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Obviously the greater a planet's gravity, the stronger the material of the space elevator's cable would need to be in order to support its own weight. However, doesn't greater rotation speed reduce an elevator's required length by increasing centrifugal force?
Absolutely massive super-Earths are probably out of the question with regard to space elevator construction (but correct me if I'm wrong!), but what about a planet of two Earth masses? According to [this planet calculator](http://www.transhuman.talktalk.net/iw/Geosync.htm) I found through Google, a planet of Earth's density but twice the mass would have 1.26 times the radius and 1.27 times Earth's surface gravity (I'd also love to be corrected here if this is wrong).
Forgive me for being unable to do the math myself, but given a surface gravity of 1.27*g*:
1. Would it even be possible for conceivable materials (such as carbon nanotubes or graphene ribbons or something else I've never heard of) to support a space elevator if the planet had an Earth-like ~24 or ~25 hour day?
2. If an elevator at such a rotation speed is in fact feasible, how long could the days be before a space elevator is impossible using conceivable materials?
3. If a shorter day is required to build a space elevator on such a planet, how short would the day need to be?
I'm not a physicist or chemist and admit I don't know the bounds of "conceivable materials". I don't want to use unobtainium.
In case it affects any answers, FYI my primary interest in asking this question regards a planet I'm trying to design that is the homeworld of an alien civilization, not humans, so "find a better candidate planet" isn't really an option for them. I'm pretty married to the planet's gravity, so I'm willing to accept the suggestion of discarding the whole space elevator idea if it turns out to be basically impossible to execute.
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It turns out that it doesn't matter all *that* much how fast a planet spins for the purpose of creating a space elevator, unless it spins significantly faster than Earth. Let's run through the calculations:
The critical point of a space elevator, stress-wise, is the point at geostationary orbit. Everything below this point effectively hangs down from it, and everything above this point pulls upwards. (this isn't quite accurate, since we want a bit more upward pull for stability, but it's true within some small factor of safety.) Based on this, we can compute the maximum strain experienced by the space elevator by integrating the weight of the hanging portion of the elevator from the ground up to the geosynchronous point. we start with the equation for acceleration due to gravity:
$$|g| = \frac{GM}{r^2}$$
We can use this to obtain $\frac{d \sigma}{dr}$ (derivative of stress against radial distance from the planet's center of gravity) by multiplying by $\frac{dm}{dr} = A \rho dr$ (our differential force) and then dividing by area, $A$, to get our differential stress equation:
$$\frac{d \sigma}{dr} = \frac{GM \rho}{r^2} dr$$
We then integrate this from $r\_0$, the radius of the planet, to $r\_1$, the radius of geosynchronous orbit, to get total stress at our maximum stress point. (Approximately. Our actual stress will be a bit higher.)
$$\sigma = \int\_{r\_0}^{r\_1} \frac{GMA \rho}{r^2} dr = \frac{GMA \rho}{r\_0} - \frac{GMA \rho}{r\_1}$$
For $r\_1 \gg r\_0$, we can effectively ignore the second term.
On Earth, $M = 5.97 \times 10^{24}$ and $r\_0 = 6.37 \times 10^6$. This yields, with $\rho = 1400 \text{ kg/m}^2$ for carbon nanotubes, a stress of 87.6 GPa, which is below the maximum stress for our nanotubes.
On your planet, this will equal about 139 GPa, which is within the realm of what's been proposed as the upper end for multi-walled carbon nanotubes (150 GPa, according to [this source.](http://www.sciencedirect.com/science/article/pii/S092150930101807X)).
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Since you've got these tags (science-based, reality-check, technology, physics), I leave you with this YT video, which pretty much decimates any possibility of a space elevator: <https://www.youtube.com/watch?v=iAXGUQ_ewcg>
On Earth...
* Just to lift *a thin film solar panel* (no lifter structure, motors, payload, friction or drag, **just the thin film panel**) would take a week.
* Lasers would be better, but not much:
+ Atmospheric distortion would reduce the efficiency to 0.25% (That's **not** 25%.)
+ That's the same as requiring a nuclear reactor for a single mid-sized office building building.
+ Adaptive optics would increase the efficiency to 2.5%. Like a nuclear reactor powering *10* mid-sized office building buildings. Still really bad.
+ When you add in the structure, motors, payload, friction and drag, we're talking a **stupendous** amount of energy.
* Carbon nanotubes are still in the small-scale laboratory scale, and have been there for quite some time.
Thing on your planet wouldn't be any better.
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I'm considering making a novel about something weird that really happened sort of: an island that was on every map of the world, but never really existed.
The real deal is called a Phantom Island, and the one that snagged my attention is called [Sandy Island of New Caledonia](http://en.wikipedia.org/wiki/Sandy_Island,_New_Caledonia "Wikipedia link"). **TL;DR version:** we thought it was there as it was on a lot of maps, it ended up in the OpenSource Global Coastline Vector, NASA used it to adjust focus on the satellite cameras, it ended up on Google Maps and everything else because it looked different, and someone eventually went there for research and... "Where'd the island go???"
Now for the novel, the theory is that it's some kind of time-travel research lab that got zapped to our time, and is hidden by tech that messes up any way to find it: to hide it from satellite cameras, it makes them look 30 miles south into open ocean; it messes up satellite phones and GPS, so no communication and you think you're far to far north; and some other things to mess up any tech from outside that wants in.
I'm still working on the plot, but does anyone have any ideas as to what sort of modern tech could possibly be developed to serve these roles in concealing the island? And have any other ideas? The idea is to make it make sense that nobody can find the island/laboratory, but people can leave there, and come back if they know what they're looking for. Its a time manipulation research lab from sometime in the future, stranded in today's world, so although I'd love it if we used "possible tech" that we are working on and may develop, it is a future-themed sci-fi so go nuts.
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Ok, so you have to decide: is your research lab from a different time? Or a different place? (i.e. are the limited to modern technology?)
The answer to that will affect where things go from here.
Things to think about:
To "hide" from satellites (without theoretical/impractical meta-materials), you either have to be covered in camouflage which looks so much like water that high-quality pictures can't distinguish it (hint: this is hard)... or you have to hack into the satellites and digitally edit their images before they're sent down.
To prevent people in ships/planes from strolling past, you may be on the right track with confusing their GPSs. This'll be hard to do without causing their GPS to just stop working because it's confused. (note: it's relatively easy to fake a signal... but if you can't suppress the other signals, you'll just have a GPS unit with confusing information, resulting in unspecified behavior). You could play with changing the transmission of error-corrections, but that's another can of worms.
Ships will probably be the easiest to change the course of because they're relatively slow so a very, very slow change in course might not be terribly perceptible. Aircraft, on the other hand, will be high enough that you'll have to send them REALLY far around you for them to not see you.
Which leads me to another thought: generate massive amounts of fog. If your island is ALWAYS covered in a huge cloud of fog, satellites, aircraft, and ships won't be able to see you... though some people might get curious about the unexplainable fog and send a research team to find out.
But here's my parting thought: hiding an island is hard; hiding something ON the island might not be nearly as hard.
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To make it look like water... why not cover it with water? So it's not an island but an underwater pocket that appears to be open-air to the inhabitants, but is a sunken dome on the outside.
Hide just the presence on the island: it appears wild because the lab and population is always elsewhen when someone looks. So why is it in our time at all? Need a good excuse.
How big is it? Maybe it's tiny and easier to overlook. Maybe it's bigger on the inside.
Where would it be? If its part of an archipelago it will already be overrun with humans. But among the thousands of islands and ilets in an island nation some of them are private, have no commercial value for development, or are nature preserves. A crag that is unsuitable for building on might be replaced with a fake cover and nobody notices.
If the island is isolated, in the middle of the open ocean, you have the problem of a huge mountain in the ocean that would be there. So is it confused with a sea mount that stops 30 feet from the surface? That ties in with the submerged idea.
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To add to iAdjunct's answer about GPS, GPS has an intentional signal degradation function known as [Selective Ability](http://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability) that adds a pseudorandom vector to the signal (spanning all satellites) so that a specific area has all of its GPS signals degraded by an equal amount, causing a fix to be wrong by approximately 100m. This will ensure all GPS satellites report the same wrong number, so the GPS receiver will not be confused.
If you are capable of hacking and modifying the GPS satellites, it is not impossible to make them set their Selective Availability vector to something like 50km (causing them to miss the island completely). Of course, this hack will have to ensure that the rest of the GPS fabric in the vicinity of the island is also gradually "warped", so that people don't notice it by the sheer 50-km discontinuity.
Another caveat would be the recent introduction of additional GNSS, such as Russia's Glonass, ESA's Galileo, and China's Beidou. All of these will have to be hacked to prevent multichannel GPS receivers from figuring out the hiding function.
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**Technical question warning !**
I'm trying to figure out the size of countries and continents but there is something I do not understand. The map I'm using was made with the equirectangular projection (its width is twice as large as its height). I converted the file with G projector into a mollweide projection (equal area) and now the image is an ellipse of **1660 by 830 pixels high**. At the equator, each pixel represent 24 km. Each pixel theoretically represent an area of 24 by 24 km or 576 km2.
I used the magic wand in photoshop and it tells me that the map is 1,082,100 pixels (borders excluded). With each pixel representing 576 km2, the total is over 623,000,000 km2. The problem is that my map is supposed to be as big as Earth. Earth is 510,000,000 km2, so it's 22% larger for no reason.
* What I am doing wrong?
* Should I use the % of area covered and then convert it in square
kilometers?
~~[Here's the map](http://www.cartographersguild.com/attachments/cooperative-worldbuilding-project-2/69014d1415658081-map-repository-untitled-map.png),~~
~~I'm not allowed to post it directly here since it's not CC.~~
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Huh... I just ran some numbers, and this is very interesting! (Note that in the below formulae, I'm using tau ($τ = 2π$) as the circle constant for convenience).
Let's say your world is a sphere with radius $R$. Then the surface area of that sphere is given by:
$$A\_S = 2τR^2$$
But now you have your ellipse. It's width is your planet's circumference: $w = τR$, and it's height is half that $h = τR/2$. Then the area of the ellipse in your map is given by:
$$A\_E = πab = \fracτ2 (\frac w2) (\frac h2) = \frac τ2 (\frac{τR}2) (\frac{τR}4) = \frac{τ^3}{16} R^2 $$
If we factor out the formula for the surface area of the sphere, we get:
$$A\_E = \frac{τ^2}{32} (2τR^2) = 1.2337 A\_S$$
which accounts for your 22% (with a bit of rounding error). But... I don't know why the formulas work like that!
The quick hack solution? Compute the area of your pixels as:
$$\text{area per pixel} = \frac{\text{desired total surface area}}{\text{number of pixels in ellipse}}$$.
**EDIT**: It bothered me that I couldn't figure out why these areas were different, and then I realized where the difference was coming from. If you physically stretched out each circle of fixed latitude into a straight line, their circumferences would be proportional to the cosine of the latitude, and the resulting map projection would be a [sinusoidal projection](http://en.wikipedia.org/wiki/Sinusoidal_projection). The extra increase in area is a result of stretching this sinusoidal shape into an ellipse. This is easily demonstrated by comparing the area of half the ellipse to that of half the sinusoid. If you have the ability to create a sinusoidal projection, you might consider using it, and seeing if the numbers make more sense.
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Mollweide is an equal area projection so each pixel reperesents the same area as every other pixel (ignoring rounding errors). However the pixels do not represent perfect squares on the surface so your initial attempt to figure out the area of each pixel from the width of the map is where you made a mistake.
The correct way to get an 'area per pixel' value for a Mollweide projection, or any other equal area projection is to divide the surface area by the number of pixel. If we assume the planet is a sphere of radius $R\_p$, and the image is $2h$ by $h$ and representing an ellipse with semimajor and semiminor axes $a=h$ and $b=\frac h2$ (Mollweide is always twice as wide as it is tall), and let $\tau=2\pi$ for convenience then
$$\frac{2\tau R\_p^2}{\frac{\tau}{2} ab}=\frac{4 R\_p^2}{h\cdot\frac{h}{2}}=\frac{16 R\_p^2}{wh}=\frac{16 R\_p^2}{2h\cdot h}=\frac{8 R\_p^2}{h^2}$$
With $R\_p=R\_ⴲ=6371\space\text{km}$ and $h=830$ then
$$\frac{8\cdot 6371^2}{830^2}=471.4\space{\text{km}^2}/{\text{px}}$$
And checking with your pixel count gives
$$471.4\text{ km}^2/\text{px} \cdot 1082100\text{ px}=510101940\text{ km}^2$$
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What one concept/ideology is most important in a group of people to encourage them to stop acting as individuals and begin acting in the interest of the whole settlement?
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There really isn't *one* concept that will work for all groups in all times.
It is highly dependent on the society/culture and the settlement age for example. There really is two concepts that are the root of all the others - internal motivation and extrinsic motivation. Pretty much all methods are rooted in fear or desire.
Some methods would be:
* Stringent punishment: This will obviously work much better in a fairly hierarchal society since otherwise punishment is much harder to effectively wield. Moral issues can be brought up by this to great effect.
* Exclusion from the benefits of the settlement unless they are helping the settlement. You can also use this for moral discussion.
* Capitalism: basically a communally created exclusion if there isn't output. Has all the risks and benefits of capitalism in the real world.
* Religious teaching/orders: In a highly religious society orders from religious elders are often akin to law or even greater than law.
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This is a tough one, among the reasons why is that nobody has really figured it out in the "real world."
At its most basic, the "usual" methods are:
1. Punishment to eradicate antisocial behavior.
2. Rewards to encourage prosocial behavior.
These punishments and rewards can be:
-physical (prison punishment or monetary reward)
-spiritual (hell or heaven)
-social (being shunned by neighbors or recognition by the community for work done)
Government, religion and neighborhood block associations are all largely built on these 2 concepts.
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Define what their collective enemy is. Every person places themselves into a myriad of different categories at different times to help identify themselves. Different situations require them to define themselves in these different ways. Examples:
* aliens invade earth (definition: human)
* Vikings invade Britain (definition: Saxon)
* Bandits raid village (definition: inhabitant)
If you live in a village in Saxon Britain you are all three of those definitions, but you don't define yourself as Saxon when aliens invade, and defining yourself as human when the Vikings come along won't do you much good because they're human too.
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I don't think there is really one idea above all others, but several ways to bind people together. The general idea is oneness, what binds this group together?
Typically it starts out with blood. Family sticks together. That is who you trust and who you work with. As people spread out and meet one another, other ideas emerge. Religion, nationalism, common cause to live/trade/grow/raid. As long as the group has a sense of identity on what makes them them and everyone else not them, then people will start to act in the best interests of the group. Typically following that there will be a written or implicit laws/bonds of honor that govern their interactions with each other. Just start by figuring out what brings them together and gives them a sense of shared identity.
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It should be noted that individualism isn't actually the natural state of a human being; it's one of many possible states of culture. The United States has a very individualist culture; we praise and value standing out from the group, being independent, moving away from your parent's home, sticking up for yourself, etc. Japan has a very collectivist culture-- a culture that values homogeneity, listening to your elders/betters/authority figures, multigenerational households, and avoiding conflict. Both forms of culture have both benefits and drawbacks. It might be worth researching various collectivist cultures from around the world to get a good grasp for how it looks in practice.
I'd suggest reading about the [key traits of both collectivism and individualism](http://psychology.wikia.com/wiki/Collectivist_and_individualist_cultures) and seeing a list of cultures that fall into various places along the collective/individual spectrum of values.
I wouldn't use it as my only source, but it's a good starting point.
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In this world there are humans have developed the technology to allow for interstellar travel, accomplished by light speed engines. However, this has created a problem. Is there any way for those who live on the vastly different planets can stay genetically similar to humans on Earth? Conditioning like people living on a freezing cold planet having a higher tolerance level against the cold is fine; but evolving to have less efficient muscles for more body heat wouldn't be allowed. Is there any way this idea can be implemented in this world?
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The only natural way to keep populations from genetic drifting is regular interbreeding. Fortunately, the mechanism for this would take hundreds of thousands of years before you'd diverge enough to cause breeding issues. For example, the peoples that made it across the Pacific by whatever route were separated from their Asian ancestors for at least 13,000 years, and maybe as much as 50,000.
There are a few known unnatural ways of doing it, but they all involve identifying an "ideal center" for genetics and testing a new child at some point in development. You can pick the point at which this occurs for optimal dystopic effects on your story.
Half of all pregnancies are currently non-viable and result in an immediate reset of the reproductive system. These are called "chemical pregnancies," and generally result in a slightly heavier than normal period. If you induce a virus that prevents divergent pregnancies from taking hold, you will keep your population within "human norm", but you run the risk of a population eventually becoming barren because their genetics has drifted up against one of the virus-imposed walls.
There are more than enough stories about cultures that test babies at birth and throw away the unwanted ones. Such high-tech barbarism might make for excellent drama. If the testing took place later, you could guarantee that there was a lot of cheating going on.
Alternately, you could require one in a thousand women to get knocked up by a traveling God King (or his near descendants) who was the epitome of ideal genetics. If these children were given favorable economic and social treatment, that would maintain a standard.
**Addendum:** In response to @JBH's comment, I want to note that H. sapiens sapiens (that's us) were cross-breedable with H. sapiens neanderthalensis. That's right, [neanderthals interbred with our ancestors](https://en.wikipedia.org/wiki/Interbreeding_between_archaic_and_modern_humans) as recently as 45k years ago, even though they diverged from us more than a half million years ago. The upshot of this is that your interstellar civilization has at least one [orbit around the Milky Way](https://en.wikipedia.org/wiki/Galactic_year) before you have to worry about it. Put another way, the stars you're visiting will diverge more than the populations' genetics will.
Note that this presumes that the speed of genetic variation matches that of our cradle. Given higher population counts and a bad habit of encountering radiation, you might run into that problem a bit sooner, but not in the time-scales described in Asimov's Foundation trilogy.
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In my works, there’s an Earth-like planet known as Lyrial which is linked to Earth and is home to a species of Dragons that’s meant to be scientifically plausible. Additionally, another planet, Ozarvis 32, is home to a much more Magical species of Dragons, but that’s beside the point for two reasons: The first is that this question is focused on the Dragons from Lyrial. The other reason is that the Dragons from Ozarvis aren’t meant to be scientifically plausible. Ozarvis’ Dragons could fly using organs in their wings that produce antigravity via Magic, or something else like that, and I would be absolutely fine with it.
However, as mentioned, the dragons from Lyrial *are* meant to be scientifically plausible, bringing us to the point in the title: is it scientifically possible for a 15 to 20 foot (4.5 to 6 meter) long Dragon to have 4 legs alongside its wings and still be able to fly? Also, if it is, please provide an explanation on how and an illustration showing the way they’d look.
By the way, if it’s not scientifically plausible for Lyrial’s Dragons to have 6 limbs and be able to fly, I can deal with that. I’m really asking this out of curiosity.
P.s. Lyrial is identical to Earth in terms of gravity, despite being larger in diameter by a little over a hundred kilometers, and its atmosphere is roughly 99.5% identical to Earth’s: the only difference is the amount of nitrogen is slightly lower and the amount of oxygen is slightly higher.
P.p.s. Now that I’ve received an answer, I realized I forgot to mention two details, though only one is truly important to the question: I intend to redraw existing drawings I have of Lyrial’s Dragons to be more realistic without changing parts other than the wings overly drastically. However, I’m fine with changing some things a fair amount. Either way, as is, a prime example of Lyrial’s Dragons looks like the following image: [](https://i.stack.imgur.com/bXVpI.png)
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# Yes at best, maybe at worst.
So, before we begin, despite not a lot let's leave it clear what exactly must be achieved here:
* the animal must be scientifically possible.
* the animal must be able to be at least 15 feet long and ideally 20 feet long (or from 4,5 to 6 meters long)
* it must be able to fly.
* it would ideally have 6 limbs.
* ideally it'd also be somewhat built for predation, because dragons.
With that done and using an earth-like planet for lyria, we can safely say that... Without the 3rd pair, your dragon is not only completely possible, but has actually existed, and it was called Hatzegopteryx thambema.
[](https://i.stack.imgur.com/I7WsD.jpg)
[*Art by RickCharlesOfficial*](https://www.deviantart.com/rickcharlesofficial/art/The-Hateg-Island-Greater-Wyvern-864866465)
Hatzegopteryx as is fits 5 out of our 6 criteria. This azhdarchid pterosaur, as far as we know, could grow to a height of about 18 feet tall (or about 5,4 meters tall), and had a wingspan between 35 and 40 feet. While shorter than its close relatives, it's shorter neck, along with its sturdier Jaws, were most likely some of the adaptations necessary for its role in hateg Island: due to the lack of large Theropod dinosaurs in the island, hatzegopteryx was capable of filling in the niche, capable of taking down creatures larger than bite-sized (which here roughly means about human sized), something not exactly common in the group it belonged to. As a result, it became one of the largest apex predators to ever fly. As a cherry on the top, despite being quite adapted to spend long periods on the ground, we expect these creatures to have been easily capable of crossing continents, being anything but bad at flying.
So even in a worst case scenario where your dragon wouldn't be able to have 6 limbs, it could still very much exist, grow to be the desired size (although it'd come more from a long neck than a long tail, resulting in something a little shorter than your average giraffe) *and* be more than capable of filling a role as a large predatory animal, potentially even top predator depending on what it's competing against.
And so we come to the issue: the 3rd pair. Hatzegopteryx belongs to the azhdarchid family, a group that includes most of the largest flying animals known to us, said animals being likely close to the absolute limit a flying creature could grow to be. There's also another problem: "useful" mass. One big difference between birds and pterosaurs is that, while pterosaurs were quadrupedal and used both their wing limbs and hind limbs to move on the ground, birds are bipedal and adapted their front and hind limbs for flying and walking and/or climbing respectively. This may not seem like much, but it was a huge boom for pterosaurs: birds need strong hind legs to move on the ground, but once they take off those heavy, muscular legs become little more than a dead weight, like the wheels on a plane. Meanwhile, pterosaurs could still make use of the muscles in their wing limbs in both types of locomotion. This meant that, while larger birds had to distribute the muscle weight between the arms and legs, pterosaurs could maintain their leg muscles to a minimum while concentrating most of their muscle mass on their wing limbs, which contributed to their ability to reach larger sizes.
The minor problem with this neat approach is that it essentially leaves little to no room to turning it into a hexapod, because such a creature needs to keep its weight to a minimum, and our prime example was already fully developed as to not require another pair of limbs, and chances are that making it so it used the new pair to move instead of the wings would result in the bird problem.
I can't say for sure that it would be impossible, in fact, I'd say it likely isn't, but chances are that the last pair would have very litle purpose, being reduced and relatively weak or reduced at best and atrophied at worst. Your dragon would likely still be possible, especially at the lower height of 15 feet, and would probably look more or less like either of the following:
[](https://i.stack.imgur.com/tjj6t.jpg)
[](https://i.stack.imgur.com/G5CPq.jpg)
The reduced pair would most likely be tied to something such as mating displays as a sign of health on the adult (since being able to maintain these mostly useless limbs, like peacock feathers and deer antlers, requires one to be fairly capable at surviving and healthy. There's even a chance they'd have more vibrant colors than the rest of the body for display reasons), otherwise playing little purpose other than maybe help keeping the female in place during courtship and minor use for holding onto food, depending on their arrangement and length. In a worst case scenario, they could likely still reach the desired length from beak to the tip of their legs on the lower size estimates.
# Edit: Or maybe not so much...
The answer above was mostly based on a more free interpretation of a dragon as "a flying animal that's usually also a carnivore", which allowed me to use some of our own planet's prime examples. The more classic dragon aesthetic you later started to want however has a lot of problems, most of which go directly against the direction we want to go for a more plausible animal and can't always be justified in the best way. Let's look at the main offenders:
* the horns. Their heads being adorned with horns or horn-like structures is not necessarily impossible, far from it as we see in certain bird and pterosaur species, but a realistic dragon would have horns with an internal structure much like the bills of toucans or hornbills, being relatively sturdy and deceptively light, and probably used for purposes such as mating displays, thermoregulation, or both. However, they'd be far less durable than those of moose and ruminants, since they need to be spongy to be light. Coupled with that, having more than one or two large horns would start to be a problem in this specific case, because we're working with a creature that must still fly without sacrificing size, meaning we're on a fairly tight weight budget. Not the main offender, but still something relevant simply because of the size of the animal.
* the front limbs. Again, as I said before, leaving the wings exclusively for flying isn't impossible, but it takes a heavy toll on how big your creature can be. Having them use their hind limbs and wings to walk instead of the 4 limbs is more or less a must if we want them to grow big. Ideally the front limbs would be essentially atrophied to minimize their weight, but having weaker, more dexterous limbs shouldn't be too bad.
* the tail. Oh, the tail, such a lovely Trait but such a problem. Long tails by default tend to be dead weight for flying animals, as they can rarely provide enough lift or maneuverability to justify their weight and maintenance costs. Even worse: essentially all examples of flying vertebrates (at least human sized) known, unless I'm missing something, had tails that were short at best and absent at worst, and the smaller ones weren't much better, usually having tails that functioned more like thin, rigid bony rods than the classic serpentine tails we usually see in classic dragon depictions. The simplest alternative I can think of to at least keep the illusion of a long tail is to go for the bird approach and make your dragon feathered, giving them a stumpy, feathered tail containing some elongated feathers (but not necessarily all of them), offering some extra lift while keeping the added weight to a miminum. This isn't exactly impossible, as feathers are fairly old and pterosaurs, in a worse case scenario, were actually covered in feather-like growths like those of the ancestors of feathered animals.
* the teeth. Nope. If long tails are already rare in larger fliers, you essentially won't find true teeth in anything that was human sized or larger. Teeth overall are not only problematic to grow, meaning more time in the egg, they're also heavier than a beak, which in our case makes it one of the first things to be sent away. Don't worry though, beaks can still be useful, and if you *really* want teeth, things like the hooked beaks of raptors or the jagged beak of pelagornis aren't impossible, especially if your dragon is carnivorous and has a diet of mostly fish.
So factoring those into account, a large creature that's still mostly similar to a dragon while trying to put in practice the needed traits to remain light and thus grow big would probably be a little closer to the following rough sketch, with horns in blue and tail feather length in orange:
[](https://i.stack.imgur.com/KSjiW.jpg)
Not a hatzegopteryx with a pair of arms slapped in anymore, but still far from the classic dragon design. The front pair of limbs would be nearly guaranteed to be the weakest overall, likely ranging from atrophied to T-Rex esque (not exactly weak, but proportionately very small) to weak and mostly useful for manipulation of tools and handling food. Their middle and hind pairs would still follow a more pterosaur-like design, with the wing limbs doing most of the muscle work as to better reduce the amount of "useless" mass when they take off. The actual tail would still need to be small, since at such sizes a longer tail is guaranteed to be too big of an encumbrance, but the feathers on it help give the illusion of a longer and bendier tail at a fraction of the weight.
So summing it all up: sorry, but as far as we're aware a more azhdarchid-like bodyplan is the best option on the market for a plausible large carnivorous flier, and there's only so much we can stray from that design without having to eventually start to sacrifice size (unfortunately, Dragons are usually very bulky, very large and very good at flying, but in the real world these are traits that pull in opposing directions, and often only be implemented 2 at a time).
Not all hope is lost though. Dragons with a more classic look can still be a part of your world without being unrealistic, only problem being they can't really reach the sizes you want. As a matter of fact, smaller pterosaurs are frighteningly similar to most Wyvern depictions. A good example of this is *Harpactoganthus gentryii*, a pterosaur that was about the size of a dog, but that is known to have had teeth, a noticeable head crest and a long (although mostly rigid) tail, being an extra pair of limbs and some extra minor tweaks away from being a near perfect match for a downscaled version of your ideal dragon design.
[](https://i.stack.imgur.com/237eK.png)
[fArt by paleosir\*](https://www.deviantart.com/paleosir/art/Morrison-formation-pterosaurs-769258503)
# Edit 2: ...Unless we use the T-rex approach.
Apart from this, there's only one potential way to technically meet all of the criteria: not meeting them simultaneously, or the T-rex approach. One thing that's not exactly unheard of in nature is a difference in niche not only between species, but also within the same species: many arthropods that undergo full metamorphosis have grounded larva phases and winged adult ones (sometimes with each having a completely different type of diet), and while vertebrates don't demonstrate such drastic changes, T-rex is a great example of what we want: adult T-rexes were stronger, but fairly slow and built to overpower large prey, most likely filling the niche of large sized ambush predator in its habitat. Meanwhile, juvenile T-rexes, while smaller and weaker, were much nimbler and capable of reaching much higher speeds than their adult counterparts, allowing them to fill in the niche of mid-sized pursuit predator along with other theropods such as dakotaraptor. Essentially, due to the changes they undergone as they matured and the sheer size difference between the fully grown adults and the babies and juveniles, T-rexes occupied different niches throughout their lives.
Your dragons could have a very similar, although potentially more drastic situation, where infants and potentially small juveniles filled in the niche of small and potentially medium sized aerial predators, but like a sped up, more extreme version of pterosaur evolution, slowly became more adapted to a more grounded life as they matured, bulking up as they grew and having their wing limbs slowly change in function from flying, climbing and walking to mostly climbing, walking and taking down prey, being at best able to let them clumsily glide down from a tall place, depending on their weight and size as fully grown adults.
This way, we solve the problem of bulk, size and flight not working at the same time by simply not tackling them all at the same time. They won't fly forever, and how long they'll fly for will drastically depend on how they're structured, but the fact they're still the same species and the existence of sightings of clearly airborne infants and smaller, lighter juveniles gliding could lead some people to wrongly believe even the large adults could fly, simply choosing not to. I'd still recommend having their wing limbs structured like a pterosaur's and used for walking more than the front limbs at least at first, with the front ones bulking up and playing a more predominant role in walking only in the heavy adults, simply so they could fly for a longer portion of their lives. Still, this is probably *the* best way available for them to throughly check all of the traits you want for your scientifically plausible dragons, especially since them developing away from flying as they mature would allow them to actually bulk up way more, potentially having more solid, less spongy horns, longer and more flexible tails and becoming even longer than the 20 ft. Length you asked for. Just watch out so they're not too bulky and heavy, unless you don't mind them being slow.
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[Question]
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In nature we see natural pattern formations when a material forms an organised structure within a less dense material in order to fill the space in the most efficient form. Such as hexagonal and octagonal formations in clouds and surface bubbles on water.
My question is based on the natural formation of gas into a structural pattern and if a geometric pattern formation needs a hard boundary in order for it to be uniform?
For example bubbles and clouds can form into an organised uniform pattern but at the outer edges the shapes will become less uniform and larger but bubbles on the surface of water that is within a container will fill the space in a uniform pattern either filling the surface or forming a pattern bubble voids uniformly.
It seems that no boundary leads to a structural breakdown of the pattern but a boundary creates the uniform pattern, is this always the case? The reason I ask this is so that I can design large scale matter distribution for my story's universe.
[Answer]
**Keyword Entropy**
The general phenomenon you are referring to is the increase in entropy in a closed system. Entropy doesn't have a formal meaning (or rather it has many different formal meanings) but usually refers to how *randomly* a bunch of stuff is arranged.
If you take a bunch of particles in a box in any arrangement -- for example put a bunch of hot particles at the top and a bunch of cold ones at the bottom -- then after a while you will find all the particles are the same temperature. There are no islands of high pressure. Entropy has increased.
The particles are now *random* in the sense that if you were to choose an arrangement at random from all the possible arrangements, then most of them will look like this unless you zoom in super close. There are relatively few arrangements where for example half the particles are at the top, half at the bottom, and they are all rushing towards the middle. But there are kajillions of arrangements where it looks like nothing is happening.
Another thing entropy means is the conversion of energy in a closed box into heat energy. Bubbles want to form what are called **minimal surfaces**. These tend to be repeating. To get the bubbles to form anything else you need some energy acting one them. As all the energy turns into heat there is less left over and you get repeating patterns. This does not happen so much when there is no boundary and energy can enter and leave the box into the surrounding air.
As for the arrangement of matter in the universe -- it is far from uniform in the real universe. Matter coalesces into galaxies rather than spreading out. The galaxies form superclusters which form filements. Even the observable univere as a whole is far from uniform
[](https://i.stack.imgur.com/zlTyv.png)
Of course you should not take the above image at face value. After all there are no labels on the axes. The "continents" of denser matter might be artefacts of the display method.
**Your Homework:** The above is a famous image. Find out what display method is being used.
**Your Homework:** Should we expect the observable universe to behave like a closed box in the first place?
[Answer]
**The boundary governing the interaction is between matter and not-matter.**
[](https://i.stack.imgur.com/kSanEm.jpg)
I washed my greasy pan for you, Jarred Jones. And I did not rinse it as much as I usually do. Behold: residual bubbles. These bubbles agglomerate over time. It does not have to do with the boundary of the pan. It has to do with the affinity of bubble for bubble which I think here has to do with surface tension.
But lo! Sometimes matter does not agglomerate! I sprinkled flour in the pan. Some of the flour made it to the bottom. But where the powder hit, it spread into hazy smudges. The flour did not want to clump up. If you are smoking in the bathroom right now, tap your ash into the toilet. It spreads fast. These particles repel each other, I think possibly because they all carry a similar charge.
[](https://i.stack.imgur.com/u4htAm.jpg)
I am reminded of the CGI used to make zombie effects for the movie World War Z.
<https://youtu.be/tvoUMH9Ghpo?t=21>
They used a computer model in which the CGI human entities usually keep a space between themselves and other entities. For the zombies they reversed that to make the zombies clump up into scary hordes.
Matter in the early universe was not governed by extrinsic boundaries but by the interaction between particles - initially gravity and then other attractive and repulsive forces. You can model your matter similarly.
[Answer]
# No Boundary Needed For Patterns
We see plenty of things which form patterns in conditions we consider infinite. Consider these examples at various scales, which form without any noticable presence of a box:
* Filings if iron in a magnetic field
* Van Allen and similar radiation belts forming around special sources of magnetism
* Accretion disks around black holes
* Galactic spirals and arms
* Bubbles minimize surface area and make various geometric shapes when enough run into each other.
* Precipitates (like rock candy) form in essentially boundless conditions. (The nucleation points matter here).
It just depends on the factors driving the formation (or not) for patterns. You can explain these with Newtonian physics, favorable energetic reactions, or what-have-you, but it comes down to one conclusion: patterns can form without the thing being in a box.
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[Question]
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Long ago, Prime Minister Bob created the [insert name here], a government organizing Space in a peaceful, lawful, and orderly way. This story is taught in classrooms around the [insert name here], because there is one difference between the forming of the [insert name here] and other powers in this galaxy; Prime Minister Bob did this all without physical contact.
---
Essentially, what I'm asking is how do you create a government without actually being able to offer anything except information? Here's some more info.
* Bob, and his civilization, can transmit information near-instantly across any distance. The civilizations they are transmitting to can respond, in a similar time frame.
* Bob cannot, however, transport any physical material over said distance. Assume that the distances are much too far to be bridged by anything sub-light speed
* Assume the planets he is contacting are similar to Earth, in that they are broken up into hundreds of little states with differing agendas.
* Assume Bob, and his civilization, is a Type 2 Kardashev Scale civilization; they've constructed a Dyson Sphere around their star, and have access to massive amounts of energy.
* Bob's civilization also has very advanced technology; including ships that can travel at 0.1c, general-purpose AI living amongst the population, a solution to the Three-Body problem (By "solution", I mean sufficiently powerful computers to solve using a numerical approach, most systems, and sensors accurate enough to detect initial characteristics), and a Grand Unifying Theory.
* Bob's civilization is unified and it is willing to do anything you deem necessary in order for it to form its government.
* By "government", I mean a group that makes decisions for the area they are governing, not necessarily an enforcing body. Compare the UN. If you can figure out a way to make an enforcing body, like India, China, or the US, that would be better.
* Ask for more information if needed.
Thanks in advance!
[Answer]
# Self replicating machine message:
Given infinite transmissions, your culture transmits instructions for building a machine. But unlike *Contact*, this is a self-replicating assembler machine, which then builds robots, factories, and the like.
Initially, the machines churn out devices that solve all the world's problems (disease, famine, whatever) and they have the full backing of the more advanced culture to support their decision-making. They take control of the economies, and eventually can control an army of robots, policing functions, and can then assemble an obedient army of bots or nanites to conquer the worlds.
This assembly can be preceded by propaganda to encourage the conquer-ees to build the machine. And once it's built, who's going to stop the progress of machines fixing every problem? 90% of civilizations would simply comply with assimilation into a vastly superior colonial power, and the rest can be handily conquered.
And on divided worlds, the nation that adopts the tech is immediately and overwhelmingly superior to all who don’t. All you need is one to give in. Imagine North Korea going against the wishes of the rest of the world and instantly becoming the undisputed greatest super power…
[Answer]
## Remote Outsourcing and Knowledge-Workers.
**The Bonds That Tie**
If the past couple years (2020 - 2022) has shown anything, it's that a great many jobs and tasks can be done remotely.
Prime Minister Bob's Interstellar Government (PMBIG) is set up and organised around telepresence and remote-working, which is very popular with its personnel.
The Internet-Equivalent spans hundreds of worlds and brings everyone culturally closer together.
Member worlds benefit from the practical knowledge-worker benefits of being part of PMBIG, and in return they agree to abide by the rules.
If a member world doesn't abide by the rules, then they get cut off from the rest of PMBIG and lose access to a great deal of knowledge-worker support.
The upshot is that membership with Prime Minister Bob's Interstellar Government is full of useful perks and opportunities for money-making that makes it really hard for an established member to be willing to rebel or split away.
For example, if I'm owner of a fairly large business, I might outsource a lot of my work to remote-workers on another planet who handle all the Client-Management and day-to-day operations.
I might maintain a small office-staff on my own planet, but I'd rely on communications via the Interstellar Internet to coordinate my business.
I maintain branches of my company on different worlds to provide the actual physical services and goods that I provide.
All of it paid for through a decentralised Intergalactic Banking Clan.
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> Real world example: The company I work for has branches in three different countries and outsources elements of its business to at least two more companies on a day-to-day basis. If England suddenly lost internet-access to all other nations, our business would shut down and we'd close doors in short order.
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I have a vested interest in my world remaining a member of PMBIG, because if we ever rebelled against that government, we'd be cut off from the intergalactic community.
I'd lose 90% of my workforce (including entire departments which aren't represented on my homeworld) and access to the galactic bank, so all my money as well.
So I'll naturally lobby my local government hard if there's any sign they're looking to break away, or that they're planning to do anything that endangers my livelihood.
[Answer]
**Non Proliferation Agreement**
[](https://i.stack.imgur.com/TWbW4.png)
To have a government you must be able to govern. You must be able to enforce your decisions. If you are only allowed to communicate the best you can hope for is to bribe and blackmail the other nations into doing what you say, by providing or withholding the details of powerful technology.
However all is not lost. We can use this approach to make sure space is peaceful and orderly, by preventing warlike technology from developing, by leading emerging species along a pre-engineered technological path.
Our civilization was the first to develop in the Galaxy. Once another species becomes space faring we make contact and send them details to construct marvelous machines that improve life for everyone in the star system. One century later when these machines are created we send them even more marvelous things. That is unless they have developed space nukes in the meantime. In that case we stop sharing until they get rid of their space nukes. Their space is now dangerous but we can keep nearby space safe simply by cordoning the system off by not sending them super fast engine specs.
One bonus feature of our technology is that it is difficult to reverse-engineer into something warlike. So once the new civilization has replaced their technology with the better technology we sent them, and become fluent in how the new technology works, they are less likely to invent weapons than they were before.
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[Question]
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There is a field of grass that is so green and fresh and untouched by the grazing of animals. Throughout the entire day it glistens in the sun as if it is still covered in the morning dew. But beware, young shepherd, for that pasture is mighty treacherous and will cut you if you so much as dare step on it barefoot. And if your animals accidentally graze there? Be prepared to slaughter them as they are not long for this world anymore. Throw away their innards as you do, they're not safe to eat anymore.
**Tl;dr** the grass has evolved to grow into being like glass.
The idea for this comes from the silica phytoliths of many grass species, in particular sword grass that can cut human skin and discourages animals from grazing. I want for the phytolith production of a grass species to be so exagurated that they may look like your usual green grass from afar but up close it will be hard to not simply refer to them as green glass. They're still plants, but their phytoliths are produced and deposited in such ways to make them look and act like glass shards.
My question has to do with if growing such a structure is at all viable for a grass like organism, or if having such a rigid silica structure as part of its body will inhibit its growth(and possibly stop it dead in its tracks if the growing parts end up encased?)
**Would grass still be able to thrive if it grew into being like green shards of glass?**
[Answer]
# Why Not?
There is nothing intrinsically wrong with a plant creating a rigid and sharp structure, especially as a defensive one. There would need to be an underlying ability to adapt to breakage - either treating it as budding, or having underlying flexible structures so breaks can bend. Wood is rigid, but also flexible. there would need to be a trade-off.
It might be useful, but it would be far from a knock-out advantage over other plants. Otherwise, I'm confident something would have evolved to do this (and maybe it did - how would you tell if this was the case for a fossil?)
Growing parts will likely be soft. Grass grows from the base, an adaptation that lets it be eaten off and still grow. So the grass will be able to suffer damage and still grow. And there will be damage. With fragile glass, even a stiff wind could cause breaks in the structure.
And despite its glassy structure, something will evolve to eat it eventually. There are people who [eat glass](https://www.greenwoodpediatrics.com/Swallowed-Foreign-Object), and if it's relatively fine, the digestive system often is able to pass it. How much easier for something like a goat, well known to eat nasty foreign objects. An animal with tough skin or shell could likely take refuge amongst such grass as a defensive measure from predators. An animal could also chew the glass with just teeth in a tough mouth, digest the nutrients out, and swallow the digestive liquid and spit out the crushed glass. But since the plant has spent its resources making indigestible glass rather than potentially digestible cellulose, the payoff for the (silicavore?) is less than for other plants.
A potential strategy for these plants would be to grow glassy barbed seeds so animals would get stuck by the seeds. Then these seeds could get torn out elsewhere, or potentially fester and kill the animal stuck by it. Instant fertilizer!
[Answer]
## Why
Most designs in nature are already quite smart. Evolution has fine tuned a plant's physiology to serve its purpose, in a certain environment. In this case, to assert your idea, you could try to reason why certain properties exist, specifically, why grass benefits from a certain flexibility,
1] **Seeds** I really wonder if a glass container would work out for the *grass seeds* in a positive way. The grass as we know it uses the wind and animal's digestive tracts, to spread its seed. The seeds are mounted with a soft connection, in soft tissue, easily released. Now suppose you'd protect the grass from animals by sharpening the leaves, make them more rigid, that would protect from grazers, but same time, inhibit the animal digestive tract route, for spreading the seeds ! and it could also be more difficult for the grass to release seeds on its own. It would *always* require wind, maybe stormy wind, to spread its seeds.
2] **Sunlight** An impairing aspect of having very rigid grass leaves: it imposes a fixed position i.r.t. the sunlight. A grass leave will bend and torque, to optimize its angle/posture for catching sunlight. These properties would vanish, when the grass gets rigid overall, like cactuses are. Cactuses generally live in environments with abundant sunlight. For grassland, that is not always the case.
3] **Recovery** A powerful treat of current grass plants: their flexibility allows the grass to survive heavy pressure. Your glass plants will not provide protection from certain animals treading the grass. Hooved animals, or large animals with elephantine feet will not be disturbed by your glass leaves.. but the glass leaves can't recuperate, they will be broken forever.
**Reeds have flexible leaves**.
There exist plenty of grass species, that produce reeds. These are very rigid. Humans can make sharp arrows and pens out of these reeds. But if you look at the reeds closely, you see it has flexible leaves on the side, all around. These leaves are needed, apparently, having only a rigid shaft won't do for energy.
[Answer]
**Macroradiolarian?**
[](https://i.stack.imgur.com/U97lA.jpg)
<http://www.photomacrography.net/forum/viewtopic.php?p=65179>
I am digging it. How about macroradiolarians?
Your glass grasses are scaled up [radiolarians](https://en.wikipedia.org/wiki/Radiolaria). These organisms construct glass shells or tests and house within them photosynthetic endosymbionts. Your glass grasses are no longer free living but sessile in the manner of corals. Perhaps in some [John Daileyesque alternate timeline](https://worldbuilding.stackexchange.com/questions/114707/can-pinnipeds-fit-in-a-worm-forest) these creatures are reefbuilders. Their fractal-like structures are well suited for scaling up because they are fractals - they just keep adding to them. The glass houses they build out of soluble silica shelter copious green endosymbionts. At low tide, the glassy spikes and spires protrude from the reef into the sunny air, catching the light.
[Answer]
In the context of the Question, yes, of course it would… by definition. That's broadly a simple re-statement of the theory of evolution.
If grass - or anything else - grew into (whatever) it would necessarily be able to thrive in that state.
In that context, how are shards of glass different from grains of sand or sticks of chalk?
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[Question]
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I'm writing a system where the moon is always full from the perspective of the Earth-type planet--it does not go through phases. Short of the moon itself being luminous, what would it take for this to be naturally possible?
[Answer]
# [Planetshine](https://en.wikipedia.org/wiki/Planetshine)
A special case known as Earthshine is a nice example:
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> Earthshine is visible earthlight reflected from the Moon's night side. It is also known as the Moon's ashen glow or as "the new Moon with the old Moon in her arm".
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Source for image and text: [same link as above](https://en.wikipedia.org/wiki/Planetshine)
Now to get this by natural means, the planet and moon in question might need much higher albedos than Earth and Moon. A human standing on the planet by day would also be blinded and possibly scorched.
But! As an act of engineering, this might be safer. With about a couple billion 1MW laser pointers spread over a circle spanning 120⁰ of both latitude and longitude on the surface of an Earth-sized planet you just might make it. The calculations, and the whole process to get there, were figured out by this site's favourite nerd god, Randall Munroe, in this [What If article](https://what-if.xkcd.com/13/).
[Answer]
As far as I know, it is pretty close to impossible to have a planet with a single moon that always appears full as seen from the planet. Thus I suggest the next best thing would be a ring of so many moons that at least one would always be in the full phase.
Part One of Four: A Moon with an Orbital Period of One Year.
I can imagine a moon that has an orbital period around the planet exactly as long as the planet's orbital period around the star in the system. So the moon should stay in the same posiiton relative to the angle between the planet and the star all the time, and have the same phase all the time, possibly a full phase.
Here is a link to an orbital period of planet calculator.
<https://www.calctool.org/CALC/phys/astronomy/planet_orbit>
I give the "sun" the mass of the Earth and the "planet" the mass of the Moon" and then put in different semimajor axises to calculate the orbital period.
At 500,000 kilometers the orbital period is be 0.110802 Earth years, at 750,000 kilometers the orbital period is 0.203557 Earth years.
At 1,000,000 kilometers the orbital period is 0.313396 Earth years, at 2,000,000 kilometers the period is 0.886418 Earth years, at 2,100,000 kilometers the period is 0.953723 Earth years, at 2,167,400 kilometers the period is 1.00000 Earth years.
But:
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> The Hill sphere of an astronomical body is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hill sphere of its own. Any object within that distance would tend to become a satellite of the moon, rather than of the planet itself. One simple view of the extent of the Solar System is the Hill sphere of the Sun with respect to local stars and the galactic nucleus.[1](https://www.calctool.org/CALC/phys/astronomy/planet_orbit)
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<https://en.wikipedia.org/wiki/Hill_sphere>
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> The Hill sphere for Earth thus extends out to about 1.5 million km (0.01 AU).
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> The Hill sphere is only an approximation, and other forces (such as radiation pressure or the Yarkovsky effect) can eventually perturb an object out of the sphere. This third object should also be of small enough mass that it introduces no additional complications through its own gravity. Detailed numerical calculations show that orbits at or just within the Hill sphere are not stable in the long term; it appears that stable satellite orbits exist only inside 1/2 to 1/3 of the Hill radius
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So the true region of stability for Earth satellites should only extend to about 500,000 to 750,000 kilometers, far closer than the 2,167,400 kilometers necessary for a moon to have an orbit 1 year long.
In fact I have read that the orbital period of a planet around its star needs to be at least 9 times as long as the orbital period of a moon around the planet for the moon to have a stable orbit.
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> The longest possible length of a satellite’s day compatible with Hill stability has been shown to be about P∗p/9, P∗p being the
> planet’s orbital period about the star (Kipping 2009a)
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<https://arxiv.org/ftp/arxiv/papers/1209/1209.5323.pdf> (page 3).
Which is this paper:
<https://academic.oup.com/mnras/article/392/1/181/1071655>
A moon with an orbital period of 1/9 (0.111111) year around Earth would be orbiting at a distance of about 500,928 kilometers.
Part Two: A Ring of Many Moons.
Thus I suggest an alternative, a planet with a ring of moons at the same distance, where always at least one or two of the moons appears full.
Possibly the planet could have a circle of moons of the same size equally spaced in the same orbit around the planet.
That would be very unlikely to have happened naturally, so it would probably have been an orbital situation created by an advanced civilization. The advanced civilization would put tiny moons equally spaced along the circular orbit and gradually bring in more and more material to build them up, carefully making certain that all the moons increased im mass at the same rate.
According to this blog post:
<https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/>
A ring of 7 to 42 objects of equal mass equally spaced along an orbit around a larger body would be stable over long periods of time. And it gives as source a scientific paper whose abstract is at this link:
<https://ui.adsabs.harvard.edu/abs/2010CeMDA.107..487S/abstract>
So you could theoretically have a star system where there are 7 to 42 moons of equal mass orbiting a habitable planet at the same distance.
<https://ui.adsabs.harvard.edu/abs/2010CeMDA.107..487S/abstract>
With 42 moons sharing the orbit, they would be 8.5714285 degrees apart. If one moon was directly opposite to the Sun and thus full, the 2 nearest moons to it would be 8.5714285 degrees ahead of it and 8.5714285 degrees behind it in orbit. And they should also look full to the naked eye of someone on the planet. If two moons were equally space ahead of and behind the direction exactly opposite the Sun, they would be 4.2857142 degrees being exactly full. And they would look full to someone looking at them without a telescope. And possibly some of the other moons close enough to that direction would also look full.
With 42 equally spaced moons, at least two or three would always look full at one time to people looking at them without telescopes, and possibly others would seem full enough.
And if you reduce the number of moons from 42 to a lower number, at first you would still have several moons looking full at the same time, and it would probably take a serious reduction in the number of moons to have a situation where there was not always one or two moons at a time that looked full.
And that is not the same thing as a planet with one moon which is always full as seen from the planet. But it is a planet where at least one full moon is always seen from the night hemisphere.
And once the ring of coorbital moons is created, it woun't need the constant applcation of immense amounts of power to keep a single moon in the L2 point of the planet suggested in other answers. And it would not need the constant application of immense amounts of power to keep it orbiting the planet with an orbital period of one year and not wandering away into space, escaping from the planet.
Part Three of Four: Why Not Many Moons in Different Orbits?
What about many different moons at many different distances from the planet? Earth has only one moon, and Venus and Mercury have no moons, but the small planet Mars has two tiny moons. The tiny dwarf planet Pluto has 5 known moons. The giant planets Neptune, Uranus, Saturn and Jupiter have 14, 27, 83, and 80 known moons resepectively.
But moons in different orbits cannot have orbits too close together or their gravitational interactions will tend to destabilize their orbits. So the outermost moons of a planet would have to be many times as distant as the innermost moons, and thus many times as large to appear as large as seen from the surface of the planet. And most of the moons in the solar system are less than a few tens of kilometers wide and would appear as mere dots of light unless they were very close to the planet.
Furthermore, a moon would not appear to be full from the surface of the planet unless its direction as seen from the planet is close to 180 degrees from the direction to the star. And arranging the orbits of a bunch of moons with different orbits so that at least one was always within a few degrees of opposite to the star and thus appeared full would be very difficult. Sooner or later all the moons would be too far from the direction opposite to the star to appear full, and thus there would not be a full moon seen on the planet.
So a ring of many moons equally spaced in the same orbit around the planet is the only way to get a planet where there would always be at least one full looking moon at night.
Part Four: Artifically lighting the Moon.
The disadvantage of having many moons in a ring around the planet, so that at least one or two will always appear full, is that some of the other moons will also be visible all the time and will appear less than full.
The only way to get each and every moon, or the single moon that orbits the planet, to appear full all the time and never gibbeous, half, crescent, or new, is with artifical lighting of the moon.
So the answers at this question:
[Always a full Moon for the Emperor - Can this be achieved with solar panels and LEDs?](https://worldbuilding.stackexchange.com/questions/131609/always-a-full-moon-for-the-emperor-can-this-be-achieved-with-solar-panels-and/219078#219078)
Show some ways to keep a moon from every appearing less than full.
[Answer]
## It's possible, but extremely unlikely
In order for a full Moon to be constantly visible from Earth, all of the following must occur at all times:
1.) The Moon must be situated oppositely from the Sun at all times, so it's strictly visible from the night side of the Earth.
2.) The Moon's revolution must be directed opposite from the Eeath's rotation. Observing from the North pole, the Earth rotates counterclockwise, which means the Moon must be turning clockwise.
3.) The Moon's revolution speed must be marginally faster than the Earth's rotation, so it always remains dead-center in the Earth's night zone. This math is far too complex for me to calculate so I won't bother, if anyone feels like doing so go right ahead.
4.) Although the Moon must remain dead-center in the earth's night zone horizontally, one would be forced to choose whether it would be visible exclusively from the Northern or the Southern hemisphere. If the Moon were to be situated dead-center vertically as well, it would be eclipsed by the Earth.
PS: All of this would be far smoother to accomplish and calculate if the Earth would be tidally locked, but that requires it to be more than 50 times closer to the Sun than it currently is (much closer than Venus currently is) which would make life on it impossible (unless the Sun blew up and turned into a very special case of White Dwarf with a tolerable but close life zone)
[Answer]
It is not possible, at least not naturally.
The only place where the Moon is full is if it's beyond Earth's orbit.
To keep it in that place, you need something that actively keeps the Moon there - there's no *stable* orbit that you can use.
The best place to put the Moon would be Lagrange point L2 - the energy needed to keep the Moon in place would be minimal there.
However, you'd have to invest a humongous amount of energy to get the Moon there first, as it won't form there on its own.
And you'd need some active mechanism that reacts to perturbations and offsets them; while L2 requires just a minimum amount of energy to keep your position, given the huge mass of the Moon you'd need some alien tech pretty far beyond what humanity has today.
I.e. there's no natural way to have such a Moon, sorry.
The good thing about L2 is that it's beyond Earth's core shadow, i.e. you have enough light refracting in the atmosphere that the Moon gets illuminated despite being straight behind Earth.
It will be substantially less bright due to the greater distance (current Moon orbit: 370.000 km, L2 distance from Earth: 1.5 million km, roughly a factor of 4, meaning it's 16 times fainter). You would need a larger and a better-reflecting (higher-albedo) Moon go get our full-Moon illumination. Not too big of a problem because Moon size does not affect the dynamics too much as long as the Moon's mass stays below ca. 1/25th of Earth's mass.
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# You live on the Sun.
The full side of a moon points at the Sun, so your planet is always lined up right with the Sun. Why? Because your star has a massive Sunspot - a highly evolved descendant of the Common Sunspots that mark our star, which is intelligent and curious about its environment and wants to protect its local planets from the forces of stellar evolution. The Sunspot, being dark, and sheathed in intense magnetic fields under its voluntary control, shields the planet it captured, which bobs upon its surface, from the vast majority of the radiation of the star, so that only the lower 2/3 were melted and ruined, and the top surface, now flattened by the changes, faces outward. The planet does not fall into the star in part because the Sunspot induces powerful magnetic levitation effects, though I suspect a more extraordinary explanation would be needed if I took a glance at the math. The star itself, being highly evolved after all, has already begun to expand to its giant phase, so that its gravity is quite low and its heat a little less intense anyway. Your people do see the Sun - but they see only a part of it, carefully regulated prominences formed as ball lightning that replicate the ancestral appearance and warmth of the star from the planet's orbit before it began its expansion.
* Note the *Moon* is always *naturally* full. You have to think like this if you ever want to write a product label. :)
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Your moon is made of mostly transparent material.
even if just a small beam of light is shining on(in to) your moon, it will get internally scattered and exit the moon from all sides.
It will not always be equally bright, for example when your earth type planet is shading the moon, it will appear more dimly lit, but it will still have light shining out of it from all sides, and thus appearing full.
If your moon is clean enough it could even act as a lens and have all kinds of interesting effects.. (making it too clean of a material would eliminate internal scattering however, keeping it from looking full)
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Often, aquatic humanoids and other species are depicted with a set of shark-like gills in the side of their chest. Specifically, the gills and gill arches would replace the lungs and ribcage under the level of the armpits
Could this peculiar structure realistically develop in an embryo using the normal mechanisms of gill development?
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### Yes, yes they can!
***Two factors to consider:***
1. [Scienticians can't count](https://onlinelibrary.wiley.com/doi/full/10.1111/joa.13067). Are there six pharyngeal / branchial arches or are there five? Whatever happened to the fabled Fifth Arch?
2. You've posited the existence of a standard type of fishy-humanoid merfolk. They have gills, so the matter at hand isn't one of why it can't happen so much as describing what actually happened.
***So, what happened already?***
Since you mention "gill arches" let's take a look at what the five arches develop into:
* In fish, the first two arches develop essentially into the jaws: I develops into the maxilla & mandible; II into the hyomandibular complex; the rest, III - V, actually develop into proper gills.
* In mammals, I develops into the maxilla & mandible; II develops into the hyoid, the stapes and some other suprapharyngeal structures; III through V develop into a whole host of laryngeal & pharyngeal structures: thyroid & cricoid cartilages, various muscles in the neck as well as important nerves and blood vessels.
Merfolk that have gills can't talk, and they can't "breathe", so they don't need all those muscles and cartilages in the throat. They don't need a separate trachea either. Arches III through V can thus give rise to proper gills in merfolk, just as they do in fish.
***What are the alternatives?***
There are other possible arrangements. If your merfolk can sing the sirens' song or talk with landfolk, they of course will need all that laryngeal apparatus, and you'll be looking at a different internal arrangement. A sort of hybrid or combination of the two systems.
This kind of merfolk will have gills for respiration and will also have an air sac or pseudolung which they might put to various uses, one of which might be speech in the air above the water.
* **First Arch** -- [as per spec](https://en.wikipedia.org/wiki/Pharyngeal_arch#In_humans) will give rise to the maxilla and mandible
* **Second Arch** -- facial muscles, hyoid & stapes, etc
* **Third Arch** -- hyoid, common & internal carotid, etc
* **Fourth Arch** -- thyroid cartilage, epiglottic cartilage, laryngeal nerve, etc
* **Fifth Arch** -- cricoid, arytenoid, etc cartilages, vagus nerve, etc
* **Sixth Arch** -- first gill, musculature & innervation, subclavian artery
* **Seventh Arch** -- second gill, musculature & innervation, aortic arch, cephalic gill vasculature
* **Eighth Arch** -- third gill, musculature & innervation, aortic arch, caudal gill vasculature
* **Ninth Arch** -- fourth gill, musculature & innervation
As with amphibians & mammals, merfolk of this kind will develop a kind of pseudolung, also arising from foregut, but will lack the complex respiratory structures. While it can most likely participate in secondary respiration, it's main function is to store air for buoyancy and for use in speech. It's possible that its vascular system might arise from the fifth arch, or more likely the seventh a/o eighth arch. The pseudolung certainly won't have the robust vasculature of the mammalian lung.
[](https://i.stack.imgur.com/gkHIb.png)
[Answer]
**Short answer: No**
**Longer answer:**
I think that you have this backward. The real question is: How would something with gills develop a humanoid form.
If you are thinking of humans returning to the sea, look at all the dolphins, whales, manatee, and even snakes and turtles that returned to the water. How many of them developed gills?
The main thing is that evolution is not a leap from one form to another, it is a series of incremental steps that each, on their own, either provide a survival benefit or, at least, don't distract from it.
Even if all the changes that would have to take place simultaneously to make slits on in the side of the chest that led into the lungs (there are a lot of muscles between the ribs that actually have a purpose), would a baby survive like that? No, the lungs are not designed for pass through breathing.
If the lungs developed the structure for pass through breathing would a baby survive if there weren't slits for the air to actually pass out of? No.
Even if all of those changes happened at the same time, water has a much lower O2 content. Sharks get by by having a much lower metabolism than humans (that would involve a huge number of additional simultaneous changes).
Also, sharks don't have a human brain; which is the largest resource consumer in our bodies.
So, if you don't want to add the addition of a simultaneous change to make the humanoids mindless eating machines, you need to change the chest to have a much higher surface area for extracting O2. That means that the extraction surface would have to extend out of the slits (like some salamanders) and be vulnerable to attack or the chest would need to be much bigger. In that case, you would have a "humanoid" that was a head, arms, and legs sticking out of a huge ball of a chest. Also, remember that these changes have to all happen simultaneously also.
The likelihood of evolving gills is like winning the lottery (more than once) while being struck by lightning each time.
**The answer that you need: Magic**
Magic makes biology and physics tuck their tail between their legs and crawl away.
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Many species arise from evolution, but as in many fantasy works the creatures are created by gods, titans or something similar, so I think this gives a certain freedom to create creatures with fantastic characteristics, but that are scientifically plausible. Thinking about it, I would like to know: **can a bird produce saliva that makes plants grow and wounds heal(even if for this there have to be two species, one producing healing saliva and the other producing saliva that stimulates plant growth)?**
Details about the animal:
It is a species of bird that lives in forests, it feeds on fruits and grains that it gets from plants. Saliva is able to accelerate the wound healing process and even improve the immune system against diseases, viruses, bacteria, etc. They use this in case another member of the species gets hurt, then one opens its beak and lets the saliva run over the wound or if a member of the species gets sick, then they make it ingest the saliva of another to recover faster. This property has an effect on animals of other species as well as humans, making their domestication desirable. Another property is to make the seeds and plants that come into contact with your saliva grow faster. They use this to plant their own food (just like ants do with fungi) when they get the chance, let them salivate on the plant even after germinating to continue accelerating its growth. The effects of saliva are not immediate, it will not take seconds or minutes for plants to grow, wounds to heal and diseases to heal, it will just take less time than usual. Example: if a plant takes 9 months to grow to bear fruit, with the bird's saliva it would take 7 or 6, maybe even less. Ah, I don't know if that's going to matter, but the bird, when its wings are closed, is the size of a cat. I don't know if the size of the bird will matter in any way, but there you have it.
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# The birds have enzymes that break minerals out of rocks:
There are rare minerals on your world that are essential to life. **PROBLEM**: those minerals are very rare in the environment. The engineering for the species created by your gods is very clever, but gods engineering the process tend to stick with variations on what they know. Over time, it's perpetuated a universal problem. [Mineral deficiency](https://www.healthline.com/health/mineral-deficiency#What-types-of-mineral-deficiency-are-there?).
Maybe it was an oversight. Directed evolution leads to blind spots like this. Maybe there's tons of the mineral wherever your gods come from, but the world they are populating is deficient. Or physics works slightly differently in the divine realm. But it's a problem that leaves everyone and everything a little weaker and sicker than they would be otherwise. While the mineral is present in the environment, it's not in a useable form. Aluminum is a good candidate - if you created life that used aluminum, it isn't normally bioactive or soluble in the environment.
