text stringlengths 22 2.11M |
|---|
[Question]
[
I want to create a world that abides completely by our understanding of reality. The whole premise is that "If the Universe is large enough, this would all be non-fiction", assuming the laws of physics are constant everywhere. It absolutely must be 100% scrutiny-proof.
Firstly, the planet is designed to be a sort of superficial "Parallel Earth". However, the actual workings of the planet and its species can be adapted as needed. The planet will have large amounts of gigantism (pun intended). The planet will include human-like natives; [ray](https://en.wikipedia.org/wiki/Manta_ray)-like whales that are 60-80m long; 'Sauropods' on par with the largest [titanosaurs](https://en.wikipedia.org/wiki/Titanosaur). But the most limiting factor is having theropod-like dragons (technically [wyverns](https://en.wikipedia.org/wiki/Wyvern)), preferably upwards of 10m in length.
I've plugged some numbers into various calculations and I've settled on the following properties:
```
Surface Area: 602,000,000km2 (18% larger than Earth)
Radius: 6.923.5km (8.5% larger than Earth)
Mass: 3.524*10^24kg (41% less than Earth I *think*)
Volume: 1,390,160,000,000km3 (28% larger than Earth)
Gravity: 4.9m/s/s (Half of Earth)
Density: 2.83g/cm3 (54% less than Earth)
```
With the atmospheric density 6x higher than Earth (around 7.2kg/m3) this gives an 850kg limit of flight if the 70kg [Argentavis](https://en.wikipedia.org/wiki/Argentavis) is used as a maximum, or a 2400kg if the [Quetzalcoatlus](https://en.wikipedia.org/wiki/Quetzalcoatlus) is used as a limit. I originally had it at 3x Earth's.
Would these figures yield a stable planet?
Would the mass of the planet have a large enough magnetic field to hold such an atmosphere? Could I increase the atmospheric density to 12x Earths or higher? What sort of atmospheric composition would it need? How would I achieve a planet with the right conditions and parameters if this isn't stable?
The larger surface area allows more room for life (and thus giant life), whilst having larger oceans to support a denser atmosphere. A higher level of volcanic activity would also be included.
I did intend for it to be a binary planet as well, but all these kinds of things can be changed.
[Answer]
If you're hoping for the answer to be "definitely" you're out of luck, but I might be able to give you "possibly."
The planet you propose is going to have some issues, so I'll outline those immediately.
* First of all, out current model for planetary formation indicates that the closer a planet lies to its parent star, the denser that planet will become. Based on local extrapolation, this would put your planet outside the orbit of Mars, which is outside the habitable zone (for *our* sun). That's not a good sign for the development of complex life.
* Your planet also requires *more* atmosphere and *less* gravity. This is somewhat counterintuitive at first glance. Both Mars and the Earth demonstrate that a small planetary body will likely have a small atmosphere, while many other bodies of smaller size have *no* atmosphere.
* Lastly, you'll need a magnetic field around the planet to protect from ionizing radiation, and to reduce atmospheric loss from solar winds. At the proposed density, your planet will be slightly denser than Pluto. This is too light to expect there to be a metallic core with which to generate this magnetic field. That's a problem.
So is there a way to overcome these issues? Possibly.
* Addressing the habitability issue, either your planet's orbit could have moved closer inward toward the sun, placing it in the habitable zone, the star is big enough that it warms the planet even at its increased radius, or the planet's atmosphere is dense enough that a paltry amount of sunlight could keep things warm. Probably some combination of the first and third solutions would make this planet more habitable and be fairly reasonable.
* As for the atmosphere/gravity issue, there are examples of small gravity wells retaining massive atmospheres. Venus is a good example, though it is somewhat strange in its own right, and the moon Titan is another. Both of these bodies demonstrate that a large atmosphere *can* exist around a small planet, so this is plausible for your planet, and perhaps even likely depending on who you ask (though be aware that in both examples the atmosphere is "super-rotating," blowing around the entire planet at hundreds of miles per hour, like a planet sized hurricane. Definitely cool. Definitely dangerous.).
* Lastly, the magnetic field. This is tough. Venus herself has a small magnetic field generated by interactions between the high atmosphere plasma and the solar winds, but this would not be enough to protect most life forms we know. On the other hand, this *would* be enough to protect against atmospheric loss from solar winds, so that's exciting. There is also the possibility of a lightweight metal core, composed of something like magnesium perhaps, that could provide a magnetic dynamo while still retaining a low density. This is pure theory, and current models of the universe suggest it is highly unlikely, but that is not the same as impossible.
So, could this planet exist? Maybe. Does it exist? Probably not. On the other hand, the chances of Earth developing just like it did were also quite low, yet here we are wasting our time on Stack Exchange when we should be working. I'd call that a win.
[Answer]
This [link is a good primer](http://cseligman.com/text/planets/atmospherestructure.htm) on how atmospheric density relates to other planetary factors. In particular, you propose a planet that has **less gravity** than Earth and **greater air density**.
Given that less gravity will reduce air density, all else held equal, because the gas will be held less closely to the surface, you have to have a compensating factor: either the gas must be much heavier (and thus easier for the gravity to act on), or the atmosphere must be a lot hotter with a lot more gas (akin to Venus). Venus has an atmospheric density around 80x Earths, so this doesn't seem entirely outside the realm of reason - but the gasses would be heavier, and therefore probably toxic as far as life-on-Earth would be concerned.
It is of note that even in this situation, your very massive creatures would probably tend towards lower elevations, where the density is likely to be higher.
The most unlikely thing is a planet less dense than Earth by a massive amount. I'm not entirely sure how to run the numbers, but such a planet is liable to be almost hollow if it has a larger solid surface, or be made up of elements that are a lot lighter than Earth's crust and core are composed of. Whether those elements could support complex life is unclear (you need a lot of heavier elements, such as Iron, for life).
As a side note, I don't believe that, for purposes of air density, the electromagnetic field has a great deal of import. It probably shields some gas leakage, but it won't act as an impermeable membrane.
[Answer]
Planet magnetic field is the result of the internal structure of planet and rotation of that internal structure or planet.
As you concerned with numbers, there is no way prove or disprove planet magnetic field existence in your case, with provided numbers and description. We may only speculate that planet is not dense enough and probably there will be not much iron and so on, but that is not necessarily true.
Magnetic field prevents heating upper layers of atmosphere with charged ions, and that prevents particles from upper layers have escape velocity, and that leads to less atmosphere leaking.
Density, as pressure, depends more on a total mass of the atmosphere. Earth had a more dense atmosphere (as science believe), Venus has 92 times bigger atmosphere pressure and $5.243 kg/m^3$ density. The same mass atmosphere and earth's recipe (N2+O2 mix) and earth temperature and venus pressure and the resulting atmosphere will be 92 times denser ($\approx 127 kg/m^3$). (not CO2, because it will be partially liquid and atmosphere will have less pressure)
If you do not take H2 as the main part of the atmosphere, a composition is irrelevant, kinda, only mass is important. Although there not so much gasses to choose from.
This way you may set your pressure as you like, and density according to your preferences of composition and temperature for that pressure.
Composition any, but if you will take earth like it will be a safe choice, but keep in mind that CO2 will condense at 53 bar pressure at 293K temperature (room temperature). So 53 bar is sort of upper limit for that temperature, because of plants etc. But if the temperature is higher than 304K, pressure is unlimited. If you wish to have winters then something like 30bar and below. Take look at [CO2 vapor pressure](https://en.wikipedia.org/wiki/Carbon_dioxide_(data_page)#Liquid.2Fvapor_equilibrium_thermodynamic_data)
As stability is the concern, Venus has weak magnetic field and atmosphere do not fly away. The main problem is hydrogen because it is the lightest and evaporation of other gasses is slower, significantly, but even in not stable cases "evaporation" is constant for a planet, so more you have initially for longer it lasts. And for our current understanding (at least my) as life was born in water, more water is better, there are some problems, especially where oxygen will go(when hydrogen will fly away) and bunch of other problems, but even if magnetic field isn't strong enough, more water initially may help, and even not strong field protects to some extent, that means lucky combination is possible. It may also explain higher pressure, but pure oxygen isn't safe, so assume there was a lot of water and lot of NH3 this will explain earth mix, and also it correlates with fact that planet is light, so probably it was formed from lighter fraction, especially in earlier stages of the universe.
Also one of the possible sources of water for earth maybe was [Asteroids](http://www.space.com/27969-earth-water-from-asteroids-not-comets.html) or [Origin of water on Earth](https://en.wikipedia.org/wiki/Origin_of_water_on_Earth#Extraplanetary_sources)
So, how much water in each particular case planet gets, depends on processes of forming this particular system and some luck, this means you may scientifically accurate, as our today's knowledge goes, set arbitrary initial amounts of water on a particular planet.
*The larger surface area allows more room for life*
Earth is large enough, to support any biological possible large creature, and it was a time when she supported it.
Short speaking 6bar pressure is not a problem, for your planet.
[Answer]
You ask a lot of separate questions, I'm just answering on the magnetic field.
The Earth has a large magnetic field because it's rotating molten iron core acts as a dynamo generating electric and magnetic fields due to the rotation.
The overall density of your planet means it would most likely not have significant amounts of iron or other heavier elements, so it would most likely lack a magnetic field unless it had some other mechanism to generate one.
[Answer]
I may point out that Titan, the big moon of Saturn, has less than have the surface gravity or escape velocity of Earth, and yet it has a denser atmosphere.
Of course the factors that enabled Titan to acquire and keep its atmosphere would probably not work if that atmosphere needs to have a chemical composition and temperature similar to Earth's atmosphere.
Similarly Venus has a slightly lesser surface gravity and escape velocity than Earth and has a many times denser atmosphere - again with a highly different composition and temperature.
] |
[Question]
[
In the Mass Effect series there's a terrestrial planet called [Dekuuna](http://masseffect.wikia.com/wiki/Dekuuna) with 10 times the mass of Earth, a surface gravity of 4G and a native intelligent race. I was just wondering if it was possible for a planet like that to exist in reality, and if yes, what are some factors that might lead to its formation assuming it formed around a Sun like star?
[Answer]
If $R$ is the planet's radius and $\rho$ is the planet's average density, then its surface gravity is $\propto \rho R$ and its mass is $\propto \rho R^3$.
Let's measure in units where the Earth's radius and average density are both 1. Then for Dekuuna we have $\rho R=4$ and $\rho R^3=10$. Therefore we get
\begin{align}
R &= \sqrt{\frac{\rho R^3}{\rho R}} = \sqrt{\frac{10}{4}} \approx 1.6\\
\rho &= \sqrt{\frac{(\rho R)^3}{\rho R^3}} = \sqrt{\frac{64}{10}} \approx 2.5
\end{align}
So that planet would have a radius of about 1.6 times the Earth's radius and an average density of about 2.5 times the Earth's average density. The radius is definitely possible, and I think the density should be, too. To begin with, the higher radius and mass would already cause an increased density, although that alone will not get a factor 2.5. But then, the planet could have a relatively bigger core, and it might have more heavy elements in its core.
I also think 4 times earth gravity should not preclude the evolution of intelligent life.
[Answer]
I'm going to work off of [celtschk's excellent answer](https://worldbuilding.stackexchange.com/a/44925/627), which correctly comes up with a radius of $\sim1.6 R\_{\oplus}$ and a density of $\sim2.5\rho\_{\oplus}$, where $\_{\oplus}$ denotes Earth. If we look at the mass-radius curves of [Mocquet et al. (2014)](http://rsta.royalsocietypublishing.org/content/372/2014/20130164), we see that the planet lies very close to the line for pure [iron planets](https://en.wikipedia.org/wiki/Iron_planet):
Some fun facts about iron planets:
* They're essentially just cores of terrestrial planets.
* They likely cannot hold water.
* They have no tectonic activity or magnetic field.
* They may be close to their parent star, meaning surface temperatures will be extremely high.
This doesn't seem like a very pleasant place for life.
[Answer]
The earlier answers have done this better, but I found a mass/gravity/distance-from-center calculator at <http://www.ajdesigner.com/phpgravity/gravity_acceleration_equation_planet_mass.php#ajscroll> and ran some rough numbers through it. After a little trial and error, it looks as though a planet 10x as massive as Earth would have as surface gravity of 4G if its radius was approximately 10,106 km. That would make it about 2.55 (again, rough math) times as dense as Earth, at about 13.85 grams per cubic centimeter. That falls between the elements Americium (13.67 g/cc) and Berkelium (14.78 g/cc). Both of those are radioactive with relatively short half-lives - not sure if they degrade into something just as dense?
My guess is that such a planet couldn't exist in reality, unless it was created and maintained by some highly tech-advanced race. Even so, I would think that the probable radioactivity of the thing would preclude the existence of intelligent life as we know it.
] |
[Question]
[
In this fantasy world several corporate empires have found a valued liquid coming from wells in shallow ocean. With only Industrial Revolution level tech is it possible for these companies to harvest the liquid off of oil rigs or similar structures?
Note:
* The companies have near unlimited resources and vast amounts of manpower.
* The liquid has all the same properties as oil for this question's purposes.
[Answer]
Yes
The way that's done is by using [Caissons](https://en.wikipedia.org/wiki/Caisson_%28engineering%29). A caisson is a structure dropped into the water, and then air under high pressure forces the water out of it. This allows workers to enter the structure and work on the water's floor. In your case, they'd build a caisson, drill the well, put in the piping, and let it flood back up. So as long as the water is shallow enough that the building materials of the day can withstand the pressure, it should pass a reality check.
Read up about how the Brooklyn Bridge was built in the late 1800's. Caissons were dropped into the East River to build the foundation. Its also where they identified the cause of a mysterious illness that afflicted workers called Caissons disease... or as we now refer to it, the Bends.
[Answer]
Depends on how you define "industrial revolution" tech levels. There is a world of difference between 1760 and 1840.
There were [iron-hulled boats before 1800](http://www.gracesguide.co.uk/John_Wilkinson), but they were not very large and not very rugged. Ships with wooden hulls and iron or [iron-reinforced](https://en.wikipedia.org/wiki/Robert_Seppings) hulls were more common, but the wooden hulls still worked under stress. [Diving dress](https://en.wikipedia.org/wiki/Standard_diving_dress#Early_history) became practical at the end of the industrial revolution. That might mean ...
* A fixed platform would be difficult unless it can be built on wooden beams.
* A floating semi-submersible platform is out, too.
* A drill ship or a similar surface platform would run into problems with maintenance after a short time.
[Answer]
I will say probably but you would want to make your world with shallow seas to put them in. Some diving technology existed in the 1800's and a little bit in the late 1700's (mostly experimental) if I recall correctly. One way you might do this and still have your oil a little deeper is put your planet in an ice age and tie up a lot of your water at the poles in ice caps. Your industrial age technology could be something newly developed by a society living along the tropics or subtropics or it could be the refinements of previously built technology created by a society that Crashed due to the start of the ice age. (edit-spelling)
[Answer]
Not likely, depends on how deep it is, can water be frozen in winter etc.
Even if some works may be done, the problem is a complex set of technologies and many technologies's involved should be mature enough for that.
10 meters - not a big deal, 100 or above and everything isn't so simple.
You just may check it in today word: who builds and can build offshore platforms.
Also try to look some films about offshore wind plants, siemens short video about that [this](https://www.youtube.com/watch?v=zUQifpcGTrg) there also more and longer more informative videos about problems involved. Even today it's not so easy.
The offshore platform will face a similar set of problems.
So it's not possible just because of lack of knowledge in first place. If you freeze your revolution maybe, not for sure, but maybe after 100th years of work ... Dig tunnel - simple tech, needs just the time.
Windmills and accumulators will be a better solution.
] |
[Question]
[
In the distant future, a multinational corporation has become more powerful than any government. To deal with individual enemies of the corporation, the company created the enforcer line which specializes in robot->human combat.
The enforcers pack a variety of weapons and gadgets but the most terrifying of all is the DNA-EYE. As people live, breath, move, and interact with their environment they release skin cells, hair, and other cells. The DNA-EYE is acutely aware of human cells and will use X-ray scattering to identify the gene sequence of the human who left the cells behind. Thus it can connect the cells to the person who left them as a unique identifier. The cells left behind last in the environment for some time and so the DNA-EYE gives the enforcers the ability to track targets for long periods before eventually catching them and dealing with them. It only needs a single cell for identification.
My questions are:
Would this be a viable method of tracking? Do we release enough skin cells often enough that the robot can simply follow the DNA trails?
How long does the DNA remain viable after it has separated from the human body? Does it depend on what type of cells the DNA is in?
What might someone do to prevent being tracked this way? Would covering yourself from head to heel in cloths be enough to cover your tracks? I think an astronaut suit would probably suffice to hold in your DNA, but what else could be done? If you use one of those showering stones to remove dead skin would that stop the shedding?
[Answer]
X-ray scattering likely wouldn't be the best way to do this. [X-ray crystallography](https://en.wikipedia.org/wiki/X-ray_crystallography) hasn't been used for DNA since [Rosalind Franklin](https://en.wikipedia.org/wiki/Rosalind_Franklin#Contribution_to_the_model_of_DNA) used it to further the identification of the structure of DNA.
What I would consider a more plausible scenario would be what [this guy](http://wonderopolis.org/wonder/what-makes-bloodhounds-good-detectives/) does on a daily basis:
[](https://i.stack.imgur.com/FVSFF.jpg "K-9 Odor Detecting Unit")
Bloodhounds are incredible at tracking down people due to their finely tuned sense of smell. They are routinely used in tracking criminals and intruders. In fact, we're currently [working hard](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3274093/) to develop machines that are as sophisticated as a dog's nose, and probably more so, if we can manage it.
Because a human's (any animal's) [body odor](https://en.wikipedia.org/wiki/Body_odor#Causes) is largely caused by [apocrine sweat glands](https://en.wikipedia.org/wiki/Apocrine_sweat_gland), and sweat glands are a biological organ based in DNA, body odor can be extrapolated to be derived largely from DNA. (I don't presume to know how, and I can't find anyone who has done that particular bit of research.)
If we make this one assumption, then we could theorize that a person's body odor could be artificially determined to within a reasonable degree using near-future technology and his/her [DNA profile](https://en.wikipedia.org/wiki/DNA_profiling) to allow a machine to identify and track the odor.
From there, it's a pretty simple task to track down a person. Bonus is, it's nearly impossible to defeat this method of tracking, as the [Mythbusters](http://www.discovery.com/tv-shows/mythbusters/mythbusters-database/beat-bloodhound/) found out time and again.
---
Alternatively, provided some advancements in technology, your machines could use some form of real-time DNA analysis, kind of like what [Biomeme, Inc.](http://www.biomeme.com/) is working on for your smartphone right now.
[Answer]
We release enough skin cells to easily be tracked. However, your method of identification will run into the opposite problem: it will be overwhelmed.
You can't rely much on "fast" methods like X-ray crystallography. [99.5% of the human genome is shared by every human.](https://en.wikipedia.org/wiki/Human_genetic_variation) This means that 99.5% of the signal you are looking for will be everywhere, and only 0.5% will actually be useful fingerprinting content. It gets even worse when you look at the kind of DNA we can test. For [fingerprinting](https://en.wikipedia.org/wiki/DNA_profiling) purposes, we are 99.9% identical! Also, that 0.5% is decidedly not unique. It's a mismash of alleles that are quite shared. What is unique is your exact mismash. If you grabbbed a dozen people and tried to sequence all of them in one big puddle, you'd find that they have most, if not all of the DNA markers you have. The unique part is that you have all of them. This means pretty much your only solution is to actually sequence the DNA on the spot. This is time consuming. There's literally thousands of false trails, each of which takes time to process.
The solution may be to have a distributed approach. Instead of having one enforcer that does everything, have an enforcer with a swarm of nanobots, each of which is capable of gene sequencing. The nanobots follow the swirling trails and report back the most promising leads.
[Answer]
The only problem with this premise is that *distant futuristic* technology cannot be reliably predicted. We can expect with high hopes that dna sequencing techniques would not only become cheaper with time, but the process would also consume lesser time. So ***theoretically*** it should be possible in the distant future.
One thing you can expect more reliably to occur in the distant future is that it would become easier and easier to scratch some cells from a living creature's (including humans) body without being noticed by the person's sensory system. For a start, chemicals present in [blue ringed octopus](https://en.wikipedia.org/wiki/Blue-ringed_octopus) are estimated to be 100 *times* more powerful than morphine in their pain killer properties. This is one of the reasons why a blue ringed octopus bite is rarely noticed by the victim.
The point is that if your robots combine [cyborg insect drones](http://edition.cnn.com/2015/01/14/tech/mci-drone-robohawk-robofly/) laced with blue-ringed octopus' pain killers, they can easily obtain genetic material **directly** from their targets, and nobody the wiser.
Note that the method mentioned in this answer is **theoretical** based on what we know today and what would *probably* be achieved in the coming decade or so.
# Defense
It may be possible to evade being genetically traced this way by covering oneself from head to toe, but would it really be worth it? Would it be a practical solution? Probably not.
If the target uses a washroom, your cyborg bots can get in the utility and obtain some fecal matter which contains cells from the person's intestines and skin. Also, as mentioned above, the cyborgs can always bite the target without being noticed and obtain genetic material directly.
One possible solution could be to use minimum range [electromagnetic pulse weapons](https://en.wikipedia.org/wiki/Electromagnetic_pulse) to neutralize the cyborg insects and possibly also jam the main robot (dna-eye).
[Answer]
Possibly yes, but not the way you describe it.
The human genome has about three billion base pairs. DNA identification techniques do not compare all of them, they just look for [specific sections](https://en.wikipedia.org/wiki/Second_Generation_Multiplex_Plus) of DNA and declare a *sufficiently probable* match if they do match. X-Ray scattering doesn't sound like a good way to get this data.
Assume that [lab on a chip](https://en.wikipedia.org/wiki/Lab-on-a-chip) technology becomes advanced enough to do a DNA match and equip your robots with those. The robot would use this to confirm a match that had been made with other, less precise sensors like optical recognition.
Just imagine. A DNA-EYE moves close to a human, swipes a sample, and says "sorry ma'am, you look like someone I'm looking for."
[Answer]
To answer your specific questions, yes humans are constantly shedding DNA which could in theory be tracked like a scent. Once the DNA has been shed it will last quite a long time. DNA is very stable molecule and is only rapidly degraded in the presence of specific enzymes. Outside I imagine the majority of DNA will still be informative even days or weeks after it is left. It really just depends on whether some other living thing comes along and degrades it.
With regards to your technology as a whole, instead of using X-ray scattering I would recommend a technology that will hopefully soon be available, the [nanopore](https://nanoporetech.com/applications/dna-nanopore-sequencing). A robot with millions of these DNA reading nanopores could potentially develop a real time sense of what organisms were around it and either by coordinating between multiple sensors in different places or by moving itself around it could get a sense of direction of a specific individual.
I think the main problem with the technology, and this goes for the x-ray scattering, the nanopore, or any other sequencing technology, is just how much other DNA is out there. Every living organism including animals, plants, bacteria, and even some viruses has DNA. This means a random sample of the air, really anywhere other than a clean room, is going to have a lot of DNA in it. Your robot is going to have to sequence a lot of dust, pollen, bacteria, and viruses to actually get a thorough sampling of the DNA in its vicinity. Even if your fugitive was scratching themselves vigorously as they fled only a small fraction of the DNA your robot sequences will be human, let alone belonging to your target. So you need to be able to sequence DNA really, really fast.
[Answer]
"What might someone do to prevent being tracked this way?"
One method some science fiction stories <https://en.wikipedia.org/wiki/For_the_Win> have mentioned is instead of trying to avoid being tracked, avoid having your specific DNA from being identified in the first place. When committing a crime, don't worry about your cells littering the scene, but instead gather dust from the subway and sprinkle thousands of other people's DNA all over. "the robot tracker brought us 2000 suspects. Put them all in the lineup and see if any of them look like the perp".
] |
[Question]
[
How would it be possible to have a planet with two defining surface features, ocean and mountains? Such a planet would have to be habitable for humans who arrive there, though it does not need to support humans evolving and developing over time. Everything above sea level has to be mountains, with valleys mixed in.
If it helps, think of the book series Riverworld. Except I'm not really getting into any rivers or anything, and I'm allowing oceans.
Oceans can have underwater plains, but I don't want the oceans taking up more than 80% of all surface area. I also don't want a planet covered by clouds of volcanic ash. This planet's geography must also be natural, with no terraforming.
[Answer]
We have the topography we do largely because of erosion rates, size of plates, and transportation rates. **To generate a "rougher" planet you need to dial down erosion rates, dial down size of plates, or dial up transportation.** (Or any combination of the three.)
**1. Erosion rates** depend largely on overall chemical composition and on hydrology. Briefly, to generate lower erosion rates you want your rocks to be more mafic (containing heavier elements) and less felsic (containing lighter elements). This is a matter of the composition of and position in the planetary disc that formed your system, so you'll want your planet to have developed in a region around its star a little closer than ours1.
As for hydrology, you want a little less vigorous of a water cycle than ours. You could make the planet contain significantly less water: say, 20% coverage rather than 80% coverage. Alternatively, you could have the same coverage but slow down the water cycle by slowing down evaporation. (This can be done either by cooling the planet or by slowing down its rotational rate2.)
**2. Plasticity of plates** and other factors will determine how large your tectonic plates are. You might think it unfortunate that all of the factors in (1) that make your rocks harder and less prone to erosion also make your plates harder, but realize that makes plates more brittle, too. To break them up into generally-smaller fragments we just need to make sure the planet's getting kneaded vigorously: ditch any thoughts of a moon and give yourself a true binary planet system.
**3. Transportation** of plates arises from convection cells in the mantle, so we want to make sure those cells are more vigorous. Unfortunately, the chemical factors in (1) that make rocks harder also make magma more less viscous, so we've got to invigorate convection cells in another way. We can either crank up the (core) heat or spin up the differential rotation rates between core and crust. Luckily, if we're creating a planet closer to its parent than we are, then it was likely created in a region of the planetary disc more prone to energetic vortices, and it's not unreasonable for it to have a fast-spinning core. Couple that with a slow binary partner and we can imagine a slow crust and fast core creating vigorous--and relatively small--convection cells. Perhaps that'll lead to smaller tectonic plates.3
**In summary**, you've got chemical composition, water coverage, surface temperature, surface rotation rate, size of orbital partner, core rotation rate, core temperature which will all impact eventual geomorphology. I hope above to have explained enough of how each works and how they might interact that you can make your choices.
There may be many more things I'm not thinking of or even aware of. Happy hunting!
---
**Notes:**
1: The relative abundance of heavy/light elements vary as one approaches the central star in a planetary disc the same way the relative abundance of heavy/light gases varies with altitude. And it only takes a difference of a few % silicon abundance to radically change rocks' properties!
2: slowing down the rotation will diminish prevailing wind bands, but will increase thermal differentials at the terminator. Effectively, your trade winds and polar/equatorial easterlies will die off (less evaporation), but pre-dawn and dusk sea-breeze and shore-breeze will get stronger (more evaporation). Since I've got no idea which would effect evaporation more, I suggest you stay with our rotation and push on some of the other levers.
3: Unfortunately, you've probably just done big things to your magnetic field: your planet has a larger metal (core) due to its original abundance-profile, and it's spinning faster. YMMV.4
4: "Your Magnetism May Vary"
[Answer]
You can simply have a planet where the water level did raise at one point in history and only mountain chains are above the water level, noone limits the amount of mountains there could be in a world. And while mountains can be created by movement, volcanoes can also create rather decent mountains so one could think the planet was completely submerged in the past and eventually eruptions created the existing mountains, this could be volcanoes not active anymore so no ash clouds, volcanic ground is also very fertile.
As for the agriculture there’s plenty of examples of terrace cultivation in our world, be it for crops needing a lot of water like rice or not. In the Andes Incas used the system a lot
[Answer]
Having a warmer world will help as well on top of the other suggestions, glaciers and freezing/thawing cycles are both major factors in "flattening" terrain and speeding up erosion. So you are looking for a highly tectonically active world with a lot of volcanoes and plates constantly hitting each other combined with a lack of ice and snow to increase erosion.
One interesting idea would be to have the planet actually be a moon in orbit around a gas giant and subject to a lot of tidal forces. The constant tidal forces squeezing and stretching at the planet would inject heat that keeps the crust thin and the volcanos active.
[Answer]
Mountains are created by upraising processes under the crust. We get mountains due to plate tectonics near the edges but not in the middle of continents.
You need to have processes that apply *everywhere*. Maybe smaller plates, or more mantle plumes.
] |
[Question]
[
The human race is spread through the inner Solar System.
Technological and scientific progression is thriving, but we still haven't developed FTL travel, research has its focus on developing a device similar to a dyson sphere.
So, travelling from planet to planet is a safe journey, but it's still a long one.
Artificial intelligence is very developed, and robots almost have unique personalities, but humans still have a work life and most work related machines are relatively archaic.
The Moon is colonized, and so is Mars, and Venus has a number of floating colonies in its atmosphere. Mining colonies exist in the moons of Mars, and many more in several asteroids.
Colonizing the outer Solar System is still a challenge; resources and distance are the two important factors to overcome.
I'm interested in hearing what you think: what is a "realistic" year for this to take place?
[Answer]
A pessimistic answer? I would argue that it's **never**.
The [Drake Equation](https://en.wikipedia.org/wiki/Drake_equation) describes the number of extraterrestrial civilisations that we expect to detect by radio communications.
$$
N = R\_{\ast} \cdot f\_p \cdot n\_e \cdot f\_{\ell} \cdot f\_i \cdot f\_c \cdot L $$
N is equal to the mathematical product of
(i) the average rate of star formation, $R\_\*$, in our galaxy,
(ii) the fraction of formed stars, $f\_p$, that have planets,
(iii) the average number of planets per star that has planets, $n\_e$, that can potentially support life,
(iv) the fraction of those planets, $f\_l$, that actually develop life,
(v) the fraction of planets bearing life on which intelligent, civilized life, $f\_i$, has developed,
(vi) the fraction of these civilizations that have developed communications, $f\_c$, i.e., technologies that release detectable signs into space, and
(vii) the length of time, $L$, over which such civilizations release detectable signals.
The fact that we have never observed any other civilisation transmitting into space implies that the expected value of $N$ is under one. Assuming spacefaring capabilities exist and it is possible for civilisations to spread across planets, we should have been visited by aliens already. This is known as the [Fermi paradox](https://en.wikipedia.org/wiki/Fermi_paradox).
Considering that a civilisation that manages to get off a planet and manages to not destroy itself before should manage to transmit significant amounts of information into space (and therefore be detected) as well as physically visiting most of the planets within known space, one explanation for the reason nobody has ever received an alien transmission is that **all civilisations destroy themselves** before managing to spread to new planets.
This is a pessimistic but plausible way to resolve the paradox.
[Answer]
From a technical perspective, this could have been done a long time ago. "Das Marsprojekt" was a fictional vision of a Martian voyage written in the early 1950's based on the technical and astrophysical knowledge of the time, written by Wernher von Braun. The visuals in the movie "2001: A Space Odyssey" were based on a relatively straightforward extrapolation of the 1960 era space program. Even today the ISS could be considered a long duration spacecraft that is missing an engine.
What is actually missing is the economic justification for colonizing space. While there are compelling non economic reasons to go (escaping from persecution and settling new worlds to carry out your social, cultural or religious ideals are well known motivators), even the Mayflower pilgrims were sailing on a commercial vessel (and the design was refined over centuries to allow for long distance commerce). Without commercial motivation, building the vessels and refining the designs to create cost effective transports isn't going to happen.
Unfortunately, while there are resources in space, there is a sort of chicken and egg effect. It is cheaper to gather water from an asteroid to refuel your ship, but unless you are planing to travel to an asteroid, there is no justification to develop asteroid mining to gather water to refuel your ship. And if your ship is the only one (like an Apollo mission), then the costs associated with mining and water extraction make no sense at all. Other Mcguffinite solutions like 3He (Helium 3) for fusion reactors only works if you have working aneutronic fusion reactors to fuel, and extracting hydrocarbons from Titan for export to Earth makes no sense at all from any economic or energetic point of view.
So unless there is some sort of economic justification to going to space on a regular basis to develop reliable spacecraft and drive costs down to the point where it becomes practical and economical to send people to colonize places (and to allow other people to piggyback on them to experiment with religious, social or economic systems, or to found business to do the service and support of the colony business, then the founding date will be a long way off. Since there is no way to determine what the McGuffinite will be or when it will be discovered, you could set an arbitrary date. On the other hand, since there are multiple reasons to go *once it becomes practical to do so*, and we do have a reservoir of technology to build from, settlement will be fairly rapid once it can get started.
[Answer]
Pessimism was never my strong suit.
I think we will be colonizing Earth orbit with permanent stations and multiple daily shuttles running within the next century. From there, I think the many tentacles of human ambition will reach out into our solar system simultaneously. Settlement/bases on our moon and Mars will come first, but asteroid mining and planet-free colonies will happen in about the same time-span.
Greed is a powerful motivator. So let's see humans spreading out across everything this side of Jupiter within three hundred years.
It will be rough out there, and will make all previous human exploits seem tame by comparison. We will forget about the Wild West of our past and teach our children about the present Wild Expanse instead. Life above the atmosphere will be where the action is, and fortunes born in that darkness will dwarf the sum of all earth-bound enterprises.
Permanent colonies on the planets you've listed will take a little time, but deep colonization will follow the money. Venus will probably turn out to be a fuel producer, mining the ammonia rich atmosphere for volatile compounds and energizing batteries from abundant solar power. Mars might be a food producer, farming the surface in domed structures and easily boosting the produce into orbit for sale across the expanse. The environmental-freedom and resulting low cost to orbit will also make Mars a manufacturing and population center, where products can been produced and space-faring workers can get a little ground-time. The asteroids will of course provide water and metals, providing the most direct path to personal-wealth that humanity has ever known. As with historic pioneer efforts, the planets and other solar system locations will be colonized in the order that serve the economic interests of the colonists, and each new colony will take advantage of some attribute of its chosen location.
Somewhere between five hundred and a thousand fifteen hundred years from now, the solar system should look something like what you are describing.
That is not very pessimistic, as I don't foresee all the horses tripping during this single race. Certainly some countries will falter as we leap to space, but the beauty of living in a multi-national and multi-corporate world is that other powers will take up the slack whenever a front-runner stumbles. There is too much treasure waiting at the finish line to think that we will ever, collectively, give up the race.
---
Edited after reading several of the newer answers.
## Boy, you guys are better at pessimism than I am!
@Thucydides has made a strong argument to the effect that the economic prosperity that I see in space, is going to be economically unfeasible due to the high start up costs and the idea that we don't really need the wealth of the solar system until we go out into the solar system. I'm not sure that that is true, but I will add a little incentive to get us over that hurdle...
Let's imagine that the global warming supporters are right and we see dramatic climatic change over the next century. Is it unreasonable to believe that humanity, finally respecting the fragile planet which sustains it, might choose to move all of polluting power-production and manufacturing into space? In order to restore our planet to proper function, we either need to give up all our planet-harming practices, or find another place to practice them.
Space and the nearby planets are that place.
---
## Many thanks to @MikeScott for helping me fix some errors in my original answer.
[Answer]
We've got 3 major hurdles to clear, technology-wise.
**Radiation Shielding**
This is currently the big issue being talked about for future manned space missions. A lot of ideas are being thrown around, but no one has a totally great option yet. With slow travel of months to years in space, that's a lot of rads you could be soaking up. Maybe if we're lucky with all the push in material sciences, we might find some kind of nano material or something that works really well at radiation shielding without being too heavy.
**Self-sustaining life support**
Those months and years of travel without resupply means food, water, and oxygen are problems to deal with. Our attempts to create enclosed ecosystems have rarely lasted more than a few months before failing. I'm distantly optimistic we'll have a better shot at this with genetically modifying plants. (Since, we're probably going to have to do a lot of that for Earth anyway, in the next 100 years between topsoil depletion, desertification, rising water levels, and carbon reduction...)
**Cheap Lift**
The biggest hurdle is escaping gravity. We need to be able to get enough stuff up in space that can allow us to get to anything else, in order to farm those resources. The problem is that it's expensive in terms of money, manpower, and material resources.
We either need to find a way to synthetically make rocket fuel, cheaply, or find some physics-changing way to get to space. It needs to be cheap enough, and we need to have the whole launching process down, to where we can just do multiple launches one right after another, to get enough tonnage of gear, ships, people, resources, etc. up into space to start going other places.
**Best guess?**
So... assuming we manage to maintain our tech levels and not fall back under ecological collapse (which...is honestly optimistic given both scientists and military projections...), let's say 100 years to GET the science and the infrastructure to start getting up into space consistently with enough gear. We could get a moon base much sooner, but it will probably hold the same position that the ISS does now - good for research, but still needing a lot of regular re-supplies and not anywhere near self sufficient.
Maybe another 200-300 years to really colonize multiple other planets? Part of the problem is that collectively we're more likely to focus on working on one planet / space resource at a time. Each environment has such different problems to tackle, and it's easier to keep building on the lessons learned than to try to go take on completely new problems.
Colonizing space is absolutely NOT like colonizing other parts of Earth - instead of moving to a new land, or a continent, it's like digging a mine shaft and trying to live in it. You don't have food, running out of air is an issue, and the only things which you can get are valuable but don't necessarily keep you alive. (yes, we could mine ice, which gives us water, and we can crack it for oxygen and hydrogen, but how far are we gonna go for that? It also doesn't give you arable soil...)
Realistically, though, I'm guessing the next 200 years of human life are going to get really rough as our food and water ecosystems fall out of kilter and non-sustainable resources that push much of our technology run out. Ecologists predict this. The scientists working for big oil predict this. The scientists working for the US military predict this. That's going to put a massive crimp in us doing pretty much anything else when basic needs start to fail.
[Answer]
Pessimistic answer: never. We crash our civilisation and Earth's ecology with global warming triggering a permafrost melt and methane driven positive feedback loop. Optimist says some humans will survive. Pessimist says they never regain C20 technology because of resource depletion the first time around.
Greater optimism involves a technological singularity. Canned primates in space won't work. Robots containing intelligences derived from uploaded human beings might. They don't need to breathe and solar panels work better away from a wet oxidising atmosphere. Alternatively humans migrate into virtual realities in computer substrates in solar orbits.
Put any timescale you like on that. As Della Lu says, the only way to understand a singularity is to create one and live through it.
] |
[Question]
[
I have just invented the Macguffin. It is ultimate wondrous power for anyone who is wise enough to wield it...
But humanity isn't ready for it yet. I need to put it out of reach for a significant amount of time, such that it cannot be recovered 'soon' - but that it should be recoverable at some point.
To facilitate its recovery, I am going to write some prophecies - that a chosen one will discover, interpret and know when the 'vault' will open.
But ... how does my vault work?
I'm aiming for a significant amount of time out of reach (beyond my lifetime). And that I can reasonably accurately prophecy its return. It needs to cope with ... well, the worst that humanity might do. So I can't use anything simple like a clock, because I'm worried it might not survive.
It can be something periodic, or a one off event. If the latter, ideally it'll be such that it can be found at any point someone decodes the prophecy (but ideally not find it by accident). If periodic, ideally it'll be fairly easy to 'unlock' if you know you should, but also hard to do accidentally.
Assume a substantial amount of resources (anything that's at least theoretically possible using real world physics), but avoiding supernatural.
Aiming for something like the clock of ages in Tomb Raider, where a certain planetary alignment is needed - specifically trying to work out how my macguffin ends up as a plot device in a future story after I'm dead.
[Answer]
Maybe you could have it placed in a space probe and launch it. Have it programed to slingshot off some distant planet then come back and crash into an insignificant location where only someone who knew it was coming could find it. I know it does not meet at lot of your criteria, but inventing something that will be able to take anything men can throw at it is pretty limiting. If we can make it, we can break it. You going to have to get it out of reach somehow.
[Answer]
You can hide it in a buoyant sealed sphere on the ocean floor. There is a thin chance of accidental discovery, but not much of it. The prophecy should contain coordinates.
Additionally you could attach ballast using radioactive bolts which will slowly decay into nothingness. With carefully picked material strength, half-life, and decay product required lifetime can be achieved.
**EDIT** It looks like making the bolts themselves of radioactive material is tricky and hard to control. Much better to use a non-corroding, non-deforming material (something like SiC? ) to 3d-print hollow bolts, and fill cavities with isotope of choice (or its compound). It should decay into something less dense, or release gas. Say ElementF2 decaying into OthrerelementF + F. As time passes, pressure would build up within cavity, finally surpassing outside pressure (which would be 300 to 1000 atmospheres) and ripping the bolt apart.
This approach requires more research than I'm capable of doing. Still it has the advantage of having no moving parts or electronics that may fail.
[Answer]
Asimov's Foundation books used something akin to ancestor worship/guardianship to have a group of people protect their prophecy machine and vault in an out of the way locale. If the guardians also know the particulars of how to maintain the vault and the parameters for the "chosen one" they would be a good interface for the protagonist.
] |
[Question]
[
On an Earth-like planet, with the technological and cultural level of ancient Rome: **What kind of terrain would be statistically best suited for a powerful city to be located?**.
The most important aspects of this city are, in order: religion, economy and military. Below are some of the things I would like to see in my city;
* The city would be the religious center of a massive empire around the
size of Russia.
* It would need to have natural defenses while at the same time
allowing for easy trade.
* Their closest neighboring city is around 27 miles away, Their closest
enemy is in the closest enemy state around 130 miles away.
[All Culturally Correct Questions](https://worldbuilding.meta.stackexchange.com/questions/3960/culturally-correct-series/3961#3961)
[Answer]
There are too many factors in the development of a city for a definitive answer, but there are some common terrain elements to keep in mind.
One of the most important features of powerful cities is good transport - navigable water has been especially important for cities to develop. The ease of trade boosts economic growth, allows a wider range of resources to be available at a practical cost, provides a robust means of supply in case of siege (unless besieged by a superior naval power), a means of disposing of sewage (an often overlooked issue), etc.
A river delta is not a wise choice due to flooding and erosion issues - some slightly elevated terrain next to a major river is probably best. Obviously these are just general trends, as everything has an exception (Venice built in otherwise unwanted marshlands on a lagoon comes to mind).
Being surrounded by fertile farmland and good fishing grounds to feed the city certainly helps (and provides a valuable export in bountiful years). Being reliant upon others to sell you basic food staples on a continuous basis is a precarious position.
Strategic resources give you a significant advantage. Once you have a wealthy enough city with good trade routes, anything can be imported, but having your own local sources gives you security in your supply and spares you the cost of importing it. These tend to be found in diverse terrains, and both availability and value very much depends on what resources your neighbors have as well.
The weather has a strong influence on a city - being buried under snow in the winter or roasting in the summer (or even both) saps a lot of productive capacity. Being prone to storms inhibits trade, flooding or mudslides destroy infrastructure, etc.
Bottom line - pick any terrain you want as examples can be found for just about any situation you can imagine. The important questions are how well do the people innovate and leverage what they do have to their advantage? How do they position themselves in regard to their neighbors and international relations? People are the true wealth and the power of a city.
[Answer]
You need water to drink and food to eat, enough to support a large population. Water can come for aqueducts not too far. The food can come for the plains nearby or it can be imported form other regions of the realm or or from other countries if you can afford it.
In any case, large cities have a large flow of traffic of all sort of goods. It's vital for the city. Some of it will come by roads but it's easier to move stuff with boats. Access to an important river is significant. It can be inland but it's a plus when it's near the sea as the city will be a trading hub with far away places. Actually, the city need trade but it's trading that makes cities grow. Merchants from far away won't come to small villages, they will go in the big market.
The city does not have to be located on a plain. It just need access to food and water. During the Tang dynasty, the city of Xi'an could not support herself with her surroundings (it's too dry) and relied on imports from Southern China. The presence of the imperial court attracted many people and demanded a lot of resources that the city had no need for before that. The city was already an important trade hub between the plains of China and Central Asia. When it became an imperial city it just made it bigger but it was not created from thin air. So, even if your city can import food, it must be possible to have a city there to grow without import in the first place.
[Answer]
Cross roads are always the best places, especially defensible cross roads.
On or near rivers to keep fresh water flowing through the city, and trade routes passing crossing that river.
You need water, food (so nearby plains that can produce lots of food is good, but being on a good trade route can help mitigate that quite a bit), and a reason for people to want to be/go there. Trade routes are where people will travel, usually those with goods to sell or trade. Several routes might converge in one spot, this will make it a destination vs. a stopping spot. It can reduce the traveling distance by half when the traders from opposite locations show up to exchange goods.
[Answer]
If you research them, the major cities almost always are along a river. It's actually considered one of the more reliable terrain features for a large city, because large quantities of water are essential.
As for coming to power, the most important thing of coming to power is not the city, but its ability to leverage the particular weaknesses of nearby groups. Accordingly, there's no way to tell what features are needed without understanding exactly the best way to leverage nearby cities. You can become an illustrious city just by being well placed, but being powerful involves not just being well placed as a city, but being placed in a position to control that which others need.
[Answer]
*Although this medieval, I will put it in contemporary Urban Planning terminology, as many successful medieval cities were successful on less-than-perfect locations, but this is to define the 'sweet spot' for your story.* And I'm an Urban Planner. I'd love to address what's inside your city as well (civic and community facilities distribution, etc.), but that's for a different question, isn't it?
**Transportation & Communication**
Critical to the growth of a successful city is a collection of meaninful connections, in this case most likely easily-traveled roadways. Which means, while you may have a mountain backdrop for protection or scenery, you should have pathways to allow transporation, trade, and commerce to access your city: so a mountain pass, a land-bridge (if you're an island) or scattered oases (if you are in the desert), a river if you're inland. Being central and accessible puts you as the pinnacle of trade and boosts your city.
**Water Distribution**
Access to clean, plentiful water is a necessity, not just for food, but for water distribution. A fast-flowing, non-seasonal (you don't want floods) river can run through or adjacent to your city. It provides nominal protection, some food, and hygiene. If you insist on a desert city, consider [qanats](https://en.wikipedia.org/wiki/Qanat) from nearby mountains.
**Wastewater and Stormwater Management**
Integral to the success of a city is a place to dispose of wastewater and sewerage; most likely this would be your river mentioned before. For stormwater, place your city at a higher elevation, with a gentle slope to the river or sea. You'll notice in any older city (London, Rome, Kaifeng, etc.) that when you're in the old-town areas, you can find your way to the river by just walking downhill.
**Civic Resources**
This is internal to your city, so not directly part of your question, but it addresses your city's location. There's a well-accepted understanding that a major city has a theoretical (not literal) radial arrangement with the smaller settlements. This is called Central Place Theory. You want to be the big city, so distribute the medium and smaller ones along this theory (not literally) around your city.
[radial], [centers of academia and governance], [well distributed comm facs]
**Regional Resources**
This may be the most important. Your city should have access to farmland (down-river to receive the urban sewerage and so as not to put livestock waste through the city) and hunting areas (up-river, as the goods are sent by raft down-river to town). Almost any geographical feature, from swampland to mountains to water features can support the town and be used for protection from outside threat. *Just ensure you have access through these harsher areas for trade*.
Happy mapping!
] |
[Question]
[
There are a number of humanoid creatures in fantasy that we more or less take for granted. Humans are almost a necessity for us to be able to relate to the story and they interact with dwarves, elves, goblins, orcs, and a plethora of other exotic humanoids. One thing often lacking in fantasy stories is how these creatures grow from infancy to adulthood.
Elves suffer the most from this lack, but it exists for most of them. Many humanoid species encountered in fantasy tales live far longer than humans. Elves are often described as living for 300, 700, 10,000 years, or even indefinitely.
Immortal elves are clearly magical, but it also raises an interesting question: How long does it take a fantasy humanoid to reach adulthood? Should this be measured as a certain fraction of their life expectancy, or is there some physical, mundane explanation for why a species achieves a (relatively) early adulthood and ceases to age until late in life?
[Answer]
I'm a fan of mundane reasons, and of calling elves and dwarves "fantasy species" or "fantasy hominids" instead of "races." Here are several mundane reasons for similar growth and maturation rates across your fantasy hominids:
# Historic Hominid Growth Rates
Very [clever researchers](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0118118) have examined the growth rates of ancient hominids. They've found that there are growth rates for hominids are all over the place! Some of them grew just as fast as modern humans, whereas others grew faster or slower. Another [paper](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2409099/) claims no correlation between body size and growth rates. The growth rates of certain variables do seem to be shared between certain species, but nothing so simple as "a creature can expect 30% of their life to be spent as a youngster."
It seems that Bonobos, Orangutans, and Chimpanzees are [giving birth for the first time](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2409099/table/tbl2/) at around 14 years old, at have a maximum age around 55. (Compared to the human hunter-gatherers, who can give birth at around 19, and live to be 85.) Given the number of related species who have their first children around the same time, the second paper mentioned concludes that the ancestral hominid likely reached sexual maturity around age 13 to 15. If your fantasy world assumes some sort of evolutionary connection between humans and other fantasy races, this baseline of sexual maturity around 14 should be kept. Obviously, this extended pubescent period found in humans could be carried over to these fantasy hominids.
# Factors of Growth Rates
There do seem to be some common factors which help determine growth rates:
* Food: the type of food and how much was available seems to determine how quickly a species can grow. The more calories you get from your food, the more you can put into growing, surviving, and rearing offspring.
* Total Body Mass: The more massive a creature is, it seems it takes longer to get that massive, given a similar diet compared to another creature. It also indicates that the babies of more massive specimen are more healthy, simply because the larger animal can expend more resources on their child.
# The [Grandmother](http://en.wikipedia.org/wiki/Grandmother_hypothesis) and [Patriarch](http://en.wikipedia.org/wiki/Patriarch_hypothesis) Hypothesis (And Another)
So why would a species want to mature quickly, and then go ahead and have a long time spent as an adult? Kin Assistance is an answer here. The idea is that longer lived, possibly infertile, adults can provide assistance to those younger than them. This assistance can guarantee their offsprings' survival, making it a good evolutionary strategy.
Alternatively, older individuals can have some better advantage in the make-babies race of evolution, so it benefits to be a *physiologically* older individual than not. This means that those who grow up fast can get to make more babies, resulting in babies which grow up fast, so they can make more babies. You see this in lobsters, but this idea is part of the core of the Patriarch Hypothesis, so you can see this in hominids.
Another answer can be found in the idea that babies are a resources drain. If two species are in competition, and the main difference between them is maturation rate, the species who matures more quickly can defend and out compete the other. The slower-maturing species would be spending resources on their babies while the other is doing other things, possibly with *more capable adults*. This is not quite the same as the Patriarch or Grandmother Hypothesis, but it *is* a good reason why dwarves and elves should grow up about as fast as humans. This is *especially* true when fantasy hominids compete for resources.
[Answer]
If we define adulthood as the period when a creature reaches sexual maturity, then adulthood in humanoid fantasy creatures can be estimated upon at least two different factors.
1. Humans have a prolonged childhood due to the size, complexity and and energy consumption of the developing brain. Because the brain takes so much energy, less of it is left for the rest of the body. A more intelligent species, or species with magical abilities on top of regular human like cognitive processes will have a longer childhood as their brains use up more resources to develop.
2. Which means their bodies- at least that of the females- will take a longer time to develop, and to reach sexual maturity, because she has to be large enough to carry a baby to term.
So... I assume elves would spend the most time in childhood, and certain species of Orc, the least.
Edit: Also, females of most species tend to mature a few years ahead of the males. This could be due to infanticide rates -males of the same species killing off babies and then taking the mother as their mate- so the sexually mature male also needs to be large enough to fend off his mate and child.
So... Male maturation rates would depend on other factors -are the women equally warlike as the men? Do non blood related males form strong friendships?
[Answer]
In Tolkein's mythos, the Elves were created whole and awakened during the Age of the Stars, so issues like birth and ageing seem to have been bypassed. (Tolkein grew his mythos over many decades, so there are various inconsistencies to the stories). Since Orcs are Elves who were twisted and mutilated by Melkor, there should also be a large but finite number of Orcs in Arda as well.
While this does not directly answer your question, it shows there is a range of possibilities that can be explored within a fantasy world.
] |
[Question]
[
Given a planet without any relationship to Earth, what does it mean for the poles to be "north" or "south"? Is it something arbitrary that can be changed?
[Answer]
**tl;dr** - North will be whichever pole is oriented most closely to Earth's north pole.
If the planet is "without any relationship to Earth" as in not in this universe, then it's completely arbitrary.
---
**For planets in the solar system-**
* [Geographic poles](http://en.wikipedia.org/wiki/Poles_of_astronomical_bodies#Geographic_poles) are decided thusly:
>
> The International Astronomical Union (IAU) defines the geographic north pole of a planet or any of its satellites in the solar system as the planetary pole that is in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North pole.
>
>
>
* Magnetic poles, for planets/moons that have them, match those of Earth. See image above.
---
**For planets in our galaxy-**
* Geographic north pole will likely be selected as which ever axis points mostly in the direction of [galactic north](http://en.wikipedia.org/wiki/Galactic_coordinate_system).
* Magnetic poles, for planets/moons that have them, will match those of Earth. See image above.
---
**For the rest-**
* Geographic poles will follow the same rules as our galactic poles, the galactic north with either be that which is closest to ours or will be arbitrary.
* Magnetic poles, for planets/moons that have them, will match those of Earth. See image above.
[Answer]
First off, any of the cardinal directions can reasonably be taken to be the base one from which we start measuring the others. The modern world has largely settled on north. Medieval Europe used east, and China used South at one point. In Tolkien's middle earth west was the primary direction. The term "orient" to mean pointing something in the right direction derives from when European maps had east at the top.
I will mostly be addressing north, and to a lesser degree, east, but you could flip things and start with west or south just as easily for an alien culture.
There are different kinds of north (and the other cardinal directions as a result).
Geodetic and celestial directions are based on how the planet spins. The difference between them is tiny and relates to differences in what the 'centre of the planet' means. The geodetic poles are where the axis of rotation of the earth meats the surface while the celestial poles are where it meets the notional 'celestial sphere'. The celestial poles trace out large circles over tens of thousands of years as its axis 'wobbles'. The land or sea at the poles varies with tectonic drift over millions of years.
The grid poles are where the meridians of longitude meet. Because of the slight lumpiness of the Earth we have many different coordinate systems. fictional worlds really don't need that level of detail so you can merge the grid poles with the geodetic and celestial poles.
That leaves the magnetic and geomagnetic poles.The difference here has to do with the shape of the surface of the earth, and the unevenness of its magnetic field. For conworld purposes it's possibly worth thinking about having magnetic poles distinct from the geodetic ones, but the distinction between magnetic and geomagnetic probably isn't worth the trouble.
So, if we now have a pair of geodetic poles, and maybe a pair of magnetic poles, that leaves the question of which is the north pole vs the south pole.
If you look at Earth from above its north pole, the planet rotates counterclockwise. Since this is tied to the rotation which defines the axis which defines the poles, this is a good candidate for "northness" such that we can apply the word beyond Earth. Venus is rotating the opposite direction so Venusian north is pointing in roughly the opposite direction to Terrestrial north. Uranus has its axis roughly in the plane of the ecliptic, but we can still easily identify one pole as north using this in a way that is meaningful for the planet. Magnetic fields change (Earth itself), may not align with the rotation (Uranus), and may be patchy or negligible (Mars, most moons).
Equivalently, you can look at the stars. The north pole is the point where the stars rotate clockwise directly overhead, and east is the direction where stars move straight up.
Treating the direction from which a rotation appears to be counterclockwise as positive(Or conversely, treating counterclockwise rotation as positive) is called the "right hand rule" and is a common convention in mathematics, many sciences, and engineering. Left handed coordinates are also possible (And are used in computer graphics), but it's important to keep things consistent.
[This is how the IAU defines north](https://en.m.wikipedia.org/wiki/Poles_of_astronomical_bodies#Geographic_poles) for dwarf planets, asteroids, and other sub-planetary bodies. The IAU has a different, older definition of north for anything that's planet sized or bigger. The solar system rotates, and so it has poles, and the pole closer to earth's north is system north, and for all the planets in the system, north is whichever pole is closer to that. To go outside of the solar system, you do the same trick with the rotation of the galaxy, and then pick the pole closer to the pole of the galaxy that's closer to Earth's North. Since the axes of rotation wobble, this can cause IAU north and south to flip as an axis crosses an imaginary plane dividing the universe in half. Smaller things tend to wobble more, which is why the IAU switched to the right hand rule north for dwarf planets.
* "planets" (the 8 specific named large bodies) in the solar system and their sattelites use the pole in the celestrial hemesphere
* dwarf planets, minor planets, their satellites, and comets use "right hand rule", and to avoid further confusion calls it *positive* rather than *north*.
By the IAU definition, north is undefined and meaningless without Earth, the solar system, and the milky way. So, you could say a fictional world in an Earthless universe has no north; the poles need some other words to identify them that can not be translated to "north" and "south". You could also assign the real world words to poles arbitrarily. Finally, you could use the
On Earth everything rises in the east and sets in the west. Assuming you use right handed north, the same tends to be true of other worlds, but not necessarily.
Except in the situation like Mercury that a planet is both rotating even more slowly than if it were tide-locked to its sun and rotating the same direction as its orbit the sun will rise with the background stars in the east and set in the west. whereas on mercury the sun rises in the west. If it's tide locked, the sun will not rise and set on opposite sides of the sky like on earth but will instead follow a figure 8 path through the sky over the course of a year. So for a sunrise in the west, you need to have a day that's longer than a year like Mercury.
Moons above synchronous orbit will go east to west (like ours), below synchronous will go west to east (like Mars's moons) and at a synchronous orbit they will trace a figure 8 over the course of a month.
"North" and "south" are also used to describe magnetic polarities. The north pole of a magnet is attracted to the magnetic pole near the geographic north pole. This means that the north magnetic pole, is a south pole in terms of magnetic polarity because magnetic fields attract the opposite polarity. When the next pole reversal occurs, the north pole will be a north pole, and will attract south poles, making all magnetic compasses backwards.
There are other ways to create cardinal directions although it's a bad idea to call them "north", "south", "east", or "west": you can treat some other point as a pole such as a holy city and have toward, away from, to the left of, and to the right of that pole as directions. Another option is seaward, landward, along the cast with the sea on your left, along the coast with the sea on your right which are defined in terms of an area.
A culture might consider toward/away from the equator more significant than north and south although that seems unlikely. Some real cultures consider 'centre' or 'not going anywhere' a 5th direction equivalent to the other 4. You can also treat four cardinal directions as 2 just directions with positive and negative polarities. Up and down (elevation) can also be added for the three spatial dimensions. Time is another physical dimension with past and future as cardinal directions. A culture might consider other opposed concepts as being akin to a dimension that can be moved along such as good and evil.
[Answer]
***Edited 7/25/2015: based upon discussion in the comments section, I've updated this answer to reflect the IAU standards***
Ultimately the selection of label for *geographic* North and South pole is ***arbitrary***. However, as in many things related to science and engineering that are arbitrary, the field has adopted a convention which should be used to ensure that there's less confusion when referring to the poles.
International Astronomical Union (IAU) has adopted two separate conventions to determine which rotational pole will be called the North Pole for Solar System bodies.
## Planets and their moons
The [IAU has adopted a standard in which planets and their moons North Pole is defined as](https://en.wikipedia.org/wiki/Poles_of_astronomical_bodies#Geographic_poles):
>
> as the planetary pole that is in the same celestial hemisphere
> relative to the invariable plane of the Solar System as Earth's North
> pole. This definition means that an object's direction of rotation
> may be negative (retrograde rotation)
>
>
>
## Other Solar System Bodies
The IAU uses a different standard for the "minor" bodies of the Solar System. This standard or convention is called the [Right Hand Rule](http://en.wikipedia.org/wiki/Right-hand_rule) to determine which pole is the North vs. South pole.
With the Right Hand Rule, you make a fist. Observe the direction your fingers curl. Align your hand so the fingers point in the direction of rotation and then your thumb points in the direction of the North Pole.
Right Hand Rule shows direction of North Pole
Rotation of Earth using the right hand rule
] |
[Question]
[
After reading hours on here, I stumbled upon alot of answers that rely on some major changes in our understanding of space and time and its tech to allow us control antimatter or some future thrusters.
From [this accepted Answer](https://worldbuilding.stackexchange.com/questions/3871/how-close-to-interstellar-space-travel-could-humans-get-in-the-near-future?rq=1) specific, such breakthrough are kind of *expected* every 100-200 years.
(see also [Kardashev scale](https://en.wikipedia.org/wiki/Kardashev_scale))
**How realistic is this assumption for our (near) future?**
Points on why it may not happen:
* such tech-jumps only happened recently and only once/twice (around industrial revolution I guess and our modern computer times)
* the future may be not this rich for a longer peroid of time regarding war/peace and ressources like fuel or rare metals, which would make it harder to focus on such kinds of science or even to develop large-scale tech
* all major parts in physics seem to be solved (what tech could quantum-physics or the *god-equation* offer in large scale?)
[Answer]
A major scientific breakthrough can be expected to happen reasonably soon. The thing is though, with virtually all breakthroughs they have not been anything we could expect ahead of time.
The sheer power available in nuclear reactions was inconceivably before Einstein. In fact there was debate about how the sun could have managed to burn for so long as no chemical reaction could provide enough energy for long enough.
The nature of machines that are powered by steam was equally impossible to imagine in a world where water and wind mills were the main sources of mechanical energy.
The people first working on early computers would have no way of comprehending the possibilities of the Internet and the world wide web. I have a mobile phone in my pocket more powerful than any computer in the world 20 years ago, that can browse the internet wirelessly, generate 3d images, and far far more.
So we can expect to see scientific breakthroughs within our lifetime. But if they are true breakthroughs then only a very few people will have seen them coming before they do.
[Answer]
Buni - I think it's less realistic than we like to think and we're prone to best case scenario futurism. In the 50s through the 70's, the image of the future was also like this...in what we now call 'retro-futurism', we get to see images of the working man kissing his stay at home wife and flying off to work in a jet pack...all with an expected arrival date of before the year 2000. It's worth noting that not only was the technology prediction a long ways off, but also completely failed to take into account the social changes and the movement away from the man + housewife + 3 kids and a white picket fence home.
One of the larger error's we make is focusing on the physical technology while neglecting the social and individual changes that come with each leap...with Industrialization came the mass movement of people from rural farms to the city factories, but it also came with a change in the perception of time. The majority of the population lost the farming schedule, working by daylight in the fields according to the season, and replaced that with a manufacturing cycle of adherence to the clock. Every step was reliant on another step being completed and had the next step relying on it to be completed in time. We would build, put it in a warehouse, and continue on. With the transition to the Information age, people are now having to deal with near instant information access and a sharp deviation away from the 9-5 manufacturing style of life...even to the point where 'on-demand' manufacturing is desirable over the 9-5 manufacture and warehousing operations. It's not a simple process and many people are struggling with the shift
If we're not ready, either as individuals or as a society, for the jump to happen, then it's going to be delayed regardless of how available the technology is. In my opinion, the next major shift in society needs to be a rejection of nationalism and an adoption of 'human' as our primary identity and a movement away from things (money) being our primary motivation (which is a natural evolution towards a post-scarcity society). Note that both of these conditions really aren't in a technological domain, but are ultimately required steps for humanity to continue forward. Of course this neglects the individual change...our move to the information age has sped everything up and removed our adherence to the clock that the manufacturing age demanded. An individual now has near instant access to information regardless of time (I can bank on my phone at 2am if I wanted). The world has become a tiny place with anyone no more than a days travel from any point on the globe to another and we get visibly frustrated from a 2 second lag time on a browser. Each step has come with pretty great changes that semi-invalidates the changes the previous step has brought in. When we begin interplanetary colonization and lets say colonize a moon of saturn, how well are we going to deal with going from a tiny world to a vast solar system where communication between two colonies comes with an hour long lag? It's a little bit of a throw back to colonial days where the journey from the old world to the new world was a month long.
My point of this is to say that the rate of technological discovery is not the limiting factor when it comes to the time frames of these leaps. The timeline on this (near) future is constrained more by our slower social and individual evolution than our technological evolution.
[Answer]
As a physicist, I can tell you we have *plenty* of areas which remain unsolved and mysterious. If we have solved most things, we wouldn't bother with LHC and other scientific endeavors. There is enough about the universe for scientists to spend hundreds, if not thousands of years, performing more research.
As for expecting certain breakthroughs, it is a very tenuous proposal. It makes the fundamental assumption that the rate of past breakthroughs keeps going. There is no guarantee about this. Even similar ideas, such as [Moore's Law](http://en.wikipedia.org/wiki/Moore%27s_law#Ultimate_limits), have limits. Therefore you need to take such predictions with a figurative grain of salt.
Skepticism about future breakthroughs being said, there are enough potential new technologies for rockets that there is no reason not to expect more experimentation and new rockets. This is especially true in light of the privatization of space travel, with companies like [spacex](http://www.spacex.com/).
Quantum Physics can have large-scale applications; some are more common while others are being developed. See [quantum computing](http://en.wikipedia.org/wiki/Quantum_computing) for a good example. Quantum Effects can also be seen in large-scale things, such as neutron stars. [MRIs and Electron Microscopes](http://en.wikipedia.org/wiki/Quantum_mechanics#Applications) work because quantum principles are being taken advantage of. To say that this branch of physics offers no large-scale benefits is *simply wrong*. It has already benefited you and I on large scales, although you may not have noticed.
Finally, while many "economically minded" people may think that space travel is unprofitable, it is happening. SpaceX and other companies are going to space. [Asteroid mining](http://en.wikipedia.org/wiki/Asteroid_mining) is a potential cash-cow. [Martian Metallurgy](http://en.wikipedia.org/wiki/Composition_of_Mars) can yield unexpected new metals or a cheap source of steel.
I would expect future innovations to happen, given all that there is to discover and explore. Anyone nay-saying future innovations is simply ignoring facts. If there is a future ceiling to technology, it will likely not happen in the next one or two hundred years.
[Answer]
Breakthroughs in *craftsmanship*, not fundimental laws of physics, are what is driving the current space privitization effort. We still use chemical fuel and Newton's Third Law to make a rocket work — don't expect that to change. There is no magic-bean powered carpet in forseeable future. It is improvements in tools and materials handling that is ongoing, and that also allows the creation of better tools as well as final goods, so it has the potential for exponential growth.
Private companies are trying to make space affordable by making vecicles lighter and more cheaply.
The entire launch vehicle and engines are just a tax on top of what you really wanted to orbit. If you could get the weight down to a feather, you still have the weight of the payload and fuel for that weight. So there is a limit.
However, what allows colleges and startups to access space is the *microsat*. Even when it still costs [\$8600 per pound](http://www.nss.org/articles/falconheavy.html) (which comes to $75,000 for a gallon of milk), a useful payload can be built that is only a few pounds.
Look at an Android smartphone: a few ounces for more compuer power than existed onnthe planet during the Space Race, sensors, optics, and communications capability.
Further improvement that could be at the levelmof a *breakthrough* in commercial availability of orbital experiments (not in physics) would be the development in infrastructure. The microsat is bloated by shielding, more powerful radio, and the need for self-contained power, so it winds up being 10×10×40 cm rather than a smartphone.
A commercial service could offer orbital hosting, where your microsat is placed in a shielded enclosure with a network connection and power, supplied by them. The *suite* with its heavy shielding does not need to get sent up every time the interesting guts gets replaced! That would reduce costs by an order of magnitude, all, without needing to discover new laws of physics or invent whole new technologies. Its just *investment* and building on continuing work.
What is happening: **smaller stuff**. Nanotechnology, spintronics, novel materials, etc.
What is *not* going to happen, because we *know* how it works and that there are limits: chemical energy won't be stored any denser than what is already found in high explosives. That is, rocket fuel won't get orders of magnitude more powerful.
(Non-chemical rockets like ion drives are not useful for getting into orbit. Thrust less than 1g is not going to get anywhere.)
So what about replacing launch rockets with something that does not carry the fuel with it? Cannon launchers have limits, and unless you build a many-miles-long railgun it won't help. Getting as much speed as you can while still in the atmosphere means you can save on reaction mass and get oxygen without carrying it all, but how much does that save? It still relies on the compound interest of the rocket equasion and cutting off the bottom saves many times the direct savings. Easy recovery and reuse of the stage (as it's a plane) needs to be weighed against the weight savings of making it disposable!
So what if you wanted to go to the moon in person? Hundreds of pounds with life-support and snacks, comes to millions of dollars.
If you can't get past chemical launch rockets until *much* later when space industry is already mature, how about making the rocket fuel cheap?
You can't have exotic toxic materials, just as cars are subject to emmission regulation now. The rocket exhaust will need to be eco-friendly, meaning not as powerful as it might be if you could choose the most potent chemicals without constraint.
But lack of rare metals and such will also make it cheap to produce. In a future with advanced chemestry and nanotechnology, potent molecules can be designed and contained safely, using only common life elements. Hey, it could grow on trees. Ultimately, if gathering and arranging the atoms is cheap, you are limited by the amount of energy you are storing. Less power per mass pays penalty exponentially via the rocket equasion, but look at what petrolium is: organic molecules. Or, liquid oxygen and hydrogen: what if that was cheap, other than the cost of energy?
Later, but before the possibility of space elevators, a commercial capability breakthrough will be to source industrial materials off-earth rather than lifting it. We will be *importing* raw material and manufacured goods, and leaving will be expensive. Since you only need to get to LEO and then all the life-support and living quarters are *from space* rather than lifted from Earth, my ticket out (a 250 pound man) will be $251,000 with today's rockets. Earning power will increase, fixed infrastrucure cost will be amortized (don't need to buy the airplane when I fly coach), and cost to produce the fuel will be smaller relative to the total consumption per person of energy. Whether that means affordable as saving up for a few years, or *cheap*, depends on breakthroughs in our energy economy. Cheap practical fusion? Or just nearly-free solar power?
[Answer]
A lot depends on what exactly you mean by a breakthrough.
Some breakthroughs like the Agricultural revolution and the Industrial revolution are really a matter of social organization. Steam engines and relatively sophisticated machinery like waterwheel powered saws and mills were known as far back as the Roman Empire, but since slave and animal power was very cheap, mechanical engines of various sorts were specialty devices used to do things like "special effects" at temples (a primitive atmosphere engine was described to open doors at temples, for example). The idea of science was considered a hobby for the wealthy, and technology for lower classes (Vulcan, the god of craftsmen, was the only god described as lame, which gives you an idea of how craftsmen were viewed). Even in the 1500's, the Venetians had developed fairly modern government and banking institutions, and even a primitive assembly line system in their Arsenal, but never took the last step.
Other breakthroughs are a result of actually changing the way we understand the universe. The Scientific revolution changed the world from a random place to one of "cause and effect" which could be quantified and reproduced. Newtonian mechanics allowed the mathematical study of things at scales larger and smaller than what was possible before, and Einstein and the various scientists who developed Quantum mechanics have expanded the scale and scope of what can be observed and understood.
Right now, we seem to be in a sort of consolidation period. As mentioned, much of the "breakthroughs" are really refinements on craftsmanship; rockets still rely on fairly basic ideas dating back hundreds of years, and even "smartphones" simply make use of transistor and integrated circuit technology that is highly refined, but based on ideas dating back more than half a century.
Not to say this isn't useful, and on the NextBigFuture blog, there is an idea being promoted of a "mundane" singularity, where the accumulation of simple refinements still leads to a massive leap in wealth and abilities.
Truly fundamental changes are difficult to predict, and do not come on a "schedule". Physical laws are fairly well understood, and any breakthroughs there will be at scales far beyond what ordinary people could expect to access (cosmology or particle physics). Fundamental changes in the way we organize knowledge and understand things *may* be possible as new technologies like Big Data become well understood and tools to exploit them become common. I would look for some sort of social change on the order of the Agricultural revolution or Industrial revolution to really be the next breakthrough. The interesting question there becomes:
What will be the driver of this change (humans were well aware of how plants worked through the neolithic era, but generally never bothered to cultivate them, and as mentioned, the Romans in the First Century AD had access to primitive engines and the Venetians had many of the institutions but never took the last step). We have lots of new tools ranging from genetic engineering to material science; are any of these going to be *the* big thing?
What will trigger the change? The tools might have been around for a long time, but the conditions to make the breakthrough possible might not happen for a long time.
] |
[Question]
[
So there is a Minecraft mod that includes various oreberry bushes. One for gold, one for silver, etc. Now I know that various plants can extract specific minerals in higher quantities that what would normally be expected, so my question revolves around concentrations in the environment. If I wanted a plant that extracted, say gold, from the environment and produce pea-sized nodules of pure gold how concentrated would the gold have to be to have a bush actually do this? I think it would be interesting to have a bush that a harvest gave a couple dozen of these little balls of pure metal instead of normal fruits. I know that this might make propagation of the bush difficult, so maybe in addition to the ore, the plant also produces something like hollow seed pods and to keep refreshing the minerals maybe the plant lives in or near an area of frequent volcanic activity...
[Answer]
Ignoring all other mechanisms, a plant can only pull as much ore as its root system can reach. It can't create gold or silver from nothing, so it's a matter of how much actually exists. If you would mine and refine some ore and end up with say, 1 kg of gold, then your plant can't ever produce more than 1 kg of gold - whether it does that in one harvest or over several is up to how efficient you want it.
But there's an alternative - what if your plants extract ores from **water**?
I haven't found a great reference for this, but it seems like on earth reasonable levels for silver and gold in river water are going to be around .1 to 1 ppb - that's part per billion. Taking the upper bound means you'd need to process 1 billion liters to get 1 gram of the mineral of your choice. Now that sounds like a lot, but major rivers have flow rates on the order of 10 million liters per *second*. Now obviously a single bush can't sample the entire river, but let's say you want a harvest of 10g per year. Then your bush only needs to sieve ~16 liters a second, which is less than a cubic foot. A larger plant that sieved a cubic yard would be able to produce 300g-400g per year.
There's a couple of issues:
1. If you plant two bushes next to each other, the one directly downstream won't get as much because a lot of its water will already be sieved. So you need to spread them out enough that random fluctuations will replenish the gold for the downstream plant.
2. There's no major benefit for a plant to provide gold or silver in easily harvestable pellets. So instead, what if the plants are genetically engineered as part of an environmental cleanup strategy? You'd have plants for major minerals, plastics and other environmental wastes, and they'd collect and concentrate them for human harvest. That also lets you plant bushes closer together, because you can alternate types to avoid diminishing returns.
[Answer]
The necessary density of the mineral would be directly related to the extent and density of the root structure of the plant in question, and the amount that you hope to harvest.
Contrary to what people might expect, most of the mass of a plant comes from the air, specifically the carbon dioxide that it filters into pure oxygen. However, the remainder of a plant's mass is generally made of retained water and minerals extracted from the earth, so, on a very small scale, all plants do what you're asking about.
The real limit for what a plant could uptake is how much metal its roots come in contact with. If a plant has a root-ball that is about a cubic meter, and each cubic meter of dirt contains, say, three grams of gold, then the most gold you could expect to extract from the plant would be three grams or less, probably *much* less.
This leads us to the first obstacle to harvesting nice little berries made of gold. If the soil concentration of a useful mineral is high enough to be harvestable from the plant, it would probably be in such high concentrations in the soil that you would still be better off just digging it up and smelting it.
Additionally, If the mineral in question was a nutrient, it would most likely be distributed throughout the plant fairly evenly, with only slightly higher concentrations in new growth.
The only good reason I can see for a plant to produce metal berries is if there is a high groundwater concentration of the metal, and the metal is a mild toxin to plant life. In that case, I could envision a plant that purified its own soil by sequestering as much of the metal as it could into tiny nodules, so that the rest of the plant wouldn't be affected. The constant flow of new toxins carried by the ground water would overcome the soil density problem too, since the trace amounts of the mineral would build up over time, instead of already being in useful concentrations in the first place.
[Answer]
Let's think about what the plant needs to do.
The metal needs to be pulled from the ore and transported. Clearly the best way to do this is chemically, so we'll assume that the process centers around a reaction which converts the metal in the ground (most likely in an oxide form) into an aqueous ionic compound which can be transported up the roots and into the foliage where it can be deposited. The depositing is very reasonable; there are countless metal deposition examples in nature.
The process of getting the metal may be a bit interesting. Some metal processing methodologies require heat, and they would be inaccessible to a plant. On the other hand, you have access to the entire repertoire of enzymatic activities, so let's assume this process works.
As has been mentioned in other posts, transport of metal is the issue. You can only collect what you can reach with the chemical processes. If you're looking for gold, you're out of luck. The average volume of a plant root ball doesn't have more than a scant amount of gold. How small, consider [this site's assay of soil](http://www.actlabs.com/files/environment8.pdf), multiplied by a sample 1 cubic meter root ball:
* 0.002 ppm Gold = 38ug
* 0.01% Aluminum = 270g aluminum
* 0.01% Iron = 780g iron
This is, of course, assuming complete extraction from the root ball.
However, we're not playing by nature's rules here. Nature doesn't reward massive strip-mining of entire countrysides to harvest metals. Nature builds things up in ecosystems, where each participant is dependent on the actions of the other participants. What if we could convince these plants (by breeding, or something more extreme like genetic engineering) to work with some helper bacteria or insects to aggregate the metals for us.
