://oceanservice.noaa.gov/facts/oceandepth.html)
about a third of the world is not-ocean. So the new average depth would be 3,7 + (3,7\*(2/3)) = 6.17 km, or 2,46 km deeper than it is now.
So yes, there would be land. But only where we currently have reasonably high mountains. In Europe for example only the Alps and Pyrenees would remain above water. The only significant land mass left would be the Tibetan plateau
I have made a map of Asia assuming water level is 2500m above sea level
[](https://i.stack.imgur.com/9sBKb.png)
[Answer]
Under the assumption that the new earth is exactly like ours, there will be small fraction of land available, when all the water in our earth flows to the new earth.
Just to explain more, lets assume earth's oceans are around 3.5 kilometers deep.
[Ocean depth ranges from around few meters to even 10 KM. But for our calculation lets use the number 3.5 KM as average]
If this is doubled, the depth becomes 5.9 ~ 6KM. If our assumptions are right, then we can see these mountain ranges and structures with elevations > 2.5 KM in the new earth.
[ 6KM {New avg depth} - 3.5KM {Existing avg. depth} = 2.5KM => Height of structures / mountains visible in new world ]
Edit : Corrected calculations. Thanks @Borgh, @Malkev and @Tim B
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So this is a small map of all the continents on the small planet of Parsas Decem. As far as most of the rivers go, I’ve got it figured out. What I’m wondering is, can salt water flowing in from the sea be filtered naturally by the soil, perhaps with specific desalinating minerals, into fresh water? If I can, I’ll try to post the map of just the north eastern quarter of Daichi.
[Answer]
Saltwater does not move far inland, **you are chasing a problem that doesn't exist**. Saltwater intrusion of more than a kilometer is all but unheard of, and then only in the driest locations and only affecting deep wells. Saltwater is also displaced outward and downward by fresh water, the fresh water is renewed by rain anywhere inland. Look at the lower picture an example of measured salt water intrusion. Saltwater permeating inland is measured in feet.
Unless you have and an inland sea that is not shown or have extreme flooding salt water intrusion is not an issue, and if you do that is a very different question.
[](https://i.stack.imgur.com/cWm2d.jpg)
[](https://i.stack.imgur.com/AJ6wD.gif)
[Answer]
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> can salt water flowin in from the sea be filtered naturally by the soil, perhaps with specific desalinating minerals, into fresh water?
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You are looking for a way to naturally [desalinize](https://en.wikipedia.org/wiki/Desalination) water.
Sorry to disappoint you, but it requires energy to happen, thus I don't think it can happen by simple filtration.
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> Desalination is a process that takes away mineral components from saline water.
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The closes you can get in a natural environment is one of the following:
First reverse osmosis
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> The leading process for desalination in terms of installed capacity and yearly growth is reverse osmosis (RO). The RO membrane processes use semipermeable membranes and applied pressure (on the membrane feed side) to preferentially induce water permeation through the membrane while rejecting salts. Reverse osmosis plant membrane systems typically use less energy than thermal desalination processes.
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Or also freeze-taw
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> Freeze-thaw desalination uses freezing to remove fresh water from salt water. Salt water is sprayed during freezing conditions into a pad where an ice-pile builds up. When seasonal conditions warm, naturally desalinated melt water is recovered. This technique relies on extended periods of natural sub-freezing conditions.
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Or, finally, solar evaporation
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> Solar evaporation mimics the natural water cycle, in which the sun heats the sea water enough for evaporation to occur. After evaporation, the water vapor is condensed onto a cool surface.
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[Answer]
Probably it is not what you asked for, but you could find it interesting
[This article](https://arstechnica.com/science/2018/10/easter-islands-statue-builders-sort-of-drank-from-the-sea/) explains that for the ancient Easter Island populations, the main water sources were brackish-water pools near the sea.
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> the Rapanui probably got at least some of their drinking water from places along the coast where fresh groundwater seeped out of the island’s bedrock and into the sea. The resulting mixture would have been brackish but safe to drink, and it could have sustained populations of thousands on an island with few other reliable sources of fresh water
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I know that it is not a desalinization of sea water (of course it is the opposite, the partial salinization of underground water), but it could sustain some settlements along the coast and far from rivers, if the soil is too hard to dig wells far from the sea.
And if the brackish water has a bad taste, you can always use it to brew beer :)
[Answer]
Well no, but...
Salt water is more dense than fresh. If you have a difficult region for wells, say very sandy or otherwise unable to keep wells from crumbling, you could flood the area with salt water that would sink and raise up the fresh water which could be harvested off the top.
(might have to do this experiment myself: take a pot or bucket and fill it one quarter with fresh water and then halfway with sand (so that sand is basically wet but no way to take a straw and suck out just water); then add seawater until it displaces the freshwater which rises above the sand and can be siphoned off)
I don't know the long term viability of this plan but as long as the ground is saturated with the seawater all the rain or aquifer seepage will be on top and able to be collected.
[Answer]
Already said, desalination requires energy. I would also add that if any subsoil filtering system exists, where does the salt go to? From your description, it must accumulate until the filtration system is no longer operable. The inhabitants must have mined that salt on a regular basis, but that necessitates some mining technology, as well as knowing about such filtration system in the first place.
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Let's say that a method of lie detection was created that was 99.99% accurate, portable, and cheap. It is also very generally applicable, and there is no known method to fool it.
Now, it is ubiquitous in society. Employers regularly use lie detectors to confirm that employees have not stolen or otherwise defrauded the company. Schools use lie detectors to confirm that students are not cheating. Even parents might utilize a lie detector to make sure their children (usually teenagers, since it is easy to tell when young children are lying) are not lying. There are of course many other uses.
Of course, most people find this very convenient. Employees need much less supervision. Students can take tests at home. Parents do not have to worry about their children doing bad things.
But a very small group of people do not like the lie detector tests. Some find them invasive. Some are opposed on obscure religious grounds. And, unfortunately, some people just want to lie without getting caught.
We will focus on people who are not trying to lie, but do not want to be lie detected for some other reason. **How can they avoid being lie detected?** (EDIT: Clarification. When I say "lie detected", I mean that the lie detector is used on them. It does not matter if it actually detects a lie or not.)
Some notes:
1. Technically, it is never legally required to take a lie detector test. That being said, people can deny you employment, schools can expel you, and people can choose to assume you're a liar if you don't. Additionally, in a court of law, no testimony is accepted without a lie detector test, so if you are accused of a crime, you would not be able to testify in your own defense. More troubling, if someone commits a crime *against you*, you can not testify against them. Indeed, police will not even start an investigation without the person reporting the crime taking a lie detector test (unless they have extremely convincing evidence).
2. This probably is not important, but I will explain what the lie detector actually detects. Technically, it is not a "lie" detector, but a "deception/misleader" detector. It detects whether or not someone is trying to deceive or mislead someone. So for example, if you shoot someone and said "I did not kill that person", which is technically true since the bullet killed them, it would still register on the lie detector. Likewise, if you said "I witnessed the shooting at noon", when in fact you witnessed it as 11:58 a.m., it would not register on the lie detector, since you were not attempting to mislead, even though the statement is technically false. Essentially, whether a lie gets detected depends on intent, not the statement itself.
3. In accordance with the [Rule of Funny](https://tvtropes.org/pmwiki/pmwiki.php/Main/RuleOfFunny), if you state something with the intent of being paradoxical, such as saying "this statement is false", the lie detector will short circuit and fume with smoke, rendering it useless. It should be noted that this is not a great way to make friends.
4. It is not possible to use a lie detector on someone without them knowing, and using a lie detector on someone without their consent would be assault, even if you are a criminal. There is currently a case in the Supreme Court about whether you can even lie detect *terrorists*.
[Answer]
# How do the Amish avoid using electricity?
Schools use lie detectors. So do the police and employers. The obvious solution is to not use schools, police, or employers. Only work for each other, never report crimes to the police, and teach your kids at home.
The ability of an insular farming community to implement this method is obvious. But, believe it or not, this works in cities too. The above statement applies almost completely to various Orthodox Jewish communities that can be found in Brooklyn, and assorted other cities in the US. How do the Orthodox [avoid driving on the Sabbath](https://en.wikipedia.org/wiki/Driving_on_Shabbat)? They make sure they live within walking distance of the synagogue.
Furthermore, it is possible to [form your own community](https://en.wikipedia.org/wiki/Kiryas_Joel,_New_York), with your own community rules, if you want to have a functioning police force that does not use the lie-detector.
Finally, it is important to note that both the examples seen here are in-fact people that object to certain things on 'obscure religious grounds.'
[Answer]
Invent a medical condition and bribe a few doctors/professors.
The easiest way I can think of to avoid this is to provide a reasonable explanation to anyone who might use the lie detector why it can’t function on you. Then whenever anyone asks you to take a test you can roll out the testimonials of doctors and previous test results showing conclusively that you have ‘LieDetectorsDontWorkOnMe Syndrome’.
All it would take is a few talented liars/ properly medicated people that can ‘break’ the test (ie give spurious results on baseline questions) and a couple of papers submitted to appropriate journals/media outlets showing that a rare few people can’t be accurately judged by the lie detector. Let the story become increasingly well known. Bribe a doctor to give you a diagnosis (or forge some appropriate looking documents). Then, whenever anyone asks you to take a test, simply say there’s no point and show them your documentation. You might have a hard time if someone becomes suspicious of you, but that’s sort of the nature of this game.
[Answer]
I misunderstood the question being asked in my previous answer, so here is another try...
Lie Detectors should have trigger phrases which activate their detection functionality in the same way as "Alexa" and "Hey Google" work in modern voice controlled systems.
For a statement to be submitted for lie detection, it must be preceded by the phrase "I solemnly swear that...". The lie detector will then verify the validity of all statements by that speaker until a second trigger statement such as "End Lie Detection" is announced or until ten seconds of silence occurs.
Ownership of a lie detector which does not require such verbal control would be a felony.
In this way, an abstainer from this technology simply needs to refrain from pronouncing the triggering phrases.
[Answer]
What about people with mental problems?
You have poor long term memory.
Say you DID eat those cookies.
Yet next week your mom will ask if you ate those.
You honestly don't know, hence the lie detector won't blip due to no *intent*.
Now, say you consume pills that hinder your memory. Pills -> eat cookies -> "I don't remember touching the cookie jar."
[Answer]
You redefine your own definition of privacy. Using a lie detector on you is an attack on your privacy because the person could ask an inappropriate question and trick you into disclosing personal information.
It's very much comparable to smartphone use today. Everyone knows you have to register an account to be able to use the damn thing in the first place and **all** your information like games played, places visited and numbers called can be traced back to this account. And only very few people refuse to use a smartphone despite all of these potential breaches of privacy.
Since lie detectors are so widely spread and used in almost any situation, there have to be reported cases of abuse. Someone skillfully questioned a VIP and got answers that revealed much more than was nessecary to answer the question because the person wanted to avoid being caught at lying at all cost.
As long as using a detector on you against your will is considered assault, all you have to do is say:
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> I'm sorry but I'm not comfortable with being lie detected. Do you remember the VIP incident? It shouldn't be acceptable to ignore a person's privacy in such a degenerate way.
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[Answer]
What you need to do is create and teach yourself a personal language, one which sounds a lot like English but has a few significant differences. The word "Yes" is pronounced "No" and "No" is pronounced "Yes". "Didn't" is pronounced "Did" and so on.
When someone asks you a question in the presence of the lie detector, you must strive to be as truthful and complete in your answer as possible, but choose the language with which you speak your truth with consideration for your personal agenda. Also, no matter how many people happen to be in the room with you and the lie detector, always talk to yourself since you are completely fluent in both English and your personal language and know which is being used in any given sentence. In this way, you are still technically being truthful, with no intent to mislead the person you are talking to; so the lie detector should be happy with everything you say.
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[Question]
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**The scenario**
In the scenario that I'm imagining, a small group of people (ideally 100 or less) travel to a parallel universe and begin a new society. The new planet that they land on has one land mass surrounded by water, with sufficient freshwater resources and enough fertile land to build a prosperous agriculturally-based society. There are no existing cultures on this planet, and they have no further way to interact with any other societies. In other words, no one can immigrate to them, and they can't emigrate to other places.
**The question**
The population needs to reach the continent's capacity (we'll say that's about 5-10 million), then remain stable. What kind of laws or societal norms would have to be enforced to ensure this quick rise and then leveling out of the population? How would this affect their society? For example, is it plausible that a society could be so focused on increasing the population, then do a quick 180 turn and change their rules/norms/familial institutions to focus on population stability?
**Assumptions about the society**
My initial thought was that, once they reach their population capacity, the familial structures would put less focus on having children biologically, and more focus on contributing to a child's upbringing as a teacher, or by mentoring them, for example. I also imagined that the society wouldn't be heteronormative because having children isn't a priority, and that the people who do have kids wouldn't be encouraged to have more than one.
However, after doing some reading on here about other isolated/stable populations (such as here: [Maintaining a constant population in a country](https://worldbuilding.stackexchange.com/questions/100924/maintaining-a-constant-population-in-a-country)), I've learned that these assumptions might be wrong. For example, in order to continue replacing the population, if not everyone is having kids, you might need an average of 4 kids per woman who does choose to reproduce.
**More info about the world I'm trying to build**
To get to this world, the pioneers travel using magic that is nearly impossible to wield. So, they can't really use it to build their new society. Also, since they don't want their descendants to find a way back to the world they escaped from, they don't pass on the knowledge of the magic's existence.
The world that they come from has a medieval or renaissance level of technology.
The new world is 'egalitarian' in nature, or at least, its inhabitants buy into the illusion that it is. The society doesn't experience wars and has very little crime (that the general population knows about, anyway), but there is some corruption bubbling under the surface, that will come to fruition in the story's plot. In terms of how the world is set up, though, it needs to *appear* as though everything is peaceful and carefully planned.
[Answer]
**Growing your population is easy**
Humans (I'm assuming humans or folks behaviorally similar to humans) naturally enjoy doing this, and like any creature on any planet, they will expand to fill the limits of their resources. Give them food, water, a bit of privacy, and a tax benefit, and humans'll breed like rabbits (and frequently will even without all that stuff).
**It's those limitations that are needed for the second step**
Stabilizing a population is the trick. There's nothing inherently natural about stopping growth. Growth is what life does. In other words, you need something antiethical to life to get it to stop.
**Life-Giving Resource Limitation:** Run out of water or food and your population begins to starve.
**External Motivation:** China's one-child policy, war, disease, forced sterilization, eugenics, or any other external force can be applied to whittle-away at the population. Thanks to a comment from SRM: depending on tech level you can add animal predators to this list.
*What there isn't is a nice, polite, humane solution. Life wants to grow. Stopping it from growing is intrinsically mean-spirited, and it's no wonder that all the solutions for "stabilizing" a population are awful. Simply put, there is no way to naturally stop growth that doesn't result in pain.*
**Edit**
My thanks to a comment from AlexP, another solution that might be more humane (from a certain point of view) is *economics.* When combined with a lack of social welfare programs, a rising standard of living would have the consequence of reducing the number of children born to the poor and middle classes.
The solution is capricious (people like breeding and children sometimes become the inconvenient consequence of recreation), but over time a society would begin to perceive large families are burdensome. Add to it laws that make parents legally responsible for their children's activities and suddenly poor kids stealing food landing parents in jail will lead to fewer kids.
Keep in mind that we're looking for plausible and believable, not necessarily "this is the way it happens in real life." The lowering birth rate in 1st-world countries has a great many factors, not just one, and many of them required hundreds of years to become part of the social psyche.
[Answer]
This answers the "*grow its population*" portion of the question.
"*An isolated world*" is no different from an isolated village.
Your little society of "*100 or less*" will have to be *really* careful in who it brings along and who mates with whom so as not to suffer in-breeding depression.
<https://www.newscientist.com/article/dn1936-magic-number-for-space-pioneers-calculated/>
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> The “magic number” of people needed to create a viable population for multi-generational space travel has been calculated by researchers. It is **about the size of a small village – 160**. But with some social engineering **it might even be possible to halve this to 80.**
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<https://en.wikipedia.org/wiki/Inbreeding_depression>
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> Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. Population biological fitness refers to an organism's ability to survive and perpetuate its genetic material. Inbreeding depression is often the result of a population bottleneck. In general, the higher the genetic variation or gene pool within a breeding population, the less likely it is to suffer from inbreeding depression.
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Since this new world will be *relatively* hostile, bring more than 160 people. No children and relatively few old people. What old people you do bring will have to be more useful than young, healthy (and thus breedable) women.
[Answer]
WAR
they might start off as one group but over time - especially as they grow up to ten million in number and things like food and water get scarce... not so much. the excuses will be ideological, or racial, or any convenient us vs them - doesn't take much. I'd think that actual scarcity of resources wouldn't be the reason given, at least not universally. there are plenty of secondary issues that result in a much better emotional response from the people you are trying to get fired up.
So there you have it. periodic, brutal wars keep the population in check when it stresses the ecosystem of the island. The fun caveat is the same one that applies to our isolated island with 7.5 billion people on it. Which is more people than probably should be sustainable... except that we figured out how to make more food and distribute it more effectively, and get water where it needs to go, and found more and more effective forms of energy to assist in all of the above. So how many people is too many people is kind of a moving target.
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A few days ago, I saw this very nice reconstruction of a *Machairodus giganteus* by Peter Hutzler:
[](https://i.stack.imgur.com/z9L9d.jpg)
More recently, I've been thinking about it, and I'm wondering A) if it would evolve without getting in the way of hunting and B) if it would have a reason to evolve. Obviously, this isn't exactly a mind-bending evolutionary achievement, and could probably happen within a handful of million years.
Since he shows it as being tawny-coloured but without dappled markings, I'm assuming that this is a predator that hunts out on open plains. If so, wouldn't the black face make it easier for prey to spot it? Most modern felids are stealthy hunters (With lions being more like large canids or hyenas ecologically), but I'm not sure how it was for Machairodonts.
The second part of my question is; would it have a reason to evolve? Obviously, if it's a display feature, then it probably could (As long as it didn't hamper hunting ability, as said). But is there anything else it would be useful for? Could it perhaps even aid hunting somehow?
Note that I'm just asking about this evolving in a "big cat" in general, not necessarily a *Machairodus* or other Machairodontine.
In short; **would a black face and throat on a tawny body hamper a big cat's hunting ability prohibitively, and if not, would it have a reason to evolve?**
[Answer]
**Eye black cuts glare.**
[](https://i.stack.imgur.com/TffU1.jpg)
[source](http://katyelliot.com/eye-black-ideas/cool-eye-black-designs-for-softball-margusriga-baby-party-the-intended-ideas-11/)
<https://en.wikipedia.org/wiki/Eye_black>
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> Eye Black is a grease or strip applied under the eyes to reduce glare.
> It is often used by American football, baseball, and lacrosse players
> to mitigate the effects of bright sunlight or stadium floodlights.
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> It is a form of functional makeup.
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A diurnal visual hunter in a bright environment could benefit from eye black for the same reason athletes benefit.
You can see that in some other predators; depicted - ferret, peregrine falcon.
[](https://i.stack.imgur.com/DlVEg.jpg)
[Answer]
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> would a black face and throat on a tawny body hamper a big cat's hunting ability prohibitively
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No, definitely no. The main purpose of the coloring in predators is achieving mimetism, and this can be achieved either by looking like the background or by "breaking" the silouette of the subject against the background, making more difficult to spot it as a clear figure.
The black face seems to be falling in the second category.
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Well, obviously the later the prey spots the predator, the higher the chances of being captured. And usually predators do not survive just on good will, but on captured preys.
Note that what you have in the drawing is not too different from the appearance of a hyena.
[](https://i.stack.imgur.com/4ZqVj.jpg)
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[Question]
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I'm creating various artificial [Time Bubbles](https://worldbuilding.stackexchange.com/questions/57925/stopping-time-by-speeding-it-up-inside-a-bubble) in my universe where time flows faster or slower inside a specified area, typically depicted as a semi-transparent bubble. Before developing any more stories with this feature I need to figure out any hypothetical size constraints.
The bubbles I am after typically do not cause any catastrophic local damage when activated or later deactivated. A little local damage is acceptable. Extinction level events or even city killers are not. Currently, I have only created "small" Time Bubbles on planets, and haven't yet created anything larger than a small hamlet or out in space.
Aside from the varying amounts of energy I assume, I will require (derived from my Unobtainium using applied Phlebotinum), **are there any *theorized* size constraints to having different sized Time Bubbles?** If I need to handwave something, I need to have some idea of what it is, right?
I was curious if, at larger/smaller scales, the square-cube law and other parameters would cause the bubble to break down and collapse, OR cause too much catastrophic damage to the surrounding environments. I don't want to accidentally create a black-hole or blast any of my cities with Gamma-rays or accidentally nuke them into smithereens.
Disclaimer: I know that Time Bubbles are hypothetical and that the *real* answer is "we don't/can't know". I'm looking for answers derived from current theories, both science and science fiction. As I'm not looking for answers in *how* to create a Time Bubble, I do not see any magic being involved. If there are no current theories about size restrictions, aside from the previously mentioned energy requirements, great! Please do let me know.
[Answer]
If anything, larger bubbles may cause *less* problems, because your temporal gradient can be less steep (much like how you would be torn apart by tidal forces near the event horizon of a small blackhole, but can pass through the event horizon of a supermassive blackhole quite intact.)
Besides the time gradient, the major concern I think would be the redshift/blueshift of light that is crossing the bubble. In particular, light traveling from the "fast" side into the "slow" side will see a blueshift equal to the relative speeds; if the differential is great, visible spectrum light can be bumped up to dangerous levels (x and gamma rays.) This could result in burns, radiation poisoning, increased rates of cancer, etc, for those in the vicinity. While size of the bubble doesn't qualitatively impact this effect, a larger bubble will be a larger source of damaging radiation.
[Answer]
It would depend greatly on whatever is generating said Time Bubble.
Say we had a machine which had to contain the time bubble inside of its operating radius. Wires running between the pylons containing/generating the bubble would cause synchronization issues, because timing data is still restricted by the speed of light (and sending your timing data *through* the bubble you're creating can only result in hardware-debugging-related headaches and causality issues). If the pylons are standalone, they would all need their own energy source now, and have to coordinate via other speed-of-light-constrained methods, like satellite uplinks. And in both cases, the pylons would be targets for abuse, whether by the enemy or by bored teenagers. And, of course, these pylons can only operate at either certain key points along the bubble (say every 10 or 36 degrees), or at certain distances from each other (say between 150 to 300 feet), lest the bubble become unstable and collapse.
On the other hand, if the time bubble is generated from the inside, with the pylons pushing the bubble outward with them at the center, then this supposes that these pylons have an operating radius. That radius could be increased with more power, but there would be a exponential drop off [similar to how light and sound drop off in intensity](https://www.reddit.com/r/askscience/comments/1lnepc/why_does_sound_volume_decrease_with_distance_does/). There's a point when that extra foot of bubble radius isn't worth the power it needs. So then you set up a second pylon with its own radius. This then introduces problems with overlap (where two pylons are affecting the same area, causing the time differentials they're producing to add together and get 4x speed when you only wanted 2x speed) and underlap (where you could well get gaps in the time bubble because the pylons aren't close enough, meaning that bit of street corner is moving at 1.5x or 1x speed instead of the desired 2x). This, adding to Gene's answer about temporal gradients, may cause issues with people's health. "Oh my, Timmy and Jenny were so looking forward to getting married, but now Timmy had to check himself into an old-folks home before Jenny could finish High School, all because Timmy's bed happened to be in a temporal pocket caused by 4 overlapping time bubble pylons...."
Basically what it boils down to is this: you must construct additional pylons.
[Answer]
The first implication that comes to my mind is that objects and light that goes into a time bubble will pop out the other side very quickly because they traversed the inside of the bubble quickly. This could allow FTL movement.
Make a time bubble 20 meters wide and with time accelerated 2x. Throw a baseball at the time bubble going 10 m/s. Ordinarily the baseball would take two seconds to traverse the space occupied by the time bubble. But looking from the outside, we see the baseball exit the time bubble only one second after it went in.
So if you've got a time bubble with a 100000x time acelleration, then an object that travels through the bubble will seem to appear on the far side at the same moment it entered the near side.
Imagine you walk into a room with a time bubble between you and a lamp. It's a smallish time bubble so it doesn't obscure the whole lamp from you. When you flick the light-switch on the wall, the photons that travel through the time bubble on their way to you will *arrive sooner than the other photons*, which is pretty remarkable if you're a physicist.
So if you make a huge time bubble, then it can be used to transfer things, light and information from one side to the other at what appears from the outside to be faster than the speed of light.
[Answer]
>
> Where time flows faster or slower inside a specified area, typically depicted as a semi-transparent bubble
>
>
>
You have a problem there: conservation of energy.
Say that you have a 2X accelerated bubble with a bulb inside pumping out 100 W of infrared radiation with a wavelength of 700 nanometers. 100 W means it gives off 100 J of energy per second *local time frame*.
When that energy reaches the skin of the bubble, it moves twice as fast, which means you have exactly twice as many waves in the same space; so the bulb, seen from *outside* the bubble, is emitting 200 W of ultraviolet energy.
A flashbulb in a 20X bubble would hit anything outside with the force of a hard gamma battle laser. This is a plot point in one of Niven's *The Long ARM of Gil Hamilton* stories.
For the same reason (time differential), heat exchange might be difficult or even impossible (I'd have to think about that), or it might be a problem - either the inside of a time bubble becomes stifling hot, or it grow wondrous cold because heat flows outside twice as fast.
It would stand to reason that a time bubble requires, to be created (or kept existing), at least as much extra energy as it gives out. So, the larger the bubble and the more energetic its contents, the more energy it requires and/or the less it can last. When the "extra juice" is exhausted the time differential drops back to normal.
On the other hand, this would mean that a slower-than-normal bubble would *supply* energy. When enough energy (light, heat, etc.) is sunk in the bubble, the bubble collapses - this would allow harvesting low-density energy (e.g. heat) to a point where the laws of thermodynamics themselves are apparently challenged; that's why I suspect that heat transfer is going to be difficult. Preventing it from happening looks like it would be Nature's easiest and sneakiest way of keeping things balanced.
] |
[Question]
[
I have made this planet for my creatures and it is constantly dark, night or day.
No it's not a rogue planet, it's dark because of the 1,000 feet tall autotrophs that suck up all the sunlight and let little pass through (think nighttime with a half full moon).
There are also hot vents sticking up out of the ground and giving off a lot of heat which is absorbed by the bottom autotrophs (I won't go into the specific but heat makes the food for them) and the average temperature is 98 degrees Fahrenheit.
And this is a problem because of this: my creatures have superb vision, since they can see from microwaves to UV radiation on the electromagnetic radiation spectrum.
So my question is: what reasons justify a creature having such good vision on such a dark planet?
[Answer]
You're asking for a justification for why heightened vision would evolve on a dark world. The answer is, "for the same reasons it would evolve on a brighter world..."
Survival Advantages!
* Creatures which can see in an environment's available light can hunt better that those which can't.
* Creatures which can see in an environment's available light can avoid becoming prey better than those which can't.
* Creatures which can see in an environment's available light can avoid fatal accidents better than those which can't.
* Creatures which can see in an environment's available light can find mates better than those which can't.
* Creatures which can see in an environment's available light can keep track of and protect their offspring better than those which can't.
Despite the relative darkness, some branch of your planet's evolutionary tree would eventually try out various eye sizes, shapes and locations; and those lucky species which received the most functional eyes for their current environment would have a spectacular advantage over those species which didn't.
Just like it happened here on our bright blue world.
[Answer]
Darkness is a concept which has to be applied to specific range of wavelengths.
Your planet is dark, yes, but dark only in a limited spectrum. Let's say it is dark if you look at it in (human) visible light. For the rest, your autotrophs are pretty much transparent, and they let all the rest of radiation pass through their bodies.
[Answer]
**Some things make their own light.**
[](https://i.stack.imgur.com/hqOPQ.jpg)
<https://www.pinterest.com/pin/218002438183780158/>
A world analogous to yours is the deep sea. It is dark but things see very well. They see because animals can make their own lights. Just as a quiet world let animals communicate with sound, in a dark world, bioluminescence lets animals communicate - finding each other, finding prey, repelling predators and so on.
Your dark world would be full of glowing creatures.
] |
[Question]
[
I've been working on a project and I'm trying to make it as scientifically plausible as I can get it to be. Since space is large, and it's physically impossible in this universe to reach the speed of light, people aboard spaceships would likely die before they get to the destination, or at least age.
I've been wondering if there's a plausible and safe (or mostly safe) way of preserving people as they travel through space. It doesn't necessarily have to be being preserved in liquid nitrogen or something along those lines, just anything that could theoretically work.
[Answer]
Cryogenics, when you get right down to it, is an attempt to slow [Entropy](https://en.wikipedia.org/wiki/Entropy), or the normal and constant use of energy in our bodies, which ultimately causes it to degrade. Extreme cold is useful for that because cold is essentially the absence of energy. Zero degrees Kelvin (-273 Degrees Celsius) is described as 'absolute zero' because at that point, there is a total absence of energy, and therefore nothing can ever get colder than that. (Deep space is around 3 degrees Kelvin)
The problem with cryogenics for complex organisms is that most molecular materials, as they cool, form solids and actually shrink in size. Water, on the other hand, *expands* as it gets colder. Water at 4 degrees C is actually denser than ice.
This is why ice cubes float in your glass of water (or Scotch, etc.).
For the purposes of cryogenics, given that complex life forms are 70% water, this effect can essentially tear cells apart.
There are some notable exceptions in nature. The [Tardigrade](https://en.wikipedia.org/wiki/Tardigrade), or Water Bear, is a small, multicelluar organism that can replace its water content with a form of sugar molecule to survive freezing temperatures and reanimate. There are even a small number of turtles, snakes and [Frogs](https://en.wikipedia.org/wiki/Spring_peeper) that can survive naturally freezing temperatures for extended periods through some natural form of cryogenic suspension. From this alone, we know that it's *possible*, but we have a long way to go before we can say that this is even a viable technology for space flight.
That said, humans (after a fashion) are already being cryogenically suspended and reanimated as a part of common medical practice. In-Vitro Fertilisation (IVF) treatments and other forms of artificial insemination rely in some cases on either frozen eggs (ova), sperm, or even [Embryos](https://en.wikipedia.org/wiki/Cryopreservation#Embryos) that are stored in cryogenics, 'thawed' and placed back in a viable host. So, it's even possible with some human tissues as a part of existing medical practice.
The real issue is that the protective chemicals that allow certain cells to survive the freezing process are at present quite toxic as well. This means that large, thicker tissue samples, like hearts, livers, complete human beings, etc. still don't have viable recovery methods after freezing, and in some cases *during* freezing. Also, we've never asked a Tardigrade or a Spring Peeper if how much they remember after their freezing, and whether or not they're really still 'themselves'. The suspension and reanimation of a complex human mind with its suite of memories and 'soft', programmable set of practices (cerebral cortex) has never been tested completely and even if we can solve the biological problems, we really don't know what it would do to a complex mind just yet.
So; as I see it, in the not too distant future, there are really two possibilities that could make cryogenics plausible;
1) Development of some cryoprotectant chemicals that are NOT toxic to human life (and by that I mean both biological and neurological)
2) Development of a different *kind* of entropy suspension method that somehow locks out energetic interaction with the universe without reducing localised energy levels (ie; making it cold).
Of these 2, I think (1) is the most plausible, but what that chemical might be I don't know. I guess if I did, I'd be making a fortune right now, but I digress.
The answer to your question is NOT the design of a new freezing model; we have that pretty much perfected. It's the design of a new chemical or water molecule control process that would allow for ice not to expand without the treatment that allows this to happen being toxic. From a world building perspective, the place I'd start would be the tardigrade and the relevant species of frogs, snakes, turtles etc. that can survive freezing and see if there's something plausible in their natural design that can be applied to a near future state to humans.
[Answer]
**Cryogenic Revival Also Means Immortal lifespans**
Realistically the tech to revive a person who has been cryogenically stored is pretty much identical to the tech required to make somebody live forever since we are talking about complete cellular regeneration. If one can feasibly freeze humans and revive them again (presumably through some crazy hypothetical tier sci-fi nano tech) you could just make your colonists functionally immortal. Think less freezer-ship and more "Methuselah" ship. If your colonists can live for as long as they have access to the regeneration tech required to revive human pop-sickles they don't need to be frozen. You also wont need as many colonists since "immortal" means they could potentially have thousands of children over a very very long time span. Plus, your population will never need to outpace a death rate since you only have to replace the odd loss to accidents that render a body totally unrecoverable. which by the way, would be VERY rare since the same tech that could regenerate a frozen body at the cellular level could just as easily be used to regenerate a body from any other kind of accident short of complete obliteration or simply being unable to find and recover the body.
With a potentially infinite lifespan the colony ship can take as long as it likes to coast from star system to star system carefully building colony after colony and monitoring and assisting each one to full maturity. From the perspective of an immortal a few hundred years to the next star is not really very long. Additionally if you have that tech level you don't even need earth like planets to settle. Literally any metal and mineral rich planetoid or sizable asteroid you came across could be converted into a self sustaining self repairing artificial station Like pic related:
[](https://i.stack.imgur.com/ED9yL.jpg)
When you are immortal it really doesn't matter how long its gonna take, and again, the same tech to revive cryogenically frozen people is the same it would take to sustain immortality.
[Answer]
The FDA has approved a simplified form of suspended animations for medical procedures and emergency transport. It is based on the techniquevshown in these clips. Warning: may disturb some people.
<https://m.youtube.com/watch?t=87s&v=f3-C-OMsVjg>
<https://m.youtube.com/watch?t=9s&v=-tCa4XLg__w>
This technique works for 2 hours, though the FDA think it can be extended to 4. But it's a start. The obvious first step is to switch to glycol, rather than water, as you can reduce temperatures further without cell damage.
The second step would be to extract the gut microbiome (which will try to eat you alive) and the other biomes you have. Bag them up and store those separately.
As long as the cells have some water replaced, the freeze expansion won't damage them.
Note: Some statements have not been tested in medical trials and may deviate from absolute physical accuracy.
Nonetheless, this is the approach I'd envisage.
[Answer]
I'd like to add some advice of my own...
First :
>
> "given that complex life forms are 70% water, this effect can
> essentially tear cells apart." Which is why food is flash frozen, so
> that the crystals are tiny and don't rupture the cell membranes as
> much when thawed. – RonJohn Mar 8 '18 at 0:39
>
>
>
The faster the freezing, the better the conservation. Maybe Pluto or even Triton are the best places to do the job.
So superlow temperature flash freezing is the solution for the first step : freezing
Though the real challenge lay in the defrosting part of the process.
Maybe you can figure a multi-sources/low energy/fast acting microwave re-heater...
Micro waves are particularily efficient on water molecules.
It aims at putting water back into the liquid state within milliseconds.
The faster the defrosting, the better the chances to find somebody's mind back altogether.
Well, probably
Sumary : One was turned into very low temperature ice thaks to a direct, short and terribly efficient exposition to Pluto's atmosphere. The 'body' was stored for decades. And now someone wants to meet the person : hyperspeed defrost using microwaves (and maybe some submillimeter and IR as well).
Then some sleep and hypothermia treatment.
Totally worth it (?)
] |
[Question]
[
Let's say an isolated colony is established in an ideal environment with the goal of growing the inhabited human population as quickly as possible. Health care is provided for them by managers, or those that own the colony, and is roughly up to twenty-first century standards with improvement on gene technology. Those in the colony are not allowed to develop technology beyond that used in the nineteenth century to quell any possibility of a successful uprise against their managers, but they are given the means to be self-sufficient. They can grow their own food, they are allowed to be educated enough to read and have a trade, and have laws enforced by their managers to kepp them 'in line'.
How long would it take for one hundred couples in the colony (one hundred men, one hundred women) - all of good genes, with no genetic diseases - to make one million descendants? That is, if Generation A had two hundred people in it and started having children at the age of sixteen (and were allowed to have as many children as possible), and every generation started having children at the same age (and are also allowed to have as many children as possible), how many generations would it take for a generation to be made up of one million individuals?
It is illegal to have sex outside of marriage, and marriages are preapproved by managers to ensure there are no genetic issues - rather, only couples with low chances producing sickly children are allowed to marry and reproduce with each other. Assuming they keep genetics records of every individual, and then get samples from all of their children to have their genetics as well so they have on record who the parents are, I assume inbreeding would still be an issue at some point. How long would it be before inbreeding became a problem? Could they hit the one million mark before that?
[Answer]
Assuming 21st century health care so that women can survive birth *and* their children survive to adulthood *and* there's a social system to support the children, then look at modern countries, you could reasonably foresee a Total Fertility Rate of 6 or more (on average a woman gives birth to 6 children during her reproductive period). Combine that with an Infant Mortality Rate equal to the best around now, which is less than 1%.
Assume no dicking around with sex selection, so you get the rough 50/50 split in births you'd expect, with equal expectations of growing up. Assume you have only 3 generations alive at any one time. Each generation, we'll take of 1% or so of newborns to represent infant mortality. Each generation represents all the children born to women of the generation before.
So, Generation 0 has 50 men and 50 women, total population 100. Generation 1 has 149 men, 149 women (average 6 children from each Gen 0 couple, with a 1% or less infant mortality rate), total population 398 (Gen 0 + Gen 1).
Generation 2 has 443 men and 443 women, total population 1,284 (Gen 0 + 1 + 2).
Generation 3 has 1,316 men, 1,316 women, total population 3,816 (Gen 1 + 2 + 3).
Generation 4 has 3,909 men, 3,909 women, total population 11,236 (Gen 2 + 3 + 4).
And so on: here's the summary of total population:
* Gen 0: 100
* Gen 1: 398
* Gen 2: 1,284
* Gen 3: 3,816
* Gen 4: 11,236
* Gen 5: 33,172
* Gen 6: 98,320
* Gen 7: 291,908
* Gen 8: 867,064
* Gen 9: 2,575,480
So by the 9th generation born on the planet, the 10th generation overall, you've blown by the 1 million mark.
Now, for time. Assume women on average have their first child at age 20, their last at age 32 (giving two years per child). That gives an average generation length of 26 years, so you're looking at somewhere from 234 to 260 years after colonization to hit the million mark.
[Answer]
# The Math
Assuming biologically humans can have one baby a year safely from 16 to 40, and that your 100 couples start at 16 years old on day 1 with 100% success rate... with no multiple births and perfect gender parity.... then my math (which is dubious) says about 115 years.
There are SO many factors though... assuming every woman is fertile for that whole period, healthy enough to bear children for 24 years... which is... ludicrous in real life, but theorhetically possible...
Honestly the men are bordering on irrelevant in this equation. Worse... detrimental... if you replaced 70 of your men with more women, you could get there sooner.
# The Logistics
Ok I reread the original question to clarify something about HOUSING... where are all these rapidly spawned folks going to live. I realized these are real world colonists that are said to be self sufficient hunter-gatherers.
My calculation (and everyone elses so far) assumes these are people in a vacuum with their needs being met, etc. Requiring them to farm and ranch to sustain themselves, and their vast families, build homes and communities. Govern. etc...
The children and men can only do so much. I think it is unlikely in this scenario that humans can breed at this rate successfully. This would DRASTICALLY diminish the birth rate.
[Answer]
# As Fast as Possible?
A human female will be able to give birth to a single child every 9 months. Across 450 months (37.5 years) you would expect to have roughly 5156 children (3% twin rate, 0.12% triplet plus rate). This puts each mother giving birth to approximately 50 children each, and if they start at 16 years old then 37.5 years conveniently puts the girls at the average age for menopause.
Therefore you produce the following data...
* Generation 1 (of 200) produces 5156 children.
* Generation 2 (of 5156) produces 132,922 children.
* Generation 3 (of 132,922) produces 3,426,721 children.
The fullness Generation 3’s offspring would arrive in just under 112.5 years from the start. All of generation 1 would have passed away at this point, and most of generation 2 would have died as well. Thus, if 100 couples had as many children as possible and their descendants did the same, you would arrive at a population of at least 3,559,643 after 112.5 years. Generation 3 would need to have approximately 30% less children to arrive at a relatively stable population of 1,000,000.
Because of that Generation 3, instead of having the 50 children average of the previous generations, would have 15 children each. 15 children each as fast as possible would take 11.25 years. They would then need to be put on birth control and generation 4, 5, 6, etc would all have two children each and then be put on birth control. **If each couple of Generation 3 has 15 children each as fast as possible then the population of roughly 1,000,000 would be achieved in 86.25 years from the starting point.**
*(Sidenote - The youngest of generation 3 would require an additional 16 years to reach "breeding age", but 1,000,000 would likely be hit before that point.)*
[Answer]
I tried to put some calculation in a spreadsheet:
[](https://i.stack.imgur.com/jFr2F.png)
And with values:
[](https://i.stack.imgur.com/XR0ca.png)
So the million is reached between generation 7 and 8. Which is 7.5 \* 16 = **120 years**
But you could use a more "realistic" scenario, like not all the women have children, some children die before reaching reproduction age, some grandparents die early, and "only" 4 children by woman:
[](https://i.stack.imgur.com/ByPvg.png)
Then you'll get 1 million between gen 10 and 11: 10.5\*20 (reasonable reprod age) = **210 years**
[Answer]
My best, very rough guess: **about 40 years** for a low estimate, a few extra decades for something more realistic
According to [this Biology StackExchange](https://biology.stackexchange.com/questions/5524/how-many-people-are-required-to-maintain-genetic-diversity) question, as few as 25 couples can avoid inbreeding if the pairings are strictly monitored, so inbreeding shouldn't be much of a problem for your 100-couple colony, especially since they seem to start out healthy. However, this is still a pretty small gene pool, so any genetic problems that do develop while on the planet could easily affect a large part of the population.
As for the time to reach a population of 1 million from 200, here's a rough estimate:
Assuming they can [get busy](https://www.youtube.com/watch?v=ypyiAT1RelU) from the start and there are no problems or twins/triplets/etc., 100 women will produce 100 babies every 9 months; 1,000,000/100 = 10,000 9-month iterations, so that means 90,000 months or 7,500 years is the upper bound to reach 1 million people from only those first 100 couples.
However, as you said at the age of 16 the descendants of the original couples can start [aiding the colony](https://www.youtube.com/watch?v=v4_M5PcJQmU). Assuming 50-50 boy/girl ration, after 16 years and about 21 kids per original colonist, the next generation, consisting of 50 women, can [start bringing bundles of joy](https://www.youtube.com/watch?v=QU-Q08b8Zos) into the colony. Using the same math above, 150 women can reach 1,000,000 in 5000 years. 9 months later there would be 200 women who could 1,000,000 in 3750 years, then 250 women do it in 3000 years, ever decreasing in smaller increments.
There is probably an equation to plot the above and get a more accurate, however since I don't remember much of my college calculus classes. From some trial-and-error diminishing returns really seem to kick in around 75 years(10,000 women), so **my best guess to reach 1,000,000 people is around 20-50 years, if they're doing nothing but making sweet, sweet love. The upper bound is probably a better guess**, since birth complications, recovery time, time taking care of the children, women passing child-bearing age, etc. will all contribute to the growth time.
[Answer]
Let's start with the math: consider that couples settle at 20 years and have 10 children between their 20 and 30's. So you roughly multiply by 5 your breeding population every 25 years. If you start with 200, you reach the 625000 after 5 generation (125y) and more than 3 million after 6 generations (150y). With optimization, you can do it within one century.
However, you need diversity to avoid genetic issues. 200 people are unlikely to avoid them without medical aid and/or genetic engineering. The concept of *Minimum viable population* applies here...
(update)
Here is a simulation showing only the breeding population (age 20 to 40).The initial glitch at year 21 is because at year 20, the first children breed and their parents are still breeding too. Year 21 is when the 100 children born 20 years before breed alone, quickly followed by all this generation. Year 41 you see the same phenomena. Year **115** is when you reach the million.
* If you use a 16y-42y breeding age, you reach the million at **year 95**.
* If instead of years, you breed non-stop (I doubt this is biologically sustainable), then years become 9-months periods, breeding start at 12 (yiks!), and you reach the million breeding population in quick **72 years**
* If you the take into account the non-breeding population, you reach the million total population in **59 years**. This is the mathematical absolute without hacks (like breeding only girls for the first generation, as they are on the critical path, not like males).
Here is a view of the population (logarithmic scale):
[](https://i.stack.imgur.com/EzulR.png)
[Answer]
I did the spreadsheet method. Assumptions are based on the number 16 for symmetry and biological plausibility.
1. Reproductive age starts at 16 and ends at 48.
2. Nonreproductive age is 49 thru 80.
3. Population will include children <16, reproductive age 16 thru 48, elders 49 thru 80
4. A woman will have 16 children over her 32 reproductive years.
5. Each year 0.5 of the reproductive age population produces 0.5 children.
6. For each the row 16 prior (-the row 17 prior) moves into the reproductive column and is subtracted from child column. The same for elders and for deaths.
Note these are not hard numbers; people do not necessarily all drop dead at 80. They can be considered the peaks of a bell curve normal distribution.
[](https://i.stack.imgur.com/WLvaL.jpg)
Using these numbers I find the population cracks 1,000,000 between year 116 and 117.
A real world comparison shows this to be pretty fast.
<http://family.jrank.org/pages/837/Hutterite-Families-Fertility.html>
>
> In 1954, Joseph W. Eaton and Albert J. Meyer published their landmark
> study on Hutterite fertility. They documented that from 1880 to 1950,
> the Hutterites grew from 443 to 8,542 persons. This represents an
> annual increase of 4.12 percent, which appears to be the world's
> fastest natural growth rate. Documenting an average family size of
> slightly over ten children, Eaton and Meyer established the Hutterites
> as the demographic standard and estimated that maximum fertility for
> humans is twelve to fourteen children.
>
>
>
That said the Hutterites did not have the benefit of modern medicine and probably suffered higher child and mother mortality than your moderns would.
---
In case anyone is interested, this rate of reproduction cracks 1 billion at 230 years and 1 trillion at year 337. Hopefully they find some way to power things down.
] |
[Question]
[
## **BACKGROUND**
*In the antiquity of my world, a college of [pyromancers](https://worldbuilding.stackexchange.com/questions/101376/how-should-i-calibrate-and-estimate-pyrokinesis) attempted to create stronger magnifying lenses so that they could apply their ability to control heat to ever more finely detailed metallurgical work. Along the way, one of them invented a microscope, and observed cells and microorganisms for the first time in history.*
---
It's been established on this site before that all you need to [invent a microscope](https://worldbuilding.stackexchange.com/questions/12116/when-could-a-microscope-first-be-made) is a profound technical insight and access to blown glass. The method is as follows.
>
> *By placing the middle of a small rod of soda lime glass in a hot flame, van Leeuwenhoek could pull the hot section apart like taffy to create two long whiskers of glass. By then reinserting the end of one whisker into the flame, he could create a very small, high-quality glass sphere. These glass spheres then became the lenses of his microscopes, with the smallest spheres providing the highest magnifications.*
>
>
> **- history-of-the-microscope.org**
>
>
>
Historians of science believe that, using this method, van Leeuwenhoek created lenses that could magnify up to [500 times.](https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek#Techniques_and_discoveries) Unfortunately, he guarded the secret jealously, and it did not survive him.
## THE QUESTION
**With a van Leeuwenhoek microscope as a starting point, and assuming they were culturally invested in the outcome, how powerful a microscope could my pyromancers develop by the end of their approx equivalent of the middle ages? That means they get a range of 500-1000 years, depending on how my timeline eventually adds up.**
## NOTES
I don't know much about the physical principles at work behind microscopy, but I've read that [smaller glass beads](https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek#Microscopic_study) will produce increasingly greater magnification. If that's the case, it may be relevant that my pyromancers are able to generate steady heat (and enough of it to melt glass) within an area as small as they can clearly see -- and that works with the aid of a lens as well.
So, barring an unforeseen problem with method or materials, they may actually be able to create glass bead lenses as small as they're physically able to mount in a microscope, and experiment from there.
---
*As a final aside, this question may actually end up being surprisingly important to the history of science in my world, especially as relates germ theory and materials science, so please indicate if there are any areas of uncertainty in your answer. Thanks.*
[Answer]
Van Leeuwenhoek did achieve better results than his contemporaries, but his methods were actually *worse*. They completely relied on those spheres, as well as on his very good eyesight.
Your pyromancers would probably be better served in furthering the *composite* microscope, whose initial manufacturing limitations Van Leeuwenhoek tried (successfully) to overcome with small round lenses.
I imagine that pyromancers would have much greater control on glass compositions and temperatures than those first lens-makers; as a result, they would quite soon develop achromatic and apochromat lenses, and from there they would proceed to telescopes and microscopes.
In particular, they would start by noticing the magnifying properties of rudimental lenses. From there, they'd start creating different types of lens, and very soon they'd come up with the notion of compounding two lenses - and would discover it doesn't work due to aberration. They'd soon discover also that aberration varies depending on the lens, and would naturally follow up by trying to develop an aberration-free lens.
Pyromancy would be of invaluable help in *experimenting*, but we're talking physical limits here, and the efforts would come to naught. On Earth it took some 120 years to observe that there were *two* kinds of aberration and that they were in some ways *opposite*; assuming pyromancers aren't any dumber, at that point it would come natural to them to do as Earth opticians did, and use two aberrating lenses to compensate each other.
Depending on how fine a control a pyromancer can exert on doped glass, they might be even be able to manufacture multilayer diffuse lenses, or not. The magnification range they could achieve goes from 800X (Earth 1850's) to 1600X (Earth 2000's with pyromancy).
One crucial technological achievement they would need and that pyromancy does not guarantee is construction of reliable focusing gears.
[Answer]
# 1500x, using compound microscopes
According to the [this website](http://www.history-of-the-microscope.org/anton-van-leeuwenhoek-microscope-history.php) (and I make no promises of the verity of the information found there), van Leeuwenhoek did not make compound microscopes. This was due to the limitations of machine tools at the time; high quality machine parts like screws were not common until the 1700s. Probably, he could not get a hold of really well made screws, and thus couldn't assemble a high quality compound microscope. In any case, compound microscopes had already been invented [in the 1590s](http://www.history-of-the-microscope.org/hans-and-zacharias-jansen-microscope-history.php), though competitor's compound microscopes with 90x magnification could not compete with van Leeuwenhoek's superior lenses.
With reference [here](http://microscopy.berkeley.edu/courses/TLM/cmpd/cmpd.html), van Leeuwenhoek's highest magnification lenses could do 275x magnification. Since the magnification power is [multiplicative](http://www.microscopemaster.com/compound-light-microscope.html), a 275x eyepeice with a 275x focal lens would theoretically result in a 75625x magnifcation. Ultimately, that is too much. The resolution of any optical system is limited by the wavelength of light to about 1500x as detailed in this [Physics.SE](https://physics.stackexchange.com/questions/38146/optical-microscope-magnification-limits) question.
So whether you improve the manufacturing of the lenses themselves, or improve the manufacturing of the machine parts in a compound microscope, van Leeuwenhoek's lenses are pretty close the maximum possible manufacturing, and there will be a hard limit due to physics at 1500x.
Of course, there is also a hard physics limit on pyromancy, so you can do whatever you like.
] |
[Question]
[
I'm hoping to develop a hybrid genre setting for a game, a 'post-singularity' situation developed from a traditional fantasy/magipunk world - though the allegory doesn't fully encompass what I want, think "eclipse phase or John C. Wrights 'golden age' via eberron".
The key themes I'm hoping to explore are the usual ones of identity in a world where it can be as arbitrary and artificial as one wants, based around the standard tropes of:
1. Identity or mind is no longer bound to body; minds can be shifted between receptive vessels as needed
2. Identity is no longer unique and inviolate; minds can be recorded, copied, forked, altered, merged, or even built from ground principles (at various levels of sentience) a'la an A.I.
However I want to explore these tropes as an outgrowth of a magical understanding rather than a scientific one.
Fantasy ~tends~ to run towards a dualism vein, where identity is separate from the physical form anyway - body/soul format. Its pretty easy to extend that to meet trope 1, decouple the soul and implement a ghost/possession system (c.f. the d&d ghostwalk setting).
Trope 2 is a lot harder to meet from that starting point; souls are usually considered pretty inviolate (barring themes like contamination or corruption), and very unique (I can't think of any stories with soul-copying that results in a full-fledged duplication; plenty of soulless abominations, but no total clones).
The good news of course is that I'm not locked to a generic dualism in my culture, so what are my alternatives?
Sci-fi post-singularities (at least the ones I'm familiar with) stem from a hard [materialist theory of mind](https://en.wikipedia.org/wiki/Materialism) view; ultimately all ones thoughts and personality etc are emergent from a physical phenomenon - duplicate the phenomenon, duplicate the individual.
Compounding this is that the knowledge to build an actual model of *how* we'd go about this stems from advanced physiology, biology, and physics.
Unfortunately, I'm constrained by my own culture, where widespread acceptance of a materialistic view is relatively recent (and may or may not be dominant even now depending on the beliefs of your local culture, though it does seem to be growing(?)), and access to the scientific models is very recent indeed.
Obviously some of this can (and will) ultimately be handwaved - ultimately a wizard will do it, and magic will stand in for sufficiently advanced science - but I'd still like an idea of how to get 'here' from a more traditional pseudo-medieval (or pseudo-renaissance) fantasy mindset...
**Thus my question, as above: what cultural beliefs could my basic fantasy settings have held originally, to encourage them to have a sufficiently materialistic theory of mind in the past, to have developed such a post-identity society now?**
As a further, leading thought (though I'm totally open to, and very keen to hear, answers that reach a conclusion from a different starting point), I suspect that I need an original belief in some alternative to a 'soul' that lends itself more towards materialist metaphors.
**edit:** Though it will push this even further towards an open question that (I presume) this community doesn't like, I'm early enough in my designs that I'm not wedded to anything settingwise, and happy to look at frame-challenging answers that allow me to achieve the effects above.
I don't mind if the solution **is** a sci fi recording of electrical impulses and a justification of how a fantasy society realised that, or whether the solution is soul copying and a viewpoint that makes that relatable and not totally alien to a reader/player.
[Answer]
Your society's cultural heritage is that of **[Animism](https://en.wikipedia.org/wiki/Animism)**.
>
> Animism encompasses the beliefs that all material phenomena have
> agency, that there exists no hard and fast distinction between the
> spiritual and physical (or material) world and that soul or spirit or
> sentience exists not only in humans, but also in other animals,
> plants, rocks, geographic features such as mountains or rivers or
> other entities of the natural environment, including thunder, wind and
> shadows. Animism thus rejects Cartesian dualism.
>
>
>
Dualism is what you do not want: that the spirit has an existence separate from the body. Animism is an older world view than the dualism found in current world major religions (Abrahamic, Hindu, Buddhist). The idea that the spirit is a manifestation of the thing itself will work perfectly as the cultural background for the materialists you want your society to be now.
Animism might still be lurking in the background...
[Answer]
A creation myth that allows for mutable 'souls' or identities would seem to be the shortest route to take. Rather than an appeal to an underlying and divinely perfect Platonic/True identity, one that emphasizes how an identity ungoes changes in its lifetime, or is composed of *degrees* of various traits, may be the trick.
For inspiration: In contrast to Abrahamic and other creation myths in which Man's identity is perfect or corrupted by the physical world, the Zuni people of the American southwest believe that [the first humans were horribly ill-suited to the world and had to be changed](https://en.wikipedia.org/wiki/Zuni_mythology):
>
> [H]ere they could see themselves for the first time because the sky glowed from a dawn-like red light. They saw they were each covered with filth and a green slime. Their hands and feet were webbed and they had horns and tails, but no mouths or anuses. [...]
>
>
> [...] So when they were asleep, the bow priests sharpened a knife with a red whetstone and cut mouths in the people's faces. The next morning they were able to eat, but by evening they were uncomfortable because they could not defecate. That night when they were asleep the bow priests sharpened their knife on a soot whetstone and cut them all anuses. The next day the people felt better and tried new ways to eat their corn, grinding it, pounding, and molding it into porridge and corncakes. But they were unable to clean the corn from their webbed hands, so that evening as they slept the bow priests cut fingers and toes into their hands and feet. The people were pleased when they realized their hands and feet worked better, and the bow priests decided to make one last change. That night as they slept, the bow priests took a small knife and removed the people's horns and tails.
>
>
>
[Answer]
I'm not certain you actually *need* any pre-existing cultural beliefs to permit the development of post-singularity magic. After all, *it's magic*. Depending on what kinds of more primitive magic are available to start, it might just be blatantly obvious that, at the very least, souls are not immutable and unique; and possibly, that they are completely materialistic. E.g., maybe you have a spell for duplicating things. Some wizard decides to try it on a person, and hey! It works! And after some observation, it's determined that you really can't tell which one is the copy, and he's certainly not a soulless abomination, so....
Outside of the realm of magic, perhaps they practice brain surgery. (This is not *quite* as completely ridiculous for a pre-industrial society as one might think; lots of such societies in real life have, after all, practiced trepanation.) And as a result, they are well aware that there is a direct connection between messing with the physical material of the brain, and psychological effects. This doesn't *preclude* a belief in dualism, but it does certainly strongly suggest materialism. Having magic in the setting potentially makes pre-industrial brain surgery much safer, and therefore more practical and more common, than it was in our world.
Put those two things together, and you're well on your way to figuring out how to build brains from scratch, and how to instantiate minds in other substrates.
But, if you really want a strictly cultural explanation, here's the best I've got: a belief in the death of gods. After all, if there's an immortal soul separate from the material body, then after the body dies the soul has to go somewhere--maybe heaven, to hang out with the gods, maybe some sort of underworld (which may be looked over by a god or gods anyway, like Hades). And dead souls clearly can't die, because there's nowhere else to go--they're already dead!
But gods don't have bodies / already inhabit the place where dead souls go. They are, in a sense, already "dead". So if a god *does* die... where does it go? The only option for a *god* to really die is to simply cease to exist. And if gods cease to exist when they die, and humans are so much less significant and less powerful than gods... why did we believe that human souls go anywhere in the first place? And if they don't, then do we even souls at all?
Of course, this depends on having some specific pre-pre-existing beliefs about how the afterlife works, and what the nature of gods is, and *then* also having a belief that a god or gods have actually "died", and *then* actually bothering to critically examine that belief. No real-world society I know of has taken that route; real religions either don't believe in the death of gods at all, or have some "out"--i.e., that the god has been / will be reincarnated, that heaven is separate from the underworld and dead gods go there just like dead humans, that there are multiple levels of afterlife and dying in one just takes you forever onward into the next, and so on.... But, you really only need one intrepid wizard, or a small group, to start wondering, and that's the best I've got.
[Answer]
What if in your culture magical tricks with souls and sentient beings are as old as any other technology? There are magicians who can create people artificially, copy and swap souls. There is nothing sacred in the act of creation. A schoolboy can do it. There is nothing sacred about human mind or human soul. It can be manipulated or created with ease.
Quite a strange world, I would say. But or course you can explore it.
[Answer]
I find that it's very easy to design such systems if you treat the nature of identity as something to be questioned, as opposed to something assumed.
There's a famous thought experiment on materialism involving teleporters. In this thought experiment, there is a "teleportation" process that operates at the speed of light. Your body is scanned, encoded, transmitted as data (on EM waves), received at the other end, and then reconstructed. Once your body is reconstructed, the old body is destroyed. For your purposes, where minds can be recorded/transmitted as well, treat those minds as part of the body (which is natural for materialism, but unnatural for dualism).
Because you are seeking a trope where such transport is possible, we'll assume this just works. Now for the fun questions. Let's transport ourselves from Earth to Mars, but the completion signal never arrives. Now we have two copies, one on Earth, one on Mars. So what happens? A purely materialist approach would be to say that the Earth and Mars individuals are copies of each other. Each has the same "importance" as the other does. This is fine, although you're going to have to rewrite property law from scratch because you now have two individuals with the same rights to the same property. A dualist approach would argue that the Earth individual has precedent because it's essence is that of the original individual.
(If your path starts going too dualist for your taste, the next version of the teleporter malfunctions, and instead of sending you to Mars, it sends you to *both* Jupiter and Venus, then the completion signal destroys the Earth body. Now which has the essence of the original?)
If there are no questions, then this is easy. Either one individual is "more important" than the other, or isn't. However, what if this isn't an obvious answer. What if there's questions? What if the teleportation process *seems* to copy everything perfectly, but it's not 100% clear whether anything is "lost?" The depths of those questions let you tailor the world to your particular level of materialism. You can have it where everyone is really confident this teleportation process works, but every so often there's something peculiar, like a "failed to thrive" teleport. Or someone who just doesn't seem to be the same. Hard to tell if that's a machine malfunction, or if there was something missing.
Another approach is to redefine individual. Language is a slippery thing. Individual means *something*, and we generally agree upon what it means in normal environments. You're building a spectacular environment. Perhaps individual has a more nuanced meaning here. Consider that most people use the word "individual" to describe something unique, and would feel uncomfortable using it to describe something copyable. Perhaps the word "individual" moves away from body/mind entirely, and stays with the unique thing: the information. This, of course, is not a new problem:
[](https://i.stack.imgur.com/Kd1h6.jpg)
We living creatures reproduce. We spread our DNA from copy to copy. We obviously see the uniqueness in each individual body, but from some perspectives, we're all just statistical samples of what happens when a 99.9% shared pattern of DNA gets to operate on an egg cell. Yet we consider "the human species" to be a thing. The information stored in that 99.9% of the DNA is treated like an individual in some ways. Your "post-identity" society may use the same rules. Copies all *share* the same identity which is the information associated with the body/mind. This solves the teleporter problem not by deciding which body is the real you, but by suggesting that you now have one identity which is expressed in two body/minds.
For a more nuanced version, take a look at family. Family is truly ephemeral, and yet it is often considered to be harder than steel, and it is constantly evolving.
Another useful tool I have found is [Holon Theory](https://en.wikipedia.org/wiki/Holon_(philosophy)). Holon theory explores things which are both simultaneously a whole and a part of something else. Your copied bodies may be treated as holons: each is their own whole, but they are also part of a bigger identity. Unconsciously, we tend to use holon theory when considering our own cells. Each one is a whole, but you can't make sense of it without considering it as part of a system. Each one is a part of a system, but you can't make sense of it without considering it as a whole as well.