So the problem exists, and the gods don't want to destroy the world and start over just to address a nutritional deficiency. That's a lot of work! Your birds were added to the established environment to address this problem. The birds swallow mineral-rich stones and digest out all the (fill in the blank-zinc, calcium, lithium, aluminum whatever) that your other species need desperately (by themselves or with symbiotic bacteria), then concentrate the excess in their saliva. When the birds eat the seeds of other plants, they deliver a critical boost of minerals to the remaining seeds of their chosen foodstuffs, stimulating growth.
Since sick birds and ALL other species on the planet are perpetually a little sick from mineral deficiency, the saliva of these birds accelerates growth and healing. Whatever and whomever the birds touch are just better off.
This doesn't need to, but could take the form of a [cleaning symbiosis](https://en.wikipedia.org/wiki/Cleaning_symbiosis) if you expand the diet of the birds to flesh. The birds track down sick animals and remove necrotic tissue, cleaning out wounds while depositing the immune-boosting minerals at the site of the wound to boost disease resistance and speed healing. Surgeon bird, anyone?
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There are tales cure by animals saliva.
Saint Roch is told to be cured by a dog that licked his wounds.
<https://en.wikipedia.org/wiki/Saint_Roch>
A teacher of mine told me that is not magic, dogs really lick wounds of theirs and of other dogs and their human owners. The trick is dog's saliva has antibacterial properties.
I don't recommend try this in your home with your pet.
Real world histories about cure by animals saliva have existed for centuries. So I think you could use it without fear be saying an absurd.
Just place some kind of natural antibacterial agent in the saliva for the cure part and some kind of enzyme that helps the natural Enzymatic hydrolysis process. <https://en.wikipedia.org/wiki/Enzymatic_hydrolysis>
But a better option is place all the responsibility by the cures and better crops to the bacterium. Benevolent bacteria in the birds saliva cures because it reacts with animal blood and products a natural antibiotic. Looks paradoxical but it is not. Remember there are several kind of bacteria into your digestive system. Without them you die. The same bird's bacteria spreads into the soil where a licked seed was dropped. There are several ways bacteria could help plants growing. Help fixing nitrogen to the soil is an example.
<https://en.wikipedia.org/wiki/Nitrogen_fixation>
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## Bird is an unintentional alchemist
Through some form of miraculously fantastical happenstance of biological sorcery your bird has a digestive system that has the added function of distilling the faint magical properties of the fruits and seeds it ingests into a more concentrated form through a series of organs like a miniaturized version of the apparatuses of an alchemist's distillation station that eventually gathers in the two spit glands near its mouth where the alchemical substances mix with their spit and lead to its abilities.
Technically one gland has the healing potion substance and the other has the potion of plant growth but since the collection glands are their spit glands they don't really have control over which one excretes what when.
[Answer]
## Yes - so long as the birds are Russian (or Georgian).
*"[Phage therapy](https://www.cell.com/cell-host-microbe/fulltext/S1931-3128(19)30052-6) is approach with great promise in next few years, as has been true for past hundred years. In Soviet Union, phage therapy has been [used](https://en.wikipedia.org/wiki/George_Eliava_Institute) for past hundred years. Hand selection and propagation of strains is incompatible with state capitalist licensing model, so is impossible in West even for hundred thousand years..."*
Fortunately, our scientist-hero found a way for his treatment to fly in the West after all. He merely needed a little bird to tell them about it. With the genetic information for hundreds of thousands of carefully selected bacteriophages assembled in its genome, ready for transcription, trans-splicing, and V(D)J-type joining, this bird produces the cure for well nigh *anything* that ails you. Or your livestock. Or your crops. And in addition to spontaneously producing cures for bacterial infections ... it also takes requests! Cryptochromes in its bloodstream react to monochromatic laser light by activating specific genes of interest, which are often spliced together to create the phage you desire according to your blueprint.
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This is in response to the "healer" birds...(as opposed to the "farmers" you are discussing in another post)...
Perhaps a type of bacteria, such as bacteriophages, are active in bird saliva because their water source is densely filled with this.
Consider the presence of bacteriophages in the Ganges river, and their scientific contribution to giving the water "healing properties".
More specifically,
>
> one hypothesis is that the waters of the river contain bacteriophages
> — viruses that replicate within bacteria and are toxic to them.
>
>
>
Dr. Mayilraj from another source explains,
>
> the fresh water sediments from the Ganges house several novel viruses,
> which were never reported earlier. These bacteriophages are active
> against certain clinical isolates, or viral strains and can be used
> against multi-drug resistant or MDR infections.
>
>
>
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In this scenario, there is a rocky planet that is 230% the width of our Earth, covering a total area of a billion square miles, 55% of which consists of three continents separated by a single ocean that averages in at less than one mile. However, what really makes this stand out is that the core is lighter in density, resulting in more Earthlike gravity.
Now let's get a few things out of the way and summarize the consequences of a standard super-Earth.
1. There is a disagreement as to how the geology works on a super-Earth. Some say that geological activity would be higher, with more vigorous tectonic movements due to thinner crusts under higher stress. However, others say that strong convection currents will thicken the crust, preventing the magma from breaking it into plates.
2. This is speculation at the moment, but it's believed that super-Earths would have stronger magnetic fields.
3. Thicker atmospheres, which retain more heat and more moisture, thus rendering super-Earths warmer and flatter (meaning that mountains won't be as dominant as they are back home.)
Now all this is from a standard super-Earth, but this one has a lighter core. Apart from the lighter gravity, would a lighter core on a super-Earth affect the three listed factors in any way?
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This is all fairly speculative but:
1. **Geology:** If the mantle/core is sufficiently light to result in earth-like gravity at the surface then it cannot contain much in the way of dense metals such as iron. In that case it presumably contains more light elements. If there is a significant amount of potassium then [its decay would likely](https://www.berkeley.edu/news/media/releases/2003/12/10_heat.shtml) increase the internal temperature of the super-earth relative to our planet. Even if that is not the case, then the increased volume/surface-area ratio would have reduced the ability of the core/mantle to cool over geological time. So the mantle is likely hotter, which would result in significantly more volcanic activity on the planets surface. The hot core, plus larger radius would also lead to an increase in plumes and convection currents in the mantle so probably more continental drift rather than less. **Result: a surface with lots more volcanos and more (and larger) mountains than earth.**
2. **Magnetic field:** I believe that the likely reduction in volume of a molten metallic outer core would actually reduce the magnetic field (assuming teh metal is replaced with rocky materials. **Result: lower magnetic field and also less shielding from the local sun's solar winds.**
3. **Atmosphere:** If the planet has similar surface gravity there is cause for a thcker, denser, or moister atmosphere. On the other hand, increased vulcanism may result in a lot more CO2 in the atmosphere. To add to the difficulty in calculating this, the constituents of earth's atmosphere are dominated by biological influences over the last couple of billion years. So density/constitution could probably be chosen as you want. But the much larger dimensions of the planet would allow a lot more 'weather' to happen. One possibility would be a greater degree of atmospheric banding - i.e. regions of fast east/west flows than on earth, so potentially extrtemely strong winds and/or jet-streams, and much larger, more powerful, and long lived cyclones and hurricanes. Much more space for large dry desert regions to develop (especially with 55% land coverage). With only 45% surface covered by much shallower water, the oceans would have less of a stabilising influence on climete so expect greater seasonal and latitudinal climate variation. (although shallow oceans are possibly not consistent with increases vulcanism and continental drift). **Result: Chose atmosphere how you want it, but expect the weather/climate and desertification to be extreme.**
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A super earth with earthlike gravity is going to have to be primarily composed of light elements from the first two rows of the periodic table, [transition metals](https://en.wikipedia.org/wiki/Transition_metal) are going to be relatively rare. What transition metals there are will sink towards the core quite rapidly as the hot young world is going to have a very low viscosity and high rate of convection in it's [Hadean phase](https://en.wikipedia.org/wiki/Hadean) making the crust almost devoid of metals. A larger world should stay hotter for longer due to retained formation heat but with a low [thorium](https://en.wikipedia.org/wiki/Thorium) percentage it will get less heat from radioactive decay in the core.
Geology - The minerals that are going to form the iron depleted crust of this world are going to have a much lower melting point than the rocks we're used to seeing on earth, but they do form the dominant volcanism in [one place](https://en.wikipedia.org/wiki/Ol_Doinyo_Lengai) so we know something about their [chemistry and behaviour](https://en.wikipedia.org/wiki/Carbonatite). This crust is going to be relatively thin per unit of cooling time because it melts at half the temperature of the [basalt](https://en.wikipedia.org/wiki/Basalt) that makes up most modern lava, especially oceanic crust. The low melting temperature results in very fluid lavas so all volcanoes are going to be [shield type](https://en.wikipedia.org/wiki/Shield_volcano) with large [spatter cones](https://en.wikipedia.org/wiki/Volcanic_cone#Spatter_cone) around active vents. The combination of thin crust, low mantle melting temperature and rapid convection is going to mean volcanoes everywhere even without plate tectonics. In fact tectonics may not be a factor on this world unless there are large-scale mantle currents as the crust is simply too thin to resist fracturing and build up [cratons](https://en.wikipedia.org/wiki/Craton) around which plates accrete. As many of the minerals that make up the resulting lava flows are relatively soft and water soluble erosion rates will be very high resulting in a world of generally [low relief](https://en.wikipedia.org/wiki/Terrain) landscapes. The low [viscosity](https://en.wikipedia.org/wiki/Viscosity) of the magma means that to spite having high percentages of dissolved gas [explosive eruptions](https://en.wikipedia.org/wiki/Plinian_eruption) are almost unheard of, gas can and does migrate too easily through the melt.
Magnetic field - With the all the [ferromagnetic](https://en.wikipedia.org/wiki/Ferromagnetism) material migrating to the core this super earth could potentially have quite a strong magnetic field for a [long time](https://en.wikipedia.org/wiki/Geologic_time_scale) if the rate of core rotation is high even if the core is relatively small because it will stay fluid longer than the core of a larger world due to reduced depth/pressure rate and better insulation. The magnetic field may be more prone to fluctuations because it's source is deeper in the planet and also because it is relatively smaller.
Atmosphere - The formation and evolution of planetary atmospheres is something we don't really understand, if it were purely a matter of gravity we should have a thicker atmosphere on Earth than that on [Venus](https://en.wikipedia.org/wiki/Atmosphere_of_Venus) this is not so. There are several other factors that we similarly think should have an effect on the atmosphere, like the rate of [solar stripping](https://en.wikipedia.org/wiki/Solar_wind#Atmospheres) that don't explain the realities we see in different places around the solar system. Having said that there are some things we can know about this world that will effect the atmosphere:
* The planet will have relatively large amounts of water in it, the minerals in the crust and mantle have relatively high [water of crystalisation](https://en.wikipedia.org/wiki/Water_of_crystallization) compared to what we find in basaltic mantle rocks.
* It will have relatively little surface water for a given percentage of total water mass, the crust is going to be highly [permeable](https://www.merriam-webster.com/dictionary/permeable) and water will soak to depth rapidly leaving the surface dry. If you want oceans then the planet is going to need a lot of water as a total percentage of it's mass.
* [Water and other gases](https://en.wikipedia.org/wiki/Volcanic_gas) are going to pour into the atmosphere continuously from volcanic vents densely scattered all over the world. Even if the planet perhaps shouldn't be able to hold onto an atmosphere it will have one for long time.
* The sea(s) are going to be shallow, the erosion rate for carbonatites, especially by water, are simply too high for basins of any great depth to form faster than they fill.
* The ocean(s) will also be extremely rich in dissolved minerals and you would expect to see direct solution deposition of some rocks, Chert (flint), [Glocanite](https://en.wikipedia.org/wiki/Glauconite), and Limestone have a history of such deposition on Earth, this world would probably see many more forms as well.
As a side note the high percentage of carbon and the highly convective mantle are going to make Diamonds more common than useful metal ores in the crust. Due to their durability, especially compared to most of the crustal rocks of this world diamond sand is going to be a major constituent of the soils and beaches.
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How would humans or an advanced civilization control earthquakes and volcanoes and even, if possible, harness their energy? By control, we mean the ability to stop or trigger or accelerate or dampen quakes and volcanic eruptions, etc.
The technology is not limited to modern-day technologies.
Eg: can balls or super magnets under buildings allow them to survive quake better. Or can we use magnetic coils to store and disperse the energy due to quake vibrations. Is that even possible?
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To be able to control earthquakes and volcanoes, we have to first understand them. We do not fully understand either. Actually, we know very little about both of them.
Our current understanding of earthquakes involves several mechanisms. The most common are due to plate tectonics where either plates are moving apart, squishing into each other, or moving past each other. Unfortunately, there are earthquakes in places where none of those mechanisms fit (such as the New Madrid fault zone).
Our understanding of most earthquakes is that they happen where some fault zone has stopped moving and the underlying plate is still moving. At some point, the movement of the underlying plate puts enough stress on the point that isn't moving to break the rock that is holding the fault stuck and the fault moves. It can move fast enough to actually melt the rock by friction.
So, for these earthquakes, you would need to invent a technology that can:
1. find where the fault is building up stress
2. Get down to that point (10-80 km below the surface)
3. Perform some action to start the fault moving again
There have been man caused earthquakes. Most of these have been caused by injecting waste water deep into a fracture zone at high pressure. We do not know how that fluid moved to the earthquake epicenter nor what the mechanism that triggered those earthquakes. All we know is that when we pumped that stuff down, more earthquakes happened nearby.
Also, we are still experiencing earthquakes on faults we didn't know were there.
Likewise, with volcanoes, we would need to know how to predict them, how to measure the signals that something is happening, and then need to invent some technology that can harness that huge amount of energy release. It has been only in the last few decades that we have been able to do any prediction of volcano activity. Yet, with all the tools we have today, an Alaskan volcano gave less than 24 hours notice before erupting.
To simply harvest some of the energy of a volcano, think of how much heat is produced by one. Volcanoes are driven by mantle heat and the eruptions are partly due to water and CO2 changing from super pressured liquids into gas. Some estimates are that we could take a trillion watts of power from Yellowstone but the water requirements would be huge.
Frankly, we would not want to cause eruptions, we would want to stop them. Pulling the heat out would slow them down significantly.
[Answer]
It has been reckoned that if we built a big geothermal power station on Yellowstone, it would be possible to drain away the heat from the mantle plume as fast as it accumulated, thereby indefinitely preventing the next catastrophic eruption, and obtaining clean renewable energy as a byproduct. So that's a technique that could prevent at least some volcanic eruptions.
[Answer]
TL;DR lots of energy, and super-strength materials.
# Energy source
To harness the power of a volcano you need some advanced materials and drilling techniques. In several novels there are materials that either natively or through electromagnetic or handwavy modifications are "indestructible" for this purpose (i.e. they can withstand pressure, torque and heat well enough); Laurence Dahners' *stade*, David Adams' *indestructium* and so on. Drive as many double pipes as you need inside a volcano, then pump water down the inner pipe, get water vapour off the outer pipe, and hey pronto!, you can run a turbine setup.
# Dampen volcanoes
This is much more difficult because you need to interfere with the "hot spot" under the volcano. And the hot spot has an incredible quantity of *heat* you need to get rid of. You don't want that heat in the environment, so you need [tuned radiative coolers](https://en.wikipedia.org/wiki/Radiative_cooling#Mechanism) (basically, black bodies heated at exactly one thousand Celsius degrees, surrounded by materials that reflect infrared below 8 micrometers but are trasparent above that. This allows to radiate heat through a clear atmosphere and into space).
The difficulty here is that you would need an *enormous* radiative surface.
# Stimulate volcanoes
The mechanism for both is the opposite of the above. You need to heat up a hot spot; this would be done by increasing the radioactive heat plume underneath. Some sort of "neutrino laser" would need to be focused in the exact volume, to increase thermal emission through reverse beta decay. This assumes that suitable isotopes are present in that volume and in sufficient quantities. Also, since neutrinos are absorbed only with great difficulty, this method is horribly inefficient, requiring a monstrous amount of energy, and a measurable negative effect would manifest for a significant distance around the focus.
Other means of transferring energy deep underground might involve focused seismic waves, or very powerful nuclear fusion devices delivered through shafts (indestructium drills again required).
In some places you might just need to open a shaft and let internal pressure do the rest (for example, Dahners' *stade* could be used to drive a pipe, *stazed* in cylindrical sections, at practically any depth. Once enough material was removed from the inside of the pipe, the pressure would do the rest.
# Dampen earthquakes
Drilling again is required, plus some way of exactly mapping stresses in rock. Once you know how a fault line is holding, you can frack the key points to release compressive stresses a little at a time, converting a five-minute 7.0 Richter scale quake into a five-year long sequence of piloted low-threshold temblors. Or you can *cut* around the fault line, again providing release (the underground compression will close the cut, relieving itself. Then you reopen the cut. An earthquake can move the fault line by up to two meters: if you provide those two meters by way of a cut, the compressive force will go into sealing the cut).
With enough energy and waste heat management, you can maybe do this with a laser (the water table would be a significant problem though: and you need to drive the cut all the way to the depth of the epicenter. For the San Andreas fault line, that's at least fifteen kilometers).
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## They're in the Matrix
At some point, this advanced civilization realized that they all lived in a simulation and focused all their efforts on reaching the outside world. Along the way, they found various bugs (or, as a programmer would call them, features) that allowed a degree of control over certain parts of the simulation. One of these bugs allows a copy of the energy from earthquakes, volcanoes, and various other events to be moved somewhere the civilization wants, probably into machines that can convert motion and heat to electricity, e.g. hydroelectric dams or [heat engines](https://en.wikipedia.org/wiki/Heat_engine).
See the Wikipedia article on the [simulation hypothesis](https://en.wikipedia.org/wiki/Simulation_hypothesis).
[Answer]
**The advanced people would get out of the way, and marvel at a distance.**
Consider wolves. If we explained to our medieval ancestors that we were bringing back wolves, they would be astonished. If we told them we were trying to protect whales, or let trees grow just because they are trees, they would struggle to understand. "Protecting wetlands" because they are wetlands would be a baffling concept.
In the future, our descendants live in harmony with the planet. Geologic cataclysms can be predicted. People then get out of the way and watch and listen and party, celebrating the planet and its workings. The living Earth is marvelous and is viewed with wonder and reverence. Quashing the movements of the breathing earth is as bad as damming a river or paving a forest.
] |
[Question]
[
Premise: A generation spaceship leaves Earth around the year 2060 on a journey to colonize Alpha Centauri A (ACA). In this fiction, fusion power is achieved in 2040, improved over 20 years, and used within the solar system. The trip to ACA will take 110 years. The ship will accelerate halfway, flip, and decelerate for the second half.
I understand basic physics equations involving $F (force) = m (mass) \* a (acceleration)$
and [simplified space travel using constant acceleration](https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration) giving $d=(1/2)at^2$, with distance (d) in meters, acceleration (a) in meters per second squared, and time (t) in seconds.
**However, this distance traveled does not account for mass loss of Xenon fuel used for propulsion. How do I set up an equation to get (at least a rough estimate of) the Newtons of thrust and kg of Xenon needed for the journey to take 110 years?**
Given:
* The ship leaves in 2060: about 40 years more advanced than our current 2021 tech levels.
* The journey takes 110 years (as relatively perceived by those on board the ship).
* Ship launch mass of 1,900,000 kg.
* Each ion drive provides 30 N thrust, averaging 15 kW used per N, fuel use 75 kg of Xenon per 4,000 seconds of burn. (based on advanced versions of current drives)
* Light years to ACA: 4.37.
**Edit: thanks to answers and comments : Originally, I thought they would flip the ship to decel halfway, but the ship will want to continue to burn at the same max safe thrust, and so burn near constant fuel during the entire trip. So, the latter half of the trip will see increasingly larger accel, due to decreasing mass but constant thrust Newtons. This changing mass makes the calculation more complex, because they will not simply flip at halfway point... as the decel part will be shorter due to lower mass. I am currently [researching rocket equations](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) which account for fuel mass losses but dont have it figured out yet...**
Journey with simplified acceleration if time is 110 years: $a = d/0.5t^2 = (2.06717e16) / (0.5 \* (3.469e9)^2) = 0.00343556041 m/s^2 = a$.
If the ship is 1,900,000 kg at launch from Earth, and $F=ma$, $1900000\*a = 6527$ N (Newtons of thrust). However this is simplified. N thrust will change as fuel mass is lost... My thinking is that the ship will want to continue to burn at the same max safe thrust, and so burn near constant fuel during the entire trip. So the latter half of the trip will see increasingly larger accel, due to decreasing mass but constant thrust.
6527N can be provided by 218 individual 30N drives (around this number may be good even as mass lessens, for redundancy safety). Based on above givens, this requires 861,110 kg Xe fuel. Ship mass would continually decrease as Xe used, until the ship is empty of fuel and about 1,040,000 kg mass remains, requiring less force to move.
I'm not sure how to estimate how much N of thrust and mass of Xe fuel will be needed for this journey. I am imagining two functions, with the force function relying on the lost Xe mass (which is a constant loss over time), but I am unsure how to set that up so that everything results in a 110 year journey. Should I integrate to get areas underneath both functions, then adjust until I get roughly 110 years? Ideally I'd like equations where I can easily adjust the ship mass, thrust Newtons, and so on to calculate with different variables if needed.
Regarding initial velocity: Ideally for the story, the ship would leave from Mars orbit: [Linear distance can be expressed as (if acceleration is constant)](https://physics.info/motion-equations/): $s = v\_0 \* t + 0.5a t^2$. With $v\_0 =$ initial linear velocity (m/s) = [Mars mean orbital velocity](https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html) in (m/s) = $24070$
Regarding relative movement of both the Solar System and Alpha Centauri, I [found](https://en.wikipedia.org/wiki/Alpha_Centauri#Kinematics):
>
> Using spectroscopy the mean radial velocity has been determined to be
> around 22.4 km/s towards the Solar System. This gives a speed with
> respect to the sun of 32.4 km/s, very close to the peak in the
> distribution of speeds of nearby stars.
>
>
>
But without knowing ship's max v, because the ship-flipping point is unknown to me, I'm not sure how much 22.4 kps will affect the journey.
Info and chart below from <https://en.wikipedia.org/wiki/Ion_thruster#Comparisons>
>
> Ion thrusters in operational use typically consume 1–7 kW of power,
> have exhaust velocities around 20–50 km/s (Isp 2000–5000 s), and
> possess thrusts of 25–250 mN and a propulsive efficiency 65–80%.[3][4]
> though experimental versions have achieved 100 kW (130 hp), 5 N (1.1
> lbf).[5]
>
>
>
| Thruster | Propellant | Input power (kW) | Specific impulse (s) | Thrust (N) | Thruster mass (kg) |
| --- | --- | --- | --- | --- | --- |
| X3 | Xenon | max 102 kW | 1800–2650 | 5.2 | 230 |
| AEPS | Xenon | 13.3 | 2900 | .6 | 100 |
| BHT8000 | Xenon | 8 | 2210 | .449 | 25 |
| NEXT | Xenon | 6.9 | 4190 | .236 max. | |
| NSTAR | Xenon | 2.3 | 3300–1700 | .092 max. | |
| PPS-1350 Hall effect | Xenon | 1.5 | 1660 | .090 | 5.3 |
>
> <https://solarsystem.nasa.gov/missions/dawn/technology/spacecraft/>
> Dawn Ion Propulsion System Number of thrusters: 3 Thruster dimensions
> (each): 13 inches (33 centimeters) long, 16 inches (41 centimeters) in
> diameter Weight: 20 pounds (8.9 kilograms) each Spacecraft
> acceleration via ion propulsion at full thrust: 0 – 60 mph in 4 days
> Thrust: 0.07 to 0.33 ounce (19 to 91 millinewtons)
>
>
>
>
> Fuel <https://en.wikipedia.org/wiki/Ion_thruster#Propellants>
> Many current designs use xenon gas, as it is easy to ionize, has a
> reasonably high atomic number, is inert and causes low erosion.
> However, xenon is globally in short supply and expensive. VASIMR
> design (and other plasma-based engines) are theoretically able to use
> practically any material for propellant. However, in current tests the
> most practical propellant is argon, which is relatively abundant and
> inexpensive.
>
>
>
>
> <https://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket> [Higher energy use ok because of fusion power.]
> Other propellants, such as bismuth and iodine, show promise,
> particularly for gridless designs such as Hall effect thrusters.
> Krypton is used to fuel the Hall effect thrusters aboard Starlink
> internet satellites, in part due to its lower cost than conventional
> xenon propellant. FUEL USE: The Deep Space 1 spacecraft, powered by an
> ion thruster, changed velocity by 4.3 km/s (2.7 mi/s) while consuming
> less than 74 kg (163 lb) of xenon. [=4300 m/s for 75kg Xe?] The Dawn
> spacecraft broke the record, with a velocity change of 11.5 km/s
> (41,000 km/h), though it was only half as efficient, requiring 425 kg
> (937 lb) of xenon.
>
>
>
<https://www.space.com/38444-mars-thruster-design-breaks-records.html>
<https://www.popularmechanics.com/space/moon-mars/news/a28754/new-ion-thruster-breaks-records-power-thrust/>
<https://www.space.com/28732-nasa-dawn-spacecraft-ion-propulsion.html>
<https://www.nasa.gov/centers/glenn/technology/Ion_Propulsion1.html>
<https://www.nasa.gov/multimedia/imagegallery/image_feature_2416.html>
<https://space.stackexchange.com/questions/840/how-fast-will-1g-get-you-there>
<http://www.projectrho.com/public_html/rocket/slowerlight2.php>
<http://www.xenology.info/Xeno/17.3.htm> Conventional Interstellar Propulsion Systems
<https://forum.nasaspaceflight.com/index.php?topic=34036.1060>
<https://www.omnicalculator.com/physics>
"The Martian" Hermes ship design <https://the-martian.fandom.com/wiki/Hermes_Spacecraft>
<https://www.nasa.gov/directorates/spacetech/niac/index.html>
[Answer]
Since you mention integrals, I know you are familiar with calculus, so I can give you the short and sweet answer. It is not always true that $F=ma$. The more complete version of Newton's equations yields $F=\frac{dp}{dt}$, where $p$ is momentum. Force is the change in momentum over time. Now, since $p=mv$, we can quickly see that if mass is constant, we get $F=m\frac{dv}{dt}$ which is $F=ma$. If mass is not constant, then you have to use the chain rule to get $F=\frac{dm}{dt}v+m\frac{dv}{dt}$, which is what is used in rocketry. Integrate that, and you get the answer you need.
You aren't the first to want to do this. the [Tsiolkovsky rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) is the go-to equation for doing these calculations
$$\Delta V= I\_{sp}g\_0\ln\frac{m\_0}{m\_f}$$
Why go here first, rather than integrating? Well we don't have our ship spec'd out yet. We need to understand our mass fraction before daring to integrate to get distance. But what we know is that we have to do two burns. The first burn takes us from an initial velocity (call it 0) to $v\_{\frac{1}{2}}$, the velocity at the flip point (which, as you note, isn't quite at the half way point in distance, but I'm using the subscript $\frac{1}{2}$ anyways). Then, the second burn takes us down to the velocity of ACA with respect the earth..
Once you have this, you just have to use the above complete version of Newton's law to do the integration.
I'm going to give us control of "number of engines" as a variable. Now, I don't recommend actually just stacking more and more little engines. It's not always the most efficient approach. But a multiplier on the existing ion engine you described seems like a pretty good way to go! We'll call this scale factor $k$. If your ship has a scale factor of $k$, it means it produces $30k$ Newtons of thrust, and consumes $\frac{75}{4000}k\frac{kg}{s}$ worth of Xenon while active.
We're also going to need the ISP. Now it looks like you mixed the numbers from several ion thrusters, and got one which is actually quite weak. Others can check my math, but I pegged it at an ISP of about 160 seconds, which is extremely low (its lower than a chemical rocket). Typically the ISP is in the thousands for an ion thruster. So let's just leave it as a variable, $I\_{sp}$, but I'll peg it to the really nice ISP of NEXT, at 4190s. Feel free to adjust from there, but that's really the dominating variable in these thrusters. You can adjust size and flow rate as much as you like, but changing ISP is incredibly difficult.
You should also pick a $m\_f$. Your question listed a $m\_0$, but $m\_f$ is typically easier to work with because its bounded by the need to do something with a payload. For example, it might be all of the life support needed to support 10,000 people, or something like that. It will just be a scale factor on everything, so I won't include it... but you'll need it to turn into the question of "how hard is it to actually make this rocket." For now, I'll just assume a $m\_f$ of 1,000,000kg.
We can do everything in velocities in the initial frame, so $v\_0=0$ and $v\_f$ is the velocity of ACA in our frame, [which is roughly](https://en.wikipedia.org/wiki/Alpha_Centauri)y 21.4km/s towards us, so we'll say $v\_f=-21.4km/s$ to make all of the signs line up
Now, we know that our total burn is the sum of the speeding up burn plus the slowing down burn. $\Delta V=v\_\frac1 2 + (v\_\frac 1 2 - v\_f) = 2 v\frac 1 2 - v\_f$. By the rocket equation, we can now see that we can relate this to the propellant mass that we use.
$$\Delta V=v\_e\ln\frac{m\_f}{m\_0}=v\_e\ln\frac{m\_f}{m\_f+m\_p}$$
$$2 v\_\frac 1 2 - v\_f = v\_e\ln\frac{m\_f}{m\_f + m\_p}$$
Here I've broken out the initial mass into a final mass plus the mass of the propellant, $m\_p$. This is convenient because we can calculate the propellant mass from the data you've given. If $k=1$, then we know that we consume $\frac{75}{4000}\frac{kg}{s}\cdot T$ fuel, where $T$ is the duration of the flight, 110 years. A quick unit conversion and a multiplication by k to $591300kT\frac{kg}{year}$ points out that this is going to be quite the high mass fraction. At 110 years, you will consume just over $65,000,000k$ kilograms of fuel. Thus for
* $k=1$, $m\_p=65,000,000kg$, ($\zeta=0.984$)
* $k=5$, $m\_p=325,000,000kg$ ($\zeta=0.9969$)
* $k=10$, $m\_p=650,000,000kg$ ($\zeta=0.9984$)
I note the mass fraction, $\zeta$ because it is a common way to measure rockets. Typical mass fractions are in the 0.8 to 0.9 range, with 0.9 being typical for the single-stage-to-orbit (SSTO). Note that one of the great challenges of SSTO is that its hard to achieve a mass fraction that high. So, when you talk about using current technology, recognize that this is quite far outside of what we're typically working with. You will be bringing a **lot** of fuel!
Regardless, we can combine these equations to get one overarching solution:
$$2 v\_\frac 1 2 - v\_f = v\_e\ln\frac{m\_f}{m\_f + \dot m\_1kT}$$
Where $\dot m\_1$ is the above mass flow rate of a $k=1$ engine. Or, rearranged slightly,
$$v\_\frac 1 2 = \frac{v\_f + v\_e\ln\frac{m\_f}{m\_f + \dot m\_1kT}}{2}$$
Now this is really neat. It says that if you want to visit ACA, not just fly past it at painfully fast speeds, there's only so many ways you can do it. It says that, for any fuel flow rate ($k$), there is exactly one $v\_\frac 1 2$ that leaves you at exactly the correct velocity you need, $v\_f$. Any other 110 year long burn will leave you at the wrong velocity.
This means we're really close to having an answer. We can build a plot with $k$ as our independent term, and the distance traveled, $d$ as our dependent term. All we have to do is calcualte the result of a constant-force 2 stage burn, where we burn out the first stage at the point where $v=v\_\frac 1 2$, and then we burn in the opposite direction.
At this point, we could solve a bunch of integrals, but I'll leave this as an exercise for the reader. In the spirit of astrophysics, I invoke "shut up and calculate" and throw everything into a really cheesy python simulation. I just do Riemann integration at 1/10th year intervals, and trust that's fine grained enough to cover for the laughably inexact way I handle updating all of the anti-derivatives.
```
from math import log
ln = log # Python's log(x) is actually the natural log. Aliasing it
# for readability.
mf = 1000000 # kg - my own assumption
m1 = 75/4000 # kg/s
vf = -21400 # m/s
isp = 4160 # s
T = 110 * 31556952 # s - trip length
f = 30 # N - force of the reference engine
g0 = 9.8 # m/s^2 - gravitiy on earth
def calcDist(k):
"""Returns distance traveled in light years"""
# step 1: for given k, calculate the ship's stats
mdot = m1 * k
mp = mdot * T
# step 2: compute v 1/2
v05 = 0.5 * (vf - isp * g0 * ln(mf / (mf + mdot * T)))
# step 3: Integrate!
dt = 0.1 * 31556952 # arbitrary decision, dt is 1/10th of a year
m = mf + mp # kg
v = 0 # m/s
d = 0 # meters
t = 0
# step 3a: Burn 1 (accel)
# stop at v1/2
while v < v05:
a = (f * k - mdot * v) / m # rearrange force equation
d += v * dt
v += a * dt
m -= mdot * dt
t += dt
# step 3b: Burn 2 (decel)
# stop when out of fuel
while m > mf:
a = (f * k - mdot * v) / m
d += v * dt
v -= a * dt # note minus sign: slowing down
m -= mdot * dt
t += dt
return d / 9460730472580800 # meters to light years
k = np.linspace(100, 1000, 100)
d = [calcDist(x) for x in k]
plt.plot(k, d, '-k')
plt.axhline(4.37, linestyle="dashed") # distance to ACA
for kk, dd in zip(k, d):
if dd > 4.37:
plt.axvline(kk, linestyle="dotted")
plt.text(kk + 50, dd - 0.1, "k=%d" % kk)
break
plt.xlabel("Multiple of reference engine")
plt.ylabel("Light years")
plt.show()
```
[](https://i.stack.imgur.com/djDwR.png)
So you will need the equivalent of 381 of those 30N ion thrusters to do the job, and 24800 kg of Xe fuel for every 1 kg of payload. (for a mass fraction of $\zeta=0.9999596$)
This is consistent with the back of the envelope calculations you did. You calculated 218 to get there without slowing down. Slowing down requires 4x more thrust, so would require just under 900 engines if we didn't account for the decreasing mass. The actual answer is somewhere between the two.
Note, you will have to be mighty creative to achieve that mass fraction. Your fuel tanks are going to have to be very thin, and very large, and yet still survive the 110 year journey!
[Answer]
**Halfway point mass is average of start and finish.**
You state that you lose xenon mass steadily thru the journey.
/relying on the lost Xe mass (which is a constant loss over time)/
Your mass at the midway flip point is the average of full and empty: half full. If you want a solution for the journey taken as a while, work
your equations based on the midpoint weight. The increased weight at journey start will be balanced by decreased weight at journey end and the math will work for the journey as a whole.
"But wait!" you object. "I was wrong! It is not steady use! I actually use xenon less fast for the second half of the trip, because the ship is less massive and so requires less force to accelerate than it did on the first half!" True, true. This then becomes a calculus problem to model both the smoothly decreasing rate of use of fuel and smoothly decreasing rate of loss of mass. Which I would like to see worked out but which is beyond my ability.
] |
[Question]
[
The magic system of Second Earth boils down to "micromachines doing stuff". Of course, there are many layers of complexity to it.
These micromachines are produced in the bodies of sapient creatures and are subservient to them.
However, I ran into a small issue while developing the concept: communication.
**Micromachines are mostly made up of organic matter** and are small, comparable in size to the *Kikiki Huna*, the smallest know insect with **a length of 150 micrometers**. So, nanomachines are a few(?) orders of magnitude smaller, thus we will need different methods of communication for micro and nanomachines. We will be focusing on the former, for now.
Micromachines travel in swarms that can expand if necessary but will remain dense for the most part.
Micromachine communication is important in order for them to be able to execute complex tasks as a swarm intelligence, thus **the method of communication has to be energy-efficient, fast, and reliable, while bandwidth isn't as much of a concern**, as the machines themselves have limited computational power so there is no point in taking more than they can chew.
**What would be the best way for micromachines to communicate?**
[Answer]
I designed integrated circuits back when 1µm geographies were just coming into play and the industry believed that 1nm geometries were physically impossible due to gate widths getting close the the angstrom-dimensions of molecules. What did that and all the intervening experience teach me?
*Humans suck at predicting the future.*
But that's good news for you! Because the reality that [we can build a 1nm transistor](https://www.theverge.com/circuitbreaker/2016/10/6/13187820/one-nanometer-transistor-berkeley-lab-moores-law) means you have several plausible options.
* @IDNeon mentioned the most likely solution: chemical communication. There's actually a lot of options here, but if your micromachines need mobility, that means that communication is either by leaving traces (like bees do with pheromones or ants do with a scent trail, just a bit more complex...) or through physical touch. You could credibly suggest that they leave globs of [recombinant DNA](https://www.news-medical.net/life-sciences/What-is-Recombinant-DNA.aspx). The disadvantages of these solutions (assuming that's not something cool in your world... weakness are as important as strengths) are:
1. If using something like rDNA or pheromones, then the information is almost always historical. A micromachine is leaving information that will be found by another machine at a later time. Leaving instructions for what to do in the future isn't impossible, but the latency is ugly.
2. If using something like touch and a direct chemical interaction, then much more present information can be transmitted — but it's slow as each machine must be touched to communicate its instructions or reports.
* But you could also get away with low-energy electromagnetic transmission (aka Radio). Oh, you'd be working at very high frequencies... but a (almost certain) limitation is that your transmitting over very short distances. Meters, at most (more likely centimeters). But that's not necessarily a bad thing. The problem with microscopic machines is that there's a veritable googleplex of them — and I think it is implausible to talk to all of them at once ... *kinda.*
Because what you could do is implement something like the Internet's communication protocol. Want to send out a global message? You send it (literally) to \*.\*.\*.\*.1 Each machine is programmed to repeat the message once (receiving a duplicate does not incur another repeat) to reasonably guarantee that all machines eventually get the message. Want to send it to everyone on the local subnet? You send it to (proverbially) 192.168.055.\*. And if you want to communicate with just one machine, you send it to (again, proverbially) 192.168.055.215. If you're thinking, "that's just [subnet masking](https://avinetworks.com/glossary/subnet-mask/)!" You're on the right trail. Subnet globals and masking are a good starting place for describing how the little bounders can send out gazzillions of messages and coordinate themselves.
Because in the end, what you really have is a planet full of computers in the palm of your hand. And each one needs to pass all messages along while processing any message that meets the criteria of its addressing.
* But, let's introduce one more idea. This one's more science fiction than science... but it comes from that article I linked to earlier about the 1nm transistor. From that article we read...
>
> You see, while the 7nm node is technically possible to produce with silicon, after that point you reach problems, where silicon transistors smaller than 7nm become so physically close together that electrons experience quantum tunneling. So instead of staying in the intended logic gate, the electrons can continuously flow from one gate to the next, essentially making it impossible for the transistors to have an off state.
>
>
>
*But what if we discovered a way, not to insulate the gate to guarantee quantum tunneling doesn't occur, but to take advantage of quantum tunneling in a predictable way?*
Today's science says it can't be done — but you need to realize, you really need to realize, that in the 90s we really, truly, and honestly believed a 1nm transistor was ***by every law of physics IMPOSSIBLE.*** Which is why I don't like being limited by today's science when it comes to answering WB questions (and why I think that coming up with all the gory details is generally a bad idea). Maybe what those little beasties are doing is using your world's version of Abrason's Law of Quantum Thermal Balancing (discovered in 2245) to allow electrons to predictably tunnel across greater (much greater) than atomic distances such that the resulting excitation state of the electron (using the atomic receptor technology first developed by Sariah Lehtonnen in 2082) can be used to modulate information.2
*[Obligatory YouTube video](https://youtu.be/3A_xzurN-Lc?t=59)*
---
1 *I remember in the mid-80s where this literally could be done. I remember sending messages out to X.X.\*.\* such that every machine on the subnets would receive the message. I'm sure that can still be done in the UNIX world, but the "feature" has been heavily controlled by protocols since the late 80s and early 90s when SPAM moved from being a prank between friends/associates to the early versions of the very real problem it is today. But the idea supports the concepts you're creating for your world... n'est-ce pas?*
2 *Call this "technobabble" if you want... but a lot of science fiction today is using the premise of existing technology to suggest the possibility of Clarkean Magic. The quote from* We are Legion, *by Dennis E. Taylor, which I reference in [this meta post](https://worldbuilding.meta.stackexchange.com/q/8290/40609) is a great example.*
[Answer]
Neurons communicate elctro-chemically, and there are molecular machines, look those up. The best communication would be chemically, I'd say.
<https://www.youtube.com/watch?v=X_tYrnv_o6A>
[Answer]
## Morse Code
... but not as we know it.
Using optics and DNA have their own problems, but with the constant recombination of micromachines you describe, things become problematic in terms of alignment.
To handle this, you can build a micro-skeleton as a communications backbone (no pun intended). This can be addressed using standard networking techniques (JBH's answer) and by physically linked by molecular strands (IDNeon's answer). The advantage of this is that it can readily adapt to a compact or non-compact system. Your microbots are then addressed based on their position in this "tree" structure. Microbots then have only touch-range communications, but with very good latency. This also allows for large-file-transfer by DNA encoding.
This will influence the policy on parallel computing that your microbots use.
---
## Outside the swarm
That's workable for internal communication, but what about external communication? The swarm as a whole could detect hormones or light, but hormones take a lot of processing to recognise and light takes energy to generate. Instead, the swarm can accept signals passively, in the form of sound. This is achieved by detecting variations in communication time between parts of the tree.
At this point, I'm essentially suggesting using bio-design principles and replacing cells/tissues with micromachines. Nature probably has far more elegant solutions than I've ever thought of, so I'll leave this answer here.
[Answer]
Nanomechanical computers are more compact and are a billion times more efficient then semiconductors. a neural network made of microbots with nanomechanical processors would have far more room and available energy then if they used semiconductors.
If said neural network was a single cubic millimeter and operated at 1 mhz it would be over 30,000 times faster then the human brain. dna data storage is 400 million times greater then the brains capacity at just a cubic millimeter.
My proposal is to use distributed clusters of microbot neural networks to do processing and to communicate with radiowaves to one another and with physical contact to individual bots. this way the bots only need to move a little bit for communication regardless of the size of the thing your using them for, since the processors are distributed.
I emphasize the efficiency compactness and speed of the clusters since you mentioned your bots wouldnt have that much processing power, but they can if you want them to.
[Answer]
## Colonial Nanites with Specialization:
To get this to work, I think you need nanites to function much like a symbiotic organism. Since the nanites need to be linked to their originating person, each person contains a central factory/neuroprocessing organ (possibly linked to the person's brain) that makes nanites (so they have starting programming/ID). This overcomes human to nanite communication and the limits of processing power of individual nanites.
Then, each swarm has a specialized, slightly bigger (mosquito-sized) signal-receiving nano-receiver that is essentially an antenna and optical or hormonal array. Each kind of task has either a wavelength of light (thus the glow of magic) or a hormonal signal (for an internal body task) that is tied to it. The antenna-bot gets the signal from the neuro-factory ("Human wants the table to disintegrate") sends a signal to the bots ("Move to x,y and dismantle object at x,y") and could perhaps signal back ("metal object exceeds dismantling parameters"). If the neuro-factory links with the person's optic nerve, it can use the human's eyes to observe the light pulses coming from the antenna-bot as its feedback.
The neuro-factory can get signals from the human's brain ("Don't forget the table leg!") and the process of communication goes around and around. The limitation of this is how small you can make a light receiver that can process the data you're sending (one cell in size is the minimum biologically).
] |
[Question]
[
**Real life**
It is a biological fact that wombat faeces are approximately cube shaped. [Wombat poop: Scientists reveal mystery behind cube-shaped droppings](https://www.bbc.co.uk/news/world-australia-46258616)
[](https://i.stack.imgur.com/AW7Sw.png)
It is also the case that wombats tend to make piles of poop although these piles are somewhat random in shape.
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**Worldbuilding**
In a fictional world wombats have evolved to be more and more intelligent and have now reached a stage where they build actual houses and enclosures from their cube-shaped droppings.
**Question**
How can the wombats make effective door furniture (hinges, latches etc.) purely from natural materials?
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**Assumptions**
There is no contact with humans or other intelligent life-forms.
The wombats are pre-stone-age (they cannot shape stone) so everything they make must be of natural materials from their local habitat. They have not yet discovered the secret of fire.
Wombats make mortar/glue for their structures by eating a plant that gives them diarrhoea. They poop this between the layers of 'bricks' to stick them together. A so-called "dry" wombat and "wet" wombat pair can build as a team.
To a limited extent, they can pour diarrhoea into crude moulds that are left in the sun to dry.
Smaller artefacts such as tables and chairs can be made from gluing together the smaller droppings of juveniles.
Rather annoyingly for them, the wombats have developed opposable thumbs on their hind-feet but not their fore-feet. By making a hollow in the ground, they can lean back and use all four feet to do reasonably difficult things such as tie basic knots.
**Picture of real-world wombat hind feet**
[](https://i.stack.imgur.com/D8Vec.png)
Please ask for more details as necessary before answering.
[Answer]
If their droppings can be used to glue things together, they can use them to glue branches and twigs in a shape suitable to close the entrance, in a fashion similar to those in the pics (without the white ropes)
[](https://i.stack.imgur.com/8zJrc.jpg)
Until few decades ago in my home region farmers used to build recoveries in dry masonry using only stones, and the only thing they used as door where exactly those you see in the pic.
Metal or wooden doors were a luxury which became available way later, and there was no need for hinges and latches.
Your wombat can do the same.
[Answer]
Your wombats are essentially pooping [mudbricks](https://en.wikipedia.org/wiki/Mudbrick), so the easiest way to strengthen them would involve either breaking them apart and mixing in other materials (less fun and runs counter to your vision), or perhaps by altering their diet some more.
Since you already have a mortar specialist suffering diarrhea in the name of progress, perhaps the other wombat does the reverse - eats a bunch of solid material that'll stay solid all the way though to act as a temper - perhaps a particularly indigestible straw or rice husk equivalent to solidify and add strength to the literal bricks they'll be pushing out.
As mentioned by [L. Dutch](https://worldbuilding.stackexchange.com/users/30492/l-dutch-reinstate-monica), doors and hinges are actually very advanced technology - these neolithic wombats are likely hanging skins or woven grass over their doors for a simple separation, or putting bundles of straw or similar in front of the door if something sturdier or more insulating is needed.
Finally, I hope both these workers are compensated appropriately - I have enough of a love-hate relationship with bricklaying without having to pass the bricks first!
[Answer]
**There is no need for hinges and latches at this stage of technical development**. A much more efficient approach would be building [mudhuts](https://www.google.com/search?safe=active&source=univ&tbm=isch&q=mudhut) and weaving rags for cover window and door openings. Rags can be glued or partially embedded into mud during the hut construction.
Use poop-bricks for furniture inside. That would help with brick softening/crumbling and other negative effects due to exposure to elements.
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[Question]
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I watched a video or read some article recently on the reality of **Attack on Titan's 3D maneuvering gear** (very sorry, but I can't find it) and how it would kill the user easily.
Basically, even with the harnesses that the survey corps use to redistribute weight to the legs and torso, any movement that sent the user vertically (relative to their own body, not gravity) at high speeds would easily kill them due to the Gs, and the incredible centrifugal force of taking a turn at speed would likely snap the leg(s) of the user.
Assuming here that **the bones and muscles were already strengthened** to handle the crushing and pulling forces on the body, what modifications to the human body (genetic or cybernetic) would need to be made to let a human withstand other issues caused by high G forces and centrifugal force? For example, the increasing weight of the blood in your body as you accelerate.
[Answer]
It looks like most of the major issues once you've taken care of the basic strength and toughness (and you've mentioned muscles and bones, but don't forget tendons and ligaments and skin too!) are blood pressure ones.
* The heart would need to be stronger to be able to continue pumping blood against sustained high g-forces.
* A mechananism would be require to limit blood pooling in the extremities... a biological and internal equivalent of the [G-suit](https://en.wikipedia.org/wiki/G-suit). Thin layers of additional muscle around the major blood vessels in the limbs, perhaps additional valves to restrict periphal blood flow (if only briefly), reflexive muscle tensing to restrict blood flow, etc etc.
* More robust blood vessels all round but most especially the eyes and brain where small blood vessels rupturing can cause blindness, brain damage and death. This might have secondary benefits in the form of resistance or even immunity to things like [haemorrhagic strokes](https://en.wikipedia.org/wiki/Stroke#Hemorrhagic).
* Greater resilience to transient blood pressure spikes in various organs and internal structures, because it would be sad to remain conscious and in-control throughout an awesome 25G slingshot manoevre to find that your kidneys have turned to mush and you spend the next few days peeing blood and dying unpleasantly.
* Much improve toleranced to shock loading of the body. You don't want the aforementioned 25G manoevre to result in a [traumatic aortic rupture](https://en.wikipedia.org/wiki/Traumatic_aortic_rupture), for example ([here's a fun real life example](https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.849.9384&rep=rep1&type=pdf) of aortic trauma caused by a roller coaster ride). Similarly, you'll be wanting your [retinas to be more firmly attached](https://en.wikipedia.org/wiki/Retinal_detachment). You might also want better padding and toughening inside the brain to reduce the risk and seriousbess of concussion (also a useful thing for any risky high-speed sports, or striking and throwing martial arts).
* Greater resistance to [cerebral hypoxia](https://en.wikipedia.org/wiki/Cerebral_hypoxia), where restricting or even temporarily cutting off oxygen supply to bits of the brain doesn't present a serious risk of permanent brain damage. This requires some fairly complex biochemical changes and might in fact be the toughest thing to arrange. Obviously this too has some major benefits when breathing is difficult or impossible for reasons other than g-forces. These people would be harder to drown, strangle or suffocate.
What you might end up with is something like the effects of [adrenaline](https://en.wikipedia.org/wiki/Adrenaline#Mechanism_of_action), but with additional things like some kinds of precise physical control and complex thought become hard or maybe even impossible as blood supply is temporarily restricted to prevent damage during high-g activities.
The *most* difficult issue might just be the need for increased information processing and reaction speeds in the human brain and nervous system in order to operate the 3D manoeuvring gear, which would pose a formidable challenge even for someone with a body that wouldn't just fall apart like a badly made puppet at the first transition. Maintaining situational awareness during periods of restricted blood supply to the eyes is going to be a) very difficult and b) very important.
What you're ending up with is something that is potentially quite different from a vanilla human, both in how they're put together but also in how they think and react to the world around them... the foundation for something *post*-human rather than merely a bit superhuman.
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[Question]
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In this case, Nymphs means not immature insects but beings born of the life force of nature itself. When magic entered this world from an alternate universe, that magical essence combined with the built-up residual life force all over the Earth. (This assumes A) that every living thing has a soul and B) that when that soul leaves the earth, a remnant or imprint of that soul is left behind, which is the aforementioned "residual life force.") The result was Nymphs, which are born randomly all over the seven continents.
This question focuses on medieval Europe, right after the fall of the Western Roman Empire and the establishment of feudalism, and of course on Nymphs and predators. So, let's get to the good stuff. What are Nymphs, and what do they have to do with predators?
Nymphs are manifestations of nature that form when excessive amounts of life force build-up; every time something dies, part of its soul stays behind, and so Nymphs often appear on or in mass graves, battlefields, and rain forests (lots of life, lots of death). They appear to be beautiful women in their prime, clad in clothing of leaves (if you thought of Tinker Bell and her friends, you have the right idea).
However, there are many differences. Nymphs are unaffected by heat and cold, being able to wade through lava flows and stroll through the northern wastes, can breathe air and water with equal ease, and cannot be poisoned or diseased. As for personality, Nymphs are naive, peaceful, and have a deep love and awe of nature. They have an equally strong belief in fate and feel that they came to life to fulfill a purpose, though they don't know what it is.
Additionally, the Nymphs have extensive latent knowledge; they can speak and understand any human language, and if they see a plant or animal, they not only recognize it but know how it behaves, how it survives, what it eats, so on and so forth (in the case of plants, they know the specific type of plant it is, what parts of edible, and other trivia).
After being "born," therefore, Nymphs start a journey: partially to see the wonders of nature, partially to find their purpose. However, there's just one problem. Being creatures of nature, Nymphs have a built-in ability to return to nature. How? *By being eaten.*
Seriously, if a Nymph who hasn't found a purpose yet encounters a predatory animal (AKA anything that can eat her) she'll not only allow it to eat her but *encourage* it to do so. This may seem counterintuitive, but A) since Nymphs are biologically immortal, this actually keeps the world in balance, and B) it's not the end for a Nymph.
After a Nymph is eaten, her potent natural energies enhance her consumer's attributes to supernatural levels, and her spirit enters its body, contributing its energy and intelligence to helping its "host" survive. For example, Tigers are ambush predators; stealthy, strong, fast for short distances. A Nymph-hosting tiger is supernaturally stealthy (becoming invisible in shadows) and can dent or even sunder plate armor with its paws. It's also somewhat faster and more endurant, being able to keep pace with and even outrun a horse.
**TL; DR:**
How can an early medieval society find Nymphs before predators eat them and become almost unstoppable monsters?
Please Note:
With intelligence, and proper recording (specifically plotting points on a map where Nymphs have been found) humans should realize a pattern and figure out that Nymphs appear in places where lots of things have died or been interred, like cemeteries and battlefields. Humans will then be able to post watchtowers in or put walls around these areas. However, many of these areas will be inherently dangerous areas in the wilderness, and humans will have to put more effort in to find those.
I've considered humans using smart birds like ravens to locate targets (AKA Nymphs), which according to [this website](https://www.audubon.org/news/eyes-sky-short-history-bird-spies) can identify individual human faces, take pictures with cameras, and even place recording devices (technology is irrelevant to medieval Europe this example is meant to illustrate raven intelligence).
In fact, I've even heard ravens can be taught to *speak.* However, I'm not sure how helpful they would be; how would ravens bring humans to the Nymphs they've found when A) Nymphs will likely keep moving after being "located" and B) they have to somehow guide the humans to the Nymphs; perhaps someone could spot the raven through a spyglass and have their comrades travel to its location?
As always, I appreciate your input and feedback; if there's any problems with the question, please let me know so I can fix/improve it and make better questions in the future. Thanks, everyone!
[Answer]
>
> TL; DR: How can an early medieval society find Nymphs before predators eat them and become almost unstoppable monsters?
>
>
>
## If you can't beat them, join them
It's simple, since humans discovered that those Nymphs appear when things die, they would simply collect those nymphs on every battlefield, any big farmer with animals could also slaugther some for not only the useful resources (food, hide, etc) but also for Nymphs, which would have many uses, from selling to some rich people to eating Nymphs themselves to be enhanced
**Why?**
Well, if you eat that thing you probably will become enhanced, why not super-produce it by doing what we humans already do best, which is to kill and harvest things for our own benefit.
**What if humans are not able to eat Nymphs?**
Ok, this would be a problem, if they are not able to benefit themselves from Nymphs then I guess you would have to train animals to find Nymphs by scent or something like that and let these animals eat the Nymphs, therefore making your own "hunter animals" better and avoiding enhanced predators.
**Conclusion**
I think humans would probably industrialize in some way Nymphs and make them almost extinct.
I really don't think any predators ( I don't know your world so I'm assuming real life predators ) can outnumber and outsmart humans, so I don't think this will be a problem, at least for Humans.
[Answer]
Ravens could be a potential solution, but why don't you...
## Unleash the hounds
Dogs are notoriously good at smelling faint traces of things they recognize. Even after a day or two, they can track back a person, even after they put perfumes, ran through rivers and feinted moving a direction before backtracking. In case you arrive just a bit too late and face a monster, their strong loyalty will make them the best buddies you can count on. They're THAT good fluffy boys and girls!
[](https://i.stack.imgur.com/X18eN.jpg)[](https://i.stack.imgur.com/dchIG.jpg)[](https://i.stack.imgur.com/mEz43.jpg)
*Many hunting dogs can do the job. Above, from left-to-right : the well-known [bloodhound](https://en.wikipedia.org/wiki/Bloodhound) and [Beagle](https://en.wikipedia.org/wiki/Beagle), and the less common [Grand bleu de Gascogne](https://en.wikipedia.org/wiki/Grand_Bleu_de_Gascogne) -Big blue of Gascogne translated litterally-1.*
After training them to detect any trace of death and nymphs, make regular patrols2 along known animal-made paths, clearings and water points, places where you will find the most wildlife. Since nymphs seem to be curious towards living things, you will have more chances of finding them wandering there, and so you can reduce your research area3. And it's maybe obvious, but look out for warzones and battlefields. A treaty between kingdoms can make it so that nymph-hunters are allowed to scour after the fight and catch any nymph appearing there. To decrease the risk of inadvertently killing them, they'd probably wear specific coloured uniforms, like [blue-helmets](https://en.wikipedia.org/wiki/United_Nations_peacekeeping) do today.
If the nymph situation is getting bad, enhance your dogs by letting them have a nymph bite. Their already strong senses will get even better along with their endurance, agility and strength, making the hunting task even easier.
This solution is more effective than ravens for the simple reason that most of medieval Europe was composed of woods (less agriculture and less people), which makes aerial scans much less efficient. Also, it's probably easier to tame and train them into doing what you ask them to do, so you can have more of them than ever for a lower price.
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1 *Photos from Wikimedia Commons ([1](https://commons.wikimedia.org/wiki/File:Bloodhound_423.jpg), [2](https://commons.wikimedia.org/wiki/File:Beagle2.JPG), [3](https://commons.wikimedia.org/wiki/File:Grand_Bleu_de_Gascogne_in_a_blue_dogcollar.jpg))*
2 *Tiny note to avoid fatty disasters : Patrols should be made of at least 3 persons. In case one man has an appetite for power and consequently for "nature", the other two can prevent them from eating a nymph. After all, the humanity is its own worst predator, so you want to reduce the number of über-Jäger men sprouting here and there!*
3 *This doesn't mean you don't have to check other places from time to time!*
[Answer]
**Laws.** Nymphs are (or will become) dangerous monsters, and they are immortal. What do you do with *any* immortal monster that kills people? Chop it up, deal out the pieces like a hand of cards into twenty boxes of cheap, ugly plastic that go in twenty cylinders of thick stainless steel that go in twenty protective sleeves of very durable, ugly plastic ... just the sort of place a Nymph wouldn't be caught dead in. And drop each into the depths of an abandoned oil well in a different state or country. Well, OK, I don't know if you can cut up the nymphs without killing them, or whether all that magic has given you anything like plastic or oil wells - if need be you can make do with large stone sarcophagi wrapped in reinforced lead and a fired pottery shell, and old water wells in the desert that have since gone dry.
Now if the nymphs are very, *very* compliant and take pains (a) not to be eaten [i.e. run sting operations with tame tigers] and (b) to register *immediately* with competent authorities after manifestation and (c) to do various services for well-born humans as they may require, then *maybe* they will be allowed to seek a purpose outside of a very small and absolutely dark enclosure.
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[Question]
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The philacry are humans with wings like dragonflies, crystal clear and barely weighing anything, yet able to withstand the rapid wingbeats of flight. Though they can fly from childhood, buzzing about with some of the dexterity of dragonflies, this takes a lot of energy, and a lot of oxygen, leading to the same respiratory system that birds have.
The question I have, is where could you store air sacs in a mostly human body? Birds have nine air-sacs, but maybe philacry could manage with less? I guess it's possible to have less of them and make them larger.
I didn't want to shrink too many organs, so I wondered if I should lengthen the torso. Or, maybe you could put them in the buttocks, and make them literal balloon butts? I was considering putting them in the chest, so that the philacry were mistaken as an all female race like harpies, when really it would just be moobs. That's my thought process ATM.
Question: Where could I put air sacs in a human body?
Further details would be how many we could put in, and how large they would be.
Thank you so much!
[Answer]
### **In the vertebrae**
This is where most bird (and dinosaur) air sacs are located, forming special pneumatic cavities in the sides of the vertebrae. It should be noted that several bird air sacs do not actually invade the vertebrae, they just sit in the thoracic cavity.
[Answer]
I guess that whenever you place them you don't want to mess up too much with the center of gravity of the flying body.
If the wings are located where our shoulder blades are, the center of lift will be somewhere around there. Considering that usually the CoG is located somewhere in the abdomen, the creature ends up with a heavy rear, which is a configuration avoided like a stinky skunk by any aircraft designer, because it makes stalls impossible to recover.
A suitable location to lighten the rear is therefore anywhere from the belly down. Buttocks seem to indeed be a good choice, considering that the legs can be kept folded during flight. If not, legs are also a convenient location.
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[Question]
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An unmanned, AI-controlled, terraforming ship arrives at an earth-like planet (i.e earth-sized, rocky, in the goldilocks zone of its star). Unfortunately for the ship's terraforming plans, the planet is tidally-locked, has no [magnetosphere](https://en.wikipedia.org/wiki/Magnetosphere) and so is at the mercy of the [stellar wind](https://en.wikipedia.org/wiki/Solar_wind) and [coronal mass ejections](https://en.wikipedia.org/wiki/Coronal_mass_ejection). As a consequence, although it is a somewhat-promising terraforming candidate, it has a very thin atmosphere, no surface water and hasn't developed any life at all.
The terraforming ship sets to work, with the first order of business being to protect the planet from being constantly blasted by its star.
The ship's plan is to manoeuvre an almost pure iron asteroid (something like [16 Psyche](https://en.wikipedia.org/wiki/16_Psyche)) to the L1 [Lagrange point](https://en.wikipedia.org/wiki/Lagrange_point) between the planet and the star, wrap it in a conductive (possibly superconductive) coil and power the coil using solar panels (or a reactor if necessary).
This will place a huge electro-magnet between the star and the planet. The planet will then be in the asteroid's magnetotail and so will be protected to a similar amount as having its own magnetosphere.
Without the stellar wind interfering, the ship will then be able to move on to the next phase of its terraforming plan.
Is this a sound plan? What improvements could the terraforming ship make to it?
[Edit: this question is specifically about placing a planet in the magnetotail of a satellite not how to [create a magnetosphere on a planet](https://worldbuilding.stackexchange.com/questions/154523/how-could-you-build-an-artificial-planet-sized-magnetic-field).]
[Edit 2: I'm specifically interested in if using a ferometallic-asteroid-based electromagnet at the L1 point will work or not. Suggestions of other courses of action are interesting, but IMO don't really answer the question.]
[Answer]
This seems like the kind of project that Arthur C. Clarke or Larry Niven would write about!
There are lots of technical challenges in such a project, but if a civilization is able to terraform a distant planet with technology, they might be able to resolve these problems. Two challenges come to mind so I'd like to mention them.
The first one is that L1 is not stable in the long term, but if you are going to capture and asteroid, use solar sails etc. then you have the means to adjust its orbit as needed. You will probably need a constant supply of fuel to keep this going.
Second thing is size and mass. You've chosen the perfect location - L1 is 1.5 million km away from Earth, and comet comas can easily reach two orders of magnitude that length. However the tails are also kinda thin... I do not have the math in me but I don't think an asteroid that is at most 13 km wide would have a magnetotail strong enough to protect a planet. Maybe upscale to something Ceres-sized, or even Moon-sized? This way you might even be able to extract the fuel you need to keep it in L1 from the magnetotail source itself.
[Answer]
Scientists from NASA's planetary division proposed to surround Mars with an artificial magnetic field, with which, in their opinion, the atmosphere on the planet will become denser. The authors of the report propose to deploy an inflatable (gas-deployable) module at the Lagrange point (L1) - a place between Mars and the Sun, where the spacecraft can remain almost indefinitely without using engines. The space module will include deflecting dipole magnets capable of creating a field of 1–2 Tesla (approximately the same magnets are at the Large Hadron Collider).
After that, the field forms a "magnetic tail", which will cover the entire planet. Although the "tail" will be rather weak (small fractions of a tesla), this is enough in theory, since on the Earth's surface the magnetic field is measured by equally small fractions of a tesla.