Yosemite [has been measure](https://books.google.com/books?id=y8lJkofybL8C&lpg=PA120&ots=0c_5X1j05N&dq=tree%20density%20yosemite&pg=PA120#v=onepage&q=tree%20density%20yosemite&f=false)d to have a tree density of roughly 130 trees/Ha (give or take). At 300,000 Ha, that's 39 million trees. If we could have them all transfer their gold to one master tree, it would be able to acquire roughly 1.5kg of gold.
At gold's density of 19.7 g/cm^3, that's 77 cm^3 of gold. 77 cm^3 is roughly a sphere 5cm in diameter. **This means, deep in the heart of your forest, you can have one tree which produces a small apple of pure gold.** *But only the true of heart would find it*.
[Answer]
There was one factor in the question that seems to have been overlooked in the other answers that may make a gold harvesting plant a little more plausible...
**If the plant evolved in an area with significant volcanic activity** you may have a reasonable explanation of both why the plant collected valuable minerals/metals and how it would have access to more significant quantities of them.
If your bush [looked more like a mangrove](http://en.wikipedia.org/wiki/Avicennia_germinans) and grew in water run off from active geysers/hot-springs, in a place like [Yellowstone](http://en.wikipedia.org/wiki/Yellowstone_Caldera) you may be be able to suspend disbelief enough to make it work.
The reason I'm pointing to the mangrove, and specifically the black mangrove, is the way that it has adapted to living in salt water.
>
> It is a hardy species and expels absorbed salt mainly from its
> leathery leaves.
>
>
>
[](https://i.stack.imgur.com/YnpTQ.jpg)
"[Avicennia germinans-salt excretion](http://commons.wikimedia.org/wiki/File:Avicennia_germinans-salt_excretion.jpg#mediaviewer/File:Avicennia_germinans-salt_excretion.jpg)" by [Ulf Mehlig](//commons.wikimedia.org/wiki/User:Umehlig "User:Umehlig") - Own work. Licensed under CC BY-SA 2.5 via [Wikimedia Commons](//commons.wikimedia.org/wiki/).
Basically you would have a mangrove like plant, that grows in heavily mineral/metal laden water, that excretes excess mineral/metal build up in nice little crystals on its leaves as a byproduct. The plant doesn't really want or use most of the minerals/metals it just developed a handy way to get rid of them so that it can live in water that is tainted with them. Perhaps the mangrove developed the adaptation in order to have access to a relatively warm microclimate that supports an active microbial ecology to feed off of.
I know this isn't exactly the "berries" that you were looking for, but this scenario may be a bit more believable.
[Answer]
Presuming that you had a plant that could extract and concentrate a particular material, the answer is that it could happen at very low soil concentrations indeed, however in such a circumstance, the yield would be very low.
A plant might concentrate material by absorbing water that contained dissolved material, or it might more actively release then reabsorb a solvent for that material. Once the material was in the plant, it would simply be a matter of transporting it to the site of expression and precipitating it out of solution.
A plant which does this might produce nodules of the material in question, separate from its seeds. As to evolutionary advantage, if a plant evolved to do this and humans discovered it, its success would be assured, as humans would cultivate and protect it. There is relatively little other advantage to the plant *except* in the presence of humans, so this would be a symbiotic relationship.
[Answer]
There are species of common flowering clover that are found to remove nickel from soil and absorb it into every cell in the planet. it concentrates the nickel at above 2% by dry weight of planet matter, easily recoverable by burning. it's been used for ground contamination cleanup. surely there's a plant out there that would consume gold, and for all the useful chemical processes it would benefit itself from the uptake of gold from the soil. perhaps even a salt tolerant plant that can pull that scant gold found in seawater that everyone says is rather pointless to try to recover. and then of course are the nanites. I mean. Why bother with plants at all when you got ant-brained nanotech swarms harvesting all the metals from the earth? nanites beat BOTH paper AND rock. but they just sort of stare at the scissors with a distrustful glare.
[Answer]
There's a modern method for extracting gold from pine trees grown on mine tailings but you're talking about grams from a whole pine tree and repeat plantings over many years to get a few percent of what's there. In the case of a custom organism the concentration in the soil isn't that important; what you *really* need to look at is the absolute amount of gold or silver in the soil because really you can concentrate that amount as much as you like by having a greater or lesser extent and retrieval efficiency to the bushes' root systems in grams (or ounces) per length of time. That will give you an idea of how many bushes you'll have in an area and how often you can make a harvest of them.
] |
[Question]
[
The concept of a "spark" is our shorthand for an idea describing some neural nets in your body (well loosely anyway), its a catch-all for anything that can be an electrical response. Some of the electrical responses in the body include: conditioned reflexes, knowledge and memories, and involuntary reflexes such as your "knee-jerk reflex". Sparks can be transmitted, but only by direct contact. You may transmit a duplicate of a spark or an "original". Transmitting an original copy which leaves you without that spark. Basically, you can do a copy-paste or a cut-paste to move a spark from yourself to someone else. Transmission is instant but forming a spark takes as much time as it does to think of what you want to send (see background below). So in a world where you have sparks that can be transmitted by touch:
**What would be the *most* significant changes in such a world that are *likely* to happen?** (I realize a lot would change so changes must be game-changing with a reason that supports its likelihood)
**Background on Sparks:**
* Sparks when used as a form of communication are succinct and perfectly clear.
* Misunderstandings are impossible when using sparks: if there's a piece of knowledge required to understand something then you'll be able to notice the "loose-end" so you can ask for clarification. It's still possible an idea isn't clear. For example, if someone communicates *FTL* and you know of that acronym as Fun-Traumatic-Lover but don't know of Faster-Than-Light then the communication of FTL will have an ID/Hash/Something that makes it noticeable that it's a different FTL and you can ask about what they meant.
The original communication could have been a larger spark that included the FTL definition.
* A spark has the same "base data" but is stored encrypted differently on each person. A dead person's sparks could be read but would require great effort. A more secretive or insane person would be harder to decrypt. Physical degradation can make it impossible to recover a spark. *So, sparks can be given but never easily taken.*
* Degradation of the nervous system can cause one to lose a spark.
* Bigger sparks can be overwhelming and take slightly longer to formulate. You could absorb the information wholesale or only allow the portion you can process in. (So someone could communicate an entire movie to me and I could either act as if I had watched it or view it piece-by-piece. Absorbing the movie wholesale would not integrate it with the recipient's knowledge it would simply make it available for perusal).
* Sparks can communicate sensory and emotional information.
* The spark is formulated at the speed of thought. So if you want to "speak" something you could do so in the same amount of time as by talking. Conversely, when you think of a burger you don't have to list off the ingredients in your head, as an object you have a prepackaged definition you can use for free. In short, specifics and novel ideas, etc. cost you prep time whereas general things and things that simply are get all the extra information for free.
* When you're passing a knowledge blob, if you communicate too much periphery definitions you risk losing the focus, as you would in any conversation.
[Answer]
**Originals** would not be any more important than now unless sparks degrade as they are passed. If a spark is just as good if I get it from the tenth recipient in the chain as from the person who originally had it, then the original is only briefly valuable. Once the spark is shared, everyone who has it is equally valuable. This suggests that the initial transfers of unique sparks will be expensive.
**Synthesizers** may become valuable. These would be people who are good at mixing particular sparks in order to make new ones (e.g. someone who synthesizes karate and aikido into a new art). If they can do this consistently as new information (sparks) is developed, then they may have as much or more value as someone who develops new sparks.
**Dead brain** access would be limited. Note that people who have near death experiences can lose memory. Harvesting dead brain sparks would need to be done within minutes of death. Digging up graves wouldn't help. Cremation would be irrelevant, because sparks would be long gone by then.
**Reality sparks** may become the new media. Instead of watching or reading about someone's experiences, live them yourself.
**Lying** would become more difficult. If you don't trust someone, force them to give you a spark demonstrating the memory. It would be interesting to see how trials work in a world with sparks. Do the witnesses give sparks directly to the jury?
**Intellectual property** would be unaffected. The reason why we have patents, trademarks, and copyrights is so as to limit things when the knowledge is already out there. Making the information more available won't impact this.
**Espionage** would get an interesting new tool. What happens if you are able to fool someone into transferring a spark to the wrong person? Physically securing the data becomes less effective if someone still has it in memory as well. Transferring secrets just became easier so keeping them became harder.
**Native intelligence** would remain valuable. Note that some people are simply better at certain things than others. For example, Johann Dase could multiply hundred digit numbers in his head. There is no evidence that he had any particular trick to do this. He was simply better at keeping track of the intermediate results. Some things simply won't spark and this might be one of them.
**Employers** will expect people to already have all the experience needed from the first day. This will greatly reduce both the official training time and the unofficial period of learning how the job works.
**Politics** would stay the same. Note that in politics it's not what you know but who you know that matters. Even if Harry Reid and Mitch McConnell transfer all of their knowledge to someone else, that doesn't mean that that person can be as effective as they are. Giving Ted Cruz or Alan Grayson the skills to compromise doesn't mean that they would use them. Politics is ruled by personality and who wants to change their own personality?
We also might discover other interesting ways that sparks won't work. For example, if a man gets a spark from a shorter female gymnast, it might be that the muscle memory simply won't work. Because of their different builds, the man might not be able to use her memories successfully.
[Answer]
Some of the most significant changes that are likely in such a world include changes to:
**Education** would likely change for the better as the benefits would far outweigh any negative effects. Things that consist mostly of memorization could be learned in days instead of years. Focus would shift to developing novel skills and methodologies. The accelerated learning is likely and taken to the extreme would result in Elementary School and College being the only two levels, one for mandatory skills, the other for preferred skills.
**Economy** would likely start to seriously trade in skills and knowledge. This is highly likely as the value of novel skills would be the only thing separating a waitress from a scientist. The skills that make a person special/unique would probably be closely guarded by the individual so they could stay both different and potentially valuable.
**Military** would be changed dramatically. The ability to transfer military knowledge and skills allows anyone anywhere to instantly be upgraded to a super-soldier and strategist in one. Body-type specific skills would be the only limiting factor. This would transform any population into a standing army so it's hard to see it being passed up. It would also make the "originals" that everyone would be cloned off of into moving targets on the level of a president (or higher).
**Law** would likely develop around the ability. With precedents in patent and copyright laws it's likely that everyone's natural ability may be regulated. Martial arts skills might be required to be registered for example. It's possible this could get dystopian rather quickly "by necessity".
**Politics** would change dramatically, since it would be laughable if it stayed the same. "I can change the world because I can \_\_\_\_", well so can I *potentially*. A politician could be asked to prove they had the skills before they got in office instead of during their stay. This would increase the average capability of public officials. Since it's such an obvious and simple solution to a universal problem it seems pretty likely to happen.
**Information** wars would get ugly by necessity and hoarding would become common. An example is the buying out of patents and crushing of competition. Just by a touch the underdog in that scenario can make a third-party completely understand their side and its benefits. As suppression of competition becomes all but impossible while it's members are alive, it would rather likely result in large numbers of corporate and government murders as the only way to deal with the problem, since you couldn't even imprison them without the guards become a liability.
**Well-being** would be interestingly distributed and possibly collapse social media. If you had a memory you wanted to forget you could, but you would have to give it to someone else. The best time of your life could become everyone's best time. Many mood-altering trades could be enacted. Since it all needs somewhere to go there could be a small number of individuals that receive all of society's crappy sparks. Just like a new drug it's unlikely this wouldn't be widespread.
**Individuality** may cease to exist. A Singularity of opinion and skills would make the human race one giant Swarm and much more of a Hive Mind than it already is. Such a Singularity is extremely likely. After-all, what are the odds of you turning down the skills to be a stunt-driver, or experience an astronauts trip to the moon? If you become a "spark junkie" then your on a one-way trip to become part of the Swarm. As the passing of skills onto the next generation would occur early in life and be highly beneficial it's highly possible the positives may far outweigh any and all negatives, or society may just notice too late.
**Lost Knowledge** would be unlikely. Anyone who wanted to know something would just have to spend some time decrypting your brain after your death to know it. Since some of the knowledge that people have taken to their graves is sorely missed by the world it seems unlikely that this wouldn't be used at-least occasionally. People may resort to cremation to avoid this of course.
And that's all the *major* ones that I can think of (some of those aren't breathtakingly major but are interesting so I included them).
[Answer]
To add on two great answers:
**Personal space and greetings:** Imagine I am arriving to business meeting quite hungry and unintentionally send that message to you through ordinary handshake. Keeping me on meeting as long as possible would bring you good advantage (I would be willing to commit for something just to leave for lunch break). So wearing gloves would be normal and greeting would be possibly more on Japanese style.
**Clothing style** As stated above, you would see more clothed people, because accidental touching by handing a burger to you could also bring you knowledge of "I hate my job, but they force me to smile"
**Pornography and prostitution** Oh my. I am not going to describe details of it, but just imagine a porn market of sexual experiences...
**Sexuality in general** In my young age, "first base" was kissing. In your setup it would be "touching skin on skin"
**Religion** You can actually pass the original ideas of your prophet. No more discussions about "what would Jesus say about gay marriage". If you are Christian, *you already know*
[Answer]
The last of these points is probably the most poignant, but they form a sort of causal trail, so they are presented in causal order.
**Loss of subtlety in the culture** What you described for the creation of sparks is a individual act which takes a long time. This means a very discrete approach to communication: question -> construction -> answer. If the question was imperfectly understood, the answer would be imperfect. There would be a compensating tendency to "overbuild" Sparks to make sure this breakdown didn't completely defeat the point of communication. People would effectively be shouting at each other all the time, and the culture would adapt such that this shouting was not rude.
There would be less subtle continuous interaction (think dancing or the old fashioned dinner date). The effects of such interaction would pale with respect to interaction using these discrete Sparks, so few would explore them. (Those few, however, may find something interesting that, for any reason you please, cannot be transmitted by Spark, creating a cultural undertow of individuals writing off sparks entirely)
**Combat** using sparks would be interesting. I am assuming there is a physical limit as to how much information you could encode into someone else's brain: over-spark them and they're out of the fight. Combat is 100% about exploiting weaknesses in the opponent, so while I am sure there would be a way to choose not to receive a spark in your world, combat would adapt to work around this barrier and exploit any holes. Dangerous fighters would walk around with terribly terribly noisy and hard to encode sparks in their head, to be offensively delivered to their foes (exactly as warlords brandish AK-47s today). Also, because you can copy the sparks, not just transmit them, there would be martial arts which teach you useful combat sparks, and there would be sparks that teach you how to defend against those. It would be a spark arms race.
There would also be a subtle side of combat (as subtle as this Sparked culture allows), which concentrates not on how to generate loud bright sparks to overload the opponent, but instead seeks to calmly work around their defenses while developing a subtle spark custom tailored to upset that individual combatant.
**Viral sparks** Just like earworms of our present day, sparks would form which push the individual towards spreading them to others. An entire new class of life would spring up, as would a "spark immune system" that you would be taught early in life to protect you against these sparks.
**Magic** Magic could spring up in response to the viral sparks. If the sparks indeed become a new class of life, they would have to hide themselves from the immune system sparks. Their influence would have be just as subtle as the subtlety lost by the carrying humans. Accordingly, magic would spring up to explain the cosmic coincidences that we cannot seem to explain, no matter how many sparks we intentionally try to convey to eachother to monitor it.
It would not be unreasonable to have children "chosen" by the sparks to live a life of destiny. From the human's perspective, it would be divine magic. From the spark's perspective, it would be nothing more than and artist choosing a paintbrush, or a warlord choosing a hill to conquer.
] |
[Question]
[
I'm thinking about the evolutionary history of life on a world very similar to earth in many ways, carbon based life, life began in the seas, creatures like cephalopods, and arthropods, evolve.
But, there is *something* different about the world, or something that happens that prevents anything like vertebrates from ever taking up much of the animal biomass on the planet. There may be some small creatures with notochord-like structures, but they never get very large, or perhaps they flourished for a time ... only to go almost totally extinct with only a few species of more obscure animals with internal skeletons extant at the time of the story.
This planet is, of course, dominated by giant arthropods, insect-like creatures, gastropods, cephalopods etc.
But what are some environmental conditions, natural disasters, or features of an ecosystem that creatures with internal skeletons are more vulnerable to than those with exoskeletons? (It might not be directly related to skeletal structure, but instead some of the knock-on effects of how a creature has evolved to support its mass.)
[Answer]
# Just do Earth again
Out of all of the clades in the Earth, only 3, to my knowledge, possess internalized skeletons: Those being cephalopods, echinoderms, and chordates. And of these 3, only two (chordates/echinoderms) have a skeleton that actually can support their body. This seems to suggest that this adaptation is an extremely rare trait. If we add in all of the other vertebrate traits, such as complex gills and closed circulation, then it is highly unlikely anything like a vertebrate will ever reemerge
] |
[Question]
[
I'm worldbuilding a whimsical, leisurely world where the livin is easy. I was thinking about, "[What would put agriculture/industry on Easy Mode?](https://worldbuilding.stackexchange.com/questions/246565/what-one-change-would-put-life-on-easy-mode)"
One answer that suggests itself is increasing [photosynthetic efficiency](https://en.wikipedia.org/wiki/Photosynthetic_efficiency): plants are the basis of most goods (food, fuel, fiber, even meat), and if they could capture more incoming energy, people would have more of everything.
Doing some research on this question led me to C3, C4, and CAM plants. [There is already work done to make C3 plants C4](https://en.wikipedia.org/wiki/C4_carbon_fixation#Converting_C3_plants_to_C4). Is this the route to go down for my worldbuilding? Should I make all plants in the world C4 producers? Or is that impossible or detrimental for some reason I've overlooked?
Another possibility: I found [this research](https://en.wikipedia.org/wiki/C3_carbon_fixation#Synthetic_glycolate_pathway) about adding enzymes that break down glyoxylate into CO₂ which is then reüsed instead of going to waste. "The end result is 24% more biomass."
Should I go with the glyoxylate-breakdown route? The C4-for-all route? Both? Other?
[Answer]
There is an easy method of increasing plant production: [more CO2.](https://www.scientificamerican.com/article/ask-the-experts-does-rising-co2-benefit-plants1/) A quote from that article:
>
> In those experiments artificially doubling CO2 from pre-industrial levels increased trees’ productivity by around 23 percent...
>
>
>
This [article](https://www.ontario.ca/page/supplemental-carbon-dioxide-greenhouses) includes tests on the net effect on crops in greenhouses, showing that the optimal level for most plants is in the range 1000 to 1300 ppm, compared to the typical outdoor values of round-about 340 ppm. That is, three to four times the ordinary values.
Many species of plants originated during periods with much higher CO2. Now that CO2 levels are rising due to industrialization, [the entire planet is greening.](https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fertilization-greening-earth) One can almost imagine the forests saying "Oh! It's a delightful breath of stale fetid air! Mmmmmm!"
By the way, humans are OK with [that sort of level.](https://www.health.state.mn.us/communities/environment/air/toxins/co2.html#:%7E:text=At%20even%20higher%20levels%20of,dangerous%20to%20life%20and%20health.) It may require some adaptation and acclimation. But they are not dangerous to health. Humans start to have effects round about 5000 ppm.
[Answer]
The metric of "efficiency" doesn't exist in a vacuum. [CAM photosynthesis](https://en.wikipedia.org/wiki/Crassulacean_acid_metabolism) works well in hot, arid conditions when plants using other systems risk being dried out. Even in the C3 to C4 link you gave above, you can see notes like "*C2 photosynthesis... has the advantage of requiring fewer steps of genetic engineering and performing better than C3 under all temperatures and light levels.*" which under some circumstances can make it a better choice than C4, especially for higher latitudes. You don't say anything about the climate in which your plants are growing, but it makes a big difference here!
Plausibly, your future genetic engineers might be using *all* the techniques they can usefully combine in order to maximize yields under some particular set of conditions. We don't know what that combination of modifications could be, because we haven't tried them yet. A reasonable assumption is probably to pick one or other of the things you linked that are actually being experimented with in the real world.
The *safest* solution is to not mention the technical details *at all*, because there's scope for getting stuff unambiguously wrong in making such claims and there's no real benefit to your story or setting.
[Answer]
**No, it couldn't.**
Just capturing more carbon is not enough. For more biomass, the plants would require correspondingly more of other nutrients as well, which would become a new limiting factor because improved photosynthesis does not create more of *them*.
] |
[Question]
[
Desire: In my world, I would like to have a (potentially unreasonably) large mountain range that is so large both in height and width that it is both entirely impassable, and disappears into the clouds with unseen peaks, even when viewed from miles off.
Confession: My knowledge of the science on this is shaky at best. I found another answer on this site that asked for hard science, and yielded that on earth the tallest possible is around 10 km, but I would like to make it much larger, preferably without handwaving.
Goal for Answer: I have no problems with coming up with fantastical *ideas* for how it became that tall (Massive flooding event that crashed tectonic plates together, remains of an unimaginably large asteroid, etc.), but I am weak in an actual scientific basis. I don't need "hard science" per se, but **would like an at least semi-plausable way to explain how it's possible** without simply being logistically inane. I'm concerned this size might warp the rotation of the planet, or cause other issues I'm not thinking of, as I'm simply a lowly politics major ;)
[Answer]
The largest mountain in the solar system is [Olympus Mons](https://en.wikipedia.org/wiki/Olympus_Mons) on Mars. There are comparisons to famous mountains on Earth on that wiki page.
It seems that it resulted from the usual processes of volcano formation. But, Mars has relatively low gravity, compared to Earth. And it has little to no tectonic plate movement.
Also, the atmosphere on Mars is quite thin relative to Earth, with very little water. The freeze-thaw cycle is not going to produce the same kind of erosion as on Earth, since there is little water ice. Water ice expands cracks and peels rocks off cliffs, eroding them.
The process of waterfalls is absent. This removes a massive source of erosion on Earth. The canyon that a waterfall forms is much like a knife through a cake, slicing off a huge chunk.
The lower gravity encourages higher mountains to be built. And, once the mountain was formed, there are reduced processes to reduce it in height.
It is thus a balance between a planet being large enough to have mountain building processes. And small enough such that the gravity lets the mountain be very tall. And inactive enough such that mountains are not removed before they can get that high.
[Answer]
So two ranges to look at for how they formed are the Himalayas and the Andes Mountains (and other mountain ranges found in the American Cordillera, which is a chain of ranges found in the western portion of both American Continents). In the case of the Himalayas, the range was fromed by two continental plates smashing into each other (The Asian Plate and the Indian Sub-continental plate). Continental Crust is thicker than Ocean Crust and thus, when Ocean and Continental Crust meets, the Ocean Crust is forced under the the Continental. However, when Continental Crusts pushes agains teach other, both plates buckle and slowly push upwards, which is what happens with the Himalayas.) which is why they are so high in some places. Moutains also do have places where it's easier to travel from one side of the range to the other, but this also makes it very easy to form chokeholds at these locations. They are infrequent, There are very few ways to pass through the Rockies in the U.S. and settlers heading were often settling west of the Rockies in areas based on which pass they took. If they arrived to late in the season, they would settle at the eastern part of the pass.
[Answer]
Limiting your fantasy based on Earth geology doesn't make much sense, it's just a one planet. We have no idea how typical it is in the universe. Rocks composition, crust, mantle, gravity - all of this can be wildly different and planet still can be habitable. You want 20 km high mountains - go for it. No one can definitely say they are impossible.
Just an example, BPM 37093 is a star (<https://en.wikipedia.org/wiki/BPM_37093>). It's core is likely one of the largest diamonds in the local region of the universe. Estimated mass is 5×10^29 kg, Earth's mass is ~6×10^24 kg. Star systems sometimes collide. If BPM 37093 ever get close to a supernova and get destroyed, diamond shards thousands kilometers long are not impossible. If one of them ever become a part of new planet, it may have very peculiar mountain ranges made of pure diamond. It is unlikely. But not impossible.
You don't really need scientific basis for high fantasy with magic. It can be harmful. The Force in Star Wars was much better before midichlorians.
Avatar is hard-ish Sci Fi. It has flying land masses. It is ridiculous, but no one blinks an eye. Pandora is a moon of other huge, very close planet, there are multiple other large bodies visible in the sky. It is most likely a completely impossible system, no one cares.
[Answer]
According to your tags
**Your World has Magic**
This means that you need not limit yourself to what is physically possible on earth. In fact doing so would be entirely unnecessary.
**Soft Magic**
If your world has soft magic then the simplest solution is that the mountains are enormous and impassable, simply because that is part of their fundamental nature. The 'will' of the mountain will see anyone attempting to summit or cross it faced with impassable ciffs, freezing temperatures, howling winds, walls of snow, savage beasts and generally inhospitable everything.
Keep the magic magical. Nobody knows how tall the mountain actually is, just that you can't reach the top. How did it form? Just like on Earth, no one actually remembers. There are legends of angry gods, powerful spirits or the will of nature itself. Wise men will form hypotheses of great power welling up from beneath the earth or stars falling from the sky but no-one actually knows.
**More Concrete Magical Solutions**
* The mountain could be some sort of growing rock; the gowth of which outpaces erosion.
* the base could be covered with some sort of magical forrest whose roots dig far into the rock and stabilise the entire mountain.
* The entire plantet (if your world actually is one) could have formed around some sort of huge rigid and angular object and the mountain is simply part of the object that protrudes from bellow the crust.
* If your world isn't a regular planet this object could simply be embedded into the surface.
* Anything that has a logical connection to your magic system.
In the end the specifics don't necessarily matter as long as you leave enough room for there to be a plausible explanation. The people in your world aren't omniscient so you don't have to be either (in case they are omniscient I don't think explaining the minutia of mountain ranges is what they do for fun).
[Answer]
The major ways to get mountains:
### Meteoroid impact
Impacts generally forms rings with raised center. There are several large examples of these across earth. Events large enough to form very large mountains are not life friendly on a global scale.
### Erosion
Glaciers and rivers can carve valleys into terrain that has been lifted by plate tectonics.
### Volcanism
Generally form on plate boundaries, with highest counts where ocean plate subsection is occurring.
If conditions are right you can have some really tall ones such as the Hawaiian Islands and Olympus mons. But generally this isn't your primary source of large mountain ranges.
If the event is large enough such as the Siberian traps. it forms more of a plateau then mountains. Which then requires Erosion to get mountains.
### Plate collisions
Many Mountain ranges were formed as result of continental plates colliding, but not subducting. Appelachian Ural mountains, are two examples of this. Swiss alps and much of south Europe are being affect by this as Afraca and Europe move towards each other.
### Plate subduction
The only way to get consistent large regions of large mountains.
* The Andes and Rockies are above where oceanic plates are/were subducting.
* Himalayas Mountains are above the subducting Indian sub continent.
### Conclusion
That is The most plausible way to get largest regions high average and high peak elevations is to have a continental plate subduct under another. Second best is to have a large run of oceanic crust
[Answer]
**Extrusion of matter from core**
A blob of iron/nickel was pulled from the core all the way to surface. Nobody knows how, perhaps micro small hole flew through the planet. The blob then erupted as a volcano chain, leaving very high peaks of hard and corrosion resistant metal alloy.
] |
[Question]
[
I'm designing creatures on my made up planet where animals evolved exceptional hearing and I'm wondering what kind of feet they might evolve to produce the least amount of sound when walking to avoid predators.
For some more context I imagined how life would evolve on a planet around a red dwarf with low luminosity. This made plant life extremely competitive to gain as much sunlight as possible with one species eventually evolving to nearly cover the entire sky with their leaves blocking out the little sunlight the animals had. Due to this animals have to mostly feed off fungi and dead leaves on a rocky environment with big tall tree like plants here and there. So prey and predator had to rely on sound to detect each other so I'm wondering.
What kind of feet would they evolve to reduce noise in a rocky/dirt environment?
[Answer]
## Cats and owls are prime examples of "silence".
Both cats and owls are nocturnal hunters with adaptations to move silently. Cats have toe beans (digital pads) which act as cushions, absorbing the sound of any footstep. Cats go completely unnoticed, even when walking on gravel. Owls have special fluffy feathers on the tips on their wings which serve a similar purpose: they absorb sound. Owls can swoop down on their prey with essentially zero sound. Even their wingbeats are silent.
Here's a video about owls to demonstrate: [link here](https://www.youtube.com/watch?v=d_FEaFgJyfA)
**Conclusion: soft paws and fuzzy fur.**
And if these two examples aren't alien enough for you, you can always use the world's quietest room as reference: [link here](https://edition.cnn.com/style/article/anechoic-chamber-worlds-quietest-room/index.html)
[Answer]
Elephants usually move very silently on their padded feet.
Excited, angry, or frightened elephants may vocalize loudly and crush bushes and animals in their way and knock over trees as they speed walk.
But elephants normally walk slowly, carefully, and quietly. So if an elephant wants to sneak away from, or toward, another creature, they usually can.
For example, in 2014 some tourists were seated watching wildlife at a reserve in Africa when the staff had a very large tamed elephant sneak up behind the oblivious tourists for a great photobomb.
<https://natureandwildlife.tv/moment-7-ton-bull-elephant-creeps-up-and-photobombs-group-of-oblivious-tourists/>
Obviously a wild elephant who had bad experiences with humans and was hunting down and killing humans could have snuck up behind those tourists to attack just as easily.
[Answer]
Deer have hooves but very small feet. They are not completely silent, but often move pretty stealthily.
For SciFi, one strategy would be to take this to an evolutionary extreme, basically dime-sized horned feet with a stubbled contact surface to minimize ground contact.
There are cliff-side goats (climbers) that have evolved padded 'soft' hooves, that give them amazing grip on a sheer cliff face.
So padded hooves, for silence, are very much within the realm of scientific evolution realism.
So is the mental strategy of some other animals; unlike us blundering humans, they don't walk blind: Like the cliff-side goats, they don't move without planning their steps. It is an evolved instinct. Many four legged animals do this, even dogs (if their morphology permits): their rear feet tend to land in or close to the footprints of their front feet; because the front legs have already tested the stability of the ground there. So that would also help with silence, if their mind is involved in finding silent steps for their front feet; even subconsciously.
] |
[Question]
[
I want to create a world where there is very little sunlight during the day -- at noon the light would be about the same as an Earth sunset. The planet would be Earth-like until something causes the sunlight to be reduced (so that life can evolve normally first).
So, what are my options? What could possibly prevent most of sunlight (not ALL) to reach the planet's ground, considering these requirements:
* It must be stable, meaning, continuously block some sunlight during
millions of years, if not forever
* It can be something completely natural or "kickstarted" by humans (because of their environmental
damage for example)
* The planet setup and the star must stay the same: an Earth-like planet with 1.4 earth masses, in a double planet system with another, smaller Earth-like planet. The star is sun-like. Anything can be added to this as long as it doesn't hijack the setup.
* It should keep the climate as close to Earth-like as possible. I read that dense clouds can have this less-sunlight effect, but I don't want dense clouds everywhere all the time. I want to keep the Earth's diversity in climate and environments.
My goal is an alternate Earth with just the sunlight being missing, I'm trying to get everything else as normal as possible, so I need to know what effect each option will have on the planet (ex. temperature drop) so I can work on solving those problems one by one later.
So it's alright if life is supposed to go extinct, the humans will have plenty of time to find ways to avoid that. I also expect life to evolve very differently with less sunlight, even if the rest is the same, so no issues about that.
Magic or a bit of handwavium is acceptable, as long as there is a somewhat clear understanding of how it works and its consequences.
[Answer]
**Orbit change**
[](https://i.stack.imgur.com/Czj0h.jpg)
<https://solarsystem.nasa.gov/news/925/what-does-a-sunrise-sunset-look-like-on-mars/>
A rogue planet plunges through the systm and alters the orbit of your planet. Your world moves farther from its sun and enters a new stable orbit. Other planets in the system did not fare so well, one plunging into the star and the other being thrown out of the system.
It is darker farther away. It is colder. That is the new way of things. Life adapts.
---
OK - exactly how far away does the planet need to move? Farther away than the orbit of sunny Mars, it turns out.
<https://en.wikipedia.org/wiki/Daylight>
>
> Illuminance Example 120,000 lux Brightest sunlight
>
>
> 111,000 lux Bright sunlight
>
>
> 109,880 lux AM 1.5 global solar spectrum sunlight (= 1,000.4 W/m2) [3]
>
>
> 20,000 lux Shade illuminated by entire clear blue sky, midday
>
>
> 1,000–2,000 lux Typical overcast day, midday
>
>
> 400 lux Sunrise or sunset on a clear day (ambient illumination)
>
>
>
So sunrise / sunset at 400 is 0.003x of bright sun at 120,000.
<https://en.wikipedia.org/wiki/Sunlight>
[](https://i.stack.imgur.com/vX8MA.png)
1 AU is the distance from the sun to Earth. Saturn is at 10 AU and is 1.1% of Earth sunlight. Uranus at 20 AU is 0.2%. You want 0.3%. So somewhere between 10 and 20 AU will reduce sunlight of your planet to the desired amount.
[Answer]
With reduced sun light, plant life won't develop as it did on Earth. With different plants there will be different plant eating animals. Similarly, reduced sun light will also reduce the temperature of the planet, which again will affect both plant life and animal life.
One way to get reduced sun light, compared to Earth, is to have a cosmic dust cloud permanently between the star and the planet. Alternatively, the star could be a reduced energy output star, such as a red dwarf.
An artificial way to get reduced star light on the planet is to have Dyson spheres or a Dyson swarm in between the star and the planet. Energy from the Dyson spheres/swarm can then be directed to the planet so intelligent life there can use it.
[Answer]
## Change the humans, not the sunlight
>
> My goal is an alternate Earth with just the sunlight being missing.
>
>
>
You still need the light of the sun for heat and growing food and stuff; so, instead of eliminating the sunlight, simply eliminate our ability to see it. For about 0.5% of the human population, this is already the case. We call it blindness. There are many ways to cause blindness. Parasites, viruses, drug overdoses, genetic disorders, and physical trauma are the big ones though.
To modify humans to be blind for millions of years you can't rely on parthenogens like parasites and viruses since human will eventually become either resistant to, or remove these things from our environment. You also can't rely truma or drugs since those only effect a single generation.
Your best bet here is a genetic bioweapon. Genetic bioweapons are the weaponized form of gene therapy where you design an weapon to manipulate the genetic composition of it targets. Such a weapon could in theory inflict a blindness by inserting a genetic disorder like norrie disease into all of its victims causing rapid retinal detachment. Unlike traditional bioweapons, this weapon would cause not just blindness in its victims, but in all of their descendants as well. If such a bioweapon were to get out of hand, you could eliminate the genes from the human races required for seeing permanently.
>
> I want to create a world where there is very little sunlight during the day -- at noon the light would be about the same as an Earth sunset
>
>
>
Many vision disorders do not cause complete blindness. Something that clouds the corneas or kills off all of your rod receptors could cause the world to appear much darker without actually blinding you completely.
Normally, any civilization with the advanced bio-engineering skills required to make such a weapon, could also fix the damage given enough time, but the problem is that once you blind all of the people with the skills required to fix it, there will not be anyone left to read the computer screens needed to fix it. Most of human knowledge will be lost simply because it is not available in braille or any other handicap accessible format. And even if you do have it in braille, 99.5% of the population would suddenly become illiterate; so, the people who need to read it will be unable to do so. In all probability, civilization will collapse long before most people can learn to deal with their new found blindness, and civilization will have to be rebuilt from the ground up were blindness is the new norm.
[Answer]
* Ancient dying star, a la Tales of a dying Earth.
* Spacetime singularity which is sucking up the star's light.
* Epidemic of opthalmological disease, reducing the visibility of light by the population.
[Answer]
## Decrease the amount of light arriving but increase greenhouse gases
Earth would be about 30°C colder if it was at its blackbody temperature, i.e. received the same amount of light but didn't have a greenhouse effect. The core idea here is to decrease the amount of light arriving while increasing the amount of greenhouse gases to maintain your planet's temperature.
One option is to be like Venus and have double digit percentages of CO2 instead of a few hundred parts per million.
There are also several relatively non toxic greenhouse gases that are hugely more potent than CO2: methane (23x more potent), CFCs (1000x more potent) and SF6 (A whoppimg 20000 - 50000x!)(1).
If methane or CFCs or SF6 are present in significant (not enormous) quantities, you could increase the temperature of Earth hugely.
Now, the amount of heat absorbed/emitted by a planet is proportional to temperature to the 4th power; if you can increase the greenhouse effect by 40 degrees, then you could have the amount of sunlight reduce by 50% and still have the same temperature; increase it 60 degrees and you can have it reduce by 65%. 100 degrees allows 85%.
See e.g. <https://www.astro.indiana.edu/ala/PlanetTemp/index.html> or other planet temperature calculators out there; this forum doubtless knows many.
Maybe mankind could deliberately set off a methane clathrate gun or produce ludicrous amounts of SF6 to compensate for some event that knocked the planet further away from the sun. Willk's orbit change suggestion would work nicely.
(1) SF6 is incredibly inert chemically but is very heavy so it builds up in the lungs of animals if present in any significant quantity, eventually choking them. Your fauna would need some way to expel it from their lungs, maybe l by totally displacing all the gas in their lungs when they breathe out, or by means of an enzyme that binds to it and transports it to the digestive tract. I assume CFCs would have the same problem. Methane won't; it's light.
Edit: I'm guessing that seasons and maybe polar-equator temperature differences get minimised by doing this.
[Answer]
**Reducing Sunlight**
There are many ways to reduce sunlight (as told in other answers):
* Move world to a farther , stable orbit.
* Some kind of sunscreen in between.
* Light is sucked away
* Fusion reaction on the sun becomes slow.
* Some phenomenon disintegrates the sun, taking many smaller fragments
away, and size of the sun is reduced.
* Small shiny spherical particles float in upper atmosphere which
reflect, refract, disperse light (like water molecules after rain).
* Some kind of light emitter, which emits light causing destructive
interference.
**Bad Effects of Reducing Sunlight on Humans**
* Low Vitamin D causing weak bones
* High Blood Pressure
* Low levels of serotonin causing higher risk of major depression
leading to mental health problems
* Reduced sunlight exposure during childhood increases the risk of
developing multiple sclerosis
* [Studies](https://parentingscience.com/kids-need-daylight/) have shown that children in dimly-lit rooms suffer learning
deficits
**Bad Effects of Reducing Sunlight on Plants**
* If plants do not receive enough light, they will not grow at their
maximum rate or reach their maximum potential, regardless of how much
of any other variable – water, growth medium or fertilizer – they
receive.
* 1% less light will give 1% decrease in plant growth, resulting in a
1% lower yield. Fruits or grains need sunlight to get ripe.
**Conclusion**
You may make a wold with low sunlight but the life will not be the same. It may finish at all or may become something entirely different.
[Answer]
# Tidally locked double planet
Early during this planet's history, its rotation was at a different rate than the orbit of the smaller planet around it. However, its rotation rapidly slowed due to tidal effects. Because the smaller planet is much heavier than the Moon, this didn't move its orbit outward nearly as much as the Moon's. Because of that, your planets have now settled into a long day that is still much less than a month, with each presenting the same side toward the other all the time.
That by itself means that there is no midday sun. Note, however, that the other planet, large in the sky, is as warm as the ground, so the loss of heat into space is also reduced.
Light can also be reduced by other effects. In our solar system, the "[zodiacal light](https://en.wikipedia.org/wiki/Zodiacal_light)" is produced by dust from Mars that extends far away from it. Suppose your smaller planet releases lots of dust due to the combination of weaker gravity, perhaps an arid landscape (all its water and air having escaped its gravity only to land on the larger world), and maybe some extreme volcanic events (maybe it isn't totally tidal locked relative to the larger planet, which would be odd, but we just suppose it originally rotated unreasonably rapidly?). This dust might fog up the local neighborhood and block the light of the star. I admit that's quite a bit of dust, but we have the example of Saturn to suggest that such astronomical phenomena *could* be highly visible with the right set-up.
[Answer]
## Exodus-style strange darkness
God is angry at some atrocity that mankind has perpetuated for too long. He sends warning and then alters physics overnight so that fusion produces 50% less light. There's probably chaos throughout the rest of the universe but most effects except the light level itself more or less cancel out in Sol-like systems. He sent a detailed enough warning that it's basically understood what has happened, at least once reality is acknowledged.
People respond by attacking the messenger, probably.
Edit: Just saw the 'science based' tag. Substitute in some undiscovered physics integer constant halving if you really dislike a theological solution. Less satisfying, IMO, but does the job. Astronomers can infer what has happened over a few decades as the night sky changes.
] |
[Question]
[
I have an earth-like planet in a fantasy setting with two moons, one of them made of crystal. It will be a fantasy crystal, properties TBD (probably by some of the answers to this question).
My main question is, would I be "ruining" night time by putting a solid crystal moon in the sky of my world? I'm not trying to fully turn night into day here.
I'm not sure I can really picture what this would look like, how the sun would interact with a crystal moon. I imagine, no more moon phases... but would the intensity of light from the moon change depending on the angle the sun hits it (not looking for math just in general)? Could it cast prismatic rainbows on the planet sometimes or all the time? And would it be dangerous at a solar eclipse, whether from intensified sun beams or extreme brightness?
If this moon would be too bright, is there a compromise I could achieve, like say, making the moon just 50% crystal? Or making sure the core is fully opaque and can't transmit light through the entire moon?
[Answer]
**Refraction/diffraction**
If you have a moon that consists of a *single* crystal, the sun may shine through as diffuse light during a solar eclipse. The crystal would show its color, like it does with the full moon, but there could be [additional shades of different color](https://gem-matrix.com/sunlightandruby), inside. To have this effect, the crystal should be high level of purity. A crystal moon polluted, or consisting of many crystals will not be translucent.
**Reflection**
Reflection will depend on type of gemstone the moon consists of. Color is most important, white will shine.. maybe too much. In any case, don't expect a shiny surface. An extremely hard stone like diamond could preserve its crystalline surface for some time, but in space, the issue is high energy particles. Diamonds [cannot handle energetic protons](https://www.hzdr.de/db/!Publications?pNid=head&pSelMenu=0&pSelTitle=11069). The shape will be preserved, though, resulting in square patterns shining through. Diamonds can have many colors, ruby's are red or blue. Inhabitants of the planet would enjoy their colored moon every month, shades seem to glow over its surface. The edge of craters are sharp, sometimes you see sparkles of light. It will be brighter than the moon, I guess.. Our moon reflects only about [3-12% of the sunlight](https://www.google.com/search?client=firefox-b-d&q=how%20much%20light%20reflects%20moon%20percentage). Planet Earth [would reflect 20-26%](https://www.google.com/search?client=firefox-b-d&q=reflection%20in%20space%20amount%20energy), considerably more. [Polished copper can do 70%](https://www.google.com/search?q=reflection%20coefficient%20materials), so you could expect a tenfold increase (or thereabout) of the moonlight, especially when the crystal is homogeneous and having a light color.
[Answer]
Your Moon would look just like ours.
Light only penetrates transparent/translucent materials up to a depth, which varies by material. Water is quite transparent for a few meters but even on the clearest lakes you can't see much deeper into them. Our atmosphere is perfectly transparent for more than a hundred kilometers, but when it gets thick you start losing some colors. This is why sunsets are reddish.
Consider Jupiter. Its atmosphere is as transparent as ours. We can see a few hundred kilometers into it and then we just see red and brownish patterns.
Solid crystals tend to be less transparent than gases. Add to that, any asteroids and comets impacting on that Moon will deposit non-transparent impurities on the lunar surface.
[Answer]
It depends on the shape and material of the crystal, the more pure the crystal and the more transparent it will be, making it semi-invisible in the sky acting like a giant magnifying glass, burning people like ants. More realistically, it wont be pure and won't be of the perfect shape, reflecting a lot of light but not enough to burn someone alive, maybe just enough to give them cancer through excess radiation. Even more realistically, it will be covered in dust from million of years of meteorite impacts distrupting the surface, making it into a normal moon. There are planets made of ''diamonds'' in the real universe, and they don't look like clear crystals.
[](https://i.stack.imgur.com/rehQU.png)
[Answer]
## Night will globally still exist
It just may be a little brigther over the whole globe or there will be thin burning line somewhere and dark night at the rest. Or anything between including rainbow effects and such.
But if it is the "moon" and not "co-planet", it means it is way smaller, than the earth - so it can get a way smaller angle of sun light (that means way less of sun energy) - an so even if it somehow reflect ALL of it to the earth, it still be way less, than Sun shine thru the day.
So "day" and "night" would still be vissibly different on the globe globally.
It may by possible (with some speacial cases) to have some area(s) on globe, which would be light at night as well as at day, if the moon would reflect large portion of its share of Sun light there, but it would be just about size of the moon (at 100% effectivity), with rest of globe in dark.
Or the night may be little lighter globally, but not as much as at day.
Anyway there is lot of stars at sky, so night is not totally dark anyway, it just may seem so to eyes, that are not sensitive enought. (And there is a problem with sensitivity range, if you want to see both under just stars and on full sunshine, so it is usually evolutionary impractical have such effective (and cost) eyes if you can cope some other way)
[Answer]
**Surface, refractive index, angle of incidence, transparency of the crystal, color of the crystal**
The amount of light received by the planet depends on type of surface, refractive index of crystal, angle of incidence of light, transparency of the crystal, color of the crystal etc.
**Rough surface**
If the surface is rough and unpolished, then reflection will be diffused. You will see a brighter moon but not very much (eye's response is logarithmic).
**Polished surface**
If the surface is smooth, polished, spherical and the crystal is transparent (like quartz, diamond, ice, sapphire), the moon will act like a big double-sided convex lens. Most of the light will pass through and little will be reflected. Light may disperse at certain angles of incidence (like in water droplets after rain causing a rainbow) and you may see rainbow like colors.
**Surface with large smooth planes**
If the surface of the moon is in the form of large smooth planes, then specular reflection, refraction, total internal refraction and dispersion will occur depending on the refractive index of the crystal and angle of incidence. You will see a multicolored glowing ball.
**Solar Eclipse**
When solar eclipse occurs, the sun will not be black but dimmed because light incident at angles greater than critical angles will have total internal reflection.
Only light incident at angles less than critical angles will pass through.
] |
[Question]
[
Some evil scientist, let's call him... Dr. BBEG, has manufactured a potent, powerful disease. He has full control over the bacteria's genome now, but once he releases it... not so much. However, in case some pesky group of Paladins, Wizards, and Rangers arrive and mess it up, he obviously needs a kill switch coded into the bacteria's genome. He doesn't want the kill switch to get evolved out, however unlikely this may be. In fact, he doesn't want the disease to change at all.
Can he create a bacteria disease that does not evolve and/or fixes errors in the genome of it's descendants?
Bacteria Details
* Similar to the Black Death in makeup and symptoms
* Vaccines don't matter, the world isn't at that tech level yet. He's using magic to make the disease.
* He can create anything that we can see today in the natural world, or that we can create with CRISPR and other genetic engineering methods.
* I don't *think* he can use artificial selection, because the whole goal is to STOP evolution, but if you can think of something, then sure, use it.
* He has ~250 years to create the disease.
[Answer]
### The problem with proofreading
The simplest way to inhibit mutation is to insert error-checking mechanisms. Real organisms use these to make genetic damage less likely - but there is a significant problem with relying on these.
Any proofreading mechanism can fail. You can reduce the chances of these failures by increasing the number of error-checkers - but the more strict they are, the more they will inhibit the reproduction and survival of the organism itself.
If a bacterium has a mechanism that will cause it to self-destruct (or even become less efficient) if it detects even a small bit of corruption, it strongly benefits the bacterium to *get rid of the error-detector itself*. Which means that strains which mutate out your constraints will dominate, and you'll be right back where you started.
In nature, there is a fine balance between checking and repairing DNA damage that will inhibit the proper functioning of a cell, and being so strict that it reduces the efficiency of the cell. Multicellular organisms are usually more strict and may include self-destruct mechanisms as well - but this is because these mechanisms protect the entire organism from cancer, so there is strong selection pressure in their favor. For a free-living bacterium, self-destruct mechanisms are pretty much always detrimental and will be selected against.
### But you don't really need to stop evolution entirely, do you?
Really, the only problem you have is the issue of the bacterium deleting the kill switch. So what you are really looking for is a mechanism to make the kill switch *itself* something *beneficial* (when it's not "activated") - and something that will become less beneficial if it mutates. That way, evolution will work in your favor - strains that delete or modify the kill switch will be *intrinsically* less fit (NOT due to an internal self-destruct switch) and weeded out by natural selection.
The question is, how?
### Social bacteria
Yes, bacteria can be social. In fact, most of them are to some degree - conjugation, quorum sensing, and the formation of biofilms (colonies of bacteria, often involving multiple specialized roles) all involve chemical communication between bacteria. The ability to exchange information about one's surroundings, cluster into groups, and exchange resources is as beneficial for microorganisms as it is for us.
If you want to make sure the kill switch doesn't change, make the kill switch part of this chemical "language". Any bacterium that alters its switch will be unable to "understand" the information from its peers and will be unable to cooperate with them.
If you want to be really fun, you can even program the bacteria to recognize cells containing the switch as "allies" and make them hostile to organisms that are *missing* the switch. This will allow them to defend themselves against rival species (and their host's immune system) in addition to actively killing off their own mutant strains.
The kill mechanism itself is simply a toxin that mimics the chemical the bacterium uses to communicate. Metaphorically speaking, it's a "killing word" and the only defense is for the bacterium to be "deaf" - which will make it less functional.
As a bonus, if the ability to cluster into biofilms is a significant part of what makes the disease dangerous to humans (it often is), even if a strain becomes solitary and eludes the switch, it will be significantly less dangerous and therefore no longer a problem.
[Answer]
**[Error detection code](https://en.wikipedia.org/wiki/Error_detection_and_correction)**
Cellular machinery already involves some error *correction* codes. This prevents quick death from accumulated harmful mutations while still allowing the right mutation rate to power evolution. The remaining bad mutations are eliminated by the affected line of descent dying out. Remaining good and neutral mutations are not eliminated, of course.
Instead of beefing up the existing error correction, your bio-engineer can do something simpler: **Make sure *all*\* mutations are very harmful**. Implement an enzyme which traverses the whole DNA every now and then, and calculates some kind of checksum; Check the checksum, and if it does not match, trigger a kill switch. E.g. synthesize something poisonous right inside the bacterium.
To be sure, include several different mechanisms like that. Theoretically, a single error detection code can be made as safe as you please, but you know, life tends to find a way. This way, when one kill switch is disabled, another one takes out that bacterium.
\* Actually, all except some astronomically improbable ones; No (practical) error detection code is perfect.
[Answer]
**The bacteria do not replicate.**
They are completely deficient in multiple pathways used for replication. They eat just fine but they do not reproduce at all. Thus they do not evolve. Each bacterium is synthetic, a product of the lab which uses machines, viruses, nonbacterial hosts and chemistry to make the bacteria.
The bacteria that infect a person are the ones they get. The bacteria will not increase in number. Those individual bacteria that get established are brutal little toxin machines and the toxins (which include human IL4 along with the typical Yersenia repetoire) leverage the excitability of the immune system to kill the host.
Fortunately the Black Death is a fine model for a disease like this. Your malefactor infects rats with loads of his synthetic bacteria, dusts them with fleas and releases them into cities. Infected fleas move the bacteria from rats to humans, infecting the humans with their attempts to feed: standard bubonic plague stuff.
Each outbreak will be limited by the number of rats released and will eventually peter out unless Baddy shows up with fresh rats. And sometimes he sprinkles bacteria over the sleeping city because he is that kind of guy.
---
Background reading: synthetic bacterium. <https://en.wikipedia.org/wiki/Mycoplasma_laboratorium>
[Answer]
>
> Can he create a bacteria disease that does not evolve and/or fixes errors in the genome of it's descendants?
>
>
>
A genome which doesn't get fixed leads to a quickly dead organism. Errors happen very frequently, because the nucleic acid is not stored in a safe buried in a concrete swimming pool under a granite mountain. It is subject to an environment with several aggression, each of which creates errors which need to be repaired to keep the code working.
In other terms, you can't wear a pair of shoes while wanting it always shiny without polishing them. With use comes dust. You have to wipe that away.
[Answer]
**redundancy**
To do this what you would want is at least five copies of all the DNA that is checked by at least four separate systems. This is needed, since if an error occurs in one it can be fixed, but if an error occurs in two strands and they match you need the remaining three to out vote the two wrong strands and fix the error. Luckily the chance of getting three errors in one base pair that are the same on three strands is very very low. You also need about four checking systems since if three of them fail due to a genetic error the remaining one will fix them all.
This will need to engineered from the ground up since nothing like this exists in nature. The only thing that is close is [deinococcus radiodurans](https://en.m.wikipedia.org/wiki/Deinococcus_radiodurans). This bacteria has two versions of its DNA and will repair double breaks with a very robust DNA repair system. It still get new mutations all the time. To make this more redundant we need to make a system that can do this but 5 way with a system that determines the most common base pair before recombining.
**compromised system**
Since this doesn’t evolve, people will become immune to it very fast. There are no strains, and anyone immune to one pathogen is immune to every other version of it.
[Answer]
A large bacterium could [self-check its own DNA](https://worldbuilding.stackexchange.com/a/26188/6933).
Otherwise, the bacterium uses a combination of protein receptors that allow it to recognize other cells and bacteria it passes by:
* no receptor match: foreign cell, do nothing
* complete receptor match: a sibling, do nothing
* partial receptor match: mutated strain, kill the cell by mutual annihilation
A substance *permanently* binding those receptors will neutralize the bug, and is your "kill switch".
Of course, the bacterium could mutate so that it loses the "kill mutants" code (B-form), and *then* other mutants could evolve; but the B-form would *also* need to out-compete the A-form.
[Answer]
In Larry Niven's *Tales of Known Space* Universe, one species in particular that stands out is the Bandersnatch. Artificially created billions of years ago, it was specifically designed to not evolve. They accomplished this goal by creating massive cells and DNA strands, as thick as a human finger, that were both robust and all but impervious to mutation. Scaled-down, that might be an angle worth pursuing.
] |
[Question]
[
Can I eliminate a dry continental high pressure spot inland by adding a huge body of water in the middle of it? Like this sample picture:
[](https://i.stack.imgur.com/vipir.jpg)
The red arrows around the continent are warm ocean currents and the light blue are cold. I have placed my deserts where the cold currents touch land, because basically that is the way that works on Earth. (Cold current = desert. Warm current = forest/good temperate land)
You can think of it at the same position as South America is on Earth. So mountain range will be like Andes, so on, so forth.
If I add a huge lake, internal sea, like the Caspian sea for example, can I avoid that the middle of a continent would turn into a desert or dry spot due to dry high pressure?
[Answer]
The short answer : yes, to an extent, depending on the unique circumstances of your continent.
I know that doesnt really answer much, so;
**The Long answer**
I am going to be assuming earth like conditions for your continent (4 seasons, 21 degree tilt, 365 day years, etc)
Vegetation levels depend on environmental water levels and availability, as well as nutrient availability and soil composition, as well as surrounding vegetation levels.
When talking about water levels, I am not referring to only the level of the water table, but to ground water, air humidity, and by extension rainfall amounts.
**Airmasses are complicated**
Rainfall is mostly based on humidity levels and water vapor content, with a bit of geological circumstances.
The amount of water vapor that air can hold (100% humidity), depends on the temperature of airmass, and that is determined by where the airmass originates.
We get 4 main types of airmasses, Polar continental, Polar maritime, tropical continental and tropical maritime.
Breaking this down, Polar airmasses are very cold, and therefore cannot carry much water vapor, so you are unlikely to get a lot of rain from them. You can see the effects of this with places that are near the south pole (Argentina, South Africa, Australia) and the North Pole (Northern parts of Canada and Russia).
Tropical airmasses however, are warm and can carry a higher amount of water vapor. When rain falls from these airmasses, you can expect a lot more rainfall (such as the gulf of Mexico, Gulf of Guinea and the Bay of Bengal)
The continental Airmasses generally do not have a high amount of water vapor to start with, do to forming over land, while maritime airmasses start at almost 100% humidity levels.
So, depending on where your continent is placed, the base vegetation levels will change. Near the poles, like Australia, you will generally be starting with a desert. between the tropics and the equator, chances are you will have a lot of vegetation even without a central lake.
Looking at a map though, and you will see there are some places that do not conform to this, like New Zealand, Chile, Mexico, most of the Middle East and Northern Africa, areas of Spain, etc.
Why?
BECAUSE AIRMASSES ARE COMPLICATED
It is not enough to just have a high humidity content, you need to get the water out of the air. For permanent vegetation, you need a permanent solution, so you can rely on the hope that it randomly rains. Take for instance the Okovango Delta in Botswana, the dry season vs the wet season.
[](https://i.stack.imgur.com/CzbUu.jpg)
[](https://i.stack.imgur.com/LBYUt.jpg)
You need a permanent, geological feature, such as a mountain range, which provides an uplifting force to the airmass. As the air rises, its temperature drops, and the amount of water it can hold decreases, which results in rain.
**Wind Direction and Lifting Force**
As shown with the answer by **L.Dutch** you can have an ocean of water right next to a desert, if the wind directions are not favorable. For Western Africa, the wind is generally coming from the north east, which is straight out of the center of the continent, blowing the warm moist air back out to the ocean.
From your image, I can see that there is a mountain range on the West coast, which would provide that lifting force. I am going to compare it to Northern South America, as it is quite similar.
[](https://i.stack.imgur.com/gjr5x.jpg)
[](https://i.stack.imgur.com/Yufsp.png)
If your airmass is coming from the West, it is going to get caught in the mountain range, and only the Western coast would get any rain, with the central continent acting as a desert. If however your winds come from the east, baring a bit of random rain over the central parts, will rain on the mountains, and the water will flow into rivers, which you can take back to the east coast, providing lots of ground water.
As to the existence of a central lake, unless your continent is very small, it would have a negligible effect on its own.
Two examples are Lake Chad and even the Caspian Sea
[](https://i.stack.imgur.com/aAAW1.jpg)
[](https://i.stack.imgur.com/ZMezC.jpg)
In both of these, you can see that other than a small area around the lake (or sea) there is pretty much still desert. While lake Chad is still quite small, only about 35km across, the Caspian sea is over 1000km length-ways, and about 300km wide, yet still does not help much.
But wait, you might say, in America, the area around Lake Michigan (+ the other 3 lakes) is extremely vegetated, and I agree, as we now come to the last bit of my answer.
**Surrounding Vegetation and Soil nutrients and makeup**
This might seem counter productive, but the reason that my example lakes do not result in much vegetation around them is because they are located in desert areas. With no vegetation to hold the water and prevent drainage, any rainwater disappears very quickly. For instance, in Western Africa, it is currently still the wet season. For the past two months there has been almost daily rain, with at least 5 to 10 times having most of the area flooded by about a foot of water, since June. unfortunately, it drains quickly into the few rivers, and washes out to the ocean without being sucked up by any plants. As it does this, it washes away any topsoil, which is basically organic matter made up of dead plant pieces, bacteria and a bit of loose ground. Growing plants need that topsoil to grow, so having it removed prevents plants from growing. Less plants growing results in more topsoil being exposed to being washed away, and the cycle intensifies. Plants also need to come from somewhere, like a tree dropping some seeds. If there are no nearby plants to spread, they simply can't.
So in conclusion, Yes a central lake can help create a lush interior of the continent, but there are other factors that play a much larger part in determining whether you have an oasis of life, or a desert of death.
[Answer]
I don't think it will help much. Just look at this image taken from our real planet
[](https://i.stack.imgur.com/oP8dP.jpg)
that huge yellowish-brown spot is the Sahara desert, and it is still a desert despite having an entire ocean next to it.
If the prevalent circulation in your region has high pressure with dry air, this will very likely result in an increased evaporation, but that water won't precipitate in the adjacent regions.
Look at the Salton Sea in Southern California:
[](https://i.stack.imgur.com/6be0C.jpg)
it makes more greenery grows only where the water is channeled, for the rest it is still surrounded by a pretty much deserted area.
[Answer]
Short answer is yes. Depending on the prevailing winds a large part of that dry inland area would benefit from higher soil and air moisture levels.
The big question? **What explains such a large body of water being there in the first place**. And of course what sustains it?
Looking at the your map and assuming a latitude similar to that of South America the only logical way for the lake to exist and be sustained would be seasonal storms (either cyclones or monsoons) driven onshore by prevailing easterly (or nor-easterly) wind patterns which are usually prevalent over that section of the eastern ocean for part of the year.
Assuming the central plain is relatively flat a large lake or more likely series of interconnected lakes and marches could form, shrinking and expanding in time with the seasons. As other posters have noted you could use the Okavango delta as a working example and just scale it up.
Like the delta it doesn't necessarily have to be wet all year every year, a series of bad 'wet' seasons' would see it shrink significantly , only to refill when the rains returns.
[Answer]
warning: I am NOT a meteorologist.
summary of answer: a central sea will make the problem larger.
My understanding is that mountains have more to do with desertification than bodies of water because they have a bigger effect on wind patterns. In the trade wind zones of the globe the lee side of mountains are generally quite dry .. like the Canadian plains are dry while the BC coast is temperate rain forest .. for that matter, the Okanagan valley, closer to the BC coast than the Prairies but 2 ranges of mountains from the ocean, is in fact a desert.
You should also factor in snowfall .. winter snow is a major factor in providing ground water in the spring when new plants need a lot of water to facilitate seeding. If they don't get it the ground is exposed to wind erosion and desertification in the long run. And on our Earth central plains do get a lot of snow, which is what keeps them from being deserts.
Your map shows prevailing winds from east to west with your mountains on the west coast, so any moisture coming from the eastern ocean will be distributed fairly evenly across the continent so no central desert.
Let us also remember that high pressure zones are downdrafts .. pressure is raised by the movement of air from surrounding areas INTO the high pressure zone. Low pressure areas are caused by conditions that create updrafts .. all low pressure weather systems, from thunderstorms to hurricanes are heat engines formed over large bodies of water that are being heated. So putting a big body of water in the centre of your continent is not going to solve the high pressure area problem.
So you need to find what land features channel prevailing winds, preferably of cold arctic air, into the centre of a continent. Sorry, I don't know of any.
-- a further update -- there is an answer that discusses continental weather patterns in some detail, have a look at it [Creating a realistic world map - Currents, Precipitation and Climate](https://worldbuilding.stackexchange.com/questions/1353/creating-a-realistic-world-map-currents-precipitation-and-climate?rq=1)
] |
[Question]
[
In my continent (On Earth), there is one specific part of the land that is pretty much all covered in trash and waste, and the surrounding bodies of water are also polluted and so are part of the surrounding regions. So my question is could there be trash on one part of the land with barely any plant life and no trash on the rest of the continent? By the way, there are no humans on this continent all the trash comes from other places.
[Answer]
# Absolutely yes.
[](https://i.stack.imgur.com/YdGqc.jpg)
None of this trash on a beach was dropped there by humans.
Much of it was dropped *many thousands* of kilometers away.
The distribution of the trash is not even though. Some places will concentrate it, some places will disperse it. It depend on the specific confluence of currents and wind patterns just *where* the trash heads to, and whether it gathers in offshore gyres or gets dumped on a beach. Wind and waves can even act to strip all the mobile trash from one location, and redeposit it some distance away, much the same way that some locations deposit sand and form a beach, while other stretches of seashore strip the shoreline down to bare rocks.
And not only oceans can carry trash, the wind does a great job of it too:
[](https://i.stack.imgur.com/xAnYF.jpg)
Now these plastic bags did not come from thousands of kilometers away, but they did blow in from the town which is some 30 kilometers upwind.
As for how far trash can travel:
Consider the very interesting case of the ["Friendly Floatees"](https://en.wikipedia.org/wiki/Friendly_Floatees)
In 1992 a ship accidentally lost a container carrying a cargo of plastic bath toys in the Pacific.
These toys have been appearing **all over the world**.
Once a floater is in the ocean, it can get just about anywhere where the ocean gets, given enough time.
[](https://i.stack.imgur.com/BmAfC.png)
[Answer]
Trash, like any other substance, can be distributed by weather agents like wind and currents, so it is plausible that it reaches even remote locations.
Take a look at what happens with volcanic hashes, dust, plant seeds, plastics and so on, just to consider a broader definition of "trash": they are carried over for even thousands of kilometers and spread around the globe.
It's however unlikely that really no trash gets deposited in a specific part of a region. You would need to have it excluded by all water and air circulation, so that nothing can carry anything from outside. Just for a reference, even remote regions like the Himalaya or Antarctica get their fair share of air carried pollutants.
] |
[Question]
[
I want my planet's atmosphere to have roughly 10% argon so that its inhabitants can easily use it to color their lights purple. But I'm not sure how to explain the cause of this high argon content. Does anyone have any ideas?
Some of my ideas include argon warfare and argon-breathing plants.
Would this atmosphere even be feasible?
Edit: Thanks for answering, it seems that it would be unfeasible. I'll ditch the argon idea and keep an Earth-like atmosphere.
[Answer]
Argon (in particly, $^{40}\text{Ar}$) in terrestrial planet atmospheres tends to come from [the decay of Potassium-40 in rocks](https://en.wikipedia.org/wiki/Isotopes_of_argon). Therefore, higher crustal concentrations of potassium would likely lead to higher amounts of argon. It's possible that a planet not subject to impacts early in its life [would retain more lighter elements in its crust](https://astronomy.stackexchange.com/a/13504/2153), like potassium, and therefore would produce more argon over the course of its life, leading to an atmosphere with a higher fraction of argon - particularly if it initially had more quite a bit more potassium than Earth. Tectonic activity might be a reasonable pathway to actually releasing this argon.
It's also worth noting that Argon is slightly heavier than oxygen and nitrogen. This means that a slightly lower escape velocity could lead to the planet losing more lighter gases while still retaining all of its argon. So pick a potassium-rich, relatively unscathed, tectonically-active, low-escape velocity planet!
On the note about plants using argon: As L.Dutch mentioned, argon is an inert gas, and as such does not easily undergo chemical reactions. Therefore, I'd be rather surprised if it played a key role in some modified photosynthetic process. On Earth, [it doesn't seem like argon significantly inhibits metabolic processes](https://ucanr.edu/datastoreFiles/234-197.pdf) provided that enough oxygen is present, but it's unlikely that it would actually be a key part of exotic reactions.
[Answer]
[Argon](https://en.wikipedia.org/wiki/Argon) is a noble gas, as its name suggests
>
> The name "argon" is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning "lazy" or "inactive", as a reference to the fact that the element undergoes almost no chemical reactions.
>
>
>
Because of this it cannot be produced by any biological activity.
>
> Nearly all of the argon in the Earth's atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earth's crust. In the universe, argon-36 is by far the most common argon isotope, as it is the most easily produced by stellar nucleosynthesis in supernovas.
>
>
>
If you want to have large amounts of argon, you need to have large amounts of [potassium-40](https://en.wikipedia.org/wiki/Potassium-40)
>
> Potassium-40 is a radioactive isotope of potassium which has a long half-life of $1.251×10^9$ years. It makes up 0.012% (120 ppm) of the total amount of potassium found in nature.
>
>
>
which doesn't seem that plausible, considering the relatively low abundance it has.
[Answer]
**Argon wells.**
Gases produced by radioactive decay can accumulate under impervious strata. Helium used to be a byproduct of natural gas recovery. Recently, helium prospectors deduced where helium would accumulate, and drilled the first helium well.
<https://www.chemistryworld.com/news/scientists-unearth-one-of-worlds-largest-helium-gas-deposits/1010122.article>
So too argon. Both in our world and yours, it should be knowable where argon would accumulate because of the geologic features of the ground. Your people have argon wells, the same way we now have helium wells.
] |
[Question]
[
I'm in the process of writing a story (just for fun with my son) that takes place somewhere around 80-100 years after an end-of-the-world event. Right now, that event is some type of plague, but that part will be secondary to the story. The story is set around 2100 or so, with very few survivors. Villages have formed throughout the US, but for the most part, people are not entirely sure of what exists outside of their own village. For most people, each day consists of farming, foraging, and just trying to stay alive.
The story focuses on a twelve-year-old boy who decides to leave his village for one of two reasons, and I'm stuck on which one (if either) is more plausible, given the time that has passed since the plague/virus/disease.
1. The boy has spent the last year or so building a radio (after scavenging for parts, books, etc.). One day, he hears someone (or maybe a recording) on the radio. He wants to tell the others, but he knows they will not believe him. The boy's father went missing a few years prior (on a scavenging expedition), and although the boy does not think the two events-the radio transmission and his father disappearing-are connected, he decides to leave the village to at least find some answers.
2. The boy, while looking at the sky one night, (he's very interested in astronomy) is positive he saw some type of blinking lights in the distance. He does not yet know it, but those blinking lights were from a helicopter (or airplane). He again does not think that the lights have anything to do with his father, but he decides to leave to find out.
In terms of world building, I'm wondering if either of these would work. I've done some preliminary research on HAM radio, but I'm still not sure if such a scenario with the radio would he possible or likely. Likewise, with most (I'm thinking close to 99 percent) of the world's population gone, how long would it take for something like an airplane or helicopter to become functional again?
Thanks for any feedback!
[Answer]
It would be very plausible that a clever 12 year old might be able to construct a crystal radio receiver (<https://en.wikipedia.org/wiki/Crystal_radio>) from electronics scrap given some simple instructions he may have found in old books or magazines. Especially if he was looking at ones targeting young readers since there was a time when they were quite common projects for teaching kids basic electronics.
It would then make sense that someone else with a decent transmitter and a bit more advanced knowledge may then actively target AM bands that would be easily received by simple radios like crystal sets if that individual's goal was to reach others by radio. In a world that's no longer impeded by government radio spectrum enforcement and thus transmission power is no longer regulated such a transmitter could have quite a large footprint around the world.
73s,
KI4PUT
[Answer]
## What fits the World?
I think you need to decide what your world looks like before you decide which way to go. With the increasing complexity of technology, the parts and equipment to either build a radio from leftover parts OR for someone to have an aircraft will require some real worldbuilding choices.
1. **Radio**: To build a radio in the reasonable near future will require a fair amount of specific knowledge your kid is unlikely to have if people in the village don't believe a transmission is possible. The nearest equivalent is if the kid were practicing witchcraft requiring a wizarding school. He wouldn't have the basic knowledge, would be unlikely to be able to read, have no real motive to build such a thing, and be viewed as wasting time or possibly doing something sinful in pursuing such a project to begin with. The parts available would be getting LESS amateur-friendly, not more as electronics becomes increasingly integrated and hostile to repair. If anyone has noticed, a lot of old electronics last longer and are easier to fix than new ones, and I'm guessing that trend will continue. As simple as this option seems, it's a stretch (unless dad left some pretty sweet parts behind for his son).
One more possibility for the radio is that people start building very durable products in the near future, and the radio requires little to make it work. That would require companies or governments to have a very different approach to products going into the future than the current trends suggest. But if engineers today started anticipating a catastrophe in the future (say, an endless series of COVID variants that might collapse society) then I could see a trend to build products that might reasonably last a REALLY long time (but be more expensive) on the premise that there might not be replacement units. This would probably mean the radio wouldn't require much more from the kid than a power source.
2. **Aircraft**: If an aircraft is flying where the kid can see it at night, then they have decent navigation. It's flying high up enough that no one heard it (I live near an airport) so that implies a decently high-flyer. The flyers don't care if others know they have tech (or they'd be sneakier) suggesting there needs to be at least a reasonable city-state somewhere with good parts supplies and decent tech/engineering to build/repair & maintain a plane this long after the industry supporting aircraft had collapsed. If you have or add such a place into your world, this is highly plausible. If you don't have areas rebuilding advanced tech, then this totally doesn't work and you need to come up with an excuse to have a radio.
[Answer]
TLDR: I feel both can work, depending on your preferred setting (clever/lucky boy with radio vs miracle with light), but I feel you should rather change some details:
**Radio** is more difficult to make for the boy, but not too implausible - the easiest and most likely approach I see is finding an old radio that is now supplied by lemon battery or something to make it work. It is not implausible that some other villages/nations/... have reinvented the radio (or never forgotten about it in the first place).
Here you have the problem that at least SOME will believe his story and try searching for signal on their own. So, the kid needs to have other reasons to not show his "invention". One suitable option is fear of an old radio being taken away - unlike crystal radio, this radio would be the only one in the village and harder to reproduce. Another option (that works for crystal radio too) is that he simply doesn't want to tell about the radio because he believes others were responsible for his father's disappearance and wants to leave in silence - while if he started babbling about a mysterious signal, he would be surely under constant supervision.
**Aircraft** is trivial for the boy, but requires functional world elsewhere. So, those villages could be simply abandoned to medieval-like life, like how there are still tribes living stone-age life.
If you want the whole world to be ruined, you might imagine to jump in a plane in a hangar and fly around. This is not all that likely as I doubt anything will be in working condition after a century, even preserved in a hangar. I can imagine future tech that doesn't have moving parts like "ionic wind" demonstrated few years ago could survive for a century if we are very optimistic. They have no idea how to make this, but it might fly again.
But there are simpler alternatives that would produce lights in a non-functional world - leds would still work to some degree even after decades in ruin, and you can easily make enough electricity for them with essentially iron-age tech if not even earlier. Maybe lemon battery again.
I also find it quite likely people wouldn't believe him if he told them about the flash, especially with a color laser pointer - because they would be used to just white sunlight and yellowish candles or similar. Also, if someone else was looking in the same direction yet the laser flash didn't hit his eyes, it is nearly impossible anyone would believe him: "Boy, I have been guarding these gates all my life and never fell asleep. There was no flash from this direction you speak of, nor any other." Everyone would trust the old guard here.
If you prefer to have something up in the air, put this pointer stuff on a glider, hot air balloon or similar, this is easy to imagine a post-apocalyptic world will manage to (re)produce.
] |
[Question]
[
Given inspiration from this post [here](https://worldbuilding.stackexchange.com/questions/120492/what-is-the-best-body-plan-to-allow-for-giant-size-in-a-terrestrial-animal), I have been working on a society of aliens in which each tribe lives on a single member of species of enormous megafauna. Let's call the megafauna the "whale" and the aliens on it the "barnacles." Both these creatures evolved on a moon (around Venus to Earth size) that orbits [Barnard's Star B](https://en.wikipedia.org/wiki/Barnard%27s_Star_b) using methane/ethane as a solvent rather and divergent biochemistry from creatures on earth. The relationship between these two would be that the whale travels through large deserts to get to the various oases around the liquid methane/ethane lakes that dot the moon. So the large body began to evolve as a method to avoid wasting away as it migrates through the desert. To get even bigger the whale developed a symbiotic relationship with the barnacles (the largest height is around six feet or 2 meters) where they, as detrivores subsist and specialize to eat its waste and provide protection from other large fauna and parasites by taking care of the whale. They build structures on their back and live on it as a nomadic [pastoralist](https://en.wikipedia.org/wiki/Pastoral_society) tribe. This allows the whales to develop a much bigger size with them being protected from being an easy, giant target and allows the barnacles to specialize in feeding on the waste of the whale and to develop intelligence and sentience to protect the whale, as a result of the vast supply of food they have access to from the whale. The whales live over two millenniums and reproduces barely above replacement rates, and the barnacles reproduce slowly and sparsely as well, living from 400 to 600 years.
So, given the anatomy of the creature in the answer to the linked question by TheBlackCat, and the description and features above, could the whale grow to have the total square feet of the top of its body be at a minimum of three acres (12140.6 meters) to hold a small nomadic tribe to live atop it, and, if not, how large could it get and would that still be enough to have a tribe larger than your average [band society](https://en.wikipedia.org/wiki/Band_society)?
Here is an image if you need a visual of the creature I am describing:
[](https://i.stack.imgur.com/ty7HB.png)
[Answer]
## You Will Need to Make it Flat
An animal is limited in how tall it can be. The taller you make it, the more weight you put on any given cross-section of it. So, if for example your whale were about 65 m wide, 65 m tall, and 185 m long (about how big it would be based on your illustration and minimum size), it's belly would be under the crushing force of ~6.5 kg/cm^2 rendering it completely immobile in anywhere near 1G of gravity. This would also cause so much compression that any blood vessels in the lower parts of its body would collapse causing it to die pretty rapidly.
For comparison, the tallest terrestrial animal ever was only about 17m tall, and that was only doable because it was not a solid mass of flesh like your whale would be. However, this limitation is not nearly so much of a problem in terms of width and length; So, if you instead had an animal that were 65m wide, 185m long, and only 1-3m tall, then any given vertical cross-section of itself could hold up its own weight with weight to spare. Infact, as long as it is not too tall you can make it pretty much as long and wide as you want as long as it has some way of providing nutrients to feed its entire body.
So instead of a giant whale, you should consider a giant flatworm, or maybe even a sort of giant millipede with many parallel lines of legs instead of just two
## But what about its central organ systems?
Another, though be it less limiting size factor is the scale of digestive/respiratory/circulatory systems on megafauna. The longer you make these system have to travel, the harder it is to get needed nutrients to all of the extremities of the body. Take blood for example, as you pump it out from your heart, all of the tissue between your heart and toes are taking up some of the oxygen. If you had to pump blood to a body part > 100m from your heart, it would not have any oxygen left to deliver to your extremities.... not to mention the extreme pressure it would create nearest to the heart for it to still have movement once it gets all the way dissipated.