For more of a magic feel, consider the special case of individuals who have *chosen* not to undertake this copying process. There are obviously risks to this: you only have one body. However, there are advantages. As an extreme example, it's not possible to torture 30 of me before getting one to crack. You have to get the information in the first try. These may seem obvious, but to a culture which is steeped in copying, these may be considered to be substantial advantages. They might even be enough to start a myth that un-copied individuals have supernatural powers. That's all you need to start the fantasy world going.
] |
[Question]
[
I'm looking for a description of how an EMP might affect a magnetic levitation train system that is NOT connected to the local power grid. Specifically, if the maglev was active, would the train be thrown off the tracks and rendered unusable, or otherwise disabled, or would it simply suffer a loss of power and then be able to reboot and run perfectly fine again?
[Answer]
To my understanding, a maglev train is propelled by magnets above and below the rails, that pulse in precise timing to send it forwards (or to slow it down when it needs to stop). These are also responsible for the levitation effect: the magnets hold the train a small distance above/away from the rails.
If your EMP pulse managed to kill the power to the magnets, the probable result would be the train dropping a few inches or so onto the rails and grinding along until it lost its momentum. Going at several hundred miles per hour, this would be dangerous in the extreme, but with such a tiny drop I don't think it would run off the rails unless there was a sharp turn (unlikely, given that you need to consider the G-forces on passengers when the train is operating normally) or the rails were unable to take the train's weight (which undoubtedly would be a building code violation).
This would terrify any passengers, beyond all doubt, and the resulting damage to the magnets would most likely render rails and train all unusable without expensive repairs, but I doubt you would have any casualties. Unless, of course, the timing is unfortunate enough to catch a train as it's about to slow down to enter a station, with another train on the same track at the other end of the station loading up with passengers.....
[Answer]
I think one might design a maglev train with induction braking that would be robust enough to use the kinetic energy of the train and permanent magnets to not only stop, but also maintain the maglev effect while the train was moving. The train would still ultimately drop onto the rails, but not until it spent its kinetic energy braking / floating.
Induction brakes are already used on some maglev trains.
<http://www.explainthatstuff.com/eddy-current-brakes.html>
>
> The simplest linear, eddy-current brakes have two components, one of
> which is stationary while the other moves past it in a straight line.
> In a rollercoaster ride, you might have a series of powerful,
> permanent magnets permanently mounted at the end of the track, which
> produce eddy currents in pieces of metal mounted on the side of the
> cars as they whistle past. The cars move freely along the track until
> they reach the very end of the ride, where the magnets meet the metal
> and the brakes kick in.
>
>
> This kind of approach is no use for a conventional train, because the
> brakes might need to be applied at any point on the track. That means
> the magnets have to be built into the structure that carries the
> train's wheels (known as the bogies) and they have to be the kind of
> magnets you can switch on and off (electromagnets, in other words).
> Typically, the electromagnets move a little less than 1cm (less than
> 0.5 in) from the rail and, when activated, slow the train by creating eddy currents (and generating heat) inside the rail itself. It's a
> basic law of electromagnetism that you can only generate a current
> when you actually move a conductor through a magnetic field (not when
> the conductor is stationary); it follows that you can use an eddy
> current brake to stop a train, but not to hold it stationary once it's
> stopped (on something like an incline). For that reason, vehicles with
> eddy current brakes need conventional brakes as well.
>
>
>
I could not find specific diagrams of how the induction brakes on maglev trains work. If I were designing them I would have permanent magnets on a deadman switch swing out when the power went and then produce eddy currents to slow the train.
Frictional losses by the train falling onto the rails and "grinding along" (to quote @Pallaran) would make the emergency induction brakes kind of pointless. There has to be something to prevent this grinding. The cheapest way would be friction pads like brake pads on the grind points. But if you are using permanent magnets for emergency induction brakes you can use the same principle and use permanent magnets for emergency induction levitation, or [electrodynamic suspension](https://en.wikipedia.org/wiki/Electrodynamic_suspension).
If there are permanent magnets on a deadman switch ready to tap the trains own kinetic energy and turn it into levitation and braking, the EMP-fried train would coast and brake until its kinetic energy was gone.
It was frustrating not being able to find a schematic of how real maglev trains accomplish these ends. Probably it is proprietary.
I envision a scenario where the heroes deactivate the brakes and trigger the Atlas rocket being carried on this train, the rocket exhaust now providing impetus and the emergency induction levitation turning back on when the train got up to speed.
[Answer]
EMP's generally will disable or outright destroy any complex electronics inside their effected radius. Maglev trains are levitated using electromagnets, so the moment the EMP hit the track, the train would fall onto the track. If the train were stationary, this wouldn't be too bad, but if it were traveling at full speed, with some reaching speeds of up to 375 mph, this would be disastrous. The train would act just as if it were a traditional train running off of its rails, only at a much higher speed.
There are some protections in place, and electromagnetic suspension (EMS) systems are designed to run temporarily in the case of a power failure, but these systems generally only run for a short period. Additionally, the systems to monitor and activate these emergency measures would more than likely be fried in the EMP itself.
As for EMP shielding, perhaps one could shield the controls themselves, but I am unsure if you could shield the electromagnets themselves, simply due to their location and function.
In the end it comes down to how paranoid the owners of this maglev system are. If they believe that an EMP threat is viable, then perhaps they will shield the emergency systems, thus allowing the train to have a chance to save itself in such a scenario. If they aren't as worried, then it will in all likelihood end in a catastrophic failure.
Note: This answer is based on my own understanding of EMP's mixed with a small amount of research I did into maglev trains while writing this, so if something I said sounds suspect to you, I encourage you to research it for yourself.
[Answer]
Maglev trains are designed with multiple levels of redundancy so that catastrophic failure is exceedingly unlikely (or rather that it is an acceptable risk), if however your EMP managed to shut off all its power and fry all its redundant systems, the train (because of conservation of momentum) would indeed fly off the tracks at high speed likely killing everybody aboard and destroying itself in the process.
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[Question]
[
I was thinking of making flying islands part of a planet ring, but the problem was that they wouldn't be able to host life unless they were inside the atmosphere of the planet, but at that point it would seem unlikely that they could just float in the sky, so I'm here asking what I should do with the planet ring/flying islands of my world. I think I will have to give up this explanation and come up with something else, otherwise.
If I used the wrong tags, or this question breaks any rule; I am sorry, I just signed up.
[Answer]
It is not possible to have a planetary ring orbiting within a planetary atmosphere. The very high speed orbital ring would encounter immense frictional heating due to interaction with the atmosphere and would burn up very rapidly. Even a ring orbiting at the very outer reaches of the atmosphere would encounter drag which would cause it to spiral lower and eventually burn up.
$$V=\sqrt{\frac{GM}{r}}$$
Where
V = Orbital velocity in $\frac{m}{s}$
G = Gravitational constant $=6.67\text{e}^{-11}\frac{m^{3}}{s^{2}}kg$
M = Mass of central body $=5.98\text{e}^{24}kg$
r = radius of orbit $\approx6371km$ at the surface
If we apply an orbit at 10km:
$$V=\sqrt{\frac{6.67\text{e}^{-11}\times5.98\text{e}^{24}}{6.381\text{e}^{6}}}\approx\frac{8km}{s}$$
[Answer]
I'm going to go with the *[Avatar](https://en.wikipedia.org/wiki/Avatar_(2009_film))* answer, which is at it's most basic, [Maglev](https://en.wikipedia.org/wiki/Meissner_effect). The islands of your flying mountain chain contain large concentrations of a [room temperature superconductor](https://en.wikipedia.org/wiki/Room-temperature_superconductor) of sufficient efficiency that it can pull up a large chunks of scenery and support them on the strength of the planetary magnetic field. Such mountains should hold pretty much stationary relative to the ground, they will drift with changes in the planetary [magnetosphere](https://en.wikipedia.org/wiki/Magnetosphere) and may fall if there is a local weakening in field strength. I'm not sure about the exact atmospheric effects of such a configuration, whether there would be frictional heating etc... High level winds will be effected by such a range, as will [Hadley Cell](https://en.wikipedia.org/wiki/Hadley_cell) formation and stability.
[Answer]
As Slarty said in their answer, you're not going to get a ring inside of an atmosphere.
**However!**
You asked for alternatives if your original idea proved infeasible. Without knowing the exact nature of your story, I can't be overly specific, but here are a couple of thoughts:
* The giant chunks of rock float at a considerable height in the atmosphere, but not higher than your sapients can tolerate. The rocks can be held aloft by anti-gravity technology of some kind, or perhaps levitation magic. This could have been done by a past civilization or a current one.
* The rocks could be the remains of asteroids hauled into orbit for exploitation. After creating a living surface, a dome would have been constructed over the top. Artificial gravity keeps the people on the surface, but the remains of the mines below may or may not be affected.
Personally, option 1 sounds really suicidal, unless the original inhabitants were escaping some surface-level catastrophe.
[Answer]
Slarty is right. One Alternative would be to make your islands buoyant. I see to ways to go about this, both would be somewhat hand wavy.
* Look into how pumice is formed. It may be possible under certain conditions to produce a pumice that is lighter then air, and would float. This would likely require a very dense atmosphere and hydrogen to be the exsolving gas which would require very high initial pressure.
* hydrogen gas can be produced through biological processes, plant life competing for access to sunlight might evolve hydrogen bladders in order to reach above other plants. Your islands could be composed of a floating tangle of such plants.
[Answer]
Normal physics wouldn't do the job. A planetary ring inside an atmosphere would be moving at approximately 8 km/s. This is the orbital velocity for an Earth mass planet. Atmospheric drag would soon decelerate the pieces of the planetary ring. It wouldn't last very long at all.
As a thought experiment: make a planetary ring magically appear in an atmosphere. At a guesstimate it wouldn't last one whole orbit.
Therefore, if a planetary ring does exist in atmosphere some form of magic or 'magic' must be at work. This could be a barrier to prevent atmospheric drag slowing down the ringlets and the flying islands or a constant force to maintain a constant orbital velocity.
For example, one can imagine a teleportation surface in front of the ringlets instantaneously transporting the atmosphere it impacts to somewhere behind them where it can rematerialize harmlessly. This would eliminate atmospheric drag. But some kind of force-field might necessary to maintain a breathable atmosphere for the flying islands.
In summary, if there is some form of protection to negate atmospheric drag, a form of 'magic' propulsion, if needed, to maintain velocity and a containment field to make the flying islands habitable. Then a planetary ring could orbit inside an atmosphere.
A simpler solution might to have a traditional, scientifically sound planetary ring orbiting outside the atmosphere and have the flying islands periodically rise up from the planet below to join the ring. The flying islands would spend a period of time as part of the ring and later on they would descend back down to the planet.
As has the advantage that the flying islands can be inhabited by lifeforms that evolved on the planet. There can be a form of antigravity that allows them to either move through the atmosphere or rise to join the planetary ring for a time. Again there needs to be mechanism to contain an atmosphere around the flying islands. However, this could be simply part of the antigravity that levitates the islands in the first place.
This idea is that the islands are habitable and can remain habitable while in the planetary ring. Also, they return to the planet to restock air, water, and whatever else they need to survive. They won't be permanently part of the planetary ring. This is only a suggestion.
This alternative solution does turn the original question on its head. But it does that the simplest solution would be to consider to make the flying islands that are part of a planetary ring habitable.
[Answer]
## This would actually be easier if the planetary ring was outside the atmosphere (or inside the mesosphere):
1. You could have your civilization advanced enough to live on the islands while in orbit, or if your main species isn't human (or just not purebred human) they could live in outer space [e.g. waterbears were proven able to live in space].
2. However, if you want your civilization to be less advance, have a previous civilization make the islands hospital. and to explain their absence have them fail to evacuate from what they were trying to escape from ( like a halo ring situation).
[Answer]
If your ring were a hollow vacuum tube, then you could have a single giant maglev train running around the interior at somewhat greater than orbital speed. That would hold up the ring against gravity, and wouldn't intrinsically require a lot of energy to keep running. Since the train would be traveling at thousands of meters per second, you'd need a very high vacuum, and the ring structure would need to be very strong for its weight, though not as much as a space elevator.
Such a ring would have lots of external forces acting on it which, left unchecked, would soon lead to catastrophic oscillations, especially in the vertical direction. This would be controlled by automatically varying the speed of the train along its track to cancel out the oscillation. That would take some energy, but it'd still be pretty efficient because when you slow down a maglev train, its energy is converted into electrical power which you then use to speed up the train somewhere else.
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[Question]
[
I am currently trying to design a kamikaze goblin. This goblin would drink explosives and have some sort of storage area within their abdominal regions. How would this goblin be able to have these explosives not go to their digestive tract, and how would they not detonate the explosives while running towards an enemy? This goblin is roughly humanoid and about four feet tall.
[Answer]
I feel I should point out the utter pointlessness of this idea.
Are you familiar with the expression [Heath-Robinson](https://en.wikipedia.org/wiki/W._Heath_Robinson) ? This is the military equivalent.
Humans developed a simple method of carry objects of all kinds, including explosives - solid or liquid, without the need to swallow them : *containers*.
Is there some bizarre reason your goblin can't carry a bag or pouch or bottle ?
There's no benefit to carrying it in your body, except it's hidden, but, surprise, containers can be hidden.
And containers can be easily dropped, thrown or dismantled if need be and easily set to explode using any number of fuses, from the primitive to the ludicrously complex.
Looking at your question in this light :
>
> I am currently trying to design a kamikaze goblin.
>
>
>
No problem with a kamikaze goblin carrying a container that swallowing one will avoid.
And if you're thinking of it being hidden, all this means is that the first time one of these k-goblins explodes, *all* goblins will immediately be targeted and the purpose of hiding explosives by swallowing is lost.
>
> This goblin would drink explosives and have some sort of storage area within their abdominal regions.
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Called a stomach in humans. Can't see a reason it can't be called that by goblins. :-)
You can have more than one stomach if you insist on this, but it doesn't make it any better as an idea.
You might consider a kangaroo-like "pouch", but what difference ultimately is there from just having a back or satchel or strapping things to the outside of the body ?
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> How would this goblin be able to have these explosives not go to their digestive tract
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As someone pointed out, this is not really an issue in a *kamikaze* goblin. :-)
But note that humans, those ingenious all-purpose crazies, actually do swallow stuff to hide it and, courtesy of certain design features of the human digestive tract and the ability to wrap objects in plastic, cow gut or a variety of other materials, they will happily survive the trip through aforementioned digestive tract none the worse for wear, so to speak.
( Think drug trafficking. )
And the trick is ancient. We've been hiding stuff from searches by swallowing for centuries. For all I know it predates written history.
And, without being too explicit because I've just eaten, we have been known to hide things in other orifices.
But unless you've absolutely no other alternative, doing such a thing is basically not useful. These methods have never been favored by suicide bombers over the more basic, but extremely practical, external carry method.
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> , and how would they not detonate the explosives while running towards an enemy ?
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... In a hail of fire which will ensure they're not going to reach any target, because pretty quickly word will spread that kamikaze goblins are active and it's shoot-on-sight time everywhere for *any* goblin.
If they had it in an external container they could throw it when they were close enough, starting the fuse when they want to.
But inside their bodies ??? If they're wounded approaching the enemy all they can do is die unless they could throw their stomachs (a rather revolving possibility which I suspect neither novel not video need explore).
This is so counterproductive from a military standpoint.
Strapping explosives *outside* your body : it works for humans, it will work for goblins.
Why make it complicated ?
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> This goblin is roughly humanoid and about four feet tall.
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Not after it's shot to pieces by paranoid guards, it's not. :-)
[Answer]
I imagine a rumiant-ish goblin.
This would have three stomachs: Two for storage, one for digesting.
The two storaging stomachs would only be connected to the mouth. There, the goblin stores excedent of food and regurgitates the food and re-eats it, moving it to the digesting stomach.
What our kamikazee goblin does is drinking two different substances that when mixed become inestable and explode. He stores one in each storaging stomach.
When he wants to explode, he simply have to regurgitate both substances.
[Answer]
What about a [Throat Pouch](https://en.wikipedia.org/wiki/Gular_skin) much like those found on a pelican or orangutan. Instead of risking the explosives in a rather active digestive track and needing a specific breed of goblin you could just as easily give all goblin's throat pouches which they can then use to hide the explosives and if they have to set it off with their tongue or remove the device entirely by a slight regurgitation.
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[Question]
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[Working off of a previous question about armor](https://worldbuilding.stackexchange.com/questions/81587/super-metal-and-the-construction-of-knight-armor), imagine yet again a world where there exists a metal
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> comparable to high grade steel, however instead of steel's density of ~8 g/cm³, this material has a density less than even aluminum at ~2 g/cm³. The ease/difficulty to work it is roughly comparable to steel. By terms of rarity it is comfortably more costly to acquire than steel is to create, but not nearly enough so to make it considered a precious metal.
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The previous question dealt with armor; I want to consider weapons.
Setting is an alternate 15th century. This imaginary metal has been in use for around two centuries, enough time for plenty of weapons to be forged, and for tactics to evolve to take advantage of its unique property (for the purposes of this question, you do not have to consider the effects of using this metal in armor). **How would this lighter metal change what weapons are used on the battlefield?**
The way I see it, in war there are cases where light weapons are better, and cases where heavy weapons are better. I just can't figure out how that balance would play out on a large scale.
[Answer]
I intend for this to complement, not replace, what Sam said.
There are many, many types of weapons used by a variety of soldiers in the medieval era (although the 15th century is more of the Renaissance-era), designed for various purposes. I will attempt to cover the major ones.
**Blunt-force weapons**
As Sam said, these weapons include maces, mauls, war-hammers, and other weapons designed to deal impact damage to bones and tissue without penetrating armor. You won't likely see any use of your ultra-light high-strength metal (which is less dense even than titanium). These weapons rely on momentum for their damage potential and require significant mass.
You might possibly see your lighter metal in maul chains to allow for more of the overall mass of the weapon to be concentrated in the end.
**Edged weapons**
There are some advantages to lighter edged weapons, again as Sam said. Faster movements allow for better targeting of the moving openings in armor and improved slashing attacks. Off-hand weapons like parrying daggers (though not really used on the battlefield) would also benefit from being lighter, allowing better protection and faster parrying.
**Thrusting weapons**
Personally, I think thrusting weapons (mostly thrusting swords) have the biggest advantage in being lighter without sacrificing strength, as it allows you to impart more force in the thrust, improving penetration of mail and the underlying tissue.
**Ranged weapons**
You won't likely see much use in ranged weapons, except perhaps in the previously steel parts of crossbows. Those, however, are peasant weapons and it's unlikely a noble would spend extra money to outfit his peasants with lighter crossbows. Crossbow bolts and arrows rely on momentum for their penetration - too light of an arrow won't penetrate the target, so those are off the table.
Early firearms might benefit from a light, strong material like yours, but those early projectiles likewise depended on their mass to do damage.
**Polearms**
Polearms, again, are peasant weapons. Though they would benefit somewhat from lighter heads, that's not going to offset the generally very heavy wooden pole.
**Material rarity**
Given the overall rarity of your wonder-steel, the weapons made will likely be restricted to nobles and perhaps their personal guard. The bulk of armies, which were generally peasants, were outfitted with cheap arms and drew strength from numbers and strategies (and having more people than the other guy).
**TL;DR - Overall, I believe your material is more likely to impact duels among nobility than it is large-scale warfare.**
[Answer]
Similar to comments in your earlier questions, there were 2 main types of ways to injure knights in medieval times.
**Blunt Force**
Weapons such as maces and war-hammers fall into this category. The source of the damage comes from the force of the weapon hitting the person, as opposed to cutting the person. This relies more on strength. In this case, the normal metal used in the past is preferable here, as it better suits their purpose.
**Bladed Weapons**
The other way to injure knights was to target the areas where the joints were exposed, and attack there. This relies more on technique and speed. For these weapons, the stronger, lighter metal is preferable as you can make stronger blades that don't weigh as much, allowing for quicker movements.
In terms of how this would work on the battlefield and the distribution of weaponry, the issue with plate mail in the past was how much it took to make a set, which is why only knights would have it. This new metal is less common than steel, which means even less troops will be able to use it. Outfitting an entire army is a bit excessive, so I don't see that making a huge thing.
[Answer]
A light weight metal with equal properties to steel would make for longer, more deadly swords and daggers. The important properties that need to be the same for weaponry are strength, hardness, and strength/volume. Longer swords allow the user to hit an opponent further away without risking being hit. If you simply stretched out a sword to make it longer it would lose stiffness and strength, so more volume of metal (aka mass) needs to be added to preserve its performance. The problem is adding mass to a sword makes it slower to swing and thrust, and more tiring over time to handle. Your 4x lighter metal would make a huge difference here - imagine a 2-handed sword that could be wielded like a saber. Or watch a video of a saber duel, but imagine the swords are twice as long and do 4x the damage on contact.
Daggers of the same size as steel daggers would be lighter while providing the same strength, making them easier to conceal and faster to wield.
If cost were no object a lightweight metal could replace the wood in polearms, similar to how titanium, aluminum and carbon fiber composites are used in modern airplanes and spacecraft.
Titanium hammers for normal people exist in our world and can be bought at home improvement stores. They cost about 5x an iron hammer but perform about 50% better than an equivalently sized steel hammer. Their lighter weight, equivalent strength, and titanium's unique elastic properties contribute to their higher performance, at least for the purpose of driving nails. Many professional carpenters swear by them.
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In 1890’s H.G. Wells famously takes a “science fiction” approach to time travel by building a machine that can move freely through time as a dimension. It was made of clockwork — mechanical gears and such. Gears can perform ordinary motion in precise ways, but nothing about that enables doing something that normal motion *doesn't*.
Later treatments use whatever the technology of the day may be: electronics and then cybernetics. But again, that’s completely implausible, since electomagnetism experiences time in the normal way just as gears do, and calculating fast is supposed to do what exactly?
Now, we really do know about some “hard” S-F approaches, but these require giga-scale engineering and exotic ingrediants like negative energy.
I'm not talking about the projects of a K-Ⅲ civilization, though, or even a national scale project like a major particle accelerator. **I'm wondering how a *small scale* effort, like a mad scientist or university professor, could (more) plausibly build a time machine.** To clarify, he uses the machine to go back in time. (Forward is easy!) The setting is “near future” (like 15 years or so).
You have to consider why it hasn't been done already if it’s doable using ordinary stuff involving current technology. Technology based on new principles only just becoming available must have some plausible reason for allowing time travel, and not just be something new and mysterious. I won’t rule out distinguished artifacts *per se*, but I want the solution to be something that anyone could have done — finding the crashed UFO in your own basement is simply cheating.
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# Notes
The [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") explicitly rules out pseudoscience, but we allow generous **handwaving**. This kind of handwaving, done well, is exactly what would make for “plausible” storytelling. Specifically, the movie [Primer](https://en.wikipedia.org/wiki/Primer_(film)#Physics_and_science) was delightful in using an effect that I'd read about, which provides for interaction between gravity and electromagnetism via a superconductor. This was [in *New Scientist*](https://en.wikipedia.org/wiki/New_Scientist#Criticism), and the theory is crazy pseudoscience. For someone who hasn’t looked into it, though, it comes across as plausible if you don’t push the details.
Note that I'm definitly allowing for invented physics *beyond* what we know. It just has to be “plausible”, and is best if it’s something we’re *expecting* like [string theory](https://en.wikipedia.org/wiki/String_cheese) [ref](https://en.m.wikipedia.org/wiki/Quark_(dairy_product)).
[Answer]
If you want a "realistic" time travel "anyone" could plausibly do, you will have to look at the gaps in modern physics. New Scientist magazine (out of the UK) recently listed 11 things modern physics cannot explain; including the inflation necessary for a Big Bang, particle entanglement, how the force of gravity is conveyed, whether black holes exist (as a point-like gravitational source), dark matter, dark energy, zero-point energy (or alternatively why it is a hundred orders of magnitude smaller than theory demands), etc. Perhaps most importantly, Einsteinian General Relativity and Quantum Theory are irrevocably irreconcilable; they cannot both be correct. the super-majority of physicists have their money on Quantum theory, and assume Einstein's use of infinities is a fudge. We definitely know from quantum dynamics and experiments within that position is uncertain; in fact tunnelling transistors are tech based on that very phenomenon. There really is a quantum foam, etc. GR does not reflect reality at any extreme: There are black holes, but they do not collapse to an infinitely small point, because those do not really exist!
Physics as it stands is plagued by infinities (even for quantum problems), which (the infinities) probably are not "real". The point of the Loop Quantum Gravity formulation, which is far along but still incomplete, is to forgo infinities: Meaning space is **not** infinitely divisible, it too comes in smallest-possible quantums like energy. (When one works out the maths starting with this assumption; the results force these smallest units of space to be like a chain-mail mesh of linked loops; hence the name.)
Remember science fiction is *fiction* so you need somebody investigating one of these unknowns to find a property of it (something you invent) they can manipulate to send something back in time, either information or something physical like a person.
Note that if time travel is possible; it means that all times exist simultaneously throughout the universe. If Loop theory is correct and there is no infinitely small sub-division of space or time, then there is a quantum of time, too; a smallest possible 'duration'.
So the answer is, for realism, pick something current science does not explain, invent a solution to that problem that **demands** time travel, and then discover a way to exploit that to allow your scientist to time travel.
[Answer]
**Here Comes the handwaving**
**Tools:** Your protagonist (antagonist?) has access to (builds?) the following: 2 [Wakefeild Plasma Accelerators](https://en.wikipedia.org/wiki/Plasma_acceleration), 2 [Storage Rigs](https://en.wikipedia.org/wiki/Storage_ring), a whole bunch of [power](https://en.wikipedia.org/wiki/List_of_nuclear_reactors#United_States), access to [LIGO](https://en.wikipedia.org/wiki/LIGO), tons and tons of shielding (literally), and a "lets turn up the power attitude" and/or reckless graduate student.
**Procedure:** The Wakefield accelerators are arranged in a track field shaped configuration, pointing in opposite directions in what would be the straightaways. The storage rings make up the curved ends of the track, with one of them modified to allow for firing at a target on some path tangent to the curve; that just happens (intentionally?) to be pointed at a facility with a cosmic ray detector. It could be hundreds of kilometers away, and let's keep the population density in the intervening distance low. One of the wakefield accelerators is primed and fired into one of the storage rings that catches the accelerated particles and stores them. After some adjustment, the particles are injected into the second wakefield accelerator and then recaptured with significantly higher energy. This process is repeated over and over again.
[](https://i.stack.imgur.com/5IVN4.png)
Storage rings in red, accelerators in green, arrows denot direction of movement.
As the process continues there is more and more time between shots for the system to cool, and the magnetic fields built up to accept higher and higher energy particles. At this point the particles aren't getting faster they are getting heavier and it's harder to contain them. The Efficiency of the system is also being affected but you are keeping track of it though heat loss and the careful measurement of particles in the storage rings.
After surpassing the energy that the [LHC](https://en.wikipedia.org/wiki/Large_Hadron_Collider) operates at (Cern should have hired me!) by several orders of magnitude and approaching the energy of the [Oh My God Particle](https://en.wikipedia.org/wiki/Oh-My-God_particle) something strange begins to happen. The energy added the particles after each firing begins to drop off, no longer following the steady exponential decreases due to efficiency losses. After checking and re-checking the losses due to radiation and heat don't account for the discrepancy. Also, your particles in the storage rings are somehow losing energy, at least more than can be accounted for by losses in the system. Your scientist (probably mad scientist at this point) continues to add energy to the particles, surpassing even the highest energy cosmic rays.
Now it gets weird. After a trip through the accelerator, the particles gained no more energy. In fact, the measurements indicate that there are now fewer particles all with much less energy. After careful review of data, there is no known way to account for the loss of energy and mass.
The particles are once again accelerated, and this time fired into the target. The blast of radiation is enormous, lethal to anyone that is not hiding being meters of lead. Exotic particles, antimatter, you name it, are detected. Your local [cosmic ray detector](https://en.wikipedia.org/wiki/High_Resolution_Fly%27s_Eye_Cosmic_Ray_Detector) registers an interesting event. Scientists at LIGO register an anomaly that they can't explain.
**Even More Hand Waving**
So great was the energy of the reaction that it had begun interacting with [quantum foam](https://en.wikipedia.org/wiki/Quantum_foam). At this scale, the particles had excited extra dimensions that have been [compacted](https://en.wikipedia.org/wiki/Compactification_(physics)), one of the implications of [string theory](https://en.wikipedia.org/wiki/String_theory#Extra_dimensions) being true. For some reason, the energy required to expand this compact dimension had been low nad decreased as it expanded. This resulted in baseball sized metastable space-time anomaly that was really a gateway into a higher dimension, one where time is a location. With some more handwaving, the scientist figures out how to use it to travel between two points in time.
**Warning:**
I'm well aware this is a bunch of hand-waving, Don't judge me.
This may also create a new universe.
[Answer]
Only science-based way to time-travel is repurposing FTL-capable spaceship. Simply because FTL = Time travel.
Something like this : <http://www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-time-travel>
So in your story, you make FTL-capable spaceships and hand-wave why they cannot be used for time travel. And then, your (mad) scientist only needs to solve this single problem.
[Answer]
There's some [research to suggest that superconductors would reflect gravity waves](http://physics.ucmerced.edu/news/2014/sharping-and-chiao-win-darpa-grant) (not gravity itself, but [waves in the structure of space-time](https://en.wikipedia.org/wiki/Gravitational_wave)).
A gravity wave resonating chamber made with superconducting walls might be sciency enough to pass muster.
Consider using the resonating chamber to sustain a very large amplitude standing gravity wave. If the energy densities are high enough, you might be able to plausibly justify new physics happening in that region. Maybe new physics with a time travel application.
If you want to go extra crazy with this idea, have two resonating chambers and have them set up to create space-time [vortex ring](https://en.wikipedia.org/wiki/Vortex_ring). If two space-time vortex rings (one ring from each chamber) then collide, we could expect extra cool sciency things to happen in the region where they collided.
Slightly related, I just went to a [talk](https://en.wikipedia.org/wiki/Tri_Alpha_Energy,_Inc.) where a physicist name Dr. Thompson discussed *plasma* vortex rings colliding in the middle of an experiment in order to produce a nice rotating plasma.
[Answer]
I beleive that artifical gravity generators might bend spacetime enough to allow circling back, assuming you are in a capsule that eliminates the gravity's pull on you over 1g. However, I am unsure if this would require a finite or infinite gravity pull.
I also read that wormholes might allow time travel, which makes sense because they work with spaceTIME. The stresses would be significant though, so survival would be unlikely.
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[Question]
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**Closed**. This question needs [details or clarity](/help/closed-questions). It is not currently accepting answers.
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I love spider tanks, ever since I watched that episode of [Ghost in the Shell: Stand Alone Complex](https://en.wikipedia.org/wiki/Ghost_in_the_Shell:_Stand_Alone_Complex), with an experimental spider tank going rogue.
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Most of them consist of three main parts:
* **The forebody**, which mainly contains the sensors, the ammunition holder of the primary (machine gun) weapon, and the Central
processing Unit.
* **The post body** contains the power generators, the ammunition holder of the secondary (railgun) weapon.
Regardless of type, all spider tanks possess
* **3 pairs of legs**, which are made out of [artificial muscle tissues](https://en.wikipedia.org/wiki/Artificial_muscle)(more precisely, [vanadium dioxide](https://forums.spacebattles.com/threads/artificial-muscle-with-1000-times-the-power-of-a-human-muscle.280308/)) and have a few traits designed after the [world's cutest
spider](https://www.youtube.com/watch?v=FhpL5h8sEHo) (the combination of a few). These legs are usually protected
by reinforced plates and have claws and retractable wheels on them
as a way of faster travel, and more effective climbing.
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[](https://www.youtube.com/watch?v=s2MVaLEEnLs)
*A military spider tank from Ghost in the Shell: Stand Alone Complex* (video link in the picture :)
Their armor and weapons are mostly dependent on their size. Larger ones usually have a "stinger railgun", that can be moved around with a high degree of freedom, enabled by the same types of artificial muscle.
Even the heaviest ones are relatively light-weight (because they're mainly built out of carbon allotropes), as all spider tanks are capable of jumping up to 15 meters high, via their powerful legs.
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**Now, I wonder, whether these tanks have some sort of a "fatal flaw", that I overlooked *(we're talking about modern day and near future settings, the 40k one was just there for the lulz)*?**
[Answer]
When we talk about reliability, there is a motto:
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> What is not there cannot get broken
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Legs and joint are the key weak point in your concept design, expecially if you want to move around some tons of body and even jump. You are now multiplying this weak point by 6, which gives both an easy target to any enemy wanting to take the tank down and a nightmare to reliability engineers trying to make the thing operate as intended.
Sure you can reinforce the hull to withstand anti tank shells, but doing the same on joints which are supposed to move around is another story.
[Answer]
Their legs are vulnerable - they have a large surface area to volume, which means that they won't be able to be heavily armored, as any added mass on the legs would greatly restrict mobility (moving legs -> moving tank, adding weight -> slower legs -> slower robot) - very similar to how cars try to minimize their unsprung wheel weight as much as possible in order to remain fast & efficient. Furthermore they have many exposed joints which are vulnerable to getting gunk / sludge / stuff stuck in them, which would make them unable to move
Speaking of efficiency, jumping is not an efficient maneuver - while I won't doubt your 15m jumping ability, as you can hand-wave an energy source, you will also need to hand-wave it as to why it won't make sense to use that energy source in a more efficient method (i.e. traditional tank, flying robot, whatever)
You mentioned wheels on the legs - All of the above still applies, you need to not only make it possible, but make it somehow better than the alternative (normal wheeled vehicle, or even compared to a tread-drive tank). Strong, light-weight armor? Why not put a plate 2x as thick on a regular tank for more protection?
That said, there is one distinct advantage that the legs give your tanks - that is they can step over large obstacles or cross very difficult terrain. You may want to reference the AT-ATs from star wars and see how their legged tanks could adapt to various terrains.
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[Question]
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I am imaging a world in which a minor plot device is that there is a strain of dogs that were genetically engineered so that they are even more loyal than ordinary dogs at first, but at some point in their lives, either due to a triggering event or just the passage of time, suddenly flip. Then they become not just not loyal but actively traitorous - biding time until a good opportunity to maximally betray its master comes along.
This trait may have originally been introduced in order to assassinate foreign leaders and terrorists, but, when engineered dogs bred with other dogs (sometimes undetected), this trait spread and is now present in some small percentage of domesticated dogs in much of the world.
Is this possible or realistic? Are the examples of existing animals that behave in this manner or something similar? What triggers might make sense for such a trait?
[Answer]
*Note : this answer assumes the classic "alpha/beta males" behavior of wolves. After a bit of researsh (thanks DonQuiKong in another answer's comment section), it turns out that this is not how wolves behave in the wild. Assuming that the seed of this behavior is probably somewhere in the wolf/dog DNA and that the question aims for a story, using this trope as basis appears safe enough to me.*
Like other answers already mentionned, the instinct is kind of already there. Let's see how it can be modeled to act like you want it to.
What makes a dog loyal? It has a strong pack instinct.
What makes a dog loyal to YOU? Because it sees you as the pack leader and it can't think of a reason of a way to overthrow you. It's fine as it is. Which I assume (not being a dog history expert), stems from the fact humans selected the most submissive kind of dog to when they started breeding them.
This last part is based on my own personal (and limited) understanding of dog psychology. If this doesn't make sense, I'm afraid my answer just won't make sense.
**So what about your dogs?**
Picture a dog engineered so that at some point in it's lifespan, it wants to be the leader, and it will. With just a few other changes in the dog's psyche, it essentially becomes a wolf that really wants to be the alpha male. And you are in its path. This gives us an easy explanation for why the beast wants to betray you.
Here's the first effect of the genetic modification : at some point in it's lifespan, the beasts gets incredibly dominant until it's instinct dictates that it must be the alpha.
**About betrayal : how can the dog do more than just beat you up and run away**
Our hypothetical dog wants to kill you (or at least that you submit to it), but it will probably just wait for an opening, beat you up real good and take the lead. At this point, we basically have an uncontrollable animal. This is probably not quite what you have in mind when you say betrayal, which is why we'll use the genetic engineering to change this.
So let's make the dog more subtle, it wants to stay close to you and cause trouble until something else kills you. This dog is patient and more methodical than your typical beast. The modifications that caused the surge in dominance also causes it to avoid confrontation with it's alpha until it's too late. This dog can actually understand playing a role and social manipulation.
Here's the second effect of the genetic modification : the beast gets unnatural intelligence (for a dog). It instinctively learned in it's submissive phase to play sneaky with it's peers. So much that to an extend it can even get close to understanding how humans thinks and work in society. This also causes it to avoid confronting the pack's alpha directly. It will play the part until you need his help and take the mantle of alpha. After all, why would it take a fair fight if it knows how to avoid it?
This behavior would probably not be good in the wild if it was widespread. But if we accept that genetic engineering is in there, it doesn't need to make sense from an evolutionary perspective.
[Answer]
I met a golden chow mix one day. I love dogs and I'm pretty good at reading them. He was wagging and happy to see me, but that was the golden talking. The other side of his nature was chow, fiercely distrustful of outsiders and prone to attack suddenly. The minute I got within two feet of him, a change came over him. He was no longer happy to see me. He lunged and snapped. His owner apologized profusely and explained: he really was happy to see you till the moment you got close.
The temperament predilection of different dog breeds has been cultivated for thousands of years. I could see how with a little advanced biology a trigger could be implanted causing a dog to go from faithful companion to terrified and vicious.
I refuse to believe that the dog could be capable of malice and foresight though. If you want that, you'll need to go with a cat.
[Answer]
Well, this is what wolves do. After being loyal to the pack leader, eventually a mature wolf will challenge the aging alpha for top spot. Can be male or female. And since most wolves would have been born into the pack and only the alpha pair breed, the challenger is invariably an offspring.
[](https://i.stack.imgur.com/aKNTD.jpg)
It's actually a genetic thing already.
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This hypothetical marsupial species raises young in a manner loosely similar to seahorses. Only the males have pouches: after gestation the female deposits the fetus into his pouch to compete development. Is this adaptation competitive?
EDIT: Here are some revisions to address problems brought up by answers:
* **Nutrition**: The male's pouch has nipples and lactates.
* **Evolution**: I would assume that they developed along a loosely similar path to seahorses when developing into mammals. As reptiles
that fertilized internally and then laid eggs, they developed a
strategy of attaching the eggs to the male, then as time went on the
male developed a brood pouch and nipples like a marsupial while the
eggs degenerated and the burden of gestation was foisted on the male.
* **Advantage**: The intended advantage is that the female foists the burden of pregnancy on to the male, allowing her to devote energy to
producing more offspring at lower cost. Polyandry would probably be
common.
* **Avoiding parasites**: If necessary, perhaps the female lays a soft shelled egg in the male's pouch to prevent parasites from attaching to the fetus. The shell later dissolves
to allow the fetus to attach to a nipple.
[Answer]
Picture a bamboo forest. Most years are quite routine. Your hypo-marsupials scavenge for (non-bamboo) seeds and other foods. In turn, they are eaten by whatever predators they have (owls, hawks, weasels, wolves, large cats, etc).
Every 50 years the bamboo forest blooms as the previous generation prepares to die off and drop its seeds. Many, many tons of food are literally dropped in the hypo-marsupials laps.
During this time of overwhelmingly plentiful food, a female marsupial that can pass on the development and growth of the younglings while she recovers from the initial pregnancy and preps for the next litter will give her bloodline a distinct advantage in out-competing and out-numbering rivals.
During this time, the predators will be well fed, but will have almost no impact on the massive amount of hypo-marsupials that will swarm the area.
Eventually, the seeds are gone (either eaten or sprouted) leaving to massive outward migrating swarms and population crashes as there is nowhere near enough food to support even a fraction of the massively expanded population.
The more progeny a hypo-marsupial has, the more likely that some will survive the massive die-off to go back to the routine year-to-year survival until the next wave of bamboo seeds.
[Answer]
In seahorses the eggs that develop in a males pouch have yolks like other egg laying species. The male has to provide no nutrients for the embryos to develop, just a place for the eggs to be safe.
Marsupial mammals young need milk for the fetus to develop, in order for a male to carry the young it would have to evolve mammary glands that function to secrete milk.
Here I am presuming that by marsupial you are not just using it as a term for a pouch bearing animal, but the proper definition.
[Answer]
I don't see a clear competitive advantage.
In such a specie the female has to be fertilized by the male, and then has to transfer the fetus from her body to the male's one, adding additional risks related to the manipulation. Having no shell to protect it, the fertilezed egg would be highly subject to parasitic infections.
The only valid reason for doing this would be a large sexual dismorphism, with the male much bigger than the female, and thus more suited for protecting the fetus. On the other hand, a much bigger body requires already a bigger amount of food, and if we add the energy needed by the growing fetus it further increases.
Harvesting more food carries additional risks (injuries, being attacked by predators, etc.). If such a specie would exist, I am pretty sure over few generations the male would turn to a female (producing the egg and hosting the fetus) and female to a male (simply producing sperms to fertilize the egg)
[Answer]
# No, this will fail
The female has breasts, the male does not. For a marsupial, the newborn, tiny creature goes into the pouch and grows on breast-milk.
Since the male does not have breast-milk, there isn't much of a chance of the infant marsupial surviving.
[Answer]
## No.
It is believed this strange trait evolved to allow seahorses to reproduce at an astonishly rapid rate, because so few seahorse babies actualy survive.
It functions like this:
Instead of having to manufacture new eggs and gestate at the same time, the female seahorse unloads all her eggs onto a male who fertilizes them and carries the resulting embryo for her.
This way she can concentrate all her energies on creating more eggs and perhaps even have them finished by the time the male gives birth allowing **a seamless cycle of continuous reproduction** (as in the male gives birth and then immediately afterwards begins incubating more babies).
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This strategy of "make as many as possible because atleast some will survive" is not usuable in the environments Earth marsupials live in.
Even the mammals who do display this stategy to a degree (mice, rabbits, etc) do not do so at a level so extreme.
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In conclusion, unless you change something about your creature or it's environment this is utterly implausible.
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Immediate to near future, we are talking about single digit nanometer size transistor and light emitting diode. That's actually very small, you can't see it with a conventional microscope let alone magnifying glass. I need a pair of contact lenses that could allow me to browse the internet for at least 2 hours when exposed to a healthy wifi signal, the electronic components such as display, antenna, processor with embedded graphic, random access memory for storing working data etc will be fitted inside a gas permeable flexible polymer. I'm missing a power source to supply ultra low wattage current to drive the comfortable super energy-efficient internet enabled contact lenses, what available technology today can I use for my lenses?
Criteria/minimum specs:
1. Compact and lightweight.
2. It must not melt or explode under any normal circumstances.
3. Must not obscure vision.
4. Must be rechargeable.
5. Built-in/ bonus points for exchangeable or support wireless charging!
Note: disregard energy consumption and handwave the antenna only.
[Answer]
As Steve notes, the great Vernor Vinge postulates such contact lenses in the universe imagined in Hugo-winning novella *Fast Times at Fairmont High* and the Hugo-winning novel *Rainbows End*.
He describes smart contact lenses being [powered by the thermal gradient](https://en.wikipedia.org/wiki/Thermoelectric_generator) between body/eye temperature and ambient air temperature. The lenses offer full augmented VR and have the added bonus of being instant protective shields from high-intensity light such as military laser weapons discharge. Vinge describes the unpowered contact lens as being foggy-white when not placed on the eye; and turns clear moments after being placed on the eye.
>
> Miri didn't seem to notice the look. She leaned her head forward, and stuck a finger close to her right eye. "You already know about contacts, right? Wanna see one?" Her hand came away from her eye. A tiny disk sat on the tip of her middle finger. It was the size and shape of the contact lenses he had known. He hadn't expected anything more, but... he bent close and looked. After a moment, he realized that it was not quite a clear lens. Speckles of colored brightness swirled and gathered in it. "I'm driving it at safety max, or you wouldn't see the lights." The tiny lens became hazy, then frosty white. "Uk. It powered down. But you get the idea." She popped it back into her eye, and grinned at him. Now her right eye was fogged with an enormous cataract.
>
>
> "You should get a fresh one, dear," said Alice.
>
>
> "Oh no," said Miri. "Once it warms up, it'll be good for the rest of the day." And in fact the "cataract" was fading, Miri's dark brown iris showing through. "So what do you think, Robert?"
>
>
>
[Answer]
We blink all the time. Maybe the motion of the eyelid over the contact could power it, either by magnetic induction planted in the eyelid (kind of like how those wireless charging pads work on phones or by parasite robbing some of the kinetic energy of the eye closing and opening and converting it to physical energy. Could pair this with solar recharging (if the system is designed to work with the eyes OPEN, not closed) to extend battery life.
You can also have a small battery slipped over behind the eye. I once participated in a research project that required me to have a thin silicone tube slid behind my eye (to see how well it would be tolerated for medications). Lived with it for a month and it wasn't very noticeable. Could easily have this be a battery pack that feeds power to the contact. Of course putting the contact in and taking it out would be more laborious, but hey, that's progress!
[Answer]
Since you rely on wi-fi communication, you can use RFID-like technology to power your circuits.
* The wi-fi can supply energy and data to your wearable device
* a tribologic generator powered by the bearer body can wireless power the device (you can use breathing movements, as they are constantly done)
* a small phovoltaic panel can do the same (only during day).
You might want to extend the area of the lens, using the display part on the pupil area, while using the rest as energy absorber, so that you avoid concetrating too much energy flow (you don't want to cook the eye, right?)
[Answer]
You can power them through the use of a resonant coil to wirelessly transmit electricity produced by an external system. For better features, the coil can be made of a very thin tube of ionic solution, using a cooling container in the very middle of the lens to mitigate the heating effect.
Using a stable neutral pH solution will make it safe in case of leaking in the eye.
Since resonant magnetism is safe, transmission of the current could be done worldwide.
A small gel battery can be used to make the power sustain on main power loss.
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What if in an alternate universe after the Chernobyl incident, the world governments decide to shut down their nuclear power plants and if so how would that affect society?
[Answer]
Chernobyl was an [RBMK](https://en.wikipedia.org/wiki/RBMK) type reactor. The RBMK is pretty unique in terms of reactor designs. Its advantages are that it is large with high power output, and it can be refueled while operating. Its disadvantages are positive coefficient of reactivity (explained below) and its large size allows different neturon fluxes to persist in different parts of the reactor.
Coefficient of reactivity is probably the most important concept to understand with a nuclear reactor. The Russian RBMK is one of the only designs with a positive coefficient. All the Western pressurized water and boiling water reactors have negative coefficients. The coefficient of reactivity is the ratio of change in reactivity to change in temperature. If the coefficient is negative, then as the reactor heats up, fissions happen more slowly. A negative coefficient reactor that is undergoing a high power casualty will shut itself down before it does too much damage. With a positive coefficient, a high power casualty will create a runaway condition where higher power generates more heat which increases power. You can see how this lead to massive explosion and containment breach. For American reactors, which are all of the pressurized or boiling water types, a Chernobyl type accident is physically impossible.
I tell you all this to inform you that the powers that be in US Nuclear power (the Nuclear Regulatory Committee in particular) will understand this. There is no way that the Chernobyl accident could happen in the US. Thus, it is very unlikely that Western countries, operating much safer reactors would shut down due to an accident in the poorly designed and poorly operated Soviet plant at Chernobyl.
Now Fukushima was a different story...
[Answer]
One of the things I think it would take for this to be realistic would be that in this alternate universe, the Chernobyl event was *far* more devastating in terms of fallout.
The second thing would be that the Chernobyl reactor was well maintained and of a solid design, but they couldn't figure out *why* it happened. I think these reasons would be the catalyst for the anti-nuclear camp to completely dominate. "It just killed 2 million people and we still don't even know why, 15 years later!"
The obvious result would be that different sources of power would have to replace the gap left by the disappearance of nuclear. I'm not sure how much this would affect society, since nuclear technology isn't exactly in everything like the world of say, Fallout, for instance.
[Answer]
Shutting down some power plant overnight is going to pose a tremendous challenge on the energy management system of any country doing it.
Let's assume the country has no short term alternatives: it will be more or less the same scenario of the [oil crisis](https://en.wikipedia.org/wiki/1973_oil_crisis) in the '70ies.
[Answer]
Germany exactly did that after Fukushima. They shut down all their nuclear power plant and completely withdrawed from the nuclear industry, even Siemens which was a big player completely withdrew. They massively switched to coal based electricity. Germany has a lot of coal so it wasn't that bad from an economic standpoint. Modern coal factories don't produce too much smog so environmentaly it was that bad from the smog perspective. CO2 however is another story...
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Dragons are kind of a cult. They are very popular in movies, books and stories in general.
It feels that the dragons are only a better dinosaur. So I wonder, would finding their skeletons affect people's judgement about dinosaurs being so special?
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Dragons...
* extinct.
* can fly.
* can breathe fire.
* have scales.
* have one, three or seven heads.
* have different colours.
* have organs indicating that they might have something similar as human speech
EDIT: I am not sure if all of the attributes can be determined from the skeleton (but that doesn't change the question).
[Answer]
Are triceratops or raptors ignored just because t-rex existed? The same would be true of dragons (although note that your descriptions seem strange, multi-headed beasts in particular are not very practical). Speech-capability might be possible to infer from the skeleton, but colour would not be.
If the dragons had always been known about then they would just be yet another form of prehistoric life. If they were a new discovery then that would be big news for a while, but only for a while then they would be catagorized in with everything else.
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Loosely theorizing from your premiss, I'd say dragons would become **more popular**.
Why?
1. Currently dragons are beasts of legend and are assumed not to be the stuff of real life.
You gain all potentially interested people that connect with what they can see and hear. You loose all people that connect with the imaginary exclusively.
2. We'll know much more about dragons.
You gain all people that get fired up as they learn more about a topic. You loose the group that has made dragons what they want to be, unhindered by pesky real life details.
Ignoring smaller effects like people denying the dragon fossil records in general and small boys limiting enthusiasm to only one big lizard from the now much bigger heap the number of fans lost will be much smaller than the number of fans gained.
[Answer]
**Dinosaurs would be much less popular, dragons it depends on if dragons are still alive**
There's a saying in paleontology: if turtles were entirely extinct today people would be fascinated by their remains. Turtles are bizarre, their bodies are so strange with their limbs inside their ribcage, skulls that make no sense compared to living reptiles, that if turtles were extinct today it would be hard for anyone to imagine how they could exist. Now imagine a turtle that is sixty feet long, has wings, and breathes fire. There's your answer for dragons.
If dragons were real dinosaurs would almost certainly be less popular, as dragons are basically dinosaurs+. Part of what makes dinosaurs enticing to a lot of people is that they were once *real*, and if dragons took that uniqueness away there isn't a lot of reason to favor dinosaurs over them. Dinosaur paleontology would be a niche subject, kind of like how mammal paleontology or paleontology of Triassic archosaurs is today, with the possible exception of a big area of interest in theropod dinosaurs that evolved into birds (but with far fewer people liking dinosaurs for being big and toothy). [Think of how the "less interesting" Mesozoic megareptiles (mosasaurs, ichthyosaurs, pterosaurs, plesiosaurs) are treated today. Always showing up as side roles in documentaries and movies about prehistoric life, almost never the stars of the show, and almost always less popular or more likely to be inaccurate because there isn't as much interest in them.](https://manospondylus.blogspot.com/2020/01/the-weirdest-things-people-have-thought.html)
If dragons were alive today there would be even more interest in them and even less in dinosaurs, as fossil dragons would be seen as important in understanding the origins of dragon biodiversity. Something similar happened with dinosaur paleontology, in the early 20th century dinosaurs were seen as big, dumb, uninteresting evolutionary dead ends that were good for attracting children but unimportant as far as science went, and instead a lot of research focus and popularization was placed on fossil mammals because fossil mammals gave rise to modern horses, cats, dogs, humans, etc. Nowadays things are reversed because of the Dinosaur Renaissance and the dino-bird connection, which has revitalized dinosaurs as active animals and evolutionarily important because they gave rise to modern birds and aren't just an evolutionary side-show.
Another aspect is that before the discovery of dinosaurs dragons didn't look that much like dinosaurs, they looked like mashups of snakes, big cats, hooved mammals, eagles, bats, and crocodiles. It was only after dinosaurs became popular that dragons started looking like dinosaurs with bat wings. If dragons were a real animal it doesn't take much of a leap to think that people would take features of real dragons to make new mythological monsters that are seen as even more alien and fascinating than we find dragons.
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From June 2011 all the way to August, the American Midwest underwent a headline disaster--the overflow of Gavins Point Dam just outside Yankton, South Dakota, resulting in a region-wide flood. The cause of it was a combination of high snowfall and cooler-than-average spring temperatures. 152,000 cubic feet of water went out at once, ruining the likes of towns in South Dakota, Nebraska, Iowa and Missouri.
108 lives were lost in that flood, as well as 8.41 billion dollars' worth of property and/or infrastructure. It has also dumped the banks with silt and drowned the groves, eroding them into steep, cliff-like edges and killed most of them with root rot.
All this damage due to **a simple overflow, one that the Corps of Engineers had been criticized for not releasing the water earlier.**
In an alternate history scenario, Gavins Point didn't overflow, but **collapsed completely**, and the Missouri River returned to its former glory. What sort of damage would we see in regards to lives, property, infrastructure and environment?
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So living in Nebraska and living near the Missouri river I can tell you it was A LOT of water.
Towns were flooded, farms were washed away roads were destroyed...plenty of damage to lives property and infrastructure.
So...this is complicated for a couple reasons.
1. The Army Corp of Engineers release plan while somewhat flawed was also a scapegoat. There is only so much water the system can handle.
2. The upstream impacts of the water were exacerbated by heavy rainfall along the Missouri river basin.
So all that aside...
If the dam were to completely fail the impacts would have been different, better or worse likely depends on specifics.
Locally (just south of the dam) the effects would be catastrophic. While not densely populated the loss of life would have been greater.
This is mainly due to the fact that there would be little to no warning for the first 50 - 100 miles.
Additionally the water would have overflowed east and west more significantly than it did, the impact being greater the nearer to the dam you are.
This is mainly due to the fact that while the river wants to follow the river bed, it is also going to follow the easiest route meaning it spreads out a lot. In short the impact of a total failure is total disaster for anything nearby.
Further downstream the impacts would probably not have been terribly different than they were. You still have time to prepare as you go further down stream. The water jumping the banks near the dam means the total volume of going down river is probably a little higher but not significantly.
If the dam is not repaired then you have all sorts of problems with irrigation and flow control in the following seasons.
So in short the failure would be a giant mess for anyone directly downstream of the dam and would probably end up similar for most other people.
The aftermath would have significant repercussions on regional infrastructure until the dam was replaced/repaired.
[Answer]
# Not much
The Gavins Point Dam reservoir [holds](https://en.wikipedia.org/wiki/Gavins_Point_Dam) about 600,000,000 m$^3$ of water.
The highest ever [flood level](https://en.wikipedia.org/wiki/Missouri_River) of the Missouri River is about 21,000 m$^3$/s.
That equates to about 8 hours of discharge from the dam at the highest ever discharge level.
Thats a lot, and a reasonably bad flood, but it simply isn't enough water to do that much harm. Seen another way, the damn holds back about 492,000 acre-feet of water, enough to put 770 sq miles under a foot of water. Consider that the [floods of 1993](https://en.wikipedia.org/wiki/Great_Flood_of_1993) covered 30,000 square miles.
Moral of the story: the dam's reservoir water capacity was small compared to the amount that had fallen as rain, and while the damn bursting wouldn't have made things better, it wouldn't have made them much worse.
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**This question already has answers here**:
[Can airborne floating/flying islands be scientifically possible?](/questions/33513/can-airborne-floating-flying-islands-be-scientifically-possible)
(16 answers)
Closed 7 years ago.
Your basic, average floating sky island. How would a floating island 1. Get up high, and 2. Stay up.
Here's the info you need to work with:
1. The planet is Earth-like (supports earth like life)
2. The islands aren't man-made
3. Gravity is a below Earth's (Gravity can be as low as .9 or .1 of Earth's)
4. Floating Islands can support life as well
Here's the bonus questions :
1. How would life evolve on these islands (would it be mainly winged or never see outside of the island.)
2. How would humans look at these islands (would they be home to kingdoms or what)
[Answer]
[Link to full avatar answer](https://movies.stackexchange.com/a/14131/43823)
Basically, you could do what they did in the Avatar movie. Their floating mountain has unobtanium in them, which is a room temperature superconductor. They float because of the Meissner effect with the magnetic field below them.
A superconductor is a material that when you cool it down to a certain temperature, it can conduct electricity effortlessly without much energy loss. This allows them to float in the presence of a magnetic field. You can look up the details, but basically, a magnetic field's flux cannot penetrate a superconductor once it becomes superconducting, so it bends and pushes around them instead, allowing the material to float in midair. So, if I add electricity into those superconductors, they'd be able to run in those materials forever. Unless the earth somehow loses its magnetic field, those islands could stay floating forever.
Now unobtanium is a room temperature superconductor, which takes away the requirement for them to be cool to their critical temperature. And since the gravity is lower than that of earth, the magnetic field can similarly be lower than that of earth, which would allow the use of metal tools and such without the tools propelling upwards.
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I'm not sure about the evolution part, so I'll just take a guess. If you want humans on those islands, I imagine life would evolve normally similarly to that of earth, up until about sailing and such.
It probably depends largely on the environment of your islands. How big are your islands? Are they massive continents with diverse biomes, or just small floating island with one single environment? After all, the reason human evolved in the first place is due to the Africa savanna. Without a floating Africa savanna, humanity might not evolve at all and you'd have monkeys eating fruits in their floating island forests happily forever.
If humanity did evolve and formed societies, then depending on how close the islands are to one another, they could build bridges between the islands. If the islands are far apart, perhaps they will never know another island until the invention of the telescope. And they'd still have no means of travel across until the invention of the hot air balloons.
As for if they'd belong to a kingdom or not, it also depends on how big of a population each island can support. Humans naturally form societies and work together. If your islands are small, perhaps they'd form tribes and villages and band together. If you islands are big enough, then they could certainly form kingdoms, given enough time.
[Answer]
## Difference in Gravitational Field
Perhaps gravity effects the island's foundational material differently than the rest of the environment, allowing the island to float. Some possible explanations for why gravity effects the island differently could be:
* **Intentional Alteration:** Perhaps gravity is being manipulated purposefully by humans or an alien race.
* **Accidental Alteration:** Perhaps accidents in gravitational manipulation have left gravity permanently or temporarily effecting the foundation material of the island less than normal.
* **Natural Difference:** Perhaps in your story a certain type of material is naturally effected by gravity less than other materials. This material would then be the foundation of the islands.
* **Natural Fluctuations:** Perhaps in your universe, gravity's effect on certain materials naturally fluctuates from time to time.
## Evolution of Life on Floating Islands
I think the main issues affecting evolution on a floating island could be termed as environmental factors. I feel it is the envionment that dictates how life can evolve. Some major environmental factors would be:
* **Size of the island:** The larger the island, the more likely life will not need to evolve to leave the island. The smaller the island, the more likely life will have needs going unmet on the island, and would therefore have to evolve to get the needs met from the surrounding environment. If the island was only a few feet wide, the possibilities for life evolving there would be much less than if the island was thousands of miles wide.
* **Movement:** If the islands are very small and moving very quickly, life evolving there would need to tolerate this movement, whereas if the islands are large and don't move at all, movements would not be as big of an issue. Also, size, direction and frequency of movements would affect evolution. Tiny movements would probably affect evolution less than enormous movements. Direction of movements, such as linear, spinning, flipping, wobbling, etc. would affect evolution. Frequency of these movements would also play an integral part in evolution. If sudden huge movements happened every day, life would have to be able to withstand such shifts, whereas if there were only a few movements per decade, life could be less affected by them.
* **Existence of other land masses:** The presence of other lands gives evolutionary reason to possibly go to them. Lack of other places to go, though, gives little evolutionary incentive to evolve to leave.
* **Limitations on travel to or from the island:** If there were hinderances to leaving the island, such as severe weather surrounding the island, then that would affect the evolution of any life trying to leave. Lifeforms leaving the island could perhaps jump, fly, float (like a blimp), glide, fall (perhaps not being able to return), teleport, or perhaps even use tools to build machines enabling them to leave the island. If waterfalls or vines were there, they could be used as travel vectors, or even fallen trees or long rock outcroppings could be used as bridges to nearby lands. Strong winds, sideways or updrafts, could also be useful for travel.
## How Human View the Islands
I think that depends on many, many factors, such as:
* **Size:** If the islands are only a few feet wide, they could be much less interesting than if they were significant landmasses. However, clouds of small chunks of land, like hail storms or like fields of small asteroids, could evolve much different lifeforms than large lands.
* **Number:** Rarity of floating islands could make them prized or revered; abundance could render then uninteresting; overabundance could cause them to be annoyances.
* **Resources:** If the islands were home to valuable resources, humans would definitely like to get there and gain control of the resources; if the islands were innocuously plain, with nothing to offer, people might have little interest.
* **Protection:** If humans were threatened by other elements, such as floods, fires, wars, predators, etc, they might want to take refuge on the islands, if the islands could provide safety.
* **Ease of Travel:** If it is easy to travel to and from the islands, they would be treated differently from islands extremely difficult to reach. Extreme difficulty could be useful in providing protection from invaders, and extreme ease of travel could give rise to effortless trade and expansion.
[Answer]
Apart magic, the only solution is see is levitating with magnetic field, like in the movie Avatar:
* The magnetic field on the planet is way stronger than earth
* On some island, there are a lot of ore of some metal that act as a strong magnet: the magnetic field is strong enough to support the island
* Violent geological event like earthquake or landslide can weaken link between island and ground, allowing the island to float in the air.
**Bonus question:**
1. Life on theses island would initially the same ecosystem in regular island when the separation occur due to the fact floating island receive the same amount of sunlight and rain than regular isles, there are just no geological activities so no hot spring. However, with no direct access to sea, animal that relies on fishing to survives will disappear or change. Moreover, the lack of accessibility will prevent new animal or plant to establish in this island, excepting bird and seeds carried by them.
2. Due to the fact that island are inaccessible and certainly moving, no country could claim theses floating island until the discovery of flying locomotion like hot air balloon. This restriction could lead to better interest in flying transportation in order to access theses mysterious island. Once flying discovers, floating island would act as regular island and be used as airport and military base. At last, the abundance of strong magnet ore on each island could be useful for any science field that use magnet.
[Answer]
The simplest and most probable mechanism would be the islands have lower average density than air (basically think of huge natural balloons).