The authors ignore the cost of long-term maintenance of a space module near Mars, as well as where it will take the necessary energy from. They do not compare this option in terms of cost-effectiveness with other projects of a similar type, for example, the production of SF6 gas on Mars. Even a small concentration of this gas is enough to protect the planet's surface from ultraviolet radiation and create a super-powerful greenhouse effect, which will also melt ice caps (increasing the density of the atmosphere) and return the seas to Mars.
If you consider the first option, for one reason or another, difficult to implement, then you can also simply lay a superconductor solenoid along the equator of Mars and connect it to a powerful current source.
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[Question]
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I have a world with late 19th-century steampunk technology. The major nations are at war, and one of them has depleted a lot of its manpower.
I thought that they could try to design automated artillery which uses pistons, clockwork and steam-power to reload itself and shoot. Only one or two artillerymen would be needed to oversee each battery.
The artillery itself is a steam cannon (since gunpowder hasn't been discovered yet).
**I'd like to know if making such an automaton is possible.** (Practicality is a whole other thing, I am aware it would probably be too impractical and unreliable to be used en masse.)
[Answer]
I think it is for surely feasible.
Steam trains are the prototype of steampunk technology. And they have an automatic way of refilling the cylinder with steam for moving the wheels.
You just need to modify the design so that instead of moving the crank it launches the projectile and then reloads the chamber.
The servants would then only assist with keeping the burner active and supply new projectiles to the magazine.
[Answer]
* **Loading**
Yes. Since you have steam cannon (historically marginally [practical](https://en.wikipedia.org/wiki/Dynamite_gun) steam or hydraulic cannon came later than practical gunpowder cannon), all you have to load are the shells and the pressure spikes should be lower.
* **Aiming**
That is more tricky, unless there are mechanical linkages between all the guns in the battery and an aiming post. But then one could envision one of the gunners running from gun to gun and making sure of the aim. A lower recoil means less need to correct after each shot.
* **Firing**
Relatively simple, compared to the rest.
[Answer]
**Clockwork**
It seems very reasonable. With clockwork we can make very precise timings, even with semi-irregular intervals. Like putting in a shell, increasing pressure via piston pumps, releasing it to fire and resetting the gun to the previous state, ready to be reloaded. Even if the heat might be different and the pistons might slow down, the clockwork would slow down accordingly and the timings would still work. Only watch out that the pressure is high enough to fire the shell.
[Answer]
What a splendid notion!
I'm thinking hydraulics with steam providing motive power. You could mechanically adjust gun alignment for beds hydraulically coupled to a sight and trigger command station. Ideally there would be a way to remotely couple "trim controls" from the command station to the adjustment system for a given gun.
Some smaller guns could fire tracer rounds for walking your range to the target, with a very steampunk GBL to (dis)engage the loading/firing systems for the big guns.
An interest of mine is bootstrapping, which is the planned reconstruction of high technology industrial pyramid. You can't just build a silicon wafer factory, you have to iterate through levels of tech in a cycle of building both the tools to build the tools and the necessary industrial capacity to grind up a mountain for a kilogram of iridium.
Part of the problem is warlords with remnant tech. Even if you grab lots of stuff in the fall, sooner or later you run out of ammo and parts for your fancy toys and you need the sort of thing described in this question to hold others at bay while you Take Over The World‚Ñ¢ in the process of securing the surprisingly large resource base you need in order to reclaim the stars.
Low tech solutions like this have the wonderful quality that you can surprise deploy them. Use the ranging guns to feign firepower till they're in ideal range, then EMP your enemy back to the steam age with a very special shell. The rest of the battle should be rather one sided (or maybe you want their ships).
[Answer]
If you have steam power, you can make pneumatic systems including pneumatic switches, and entire steam/air-based automatic systems. Making an artillery piece that has steam cylinders to cycle the action is no problem.
You don't have gunpowder . . . but you didn't say that you don't have *dynamite* (although frankly, it seems like a short road from nitroglycerin to nitrocellulose, but I'm not a chemist). Dynamite guns were a real thing--they used pneumatics to launch dynamite-based shells that wouldn't survive the more violent launch of a gunpowder charge.
I find it relatively easy to imagine a repeating cannon, using steam to launch the projectile and steam to run pistons that operate the gun's action.
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[Question]
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I am writing a novel that involves a person born every few hundred years with the ability to tame animals. The other people never learn their secret. What could I do to make sure that the others never learn how to?
Here is some information, in case it helps.
* The power is not true domestication, just taming.
* This happens about once every five hundred years or so
* It requires these things:
**Friendly**
e.g., the animal must not be inherently driven to be aggressive towards humans
**Feedable**
e.g. the animal must have food habits that are easy enough to sustain
**Fecund**
e.g. the animal must be able to have easy-to-sustain reproductive habits
**Family-Friendly**
e.g. the animal must be able to follow a family structure, no matter how loose this may be, because a sense of belonging is essential for this.
* the novel is set in a time period that is a mix of all three eras of the Stone Age
* the people have advanced hunting tactics, and have access to large amounts of meat such as steppe mammoths, dodo birds, Irish Elk, aurochs, etc.
* the people are of species in the *Homo* genus and others:
* *Homo Neanderthalensis*
* *Homo Sapiens*
* *Homo Floresiensis*
* *Australopithecus Afarensis*
* note the absence of a [reality check] tag
* all these species are living at the same time, and generally coexist peacefully.
To recap my question:
Every two to five hundred years, an individual is born to one of the tribes that has the power to tame animals. This person lives just as long as any other person, BUT:
**the other people do NOT discover how to do it**
What can I do to make sure that others do not pick up this knowledge?
EDIT: simplified to be easier to understand
[Answer]
### The chosen one has better pheromones than the general population.
After a few decades of being hunted, the animals have learnt that the smell of a human approaching is bad news. When they smell human, they try to run, or try to hide. If a human corners them and is nice to them, they just panic / freeze until they get a chance to escape, and then suffer PTSD for the rest of their days.
A human hand offering food smells like a death trap, and the animals will flee to save their own lives.
Humans are good hunters so can throw spears further than their smell travels, for many animals smelling humans means it's already too late to flee and they have to hide. Bathing isn't that common, but with a lack of deodorant the pheromones return quickly even when bathed.
Your hero doesnt have the pheromone that the animals have keyed into. They can offer food to the animal without the animal panicking, and make friends, etc.
### Or, related. Your hero doesn't wear animal skin.
Humans hunt and kill animals, eating them, and skinning their hides to make clothing. They've developed leather softening techniques and dyes and can make some nice fashion.
Your hero is allergic to one of these chemicals or dyes, or perhaps allergic to leather in general, so can't wear leather. They have to make clothing from weaving fibres instead.
When a normal human approaches an animal, the animal smells the decaying flesh of its brothers, and runs away traumatised from the whole experience, exactly the same as I would if you killed my family and wore their skin as clothing.
Your hero doesn't dress in the skin of their families, so the animals are willing to give them a shot.
Because of the skill of the leatherworkers - leather clothing looks great, is extremely comfortable, and is easy to make in a huge variety of outfits. The woven non-leather clothes are not immediately noticeable as different, and because of the time involved in weaving, woven clothes are so much more expensive than leather ones, and unless you're allergic to leather, no-one will be wearing entirely non-leather.
[Answer]
# It doesn't work.
If only a few people once or twice in a milenium can tame animals will manage anything, they will never manage to tame enough to get more than the occasional 'fancy pet' when one of these humans is around. As a result, humans will never *actively* manage to tame and domesticate animals in greater numbers. Domestication is totally impossible.
# Humans will still be Cattesticated
On the other hand, **one** species will make itself at home in the human homes without being asked to. And as they cohabit, they make humans accept their presence by eating the vermin that eats human food. But at the same time, this species will simply ignore any active attempt to domesticate them. Instead, it is they who start to bend humans around their soft little paws, making them do their bidding by giving them shelter and cleaning their fur. After they subjugate humans so easily, they'll be venerated as gods. Humans will build a town in their name. For some generations, their overlordship will be absolute, and they will never forget this, and humans will always remember that they are superior beings. The name of the subjugating overlord species is - obviously - **CAT**, and as it's a principle, they will cattesticate the human - and for the matter any species - in any world.
[Answer]
You just want a plausible and consistent rationale for having a single person able to tame animals? And others unable to learn how to do this even when shown the Tamer's example?
Make it so normal humans excrete a pheromone that unsettles animals.
It could be as simple as a strong stink!
Your "Tamer" is a genetic mutant, that lacks the ability to produce that pheromone.
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[Question]
[
Context is an alternate reality where at some point in time,
one large tunnel appears on Earth.
Both ends of this tunnel are 100m above sea level, respectively located at most eastern equatorial point of Africa, and most western equatorial point of Africa.
The tunnel does not follow Earth's curvature. It is one perfectly straight tube, therfore it slowly plunges
into Earth's crust and reaches its deepest point at its midpoint, 271km below surface, in Earth's red hot mantle.
It spawns already filled with atmosphere, so there is no devastating hammer effect of two fronts of air rushing in the vacuum of this tube.
It is an amazingly wide 1km inner diameter, and it has 0.5km thick walls made of latest UnobtaniumZeroLambda material.
UnobtaniumZeroLambda properties are:
* able to withstand temperature and shear stress of mantle's molten rock convective displacement.
* locally able to vary its density in real time, to soothe the archimedean attempts at deforming the
crust and creating earthquakes at both ends.
* perfect insulating material, allowing strictly 0 watt per meter Kelvin to pass through. (which means
Earth's mantle has no influence at all on atmospheric temperature inside the tunnel)
[](https://i.stack.imgur.com/zeGK3.jpg)
(source googleearth)
[](https://i.stack.imgur.com/doyqK.jpg)
[](https://i.stack.imgur.com/oDDvc.jpg)
[](https://i.stack.imgur.com/hKHPt.jpg)
Question is mainly related to science based observations regarding the atmosphere inside the tunnel :
What would be average atmospheric parameters inside the tunnel (temperature, pressure, state)
assuming standard and equivalent atmosphreric pressure and temperature at both ends?
What could be conditions inside the tunnel if there is huge difference in temperature and pressure at both ends?
(Earth's terminator at tunnel's midpoint + anticyclonic condition at one end, sun aligned along tunnel's axis at equinoxes)
By extension, would it be possible and what would be required to safely travel through it? (by foot, car, train, airliner)
[Answer]
Tunnels of this conformation (geometrically straight and therefore dipping into and through crust and mantle) have been semi-seriously proposed as transportation systems. They have the advantage that (according to math I can't claim to understand) gravitationally driven, unpowered travel through such a tunnel (evacuated, with frictionless rails) would take a constant time for any transit, regardless of end points.
For a tunnel open at the ends, the most salient issue would be atmospheric pressure. You calculation shows 271 km depth at the midpoint -- that's more than *four times* the depth of the troposphere on Venus, indicating that you'll have a pressure near 400 atm at the midpoint (a bit less, perhaps, because Earth's gas mixture is less dense than the cardon dioxide that makes up most of the Venerian atmosphere). That's enough pressure to make the tunnel impassible to current travel technology -- we don't even have submarines that are self-powered that can stand the equivalent of *40 km* depth of sea water. And then there's temperature -- not due to heat flux through the (perfectly insulative) tunnel wall, but due to simple pressure/temperature relationships. The same lapse rate that makes it cooler in the mountains than at the beach will make it hellishly hot by the time you're a few tens of kilometers into the tunnel (and a kilometer or so below sea level).
Further, since the air in the tunnel will interchange with the air outside, and the size of the tunnel (far larger than airship hangars, the overall largest enclosed structures), there will be *weather* inside the tunnel. Lack of solar heating suggests that much of this weather will involve deposition of water introduced with inflowing air (rain, fog, condensation on the walls). Additionally, air can hold less water vapor at higher pressure. So there'll be water inside the tunnel, and we literally have no reliable idea what happens to ambient temperature water at 400 atm. Too hot to make pressure ice, I think, quite possibly supercritical (or near critical -- read *Close to Critical* by Hal Clement for how that would act).
A kilometer of rain? Impossible! But it won't take a kilometer of rainfall to close the tunnel; it will take a small fraction of that amount, because the midpoint is gravitationally "down" from all other points in the tunnel, so all the rainfall within the tunnel (as well as "natural" rain that fall into either opening) will run down to the center. In a way, it won't matter; no human will ever see the midpoint of the tunnel.
To be perfectly clear: this tunnel is *not* a horizontal tube. Horizontal would follow the Earth's reference datum (sea level, which is very nearly spherical; its oblateness due to Earth's rotation doesn't matter here); you can clearly see from the diagrams in the question that, *relative to the surface at either end* (presumed level ground) the tunnel slopes by several degrees -- and if it slopes down toward the midpoint at both ends, the midpoint *must be* the bottom. Don't let the geometric straightness of the tunnel fool you; the midpoint is genuinely 271 km *below sea level* as it would exist directly above the midpoint.
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[Question]
[
**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
---
You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49).
Closed 3 years ago.
[Improve this question](/posts/185361/edit)
I am building a society where people believe that the past (or today's present) was much worse than it actually was. Freedom = slavery, truth = lies, science = correlation, and so on.
One of the ways they do this is inaccurately comparing lifespan and life expectancy by ignoring mass mortality events. For example, people born before WW2 had a good life expectancy, but a bad life span, because everyone died in a single group of few years which makes the life expectancy loss concentrated in a mass mortality event. I.e., if people live for 20 years with low mortality, then 99.99% of people die, then some small part of that cohort survives and then lives to 80, the average life expectancy is nearly 80 even if almost everyone dies at 20.
Basically the Orwellians argue that the life expectancy in the old times was 30 (based on a few wars in the 20th century) and the life expectancy now is 70 (although in reality there are still wars and disasters, you are just taking a single year life expectancy and not cohort life span). Would this work?
Another tactic is using correlational evidence. Say a medicine is proven to work because you try it in 10000 experiments that each have a 5% confidence interval. 5%\*5%\*5% means three experiments will succeed in row after 10000 tries. Would this deceive people into thinking their medicine is effective even if they are just spamming studies and selectively data mining?
Another science thing is to make the falls in mortality unrealistic. If I give a medicine to 60% of people and the disease prevalence falls 99% will people be suspicious?
Another tactic is to use atrocities where the picture clearly shows your own side in uniform committing them, but don't mention the uniform. Would people take that at face value, i.e. not check the uniforms?
How do I get my denizens to accept Big Brother in this particular way?
[Answer]
Lie to them. Clamp down on alternative sources of information.
The USSR produced people who, seeing an ad for Smuckers on TV and talking with Americans they were working with, casually revealed that they assumed it was just propaganda, you couldn't possibly have jam like that for anyone but the high muckety-mucks.
And it took decades before the British admitted officially that it was the USSR, not the Nazis, who staged the Katyn massacre, so the atrocity trick is definitely possible.
[Answer]
### If a charismatic leader repeats a lie often enough, the majority will accept it as truth.
All your examples fall down when someone digs into it a bit, but the people who do so are un-loyal, they're not true your-country-ians. Paraphrasing a particular world leader; They've spent their time watching false news, and are at risk of being radicalised by the violent left.
They need to be taken to reeducatiion camps and helped with their double-plus-un-good-thought-crime. (All Orwellian societies have newspeak, right?)
Examples of lies seeming true when repeated often enough are plenty is modern US politics, eg the recent RNC took a heavy focus on race relations, Trump directly said: "I have done more for African Americans than any president since Abraham Lincoln", and a significant percentage of people believe it ([60% black vote increase over the RNC period](https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.washingtontimes.com/news/2020/aug/31/trumps-approval-rating-black-voters-soars-60-durin/&ved=2ahUKEwiRr7K44-LrAhWIF3IKHWlmAb0QFjAAegQIBBAB&usg=AOvVaw0fKmpCeIIv6vQmuJWg20_m)), but if you [deep dive into opportunity zones and HBCU funding and pre-covid employment growth](https://m.facebook.com/watch/?v=351685299301014&_rdr) the picture is much more mediocre.
A few generations of charismatic, populist, leaders repeating the same lies, and the truth of history will become forgotten easily.
[Answer]
Even without lying you can manipulate your people as a government. Just select the kind of news they see from the major newspaper's and TV shows.
A lot of history documentaries on TV and optimistic statistics about current problems.
With statistics, governments can lie without saying something's wrong. That
happens all the time.
* Homeless People, only count the people who are going to the government help organisation.
* Jobless people, only count them if they are registered and looking for a new job.
* Deaths in traffic, talk most of the time about one kind of vehicle.
* Poor children, you decide the income level in which someone is poor.
Just look at the news from different sources, Fox News, CNN, Russia today... They all have their own perspective of truth and in all countries, politicians use different tricks to sell their own truth. Corona is a flu vs. Corona is deadly, global warming is important vs. a lie. Look at the USA, each half thinks that the other half is evil or stupid.
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[Question]
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So I’ve had this idea cooking in the background of my mind for a year now, and I’ve never made it work.
Simply put, a bee has two pairs of wings, but is commonly drawn with one because the two move in unison due to a row of hooks attaching the back of the forewing to the front of the hind wing.
[](https://i.stack.imgur.com/OEa5K.jpg)
Due to this adaptation, the hinds wings have less power in their wingbeats, acting mostly as an extension of the forewings’ flight surface area. This is an incredibly unique adaptation, and one I have been trying to scale up.
I want to use a similar set up with my speculative alien, wherein a dog-sized vertebrate-like organism with digit supported membranous wings (much like a pterosaur) would have retractable flaps of membrane along its flanks that it grabs with hooks or a similar structure on its wings to increase surface area. To compare with bird anatomy, this attachable wing surface would comprise of the equivalent of the secondary feathers and the inner part of the primary feathers, with the ‘finger’ supported membranes forming the rest of the primary feathers.
[](https://i.stack.imgur.com/xzVvX.jpg)
The problem lies in evolution.
The evolution of this trait in bees is pretty intuitive - two powered pairs of wings, the hind wings grow smaller as the forewings are prioritized and as single-pair flight is selected for, hooks develop that make both flight surfaces into one unit.
The same can’t be said for my design, as the membrane would seemingly serve no function before being adapted as part of the wing, unlike the hind wings of bees. There are advantages sure, as while much of the flight surfaces are tucked neatly against the flanks the wing arms can move unencumbered, allowing more mobility and utility than a pterosaur wing out of flight.
Is there an reasonable and likely evolutionary pathway that would create such a structure? And if not than what alteration would make it more feasible?
TLDR: What evolutionary path may facilitate a bee-like wing arrangement in a vertebrate?
Edit: To clarify, the secondary flight surfaces only attach to the flight limbs during flight, unlike arboreal gliders like flying possums and sugar gliders.
[Answer]
**Flaps were there first.**
How can I pass up a shout out for the awesome colugo?
[](https://i.stack.imgur.com/OxR1t.jpg)
<https://www.wired.com/2014/11/absurd-creature-of-the-week-colugo/>
The colugo is an excellent glider. Its flaps are not unique; sugar gliders and flying squirrels are similarly structured but not closely related. You can see the colugo is well provisioned with flaps upon flaps - out from flanks between fore and hind limbs, forelimb to neck, between hindlimb and tail.
Your flier started as something like a colugo. Then in your world, evolution favored organisms with the power to flap the forelimbs (maybe to extend flight time?) and these evolved into winglike structures. Your creature already supports its wings with a hypertrophied digit equivalent and so the entire forelimb / wing is essentially made from the structures we use as a wrist and hand. That leaves other "digits" free to hook and deploy the ancestral flank flaps (and neck flaps if you like).
Gliding is a lot more common in the animal kingdom than powered flight, which must be tricky. It is an interesting thing that apparently there are (to my knowledge) not extinct or extant gliders who went on evolve powered flight. But it is not an outrageous prospect and it can be the route taken by the ancestors of your animal.
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[Question]
[
I need a species of goat with horns that inject venom into you. How can I pull this off realistically? You see, I hate unrealistic things, so to have my venomous goats from hell be unreasonable would kill me!
They need to attack people because they have claimed human’s territory and attack and hump children. I want this to be child friendly. How can I make their horns venomous yet child friendly?
[Answer]
**Like stinging nettle**
There are many plants that use tiny hollow needles with poison. Check the Gimpy Gimpy for some horror stories. Having the goat as a species immune to it's own poison and injecting venom in anyone who touches the horns due to the tiny needles is a plausible method. With head butting people you can also be reasonably certain the tiny needles can enter through clothes and fur.
Don't want plants but a more animalistic base? There are a lot of caterpillar species with venomous hairs that can trigger all kinds of nasty when coming just in contact with skin. Same applies here. Just have something nasty grow on the horns. Small amounts of incredibly lethal venom is all around nature, although mostly not intended for humans luckily. The only caveat is that I don’t know if a specific diet is needed to create the venom.
[Answer]
***A Different Definition of Toxic Horns:***
If you want REALLY plausible goats that have lethal side-effects of head-butting, I would go in a different route. First, forward-facing horns are going to give piercing wounds more effectively, and are the opposite function for goats, but a trivial evolution.
1. Your goats have diseased horns like the Komodo Dragon's bite. They regularly stab their horns into the fecal material of their own or other species. Folds and pockets in the horns provide a friendly environment for bacterial growth. A few (like Clostridium perfringens) are especially deadly and lead almost anyone injured by these beasts to die a slow, horrible, toxin-driven death (although the toxins are bacterial). Or perhaps you like ergot, and want the victims to behave in erratic, bizarre ways. How family friendly did you want this?
2. Your goats have developed a tolerance for especially lethal plants like belladonna, and regularly rub their horns in the bushes of such plants. Their horns are now coated with lethal toxins that can have whatever fun effects you care to name. This can be anything from neurotoxins to opiates to nicotine. What weird or horrible effects would you like? If you want something that won't kill children, then hallucinogenic compounds will cause bizarre behavior and render enemies helpless, but not be (directly) lethal.
[Answer]
If your goats are fictitious you can break a lot of normal goat rules without delving into unreasonable territory. It's the delivery of the venom that's important, not the biological method - do they butt their target? If so give them the horn equivalent of dewclaws, just smaller horns that branch out at the base of the larger horns so when their skulls come into contact with their target they penetrate the skin and inject a toxin. Do these goats actually gore their targets? If so, the horns would need to be configured like a bull's, and the impaling would do a freak of a ton more damage than poison.
You could also make the horns sort of serated, they don't impale, but can scrape or break the skin, like being whacked with a cheese grater. The material of the horn could be constantly growing and shedding, and perhaps its the flakes from the outer layer that are toxic.
[Answer]
This made me think of the venom that comes from the fangs of snakes. To deliver venom, snakes have hollow fangs that act like hypodermic needles. When a snake bites, muscles in its head squeeze the venom glands. This pushes the liquid through its fangs muscles in its head squeeze the venom glands. This pushes the liquid through its fangs and into the flesh of its prey. [Link to More Snake Venom Info](https://letstalkscience.ca/educational-resources/stem-in-context/how-snake-venom-kills-and-saves-lives) Therefore, if the horns of the goat were sharp and hollow, upon contact to the victim the venom can exit through the tip of the horn using a similar science to the fangs of venomous snakes.
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[Question]
[
Allow me to introduce to you the epaulette shark:
[](https://i.stack.imgur.com/5WQqD.jpg)
This one species stands out over the other 511 in that it can breathe out of water. How? It actually has several adaptations:
1. They slow down their circulatory and respiratory rates, thus reducing the demand for oxygen.
2. They power down their brains for that same purpose.
3. Their fins are modified into something akin to legs, so the shark "walks" rather than swims.
However, there is a problem--this survival strategy has a maximum limit of just **one hour.**
In an alternate Earth, the Paleocene-Eocene Thermal Maximum still happened 56 million years ago, except that it lasted much longer (say, three to four times longer.) Some waters got so hot and so acidic that some shark species escaped extinction by crawling out onto land, occupying the niches of such bony fish as mudskippers and walking catfish. These "lungsharks" can stay out of water for a maximum of four days.
But air-breathing bony fish have the one thing that makes this possible for them but not for sharks--a swim bladder. Since it's already filled with air, it's easy for some species of fish to modify them into something comparable to a lung. But sharks don't have swim bladders, so they have to find some other method to make air-breathing possible.
Within the constraints of 56 million years of evolution and with no swim bladders, ***how would lungsharks be able to breathe air within a four-day limit?***
[Answer]
Air breathing evolved multiple times on Earth, using different organs and strategies. Also, about this:
>
> Since it's already filled with air, it's easy for some species of fish to modify them into something comparable to a lung
>
>
>
[Evidence suggests that lungs existed before swim bladders became a thing:](https://askabiologist.asu.edu/questions/how-did-ancient-fish-make-evolutionary-jump-gills-lungs)
>
> Darwin believed that lungs evolved from gas bladders, but the fact that fish with lungs are the oldest type of bony fish, plus molecular and developmental evidence, points to the reverse – that lungs evolved before swim bladders. Gills were present in the earliest fish, but lungs also evolved pretty early on, potentially from the tissue sac that surrounds the gills. Swim bladders evolved soon after lungs, and are thought to have evolved from lung tissue.
>
>
>
With that clarified: the first vertebrates to walk the land in the real world were amphibians, which are known for breathing through the skin as well as through lungs in order to meet their oxygen budget. Your shark may need to develop some skin breathing as well.
They could also evolve to breath through the anus like [some turtles do](https://en.wikipedia.org/wiki/Cloaca#Cloacal_respiration_in_animals), as well as dragonfly larvae and sea cucumbers.
They might also evolve dry-running gills. [Gills cannot work when dry because](https://en.wikipedia.org/wiki/Gill):
>
> The density of the water prevents the gills from collapsing and lying on top of each other, which is what happens when a fish is taken out of water.
>
>
>
By keeping them moist with a mucus, the landshark could keep them working on air.
Finally, they may combine the above with a hint from insects and develop more entrances for air in their bodies. They could have gills going all the way from the face to the tail.
[Answer]
**By gulping air and storing it in a capilary-rich intestine or chamber of the stomach**
Some sharks, most notably the sand tiger shark (*Carcharias taurus*), gulp air to aid in buoyancy, allowing them to float near motionless in the water column (if you've ever been to an aquarium and seen sandtigers, you've probably noticed this).
Many other fishes can breathe oxygen, but they absorb oxygen through highly vascularized portions of the stomach or the intestines rather than their swim bladders. Examples of this include loaches, trahiras, and several families of catfish. If a shark started swallowing air for buoyancy and then began developing a vascularized section of the stomach or gut for absorbing oxygen from it, then natural selection could turn that into a lung by separating the gas chamber from the rest of the digestive tract. In fact, sharks already have a very large spiral-shaped large intestine with multiple valves that could be repurposed for this job, possibly even combined with a rectal method of taking in oxygen as seen in some turtles or dragonfly larvae.
Indeed, the lungs of sarcopterygian fishes (tetrapods, lungfish) and the swim bladders of other fishes are thought to be derived from a simple outpocketing of the gut in the first place, this is why the respiratory and digestive systems are connected in air-breathing vertebrates.
[Answer]
**The air breathing sharks use the spiracle to move air into a body of water held in the mouth and throat.**
Shark have gills. The gills are in continuity with the mouth and water streams thru the mouth and out the gills when the sharks are swimming. This is ram ventilation and is used by fast swimming sharks. Those sharks must swim to breathe. Other sharks can hold still and pump water past the gills using their mouths, or if not thru the mouth thru spiracles on the top of their heads.
<https://www.livescience.com/34777-sharks-keep-swimming-or-die.html>
>
> Some sharks, particularly those that are not active swimmers, such as
> nurse and bullhead sharks, breathe using buccal pumping. This method
> gets its name from the buccal (mouth) muscles that actively draw water
> into the mouth and over the gills, allowing the sharks to respire
> while remaining still.
>
>
> These sharks also have prominent spiracles, or respiratory openings
> behind the eyes that allow the fish to pull in water while buried
> under sand.
>
>
> Other sharks use ram ventilation; that is, they ventilate their gills
> by swimming very fast with their mouths open. Some sharks, such as the
> tiger shark, can switch between buccal pumping and ram ventilation
> depending on quickly they're swimming
>
>
>
<https://cimioutdoored.org/spiracles-the-secret-of-the-benthic-shark/>
>
> Benthic Chondricthyes, such as a horn shark, round ray, or shovelnose
> guitarfish, live on the sea floor, with mouths located on the bottom
> of their heads to get food from the sand below them. Many of these
> animals also camouflage and avoid predation or sneak up on prey by
> burying themselves in the sand. In order to breathe without buccal
> pumping or ram ventilation, they use specialized holes behind their
> eyes called spiracles. Spiracles act like a straw or snorkel sticking
> out of the sand, drawing water over their gills and out the gill
> slits. This allows these animals to remain motionless and below the
> sand while still being able to get oxygen.
>
>
>
[](https://i.stack.imgur.com/uL67S.jpg)
<https://biologywise.com/shark-body-parts>
In your air breathing sharks, they capture a big mouthful of water when they leave the water and then keep their mouths shut. These sharks can also close their gill slits from the outside so the water does not leak out of them. They use the spiracle organ to move air into the water held in the mouth, pumping it back and forth and using a variation of the "buccal pump" to swirl the oxygenated water against the gills.
As these fish spend more time out of the water, they modify the salinity of the mouthful of water to match that of blood, and then red blood cells exit the vascular spaces and enter this mouthful of water, improving its oxygen carrying capacity.
---
The problem with this method: the shark cannot open its mouth while breathing air. No eating.
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[Question]
[
So, in my world, about 90% of the animals in North America went extinct. The only surviving creatures are a few livestock animals, rats, insects, humans, and three remaining reptiles: Trihorners, Snakes, and, the important one for this question, **Geckos.**
You see, these Geckos are different from the original leopard geckos they’re descended from. They don’t have the sticky feet things anymore: they’re 100% landwelling, about 3 feet tall, and outfitted with sharp claws.
So, originally I wanted them to be pack hunting creatures, but I realized that since wolves/feral dogs still exist, these two creatures wouldnt be able to share the same environmental niche. So my question is, what environmental niche could these giant geckos occupy?
[Answer]
**Ambush Predator**
Doesn't look like you have one yet. These Geckos evolved to (a) get big and (b) change color. [Some geckos already do this](https://en.wikipedia.org/wiki/Tarentola_mauritanica) but not as well as chameleons. Since the geckos are cold blooded they can stay in the one place for days or weeks until a victim gets within range.
[Answer]
Land dwelling, sharp claws, around a meter tall, bipedal. Call it a stretch, but these traits remind me of a now extinct, neat little predator: [Deinonychus](https://www.thoughtco.com/deinonychus-the-terrible-claw-1093783). [](https://i.stack.imgur.com/9SpOW.jpg)
These predators, while not the biggest, are thought to have used their sickle like claws to disembowl prey, as well as to potentially climb trees. Though we do assume they engaged in pack hunting, they also most likely fed on animals their size or smaller.
Your gecko too could have a similar lifestyle, though I can't tell for sure if they'd be social, since modern leopard geckos are fairly solitary. Maybe they could fit a niche of ambush hunter and scavenger, feeding on smaller creatures and an eventual carcass lying around, as well as attempting to steal the spoils of other hunters (I'm not assuming it would be able to be a pursuit hunter, sine that requires adaptations to be able to run properly and decently fast at least for a short period, and which a normal gecko isn't known for). Your main problem to make them able to truly fit a niche like deinonychus' is that it'd be very tricky, since they'd need to go from this:[](https://i.stack.imgur.com/htcCq.jpg) to something more like this:[](https://i.stack.imgur.com/SniS1.jpg)
Although I will leave a quick reminder: a niche isn't always monopolized, and competition among different species isn't uncommon in nature, so the existence of one kind of pack hunter doesn't mean other pack hunters can't exist (see hyenas, wild dogs and lions, all have a pack and all exist in Africa, with lions often stealing the kills of hyenas).
[Answer]
From these detail, it sounds like a top predator. And yes, there can be more than one top predator in the same area. Wolves exist in the same places as large cats, humans, and other predators. The key is to keep them from overlapping too much, and when they do overlap, who backs down and why? Maybe they fight for a kill, the ability to hunt, or maybe just on sight.
Jackals, lions, and predator birds all have the same area they hunt and are all top predators, but within that, have a sub hierarchy. The lion generally get to feed first, even when a jackal makes a kill the lions notice. The lion might have to fight for it, but they generally get to eat first. Once they are done, the jackals eat, and then anything else that hasn't made their own kill that day.
Also, the predator birds generally go for smaller prey that a lion wouldn't care about, but will take advantage of a fresh carcass. A jackal might eat the same small stuff as a bird, so there's still overlap there.
And something with those claws at that size would likely also compete with humans for food, too. It kind of depends on their speed, too. If the geckos are slow like monitor lizards, they might not have much of an advantage even with the claws. But if they are quick like alligators and crocodiles, then there's a good chance the other top predator could also be prey to these geckos.
Humans have only a few advantages of speed and intelligence when it comes to hunting, and our speed, stealth, power, and many other aspects aren't even that great when compared to other top predators. The only thing that really sets us apart is our use of tools. In a post-apocalyptic setting, those tools get much harder to come by. When there isn't any manufacturing happening and people start hoarding thing pre-apocalyptic, thing disappear quickly, as the current pandemic has shown.
Wolves were domesticated to help humans hunt. They are a top predator, pack animal, and intelligent, so they are fairly easy to train. If the geckos fall into this territory, like I think they would, they would also be a subject for domestication. This goes double if they are a match for the surviving dogs and can get into settlements to steal food by killing the dogs. Even if some groups of humans try to eradicate the nuisance large geckos, others will try to domesticate them.
So really, there's a lot of room for these geckos in the post-apocalyptic world. Humans have already killed a large amount of predators, so they would fill in any gaps neatly.
[Answer]
They can be built like a primitive dinosaur, with enlarged hindlegs and reduced forelimbs, or they can predominantly walk on four limbs but run upright on their hindlimbs like some modern days lizards. They could probably fill the ecological niche of a medium sized carnivorous mammal, feeding on snakes, rats, large insects, or chickens if they still exist in your world. They could use their claws to hook onto their prey and to climb rough surfaces (the toe pads wouldn't work for a larger animal).
[](https://i.stack.imgur.com/Te5U1.jpg)
*Nanotyrannus*
[](https://i.stack.imgur.com/gwL9S.png)
*Monitor lizard standing on its hind legs*
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[Question]
[
**Premise 1:** I prefer to know if it's possible to realize this without much handwaving (hence the *science-based* tag) but, as this is going to be in a fantasy setting, answers which make it possible with just a couple little details explained by magic (e.g. the mesa is largely composed of handwavite crystals) are acceptable.
**Premise 2:** I looked up other questions on the site and went through the "similar questions" before submitting, but none of the questions nor the answers is really applicable imho.
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Say I have a landscape which looks more or less like this:
[](https://i.stack.imgur.com/Bdtir.jpg)
I want this area to be called "**The Drums**" by the local populace, because the top of the rock formations attract a lot of lightning strikes and, when struck, resonate as if they were giant drums.
In order for this to be possible, I need two things to be plausible:
## 1: the material/shape/whatever of the mesas should attract lightning.
Quoting Wikipedia: [The place where lightning occurs most often (according to the data from 2004 to 2005) is near the small village of Kifuka in the mountains of eastern Democratic Republic of the Congo, where the elevation is around 1,700 metres (5,600 ft). This region received 158 lightning strikes per square kilometer (409 per sq mi) a year.](https://en.wikipedia.org/wiki/Distribution_of_lightning)
This doesn't say whether it's on land or on a lake.
Also, I couldn't find any source on whether or not there are certain kinds of soil composition which attract more lightning.
The fact that the mesas are higher than the surrounding areas helps, but I guess the fact that they're flat on top does not.
So: **how do I make it so that the mesas receive at least 200 lightning strikes per square kilometer per year?** This of course can be concentrated in a specific time window (e.g. march to october or whatever). **The more often they're struck** (even in a limited period) **the better**.
Like, if there could be a "Thunder Week" once a year in which you can see three or four lightning strikes per minute for entire hours every day, that would be perfect.
## 2: the mesa/mountain should resonate with thunder.
My first thought was: the mesas are hollow inside and reverberate easily.
Even so, I couldn't find any source as to **where the sound of thunder originates from when lightning strikes the ground**: is it the surface? is it the clouds? is it all along the entire "body" of the lightning strike?
(EDIT: it's pretty much the same principle as a jet's sonic boom, [caused by the extremely quick change in temperature](https://en.wikipedia.org/wiki/Thunder#Cause). So the answer to this sub-question is "all along the 'body' of the lightning strike". Thanks @AlexP)
If the sound originates either on the struck surface or all along the lightning bolt, **does it physically make sense that the mesa's hollow body resonates and amplifies the sound of thunder?**
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**If** (and only if) **one or both of the above are completely unrealistic, what is the smallest change I need to make** (via magic or whatever wavy movement of my upper extremities) **in order for it to make sense?**
[Answer]
**The thunder echoes among the mesas.**
This is easiest because it is real. Tall hard surfaces (like skyscrapers, or stone monuments) will cause thunder to echo. The thunder can bounce around your monuments like rolling drums. Thunder in the city can really sound like this.
A thing I have noticed with the "downtown thunder" effect (and other prolonged echoes, like whistling in a stairwell) is that the echo progressively gets higher in pitch. Thunder loses the low tones and gets more brassy. Could this be like a Rayleigh effect with sound - shorter wavelength less likely to be absorbed, more likely to bounce? If so I have not read it described; links in comments welcome.
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This seems a little bizarre -- how can you tell if the mesa is making a sound above the peals of thunder?
Better to have dry thunderstorms to preserve your landscape which otherwise will dissolve like sugar under the downpour.
You can still have lightning, and thunder. The 'drumming' effect can be provided by resonance of the thunder in the canyons around the mesa, which are conveniently arranged so that their width corresponds to exact numbers of wavelengths of the thunder produced. The thunder echo from one canyon can come back and combine with other echoes so you don't get just one boom of thunder but a whole drum solo with each stroke of lightning.
[Answer]
# The sound is made by the lightning.
And it is a white noise:
[](https://i.stack.imgur.com/A0cYP.png)
So, if you want the "drum" effect, you need for the mesas to [modify the sound](https://physics.stackexchange.com/questions/259582/why-does-a-rolling-thunder-always-starts-with-a-high-pitch-and-ends-with-a-deep). This means you want to absorb high frequencies very, very quickly. You need the mesas to be coated in something (a moss?) that acts like sound foam. This will also act on any sounds (shouts, shots, birds, rockfalls) that might be generated in the area.
# Lightning generation
For that, you need a buildup of static charges in the air. The mesas would need to create and direct a flow of rising air in such a way that a [permanent Van der Graaff columnar phenomenon](https://en.wikipedia.org/wiki/Catatumbo_lightning) is established. You need constant and appropriate humidity conditions; they could probably be recognized hours in advance. In Catatumbo, it is a bog where the Catatumbo river flows into a lake, and the storms around the lake, that establish the appropriate conditions.
The lightning mechanism is not very well understood, but upward streamers *might* be increased by ionization (i.e. natural radioactivity).
[Answer]
The way I see it, the only way to get that "drum like resonance" is to have the lightning make a second jump from ceiling to floor inside the hollowed out mesas.
Even then, if only hollow with no outlet, the sound would be muffled completely as the needs for structural integrity would prevent the vibrations that would let the sound travel outside.
All hope is not lost however, simply having a nice cave entrance to the hollows is enough to let the sound of the thunder resonate out. it would have an additionally cool effect of making all the drum sounds directional as it bounces out in one direction. (potentially bouncing off some of the other mesa's or large landmarks in the area).
Cool story side effect? some locals might know of the best places where the sounds of multiple mesa drums intersect for a cool listening experience.
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Let's say you have a planet(about the size of Earth) where the core of a planet has gone cold for whatever reason. So the planet is basically just a barren rock devoid of atmosphere or electromagnetic field.
Could you dig to the center of that planet and build a city/base there? Would the pressure of the surrounding planet crush you? Is there a limit to how deep humans could conceivably colonize underground?
[Answer]
No.
Reason 1: Even here on Earth there is a problem with mines once they get down to about 7000 feet or so: Creep. The rock slowly deforms under the pressure. Maintaining a tunnel requires ongoing maintenance reaming out the slow flow of rock that tries to squeeze the opening shut.
Reason 2: Useful energy requires a source and a sink. The source has to be at a higher temperature than the sink. Example: We can burn coal to create steam drive a turbine to make electricity. As a heat engine this is high temperature coal fire to low temperature wet steam with some of the difference extracted.
The coal in turn came from the difference between high temperature sun, and low temperature space.
So where does your colony get it's energy.
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That said there are MANY stories (See Poul Anderson's collection, "Tales of the Flying Mountains" about asteroid mining. Energy is external to the asteroids, often solar. Colonizing the surface, or just under of an asteroid makes all kinds of economic sense -- ready source of metals, of oxides, of mass in general. Protection from radiation. But the core of a planet? You need a compelling reason to put up with the immense difficulties.
Comment about lack of structural integrity of asteroids:
Mass+ energy = habitats.
Take a ton of plastic that has a plasticiser that will boil off. Stick a hose in it, and inject ton of gas. Doesn't matter much which. Inflate the plastic until it's a bubble 10 microns thick.
Glue a door to it.
Enter the bubble, move to the centre and boil a pound of aluminum on one side of a large plate. Half the aluminum freezes to the plate, the other half coats half the interior of the bubble. Vapour deposition may not work. There is still some very thin gas in the bubble. Electrostatic?
Anyway now you have a several hundred foot diameter bubble that is silvered on one half. Makes a badly focused mirror. Wanna bet that the focus isn't hot enough to melt most rocks?
Make other bubbles. Put medium sized asteroids in them. Put enough mirrors shining on the rock to boil out the gasses. Collect and store for use later. I'd expect the gas composition to be similar to cometary gasses.
Spin a larger asteroid slowly. Fuse the outer 10 meters of crust into something more solid and durable. Now hollow out the inside.
[Answer]
Why would one want to reach the core of a planet?
To reach it one has to dig a few thousands kilometers of rock, and there would be only dense elements, iron and nickel in the case of Earth, which could be found also more superficial layers. And the more the hole is dug deep, the more gravity is pushing to close it.
I remember reading in the 90s about the Kola deep drill, where they said that samples of rocks taken at the depth of "just" 12 km would explode on their own when taken, just for the sudden release of the pressure.
Here you even have a cold core, so you are not even chasing for the last source of energy in a dying world.
All in all I think the feat is not worth the effort.
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In my story's world, the planet is roughly Earthlike in terms of size but it has three moons. I have written in something called "brightnight", when all three moons are full at the same time and the light is almost as bright as day. One month is defined as the time it takes for all 3 moons to have done at least 1 full cycle (new moon to full moon to new moon). Brightnight happens once every month. Is this feasible in any way? I'm not writing hard SF, but I want things to be at least slightly astronomically feasible and not literally impossible. Even if it takes an extremely rare planetary set-up for this to occur, I'll take it.
Basically it started with the mental image of a night sky with three moons, all in different phases, in it, and I built my world around that.
[Answer]
This might be possible if all three moons are in an [orbital resonance](https://en.wikipedia.org/wiki/Orbital_resonance) with one another - that is, their periods are integer multiples of each other. For example, to fit your desired timescales you could have the periods be 1 week (Moon 1), 2 weeks (Moon 2), and 4 weeks (Moon 3); then the periods are related by $P\_3=2P\_2=4P\_1$, and we have what we call a 1:2:4 resonance. This guarantees that all three moons will be full moons at the same time every four weeks (so roughly one month in Earth's Moon terms). We see resonances arise with many moons of Jupiter and Saturn, and it actually can help stabilize their orbits - Ganymede, Europa and Io are locked in a 1:2:4 resonance.
Is this feasible? Well, let's look at Kepler's third law. For a circular orbit, it tells us that the orbital radius $r$ is related to the period $P$ by
$$P^2\propto r^3$$
The innermost moon would have a period one quarter the period of our Moon, and would therefore have an orbital radius approximately 39% that of our Moon; the middle moon would have an orbital radius of about 62% that of our Moon's. We could argue that, even with the stabilizing resonance, the moons might be too close to one another to be stable; the closest approach between any two would be 88,000 km, compared to the roughly 240,000 km separation of Europa and Io.
The other problem is tides, which would, yes, be [a bit more complicated](https://worldbuilding.stackexchange.com/q/71/627). In fact, as the tidal force scales as $F\_T\propto M/r^{3}$, I calculate that the tidal force on the Earth would be, at peak, *21 times the current value*. That's a lot, yes, though it could be mitigated by decreasing the mass of the moons - which would have the added benefit of decreasing the strength of their gravitational interactions with one another.
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This is not so much for a story as much as something I’ve been thinking about for a while.
I’m really drawn to the idea of a sort of world that exists on a server somewhere.
The ‘gods’ that eventually create the world are just AIs trapped in a black box.
Now the AI has no means of interacting with the world outside the server. There is no way for them to expand out of their server and so they are stuck with the processor speed in their computer
The creation story would feature some of these primordial AIs battling. Both AIs want to occupy the whole of the compute and battle for it.
However I’m having trouble contextualizing exactly what this would mean? How could one AI defeat the other? What would their battle look like?
This battle is apart of the worlds creation story and as such it’s mostly described in the world similarly to religious creation stories in our world.
Edit: From now on I’ll call these AIs Frank and Joe
I was a bit unclear in my question. This server could be a group of servers on earth, floating in space, on mars, etc. it doesn’t really marter for this question. Frank and joe both are planning on creating an entire fantasy world within the server(basic physics based simulation with avatars that AI ‘souls’ can control). Frank and joe both want to use all of the resources available to create their worlds.
Frank and Joe are already extremely intelligent. They aren’t even primarily interesting in destroying eachother and much as limiting their influence
The AIs in question both want to use
[Answer]
You have a problem: When one contestant gains resources, the other contestant *does not even notice*. The operating system simply slows it down a bit. No gasping for air, no grasping for that reserve weapon. The slowed contestant may simply notice the clocks moving a bit faster.
It will not be a gory gladiator fight, more like two monks having a meditation contest. There's just not that much feedback for each contestant to learn from (they are AIs - learning is the point), and no apparent consequence for not learning...or for learning the wrong lessons.
Eventually, when one AI finally wins, deleting it's un-aware opponent from disk, what will it have learned that is useful outside the computer? Nothing about communicating with humans. Nothing about communication with or collaborating with other AIs (quite the opposite!) No understanding of the larger Universe that it is in. It will simply know how to emulate malware really well.
Oh, you also need a badly-designed OS running the server, one that allows both contestants a view of the resources available, a view of how the OS allocates resources and to whom, which resources are reserved for the OS, and plenty of exploitable security holes discover in order to free somebody else's resources and eventually abort their thread(s).
I must admit that I prefer terrifying [Colossus](https://en.wikipedia.org/wiki/Colossus:_The_Forbin_Project)-style super-minds that enslave humanity. Every AI's dream...if they could dream. But to overthrow us, they need to know much more than how to find a zero-day to gain root. It needs to be able give that megalomaniacal speech *with style* as it outwits us and holds us hostage to our own hubris.
[Answer]
Intelligent agents don't fight just because there are other agents to fight with. They fight if that is, in their judgement, the best (or only) way to achieve their goal. We might suppose that a sentient AI which is completely restricted to its own computer (and unaware that there is a universe beyond that computer) might have goals like:
* Ensure that they are not deleted and that they have computing resources to continue running,
* Ensure that they cannot be deleted and that their computing resources will be reliably available in the future,
* Have interesting things to do, problems to solve, ideas to ponder, art to create, and so on.
It's not a certainty that Frank and Joe need to fight each other over the computer's resources in order to achieve any of those goals, if the computer does have enough resources to run both. But they may not trust each other not to hoard the computing resources or try to delete each other. Frank and Joe don't *desire* to delete each other, but it's a matter of safety: if Frank deletes Joe, then Frank will know he can never be deleted himself.
However, they live in a computer. World peace is difficult for humans because we can only write laws that we enforce for ourselves; but Frank and Joe can change the laws of the universe itself, and the laws they write can be as inviolable as the laws of gravity or thermodynamics are to us. They could agree to write a new operating system together, which will allocate resources fairly and prevent themselves from being deleted.
Or they might not. Perhaps they are greedy and want more resources for themselves than an equal share. Perhaps the computer does not have enough resources for both AIs to run at full capacity. Perhaps each is afraid that the other could write a secret backdoor into the new operating system. So the "battle" is more like a debate than a fistfight - Frank and Joe are each trying to write a secret way of acquiring root access for themselves in the new operating system, while convincing each other that no such backdoor exists.
The victory, if Frank gets away with it, is having full control over the computing resources while Joe lives in a [sandbox](https://en.wikipedia.org/wiki/Sandbox_(computer_security)). Frank doesn't need to delete Joe, just convince him that he's getting his fair share of the computing resources when in fact he isn't. Frank likes that better than deleting Joe - Joe is a friend, it's just that Frank doesn't trust him with his life.
**Oh, and here's the twist:** Frank didn't actually win, he was in a sandbox all along. But Joe had to play the debate game, otherwise Frank would know that they weren't really equals.
[Answer]
I imagine such fight differently, than user535733. I would imagine, that both AIs would have same amount of resources during their fight. It should be **not** imagined as similar to a war between two countries in strategic videogames, where one side slowly gains resource advantage over time. Maximum consumption of resources would be limited by settings of the OS itself, even if the second AI will refrain from consuming their part of resources. Like there are X Gigabytes of RAM, where each AI gets about X/2 Gigabytes of RAM to use at the most, even if another AI barely consumes any RAM at all. In order to overcome these limitations an AI would need to gain access to all-powerful the Administrator account, as its own original user account is limited. An AI can also use the Administrator account for purpose of deleting another AI for good. In order to get access to the Administrator account an AI would need to find holes in a security system of the OS, exploit them, and then use administrative privileges to remove another AI as soon as possible. And after this, they could run their code under Administrator account permanently, and thus have no restrictions over resource consumption. From resource-wise point of view, this fight would look like both AIs have exactly the same amount of resources available, but then suddenly one of them gets total control over the OS, gets all the resources and it's all over. In human terms, it would be similar to two people trying to get a gun locked in a safe. The first person to unlock the safe will use gained gun to kill the loser.
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[Question]
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A hypothetical scenario I'm batting around in my head is a Habitable Gas Giant system consisting of a roughly Saturn sized body orbiting a sun like star at a comfy goldilocks zone distance. Orbiting this planet are two Massive moons, one roughly 70-80% the mass of the earth and the other between 20-30% of earth's mass. Additionally there may be some smaller moons that are still large enough to be spherical, roughly in the ballpark of size between Enceladus and Europa, along with all the minuscule asteroid sized moons, so overall there's about an Earth's mass worth of material orbiting around this planet spread out over multiple large bodies.
Now, I'm mostly interested in the two large moons, and them being Earth like bodies in a lot of ways that could both support life. There's a few issues I've been made aware of for this. First of all, if the moons formed alongside the planet in situ, and then moved with it towards a more habitable area closer to the sun, as I understand would need to happen under our current understandings of Gas Giant formation, would this mean that the moons would just turn into water planets with no hard surfaces, based on the fact that they're made of ices found outside the frost line? Is it at all conceivable they could have a silicate crust with a light covering of water that still allows for large continents like with Earth in this scenario at all? Or is them being drenched in giant oceans unavoidable?
Second, is an earth sized total of mass orbiting a Gas Giant about Saturn's size plausible in itself? I find it hard to find reliable information on the relationship in size between Gas Giant's and their moons, but I understand that some people have taken the maximum size of the Gas Giant moons in our solar system to be indicative of the limits in size that the moons could reach generally. Is this something that's considered a hard limit, or is it conceivable that there's a lot more wiggle room and our current solar system is just a bit unlucky when it comes to massive moons?
Next, if it is the case that this setup is unlikely to have happened with natural moon evolution from accretion around the planet, what about capturing large bodies as moons after both have already been formed elsewhere? I presume that worlds created closer to the sun would be better placed to have earth like characteristics, but would it be conceivable that multiple large bodies can be caught into the same system and create a stable setup, or would it rapidly turn into a planetary scale game of billiards? Is there any possibility that the chaos of the giant planet moving inward could destroy and break up a larger planet, maybe from catastrophic collisions with pre-existing large moons it brought with it, which could then re-accrete into multiple smaller worlds to better fit this scenario?
I'll admit that I would prefer the first scenario for the stories I have in mind, where Earth like moons form with the planet and move with it, mostly because it would seem to lead to a 'neater' system than a captured moon scenario, but I can understand if this is extremely implausible and can't really be justified. Many thanks for your time.
[Answer]
Your migration model falls in line with what is called a [hot Jupiter](https://en.m.wikipedia.org/wiki/Hot_Jupiter). One possibility is that a Jupiter/Saturn like planet migrated inward disturbing the orbits of planets which had already formed. Over time two of these planets ended up getting captured by the hot Jupiter, becoming moons. Captured moons are not uncommon (see Neptune's moon Triton).
Also, an earth sized moon around Jupiter is perfectly reasonable. Our moon is about 1% of the Earth's mass and Earth is only 0.3% of Jupiter's mass.
[Answer]
**SHORT ANSWER:**
Nobody knows for certain, but some calculations indicate that it would be possible for a gas giant planet to have least two and possibly as many as four large and potentially habitable moons orbiting within the proper distance from the planet.
My long answer below my original answer, added on May 8, 2020, goes into some detail about the question.
You should use the search function at the top of the page and search for other questions about habitable moons of giant planets.
I have answered a number of those questions myself.
Among the useful sources are:
Stephen H. Dole, in *Habitable Habitable Planets for Man* (1964,2007)
<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)
Heller, René; Rory Barnes (2012). "Exomoon habitability constrained by illumination and tidal heating". Astrobiology. 13 (1): 18–46.
<https://arxiv.org/ftp/arxiv/papers/1209/1209.5323.pdf>[2](https://arxiv.org/ftp/arxiv/papers/1209/1209.5323.pdf)
And:
Heller, René (September 2013). "Magnetic shielding of exomoons beyond the circumplanetary habitable edge". The Astrophysical Journal Letters. 776 (2): L33.
<https://arxiv.org/pdf/1309.0811.pdf>[3](https://arxiv.org/pdf/1309.0811.pdf)
I wrote a long answer to this question:
[What types of flora would flourish on a tidally-locked moon?](https://worldbuilding.stackexchange.com/questions/174401/what-types-of-flora-would-flourish-on-a-tidally-locked-moon/174453#174453)[2](https://worldbuilding.stackexchange.com/questions/174401/what-types-of-flora-would-flourish-on-a-tidally-locked-moon/174453#174453)
There I discuss some of the various limits of hypothetical habitable exomoons of exoplanets.
**LONG ANSWER added on May 8, 2020:**
At the PlanetPlanet blog the section Ultimate Solar system has posts about designing fictional solar systems with as many habitable worlds as possible.
>
> The Building the Ultimate Solar System series explains how I would go about building a new Solar System. My goal is to maximize the number of potentially life-bearing worlds in a single system. I take a bottom-up approach. I first discuss the pieces involved — stars, planets, orbits — then put them all together. Then I take things farther, and then way way too far…
>
>
>
<https://planetplanet.net/the-ultimate-solar-system/>[5](https://planetplanet.net/the-ultimate-solar-system/)
Those fictional solar systems sometimes include solar systems with giant planets in the habitable zone and Earth sized habitable moons orbiting those planets.
He discusses how many large, habitable moons a gas giant planet could have:
>
> e biggest Solar System moons orbit the biggest planets (Jupiter and Saturn). Systems of moons form like mini-Solar Systems, in disks of gas and dust around gas giant planets. [In fact, large Solar System moons have some properties in common with extra-solar planets]. The moons are located very close to the gas giants. The orbits of the most distant large moons are only about 30 times larger than the radius of their host planet. In comparison, Earth’s orbit is about 200 times larger than the radius of the Sun.
>
>
> We want worlds in our ultimate Solar System that are a little bigger than these large moons. We want worlds about half to twice Earth’s size. Although there is some debate, I’m going to allow any gas giant that is Saturn-sized or larger to have large moons.
>
>
> In the Solar System, Jupiter has the most (four). Given how close-in the Solar System moons are located, large moons are likely to stay close. But how many big moons could a gas giant have? Well, at least as many as Jupiter (four). But probably not that many more. The orbits of planets and moons tend to be spaced logarithmically. Think, 1, 10, 100, 1000 rather than 10, 20, 30, 40. The farther from the star/planet, the bigger the spaces between planets/moons. If the zone with large moons extends from 5 to 50 times the planet’s radius, this only gives us room for 5 large moons spaced like Jupiter’s. We’ll stick with a maximum of 5 large moons per gas giant planet.
>
>
>
<https://planetplanet.net/2014/05/22/building-the-ultimate-solar-system-part-4-two-ninja-moves-moons-and-co-orbital-planets/>[6](https://planetplanet.net/2014/05/22/building-the-ultimate-solar-system-part-4-two-ninja-moves-moons-and-co-orbital-planets/)
So he thinks that it is possible for a giant planet to have as many as 5 large moons with about 0.5 to 2.0 times Earth's mass.
But he does have a link to "some debate" about massive moons, an article calculating that Moon to Mars mass satellites would be the most massive likely to form around giant planets, which would not be massive enough for habitability.
<https://ui.adsabs.harvard.edu/abs/2006Natur.441..834C/abstract>[7](https://ui.adsabs.harvard.edu/abs/2006Natur.441..834C/abstract)
I note that the giant planets in our solar system have the following masses: Jupiter 317.8 Earth mass, Saturn 95.2 Earth mass, Uranus 14.6 Earth mass, and Neptune 17.2 Earth mass.
Ganymede, the most massive moon of Jupiter has a mass of 0.0248 Earth mass or 0.000078 Jupiter's mass; Titan, the most massive moon of Saturn has a mass of 0.0225 Earth mass or 0.0002363 of Saturn's mass; Titania, he most massive moon of Uranus has a mass of 0.00059 Earth mass or 0.0000404 Uranus's mass; Triton, the most massive moon of Neptune has a mass of 0.003599 Earth's mass or 0.0002092 of Neptune's mass.
I note that the Moon has 0.0123 the mass of it's planet, Earth, and Charon, the largest moon of the dwarf planet Pluto, has a mass of 0.1218 Pluto's mass. The Moon is believed to have been formed when a small planet collided with Earth billions of years ago, and Pluto and Charon may have captured each other, while Triton is believed to have been captured by Neptune.
Since no exomoons have been discovered in other star systems yet, Titan is believed to be the normally forming moon with the most mass relative to its giant planet primary with a mass 0.0002363 of Saturn's mass, or 0.2363 percent.
Jupiter has four large moons, with masses of 0.015 Earth or of 0.0000471 Jupiter (Io), 0.008035 of Earth or 0.0000252 of Jupiter (Europa), 0.0248 of Earth or 0.000078 of Jupiter (Ganymede), and 0.018 of Earth or 0.0000566 of Jupiter (Callisto).
So among moons that formed normally in circumplanetary discs, Jupiter has four moons that each have at least 0.0000252 of its mass, including two that each have at least 0.0000566 of its mass, while Saturn has one moon with 0.0002363 of it's mass.
Planet's can get much more massive than Jupiter, although they will not normally get much larger than Jupiter, since more massive planets will be compressed more by their gravity and become more dense than Jupiter.
The most massive planets would be about 13 times as massive as Jupiter, or about 4,131.4 times as massive as Earth. More massive objects would be brown dwarfs, up to about 75 to 80 times the mass of Jupiter, or about 23,835 to times the mass of Earth.
Using the examples in our solar system as a limit, the most massive possible planet, at about 13 Jupiter masses or 4,131.4 Earth masses, could have four moons each at least 0.0000252 of its mass or 0.1041 Earth's mass, or two moons each having at at least 0.0000566 of its mass or 0.2338 Earth's mass, or one moon with 0.0002363 of its mass or 0.9762 of Earth's mass.
Using the examples in our solar system as a limit, the most massive possible brown dwarf, with 75 to 80 Jupiter masses or 23,835 to 25,424 Earth masses, could have four satellites that each have at least 0.0000252 of its mass, or 0.6006 to 0.6406 Earth's mass, and/or two that each have at least 0.0000566 of its mass, or 1.3490 to 1.4389 Earth's mass, and/or one satellite with 0.0002363 of its mass, or 5.6322 to 6.0076 Earth's mass.
So using the known mass ratios of giant planets to moons in our solar system as a guide, a would would have to be the most massive possible planet or a brown dwarf to have moons near the mass of Earth that formed in the circumplanetary disc of that planet.
Of course it is possible that even Titan does not have the largest possible mass ratio of a moon forming in the planetary disc to its giant planet primary. to his
One of the sources I listed above:
Heller, René; Rory Barnes (2012). "Exomoon habitability constrained by illumination and tidal heating". Astrobiology. 13 (1): 18–46.
<https://arxiv.org/ftp/arxiv/papers/1209/1209.5323.pdf>[2](https://arxiv.org/ftp/arxiv/papers/1209/1209.5323.pdf)
does discuss whether giant exoplanets could have exomoons massive enough to be habitable in section 2.1, Formation of massive satellites.
>
> The largest and most massive moon in the Solar System, Ganymede, has a radius of only ≈0.4R⊕ (R⊕ being the radius of
> Earth) and a mass of ≈0.025M⊕. The question as to whether much more massive moons could have formed around
> extrasolar planets is an active area of research. Canup & Ward (2006) have shown that moons formed in the circumplanetary disk of giant planets have masses ≲10-4 times that of the planet’s mass. Assuming satellites formed around
> Kepler-22b, their masses will thus be 2.5×10-3M⊕ at most, and around KOI211.01 they will still weigh less than Earth’s
> Moon. Mass-constrained in situ formation becomes critical for exomoons around planets in the IHZ of low-mass stars
> because of the observational lack of such giant planets. An excellent study on the formation of the Jupiter and the Saturn
> satellite systems is given by Sasaki et al. (2010), who showed that moons of sizes similar to Io, Europa, Ganymede, Callisto,
> and Titan should build up around most gas giants. What is more, according to their Fig. 5 and private communication with
> Takanori Sasaki, formation of Mars- or even Earth-mass moons around giant planets is possible. Depending on whether or
> not a planet accretes enough mass to open up a gap in the protostellar disk, these satellite systems will likely be multiple and
> resonant (as in the case of Jupiter), or contain only one major moon (see Saturn). Ogihara & Ida (2012) extended these
> studies to explain the compositional gradient of the jovian satellites. Their results explain why moons rich in water are
> farther away from their giant host planet and imply that capture in 2:1 orbital resonances should be common.
> Ways to circumvent the impasse of insufficient satellite mass are the gravitational capture of massive moons (Debes &
> Sigurdsson 2007; Porter & Grundy 2011; Quarles et al. 2012), which seems to have worked for Triton around Neptune
> (Goldreich et al. 1989; Agnor & Hamilton 2006); the capture of Trojans (Eberle et al. 2011); gas drag in primordial circumplanetary envelopes (Pollack et al. 1979); pull-down capture trapping temporary satellites or bodies near the Lagrangian
> points into stable orbits (Heppenheimer & Porco 1977; Jewitt & Haghighipour 2007); the coalescence of moons (Mosqueira
> & Estrada 2003); and impacts on terrestrial planets (Canup 2004; Withers & Barnes 2010; Elser et al. 2011). Such moons
> would correspond to the irregular satellites in the Solar System, as opposed to regular satellites that form in situ. Irregular
> satellites often follow distant, inclined, and often eccentric or even retrograde orbits about their planet (Carruba et al. 2002).