You can solve for this with segmentation. A tapeworm for example is made up of many chained together body segments that can each function on its own. So your giant flatworm may in fact be made up of thousands organ sacs that are each responsible for its own respiration, circulation, and digestion. One way to do this is to treat your whale kind of like a lichen. On Earth, lichen is a symbiotic relationship between a producer (algae) and a consumer (fungus). In your world, many plants may be unable to survive indefinitely in one place due to water (or in your case, methane/ethane) deficits; so, your whale travels between sources consuming entire reservoirs at a time, and on its back grows plants that it gives some of that liquid reserve too, while also feeding off of the plants. Since it can simultaneously feed off of all of the plants from each of its body segments, it does not need centralised digestion or circulation; so, you can make it as wide or long as you desire.
## Explaining Barnacle Symbiosis
Instead of living off of the whale's waste directly, they could live off of the vegetation on the whale's back. They could eat the plants for food, tap their sap for hydration, and even use their wood for building homes, all without harming the whale ... and this is where the barnacle symbiosis comes in. On a whale with no barnacles, the layer of vegetation on a the back would be harder to maintain. Sometimes it would flourish, and sometimes a swarm of parasites will come along and eat all of the vegetation, and sometimes noxious weeds will take over poisoning the whale, and sometimes a larger predator will come along and try to make a meal out of the whale itself. But the barnacles are essentially an agrarian society. They deliberately cultivate the whale's back for crops of good vegetation that is safe for both the barnacle and whale while making sure to weed out any noxious plants and fend off parasites and predators.
[Answer]
It seems like there would be a finite limit to its growth, due to make a comparison of the limited size of land animals on earth. While biology could certainly allow for the whale to grow larger than most animals on earth,it seems as if it's size would then end up being limited to the strength and forces that the biological compounds and structures that make it up, that and internal bouyant sacks. Presuming they're carbon-based, some of the strongest materials biological materials they could potentially be made out of would-be diamond and carbon fiber, which have compressive strengths of 889 MPa and 470.4 GPa accordingly. I don't however, how to calculate the maximum load or size accordingly. According to this information, it does seem to be perfectly plausible. As for the potential size I can't tell you that.
[Answer]
**Frame Challenge: No Explanation Needed**
You ever hear of Rule of Cool? It's a trope where something just happens because the writers think it's cool, and the audience willingly suspends disbelief to enjoy the awesomeness of that thing. This is the "science" behind giant spiders, dragons, and countless other staples of fantasy *and* sci-fi.
In other words, you may not *have* to explain it at all! If you do, though, here are some ideas:
1. Quantum physics/magic
Due to some mind-boggling distortion of reality caused by the whale itself (or some ingested alien artifacts, like in that one Russian story I can't recall the name of, it starts with S and it's an acronym), the whale can handle the forces of gravity far better than the square-cube law allows. In other words, it can be gigantic and function normally because handwavium.
2. Alien materials
No one ever said aliens had to be like Earth animals, and you clearly understand this, but you haven't followed that to its logical conclusion, which is: *anything* can exist in this big, beautiful, and very much surprising universe. Perhaps the alien's biology is designed in such a way it can handle the strains of gigantism to function normally, or perhaps it's just made of materials far superior to the carbon compounds that form life here, things like tempered steel, titanium, or graphene (yes it's a carbon compound but it's not *organic* now is it?)
Seriously, it's an alien lifeform, you have room to work with. Intelligent design also works wonders if you want to go that route. Anyway, I hope this helps!
] |
[Question]
[
Airships fly thanks to their weight. The m3 you occupy should be lighter than the m3 of whatever you want to float around in (bit of a simplification). To achieve this they make a big balloon and fill it with a light gas, making it overall lighter than air.
Theoretically a vacuum airship is thus the best method to fly. Without mass in the bag it gets a whole lot lighter. However, the creation of a vacuum chamber requires such sturdy materials that it automatically becomes heavier than air. The problem is the atmospheric pressure that puts too much force on the shell of the vacuum chambers.
Using modern materials, at what kind of **atmospheric** pressures could we make a vacuum airship that can function? For more details: Imagine an airship that can carry about a hundred people including crew, sleeping quarters, dining and such. I think about 200.000kg not including the balloon, but using modern materials you might get that down a few pegs. The atmosphere is most preferably akin to ours in composition and assume earthlike gravity.
Any pressure, high or low, is acceptable if you can support it with facts. Venus has a tremendous pressure, allowing even a shipping container to float. However, could it support a vacuum airship under such pressures? Lower pressures have a different problem, because the lower the pressure, most often also the lower the mass per m3. That means the balloon needs to get much bigger. In the end it also needs to support the dirigible, which requires to withstand the outside pressure as well.
For extra creativity I'll not add the hard science tag, but sources are very welcome.
This question is not the same as [vacuum instead of gas](https://worldbuilding.stackexchange.com/questions/11369/vacuum-instead-of-light-gas), as I'm interested to make it work by altering the atmosphere it floats around in.
[Answer]
## Use mars
A mars like atmosphere is a good bet. Also use a lower gravity. this would allow you to build thin walled, and therefor lighter vacuum. This is not a problem because the pressure of a planet's atmosphere is dependent on its mass anyway and the simplest way to change it is to change the mass.
There is some documented evidence of this being viable on mars in real life.
Sources:
<https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Evacuated_Airship_for_Mars_Missions/>
<https://space.stackexchange.com/questions/23709/mars-vacuum-blimp-feasability>
<https://curious-droid.com/302/zeppelins-mars-havoc-venus-nasas-new-planetary-airships/>
[Answer]
>
> Using modern materials, at what kind of atmospheric pressures could we make an airship that can function?
>
>
>
[Aerographene](https://en.wikipedia.org/wiki/Aerographene) is porous but less dense than helium, and while different sources report different structural properties, it seems that it can withstand compressive forces almost as well as steel.
So, it would be possible to have a sphere with a diameter of two meters, 10 cm thickness, covered in airtight aluminum foil, withstand pressures up to 100 atmospheres (a depth of 3,000 feet of water) like bathyspheres do. The outer volume would be about 4.18 cubic meters, the weight about 1200 grams (182 grams of graphene and about one kilogram aluminum). The net lift in ordinary air would be about three kilograms.
Put together one thousand such spheres - a cube twenty meters each side - and you've got yourself three tonnes of lift. Actually, since the [packing factor](https://en.wikipedia.org/wiki/Close-packing_of_equal_spheres) of spheres is about three fourths, one thousand 4.18 m^3 spheres would occupy an average volume of 5.6 cubic meters each; 5600 cubic meters would be a cube only about 18 meters each side.
Fill with those a volume equivalent to the Hindenburg (200,000 cubic meters), closely packed, and you can fit 35714 spheres, with a lift of 107,14 tonnes on Earth. Not bad considering that the Hindenburg (filled with explosive hydrogen) could lift 232 tonnes.
I have padded my calculations; it's likely that these results might be improved.
For example, having more spheres together might allow using a less sturdy sealant than aluminum for the outside of each sphere, leaving the job to the external bag. Or maybe a less sturdy sealant or less thick aluminum foil is enough anyway; or the sphere can be made less thick, even if that wouldn't change things very much - of the 1200 g of each sphere, only 180 or so are the graphene. Or smaller spheres or "caltrop" shapes might be packed between the 2m spheres, increasing the packing ratio from its 0.75 baseline (with perfect packing, a 33% increase in lift might be possible).
Making the sphere twice as large, the surface increases fourfold (so 1kg aluminum becomes four), the volume eightfold (so 180g graphene becomes 1.44 kg), and a 5.44 kg sphere has now eight times the lift - about 33 kg net, giving about 27 kg net lift versus the 24 kg of eight separate spheres.
Spheres three times as large would need 9 kg aluminum, 4.86 kg graphene, weighing about 14 kg with 27 times the lift - 110 kg net, giving 96 kg lift versus the 81 of 27 separate spheres. And so on. Note: the pressure on each sphere grows with the same ratio. Past a certain point, either we increase the thickness again, or the sphere will be crushed by atmospheric pressure.
[Answer]
### Frame challenge: Why bother with the vacuum balloon if we can vary the atmosphere?
So we need a engines for thrust, a way to climb and descend as needed, a way to steer and pivot and roll and pitch, a passenger compartment, a baggage compartment, toilets, a kitchen, enough to keep the passengers comfortable on their long journey. If only there was some ready made object with all these things we could use as a base....
This is Us Airways Flight 1549, with everything we need to make a long voyage comfortable, floating in a fluid of density 997kg/cubic meter:
[](https://i.stack.imgur.com/PZ5DG.png)
I've been struggling to calculate the actual density of a modern aircraft (no-one publishes volume information for the entire airframe), I've been calculating around 100 - 300 kg/cubic meter but I'm unsure. However from the photo we can tell it's floating quite high in the water. The underside of the nose is above water, as well as the rear decals that's midway up the fuselage, It looks like its about 80% out of the water. From this I'm estimating it's density at ~150kg/cubic meter.
This suggests the plane will be neutrally buoyant at 125atm of air pressure. This is 12MPA of air pressure with our current atmosphere. This is a lot (and we don't need to push back the whole lot, just the difference between the passengers and the outside), but not beyond our engineering. Lightweight carbon fibre 3d printing that even my cheap 3d printer works with [can handle 50-300MPA](https://iopscience.iop.org/article/10.1088/1757-899X/406/1/012042/pdf), so surely professionals could come up with something, **although it may be a bit excessive to literally retrofit an airliner**, this should give a guide as to what we can be building if we can tweak the atmosphere to accomplish it. Humans can actually breathe an atmosphere of oxygen and helium at these pressures (up to [19 mpa](https://en.wikipedia.org/wiki/Heliox) actually), with acclimatization, so you walk outside without a respirator.
However since we can tweak the atmosphere, and it's not actually a requirement that it be breathable, lets **make the atmosphere Radon**, a noble gas. At 9kg/cubic meter at STP, we only need ~15atm of pressure before our plane floats up like a balloon. That's **only ~1.5MPA**. That's much easier to work with!
Your "airships" launches by pumping air out the fuselage until its down to minimum comfortable levels, and then by releasing the docking clamps and it slowly floats up. A little bit of thrust from the engines and forces applied on the rudder and flight controls and it's able to steer. The engines can power it in the horizontal direction at speed, and when it arrives, the flight controls can bring it back down to ground, where it can let air in / pump oxygen in from the terminal, (depending on which atmosphere we went with) , where it will get heavy and sink to the ground, where it can be roped and held onto the ground.
---
To make it directly answer the question in a tongue in cheek way, you can duct tape a small, rigid, Thermos to the inside ceiling of the plane - [they have chambers of pure vacuum](http://www.physics.usyd.edu.au/super/physics_tut/activities/Thermal_Physics/Thermos_Flask.pdf). Now we have a vacuum chamber at the top of a large comfortable pressure vessel carrying passengers, which floats in the custom atmosphere.
[Answer]
A pressure cooker clearly can withstand vacuum and float in water, which also is gas in liquid form. Soo then floating vessel with a difference of pressures of inside and outside is possible, in some conditions, then what about the generalization of that.
problem isn't simple if we approach the problem more seriously. Constructions working against compressive forces are a bit more complex subject and is as an example the serious field of research in NASA - as it is directly connected to the mass of a rocket and all that - they have a lab of experimental researches how exactly basically a thin-walled cylinder crumbles under a load.
The necessity of that lays in a difference of theoretical ideal construction and how much influence on a result imperfection of construction and materials have on the situation. The same applies to bridges and house building - finite element analysis goes hand to hand with experimental testing, and the safety factor is quite high, not only because it has to last long, but also for that negation of imperfection influences.
one of the places to start with theoretical parts is [Euler's critical load](https://en.wikipedia.org/wiki/Euler%27s_critical_load) and material science in general. I won't, not competent enough, I'ma doomer and it easier for me to look at Hydraulic press channel and they's not so long ago established dive 3km deep setup v.onemillion [Shrinking Styrofoam Cups with Deep Sea Chamber](https://www.youtube.com/watch?v=Jh6-0aqft1k) and alike.
in general attempt to google how much a sphere will hold of outside pressure leads to strange places u never been and does not bring clear answers, even if it is a typical modeling task for the mechanics of materials field of science, and not much luck for those who aren't familiar with all that.
All that said, all below is not perfect, and no guarantees.
## a little bit of trivia and water again
A submarine is a relatively big underwater vessel, which is capable to dive at significant pressures like 60 bar down, or ones of WWII like 20 bar typical.
And steering in direction of venus - density of liquid carbon dioxide is
>
> 1101 kg/m3 (liquid at saturation −37 °C (−35 °F))
>
>
>
>
> Critical point (T, P) - 31.1 °C (304.2 K), 7.38 MPa (72.8 atm)
>
>
>
So a modern submarine potentially can float in liquid CO2, in all 1-74 bar pressure, in conditions when CO2 is liquid. The density of CO2 will change with the rising of temperature, but no so essential for us, a change of 10-20 percent or something - a difference in a range of ballast tanks.
## let's start our speculations
>
> The compressive strength of ductile materials such as mild steel used for most structural purposes is around 250 MPa.
>
>
>
that is the stuff nails made of - not the best, bends easily and all that, but we take that number as a measuring stick.
unfortunately lost my gnuplot skills so, let's jump straight to how it looks like for 100 bar.
Sphere 1m radius, crushing force will be 31MN, so crossection has to be 0.1256m2, hence wall thickness 0.02m, and resulting mass of our sphere around 1885kg
The volume of that sphere is 4.2 m3.
So the thing will float in something of a density of 450 kg per cubic meter.
* However, if we apply safety factor for all imperfections and all that, it may sink easily, but to not mess with it we took not the best material, even among the steels - one negates another and we can assume to have enough of safety factor here.
So half of the density of water, not bad, and considering real constructions which did dive at Mariana Trench, we are not that far off with all that.
### how all that scales up/down?
pretty much linearly - crushing force scales proportionately to the square of linear sizes, so as resistance is proportional to the surface of cross-section, the strength of materials, mass proportional to cross-section aka wall thickness multiplied by surface area aka volume as the result, lifting capacity proportional to volume.
so no cheat codes like square-cube law. A variety of sizes is big enough before there will be some nonlinear effects, and they are, and 10m radius and we probably have to account for them, 10-20 percent range with steel, less for titanium.
## let's plunge into Venus. Venus, my love, I come ...
what is the density of those 93 bars of pressure, near-surface of it?
[wiki](https://en.wikipedia.org/wiki/Atmosphere_of_Venus)>>The density of the air at the surface is 67 kg/m3, which is 6.5% that of liquid water on Earth.
Soo, it seems we miss our target by 6.7 times. Density isn't high because of the high(relatively, 740K) temperature there, so we have the additional challenge of the steel to lose structural strength at the temperatures, but not a huge deal, the second order of magnitude effect, as there are steels which work well enough with higher temperatures.
unfortunately, there is no positive, for us in the case, square cube laws, so we can't outnumber the situation by changing the size. (maybe wrong, but do not see any, but can be mistaken)
So the variables to change are mostly density and strength of material with that density, composites, more sophisticated ways to squeeze their all from available materials.
But perspectives do not look that promising if we do not bring the new game in town like carbon something. it much easier to have carbon monoxide as lifting gas for those purposes. And if we cross the threshold with conventional materials then just barely - so imperfection of our original assumptions may be detrimental for the answer, as so the importance of experimental data can't be underestimated here.
] |
[Question]
[
Is currently hard to find a way in which classic dragons could develop and use the fire-breathing, so find a way in which this could happen for blue fire of complete combustion is even harder. Read this
[How could dragons be explained without magic?](https://worldbuilding.stackexchange.com/questions/313/how-could-dragons-be-explained-without-magic)
I was wondering this because blue fire have some important advantages, is hotter, is more efficient, more controllable (it does not expand so quickly and chaotically) and therefore precise, it also does not produce ash, soot or carbon monoxide, besides it can be said that it is capable of "burning" normal fire.
The notorious problems for blue fire breather dragon is that blue fire is hotter and if it's hard to deal with the normal fire temperature this is even harder, and the other problem is the raw material, I don't know if a biological system is able to produce or get in a relative easy way the required composals, a good material for complete combustion is the n-heptane.
And finally in an evolutive vision, why would a fire-breathing dragon need this fire?, if normal fire is enough.
[Answer]
# Methane.
Methane flame is blue, and methane is very easily produced by several biologic processes that might take place in the dragon's gut.
You start with a grisou-belching reptile. Then it acquires flame bombing capabilities, because if it clicks its teeth *just so* while belching, the toroid of explosive gas will detonate at a safe-ish distance from the mouth. Several variants misfiring dragons exploded before reproducing and are now extinct.
The capability of stunning prey with a gas explosion turns out to be a decisive advantage, and dragons evolve that produce more and more methane, and finally become capable of storing it for lengthy periods, releasing it at will.
From there, we get a dragon that can expel a mostly pure methane jet at high enough speeds that it's safe from *most* of the heat (nonetheless, they also evolved thick, horny, heat-proof muzzle scales).
And that's a blue flame dragon.
[Answer]
Yeah this is a stretch, but it's all I've got...
### Your dragon burps Chlorine gas, and has half a knight caught in it's mouth.
Years ago a knight attacked the dragon, and while the dragon ultimately won, the knights copper chainmail armour got caught in the dragon's teeth, the copper is stuck in the dragon's mouth and has been for considerable time.
The dragon has a different digestive system to what we know today, resulting in chlorine gas burps.
When the dragon breathes fire, the chlorine gas and the copper get heated to over 400 degrees C, forming [Copper Chloride](https://en.wikipedia.org/wiki/Copper(I)_chloride), which has the property of dying a flame blue.
**Copper Chainmail**:
[](https://i.stack.imgur.com/WhpWd.png)
**Copper Chloride added to a fire**:
[](https://i.stack.imgur.com/pWsLR.jpg)
[Answer]
Flames turning different colors is so common that the "flame test" is routinely used to determine what something is by what color it burns.
Here is a [list](https://www.thoughtco.com/how-flame-test-colors-are-produced-396397) including all sorts of colors. Some blues are arsenic, copper(I), and lead.
As for how it evolved, metals can be cumulative poisons. The dragons evolved this way to concentrate and then expel them from the body.
[Answer]
Potassium chloride, copper(I) chloride, and butane all create blue fire when burned. Copper(I) chloride could be synthesized organically. Alternatively, you can raise the temperature of the fire to 2,600-3,000 degrees Fahrenheit, which would create blue flame.
[Answer]
The Primary method that flames are coloured by is [atomic transitions](https://en.wikipedia.org/wiki/Emission_spectrum).
The light emitted from Atomic transitionscomes from an electron changing from one 'orbit' to a lower energy 'orbit', the change in energy is emitted as light. but the exact energy (which gives the color of the light) of the orbits are dependent on the specific atom, so different atoms give different colours through this method.
There are many methods to change the colour using atomic transitions, which would give flames that behave like normal fire but are just a different colour. To make the flames blue you could include in the flames some thing like copper ions [](https://i.stack.imgur.com/15CxL.jpg)
or sulphur.
[](https://i.stack.imgur.com/zwBt5.jpg)
The copper ions could be present as a compound in the mouth, possibly as a toxin, as metals can have significant biological interactions (for example, [Heme](https://en.wikipedia.org/wiki/Heme), the core of red blood which contains iron).
If it uses sulphur then it could use that as its fuel as sulphur burns on its own, and is a liquid at ~115 °C so could be sprayed out as a liquid. But it would have to consume a lot of it, maybe from volcanic deposits
[](https://i.stack.imgur.com/1W5cM.jpg)
An unfortunate downside of sulphur is when it burns it releases a gas called [sulphur dioxide](https://en.wikipedia.org/wiki/Sulfur_dioxide) which, along with smelling like rotten eggs, forms an acid when it dissolves in water, so your dragon would have to have systems to cope.
Alternatively you could use more oxygen with your fuel, possible using a something like an [Vacuum ejector](https://en.wikipedia.org/wiki/Vacuum_ejector). This would give you the blue seen with oxy-acetylene torches,
[](https://i.stack.imgur.com/LsqHX.jpg)
but this would cause a hotter flame, a few methods that could reduce the possibility of burning the dragon are, it could have insulation possible using [Aerogel](https://en.wikipedia.org/wiki/Aerogel) like material in its scales around the mouth as aerogel is highly insulative
[](https://i.stack.imgur.com/lA4ht.jpg)
hopefully that helps.(i may add/adjust more later)
[Answer]
**Ethanol makes blue flames.**
[](https://i.stack.imgur.com/ZXv1I.jpg)
<https://en.wikipedia.org/wiki/Ethanol>
Ethanol is of course compatible with biochemistry. Usually we make it with yeast if we want it but it is possible to have an onboard brewery, where commensal microbes make ethanol: auto-brewery syndrome. <https://en.wikipedia.org/wiki/Auto-brewery_syndrome>
I suspect that exactly this goes on in the guts of large ruminants which is why it is hard to get horses drunk - they are making ethanol all the time. That said, elephants apparently like to get drunk and supposedly will raid a place for liquor if they smell it.
---
All that said - ethanol is a fine biomolecule and would make your blue flame but I am not sure what about blueness confers all the awesome properties of blue flame you describe. There are lots of different blue flames. Ethanol flames are not very hot which is why you can screw up your flaming Bacardi 151 shots and not get hurt that bad.
Ah yes, the dragon. It is a vegetarian and a ruminant along the lines of a sauropod. It has autobrewery syndrome going like mad and is drunk as a lord all of the time. Flames are used to clear away mosquitoes and biting flies.
] |
[Question]
[
So I'm setting up a setting for Genesys that I have placed in a alternate dimension inhabited by humans from ancient Greece that would build their own world according to how they perceive their previous life. I am starting with a origin story of course and have a few questions that I would like a new eye on.
### The origin of Thurian
>
> In a sea of chaos and force there flows a string of pure magic through uncontrolled collisions that ignites a spark that after millennia creates a parallel universe to all the others in the time-space continuum with a massive explosion. This explosion of an unparalleled force creates a rift in time and space into which twelve entities from our own universe are pulled.
>
>
>
>
> The surrounding force recognizes these new entities and grants them the ability to wield the force itself to control their surroundings.
>
>
>
>
> With this power, the long lost humans of a classical civilization start to build up a world of their own, in the manner in which they have long been familiar. They build a sun that has one single planet in its field, a planet that has a resemblance to earth itself insofar as its atmosphere and climate. The landmass is what they believe the earth looks like, and since they have just been around their local areas this is quite random.
>
>
>
>
> On the planet they start with one island, an island that also is the home of the volcano Olympia that holds the golden doors to the eternal plane that is their own home. One by one they form races, animals and all entities that are needed in a ecosystem, entities that can worship them and give them more powers.
>
>
>
### But what I would like is your take on this:
**How should the race of humans come to existence?** Even though the gods in this world have been humans in another time and space, why would they create these again? Why would anyone create a race with a free will that will in time question their existence?
**Would a god build a secluded (but accessible to those with the strength) palace for themselves on a mortal plane?** I do want to keep planes to a minimal at this stage, but I think this might be a port to another plane, or they do live with the humans in a different part of the world. That is, would gods build a home on Mount Olympus or would Mount Olympus be a plane itself?
[Answer]
**Because it is familiar.**
Some ancient Greek people are given godlike powers and put in a *blank canvas* type universe. Since they are still humans, they don't want to live in an empty universe and try to create something familiar. So they create. . . . Ancient Greece.
Okay not exactly Ancient Greece. But the world they create is similar enough to Ancient Greece that they feel comfortable living there.\* But it quickly becomes apparent there is one big difference between this new world and the old -- hundreds and thousands of people.
It's only a matter of time before someone creates more people. The real question is how do they rationalize it to themself. Some examples:
**Loneliness:** There are only a small number of gods and a big big world. Many are off having adventures on their own. One god gets lonely and tries to create some companionship.
**A Prank:** Mythology is full of trickster gods. Somehow creating humans was a prank that got out of hand. The stupider the prank the better. For example Loki creates a duplicate of Thor and Freja to wipe his ass at the toilet. Due to hijinks they escape and start the human race.
**An Accident:** Humans were not supposed to have free will. Someone just created a whole Athens full of *background characters* who were not supposed to have souls. But on accident one got a soul and that's where humans come from. Perhaps some god has a favourite human who they give a shred of free will, the same way you might give your dog a dog biscuit. This is the beginning of the end.
Once humans are created they will stick around. It's easy for a former human to say they *shouldn't be created*. It's much harder to say they should be eradicated.
I mean, presuming the humans you created were dignified Greek citizens, and not the savage barbarian flavour.
\*Interesting point: If there are already planets, suns, moons etc in the empty universe, they might create Planet Greece. Otherwise they might create a flat world with a moving Sun, or otherwise base their cosmology on Ancient Greek mythology. Someone might even take the role of Helios to be the sun. So that cosmology which was not real to begin with them becomes real.
**Mount Olympus**
To justify mount Olympus being accessible you can put a power limit on your gods. Remember Greek Gods are not as powerful as the Judeo-Christian type. They can only do such great deeds as building the world by sacrificing members of their own. In this case the ones who would be Gaia, Oranos, and so on. In the beginning those guys were happy to sacrifice themselves to create the world. But now the world is created no one is willing. So the best they can do is build a big mountains and live on top of it.
[Answer]
To worship them.
The mark of apotheosis in ancient Greece was for the humans to offer you sacrifice. Creating automatons that will do automatically doesn't give them the same effect; it feels like a little girl pushing around dolls to offer *her* sacrifice.
Besides, if the humans doubt, these gods intend to be right on the job. Blasting the doubters with lightning and demanding that all the listeners offer sacrifices to purify themselves will fix that.
As for accessibility, they've undergone apotheosis themselves. They may offer it as a bonus to humans. They may even need it to increase their numbers. Also, it keeps the bolder humans in line by giving them something to strive for. (If an insolent one appears to be succeeding, blast him with lightning.)
[Answer]
Greek gods were all but ascetic in their divinity: lust, gluttony, jealousy... none of the human vices was unknown to them.
And what's the point of being a god if you can't fornicate with some pretty hot human or you can't enjoy the fragrance of those sacrifice that they are so good at doing?
Give them a month sitting on their throne and they will get bored. Humans are such a source of entertainment, I guess they see us as their board game. While we sometimes prefer Risk, Monopoly or Ticket to ride, they play with us the 1:1 scale version of those games.
] |
[Question]
[
If 19th century workers needed to be working [in an environment much like](https://worldbuilding.stackexchange.com/questions/183710/how-could-we-modern-humans-get-established-on-a-hot-planet) the inside an active volcano for several hours, would they have materials to make a proximity suit to do this? Assuming working in air at temperatures of 900°F for 4 hours, and the time is 1890. Assume they have chemical oxygen candles (rebreathers) as well. Their job is [maintaining airships](https://worldbuilding.stackexchange.com/questions/225212/how-to-maintain-large-ships-in-hostile-atmosphere) on a [very hot alien planet](https://worldbuilding.stackexchange.com/questions/183710/how-could-we-modern-humans-get-established-on-a-hot-planet)
**Note:** Proximity means “near the hazard.” No one is swimming in magma.
[Answer]
**QUITE POSSIBLY.**
Iron workers were probably the closest human workers have ever gotten to working in Weyland's smithy.
[](https://i.stack.imgur.com/J9f8Q.jpg)
Do take note that in the 19th century, the fashion for iron workers appears to be britches, vests and bowler hats; or else top hats and frock coats.
Asbestos has been known for ever, and [according to this resource](https://www.asbestos.com/asbestos/history/), seems to have been known and used for fireproofing clothing for a very long time. I think it comes down to a matter of timing: the industrial mining, use & application of asbestos just came too late for 19th century volcanic spelunkers.
In a world where the properties of asbestos are known, where it's relatively easy to obtain, and where the need to work inside volcanoes has spurred the growth of this particular industry, I see no reason that such a suit couldn't be made, if crudely, in the 19th century.
[Answer]
**You will need to remove heat from the workers.**
[](https://i.stack.imgur.com/sMoAF.jpg)
<https://en.wikipedia.org/wiki/Diving_suit>
900 F is too hot to breathe. The workers will need diving suit - like helmets to provide cooler air. Since they are in suits they can also have a water circuit to cool the suits. The hose providing cool water will itself stay cool from the water inside it and the water hose can jacket the air supply hose which otherwise would itself catch fire.
The materials for the suits are not waterproof; the opposite as much of the water pumped into the suit comes thru the canvas pores and drips away or evaporates, carrying away heat.
You would need to keep the cool water coming fast to keep your workers cool. You had better have a lot of it topside if they are going to be in 900F for 4 hours. You could pump the water back up to reclaim and cool it. Alternatively it could just fall out the pores of the suit and then it would keep working to cool the immediate environs of the workers.
There would be a lot of steam!
[Answer]
**The short answer is yes**
The long answer is that all the necessary materials were already available (especially if they can travel through space) the answer is asbestos.
Asbestos was the first material used for high temperature protective suits (for the explanation I will work with degrees Celsius as this is the unit of temperature measurement in the international system of measurement, 900F is 482.222C) the first asbestos fire suits could protect from up to 285C while thicker versions for industrial use could withstand 1000C.
The main problem is that the insulation also prevents the human body is normally at 37C and can withstand up to 50C. Although this is simple to solve with a tank of cold water for the worker to drink, 4 hours is entirely possible.
] |
[Question]
[
I'm imagining an artificial planet of almost pure water constructed by an advanced aquatic species. It's "almost pure" because they included enough impurities in the water for life to thrive, resulting in a composition similar to Earth's seawater. This species wants the entire volume of the planet to be liquid so that it's habitable to life (even if the depths would only be habitable to life adapted to high pressures). They don't want any [high-pressure ice](https://en.wikipedia.org/wiki/Ice#Phases) in the core. That brings me to my question: how big could this artificial water planet be and not have an ice core?
Note that gravity isn't a concern here, as the artificial planet would be enclosed in a transparent membrane that stops the water being lost to space even if the gravity is low, and its inhabitants can acclimate to a range of potential gravity levels.
[Answer]
**1000-10000km**
Depending on conditions oceans could be very deep indeed. If the planet had a very high proportion of water and had a warm enough core, then thousands of kilometers should be possible. The limiting factor would be the formation of ice, however according modest extrapolations from [this](https://www.google.com/search?q=water%20phase%20diagram&safe=off&rlz=1C1CHBF_en-GBGB888FR888&tbm=isch&source=iu&ictx=1&fir=sdMi0lAc1lsURM%252CgNswwOMUqqr4pM%252C_&vet=1&usg=AI4_-kQZk05FNq28XmKsUIPBiZOKUqkQTA&sa=X&ved=2ahUKEwjZkeXgu6ztAhVDsaQKHZ8XBa4Q9QF6BAgCEFU&biw=1536&bih=666#imgrc=y7-XWbTS-C8RGM) phase diagram it would appear that water might remain a liquid at pressures of 100 GPa at temperatures well in excess of 500 degrees C.
At 1 metre depth the pressure is around 10,000 Pa so that might allow 10,000km of ocean. Even allowing for compression that’s still thousands of kilometers. A 10000km deep ocean would obviously not be possible on Earth as Earths diameter is only around 12000km. But it might be possible on a bigger planet. If Earth’s crust and mantle were replaced by lighter water then there would be a significant depth increase. [See this link](https://earthsky.org/space/exoplanet-water-worlds-deep-oceans-2019-study#:%7E:text=Earth%27s%20oceans%20are%20nowhere%20near,bottom%20of%20the%20Mariana%20Trench.) for related information.
[Answer]
I pulled out the program I used to answer [this question](https://worldbuilding.stackexchange.com/questions/106732/what-would-the-minimum-mass-of-a-water-world-need-to-be-to-form-ice-vll-due-to/106853#106853), plugged in some numbers for different temperatures, and got the following:
| Temperature | Radius |
| --- | --- |
| 647 K (374 C) | 2916 km |
| 373 K (100 C) | 2626 km |
| 298 K (25 C) | 2063 km |
| 273 K (0 C) | 1827 km |
The hotter your planet is, the larger it can get. At the lower end, you've got a thin skin of ice surrounding a ball of water with a radius of about 1800 km, slightly larger than Earth's Moon. At the high end, your membrane is pressurizing a 2900-km radius ball of barely-subcritical water to a surface pressure of 22 MPa (about 200 times Earth's atmospheric pressure).
As the temperature drops below 0 C, the layer of surface ice gets thicker, but you don't lose the ability to have a liquid core until the temperature drops to 251 K (-22 C). At the high end, if you raise the temperature any further, the water transitions to a supercritical fluid. It's up to you to decide if you want to call this a liquid or not.
[Answer]
## Insulate your membrane or choose a good sun
In this system, any heat would escape outward. If you have heat inside, **the only way it can leave is through the surface**. You said that the planet is enclosed in a membrane, so make that membrane insulated to keep heat from inside escaping to the outside.
Now, this will have the side-effect of not allowing any heat *in* either. So how can you keep the ocean liquid? I'd say your best bet is [tidal heating](https://en.wikipedia.org/wiki/Tidal_heating). The idea behind this is that rotating around a big object will cause the liquid to move around, generating heat. Moons like Europa and Io have vast sub-surface oceans because of tidal heating, Europa even having twice the volume of water of Earth despite being smaller than our moon.
If that's not enough heat, you can always have some sort of heater to input extra energy into the system when it runs low on energy.
Given that, I think you could get easily large enough to thousands of species. If heaters don't work for your story, you'll have to make it small enough for the sun's energy to heat the whole thing. I can't give you any specs on this, because **it depends on the sun.** **You'll need to be as close to the sun as possible, but you have to be outside the Roche limit, or your planet will break apart.** So brighter sun = more energy that can get to your planet, but that usually is paired with larger sun = the further away your planet has to be, allowing less of that energy to reach it. You'd want the brightest yet smallest mass sun possible to get the largest planet.
The next part of the answer will deal with the assumption that you're using my first solution, because you'll probably want to go bigger than the sun allows.
Now here's your problem: How are these creatures getting their energy? There probably aren't sufficient nutrients in the water (okay, you said they put impurities in the water, but it'll have to be constantly replenished) and definitely no source of energy (unless you're also constantly throwing food in as well). Energy would have to come from the sun, which is blocked out by our insulation. If we removed the insulation, the inside might freeze, but at least energy is going into the system.
And really, even if your inside is liquid without a membrane or anything like that blocking the sun, it wouldn't be habitable to life. Deep-sea ocean life on Earth is only possible because of hydrothermal vents, which couldn't be present in a solely-water world. These vents input energy and nutrients into the system, because absolutely no light from the sun is reaching that depth.
So, in conclusion, the only way I know to have a large, 100% habitable planet is to **constantly feed energy and food into the system** or to **have an ultra-hot yet very small sun**. If that works for your story, great. If not, just make it a watery planet without having to worry about ice at the core or anything like that. That way you can have hydrothermal vents and stuff to keep the inhabitants alive. That's my suggestion. It'll also have a lower Roche limit than a 100%-water planet so it can be closer to the sun and get more energy from it.
I hope that helps you. If not, let me know and I'm happy to add anything you need to my explanation.
] |
[Question]
[
In my steampunk world (developed to roughly 1870-1910 levels of technological development), there are no oil deposits and flatlands are highly valuable due to their relative rarity (the entire thing is located on basically a humongous vertical rocky cliff, with only some ledges reaching the sizes of small islands, which are mostly used as strategically important locations for farming).
Since oil is required to make light and powerful enough internal combustion engine be viable, and the land is too valuable to waste on building landing strips - would that be enough to strangle the concept of a heavier than air aircraft in infancy (Other than engineless gliders, maybe?) and not worry that it would displace airships as the most efficient way to travel by air?
[Answer]
Biodiesel or Alcohol both make *great* fuel for engines, and can be made from any foodstuffs.
It you people can eat, they have the base materials to make fuel.
[Answer]
I think you're strangling the development of engines nicely. :)
However there are also many other moving parts that need to use lubricants like oils in order to operate - doors, gates, anything with a hinge; telescopic sliders in binoculars; gears in wind-up toys and watches; guns guns guns, from flintlock through to fully automatic repeating weapons, etc. If it has two bits of metal touching or scraping together it'll need lubricant.
So for these you may need to investigate some type of substitute.
Perhaps you might like to make your people more agrarian, in which case good old soybeans might be useful:
<https://www.resourceefficient.eu/en/good-practice/soybean-oil-lubricant-substitute>
On another Stack Exchange, they've discussed this here: [https://diy.stackexchange.com/questions/7079/what-happens-if-i-use-vegetable-oil-instead-of-machine-oil-or-grease#:~:text=Oil%2C%20WD40%2C%20or%20any%20petro,a%20bit%20messy%20to%20use](https://diy.stackexchange.com/questions/7079/what-happens-if-i-use-vegetable-oil-instead-of-machine-oil-or-grease#:%7E:text=Oil%2C%20WD40%2C%20or%20any%20petro,a%20bit%20messy%20to%20use).
I noticed one poster mentioning silicon-based lubricant. So silicon might be a go-er for you. Here's a page I've found helping explain the basics of it: <https://www.naturalhandyman.com/iip/infxtra/infsil.html>
Of course these bring engines back into play, but maybe you can create a supply/demand problem much easier with these alternatives eg soybeans can only grow in flatland areas, or silicate mining is eroding places to live in the cliffs etc.
Hope this helps!
[Answer]
**Engineers will only develop things that work**
The 19th century.. In that period, on Earth, diesel engines were invented. But this invention was feasible *and* successful, *because* it depended on a ready available fuel. There exists no fuel on your planet, so engineers would not imagine/design/draw/build any type of engine that uses it. Problem solved, keep optimistic. There is no need for fuel because nothing uses fuel. In short, as a consequence of your world's limitations, a fossil fuel or biomass fuel engine design would never have happened.
**Sail powered airships**
A wood-fueled manned balloon was invented in the 18th century. [Lilienthal](https://en.wikipedia.org/wiki/Otto_Lilienthal) flew a glider in 1891, and on your planet, there will be someone attempting the same thing. Humans always want to fly. Your people may accomplish flight. Actual air transport we accomplished in 30-40 years, using motorized aircraft (Wrights brothers, Blériot, DC-3) but without diesel fuel, that would not have happened. No Hindenburgs either... This airship was just a balloon with some diesel engines mounted on it.
Probably, your airships will require sails at first, like [this](https://aviation.stackexchange.com/questions/50529/could-a-blimp-maneuver-using-a-sail) baby,
[](https://i.stack.imgur.com/oU0f1.png)
See also WB topic
[How could a sail powered airship work?](https://worldbuilding.stackexchange.com/questions/8485/how-could-a-sail-powered-airship-work)
**Electric flight**
Modern insights - after 1870 - have found there are *three* energy sources for engines, that is fossil fuel, biomass fuel, *or*.. electricity.
The electromotor could be an option. It will need steel for some of its parts. Steel could be produced manually, or using machines and lots of energy. It needs to be precise. In Sweden, they use machines and energy, but they say they can do it *without* the fossil fuels,
[](https://i.stack.imgur.com/ZHg9D.png)
<https://www.weforum.org/agenda/2021/08/sweden-hybrit-first-fossil-free-steel/>
What if your steampunks would set up some generators ? wind energy, or tidal energy. Harvest Earth heat.. Solar heat collectors.. or let your people discover fission energy and try the nuclear option to generate electricity. There is no science tag, what about cold fusion ?
Based on electricity, an electric motor will be invented. Next step would be to develop light weight batteries.. and off the cliff you go ! With small aircraft, landing won't be an issue. STOL landings require very little space.
[](https://i.stack.imgur.com/5R3rn.png)
Earth 2020
Upscaling the electric aircraft to make it an actual means of transport will be an issue to overcome. Nowadays, on Earth, we are about in that stage. We have very agile Pipistrel aircraft: two-seaters. For more passengers or transport, things are in an experimental stage, the electric Cessna Caravan can fly 14 passengers,
[](https://i.stack.imgur.com/0taBi.png)
<https://robbreport.com/motors/aviation/worlds-largest-electric-airplane-takes-flight-2930460/>
**Be patient.. some time it will happen**
We developed electric flight in 120 years or so. Keep in mind developments on your steampunk world, without fuel, could take centuries instead of decades. But they will result in *super-lean* designs, with energy usage efficiency we can only dream of.
[Answer]
It's pretty easy to [run planes on ethanol](https://www.flightglobal.com/corn-to-run-can-ethanol-be-used-as-a-clean-alternative/71449.article) if not jets. It's a low vibration fuel, and easy enough to make.
Since you want such planes to not be a thing, just have it be common to have birds that love the smell of ethanol and other fuels and will fly at planes which carry it.
Airships can carry fuel tanks deeper inside them and stay safe, be they coal or ethanol.
] |
[Question]
[
I have heard of the Chrysler TV-8 design, an amphibious armored vehicle powered by an onboard nuclear reactor...basically a nuclear-powered tank. The TV-8 never made it off the drawing board; the Corporation axed the project in 1956.
Surely there must be other ideas for nuclear-powered land vehicles out there. How about a nuclear-powered tree-clearing vehicle? If applied tactically, this could clear paths through forested terrain and increase mobility options for armored units.
What else could I do with nuclear-powered armored vehicle tech?
[Answer]
If you are asking specifically for military vehicles, it won't really ever be practical. There are very good reasons it was scrapped at the drawing board.
If you are willing to consider more infrastructure/industrial related applications, I could see the benefit of something like the <https://en.wikipedia.org/wiki/Bagger_288> utilizing a nuclear power plant to mine surface coal deposits.
[Answer]
Back in the 1950s, there was a project for a *nuclear powered strategic bomber aircraft* -- designed to stay aloft for months at a time, even to the point of allowing crew changes and reprovisioning in flight.
If you can make a nuclear reactor fly (and it was done, once, with a submarine reactor aboard a B-36), you can surely make it into a crawler tractor -- and a big enough crawler tractor can carry almost anything on almost any terrain.
As suggested in another answer, strip mining or dredging shovels, tunnel boring machines, large scale forest clearing equipment (clear for an eight-lane divided highway at a couple miles an hour, instead of a couple miles a month?) -- any task that can become more efficient by scaling up, but is limited by the practical size of diesel power, is a potential task for a compact submarine type nuclear reactor.
The big limitation on these, out of the water, is getting rid of waste heat; whatever they are, they'll need huge radiators or a lot of water for evaporative cooling.
[Answer]
I reckon this could get some use in logistics, and maybe army engineers:
* Powering a large truck or train. A supply line which doesn't need to move petrol to fuel the next / return leg is much more efficient, and is much more resilient.
* Army engineers will often be tasked with earth moving - an these beasts use a tonne of fuel:
[](https://i.stack.imgur.com/vdsJM.png)
Also you could drive it into a town you don't like and blow it up - instant dirty bomb.
[Answer]
The Ford Motor Company explored the idea of a nuclear powered car, although it is not nuclear powered using a conventional reactor.
[](https://i.stack.imgur.com/L6xGd.jpg)
*Ford Seattle-ite XXI*
[](https://i.stack.imgur.com/wI6kp.jpg)
*Another view*
>
> Here’s the 1961 Seattlite XXI concept car from Ford. This used a small RTG with 106.5 grams of Polonium 210 to boil water creating a 20 horsepower thermal source. High pressure steam was stored in tanks. This drove a 1/4 horsepower turbine that operated continuously that kept the batteries charged and control system in tact. The car was continuously lit heated and air conditioned with the heat from the system.
>
>
>
>
> The high pressure SCUBA style tanks operates the car for hours at up to 1000 horsepower. On long distance runs ‘gas’ stations equipped with a nuclear reactor type boiler could recharge the tanks for another few hours operation. Matching the performance of legacy autos on long trips while exceeding performance as daily driver. On shorter distance runs, the tanks would automatically recharge using the onboard nuclear thermal source when the vehicle was parked.
>
>
>
<https://www.quora.com/What-substances-can-be-used-to-create-nuclear-energy/answer/William-Mook>
This particular show car was actually more versatile, the front section (with the 4 wheels) was modular and detachable, and other modules using conventional engines, fuel cells or other forms of propulsion were supposed to be offered as well, depending on the customer's wants and needs. An atomic power module would likely allow you to drive across America and back without stopping for fuel at any point, a giant highway cruiser moving at highway speed the entire time....
However, the preliminary engineering studies were about as far as things got, issues like cost and safety likely killed the idea before any sort of practical hardware was ever built.
[Answer]
Some submarines use nuclear power so that they don't have to surface and recharge their batteries (or surface to take on fuel for their air-independent propulsion). Some aircraft carriers use nuclear power so they don't have to meet replenishment ships even more often than they do.
For a ground vehicle, the first issue is not an issue. So it would have to be the second -- long, unrefueled range.
* Cross some desolate, gas-station-less wilderness.
* Travel fast enough that bringing up supply dumps is impractical. That tends to kill the forest-clearance machine, because that one *will* be relatively slow.
* Operate in terrain where relatively large vehicles are not at a disadvantage. Plains, not forests or hills.
So think of nuclear variants of the [Vityaz](https://en.wikipedia.org/wiki/Vityaz_(ATV)) or the [Snow Cruiser](https://en.wikipedia.org/wiki/Antarctic_Snow_Cruiser), or something like it for desert use.
] |
[Question]
[
*I asked a [similar question](https://history.stackexchange.com/questions/60643/how-did-bank-transactions-or-data-transactions-work-when-it-took-people-week) on the History Stack Exchange, but it was suggested I might get better feedback here.*
**How can you guarantee [atomicity](https://en.wikipedia.org/wiki/Atomicity_(database_systems)) of a [transaction](https://en.wikipedia.org/wiki/Transaction_processing) in a high-[latency](https://en.wikipedia.org/wiki/Latency_(engineering)) system?**
High-latency systems are sometimes ones where information must travel vast distances (such as between planets, stars, or galaxies). Atomicity means that only one being can modify the record at a time (basically), and it is guaranteed to either succeed or fail, not partially be applied (as in a bank transaction subtracting from one account and adding to another account).
Or if you can't guarantee it, how do you **handle** important transactions, such as financial transactions, real-estate transactions, war transactions, trade transactions, etc. if they are operating on time frames of weeks or months?
How was this done in ancient times? Has anyone in history solved this problem? How would you go about building a world where two people can be in separate places billions of miles away, and yet make a trade (financially or otherwise)?
I also thought of this in terms of video games. Say you wanted to play a multiplayer game with someone. The only way you can play a *real-time* game with someone is if they are within a certain distance from you. If they are on the same planet like Planet Earth, then the latency is small enough as to be imperceptible. But larger latencies such as if you were on Jupiter or separated by planets or stars, there would be no way to play a real-time game with someone (as far as I can tell). But transactions are a bit different, they don't *necessarily* need to be real-time, they just need to be truthful or something, in the long run, and not run into erroneous states.
How do you do this?
[Answer]
What they did in the olden days was one of two things:
* Either have a trusted party hold the data and record the transactions. This was the method of choice for just about everything except real estate, which, in some places and at certain times,
* Linked ownership to the possesion of the deed / title to the property. This method was used when there was no reliable central registry -- think the Middle Ages.
The principle of ensuring the atomicity, consistency, isolation, and durability of a transaction by means of having *one* trusted third party hold the data is simple: there is only one register, and only one party who can update it. If the transaction is in the register, it is considered executed; if not, not.
The trusted third party can be the central office of a bank; or the land registry (called cadaster in some countries); or the shareholder registry.
Banks with international branches used this method on a worldwide scale. In practice, the local branch in, for example, Hong Kong, would immediately honor the transaction without waiting for confirmation from, for example, London, but it will hedge its exposure by getting a conditional letter of credit to be released when the confirmation came through.
As I said, at some times and in some places, transactions involving real estate used a more primitive method linking ownership to the possession of the title / deed to the property. Whenever a conflict arose related to the ownership of a piece of real estate, the party which could produce the actual document won.
It's that simple.
Yes, having one central trusted party hold the data and register the transactions communicating over very high latency links limits the speed and the amount which can be transacted. In modern days, what they do is take some risk. For example, when paying with a payment card, if the amount is low enough the payment network may confirm the payment without waiting for the bank to check the transaction; there is a risk that the bank will reject it, but it is assumed that overall the speedup is worth it.
[Answer]
**For really long distance travel you must take your wealth with you**
I agree entirely with AlexP, but there are additional factors that needs to be taken into account when considering the entirely astronomical distances involved - the expected lifespan of the participants and ability to realise the wealth being transferred.
The following assumes that there is no faster than light (FTL) travel or information transfer available. If there is FTL but it is non-instantaneous then the principle below still holds but the distances for each example increase.
Short range example:
* Person S lives on Earth and accumulates considerable wealth (buying power) on Earth.
* Person S travels through space for 2 years to observatory O that is 0.3 light years from Earth (in the Oort cloud)
* Before leaving Earth, Person S initiated a credit transfer from Earth to observatory O (signal travelling at lightspeed), so his money is available when he arrives.
* Note that this presupposes that observatory O has a financial agreement with Earth which would require at least 0.6 years to establish – 0.3 years for a signal from Earth to reach observatory O and 0.3 years for observatory O’s acceptance to be received on Earth – but this is quite feasible. Even if observatory O didn’t like the terms of the first contract offered and it took multiple offers and counter-offers to come to an agreement, this could still be achieved within a few years.
* Person S arrives and makes a purchase. Observatory O happily accepts his money, because they can use it to purchase supplies, information / entertainment etc from Earth that: a) they want; and b) are confident they will receive. Even if there is a dispute with the vendor that delays delivery by a year or more, the money can still be spent.
Long range example:
* Person L lives on Earth and accumulates considerable wealth (buying power) on Earth.
* Person L spends half their wealth purchasing a starship and leaves the rest on Earth.
* Person L travels through space for 1500 years (Earth frame of reference) in suspended animation and arrives on small planet B in the vicinity of Betelgeuse, over 600 light years from Earth.
* Before leaving Earth, Person L initiates a credit transfer from Earth to planet B,
* Note that this presupposes that planet B has a financial agreement with Earth which would require over 1200 years to establish – more than 600 years for a signal from Earth to reach planet B and the same for planet B’s acceptance to be received on Earth. If multiple communications were required then negotiations could drag out for ten thousand years or more – which is likely because...
* Person L arrives and wants to make a purchase. The question for the vendor on planet B is – what are they receiving in return? The minimum time to realise the wealth is over 1200 years, in the event that they want to purchase some information that can be transmitted by Earth. (They transmit the credit back along with an order and 1200 years later receive the *Friends* episodes they ordered.) They are losing the use of their money for a vast period; there is a high probability that any vendor, bank or civilisation they attempt to deal with will no longer exist by the time their order arrives; and they have no recourse if the "money" is not honoured.
**Broad principle:** Once the latency of transactions approaches a certain percentage of the expected lifespan of the participants, transactions will not occur. Once the latency approaches a percentage of the lifespan of the financial institution, transactions are impossible. (By the time an agreement is reached and a transaction is commenced the financial institution will not exist to complete the transaction.)
* Looking at a historic example - there is a reason that European explorers carried trade goods rather than letters of credit when dealing with tribal peoples. Even if the tribes understood the financial model involved they would have been unable to redeem the letters of credit.
* The most hard science fiction example I can think of is [Flare Time](http://news.larryniven.net/biblio/display.asp?key=118) by Larry Niven - the ramships traded information and technology they had acquired at their previous stops but never counted on the same market still existing even if they eventually returned to a planet.
[Answer]
It’s been proven to be impossible — it’s known as the [Two Generals' Problem](https://en.wikipedia.org/wiki/Two_Generals%27_Problem). Given a communication channel that isn’t 100% reliable, it’s impossible to use it to synchronise certainty of message delivery. It’s reliability that’s at issue, not latency — if your channels have high but known latency and are 100% reliable then there is no problem, just a long time lag. However, it’s hard to see how such a channel could be 100% reliable — there’s always the danger of a power failure or misaligned antenna or natural disaster at the other end.
[Answer]
## Managing "state"
In software design, there's a concept called the "source of truth" (SoT). The idea is that, to guarantee atomic updates to some data, the change must be fully written to a SoT as a transaction. Once this is performed, the transaction is "committed", and cannot be undone. If the write fails, the entire transaction is discarded.
For many systems, there is a single source of truth that records all transactions.
However, this doesn't have to be the case. Each piece of information must have a single SoT, but unrelated data can be safely divided between several SoT.
(Aside: The plural of "Source of Truth" can be "Sources of Truth", to avoid the strange `s` in `Source of Truth`'s)
One trick I find pretty interesting, is that a source of truth can be moved (or more precisely, migrated).
## Migrating
To migrate, the "old" source of truth just needs to record the location of a "new" source of truth, then stop accepting transactions.
Any system which relied on the old SoT can then just connect to the new SoT instead.
In practice, this can get very complicated, though it's relatively simple in concept.
### Migrating: Bonus exercise
>
> If the location of a SoT can change, does the "location" information for this SoT also need to be stored in a SoT?
>
>
>
>
> Answer: Yes. I've already dealt with this in the migration section, how did I do it?
>
>
>
## Regarding latency
All that really needs to be done, is to move the SoT for each piece of data closer to where it's needed, using the migration described above.
For example: bank accounts could be migrated as people travel around the galaxy. For a shared/company account, funds within the account could be broken down and given to separate branches.
## Things to remember
* There's no free lunch. If the SoT is far away, at least one round-trip is required to access it, or alternatively, to request that it be moved.
* Data that doesn't ever change can be duplicated without risk of being incorrect. (caching)
* Sometimes slightly outdated data is "good enough" for now and can fixed later. (the common example for this is the view count on a youtube video)
[Answer]
All those problems existed in medieval Europe, including months-long delays or even years in case of war, and transactions nonetheless took place.
Essentially they worked by either
* producing physical objects which act as the registry, either definitively, or until the transaction can be authoritatively recorded in a central registry
* Making more people aware of the transaction, treating the general public or specific individuals as an ad-hoc registry
**Financial Transactions**
These were handled by letters of credit, akin to banker's drafts. In a nutshell, a bank in one location takes a deposit of gold or other valuables, and issues a letter which can be drawn on a bank in a distant location. For this to work the banks must have a stock of gold to draw against. For gold you can substitute uranium, plutonium or unobtainium. Letters of credit were easier to transport, conceal and protect from theft.
The primary responsibility for proving authenticity of such letters and detecting forgeries lay with the receiving bank, and many secret methods were used to verify them such as seals, embosses, secret marks, handwriting and so forth, just as today banknotes have anti-forgery holograms and watermarks.
**Real estate transactions**
To obtain good title to land, you would have possession of a bundle of documents (called "title deeds") proving a chain of title, from some original grant of title which is uncontested. Each document would be a deed setting out what title was transferred, any conditions attached (such as a duty to pay rent, a duty to pay towards maintenance of churches, limitations on permitted use and so forth).
To convey title (e.g. to sell the property) you would hand over the entire bundle, together with a new deed documenting the transfer. In this way the bundle grows with every transfer.
The advantages is that a central registry is not required, but this system can be combined with a system of registration, registering the title as it exists at certain points is a protection against loss of the documents or forgery.
Note that this is still commonplace in England even though England has now moved to a central registry system for recording title. For properties which haven't been transferred in the last few decades, the bundle is still definitive.
**Witnesses, notarisation and publicity**
Contracts and agreements are written in physical form which is difficult to alter, and witnessed by persons who give their name, and the location where they can be found. In case of dispute, these witnesses can testify that the contract is valid.
Notaries are a special case of witnesses. A trusted person can record a copy of the document (or just details of when the document was notarized, who signed etc), and keep it safe. In case of dispute, he can consult his records.
The general case of this is essentially "spreading it around". The agreement can be published in newspapers, posted in the town square, and so forth. As long as enough people know about the agreement, it becomes impractical to deny it.
So war agreements can be proved by announcing them widely:
* posting in the public square,
* broadcasting on radio and television,
* Memorializing in stone tablets or monuments
* having them cried about town by "town criers" (officials whose job it is to make public announcements):
"Hear ye, hear ye, hear ye! On Michaelmas his Majesty the King did treat with the King of France that ..."
* having lavish ceremonies to celebrate the agreements with large public attendances attracted by free food, drink and entertainment.
The public ledger of crypto-currencies are a special case of this.
**Indentures**
Two copies of the contract can be written side by side on a single piece of paper, and both signed and sealed by all parties. The document is then folded (indented, hence the name) and torn down the middle, so that each party has a copy. Proof that the two halves belong together is given by the shape of the tear, which is unique. Proof that the documents haven't been altered, is given by the difficulty of erasing the ink used. If words appear on one copy and not the other, then these must have been added later.
These were typically used for contracts for a number of years of personal service such as apprenticeships.
**Distant transactions**
These were handled by "powers of attorney". (The word "attorney" means "appointed person").
You appoint a person in a distant location to exercise a limited power to undertake certain transactions on your behalf, and record the powers they have in a document using one of the above methods.
They then transmit to you what they have done in a similar method.
In this way you can enter into an agreement to buy a distant property (land in another country, or on another planet). An attorney in London will have instructions to sell the property. When you agree to buy, you get a physical document proving the agreement, which you take with you to your new residence in Northumbria. You present the letter to the attorney in the new location, who conveys title to you. This works because to take possession, you need to travel, and you take your proof of entitlement with you.
Sometimes ambassadors were given limited powers to enter into agreements on behalf of the sending country.
] |
[Question]
[
Try to stick as close to real-life history as possible, but what would be the most logical progression which could lead to the Argentine military deploying anti-satellite weaponry? Ground, sea, or air-based options are all on the table. Bonus points if you can make it happen before the Falkland Islands War.
EDIT: The POD can be any time between 1947 and 1982.
[Answer]
**What you're asking for is highly implausible prior to the Falklands War without a really big butterfly**
Almost no one IRL had anti-satellite capabilities by the Falklands War. The US and USSR didn't really do much with the concept until 1982, the year of the Falklands War itself. The USSR had a longer research program with at least one successful intercept by 1970, but amped up research in response to the US's declaration of an SDI program in 1982. The US didn't even get into the game until 1982 with the SDI and didn't have a working program until 1985. No other country has even tried interception technology until India and China in the last one and a half decades.
Basically, for years and even now anti-satellite technology has been the domain of superpowers. If only the two big superpowers (and arguably only one, the USSR) had the power to shoot down satellites by 1982, it's highly unlikely there is anything Argentina could do to get that technology within the time frame you ask (1947-1982).
The only possibilities I see are either:
* Argentina goes communist and the Soviets lend them their technology, creating a situation akin to the Cuban missile crisis. But this is unlikely because the Soviets had personal motivation for putting nukes on Cuba.
* Some massive butterfly effect happens and Argentina becomes a superpower. But this would require a divergence way outside your bounds, and would require something like Argentina conquering Chile, Bolivia, Paraguay, Uruguay, and maybe more to have the size and resources necessary to compete as a superpower with the US and USSR. However, this would completely screw up the Cold War (the whole reason the Cold War happened is you had only two competing superpowers, rather than a third that could break the stalemate) and Argentina would be almost unrecognizable culturally and politically. The Falklands War would probably turn into World War III in this scenario as an invasion of the territories of a NATO-member country by a rival superpower would provoke all out war between Argentina and the US/Europe, compared to OTL where other countries mostly provided support and very limited amounts of materiel.
[Answer]
**The Argentinians were the first Latin American country to put a rocket into space with domestic technology.**
[https://en.wikipedia.org/wiki/Orión\_(rocket)](https://en.wikipedia.org/wiki/Ori%C3%B3n_(rocket))
>
> Orión was the designation of a sounding rocket of Argentina, [1] which
> was started between 1965 and 1971 at CELPA, Mar Chiquita, Tartagaland
> Wallops Island.[2] In November 1966, three tests of the
> Argentine-built Orion rockets took place. [3] Developed by the
> Instituto de Investigaciones Aeronauticas y Espaciales (IIAE), [4]
> Orión marked Argentina's entry into the club of space-faring
> nations.[5]
>
>
>
In the 1970s there was interest in militarizing the space program. This accelerated after the Falklands War but there was work being done even before.
<https://www.nti.org/learn/countries/argentina/delivery-systems/>
>
> In 1979, Argentina began to seriously embark on a missile program.
> Through the Swiss Consen group, Argentina contracted the German firm
> Messerschmitt-Bölkow-Blohm (MBB) to produce Condor-1, a single-stage
> missile capable of delivering a 400kg warhead over 150km. [11] Under
> the authority of Argentina’s Air Force (Fuerza Aérea Argentina, or
> FAA), the Condor-1 came to involve a complex consortium of
> “unprecedented complexity,” … By Janne Nolan’s account Condor-1 thus
> grew into one of several third-world missile consortia at least
> partially “fueled by illegal or quasi-legal transactions made through
> commercial firms or renegade governments.” [14] Work progressed at
> home as well, with the completion of a missile design and research
> center in Cordoba in 1981…
>
>
>
-
Many satellite weapons enter orbit, which is a more sophisticated undertaking than just putting a rocket into space at the same altitude as a satellite. Orbit requires both the altitude and also lateral movement fast enough that the satellite keeps missing the earth as it falls. The Argentinians in 1982 could not put a satellite into orbit, but they could reach space.
In this alternate timeline, the 1982 Argentine antisatellite weapon uses their Condor sounding rocket. Rather than an explosive payload (they knew that it was likely their rocket would only be within a few km of the target, if they were lucky) they use a non-nuclear EMP device powered by an [explosively pumped flux compression generator](https://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator.) The electromagnetic pulse disables the satellite at a greater distance than would be possible with a conventional explosive.
[Answer]
It might be possible for Argentina to develop the capability to boost a payload to LEO satellite altitude in that time frame. It wouldn't have to achieve orbital velocity, just be able to get near the satellite before it fell back to earth.
However, one has to remember the reason Galtieri started the Falklands war: to distract the people's attention away from Argentina's dismal domestic economy.
So, while getting a payload into space, and attacking a satellite might be possible, Argentina did not have the economy to fund such an effort.
And if they did have the money to develop such a system, they probably wouldn't have started that war.
Also consider that most satellite data available to the UK, came from US satellites. Attacking them would have had far reaching consequences.
A more realistic scenario would be Argentina developing its own anti-ship missile technology. Far less expensive than ASAT, and far more effective for that particular conflict.
At the start of the war, Argentina only had a few Exocets, and shot almost all they had. If they had possessed more, and were able to take out the UK's two carriers, they could have defeated the UK invasion force, as the British would have had no air cover for their ships, or their troops on the ground.
That conflict was a lot closer than the outcome might suggest.
[Answer]
* **Imagine a commercial space program.**
That is somewhat improbable but not completely impossible. Perhaps they watched the [Chinese](https://en.wikipedia.org/wiki/Fanhui_Shi_Weixing), or perhaps the [Israelis](https://en.wikipedia.org/wiki/Israel_Space_Agency) started a decade earlier than in the real world, and the Argentine said "we can do this, too". They might have believed that there were commercial possibilities, selling launch slots to other countries, but once it was started national prestige was on the line.
The result is something between the performance of the [Europa](https://en.wikipedia.org/wiki/Europa_(rocket)) rocket and the [Ariane](https://en.wikipedia.org/wiki/Ariane_(rocket_family)), operational in the early 70s and going through successive improvements.
* **Imagine a military recon program piggybacked on the commercial launchers.**
Once the launch vehicle is there, and perhaps not as much of a commercial success as hoped, the military *first* buys a couple of launches and *then* looks for a credible mission. Commo and recon sats. It turns out that photo return and high-end cameras and film are *quite* difficult, so the program never really shows a success. The real imagery is classified, of course, and pundits argue how many years the Argentine sats are behind the US.
* **A few staff studies lead to in-orbit ASAT.**
Still looking for a way to prop up the space industry, and unwilling to admit failure, the military buys kinetic-kill sats.
[Answer]
As with other technology, they would get it as soon as the US decided to sell or lease it to them.
Simple scenario: by the 80's Argentina has long been used by the US to help covertly with its 'dirty wars' in Latin America, epitomised by the famous School of the Americas.
The US wants to extend their use of Argentina as a puppet, to take action against satellites, real or potential, launched by the Eastern Bloc. So the CIA fabricates an Argentinean rocket program, complete with famous escaped Nazi rocket scientists from the 40s (we all know they went to Argentina, Operation Paperclip notwithstanding), and uses it as a cover to transfer US ASAT technology to Argentina.
The Junta then has access to a weapon which it may or may not use as the US intended.
[Answer]
As an Argentinian let me tell you that there is a way Argentina could have that technology and, surprisingly, it wasn't that deviated from current history, it only needed 2 little "pushes":
* ***USA decided to kill ALL the Germans scientist instead of going with operation paperclip***: the brain power the Nazi had now needed a new place to escape, and Argentina was very welcoming to them. heck, in disclosed papers of the CIA they even said that [Hitler actually escaped and came to live in Argentina](https://www.foxnews.com/science/hitler-wwii-escape-investigated-by-the-cia-bombshell-document-reveals), so it's not that much of a leap that they could choose Argentina instead of USA, and with them also comes the knowledge that made possible the Apollo program.
* ***Argentina never went down the path of "Peronismo"***: Argentina was a country which received a huge influx of immigrants from the war-torn countries, having the same conditions as USA had as a "land of promises", [which showed in his increasing economy before the 1930](https://en.wikipedia.org/wiki/Economic_history_of_Argentina).
Most historians claim that before the military coup that put Peron in power (which was made to avoid what USA considered the "lefties" coming into power) the central bank of Argentina was full to the brim with gold, part came from selling food to all the countries involved with the war (on either side), and part came as the price to let the Nazi escape here without asking questions. The new military government, and subsequent ones made a show of wasting that economic power on inefficient bureaucracy and plain theft.
After WWII, with every country exhausted because of the war, the economic power resulting from good trading and economic growth, and a new scientific personal
ready and motivated to "recover" their place at the top of the world it's not far fetched to say Argentina would have turned into a new Superpower.
Of course this is Argentina we're speaking. Even if they made it it only takes a bad politician to set the whole country 50 years back. We're still dealing with the aftermath of what happened in 1930.
***note***: Some will say that things got worst for Argentina with the depression of '29, but that also hit the USA, yet they powered through it while Argentina failed. The key difference was the political stability USA had, while argentina went from coupt to coup until the 83
] |
[Question]
[
I have settings with orbital colonies around the earth. First off my idea is, if it is not profitable we would not fund it en masse. Therefore I came up with the idea that in the future we discovered that Space foundries create amazing alloys, basically near-perfect alloys - for example leading to the development of room-temperature [superconductors](https://en.wikipedia.org/wiki/Room-temperature_superconductor#Theories). And of course other fine goodies, research (most notably some progress in Graviton research - which is one of the sub-plots) and most notably - staging area for lunching first long term self-sustainable Arc, which will serve as a habitat and base for Mars Ring Assembly construction workers. Mars still suffers from tedious and expensive sky-cranes.
Some techno babble tools, rules and hand-waves for my question:
* Where gravity is desired, I have classic centripetal rings where it's a pain to pour water into a glass.
* Power is solved with solar farms or [SMES](https://en.wikipedia.org/wiki/Superconducting_magnetic_energy_storage#Advantages_over_other_energy_storage_methods) battery deliveries from the surface.
* Cooling, especially of foundries is made with another Unobtanium Alloy used as a heat-sink, ejected into space.
* Atmosphere is made with closed cycle life support systems which are effective but still require resupplies on average once per month (can function 3 months on emergency protocol)
* Food is partially supplied from the surface (the good stuff like meat, branded alcohol...), but a lot of the pressure in logistics is handled with commercial 0G hydroponics selling spacetatoes.
* Thanks to Room-temperature superconductors, we built a really cool Orbital Ring, lowering cost of surface-orbit transfer to 20 bucks per Kg. use allowed by everybody, profit shared by nations and corps who funded it.
* Inter-station trade and travel is done through shuttles either directly station to station or Ring train station to space station - I wanted space truckers for 'rule of cool'.
* To avoid collisions, orbital lanes are taken by "first come first served". Better lanes become expensive properties sold by moving your station to different orbit, allowing the buyer to move his station to your former place instead. Enforced purely by politics and economic embargoes - nobody wants tons of space debris flying around. Position is stabilized and corrected with thrusts, but there are emergency tug-ships which WILL for a big fine correct your position.
* Health effects of 0G are mostly hand waived by Centripetal habitats and advanced medicine.
**And finally my question:**
Are space stations feasible, under these rules, to for example have spacious corridors where one can "fly thru 4 people abreast"? Could there be Centripetal Rings with diameter 1600m (circumference 5000m) with speed around 1RPM to maintain 1G (correct me if am wrong here) made from CURRENT materials (To give me some perspective so I can scale my stations properly when super-alloys are applied). That must be MASSIVE structural strain right? And now... could there be maybe even hundreds of them around Earth in various distances, with collision safe orbit distance and still keep all of them in the planet's gravity well?
Feel free to pinpoint major red flags in my rules too (but keep in mind it is a sci-fi), but my main concerns are those stations. Thank you.
[Answer]
Mmm, quite pleased with answers which are placed already, seems WB does better those days, nice to see. Here my own 2 cents on your problems(and solutions).
**Reasons**
As for the reasons, it not necessary to introduce some unobtanium at this point in time. Unobtanium is more suitable for small scale like it is now, there are examples of producing fiber optic in 0g, and thanks to the absence of weight it turns to be of better quality for some reasons.
Proposes by SpaceX network of satellites can be a significant driver for expansion, and servicing them in orbit can be a start for having production capabilities in orbit, which can serve as a seed for further expansion and scaling up. Having them being serviced in orbit solves few challenges - one is a more relaxed choice of materials used in those satellites, as a strategy of their disposal is not anymore a burning of them in the atmosphere but refurbishment or scraping for materials for the production of something useful in orbit(for that production facility or for energy collection or else). So it's a natural extension to reuse materials which you already send in orbit. And it basically half'ing the price - whatever it is cheap or expensive.
Cleaning orbit maybe another activity which primes the bigger things, as there about 8000t(around that number, may remember it wrong) debris in orbits, it is scattered but, there are proposals of different mini space crafts which goal is to service present satellites in orbit in terms of repair, and moving them in a graveyard - thus extending their operational lifespan. You can scavenge for some bits on [Robots In Space LLC](https://robots-in.space/) site/blog the guy has some good ideas, but there are more out there.
ESA announced few years ago about [air-breathing electric thruster](https://www.esa.int/Enabling_Support/Space_Engineering_Technology/World-first_firing_of_air-breathing_electric_thruster) which can be nicely combined with ideas of servicing satellites.
Both thruster and servicing incentives can be combined with in orbit refurbishing of those electric engines and their energy-producing setups, by some production station, and then it may not matter that much how scattered debris is - one can collect it all(but timewise(reasonable time), more like a good portion of it).
so that servicing fleet can be expanded using the debris, if it half of it then 10 times of that ISS station we have, by mass. And it quite a significant portion of the material to work with and it may be capable of different kinds of things.
[Here](http://toughsf.blogspot.com/2017/09/low-earth-orbit-atmospheric-scoops.html) is quite an extensive article on in orbit air scooping. And that air can be used to refuel some stations(current or future ones) so it may be useful as for now(making some profits here) so as for your stations and their air loss.
the same air can be used as reactive mass for those ion engines as a reactive mass in transits between Moon and Earth. This may be a significant expense slashing solution for all programs connected with the moon, which you mention in some of your comments.
**Expenses**
I'm not the fan of unimaginable expenses positions, so as the unifying goal, it more likely some enterprise or smart gov(if there is some - china is that you?)
Combining technologies and business as which are mentioned earlier and more, it possible to create some specific in orbit solution that may prime further expansion, in form of some production platform of 10x ISS, which we may operate remotely, so no humans there, and which may be an integral part of solving current demands and which on its own providing additional options and possibilities.
If we take that Starlink proposal from SpaceX, I'm a firm believer it will be a cash cow with a good yield, as it is way too convenient for many applications to have a good connection in all the places. So it will pay itself off easily. Even smaller satellite servicing startups if they would hold a bigger picture and path in their view they have a chance to prime that 4000-8000t production station in orbit. And make that cheap connection between earth and the moon.
So do not fix on great capital investment at the start, it more about will, vision and some money not trillions one trows in the project. Thanks to the sci-fi will and opportunity and negotiations are those you can easily handwave by the power of your letters, which in reality is slower and more painful to achieve. One has money there are easier places to invest, one has ideas but didn't the homework in being wall street wolf.
There are really more tricky and crazier options, to prime stuff with small scale rockets like the scale of [Electron (rocket)](https://en.wikipedia.org/wiki/Electron_(rocket)), and there are even more out of ordinary proposals(still rocket-based, with some tech and support of that production orbital base that Electron rocket could deliver up to 10x what it can do now).
**Economical reasons**
Looking at the Moon, you do it right.
Besides supporting our current space activity by cleaning orbit, by extending the lifespan of satellites with the same launch expenses, by providing air supply, by recycling space trash flying and produced by stations, by producing something which may be done better in 0g(it not only optics, chemistry, crystals, electronics etc) - participating in all or some of those can provide some pocket money, but the real deal is sure the moon as a source of materials - not necessarily some specific materials but any materials which can be used in construction for space structures.
By coincidence and magic of 0g, any material you scoop from the surface of the Moon can be used in construction, as one of the main things, there is no weight so it has just to not fly apart. So glass fiber(or more likely basalt) fiber, so as sintered "bricks" can be used pretty much as is to build habitable volumes aka space stations for humans.
Even with current or projected prices from SpaceX, the price of any dirt you may deliver from moon to earth orbit is quite high, if you may sinter it to some usable construction. Sintering process for producing and using for moon bases is an actual topic that is researched by different people, and it is possible and maybe even easier in 0g as it does not need to be that high grade, to begin with. More you can do on that in orbit seed production platform more you can produce from it, including extraction metals and our usual tech for use of those.
So that link Earth-Moon-Earth is essential for making more profits and do more.
Even with your mentioned 20 bucks per kilo, it means 20 thousand per tonne, and with relatively simple means you can massdrive from the surface of the moon millions of tons. 2019 article [this](https://theconversation.com/how-spacex-lowered-costs-and-reduced-barriers-to-space-112586)
* *For a SpaceX Falcon 9, the rocket used to access the ISS, the cost is just $2,720 per kilogram.*
So the main trick is what you do on the moon, how you do it, I guess you have your own ideas about that, but there are also ways in line with that production seed station. But being delivered on proper orbit, any dirt costs around 2 million per tonne(as of now) if you can shape use it in some useful way, and it(shaping in a useful way) can be done with moon dirt.
**Economical reasons, real money**
Having a link between Moon and Earth this creates the opportunity for having real money flow, if you need it, as at that point you need more technologies and improving technologies to achieve your stations or orbital rings whatever. But okay, for the shake of those technologies be developed by people you hire, one needs money, where to get them.
There are several ways and ***Energy from space*** maybe another cash cow. There are plenty(several) of project proposals of that kind, and some are studied in depts by NASA-related folks. The main problem of those as it seen from all those studies, and as it is seen now is the cost of launching stuff in space from the Earth. And that part is covered if you have Earth-Moon link.
Energy is essential for all parts of our technological life, so as the energy from space is all green(almost) and cool, it does no run out ever, no fuel of any kind is required it already there and will be for next few billion years, and you merely redirect it.
***Data processing*** is another very essential and somewhat money earing direction that has broad application/use/list of consumers. Training AI's for different fields may be expensive as I have read from OpenAI guys which made their bots for Dota competition year a few years ago and for AlphaGo, they would like to run mass training more often but it costs them 10's of thousand for a single deep run session. And that problem of teaching AI's networks as for now it does not require top-notch processors it requires many many of some good enough processors, so it a venue which can be explored - by producing them in space and having data centers in space, in similar ways as that Starlink project. And some huge huge setups which dwarf the whole Top500 list, in some of Lagrange points. [There](http://server-sky.com/) is a proposal of cheap grid computing using solar energy for free, no sms - the direction of thinking is actually quite good.
At that point, some ***planet-scale*** moves may be possible - cooling the planet starting from dusting atmosphere(like vulcanos do) to make manageable sunshades which more fine-tuning who and how much energy gets on the surface of the planet. And it has a direct connection to another essential - food production, weather, temperature, CO2 consumption speed, AC usage in cities, the habitability of some countries in general which may be(or may not) a problem in the future because of the peak temperatures(they are on the threshold already).
So there are broad and deep money wells to tap into if one can deliver stuff from the Moon.
Thanks to all that, ***actual living*** in space on a great scale may be made possible so as the price of delivering stuff from the planet into space maybe not that much relevant, as that energy from space may work on the rocket making business supply enough energy for them to produce one rocket per hour in the middle of pacific as an example.
Making ***Research and Development*** cheap. For our technological society, it is a core being able to develop new stuff and fix problems etc. This necessity permeates the whole society - all the needs are connected to some RD done. And space resources can make it cheap, pay 10 times less, get 10 times the result. So some remote labs rented, sold whatever - and customers are whoever develops technologies, basically everyone. Sure it hard to provide everything for all at once, but it is a big market to be consumed by a combination of different means.
Quite skeptical on Bezos statements of moving production from the earth, he is far behind the current wagon with this one, we do not need that, we just need more energy to recycle the waste, but moving RD processes in space - that a totally different deal, making something from Top500 as your desktop PC for your lab or fiddling with the artificial intelligence of game server, a similar transition which happened in 70's - that's a deal which is not possible(almost, fusion) on earth, but which can be done just by scaling in space.