This would be more probable in environments where there is lots of air (increasing the average density of the air). It would require some natural mechanism that forms gas traps and a mechanism that produces lighter than air gas in large quantities. Membranes trapping large amounts of light gasses could form, albeit this would require some exotic chemistry. On microscopic scales this does happen in earths oceans - a variety of plankton organisms enclose oils/fats that makes them lighter than water.
But anyhow in an environment that facilitates earth like life, huge islands would not be stable over geological time frames. Erosion by rain would disolve them in comparably short time frames; any matter lost to erosion does end up leaving the island eventually. Collisions between islands would also act to accelerate their eventual destruction. This would happen regardless of what their mechanism for keeping afloat is.
Without a basis for stability over geological time frames, life spread on these islands would not have time to specialize too much for their environment. Also, most likely islands would be very dry, arid environments. Rain would either run off, or if the geometry traps it in a pocket make the island so heavy it sinks to the ground in a few years. They might be still host universalist species, or seasonally (e.g. as breeding ground for avain species).
Working up a scenario where floating islands can believably exist (for the sceptic reader) will be exceptionally hard, if not impossible.
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I'm trying to design human like race where all the children are born as girls, but later in life **some** of them switch to male, but no sooner then 15. Usually only the most dominant women switch, so in normal times women are majority of the population, but in exceptional situations like war or overpopulation gender ratio might be reversed.
As soon as transformation starts woman is infertile until the transformation is finished. I have chosen this in order to avoid self impregnation. Transformation is irreversible, man can't transform back into woman. The woman must start transformation before certain age, otherwise she will stay woman for good. I haven't decided on the exact age until I know how long should the transformation last.
How many years should the transformation from woman to man take?
I don't know much about biology but I'm expecting some plausible approximation rooted on examples in either humans or animals, like Frostfyre's links about [genetic disorder](http://www.newsweek.com/rare-condition-causes-girls-become-boys-puberty-374934) and [mice hormone experiments](http://www.popsci.com/science/article/2009-12/gene-switch-transforms-adult-female-mice-males).
[Answer]
clownfish take about a month, hormone therapy takes about 2 years to show strong effects, so assuming they stay active approx six months to a 1 year a decent number for a natural process in a human size animal. if they go into a immobile cocoon metamorphoses stage like insects you could get away with a month, not including the binge eating build up.
there really is not that much difference between male and female, growing the new nerves and organs is what takes the longest.
basically the faster it happens the less other things they are going to be able to do at the same time.
[Answer]
# About six months
As we live and grow, our bodies shape and reshape theirselves, in very young children at a rate of approximately their body weight in new growth per year, tapering off as we edge towards 25 years of age. While reforming skin and nerves already laid is complex in humans, it needent be in this putative breed, and we can use the base regrowth rate.
For (human) children around ten years of age; something on the order of a lost fingertip can be completely regrown in a month, so for something more complex and sizable, but not *so* sizable, about six months at the base growth rate would likely do. (We are after all talking about reformation of existing structures, and nothing so dramatic as a lost limb.)
[Answer]
How about half an answer?
We have an example with humans. Normally we have males whose body responds normally to testosterone and they're male. We also have "males" whose body does not respond properly to testosterone, they appear female but test as XY and often exhibit failures of the reproductive system.
However, testosterone actually comes in two versions. There is a very potent form released in-utero that causes boys to be boys. It's possible to have a failure to respond to this form of testosterone but still respond normally to normal testosterone. The result is an apparently female baby that turns male when puberty hits.
<https://en.wikipedia.org/wiki/5-alpha-reductase_deficiency>
Unfortunately, I haven't encountered anything that says how long it takes but it never even occurred to me to wonder until this question came along. I'll leave tracking down this number as an exercise for the reader.
[Answer]
However long you want it to take.
When the females of your species already have a fully developed penis and working testes, these could activate immediately.
When the females have these organs fully formed but dormant within their bodies and they first need to migrate outside and become active, it could be a matter of days or weeks. Human sperm cells have a [gestation period](https://en.wikipedia.org/wiki/Spermatogenesis) of about 3 months, so when the testes were completely inactive before the transition, it would take at least that long until the specimen produces fertile sperm.
When these organs need to form from scratch, it might take month to years.
In either case, it might take longer for secondary sexual characteristics to change than for becomming fertile.
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This is a religion i am creating for a possible book in progress. It takes place in a world created by gods. This is a world of humans, dwarves, elves, and magic. I would like to create a religion which all three races follow, but which is based on a lie. My three gods are as follows:
**Appolyon**
* "The Destroyer"
* He created\* the dwarves and based them on himself. Their natural instinct to mine into the earth and to create things by chiseling into stone comes from his destructive tendancies.
* He gifted the world with Destructive magic: spells related to fire and lightning and the ability to raise and control the dead.
* He seeks to destroy the world and its inhabitants out of jealousy. He is angry because Leda took the dwarves away from him to protect them from his wrath.
**Dusan**
* "The Holy Judge"
* He created the humans, based on his own desire to learn. Humans are more changeable than the other races and are curious, seeking new knowledge instead of sticking to old ways.
* He gave the world Control magic. The ability to move objects, to predict events, and to scry to obtain knowledge.
* He judges the dead, deciding whether they should go to Leda's heaven or be cast into the abyss where Appolyon is imprisoned. He also rewards his followers with knowledge and, with that, wisdom.
**Leda**
* "The Creator"
* She created the world as a barrier to protect the three races from Appolyon, and to stop him from returning. She created the elves as a graceful and long-lived race. The elves revel in life and creation, and refer to their god as "Leda-Aurora" - Creator of Light.
* She gave the world Creation magic to grow and heal. Only the god herself has the power to create matter, however her followers can use her magic to heal wounds and to encourage growth in living things (the elves use this magic to enchant trees to grow into houses, and to sustain vibrant life in their woodlands).
With these three gods, there comes a religion in the world. There are few who doubt the existence of these gods, since without them magic would not be possible. Any person studying the arts of magic can learn basic spells, but it takes true loyalty and devotion to be able to use the magic gifted by a particular god. Training mages can choose to follow either Dusan or Leda and spent years in study in wizard towers. The religion is based purely on these two gods, since anyone found to follow the ways of dark magic is punished with execution. Dwarves rarely use magic, since their affinity to destruction constricts their abilities with other types of magic. They despise Appolyon and worship Leda, their saviour, however few Dwarves have the ability to become true mages.
**Here's the catch**
Everything you have read so far is what is believed by the elves, dwarves, and humans. It is in fact only half-true. The truth goes as follows:
* Appolyon seeks to destroy the world not to seek revenge, but to free the races from their prison. He wants them to return to their home and re-populate the abyss with life and matter.
* Leda created the world out of selfishness. It is a prison to contain the three races for herself and Dusan to share.
* There is no heaven. When a soul dies it simply wanders the world, imprisoned there forever.
* Dusan is the one with true control. He whispers to people in their dreams and influences events in the world. He also manipulates the gods themselves, pitting Leda and Appolyon against each other for his own amusement.
**What affect does this have?**
Mages worship gods, the people follow the mages. If the gods are corrupt, what effect does this have? Leda and Dusan are both evil, imprisoning the races on earth while Appolyon is attempting to free them. The higher you get in the church, the better you get to know your god. Since the gods can choose who to bestow their magic onto, this means that the most powerful mages of creation and Control are corrupt people. people who sympathize with their respective gods. The leaders of the church lie to the people to gain favour. How can i represent this?
**The actual question, finally**
How can a corrupt religion such as this control so many people? How do you appear benevolent and holy and mislead people at the same time? What sort of political systems would be best suited to this religion? **How can I lie to literally everyone, and still have complete control over them?**
>
> \*On the subject of creating races. Yes, i am aware that a god of *destruction* does not simply *create* Dwarves. My answer to this is that the three gods worked together. The universe contained energy and matter. Leda created life, Dusan formed bodies to contain it, and Appolyon added death to make the races precious. With this prototype, the individual gods then put some of their own characteristics in to create the three races.
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[Answer]
Disclaimer: *Unfortunately I suspect any answer to this is going to be quite provocative about the nature of religion, that is not my intent, merely a side effect.*
Let's start with a question: **What is religion?** With the answer simply being: **What people believe to be true**. Actual truth has no bearing on this, otherwise how could a world like ours support so many contradictory religions. The vast majority of people have to be wrong, following something that isn't true while believing, often wholeheartedly, that it is.
Let's simplify your model. You have a world with a choice of three gods.
1. A god of destruction
2. A god of justice
3. A god of creation
Which of these do you choose to follow?
This is the choice as far as the normal illiterate peasant in your population sees the world. There are no subtleties as there are in the descriptions you give. You argue of course, that a god of destruction is required for the normal order of things, to ensure that the circle of life is complete. However not many people are going to choose destruction as their way of life, and those who do possibly aren't the most sane anyway. On the whole, the credulous are going to choose between justice and creation.
As with any large group, people at the top of the pile aren't necessarily there because of how dedicated they are to the cause, but often how dedicated they are to having power over others.
Your world is no different from ours, power corrupts, the people who seek and gain power are corrupt. They find as they rise that everyone is corrupt, all the way to the top, gods included, what's new?
[Answer]
Why do the God's motives matter at all in this case?
Think about these questions answer these questions:
* Leda gave the 'mortals' them the world that they exist in and the world that is all they know. What has she taken from them? In what sense is she selfish?
* Leda gave the mortals their entire existence, but 'trapped' them inside this existence she made for them. How is it relevant that there is more universe out there that they can't exist in? Does it make someone selfish if they give you a million dollars for free instead of 10 million dollars?
* Apollyon wants to 'free' mortals by destroying them. Do they want to be destroyed? This is the same problem from the Matrix, except instead of offering someone the choice of red pill/blue pill, you are forcing them to take the red pill and wake up to some nighmarish existence that they probably aren't interested in. Did Apollyon ask them if they wanted their world destroyed? How does this make Apollyon the good guy?
* Dusan incites people to evil or violence by pitting Apollyon and Leda against one another. Apollyon on the other hand, wants to destroy the world. Given the choice, would you rather have a high murder rate, or a high genocide rate? Living in a violent world sucks, but it beats not living at all.
* Who on god's green earth would believe a guy (Apollyon) that says he wants to destroy the world so he cane move you to another world that he made? To any rational person, that would sound like a lie; to any fearful person that would sound like a threat.
From the perspective of the 'mortals', there is one god trying to destroy them, and two other gods trying to protect them. Which one would you worship?
While Apollyon may seem to be corrupt to a third person omnipresent viewer, when taken from the perspective of an actual person (or elf, or dwarf) living in this world, there is no doubt that, even given all the information in this post, those persons would conclude that Leda and Dusan are in fact the good guys. They **protect all creation from utter destuction** even if they have some personality flaws.
Your religion isn't corrupt at all.
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To answer your first question yes I think that's top members of the mages/ priest would be corrupt but that doesn't mean that all the Mages/ priest would be. Fact I believe many would be very sincere. After all too much corruption in the ranks will make the organization uneffective. I don't think the gods want that.
As for how to religion would be able to put control people same as my above answer. While the leaders may be corrupt the lower and middle ranks are very sincere in their beliefs, they are the ones that people have the most contact with and then since they know if they're not lying to them they believe their representation of the gods. Would be actually very easily as long as the evil gods don't do anything to evil, the occasional atrocity could always be blamed on the God of destruction.
As for how you lie to everyone and still maintain control over them look at Adolf Hitler, he said once tell a lie big enough often enough and loud enough and the people will believe it.
As long as you live isn't mixed with just enough truth as to appear viable and discovering the truth on their own is difficult or impossible for the people, there will be very easy to control them and yet continue on them. governments do this all the time
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In a world I am building, birds have become the dominant order instead of mammals. Among all of the birds, the New Caledonian Crow has become the dominant sapient species. In a [previous question](https://worldbuilding.stackexchange.com/questions/53098/planet-of-the-aves-low-tech-weaponry), I asked about weapons a bird would use while flying, now I wonder about their armor.
Is it possible for a set of medieval age armor to exist that would allow for a bird to still fly while wearing it? If so, what would it look like?
A list of all Planet of the Aves questions can be found [here](https://worldbuilding.meta.stackexchange.com/questions/3939/planet-of-the-aves-series/3940#3940)
[Answer]
Flight is very much dependent on lift and weight.
* Modify the armor so that it helps with flight--extending wingspan, rockets, propellers, that kind of thing, just a little something extra. I think that this can compensate for the extra weight of the armor. (this all depends on the level of tech). Even though this is Medieval, since these folks think more in terms of flight than we do, they would be more advanced in thinking when it comes to this.
* Use lightweight paper or cloth armor. Armor would have to be extremely lightweight but still able to protect. Here's a [link to a great paper on paper armor](http://mandarinmansion.com/articles/Chinese%20Paper%20Armour.pdf). Mythbusters [also covered it](https://www.youtube.com/watch?v=dvhcVCmF9a0). Layers of silk, wool, certain weaves will be helpful. Silk is EXTREMELY effective as a final layer, so do research that, and its qualities. Metal is death. It's just too heavy.
Center of mass can be covered, underneath would likely be more important than back coverage, if you are specifically worried about ranged attacks. Your main problem is that wings will necessarily be vulnerable because it is their design which enables flight. To cover them with armor would hinder that.
Weight, when it comes to armor and weaponry is going to be very important. I would venture that invading armies might build temporary invasion towers, so that soldiers wouldn't have to take off from the ground with all that stuff. If you have armored troops, that would be what you would do, otherwise the space for take off would be pretty large and it would be difficult to deploy troops quickly. It creates another vulnerable point, certainly. But take-off towers would be helpful to armored birds.
EDIT: Thinking about this, I would say that nearly any principle of gliding/flight that we've discovered, these creatures likely know (the physics, not engines or anything). Further, I would say that they would develop gliders, for the same reason we developed carts with wheels. While we naturally walk on the earth, designing things to do it more efficiently, carrying more of a load is something that we developed as we needed it. Just because these creatures think in terms of flight and this is their ordinary method of egress, I would posit that they would look for ways to carry more in order to drop things on others in battle. They might well be on the level of [Davinci's flying machine](http://www.da-vinci-inventions.com/flying-machine.aspx), if not further. Yes, they can fly, but having a machine which can offer better protection (as a kind of armor) might well be what they might do. In fact, I would venture that they would develop methods of flight far faster than they would something like a car, especially if flight is their major method of transportation. There might not even be roads because of this. For troops to move heavy things, they might have to go on foot, but they will constantly be looking for ways to move things through the air. If you attach a glider/flying apparatus to wings, using the wings as a control method, you can get away with more weight in the armor, with a way to bail out and glide down with your natural wings.
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Watching how a bird flys (I live with one in the house), I see that he has great control over the aerodynamic surfaces and **reconfigues** constantly, as part of flapping, steering, complex intair maneuvering, and choice of speed.
Any rigid covering would seriously spoil that.
Look at the tail alone: it can fan open or closed, and bend downward and move left to right and twist down-left or down-right.
Any covering would have serious problems.
Only thing I can think of is a **per feather** coating or re-enforcement! Recall the earlier posting on battle. Feathers can be fouled or disrupted very easily.
So what if, after a perfect grooming, he coated individual feathers with resin to prevent them from coming unzipped so easily or being cut or allowing blades to pass through them so easily? They could also apply thin foil of some kind at the same time.
That is, as an evolution of *repairing* cut and damaged feathers, they reenforce “armor” individual feathers or portions of the feather. This makes it harder to fold up when resting as it’s bulkier, but mostly doesn’t interfere with the full motion needed.
Also, you know how clipping wings huts flight? And they learn to repair flight feathers? Well, why not **extend** the flight feathers? They can adapt themselves to bear more weight or have razor edges or whatever.
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I think a major drawback to birds wearing armor, is that they most likely will not be able to armor their wings. Wings need to be in contact with the air to work properly, so wing armor would need to be at once skintight and offer projection. Metal is out of the question, as are almost all man-made materials. Maybe a thin film of kevlar could work, but that's about it. Birds are more than 50% wing by area(and the larger the bird, the higher the percentage), and probably most vulnerable at the wing. So individual bird-armor seems unrealistic.
However, I don't think this entirely rules out armor, just individual bird armor. Several birds would be able to carry a large cloth capable of stopping most projectiles, providing tactical cover for other birds to shelter behind(the cloth can be extended upward with wire so it protects the birds carrying it). These cloths would be like mobile trenches, and battles might turn into encirclement contests between these mobile defenses. You could add slits to fire projectiles through.
You could get creative, either way I think this is how bird armor is going to evolve. Some birds will carry the armor, while others will perform combat function. Individual armor just doesn't seem to make much sense.
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In this context, my world assumes an infinite universe so parallel Earths are possible and probability isn't an issue. My planet has half the gravity of Earth but an atmosphere 12x denser, although, answers do not have to be restricted to this planet specifically and can be general in nature.
I've read that Insects, for example, walk very differently to larger creatures as gravity doesn't affect them in the same way - See [this article](http://www.wired.com/2015/07/physics-says-tiny-ant-man-running-weirder/). So on a planet with less surface gravity, how would it affect the ways things walk, look and evolve? Presumably, the weight of a creature would scale proportionally to the change in gravity. In this case, things could grow [1.26x](https://en.wikipedia.org/wiki/Square-cube_law) larger at $0.5g$. A T-rex parallel, for instance, could be 15.5m long instead of 12.3m. And the weight limit of flight would be doubled (not accounting for Air Density).
I've outlined a few things I feel might be effected:
* Would bipedals have more of a spring in their step so-to-speak?
* Would animals in general evolve to move slower as each step would
propel them forward with more force?
* How would falling be affected with a lower terminal velocity? Would
falling no longer be an issue?
* If land-animals first evolved with 6 limbs, would the increase in
stability make them more likely to retain the extra limbs through the
evolutionary process?
* Or would the reduced weight of these creatures counter-act the change
in gravity? So a human with half the mass in $0.5g$ would look the same
as a regular human on earth whilst walking (if you were watching a
video per-se).
I'm thinking more about how it translates into a visual medium so I am specifically interested in how the motions of movement would be different.
Bonus points if you can work Air Density into your answer.
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The question already deals with possible answers. However, terminal velocity is more affected by air density than acceleration due to the reduced gravity. Expect terminal velocity to be fairly low. Drag forces increase proportionally to the mass density of air. The terminal velocity for a falling human, on Earth, is approximately 120 miles per hour. On your planet this would be reduced to about ten miles per hour.
Evolution would favour flight, so flying and gliding organisms will be in abundance. This could include creatures that simply fall as terminal velocity would be so low.
Slower rates of falling could result in slower reflexes and neural speeds. Creatures wouldn't need to correct so rapidly to falling so they would react in what would appear to be slower motion (not slow motion as seen on film or TV). They only need to act, react and save themselves more slowly than high-gravity creatures like humans from Earth.
Hopping and jumping forms of locomotion would appear to have an advantage in low gravity of 0.5 g, but the denser atmosphere would be an impediment. However, this is an impediment that lifeforms could take advantage of, by short-rang gliding.
Normally gliding animals drop from trees to gain the speed they need to glide. On a low gravity, high atmospheric density planet, gliding speed might be achieved at ground level enabling creatures to travel in short, low bursts. This might consist of a kangaroo-like jump, spreading its glider possum-like wings and gliding further than the jump normally allow.
Hexapods might be more probable on high-gravity planets. They are more likely the result of benthic lifeforms (ones that live sea bottoms). On Earth, most land animals are tetrapods because our remote ancestor was a teleost fish and its four fins eventually became our four limbs.
Whether low gravity planets have their animal life as tetrapods or hexapods depends on the quirkiness of the planet's evolutionary history independently of its gravity.
## EDIT:
Almost so obvious it's easy to forget. The wind on a planet with twelve-times air density will be an exceptionally powerful force. This makes the possibility of wind-born lifeforms a high probability. On Earth there are many seeds and spores that are wind-borne. Even spiders, particularly social spiders, can create masses of web that can be carried on the wind.
Recently in Australia there were outbreaks of the [Russian wheat aphid](http://www.outbreak.gov.au/current-responses-to-outbreaks/russian-wheat-aphid) that had arrived from South Africa and carried by wind.
High-density winds will make wind-surfing lifeforms effectively a certainty. Compared to wind-borne organisms on Earth on your hypothetical plabet they will be reasonably large.
[Answer]
Retaining air is largely dependent on the strength of gravity. Gases expand until they hit the wall of the container; planets have no container, so the only thing stopping the atmosphere from slowly bleeding off as individual molecules achieve escape velocity is gravity. This is why Mars' atmosphere is gone; at .38G, lightweight gases like water and oxygen will slowly waft away into nothingness. At .5G, this will probably still happen.
So one of the effects is that your superdense atmosphere is going to be composed almost entirely of denser-than-air gases. What those gases are will greatly affect evolution; the most common organic gasses I know of would be various hydrocarbons (propane, etc) or alcohols. There won't be much oxygen, so fire won't be a big concern. There won't be much water, because in gaseous form it will tend to waft away too. So any oceans will be exotic, like a hydrocarbon sea.
Life forms living there will be utterly alien biochemistry-wise.
As for size, .5G makes life much easier for organisms; it's easier to support your own weight around, it's easier to pump blood through your body, it's easier to move around and not as hard to get up to really high speeds.
Look at the biggest land-based lifeforms on Earth. They died out, because it's really hard to be a ginormous land animal. But huge sea animals are still relatively common. Because it's easy to be huge in the sea; you just have to be buoyant, and the water will literally support your weight for you. So I'd expect a lot more megafauna and megaflora.
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Try walking chest-deep in water. This will reduce your weight *and* illustrate the effect of viscosity and drag. How do you change what you do to try and make progress?
When you walk, you *fall* forward. If that is happening slower, you must wait for it! Your normal gait would be impossible. Meanwhile you must reach forward with the limb, and this now has significant resistance.
I predict different useful modes:
① hopping with gliding. Once you loft, you can “swim” against the thick air and continue to control your motion.
② high-traction crawling. Think of a lizard walking. You don’t want to lose contact with the ground at all, and your reduced weight makes it more difficult to generate thrust, so you need large feet or gripping of items as you pull yourself forward.
[Answer]
In your description, the 12 atmosphere pressure is more appealing than the halve gravity.
## Lighter than air flight
As everybody notice, the combination would favor flight. But maybe, they underestimate it.
12 atm means 12 time the Archimede force. There could be lighter than air animals.
Even for heavier than air, it is very possible that they'll get easily blown by the wind (especially on a standing position).
Also dense atmosphere means strong wind and land erosion. Your world may be super-flat making ground effect flight possible (like [flying fishes](https://en.wikipedia.org/wiki/Flying_fish) or [ekranoplan](https://en.wikipedia.org/wiki/Ground_effect_vehicle) (yes, I love ekranoplan idea))
## Insect rules
Arthropods have a different breathing system (actually, they do not breath) making them very dependent on oxygen partial pressure (is it also \*12? ). In your world, dragonflies may prey on birds.
## East to west
Dense atmosphere means strong winds.
On an earth-like planet, winds will blow toward west in one hemisphere and toward east in the other.
If the winds are strong, it may happen that animals continuously migrate in this direction. Especially if lighter than air.
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Inspired by this [answer](https://worldbuilding.stackexchange.com/a/51459/4995), If that Lunar-plant is used as a weapon (pointed toward specific cities/forest/seas/lakes), how much damage it could really do? Is that able to burn cities, or anything?
I assume for fun Full Moon.
To recap here's how the weapon works:
* Fill the moon with mirrors, and direct them to reflect light on a specific point of the Earth
* Due to mechanical orientation errors, and small imperfections the light is not concentrated into a dot, but into a small circle of about 3 kilometers diameter and with a gaussian distribution of sunlight.
* Like in solar plants, mirrors are slightly curved (parabolic shape, with focus point on Earth) in order to try to focus sun of a single mirror to a single spot.
The working principle is the same of Solar plants, just on much bigger scale:
[](https://i.stack.imgur.com/BvYOv.jpg)
(picture from [wikipedia](https://en.wikipedia.org/wiki/Solar_power_plants_in_the_Mojave_Desert))
[Answer]
First of all, **see @MichaelKarnerfors's answer** for why you cannot actually build this with mirrors. You'll need more sophisticated equipment that absorbs the sunlight and re-emits it towards Earth in a focused beam. The laws of themodynamics require you to waste a good portion of the energy in the process. Assuming you do this...
Solar irradiance to the Earth's surface, not accounting for atmospheric absorption, is about $1200\;\frac{\text{W}}{\text{m}^{2}}$. Let's assume that the full Moon is the same distance from the Sun as the Earth, and that the mirrors are perfect, so that $1200\;\frac{\text{W}}{\text{m}^{2}}$ of the moon's surface is reflected onto the earth.
The moon's surface area is [38 million km2](http://www.space.com/18135-how-big-is-the-moon.html). Given that half of it is illuminated, let's say we can use about 15 million km2. Focusing this on an area of 7 km2 means that the power delivered to the target is two million times that of direct sunlight, or $2.5\;\frac{\text{GW}}{\text{m}^{2}}$.
### The first second
Initially, the atmosphere is mostly transparent. Normally, about 20% of solar heat is absorbed or reflected by the atmosphere; let's say 10% is absorbed by the atmosphere, which is $0.25\;\frac{\text{GW}}{\text{m}^{2}}$. In one second, this delivers $0.5\;\frac{\text{GJ}}{\text{m}^{2}}$ to the atmosphere.
The other 80% of the power, or 2 GW - shines on the land or ocean below. Everything flammable immediately catches fire.
Given that "the mass of a column of air with a 1 cm2 cross section is almost exactly 1 kg" [1](http://www.indiana.edu/~geog109/topics/10_Forces&Winds/GasPressWeb/PressGasLaws.html), we can [calculate](http://www.wolframalpha.com/input/?i=(first+ionization+energy+of+nitrogen)+*+(1+mol+%2F+14+g)+*+(1+kg+%2F+cm%5E2)) how much energy is needed to ionize the nitrogen in the atmosphere; we have more than enough.
The entire atmosphere over that city-sized area would turn to opaque plasma in less than a second, sheltering the earth for a little while, until it approaches equilibrium (about the temperature of the sun's surface). Then it glows very brightly, delivering all its energy either back out into space, or at the ground below.
### Afterwards
Let's say that half of the energy is radiated outwards, and the other half inwards, delivering about $1\;\frac{\text{GW}}{\text{m}^{2}}$ in each direction. Everything exposed on the surface is vaporized by the light of a million suns, and most of it turns to plasma too.
As for lakes, let's assume that the entire 1 GW is used to boil water. Heating water to its boiling temperature, then boiling it, takes about [$2500\;\frac{\text{k}}{\text{kg}}$](https://en.wikipedia.org/wiki/Latent_heat). If the clouds of steam and denser water plasma don't block the light, the weapon vaporizes water at [0.4 meters per second](http://www.wolframalpha.com/input/?i=1+GJ+%2F+s+%2F+m%5E2+%2F+(2500+kJ+%2F+kg)+%2F+(density+of+water)), which means a lake of average depth 40 m would disappear in about two minutes.
Worldwide geological effects would probably be small, since this light is a small percentage of what normally falls on the Earth, just more concentrated, and sunlight doesn't currently affect worldwide geology. However, I imagine that if the atmosphere doesn't spread out the heat too much, this weapon could create some volcanoes by melting a hole through the Earth's crust.
See also <https://what-if.xkcd.com/13/> and especially <https://what-if.xkcd.com/141/>. The lunar reflector is millions of times weaker than focusing the entire sun in the latter link, so in this situation the earth's surface wouldn't be stripped away, there would be no x-rays, and people on the other side of the Earth would survive.
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# You get two Suns. You do not get a fire.
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> Due to mechanical orientation errors, and small imperfections the light is not concentrated into a dot, but into a small circle of about 3 kilometers diameter and with a gaussian distribution of sunlight.
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The error in your reasoning is to assume that the Sun's reflection from any of these mirrors will end up on a 3 km "small circle". That will not happen. The smallest circle you can get has a radius of slightly more than 1700 km.
This is because each of your mirrors will be the equivalent of a [pin-hole camera](https://en.wikipedia.org/wiki/Pinhole_camera); they just have the added "bonus" function that you can reflect the resulting images anywhere you want.
[](https://i.stack.imgur.com/ct0Zk.png)
The radius of the resulting Sun image from each mirror will be:
$Radius\_{Sun Image} = \frac{Radius\_{Sun} \cdot Distance\_{Moon To Earth} } {Distance\_{Sun To Earth}}$
We do not need to pull the numbers on this because we know that ratio already, from Solar eclipses: when viewed from Earth, the Moon appears as large as the Sun, so the resulting Sun-images on Earth, as projected by all your Moon-mirrors, will be as exactly as large as the Moon.
So if all your mirrors are perfectly flat, and perfectly reflective, the mirrors simply transfer all the incoming sunlight from the Moon and instead deposits it on an area on the Earth that is as large as the Moon.
**So if you manage to align all your mirror perfectly, and the mirrors have a an absolutely perfectly flat surface, and are 100.00% reflective, the only thing that happens in practice is simply that you get two Suns instead of one.**
And this only happens on the parts of Earth that are actually covered by this Sun-image, which will be less than 5% of the Earth's surface.
And while this is an impressive feat, it has some pretty severe downsides:
* You do not fulfill your objective of creating a weapon of mass destruction.
* You get a very cold Moon, at least on the side facing Earth
* On 95% of the Earth's surface, you can no longer see a beautiful Moon
* On the remaining 5% you get another copy of the Sun instread of a Moon.
* You wreck your entire military budget that could be spent on better things, like throwing rocks at your enemy.
Oh trust me, if you take the entire budget you would have spent building Moon mirrors and convert that into tossing rocks in a 3 km radius circle on Earth, I guarantee your enemy will yield soon enough. :D
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Technically it isn't a laser since you are just reflecting sunlight, which comes in incoherent wavelengths. A laser with that power would be far more effective, especially since you could "tune" the frequency to go through one of the spectrum "windows" where the atmosphere is transparent to energy of that frequency (note, this isn't 100% transparency, just "more" transparent).
OTOH, most laser mechanisms suck at converting energy to laser light, as little as 20% of the incoming energy could are converted to laser light. Even the theoretical maximum efficiency of Free Electron Lasers tops out at @ 65%, which is nothing to sneeze at, but we would have to hope that the tuning to shoot through one of the "windows" and the efficiency of laser light vs incoherent light will more than make up for the conversion losses.
Like then solar mirror described by lirtosiast, there would be a moment where the incident energy would flash the atmosphere into plasma, but since we tuned the beam, the energy would strike the ground first before the energy of the beam interacted with the atmosphere. The diameter of the laser could be arbitrarily large, the minimum diameter would be defined by the lasing mechanism, wavelength and focusing mirror
From [Atomic Rockets](http://www.projectrho.com/public_html/rocket/spacegunconvent.php):
>
> Laser beams are not subject to the inverse-square law, but they are subject to diffraction. The radius of the beam will spread as the distance from the laser cannon increases.
>
>
> RT = 0.61 \* D \* L / RL
>
>
> where:
>
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> RT = beam radius at target (m)
>
>
> D = distance from laser emitter to target (m)
>
>
> L = wavelength of laser beam (m, see table below)
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> RL = radius of laser lens or reflector (m)
>
>
>
Obviously you will have to set the parameters for whatever effect you are hoping for.
I suspect that the time and effort needed to build an actual laser powered by the energy collected by a massive lunar mirror farm will be counterproductive, since the mirror itself will be pretty effective against the Earth. Where building a laser becomes useful is not to target the Earth, but as the drive system for an interstellar starship, for high speed solar sail commerce across the solar system, and as the ultimate weapon to threaten planets, moons and asteroids anywhere in the solar system ("[That's no moon](https://www.youtube.com/watch?v=EVekNsgUqn4)!")
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The [tomte](https://en.wikipedia.org/wiki/Tomte) is a creature from scandinavian mythology. It's pretty small, humanoid and has clothes and a beard. They live on farms and in houses where they help out with farmwork and other labour, though they stay out of sight. They don't require much except being respected and having food (like porridge) offered to them once in a while. Their abilities include having the strength of several grown men despite their small size and being good at taking care of animals. If offended somehow, their behaviour switches around to vengeance and spite. They can destroy the crops, make the animals sick, assault the offender or just cause general mayhem. There is usually only one tomte per farm, they don't live together.
Is there a realistic way this creature could evolve? Could they have existed on earth with our current understanding of physics and biology and, if not, how close could we get?
[Anatomically Correct Series](http://meta.worldbuilding.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
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Sounds like a chimpanzee.
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> small, humanoid
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Obviously, that's what they are.
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> clothes
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Anything can wear clothes. The hosts expect it of them and train them as such. Or, they may need warmth in the climate same as the humans.
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> and a beard.
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Ok, they don't shave. Again, nothing odd here except for style choices.
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> They live on farms and in houses where they help out with farmwork and other labour, though they stay out of sight. They don't require much except being respected and having food (like porridge) offered to them once in a while.
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That describes any smart domesticated or socialized animal. You could be talking about your dog here, or the barn cats.
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> Their abilities include having the strength of several grown men
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This in particular makes me think of nonhuman apes. A chimp has enormous strength relative to us.
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> If offended somehow, their behaviour switches around to vengeance and spite.
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Nothing novel here. Non-human intelligence like a farm animal or pet does that.
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> despite their small size and being good at taking care of animals.
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They learn the chores and can perform them. Dogs learn their roles but it sounds like you mean general farm hands which require *hands*. Have you heard heard about the [baboon who got a job as a railroad switch operator](https://en.wikipedia.org/wiki/Jack_(chacma_baboon))?
Most of what you describe is not special. What is specific sounds like it could be a real-world ape. More interesting to the story would be to make them a homonid that did not go extinct but took up with the modern humans when they started agriculture.
Nothing special is needed to *explain* their form and abilities. All that is normal for a homonid and for most of their existance there have in fact been multiple [hominin](https://en.wikipedia.org/wiki/Hominini) species extant at the same time.
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So, consider the story of wolves and modern humans and contrast with the case of [neandertals](https://en.wikipedia.org/wiki/Neanderthal). Suppose that a species of [hominin](https://en.wikipedia.org/wiki/Hominini) smaller than moderns were hunter-gatherers. Accept the general idea that moderns traded muscle strength for finesse: being able to throw things accuratly became selected for and we lost the raw strength of our relatives. Just as some wolves decided to throw their lot in with the modern humans, these hominins did something similar. They contributed their greater strength and efficency (does chores for less food than a grown modern human) and got the benifits of sharing agriculture, clothing, expansion into new areas, etc.
Just as dogs evolved breeds based on their roles, these tomte evolved to fit their role, *especially* if the modern humans influence their breeding.
So they have the specific traits they were adapted for:
They have great raw strength. They can lift and carry, but can't throw worth anything. They can’t thread a needle or make precision tools.
They are smart enough to do their work, but have a small brain and need **half the calories** of a modern human at rest. The brain uses a lot of power. That along with smaller overall size saves energy.
Living with us and eating the same food, they also lost the huge chewing muscles and long gut, and rely on cooking of cultivated food. But like dogs they eat what we throw away. They scavenge most of their diet and consume byproducts generated as part of their work so we don’t generally notice that. But they need some **dietary suppliments** such as cooked grains and some fruit. So, the farmer prepares them porridge, sharing his own breakfast, but they eat on their own throughout the day.
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There are some real-world examples we can point to that indicate the possibility of a realistic small humanoid. Since we don't need anything exotic like antlers, carapaces, or magic, this should be simple.
The [shortest human on record](https://en.wikipedia.org/wiki/List_of_shortest_people) was a mere 54.64 cm (21.51 in) tall. I'm not sure how that compares to anyone's image of a tomte, but I suspect we want to go smaller.
The smallest primate of all is the [mouse lemur](http://animals.nationalgeographic.com/animals/mammals/mouse-lemur/). Its body is only 6 to 12 cm (2.25 to 4.75 in); including the tail, up to 24 cm (9.5 in). I think this might actually be too small. But here we have a nocturnal creature with fully prehensile appendages. Just a few evolutionary advances in intelligence and it would make a nice farm helper.
Slightly better, the smallest "monkey" is the [pygmy marmoset](http://animals.sandiegozoo.org/animals/pygmy-marmoset). They are just a centimeter or two larger than the mouse lemur, but have a more human-like overall anatomy.
I think some appropriate mix of an existing small primate and the right accidents of evolution could easily have produced the creature we want at least in terms of size, intelligence, and personality. The only problem is the strength. Here, I think we come up against an improbability due to an oft quoted rule here: [the square-cube law](https://en.wikipedia.org/wiki/Square-cube_law). As the creature gets smaller, it will get stronger *as a proportion of it own size* but will be necessarily weaker overall. A marmoset stronger than a full-grown human would require bones denser than lead.
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That strong but tiny means your tomte is dense. There's no riding on the back of a goose for them, their weight would crush it.
No females? I saw one picture of a lady version on the info link you provided, but all of the descriptions mention a little bearded old man. This detail, if they have females or not, will contribute to their anatomy.
They sound like [solitary animals](https://en.wikipedia.org/wiki/Solitary_animal). We have a lot of animals which are not together, are highly territorial and give each other lots of space. Until it comes to breeding. I would assume that these are all male or at least look it, despite the one picture on the wiki article with a doll that had a lady version. However, there could be a female version which is mobile and doesn't serve the farm, just wanders, visiting the men when no one is looking and raising children until they are ready to take over a farm or wander. If they are all male or don't actually have a sex, then you have a bit of a problem. Because right now, anything that advanced uses sexual reproduction on this planet. Still, it's worth looking into [asexual reproduction](https://en.wikipedia.org/wiki/Asexual_reproduction) as a method of making more. They may have a way of separating themselves, and then as soon as they do, the "child" searches for appropriate territory to take over.
This is all pretty alien for higher forms of life.
The other strange thing is that they seem specifically adapted for farm life. I would say that there has to be a "wild version" of them, who does the same thing, but in the forest, as gnomes traditionally do. These don't get angry and ruin things, because no one owns it. When they do get angry at the farmer and ruin things, the effect is to make things less profitable, and run them off the land because they believe they aren't good stewards of it. Once the farmer is broke and gone, they start again...the wild ones don't have the farmer problem. The farm ones adapted their nature stewardship in light of the inconvenience of farmers. I just think this is an evolutionary thing that had to happen. Because there haven't always been farms.
Why take care of the land? Why follow certain rules? How does this tie in with biology and how does it get them what they need? There are other animals who take up a stewardship--birds. Their reasoning is a mate. Conditions have to exactly correct for them to get a lady. So they work hard, decorating sometimes a large area, rearranging branches, that kind of thing, to show the lady that they are worth it. This could be why you never see any ladies. The guys stay in place, showing that they are worthy and fit to breed by taking care of the surrounding land, hoping that the conditions are exactly right to catch a lady. They get angry when conditions aren't right because it might ruin their chances.
Even if this isn't the reason, there has to be a bio-reason for this regimented behavior, an advantage, an edge that helps them as a creature and perpetuates them as a creature.
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How would a species be able to communicate using colors, flashing, and images on their skin (like some deeper water fish) with someone who speaks verbally, like a human?
Is a translation devise even plausible in this case? Especially with a water based species (technology and water issues)
I should specify that, given the nature of the relationship, these two beings would need a quick and direct means of communicating. Writing isn't quite as split second of a communication as shouting is.
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If you're talking about split-second communication, like shouting, I think touch is your best bet - it is immediate, while something like writing or visual signs or gestures require the other person to be looking in the right direction, at the right time. Tapping at or thumping someone will get their attention *immediately* - the direct equivalent of shouting, since it actively *draws* the attention, not waits to be noticed. if someone needs to pay attention, being twapped will draw attention from the most distracted, if they need to move, being dragged out of the way is better than being run over. Most basic, urgent communication will have a touch translation *anyway*, since basic, urgent communication is very likely to have equivalents in every method of communication we can find, create, or imagine - the better to survive in any situation where they might be needed.
If someone's outside of physical range, slapping at *something else*, like a wall, or water surface, or instrument, will create sound to alert your humans, and create waves/motion/disturbance in the water or whatever the equivalent sense is that your other people use to alert themselves to non-obvious motion. Or use a flashlight or something, for communicating *pay attention* across the distance... it will be needed to grab attention in case someone is looking the other way when they really need to be listening.
For less urgent communication, some combination of sign language or gestures would probably be more versatile (and again, touch bridges that gap between what a person is looking at and what they need to "hear" right away). You can also involve writing or better yet, *drawing* for precise details once there's time for explaining. translation passbooks, machines, pidgin, or anything else can be developed or used at their leisure.
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You would need to communicate within an overlapping sense area.
A creature who can communicate with visible displays and is unable to hear sounds would need to communicate in the common sense area of visual displays.
Both species could likely learn to use a gestural/pictographic language to communicate with one another, building from basic images and body language, moving on to more complex concepts similar to Earth's pictographic languages (Egyptian, Chinese etc.)
This method wouldn't require any more technology than a desire by both species to communicate and the concept of a written language. Contact between the species might actually spur the development of written language.
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The grammar and vocabulary would be so different as to make direct transliteration unhelpful without learning the language. That is, the colors, patterns, dynamics, etc. can be converted to a code so we can sense it. But the *meaning* will involve ways of manipulating the codes that are unlike anything in our verbal languages.
The coding process might be something the natives have developed anyway: we call it *writing*. Note that writing has nothing to do with frequency modulated sound waves, so someone without a sense of hearing can make use of it. Some sonic features are replaced by punctuation marks.
A computer might translate native chroma speech into coded form based on their writing system, instantly, even though *translating* that is beyond its ability. The team can program it using writing and examples provided by the alien half of the team, to speed up work on actually learning each other’s languages as they won’t have to write everything but will get it displayed instantly. They will see us doing that on our end: speech to writing on a screen with a permanant printed log for them to take with them and annotate with their observations. So even before serious detail is done on learning their language, they will get the idea of using the machine to transcode their chroma-speech.
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It is possible. In fact there are several ways. For example, the communication could be coded as a binary system with two colors. But every base is possible if each letter is distinguishable from the others. Or they speak via changing frequencies (like the morse alphabet).
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Well, if the alien "speaks" in colors and patterns, and changes in lighting, Humans already can recognize and translate this language as the visual range is not something we don't use.
Additionally, Sign Languages exist in human cultures around the world as languages used to converse with deaf and mute peoples. I know that you are considered bi-lingual in the United States if you also "speak" American Sign Language and translators are typically provided at live events that will be publicly viewed by those hard of hearing (such as Governor's Press Conference). You do not need Star Trek Universal Translators for this as we've used hands for speaking for years.
One problem you might encounter is that an aquatic species would likely not have a lot of red in their language as red light does not travel well in water and their visible light spectrum is could be different than ours... Consider the knowledge gap that could happen if there is no Ultra Violet light.
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Let's say I have been chosen to evaluate whether or not alien worlds contain sapient life before we terraform them. Just assume that we learned to work together and live as a species in peace, treating intelligent life equally (though in reality we never will).
Obviously this is a hard job and since I don't want to be fired, I can't make a mistake. This becomes even harder when I look at all the possibilities of stone age intelligence. [Tool use](https://en.wikipedia.org/wiki/Tool_use_by_sea_otters) is not a trait that is exclusive to sapient animals, after all. If the species was a [sapient plant](https://worldbuilding.stackexchange.com/questions/5097/could-plants-develop-intelligence), I couldn't use earthly evolutionary rules. If they had [multiple bodies](https://worldbuilding.stackexchange.com/questions/46962/what-would-a-collective-consciousness-look-like), I couldn't rely on the rules of monobodied aliens.
And these are just aliens that can be explained. For more extreme cases, it becomes impossibly difficult to tell. How can I, to within reasonable doubt, determine whether or not an alien species at a stone age level of evolution is sapient?
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Start with tool use. It may be that non-sapient animals use tools (however, the 'sapience' of tool using species may be reevaluated as our understanding changes). It may be you have sapient beings that do not, for whatever reason, use tools. However, it should be a relatively visible criteria to start you off - and I would suspect *very strongly* that you'll need more than one criteria anyway.
Any tool-using species should then be put on a "maybe" list for further evaluation (and I second a4android, tool using plants get a "yes" from me) - and depending on relative abundance of terraformable planets, maybe that planet or at least the relevant habitat should be avoided anyway - because even if they are not sapient, they might still become so, at some point. When it comes to ethics, a few false positives (protecting a non-sapient species) is far preferable to even one false negative (that would be effectively genocide of a sapient race)... and it's a lot easier to go back and terraform later, than to undo the process if you were wrong.
Maybe the next criteria would be alteration of the environment - obviously the more 'unnatural' the alteration, the easier to find and evaluate. Maybe something like bird's nests doesn't qualify, but maybe the more elaborate construction of [termite mounds](http://www.pbs.org/wnet/nature/the-animal-house-the-incredible-termite-mound/7222/) will make them worth a second look. Beaver dams fall somewhere between. Or moving from benefiting from fires to using embers from one area to [start new fires](http://www.answers.com/Q/How_do_other_animals_use_fire) (unsubstantiated, but the idea is there) in a different one. Actually, I'd put any fire-using species on the 'maybe' list anyway, its a pretty dangerous thing to use.
A third criteria you might want to look at it communication - if there are analyzable long-distance signals, that again becomes a reason to go on the 'maybe' list. If they're unusual to the planet's wildlife, or 'unnatural', that might be worth some extra consideration - for example, if the animals use sound and scent, then drawn pictures might be worth a second look (or radio waves, but you said stone age). Also, most animals will want to communicate at a relatively short range, since they're concerned with their immediate surroundings, so something broadcast over half the continent away is worth looking into (relay towers, beacon fires?). Any obvious signs of organization - especially large scale organization, or coordination and cooperation between separate groups, should draw your attention for a second look.
And on that note, cooperation between species should also be worth a second look - it can signal compassion (protecting vulnerability even in other species) , or domestication (putting other species to work). You might get some false positives from animals who developed symbiosis, but probably the more similar the species are, or the more the relationship costs either, the more I would think it likely to be the action of sapient beings. If the species is after similar resources (like both hunters) cooperation is more difficult than if the species are specialized and non-competing; likewise if a species is taking actions that benefit the other but cost the first in time or energy (driving off predators, caring for injured), it seems more likely to be reasoned than pure instinct, as opposed to actions that simply happen to benefit both (feeding off of parasites).
So now you have a few criteria for a shortlist, how to evaluate further? Go in person, and study a lot more closely. Check to see how these species react or adapt to something new, if you can find any kind of mutual communication, how these species will react to an alien presence (er, that's *you*). Take environmental factors into consideration, as much as you can - how much their behavior is different from other similar species on that planet, how much is *taught* as opposed to instinctive, or how much might be reasoned and how much reactive, and so on. As a bonus, you might make a final communications check by visiting the planet directly, and wandering about for a bit - the better to see if anyone tries to communicate with you.
Then you've got your planets all lined up - some with nothing concerning, some that are still 'maybes' - with a probably sliding scale of maybe-just-animals to likely-to-be-sapient, and some where you will definitely want to say leave it be and find a new planet. Depending on how many planets are capable of being terraformable, and how much stock your culture puts into preserving diversity and preventing extinctions of even animals, your organization might be happy crossing off all the 'maybe' planets, or might only protect the really truly likely ones.
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Firstly if a plant had paleaolithic tools and it was making and using them you can be fairly sure it is sapient. Animals do have a capacity for tool use and relatively limited ability in tool making, but plants don't use tools full stop.
Secondly the real problem is how sapience is understood. Currently there is a reevaluation of constitutes intelligence. This means it all to likely that by the time we get around to evaluate the sapient quotient of plants and hive organisms the parameters for determining sapience will have changed considerably. Many Earth-evolved species may be deemed sapient. This includes various birds like parrots and crows. Even dogs, dolphins and other cetaceans.
One thing about sapience is the environment is a major determinant in shaping the evolution of intelligence. For example, parrots from the Vanuatu live in an environment with rich complexity and is relatively free from predators. This enables them to develop a remarkable degree of tool making and use. Take into the various environmental factors present to provide supporting evidence for your evaluation.
Industrial relations and personnel management should have improved in the future and especially so for interstellar expeditioners. So if you make a mistake you won't need to worry about losing your job. You get counselled on doing a better job in sapience evaluation, but that isn't a great hardship, is it?
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You could observe them and determine how much **forward planning** they are doing, then (hopefully) make some judgement on whether the forward planning required being able to cope with **abstract concepts**.
For instance, squirrels do forward planning by burying nuts for the winter. But there is not much abstract thought there. Just *"I need food for later"*. (Possibly no thought at all, since the squirrels who don't bury nuts all starve to death and don't pass on their genes).
Stone Age guy also needs food to survive the winter, and also likes eating nuts. However, what he does is make a lot of stone spearheads. Then he goes to his neighbour's cave and swaps them for a tiger skin. Then takes that tiger skin to the village down the road and swaps it for an enormous pile of nuts and some help to carry them back to his own cave. His forward planning is much more complex than the squirrel's. And it involves a more abstract concept: trade and payment.
If the stone age aliens are using any object with zero survival value as an 'institutionalized favour' or IOU, then they've invented currency, and have a very sophisticated level of culture that goes way beyond the animal. A caveman giving another a stone tool for a tiger skin is not currency. A caveman giving another a piece of clay with some marks on it that mean "I owe you a stone tool" is. (I promise to give the bearer on demand...)
Meanwhile... art. If there is anything resembling art which isn't directly associated with getting laid (so more than a bower bird's decorated bower), then there's that abstract thought again. If the aliens are putting a lot of effort into making paint pigments, processing clay to make sculptures, tattooing each other, etc and it has no survival value, then they are again beyond mere animal intelligence.
Of course, being alien, their art may be difficult to recognise. You may think they are scent marking their territory. They make think that they are arranging their poo in alphabetical order by colour to please the forest spirits. :-)
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One of the main tenets of the Science of Discworld books is that the storage and transmission of knowledge has been key to the advancement of the human race.
Making sure that accumulated knowledge is not lost upon the death of an individual is vital to progress. This is very similar to how a positive mutation in Darwinist evolution must become spread throughout the population; as long as it remains restricted to a few individuals it could easily be lost.
For another example, look into how the loss of Fermat's last theorem has caused hundreds if not thousands of scientists to try and recreate what was lost.
So there is some ground to state that an individual might be sentient, but only a species may be said to be sapient, namely when they are commonly exchanging knowledge amongst individuals and are using this strategy to gain more knowledge.
Tool use alone would not be enough. You would need to see tool use being tought to subsequent generations and those generations would need to build upon the knowledge they received to develop new uses for existing tools or new tools.
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This was discussed in another question related to reaching earth's core using nukes. I re-ask it here to (1) stop unintentionally hijacking other topics, and (2) be able to respond (as someone cut my newbie score from 50 to 49).
My position, to be clear, is that it *might* be possible (depending on the scale of things) but is highly improbable today, despite the landing of a small unmanned craft on such a celestial body. I stress that point since either long-term contact or penetration of such a body would seem to be a must, given the fact that a nuke does little in the vacuum of space other than produce enormous light, heat, EMP and other forms of EM radiation for the briefest instant. Landing and anchoring a robot capable of drilling into an object possibly made up largely of iron would be a far cry from anything that's been done.
Surely one giant step has been taken. Further, a small nuclear reactor (Rover) has been successfully deposited on Mars. But the details of a mission that cannot fail have to be ironed out. I have a good deal of experience with defense projects, and while most are remarkably successful, they are also remarkably time and effort consuming, including very long test phases. Asteroid test environments aren't easy to come by.
So (a) could it be done at all, (b) if so, what stages of reasonable development effort would have to be met, and (c) how long would a concentrated effort to produce something with likelihood of success take?
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It's actually trivial to change the course of an asteroid, even if you don't have a nuke. Any impact will do. When you do, you apply a change in velocity (delta-V) to the asteroid. The further the asteroid is away from the Earth, the less delta-V you need to protect the Earth because you have a longer time for that change in velocity to take effect.
I don't remember the study, but a few years back I read that we could easily redirect an asteroid with the present day technology. However, our ability to **detect** said asteroid early enough to avoid needing a stupendous amount of delta-V was lacking. By the time our current technology can detect an asteroid and determine that its trajectory intersects the Earth, its too late.
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Placing a nuclear device on the surface or even buried inside an asteroid (as suggested in some SF movies) could be positively dangerous, especially if the asteroid is a loose pile of rubble. Instead of a diverted asteroid you now have a cloud of fragments mostly rushing towards you on nearly the same trajectory as before.
A nuclear device at a stand off from the asteroid can ablate some of the surface material with the X-ray pulse, essentially creating a rocket motor out of the asteroid. Much more efficient would be to create a sort of nuclear shaped charge and direct a high velocity plasma stream at the asteroid, much like the ORION nuclear pulse drive, transferring a great deal of momentum. This would,be a high thrust/high ISP drive, one of the few known to science.
[](https://i.stack.imgur.com/BtQEo.gif)
This image (via Scott Lowthar's [Unwanted Blog](http://up-ship.com/blog/)) gives you a good idea of what is being described, and the scale image of the asteroid in question is the Chelyabinsk meteor. For a larger one, a series of small devices detonated in sequence is probably more efficient and provides more control than trying to apply one massive impulse.
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<http://www.nasa.gov/pdf/171331main_NEO_report_march07.pdf>
To quote this 2007 NASA study
* Nuclear standoff explosions are assessed to be 10-100 times more effective than the non-nuclear alternatives analyzed in this study. Other techniques involving the surface or subsurface use of nuclear explosives may be more efficient, but they run an increased risk of fracturing the target NEO. They also carry higher development and operations risks.
* Non-nuclear kinetic impactors are the most mature approach and could be used in some deflection/mitigation scenarios, especially for NEOs that consist of a single small, solid body.
* “Slow push” mitigation techniques are the most expensive, have the lowest level of technical readiness, and their ability to both travel to and divert a threatening NEO would be limited unless mission durations of many years to decades are possible.
* 30-80 percent of potentially hazardous NEOs are in orbits that are beyond the capability of current or planned launch systems. Therefore, planetary gravity assist swingby trajectories or on-orbit assembly of modular propulsion systems may be needed to augment launch vehicle performance, if these objects need to be deflected.
So in summary, nuclear is actually our most effective option at the moment, but it is crude and very "brute force-ish". And as others have mentioned, the composition of asteroids is often unknown, and if they are more or less loose piles of rubble, an explosion will only fragment it into pieces and turn it into buckshot headed towards Earth. Also worth noting that there are treaties forbidding nuclear weapons in space, although in a scenario like this, international law probably isn't the top priority.
In the long term, slow push technologies (gravity tractors, pulse drives) *could* work provided that we have enough warning.
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Can you? Sure.
Should you? Probably not.
Blowing stuff up might look cool and dramatic in movies, but blowing up an asteroid with a nuke isn't a very good idea - instead of one big rock, you'll wind up peppering the Earth with a whole bunch of smaller ones - which means that the chances of major population centers being hit will be much higher. Also, the rocks will now be radioactive.
Instead of blowing it up, deflecting the asteroid is a better idea, and yes, you *could* use nukes for this. The problem is that detonating a nuke on the outside of an asteroid means that most of the nuke's energy is being blown into space rather than deflecting the asteroid itself. Kind of a waste.
The most sensible way of dealing with an incoming asteroid threat, unfortunately for Hollywood, is also the most boring - gently push it out of the way over the course of several months or years. You can do this with rockets, reflected sunlight, or laser ablation. Slow and steady saves the species.
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Life on Earth has developed with one Earth-gravity, more or less, as a constant for epochs. Our bones and organs both are adapted to this amount of pull, (or push, depending on how sciency you want to put it, right?) but could a larger planet have a similar pull (at the surface) based on various factors such as less planetary density, slower planetary rotation, or a counter-pull from another structure, like being surrounded by a dense shell?
Based on this conception that it's possible to explain a larger planet with one Earth gravity at the surface supporting life as on our planet, how large could that other planet be, and how could that happen?
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For a spherically symmetric planet, surface gravitation is determined by just two quantities: The average density, $\rho$, and the radius, $R$. In particular, due to spherical symmetry you can consider the whole planet's mass to be concentrated in the center, and then you get for the gravitational acceleration at surface:
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and therefore
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This means if you want the same gravitation on the surface for a larger planet, you need to reduce its average density by the same factor.
The problem is that you cannot arbitrary reduce the density, as sufficiently away from the surface, the pressure will make sure your material is compressed to have no significant holes, and therefore it will only the substance itself that determines the density.
One possibility is to not have an iron core. However that would in turn mean there's no magnetic field to protect you from cosmic radiation and star wind. According to [this page,](http://www.rocksandminerals4u.com/earths_interior.html) the core (inner and outer combined) has a radius of 3400 km (2100 + 1300), and makes up 32% (or roughly 1/3) of the earth mass. With an earth radius of about 6400 km, it is slightly more than half the earth radius, which means it has a bit more than 1/8 of the earth's volume. Thus replacing it with mantle material would reduce earth's density by roughly 25% (actually less because the core is under larger pressure and therefore denser). Assuming this density doesn't change significantly when making the planet larger, this would mean you would end up with a planet whose radius is about 4/3 the earth's radius (and the surface is therefore 16/9 the earth's surface, or 77% more than earth's surface).
Since the mantle is also denser than the crust, I think another density reduction (and thus radius increase) should be possible (but maybe at the cost of continental drift/geologic activity; those might have played a major role in the emergence of life).
Note that a spherical shell around the planet would not affect the gravitation on the surface at all, since such a shell doesn't cause a gravitational force in the inside.
A fast rotation would reduce the apparent gravitation near the equator, but any rotation fast enough to make a noticeable difference would also make the [Coriolis force](https://en.wikipedia.org/wiki/Coriolis_force) quite strong. Also, it would do nothing for the polar regions, so you'd get a steep [gravity gradient](https://en.wikipedia.org/wiki/Gravity_gradiometry) over latitude. I'm not sure that would be very life friendly.
A "counter-pull" from another structure is known as tidal force. I'm pretty sure that before it would make a noticeable difference on the gravitational pull (note that you don't feel the tidal force of the moon on Earth, you only see it from the tides) the tidal forces would tear the planet apart.
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If your planet is made of water, you could have a radius around four times that of Earth with about the same gravity, using no additional forces or artificial means of lessening the force of gravity.
We can calculate this based on celtschk's equation for gravity: $g=\frac{4πG}{3}ρR$
To use this to calculate the size of our planet, we need to know roughly the density of water, which will depend on the pressure it is under. Water, at pressures it encounters in Earth's ocean, is a roughly incompressible liquid, but at sufficiently high pressures it can change phase into a variety of different ices. For our water planet, let's assume that the pressure is mostly similar to the pressure found at the base of Earth's mantle, or within an order of magnitude of that pressure. This gives a pressure of around 140 GPA, which corresponds to a form of ice called [ice X](http://www1.lsbu.ac.uk/water/ice_x.html).
Unlike run of the mill ices we encounter on Earth's surface, which are less dense than liquid water, ice X has a density of around 2.5 $\frac{g}{cm^3}$. This is roughly a quarter of the density of the rock that makes up Earth, so based on our equation for gravity, we should be able to have a planet with about four times the radius of Earth with the same gravity, if it were made mostly of water. This planet could support life as we know it if "life as we know it" can be taken to mean "fish".
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Building on the other two answers, the rough answer is about the size of earth, plus maybe 10 to 12%. This assumes no magical building materials - just rock.
As celtschk has pointed out, the surface gravity (for a uniform sphere) is equal to the product of radius and density. The average density of the earth is about 5.5. While the core is denser than the crust, which contradicts the leading assumption, the core isn't all that large, so let's go with the average.
The specific gravity of magma runs about 2.2 to 2.8, or a bit less than half of 5.5. While it's true that the density of rock increases with pressure (so the core will be denser even without any iron) this figure[](https://i.stack.imgur.com/X7KnL.jpg)
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> <https://en.wikipedia.org/wiki/Structure_of_the_Earth#/media/File:RadialDensityPREM.jpg>
>
>
>
shows that the core (while twice as dense as the outer layers, only makes up about 1/4 of the total mass of the earth. The core's radius is about 1/2 that of earth, so its volume is 1/8. Swapping iron for rock will only reduce the total mass (and average density) by 1/8, so a best-case number would allow an increase of about 12% in the radius of the earth.
Of course, with no heavy core, there is no magnetic field and no plate tectonics. The source of the earth's internal heat is radioactive decay of heavy elements. With no tectonics there will be no mountain building (orogeny) with the result that all land above the ocean surface will be eroded away, and an otherwise earth-like planet will be a water world.
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**Gas giant size.**, although it would take a lot of future tech to realize humans living on top of huge hot-gas balloons floating in the upper atmosphere of Saturn. I'm not sure that it is physically possible: the failure mode is just too catastrophic and the weather is ... difficult. You'd certainly need multiply redundant fusion power ststems and super strong materials.
But if you could solve the technical issues, gravity on the surface of such a platform would be Earthlike.
Gas giants are much the same size across a vast range of masses. The more mass they have the more it is compressed at the core. They range from planets like Uranus up to brown dwarf not-quite-stars. You get Earthlike gravity at the low end, like Saturn.
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Several previous answers provide you with values for Rocky (about Earth sized), Water (about 4x Earth sized), and Gaseous (about Saturn sized) planets when just gravity is considered.
But you could make a significantly more massive planet that maintains a surface gravity of 1 g if you put it under extreme rotation. As celtschk mentions, such a planet would possess a surface gravity that increased tremendously with latitude.
A planet such as this is limited to certain maximum spin properties or it would tend to fly apart. An article I read indicated that a 1 rotation every 2.5 hours was about the maximum. Using this as my limiting factor I provided an [answer](https://worldbuilding.stackexchange.com/questions/15062/stumped-how-can-i-get-a-huge-earth-like-planet/15076#15076) to a similar question a while back.
When you add in spin, you could get your rocky planet's size up to
* mass $\approx 1.25 \times M\_{Jupiter}$
* radius $\approx 10 \times r\_{Earth}$
* equatorial gravity - $g\_{equator} = 1 g$
* polar gravity - $g\_{polar} = 16.6 g$
* gravity variation by latitude - $g \approx 1 + \sin\left(latitude\right) \times 15.6$
Only a relatively thin strip along the equator would be inhabitable to *surface dwelling* humans. However, humans adapted for aquatic life could probably use the whole planet. Buoyancy would also vary by latitude and this could make an interesting story plot.
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**There is no limit**
If you are looking for only natural gravitational force than you need to use the Law of Universal Gravitation and the planet can have less and less mass until it can no longer maintain Earth-like properties (primarily geothermal properties). However, you can substitute gravity with other forces if you will allow your planet to partially artificial, most notably centripetal force.