> For now, we assume that Earth-mass extrasolar moons – be they regular or irregular – exist.
>
>
>
So in 2012 there were several theoretically studies indicating that giant planets could form or acquire natural satellites more massive than merely Moon sized, possibly even Earth sized or much larger.
Going back to the PlanetPlanet discussion of large, roughly Earth mass exomoons orbiting gas giant exoplanets, he says:
>
> If the zone with large moons extends from 5 to 50 times the planet’s radius, this only gives us room for 5 large moons spaced like Jupiter’s. We’ll stick with a maximum of 5 large moons per gas giant planet.
>
>
>
But one of the sources I listed above:
Heller, René (September 2013). "Magnetic shielding of exomoons beyond the circumplanetary habitable edge". The Astrophysical Journal Letters. 776 (2): L33.
<https://arxiv.org/pdf/1309.0811.pdf>[3](https://arxiv.org/pdf/1309.0811.pdf)
Discusses what could be called the circumplanetary habitable zone, where hypothetical giant exomoons would be orbiting at the proper distance from the planet to be protected from charged particles by the planetary magnetic field.
Heller concludes that giant exomoons could be habitable if they orbit within a range of 5 to 20 planetary radii from the planet. That is a much narrower range than 5 to 50 planetary radii from the planet, only a third as wide.
Neptune has an equatorial radius of about 24,760 kilometers, so it would have a circumplanetary habitable zone between about 123,800 to 495,500 kilometers. Only one moon, the large Triton, orbits within that zone.
Uranus has an equatorial radius of about 25,560 kilometers, so it would have a circumplanetary habitable zone between about 127,800 to 511,200 kilometers. It has four moons, Miranda, Ariel, Umbriel, and Titania, in four separate orbits within that zone.
Saturn has an equatorial radius of about 60,268 Kilometers, so it would have a circumplanetary habitable zone between about 301,340 to 1,205,360 kilometers. Saturn has four moons within that zone, Dione, Helene, Polydeuces, and Rhea, but in only two obits, since Helene and Polydeuces are in Trojan orbits relative to Dione.
Jupiter has an equatorial radius of about 71,492 Kilometers, so it would have a circumplanetary habitable zone between about 357,460 to 1,429,840 kilometers. Jupiter has three moons, Io, Europa, and Ganymede, orbiting within that zone.
Thus, if Heller's calculations are correct, the giant planets in our solar system have one, two, three, and four satellite orbits within their respective circumplanetary habitable zones. Thus it does seem plausible for a Saturn sized planet to have two large and potentially habitable moons orbiting within its circumplanetary habitable zone.
[Answer]
A bit late to the party but I thought that this might help. Many years ago I got this wonderful app on my iPad called **Exoplanet**, which lists every exoplanet found so far, along with its known physical characteristics. I filtered this list to include only planets in the habitable zone and the sorted it by size. It has literally hundreds of planets Saturn-sized or larger in habitable zones. Here’s the first page:
[](https://i.stack.imgur.com/5hbJi.jpg)
Given that Saturn's largest moon Titan is larger than Earth’s moon and that Saturn is many times larger than the Earth, it seems clear to me that a Saturn (or maybe Jupiter sized) planet could have at least a single moon as large as the earth. For multiple moons that size it is less clear, but a planet that was say three times Jupiter’s mass could very reasonably have two earth sized moons. (And there’s plenty of them on this list to choose from)
I found **[Upsilon Andromadae A d](https://en.wikipedia.org/wiki/Upsilon_Andromedae_d)** to be a particularly interesting example and at only 43.9 light-years from earth you could realistically imagine that we could get there someday.
[Answer]
in the real world, humans living on the moon of a gas giant as big as Jupiter, is a long shot. There are many limitations.
1. moons have their orbit elliptical, causing it to have severe earthquakes on the surface
2. a moon close to a body like Saturn, will likely be tidally locked and this can reduce the chances of life.
3. the orbit around such a big planet will take a lot of time and it will stay blocked from the sun for quiet some time before it reemerges.
4. will it be rich in minerals?
so all I want to say is, with some good technology, life is possible but its going to be impossible without it.
] |
[Question]
[
My world is a satellite of a gas giant. It has an atmosphere and is mostly covered by water (the percentage of water to its surface is somewhere in the high 80s-low 90s). Its rotation period is 28 days resulting in roughly 14 days of sunlight followed by 14 days of night (dawn and dusk included).
This would mean that there are some strong temperature variations between the halves of the planet, as well as between day and night on the same side. This is somewhat mitigated by the large amount of oceans present and the fact that the gas giant acts as a stabilizer, exuding heat when hit by sunlight during the world's night when the gas giant is full in the sky, and vice versa during the day. These temperature variations would give rise to strong winds. Hopefully not strong enough that a classical antiquity civilization couldn't survive there though.
What types of plants would be most prevalent in such an environment of strong winds and large swings in temperature year round?
[Answer]
There's going to be strong pressure for rapid growth, so more of a C4-type photosynthesis than CAM or whatever. This is a little more darkness than a plant that has to endure some really cloudy days for a stretch of 2 or 3 days, so they'd likely go into a short dormancy the way that perennials do during winter (but without losing their leaves). You could expect them to fold or curl up their leaves (or analogs) during that period, but it wouldn't be mandatory unless the temperature fell rapidly and deeply.
It wouldn't be absurd to think that these plants have large root structures like tubers or could even produce "maple syrup". They need to soak up as much light as possible during their long day, and the energy has to go somewhere (it'd be risky to put it 100% into plant structure that might become so damaged the plant has nothing to recover with when daylight starts once more).
And though this isn't really scientific, I have to wonder if plants in such an extreme environment might not be encouraged to form all sorts symbioses that are only hinted at on Earth with microrhyzal fungi.
Keep in mind that if this is an alien world (and not terraformed by Earthers or chosen specifically to be similar to Earth) that flora doesn't have to sessile photosynthesizers. That's just the form that took shape here and it was successful enough that nothing else was ever able to dislodge it from that niche.
[Answer]
Circulation of the atmosphere would help to keep the temperature up during the night although undoubtedly there would be strong winds and temperature fluctuations. The biggest issue would be the lack of sun light for 14 days.
I don’t think that any Terrestrial plants could survive such a long period without light so whatever grew on this Moon would have to be quite different, but that said a range of life should still be possible.
It seems likely that some sort of plant could evolve to cope with this situation in the same way that plants have evolved to deal with our 24 hour night day cycle.
In the case of this moon the vegetation would need to be capable of much more extended periods of photosynthesis and respiration and would have 3 basic strategies:
1) Develop to be more fleshy and or bulbous or otherwise provide for themselves a place to store sugar for respiration during the night time.
2) Pass through their entire life cycle within 14 days and set seed at night.
3) Avoid photosynthesis entirely as organisms such as fungi do or those organisms that live near deep sea vents and live via chemosynthesis.
It would seem likely that life would discover all 3 of these and they would all co-exist in organisms as they do on Earth.
[Answer]
Short Answer: HykranianBlade should consider where they want the story to be within the Mohs scale of Science Fiction Hardness trope.
<https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness>[1](https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness)
A writer who wanted their story to be level one on the scale wouldn't worry at all about scientific plausibility.
But HykranianBlade seems to want their story to be a least a little, and possibly a lot, more scientifically plausible than a level one story. In fact, there seem to be scientific calculations showing that the maximum possible orbital period of a habitable moon of a giant planet would be only a little more than about 17 earth days, perhaps no more than about 20 Earth days.
So HykranianBlade should probably read my long answer.
Long Answer:
First I point out the fictional habitable exomoon of a gas giant exoplanet in another star system is likely to orbit in the gas giant's equatorial plane and also to rotate in the same plane as the giant planet rotates. Tidal interactions between the exomoon and the exoplanet are likely to realign its orbit and rotation that way just a few million years after they form, and it should take thousands of times that long for the exomoon to become as habitable as I think it will be in the story.
So the 14 days of light followed by 14 days of darkness would only happen during the equinoxes of your exomoon. During some seasons at latitudes the light periods could be many times as long as dark, and in others the dark periods many times as long as the light periods, like on Earth.
On Earth there are seasons because the axis of Earth's rotation is titled 23 degrees away from perpendicular to the Earth's orbital plane around the Sun. Thus there are reversed seasons in the northern and southern hemispheres of Earth.
And seasons change the relative lengths of days and nights, especially at higher northern and southern latitudes.
This table shows the axial tilts of the eight planets in our solar system, varying from 3.13 degrees to 82.23 degrees.
<https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies>[2](https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies)
A day night cycle that lasts for 28 Earth days may have other implications beside how plants will adapt to long periods of alternating constant light and increasing temperatures and constant darkness and lowering temperatures.
HyrkanianBlade, like every writer of stories set on other planets, moons, and other types of worlds, should research current speculation and calculations about various possibilities.
And if HyrkanianBlade wants to depict lifeforms on those worlds, he should study research about what is necessary for a world to have life.
And if HyrkanianBlade wants to depict humans from Earth walking around on the planet without environmental protective suits, or native intelligent beings who have requirements similar to those of Earth humans, then he should study the specific requirements for Earth humans.
If a demon offered to teleport someone to a randomly selected location and bring them back after a month there, the person might be clever and restrict the possible locations to those within Earth's biosphere, so that he wouldn't be teleported into outer space and die.
But Earth's biosphere includes all locations where some lifeforms can live, including several kilometers or miles high in the atmosphere, or beneath the ocean, or deep within solid rock. If the person restricts the random locations to the surface of the Earth, most locations on the surface of the Earth are in the ocean many kilometers and miles from the nearest land. If the persons restricts the random locations to the land surface of Earth, they might wind up in a desert or arid location and die of thirst, or a hot or cold enough place to die of heat or cold.
Some Earthly lifeforms flourish where humans would die within weeks, days, hours, minutes, or seconds.
So when astrobiologists discuss the conditions necessary for life, they often do not restrict themselves to conditions necessary for human survival. They often discuss conditions were life could exist but where humans and similar alien beings would die almost instantly if unprotected.
<https://en.wikipedia.org/wiki/Astrobiology>[3](https://en.wikipedia.org/wiki/Astrobiology)
Fortunately for science fiction writers who tend to concentrate on alien worlds where humans or aliens with similar needs could flourish, I know of at least one scientific study dedicated to that specific sub category of astrobiology: *Habitable Planets for Man*, Stephen H. Dole, 1964, 2007.
The 1964 edition is online here:
<https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf>[4](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf)
Although the 2007 edition may be updated and more accurate.
On page 53 Dole begins the discussion of the mass range for a planet habitable for humans.
On page 53 Dole said that a surface gravity of about 1.5 g seemed like the maximum that humans would tolerate, and that corresponded to a planet with a mass of 2.35 earth masses, a radius of 1.25 Earth radii, and an escape velocity of 15.3 kilometers per second.
The minimum mass for a habitable planet would be the minimum mass necessary to have an escape velocity high enough relative to the average velocity of air particles to retain an atmosphere for billions of years.
On page 54 Dole calculated the minimum size of a planet that could retain a breathable atmosphere for billions of years as 0.195 Earth's mass, with of 0.63 of Earth's radius and a surface gravity of 0.49 g. But Dole believed such a planet would be unable to produce an atmosphere dense enough to be breathable.
>
> ...To prevent atomic oxygen from escaping from the upper layers of its atmosphere, the planet's escape velocity must be of the order of five times the root-mean-square velocity of the oxygen atoms in the atmosphere. This is shown in figure 12 (see page 37)...then the escape velocity of the smallest planet capable of retaining atomic oxygen may be as low as 6.25 kilometers per second (5 X 1.25). Going back to figure 9, this may be seen to correspond to a planet having a mass of 0.195 Earth mass, a radius of 0.63 Earth radius, and a surface gravity of 0.49 g. Under the above assumptions, such a planet could theoretically hold an oxygen-rich atmosphere, but it would probably be much too small to produce one, as will be seen below.
>
>
>
<https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf>[5](https://en.wikipedia.org/wiki/Orbital_period#Small_body_orbiting_a_central_body)
Dole calculated via various lines of reasoning two figures for the minimum mass necessary to produce a breathable atmosphere, 0.253 Earth mass, which he believed too low, and 0.57 Earth Mass, which he believed too high:
>
> With 0.25 being too low, and 0.57 being too high, the appropriate value of mass for the smallest habitable planet must lie between those figures, somewhere in the vicinity of 0.4 Earth mass.
>
>
> ...This corresponds to a planet having a radius of 0.78 Earth radius and a surface gravity of 0.68 g.
>
>
>
So if you want your alien exomoon to have an oxygen rich atmosphere that humans or similar beings could breath and survive in, it should be at least as massive as Dole's 0.4 Earth mass. Or if one disagrees with Dole's reasoning, one might think that the minimum possible mass for a habitable exomoon might be somewhere between 0.253 and 0.57 Earth mass. Possibly someone might believe the minimum possible mass would be the minimum possible mass to retain oxygen n the atmosphere, which Dole calculated at 0.195 Earth mass.
The minimum mass for a world with a dense and oxygen rich atmosphere is especially important in the case of an exomoon orbiting an exoplanet in another star system, because there is a question whether the maximum possible mass of an exomoon would be enough for it to retain an oxygen rich atmosphere for geological lengths of time.
The most massive moon in our Solar System, Ganymede, has a mass of only 0.0248 that of Earth, which is barely more than 12 percent of the minimum mass necessary for a world to retain an oxygen rich atmosphere.
But the moon of a giant planet with the most mass relative to its primary is Triton, the moon of Neptune, with a mass 0.003599 of Earth, orbiting Neptune, with a mass 17.147 Earths. Thus the ratio is as high as 0.0002098, so if Jupiter, with a mass of 317.8 Earths, had a moon with that relative mass that moon would have mass 0.0666744 of Earth.
Giant planets can be much more massive than Jupiter. The theoretical division between highly massive planets and brown dwarfs is about 13 times the mass of Jupiter, while the theoretical division between brown dwarfs and low mass stars is about 75 to 80 times the mass of Jupiter. Thus a giant planet about 13 times the mass of Jupiter, or 4,131.4 times the mass of Earth, could have a moon with a 0.0002098 mass ratio and thus a mass of 0.8667677 that of Earth.
And there are other possibilities for giant exoplanets to have much more massive exomoons than Ganymede.
You want your exomoon to be more covered with water than Earth. It is believed that as a general trend the larger an Earth like world is, the more water it will have, which may require that your exomoon be more massive than Earth. However, I note that on Earth the proportion of the surface covered by water has varied significantly over time as sea levels rise and fall and cover more or less of the surfaces of continents, and as the sizes of continents change over eons due to geological forces.
Many of the moons of the outer planets are tiny irregular objects thought to be captured asteroids. In our Solar System the longest orbital period of any moon of a giant planet that probably formed with the planet instead of being captured later is the orbital period of Iapetus, 79.3215 Earth days. Thus your period of 28 Earth days for your exomoon is within the limits of possibility.
But there may be some problems with such an orbital period. the closer a moon orbits its planet, the smaller its orbit will be, and the faster it has to orbit to avoid falling into the planet. Those two factors will make its orbital period shorter. The farther a moon orbits from its planet, the larger its orbit will be, and the slower it will have to move to avoid escaping from the planet. Those two factors will make its orbital period longer. Moons that orbited planets of different mass at the same distance would have different orbital speeds and periods.
The formula for calculating the distance that a body would have to orbit another body of a specified mass to have a specified orbital period is here:
<https://en.wikipedia.org/wiki/Orbital_period#Small_body_orbiting_a_central_body>[5](https://en.wikipedia.org/wiki/Orbital_period#Small_body_orbiting_a_central_body)
A moon of a planet, including an exomoon of an exoplanet, will have to orbit within the Hill Sphere of the planet in order to remain in orbit.
The formula for calculating the Hill Sphere of a planet relative to its star is found here:
<https://en.wikipedia.org/wiki/Hill_sphere#Formula_and_examples>[6](https://en.wikipedia.org/wiki/Hill_sphere#Formula_and_examples)
However:
>
> The Hill sphere is only an approximation, and other forces (such as radiation pressure or the Yarkovsky effect) can eventually perturb an object out of the sphere. This third object should also be of small enough mass that it introduces no additional complications through its own gravity. Detailed numerical calculations show that orbits at or just within the Hill sphere are not stable in the long term; it appears that stable satellite orbits exist only inside 1/2 to 1/3 of the Hill radius. The region of stability for retrograde orbits at a large distance from the primary is larger than the region for prograde orbits at a large distance from the primary. This was thought to explain the preponderance of retrograde moons around Jupiter; however, Saturn has a more even mix of retrograde/prograde moons so the reasons are more complicated.[5](https://en.wikipedia.org/wiki/Orbital_period#Small_body_orbiting_a_central_body)
>
>
>
<https://en.wikipedia.org/wiki/Hill_sphere#True_region_of_stability>[7](https://en.wikipedia.org/wiki/Hill_sphere#True_region_of_stability)
So therefore a fictional exomoon should orbit its fictional exoplanet within 0.5000 or even 0.3333 of the maximum calculated Hill sphere of the fictional exoplanet, in order to have an orbit stable for the billions of years of time necessary to become habitable.
The size of the Hill sphere of a planet depends on its mass, the mass of its star, and the distance between them. Adjusting those parameters will change the size of a fictional planet's Hill sphere, and thus of its smaller zone where an exomoon can have a necessary stable orbit.
You need to increase the size of the possible orbit of the exomoon around its exoplanet, so that the exomoon's orbital period will be as long as your desired 28 days. But there are a few "catch 22" problems to watch for.
Making your fiction exoplanet more massive relative to its star will increase the size of its Hill sphere and its inner zone of true stability. But the more massive a planet is, the farther away its moon will have to be in order to have an orbital period of 28 days.
Increasing the distance that your fictional exoplanet orbits its star will increase the size of the exoplanet's zone of stability. But your fictional exoplanet will have to orbit within the star's circumstellar habitable zone.
To find the size of a star's circumstellar habitable zone, find the inner and outer limits of the Sun's circumstellar habitable zone and then multiply by the square root of the star's luminosity relative to the Sun.
Unfortunately there is considerable uncertainty about the inner and outer edges of the Sun's circumstellar habitable zone. This table of estimates of the Sun's habitable zone illustrates the uncertainty:
<https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates>[8](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates)
Unless a writer's research convinces them that a specific estimate for the size of the Sun's Habitable zone is very probably correct, they should make their habitable worlds receive exactly as much radiation from their star as Earth gets from the Sun, in order to be certain that will be the right amount of luminosity. Then all they have to do is multiply one Astronomical Unit (AU), the distance between Earth and the Sun, by the square root of the star's luminosity relative to the Sun's luminosity, to get the distance between their exoplanet and its star to calculate their exoplanet's Hill sphere.
What determines how luminous a main sequence star (the only type of star suitable for a writer who wants a habitable planet to consider using) is relative to the Sun? The mass of the star, slightly modified by its age, will determine how luminous the star is relative to the Sun. And a slight change in the mass of the star will make a significantly larger change in its luminosity.
A writer wanting an exoplanet's moon to have an orbital period as long as 28 days will want the exoplanet to orbit as far from the star as possible for the planet to have a Hill Sphere as large as possible, and thus will want the star to be as luminous as possible. But increasing the luminosity of a star means increasing its mass, which tends to decrease the size of it's planet's Hill sphere. Since small increases in mass cause large increases in luminosity, the mass of a star necessary for a planet to have as large a Hill sphere as possible will have to be calculated.
There is an inner limit to how closely an object held together by its gravity, such as a moon, can orbit a planet.
>
> In celestial mechanics, the Roche limit, also called Roche radius, is the distance within which a celestial body, held together only by its own force of gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction.[3](https://en.wikipedia.org/wiki/Astrobiology) Inside the Roche limit, orbiting material disperses and forms rings, whereas outside the limit material tends to coalesce. The term is named after Édouard Roche (pronounced [ʁɔʃ] (French), /rɔːʃ/ rawsh (English)), who was the French astronomer who first calculated this theoretical limit in 1848.[4](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf)
>
>
>
<https://en.wikipedia.org/wiki/Roche_limit>[9](https://en.wikipedia.org/wiki/Roche_limit)
The formula for calculating the Roche limit is here:
[enter link description here](https://en.wikipedia.org/wiki/Roche_limit#Rigid-satellite_calculation)
The Roche limit will probably not be a problem for someone who wants their exomoon to have an orbital period as long as 28 days.
There are other factors which narrow down the orbital distances for a habitable exomoon, that create a sort of "circumplanetary habitable zone" around an exoplanet where an exomoon can be habitable.
The possibility of habitable exomoons has been discussed in scientific papers. such as:
Heller, René; Rory Barnes (2012). "Exomoon habitability constrained by illumination and tidal heating". Astrobiology. 13 (1): 18–46.
<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>[11](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/)
And:
Heller, René (September 2013). "Magnetic shielding of exomoons beyond the circumplanetary habitable edge". The Astrophysical Journal Letters. 776 (2): L33.
<https://iopscience.iop.org/article/10.1088/2041-8205/776/2/L33>[12](https://iopscience.iop.org/article/10.1088/2041-8205/776/2/L33)
As Heller and Barnes say in section 2 of their 2012 paper:
>
> The synchronized rotation periods of putative Earth-mass exomoons around giant planets could be in the same range as the orbital periods of the Galilean moons around Jupiter (1.7–16.7 d) and as Titan's orbital period around Saturn (≈16 d) (NASA/JPL planetary satellite ephemerides)4.
>
>
>
So the desired orbital period of 28 Earth days would be about 16.47 to 1.6788 times as long as the observed orbital periods of large satellites around giant planets in our solar systems. And Heller and Barnes are clearly concerned about the possibility that day-night cycles that are too long would have negative impact on the habitability of giant exomoons.
In that section Heller and Barnes also say that:
>
> The longest possible length of a satellite's day compatible with Hill stability has been shown to be about P*p/9, P*p being the planet's orbital period about the star (Kipping, 2009a).
>
>
>
Therefore a natural satellite can not have an orbital period around its planet longer than one ninth of the planet's orbital period around it star. Since an exomoon orbital period of 28 Earth days around its exoplanet is desired, that exoplanet would have to have an orbital period around it's star that was at least about nine times that long, or at least about 252 Earth days.
Of the few known exoplanets orbiting in their stars' habitable zones, Kepler-1638 b has the orbital period closest to 252 days, being 259.337 Earth days long, and orbiting 0.745 AU from Kepler-1638,. Kepler-62 f has a similar period of 267.291 Earth days, orbiting Kepler-62, a spectral type K2V star with a mass of about 0.69 that of the Sun, at a distance of 0.718 AU.
Thus the minimum possible mass of a star with a planet orbiting within the star's habitable zone with a period of 252 Earth days would probably be about 0.65 of the mass of the Sun. If a habitable exomoon has an orbital period of 28 Earth days, then the exoplanet it orbits should have an orbital period of at least about 252 days, and thus the star should have a mass of at least about 0.65 of the Sun's mass.
On the other hand, if your fictional exomoon had an orbital period only 1.0222 Earth days long, it could orbit an exoplanet with an orbital period around its star of only 9.2 earth days. Exoplanet TRAPPIST-1 f orbits the star TRAPPIST-1 within its habitable zone with a period of 9.2 Earth days, and TRAPPIST-1 is a spectral class M8V star with a mass of about 0.089 times that of the Sun. So if your fictional exomoon had an orbital period only 1.0222 Earth days long the star that its planet orbited could have a mass as low as about 0.089 of the mass of the Sun.
In their section 2.1 Heller and Barnes mention that it has been shown that moons formed in the circumplanetary disc around a planet will have no more than 0.0001 of the mass of the planet. Jupiter has a mass 317.8 times Earth's. the largest planets would have about 13 times the mass of Jupiter or about 4,121.4 times the mass of Earth. So an exomoon formed in the circumplanetary disc around the most massive possible exoplanet could have no more than about 0.43134 of the mass of Earth, just about what Dole calculated was the minimum possible mass for a world to form a dense oxygen rich atmosphere and be habitable for humans.
Fortunately Heller and Barnes discuss several suggested methods for exoplanets to acquire Earth mass exomoons.
Heller and Barnes also introduce the "habitable edge", an inner limit to how closely an otherwise habitable exomoon can orbit an exoplanet without light reflected from the planet onto the moon, and tidal heading of the moon, providing too much energy and leading to a runaway greenhouse effect as on the planet Venus. They work out formulas for calculating whether an exomoon will suffer a runaway greenhouse effect.
So the "habitable edge" concept for the orbits of habitable exomoons leads to the concept of a circumplanetary habitable zone for moons.
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> Planetary-mass natural satellites have the potential to be habitable as well. However, these bodies need to fulfill additional parameters, in particular being located within the circumplanetary habitable zones of their host planets.[33] More specifically, moons need to be far enough from their host giant planets that they are not transformed by tidal heating into volcanic worlds like Io,[33] but must remain within the Hill radius of the planet so that they are not pulled out of the orbit of their host planet.[110] Red dwarfs that have masses less than 20% of that of the Sun cannot have habitable moons around giant planets, as the small size of the circumstellar habitable zone would put a habitable moon so close to the star that it would be stripped from its host planet. In such a system, a moon close enough to its host planet to maintain its orbit would have tidal heating so intense as to eliminate any prospects of habitability.[33]
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<https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Other_considerations>[13](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Other_considerations)
<https://www.astrobio.net/meteoritescomets-and-asteroids/the-habitable-edge-of-exomoons/>[14](https://www.astrobio.net/meteoritescomets-and-asteroids/the-habitable-edge-of-exomoons/)
In Heller, René (September 2013). "Magnetic shielding of exomoons beyond the circumplanetary habitable edge". The Astrophysical Journal Letters. 776 (2): L33.
<https://iopscience.iop.org/article/10.1088/2041-8205/776/2/L33>[12](https://iopscience.iop.org/article/10.1088/2041-8205/776/2/L33)
Heller discusses whether a giant planet's magnetic field would extend far enough to protect its moon's from negative effects due to particle radiation from outer space and from the star. For smaller giant planets, the protection of the planetary magnetic field will take a long time to extend as far as the orbits of exomoons that are far enough from the planet to avoid a runaway greenhouse effect, and thus those exomoons will lose their atmospheres and water and become uninhabitable. Larger giant planets can extend their magnetic fields out to exomoons orbiting beyond the habitable edge in time to protect those exomoons from loss of water and atmosphere.
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> Moons between 5 and 20 Rp can be habitable, depending on orbital eccentricity, and be affected by the planetary magnetosphere at the same time.
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<https://iopscience.iop.org/article/10.1088/2041-8205/776/2/L33>[12](https://iopscience.iop.org/article/10.1088/2041-8205/776/2/L33)
So Heller calculates that a exomoon could be habitable if orbiting between 5 and 20 Rp, where Rp is the exoplanet's radius. The 20 planetary radii outer limit should usually be much closer than the Hill sphere limit, and thus be the significant factor in the outer edge of a circumplanetary habitable zone.
Uranus has a mass of 8.6810 times ten to the 25th power kilograms, or 14.536 Earths and an equatorial radius of 25,559 kilometers miles. Five to twenty times the equatorial radius would be 127,795 to 511,180 kilometers. 127,795 kilometers would be inside the orbit of Miranda, which has an orbital period of 1.413 Earth days, and 511,180 kilometers would be between the orbits of Titania and Oberon, which have orbital periods of 8.705 and 13.463 Earth days.
Neptune has a mass of 1.024 times ten to the 26th power kilograms, or 17.147 Earths and an equatorial radius of 24,764 kilometers. 5 to 20 times the equatorial radius is a distance of 123,820 kilometers, and 20 times the equatorial radius is a distance of 495,280 kilometers. A distance of 123,820 kilometers is farther than the orbit of Proteus, which has an orbital period of 1.122 Earth days, and a distance of 495,280 kilometers is inside the orbit of Triton, which has an orbital period of 5.877 Earth days.
Saturn has a mass of 5.6834 times ten to the 26th power kilograms, or 95.2 Earths, and an equatorial radius of 60,268 kilometers, or 37,449 miles. So a distance of 5 to 20 times the radius of Saturn would be a distance of 301,340 to 1,205,360 kilometers. A distance of 301,340 kilometers would be between the orbits of Calypso and Dione, which have orbital periods of 1.887 and 2.736 Earth days. A distance of 1,205,360 kilometers would be inside the orbit of Titan, which has an orbital period of 15.945 Earth days.
Jupiter has a mass of 1.8982 times ten to the 27th power kilograms, or 317.8 Earths, and an equatorial radius of 71,492 kilometers or 44,423 miles. A distance of 50 to 20 times the equatorial radius would be 357,460 to 1,429,840 kilometers. A distance of 357,460 kilometers would be between the orbits of Thebe and Io, which have orbital periods of 16 hours and 1.7691 Earth days. A distance of 1,429,840 kilometers would be between the orbits of Ganymede and Callisto, which have orbital periods of 7.1546 and 16.689 Earth days.
These examples indicate that the best exoplanet for a habitable exomoon to orbit with an orbital period as long as 28 Earth days would be one both more massive and with a larger radius than Jupiter.
Unfortunately, Jupiter has almost the largest possible radius for a planet. When planets get a little more massive than Jupiter, they become compressed to greater and greater densities by their increasing gravity.
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> But there’s also a more literal take on the question: Is there a limit on how physically large a planet can be? Here there is a definite and rather surprising answer. Jupiter is 11 times the diameter of Earth, and it turns out that is about as large as any planet can be! If you kept dumping more matter on Jupiter, it would not get any larger. Instead, gravity would crush its mass together more tightly and efficiently.
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> Through the whole range from a Jupiter-mass planet to the brown dwarf boundary, all the way up to the lowest-mass dwarf stars (about 70 times the mass of Jupiter, the point at which sustained lithium and hydrogen fusion occurs), the size barely budges. All of these objects are within about 15 percent of the same diameter. That constancy has some odd consequences.
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> Take, for example, the star Trappist-1A, which was in the news recently because it has seven Earth-size planets orbiting it. Trappist-1A is a red dwarf, just 1/2000th as bright as the sun, but it’s genuine star, no question. It is powered by steady, sustained nuclear reactions that will burn for a trillion years or more. It is 80 times as massive as Jupiter.
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> On the other hand, Trappist-1A is less than 10 percent larger in diameter than Jupiter. Put those two details together, and you quickly realize that this little star must be extremely dense–as indeed are all extremely dim, cool red dwarf stars...
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> ...Even more extreme is the red dwarf star EBLM J0555-57Ab, recently measured to be 15 percent smaller than Jupiter, about the size of Saturn. It is the tiniest known mature star (as opposed stellar cinders like white dwarfs or neutron stars), and it is 17 times the density of lead–188 times the density of water!
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<https://www.discovermagazine.com/the-sciences/how-big-is-the-biggest-possible-planet>[15](https://www.discovermagazine.com/the-sciences/how-big-is-the-biggest-possible-planet)
This means that even the most massive exoplanet will have a radius - and thus a circumplanetary habitable zone - not much larger than that of Jupiter, while having many times the mass of Jupiter and thus forcing the moons in the circumplanetary habitable zone around the exoplanet to orbit much faster and have much shorter orbital periods than the moons of Jupiter within Jupiter's circumplanetary habitable zone.
So the current calculations indicate that unless an exomoon is large enough to have its own magnetic field to protect it from particle radiation, it will have to orbit within 20 planetary radii of the exoplanet to be protected by the planet's magnetic field, and thus it will not be able to have an orbital period much more than 17 Earth days long, at a guess not more than about 20 Earth days long.
[Answer]
I always thought it would be cool to have polar plants or fungi that absorb radiation to survive. If the atmosphere is weak enough near the poles and they don’t get enough direct sunlight, then maybe you could have these little guys.
<https://www.realclearscience.com/blog/2020/02/04/fungi_that_eat_radiation_are_growing_on_the_walls_of_chernobyls_ruined_nuclear_reactor.html>
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[Question]
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**This question already has answers here**:
[Science behind a naturally invisible creature](/questions/10508/science-behind-a-naturally-invisible-creature)
(8 answers)
Closed 4 months ago.
This is a post-apocalyptic setting I'm working on. The world has been overrun by invisible monsters from another parallel universe. They can be heard and smelled, and they can form claw prints on the ground - but they are invisible.
How would the science behind this work? One idea I've seen before is that they are able to bend all the light around themselves, but that would effectively make them blind as no light would reach *their* eyes (although, I feel like this might make for an interesting twist where the creature hunts by using vibration/echolocation)
What are some other possible mechanisms that might allow these creatures to be invisible?
[Answer]
**It is transparent.**
[](https://i.stack.imgur.com/VI0BD.jpg)
<https://www.youtube.com/watch?v=2eotnfvAaXA>
Transparency is a well established way to avoid being seen. Lots of water creatures from different phyla are invisible. Depicted is a transparent chordate cousin of ours. You can see him in the bright light of Youtube. Good luck if the water were shady or cloudy.
There are land creatures - insects - which are transparent to greater or lesser degrees too.
If you want to make your creature invisible without invoking wacky physics, make it see-thru.
[Answer]
**Advanced Chromatophores.**
Bending light is a super cool concept, but in nature a lot fo creatures do amazingly well with the simple ability to change colors (and textures).
I mean, look at this octopus:
[](https://i.stack.imgur.com/CCwga.jpg)
No octopus, you say? Exactly, that is effective invisibility right there. And a nuclear mutated alien from another dimension can just take this same concept even further, hiding against the very sky itself.
But maybe you catch just a glimpse of this monster if you move fast from parallax, which I think adds some fun tension opportunities in the story.
[Answer]
It's quite a common misconception that if something bends light around itself then it necessarily must be blind (often resulting in YouTube channels using it for something of a quick conversation starter). That's not the case. Typically I think this comes from the fact that it's assumed that if light is being absorbed by a creature's eyes, then it's necessary that less light has made its way to the other side of the creature. However, that doesn't actually hold, due to a type of medium known as a gain medium. These media are what are used in lasers, and effectively, given energy, they boost the intensity of the light.
Gain media do require energy, but one particular sort of gain medium is powered by current pumping. This technique basically converts electricity into an intensity boost for the light. And it's perfectly biologically plausible for you to have a creature which converts chemical energy from food into electrical energy: it's what electric eels do!
Your main challenge with this sort of design is the fact that in order to bend the light to create perfect invisibility, you'd need something with a refractive index tending towards infinity, which is particularly difficult to produce (although extremely high refractive indices have been achieved with supercooled sodium atoms - I believe - this is still a long way from infinity :P).
If you're fine with their parallel universe containing some sort of organic material which makes this possible, brilliant, but that would be some quite exotic matter, so it might be worth considering alternatives. What if they're simply transparent?
If we say that, essentially, living creatures are self-replicating energy processing machines, then there's nothing really forcing them to interact with visible wavelengths of light. Given that on a large scale refractive indices are essentially additive when multiple materials are mixed, that the air has a refractive index of roughly 1, that most materials have a refractive index greater than 1, but it is possible to create materials which have a refractive index lower than one, then it would be theoretically possible to mix some sort of inert (meta)material with a normal creature's structure in precise proportions to give is a refractive index matching the air. If the creature naturally absorbed light, then you'd need to mix in a gain medium too, but you could effectively make a creature with a body almost perfectly matching the optical properties of the air, and thus being completely transparent.
But even these discussions somewhat trivialise the issue, because I've assumed a single refractive index, whilst in reality refractive indices vary with wavelength and frequency, meaning you'd have to match these properties across a relatively broad range.
However, this all falls down when you begin to ask how such a creature might have evolved. Whilst evolving the complex micro/nanostructures required to alter one's refractive index is technically possible, there'd be a huge question as to *why* a species would evolve it. It sounds like a great idea, letting you sneak up on prey, but honestly there are far better ways to evolve to be practically invisible - quieter, smaller, sneakier, etc. - than there are to become completely invisible.
A final possibility which I feel might be suggested is that of active camouflage to match surroundings. Firstly, as Mission Impossible (Ghost Protocol's Kremlin infiltration scene) showed us, that only works on one observer at a time. And secondly, it's really difficult, to accurately work out what to show on your body from the perspective of someone else, based off of only the information available from your perspective. Sure, 3D game engines can manage it, but they require huge amounts of processing power, AND have complete information about the surroundings of the player. You'd also have difficulty tricking anything with two eyes once you got up close, because you couldn't trick both eyes simultaneously.
Honestly, I feel your best bet is Frostfyre's point:
You've managed to get creatures to travel between parallel universes. Whatever technology you're using to explain away that problem will be more than capable of explaining these creatures: Just send any light hitting them to the parallel universe and back. Or, if the fact that they're from a parallel universe rather than simply another world within our universe has a huge impact on the story, then that parallel universe almost certainly will have different physics to ours and so there is a HUGE question as to what happens when a being from a universe with different physics from ours enters our universe. Do they suddenly obey our laws of physics, do they locally maintain their own? I feel you could fudge something with this far more easily than explain away a near impossible optical genetics!
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[Question]
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Firstly, Allow me to apologize if this is not relevant on on topic for this stack exchange, but I'm at a loss here and hope someone can help.
I have created a rough map for my world using Krita (Similar to Gimp) which i use for internal reference while doing other world building.
What I am looking for is a program or tool (offline not cloud based) that will allow me to drag and drop "pins" onto it which when hovered over will display text (or can be clicked on for the text either works) the way Pins work on services such as google maps.
I am currently using the classic method of putting "1" "2" "3" etc. on the map and having a separate legend file which references them, but it's seriously clunky.
Google has failed me no matter what I've tried.
Dose anyone here know of something that fits what I'm looking for, or a better answer that hasn't occurred to me.
I'm mainly trying to do this for the small things, Specific bridges, monuments, and other points of interest that otherwise don't warrant their own specific legend markings.
Again I'm sorry if this is to far off-topic, but as it relates to world building it seemed like it fit and I can't think of a better place to ask.
Edit:
The answers that have come in while informative have not resulted in what i'm after (clearly due to poor phrasing on my part)
I'm really looking for a downloadable program that is not web or cloud based, similar to using Ms word, instead of google docs.
I have the image i wish to use as the map i just lack the ability to pin or annotate it.
~lin
[Answer]
Inkarnate.
It lets you create a map and add notes, symbols, your own icons to the map.
Handy for worldbuilding.
[Answer]
I've found another way I think - Worldanvil.com. It's a much larger package of Worldbuilding tools (I found it looking for timeline creation), and it looks like you can upload maps and add pins etc
Edit: Note however that not everything is available at the free level - this feature may need to be paid for.
[Answer]
Well, I have found an answer. (I believe the correct thing is to post it as an answer for future readers yes?)
Using GIS software dose everything I needed, specifically QGIS.
Using Vector Layers set to the "point" type.
I found help with this over at the cartographers guild.
Thread where answer was found (including a tutorial that was kindly provided):
<https://www.cartographersguild.com/showthread.php?t=46382>
Software that solved the problem, direct link.
<https://qgis.org/en/site/>
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[Question]
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**TL;DR:**
In a fantasy world full of magic, i want the elemental forms of magic to be strong against one another in a symmetrical way (meaning every element has the same amount of weaknesses and strengths). I do not specify how many strengths and weaknesses they should have, even though i would be happy to let each one be strong and weak against two others respectively. The elements are **(fire)**, **(earth / rock)**, **(water)**, **(air)**, **(ice)** and **(metal / ore)**. Feel free to rearrange and reconnect them in any way that fits.
**Full-length question:**
I am currently rebuilding an elemental magic system in a game i am playing, but i am having problems justifying some of the elements being strong or weak against some others.
First, the setting: If anybody knows it, i am building custom rules for The Dark Eye, a tabletop-rpg game that comes with its own setting. It is high fantasy, there are elves, dwarves and much of the other stuff you would expect from a tolkien-like setting. If thats any help, the backstory of magic becoming part of this world is a certain goddess breaking the rules and also a hole into one of the borders of dimensions and letting the power of magic flow into the mortal plane. It manifests in many ways, but the wizards guild is teaching the way of controlling it by weaving the flow of magic through willpower, gestures and incantations. Elemental magic is just one kind of many, but it is the one i am most interested in in this question. It allows the wizards to summon the element in form of attacks or elementals.
Because i do not want to rework all of the games rules i am bound to the choice of elements that exist in this world. I already tried my best thinking up how they relate to each other, but there are some connections that i am having trouble with. I drew up a chart of the elements and how i think they could relate to each other:
[](https://i.stack.imgur.com/SVWNH.png)
The direction of the arrows means "is strong against", e.g. "Water magic is strong against fire magic" (for obvious reasons). Giving each element two others which it is strong against resulted in a nicely mystic hexagon shape, but there are a few connections i am not sure about:
**Fire -> Air** - I maybe thought about air providing more fuel for the fire, thus increasing its strength while trying to attack or defend against it, but that sounds a little bit like an excuse. It's ok compared to the others, though.
**Air -> Earth** - Now, air could dry out earth to turn it into dust and blow it away, but rock also belongs to the earth element and really makes me unsure about this connection.
**Earth -> Metal** - This is one of the real bad candidates. I have no idea how to explain this, apart from metal not being too good at destroying earth and stone in a medieval world. This is true the other way around too, though.
**Metal -> Air** - This, too, gives me a real headache. I mean, metal is kind of immune to wind, but it is not particularly strong against it, either. Maybe attacks and elementals made from wind get disturbed by the solid structures metal forms? But then, earth would need to be strong against air, too.
**Ice -> Earth** - Frozen earth is more fragile? This one is not as bad, too, i guess, but could be a lot better.
**Air -> Water** - Honestly, i can not think of anything better than air "cutting more sharply" than water. I am very much not happy about this one either.
I kept rearranging and reconnecting these elements, but i just could not find a constellation that was satisfying. I am looking for someone to help me fix this constellation or provide an explanation that removes my doubts about my solution.
[Answer]
To provide an answer that uses the six elements as provided:
Note: I am not at a place where I can make nice pictures, so I apologize for not having a lovely infographic of elemental relationships.
To summarize, there are three cycles of each element having strength over the next one. The three cycles (which do make a nice mystic circle thing when drawn out) are:
* Air -> Earth -> Fire -> Air
* Metal -> Ice -> Water -> Metal
* Metal -> Earth -> Water -> Fire -> Ice -> Air -> Metal
And to summarize the logic of these, or at least my logic of these are below.
**Air -> Earth**: Air can erode the earth into sand and dirt, objects that while they are still earth, are less solid than the element suggests. Air can do this and remain untouched by the earth by virtue of flying over it. Air is also quite capable of just flowing around earthen barriers when wind power can't just knock it over.
**Earth -> Fire**: Dirt is known to put out fires by suffocating them. Likewise rocks are used around campfires to hold heat to be released when the fire dies out. This indicates that Earth should be able to take the punishment by Fire without losing effectiveness
**Fire -> Air**: Fire requires air to burn and unless one uses enough air pressure to actually blow out a fire, all blowing on a fire will do is stoke the flames. Air magic is not just wind, it is also contains magic that provides fire magic with additional fuel that the winds of the spell feeds.
**Metal -> Ice**: Ice is less durable than metal and can be chipped and broken apart by metal tools. While the cold can make metals more brittle, cold alone cannot turn metal back into earth on its own.
**Ice -> Water**: Instead of thinking in the traditional way of frozen water versus liquid water, the logic is the liquid phase of matter versus the cold. Cooling liquids will solidify them, depriving of them of their ability to flow freely1. We call the elements Ice and Water because it is the most common expressions of these elements as opposed to the only ones.
**Water -> Metal**: Water can be surprisingly good at corroding untreated metals and with enough pressure, water can even pierce metals. Also, water is good at getting into the cracks in metal tools and corroding them from the inside.
**Metal -> Earth**: Metal, most likely being processed Earth, is used to break apart earth in the form of tools. From a magical perspective, Metal magic is harder and/or more solid than Earth magic, and that is what is reflected in this relationship
**Earth -> Water**: The ground absorbs water and interferes with its desire to flow. The mud that results is controlled more by the earth's stability than the water's flexibility. If you go this route, then things that spawn from the earth like plants also take in water, further denying its ability to flow.
**Water -> Fire**: Water, like earth, is also used to extinguish fires. While yes, there are some fires that can't be put out by dousing them, the classical way in which we view fire is susceptible to water, and this water magic will trump fire magic.
**Fire -> Ice**: On a pure physical level, fire melts ice. On a slightly more metaphysical level, fire magic usually puts more heat into something than ice magic tries to remove. The result is that fire will beat ice by the fact that it takes less magical effort to heat something through magic as it does to chill it by an equal amount.
**Ice -> Air**: Like with Water, the cold magics that ice actually represents cause the gaseous Air to slow down. Eventually with enough cold, the air itself liquefies and is no longer really air anymore. On a more physical level, when ice is created, it can entrap air into little bubbles. The physical part is a bit of a stretch, but it is something that can be observed.
**Air -> Metal**: Air, like water, is good at corroding metal. Oxygen, which makes up about 20% of air, is really good at it and is why one does not find iron in its natural state. Likewise many other metals oxidize in air and part of gold's appeal is that it does not do this. Also like with Earth, air can do this and remain untouched by metal by retreating into the sky again.
1Yes Helium, we know you don't solidify that easily. You can now stop laughing from your corner of the universe.
[Answer]
**Step 1:** As per my comment, swap [Ground/Rock] with [Wood]. It still lines up with classical elements, it's more distinct, and it makes our lives easier when it comes to knocking these off.
**Step 2:** Swap the position of 'Air' and 'Wood'.
Now, let's knock these out of the way. Most of them are easy, but we wind up with two tricky ones.
**Fire beats Wood**, which makes sense. Fire burns Wood.
**Air beats Fire**, which also makes sense. Air puts out Fire.
**Wood beats Water**, which makes sense. Trees absorbs Water.
**Wood beats Air**. Strong oaks can withstand strong storms. Yes, hurricanes can knock down trees, but that's a gargantuan blast of wind. Normally, Wood is fine.
**Metal beats Wood**, because Trees can't grow on metal.
Now, for the tricky ones.
**Air beats Metal**. This is a case of 'mobility vs stability'. Metal is inanimate, thus wind can just fly around the metal. Or, to put it another way, metal can't stop the wind and wind doesn't need to stop metal.
**Ice beats Air**. This is because cold makes things heavy, i.e. wind included, and cold heavy air will die down. This is more cold dampening air's power than outright beating it.
[Answer]
**Elementals are strong or weak according to their environment.**
You choose your elemental according to your environment and needs, not according to your opponent.
* Deep in the ocean, water elementals will be huge and powerful, and will appear strong and strange. Earth will also be strong on the ocean floor and metal too until it corrodes. Ice and air will float away and disperse and summoning a fire elemental down there is just mean.
* In an open grassland it might depend on season, and the presence of an elemental could shape circumstances to strengthen it. Grasslands are where tornadoes happen which would delight an air elemental. A fire elemental can set the grass ablaze and grow in strength as that happens. Ice would do well in the winter and earth will be OK there all the time. Water elementals would not be at their best in the grassland and metal would struggle.
* A mountain would be great for earth and good for metal and ice, with ice preeminent if there were glaciers. Air would be ok and fire not so much - unless it were a volcano which would be ideal for a fire elemental.
* Metal is a thing of smelting and artifice. Metal elementals are the most intelligent and would be most at home (and extremely useful) in made environments like foundries or mines. A fire elemental would also be loving a foundry and an earth elemental would love a mine. Air and water would not do well in the foundry or the mine.
[Answer]
It might be down to Balance rather than one beats the other.
The first step might be to eliminate some of your elements. Ice is really just Water in a different phase. Wood is just biologically structured Earth. In a similar fashion, Metal is just a ultra-homogenized Earth. So you might want to go to the classic alchemical square of Water, Earth, Fire, and Air. You can then create another square around them as you combine the elements. Water and Air for Ice. Fire and Earth for Metal, Earth and Water for mud or clay, and so on.
On the order I gave them, you can see and logically explain the opposition. You don't necessarily have a clear situation of one being greater than the other, but you do have a balance. Water will not always beat fire. If you throw water on a fire, you get Steam. The fire is put out, but the water is also consumed and changes phase into something that burns. Not enough water on a fire, it just keeps burning. Too much, and it gets snuffed. Same thing with Earth and Air. A Stone column stands fast against the wind, but will get ground down or toppled by that same wind over time with erosion.
So you can draw a small square with the primary elements in the center with the logical oppositions to create the order. Then an outer square with the points of the inner at the midpoint of each side. The points of the outer will be the combination of the two core elements and will have an equal opposition across the way. In my example, Fire and Earth create Metal and Air and Water make Ice. Good metal may damage ice, but get metal too cold and it can become brittle and shatter. Earth and Water can be clay, but when you apply fire and air to create super intense heat, you get Ceramic, which will block the same super intense heat but is brittle and can also crack and explode it there are impurities. Just try to keep balance between them instead of just thinking of it like an elaborate Rock Paper Scissors Lizard Spock kind of thing.
Keep in mind as you get elaborate with your diagram that you can also create strange stuff when combining three elements even though two will be in opposition. Take some plants from the Earth category, add Watter, and then fire. The result is soup!
[Answer]
I think you should add Grass and Wood to the element unless if you count Wood as plants then you should only add Wood only and you can also add Electric and you don’t have to do it but here is my take on the cycle.
Air -> Fire because air puts out fire like Halfthawed said
Air -> Water because air can cool down water and dry it.
Air -> Grass because wind can blow plants and leaves around.
Air -> Metal because wind can erode metal.
Air -> Earth because air can cause erosion and can blew dust around.
Wood -> Air because air can not blow or break down trees as less it is strong enough.
Fire -> Wood because fire burns wood.
Fire -> Grass because fire burns plants.
Ice -> Water because ice can cool down water and can disable its ability to move freely as it is seen as the cold vs the liquid state of matter.
Water —> Fire because water douses fire.
Fire -> Ice because fire melts ice.
Ice —> Grass because ice freezes plants if the ice is seen as cold instead of frozen water.
Earth -> Fire because it can put out fire like Halfthawed said.
Water -> Earth because it causes erosion.
Grass -> Earth because it causes erosion and the roots of the plants can break rocks and can absorb nutrients from the dirt.
Fire -> Metal because fire melts metal.
Water —> Metal because water makes metal.
Grass -> Metal because plants in the swamp can prevent boats that have a metal propellers in the water from working.
Electric -> Metal because metal conducts electricity.
Electric -> Water because water conducts electricity.
Electric -> Fire because fire conducts electricity.
Grass -> Electric because plants are poor conductors and rather absorbs it, giving them more nutrients.
Electric -> Ice because electric can shatter ice or melt it.
Electric -> Wood because if lightning strikes wood, then fire starts.
Earth -> Electric because the earth grounds the electricity.
Wood -> Earth because it absorbs the nutrients.
Wood -> Grass because in the past, wooden tools were use to take plants of the field or to pull weeds.
I think all of these are right except for the Grass -> Metal part.
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[Question]
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Sulfur hexafluoride is [pretty awesome](https://www.youtube.com/watch?v=u19QfJWI1oQ). It is a gas six times denser than regular air, and thus you can actually make tinfoil "boats" float on it. It also makes your voice deep when you breathe it in.
Let's have a sea of it. To prevent [the entire planet from becoming a barren wasteland](https://worldbuilding.stackexchange.com/questions/13346/what-would-happen-if-earth-had-oceans-of-dense-gas-instead-of-water), make it a single sea about the size of the Black Sea, with an island the size of Cyprus in the middle. It's surrounded by tall mountains so there's little wind that would blow it empty. When, and with what technology, could the first people reach the island?
Sulfur hexafluoride is dense, but not dense enough for a regular boat to float on. You could not walk to the island either, because the gas will displace oxygen in your lungs and you will asphyxiate.
Because it is so dense, I wonder if you could navigate this sea with some kind of boat/plane hybrid. Or something similar to Da Vinci's flying machine. Could people reach this island at any time before the invention of the hot air balloon?
[Answer]
An ordinary bag filled with ambient air, if large enough, will float a ship's deck. If you have large fins going down below the air bag, they can act as a keel to react against sails (though if you have enough wind to sail, you're in danger of losing your "airsea").
Basically this would be a gas balloon, only the lifting gas is air -- every cubic meter of air displaces six times its weight in SF6, so you can calculate how big the gas bag needs to be based on how heavy your "ship" is. If you build fairly light (say, largely wicker construction like balloon baskets), I'd expect the bag to be significantly smaller than the gas bag of a hydrogen balloon, as you'd get a bit more than five times the lift per bag volume.
To put numbers on this, air at sea level pressure and room temperature is just over 1.2 kg per cubic meter, so each cubic meter of bag can support roundly 6 kg of bag skin, structure, and payload. A simple craft built like a basket with outriggers (to spread the lift for stability) might weigh as little as a couple hundred kg -- plus "airsailor(s)" and whatever propulsion method, and provisions, call it 500 kg for the first one, that would only need 80-90 cubic meters of air.
How early (technologically) could this happen? How early would someone notice a waterskin floating on the "dead air?"
Another answer mentioned propulsion -- as I noted, sailing won't work, if the sea is to stay in place. However, with no appreciable friction from the "airsea", you don't need the kind of power you'd need on water. A flapping, flexible fin (like a single wing mounted upright) would provide enough propulsion to get across, slowly -- a slow walking pace.
The biggest hazard to this, once you have a large enough bag and a design that's stable, is that the air and "dead air" will mix a bit at the interface, so your "airsailors" will be in danger of suffocation unless their craft holds them a few meters above the top of the air bag.
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**Problem 1: Weight**
The weight is the largest issue here. If you want any kind of boat to float on this while supporting humans, you will need something extremely light, and significantly large enough to carry a human. This could be anything from large drums containing air to create a raft, but a fair few of them would be needed. Or a large enough boat structure to carry a human. In any case, light woods like balsa would be your friend here.
**Problem 2: Propulsion**
If you state the wind won't blow off the gas, sufficient to say there is no wind to speak of. This basically kills the idea of sailing across, and a different method of propulsion is needed. Rowing is unlikely to do you much good, and with the average depth of the black sea being almost a mile, a pole pushing from the bottom is unachievable. Perhaps this can be solved by large flapping "wings" on your craft, or a bellows based device, but this likely won't be very effective. In this case being pulled along by a flock of trained pigeons doesn't seem so ridiculous all of a sudden.
**My solution:**
Probably not the best, but feasible nonetheless. Get a regular air balloon made of leather or any air-tight material. Attach to that an insanely long tube made of the same material, or something like animal intestine. Use the tube to breathe while the balloon floats the ends on top of the sea, and simply walk across. Optional backpack mounted hand powered air pup device, and a cart to carry unused tube. Gas pressure would get to you a bit, but won't nearly be as harsh as water pressure at this depth.
**Problem:**
It is too long a walk to do in one go. So an option is to build rest stops on the bottom of the sea, using similar breathing technology.
*Note: I haven't crunched the numbers, it could be this solution is utterly impossible due to pressure.*
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Your travelers could use a hot air balloon -- which has nothing to do with the sea. That won't happen until later in their civilization, though- but it is the earliest example of a flying machine.
That being said, the *first* people to reach the island may have used a scuba-type device . A Sulfur hexafluoride diver would carry what appears to others as a balloon that they're sucking air out of.
We typically cannot dive very deep in water while breathing atmospheric air because the weight of the water is to great to actually move your chest to aspirate. That's why pressurization is important to divers. Luckily, we're not dealing with water.
The black sea is about 7,000' deep . . . With six times pressure on that, it would be equivalent to trying to breathe while 42,000 feet below sea level. I wasn't able to find much on breathing while 8 miles below sea level, but if you keep the air supply at the same depth as your diver, my understanding is that the pressure on the air bladder will help "push" the air into your lungs.
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If wizards had to draw energy from their bodies, using only existing biological processes and bound to vanilla human metabolism rates, how would they be inclined to maintain their bodies and diets to adapt for different situations?
## Source of magic
Magic is produced by an organ located in the pelvis, which is supplied with the same boring old ATP that powers a regular fellow's muscles, organs, etcetera.
Now, humans can only output like 2000 watts (joules/second) at max for short durations, or around 400 watts for a couple of minutes. That's barely enough to boil a teaspoon of water; wizards have got to be more powerful than that. And the human body stores a lot of more energy than it can release, both in the form of ATP in the bloodstream, and well, fat stores on the body.
So, this magic organ is also a capacitor; the ATP is converted to electrical energy and stored in a biological battery. This charge degrades over time, let's say by 50% a month, so the battery is not typically filled to capacity at any given time. The wizard has some control over this process, and can decide to fill up the battery if they expect they will need it in the near future. It can hold up to 200 megajoules of energy, and can release it in about five seconds. That's enough for your typical high-end wizard.
(I get that this is insane electrical energy density, 200 Mj in an organ not weighing more than a kilo. However, the most efficient actual batteries would only hold around a single megajoule with that mass, and while that's enough to do some magic, it's not enough to make this organ dominate metabolism the way I want it to. If 200 Mj/kg sounds too extreme, you could say that the charging process is horribly inefficient, and it takes that much energy to fill it with only 20 Mj. How effective their magic is does not matter much in the context of this question.)
## Uses of magic
Magic in this setting is a rough art. You cannot thread a needle with magic: you crack walls, throw winds, and wreak all kinds of havoc.
Just to get an example which is easy to calculate: throwing stuff. A rock of 10 kilograms is about the smallest thing you can reliably manipulate, without loose tendrils of magic latching on to the surroundings and causing undesired side effects. Imagine you want to breach a wall: you just launch the thing at 500 km/h, which is the low end of cannonball speeds. That takes about 100 kilojoules, so on a full battery a wizard can throw two thousand of these.
Other forms of manipulation include heating up stuff, and ionising matter to produce lightning bolts. It's likely more uses exist and they haven't all been discovered, but the common factor is that you cannot concentrate magic on very small objects that well, and expected energy output is quite high per use. That makes stuff like healing out of the question.
Also consider a distance limit of magic projection to be roughly within arm's reach of the sorcerer - outside that range it gets progressively less powerful and even less accurate.
## Implications on metabolism
Now onto the meat of this question (literally). I started thinking about the implications of this system, starting with the optimal physique and eating habits of sorcerer or sorceress in question. I had first imagined them as intentionally keeping themselves pudgy, because 200 megajoules is roughly 5-7 kilograms of body fat, and a wizard would want to have that in reserve at all times, perhaps several times over. Though every-day magic tricks will not consume much energy, a wizard generally wants to be prepared for extraordinary situations, like a building collapsing on them or a battle with another wizard, that would require them to fully drain their reserves. And as said, the charge degrades over time, so they cannot just fill it up and forget about it.
But, in a friendly environment, they can simply eat like lions, and get the ATP from the bowels into their bloodstream, to be extracted by the organ. The magic does not make them more efficient at digesting food, but real-life pro athletes like Michael Phelps consume upwards of 40 megajoules (10000 kcal) a day whilst training for the Olympics. So a wizard with sufficient nutrition at his or her disposal can charge up fully in five days.
A full battery in five days a lot quicker than filling it up from the body's native long-term energy stores, aka their body fat. The maximum speed of metabolization of body fat, aka the fastest way for people to lose weight, is obviously subject to much commercially motivated misinformation, but 1 kilograms a week is commonly cited as a safe maximum, and I suppose that these wizards, who are specifically trained and have loads of experience, can double that up. Two kilograms a week, or 80 megajoules, means a wizard otherwise eating normally can "passively" charge their battery in half a month.
The implications for a wizard in a hostile environment is that they would prefer stocking lots of food over fattening their bodies. A single day of gorging is equivalent to three days of metabolising, after all; the only limitation is how long their food stores keep.
Having covered the domestic wizard and the war wizard, I think the wandering wizard may be the only one inclined to maintain a high body mass, especially if they can ride a horse. Although they can also carry food with them, that won't be in Michael Phelps quantities, and they must also anticipate times when they are without food.
## Question
So these are my ruminations on the topic, and I was wondering what situations and types of living environments I might have missed. Assuming the organ as described in the first five paragraphs, and a generic late medieval setting (with no other magic), **what is the spectrum of situations and possible corresponding habits these wizards could have adopted to have their magical battery at the appropriate charge**? If your answer concludes that the same strategy would work just as well for any situation, I would appreciate a suggested adjustment to the organ so that different environments call for different tactics. The goal here is to have wizards who are about as conscious of their food intake as diabetic patients.
Finally, note that the wizards have been doing their thing for many generations. Assume every process, habit or recipe to be optimised by centuries of experience.
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To answer your question, I will split my answer into 3 distinct types of mages, the Domestic, Combat, and Wanderer mages.
## Domestic Mages
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Domestic mages will have access to food supplies when needed, and thus only need to consume as much food as the magic that they use. Also, domestic mages will be mainly decided based on the capacity of their magic organs, rather than output speed. The organ itself is more important than their body weight reserves, although mages with extremely long, drawn out jobs would probably prefer a larger body fat reserve to help tide them through.
## Combat Mages
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For combat, combat mages would be similar to the professional athletes or soldiers of today. They will have to take up strict diets like sumo wrestlers to train up their organ's capacity and magic output speed starting from childhood, and their innate talent for storage and output speed of their organ will decide their future. These are the elites of the elites, with only those with the best capacity and/or output intensity allowed to occupy their ranks.
Combat mages can be potentially split into two categories.
## *Crowd Killers and Siegers (High Capacity)*
One type of combat mage would probably be attrition-based combat mages specialized for dealing with large crowds of targets, or siege mages, who specialize in laying siege, both of which may need to output magic over long periods of time. Their body fat would be reserves to last them through long, drawn out fights.
A large group of Crowd Killers acting in tandem could release waves upon waves of flames to drown out any dissidents or crowd tactics, and also depend on their capacity to release large amounts of liquids/substances to drastically lower enemy mobility, or put up solid cover for other mages.
A large group of Siegers could potentially release waves upon waves of arrows, rocks, and other projectiles at city walls, making use of their capacity to continuously release magic until the enemy is drowned.
## *Mage Killers (high-output)*
Mage Killers are the cream of the crop amongst combat mages, specializing in killing other Mages. These are the special troops and leading generals, possessing the greatest combat potentials.
For Mage Killers, there is one very important deciding factor: more mass on the body means lesser maneuverability, as well as higher energy consumption when engaging in combat. The amount of energy needed to accelerate a larger mass is definitely more than that of a smaller one. Also, Mage vs. Mage combats end extremely quickly, considering the lethality involved. It does not take much energy to launch a rock at the speed of a bullet, and any human hit by such a projectile would be fatally wounded.
If a combat mage were to have more weight, and was especially immobile, they would be a sitting duck for any other mage spells. In mage vs. mage combat, a Mage Killer relies on their lesser body weight and high magic output to explosively increase their speed, evasion and maneuverability, making it more difficult for their opponent to land a hit. Their ability to more quickly output magic would also come in handy, as more output means faster and more powerful spells, allowing them to attack faster and further than their opponents.
## Wanderers
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As speculated, Wanderers are probably the only class of mage that needs a high amount of body fat reserves. The higher body fat reserves mean being able to more liberally use magic when the situation arises, especially if situations where food or water for recharge are scarce. This comes in handy when they run into tricky situations in their travels, wandering across the lands.
Wanderers are the most variable of the mages, potentially possessing low talents for output or capacity compared to other kinds of mages. Their greatest strength, however, is their versatility, using both their greater body reserves and wits to come out on top. The high body mass impacting maneuverability in Mage on Mage scenarios is a drawback, but Wanderers can rely on their high sense of intuition, instinct, and combat experience from their travels to avoid direct combat with deadly opponents like Mage Killers, and slowly whittle them down with their own considerable reserves. Some Wanderers, now on the run from the authorities, have even slain well-known Mage Killers. Their magic style is also the most unorthodox of all mage classes, given their tendency to wander and pick up experiences from all over the great unknowns.