**Back to station**
as for the size of the station, I may suggest looking [this](https://worldbuilding.stackexchange.com/a/46325/20315) answer of mine, even if cylinder design has its problems, stresses induced are calculated in an okayish way, so km's sizes are achievable. In general look at ***Kalpana one*** design, it quite reasonable, and good enough for starters.
In general, the diameter isn't that limited by materials used, if you imagine it like some sort of bearing which one part is rotating and another is not and that no rotating part of the construction takes all required loads. And you can make that external part as big as it needs to be. Sure there are still some limitations and challenges, but they far beyond a few km's sizes.
One can easily place a hundreds of them even on the same orbit, km's apart like a cluster of those or 100's km apart. Yes sure you need some monitoring orbit correction system for those, but not a big deal as of today, and if you have air scoop then you do not have any shortage of reaction mass for corrections.
* *where it's a pain to pour water into a glass.* - guess it is a joke all isn't that bad.
* *Power is solved with solar farms* - yeah, a way to go, and you do not need SMES for energy storing, in rotating of the station itself or similar structures plenty of energy can be stored.
* *Cooling* - as mentioned in one of the answers it has better options, in general it is not a much bigger problem than cooling a station itself. It isn't a big problem if you do not do huge huge things in one solid piece by casting - but there no heatsink can help you to solve that, and it needs just different ways of making stuff.
* *Atmosphere ... resupplies* - not such a big problem with scooping, and in general, it should hold and easily can do much more than 3 months without resupply. IDK I guess your plot may require that, so just noting that. Volume grows proportional to a cube and surface proportional to square and that creates a big reservoir of those gases, for any big enough station.
* *Food is partially supplied from the surface* - you need only branded stuff, the rest can be produced locally relatively easy and it is a way to close cycles by air water and stuff.
* *we built a really cool Orbital Ring* - yeah, why not, mine Moon well, and you will have it.
* *Inter-station trade and travel is done through shuttles* - idk, maybe focus more cyberpunk style, more on immaterial digital goods - technologies of production. Still, there is a place for cool drivers transporting expensive cool handmade one of its kind stuff, it more elite and cool than transporting toilet paper between stations in space trailers.
Here it needs to focus more on the aspect. Production on stations can be fully self-sufficient. Reason being - cheap and abundant energy supply. It way cheaper to get energy in space than here on earth, there are many reasons for that, but consider one of them - a thin foil shaped in a spherical way is all you need in space to heat something to stunning 5000-6000K temperatures, so your steam or CO2 or Na-steam turbines will work like a charm. (in orbit, especially at LEO, it may be bit trickier but not by much). So it simple as technology, as the production of those etc etc, and it weighs less as there is 0g so fewer materials required in places which are wasted on supporting structures, protecting them from the atmosphere, rain, wind etc.
So big factories which we build here on earth are for efficiency - energy efficiency of processes and other benefits of scale. But if you have cheap energy, if one is 10 times more wasteful in terms of using the energy it does not matter as you may have as much as you need. Sure there are more reasonable and less reasonable ways to do things.
You aren't constricted by flat area, so a by territory limitations in general. So, in general, you may have all the technologies we have today on some smaller scale, as big as you need it to be and to not worry about being a few times less efficient in production as those surface bigger counterparts are. So your cost more in RD, and here you can tap for the earth and send the plans via email and such. I mean if there is some stuff you need and if it can be produced in a lab(and basically all stuff we do is produced in a lab for the first time) if it does few times 10 times less efficient than big factory you still can stick to lab way of doing stuff. And scale the process according to your demands.
* *To avoid collisions, orbital lanes are taken by "first come first served"* - no need for that really. You can easily have a million crafts swarming near the station waiting for their time or just hanging there. So as orbits are big, a single plane LEO orbit is about 40000 km, so there plenty of space considering every 100 meters is basically a new orbit. Some unified system which guides the crafts sure is needed, so as the preferred direction of the orbit may be useful, because 2 space crafts separated by 100m orbits, they move very slowly relative to each other if they move in the same direction.
So limits are high, you basically can launch a million of spacecraft from your ring, each minute and still easily manage them in orbit +72km.
* *Health effects of 0G are mostly hand waived by Centripetal habitats* - no problem here, as for me.
[Answer]
**Your technology seems fine** except for the heat disposal methods. What's wrong with **good old radiators**? Try liquid tin droplet radiators or ones using vacuum oils as a coolant to reduce the mass. Furthermore, **heavy space industry** would be better off around or **on the moon** in many cases since it is safer there if accidents happen and Luna can be mined without any concerns for the environment.
I'm more **optimistic towards orbital rings** than others here, maybe too optimistic. The only way to settle this is to wait until the first active support structures have been constructed. One worldbuilding detail to note however is that orbital rings don't come in a vacuum. **Atlas Towers, Looftstrome Loops, and actively supported intercontinental bridges** would precede them. Have them in your setting to make it more believable.
Your space habitats are impossible I'm afraid. Not generally but in the configuration you want. "Gravity", RPM and radius aren't independent of each other. You may pick two, then you get the third for free. If my math is correct, you can get:
$$gravity: 10 m/s2$$
$$rotation: 1 rpm$$
$$radius: 911.8913 m$$
You can calculate it via:
$$gravity = round(pow((rotation / 9.5493), 2) \* radius, 4)$$
$$rotation = round((pow(gravity / radius, 0.5) \* 9.5493), 4)$$
$$radius = round(gravity / pow(rotation / 9.5493, 2), 4)$$
Note that 1 RPM is quite conservative. I use gravity: baseline: 6.8 - 15, adapted: 1 - 35, RPM: baseline: > 2, adapted: > 6 and radius: baseline & adapted: 17 m (due to tidal forces) for my world-building. Those are decently researched ranges, the only way to get something better is to actually build a space station.
Assuming you want about 1 meter of water, 2 meters of soil and 3 meters of 200 kg/m3 infrastructure and no aerogel for better landscaping per square meter and a 1 atm atmosphere I get:
$$pressure vessel shell: 0.13859607895875 m$$
$$structural hull: 1.1357 m$$
$$average thickness drum: 7.2743 m$$
$$mass per square meter: 14239.7633 kg/m2 or 14.2398 t/m2$$
using steel for structural support or
$$pressure vessel shell: 0.21655637337304687 m$$
$$structural hull: 0.3562 m$$
$$average thickness drum: 6.5727 m$$
$$mass per square meter: 5302.2579 kg/m2 or 5.3023 t/m2$$
using a carbon fiber material.
If you have more concrete ideas about the parameters you want, tell me in a comment and I'll run the number for you.
[Answer]
**Where there's a will, there's a way**
This mission is technically possible, especially if you fill in some of the blanks with a little sci-fi hand waving. With current technology, you'd be talking about a plan that would cost hundreds or thousands of billions of dollars. You would need *massive* popular and political support to dedicate that kind of funding to a space project when there are real problems here on Earth.
What ultimately killed the Apollo program wasn't any hard limit of technology, it was [political will](https://www.scientificamerican.com/article/canceled-apollo-missions/). I'm currently reading the book [Gateway to the Moon](https://www.goodreads.com/book/show/776444.Gateway_to_the_Moon), which describes the development of Cape Canaveral. There were some drawing board plans for the level of space launch capacity that you would need for your mission. There are even a few places where infrastructure started being built to support additional facilities before plans were scaled back. The Space Shuttle program was designed to fly "[on-time and often, like a fleet of cargo airplanes.](https://www.wired.com/2012/03/what-shuttle-should-have-been-the-october-1977-flight-manifest/)" Those plans, too, were severely scaled back due to a lack of support.
Remember that the US Congress just passed an economic stimulus worth trillions of dollars. If a similar amount of money were directed towards your project and the project generated financial returns to offset some of the investment, it's plausible. The biggest problem is coming up with a reason that the public and Congress would support it. Even in sci-fi, this is a real problem. Here's an [excerpt from Stargate: SG-1](http://www.stargate-sg1-solutions.com/wiki/1.08_%22The_Nox%22_Transcript) where the Secretary of Defense questions the economic value of the Stargate project.
>
> SECRETARY Do you have any idea what's out there?
>
>
> O'NEILL No, sir. That would be why we're going.
>
>
> SECRETARY I'm not sure, Colonel, is it? Because to be perfectly frank
> this administration is not satisfied with the current progress of the
> Stargate program.
>
>
> [The SG-1 teammates exchange concerned glances.]
>
>
> CARTER Begging the secretary's pardon, sir, but we've already visited
> nineteen separate worlds.
>
>
> HAMMOND I believe he is referring specifically to the volume of
> technology being retrieved on our planetary missions.
>
>
> SECRETARY The President and Joint Chiefs were under the impression
> that the SG teams would be bringing back superior technologies.
>
>
> [Daniel comes forward.]
>
>
> DANIEL I'm sorry, I…I thought we were explorers.
>
>
> SECRETARY Oh, you are Dr. Jackson. But even Marco Polo when he came
> back from the Far East brought back more than just a few…exotic
> spices.
>
>
>
[Answer]
`reality-check` eh? Then check this reality:
**Politics of power**: if a nation has enough materials/energy to place gigatons of materials into orbit, it has enough materials/energy to drop on anyone it wants to call an enemy.
Don't hold your breath, it's not gonna happen in out life-time.
---
You will need to use Moon as the source of your raw materials, extracting them from the gravity well of the Earth is simply too expensive. Probably - for causes better not explored here - the political heads got convinced of this already, with the attempt to kick-off the [Artemis Accords](https://www.reuters.com/article/us-space-exploration-moon-mining-exclusi/exclusive-trump-administration-drafting-artemis-accords-pact-for-moon-mining-sources-idUSKBN22H2SB).
[Orbital Ring](https://www.youtube.com/watch?v=LMbI6sk-62E) - video exploring in more details the feasibility and problems of such a superstructure. Hinges on gigatons of materials placed in orbit and the stabilisation of it (it does require lotsa magnets). Everything boils down to the energy expenditure you can afford to invest into it.
If you have this level of energy\*\*, then the rest are engineering and logistic problems that are solvable.
\*\* energy that you can obtain in ways which don't place a gigaton of toxic poop into the very place you want to start from (Earth)
---
Costs? Hey, with an orbital ring we're talking about a superstructure 40000km+ in length and with a "thickness" at least in the order of 100m for useful applications.
From one of your comments:
>
> Report outlines a design for an orbital ring with a cost estimate of $9 billion that can be built using existing technology
>
>
>
Say what? Using [$7M per 1mile of 6-lane Interstate highway in rural areas](https://medium.com/@TimSylvester/i-agree-it-sounds-astronomical-but-i-actually-understated-the-costs-according-to-artba-2e8baeac2a46), a 40000km (=24855 miles) of a just-gravel-and-bitumen-orbital-ring is \$174B.
Think a bit about the amount and price of room temperature superconductors and permanent magnets to replace that gravel (and you need them to keep that orbital ring... umm, well... orbiting) but stop quickly from thinking, the number with \$ in front will be so astronomical it will lose any meaning that a human mind can comprehend.
] |
[Question]
[
I was wondering how/if it would be possible to create an earth-like (atmosphere, gravity, average temperature, etc. are close enough) rocky exoplanet with more than two or three significant temperature oscillations (like our seasons and day/night cycle). Creating basically a Game-of-Thrones esque scenario for intelligent life on this planet with seemingly unpredictable seasons until the advent of (advanced) astronomy.
Could orbital mechanics provide for more cycles?
How complex could it get?
[Answer]
One way of doing this is to start with a binary of A- or F-type dwarf stars, orbiting eachother closely (required for long term stability). Then, place a late-K or early M dwarf in an eccentric orbit that's not exactly planar-aligned (when it comes to both star systems) with the pair at a much bigger distance; on the order of $5-10AU$ away.
We want our larger stars to be heavier to create multiple year cycles of different lengths: they need to have a significant luminosity at larger distance, and be heavy enough that the gravitation of the red dwarf does not destabilize them. On the other hand, making the central stars too heavy would reduce their lifespan by too much: having at least a billion years of stable main-sequence burning means anything bigger than an A-type dwarf is too short-lived. We would like our red dwarf to be stable though; and for that it may need to be much older than a billion years.
That can be explained as the smaller star being captured at some point by the pair, which is actually very young still (A- and F-type stars achieve main-sequence stability much faster). It can also be used to use a larger age for the smaller star; giving life more time to develop on the earth analog; albeit on a frozen world in subsurface oceans. Then the analog of the cambrian explosion can happen once system capture occurs and surface temperatures rise above freezing for the first time.
Solar masses of around ~$1.6M\_{sun}$ to $1.8 M\_{sun}$ for the large stars and $0.5 M\_{sun}$ for the smaller star get us reasonably close to the goal.
Place our rocky planet in orbit around the red dwarf, actually outside of its normal habitable zone (further away). The stars each make a significant contribution to the light on the planet, with most of the light coming from the dwarf, and the sum is enough to make the planet habitable. Even though their spectra would normally be significantly different from ours individually, the mix will get us a light spectrum that's actually closer to ours than each individual component.
Then make sure the rocky planet's orbit around the red dwarf also has a mild eccentricity and earth-like axial tilt. Now we have at least 8 causes of seasonal variation in climate with varying periods and strengths, most being significant (more than a few $^{\circ}K$ at mid to high latitudes).
One can also assume (due to the capture history) that the orbital planes of both star systems don't necessarily align: there might be some inclination.
1. Planetary axial tilt.
2. Day/Night cycle.
3. Axial precession / Milankovic cycles.
Just like on earth, the axial tilt of the planet will create seasonal variations, with greater effects near the poles. There's a day/night cycle with the red dwarf, and a much longer cycle of axial precession.
4. Second day/night cycle
There's also a second day/night cycle with the binary system. If there's inclination; this second day/night cycle isn't synchronous with the first: there's a second 'equator' pointing to the binary system intersecting the one with the red dwarf.
5. Eccentricity
The much greater eccentricity of this planet compared to earth makes it a substantial component. Depending on the position in the milankovic cycle, winters and summers on one hemisphere will be more intense, while on the other hemisphere, the effects counteract.
6. Inner/Outer system cycle
The planet will cycle from being further away than its parent star from the barycenter, to being closer, in a cycle lasting either slightly shorter or longer than its year (depending on whether the orbit around its parent is retrograde or not compared to the orbit of the red dwarf around the binary).
During one half of the Inner/Outer cycle, the whole planet will be to some extent lit. This is due to the planet being in between the stars. Instead of applying to half the planet like axial tilt.
This effect may increase temperatures, because the planet is much closer to the heavier stars while in the inner system, and vice versa.
7. Eccentricity of the red dwarf orbit.
This is an oscillation with a long time period; up to several hundred of the smaller 'years'. It also affects the amplitude of oscillation [5]; during the 'winter' period wrt the binary the type [5] oscillation will have a smaller effect. The orbit of the red dwarf takes the planet closer and farther from the binary stars.
8. Eclipsing
The stars in the binary star system eclipse eachother. This causes a variation in light where during the eclipse (the closeness and size of the stars mean these eclipses are common and long-lasting) the luminosity from the binary is nearly halved, causing a predictable drop in temperature everywhere it's 'day' wrt the binary every time an eclipse happens.
9. Eclipsing precession
If the orbit period of the binary is by coincidence close to (a multiple of) the length of a day, then it might occur that the eclipse happens at the time where the binary system is brightest (or not visible) each time it happens at a certain location on the planet. As each member of the binary is similar in luminosity, there's a significant difference in light intensity between these two cases. A slight difference between the lengths of the two cycles creates a precession. A pattern where there's a variation of temperature/climate by longitude; with a thin 'wedge' where the temperatures are colder due to the eclipse repeatedly occurring during the time the binary is visible in the sky.
10. Eclipsing and inclination
The effect of [7] only happens while the planes of both the binary and the captured system (nearly) align. If there is enough inclination, then eclipses of the binary could only happen during the 'spring' and 'autumn' phases of oscillation (6). If there's a lot of inclination then neither this effect nor the previous effect happens; the 'eclipse of the binary' becomes a very rare event; observed twice during the binary 'year' and only on certain locations.
[Answer]
I would argue that Cixin Liu did this in *The three Body Problem*, but maybe more of this than you want:
>
> Over the course of the first book we get to learn a bit about the Trisolarans: theirs system has three suns and orbits are utterly chaotic, the planet may enter a closer orbit for a while and become mercury hot for a few years, decades or centuries, it may be flinged into a very wide orbit and freeze (as in: it's raining nitrogen) and back again. The trisolarans have (or claim to, we don't really meet them as far as I've read) a remarkable ability to dry out and hibernate during their planets inhabitable spells. The point here is that a system of three suns is utterly chaotic and unpredictable even with advanced astronomic knowledge.
>
>
>
] |
[Question]
[
Are there any areas of space where an antimatter object, the size of a small house could survive without coming into contact with any or extremely minimal amounts of matter?
I had assumed in all areas of space the object would come into contact with enough dust and gas to make it explode/ disappear eventually, when researching I have had contradictory information, some saying it is possible in the galactic voids or some areas of interstellar space and others say it would not last long in all areas of space over cosmological time spans.
Where in the universe would be the best places for an antimatter object to reside and how long could it survive there?
[Answer]
## A cosmic void.
Your best bet would be in a [cosmic void](https://en.wikipedia.org/wiki/Void_(astronomy)). While not entirely empty - they do contain small numbers of galaxies and clouds of gas - they are substantially rarefied compared to your average patch of the universe. Although I've been unable to find concrete numbers for the low-density gas that would permeate a void, we do have estimates for [the mean galactic number density](https://astronomy.stackexchange.com/a/16146/2153), which is roughly $\mathcal{N}\sim0.004\text{ Mpc}^{-3}$, in units of galaxies per cubic megaparsec. If each of these galaxies is the mass of the Milky Way, they contribute a number density of $n\sim0.25\text{ m}^{-3}$ - assuming the galaxies are largely composed of neutral hydrogen.
It seems not unreasonable enough to assume that these galaxies are a decent proxy for the mean void density, and so we can safely assume a particle number density substantially lower than the numbers L.Dutch mentions - by many orders of magnitude!
So let's say you have a cube of hydrogen atoms of side length $l$ with a cross-sectional area $l^2$ of one square meter and the density of water $\rho$, moving at close to the speed of light relative to the gas (which is the worst-case scenario, as it implies a higher collision rate and therefore a higher annihilation rate). Over a time $\tau$, it sweeps up
$$N\_a=\tau vl^2n$$
atoms of the void. It is composed of
$$N\_c=\rho l^3/m\_H$$
atoms itself, and the cube is entirely disintegrated when $N\_a=N\_c$, or
$$\tau\approx\frac{\rho l^3}{m\_Hnvl^2}\approx2.5\times10^{14}\text{ years}$$
If you just want one millimeter shaved away, that should take three orders of magnitude less time - about $\sim10^{11}\text{ years}$.
Over a time $\Delta t$, the cube will pass through
$$N=\Delta t v l^2n$$
atoms, releasing
$$E=N\cdot 2m\_Hc^2$$
energy. The power emitted is then
$$P=\frac{E}{\Delta t}=vl^2n\cdot 2m\_Hc^2\approx 22.5\text{ milliwatts}$$
which is surprisingly little.
Of course, the whole thing is kinda moot because any void is finite. After all, the [Boötes void](https://en.wikipedia.org/wiki/Bo%C3%B6tes_void), for instance, is only 330 million light-years across, and so, traveling at the speed of light, the cube will only spend 330 million years inside, shaving off about 1.3 *micrometers* in the process. (You can of course increase this time significantly by decreasing your speed!) Your mileage may vary, of course, depending on both the size of your object and whether I actually did the calculations right.
## Notes
This is really just a toy model to get you an order-of-magnitude idea of how slowly annihilation will occur. A one cubic meter cube of hydrogen is an unrealistic object and would of course dissipate quickly, regardless of its environment - it's almost certainly not self-gravitating. Therefore, we can't really model the effects the annihilation would have on it. However, a *realistic* object would indeed see some more complex effects. For instance:
* Some of the emitted byproducts of annihilation (e.g. gamma rays) would be directed inwards, and would potentially ionize or (more likely) knock loose additional atoms of the object.
* The object would likely be slowed down by the drag of traveling through this sort of medium (even such a rarefied one).
* At the (again, unrealistic) relativistic speeds our toy model is moving at, there would indeed be special relativistic effects.
But again, this is just a toy model designed to point out that a cosmic void is an excellent place to set down your antimatter object.
[Answer]
How empty is the [vacuum of space](https://en.wikipedia.org/wiki/Outer_space)?
>
> even the deep vacuum of intergalactic space is not devoid of matter, as it contains a few hydrogen atoms per cubic meter
>
>
> The density of matter in the interstellar medium can vary considerably: the average is around $10^6 m^{-3}$, but cold molecular clouds can hold $10^8–10^{12} m^{-3}$
>
>
>
Considering that a mole of matter is made by $10^{23}$ atoms, to be fully annihilated that mole would need to cross a volume between $10^{13}$ and $10^{17}\ m^3$, if it was made of hydrogen.
$10^{13} m^3$ is the volume of a cube with side as large as the solar system, while $10^{17} m^3$ is the volume of a cube with side as large as the distance between the Sun and Tau Ceti (a bit more than 11 light years).
Though humongously large, those volumes are small when compared to the size of the universe, even if you scale up the mass to account for more than a mole.
How fast the object could last would depend on the velocity with which it is traveling. If it was traveling at 1000 m/s and had a cross section of 1 square meter, to swipe a volume of $10^{13} m^3$ would take $10^{10} s$, about 10 centuries.
If your criteria for "surviving as an object" is that at leas one atom of the original object is present, then the above is the estimate of the life span. If you are more strict and the first annihilation destroys the "object" as such, then the lifetime is much shorter, as the first impact will do.
[Answer]
There is a hypothesis that the Universe was formed with equal amounts of matter and antimatter. We know there is a lot of matter in constant expansion after the Big Bang. So, we have two options:
a) Some unbalance happened among them, and antimatter is rare. Far away of gravitational field of galactic groups the antimatter can remain for an undefined amount of time.
b) The Big Bang expansion split somewhat and there is an unreachable 'anti-universe'. In this scenario, antimatter remained and will remain like regular matter in our universe.
The wiki article [Baryon asymmetry](https://en.wikipedia.org/wiki/Baryon_asymmetry) explains both.
] |
[Question]
[
My fantasy setting is on a wet and humid world of innumerable islands; many of which are quite mountainous.
With conditions ranging from Mediterranean to Tropical.
The culture here experience only two seasons Wet/Rainy and Dry.
Their Calendar divides the year into two seasons.
Which in turn divides each season into three phase of Waxing, Apex and Waning, the beginning, middle and end of the season; each phase divides into months.
With mountain regions often being cooler than the low lands in reality.
**I thought that the Mountain folk might experience different season, and develop a more earth like Calendar?**
If the above/bolded not plausible then what would be?
* Would the Mountain folk use the same Calendar system as the low landers?
* Would the Mountain Folk experience a different enough condition from the low landers and most real worlds cultures to need a unique Calendar?
* If the immediately above is true, what are mountain seasons and weather like?
[Answer]
**The mountain folk use an older calendar.**
The Julian calendar was introduced in the time of the Roman Empire and was adopted throughout the western world. In 1582 the Pope introduced a revised calendar called the Gregorian calendar, and over the ensuing centuries this calendar supplanted the older Julian calendar.
Except where it didn't. The Berbers in North Africa still use the old Julian calendar.
<https://en.wikipedia.org/wiki/Berber_calendar>
>
> The current Berber calendar is a legacy of the Roman province of
> Mauretania Caesariensis and the Roman province of Africa, as it is a
> surviving form of the Julian calendar. The latter calendar was used in
> Europe before the adoption of the Gregorian calendar, with month names
> derived from Latin.
>
>
>
Berbers are to some degree set apart from the larger populations in their regions. They are the equivalent of your mountain people - an insular group who sticks to the old ways. Your mountain people use the old calendar of the empire that used to rule their area thousands of years ago, like the Berbers do.
[Answer]
Calendars are almost entirely social constructs. A calendar typically marks divisions of a solar year, so presuming that your planet goes around its sun in a manner that's observably consistent to both cultures, then their calendars would be of the same length. The smallest division would presumably by a day period, though on a tidally-locked planet, this might not be the case.
Between the cycles of years and days are seasons if your planet has an axial tilt, but only then. Two cultures would observe the same length of seasons, but wouldn't necessarily experience them the same (summer in the northern hemisphere is winter in the southern, and vice-versa).
Beyond seasons, the rest of the constructs are entirely artificial. The day of the year that's marked as the start of a year (presuming you have a convenient solar year divided into an even number of days; no leap years) would be different between calendars, as would the length of any other units like weeks (for us defined as a half-moon) or months (defined almost arbitrarily).
So use a basic framework to lay out your planet's solar and lunar cycles, then decide for yourself how the different societies observe them and count them.
] |
[Question]
[
Say you somehow invented 50 thousand nanobots that are the size of medium sized bottle caps. Each are capable of hovering for a limited amount of time but do recharge with both solar energy and plug ins.
Now say you you want to control them and make them act like a single entity, to the point in which you can make a hand with them and make it grab things.
**what method or how can a human be able to control over 50 thousand nanobots to perform like a single object, and is such an idea feasible?**
Also, their is no magic in use.
[Answer]
**Flocking behavior.**
You will not directly control your many drones. You will set a task and the drones will communicate between themselves and figure out how to do it. Like an ant or bird, each drone will have a set of rules that govern its behavior according to its position and motion, the position and motion of the target and the position and motion of other drones in its flock.
<https://www.wired.com/story/how-a-flock-of-drones-developed-collective-intelligence/>
>
> ...In contrast, each of these 30 drones is tracking its own position,
> its own velocity, and simultaneously sharing that information with
> other members of the flock. There is no leader among them; they decide
> together where to go—a decision they make on the literal,
> honest-to-goodness fly.
>
>
> They're like birds in that way. Or bees, or locusts. Or any number of
> creatures capable of organizing themselves majestically and somewhat
> mysteriously into cohesive groups—a so-called emergent property of
> their individual actions...
>
>
>
You will not be directly controlling them but rather sipping a mojito and cheering them on. Your work was devising and testing and revising the algorithm governing the flocking behavior.
[Answer]
From a comms perspective what you need is a technique called [Multiplexing](https://en.wikipedia.org/wiki/Multiplexing). This technique has been around since the telegraph and in general terms allows one to share multiple signals on a single 'line'. In the case of your nanobots, this is probably a single wireless channel.
The link provided talks about the different types of multiplexing techniques and I don't believe that there is one among them that will *easily* manage up to 50k streams, but it's possible even if you have to split the units up into multiple channels to communicate with them all as a whole.
As for how you get them all to do your bidding as a single unit, there is no way you can individually control that many drones to operate as a single hand by programming them individually in real time. That said, it will be possible to record a set number of 'patterns' or tasks into your drones, and manage them macroscopically, so to speak. In other words, you can issue a command like 'grab thing at this location from North' and the drones will be given the commands that render that effect.
Another way to put this is that to make your drones useful, you have to surrender some of their flexibility by functionalising larger tasks, then sending signals that tell the swarm what to do as if it was a single unit. That then allows the software that renders the function to design a multiplexed signal that tells each drone what part of that function they need to perform.
In short, it is certainly possible with existing techniques, if not existing technology, but to do it you have to build an abstraction layer over the top of the drones that treats commands to them as a single unit, rather than trying to get creative and building a bespoke drone configuration for every task. Over time, your knowledge and experience will develop to the point where you end up with more sophisticated and configurable functions and tasks as an asset base of actions for the drone swarm but ultimately what makes it useful is that abstraction layer that interprets what a swarm function means to each individual drone and sends out the commands accordingly.
[Answer]
Your nanobots, just like living beeings create a new generation any x-lifecycles.
They do this to repair, get more numerous- and to pass on instructions- via genedrive. Meaning.. a new nanobot with a brand new instructionset, overrides previous instructions by his ancestors writting over the instructions of the previous generation.
So to pass out new information, you need to wait the time of the genedrive to pass through the population.
Even then pockets with old information may survive.
] |
[Question]
[
In traditional Elfland stories, and in C.S.Lewis' Narnia, when a character enters the alternate reality they start with their current age and age normally in that reality, but on return to their origin while they retain their memories, their age is 'corrected' to their origin calendar: some folks crumble into dust, the Lewis characters are no older.
Re-entering Narnia, the children are not 'corrected' to their last time in Narnia, but start at their latest 'real' age again. (I don't know what happens to someone re-entering Elfland.)
In contrast, a harder sci-fi approach would have a character ageing according simply to the number of days experienced, regardless of the time distortion between two realities - a bit like travelling near the speed of light.
1. Are there established terms for these models?
2. Are there other models?
[Answer]
In classical fairy stories, people who entered a hill of the fae for a single night of partying would return and find that many years had passed in the real world, without themselves having grown any older. Usually, their spouses have died and their children have grown up. Ursula Le Guin has a science fiction version of this in her 1964 short story "The Dowry of the Angyar" (aka "Semley's Necklace"), where time dilation makes many years pass at home while Semley is away on a trip to a distant star.
You mention Narnia, where many years pass in the fantasy land while only a day or so pass in the real world, with visitors reverting in age upon exiting. I am not familiar with other stories with this exact model.
There are, however, many stories where time passes far more quickly in the fantasy world than in the real world, as in Narnia, but visitors don't revert in age.
For example, in Stephen Donaldson's *Thomas Covenant* books, roughly a decade passes in the Land for each week between Covenant's visits. Similarly, in A. Merrit's 1924 book *The Ship of Ishtar*, the protagonist visits a fantasy world several times during a single night, with several weeks passing in the fantasy world between each visit and the last visit lasting many months, still in the course of the one night in our world. That there is no ageing reversal is seen from that fact that wounds that heal in the fantasy world don't reopen when he returns to the real world.
Also common is that there is no time differential at all. This is e.g. the case with Lord Dunsany's *The King of Elfland's Daughter* (1924) and Susannah Clarke's *Jonathan Strange and Mr. Norrell* (2004).
I believe I have also read stories where the time differential is chaotic with time sometimes passing faster, sometimes slower, in the fantasy world. I can't however, immediately think of one, other than Roger Zelazny's *Amber* books, which has many worlds each with their own pace of time, and if you don't know that, you can get pretty surprised about how much or little time has passed elsewhere during a visit.
If there are other models used in fantasy, I am not aware of them.
[Answer]
## There are a lot of options, depending on your world
Depending on the rules of your portal world and the specific method in which you enter it, almost all aging scenarios are possible and many have been done before. Rather than list all the examples, I'm going to look at one scenario, and calculate the aging options in it.
We are going to look at the scenario presented by *Jumanji: Welcome to the Jungle*. In this movie, a group of kids magically transported into a video game, where their bodies are transformed into video game characters.
Here are the questions we can ask in this scenario:
* Does time pass in the real world while they are in the game?
* Do they return to Earth at the same time they left?
* Do their earth bodies age while they are in the game?
* Do their game avatars age?
* Is the rate of time passing the same in game as on Earth?
With these 5 questions, we can have at least 120 different versions of aging between the two worlds. (The last question could be reworded to have more than two states)
So depending on how your worlds work, there could be a lot of options to explore. You could probably also just use the questions from above and answer it about your own scenario as well.
[Answer]
There are three main approaches that I know of.
**Fixed Time**
There's no difference in time between alternate worlds. Time passes at the same constant rate for both places, so a year in World A is the a year in World B. Useful if you're doing a lot of world jumping between locations, like Planar Travel in a D&D inspired-setting, or something of that nature. Also helps to keep the protagonists with the ability to jump between planes from abusing the time dilation for their own end.
**Time Dilation**
This is the 'Hour Inside, Year Outside' model, where time is dilated between the two worlds. This is a model usually used for travel to the fae realms, and also a good pick for science fiction due to time dilation because of near lightspeed travel. This can be used alternatively, that is Earth can move at a faster rate or Earth or Earth can move at a slower rate. This also has two subcategories: Fixed vs Variable.
* Fixed: The rate of the time dilation is a constant, that is for every hour on Earth, a year passes in the fae realm or something of that nature. Because this is a constant ratio, this is useful for hard magic systems and also the de facto for science fiction. Be very careful with who you allow access to cross worlds with this one, because computer programmers will happily install server farms to take advantage of this. Among other things.
* Variable: The rate of time dilation is *not* a constant. When spending time in either realm, either years could pass on the other side or possibly even seconds, seemingly at whim and cannot be controlled, except perhaps by beings of great power on either side of the worlds. This is appropriate for soft magic systems. Also not as dangerous to give access to cross worlds because the whimsical nature of the time dilation will serve as an adequate warning against all but the most desperate of travelers.
* Shifting Variable: (Thanks to SRM for pointing this out) The rate of time dilation isn't constant, but it shifts on a predictable pattern. I've never seen this used, but it is a viable derivative that requires different handling than the previous two, as it doesn't have the benefits of Fixed all the time and doesn't have the problems of Variable.
**No Time Passes**
This is the last approach, and also a very difficult one to work with. No time passes means that when the main character changes worlds, *no time whatsoever* has passed. That is, the two world run wholly independent of each other and time only passes when the main character is there. This must be handled *very carefully*, as the nature of this dilation means that (traditionally) only the protagonist can be given access to this power and a suitable explanation has to be given as to why this actually works. That said, it's an entirely suitable approach for certain types of stories, though also the rarest.
] |
[Question]
[
The long fall boots are special footwear that extend from your feet to your knees. They enable you to fall from an indefinite altitude in Earth-like gravity without damaging your body when you land.
How can I create something like this? If “indefinite” is impossible, what is the maximum height that boots could theoretically protect the wearer?
An example of what I'm looking for is the long fall boots found in [Portal](https://theportalwiki.com/wiki/Long_Fall_Boots).
[Answer]
All you really want to do is decelerate. Landing on the ground with a big splat is technically also deceleration, it's just far too sudden.
Work = Force \* distance.
We need to do a certain amount of work to slow down. We could do this with a lot of force over a small distance (say, splat on the ground), or we could do it with a smaller force while increasing the distance.
$$Work = {KE}\_{final} - {KE}\_{initial}$$
We want our final kinetic energy (${KE}\_{final}$) to be 0 (because we want to stop), so, in our case,
$Work = -{KE}\_{initial}$
Stealing a different posts numbers, we know that a human's terminal velocity (basically worst-case scenario) is $50\frac{m}{s}$. If your human weighs 60kg, the formula $KE\_{inital} = \frac{1}{2}mv^2$ gives us 75 kilojoules.
So, using
$$Work = -{KE}\_{initial}$$
$$Work = Force\*distance$$
We get $-{KE}\_{initial} = Force\*distance$.
We can forget about the minus because in this case it only has to do with direction, which is easy enough to understand in this case anyway.
So, 75 kilojoules = Force \* distance.
Here's the question, how much force can our human withstand?
Trained fighter jet pilots with special suits can withstand up to about 9g of force, or about $9\*9.81kg \frac{m}{s^2} = ~88 kg\*\frac{m}{s^2}$ while maintaining consciousness.
We have our force!
Plug it in, and we only need to solve for distance:
$$75 kilojoules = 88 \frac{kg m}{s^2} \* distance$$
*drum roll*
$$distance = 0.85m$$
The boots would have to extend almost a meter below one's feet and then somehow absorb all that energy over the whole distance. 85cm is quite a lot, but maybe it would be easier to do if the boots didn't have to absorb all of the energy and left some of it to the user's legs. Maybe the boots are more like an exoskeleton around the legs, meaning they wouldn't have to extend far below the feet. Then again, I didn't include the weight of such a contraption in my calculations.
All in all, it's not absolutely impossible from a physics standpoint, but it would be very uncomfortable (9g are not fun) and you'd still have to do something with all that energy. You could turn it into heat, but that would require a lot of cooling. Or maybe, you could use it to power an Aperture Science Quantum Tunneling Device...
[Answer]
**Large soles.**
Let us consider how footwear might slow one's fall to a slow and harmless pace. We want these boots to limit terminal velocity.
Variables we cannot control: my weight which we will set at an ambitious 90 kg (I did once weigh 90 kg), gravity on this good earth and air density.
I am falling feet first, so cross sectional area is my soles and any parts higher up which might protrude farther than my soles. Using this terminal velocity calculator and setting my cross-sectional area at 100 square cm or 0.01 square meters I found this as terminal velocity.
[](https://i.stack.imgur.com/SRtkg.png)
361 meters per second is 807 miles per hour which my Yankee brain can comprehend more easily. Too fast!
A variable we can adjust with footwear is cross sectional area. I want something that will let me land at less than 10 mph. With successive iterations I determined this.
[](https://i.stack.imgur.com/U0ZzF.png)
With my same mass, a sole measuring 100 meters squared slows me to a leisurely 3.6 meters per second terminal velocity or 8 miles per hour. I feel like I could land on my feet and be OK with that. The fall slowing boots will therefore have soles measuring 100 meters squared.
Considering practicalities I think a shared sole might be better than two soles each measuring 50 meters squared. With two soles I think there would be a tendency to force my feet apart, letting wind blow up my skirt and decreasing the cross sectional area / increasing terminal velocity. One sole with a snowboard-like pair of foot clips would be better.
A nice thing about this setup is that with practice you should be able to steer fairly well on the way down. Also there is no risk that these shoes will explode, or run out of charge, or fail halfway down: they do not require any source of power.
The bottom of your sole should be painted sky blue, possibly with a large bird silhouette to be inconspicuous.
[Answer]
By itself almost certainly not in any kind of practical package. This would work better if you added a parachute for the extreme distances in which it would be effective. Felix Baumgartner [set](https://felixbaumgartner.com/base-jumper/) the minimum altitude limit of 30 meters, jumping from the hand of the Christ the Redeemer statue in Rio de Janeiro. This also requires a static line parachute that is tied off. You'd have to have some kind of smart system to determine you're in freefall instantly and deploy your parachute.
So, at that altitude, you'd otherwise have a final velocity of just under 25 m/s, vastly better than the true terminal velocity of a falling person. Shoes to handle this impact might actually be physically possible, though I otherwise have no idea how you'd do it. [Dan Koko](https://people.com/archive/when-dan-koko-was-offered-a-cool-million-to-set-a-world-stunt-record-he-really-fell-for-it-vol-22-no-12/) set the world record for falling onto an airbag at around 100 m. Unfortunately for the shoes concept this required a 7 meter tall airbag that weighed nearly a ton. An inflatable airbag that also increased air resistance without tippling you over might actually work for the smaller required height, but it would really only work once. You'd need something ridiculous to be able to repack itself to be used with the frequency seen in the games.
] |
[Question]
[
If a space station were to be built in the outer solar system, is there an asteroid beyond Jupiter with a ratio of rare earth elements high enough to make it worthwhile to mine for the rare earth elements, to supply this space station with those materials it needed?
[Answer]
We don't know if there is such an asteroid made of decently concentrated rare earths, for the simple reason we are not able to survey all the asteroids for this.
Of course you can postulate the existence of such a body, which can be found and used by the crew. Just make sure that the abundances make sense, in other words 500 tons of pure Gadolinium are less credible than 500 tons of other metals with a few percent of Gadolinium in it.
[Answer]
Research on Ceres indicates that cryovolcanism causes water ice to seep to the surface, where it sublimes and leaves salt deposits. We have not analyzed these deposits yet, but they are practically guaranteed to contain concentrated useful elements. This is similar to Earth where salt flats are important mining resource.
Farther there it is too cold and water ice is too hard, but there too are geological processes with nitrogen ice. If you remember the first photos of Pluto by New Horizons, the surface shaped by active geology was a great surprise. And active geological processes means that rare elements get dredged up and eventually concentrated in veins/deposits like they do on Earth.
I believe we can safely say that all dwarf planets have active geology in some form and thus interesting deposits. Many moons too, even if they are smaller they can still can have geology powered by tidal heating.
[Answer]
Rare Earth elements aren’t rare, however separating them is difficult. On Earth, most ferro-phylic element were drawn into the Earth’s liquid Iron core. The Gold and other heavier elements (like rare earths) in the Earth’s crust came from ‘late great meteor bombardment’ after the Earth solidified. Otherwise the solar system abundance of elements depends on 1.) nuclear stability and presence in solar fusion reactions and 2.) the peak nuclear stability of Iron/Nickel (higher elements not created by solar fusion, only in supernova). Carbon and Oxygen are common because they are part of the CNO fusion reaction. Lithium (Deuterium, Beryllium, etc) is not common because it decomposes at solar fusion energies. Answer: The Earth was lucky to have Rare Earths, unlikely in the outer solar system.
] |
[Question]
[
The chicxulub asteroid impact caused climate change, and the climate change caused a mass extinction. But many land-based animal groups survived, crocodillians, lizards, snakes, turtles, frogs, salamanders, birds, and mammals, including primate ancestors.
How would a radiation-based mass extinction event affect current animal groups? Specifically, **what would be the apex predators and/or herbivorous "[apex species](https://english.stackexchange.com/questions/347229/animal-with-no-predators)" (term for "animals/organisms with no [significant] natural predators" that encompasses herbivores) that survive?**
Assumptions, limitations, details, etc:
1. The scenario is akin to nuclear world war 3, all sides throwing all the nuke they have, etc.
2. Assume exactly enough radiation is released in to the atmosphere to kill all humans through radiation related effects, but no more. Higher radiation concentrations are allowed in directly attacked areas, but even the most remote human populations are still killed by absolute minimum lethal doses.
3. Assume nuclear winter is negligible. This is about radiation-induced, not climate-change-induced, extinction.
4. Sea life and plant life can be disregarded (unless it directly affects a population of land-based animals that would otherwise survive), stick with land-based animals.
**To summarize and reword the main question, for clarity**: At this level of global radiation, many species would die off due to radiation poisoning many more would survive the radiation itself but their prey would not, so they would also die off. Food chains/webs would be massively disrupted. **Which apex species(singular) or apex species(plural) would end up at the "top" of whatever food chains/webs were left after things stabilized?**(because they can both survive the radiation, as well as have a food source that also survives the radiation)
**EDIT**: I used the term "Stabilized" to mean just that the "apex species" can live long enough to reproduce for 1-3 generations, depending on the length of their reproductive cycles. And the radiation itself is no longer having any significant effect on food chains and food webs. I'm not talking about geological or evolutionary time-scales.
**EDIT 2**: The "spirit" of the question is meant to be about animals with higher radiation tolerances than humans, either due to biological differences or (as pointed out in an answer) lifestyle differences. Not about just how difficult it might be to wipe out every last human on the planet with radiation alone (after all, that wouldn't leave anyone left for the story...). So the radiation levels involved should be considered to be lethal to unprotected human populations. Not necessarily those that made it to shelters that don't suffer direct nuclear strikes.
[Answer]
The capability to survive the event depends, in part, on the species capacity to heal its own genetic and cellular structure. Higher-order mammals that evolve quickly have the least ability to repair this kind of damage, since its why we evolve so quickly compared to creatures like crocodiles and cockroaches. Mammals have changed immensely while other species are nearly identical to their ancestors from eons ago.
From the [graph](https://books.google.com/books?id=iH-ty5d92ZQC&lpg=PP1&pg=PA481#v=onepage&q&f=false) below, 10 Gray is the radiation level that will kill mammalian cells. And some bacteria are susceptible at ~40 Gray.
(1 Gy (gray) == 100 rad)
[](https://i.stack.imgur.com/UfjG9.png)
And from this [table](https://books.google.com/books?id=iH-ty5d92ZQC&lpg=PP1&pg=PA481#v=onepage&q&f=false), we can see the relationship between mammals and a few other species.
[](https://i.stack.imgur.com/b3dGx.png)
Since you are specifying worldwide extinction of humans by lethal levels of radiation, most surface-dwelling mammals and birds are dead too but subsurface dwelling mammals like shrews and voles probably survive.
If the war started in the deep winter, then maybe hibernating bears survive when they leave their dens in the spring.
Lots of reptiles most likely survive, especially Tortoises, crocodiles, and alligators.
If the ocean life cycle survives then while their numbers would be attenuated I would think that Deep-sea monsters like giant squids and the big sharks would survive since the radiation will be attenuated by the depth of water. Same for deepwater fish. Shallow water fishies might succumb to radiation though.
On land, Croco-gators would be the most likely apex predator and possibly bears. I can't think of an apex-herbivore that would survive since the only one I can think of is the Elephant and I am pretty sure they are dead.
In the air, I think only bugs remain. Maybe bats since they are rodents and they have a slightly higher tolerance for radiation compared to humans.
In the sea, I think whales, sharks, and giant squids are alive.
[Answer]
**Framing Challenge**
You're getting a lot of pushback over the specification on radiation levels, but realistically (and most in what I think is the real spirit of your question), it's not actually radiation that's going to kill all the humans, it's starvation.
[From a 2007 study on widespread global nuclear war:](https://en.wikipedia.org/wiki/Nuclear_winter#2007_study_on_global_nuclear_war)
"A global average surface cooling of −7 °C to −8 °C persists for years, and after a decade the cooling is still −4 °C (Fig. 2). Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about −5 °C, this would be a climate change unprecedented in speed and amplitude in the history of the human race. The temperature changes are largest over land … Cooling of more than −20 °C occurs over large areas of North America and of more than −30 °C over much of Eurasia, including all agricultural regions."
[From an even more recent study:](https://en.wikipedia.org/wiki/Nuclear_winter#2014)
"... the coldest average surface temperatures in the last 1000 years. We calculate summer enhancements in UV indices of 30–80% over Mid-Latitudes, suggesting widespread damage to human health, agriculture, and terrestrial and aquatic ecosystems. Killing frosts would reduce growing seasons by 10–40 days per year for 5 years."
So I think it's not so much a question of radiation tolerance (although that's certainly relevant), but also which species are most likely to be able to persist through the disruption of the food supply. This is what will get rid of all your large terrestrial herbivores for starters, and likewise anything that relies exclusively on them for food.
Even with that, you're going to have SOME small localized pockets of humanity that make it through, prepper communities in Idaho perhaps, or the North Koreans who have been preparing to get nuked for the last seventy years, but that's not really germane to your question anyway.
All of that said, I agree with @EDL's answer that crocodilians and sharks are going to be the most likely winners there not only for the reasons he specified, but also because they're able and willing to eat absolutely anything, and have a metabolism well suited to surviving prolonged famine. Certainly they've survived similar extinction events [several times in the past.](https://en.wikipedia.org/wiki/List_of_extinction_events)
] |
[Question]
[
Many anthropologists believe that equatorial Africa became super culturally-advanced and technologically stunted compared to the rest of the Old World in large part because of
1. Lack of trade routes, and
2. An environment that was naturally suited to human occupation without need of many tools.
My story takes place in an area of Earth-like savanna, mixed forest, and seasonal tropical forest, very similar to coastal West Africa. Much of the rest of the world is just emerging out of the middle ages. However, this species has the ability to have parts of their body temporarily take on a single physical quality of something they touch and temporarily removing that quality from the object. Need to crack open a nut? Make a fist, touch a dense rock, and lo! you have a nutcracking hammer for the next few minutes. Absorb the stiffness out of a log and someone else can bend the log into a pretzel before it re-hardens.
So basically, the environment is very accommodating to life and any need for tools can be mitigated by interaction with their immediate environment. There is really no 'need' to advance beyond stone-age technology. I frankly can't think of any cultures we know about that advanced into the bronze age for any other reason than
1. The environment or neighbors changed faster than they could adapt or
2. First contact with an exploratory/conquering culture.
So! Question. Aside from outside influence/trade (and thereafter likely 'collecting' trade goods with qualities they want to emulate like steel or a sponge), are there any historical reasons a human-like culture such as this would ever want/need to leave the stone age?
[Answer]
In reality, examples for the behaviour you describe exist. Yet, your question asks for possible motivations to start such a cultural evolution. I want to present two possible ones:
First, by considering only external motivations/pressure in your question you seem to forget about one of the most imporant internal motivations and driving forces for human advancement: **curiosity**. Do you need external pressure to advance in order for the most curious to start wandering further from their homelands looking for new materials with new qualities, maybe to use, maybe to sate their own curiosity or even to impress others with the rare and wondersome?
Second, a part of the gathering/'collecting' nature of humans is the **appreciation of the wonderous and beautiful** - coloured jugs with basic motifs, woven cloth dyed in different ways or jewelry made of bone, stone, wood is found in stone age cultures already up until highly advanced ones The **appreciation of arts in all its** forms is part of our nature. Also, no external power enforces the creation of instruments, yet you find instruments or the most basic of instruments - the human voice - in any culture around the world.
[Answer]
### Pain, Suffering, and Medicine
People get desperate when they suffer. Diseases are everywhere. You can't develop modern medicine without modern technology. A parent watching their child suffer and die painfully is (thankfully) considered a rare occurrence in our modern world. In fact, I'd encourage you to look more into [child mortality rates](https://ourworldindata.org/child-mortality) - the number of children who die before five years of age was around 30% in much of the world, and as high as 50% in many places until the late 1800s - and that's crazy!
Pain and suffering are motivators - such a civilization (especially one with more ability to absorb / experiment) - might be willing to travel farther and explore further into unknown regions, or to invest more time into thinking beyond stone-age technology out of the desire for alleviate the suffering of loved ones - especially children.
From limited resources, to simple things like plumbing (the toilet has saved many lives), to medicine, to even ultrasounds and c-sections, there would be great emotional desire to reduce suffering.
### Greater Comforts
@Alex2006 gives great points here so I won't duplicate him: curiosity, appreciation, arts.
But even ideas around controlling temperature (A/C units), making certain specialties easier (the printing press), or automation (computers) would increase comforts.
### Population Density
What could occur on it's own, but almost certainly would occur as an extension of the above points (lower child deaths, less suffering, better comforts), would inevitably lead to a denser population.
As populations get closer together, the opportunity for specialties rises. As well as the needs of the population. Traditional farming only grows so much - the first industrial revolution changed that, and then again the second! The need to optimize farming for more people in a smaller area requires people to think more about issues not previously thought about - can we make food grow faster/bigger? Can we grow food inside a building? Can we make buildings more than two stories high (that will require more than simple mud-and-straw bricks).
Structural issues, transportation, food, policing tactics, cultural reforms, etc, are all issues that can arise from denser populations, and would encourage the society to advance technologically.
### Threat From (Future) Advanced Civilizations
Much to your own point of outside threats, no matter how sustainable a civilization is, there will always be the possibility of a greater civilization. Even if your society is not *currently* being addressed by an outside threat, there can / will be an outside threat at some point. If your society is aware enough that there *might maybe someday* be an outside threat, you don't want to wait to meet them to begin developing technology. This is like meeting tanks with arrows, or atomic bombs with tanks, or UFOs with missiles. The *possibility* of an enemy is a great motivator.
We see this even in the past hundred years with the advent of atomic weaponry - once we understood that greater weapons were *theoretically* possible, we began building technology not around what our enemies have *today*, but what we think they might possibly have *tomorrow* - that's a far scarier (and greater challenge for progress) than ever before. Even if a society is "stable" economically, socially, religiously, etc, an enemy with an atomic weapon could wipe you out instantly. Simply put, the only limit to a theoretical *future* threat is your imagination - not the (disease/weapons/technology/people/creatures) which exist now. No matter how advanced you get evolution-wise, the technological capacity of humankind significantly out-grows the capacity of humankind on individual biological basis.
Although your society might be able to "absorb" a metal, rock, log, etc - this necessitates that the thing they acquire *already exists*. This is problematic. The creation of atomic weaponry (to stick to the example), necessitated the technological combining of many different rare elements (like plutonium and uranium) - and acquiring these resources means traveling great distances and transporting sensitive material great distances. Then, of course, comes the issue that radiation is dangerous to most forms of life, and is obviously something your creatures would not want to absorb without very costly consequences.
So the idea of a potential future threat would drive technological progress.
[Answer]
First, I would say that the terms like 'stone age', 'bronze age' and 'iron age' are pretty vague. It's not the only natural progression of events, but rather the accident of the history of the whole region of Eurasia and Northern Africa, that was interconnected pretty early. Even if we take a look at the Mesoamerican civilisations, the division is much more hazy there. That on itself is a good example that your can have complicated architecture, capital cities, division of labor and hierarchies even with stone tools.
From what I know if anthropology, the complexity of social structure depends on population pressure and difficulty of feeding the given population with available tools. Obviously, there are other important factors like the level of healthcare and so on.
So this is for you to decide, how densely does this species populate their territory, how hard is it to feed them all and how specialised do the food producers need to be - their social structures would rather depend on the patterns of food production then on the material of their tools. And I wouldn't call their tool use 'stone-age' either. They, obviously, use tools, but not directly to perform a task. Most likely, they would carry the examples of different materials and use them to 'borrow' their qualities.
[Answer]
# **War**
Even in "not so competitive" environment, humans have been known to enter into tribe fights and the like. so yeah, At one time or the other, your humans will fight.
From here on, absorbing harder rocks than your opponent is a decisive advantage. So you will refine "better rocks" eventually leading to metal, eventually leading to weapons, and now your absorbing capacity is fine for cooking without burning yourself, but won't compare to throwing pointy/flaming/exploding sticks on people. Even if it does, you will need to defend homes and goods (food, at first), so you will have walls, then houses, then forts..
In our current society, technology improvements are pushed by the military for attack or defense. It goes from pointy rocks to the internet, but also horse riding and creating new drugs. If there is one thing where humans have been proven creatives, it's getting new ways of killing people.
In your preset universe, you need only 3/4/5 tribes to hate each others for whatever reason (some unoriginal greek mythology stuff works fine, forbidden love, stealing food or goods, even some random accident, then some vengeance, then some more, and boom, perpetual war), evolving to fight one other one, to try and get the leading edge.
But as soon as one got an advantage, the others will fear annihilation and group up, one will go with another tech, maybe even share it, and you can keep status quo going for ever and ever, like European kings with their alliances did for hundreds of years.
If you play any 4X game with some decent AI, or good players, you will see that diplomacy has a tendency to keep things going for pretty long if everybody wants to stay alive and compete. Europa Universalis is a good example at bringing coalitions as soon as some power gather too much under one authority.
So yes, just fighting each other will make tribes evolve, and one won't be able to annihilate the others once one step is reached.
] |
[Question]
[
If humans were to live in an earth-like planet with an atmosphere with a significantly higher concentration of $\mathsf {CO}\_2$ (Higher than what can be tolerated by normal human for a long period of time, but otherwise with the same concentration of oxygen), what sort of modifications would they need in order to survive, assuming that they have the technology to alter DNA and their own bodies, but with no external breathing apparatus?
[Answer]
**The kidneys will deal with high CO2**
The high CO2 levels you describe would produce chronic respiratory acidosis.
<https://www.ncbi.nlm.nih.gov/books/NBK482430/>
>
> The primary disturbance of elevated arterial PCO2 is the decreased
> ratio of arterial bicarbonate to arterial PCO2, which leads to a
> lowering of the pH. In the presence of alveolar hypoventilation, 2
> features commonly are seen are respiratory acidosis and hypercapnia.
> To compensate for the disturbance in the balance between carbon
> dioxide and bicarbonate (HCO3-), the kidneys begin to excrete more
> acid in the forms of hydrogen and ammonium and reabsorb more base in
> the form of bicarbonate. This compensation helps to normalize the
> pH.[1]
>
>
>
Usually people who have this issue are not moving enough air when they breathe (alveolar hypoventilation). They have symptoms from the underlying problem causing it, or from low oxygen levels - examples include obesity hypoventilation, emphysema, etc.
Your folks would be moving loads of air, breathing as hard as they could because high CO2 is what triggers the need to breathe (and why you can hold your breath longer after hyperventilating and blowing off CO2). I think eventually that trigger gets numb because people with emphysema are not breathing as hard as they can despite having high CO2 levels. The lungs are not going to help those folks or on your world.
The kidneys step up to maintain pH by excreting more acid and retaining bicarbonate which moves the blood back towards alkaline. I think that if pressed normal kidneys can do more and more of that, presumably with some upper limit. Over evolutionary time having kidneys which could compensate better would probably confer better genetic fitness.
A short term fix might be to eat more bicarbonate; that helps people with problems on the kidney side where their kidneys don't make enough. If your needs are beyond what your kidneys can produce, you can eat more. I think calcium also has to do with generation of bicarbonate (sort of getting int he weeds here) and they could eat extra calcium too.
Sweat offers a route to dump excess acid from the blood. I don't think that actually happens with humans but it would not be that outlandish a mutation to take place. Your people could have very acidic sweat. Feces offers another fairly voluminous space to offload acid. Sour poop.
---
Unfortunately this sort of thing is not that cool for a story because the adaptation turns on altered salts in the urine and blood pH as opposed to growing a tentacled hump or something. I have not yet seen acid-base physiology turned into gripping high science fiction but I am so ready.
[Answer]
If you're prepared to have a good fiddle with your own DNA, then there are some species out in the world that might serve as a useful template, or at least inspiration.
[Crocodiles have some interesting adaptations](https://pdfs.semanticscholar.org/1b59/f9c030e004a85447b5cd94ebced0df9e33d6.pdf) that cause oxyhaemoglobin in their blood to give up its oxygen more readily in the presence of higher levels of biocarbonate ions in the bloodstream. This means they can more effectively make use of the oxygen that's already in their blood whilst holding their breath, but it also means that there's more spare haemoglobin available to bind that that CO2 as [carbaminohemoglobin](https://en.wikipedia.org/wiki/Carbaminohemoglobin). CO2 bound in this way, instead of as bicarbonate ions, does not contribute to [respiratory acidosis](https://en.wikipedia.org/wiki/Respiratory_acidosis) and as such reduces the problem of [hypercapnia](https://en.wikipedia.org/wiki/Hypercapnia). The Martian settlers in Kim Stanley Robinson's *Mars* trilogy used a crocodile-derived genetic modification to allow them to better tolerate higher levels of CO2 in the martian atmosphere during terraforming.
The other animal isn't quite as... marketable as a crocodile. Yep, its everyone's favourite burrowing mammal, the [naked mole rat](https://en.wikipedia.org/wiki/Naked_mole-rat).
[](https://i.stack.imgur.com/y0ODp.jpg)
Whilst they're some of the least photogenic mammals on earth, they can survive in atmospheres of up to 80% CO2 and as low as 5% O2 for hours at a time, which is no mean feat. Their haemoglobin has a higher affinity for oxygen, but they also seem to have a number of interesting (and poorly understood) mechanisms for coping with [acidosis](https://en.wikipedia.org/wiki/Acidosis) which has also apparently contributed towards a high resistance to pain. What's more, they seem extremely resistant to cancers and are very long lived for rodents. I don't have any more details of exactly *how* they do all this (and I suspect a lot of the important trick are currently poorly understood, if understood at all) but hopefully this will give you a good starting point for further investigation.
Now I think of it, all of this tolerance of terrible atmospheres, the lack of need for light or circadian rhythms and the high resistance to cancers suggests that an uplifted molerat would probably make an excellent interplanetary or interstellar colonist. They do make a brief appearance in Charles Stross *Singularity Sky*, though these beneficial attributes are not mentioned there.
] |
[Question]
[
The People of The Shining Isles have long been exploited. They are cruelly used in mines, excavating tonne after tonne of rock and dirt in pursuit of what the Warriors from Away call ‘diamonds’. These small, shining rocks are apparently of great value to the invaders for some reason or another, though the People have always ignored them, preferring to grow vegetables to sacrifice in order to prevent the ancient Smoking Gods from waking.
The question here is pretty simple: Is there a set of circumstances that can lead to high concentrations of diamonds on an otherwise volcanic island chain (think Hawaii), or will the production of such islands always act to destroy the gemstones before they can be mined?
The length of time required is of no consequence (this is an old world), and the number/distribution of tectonic plates is similarly unimportant. The world does have to be earthlike though, so keeping gravity/atmospheric composition the same would be appreciated. I’m open to ridiculously unlikely chains of geologic events leading to this state, but in deference to William of Ockham simpler answers are better.
[Answer]
Diamonds are formed by crystal growth of carbon in suitable conditions, therefore you need to have:
* suitable pressure and temperature
* suitable chemicals (carbon to begin with)
* time to allow crystal growth
This usually means that you have an intrusion of magma deep underground, which slowly cools down, and then it is lifted closer to the surface by either tectonic or erosion.
With an active volcano that magma would diffuse to the outside rather quickly. Unless diamonds have already formed in there, and can withstand the sudden change of conditions (unlikely, hot lava, oxygen and carbon mean an expensive bbq bed), you cannot have diamonds.
[Answer]
As has been mentioned already, your volcanic island is not a typical environment to find diamonds. So if the diamonds formed in an early geological formation, that later eroded and cast the diamonds into a strong current where they lay on the seabed. They could reasonably get pushed up by the forces that produced the volcanic island chain.
If this sounds too implausible for you since it depends on a very specific occurrence of unlikely events, you might consider having other [valuable materials on the island that do occur with volcanic activity](http://gem5.com/tag/volcanic/)
[Answer]
If you want diamonds, you pretty much want [kimberlite pipes](https://en.wikipedia.org/wiki/Kimberlite).
If you want kimberlite pipes in your islands, you might want the island of [Malaita, in the Solomon Islands](https://www.nature.com/articles/287718a0).
I don't know if there are actually any diamond on Malaita, but it looks vaguely-plausible enough from here.
[Answer]
1. Meteorite comes!
2. Meteorite slams into carbony crust. Impact diamonds are formed, like those in [Poigai crater](https://en.wikipedia.org/wiki/Popigai_crater).
3. Also meteorite itself was full of [space diamonds](https://en.wikipedia.org/wiki/Extraterrestrial_diamonds) so doubly diamonded.
4. Meteor hit hard. It made a volcano happen right there.
[](https://i.stack.imgur.com/l29nh.jpg)
<https://www.newscientist.com/article/dn3171-earths-volcanism-linked-to-meteorite-impacts/>
5. Volcano carried up a mix of space diamonds and impact diamonds.
Fortunately no-one but microbes was around for all of that. Later on things settled down and your islanders moved in.
[Answer]
Yes, if you are flexible with what you call a volcanic island.
An island on continental crust could have diamonds one on oceanic crust will not. You can have islands with volcanoes that have diamonds but the volcano would not be responsible for the island. you need a island like iceland A chunk of continental crust that has been moved far from the mainland. but unlike iceland you want the island on a subduction zone more like japan. This means your island will be big Iceland is probably the lower limit for the size of an independent portion of continental crust without so truly unique circumstances. large enough they are unlikely to have a single political structure.
] |
[Question]
[
OK, OK, I know, darkness is nothing but absence of light, so there can be no substantial darkness. Darkness, on its own, doesn't exist.
But, can we not get pretty close to this?
Can there be *something* - I don't know what, smoke, gas, clouds, fog, atmosphere, dark matter, whatever - that could be ubiquitous in the atmosphere in large areas, spanning whole cities or, in extreme cases, even whole countries, that would have the following properties:
* It would absorb light, therefore darkening areas it would affect. That it would be dark around would be its only visible trait.
+ In places where this something would be moderately concentrated, bright day would present itself about as a night with a full moon - so while people could go around with a naked eye, they would have to use lamps to read; more severe concentrations would mean that even during a bright day strong reflectors would have to be used to not bump at the wall; in extreme cases no practically feasible amounts of natural or artificial light would help and people would simply see nothing.
+ This differs this mysterious substance from stuff like smoke or fog; while both obstruct vision, both do this in a different way than simply reducing the amount of ambient light and are visible on their own.
* It would otherwise not be detectable in obvious ways. It would have no smell, it would not obstruct movement, it would not make people breathing it in ill, etc etc.
* It would be ubiquitous, reaching wherever air would reach. So air purifiers wouldn't help. Nor would help shutting oneself in a cellar or a bunker, unless this cellar or bunker had no air supply. However, shutting oneself in an extremely air-tight room and scientifically synthesising air somehow would help.
Can such a substance exist? What would it be like? Could a Dark Lord realistically summon such a substance without having to resort to supernatural explanations?
[Answer]
Have you ever heard of the sound suppression system used in some headsets? It works by creating a sound wave with the same amplitude and frequency of the sound you want to suppress, but just with the opposite phase.
In this way the interference between the two waves causes silence.
The same principle can be used for your darkness: electromagnetic waves with the same intensity and frequency of the electromagnetic waves you want neutralized, on opposite phase.
[](https://i.stack.imgur.com/rdxRo.jpg)
Just shift the phase a bit, and the zeroing will not be perfect, leaving some light visible.
[Answer]
*Disclaimer: I misunderstood aspects of the question, so this might not be the kind of answer the OP is looking for. But I had a tremendous amount of fun writing it, so I'm leaving it up. But! like I explained to Soan, if the Dark Lord had mastered the science of photonic resonance, allowing him to shift normal photons into daniels, it could work! Muahahahahaha!*
**You might not be thinking about this in the right way**
Photons don't "emit" anything. They are the thing "emitted." Our eyes (rods & cones) "detect" this object and our brains interpret that detection.
*Which means you're not looking for a particle that "absorbs" light. You're looking for a particle that our eyes detect but our brains refuse to interpret. The result would be darkness.*
That distinction, detect but refuse to interpret, is important. Our eyes *don't* detect x-rays, for example. Which is why X-rays don't cause "light" or "darkness" as far as our brains are concerned.
**So, let's create a particle**
I can't call it an "antiphoton." [Antiphotons](https://physics.stackexchange.com/a/13656/180871) already have a connotation/definition in the world of quantum physics, and it isn't as a particle that our eyes can detect but our brains can't interpret. That's truly unfortunate, because "antiphoton" would be the most obvious name for this particle.
So, let's call if "Daniel."
**What are Daniel's characteristics?**
Daniels have all the same characteristics of photons with one exception, our brains don't know what to do with them. The rods and cones of our eyes think they're photons, but when that data is sent to the brain, it's response is "huh?"
From a scientific standpoint, this would be hard to justify other than by hand waving. Simplistically, rods and cones are little more than frequency-sensitive switches. The impact of a photon turns the switch momentarily on. When the brain is told that a particular switch was turned on, it uses that fact to build an image. In other words, rods and cones are chemically complicated but systemically simple.
In a sense, we're asking the brain to not understand that the switch was turned on. In this case, it would be helpful if someone with more medical knowledge than I could edit my answer and fill in this blank. Is there the equivalent of *two* data paths from the rods/cones back to the brain? One that indicates the closure of the switch, another that tells the brain what the switch means? If so, then all we're asking the body to do is not send the interpretive data back to the brain. (But, if it's as simple as I think it is, hand waving is all we have left.)
**What does this mean if both photons and daniels are present?**
Obviously, if all that exists is a room full of daniels, then effected humans are blind as the proverbial bats. Darkness abounds.
*But...* Let's say that a candle is burning and someone has a bunch of daniel-emitting flashlights who are the polos in your game of visual marco-polo? As you try to find the candle, they're casting the beams of daniels about causing blindness and distraction. Your eyes would be getting a mix of photons and daniels (and your brain might get a splitting headache). In a normal room, the image of the candle would be varying in brightness and occasionally spotty.
*Actually, make this a room with mirrors for walls and this game might be really fun.*
**Conclusion**
What you need is a particle having all the basic characteristics of a photon, making it detectable by the rods and cones in our eyes, but is otherwise incomprehensible by our brains — meaning the brain will only interpret the particle as "darkness."
I've lovingly called this particle a *daniel.*
[Answer]
The thing that makes fog visible is that the shape of the water droplets causes them to refract light, but a glass of water with a dye in it will reduce light inside it without the water necessarily being "visible" on its own to creatures living inside it.
If you had a dense smoke or extremely sparse liquid, made of a translucent substance like a glass of water, whose particulate was shaped in a way that didn't refract light the way particulate steam does... or maybe like a "dye for air", which wasn't quite visible on its own the way dust is, but which nonetheless absorbed or changed light on the way through it, you could achieve this kind of effect. I don't know about any substance with those properties IRL, but IMO it's conceivable that one could exist.
Also, I'm not 100% sure if I'm right about how this works, but I'm lead to believe that the reason far mountains look blue is because air is blue. Imagine if air was black -- the mountains in the distance would just look darker. Air can't be seen on its own, but sometimes I can see far mountains well, sometimes they're blue, and sometimes they aren't visible at all amidst the blue haze. All you're doing is just reducing the basline render-distance for real-life objects, and changing the color of that haze.
[Answer]
*Can such a substance exist?* **Propably not**
**Whats the problem?**
It needs to be in such a small amount that you are still able to breathe but at the same time absorb [99.999%](https://en.wikipedia.org/wiki/Daylight) (or more) of sunlight to [create moon like circumstances](http://www.lumenbasic.com/blog/whats-the-difference-between-lumen-and-lux/). Even the [darkest substance known](https://www.wolframalpha.com/input/?i=darkest%20material) is not capable of absorbing so much light. That being said there could be a material absorbing even more light.
The problem this unknown substance would face is that it has to absorb 99.999% of light while being spread out in the air like fog and not damage the inhabitants.
*What would it be like?* **Hot**
**Why?**
When a material absorbs light it gets warmer this is not that big of a problem with most materials because they reflect enough back to keep survivable temperatures. (even then the sand in the Sahara can reach 70°C. Problem is when that’s not the case it can get even hotter. So during the day nobody would leave the house except when there are enough clouds around.
*Can a Dark Lord realistically summon it?* **Maybe**
Depending on how this material is created it could be “summoned”. Even if itself couldn’t be summoned it could be moved with wind probably. So If your Dark Lord is sufficiently powerful he should be able to at least let it seems like he can summon it.
[Answer]
Using our existing physics, I can think of a few ways.
For a start, let us consider what "darkness without obscuring" means.
It means that things in the dark area will look dark, but if you look through it to a light area, they will look light. Like looking under a bridge, the stuff under the bridge is in shadow, everything else is lit.
1) So one way is to have the darkness be at a high altitude, as a canopy over everything. This doesn't work so well, but at a low enough level (10ft or so above the ground) and impenetrable enough, it could work better than clouds. The canopy could be flying insects, nanites, smoke, or some light buoyant film.
2) Other than floating above people's heads, another way is to consider that particles need not have the same dimension at all angles. They could be very flat micro-particles covered in a vantablack-like substance. Their shape permits these particles to fly using the absorbed solar energy, but also means that they mostly block light in one direction.
They'd only need to be further apart than 1 micrometer in order not to block visible light horizontally, and average complete coverage to block vertical light from the sky; that's perfectly doable with super-thin stuff particularly if it's designed to seek sunlight to fly.
These particles would also make flashlights less efficient, since they'd angle towards light sources, but then have to level up as that caused them to fall.
These particles could also make the darkness harmful to flesh, if the thin particles were sharp, like tiny flecks of obsidian; you'd have to venture into the darkness wearing goggles and swaddled in cloth or leather, or risk going blind and being flayed alive by the swirling darkness.
3) But really - what's the EFFECT of darkness? It makes things look dark. So what if it's not in the air, but rather a thin layer over all surfaces? If you tread on the ground, you too become Darkened. You likely don't want that stuff on your eyes, so goggles again recommended.
What the layer is (mites, nanites, slime, dust) doesn't matter, other than that it'd affect the specific way the locals handled the Darkness. Having it be small insects makes it ooky and also explains why carried torches work, if the bugs avoid fire. Depending on the setting, it's reasonable for the reader to believe in insects being controlled as a colony, so sticking together in patches of slowly expanding blackness, etc, and leaving someone who walked out of the blackness.
[Answer]
We could change the sun to achieve such an effect. If our central star happened to emit light concentrated on a few wave lengths (similar to laser light, also found in some unusual types of stars) and we had a gas which happened to absorb light at those frequencies, we'd get what you want. Ideal would be a gas like argon or xenon, which would have to make up a large part of the atmosphere (more than our 1%) and have some (volcanic) sources. Being a noble gas, it's difficult to isolate, doesn't harm us, doesn't smell, and so on.
] |
[Question]
[
So a friend of mine came up with an interesting question. Considering the fairly universal following facts about western-style fantasy dragons:
a) dragons can breath fire
b) dragons themselves are fireproof
c) dragons have large wings, allowing them to fly (though the actual science of this is well-known to be fishy, let's for now pretend a dragon such as Toothless or Smaug can actually fly. Super light bones or whatever.)
d) hot air rises and creates lift
If the dragon can produce a large quantity/sizable blast of extremely high heat, could it be useful to the dragon for it napalm/torch the ground beneath it as it was taking off, in order to create additional lift for itself? Or would the effect of doing this be so negligible that it wouldn't be worth it to bother?
[Answer]
Unlikely if not impossible. The lift created by heat (pressure differences) is different than the lift created by the wings (mechanical). The "help" given by one is unlikely to help the other - and the difference would likely be negligible.
### Mechanical Lift
Lift as a mechanical force is created by motion. [Here is a good explanation](https://www.grc.nasa.gov/www/k-12/airplane/lift1.html), and Wikipedia has a [decent article on lift](https://en.wikipedia.org/wiki/Lift_(force)). You can read more about [how birds create lift here](https://en.wikipedia.org/wiki/Bird_flight#Basic_mechanics_of_bird_flight).
### Pressure Lift
Lift by pressure differences is [how hot balloons work](https://en.wikipedia.org/wiki/Hot_air_balloon#Generating_lift) - but this is because of the density of the balloon (here, dragon) in relation to the surrounding air. Unless the dragon could contain the heat entirely beneath it, the heat would dissipate *very* rapidly - especially if it is significantly hotter than the air around it. This would make for a very bad way to create lift.
### Cannons
I suppose, in theory, if a dragon was stuck upside-down inside a pipe, then a good heave might push it out. But this would be more like how cannons and firearms work than any concept of actual lift. In such a scenario, the dragon would be "pushed" out, and could then flap it's wings - assuming that it could create enough of an explosion (fireball) to force itself loose.
[Answer]
# Thermal Soaring
I think its possible:
* Birds like raptors (eagles/hawks etc), vultures, and storks can gain altitude without flapping by hopping a ride on a rising column of warm air. This is called [Thermal Soaring](https://en.wikipedia.org/wiki/Lift_(soaring)).
* We assume (according to your point c) that dragons can fly reasonably well, but can they soar? Soaring ability in dragons seams likely, as dragons are typically thought of as carnivores which means they have to fly around looking for prey to catch (like eagles/hawks) or fly around looking for dead prey (vultures/condors). All that flying around means you need to be energy efficient and be able to soar. If dragons are capable of soaring in general, then they should be capable of thermal soaring as well.
* According to my googling, wildfires can cause thermal columns.
Thus, the dragon starts a wildfire, takes off for flight (likely by jumping up like [giant pterosaurs](https://www.scientificamerican.com/article/how-pterosaurs-first-took-flight/)) and flaps a few times to get in the air over the wildfire, and then can thermal soar up high.
] |
[Question]
[
I am currently writing a story that involves the never-ending-theme of alien invasions. Assume Humans are roughly at a Type I civilization at this point. Humans have unfortunately wandered into a middle of a galactic battle, and because we always make great decisions, we chose a side to join, let's say the Galactic Empire.
The other side, the First Order, is not very happy about this and decides to completely annihilate Earth. Their planet-destroying weapon is going to lock on Earth and destroy it. However, its preparation time is long and needs a very accurate lock-on of the target. Therefore, in defense, Earth has came up of the idea of a Decoy Earth:
* The Decoy Earth would be an obloid spheroid in the same dimensions and the shape of the Earth, except that it is actually completely hollow and only consists of surface light emitting panels.
* The Decoy Earth would be placed on the Earth Orbit at the point directly opposite the current Earth, and be given a rotational velocity exactly equal to that of Earth's, so that the two Earths are always directly opposite each other.
* The light emitting panels of the Decoy Earth emit light of the same spectrum as the true Earth.
The purpose of the Decoy Earth is for the First Order to not know which Earth is the real one and thus have a $1/2$ chance of locking on the wrong planet. Assuming the weapon takes an extremely long time to recharge, this would give humans more breathing time for us to figure out a plan.
Now my questions are:
* How well can this Decoy Earth actually serve as a Decoy from distances of $\sim 1000$ light years? From my (very basic) understanding of astrophysics, the Decoy Earth would seem to do pretty well under direct imaging and the transit method. Clearly the mass of the two objects are vastly different, so gravitational microlensing can potentially reveal the truth, but is microlensing capable of discovering Earth-like planets at that distance?
* (Optional) What would be the minimal distance in which this Decoy is effective, assuming current human technology in telescopes? You are welcome to assume that all current telescopes in full construction (e.g. JWST) as usable.
[Answer]
How well can this Decoy Earth actually serve as a Decoy from distances of 1000 light years?
Well nothing travels as fast as light so it's 1000 years before they detect the fake Earth and at least 1000 years for the weapon to arrive. If they miss, another 1000 years before they know and another 1000 years before shot two arrives.
In reality, the fake will make no difference. We currently detect planets by the wobble the star has which is due to the mass of the planet.
The fake doesn't have the mass and therefore won't affect the sun so a fake won't fool anyone and depending on how they target, they may not even notice the fake.
[Answer]
**PAINT VENUS**
Just kidding, what a stupid idea. To the point, as nobody knows the tech behind our attackers' weapon we cannot know how effective the decoy would be, what we can ascertain from this question is that your humans are super advanced. So this gives me an idea that doesn't directly answer your exact question but I believe could be useful to you.