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In an unfortunate miscommunication between a director and the special-effects company, a request for a prop version of The Matrix got mistaken for a request for the real thing. The director's going to freak when he sees the final bill, but we'll deal with that later. The real issues is that the director expressed a desire for his series to last longer than the Friday the 13th franchise, which is to say, a really long time, and that means it's built for the long haul giving it plenty of time to perfect turning all of us into batteries (and solving the whole conservation of energy thing... we really do make poor batteries, don't we)
The SFX team took the director's desires to heart, and designed their Matrix to last as long as possible before someone eventually discovered that they're stuck in The Matrix.
My question is this: how should the SFX team design their Matrix to ensure it takes as long as possible for someone to actually discover the Truth, but at the same time make sure that someone eventually does.
* Answers should provide details of the "flaw" which eventually lets the hero of the story realize they're in The Matrix. The longer it takes for us to eventually discover the Truth, the better. (If clarification is needed, target the statistical expectation of how long it takes to discover The Truth, but creative interpretations if this clause are permitted)
* Humanity must eventually discover the flaw. This means we have to be careful, because humanity is pretty darn good at demolishing itself. If there's a WWIII, the flaw better present itself before we all die in the nuclear winter.
* The special effects team made "the real thing," so they don't get to do normal SFX hacks. In particular, anything which is preventing us from finding the flaw must rely on in-world logic to do so. No fair simply declaring "only humans whose ID number is above 10,000,000 can realize we're in the matrix." (If you believe in human freewill, assume that *any* human should be capable of realizing they are in the matrix, but make it so that its hard for the first few to realize it unless they're *really* determined)
* Solutions involving artificial intelligence are permitted. In fact, they're encouraged, since that makes for a more interesting storyline!
The best answer gets to present their bill to the director. After all, SFX companies need to get paid!
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Step one: You need to start your matrix in the [insert really old time, eg: bronze age/stone age/1100's/1300's/1600's/however long you want the matrix to last] time frame.
Step two: Place an impossible construct behind the [moon, or mars, or pluto, or the next closest solar system, etc] which, upon discovery, will instantly reveal that this is a simulation - for example, if you have a set of Penrose stairs on the dark side of the moon, it'll be obvious that its a simulation.
Assuming your humans never kill themselves off completely (Luckily, humanity seems to be pretty good at surviving), this setup allows you, as the writer, to have fairly good control over how long you want the simulation to last. The farther back you start the simulation in time, combined with the further you place your impossible construct from the Earth, the longer it will take for the species to eventually be able to travel to said construct and thus, discover it (and the simulation).
Of course, this would mean that your "hero", would have to live in in a fairly futuristic setting if you placed your construct really far away. Alternatively, your hero could live in the present if you had him be an astronaut exploring the dark side of the moon.
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Give the inner world slightly broken physics. Specifically, metal in the virtual reality doesn't conduct electricity. If this is the only thing that is different, biological processes and pre-electricity tech should work fine, but humanity wouldn't be able to develop information processing technology more advanced than room-sized equivalents to pocket calculators. A bio-computer would be possible, but designing and building one without computer aid probably wouldn't. Science could advance, but post-Renaissance development would be slower and most likely end up steampunk.
After a few hundred years, technology would be advanced enough that people would notice the inconsistencies of metal not conducting electricity, and the question of why will be of similar significance to them as the question dark matter/energy is to us. In our case, the inconsistency is caused by some misunderstanding of how the universe works which will eventually be corrected, but in the case of our simulated world the universe itself will be inconsistent.
The inconsistencies will be the only evidence that the reality they are experiencing is simulated, and without any information processing technology, they will be unable to simulate anything. The thought that their reality is simulated will never cross their minds because simulation as a concept is foreign to them.
The Flaw is there for them to discover but someone with an extraordinary aptitude for abstract thought would need to end up interested in just the right niche of theoretical science/mathematics to even bring up the idea, unlikely enough that statistics would make it take a very long time.
Even after this happens, one person thinking it's possible is very different from an organisation with sufficient resources looking into it and finding a way to escape the system, so far more time is likely to pass before anything resembling the plot of *The Matrix* comes to pass.
Regarding humanity not dying, measures don't need to be taken. The worst that could possibly happen (human caused or natural) is an extinction level event on par with Chicxulub. Even if something killed everyone in a huge area and caused a huge change in the environment worldwide, humanity would survive. Civilization would likely collapse and need to be rebuilt from almost nothing, but this helps "as long as possible" without contradicting "eventually."
In summary, start the simulation with a pre-electricity civilization and make metals nonconducting. Metal atoms and ions must behave normally, but electricity should be unable to travel significant distances. This is deliberately self-contradictory if you look closely, but limits the development of technology that makes it either easy or useful to do so.
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I think the Matrix movies already answered this: nested Matrices.
In the first level of the Matrix you want to deliberately create rules that are relatively easy to break (superhuman speed and strength). Hell even prime the pump with a "chosen one" cycle and antagonize them by telling them that their jailers are using them as batteries (they'll believe anything). Be carefull of building the facade too thin, even the machines at this level shouldn't know that they are nested.
Once they have "broken out" into the "real world" you can buy yourself a ton of time. Create the "real world" to be ugly and inhospitable (many of them will actually WANT to go back to the first level). It will take them a good long while to realize that they might have been hoodwinked twice, specially if you make the rules at this level harder to break (the speed of light, quantum decoherence, local realism, etc).
Temper the number of nested levels with the desired run time of the series vs how far you can push the budget without ending up in an unmarked grave.
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Have a matrix inside the matrix, etc.
I believe this is a movie-theory as well. (Although wrong simply because the coloring scheme is distinctly different iirc)
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The matrix prevents world ending catastrophes in obvious ways. The people say "Huh, the world should've just ended, it didn't. We must be in the Matrix"
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A polygonal scientist grows up in a polygonal world, he was born and raised in this world so he has never had any cause to question it, until one day while walking through a park he finds a little shiny ball bearing. He might consider it nothing more than a pretty thing, the polygon count being so high he cannot see what 2D shapes its comprised of. Obviously everything is comprised of 2D shapes, everyone remembers the class where the teacher folds up a cube explaining how 2D shapes push out into the third axis of 3D space to create 3D objects. That's just the way the world is...
A few months later he's in an insane asylum screaming nonsense about higher dimensions and simulated realities, nobody believes him of course.
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One of the comments the machines make in *The Matrix* is that "there are levels of survival we're willing to tolerate" meaning that the human crop need not constantly increase. If your Matrix has a hard cap on total population and/or a flexible topology such that population densities can be kept perpetually low you can keep the occupants as a hunter gather society that never develops agriculture. Without the advanced material sciences that can only develop in societies that are population dense, and can thus be highly specialised, measuring physical reality and recognising inconsistencies is impossible. Many inmates may realise that strange things happen but it will take someone exceptional to contribute it to outside forces and start to organise resistance, probably starting with the agricultural revolution. This will happen eventually but it's an essentially random event.
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Use the original idea behind the Matrix as your solution: brain processing power. They switched to "humans be batteries" because they thought audiences wouldnt understand using human brains for processing power. But since you are using the "humans are power" you can use the latent processing power for the Matrix.
The premise: while turning humans to power you use a Matrix to keep them docile. You engage unused parts of their nervous system or when dreaming etc. to aid computers in simulating the entire matrix, this reduces energy requirements as you need less computers and powering something else than the Matrix is kinda the point.
Now each brain helps calculate parts of the Matrix fed to it by computers, which goes pretty fine most of the time. However when a lot of physics happens in one area the brains allocated cant keep up and that local part of the Matrix will slow down...
Like around a Black hole where time dilation takes effect. Now us humans have actually discovered this and have described this graphical bottleneck with physics equations because they cant do otherwise.
So when will humanity discover the truth? During a world war. As people are dying en mass, large sections of the Matrix need rerouting to computers outside/inside the Matrix, which would take time to spin up or clear of the data it held previously. Normally deaths would only create minute errors which redundancy could solve, but the scale of death would make physics and the graphical calculations that come with it go wonky. To make the connection, your inhabitants need to know about computers, the potential that we ourselves are a simulation (and thats likely as a civilization would want to use one for in-depth study of the universe and theres likely more of those simulated worlds than real one's, ergo chances are we are a simulation), and enough physics that we can suddenly discover the discrepancies. If a simple dead pixel wont give it away first ;).
No world wars? Matrix tries to steer clear of large deathtolls by manipulating the inhabitants? Eventually mankind will grow so incredibly fast that their brainpower starts being able to do wonderful things for the Matrix. Such as finally having enough processing power to get physics around Black holes much closer to the intended speed! Whoops, humanity just realized that something's up, lets hope the Matrix doesnt have a failsafe designed to quickly revert it back to older settings so Black holes have slow time again, or you might end up with an even bigger red flag and now not just one but half of humanity knows its a simulation.
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Hide the keys to getting out of the Matrix by scattering various religions/ secret societies with each group having only a piece or few pieces of information, essentially compartmentalizing the Truth. Forcing them to evolve over time, developing technology until global communication is reached. Once global communication is achieved they would put the various pieces of the puzzle together and self realize.
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I'm designing a city at the moment and I want residential construction to follow an iterative design. Houses are made of connecting hexagonal rooms.
Families grow very large in my city due to some unrelated social things and construction is often done by residents. So the rules need to be simple enough to be understood by the general population and executed using only ruler and compass, in a reasonable amount of time(no huge algorithms that need a computer to execute). This ruleset needs to leave a minimum of 2 meters of space between houses(for walking and cycling). There can be no collisions, overlaps, or entrapments(a slow growing family shouldn't get trapped by their faster-growing neighbors).
The only solutions I've come up with result in an incredibly regular and boring city and can't handle irregularities of any form. I want my city to have an organic/fractal quality to it.
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The reason your design comes out boring is the rules you've put in. A city is organic, most of the old "interesting" cities had the strangest of rules. Amsterdam houses were taxed by width. In Paris the balconies had to align. In old walled cities there was incentive to stay within the safety of the city walls, so you swap space for safety and build small.
If you introduce some arbitrary esthetic rules rather than logical ones, you'll get a more organic system. Lose the enforced gap between every property in favour of a hexagonal road network for example. This means that as people overexpand their plot due to family size, they have to move to a new plot with more room to expand.
Land is more expensive in city centres, people will build up on a smaller footprint rather than out. It's cheaper to build out away from the city, but as the city expands you'll get big old out-of-town houses now in the centre surrounded by small high density housing.
This will allow a build up of small properties in the city centre and larger ones in the suburbs but with occasional oddments like old country mansions near a town centre (see [Lauderdale House](http://www.lauderdalehouse.co.uk/) or Buckingham Palace as examples of this effect.)
New properties will build up along existing roads before new roads are built, so major routes will have longer blocks of larger houses set in more land, then minor roads will build up with smaller blocks of smaller houses as the land value goes up.
**Things to do:**
Introduce areas where people want to be: This causes higher density more expensive housing.
Introduce areas where people don't want to be: This gives higher density low value housing (slums), maybe even make these square, that way they'll stand out as cheap housing. Then regeneration will have hexagonal housing in square plots.
The suburbs: Slightly boring, property value linked to plot size.
Add noise: Rivers, parks, lakes and reservoirs as well as topography.
**In summary:** *Strict rules make boring cities*.
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Add noise. If your terrain is uniform, the city will be also. Run a [Perlin](https://en.wikipedia.org/wiki/Perlin_noise) or [Simplex](https://en.wikipedia.org/wiki/Simplex_noise) noise generator across the map first, creating locations that can't be used because they are to high or too low. You could also impose 'open space' ordinances that require 1 hex left open for every 3 built. You could have superstition that some percent follow and will never connect to a specific hex edge number. You just need to allow for some randomness.
On organic design, look into [L-systems](https://en.wikipedia.org/wiki/L-system). Set your roads first, run random distances, then either place a fork(Y) or shoot off a smaller side street, or a building lot. Each iteration you either continue growing the roads at endpoints or building houses at lot points.
A search on Procedural Road generation will give you lots of research people have done, you just have to apply it to your system.
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There are many software programs that specialize in procedural generation of cities; like this one: <https://youtu.be/yI5YOFR1Wus>
I would survey a bunch of them, either to find one to use, or try to figure out what they are doing that you like. Otherwise as the person above said, try the math board.
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Just apply the rules you have, but apply them organically.
Split the map into hexes, each the size of room. Put the "roads" around the hexes as well.
Scatter "seed points" around the hexes to be your starting point.
Use a random number generator from 1->X+1 where X is the number of occupied hexes to generate a number.
If the number matches a family it expands. They pick an empty adjacent hex and expand into it (color it in their color) and fill in the road between those two hexes. Note that if any hex they occupy get selected they can grow their building from anywhere, not just from that hex. If there are no empty adjacent hexes they grow upwards - one of the hexes becomes 2 story (or 3 or whatever).
If x+1 is rolled then a family has split, pick a new point and fill it in a new colour.
In general have buildings expand away from their nearest neighbors rather than towards them and avoid encircling.
Stop when you think your settlement is populated enough.
This will give you an organic feeling city with buildings of different sizes, more crowded areas growing upwards, etc.
The algorithm as described will tend to favor larger families growing larger, so you will get more variation in sizes and it will tend to favor sprawling single story buildings.
If you prefer more uniform sizes you could select a random family to grow giving them all the same possibility.
If you prefer more height then you could stick with the first algorithm but require the growth to happen from the selected cell. The center of houses will then tend to rise even when the edges still have spaces to expand into.
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To be terse, **do a bee hive configuration**.
What I mean is each family has an allocated lot size. This lot is a large hexagon with space for a set amount of rooms.
Now surround each lot with a 2 meter "road" for commerce.
In this way, each family is able to expand as needed, there will always be space for traveling between houses, and all houses are made of interlocking hexagonal rooms.
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A group of biosphere conservation activists from a type three civilization come across the earth. Using their technology and observations, they see that throughout human history , humans have blatantly disregarded the well being of their fellow multi-cellular life forms , and due to this , they are leading their biosphere down a path of self destruction. they are outraged and greatly desire to safe the biosphere , but due to intergalactic bylaws , they are not allowed to
A) **Directly interact with any civilizations below type 1**
B) **Disrupt the natural ecology of any planet or Moon that they are not native to**
C) **Land any Individual or Craft on th any planet or Moons whose inhabitants have not reached Type 2**
D) **Tamper with the orbits of any bodies in a solar system that contains lifeforms below type 2**
The violation of one or more of these laws could result in anything from planet arrest ( where the perpetrator(s) may not leave the planetary system of their home world ) for 150 years , to digital purgatory ( where their consciousness is uploaded to a matrioshka brain to survive as primeval sapiens until the heat death of the universe ).
My question is: what is the least Impactful thing that could be done to wipe out the human race without disrupting the natural world?
* *Note:All "type" figures are in terms of the kardashev scale of civilizations*
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## Cause geomagnetic storm
Last really bad storm of this type in year [1921](https://en.wikipedia.org/wiki/May_1921_geomagnetic_storm) caused telegraphs to go out of the service.
Your rules forbid playing with a **planet** , whereas the Sun is a **star** (obviously). So it should be safe to play a little bit with Sun and cause it to produce huge geomagnetic storm which will cause massive electric blackout on whole Earth
I know it does not wipe all the humans. But I think that it will result in era of Dark Ages, where lot of humans will die in unrest and wars.
Also, when you "rinse and repeat" the process, you can put humans effectively back to medieval settings. They will still cause harm to the nature, but I think that given the rules this is pretty good solution.
## Alternative: How strongly are the rules enforced?
There are fines for messing with low level species. I get it. But there are also fines for speeding in most countries on Earth. And we all know that in certain parts of roads in certain parts of a day you can go well over the limit without getting caught.
Last time [I asked about aliens being limited by some rules](https://worldbuilding.stackexchange.com/questions/15105/buying-jupiter-for-prize-of-iss) I got also answer: Screw the rules and go for it!
But that depends on your setup. How often do you get caught for messing with the planet? What is the probability that police ship is hiding behind dark side of Moon and waiting for you to get caught up in the moment and push the pedal to the metal?
And how much are the aliens willing to break the rules? If they are willing to go for it, then go for nuke from the orbit\* and claim solar flare did it
\* *This advice is just figure of speech. I strongly recommend you to follow intergalactic rules and not mess with humans at all. Should you break the laws, I hold no responsibility for advicing you that. Anyway if you do so, send pics!*
[Answer]
**Supervirus**
Kardashev Type III civilizations would likely have mastered completely genetic engineering and possibly even removing biological matter from their bodies entirely. To genetically engineer a plague that would look for specific markers in the host, identifying targets to be human and killing them off before self-destructing wouldn't necessarily be out of the realms of possibility for them.
**Ignore the rules**
Civilization so advanced it's colonizing the galaxy would likely be advanced enough to simply wipe humanity out by tampering with our nuclear arsenal. Sure, it would wipe out a significant portion of the flora and fauna alongside with human, but at the stage this alien race is at, a few millenia won't matter, and the earth will eventually heal without humans to poison it. Should someone come asking, they can just claim to have only just arrived, a bit too late that these silly little chimps just nuked themselves out of existence.
Nevertheless it would still disrupt the native ecological systems. Mankind is a part of it, regardless of the destruction we cause. The rules if followed to the T prevent pretty much any interference until the species read Type I level of technology.
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If they can't directly interact with humans, or affect the biosphere, then I think that leaves them with one general solution:
## Just show up, and let the humans to wipe themselves out.
One way of doing this would be just to make their aircraft visible to the humans. Done at the right time and place, this could be devastating.
For instance, if highly advanced vessels appeared over hidden Soviet military sights at the height of the Cold War, the USSR would assume the craft belonged to the US, and might be provoked to attack.
The ensuing nuclear exchange would severely set back humanity, if not wiping them out entirely, and the Earth's ecosystem would likely recover in time.
Since they aren't communicating with the humans in any way, then they can argue that they aren't actually "interacting" with them.
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Multiple answers have mentioned viruses--but there is the problem that there's nothing that will give a 100% kill. However, look at what happened to the New World--**multiple** diseases. Immunity to one doesn't mean you're immune to another.
Infecting everyone first isn't actually an absolute requirement as you can have an airborne disease and keep raining it down.
However, if you want to infect everyone first the answer is simple--something that spreads rapidly but has a long incubation period. Nothing like that exists at present but what if you combine two existing diseases? Lets hop back to 1980, the evil aliens tack the HIV code onto the influenza bug, make a few antigen changes so nobody resists it. Hit all the major cities of the world (make fake meteors that protect it through the fire, then break up.) People get the flu, they get better, after a while their immune system starts to break down. It will hit too fast for the researchers to find a solution. (And the fact that just about everyone is infected will make it much harder to pin down the problem.)
This won't be a complete kill, though--something under 1% of the population is immune. However, do the same thing with the cancer-causing versions of the HPV virus. While I'm not aware of any immunity there there probably are some--but it's not the same people as were immune to HIV. Those are the two slow viruses I'm aware of but I'm sure there are more. The aliens use as many as they can.
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I suggest you read James Tiptree, Jr's classic "The Screwfly Solution". Aliens seed the atmosphere with a substance which cross-links the (already cross-linked) sexual and aggressive drives, causing the men to kill off all the women. A very good story, but really depressing.
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Autoreplicating nanobots, replicating on strictly human cells --- with a DNA check that should be simple for a type III civilization. Like a supervirus, but more specific. The nanobots can die and auto-destroy to basic component after a while... you can spread them in the atmosphere to get started.
(Idea from Hugh Howley "wool" sequence)
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## The simplest solution:
*Step back and wait it out.* At current rate of destruction it's just a matter of time. The planet has a way of recovering from mass extinction events, it'll all be back in some way, shape or form within a million years or so. Maybe in due course intelligent life will once again arise from the ashes.
## Electronic interference
Your rules don't exclude remotely interfering with our technology, something we'd be particularly vulnerable to just at the moment. Faking a couple of missile launch signatures onto the great power's tracking systems should do the job fairly quickly.
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Does "interacting with civilisation" include (a) interacting with individuals in it, or (b) affecting individuals without "interacting" with them?
Level 3 implies some extremely high level technical abilities, including changes specific to the immediate environment around each person. Perhaps distortion of electromagnetism - light we see, electrical impulses from our senses or in our neurology. Changes to the immediate environment of each person - changing the partial gas pressures to prevent respiration would be a neat one. So would transforming all food at the point of eating to remove key nutrients as they are ingested. Doing this for a few billion people over a few years (if not all at the same time) wouldn't be much of a challenge.
I'm reminded of a SciFi comment whose source I cannot remember, that to prevent the rise of Hitler, all that would have been needed would to create sound waves of voices next to his ears, day and night, preventing concentration and disrupting purposeful behaviour, and consigning him fairly quickly to an asylum, suicide, or to behaviour that gets him ignored rather than followed.
There are probably thousands of ways your aliens could do something similar to the environment people live in. Modify sperm cells before conception (not strictly "part" of a person), create distortions to vision calculated to cause fatal accidents, transform nutrients, transform the immediate atmosphere, tamper with human knowledge and communication to create harm directly or chaos, or to insert false harmful information into human knowledge, just name it. Imagination is the limit.
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You can obtain a large amount of DNA sample from the desired organism and analyze it.
Then you could manufacture a technology that scans a certain amount of land searching for and identifying the DNA.
After it identifies the DNA the technology will kill the organism off by releasing bugs that make it sick.
If you want a catch then the device could be faulty: it doesn't identify all the population, just about 80%. Think of it like a missile that tracks it's target.
After several scans the organism is extinct, another technology will proceed to remove the trace of the organism, buildings, farms, deforestation, etc.
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A highly contagious (likely water and airborne, and not temperature sensitive) viral illness that prevents reproduction would slowly kill off the entire human race without touching any other organisms -- assuming it doesn't jump the species barrier. If this isn't fast enough, then a virus that attacks the telomeres in the DNA. From my understanding, this would accelerate the aging process sufficiently that youth would die quickly before reproducing, and adults would die off quicker.
Recall that the influenza virus has, on a couple of occasions, wiped out substantial fractions of the human race. And SARS (a coronavirus) scared more than a few people as well.
One could also invoke prion diseases, or similar phenomena.
If you use a disease, it would likely have to be something completely unlike anything humans have seen before, otherwise there is likely to be some cross-immunity. It would have to be highly virulent, highly transmissible, and highly contagious. I would think that it should have a long period of shedding before symptoms show up, otherwise people die before they can transmit the disease. It should have at least one, ideally multiple non-human reservoirs (fruit bats are good for this as they go almost everywhere; I wonder if cockroaches or ants could act as a secondary reservoir?)
If you don't want to go the disease route, then consider technology. Nanotech could easily be designed to target unique segments of the human nervous system and/or brain. And a rogue AI could, given the pervasiveness of online connections, likely wipe out most of humanity.
Or, like has been said in other comments, simply wait. Humanity is fairly likely to wipe itself out, given sufficient time.
EDIT (2019/01/04) - there is an interesting podcast that addresses the concept of existential risk for mankind (though necessarily superficial due to time constraints) - it's called *The End of the World by Josh Clark*. It may be worth taking a listen
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[Question]
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Today we take salt for granted and we even dare to spread it on streets but **salt was a critical element for human life up until not so long ago**. Salt production was probably in many ways the world’s first industry; powerful cities and sometimes entire empires rose and fell with salt production, its commerce and its shifting routes. Significant religions, like ancient Egyptian’s, revolved around the availability of salt from Lake Natron and the discovery of its properties in mummification. Salt was so precious that people were occasionally paid in salt (*a salary*) and for the same reason it was the first commodity to be taxed, **ultimately playing a critical role in determining the very nature of the relationship between the rulers and the ruled.**
In my world (an alternate future Earth, same world as [here](https://worldbuilding.stackexchange.com/questions/39579/can-you-help-me-design-a-realistic-climate-map-for-my-world-alternate-earth) and [here](https://worldbuilding.stackexchange.com/questions/39748/how-would-the-relics-of-extinct-human-society-affect-future-civilizations)), the now closed off Mediterranean Sea is the Mediterranean Waste, a gigantic and utterly alien salt flat 3500 mt below sea level. Needless to say, salt is the most common resource in the continent, and religious sentiments developed around the white, sparkling abyss.
**How differently would the societies be if salt was a widespread commodity?**
**How will the economic relationship between those who have access to this infinite salt mine and those who live in relatively salt poor areas evolve?**
[Answer]
Deceptively simple question but actually rich in cool and unexpected outcomes. Let’s start by saying in part you already unknowingly answered your own question: **ancient societies would have treated salt as modern ones do**. Salt wouldn’t have been precious, and people could have used it in new “wasteful” ways. Before starting anyway be aware that “salt” is a very generic term chemically speaking, but given that you gave a very specific context (an evaporated sea) I take it as meaning [evaporite minerals](https://en.wikipedia.org/wiki/Evaporite), exactly the kind of stuff you’d find on the bottom of (at least partially) evaporated sea along with “common salt” (sodium chloride). Now let’s see the consequences of a relatively inexpensive and easy exploitation of these evaporite deposits.
# MORE WAR, EXPLORATION AND COMMERCE
The most important consequence here would have been **IMPROVED FOOD PRESERVING**, which is maybe the [most appreciated characteristic](https://en.wikipedia.org/wiki/Salting_(food)) of common salt. The ability to prevent the growth of bacteria, fungi or other micro-organisms from the early stages of society **would have impacted settlement patterns**. Being able to conserve food in a cheap and efficient way would allow for new areas to be settled that are not on a natural channel of transport (e.g. a river) that may have otherwise not been settled. New unpopulated areas would be settled earlier and better: exploration can potentially mean laying out new commercial routes or faster colonization by a possible salt empire, **especially considering the immense utility of preserved food in feeding a marching army** (think of food rations in modern armies). In brief: **improved contact (benign or not) between distant civilizations**.
# MORE AND BIGGER CITIES (but frailer early societies)
The possibility to conserve food for longer periods of time means that **goods can travel farther from the farm** and selling can occur on a wider scale than a local one. Think of how the invention of the refrigerator made possible to ship perishable food products long distances: same but in a smaller scale. Without food preserving land for agriculture must be necessarily evenly distributed across a populated area, but with cheap means of preservation a fertile **small portion of the existing land can produce food for all the others** and sell the surplus in a wider area. This mean professional farmers which in turn mean more people that can do other things other than farming to survive (e.g. merchants, smiths, scribes, philosophers, etc.) **more cities and more complex societies**. All of this actually happened in real world, but with an easier access to salting it will happen earlier.
Without a mean to preserve food your diet and health is affected heavily by the seasons and what could be grown relatively close to your region, but with salting accessible to everyone, population will no longer be restricted by these limitations. As well as changing the goods purchased at the market, the ability to store these foods for extended periods of time will led to an increase in leisure time, because without accessible food preservation, people would have to shop on a daily basis for the supplies needed for their meals. Note that increasing population will led to an increasing demand for agricultural products, which has to be met through expansion, improved technology and inventions **or the civilization will collapse under its own population pressure** (many evaporites have fertilizing properties, so this can be of some help, we’ll see that later). All this trade and concentration of farming activities can have serious downsides though: harvesting failures, famines and epidemics will travel quicker and will have more significant consequences. **Empires, at least at early stages of civilization, will rise and fall abruptly.**
Another downside is that all this sodium consumption can led to severe health problems (that can indeed balance excessive population growth though).
# FERTILE SOILS?
Somewhat related to the previous topic. I’m aware that nitrates obtained from many evaporites are excellent fertilizers. Gypsum for example was regarded almost as a miraculous fertilizer in the 19th century and even [a war was fought over it](https://en.wikipedia.org/wiki/Hants_County,_Nova_Scotia#Plaster_War). I’m no chemist nor agronomist though so I’ll leave this one to experts.
# EXCELLENT CHEAP MATERIALS FOR ARCHITECTURE AND ARTS
With all that “salt”, a lot of it can be used for artistic or masonry purposes. For example during late antiquity in Rome and later in medieval Germany many churches had selenite **used in for panes in windows** as a cheap and beautiful way to replace glass. Gypsum blocks can also be very useful in architecture, being a **massive lightweight building material suitable for fire-resistant non-load bearing interior walls**. Furthermore **gypsum** is a key component of **plaster** which has many uses in architecture and art. Speaking of art, another material commonly found in evaporite deposits is **alabaster** which is a superb material for sculpture and it was also used in architecture especially in the ancient world before steel was developed, when its relative softness made it much easier to carve than other stones. Also, salt is important in pottery in the process of glazing, and plaster is excellent for casting.
[](https://i.stack.imgur.com/T0Cal.jpg)[](https://i.stack.imgur.com/hRton.jpg)
# CIVILIZATION HAS POTENTIAL TO EASILY SPREAD NORTH (or up a mountain chain)
All these excellent insulating materials mean that theoretically **buildings can be heated more efficiently** and civilization can advance more easily in harsher climates, especially if one can afford to **melt snow by spreading a lot of salt around.**
# BUT (speaking of architecture) CONCRETE INVENTION WILL BE somewhat HINDERED
Just a wild guess but in a context in which salt spreading for melting purposes is invented before concrete, the latter has a few chances to be invented and extensively used since [**salt is reinforced concrete’s worst enemy**](http://cretedefender.com/how-salt-damages-concrete/): we can afford to use it in modern world just because we spend a lot of money in building maintenance but this is still really an unbelievable architectonic nonsense.
# CLEANER PEOPLE
**Salt is very important in the process of manufacturing soap**. To make it obscenely simple soap is made up by fat or tallow and alkaline salts. The salts were the expensive part so soap was a thing for riches. But in this salty utopia soap is a cheap byproduct of animal processing, since a vast variety of salts can be found with relatively little effort.
# MINING SALT WILL SPEED UP INDUSTRIAL REVOLUTION
**Mining salt was one of the most expensive, laborious and dangerous of operations**, due to rapid dehydration caused by constant contact with the salt (both in the mine passages and scattered in the air as salt dust), among other problems borne of accidental excessive sodium intake. While salt is now plentiful, until the Industrial Revolution it was difficult to come by, and salt mining was often done by slave or prison labor. **This is obviously not true** in a society in which salt is found at surface level and is also nearly infinite. There will probably be **professional salt miners and refiners** and the industry will be extremely well developed. And there are other substances you can come by while mining salt, such as **sulfur, natural gases and even petroleum** ([trapped under salt slabs by the their impermeable nature](https://en.wikipedia.org/wiki/Structural_trap)). All of them are important substances for technological development and their discovery and exploitation will probably come earlier than in real world because of all this salt mining activity. Obviously all this line of reasoning assumes you can access a 3500 mt deep incandescent basin without consequences, ~~which I anyway doubt (see later, *An Impossible Utopia*).~~
[](https://i.stack.imgur.com/PhkUT.jpg)
# EVEN MORE MINING (AND WAR)
Did you know Nitrate minerals are often mined for use in the **production of lethal explosives?**
# AFTERLIFE WOULD NOT BE THE SAME AGAIN
Unlike real world salt would not be considered a “sacred substance” (but I guess that a nearly endless salt desert will be regarded with a certain reverence, same way as sand is not a sacred substance but a desert can be a holy place). I don’t know if this is necessarily true since according to gospels Jesus, who lived in a [geographical area plenty of salt](https://en.wikipedia.org/wiki/Dead_Sea), still used salt a metaphor to indicate something very precious (but that can be cultural contamination).
Sure thing, sooner or later primitive societies around this sparkling abyss will discover the important **mummification properties of salt**, and not unlike how ancient Egyptian did with [Natron Valley](https://en.wikipedia.org/wiki/Wadi_El_Natrun) and the substance which goes by the same name, mummification and body preservation in the afterlife could become an important part of their religious consciousness.
[](https://i.stack.imgur.com/Vy3HO.jpg)
# THINGS CAN GO REALLY WRONG
In a certain sense the civilization depicted up to this point is an **unbalanced society** in which the access to a “modern” comfort such as mass food preservation is unmatched by other solutions to manage population growth such as medicine and fast travel, although the former can supposedly benefit from the salts mining industry (e.g. soap). Primitive societies will be confronted early with the problem of overpopulation, and the ratio between resources and mouths to feed is very reminiscent of [the story of a people who loved to build giant stone heads](https://en.wikipedia.org/wiki/Easter_Island). **Factors like increased interaction between different civilizations, war over resources (with explosives!) and population booms due to better diet and better hygiene will all play a role in a fast changing and complex society.** And let's not talk about salt tornadoes ravaging the countryside. However all things considered I think that if certain conditions are met it can find its balance. *If only this wasn’t…*
# ~~AN IMPOSSIBLE UTOPIA~~
The amazing advantages which came from having an endless reserve of useful minerals is almost too incredible to be real. I know this is not part of the question, but since you provided a specific setting I think it's fair to point out its glitches. The real problem with this scenario is that the conditions which are to be met to make this unbelievably vast salt flat possible will at the same time make human colonization impossible. Not only the intolerable climate will hinder any colonization attempt, but there will be no fishing industry and no farming; in short, nothing to use the salt for. Sure, all the other important properties will be of some value, but the impossible climate will render salt mining in this area as expensive and dangerous as in real world, essentially canceling out the advantages.
[](https://i.stack.imgur.com/NTXq9.jpg)
**EDIT: I saw others pointed out the same criticality and you readily linked a scientific paper which directly addresses the topic. I’m amazed at the complexity of climate. And as naive as it may sound, I really didn’t consider the extensive mountain chains which surround the Mediterranean Sea. If I understood correctly the paper, you can legitimately have cool, even humid (!) climate on land above sea level while still having an arid extreme environment below. That’s amazing. I suppose that this is made possible by the fact that this dry pit of hell was not caused by climate but rather by extreme depth. Fascinating, thanks for making me discover this unbelievable phenomenon.**
[Answer]
This already exists.
**The Dead Sea**
If you wanted salt from the dead sea all you needed was a hammer, a shovel and a bucket.
It would be most sensible to look at the real world effects of the dead sea on commerce back then.
[](https://i.stack.imgur.com/6GSrL.jpg)
[](https://i.stack.imgur.com/ZPdzL.jpg)
Salt is only valuable to the extent that it's rare. Without the Mediterranean sea most of southern europe and northern africa would be an inhospitable desert. It doesn't matter how much salt you have if you don't have fresh water and food.
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[Question]
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Giants do exist. It's just that they can't be anywhere close to being as big as those in Norse mythology or the story of Jack and the Beanstalk. The best we'd ever have for a giant was Robert Wadlow, who grew to a height of eight feet and 11.1 inches.
[](https://i.stack.imgur.com/xoxym.jpg)
People of his stature suffer the following biological and medical issues:
* Pituitary tumor, which can get large enough to shove nerves into the brain, causing headaches and vision problems
* Excessive sweating
* Such sleep disorders as insomnia
* Delayed puberty
* Irregular menstrual periods
* Deafness
Now let's say that the giant, as a species, does exist and grow no bigger than Mr. Wadlow. What kinds of anatomical differences from ours would they need to deal with the listed problems?
[Answer]
**A Larger Heart**
Having a large heart , especially in proportion to the giant, would counteract any negative affect associated with blood flow, hormone circulation, and lack of oxygen to the brain
**Larger hormone production centers**
Such as the thyroid, testes, thymus, pituitary, and adrenal glands , to increase the amount of the hormone in proportion to the body, and it may fix your puberty & menstrual issues
**Thicker Bones**
This will not only increase bodily support , but also ramp up the production of red blood cells. This may also solve your deafness and insomnia problem by making the bones in the inner ear more sturdy , and increasing the amount of oxygen that gets to the brain
**Stronger Tendons / More Skeletal Muscle**
To allow the giants to move their added skeletal weight & the added weight in general due to the square-cube law
**Larger Cerebellum**
Increases coordination proportionately to the larger body
**More Mitochondria**
Since the muscles will have to do a disproportionately large amount of work , the added mitochondria will be able to compensate
**More Capillaries**
Especially near the surface of the skin , to increase effective temperature regulation, ( which many other large mammals have issues with ) which fixes the sweating problem
Everything else can be scaled up normally , except for the cerebral cortex, as that might have the side affect of increased intelligence, that is , above that of the average human , but hey , if that's your intended effect , knock yourself out
[Answer]
The reason human giants have so many problems is because their systems are not designed to cope with that increased size. If they had actually been evolved to that size though then evolution would have provided solutions. After all look at the size of elephants, giants, even giraffes and horses. They all do fine being much bigger than us.
You would expect proportionally thicker legs and arms, a larger chest and heart. An obvious improvement would be to increase the secondary pumping action of our leg muscles to help lift blood out of the legs, etc.
Take a look at the adaptations in existing large mammals and it should be reasonably easy to transition the same over to humans.
[Answer]
**What's the cause and what are the signs of a problem**
Some of the problems listed are the cause for gigantism. A problem with the pituitary gland can cause gigantism and very often that problem is a tumor. The Pituitary also produce hormones that control sexual development (and related), control of body temperature, metabolism and more.
Gigantism is a condition that has a cause, the size increase is a sign of that cause. Being a giant instead would not be a condition but someone that evolved to be of a bigger size than us and in that case the health problems you listed are a non issue.
[Answer]
In addition to other answers, one aspect would be [Gigantothermy](https://en.wikipedia.org/wiki/Gigantothermy): bigger animal tend to have higher body temperature.
Applied to a warm-blooded (i.e. constant temperature) animal, it means it would be easier keeping warm (saving calories) but also easier to overheat (limited endurance).
Human body is kind of specialized in cooling. We have long limbs, no hair and we sweat more than most (if not all) animals. So if your giant derive from homo sapiens, it would not need much adaptation; but wouldn't compare with human for long-distance running.
If he is only humanoid or derive from homo habilis, you can imagine anything.
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[Question]
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I am creating a world that consists only of cities. There is an 'outside' but the people never go there and the cities are connected with long underground tunnels.
There is a king, and he would of course need to have some kind of military power. But how would a military look like in this setting? There are no open battlefields to fight, or cavalry to win battles with. Siege weapons are also completely useless. So in what way would a military work? Will they have the same standard weapons, swords and shields, or will those be useless in the streets of a city and are there weapons better suited for this?
Edit:
It is more a medieval setting than a modern one. There is one king, and a servant/representative of the king in each other city. The 'known world' is just one country, with a few big cities and a few smaller ones. The tunnels can fit a group of men, but not to much. In between the cities are smaller settlements and markets, in the tunnels underground. A trip via the tunnels between cities is approx. 2 weeks. No flight. The walls of the cities are also to big and high to be able to climb on, although there are inner walls pressed against the bigger ones for some kind of control.
[Answer]
Assuming no one can cheat or think outside the box because the outside is somehow toxic or hostile to human activities, then military forces will devolve into Infantry forces, and the Infantry forces will have their characters based on the wants and needs of the owning polity. (more on that later)
Since urban operations are pretty intensive, the first thing that will become clear to every force is the need for lots of manpower. Attackers will find themselves rapidly reduced to small, squad sized forces operating in very tenuous contact with the main body due to the nature of urban geography (once you turn the corner into an ally or enter a building, you are out of direct contact with the larger formation). Defenders have the same problem, in order to "cover" approaches and have forces available to meet the attackers, they will also need lots of manpower.
The next issue will be what sorts of weaponry will be appropriate? Fighting will be done at short ranges for the most part, so the bulk of the soldiers will have weapons that work best at close range. Since buildings act as impromptu fortifications, there will be a need to breach walls and clear closed spaces, so weapons like grenades, flamethrowers, short range rockets with large warheads and so on will be developed. In a medieval setting, many troops will become miners, sappers or engineers to do the same things with picks and shovels, making an opening for a grenadier to throw the flaming hand grenade into the hole...More modern settings will see the development of submachine guns, assault rifles and carbines, shotguns and handheld grenade launchers, or their futuristic equivalents (Metalstorm, anyone?).
Vehicles, if used, will be heavily armoured to withstand attacks at close range, including IED's, mines, suicide bombers, RPG's or whatever exists in your scenario. They will fight back with weapons that can deliver high volumes of fire, or explosive breaching charges. Engineer vehicles will also be heavily favoured to clear paths and demolish strongpoints. IDF vehicles like the ACHZARIT and PUMA have evolved in this direction for this reason. Tanks, if they exist, would probably evolve into smaller fire support vehicles much like German StuG's of the second world war, capable of moving down narrow streets and having a short barrelled weapon firing high explosive shells rather than a long barrelled, high velocity cannon.
[](https://i.stack.imgur.com/qKVtP.jpg)
ACHZARIT
[](https://i.stack.imgur.com/TNdvR.jpg)
PUMA
[](https://i.stack.imgur.com/xyEx9.jpg)
StuG III
In all cases a very robust logistics organization is going to be needed to push supplies forward through contested ground and retrieve killed and injured troops and damaged equipment. Getting meals forward will be a huge chore when every corner could expose the logistics troops to sniper fire or an ambush. "Loggies" will also need to be adept fighting men, in addition to doing their usual duties on the front. (the deep rear troops like clerks and third line maintenance will probably be deeply resented "REMF's").
As for the character of the militaries, much will depend on the owning polity.
A polity which is mostly interested in protecting itself and not in conquering may develop a universal citizen militia on the Swiss model, where everyone has training and everyone carries and keeps military grade hardware at home or on their person. Invaders will not meet a conventional coordinated defense, but literally have to fight house to house as every single person will be capable of fighting and will be protecting their own personal property. A small permanent force might exist to use technical devices like AFV's, electronic warfare or protect from chemical and biological attack, and a skilled engineering force will exist to reinforce and rebuild structures both during an assault and after hostilities cease.
A polity which is interested in conquest will invest in legions of troops, well equipped and disciplined, capable of going into these deadly fights with as much manpower and equipment as necessary to overcome resistance. Only fairly large polities can afford the manpower and resources to do so, so only a few "empires" will exist in this setting.
Smaller polities which feel the need to project forces may evolve a more commando like force of raiders who can swoop down the tunnels and deliver a swift blow to knock their opponents back o their heels before the enemy can react. Once again, depending on the setting we can be talking anything from Ninja's to SoF forces. Given the restricted access through tunnels, they will mostly operate under cover to get in and out of targets. Soviet Era GRU "Spetsnaz" troops were often concealed as truck drivers for long range trucking firms, crewmen on merchant ships, communications troops in headquarters units (every HQ has lots of signallers) and embassy personnel, to give you an idea.
And of course every polity in this setting will have large and effective intelligence units busy placing spies and agents in every other city, in order to get up to date maps, profiles of leading citizens and military commanders, economic data and so on. The real war will be going on continually as intelligence forces battle counterintelligence forces in the shadows between actual hostilities.
[Answer]
One thing to keep in mind here is that you've given defenders a massive advantage. Having choke points that can be easily fortified and where forces can be concentrated is a defender's dream.
In contrast to the top voted answer (which I up voted) I argue that actually army sizes are going to make much less difference than it does in our world. If only 10 people can get down a tunnel at once then whether you have 100 people or 100,000 people behind them makes much less difference than if the 100,000 can swarm you from all directions.
Invasion would focus on stealth tactics to capture the defensive points by surprise or on digging new tunnels to bypass them. Defense would consist of multiple levels of defenses each arranged to deal as much damage as possible and culminating in completely collapsing the tunnel (ideally with the invading force still inside it).
"special forces" would be a really big deal here. If one special forces unit can capture a chokepoint and let your army flood into the city then they would achieve more than doubling the size of your army would.
[Answer]
# Weapons and warfare will focus on tunnel defense
Since the tunnels are the only way to attack another city, busting through tunnel defenses and creating tunnel defenses will occupy the majority of a commander's time.
## Military Organization
Much the same as medieval militaries. The king is commander in chief supported by a hierarchy of nobility, followed by mounted troops and infantry. Exactly how the military is organized beyond that rough hierarchy will greatly depend on the city, its resources, political culture and available armor/weapons.
## Internal threats
The king will also need to worry about internal threats such as insurrections or rebellions that his military will need to deal with. The size and make up of these forces will depend on the size, culture and disposition of the city's inhabitants. Heavily equipped inhabitants will require a correspondingly heavily equipped military/police force to counter them.
Heavy infantry or light mounted cavalry would be sufficient in this case to maintain order. Note, that you don't need the horses for mobility across open ground but for the added bulk/power that a horse brings to a situation.
## External threats
Since travel between cities must be done exclusively through these tunnels, the ability to choke them off will greatly strengthen the defenders hand. Even if rapid tunnel digging is possible, doing so is a noisy endeavor which is sure to alert the defenders.
## Feasability of Extreme Distance Tunnel Building
Assuming that the average human can walk 30 miles a day, a two week trip is 420 miles. Note, that even with modern earth moving equipment, tunnels even a [tenth as long](https://en.wikipedia.org/wiki/List_of_longest_tunnels_in_the_world) as described the OP are very very rare (Thankfully the Ancients had magic to help them with the tunnels). Maintaining these tunnels would be an exceptionally expensive endeavor with cave-ins, dead-air pockets and vermin infestations.
[Answer]
Clearly, if you need to go through tunnels to invade a city, some of the military would be tunnel builders. This is identical to medieval times where it was not uncommon to use tunnelers to either build a tunnel into the enemy city, or to get a wall to collapse. The defenders also built tunnels to enter the attacker's tunnels and collapse them.
Sword and shield, club and shield, axe and shield, spear and shield, etc were common all around the world so it's safe to say these would still be used to fight in the tunnels and cities.
The usual risks also apply, such as mercenaries who are tasked with defending a city turning against the city once they are inside, a city being starved due to a prolonged siege, hidden agents poisoning the wells of the city, etc.
[Answer]
## **Weapons**
I would suggest bows would be much less prevalent, there would be no need to hunt and the only bows would be specialist bow units who can be sent on top of walls/houses to shoot advancing enemy troops. The majority of soldiers would fight with short range weapons which are easy to use and without to much risk of them getting trapped in tunnels. Short swords and small shields with a few axes for breaking down doors/wooden walls. A couple of short spears may be used but probably not pikes or halberds as they would be hard to use in cities and tunnels.
## **Tactics**
The main defensive tactic would be to blockade, barricade or trap the major tunnels then surround smaller tunnels so only one or two enemies can enter at once. The best offensive tactic would be to mine side tunnels so you could bring men up in unexpected places. A good one would be to come up in a leaders house and kidnap them. You would then surround or block the defenders in a small area and then kill or capture them.
**Edit after reading material limits**
Scrap the bows, they are too hard to make without wood, I would use slings instead. In ancient times slings were respected elite fighting weapons so it is feasible as a weapon of was, also portable so a soldier could have slings and swords. Spears and axes should have bone handles or metal handles. Shields could be bundles of reeds wrapped in leather, this would be o.k. but quite heavy and not brilliantly durable so maybe shields would be used less and they would use perhaps a padded sleeve on one arm to turn away blows.
[Answer]
## Watchtowers :
Put [watchtowers](https://en.wikipedia.org/wiki/Watchtower) in every city, they provide a military advantage especially inside the city's walls :
>
> A watchtower is a type of fortification used in many parts of the world.
> It differs from a regular tower in that its primary use is military,
> soldiers and from a turret in that it is usually a freestanding
> structure. Its main purpose is to provide a high, safe place from
> which a sentinel or guard may observe the surrounding area.
>
>
>
] |
[Question]
[
Ignoring how this sort of atmosphere would come about, what are some things that happen regularly on Earth that would be altered by this sort of atmosphere?
Example: Would firearms still ignite normally with that much argon present? Would humans have trouble breathing? How easily would light pass through without reflection/refraction?
[Answer]
You've basically replaced nitrogen in Earth's atmosphere with argon, but left the ratios otherwise intact.
Argon is slightly denser than nitrogen; as a result, there would be slightly more light refraction in your argon atmosphere, but unfortunately I can't tell you what that would end up looking like to an observer. The speed of sound would also be ~10% slower, which isn't likely to be noticeable until timed.
Combustion (including firearms) would not be significantly affected, since that's really just oxidation of a fuel and you've left the ratio of oxygen in the atmosphere untouched. One thing that does change, however, is that you've eliminated less common byproducts of combustion, such as NO and NO2
The biggest problem is that you've eliminated the [nitrogen cycle](https://en.wikipedia.org/wiki/Nitrogen_cycle), which makes impossible the biology we know here on Earth. Nitrogen is crucial to every living organism we know, with atmospheric nitrogen being a staple of the process: Plants take it in, animals eat the plants, other animals eat those animals, and everything releases it back into the air during decomposition. Nitrogen is a critical piece of our biology, being a foundation of amino acids, and without it in the atmosphere we have no nitrogen cycle, and thus no (or at least insufficient) nitrogen to live on.
Unfortunately, argon is a noble gas, so it can't plausibly replace nitrogen in a hypothetical "argon cycle"-based biosphere. You have to either come up with a biology that doesn't depend upon nitrogen, or find a way to get it back in somehow (which, since it's a gas at anything above 77K, is pretty much impossible without it getting back into your atmosphere).
The good news is that argon is inert, so since there's adequate oxygen it's almost certain that humans could visit this planet and breath without needing full spacesuits and carrying heavy oxygen tanks. The slightly denser atmosphere would result in their voices sounding slightly deeper (think the opposite effect of inhaling helium, but much less pronounced), but otherwise they'd not really notice anything. They may just need to have access to foods that were part of the nitrogen cycle, and/or ship in nitrogen supplements for long-term habitation.
[Answer]
I think plants would get into trouble. Plants need nitrogen compounds, which many of them get from bacteria that take the nitrogen from the air. Without nitrogen in the air, those bacteria cannot create nitrogen compounds, and thus those plants are in trouble.
Note that the nitrogen compounds in dung indirectly come from plants, too. So that's no way to get *new* nitrogen into the cycle. Ultimately all that nitrogen comes from the air.
And the nitrogen in artificial fertilizer is taken from the air as well, so unless there's another source available, even that won't work.
Note that Argon, as a noble gas, cannot replace nitrogen in chemical compounds.
[Answer]
Argon is an *inert* gas. It takes a great deal of effort to get it to react with anything.
**Would firearms still ignite normally with that much argon present?**
Firearms (specifically, bullets) include their own oxidiser. That's why many guns will [happily fire while underwater](https://www.youtube.com/watch?v=cp5gdUHFGIQ).
**Would humans have trouble breathing?**
A little bit. Argon is ~43% more dense than Oxygen. We'd have a harder time breathing, but our bodies would very likely adapt to that change just fine.
**How easily would light pass through without reflection / refraction.**
The refractive indices of [Argon](http://www.wolframalpha.com/input/?i=refractive%20index%20of%20argon) and [Nitrogen](http://www.wolframalpha.com/input/?i=refractive%20index%20of%20nitrogen) are pretty similar. Interestingly, [Argon's absorption spectra is quite a bit more lively](http://www.wolframalpha.com/input/?i=absorption%20spectra%20of%20argon) than [Nitrogen's](http://www.wolframalpha.com/input/?i=absorption%20spectra%20of%20nitrogen). Despite it being a colourless gas, I imagine an atmosphere full of it would tint the sky with a tiny amount of green.
Argon's thermal conductivity is a lot lower than Nitrogen. Blowing on your hot coffee won't be as effective.
[Answer]
Argon is *inert*, meaning that in doesn't really interact much with anything. Like the other *noble gases*, it is much less reactive than the major components of the atmosphere. Therefore, to look at changes in this atmosphere, it's important to look at what we'd lose if the nitrogen was this substantially reduced.
That said, atmospheric nitrogen (N2) doesn't do much, either - it's also quite inert. So indirect results are what we need to look at - specifically, the [nitrogen cycle](https://en.wikipedia.org/wiki/Nitrogen_cycle).
Things that are impacted by the nitrogen cycle:
* No [*nitrogen fixation*](https://en.wikipedia.org/wiki/Nitrogen_fixation), leading to a lack of [ammonia](https://en.wikipedia.org/wiki/Ammonia#Ammonia.27s_role_in_biological_systems_and_human_disease) produced by nitrogen-fixing bacteria.
* Highly reduced amino acid synthesis (it needs that ammonia)
Really, atmospheric nitrogen isn't that important. Other sources of nitrogen exist, and organisms get quite a lot of their nitrogen from the ground and elsewhere.
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I am working on a world situated on the Earth.
There is normal gravity, normal conditions of living - normal everything, except the human population itself.
The situation:
Humanity as a species evolved to its peak, and now everybody has slight elemental powers based on fire, earth, water and air.
Nothing is overpowered. If you have no source, you cannot do voodoo elemental stuff. If you have a source, you can manipulate with it to the max range about 10 meters. I can not create a resource of my manipulation neither can turn in it. I can sense the water, I can do waves, for example, or water walls.
**Here is a problem. I am a water "elementalist". Can I walk on water in the Earth environment?**
[Answer]
# Sure
[Water tension](https://en.wikipedia.org/wiki/Surface_tension) is what allows those bugs or a feather to float on water. As you increase gravity, however, the tension is not strong enough, and the bonds between the water elements break.
Since you are able to manipulate the behaviour of elements, such as water, you would simply strengthen the bonds between water molecules below and around your feet. This would look like standing on a trampoline. The longer you stand still, though, the further out you must strengthen the bonds, until you've covered the whole, say, lake. This is because somewhere further out, the bonds will begin to break, and your whole platform sinks. Keep moving, keep manipulating.
[Answer]
It can be done...but maybe not in the way you imagine.
Meet the basilisk lizard.
[](https://i.stack.imgur.com/utokS.jpg)
This lizard uses a combination of **light weight, large fast feet, feet hair, and air bubble pockets** to run on water.
How does this help our human? Well, it doesn't really, but it does give you a formula for what it takes to walk on water. For humans to do this technologically unaided our feet would have to be massive, hairy and able to be propelled at an amazing rate...
In the end, to do this you are going to have to find a way to manipulate the water currents to push you up...or remodel your water folks' feet, I suppose both would work too...
Keep in mind that if your person is manipulating currents upward they are not going to be walking on a smooth surface, the water under their feet would be rolling and bubbling...they definitely are not going to be staying dry when they do this.
[Answer]
With the ability to create waves and walls of water, I believe you would be able to hold the water beneath your feet "solid" enough to hold you up.
Holding the surface solid enough to walk on would still take quite a bit of balance and practice, as the water movements below this surface would continue to flow and move with its currents, tides and waves.
Picture it as running across a very large waterbed, or perhaps a pool cover that is connected all around the edges.
[Answer]
You can also manipulate temperatures by absorbing/channeling heat and freeze water on your path. A 10cm thick layer of ice would be sufficient.
But how fast would be the heat transfer? If it's too fast, then water wouldn't have time to crystalize, losing ice's floating properties.
Another option is to avoid water displacement. When you step in, water molecules just go elsewhere. If you can manipulate water and its molecules, then you can order the thin layer of water molecules under your feet to stay in place.
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I'm working on a setting in which all humans have been genetically modified to have access to telekinesis ages ago, and it is now considered a normal thing. It works somewhat like a muscle in that the more you use it, the better you get at using it. It's upper limit, is that you can only impact an item of less than half your weight, less than your own body length away from you. On average, people can only lift between 5% and 10% of their body weight at half their body length away from them. This power cannot be directly used against living material, and the acceleration of an object can't be thrown with any more force with telekinesis than throwing it with muscle force instead. It is not physically strenuous to use telekinesis, but it is mentally strenuous when overused, although it's limits are similar to physical strength in that minor uses don't exhaust you, but using your power beyond your endurance level will leave you tired. Overusing this power way beyond your limit will result in the user passing out or falling asleep with maybe a slight headache when they wake up.
This is intended to be a background element that isn't directly important in the story, so I'm looking at finding out how to limit this power so that it isn't the main focus of the story. Now to the point, there are three primary areas where I'm curious as to how this would impact a society.
1. How would this impact a medieval society equivalent to our own middle ages?
2. How would this impact us if it were to happen in today's world?
3. How would this impact a more technologically developed society than our own?
[Answer]
We can handle very hot objects. We can handle contaminated objects. We can handle sterile objects. We can handle acids and bases. We can even handle high-voltage equipment not risking electrocution.
Opportunities are countless. Soldering, ironing, metal works is completely different (for starters, a soldering iron doesn't need a handle; fire iron is not needed whatsoever). Eating habits are completely different (no forks nor chopsticks). Chemists do not use gloves. Artists etch with much stronger acids.
I don't know how obstacles interfere with telekinesis in your setting. Can we reach objects inside a container? If so, [healer-style](https://en.wikipedia.org/wiki/Psychic_surgery) surgery is a possibility. Also, I expect all locks to be totally redesigned.
Alas, soccer would die instantly.
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**I think the sociological/psychological/interpersonal ramifications far outweigh the technological.**
Inside our brains is a structure commonly known as the [motor homunculus](https://en.wikipedia.org/wiki/Cortical_homunculus): that part of the brain that specializes in awareness of body-position ([proprioception](https://en.wikipedia.org/wiki/Cortical_homunculus)) and motor coordination.
It is known that those who are expert in the use of a body-extending tool see enlargement and development of the corresponding portion of their motor homunculus. For instance, a professional violinist not only sees hyperdevelopment of left-hand areas (fingering on the bridge), but an enlargement of the right-hand areas (bowing). Startlingly, fMRIs will show that a violinist's reaction to someone tapping on a bow held in the right hand will generate the same stimuli in the brain as someone tapping on your or my right index finger. *The violinists wetware body-representation has grown to absorb the bow!* The same thing happens with tennis players and racquets, painters and brushes, &c. (See [You Are Not a Gadget](http://rads.stackoverflow.com/amzn/click/0307389979) for some discussion of this; I'm sure there are even-better references; feel free to edit them in.)
What's my point? People growing up in a world where the 6' sphere around them is under their motor control and feedback (presumably--otherwise, how would you control your tele-objects with any precision?) would see corresponding enlargement of the corresponding brain structures. Effectively, *'all of that space I control, physically, **is** me.'* But some of that space is shared: this is a world where **personal space overlaps.**
The impact of this? People would require much more square-footage in order to feel as independent as we do. Or perhaps people would develop much closer forms of community (and communication!) as living in "normal" proximity feels like we're crawling all over each other. Show one of these people a basketball game and it'd read as unspeakably-violent--sadistic levels of interpersonal violation, perhaps.
(On the other hand, watching a married couple folding laundry in the same room might look like almost-pornographic levels of intimacy!)
**The technological upthrust:**
The way you've laid it out is pretty restricted: medievalists wouldn't do away with the plow, or beasts of burden, water-powered mills. But domestic industry--spinning, tinkering, carving--might take a lead over 'larger' industries, compared to our history.
**One thing I know: if this happened in today's world...**
I wouldn't want to be holding stock in a spatula company.
[Answer]
As described, possessing telekinesis does not actually do much good. You can't lift more than you might by mundane means, and you can't do it beyond arm's length. It's basically like having an invisible set of arms. Oh sure, it would come in handy for those cases where you've got your arms full and want to unlock your door, and it would make for jugglers with mad skills, but nothing earth-shattering.
As such, it wouldn't make much of a mark on modern or futuristic societies, but it would have a profound impact of the development of medieval societies.
They wouldn't believe in magic.
And, by extension, they would be unlikely to be dominated by religion in the same way medieval Europe was.
When you can move things without touching them, all the things that magic is supposed to be able to do would likely be attributed to people with talents which, while hidden, are not at heart mysterious. And with miracles not being what they were, the hidden powers of God would not be as credible either, with the result that religion can't take credit for the unknown in the form of miracles.
At the same time, given the limited scope of powers available to most people, the development of technology in post-medieval society, culminating in the Industrial Revolution, would probably not be impeded much.
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In a project of mine, I've contemplated an alien species that uses a weapon that shoots liquid nitrogen (or something similar) that makes enemy armour brittle by freezing it. Is there a way they could avoid damaging their own weapon with the freezing liquid?
[Answer]
While this is not exactly a response to the question you asked, it is too long for a comment, so I'll do it this way.
Weakening armor by spraying very cold liquid on it is not particularly practical. The problem is that even liquid nitrogen doesn't cool stuff very quickly, especially if the LN2 is sprayed on (as opposed to being an immersion bath). Consider that a [reasonable goal](http://www.spartaengineering.com/effects-of-low-temperature-on-performance-of-steel-equipment/) for making steel brittle is -46 C, or just about 70 C below ambient.
From [this link](http://web.mit.edu/21h.416/www/militarytechnology/armor.html) it seems reasonable to assume plate armor has a nominal thickness of about 2 mm. Let's take an area of 0.1 square meters as the target. How much liquid nitrogen is needed? The volume of the armor affected is $$V = A \times T = .01 m^2 \times 0.0002 m = .0002 m^3$$ which has a mass of $$m=V \times \rho = .0002 m^3 \times {8000kg/m^3} = 1.6 kg$$
Steel has a specific heat of ~.5 kJ/kg deg, so the total energy required to drop the temperature of the armor by 70 deg is $$E= 0.5 \times 1.6 \times 70 = 56 kJ$$.
For any armor temperature above 77 K, the interface between the LN2 and the armor will consist of boiling LN2, so the energy transferred will be dominated by the latent heat of vaporization, which for LN2 is (about) 26 kJ/kg. Therefor, in order to cool the armor to -46 C will require $$M = \frac {56}{26} = 2.15 kg $$ of LN2.
Of course, most of the LN2 sprayed on the armor will never contact the armor - it will be forced away by the gaseous nitrogen created by what vaporization does occur, just as most of the surface of a very hot object is protected in water by evolved steam. Worse, a suit of armor is overwhelmingly vertical, in that liquids drop away from it due to gravity, so very little spray will actually make thermal contact after it is repelled by vaporized nitrogen. Even assuming (and I consider this a *very* optimistic number) 10% of the spray does its job, this is going to require delivery of about 20 kg of cold liquid to each armor surface in order to get it cold enough. In the case of LN2, with a specific gravity of 0.8, this amounts to about 25 liters of liquid. Assuming this has to be delivered in 2 seconds, this is a flow rate of about 25 cubic feet per minute, or about 187 gallons per minute, or 11,000 gallons per hour. For contrast, a fire hydrant typically produces a pressure of ~50 psi and a [standard requirement](http://www.codepublishing.com/wa/puyallup/html/puyallup16/Puyallup1608.html#16.08.040) for hydrant flow is 1000 gpm. In other words, your cold liquid sprayers will need to be roughly on a par with a fire hose.
Frankly, I'd be inclined to give it up as an idea that sounds neat but doesn't seem particularly practical.
[Answer]
WhatRoughBeast does an excellent job of expounding on the issues of a liquid nitrogen weapon. It is rather impractical, as it takes a lot of work to get the "amunition" prepared, and continued effort to keep it in that state, and then immediate loss of effectiveness when shot over any distance.