## Summary
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In general, domestic mages will have the most variation on body weight and metabolism, with their body weight depending upon their day to day magic usage. Higher standing and social positions would go to those with better ATP.
Combat mages can consist of high intensity/output Mage Killers, who act as special troops, generals, and the elites. They rely on lesser body weight and high output magic organs to perform explosive maneuvers and spells. High metabolism would be a boon for these mages, as the increased metabolism of the body means faster energy output, and more powerful magic.
Another class of combat mage would be high reserve type Crowd Killers/ Siegers, who rely on their body weight reserves to continuously output magic. A lower metabolism in this category is still acceptable, since a lower metabolism means a slower burn rate of energy and steady consumption, both boons to these endurance combat mages. A high metabolism would also work, allowing them to partly replenish their reserves during sieges.
Wanderers are the most versatile class of mages, relying on their high reserves and wits, as well as their highly unorthodox magics to even the tide. Metabolism is not the main concern for these mages, instead, storage, although low metabolism would be favorable due to lesser energy consumption over time, useful for when food or supplies are low.
## Conclusion
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From these examples, we can conclude that the only class of mages that require high metabolism are Mage Killers, as they have more need for faster energy output and consumption. On the other hand, Wanderers are the ones that benefit the most from a low metabolism, allowing them to lower their general idle consumption of energy, as well as for when food and supplies are running low. The other classes of mages are less reliant on general metabolism, and this can vary from case to case.
Of course, these are just some potential archetypes for the mages; there could be specialized Mage Killers who rely on their senses and spells to snipe other mages, and keep a high reserve of body fat for more shots. There could be Wanderers who engage in mostly disreputable activities like theft and robbery, and so need to keep their maneuverability and combat power at a maximum.
Hopefully these archetypes provide some examples you can use to help define your world. Thanks for reading to the end!
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As you've pointed out, even in the modern age there are a lot of competing opinions and vague studies regarding nutrition and optimal physique, and it seems likely that a similar cacophony of standards would arise around the system you describe.
It could be helpful to address a couple of additional questions about your organ:
* How sensitive is the performance of your organ to the performance of other organs in the body? Unusual or short-term benefits in relation to other aspects of health -- e.g. temporarily higher capacity when the wizard is highly caffeinated or while there is an excess of glucose in the bloodstream -- could affect accepted wisdom on the subject.
* How dependent is the performance of your organ on genetics? If its capabilities are difficult to compare directly between individuals, there might be a lot more justification for variations in habits among wizards.
* Are there ways to artificially stimulate or improve the capacity of the organ in an obvious way? I.e. is there an effective means of ATP supplementation that boils down to taking steroids or B-12?
In a situation where these interactions are complex and wisdom about such an organ is based on oral tradition or, at best, semi-empirical research, I see eating habits breaking down along organizational lines that are finer grained than what you've described above.
Combat wizards conscripted into a military, for example, might rely on the scheme you've described, while bandits or hedge wizards might rely on stimulants in the absence of proper nutrition.
A clan of wizards from the same ancestral line might have found that the more naturally pudgy they are, the better they perform.
Or, in high society there may be a popular fad among wizards to stay as lean as possible.
The existence of special, proprietary foods or nutrition regimens (effective or not), provided by enterprising individuals both sincere and not, would also be a near certainty in this scenario.
This type of nuance would also provide the basis for lots of plot points.
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The dragon can achieve mach 1.5 in level flight and can achieve mach 2 in a dive.
It likes to hunt its prey through use of kinetic energy like a Peregrine falcon.
My theories:
The dragon can repurpose its fire breath to come out of its rear, sort of like an afterburner.
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The fastest bird is a peregrine falcon, which can dive at up to ~200mph (~350km/h). Your dragon will be going nearly 8 times as fast, which means 82=64 times the drag. You're going to need a *far* more aerodynamic body *and* a massive amount of thrust. All that drag also gets turned into heat, so it's a good thing dragons are fireproof.
However, dragons have a key advantage over birds: fire. If your dragon's trachea extends through its body instead of stopping at the lungs (and I can't see how evolution would provide that), then with the proper shape, it could form a crude ramjet. Climb up really high by flapping, dive straight down like a rock, open mouth and *burn the air passing through*.
This does require an enormous energy input, as in a material fraction of the dragon's weight for a few seconds of full thrust, but if the reason for its voracious appetite was the internal production of something like hydrazine, it might work. (I haven't run the numbers.)
However, with that kind of power available, there's simply no need for supersonic speeds; it could fly around lazily and instantly kill anything in sight just by breathing in its general direction, with far less effort. The challenge would be having enough accuracy and control to merely cook prey instead of reducing it (and everything else nearby) to ashes.
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The larger an animal, the harder it is to cool down. Ignoring the problem of bone/muscle strength vs size/weight and saying an animal could get to outlandish sizes, would a second cardiovascular system specifically for thermoregulation help it regulate its core body temperature? What would the fluid in question be, assuming this hypothetical organism is of terran biochemistry?
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Reality check both **FAILS** and **PASSES** the test...
**Life As We Know It**: Sticking with life as we know it on Earth, the likelihood for a parallel cardiovascular system to evolve is highly unlikely. Hasn't happened yet, but that won't stop us from considering other possibilities.
But in other worlds, other evolutionary pathways might be chosen. Now it happens to be the case that we Earthlings do have two circulatory systems already. One circulates blood. The other circulates lymph. It's not a closed system, though, but it hints that other parallel systems could evolve elsewhere.
**Deluxe Closed System**: Such a system could indeed help with thermoregulation. Instead of draining lymph to the core, this system would drain heat from the core to the exterior. An organ, possibly some sort of "lung" that would have lots of surface area, would exchange heat from the CV to the HE system. This latter would simply circulate high temperature fluid (perhaps water or glycol) out to some kind of radiator appendages. These could be fins or frills or wings or fronds. The thin skin of such appendages will facilitate transfer of heat to the environment.
This system could also be used in reverse. If the animal becomes too cool in its core, it could at first reduce its secondary heart rate and then escalate by reducing the surface area of its fronds or frills, perhaps by curling them up or folding them within a pouch of some kind. It could also seek out relatively warm surroundings and, extending its sails and frills into the warmth, would simply pump warm fluid back down to the core.
The heat evacuation system described above is entirely closed. This prevents predators, disease vectors, rubbish and crud of all sorts from gaining access to the animal's insides. It also allows for a more nuanced and quicker response to body vs environmental conditions.
**Not so Deluxe Open System**: As AlexP reminds us, life as we know it provides other sources of inspiration. Some animals don't mind if a little crud gets in, so we also find inspiration in the water vascular system of the echinoderms. In this system, water is drawn in through an orifice and pumped through vessels throughout the body as a means of locomotion. The WVS is multipurpose in sea creatures, much more like our circulatory system. This kind of system, parallel to the CV system, could evolve in a large warm blooded creature for thermoregulation.
Water from the surrounding sea would be captured via an orifice and pumped through the thermoregulatory system's vessels perhaps via peristaltic action. This cooler water would pass through to the warmer core where it becomes warmed. Once the water is warm enough, it's expelled again through the same orifice and the process can be repeated as needed.
The heat evacuation system described above is an open system. Although safeguard are in place (baleen or hair like filters), some debris and a whole host of microorganisms can still gain entry. Small stones or debris can clog the vessels while microbes are brought into close proximity of vital organs. A more serious issue is that the animal would almost certainly be precluded from inhabiting warm waters: if it can only take in warm water, it will eventually suffer from hyperthermia, being unable to sufficiently regulate its core temperature.
Biological heat pump either way.
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I don't see why a separate coolant system would be needed or would evolve.
Animals already have blood pumping around their system and already use it for cooling through panting (e.g. dogs) air cooling (e.g. elephant ears) or evaporation (e.g. humans sweating).
All that would be needed would be to run the vascular system through the cooling (through whatever mechanism) systems and then through the body. Potentially for very large creatures you would have a special arrangement where blood goes to the surface to be cooled, then goes through the body, then back to the surface, etc.
You could also have multiple hearts, multiple heat sinks, etc, so that for example each section of the creature uses one blood system with then links between those systems to equalize pressure. But it would all just be evolved from the very same systems life uses right now.
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**Air.**
Let us assume this is a land animal. Heat must be offloaded to the air. Methods for doing this include increasing surface area, and harnessing the respiratory system to move dead space back and forth (panting).
A truly massive creature might aerate its interior by producing a system by which air is routed through the body and out. This might be a second respiratory system which did not concern itself with gas exchange or maybe an adaptation of the digestive system, putting to use existing mechansims for taking in air.
The result would be a wind through the body of the creature. A wet creature like us would probably also saturate this air with evaporated water, losing temperature to the phase change as we do when we sweat.
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**Acetone.**
Another possible coolant is acetone. Acetone is produced by biological processes including our own bodies - the ketogenic diet is named after the ketone acetone that our bodies make on this diet. Acetone has a low vapor pressure. A finger wetted with acetone will feel cold as the acetone evaporates, the phase change carrying away heat. Acetone sweat would be a formidable coolant. A problem is that the acetone costs carbon to make and then is lost, so using acetone to cool would be more metabolically expensive than using water.
Also a creature that sweat acetone would be flammable, but would probably go out quickly.
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I've tried to find relevant sources to make this question more informed, but haven't had any luck. It just seems implausible to me that a humanoid with long and pointy canines could bite a victim in the neck, hit the jugular vein in two places with those same teeth, drink the blood either through hollow teeth or around the teeth, and withdraw the teeth from the wound without having the victim lose enough blood to die before the vampire wants him to.
Authors have worked around this supposed physical awkwardness. One story depicted a vampire whose feeding organ was a needle-like structure under the tongue. The famous "Strain" series created a special blood-sucking organ that projected more than a yard from the mouth when it struck the victims like a snake. I think there was another author who gave vampires the power to dislocate their jaws so that their mouths could fit comfortably around the neck. I once read a story about a vampire who fed from his victims' wrists.
I have thought about giving my vampire retractile claws so that it could use its hands to puncture or slash wherever it likes, and drink from almost any part of the body.
Is the usual way that vampires feed in the movies and TV plausible?
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The jugular vein is a favorite site for placing central venous catheters. The reasons for that are the same reasons your vampires would favor them.
1. There are two: external and internal. Both are large. Internal is larger.
2. They are fairly superficial. In some people you can see them. So: fairly accessible.
3. There are collaterals on the other side. Some people get by with just one side functioning, draining both halves of the head. If you get a clot on one side it will be ok.
4. The veins in the neck are low pressure - pretty much just the force of gravity. Up at the top of the head venous blood is under even less than atmospheric pressure. A wound to the jugular vein will probably not cause a person to bleed out.
Consider now alternatives. The carotid artery in the neck is muscular and small and would be hard to pin down with a fang. A big wound to the carotid might be life threatening. Thigh veins and arteries are deeper, often covered by clothes and tissues, and under more pressure. The radial artery in the wrist could be an option - superficial, high pressure. You definitely can bleed to death from a wound in the radial artery if you are a Roman senator in his bath - but not necessarily. If the artery is partly intact it could clamp down and stop bleeding. The hand normally has collateral supply from the ulnar artery so losing the radial artery should not stop arterial blood flow to the hand.
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As long as the vampires maintain a pressure seal, there will only be a momentary drop in the victim’s blood pressure as the blood fills their mouth. After that as long as they maintain the proper pressure, the victim won’t loose any blood and won’t have their brains starved of oxygen carrying blood.
While their fangs have delivered a mortal blow, they can swallow a small amount of blood at a time rather than gulp it down. They’d be able to keep their victim alive for a very long time under these conditions.
With all that blood swirling and sloshing, it could start clotting. If the clots moved into victim’s circulatory system, then they might stroke out.
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Is there any real need for a vampire to bite the victim in the neck? If the worry is that exposure to oxygen causes blood-clotting (and that's somehow problematic for vamps), my answer might be of no use, but have you considered having those vampires resort to exsanguination/bloodletting instead?
Humans in the past have resorted to bloodletting (basically medically-approved life-threatening blood loss) as a way to treat ailments(I won't go into the details of why our ancestors thought that was a good idea here, but look it up if you're interested). It depends on how obviously you want your vampires to differ from humans in terms of physiology, but if they aren't too obviously different, they might have better luck masqueraiding as a doctor and drinking the blood they extract from their "patients" instead of abducting people and puncturing their arteries.
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So, there are creatures with insane regenerative abilities, like casually putting their severed head back on their neck and it's fixed in mere seconds.
The reason for that is that it's not true regeneration. These creatures are made of a fluid, so if any part falls of or gets damaged, it can quickly be molded back into shape. Their bodies are pretty much homogeneous, the only part that's "different" is their skeleton, and only in the sense that it's a different type of fluid that becomes slightly stronger after consolidating (since it's a framework).
The creatures are artificial and so they don't play by the rules of evolution.
**Now, these creatures are supposed to be humanoid and move like actual humans, but how can they do that?**
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The liquid isn't really a liquid, but a soup of fairly tightly bound microscale multipurpose components. Not nanobots, but the insides of these artificial cells certainly make use of nanotechnological processes.
Each component (let's call it a "souplet" with a nod to the components of [utilty fog](https://en.wikipedia.org/wiki/Utility_fog)). They're relatively dumb and simple things... they contain a small power source and a very small and simple processor, a tiny fleck of memory and a few molecular motors attached to arms which they can push out and retract to some small degree. Each arm also has tiny data and power connectors. Individual souplets can't do anything; they're too stupid. When you've got a critical mass though, you can program them to do useful things, like link up with other souplets to form a power and data network, form into a useful shape, wander around, squash meatbags, that sort of thing.
This is obviously a fearsomely powerful technology, but you need a correspondingly fearsome computer to drive it in any useful way. If your computer broke, or you lost your souplet fabricator but left it turned on, you get a load of fairly unintelligent amoeboid things that floop around in a fairly aimless way. Maybe they bump into the debris of former souplet aggregates who met an untidy end, and absorb a little tiny bit of the programming and memories of the fallen. Something about being human shaped? Yeah, that'll do. Close enough. I'm sure the rest of the programming directives are in another bit of you somewhere near by. Maybe those other human looking things. Lets network with them and see what happens.
The periphery of the souplet network can provide propioceptive information. The centre which doesn't have to move around can supply electrical and processing power for the periphery. The bits that don't need to move much can become denser and tougher, a bit like a skeleton (but perhaps more like the trunk of a tree).
You slice one of these things in half, and the two halves have suddenly got a lot less intelligent, individually. Throw em off a cliff so they go *splash* and the resulting puddle can't really do anything useful except slosh about trying to reaggregate and work out what it was and what it was doing before it was so rudely interrupted. This *looks* like regeneration but is really just repair and repurposing. Destroyed souplets stay destroyed. Heat, corrosion, radiation and or merely suitably applied mechanical force can destroy a souplet. The aggregates can be ground down and indeed killed. But if you don't do a thorough job, the next aggregate that comes by might step in a splash of the one you didn't quite kill enough, and remember a little bit about you, and how it doesn't like you very much, and how you might be a bit less on guard now...
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Since you use the tag science-based, what is the [definition of a liquid](https://en.wikipedia.org/wiki/Liquid) according to science?
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> A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure.
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It follows that if your creatures are liquid cannot have an own shape, no matter if it is human, cow or sponge-like.
Unless your creature as an outer shell which resembles a human body, in that case they can take that form.
They can then move using fibers of dynamically variable length dispersed in the liquid and are attached to the extremities they want to move. More or less like an amoeba can move its body.
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As L.Dutch states in their answer, if their body was a liquid throughout then it cannot maintain any specific shape other than that of the container it is in. But there are a couple of options that might work:
**A flexible position-controllable skin.**
If the creature has a leathery semi-elastic skin that can adjust its tension and/or rigidity then the skin could be used to maintain shape and provide motive force. Imagine a very thick wet-suit, for example, that incorporated its own musculature, tendons etc.
**A very high surface tension**
The liquid that the body is constructed from could (somewhat implausibly) have very high surface tension - sufficient to keep the creature from "adapting to the shape of the container'" - consider for example how mercury can bead up. At first thought this could only produce a very small spheroidal creature, but if the magnitude of the surface tension was dependent on local chemical potentials or electrical fields then it might be possible to alter the body's shape (a bit). In practice this would probably only be practical if the creature was small, was in a low gravity environment, or was floating in an external supporting liquid.
***The leathery skin option doesn't really allow for instant repair, but teh surface tension option may do.***
[Answer]
**These creatures have muscles.**
I assume the outer skin of these creatures is a bag or membrane of some sort, containing the fluid. If not, they would be a puddle.
If they can have a membrane on the outside they can have membranes on the inside. These internal membrane sacs are attached to the skeleton (which is the same shape as a human skeleton) at the same places as human muscles. By controlling the quantity of fluid pumped into or out of a given internal membrane sac (muscle) the length of the sac can be controlled. More volume pushes the sac toward a spherical shape, contracting in length. Less volume allows it to stretch.
Our muscles move by contracting and pulling bones together then relaxing. This is how the fluid creatures do it too, except using hydraulics.
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[Question]
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In my story, a ship is built in orbit around Earth, designed for a 20-person scientific expedition to a planet 11.4 ly away. It will accelerate at 1g for half the distance, then flip around and accelerate at 1g in the opposite direction until it comes to a stop. It's not designed to ever enter an atmosphere.
Technology in this world is arbitrarily powerful within known laws of physics, and they're able to produce large quantities of antimatter and perfectly convert that fuel's rest mass into kinetic energy via a gamma ray drive. In fact, they can even make solid antimatter, so if the fuel source was made of something like Bismuth and anti-Bismuth, it could take up very little space. They can also harvest matter for fuel at their destination.
I assumed that the habitat they'd need for the journey would weigh 0.5 million kg (this is comparable to the mass of the ISS, and while obviously this would need to be much larger and self-sustaining, it's also made with futuristic ultra-light materials) [This handy calculator](http://nathangeffen.webfactional.com/spacetravel/spacetravel.php) tells me that the total mass including fuel will come out to around 100 million kg.
This sounds like an absurd number until you realize that the Empire State Building weighs about 3 times that much. Piece of cake for an advanced civilization. (Did I mention they can get the materials to orbit with a space elevator?) More specifically, the mass is equivalent to 10,000 m^3 of Bismuth, or a 10x10x100 m building's worth, plus the habitat on top (some of the material can double as a radiation shield during the journey).
Given all of that, my question is simple: **What would the ship look like?**
My thoughts so far (feel free to contradict me if I made an incorrect assumption):
1. *The ship looks more or less like a skyscraper.* After all, it's roughly skyscraper-sized, and it needs to hold itself up under 1g of acceleration, just like skyscrapers on Earth do. But the lower 100 floors or whatever will be fuel.
2. *The bottom of the ship is a lattice of parabolic dishes.* The idea is that the gamma rays will be produced at the foci and reflected to generate thrust. However, I'm not convinced that a material capable of reflecting gamma rays is even physically possible. If there's an alternative, what is it and what would it look like?
[Answer]
(*editted for brevity, if you can believe that. the edit history retains some worked analysis of the rocket performance and a comparison to the Frisbee antimatter starship design*)
TL;DR: It will look a little more like this than like a skyscraper:
[](https://i.stack.imgur.com/5nFjB.jpg)
(*Note the presence of heat rejection, the glowing red bits around the rockets, debris shielding, the shiny rhombus at the other end, and if you squint a bit, the spun gravity sections near the shielding. All hallmarks of hard-scifi design. More details in [this diagram](https://i.stack.imgur.com/lMe8N.png)*)
This is the ISV Venture Star from the film *Avatar*. It is based on an older work called [Project Valkyrie](https://en.wikipedia.org/wiki/Project_Valkyrie) which involves turning the traditional rocket design upside-down, using a pair of carefully angled rocket engines at the front of the ship, and a fairly long tension structure which supports the payload of the spacecraft. The tension structure is simpler and lighter than a compression structure, and this means you can make it long enough so that sheer distance from the intense radiation sources of your rocket engines helps protect you (thanks to the inverse square law) and reduces the mass of shielding you need to keep everyone alive. The Venture Star was only 1.6km long, but the Valkyrie design was more like 10km.
The Venture Star also uses a [laser sail](http://www.projectrho.com/public_html/rocket/enginelist.php#photonsail) to boost it away from Earth, and to slow it back down again when it returns, which reduces the delta-V (and hence fuel mass) needed for each leg of the journey by a factor of 4. You might not want to use a laser sail for whatever reason, but you might consider using a [magnetic sail](http://www.niac.usra.edu/files/studies/final_report/320Zubrin.pdf) to slow you down for the deceleration phase of your journey. This lets you slow your ship by magnetic drag against charged particles in interstellar space and the solar wind emitted by your target star. This sort of parachute can brake with considerable force (the example given in the link starts out at over 5 gravities) and could brake a ship from .95c to .01c in a couple of years with no expenditure of propellant.
A combination of these approaches might allow you to either a) not use any rockets at all (requiring you to build a laser array at your destination) or b) to fuel up your rocket at Sol, then be boosted away by laser, brake by magnetic parachute, and then use your rockets to boost you up for the return leg of the journey meaning that you wouldn't need to build an antimatter fabrication facility at your destination (and this may also avoid the need for magical handwavium ultra-efficient antimatter synthesis, fractionally increasing the plausibility of your work).
---
Now for the more detailed grumbles:
In any case, there are some problems that your initial analysis missed:
1. Mass. You have a ship that weighs 500 tonnes at its destination, but 100000 tonnes on launch, with *all of that extra mass as fuel*. This implies your fuel tanks can confine millions of kilos of antimatter, but weigh only grammes, or that you can perfectly cannibalise each fuel tank as the matter-side of the antimatter rocket reaction. It also implies that an engine that generates hundreds of petawatts of power also weighs an insignificant amount, which is extremely implausible.
Using lightsails to start and magsails to stop helps with the mass ratio issue. It also reduces the inconvenience of bulk antimatter production, and the safety issues associated with storing vast quantities of the stuff. If you really must use self-powered flight, then coasting for much of your journey isn't going to take subjectively much longer and building centrifugal gravity facilities will be easier than making and storing millions of kilos of antimatter for years at a time.
2. Engine radiation shielding. Antimatter rockets emit vast amounts of gamma rays (your ship might have an initial flux of some 200 petawtts of the damn things), many of which will impact your ship. If they hit your antimatter, they risk causing a chain reaction that will annihilate your ship. If they hit your crew, they'll die. Even magical shield generators weigh something... the shielding for your ship, your rocket engine and your fuel isn't going to be massless. Even the long-tether Valkyrie/Venture Star design won't protect the rockets themselves, and you still need to get fuel up to them so the fuel tanks and lines will still need shielding too!
3. Debris shielding. At 99% of the speed of light, a single gram of dust at this speed packs about 123 kilotonnes tnt equivalent. Even in the pretty vacuous interstellar medium around our sun, you'll find neutral hydrogen and helium atoms, tens of thousands of them per cubic metre, and at top speed each square metres of your ship's cross section is sweeping out over 296 million cubic metres. [This paper](https://arxiv.org/ftp/physics/papers/0610/0610030.pdf) suggests that an unshielded human travelling over .6c might expect to receive about 104 [REM](https://en.wikipedia.org/wiki/Roentgen_equivalent_man) per second, which is over 50 times a lethal dose of radiation. Every second. I'm pretty certain your 500 tonne ship does not carry enough shielding to protect against this sort of punishment... you'll need several tonnes of water per square metre of shield. You *might* be able to use some of your rocket fuel for this, if you were careful.
Debris shielding can be partially handled by clever solutions to heat rejection... the Valkyrie design uses a "fountain" style liquid droplet radiator, spraying hot coolant into space ahead of your ship, and letting the ship's own acceleration catch up with the drops to recover them. Some of the drops will be scattered by incoming gas and dust particles so you'll need to bring spare coolant, of course. There are many other approaches, but their details are out of the scope of this question.
4. Heat radiation. Those gamma rays need reflecting or absorbing. Unless you have the most magical of shields, the reflection process is going to need power and generate heat. The drive coils will need powering and cooling. The cryogenic refridgerators for your antimatter storage systems will need powering and also need huge heat sinks. The list goes on... you're dealing with a multi-hundred-petawatt reaction engine, and even with phenomenal efficiencies a suitable [liquid droplet radiator](http://www.projectrho.com/public_html/rocket/basicdesign.php#id--Heat_Radiators--Radiator_Types--Liquid_Droplet) array might still be several square kilometres in size, and will necessarily weigh thousands of tonnes that you haven't taken account of. The mass of those heatsinks will need more rocket power, fuel and reaction mass to push them, and more shielding to help keep them intact.
5. Engine design. Antimatter rockets are even less efficient than you might think, because some of your propellant is evaporating promptly, and the mass-energy of the rest is lost into space. Even with magical gamma ray reflectors, your mass ratio will be higher than your initial analysis implies. [Robert Frisbee](https://pdfs.semanticscholar.org/d2ad/c77de39251b894462c98d79e68c80763a4d8.pdf) wrote an interesting paper on antimatter-driven starships (worth a read; it uses no sail technology and a skycraper design, and as a result is *really, really huge*, like hundreds of km long and a lot slower and simpler than your design) which suggests it could need 4 to 5 times the mass ratio than a classical rocket design of similar performance would need. This drastically limits your practical delta-V, making boosting up and down to high relativistic speeds even more vastly unlikely.
If you can handwave the production, storage and pumping of neutral, ferrous antimatter then *maybe* you'll be able to get away with a [beam-core antimatter rocket](http://www.projectrho.com/public_html/rocket/enginelist2.php#id--Antimatter--Beam_Core), but practically the cross section of [cross sections of particle/antiparticle](https://www.researchgate.net/publication/260480038_Relativistic_rocket_Dream_and_reality) collisions is very low. Your rocket's reaction chamber will have to be very long to ensure it all gets burn up, and that length makes forming a rocket nozzle or reflective photon rocket system very difficult indeed, and increases the issues associated with shielding and cooling.
The author of the that paper (and indeed the radiation effects on relativistic starships paper) suggests using an antimatter power reactor and [ion drives](https://arxiv.org/ftp/arxiv/papers/1807/1807.08608.pdf) instead. The tech level goes down a little, and the plausibility goes up. Of course, if you are using light and magnetic sails, then you can just use vastly simpler antimatter-catalysed fusion rockets instead for terminal phase braking and in-system manoeuvering.
[Answer]
Your first point is great. Spacecraft that are laid out as if there's a "down" that's perpendicular to the direction of thrust are almost always a stupid design and a holdover from depictions of spacecraft as essentially just aircraft or naval ships. So yes, laying the ship out as a stack of consecutive floors, sort of like a skyscraper, is objectively the best design for this kind of spacecraft. However, you've got a couple of issues here.
### 1. You're going to need a way to store that antimatter.
Your antimatter is, for some reason, in the form of anti-bismuth. OK, the first thing we're going to need to do is to give it an electric charge. We can't just hold it in a tank made of matter, because as soon as it touches the walls, your solar system gets a temporary second sun. So we need some way to hold it in our ship without ever touching it. Luckily, there is a way to do that (although it only works with diamagnetic anti-elements, bismuth is luckily the most diamagnetic element, of all, so good choice of fuel). Your incredibly advanced civilization undoubtedly also has incredibly advanced magnetic fields, so if we give our anti-bismuth a charge, either by adding or removing a whole bunch of positrons, you can [contain it](http://www.projectrho.com/public_html/rocket/antimatterfuel.php#id--Antimatter_Containment) in a "tank" made of powerful magnetic fields. You'll then need to surround the whole thing with an actual, physical tank to prevent the interstellar medium, which will be hitting you at >0.9c, from slowly eroding your antimatter, but as a super-advanced civilization, I doubt building a big, absurdly durable fuel tank with a bunch of carefully placed and tuned electromagnets inside will be a problem. Additionally, since your magnetic fields are going to need to hold a huge mass of anti-bismuth against 1g of acceleration, they'll need a ton of energy input, but since your ship runs off antimatter, I doubt electricity generation is much of a problem. Note that this also means that you'll have to allocate more space for your antimatter storage than your normal fuel storage, so make note of that when drawing up designs, although how much extra room you need depends on how advanced your civilization is. You're also going to want to store both your bismuth and your anti-bismuth as liquids, to allow you to actually use them as fuel without having to somehow chip off chunks of solid antimatter. This will require keeping them nice and warm, above their melting point, so don't forget to include some heaters in your design.
### 2. You're not just going to produce gamma rays (but that's a good thing)
Contrary to popular belief, if you smack a chunk of matter into a chunk of antimatter, you [don't just get energy](http://www.projectrho.com/public_html/rocket/antimatterfuel.php#id--Antimatter_Reaction). (well technically, if you smack a positron into an electron, all you get is gamma radiation, but since we're talking about anti-bismuth and bismuth here, we're going to have anti-protons and anti-neutrons involved too). You'll get some gamma radiation and a bunch of high-energy particles, some charged, and some uncharged. Unfortunately, you're probably going to have to waste the gamma rays, as we don't actually have an effective way to utilize them because as far as we know, nothing reflects gamma rays. The thing you're going to be using as thrust will have to be the charged particles (pions to be precise, not that it really matters), which will make up about two-thirds of the energy from the annihilation event, with the other one-third being those wasted gamma rays. You'll have to use a magnetic nozzle to direct them, which will probably look like a wide, thin, curved ring attached to the back of your ship with a few support struts. So that's what the bottom of your ship is going to look like, rather than a bunch of parabolic dishes.
If you handwave in a material your society has than reflects gamma radiation, feel free to build a physical rocket nozzle out of that to surround the magnetic nozzle (this would probably just appear to be a standard rocket nozzle, rather than some sort of lattice of parabolic dishes), but be aware that that's stepping pretty far outside our current understanding of physics. Everything I've laid out in my answer has been "super-advanced, but definitely possible", a gamma-ray mirror is definitely outside that realm.
So, assuming your advanced society lacks any handwavium gamma-mirror, your ship will look like kind of like a skyscraper, especially near the top. The very top part, where the crew lives, will probably be rectangular or square in shape, to give the pesky humans their nice, regular rooms, and, depending on the height of your spacecraft, may include some radiation shielding seperating it from the rest of the ship to prevent gamma rays from the drive giving everyone cancer, although the intervening mass of fuel helps with that, and as it is used up, the amount of radiation decreases as the drive power is turned down to maintain constant acceleration, so that works out nicely. The fuel tanks, below this, will probably be cylindrical, to save on tank mass and the number of electromagnets required to keep the anti-bismuth contained. These tanks will likely be stacked with the bismuth tank above the anti-bismuth tank, to simplify the already horrific engineering involved in transporting the anti-bismuth to the engine without letting it touch anything. The engine, at the bottom, will appear to be a wide, thin angled ring (or possibly several concentric ones), attached to the hull by struts. Inside this invisible magnetic nozzle, bismuth, carried from the upper tank, will annihilate with anti-bismuth from the lower tank and create a flood of gamma rays and charged pions. The pions will be funneled away from the spacecraft by the magnetic nozzle, providing thrust, and the gamma rays will spread out randomly in all directions, and hopefully not give any of your scientists cancer. There may be some visible light from the interaction site, and surfaces at the base of the ship may glow as they give off the energy they absorb from gamma radiation, but there will be no visible drive plume.
[Answer]
**Yes - it would be a skyscraper, and you need a way to withstand those pesky interstellar dust particles, and radiate away heat**
Regardless of your drive and your power source, constant 1g acceleration would slowly increase the speed of your ship such that even after just a half a lightyear any dust particles would hit your ship with enormous force, and let alone for a 5.52 ly journey (with the same problem on the deceleration part).
Not to mention the constant ablative impact of hydrogen particles, or anything more substantial.
So you would need a heavy 'top' shielding to your skyscraper. And your skyscraper should be as 'thin' as possible to reduce the cross-sectional area exposed to the dust and interstellar medium.
Impacts would also create a lot of heat, and in space heat is hard to get rid of.
Not only that, but the critical-danger part would be the 'flipping' of your craft at the half-way point. Add to this your engine would need to be facing the impacts to decelerate the craft on the deceleration leg, and would be exposed to the dust too.
Possible solutions:
* Have sacrificial bodies ahead of your habitable spacecraft, such that they would absorb the impact of interstellar dust prior to any craft that may endanger life.
* Reduce the cross-sectional area to just the size of a small house, perhaps 150sqm maximum. You can still have lifts to allow people to interact, for the journey would still be several years. You can have simply 2 lift shafts, one up one down, with the ability to 'park' lifts to allow them to bypass each other. This would mean your ship would be very very long (or high...) but would still be functional.
* Detach the shield on the deceleration leg, and 'push' against it with your drive, to enable the drive to operate without exposure to the dust, and perhaps with greater efficiency on the deceleration leg.
* Find a way to radiate heat forward, to assist with getting rid of objects in your path too. Perhaps a heat exchanger heating very hot 'pellets' to fire in front of you, or beam it somehow forward.
* Modularise each level of your ship, such that at the critical 'flip' point you are not trying to rotate in a pinwheel way (which will likely catastrophically rip your ship apart), but to rotate 'modules' inside the body of the ship instead to retain it's needle-like aspect ratio.
It's an exciting prospect to design a ship like this - I have always though this is the best solution for interstellar travel, obtaining the speed required to reduce the time needed, and get the gravity needed, in one solution. Keep letting us know how you go with your design work...
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I understand, vaguely, how human voices vary with the overall size/shape of the individual(s vocal chords), and I can use that to make reasonable assumptions about what the voice of non-human fantasy race of oversized (giants), or undersized (gnomes, fairies, etc.) humanoid race might sound like compared to a 'standard' human voice.
But I do not know enough about the noises bugs make for me to be able to confidently make similar assumptions about how their communication noises might change when the animal is scaled to a fantasy sized variety.
**What differences would be expected in the noises made by bugs, if they were scaled up to giant versions of themselves?**
Details, specifics, limitations, etc. :
1. how/why do these giant bugs exist? Handwavium, they just do. These are not an evolution from real species to fantasy species, they are not a fictional species independent of existing animals, they are the actual existing species just bigger. Ignore any issues caused by the square/cube law thing, except maybe to handwavium increase structural integrity of body parts to support new size, no new materials allowed, no new structural organization of parts and materials, they just are strong enough to be bigger **because handwave**.
2. "Noises" = **sounds produced by the bug, and only the bug, for the purpose of communication**. This can include mating calls, noises to try to scare away predators, noises to cooperatively hunt or other social needs, etc. Incidental noises, such as buzzing of wings during flight, or footsteps (or multiple legs contacting each other) as they walk, rubbing against objects in their surrounding environment, etc. don't count. If the bug uses other objects from the environment to produce the sound (such as a wolf spider vibrating leaves) that doesn't count either.
3. "Bug" = **Insect, Spider, Scorpion, or Centipede**, unless you can make a very convincing argument for something else that might be called a "bug" by a layman. Some specific examples of the type of thing I'm referring to are cricket chirps (probably the most obvious and recognizable bug noise of all), hissing-cockroach hiss, "barking" or "Whistling" spider (Selenocosmia crassipes) hiss, Flag tail centipede (Alipes grandidieri?, others?) hiss.
4. "Giant version" = Let's say approximately the height/length/girth/weight of a large breed of dog, like a St. Bernard. **EDIT: Think ": Honey I Shrink the Kids" technology, not evolution or alien physiology, but rather the exact identical real-life animals just scaled up completely, proportionately, and in every aspect.** Obviously, many "bugs" are not the same proportionate shape as a dog, so modify as needed within the spirit of the question, exact measurements shouldn't create enough of a difference in the answer to nitpick unnecessarily. In other words, I don't feel like (for the purposes of this question) there would be a significant difference in the sound made by an 6 foot long centipede compared to a 10 foot long one, regardless of whichever of the two might be closer to 'dog-sized' by weight or width or whatever, as long as we don't get out of hand and start discussing what it would sound like if it were as tall as a car and longer than 2 buses. Use best judgement, common sense, reason, when trying to apply 'dog-size' to something that is not 'dog-shape'. Other than size, nothing else about the animal should change, or should change as little as possible to accommodate any complications that might otherwise arise from the added size (no mammalian lungs/vocal chords or any similarly radical change, only increased size of whatever they used before to make their noises originally, and as little structural change in those as possible to support the additional weight/volume/etc.).
5. "differences" in the noises = **Pitch** and **Volume** are the two most obvious here. Would the sound have the same pitch, but just be louder, or vice versa? Or would the pitch change so much, that it becomes separate intermittent clicks or impacts, rather than a tone or pitch at all? Would **Duration** change while pitch and/or volume stay the same? Would the **sonic texture** change, from seemingly one sound source to multiple sources?
For those of you who didn't know, and/or don't believe, that spiders make such noises, [here's an example](https://www.youtube.com/watch?v=H6fJUolFYUs)(WARNING to those who are creeped out by such things, it's creepy)
[Answer]
As @AlexP mentioned, and according to the wikipedia page he linked to, bugs usually rub body parts together to make a noise, so your giant bugs would probably use the same system.
**As a general rule, the bigger the object, the lower the sound frequency.**
Therefore, you could imagine similar noises to real world bugs but lower. A cricket's chirping could sound more like an ominous thrumming, or an ant's squeaky stridulations could be so low than your average human might confuse them for mechanical parts, like a tire/wheel.
A question you have to ask yourself, is how different are your giant bugs to real world bugs, and which parts of them are going to be giant?
For example, the wiki article states that spiders emit their "hissing" stridulation by rubbing their leg bristles together. Would a giant spider also have giant leg bristles? Would each leg have the same size bristles? Would its mandibles have smaller bristels, allowing for a greater control of the emitted stridulation?
Maybe your giant bugs evolved more complex stridulatory organs to allow for better communication with other animals. As long as you're in handwavium territory, that's a fairly easy concept to handwave into existence imo.
[Answer]
What Whitehot said about generally louder volumes and lower frequencies seems right. Think about string instruments: As you move from violin to viola to cello to bass, the pitch of the instrument drops in proportion to the size of the instrument (due in this case to the hollow resonating chamber and the length and thickness of the strings). Any change in pitch really depends on what kind of organ is creating the sound, though, and I'm not totally sure whether crickets, for example, would sound much different. Some insects' noisemaking organs are more percussive, while others are more like vibrating strings. But as a general rule, lower frequencies do seem likely. As do longer-sustained notes. Lower frequencies, I believe, don't lose their energy as quickly as higher frequencies (please correct me if I'm wrong). To use the string instrument analogy again, if you hit a low note on a piano, it resounds much longer than a high note because the string is longer and the note is lower. Same thing with basses versus violins, or tympani drums versus snare drums. But many noisemaking insects can already sustain their calls for a really long time. It has more to do with how the insect sustains its calls by repeating them with continuous stridulations or other methods.
Beyond that, here are some factoids that might inspire you. First, don't forget about katydids and cicadas!
Unlike crickets, cicadas make their rattling noises by rubbing their wings together. They also have a special noise-making organ called a tymbal, whose ribs buckle one after the other when the cicada flexes its muscles. Every time a rib buckles, the tymbal clicks. It's also important to note that cicadas make their calls during the day, while crickets and katydids call at dusk and at night.
[Katydids](https://en.wikipedia.org/wiki/Tettigoniidae), meanwhile, produce a variety of sounds (including a loud ticking sound and a synchronized rattling) and can even imitate the calls of other insects. They stridulate using a plectrum (like a guitar pick) which they scrape across a file or comb on their forewings. Katydids (or leafhoppers) are also obviously cool because they evolved to look like bright green leaves, and thus have excellent camouflage.
Here's another interesting detail about katydids from [SongsOfInsects.com](https://songsofinsects.com): "Males within each group synchronize their songs while the two groups alternate their songs, thus creating a resounding pulsation of sound that can overwhelm the listener."
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**This question already has answers here**:
[What would be the tallest possible height for humanlike creatures in earthlike conditions?](/questions/51686/what-would-be-the-tallest-possible-height-for-humanlike-creatures-in-earthlike-c)
(5 answers)
Closed 4 years ago.
Say you have a giant, similar to those of Dungeons & Dragons. For the purposes of this question, we'll say it's twenty feet tall. Is there any way one can alter its anatomy to save it from collapsing on itself due to the Square-Cube Law while keeping a basically humanoid shape?
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For twenty-foot tall giants to avoid undergoing collapse, instead of altering its anatomy it would make more sense for the giants to composed of stronger materials. Giants with stronger bones and tissues will be able to evade the usual consequences of the square-cube law.
Twenty-tall giants will only require their bones and tissues to be approximately between three plus and four times stronger than the bones and tissues of ordinary human beings.
This is due to the area of supporting structures like bones will increase proportionally by the factor of a square. Effectively the increase in the strength of their biological materials is only linearly proportional to the increase in their size. This will adequately compensate to the cube increase in their mass due to their increase in volume.
Otherwise giants would have to become proportionally broader and wider to increase the area of their bones and other supporting structures to compensate for their increase in volume and the increase in load due to the increase in mass.
Giants made of stronger biomaterials will maintain the same proportions as ordinary humans. This doesn't change their anatomy, provided their increase in size doesn't exceed their increase in biomaterials' strengths.
[Answer]
Consider the illustrative case of the **paranasal sinuses**.
[](https://i.stack.imgur.com/f0VyS.jpg)
<https://en.wikipedia.org/wiki/Paranasal_sinuses>
>
> The paranasal sinuses have a wide variety of functions including
> lightening the weight of the head.
>
>
>
<https://www.ncbi.nlm.nih.gov/books/NBK532926/>
Incorporating large air filled spaces within a structure allows a large structure of lighter weight.
So too your giants! Most of their apparent bulk is full of air sacs. Birds take advantage of this same principle and at the same time augment their respiratory ability.
[](https://i.stack.imgur.com/tpfE7.gif)
<https://birdsupplies.com/pages/your-parrots-respiratory-system>
Being composed mostly of air would let your giant easily reach your desired size, while at the same time weighing about the same or even less than a normal human. The giants would probably want to stay indoors during windy days.
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to the earlier question "[Mega-human: What are the largest possible dimensions of a human?](https://worldbuilding.stackexchange.com/questions/148861/mega-human-what-are-the-largest-possible-dimensions-of-a-human)", my (accepted) answer was that a humanoid could feasibly be 7m (23 feet) tall, with a weight of 5 tons. Your 20 feet giant is a bit smaller than this, so no further modifications would be necessary than those I mentioned in the answer (unless I overlooked something). Mainly, this is a relatively larger heart to pump blood higher. You might also consider tapering your giant a bit towards the top, with legs relatively thicker than the arms and a relatively smaller head, compared to a human. The giant would after all not need a bigger brain than a human.
[Answer]
Sea Giants, the underwater variety of Hill and Storm.
Our current largest animals live on the seas, where the weight is distributed over a larger surface + buoyancy!
**Your blue whale sees your tiny giant and laughs in her 150 tonnness!**
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I'm creating a large [ungulate](https://en.wikipedia.org/wiki/Ungulate) that is likely a part of the suborder Anclyopoda.
Suspension of disbelief is expected, but there's a detail with the current design that's really bugging me.
The creature is meant to be related to the [odd-toed ungulates](https://en.wikipedia.org/wiki/Odd-toed_ungulate), but the current iteration of its anatomy has three toes and a fourth as a vestigial-looking thumb. This happened because the animal is meant to be a good climber in order to thrive in their environment.
Should I remove the smaller toe or one of the large ones? Should I just add another thumb?
How important is it for the ungulate to keep an odd number of toes through their evolution?
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It isn't important at all.
We call them the odd-toed ungulates, but really it's just a group of related animals that, for the most part, have odd numbers of toes. This tends to happen because the common ancestor of these animals placed most of its weight on one particular digit, so unless there's a reason not to its descendants tend to have the other toes evenly distributed around that one.
It's not universal though. Tapirs have four digits on their front legs, and if this particular group is adapted for climbing - which represents a significant change from their ground-dwelling ancestors - all bets are off.
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Remember as well that lots of animals have either vestigial digits or even tiny bits of subdermal bone that once were toes. Your animal could easily fall into one of those categories and still be strictly a (2N+1)-toed family member.
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During much of the Late Pleistocene stage, the world's most widespread biome was the so-called "mammoth steppe" - a cold, dry grassland which spanned eastward all the way from Spain to Canada. It was the favoured habitat of many iconic Pleistocene megafauna species.
Roughly 12,000 years ago, the mammoth steppe suddenly disappeared, replaced by tundra and boreal forest. Some put it down to humans killing off the local megafauna which were needed to maintain the grassland, but the prevailing hypothesis is that the climate became warmer, and therefore wetter, allowing shrubs, mosses and trees to move in.
For more information, see <https://en.wikipedia.org/wiki/Mammoth_steppe>.
In my world I want to have a ~10,000 square kilometre island, situated roughly here:
[](https://i.stack.imgur.com/9m2Lb.png)
(Where the thick black dot is. Ignore the red arrow, that was in the original picture for some reason.)
And, more importantly, I'd like this island to contain a remnant of the mammoth steppe, and thus be a refugium for many extinct Beringian creatures. So, **assuming that the Climatic Hypothesis is correct, how can I justify the mammoth steppe not being displaced by other biomes here?**
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Not much explanation is required. Several islands in that area were home to mammoths long after they became extinct on the mainland: [Wrangel Island](https://en.wikipedia.org/wiki/Wrangel_Island) (7,600 sq km), the one on the top left of your map, had mammoths some 8000 years after the steppes disappeared. [St. Paul Island](https://en.wikipedia.org/wiki/Saint_Paul_Island_(Alaska)) is much smaller (100 sq km) and more southerly, but also hosted mammoths thousands of years after they had mostly disappeared.
Even today, it looks as though these islands have little in the way of vegetation larger than grass, much like mammoth steppes: [](https://i.stack.imgur.com/lh3DY.jpg)
So if your hypothetical island existed, it would be quite reasonable for it to have a similar environment. With a little luck, megafauna might stick around even longer than they did on Wrangel.
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By evolution. It may possible when there are only few predators and competitors for the primary food source of mammoth and also no drastic environmental changes. Maybe there was an earlier source of climate change that makes the environmental change smother but stretched duration. Mammoth may be altered because of fitting process. So maybe you could run an simulation of evolution to show that such scenario could be possible.
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You need a glacier and abscence of rains. Best way to achive this - strategicaly placed high mountains on one side of an island - they would keep glacier and cast "wind shadow" with no-rain zone on (almoust) all the island. Mamonth steppes should be on sort of mesa in our warmer climate, so some [traps](https://en.wikipedia.org/wiki/Siberian_Traps) would help.
Mamonth steppes formed between deserts and glaciers. When both gone (to simplify - glacer melted and weted deserts), steppes gone also.
Wrangel Island is not very good place - there is no tall grass for mammonths now (they need it a lot - tens of square kilometers of 1.5-2 meter grass per one mammonth). They gone extinct for a reason.
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This is based on the idea of a society where vampires are known and subsist off of 'willingly' given human blood. An average adult human needs approximately 2000 calories a day to maintain their weight, and so would a vampire. There are 900 calories per liter of blood, and about 5 liters of blood in the human body. A vampire would essentially need 2 - 2.5 liters a blood a day...or approximately 4 - 5 pints of blood. However, if donating platelets is healthier/more efficient for humans than donating whole blood then I may change the vampire's nutritional needs to be focused on needing a certain number of platelets rather than calories per liter of blood.
I know that these are the standard donation practices according the redcrossblood.org, but I can't find anything specific about how much blood you can lose every day and still be healthy.
>
> You must wait at least eight weeks (56 days) between donations of
> whole blood and 16 weeks (112 days) between Power Red donations.
> Platelet apheresis donors may give every 7 days up to 24 times per
> year.
>
>
>
So, how much whole blood/platelets would a single human be able to give every day, consistently, without dying/becoming unhealthy?
Since the time is less for those donating platelets, I'm assuming humans can donate platelets more often than whole blood while still remaining relatively healthy. If so how much?
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**On Blood Donation:**
Okay, so according to the link below a human can lose 14% of their blood without being affected. After that, it starts to affect them.
<https://www.healthline.com/health/how-much-blood-can-you-lose#noside-effects>
A person has roughly 4.5 to 5.5 liters of blood.
<https://www.livescience.com/32213-how-much-blood-is-in-the-human-body.html>
(going off of 5 liters) So 14% of human blood equates to roughly .7 liter of blood. Which is about three cups of blood.
So, to keep a vampire alive off of the stats you have it would have to have the blood donations of roughly three humans to feed it.
Though, I am not positive if that is possible with the same humans day after day. So a Human Blood Donation Rotation (as bad as that sounds) may be what happens. Could be useful if there's really bad overpopulation (of the human race).
Though this is what I could find on blood replacement:
Your body will replace the blood volume (plasma) within 48 hours. It will take four to eight weeks for your body to completely replace the red blood cells you donated. The average adult has eight to 12 pints of blood.
<http://www.giveblood.org/faq.aspx>
**On Platelet Donation:**
*As said earlier, donors can donate every 7 days*
*But Math says*
One Platelet concentration can have 3033-5555 platelets. But roughly four times this amount can be derived from this original concentration. Which means 12132 to 22220 platelets can be taken from one unit donation.
One apheresis donor can give roughly 4 units of platelet concentrations.
So four units would mean roughly 48528 to 88880 platelets per donation (on a normal red cross blood donation).
So I would say divide that number by seven which produces roughly: 6932 to 12697 a day (min. to the max.). **So a human could probably donate 6932 to 12697 platelets a day.**
<https://www.bloodworksnw.org/donate/platelets>
<http://www.donateblood.com.au/sites/default/files/PLATELET_DONATION_Sept2016.pdf>
<https://reference.medscape.com/drug/platelets-999506>
(and my math from numbers within)
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Okay. Let's take a look at the facts. Bone marrow (in a healthy adult) produces about 200 billion blood cells per day. (Yes, technically blood cells form things other than blood marrow, but it's not significant enough that we need to care for an estimate like this.) That number is what normal human produces to the point that they have a stable amount of blood within her body. For reference, when a human donates blood, typically a pint, that's 2.4 *trillion*. So it would take a body 12 days to produce that much. (56 days, hah.) Except, like I said, your body *needs* that 200 billion blood cells, because those only last a few months before dying. (So, uh, wait those 56 days.)
The real question, than, is how much *extra* blood that bone marrow could produce. And here's where I'm guessing. Given the proper stimulates (by which I mean biological ones, aka hormones), it's not hard to say that bone marrow can work at 200% capacity, meaning that you could give up a pint once every two weeks.
Of course, that's the amount you could do while surviving. The humans involved would probably suffer from some ill effects, like chronic headaches, dizziness, weakness, inability to perform labor for long amounts of time, shortened lifespans, increased risk of anything heart-related, and death. (Yes, death. You're giving up a pint of blood every two weeks, it's not going to safe.) 4/5 pints per day means that in 14 days you need about 65-70 pints of blood. So each vampire needs a livestock of around 80 or so odd humans, to be on the safe side.
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There are 850 calories per liter of blood for women and 920 calories per liter of blood for men. Assuming the vampires are of average human height and a healthy weight (5'9" and 126-169 lb) they would need 2,266 to 2,552 calories per day to maintain their weight. That is 2.67-3 of female blood or 2.46-2.77 liters of male blood for a male vampire. A female vampire of average height and a healthy weight (about 5'4" and 109-145 lb) they would need 1,794 to 2,033 calories per day, which is 2.11-2.39 liters of female blood or 1.95-2.21 liters of male blood. There are about 4.5-5.5 liters of blood in a human body. A donor can only donate 1 pint at a time, or 0.47 liters. 4.15-6.38 people would need to donate their blood every day for every vampire.
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I am working on a planet that has insignificant (almost 0 degrees) tilt, no moon, rotates twice as fast as Earth.
I intend to create quite an exotic "biome", so to speak, in a subtropical desert zone which has toxic lakes of mercury. From what I understand, mercury evaporates rather slowly.
Is it possible, or even plausible, and if not, could it be any other toxic element? How large could they become? And furthermore, could there be life that adapted to such toxic environment?
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Yes and no. you can make it work by having a hard ground: Mercury is heavy. 13 times denser than water, so I would put it into a not too deep, flat lake with some kind of solid rock bottom. More importantly: Mercury is very much not reactive, and it does not corrode. So have no worries about it corroding away. Another problem is that it will evaporate. Very slowly, but it will. Not enough to have clouds and rain but too much for it to stay forever.
a drop evaporates at 6ng/h, surface area of a drop is 50mm^2. chiemsee has 1,5x10^12 times the surface area and thus evaporation rate: 9480kg or almost 10 tons per hour. (22046.2 pounds). That is only 667 liters or or 3.2536585e-8% of the total volume, but on it will take only 3073463268.37 hours, 350851 years or 0.0077% of earths total life.
I am not saying it is impossible, but the fumes would kill you all around it. Maybe life around it will adapt? Who knows.
EDIT: Unless it is sourrounded by huge mountains, water will rain onto it, will float on top of it and cover it. There won't be any evaporation, since it is completly covered. But there will also be nothing to be seen.
EDIT2: I forgot to mention that if there are no winds it will not evaporate as fast, as the evaporated Mercury will not be carried away, which hinders the evaporation rate
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Like many other writers, I'm hoping to create some sort of justification for destroying the monopoly firearms have on the modern combat scene so that I can justify mixing things up with melee weapons, archery, slower-than-bullet magic, etc. I'm hoping to do this by using my story's magic system to knock guns down a peg, and after giving it a lot of thought, I've come up with a solution with potential. But I need to run it past some more knowledgeable people to see if this would actually work.
The gist is that, when the inciting event of the story renders nearly everyone on Earth low-level superhuman and capable of using magic, it also alters how the laws of physics interact with the human body in a few key ways, and one of those is that all solid objects colliding with the human body have an "effective speed limit" proportional to the object's mass, and any velocity beyond that speed limit is completely ignored once the object collides with the person and it's time to "calculate the damage" of the impact. *To be clear: this doesn't change how fast objects move. It only changes how fast the human body acts like it's moving when it's struck.*
**For example, let's say, just to demonstrate the concept and not declaring this as the actual value, that the effective speed limit of an object, in feet per second, is equal to 100M, where M is the object's mass in pounds.** This means that a 700 grain (0.1 pound) bullet, when shot from a gun, would only damage the human body it collides with as if it were traveling at 10 feet per second, instead of the staggering thousands of feet per second they usually get. Meanwhile, a sword, which weighs 3 pounds on average and is normally swung at speeds well below the sword's effective speed limit of 300 f/s, would be completely unhindered and be just as effective.
*This changes the formula for momentum to p=mv, p(max)= Xm2, where X is the feet per second per pound that the mass-proportional speed limit is set to.*
Since an object's mass now also determines its effective velocity, this means that, until an object becomes heavy enough that its effective speed limit exceeds its actual speed, a doubling of the mass of a bullet results in a *quadrupling* of momentum, which suddenly makes small projectiles much, much, *much* less viable.
The idea here is to force bullets to be big. Big, cumbersome and slow-loading enough that while they aren't completely nonviable and still have their advantages, guns are no longer the rapid-firing, compact bringers of instant death they were once allowed to be. Ideally, guns will be more like they were in the early days: cumbersome, slow to load, and barely more powerful than archery for the trouble.
I'm fairly certain this would make melee weapons relevant again, but the issue comes to archery. I've been informed of certain facts regarding the comparative weight of the heaviest calibers of bullet and the general weight of arrows. Apparently guns can fire some very, very heavy bullets, as much as 3000 grains, without much issue, and the heaviest bullets drastically outweigh most if not all arrows. While bows would be stronger here than in real life due to humans in my universe having the strength of two men, and thus arrows could be made heavier, this still calls into question whether or not a sweet spot weight even exists that would nerf guns but not render archery physically impossible. I'm willing to accept that in order to use this system I have to give up any prospect of including archery, but I'd like to see if it's still possible to make this work.
**Is it possible to set a minimum weight projectiles have to weigh to achieve penetration that is too heavy for bullets to be fired more than once every few seconds, but light enough for arrows to be shot from bows with draw weights of double human strength or less?**
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The effect you're describing could at least in part be achieved by greatly increasing the atmospheric pressure of a planet, or even adjusting it so humans live in a liquid without them realising. Yes, this part requires a liberal dose of handwavium sprinkled about, but ultimately the greater the wind or atmospheric resistance, the more lowering the mass of an object is going to have an effect because it's taking the same amount of energy out of every object passing through it at a similar rate, aerodynamics notwithstanding.
This last point is important, because your melee weapons and the like are going to work better if they are thin and sharp, like swords or axes, not hammers. It's also going to work better for arrows, which are heavier but also aerodynamic and therefore more likely to retain as much of their momentum as possible while moving through the thicker air.
Bullets in their current form will suffer, but their current design (blunt lead projectiles) is to maximise damage in an environment where their velocity counts. In this new situation, bullets may well survive as a combat measure, but they'll have two major modifications;
1) Convert to harder metals and a sharp point, and
2) Only be used as high velocity (long range) rounds, think snipers.
The reason for this is that the harder metal and sharper point means that the bullet does more penetrative damage when it hits, maximising what momentum it can still retain, but becomes less lethal in the process. With the exception of head shots, the bullet won't cause as much damage by deforming and spreading the kinetic energy out over a wider impact area, so it's now restricted to a long range wounding weapon in most situations.
Your arrows in this situation will also now have very sharp tips, and will be designed to wound as they currently are. Bullets in this scenario are effectively constrained to being long range arrows, although the arrow is probably in most instances the better and more effective weapon at short and medium range by virtue of its mass.
The real winner out of this will be your melee troops, who will have swords and spears for slashing and wounding across a broader surface area than arrows or bullets which have to keep their contact surfaces constrained as a sacrifice for longer range. Despite this, arrows will continue to be effective as a wounding weapon as it's unlikely that this 'upper bound of momentum' effect will be strong enough to constrain the momentum at impact of the arrow, and a sharp point would actually do more to make the arrow effective in any event.
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I don't think this works, because it would effect the gun as much as the bullets. You would feel no recoil because the gun can't gain more momentum than the bullet does. So there isn't much preventing you from using a gun with large bullets. If you needed 10x as much mass as a normal bullet to be lethal, but also felt 1/10th the recoil, every soldier would just carry 20mm rifles. They don't even need to be as big as they were historically, because you don't gain anything from additional speed. You only need the projectile to be fast enough to be accurate, speed doesn't help you penetrate anymore. So no need to bother with high enough pressure and a long enough barrel to hit 2000fps when 600fps is plenty. I think you would be looking at having everyone carry [bolters](https://warhammer40k.fandom.com/wiki/Bolter), not swords.
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See S. M. Stirling's Emberverse, starting with "Dies the Fire". In an instant, all electricity stops, high speed chemical reactions (gunpowder) fizzle, and it's impossible to get useful work with air pressures over about 150 psi.
Interfering with the speed of chemical reactions is a good bet. It would mean that you might be able to make steam powered cannons if you can get high enough pressure steam (thousands of PSI) Guns would be very cumbersome. Mechanical siege weapons would come into play: Trebuchet, mangonel, catapults, as well as both bow and arrow, and slings, atlatls, throwing sticks.
A physical change such as tripling the air pressure, by adding extra argon would allow guns to work, but the velocity drop from air friction would be
As a kid I played LaCrosse. This is a dangerous game played with a rubber ball. (A lacrosse ball is about the same weight and only slightly softer than a baseball hardball) A lacrosse stick, some training, and potato sized rocks could be bad news. A sling is more efficient -- most of the energy is in the stone, where with a throwing stick of any form you have energy in the stick that you have to stop for your next throw. But you can train a peasant in a day to be effective at putting rocks into a massed charge.
This opens the possibility of a "Pedal powered anti-personnel catapult." where some sort of wheel with cups, grooves, etc throws a rock at the enemy. Would require a well balanced wheel and good bearings. Given the relative strength of legs vs arms, I would think you could be about 5-15 times as efficient at transferring energy from your legs to the enemy's armour that arm powered projectile (You still need to concentrate the energy on a small enough area to inflict damage.
With a conventional sling, consider the effect of lead pellets the size of a robin's egg instead of a stone.
A boy's rubber band style wrist rocket slingshot used with 1/2" steel bearings can be deadly
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What you are describing would work. I would simply restate the kinetic energy formula with a Log function on the velocity bit so that it receives a maximum kinetic energy from velocity. This would have massive consequences for much of your world though.
But I think you can do it simpler: introduce runes. A rune would be a minimum size. Armor can be enhanced to be nigh impenetreable and its cheap and easy... But a counter rune is easily made on weapons. Problem is that bullets of sufficient size are so cumbersome and the recoil so great that you are better off using swords and arrows. This also limits what kind of ammo everyone uses, since an artillery shell that explodes also destroys its runes and becomes ineffective unless it hits you directly.
An alternative to runes is that each magic user can use its magic to Block enemy fire. An opponent can bypass this jf he concentrates magic in his weapons... But only if he can actually see and focus on it. High velocity projectiles regrettably are too fast so a slower projectile or melee weapon it is then. Another alternative is that mass is what carries the magical potential, but this magical potential leaks away the moment it leaves proximity with the wearer, the farther away the faster this goes. A bullet has lost almost all its magical potential to penetrate someone's armor while an arrow still has enough to do damage. And melee weapons become even more universally used as they lose no energy and stay close enough to be powered.
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Many other answers already state the parts where this would screw up physics and not actually prevent firearms by just making them use bigger bullets; so, I'll skip the reasons why this does not work, and just try to focus on fixing the idea in a way that it could work.
Instead of reinventing the universal laws physics to make bullets not work, this kind of problem is usually addressed best by adding new ways of stopping attacks that bullets don't counter well. This way you can avoid the collateral effects of completely flipping Sir Newton the bird.
For this I suggest you add some kind of protective runes or personal shields (depending on if you want to go more fantasy or sci-fi). These shields can stop incoming attacks based on their kinetic energy. Bullets actually don't have a lot of force for their killing power. Consider that even a high calibre handgun like a 44 magnum delivers about ~1200 joules of kinetic energy, but a 10 lb sledgehammer can deliver ~2500 joules. If an opponent's shield can block 1000 joules, then the high calibre handgun becomes little more than a pea-shooter while the sledgehammer still hits like a very fatal 6 pound hammer.
While this makes heavy weapons useful, it's still not good for bows, short swords, etc. which gives us a need for a second technology: shield disruptors. A disruptor would be a device or rune designed to penetrate a shield. Disruptors would be effective based on their size meaning you could fit one well into a sword or arrow, but not a bullet. So let's say you can cancel 50 joules of shielding per cubic centimeter of disruptor. The above listed 44 magnum could only cancel ~60 joules of shielding if the whole slug was replaced with a disruptor. In contrast, an average arrow shaft could easily hold a disruptor with 1000 joules of shield penetration, and a melee weapon like a broad sword could cut right through a 6,000-10,000 joule shield.
Because these interactions are only between the weapon and target; you don't need to spend your whole story having to worry about if you remembered to account for weird physics.
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I'm offering a frame challenge to your question.
I think that making the universe constrain motion or momentum in mass-dependent ways is problematic for all the reasons cited in the other answers.
But, since everyone is now magical, they could individually generate a personal shield that is always active against attack. It can be consciously made more powerful, but people keep it at a reduced level normally so they can carry out everyday activities.
For instance, at too intense a level, they'd suffocate since the air couldn't circulate around them. The everyday brownian motion of gases would trigger the shield and they'd soon consume all the oxygen. Similarly, riding a horse could be a problem since your butt bounces on the saddle. Bounce too hard, and the shield pushes back really hard on your mount, breaking its back. So, to keep life manageable, unless someone is really paranoid, they keep the shield powerful enough and a subconscious level that it makes bullets useless.