What if instead of a literal decoy you make the enemy ships and databases simply believe there is a decoy? But now we have the issue of if their computers would detect this. If not great but otherwise we could beam light from a single point, at their ships sensors that looks like there is another planet from their perspective. Either one you do I believe has great potential in saving earth. Just think, with either of these methods you could create many more than one decoy at an incredibly nominal portion of the cost and effort of your initial idea. Hope this is helpful :)
[Answer]
Unless enemy is using extreamly large telescopes(or star's gravitational lensing) he cannot resolve any details, so we need to simulate only spectrum and most basic time patterns.
If decoy emits a ray with divergence about second of arc(at 1000 ly it would be some 10 000 of AU) then it requires very little power - about 100 kW.
So decoy could be quite cheap and in this case it would make sense to make thousands and even millions of them.
[Answer]
Fake is not really practical.
First consideration is the amount of time you had to create the fake before the aliens started aiming. If the fake was ready N years ahead of time the aliens will not even notice if they are further than N light years away.
And if they are close enough to see the fake, they will see two planets in the same orbit and will take steps to verify which they want to shoot. The same steps they are taking to avoid shooting Mars or Venus. So unfortunately they are already forced to take the exact countermeasures needed to make the fake useless anyway by the existence of those other planets.
Your fake is not going to be better at fooling them than an actual planet. Unless you assume a **REALLY** dumb targeting system.
Which you totally can. The classic trope is that the aliens have placed some sort of a targeting beacon on the targeted planet and you *simply move that beacon* somewhere else. Only real issue is that this has been used enough that it is kind of a cliché. Otherwise it is a perfectly fine way to solve this, it is a plausible way to exploit a plausible weakness of a plausible way to aim a super-weapon.
Otherwise... If I was allied with a bunch of super advanced aliens I'd just ask their help to colonize the asteroid belt and other such small targets within the solar system. Then move there with all the people I like. This could be funded by selling everything we own on Earth to people I do **NOT** like. I mean, we cannot stop the planet from being destroyed so there would be no real reason to cause an useless panic. Let people enjoy their final moments and the wheels of economy to turn normally until everything has been sold and all the supplies have been bought.
That said, generally in fiction such super weapons pretty much exist to serve as targets for daring attacks. You should have that at least considered. A super weapon capable of destroying planets is at the very **minimum** worth the same as an actual planet as a target, usually it is worth entire star systems. And it is generally much easier to destroy and is generally less morally questionable than destroying the equal value in inhabited planets. In all ways an excellent target. Except for the minor fact that the enemy also knows this and, yes, it will be a trap. But for a story that is just a bonus.
] |
[Question]
[
The civilization I'm talking about is marked in pink (cities A and B).
The trade routes are marked in yellow.
Owning the city B (the entire island) means they only need to travel across two relatively small gaps by sea, unlike other civilizations, in case they decided to get rid of the middle-man.
Could this advantage be enough to sustain cities without proper farms? (instead the food would be bought from their neighbors).
[](https://i.stack.imgur.com/IyhNa.png)
[Answer]
A real-world, real-history example:
## The Sound Dues
[The Sound](https://en.wikipedia.org/wiki/%C3%98resund), known by the natives as the Øresund `[ˈøːɐsɔnˀ]`, is one of three natural waterways connecting the Baltic Sea with the ocean; the other two are the [Great Belt](https://en.wikipedia.org/wiki/Great_Belt) and [Little Belt](https://en.wikipedia.org/wiki/Little_Belt). Of the three, the Sound is the most convenient for traffic, so that it was a very busy waterway since times immemorial. In the Late Middle Ages and the Early Modern period, the strait was controlled by Denmark; nowadays, the western shore belongs to Denmark and the eastern shore to Sweden.
[](https://commons.wikimedia.org/wiki/File:Belte_inter.png)
*The Baltic straits. West to east, the Little Belt, the Great Belt, and the Sound. Map by [Ulamm](https://commons.wikimedia.org/wiki/User:Ulamm), [available on Wikimedia](https://commons.wikimedia.org/wiki/File:Belte_inter.png) under the CC BY-SA 3.0 Unported license.*
>
> *Political control of Øresund has been an important issue in Danish and Swedish history. Denmark maintained military control with the coastal fortress of Kronborg at [Elsinore](https://en.wikipedia.org/wiki/Helsing%C3%B8r) on the west side and Kärnan at Helsingborg on the east, until the eastern shore was ceded to Sweden in 1658, based on the Treaty of Roskilde. Both fortresses are located where the strait is 4 kilometres wide.*
>
>
> *In 1429, King Eric of Pomerania introduced the Sound Dues which remained in effect for more than four centuries, until 1857. Transitory dues on the use of waterways, roads, bridges and crossings were then an accepted way of taxing which could constitute a great part of a state's income. The Strait Dues remained the most important source of income for the Danish Crown for several centuries, thus making Danish kings relatively independent of Denmark's Privy Council and aristocracy.* (Wikipedia, *s.v.* [Øresund](https://en.wikipedia.org/w/index.php?title=%C3%98resund&oldid=884470978))
>
>
> *The Sound Dues (or Sound Toll; Danish: Øresundstolden) was a toll on the use of the Øresund which constituted up to two thirds of Denmark's state income in the 16th and 17th centuries.*
>
>
> *All foreign ships passing through the strait, whether en route to or from Denmark or not, had to stop in Helsingør and pay a toll to the Danish Crown. If a ship refused to stop, cannons in both Helsingør and Helsingborg could open fire and sink it. In 1567, the toll was changed into a 1–2% tax on the cargo value, providing three times more revenue. To keep the captains from understating the value of the cargo on which the tax was computed, the elegant solution was chosen to reserve the right to purchase the cargo at the value stated.* (Wikipedia, *s.v.* [Sound Dues](https://en.wikipedia.org/w/index.php?title=Sound_Dues&oldid=871192330))
>
>
>
[Answer]
City states at a 'change of transport' point or cross roads may be able to do this. Whole nations? I doubt it.
I can't come up with a pre-industrial city that was unable to raise essential food in the local neighbourhood.
Rome, after the established an empire, transported grain in by the boatload. But that was just Rome the city. That wasn't true of the countryside around Rome.
Might check out the history of Damascus and possibly other cities on the Silk Road.
[Answer]
In times of prosperity and while they're at peace with their neighbours such a solution might work, if there was enough traffic to tax and enough food was available. But if their neighbours harvests were poor then buying in food would become impossible long before the neighbours were starving. Furthermore any political dispute that led to even a short cessation in trade would be disastrous for any nation without independent means.
] |
[Question]
[
[](https://i.stack.imgur.com/ADObV.jpg)
[Caulerpa taxifolia](https://blogs.plos.org/biologue/2015/02/13/understanding-images-a-giant-single-celled-plant/), an algae species popular with aquarium owners, is the largest single-celled organism known to us as of today. It is notable for being able to regenerate from any part of the body and shows structures mirroring normal plant organs, with RNA differing throughout different parts of the organism. It is an invasive species.
In my story, the (zero-G and centrifugal) STL habitats and colony ships of a giant settlement fleet as well surface stations on inhospitable planets extensively farm C. taxifolia for the purpose of human nutrition and feeding cattle.
My question is:
* Why should C. taxifolia be utilized as the primary nourishing plant in a hard sci-fi, outer-space environment? Which advantages does its macromonocellular structure encompass?
[Answer]
# Ease of genetic engineering.
[Production of genetically and developmentally modified seaweeds: exploiting the potential of artificial selection techniques](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4362299/)
>
> Macroalgal stocks with altered morphological traits can either be
> continuously collected from the wild or generated on demand in culture
> facilities using a combination of techniques likely to modify the
> developmental traits in a stable way.
>
>
>
As opposed to vascular plants, which must be engineered to breed true and then cultivated/sustained from seed through their life cycles, an alga like Caulerpa can have a somatic cell engineered and then be maintained indefinitely from that single cell - much as is the case for engineered bacteria. In theory it is much, much easier. That can be the rationale - various Caulerpa stock have been made with different flavors, vitamin and protein characteristics etc. Your near future astronauts are master engineers of the Caulerpa and just tweak it to be whatever they need.
[Answer]
Not knowing anything about this species except what you've given us, I would go with...
# It's easier to genetically engineer than anything else
Genetics is complicated. Although we can now sequence DNA, the chain of interactions between all the moving parts of a complete organism are too complicated to work out on a chalkboard or even in a powerful simulation. Re-engineering a species like a human, or even like a honeybee, is something that an entire society can work on for decades and still only make breakthroughs by trial and error.
But with this one species, the system is much simpler. Not *simple*, but much simpler, with a more direct link between the gene and its expression. We could say that (in your near-future sci-fi story) it has proven within the grasp of genetic engineers to do quite a lot of interesting things with this species. Since they're a "settlement fleet" spreading out to all kinds of different locations, including "inhospitable planets", the practical application is that
they can re-engineer variants of the plant to grow in very different environments, and even create varieties that might help to terraform those environments.
[Answer]
### Flexibility
>
> It is notable for being able to regenerate from any part of the body
>
>
>
This leaps out at me as a reason to grow it. You can harvest just the amount that you want, when you want. The only restriction is that you need to retain some portion of the plant (ignoring whether this is technically a plant). So you may have to harvest from multiple plants.
This flexibility seems key if you are stuck with relatively few plants. Contrast with a tomato. With tomato plants, you only eat the fruits. You need to harvest the entire fruit, even if you only want half of it at the moment. You have to harvest on a particular schedule. Too early and it's not ripe yet. Too late and it's rotten. You'd have to plan for usage months in advance. And if you grow too little, there's no fix. If you grow too much, you could turn it into sauce and freeze it. But you can't really substitute sauce for sliced tomato the next time you're short.
Assuming this is far enough forward that you can have the plant genetically engineered for nutrition and flavor, this flexibility may make it the plant of choice for long term harvesting. And next door you can have the cultured [chicken heart](https://embryo.asu.edu/pages/alexis-carrels-immortal-chick-heart-tissue-cultures-1912-1946). Or some more modern [cultured meat](https://en.wikipedia.org/wiki/Cultured_meat).
I'm thinking that the plant may come in multiple flavors so that chefs (possibly robotic) could mix the flavors so as to make a delightful repast. Or at least that's what the advertising would say.
[Answer]
### It's hardy and can clean sewage
Caulerpa taxifolia is a very hardy organism that thrives in cold water, which makes it both popular for aquariums and a problematic invasive species. It is also resistant to many toxins as well as ultraviolet radiation that would kill other algae and plants, and can live in sewage (and actually absorbs it, helping to clean the water). These make it useful for prospective space travelers, since it can live in many environments and can help with water purification.
### ...but it's poisonous!
C. taxifolia produces caulerpicin, which is poisonous to eat (although it does not poison the water around it) - this is the other reason why it's an invasive species, it's inedible. Only a handful of animals can eat it and these animals accumulate its toxins in their body to the point where they become toxic themselves. So you're going to have to make a genetically engineered non-toxic strain if you want to use it as a food source. Nevertheless, it may be worthwhile, since it only really has one toxin and it's a lot easier to genetically engineer an organism to not produce a single toxin than to breed a non-toxic species to live in completely different environments.
] |
[Question]
[
We know that Gor, or Counter-Earth, [is not stable](https://worldbuilding.stackexchange.com/a/8658/22685) in a long-term sense. Let's handwave that away, or assume that we are dealing with a temporary span of time in which the instability is immaterial.
Mid-20th to early 21st century Gor and Earth have finally [discovered](https://worldbuilding.stackexchange.com/q/106739/22685) each other and made contact. An alliance of nations on Gor have succeeded in building a space station in Low Gor Orbit (LGO) and are very interested in starting regular passenger/cargo shuttle flights to Earth's International Space Station.
What trajectory would a more-or-less contemporary *crewed* spaceship use to travel between Earth orbit and Counter-Earth orbit? We are dealing with civilizations that are, technologically, more or less anywhere between Earth's mid 20th century and a few decades from now. That is, incremental advances in technology (e.g. slightly more accurate thrusters, 10% more effective radiation shielding, or tastier meals-in-a-pill) are fine, but no Stargates or Millenium Falcons. The trip should be as *short* as reasonably possible, but should keep the persons on board reasonably safe. Spaceman Thumper reminds you that if you fly directly into the Sun, you are going to have a bad time.
I'm imagining that ships would simply drop into an elliptical orbit that would put them onto a trajectory to intercept the other Earth, but what would that look like? Would such an orbit be quick and reasonably achievable, or are our hypothetical cross-world pioneers going to be wandering around the Solar System like Odysseus?
Economic issues (exactly who pays for what, who gets to purchase the first interplanetary tickets, etc.) are out of scope for this question unless there is a particular reason they need to be included. Assume that governments on both planets are treating this as a high priority project and are able to provide at least as much funding as modern-day space programs receive.
As for spacecraft design, I am imagining something reasonably similar to modern designs, with the obvious caveat that such an interplanetary shuttle won't need to take off or land and so could forgo much of the equipment found on, e.g., the Space Shuttle or Soyuz. Instead, such a ship could that space for whatever it needs to maneuver in space or keep the occupants alive. Modern designs for non-atmospheric craft that have never been built but appear spaceworthy are obviously acceptable.
[Answer]
# Orbit phasing
### Or the art of doing things backwards to the way you'd expect
*With content and images largely extracted from the Wikipedia article on [Orbit Phasing](https://en.wikipedia.org/wiki/Orbit_phasing)*
>
> In astrodynamics, orbit phasing is the adjustment of the time-position of spacecraft along its orbit, usually described as adjusting the orbiting spacecraft's true anomaly. Orbital phasing is primarily used in scenarios where a spacecraft in a given orbit must be moved to a different location within the same orbit.
>
>
>
You have two points in the same orbit and you're trying to transfer from one to the other. Normally this procedure applies to objects in Earth orbits and hence the [phase angle](https://en.wikipedia.org/wiki/Phase_angle_(astronomy)) refers to the position of the object relative to Earth and the Sun. In this case you're looking at the Solar orbit but the principle is the same.
**If you want to go backwards, you accelerate. If you want to go forwards, you decelerate.**
Yes, the opposite of what you'd first think. The principle is that by decelerating you put yourself into a smaller, faster orbit and hence increase your phase angle faster. By accelerating you put yourself into a larger slower orbit and the point behind you catches up.
>
> [](https://i.stack.imgur.com/l2Y42.jpg)
>
> [](https://i.stack.imgur.com/b05iH.jpg)
>
>
>
[Answer]
These kinds of questions are fun.
1. The preferred path will always be counter-orbit. I don't want to move forward toward Gor because it's moving away from me and that will lengthen the mission. We want to move backward, so Gor is approaching us as we approach Gor.
[](https://i.stack.imgur.com/xtL7T.png)
In this case we have the most fuel efficient solution because all we need is to get the ship out of our atmosphere. If all it did was sit there with a relative velocity of zero, 180 days later it would collide with Gor. However, cheap as it may be, time is money! We need a faster solution, but preferrably one that doesn't cost us a mint.
2. Trivially, we can give our space ship constant thrust. We can leave it on the same path — the planetary orbital path — and reduce the number of days waiting by the allowed thrust period. OK, it's fast. But we can do better.
3. We're using contemporary technology, the cost-vs-time trade-off (which *always* exists) is basically the size of the boosters + the capability of the onboard engines vs. how long we're willing to wait to get the job done. Frankly, we're basically in the hands of newtonian physics anyway — but that includes the sun! If we pull the flight path closer to the sun, we actually get a boost from the sun (both in terms of acceleration and deceleration), which speeds us up without additional cost, and shortens the path.
[](https://i.stack.imgur.com/74MNf.png)
Let's use some real data to ship some cargo. Humans will be slower because, well, we hate being squished. Therefore, let's use New Horizons as our benchmark. It left the Earth at a screaming 16.26 Km/s and passed the moon's orbit in just 8.5 hours. Smokin'! But the moon's a kicked can compared to Gor.
Now, here's where I'm very happy you didn't include the [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") tag. I stink at orbital mechanics. I'm slowly working through a textbook on it, but I'm not to the point I can just pull the math out of my head. Not by a long shot. But, here's the gist.
* We're working with a sphere (a sphere described by the orbits of Earth & Gor) and there's a reason we fly over the pole here on Earth. But remember that our launch point and destination are both on the "equator" of that sphere. therefore, the sphere actually buys us little if anything at all.
* We have an initial velocity that's fixed at 16.26 Km/s. However, we'll speed up as we approach the sun. We want to get as close to the sun as our heat shields and (and this is important) the oribit of Gor will allow. That minimizes the time of transit.
* We do need to miss Venus and Mercury. They're not particularly in the way, but there are certain times of the year where they might (I stress, might) be inconvenient. However, we can always lift the path of the ship on the sphere such that it flys over or under the inner planets and avoids them completely — so they're really not much of a threat.
* Earth's orbital path does have an eccentricity, which I'm going to completely ignore. The biggest reason for this is that, when thinking of the orbit of Earth as the reference plane, there is no eccentricity between Earth and Gor. Huzzah! (On the other hand, the gravitational effects of Venus and Mercury might be non-zero. OK, lift the flight path higher on the sphere so we can ignore that, too.)
What would be the actual shortest path given all of the above? Well, you need the circumference of the orbit (940x106 Km) and you need the effect of the Sun's gravity (274 m/s2) and you need our reference intial velocity (V0 = 16.26 Km/s) and then *[magic happens here].*
What can I say. I'm not to that point in the book, yet.
*If HDE 226868 or Kingledion answer, be sure to upvote them. They are initiates of the inner circle and know the correct incantations and which Demon to invoke to provide an actual, numerical answer.*
[Answer]
**The travel time is dependent on your $\Delta v$ budget. More $\Delta v$, the quicker you go.**
The bare minimum (least fuel costly) you can do is a $\Delta v$ burn arbitrarily close to Earth's escape velocity (about $11.2 km/s$) where you could slowly inch ahead of the Earth on a slightly faster orbit until you reached the L3 Lagrange point (the position of Gor), where you would perform a near-zero $\Delta v$ burn to slow to a stop relative to Gor. This approach necessitates very, very long travel times, which we do not want, yet, it is the most fuel efficient. This approach also gets you at L3, but you could just as easily carry the fuel instead to inject into a circular orbit around Gor (for LEO, a $\Delta v$ of $3.4 km/s$).
To quicken the journey, as stated in the first sentence, you'll need more $\Delta v$ at your disposal. The best that you can do is approach L3 in 1/2 Earth's orbital period, which is half a year. To do this, you'll need a $\Delta v$ of around $18.3 km/s$ *in total*. That is, $4.3 km/s + 11.2 km/s$ to break Earth escape velocity and approach L3 as quickly as possible (for non-Brachistrone trajectories), and $2.6 km/s$ to transfer into circum-Gor orbit ($10.6 km/s$ to come to rest at L3 *minus* LEO velocity of about $7.8 km/s$).
Again, the net end result is about $18.3 km/s$ $\Delta v$. (An identical journey would be made to return from Gor to Earth.)
This trajectory would take you $38,700,000 km$ from the Sun, still a greater distance from the Sun than Mercury, so you probably don't have to worry about the whole solar atmosphere thing. However, $18.3 km/s$ is quite a lot of $\Delta v$. For perspective, the multi-stage Saturn V had a total $\Delta v$ of about $17.9 km/s$ (if launched from rest in empty space).
] |
[Question]
[
I just won the national lottery! I am a billionaire, and can do whatever I want with my money!
Tv interviewer asks me what would I do with this money. Then, come the Idea.
I remember this guy when I was young, Kevin, if I remember correctly. His parents were rich, way richer than mine. And therefore, he had much more Lego than me. As he was my direct neighbour, he used to play in the garden, or to expose his big towers on her balcony, so I could see that he had more Legos than me.
I still remember him, and want my revenge.
Here is my plan. Kevin lives in a rural area, and there are only fields across the roads. I buy them all. Now, I want to build the highest Lego tower possible, just in front of his house. Money isn't a problem anymore, the sky is the limit.
* I would be ok if the foundation are not in Lego, but otherwise, all the towers must be simple Lego bricks.
* width/length shouldn't be a problem, as I have a big land
## How high could my Lego tower be?
PS: This have been asked/answer elsewhere, but I'm not ok with the answers. For example:
* [Quora](https://www.quora.com/How-high-can-a-Lego-brick-tower-be): Just tell us a random number, without showing us the calculations. Bonus point for wondering if we have enough pieces.
* [BBC](https://www.bbc.com/news/magazine-20578627): Base theorical heigh according to pressure/weight until a brick collapse, before telling us it would be impossible
Other articles are similar, based on the weight, but don't include the need of foundations, wind resistance...
[Answer]
## 10.8km high.
I wrote up a little program (code below) to find the exact break point at which we reach the 4240 Newton limit that was provided as enough to crush a lego block by your BBC article. I picked a pyramid, an extremely stable structure, and one that has a very wide base to properly distribute the weight above it, allowing it to get much taller than a tower. I hope you really do have plenty of land! I am running off of the following assumptions, that or course aren't necessarily true:
1. Your legos are being built on a perfectly flat surface.
2. The legos distribute their weight perfectly
## Results
1125001 lego blocks high. 1125001 \* 9.6mm ~= 10.8km
You could get this result for a while, bot note that your tower will slowly sink down over time, plastic deformation is bound to happen! You now have the pleasure of owning the biggest lego tower ever, but also the tallest man-made structure ever! Now just to watch it slowly melt...
## Code
```
i = 1
weight = 0
totalLegos = 0
while True:
# Size of new bottom layer
base = i**2
totalLegos += base
# Add size of previously added layer to
# total weight load on the base layer
weight += ((i-1)**2) * .001152 # Weight of lego is 1.152g -> kg
# Too heavy?
if weight/base >= 432:
print("Maximum reached!")
print("{}/{} = {} >= 432".format(weight, base, weight/base))
print(" Levels: {}".format(i))
print(" Total weight: {}".format(weight+base*.001152))
print(" Total legos: {}".format(totalLegos))
break
else:
print(i)
i += 1
```
## Output
```
546752187002808.0/1265629500004 = 432.00019200017067 >= 432
Levels: 1125002
Total weight: 546753645007992.0
Total legos: 474612539069437505
```
Sources:
[BBC](https://www.bbc.com/news/magazine-20578627 "BBC lego pressure threshold")
[Exact lego dimensions](https://bricks.stackexchange.com/questions/288/what-are-the-dimensions-of-a-lego-brick)
] |
[Question]
[
**tl;dr** What is the strongest glass that can be concocted from a single reasonably abundant, natural source? (Without nuclear or quantum manufacturing)
So I am developing a character for a story. He has powers that are very similar to alchemy in [Full Metal Alchemist](https://en.wikipedia.org/wiki/Fullmetal_Alchemist) and in FMA they have the Law of Equivalent Exchange which states:
>
> Humankind cannot gain anything without first giving something in return. To obtain, something of equal value must be lost.
>
>
>
So basically he uses magic to make a thing from other things. On the atomic level (let's not be cute and bring quantum mechanics into this. He transforms elements.)
Also, he can't guarantee a crystalline shape due to failing geometry and geology (no diamond cuteness). His life is a mess but he does not apologize. Failing chemistry is why he can't just whip up an explodey or a chemical weapon.
But that's all fine with him. He can just make hard stabby things appear from the nature, preying on the fear that living things have of being stabbed. So basically he is creating [glass](https://en.wikipedia.org/wiki/Glass) (this includes [metallic glass](https://en.wikipedia.org/wiki/Amorphous_metal)).
So my question: what is the strongest glass he can make strictly from commonly occurring natural surroundings?
Key points I will use to judge an answer:
* It shouldn't be crystalline. I am looking for a glass, e.g. a non-crystalline amorphous solid
* It doesn't require anything man made. Pretend the world is a wonderland untouched by man.
* It doesn't require anything living. PETA, TreeTA, and PeoTA really screwed up this guy's life. He doesn't need another lawsuit. Dead is fine though.
* It doesn't require carbon. This is a bonus, but I like it because some people don't count trees and bacteria and mollusks as people. But a lawsuit from BacteTA sealed that deal.
* It's transparent. This is also a bonus, but if a person makes a shield, it helps if they can see through it.
* It is fine if any carbon or living organism get caught up in the creation, they just can't be ingredients in the creation.
[Answer]
There is a common misconception about the difference between tough and hard. Tough materials can take a lot of stress without *breaking*. Hard means the material is hard to indent. So I wonder: Drop a ruby (hard) from a tall building. Will it be scratched? No. But will it shatter? Probably. Even worse, there are math equations that show that a material can’t be insanely hard and tough at the same time. So I tried to find a glass that was at least somewhat hard and somewhat strong. I present:
<http://www.pnas.org/content/105/51/20136.short>
**Titanium BMG**
This glass uses titanium (famous for hardness) and zirconium in glass to produce a glass harder than steel and *more importantly tougher*. If you are going against flesh then I’d suggest something with more hardness and less toughness, but any kinda armor and your glass or corundum spear will shatter. Try this one instead!
[Answer]
>
> what is the strongest glass he can make strictly from commonly occurring natural surroundings?
>
>
>
While not crystalline, glass still is made up of a ionic lattice; it's simply highly irregular and nonrepeating.
What you want to obtain is strength, i.e. resistance to fracture. This can be obtained by having the ionic latticework subjected to a really strong compressive tension, so that a fracture would have little to no chance to form.
One way of doing this is to heat the glass at a precise temperature range, then suddenly cool it so that the outside shrinks at a different rate from the inside, giving rise to large [residual stress](https://en.wikipedia.org/wiki/Residual_stress). To break the glass, you first need to overcome that stress; this is how Batavian tears (aka Prince Rupert's Drops) can withstand the impact of a bullet.
Another way is to force the lattice out of its natural shape; this is still a poorly exploited branch of chemistry, but it gives origin to things that explode more than they should ([octanitrocubane](https://en.wikipedia.org/wiki/Octanitrocubane)), springs that are more elastic than they ought to be, and glass that it's way stronger than it had any right to be.
The lattice stretching process is usually performed by replacing atoms and groups with other atoms and groups that are compatible, but much smaller, or larger, than the ones they replace. Replacing sodium with potassium gets you Gorilla glass; replacing it with other metals gives you "transparent aluminum" (not real aluminum, Mr. Scott, I know!) and other high-tensile strength glasses.
I have read that Gorilla glass is about 20-30% of the maximum theoretical stress that the lattice can withstand (i.e., if you made it ten times stronger, it would explode by itself). This is using normal soda aluminosilicate glass to start with, which I think is your case - otherwise you'd have some other ceramic.
So, I think that a strength three to four times that of Gorilla glass is achievable if you have a fine enough control on matter.
[Answer]
## Silicon Carbide is pretty amazing
This is also known as Moissanite (SiC) . It's almost as hard as diamond. Color varies but is generally transparent.
If the absence of carbon is a hard requirement then corundum ($Al\_2O\_3$) would work too. Generally transparent except when contaminated with impurities. When contaminated with chromium, corundum goes red to form ruby. Corundum is just behind diamond on the Mohs Hardness scale.
As long as these are stabbing only weapons, then Moissanite and Corundum should do nicely. If none of these are acceptable, further reading can be done on hardest crystals. Remember, the only difference between boring mundane graphite and a diamond is how the crystal is shaped.
Silicon, carbon, boron, oxygen and nitrogen are all very common elements. Forming into the right crystals is what makes them mind boggling strong. Most every rock you see is made of silicon and oxygen. You'd be very hard pressed to run out of raw materials.
] |
[Question]
[
I have a character (who is human) who, for his own reasons, decides to act bat-like and sleep hanging upside-down.
Handwave the feet/attachment issue.
Which parts of a human body would be affected by sleeping upside-down for 8 hours at a time?
Related: [How would a humanoid need to change to sleep upside-down?](https://worldbuilding.stackexchange.com/questions/116848/how-would-a-humanoid-need-to-change-to-sleep-upside-down)
[Answer]
Not a single part, the whole body will suffer.
Hanging upside down a person was a technique of torture used in Japan, called [Tsurushi](https://en.wikipedia.org/wiki/Tsurushi):
>
> Tsurushi (Japanese: 釣殺し), or "reverse hanging", was a Japanese torture technique used in the 17th century to coerce Christians ("Kirishitan") to recant their faith. [...]The technique was said to be unbearable for those submitted to it. The body was often lowered into a hole,[...] Typically, a cut would be made in the forehead in order to let blood pressure decrease in the area around the head.
>
>
>
Our circulatory system is made so that the legs can withstand the higher pressure resulting from being below the hearth, [while the head is not](http://torturemuseum.net/en/suspension/).
>
> it was found that, unlike the veins in the legs, the veins of the upper body do not have the valves that prevent the reflux of blood.
>
>
>
Thus not cutting the forehead was even worse: (graphical description)
>
> When torture was further prolonged, the victim's eyeballs would burst from the immense pressure, and the victim’s face would be covered in disfigured, gaping holes.
>
>
>
[Answer]
**Aneurysm, Asphyxiation, Death**
The human body is for obvious reasons built to handle the force of gravity from top to bottom, and not their reverse. When hanging upside down blood-pooling in the head will eventually cause brain aneurysm. A more immediate threat however is gradual asphyxiation due to the weight of organs pressing down on the lungs and diaphragm. Assuming these two health risks don't happen you will also suffer damage to the eyes as the pressure inside the eyeball doubles when the body is turned upside down, over prolonged periods this can cause permanent damage to the persons vision, possibly even blindness.
] |
[Question]
[
I need to keep a radio station running after an Apocalypse. There is no power grid of course.
Details of apocalypse are not entirely set in stone. The only rules to this question are those annotated below.
1. No zombies.
2. No power grid.
3. Those who can not listen to this broadcast slowly lose their sanity.
4. The broadcasts played by this station keeps people from going mad (the Madness).
5. If the broadcast stops playing, you have a few hours before you go raving mad.
6. The only survivors are those listening to this station.
7. Everyone else has gone all sorts of mad, raving, & crazy, losing their self identity in various ways.
8. The station owner knows these facts.
9. So do the survivors (eventually)
10. The station crew must keep the station transmitting even after loss of the power grid.
11. They must maintain all required upkeep as well.
12. The Station must listen to it's own broadcasts to stay sane.
13. Any thing broadcast by the tower protects against the Madness.
14. Once you succumb to the madness there's no recovery.
15. If it's only been couple of hours without a broadcast and you haven't fully succumbed to the Madness, you might sometimes recover slowly by listening to the broadcast.
16. It's only this station and none others that has this effect, and those outside of its range are doomed.
17. Broadcast Range is perhaps 200 miles.
18. Location is a made up small town near Savannah, Georgia.
19. The broadcast must be playing within earshot while you sleep, or you wake up mad.
20. The station is not the cause of the Madness.
21. As I do not know with good knowledge all of the supplies needed in detail to run a Radio Station, all I can put out at this moment is the following :
a. There are multiple nearby military bases, and they have not been too looted.
b. The mad/crazy people don't use many supplies (if any), and they make up the majority of the population. This allows for extra resources.
c. Since not everyone listened to the station, only a few people are even active utilizing supplies. So resources are not scarce.
d. Supplies with shelf lives/expiration dates are unusable in some instances.
e. This is a simple small town with only a couple of fast food restaurants, some gas stations, and a Wally-Market.
NOW BACK TO THE QUESTION:
How do I keep my radio station running and supply power and other necessities?
[Answer]
In the long run this is hopeless. You do not have the population to repair things as they wear out, and the requirement to listen means you can't go very far away to scavenge stuff.
The problem is even worse for everyone else--you have to power their radios also.
Edit: Last night I had another thought: Since it doesn't matter what the station is sending out the real reason must be something unintended going out on the signal. As things break down and get repaired/replaced someday you're going to replace the wonky part that causing the unintended signal. By the time you realize what's happened it's going to be too late to save the day.
[Answer]
Well clearly the radio station is the cause of the madness due to subliminals hidden in the audio stream.
While you listen to it, it's under control but kicks into gear once it stops kinda like a drug withdrawal effect.
Keeping the station going is easy. You can have wind and solar power on site or even nuclear batteries that last for hundreds of years.
The problem with your story isn't the station but the listeners. How will everyone keep a radio going 24/7? Where are the batteries?
A minute is far far too short a time without the effects kicking in. It would be too dangerous to leave the station to scavenge food and water let alone spare parts.
Dropping your radio is a death sentence because you have no time to find another or fix it. Even trying to change the batteries is risky.
I'd recommend a at least a week which would allow survivors to travel to get spares if something breaks.
A minute means everyone would go mad before you could replace a simple fuse.
[Answer]
If you want it to keep running then you need power. If you want it to keep running forever with no interruption, then you need a reliable source of power.
Your literally going to use back up generators. Nothing else will have close to that level of reliability.
There are three generator types I could imagine being used which would be reliable enough. Petrol, Coal and Hydro.
* Petrol: Scavenge around and take petrol from gas stations and cars. This should last you a while and you can probably use anything oily as you start to run out
* Coal: Coal or wood, basically a steam engine. There should be plenty of vegetation you can use and plenty of bodies you can try burn. You could probably also use oil or gas if you really need to.
* Hydro: Build an engine run by a stream or multiple streams. This would probably more long term than coal and petrol but it really depends on your location and the weather.
You would also throw in a couple of batteries that can last an hour or two so if anything goes wrong or anything is sabotaged you have some time to fix the problem.
Now your probably wondering why not renewables like solar or wind. You could use solar or wind, but it has to be in conjunction with a back up power source above because you can't guarantee that solar or wind will be reliable enough on its own. You can have a massive battery if you want, but a weeks worth of run while you need to power a radio station 24/7 is going to be difficult. A weeks worth of ran could take out your solar and with your batteries degrading over time your not going to last as long over time. With wind your going to have problems if the wind speed is too high or low when you will need to shut them off so you don't damage the turbine.
You could also go nuclear or geothermal, but I don't think your radio station staff will even know where to start with that stuff.
If you happened to have a large Dam, I would go with hydro, it should be able to support you for an extremely long time, but all power sources will fail over time if they are not maintained and aren't constantly refueled.
[Answer]
The easiest short terms solution would probably be diesel or gasoline generators. The other solutions offered are great, but have the requirement of needing a long time to install. Unless the station owner rigged the broadcast tower weeks before the madness began, I doubt anyone would be sane long enough to get anything done.
Portable generators, however, can be found in hardware stores, garages, and construction sites fairly easily. Fuel for them would also be easy to find (at first). Just siphon the gas tanks of abandoned cars. This wouldn't be a permanent solution, mind you, but its a great way to keep everyone sane enough to look for a permanent solution.
Before I move onto some of those long-term ideas, I agree that emergency batteries would be a smart idea. If one of the survivors is cleaver enough, maybe they would rig up an array of car batteries and a transformer. Its not exactly elegant, but it could buy everyone a couple hours while the generator is being repaired or replaced.
Okay, long term ideas:
* Tap into an existing power source. The main grids may be down, but the hydroelectric dam or modern windmill didn't stop turning motion into electricity. Then again, both of those do tend to break when not maintained. I guess this depends on what skills the survivors have.
* Build a steam generator. Yes, this is a technological step backward, but it allows the survivors to get power from felled trees, decimated houses, bags of barbecue charcoal, and literally everything else than can burn. Plus its a lot easier than trying to divert a river or run miles of cable. That being said . . .
* Get a PA system installed, aka the announcements you hear in schools and supermarkets. This would cut down on the number of handheld radios (and handheld radio batteries) needed, as it could share the same power source(s) as the radio tower itself. Strapping speakers to the outside of the tower would be a good start and establish a base-camp, but the long term goal would be a network that covers the entire town and whatever lands are being used to farm.
Lastly, classical music is a good choice, but the station owner has some other options. For example, you could try to rule the group like a cult leader by broadcasting a "magic spell", which is just a recording of his own voice saying meaningful-sounding nonsense. Or maybe he is of a more traditional religious mindset and broadcasts hymns, only stopping when the group starts persecuting the unbelievers in their midst. Maybe the broadcast starting out as continuous SOS with their coordinates and switched to something more pleasing to the ear when it became clear no help was coming. Just spit balling some plot points, really.
[Answer]
# Power
PV cells, windmill, and watermills are all viable options for the medium term.
PV cells will work as is for some time, especially if you can scavenge and trade for replacements, and store these replacements safely for long term. There will be a bunch lying around in various installation; especially in Florida, not too far from your location. However, there is no real good answer for generating power at night, or storing power overnight, so this might not work.
Windmills and watermills can provide electric power with primitive dynamos. The wind and watermills themselves are decidedly ancient technologies, and with sufficient technical expertise, they can be kept working just with masonry and wood, although iron/steel parts would be better. On the minus side, Savannah is low and flat and none of the nearby rivers will be good for power generation. It also isn't generally windy, but when it does get wind it is a hurricane.
Honestly, I'd head upriver to the Piedmont (Anderson, SC or at least Augusta) to get enough flow power in the rivers to effectively generate power.
# Radio equipment
A radio transmission antenna is just a piece of metal, so that can be maintained with near-medieval blacksmithing skills. That part isn't a problem.
Transmission range is just a function of power and frequency. The radio doesn't have to be AM (amplitude modulation) unless you want it to be; the advantage of using AM and FM in the established frequency ranges (in the US at least) is that off-the shelf radios can pick up their signals. But a frequency tuner is a very simple electric device, easily modified with a soldering iron (some labeled resistors from Radio Shack or an ohmmeter would be handy, though). There isn't a need to restrict yourself to those frequencies; the motivation to change frequencies is to get better signal transmission. For example, in the HF range, sound quality goes down but transmission distance goes way up.
I bring this up because there is a reliable source of high quality, high power, high reliability radio equipment near Savannah: Fort Stewart, home of 3rd Infantry Division. Military personnel radios are just perfect for this job: they are super rugged, have parts on hand, manuals for repairing them, and last forever. I can tell you first hand that as a radio technician in the Marine Corps, ~2004, we pulled Korean War era radios out of the junkyard and had them serviceable within a day. These things hadn't been powered in 30 years, but they started right up, and were able to transmit clearly from Florida to Hawaii with a bit of cleaning.
VHF radios are only going to be line of sight, and both traditional AM and FM ranges are VHF. To get a 200 mile line of sight you are going to have to built some real tall towers, especially with all the trees in Georgia; probably not feasible post-apocalypse. HF radios will give you that range on the cheap by bouncing signal off the ionosphere. Military HF radios that you might find include the [PRC-104](http://www.columbiaelectronics.com/an_prc_104_hf_portable_radio_set.htm), which is man portable, and the [GRC-193](http://www.columbiaelectronics.com/id137.htm) which is usually vehicle installed.
The size of the radio itself doesn't really matter, you will need to rig up some amplification system to get the signal strong enough out the antenna. I could go into detail here, but suffice to say that any old electrical engineer that paid attention in class can probably make this work, once you have a stable power source (from a watermill).
# Conclusion
Totally doable! The limitation in time is when the military radios start breaking down. As long as you get a good sized cache of them (and there are plenty of other very large military bases within a few days travel of you; Marine Corps Air Station Beaufort; Fort Benning in Columbus, GA; various Naval Bases around Jacksonville, Fl; Camp Lejeune and Fort Bragg in North Carolina, etc.), you could expect at least some of the radios to last > 50 years.
After that, you are on your own with the Madness, but suffice to say the radios should last as long than the people alive at the time of the Apocalypse.
[Answer]
Any car with an alternator is effectively a portable generator and before the petrol runs out you should be able to get a diesel engine running on vegetable oil and animal fats. In the long run you'll be better off relocated to the nearest hydroelectric power source, if you do some research you'll be surprised how common they are.
I had an idea like this a while back, I figured some eldritch god or whatever was attacking humanity and although it couldn't overcome our conscious minds it could manipulate us subconsciously. Music drowned out its influence much like wearing headphones drowns out someone trying to speak to you, without music people become increasingly unstable as the god plays on their fears, insecurities, anger and paranoia. It's possible to recover from the god's influence, it's like having a bad friend trying to convince you that your girlfriend's cheating on you. If you know he's full of shit you'll recover easily, if there's some truth to his accusations or you're insecure his influence may have permanently damaged your relationship.
Someone's ability to resist the god's influence depends upon their willpower and emotional maturity, people who fall to its influence become unpredictable and violent, or kill themselves.
[Answer]
POWER:
- An array (big enough) of solar panels to get energy from the sun in the day.
- Eolic generators (wind turbines) to get energy at night (and day also).
- An array of rechargable batteries to have a buffer.
FOOD:
Assuming there are no Walmarts available, you will need:
- An orchard big enough to provide the broadcasters with vegetables and fruits.
- A little farm (perhaps chickens and a cow or a goat) to have milk and eggs.
- The animals will also be feed with the production of the orchad.
- If you have no water, you will also need to dig a water well, or build an atmospheric water condenser. Have you seen how the water drops from an air conditioner? That is the basic process. You can see an example here:
<https://www.youtube.com/watch?v=s6w0-RkDnLA>
- Also a big container and a plumbing system to gather water from the rain and store it.
RECYCLE EVERYTHING
- Since there will be no stores around, you must reuse and recycle as much as you can.
And of course, without electricity you will need fuel to burn (for light, heat and cook). You can cultivate potatoes to get alcohol. Details here:
<http://iopscience.iop.org/article/10.1088/1755-1315/73/1/012003/pdf>
And finally, soon or later you will eventually need to scavenger the surroundings in order to find spare parts for your survival machines.
[Answer]
Easy solution? There is river in Savannah, and you can use watermill scrapped from e. g. nearby open air museum combined with some gears to power up dynamo, you can have 2 wheels, and being able to switch which one powers broadcast, for maybe routine conservation, it sounds like too much? You do not need to power *Savannah in georgia*, you only need to power ***broadcast*** from Savannah in Georgia, also you might lower usage by leaving oceans without broadcast and sending signal only over land. and survivors could use dynamo+battery combo to power up radio recievers on their side, this might seem hard, until you realise that bike will do.
[Answer]
I'd like to throw my 2 cents in, but I'd need a start.
Say, 'apocalypse'.
What happened, EXACTLY? Asteroid? Nuclear war? Epidemic? Without understanding how badly was the environment affected, the lack of power grid is the LEAST of the problems. We need to know what stripped civilization on a global scale and see if there are the conditions to operate so that the broadcast can continue.
] |
[Question]
[
Is it possible for Wolverine style retractable bone claws, to work in real life? Either from the knuckles, or from the wrist (hidden blade style). How would such claws, if possible, change the appearance of the person?
If not Wolverine claws, then what other retractable claw designs are feasible in reality? What about shorter and thinner versions of Baraka's claws? <https://upload.wikimedia.org/wikipedia/en/thumb/4/44/BarakaMK9render.png/220px-BarakaMK9render.png>
Or a single claw extending from below the wrist? Doesn't have to be too long. Like the hidden blade from Assassin's Creed.
[Answer]
For anything like a human hand (or vertebrate hand) only with super healing, Even in the most realistic iterations (aka ones where the claws sit entirely in the forearm when retracted and in between the metacarpals when extended) the path his claws take lies between the bones of the wrist, he is dislocating all the bones in his wrist every time. The movie [illustrates this nicely](https://www.youtube.com/watch?v=JLiNyglOyJY), note two of the wrist bones even have an extra joint to allow the claws to pass through them. Your wrist would not work after that the tendons would be too damaged. Sliding them above the wrist might work but then there is nothing holding them in place, and they would be useless. If you tried to slash with them they would just rip out of your hands.
With an alien hand, constructed in a different way than earth vertebrates, and a single claw it would be possible. for strength reason they could not be very long. Although you have the issue of what is extending them, you need some weird muscle arrangements, but not impossible ones.
[Answer]
I would like to say first that I have no medical training and so, I'm far from an expert. However, I did look into the possibility of retractable claws in the past, and came to several conclusions.
The answer, in my opinion, can be divided into two cases:
## **1. Retractable claws in a human hand structured as it is normally.**
In this case, I don't believe such claws are possible. The human hand is a complex thing and there are tendons and nerves that run through the back of the hand that would have to be 'rewired' or moved for such an arrangement to work. The structure as it is cannot support anything more than there is.
## **2. Retractable claws in a human hand with alternative structure.**
This case, I believe, holds more potential. Such 'claws' would have to be made out of or bone or better, keratin, with a likewise ability to be regrown if broken and be sharpened manually. They would not be as long as Wolverine's claws, as they can only be as long as the cavities holding them and the size of such cavities is highly restricted by the size of the part of the hand they sprout from.
There are three options for the placing of such claws:
**1) Claws located in the fingers.**
This is the location I initially researched, as my need was for feline-like claws.
Such claws would have to be short and probably curved, as there is not enough room within a finger, even a restructured one. I immediately ruled out the tip of the finger because it wasn’t what I was looking for. I wanted normal fingernails and hidden claws. This left the middle and proximal phalanges of the fingers. While the proximal phalanx of the fingers is longer and offers room of larger claws, I believe the middle one would offer more mobility, but essentially, the same would work for both.
I believe the structural changes necessary would be as such:
[](https://i.stack.imgur.com/E02bK.png)
[](https://i.stack.imgur.com/RL5WY.png)
(pictures modified by me from one found [here](https://humananatomyly.com/hand-structure-anatomy/))
The phalanx bone would have to be split into two bones and the 'sheath' and mechanism would have to be fitted between them. (As in, muscles, tendons and the claw itself). The tendon running through the back of the finger would have to be rerouted, maybe split along the bones and mended at the next knuckle, so that when the hand is curled and the claws extend, the tendon would be held out of the way on both sides. Same for nerves.
the claw mechanism itself would have to resemble somewhat of a feline's claw mechanism so that they are unsheathed when the fingers are curled.
Note that this would undoubtedly make the fingers thicker, and the corresponsive phalanges more fragile and more susceptive to compression pain.
**2) Claws located along the metacarpal bones (the back of the hand).**
In this approach, we can either employ the same method as with the finger claws, namely splitting the metacarpal bones and fitting the mechanism between the split bones, or fit the mechanism between the existing bones.
there is also the option of making the bones hollow and the spines be sheathed inside them. However, I am not sure how the sheath/unsheath mechanism would work in this case. Perhaps by combination of a ring of muscles at the exit of the sheath and a piston-like effect of a liquid or gas filled gland. This, however, would make the mechanism more complex than my level of anatomic knowledge can scope. It would also require lubrication within the ducts. It can be achieved by oil glands or some liquid like saliva.
In any case, these claws would need to be straight and would not be much longer than the finger claws.
**3) Claws located along the forearm bones.**
This, I feel, is the most plausible of the choices, since it requires less modifications. In this case, since there are already two bones in the forearm, the structural difference would have to be made between the bones to accommodate a long, narrow sheath in which one claw or spear like protrusion will be housed. It too will be made of keratin or bone, but I cannot envision more than a single such claw in each forearm. It can, of course, be as long as the forearm itself which would make it more viable as a weapon.
The unsheathing mechanism would have to consist of rings of muscles and tendons, a lubricating system and a fleshy sheath, since the normal claw sheath found in felines would not support such a claw. It is simply too long and would have to absorb or filter debris to some extent, as a means of hygiene. The forearms would look thicker, but not by much.
Such a claw would probably have a detachment mechanism since it can be torn or broken. The mechanism would guarantee there would not be lasting damage to the muscles and tendons of the retraction mechanism. The claw would then regrow, much like a horn or a nail.
[Answer]
In realistic terms, you cannot have any of those "retractable" claws because you'll be modifying so much of your bones and muscle so that it can withstand every strain you put into it.
Say for example Wolverine's claws. You need something that could really keep it in place, and as [John already mention](https://worldbuilding.stackexchange.com/a/109816/28789), if you try to slash something with it, you WILL rip your arms open. So bones need to be present for your claw.
Another thing is your claws composition. Imagine having a metal claw inside you, without having the strength to hold your claw. It might dig deep within your body if it's very sharp. PLUS, if it is sharp, imagine something ripping your hands every day if you are going to use it.
Bones are required to lessen your injury. This is if perhaps you don't have the healing properties of wolverine. What's more is that if you have to use it immediately, muscle alone cannot be controlled as to how far and how fast your claw would appear. It might be so fast your claw went flying or so slow that you're already dead before the claw even appears.
Bones are really needed to push and pull the claw, have it in place, protect your arms from being ripped open, and how fast the claw can appear, or sheathed.
Baraka's claws are another thing. That humongous claw is so unbelevable, you can defeat that guy if you just concentrate on hammering his claws - you can remove his arms if you are successful.
What I think is the most possible creature with a "Claw"-like structure based on what you describe would be someone that is a giant, does not have a retractable claw, but an extended bone that has a sharpened edge. Preferrably the bones of the knuckles are extended up until maybe a half foot far from the knuckle.
To support the claw, the Giant would have gloves so his hands won't be injured when picking up things, but his main problem I think would be if he was a male giant.
That said, I'll be saying that your claws sir, are realistically **impossible**. If you really want to have claws, make them cat-like claws instead.
[Answer]
A single claw coming out of the wrist would have to fit in between the radius and ulna. I think that if you wanted something more realistic/easily explainable that doesn't limit mobility, then the wrist-claw option is good, since a single claw coming out just above the palm wouldn't be coming into contact with any of the bones in the hand, preserving movement there (but not in the wrist, since wrist flexion would be prevented with the claw out); if the claw is the right shape and size, then it could fit between the radius and ulna without inhibiting the twisting movement or noticibly changing the appearance of the forearm. The anterior side of the forearm (the side you see when you look at your palm) is [mostly muscle and tendon anyways](http://cdn1.teachmeseries.com/tmanatomy/wp-content/uploads/20171222220540/Prosection-of-the-Intermediate-Layer-of-Anterior-Forearm.jpg), so it's pretty easy to imagine a sheath that the claw could retract into without damaging or disturbing any of the real-life anatomical features the way Wolverine-style claws would. An opening for the claw to come through could, if the claw was shaped right, simply look like a small scar.
[Answer]
Yes. And unfortunately that would hurt like hell.
There could be two option on how it can happen.
First is metacarpals splitting in two (or having just two pair of each, ind of like extra teeth) with the tendons still attached but the extra meta not connected to anything else. So every fist clench would move the tendons and extra bone structure forward.
Second solution is more "mutanty". You could have saliva outlet on your hand, with a stone in the duct. Muscle contraction could push part of the stone out creating a little spike. Here a video that show how it works in humans mouth.
[Saliva stone poking out](http://boredombash.com/salivary-gland-stone/)
Also some kind of degeneration that stores silica in hand and form tubelikes structures.
[Answer]
Yes. It is, in fact, possible. There would have to be an opening in the skin where the claws would protract, and it wouldn't be very large. It would protrude from the knuckles, and would behave like an animal's claws. You would lose the mobility of your fingers, however.
] |
[Question]
[
The basis of my story revolves around a single survivor escaping a massive colony ship gone critical above the skies of an alien world. After his escape via escape pod, the ship crashes halfway across the world on a separate continent. This got me to question what events might occur if a ship as large as say, 8.5 miles in length, made a crash landing into the planet.
I have not fully developed this planet, but I have a general idea and theme going, with a few micromanaged details here and there. But the general idea is a planet similar to the concept of a "Super Earth", with a larger diameter, thicker and heavier atmosphere, hotter climate, and stronger gravity.
For reference; let's just ask what would happen if this were on Earth instead. We can make adjustments to the data later, accordingly. Even with near-future period technology in science-fiction, the ship is already coming in for a landing when the crash occurs, so the speed must be significantly slower than say normal travel. The cause of the crash appears to be a stellar anomaly which leads to a critical engine failure.
If the failure occurs say within a few hundred KM of Earth's atmosphere whilst the ship is probably clocking close to 5 KM/S on a gradually slowing and controlled descent and in the midst of positioning a vertical landing, depending on the angle of the ship at the time of the failure, how hard would it hit the Earth as it picks up speed?
Assuming a slightly tilted angle, how would that change during the descent? If protagonist lands in Albania, and the ship lands in China, how would this affect his environment, if at all? Would this sort of thing be a local disaster, a regional disaster, a planetary event? The ship is clearly denser than most asteroids, being made of fictional metallic alloys and substances, so how would this change the scenario? Would the presumed hollowness of much of the structure change anything?
[Answer]
The internet is full with happy ladies and meteor impact calculators.
This [one](http://simulator.down2earth.eu/planet.html?lang=en-US) even let you simulate the impact crater.
I put there the data for an 12 km diameter iron meteorite (I assume your ship is made of metal, so iron is the closes thing), travelling at 6 km/s and hitting the ground made of sedimentary rock at 45 degrees.
This is what the impact crater would look like if hitting Albania
[](https://i.stack.imgur.com/sTxg1.jpg)
This other [one](https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/) gives a description of the effects at 5000 km from the impact point:
Seismic effect
>
> The major seismic shaking will arrive approximately 16.7 minutes after impact. Richter Scale Magnitude: 9.6 (This is greater than any earthquake in recorded history)Mercalli Scale Intensity at a distance of 5000 km:
>
>
> III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck.
>
>
> IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
>
>
>
Ejecta
>
> The ejecta will arrive approximately 26.2 minutes after the impact.At your position there is a fine dusting of ejecta with occasional larger fragmentsAverage Ejecta Thickness: 1.23 mm ( = 0.486 tenths of an inch ) Mean Fragment Diameter: 23.8 microns ( = 0.937 thousandths of an inch )
>
>
>
Air blast:
>
> The air blast will arrive approximately 4.21 hours after impact.Peak Overpressure: 4540 Pa = 0.0454 bars = 0.645 psiMax wind velocity: 10.5 m/s = 23.5 mphSound Intensity: 73 dB (Loud as heavy traffic)Damage Description: glass window may shatter
>
>
>
[Answer]
First, your ship is unlikely to be denser than an asteroid, because asteroids are solid while ships are mostly hollow. It may be made of denser materials, but will still be much less dense overall. Let's assume it is a cylinder 10km long, with a diameter of 1km, and the density of water. Then its mass is about 8 quadrillion grammes.
At a speed of 5,000 m/s, the angle of approach and any gain in speed as it approaches are irrelevant. Its kinetic energy is 1E23 joules. That's about 24 million megatons of TNT. It's pretty much the same as the estimated energy of the Chicxulub impact that is believed to have killed off the dinosaurs, so it's going to wreck the global climate for a while and possibly cause a mass extinction.
[Answer]
More reading for you on this page:
[If a generations ship was destroyed while in low Eath orbit (LEO), would debris fall to the surface?](https://worldbuilding.stackexchange.com/questions/99053/if-a-generations-ship-was-destroyed-while-in-low-eath-orbit-leo-would-debris/99060#99060)
The key thing here is kinetic energy of the incoming impactor and also the air resistance it encounters. The atmosphere can slow things in orbit down to terminal velocity. 8.5 miles long is a lot of air resistance and I would guess this thing will break up into many parts on the way down, the component parts which are not consumed by heat each striking at terminal velocity over an enormous debris field.
from
<https://www.amsmeteors.org/fireballs/faqf/#12>
>
> Due to atmospheric drag, most meteorites, ranging from a few kilograms
> up to about 8 tons (7,000 kg), will lose all of their cosmic velocity
> while still several miles up. At that point, called the retardation
> point, the meteorite begins to accelerate again, under the influence
> of the Earth’s gravity, at the familiar 9.8 meters per second squared.
> The meteorite then quickly reaches its terminal velocity of 200 to 400
> miles per hour (90 to 180 meters per second). The terminal velocity
> occurs at the point where the acceleration due to gravity is exactly
> offset by the deceleration due to atmospheric drag.
>
>
> Meteoroids of more than about 10 tons (9,000 kg) will retain a portion
> of their original speed, or cosmic velocity, all the way to the
> surface. A 10-ton meteroid entering the Earth’s atmosphere
> perpendicular to the surface will retain about 6% of its cosmic
> velocity on arrival at the surface. For example, if the meteoroid
> started at 25 miles per second (40 km/s) it would (if it survived its
> atmospheric passage intact) arrive at the surface still moving at 1.5
> miles per second (2.4 km/s), packing (after considerable mass loss due
> to ablation) some 13 gigajoules of kinetic energy.
>
>
> On the very large end of the scale, a meteoroid of 1000 tons (9 x 10^5
> kg) would retain about 70% of its cosmic velocity, and bodies of over
> 100,000 tons or so will cut through the atmosphere as if it were not
> even there. Luckily, such events are extraordinarily rare.
>
>
> All this speed in atmospheric flight puts great pressure on the body
> of a meteoroid. Larger meteoroids, particularly the stone variety,
> tend to break up between 7 and 17 miles (11 to 27 km) above the
> surface due to the forces induced by atmospheric drag, and perhaps
> also due to thermal stress. A meteoroid which disintegrates tends to
> immediately lose the balance of its cosmic velocity because of the
> lessened momentum of the remaining fragments.
>
>
>
Of note: a 10 ton meteoroid is extremely dense - a solid chunk of metal. I am sure your ship weighs much more than that but it will be nowhere near as dense - for one it needs open area inside for crew and for 2 unneccesary density means more energy need to push it around, especially if it routinely does stuff like descending into the gravity well of a planet like this one was trying to do.
The thermal energy generated by these ship pieces slowing in the atmosphere will heat up the atmosphere. To calculate the amount of energy one needs to know the mass of the ship. Once that energy is calculated you could figure out how much it would heat the atmosphere that slowed it down.
] |
[Question]
[
This is a submission for the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
Kappa are creatures from Japan said to lurk in rivers and lakes. They are described as small humanoids resembling a cross between a monkey, a frog, and a turtle with either a water filled depression or a patch of water soaked flesh atop its head (which is supposedly the source of its strength) surrounded by a ring of hair. It’s said to have a penchant for drowning people and eating their intestines, has a fondness for cucumbers and sumo wrestling, and the ability to fire off high powered farts at will. The question is whether they could evolve in nature.
[Answer]
They could be large salamanders, or something similar, that never lost their feathery gills, but adapted to come on land despite this. The bowl could be a depression on the head to keep the gills moist, while the gills themselves could become even more feather like as a second method of holding water, like how hair can stay wet for hours, and this could give the appearance of hair surrounding the bowl as some of the extended gills might flop out the edge of the bowl a bit.
It could have a thick temnospondyl-type body to give the vague appearance of a turtle, while it's forelimbs could be spindly grasping ordeals for the monkey comparison.
Big meat eating amphibians might supplement it's diet with cucumbers, and people for that matter, though mostly children due to the threatening size of adults, but never underestimate a starving endangered animal. The enjoyment of sumo wrestling might just be an extension of an adaptation for waiting out fights between other species with the intent of drowning the weakened loser. This obviously won't be possible with the Sumo wrestler, the adaptation is there.
[Answer]
For evolution it makes sense to start out with an aquatic salamander, like the axolotl. They require water and have arms and legs. Lengthening them and growing larger could help them to catch land animals and drown them to eat them, and with sufficient size and strength humans could be on the menue as well.
Various amphibious creatures that have gills can survive on land for a few hours if they keep their gills wet (crabs are common examples). This could not really become a water-filled depression, as that wouldn't make much sense for hunting outside of water, but it would be the closest to a water-filled sponge. As omnivores, they probably could have dietary reasons to eat cucumbers and intestines (carnivores eat intestines because they can't process a lot of plant-based food, they rely on their quarry to, umm, pre-process some of it).
[Answer]
The kappa could start out as a turtle that becomes able to grasp with its forefeet, and also becomes more intelligent. It will eventually learn to hold itself upright, so that it can reach higher. It may also evolve a ring of many ossicones connected by colourful skin, for sexual display. This would fill with water when it exits a river or lake. Due to the cage-like ossicone array keeping away large predators, the braincase inside the bowl may be thin to allow more space for the brain, requiring that they wear a metal cap to protect themselves around other intelligent species. They may have compacted bones in order to weigh down and drown their prey, which they will then use an enlarged sickle-claw to disembowel, and then eat the internal organs, and then use the muscle tissues to feed animals they have domesticated. Finally, their shells may be reduced, and their reproductive organs may shrink to a size where a cucumber shell could be easily turned into an artificial vagina
[Answer]
No
Most of it yes but the water filled depression in the head no. You need a reason why evolution would favor a water bowl for a head over not having a bowl and there is no reason for and lots of reason for why not.
I'm also not sure but I don't think there is a genetic component to enjoying watching two fat guys wrestle.
] |
[Question]
[
If there was an island civilization, somewhere deep in the Atlantic, how would this society prevent the outside world from discovering it?
This society has been around since the Roman Empire, and is quite in touch with the outside world. They have all modern technology, except all members of this society have possession of elemental magic. In this society, their secrecy is vital and super important. They want to be able to access the world without the world accessing them.
Could there be any geological explanations for the island somehow remaining undiscovered?
Or would their technology need to be more advanced than the outside world? In terms of a magnetic field etc.
[Answer]
>
> the Atlantic
>
>
>
This is the worst choice possible. It was being explored and fished in for as long as we have paper records, and maybe before that. It's not a place you can hide an island bigger than a family car. And because European governments were always keen on grabbing every bit of land they could find and stuffing a flag and some troops on it (it's a habit we got into) you'd be an English/French/Spanish/Dutch/Portuguese colony in no time - if not all of them in turn.
So not the Atlantic. The Pacific was lovely and quiet by comparison (until WW2).
**In practical terms the best approach is to *hide in plain sight*.**
Visually hiding it is no good - radar and thermal imaging would spot it. Hiding the civilization underground won't work either - they would have thermal signatures and military surveillance is particularly interested in looking for underground complexes.
You mentioned magic and this does tend to mean they can just magic themselves out of the way, but it's so arbitrary I am ignoring it.
People travel everywhere and mysterious bit of unexplored area tend to attract the curious. The words "no one ever checks that bit" would be like a magnet to geologists, oceanographers, explorers and people trying to get away from everyone else.
Short version: you can't hide so don't.
You hide in plain sight.
You create an apparently poor looking culture, not great climate, no attractive beaches and dull as a very dull thing landscapes. That should keep most people away. Be entirely unhelpful to any visitors.
Stick a bunch of natural obstacles around the island to deter visitors. Nasty jagged rocks just below the sea which are tedious to navigate through, lousy currents prone to drowning the unwary and just be a nuisance enough to deter those determined to be nosy.
Geographically a hilly, rocky place where not much grows but you can graze cattle and live a minimal life (or so it seems). No area large enough to e.g. plonk a runway. No bays ideal for sheltering the fleet. Cliff faces that deter the beach dwelling types and no exciting hills or volcanoes that attract climbers or geologists. Dull, boring, unattractive.
Initially, these things would deter most explorers (although not European monarchies that will colonize places like the Falklands/Malvinas, which are exactly as described :-) ).
Now you can hide the real civilization just behind the scenes.
This part is important: minimize EM radiation - island wide wi-fi is not a good idea to stay hidden. If you set up any comms use carefully hidden wiring.
Likewise, keep thermal emission low or find an excuse for that big thermal hot spot where your generators and industrial equipment are: the island is, after all, allowed to have some industry to keep it going, and it's probably inefficient (or so it appears) and maybe that will do it.
Get rid of any wildlife that could even remotely interest a biologist - those guys are a pain to get rid of.
So people visiting glance at it and go, "bit dull, no beaches, no oil, no minerals, no agriculture worth speaking of, no internet - get me out of here !".
Keep in mind that you mind find that periodically your island is occupied for strategic reasons in times of war. This normally results in the said military leaving when the need of the moment is past and leaving nothing more than a mess behind.
Likewise, by hiding in plain sight, you allow your own people to quite legitimately visit the outside world without raising any real interest beyond "what's Mystery Island like anyway ?", "quiet, dull, poor, no internet" - conversation ends. You can even join the UN and do the normal things: never support any vote or initiative that would draw attention to yourselves.
I'm sure you can do a better job of this idea if you give it a go.
Now I consider magic to be a cop-out, but maybe your islanders can use magic a little to help with this. Whip up a nasty storm that sinks or damages a lot of ships when someone starts parking their fleet around you, that sort of thing ("luckily" the islanders will survive, shaken but in one piece).
[Answer]
My answer is based on some ideas from Stephen's.
You don't hide from detection, you hide in plain sight. What you need is a privately owned island, such as [Necker Island](https://en.wikipedia.org/wiki/Necker_Island_(British_Virgin_Islands)).
Since your atlanteans have been around for ages, procuring the means to eventually own the island should be easy.
Now they should start a facade crackpot cult that call themselves "the Atlanteans" - seriously! Just start a website claiming that the atlanteans have achieved illumination, and as such they know that vaccines cause autism, the Earth is flat and mankind has never made it to the Moon, which happens to be infested with aliens. Also, Xenu sent 75 billion aliens to die on Earth aeons ago and electromagnetic therapy is true and psychology is false.
And then Bob's your uncle. Atlanteans are free to do whatever it is that they do, and as long as they keep the crackpot facade they will be left to their own devices.
Just think of it. Any non atlantean who visits their island -or gets in contact with them anywhere else, really - and then comes back to civilization claiming to have witnessed supernatural feats (elemental magic), or to have seen wonders of hitherto unseen technology, will be dismissed as just another crackpot.
The atlanteans may even fabricate tales of defectors among themselves just to further discredit those who would reveal their secrets.
As a bonus, they can make an expletive amount of money by:
* Selling books and merchandise for crackpots;
* Youtube channels that have conspiracy theories as the main theme;
* New age tourism for those who believe in things such as humans substituting sunlight for food.
[Answer]
# It might be easier in the Pacific
There are a few islands left with [more-or-less uncontacted people](https://en.wikipedia.org/wiki/Uncontacted_peoples#Oceania), like the [Sentinelese](https://en.wikipedia.org/wiki/Sentinelese) or the [Jarawas](https://en.wikipedia.org/wiki/Jarawas_(Andaman_Islands)). It would be quite plausible to add another island with another tribe, or to take one of the existing islands.
As Stephen pointed out, the Atlantic may be a worse location than elsewhere.
* Place your island on the Atlantic coast of Central America, as a mirror of the fictional [Isla Nublar](https://en.wikipedia.org/wiki/Isla_Nublar), or somewhere near the Amazon estuary.
* Or on the Atlantic coast of the [Terra del Fuego](https://en.wikipedia.org/wiki/Tierra_del_Fuego).
In either case, people would know generally that the island exists, and *there would be a government claiming it.* The people who think they own it just never got around to using it and they have no idea that there are "native people" on it. Or perhaps they know, but they think the "natives" are underdeveloped.
[Answer]
Since we are talking about elemental magic here and modern technology.
* Location would probably somewhere underwater. Deepest level underwater like Marianas trench? or somewhere in Bermuda triangle? (since people are afraid to go there for some reasons.)
* Use your magic to create a sphere of air underwater. Start building from there.
* Create some kind of mirror or glass reflector barrier to avoid being seen by any living creatures.
* Also consider putting some teleportation factor so if ever they hit the magical barrier, they would just be teleported to the other side like nothing happened.
* Explorers usually uses sonar technology to locate things underwater that can't be seen. So also put that in your magical barrier. Make it absorb or negate sounds that would pass through.
* For the heat scanners, I'm not sure if the currently can do it
] |
[Question]
[
So recently I'm working a speculative science fiction universe where I'm trying to adhere as close as possible to the laws of physics and the possibilities of technology. I want to have mecha (because they're cool) but the square-cubed law obviously makes such things very difficult to make since current materials need to be pretty heavy to provide tank level protection.
So I ask: Are there any materials, real, almost real, or could be real that could provide protection similar to tank armor at a fraction of the weight?
Note: The practicality of producing the substance is of no object. Just the possibility of its existence.
[Answer]
A particularly interesting armor that exists currently is the "Dragon Skin" armor.
<https://en.wikipedia.org/wiki/Dragon_Skin>
Basically this armor is made of small overlapping ceramic plates that are covered in in a textile, much like scales. As a result the armor is very good at stopping projectiles without adding too much weight. Now, instead of just ceramic plates and fabric, make it out of multiple graphene layers on top of titanium plates. This should make for some seriously tough armor that has a great strength to weight ratio. Maybe put an inner layer of some type of rubber, or if you want to be really fancy some kind of non Newtonian fluid that hardens on impact so that your armor can absorb some extra kinetic energy. Keep in mind, however, that generally better armor means the other guy just brings bigger guns and eventually the guns will win. So unless you can dodge, (very difficult), you need to either strike first, have some really fantastic point defenses, or both!
[Answer]
I propose you use reactive armor without the standard armor components.
The Wikipedia has some cool stuff.
<https://en.wikipedia.org/wiki/Reactive_armour>
[](https://i.stack.imgur.com/d9pMr.jpg)
from <https://media.defense.gov/2017/Mar/07/2001708258/400/400/0/170228-A-ZZ999-777.JPG>
Standard reactive armor is explosives outside the normal shell. The soldiers here are putting the reactive armor components on their tank. Your armor would just be shaped explosives. When hit, they go off with the explosions knocking back whatever impacted the armor. Explosive chemicals are lighter than the equivalent volume of metal. You can make them lighter yet because this is science fiction. The Wikipedia calls this [directed energy reactive armor](https://en.wikipedia.org/wiki/Reactive_armour#Directed_energy_reactive_armour)
---
Another very cool idea and from the same Wikipedia page: [electric reactive armor](https://en.wikipedia.org/wiki/Reactive_armour#Electric_reactive_armour)
Your armor is two thin conductive plates with a gap. An incoming penetrator closes the gap and the circuit. A capacitor then pours current into the incoming missile, and resistive heating turns it to plasma. I think my superconducting railgun projectile would go right on through that so good for you we are on the same team.
---
My own idea: deflective induction armor. Instead of armor there is a magnetic field. Incoming conductive projectiles develop eddy currents and consequently magnetic fields in opposition to the one on the armor. A field out far enough from the tank (possibly maintained with antennae) could produce a field which could deflect incoming projectiles so they did not hit. This sort of armor would work well against particle beams and also my superconducting railgun projectile.
[Answer]
# Boron Nitride (BN)
Some people mentioned carbon nanotubes, but for heavy duty armor, they might not have the best properties. In particular, they are susceptible to heat damage and can undergo adverse chemical reactions at high temps, such as decompostion in air.
[Boron Nitride](https://en.wikipedia.org/wiki/Boron_nitride), on the other hand, is a viable option. Not quite as strong as carbon nanotubes, they can be formed into similar molecular structures. There are also diamond analogs of BN, which have a similar hardness.
Ceramic plating (such as [silicon nitride](https://en.wikipedia.org/wiki/Silicon_nitride) ceramics) reinforced with BN nanotubes would have significantly increased strength and resistance to thermal shock.
[Answer]
This breaks the "like tank armor" rule, but...
# Shoot the incoming projectiles
This is very, very hard to do, but you said not to worry about that ;)
When two projectiles collide at these kinds of speeds, they will tend to behave much more like liquids than solids. Imagine shooting an egg that was being thrown at you. The egg will still reach you, but it will be broken up and the pieces distributed over a large area. The same sort of thing would happen to an incoming slug, completely negating its effectiveness.
High explosive rounds would behave a little differently, and, depending on the type of explosive used, would maybe explode prematurely.
If the incoming round is made of something very hard like tungsten, it might shatter rather than (for lack of a better word) splat, but the effect will still be the same.
This is a real-world technology for larger, slower moving projectiles such as missiles. A quick google search found me [this German armament](https://en.wikipedia.org/wiki/N%C3%A4chstbereichschutzsystem_MANTIS) that seems to attempt this for incoming artillery, mortars and missiles.
This might be easier if you can use a high-power laser to superheat the projectile as it flies towards you, but it would have to be a very powerful laser. The time the projectile spends in the air is very short, and convection will be working against you.
[Answer]
The shells of Crayfish, notably mantis shrimp claws can withstand a bullet, and they are relatively lightweight, and naturally occurring, you'd just need a safe way to farm them.
] |
[Question]
[
I was doing some research on how to design a scientifically possible alien, when I came across an interesting section on metabolism. I found it very interesting and read about the weak force, as opposed to our electromagnetic radiation metabolism. I did more research on it, but all I found was a thought that creatures with that would manipulate their surroundings and absorb the difference. Additionally, they would be made of radioactive particles, but only become radioactive when they die.
So my question is, what element or elements would such a creature likely be based on (Pb, Uuq, etc.), and what environment would support such a creature?
---
This link will sum up what most of the websites I visited said, basically the same thing:
<http://www.xenology.info/Papers/Xenobiology.htm>
[Answer]
It is doubtful your weak force xenobionts could be composed of any elements or atomic matter.
>
> Weak force lifeforms would be creatures unlike anything we can readily imagine. Weak forces are believed to operate only at subnuclear ranges, less than 10^-17 meter. They are so weak that unlike other forces, they don't seem to play a role in actually holding anything together. They appear in certain kinds of nuclear collisions or decay processes which, for whatever reason, cannot be mediated by the strong, electromagnetic or gravitational interactions. These processes, such as radioactive beta decay and the decay of the free neutron, all involve neutrinos.
>
>
>
Source: [General Xenobiology](http://www.xenology.info/Papers/Xenobiology.htm)
The fact alone that the range of the weak force is limited to 10^-17 metres and they don't bind anything together in the material sense suggests weak force organisms would have to be extremely small, of sizes far less than 10^-17 metres, probably several orders of magnitude less, in fact, and they would need some other force to hold them together.
In summary, this answer agrees with the proposition that: "Weak force lifeforms would be creatures unlike anything we can readily imagine."
**ADDENDUM:**
Sometimes the obvious can easily escape one's attention. What environment could sustain such weak force organisms especially since the range of the weak force is so extremely short. There is only environment where matter could be readily accessible to organisms with such a short range. Namely, the interior of a neutron star.
Inside a neutron star matter will be within range of the weak force. However, what kind of nuclear chemistry would be necessary to sustain weak force creatures is effectively beyond current knowledge. Although there could be experts who have considered the interactions inside neutron stars to be able to have a good idea of what they are. This, if it exists, will be buried deep in the technical literature.
One possibility is that weak force lifeforms will be unable to exist outside of a neutron star. If they can exist outside neutron stars, it will require super-scientific technology on a mind-boggling scale.
[Answer]
# TL;DR
I'd propose that weak force life has a tiny change of existing in environments where particles travel at high speeds. A possible example is the jets produced by an active galactic nucleus. At the high energies (and high speeds) particles reach in these jets, the range of the weak force could be sizably extended to the point where it is less negligible than for a low-energy environment, because at high speeds, the $W$ and $Z$ bosons' lifetimes can be dramatically extended. While it's difficult to speculate as to what structures and processes - let alone life - could coherently arrive, I would bet that proton-antiproton collisions and the decay of charged leptons (muons and tau particles) might be potential sources of the $W$ and $Z$ bosons.
# The decay problem
The weak force is mediated by three particles: The charged $W^{\pm}$ bosons and the neutral $Z$ boson. Unlike the photon, their cousin, these bosons have mass, approximately 80.4 GeV and 91.2 GeV, respectively. Also unlike the photon, the bosons decay. The $W^+$ boson has [several decay paths](http://pdg.lbl.gov/2012/listings/rpp2012-list-w-boson.pdf), including hadronic paths (dominated by quark-antiquark pairs) and leptonic paths (a positively charged lepton and its associated neutrino); the $W^-$ decays involve the corresponding antiparticles. For the $Z$ bosons, [hadronic decays to quarks are also the main contributors](http://pdg.lbl.gov/2012/listings/rpp2012-list-z-boson.pdf), although pairs of charged leptons and their antiparticles may also be produced.
Both particles have half-lives of $\tau\sim10^{-25}$ seconds, and so the range of the weak force is approximately $r\approx\tau c\sim10^{-17}$ meters, even in the case of relativistic particles. Another way of expressing this uses [the derivation of the half-life from Heisenberg's uncertainty principle](http://hyperphysics.phy-astr.gsu.edu/hbase/Forces/exchg.html):
$$r\approx\frac{\hbar}{2mc}\propto\frac{1}{m}$$
where $m$ is the mass of the boson. Therefore, by decreasing the mass of the $W$ and $Z$ bosons, you could of course extend the range of the weak force. That said, [changing the mass would involve changing weak force coupling constant across the universe](https://worldbuilding.stackexchange.com/a/48885/627), which would cause serious issues.
# Time dilation
Changing our fundamental constants seems to be right out, then, so let's stay away from those. Instead, let's see what happens if we try to extend the lifetimes of these bosons through time dilation. Time dilation comes in two flavors: gravitational and special relativistic. It turns out that to dilate time enough to significantly extend $r$, you need to be in a steep gravitational field, quite close to a black hole; this seems an unlikely and unsafe (certainly short-lived) setup.
However, we *could* extend the range of the weak force by instead having these bosons travel quickly, as happens with muons in Earth's atmosphere. The boson's lifetime should be $\tau=\gamma\tau\_0$, where $\gamma$ is the Lorentz factor and $\tau\_0\sim10^{-25}$ seconds, from before. The highest Lorentz factors we've seen come from ultra-high energy cosmic rays; the [Oh-My-God particle](https://en.wikipedia.org/wiki/Oh-My-God_particle) had a kinetic energy of $3.2\times10^{20}$ eV, and thus (as you can determine by calculating the relativistic kinetic energy, $T\approx m\gamma c^2$) a Lorentz factor of $\sim10^{11}$, corresponding to a speed that differs from $c$ by less than one part in $10^{23}$. The boson's lifetime is then $\tau\sim10^{-14}$ seconds, and the weak force's range is a surprising $r\sim10^{-6}$ meters.