However, the concept of a freezing weapon is interesting. The bombardier beetle uses a rapid oxidation agent to shoot an exothermic reaction that exceeds the boiling point of water. It has a complicated system with the reagents, an inhibitor, and an inhibitor-remover. Adapting this design to your idea, but using a violently endothermic reaction to cause rapid drop in temperature, I think you could do it. Now, google did not provide me with a good enough endothermic reaction to use as an example, but your aliens should be able to find one. Also, if your aliens coat whatever their armor is with a reaction inhibitor, or a method to neutralize one of the reagents, they would be immune to their own weapon. This would still be able to freeze the ground and other objects around the aliens, causing terrain hazards.
Having the "freeze" action occur closer to the target by aiming the two sprays to mix in front of, or immediately on, the target would reduce the efficiency issues brought up with the liquid Nitrogen design.
Now you say this is for use against a personal armor, so there are joints and flex points to consider as well. Perhaps this endothermic compound sucks the heat from what it touches as it grows and hardens. If its stable form is a crystaline structure, it could cause armor to turn brittle by cold while also applying pressure from its growth.
Maybe it immobilizes instead. Think of the Kenbishi AMPT Sticky Gun from Ghost in the Shell [](https://i.stack.imgur.com/lpFJK.jpg)
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Yes they can avoid the damage of their own weapons by:
1- Using different type of armor. Metal armor would indeed lose tensile strength and break easier when at extremely low temperatures. But an armor made of nylon would retain it's characteristics and not become brittle. Of course you don't expect a 100% nylon armor for space battles, but you can have an armor that has nylon on the outside layers and metal on the inside. When hit with the liquid nitrogen, it will hit the nylon layer. Nylon is a bad conductor of heat so the metal layer will not drop to lower temperatures and keep working effectively.
2- By using quick heaters. When hit by a jet of their own deadly liquid nitrogen, the soldiers would quickly turn on the internal heating for their armor plates which would return them to normal temperatures quickly. Notice that these heating systems do not heat the army directly by flame, but through a very hot blow of gas, like a hair dryer.
[Answer]
This weapon could consist of a medium that gets really cold on contact with air, thus freezing itself and super-cooling what it hits.
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I am an evil genius owning a space station in a 400km orbit around Earth. As part of my plan for world domination I would like to equip this space station with a ground-attack laser cannon. Approximately how powerful (in watt) would an orbital laser need to be so that a one-second burst could destroy:
* an unprotected person
* an unarmored car
* a one-family house
* a battle tank
* an office building
* a small town
Assume that the target is on normal-null altitude, directly below the orbit of my station and that the weather conditions are as favorable as can be reasonably expected.
[Answer]
*So I'm no rocket scientist, but here goes. Much of this is shamelessly lifted from Project Rho.*
First, lets ignore the diffraction caused by passing through the earths atmosphere for the following. I'm also assuming you're talking an actual laser, not a particle weapon, blaster, or some other variant.
A general idea to start with is for the US military, the minimum threshold for a tactical weapons-grade laser is 100 kilowatts.
Maximum range will be a few hundred thousand kilometers, otherwise almost every shot will miss due to light-speed lag, Unless we are shooting at targets that don't move.
First we calculate the beam divergence angle θ (θ = 1.22 L/RL)
```
$θ = beam divergence angle (radians)$
$L = wavelength of laser beam (m, see table above)$
$RL = radius of laser lens or reflector (m)$
```
Next is beam power BP, then calculate the beam intensity at the target (the beam "brightness"):
$$BPT = BP/(π \* (D \* tan(θ/2))2)$$
```
$BPT = Beam intensity at target (megawatts per square meter)$
$BP = Beam Power at laser aperture (megawatts)$
$D = range to target (meters)$
$θ = Theta = Beam divergence angle (radians or degrees depending on your Tan() function)$
$π = Pi = 3.14159...$
```
The following equation will be of use for determining the diffraction:
$$R\_T = \frac{0.61 D L}{R\_L}$$
where:
$R\_T$ = beam radius at target (m)
$D$ = distance from laser emitter to target (m)
$L$ = wavelength of laser beam (m, see table below)
$R\_L$ = radius of laser lens or reflector (m)
As for laser wavelengths:
* Near Infrared 2.5$\times$10-6 to 7.5$\times$10-7 m (2,500 to 750 nanometers)
* Red 7.5$\times$10-7 to 6.2$\times$10-7 m (750 to 620 nanometers)
* Orange 6.2$\times$10-7 to 5.9$\times$10-7 m (620 to 590 nanometers)
* Yellow 5.9$\times$10-7 to 5.7$\times$10-7 m (590 to 570 nanometers)
* Green 5.7$\times$10-7 to 4.95$\times$10-7 m (570 to 495 nanometers)
* Blue 4.95$\times$10-7 to 4.5$\times$10-7 m (495 to 450 nanometers)
* Indigo 4.5$\times$10-7 to 4.2$\times$10-7 m (450 to 420 nanometers)
* Violet 4.2$\times$10-7 to 3.8$\times$10-7 m (420 to 380 nanometers)
* Ultraviolet A 4$\times$10-7 to 3.15$\times$10-7 m (400 to 315 nanometers)
* Ultraviolet B 3.15$\times$10-7 to 2.8$\times$10-7 m (315 to 280 nanometers)
* Extreme Ultraviolet 1$\times$10-7 to 1$\times$10-8 m (100 to 10 nanometers)
Below Extreme Ultraviolet, you can't use the laser outside of the vacuum of space as the atmosphere would absorb it, so we can ignore those.
An example of how this works is as follows:
>
> Say you have an ultraviolet (20 nanometer) laser cannon with a 3.2
> meter lens. Your hapless target is at a range of 12,900
> kilometers (12,900,000 meters). The Beam Radius equation says that the
> beam radius at the target will be about 4 centimeters (0.04 meters),
> so the beam will be irradiating about 50 cm2 of the target's skin
> (area of circle with radius of 4 centimeters). If the hapless target
> had a hull of steel armor, the armor has a heat of
> vaporization of about 60 kiloJoules/cm3. Say the armor is 12.5 cm
> thick. So for the laser cannon to punch a hole in the armor it will
> have to remove about 625 cm3 of steel (volume of cylinder with radius
> of 4 cm and height of 12.5 cm). 625 \* 60 = 37,500 kiloJoules. If the
> laser pulse is one second, this means the beam requires a power level
> of 37,500 watts or 38 megawatts at the target.
>
>
>
A note: using a pulsed laser rather than a single focused beam would require less power, in effect drilling into the target rather than trying to vaporize it.
Now aside from all of that, you're generating a massive amount of waste heat that will require dissipation, but that's a whole extra problem.
There's also a neat laser maker calculator [here](http://panoptesv.com/SciFi/LaserDeathRay/DamageFromLaser.php) that I would recommend for those that don't math.
Also to read the source of this information, you can find it [here](http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Laser_Cannon).
[Answer]
1 watt second is a joule, so I will use J instead of W/sec
To be accurate you need to determine what is a definition of destroy. For example, to burn a person could mean incapacitate by 2nd or 3rd degrees burns of much of the body, or it could mean turn to ash.
Published data from atomic testing suggested that 8-10 cal / cm^2 is enough to cause 3rd degree burns on unprotected flesh. 10 cal / cm^2 is about 420 KJ / m^2. Average adult has about 2 sq meters of skin, but since you can only irradiate 1 side, you have to settle for burning one side of a person, so 400 KJ one the target will incapacitate a human. Without medical treatment 3rd degree burns over 50% of body is often fatal due to shock, fluid loss and infection. To actually guarantee a kill, you need more power on target of course, 10 MJ is probably enough and their clothes will catch on fire too overriding more common forms of protection outdoors.
Setting hardwoods on fire requires about 1 MJ / m^2 this would be sufficient for many homes, but a crushed white rock roof would be mostly unaffected, perhaps 10 MJ / m^2 would be enough -- 200 sq meters would include most homes so you need 2000 MJ or 2GJ on target.
A car again is difficult determine what destroyed requires. Unlike on TV cars to not catch on fire or explode at the least provocation. To temporarily incapacitate a car via space laser, the softest target is probably the tires, could not find direct data, but I suspect 1 MJ / m^2 would ignite the tires most of the time, but since the tires are often shielded by the vehicle they would often not catch on fire until far beyond this point and in any case you could easily fix this. To destroy a car you need to get it hot enough to destroy vital components like electrical wiring or engine belts - though again belts are easily replaced. I believe if you can heat the car to 500 C you will destroy most of the wiring as well as other soft components (seals, etc). So, how much energy to raise a car temp by 500 C (it could be winter). Curb weight on a new Ford Exposition is up to about 6000 lbs, as a first order approximation lets model this as 2720 kg of iron. Iron has a heat capacity of 0.45 J/g/deg. So 2720 kg \* 1000 g/kg \* 500 deg = 612 MJ on target.
Tanks are a lot like cars, so I will use the similar assumptions but I will require 800 deg and 63,000 kg (Leopold 2) and I will need about 22.7 GJ on target.
Office building. Likely brick, stone, steel in construction. Again how much is enough to consider it destroyed? If you really want to be sure, you need to err on the high side. The Empire State building used 60,000 tons of steel, 200,000 cubic feet of limestone and granite, 10 million bricks and 730 tons of aluminum and stainless steel. To simplify, I will assume 200,000 cu ft of limestone and ignore the bricks and aluminum. How much does granite weigh about 2.75 g/cm^3 and a heat capacity of 0.19 J/g/deg. Total granite mass 15,600 long tones. For a 500 deg temperature rise I need 13,500 GJ for the steel plus 1,482 GJ for the granite or about 15 TJ to take out the empire state building. In actually fact, you don't heat up the lower floors in this case as the upper floors absorb nearly all of the heat. A 1 second pulse would need to essentially vaporize the upper part of the building in order to destroy. But that is not even enough as the vapor cloud itself would absorb and scatter a large percentage of the laser blast. A thousand times might be enough though.
A small town, again what is threshold of destruction, and just how big is this. I was raised in Columbus Indiana, so seems like a good model to me. Columbus IN, population 44,061 (2010 census). Area 72.23 sq km. 500 deg temperature rise and steel & concrete destruction (to take out all of the buildings). I will simply revert to the energy per unit assuming the 100 MJ per sq. M is enough to take out everything (100 times the energy to ignite hardwood). 100,000,000 MJ / m^2 \* 72,230,000 m^2 = 7.223 PJ -- petajoules on target.
Needless to say, there are no experimental confirmations of the beam attenuation that would be encountered firing from orbit to surface targets, certainly not anything approaching these energy levels. However, I did find [Laser Atmospheric Attenuation Tables](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCQQFjAAahUKEwjMsKH47NvHAhUEUZIKHaAgC50&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3DADA325417&usg=AFQjCNF9m8BbK4iFz69HsZb1AHfiA9AWNQ&sig2=IPatJW3ZVNjxS_eDQ6nzMQ) for LTAS. Without going through the justification at this I think you would need about 20-50 times as much light at the source to reliably punch through the atmosphere as you have at the target. I have not yet performed more detailed calculations to confirm this. So, take all of the amounts above and multiply by 50 if you want to be able to destroy targets with reasonable certainty. This is based on bad weather conditions. For best case but still realistic weather conditions it would appear that you only need 5-10 times the on-target energy at the source.
The higher energy levels deserve better accuracy as their are many non-linear and probably classified effects that doubtless come into play.
---
I am also understating the actual power required because I generally ignored that fact that for everything except the unprotected human case, the target will ablate. The surface layers will cook off turning into gas and taking much of the incoming heat with them, and continuing to absorb and scatter the incoming laser light. I also generally ignore the fact that the target will reflect some of the laser light, when in can reflect at least some of the incoming light. At most of these energy level, a mirror will not provide protection, at least not for long as even a good mirror will absorb enough energy to quickly be destroyed.
These power levels are beyond ridiculous. For everything larger than a car, the power at the target exceeds that of even the largest electrical generation stations. The entire United States only has a electrical capacity of 1060 GW.
For our simple 3rd degree burns on a single human 1MJ on target requires a minimum of 5 times that at the source and 5 times again for the loss of electrical conversion to laser energy, i.e., 25 MJ. A common comparison is that 1 MW will power 1000 homes, so 25 MW is over half of the power needed to supply Columbus Indiana just to incapacitate 1 person.
Using capacitors to store up for a bolt from the sky may sound like a good idea, but your requirements dwarf standard capacitors. The [largest capacitor bank in the world is only 50 MJ](http://functionspace.com/topic/1612/Largest-Capacitor), built at a cost to 10 million Euro
Somewhere during your construction phase people are going to wonder what you are building and will get motivated to put a stop to your evil plan.
[Answer]
Most of the numeric factors have been accounted for, but there are a few other things you need to consider in your orbital fortress.
Punching all that energy through the atmosphere, even in "window" wavelengths will cause a huge amount of energy to be deposited in the atmosphere. To a certain extent the initial thermal blooming and other distortion effects can be accounted for using "adaptive optics" (AKA a "rubber mirror") which flexes to compensate for atmospheric effects. At higher energy levels, like those needed for burning hardened targets like tanks, the amount of energy could easily cause air molecules to dissociate into plasma, blocking the beam entirely as the plasma absorbs the energy and radiates it away as incoherent light and heat. Luckily, since you are in orbit, you will miss the worst effect of the plasma running back "up" the beam to the emitter and depositing the energy on the mirror.
The second consideration is that lasers in general have very low conversion efficiencies, so if you need as much as 5X the actual beam power as input energy for your laser system. This also means that you are join to be dealing with incredible amounts of waste heat, so your space station will be dominated by the energy system and vast arrays of radiators. Even at 400km altitude, the sheer size of all this could cause enough atmospheric drag to bring you out of orbit. The mass of all the stuff will also make your space station virtually immobile in terms of orbital manoeuvres, so people who object to being lasered from orbit won't have much difficulty in sending clouds of ball bearings or even sand into the orbital path of the space station, meaning that even with the impressive laser weapon, it could be destroyed.
Now the most impressive laser weapon that I have ever seen described is also on the Atomic Rockets website (<http://www.projectrho.com/public_html/rocket/spacegunconvent.php>); the Ravening Beam of Death (RBoD), which uses a kilometre diameter accelerator ring to power a Free Electron Laser (FEL) capable of vaporizing metal, ceramic and carbon fibre a light second away in milliseconds, and I don't think that has the energy levels described to vaporize entire towns in a single shot. But it does provide an alternative, since a light second is almost the distance from the Earth to the Moon (and the beam itself is dangerous far beyond, a light second is arbitrarily chosen to make targeting responsive, since no target can move very far in a single second or the two seconds needed to see the effect of the shot and correct).
So set up your fortress on the Moon, fire short pulses of laser energy rather than long beams, and remember to allow for the energy dumped in the atmosphere to dissipate between shots.
[Answer]
The biggest problem for your laser of death is going to be the atmosphere. As Thucydides noted, even at wavelengths specifically chosen to not interact with the atmosphere, a considerable portion of your power is going to be transferred into the air. If your laser is powerful enough to punch through the armour of a tank (as worked out by Gary Walker) then the beam has to be about 22 GJ \*20 (minimum attenuation) or 440 GJ. Lets assume that 40 GJ of energy gets through and the rest is lost to atmosphere, so 400 GJ pumped into the atmosphere. A lightning bolt delivers 1-10 GJ and turns the atmosphere to superheated plasma in a fraction of a second. I'm not sure what the energy flow rate is going to be like for your laser, given the atmospheric pressure gradient, distortion, diffraction and other effects, but I think it's fairly likely that with even a conservative estimate of the energies involved you're going to literally set the air on fire.
You're looking at energy densities that can break water molecules apart and then set them on fire, ionise the air and generally do all sorts of bad things to the medium you're trying to push the laser beam through. If the laser makes it harder to push the beam through to the target you'll have to pump in more energy to hit, which will cause even worse things to happen, all the way up to turning the air into plasma and literally forcing it out of the way in order to make a path for the laser beam to travel through. This sets fire to an awful lot of other things too.
In essence: this weapon will not be precise, will require an ungodly power source, and is generally hideous to try and build without anyone noticing.
Or... You could just drop ceramic coated lumps of tungsten with some guidance packages on them... From your altitude you could knock out a city with something the size of a car, a tank with a computer tower, and a person (and his mates) with a tangerine...
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For an intelligent species of life to attain so advanced a level of technological development and operation as to be considered a type-I civilization, in a number of evolutionary scenarios they'd first need at their disposal hundreds of millennia. In the case of humanity, systems of time are often politically or religiously motivated--a number of different civilizations having their own calendar eras. For example, at present, in the West, we use the Gregorian calander, which incidentally is also called the Christian Calander. Most of us know when time supposedly started within it or at least according to Christian mythology.
When we look at these religiously or politically motivated biases it's easy enough to criticize, but then when we look at the alternatives, say Unix time, it's quite easy to appreciate their formats. My question incorporates both issues. How would so intelligent a species possibly or probably keep track of time?--Would they simply hold to ancient societal formats, such as those inspired by religion, or would they have possibly implemented a fabricated format based on atomic time with, say, the "beginning" being placed at the same "time" as the big bang, supposing that they espoused such a scientific theory? Would they use their sun, in all likelihood, just as we do for years and days and so forth?
The obvious answer is that we have no way of knowing what a superorganism so many times more intelligent than us would do as regards the recording and implementing of time. However, perhaps certain factors could be fleshed out in the same way that we have come up with a Drake equation or the Fermi paradox. The point I make in my last sentence is only that I am looking for plausability, not deductive inference.
Just in case, my question again is: what are some likely ways a type-I civilization would keep track of time; and, from what point of beginning? If you answer, please explain why you think such. If you go with something like unix time, how would that translate into years and what would the format look like and, again, is there any reason for thinking such?
Thank you.
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Humans have been keeping time for a very long time (or so the timekeepers tell me), but just like government computers and old computer scientists, we really don't like updating our software. For instance, look at how we still maintain the Babylonian method of keeping time (seconds in a minute, minutes in an hour), even though we use a base-60 number system *absolutely nowhere else*. Plus, even though there have been many events more world-changing than the birth of Jesus of Nazareth, no one seems to want to go back to zero (you mentioned Unix time, but I don't think too many people would say that today is July 24th, 0045 AU).
At least for humans, the desire to stick to old, obsolete systems seems to be a pervasive part of our culture. Many people prefer magical, mystical, religious, or 'alternative' medicines to the scientific ones, Americans outright refuse to switch to the metric system, and schools still let out for the summer even though very few students have to get home for the harvest. It is conceivable that even far into the future, we'll still be desperately holding onto our traditions, instead of embracing new ideas. This holds especially true for time, since it won't really help to change it in most cases, and will really screw up meetings if some people switch and others don't.
So, for your civilization, time will most likely be kept based on some ancient system. Years will probably exist, and be as long as it takes for their home planet to go around the sun. If the planet rotates, there will be days. As for the other time periods, it depends on how long the day and year are: for example, if a year is only seven days long, they won't really need weeks, but there will probably be some new ways to split up the extra-long days.
If the civilization has expanded to other planets, there may be local time systems based on that planet's rotation/revolution, but the standard will most likely remain based on the home planet. This is especially true if your civilization maintains their original bodies; even humans in space or on the moon are still going to want to sleep for eight hours every twenty-four hours, it's just how we're built.
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I would not worry about the "beginning" event in your system, an event known as an "epoch." Times and dates are really only useful when talking about the difference between them. The epoch has little, if anything to do with reality.
For example, nearly every time system we have is fixed to a date described in Julian dates. Julian dates start at January 1, 4713 BC in the Julian calendar. Why that date? Because it turned out that, if they started then, the entire Christian recorded history was in positive numbers, and that was the start of a major cycle in the Julian calendar (the conjunction of 3 important cycles). We've literally based every date since off that calendar!
Now the units of time, those are more interesting. We have a system of units, hours minutes and seconds, which are very closely tied to the 24 hour cycle of Earth. These would likely shift to something more convenient as we expand. However, I would expect this shift to occur around the type-II boundary, not the type-I boundary. Generally speaking, I would presume that biology and nostalgia would keep us using Earth time for a reasonable time after we leave our planet.
However, it would be interesting to see if the march towards SI continues. Once we break free of our diurnal rhythm (which will not be easy), measuring time in seconds, kiloseconds, and megaseconds might be very reasonable. However, until that diurnam rhythm within our bodies is understood and reigned in, I expect the value of a 24 hour day to not recede.
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Already with interplanetary travel and mapping, *time* is not a simple background but needs to cope with SR and GR. We do that *now*. A civilisation that spans this scale will naturally include the concepts that time is not independent of space and flows at different rates. A unified coordinate system of *space-time* is needed.
There is also a broader understanding similar to time zones: not only "what time was it at X when it was time=t1 at Y", but realize that time flows at different rates, so the relationship is not fixed and there are differences in *durations* as well.
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Businesses and civil use won't use the full complexity that's present for scientific use and navigation. On a human time scale, counting days, I don't care that time passes faster on Mars, but might care that Mars uses a different day-length cycle.
For legal and banking use, I need to specify actual unambiguous periods, like Earth's civil solar day, and while at it I can specify that it's measured *at* Earth, so interest accrues at the specified time as measured at the specified place. The purpose they care about is making sure payment is received before that point, so communication delays and such are responibility of the pay-or. But the tiny SR/GR differences are handled the same way, by indicating a specified time *and place*, never a time alone.
The oldest laws deal with shipping responsibilities, and lots of terminology and standards have emerged. With information taking the role of goods, and possible light-speed transit, the ideas carry over regarding shipping and destination ports and who's responsible at which stage.
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Some counter arguments based on Human history:
Every "new" social organization likes to consider that they are the "start" of history. Ancient Egyptians measured time in Regnal years (i.e. from the ascension of the Pharaoh), so dates would be something like "on the 14th day after the flooding of the Nile in the 6th year of Rameses III". One inference is that things that happened prior to Rameses III really aren't all that important.
We see the same in the French Revolution, when the traditional calendar dates were thrown out for a "Revolutionary Calendar", or the the chilling declaration that "This is the Year 0" when the Cambodian Communists under Pol Pot defeated the government and took over to start their genocidal regime. Even the UNIX calendar is based on a unique event: the introduction of the UNIX OS as "second 0", with all other events recorded as seconds before or since that event.
I would think that a Type 1 civilization would probably start their calendar from some epochal date, with everything measured from and too that event. If the civilization is not "unitary", then there will actually be several competing calendars in use, much as the "Georgian" calendar we use is *not* universal outside of business and aviation, or "Zulu" time is not commonly used outside of the military. Holdouts might be trying to preserve a different culture or religion, or perhaps use this as a means of differentiating themselves from the mainstream (the "Hipster calendar").
I suspect that even a type 1 civilization may also have destabilizing events, and perhaps their civilization might have several calendar "resets" over the lifespan of the civilization.
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Not sure how useful this is but a hugely advanced civilisation will probably count in base sixteen or base twelve. Can't remember why but this is supposed to be the best base to count in. Although your civilisation may count in whatever number of fingers they have so there time may respect that. For a universal or multi-planet civilisation a base 16, or base 12 as these are good systems and are not reliant on biology or day length meaning it will be potentially easier for other races to understand.
Choosing a start date has many possibilities. If the society is religious then they would chose a date that reflects this, birth of messiah, date of universes creation, birth/death of prominent saint/saints etc. If they are very proud of there science they may chose a scientific date, birth of famous scientist, discovery of space travel/nuclear fission/other major discovery etc. If they are a race which meets with many others then they may adopt a time system similar or the same as a race they trade with for ease of communication.
An alternative to a number based system is a naming of years, similar to the Chinese, or just no naming of years. Why not just count days, why do we need to number years at all? Although this still would require a day 1 somewhere in the past it need not be a famous date like 0 A.D.
Sorry this answer is not very well organised, if I get time I may improve it later.
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A type I civilization could eventually end up choosing different time systems and starting basis for different sets of solar systems or galaxies.
Starting basis:
Over the many millennia they have explored and studied so many different star systems with all their different expressions of time within each of the systems that they found it easiest to simply set up a new time system per locality rather than bothering with constantly making conversions to one primary system. Oh sure, they'll still have the algorithms set up so anyone could make the conversions between time systems if they want to, but most will choose to just go with the flow. More energy efficient that way.
So they will initially calculate the star's birth based on the oldest known system's star death. Set that as date "zero".
Incremental time within the systems:
They figure out for each system its most stable elemental decay rate. They set up a clock based on that specific decay rate and possibly if it makes sense to do so (staying there a while, or there's local intelligent life to continue to interact with, etc.) choose larger increments of time based on the amount of time the farthest or closest planet takes to rotate it's main star or group of stars. Or based on just the one planet if there's intelligent life on only one at the time they setup timing. Or maybe based on the center point of rotation within a rotational galaxy. They are complex folks who enjoy variety, and some systems just make more sense to do it one way over another. Some are so young they won't bother with more than most basic decay rate clock. Then while they "spend time" within that system or galaxy, they use that time system.
When traveling between systems they may keep the last system used if they like it, or revert to whichever home system they are from, as they will not all be from the same places by the time they are Type I. Time will truly be relative at the traveling distances they experience, and they are extremely adaptable or they would not have lasted as long as they have. They are also comfortable with non-temporal states of being, and find the simplest choice is often to adopt the local environmental constraints.
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Take a 'mage' whose magic takes the form of manipulating (non-magical!) energy and matter in an approximately 10m radius around them. Examples of this include high speed air currents around the mage that serve as protection or forcing oxygen away from a person to cause suffocation although they can't affect anything below electrons and neutrons etc. They also can't turn matter into energy or vice-verse.
Knowledge of science isn't required for them to perform magic- their mind 'magically' (haha!) works out how to make their spells happen, but they do have to obey any laws of physics magic doesn't directly ignore by its existence (meaning they can't create energy/matter etc). Their greatest weakness is that they can't make use of chemical energy, from themselves or batteries.
What could a mage like this-call her Anna- use as 'mana' batteries to store energy to power her spells? Ideally, the object in question should be:
1. Light weight, so she can carry a few of them
2. Inconspicuous, so she doesn't stick out like a sore thumb
3. Not made of illegal substances- she should be able to acquire it through legal channels, although paperwork is fine.
4. 'Rechargable' in her own home.
Magic in this universe is a legally accepted thing with compulsory magical education for mage-kids and various licenses for using magic in cosmetic surgery, construction etc.
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An interesting idea for this ( which shows up in one form in the *Fionnavar Tapestry* books ) is that the ability to carry magic is a talent a little like the ability to shape it, so the unobtrusive magical battery is another person. No extra weight to carry, not something obtrusive or obvious, but also a potentially challenging relationship with all kinds of intriguing ramifications:
* Perhaps two people have to be attuned to be able to work together.
* Perhaps the power can come through anyone, but it is dangerous to take it from someone untrained.
* Perhaps only a very few people have either talent and seeking them out is a major endeavour for magical colleges.
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If I understand your magic rules correctly, the magic can convert/extract all the energy of matter in the 10m around to produce a magic spell.
There is nothing that would produce more energy than the binding energy of its constituants (atomic+nuclear scale). Even in a nuclear bomb, you release the binding energy of the Uranium in rapid succession, which makes the Big Boom. Your magic is more efficient.
The only interesting point you could consider is to add matter. Indeed, if you carry around more matter, you have more reserve of energy with you, that can be used to produce magic. You thus have an advantage compared to if you hadn't that matter. What to choose? Probably a high densitity material (to limit the bulkiness). Sticks of [Osmium](https://en.wikipedia.org/wiki/Osmium), [Platinium](https://en.wikipedia.org/wiki/Platinum) or [Mercury](https://en.wikipedia.org/wiki/Mercury_%28element%29) would be an idea.
The problem being: what prevents the opponent mage to use your sticks?
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How about having your magicians carry something with them that has a high [specific heat capacity](https://en.wikipedia.org/wiki/Heat_capacity), and then store your energy as heat?
Even at a low technology level, the magician could heat up 5kg of water (about 10 lbs) heated 50 or so above room temperature (25C) for a stored energy of about 1 MJ. They could use even more of that energy if you allow the water to go below the ambient temperature.
1 MJ of energy is a lot. It's the equivalent energy of about 210 AA batteries, or enough to lift a 100kg mass 1000 meters!
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Idea: the 'battery' takes the form of a metal ingot or bar. To 'discharge' the battery, the user magically induces atoms in the bar to transmute, releasing energy. To charge the battery, one can reverse the transmutation (magically, of course), drawing on an external power source to provide the necessary energy.
We can divide such batteries into two types based on the type of reaction they employ:
* **Primary (non-reversible):** These batteries use nuclear reactions which emit particles (e.g. neutron/proton emission or alpha decay). Since these emitted particles are lost, these batteries cannot be charged without a particle source to 'reseed' them.
* **Secondary (reversible):** These batteries utilize transmutations between isotopes of the same mass number (e.g. electron capture or emission). Since the total number of nucleons is unchanged, the transmutation can be easily reversed in order to 'recharge' the battery. A second advantage is that a secondary battery emits no radiation when it's discharged.
There are a couple restrictions that we can make on candidate reactions:
* Both the reactant and product isotopes should be stable, with half-lives longer than a hundred years or so.
* The host metal should have acceptable mechanical properties and should be safe to handle.
Note that the isotopes need not be naturally occurring, since large-scale magical nucleosynthesis should be possible.
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I'll just consider the case of a secondary battery (it turns out that primary batteries using alpha decay are only energy-dense for heavy, radioactive nuclides, and proton or neutron emission are almost never energetically favorable). Looking at a [table of nuclides](https://en.wikipedia.org/wiki/Table_of_nuclides_(complete)), we want two stable isotopes on a diagonal from each other (i.e. with the same mass number). Considering only elements that are found alloyed with various metals, this leaves us just a few possibilities:
$$
{}^{14}\text{C}\leftrightharpoons{}^{14}\text{N}\\
{}^{26}\text{Mg}\leftrightharpoons{}^{26}\text{Al}\\
{}^{32}\text{Si}\leftrightharpoons{}^{32}\text{S}\\
{}^{50}\text{Ti}\leftrightharpoons{}^{50}\text{V}\leftrightharpoons{}^{50}\text{Cr}\\
{}^{53}\text{Cr}\leftrightharpoons{}^{53}\text{Mn}\\
{}^{54}\text{Cr}\leftrightharpoons{}^{54}\text{Fe}\\
{}^{58}\text{Fe}\leftrightharpoons{}^{58}\text{Ni}\\
{}^{59}\text{Co}\leftrightharpoons{}^{59}\text{Ni}\\
{}^{60}\text{Fe}\leftrightharpoons{}^{60}\text{Ni}\\
{}^{63}\text{Ni}\leftrightharpoons{}^{63}\text{Cu}\\
{}^{64}\text{Ni}\leftrightharpoons{}^{64}\text{Zn}\\
{}^{92}\text{Zr}\leftrightharpoons{}^{92}\text{Mo}\\
{}^{93}\text{Zr}\leftrightharpoons{}^{93}\text{Mo}\\
{}^{94}\text{Zr}\leftrightharpoons{}^{94}\text{Mo}\\
{}^{96}\text{Zr}\leftrightharpoons{}^{96}\text{Mo}\\
$$
Let's go over the more plausible ones:
* **Carbon and Nitrogen:** This reaction would be possible using iron as the host metal. The charged state would be high-carbon steel, and the discharged state would be a through-hardened nitrogen steel. [Nitriding](https://en.wikipedia.org/wiki/Nitriding) is usually only applied to the surface in a case-hardening process, since it causes the steel to become brittle (although hard and wear-resistant). The energy capacity of this reaction is on the order of $15~\text{kWh}/\text{g}$, since nitrogen typically only makes up around 5% of nitrided steel. Note that, unless nitriding processes are available in your world, these batteries would be produced by magically controlled neutron bombardment of regular carbon steel to result in 14C steel.
* **Magnesium and Aluminium:** Magnesium is commonly alloyed with aluminum: in alloys like [5456](https://en.wikipedia.org/wiki/5456_aluminium_alloy) and [5356](https://en.wikipedia.org/wiki/5356_aluminium_alloy), the Mg content can be as high as 5.5%. Higher magnesium content leads to a brittle and less corrosion-resistant metal. The energy capacity is an impressive $230~\text{kWh}/\text{g}$, with low-Mg aluminum as the charged state. This would also require magical production, as 26Mg typically makes up just 11% of typical magnesium, and 26Al is slightly radioactive, and thus not naturally occurring.
* **Chromium and Manganese:** [Mangalloy](https://en.wikipedia.org/wiki/Mangalloy) is a steel with up to 15% manganese content that is abrasion- and impact-resistant, but hard to work. Stainless steels, such as the common [304 stainless](https://en.wikipedia.org/wiki/SAE_304_stainless_steel), have similar chromium content (up to 20%). This makes a mangalloy/stainless steel battery possible, with mangalloy as the charged state and an energy density of $45~\text{kWh}/\text{g}$. Again, the 53Cr would need to be magically enriched from its normal concentration of around 9%.
* **Chromium and Iron:** As mentioned before, chromium is alloyed in large fractions with iron to make stainless steel. With a typical carbon steel as the charged state, and stainless steel as the discharged state, such a battery could hold $50~\text{kWh}/\text{g}$. Unenriched steel has about 5% 54Fe, so this battery would be fairly easy to produce.
* **Iron and Nickel:** There exist a large range of nickel-iron alloys, including [Invar](https://en.wikipedia.org/wiki/Invar) (36% Ni) and [mu-metal](https://en.wikipedia.org/wiki/Mu-metal) (80% Ni). This makes a nickel bar an extremely powerful battery, storing an incredible $890~\text{kWh}/\text{g}$. Even with a naturally-occurring isotope fraction of only 68% 58Ni, you'd still get over $600~\text{kWh}/\text{g}$ when discharging to an Invar-like alloy.
The nickel/iron battery is probably the one you want to go with; not only does it have high energy density, but such batteries could literally be forged from [fallen stars](https://en.wikipedia.org/wiki/Meteoric_iron), giving them an additional magical flavor (if you're going for a "traditional fantasy" magic feel with hard-science backing).
Note that the amount of power contained in such a battery is *enormous*: a one-ounce coin of enriched nickel can release enough energy to:
* launch a person out of the solar system (from rest at the Earth's surface)
* vaporize two tons of rock or 41 tons of water
* supply an average American household with electricity for two years
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Why not chemical batteries? Rig them up so you can create a 'short-circuit' which sparks or otherwise releases the energy, and then tap that. Accidentally activating your battery could be dangerous, and in use it might be a little obvious, especially if the mage can't convert all of the electricity to magic. Maybe there's a brief flash of light before she starts channeling the energy->magic.
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Just some loose ideas:
How about a genie bottle? Where you push magic inside and draw it out later?
If needed a genie bottle containing a magic cow? It will need to be fed but can be milked for magic at regular times.
Jewellery with magic storing gems would go at a premium, large ones being valued heirlooms in established magic families.
Less ethical and harder to control are apprentices that provide energy for teaching. Cannot be carried, have to hide in plain sight.
Magical potions that release energy on drinking have potential and can be traded as well.
Well-stored magical circles are SUCH a nuisance to fold up without spilling to carry around, after all.
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What you are essentially looking for is a system with a higher energy than another relaxed state but metastable. This is common but the magic just makes it easier to do something interesting. A good way to do this would be to transition highly ordered structure to disordered ones. Unlike reality, you don't have to design a safe mechanism to extract the energy so almost anything would work.
Examples:
Crystals degrading into a tarnished state. A diamond to carbon black would be dramatic (despite being quite low energy). For less destructive situations, the formation opacifying defects and (possibly) oxidation on the surface would suffice. You can imagine her using water or forming crystals in a water bath to recharge it. Simple salt crystals could serve this purpose (and the water solubility could be an interesting tool for the story). Crystals hold alot more physical energy than most realise but the difficultly is in extracting it. Thematically, these are great for earth or water magic (again salt). Sugar crystals wouldn't fit well with earth but hold alot of energy too.
Pure metals are kind of like crystals but less conspicous. Braclets, buttons, swords, etc can corrode or homogenize upon activation. This is a showy version of how most batteries work. As the manufacture of this would best be done with electrolysis, this would be great for mechanical or electrical magic.
Organic polymers burn good if you get them hot enough. Everything from pockets of lint, bundles of paper, clothings, etc can be made of cellulose which burns well. Wax, hair, surrounding plantlife will work too. For a battery shape, compress the material and use magic to rend it apart and speed up the burning. Of course added sulphur, charcoal, and saltpeter will work amazingly (gunpowder). Obviously my hint here is that these would be useful for fire magic. It would be fine for air magic too if you focus on the oxygen element.
Finally, you can discuss the use of alchemy for the really potent masters. Of course Azoth (i don't mean mercury) and Arcanum are the ultimate stores of energy and this idea can easily be romaticized. There was an alchemist who claimed to keep Azoth in his sword hilt. You can pay special attention to the connections between planets and metals or zodiac signs and chemical sythesis techniques. While Azoth can be viewed as medicinal and good for healing magic, a laymen could just used extracted vials of cholophyll or blood (maybe the 4 humours). They don't need to know what they do to know the indicate health and energy. Imagine the sangine vial turn black or the green one brown. Yellow sulphur was also considered a vital element of life by alchemists and (in the right form) has alot of energy too.
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As an alternative to *storing* mana, consider the possibility of *streaming* it from a remote source. The mage would have an antenna of some sort, either hidden on their person (e.g., sewn into the lining of a jacket) or perhaps even used as a wand. The mage's allies would have a device that takes input energy (from whatever source you want to use) and broadcasts it in the mage's direction. The mage's antenna receives the energy, allowing the further use of magic. This is the same general principle behind [wireless phone chargers](http://powermat.com/), and some of Nikola Tesla's experiments. Instead of applying the principle to electromagnetism, you'd be applying it to mana (which you could potentially treat as a fifth [fundamental force](https://en.wikipedia.org/wiki/Fundamental_interaction)). The physics of mana and its transmission would be completely up to you, so you can define things like how far mana can be transmitted, whether it has to be broadcast or can be transmitted in a narrow beam, or what sort of antennas are necessary.
This approach solves your general problem of the mage needing more energy than is ambiently available in their immidiate vicinity. It also opens up logical explanations for story elements like shielding a room against an opponent's magic, intercepting/stealing mana, creating powerful spells by having several mages combine magic, relationships between a mage's power and the quality of their gear, government limitations on magic by "metering" mana, etc.
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Why not use magical ink?
I mean, you say that the "energy" has to be stored somewhere, but there is no real limitation on what it is. Magical inks can be used to scribe incantations in a book, and as you use spells the ink evaporates (or disappears, because magic) and once all the ink in the book is gone, you're toast.
Everybody can carry a book, be it a journal, a recipe book, a law reference book, or something else, it doesn't stick out
You can write on the book back at home, so it's rechargeable.
The magical ink can be made of various substances and therefore have a variety of inks with different amount of energy stored in each, say, milliliter or something. The production and sale of this ink could be regulated by the Mages Guild or something.
A book is naturally lightweight and everybody can carry a few. The richest of the rich can buy the most powerful inks with a lot of energy stored in them, so they only need to carry a thin book instead of a few.
Example:
Suppose that there are 3 tier inks: Standard, Premium, and Ridiculously Strong.
The standard of this tier is how many Fireballs one can expect to be cast.
The mechanism of magic is that you write the incantation on a paper and as you use the energy in it, the ink evaporates, causing the text to appear more and more translucent until it's gone. The incantation used for testing has a standard size, typeface and boldness.
The standard of energy used to count the Fireball is each Fireball should be able to burn a 200 grams raw beef into a medium steak in 1 blast, not medium-rare, not well-done, but precisely medium-rare. About 5% margin of error is acceptable.
So say that Standard ink can cook 3 beefs before the ink evaporates, Premium can do 6, Ridiculously Strong can go 12.
The entire energy can be spent in an instant of big blast or used very sparingly in a small flame that it lasts way longer.
Suppose that the incantation of Fireball is the word "fireball" written in lower caps, and a standard sized paper can hold the word "fireball" in 4 columns and 12 rows for a total of 48 standard fireball words, using a standard ink will allow you to cast 144 standard fireballs before you run out
The poor and inexperienced will need bigger and more books to hold all the inks in case their spells miss or they went overkill too many times, the experienced can go with fewer and smaller books
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If I understand the premise correctly your mage can take energy from their surroundings and re-purpose it; like taking heat energy and turning it into kinetic energy, but they can't directly draw energy from chemical sources.
The simple work around seems to be to carry a battery (or chemical energy source) and a device that turns that energy into something usable, like heat.
The simplest thing I can imagine would be a lighter or something similar. Quite a lot of chemical energy stored in the lighter fluid which can quickly and easily be turned into heat, which your mage can then manipulate. Small, unobtrusive and cheap too.
If they can extract electrical energy then even something like a phone might work, or really any electrical device. Perhaps a taser if you want to increase the available power (and if you needed the electrical energy to be more accessible then running through a device).
If light is a possible energy source they could carry torches (though to be honest, if light is a usable source then the sun is a far better source of energy most of the time)
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Based on the wind example, it sounds like kinetic energy is one of the forms of energy that a mage can harness. What about springs or flywheels as potential energy / kinetic energy storage devices?
You'd have a nice little "battery" that runs on angular momentum, or release a spring (with some kind of trigger) to get a quick burst of energy to work with. Maybe you could use the flywheel to generate mage-usable heat via controlled amounts of friction, and there might even a way to convert a spinning metal wheel into usable electrical energy as well.
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**This question already has answers here**:
[Where in the solar system is the most viable place to put my colonists, after Mars and Luna?](/questions/2507/where-in-the-solar-system-is-the-most-viable-place-to-put-my-colonists-after-ma)
(17 answers)
Closed 8 years ago.
The answers to this question may be subjective but I am interested in other's opinions (I have some myself), so please include your selection criteria. Also let me bound the question:
You can only use near term (next 50 years) technology.
Consider environment factors
* Gravity (too little is harmful to us, while there aren't many spots with too much in our solar system)
* Atmosphere (too little can be overcome, but too much is difficult)
* Temperature (cold can be overcome, but too much heat is difficult)
* Radiation (some provision for radiation protection)
* Resource availability (volatiles, construction, metals)
* Energy availability (solar, fission, fusion)
* Living space/carrying capacity
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Luna, Phobos, Deimos, Mars, and the asteroids. I'd love to give some detailed and precise and insightful explanation, but the reality is that with near future technology space colonization is all about orbital mechanics and the amount of delta-V needed to get to or from somewhere. Note that the order of the above destinations depends on the mission. For example, Mars is easier to get to than the asteroid belt but has a much deeper gravity well. So for one way trip Mars is better, if you want to bring something back the asteroids start looking better.
Also, it should be noted that much of Earth is still uncolonized. It is probably easier to colonize the oceans or the Antarctica than the Moon. It is much simpler to terraform the Sahara or other deserts than Mars.
Additionally, if you want a research or mining colony, with near future technology it is probably easier to send robots to do the work by remote control and local AI. It isn't as good as humans on site, but you can ignore gravity, atmosphere, life support and lots of other messy stuff needed by humans long term.
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Several answers, it really depends on answering the 'why' question.
* Survival of the human race.
One of the bigger arguments to get us to space ultimately comes from human redundancy department of human redundancy (HRDHR?). From a purely survival standpoint, we are currently 100% dependent on the Earth and had an extinction level event occurred here, the human species is potentially gone. From a purely survival standpoint, getting off of Earth and somewhere else is the survival through redundancy option...if Earth is eliminated through events out of our control (yellowstone become a volcano the size of Wyoming?) then our species only hope for survival is not to be on just Earth.
If survival of the human race / species redundancy is your goal...I would suggest a moon of Jupiter as our first colony. This gives a few advantages...if the sun enters a dormant phase that heavily impacts earth, this Jovian colony wouldn't care much as it could be dependent on Jupiter for energy derivation instead. Mars, moon, and venus are far less desirable as a large scale event could effect both Earth and this new colony. The further away from Earth and into the outer solar system, the better.
* Stepping stone to bigger and greater.
If this is the first step towards a bigger goal of space colonization, then the very obvious choice becomes the moon as it becomes a space dock / construction yard. Ultimately it takes a lot of energy to get away from the Earths gravitational pull and even more energy to get up to an orbital speed. Reversely, the moons gravity is significantly easier to escape and you're already orbiting earth. It makes it far simpler to create the ships on the moon and use it as a construction site to create the infrastructure required for further expansion
* Home sweet Earth like home
It's a bit of retro-futurism...the idea that we can take 60's Earth culture and simply transplant it to another world. Turn some planet into Earth and setup white picket fences and perfectly mowed lawns as far as the eye can see. If we are looking for this second Earth like home, the terra-forming Mars effort is likely your best bet.
* Mining and space faring
A little further out there...but our current human species is ultimately bound to Earth. We function with the gravity and atmosphere here...the food and water that are a core requirement to us is found here. That said, there isn't that much Earth out there and we need to have the realization that different colonies need to adapt differently...assuming there isnt a magical solution that allows faster than light travel, we need to admit that isolation of humans in different environments is going to create new races and subspecies of what we currently consider human. Whats a human that's never been exposed to gravity greater than microgravity going to look like, and how much isolation and time do they need before we call it a new human species? What will a high gravity human look like? If you're looking to expand human evolution and create a zero-g specialized human and a human race that's independent of Earth, then the asteroid belt becomes a decent choice.
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The moon.
It's a resource for materials, unlike empty space which requires materials to be brought in. It provides protection by digging down. It's *close* so emergencies can be assisted in 3 days travel, and it doesn't need to be as self-sufficient from day 1.
It is *the* natural first step.
It would serve as a shipyard for Mars craft etc. Because it's more practical to get stuff off of it, and open stip mines are there for the taking with no environment to worry about.
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As you can see from this chart, every planet with similar gravity to ours has a horribly extreme temperature. The most moderate temperate besides ours is the moon and then Mars. So if the moon isn't an option, go to Mars and terraform it.
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Well, I'm pretty sure there's going to be a [mars colony](http://www.mars-one.com/) inside the next 50 years, considering they already plan on sending people there starting in 2026. People have been lining up and are getting wait listed for a one-way ticket to their certain death on mars (literally—there's no return flight—they will go there and die there—how they die is yet to be determined, but they're hopeful that it'll be of old age).
We've already put men on the moon, but we haven't gone back since the initial exploration efforts because there's really nothing up there. Japan and Russia plan on establishing bases on the moon in the next 20 years, but there's not much more there than worthless rock, its only true value is measured by the effect it's gravity has on the earth, and the light it reflects at night. There might be some Helium-3 mining in the future, but probably not.
The most hospitable place in the universe to set up a colony, which wouldn't have to be in a station which generates it's own atmosphere, would be [Gliese 832 c](http://en.wikipedia.org/wiki/Gliese_832_c). But it would be an epic exodus to get there, and any ship we send will most likely get ripped apart by space debris before they could reach the planet.
Colonizing the Solar System won't be feasible until we can develop a more efficient method of transporting objects into orbit. You need to have a port before you can have an expedition, and the best place to build that port would be in high orbit.
A [space elevator](http://en.wikipedia.org/wiki/Space_elevator) is still our best bet for transporting objects and materials into space, with a space elevator, you could build a large spaceport in high orbit, where you could construct a ship much larger than anything we could launch from the surface. This would be the staging area for colonizing other planets and moons.
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In the far future, cities are spreading across continents, some cities are as large as france (~1000 km across) after smaller cities have grown together - Into Super Cities.
Now [Marchettis Constant](http://en.wikipedia.org/wiki/Marchetti%27s_constant) states that a city's limit in size is estimated one hour commuting.
* How would public transportation and the roadways look if you need to move at an average of 1000km/h?
* What kind of vehicle would you need to achieve that (Vacuumtube trains?, Flying cars?, Micro stargate'ish- Teleportation?)
* Given any imaginary techonology, how could this be achieved ?
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First of all, let's clear up a fundamental misunderstanding: Marchetti's Constant does *not* state that a city's size is limited to one hour of commuting, but rather that people will adjust their routines such that they spend, on average, one hour commuting. This means it does not impose any restrictions on city size, it only supposes that people will live up to ~30 minutes from where they work (giving an average daily commute of 1 hour). In fact that's evident today already, where numerous cities take much more than an hour to commute from one side to the other (especially if you catch traffic at the wrong time!), though on average people live much closer than "the other side of the city" from where they work.
It does have implications on urban planning, though, such as implying that a residential zone without much work available in a 30-minute commute probably won't be much lived-in.
That said, the Supercities of the future are still likely to have very interesting modes of transport for when people do want to travel further than 30 minutes, and even for extending how far 30 minutes actually gets you:
**Trains** and **Flying Cars**
AndyD273 has already addressed these in his excellent answer. I'd just point out that China's 2010 1000kph train is no doubt *slower* than the express trains of the future, especially if vacuum tube trains become a reality. I'd also add that flying cars, barring some sort of hand-wavium that (at least partly) negates gravity, would necessarily be much more energy-intensive than surface-driving cars, meaning they'd never fully replace the latter.
**Expressways**
The expressways of today are pretty much just wide boulevards with limited traffic lights so that you can drive from Point A to Point B more quickly. We're already on the cusp of the next generation, though: Expressways designed expressly for self-driving cars.
This would work in a way that blends high-speed trains with taxis: You would hail a car, get in, and it would take you to where you need to go. No having to bother with all that lane and signaling nonsense, either; advanced computer algorithms would dynamically adjust the paths of each individual car (in much the same way that air traffic controllers guide airplanes) so that each one has a clear path from Point A to Point B.
With expressways closed to any other vehicles, these computer-guided cars would be free to run just as fast as we can make their engines capable of, without fear of collisions; while unlikely to beat a high-speed train in a speed challenge, they would have an extraordinary advantage: There'd be no need to get out and transfer to a local leg, because your self-driving car could simply get off the expressway and -- albeit at a slower speed -- navigate surface streets to bring you directly to your destination! [NB: You'd probably put opaque windows in these things, at least while on the expressways, because your human passengers would very likely find themselves in a heightened state of anxiety if they can see the seemingly-chaotic mass of cars driving at high speeds through laneless roads, weaving between one another as they approach at deadly speeds head-on before veering off -- very often the most expedient path is *not* what we're used to seeing with our static concepts of "lanes" as "safe passing zones"!]
You could even physically separate the self-driving cars from everyone else by having them suspended underneath the expressways (a la the Total Recall reboot), freeing the surface to be available for manually-operated cars (if those even still exist...) or even high-speed trains.
**Telepresence**
This is already a thing today; I spent 6 years working from the office in my home for a company that would have otherwise required an 8-hour flight *one way* to get to their offices. That was your run-of-the-mill telecommuting though, where I'd be typing on my computer or talking on the phone all day; these days you can get yourself [telepresence robots](http://www.doublerobotics.com/) (link is just one example) to have a physical, mobile presence in an office on the other side of the globe, let alone one merely 800 km on the other side of the Supercity.
As these become more ubiquitous in office environments, commuting will become a lot less of a consideration.
In a very similar vein, MMO games have given us another option: The *virtual* office. After all, if you can get 25-50 people together for 8 hours to battle a pixelated dragon, certainly you could hold a 1-hour staff meeting in a similar manner? The advantage this has is that you can base your avatar on your own appearance, allowing others to still connect with you visually, and/or customize your avatar to your personal preferences (similar to the MMORPG character generators today), which has many of the same benefits (assuming you don't frequently change your appearance, that is). As VR systems improve, this is likely to become even more prevalent and more accepted.
After all, even today there's really no need for countless individuals to ever set foot in an office; as this becomes a more widely-accepted fact, and the various telepresence technologies provide comfort to the clingers-on of the "old ways", commuting will become more and more an artifact of a bygone era.
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**Trains**
Back in 2010 China was looking at making a [1000kph train](http://www.dailytech.com/China+Plans+1000+KPH+Super+Train/article19268.htm). The problem with having a train like this in the mega city is the stops. You'd want to get it up to speed and then only stop when you got to the other side, but it would skip everything in the middle. If you were stopping a lot for passengers then you'd lose a lot of time/momentum. You'd have to have to have several layers of trains to make it work.
Local, to get around the neighborhoods, like a modern subway system. Maybe have a stop every couple blocks.
Short Range, to move between local groups faster than hopping from line to line.
Express, to travel from once side to the other very fast. This would be the 1000kph train.
Having the 1 hour commute be a hard limit would still keep the cities from being 1000 km across, since you'd have to travel from home --> local --> express --> local --> work... but it would be close.
**Flying cars**
As Frostfyre said, see Coruscant as an example of what this would look like...
**Teleportation**
This is probably the best possible way, as there would be no theoretical limit on how large your city could grow without you being able to get anywhere within a couple minutes.
An example is Niven's teleporation booths and stepping disks:
>
> STEPPING DISKS
>
> Earth uses teleportation booths to provide near instantaneous travel throughout the world, but the Puppeteers have created a series of stepping disks on their homeworld which allow them instant travel; they can walk the entirety of their homeworld in minutes, giving them "seven league boots". Unlike the booths, the stepping disks can be installed anywhere and are portable. Transfer booths, used for transport on Human worlds, are an inferior variant on the stepping disc, using technology secretly sold by the Puppeteers to one of Gregory Pelton's ancestors.
>
>
>
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I would bet on mini-low capacity maglev trains as means of mass transportation...i was planning a story with mega cities like that so i've think about that. I'll cite my reasons.
* In a mega city you got millions of people that want to go to different places and they want to get it here fast safely and comfortable (nobody likes the insane overcapacity trains/metros of today right?)
* How would you concentrate insane amounts of people in a station to wait for trains or whatever? Nobody would like that and no matter how big and fast your tech are you will always have more people wanting to use it than you can provide.
+ Most of people are alone or in small groups.
That's why I think mini-low capacity maglev trains are better , they don't make any noise they don't pollute and in future they will probably go 2000km/h or more but as others have pointed the problem of centralized networks and stations are the stops you would never get to 2000km/h if you stop every 1km or less.
You could have 4 lanes of maglevs trains , one for near maximum speeds , one for 50% to 70% speed and one for low speed for short travel and one lane that is exclusively to stop and pick/drop people.
Make it connected so any maglev train can go to any lane if needed and let an AI handle the driving and optimization of the system. Make it low-capacity like 5 to 7 people so you don't gather a crowds waiting for it.
Built it so that any person can request an maglev train anywhere at anytime on city(i think suspended lanes above the ground will work the best) and if you want you can have the AI to pick people that are going very close to the end destination.
And forget cars they just don't work on big cities driverless or not they will never be a mean of fast mass transportation and they are messy chaotic and require lots of space to be built for them.
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If you're happy to go more down the route of pre-planned megacity or to have a city-wide transportation upgrade programme then potentially something like a [PRT network](http://en.wikipedia.org/wiki/Personal_rapid_transit) could be useful. The joy of an integrated, automated network is that you can then incorporate multiple different transport networks to efficiently route traffic across the city. This automation is the key component, as the problem with such a large city is not necessarily straight line distance, but is more likely to be [traffic flow management](http://en.wikipedia.org/wiki/Traffic_flow). I spend most of my commute time waiting for trains that are late or stuck behind red lights when there are no other cars on the junction.
For example, Joe Bloggs orders a PRT pod for work. He gets in and directed the automated system to get him to work ASAP. The pod acknowledges, closes the doors and accelerates at a gentle pace. Route planning software is already tracking all other PRT modules, and decides the best way to get Joe to his workplace is to shuttle onto the nearby Heavy Rail Transit network, where a larger scale Maglev train with a dedicated PRT pod carriage (or two) is waiting. The HRT then takes Joe across the city (along with an efficiently packed number of other cars), his PRT pod completes the rest of the journey and Joe steps directly into his office.
On the journey home, however, the HRT network is not running in the same direction as Joe. The transit network analyses current traffic rates on all major thoroughfares, shunts Joe's pod onto one of the lower level, lower speed lines, handily routing him around the major blockage points caused by the evening rush. Halfway home Joe's pod unexpectedly veers into a siding station a few seconds before a medical transport rushes silently by. The medical transport continues at breakneck speed until it hits the airport, barely decelerates in time to come to rest in the cargo hold of a ramjet aircraft which immediately begins its takeoff run to deliver a still beating heart to the other side of the world for transplant. Meanwhile Joe arrives home and is greeted by his adoring LoveBot 5000
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Without getting into magical systems like teleporters, I would suggest that huge urban conglomerations like that would actually morph into more three dimensional structures similar to Arcologies.
As a three dimensional structure, everything is much closer at hand, and elaborate and expensive epress transportation systems are not really needed inside, but can be optimized to provide transportation between cities. As well, the Arcology, like a normal 2 dimensional city, would also be divided into neighbourhoods, where people would probably define their neighbourhood as the place where most of why they need day to day is available in a short walk or elevator ride (how far might be cultural or social, a "five minute walk" for a young man might be impossibly tedious for an 80 year old woman).
The resource bill for a "city" the size of France would be immense, and I suspect much of any "real" city like that would actually resemble a shantytown like those surrounding a third world megalopolis, with most of the people unable or unwilling to move very far from their cardboard and tin shacks.
[Answer]
# What people want
People usually try to find equilibrium between two things:
* They want to breath clean air, sleep undisturbed, have kids playing in the garden, not too expensive yet big house and with a nice view. This would be a remote countryside or a small village.
* They want to be close to the office, facilities and social/cultural life, this would be a city centre.
Marchetti described the relation that exists between the two: 1 hour commute is the compromise. If you enhance the transportation speed, people are still going to live at 30 minutes from a place where things (work/museums/bars/shops/…) happens . So if you create a very efficient transportation system, it’s very likely that people are going to live even further to the place of work and keep commute 30 minutes.
# Teleportation
If you go to the extreme and invent tele-transportation, or generalize remote office, people are not going to group into cities. I would go to a mountain, in an isolated woodhouse, and jump in my tele-transportation machine every time I want to go to work or to see my friends.
The territory will look like many isolated houses, small villages, isolated companies’ buildings (*I have a cool company, our offices are at the north pole!*). Maybe a pub street in the middle of nowhere, to go pub crawling without having to take the teleport machine between bars.
# Your case
Now, your case. Even if, seen from space, your country looks like a big city, it will have many sub-systems, many “downtown” areas. These centres areas are going to be, according to Marchetti’s law, about 1hour commute time from each other (well, ok, this assumes that transportation speed is the same between centres than between suburb to centre, which is not true. It’s usually faster to go from one centre to the other than from the centre to the suburb, but let’s assume it).
So transportation is not as primordial as city planning. You can, if you want, keep the current transportation hardware and make a city of any size work fine, as long as it is well planned for this kind of transportation.
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What changes to the culture of 1950s Britain/England would be needed for a Female [Archbishop](http://en.wikipedia.org/wiki/Archbishop) of Canterbury, of the Anglican Church of that time period?
She also has as much political power and social capital and all that kind of stuff as the OTL Anglican Church...
So no "She's just a figurehead to appease the Feminists" or something like that.
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In terms of cultural reception, there are certainly precedents. Widespread sexist attitudes didn't really slow down Margaret Thatcher, for example; although there was still plenty of that around in the 1950s-1970s, I think she got around it for the simple reason that, while sexism had a lot to say about how women should act at home, it didn't define whether or how women should act as government ministers, simply because the situation had almost never come up before.
Another relevant example would be the [Chevalier d'Eon](http://en.wikipedia.org/wiki/Chevalier_d%27Eon), widely accepted in 18th century society despite being transgendered. If trans people were frequently trying to gain positions at court, they'd have been systematically shut out, but as a one-off it was just seen as an unthreatening curiosity.
So, I could easily believe a one-off instance of a female bishop, especially if she *weren't* campaigning on the issue of female clergy in general. As long as you can come up with a plausible story as to how she got her foot in the door (demographic exigencies during WWII?), it's not entirely far-fetched that she could distinguish herself and end up a bishop.
There would have been legal obstacles, but I'm sure they could be overcome somehow if everyone played along. The appointment of bishops in England is subject to royal (i.e. government) approval, but that level of the establishment has notoriously always functioned as an old boys' club, not strongly constrained by legal details.
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I think many of the factors that would be needed for this already existed. The first women were ordained in the Anglican church in the 40s. Ordaining bishops in the 50s would be faster than what actually happened, but not infeasible.
Several women have founded churches before, especially after claiming to have received visions. The most well known is [Ellen White](http://en.wikipedia.org/wiki/Ellen_G._White), a co-founder of Seventh Day Adventism. Others include [Anna Norbäck](http://en.wikipedia.org/wiki/Anna_Johansdotter_Norb%C3%A4ck), [Christiana Emanuel](http://en.wikipedia.org/wiki/Christiana_Abiodun_Emanuel), and [Mary Eddy](http://en.wikipedia.org/wiki/Mary_Baker_Eddy).
The Pentecostal movement started in the first decade of the twentieth century. If Pentecostalism had a much greater influence in the Church of England than it did in reality at that time, then there could've been a large Anglican community who were receptive to prophecies and visions.
If an Anglican woman claimed to have received visions and her words were widely regarded as both inspired and practically helpful (perhaps she prophesied about WW2), then she could've gained a large supporter base who might've pushed for her ordination to the bishophood. The question ~~doesn't~~ didn't specify whether you meant the Archbishop of Canterbury, or just any archbishop - the former would need nation-wide support, but the later could depend largely on the decisions of a single diocese, so if these Penteceostal Anglicans were clustered in one place it would be quite feasible.
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An alternative approach could hinge on anti-Catholic sentiment, plus a dash of anti-Semitism.
One classic objection to women in the priesthood comes from an early exegesis of a Levitican definition, which says that priests must be physically perfect. That is, no deformities, including also certain skin diseases conceived as equivalent to leprosy. In the exegetical text, they enumerate all the minimum criteria of wholeness, including "two fully-descended testicles." Women don't have those, so no woman priests, QED.
Now if you spin this as typical Roman Catholic superstitious nonsense, based on Jewish nonsense, you could elevate a woman to the priesthood in England around the time of universal suffrage. From there, you just need a bio of a truly extraordinary woman who rose during the War and became Archbishop around the time Elizabeth was crowned.
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I think the doctrinal objections would be the bottleneck. Legal or social objections might well be fudged in good old British fashion, but altering the laws of the Church of England, which are believed to be "agreeable to the Word of God", not to mention going against the deeply ingrained beliefs of many millions of people, that's a much bigger deal. The C of E is both a rule-bound and a moderately democratic organisation. Both of these factors mean it has huge inertia against change, as the complex real-world history of the ordination of women in the Anglican Communion shows (<http://en.wikipedia.org/wiki/Ordination_of_women_in_the_Anglican_Communion>). Incidentally, some of the most committed opposition to women priests and bishops comes from women.