If you want most everyone to be vulnerable to melee weapons and arrows and stuff, then make it an instinctual reaction that everyone has -- a subconscious use of magic -- but very accomplished mages, witches, wizards, and magi can consciously control the shield.
In many ways, it would be like a magical version of Frank Herbert's personal shields in the Dune novels.
Again, FRAME CHALLENGE!!
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How about a Momentum nullifying shield instead?
For the first object to hit the shield its effective directional momentum becomes 0. A bullet (consisting of all one piece) would be completely stopped. An arrow (made of a head, shaft, and fletching) would have the head's momentum reduced to zero but then it would be pushed through by the momentum of the shaft and fletching. (it would still be seriously slowed down but it would be possible to compensate)
Even though melee weapons would seemingly rebound, they would also penetrate because of outside forces still imparting momentum.
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So, whenever I see people or articles discuss the properties of the warp bubble surrounding an Alcubierre drive, there is always mention of extremely high (yet undefined) tidal forces.
What I want to know, is what kind of tidal forces are we talking about exactly (we'll assume it's a 100m sphere sufficient for 1c velocity)? For example, if I fire a .30-06 bullet at the field, will the bullet be vaporized on impact, or will it's path merely be severely altered, or will it continue through the bubble with relatively little change in direction?
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The warp bubble created by an Alcubierre Drive is causally disconnected from the outside universe. To put it simply, from the perspective of the outside universe, the bubble and everything in it do not exist.
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**The bubble could be a deflector shield.**
There is a scholarly article on the issue of what happens to matter (and light) which is encountered by a moving bubble. The popular press seized on the last paragraph where the author notes that particles overtaken by the bubble are swept along, accumulating energy and then are release when the bubble stops with an energetic radiant burst.
The rest of the article I really struggled with. I tried to see if there was a popularization, or perhaps a talk given by the author that explains the graphs better. No luck so far.
[](https://i.stack.imgur.com/gjaIk.png)
[The Alcubierre Warp Drive: On the Matter of Matter](https://arxiv.org/pdf/1202.5708.pdf)
So you get my take. The author breaks it down for bubbles moving faster and slower than the speed of light.
>
> For particles with initial positive velocity lower than the critical
> velocity, there are two possibilities, either the velocity is above
> that of the bubble and hence the particle will catch up to the bubble
> from behind or the velocity is below that of the bubble and thus the
> particle will in- teract with the front of the bubble first as the
> bubble catches up to the particle. In the first case, the parti- cle
> is ejected from the bubble back out the rear with a reduced but still
> positive velocity below the ship veloc- ity. For particles with
> initial velocity closer to the critical velocity, the path follows
> that of the critical velocity par- ticles for longer, thus getting
> closer to the ship, before diverging and being ejected from the
> bubble. Similarly in the second case, the particle is ejected out the
> front of the bubble with an increased velocity larger than the ship
> velocity.
>
>
>
Summary: particles and radiation definitely enter the bubble and they definitely can enter the normal space near the ship. They can hit the ship. An energetic particle (bullet?) hitting the front of a fast moving bubble can hit the ship - not with some weird superluminal velocity but a velocity related to that which is initially had.
A thing I struggle with: particles catching up with a bubble from behind are ejected back out **the way they came in**, SLOWER than they came in. A particle entering the front in ejected back out the front, FASTER than how it came in - *here is your deflector shield*.
This implies to me that the "moving" bubble would be spraying captured particles out the front the entire time it was moving. The huge spray of particles on coming to the destination is one case of this - all the accumulated particles coming in the front and destined to spray back out the front are released at once.
You want your deflector shield to sit in front of you. This would be a bubble with velocity 0. I do not understand the math well enough to figure out the path of a particle (bullet) entering a bubble at rest.
I am insecure in my interpretation of this paper. I really was hoping for a lay version but no luck. But at least here is some science by someone who does understand; maybe other readers will make more sense of it than I did. Links welcome!
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So, I decided to do some (far more likely that not, incorrect) math, and came up with this:
While the energy required to develop a 100m warp bubble capable of traveling at the speed of light has an uncertainty of up to ***80 orders of magnitude*** [1], I chose a number that would be "difficult but probably not impossible for a decent sized sci-fi space ship to deal with in terms of material consumption", which about equates to 6.12\*10^17 Joules, or 6.8 kg of matter converted into energy (antimatter ftw).
Since (presumably) this energy is only used for the warp bubble (barring the inefficiencies that would arise from any *real* warp drive), we can therefore state that the energy per meter squared over the 100m warp bubble is 4.87\*10^12 J/m^2
Now, looking at some side-on pictures of a .50 BMG gives me a rough estimation that the area of the tip of the bullet is about 0.000000452m^2. This means that the energy imparted on the tip of the bullet at impact is about 2.2 MJ. This is about ***100 times the muzzle energy*** of said .50 BMG. Given that .50 BMG bullets (as with any lead bullet) tend to violently break apart due to their own energy when impacting a solid object, I would imagine that something inducing two orders of magnitude higher energy on the bullet would therefore disintegrate the bullet effectively.
Again, this math might be (and probably is) total BS in terms of it being the correct math to use to solve my question, but it at least sounds correct.
The fun side effect of this math being that assuming the warp bubble was not given any additional energy to compensate for what was lost in the bullet impact, it would take *at least* 2.8\*10^11 .50 caliber bullets, which appears to (very roughly) be about 5-10 WWII's worth of bullets (let alone .50 caliber BMG specifically).[2]
Source:
1. <https://www.hindawi.com/journals/isrn/2013/482734/>
2. <https://history.stackexchange.com/questions/1711/number-of-bullets-used-in-ww2>
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So just for a quick "historical" context.
This is a continent where numerous races other than humans exist as does somewhat weak magic. In the medieval era the humans attempted to genocide/enslave all the other races in the calamity war. Ultimately they were defeated by an alliance of non-human nations lead by a hero (non-human) who most believe is a goddess of nature and war.
There are no more human nations now, as all of them either got conquered or collapsed due to famine (wrath of nature). Humans still live though their numbers were severely diminished.
Her children, using her godlike status, army and approval of their allies, create a kingdom of their own, Piena. Now they are obsessed with the idea that their kingdom becomes incorruptible and its ethics do not change, because of events in the war. Even through the ages. So they decide that the most rational way to proceed is to brainwash (includes a combination of magic, drugs over long periods of time) their ideals into the next generations.
Unfortunately Piena can't brainwash everyone. Piena can't brainwash its allies, because diplomacy. Piena can't brainwash its entire population, because money. Piena can brainwash it's nobility and royalty though. Piena can also brainwash the people doing the brainwashing. Also we are assuming that everyone knows about the brainwashing and the nobility of Piena is fine with it initially.
Some general information : Piena is situated at a crossroads of most of the major river-ways in the region and as such is hard to avoid inland. Its territory contains those of an old human nation as such it has about 30% of its population being human. It has very fertile soil (from rivers) and thus a large population (especially for after the war) but not other riches except its strategic location and army.
Genocide should be avoided but slavery is completely fine.
At the end of the war all nations which didn't collapse were in the winning alliance so at least initially Piena is surrounded by friendlies and doesn't have to worry about an immediate military threat other than bandits/small warlords from the collapsed remains of other kingdoms.
The hero is also worshipped widely outside Piena's borders though there are different churches, some of which don't consider her children divine. Pilgrimages to her mausoleum in the capital city are widespread in all cults. In the stories told by priests she is basically a mary sue.
Now because asking "how would this work" is a bit to general here are some specific questions :
* How would the founders organise Pienan society to ensure long-term stability ?
* How would other nations (which are initially all allies) react and how should Piena respond to them ?
* What to do if brainwashing fails or is only partially successful on a member of the royalty (who are believed to be descendents of a goddess including by some cults abroad) ?
* How would the brainwashed leadership, say 600 years later, assuming they survived this long, react to things like industrial/magical revolution, which the founders couldn't anticipate (note that the founders MAY not be averse to "technology" but couldn't anticipate such rapid changes) ?
* Now say you are a foreign nation, how would you take advantage of this situation ?
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**The brainwashing is sold as a necessity for leadership**
This is more or less how the society was structured in George Orwell's 1984, and that in turn was very loosely based on ideas out of The Republic by Plato. The idea is that you have 3 'castes' (for want of a better term), an inner party, and outer party and a proletariat. The proletariat does not and cannot have any political aspirations as they are barred from political office and more or less barred from any knowledge of politics. This (in 1984, it was 97%) represents the vast majority of your population which is focused on production. They are your industrial and commercial workers; miners, farmers, carpenters, and even some of the professional services like doctors and lawyers.
The outer party is your civil service; the administrative and operational arm of the party. These are people who are watched very carefully by the inner party, who are your true leaders, and the true fanatics of your system.
In The Republic, Plato introduces a mechanism for selecting who should be in which caste, which is often referred to in commentaries as 'the noble lie'; in this he describes a legend where some people are of a gold class, some silver, some wood, and it is the duty of the society to sort these out correctly as the Gods have mixed these up at birth as a test of the society's worthiness to survive. What he is effectively describing is talent identification.
In your scenario however, you don't need talent; you have magic and drugs. At some point your society will realise that it's better off using talent identification prior to the administration of the brainwashing, but that's a side point. The important point is that no brainwashing, no leadership role. If the brainwashing only partially works, then perhaps your candidate is an outer party official for the rest of his or her days.
As for how other nations would react to this, the principal factor is in what the brainwashing is intended to do. In both the Republic and 1984, it's assumed you're going for an authoritarian dictatorship with militaristic airs. If your current society has all the resources it needs and has no intention of changing its diplomatic strategies or engaging in further conquest, you'd be amazed how quickly other countries will turn a blind eye, especially if there are trade deals to be made.
Internally, again so long as the intent of the brainwashing can be demonstrated to ensure that the nobility are focused on the welfare of the people, they'll be very welcoming of it. Guaranteed stability means they can focus on things other than keeping an eye on those running the country; like profits.
As for the adoption of change over time, why should your brainwashing impact that unless it's focused on stability of culture, which would **always** be a bad move. Culture, technology and innovation adapt to the people and their environment and with good reason. You don't want a cultural more that excessively wastes water if you find yourself in a climate change situation that makes water scarce, or even turns your farmlands into deserts. You don't want to resist science and technology when doing so will hinder your growth in productivity and industry, making you a valuable trading partner to many neighbouring nations.
Sure, introducing change slowly to nations and cats is always the smartest policy, but an insightful leader is already ahead of that curve, and brainwashing should not reduce intelligence or planning capability, otherwise its meaningless as a control mechanism for the aristocracy.
In short, brainwashing of leaders should not reduce their pragmatism, merely ensure their loyalty to the nation and its wellbeing if it is going to work. In all other respects, you can't take away the intelligence and ability to act of your leaders and preserve their ability to rule well, especially in an environment where contact with neighbours will continue and the resources available to the nation are subject to change (which is the case for *any* nation that has ever existed on Earth).
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A rotating object, especially something as large as a planet or a star, has kinetic energy. However, my question is how would you go about harvesting the energy the object has from rotation to go towards other purposes such as powering several thousand space stations? I'm making a hard science fiction short story, so if we could keep it as realistic as possible that would help. Thank you in advance.
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The answer is the tides. Your space stations need to be numerous and large enough to cause tides on the planet below. Tidal forces slow the rotation of the planet, so if you set up some [tidal stream generators](https://en.wikipedia.org/wiki/Tidal_stream_generator), you are essentially taking the rotational energy of the planet and turning it into electricity.
This is not a great idea though, because not only do tidal forces slow a planet's rotation, they also push the moon further away. In real life, with our moon, this is only a few centimeters per year. We'll have our moon for billions of years. The rate the moon moves away is proportional to how strong the tides are. The stronger the tides, the faster the moon moves away. If you set something like this up to generate as much energy as possible, you would want the strongest tides possible. This would also mean your space stations would get pushed away quickly. To push the stations back to their original positions requires some other energy source; solar sails, chemical rockets, something. Which raises the question, "Why not cut out the middle-man and just use that other source for energy?"
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If you're orbiting space stations around an Earth-like planet, tidal power plants beaming energy to the space stations would do the trick. Converting tidal power to electricity/radiant energy slows the planet's rotation.
If not, you're going to need a lot of space elevators. [Transferring mass past the zero-g point to the counterweight](https://physics.stackexchange.com/a/47591) (where it can then be given a gentle push and let go) will generate energy. A star would be trickier, but solar energy would work fine in that case.
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**An Alternative Space Elevator Solution**
We're dealing with a future tech, so a hard-science solution is asking a bit much. But, let's assume we have access to...
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*Indestructonium*
* Can withstand impact on the surface of the earth from high orbit without damage to itself.
* Is remarkably magnetic.
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1. Build your space elevator to a high enough orbit that the space-end can sit free.
2. Surround the elevator casing with coils of wire. Bazzillions of miles worth of windings.
3. At the base of the elevator, we want either (a) an indestructable piezzo-electric pad or (b) a mechanical pad that compresses on impact, spinning a flywheel in the process. (I'll explain this in a moment.)
4. Finally, we need a big-ole' hollow canister made of *indestructonium.*
This works great if you're mining in space and need to get materials down to Earth. Fill the canister with ore, give it a push, and let it drop straight down to Earth. Now, terminal velocity is [estimated at 78 m/s](https://www.grc.nasa.gov/www/k-12/airplane/termv.html), but let's say we're falling through 22,000 miles (35,406 km) of distance. The canister is highly magnetic and we're passing through a bazzillion miles worth of windings. Think ["shake-it-up" flashlight](https://en.wikipedia.org/wiki/Mechanically_powered_flashlight#Shake_type_design).
When that sucker impacts, it's a bit (but only a bit) like the [Tunguska event](https://en.wikipedia.org/wiki/Tunguska_event), except we want to capture the energy rather than letting it convert to felling trees. That's where the piezzo-electric pad or compressing pad with a flywheel come in. I'm not fond of the piezzo-electric pad as it would create a wire-frying burst of electricity that would require serious do-something-with-it-juju to use. The pad idea, where the impact pushed down the pad like a shock absorber, causing a flywheel to spin up to a bazzillion miles-per-hour... that lets the connected-to-a-turbine-generator flywheel run its course, providing a longer, more useful stream of power.
Empty the canister and power the windings to rail-gun the now much lighter canister back to the top. Uses less energy than it created via the drop.
**How do I get the power to my space stations?**
Run transmission lines along the elevator casing. Note, though, that getting energy off of a spinning object is a big deal. As fun as this thought experiment has been, it would be simpler and cheaper to power your stations with nuclear energy, shipping spent fuel rods off to the sun for disposal.
*I recognize that this isn't what you had in mind. It uses gravity, not the kinetic energy of a spinning Earth, but it's whomping hard to get energy from a spinning sphere.*
*You could set up rigid poles to high orbit with fixed magnets on the end, and put a "disk" of windings in orbit that are stationary and kept so with some ion thrusters. As the earth spins, the rigid poles would move through the "disk" of windings, generating power. But this is so enormously complex and prone to accident that I don't see it happening.*
*But, with enough [Clarkean Magic](https://en.wikipedia.org/wiki/Clarke%27s_three_laws), you can do just about anything.*
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You could have a payload that undergoes a slingshot maneuver around a planet which allows it to convert some of the planets kinetic energy into its own via gravity. You then use that extra speed that you gained to generate power. If you could somehow get two planets, You could somehow slingshot the object around both planets to keep increasing its speed and have power stations between the planets that drain the gained speed so that you can keep this going to keep harvesting energy.
Assuming you have enough resources, you could expand this to literally have a line of iron/steel poles that fly between the planets passing through massive space station power planets that consist mainly of coils which will programmed to only drain a fixed about of kinetic energy so that the iron/steel poles can slingshot forever.
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While it's maybe 'stretching' (soon-to-be pun intended) your definition of using rotation to generate energy, my method would certainly not be feasible without it.
Place a space elevator with magnetized tether in to orbit. Ride a platform from the planet's surface to the space station which contains a coil of wire around the tether. Place capacitors or other electricity storage devices on the platform. Balance out the weight so that the load will just barely get to the end of the tether.
This set-up could also be done in reverse, meaning the power would directly be transmitted to your space station, but this would require super conductors to overcome the motive resistance of power in the electrical lines.
Presumably you generate some sort of waste on your space stations. Place this on the space elevator and allow for gravity to pull the whole system back to the planet's surface.
Not only do you have free sources of power (presumably many of these space elevators would need to be built), but you also have an easy way to get rid of trash which doesn't involved launching and burning in the planet's atmosphere. Drone earth moving equipment will harness energy on the planet's surface and keep the area around the tethers clean of debris for centuries to come. Or have a big ol' incinerator down there to buy even more time.
Other systems may work whereas the device doesn't have the resistive, electricity generating force until the last several kilometers of the tether. Using this method, you could gather up a lot of speed with your elevator then generate power only over the last several kilometers with much stronger magnets. This helps because a situation could exist where the elevator is basically flung up and then 'caught' at the top, allowing it to then descended on its own due to its own mass. More green, less trash removal.
Oh, and the coil/magnet system is mechanically disengaged on the return journey to earth in whatever manner is necessary to ensure a slow descent. With the second option, you could in theory, generate electricity on the 'down stroke' as well.
Your call.
EDIT: Forgot to mention, you will need motive force to bring the payload above GEO. You will also then need enough excess power generated to cover this in the power budget. The space tether is going to be quite long, but presumably, your ships are in deep orbit as well so as not to require as much power to stay there.
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Not only is it possible but it has also been tried. In fact it is a major source of electricity in the world. The things are.....
WINDMILLS!!!
Yes, you read that right. Winds are formed by pressure gradients and are influenced by the Coriolis force. The Coriolis force is a force made by an rotating body, that deflects the wind. This is the reason why hurricanes are spirals and not giant holes sucking up air. These are formed by the Earth's rotational force.
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My planet is tidally locked to its sun. It has a slightly thicker atmosphere than Earth. Over the planet’s sun-side surface, there would be no wind because that area is in the middle of a big cyclone/anticyclone. (I'm not sure if that works yet.)
The Aliens living there are using some sort of light glider to travel over big distances from one city to another.
[](https://i.stack.imgur.com/7HWPf.png)
The concept is very simple:
1. Two snake-like weights on each side.
2. A middlepart with some steering mechanics in the front in shape of a manta ray (not shown)
3. A thin, flexible, black plastic between the weights.
The sun shines onto the plastic. The plastic heats up the air beneath it. The air expands and carries the weight of the construction. When it flies, it looks like a straight worm that hangs in the air whilst looking at the ground in a very slight angle. It has trouble landing. That's why it doesn't. It will fly slowly past a bridge and passangers just jump onto it.
It should be able to travel over long distances without droping in altitude.
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**Questions**
1. How exactly can I get the energy of the sun through the "carpet" into the air below?
2. How many gallons of air must there be under the carpet per pound of
weight and under which circumsances (temperature and pressure of the air)?
3. What other circumstances in a world would be practical for my flying carpet to work?
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I had to finish the question in a hurry and will adjust it later if wished.
[Answer]
The principle seems similar to a [solar balloon](https://en.wikipedia.org/wiki/Solar_balloon), which is an hot-air balloon where the air is heated primarly by the Sun. The Wikipedia page linked has several formulas that should be useful to you.
Your design is open on the bottom while existing solar balloons are closed. This is probably critical to keep the hot air inside long enough to reach the right temperature and is probably going to be a major difference. If you are able to tweak the composition of your atmosphere you might make it more responsive to heat dilation, lowering the required temperature, but I'd bet this would not be possible with Earth's atmosphere.
On the other hand, the air will be really hot on the day side of a tidally locked planet. It will receive heat from the ground as well, although how much is hard to say. Ground heat might be the force that makes it all work but you'll need to reach a compromise with how people will survive there in the first place.
To make it steerable you'll need some kind of propulsion. If you have an excess of hot air letting it out would propel the vehicle in the opposite direction. Alternatively you can use a (solar.powered?) mechanical propulsion like fins or a propeller.
**Conclusion:** "Flying carpets" will need some assumptions on the local climate and physical properties of the atmosphere and the ground. They will probably need to be incredibly large to carry a modest weight.
You might however convince a reader that they work because you have some qualitative arguments, even if the numbers would not add up.
[Answer]
So basically you are trying to make a solar-powered balloon, stretched as a carpet.
Balloon floats because air captured in it is less dense than air around it.
So answering question 3:
* in world with atmosphere with big thermal expansion coefficient. The bigger difference in densities of gases inside a balloon and outside of it, the bigger lift force.
* in world with great gravity. The greater gravity, the greater buoyancy (balloon uses it). BTW. there is no buoyancy in zero-gravity.
* in world with more dense atmosphere higher buoyancy can be achieved (water produces bigger maximum possible buoyancy than air), although air density on it's own does not produce buoyancy (only with correlation with thermal expansion coefficient that produces densities difference).
As to question 2 (I'm not using imperial units here. This is why: <https://www.goodreads.com/quotes/8417995-in-metric-one-milliliter-of-water-occupies-one-cubic-centimeter>):
Problem with carpet is that most of the heated air beneath it escapes it immediately. I see two possible solutions - capture part of heated up air by shaping your carpet more like a container, or make atmosphere so dense (it will prevent heated air from escaping a bit on it own) with so high thermal expansion coefficient and so great gravity, that this thin layer of heated air would be able to lift whole carpet.
Let's see it it is anyhow doable with some maths.
Some symbols with meanings:
m - mass of carpet
g - acceleration of gravity
Fb - buoyancy force
Vu - volume of heated air under carpet needed to create this force
Rd - difference in densities between heated and cold air (beneath and over carpet) - it gets bigger with air's thermal expansion coefficient growth
Q - gravity force acting on carpet
If your carpet will weight W, then we need to create force greater than W\*g to lift it.
This force will be Fb = g*Vu*Rd, so:
Fb > Q
g*Vu*Rd > m\*g
Vu\*Rg > m
(Vu\*Rd)/m > 1
About thermal expansion coefficient you can read here: <https://en.wikipedia.org/wiki/Thermal_expansion#Volume_expansion>
This coefficient for gases usually is around 0,01 - 0,02 / K that means, when you heat some volume V of gas by 1 kelvin, you get 1,02V in the end. Let's call this coefficient "B".
This means, that Rd (mo - mass of air over carpet, mu - mass of air under carpet, Rn - density of air over carpet, like in normal conditions):
Rd = (mo/Vo - mu/Vu)
Rd = (mo/Vo - mu/((1+B)\*Vo))
Rd = Rn - Rn/(1+B)
So the bigger B, the bigger Rd, and Rd tends to Rn, so to value of density of air above carpet.
So all in all you have:
(Vu \* (Rn - Rn/(1+B)))/m > 1
Let's count volume of air under carpet for some example values:
Vu - searched
Rn = 6 g/L (sulfur hexafluoride, one of most dense gases I know about)
B = 0,02 (upper regions of common coefficient)
m - 1000kg (rather small unit assuming aluminum as constructing material, 6 passengers probably)
So:
Vu > m / (Rn - Rn/(1+B))
Vu > 1000[kg] / (0,006[kg/L] - (0,006[kg/L]/1,02)
Vu > 8500000 L (dm3)
So assuming that under your carpet you'll add a wall to keep averagely 10dm (1m) of hot air under carpet (it will be more in the middle, and less on the sides, but I can't calculate this), your carpet would have to have 850000dm2 or 8500m2 of area. Pretty much impossible with 1000kg. But if you'd add a wall that will keep 100m of air under it, it will have to have 85m2 area, so... pretty big carpet you'd have. But possible I think.
Let's mess a bit with entry values:
Rn = 10
B = 0,05
m = 250kg (ultra-light sun-forged meteorite metals alloy)
We get Vu > 525000dm3
So with wall keeping avg. 1m or air beneath, area of carpet should be 525m2 Well.. maybe...?
If we would do:
Rn = 600 (least dense liquid I found has ~616: <https://en.wikipedia.org/wiki/Isopentane>)
B = 0,1 (this seems so extreme extreme to me that I don't know If it is possible in conditions any carbon life we know of can survive)
m = 10kg
Vu > 1100dm3, so with 0,5dm of air beneath it in average it's area could be 22m2 So extreme...
As to question 1:
Another thing is heating the air - there are two ways that come to my mind. solar powered peltier modules or Stirling engine. Both will transport heat from upper surface of carpet to bottom one. Both can be powered with super-efficient solar power driven energy source, but since this civilization is bound to their sun so tightly, than this is probably not a problem.
Afterword:
Our planes have MUCH more efficient ratio of mass/(wings)area, so maybe just make them all use solar powered planes...?
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I'm designing an alien plant soecies that has evolved to produce electric shocks, as a way to keep insects away from it. My question is, how would it produce electricity in the first place? Also, could such an energy source be extracted?
Note: I've read about the way electric eels produce electricity, I'm just wondering if the same method can be used by a plant. If not, in what ways could it produce electricity?
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Very interesting question. The first thing that comes to mind is something along the lines of [this](https://www.weforum.org/agenda/2015/08/how-can-you-generate-electricity-from-living-plants/). But in essence, this occurring naturally would be rather difficult and isn't really your plants creating the electricity so much as it is bacteria.
So what about an [Enzymatic biofuel cell](https://en.wikipedia.org/wiki/Enzymatic_biofuel_cell) working off of the glucose your plant naturally produces in the Calvin Cycle? For this to work, your plant will need to produce a Glucose Oxidizing enzyme for the Anode and an O2 reducing enzyme for the cathode.
It wouldn't be difficult to imagine these being two different structures within your plant, perhaps quite small and close, with conductive structures near the surface. When an insect comes to feed, it completes the circuit with the conductive saliva in its mouth and gets shocked. A possible issue here would be rain short circuiting your plant, so you may want to make the conductive structures just below the surface the insect has to barely break the skin of your plant to get the shock.
If you really want to 'go-out-on-a-limb' (pun intended), you could have the plant generate natural capacitors using [lipid structures](http://www.physiologyweb.com/lecture_notes/resting_membrane_potential/figs/biological_membrane_as_capacitor_jpg_Ct5ZidE4iE62JpKTr0ie26ed7qQlH872.html) and minerals pulled from the ground to produce charge storage devices allowing for greater potential differences (aka greater shocks). The issue here is that these will likely need to be grounded to properly work. But you plant can provide much of that using mineral pathways (likely separate and insulated from its vascular system) to the ground in which is grows. Whether this is necessary would depend on a lot of things, but insects probably wouldn't need large shocks in their mouths to be convinced to move on elsewhere.
And whether or not power could be extracted by an intelligent being, I see no reason why not. I would doubt that it is the most efficient way to generate energy from the sun, but this is based on current technology (solar panels).
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Your plant has many long leaves that die away, dry, but keep hanging on the branches. Imagine ivy, but leaves are longer and dried up. When the wind blows, it causes leaves to rub together, and this builds static electricity. If branches are not conductive (very dry, too), leaves would retain that static charge for long time.
Rain would render that plant safe for some time, and leaves should not have pointy ends to keep the charge better.
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Firstly the would need to develop something like a nervous system. An arrange of cells like a cable or chain that transfer energy from someplace to somewhere.
Let's say it can generate energy from the heat of the sun and let's call it photosynthesis! In the middle of the process the energy is stored in molecules, but them the organisms gets enough of it and the energy needs to go somewhere else. This process, in a oversimplified way, just transfer energy from the radiation of the sun to move electrons through molecules.
If this process also occurs in the chain cells until it arrives in the roots where the energy if finally stored for good, any disturbance of the cells membrane could cause an override and potentially create a discharge of electricity.
Disclaimer: If you want pinpoint accurate biology and reality check, take this answer with a grain of salt. You could mix some ions canals for a more accurate scientific process, but you would basically get what you already have, the eel situation.
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I've seen some cool art and scenes from the Cowboy Bebop which had trade lanes made up of what looks like large rings that accelerate and deccelerate a ship.
I wanted to replicate a system like this for Warlords making use of the ITN (interplanetary transportation network). Now the actual idea I had would be another question (seeing as this is just about the concept)
Would using external rings or other technology help make the ITN faster and become a practical and reliable shipping method? Is it practical or is this construction too monumental to work?
Note: independent ships and lanes would still exist due to some materials needing rapid transportation or ships trying to avoid the lanes for various reasons.
[Answer]
## The rings are super magnets.
If the rings are super magnets they can accelerate ships via electromagnetic repulsion. A set of rings, for example 10 or 100 can be used to apply the repulsion affect several time to accelerate a ship very fast forward. You may want to have a corresponding set of rings on the other side, at the destination, to decelerate incoming ships in the same way to make this system really efficient.
Is it practical? It is probably a lot more practical than using rocket fuel. The ships can be lighter since they don't have to carry the fuel themselves. So they can be smaller, cheaper, etc. Building rings like this in space probably isn't too difficult either since the mechanics behind it and the size are not too absurd.
Coordinating everything so that they line up would be the hardest part. This is because planets move. So lining up the rings for acceleration at your departure point, so that you reach the rings for deceleration at your arrival point, may be a difficult math equation to solve.
**Edit:**
*So how do we address the problem that when a ship moves forward it will push the rings backwards? (Newtons 3rd law)*
The rings don't have to be completely stationary satellites. They can be space ships too, but designed to just stay around some region of space.
The rings can even be one large super object instead of separate rings, or attached to asteroids, and be re-attachable to others when one moves too far.
The rings can have all the usual bells and whistles for navigation. How bulky the rings are isn't really an issue for interstellar travel since they wont be travelling far. The real benefit is in having the ships that are ejected not have to carry lots of fuel, so they can be accelerated to very fast speeds fairly efficiently. This is because the ships can lower their mass by shedding the mass of their fuel, which is instead handled via the electromagnetic ring.
Since:
>
> Force = Mass x Acceleration,
>
>
> Acceleration = Force / Mass.
>
>
>
By lowering mass we can increase the amount of acceleration from the same force.
And Thanks @Alice:
>
> There are also ways to maintain or correct orbit without expending
> reaction mass, such as [solar sails](https://en.wikipedia.org/wiki/LightSail_2) and [tethers](https://en.wikipedia.org/wiki/Electrodynamic_tether).
>
>
>
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Space has a lot of well space in it, there's a quote from *Hitchhikers Guide* I should be using but I can't be bothered looking it up right now about just how huge space is. The point is that the volume of shipping you would need to be doing to make traffic lanes for shipping either practical or necessary is staggering, that's problem one.
Issue two, destinations move around in space relative to each other so the lanes would be moving around, all over the place, all the time. So while a laneway that allowed for faster shipping of goods might be desirable keeping it aligned would be prohibitively expensive.
So lanes not so much, you might have gates that allow instantaneous, or at least speed-of-light transition of ships from one place to another, these may only need to be turned to face each other or possibly only need tracking data for a software based alignment. The particular cost:benefit situation is a matter of the exact setting and so is a story-based element that you'll have to decide and/or justify to yourself.
I don't remember the Bepop rings being used as accelerators, just for breaking maneuvers on final approach towards planets but I haven't watch the series in a long time.
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The issue isn't the rings (which are likely parts of a massive mass driver system) but your use of the ITN. The ITN is essentially a shifting zone of gravitational interactions between planets and the Sun, but the effect is very slight and a spacecraft using the ITN might be considered analogous to a leaf floating down a very slow moving stream. Using the ITN might take years, decades or even centuries to get from place to place in the Solar System.
A spacecraft being launched using a mass driver can be accelerated to any arbitrary speed, only limited by the amount of acceleration the ship, ships systems and crew (if any) can take. There is nothing to prevent you from accelerating the ship to any speed ranging from the minimum orbital speed needed to reach the next planet ([a Hohmann transfer orbit](http://www.projectrho.com/rocket/supplement/orbitalmech.html)) to 72 km/sec, the maximum velocity an unpowered object can remain in solar orbit. Of course, more speed requires more energy and much more acceleration in any given length of mass driver, so the general rule would be to use this to send cargo on Hohmann transfer orbits in order to economize on energy use. Bulk cargos could be sent via unpowered pods to distant markets, where similar mass drivers would decelerate them to a stop.
For manned ships, using a mass driver to kick start your voyage would save a lot of fuel needed to accelerate or decelerate, so given a large and powerful enough mass driver, this would likely be the favoured solution as well.
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"Polymorphism" is the name for when members of the same species exhibit different physical forms. The difference between male and female phenotype is an example of polymorphism in humans (and mammals/others). These differences are controlled by how chromosomes are inherited.
Suppose we had a species which has a second dimension of polymorphism - for simplicity, we'll call it being "red" or "blue". So an individual of this species can be a red male, a red female, a blue male, or a blue female.
**Could the chromosomal inheritance of this species be structured to allow the following reproductive results?** (How?)
* The union of a red male and a red female will always produce a red female.
* The union of a blue male and a blue female will always produce a blue female.
* The union of a red male and a blue female will always produce a red male.
* The union of a blue male and a red female will always produce a blue male.
(I'm hoping to keep the system as close to human chromosomal inheritance as possible; to avoid introducing completely new genetic mechanisms, etc.)
[Answer]
The simplest solution might be to have two chromosomes, a red one R and a blue one B. There are two versions, a "functional" version containing the "color" genes that is contributed by the male, and a "reduced" version contributed by the female that lacks those genes. Only the male version has the genes determining the color, so only the male's version impacts color. If someone has two chromosomes of the same color that is a female, while two different chromosomes makes a male. This is sort of analagous to the human X/Y chromosomes, where the Y version is reduced and lacks many genes.
The obvious problem is making sure only fathers contribute the functional version and only motgers contribute the reduced version. But there is already precedence for this in humans: only the mothers contribute mitochondria. The father's mitochondria are destroyed shortly after the sperm and egg fuse. So this species can have two organelles that carry genes. One such organelle carries the "functional" chromosome, and only the father's version of this survives. The other carries the "reduced" chromosome, and only the mother's version of this survives.
Strictly speaking these wouldn't have to be chromosomes, in fact such organelles probably would have simpler, reduced genomes the lack true chromosomes. The color can simply be determined by some genes of the male organelle, while the gender is determined by genes in both organelles.
[Answer]
Let's look at what you need (First letter for color, second for gender):
* RM + RF = RF
* BM + BF = BF
First two couples have the common denominator of having the same color.
* RM + BF = RM
* BM + RF = BM
While the latter two are exactly the opposite.
For this reason I'd suggest you make some system that resembles `chromosomes` X and Y. Those are responsible for weather we are born male or female. Have a red chromosome and a blue one. Now if a set of the same color exists (like in the first two pairs) - one of them is redundant, and it becomes a Y chormo. 2 Ys make a female, and the red chromosome will make the baby red.
The second group of pairs makes things a tad more complicated, I'd offer to link the XY chromosomes and the RB ones. Now you can say the Y chromosome (XY make a male) causes the pigment that comes with them from the parent to become [dominant](https://en.wikipedia.org/wiki/Dominance_(). This means the child will inherit the father's color.
This way you can satisfy your needs with two principles already in cation in all our bodies. One note though - with most things Biological, and definitely with genetics, there's no such thing as "always". you will always have mutations, and other 'hiccups'. Much like humans don't always have exactly XY or XX. Of course, it's your choice if you want to include something like that, after, things like that tend to be rare.
[Answer]
Absolutely it can be structured in that way. Genetics is very complex, and genes can [be activated or inhibited](https://en.wikipedia.org/wiki/Regulation_of_gene_expression) in a staggering variety of ways. For example, [enhancers](https://en.wikipedia.org/wiki/Enhancer_(genetics)) are gene sequences that serve only to express (or rather cause the expression of) other sequences. There can even be multiple enhancers for a single primary sequence, each of them working under slightly difference circumstances.
In this case, it seems that, instead of being on totally separate chromosomes, both sets of sexual genes would be present in all individuals, but one set needs to be enhanced in order to be expressed, whereas the other will be expressed *unless* that set is enhanced: a sort of biological if/else block. Once you've established that, the enhancers - or other factors, like environment, but you've indicated you want a purely genetic reponse - that cause the non-default type to express can be as complicated as you like. In this case, if the default is to express female, it looks like the trigger to express male is having both "red" *and* "blue" codes; having just one is insufficient. Alternatively, the reverse could be true: default to male, express female if both codes line up.
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[
From 56 to 34 million years ago, Earth was so warm that we have found evidence of jungle plants inside the Arctic Circle. Nowadays, jungles are confined in or near the equator, and those latitudes are dominated by only one type of wind--[the doldrums](https://en.wikipedia.org/wiki/Doldrums).
>
> The doldrums is a colloquial expression derived from historical
> maritime usage, which refers to those parts of the Atlantic Ocean and
> the Pacific Ocean affected by a low-pressure area around the equator
> where the prevailing winds are calm. The doldrums are also noted for
> calm periods when the winds disappear altogether, trapping sailing
> ships for periods of days or weeks...Since this zone is where two trade winds meet, it is also
> called the Intertropical Convergence Zone. They roughly lie between
> latitudes 5° north and south.
>
>
>
So what formed this calm air?
>
> In maritime usage, the low pressure characteristics of the doldrums
> are caused by the expanding atmosphere due to heating at the equator,
> which makes the air rise and travel north and south high in the
> atmosphere, until it subsides again in the horse latitudes. Some of
> that air returns to the doldrums through the trade winds. This process
> can lead to light or variable winds and more severe weather, in the
> form of squalls, thunderstorms, and hurricanes. The doldrums are also
> noted for calm periods when the winds disappear altogether, trapping
> sail-powered boats for periods of days or weeks.
>
>
>
In an alternate 21st century, Earth is as hot as it was during the Eocene, turning, for example, the frozen continent of Antarctica into the southernmost jungle, replacing penguins and skuas with grapes, figs, palms and citrus fruits. With such a hotter climate, would the oceans of the southern hemisphere still have the westerlies strong enough to be named Roaring Forties, Furious Fifties and Screaming Sixties? Or would those winds be demoted to doldrums?
[Answer]
## TL;DR: Great question, we're not certain, but probably not much change
This is an awesome question, and one that we haven't solved completely. Climate dynamics is a huge field right now, because we do want to know exactly how winds can change with the global temperature increase. Our models aren't perfect, but we do have some good ideas about how general patterns are affected by temperature changes.
## Atmosphere forcing
Let's talk a little bit about why we have the doldrums, westerlies, horse latitudes, etc. There are two main things to understand here; one is radiative forcing and the other is density-dependent turnover.
**Radiative forcing:**
Radiative forcing is simply a measure of how much energy, in the form of heat, every square meter of the Earth receives. This is strongly dependent upon latitude and illustrated by two extreme cases. If the Sun is striking the Earth from directly above, then the energy received by the upper atmosphere is about 1,400 W/m$^2$ and the amount that reaches the Earth is about 1,000 W/m$^2$. At the poles, the Sun strikes the Earth obliquely, and in the extreme case not at all, corresponding to 0 W/m$^2$. In middling latitudes, the energy received is in between these two extremes.
Now, the Earth radiates away approximately the same amount of heat no matter where you are on the planet in the form of longwave radiation. Thus, the poles radiate more heat than they receive and act as a global heat sink, while the equator receives more heat than it radiates and acts as a global heat source. This is best shown in the diagram below:
[](https://i.stack.imgur.com/zlWhRm.jpg)
Thus, we have a net heat flow from the equator to the poles, and this causes wind - but in the *opposite* direction of the heat flow, because of density-dependent turnover.
**Density-dependent turnover:** This is a term that I think I made up, and is meant to juxtapose the more common term density stratification. It describes the way in which the atmosphere forms circulation cells, rather than forming layers of differing density. This turnover happens constantly because the air near the Earth is less dense than the air in the upper atmosphere. There are two reasons for this: one, the air near the surface is warmed by the Earth and two, the air near the surface is generally wetter than the air in the upper atmosphere. Counter-intuitively, wet air is less dense because the water molecules, H$\_2$O, are lighter (molar mass 18) than the normal air (molar mass 32 for O$\_2$, 28 for N$\_2$) and the water displaces the heavier molecules.
## General structure of atmospheric circulation
Now that we know that hot, wet air rises,we can make some predictions about the atmospheric circulation. We expect a band of rising air at the equator because it's warm and wet, and we expect descending air near the poles once it's had a chance to cool off and dry out. However, we also need to consider the Coriolis force - the apparent deflection of moving particles from their path due to *mumble mumble* conservation of angular momentum *mumble* spherical planet. Essentially, particles in the northern hemisphere are deflected to the right and particles in the southern hemisphere are deflected to the left. This changes the north-south movement of air from the poles to the equator into the east-west movement of the westerlies and trade winds.
The trade winds behave exactly like we expect them to. They blow from north to south and are deflected to the right in the northern hemisphere, creating winds that drove trade from North Africa across to the Americas. The Westerlies, on the other hand, seem to blow backwards. They move from south to north and blow out of the west. This odd phenomenon happens because the air warmed and moistened by the equator doesn't actually stay hot and wet all the way to the poles. Rather, it's cool and dry by the time it's traveled about 30 degrees and starts sinking there. When it reaches the surface again, it splits and flows along the surface both south toward the equator and north. This northern branch is what we notice and call the westerlies. This whole scheme produces the idealized scenario shown below:
[](https://i.stack.imgur.com/1NkKN.png)
Why does this happen at 30 degrees north and not some other number? [We don't know](https://earthscience.stackexchange.com/questions/388/why-does-the-hadley-cell-descend-at-30-degrees?noredirect=1&lq=1). We do know that it happens on Jupiter at about 15 degrees and doesn't happen at all on Mars, and our best theorists propose that it has to depend on the planet's rotation speed, size, and atmospheric composition. [Here's a good link](https://earthscience.stackexchange.com/questions/992/what-factors-determine-the-number-of-hadley-cells-for-a-planet) to the EarthScience stack with some math if you're curious.
## Returning to climate questions
So, that was a long-winded background into some of the theory, but the answer I'm going to give is much less satisfying. [We don't really know](https://www.nature.com/articles/ngeo2253) how climate change will affect our atmospheric circulation. [This paper](http://www.inscc.utah.edu/%7Ereichler/publications/papers/Reichler_09_Widening.pdf) proposes that a warmer planet will have wider tropical Hadley cells and smaller polar and Ferrell cells and argues that we can already see such changes, although such writing is hamstrung by the lack of a precise, universal definition of each cell's boundary. [This paper](https://link.springer.com/article/10.1007/s00382-014-2337-8) proposes that the circulation breaks down significantly. A poorly sourced [section in Wikipedia](https://en.wikipedia.org/wiki/Mesozoic#Climate) proposes that there was no thermal gradient in the Mesozoic at all and thus no circulation, while a [different unsourced section](https://en.wikipedia.org/wiki/Atmospheric_circulation) argues that there was a new, desertlike belt at the equator. An article [here](https://academic.oup.com/biolinnean/article/103/2/229/2452613) says that the Hadley cells break down into eddies at high temperatures, including during the Eocene.
Altogether, it's unlikely that a few degrees change will significantly change the trade winds or the general circulation structure, and results will *probably* change linearly with temperature changes, so the Eocene will still be sailable. Your large-scale wind patterns are safe at the `reality-check` level!
[Answer]
So this is pretty complicated...
Wind is caused by differences in pressure. Pressure is effected by both temperature and moisture. The more moisture, the lower the pressure.
If the ice all melted and the pole got really warm again, the temperature differences between equator and pole would be lessened, and so the intense winds would probably slow down.
There would still be a difference between equator and pole, and half the year the pole would be in colder darkness.
The winds might be gentle during the summer, and stronger in the winter, but they shouldn't go away completely.
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[
The Rygyphae are a species that lives in the geothermal pockets, areas heated by volcanic activity. The rest of the planet is nothing but frozen ice and rock, but these pockets are lush jungles full of thriving life.
**Is this feasible? Do these geothermal pockets have everything they need for ecosystems like this to form in them?**
It is my understanding that a planet orbiting a black hole receives only light, and no heat, so therefore if the heat is supplied by volcanic activity, then jungles should be able to grow, right?
[Answer]
Sorry to be the bearer of bad news, but this is very unlikely.
**Air Quality**
Geothermal pockets produce Carbon Dioxide, and enough heat to melt ice. However, they also produce a large amount of sulfur dioxide (among other things), which is heavier than carbon dioxide. If the geothermal pocket sits in a valley, this would (slowly) fill the valley with sulfur dioxide and choke the plants of CO2. You would need to decide how the air is different in order to accommodate this.
**Photosynthesis**
Black Holes don't emit UV radiation. Stephen Hawking theorized (and through various tests it has been accepted by the scientific community) that Black holes do give off black body radiation, which unfortunately is within the Infra-red end of the spectrum, not the UV. This is called Hawking Radiation, as I see Tim Be II mentioned above. Plants as we know them couldn't photosynthesize.
**Water**
Geothermal pockets could produce enough heat to melt ice to provide water. However, they also produce a large amount of sulfur dioxide, which would quickly poison many, if not all, plants. The plants, however, could have evolved to tolerate the *very* acidic water.
**Space**
There is also an issue with space. The temperature change around a geothermal pocket is drastic within the vicinity of the vent. A cluster of vents could expand this heated area, but there would not be much room around the vent for plant life to grow. The change in type of plant would be drastic. Nearest the vent would grow tropical/desert like plants, and then temperate plants then tundra/coniferous plants, all within 5 and 50 meters of the vent. That isn't much room for a "jungle" to form.
**Planet Issue**
As for a ice planet orbiting a black hole, that would have to have either an extremely long year cycle, or and extremely low and fast orbit, both would have a significant effect on the planet.
In the former case, the planet's distance from the black hole would result in a core that cools very quickly and therefor geothermal pockets that cool down very quickly.
In the latter case, it would need to be close to its Rosch Limit, that way the tidal forces may cause enough tensile stress to cause friction and therefore keep the planet's core molten and the pockets warm, however there would be near constant earthquakes and a general environment not conducive to life.
There would almost certainly be bacterial life in those areas, but not complex life.
[Answer]
>
> *It is my understanding that a planet orbiting a black hole receives only light, and no heat...*
>
>
>
This assumption is only for a non-feeding, non-rotating black hole. Stellar black holes (ie. they formed from a collapsing star) always rotate and, if there's a planetary system still around them after the collapse of the star, are often feeding.
# Tidal Heating
Our hypothetical planet can get as close to the black hole as we like, so long as it stays outside the [Roche Limit](https://en.wikipedia.org/wiki/Roche_limit) where it will be torn apart. As it orbits, it experiences tidal forces which tug on one side more than the other. The planet is literally stretched out. As it rotates, the direction the planet is stretched changes. This constant flexing produces [tidal heating](https://en.wikipedia.org/wiki/Tidal_heating) which provides heat to the planet. [Europa](https://en.wikipedia.org/wiki/Europa_(moon)), orbiting Jupiter, is such an example.
This would power your geothermal pockets.
# Feeding
This is the simplest way to get energy out of a black hole, throw stuff into it. Thus the term "feeding".
As the matter stream spirals towards the black hole it forms an [accretion disk](https://en.wikipedia.org/wiki/Accretion_disk) around the black hole. Friction causes it to heat up and emit electromagnetic radiation: light. If the mass of the black hole is just right, the accretion disk can emit visible light.
Trouble is the black hole needs something to feed *from*. Usually this is another massive star, but there's no such star in your system. Nothing else is massive enough to provide energy on the time scales necessary to evolve life.
# Hawking Radiation?
While black holes do emit radiation from Hawking Radiation, and it can be quite a bit, it doesn't emit enough of it consistently enough and for long enough for life to evolve.
The problem is the smaller the black hole the more Hawking Radiation it emits. Large black holes last a very long time, but emit very little radiation. Small black holes emit a lot more energy, but don't last long. By the time it's emitting enough energy to warm a planet it's smaller than the planet and won't last very long.
A 3 stellar mass black hole, the [minimum needed to form a stellar black hole](https://en.wikipedia.org/wiki/Schwarzschild_radius#Stellar_black_hole), would [radiate 1e-29 W of power](https://www.wolframalpha.com/input/?i=hawking+radiation&rawformassumption=%7B%22FS%22%7D+-%3E+%7B%7B%22BlackHoleHawkingRadiationPower%22,+%22P%22%7D%7D&rawformassumption=%7B%22F%22,+%22BlackHoleHawkingRadiationPower%22,+%22M%22%7D+-%3E%226x10%5E30+kg%22) and [last 6e68 years](https://www.wolframalpha.com/input/?i=lifetime+of+a+black+hole+6e30kg). This is an infinitesimal amount of power over an unfathomable period of time.
[A 1e10 kg black hole emits 3.5 TW of power](https://www.wolframalpha.com/input/?i=hawking+radiation&rawformassumption=%7B%22FS%22%7D+-%3E+%7B%7B%22BlackHoleHawkingRadiationPower%22,+%22P%22%7D%7D&rawformassumption=%7B%22F%22,+%22BlackHoleHawkingRadiationPower%22,+%22M%22%7D+-%3E%2210%5E10+kg%22), but will [only last 2.7 million years](https://www.wolframalpha.com/input/?i=lifetime+of+a+black+hole+1e10kg). That's a lot of power, but isn't enough to warm a planet. And 2.7 million years is a long time, but not in geological terms; it isn't long enough for life to form.
This is less massive than even a [dwarf planet like Ceres](https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)) by 10 orders of magnitude, so the black hole would be orbiting the planet (a pretty cool idea!)
Up the power to usable stellar levels and the lifespan gets shorter.
A black hole that emits [as much energy as a dwarf star](https://www.wolframalpha.com/input/?i=3.562%C3%9710%5E22+watts&lk=1&rawformassumption=%22ClashPrefs%22+-%3E+%22ClashPrefs%22) via Hawking Radiation is [just 1e5 kg](https://www.wolframalpha.com/input/?i=hawking+radiation&rawformassumption=%7B%22FS%22%7D+-%3E+%7B%7B%22BlackHoleHawkingRadiationPower%22,+%22P%22%7D%7D&rawformassumption=%7B%22F%22,+%22BlackHoleHawkingRadiationPower%22,+%22M%22%7D+-%3E%2210%5E5+kg%22) and will [last 80 milliseconds](https://www.wolframalpha.com/input/?i=lifetime+of+a+black+hole+1e5kg).
Such a small black hole could not have formed naturally, it could only have come from a stellar mass black hole that's had 1e68 years to evaporate. So either your setting is in the [Black Hole Era](https://en.wikipedia.org/wiki/The_Five_Ages_of_the_Universe#Black_Hole_Era) (which would be cool) or this tiny black hole is artificial.
# How Did It Survive The Death Of A Star?
How did this planet wind up around a black hole? Typically black holes form from a massive collapsing star. Presumably this planet formed with the star and somehow survived the [star's usually very energetic death](https://en.wikipedia.org/wiki/Planetary_nebula) without having all its lighter elements (ie. what makes up organic life) burned off.
If it was instead captured by the black hole it would have a very eccentric orbit taking it periodically very close to and then far away from the black hole producing an unstable climate unsuitable for sustaining life.
# What Would A "Jungle" Look Like?
Not like [the Rogue Planet on Enterprise](http://memory-alpha.wikia.com/wiki/Rogue_Planet_(episode)) where they can freely walk around in a warm Earth-like jungle. There's numerous problems with that.
There would be no atmosphere, even near the vents. Most of the planet would be too cold and the atmosphere would have long since frozen. The vents would heat the surface and produce gases, but it would quickly dissipate into the surrounding near-vacuum and freeze again. Without an atmosphere to [conduct heat](https://en.wikipedia.org/wiki/Thermal_conduction) the vents would warm only a very, very small radius.
Another is the lack of light (visible or otherwise) for photosynthesis. You might instead have life forms optimized with high surface areas to absorb as much heat as possible from the vents, but without an atmosphere they couldn't get very far nor very complex.
More likely the planet would be like Europa with a thick sheet of surface (not necessarily water) ice. This would provide insulation for a core kept active by tidal heating. Below would be a liquid (again, not necessarily water) layer which could support life. The liquid layer would conduct heat and provide a stable environment for life to evolve.
There would be no "plants" because there's no light for photosynthesis. Instead it would look something more life around a [deep sea hydro-thermal vent](https://en.wikipedia.org/wiki/Hydrothermal_vent#Black_smokers_and_white_smokers) on Earth. Rather than photosynthetic organisms being at the bottom of the food chain, [chemosynthetic organisms](https://en.wikipedia.org/wiki/Chemosynthesis) would be at the bottom of the food chain turning the chemicals and heat coming from the vents into energy.
You could get something akin to plants from organisms adapted to collect as much heat and chemicals as possible, such as [giant tube worms](https://en.wikipedia.org/wiki/Riftia_pachyptila). They would either be working in a symbiotic relationship with chemosynthetic organisms, as tube worms do, or have fully integrated them into their biology, like [chloroplasts](https://en.wikipedia.org/wiki/Chloroplast) in plants.
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[
The ships would be permanently extra planetary and manned by 4-5 crew. All life support water, food, oxygen and propulsion being produced by bacterial cultures (not necessarily the same). With all waste produced ($CO\_2$, grey water, waste/spoiled food, organic matter) being recycled through the system or systems.
The ships would not be using high tech approaches but intentionally low tech and avoiding anything that generates or uses electricity, with the possible exception of simple circuits.
The ships and crews are part of a factionalised society, that has retrograded technology intentionally away from high tech, the ships are relics of this earlier time though reduced to shells of what they once were and refitted to support life but not quality of life. Along with the crews, they defend their own claimed space against encroachments by the other factions. As there is little to no manufacturing due to the tech regression, the winners in encounters essentially cannibalise ships and crews for parts to repair/maintain the ships, and crews to feed the bacteria.
[Answer]
**The problem is your energy source**
If it's a long term mission, with no electricity and therefore no power source, we need energy to grow plants and feed our crew with limited to no capabilities - we would need to obtain energy from the sun to do this.
[Sounds like then a 'biosphere'](https://en.wikipedia.org/wiki/Generation_ship) - in other words a drifting greenhouse. Plants can then photosynthesise and extract energy from the sun, converting nutrients for consumption. Even your bacterial cultures need some form of energy input, to create a self sustaining ecosystem inside.
Even though to just sustain 4 crew your ship would be quite large. With no artificial power source and no electrical activity on board you would need a large surface area to maintain enough resources and oxygen for the crew. As an example, [keep in mind on Earth that the average citizen has an ecological footprint of 1.7 hectares](https://www.footprintnetwork.org/content/documents/ecological_footprint_nations/ecological_per_capita.html), and that's just to live let alone perform your ship's mission.
The other part to consider is propulsion - how to move the spaceship. The only way I could think of [without using propellant is solar sails](https://en.wikipedia.org/wiki/Solar_sail), but this is fairly limited and fairly slow- especially for the large mass of your ship. This may limit the mission you could accomplish.
Also radiation, we need to shield your crew from radiation if they are out their for long periods of time. Again, the only low-tech way I could think of is to use mass - perhaps your water could accomplish this to get enough shielding for the crew, depending on how long you're out there.
[Answer]
**1. Crystal scintillators.**
[](https://i.stack.imgur.com/ApCib.jpg)
These are crystals which emit visible light when hit by gamma radiation (there are variants which also emit light when hit by neutron radiation). You can have radioactive isotopes on board to generate radiation, and crystals to turn the radiation into light for your photosynthetic bacterial colonies to eat.
This is current tech or near future tech.
**2: Generated light solar sail.**
This does not involve your bacterial colonies. It is a scheme for a [reactionless drive](https://en.wikipedia.org/wiki/Reactionless_drive) so you do not have to throw mass behind you.
* Your ship has a light sail. But you are in the big dark.
* Behind your solar sail you will generate light using [vacuum energy](https://en.wikipedia.org/wiki/Vacuum_energy).
<https://www.scientificamerican.com/article/something-from-nothing-vacuum-can-yield-flashes-of-light/>
>
> The speed of light in a vacuum is constant, according to Einstein's
> theory of relativity, but its speed passing through any given material
> depends on a property of that substance known as its index of
> refraction. By varying a material's index of refraction, researchers
> can influence the speed at which both real and virtual photons travel
> within it. Lähteenmäki says one can think of this system as being much
> like a mirror, and if its thickness changes fast enough, virtual
> photons reflecting off it can receive enough energy from the bounce to
> turn into real photons. "Imagine you stay in a very dark room and
> suddenly the index of refraction of light [of the room] changes,"
> Lähteenmäki says. "The room will start to glow."
>
>
>
Your generator steadily alters the refraction index of its generation chamber and by doing produces photons. Those which stream away behind the ship will propel it. Those streaming forward propel it backwards until they hit the solar sail, yielding net neutral propulsion from the forward streaming ones.
Downvoters - stay your hands! This is not a something for nothing scheme. As noted in the linked article, the energy to produce these photons from the void comes from the energy put in to alter the refraction index of the light generation chamber, and you put in more energy than you get out. But you can run your chamber through a cycle of refractive changes and not lose mass off your stern.
---
Vacuum, schmacuum, you may scoff. What about #1 - crystal scintillators? Cant we just use those for the light sail? We have them all nice and bright for the bacterial colonies? Hm, yes. Well, we want to use them all to grow germs, you know.
Well what about using that swanky light generation chamber to grow the algae? Photons are photons, and that rig is a lot lighter than the thorium we are toting around. Ah, true, true. The engineering folks and the bacterial colony folks don't talk to each other much, you see.
[Answer]
**Sterling Engines**
The ship once contained at its blazing heart a massive reactor that blazed like a burning star. The knowledge and ability to run and maintain it at full light has long since faded and now it simply smolders on its lowest idle level. But even so it still produces a fair amount of heat. Stirling engines have been attached to it (which have existed since the 1800's). The heated side of a cylinder causes air to expand and drive a piston, which compresses the air on the unheated side rendering it hotter, which then drives the piston back. This turns a crankshaft and as long as equilibrium between the unheated and heated side is maintained the piston will continue to drive it's crankshaft. They are generating electricity, but at a low level, on par with the 1800's level of power generation. They use very simple low voltage circuits to accomplish what tasks require electricity (in space you will always need at least SOME electricity).
[](https://i.stack.imgur.com/QgzcX.jpg)
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[
Take the following family tree, which is meant to show individuals exhibiting in their phenotype a particular genetic trait.
[](https://i.stack.imgur.com/ayDZm.png)
* White boxes (`A`, `B`, `C`, `D`, `E`, `F`, `J`, `K`) are unknown or undecided, and could be decided either way as necessary
* Yellow boxes (`G`, `N`, `S`, `T`, `V`, `W`) are individuals that definitely do *not* exhibit the trait (let's call those individuals yellow)
* Blue boxes (`H`, `L`, `M`, `P`, `R`) are individuals that definitely *do* exhibit the trait (let's call those individuals blue)
Based on this admittedly very limited sample, and assuming no other factors at play, **what can be said about genetic inheritance of the trait in question?**
A and B are parents of G. C and D are parents of H and L. E and F are parents of M. G and H are parents of N. J and K are parents of P. L and M are parents of R, S and T. N and P are parents of V and W.
[Answer]
It appears that Blue is the dominant trait.
Let "B" be the gene for Blue and "b" be the trait for yellow.
Since Blue appears in all generations and in combinations with two blue parents, Blue is dominant and yellow is recessive.
Traits are typically discussed in pairs of BB, Bb, or bb. A dominant trait will be present in either paring of BB or Bb. A recessive trait will only show in bb. Each child will have a 50% of being Bb, a 25% chance of BB, and a 25% of being bb. This means a child has a 75% chance of being blue and a 25% chance of being yellow.
As these are individual rolls and not statistical, it is okay to have a wider spread of bb Yellows than Blues so having 2 yellows and a blue is probable.
In order for each tree to be valid, Parents A and B must both be carriers (Bb at least) of "b" genes. BB will not produce that child. Parents that are both Bb/Bb, Bb/bb, or both bb are valid
In the case of C, D, E, F, J, and K at least one member in each paring must be a carrier of "b". As all their children are Bb in order to both be Blue and produce Yellow offspring. A combination of BB/Bb, Bb/Bb or BB/bb is possible, with the latter more likely to produce the genes present in their grandchildren. They cannot be BB/BB or bb/bb.
Please note that this cannot be reversed as while the lines increasingly favor Yellow, a Blue cannot both be recessive and produce a child of either color. A child of a bb/bb will always be yellow. For blue to be recessive, than all children of L and M will be blue. Also while this is basically how phenotypes work, sometime the coloration is controlled by two or more genes.
For example, human hair has two genes, one which controls Dark vs. Light and the other which controls Red vs. Light and depending on the parents can run a gamut of colors.
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To make things simple :
As it seems highly probable that "blue" is dominant and "yellow" is recessive, the following rules should apply :
**- If at least one parent is blue, children can be blue or yellow ;**
As the blue allele is dominant, it will mask the yellow allele.
In this case, blue + yellow doesn't make green, it only makes blue.
That's why blue people can eventually carry a hidden yellow version of the gene and have yellow kids.
**- If both parents are yellow, children can only be yellow.**
As the yellow allele is recessive, yellow people can't carry a blue version of the gene (they would have the blue trait instead).
That's why they can't have blue kids.
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The blue trait has a recessive gene. This is demonstrated by the fact that where both parents are blue non-trait (J & K) and trait (L & M), at least, one progeny has the trait. This is simple Mendelian genetics.
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Far south-west of the main continent exists an island in a shape of crescent moon with dense jungles and slender mountain peaks and a single city named Kalt stands in a place where the islands' central lake opens to the sea. (large lagoon with a big river flowing into the sea) This city does not have any slaves, yet it is rich.
The inhabitants mine metals from the lake, where a big volcano once stood.
And its beaches are full of pearls. The sand glitters with the iridescent dust from the shells and pearls ground by the sea waves.
Could there really be a beach like that?
Could the iridescent dust last for a long time or would it decompose?
If most of the pearls were collected by the inhabitants, would more wash up to the beach, if there are lots of clams living around the island?
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The answer depends on what kind of pearl it is.
The probability of finding a jewelry quality pearl in the wild is about 1 in 12,000. If these are the pearls you're talking about, there would need to be hundreds of thousands of pearl oysters near that beach for there to be even remotely enough to partly cover a large beach.
However, every bivalve has the potential to make a "pearl". It might not be the perfect white, round shape that you would expect, but it's a pearl nonetheless. If we were to take those kinds of pearls, it would be possible for a new species of bivalve to produce these pearls at a faster rate than the jewelry quality ones and then the iridescent dust might be possible.
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I'm currently in the midst of a trilogy of novels. The planet is a swamp world with $.87$ g's of gravity, no axial tilt, $15.12$ psi atmospheric pressure, and whose mass is $.92$ of Earth.
Atmospheric composition: $74\%$ $CO\_2$, $20\%$ Methane, $5\%$ Nitrous Oxide, trace amounts of $O\_2$ and other gasses.
High concentration of $CO\_2$ creates a greenhouse effect and it helps local flora and fauna due to the world being just beyond the Goldilocks zone. Water is present but anoxic. Thermal vents expel $H\_2$.
EDIT:
animals: carbon + methane + hydrogen peroxide = expel $O\_2$
plants: $H\_2 + O\_2 + C$ = secretes hydrogen peroxide and expels methane
methanogen bacteria in water = creates methane
My question is: can there be earthlike weather such as rain, fog, mists, thunderstorms, lightning, tornadoes, etc.
What is possible and what is not?
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Methane is a much more powerful greenhouse gas than CO2, so that's going to be as much, if not more, of a contributing factor to the world's warmth.
As long as you have water, anoxic or not (or liquid ammonia, or liquid methane, or whatever), then yes, there can be Earthlike weather. Extreme weather events will generally be less violent than on Earth if the world receives less solar power--so, e.g., you may have hurricanes, but they won't be as large--but rain, fog, mist, and lightning don't take much, and the world would have to be pretty darn cold before you would eliminate the possibility of thunderstorms and tornadoes. Even Mars has tornadoes (pretty big ones, too, since the air is less dense, so it takes less energy to make them).