There are some caveats:
* Propelling a particle to this energy requires an active galactic nucleus, and therefore, ambient $W$ and $Z$ bosons can only survive in the jets emitted from such an AGN.
* The jets should be dense with leptons and hadrons, an extreme environment that produces gamma rays and cosmic rays. Interactions should be frequent, and it seems that bosons could very quickly interact with these ambient particles, limiting their range. There could be a limit similar to the [GZK limit for cosmic rays](https://en.wikipedia.org/wiki/Greisen%E2%80%93Zatsepin%E2%80%93Kuzmin_limit), albeit involving these ambient fermions.
* The bosons presumably can't be accelerated to these speeds in the same manner as normal cosmic rays, but they *could* be produced by high-energy particles in the jets. [Proton-antiproton](https://www.physi.uni-heidelberg.de/%7Euwer/lectures/ParticlePhysics/Vorlesung/Lect-8a.pdf) interactions can produce both $W$ and $Z$ bosons; if these interactions transferred the majority of the progenitor's energies to the bosons, we might well see the bosons reach the required energies. This is guesswork on my part, though.
While I would propose AGN jets as an alternative to a4android's neutron star suggestion, simply because they're the only energy sources that could create these Lorentz factors, it seems clear that only these extreme environments could host anything akin to life based on the weak force.
# What particle(s) would life be based on?
As you might have guessed, you likely won't see elements *per se* in these jets. Nuclei, yes, primarily protons. What you *will* see is, as I mentioned before, a messy soup of hadrons and leptons, producing synchrotron radiation and gamma rays. These particles will make up your building blocks of life.
How will these bosons be produced, then? There are two basic types of weak force interactions: charged current interactions (involving the $W$ bosons) and neutral current interactions (involving the $Z$ boson). Examples include:
* [Quark-antiquark interactions from proton-antiproton collisions](https://cds.cern.ch/record/2103277/files/9789814644150_0006.pdf), as I mentioned above. We see these occur in colliders. Typical pathways involve up and down quarks ($u$ and $d$) and their antiparticles ($\bar{u}$ and $\bar{d}$):
$$\bar{d}u\to W^+,\quad d\bar{u}\to W^-,\quad u\bar{u}\to Z,\quad d\bar{d}\to Z$$
* Lepton decay, e.g. a muon decaying to a muon neutrino and a $W^-$ boson, which then decays to an electron and an electron antineutrino:
$$\mu\to\nu\_{\mu}+W^-\to\nu\_{\mu}+e^-+\bar{\nu}\_e$$
There are other hadronic decay processes, of course (e.g. pion decay); I list the above just as examples. The dominant production processes depend on the ambient fermions and hadrons.
### A note on WIMPs
I'd like to second [Spencer's suggestion](https://worldbuilding.stackexchange.com/questions/100749/what-element-would-make-up-a-creature-if-it-used-the-weak-nuclear-force-during-i/149115#comment301361_100749) of [weakly interacting massive particles, or WIMPs](https://en.wikipedia.org/wiki/Weakly_interacting_massive_particles), which remain prime dark matter candidates. They're high-mass particles that interact only via gravity and the weak nuclear force, and hence would be excellent candidates for a creature that primarily uses the weak force insofar as it really couldn't interact in any other way. It does seem unlikely that they would combine in high densities, as dark matter doesn't clump quite like normal matter does, but they remain an interesting possibility.
] |
[Question]
[
I am currently in the early stages of mapping out a conlang for a race of boar-people. I was stumped trying to think of what limitations, if any, having pronounced lower tusks would have on the development of their language. These creatures do have snouts, but [this question](https://worldbuilding.stackexchange.com/questions/45328/what-phonemes-would-a-snouted-animal-e-g-dog-or-cat-be-able-to-pronounce) more than handles my needs on that front.
I'm really more curious about the effects tusks would have on their speech from that point on or in general.
[Answer]
They will have the ability to develop an oral language much like ours, but the details will depend a lot on the precise anatomy of the mouth, especially the lips.
Unless they cannot close their mouths completely due to their tusks (which is highly unlikely), I think they will have no trouble producing bilabial stops (/p/, /b/ and nasal /m/). Even if the lips cannot seal the mouth, if a reasonable length is closed, the "popping" effect of a bilabial stop can be achieved. It may be that these sounds will not be distinctive enough, though.
The same goes for labiodental fricatives /f/ and /v/, which don't need full closure of the lips. Indeed the tusks could conceivably function as a secondary fricative articulation.
They might run into trouble pronouncing rounded vowels (such as /o/, /u/ and the front rounded vowels of French and German) and the consonant /w/, if the lips are not flexible enough or the tusks are too close to each other.
As for new sounds, I'm picturing maybe a bilateral fricative or approximant made by letting air out the corners of the mouth, left and right of the tusks, while the lips are pinched in the middle. You can do this yourself if you pinch your lips right behind your nose using your index finger and thumb and forcefully blow some air.
[Answer]
Well sounds that are generated by putting your lips togheter like 'm' , 'b' or 'p' would certainly be much harder to make due to certain parts of the upper and lower lips not being able to join especially the labiodental fricatives like 'v' or 'f' .
But other sounds would probably be developped, based on the flow of air around the tusks, if their entire culture developped with this physical particularity, they'd probably still have pretty effective speech, some of it would just sound much more different.
Another thing I can think of is, due to the lips curling slightly inwards and the tiny gaps between the lips around the tusks, their voice might sound slightly cavernous.
] |
[Question]
[
Is arsenic, or arsenic alloy (arsenic + lead), deadly and can it be used for weapons in medieval / classical era?
If a leader of assassins' guild wants a special (reusable) toxic weapon (from dagger to the size of small sword), Is it a good idea to make it from arsenic? (what about arrow heads from arsenic?)
I know that arsenic was used to make bronze, but from what I know it wasn't significantly more poisonous than other copper alloys. (the copper oxides would probably do better job at that point)
>
> Lets say that there is a lot of pure arsenic, enough to make an entire
> short sword. Could people at that time make a short sword out of it?
> And would it be any good? Would it keep its shape?
>
>
> And would adding the lead help in any way (could it make a similar reaction as copper and lead and copper and arsenic do with bronze?),
> or is it better to have just pure arsenic?
>
>
> I know that there are several questions now, but I think they are all
> just clues pointing at the answer for my original question. And you
> don't have to answer these.
>
>
>
[Answer]
1. Arsenic is brittle. A pure arsenic tool would just break.
2. If you stick a weapon in someone then pull it out, the only arsenic in the person would be what rubbed off while the weapon was in them. I suppose if it broke off inside them like some Morgul blade it would leach off arsenic, sort of like [Andrew Jackson supposedly had chronic lead poisoning](http://www.nytimes.com/1999/08/11/us/a-president-s-doctors-are-finally-exonerated.html) from the bullets in him. It did not slow him down much.
Arsenic poisoning is by ingestion or possibly inhalation or topical absorption. Even then it is very slow and not reliably lethal. The assassination attempt might even backfire - the Italian artist Benvenuto Cellini was famously poisoned ([with either mercury or arsenic](https://archive.org/stream/b22330185/b22330185_djvu.txt)) which made him sick as a dog. On recovering he had been cured of syphilis.
[Answer]
Arsenic bronze is not poisonous. It is arsenic fumes that are produced during bronze melting that are poisonous. I sometimes wonder what early invention of respirator (that would make arsenic bronze safe to process) would do to [Late Bronze Age collapse](https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse) - is could be caused by problems with mining and transporting tin.
Arsenic by itself has poor mechanical properties and it works slow as a poison. If you want poisonous weapon then your ordinary metal with ordinary poison on it is orders of magnitude better and more useful than anything from arsenic.
] |
[Question]
[
In my world, there is a forest of giant trees on both poles. The trees create a canopy that is perpetually covered in ice. This frozen canopy extends so high that it supports a "land" of frozen clouds. There live the Yeti of this world.
**How strong could this frozen cloud land be?** Is it strong enough to support a village of 100 humans (although they are Yetis instead of humans)?
I'm imagining it will be more like frozen snow, instead of a block of ice, but I can be wrong. The strength of the canopy is assumed to be strong enough for any mass of the solid ice needed.
This frozen cloud would have some parts extending away from the canopy. My main concern is how strong this extension will be, and how to calculate the minimum thickness of the extension and how far it can be.
[Answer]
A solution can be found in Canada:
>
> During the Second World War, G. Pyke proposed that an iceberg be used as an aircraft carrier in the Atlantic. When it became apparent that natural icebergs were too small, proponents then launched a plan to build a giant "bergship." They found that the mechanical properties of ice were not up to the task, howeverthe tensile strength was too low, and the ability to withstand ballistic impacts and explosions was unacceptable. In February 1943 it was discovered that wood pulp could solve the problem; for instance, the addition of four percent Canadian spruce more than doubled the strength and, on a weight-to-weight basis, increased the shock resistance to that of concrete.
>
>
>
Source: <http://www.tms.org/pubs/journals/JOM/9902/Schulson-9902.html>
Since you already have trees, you could come up with an explanation as to why some wood pulp would be in the ice. Perhaps the yetis added it?
[Answer]
# No Yeti Castles in the Clouds
The frozen canopy is basically a giant ice sheet that's arbitrarily thick; thick enough that we can forget about the trees that are under it.
Clouds are made up of water vapor or ice crystals. They stay suspended because they are small enough to stay suspended in the air. Once they reach a certain size/density the air currents that kept them suspended are no longer able to support them and they fall in the form of some kind of precipitation.
It's certainly plausible that the Yetis live on the ice sheets and are frequently enveloped in fog of some kind ([freezing fog](https://www.accuweather.com/en/weather-glossary/what-is-freezing-fog/3504875) is especially unpleasant) but the micro-currents in the air aren't going to be able to support a full weight human in any way.
[Answer]
I would be curious about how it formed (did the tree tops grow through the ice somehow? did the ice cloud form only after the trees were that high, how do the trees get light?), but I think your question is answerable.
Ice has a tensile strength of 0.7 - 3.0 Mpa and a compression strength of 25Mpa. In comparison, concrete is 2.2 - 4.2 Mpa tensile, and 17-28 in compression. It will fail in tension, so it would be better if you can use something as tensile reinforcement (such as tree branches).
Interestingly, ice is 1g/cm3 and concrete is 3g/cm3. What does this mean? Combined with the difference in strengths, it means that a structure made from ice should be twice as thick as if it were made from concrete, and then it will have about the same total mass and the same sort of strength.
So if you think your trees are strong enough to hold up a 100m platform of concrete, then they can also hold up a 100m platform of ice. And we have built boats out if concrete, so, at least with engineering(!) someone could build a sky-ice-city.
Note that this answer assumes a solid block of ice.
] |
[Question]
[
Let's assume we have an otherwise Earth-like planet orbiting a star just like our own. Our planet has an axial tilt of 0 degrees, meaning its axis is perpendicular to its orbital plane.
Could this planet have seasons based solely on where it is in its orbit? My thought was to increase the eccentricity of the orbit, so that at aphelion it's significantly further away from its sun than at perihelion. But the question becomes how much eccentricity do we need to get seasonal variations similar to what we're used to on Earth? And is there even time for the planet to cool enough on its way to aphelion and winter?
[Answer]
Elliptical orbit can definitely be a replacement for the lack of axial tilt.
While all other climate impacting factors, like ocean currents and air systems are able to create significant variations, they all ultimately depend on sun's energy. If this energy remains constant, it is difficult to imagine regular temperature fluctuations like we observe here on Earth (outside of equatorial latitudes).
[Earth's orbit](https://en.wikipedia.org/wiki/Earth%27s_orbit) has an eccentricity of 0.0167. While this means that it is almost a circle, still there is a difference between perihelion and aphelion of 5 million km (147.1 vs 152.1). This translates to solar irradiation variation of 7% between the two points.
Axial tilt contributes much more than 7% to seasonal variations, in fact, it is unnoticeable that summers in southern hemisphere (that's when the Earth is in perihelion) are supposed to be warmer. Northern landmasses more than compensating for the difference, because land warms up faster than sea.
How much variation in solar energy do we need to have real seasons? According to [this article](http://www.ccfg.org.uk/conferences/downloads/P_Burgess.pdf), at the Cairo's latitude (30N) variation between summer and winter is 2 times. At London's latitude (51N), it is about 5 times. If we want to have a higher eccentricity orbit with no axial tilt, effect will be uniform for all of the planet.
Let's say we want the solar energy difference of 3 times. This means that the orbit must have aphelion to perihelion rate of SQRT(3) = 1.732, which will lead to eccentricity of 0.268
It also has to be noted that high eccentricity orbits have bodies travel faster in their perihelion than in aphelion. This means that winters on such planets will be longer than summers.
[Answer]
**Our tilted axis isnt the sole cause for seasons**
First, let me thank you for not providing these restrictions:
-Did not say the answer had to be entirely science driven
-Did not say that seasons had to be globally uniform (even ours isn't)
**So a science driven answer:**
In addition to tilt there are other factors that affect climate and thus our perception of "seasons".
* **Pressure Systems:** pressure systems can define the climate of region more so than tilt. For instance: the permanent pressure system over the Sahara has locked its climate into a desert where in similar latitudes you would see rainforest and occasionally even snowfall.
* **Ocean Currents:** Currents are huge circulating streams of water within the ocean (almost like a river). The gulf stream is a huge climate changing current. It delivers cold water to hot places and hot water to cold places and its effects are madness. Great Britain alone owes its warmer climate and rain to the gulf stream. At its latitude it should be much colder. Currents are also very stationary and can exist for many thousands even hundreds of thousands of years.
* **Jet Streams:** like the ocean currents there are similar constructs in the atmosphere with similar effects. Though not as dramatic as the gulf stream jet streams can drive plenty of in seasonal climates.
* **The sun:** this thankfully doesnt drive our climate diversity, our sun is very stable. However, it is theoretically possible that a stars output can be variable enough to drive climate change.
**Answer #1:**
Play with these variable driving some to extremes to generate your desired seasonal system. Recently, a planetoid was discovered with winds so strong that its tidally locked solar generated hot spot was actually shifted from its face. So nothing is unreasonable when playing with these.
**Answer #2 - My favorite answer:**
Your own personal Night king to drive the world's seasons for you.
[](https://i.stack.imgur.com/ZpyxB.png)
] |
[Question]
[
So basically, a guy (criminal, fraud, con artist and generally very untrustworhy person) is involved in an accident and suffers total memory loss. He remembers absolutely nothing about his previous life. Naturally, he gets captured almost immediately and interrogation ensues. Of course, everybody thinks he is just trying to pull some stunt and do not believe a word he says.
**How could this guy possibly prove (or at least convince those people), he really lost his memory?**
Notes:
* It is a fictional kind of amnesia, meaning no memories whatsoever up until the accident, no side effects, undetectable by brain scans or similar things, and permanent
* People who captured him are not police, more like some entrepreneurs he ripped off before
* No friends or relatives are available, very little is known about the guy
[Answer]
You aren't going to like my answer. He can't.
Proving that something does exist is possible. Proving that something doesn't exist...that's a harder thing.
The best you can do is provide [evidence of absence.](https://en.wikipedia.org/wiki/Evidence_of_absence) Your guy is trying to prove a negative, which, [while not impossible](https://www.psychologytoday.com/blog/believing-bull/201109/you-can-prove-negative), is not completely provable.
In your notes, you have "no friends or relatives" which is bad, because the first thing I thought of was that they could threaten or kill people he formerly loved, and his reaction would tell them that he does not remember them.
This isn't proof, but the best you could do do is set up a situation where him remembering is in his best interest or the best interest of someone he cares about, but he doesn't. Unfortunately, your criminals will already be doing this with torture, and they might just believe that he's difficult to break.
In this case, you don't want to look at what is, but what other characters coming into contact might believe.
If one of them knew him well, they might set up a situation, a test, where they know how he would react if he had all the info that he claims he does not have. This would have to be something more clever than mere torture, and it would not come under the purview of worldbuilding--this would be a plot point, and this site isn't for that.
[Answer]
There are things people forget and things they will always remember. A good psychiatrist will be able to tell the difference between fake and real amnesia, madness etc.
One of the questions will be along the lines of "how many legs does a cow have?" as it's something that you'll never forget but someone feigning amnesia/madness might think they're supposed to have forgotten. However, this is consultant psychiatrist grade examination, whoever picks this guy up off the street is not going to be able to do it.
You're talking about classic fictional amnesia, it doesn't work that way in real life, so you'd need a matching fictional psychiatrist to tell if it was true.
[Answer]
I think you also need to explore the question of **"Why bother?"** What is the goal of the people who have captured him? Certainly some criminals who have been cheated aren't going to release the guy just because he has amnesia; they'll just kill him anyway. Ask yourself: what difference would it make to their plans if he has real amnesia or is just faking?
Perhaps they think he might know where the money went or somesuch. In that case, they'd likely just treat him like he's pretending amnesia as a way of getting out of torture, and torture him all the harder. Whether the guy resists torture by being tough or by having amnesia doesn't really matter.
I think the others have covered your actual question: bring in psychologists to question the guy, try to trip him up. Shows like **Lie to Me** and **The Mentalist** provide good background for how such people might get a faking amnesiac to spill the beans. The motivations of the capturers will be important in picking what experts they might be able/willing to bring in.
[Answer]
So, you give this fictional character a fictional kind of amnesia and want to know how he would go about proving he had it. If he cared, then that would prove he was able to understand his predicament. If he understands his predicament, he clearly hasn't forgotten everything he's learned. The attempt would disprove the claim. I love the inability of people to see the stupendously obvious contradictions in their own thinking.
] |
[Question]
[
Let`s suppose there is an alien supercivilization whose interstellar vessel has «exited hyperspace» in a close proximity of the Earth (i.e. a certain volume of physical space only filled with vacuum suddenly gets occupied by a macroscopic object).
Let`s also suppose there is no way to detect it by conventional means.
The question is: can we, in theory, use our existing gravitational wave detectors to tell where the vessel exited, if exited at all? Which are the probable restrictions on its linear size, or mass, or distance, or direction to the exit spot?
Clarification: the only noticeable effect of «exiting the hyperspace» is the ship popping up where there used to be nothing. So, where the spacetime metric used to be more or less flat, a sudden curvature appears, just like when a guitar string gets tapped.
[Answer]
The answer to this question resolves itself into two parts. First, whether a spaceship exiting hyperspace will be a source of gravitational waves. Second, whether gravitational wave detectors can detect these gravitational waves.
>
> Any object with mass that accelerates (which in science means changes
> position at a variable rate, and includes spinning and orbiting
> objects) produces gravitational waves, including humans and cars and
> airplanes etc. But the gravitational waves made by us here on Earth
> are much too small to detect. In fact, it isn’t even remotely possible
> to build a machine that can spin an object fast enough to produce a
> detectible gravitational wave – even the world’s strongest materials
> would fly apart at the rotation speeds such a machine would require.
>
>
> Since we can’t generate detectable gravitational waves on Earth, the
> only way to study them is to look to the places in the Universe where
> they are generated by nature. The Universe is filled with incredibly
> massive objects that undergo rapid accelerations (things like black
> holes, neutron stars, and stars at the ends of their lives).
>
>
>
Source: <https://www.ligo.caltech.edu/page/gw-sources>
For a spaceship to be a source of gravitational waves as it exits hyperspace this spaceship must physically act as if it is an object with mass undergoing an acceleration. Effectively, the spaceship might be apparently *decelerating*, but this is still an acceleration.
Presumably the rate of acceleration will be determined by the time it takes the spaceship to exit hyperspace. The shorter the exit time, the higher the acceleration will be. Also, the more massive the spaceship is, the stronger its signature as a gravitational wave will be.
The strength of a gravitational wave signature is the more detectable it will be. Now existing LIGO systems can detect black holes merging, binary neutron stars, and supernovae. Therefore, the parameters that need to be manipulated to ensure the probability of a spaceship exiting hyperspace are its mass, the time to exit hyperspace, its proximity to the detector systems, and the sensitivity of gravitational wave detectors.
Since the OP wants the spaceship to be detected only by its gravitational waves, this sets an upper bound to the mass of the spaceship. For example, a Jupiter-mass spacecraft exiting hyperspace in a fraction of an attosecond might be the source of gravitational waves of sufficient strength to be detected. However, if a Jupiter-mass object arrived near Earth it would be readily detected because it would change the orbits of Earth and the Moon plus the satellites orbiting the Earth. Also, it likely to be big enough to be seen in the sky from Earth. So this example fails the only detectable by gravitational waves test.
However, what this example does is set out the parameters that need to be meet. However, there are factors that cannot be readily determined. Assume a spacecraft that is sufficiently massive, which exits hyperspace in a manner that is effectively an acceleration and acts a source of gravitational waves, the key question is can it generate a sufficiently strong enough burst of gravitational waves to be detected?
Fortunately, the spaceship will be exiting hyperspace close to Earth, so proximity of the source to the detectors is in their favour. Now gravitational wave detectors are incredibly sensitive instruments. On the other hand, gravitational waves themselves are incredibly weak which is why LIGO and other GW detectors are so mind-bogglingly sensitive.
This puts us in the realm of speculation, because we don't know exactly how strong any gravitational waves generated by a spaceship exiting hyperspace will be. In a work of fiction, the author can optimize the factors to ensure the alien spaceship could be detected. But if the author of this answer had to guess, he would guess against its detection. The gravitational waves wouldn't be strong enough.
The mass of the spaceship would have be absolutely massive. Its exit time from hyperspace has to be close to Planck intervals. Both the proximity and sensitivity of gravitational wave detectors need be better than existing devices. So, possibly future detectors will be good enough. if all these factors are in the right proportions, then yes it can be done, theoretically, at least, but guaranteeing requires dramatic licence and every fiction writer should have one.
Plausible, yes, Possible, uncertain.
[Answer]
Well this isn't really a question anyone can answer, as we don't know what "hyperspace" is and hence we have no idea what the gravitational effect of something suddenly popping into real space from hyperspace would be.
But we could not in all probability detect it.
Why say that if I say I don't know all that much about the scenario ?
Well first things first : [gravity is an incredibly weak force](https://physics.stackexchange.com/questions/4243/what-does-it-mean-to-say-gravity-is-the-weakest-of-the-forces#4255). So it's effects are tiny.
If I popped a new moon near Earth (\*what does "near" mean ? :-)) the effects will be quite small. All we get from the moon we have (which is a large moon) is a tiny tidal effect on our ocean. So a ship won't deliver much of a gravitational field.
And the gravitational waves are way, way, way weaker than the gravitational forces.
So we wouldn't notice them.
We notice the huge events that LIGO detects simply because they are powered by the almost instant conversion of multiple solar masses into gravitational energy - an exceptionally energetic event. You might think of it this way : a star going nova can be seen a really long way away, but a grenade ? Not so much. :-)
It's worth reading [this section of Wikipedia's article on Gravitational Waves](https://en.wikipedia.org/wiki/Gravitational_wave#Basic_mathematics) to get an idea of the relative strength and practicality of detecting waves from small objects.
Our existing detectors would need a huge object (like a large planet) to pop into existence "close" to Earth to be detected, I'd say. But, again, that's not knowing or having any basis for the effect of something switching from "hyperspace" to real space and just making rough guesses.
Finally LIGO can't work out location or direction as you wish. [This article](http://www.thephysicsmill.com/2016/03/06/direction-ligos-gravitational-waves/) explains what its limitations are in that regard. So locating alien space ships is way beyond it.
[Answer]
In the service of the story being told by the OP: Don't worry about the gravitational **wave**, just detect the **gravity**. See [this map of the highly inconsistent gravity field on the surface of the Earth.](http://io9.gizmodo.com/new-high-res-maps-of-earth-s-surprisingly-inconsistent-1171851670)
As the article says, it can map gravitational pull on the Earth with a 7.2 arc-second resolution: That is 0.14 miles, or 738 feet across. smaller than a typical stadium.
One of the satellites being used for this is called GRACE (Gravity Recovery And Climate Experiment), [here is the NASA technology page](https://www.nasa.gov/mission_pages/Grace/spacecraft/index.html) describing how gravitational pull is detected (it requires multiple satellites).
The other data incorporated into the model comes from GOCE (Gravity-field and steady-state Ocean Circulation Explorer, [here is the Wiki page](https://en.wikipedia.org/wiki/Gravity_Field_and_Steady-State_Ocean_Circulation_Explorer)).
Gravitational *waves* are momentary, weak, and difficult to detect. Gravitational *pull* is not!
In fact, for the purpose of fiction, Satellites similar to these (GOCE is over, I think Grace is over too) can act as your detector, if the ship has the mass of a mountain. These satellites were mapping the **Earth**, but the gravitational pull of the spacecraft will affect these satellites (and our GPS satellites too, for that matter).
Say we launch several new mapping missions, to cover the poles and ice caps, to increase our resolution by a factor of 10, or for some other excuse. Military reasons, perhaps. We launch several because we want continuous mapping, updated daily, able to track ships and planes, tectonic movement, underground facility construction, new buildings, and so on. Finer gravitational mapping could easily discover tunnels used for drugs and smuggling, for example (the absence of Earth reduces gravitational pull above the tunnel, if it is not extremely deep). It is another lens on the Earth.
The alien ship gravitational mass will **distort the map of the Earth the satellites are producing** in a very consistent way; since the aliens are not moving. A clever mathematician at NASA or ESA (there are boatloads of them), learns that the distortion is the same in all the mapping satellites (so is not a glitch or bug). But she computes the distortion is completely accounted for by a single new gravitational source, and given a few weeks of super-computer time she can compute the location and mass of the object.
This may not be the gravitational waves the OP was hoping for, but it is at least *gravity* and real life tech already used and in the history books. A little fictional liberty, and the OP could say we have secret military satellites already up there and engaged in precisely this activity, from multiple nations (e.g. US, Russia, China, Japan, EU). I would not find that implausible at all.
P.S. Added: With a continuous series of such maps; she could tell which day it appeared, that it did not move into place but appeared more or less instantaneously, and also whether it is moving and in what direction and at what speed.
] |
[Question]
[
I was wondering would a planetary drill be possible?
The drill should go inside the planet on one side and exit on the other.
Would that kind of a drill be possible on Earth and if not on what kind of planet would it be possible?
Could it be possible with the technology we have today and if not what kind of future technology would we need?
[Answer]
When drilling through a planet, one has to face two main issues:
* Increasing pressures while going deeper down
* Increasing temperatures while going deeper down
The increasing pressure will tend to crush the hole, and will have the side effect of turning each piece of material released by the drilling into a grenate when the pressure is released. One could coat the walls of the drilled hole with a resistent material, kind of a steel or concrete pipe, but with the increasing pressure the thickness of this coating would increase dramatically.
The increasing temperature will make any material useless for drilling, either by making it too plastic or making heat management problematic. To make thing worse, it would also weaken the hole walls.
The only way I see to make this problems negligible is to shrink the body you want to drill. In Kola drill hole we managed to reach 12 km below the surface. That size is comparable with the diameter of some asteroid or comet out there (with the wild assumption we can use the same technology we used in Kola also in the outer space).
We have already sent some drilling heads on other bodies, like Mars, the Moon and some comets. In all the cases they drilled a very shallow hole.
Main reason for this is the low power available to drive the drilling head. Even my flimsy home driller, with its 800 W, has more power available.
After the power issue, one has to keep in mind that drilling produces a lot of friction, and friction translates in heat.
Heat dissipation on Earth is achieved by lubricating the head with some liquid, which also helps in taking away the debris from the drilling zone.
Now we know that liquids in vacuum are not stable and tend to become gases, so a proper medium has to be developed.
Another aspect to keep in mind, on a 12 km diameter body, is that gravity is low. Therefore if the drilling arm pushes too hard while drilling, it will "simply" kick itself above the body. Proper anchoring needs to be in place, too.
[Answer]
See Tides of Light by Greg Benford.
Of course don't expect to be able to live on the planet afterward. If you can't find a convenient superstring a magnetically guided singularity would do the job. It would have to travel pole to pole and be travelling with sufficient velocity not to fall back to the centre of mass. And you would of course need to catch it on the other side.
This is engineering at the Kardashev type II or better level.
[Answer]
This is not possible simply because earth isn't fully solid. If drill deep enough there will be magma and if you go deeper there are molten metal. You simply can't drill anything that's liquid as it will just fill the hole. Only way would be sliding a tube inside and drilling in that, but as I said - molten metals, that means anything you put in that will ... yes you guessed it MELT.
So where could you drill a hole from one end to another? on something smaller that has cooled in center.
] |
[Question]
[
On planets of have different temperatures, conditions and chemical makeup of the lava/magma, what would be the least viscous lava around?
(Relevant to an earlier question - [What would an efficient swimming creature in magma be like?](https://worldbuilding.stackexchange.com/questions/84412/what-would-an-efficient-swimming-creature-in-magma-be-like))
[Answer]
## Hotter planets will have less viscous lava
This one is pretty self-explanatory, since the hotter the temperature, the less solid almost all materials tend to be. Also, [from the Wikipedia page on lava compositions](https://en.wikipedia.org/wiki/Lava#Lava_composition):
>
> Greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour.
>
>
>
Basically, even for viscous materials, heat tends to destroy any bonds between the molecules, allowing them to slide past each other more easily, and making the liquid less viscous.
## Chemical composition plays a big part too
Viscosity can be defined as "resistance in the flow of a liquid." Therefore, materials with molecules that:
1. Are bigger
2. Have stronger inter-molecular bonds or attractions
3. Are weirdly-shaped
tend to have a harder time flowing past each other, and thus are more viscous. Some examples of real-life lava materials, in order of decreasing viscosity (again from [this wikipedia page](https://en.wikipedia.org/wiki/Lava#Lava_composition)):
1. **More viscous**: silica, aluminum, potassium, sodium, and calcium (think [quartz](https://en.wikipedia.org/wiki/Quartz), with its highly structured molecular form)
2. **Less viscous:** iron, magnesium, magnesium oxide
## Summary
If you are looking to make a lava lake that creatures can plausibly swim through, a mixture of **super high temperatures** and **compositions of iron and magnesium** will most likely yield the best results.
[Answer]
# Viscosity increases with increasing silica content
There are a lot of ways to classify rocks, but the relevant classification axis in this case is the [TAS diagram](https://en.wikipedia.org/wiki/TAS_classification).
[](https://i.stack.imgur.com/p54eO.jpg)
This two way diagram maps alkali content on the vertical axis agaisnt silica on the horizontal axis. The most common volcanic rock chemical components may have either a primarily silica content (like quartz), a primarily alkili content (feldspathoids) or a mixed content (feldspar).
To make this more complex, there are the terms [mafic](https://en.wikipedia.org/wiki/Mafic) and [felsic](https://en.wikipedia.org/wiki/Felsic). Mafic rocks are rich in iron and magnesium, often in the form of [olivine](https://en.wikipedia.org/wiki/Olivine), while felsic rocks are richer in feldspar and quartz. As a result, felsic rocks have more silica. Low viscocity rocks will be mafic or ultramafic rocks with silica ontent below 45%.
Going back to the chart, in order of increasing viscosity among common igneous (volcanic), extrusive (rocks that erupted from the Earth's surface) we would get [basalt](https://en.wikipedia.org/wiki/Basalt), [andesite](https://en.wikipedia.org/wiki/Andesite), [dacite](https://en.wikipedia.org/wiki/Dacite), then [rhyolite](https://en.wikipedia.org/wiki/Rhyolite). So basalt is the least viscous of the common lavas, as well as being one of the most common.
However, to get really free flowing lava, you would want ultramafic picrite basalt or foidolite. [Picrite basalt](https://en.wikipedia.org/wiki/Picrite_basalt) has a high concentration of olivine, and has been found coming out of volcanoes on Hawaii island, Curacao, and Reunion. [Foidolite](https://en.wikipedia.org/wiki/Foidolite) minerals are rare, but an example of a foidolite mineral would be [afghanite](https://en.wikipedia.org/wiki/Afghanite). This was found in the Pamir mountains of (you guessed it) Afghanistan, and probably formed during the vulcanism that raised those mountains. It has only a 1/3 silica content (much of its silica is aluminized) and a cool blue color when it cools and hardens. Check out the various [feldspathoids](https://en.wikipedia.org/wiki/Feldspathoid) for other options for your volcanic minerals.
[Answer]
In addition to Jan's answer, we have the rare [Carbonatite](https://en.wikipedia.org/wiki/Carbonatite) lavas - molten carbonates formed by phase separation from *very* carbon dioxide rich melts. These have very low temperatures (for lava), and very low viscosities.
There are also the [komatiite](http://blogs.agu.org/georneys/2011/01/15/geology-word-of-the-week-k-is-for-komatiite/) lavas, with extreme temperatures and low viscosities; as per Jan's answer, these are very rich in magnesium, low in silica and hence of low viscosity.
If you want a creature to swim in lava, these are the ones to go for.
] |
[Question]
[
A quick glossary to show how the magic works:
Spell - The usage of materials to magically produce an event. Not widely used because it takes time and physical resources.
Talisman - An item that can be used to produce or amplify magic. Common, because a talisman expands a mage's range of magical abilities and bring magic to non-mages and is thus in high demand.
Power - The ability to use magic without needing to cast a spell or use a talisman. May be learned or inborn. As common as any magical ability is and different for everybody.
Feel - The ability to learn spells and powers by detecting magical properties as well as predicting magical connections and reactions. Each mage has a *feel* for certain areas of magic, such as plants, minerals, the weather or transformation.
Each method of magic is based on the same principle - re-arranging the invisible force of magic within oneself or in one's to create a certain type of magic and activating it to create a reaction.
Most mages have powers of shapeshifting into one animal -different for everybody- without a *feel* for shapeshifting because they can manipulate the magic inside themselves. But a mage with a *feel* for transformation could turn into anything they want to be, or even change somebody else with enough skill and practice because they can "grab" the magic, manipulate it and then activate it to make the change happen.
The idea in question is for a mage to have a *feel* for transferring and storing magic in items to make them into talismans that essentially serve as transferable powers. Like making a hat that gives the wearer the ability to set things on fire with magic or a cotton quilt that's bulletproof.
Given this system of magic, is there a way for a mage to have a *feel* for making talismans without making them OP?
[Answer]
## Limit by "feel" (affinity)
You can only make talisman if you have feel of the required magic. For example, to make a Fireball talisman, you must have both feel for talisman and fire.
## Limit by mana/magic quantity
You can only manipulate certain amount of magic into a talisman. Think about this as "magic strength". If you are not well-versed in making talisman, you can only make low-level talisman from low-level spell or power.
## Limit by talisman material
You can only enchant certain spell or power into specific material. For example, you can only enchant wind magic into silk clothes, or fire magic only for dragon scale armor.
Or you can give low capacity to low quality material, meaning they can only have low level enchantment or fewer enchantment.
## Limit by complexity of talisman making
The process of creating talisman is very cumbersome and need great precision.
It also takes long time and preparation, not including collecting the required ingredients and materials.
Beginner to talisman making often accidentally create a catastrophe when trying to enchant talisman, so it requires a strict certification to be able to legally produce talisman.
## Limit by talisman charges
Similar to a battery, a talisman can only be used a number of times before depleting its magical energy. High level talisman requires a lot of magic and usually can only be used once. It can only be recharged by certain individuals (cannot be charged by general magic/mana)
## *Pick one.*
[Answer]
Sorry I understand english but I can't write very much so I write in spanish. You could use translator.
Una manera de limitar el overpowering de un mago haciendo talismanes es que el talismán guarde parte del poder del mago. De ésta forma un mago tiene un poder limitado y mientras parte de su poder esté en el talismán él no puede usarlo apra otra cosa.
---
Translation:
One way to limit the overpowering of a magician by making talismans is for the talisman to retain some of the mage's power. In this way a magician has limited power and while part of his power is in the talisman he can not use it for anything else.
[Answer]
Consider this. A talisman is not an object in the way that a pocketwatch is an object. The talisman is both an object and a "feel". A person can have a "feel" for making talismans, but this person would have no "feel" for anything else. The talisman-maker would not make talismans by enchanting any random object, the talisman-maker would instead, for instance, make a fire talisman by burning rowan wood and pouring the ashes into a hollow ring with a stone of obsidan. The mage in question would be able to make as many talismans as necessary, but would have to own the required ingredients for a spell, **AND** have a "feel" for talisman-making. Unlike spells, talismans would be reusable, and the magic would never decay. An interesting possibility for this would be to have an ancient, utopian civilization that existed for thousands of years before falling to conquering outsiders. During their reign, they made some of the most powerful talismans the world ever has or will see. If these include time or mind control talismans, they will be sought after by every person in your world.
] |
[Question]
[
**My AEROSTAT CITY is under siege by space pirates!**
Picture Dubai on air pillows. I imagine a chain of a few dozen aerostat "city blocks" linked together like a pontoon bridge to form a long flexible wing, each are an industrial "pillow" with luxury residential towers on top. During the attack they will break apart or deliberately separate into disconnected islands. See my placeholder art, but (like an iceberg) there is more volume beneath the cloud deck (and thanks to Worldbuilding, I now know the towers will not poke out of the clouds like this).
There's no chance the pirates will try to occupy the city, there are not enough of them and they aren't well organized. Their strategy is to "shake the tree" until the wealthy and powerful evacuate in private yachts. The pirates then pick and choose which targets they will follow into deep space where they will be isolated, easy pickings. They might keep this up for weeks or months before a naval force arrives from another system.
They will be aided by colluders from within the city performing acts of sabotage, so the strategy is to overwhelm the city's rescue sevices and induce a panic. Normally pirates would not be this bold, and the city is slow to understand the strategy.
[](https://i.stack.imgur.com/18chW.jpg)
(my placeholder artwork)
Since the city is an aerostat it's no fortress. It can rise and lower in the atmosphere and surf the winds to maneuver. It has a squadron of jet fighters and short-range energy weapons. It's defense relies on gunships patrolling in orbit, so the pirates are staying out of range.
**Can the pirates use torpedoes and depth charges to attack the city?**
Here's my strategy:
1. Pirate ships draw away the gunships with distraction attacks.
2. Torpedo ships sneak into the planet's lower atmosphere.
3. They launch torpedoes laterally under the city.
4. Torpedoes disperse a swarm of (barrel bomb? chemical?) explosives that rise like reverse depth charges.
**What I don't know**:
* How does traveling lower in the atmosphere effect the torpedo boats? Can I use common submarine tropes and say the boats are designed for deep atmosphere? I am assuming the city must eventually find and destroy the boats to stop the attack, but I don't know how far I can carry a submarine metaphor. Can a deep atmosphere torpedo boat "hide" from the city above – maybe in the shadow of the explosive swarm?
* What are the explosives and how nearby do the explosions need to be? I am assuming they can't simply detonate an atomic bomb deep under the aerostat – or can they?
* The pirates want wealthy targets who are fleeing the city with their valuables intact and radiation free. They are not trying to destroy the city outright, but they don't necessarily care about the welfare of any refugees – however for the sake of pirate morale, how might the attack be modulated to maximize panic and confusion, without simply nuking everyone or sinking the city?
* I'm looking for a "death by tiny cuts" strategy that would also make economical sense for pirates (no exotic weapons, no suicide missions, just ad hoc ships being sneaky).
[Answer]
The atmosphere of Venus is a hellscape. Forget the temperature and pressure, the whole thing is intensely acidic (sulphuric acid, if I remember correctly). Your pirate's deep atmosphere ships (while possible) will need to be made of some seriously tough material and have engines that can deal with the wind.
Oh, yeah, the wind. It's like a hurricane. A really strong hurricane. All the time. The heat is enough to drive some seriously serious weather. Which raises an issue for your plan:
'Dropping' your depth charges will require you to have pretty good knowledge of the weather conditions between your ship and the aerostat. Getting that information may (and I say may because I'm not a Venusian meteorologist) be incredibly difficult, and accurately plotting a 'drop' course will be hard, if not downright impossible.
However this gives us an option for an alternate avenue of attack. If the aerostat is anchored then it will be designed to stand up to those winds on a pretty much constant basis. If it isn't anchored then it will be designed to stand up to some insane wind shear anyway, since it won't be large enough to streamline properly. What it probably won't be designed to stand up to (since they're pretty rare in the high atmosphere) is a series of hard objects being hurled through the air by 100 m/s winds. If your pirates can fill the air on the windward side of the city with such projectiles they can cause quite a lot of damage. If we make the projectiles the right shape then they can get up to truly horrendous amounts of kinetic energy.
So we launch the depth charges some way off the city and use a small amount of explosive to distribute the projectiles rather than cause direct damage. We then let the wind take the projectiles to pierce the city.
Ah, yes. I said pierce. That's because my ideal projectile would essentially be a polymer coated, sharpened tube with a parachute (or soft plastic bell) attached to the sharp end. This would give your pirates a hail of hollow harpoons peppering the city (with the added benefit of it being a scattershot attack, hitting all the segments of city and any nearby defenders).
Remember that sulphuric acid atmosphere? Imagine that slowly flooding your home. Wouldn't you want to get away from that?
[Answer]
One problem with the "depth charge" analogy is that depth charges rely on a property of liquid water not shared by a gaseous atmosphere: water cannot be compressed. They use this to greatly amplify their range of effect.
Second problem is modern ground-based skyscrapers are already engineered to withstand shocks, and buildings on floating platforms in a thick atmosphere would have to be be engineered against even stronger shocks by their very nature.
---
# Shock Wave In Water
Unlike a gaseous atmosphere, the density of water does not change with depth or pressure. It's always going to be about 1000 kg/m3. It's *incompressable*. The increased pressure with depth comes from your vessel having to hold up an increasingly large column of water above it.
When a depth charge goes off underwater, the volume of the formerly solid bomb is rapidly turned into very high pressure gas. This expands against the surrounding pressure of the water. Since water is incompressible, the expanding gas shoves it out of the way in an expanding shock wave until the pressure of the gas equals the pressure of the water, then water rushes back in creating another shock wave. This goes on until the pressure equalizes, or the bubble reaches the surface.
The first shock is damaging, but the following cycle of inward and outward shocks can break a submarine's back as it is first bent one way, then the other.
The effect is devastating, but because the pressure underwater is so high, and water is so dense compared to air, the range is rather short. 100 kg of TNT needs to be within 3 to 10 meters to disable a submarine.
---
# Shock Wave In Air
A shock wave in air is different. Air can be compressed. Again, the solid bomb becomes a ball of gas expanding at supersonic speed pushing against the surrounding air. The air cannot get out of the way fast enough, so it compresses into a pressure wave in a sphere around the explosion. The explosion is like a plow going through the earth building up a bigger and bigger pile of dirt in front of it.
That pile of air, the pressure wave, smacks into things. Since it's so much less dense than water the wave can travel further, but it has a much diminished effect from a depth charge.
There's also no cyclical rebound effect to cause the flexing that is so damaging to ships. Instead, as the explosion expands there will be a brief low pressure zone in the center and you'll get a second, much weaker, pressure wave going back towards the center of the explosion.
You can see this in [old atomic bomb test footage](https://www.youtube.com/watch?v=RqyBzXYZPoM). First the target starts to smolder, that's the light and heat hitting it first. Then the shock wave hits and typically blows everything apart, followed by a second rush a air backwards.
---
# Shock Waves Vs Buildings
If your buildings are engineered to withstand the rigors of flying through a turbulent atmosphere, they're already built to withstand shock waves.
Your buildings have to withstand the shifting of their bases as they float and maneuver through the atmosphere. This would be very similar to modern [earthquake engineering](https://en.wikipedia.org/wiki/Earthquake_engineering) designed so the building will dampen the effect of the ground shifting under it. The shock of a bomb going off well under the city would have a similar effect and the building would be designed to weather it.
Tall buildings also have to be engineered to withstand the wind pushing against their sides, the [lateral wind load](https://en.wikipedia.org/wiki/Wind_engineering#Wind_loads_on_buildings). A flat slab skyscraper is basically a big sail. Too rigid and it will snap. Too flexible, and it can oscillate; if the wind gusts just right, it will tear itself apart as [what happened in the Tacoma Narrows Bridge](https://www.youtube.com/watch?v=nFzu6CNtqec).
Modern skyscrapers are engineered to be flexible, but also have buffers to prevent oscillation. They're also engineered to be aerodynamic to cut through the wind.
All these engineering necessities of a ground-based skyscraper are even more necessary for a skyscraper on a moving platform in a thick atmosphere. They'd be greatly buffed up and even more able to withstand the shock wave from bombs bursting nearby.
---
# How To Induce Panic In An Aerostat
Since this city is a lighter-than-air vehicle, there's two possibilities: the atmosphere is so thick the city is naturally buoyant, or the city requires vast chambers of low pressure to be buoyant.
If it's the former, a very dense atmosphere, the residents presumably cannot survive in the atmosphere. The buildings are presumably sealed. All the pirates have to do is break that seal, either from outside or inside. Some will run to sheltered internal areas, but others will make a break for it. Probably the richer residents with private vehicles and somewhere else to go.
If it's the latter, the city is held up by buoyant chambers, then they have to threaten to puncture those chambers; to sink the city. They don't have to actually do it, just cause enough damage for the richer residents to make a break for it in private vehicles. Again, this could happen from the inside or the outside.
[Answer]
When predators attack a group of large prey animals (like wildebeest) they try to separate a smaller or weaker individual from the herd. I propose this strategy would be good for the pirates too.
/ During the attack they will break apart or deliberately separate into disconnected islands. /
Once this happens the pirates attach hooks to a smaller city component, cut whatever moorings it has and make off with the entire thing. One little piece of city will exhaust its defensive capabilities pretty quick. They just hide it in the clouds elsewhere on the planet and hold it and its inhabitants for ransom. This is sort of like what the Somali pirates do now.
I can envision a very cool story where something like this happens and then a twist: within this stolen citylet is something unexpected. The pirates wind up with more than they bargained for.
[Answer]
If pirates can afford some sort of craft that can run for long periods of time deep within the atmosphere of Venus or a gas giant, why wouldn't the colony be built there themselves? The biggest hurtle for both is purely the durability of the structure in extreme gravity. Likewise, the people in the ships and city would be subject to those extreme forces unless you have some sort of anti-gravity technology (which would be even more difficult to produce than artificial gravity). The most effective strategy would likely be to SLOWLY sink the city so that the inhabitants evacuate to avoid the extreme pressures below. It's almost like Venice (on Venus) sinking into the ocean. Eventually the structure will flood (or compress) and the previous inhabitants have to leave. Queue pirates waiting in ambush.
] |
[Question]
[
Would it be possible that other planets, or even other random celestial bodies, contain different types of pathogens?
According to Wikipedia, the known types of pathogens are: virus, bacterium, prion, a fungus, algal or eukaryotic organisms.
So, is the universe limited to these types of pathogens, or is it possible that somewhere out there, there exist another, or multiple other types of, pathogens?
If so, how many types could there be?
If nature fails to deliver, could a hypothetical, very advanced, civilisation create new types of pathogens?
The goal is to affect life on earth, by for example, storing the pathogen inside a comet that is on a collision course with earth. Other suggestions concerning the delivery method are welcome as well.
[Answer]
There could be as many pathogens as there are types of self-replicating organisms or molecules.
Bacteria and eukaryotes are earth organisms. Other planets would likely have radically different organisms, any of which could be a pathogen. Both single-celled and multi-celled organisms can act as pathogens here on Earth, so alien single-celled and multi-celled organisms (or even organisms that lack anything we could identify as a cell) could be pathogens.
It wouldn't have to be a full organism, any self-replicating molecule could be a pathogen, as long as it can successfully enter the body and find the raw materials to replicate inside. This could include molecules not found on Earth. It can also include molecules that are found on Earth that have the potential to self-replicate, but don't currently self-replicate on Earth, such as RNA or DNA (there are "naked" RNA pathogens, [viroids](https://en.wikipedia.org/wiki/Viroid), but they use a cell's replication machinery rather than replicating themselves, and in the cell RNA and DNA need other molecules to replicate). Similarly, [prions](https://en.wikipedia.org/wiki/Prion) work by causing other proteins to mis-fold into more prions. But RNA and DNA also fold in important ways, so there is a potential for RNA or DNA equivalents of prions to exist (although as far as I am aware none are known).
Finally, from what I have found there is one (and only one) group of organisms on Earth for which no known pathogenic forms exist: [archae](https://www.ncbi.nlm.nih.gov/pubmed/14579252). However, archae are particularly hardy, often living in extreme environments. This could make pathogenic archae hard to defeat with our natural defenses or medicine.
[Answer]
Don't forget all the large (visible sizes) parasites.
Some pathogens are inadvertent. E.g. Botulism and typhoid both kill accidentally -- they produce a chemical that is toxic to their host.
Your aliens could drop a mold on the earth that ate grass, and produced ricin (the poison in castor beans) as a byproduct.
[Answer]
Different answer because different concept:
Bugs can also be anti-technology, rather than anti-personnel.
The puppeteers destroyed the Ringworld civilization by introducing a bug that ate super-conductor plastic.
There was a series in Analog some years ago about 'the oil bug' that turned oil into black crud. Didn't care if was refined into gasoline or diesel first.
Consider the effect of a bug that got it's main energy from 4Fe +3O2 => 2Fe2O3 Turning every exposed piece of iron into flakes of rust.
Another wayward thought is to make them anti-ecology. A virus that needed magnesium, and would take it out of chlorophyll. A bug, designed as an anti-climate change agent that fixes carbon dioxide as calcium carbonate -- And it works too well, dropping CO2 down to 100 ppm, and the planet freezes, as plants do poorly due to lowered CO2 levels.
] |
[Question]
[
In a [world](https://worldbuilding.stackexchange.com/questions/63975/what-american-animals-would-have-been-domesticated-had-they-not-gone-extinct) where man entered North and South America without causing a mass extinction, all of the paleofauna which became extinct ~10,000 BC in the Americas are still around. There are several families of giant ground sloths, mammoth and mastodons, horses, many llamas, glyptodonts, sabretooths, scimitar cats, short-faced bears and more.
South America is a wet continent and has many freshwater aquatic environments. Two of the biggest river systems in the world, the Orinoco and Parana, run through savanna, along with many smaller rivers.
In Africa, there is a niche occupied by the hippo, a large, aquatic grazer of both water plants and grass (usually by night). It thrives in rivers that run through the savanna. What animal in the Americas, particularly in South America, is most likely to have filled this niche?
[Answer]
You ask what animal in the Americas would fill the niche? Not hippos. Or anything as agressive. More like a **Dugong or Manatee-like creature**. They are day eaters, but they fit into the aquatic grazer mold.
See [this](http://www.savethemanatee.org/news_feature_sirenian_fossil_13.html) on where they came from, where they went, and how they have changed (early models had legs). They first developed during the Eocene, and have been around ever since in various iterations. Anywhere the water is warm and there's aquatic stuff to munch. They can swim the ocean, and do, but prefer to swim up rivers where they can.
They would have had time to develop by the pleistocene. Here's the [wiki](https://en.wikipedia.org/wiki/Evolution_of_sirenians) on Sirenian evolution.
Apparently at various times there were [multiple models](http://www.livescience.com/18945-ancient-sea-manatee-species.html) of sea cows swimming around, filling various niches. And there were a lot of them during the Pleistocene:
>
> Pleistocene-age manatee bones have been excavated from over 24 sites in Florida, and men hunted them as soon as Indians arrived in the region. [link to source](https://markgelbart.wordpress.com/2016/11/28/pleistocene-manatees-trichechus-manatus/)
>
>
>
Here's a link to [a scientific paper](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0031294) regarding the various kinds around the world. Notice that the ones in Florida that were found, were linked to a period just before what you are looking for.
See this [handy link](http://patagoniamonsters.blogspot.com/2010/10/patagonian-sea-cows-manatees.html) for the current ranges of the species in South America and some of the fossil records of it for the area. It's pretty extensive and likely that they were there, by the time period you are seeking.
An earlier version might have been less docile, and there's plenty of extinct versions to choose from.
Anyway. it's a place to start and they do, at least somewhat, fit what you are looking. Only a hippo is a hippo. As far as I can find, a specifically night feeding, aggressive aquatic feeder is a pretty specific niche--hard to find something exactly the same that isn't a hippo--but some of the early evolution pictures of the sea cow look a bit hippoish, from before they lost the legs. Problematically, by the era you indicate they would have lost the legs again, but maybe you can tinker with that--evolutionarily they've been in and out of the water a bit...
Early model:
[](https://i.stack.imgur.com/dJJAg.jpg)
Latest model:
[](https://i.stack.imgur.com/xS3e1.jpg)
Quite a bit smaller, but still reaching into this niche: **the capybara**. During this time and in this place, they reached about 100 pounds. Not huge but still interesting.
>
> Capybaras graze in meadows, bed down in the woods, and spend much of their time in water. They require habitat that offers all 3 of these environments. They use water to escape from predators and to cool down during the heat of the day. They are not as helpless as they look for they are fast runners and swimmers, and they have thick hides. Nevertheless, jaguars were likely their most dangerous enemy in North America during the Pleistocene. The extinction of capybaras here probably contributed to the extirpation of jaguars in this region. [link to source](https://markgelbart.wordpress.com/2015/12/07/megafauna-habitat-modification-and-pleistocene-capybaras-in-southeastern-north-america/)
>
>
>
Here's a modern photo of these guys, which are about 1/4 the size they would be in the Pleistocene.
[](https://i.stack.imgur.com/HV6Qq.jpg)
[Answer]
# Giant Sloth
[](https://i.stack.imgur.com/28uaX.jpg)
There were at least 4 different families of giant sloths living in the Americas at the end of the Pleistocene. In those families, there were something like 8 different genera, with some larger number of species. In short, there was a lot of sloth variety at that time.
There is one genus of sloth, [Thalassocnus](https://en.wikipedia.org/wiki/Thalassocnus), that is suspected of being a semi-aquatic marine (as in salt water) sloth. This genus has such specialized adaptations as heavier bones to provide neutral buoyancy and an extended flattened radius (forearm bone) to act more like a paddle.
Thalassocnus was extinct, but the fact that it appears to be aquatic makes the many varieties of sloths a good bet for a hippo-like grazer. The closest relatives to Thalassocnus alive in the Pleistocene were the Nothrotheriidae, like the [Shasta Ground Sloth](https://en.wikipedia.org/wiki/Nothrotheriops). however, these various Nothrotheriid sloths all seem to come from rather mountainous and dry areas.
The next most distant branch of the sloth tree are the Megatheriidae. of these there were two living genuses, [Megatherium](https://en.wikipedia.org/wiki/Megatherium) and [Eremotherium](https://en.wikipedia.org/wiki/Eremotherium). These two are distinguished as the largest Pleistocene ground sloths, being up to 6m long and with estimated weights at 3 tons or more.
These two sloths are traditionally seen as more of a giraffe analogue, being able to prop up on two hind legs and a tail to reach as high as giraffes can into trees. But since the two sloths coexisted, and overlapped in range, what if they filled fundamentally different niches? Megatherium is present in places that were projected to have been parkland and semi-arid regions. Its range corresponds closely with the places a giraffe would be comfortable in the Americas. [Eremotherium](http://fossilworks.org/) is [only present](https://en.wikipedia.org/wiki/Eremotherium#Species) in tropical rainforests and the wet southeast United States.
Conclusion: Eremotherium has the attributes to replace a hippo in tropical american ecosystems.
] |
[Question]
[
Today, most mammals have **dichromatic vision**, meaning that they have two color receptors. Which color depends on which species you're asking. For example, the real reason bulls charge at matadors is the way they flaunt their flags--cattle CAN see color, but red does not register.
Other mammals, like dogs, have a different kind of color blindess:
[](https://i.stack.imgur.com/ZAbCc.png)
**Trichromacy**, having three color receptors, is pretty common among the whole animal kingdom--[for example, we have recently found the "red" gene in turtles](https://www.sciencedaily.com/releases/2016/08/160802192704.htm)--but when talking mammals, exclusive to only one order--the primates.
Regardless, reports have been popping up in recent years of humans possessing the gene that results in **tetrachromacy**, FOUR color receptors. As proof, just Google up Concetta Antico, an Australian artist who has been getting quite a popularity for letting her genetic condition inspire her paintings.
In Antico's case, tetrachromacy is a mutation that is not routine in the human genetic structure. But in this alternate scenario, tetrachromacy is a genetic normality among all primates and trichromacy among all non-primate mammals. Among humans, would this improve our night vision?
[Answer]
Night vision is primarily handled by rod cells, which have little colour perception - so it seems unlikely that tetrachromacy (which presumably affects cone cells) would improve it at all. In fact, you may find the opposite happens - if it requires an increase in the number of cone cells then it may be at the expense of rod cells; this certainly seems to be the case in nature where animals with better night vision than us (such as cats) have worse colour vision.
[Answer]
**Probably not.**
The Wikipedia article on night vision lists the main reason for humans' mediocre night vision as the lack of a [tapetum lucidum](https://en.wikipedia.org/wiki/Tapetum_lucidum). Many dichromat animals possess this and have excellent night vision, so tetrachromacy would be unlikely to help.
There would be some interesting other effects, too. According to various sources, tetrachromats experience an extremely wide range of color variations imperceptible to normal trichromats. If everyone was a tetrachromat, everyone would have this extra experience. I would predict that visual art would become even more important in society than it is in real life. Other mammals would no longer be color-blind by real-life human standards, but would still be by fictional human standards. And then there would be pentachromats arising from mutations, too... Apart from that, not that much would probably change.
[Answer]
**No, It would do the opposite** To have color vision with more pigments we would have more cones in the eye, thus we would have fewer rods in eye, making our night vision worse. Rods are the cells that can handle low light cones don't work in low light. There is a reason mammals have better night vision than birds. Tetrachromacy is actually the norm for most terrestrial life, mammals lost most of their color vision (2/4 pigments) in return for much better night vision.
] |
[Question]
[
To elaborate on the title, can alien plant life on an Earth-like planet look similar to ours, or would plants on an alien planet be radically different, unrecognizable, or incomparable to Earth plants in the eyes of a human traveler?
I've heard things about different pigmentation based on what wavelength of light the planet's mother star emits, but I'm talking more about the broad strokes. Would leaves still look like leaves? Would trees still look like trees? Or would they be as different to Earth plants as some aliens in harder science fiction are to us?
[Answer]
Assuming the same principles of competition and selection are in play, and that plants evolved, there should be various obvious analogues between Earth and Xeno plant life (plant being defined as sessile phototrophic organisms). The exact details – the shape, colour, structure – will depend on local circumstances.
On Earth, [leaf morphology correlates with water and light availability](http://www.sciencedirect.com/science/article/pii/S1002007109003013), because various shapes when combined in overlapping clusters are optimized for catching light. The shape of the leaf also determines how much light reaches leaves below and at what distance that penetration reaches zero. (You may have heard of Planet Furhaha, a worldbuilding ecology project; here is the study the author did looking at [light penetration and leaf shape](http://planetfuraha.blogspot.ca/2013/11/layers-of-leaves-alien-plants-v).)
Colouration of xeno-analogue photosynthesizers will be determined by available wavelengths from the star and absorption by the atmosphere.
>
> Extraterrestrial photosynthetic plant-type life may look quite look
> different in color because they will have evolved their own pigments
> based on the colors of light reaching their surfaces. Nancy Kiang of
> NASA's Goddard Institute for Space Sciences has modelled the light
> reaching the surfaces of Earth-sized worlds orbiting their host stars
> at distances hospitable to Earth-type life, where liquid water could
> exist on a planetary surface, where depending on the star's brightness
> (and color) and the planet's atmosphere. Kiang found that "plants" on
> Earth-like planets orbiting stars somewhat brighter and bluer than the
> Sun might look yellow or orange, and even look bluish by reflecting a
> dangerous overabundance of more energetic blue light. On the other
> hand, plants on planets orbiting stars much fainter and redder than
> the Sun might look black. ([Source](http://www.solstation.com/life/a-plants.htm); referencing [this](http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html).)
>
>
>
And it's reasonable to expect similar growth strategies would be used: grow up and/or grow out. Plants can avoid being shaded out by competition, to the point of stifling the growth of competitors, by growing taller or wider (or both).
[Answer]
I think leaves are close to optimal, thus expect leafy plants. Color could be quite different, leaf shapes could be quite different as well. They might not have conventional bodies, they could easily end up being supported by strengthened vines or could be similar to ferns. Thus it might look quite similar.
On the other hand, I could say, there could be photosynthetic mobile life forms. They don't have to be plants like our plants. In this world, it is possible that there are no tree like creatures exists. But being pinned to the ground has quite a lot of advantages but it is not impossible for a world like this to develop. Flying photosynthetic creatures would be quite nice.
[Answer]
Plants would look very similar to earth plants. The biggest difference would likely be in flowering plants since flowers are based on animals, but I'd suspect very similar adaptations...
But "Plant" isn't really the correct way to look at these things. Plants will only ever be descended from the plants we have here on earth. There will be things on other worlds that share in the role plants play here on Earth, but they won't be the same. They may in fact be wholely different. You might find many of the characteristics of what you would think are plants to be from what we normally associate with animals and vice verca. There is a reason things go the way they do and that generally forms the same type of biology, but just because plant cells are better for plants and animal cells are better for animals doesn't mean you won't find the plant like cells in what you'd consider an animal.
] |
[Question]
[
Let's imagine that people, if they'd want could freely leave Earth to pursue their own destiny on other planets etc. How far could we get assuming following:
**Assumption No. 1**: It's trivial to get any item up to 260 metric tons ( fully loaded Boeing 777F weight ) into space ( 800 km from Earth's surface ). Anyone could save up money to buy the Space Elevator ride and get whatever they'd want into space.
**Assumption No. 2**: Every person has a life-span is ~500 years thanks to curing cancer and discovering how cells can replicate almost indefinitely. Then, however, the brain-structure starts to fail rapidly and no cure is found.
**Assumption No. 3**: People can be put into stasis up to 100 years and can reenter stasis after a year.
**Assumption No. 4**: No significant progress has been made in any field from today's standard. Can't use dark-matter as fuel, no opposite pole of gravity is discovered etc.
**Assumption No. 5**: Our hero is an engineer, has good technical education, young - only 30 years old and totally sick of Earth and how things are. He's not rich, but is definitely high-end of middle class.
So our hero wishes to take to space and establish a utopia in his understanding (doesn't matter what it is). How realistic is it for him to reach an Earth-like planet in his lifetime?
There's no pre-defined blueprint of a spaceship, whatever he puts together he'd fly, but for the sake of simplicity let's say that base components are available and wouldn't cost too much just like getting a cell-phone was a luxury some 25 years ago and now everyone has a smartphone!
Things that our hero decides to take with him:
* **Worlds library** - the largest collection of books in digital format on every subject in most of the languages. Not complete collection of every book ever, but the largest that we have at this point.
* **A super computer** - a PC that would seem like a super computer to us, some x10 000 times more powerful than average computer today.
* **A telescope** - powerful enough to see a persons face on The Moon from Earth if the sky is clear.
* **Large solar panels** that would be enough to power a large apartment if there's light.
* **A 3-d printer** that can print both circuits, plastic, metal and compose diamond. It can actually refill its matter storage from rough material (eg. CO2 → diamond)
So, knowing that space is full of radiation, small razor-sharp particles, magnetic waves etc. How possible is it to construct a space-craft that would be sustainable enough for at least 120 years in-between repairs? And how safe would it be?
And finally - how far could the hero get in his lifetime if the speed he could travel is roughly twice the speed of sound (relative to Earth's atmosphere) while in vacuum of space and around 900 Km/h in atmosphere similar to that of Earth's density?
EDIT: if some of you are unimpressed by the stats that the said spaceship would have — please note it's built by finances of a single individual. It's very very possible that once landing on a planet the spaceship would not be able to leave the orbit again. So when answering the question — think in terms oh what could go wrong on his way to Planet Paradise. Also feel free to specify what our hero should prepare for/bring with him to even attempt a journey like that.
EDIT2: Made some calculations and found out that even with speed like 40 000 km/h it would take thousands of years to reach a different solar system ( and no promise that it could have Earth-like planets ). So unless there's a way to travel at least 1/4 speed of light it would seem impossible to get very far and be able to see different planets.
[Answer]
Getting feet confused with meters and screwing up your reentry plans. Resulting in a fiery death.
Close encounters with space clutter. Resulting in violent death.
Overestimating how long equipment will remain functional while you're in stasis. Resulting in eternal sleep, AKA death.
Technological advancements while you're in stasis. Resulting in being salvaged for scrap by faster ships that put you on display in a museum, after 'accidentally' causing your death.
Actually making it where you're trying to go and finding no one else survived and nothing interesting to do. Resulting in being bored to death.
[Answer]
I think you have your metrics off by several orders of magnitude.
Twice the speed of sound may seem fast here on Earth, but it's snail pace in space (it would take 13 days to get to the Moon and more than 14 years to get to Mars).
To get anywhere in the (extended) lifespan of your (misguided) hero you need speed which is a sizable fraction of the speed of light.
Said that your biggest problem is the size of the task.
Unless your hero's Utopia is hermit life he will need a certain amount of people with him. That means to have a generation ship, which is something probably bigger than an aircraft carrier, 747-size is surely inadequate.
Dangers of long space trips are:
* Lack of possible repairs/refueling for long period. This means recycling is a must and it's not allowed to fail; double/triple systems are needed and spares should be available (or possible to build with your "3D printer").
* Some system failure is the main concern.
* Impact with debris is a (rather remote) concern while still in our Solar System; outside the Void is... unsurprisingly empty. Chances of an impact are very low.
* You say no major breakthrough is available, so energy production is a concern (solar panels will be unusable as your hero gets farther from the Sun); probably You need a nuclear generator with enough fuel to last (probably more than one, for above reasons).
* Concern surely needing addressing is lack of gravity which, on the long run, has adverse influence on human health. This can be easily simulated by spinning your ship; if ship is small then deploying a counterweight (e.g.: the nuclear reactor) with a long cable and spinning "bolas like".
* Boredom. Even with help of stasis our hero is going to be more isolated then any man ever existed. Suicide is likely.
If your hero survives all this and reaches a star system with a suitable planet then a whole new bunch of perils await him:
* To start a community, with enough biodiversity a sizable gene pool is needed (>>1000).
* To have a reasonable competence in all fields needed to keep a "modern" society running a large number of brains is needed (>10000).
* To terraform a planet you need a large amount (>>1000000) of different plant/animals (it's highly unlikely local flora/fauna, if present, would be any help... regardless whatever Star Trek said).
[Answer]
Let's establish our reach:
he's 30. He has to be awake 1 year every 100 years and can reach 500, assuming he needs no medical attention. So he will die at a calendaric age of 30+470\*101=4777 years, afer 4747 years of space travel. Let's assume he travels without acceleration after some initial lob to somewhere...
# V=340 m/s
Speed of sound. Let's see where he gets... he has a whooping 149,800,728,101.76 seconds of absolute max travel before he begins to die... so his reach is $50.9 \* 10^{12}$m, plus the headstart of 1AU or $149.6^{12}$m. That's roundabout 1.3 AE... he hasn't even reached mars.
# V=11.3 km/s
Let's assume he is Pioneer 11. He takes 43 years to get out to 95.3AU, then travels constantly at 2.4 AU/y. After the following 4704 years he will have managed a total of 11,384.9 AU - or 0.18 LY. He is out 4% on the way to Alpha Centauri as he dies.
# V=17 km/s
Ok, update that to be Voyager 1 instead. Now he travels at 3.6 AU/y and only needed 40 years to get to speed with slingshots and such... his headstart is 180 AU as we take that speed. So he ends up at 17,125.3 AU... or 0.27 LY. 6% out to Alpha Centauri.
# V=6506 km/s
Let's do the math the other way round. To reach Alpha Centauri, we need to get to about 268,770 AU or something in the margain of $4\*10^{16}$m. To be traveled in 4700 years, so he needs to get up to around 6506 km/s. That is 0.02c. Not really relativistic... but you should verify your calculations relativistically. Yet I have no clue how he should get about 40 times more speed than the fastest manmade object from the solar system with the current tech. It hasn't advanced much in these regards to this from 1977 when Voyager was launched, and both Voyagers had a pretty damned good row of slingshots.
So at the moment, that's it. I postulate the following to be happening when the poor young man enters the ship he bought third hand after it's latest refit for the first time:
## Welcome Aboard, Captain!
I am Lysander, your dutyful ship AI. Please take your time to familiarize yourself with the controls and make your bunks as comfy as you can. We have uploaded the ship computer with videogames, TV shows, Books and music for at least 5000 years. Yet we advise you to just make a quick tour to Mars instead of targeting the unexplored depth of space, where you will just find just lonelyness.
Be advised that refit did not remove any harmful objects from your ship, including the current [TP-82](https://en.wikipedia.org/wiki/TP-82) successor in your portable emergency survival kit or the highly toxic and caustic [hydrazine](http://Hydrazine) in your RCS fuel tanks. Both these could become handy if you should want to commit gruesome suicide because you can't stand the lonelyness of being confined to your spaceship any longer and knowing you can't reach any spot out of the solar system.
Our current service time before you need to dock at a maintenance base is 120 years. This is well enough time to have a grande tour with all the planets, making a stop at the docks of Neptune, and then make a trip to Pluto and back. Yet be adviced that due to the loss of efficiency of the solar panels, any non-essential system for the function of the ship will be shut down past the astroid belt[1](https://www.jpl.nasa.gov/news/news.php?feature=4818). If you didn't bought the [BES-5 RTG Upgrade](https://en.wikipedia.org/wiki/BES-5) to heat your ship and power your life support, any travel beyond this point is unadvised. If you bought it, please don't hang your wet towels over its radiators, as you might set them ablaze and make the core melt.
If you need conseling, please schedule ahead because of the huge [communication delay](http://www.spaceacademy.net.au/spacelink/commdly.htm). While you still will be able to receive incoming messages and television programs, the lag will delay communication with earth and thus can create a huge bill for you, as the doctor can't work on other cases during this time.
Should you need serious medical assistance due to human stupidity (including knocking your head in the spacesuit while shooting at the junk you dropped for [target practice](https://www.livescience.com/18588-shoot-gun-space.html)), please freeze yourself as soon as possible after setting auto return to a medical facility. Should you remain active in 0-E environments for a considerable ammount of time, please be advised [Space Adaption Syndrome](https://en.wikipedia.org/wiki/Space_adaptation_syndrome) is common and can be helped with. If you are concearned about long term effects, please read the [NASA’S EFFORTS TO
MANAGE HEALTH AND
HUMAN PERFORMANCE
RISKS FOR SPACE
EXPLORATION](https://oig.nasa.gov/audits/reports/FY16/IG-16-003.pdf).
Be advised that the tether of your space suit is not made to withstand cutting or sawing motions along the edges of solar panels and that the ship can't turn around to pick you up in time. Also please [don't try to mess with the piping or wiring](https://worldbuilding.stackexchange.com/questions/51129/damaging-a-near-future-spacecraft-by-hand/52319#52319) or I might need to activate the [Self-Defense-Protocols](https://en.wikipedia.org/wiki/HAL_9000).
[Would you like to play a game?](https://en.wikipedia.org/wiki/WarGames)
---
1 - "Jupiter is five times farther from the sun than Earth, and the sunlight that reaches that far out packs 25 times less punch [...] our massive solar arrays will be generating only 500 watts when we are at Jupiter." Rick Nybakken, Project Manager "Juno" @ JPL Passadena, Calif.
[Answer]
I hate to be that guy, but... not safe at all.
Unfortunately, that 'minor' issue of radiation is still under study, but we already know that it can change gene expression. In the recent case of astronaut [Scott Kelly,](https://www.cnn.com/2018/03/14/health/scott-kelly-dna-nasa-twins-study/index.html) up to 7% of his genetic expression has not returned to normal in the two years he's been back on Earth.
Take into account that Scott spent only 340 days in space, compared to the 120 *years* you're proposing. If scientific advances aren't made before your plot takes place, there's no telling what your character might look like by the end.
That's not even mentioning a myriad of currently inexplicable and untreatable [health issues](https://www.space.com/25392-manned-mars-mission-astronaut-vision.html) such as vision problems caused by prolonged space flight.
Ship integrity may pose a bit of a problem as well. Even the space debris the ISS encounters while simply orbiting the Earth [can tear holes in the station's protective kevlar.](https://www.extremetech.com/extreme/185150-heres-what-space-debris-does-to-the-kevlar-shielding-protecting-the-international-space-station) At the speed of sound, you'd most likely run into more debris than that. The ISS has cost around 150 Billion USD to date, so parts better be a lot cheaper in the future, or little timmy there's going to be hurtling through space in swiss cheese.
] |
[Question]
[
Having recently learned about the [Interplanetary Internet](https://en.wikipedia.org/wiki/Interplanetary_Internet) in development by NASA's Jet Propulsion Laboratory, and inspired by Kim Stanley Robinson's novel *2312*, I began to wonder about the actual reality of a dense information network spanning the whole Solar System.
**Question**
* What would a typical user use such a network for?
* How reliably would it work?
* What would the expected bandwidths be?
* Would using it be exorbitantly expensive?
* And how would it actually feel to use such a system?
**Considerations**
First of all, the network infrastructure would be there. Relay clusters are in place in various orbits around the planets and the Sun, some even around dwarf planets or asteroids.
Second, the methods of transmission would be ones currently known to us: Laser and radio (and data mules, where necessary).
Third, there would be a significant diaspora of the human race all over the Solar System. Though travel is relatively cheap, it is not necessarily convenient.
**EDIT (14.8.2016), bandwidth hints:** NASA tested a Moon-Earth laser broadband in 2013 achieving a nice 622 Mbps with a puny, low-powered device. They are testing a more advanced setup in 2017: "The LCRD will be capable of shifting 1.25Gbps of encoded traffic, or 2.88Gbps of uncoded data using laser equipment that is just four inches long and which uses considerably less power than a radio communications system." [Link to article.](http://www.theregister.co.uk/2013/10/23/nasa_fires_up_622mbps_broadband_link_to_the_moon_and_back/) Exciting times!
[Answer]
Actually, there is a network with properties similar to those that would likely be seen on an interplanetary version of the Internet. We can use it for comparison.
It's called **[FidoNet](https://en.wikipedia.org/wiki/FidoNet)**.
FidoNet uses a store-and-forward architecture to cope with high cost of long distance transfers, and batch processing of messages and requests. It has a highly hierarichal address structure where the node addresses encode information about each node's location. Communication between nodes has historically been over dial-up modem links, but Internet links have also been used.
The three main services provided by FidoNet are netmail, echomail and file requests (freqs).
Netmail is mainly one-to-one communication, similar in principle to Internet e-mail. It is what all other services provided over FidoNet are built on top of, similar in a way to how everything on the Internet is built on top of IP.
Echomail is one-to-many communication, similar in principle to Usenet or later-date web forums or question and answers sites.
Freqs is usually person-to-system communication, with the purpose of obtaining files made available by a remote system. It was often, but not exclusively, used for software distribution, where each system didn't have to have everything locally available. At a time when significant storage capacity came at a hefty cost, this helped reduce the up-front cost of setting up a node but transferred that cost to an on-going cost of transferring files requested by the users. Because of these ongoing costs, excessive freq'ing was commonly seen as disrespectful.
Because FidoNet used store-and-forward techniques and often multiple hops, delivery times of hours or days were not uncommon. Because dial-up links were the norm during FidoNet's days of glory, instead of tying up the phone line (and preventing others from reaching the node you were on), reading and writing messages offline then connecting to make a batch transfer of anything new was common. There were several specialized software packages that provided nice, relatively user-friendly user interfaces for managing netmail, echomail and freqs. Systems often exchanged messages during the night, as not only was expected usage often lower, cost was often lower as well.
FidoNet also allowed for "crashmail", which was generally reserved for high-priority traffic. Crashmail was identical to netmail, but requested any system it passed through to pass the traffic on as quickly as possible. Unwarranted use of crashmail was seen as exceedingly rude, because it incurred an additional cost to every system administrator along the message delivery path, but it did have legitimate uses. Some systems disallowed crashmail, treating it as regular netmail.
See how this might be similar to how an interplanetary Internet might realistically function?
* **Links are intermittent.** Deploying sufficient nodes to always guarantee a direct path from one endpoint to another will likely be prohibitively expensive, and nodes are bound to go offline every now and then for any of a phletora of reasons, and nodes will sometimes be busy handling (possibly higher-priority) traffic to or from a different node. Designing around a store-and-forward architecture reduces the impact to the end user of such intermittency; the end user will simply see that the message took slightly longer to be delivered, and if they look at trace data (similar to e-mail's `Received:` headers) they may see that the data took an unexpected path toward its destination or even was re-routed while in transit.
* **Speed of light propagation delay is considerable.** On Earth, even a one-second propagation delay is a long time; for an interplanetary Internet, it takes one second just to get from Earth to Earth's moon, let alone send an acknowledgement back. Any form of interactive use will be prohibitively slow, so batch, likely message-based, processing makes sense.
Combine these two, and we get a network based around **the idea of taking some kind of "message" or "package", accepting responsibility for its delivery, and arranging for its *eventual* delivery to a base station near the recipient** (where "near" might mean "on the same planet"), from where it would be routed in a manner more suitable for planet-local traffic. While interplanetary, the traffic could then be routed by a variety of methods or links, depending on its priority and what links are currently online and available. Correspondingly, users may be charged different rates for different-priority traffic, and some ultra-high priority classes may be restricted to certain users of the network or even the network itself. Correspondingly, the lowest-priority traffic might simply piggyback on a transport spacecraft, with all of what that means in terms of delivery times.