However it might be possible in unusual circumstances. One might be that the archbishop is, despite being externally male, actually an intersex person. S/he had grown up assuming s/he was a normal male but discovers she is female internally after being appointed archbishop. That would not invalidate her ordination as a priest or consecration as bishop. To take a parallel from real life, the Roman Catholic church does not allow its clergy to marry, but does have some married clergy, in the form of already-married Anglican priests who converted to Catholicism and remained priests. The RC church held that it could not *undo* the sacrament of marriage.
Having read the Wikipedia page linked to above has made me think of a less unusual possibility. It says the first real life woman Anglican priest "was Florence Li Tim-Oi, who was ordained on January 25, 1944 by Ronald Hall, Bishop of Victoria, Hong Kong in response to the crisis among Anglican Christians in China caused by the Japanese invasion. To avoid controversy, she resigned her licence (though not her priestly orders) after the end of the war." So, you just have to kill off or incapacitate all the other bishops.
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**This question already has answers here**:
[Are there techniques for creating alien or foreign sounding names?](/questions/3478/are-there-techniques-for-creating-alien-or-foreign-sounding-names)
(13 answers)
Closed 8 years ago.
I've always had trouble with inventing names. They refuse to come, or when they do, they sound funny or cheesy. However, a name will occasionally pop into my head, fully formed and sounding perfect. The only problem is that all of the names I think up sound similar.
For example, I am developing a fantasy world. I have elves, dwarves, and other races of my own creation. I want all the names of one race to be similar to each other (elves are soft, dwarves are guttural, etc.) , but at the same time, they need to be different enough within the same species so that readers won't confuse them.
**How can I accomplish this?**
Examples:
For elves, I've found that names ending with 'ir' or 'mir' work well, as well as names ending with 'in'. This is fine as far as it goes. But *all I can think of* are names that end like that, and some of them are too similar for readers to distinguish at first. How can I keep the names similar, yet different?
EDIT: The answer I found the most helpful, was the answer to the question linked to by James in the comments below.
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One trick is to not use all the letters. For elves, you might limit vowels to i and e, and consonants to n, r, b, m, l, and other 'soft' sounds, while dwarves could use u and o, and d, k, l, r, t, g, x, etc. There are a lot of letters like n and m that work for about any type of name, and different types are defined by inclusion or exclusion of just a few letters.
Or you can let your computer do the hard work for you. I myself use a Python script to generate pronounceable random words suitable for names:
```
def word(syl,p1,p2,con,vow):
w=''
for s in range(syl):
syllable=''
if random.random()<=p1:
syllable=syllable+random.choice(con)
syllable=syllable+random.choice(vow)
if random.random()<=p2:
syllable=syllable+random.choice(con)
w=w+syllable
return w
```
Just type `import random` first. `syl` is the number of syllables, `p1` and `p2` are the probabilities of consonants on each end of the syllable, `con` and `vow` are list of consonants and vowels. There's probably a cleaner way to do this, codewise, but it works well. By tweaking the probabilities, I can usually get one in four of these random words to be usable names (YMMV) and many more just require simple tweaks like substituting a letter.
For suffixes, you can put `+random.choice([list of suffixes])` after the function. I find this is good for place names with suffixes like 'bury', 'ton', etc. but it could work well for names too.
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This problem crops up so often that many people have made automated name generators publicly available. There are several workable computer algorithms that give reasonable results, in that names will feel like they have the right category and be pronounceable. Whether or not they suit your purpose is a matter of taste. But there are so many, you can just Google for them, find ones that are close enough and maybe customise the results to suit you. Search for "fantasy random name generator" or similar will get 100s of hits.
Here is one I quite liked on a quick recent search: <http://fantasynamegenerators.com/#fantasyNames>
Once you have found one you like, I suggest you run it a few times and note down your favourite names into quick pick lists ready to use. You don't need to use them exactly as-is, you can add a human touch by altering the results. Or you could just treat the output as a starting inspiration, to break out of your block on the small set of endings that have worked for you so far.
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One laborious way to approach this is to construct your own language for your races.
It may be a bit too much for just names but the benefits are that
you can create other words as well and by following your rules
your names and words are consistent.
You at the very least have to decide how the language
sounds and create the lexicon. Further steps would be to create
grammar and design an alphabet but they are not necessarily required
if you only want to come up with names.
So, essentially you have to define what the language sounds, or to simplify:
decide what kind of syllables the language has and only use those to construct
your names.
I'd advice you to head to <http://www.zompist.com/kit.html> for further information and try out
the lexicon generator ( <http://www.zompist.com/gen.html> ) that allows you to create words or the use the more complex Derivizer at ( <http://akana.conlang.org/tools/derivizer.html> ) to create new derivate names from existing ones.
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This is the extremely similar to [How do you prove you're from the future?](https://worldbuilding.stackexchange.com/q/12348/2138) with the crucial difference that objects cannot travel with you and you are not actually from the future - you've just been to it. The points below also mean that the inventor isn't really prepared, with a plan, on how to convince people before he is actually back in his time.
1. The Time Travel device was created by accident. The process/materials unknown, it cannot be recreated. It was consumed/lost when sending our inventor into the future, to the year 2100. The inventor believes he is stuck in the future, but after ~(a year's) time he will actually revert back to his own time (*to continue exactly as if he never left*). Time travel was not re-discovered by year 2100 - and actually may never be.
2. No object traveled with him, and no object can come back with him (*plus, he doesn't realize he will be going back*)
Having learned of a major natural disaster that affected all of man-kind, he now needs to prove he's been to the future so that people take his claims seriously. He has learned a lot, but what can he tell them that wouldn't just be taken as new breakthroughs in research/technology? If its too advanced, it may just look like a crazy new theory with possibility - but it probably can't be proved yet.
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**He could send a message to his future self, telling him to prepare.**
Of course this is one of those paradox situations, as with most time travel situations. Once he's popped back to his own time he can simply fashion a message to his future self letting him know what's about to happen. He'll have the idea already, because he himself was warned by the past-future version of himself. Duh.
Now, upon receiving this message from his past self, he has a year to prepare his case of proving he's been to the future. He can do this by memorizing the outcome of elections, lottery numbers, sports matches, and natural phenomena. A year is sufficient time to commit all manner of facts to memory. He will, in fact, know if he was successful by reading about himself in the future. He'll know exactly what it took to convince people.
If you want to avoid this utterly obvious solution, send him much further into the future. To a point when data about his time is vague or lost completely.
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Since we all live in a time that has a fairly unbroken history going back at least several hundred years, it is easy to overlook the disruption that a truly massive disaster can have on the transferal of knowledge across the ages. Samuel's suggestion that the returned time traveler leave his future self some message, relies on the events of the next hundred years not obscuring or obliterating that message.
If for example, a plaque wiped out most of the first world it would take with it most of our technology and infrastructure. The new civilizations of earth might rise, not from our ashes, but from the isolated third world countries which somehow escaped the illness. A hundred years from now, they might be just starting to reclaim the former first world. Your time traveler might therefore not be able to get back to his hometown during his visit to the future. Nor could your returned time traveler go to the places that his future self went in the future. Even if he did, what medium could protect the message during its disaster-ridden journey into the future.
Similarly, those same disastrous events which encumber the sending of present day messages to the future, would also disrupt the flow of information in the opposite direction. Studying the past, especially the years just before the disaster, might be impossible due to the technology loss. We live today in a highly digital age where only a fraction of our news and current events get memorialized on paper. If the internet and the electrical grid fell, most of the history of the last couple decades would go with them; and future historians might have an extremely hard time learning much about us.
...or what caused the disaster.
I'm going to therefore take the pessimistic stance that there is nothing your time traveler can do to convince his present-day peers of the coming doom. All he can do is hunker down and prepare for the bad times that are coming.
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I'm assuming he researched events from his original time and the history of the intervening 85 years at some time during the stay in the future, both from curiosity and out of an attempt to explain what happened to him.
With that information, he should be able to become seriously rich on the stock and commodity futures market. Once he made his first million from humble starts, he will be taken more seriously. At the very least he will be in the tabloids once he claims to come from the future.
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Actually, he would waste more time trying to prove he is from the future than it would be worth. Most would still consider him crazy. So his best bet is to use what ever knowledge he has retained from the future to work toward his goal (in this case stopping a disaster).
As others have said I'm sure he would have done a little snooping to what happened and what is known around the time he left +/- 5-10 years so should have some idea about events. Stock market and sporting events might prove lucrative, the more money and power he can amass the easier time he will have trying to prevent the disaster with out going through the 'he's crazy' rigmarole.
And when did the disaster happen 5 years after he left? 5 years before he showed up? What kind of timeline does he have to work with? Can the timeline actually be changed?
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I am rephrasing the question a bit: What can he do to prevent the disaster?
With knowledge from the future the protagonist can earn a lot of money on stock markets. Or even better on option and derivative markets because these yield a higher profit.
With the obtained money he can either work on preventing the disaster himself or buy influence that helps prevent the disaster.
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If he looked back at celebrity gossip to see what happened to everyone from his own timeline - and can remember it - he can easily show he has a knowledge of the future , which is what is needed here.
Even better if he can remember/predict other minor natural catastrophes as that's the sort of prophet he wants to be.
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It depends what he's interested in, and the time frame he has.
As stated in many of the answers here, he might not be able to find out exactly everything that happened since he left in minute detail. Historical documents may be lost/destroyed and he cannot find out what happened immediately after he left.
Also, he is unlikely to look at everything that happened right after his departure even if it was available. If you think of the amount of information available today, you couldn't possibly learn every sporting result that happens around the world without spending the entire day doing it, never mind learning stuff that happened 100 years prior.
However, it entirely depends on what he is interested in. If he is a businessman before he gets sent forward, he would likely find out what businesses made it big since he was sent forward in time. If we was a sports fan, he would want to find out who won each superbowl/world series/world cup (depending on his specific sport of interest) since he left, just out of curiosity. If he was into politics, he'd find out all the presidents since he left. That wouldn't take much time to do.
Personally, I'd want to find out things like which books are now considered classics in the year 2100, that were actually written since I left. I would also maybe want to find out what video games had been made and how they developed over time from when I left until 2100.
These things will likely be common knowledge, and wouldn't need to be researched, you could probably find someone who knows, and in the year you were in the future you would definitely have found out.
Once he has been sent back, even if he doesn't remember every result or every outcome, he would have a general idea. He would almost certainly remember what happened in the 1 or 2 years after he left.
The important thing to do now is to prove he knows, but without telling anyone, because it might affect the future. So he gives someone a sealed letter, to open once the event (election, tournament etc.) is finished. If the information is correct, that person will know he is from the future.
Think about it. In a sporting event like the world cup you have 16 teams in the final tournament. If anyone picked the correct 2 teams in the final, and then which of those wins (even without a score), I'd be pretty willing to believe they'd been to the future. You would only need several other minor details to prove beyond a doubt.
So even if he only has 5 years, within 2 he could convince plenty of people. If he has 50, he can play the long game and successfully predict most, if not all the outcomes, and convince everyone.
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It should be possible to prove the case by having a highly confidential message sent to herself in the future.
So she returns from the year 2100 and to prove it asks someone to send her a top secret message whose content only they would know, to a specific destination that she provides.
She then tells an independent third party what the message contains as she already received and read it in the future.
When the message is sealed and sent, she is able to confirm to the sender that she has already read their message in the future, the third party can confirm the veracity of this statement.
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Bring new science and/or technology.
Even casual, superficial knowledge of science and technology can be immensely valuable, if you can bring it back to before it was known.
"The speed of light in a vacuum is the absolute speed limit in the universe, and it's the same to two observers that are moving relative to each other."
"Many of our diseases are caused by armies of tiny creatures, too small to see"
"You can avoid scurvy by drinking lemon juice"
"Some atoms spontaneously do fission. If you squeeze many of them together, you can have a chain reaction"
Science and technology are bound to have made some big leaps by 2100, and he's bound to have learned some of it.
Unfortunately it will take a handful of years of hard work to turn something so crude into a coherent theory or marketable product. Hopefully we can afford to wait that long.
Once he revolutionized one field, cash and/or credibility will allow him to speedrun the next one.
Once he revolutionized five or six wildly different fields, even "I'm actually a time traveler" will be taken as a real possibility.
The "inventor" stereotype is much nerdier and scholarly then the general population, so we have a reasonable chance of in-depth, detailed knowledge, much more valuable and quickly actionable.
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This answer is only tangentially connected to your actual question, but it ties into the question you are asking. In addition to the 'how do I convince people' problem, you *also* have an Oracle of Delphi problem, so any solution needs to solve both.
# Time travel eliminates the distinction between the future and the past
What can be done to change things? Nothing. When this man learns about the "past disaster" he is really learning *his own future*. So if he learns that the disaster struck and the world was woefully unprepared, that is what *will* happen because it *already did* happen, from another point of view. He can't 'change things' so something else happens, because at the point in spacetime where he learns about them, they've already happened.
In other words, if what the man learned convinces him to go back and spread the word, *he already knows the outcome*. He learned about it from the history books. He would in effect be following a script that he already knew the ending for in advance. The net effect of whatever he does (if it has any effect) will have already been factored into the course of events.
# The obvious conclusion
His actions will turn out to have already been a footnote in the history that he learned when he was in the future. Perhaps he will have been cast as a prophesier of doom. Perhaps he will have managed to save a small community of folks who now worship the ground he walks on. Or perhaps he's the reason "only" 90% of the Earth's population died in the disaster, instead of the originally-projected 99.82%.
# The devious conclusion
He really does manage to avert the disaster. Some mad scientists realize the time travel problem, that this creates an apparent paradox. In addition to whatever else has to happen to solve the Crisis on Exfinite Unobtainiums, they *also* need to set up a [phony reality](https://en.wikipedia.org/wiki/Future_Imperfect) for the man to arrive to when he timeslips, so that what he remembers happening actually happens. (This implies every single 'person' he met was really an actor.)
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Ok, so I have started the worldbuilding process by creating several different communities and giving them each their own personalities. I ran into a problem, though, when I created a desert dwelling community that doesn't identify with the rest of them. While all of the others could be considered portions of the same thing, this one, due to its history, demands to be separate.It's separate not only metaphorically, but probably physically, by maybe a mountain range (haven't made much of a map).
In a situation like this, should I make a second language that this desert dwelling community speaks, or should I make a similar language, or just give it the same language as the rest of my world?
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Languages form by populations splitting, forming accents, that become more and more extreme, until they are mutually unintelligible. Your split communities would do the same thing, unless both versions of the language are artificially kept in stasis by the speakers. Pedantic teachers with rigorous pronunciation and grammatical rules could keep a language the same forever.
The creation of a new language does take hundreds of years though, so if the isolation is recent (relatively), you could get away with thick accents and a few words that need translation.
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It depends on the interactions they have with each other, the more tied they are the more likely the language would stay the same, the less, less. China has so many dialects, sometimes people on different sides of the same mountain can't understand each other.
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If you want people to be able to talk to each other, but want some realism in handling the separation between the two societies, you can have them speak and/or write in different dialects of the same language. That will let the characters communicate with each other, but still introduce a level of communication difficulty that one would realistically expect in those situations.
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(This is an offshoot of [@Fungo's answer](https://worldbuilding.stackexchange.com/a/12968/21222) about "Pedantic teachers with rigorous pronunciation and grammatical rules" maintaining a language.)
The desert people could have a collection of sound recordings (or videos) that they listen to regularly, across generations. That would likely keep the pronunciation from varying too much. One type of recording that would probably be listened to over and over is recordings of religious events such as miracles, sermons by holy figures, or readings from sacred texts.
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Give it a differed language! Living separately means living with things that need new or different names, and words that have little meaning, (Ocean, snow, mushroom, things that aren't in deserts,) not sticking around. They have a totally different set of things that 'matter,' and thus, things to be talked about.
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One of the central conceits of the world I am next trying to build is that all forms of magic are considered divine. There are theological differences among the cultures as to *how* the Divines created magic, or *what purpose* it is supposed to serve, but everyone agrees that the Divines created magic, and that the use and practice of magic is impossible without the Divine influence.
How would these cultures
1. be different from "traditional" fantasy cultures (J. R. R. Tolkien's books, etc.)?
2. be different from existing religious cultures in the real world?
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One major potential difference in both points is that some cultures may not be *religious*, at least in a common sense.
Assuming from the details in your question that there is no regular *direct* contact with the Divine, it is natural that some people would doubt their presense. Some people could take a Deist view of things: that the Divine created magic, and magic draws on their power, but they don't actually involve themselves in the world. Others could take a related scientific, not-quite-agnostic stance: if we don't have contact with the Divine, and they are not observable, then we can't really know anything about them, and we should base our actions on things we *can* know. These people may accept "Divine influence" as the cause or source of magic, but they would consider magic on its own and not be particularly concerned with any form of theology or worship.
Please don't misunderstand me—I'm not dismissing religion, or saying that this is the "correct" way for people to act. However, I think it is natural for *some* people to respond this way—but by no means all. If the Divine do act in the world at all, then there would be people who have interacted with them or witnessed their actions. Even if they don't, some people would probably claim to have had Divine experiences anyway. So there would be religions built on these experiences or claims.
Exactly how they would be different from existing religious cultures depends on how the magic works, mechanically. If there is any organized compenent necessary to magic, like a ritual, then that would become central to that culture. If there are no rituals, no incantations, and it is more a matter of will, focus, and intention, then the religion might look more animist or pantheistic, and meditation would be important.
Of course, this all assumes that the Divine beings are not frequently showing up in the world, performing heroic deeds or impregnating princesses. If you borrow a page from the late, great, Terry Pratchett, and create a world where the gods have a habit of going around breaking atheists' windows, then things would be different.
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# Ancient Magic is Often "Divine"
In reality, magic [appears](http://en.wikipedia.org/wiki/Magic_(paranormal)#History) to have been mostly associated with divinities and divine powers. It was not until more recently in the history of Humanity (and western culture) that we think of doing magic without divine influence. This means your people would have a similar attitude as the ancient world had towards magic.
For instance, [Voodoo](http://en.wikipedia.org/wiki/Louisiana_Voodoo) appears to be reliant upon relations with spirits to perform magic. One can call these relationships "divine" and therefore this is "divine magic." This is true for most (if not all) ancient cultures; the practitioners of magic were those who are close to spirits or gods, and this relationship allowed them to perform magic.
The wikipedia article on [Magic in the Greco-Roman World](http://en.wikipedia.org/wiki/Magic_in_the_Greco-Roman_world#Terminology) has some interesting insight into the difference between "arcane" and "divine" magics. The arcane, according to this discussion, involves tricking gods or spirits, instead of supplication to those spirits or gods. D&D players would generally label all of these magic-users as "divine," as the actual source of the magic comes from divine sources. (More on D&D later!)
Astrologers and other fortune-tellers may be the closest thing we have to ancient magic users who do not need direct connections with divinity to perform their work. Of course, astrologers would read the stars, and it would be much less about exercising power as simply being trained to read those. The same argument could be applied to many types of fortune-telling; that it isn't magic, but simply being well versed in drawing conclusions from natural processes.
# Vs. Other "Traditional" Magic Systems?
First off, Gandalf is more like a [demi-angel](http://en.wikipedia.org/wiki/Gandalf#Concept_and_creation), so the magic he uses is therefore divine. Sauron's [magics](http://en.wikipedia.org/wiki/Magic_(Middle-earth)) would also be seen as divine, although divine in the sense of "above mortal power," as he is on the same level of "divinity" as Gandalf. The magic, or sorcery, of the elves seems to be not divine, but may be seen as divine gifts. Your culture of magic use may be seen as more religious than in Tolkien's Middle Earth, but could easily have a similar setup. It depends on how codified and formal your religions are.
Even [Merlin](http://en.wikipedia.org/wiki/Merlin), from the tales of Arthurian Legend, supposedly has some divine blood in him. In some renditions, he was born from a succubus and a mortal man, with the succubus part of his heritage giving him magic. While this is could be seen as a basis for "individuals casting magic without divine help," the fact that a succubus was involved could make his magic fall into the "divine" magic camp. Once again, your magic system would be different than the magic seen in Arthurian Legends, because this divine influence is well established.
The advent of D&D may have helped cement the idea that you can use magic without the need of divine help. Once again, this may be due to figures like Merlin or astrologers, who may or may not have had an explanation for their magic. Obviously, such a notion in this world your making is an impossibility, but perhaps one that people wish for. You may want to consider borrowing cultural elements from divine casters in D&D. Divine casters often acknowledge or at least nod to their patron deities.
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I find that the socio-religious implications of magic too often get overlooked in fiction. If your average priest can perform miracles, that's a rather striking blow to atheistic scientific thinking.
In a society where resurrection is regularly acheivable, for instance, people might use that as a tool to explore the afterlife, which might debunk certain religious viewpoints. Those religions would be forced to suppress magical exploration of faith (if they are politically powerful enough to do so) or change the affected faith structures.
Conversely, if EVERYONE can perform those miracles, as magic is merely a tool provided by divine entities accessible to all, then over time it will become "old hat," depending on the strength and limitations of that magic. This might mean that, over time, people forget/ignore the implications magic has on their religious beliefs.
If this was a product of multiple Divines, that poses a challenge to all modern monotheistic religions. Otherwise, I don't expect many modern religions to change their tune vis a vis the others...
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Near the beginning of my story, my main character loses an arm, and is going to get a prosthetic replacement. I've done some research on prosthetic limbs, and as one might expect, you're not good to go in a week.
The problem is, I had intended for everything to be occurring during a serious winter storm, in order to limit communications in a fairly remote area. I'm willing to scale this back to an especially bad winter season, but I still don't seem to have enough time for recovery. I'm somewhat limited in using different ways to knock communications out, because the story is drawing a parallel with a storm, and doing almost meta-commentary with it.
The good news, is I'm operating maybe 5-15ish years in the future, so that I can have some more advanced genetics/biotech stuff going on. I don't mind saying that the hospital he will be at is the world's leader, as a major plot point is a nearby top-tier research lab.
Is it plausible that prosthetic technology might advance enough in that timeframe, so that I could have my main character up and active in 2-3 weeks? I wouldn't even mind if he has some ongoing pain/fatigue from cutting things a bit short.
Thanks!
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>
> **TL;DR**
>
>
> Screw an ITAP into the bone stub, reinforce it with some titanium
> bands, take some drugs, and pet a kitty with your new cyborg arm.
>
>
>
Ah, *cyborgs*. Personally, I design the electronics (neurostimulators) for cyborgs (usually old people), but the mechanical stuff is pretty rad, so I follow it too.
There are some relatively recent advancements in prosthetics that you should be aware of, though it doesn't currently reduce healing time, I think this method would be the easiest to start with in order to accelerate healing time.
## The Prosthetics
***Intraosseous transcutaneous amputation prosthesis or [ITAP](http://www.stanmoreimplants.com/itap-implant.php)***. Translated to English that means, in-the-bone and through-the-skin limb replacement. The very cool thing about these prosthetics is that they attach directly in the bone and don't rest on a healed over stump. This means that loads experienced by your character, such as shoveling snow, can be taken through the skeleton rather than through soft tissue. The lost limb is better replaced because the user regains sensory signals to the bone; so called [osseoperception](http://dukespace.lib.duke.edu/dspace/handle/10161/4806). This reduces the learning time compared to normal prosthetics, because it's much more like the original limb.
The most famous patient, currently, for these special prosthetics is [a cat named Oscar](http://www.theengineer.co.uk/news/cat-fitted-with-bionic-feet/1003200.article).
There are several human patients, and most of the photos for them are a bit more gruesome looking, so I won't add them here. But have yourself a google image search.
## Accelerating Recovery
The main concern you'll have is allowing sufficient time for the bone to heal and hold onto the titanium bone implant. I think you can accelerate the bone healing [with drugs](http://www.drugs.com/news/scientists-find-way-heal-broken-bones-faster-24104.html) and by reinforcing the bone with a custom boot or bands. There are a few examples of this with femur fractures or hip replacements, but typically medicine is not concerned with making someone better in three weeks, because we're still working on the getting better part. The best path for further research, since ITAP is still fairly new, is with osseointegrated titanium implants in general. Any advancements there will, for the most part, also apply to ITAP devices.
Once the bone part is taken care of the rest is not as much of a concern. The skin and other soft tissue around the titanium will not be load bearing, so it can take longer to heal. This can be made easier for your character by having a 'convenient' amputation location, like just below the elbow.
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Nueroscientist Miguel Nicolelis has been working on a brain machine interface. He claims this interface has allowed monkeys to control robotic arms. Here is a [Nicolelis TED talk](http://www.ted.com/talks/miguel_nicolelis_a_monkey_that_controls_a_robot_with_its_thoughts_no_really?language=en).
Dr. Nicolelis is hoping this will restore ability to those with spinal cord injuries.
It might also be an interface to remotely operate tele-robots. I am hoping tele-robots will become more common in industry doing work in hard to reach or inhospitable places. ROVs are already doing work on the sea floor.
If someone has grown practiced at using a Nicolelis cap to operate a tele-robot, it would be a small step to use the same interface to operate a robotic arm prosthetic.
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Now available! **3D printing** for all your instant prosthetic needs.
In just minutes your patient will be moving around with his new leg thanks to our patented technology.
We are not responsible for broken prosthetics; pressure sores; nerve damage or bruises due to bad fit or misuse. Home-printed 3D prosthetics are not a long-term substitute for actual medical care.
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We know that humans are capable of incredible feats, as displayed by Olympic athletes. However, the superhuman heroes that appear in comic books and fantasy novels tend to not only be able to perform such feats, but to be able to sustain such action over a period of time. Not only that, but athletes tend to focus on just one sport or exercise, while these fantasy characters seem to do everything equally well.
So what would a such a superhuman look like assuming human biology? Would he have biceps so muscular they would be at risk of crushing his own head? Or would he really look like Captain America?
To prevent this question from being too darn broad, I'm going to specify what this person's limitations should be:
1. Able to lift maybe 300-ish kg for several minutes before becoming fatigued.
2. Capable of running at about 10 m/s at a sustained pace for over an hour.
I don't particularly care if its not realistically possible, I'm just interested in what such a person might look like, particularly his physique. If the above numbers are too over the top, feel free to use a lower number.
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As has been mentioned, they would need denser muscles to look even remotely human.
The world record for the one hour run is held by [Haile Gebrselassie](http://en.wikipedia.org/wiki/Haile_Gebrselassie), a 65 kg man who managed to average a speed of 5.9125 m/s over an hour.
If we look at the weightlifting side of things, [Eric Spoto](http://en.wikipedia.org/wiki/Eric_Spoto) weighs somewhere between 140 and 150 kg and managed to benchpress 327.5 kg without special equipment and has mananaged 4 reps with 294 kg.
What I'll do now is estimate how much more energy a man the weight of Eric Spoto would need compared to Haile Gebrselassie in order to run 10 m/s for an hour. I'm (falsely assuming that a 150 kg person generating enough energy would actually be able to perform the feats he can technically do. I'll justify this by handwaving and saying "denser muscles".
When exerting a constant force on a moving object, energy used is proportional to force exerted in the direction of the movement times the magnitude of the movement.
$$
E = F\times\Delta x
$$
Since we can assume the speed is constant, there is no resulting force operating on our athlete. This means that the force the athlete is exerting has the same magnitude as the force he experiences by aerodynamic drag. according to [this paper](http://onlinelibrary.wiley.com/doi/10.1256/wea.29.02/pdf) we can approximate the drag working on a human by:
$$
F = AV^{2}
$$
With $A$ being the cross-sectional surface of the human.
Assuming that two humans are to scale versions of eachother, we can get the ratio between their cross-sectional surface as:
$$
\frac{A\_{1}}{A\_{2}} = (\frac{M\_{1}}{M\_{2}})^{\frac{2}{3}}
$$
We can now reduce the ratio between energy consumed to known factors:
$$
\begin{align\*}
\frac{E\_{1}}{E\_{2}}& = \frac{F\_{1}\times\Delta x\_{1}}{F\_{2}\times\Delta x\_{2}} \\
& = \frac{A\_{1}V^{2}\_{1}\times V\_{1}}{A\_{2}V^{2}\_{2}\times V\_{2}} \textrm{ (Distance covered is proportional to speed)} \\
& = (\frac{M\_{1}}{M\_{2}})^{\frac{2}{3}} \times \frac{V^{3}\_{1}}{V^{3}\_{2}}
\end{align\*}
$$
Filling this out with the values we have gives:
$$
(\frac{150kg}{65kg})^{\frac{2}{3}} \times \frac{(10m/s)^{3}}{(5.9125m/s)^{3}} = 8.4
$$
That's 8.4 times more energy needed than Haile Gebrselassie used to set his world record, assuming that the lost energy will be proportionally the same.
The good news is that this formula predicts that the required energy scales with "just" $(\frac{M\_{1}}{M\_{2}})^{\frac{2}{3}}$ this means that doubling the mass only increases the required energy by roughly 1.59 times. This supports that a taller man, bigger person could possibly achieve this. My guess would be that this person would need to be well over 2 meters (approaching the height of the tallest people who ever lived) and weigh at least 300 kg of mostly very dense muscle, eat like a horse and have a heart that's about 3 times bigger in length than a normal person.
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My biggest guess would be that their muscles would be much denser than ours. Muscle density allows for more power in a small physical muscle. Orangutans, Apes, and Chimpanzees all have much denser muscles than humans. This is not to say they still won't be bulked up, but for them to still function without being muscle bound, the density would make a big difference.
The next would be a large 'powerful' chest because they would need a large powerful heart to keep moving the blood with enough quantity. Large lungs are needed to facilitate the rapid exchange of CO2 and O2. While they might be able to perform great feats of strength anaerobically (and the dense muscles could allow for longer than the rest of us), for something to be sustained for any length of time, (and not require a large time to recover) there needs to be the ability to send energy to the needed muscles and remove the waste products quickly and efficiently. This also suggests that they have high efficiency or extra large kidneys to help remove wastes.
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The superhuman would look a lot like a sled dog: <http://www.outsideonline.com/fitness/endurance-training/It-s-the-Dog-in-You.html> They can certainly do the running at ~20 mph for an hour or more. I don't know exactly how you would compare lifting, since dogs aren't built to do that, but they run like that while pulling a sled.
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[According to Wikipedia](http://en.wikipedia.org/wiki/Back_%28horse%29), "The average horse can carry up to approximately 25% of its body weight." A large draft horse can weight over a ton, 2200 lbs or 1000 kg, so the most a horse can carry is about 550 lbs or 250 kg, close to what you specify.
But, a horse could only gallop at 10 m/s (22 mph or 36 kph) for maybe four or five miles, around 10 minutes ([Again using Wikipedia](http://en.wikipedia.org/wiki/Horse_gait#Gallop)).
However, humans are extremely efficient at running. [Regular sized humans can even compete with horses in long-distance running.](http://en.wikipedia.org/wiki/Man_versus_Horse_Marathon)
Taking all this together, I see a human 8-10 ft tall (2.5 to 3 m) with muscle mass similar to a horse being able to accomplish the feats you describe.
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Is it a good idea?
No. A very definitive no.
However, that's not stopping a young aristocratic terrestrial cuttlefish (long story) that lives on this world's equivalent of a highly mountainous and densely forested version of Australia on steroids from attempting to make one! That, and to make sure he doesn't lose the wager he made with the heiress of a rival house on whether or not he could do it.
Now, with the reasons *why* anyone would attempt such a thing (since if you wanted to just make it portable, folding has been proven and has been done many [multiple](https://en.wikipedia.org/wiki/OSV-96) [times](https://www.maxim.com/gear/xar-invicta-folding-rifle-2017-7/) [over](https://www.keltecweapons.com/firearm/rifles/sub2000/)), let's ask the question:
## **What sort of mechanism could a telescoping barrel operate on?**
## Goals
* The barrel has to extend over a preexisting barrel that then physically extends the length of the barrel. Thus extending the duration a bullet spends accelerating in the barrel.
* Should, in theory, be reliable and sturdy (now isn't that an oxymoron) enough to be implemented; assuming the technology is a available. Speaking of which...
* The cephalopods in this setting a very advanced compared to us, so our young aristocrat has access to advanced [diamondoid's](https://www.orionsarm.com/eg-article/464b9c37d9887), [corundumoid](https://www.orionsarm.com/eg-article/4642806f24deb), future alloys with favorable strength to weight rations, compact power storage, strong mechanical and miniaturized motors etc, etc.
* Have access to advanced manufacturing techniques, thus manufacture or parts that would be impossible to be made traditionally are not a concern.
Now, let's see if we can help our young lord. Cause's I know I have been thinking about this issue for too long now.
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The big issue is your internal diameter of your telescoped Barrel...
But there's two possibilities that spring to mind:
1: Sub-calibre, Sabot'd projectiles - essentially, as the projectile flies down the telescoped barrel, the Sabot is 'caught' on each telescoping segment, until the final projectile leaves the barrel. There would need to be a mechanism to clear the sabot components out after firing - most likely collapsing the barrel and re-extending it, kinda like how some Tanks do the 'tank salute' after firing.
2: In much the same vein, Squeeze bore projectiles - if you could make the inside diameter contiguous with each segment, you could use a squeeze bore type projectile - IIRC, they were used in WW2 to increase muzzle velocity for some tanks (with reasonable effect)
However... if Accuracy isn't your primary concern....
Shotgun. Firing Shot, instead of a solid projectile means that it's much less sensitive to changes in the barrel - so you could get away with any of the above technical issues, it just means that there's no *actual* benefit (such as increased range/accuracy/penetration power etc.).
[Answer]
Not quite "telescoping" in the usual sense, but...
First part of the barrel (including chamber) is fixed. Around it is a closely-fitting sleeve, and then around *that* are the extension of the barrel in 3-4 longitudinal segments (think barrel staves). Those segments extend forward and move inward, interconnecting with the end of the main barrel and with one another, and then the sleeve slides forward to surround the joint and the segmented barrel, providing additional hoop strength to it.
The machining tolerances would be tight and it'd probably blow up in your hand given half a mind to, but at least on paper it sounds like it'd work. üòÖ
(note: Not recommended for use with +P+ rounds. For novelty use only. Use at your own risk.)
[Answer]
German ww2 tech has the answer for you:
Research into the Krummlauf has basically stated as long as the barrel extension is firmly attached and centered, a same diameter barrel extension is good enough.
The rifling doesn't even have to be matched perfectly either.
Source: [Forgotten Weapons (video)](https://www.youtube.com/watch?v=HSsFiS2Voxg)
Granted this is *Curved* barrel extensions. I'd wager that more detail oriented research would be need to be done but generally bullet would be effectively travelling down a longer barrel and stands a small chance of fragmenting in the barrel like was in the Krummlauf if the extension was not curved.
This will not be telescoping though, but can be a folding or bolt on extension.
As for a true telescoping barrel, I'd probably suggest the barrel being split into two sections lengthwise with flanges that'd allow for a clamp to slide over along with a spring loaded barrel sleeve that'd slide the clamps in place. in a stowed position, the barrel halves would be sitting beside the base length, and when a latch is released, the barrel sleeve first drags the barrel sections into place and then slides the reinforcing clamps all in one motion. Since you said your cuttlefish had very advanced manufacturing techniques, I'll not worry about tolerances or complexity.
If we're talking about a gun that isn't strictly gunpowder based and is a gauss gun or even a railgun, then they could easily have collapsing rails that the bullet would ride on and the coils would simply compress back into one place whereas there was space between them when fully extended for firing.
[Answer]
**Paper yoyo.**
[](https://i.stack.imgur.com/OeexHm.png)
[source](https://ae01.alicdn.com/kf/H69ccf7b17564429da41d45743775277fw.jpg)
Your extendible barrel is a concentrically coiled flat strip.
At full extent, the interior overlap between adjacent sections of strip serves as the rifling of the barrel.
[Answer]
What do you need for a barrel to be effective for gas projectiles? You need precise sizing and rifling.
Putting aside the issue of materials, the problem I see is automating the process. It seems like you want the barrel to automatically slide out. If your character carried multiple segments of barrels and clipped/screwed them together to suit the particular situation, you'd be fine. You could more or less do the same thing now. There are a number of firearms that can accept different barrels and bolts easily and quick-release barrel systems are not uncommon.
If your barrel was a long, coiled sheet that could stiffen so that it could extend out (like the paper yo-yo above), I do not see how a rifling groove would work. You could extend the barrel, but the rate of coiling would change along the whole barrel, altering the rifling twist rate. Rifling changes a musket in a rifle and is hard to get around.
If your barrel was stored in segments or segmented sleeves that rolled out and clacked together, I don't know what mechanical force would be strong enough to hold them together when the projectile and the gasses pass through, even if you don't worry about the barrel itself withstanding the forces.
I think the best way to go is to change the game. Gyroscopic stabilization is not going to work for you. You likely want a magnetic impeller or a railgun.
If you go with a linear accelerator you want to have projectiles that are thin and light so that you can accelerate them to high speed quickly. You don't spin them because they aren't stabilized. They move so fast and their mass is so low their trajectory is basically laser-flat. They're essentially hypersonic needles. In that case, each barrel segment could be an acceleration stage of impeller coil and a gating electromagnet. Adding more length to the coil would always give you more distance to accelerate. While you could just dump more power in to a shorter segment to accelerate to the same speed in a shorter distance, the electronics may be unable to handle switching that much power at once and accelerating that fast might warp the projectile, causing it to impact the barrel going extremely fast (which would be 'bad'). You are relying on linear acceleration and not gas pressure, so you don't need to hold the barrel together all that tightly. There will be resistance, but given you already have a wire coil, you more or less just need a sleeve to hold it.
As for the actual movement of the barrel, I could see largely two solutions. One is the paper yo-yo layout above. If a material sheet had impeller lines built in, then it could slide out and in. The only issue is that the coils at the back of barrel would be tighter than the front, and you want it to be the opposite way around. The other solution is a bullpup design.
Bullpup rifles have their magazine and receiver behind the handgrip, so by the time the barrel runs from your shoulder, along your arm and to your hand, you've already gone through over a foot of barrel before you hit the grip, so the overall length of the firearm is rather short. If your impeller gun had a barrel along the whole length, but only fired through the segment past the handgrip and used the rest of the stock to essentially store the rest of the barrel, it could then be ratcheted out as needed. The barrel couldn't be one solid piece since you'd need a way to get the projectile in, so it could be constructed in segments. It wouldn't be hard to have an internal mechanism hold the front in place, screw in the next segment and roll the front forward.
It would not be quiet, though. Motors generally only get louder over time. It could be manual, like a bolt-action rifle.
While the same setup could in principle work for a gas projectile, the fact that the barrel could unscrew in multiple places would present problems. The stress of the gases and the projectile's rotary motion as it traveled through the barrel would cause all the joints to loosen. It would essentially disassemble itself. Parts can be reverse threaded, tightening themselves each time you fire, but then you need to overcome how tightly they need to be (and then became..) screwed together in order to extend or retract.
I think a bullpup extensible linear impeller is your best bet.
You would need very good power storage and delivery, however you mentioned advanced science and materials are available.
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[Question]
[
**This question already has answers here**:
[Methods of containing/combating "grey goo" Von Neumann nanomachines?](/questions/453/methods-of-containing-combating-grey-goo-von-neumann-nanomachines)
(7 answers)
Closed 1 year ago.
Let us imagine a scenario where the apocalypse has come in the form of gray goo: tiny nanotech replicators that are set to consume all the biomass on Earth while replicating themselves. Humans, oddly enough, don’t want this to happen, (considering that is basically what *we’re* doing). Therefore, I am trying to stop this.
Some background info: the nanites grow into “clumps” of grey material about the size of grains of sand, with the general consistency of ash. They are powered by sunlight but require very little energy, and can continue to thrive even in twilight conditions. They are composed of carbon, hydrogen, and nitrogen; they spread rapidly, covering about 4.3 meters per day over land, though they can be distributed by the wind as well.
How can I halt and maybe reverse the damage done by these critters, preferably in a timespan of 10-20 years?
[Answer]
**Anti-Nanite Beam**
[](https://i.stack.imgur.com/ak9Nk.gif)
Gray goo nanites getting you down? Need a weapon to render them harmless? Look no further than the anti-nanite beam?
**But how does it work?**
Glad you asked. As we all learnt in grade school, nanites work based on the Stern-Glochspeil principle. Each nanite creates a inverse Trojan field (commonly called just a nanite field) that resonates constructively with nearby nanites. This is what allows them to perform surgery on molecules and break and reforge atomic bonds without breaking their own atomic bonds in the process.
The anti-nanite beam works by producing an inverse-INVERSE Trojan field. This cancels the nanite field and makes the tiny robots collapse under their own weight. They return to inert organic substances.
For small nanite spills the robo dinosaur is your man. She can move and aim the beam to avoid people and cars and dogs. For large spills, we suggest prolonged exposure by a wide-angle beam. Ideally from a tower or satellite in geosynchronous orbit.
Prolonged exposure of 10-20 years can be necessary if the nanite spill is particularly deep. You see the layer of dead nanites on top insulates the living nanites on bottom. And the nanites on bottom keep turning the dead nanites into more living nanites.
[Answer]
**Vacuum cleaners and glass containers!**
"Oh, god! It broke free!"
[](https://i.stack.imgur.com/LKxx5.png)
"Quick! Let me grab my vacuum cleaner!"
[](https://i.stack.imgur.com/yhEQ6.png)
Based on the replicators constitution, it is safe to assume that they cannot consume things that aren't organic in nature. And even if they could it would be slow and inefficient. Something like a glass container should be quite effective at keeping them in check (at least long enough until they can be disposed of). When the nanites are trapped in a glass jar the only way they could break free would be to either 1. work together like a muscle to shatter the container or 2. slowly chip away at the glass wall with their microscopic parts. Either way, there's plenty of time to react so long as they don't get into your body.
A vacuum cleaner connected to a glass container would be all you need to capture chunks of the grey goo. Afterward they can safely be chunked into a sealed vat of sulfuric acid.
How long would it take? The answer ranges between a few seconds to never. It all depends on where the goo first started spreading. Places with little to no human activity and lots of sunlight and biomass would make the ideal place for the goo to get a foothold and destroy humanity. Worse case scenario: if it gets released into the ocean we are all screwed.
[Answer]
**Be Smart, Make Sure There is an Off Switch**
Any nanotech is going to be programmed and built by a mind that has an answer to, “what happens if this gets out?” So given the fact that these tiny machines are going to be created by someone who is smart, they are going to make sure that if the grey goo breaks containment they could turn it all off. Install an off switch, install a kill switch, program a virus that will completely delete its programming what ever it takes to stop the goo dead in its tracks.
**If the Off Switch Doesn’t Work, Fire Up An EMP**
In the same way very few people that can outsmart a bullet, very few electronics can outsmart an EMP. So if simply turning the goo off won’t stop it once it breaks containment, frying the circuitry of everything in 10 square miles should do the trick.
[Answer]
**Hack the power generating structure**
/They are powered by sunlight/
Capturing radiant energy and using it for biological purposes is not a trivial matter. Grey goo samples will be studied and their power generation method understood. It must be based on organic molecules since these goo particles subsist on carbon nitrogen and oxygen.
Then hack it. Fastest would be a poison - something which is to these power generating molecules as cyanide is to our own metabolic hardware. This can be used through human agency to directly treat infected areas and entities.
Next is to produce a synthetic virus. The virus targets the power molecules and also hijacks the goo reproduction machinery to make more virus. When a goo particle falls apart because its power has failed, it will release virus particles and infect adjacent goo particles. Infected airborne goo particles will spread far and wide. Unless the goo has adaptive immunity, the virus will quickly clear the goolands. Goo might survive in isolated refuges (perhaps in the deep earth) and so repeated outbreaks could be possible.
[Answer]
# Nuke in a circle around the infected area.
[](https://i.stack.imgur.com/dRKO1.png)
As quickly as you can, you'll want to nuke the area around the grey goo. Make a ring of nukes timed to go off at the same time around your goo. You don't want any nanites to escape on the wind or in a fragment that gets tossed ahead.
# Build a nanite wall around the infected area
Build nanites with no self replication ability around the nuked area. They would be designed to hunt and kill the remaining nanites and prevent any that hid under the ground from escaping out. You can build them at an external facility so they can't be corrupted by the nanites remaining.
[Answer]
Let’s assume it escapes the lab. It’s growing in various hidden places. It is a... pandemic! How do you fight a pandemic? With vaccination.
You’re going to need a second gray-ish goo, one that replicates itself in a regulated way: it ramps production in presence of the original gray goo and remains only mildly vigilant otherwise. Then you seed it everywhere.
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[Question]
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So I basically have a medieval fantasy world, where there are several empires on an Earthlike planet. These empires originated from early Bronze Age civilizations, and have stood the test of time in one form or another. Now they are all more or less in the "medieval" era, technologically speaking. And yet socially, these empires are more like medieval China, medieval India, or the ancient Roman empire, or the 19th century Russian empire, rather than medieval European kingdoms. Meaning that they have a standing army, established beurocracy, and they are comparatively as large as the above mentioned empires, having a similar, if not greater level of manpower.
They may be a little bit more advanced than our medieval world, having invented mass production of plate armor and weapons, like a little industrial revolution of sorts. They also have a light magic system, which is primarily used for healing, hypnosis, paralysis, hallucination, mind reading, brainwashing, emotional manipulation, and enhancing mental and physical abilities for some amount of time. Boat technology is retarded however, having only ships like galleys and triremes. Despite this, the entire planet has been mapped out by now, and these empires know that they live on a globe, and they know where all the continents and straits are. However there is no gunpowder in this world.
The entire planet is divided up into six big empires, and numerous smaller kingdoms which are vassals or dependent states of each of these empires. Tensions have been building up over the past century, empires have been making alliances and enemies, two roughly equal sides, three empires and their vassals vs the other three empires and their vassals. Finally war breaks out over border disputes and past grievances.
My question is: what is the feasibility of a world war happening between these empires, on the scale of WW1 or WW2? I mean, armies roughly of that size, but armed with medieval weapons and war elephants instead of tanks. Most of the battles will be fought on land, but some of them will be fought at sea, and of course large numbers of troops will need to be transported to other continents, for the first time in history. What would happen in such a scenario? Even if the rulers of these empires want to wipe their opponents off the map, Hitler style, would they be able to do it?
[Answer]
I believe that in practice one might find that world wars, and total war generally, were only made possible by two concurrent but distinct developments, and how these factor in to the 1) capability, and 2) motivation of waging a total war.
First, capability. I think it may be argued that civilization-wide total war was only possible because of the tech level. And I don't mean the weapons; I mean the logistics. In the Roman period, dozens of legions could march into the forests of Germany, or an emperor could personally lead a host against the Persians, and these could very easily be matters approaching life-or-death for the whole empire. But the only people who could have any impact on the proceedings once a war had already started were those within a day or two's walk from the front line (or "front point" morelike, being one of the armies' camps). So what if there were thousands of swords being made in Gaul every day? So what if there were bounteous crops on the Nile? The underequipped, starving troops would win or lose months before any serious supply could reach them. This isn't to say that a civilization couldn't undertake and maintain a serious, long term war effort against another. Only that, unless both the production and logistics tech were advanced enough to make them relevant, it wouldn't be likely to take on the shape of a "total" war.
Second, motivation. If you're going to go to total war, you need a society which is willing to endure sacrifice and loss in order to do it. And, in practice, that loss is almost certainly going to be much more than any loot the country would take in from a victory (as if the average citizen would see any of that, anyways). Why should the peasant in Iberia pay more taxes, work harder, go off to war, just to annihilate a group of people that are a lot more like him than his own rulers that are making him do it? This requires an ideology; a sense of "us" as well as "them", and a belief that wiping "them" out (or at stopping them wiping us out) is worth the massive sacrifices a total war entails. Even back in the professional army period of the Roman empire, it wasn't patriotism that motivated the legions: it was the premise of getting pay, getting privileges, getting citizenship, loot, and land. When these things dried up, so did the legion's mettle. Europe could do total war because it had the idea of the nation. And it wasn't really until the invention of the printing press that national identity started to form amongst the average people.
So what would give your medieval people the drive to maintain a massive drain on their lives, persons, and pocketbooks? Especially when the "world war" in question would actually seem to be 4 or 5 distinct "worlds" away? These are questions for you to answer, but I think they're more or less mandatory.
[Answer]
## Maybe. Geography will matter
Rome could never have waged war on China, or vice versa, because of the distances involved.
This is greatly exacerbated by your world's bad naval technology. Triremes were not suitable for crossing large oceans, let alone waging war across them.
If geographical barriers are sufficient, war will be totally infeasible; if lessened a little bit, you'll have stalemates, as supply lines on offence become unmanagable.
Think:
* A) Rome v Australia (forget it)
* B) Rome v China
* C) Rome v Persia (stalemate)
* D) Rome v Britain
* E) Rome v Greece. (inevitable).
Maybe someone can compute how many days travel the Mongol Empire was; that represents the absolute best a completely equestrian medieval society can do travelling across (admittedly quite hostile) plains.
Ultimately, you need a map so that travel times can be ascertained.
[Answer]
It is possible but the devil is in the details. It would depend on how widespread the war was and what the layout of the world was geographically and politically as not even the Second World War involved every country. Large parts of South America and central Africa were not at war during this period (with some exceptions).
But given the right collection of hostile nations in close enough proximity then very large, protracted and destructive wars would be possible. Case in point the Thirty years war that ravaged Central Europe between 1618 and 1648 with millions of dead
<https://en.wikipedia.org/wiki/Thirty_Years%27_War>
This is a little after the traditional medieval period, but it was suggested that technology had increased beyond medieval levels anyway and technology was not advancing at a vast rate then.
[Answer]
Geography wise, it's probably theoretically possible, but the bigger question is *why*.
But lets address it on two fronts, using ww1 as our example, because WW2 was almost directly as a result of WW1.
# Geography
Although The Great War was a world war, it wasn't necessarily like it was continuously fought all across the place by everyone all the time, it was more that it was two large groups allied together fighting on multiple global fronts. So the bulk of your trench fighting is in continental Europe sure, predominantly in France, Belgium and to a lesser extent Germany, but there's a whole other front in Russia, there's stuff going on in Italy and in this war, Japan are part of the Entente or allied powers, but in the next one they've switched sides. But most of what's happening here is, relatively speaking, pretty local.
Gavrillo Princip assassinates the Austro-Hungarian Arch Duke Franz Ferdinand, and he's Serbian, so in response, Austria-Hungary invade Serbia. Serbia has an alliance with Montenegro so they drag Montenegro into the fight. So far, so small. But then, this is where the alliances start coming in, because Austria-Hungary, German and Italy have an alliance. So German troops, supporting their pals in Austria Hungary get invovled and march into Belgium and Luxembourg, but these countries were declared Neutral, because this is very much a time of empire and the big empire having countries didn't want to fight amongst themselves all the time when they could be off doing terrible things in far off lands. So now you have your other Alliance coming into play, because The UK, France, and Russia have a treaty to protect the Neutrality of Belgium, and now its time to uphold that.
And for a long time geographically speaking, this is where it's all happening. It's in the fields in france, and it's people who are being ferried over to do it.
You're sort of past the age of sea battling by WW1, but when there were some, they were being conducted in small areas like the channel (or La Manse if you prefer). Certainly if you go back towards the reign of Elizabeth the 1st, thats where sea battles with this sort of ship technology were happening. The crucial thing here is that you've got friendly forces making a big land corridor, or a small sea corridor. If Russia needed to go all the way to Italy to do its fighting with no promise of food and supplies? They'd have issues!
# Why though?
Politically speaking, this might be relatively easy to answer. WW1 started because of a land grab in the break up of the Ottoman Empire, WW2 started because Germany felt, perhaps quite fairly, that they were done very badly by in the wake of WW1. Your kingdoms might simply want more power or more space. For example the current Russia Ukraine War, or an aggressor might attack for religious reasons (The war in Afghanistan and Iraq).
What's harder to answer is the "why" for the every day person. Why do they want to become soldiers or go off to war or make munitions or buy war bonds?
Again, you can look to history for your answers.
The Spartans have a culture of war. You go off to war and you come back with your shield or on it. So victorious or one of the glorious dead. The entire culture lives and breathes this, and so it's perfectly possible to imagine a massive spartan empire declaring all our war because to Spartans, war is the entire point of life.
The Greeks you have this idea of societal taxes, you earn enough money and there's no question, you're fitting out war ships or you're fitting out choruses for the next play. One or the other.
Certainly a common thread for why people become soldiers throughout history has a lot less to do with any kind of civic pride and a lot more to do with being paid well, fed moderately and housed mostly. Especially if you're looking at a medieval style fantasy era, the promise of regular meals might well be enough to build an army with, they won't necessarily give two hoots as to who they're fighting or why, so long as they get paid afterwards.
Or you can engender some degree of national pride, combined with a fear of what will happen to their loved ones. The "Your Country Needs You" posters, if you don't fight off these aggressors they'll invade your homeland and do terrible things to your women and children.
Often I suspect its a bit of both. Keep the other guys out, get paid, try not to die yourself.
So, those are the questions you need to answer. Why are they fighting, whats the end goal, and does the geography allow for it?
[Answer]
**Being generous, at most something on the scale of WW1**
Whilst other answers address some important considerations with geography, there is something that is being heavily overlooked. **Logistics**
Perhaps the single greatest thing that contributed to the scale and brutality of both World Wars wasn't any weapon, rather it was industry.
The industrial revolution brought with it many changes that greatly changed warfare in general. On the more technical level, more advanced metallurgy, higher quality smaller parts that could be made on mass. Increased production of traditionally expensive weaponry, better ships/hulls, better clothing etc.
Scale and quality greatly improved. Whilst you have no gunpowder in your setting, you still have to answer to the scale question.
The industrial revolution not only improved quality but churned out numerous pieces of items at a much larger and faster rate than ever before. The advent of better machinery and tools had also meant that labor and manpower hour for production were sharply cut down. Equally important, it also standardized the quality of equipment.
The mass production of military equipment had meant that warfare took a more deadly and wider scope. One of the first modern wars, the American Civil War, was particularly brutal due to better weaponry that was produced on mass. The quality of a musket or rifle wasn't dependent on the skills of a certain blacksmith. Rather the tools and quality control of a factory. This means that both sides, but especially the North, could field large armies very quickly. The training needed to fire off a musket or rifle was significantly smaller than that of a spear or sword. It takes less time to make a soldier proficient with a firearm compared to that of knights, bowmen, calvary, siege engine crews etc.
However, you want something on the scale of World War 1 at least. By now the industrial revolution has more than matured and left its mark. The scale of industry is far larger than compared to the mid 1800s. Rifles, artillery, bullets and artillery shells are produced at an incredibly large level but in a short time as well. HMS Dreadnought set off an arms race for the ocean as engine, artillery, and metal technology saw massive gains compared to the days of early ironclads. This technology percolated throughout the rest of the military and rest of society.
Staying with the first World War, some of the things that made it so deadly and large in scale were:
1. Access to firearms that can be quickly and easily trained with.
Deadlier ammunition that could be created on mass. Conscript armies
that are of higher quality than any peasant conscript army with the
ability to inflict far more damage.
2. Large scale production of artillery and ammunition
3. Better engines
4. Armored ocean going vessels capable of holding significant weight and
weapons.
5. Transportation ships that could haul far more in goods and much
faster. So much so, that the United States and Canada could heavily
support the United Kingdom in both wars, as well as the Soviets
during the WW2
6. Better clothing for adverse environments
7. Factories with the ability to change production and address
deficiencies in certain areas (see Shell Crisis of 1915).
8. Long and better range communications. Radios changed warfare greatly.
9. Better medicine as well as hospitals. Combat medics and surgery for
injured soldiers were far more intensive than compared to previous
wars.
10. Increased attention to media, literacy and education. With the power
of nation states having increased so greatly by now, the idea of a
national spirit/unity cannot be understated. Technology, improved
literacy and propaganda allowed people to reach a much larger
audience.
11. Railways/trains. It cannot be understated how important rail was for
both World Wars. Not only did they move soldiers to a frontline in
the event of mobilization, but they greatly aided in transportation
of equipment from factories to the front line.
Plus, many more.
**However, your fantasy setting has some roadblocks in the way of getting a true WW1 or WW2 scale. Even with a light industrial revolution.**
For example, the lack of ocean shipping means that logistical support over ocean or force projection is basically impossible across water bodies. You simply don't have the sea faring capabilities to sustain an invasion across an ocean or a large water body. You won't be doing any island hopping, massive multi front amphibious assaults (Operation Overlord + Operation Dragoon). Supporting allied factions across a body of water in a meaningful way on the likes of WW1 is going to be very hard if not impossible. Whilst a land army can march (Grant+Sherman and the Romans for example), they're going to either have to rely on the land or strain their logistics heavily. If you don't have food preservation technique on an industrial scale, you have an even larger problem (especially for war elephants). Your army runs the risk of starving out if any defending and retreating faction employs a scorched earth policy if your invading force scavenges for food.
**Combat Losses-** Replacing combat losses is going to be much harder than say WW1. Even if we are being generous and mass arming your soldiers with crossbows capable of piercing plate armor reliably and spears, both still require a decent amount of training to become battlefield proficient. Every soldier that you lose, especially veterans, is going to heavily impact your army. Reinforcements are going to take a lot longer to come up to speed and perform cohesively. A faction runs the risk of being steam rolled should they sustain either mass or even key combat losses. You have no artillery to equalize or force multiply. You can't just spend a few weeks training a conscript how to use a crossbow or spear and then ship them off to the equivalent of Gallipoli or Verdun.
The mass casualty combat events on a scale of WW1, even worse WW2, isn't going to be sustainable for both your army and your industrial system.
**Industrial production-** The lack of things like gunpowder and advanced industrial mining means that getting ores and metal is going to be a costly and time consuming process. Especially on short notice. The machinery brought on by the industrial revolution by the turn of the 20th century greatly allowed nations to quickly mine and produce goods and equipment. Complex networks existed to supply factories.
**Fortifications-** Forts are going to prove to be far more deadly than that of WW2. WW2 introduced the concept of large-scale maneuver warfare. Forts could be bypassed, left to be dealt with at a later day. While both the Allied and Axis forces did fight battles over forts, they didn't pose the same power as pre cannon days. The invention of bombardment types of weaponry gave rise to an entirely different type of siege warfare that your forces don't have access to. Forts and trench lines in WW1 proved to be a difficult task to break through, tanks helped alleviate some of the issues. Heavy artillery helped as well. However, your fantasy army will have to deal with them. Starving them out takes time and requires a contingent of soldiers to watch over them. Taking a fort by force is going to be costly, even if you have a lot of siege weapons. This is going to break up your force concentration ability. Sieges also take a toll on both factions' logistics. Whilst this may appear to make a static frontline like WW1, you are going to lack the force maneuvering that WW2 saw. Theater wide scale will be brought down; however, you will now have an established frontline.
**Transportation-** The lack of trains and rails means that you can't transport troops and equipment quickly across long distances. You also won't be able to quickly redirect reinforcements or resupply a frontline. Every horse, or pack animal, that you lose, is significantly hurting your ability to wage a world war. Living animals take time to grow. Yes, ancient and pre modern armies marched and supplied themselves on foot. However, their scope of conflict didn't have the same breath/width of combat that WW1 and WW2 experienced at the same time across fronts.
**Electric Communications-** Whilst large land campaigns have been conducted without the use of electronic communications, both WW1 and WW2 heavily benefited from things like wire and radio communications. Whilst soldiers in WW1 didn't have personnel radios like now. Larger armies, generals and nations had the ability to quickly communicate with each other. For your fantasy setting, your central headquarters is going to have some issues in getting information about the frontline, who is maneuvering where, and creating a composite image of enemy force concentrations and dispersion. Even if you leveraged your magic system for tradecraft, it still is going to take time for that information to reach someone, and for an action to be taken in response.
**So how do you get something near World War 1?**
As others have stated, geography. Each faction has to be close enough in that they can quickly bring reinforcements and equipment to the frontline. With little space in between, invasions are more easily to be sustained. Your light industrial revolution has also caused the explosion of maintained roads. These roads will be the closest thing to rail you can get. Because of the close proximity of sorts, a cold war of sorts has been developing. So, your standing army also has significant reserves back home. Even better if something like a national guard or home guard exists. World War 1 was mainly fought in Europe and adjacent regions. There was no island hoping, daylight bombing raids on the scale of the Second World War, maneuver warfare using mechanized forces like Operation Cobra or Arracourt. After the initial German breakthrough buckled and slowed by Paris, trench warfare and stalemates started to become more of the norm. You can replicate this through the use of fortification lines with numerous forts. Each fort should have enough resources to sustain a siege and supply and reinforce another fort in danger.
Lastly some perspective. The Thirty Year War claimed some 4.5-8 million soldiers. Germany fielded an army around the size of 3 million in just the invasion of the Soviet Union during Operation Barbarossa. The Soviets would lose about 4.5 million soldiers during said invasion.
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Since apparently you want it to be possible, there are two major factors you have to work out.
First, an army marches on it's stomach. That means, unless you can sustain your troops for the entire duration of the war, you won't be able to win it.
While that does include weapons and armor, the bulk is food and fodder.
To get that to the troops, you should have either a very good road network and excellent logistics, or you might even consider a railway network, maybe horse- or ox-driven. Still, it is an enormous endeavor, and you may need to involve quite some magic to pull that off without steam or combustion engines.
Thinking about it: Sail-driven railway would surely look really cool...
The second aspect is information.
In order to get your armies to march in the first place, they need to be informed that they are to march, and where to. They also need to report their progress, casualties, needs, intelligence, and whatnot. Communication is absolutely necessary both for tactics and for the coordination of logistics.
Fast flow of information is also necessary to levy troops and to get the population to support the war. Again, with magic you can have telepaths do hat job, or magic devices that enable long-distance communication.
On the side: unless you have high levels of literacy, neither will you have very efficient propaganda, nor will the opposition be able to print pamphlets.
What you won't have, however, is the level of destruction and devastation that our world wars brought. With mostly melee, catapuls, (cross -)bows and such, you can never cause the same amount of destruction as explosives do.
So yes, if you really want that you can have a world war in your settings. You should still have to think of a reason why your nations should want that, and it will look and feel a lot different than our world wars did. Also, keep in mind that your army is taken from the workforce, so you should find some kind of explanation how you are still producing enough food for everyone.