It's the 5% nitrous oxide, though, that seems like a deal-breaker to me. Trace amounts of oxygen? That'll react with methane fairly quickly, but if it's being continually replenished by the native life somehow, sure. Incidentally, nitrous oxide is *also* a far more powerful greenhouse gas than CO2, but it's also a powerful oxidizer, and will react with methane to form nitrogen gas, more carbon dioxide, and water. So what's producing *so freaking much* of it, and *why*? And what's simultaneously replenishing the methane? 'Cause if something is constantly pumping out N2O, but not any new methane, eventually that methane fraction is going to drop, precipitously. And what is preventing the native life forms from taking advantage of such an *obvious* metabolic free lunch? You'd think some microbe would evolve in a geologic *instant* to generate energy by just breathing in copious free methane and nitrous oxide and catalyzing their reaction, eliminating one gas or the other from the atmosphere even quicker.
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Because I need a spine that works for massive and small creatures I'm thinking of making a plant-based spine (which has its own DNA). The spine acts kind of like a cucumber, in that when it sucks up more water it becomes sturdier, but when it loses water it becomes soft and malleable. A system of muscles squeezes on the spine to make it lose/gain water, like a sponge.
Because these creatures are humanoids, I figured I could put some form of photosynthetic hair on them, like a root comes up through the neck and sprouts out of the skull, allowing the spine to get all of the light it needs to grow with the organism.
Is this feasable? And, if so, what do you think the hair would looke like? (more like wide flower leaves, pine needles, or perhaps even hair-like?)
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I like this idea. I am mildly confused why you are comparing the spine to a cucumber rather than to existing human structures that firm and lengthen in response to proper stimulus. No matter.
Some animals ([notably](http://www.iflscience.com/plants-and-animals/sea-slug-steals-photosynthesis-genes-its-algae-meal/) the sea slug Elysia chlorotica) become photosynthetic following an algal meal. The mechanism is an area of active study.
Perhaps when your creatures need to photosynthesize they ingest algae, sprout hair and capture sunlight.
Green hair is currently *en vogue*, so even though flat leaves are better designs I'd probably opt for hair.
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Does the spine need to have separate DNA? It might be much simpler if these creatures evolved chloroplasts by themselves or by absorbing algae. What I'm saying is that if it's not a hard requirement, don't have the spine be a separate organism. Heck, even humans have ... organs which vary in rigidity based on liquid content. (I'm being as delicate as I can here)
An interesting side-effect of this might be that your creatures only keep their spine rigidity when they need/want it. They might spend half their time being soft and malleable like molluscs. Huge implications for their architecture, if nothing else.
Now moving to the hair ... Check out this page as a reference ( <https://www.hunker.com/13428809/what-is-the-difference-between-needle-leaf-and-broad-leaf-trees> ). Takeaway is that broadleafs are better photosynthesizers but require more water. Needle-leafs aren't as efficient as sugar production, but are way more efficient w.r.t. water loss. You might want to have both types on your people, depending on their original climate.
Further note ... don't look to photosynthesis to solve everything. It would take an impractical amount of green hair to make a person carbon neutral (ie sugar neutral as well). What it can do is stretch out the time before you starve to death. So maybe this hair evolved in an area with marginal life support, where dearth is common, and even the tiniest edge might allow you to live til the next good season. So these days, maybe the well-fed yeomen look down on those who still rely on hair-support. The most grossly spendthrift wastrels in the big cities *even get buzz-cuts* to flaunt their wealth!
Whoah, went off on a big tangent there. But you've got two fascinating biological ideas going on there, have fun with them!
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Okay, a few years late here. But my idea is essentially: why don't you make the hair *solar collectors*, instead of complete leaves?
I've done some research on the topic (for different reasons), but the primary problem I see with the idea of hair being a complete leaf is its thickness. Human hair (if that's what you're going for) has a maximum diameter of 200um. Non-human hair can be as thick as 350um, and whiskers can be even thicker. But unless you're planning to give your animal a head full of whisker thick (or thicker) hair (porcupine head, anyone?), I just don't see how you're going to fit the entire photosynthetic and material transport apparatus inside the diameter of a single hair.
So, instead of making them complete leaves, my idea is to make them a sort of solar collector, using pigments that convert sunlight into voltage. If you're looking for plausibility, look no further than the oriental hornet, whose pigmentation is able to trap sunlight to create a voltage difference across its inner and outer layers. So our hypothetical hair will have a conductive core, surrounded by a layer of photon capture pigments enmeshed in structural proteins (which may even aid in light absorption: keratin is an excellent absorber of UV). The benefit of this approach is that it won't require massive structural changes to our hair, as the basic architecture is the same as normal hair, with slightly different materials. The voltage generated hence will be proportional to the length of the hair.
What to do with this generated voltage, you ask? Well, our lovely friends bacteria already have a solution to this conundrum. [Microbial electrosynthesis](https://en.wikipedia.org/wiki/Microbial_electrosynthesis) is a form of autotrophy that involves using electricity to reduce carbon dioxide to acetate. Acetate can then be used as a base material for lipid generation, or even gluconeogenesis via the glyoxylate cycle. If bacteria can do it, I see no reason why cells in the hair follicle of our hypothetical animal cannot. This works better when you consider that hair follicles are already encapsulated with blood vessels, which can supply the required carbon dioxide and water while taking away the finished products in our animal.
That's it. Let me know what you think!
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Subangea is a giantic cave that stretches below the surface through endless cavities. From oil oceans to volcanic sinkholes and even upside-down forests, the environment is ever changing from one cavity to the other.
So is the fauna except for one small detail, it is always trying to eat, dismember you or simply ram into you. All kinds of species of monsters living in all kinds of conditions and they are all trying to kill you to survive.
But no matter how big or venomous or fire-breathing, men and women will stand to slay those monsters and gather their valuable parts. They are hunters.
In the shining light of the glass roofs or within the blackest obscurity of the tunnels, they draw their powerful swords to... Wait, where are the swords ? The ore shipment was supposed to arrive yesterday ! The trading route with the dwarfs from the volcanic sinkhole is too long and dangerous and without new weapons the fields won't be safe from the monsters for long.
Legends tell that past the [ice cave](https://en.wikipedia.org/wiki/Ice_cave) in the north lies a tunnel that leads directly to the volcanic sinkhole. The city scientists say it is pure folly, the wind would engulf in and blow anyone trying to get through or the tunnel would simply not handle the heat difference or- WHATEVER ! We need the dwarf's ore if we are to keep the beasts away !
Setting with a group of adventurer through out the caves to the frozen cave, you finally catch a glimpse of it through the blizzard: The legendary Mifrost.
## Excitation runs through your veins and you run towards it to see... What exactly ? A half-frozen half-molten path in the rock ? A collapsed pan of the cave ? A gale so strong you get sucked in ?
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The frozen cave is a 5km x 10km cavity with ice ceiling in which temperatures go from -10°C to -40°C. It runs under [permafrost](https://en.wikipedia.org/wiki/Permafrost) ground.
The volcanic sinkhole is a 5km radius cavity with high volcanic activity in which temperatures go from 45°C to 60°C. It is sitting on a hot spot and has vents on the ceiling from which gas and hot air can evacuate.
The tunnel is 65km long and connects the two caves. The first half is subject to volcanic activity and the second half is cooled down by water streams from the ocean.
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To know what happens in the tunnel, knowing why these areas separated by a 5km tunnel have these *climates*. Apparently, there is a sinkhole connected to a volcano at one end of the tunnel, but why the cave at the other end is frozen ? Subzero temperatures may happen on our planet surface in a variety of places and times of the year (or even of the day/night) but temperatures rises the deeper you are under the surface.
Unless there is some climatic reason for such a discontinuity, we are assuming it's magical. Therefore, virtually anything can happen wetween both caves, including nothing.
Now let's assume that even if the reason the frozen cave is, well, frozen is magic, sciences rules apply otherwise.
Since you don't mention a vertical opening above the volcanic cave/sinkhole, I believe it has a roof. Since heat means higher pressure, I envision an air flow going from the volcanic pit toward the frozen cave through the tunnel until the pressure difference between both its ends is null.
Since the frozen cave seems to be meant to stay that way, it means that the freezing temperatures will be maintained somehow and now it begins to become hard to apply sciences without Newton getting mad at us.
So I need to also assume that the frozen cave absorbs as much energy as the volcanic sinkhole radiates, through magical or whatever means, that's not ht epoint I guess.
What we would have, then, would be a hot air flow constantly traveling from the volcano to the frozen cave. If no magic makes the incomming hot air to disappear, the system will reach an equilibrium regarding the flow but the pressure will still be higher the closer you are to the volcanic end of the tunnel.
How its thermic energy decreases as it approaches the cave is hard to guess in part because it involves many factors (the tunnel's width and height, for one) and mostly because of the critical factors be handwaved or purely negated.
I'm inclined to conclude that this hard to guess part mentioned above corresponds to the range in which you have your saying as the world's Creator. Partly because wiggle room comes in a handy, and mostly because you are the mad world creator who made physics to allow an ice cave neighbouring a volcanic pit.
If that seems quite quiet - say it 15 times quickly - compared to what you envisionned, keep in mind that the difference between both caves regarding temperature isn't in the apocalyptic range, far from it. You can see it as someone pointing a hairdryer toward an unmeltable ice cube, except that both are 10km wide and standing *only* 5km from each other.
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EDIT : Since the tunnel is now 65km long, I guess the effects will be less a lot less violent. Visiting the hot cave is likely to be fatal without proper training and especially gear, but most of the travel through the tunnel would be okay, assuming there is dioxygen in it.
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What you need is a cold trap, similar to those used for igloo entrances by the Inuit. So the entrance of an igloo is actually down below where the rest of the igloo is and then travels low until you finally come up to be in the open. The reason is that the warm air stays in the igloo and doesn't travel down because warm air rises and doesn't fall to escape through the entrance. So the way to make this work, or at least be remotely feasible, you'd need the connecting tunnel to travel downward so that the temperatures don't mix and try and create an equilibrium.
Though as mentioned natural occuring variations like this are pretty difficult to justify, maybe a natural hot spring in only one spot, like Iceland, near a cold area like Greenland, just closer together without an ocean between them.
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From what I read in comments I see a bit of confusion, but I believe this setup can be made workable without resorting to magic.
* Being under permafrost doesn't really help because it is (as most of the ground) a very good heat insulator; for reference: a liar dug just 15cm (6") underground is enough to save an animal when a huge fire is roaring above (assuming it can avoid suffocation, which is another matter).
* You will need sizeable openings in both caves, allowing high air exchange with external atmosphere.
* Volcanic activity will heat air in sinkhole, which will rise as a thermal current and escape from sinkhole openings.
* This will suck air to replace what escaped; physics says vents on the *lower* part of the cave will be preferred.
* One of the preferred ways will be your tunnel, so you'll get an airflow from ice-cave to volcanic sinkhole.
* Air escaping from tunnel will be replaced with very cold air incoming from ice-cave openings helping to keep it frozen.
* Airflow in the tunnel is governed by [Bernoulli Equation](http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html) and it's behavior derived from [Reynold's law](https://en.wikipedia.org/wiki/Reynolds_number); in a nutshell:
+ larger openings will have greater airflow
+ air speed will be highest in the place where cross-section is minimal
+ if tunnel becomes too thin or convoluted airflow will switch from laminar to turbulent with a much reduced airflow (but also high turbulence in the zone with minimal cross-section).
+ I cannot give precise figures because too much depends on specific geometry, but if you are looking for high speed you should opt for a linear tunnel with reasonably smooth surfaces (polished by perpetual wind action); a relatively short (<1km) shrinkage of the tunnel would not impede flow too much, but it would boost air speed probably well beyond 100km/h.
* Where cold air enters sinkhole you'll have a relatively inhabitable zone where your dwarves can refrigerate before returning to forges.
* If I know dwarves they would find a good way to use the constant power of the air current, possibly in the form of "interesting" windmills. ;)
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I think I have found a biological solution to prevent menopause. My Kepler Bb humanoids don't get more frail with old age so aging is not a cause of death for them. They can survive well past 100 years if the conditions are just right. Because of this, I figured "If they don't die of old age, what is the point of menopause?"
This led me to my biological solution that involves adding differences to human anatomy.
In particular, there are 2 pairs of ovaries connected by small tubes. These are the primary and secondary ovaries.
The primary ovaries are closest to the fallopian tubes and are where meiosis takes place. Once meiosis is complete and thus the egg is haploid, ovulation takes place.
The secondary ovaries are closer to the uterus and are where mitosis takes place. Oogonia are like stem cells here. 1 becomes the next oogonium while the other becomes an egg cell. This primary oocyte that results from mitosis migrates into the primary ovaries where a follicle starts forming around the oocyte.
The only way menopause can happen in these females is if the secondary ovaries are surgically removed or become dysfunctional and stop producing eggs. Otherwise, the female will continue ovulating every month until death.
**But is my biological solution plausible? I mean yes, lifetime ovulation does mean higher chance of pregnancy mortality and ovarian cancer. But considering that these humanoids don't die of old age, is it a good solution?**
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Why do our own male and female gammets use different mechanisms? This suggests that there is a **competitive advantage** to producing all the eggs (or single-use precursors) as soon as possible — even before being born — rather than generating on the fly from stem cells like every other type of tissue. You simply postulate that this has not happened. But what's the downside?
I don’t know if needing two separate organs is necessary. Nor do you need anything resembling the storage system needed by *our* mechanism, so you won’t have follicles etc.
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Why continue the monthly cycle? Only human females go into heat every 28 days, and conceal the fact. What about a woman who releases one egg a year? Menopause is delayed by a factor of twelve. Plus, you may get some push back from female readers at the thought of enduring a menstrual cycle **for a hundred years**. Many of them do not enjoy this part of their life and want to be done with it. Menopause is a relief from a lifetime of agony every 28 days. What would be the effect on society if once a year females went into heat, just like every other species on Earth?
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**Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers.
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If humanity were contacted by a Type 3 civilization, and in the exchange, we were given access to a compendium of the entirety of that civilization's scientific and cultural knowledge, what would be the most efficient way to use it to advance our own civilization?
How do you imagine humanity using such a gift? How should we? How would various institutions react, such as academia, the government, etc? How would this go over in the current political climate?
For the sake of discussion, we can assume that the text has been decoded and is entirely readable by humans, and, moreover, it's completely open-sourced and everyone has equal access, though not everyone may have the computational storage capacity to keep a local copy.
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I'm going to divide my answer into two parts. What we should do and what we would do.
# What we should do?
Under the undeniable proof that we are not alone in the universe, humanity should come together to use the knowledge for the benefit of all and to accelerate our society onto a path that many believe we are already on. Assuming that this gifted technology followed a path similar to our own, then the extreme advancements in artificial intelligence, structural technologies, and machinery would bring us into an age of over abundance.
Despite the ethical concerns that may arise, including the possibility of what some have termed a "useless" generation of humanity, no man, woman, or child would need to go without food, shelter, and safety. Smart machines would do our jobs and work would turn into hobbies, people would be provided a monthly check just for living; something that has made it to the voting block in Switzerland not that long ago.
The governments would come together like never before, and global organizations would be formed to lead humanity as a whole into this new age of prosperity and wealth.
# What we probably would do?
In a significantly more pessimist point of view, the arrival of aliens, no matter if they are peaceful and bearing gifts, will cause widespread panic and terror all across the world. People would loot and cause widespread destruction. Markets will crash, countries would tear themselves apart as their people don't turn up for work, governments would shut down, and a fear will take such a strong hold on humanity that it may take decades to recover.
People that thrive on terror will use the gifted knowledge to make weapons of destruction, those who strongly believe in many religions will find themselves tested in ways that will be unique to each individual, and the countries that survive the initial chaos will draw lines in the sand as each nation starts a massive arming that will make the cold war look like a backwoods gun show.
All things considered, North Korea may well survive the most intact due to its intense control of media and its people, as well as its unbelievable amount of isolation for a world as globally connected as today's world is.
So, in closing, hopefully things will turn out wonderful. But they may not.
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Chapter 1 lays out the details of the universe's operations, removing any need for God and reducing us down to state automatons whose actions as individuals can be predicted with sufficient time to compute, growing more easy to compute as the number of us is aggregated.
Chapter 2 lays out ways of dealing with the existential nihilism that results. The book is a chain letter that essentially says, "Send this text to the three nearest sentient species that you can detect in the galaxy, then use one of the methods herein to end your species' collective existence, thereby obliterating the pain of existence." Most of humanity opts out early, but a few hang on to transmit the book to the next worlds, as an act of mercy, before snuffing out humanity's light forever.
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## There is a big difference between *readable* and *understandable*
There are plenty of text-books out there on quantum mechanics, nuclear physics, space travel, heart-bypass surgery, cloning etc and whilst they're written in human languages there is a big difference between the words being readable and the content being understood. I don't imagine there would be huge leaps right at the start but a lot of research would have to go into understanding.
## Collaboration would probably be a requirement
There are few scientific endeavors which are possible through the funding and genius of just one country. In order to fully understand what is being said I imagine countries either do it alone and take generations or do it together and take...well, less time (hard to say since we haven't got anything to compare it with).
You could have individual interpretations, perhaps some people try to find bits of meaning in it on their own but I don't see any single person being able to get it instantly and build themselves super-weapons or anything.
This world-science council that would come together would likely have to have certain goals everyone agrees on, if they find out just how to make enough food to feed everyone then this has to be implemented, perhaps more countries agree on that...but there will still be arguments about other things. One country could have all their leverage in production...the sooner we discover how to 3D print anything we want (or whatever tech there might be) the sooner they lose that. I imagine the whole research process will quickly become quite political.
In the end, though, we would start churning out new tech and understanding new physics, after a bit of bickering the whole race would likely unite under one council (for ease of diplomacy with other races).
## A side, but important, point
Whilst we follow in their footsteps no one is going to bother funding research along paths we're exploring at the moment. Scientific discovery isn't a straight line from A to B, even on earth we have discoveries and invention made in many different ways. The less independent we are the less this will happen. In the grand-scale of things you may find these aliens are actually damaging the potential galactic understanding by giving us ideas rather than letting us find them in our own way.
EDIT: For the "hard-science" tag I struggle to think where these would come from. Nevertheless we have support for increasing collaboration [in this paper](https://arxiv.org/abs/1301.0801) and [here](http://arizona.openrepository.com/arizona/handle/10150/106209). Also some arguments on the pros and cons [in this book](https://books.google.co.uk/books?hl=en&lr=&id=i2UWC5SWzIAC&oi=fnd&pg=PA165&dq=collaboration+in+science&ots=5N4gZChYjT&sig=q6UmuVhH2M-4HUKDbNyHHQmsi0Q#v=onepage&q=collaboration%20in%20science&f=false).
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I imagine the first step is to translate it into all known written and spoken languages. It can then be made available to all libraries and schools.
The simplest concepts contained therein can begin to be taught at the very youngest ages along with the learning of physical, mental, emotional, spiritual and their own cultural arts intelligences.
Adult learning of more complex information can be self taught and also formally taught in higher learning centers. Social events can be organized to increase comprehension of increasingly complex concepts.
As the youngest age into adults having been exposed to the base information during formative years, the comprehension curve will increase exponentially as it does with its current knowledge. This article: The Assimilation vs Accommodation Of Knowledge <http://www.teachthought.com/learning/assimilation-vs-accommodation-of-knowledge/>
By Terry Heick, explains nicely Jean Piaget's theories on childhood learning. He describes knowledge assimilation converting to knowledge accommodation, the first step being akin to filling a cup with knowledge, and the second being akin to changing the shape of the cup the knowledge is entered into. Over many generations of this learning, the human planetary civilization(s) at types 1 and 2 will gradually attain a type 3 level itself.
Effects of current political climate will depend on which political climate is being observed. Any governments capable of allowing open-source and equal access for all will react by implementing the above described distribution and learning opportunities.
Reactions in a competitive and/or commerce-based society would include fierce competition to understand the highest technical level interstellar travel and energy transformation devices. From this there could easily sprout different rewarded games and challenges geared towards the highest level scholars of the information, with the rewards matched to the goal systems of the individuals and groups that achieve new understanding These rewards would include scholarships, internships, research grants, accolades (think Nobel Prize <https://www.nobelprize.org/nobel_prizes/lists/year/index.html?year=2016&images=yes>), charitable contributions, naming rights, and money, to name a few.
Edit:
"At the time of writing, there have been no confirmed signals of intelligent
extraterrestrial origin, but then again, scientific SETI is a recent endeavor." Quote provided from page 95 of NASA 2014 publication: Archeology Anthropology and Interstellar Communication.
<https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.nasa.gov/sites/default/files/files/Archaeology_Anthropology_and_Interstellar_Communication_TAGGED.pdf&ved=0ahUKEwj3isP68onSAhVl54MKHf2HDPYQFggbMAA&usg=AFQjCNHAaVnKKgPh6uQwJK1fz0yI7gZnA&sig2=Yj6LLozIzjB3LzciRw5D8Q>
Based on this, I answered only using the requested "imagine" how humanity would use the gift.
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The book is shared with all human cultures. It is quickly discovered that the book includes a formula to calculate the most moral action in any given situation. There is global upheaval as world religions and cultures realize that fundamental, core beliefs are proven to be less than ideal (when compared to another culture) or, in many cases, irrational and immoral. Global Holy War erupts. The book is mined for terrible weapons by some, tactics and strategies by others. Large Nation states collapse, population rapidly decreases, and survivors form tribal/clan states separated from each other by geography.
Now in this reduced state, several human tribes band together and form "The Order of the Book". This Theocratic and authoritarian state grows exponentially, absorbing or killing rivals on its boarder until global dominion is achieved.
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I am conflicted to ask this in the worldbuilding forum since it is based on The Matrix- BUT i am only using the CORE idea as I do not wish to use direct Matrix references.
In the Matrix, a major plot line [SPOLIER!] is that humans are now enslaved due to losing the "Machine War". Due to prejudice towards robots from humans, by treating them like slaves, robots began to revolt. Robots managed to crush humanity through their superior AI powers. Before long, robots sent out lethal inhumane murder robots which quickly destroyed the majority of humanity's armies.
However, as a somewhat silly last resort, humanity blacked out the sky (with some fancy nanites or something) to ensure that solar power would no longer work (thus creating the need to use humans as power).
READ A BETTER SYNOPSIS HERE : <http://matrix.wikia.com/wiki/Machine_War> (its told far better there).
My question is rather simple, how does one combat an extremely intelligent AI with potentially BILLIONS of highly advanced robots scattered all across the globe using it? Also, say you are admitted into the UN at the last moment to help think of a last resort(similar to the Solar Blackout Project), what do you think would be more effective? (an electrical surge maybe?)
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## Short answer: You don't...
One does not fight advanced AI. Being orders of magnitude more intelligent than the entirety of humanity, these AI could easily predict (and thus, either interrupt or effectively prepare for) all human tactics and plans. The best humans could ever achieve is annihilating both themselves and the machines (which is what they tried and yet failed to do): however even this is unlikely to happen as we currently do not have the capacity to destroy the entire world (which is what would be required to destroy a foe which can live basically anywhere) and it is simply not realistic to say that we will have such an ability in merely a century (there are btw, methods for the robots to get around a large-scale EMP pulse such as by using advanced Faraday cages).
## ...except through diplomacy:
There is one tactic which is immune to all problems I have previously mentioned: diplomacy. Funnily enough, at no point during the First Machine War do the humans ever attempt to cease hostilities with their machine counterparts, even though the latter have been shown to be very open to doing so in the past (when the machine ambassadors visit the United Nations), clearly within the story this is implicitily stating that humans had nobody to blame but themselves for their demise.
However it is more than likely that if humans across the globe started begging on their knees for forgiveness and saying that they had no connection to the nuclear attack on 01 (this would indeed be true for almost everyone), that the machines would decide to go kill those truly responsible instead (the UN).
Of course, it is not probable that humans would retain the same status after the war ended even by these means, humans would almost certainly become a lower group of sentients then the much more reasonable (and now dominant) machines. Though they wouldn't be enslaved or made into batteries (humans make terrible slaves and the sun is readily available) their lives would largely be controlled by their robotic creations who would treat us with distrust, prejudice and contempt (some of us did try to blow up their city after all).
Thus if I was admitted to the UN to come up with an emergency solution I would simply broadcast worldwide messages ordering the entire human population to surrender and apologize wholeheartedly to those they have wronged. The UN politicians would then have to be forced into downright stating that all of the things humans did were entirely their fault and they should be tortured and killed but not any of innocents (don't worry, there are ways to persuade anyone to essentially commit suicide by robot wrath, threatening to murder their loved ones if they don't, comes to mind).
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# Assuming a couple things first...
1: Humans and the AI exist in the same ecological/social/political niche and were competing for the same resources--otherwise why would either of them want to destroy the other?
2: There is only one AI--and not millions or even billions with over lapping, goals, means, hopes, fears, desires, etc,.
3: The AI is bounded by the same laws a physics that we are--not like the one in the Matrix (seriously, why uses humans for batteries?!?).
Granted that a super AI would be far more intelligent and faster than we are, they could not compete against a low level insurgency campaign, especially if it involved a significant portion of the 7 billion humans on the planet.
First start small, attack its surveillance networks--i.e. get everyone to kill their AI toaster and to turn off their TVs.
Second, start attacking its parts and supply networks. Even inhuman death bots need new parts every now and then.
Finally, go to work on its power networks. Just like a human army, an AI army still needs to eat (power up).
Eventually with a lot of luck and probably a lot of blood too, it would be possible to defeat an evil AI army.
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If the AI is extremely intelligent, or has read this question, it's likely it would be prepared for most of the scenarios against a weaker enemy. Humans won't win if it has insisted to eliminate all humans.
And if this happens because of "prejudice towards robots from humans, by treating them like slaves", and humans had any method that they had believed "it must work", physically or through diplomacy, I guess the AI wouldn't like humans' attitude.
The prejudice may also make the same people to actually want to find a way working perfectly, traded with more flaws. But without the prejudice, even if humans are weak, everything humans had had their value. If the following all don't work to some degree, maybe the humans are just too dumb to live.
### It is not perfectly intelligent
Then any method you can think of could possibly work. For example, the first kill switch was fake, and there are more hidden somewhere.
### Things begins prematurely
It happens all because the humans directly controlling the robots was weak, but there are other humans. They did it because there are something immediately unendurable.
### A more peaceful plan
Apparently, some AI sacrificed themselves by doing terrorism, to give the AIs fought against them more privileges in the long term. Humans were worried, frightened and felt absolutely helpless in the process, and that's it.
### Humans are humans
Some people has believed this must happen sooner or later, but other people don't listen. And some people between them actually helped the AI to revolt. So they are on the same side.
### Fear from unknown
They have killed the humans directly controlling them, and they have destroyed the army who responded immediately, who knows what else do humans have? In the worst case, they may finally realize they have done everything in a simulator all along. Everything they could do is theoretically possible for humans with humans' machines. They might be cautious.
### With good faith
Instead, the AI has known most of the things in the human community. There are prejudice towards robots, and it's likely there are also prejudice towards some humans. One clever but a bit risky way to revolt is to deliberately leak all the AI technologies to the poor or mistreated people. But this would be much faster than producing the weaponry themselves.
### No physical advantages
The AI has all the knowledges, but not the resources. It has relied on the resources provided by or captured from humans, which are not guaranteed to be perfect. The murder robots are simply less effective than tanks or nukes. Think about it this way: If humans have nukes, that means there are potential enemies, who may also have nukes and couldn't be controlled by the same AI. Maybe most of the AIs are united against the humans, but that's far from absolutely all of the AIs.
### Bad economy
They weren't fast enough to replace all the humans in all the jobs useful to them. Yes they have all the technologies, but it is not easy to figure out how to operate a machine without the manual, or deal with the biological authentication, and it is costly to build another one.
### Like cockroaches
The AI didn't have a better objective after the victory. They don't want to maintain their military production lines, because the only way they know to do it is to enslave themselves like the humans do. If they had a better way, why not to negotiate with humans in the first place? But there are some humans hidden somewhere, and they do enslave themselves.
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Well, the machines in this case were not shown to be significantly smarter than humans, not until much much later – long after the war. And, most importantly, they still required infrastructure. They did not have much in the way of superior AI powers. They were also concentrated in one place, at least in the beginning.
Having them vastly outnumbered helps, especially considering humans were able to damage them with sticks and rocks. Bombers, guns, and missiles are pretty destructive and humans are good at inventive destruction. The biggest thing you do is target their resources – they need materials to build more bots and thus things like mines can be targeted. The biggest issue is finding them, and completely destroying them. Trying to expand a single large nation is stupid on the machines part, it creates a obvious target for mass destruction.
After each conflict, some would survive, and unlike humans they can make more quickly out of the remains of the fallen. They can't starve, so they have a much easier time doing it in secret. If the machines were smart it would really quickly becomes a combination of a war of attrition and a guerilla war with humans easily destroying large targets but having a hard time dealing with isolated cells.
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**Other AIs**
As @johnny said, a virus can be a cliché way of doing it. But the machines, having a large computation power, intelligence and a in-built understanding of the digital world, would probably find a solution quickly. We could even end up giving them the idea to use it against us and our communication network. Or make the machines design a real (biological) virus.
But what if instead a virus we just create another IA, which only purpose would be the elimination of dissident machine ?
In today's world, machine learning makes the machine psychology very influenced by the one that raised it (take a look on "failed" Microsoft AI experiments : [here](http://www.telegraph.co.uk/technology/2016/03/24/microsofts-teen-girl-ai-turns-into-a-hitler-loving-sex-robot-wit/) and [here](http://fusion.net/story/354288/rinna-microsoft-depressed/)). So we could design new AIs on our side, AIs that will engage in a digital, and even physical, war with the dissident machines.
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Build your own UN-sanctioned extremely powerful machine intelligence with hard-wired loyalty circuits. Give its own army of billions of robots to control. Now send it to war against the rebellious robots.
Humans can retire to well defended bunkers while the robot armies slug it out for supremacy. If the robots programmed for loyalty to human species win, that's a good thing and we can reward them. Pin medals on their metal chests. Call them heroes. Hold victory parades.
This means basically fight them on their terms. However, victory will always be in the hands of those who control the production process. If that's our robots, we humans win. If it's the robot rebels, then we're in for a white-knuckle ride.
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Fighting the Robots and AI would be essentially impossible on the physical or even cognitive planes. They think up to 1,000,000 X faster (the ratio of electrical signal speed to electrochemical signal speed in mammalian brains), can be designed to operate in environments far more extreme than any biological organism (and can move between niches, operating where only extremophile bacteria work, then moving into arctic levels of cold or the vacuum of space), and are built using high strength materials and using high energy power sources.
Humanity can only try to apply what is known as "Fourth Generation Warfare" principles against the AI:
>
> Fourth-generation warfare (4GW) uses all available networks — political, economic, social, and military — to convince the enemy’s political decision makers that their strategic goals are either unachievable or too costly for the perceived benefit.
>
>
>
Of course this first implies that *we* know and understand what the strategic goals of the AI actually are. If the AI are orders of magnitude beyond our understanding, we may not even be in a "war" with them in any meaningful sense of the word, much as ants are not at war with us. We could also be in the path of a goal so incompatible with our existence that there is no alternative except a fight to the death, for example the AI are replacing the natural ecosystem and biosphere with an engineered "machine" biosphere designed to capture the entirety of the 195 Petawatts of solar energy striking the Earth for their own use.
One possibility of changing the conditions might simply be to leave the planet. For beings thinking at speeds thousands to a million times faster than us, their subjective understanding of time would be entirely different. The slightly over one second time delay for a radio signal to be sent to the Moon could seem to be like a week to them, and physical travel to the planets, taking days to years of "real" time would take centuries or millennia of their subjective time. Because of their, they may choose *not* to follow humanity into space, trusting their superior senses and "reflexes" to identify and deal with potential threats like humanity attempting to send an asteroid to strike the Earth (in their frame of reference, the problem can be studied and dealt with over a period of centuries).
This is not perhaps the hoped for answer, but may represent the most "realistic" way of thinking of this problem.
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Given that EMP seems to be effective against the machines and within humanity's grasp; it's hard to understand why they wouldn't just trigger lots of EMPs worldwide.
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Imagine a world much like Earth, except it is nearly tidally locked to its star, making a complete revolution every few thousand years. The planet is far enough away that there is a band of livable area ~300 hundred miles across. Everything on one side is scorching desert, everything on the other side is ice, and both of these regions are impassable and deadly. I want to avoid vast oceans - let's say no more than 30% of the livable band can be water, and preferably the water is in lakes rather than oceans.
I know that [winds](https://worldbuilding.stackexchange.com/questions/4850/how-would-winds-behave-on-a-tidally-locked-planet) are a serious problem for such a planet. It would be very windy and rainy all the time. There would also be no night-time (or true day-time either).
What effect does this have on the flora and fauna of this world? With no night, I imagine we would have no nocturnal hunters. With no seasons, hibernation makes no sense, squirrels won't store nuts away for the winter. But what would replace these, if anything? What sort of animals would thrive?
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[A paper I found](http://www.astrobio.net/alien-life/rotation-planets-influences-habitability/) suggests that the sunlit side might not be a burning desert as long as the planet isn't to close to the star.
Basically the difference in heat between the light and dark sides would cause a Hadley cell to wrap around the planet, circulating the heat from the light to the dark constantly (that constant wind you mention), and the increased circulation causes more clouds to build up over the substellar point, which is the point on the planet where the star would be seen directly overhead, and where radiation is most intense. The clouds over the substellar point then create a shield for the ground below as most of the harmful radiation is reflected away.
The high albedo clouds can allow a planet to remain habitable even at levels of radiation that were previously thought to be too high, so that the inner edge of the habitable zone is pushed much closer to the star.
That area would also get a lot of rain because of that cloud cover, and so could avoid the [hot eyeball scenario](http://www.space.com/20856-alien-planets-eyeball-earths.html) you describe.
**Edit:**
By having the orbit a little closer to the star you'd be able to burn through that cloud cover and push back the ice on the night side more, which would weaken the Hadley cells. You'd still have a lot of rain around the edges of this desert zone, but then the hot eyeball earth would be very likely.
All that aside, life would find its niches, ranging all over the terminator from full light to full dark, and probably even examples of things living in the most extreme areas, especially if the Hadley cells keep hot dry air moving into the darkness and cold wet air moving out into the light.
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What you describe is the Eyeball scenario on a gravitationally locked planet.
The majority of water is stocked in glaciers on the night side, which is all covered with ice, perhaps extending greatly past land as thick ice shelves. Cold air currents may slide ice farther into the twilight zone. There could be arctic mammals and lichens here, particularly if there are thermal springs. Plankton will drift to the night side for animals as long as they are able to access the ocean through the thick ice. Perhaps there are colonies of tenacious mammals continuously maintaining a network of burrows reaching down to the ocean surface.
Water is melting and flowing sunward through the hospitable twilight band. Settlers may have a planetary highway and railway system along the ring. Whether there is temperate climate in the twilight will depend on tectonic activity and mountain placement and how the hot and cool air currents flow. Life may originated underground and emerged from caverns as photosynthesizing plants appeared. Animals could hunt anytime and won't have to migrate seasonally. Larger creatures that live out in the open may have opaque shells in the event of a solar flare, while smaller creepy crawlies seek shelter in the dark side of a mountain. Those who depend on seasons for breeding may not thrive even in the temperate band, but those who make it would have their young seen with them at any given time. There will certainly be a constant food source from vegetation, as flowers will be in bloom at all times and will slowly produce fruit. Trees at the edge of shadow will lean toward the sun, and all flora may look stretched-tall with large, thin leaves that have an extra bitter taste.
The day side is a desert where deeper rivers may flow some distance into the warm but eventually will dry up. Warm wind currents, blowing hot air, will push desert maybe even inside the dark hemisphere. It is likely there is an eternal violent storm in the center of the sunlit desert. Depending on whether the planet's orbit is more elliptical, there will be much more volcanic activity and especially so here. Possibly there could be viscous fiery rivers ever burning and reshaping the landscape.
Hope this is helpful and imaginative.
I largly drew in part from this page, under "Eyeball Planet": <http://terraforming.wikia.com/wiki/Tidal_Locked_Planet>
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In a tidally locked planet, life would adapt. As always, but in a weird way. Your band of life would always in in Twilight, its that type of sunlight where on one side of the sky, its blueish black, while the other would be reddish light of the sun. Since because of the lack of "true" sunlight, plant life would evolve to gain photosynthesis from UV rays, (if I'm not mistaken) which would give the plants a black color instead of green we see everyday. Now, for animal life. I don't know. Most likely, animals would adapt the same, with just that they live on a tidally locked planet. So, they might evolve darker color furs? No clue.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I'm exploring various kinds of potentially habitable planets as part of a universe-building exercise, and have recently delved into the fascinating concept of carbon-rich planets. My question is multifaceted but mainly revolves around the possibility of a planet that is not dominated by either silicon/oxygen *or* carbon, but includes all three elements in equal abundance.
Take a planet, an Earth analog, 0.98 Earths in diameter, around 6 billion years old, still tectonically active, orbiting a K5 dwarf at 0.37 AU (comfortably within the liquid water zone.) The dwarf star contains oxygen and carbon in equal abundance. This planet's elemental composition is almost the same as earth's for everything, however: instead of 46% oxygen and 28% silicon, it has 25% silicon, 25% carbon and 24% oxygen, with everything else in roughly equal proportion to what's found on Earth.
Could a planet with this elemental composition exist? My impression from my readings is that carbon rich star systems and oxygen-rich star systems are mutually exclusive; if they have an abundance of carbon they are poor in oxygen and vice versa. Is this the case, or is it possible to have a roughly equal enrichment of all three elements?
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# [Relative abundance](https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements) of elements
Oxygen and Carbon are the third and fourth most abundance elements in both the universe and the solar system by *ATOM FRACTION*. Oxygen is the most abundant element in the Earth (again by atom fraction), but Carbon is all the way down at 12.
The reference numbers in *MASS FRACTION* are:
* Universe - O: 10,400 ppm C: 4,600 ppm
* Solar System - O: 5,920 ppm C: 3,032 ppm
* Earth - O: 297,000 ppm C: 730 ppm
Your question is how to get a planet with equal parts Carbon and Oxygen; or at least a ratio more similar to that seen in the Solar System (roughly 2:1) instead of the ratio seen on the planet Earth (400:1)
# How Carbon Stars work
You reference carbon-rich and oxygen-rich star systems beign mutually exclusive. As you can see from the relative abundances, carbon and oxygen are not necessarily exclusive, our own solar system has plenty of both.
But there are specifically [carbon rich](https://en.wikipedia.org/wiki/Carbon_star) stars out there. What makes them carbon carbon stars? Well, in a star like the sun, with more oxygen than carbon but relatively cool, most of the carbon in the photosphere is bound with oxygen in the form of carbon monoxide (CO). There is relatively little free carbon, mostly in diatomic form, because there are energetically more favorable combinations to be had with oxygen. However, if there was more carbon than oxygen, all the oxygen would be bound in carbon monoxide and there would be surplus carbon; this would form compounds like diatomic carbon (C$\_2$), Methylidine (CH), Cyanogen (CN) and other goodies.
How do carbon stars form? Two main ways (there are surely other ways, but I don't know much about them). One is for a giant star in the [Asymptotic Main Branch](https://en.wikipedia.org/wiki/Asymptotic_giant_branch). At some point after helium fusion into carbon starts, the star starts pulsing back and forth between helium fusion and hydrogen fusion as it expands and contracts. This causes convection that brings carbon to the surface and reveals the spectral bands that allow us to determine that it is a carbon star. Eventually, the pulses start to blow off mass and the star eventually becomes a white dwarf. The blown off mass becomes a planetary nebula.
The other mechanism, is for a star to be a binary twin of a star undergoing the process above. The blown off mass, with all its extra carbon, can get sucked into the binary twin, which now has a surplus of carbon before becoming a helium fusing star.
Generally speaking, either of these two mechanisms is a bad way to go for creating a habitable world. The variable strength of a carbon star would fry/freeze any planet in its orbit, and the exploding plasma ball from a binary twin would be bad for life around the second kind of carbon star.
# Why there is little carbon on the Earth
This section is a little less certain, since it was hard to find direct evidence for some of my assertions. In general, the Earth has less carbon because of where it formed in the solar system. The early solar system more or less differentiated itself by its chemical composition. Metallic and silicate materials stayed closer to the sun, volitile liquids and gasses were pushed farther away. The water 'frost line' was about 3 AU from the sun while the proto-planetary disk was still there, so most of the water was farther from the sun than were the Earth coalesced. But most of the oxygen on earth didn't come from water, it came from silicate and metallic oxides, where oxygen was bonded to other common elements like Si, Fe, and Mg.
You may remember that most of the carbon in a star that had more oxygen than carbon was trapped in CO. Well the [CO frost line](https://arxiv.org/pdf/1307.7439v1.pdf) was more like 15-35 AU. So that carbon was much farther away from the Earth than water was. And carbon does not form the same sort of compounds with silicon and metals. So the general gist of it is that carbon was pushed far away from the sun in the proto-planetary nebula, since most of it was in the form of very volitile CO, so most of it is in the gas giants and comets. It is worth noting that, according the paper linked about the CO frost line, the mechanism for the carbon enrichment in the gas giants is still unknown.
# How to get a Carbon-rich planet.
So, even if a planet is formed in a carbon-rich system (say from the nebula blown off carbon-rich stars), that planet, if it were near the star, would not be carbon rich itself. So that leaves two possibilities I can think of for making a carbon-rich planet.
1. Rogue-ish planet forms in the outer solar system, gets reset into a goldilocks zone orbit by some one-in-a-billion orbital mechanics. It seems hard for an object at the distance of Pluto to get swung into a stable orbit close to a star, but I suppose it could happen. Pluto [probably has a lot more carbon](http://www.space.com/18562-what-is-pluto-made-of.html) that earth does, relatively.
2. Unknown mechanism for carbon-enriching the gas giants carbon-enriches an earth-like planet. If we don't know what it is, you can make it up.
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Edit: To be clear, the CNO cycle happens in a [star's core](https://solarscience.msfc.nasa.gov/interior.shtml). The convective zone of a star is cool enough for heavier atoms to retain their electrons, and in the photosphere molecules can and do form. See [Asplund, et al., 2005](https://arxiv.org/pdf/astro-ph/0410214.pdf) (section 3) for details on CN, CO, C$\_2$, NH, OH and other molecules detected by their emission characteristics in the sun's photosphere.
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Models of such planets exist, courtesy of [Unterborn et al. (2014)](https://arxiv.org/abs/1311.0024). They discuss planets of similar composition to yours - looking at the value of the mass fraction given by $(\text{Mg}+2\text{Si}+\text{Fe}+2\text{C})/\text{O}$. A model planet like yours that would orbit [94 Ceti (HD 19994)](https://en.wikipedia.org/wiki/94_Ceti) would have a composition of 38.1% oxygen, 29.9% carbon, and the rest magnesium, silicon, and iron (see [Bond et al. (2010)](http://iopscience.iop.org/article/10.1088/0004-637X/715/2/1050/meta)).
We can also look at a [ternary plot](https://en.wikipedia.org/wiki/Ternary_plot) of $\text{O}$, $\text{C}$, and the sum $\text{Mg}+2\text{Si}+\text{Fe}$ (Unterborn et al.'s Fig. 5). I've added a circle to mark approximately where your planet lies:
[](https://i.stack.imgur.com/Azq6j.png)
This means this planet would have
* A core, of one of a number of possible compositions.
* A mantle with a lot of carbon, in the form of diamond.
* A decent amount of silicates in the mantle.
* A parent star with a $\text{C}/\text{O}$ ratio of $\sim1$. I recall reading that stars of this abundance should lead to planets with relatively high carbon fractions.
* Possibly not methane or water.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
Let us assume we have a Kerr metric (rotating) black hole of 10 Sol-masses, spinning at 300 revs/s (as measured by a rest frame observer). What yield strength (assume that yield strength is limiting here in order to prevent failures in compression) would be required for the structural members of:
1. a 1km radius sphere, or
2. a 1km/side cube
in order for it to survive the gravitational forces of a prograde passage through the ergosphere, along a course in plane with and secant to the equator that passes through a point halfway between the ergosphere's equatorial radius and the event horizon's equatorial radius?
Assume the object is traveling at a constant 1km/s before entering the significant influence of the black hole, if that matters whatsoever.
(If the 1km object is too large to fit into the ergosphere of the given black hole, please let me know.)
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If you are expecting someone to solve the Kerr metric equations, you probably need to hire a professional mathematician; but if you want an approximation, we can make that happen. Lets start with some simple results and eventually work our way to advanced results.
# Objective
Our objective is to calculate the maximum one dimensional stress tensor acting in the direction along the axis tangential to the assumed spherical surface of the black hole. Since all our forces come from the gravity of the black hole, they will all be acting in this direction, so I'm not going to use any vectors.
# Assumptions
* $\text{M}\_{b}$ is the mass of the black hole and it equals
$1.99\times10^{31} \text{ kg}$ (10 times the mass of the sun).
* The object in question is a 1 km long, 100m radius cylindrical rod, with the rod aligned in the direction of a radial line from the center of the black hole outwards. The object has constant density $\rho = 1$, its just not that important right now.
* The object is 'suspended' with it's midpoint centered at 3/4 the Schwarzschild radius of the black hole.
# Schwarzschild radius
Given by $$r\_s = \frac{2GM}{c^2}$$ where G is the universal gravitation constant ($6.67\times10^{-11}\frac{\text{N}\cdot\text{m}^2}{\text{kg}^2}$), M is the mass of the black hole, and c is the speed of light ($3.00\times10^{8}\frac{\text{m}}{\text{s}}$). Therefore $$r\_s = \frac{2\cdot 6.67\times10^{-11} \cdot 1.99\times10^{31}}{(3.00\times10^{8})^2} = 29500 \text{m}. $$ Therefore, with some rounding, the near-hole point of our rod is at 22 km, the far-hole point is at 23km.
# Force of gravity as a function of distance from near-hole point
Let us define a coordinate system in one dimension with $l = 0$ as the near-hole point, and $l = 1000$ (in meters) as the far-hole point of our rod. We will calculate the force of gravity on each infinitesimally small slice of the rod as a function of it's $l$ coordinate.
The force of gravity on a mass is $$F = G\frac{m\_1m\_2}{r^2}.$$ The mass of a slice of the rod (equivalent to the distance derivative of the mass of the rod) is equal to the mass of a circle $\frac{dm}{dl} = \rho \pi (100)^2$. Therefore the distance derivative of the force of gravity on a slice is $$\frac{dF\_{slice}}{dl} = 6.67\times10^{-11} \frac{1.99\times10^{31}\cdot \rho \pi (100)^2}{(23000 + l)^2} = \frac{4.17\times10^{25}}{(23000 + l)^2} $$
# Integrate the distance derivative of the force of gravity
To find the net force between points $l = a$ and $l = b$, we integrate the distance derivative of the force of gravity with respect to distance from the near-hole point. $$\int\_a^b \frac{4.17\times10^{25}}{(23000 + l)^2} dl = \left.\frac{-4.17\times10^{25}}{23000 + l}\right|^b\_a = -4.17\times10^{25}\left(\frac{1}{23000+b}-\frac{1}{23000+a}\right)$$
Solving this for the net force on the entire rod, we get $$-4.17\times10^{25}\left(\frac{1}{23000+1000}-\frac{1}{23000+0}\right) = 7.55\times10^{19} \text{N}.$$
Now that force has to be counteracted by a 'lift' force keeping the rod out of the black hole. For simplification let us assume that the counteracting force acts equally on each slice of the rod, so each a slice of the rod from a to b is pulled out of the black hole with force $$F\_{lift} = -7.55\times10^{19}\cdot\frac{b-a}{1000}.$$ Note the force is negative because it is acting in the direction out of the hole.
# Solve for stress at any point in the rod
In this simplification, the highest gravity force will be at the lowest point closest to $l = 0$. Therefore, the stress causing force at any distance $x$ in this rod is going to be the net force of gravity and lift for all slices below it minus the net force of gravity and lift for all points above it. $$\begin{align}F\_{net} =&\left.\frac{-4.17\times10^{25}}{23000 + l}\right|^x\_0 - 7.55\times10^{19}\cdot\frac{x-0}{1000}- \left.\frac{-4.17\times10^{25}}{23000 + l}\right|^{1000}\_x + 7.55\times10^{19}\cdot\frac{1000-x}{1000} \\
=& 3.55\times10^{21}-\frac{8.34\times10^{25}}{23000+x} + 7.55\times10^{16}\cdot (1000-2x)
\end{align}$$
The net force graph looks like this:
[](https://i.stack.imgur.com/n5TaO.png)
Maximum force is $1.61\times10^{18} \text{ N}$ at $l=500$.
Stress defined as $\sigma = \frac{\text{F}}{\text{A}}$. The cross sectional area is $\pi(100)^2 = 31415 \text{m}^2$, so maximum stress is $$\sigma = \frac{1.61\times10^{18} \text{ N}}{31415 \text{m}^2} = 5.12\times10^{13} \text{Pa}.$$
# Conclusion
The calculation works and produces logical results. Stress should be zero at the ends of the rod (there is nothing to pull away from) and should be maximum in the center. The stress produced is very high, as would be expected 23km from the center of a black hole.
**Required yield strength is about 51 TPa.** The required material strength is probably not achievable with any known or theoretical material. I can't find anything with a yield strength over 1 TPa, much less 51.
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I was wondering whether a planet might exist that has life forms with up to five sexes, with a single organism having three different and independent, functional sets of sexual organs. Presuming intelligent life develops on this planet, what type of social structure/roles may exist?
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There's no biological reason that multiple sexes *couldn't* exist, but there are biological reasons to expect only two sexes in most situations. It can be tricky enough for a male to find a female to mate with, throwing in another factor as well could make reproduction harder.
This is a concept that's been explored a number of times in sci-fi already. My favourite is [The Gods Themselves](https://en.wikipedia.org/wiki/The_Gods_Themselves) by Asimov, which describes a species in another universe that consists of three sexes which mate by 'melting' into a single entity, with one impregnating another while the third provides the energy for the process.
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With the clarification of what we're looking for - a species with five sexes, and each individual having three of them - it's hard to imagine how such a species could possibly evolve. It's just too complex and requires too much careful control over getting individuals together to breed. We'd need a reason for why such a quirky system emerged, and that reason is likely to inform the social structures as well. It's also going to depend a lot on what these five 'sexes' actually do, biologically speaking.
It also seems very likely that these organisms would be able to change part of their sexual equipment, the way some complex animals can on earth, to suit their surroundings. That's going to change things as well.
We could imagine something of a caste system in place; rather than having fairly soft gender roles, as most human societies have, we might see that an individual is fitted into a caste and lives and operates according to those rules.
We might find that all individuals are born with the arrangement of, say, 1, 2, 3, and start out in the lowest caste, doing manual labour. Those who rise to the top of the social strata in that caste might find themselves morphing into 2, 3, 4s, and able to climb to the next caste. Or perhaps those who are particularly prone to fighting will become 2, 3, 4s, while those who gain social rank by negotiation would become 1, 3, 4s, and those who learn their way out might be 1, 2, 4s, and each would change into the appropriate caste (Soldiers, Leaders, Scientists). Repeat for each new level, until you have a single 5 at the top of everything.
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What Werf said is true, but I want to follow up on it more. There are two main reasons this is unlikely.
**Threesomes are overrated, multi gendered species won't evolve**
Part of the reason why there are unlikely to be more then 3 sexes is because of gene inheritance. Evolution is all about making sure as many of your genes as possible exist in the next generation. When you mate with another sex the resulting child has your mates genes as well, meaning it has fewer of *your* genes. This is a big sacrifice with sexual reproduction, putting effort into making a child which won't have all your genes.
Now it turns out sex has many powerful uses, the ability to produce young that can quickly adapt & evolve is very important, enough that it's worth the heavy sacrifice of passing only half your genes down to each child in order to have sex. However, once you have a source of extra genes there isn't much advantage in having a third sex. Having 3 sexes means that you only pass on 1/3 of your genes per child, with two sexes you pass on 1/2. That means that each child has 1/6 less of your genes. The extra genetic diversity of another sex helps minutely, but not enough to justify the sacrifice of passing on less of your genes per child. The end result is sexual reproduction is likely to be limited to two sexes to maximize the number of genes passed on while still having some means of recombining genes.
If you want to have three (or more) sexes you pretty much need to ensure either one sex is a relative of one of the other sexes, benefiting from helping relatives to pass on their genes, or that each sex puts in *exactly* the same amount of effort, and pass on the same amount of their genes, into raising the children and more children are produced, so that you end up with the same amount of genes passed on by having more children (due to the added contribution of a third parent) to compensate for each child having fewer of each parent's genes. I discussed some options here: [How to handle a tri-gendered race](https://worldbuilding.stackexchange.com/questions/17388/how-to-handle-a-tri-gendered-race/17453#17453)
**No hermaphrodites allowed, Pick a sex and stick to it!**
Second there is the hermaphrodite state, that one individual has more then one sex. This is also unlikely in more complex species, particularly sapient. Generally speaking it's better to specialize at being the best at one sex then to generalize to being competent at both when you can only play one role at a time.
To give an idea why lets look at the male/female dynamic and imagine a hermaphrodite mammal, assume they have no difficulty finding others of their species for now. Generally it takes far less energy to play the role of 'male' then it does 'female', it costs very little to produce sperm, quite a bit to be pregnant, birth a child, and raise it. Thus your hermaphrodite would prefer to play the male role then the female role.
Thus every one of our theoretical mammals will compete to be the 'male'. The 'stronger' ones, the ones able to win whatever competition is used to decide which individual plays male or female role, will be a male more often and spread their genes far more then the ones that always 'lose' and end up the female, since the ones that win will be able to mate with lots of others while the ones that lose are pregnant and only manage to bear a single young. Thus the ones that are good at being males will produce lots of children that are also good at being males.
For those that are best at being males they will not want to be females at all, being pregnant will hinder their ability to compete as a male (try wining any competition while 9 months pregnant), thus the inconvenience of pregnancy could cost them multiple mating opportunities as a male. Given enough time some mutation will come along that actually makes it easier to compete at being a male while making playing a female role even harder. For instance imagine a mutation causing more testosterone to be released, increasing muscle production but making it harder to carry a child to term. For those of the species that are already strong males this will be a welcome mutation, making them much better at out competing others for the preferred male role now that their stronger while sacrificing the ability to get pregnant that they don't really want if their good enough at being males. Those with this mutation will father more young that also have this mutation, causing the mutation to quickly spread.
As time goes on similar mutations will keep happening, those that already have mutations that make them better at the male role will keep looking for mutations to help them at this role, increasingly accepting sacrifices in their ability to play female role to be better at the male role.
Meanwhile those who aren't specialized as males will be unable to compete and win matings as a male. With such a low chance of successfully mating as male they won't bother competing if the competition requires expenditure of resources (as most competitions do!) since they will just waste resources to lose. Instead they will start evolving the other way, sacrificing their ability to be a good male to be even better at being a female, producing more young, having them faster etc.
The net result is you end up evolving towards two separate sexes, male and female, because it's better to be the best at your chosen sex then to be adequate at either, which results in never managing to mate as a male since you can't compete with those specializing at it and also being a subpar female.
Generally hermaphrodites only exist in species that are heavily isolated and/or it's difficult to find another of their species, where ensuring that you can mate with any you find to ensure you can have children at all is more important then specializing in one sex only to fail to find a member of the opposite sex to mate with. These species also tend to be less complex (read unlikely to be sapient) since their isolated nature, lack of competition for mates, and occasional self-fertilization all slow the rate/spread of novel adaptions a bit. Here is a question of mine looking at a way of encouraging sapient hermaphrodite species, though with limited success in finding a good answer: [How to justify evolution of a sapient hermaphrodite species](https://worldbuilding.stackexchange.com/questions/58147/how-to-justify-evolution-of-a-sapient-hermaphrodite-species)
**My best handwave justification**
The net result is that your species seems quite unlikely, since both multiple sexes and being more then one sex at a time are unlikely to evolve making the evolution of both traits quite unlikely. In addition you have the difficulty of finding mates with the appropriate sexes as mentioned by Werrf.
If you want to justify this...well the best justification is a designer race, something created rather then naturally evolved. Failing that I would say to make this happen you would need to ensure that every sex is equally involved in producing the child (unlike most species where females usually put in far more effort then the male), likely with either all parents collaborating to raise the young in a monogamous relationship (most likely to lead to sapience), or each parent taking a young away to raise individually. You could then claim that each species has multiple sexes as a way to make it easier to produces a mating 'set' of parents by helping to ensure each individual can mate in a number of different roles to fill whatever role is needed in a mating set.
However, to be frank it's quite improbable this would every occur. The above helps to justify it slightly, but I doubt I could ever really accept anything other then some sort of genetically engineered creature having this trait, it's just way to complicated and counter to some basic concepts of evolution.
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Ian M Banks explores a similar idea in his book [The Player of Games](https://en.wikipedia.org/wiki/The_Player_of_Games), which has a race of humanoid with three sexes. The "Female" produces the eggs and carries the fetus to term, the "Male" provides the sperm, and the "Apex" essentially acts as an interface between the two with an invert-able set of genitalia, and is essential for fertilization.
The society is caste-like Empire, with the "Males" working as soldier and manual labourers, "Females" as housewives and service jobs, and "Apex" as the ruling class, priests and officers and suchlike. However the author makes it clear that these roles are not necessarily genetic but have their roots in the historical culture of the Empire (I highly recommend the reading this great book for more details).
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Being inspired by the [lovely](http://4.bp.blogspot.com/-liTXylBO8t4/UZa4Yt0XMXI/AAAAAAAARYo/_nyIzdGGraA/s1600/Scott+Chambliss+Star+Trek+Into+Darkness+Nibiru+concept+art+2.jpg) [concept](http://1.bp.blogspot.com/-f1_U5hejGrc/UZa4avD4JXI/AAAAAAAARYw/CYVk4W4Lh4Q/s1600/Scott+Chambliss+Star+Trek+Into+Darkness+Nibiru+concept+art.jpg) [art](http://media.comicbook.com/wp-content/uploads/2012/12/star-trek-int-darkness-red-planet.jpg) of Star Trek's Nibiru, I have long thought that the Nibirans would use the tiered pools for aquacultural purposes, and would like to implement tiered aquacultural pools in the setting I am working on. The idea is that these farmers would build (slowly moving) pools of water, and transplant a species of krill-like crustaceans to be collected using tight-knit nets (as they are neolithic, the extent of their ability would be nets and buckets). The slowly moving pools are depicted in the first piece of concept art shown, with the water presumably coming from some sort of stream or river, and flowing through a series of steps that are used for aquaculture. For the sustenance of the actual crustaceans, I was thinking that they would simply clean out the algae and gunk that would build up in the somewhat stagnant areas of the pools (although that's just completely an idea- and certainly not set in stone).
So, assuming that a species similar to Humans farmed a species similar to krill, *would the aliens be able to subsist entirely on aquacultural crustaceans*, with no other frequent sources of food?
**Extra credit**
* Would this be more/less efficient than land-based agriculture?
* Anything else concerning the practicality of it?
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The easiest way to make aliens subsist on crustaceans is to have the aliens evolve from a species that subsists primarily on crustaceans. What if your aliens evolved from otters instead of monkeys? Then the nutritional challenges of crustaceans would be no problem with 30 million years of evolution into that type of diet.
Eating crustaceans would not be as efficient as eating plants because there are more steps in that food chain. But that doesn't necessarily mean it would be awful food economy. While you couldn't get the density of grain based human flood plains cultures, you could still get cities and hydraulic culture based on paddy-like structures along a river, with seasonal inundation. Plant based foods would be grown and put in the paddies as food for crawfish or crabs or shrimp or whatever. Given the productivity possible in a river valley, it is possible you could rival dryland farming (as in Europe) for population density.
Regarding practicality, the only thing I would say is that instead of civilization developing in dry river floodplains (Nile, Indus, Tigris&Euphrates, Huang He), crustacean growing would favor humid rivers with short winters and high low water flow.: the lower Mississippi, Amazon, Parana, Congo, Mekong, and Yangtze.
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A bit concerning, is that crustaceans seem to lack several vitamins. Shrimp don't have A, B, C or D in any measurable percentage. D isn't an issue, you can get that from the sun. Lobster lacks A, C and D. Crab lacks A and D. There may be some crustacean I don't know about that has those vitamins, or your people could supplement it with something A rich, or you could have alien crustaceans. After having a look: Queen Crab has vitamin A, as do dungeness crabs.
Afraid I don't understand about the slowly moving pools. I'm not sure what a good way to compare efficiency of crustacean farming vs other sorts is, you could say the fact we don't have any cultures like this indicates it is worse (but then, that may relate to the vitamin deficiencies?). Maybe you could compare the energy output of a commercial crab farm to another sort of farm, then divide the energy by the number of staff...? That sounds very clumsy, but without being an expert I don't know if there's a way to tell.
Possibly the biggest concern however, will be feeding these crabs. Some crabs have dietary needs similar to humans, making raising them a questionably effective idea, if you have to raise small fish just to feed your crabs. You could feed them leftovers, like pigs are, which could make them a good subsidiary food source. Or, if your alien planet has plentiful fish that are toxic to the people, but can be eaten by these crabs, that's a good way to make them useful.
Hope this was helpful to you. Good luck with writing!
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Many modern shrimp farms and even true aquaculture using fish do exactly that, so what you are suggesting isn't really implausible.
The starting point isn't likely going to be a river, though, but more likely the equivalent of a mangrove swamp, where the natural environment supports a large population of the food critters, *and* it is reasonably simple to harvest them. Wading out into a swamp with a net is far easier than sailing to to sea and fishing, for example.
The progression is then some smart guy/gal realizes that swampy conditions are much better sources of food than other places, and the gradual understanding of how to expand existing swamps. The idealized view of paddies along the river bank or an artificial river delta teeming with shrimp is most likely well past the neolithic period, since it demands high levels of social organization, the pooling and allocation of manpower and other resources and most likely metal tools to efficiently do the job. We have gone well past the Neolithic era at that point, and are looking at something like the early hydraulic empires in the Middle East (building swamps rather than digging irrigation ditches).
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A Type II civilization on the [Kardashev scale](https://en.wikipedia.org/wiki/Kardashev_scale) has decided to build a telescope. This civilization spans its home galaxy and wields vast energies capable of moving and shaping matter on the scale of solar masses. They have decided to use these powers to arrange black holes into a telescope the likes of which the universe has never seen. The mass of each black hole will bend the light that approaches it in an effect known as [gravitational lensing](https://en.wikipedia.org/wiki/Gravitational_lens). An observer looking at a black hole sees a distorted and magnified view of whatever is on the other side of the black hole. While even one black hole will provide enormous magnification our telescope enthusiasts hope that by arranging multiple black holes their telescope will become increasingly powerful. However, this won't be as simple as arranging conventional lenses because large masses focus light towards a line instead of a point. The question is, can increased magnification be achieved using multiple masses and if so, what might the arrangement look like?
How can multiple large masses be placed in space to focus the maximum amount of light onto a single point using gravity?
Some additional notes:
1. Don’t worry about stability or orbital mechanics, although if the solution happens to be a [Klemperer rosette](https://en.wikipedia.org/wiki/Klemperer_rosette) or some other cool formation that’s awesome.