Under the hood, strong cryptography and advanced compression and error-correcting algorithms will very likely be used to detect and correct for data corruption, reduce the amount of data that needs to be transmitted, ensure data privacy against eavesdroppers, and ensure that the correct user is appropriately billed for their own traffic and not anybody else's, among other possible uses. Remember that at anything resembling interplanetary distances, bandwidth is at a large premium (the terrestrial connection to my home could pretty much saturate that about a gigabit per second you mentioned NASA toying with for the LCRD for next year, if I simply spoke to my ISP and paid for more upstream bandwidth), and retransmissions are very expensive for the network, so there are incentives to reduce both as much as possible. All this will be transparent to the user of the network, who will simply see the end result of their messages being delivered and billed for.
Thus we can answer your questions.
# What would a typical user use such a network for?
Batch- or message-oriented communications. It takes too long to deliver anything for any real-time use, so once you leave your own planet's *planetary* network (which might possibly include the moons and spacecraft in orbit of that planet), you give up getting an immediate response.
Thus, for interplanetary traffic, the user experience will be more like sending paper mail, or posting on a web forum, or sending an e-mail, and waiting to get a reply, than the back-and-forth of instant messaging or video chat. If adequate bandwidth is available, it's certainly possible to send images, audio or video back and forth, but directly interacting with the person or system at the other end of the link will generally not be practical simply due to the inherent latency of the physical distances involved, let alone those potentially introduced by there existing no complete, direct path between the two endpoints at the time.
# How reliably would it work?
A store-and-forward network can be *very* reliable (almost arbitrarily reliable), especially if the individual nodes and link hops are sufficiently reliable and the hops are short enough that immediate confirmation from the next node is reasonable. Because any node will retain the message at the very least until it receives confirmation from the next node along the way that the message has been successfully received and passed all relevant checks, a message can always be retransmitted, possibly through a different node or path, should the need arise. Borrowing from [one approach of mitigating the Two Generals' Problem](https://en.wikipedia.org/wiki/Two_Generals%27_Problem#Engineering_approaches), high-priority traffic can be sent through multiple paths simultaneously, to improve the chances of one of the copies making it through quickly in case a node along the way becomes unavailable while the message is en route. The nodes would likely be made sufficiently autonomous that they are able to determine themselves the most appropriate "next" (closer to the ultimate destination) node to send the data to, which would allow the network to gracefully handle nodes becoming unavailable while data is in transit.
# What would the expected bandwidths be?
Impossible to say. Ultimately, the limiting factor will probably be the [Shannon-Hartley theorem](https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem), which gives the maximum theoretical information rate of a communications channel of a given bandwidth and a given signal-to-noise ratio. We can improve the S/N ratio by increasing power to the transmitter, but that costs energy. This is one of the places where different classes of traffic may be employed; a high-priority message may warrant using some reserve battery capacity to increase the transmitter output power, to help ensure its successful delivery, at the cost of reduced ability to do that again in the immediate future (until the batteries have been recharged from whatever primary electricity source, such as solar panels or [RTGs](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator), that the node uses).
# Would using it be exorbitantly expensive?
Not necessarily, but that depends very much on your definition of "exorbitantly". As I have already said, different traffic priorities could be charged at different rates, and the user would select the traffic priority level appropriate for the message they are sending or the request they are making. The vast majority of traffic would likely use a "bulk" classification of some kind, which basically means best-effort and transmission whenever the network would otherwise be idle, with no real delivery time guarantees. Higher priority classes would be used for any traffic that requires some form of expediated delivery, kind of like how you can choose between priority mail and economy mail when sending a postal package to someone.
The major cost for something like this will be up-front, in deploying the large number of nodes that will be required to provide reasonable latencies. That cost will need to be recouped *somehow*, and it's likely that user fees and data transfer fees will be a major part of how the cost of establishing the network is recovered. Because in your world "travel is relatively cheap" but "not necessarily convenient", the cost of establishing the network might be lower than it would be in our world, and the ultimate cost to the end user for using the network should, in an ideal world, reflect that lower cost to the network operator. There will be ongoing costs for replacing nodes that become unusable for various reasons, but with some planning ahead, those costs can be spread out over time.
# How would it actually feel to use such a system?
You would be considering everything rather carefully. Not only because even in the best of cases delivery can easily take hours (and there will likely be no guaranteed way to recall or change a message once you have sent it), but also because you lose much of the back-and-forth available with today's Earth-bound Internet where traffic roundtrip times are measured in fractions of a second.
Using an interplanetary network will probably feel more similar to e-mail, or FidoNet, or even mail order, than it will feel similar to casually browsing the web, looking at whatever you find that looks interesting. Planet-local storage and "package" preparation will be an absolute requirement to make the end-user experience reasonable.
[Answer]
# What would a typical user use such a network for?
Well we talking about interplanetary **internet** so the user will (want) to use it for what we use it today.
* Communication
* Information
* Entertainment
# How reliably would it work?
I would assume that the network would be very reliably (on the higher layer). The question would not be if the message arrives, but when. However interference could delay a message for hours (or days?).
# What would the expected bandwidths be?
I think we can build a network that has enough bandwidth, but I didn't found information on this. So the rest of my answer assumes we have enough bandwidth.
# Would using it be exorbitantly expensive?
I think the network would be quite expensive. However not necessary for the end user. A system wide internet could be subsidized by government and content provider which want to sell there content to the users. That's what happens today in not so dense populated regions to get fast internet there.
# And how would it actually feel to use such a system?
If the user access planetary (his current location) resources there won't be a difference from today. As soon as he actually uses the interplanetary network, however somethings most likely will change drastic.
**Entertainment**
Any online game that has real-time interaction won't work. You could still have something like racing against ghosts of other players, simple leaderboards or playing something like chess. Like in the time when you played chess via mail (not E-Mail).
Instant Video wouldn't be so instant as long as it is not cached anywhere. Big players could maybe hold a copy of all there content in different datacenters around the system. However if you want to use a service that don't provide this, the question would not be "what should we watch (now)", but "what should we watch tomorrow". So you will request the content and watch it when it comes. If you have an abo for series they will start sending you a copy to watch offline as soon as it is released (maybe still DRM protected).
**Information**
News will be as today. You will still be notified but it will take longer. This could result in a trend back to traditional media. If you need to wait several hours for your information maybe you can wait an hour longer for verified information.
Surfing the internet from link to link will not work. There could be an indicator how long it would take to load a Link. Is it a local resource or it is already cached. Often accessed sides will (as already today) be cached. But good caching will get much more important. Surfing will often result in I want to read this and that later. On the technical site requesting a Website would not only deliver the site but also other sites of the domain and other linked content directly.
**Communication**
We would not use messengers as much. There wont be any direct communication. We will go back to E-Mail, or something similar. Maybe we would write more and longer letters, like in the time where there was no telephone. Communication on websites should change to (in order to be still somehow use full).
Forums will need to structure the communication better. You need to know which post related to which other in order to follow the discussion. Some websites will only used locally because the discussions are to fast to allow anyone from far away to participate. Other Sites could use some mechanism to counter this by showing posts only after a specific time they where posted (when the user pressed send, not the server received the post).
---
I would assume a raising popularity of IaaS provider that will replicate your content over the howl system. Even small blogs that currently are hosted in private environments maybe want to migrate to bigger providers. We would maybe also see more toplevel domains that indicate the location, like .us.earth or .mars, .pluto and .sun.
The underling protocols of the internet must change drastic as the application the end user uses must change in order to give him enough information what will happens if he clicks this link. Nobody wants to click a link in twitter and sitting there for hours until the site loads.
I think log distance communication will feel more like in old days before telephone. There wont be any non local news with live broadcast from the place where something happens. Nobody can ask questions to the journalists at the place. Most likely the information will still be published as soon as it is available. But the livetcker would not be live anymore.
[Answer]
It seems inevitable that the network and its content would be divided up, as viewed from any given place, by bandwidth and latency. For example, assume you're on Mars. MarsNet is accessible with the kind of latency we experience on Earth at present. Phobos and Deimos are close enough to be part of MarsNet.
But I want something that isn't on MarsNet. Where do I look next? EarthWeb is plausible, but Earth is between 3 and 25 light-minutes distant in each direction (allowing for a bit of relaying around the Sun for high-bandwidth connections) and nobody wants to wait that long for an interactive search request.
So there will be a cache of EarthWeb on Mars, and of MarsNet on Earth, and those will be updating continuously. Search engines' indexes should get high priority for updates, so that you can find out something exists fairly easily, even if you have to wait for it to arrive, which is more acceptable.
And Mars' copy of EarthWeb will be being sent on to asteroid settlements that are nearer to it than to Earth, and to the moons and trojans of Jupiter, when it's a shorter hop, and so on. The usual way of doing a search will be "Local web plus local caches" and the details of the addressing and caching will take some work, but chunks of them are already solved by archive.org.
] |
[Question]
[
Hunting is dangerous; even for the predator, hunting can result in death. There have been countless example where a predator was killed by what was supposed to be prey. Animals have evolved many ways to combat this; from a cat's pouch, to a wolf's pack, to a bear's size. Another idea that to my knowledge does not exist is putting prey to sleep.
Could a predator that uses heavy amounts of pheromones as sleeping gas exist? What would the evolution of such a creature be?
[Answer]
Check out the [**cone snail**](https://en.wikipedia.org/wiki/Cone_snail).
Cone snails like to [stupefy their victims](http://www.iflscience.com/plants-and-animals/killer-cone-snails-drug-prey-weaponized-insulin/) (see also [Safavi-Hemami et al. (2014)](http://www.pnas.org/content/112/6/1743)) by either
* Using an extremely fast "harpoon" with venom to stab their prey.
* Releasing a small cloud of dense insulin to daze their prey, which is used for slower-moving animals. The cloud may then kill the prey. This isn't used quite as often, but it's still possible.
Note that cone snails are aquatic, and so the cloud forms and spreads underwater. However, I see no reason to believe that a) this couldn't be used in the air, and b) a larger terrestrial creature couldn't evolve to use it.
---
The [**tobacco hornworm**](https://en.wikipedia.org/wiki/Manduca_sexta) also [releases a cloud of gas into the air](http://phenomena.nationalgeographic.com/2013/12/30/toxic-halitosis-protects-tobacco-eating-caterpillar/) (see also [Kumar et al. (2013)](http://www.pnas.org/content/111/4/1245)), but it's used as a *defense* mechanism against predators, and it can kill the predators, rather than put them to sleep. However, it shows that clouds of gases *can* be released in the air and have potent effects against enemies; a predator could use the same mechanism as the tobacco hornworm.
[Answer]
What if the predator mesmerizes the prey by flashing colored patterns on its skin? Many octopus species can change their skin color, and cuttlefish can even flash strobing patterns.
A large amphibian with cuttlefish-like skin might be able to lull its prey to sleep. At least it would be a link in the evolutionary chain.
[Answer]
This could be an ambush predator of the type that digs a burrow and lies in wait of its prey. Something like an antlion. The predator has a pit that acts as a trap and while it lies in wait it exhales carbon dioxide into the trap. CO2 being heavier than air it will accumulate in the pit.
The prey species drops into the gas-filled trap and provided the air-CO2 mix is right or close enough this will act as an aesthetic gas. The prey will be anaesthetized and falls 'asleep'. Next thing it's munchies time. Good for the predator, but not so good for the prey.
Most probably this form of predation will only work with small organisms. Creatures the size of spiders and ants, and similar. However, old mine shafts do tend to accumulate CO2 and this can be fatal for the unwary. Perhaps, if the environment is right and if the predator can dig its trap deep enough to connect with underground fissures then this might provide a natural source of CO2. So larger predators and prey using Co2 anaesthesia might be larger organisms.
With humans 30% CO2 mixed with 70% oxygen results in intoxication leading to unconsciousness. See [here](https://www.netl.doe.gov/publications/proceedings/04/carbon-seq/169.pdf). This suggests that if a predator can set a trap filled with enough CO2 it might anaesthetize its prey. While this isn't exactly inducing sleep in its prey anaesthesia is the next best thing.
] |
[Question]
[
This question is very similar in intent to [this one](https://worldbuilding.stackexchange.com/questions/32657/how-would-people-tell-time-if-it-was-always-day) and merely takes place in a revised version of that world.
So, I have a civilization that lives in what could be considered a flat world. And no, I don't mean a flatworld. I mean flat as in what Earth was once considered to be. The only difference is that when you reach the edge, you magically are transferred to the opposite one. (The world is actually elliptical.) There is a certain type of stone similar to lodestone that attracts to the center of the world. (For reference purposes, there is a mountain where the three ranges intersect that is the tallest in the world. It is also the center.)
This world also has little or completely unpredictable winds, and a constantly changing night sky. Also, the entire world experiences the same seasons, and the sun never rises or sets. It just sits in the middle of the sky.
**My question is, what are the most likely ways for people to orient themselves and stay that way? What would influence directions on a map other than geography?**
[](https://i.stack.imgur.com/5z3mD.jpg)
[Answer]
If the world is flat, circular and people know it, and if the sunrise and sunset are not reliable indicators of directions (since they are absent), then your world has the following four cardinal directions:
* Rimward
* Hubward
* Clockwise
* Counterclockwise
Your civilizations could come up with their own names, or use other existing ones, for those directions. In Sir Pratchett's Discworld, for example, clockwise is "turnwise", and counterclockwise is "widdershins".
Edit: this may be pretty obvious at this point, but once they map the world, they'll probably pick a center to be the "zero-coordinate", and then all coordinates are relative to that.
For example, 3R30Cw would be three miles towards the rim from the center, 30 degrees clockwise relative to a standard radial line. Notice that since the hub-rim directions don't form circles, it's probably more practical to use absolute distances than degrees on this part of the coordinates system.
[Answer]
I would start out by referencing ancient maps. In ancient maps, you will often see that they are drawn from the perspective of the people who drew them putting what was most important in the middle. Persians never centered their maps on Europe and North was not always the top of the map. In your case with the sun unmoving with a seemingly magical transference from one side of the world to the other, the people living there wouldn't understand this and would likely not be able to make accurate maps as they wouldn't know where the true center is. As a result, every map would be different when drawn.
(few minutes of contemplation inserted here....sorry...I'm typing as I think...)
Ok...as travelers traversed the world, they would find that as they walked, the sun which was behind them (as for being located immediately above the center of the world/map would instantaneously be in front of them. This is the moment when they walked over the edge of the world and found themselves on the other side because they would now be facing the middle. This system would also mean that all shadows would face away from a central point in this world which is the key. In our world, Mariners would use a device (sadly the name of it eludes me at present) which measured the angle of the sun. This allowed them to calculate their position in the longitude/latitude system. My thought is that instead of the straight lines drawn vertically and horizontally across our map, they would have a series of circles centered on the point beneath the sun. The device they will use is twofold. It will possess a bubble level to ensure that when used, it is, well, level. The other component will be shaped like an "L." It will be aligned so that the part sticking up into the air will cast a shadow on the part that is flat on the ground/flat surface which has a series of tick marks on it to measure the shadow which would determine distance from the sun (we experience longer shadows in the morning and evening when the sun is in the distance) and from that you determine which ring on the map you are on (this is assuming that the sun is unreachably high...as if it isn't that high in the sky, elevation would throw this completely off and it wouldn't work at all...). The tick marks closest to the corner on the device would have to be closer together than the ones further away and the degree of this would be based on how high your sun is in the sky...I know this much but not the specific math that would determine it...would be a bunch of trigonometry and utilize Pythagorean Theorem...
This is great and all; however, we are only halfway there. I've only placed us on a 360 degree ring a certain distance from the sun-point.
You've already said that the night sky is ever changing which eliminates star navigation...
The only thing that I can think of is that you would need a secondary fixed point that was ascertainable to everyone at all times (magnetic north on earth). With this point, one could determine a degree of angle (with a compass - the kind you used in geometry class) between the sun-point and that fixed point. There would only ever be four locations on the map that would share that particular angle. When looking at a map, one could easily eliminate two due to knowing which of the two points was on the left and which was on the right. The third would be eliminated by knowing your distance from the sun-point.
That's the best I can come up with. Either you need to add a magnetic point within your world or something that would be visible from most all locations.
If not a single point, I would say that there would need to be some kind of key points like a lonely mountain/tower/smoking volcano scattered about throughout your map so that they could be used as fixed points. I understand that there would be certain areas that would be impossible to determine location within and as such, roads would likely be made through forests or mountains which would be drawn onto maps so that travelers could find their way from one mappable location to another.
Hope this helps!!!
] |
[Question]
[
For the past few days I’ve been thinking a lot about the idea of a medieval-style siege occurring at a planetary level—that is, an aggressor attempting to “starve out” a planet by cutting off its supplies rather than attacking it directly. Here we’d assume that, for whatever reason, the aggressor does not want to cause any geological or significant ecological damage to the planet it is attacking.
Given that, in most cases, you’d imagine that an entire planet would be self-sustaining and could survive indefinitely with its outside trade being blocked, how might this scenario play out? Would the attacker try to disable the major infrastructure of the planet with tactical strikes? What technology might achieve this?
Any thoughts on this (or, even better, examples from Sci-Fi) would be greatly appreciated. Thanks!
[Answer]
I very highly suggest reading these two resources:
* [Atomic
Rockets: Planetary Attack](http://www.projectrho.com/public_html/rocket/planetaryattack.php)
* [Rocketpunk
Manifesto: The Gravity Well](http://www.rocketpunk-manifesto.com/2009/06/space-warfare-i-gravity-well.html)
Much of the details of the siege will depend upon the exact objective of the aggressors. For instance, what do they need to keep intact?
* anything?
* biosphere?
* industrial infrastructure?
* population?
The more of the planet you need to keep intact, the more effort and time it's going to require to conquer.
If you're just trying to eliminate a threat, then bombard the surface with enough asteroids and/or nuclear weapons to destroy all civilization, it doesn't matter very much whether you kill the population or not since the survivors will be too busy just trying to survive to think about getting even.
Presumably your attackers want to do more than that and they want something on the surface of the planet captured relatively intact. Since the attackers don't have the troop strength to capture it directly, they're resorting to breaking the will of the population to make them give up that item.
## The Attackers
Let's assume the attackers are coming from another solar system.
### Advantages
Then the advantages that the attacker has are:
* They get to choose targets
* They can concentrate their forces
* They can run away if/when needed/wanted
* They can change their strategy as needed
* They know the defender's objective (to make the attacker leave)
* They can see large concentrations of the defenders (either military,
industrial, or population on the planet surface).
* They can hold valuable features on the surface of the planet hostage
(e.g. "if you don't surrender, we'll nuke LA")
### Disadvantages
* A **very** long supply-line, so long that, in effect, anything lost
during the conquest you can assume can't be replaced.
* They will be completely visible to the defenders at all times (you
can't hide in space).
* Unlike normal siege operations, the attacker doesn't get resupplied.
Presumably the defenders planet is the only inhabitable one which
means the attacker might run out of food before the defender does.
## Defenders
Assuming the planet is inhabitable to begin with (siege of an airless body of the Moon would be totally different), the defenders have many advantages.
### Advantages
In a planetary siege the defenders have many advantages:
* You have access to your industrial base
* You have access to your population base
* You have more troops
* You have more resources
* You can replace your losses
* You have access to terrain in which you can hide (e.g. oceans,
mountains, etc.)
* You have a tremendous ability to dump waste heat (for those super
powerful laser beams to sweep the enemy from the sky)
* You mostly should be able to feed yourself (this might actually lead
to mass starvation of the population but a suitably determined
defender might allow an excess population to starve while he kept his
military fed)
* If the defenders know the attacker's objective (e.g. capture the
biosphere relatively intact for colonization), then they can hold
that objective hostage (i.e. "if we lose we're going to bombard the
surface with our remaining nuclear weapons so you don't get it
either!")
* If the attacker doesn't have enough vehicles/satellites to watch the
planet from all sides, the defenders can hide activity (ground
movement, launches, etc.) from the attacker using the bulk of the
planet.
If necessary, a war of attrition strongly favors the defenders. Exchanging almost any number of defenders to get a single attacker is probably a winning strategy for the defenders.
The ground and especially the ocean provides an awesome opportunity for mobile forces to remain hidden from view. The defenders need only use passive sensors to watch the attackers, move nuclear powered submarine nuclear missile boats into the path of the attacker's orbits and then launch missiles when they're out of view. Once the rockets finish the boost phase they become much harder to detect.
### Disadvantages
Due to the nature of the engagement, the attackers can see any concentrations of effort (industrial, population, military, etc.) and bombard them to keep the population properly subdued.
In space combat and under normal circumstances any object that isn't thrusting is at risk. If your enemy can predict where you'll be at a certain point in time, they can ensure an asteroid or similar unwelcome event happens at that point in space and time. If you are on a planet's surface, this means you.
Any fixed defensive installation that you have will get *at most* one shot before the attackers figure out where it is. Then they'll stay out of your firing envelope and ensure you get to see the closeup view of the underside of an asteroid.
## Planetary Sieges are not Medieval Sieges writ large
Based upon the above, there will be almost no similarity between the two. The attacker is the one who will worry about the duration of the siege.
But really, read those resources. There's a bunch of information there and many people put a lot of thought into them.
[Answer]
It depends on how much damage to the planet is acceptable.
If you're okay with banging it up a little bit (collateral damage is a thing, after all), but don't want to cause too much long-term damage, it would be pretty easy to bombard the major food production sources from orbit. Just imagine what dropping a few tungsten rods on Nebraska and Iowa would do to America's grain production.
If you don't want to harm the planet at all, it's a bit trickier, but still doable. Remember that the key to a siege is making the besieged want to surrender. It's majorly an issue of morale, and food just tends to be one of the easiest ways to hurt an enemy's morale. It's easy to say that you'll fight to the death when the table is full, but it's much harder when you're trying to extend your last loaf of bread another day, when you're giving up your portion so that your child might survive.
The battle of morale is a battle that you can fight constantly, even without trying. Never let the people on the planet forget that you're there; plan your ships' orbits so that there is always a ship in view of every major population center, and they can't look up without seeing you. Maybe you could drop a rock into an ocean, causing a tidal wave to crash into a city. Communications on such a short distance are easy, so send video of your crew eating, laughing, generally having a good time (with the implication being "Surrender and join us, and you can be happy too!"), and generally not living under the siege of an armada of spaceships.
The entire time, though, you'll be wanting to watch out for the planet fighting back. You have spaceships, they have missiles that can reach space. If they're capable of space flight, you may need to destroy their shipyards so that they can't fight back as easily. That's really the big issue with a siege; you only besiege a place when you can't conquer it in an outright assault, so the planet must be about as advanced as you are. They will fight back, so at some point you'll have to ask yourself how much you're short-term damage you're willing to do to the planet.
[Answer]
This kind of sci-fi setting treats planets as nations or islands. A planet may be all industrial or have some resource it sells, and imports food. Treat it the same as islands and ignore most scaling issues; e.g. Star Trek was an allegory of south pacific islands and some have noted the correspondence between Kirk and Hornblower.
For a specific example in well-received fiction, look at Trantor in Asimov's Foundation series, and the Puppeteer homeworld in Niven's Known Space.
[Answer]
Assuming the following:
* the planet *is* self-sustained;
* both sides are at comparable/same tech level;
* the defenders are capable of destroying the invading fleet if it comes close (as in @Jim2B's answer);
* the invading fleet is capable of keeping the defenders grounded for a long time (\*);
* efficient interstellar signaling requires going to space;
-- a siege looks possible and feasible.
The shortage of food/resources/goods is not a big threat. Yet the defending planet would be **deprived of technical progress**, as reinventing all the wheels on one's own is much less efficient than knowledge sharing.
Based on the speed of progress in the given universe, being suspended for several years may become a huge and long lasting setback. Many would consider surrendering a lesser evil in such case. This also depends on attackers' claims and reputation, of course.
Defenders' internal politics could also tip the balance, for instance a government might want to keep themselves in power at all cost for as long as possible, and screw the progress.
(\*) As for the "keep defenders grounded" claim, I think that such balance is possible. An ascending ship should suffer from the same issues as ones in space, plus it must struggle against gravity.
Attackers could organize rotation of forces (not to be confused with orbiting :) ) and maybe even build a temporary base on a nearby uninhabited planet. This would decrease the wear of their fleet.
] |
[Question]
[
I have a creature that, thanks to its [multiple, unique DNA chains](https://worldbuilding.stackexchange.com/q/33040/6986), is [impervious to cancer](https://worldbuilding.stackexchange.com/a/33131/6986). So now I will move on to the next aspect: energy production.
This creature has two types of energy production methods: long-term, endurance energy, and short-term, sprint energy. The endurance energy is produced in the normal fashion: by eating food and digesting it. Endurance energy is used to power normal cellular functions, keep the heart beating, allow brain activity, etc.
Sprint energy, however, needs to be able to produce tremendous amounts of energy in a very short time, but doesn't need to be maintained for more than a few minutes at a time. Because my creature is impervious to cancer, I'm not worried about high-energy reactions causing harm to its cells. Since I like the unknowns in fringe sciences, I've settled on [cold fusion](https://en.wikipedia.org/wiki/Cold_fusion) as the engine for sprint energy.
However, nuclear physics isn't part of my knowledge set, so I'm asking the community the following two questions:
* How realistic is an internal, organic cold fusion engine?
* How would such an engine work?
---
I'm aware cold fusion is an oft-discredited field of science with many detractors claiming it's impossible, so cold fusion research doesn't get the same attention as the mainstream sciences. As such, I am not tagging this as either science-based or hard-science, but answers based in science are strongly preferred.
[Answer]
As someone with a strong physics background:
Not a clue. That's not me admitting that I don't know, that's me saying that experts in cold fusion still completely disagree about how it works, and experts in fusion of any kind still completely disagree about whether it works (as you noted in your question). So: Given that no-one seems to have a clue, and we're going into biology as well (which, in many ways, we know less about than cold fusion), the only answer I can give is (at best) a guess.
Your creature ingests a lot of hydrocarbons. Somehow the carbon is stripped from the hydrogen and energy is liberated, leaving an abundance of hydrogen in the creature's stomach. This passes by a membrane which (though processes unknown) strips out the hydrogen and stores it in a special 'nodule' inside the creature's flesh, made out of an as yet unknown material that stores hydrogen at above average densities. Electrical conduits around this nodule create undulating magnetic fields that gently massage the hydrogen into a configuration more favourable to fusion (How this happens is unknown), and the hydrogen starts to fuse at body temperature.
This gently raises the temperature of the nodule and keeps this otherwise cold blooded creature warm even in the dead of night (that's the only reason I can think of for a cold fusion reaction in an animal). The excess helium (and most of the hydrogen, given that we're still talking very low levels of fusion) are expelled into the darkness as part of the most unknowable flatulence in history.
[Answer]
*My general opinion is that no living creature could manipulate subatomic events on a cellular level.*
---
**Reasons to back that opinion:**
* Every known biological event happens on molecular (or higher) level which is at least two magnitudes larger than subatomic.
* Every known biological structure is carbon based and any sort of nuclear reaction (I can't deal anything with "cold" in cold fusion, so I will assume it means "controlled" in contrary of hot as in "exploding".) happening inside a carbon-based cell would produce enough heat to burn the proteins of that cell.
* Every known creature utilities some sort of chemical energy. (Plants transform electromagnetic energy to chemical before utilizing.)
---
**So, how could that work if it worked:**
You would need an alternative digestive system to utilize fusion energy which has nothing to do with the regular one.
**Creating the energy:**
I would suggest to have one use only "reactor cells" which are cell sized hydrogen bombs, and a "reaction chamber stomach" where those cells would explode. (*Please note that I don't have the slightest idea how a cell would be able to create fusion!*) The stomach should have a very thick wall made out of non-organic material (preferably containing lots of heavy metals to reduce radiation) which would be consumed using the regular digestive system.
**Protection from the heat:**
Even if the reaction is under control, the *"nuclear stomach"* will undoubtedly heat up, therefore it must be bedded in an organ which is capable to cool it down (possibly by some liquid). The liquid will become extremely hot and somewhat radioactive so will be emptied from the body.
**Utilising the energy:**
At least this is something that is done in real nature: electromagnetic energy can be utilized using some version of photosynthesis using special energy draining cells which are injected to the nuclear stomach together with a few fusion cells. Those cells could transform the nuclear energy to some high energy-density chemical fuel which could be utilized in other parts of the body. Please note, that these cells will also die in the nuclear booms so they must be replaced after every "boom".
**Cleaning up after using the "nuclear stomach":**
The nuclear stomach is something that should be frequently replaced, because it would become radioactive very soon and consists of a material that can resist tiny nuclear explosions so the body will not be capable to decompose it. The tissues around the nuclear stomach will also need replacement for the same reason.
---
**Please note:**
I'm neither a biologist nor a nuclear physicist and can't back my statement with more than common sense.
[Answer]
**I'm afraid I can't picture it happening.**
Cold fusion is not, to our knowledge, even "a thing".
Bringing two positively charged nuclei together in order to perform fusion requires *a lot* of very specifically concentrated energy.
This would be an incredibly delicate process. If ***anything*** went wrong there would be little bits of "creature" raining to the ground for miles around.
How could a living organism *evolve* to perform this kind of process internally, and unconsciously?
You can wave a lot of science away in a story, but this is just too much to swallow without completely giving up on plausibility.
[Answer]
I learned about [muon-catalyzed fusion](https://en.wikipedia.org/wiki/Muon-catalyzed_fusion) reading up for another question: [Multi-purpose Fictional Chemical Element Needed](https://worldbuilding.stackexchange.com/questions/85902/multi-purpose-fictional-chemical-element-needed/85924#85924)
It is not cold fusion or typical "hot" fusion but a third type, which can operate at room temperature but which relies on catalysis by muons. It is not done much because muons are scarce. If you could give your creature a source of **[Muonium](https://en.wikipedia.org/wiki/True_muonium)** they could use that to catalyze the low temperature fusion.
Muons are heavy cousins of electrons. On replacing an electron in hydrogen, this muon hydrogen can participate in room temperature fusion reactions.
In regard to an organism taking advantage of this, I am not worried about the great energy released by fusion. Fusion is energetic, but so is oxidation of fats. We do not have grease fires inside our body: the reaction is wrapped in chemistry that slows it down and lets use convert the energy released into ATP, the energy currency of cells. So too with fusion.
I think probably the way to do it is to have the energy output from the fusion reaction absorbed by a chemical reaction - for example some large molecule (I envision a ring with many metal atoms) that is moved to an energetically unfavorable state by the muon fusion. The individual metal atoms then revert back to their low energy state in an orderly fashion, allowing the energy to be captured gradually at ATP.
] |
[Question]
[
As we all know, terrorism, by its very nature is difficult to combat.
A certain famous stage hypnotist uses the following trick when performing. He puts the whole audience in a trance at the start of the show. He hypnotises them to believe they have had a wonderful time and to tell their friends how great it was. In fact there is no show. He eats his dinner, reads the newspaper and watches a bit of TV. Finally he wakes them up and they go home talking excitedly about what they've seen.
There is a war on terror and the government want to use the hypnotist to help them win.
How can our hypnotist modify/refactor his skills to successfully wage war on the terrorists?
>
> **EDIT** in response to answers and comments
>
>
> The vital part is that the hypnotist is working for the government. He must therefore work within the laws of the
> country he is operating in. At least, he must ***appear*** to work
> within them. So for example he can't just hypnotise someone to commit
> suicide. Even if he did it covertly, the suicide would cause police
> and press attention.
>
>
> He must always appear to be squeaky clean. Nothing must be traceable
> back to him or any authorities. A government enquiry must find not
> even the slightest evidence of anything that violates human rights
> legislation. If he can successfully fake this then all well and good.
>
>
>
[Answer]
Your best bet? To find people who are known terrorist, capture them, hypnotize them and send them back to their cell with the directive for the cell to be the target, not innocent people on the street. Thus they blow up themselves and their fellow conspirators reducing the number of terrorists out there and making the rest much more skittish, giving them a taste of their own medicine.
Edt: With the edit to the question, the Hypnotist needs to be a 'counselor' that will counsel the disturbed individuals. Taking notes of their 'sessions' while really sending them off to do his bidding (what ever that is).
[Answer]
Your hypnotist could become a **trusted leader** by working his way up the chain, so hypnotize higher and higher elements of the terrorist organizational hierarchy, using each tier to talk to the next and work your way between groups.
Once you're a trusted leader, use that access to talk to the terrorists in person and hypnotize them into taking different actions.
Note that making them simply stop might not be effective, as it will disincentivize other groups to meet with you. Instead, it might be better to hypnotize them into continuing to be terrorists, but ineffectual ones that make mistakes, are easy to catch and give up intelligence on other terrorists cells.
[Answer]
I don't think this could help with defeating the terrorists directly: they just will not be hypnotized (in many cases the hypnotist won't speak their language but in all cases they just won't listen).
How seriously governments regard 'defeating terrorism', is debatable: there are many advantages to keeping a terrorist enemy as an excuse to spy on political rivals and other troublemakers and to divert money to your friends.
This 'weapon' could be particularly useful in ways that could conveniently come under the banner of "defeating terrorism". Politicians, journalists and other influential people can easily be hypnotized to support their methods. These people can and will then influence the public to support them too.
With this in place, they can behave with much greater impunity. That might be quite useful in the ostensible objective of "defeating terrorism" ('necessary' 'legal' invasions would be far less controversial for example) but only if their methods are actually effective to that end. (e.g. Would boots on the ground in Syria reduce terrorism or increase it?). Its usefulness to the powers-that-be would be far greater than that and in far more important areas (such as getting reelected).
Expect to see this great hypnotist, in disguise, giving speeches to press briefings, parliaments, senates, rallies, etc. I doubt he/she would have time for much else.
If only we could find a way to use this to influence the markets...
] |
[Question]
[
I read that Venice was built on the lagoon because the population was on the run and wanted a place isolated from the Huns but gave them access to the sea. But, is this the only reason for founding a city on water? Tenochtitlan for example was on an endorheic lake and had floating gardens for some agriculture. Wouldn't the banks of some river be much better?
In other words, what specifically makes a lagoon, lake or other bodies of water a good place to form such powerful cities like Venice or Tenochtitlan compared to other places? It's a pros and cons question, basically.
[Answer]
**Pros:**
*Drinking water access* - When inhabitants need water, they just take a walk.
*Access to food* - Fishing is an excellent way to provide protein to a population.
*Ease of heavy transport* - There is no transport system as capable of moving massive amounts of cargo as water via ships.
*Beautiful scenery/tourism* - Pretty views and water-side parks are a huge draw. Make them pretty/magnificient enough and people will come from all over to see them.
*Strategic Control* - Especially in the case of rivers, placing a city along a river offers an excellent way to control access to up-river, down-river.
**Cons:**
*Disease* - If the city isn't aware of or ignore proper sanitation of waste water then cholera, dysentery, and other nasty diseases will appear.
*Ease of raiding* - Ships that bring in cargo also bring in pirates though this may become a motivation to become a greater sea power.
*Natural disasters* - Floods, tsunamis, epic log jams, climate change.
*Shifting trade routes* - Cities rise and fall on trade-routes. Shift the trade-route, the city wastes away.
*Contest for strategic control* - If the city is strategically located then expect frequent attacks by competing factions.
[Answer]
You already pointed it out, and Green has a good review of other pros and cons. However, I would like to insist about the military strategical advantage offered by such placements.
The two examples you have provided are pretty clear: back in their respective times, people were living in tribes, which were hard to protect from other tribes. I'll focus on the case of Venice, as I am more familiar with it.
Back in those days you had three ways to protect yourselves: have a strong army (like the Roman Empire, up to some point) or allies, or build in some defensive protection. Even that was not that easy, as you had to man your defences; and finally be ready to run.
A better documented illustration can be seen in the [100-Years' War](https://en.wikipedia.org/wiki/Hundred_Years%27_War), some "[free companies](https://en.wikipedia.org/wiki/Free_company)" were plundering the (now) territory of France. Cities started to surround themselves with walls. Previous small castle expanded to authorized the neighbouring population to come in in case of attacks. In the country-side, they had a strategy to run and hide. I reckon that it is not easy, but a visit to a village like [this one](http://www.brittanytourism.com/to-see-to-do/other-activities/village-de-l-an-mil) gives a good impression. If such a free company were to come in on the villagers, you could expect murders, torture, rapes, etc. So people had very little so that once those companies were spotted, they could run away, hide in the forest or the nearest castle. Sure, they would loose food, homes, etc. But at least be safe.
Now the population of Venice, they had been protected by the Romans, but their military might were falling apart quite fast. Building walls take time, especially if the same people have to provide some food. And who to man your walls? Being in the middle of a lake gives you a very good natural defence. Indeed, your opponents have to either bring along ships, or build them on the spot. Both giving you enough time to effectively run away, or counter-attack (or harass). Furthermore you have a lot of directions to run away and you clearly see your opponents coming.
I disagree with Green on the "ease of raiding" part. Pirates are forced to come on ships, and you have more ships and see them coming. For Tenochtitlan, ships could not be sailing for far. For Venice, the high-grounds of the laguna, protected the city. When pirates were actually organised enough to try to raid the city by sea, Venice was already all-too-mighty to risk it.
Now you did not mention it, but Paris was also built starting from the *[Île de la Cité](https://en.wikipedia.org/wiki/%C3%8Ele_de_la_Cit%C3%A9)*, which is an island in the middle of the Seine River. They also used the same protection.
But why, then, wasn't there more people doing it? Well you need to be able to sustain yourself in the middle of the lake. As Tenochtitlan shows with their floating gardens, you really need to procure enough food for your population. If it's easy for you to see your enemies coming, it's as easy for them to see you leaving.
] |
[Question]
[
I had a look at [this question](https://worldbuilding.stackexchange.com/questions/628/explaining-where-energy-comes-from-to-power-magic), and though about magic and the human body's energy output.
I remember calculating the energy require to walk up a 3.4m staircase quickly in a school physics lesson once. I looked up the results in my old book, and I got the power outputs of everyone in the old class. The greatest output was around 840W in 4 seconds, and the least was 130W in 14 seconds.
I remember being surprised by this, especially considering that a really good lightbulb is 17W, and an LED lamp is about 60W. It doesn't take too much energy to start a fire, either, though admittedly it probably takes much more to sustain one.
If 'magic' in humans were possible by using energy produced by the human body, what limits would this magic have? How would this magic differ from the Stereotypical, Tolkein or Harry-Potter style magic we're used to? What effect would this have on people using magic?
And, more importantly, what would magic be able to do that we can't do better with electricity?
In response to PipperChip: I don't see why it should be constrained to any type of energy, so molecular energy and such is viable in my eyes.
[Answer]
There is, I think, a problem with your question. The problem is that specifying total energy is not enough. Additionally, specifying power is not enough. Adding force is not enough. Adding speed is not enough. Let me explain.
Let's say energy is the only constraint. Then you can levitate rocks to high altitude and let them sit there, waiting for the command to drop. Making a modest assumption of 100 J/sec, you can lift a 1 pound rock about 20 meters in one second, do this for 50 seconds for a final height of 1 km, and it takes no energy to leave it there. Doing this for an 8-hour day will give you about 500 man-killers. Doing that for a month will give you a cloud of 15,000 rocks, enough to obliterate any village or small army.
Is this reasonable? Many don't think so, since it seems obvious that nobody can hold up 15,000 pounds. So applied force needs to be considered. And once you start considering force, how does magic deal with mechanical advantage? And how fast can a magician apply force? Consider throwing a rock. A major-league pitcher can throw a 5-ounce baseball 100 mph. That's 140 grams at 44 m/sec, or about 140 J. A 9 mm pistol slug has about 500 J, but is far more lethal than a baseball. Can a magician accelerate a small, dense body faster than a pitcher accelerate a baseball? Let's take a 1/3 oz flechette, a small dart about an inch long. At 140 J, it will have a speed of 140 m/sec, and will pierce a person's body all the way through. Remember those floating rocks? Replace each one with a 1 oz metal dart 3 or 4 inches long. Dropped from 1000 feet, one of these will punch all the way through a person - lengthwise. And a cloud of 320 of them will only weigh 20 pounds, and almost anybody can hold that weight indefinitely.
And then there's power density. Sunlight, with a power density of 1 kW/sq meter, can be focused by a 6-inch diameter magnifying glass to a spot size of less than 1 mm (as lots of kids have discovered, to the detriment of the local ant population). That's less than 20 watts to produce a nasty little burn. So it's clear that, if only power or energy is limited, 100 watts can do very bad things to one's enemies.
Finally, it gets worse if rather specialized knowledge is invoked. Creating light is a staple of magic. Knowing it's possible, what's to prevent the creation of coherent light? A laser beam of less than 100 mW is more than capable of temporarily blinding someone. Is there any good reason that a magician can't do it, rendering an attacker helpless at almost no energy cost? Focussed acoustic energy of a few watts is more than enough to destroy a person's eardrums. Is this allowed?
[Answer]
There are a few aspects I'd raise: type of energy, looking at power vs. energy, and the most interesting one for me: lack of physical requirements / infrastructure.
**Type of energy (and entropy)**
Electricity is a low-entropy form of energy, so it's very organised, whereas heat is very chaotic. Converting from electricity to heat can be simple and efficient (just use coils of wire!), but the other way around is more complicated (we can get ~40% efficiency with [some setups](http://en.wikipedia.org/wiki/Energy_conversion_efficiency#Example_of_energy_conversion_efficiency), and even then it takes a bit of engineering).
So: is the energy you're using high-entropy or low-entropy? Does it translate into some forms of energy more easily than others? (e.g. motion is easier than light?). What if you can only output one form of energy, and to produce light you need a "light generator" to convert it?
**Power vs. energy**
Something like a bullet obtains all its energy at once. However,
if your magical system allows action at a distance, then you shouldn't just compare instantaneous force/energy, but total over a period of time.
Say one magician can lift a cannonball (comparable to human muscle) - that means they can apply as much force as gravity can. If a second magician applies the same force sideways, the cannonball can "freefall" in any direction you like.
In fact - I'm capable of giving a heavy friend a piggyback. That means I can exert an extra force of ~1000 kilo-Newtons (on top of my normal standing around) for at least ten seconds. That means I can accelerate a 1kg weight to three times the speed of sound in only a second.
**Physical requirements**
You asked "what would magic be able to do that we can't do better with electricity?". For that, I would respond with the biggest advantage that magic has in most representations: it requires no infrastructure.
So with a long enough lever I can lift pretty much anything - but I need space for the lever. With electricity, I can produce a bright light on demand - but I need to have placed a bulb and electricity source there first.
If magic can work at any kind of distance, then this requirement is freed up. I really *can* unlock the box with the crowbar that's inside it - more relevantly, I can easily walk through any door that can be opened from the inside. I can punch someone in their internal organs - or perform surgery without having to open them up. In the previous examples, I can accelerate an item without having to attach the energy source and conversion apparatus (like in a rocket) to the item itself.
This, I think, is often the most effective part of a magic system - even if you have to waste magical energy to get it in the form or place you want, you don't have to set up the physical infrastructure to deliver it, in the way you do when dealing with physical energy sources.
**Mitigation**
When viewed from a point of view of energy alone, it's easy for magicians to become insanely overpowered. If you want to avoid this, you could hobble the above properties - e.g.:
* an awkward form of energy that's hard to translate (and then a better generator/convertor could be a plot point / force for change)
* limiting physical distance to avoid extreme kinetic buildups
* requiring magical infrastructure (so spell-casting to launch something is the equivalent of building a catapult in "magical space")
* requiring physical infrastructure
] |
[Question]
[
Currently I am working on how to explain a character that can "phase" through objects in a similar manner to Martian ManHunter. His abilities are negated by certain (rare) metals. His ability could be meta-human (like The Flash etc.), biological (ManHunter), or technology based.
What scientifically-plausible ability (*not principle*, though if you can show a principle and a way to manipulate it that's fine) would make the most sense for him to be able to doing this?
**Superpower:**
1. Must be able to pass through most materials at will.
2. Must have at least one material that cannot be phased through.
3. Must be able to phase himself and any object within two feet that has less mass than his body mass.
**Edit:**
4. Must become weightless or have a way to maintain current elevation so he doesn't go falling through the floor.
[Answer]
**Hyperspace!**
I think it would be difficult for someone to alter themselves to pass through ordinary matter without altering themselves into something for which the chemistry life depends on wouldn't work. But it might be possible to achieve a similar results.
He doesn't go through the matter physically. He jumps at the wall he wants through and, just before impact, shifts himself into a pocket universe for a second. When he comes out, it's as if he's kept moving that same direction in normal space-time for the time he was gone. He doesn't go FTL -- if he's moving one foot per second when he goes into his pocket universe and emerges one second later, then he's one foot from where he started.
It's a "pocket universe" that is precisely the same volume as he is, so he doesn't have to worry about being in a hard vacuum while there. There isn't any vacuum outside him in the pocket universe, because the pocket universe ends at the outside of his skin. He can't breathe in there, though.
Objects he pulls along come with him, in their own universe, but they emerge into normal space-time when he does.
When he emerges from the pocket universe either whatever would be in his way is sent into its own pocket universe forever, or he emerges from it like going through a door. Either way, any air where he is going to emerge is taken care of, but this does make a difference if there was something solid where he emerges. Either he ends up in a him-shaped hole in the wall (which could be the end of our hero -- since he's at a standstill in the wall, even if he hyperspaces he'll end up back in the same place when he emerges), or he can't come out there.
There could be logical limitations like not being able to do this upwards -- if he coasts upward for a few seconds in his pocket universe, when he emerges, gravitational potential energy has appeared from nowhere. Going downward would be OK if the gravitational potential energy that was lost appeared as heat (as long as there isn't too much of it!), but the reverse (heat disappearing if he goes upward) might violate the Second Law of Thermodynamics. But this part is a minor nit, and you might be safe ignoring it.
As far as a substance he cannot get through, maybe something significantly dense casts a "shadow" outside normal space-time, one his pocket universe cannot get around. Or maybe electric current -- someone turns on a light switch at the wrong time and he cannot get past that.
[Answer]
First, I will mention a particle that can do this extremely well: the neutrino. Why can it do this? It can because it has little mass and no charge (I could explain why these properties allow this, if you want me too, but it would take 1-2 good paragraphs). Therefore, as we approach these conditions, we phase through matter more easily. We can satisfy your conditions be given your superhero the power to reduce mass (both his and that of objects). This immediately satisfies 1 and 3 but not 2. 2 is satisfied, if we limit his power. He can only lower mass to a certain extent. Since he cannot lower it indefinitely, very dense objects would stop him.
Due to comments, I will explain why low mass matters. It is mostly due to momentum, and a low mass means a low momentum. The lower a particles momentum, the more prominent is its wave nature. Therefore, this superhero's power is the ability to have a prominent wave nature. Having a neutral charge is important as well.
[Answer]
I understand that you want to pass through walls and such, but have no idea why you refer to it as a *phase*. You mean like different phases of matter like he turns into a gas?
In the hard sf novel [*Pushing Ice*](http://rads.stackoverflow.com/amzn/click/0441015026) a character from the near future is transported via a "travel cowl" from the far future, where nanotechnology is perfected. Shenis astonished how she got sevel levels and past several security doors, instantly. "In small pieces" was the reply.
More along the lines you're thinking of,
The particles in his body could be changed into something else, which have analogous properties relative to themselves. That is, atoms and molecules exist unchanged because the use of electric charge is changed to X charge in a uniform manner. But it won't interact with normal matter at all, so, he can pass through walls and would fall through the floor.
How about an envelope that changes the nature of space by fiddling with some parameters, and whats inside seems normal within but acts as explained above. Now how to *selectively* interact so can see, push against the floor, etc? It provides an interface layer that can be tuned to touch normal matter when needed. Recall that *charge* is not enough to be solid, but that has to do with being (exactly) electrons, so the envelope would need ro prodice an exposed layer of matter and somehow react with *that* in some other way.
E.g. the bottom of the shoe and anywhere touchnis desired is coated with a thin layer of room temperature superconductor. The envelope contracts to expose the conductor and manages to still stay connected rigidly woth it by using flux pinning and thus a pure electromagnetic effect that applies to anything with charge. The interface (on the inside of the envelope) produces a transition material that interacts (at half strength) with both the X force and the electric force. Superconductive currents of these intermediate particles (since only pure X-regime electrons touch in the normal manner) can be controlled with X-regime electrons and induce a charge in the normal superconductor, so flux pinning can keepmthe sandwich together.
The exposed material then interacts with matter in the normal way.
To get your shoe through the wall too, the envelope is extended to cover everything. This has to be orchestrated carefully to change the properties and the tuning of the mechanisms that hold it together. And that provides our Hero with (quite literally) his Achilles Heel. I think it would only be vulnerable when shifting, but if he's walking through a wall that needs more than one step to pass through, the shoe needs to turn On interaction whike still embedded inside matter, and thus not take up any room. Without going into how that might be done, note that the whole interface business uses superconductors and strong localized electromagnetic fields. What if the surrounding material interfered with that?
If the mechanism were compromised he would not only be unable to take a step but would not be supported by the floor and would fall into the earth never to return until he ran out of air or power.
If he passes through something that damages the interface but succeeds; e.g. jump through a thin wall and then turn it completely off before hitting the ground; it would render him crippled, only able to safely use the power by jumping while running at the wall and then turning it on.
[Answer]
<https://www.sciencealert.com/99-9999999-of-your-body-is-empty-space>
There are two ways to go about this. The first would be to nullify the charge of the electrons. That seems problematic, as molecular connections rely on those charges, meaning your body would probably just fall into a pile of subatomic particles if they had no charge.
The second option would be to stop the motion of the electrons. Because they are moving so fast, they exist throughout the entire space of the atom all at once. But if you could somehow stop their motion, there would be enough empty space for you to slip through the atoms of other materials. Their analogy is that electrons are like the blades of a fan. While spinning, they prevent anything from going through. But stop them, and you could slip between the blades easily.
To prevent yourself from falling through the Earth, you would need to be able to selectively control the movement of those electrons. So they aren't moving in any kind of vertical movement, but they do move horizontally, so that you aren't impeded moving horizontally, but are impeded vertically. Think of it like tipping a fan face down. You can move your hand above and below the blades freely, but try to stick your hand down or up into the blades, and you'll get hurt.
[Answer]
Dark matter seems to fit the bill here. Recent observations suggest minor "dragging" occurs in the dark matter halos, implying some forms of self interaction. But this means your superhero would only be stopped by dense dark matter "walls!"
There's a more fundamental constraint:
Since they can't interact with normal matter, they can only "breathe" what limited air they convert with them into dark matter form. This appends a time limit to their transition that makes it akin to "dark matter diving." Heck, they might even bring along an oxygen tank and/or a CO2 conversion unit to extend their transition period.
Though their "real" vulnerability would be hard to construct (except by a parallel baddie with similar powers), they wouldn't be able to phase back into normal matter in the middle of a solid object (without dying, anyhow), so solid ground too thick to pass through without transitioning back would still stop them.
[Answer]
Another angle that could be considered, rather than changing physical composition or density, or jumping into alternate spaces, would be changing "reality" itself.
What if the person is able to walk through a wall because he caused the reality of the wall (completely altering all physics in a localized area) to be that he can simply just walk through it. It just ceases to be an obstacle as if it wasn't there... a "ghost" image.
Some objects, or areas, may be impassible due to their age (their reality has been set for millennia and as such cannot be altered easily), or magic (which also bends reality), or mental blocking (the reality is altered because he wills it so, thus if he doesn't think he can... he can't), etc.
Just a thought.
[Answer]
4D movement. The analogy of this would be, that, say there were humans who existed in two dimensional spaces. If I were to build a 3D 1 foot tall around these individuals, than that barrier would be impossible for them to escape from because they cannot traverse height, only width and depth. They would find themselves in a room with no way out. Now, if by some mutant ability, one of the 2D people could become 3D or some how shift himself into 3D space, he would be able to walk over the fence... but to his 2D buddies, he would appear to go through a solid wall, because they only see him in 2D space.
Essentially, your character could have the ability to shift into an X-dimensional, which would ad a movement that cannot happen in 3D space. Human construction is not built in this dimension cause we cannot percieve it. In essence, you can move through this space, which lack barriers, and to your non x-dimensional buddies, they don't see the trick and think you just phased through the wall. You won't fall down, because you will still have your original 3Dimensions, so the floor is not being phased through... but you could leap from that floor by to go through it through the dimension gaps. Similarly, can easily extend the field to most other objects.
I would say that a governing componant is that while you are moving through the dimension gaps, you are not aware of the new dimension, which allows you to see it as a phase through solid stuff... This means there is an subconcious correction method which automatically finds a gap you can move through and moves you in your intended direction. This can also allow bullets to pass through you as it is not accounting for your XD measurements which can be some distance off.
While the single impassable container would not work here, you could say that the thickness of the object will affect your travel time through the gap, so if it's a few hundred feet thick, you have to pass through a very long doorway... as the thickness increases, the door becomes less of a door and more of a tunnel. So very thick walls could block you because they take longer for you to travel through and you lose energy to maintain a dimensional shift and cannot get through without a rest, essentially pushing you back into a 3D space. This means that the bad guy doesn't have to build with exotic materials, but rather build the prison extra super thick to keep you inside.
] |
[Question]
[
I am working on the development of a humanoid species. I figured they'd have split along the evolutionary chain around the same time as humans. They'd live in a warm climate, resulting in little hair any where, but their head, since eyebrows and lashes protect against debris and head hair protects against the sun. I also gave them horns, a tail, claws, long canines, black scleras, and grey skin. They each have both sets of genitals, but the 'boy' part is sheathed, and their bodies adapt when they become pregnant. I think I have a decent backing to each evolutionary trait, but I want to know if it seems too unrealistic.
[Answer]
When looking at whether a trait makes sense, the important thing is to consider if it would help the animal go about its life. Many of these traits exist, or at least, there are genes that could cause them to exist, in humans. However, I'm not sure they all make sense in the same organism. First, let's go through all of the traits that would be perfectly fine in a humanoid.
**Grey Skin** There are grey skinned animals out there, so this is a possibility. I'm not aware of any particular downsides to having grey skin, either.
**Black Sclera** Most of our close relatives, evolutionarily, actually have dark or black sclera. Chimpanzees are a prime example. It's hypothesized that we evolved white ones to aid in communication, but it's perfectly reasonable that this mutation never occurred in your creatures.
Then there's a few evolutions you've listed that make sense, but require some shifts to the way your humanoids will behave:
**Claws & Teeth**
These are reasonable things to evolve, assuming that your humanoids hunt with them. Heavier canine teeth are good for eating meat, and claws can be powerful weapons for catching prey. For large animals, nails might be worse for climbing, since they get in the way of gripping around small branches, but if bipedalism evolved in a small climbing creature instead of a large one, they might evolve.
**Tail**
This could exist in a humanoid, particularly one that actively uses arms for fast hunting. I'd expect a tailed humanoid to have evolved to sprint down its prey and dispatch it on the run with swipes from its claws, necessitating the evolution of a tail for balance instead of using the arms, as humans do.
The other traits are less likely to evolve. Yes, humanoids could potentially have the genes to create this things, but ultimately, it seems like evolutionary pressure would favor individuals in the population in which these traits were reduced or absent.
**Horns**
A predatory creature with claws and large teeth is unlikely to evolve horns. Unlike herbivores, carnivores have evolved to kill things, and don't tend to need to evolve extra weapons like horns. Furthermore, effectively using horns would require that the creature put energy into growing them, and into growing and sustaining the supporting structure needed to make them useful. Horned creatures need strong necks to support use of their horns, and the neck musculature wouldn't be critical to anything else for a creature evolved to run down and claw up its prey.
**Hermaphroditism**
This is unlikely if your humans raise young in pairs or in groups. OR rather, it's unlikely that the same individuals would be able to function both as a male and as a female *at the same time.* The more organs and structures an animal has, the more energy it requires to live. Maintaining both sets of reproductive organs, and having both be functional at the same time, would require that the creature consume more food than if they focused solely on being male or female. Truly hermaphroditic animals, like snails, some worms, and brine shrimp, generally don't put a lot of effort into raising their offspring, and as such can increase their reproductive fitness if most of the population can be simultaneously impregnated.
Sequential hermaphroditism, on the other hand, would be much more feasible for a group living child-rearing creature. Sequential hermaphrodites are born either male or female, and then switch later in life, generally with the most dominant creature in the group becoming the other gender. If your humanoids were born exhibiting female traits, this would allow the fittest of the creatures to share its genes the most, since only the most powerful of the females would be able to become male, increasing the number of offspring it could parent at a given time.
It would also make sense for your creatures to become truly hermaphroditic when solitary for extended periods of time, since this would allow them to self-fertilize and reproduce even in the absence of anybody else.
[Answer]
The main issue is the hermaphrodites, the other properties are extensions of existing mammalian traits so should be fine.
Hermaphrodites though are much harder to explain. In particular a lack of females would not explain hermaphrodites at all, if a species lacks females then it dies out - but it can't prompt boys to turn into girls to balance the sides.
I think a more plausible explanation would be to have occasional fertile hermaphrodites to have occurred spontaneously. For whatever reason they were seen as sexually desirable or even worshiped by the other members of the species. As a result those hermaphrodites got to breed, a lot.
When the hermaphrodites started not only having children themselves but impregnating females then those properties would spread rapidly through the population. You might even have a temporary phase where 3-way marriages are common (one male, one herm, one female) in the society.
Either way over time things would shift until hermaphrodites were the most common members of the species, while male and female would both be rare throwbacks.
[Answer]
It's out there, but let's try to see what we can do.
**Horns** - Since they share a common ancestor with humans, and there are [humans born with horns](http://blog.medfriendly.com/2012/02/bizarre-images-of-cutaneous-horns.html), it is possible that those of your species who were born this way, were highly revered and bred very often, at the expense of others. Soon with each other as more of the genetic mutation started showing up, it resulted in evolving to popularity, eliminating any 'freak' born without horns over the millennia.
**Tail** - Same as above.
**Long Canines** - Wow, same as above.
**Grey Skin** - Same as above
**Genetalia** - Same as above, but sometime later, the chromosomal [genotype](http://en.wikipedia.org/wiki/Genotype) became the norm, and it was very rare for an XX/XY to be born. The more 'successful' [interexed](http://en.wikipedia.org/wiki/Intersex) (those with very distinguishable double genatalia), were selected naturally. If you want a person to be able to breed with themselves, I can't help you there - I think your species would suffer tremendously from that.
**Black Sclerae** - Scientists belive we have bright eyes with whites, because [it helped with communication](http://www.nbcnews.com/id/15625720/ns/technology_and_science-science/t/did-evolution-make-our-eyes-stand-out/#.VTV6A5OIPEY), unlike our evolutionary cousins. In the case of your folks, they maintained the dark eyes of our common ancestor, because (taking a stab here), certain survival behaviors depended on not knowing where someone is looking. In your prehistoric times, tribal warfare was a staring contest: as soon as the opponent looked away, they got gored by the horns. So, over time, those with darker scleras were more successful.
One thing however, I'm not sure that we would both evolve so distinctly as we would compete, but then again, we share a common ancestor with apes.
[Answer]
This is not too unlikely, except for the sheathed penis, the rest can be seen in some form in regular humans to one degree or another. I take it from your apparent discomfort with the word penis, that the required 'sheathing' was for the same reason. Don't be afraid, if you let them rock out with their cocks out then it's not a terribly unlikely creature. You can check out some diagrams of hermaphrodites for what to expect, like any naked man, it's not going to be pretty.
**Horns**
This is not going to likely come from the human genome. There are cases of [people with horns](https://en.wikipedia.org/wiki/Cutaneous_horn#Prominent_cases). But they're most likely caused by exposure to radiation (or perhaps a virus). In either case horns can be added to children in a ritualistic way, similar to the [artificial cranial deformation](https://en.wikipedia.org/wiki/Artificial_cranial_deformation) performed by some groups of early humans. The virus is easier, since the sites could be infected until the virus takes hold. For the radiation case, it's less likely to work so frequently. Unless they are particularly disposed to that reaction and a reliable source of radiation is used, the normal source is the sun, but perhaps they have some ceremonial lumps of radioactive rocks.
**A tail**
There are cases where [humans were born with tails](https://en.wikipedia.org/wiki/Tail#Human_tails). So the trait exists in our DNA in a way capable of being expressed. While this is quite rare, it could have been a desirable trait in this species.
**Claws**
What are claws besides thick fingernails? Not a difficult adaptation to believe.
**Long canines**
This, again, is not a huge deviation from normal humans, so it not terribly unlikely or hard to believe.
**Black scleras**
This is not going to be very satisfying. Fully black scleras don't occur. The best way around this is to have *very* dark and large irises, like a canine. These would appear like black eyes, but the scleras would still be white.
**Grey skin**
Humans come in all colors of the human colored rainbow. Grey is not very specific, but I don't see any reason the species could not appear grey compared to a normal human.
] |
[Question]
[
No one knows for sure the composition of Greek fire, but there is almost certainty that it truly existed.
Question:
What would be the effects of earlier Greek fire during the time of the Western Roman Empire?
Could it turn the tide of war against the barbarians? Would it prevent a sieging army from storming walled cities? Could dedicated machines be created to move greek fire throwers around battle field in order to use it as a - frightening - flamethrower superweapon? Had this been done, could a smaller Roman garrison stop the maraunding barbarians? (Huns, Goths, etc.).
[Answer]
I love your drawings.
I don't think this would work as you intend...greek fire is a napalm at best and doesn't work well like this. If you could pressurize it, it could be shot in a stream, but I doubt the range would be much more than a super soaker. Romans did make decent use of greek fire in their catapults as is, so the idea is there.
I get the feeling the structure would be most likely to set itself on fire.
>
> What would be the effects of earlier Greek fire during the time of the Western Roman Empire?
> ....
> Had this been done, could a smaller Roman garrison stop the marauding barbarians? (Huns, Goths, etc.).
>
>
>
Unfortunately no, Western Rome did not fall to marauding Barbarians, it fell to economic and political reasons, the barbarians just took advantage of a crumbled empire. Even the presence of a super weapon wouldn't have helped the situation much...infact attempting to pay for said super weapon would likely increase the speed at which it crumbled. With all the infighting going on, this weapon would have seen more use on other Romans than on barbarians anyway.
Going to change the question a bit...to what could have saved the Western Roman empire from collapse.
If you want to get to the core of the fall of the Western Empire, you need to see the state it was left in. From 150ish AD to it's final fall, more Roman emperors died to assassination than any other cause. At one point it was split into three empires as Gallic Empire, the eastern Palmyrene Empire, and the central Roman empire. The resulting civil war lasts for a good 100 odd years with well over 50 people claiming emperor status before Diocletian comes around 285ad (after a bloody civil war that ended with his opponent killed by his own troops...being killed by your own body guard or own army is actually a pretty consistent theme of this time). It was ultimately Diocletian that seeded the western/eastern empire view with a Tetrarchy view (one senior and one junior emperor for western and eastern empires). After Diocletian retired, Constantine the great sees his 31 year reign (and probably the height of the Roman empire here) and when he dies the three sons divide the empire up once again (interior, west, and east)...get into a dispute about it...and start off another civil war. (the winner of this civil war is killed 10 years later by his own troops).
As you can see, the Western empire is changed about several times and exists as everything from Europe and including rome / Africa, to at one point simply being the former Gaul lands and Britannia. This constant state of flux and civil war provided nothing but uncertainty and led to extreme economic depression. The problem with an empire the size of Rome is your emperor is going to die (natural or otherwise) and the replacement for tends to be disputed.
Finally, after all the infighting described above, now the barbarians enter and see a financially crumbled empire barely able to feed it's own people let alone defend them...there was actually a period of time here where there was no Western Roman emperor and when there was one, he was rarely recognized by the eastern empire as a legitimate claim. The capitol was no longer Rome (Milan for a time before moving to Ravenna) and a couple of the last emporers never exercised any control beyond Dalamatia. Peoples such as the Goth struggled massively under Roman rule (Romans hatred of the Goth people is very obvious), so it took very little to convince entire populations of the Roman empire to chuck Rome aside and join the barbarians.
As you can see, the Western Roman empire had defeated itself long before the Barbarians ever invaded. If you can address this political turmoil, then you have the route to which Rome could survive.
I should also mention that had Rome survived, it was facing another series of challenges from the Franks, England, the Umayyad Caliphate, viking invasion, challenges to the throne by leaders of the Holy Roman empire, and a whole slew of other challenges. It was not an easy time for an empire to survive.
Edit:
Just to give you an idea of the level of absurdity some of this reached...Year of the 6 emperors began in 238 AD with Maximinus Thrax. He was accused of being a very tyrannical ruler...in Carthage, tax collectors were murdered leading to the proclamation of Gordian I the new emperor. He was quite old and declared his son co-emperor. This lasted for 20 days when a neighboring governor that hated the Gordians led an army and defeated them in Carthage with both Gordian I and II dying in the fall out. Two elder senators were then made Emperor, but they fought/argued heavily. Maximinus Thrax still commanded an army and was marching back to Rome...but he was slain by his own army. Shortly after, the two senators got into such a fight that the praetorian guard intervened and killed them both.
[Answer]
Why stop there? If we're jumping the shark, let's jump over sharks with lasers.
Make it portable! This way you can have Legio Vespertilionis Incendii (aka Firebats!)
The original greek fire consisted of either inflammable pots of what is essentially tar or of a pressurized liquid shot by the use of a bellows. Your Incendiari would carry a pot of flammable liquid on their backs and a metal tube with a thin bellow driven nozzle, with the top end burning like a candle. Besides the firebackpack, they'd carry a big shield. A second person behind would power the bellows.
] |
[Question]
[
Imagine Europe around 1810. Imagine the Netherlands. Imagine that it is the colonial age. Imagine also that the colonies are mostly under open rebellion. Imagine that the region of Netherlands (imagine only) and the surrounding states already have the following technologies:
1. Telegraph (telephone probably 3 generations away)
2. Intercity steam-based locomotive (electrical-based trains almost a decade away)
3. Some steamships but not in popular use (and no ironclad military ships)
4. Common steel (no stainless steel yet)
5. The sail technologies that would have been known in Victorian Era
Rifling technology is still new, so there are no rifled cannons. But they do have rifles, imagine the Sharps rifle.
The kingdom of *Just Enough* is a colonial power similar to the Dutch that uses 3 types of currency: Ema (gold), Catty (silver) and Luca (copper). The precious metals exchange rates are as follows:
1 gold ema = 10 silver catty
1 silver catty = 25 copper luca
Originally based on precious metals, inflation and economic collapse brought by hoarding and colonial uprisings had prompted the king to take the value of each coin off its precious metal standard. So it becomes the following:
1 gold ema = 3 paper ema
1 silver catty = 2 faux silver catty
1 gold ema = 60 faux silver catty
1 paper ema = 20 faux silver catty
Copper is unpegged from silver and pegged to faux silver instead, which means 1 gold ema equals 1500 copper luca (say what?)
Assume that the average daily wage for a day labourer (farms, mines, server) is 10 copper luca. A long loaf of french bread is 5 copper. A train ticket is 30 copper per person. A slice of fish enough for 4 person gruel/stew cost around 2 copper.
The kingdom institutes the following taxes to those in the crown territories:
1. Head tax
* for men above 16 - 5 faux silver every 3 months
* for women above 18 - 3 faux silver every 3 months
2. Land rent
* only for non-noble landowners in crown territories
3. Wealth tax
* applicable to owned houses, gold, silver, gemstones and pearls
4. Business tax
* only applicable to businesses operating in crown territories
5. Wedding tax
* only applicable to marriage between Just Enough women and foreign men.
Taxes are paid preferably in faux silver.
**Question**:
1. How much would an average household of 2 adults and 3 children (not taxable age) earn for a year? This is in relation to the societal norms of Victorian Era Netherlands. As in do both parents work, only the father works, or do the father work two jobs?
2. How much would said household spend on food for a year in the city/town? Or for a month?
3. Is the current currency and taxation humanely feasible or is it in violation of human rights at the time of Victorian England?
If I wasn't being clear on anything, please ask. I'm afraid I left something out. Of course, feel free to nitpick anything here. Average daily salary too low? Argue about it. French loaf too expensive? Argue about it. I have no problem with it.
[Answer]
1. Who is working in the family depends at which social class it
belong.
If they live on a farm everybody will contribute.
If they live in a city, during the industrial age, it was common for
children to work in the factories. Women also worked in the
factories with very low wages. The shifts at the factory can be
really long. At 16 hours per day, I doubt the father could have 2
jobs.
If they are wealthy enough, it's possible that the women will stay
at home instead of working. The children can go to school longer and
might not need to work before adulthood.
The average family would earn enough money to buy a couple of
presents for Christmas (like an orange, that's exotic) and save for
a couple of treats here and there during the year, mostly for
religious holidays. They are almost incapable of saving money for
the long term even considering that everyone is working and that
they make everything possible to save money. Good news !: retirement plan is
useless since they are likely to die before their 50's.
2. Most of the revenue of poor people go into housing and food. I
don't know how much exactly. It depend how much they spend on
housing. They probably live in a small apartment in a crowded
area not too far for the industries.
3. Too much calculation for me. As WeekzGod mentioned. they have no concept of Human rights, although they might offer some \*charity for the poor, unless they still consider it a disease. At that time, slavery was still legal in some of the colonial states and the British continued to use Coolies afterward. That's barely better than a slave or the Russian serfs. Furthermore, the Victorian Era started with the Crowning of Queen Victoria in 1836.
I should also add that the industrial revolution started to really kick off around 1820, even in the most developed countries. The first factories and railroads. I based my answer more closely to the level of industrialization around 1850-1870 (rail network) since the level of tech of 1810 is probably less advanced than in your description. But it's ok since it's steampunk.
[Answer]
Disclaimer: I mostly agree with Vincent's and Brythan's answers, but wanted to added my own twist/considerations to Brythan's thoughts.
Too many taxes.
First, your state nearly does not provide any service other than the government, the army and (very little) police. Administration is small, both due to the small size of the government and the low rate of literacy.
Most of your taxes are "modern" taxes that require quite some modern management to process.
Head tax? How do you ensure that everyone in the neighborhood has paid it? Most probably, you do not even know who lives there, or at which house, as there is no actual census nor identity documents. The same goes for the business tax.
Additionally, with most of the population barely surviving, either they won't have money to pay the head tax (and you cannot imprison 90% of your population) or it amounts to so little that it provides less than the cost of tax collectors.
Wedding tax is strange, since it gives the people an incentive just to don't wed. Ok, at first it would be uncommon and perhaps there will be social resistance, but those things change1.
Land rent and wealth tax are appliable, but only to things that are public and notorious. No sense taxing gold and pearls, since I can hide them deep in my dungeons and claim I have none. I cannot claim that I don't have my *palazzo* because it is in plain view from the street.
From the historical POV, governments of the age **loved** tariffs, because:
* It made easy identify who had the money: if you were importing a million of socks at a silver catty the unit, you had 1 million silver catties. It made easy to calculate the government's cut.
* The theory of the time was that the states had to hoard precious metals (mercantilism). When someone in your kingdom imports one million socks, a lot of silver gets out of your kingdom to pay those socks. And local sock-makers could get broke due to the foreign competence, leading to unemployment and social issues. Heavy taxation helped to make that class of business less profitable and less frequent.
Brythan's comment is also good. Either the government controls the issue of fiat money with an iron fist (that is, you cannot print 2 faux silver catties without holding 1 true silver catty in the Treasury/Central Bank), nobody will want the unbacked currency without a discount. Being in a position to chose, the government will ask for payment in currency backed by bullion.
UPDATE: Additionally, making "false" part of the denomination (the official name) of a coin sounds like very bad marketing (not to mention confusing; if I mint my own catties would those be "false faux catties"?). I would stick either to "paper [something]" (paper catties) or just create a different name for the denomination.
1 For example, in my country - Spain - for some income ranges the formula used for calculating taxes led to married couples paying sensibly more that those two people paying taxes each on its own. That lead to such a surge in "fake" divorces (people getting divorced for tax purposes while still living as a marriage) that finally the Government allowed married people to fill taxes individually if they wished to.
[Answer]
I don't have the historical background to answer the first question. To address your third question, I find it extremely unlikely that human rights would be an obstacle to anything in 1810. The question would be if it is fiscally feasible. I'll get back to that.
Most households in 1810 did not pay anything for food. They grew it, as most households would be farmers (roughly 90%). A substantial portion of the remainder would have been servants, who would get room and board from the houses where they worked. Then there's the military, who also get room and board. Of the remainder, a distinct portion would be considered well-to-do. So we're talking about a small portion (5%?) who could be considered laborers and make a "typical" working/middle class salary.
So to get back to the tax question, most people couldn't pay a head tax as they'd have no money. The farmers have no money because they are serfs working someone else's land. The laborers would have no money simply because they needed everything to get by. The servants and military would have a small amount of money. The well-to-do would pay most all of the taxes. So a head tax seems unlikely.
How would a wealth tax be assessed? Would tax collectors come into a household and search for jewelry? This seems unlikely during this period, as so few people would have sufficient money to pay it. A tax on houses seems more feasible.
You mention a business tax, which is not quite correct. There would actually need to be many business taxes. Blacksmiths and tailors would not pay the same tax. They couldn't, as their businesses would be quite different.
What we think of modernly as taxes wouldn't work in 1810, as banking was nowhere near advanced enough to support it. Our wealth sits in banks while our income is the movement of money from one bank to another. That makes it possible to audit taxation of our rather abstract concepts (wealth, income, etc.). In 1810, taxation was based more on real property (land and houses) or fees (travel, paperwork, etc.).
The biggest concern with the monetary system that you propose is the question of how it would get people to support it. Presumably taxes can be paid in faux money, but imports can't be purchased that way. That only works for us because we worked up to it slowly. It sounds like they're trying to mandate fiat money. The more likely result is an official exchange rate and an unofficial rate. The official rate is how much faux money you can get for gold, silver, or copper. The unofficial rate is how much gold, silver, and copper you can get for faux money. The unofficial rate is likely to be better. People will hoard metals and trade in faux money.
Under the circumstances described, it is likely that most will export their metal money to avoid confiscation. It is unclear how well the substitute will work in its absence.
Hoarding money causes deflation, not inflation. That's why you counteract it by devaluing the currency, which does cause inflation.
[Answer]
1. I'm a new comer here so I don't know what convention is but is that really fair of you to in essence ask us to do the math for you?
2. I would say the depends on the type of person your character is. It doesn't matter if he makes x amount a year or 1000x, if he's a miser he won't spend a lot, if he's careless with money he'll spend his last nickle before his bills are paid. You need to figure out what kind of characters you are dealing with. find out their personalities, habits, proclivities, etc.
3. Your taxation scheme is entirely feasible. Rulers did what they wanted to all the time, particularly to the poor. Violation of Human rights? Unless you were a wealthy, white, male, there wasn't great treatment of most people in society. No such thing as work safety, no public welfare, no 8 hour day, etc. Not to mention slavery still existed.
[Answer]
There is a helpful list of wages and costs for medieval england based on a [medieval sourcebook](http://web.archive.org/web/20110628231215/http://www.fordham.edu/halsall/source/medievalprices.html) compiled by Kenneth Hodges. Its not a perfect source but it is decent and well referenced at least and compares well with [other](http://www.medievalcoinage.com/prices/medievalprices.htm) similar attempts. The victorian era is more tricky because wages changed a lot during that period, usually only single documents like [this](http://www.victorianweb.org/economics/wages2.html) were comparable. Oddly you can find very good resources on this period in America because of government records. Thankfully there are some studies of victorian england costs I will discuss at the end.
In [medieval england](https://thehistoryofengland.co.uk/resource/medieval-prices-and-wages/) a gallon loaf ([~9lbs of bread](http://www.theoldfoodie.com/2012/08/a-gallon-of-bread.html), enough to feed one person for a week) costs about 0.75 Shilling, an unskilled laborer was paid between 40-80 shillings a year or roughly 1/6th to 1/4th of a shilling per day.
So your average laborer made between slightly more than what they needed to feed themselves, to twice what they needed to feed themselves. So it sounds like your prices and wages are reasonable. Assuming of course a "long loaf" is enough food for a day, they might even be on the upper end.
Farmers were not really paid, they grew the food they ate, and sold what they could. Even if they were paid most of their "pay: was not actually money so a wage is misleading. Many jobs had benefits besides wages, workers would be paid in goods as well. A swineherd looks like they are paid horribly but they also received food, housing, and trees for firewood. Similarly a victorian milkmaid seems to have a very low wage, but they you realize she likely also received food and housing at the very least.
**For the victorian period costs and wages** changed drastically] making it harder to get exact numbers but a [MIT study](http://piketty.pse.ens.fr/files/Gilboy1936.pdf) on prices and cost of living says:
`The average laborer spent 40 per cent of his total expenditure
for bread and flour, 20 per cent for animal
products, 9 per cent for sugar, tea, beer, etc.,
4 per cent for "groceries" (soap, candles, etc.),
I5 per cent for rent and fuel, and 8 per cent for
clothing`
**Based on this your costs look a little high but not impossibly so.** Again assuming of course a "long loaf" is enough food for a day. Also note prices will vary by region of course a city might have higher prices on bread but lower prices on cloth. The paper notes that the cost of bread fell towards the end so the later you set it technologically the cheaper bread should be.