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# If magic enhances food production
You mentioned that you have physical enhancements from magic. If they also enhance crop production then you can have a world war.
The main limitation on moving armies was food and clothing. Food runs out, shoes wear out, and you can't move them any further. With effectively infinite food, moving huge armies is no longer an issue.
This also makes mounted infantry a lot further ranging. The main reason tanks and trucks replaced horses was because petrol is very easy to transport, energy dense, and allows much faster movement. If your horses have unlimited food then they can act like trucks.
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While a bit late for your timeline, The Seven Years War was a global conflict that started in Europe between the alliances of England, Prussia, and Portugal, vs. Spain, France, and Russia and Austria. Mixed in were several minor German powers which either directly fought with major power allies or sold mercenary services. The war had theaters opened in Europe, North and South America, and Asia.
The U.S. Revolutionary War, saw the American Colonies allies primarily in France (Because in the late 18th century, it's more surprising if the British Empire is at war and France isn't involved) but also Spain and The Dutch Republic face off against British and German allied Mercenaries. It wasn't on the scale of the 7 Years war, but was a direct consequence.
You also have the Napoleonic Wars which was a series of wars that was France vs. all of the rest of Europe (At the greatest extent of the France's control, Continental Europe was under France's control with exception to Portugal, Wallachia, Moldavia, Russia, and the European parts of the Ottoman Empire. Additionally, the British Islands, Sicily, and Sardinia were also out of Napoleon's control). The Napoleonic wars would also serve as the last major conflict in Europe until WWII nearly 100 years later.
As mentioned earlier, the Mongol Empire at it's height Controlled an Empire from the Pacific Coast of Russia, and as far east as Ukraine and much of the Persian Gulf, the largest contiguous empire ever held and largely assembled in Ghengis Khan's life time alone, mostly through war.
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I have a universe where space travel is common. A large group of settlers veered off course and crashed on a desert planet and have not yet been rescued for 50+ years and had to fight amongst themselves to survive.
I'm looking for a way to explain why nobody noticed people were living there. I'm thinking some element in the atmosphere prevents scans, and potentially even throws off sensors which is why they (and the main character) crashed there because the planet was effectively invisible and they didn't notice they were going into the atmosphere of the planet until it was too late.
Does anyone know of something that could cause this?
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## Needle in a haystack
Angry Muppet is right: unless you tell us how a "scan" works, we can't speculate about sources of interference.
*However*, the body of your post says that what you want to do is:
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> explain why nobody noticed people were living there
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So, let's not make this an [XY problem](https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem) by getting wrapped around the axle of *Star Trek*'s "scanner" nonsense.
Here is why nobody has found these settlers: there are countless billions of planets in space. Depending on how your space travel works, there could easily be tens of thousands of planets within "reasonable" travel range of your main civilization. Given this, it is vanishingly unlikely that anybody else would be looking at this one planet.
This situation is compounded by the fact that your travelers went off course and crashed on an *undesirable planet.* Nobody else is going to scan a desert planet because it's a frikkin' desert.
If there's anybody looking for your travelers, they will be looking on the destination planet, and that search could take months or even years depending on its size and terrain. The search will probably expand outward from there, along the travel route.
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# Being in another solar system
[Read this](https://en.wikipedia.org/wiki/Proxima_Centauri_b) and see how much we know about the nearest planets.
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> Before 2016, observations with instruments[a] at the European Southern Observatory in Chile had identified anomalies in Proxima Centauri[12] which could not be satisfactorily explained by flares[b] or chromospheric[c] activity of the star.
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Without a very powerful telescope in a nearby system you're not gonna get much better than that, knowledge that based on tiny colour fluctuations that maybe there's something earth sized there which isn't just the star.
A spaceship is much smaller. It's gonna be almost impossible to detect that from lightyears away.
In system, nothing could conceal a planet. Basic newtonian calculations about the movement of planets and the star would quickly reveal every major source of gravity in system.
[Answer]
Question provides too few details on the universe it's trying to describe, making it difficult to answer.
Currently we, as a spacefaring species would face two distinct, yet connected, challenges: travelling and/or communicating through the space-time continuum. In other words, we are limited to slower-than-light speeds. In addition, the distances aren't making it any easier.
Consider radio transmitter - it can be used to communicate over vast distances on Earth, using (relatively) weak signal, because it's bouncing off the various layers of the atmosphere (typically ionosphere) or Moon (but that's atypical). Normally we use satellite network (sending signals from one point to another by passing it between the satellites if distances are great). There is no ionosphere in space, and there are a lot of other factors that actually dampen signals a great deal in interplanetary and/or interstellar space - for example frame-dragging effect of a sun, number and movement of gas giants (if any) or other celestial bodies, type of a star and it's emissions...
So, in order for our castaways to be able to send emergency signals they need one or more of the items off the list:
1. FTL mode of interstellar communication or
2. Be "close" to the interstellar route and FTL travel is not preventing receiving STL communications
3. Powerful transmitter
4. Know their location in terms of galaxy
5. Know the location of the target of their transmission
If our castaways veered off course and crashed on an uninhabited planet in a binary star system, on the wrong half of the planet and in the process losing ship's power plant they may have to first relocate to a spot from which their signal will reach the part of the galaxy they need, restore their power-generation capabilities... Then their signal may be sub-light only and takes 50 years to reach the travel lanes and they have to have just a tiny window where they and the spot they send signal to have unobscured (by other planets, for example) Line-Of-Sight - yes, some sort of anti-conjunction of planets... Their star needs to go into the calm period of it's cycle, emitting much less solar wind or other radiation...
There are ways, but you need to decide what your conditions are.
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**No need to be undetectable**
They could simply be too far. The SOS signal after all will travel at light speed and after it is picked up it takes time to organise a rescue mission. Furthermore if the transmitter is not properly pointed a man made signal easily fades away in few light years.
A navigational error made at the beginning could send your settlers many light years away from the intended destination, in a sector of the galaxy that is unexplored and in the middle of nowhere.
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## What would an eclipse with a translucent crystal moon look like?
In one of my worlds, a special moon orbits the planet — it's made of a translucent crystal, blocking only 80% of the incoming light. It's purple. And on certain days, just like earth, this moon covers the star the planet calls home, and creates an eclipse. What would this eclipse look like?
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More info if you want:
* This isn't a question about how the moon is made of crystal; that's handwaved for the purposes of this question.
* At the center, the moon blocks 80% of the light, but towards the sides this number drops off as the crystal gets thinner.
* It's a total solar eclipse.
* Assume star = sun, people viewing = humans, and planet = earth if it matters.
* If you need more info, ask.
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The focal length of a ball lens of radius R with index of refraction n is nR/(2(n−1)), and if the planet/moon is "just like earth", then the distance from the moon to the earth is approximately 200\*R. So there are three scenarios, depending on the properties of your magical crystal.
1. n > ~1.005 : (most likely the case if the crystal is similar in properties to traditional transparent/lucent materials). In this case most of the light that isn't directly blocked by the moon will be refracted away from the earth, so the eclipse will look similar to that produced by an opaque moon.
2. ~1.005 > n > ~1.001 : (the oops scanario). In this case a significant proportion of the un-blocked light will be focused onto the earth so the moon will appear as a bright object in some regions of the planets surface. The situation will get more 'interesting' as n approaches 1.0025. In particular, if n is very close to 1.0025 then there could be a small patch of the earth's surface where the intensity of refracted light could be significantly greater that that of the naked sun (images of ants under magnifying glass type of scenario).
3. ~1.001 > n : (the more artistic scenario - needs a refractive index not dissimilar to that of the vacuum). In this case the moon will not appear to significantly refract the light, so during the eclipse it will appear as a big ball thar is brighter (whiter) towards the edges and darker (purpler) towards teh centre.
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This will actually look remarkably like a total eclipse on Earth.
Since the crystal the moon is made out of presumably has a [refractive index](https://en.wikipedia.org/wiki/Refractive_index) greater than one (quartz is 1.46, sapphire 1.77 and diamond 2.42) and the moon is approximately spherical, it will act as a lens.
We don't know the focal length of the lens, but any plausible value will be much less than the moon-to-planet distance, so the light passing through the moon will be widely dispersed and the moon will look dark. Just like an opaque moon.
And that's ignoring the issue of the crystal moon being totally opaque if it's actually made of any known kind of crystal. A thickness of more than a few tens of feet would absorb all the light.
If the moon were not solid, but a shell a few tens of feet thick, it would have a much longer focal length, dependent on the shell's thickness. Sadly, such a shell the size of Earth's moon will collapse under its own gravity, into a disorganised ball of fragments.
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Upright; no tail. This is a creature that requires a more efficient respiratory system for longer intense physical activity. But it needs strong bones like mammals have. Bird air sacs extend into the bones, though, which would probably weaken the bones. It does not fly. By bird system efficiency I'm referring to the fact that birds have air constantly moving through the lungs, unlike mammals that have a pause between fresh air.[](https://i.stack.imgur.com/dkCkN.jpg)
Can this creature have an efficient bird like respiratory system without having the air sacs needing to extend into hollow bones(pneumatic)?
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## You don't need pneumatic bone (hollow bone) to have air sacs.
air sacs evolved before hollow bones, pneumatic bones is just a useful extra thing you can do with air sacs once you have them, (you can make bone stiffer). pneumatic bone is not necessary for functional air sacs, most air sacs are not even in bone but in the body cavity.
see the six big air sacs in this image here, they are in the body cavity not bone.
[](https://i.stack.imgur.com/9Z1pA.png)
you can see it in air sacs casts, in B the light green portion (LVD and CV) is the only portion actually inside bone.
[](https://i.stack.imgur.com/hBwuN.png)
Air sacs evolved outside bone, but get moved into bone fairly quickly evolutionarily because it has several benefits (stiffer lighter bones for a given size for a start) but it is not needed for the air sacs to work.
You may want to check this out (<http://people.eku.edu/ritchisong/birdrespiration.html>)
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**Sure.**
The main advantage of the avian respiratory system over the mammalian one is that the airflow is unidirectional. This is a huge advantage for oxygen transfer, but it's a challenge to get there evolutionarily from a bidirectional lung system. Birds got there, mammals haven't.
There's another example of the same limitations of bidirectionality in systems. Many more primitive animals like cnidarians have a blind gut -- their digestive system is bidirectional in the same way that mammalian lungs are bidrectional. This isn't ideal -- to the extent that the formation of the gut happens remarkably early in most embryos of more advanced animals. Evolution "decided" that a unidirectional gut was the only solution to this problem for most animals.
It's perfectly reasonable to describe an avian-style respiratory system where the air sacs are discrete structures in the body, separate from bones. But the avian system has only gone most of the way towards unidirectionality -- quite a bit of its complexity is around allowing unidirectional flow over oxygen transfer surfaces while still using the same upper respiratory system for both inhaling and exhaling. If you want to describe an even more efficient system, and are not constrained by "easy" paths from current mammalian biology, a two-orifice unidirectional respiratory system fits the bill. A single lung for oxygen transfer (more if desired for redundancy), a single inhalation port, a single exhaust port, and either a peristaltic or heart-style chambered pump to push the air in one direction.
There's more than one solution possible here, of course; but this shows there's at least one viable path, which means that there's a way forward here. The evolutionary history of your creature (if any) might determine the details.
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## A bird's respiratory system is about 8x as powerful as ours, but not 8x as effecent.
* A bird's lungs are about 2x the proportional size of a terrestrial mammal's.
* Air sacs approximately double a bird's respiratory volume as compared to a terrestrial mammal's lungs making the total volume of their respiratory system about 4x that of a terrestrial mammal's.
* Birds typically have about 1/2 of their air sacs inside of pneumatic bones. This means that by virtue of their bones, they can reduce how much body cavity space they need for their respiratory system by 25%.
* While a bird's respiration is unidirectional thanks to its air sacs, this does not make their respiratory system inherently more efferent. What it does is normalizes the oxygen intake so that the bird can absorb oxygen on both the inhale and the exhale which means that it does not have to stop intaking oxygen to exhale. While this doubles the efficiency of the lungs, when you add in the extra volume the air sacs take up, it is kind of a moot point in terms of size efficient but they are more efferent in terms of weight since they are just empty sacs instead filled in organs like lungs In contrast, bats achieve the same levels of oxygen exchange as birds just by using bigger lungs.
* Bird lungs have about 2x as much exchange surface for their size as mammal lungs.
So what all of this tells us is that the **efficiency** you see come directly out of pneumatic bones in terms of respiration is that it allows you to reduce the needed weight and body cavity space of your respiratory system by ~25%. Everything else that is beneficial about a bird's respiratory system either does not contribute directly to respiration efficiency or it could be easily replicated just by making lungs bigger, have more surface area, or by using air sacs purely inside the body cavity.
## Solution: Give them a higher Myoglobin based Oxygen Intake Mechanism
All this said, both mammals and birds tend towards hemoglobin based oxygen intake. Most animals prefer hemoglobin because it forms weaker oxygen bonds than myoglobin making it require less energy to release the oxygen when needed. However, the stronger bonding force of myoglobin means you can uptake oxygen several times more quickly and completely. In fact, some mammals have been shown to boost how much myoglobin they use for oxygen transport and absorption when injured, living at higher altitudes, or requiring a more energetic lifestyle to help compensate for higher oxygen needs; so, the mechanism required is already in place. You just need to activate it.
While hemoglobin only allows animals to absorbs ~15% of the oxygen it breaths in, mammals which use primarily myoglobin based intake (like Whales) are able to absorb up 90% of the oxygen they inhale. So, by increasing your myoglobin dependence by just a little bit, you can increase your oxygen intake by 25% to compensate for not using pneumatic bones as part of your respiratory system. In fact, if you were to switch to a purely myoglobin based exchange system, and increase the surface area of your lungs to the same density as a bird's you could achieve the same total oxygen exchange as a bird gets without even needing to make your lungs any bigger.
## Other reasons to favor pneumatic bones.
The big downside, and thus the reason most organisms don't do this, is that it will take more calories to release the oxygen when needed. While inefficient calorie use is normally selected against, your creatures may be in a situation where they are genetically engineered and/or fulfill a niche where the extra calorie needs are not a major constraint.
Furthermore, most terrestrial body plans would overheat using this kind of respiratory system. Part of what a bird uses its pneumatic bones for is temperature control. Burning more oxygen means more body heat; so, birds use these bones as heat sinks to help remove this extra heat from their bodies.
So, if you are going for a body plan that prefers solid bones, you should consider that your organism may need to live in a colder environment, and/or have specialized structures that act as heat sinks like an elephant's ears or a bat's wings.
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Setup:
**Avians** are a humanoid species with bird characteristics, they all posses the ability to fly. Just as other species they can learn to use bows, swords and magic. Their main fighting tactic is using long spears to charge down attack and fly back up, they are aware using bows from high above would be safer but they are reluctant to change their old ways but will change if things get too bad. Their aesthetic and culture is *vaguely* based on Qin dynasty China.
**Leonins** are a humanoid species with lion characteristics, they posses enhanced strength. They are also capable of use of all weapons and magic. Their main fighting tactics are their world-wide famous unbreakable shield walls. Their aesthetic and culture is *vaguely* based on the Roman Empire.
**Rules:**
* They both have access to magic but they are both bound by an international pact forbidding them from using magic for large scale destruction on the battlefield, but they are allowed to use magic for healing and strengthening their troops (main examples being making troops bigger or smaller, magically protected, stronger, faster and braver).
* The avians have most of their important cities high in the mountain making them difficult to attack while the leonins live in the plains south of those mountains but have more territory and people.
* The conflict started because the leonins took in a prince that failed to set up a coup. This is the excuse for the war but the avians are interested in expanding their territory, weakening their neighbor, in glory and in their prince. The leonins originally wanted to destabilize the avians but now want to prove their strength and keep their pride, they also want a bit of glory.
**Question:**
I want this conflict to generate a big number of refugees from both sides and a large amount of animosity. In my view the conflict seems to favor the avians heavily, making it an easy victory due to their abilities to **fly over the enemy's armies and walls** and to **attack from a distance** with long spears or bows. How can I balance this and draw the conflict out into a long and bloody war, preferably displacing many civilians?
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## You can't fly in any but the lightest armour
Birds must be very light to endure staying airborne for very long, and though the largest birds of prey can lift animals as large as goats, it's only for shorter distances. Most avians would only be able to cover their most vital organs with metal, meaning they would not be able to fly into a volley of arrows with the same confidence as a heavily armoured foot soldier.
Furthermore, their large wings would be even harder to armour, and even if they fold them up when diving down on enemy soldiers, they need to spread them afterwards to fly away again, making them vulnerable to crippling wing shots.
The Leonin could counter Avian spear fliers by mixing archers (bow or crossbow) with their shield bearers (who could use spears just as long as the Avians'), allowing the shield bearers to protect the archers while the archers engage the fliers whenever they're out of spear's reach.
The hardest weapon to counter for the Leonins would actually be common rocks, as a rock dropped from 100 metres height will break your arm weather you have a shield or not. In order to avoid these, the Leonin army would have to disperse so each soldier can dodge rocks on their own, and the Leonin army would do well to avoid fighting in open, rocky places. The Leonin might also invent shields with a supporting leg that can take the force of a falling rock, but the added bulk would make them much less fit for use in melee.
## Supply trains can't fly
Even if the Avians can fly in battle, they need tents for sleeping, extra clothing, cooking utensils, food rations (to supplement whenever raiding the local countryside won't work), tools for repairing weapons and fletching new arrows, and so on. All these things are probably too heavy to fly around with, so they need to travel overground, not to mention a supply of rocks for whenever they're campaigning in less rocky places. Furthermore, after a few rounds of flying up with heavy rocks, tired Avians would need a place for falling back to rest.
Over time, the Leonin tactics could shift toward surviving the initial onslaught, then charging this camp. The Avians, poorly suited for land-bound combat, have no good way of protecting the camp if they fail to stop Leonin from reaching it.
## Mounting casualties encourage non-confrontation
As battles become bloodier for both sides involved, both sides are encouraged to find some target to attack which isn't the other army. Here you can think of the Thirty Years' War: Armies marching around, pillaging the lands for food and plunder as they siege down castles and cities currently held by their opponent. Not a lot of people are killed in battle, more are starved as their food stores are raided over and over, or just killed for being perceived as sympathisers of the opponent. Anyone who has the chance to leave will leave. Hundreds of years later, Leonin parents will still tell their children to behave or the Avians will come, and vice versa.
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## Thoughts
* Make the invention of counter tactics play a part of explaining the ebb and flow of the war. So the Avians start out really proud of their spear fliers, making it the core of their army, but at first confrontations they suffer crushing defeats, allowing Leonins to penetrate far into Avian lands before the latter switch to simple rock dropping out of desperation. This proves super effective, putting the Leonins at full retreat and allows the Avians to retake all lost land and then some. Then this culminates inside Leonin lands as the latter learn to protect themselves and ambush the Avians.
* The mountain homeland of the birds is going to be very hard for the Leonins to penetrate, since they're slow to travel through, more sparsely populated (i.e. have less food to forage off unfortunate farmers along the way) and provide the Avians with plenty of safe spots to strike out from. However, no city can survive without adjacent woodlands for fuel, giving the Leonin somewhere to hide in relative safety while laying siege to the cities. Maybe the Leonin have good night vision and the birds don't, allowing the former to advance and attack during the night. And maybe the Avians never built very strong fortifications in their homeland, never having experienced an invasion from land-bound enemies before now and finding walls mostly ineffective against local warlords.
[Answer]
Assumption both groups are omnivores. Thus are in competition for food thus leading to prior wars/violence that caused the avians to be pushed into the mountains where they have a strong military advantage over the leonins.
Thus the two groups are in balance. The avians can do harassing aerial attacks and resource raids. But if the avains want to claim the better non mountainous territory they need to have boots on the ground. The ground upon which the leonins have clear physical superiority.
This is the same problem that the us air force has. They can destroy cities, but that can't hold any territory without putting boots on the ground.
The civilians are already mostly displaced. The leonins are in the lowlands the avains are in the highlands/mountains. The latest outbreaks of violence would just cause the civilians closest to the borders to move.
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**Lions jump high.**
[](https://i.stack.imgur.com/bnJVE.png)
<https://www.youtube.com/watch?v=5FN1GX46oc0>
This looks like a tiger to me. It is definitely a big cat and it is really jumping. I figure the back legs are 5 feet off the ground and the paws are probably 6 feet above that.
Even with long spears, when your bird people get down into spear range the lions can grab them. And the lions are crazy quick; much faster than the birds because they have traction on the ground and they are cats. If the bird is higher than they can grab they will parkour up off a tree or off the top of a buddy to get some extra height. If a lion person can touch a bird person it is all done for the (delicious) bird person.
[Answer]
Both sides indulge in attacks on food and water supplies.
Perhaps these are new spells, hence the lack of agreement against them.
Perhaps their subtle differences allow them to be indignant at the other side: the avians declaim on how the leonins' magic fouls a well for months on end, leaving anyone who drinks it sick, and the leonins, on how the avians' magic renders a well *deadly* even if only briefly. Perhaps leonins concentrate on the smaller animals, such that the avians can carry them off, and the avians retaliate by slaughtering larger animals, leaving most to go to waste while they carry off what they can.
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**Beefcake Wizards**
[](https://i.stack.imgur.com/pMEfU.jpg)
Other answers point out the Avians cannot stand and fight a shield wall because they are too flimsy. Even staying in the air they cannot use powerful bows because they are too weak. They need to be light enough to fly after all.
They can only harass civilians and [poison water supplies](https://www.youtube.com/watch?v=PDyccd5qx2w) and such. They cannot capture territory. Their raiding parties cannot stray more than a day's travel from their own territory because their supply wagons cannot fly.
Of course this assumes no magic. With magic they can scry the location of the enemy forces, and teleport their strike forces to rain down acid bolts on the unprotected granary on the other side of the map. When the Leonins muster their troops, the bird people simply teleport back.
This is a problem because typically Magic doesn't care about how strong you are. If your bird people "cast from their INT stat" then their mages have a huge advantage. They can fly and their acid bolts are just as powerful as the Leonin's acid bolts.
To remedy this I propose the mages instead "Cast from their CON" stat. They cast from the energy stored in their body. Thus a larger Leonin has a larger mana pool. A 100kg leonin can cast more acid bolts before tiring out than a 20kg Avian can.
[Answer]
your setting is interesting and I believe one of the answer in the background of your world.
* Avians population is limited:
Avarian live in very hard to access cities. As such they have an hard time producing enough food to maintain a large population.
* Avians flight capacity is invaluable they're able to move quickly, to conduct intelligence operation from the sky and harass their opponent.
* Avians do not have effective CAS (Close Air Support), destruction magic is forbidden, they can harass with bow, rock their opponent, but it is not as effective as today CAS.
* Leonins learn that if they move by night using their superior night vision and/or under the cover of forest they can avoid avians detection as long as they move in small columns such as to not let large and visible trace from the air. (example a thousand marching in field will make an easily noticeable from the air trace in the field)
* Leonins launched successful attack on Avians "accessible large cities" forcing survivor to flee and abandon offspring and eggs.
* In retaliation, Avians started a scorched earth policy, burning Leonins field. Forcing thousands to leave to find food.
From this setup you can then use the old and universal shield and sword trope. One of the group find a new way to parry others attack and the other find a new way to inflict damages.
But the main equilibrium come from the fact that Avian are not strong and numerous enough to directly attack leonid cities. And Leonind can't acces Avians cities. They may try but the terrain make them easy prey for the flying Avians.
War may then be prolonged as more Leonid field are burned, and time to time and Avians cities are raided and pillaged.
You can even imagine Avians raiding small cities in force, as they can quickly assemble and move a large force in the air.
Forcing the Leonid to develop counter measure. e.g. net over the city. Network of Anti-air ballista ect...
[Answer]
Set the battles in a location where flight is difficult, for example underneath a thick jungle canopy or in rocky valley with strong winds. Have a naturally chaotic magic field in the region that limits both sides to simply spells such as casting fireballs and healing, which would create a war of attrition with neither side being able to gain a magical advantage, but being able to create a lot of injuries.
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While Avians have flight, it comes at a cost: Their bones are hollow, and thus fairly weak to blunt force. Even with armor, it would require less force to break a bird's bones than most land animals. Given that they need to be able to fly, armor strong enough to protect them probably won't be able to be worn in the air.
Add to that the facts that birds have to land eventually, there will come times when it will be easy to land physical hits.
Magic can greatly change this, depending on how it is used. If, say, there was a spell which would allow a large thrown rock or boulder to home in on a target, birds would immediately be at a huge disadvantage. While a strengthening spell could be used by avians, it would normally come at the cost of energy required for flight. Stronger bones = heavier bones = heavier object trying to fly.
Effectively, Defense and Mobility are inverses of one another.
So for large numbers of refugees and animosity, have the Avians aerial raid the Lionins, and have the Lionins snap the Avians' bones to ground them and keep them from their high-up cities.
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## Leonins have a superior economy and population
Avians are more deadly one on one, but leonins have superior carrying capacity, stamina, lifespan, and lower metabolisms. Their plains are also much more productive than the avians' mountains.
As a result, leonins can field well armored, well supplied armies many, many times larger than the avians, with better siege engines and better trained mages.
In winter, their logistical disadvantages increase but their metabolic advantages comfortably compensate.
They can erect forts overnight that would take avians a week.
Sure, the avians can kill quite a few of them as they travel to avian cities, but actually repulsing them is difficult.
Like any number of obscure steppes peoples, the avians are destined to one day be the shock troopers of the big empire next door.
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I want my world to have an Alcubierre drive for slower-than-light-travel. One third the speed of light will do. Since there is no FTL we don't have to worry about causality paradoxes. However the drive still has problems! [They are about radiation.](https://en.wikipedia.org/wiki/Alcubierre_drive#Survivability_inside_the_bubble)
Hawking radiation inside the bubble will heat the ship and cook everyone inside it. Also on arrival the ship will release infinitely blueshifted radiation and cook everyone at the destination. Is there any scientificaly plausible way to fix these problems and make Alcubierre safe both for ship and its destination?
Maybe it is possible by adding fictional negative energy exotic matter in the story? Maybe some specific spacetime curvature would do? Maybe the problems don't arise at all if we travel at sublight speeds.
Upd.: abovementioned wikipedia article says that there is no problem with Hawking radiation if the bubble is subluminal. But there is still dangerous blueshifted radiation at the destination if I understood correctly: <https://arxiv.org/pdf/1202.5708.pdf>
Or maybe I'm wrong?
Any ideas besides careful navigation?
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The warped space is supposed to create a flat region in the center, so any blue shifts going through the warped space should be nullified by complementary redshifts, I believe.
However, there is still a blue shift for your cruise velocity.
You're looking for the [doppler equation](http://astronomyonline.org/Science/DopplerShift.asp) for light :
${{\lambda} \over {\lambda\_0}} = {{v} \over {c}}$ which, in your case $ = 0.3$
To get the energies of these photons
$E = {{hc} \over {\lambda}}$
Putting them together ${{E} \over {E\_0}} = {{\lambda} \over {\lambda\_0}} = {{c} \over {v}}$ which, in this particular case $ = 3$
The energy of each photon is what matters, and for water the absorption depth for ~37% of the incident light the be redirected follows a linear logarithmic relaitionship. You can see a graph [here](https://en.wikipedia.org/wiki/Penetration_depth).
Since the relationship to frequency is logarithmic, tripling the photon energy does not change the amount of shielding material your ship will need as much as your might expect. You will need 1.5x times more radiation shielding.
According to the answer to [this](https://space.stackexchange.com/questions/1336/what-thickness-depth-of-water-would-be-required-to-provide-radiation-shielding-i) question, that baseline amount of shielding is about 1 meter (1 yard, or about 3 feet) thick. You might have "sci-fi" technology that reduces that amount.
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**Not a Problem**
I do not understand the maths behind the Alison Cubert Warp Drive. But I am VERY good at reading Wikipedia articles. On a good day I can also read the Abstract and Summary of an academic paper.$^{1}$
EAT THIS!
>
> Of course, all the aforementioned problems disappear when the bubble remains subluminal. In that case no horizons form, no Hawking radiation is created, and neither strong temperature nor white horizon instability is found. The only remaining problem is that one would still need the presence of some amount of exotic matter to maintain the subluminal drive.
>
>
>
This is from [Semiclassical instability of dynamical warp drives](https://arxiv.org/pdf/0904.0141.pdf). The paper cited in this bit of Wikipedia:
[](https://i.stack.imgur.com/mUYVa.png)
See that [4]? That's the paper I'm talking about.
The take home is that for a subluminal drive there might be no radiation problems. There might not even be a bubble!
The take home is that you can sometimes answer your own questions by scrolling down on Wikipedia and following some of the citation links. The power is yours.
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$1.$ Just the one though. Then I need a little lie down.
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If life did evolve on a planet around a blue star, what sort of adaptation could be expected? I so far have the autotrophs being yellow/orange or blue to absorb the light. I also thought the animal life would have blue reflective skin.
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Physical adaptations would be less about *hue* and more about shielding. Colors would tend to be **darker** - consider that albinism is more dangerous and susceptible to more radiation damage. [This article on plant color](https://www.quantamagazine.org/why-are-plants-green-to-reduce-the-noise-in-photosynthesis-20200730/) has some interesting insight. Instead, **indirect light blocking** would be a bigger deal, such as heavy fur, scales, or shells. With higher solar flux, **body heat regulation** might also be a higher priority, of which there are many different strategies. A shiny exterior would have more to do with heat dissipation than damage protection. For that, any opaque surface will do.
Also, **light-averse behaviors** would be much more prevalent - burrowing underground, keeping to shade, **crepuscular and nocturnal** rhythms, etc. I would expect greater differences between night and day in general. **Cloud cover, weather, and water evaporation rate** may have a greater impact on the landscape and animal behaviors (though weather specifics belong in a separate question). Creatures capable of tool use might learn to build parasols! Plants might actually worry more about **too much light** than not enough. You might expect an oasis of more vibrant life in a shaded area instead of a well-lit area.
**Ocean life could thrive**, as there would be more available space that is warm and well-lit, while still shielded from much of the more harmful wavelengths. **High altitudes and deserts could be more harsh**, though on earth creatures still make a living there. Perhaps life in those climates on earth could offer some more inspiration.
If your planet has much axial tilt, creatures might find **reversed seasonal relief in higher latitudes** - perhaps life there hibernates through the summer and blooms in the fall and winter. It may also shift the most vibrant life **away from the equator** and bring more deserts there. However, these locational effects would depend greatly on where in the goldilocks zone the planet rests.
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There are way more factors than just the classification of the star in picking the adaptation of the organisms living under it. And don't forget that the color in the star name only indicates the predominant color, but stars emit on a continuous spectrum, not on a narrow line.
Our sun is a yellow dwarf, yet we have white bears, black crows, brown bear, red scorpion fish, blue jay, green lizard and so on.
Also autotroph-wise, we have green plant, blue algae and even red ones.
In short, life would adapt to the specific environment where it is settling.
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There is a serious doubt that complex life could evolve near a blue star. Conventionally, stars of classes O and B are called blue. According to the table here <https://sites.uni.edu/morgans/astro/course/Notes/section2/spectralmasses.html> and the calculator here <https://rechneronline.de/planets/lifespan-star.php> , the lifetime of the smallest B-class star is less than one billion years, which is, if our life on Earth is any indicator, not enough even to develop multicellular organisms. Even if we stretch the definition of blue to the late A-class stars, we have only 3 Gyr, which is also not very impressive given that this is around the timeline of apperance of multicellular life on earth. However, it will not come to that most likely, since the change of the luminosity of the star nearing the end of its main sequence life will probably boil or evaporate all the oceans on the planet long before that. For comparison, this is supposed to happen on Earth around one billion years from now, which makes around 5.5 Gyr of the Sun's projected lifespan of 10 Gyr suitable for life.
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By “Police State” I mean a despotic sort of government in which the state is actively trying to spy on its citizens for political ends. Something like the German Democratic Republic (East Germany) or the People’s Republic of China.
By “Widespread and Reliable Communications Technology” I’m referring to everything from the Telegraph to radios to the internet.
For this world the printing press is what counts as information technology. The state in question is preindustrial but highly organized. It’s not like something you’d see in medieval Europe but more along the lines of an early modern state or Edo period Japan. The state in question is mostly concerned with using its police apparatus in its capital city, which has just over a million people.
The political ends of this police state are primarily to prevent rebellion, instill ideological conformity and prevent the emergence of organized labor
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Considering this statement '*The state in question is mostly concerned with using its police apparatus in its capital city, which has just over a million people.*', there is no real need for modern communication technologies to manage a described police state effectively.
Preindustrial cities were rather small when it comes to land area. For example, the known area of the ancient city of Rome was only around 14 km2 (the area enclosed by the Walls of Aurelian**1**) in the early Empire period (around 1st century CE) when the population of Rome was estimated between 500 000 and 1 000 000. Chang'an is another example of a preindustrial city with around 1 000 000 residents. It is estimated that Chang'an had this population during the Tang dynasty (more specifically in 700-800s CE). The land area of the city was also small - [about 86 km2 inside the city walls](https://www.worldhistory.org/Chang%27an/).
Chang'an has a much larger land area because it is a city planned and built in accordance with Chinese tradition of geomancy and ideals of an emperial capital. A significant part of the city is forbidden grounds where the emperial palace is located. Rome is much more chaotic and most parts do not involve a lot of urban planning. The streets are also much narrower.
For comparison, the [land area of today's New York](https://www.wikiwand.com/en/New_York_City) (city) is 778.2 km2.
If your capital city is similar to historical cities, the land area will be equally small. It also means that the time required for news and information to travel is relatively short. Even if the government does not use pigeons (or similar methods of 'fast' news delivery), regular messengers (no horses) can deliver packages/news/orders/whatever within a few hours. Secret police can have even faster messengers.
It is also easy to monitor the residents due to high population density. If citizens are encouraged to report all suspicious activity the effectiveness of monitoring and policing will only increase. It is worth noting that totalitarian states never rely on mass media and police alone. They also rely on 'concerned citizens' to get the job of controlling people done.
The small area of the city and high density of population also mean that it is much easier to control businesses and supervise various activities. For example, there are only so many places where an illegal printing press could potentially operate. And it will be very challenging to hide them from the police.
It is worth mentioning that the goals such as '*prevent rebellion, instill ideological conformity and prevent the emergence of organized labor*' do not really need a police state. The US is a prime example of all these goals being more or less achieved. The methods used are very different from the German Democratic Republic (East Germany) or the People’s Republic of China that are used as a model for the proposed police state. The specific methods of achieving these goals are outside the scope of this question.
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**1** According to [this estimate](https://www.cambridge.org/core/services/aop-cambridge-core/content/view/BACD7DF32B0B77609CD6713B8AF88882/S0003598X00085859a.pdf/population_of_ancient_rome.pdf), the population inside the walls was around 440 000. The population density is estimated to be around 30 000 persons per km2.
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**The law of 'Divide and Rule'**
Yes! The law of 'Divide and Rule' has been a very effective way of governing the police state.
* Install local rulers who are power and wealth hungry, with no passion
like mercy or humanity. Give then enough money to maintain a small
army to snub their people.
* Create rivalries among local rulers and groups.
* In case of a fight, supply arms or support to both sides in such a
way that each side thinks you are with them.
* Encourage or even force your faithful rulers to fight with the
rebellion groups.
So all you will need is to control those faithful paid off vulture like local rulers by exploiting their weak points and let them take care of the rebellion groups.
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You don't police the population, you let them police themselves.
Make them look up with jealousy, and down with disdain.
It's a tried and tested method of controlling behaviour and preventing dissenting thought from ever effectively blooming, and is at the root of most religious organisations, and even things like the Indian caste system and the British class system.
It works so effectively because if somebody does try to step out of their place in the system, not only do all the ones above them automatically close ranks to prevent it, but those at their level and below will quite often be just as against it, if not more so.
To take an example close to what you are looking for, just take a little boat trip over from Edo-era Japan to Korea. Their strict caste system effectively created a society that went fundamentally unchanged for over seven hundred years. The only major upheavals were the upper echelons fighting amongst themselves, and occasional outside wars with China, Japan and the like. There was very little in the way of violent unrest by the common man, because the common man knew damn well he wasn't worthy of any better, and his life meant nothing.
The best thing is, the longer that this type of system goes on, the more the idea becomes entrenched, not just in the social psyche, but in the individual psyche. People begin to *believe* in their place in the system, and actively *defend it*, especially it the system is stable. People love stability.
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The important point is to control what gets printed. Make printing into a "Crown Service" where anyone else printing something gets executed. If you can control the information flow, then nobody else can organize resistance. Yes, you can have unorganized resistance, but organized force can almost always beat unorganized. (The few times it can't are when the mob totally overwhelms by number.)
The earliest example of what you describe that I know about is the Mycenaean Greeks who had a centralized control over most industries. The clay tablets record who had what. Essentially, those who could read and write were in the service to the palace. Those who couldn't read and write did other stuff.
Another way to spy on the population is through religious "confession". When the priesthood is "conservative" and in the service to the state, then what people say in confession can be passed up the line. This is one reason why having a state religion is so important to rulers. Think also of the level of control that the church had in the Papal States. (Also, "sermons" are a great way to communicate to those who can't or won't read.)
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There is historical precedence for this. For example, the Hasburg Monarchy in Austria established a secret police force (Geheime Staatspolizei) in the late 1780's. They monitored internal and international mail, hired/bribed domestic servants to spy on their employers, and secretly detained and tried people suspected of 'political crimes'. They also vetted all newspapers before publication and controlled/banned most foreign literature.
It may be argued that the Holy Roman Empire was not a police state, but during that time in Austria, it was a ruled by a 'despot' (the Archduke), the secret police force was long-lasting (at least from late 1790s to 1850s), and the secret police were specifically established to monitor and suppress political viewpoints that were not favourable to the Archduke - so it is a pretty good fit to the question.
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Sure, money, wealth, brutality and effective slavery can accomplish anything. How do you think the early kings managed to rule?
Those romantic Knights were paid off thugs, the armor was to protect them in battle as they slaughtered any that defied the King, refused to pay taxes, or plotted against the King.
If you don't want workers to organize, publicly burn alive any workers that even try to organize. Have them publicly drawn and quartered. Or skinned alive, screaming. When they act on your orders, make your Knights Judge, Jury and Executioner without appeal.
Same thing if you want to prevent rebellion. If anybody foments rebellion, your Knights come after them.
Offer rewards for turning in Rebels, with extreme punishments for lying.
In the meantime, do what the Romans did: Provide public rewards for being good little boys and girls. Not just for tattling on your neighbors, but (for the Romans) free entertainment, bread and beer, public baths, plenty of clean water. The (free) "Bread and Circuses" strategy works great.
A benevolent brutal king can rule for life.
People need a reason to risk their lives to rebel, organize labor, or preach a disruptive ideology. They won't rebel or organize until they just cannot stand continuing their current deprivations, poverty, and misery, and cannot stand their children suffering the same. They'd rather take the risk.
So the strategy is, offer enough on the good side so very few get to that point of deprivation, poverty and misery. They are not going hungry, or being worked every waking hour. Simultaneously, make the punishments for dissent fast, brutal and public. Strip the traitors naked and feed them to a hungry pack of wild wolves in the Colosseum.
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I’m building a world nearly equal to earth; i need a catastrophic event that make the moon start spinning breaking the tidal lock, a really slow spin, like 500 years for a full spin. i thought about a strong impact with great angle.
It will be possible while retain its orbit mostly unchanged?
Every scientific objection are welcomed
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A lunar day, equal to lunar orbital period, is ≈28 (Earth) days, adding a 1/500 yr^-1 to it corresponds to a relative change of (1/(500×365))/(1/28), which is about 150 ppm. Such a small deviation will likely be compensated by the orbital resonance attractor in the spin-orbit phase space, even given a low eccentricity of the Moon orbit. My *feeling* is that the Moon would return to the 1:1 resonance barely after 1-5 axial spins at the increased (or decreased) rotation rate. Since the Moon orbit eccentricity is very low (≈0.06), the resonant band of the spin-orbit phase space is quite narrow, and, as you likely know, separated from other resonant bands by chaotic bands. It is possible that the rotation speed will enter the a band of a chaotic regime, so that the rotation rate would not decrease smoothly back to where it were. The tidal heating will also vary then. In the final phase, the process shifts from the chaotic regime to librations of decreasing amplitude which may be protracted; surprisingly, this part is modeled by a dumped pendulum equations quite well.
The heat dissipated in the process could in principle start some volcanic activity on the Moon, and will certainly initiate outgassing in the heating rock, but I cannot speak to this, unfortunately. The excess energy, about 150 ppm relative, i.e. 1.5×10^-4 of the total rotational energy, is quite low. The largest unknown here is the *time* over which the energy dissipates. My *feeling* is the process should be quick, on the order of 10^2 to 10^3 years. Unfortunately, I'm not familiar with energy models when establishing an orbital resonance; I studied only the dynamics of it, where energy “just gets lost,” so I have no intuition how much heating this will cause, and what the heating profile over time would be.
Sorry that this is a little bit handwavy. This is rather just my thoughts about how complicated the situation is, and that its outcome may be predictable or not, depending on how far off 1:1 resonance the system will be thrown, i.e. whether it will reach the chaotic band in the phase space. The Moon will not necessarily disintegrate from a glancing blow, as @l-dutch helpfully estimated. Such a blow will impart both spin and orbital velocity change, and the exact figure will depend on the angle of impact and the mass and speed of the impactor. A head-on impact will change orbital velocity without affecting spin, which will also disturb the resonance. Any impact, central or glancing, actually will. The impact itself will also produce significant amount of heat in an instant, which should also be accounted for. An off-equator blow will also send the rotation axis tumbling, which will eventually stabilize in the presence of Sun's gravity, that also should not be discounted. Planetary dynamics is already horribly complex even when these effects are ignored. I'd turn to numeric modeling rather than trying to write and solve equations accounting for all factors; they aren't likely even solvable (welcome to the wonderful ~~under~~world of the systems of PDEs!). But an impact that throws the Moon out of resonance by just 150 ppm is not catastrophic at all for the Earth-Moon system, and things will “get back to normal” almost instantly on the astronomic timescale, although the new “normal” may end up a bit different, due to a shifted rotation axis of the Moon and a different eccentricity and, albeit very slightly, radius of its orbit.
As a wild guess, does *The Universe Sandbox* has a model of tidal resonance?
Since you have a wide literary licence, you may assume any sensible regime in the range that I tried to describe, even if rather qualitative. If you want lunar volcanism, it's possible. If you want the impact ejeca reaching the Earth, it's also possible. A recovery time of hundreds to tens of thousand years is reasonable. Finally, if you want the Moon to end up rotating on a tilted axis with precession after the event, it's not only possible but very likely. If you do not, that's also does not violate physics, just requires a more or less precise nearly-equatorial momentum transfer, which is also realistic, given the relatively low energy gain.
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The [rotational kinetic energy of the moon](https://www.wolframalpha.com/input/?i=moon%20rotational%20energy) is $3 \cdot 10^{23}$ J. In order to change the rotational speed of the moon, you will need to play with an energy of that order of magnitude.
The [gravitational binding energy of the moon](https://www.wolframalpha.com/input/?i=moon%20gravitational%20binding%20energy) is instead $1 \cdot 10^{29}$ J, which is about 1 million times higher.
Therefore you can "safely" spin up the moon by grazing its surface with asteroid impacts.
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The Moon rotates around the common Earth-Moon barycenter in a given time T1, and it *also* revolves around its own axis in a time T2.
Being tidally locked just means that T1 = T2.
And one solution to make it *not* tidally locked would be to vary T2. This would require to either brake or increase the Moon's rotation.
A different - actually, exactly opposite - approach would be to vary T1 by altering the Moon's orbit. This you can do by crashing a very large comet against the Moon, thus increasing (or decreasing) its orbital speed. The Moon's rotation would remain unchanged, and therefore would fall out of sync with the new duration of the Lunar month.
To decrease the effects of the impact on the Moon's integrity you might imagine the comet having recently broken up in, say, a close encounter with Jupiter. The impact would take place on a very large portion of the Moon's surface (a more catastrophic version of this impact is depicted in Jack DeVitt's [*Moonfall*](https://en.wikipedia.org/wiki/Moonfall_(novel)).
Even in a non-completely-catastrophic scenario (say, something like Bob Shaw's *The Ceres Solution*) you would get lots of ejecta, a considerable portion of which would certainly re-enter Earth's atmosphere, as well as very probably triggering a Kessler chain reaction.
A less catastrophic scenario would have the Moon *narrowly missed* by a much larger celestial body than a comet: large enough to "pull" the Moon outwards in its orbit. This would inevitably gravitationally influence the Earth and its orbit also, so most timebases would need to be recalibrated.
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Volcanic eruptions can [release enough energy to be comparable to](https://www.frontiersin.org/articles/10.3389/feart.2014.00010/full) the kinetic energy of the moon's motion.
Perhaps a glancing hit by a massive meteor could have ripped off the surface of this moon, and the intense tectonic response could spew enough lava into space to make the moon spin? The moon might have a glowing spot for a hundred or so years before it settled down.
Our moon isn't tectonically active, but yours could be.
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My setting includes several natural and terraformed earth-like worlds orbiting various main sequence stars, from M class dwarfs to A class giants. Humanity has independently developed from stone age to space age across each of these worlds, and though they share common ancestry and little genetic deviation from Earth humans, they have had ample time to physically adapt to their “new” environments.
My current model for physical traits across different stellar spectra is that low-mass, dim stars have pale-skinned people, while high-mass stars brighter than Sol favor dark skin. Hair and eye color is generally black or brown, although I describe many of my pale-skinned characters as having bright colored hair and eyes, in accordance to most such real-life humans. This is a pretty common interpretation in science fiction, and on the surface it makes sense.
However, after doing some research, I found that since a dimmer star’s habitable zone is closer to the star, it may receive *more* radiation than a brighter star, while at the same time providing less visible light. In the same way, a star brighter than Sol may emit less radiation at habitable distances. Does this throw off my current assumptions of stellar spectra-based skin tones? How realistic is all of it? Does hair and eye color factor into this?
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## Why Do Humans Vary?
First, let's ask why these changes happened in humans in the first place. But remember, these changes took place over thousands of years.
## Skin
We don't know for sure why human skin color varies the way it does, but leading theories have to do with UV exposure. Lighter skin colors did not encounter much UV, so developed their skin color to maximize Vitamin D creation (a somewhat unique feature of humans exposed to sunlight). Darker skin colors encountered a lot of UV, so their skin color is to maximize protection against excess UV levels.
So for skin features, decide what your UV exposure is. You're on the right track talking about your star, but also consider *where* on the planet your people might be. The poles and the equator might offer very different experiences.
## Eyes
Our best evidence right now is that lighter color eyes are connected to skin color, and did not evolve on their own. This is a great example of how one gene rarely does just one thing. Eye color may not be "optimized" at all, but connected to skin color. Decide skin color and why it is the way it is, then connect eye color to that.
## Hair
Lighter colored hair has evolved multiple times among humans and in multiple geographical locations that can't possibly be connected. Our best evidence right now is that lighter hair colors are purely ornamental, designed to give a competitive advantage in mate selection. Apparently, whenever humans have limited mating opportunities, lighter hair may evolve. Since you're in a high tech scenario, this is unlikely to be a concern, but if you are imagining some massive disaster in the past, sexual selection could do some interesting things to hair color.
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## Local Fauna Will See Differently Than We Do
While Michael already pointed out the UV theory about skin color diversity, another has to do with natural camouflage. Most animals on Earth develop natural camouflage to either hide from predators or better sneak up on prey, and there is no reason to think that humans are any different. Light skin evolved in places that would have been normally frozen over in the ice age, and dark skin in places where the world remained unfrozen.
So for skin color to experience any major pressure to change over time, your humans will need to undergo a long period of predation from local fauna where natural camo is again important. Otherwise, inner breading will just lead to a homogenized medium skin tone over time.
However, sun color may still be important in ways you do not expect. On Earth, Yellow is pretty much central in the visible light spectrum to maximize our ability to use sunlight to see, but the local fauna under a red or blue star may have a very different visible light range than we do. Overtime your humans could evolve to see deeper into the IR or UV spectrum and our skin color could also become specialized for that as well. This being the case, humans could very well start treating colors outside of the visible range of predators as either anything or nothing goes.
A classic example of this on Earth of anything goes are blackbirds. In our visible spectrum, there are many species of birds that appear black or gray, bur in a bird's visible spectrum, they are brightly colored like a parrot. Since most predators can't see their bright coloration, UV colorization became a perfect secondary trait for mate attration.
[](https://i.stack.imgur.com/9cKZy.jpg)
Or for an example of nothing goes... consider transparent cave dwelling fish that have evolved to not need pigments at all.
[](https://i.stack.imgur.com/S5Mjk.png)
A human population given enough time to evolve under a foreign sun could go either way when it next comes time to be around a good old fashioned yellow suner.
[Answer]
What is the only known species they all humans consider to be more less "people"?
*Homo sapiens*.
Where do members of the species *Homo sapiens* live?
On the planet Earth, sometimes called Terra or other names.
What star does the planet Earth, where members of the species *Homo sapiens* live, orbit?
The star called The Sun, or Sol, which is a G2V, or posibly a G0V, class main sequence star.
So what is the color of *Homo sapiens* skin, and what is the color of *Homo sapiens* hair, and what is the color of *Homo sapiens* eyes?
There is no one single color of *Homo sapiens* skin, *Homo sapiens* hair, or *Homo sapiens* eyes. Instead there are different possible ranges of colors, shades, and hues of *Homo sapiens* skin, *Homo sapiens* hair, and *Homo sapiens* eyes.
Clearly each and every actual and existing color, shade, and hue of *Homo sapiens* skin, *Homo sapiens* hair, and *Homo sapiens* eyes is a possible one in the environment where *Homo sapiens* live.
Other colors, shades, and hues of skin, hair, and eyes might or might not be possible in this environoment, but are not produced by specimens of *Homo sapiens* at this moment so we can't tell whether *Homo sapiens* specimens with those colors could survive in the present environment. Possibly they could not survive in this environment. Possivly there is simply no biological method at the present for members of the species *Homo sapiens* to produce those colors.
If planets orbiting stars of different spectral types are colonized during the future, there could be selection processes favoring various skin colors.
If a planet orbiting a star with a hotter surface temperature that produces a higher percentage of ultra violent ultrviolet radiation is colonisted by nudists, they should have a higher incidence of skin cancer and other ultraviolet induced conditions that people living on Earth. Over the generations, centuries, milllennia, tens of millenia, etc. the highter average survival rate of people with darker skin might make the population have a darker average skin color than the original colonists had.
And if a planet orbiting a star with a lower surface temperature that produces a lower percentage of ultra violent ultrviolet radiation is colonisted by nudists, they should have a lower incidence of skin cancer and other ultraviolet induced conditions that people living on Earth. Over the generations, centuries, milllennia, tens of millenia, etc. the higher average survival rate of people with darker skin would be less than on Earth. So the poplulatin would tend to retain it oribinal proportion of lighter skin tones much longer than on the high ultraviolet planet, and even much longer than a nudist colony on Earth.
And what if the colonists are not nudists, but wear clothing?
What if the colonists wear sunblock when outside, as well as broad brimmed hats and other sun protective clothing?
What if the colonists get so used to living indoors durinb the voyage that they continue to live indoors on the planet, each of their settlements consisting of a single multistoried building containing an anetire village, town, or city, and thus they can all be inside opague walls and ceilings and ultraviolet stopping windows?
What if the planet has a strong ozone layer and other atmospheric gases and airborne particles which absorb or reflect ulta violet light?
It is possible that even if the star emits a higher percentage of ultraviolet light than the Sun, the surface of the planet might possibly receive a lower percentage of ultraviolet light than the surfece of the Earth does, due to increased atmospheric blocking of ultrviolet light.
And on the other hand, even if the star emits a lower percentage of ultraviolet light than the Sun, the surface of the planet might possibly receive a higher percentage of ultraviolet light than the surfece of the Earth does, due to decreased atmospheric blocking of ultrviolet light.
I also note that a star with a specific luminosity will have an oribital distance for a planet where a palnet would receive exactly as much radiation from that star as Earth receives from the Sun. I call that the Earth Equivalent Distance or EED.
The answer by user177107 to this question:
<https://astronomy.stackexchange.com/questions/40746/how-would-the-characteristics-of-a-habitable-planet-change-with-stars-of-differe/40751#40751>
Has a table describing the properties of various types of stars. Including what I call their EED.
So if a real, hypothetical, or fictional planet orbits a star in the EED of that star the upper atmosphere of the planet will receive exactly the same total radiaiton as Earth gets from the Sun. But both the distribution of that radiation among various frequencies and the reflective and absorbing properties of every layer of the planet's atmosphere will determine how much radiation reaches the ground and the distribution of that radiation among varius frequencies.
As a general rule, more ultraviolet radiation will reach the surface of planet in the EED of a hotter star than a planet in the EED of a cooler star, if the two planets have identical atmospheres.
What happens if a planet orbits its star closer to the star than the star's EED?
The planet will receive more total radiation from its star than Earth gets from the Sun.
What happens if a planet orbits its star farther from the star than the star's EED?
The planet will receive less total radiation from its star than Earth gets from the Sun.
A planet too much closer to the star than the star's EED will get too much radiation and will be too hot for humans, and a planet even closer to its star will be too hot for any type of liquid water using life.
A planet too much farther from the star than the star's EED will get too little radiation and will be cold for humans, and a planet even farther from its star will be too cold for any type of liquid water using life.
The inner and outer limits to where planets can have the right temperatures for liquid water using life forms define its circumstellar habitable zone.
Various estimates for the inner and outer edges of the Sun's circumstellar habitable zone can be seen in the table at:
[circumstellar habitable zone](http://circumstellar%20habitable%20zone)
And they vary a lot.
A writer who plans to have only one habitable planet in the circumstellar habitable zone of a star can put it within one percent or so of the star's EED and not worry about later discoveries putting it outside the habitable zone. But if a writer wants to have two, three, or four habitable planets in a star's circumstellar habitable zone they will have to make the habitable zone a wide one, and will have to worry whether later discoveries will prove that a habitable zone can't get that wide or hold that many planetary orbits.
Anyway, it seems to me that there is a rather small probability that the skin, hair, and eye colors of human colonists on planets of other stars will change over ages of time due to the spectral types of the stars of those planets.
Of course people with different skin, hair, and eye colors might have preferences about the types of stars they would desire to settle on planets of.
I note that when people move from indoors with artificial lighting to the outside, or between indoor regions with different types of artifical lighting producing different wavelengths of light, their apparent skin, hair, and eye colors change slightly.
So even if the skin, hair, and eyes colors of colonists on a distant planet are not likely to slowly change due to the different wavelengths emitted by the star of that planet, the difference strengths of different wavelegenths to reflect will make their skin, hair, and eye color look slightly different in the light of those stars than on Earth.
And perhaps I should point out that there are restrictions on the classes of stars which can have planets that are naturally habitable for humans - and all other lifeforms which require oxygen rich atmospheres to survive.
Such restrictions became known to some scientists at least as early as the 1950s, and some science fiction writers soon learned of them.
For example, Robert A. Heinlein mentioned such restrictions in his juvenile science fiction novels *Starman Jones* (1953) and *Time for the Stars* (1956).
As far as I know, there is only one scientfic study of what is necessary for a planet to be habitable for humans specifically, instead of for liquid water using lifeforms in general. You may note that there are many lifeforms on Earth surviving and thriving in conditions where unprotected humans would swiftly die if teleported to without warning. A planet habitable for some forms of Earth type life is not necessarily habitable for humans.
This single scienftic study that I know of about what is necessary for a planet to be habitable for humans is *Habitable Planets for Man*, Stephen H. Dole, 1964.
<https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf>
And it explains the limitations on the spectral and luminosity classes of stars which can have planets habitable for humans, planets which humans would be able to settle without extensive terraforming.
So you will see there are limits to how blue or how red the light of a star can be if it has a planet which humans can colonize.
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A follow up to the previous [post](https://worldbuilding.stackexchange.com/questions/214636/breathing-on-high-oxygen-world-what-can-be-done-to-stop-humans-from-dying) question, one of the point's raised in the question was that the atmosphere that is presented has around 0.7% of it's atmosphere made up of Ammonia which is replenished through biological means.
In said post, a group of humans has been transported to a habitable super earth unspecified means and is stuck there. Fortunately, said transportation through unspecified means has also modified the humans to be able to breath in said atmosphere.
So:
**Are there any possible physiological changes to the human body that can be done in order for humans to survive in this amount of atmospheric ammonia?**
[Answer]
**Glutamine synthetase and lots of it.**
[](https://i.stack.imgur.com/j338S.gif)
<http://education.med.nyu.edu/mbm/aminoAcids/ureaCycle.shtml>
Emphasis mine. In your cells, ammonia (NH4 in the body) is detoxified by adding it to the amino acid glutamate to make glutamine. Glutamine is useful for all kinds of other things like making other amino acids. Mostly this happens in the liver.
In your engineered folks it also happens in the lungs. Huge amounts of glutamate and glutamine synthetase are in the alveolar spaces and when ammonia is absorbed it is grabbed and added to glutamine, fast. The added protein (as ammonia) can be used to make more glutamate later.
Ultimately this nitrogen excess can be handled by the liver and kidney. For your engineered folks it is the functional equivalent of eating a very high protein diet.
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Atmospheric ammonia is gonna be a less of a problem. **It is the ammonia dissolved in available water that raises question on the ability to survive a planet with 0.7% atmospheric ammonia**
[less relevant consideration deleted]
The planet is defined as habitable, so the planet does have water. Ammonia is 31% soluble in water weight by weight at 20C (increases as the temperature decrease) and 1atm - at 1.5 atm, it will be more.
To have that amount of *free* ammonia in air would mean the surface water of the planet is close to saturation. 25% w/w is way of a conservative figure.
**A quarter of the planet's surface water *by weight* is ammonia?** This spells a way much bigger trouble for human presence than the atmospheric ammonia.
At this ammonia concentration, **the pH of water on the planet will be between 11 and 12**. Not as corrosive as caustic soda, but an Earthling body left in water will probably dissolve in about a week (except the bones)
The first pure water rain (like we have on Earth) will clear the air in the area where if falls to a 0% ammonia concentration\*\*. The only way to make it rise again is to have the place where the rain falls more alkaline than pH 12. Which you'll get only by [dissolving alkaly or earth-alkaly metal hydroxides](https://www.aqion.de/site/ph-of-common-acids#bases)
As a Lewis base, the ammonium ion is a pretty good complexing agent too. Many transitional (read heavy-) metals, usually insoluble in water, will now be [present in higher concentration in planet's "water"](https://en.wikipedia.org/wiki/Metal_ammine_complex): copper, nickel, zinc, cobalt, chromium, silver, gold and the entire platinum group. Which means that any existing life on the planet will have a biochemistry alien to humans or Earth. As some examples:* silver and copper ions - germicidal for Earth microbes. Meaning any life there must've started and continued on totally different evolutionary paths
* if you have copper on the planet, say goodbye to cellulose - it dissolves in almost all tertaaminocopper solutions (I've done it myself starting from copper carbonate + ammonia solution - [Schweizer's reagent](https://en.wikipedia.org/wiki/Schweizer%27s_reagent) is more effective). The native grasses and trees in there must use another biopolymer for their structure
The tidal pools that started the life evolution on that planet may have show quite interesting colors due to copper and chromium salts.
Even if there's no life on that planet, it means the conditions there are improper to terrestrial life and agriculture. While staying indoor can keep the atmospheric ammonia within safe levels, **there's a snowflake chance in hell a Terran agriculture can be practiced on that planet - what food reserves they have available**?
Otherwise, maybe "said transportation through unspecified means has also modified the humans" so that they are adapted to a diet rich in heavy metals. Probably switched their blood oxygen transport from hemoglobin to hemocyanin.
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\*\* [First detection of ammonia (NH3) in the Asian summer monsoon upper troposphere](https://acp.copernicus.org/articles/16/14357/2016/)
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> Three-monthly, 10° longitude × 10° latitude average profiles reaching maximum mixing ratios of around 30 pptv `[parts per trillion in volume]` in this altitude range have been retrieved... On a global scale, outside the monsoon area and during different seasons, we could not detect enhanced values of NH3 above the actual detection limit of about 3–5 pptv. This upper bound helps to constrain global model simulations.
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Once produced it will quickly raise in the upper side of the atmosphere. (further research confirm
@LoganR.Kearsley note, the gases tend to be well mixed in troposphere. [Example for methane - lighter than air - in Earth's atmosphere](https://www.tandfonline.com/doi/pdf/10.3402/tellusa.v18i2-3.9677))
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Ideally animals store water in their blood or metabolize their fat reserves. I am aware of these methods but that’s not the approach I’m going for. Instead I though of an animal that secretes a slime sack which serves to store water in large quantities. The animal is closely related to amphibians like frogs and salamanders. It uses this adaptation travel on dry land in order to reach distant lakes or ponds, which would be otherwise distant for ordinary amphibians due to drying out.
**You're probably thinking “why not store water normally?”**
Cane toads have dry and warty skin that makes them less susceptible to the environment. This slime-sack adaptation however allows the animal to absorb ambient water like dew or rain during its journeys. In addition it allows the animal to store more water compared to its body size, though of course a larger sack is harder to carry. Due to gravity the sack will hang under the stomach, shielded from the sun. Thin mucus on the skin also absorbs water and transfers it to the sack via gravity.
**The mucus is similar to hagfish slime which has the desired properties.**
Hagfish slime is a protein-based, jelly-like substance emitted by hagfish as protection against predators. The slime is made up of strands that are stronger than nylon, thinner than human hair, and very flexible. Because of these unusual properties, hagfish slime is used to produce durable, environmentally-friendly fabric.
Unlike other types of mucus, however, hagfish slime doesn’t dry out.
The [mucin](https://en.wikipedia.org/wiki/Mucin) is made up of long, thread-like fibers, similar to spider silk. These strands, which are arranged in bundles called skeins, are thinner than human hair, stronger than nylon, and extremely flexible. When the skeins come into contact with seawater, the glue holding them together dissolves, allowing the slime to expand rapidly. It is said that one hagfish can fill a five-gallon bucket with slime in only a few minutes.
**Would this adaptation work? If not, why? What additional adaptations would the animal need to make use of this?**
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[Camels](https://en.wikipedia.org/wiki/Camel) store a large volume of water/fat emulsion in their humps to help them survive lean times. [Honey ants](https://en.wikipedia.org/wiki/Honeypot_ant) store high glucose water for similar reasons. Bees also store honey but do it externally in fixed structures.