] |
[Question]
[
**Closed**. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers.
---
**Want to improve this question?** Update the question so it focuses on one problem only by [editing this post](/posts/7261/edit).
Closed 9 years ago.
[Improve this question](/posts/7261/edit)
Here's the question:
What do you believe would be the social and cultural implications in a world that has floating landmasses (floating as in "floating in the air")? These "islands" float much like a boat does in open sea, moving at random (see note) (but with no possibility of flipping over itself).
What I would like your opinion is on each of these islands cultural traditions and political views would be, considering this weird feature...
These islands occur naturally, at both the surface of the planet and these islands are populated by intelligent beings. Also, I believe the randomness in its movements prevent the islands from being used as efficiently for military purposes such as dropping stuff on the surface.
The technology on the surface is steampunk-ish, there are flying airships, cities are huge and large government bodies exist. The people on the Islands try to live in a environment friendly way, since they can't extract resources from the Islands without severely reducing the habitable area they have. However, there are enough resources (food, water) on the Islands to sustain life. In regards to the weather, it varies with an island's geographical position.
Magic does exist in this world and can be wielded by anyone with the appropriate training, but you need to understand the underlying process to be able to use it correctly (that is, to magically heal a wound, you must understand the physiological process of healing).
Both the surface and the islands are populated by intelligent beings, but not exactly of the same race. Trade between civilisations is possible, and occurs rather frequently. There is a common organization to mediate politics between surface and the Islands, but there are sovereign states (Islands are like city-states, and the surface has "regular" kingdoms).
As a side note, this is a fantasy setting, so anything is possible. A source of inspiration for this is the Kingdom of Zeal from Chrono Trigger
(see e.g. [this fan art](http://lcaico.deviantart.com/art/zeal-212694939)).
Note: Just clarifying the random movement point, it was a bad choice of words. The movement would not be random, but it would be subjected to the direction of the winds, similar to a boat on sea.
[Answer]
They would block out sunlight below them. If they are of any noticeable size the risk of having your farmland get no light due to these islands would be a major concern. People would thus consider them hazards and concerns and avoid areas where landmasses regularly floated. Ideally they would move fast enough to not block any one area of light for any significant amount of time, but none the less no one is going to want to be below them.
It would be nearly impossible to get to these landmasses, until you have at a minimum hot air balloon level of technology, making it rather difficult to exploit or take advantage of them. If we assume there already are people on them perhaps they would build some equivalent of giant ladders, but either the islands are dangerously close to the ground, making them a hazard for any large towers or buildings, or they are so high up that climbing up and down ladders to get to the landmasses would be impossible for a normal human. Thus anyone on the landmasses would be mostly independent of the ground. Potentially multiple landmasses may interact, if they float close enough together and at speeds slow enough that build temporary bridges between them..
However, if these landmasses are small it would make it difficult for them to support living people. You need a certain minimum amount of land to support a breeding population without inbreeding. If landmasses 'collide' regularly enough to allow interchange of people between them that would help, but it seems unrealistic to expect these masses to come close enough to have regular travel between them be possible. This would mean living on the masses would be difficult. At the very least there would be heavy incentive to encourage your people to move, while bringing in new people, to combat inbreeding. Thus, with travel off of the landmasses being so hard, any opportunity to for transfer of people would need to be pounced on. Rather this is to another land mass or being close enough to a mountain to make it not be life-threatening dangerous to try to travel off of the lands. Ultimately though the small size, the high atmosphere (making it hard to breath), and major wind and weather concerns would make living on the landmasses quite difficult, most would prefer the ground unless the landmasses are *HUGE*.
Frankly I see them as nothing but an inconvenience until you have a more reliable means of travel. You would need airships of some sort, or equivalent magical transportation, to make these landmasses viable and useful. Travel and trade between them and the ground is mandatory. Of course once you have airships you have the question of rather someone would try to 'drive' your landmass, with either an airship or a gigantic land-sale, to control where it goes.
If you make magical transport from the landmasses to the ground immediately below it possible, but otherwise keep transportation limited to middle-ages level, I think you get a more interesting story. Then the landmasses are possible, though with a heavy need to trade with land below them, and to constantly have a flux of people in and out of the lands to avoid inbreeding. This would lead to nomadic sort of people, who trade with whoever they run into. They would have to be pretty friendly, they have no control over where they go and the people below them will always curse their blocking out the light, so it's important to be able to keep on the good side of those below. Unless, of course, they are the only ones who can do the magic-transportation to the ground thing. Then they can simply not go down near hostile peoples. They would, however, be at the whims of fate as to when they can trade. I imagine issues with stockpiling of supplies and risking the supplies you want running out because you haven't drifted anywhere that have people that will trade favorable with you.
[Answer]
Such islands, unless powered and controlled by a random number generator, could not move truly randomly on their own. As Henry Taylor says, their movement would be governed by the prevailing atmospheric winds.
However, the societies on these islands could be completely separated from the people below. They would be able to support some number of people depending on their size (see my answer to [this question](https://worldbuilding.stackexchange.com/questions/7155/how-big-should-be-a-terrarium-to-be-self-sustained) for a detailed estimation of the size required). In short, to support one person you need around 500 square metres of space (in terms of a rectangle, that's $\sqrt{500} \approx 22.5$ metres per side). You need the same amount of space again for every extra person. Therefore, an island one kilometre per side could support $1,000,000 \div 500 = 2000$ people. That's a reasonable number of people: such a society would have most of the services and social phenomena such as crime that we know today.
However, these islands could quite easily be weaponised. If a country wanted an island for its use as a nuclear base, they could quite easily take it, given their better resources and larger military. They could proceed to install jet propulsion systems, albeit on a much larger scale than those used in aircraft. This would, however, be very fuel costly, so there would need to be a good reason to bomb someone before they use it.
[Answer]
I doubt that they would move randomly. If the planet has high winds at the altitude of the islands, they might follow those winds, which might appear random over short periods of time, but would have prevailing trends. If the planet had no such winds, the islands would probably appear to follow courses counter to the planetary rotation as the fixed surface below them is dragged along while they stay relatively stationary.
The islands' cultural role would depend on their size, number and the scale of the governments under them.
If the government rules all the lands that the island might float over, then the island could serve as a center of power with great castles and towers; easily defensible and symbolically above their subject lands.
If more than one government rule the lands beneath the island, they would probably remain undeveloped since one ruler wouldn't want to invest resources in lands that would soon change hands to the next down-wind ruler.
If the islands were large enough with farm-able land and water, they might be separate nations, like gypsy caravans wandering above the fixed nations of the world.
[Answer]
One possibility to consider is that some of the islands may become colonized by the equivalent of viking raiding parties. They would have a walled village in the center of their island, and crops and suchlike on board. Lookouts at the edge keep an eye out for suitable targets.
Whenever their island drifts close enough to a target they all drop down from the island on ropes and go raid the target, hauling their loot back up to the island when they are done.
Even if only some islands have raiders on board this could make the appearance of an island be a cause of terror for anyone who sees it approaching.
The drifting would give them a constant source of new targets, while their own position would be very hard to attack.
One thing you don't seem to have considered though is collisions. What happens if two of these islands drift into each other?
] |
[Question]
[
I have been pondering on this for quite a while. With all the recent developments in the world, more and more people are driven from their homes and have to rely for a prolonged period of time on aid. Refugee camps have, on average, 12.000 'inhabitants'.
If someone with sufficient capital decided to buy up a piece of land and said to those people: 'Okay, I have a plan. I now have all this land. If you want, you can start over. You can build your houses, build a community, and I will provide the initial materials necessary to realise this (also using the environmental resources, for example, in central African areas there would be plenty of wood). The only thing I ask in return is 'some kind of tax'.
Taken that all regulations are taken care of, and that the people actually would be willing to do this, would it not be cheaper to set up a self-sufficient camp, instead of providing continual aid supplies?
I am not asking you to do all the maths for me, I am asking what the mayor factors I would have to take in to consideration to set this up and make it work. In other words, what would be the primary obstacles?
[Answer]
a self sufficient refuge camp is pretty much a city. It will have to provide it's own food, water, medical support, shelter, and most importantly logistical infrastructure to manage it. I'll focus on only on the most obvious issue, food.
The only way for a refugee camp to provide food is to grow it or hunt for it. The number of refugee's involved in your average camp is so large that hunting and foraging would be insufficient to feed them for long, you would kill all the game. Thus a self sufficient refugee camp is one that grows it's own food. Were talking about farm land, lots of farm land, and year or more from beginning to set up farm before your first crops can be harvested. Before you ask raising animals is actually less efficient then raising farmland. It makes sense on certain types of land where traditional crops don't grow well, but if you assume land that doesn't support traditional crops all of this becomes harder and a longer en devour.
In reality growing your own food isn't that easy. It takes, very roughly, one acre of land to produce enough to feed a single person (though refugees would likely be willing to survive on a little less). still were talking about 12,000 acres of farmed land, or about 18.5 square miles of fertile farmed land. Actually, that's how much farm land we need with modern technology and tools, the amount of land increases if you are doing this without modern technology and techniques used by first world farmers. The actual amount of land needed is MUCH larger then that, not all land can be farmed, some of the land would have to be devoted to housing, roads, and infrastructure, etc etc. in other words 18.5 is a extremely generous understatement of how much land would actually be needed. That's allot of land to find in the middle of a warzone or disaster area, and that's assuming all the land is fertile!!
There is also the effort and infrastructure required to get your refugees to learn how to farm land and distribute the results. Just teaching novices to farm land remotely efficiently would take at least 5-10 years. Really probably much more, but I'm being quite generous with these estimates to prove my point.
In short you would need a huge area and extensive time and organization just to address the issue of food. For the first 10 years you would still have to be shipping food to them while farms are built and farmers are trained. This is ignoring the *real* time consuming issue of infrastructure and logistics it takes to do something like this. Trying to organize a bunch of untrained and scared refuges to do something like this is an...astounding challenge I can't begin to estimate, but it's definitely a significant factor in all of this which shouldn't be ignored.
People don't live in refugee camps for years. These camps are designed to be quasi-temporary as people are moved out to other areas that can sustain them better. The camps may last for awhile, but only because new refugees keep showing up, even as old ones are moved on to more perminate locations. the refugee camps is the thing that exists while we figure out how to ship people to wherever they will be setting up a new city.
So the real question to ask is how hard is it to build a city from scratch, and then start shipping refugees there. During the original building of a city it's easier to *not* have all your refugees, more people means more logistics keeping them all alive and more overhead. Instead a select few with skills could be sent somewhere to start building, and slowly more immigrate in to the land as more farms and housing build up....it's a city being built.
And finally, of course, someone claims pretty much all fertile and livable land. Finding any land on the world large enough to support people is not easy. GETTING people there is not easy either, unless you happen to own the exact spot of land where refugees are congregating your need to set up transportation to get them there, and while their waiting to be transported your have...a refugee camp lol. these camps are only designed to last as long as it takes to figure out where to send refugees and how to get them there after all.
[Answer]
A self sufficient camp is alot easier with less people. if you had 50 or so it would be much easier to feed, it would be almost impossible to feed 12,000 people from the surrounding lands.
I think a semi-self sufficient camp would be a better approach, at least for 5-10 years while they build all the stuff that makes them self sufficient. provide them with food and basic shelter and they can go about building their own homes and preparing land for farming.
If you were going to make this self sufficient from the get go, You would have to build up, slowly add people to this camp so they can grow as required. I would think with 12,000 people dumped in a camp and told to work for housing you would have issues with crime and such, slowly building the community could help with these sort of issues.
[Answer]
Semi-permanent refugee camps already exist. [Palestinian refugees](http://en.wikipedia.org/wiki/Palestinian_refugee) are a good example; more than 60 years after they (or their ancestors) fled from what is now Israel, some of them are still technically living in "refugee camps". They have not spent all this time subsisting off Red Cross food parcels, and there is some economic activity in refugee settlements. The distinction between "refugee camp" and "impoverished ethnic minority suburb/town" is not entirely clear-cut.
Given enough time, refugee groups may fully integrate into the host society. An example is the [Huguenots](http://en.wikipedia.org/wiki/Huguenot#England), who fled from religious persecution in France after 1685. Approximately 50,000 of them went to England. At first they formed distinct communities, but by now their descendants are no different from any other English people.
[Answer]
In order to feed your 12000 refugees, you need land. Land for crops, land for animals to graze. To get that land, in most parts of the world, you need to displace the current residents who are already using that land. This creates more refugees....
[Answer]
In this day and age of transportation and technology, instead of being completely self sufficient (farms) I suggest setting up some sort of manufacturing plants to supply the majority of jobs (sell the products to buy the food needed). Plus schools (therefore need teachers and staff etc.) and medical clinic (Dr.s and nurses and staff etc.) and shops (clothes...food...furnishings etc.) Restaurants, police, politicians :oD, Banks, a local Barter System tied in to the nearby local economy as well as people knowledgeable in import/export... Construction workers for the infrastructure (we need this in the USA now).
The initial homes could be modest apartments with parks and playgrounds. This could be set up, not as a temporary cardboard city with subpar sewage and power, but a place for people to live and feel safe and raise their children etc.
] |
[Question]
[
Could it be possible that a large portion (80%+) of a gas giant has thin enough atmosphere that the ships don’t suffer from re-entry effects, but thick enough that conventional dogfighting tactics would work?
Bonus: if possible could jet engines be used in said atmosphere?
[Answer]
**No**
In order to be able to have a "conventional dogfight", the atmosphere must be thick enough that the control surfaces of the hypothetical fighter aerospace craft are able to interact with it. (Otherwise the fighter is in vacuum and can only change its vector by expending reaction mass, which is what you are presumably trying to avoid.)
The problem is, that as soon as there is enough atmosphere that it is possible to change direction by interacting with it using airfoils, there is more than enough atmosphere that re-entry will have occurred. If you look at [Earth's atmosphere](https://en.wikipedia.org/wiki/Reference_atmospheric_model#The_U.S._Standard_Atmosphere), by the time you have even 10% of the air density at sea level (meaning that, to a rough approximation, all maneuvers will require ten times more distance to complete than they would at sea level) you are well below an altitude of 20 km and have definitely undergone atmospheric re-entry.
To try to give an intuitive feel for this, imagine that a Q-wing space fighter above Uranus is being pursued by a R-wing fighter. (Hopefully neither of these letters have been trademarked by a certain space fantasy franchise.) The Q-wing wants to dive into the atmosphere so it can pull an [Immelman turn](https://en.wikipedia.org/wiki/Immelmann_turn), make a quick firing pass and fly in the opposite direction to escape, without expending vast amounts of reaction mass. The problem is that the escape velocity of Uranus is 21.3 km/s, almost twice that of Earth. Assuming that the pilot and fighter can withstand a sustained 10G maneuver and survive the re-entry (handwaved), it will take over half an hour to shed its "forward" momentum before it can start flying in the opposite direction - undoubtedly the longest Immelmann turn in history.
If you really want to have atmospheric dogfighting then you are better off with a very small planet with (somehow) a comparatively dense atmosphere. This reduces the re-entry velocity - which is basically the escape velocity - to a much more manageable number. However, there is still no way to avoid re-entry.
My personal suggestion would be to embrace the zero-G, no atmosphere conditions and use the type of maneuvers that the Star Furies in [Babylon 5](https://en.wikipedia.org/wiki/Babylon_5) used - take advantage of the absence of an atmosphere to pull stunts that are not possible in one. (I think it was the start of the season 2 final The Fall of Night where they are training in some of these.) Of course, both sides have to cooperate to have a low-relative-speed dogfight, it is generally more realistic to have a single high-speed firing pass followed by hours of changing vector before the next pass.
[Answer]
Only if you discard the `science-based` tag, ignore how large space is, how large gas giants are, and have "spaceflight" happening at speeds that seem to be a few hundred miles per hour. That's how space combat works in *Star Wars*, which seems to work a lot like WWII dogfighting.
Under assumptions like that, diving into a gas giant is rather like going into a cloud in WWI or WWII aerial combat: it lets you hide, and if your opponent follows you, you can have a tightly-turning fight justified by atmospheric control surfaces.
Depending on how the engines of your space fighters are claimed to work, you may well be able to claim you can use the atmosphere for propulsion. Nuclear-heated ramjets might well be more plausible than the rest of the scenario.
Taking this route means you aren't dealing with science fiction any more: you're doing fantasy with SF trappings, and could perfectly well swap out your spacecraft for winged horses. If that's satisfactory for your aims, go ahead.
] |
[Question]
[
This is Timmy. It’s a massive planetary eating monstrosity (don’t ask about Timmy), who likes to target inhabited planets. On this occasion, Timmy has chosen to feed on earth. What would the nutritional label of Earth be for Timmy? (Assume it eats earth in one sitting. Also assume he can fully process all the elements in earth for energy/nutritional needs)
Template (example, by all means make your own. I’m just copying an online one)
Calories:
Total Fat:
Cholestrol:
Sodium:
Total Carbohydrates (Dietary Fibre and Sugar)
Protein
Vitamins and other nutrients
[Answer]
>
> ignore the nutritional value of humans
>
>
>
The nutritional value of Earth is [to some extent humans.](https://www.pnas.org/doi/10.1073/pnas.1711842115)
[](https://i.stack.imgur.com/Ts6yE.png)
At a planet-eating scale, you only care about total carbon.
Total carbon is 2 billion tons from animals plus 540 from plants, microorganism, and others.
The caloric content of animals will be about 5 kcal/gram \* 2e9 tons = 5*1e6*2e9 = 1e16 = 10 quadrillion kcal.
Most plants and other lifeforms are not digestible, but if burned, they would add ~3.5 kcal/gram ~= 1.9 quintillion kcal total.
If Timmy needs heat, he'll absorb [Earth's internal heat budget](https://en.wikipedia.org/wiki/Earth%27s_internal_heat_budget), which is mostly nuclear heat being released over time.
[Answer]
If you assume that the 545.2 Gt (Pg) biomass shown [in @Therac's answer](https://worldbuilding.stackexchange.com/questions/244771/what-is-the-nutritional-value-of-earth/244778#244778) has about the same overall macronutrient breakdown as the human food supply: 27% carbs, 20% fat, and 10% protein, then we have:
* Carbohydrates: 147.2 Pg
* Fat: 109 Pg
* Protein: 54.5 Pg
The standard calorie-counting formula is 9 per gram of fat plus 4 per gram of carbohydrates and proteins. That works out to about 1.78×1018 (kilo)calories in total.
Mineral-wise, Earth is extremely rich in iron and nickel (in the core) and silicon (in the mantle and crust). But of these elements, only iron regularly occurs on nutrition labels, so I'll focus on that. [Wikipedia](https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Earth) says that iron is 32.1% of the planet's 5.97×1024 kg mass, which works out to 1.916×1024 kg.
The US FDA has a recommended daily value (DV) of 18 mg for iron, but that's based on a 2000-calorie diet. If you assume that Earth's 1.78×1018 (kilo)calories are a normal day's consumption for Timmy, then his DV for iron scales up to about 1.6×1010 kg. So Earth may have [way too much iron](https://www.healthline.com/nutrition/why-too-much-iron-is-harmful) for him.
[Answer]
# Mostly Fat
The nutritional info of something depends on who is eating it. For a human being, wood has zero calories. It is made of cellulose. Essentially a carbohydrate that is too complex for a nonspecialised herbivore to bother with.
If you eat sawdust you will gain no energy. Your poo will be full of sawdust. However, for a woodlouse or elephant, that block of wood gets broken down like you break down your daily bean ration, and the poo has whatever remains once the chemical bonds in the wood are broken to release energy.
For a nuclear reactor, the block of wood has $mc^2$ energy like any other mass. This is what you get by converting the mass to energy.
Timmy the planet-gobbling super entity does not care about cellulose. He cares only about the most nutrient-dense hydrocarbons beneath the planet surface. We're talking oil, coal, and natural gas. There is more energy available from fossil fuels in the crust, compared to the thin layer of organic matter on the surface.
Timmy gobbles up these hydrocarbons like you gobble up bacon grease. Yum yum yum. He eats all life forms as well, as a matter of course. But they just get crunched up and pooed out undigested.
] |
[Question]
[
Imagine an alien world populated by silicon based lifeforms, the mega fauna can only be animated by exposure to adequate lights from the star or the moon. This world concept is inspired by a automatronic killer giant doll in a mega hit Korean TV series, so I design all the creatures to only become animated when it receives sufficient energy from the electromagnetic radiation at specific threshold but I couldn't come up with a sound evolution driver that this mechanic can triumph over our familiar metabolic system where energy comes from food we ingested and excess is stored as fat. I am not sure why nature would prefer it this way over cat and mouse aka survival of the fittest where species evolve certain traits to aid them to eat others or to avoid being eaten, is my species doomed to extinction if they never adopt metabolic lifestyle?
[Answer]
Creatures that become alive only with enough sunlight basically describes any deciduous plant. When winter and its short and cloudy days come, being alive becomes a liability. Better wait for summer and its long sunny days.
Independently from being carbon or silicon based.
[Answer]
# Junk Yard Dogs:
Light is the basis of the food chain, whether it is chemically stored first or directly used. That would need to be some fairly intense light, or the organisms would move slowly in the dark and increasingly faster in the light. Usually, light is not a very dense form of energy in most places (but it could be - imagine organisms living on something like Mercury, although that brings it's own problems).
A biochemically-driven species on your planet would die, because the biochemical system depends on biochemical energy in it's food sources. There would simply be nothing to eat. Energy in your system isn't biochemical. It would be like a person trying to eat a car. But a car (even a solar-powered one) can move, and takes lots of energy to build, as do the parts that go into it. So parts form the basis of your food chain.
If animated species (read "herbivores") depended on difficult to manufacture/energetically costly components (like solar collectors) from passive species (read "plants"), then they would still be supplied by solar energy, but need to move so they could take advantage of resources. Species (read "predators") that obtained components from the richer, motive sources (the herbivores) would hunt.
Perhaps optical storage systems that store light and gradually absorb it slowly would give some species a competitive advantage. The "Waste" of the light in such a battery would actually be the absorbance of the energy over time. This way, a species could have a "light capacitor" that would prevent them from being immobilized the moment they went into a shadow (which suggests interesting hunting techniques...)
Mirrors would be extremely critical parts of species, so they could shelter in the dark or concentrate light onto absorptive surfaces while still obtaining energy. If the light is hot and intense, organisms may need to limit their exposure so components are not damaged by long-term overheating or radiation. Mirrors and reflective surfaces could be protective, as well.
So while energy is still the basis of the food chain, it comes from the increasingly predatory species operating with higher efficiency and sophistication due to the increasing concentration of quality components and taking advantage of the "lesser" species. The energy of "plants" is stored in components, not chemical batteries.
[Answer]
**Crystal radio creatures.**
[](https://i.stack.imgur.com/Oy0il.jpg)
<https://en.wikipedia.org/wiki/Crystal_radio>
>
> A crystal radio receiver, also called a crystal set, is a simple radio
> receiver, popular in the early days of radio. It uses only the power
> of the received radio signal to produce sound, needing no external
> power. It is named for its most important component, a crystal
> detector, originally made from a piece of crystalline mineral such as
> galena.[1](https://i.stack.imgur.com/Oy0il.jpg)
>
>
>
Your creatures live on a world where chemistry does not lend itself to oxidation / reduction types of life. But there is ample radio energy from their star. The creatures are in essence crystal radios. We oxidize reduced carbon and use the resulting energy to make electrical signals and contractions so that we might dance the merry jigs we dance. Crystal radios (and silicon carbide is an acceptable crystal for this) turn radio energy into electrical current. The depicted set produces enough energy from radio waves to power the headphones attached. I have seen a crystal radio that powered an LED. Your creatures use radio energy turned into electrical energy to power their activities.
There would, it seems to me, still be evolutionary benefit in being able to store energy so your crystal creatures could dance their merry jigs at night. It also seems to me there would be benefit in animals not needing to sleep so we could dance our merry jigs all night. Yet all animals sleep. So too your crystal beasts. They are up when the sun is up, jigging their crystal selves around with radio wave power. When the sun goes down they fall asleep.
[Answer]
You are basically describing plants, but with two twists:
* those beings move
* those beings don't store energy
Plants usually don't move, because it takes a huge amount of energy and sunlight doesn't provide a lot of energy density. So during the winter they turn on power save mode instead of migrating.
If your planet is exposed to intense sunlight (giving plants enough energy to move) and a very slow day/night cycle with super frosty nights, it might cause plants to move to keep tracking the sun. But then again, with these circumstances the current day side will probably be incredibly hot and will kill all living things there. So maybe the plants will chase the twilight zone of the planet?
Regarding the energy storage point: It would be a huge disadvantage for a creature not to be able to store energy, since walking into shadow would be equal to death. That's not really advantageous.
[Answer]
### A planet with a very long day/night cycle
Basically, this is a planet where each day or night is an entire season.
On Earth, it is normal for plants to shut down in the winter, which creates a chain reaction through the entire food chain - many animals either migrate, hibernate, or in the case of many insects simply die off and leave their eggs to re-awaken in the spring.
But plants and animals on Earth can't simply use the presence or absence of light to trigger these behavioral changes, since day and night still happen in both the summer and winter. They use a complex system of recognizing when the days are shortening and the temperature getting colder to determine when it is time to enter the winter-phase behavior. In addition, there are evergreen plants that can survive the cold, so some animals might still stay awake - food is more scarce in the winter, but not completely absent.
On a planet where day and night are essentially seasons, the difference between summer and winter would be even more extreme - there would be no "evergreens" adapted to resist the cold, because there's no sunlight anyway. During the night, all plants would hibernate or die, and all animals would need to do one or the other (unless they could migrate around the entire planet every cycle). For hibernators, the process could be triggered simply by the absence of light, because day and night *define* the "seasons", rather than merely being altered by them.
] |
[Question]
[
In this setting magpies and mammoths have been domesticated for hundreds of millennia, allowing them to become far more diligent and trainable than dogs by a wide margin.
The mammoths come in full sized and dwarf breeds, and the magpies similarly come in breeds from wild magpie up to raven sized.
Both these species have become smarter, but not dramatically so. They do *come off* as ***much*** more intelligent however, as they have very good memory, can learn huge numbers of words, and are all incredibly attentive to body language like [Clever Hans.](https://en.m.wikipedia.org/wiki/Clever_Hans)
The animals are also more dextrous than their wild counterparts when manipulating objects, but not up to a point that would require major physical changes.
For reference the magpies capacity for rote memorization is such that it has allowed the construction of an entire bird based internet. So many jobs that requires minimal intelligence and no manual dexterity will be replaced.
What I can't predict however is exactly which tasks are and aren't limited to humans by virtue of the required dexterity.
For instance mass manufacturing of some goods like pottery is *extremely* old, but I don't know how much finesse a pottery wheel requires.
**Given these mammoths and magpies physical and cognitive limitations, what physical labor would still be limited to people?**
Part of series with:
Just How Omnipresent Would Cheap Cross Laminated Spider Silk Be?
How much would this alien parasite increase crop yields?
How Big Can An Ancient Bird Powered Glider Get?
[Answer]
In this case, I am considering "the bronze age" to be the period from ~3200 BCE to ~1200 BCE. Note: The question is *not* which tasks they could perform, but which ones they *couldn't*. Here is a brief, but non-exhaustive list. I'll include some non-purely physical tasks, just for the sake of closer completionism.
* Potter (yes, a pottery wheel is *much* too fine of a craft for animals to master)
* Farmer (even mechanization hasn't replaced farmers, and it's considerably more advanced than domesticated animal labor)
* Smith (Silver, gold, bronze, copper, etc)
* Prostitute (*hopefully* not replaced by magpies or elephants, but up to you)
* Baker
* Brewer
* Priest
* Scribe
* Engineer
* Mason
* Quarryman
* Miner
* Weaver
* Tailor
* Doctor
* Tanner
* Cobbler
* Carpenter
* Driver
* Sailor
* Carter
* Merchant
* Money changer
* Musician
* Soldier
* Cartwright
* Cooper
* Lumberjack
* Barber
* Butcher
* Shipwright
* Fletcher
* Leatherworker
* Charcoal Burner
* Oarsman
[Answer]
**Mammoths:**
*Transportation:*
Hauling and transporting would be the obvious answers to this one. I'm assuming you've already considered that. If someone could keep them fed (no easy feat, there is debate on how much they would eat a day but people agree that it be a **lot**.). That food requirement might make smaller breeds of these creatures more practical for common use. For farms or transport of persons or goods, smaller breeds would be best and save the massive ones for large-scale hauling.
*Warfare:*
Mammoths could dominate on a Bronze Age battlefield. A mammoth that could be trained to plow straight into humans could turn the tide of a battle. Using them as pack animals for hauling an army's wagons would also be viable. Same for hauling/pushing siege weapons.
*Food:*
A mammoth packs a good amount of meat. As well as hide, fur, and ivory. Even milk if you're into that.
*Miscellaneous:*
It's believed that mammoths cleared away snow with their tusks to get at grass during the winter so a city would utilize a mammoth team to clear their streets when it snows. Training them to perform tricks for an audience also wouldn't be out of the question. There was a dog breed whose entire job was to run in a wheel to turn a meat spit over a fire, don't see why a mammoth trunk couldn't do the same. Same with other repetitive motions like fanning a forge.
**Magpies:**
*Messenger:*
Depending on the level of intelligence you want to allow they could be used to deliver messages. Repeating the message word for word. This could be even more useful if the birds could be trained to recognize individual people or uniforms.
*Search and retrieve:*
Magpies like shiny things, so do humans. They like food more. Training a magpie to search for food or other animals to hunt and bring them to the attention of their human handlers would be useful.
*Record keeping?*
The question mark on this one because it is up to your definition of "very good memory, can learn huge numbers of words". If I could train my bird to recount certain bits of information in response to different commands I certainly would. Especially if I didn't trust that information to be written down.
[Answer]
My two cents..
Your **magpies** could keep to their old profession: silver was a very precious metal. Magpies love to steal shiny objects, so you could train them to steal silver for you. Let them gather all the treasures hide in a secret place.. also, if you have 100,000 years, magpies will develop language along with humans. By conversation, they can help humans to structure their language. Magpies could become the first *messengers*.
The **mammoths**.. small ones will be employed to take care of the children and play with them. Small mammoths serve as intelligent pets, keeping an eye on the surroundings, and providing emotional support, like Earth dogs can do. They may be able to prepare a meal.
You could learn the big mammoths to help building settlements and fences around settlements, or to prepare land for agriculture. Digging, for water, or to find copper. Unlike the animals helping Earth bronze age people developing agriculture, these animals would be able to perform tasks autonomously, really freeing men of work.
[Answer]
All labor that required the use of small hand motions and opposable thumbs would still require human labor, as would everything involving literacy or supervising others labor.
The tasks animals can be used for, even extremely intelligent animals would be limited based off of their body plan and senses. For example, your mammoths would be excellent at hauling lumber, as Asian Elephants are used in that very task in modern Thailand, but you really couldn’t employ an elephant to bake a cake.
] |
[Question]
[
Rust and Cannonball are two very different worlds in most ways, with very different chemical environments and very different types of life\*--but they have one important feature in common: they have no large natural bodies of liquid on their surfaces, and native lifeforms don't require any environmental supplies of liquid to survive.
Approximate equivalents of plants and fungi do just fine in these environments--there is a clear path from single-celled organisms clinging to sand grains to colonies that spread over a wide area as cells divide, to truly multi-cellular sessile organisms whose cells grow and divide in an intentional, directed manner to form rhizome networks, and grow reproductive structures above the ground for spore/pollen/seed dispersal on the wind.
But what about animals? How do macroscopic mobile heterotrophs evolve when there is no sea to support their bodies in the early stages?
[\*] I don't expect it's particularly relevant to the question, but for the curious: Native Rust life is packed with deliquescent compounds that suck small amounts of water vapor out of the air to maintain a super-salty, but liquid, intracellular environment, with energy metabolism based around hydrogen peroxide as an oxidizer and hygroscopic agent. Native Cannonball life, on the other hand, absorbs iron from the soil and CO2 from the air to photosynthesize iron pentacarbonyl as an intracellular fluid and energy storage molecule, and decomposes various metal carbonyls to regenerate CO2 and release energy.
[Answer]
**A path of relative advantage**
What makes an "animal" in alien life? For this purpose, I'll say "something which eats other lifeforms, doesn't gather its own energy". The simplest way to do that is parasitism. I've sketched out one possible series of changes which could lead there, given the right ambient conditions, and *if* those mutations occurred.
---
So, let's start with a fungal spore. Now add a few more cells and an outer coating, to protect it from the equivalent of dehydration, maybe some reserve supplies in case nutrients require some deeper roots to extract.
What if seeds regularly land on occupied ground? It will be beneficial to survival to sink roots in anyway and start drinking nutrition, claimed or not. Especially if much of the world is covered in a mat of organisms, this will happen occasionally.
As the world becomes covered in vegetation, this "land on something else" becomes more and more certain. Some seeds develop hooks and barbs which snag in good spots. The hooks and barbs become sensitive, then reactive. That's still not a recipe for animal life as we know it, but we have multicellular braking. Now for mobility.
Day/night cycles may deform some of the hooks periodically. This can adapt into a crude form of push-along, to find the best spot to root. Once that exists, promoting it (then inducing it) biochemically is a smaller step than it was.
Now that we can move, we start shifting lifecycle to let us eat before fully rooting. And we start to keep extra storage on-board until it's time to set seed. Speaking of which, those winds are still around, it'd be nice to be able to re-root if we're hurled away.
Drat, we got too good at draining hosts, and they're turning necrotic where we eat. Some have started forming bark/cycts where we touch. Some of us have a "spreading" mutation, but others just let the wind throw them to the next host.
We're on that thrown-about branch, and those who can periodically stop catching the wind breed better. Especially if they do that when the smell of hosts is in the atmosphere. Of course, we spend our time around hosts, it'd be useful not to go too far if we don't have to. Short-hops and biochemically-cheap drilling-for-sap leave more energy for breeding. Being able to easily catch-and-release feels increasingly like muscle, and drilling like mouthparts.
What if we didn't need the wind, but spasmed our way around independently while it wasn't around? And moved from one host to another, if the first died? What if our seeds could plant themselves nearby - even adjacent - and drink the sap we *know* is there?
**At this point, we have something like an aphid.**
---
Epilogue: A new evolutionary pressure.
We've sucked most of the life around here dry ... but you're looking very energy-dense there. Hold still.
[Answer]
It starts with something resembling a [biofilm](https://en.wikipedia.org/wiki/Biofilm): unicellular organisms living together discover that there are some advantages in the number, and some evolve to be pluricellular goo.
>
> A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA. Because they have three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes".
>
>
>
[](https://i.stack.imgur.com/PYn4P.jpg)
From there some can start developing support structure, which can give rigidity and mobility, in the same way vegetal organisms have developed to be trees starting from grass and seaweed.
However for all of this to happen, there must be an advantage, meaning that for example also the autotroph should take the "big number" path.
[Answer]
The equivalent of animals develops from the equivalent of slime molds.
Dictyostelid cellular slime molds pull of the neat trick of being able to exist in both unicellular and multicellular modes. When food is plentiful, they exist as individual single-celled amoebae, which can move around on micro-scale surfaces by extending pseudopodia. However, when food becomes scarce, they aggregate into a multicellular *pseudoplasmodium*, which can be macroscopic in size (up to 4mm long) and moves in response to heat, light, and humidity in order to seek out a more suitable environment, engulfing bacteria and fungi along the way. Larger pseudoplasmodia are capable of moving more quickly, and with more efficiency in terms of slime production (due to lower surface to volume ratio); given a sufficient population in the absence of pre-existing animals, intraspecific competition for speed and resource efficiency, allowing some colonies to travel farther and faster to beat out others for access to new food sources, would thus produce evolutionary pressure towards larger sizes. The ancestor of all complex animal-analog life would thus be something like a minimally-differentiated slug with no distinct mouth, gut, or limbs, which feeds by engulfing its food and directly absorbing prey cells through the skin. Of course, there are a *lot* of potential means to make that more efficient, so it's not hard to imagine the analog of a Cambrian Explosion in diverse body plans developing from that sort of basic ancestor on many different worlds.
] |
[Question]
[
A character of mine gains certain abilities after a creature fuses with em as he dies. However, I don’t know of any supernatural creature that would do this or something similar which might explain the phenomenon in the story. I could make one up, but having it based on something would help me make decisions about the world around it and keep things related.
The story itself centers around disillusionment, and the abilities the character obtains is supposed to reflect a drastic psychological shift in the character.
Any creature or being that might bind to a person, react to/be affected by their psyche, and give them supernatural abilities is what I’m looking for.
For more context:
The story itself explores disillusionment.
The character is outcasted royalty (survived an insurrection against the royal family) whom is betrayed by es would-be lover and left to die in a mysterious wood.
This event, compounding on past events over the character’s lifetime, inspires a passion for vengeance in the character and a drastic psychological shift.
This shift results in the character’s yang and yin traits inverting, (essentially replacing each-other), reflected in how the supernatural abilities gained are based in fire, light, and rigid kinetic energy.
Additionally, the character’s body is warped somewhat thematically, as es hands— which used to tend gardens and write— rot away, and the only way for the character to sustain itself is through extracellular digestion (like fungi); e’s weakened substantially by darkness, cold and water (unless it's boiling hot); and es eyes glow among other aesthetic changes (sharp teeth, floaty hair, constant buzzing noise)
[Answer]
**Possessed by devils**
[Book of Mark, 5](https://www.biblegateway.com/passage/?search=Mark%205%3A1-20&version=KJV)
>
> 5 And they came over unto the other side of the sea, into the country
> of the Gadarenes.
>
>
> 2 And when he was come out of the ship, immediately there met him out
> of the tombs a man with an unclean spirit,
>
>
> 3 Who had his dwelling among the tombs; and no man could bind him, no,
> not with chains:
>
>
> 4 Because that he had been often bound with fetters and chains, and
> the chains had been plucked asunder by him, and the fetters broken in
> pieces: neither could any man tame him.
>
>
> 5 And always, night and day, he was in the mountains, and in the
> tombs, crying, and cutting himself with stones.
>
>
> 6 But when he saw Jesus afar off, he ran and worshipped him,
>
>
> 7 And cried with a loud voice, and said, What have I to do with thee,
> Jesus, thou Son of the most high God? I adjure thee by God, that thou
> torment me not.
>
>
> 8 For he said unto him, Come out of the man, thou unclean spirit.
>
>
> 9 And he asked him, What is thy name? And he answered, saying, **My name
> is Legion: for we are many**.
>
>
> 10 And he besought him much that he would not send them away out of
> the country.
>
>
> 11 Now there was there nigh unto the mountains a great herd of swine
> feeding.
>
>
> 12 And all the devils besought him, saying, Send us into the swine,
> that we may enter into them.
>
>
> 13 And forthwith Jesus gave them leave. And the unclean spirits went
> out, and entered into the swine: and the herd ran violently down a
> steep place into the sea, (they were about two thousand;) and were
> choked in the sea.
>
>
>
All that you are looking for. Unclean spirits get in this guy. He has super powers, and cannot be bound. He is tortured by the devils in him, crying and cutting himself. And when Jesus shows up, it is the devils that recognize and address Jesus, and plead with him.
It is what you describe: demonic possession. This is a compellingly weird passage and I think it lurks in the backs of the minds of anyone raised in the Christian tradition. The fact that the supernatural powers have a voice and worship Jesus and plead their case makes it extra creepy. They are
malign supernatural powers but they did not hate Jesus as we are accustomed to think such things must. And also creepy that Jesus actually respected their request - he did not send them out of the country but just out of the man.
If you are writing a story, opening with a biblical verse is a fine way to start. And "My name is Legion" is one of the most chilling verses there is.
[Answer]
**[The Alkonost](https://www.topinspired.com/mythical-birds/)**
This creature of Russian legend is said to be able to sooth all worries and remove all longing by its song:
>
> The Alkonost is a mythical creature with the head of a woman and the
> body of a bird. What makes it unique? The Alkonost sings the most
> enchanting melodies. Those who heard its song let go of everything
> they had ever known. They desire nothing more[...].
>
>
> Before Christian influence, many considered the Alkonost a wind
> spirit, able to summon up storms. This bird lays its eggs on the
> gently sloping seashore and moves them into the sea to hatch.
>
>
>
However, seeing as this just applies a psychic soothing balm, as soon as your character stops singing, their problems and troubles are still very much there.
[Answer]
>
> Additionally, the character’s body is warped somewhat thematically, as es hands— which used to tend gardens and write— rot away, and the only way for the character to sustain eself is through extracellular digestion (like fungi); e’s weakened substantially by darkness, cold and water (unless its boiling hot); and es eyes glow among other aesthetic changes (sharp teeth, floaty hair, constant buzzing noise)
>
>
>
This could be one of a number of parasites. There are a lot of [behaviour-altering parasites](https://en.wikipedia.org/wiki/Behavior-altering_parasite). [Ophiocordyceps unilateralis](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis) is a fungus that alters the behaviour of ants, making them move to locations with specific temperature and humidity (though the fungus likes high humidity).
You could even use a [hyperparasite](https://en.wikipedia.org/wiki/Hyperparasite), where a fungus infects insects, and those insects infect the character. Some of the changes you want can be due to the fungus, and some to the insects. Maybe the insects are drawn out of the body by water, but the fungus wants to stay in the body, so it makes the person avoid water. The fungus could [glow](https://en.wikipedia.org/wiki/List_of_bioluminescent_fungus_species), and the backlight in the eyes makes the person's vision weaker, so e avoids the dark. The insects make the buzzing sound. The fungus does the extracellular digestion and rots the hands. The whole systems messes up the person's body, so their gums recede and teeth get brittle and chip sharp, and their hair gets thin so it stands up more easily - e gets a lot of static since e stays in hot dry areas.
Since the story is about disillusionment, the character might have to agree to let the fungus take over to prevent the insects from just eating em.
] |
[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.
**This question already has answers here**:
[Universal calendar creation for intergalactic empire [duplicate]](/questions/154482/universal-calendar-creation-for-intergalactic-empire)
(7 answers)
Closed 2 years ago.
I have some ideas for how to synchronize a galactic time system given the constraints of modern physics. However, my understanding of relativity is pretty limited so I was hoping for feedback or corrections if what I'm suggesting doesn't work, or if there are better ways of doing it. Thanks!
**The Setting/Problem**
In my setting, there is an established galactic community, but it is constrained by the limits of currently-understood physics. This means that travel between solar systems takes dozens of years for close ones, and requires massive nuclear-propelled starships to send even a small payload. The result of this is that almost all galactic trade, interaction, and commerce is digital, with comm-buoys set up orbiting most stars to relay messages between empires. Transmitting a message across the galaxy will still take 100,000 years, but this is far faster/cheaper than conventional travel.
Under this system, most everyday timekeeping is kept local (planet rotations, etc), due to relativity making time pass at different speeds in different places. But, there is a desire to have some sort of standard that people can share & convert from. So someone can say "the war lasted 10 [GALACTIC TIME UNITS]", and we can convert it to earth years ourselves.
**My solution:**
Here is the system I came up with:
1. For most everyday people, the time-units they deal with are entirely local to their setting, so people on Earth still use seconds, days, years, etc.
2. People on ships traveling at relativistic speeds will use the time system of their birth world, but will localize it and count up using onboard clocks from the moment their ship was first commissioned (with that being their Year 0). Ships will also manage a local day-night cycle like the planet their species first evolved on. This lets people get on with their everyday lives without having to think about it.
3. For scientific measurements, there is a galactic unit of time based off the half-life of a known atom. This should be the same anywhere (right?), albeit relative to the speed at which time is passing in that place. So a scientist can describe an experiment in these units, but it's not useful for knowing how long ago for you the Glubglub War ended since time on Glubglug passes differently.
**The Hard Part:**
4. The tricky part comes in when syncing up a common understanding of the passage of time. What I want is for the galaxy to have determined one singular "location" where time passes canonically, and everyone else converts to/from that for their local needs. This way you can say "this happened at 147 Galactic Standard Time" and everyone immediately knows that that means. The problem is, what to synchronize off of, and is said synchronization possible? There is a good answer [here](https://worldbuilding.stackexchange.com/questions/185852/how-to-calculate-the-time-on-planet-b-for-an-event-that-happened-on-planet-a), which is similar to the above, but is skirts around that issue.
One idea I had was to have everyone synchronize themselves off a commonly observable stellar phenomenon. Galactic rotation seems too slow and imprecise, but if we can theoretically measure it with any kind of precision it would be perfect. (It's probably OK for local clocks to "drift" a bit, as long as they can eventually resynchronize so the error doesn't compound).
Is there some star or black hole in our galaxy that sends out a burst of light or radiation at set times which everyone can observe and measure? If so then it would be perfect as everyone can just check their clocks against said star.
Another idea is to have one of the founding members of this Galactic Community just set their home planet as Galactic Standard Time, and make it's gravity/relativistic time speed known to everyone. This means that once someone knows how fast time is passing at said planet, they can convert it to their local time. The problem here is everyone needs to maintain 2 clocks, one for their local time, and one that tries to track the time on a planet where time passes at a different speed. The question then becomes, do you always know how fast time is passing for you, to allow for said conversion?
Finally, is there some other system I'm not thinking of which would do the trick?
Thanks, I appreciate the help/input!
[Answer]
It's a great question, and I think the answer is no - you wouldn't be able to synchronize based on an event like that because of the precision required in determining when it happened. The issue actually comes down to determining *where* that event occurred.
Let's say civilizations on planet A and planet B try to synchronize based on a supernova, which occurs at a time $\tau$ and lies a distance $d\_A$ from planet A and a distance $d\_B$ from planet B. They observe the supernova at times $t\_A$ and $t\_B$, respectively. Light takes a finite time to propagate through space, and so - not accounting for any delays because of travel through the interstellar medium - civilization A knows that the supernova occurred at $\tau=t\_A-d\_Ac$, and civilization B knows that the supernova occurred at $\tau=t\_B-d\_Bc$. Therefore, civilization A can calculate $\tau$ if they know $d\_A$, and likewise for civilization B. They can then synchronize their clocks, right?
Here's the issue: This assumes that the distances are known to the requisite precision. In reality, this is quite difficult to do. [The Uncertainties of distance measurements to stars are often in the range of ~10-20%](https://ned.ipac.caltech.edu/level5/Jacoby/Jacoby1.html). Given that the supernova is (ideally!) hundreds of light-years away from both planets at the minimum, the civilizations may have measurement errors on the order of 10-20 light-years, meaning their clocks could be off from one another by 20-40 years. That's not great!
As an example, [we don't have the distance to Betelgeuse - a luminous, important star - pinned down very well](https://astronomy.stackexchange.com/q/36365/2153), with errors in the area of 25% or more in some cases (see e.g. [Harper et al. 2008](https://iopscience.iop.org/article/10.1088/0004-6256/135/4/1430)). The thing that's even more striking is that Betelgeuse can be observed continuously, and has been for decades - and yet, for various reasons, we still can't determine its location to a high precision. A one-off event like a supernova really doesn't given you the option of having more measurements, because the remnant is likely dim and difficult to observe at any wavelength.
A true galactic civilization, of course, will have to deal with a galaxy roughly 100,000 light-years across. This means that we're dealing with distance likely of several tens of thousands of light-years. Sure, technology has likely gotten much better than ours (and I very much envy those astronomers), but to have initial synchronization errors on the order of a year, you'd need distance measurements accurate to 0.01%, and that seems quite difficult. For example, say the event occurred near the center of the Milky Way. We don't even know that distance well; it's around 25,000 light-years, but many of the measurement errors are around 1,000 light-years ([Malkin 2013](https://arxiv.org/abs/1301.7011))!
You could also ask about whether time dilation will be an issue, due to both the gravitational field of the Milky Way and the motion of stars within it. We can do those calculations, and determine that the fractional difference in time between the inner regions and an observer at infinity is [$\Delta=7\times10^{-6}$ due to gravity](https://physics.stackexchange.com/a/161482/56299) and the difference between an observer orbiting with the Sun and an observer at infinity [$3\times10^{-7}$ due to special relativity](https://physics.stackexchange.com/a/158977/56299)$^{\dagger}$. Those are both at least 5 orders of magnitude lower than the discrepancies we'd be looking at due to measurement uncertainties - and they wouldn't change substantially if we compared any two star systems.
---
$^{\dagger}$Time dilation due to a potential difference $\Delta\Phi$ can be written as
$$\Delta t\_r=\Delta t\_{\infty}\sqrt{1-\frac{2\Delta\Phi}{c^2}}$$
for bodies at radii $r$ and $\infty$. From special relativity, we get that a star moving at a speed $v$ experiences
$$\Delta t\_v=\Delta t\_{\infty}\sqrt{1-v^2/c^2}$$
For a typical galactic potential and a stellar speed typical of the Sun, you can check that you get the results I listed above.
[Answer]
First I agree with the points made that this time synchronization would not be very important in a galactic "civilization" with such limited interaction. Also that time dilation would have a slight but not huge affect on planets in different solar systems because they're all in similar gravitational fields and all moving at far less than 1% the speed of light relative to each other.
Rather than half life of an element I would look to the oscillation period of a neutral hydrogen atom. The [Hydrogen Line](https://en.wikipedia.org/wiki/Hydrogen_line). This is what NASA used on the [Golden Record](https://en.wikipedia.org/wiki/Voyager_Golden_Record) on the Voyager Probe to indicate a recognizable unit of time to any aliens that might intercept it.
The easiest way to keep time between worlds would be to put [atomic clocks](https://en.wikipedia.org/wiki/Atomic_clock) on all the starships to keep time from the time they leave earth. These remain accurate to within one second after running for 300,000 years. However, assuming these starships travel at any notable fraction of the speed of light (anywhere near 1% or more) you'll worry about time dilation. If it was my galactic empire I would come up with some technology to receive the radio signal from some [quasar](https://en.wikipedia.org/wiki/Quasar), presumably the one with the strongest signal on average across the Milky Way. Quasars aren't found in the Milky Way but they would be detectable throughout it. Everyone would receive the same radio pulses from the same quasar but, for instance, if you were traveling at 10% the speed of light on a starship, you would observe the frequency to be lower than would observers living on a planet. Maybe time 0 is the time the first starship left earth and you count galactic time by the number of oscillations of the radio frequency of the selected pulsar since then.
This would be different periods of perceived time to different people and planets, but it would be a reliable galactic standard. This would be useful for galactic historical records like you mentioned but of course it wouldn't be relevant to the average citizen or even scientist on any given planet. More for record keeping and communications protocols than anything else I would think.
Also should be noted that there are other bodies in space that give off frequencies in the radio spectrum any many others. But, my understanding is that quasars are very powerful and would be reliable for this purpose. Google tells me that they tend to last 100-1000 million years. On some timelines it could take around this long for us to actually populate the galaxy but I would also think that that's plenty of time for us to come up with an artificial radio pulse powerful enough for everyone in the galaxy to pick up on. Once that is constructed the galaxy could be instructed to switch to this artificial frequency after some determined (upcoming) oscillation number of the pulsar. Alternatively, there may be another type of body with similar useful properties that also lives longer. It guess it all depends on how long it's been since first launch in your world.
P.S. If you haven't seen Sharkee's video on how we could feasibly populate the galaxy with reasonable limits like these you should check it out [here](https://www.youtube.com/watch?v=3WtgmT5CYU8). One of my all time favorite YouTube videos.
Edit: if you picked a quasar that is "off to the side" of the milky way, the close side would receive the pulse 52000 years before the far side. If you chose a quasar that is "above" the disk galaxy, then everyone would receive the pulse at closer to the same time in a sort of radio wall passing through the whole galaxy at once. Alternatively, if you picked an off to the side one, the receivers could just account for the difference because it would be well known where they are in relation to the rest of the galaxy and the pulsar.
[Answer]
Frame Challenge:
If you are limited to light speed transmission you aren't going to have a 'galactic civilization', you might have clusters of star systems in (very slow) communication but they are each going to use time systems that make sense to them. Most likely the time system of the source system of the local diaspora.
The point is, what possible information could civilization A on one far end of the Milky Way have to say that would be of any interest to civilization B 100k LY away (other than perhaps 'we were here'), but that doesn't require any sort of agreed-upon system of time units).
[Answer]
There's not really going to be a huge difference in times between solar systems within the galaxy; the galactic gravitational field is not *that* strong, and relative velocities between stars are only of the order of hundreds of km/s, which won't produce vast time dilation effects. Keeping clocks synchronized to the millisecond will be hard, but keeping them synchronized to within a few seconds should be do-able.
This is in some sense a vastly scaled up version of the problems encountered in timekeeping even here on Earth. The consensus seems to be to use a standard reference ellipsoid (the world geodesic system) and synchronize clocks to this, adjusting clock rates for local conditions like height. There's a lot of finicky calculations to do this: modern atomic clocks are in fact sensitive enough to detect differences in the passage of time due to height differences of less than a meter, so even here on Earth relativity must be taken into account.
I would imagine that your galactic civilization could come up with some similar "standard" galactic reference surface (perhaps a disk or sphere centered at some point near the center of the galaxy). Correcting local time to match the notional standard time will be harder than it is on Earth, since broadcasting time will be *slow*. But everyone could use a set of reference pulsars as a starting point.
EDIT: in order to fulfil the "hard science" requirement: the formula for time dilation due to relative velocity $v$ is $t' = t \* sqrt(1-(v^2)/(c^2))$. Gravitational time dilation is proportional to the gravitational potential, and in fact is equal to the relativistic time dilation of the escape velocity from the potential; escape velocity from the galaxy is about 550 km/s, so this gives an upper bound of 53 seconds per year for gravitational time dilation within the Milky Way. Relative velocities of stars within the Milky Way are clearly less than the escape velocity, so special relativistic (non-gravitational) time dilation will be less than this.
A good reference for time keeping in the GPS, which discusses some of the subtleties, is [Relativity in the Global Positioning System](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5253894/)
] |
[Question]
[
Earth has animals that have a photoreceptor in the near UV that obviously provides them some sort of benefit. (Given how biological material often glows under UV this might be of hunting benefit.)
Earth also has animals that have infrared sensitivity, although my impression is that it isn't in the eye.
I'm curious how far this can **usefully** be extended (Superman's x-ray vision can't work, there's no meaningful source of x-rays), both from a biological standpoint and from a standpoint of frequencies that would convey useful information. Things like the cornea not passing UV isn't relevant--that's a biological flaw, not an actual limit. I cited two examples showing that there is both the biological possibility and useful information to be gained beyond both ends of what we can sense--although whether the near IR is biologically possible for a warm-blooded creature isn't established. How far does this extend?
[Answer]
For visual wavelength
[](https://i.stack.imgur.com/Jktwl.png)
* Transmittance through the human cornea as a function of wavelength. [Source](https://www.sciencedirect.com/science/article/pii/S1350946215000488)
A bit of closer look at UV bands
[](https://i.stack.imgur.com/WiiSw.png)
* Ultraviolet action spectra. (Cullen, 2002). These are spectra of for threshold ultraviolet damage to the corneal epithelium for different species as derived by different researchers. Note the similarity and overlap of the curves. The green curve is for damage to human conjunctival epithelium. UV-A is far less hazardous to the cornea than UV-B and UV-C. (Figure created by Ms. Erin Chaney, US Army Center for Health Promotion and Preventive Medicine. Aberdeen Proving Ground, MD 21010-5433 USA.) [Source](http://photobiology.info/Cullen.html)
Sooo, how wide is more or less from 320nm to 2000nm something, and is defined by transparency of mammal cornea.
U can put hundreds of pigments in there and have unprecidented view of everything, rainbow included, and next bottleneck are the brains I guess.
As for xray and shtuf, no idea.
[Answer]
To complement [MolBorg's answer](https://worldbuilding.stackexchange.com/a/202967/30492), you also need to take into account the transmission coefficient of the medium standing between the eye and the seen object, in most cases the atmosphere.
[This](https://www.slideserve.com/ceri/atmospheric-transmission) is the transmission coefficient of the atmosphere
[](https://i.stack.imgur.com/HeNDO.jpg)
As you can see we human have somehow already managed to extend our spectral sensitivity in the spectral windows where the atmosphere is transparent.
In general it's pointless to develop a sensitivity for a frequency to which the medium is opaque (again, that's why we send x-ray telescopes into space).
[Answer]
There is actually a rare condition called **Tetrachromacy** caused by a mutation of genes in the retina that let a small number of people see into the UV spectrum. Attached is a link to a BBC article about one such person.
[BBC -Tetrachromacy](https://www.bbc.com/future/article/20140905-the-women-with-super-human-vision)
As to your question about how *useful* this would be the answer really depends on your point of view. According the the article the main effect is that the people concerned see a large range of colors in objects that normally don't appear to be very colorful to people with normal vision.
This is because the objects concerned don't reflect much color in the normal spectrum but do in the UV. An example given in the article was a gray/dull colored pebble pathway that to the person with Tetrachromacy sparked like multi-colored jewels.
So the chief advantage would I guess be that you would see more color/beauty in the mundane world. Which I would argue falls under the heading of '*Nice to have*' rather than *Useful to have*. This would also explain BTW why the mutation is not more common, it doesn't bestow any particular evolutionary advantage to a carrier of the mutation but at the same time it doesn't seem to be disadvantageous either so there's no real evolutionary pressure selecting for or against it - at least in humans.
On a societal level I think it would be a 'cool' (good adaptation) because the world would be more beautiful/colorful for everyone but that seems to be about the limit of its impact.
Lastly as a frame challenge - I would suggest mutations/adaptations to the eye that gave us better night or distance vision would be more useful than one making different spectrum of light 'visible'. That said seeming into the IR range would be difficult. As I understand it the size of the human iris would have to increase considerably in order to capture enough IR photons to be useful. (Someone can correct me if I wrong on that last bit!)
] |
[Question]
[
I want a planet with roughly the same mass and volume of earth to have tides on a much larger scale than earth, enough that the coast would be extended for at least several hundred feet at low tide in many places. I don't mind if the frequency of the tides is altered along with it. It would also be very convenient if I could do this without significant change to the day/night cycle. I'm afraid that I have practically no knowledge on the matter, so I apologize if I'm wasting your time. Initially, I was thinking of just making the moon larger and closer than earth's, but I'm not sure if that would be enough to change the tides that much without complications like tidal locking. To summarize:
**Criteria**
* Much larger tides
**Constraints**
* Planet must remain habitable
* No significant change to the day/night cycle
Is this possible? If so, how? (If this could be answered in layman's terms, that would be appreciated)
[Answer]
Short Answer:
The problem with a human habitable planet having very large tides is that astronomical parameters - including those responsible for tides - change very slowly but steadily with time, and a lot of time is necessary for a planet to become habitable for humans, thus a planet which starts out with large tides might have very small tides by the time that it becomes habitable for humans.
And as L.Dutch - Reinstate Monica‚ô¶ said, if the moon is too large or too close, the planet may become tidally locked to the moon and thus no longer have moving tides but permanent tidal bulges on opposite sides of the planet.
Long answer in Eight Parts:
Part One: How High Can Tides on a Habitable Planet be?
You should look at *Habitable Planets for Man* Stephen H. Dole, 1964, which discusses planetary habitability for humans.
[https://www.rand.org/content/dam/rand/pubs/commercial\_books/2007/RAND\_CB179-1.pdf[1]](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf%5B1%5D)
Pages 61 to 63 discuss the necessary age for a planet to be habitable, outlining the various successive processes and stages which eventually resulted in Earth acquiring an atmosphere with a high oxygen content. And ends with:
>
> In general, it is probably safe to say that a planet must have existed for 2 or 3 billion years, under fairly steady conditions of solar radiation, before it has matured enough to be habitable.
>
>
>
The relationship between a planet and its satellite are discussed on pages 72 tp 75.
Dole discusses both the case of a habitable planet with a large satellite and a habitable "planet" which is actually the satellite of a giant planet many times as massive.
He notes that if a habitable planet has a companion moon or planet whch is massive and/or close enough, the tidal effects will slow down the rotation of the planet until the planet is tidally locked to the companion world.
Dole says that a planet tidally locked to a companion world can still be habitable, if the days are short enough that the variations in heat and cold between day and night are not too intense. Dole suggests that a day of 96 hours or four Earth days would be the more or less arbitrary maximum length for the day of a habitable planet tidally locked to its companion world.
The circumsteller habitable zone is the zone around a star there a planet can have temperatures suitable for liquid water, and thus possibly have life if other conditions are good. Dole uses the word "ecosphere" to describe the circumstellar habitable szone.
In the section about the suitable types of stars for habitable planets, Dole wrote that the lower mass stars would have "ecospheres" very close to them, and thus planets in those "ecospheres" would experience very strong tides, and so would soon become tidally locked to their stars. Thus one side of the planet would have eternal day, and the other side would have eternal night. Dole believed that would make a planet uninhabitable.
In the section on satellite relationships, Dole says that if a planet or moon becomes tidally locked to their companion planet or moon, they won't become tidally locked to their star, and thus they will have an alternation of day and night and could remain habitable.
>
> As we have seen, for stars at the low temperature end of the main sequence, there is an incompatibility between the tidal braking effect and the temperature requirements of a habitable planet. the lower limit of mass of stars that could have freely rotating planets withing an ecosphere was determined to be 0.72 solar mass. In this section we see a mechanism whereby the lower limit on stellar mass may be reduced still further. If a planet had a large, close satellite that maintained the planet's rotation rate so that the solar day was shorter than 96 hours, it could orbit within the ecosphere of a star less massive than 0.72 solar mass. However, a new limit would be reached when the tides on the lanet due to the primary reached a destructive level. If we assume that the destructive tide limit is 20 feet, the new limit on stellar mass would be 0.35 solar mass.
>
>
>
So Dole estimated - accurately or not - that tides of 20 feet would be incompatable with habitability for humans.
Part two: Comparison with Tides on Earth.
But what did Dole mean by tides?
>
> Earth tide (also known as solid Earth tide, crustal tide, body tide, bodily tide or land tide) is the displacement of the solid earth's surface caused by the gravity of the Moon and Sun. Its main component has meter-level amplitude at periods of about 12 hours and longer. The largest body tide constituents are semi-diurnal, but there are also significant diurnal, semi-annual, and fortnightly contributions. Though the gravitational force causing earth tides and ocean tides is the same, the responses are quite different.
>
>
>
[https://en.wikipedia.org/wiki/Earth\_tide#:~:text=Earth%20tide%20%28also%20known%20as%20solid%20Earth%20tide%2C,at%20periods%20of%20about%2012%20hours%20and%20longer.[2]](https://en.wikipedia.org/wiki/Earth_tide#:%7E:text=Earth%20tide%20%28also%20known%20as%20solid%20Earth%20tide%2C,at%20periods%20of%20about%2012%20hours%20and%20longer.%5B2%5D)
According to the table, the vertical component of semi-diurnal Earth tides is 384.83 milimeters or 1.2625 feet. So the highest vertical compnent of Earth tides when the different tides work together should probably be about one meter or 3.2808 feet.
Ocean tides in the open ocean have a similar range.
>
> The typical tidal range in the open ocean is about 0.6 metres (2 feet) (blue and green on the map on the right).
>
>
>
The range of tides on coastlines, where people notice them, can vary greatly.
>
> The tidal range has been classified[9] as:
>
>
> Micro-tidal, when the tidal range is lower than 2 metres.
>
>
>
>
> Meso-tidal, when the tidal range is between 2 metres and 4 metres.
>
>
>
>
> Macro-tidal, when the tidal range is higher than 4 metres.
>
>
>
So the micro-tidal range is less than about 6 feet, the meso-tidal range is about 6 to 13 feet, and the macro-tidal range is above about 13 feet.
>
> Closer to the coast, this range is much greater. Coastal tidal ranges vary globally and can differ anywhere from near zero to over 16 m (52 ft).[3](https://en.wikipedia.org/wiki/Mudflat) The exact range depends on the volume of water adjacent to the coast, and the geography of the basin the water sits in. Larger bodies of water have higher ranges, and the geography can act as a funnel amplifying or dispersing the tide.[4](https://en.wikipedia.org/wiki/Retrograde_and_prograde_motion#Natural_satellites_and_rings) The world's largest tidal range of 16.3 metres (53.5 feet) occurs in Bay of Fundy, Canada,[3](https://en.wikipedia.org/wiki/Tidal_range) a similar range is experienced at Ungava Bay also in Canada[6](https://historicalragbag.com/2020/06/22/king-john-his-treasure-and-the-wash/) and the United Kingdom regularly experiences tidal ranges up to 15 metres (49 feet) between England and Wales in the Severn Estuary.[7](https://www.nola.com/news/environment/article_aff2af21-e1fb-58ab-97e0-6874df798407.html)
>
>
>
[https://en.wikipedia.org/wiki/Tidal\_range[5]](https://en.wikipedia.org/wiki/Tidal_range%5B5%5D)
So did Dole mean that a habitable planet could not have a tidal range of more than 20 feet anywhere on the planet?
Obviously not, since he should have known, like many children, let alone many scientists, that there are a number of coasts on the habitable planet Earth which have tidal ranges greater than 20 feet or 6.096 meters. Tides of 20 feet or more do not make their coasts lifeless deserts, nor do they make the entire planet Earth lifeless and uninhabitable.
Perhaps Dole meant that the average mid ocean tide range on a habitable planet could not be more than 20 feet. Since that is about 10 times the height of typical mid ocean tide range, the maximum tidal ranges on various shores of a planet with 20 foot mid-ocean tides would vary from much less than 20 feet on shores which have very low tides, to ten times the meso-tidal range of 6 to 13 feet - 60 to 130 feet, to ten times the macro-tidal range of 13 to 53 feet - 130 to 530 feet.
So if Dole's limit of 20 foot tides means 20 foot mid ocean water tides, and if it is correct, and if the planet has various shores which amplify tides as much as some shores on the planet Earth do, then the higest tidal ranges in the shores with the highest tidal ranges could be up to about 530 feet.
Of course, it is possible that some planets could have configurations of land and sea which amplify the tides much more than any place on Earth does, and so some places could have much greater tidal ranges than the approximately 530 feet calculated.
Tidal flats or mud flats are flat areas which are covered and uncovered by the tides.
>
> Mudflats or mud flats, also known as tidal flats, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A recent global analysis suggested they are as extensive globally as mangroves. [1](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf) They are found in sheltered areas such as bays, bayous, lagoons, and estuaries; they are also seen in freshwater lakes and salty lakes (or inland seas) alike, wherein many rivers and creeks end.[2](https://en.wikipedia.org/wiki/Earth_tide#:%7E:text=Earth%20tide%20%28also%20known%20as%20solid%20Earth%20tide%2C,at%20periods%20of%20about%2012%20hours%20and%20longer.) Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and aquatic animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily.
>
>
>
[https://en.wikipedia.org/wiki/Mudflat[3]](https://en.wikipedia.org/wiki/Mudflat%5B3%5D)
If a tidal flat has a rise of one percent, it will rise one foot for every 100 horizotal feet. Thus a tidal flat with a rise of one percent will extend 10,000 feet or 1.89 miles horizontally for every hundred feet of tidal range. And I supect that many tidal flats are much more level than that.
---
Added 06-06-2021
I quote:
>
> In this earlier ice age, sea levels along the Gulf Coast were about 400 feet lower than they are today, and the Gulf shoreline was between 30 and 60 miles farther offshore than our modern beaches.
>
>
>
[https://www.nola.com/news/environment/article\_aff2af21-e1fb-58ab-97e0-6874df798407.html[7]](https://www.nola.com/news/environment/article_aff2af21-e1fb-58ab-97e0-6874df798407.html%5B7%5D)
So if about 400 vertical feet equals 30 to 60 horizontal miles, or 158,400 to 316,800 horizontal feet, there is an average rise of between about 396 to one and 792 to one. If a location where the shore is that flat has a tidal vertical range of 530 feet it could have a horizontal range between about 209,880 feet (39.75 miles) and about 419,760 feet (79.5 miles).
And possibly there are even flatter landscapes where a tide 530 feet high would travel much farther horizontally.
---
Thus it seems possible for a habitable planet to have a few large tidal flats where the tide goes out and comes back in much faster than a human can travel, even if the human doesn't get stuck in the mud. I note that on Earth, even in places with normal tidal ranges, people have often been caught by incoming tides and drowned. See the famous stories of the lost treasure of King John for example.
[https://historicalragbag.com/2020/06/22/king-john-his-treasure-and-the-wash/[6]](https://historicalragbag.com/2020/06/22/king-john-his-treasure-and-the-wash/%5B6%5D)
Part Three: The Evolution of the Orbits of Moons over Time.
But can a planet keep extremely high tides long enough to become habitable?
There are many natural satellites or moons in our solar system. Some of them are believed to be regular satellites, formed with the planets they orbit. Others are believed to have been captured by the planets millions of years after they formed.
All regular satellites have prograde orbits, orbiting their planets in the same directions as the planets rotate. Captured satellites can be captured in either prograde or retrograde orbits, which are orbits in the opposite direction to the rotation of the planet. The captured satellites in our solar system include ones with prograde orbits and ones with retrograde orbits.
If a prograde satellite orbits its planet at less than the synchronous orbital distance, tidal interactions will cause the satellite to slowly spiral closer and closer to the planet, and eventually that will result in the destruction of the satellite and probably the extermination of all life on the planet. A few moons in our solar system orbit below the synchronous orbits of their planets and are slowly approaching their planets.
If a prograde satellite orbits its planet at more than the goesynchronous orbital distance, tidal interactions will cause the satellite to slowly move away from the planet, so that after billions of years when the planet finally becomes habitable for humans the satellite will be orbiting many times farther away than at first, and the tides will be many times smaller than originally.
Retrograde satellites will spiral inward towards their planets.
>
> All retrograde satellites experience tidal deceleration to some degree. The only satellite in the Solar System for which this effect is non-negligible is Neptune's moon Triton. All the other retrograde satellites are on distant orbits and tidal forces between them and the planet are negligible.
> [https://en.wikipedia.org/wiki/Retrograde\_and\_prograde\_motion#Natural\_satellites\_and\_rings[4]](https://en.wikipedia.org/wiki/Retrograde_and_prograde_motion#Natural_satellites_and_rings%5B4%5D)
>
>
>
>
> Tidal interactions also cause Triton's orbit, which is already closer to Neptune than the Moon's is to Earth, to gradually decay further; predictions are that 3.6 billion years from now, Triton will pass within Neptune's Roche limit.[25] This will result in either a collision with Neptune's atmosphere or the breakup of Triton, forming a new ring system similar to that found around Saturn.[25]
>
>
>
Part Four: A Planet With a Retrograde Moon.
So if Triton has already been orbiting Neptune for billions of years, and still has another 3.6 billion years to approach closer and closer to Neptune before being destroyed, it shows that in some cases a captured retrograde satellite can get closer and closer to the planet for billions of years before the final disaster. Billions of years during which the planet could become habitable for humans.
So hypothetically an Earth like planet could capture a large moon in a retrograde orbit, and the the planet might endure for billions of years and become habitable for humans, before that retrograde moon crashes into the planet and turns the entire crust of the planet into molten red hot lava, destroying all life.
So maybe the planet in your story captured a large object into a retrograde orbit and that moon is now very close to the planet and about to cause a terrible disaster in a very short time by astronomical and geological standards,though perhaps in a very long time by human standards. In that case the tides produced by the moon would be almost as high as they will ever get.
Part Five: A Old Planet with a Recently Acquired Prograde Moon.
Or maybe the planet formed and developed for billions of years and became habitable for hamans, and then relatively "recently" on an astronomical time scale chanced to capture a large object into a prograde orbit.
If the newly acquired moon was in a prograde orbit just above the synchronous orbital distance, it would start to slow down the day of the planet and move outward from the planet, lessening the height of its tides on the planet. But if the capture was relatively recent on a cosmic time scale, the moon would not have moved far away and the tides would still be almost as strong as at first.
If the newly acquired moon was in a prograde orbit just below the synchronous orbital distance, it would slowly spiral down toard the planet and a terrible disaster which would wipe out all life on the planet. But if the capture was relatively recent on a cosmic time scale, the moon would not have moved much closer and the tides would still be only a little bit stronger than at the synchronous orbital distance.
Part Six: A Young PLanet Which Has been Terraformed While its Moon is Still Close.
Another possiiblity is that the planet cold be young and have a newly formed large moon whch is still very close to the planet, and an advanced ciivization has terraformed the planet to make it habitable.
Part Seven: A Habitable Exomoon Orbiting a Giant Exoplanet.
Or possibly your planet isn't a planet, but a giant, planet-sized, habitable, exomoon orbiting a giant exoplanet. Thus the planet would be tidally locked to the giant exoplanet. That would normally freeze the tidal bulges into two oppose sides of hte exomoon, one directly facting the planet and one directly facing away from the planet. But if the giant planet has other large moons orbiting it, their gravity will cause the moon to have tides which move over its surface as the relative positions of those moons change.
If you want the day of the tidally locked exommon to equal about one Earth day, the exomoon will have to orbit the exoplanet with a period of about one Earth day. And since the exomoon and exoplanet will also be orbiting the star of the system, the day-night cycle of the exommon will actually be somewhate longer than its orbital period around the exoplanet. See synodic day and sidereal day for an explanaton.
Assumming that the exoplanet is exactly like the planet Jupiter, an exomon with an orbital period exactly one Earth day long would orbit many thousands of kilometers beyond the orbit of Thebe, with a semi-major axis of 222,452 kilometers and aperod of 0.6778 days, and many thousands of kilometers inside the orbit of Io, with a semi-major axis of 421,70 kilometers and an orbital period of 1.7691 days.
It has been suggested that exomoons orbiting exoplanets at distances of 5 to 20 planetary radii can be habitable, if other factors are correct. The equitorial radius of Jupiter is 71,492 kilometers, so 5 to 20 planetary radii from Jupiter would be about 357,460 to 1,429,840 kilometers.
Part Eight: A Habitable Planet With Large Tides from Neighboring Planets.
The TRAPPIST-1 system has several planets orbiting in the circumstellar habitable zone of their star which are very close to their star and thus to each other.
>
> The orbits of the TRAPPIST-1 planetary system are very flat and compact. All seven of TRAPPIST-1's planets orbit much closer than Mercury orbits the Sun. Except for b, they orbit farther than the Galilean satellites do around Jupiter,[43] but closer than most of the other moons of Jupiter. The distance between the orbits of b and c is only 1.6 times the distance between the Earth and the Moon. The planets should appear prominently in each other's skies, in some cases appearing several times larger than the Moon appears from Earth.[42] A year on the closest planet passes in only 1.5 Earth days, while the seventh planet's year passes in only 18.8 days.[40][37]
>
>
>
Four of the planets orbit within the circumstellar hitable zone, TRAPPIST-1d, TRAPPIST-1e,TRAPPIST-1f, & TRAPPIST-1g. Since all of the planets have many times the mass of the Moon, and their closest distances are only few times the distance from the Earth to the Moon, any tides they might raise on any water on their surfaces would usually be several times as strong as the tides on Earth.
[Answer]
Tides primarily come from the moon, not the sun. Making higher tides without touching the day/night cycle is easy--move the moon closer. Like it used to be long ago.
The problem is with the first constraint. The thing is tides don't magically only move water. It's just the land is a lot more solid, it moves a lot less. Make the tides huge and the land movement matters, also.
Observe some of the moons of Jupiter--nasty things happen because of the tides. I don't know how far you can go while keeping a habitable planet.
[Answer]
I would be careful with doing the moon more massive: it would made higher tides during the transient, but those tides would on the other hand quickly tidally lock both bodies, leading to no tides, just a permanent bulge.
You might try with [local geographical features](https://tidesandcurrents.noaa.gov/faq2.html#26) to amplify the tide height
>
> The tidal range of a particular location is dependent less on it position north/south of the equator than on other physical factors in the area; topography, water depth, shoreline configuration, size of the ocean basin, and others. For example, let's consider the southern coast of Alaska and British Columbia. The configuration of this coastline is very similar to a funnel, with the narrow end at Cook Inlet. The tides travel as a "wave" across the oceans, and in many other respects act as a "wave"; this type of configuration tends to accentuate the "wave" at the narrow end of the funnel. This is part of the reason for the large tidal ranges, 30+ feet, in the area of Cook Inlet. If you look at the tidal ranges for stations on the Bering Sea, outside this funnel but at the same latitude, you will find a tidal range of 5-7 feet.
>
>
>
[Answer]
**Crowded sky.**
First - how does there come to be occasional very high and very low tides on Earth?
<https://oceanservice.noaa.gov/facts/springtide.html>
[](https://i.stack.imgur.com/lN0At.jpg)
The sun and moon either team up to pull on the ocean, or counteract each other.
On your world there are more bodies in the sky that affect tides. Maybe your world has 2 or more moons that line up, or a binary star. Maybe your world is the moon of a gas giant, and itself has a moon and sometimes the giant and the moon and the star all team up to make megatides.
As far as habitable, people who live in areas affected by the tide will not be caught by surprise. It will be pretty clear where high tide and low tide are and seafarers will make allowances.
Serious tides will also affect the crust and could produce quakes. Tidequakes will also be predictable. Tidequakes might augment the effects of plate tectonics on your world and those effects as regards earthquakes and possibly volcanism will be less predictable.
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.