So water-and-other storage is a mechanism that does exist and work in nature, the main difference in this case is that you're swapping in body storage for external storage but trying to stay mobile.
The main issue that I foresee is loses to contamination and surface adsorption as the environment your creature is travelling through sticks to its slime pouch and/or steals water from it. The strands don't dry and fragment like most sliming materials but they have to be able to dewatered to some degree or they don't make an effective storage mechanism for a creature that wants to use the water thus stored. If the sac can be reliably kept off the ground, or an outer crustal layer can be formed to protect the bulk of it's contents, then I see no reason that it couldn't be a successful strategy.
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We currently have polymers which are used to absorb and/or store large amounts of water by swelling. Think of diapers and those gel spheres used in some pots.
Polymers are made of carbon chains, so it's plausible that something similar could be evolved by an organism. The only requirement would be to be capable of sustaining several load/unload cycles with minimal or no damage, so that a dry period will not harm the bearer.
[Answer]
**Storing water as a gel is done all the time.**
[](https://i.stack.imgur.com/KpbJG.jpg)
[Pharmacological Update Properties of Aloe Vera and its Major Active Constituents](https://www.mdpi.com/1420-3049/25/6/1324/htm)
Although water storage as a gel is much more a plant thing than an animal thing. Succulent plants use long carbohydrate polymers to stay hydrated, the example above being from aloe vera which is full of a hygroscopic gel. It is not outrageous that an animal would do the same.
Why don't animals store water as mucus? It is a good question. I thought land snails probably also stored water in their mucus within the shell but I could not find that states explicitly - I think snails like other land animals store water within tissues more generally. Estivating desert frogs and toads use mucus to store water but their mucus forms an impenetrable barrier and the water is once again in the tissues of the animal.
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In [*Dragon's Egg* by Robert L. Forward](https://en.wikipedia.org/wiki/Dragon%27s_Egg), a neutron star gives birth to a unique type of life, based on "compounds" constructed of nuclei bound by the strong force.
This life evolves to sapient creatures, called "cheela". Eventually they manage to build civilization and design spacecraft.
The book states that:
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> We do not know the propulsion technique used by the cheela to lift their spacecraft off the surface of the neutron star (the escape velocity of Dragon's Egg is 39% the speed of light). ... they suspect that the cheela used some sort of antigravity catapult to get off the star
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Are there any realistic ways for take off from a neutron star?
I suppose the best way would be take advantage of the magnetic field and produce lift with the Meissner effect ora diamagnetic "sail". Of course it would be hard to make a superconductor or diamagnetic material even work in neutron star conditions...
Are there any hard science based designs that show the possibility/impossibility of space launch for the cheela?
[Answer]
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> Are there any hard science based designs that show the possibility/impossibility of space launch for the cheela?
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Given that Robert L Forward was a professional physicist who did a lot of work on things like space fountains (the method used by the Cheela to leave Egg the first time around) I'm inclined to think that the methods in the book are reasonably realistic... if reliant on some materials science that is completely beyond us. Since we're unlikely to survive anywhere close to an actual neutron star I don't imagine that we're too worried here about what humans are capable of.
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Actually, that's just the humans in the story not knowing what's going on down on the surface. The story itself goes into quite a bit of detail from the perspective of the Cheela.
There are two main technologies the Cheela use to escape from (and return to) Egg:
* Space Fountain (Dragon's Egg)
* Gravity Catapult (Starquake)
### Space Fountain
In "Dragon's Egg" the Cheela develop a space fountain composed of stabilized magnetic monopole blocks fired nearly to orbit by a magnetic accelerator. They magnetically couple to the fountain to raise a platform at a sedate pace until the reach a height limit based on their need for a high gravity field to keep their body together. From there they can make it the rest of the way into orbit relatively cheaply.
The science behind this is reasonably sound, except perhaps for the magnetic monopoles. While these are theoretically plausible we have yet to find any examples of them in the real world. The energy requirements are fairly insane, but that's just an engineering problem. A species that developed on the surface of neutron star will probably have different limits than we do, so I'm happy to cut them some slack on the little details.
Space fountains are an alternative to a space elevator, and are better suited to a neutron star. A space elevator requires a high-tensile tether material even in relatively low-gravity environments like Earth. We'd need something about on par with scrith to do the job on a neutron star.
### Gravity Catapult
In the second novel "Starquake" the space fountain is destroyed, leaving a number of Cheela stranded in space with no way to return to the surface of Egg. After several generations the space-going Cheela manage to recreate an older technology for manipulating gravity via counter-rotating charged singularity (black hole) dust. They land a small gravity catapult by throwing it at the surface and firing it downward at the right time to slow it enough to land safely, then reverse it to catch small ships. They build a larger version to launch the ships again, establishing two-way traffic between orbit and the surface.
Ignoring the material science requirements, the idea of twisting space into pretzels uses some of the more interesting ideas from general relativity. The effect of large rotating masses were predicted by general relativity, and was demonstrated when the effect turned out to perfectly explain the discrepancy in Mercury's orbit. The Cheela's gravity catapult could operate on a related set of principles. If you could make specific "shapes" in the curvature of spacetime - our best current guess as to the underlying mechanism of gravity - then it's conceivable that we could use gravity to move pretty much anything anywhere. Hell, with enough power you could open the event horizon of a black hole.
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Other ideas (as I think of them)...
### Magnetic Levitation
The magnetic levitation idea isn't impossible either, again dependent on some material science that we don't have access to here.
A big deal is made throughout both novels about the strength of the magnetic field on Egg, and its pervasive nature. It's strong enough that the locals are shaped by it, and build all of their stuff along the field lines. The field lines are 'frozen' into the star's structure, giving a nice strong and reliable field to push off.
Given that the Cheela have the ability to build things out of magnetic monopoles it could be possible to create a field rider that engages with the field lines and travels along them. If the magnetic field lines aren't too constrained you might make it high enough to reach orbit, or hopefully get close enough to make the rest of the way under power.
The downside to this idea is that a neutron star rotates *very* quickly. If the magnetic poles are aligned with the spin poles then Coriolis is going to rip you off the field shortly after you leave the vicinity of the pole. For this to work you're going to need a very specific type of neutron star where the magnetic poles are on the equator. On the plus side, you'd probably get some assistance from Eotvos forces. Still, it'd be a hell of a ride.
### Warp Drive/Exotic Matter
Alcubierre drive, as Willk suggests, is an interesting option. We'll hand-wave the exotic matter requirements. It would need to be extremely powerful to warp space sufficiently to counter the existing warpage of the gravity well itself. The energy and the sheer amount of exotic matter required to effect that sort of field would be... tremendous.
If you think about it though, there's a more direct way to do it. The Alcubierre drive requires exotic matter with negative mass. Negative mass means the force of gravity is reversed. Instead of being crushed by millions of gravities the exotic matter will be forced upwards with force proportional to its mass. This could be used directly to provide lift without all that fooling around with spacial curvature.
[Answer]
Don't try to take off straight up. Get going along the surface, performing very many orbits of the star before you finally escape its gravity well. The first few orbits will be only millimeters above the surface, and it will be necessary to smooth a track around the equator into a perfect circle so these first few orbits can happen.
A neutron star at its equator rotates at a significant fraction of the speed of light already, so that will help overcome the gravity well if the ship begins take-off in the same direction as the star is rotating. The track may be lined with electromagnets that help speed the ship while getting it off the ground, like a maglev train. Ground-based lasers along the track will help accelerate the ship further, once it is out of reach of the electromagnets, by pushing on a light sail mounted on the ship.
An alternate method - perhaps more economical, if available - to get explorers off the star would be through radio communication with aliens that are already in space. Just beam up the mind-scans of your explorers, or the plans for a machine that can manufacture members of your race, and the aliens will create your astronauts for you, already in position.
[Answer]
**Alcubierre drive.**
[Alcubierre Drive without FTL?](https://worldbuilding.stackexchange.com/questions/176134/alcubierre-drive-without-ftl)
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> The Alcubierre drive works by distorting space around a bubble:
> expanding space behind it and contracting space in front of it. It's a
> nice way to get faster-than-light travel without, well, technically
> traveling faster than light. But the basic mechanism behind it can, it
> works out, work at any speed. Nothing in the equations forbids
> sub-light speed travel... answered May 11 '20 at 16:53 HDE 226868♦
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Using an Alcubierre drive you are fake-accelerating by altering space. That means you can fake-accelerate your ship to cancel the acceleration caused by the gravity of your star. It is a great use for an Alcubierre drive and a different one from its use to effectively traverse spaces faster than light. Of course it requires negative mass but that should not be a problem for the cheela.
[Answer]
There are some designs in sequel, Starquake.
Gravity catapult
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> The workhorse of early cheela space transportation was a gravity catapult. We are not sure exactly how it works, but again the Einstein General Theory of Relativity gives us a clue. It has been shown , that the Einstein theory of gravity has a number of similarities to the Maxwell theory of electromagnetism. In electromagnetism, the basic source of all the forces is the charge on the electron. The charge generates an electric field. If you move the charge to form an electric current, the current generates a magnetic field. It is also known that if you increase or decrease a magnetic field, that changing magnetic field in turn generates an electric field.
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As it assumes some physics beyond Theory of Relativity, it is not hard science.
Also [space fountain](https://en.wikipedia.org/wiki/Space_fountain)
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I'm currently writing a far-future sci-fi novel. I have officer ranks and their equivalent positions sorted for my space force, I have decided to follow my in-universe naval rank structure for a variety of reasons.
However this all comes with the caveat that I want an alternative to 'Admiral' for my 1*-5* ranks, so as to give the space force its own identity and not have it be just another naval-carbon-copy. So any suggestions would be appreciated. Ideally I would like a name that has a space-y etymological connection or flavour, but any uncommon and sensible suggestions are appreciated!
I wouldn't normally post a general request for ideas online but I have been failing to come up with a rank on my own for months and just wish to resolve this sticky little worldbuilding issue.
EDIT: To be absolutely clear I am trying to **avoid** naval connotations in this rank. Also I should mention that I am looking for a more practical grounded military flavour, over aristocratic themes like 'Lord'. Latin is out of the running as well as I use it a fair bit already in other contexts and don't want to come off as too 40k. As for variations (such as the rear, vice or fleet variants to denote the grades of Admiralty) I already have those sorted, I am just looking for assistances with the core title word.
Thanks in advance!
-Frank
[Answer]
**Controller**
I suggest "Controller" as a throwback to the (current) days when "Ground Control" were the ones giving orders. Sure the astronauts/cosmonauts in the capsule/station have a commander, and he's in charge for split-second decisions. But in general both the day-to-day general tasks, the overall mission, and Big Problem Situation orders get relayed from/decided on by ground control. That's obviously changed, but perhaps "ground control" becomes slang for "the one calling the shots who isn't on the ship." Eventually "Ground" drops out of use, as that person may well be on the earth or a space station or even another ship. Eventually through cultural osmosis "Controller" becomes the word for anyone in charge of a group of starships.
This is very similar to how lots of other military rank titles arose in the past.
Sidenote: The actual title of the person (in the US) in charge of Ground Control is "Director" but as that's in current-use as a common civilian manager title I think it has less chance of becoming the space-navy "admiral" equivalent.
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I'd suggest variations of "Marshal" -- Grand Marshal of the Space Force (equivalent to Fleet Admiral of the Navy), Grand Marshal, Marshal, Lieutenant Marshal, and Vice Marshal, or variations thereof, should avoid any naval connotation. These are similar to the ranks used in some ground armies, going at least as far back as Napoleonic times.
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This is more of a Writing SE question, although I admit there is a valid worldbuilding aspect to it.
Do you want to completely eliminate all connections with fleets and ships, or you just don't want any titles normally associated with it? Also, is your world directly or indirectly associated with any of the known human culture?
One common approach to worldbuilding is to base your society on one (or more) existing cultures. If this is what you are doing, then it would be natural to use words that were used in those cultures, for example [Navarch](https://en.wikipedia.org/wiki/Navarch) or [Procurator](https://en.wikipedia.org/wiki/Procurator_(ancient_Rome)).
If you want to invent your ranking structure from scratch, it still needs to have connections to modern English. As others had suggested, "General" or "Marshal" titles are the first ones to come to mind, and those titles are perfectly fine if your want to model your space fleet after Army rather than Navy.
When you invent something completely new, you lose connection with modern English, there will be a lot for you to explain, and a lot for the audience to guess. You may come up with something like "[Moff](https://starwars.fandom.com/wiki/Moff)" or "[Grand Moff](https://starwars.fandom.com/wiki/Grand_Moff)", but need to understand that this would require more worldbuilding on your part.
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## The USA has an actual Millitary Branch called the Space Force with official ranks
This ranking system is more or less taken from the air force rather than the navy; so, the highest ranking officer in the actual real world Space Force is a "General".
**Specifically:**
* 1-star: Brigadier General
* 2-star: Major General
* 3-star: Lieutenant General
* 4-star: General
There is currently no official position for a 5-star General in this branch, but if thier was, it would logically be called "General of the Space Force".
<https://www.military.com/space-force/officer-ranks.html>
<https://www.military.com/space-force/enlisted-ranks.html>
French Space Command and Russian Space Forces also seem to have taken to using thier own languages equivalent to General in thier naming conventions (Général and генера́л respectively)
<https://en.wikipedia.org/wiki/Ranks_in_the_French_Air_and_Space_Force>
<https://en.wikipedia.org/wiki/Russian_Space_Forces>
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I may suggest titles like flotilla leader, squadron leader, subfleet leader, fleet leader, grand fleet leader, superfleet leader, and so on as admiral equivalents.
Or possibly substitute "commander" for "leader" in those titles and ranks.
Those titles are based on the assumption that "admiral" equivalents will command various sized groups of ships operating together in war games or actual space battles.
Of course in real life admirals are also given command of geographic regions of the ocean, and ships are transferred into and out of their command areas, and so the nuumber of ships they have command of varies over time witout changing the rank of hte admiral in charge of that region.
So possibly you might want to base your ranks on the different levels or areas where the officers command.
If it is a space opera set in interstellar space, "admiral" ranks might be based on the number of star systems where the officer commands the forces.
So the commander of spaces force assets in a singler star system might be a star commander, and the commander in ten systems might be a ten star commander, and the commander in 100 systems might be a hundred star commander, and so on.
Or the commander of forces in one star system might be a first level star commander, the commander of forces in 10 systems might be a second level star commander, the commander of forces in 100 systems might be a third level star commander, and so on.
Or maybe the commanders are given command of forces in cubical regions of space with specified dimensions and volumes, without counting the varying number of stars within them. Each cube of space would be surrounded by other cubes in a three dimensional grid.
In science fiction various regions of interstellar space are often called sectors or quadrants.
If your space realm is large enough, it could have great, ordinary, and small versions of both quadrants and sectors, and thus a total of six levels in the hierarchy of command volumes. And so "admiral" ranks could be given as sector commander, small quadrant commander, great quadrant commander, etc, arranged in the order that you put the hierarchy of command volumes.
I note that your imaginary space force could have different hierarchies of "admiral" ranks. In the late Roman Empire a *dux* was the commander of frontier defense forces permanently stationed within the region he commanded, while a *comes* was commander in or of a mobile field force stationed at a central location and sent to the sites of serious conflicts like civil wars, Persian wars, or barbarian invasions.
So a sector leader could command the fores within a star sector, a second level sector leader could command the forces within several sectors, a third level sector leader could lead the forces within several groups of sectors commandered by second level star leaders, and so on. And a first level star commander could command a group of maybe ten space battleships, a second level star commander command a group of 100 ships, a third level star commander command a group of 1,000 shps, and so on.
Or maybe a defense commander one commands defense forces in one sector, a defense commander two commands defense forces in a group of sectors, etc., while a strike commander one commands ten ships and a strike commander two commands 100 space warships, and so on.
If your space realm rules a significant proportion of the Mikly Way Galaxy, it will have a very complex civil governmeent and military command structure.
There are about one hundrd billion to four hundred billion stars in the Mikly Way Galaxy.
So if there is a decimal command structure, an officer or official with authority in one star system would have a 2nd level boss with authority in 10 systems, who would have a 3rd level boss with authority in 100 systems, who would have a 4th level boss with authority in 1,000 systems, who would have a 5th level boss with authority in 10,000 systems, who would have a 6th level boss with authority in 100,000 systems, who would have a 7th level boss with authority in 1,000,000 systems, who would have a 8th level boss with authority in 10,000,000 systems, who would have a 9th level boss with authority in 100,000,000 systems, etc.
Ruling 100,000,000 star systems would be ruling only one percent or less of the Milky Way Galaxy, and such a realm would look rather small on a map of the entire Milky Way Galaxy.
So if a space realm rules only a few thousand star systems, and has only thousands of space battleships in its fleet, it can get by with only a few ranks equivalent to admiral, like modern navies on Earth do. But if a space realm is much larger than that - and a space realm that is much larger than that could still be very tiny on a galactic scale - the space navy would have millions of space warships, and there would probably be more admiral ranks than lower officer ranks.
So it is possible that an outstanding space navy officer might start as the equivalent of an ensign and get promoted once every 4 years until becoming the lowest grade admiral equivalent after 24 years, and continue to get a promotion every 4 years in the admiral equivalent ranks, and get promoted to a 9th level admiral equivalent after 36 more years and 60 years in the service.
And yet his realm might be so tiny compared to the whole galaxy that its main strategic worry would be that some as yet undiscovered realm tens of times as powerfull might invade and conquer it with overwealming force.
It is often said that aviation went from the Wright Brothers at Kitty Hawk to the first moon landing in only 66 years. But space travel is not a branch of aviation.
Space travel went from the first liquid fuel rocket launched by Dr. Robert Goddard - with space travel the ultimate goal of his research - in 1926 to the first moon landing in 1969 in only 43 years.
So I hope that you will not make your space armed force too much like a space air force, since aviation is just as different from space flight as sea travel is.
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General, Fleet commander, High commander, Supreme command, warmaster, warleader, Battle leader, Grand battleleader, high prince. A lot depends on the structure of your military and the state for which it fights.
In light of the new edits
I recommend something like warmaster or supreme commander or high command. Some less flash more Utilitarian sounding.
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**A Few Ideas:**
* Space Lord: From the British Sea Lords. However, they operate from central hubs withing the fleet. Goes backwards in rank [ie. rank 3 is higher than rank 1.] Above all is the Lord of His/Her Majesty's Suns, the entire fleet commander [rank 5]. The rest are Space Lords [2-5]. Their rank is told by saying referencing fleets or fleet number. Example, Space Lord Joshua Andrews of the 8th and 9th fleets [rank 2] or Space Lord Kate Rose of 4 fleets [rank 4]. Would work well with any galactic empires.
* War Chief Luzmila: For when the migration of tribes into the stars. Either sedentary, on a planet, or nomadic, residing in a generation ship. They are family. A family of families. There are large families that mainly work family trades, but some become warriors who act as elites and officers during a call to arms, where the warbands move to battle stations. Warriors [5], War Chieftain [4], War Chief [3] War Leader (an elder)[2] The Patriarch or matriarch [1].
* Praetor, Governor, or Consul: The method of the roman senate, and all who wish to emulate. Perfect for fascists, Caesar's Legion, or the result of a time traveler saving Cicero and bringing him to the future.
* Feudal: The lords of vast wealth and space. They are trained from childhood, serve in the military, and, upon their ascension, lead their personal forces. The highest noble is the Fleet Commander or is given charge by the king's orders. Generally a Duke, but really any noble. Rank varies.
* High Military Commissar/High Commander: The Galactic Communist Union and the Union Chairman employ Commissars at the highest level to prevent capitalist subversives. From High Commander to Ship Commander, the Commissariat watches all.
* Commanding Executive Officer (CXO): They say war is unprofitable, I say they are sore losers. Supported by my 1nd Executive Officer down to my 5th Executive Officer (XO ranks 1-5) in the military and the members of the Chief Executive Board with various Chief Executives. And the Board and shareholders to report back to.
* The Marshall: Boats have nothing to do with space, the army created the air force. Now, we will command the Space Force. (just trade navy with army)
* Starategos: Think of independent greek city states but there planets. Freemen will only fight under renown figures such as Nikos Angelis III, the III is his senior officer rank, but all officers fight under their a Starategos from the military council. Governments: Monarchy, Oligarchy , Tyranny, Democracy.
* The Pharaoh: Overseer of the Military (1), Star Commander (2), Overseer of the Frontier Stations(3), Overseer of the Garrison Stations (4), Garrison Commander. Sometimes the Pharaoh and his guard fleet would lead their fleets. A system of Planetary Vizers and Nobles with offices managed the central state with scribes, and the priests practiced religion and provided social services. Last are soldier. The rest are commoners.
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The experiment requires 250 million people and a lifetime dedication; once in there's no way out. It consists on enclosing people in 5 artificial countries, each country with fixed rules. Each person can choose their country but once they are in, they can't get back.
The goal is to convince at least 50 million people to join each country.
The second country is:
**Law of the wild**
The basic premise of this country is that everything is permitted and legal, except leaving the country.
New people joining as citizens are given the basic tools and resources to survive and prosper for 1 year and then they are left on their own. No security is given to the citizens, they will have to make their own economy and pay their own protection with private police, guards and whatever they can make up.
People joining as new citizens can bring in the new country everything they want with them, and if they bring people they must consent too and be over the age of 18.
Oh also, this being an experimental environment, privacy does not exist, everywhere one goes there are hidden security cameras to record everything that happens.
Clarifications: Those experiments are not made to see if the systems work or not, those experiments are made to play with the human psyche and learn more about the biological behavior of people.
I also understand that societies based on disorder naturally will slowly develop in societies with laws, defeating the Anarchism theme, but we want to see it actually happens and how and not just imagine it, imagination is often wrong about scientific facts and the human mind. We also want to catalogue all the possible survival ethical system which can be developed, so many of these experiments will be repeated.
How do I get a minimum of 50 million people to voluntarily join a country where they could be killed on sight for no reason by a person they've never met?
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> If the system is not full of people that disagree with it, its not a good test of the system. - John
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But that's the point, of the experimentation, if one wanted data on good system they would simply look into history and modern times, where functioning systems already exist.
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You got it backward.
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> How do I get a minimum of 50 million people to voluntarily join a country where they could be killed on sight for no reason by a person they've never met?
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You will have problems STOPPING PEOPLE GETTING INSIDE!
Think of all the people that run from their countries for real reasons.
Then add all the conspiracy loons with a perceived grudge against their government.
Then add all the cartels. Getting cameras taped, broken, bribing operators. You have just handed them free reign over the place.
Again, your main problem is going to decide who gets in when you are overwhelmed by millions upon millions of people bribing, murdering, and extorting their way further into the line.
As an anecdote: when the project for Mars One (which wasn't viable for the $ involved) asked for people to get a one-way ticket.
They got plenty of applicants, even married people with children were eager to leave everything behind for a chance of adventure.
Let that sink in.
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The most obvious option is to appeal to those who already politically align to such a system. Anarcho communists, anarcho-capitalists, and voluntarists, for example, advocate for a system without the existence of a state. While their fundamental beliefs may vary significantly (e.g. whether wage labour and private property should exist), this country would give them a perfect blank slate to start their own communities aligned around their political beliefs. Advertising heavily to these groups would be a good start, and once you start getting traction they will likely start pushing the idea within their own communities.
The next would be people with a 'frontier' mindset- offer them the chance to start anew in an untamed area, and found their own homes. For certain people, this would be a very exciting opportunity.
Finally, appeal to those who are disillusioned with society- those stuck in a dead end job, the homeless, criminals, those heavily in debt, social outcasts etc- this country would give them a chance to start from scratch, and their past wouldn't matter. You can probably find many people desperate enough to gamble in this category.
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**You don't need to do any recruiting**
If you recruit normally terrorist and dictators will invade immediately. ThIs senario is a middle East power vacuum and everyone knows it. Therefore, we do the easiest thing.
**Drone strikes**
The north west of Africa is fairly populous and has roughly 100 million people depending on where you put the border. Draw that line and begin drone striking any leaders, law enforcement, or army in the area. Deliver aid in the form of the one year of supplies as long as people agree to the invasive surveillance. A rebellion will occur, the answer is more drone strikes. So long as you don't care about killing half of the population things will be fine. Eventually it will become clear that no laws in the country are enforceable and people will do anarchy.
**Alternative target**
Somalia is a country that had [no government for over a decade](https://www.bbc.com/news/uk-politics-42570823). Offer aid to the country in exchange for universal surveillance. Then supply the local warlords with weapons and explosives. Your experiment can then last as long as foreign nations don't attempt to fix the situation. In fact, if you don't want to supply warlords you can just wait and constantly re-chip the people and eventually you might get anarchy without doing anything.
**Wait, they do need to be new recruits**
The second the country starts various dictators will war for power using the guns they brought with them. This is a standard power vacuum and anyone who is here is here because they think they can survive that.
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Note 1: in preparation of the experiment, it may be wise to select people using two simple criteria: they have no criminal record and they don't carry fire arms. Also I would recommend seeding federalism. Split your population into 100-200 large groups. Use natural boundaries like rivers and mountain chains to allow isolation in smaller urban or larger rural provinces. After that, free traffic exists within the country and between the groups.
Note 2: we can assume political idealism will be an incentive for people to join and with your initial 50M, you'll need a lot. And also take into account, your subjects may join the experiment freely, their future children have not !
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**PARADOX #1 Acknowledment of competence is accepting authority**
At first, your subjects will have the basic means to survive, as you planned. But after a while, you have 50 million inhabitants in a closed country. To maintain autarchy, creative new ideas will be needed to let things work out. You bring modern people in. When you want them to stay alive *and* make use of their specialized talents, some acknowledgement of people's competence will be needed. That is a challenge for anarchists to accept, because that would imply these people would gain authority ! Anything enabling authority is to remain absent in anarchy ! This ideological block undermines vital activities, such as housing, education and medical science.
*Solutions*: practice over principle, council democracy, common sense, compromise
**PARADOX #2 Anarchist guru**
The main challenge will be to assure authoritarian leaders won't emerge. In the real world, the emerging of leaders has turned out to the big pitfall of any anarchist community experiment.. Political gurus will appear in the community. People listen to them. Subsequently, some wise old men will go define "proper anarchism" and impose it on others. Anarchism is actually eliminated at that point.
*Solutions*: hide the guru, ritualize collective thankfullness, keep freedom of thought
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**You'll have your volunteers in no time. Your real problem is getting the word out and convincing people that its not a hoax.**
Look at all the refugees all over the world fleeing economic collapse or war or whatever persecution you can think of.
Those people aren't necessarily thinking of the danger they're heading to, but the danger they're running from. So anarchy cant be much worse. To them anarchy is a chance to build from the ground up.
Also, think of all the people in the U.S. alone that vehemently voted one way in the last election and still cant accept the loss. If the other candidate had his own country and invited them I think they'd go.
So, as to the problem of getting the word out- a few things: (Assuming your world is Earth)
1. The internet, social media. Use that.
2. How to reach people who might not have internet? (yes they still exist, and your refugees might not) have ambassadors literally travel the world as recruiters. Maybe the U.N. would even help in that regard.
3. Get them there. Offer free plane flights there.
4. The chance to start over in a new place where you can do as you please without persecution is an awesome incentive all by itself. But add giving them a few acres scott free...? I might just go!
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**Recruitment will be a big challenge**
Global international migration (people moving to a country different from a country of their birth) in 2019 was [272 million people or 3.5% of the global population. Two thirds (2/3) are labour migrants](https://www.un.org/sites/un2.un.org/files/wmr_2020.pdf) (people who move to another country because of their jobs). The main migration patterns are related to the economy: People move from less developed countries to more developed countries. However, [most international migrants move between countries within the same region](https://www.un.org/development/desa/en/news/population/international-migrant-stock-2019.html).
Despite what other answers say, recruitment will be a challenge. People do not move to another country randomly or on a whim. They do it chiefly for 2 reasons: 1) The destination country offers *concrete* opportunities (an existing and confirmed job offer, existing support networks [family, religious, ethnic, and similar networks]); 2) It is no longer possible for them to reside in their own country due to war, famine, etc. (still most people will not move far).
Personal motivations of migrants are a complex topic outside the scope of this question. I just want to mention that there is no consensus when it comes to migrants. A lot depends on countries of origin and destination, history of migration for both countries, family situation, reasons for migration, and so on.
You also need to consider that migration is not a personal decision, but rather a household or family decision. When you recruit people for your experiment, you need to convince all people in the household, not just one person. Moreover, this is not limited to nuclear families. Extended families (grandparents, uncles and aunts, etc.) will often have a say as well, especially in cultures with traditions of filial piety.
Please also note that it is rather rare for the poorest strata of society to migrate. Poor people cannot afford to move to another country and do not have the necessary social and economic connections.
Your recruitment strategy should focus on:
* offering people security if they move (since this particular country is a lawless country where every man for himself, you should offer benefits for those who are left behind, e.g. monthly payments to the family, educational and job opportunities for children);
* recruiting 'villages' instead of individuals (you need a lot of people, so offer to move entire communities instead of people, you have to promise that you will keep them together [whether you stick to it or not is up to you, but if you don't make sure that no one knows about it]);
* use targeted advertisement strategies (hire someone like [Cambridge Analytica](https://www.wikiwand.com/en/Cambridge_Analytica) that can target small segments of the population with messages tailored to their preferences; it will also save you some money);
* paid relocation expenses (all expenses should be covered by you, this will make it possible to recruit the poorest people);
* simple procedures (all immigration procedures should be very simple, so people with low educational levels or people with low attention span are not disadvantaged; again, you need to recruit a lot of people and people do not like to move, so you cannot be choosy);
* allow families to migrate and stay together (if you limit immigration only to persons of age above 18 you will miss a lot of family men and women who refuse to leave their children behind);
* you have to be extremely careful when informing people that they are a part of the social experiment (no one likes to be a guinea pig; it is better not to tell them at all but if you must you might want to mislead them to avoid compromising your research data).
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With this said, **I seriously doubt that you will be able to find 50 million people who will voluntary move to a lawless country where they can be killed on sight for no good reason.** Self-preservation is a strong biological imperative. Most people will avoid placing themselves in situations where they can suffer harm for no reason.
What you can expect is a quick formation of law and order in your country. People will form alliances to protect themselves and establish rules. And they will start doing it even before they board whatever is used for transport.
If you try to enforce lawlessness people will band together against you. It would also not be unexpected if your country population develops hostility toward experimenters if their involvement is not limited to discreet observation (which means no cameras). You can check the history of space flights and research in isolated environments to see how relationships between crews and remote control centres can deteriorate.
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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.
Assume we developed a perfect rocket, say a ramjet using a very efficient matter to energy conversion drive, within a few centuries. How far could settlers get with such a technology? The local group? Vrigo Supercluster? Laniakea Supercluster?
Given that the universe is expanding and that one would have to slow down again to settle a region, **how far away is the farthest reachable place today**?
I'm aware that the velocity and vector of the distant objects will be quite relevant in answering whather or not a specific target can be reached. So I'm looking for a rough boundary.
Can humanity reach any of these?
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Per this source (<https://phys.org/news/2019-09-fast-universe-mystery.html>) the universe is expanding at between 70 and 90 km/s/megaparsec. With the middle value being 82.
A rocket, even a perfect one, is limited by the rocket equation: dv = ve (mo/mf)
Substitute c for ve, and dv of 0.3c has an mf / mo of 74%. Just on the acceleration. Squared to include braking 30%c requires about 96% of the craft to be fuel.
So, let’s call 30%c a practical upper-limit to rocket-based space flight.
So, anything far enough away that it’s expanding faster then 0.3c is beyond us forever, with rocket technology. Roughly 300000 x 0.3 = 82 x distance. That gives a distance of roughly 1,097 megaparsecs. 1 megaparsec = 3.2 million light years. Our reachable universe with rockets, then, is 3.2 billion light years.
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Part One of Four:
Assuming relatively realistic and probable space travel.
Assuming that humans will eventually be able to build spacecraft that can accelerate to speeds of 0.001 to 0.1 of the speed of light, and decelerate at the end of their voyages, it should take those spacecraft about 10 to 1,000 years to travel one light year.
Assuming that humans can colonize star systems without habitable worlds by building space habitats, and that the average star has several star systems with 10 light years, and a voyage of 10 light years taking 100 to 10,000 years is the maximum length, a world will colonize all the star systems with 10 light years within 100 to 10,000 years of sending the first colony ships.
Assuming that it takes 100 to 1,000 years for each colony system to become populated and adanced enough to send out colony ships of their own, a world should colonize all the stars within 10 light years within about 200 to 11,000 years after being colonized.
Thus humans would be able to spread across the galaxy at the rate of 10 light years every 200 to 11,000 years, at an average speed of 0.000909 to 0.05 times the speed of light, and thus spreading at an average rate of 0.000909 to 0.05 light years per year.
Since the farthest parts of the galactic disc are probably much less than 100,000 light years from Earth. at that rate it should take less than 2,000,000 to 110,000,110 years to colonize the entire galactic disc of the galaxy.
But it would be impossible to colonize those parts of the galactic halo where the density of stars is low enough that most stars are more than 10 light years from their nearest neighbors. Thus it would be impossible to reach most or all of the globular star clusters and most or all of the small satellite galaxies of the Milky Way Galaxy, let alone more distant galaxies in the local group like the Andromeda galaxy, let alone galaxies tens or hundreds of millions of light years away, let alone galaxies billions of light years away.
Part Two:
Assuming much faster and less probable space travel.
But if humans are able to built spaceraft which can travel much faster than 0.001 to 0.1 times the speed of light, and/or are able to build spacecraft capable of deliving human colonists to distant stars after voyages much longer than 100 to 10,000 years, humans could spread much faster and reach much more distant locations within a single voyage.
Thus humans might be able to spread from star to star even among the widely separated stars in the halo of the Milky way Galaxy, and thus reach globular clusters and even the small satellite galaxies.
Part Three:
Assuming the space travel capabilities in the original question.
And if humans develop spacecraft which can travel at almost the speed of light, so that time dilation slows down time aboard the ships to a tiny fraction of the passage of time in the outside universe, a ship could travel 100,000 or 1,000,000 light years in only a few decades of ship's time, and humans could conceivably spread from galaxy to galaxy. Thus humans could conveivablye reach every galaxy which is not so far away that it is receding faster than light, or faster than the very close approximation to the speed of light which such ships could achieve.
So humans could probable colonize every galaxy that is now no more than a few tens of billions of light years away.
Part Four:
Assuming FTL
And if it ever becomes possible to build ships with Alcubierre drive or some other form of faster than light travel, the sky will be the limit, as the saying goes.
[Answer]
Adding to what M. A. Golding and GrumpyYoungMan said, there's reasonable reason to believe that we'll never even leave *Earth*, let alone colonize space. If you're talking about exploring the entire universe we could set up a sleeper ship with a theoretical total conversion rocket and just go in any one direction, but the thing about colonizing space (as well as long-term space exploration) is you have the massive baggage of caring for squishy, organic tissue, which has to be fed, watered, and oxygenated.
Even assuming total efficiency of recycling organic matter and water from feces and urine, the problem is eventually the food will run out of stored energy because there is no external source of energy to catalyze the conversion of carbon dioxide and water to sugars. On Earth there is an external energy supply in the form of the Sun, but this may not be available in sufficient amounts, especially in deep space. You are constantly losing energy from the system due to heat output from human bodies. Most of the space travel technology we have now depends on rationed food and capturing CO2 via [artificial methods such as zeolite](https://phys.org/news/2018-11-space-station-astronaut-exhalations-earth-based.html#:%7E:text=The%20CO2%20breathed%20by%20astronauts,to%20the%20vacuum%20of%20space.&text=The%20new%20system%20works%20by%20having%20a%20series%20of%20zeolite%20adsorption%20beds.) rather than creating a true closed ecosystem.
On top of that, we are rapidly finding that most planets have some really funky geochemistry that make them untenable for colonization. Mars is often cited as difficult to colonize because it has little atmosphere and no magnetosphere. What is becoming more apparent is that [the Martian soil is actually](https://www.lpi.usra.edu/planetary_news/2020/08/24/martian-soil-may-not-support-astronaut-agriculture/) *toxic* to Earth life due to lethal levels of perchlorates, so even if one were to create a totally enclosed bubble on the Martian surface it wouldn't be possible to grow food. So one would have to bring soil from Earth as well as water and the proper atmosphere. The expenses of maintaining a Martian outpost would be astronomical.
On top of *that*, there are a number of problems with human physiology that make us very unsuited for space travel. Such as the bone loss issue, even with copious exercise astronauts frequently lose non-trivial amounts of bone mass while in space, and they never get it back. Other concerns include the negative psychological effects of long-term isolation or confinement, or what long-term exposure to radiation might do in deep space where you only have a small thickness of metal to protect you from radiation exposure. If humanity is going to travel to space, they would only do so via such copious degrees of genetic engineering that they wouldn't be *Homo sapiens* to begin with, physiologically and possibly even psychologically.
It might be possible to land humans on the Moon, Mars, or even extrasolar planets using a sleeper ship, but maintaining an active colony there would be extremely expensive, next to impossible, and provide next to no benefit to whatever society decided to send a mission. Even the whole "Noah's Ark" argument, that humanity or a group of humans should set up a colony elsewhere to avoid extinction or preservation of their culture (i.e., the Puritan argument), would be completely stymied by the fact that even planets with life would likely be incompatible with human biochemistry at best.
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I understand that your question is for today's capabilities but a ship would travel for long distances needing to repair part and upgrade along the way.
Even if a ship is limited to the knowledge and capabilities of those and the technology on the ship and limited by their slow speed of travel, information from other colonies is only limited by light speed, so they can be updated on new ways to increase their performance.
This goes against your question, so I only put this out as extra information but it is futile with our current technology to expect to reach anywhere past our local stars without major damage or wear and tear to the ship and the need to fix parts or replace parts. By that time a ship which had left 50 years after yours with more advanced technology could have caught up and passed you.
So I suggest thinking about leaving to create outposts and thinking about how the future will involve AI bodies and minds, ones that can be sent on tiny pea sized ships that can be propelled close to the speed of light, meaning those AI minds can reach at least 2 billion light years away and upon reaching the giant superclusters like Horologium-Reticulum and beyond the Great Sloan Wall they can have mechanical bodies built for those minds that have been sent.
Not the answer you were after but an option to consider when thinking about the future of human capabilities with technology and the very furthest distances in the universe that could be reached.
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[Question]
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I've begun to consider an Alternate Reality in which the natives of Australia formed a nation that spanned all of Oceania. This Australian Nation would be formed after several centuries of the kingdoms oppressing the people to the point of them overthrowing the kingdoms in which both republics and kingdoms would be formed after the overthrowing of the original kingdoms which there existed about 3 kingdoms. Australia would be split between them. All of the nations would eventually be united in a very long unification war.
One would cover all of western Australia, One would take up the northern territories and what is known as Queensland in our world including northern parts of southern Australia and the island of Papua. The third kingdom would cover the rest of Australia and the islands in Oceania. After the collapse of the three kingdoms, several nations either democratic or monarchies would be formed. All of Oceania would eventually be united by the Australian Social Republic in a century long. The time frame would be early 700s to late 1700s.
Kingdoms would be formed in the early 8th century and would last till the mid 15th century. After that several nations would be formed and a century later , a century long unification war that would last till the late 17th century would begin. After that, the Newly formed Social Republic would begin to develop both socially and technologically as well as economically when they begin expeditions in search of foreign land.
What I haven't thought about is what would drive the native tribes of Australia to form kingdoms.
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### Change in their core beliefs and values leading to large population growth.
*(And they need to be world-leading boat builders too.)*
The hundreds of Aboriginal "communities" (I was told "tribes" isn't PC) weren't all isolated. They had trade, connections, and shared identities with their neighbouring communities. These groupings among these peoples were into what was analogous to "nations". Some of their borders fit quite well with your segmentation.
Referring to a [a handy overview of the aboriginal peoples names / identidies / "how should I refer to you" guide](https://www.commonground.org.au/learn/aboriginal-or-indigenous):
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> One would cover all of western Australia,
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This is basically the Noongar peoples already.
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> One would take up the northern territories and what is known as Queensland in our world including northern parts of southern Australia and the island of Papua.
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This is basically the merging of the Melanesians, Murrie and Anangu peoples.
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> The third kingdom would cover the rest of Australia and the islands in Oceania.
>
>
>
This is the merging of the Koorie, Nunga, Palawa and all the Torres strait islanders and the rest of Oceania. This is quite a conquest, and leads to what I think is the biggest hurdle for your story:
**The sea links will need a 100,000 workers alone just to stay connected. Plus epic tech**:
Your empire include a lot of disconnected islands: Fiji, Micronesia, Kiribati, Tonga, Vanuatu, Solomon islands, all of NZ, PNG, Tasmania, Timor, Norfolk Island, KI, Christmas Island, and so many more. 10,000 islands in Oceania alone. They all are going to require basically a ferry service such they remain in constant contact with the rest of their empire. That will require many people to maintain and operate the fleets of ships needed for this.
You'll probably also need improvements in manufacturing, science, and maths in order to build reliable ships that get out into Oceania with decent safety. I've done Australia to Vanuatu on a massive modern cruise ship and it was rough and unpleasant and took days. If your tiny wooden ships are smashed to pieces by big waves, the empire is disconnected.
These improvements to science, manufacturing, maths, chemistry, etc may tax the verbal-only communication and education methods of the aboriginal people. They may need to develop a complex written language too such that this knowledge can be taught forward. Unless you want to try to picture an elder telling the young adults "the Dreaming story of that snake that raised e to the power of i \* pi".
**So - how do we build kingdoms here?**
To maintain a kingdom over these distances, you need good communication to exert control over it. The excellent shipping links need to be complimented by messengers travelling between settlements carrying stuff. You need to have allegiance sweared between cheifs and the king, you need to have taxes paid and transferred, goods transferred where they're needed, plus information like orders need to be transferred. You'll need communication networks between settlements and a hierarchy of lords / chieftains / etc all ultimate loyal to the king. This requires a lot of people to implement, especially pre-telegraph.
Roman-style roads would come in handy here, but the distances are so vast and the population so tiny its unfeasible.
The population density of Australia in this time period was low, estimates range from 318,000 to 1,000,000 over 8 million sqkm. This is very sparse. 1 person per 30sqkm. If each lord needs 2 guards, a messenger, a tax collector, and a personal servant, the settlement extends out to 180sqkm before it even includes subjects. Large towns will obviously get better scaling, but they'll be so far apart that communication will be hard.
The roman empire was about 70 million people in 4 million sqkm. Australia and all the islands you're including is about 10 million sqkm. You'll need to crank this population up by orders of magniude in order to make it possible to unify them under one kingdom. Cranking the number of people up will strip the land of food - you'll need agriculture to support such a large population.
Destroying the outback and replacing it with big farms are totally against the Australian Aboriginal cultural identity. So, to achieve what you want, you'll need to essentially replace their culture with one not focused on being close to the land.
[Answer]
**Some kind of staple food source to drive population growth**
To put it bluntly, Australia is a terrible place to try and build a civilization. Most of the country is a desert, the soil contains very little nutrients for plant growth due to a lack of mountain building and erosion except in New Guinea. The big lakes that made east-central Australia at least somewhat habitable greatly reduced in volume at the end of the last ice age.
A large, populous, at least somewhat sedentary civilization needs food to support it. There is no point in having a kingdom if there is no social need for greater organization. Every major sedentary civilization on Earth is based around some kind of staple crop. Wheat in western and central Eurasia, rice in south and eastern Asia, corn in the New World, cassava and yams in Africa. Australia doesn't really have a staple crop. Aboriginal cultures are known to have made bread out of native grains, but they never domesticated and planted them en masse like most other continents did.
Probably the closest any Australian plant came to domestication was the cycad *Macrozamia*. This cycad produces abundant seeds which can be ground into flour. Harvesting and processing of *Macrozamia* is thought to have driven the formation of some of the most populous Aboriginal cultures and most complex forms of social organization. However, the reason for this is that the zamia cycad is poisonous in its natural state, and requires extensive work and processing in order to leech the poisons out of the seeds and make it safe to eat. Unfortunately, the work-to-product ratio is a lot lower than for grains in other parts of the world (which is one reason why it's been suggested that zamia cycad usage drove Aboriginal communities to work together, it took a lot of labor to make the cycad safe to eat).
Another option is the bunya pine (*Araucaria bidwillii*), whose nuts were harvested by Aboriginal cultures for food. The cultures in these areas had a form of property rights, in which groves of bunya pines would be owned by particular families. However, bunya pines only grow east of the Great Dividing Range.
The other issue would be a lack of domesticatable animals for foodstock. If most of Australia is unsuitable for large-scale plant agriculture, the only way to support a large population would be to use its more arid spaces for ranchland. Australia has a dearth of large wildlife since its megafauna were all wiped out, and even the largest surviving Australian mammal, the red kangaroo (*Macropus rufus*) is only a fraction of the size of the largest mammal on any other continent. It's not clear how suitable kangaroos are for domestication. Other large cultures did get by without domestic animals for labor, milk, and meat, but at the same time they often had abundant wild game that were often fairly large to fall back on (and even Mesoamerica had turkeys). However, kangaroos are sensitive enough to hunting that shrinkage in the size of living kangaroo species has been documented in the archaeological record in some places due to Aboriginal hunting. This is one reason why interior Aboriginal communities practices fire-stick farming, it was a more efficient way to manage land and create an abundance of small animals to hunt, though it probably couldn't be modified to the point that it would support the kind of society that would form a kingdom. Maybe one of the big vombatiforms like *Diprotodon* or the mihirung *Genyornis* would be a better option for a domesticate (especially *Genyornis* as it is adapted to the desert and produces abundant eggs that can be used both as food and storage containers like how the Malagasy people used elephant bird eggs), but they went extinct.
Aboriginal people did domesticate the short-finned eel (*Anguilla australis*), which might make a useful start for a civilization, though it would only be possible to raise along the coast and it would make most of the interior of Australia useless for settlement by these cultures.
It's even been suggested by some Australian ecologist and biologists that Australia *cannot* sustain European-style sedentary agrarian civilization in the long term. Even today, agriculture and livestock rearing only work in Australia through copious use of technological aids such as provisioning livestock with water troughs, and the way in which crops are farmed and livestock are raised in Australia are said to exploitatively strip the land of most of its nutrients. It's been suggested that some time in the future the agricultural industry in Australia will just...collapse. A lot of the inventions that make European-style agriculture possible in Australia today probably wouldn't be the first thing to come to mind for a culture that is just starting to consider whether agriculture would be a good idea, simply because trial-and-error with agricultural practices is much less forgiving in most of Australia.
The broader issue, though, is if you don't have a good food source to feed these people, you will never get population densities high enough to require more complex forms of social administration such as kingdoms, nation-states, large confederacies of different groups, etc. There really isn't a social need for the practice's adoption otherwise.
[Answer]
Probably just a lot of time. To form a kingdom, they would need more people, and an agricultural revolution... which is itself the result of finding a way to feed more people.
This kingdom will be restricted to the few parts of Australia that are farmable.
[Answer]
If there was a big threat for all of them, that could definitely unify them, at least for long enough to defeat a monster, survive a drought, recover after a natural disaster, etc.
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[Question]
[
The zombie outbreak is contained and people survived in fortified cities and on islands and so on.
Humans who die in any way that does not destroy the brain will turn into zombies.
Rules of that is simple: 5-30 minutes until they start changing. Once they start the change they turn within a few seconds.
The biggest problem here is simple: What prevents a person from killing someone, then claiming they died and turned, then the person doing the killing were forced to kill them?
There are many many ways you can kill a person without showing signs of resistance or destroying the brain...etc.
The governments of the setting are exactly like ours.
**Can the government in anyway figure out if a person who turned and got killed did in fact die naturally or was killed and then the murdered waited for them to turn to cover it up?**
**I mean using science or any certain methods not simply investigate the case. Not a 'torture suspects until they confess' sort of solution. Like how DNA testing is scientific**
Edit: I'm not suggestion that police work is useless. I'm trying to explore other methods or at least how will the zombie factor change things. Because normal police work is not a mystery I'm not focusing on it as much.
---
## Extra fluff
I'm only interested in can it be done or not. Suggestions outside of this don't seem to fit. Suggestions of put cameras everywhere don't sit will. But I'm **not** saying don't try to provide a solution, I mean I can't stop anyone, just saying that we are trying to solve a specific problem here.
I also understand that if a person did the killing on camera it's a done deal. This is for situations where no video evidence exists and there is a distinct lack of forensic evidence...etc
*Suggestions of: "Police work" will fall apart here.*
Sure hating someone might make you a suspect if they died by your hands. But that's not concrete evidence. A couple who fights daily, does not mean that one of them will murder the other!
*If a person dies young then that makes it extra suspicious.*
True. But since we don't have an exact time and date of the death of people, again a murderer can simply claim they died naturally and turned. Death just happens.
*Pass a law to require people to report the deaths immediately.*
That's not a terrible idea. But again people can work around it. Like you wake up to your partner shaking violently in the bed. Naturally you picked your pistol and killed them before they can kill you or the kids. But a worthy idea.
Also understand that in the post outbreak cities people carry weapons and are expected to murder zombies on sight. The survival of the block and entire city is more important than anything.
So. It would be easy to exploit the system to get away with murder.
Anyway I don't want to bore people with my own ideas and suggestions here. Feel free to agree or disagree as long as it is detailed please.
[Answer]
Assuming zombies don't heal or convert the entire body's biochemistry, current biochemical-based forensics should still work, if a lab and trained people are available of course.
Some things are easy: Poison should still be detectable, signs of disease and infections as well, things that would establish a cause of death. Oxygen deprivation should also be traceable or even visible with one look at a purple-faced zombie. Most ways that a body fails and dies are accompanied by a specific cascade of biochemical processes that should leave their marks.
For all injuries, the key would be to look for signs that the injury triggered the body's fight/flight and/or healing processes. Blood coagulation, platelet accumulation at the site and possibly high adrenaline levels would indicate the person was still alive when the injury was inflicted.
Unfortunately, the time you specify for turning is still in the range where the blood might still be somewhat alive and functioning and thus coagulating. So if the person is killed, turns zombie and then immediately is cut, the blood might still coagulate as normal. After a few hours, it will not anymore and the zombie would bleed out from a cut.
If you specify that zombification also changes the blood itself, the forensics get a lot easier: The presence of *any* fresh/unaffected blood on the body or crime scene indicates injuries happened before death. That would require a law forbidding you to proactively destroy the brain of a deceased person until they turn, I suppose.
[Answer]
**Mandatory life signs monitors + normal police work**
I am going to focus on one very specific aspect of the world you propose:
>
> That means if a person dies in any form without destroying their head
> then the following will happen: Within less than half an hour they
> will start to turn.
>
>
>
Very few accidental / natural causes of death will destroy the head - the number can be rounded down to zero. This means that from the government's point of view, *every person who dies will be a dangerous zombie within 30 minutes*. This is a hideous risk that cannot be left untreated.
In such a situation and with the equivalent of today's technology, the only sensible course of action is for everyone to be required by law to wear a heart monitor with a transmitter and strobe light. To keep the civil rights people happy, the only time that the transmitter and strobe are activated is if the heart monitor indicates a flatline - Big Brother gets to know when and where you died but nothing else. (Places where civil rights are disregarded may have additional functions on the monitor, but that is not relevant to this question.) This also makes it hard to argue that you thought someone was dead - if the strobe on a persons' monitor is not going off then the person is not dead. A result of this is that any death will be investigated *very* quickly - murderers cannot hope that evidence will degrade with time.
While it is not specified in the question, if "zombies" do not have circulating blood then forensics can easily determine whether a person was alive or dead/zombie. So standard police work already has a means of telling whether the person you shot / stabbed / axed was alive when it happened - this can be determined from visual examination of blood spatter patterns alone even without using more sophisticated tests.
Finally, it should be noted that "mysterious" murders are really unlikely unless you live in a town called [Cabot Cove](https://en.wikipedia.org/wiki/Murder,_She_Wrote) or that starts with the name "[Midsomer](https://en.wikipedia.org/wiki/Midsomer_Murders)". People are even more likely to work together and have a sense of community when they are confronted by an external threat, which zombies would definitely be.
[Answer]
## Cause of Death?
It should still be possible in at least some cases to determine the original cause of death. I mean, you have the extra step of killing (ending? re-killing? whatever new hip word the kids come up with for it?) the zombie. But after that, you can still look at the wounds and make a determination of whether the wound happened pre or post death.
So if there's a mortal knife wound and the medical examiner determines it happened pre-zombie based on typical forensic evidence, then you've got a murderer on your hands. If the wound happened post-zombie, then it was clearly a non-murderous self-defense.
Same with poisons: IF they are detected in the zombie goo (blood? Is it still blood?), then it was clearly murder. But you can't really poison something post-zombie, so...
## But not always
I would argue that just like some murders today go unsolved or get chalked up as accidental deaths or suicides, the same would be true here, only more so. It wouldn't be *impossible* to tell that a murder took place. But it would be *harder.*
Some wounds would be obscured by the transformation or may be harder to determine the timelines for, since the transformation would change the zombie.
And it may take a few years for medical / forensic science to catch up with the new rules. There'd need to be new studies done. The "[Body Farm" at University of Tennessee, Knoxville](https://fac.utk.edu/) would have all kinds of new and terrifying studies to perform -- while being one of the scariest places in the country to work.
## End result
So yes. Eventually, the scientists would catch up and there'd be ways to determine the timelines and figure out if a death was murder or not. BUT there would also be all new ways for creative murderers to hide their tracks. So sort of a mixed bag. In the end, determined murderers would be wise to kill them in a way that CAN be disguised as a non-murder, but to also quickly kill the zombie. Because no one wants more zombies. Well, mostly no one. Luckily for the police, most murders are [crimes of passion](https://en.wikipedia.org/wiki/Crime_of_passion) and not planned out carefully ahead of time.
[Answer]
Forensics would be the real deterrent here. The "original" cause of death should not be so difficult to figure out.
Apart from forensics, two measures should really set the things straight: First is the requirement to report any death immediately. People in this post-apocalypse would typically live in close quarters, so just yelling "Dead!" should be enough. Second is requiring all people to wear muzzle when sleeping.
[Answer]
### If you have current forensics, you should be able to reconstruct the events from forensic evidence alone.
So many years ago, I did some work on a 3D blood spatter analysis tool for crime scene reconstruction. Our goal was the cops go into a crime scene with a laser scanner with integrated high res camera, record the entire scene in a few hours, and then clear out, and do the proper analysis later in a 3D CAD software environment over the following days. Each spot on the wall tells its own story - the spot encodes its angle of incidence, the impact speed, the victim body orientation and momentum, etc. Layers of blood spatter on spatter tell ordering of events.
If foul play happened, there will be forensic information left from the first killing. Plus assuming there is a difference between zombie blood and human blood if you find a corpse with pools of both blood types then you know there was foul play - as the dying human made one bloodstain, and the dying zombie made the other.
If your police find a zombie with a spike in its brain it may look like an open-and-shut zombie killing, but the tiny drops of high velocity impact spatter of blood on the ceiling imply that the human was shot while still alive. The areas with no blood staining indicate where perp and victim were standing. The whole scene is reconstructable.
If a scene is cleaned, even with bleach, the blood spatter marks will survive and can be bought to the surface with Luminol or similar tools.
My advice - binge watch "Forensic Files" on Netflix, there are hundreds of stories about dead bodies found in particular situations, but analysis discovers additional information including that the body was moved between first impact and death, or a person was injured and got up and struck a second time, etc.
This is not even mentioning trace evidence - eg transfer of microscopic fibres, etc.
A trained forensic expert could determine what happened from the evidence alone - just like they do in our current world.
[Answer]
## Perform a forensic autopsy
Since the question does not indicate anyway of reversing the process of 'zombification' all victims are technically 'dead' anyway. So capture, kill or otherwise contain the zombie. (Capture is of course preferable in the first instance but may not be possible in all circumstances.)
Then have a pathology team examine the corpse. Conduct hi res CT scans of the body - looking for broken bones internal damage etc, do tox screens on blood and organ samples. If the zombie has been shot do ballistic comparisons to identify any rounds *not* fired by Police. Examine the skin for signs of ligature marks on the neck or limbs. Take forensic swabs to locate any foreign substances or DNA on the skin.
And have normal evidence collection procedures going on at the same time.'Crime' scene photographs, witness statements, alabis and background checks on the victim etc etc
In short **nothing changes** just because the person 'turns' *after* death. It's the stuff that happens to him/her BEFORE they died that's important. So do all the stuff that is normally done with any suspicious death and see what comes out in the wash.
[Answer]
You can't kill dead person. Neither you can kill a zombie. You can "deactivate" it.
To save dead person from turning you need to decapicate them. This is EXACTLY the moment "police work" comes into play. You don't have to tie dead body down to cut it's head (and even if the marks look different).
Also excuse of "I removed the head because they died" still don't answer the question "how they died?". But it asnwer some type of them. If the person died of natural case there is no need for it to have a 47 stabbing wounds. If the person fall from window the place where the body lies is kinda secondary to "how and why they were near the window".
>
> But again people can work around it. Like you wake up to your partner shaking violently in the bed. Naturally you picked your pistol and killed them before they can kill you or the kids.
>
>
>
Again - how they died? They need to die somehow. Doing something with the body with the excuse of "unzombiefying" it still leave you with very narrow options to do so. You would claim they had some type of brain cancer that you removed with the bullet so there is no trace of that cancer? That's easy to prove as typical cance markers in blood.
There is also thing in "police work" that is called "people have hard time believing their loved ones died". Which we knows because people held vigils next to bodies until they started to smell to be sure they are really dead. So "they were electrocuted when changing light bulb and first thing you've done was to guillotine them?" question would be asked with handcuffs on your hands.
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[Question]
[
So I did the numbers using atomic rocket's page on worldbuilding and it appears my super-earth would retain the helium gas in its atmosphere from its early formation. What effects would this have on life and the planet itself? I don't know how much helium it would have either I am not sure what percentage of its atmosphere should be helium. I hope this is enough information. Am I correct that it would even still be a super earth and not a mini neptune? For further information the gravity of the planet is 1.75 times Earth's gravity, and its mass is 5.59 Earth masses and its radius is 1.79 that of Earth's. Its atmospheric pressure according to Artifexian's spreadsheet on planetary atmospheres is 1.7 atm.
[Answer]
**It depends on what effects you are looking for**. In terms of breathability, there would be none per se. That is to say that whether the atmosphere has helium in it or not is not important for oxygen metabolizing lifeforms. In fact, SCUBA divers frequently use a helium/oxygen mix called heliox for deep dives, because Nitrogen is a dangerously narcotic beyond certain pressures and helium is not (well...it's complicated, but for our purposes helium extends the depth you can dive at. That's not to say that it's 100% safe all the way to the bottom of the ocean). So if there is oxygen at an appropriate partial pressure, then oxygen breathing lifeforms are OK.
As the comments stated, helium is SUPER non-reactive, so as a gas in the atmosphere it is also unlikely to harm anything.
The real question is: what is the helium replacing, if anything. This will affect your atmosphere. One particularly important metric of an atmosphere is called the scale-height. A simplistic approximation to it is:
$$H = \frac{kT}{mg}$$
where $k$ is the Boltzmann Constant, T is the average atmospheric temperature, m is the average mass of an atmospheric molecule, and g is the acceleration due to gravity on the planet.
The scale height dictates how quickly your atmospheric pressure drops off, so a larger scale height means a slower drop-off.
If your atmosphere replaces Nitrogen with Helium, say, then the average mass of the molecules in the atmosphere will be lower, and your scale height would be higher. This has several practical consequences:
1. Mountains are more easily climbable **from the perspective of air pressure only**. Your larger planet likely has smaller mountains, but they'd be harder to climb because you are heavier
2. It would be harder to reach orbit - all else being equal, an atmosphere with a larger scale height would extend further beyond the surface of the planet and therefore you'd need to go higher to get into orbit. This is especially harder for your planet, since it is also bigger and more massive than Earth, so you'd have a big problem with space travel
3. Aircraft would be easier to fly at low speeds, but harder to fly at high speeds. At low speeds it is the density of the atmosphere that matters, while at high speeds it is the air drag that matters. You'd need to go higher to get away from the atmosphere, but at low speeds you'd have an advantage. This means that it would be easier to fly in the higher gravity, but harder to go fast.
[Answer]
You have to redesign most electronics. Crystal oscillators change frequency in the presence of helium. (Exposure to a helium leak will kill your cell phone for some hours because of this.)
[Answer]
# Helium is quite inert, but it penetrates *everything*.
For example, your civilization will never have functional vacuum tube technology, as the helium will leak in. Ditto for cathode ray tubes.
This presents a serious obstacle in early electronic work. With no vacuum tubes, no CRT displays, early electronics, tv, radio, radar, x-ray generation *and* detection, are all greatly hampered. There are likely ways to work around that, but we have no idea how as the "Easy" pathway via vacuum tubes was available to us.
Then they develop semiconductor technology. And THAT also acts erratically. The smaller you make the junctions, the *more* the helium affects them. Resonant crystals change frequency, resistors change resistance. Airgap capacitors behave erratically.
<https://www.phonearena.com/news/Helium-exposure-can-prevent-your-iPhone-from-working-right_id110568>
There will be no such thing as utterly pure gases or liquids.
Example: If you make a sealed glass container of 100.000% of Oxygen-17, then a few days later it will be a 99.95% Oxygen-17 contaminated with 0.05% helium! A few years later, the contamination will match the Helium gas percentage in the atmosphere.
<https://pubs.acs.org/doi/abs/10.1021/ed006p108>
And then there are biological effects: If you put an ordinary Earth creature in a high helium concentration, then the helium enters into the cells and wreak (small scale) havoc in there.
<https://pubs.asahq.org/anesthesiology/article/112/6/1503/10306/Cellular-Effects-of-Helium-in-Different-Organs>
Helium can also penetrate molten & semimolten metals during working, resulting in microbubbles in the material. This is almost never a problem for us, but who knows if the helium abundance is, say, 5%?
Most of these adverse effects only appear because organisms and devices from a non-helium environment are getting exposed to a high-helium environment. It will almost certainly not be a problem for native people and devices.
[Answer]
It'd be hard to light a fire on such a planet. Light gases (He and H2) are very good heat conductors. The difference is very noticeable already at lower contents.
Windchill might become problematic depending on your scenario.
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