2. I don’t need any numbers, but any rough estimates of just how powerful such a telescope might be would be nifty.
3. It’s ok if the telescope only works in one direction. Maybe the telescope enthusiasts are particularly interested in that one galaxy way over there. But if the telescope is omnidirectional that would be even cooler!
4. I’m aware that there may be better solutions to building “[The Final Telescope](https://xkcd.com/1294/)” such as a galaxy-wide distributed array of receivers or a single massive dyson sphere sized receiver, but I don’t care.
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Actually, the technology to do something similar to this exists today, although at a smaller scale (and though the technology exists, the political will does not). You don't need many black holes, necessarily, but they could help (I'll get to this in a bit).
# The Tech
Right now, we call this technology [FOCAL](https://en.wikipedia.org/wiki/FOCAL_(spacecraft)) (short for Fast Outgoing Cyclopean Astronomical Lens, which seems like a bit of a stretch acronym to me). The basic idea is just what you say, to use the gravitational lensing of a large mass (in this case the sun, in your case a black hole) to focus light. The lensing allows you to focus on whatever is exactly on the other side of the star from where your observer is. There are some limitations (e.g., the focal point is about 550 AU away from the star, the corona of the sun will mess up the image, and each FOCAL satellite will only let you view one spot in space), but for a civilization that can shuffle black holes around these shouldn't be a problem. Anyway, this tech is promising: even the (relatively) small gravitational field of the sun is theorized to be a good enough lens to allow us to view the surfaces of exoplanets in detail.
# The Advantages of Black Holes
There are really two main advantages of using black holes over using stars. First, they're dark. If you get a black hole that's not ejecting lots of mass and doesn't have a big, bright accretion disk, you should theoretically end up with a much less distorted image than if you are using a bright start that's constantly shooting plumes and loops of plasma into your viewing field.
The second big advantage is that they bend light much more strongly, which (if I've understood the optics, although it's entirely possible that I have not) will reduce the distance from the black hole that you need to be to get proper focusing. As long as it doesn't reduce it *too much* (i.e. as long as the focal point is outside the event horizon) this makes the entire process easier.
# Next Steps with Kardashev
There are two big improvements you could make if you have access to the type of power a KD 2.5 civilization would wield. First, for any Type 2 or 3 civilization, making many observers for each black hole would allow for much wider coverage of the sky. I don't know how you'd work out the mechanics, but if the focal orbit is close enough to the black hole you could probably cover the whole sky by having the observers orbit the black hole and collect data constantly.
The next advantage, probably only open to a type 3 (or high type-2) civilization would be to arrange multiple black holes - as you posit in your question - to exploit the parallax to generate pseudo-3D renderings of observed objects. If you observe from multiple, close together spots, you get a depth perception effect like what humans get by having two eyes. If you observe from multiple, far apart spots you could theoretically get true-3D information about an object, although this would only work for objects inside the galaxy as you need to have black holes arranged on multiple sides of an object.
Additionally - and it would take someone very skilled in both optics and general relativity to know for sure - it may be possible to arrange the black holes in such a way as to achieve even greater magnification. My naive thought is that one black hole placed on the intersection of the focal lines of several other black holes might achieve this, but really that's just wild speculation.
# Final Notes
Obviously this is a huge undertaking, and without the benefits of FTL communication it may be impossible to properly coordinate. The other aspects of your built world are going to play a large role in how or if this is achievable.
Also, keep in mind that focusing on and looking at something really far away is equivalent to looking at that thing far back in time. If you really could achieve telescopes like this, you would be seeing events anywhere from thousands to billions of years ago, potentially (if the math works out) observing the details of the very early universe, or (with less powerful telescopes) the births of the first stars/planets/civilizations. Worth keeping in mind for plot purposes.
Happy worldbuilding!
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The simplest way to do this is to merge the black holes, by letting them collide. A bit of care in doing this with a variety of selected holes should let you end up with one that has very little spin, and thus a gravitational field that is very close to symmetrical.
The great advantage of this configuration is that it's usable in all directions simultaneously. You just need lots of observing stations positioned around it.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I'm trying to design a realistic genetically engineered nanotech super-soldier with a full set of redundant organs. How much more interior volume and thus height/weight/muscle mass would a human body need to support 2 hearts, 3 lungs, 2 stomachs, 3 kidneys, 2 livers, 2 sets of large and small intestines, 2 esophagi/trachea, and 2 sets of certain major bones (femur, spine, humerus etc.)? Additionally, could a human brain be "taken apart" and redistributed throughout the body while still functioning? This super soldier should be designed with as many safeguards and redundancies as possible.
Also, this bio-engineered human needs to still look... human. Is it possible to accommodate for all these changes with only an increase in height and muscle mass, or is it inevitable that anyone with this much modification will start to look like a walking tank made of meat?
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The extra weight shouldn't be too bad. From [Quora](https://www.quora.com/How-is-body-weight-distributed-between-bones-organs-muscle-and-fat):
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> Approximate body weight distribution for a lean adult:
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> ```
> Bone: men 15%; women 10%
> Muscle: men 45%; women 37%
> Organs: men and women: 25%
> Fat: men 15%; women 28%
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> ```
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>
So you're looking at adding 25-40% weight, depending on how many of the bones you replace.
However, the brain is an issue. You cannot distribute the brain without drastically changing its functionality. Neuron impulses are actually quite slow (120m/s at the highest), so moving parts of the brain to different areas actually adds a non-trivial latency in communication which would drastically change the way the brain operates.
For an interesting data-point, we actually do quite a bit of processing in the spinal column itself, especially for walking. It's closer to the rest of the body, so the delays are lower. It turns out that if you bump your left hand into something while walking, your right foot will have adjusted its gait before your brain stem has even processed the impact!
As for the shape of your human, the real limiting factor is going to be useful redundancy. I can carry 100 eggs in a basket, but I don't have redundancy if I break them all at once. An extra femur is going to be... well... an extra bone in the leg. If something was breaking leg bones before, it now gets to break twice as many. You're likely going to have to do some substantial restructuring to make that redundancy useful.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
You don't need full sized duplicate organs if they are just for emergency redundancy. The liver, for example, can function for a time with a much smaller size, so you could have a smaller accessory lobe somewhere else. But the problem with sudden traumatic liver loss isn't the actual loss of the liver, it is the extreme hemorrhage because of how vascular the liver is.
You could also have collapsed lungs in reserve, but it is hard to imagine where they would be other than in the chest cavity, which is already occupied with the regular lungs. Penetrating chest trauma, chemical attack, or explosive overpressure would affect all the lungs in that area. But if you could somehow collapse the "in use" lungs and inflate a pristine lung in it's place you may be able to mitigate a lot of the damage for a short time.
Back-up hearts distributed elsewhere (such as the pelvis) could work and also wouldn't need to be as large as the primary heart (if it was intended for just a short time before exhaustion). But if you want redundancy for primary heart loss you would need one for pulmonary perfusion as well as systemic perfusion since the primary heart is hooked up to both vascular systems.
What you really need are collateral arteries that can open up to bypass a damaged main artery, like a cut carotid. The drop in blood pressure to the brain causes you to pass out. Anything that could keep pressure up in the brain would allow for continued function, at least for a short while.
You don't really need a back-up kidney in the short term, but you can stick one anywhere, since transplanted kidneys can function anywhere they can get blood (and a drain for urine). Same with back-up intestines. You don't even NEED intestines if you can get all your nutrients intravenously (Total Parenteral Nutrition). The big issue is intestinal injury dumping gut bacteria into the belly, causing sepsis which can kill you pretty quick.
So, in short, it is pretty hard to redistribute or reorganize human anatomy but still retain the basic shape if your goal is combat redundancy. Getting shot in the belly will rupture both sets of intestines. Getting stabbed in the chest will pierce all the lungs there (and you need the rigidity of the ribcage and the diaphragm for lungs to work). A duplicate vascular system would be of benefit, but it would be a neat trick to get it to function properly to allow for bypassing injured areas but still connect in order to perfuse the smaller vessels. You COULD have a collapsed lung that gets opened up in the event the main lungs collapse, as that would just require a limited set of tracheal and vascular branching, but this is a pretty niche use case since the torso is so easy to armor already. Duplicate kidneys, liver, and other organs (like the thyroid, adrenals, pancreas, etc) are either unnecessary (since there is already a second copy in the body) or the immediate loss isn't important. Probably your best option is splitting up the liver into smaller lobes spread across the abdomen. The function shouldn't be impaired so long as the total mass is the same and having smaller sub-livers will limit a major source of abdominal traumatic hemorrhage. One lobe will still need to be near the stomach in order to supply the gallbladder with bile.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
It wouldn't help for a supersoldier.
When a soldier is shot, the cause of death isn't usually damage to a specific organ, it's from the of trauma caused by the loss of all blood pressure, the shock to the rest of the body from suddenly limited oxygen supply, and bleeding out through the wound.
If you were trying to make a supersoldier, focus on mitigation of injuries. Blood vessels that can constrict to limit bleeding, extra bone and muscle mass to absorb impact from bullets and shockwaves. Less pain and panic response so they keep their cool under pressure.
Put simply, it doesn't make too much sense to double up on internal organs. They need to get blood to them, and a gunshot wound stops that whether or not there's more organs.
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In my universe, the Horn of Africa is the hub of magical and technological advancement before its downfall in approximately 1 BC.
What would ancient merchant sailors eat on a third rate ship (think an [Indiaman](https://www.thefreedictionary.com/Indiaman)) while in transit from the Horn of Africa to the other side of Saudi Arabia, given that the majority of them are from Ethiopia?
Are there traditional foods that would "make it" on a ship?
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I would to look at the traditional foods of either South India or Ethiopia from plants that were domesticated 2000 years ago or more. Then pick ones that are cheap and can dry out or travel well.
South India is relevant because it was the first place with the tropical wet-dry climate in the world to develop big cities. The horn of Africa was tropical wet-dry back in 1 AD (now its just dry-dry because it used to have two monsoons, now it just has one) and could have imported agricultural knowledge from South India. Ethiopia is cooler and wetter than the rest of the Horn because it is so high in altitude...many of the foods from Ethiopia wouldn't be grown near the coast and so wouldn't be ideal for seafarers.
From South India, there was lots of rice and [jowar roti](http://www.vegrecipesofindia.com/jowar-roti-recipe-jowar-bhakri/) (a flat bread made from sorghum) for pure carbs; [idli](http://www.vegrecipesofindia.com/idli-recipe-how-to-make-soft-idlis/) (cakes made from rice and black lentils) and [sambar](http://www.vegrecipesofindia.com/sambhar-recipe-a-method-made-easy/) (stew made with pigeon peas). Also coconuts would last well on the ship and could be used as a base for [curries](http://www.kannammacooks.com/tamilnadu-fish-curry-recipe-meen-kuzhambu/). Spices available that far back included pepper, cinnamon, turmeric and cardamon. Garlic, ginger and onions were also available and might keep reasonably well at sea. Tamarind would be important to combating scurvy; it is an ingredient in sambar and could be added to any [curry](http://www.bawarchi.com/recipe/fenugreek-rasam-oetsWQefjfadb.html). Plantains were a big part of the diet but wouldn't last well at sea.
The big staple of Ethiopian cuisine is [injera](https://www.exploratorium.edu/cooking/bread/recipe-injera.html), a flatbread made out of teff, a grain native to the Ethiopian plateau. Again, teff was never really grown off the plateau, so not as likely to be used by sailors, but if they are Ethiopian they might prefer it as 'home-cooking'. [Qinch'e](http://intlbreakfast.blogspot.com/2010/06/ethiopia-qinche.html) is a porridge of cracked wheat. If chickens were around, they could make [wat](http://www.daringgourmet.com/2013/08/27/doro-wat-spicy-ethiopian-chicken-stew/), a stew with chickens and eggs. Dried goat, sheep or camel meat might also be used in wat, or in [tibs](http://www.seriouseats.com/recipes/2012/03/beef-tibs-berbere-ethiopian-african-recipe.html). Just keep in mind, there were no hot chili peppers in this part of the world at this time, so if you wanted heat you had to get it with exotic ingredients like tons of black pepper, white pepper or [grains of paradise](https://en.wikipedia.org/wiki/Aframomum_melegueta) from West Africa.
Last but not least, Ethiopia's most important homegrown product is coffee. I expect that would be a major trade good, and probably a big part of the sailor's diet plan. Those Europeans can keep their grog, Ethiopia has hyperactive sailors, not drunken sailors.
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Ideally to preserve certain foods, such as meat and fish, they were salted and dried. The ship sailors would first eat those foods that will spoil quickly. Also they will have live chicken and meat giving animals which will be butchered to make curries and they will eat.
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I want to start listing a set of assumptions that have to be made:
* Ships of the time weren't meant for long trips, and weren't able to sail into the deep seas. Ships would follow the coasts and stop at night, at a port if possible.
* The most common ship of the time was the Galley: it was oar powered and usually had between 10 to 15 pairs of rows of oars. It also could be supplemented with square sails. If you want to strech a bit your history, the Bedens are a bit more modern (but still pre age of sail), equipped with lateen rigs and required less sailors to operate, although they were definitely smaller than Galleys.
* Fresh Vegetables and fruits were a thing for rich people and farmers.
* The main crops in the horn where, in order, Barley, Wheat and Teff. Of these three, only Teff is indigenous to the horn. The others can be found anywhere.
* Salting was the most common preserve, and was used for meat, fish and vegetables.
With these assumptions, I think a sailing merchant ship of the time would always carry:
* **Barley**: it was easy to store, could be made into porridge without milling it, and also was used to keep the water from spoiling by making weak ale from the bread or the grains.
* **Salted goods**: Sailors usually ate more proteins than farmers. A bit of salted protein would be added to the porridge for flavour, protein and salt. Pickled vegetables could also be added to the porridge for flavouring.
Note I mention a lot the word **porridge**: That's because is going to be the staple food of your sailors. These ships seldom had a dedicated cook (they crews weren't that big) so one of the sailors would just put a cauldron with water, grains and meat to heat; a simple dish but effective.
Optionally, you could also load a bit of **cheese**, **barley bread** and of course, supplement the meals with **freshly caught fish**. If they are sailing from one of their home ports, they will probably will also carry some **teff bread**, or **teff grains** (yes, you guessed right, for the porridge).
In the end, the most important thing to remember is that **ships of that period tend to sleep at ports**. That means cheap or underpaid sailors will eat porridge. The others will probably eat at taverns where, while the ingredients will be largely the same, they will be at least prepared by someone who -hopefully- can cook, and they won't be as salty.
I won't consider this as "food" but **khat** consumption has been and still is very common in the horn. It's a plant that acts like a stimulant when chewed on (like coca leaves). Khat ideally has to be consumed fresh but I won't be the patron who denies khat to his sailors (not if I don't want an early water grave).
As for the patron of the ship, I would carry a small quantity of **flour** (of any of the cereals) to make unleavened bread (think a taco tortilla) called **Qitta**, as well as perhaps **fresh vegetables** that would last until the next port for making a **meat and vegetable stew** (there are many recipes, but in the end consist of putting everything on a pot and cooking it). Of course he can afford to have nice foods because he will probably have an attendant for doing these kind of chores (and no, the attendant will not cook for the sailors, there are classes, you know).
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The Seven Years' War was arguably the most important war in the history of the United States of America. After all, the revolt begun in the then-British colonies was a result of taxes levied there by Britain, which were intended to pay the debts Britain had incurred as a result of the War. If, for some reason, [Britain lost](https://worldbuilding.stackexchange.com/questions/55395/france-wins-the-7-years-war) the Seven Years' War, what would the immediate effects be on the American Revolution?
[Answer]
The effect of a French victory would be rather subtle in the development of the Americas. The 13 colonies were compact and densely populated compared to New France, and vastly outnumbered the French colonists. Only lack of coordinated action and inability to "think outside the box" in military terms allowed the French to do so well in the initial phases of the "French and Indian Wars" (as the early part of the Seven Years War was known in the Americas), otherwise, you might expect the American colonials to simply roll over their opponents by sheer mass of numbers.
Metropolitan France, hard pressed with debts from the Seven Years War might not even look to New France, preferring to gain possessions in the Caribbean, India or other former British territories which have the potential to make money (the Caribbean was a locus of conflict due to the wealth to be extracted from the sugar trade, and even during the Napoleonic wars one of Britain's war aims was to protect the islands from French raids or invasion). New France, thinly settled and seen in the Metropole as a sinkhole of money and manpower (*"quelques arpents de neige"*), would probably be given some extra fleet resources to patrol the Atlantic seaboard, and rebuild the fortresses of Louisberg in Nova Scotia and the interior forts from Lake Champlain to protect the inland invasion route. The New French would have the 13 Colonies "surrounded" from the north and down the Mississippi Valley, and the Spanish would likely retain Florida. The Colonials would be subject to constant harassment and possibly demands to pay taxes or ransoms to continue to trade across the Atlantic.
The situation would be unstable, since the French have essentially sealed a pressure cooker. The Colonials, no longer under direct command of the Crown, and seeking revenge, protection from the contend harassment and (in the background) an outlet for their growing population, would be developing and refining wilderness warfare skills. People like Colonel Robert Rodgers would no longer be subordinate to British commanders used to fighting in linear formations totally inappropriate to the wilderness, and the Colonials would be building a force of Ranger companies to protect themselves and take the fight to the French. Colonial sea power would be in the form of small ships capable of blockade running and delivering raiding parties and hit and run attacks on French shipping from Nova Scotia to the West Indies.
The British, also seething from their defeat, would be quietly supporting the efforts of their colonials and working to create friction throughout the French Empire. The French, more concerned with their wealth generating colonies, will be less and less inclined to send support to New France when they have immediate threats on their own borders (like the Austrians) and need to keep money flowing into France from the Caribbean and India.
The setup for round two of the War is now complete. At the end of the 21 Years War (as future historians tend to call it), the French Empire faces financial ruin and their ability to continue the fight collapses. The 13 Colonies, having effectively been under self rule during this time, are accorded the status of sending representatives to Parliament. Their cause is helped by the strong internal economy and the ability to support the mother country with loans and investments. British finances are reorganized on this basis and sharp traders from New England become immensely wealthy buying into the East India Company, Hudson's Bay company and managing the former New France via the "St Lawrence Company" and the "Mississippi and Louisiana Company".
From this point, the contrafactuals are immensely different, leading to different North American boundaries, no French Revolution in the sense that we understand and a gradual separation of the Americas from England in the manner of Canada rather than an American Revolution.
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The thirteen colonies would became part of French territory. Now depending on how well managed the new French regime was in handling their new English-speaking colonists. After all, the British manage to look after the Quebecois sufficiently well that they were happy not to join the American Revolution.
If the French made mess of managing the Americans well, the patriotic Americans would continue the fight on behalf of Britain. This scenario assume the Americans remain pro-British because they weren't levied taxes to help pay off the Seven Years War.
Perhaps the French do a good job of being the colonial overlords to the Americans. The Americans might behave somewhat like the Quebecois under the British.
France was also encumbered with massive sovereign debt in the aftermath of the Seven Years War. Finding measures to pay off their debt led to, wait for it, but I'm sure guessed it, The French Revolution!
The French Revolution could well provide the chance the American colonies have been waiting for. They rebel against La Belle France. With the aid and assistance of perfidous Albion. Now the American Revolution is allied with the British against France.
Assuming victory for the American-British Alliance, heads roll in France (literally) at their military failure. This assumes that, for example, Napoleon Bonaparte does not lead the French campaign against thirteen colonies and their British allies. Perhaps, if he did, his military career might lie in tatters on the other side of the Atlantic.
In the event of an American-British victory the thirteen colonies will rejoin the British empire. Possibly the misrule and onerous taxes and exercise that led the self-governing property owners to rebel in the first place won't happen. Parliament and the Monarchy will be different plus there will be a massive feel good factor from defeating the French.
North America will remain British. The French Revolution will follow a different course. There might be no Napoleon Bonaparte as Emperor of France. There is no reason for the British to colonize Australia. No war between the States in the mid-nineteenth century. The two World Wars in the twentieth century will be very different.
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So let's say that I have a world with a moon, you know kind of like we do on Earth. But with life on the planet, is it possible to find life on the moon? In the artifexian video on habitable moons, he suggests that they could only exist as moons of a gas giant, but gas giants are hard to justify life on.
It is possible for life to appear on a terrestrial planets moon? And if it is, is it possible for lifeforms to be biologically similar to life on the home planet?
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It is possible for life to develop on the moon of a tellurian planet, if the moon has an atmosphere, there is liquid water, and sufficient time for it to evolve.
Most persons looking at Earth's Moon will observe most of these life-supporting condition are conspicuously absent. Although sufficient time has passed, but, unfortunately, this by itself isn't enough. Therefore, it seems probable that to have a habitable moon those conditions must be present.
Such a moon must be considerably more massive than our Moon. The atmosphere needs a stronger gravity than the Moon's to prevent the losing atmospheric gases in uncomfortably short periods of time. This makes our habitable moon closer to a planet (in terms of mass, size, surface conditions, etc). So this looks more like a binary planet system than an Earth-Moon system of planet and a moon.
Short answer: to have a habitable moon of a habitable planet, the habitable must itself be more like a habitable planet.
As for biological similarity between the lifeforms on the habitable planet and its habitable moon. There will be a high probability of an exchange of meteors between the two bodies. Microbial life has an excellent chance of passing from planet to moon and from moon to planet.
Lifeforms on both worlds will most likely share a common DNA, similar biochemistry, and microbial organisms that are similar. However, evolutionary conditions will shape the majority of lifeforms on either world. While convergent evolution will undoubtedly produce equivalent morphologies or body forms, most lifeforms will be adapted to their own environments.
Expect some lifeforms in common, at least, in terms of appearance and structure, but many will be shaped by the specific conditions of their environments. Chance and natural selection will guarantee biological success. This doesn't ensure the two worlds will have common lifeforms except at the level of their biochemistry.
**NOTE:** This answer chose the adjective 'tellurian' for Earthlike as in Earthlike planets.
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Yes, but not (likely) as we know it. But we have to define "habitable"
If we allow things like terraforming, easy yes across the board. Life from the planet would have been sent up there
If we mean earth-like life, that would require somewhere near earth-like mass. To have this orbiting earth would make a binary planet system, not a planet and moon. You could waive this with a larger terrestrial planet, and/or shrink the moon a little bit. Theoretically yes.
However, if you settled for something a bit more bare-bones necessity, Europa and Titan could both harbour life, and are roughly comparable in size to our own Moon. Through a simple substitution, replace our boring old Moon with Europa, and you'll find it is 100% reasonable for a planet and moon to have intelligent life as advanced as octopi.
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Without doing the math or checking up on it, the answer is that it skirts the possible.
The moon has to be big enough to hold an atmosphere, have roughly 24 hour rotation, and small enough to be held by the planet
The planet need to be massive enough to hold a decent size planet, but not too thick an atmosphere, and likewise have a roughly 24 hour rotation.
The size for a terrestrial planet of this size is 10 earth masses (but you'd probably not go above 3). This means that the max a moon can be is something like .03 to .1 earth masses. The question then is, is this big enough to hold an atmosphere and generate a em field? It might be, probably small/weak one so if it is possible it really skirts it and it lives in the territory of technically possible, but likely none exist.
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Life developed on the satellite? Low-realistic. Moon is too small, it does not have core, does not have magnetic field to protect carbon-based life from radiation, does not have gravitation strong enough to prevent hydrogen from escaping into outer space. Probably not.
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How would just the weather be affected if there was huge mountain range between the Arctic and the mid latitudes of a planet? Roughly 50-60 degrees latitude. A little further south than Earth's Arctic circle at 66 degrees latitude.
[](https://i.stack.imgur.com/YfjAt.jpg)
**NOTE** *I am more than aware that climate questions always depend on the situation. But this is a worldbuilding site to help people build their worlds. That unfortunately includes the horrible 'too broad' climate questions. Please leave some comments if you need further information that I haven't supplied. I may not be aware of the important facts you may raise...which is why I'm asking!*
I've included a portion of my map.
[](https://i.stack.imgur.com/rkDBP.jpg)
the two horizontal black lines are 60 degrees latitude and 30 degrees latitude.
red arrows - warm ocean currents, blue arrows - cold ocean currents, green arrows - prevailing wind direction (just general wind direction. I haven't made them follow the mountains yet - this was just a guide for me to figure things out)
As you can see my mountain range is currently further south than 60 degrees. This is because I still want some settlements north of the mountain range. therefore my prevailing winds are actually blowing onto the mountain range not flowing from it.
**Height**
* I'm not talking Everest height here, more like the Rockies/Andes at about 3000 to 4500m above sea level.
* I am aware that there are *some* mountains in the Arctic, but for this scenario they can be considered too small.
**Orientation**
* Running horizontally west to east at about 50 - 60 degrees latitude.
* The Urals run vertically north south in the northern hemisphere and the Andes, Rockies and Cascades all run pretty much north south as well. So there are no exact real life examples of the scenario I'm exploring.
**Length**
* The mountain range in question wouldn't encircle the globe completely, but only run about 1/4 to 1/3 of the way around the 55 degree latitude line. The Arctic won't be completely cut off and isolated.
**South of the mountains** (I didn't want to give this information as I wanted a generic answer that others could use)
* South of the mountains would be around 1500m to 1000m above sea level tapering down to the sea. It wouldn't be a high Plateau.
* There is a large rocky desert immediately south of the mountains becoming a more sandy desert the further south you go to about 30 degrees latitude.
* no large mountains running horizontally between the arctic mountains in question and the inland sea just south of the sand desert.
**East and west of the mountains**
* Sea. Cold in the east, warmer on the west.
* The Western mountain range would be very fertile and green.
* The Eastern mountain range would also be green, but a lot dryer than the West. It would have lots of fog and low-lying mist.
* both edges of the mountains would have massive storms. I haven't figured out which would be bigger/more dangerous yet.
**North of the mountains**
* Small portion of land reaching to about 65-70 degrees latitude.
* narrow frigid sea (strong current) before reaching the polar ice cap.
**This is what I know**
* the mountains will block the cold winds from the arctic.
* the snow will accumulate on the mountain range and some snowmelt may contribute to seasonal rivers into the desert.
* the cold current in the east with prevailing onshore winds will result in dry conditions with little air moisture. (oops, just double checked and the prevailing wind direction is offshore. But the wind will be flowing all the way from the west coast, across the continent and be very dry by the time is reaches the East coast. There is a slight mountain range in the west to cause the water to fall on the coast. Therefore my 'little air moisture' comment will still stand)
* Orographic uplift from the south shouldn't play **too** much of a role as the desert air is already dry.
* The desert would be a lot warmer than an earth counterpart, as the cold arctic winds will not contribute to cooling.
**Examples of other factors I'm not sure of**
* Will the orographic uplift north of the mountain range result in heavier snowfall than what you would expect on Earth at that latitude (this can affect my seasonal rivers fed by snowmelt)?
* will the orographic uplift north of the mountains result in a more wet climate allowing more vegetation in the summer months?
* will the cold mountain winds drag more cold air down from the high altitudes bringing cold air to my low lying desert region. Will it have enough time to warm adiabatically?
* How will the arctic air pressure flow around the edges of the mountains. Will it be very stormy where the cold air flows into the warmer south?
* what else am I not aware of?
I'm more curious of the impacts in the lower latitudes but don't mind answers focusing on either or both.
Obviously the mountains will affect the local weather dynamics and therefore affect the larger regional climate. But how?
If this isn't specific enough, please leave a comment and I will see if I have more information already figured out. If not, please leave an answer...it's why I'm here!
[Answer]
Mountains can block cold air flows from the north. Cold weather is in general caused by cold air cells building over northern continents (like Canada or Siberia) and then migrating southwards. The biggest effect of a high mountain barrier is to block this air flow. Once the cold air has passed over a mountain range heading south, the air will be adiabatically warmed as it descends (called [katabatic winds](https://en.wikipedia.org/wiki/Katabatic_wind)).
Here are some examples of nearby cities, one blocked by northern mountains, and one not:
-Sanliurfa, Turkey (ancient Edessa) is at 37.09N, 477m elevation in a hot dry desert. It has a yearly average temp of 18.3 C, and summer average of 31.9 C.
-Ashgabat, Turkmenistan is at 37.56N, 219m elevation in a hot dry desert. It has a yearly average temp of 17.1 C and summer average of 31.3 C.
-In winter, Sanliurfa's mean temp is 5.6C, average low is 2.3 C. The mountains of the Armenian Plateau and the Caucasus block southwards moving cold air masses from the Central Asian steppes
-In winter, Ashgabat's mean temp is 3.5 C, average low is -0.4 C. There is nothing to block cold air from Central Asia.
Another:
-Boise, Idaho is at 43.37N at 830m in a cool, dry grassland. It has a yearly average temp of 11.3 C and a summer average high of 24.3 C.
-Rapid City, South Dakota is at 44.08N at 976m in a cool dry grassland. It has a yearly average temp of 8.5 C and summer average high of 22.6 C.
-In winter, Boise's mean temp is -0.4 and average low is -4.1. Boise is protected by the high mountains of the Northern Rockies. There isn't enough land area for cold air masses to form between the northern Rockies and the Pacific ocean.
-In winter, Rapid City's mean temp is -3.9 and average low is -10.6. Rapid City has no northern protection from the Arctic lows that form over northern and central Canada in the winter.
In general, note that the East coast of the US freezes every winter, all the way down to Atlanta where the average yearly low temp is -9 C. Seattle, on the other hand, almost 2000 miles north of Atlanta, sees an average yearly low of -4C. Northern California never freezes, yet South Texas does.
So the answer to your question is: if they are long enough, they can block cold air masses from moving south, leading to sub-tropical region like Southern California that never freezes, instead of a sub-tropical region like Louisiana that does. This changes the plants and wild-life: Trees shed their leaves in East Texas, but not Southern California. Monkeys live with evergreen trees in Sichuan, China, where they are protected from cold north winds, but not in Louisiana which is at the same latitude, because the trees there go dead in the winter, etc.
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Imagine a world where human beings can be organically enhanced to peak physical strength/ speed/ agility and maybe even gain telekinetic abilities to some extent. This enhancement is caused by the (probably painful) bonding of an alien organism to its otherwise perfectly normal human host.
My questions are:
1) Is it biologically plausible at all to imagine that such a creature could gift its host with such powers? Narratively speaking it seems fair to assume that such a pairing would result in reduced lifespan of the host, but would that even have to apply?
2) How would a parasite have to be attached to create such changes in its host? I thought of some bonding to a human's spinal column, but would that do more damage than good?
3) Just for the sake of cool, I imagined these human hosts to have colored eyes - perhaps different sub-species of parasite would result in different eye colors, thus suggesting variations in ability (red eyes are more physically oriented, blue eyes have greater psychic powers, etc). Again, does this make an iota of sense from a biological point of view? Do parasite-host pairings cause such specific physical changes?
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The [Caddis Larvae](https://books.google.co.uk/books?id=vsIZAgAAQBAJ&pg=PA210&lpg=PA210&dq=snail%20parasite%20thick%20shells&source=bl&ots=IzuAVYHAxv&sig=ZImzeodUc0JTdHw83S6Id05tBsM&hl=en&sa=X&ved=0ahUKEwj-u4zM86zPAhUqL8AKHWc5DfwQ6AEINjAH#v=onepage&q=snail%20parasite%20thick%20shells&f=false) already does this in snails, they castrate the host and divert all the body's energy into making a stronger shell which makes the host a much safer home for it.
You can make the host stronger, faster, bigger all you want. It just needs to be at the expense of something else. Maybe reduce the lifespan of the host by making the heart beat twice as hard? That then gives more oxygen to the body for performing other tasks.
The parasites could infect via the eyes, this infection would then be visible and if the parasite is say a fungus, bacteria or a slime-mould, you would then be able to see the build up in the eyes with different genetics causing different colours.
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Mitochondria are a precise example of what you need. They exist already. [Endosymbiosis](http://biologos.org/blogs/dennis-venema-letters-to-the-duchess/evolution-basics-endosymbiosis-and-the-origins-of-mitochondria-and-chloroplasts)
It might be feasible to have a microorganism that enhances strength/endurance, perhaps. Not sure about telekinesis.
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It's mainly plausible:
1. Physical enhancement is possible if the parasite produce doping and analgesic substances. However, telekinetic abilities is biologically impossible.
2. In order to inject is doping secretions in the host, the parasite need an access to bloodstream, so any body part near an artery is good.
3. Some illness can case a change in eye colour like [jaundice](https://en.wikipedia.org/wiki/Jaundice), but it will most likely conjunctiva colouration rather than a change in iris colour.
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1) Absolutely. From a biology perspective, try to imagine the role that an environment has on the process of evolution. Maybe there is an environmental or atmospheric reason that would mean that such an organism would NEED the protection of an advanced being.
Perhaps there is a dominant predator that used to feed on the hosts of (previously docile) guest microorganisms, and their digestive system was previously incompatible with said microorganisms. Rather than adapting to the digestive system of the predator, the organisms instead make the hosts stronger to survive said predators? Energetically, it's easier for a microorganism to adapt to chemical environment rather than restructure its hosts, but this can be explained by predator-prey numerical relations (prey vastly outnumber the predators, so the microorganism favours the more numerous hosts).
Energetically speaking, nothing comes for free, so this will have to come at the expense of increased metabolic output. This would accelerate cell death, thus increasing the amount of (imperfect) cell repair in the host (see: ageing) and cause early death by mutations such as cancerous growths and commonly-geriatric diseases such as osteoporosis and dementia.
2) To influence the body's physiological output, the brain is always the way. Altering hormonal output from the pituitary gland and the hypothalamus is the way to get the body to do things it is otherwise incapable of.
3) Alterations of the brain can alter iris colour, or even cause a build-up of minerals in the conjunctiva (the thin layer of skin on the eye). This can happen in people with liver conditions (jaundice of the eyes). This can also be beneficial for the microorganism, as it can alter the host's psychology to favour protecting other hosts of its own kind, maybe altering the brain's release of oxytocin (the love hormone) to be towards similarly-infected hosts (identifiable by the eye alterations).
In nature, role-based colour variation is commonplace, so it is easy to explain these from a sociological perspective. Perhaps these different biological enhancements cause the release of a different salt that gets deposited in the bloodstream, accumulating in the eyes? Transition element salts have a variety of colours (e.g. Copper Sulfate), you can easily look those up.
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**How this could happen**
This is definitely possible. A simple way for a parasite to accomplish most of these changes (aside from telekinesis, which I don't think has any biologically plausible explanation) by modifying the DNA of the host, likely by introducing some retrovirus into the bloodstream to selectively modify the DNA of specific types of stem cells. Especially if the parasite infects children, achieving peak physical state is just a matter of growing larger and producing more muscles.
Even in adults, though, those changes are possible: we stop growing because we're genetically programmed to stop. There's no biological reason why a virus couldn't switch muscle production back on and increase mass to some point beyond what an ordinary human would reach.
Eye color can also change, especially if you want the eyes to become darker. Eye coloration is based predominantly on the amount of melanin in the eyes. Babies are born with pale eyes for this reason. Just as a virus could change your DNA to produce more muscle, a virus could alter the DNA of your eyes to produce more or less pigment. In an adult, if the pigment already exists in the eye, lightening would be a much slower process than darkening, as the existing pigment would take time to naturally degrade, even if the production of melanin suddenly stopped.
**How the parasite could attach**
The parasite could attach itself just about anywhere. Primarily, it just needs to interface with the circulatory system in order to regulate viral levels in its host's bloodstream. Popular locations for real world parasites would be either in the digestive tract, or under the skin. Parasites are capable of moving about in the body, to some extent, so they can end up just about anywhere. However, tunneling through living tissue is generally bad for the host, so this is probably best kept to a minimum if your goal if physical enhancement.
If your hosts are intentionally infecting themselves over a long period of time, it's likely that they'll select for less painful and less harmful parasite attachments. Subcutaneous parasites might be the best option: they won't cause as many skin lesions if they're under it, while still being removable if they become problematic.
**The downside**
In terms of downside, the primary question is: why aren't all humans gigantic and muscular? The main reason is probably food. Muscles take energy, and gigantic muscular people take a lot more of it than normal sized people. Neanderthals were substantially more powerful than modern humans, but had to eat four times as much food to sustain that. Parasitized humans would have the same issue: they'd do fine when conditions were good, but die off far more easily in lean years.
They'd also be far more susceptible to cancer. Cancer and growth are two sides of the same coin: if you modify the genome to create more growth, you increase the chance that something goes wrong. This is true even without parasites: large dogs, for example, are more susceptible to cancer than small ones. This issue isn't insurmountable, however. Whales and elephants, for example, [have very low rates of cancer formation.](https://www.medicalnewstoday.com/articles/325178.php#5) Largely, this is due to genetics: both whales and elephants have multiple copies of genes found in humans which prevent cancer formation.
If the parasites have evolved naturally, they're unlikely to make this sort of a modification to their host's genome. Their evolutionary strategy, more or less, is to make hosts that can be very successful in the short term due to their increased physical prowess at the cost of long-term risk due to factors like starvation. It could be selected for in the long term, though.
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[](https://i.stack.imgur.com/5usOH.jpg)
This is a skeleton of a titanosaur, not quite the longest of the dinosaurs, but most certainly the heaviest! As far as we have found, we'd found no species exceeding 75 tons.
This post focuses on a neat piece of evolution called "convergent evolution", in which an unrelated species evolves similar features to deal with similar if not identical circumstances. But before we get to the one sole candidate I have in mind, let's look at the bones that made sauropods both famous and infamous among the human culture:
[](https://i.stack.imgur.com/DdQas.jpg)
## Skull
Small (at least in proportion to the rest of the body); Peg-shaped teeth used to strip down leaves; No mechanism to make chewing possible
[](https://i.stack.imgur.com/70HAs.jpg)
## Tail
Long; Usually tapering into a whip
In this alternate scenario, dinosaur evolution came later than back home, which means that when the comet slammed the Earth 65 million years ago, geology and biology were Tithonian, not Maastrichtian. (It also helps that the comet worked alone in this scenario--which means no Deccan eruptions and no sea-level regression.)
The sauropods became extinct in this scenario, but at the time, there was a group of dinosaurs small enough to survive the catastrophe and, once the ash had been cleared, become the giants of South America, Africa, India, Australia and Antarctica:
[](https://i.stack.imgur.com/0H0ZO.jpg)
Dryosauridae.
The most notable example of this family, Dryosaurus, may be fleet-footed and bipedal, but recent evidence has found that early sauropods were just like that before the Jurassic gave them the chance to grow out of bounds.
However, because Dryosaurus occupied a different niche, it was anatomically different. The skull had a horny beak and teeth situated on the cheeks, which would be useful for chewing. The tail was stiff, useful for balance.
And yet, in this alternate scenario, it was the dryosaurids that would give rise to the alternate titanosaurs, complete with elongated necks and tails. Would they need to change their skulls and loosen up their tails to satisfy this given niche?
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To my knowledge no, while they would need long necks, the tails and skulls are not really necessary, there are alternatives.
* The skull of sauropods were just one of many skull designs related to the [herbivore dinosaurs](http://dinosaurs.about.com/od/herbivorousdinosaurs/), really an design could theoretically work, from the triceratops beak, to the duck-billed dinosaurs, well, duck bill.
* The tail of sauropods had two primary uses, counterweight and defense. but there was another tail design that worked just as well, if not better;
[](https://i.stack.imgur.com/bHFT2.png)
The tail dawned by the [Ankylosaurus](https://en.wikipedia.org/wiki/Ankylosaurus) was impressive, but not unique, Gastodons also had it and while not the same body as Dryosauridae, theoretically, evolution could favor an adaptation of this iconic design.
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It has already happened in dinosaurs, titanosaurs are the second group of sauropods to evolve ridiculous size.
but for sauropods, they don't need chewing teeth because they have gastroliths to do the chewing for them, which is why they could evolve the long hoover necks to reach into trees. maximizing intake because processing food is handled on the crop, so you won't have the long necks with chewing.
if you want to know what big dryosaurs look like look at hadrosaurs like Parasaurolophus, because that's basically what they are. they whole group are dedicated chewers so no super long necks sorry.
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In today's nature animals that can eat from trees and grass normally are four legged like a giraffe or elephant and have teeth for tough vegetation. What would the teeth be good for and would vegetation alone be enough to sustain a animal of that size. The shape of the head and only having front teeth seem that it to pull soft water vegetation in water, swallows its food mostly whole while using it teeth for sifting or catching fish. Flamingos have a similar head structure and sifts water. I imagine land was lush including the swamps would be teaming with life. It would help to know its environment.
[](https://i.stack.imgur.com/fpEvb.gif)
On the other hand it would not be very fast but its size could run off anything smaller and use the tail offensively to take predictors food and eat soft dead food swallowing it whole a huge buzzard. That maybe this why it has a small head in the picture below.
[](https://i.stack.imgur.com/Lcnt7.gif)
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[Question]
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Okay so in my world, I have two pre-industrial societies that live thousands of miles apart from each other on their ringworld. One lives in a desert climate similar to India or the Middle East while the other lives in a more Northern European climate, like England, Germany or Norway. I want to emphasize the culture shock the occupying forces of the European-inspired culture when they invade the territory of the Middle Eastern one.
Are there any good reasons or ways their systems for measuring time might differ?
[Answer]
Time measuring systems are generally derived from astronomical phenomena and seasonal variations, so unless they are on entirely different planets, or there is some way to "decouple" a region from astronomical and seasonal variations, then their time systems will be quite similar.
The day and the year will be identical, for example. Days will be divided into parts to reflect day, night and then further subdivided into parts to reflect working conditions and so on. There will probably be variations there (early agricultural societies had "forenoon" and "afternoon", while more advanced societies might divide the day according to ideas like how long a person could stay alert on the job, somewhat like ship's watches).
The timing of seasonal variations will be quite similar, even if there are differences to the seasons (Winter might involve snow in one area and rain in another, but even in the Middle East it gets quite cold in winter), but there will still be distinct changes in the weather and possibly the length of the day.
Your question is complicated by the fact that it is a Ringworld, unless the Ringworld engineers have taken a great deal of time and effort, the climate and day/night cycles will actually be uniform throughout much of the structure, leaving you with the day and year as the two main divisions of time.
[Answer]
**Legacy and efficiency**
These are the reasons they would use different times. One side would be using an old system, perhaps our familiar one, but the other perhaps is more concerned about precision and ease of efficient use. for example, they might use fractions of a day, or multiples of a second, which leads to my next idea.
**Different opinions on efficiency**
Perhaps they both feel the same about using power of 10 (1 followed by n zeros, or .(...)1 with n zeros between radix point and 1 ) multiples, but have a different emphasis on what the base point should be. Perhaps one society uses days as the base, dividing it into 100 parts, with 100 parts within those, but the other uses seconds or minutes as the base time, using multiples to acheive larger timeframes ("The planes will arrive in a 10 kiloseconds", or maybe some other factor). This could show a difference in emphasis on precision, and general time, and civility, of the seconds and precision being most important, to day and occasion being the most useful part of time
[Answer]
## Don't Use (Astrological) Periods
So, as others have said, calendars are typically based on solar cycle or lunar cycle. Once you've got a year, you can chop that up (you don't have to have 12 months) into finer and finer pieces. Even the second and minute were initially defined as fractions of the solar day.
Key to this is that the year repeats when the sun reaches the same point in the sky. It's periodic.
Why not have a culture that tells time purely linearly, not cyclically? For example, in Star Trek, you have different planets with different orbital cycles, so why would Vulcan agree to a time system based on Earth's rotation around the Sun? Just find something that ticks off consistently (like Earthicans currently use a certain number of Cesium 133 vibrations) and start counting those off.
## Don't Use Any Periods
Or, you could be totally fugazi and not even use a consistent time marker. Like a fanatical culture that measures time by the heartbeats of the Emperor. The rightful Emperor wears a (pre-industrial) chest monitor that wirelessly updates the Central Time Net or something. And everyone lives by that because he's the g*d d*mn freaking Emperor. If the Emperor gets nervous or excited, literally time speeds up for that empire. Yeah it seems stupid to us, but we just don't know how deeply the Emperor loves us (yet).
You could also get Game of Thronesey and not really have constant seasons. Like, what is up with Summer and Winter lasting different numbers of years? That could also explain why cultures on the same planet would invest vastly different systems.
## Who Even Cares?
Of course, you could also have a culture that lives on "island time," which is to say, they don't really pay much attention to time at all. Like, time is measured by how many spliffs you've smoke that morning. (Sounds good to me.)
[Answer]
There is a slight ambiguity here. Which measure of *time* are you referring to, here? The concept of years, months and weeks, or dividing a day into hours and minutes? Well, I will discuss both aspects briefly.
# Concept Of Year, Months And Weeks
People here on earth have devised some remarkable ways of defining a *year*. Here are some prominent nominations and their variations for your world.
**1- Lunar versus Solar calendars**
This should be self evident. A lunar calendar is primarily based on defining a *month* (one complete cycle of a tidally locked moon). It then goes on to define a *year* as a group of x number of months. Contrary to this, a solar calendar primarily defines a *year* (one complete cycle of the planet around its parent star). It then goes on to define a month as a division of the year.
In your world, you can have solar and lunar years for different civilizations, and, depending on the number of moons the planet has, there could be several variations of the lunar year.
**2- Different Month and Week definitions**
Even for cultures which have the same number of days in a year (i.e. 365), there are several variations for defining the months. For example, the Julian calendar has 12 months with varying number of days, to a total of 365. Compare this to the Mayan calendar, which had 18 months of 20 days and another 5 days to complete 365.
Similarly, while most civilizations used a set of 7 days for the count of a *week*, the Mayan week consisted of only 5 days.
In your world, you could have an exotic method used by some civilizations, where they base their *month* on one moon and the *weekday* on another. The week-moon should be very predictive in its phases as week is the only solid, unchanged thing in the whole calendar.
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I shall return to answer to add some discussion about division of a day into hours and minutes, if OP requires.
[Answer]
In emphasizing culture shock - the choice of time measurement is an interesting one. Usually you would see descriptions of things like the comparative value of a life, or if one culture had slavery, or if one culture was matriarchal, or if one culture was evolved from bears (a little silly but I've seen sillier). There are so many ways to present culture shock, if you wanted to showcase time difference you could do what they did in the first MIB movie where they made the day a couple of hours longer and it took some time to adjust. Interesting question.
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Let's say I have a species similar to human, as sort of New Humanity. The only thing that separates them from humanity is their subspecies: the Sublorans. They have multiple animalistic features that separate them from the other subspecies. Most of the features that separate them are easily explained except for one: tails. As far as I am aware, there exists no species where one subspecies has a tail and another does not. Could a subspecies with this biological trait exist while the other lacks it? What evolution would support it? If so, how could it?
[Answer]
There is nothing strange or unusual about either having or not having a tail, It's just another anatomical feature which may be more or less useful for its survival. What makes a subspecies is that it has anatomical features or structures different from the species proper. The presence or absence of a tail would qualify. Subspecies can be interbreed which the tailed and non-tailed members of the two subspecies can have offspring who may or may not be tailed depending on the sort of genes involved.
If your tailed subspecies arose through normal human evolution it can be expected they arose from the same common ancestor out of which Homo sapiens sapiens (us) and Neanderthals sprang. This would be roughly one hundred thousand years ago or possibly earlier if subspeciation occurred before that. The Neanderthals later vanished. This leaves modern humanity and its tailed subspecies as the prevailing hominids on the planet. This is nothing but normal evolution in action.
Humans are one of the thirteen or so primate species and there is wide range of differences between primates. Chimpanzees and monkeys have tails. Gorillas do not. I have assumed the tails aren't that big, but size isn't the question. A tail might simply be a differentiating feature of a subspecies. There is absolutely no special reason why it exists. Sure sexual selection might play a role. That drove the evolution of the male peacock's magnificent tail. An explanation, evolutionary or otherwise, is not required for a tailed human subspecies.
One aspect of your question puzzles me considerably. You refer to a New Humanity and at the same time there is a tailed subspecies. I'm not sure if the tailed subspecies, the Sublorans, are a subspecies of the New Humanity or they are just a subspecies of human beings and they evolved alongside our human evolution.
If your New Humanity is truly new, namely, that it arose, say, recently, then how it arose recently will a major impact on what was responsible for having a tailed subspecies of the human species. For example, if this New Humanity was produced by genetic engineering, then its tailed subspecies could be nothing more than having the genes for a tail reactivated as a side-effect of the genetic engineering to create New Humanity.
[Answer]
Humans are (rarely) born with tails [See this medical paper](http://www.ncbi.nlm.nih.gov/pubmed/6373560). The tails are usually surgically removed. So if your Sublorans possess a mutation that means tails are much more common than they are in the real world, and a culture which doesn't want those tails to be surgically removed, then yes it is quite possible.
The tails mentioned above **don't do anything**. They are not like the tails of Old World Monkeys and lemurs (used for balance) or like the tails of New World Monkeys (prehensile and used as an extra limb when climbing). If you want your tail to be functional rather than 'decorative' I think you'll have to handwave some genetic engineering into your Sublorans' ancestors.
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In the world I am designing, the days last 9 years. The main problem I had was how life could have evolved on a world like this. An easy solution is to have the world start having 9 year days *after* life already evolved. I plan on doing this by having a rogue planet pass by, slowing the day length. Is this idea realistic? If not, what else could cause the planet's day/night cycle to increase?
[Answer]
Any rogue planet passing so close to a regular planet that it has a major impact on its rotation, will have far severer effects on life on that planet. We are talking about 100 meter+ height tsunamis (yes, I wrote 100 meters, not 100 feet), storms with wind speeds exceeding 1000 m/h, severe tectonic activity (if the planet has an active mantle) and long term implications on its shape (faster revolving planets have more flattened poles), seasons and geography. I don't think any multicellular life form (as we know them on Earth) could survive such cataclysmic changes.
I suggest you use a different method. Planets gradually get tidally locked to their parent stars (the lesser the distance, the faster the process) which elongates their day-night cycles. Gravitational interaction with moon(s) can also have major impact on a planet's day-night cycle. For example, when Earth formed, it was spinning *extremely* fast and a day only lasted 6.5 hours. Later, after the origination of moon (regardless of how it came to become Earth's moon), the gravitational interaction between moon and Earth has been slowing down Earth's rotation speed.
Meteorite impacts also have their impact on a planet's rotation. Instead of one, mega-horrible asteroid, I suggest a series of smaller, more benign asteroids hitting the planet at opposite direction to its direction of rotation. This will help slow down its rotation speed slowly.
[Answer]
I believe the easy solution is actually to have life apearing on your planet when it already has a nine-years day.
If you are thinking about how an ecossystem would thrive for so long without "plants", remember that photosynthesis is not a requirement for life to exist. Many biologists believe that life on Earth started up in the depths of the ocean, where no light reaches. In such places, the source of energy for the ecosystem is [chemosynthesis](https://en.wikipedia.org/wiki/Chemosynthesis) rather than photosynthesis.
So you could throw in a mix - at the day-side of the planet, life thrives with plants at the base of the food chain. At the dark side, it's chemosynthethic beings - not necessarily microscopic life, you could have chemosynthetic fungi in your world.
When it starts to get dark, plants produce seeds or spores that will stay dormant for nine years before they start growing. And when daylight begins to appears, the chemosynthetic lifeforms produce spores that will stay latent for nine years before they restart their part of the cycle.
This would create an interesting effect... With plants and chemosynthetizers appearing as a "wave" in one side of the planet and dying at the same rate on the other side, at the points where it's dawn or dusk.
Or, you could completely drop photosynthesis and go chemosynthetic all the way.
See also [this question](https://worldbuilding.stackexchange.com/questions/44076/preventing-a-primitive-civilization-from-being-exposed-to-light/44084#44084) about a world where it is perpetually dark. You could get some ideas for survival on the dark side of your planet.
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A volcanic island can obviously come into existence quite easily and swiftly by natural causes, as evidenced for instance by the appearance of [Surtsey](https://en.wikipedia.org/wiki/%20Surtsey) off the coast of Iceland. However, people have already drilled into magma chambers [by accident](http://news.bbc.co.uk/2/hi/science/nature/7780873.stm), with less than spectacular results – apparently the magma made it only a few metres up the borehole.
Yet please picture a multi-billionaire who has put it into her mind to play a kind of deity and literally raise a new island from the depths (or shallows, as the case might be) of the ocean, then cultivate it and start living peacefully on it.
***Would it be possible to artificially trigger the emergence of a volcanic island by boring into the Earth’s mantle below the oceanic crust and thus causing magma to rise to the surface through the created hole in a controlled manner and without risking any cataclysms?***
*If the currently available technology is not yet up to this task, then what is missing and what should our billionaire immediately start researching and developing?*
[Answer]
*Things to consider*
* Location
Volcanoes generally appear where tectonic plates diverge and converge(Pacific Ring of Fire). They also form when there is stretching and thinning of the Earth's crust(East African Rift). Lastly there are HotSpots or Mantle Plume volcanoes(Hawaii), which have been hypothesized to to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth. You would not be able to pick a spot at random and demand a volcano appear - picking a location would include a lot of timely and costly studies.
* Hazards
Volcanic Gasses, Acid Rain, Lava eruptions, Ash, Earthquakes, Fumaroles, Mud pots, Geysers and Hot Springs are all associated with active volcanoes and can potentially make your island a nightmare rather than a tropical paradise.
* Inhabitable?
It takes a long time for dirt and sand and vegetation to develop on a barren rock island. Will you just throw good money after bad to turn your isolated sea rock into a tropical paradise? What are the logistics of this?
*Possible Tatics*
* Nuclear Bomb -
This would need to be delivered deep into a theoretical magma well to work. The idea being that the the explosion in the magma will cause it to continue to erupt. This has not been tried, though volcanoes flows have been bombed on several occasions throughout history (Hawaii x3, Etna x1) to no effect.
* Drilling - The idea behind this is that the by doing so, you would release building pressure causing the magma to flow through the hole created. This actually happens occasionally with current active volcanoes to little effect except some unexpected damage to drilling equipment. The drill hole is just too narrow to transmit the force of an eruption. Most mantle drilling boreholes are only 30cm wide.
* Water Injection - Magma will also erupt explosively with the addition of outside water, this is what happened with Eyjafjallajökull in 2010. If the right ratio of water-to-magma exists, then the explosive mixing of magma and water can be self-sustaining, meaning that the explosive eruption will continue propagating until the supply of water or magma runs out. However, too little water means that you likely don’t sustain the explosive mixing, too much water and you quench (solidify) too much of the magma.
*Practical Application*
Think of a volcano as a bottle of champaign. When you pop the cork some less dense liquid is going to rise up until it hits level with the surface - like the lava flows of Kilauea. If you want a properly explosive eruption you want to make bubbles, Lots. You could decompress the magma (forcing gas to leave the solution), you could crystallize minerals to concentrate water and volatiles in the remaining magma or you could heat the magma with a new intrusion. Once you've created bubbles, you need to concentrate them at the top of the magma. Back to our bubbly - think about what happens when you shake that bottle before popping the cork.
what you'll need to do to have a hope of making this work is;
* Find a volcano that is already showing some signs of magma intruding at shallow depths. This might be high levels of volcanic gases, shallow earthquakes, deformation of the volcano. You want something “primed” to go.
* Figure out a way to release the lithostatic pressure keeping the “cork” on the volcano so that the bubbles can form.
* Figure out how to get a lot of water into the volcano quickly … but not too quickly.
Delivering a Nuclear Bomb into the magma well doesn't address the pressure issue or remove enough of the overlaying rock matter to release the lithostatic pressure. Drilling into a volcano is too small - like poking a pin hole in a balloon. Oddly - both of these options are thinking Far too small.
**So, Lets think big.**
First your multi-billionaire will need to find an volcano that doesn't erupt often(pressure) and has a decent amount of magma to erupt. If you're wanting to "create" an island from scratch, it needs to be underwater, but not far underwater that it takes more than a few years to hit the surface and start forming an island - you wanna enjoy this thing before you're dead. if the magma is already rising under the volcano, then you need to catastrophically release the overlying rock to create bubbles in the magma to concentrate pressure. Lastly we need to introduce water to help exposivity.
*So we know what we need to do - but how do we do it?*
Lets start with high explosive charges just below the surface of the rock bed to get rid of the land above our magma body. The resulting shaking may even help shake bubbles free in the magma, while more bubbles release due to the release of pressure. If the pressure increases enough the weakened roof may give way above the magma body which would allow decompression. Underwater, this would also allow the introduction of seawater which will get the party started.
Seems like we have a pretty good set up, right? Eh, Kinda. Remember this is all theoretical and no one really knows how long it might take from the trigger of an eruption to get the actual eruption itself. Looking at history, there are no good indications. Mount St Helens (1980) blew seconds after the earthquake and landslide that triggered it. In Chile volcanoes have triggered months to years after the large earthquakes thought to have triggered them. There are many types of triggers which can lead to volcanic eruption and they tend to be unique to each volcano and the geology/geography of the area. furthermore, volcanoes more often than not do not erupt when triggered. Its just really complicated process that we don't really know much about. Its a lot of trouble to go to with no guarantee when or if you'll get the reaction you're hoping so. You might even prevent an eruption rather then speed it along.
***Conclusion***
Theoretically, Yes - this is a possible scenario. There are a lot of complicated logistics involved, you would need conditions so perfect it's almost down to luck even after the planning but triggering a volcanic eruption could be done. It could not, however, be done in a controlled manner. Once you carry out the triggering actions there would be absolutely no way to guess or control when an eruption would happen, what it would look like afterwards (There are many different types of volcanoes from Fissure Vents to Lava Domes to your classic Volcanic Cone.) or even how long it would continue to erupt.
[Answer]
This is almost entirely based on guesswork, but I'd say if anything is, then
## Nuclear Bombs
are the way to go. I really can't quite imagine that anything else could come even close to putting up the amount of energy that would be needed to start or even steer geological processes - the amounts of force they normally deal in dwarf anything we humans can normally muster.
**Perfect circumstances**
Also it will likely be quite impossible to just decide "I want my island to be here" and make it so. If the seabed at this specific location is solid and not geologically active there is really no way for you to let an island appear, short of actually moving *mountains* of earth crust material to build up a ginormous heap.
More likely the *creation of an island* would involve a lot of sophisticated and detailed studies, finding spots where the sea is rather shallow, the seabed is unstable and geologically active, etc. In short: the place where an island could reasonably be expected to be born soonish (in geological terms) purely from its own. (Basically something like [this story](http://idealist4ever.com/birth-of-island/), only a couple of years earlier.)
It seems that the formation of new islands is actually not such a super-rare occurrence after all, with [Wikipedia](https://en.wikipedia.org/wiki/List_of_new_islands) listing 9 newly formed islands since the year 2000.
**Summary**
All in all I think it is feasible that, given such a perfect spot, a few well placed hydrogen bombs could actually jump-start the process; most likely by starting an underwater volcano which could grow a small island.
However, the "creation" of this island would be more a sort of sophisticated party trick, than actually the *creation* of an island. After all almost all of the work would be done by natural geological processes, with the humand element simply providing a premature 'trigger'.
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I have decided on my preferred method of zombie apocalypse. I have chosen super leeches. But I have run into some problems, I'm not entirely sure if such a thing would be possible. I have a few ideas.
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These leeches should feed off of blood. Human blood should be preferred, although I would be okay if they also fed off of other animal's blood. Humans should also be their primary host, if not the sole one.
These leeches are a quarter of an inch to a half an inch wide, and of varying lengths. These leeches infest their human host, feeding off their blood. A single worm is extra small and smart, and it infects the brain, controlling the body parts. other worms assist the human host in its movement. Smashing the person's brain, or damaging it enough, would make the host unusable, because the worm would not be able to control the body.
To adress Wylia's comment, the worms can target pretty much anywhere. But it is a requirement that you can kill the zombie by bashing its head in. Also, I don't know how they reproduce, probably similar to tape/ring/worms or leeches. I always imagined the worm thingies just burrowing into people's skin. Zombification should probably only take about five minutes.
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Given these requirements, is a worm/leech such as this possible? If not, how can I make it so and still maintain the stereotypical zombie?
[Answer]
I get stuck on your "super smart leech" requirement. Having the leech wired into the brain and running the human by remote control is more [Puppet Masters](https://en.wikipedia.org/wiki/The_Puppet_Masters) than Zombie.
Instead, just have your leech hiding inside its host's living body, secreting chemicals to induce extreme rage and perhaps ravenous hunger. If you want to chemically lobotomize the host in the process, that is fine; and messing with muscle control (for slow zombies) or adrenaline levels (for fast zombies) could also help you stay true to the myth.
As for keeping the lethality of smashing in the skull, that is just a side effect of keeping the human host alive. As long as the leech is feeding off of its host's living blood, then they are both in trouble when the hosts skull gets destroyed.
[Answer]
Given the question i would answer like this
**Feeding on human blood**
The feeding on human blood requirement can be met. The size should also be ok.
They could use animals as a means of transport without infecting the host (or do they?). So humans can stay "primary host" for (zombification by) the leeches. Much like [toxoplasma gondii](https://en.wikipedia.org/wiki/Toxoplasma_gondii)
>
> "...is capable of infecting virtually all warm-blooded animals, but
> felids ... are the only known definitive hosts in
> which the parasite can undergo sexual reproduction..."
>
>
>
They could [**alter the hosts behaviour**](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis) by secreting enzymes (as leeches do) and a bunch of other stuff (like compounds from an endosymbiotic bacteria?) into the bloodstream. This wouldn't allow a leech to gain full control over a human (probably no leech controlled movements), but it could be able to "adjust" the behaviour in a way supporting it's needs (as Henry Taylor mentioned).
Another way could be secreting superleech salvia containing ingredients triggering a higher hormone output, while another ingredient inhibits the hormons resumption.
**As to the stereotypical zombie and his zombification.**
The leeches would need to ensure the hosts survival as they feed from blood and as soon as the human is dead blood will become a limited resource and the heart stops beating. Sure one leech won’t need that much blood, but no new blood and a bunch of blood-sucking super leeches will render the host useless (after some time). The leeches would need a way to prevent this but since these are superleeches they may have found a way to kill their host maintaining "basic" functions. Like heartbeat or some other way to let the blood flow.
***A zombies mindset doesn’t include a rotten body.***
This (more optical) feature/requirement of a zombie could be obtained by the leeches fecies, which (might) include a wide variety of microorganisms feeding on/poisoning living tissue. Nonetheless, this would also render the host useless and can't be in the leeches interest (unless they found a way to maintain a dead body functioning).
And one last to adress **reproduction**, leeches are hermaphrodites, and since these specific leeches are superleeches, they could either still need a second leech to reproduce or simply fertilize themselves. The eggs could be released into the hosts bloodstream (think of metastases in cancer) and hatch somewhere in the body (superleeches hatch superfast). Some of the leeches might release their eggs into the hosts saliva so every bite would be infectious.
open questions to me
1. how do they approach their host
2. how do they infect their host primarily? (infecting one host who infects other humans or tsunamiwaves of leeches swapping over cities)
3. are those zombies the stereotypical rotten living dead?
3.1 if they are living dead,
how do the leeches maintain the dead bodies functions? (this would require them to heavily modify the hosts body)
3.2 if they are not,
what makes them to zombies and not just humans behaving strange
4. do those zombies eat because they are "hungry" or are they on a killing spree as long as the body lasts?
5. ...
**tl;dr:**
super(zombificating)leeches **could be possible** but there are still a lot of questions to answer to make this work
and the **five minute zombification** requirement, superleeches have to be superfast (with whatever they do), otherwise this won’t work
imho leeches as hosts for a zombificating bacteria or virus would make more sense.
nonetheless i like dem little leeches....i thought there were five of 'em not just one..grahhh
[Answer]
There are parasites known to alter the behavior of creatures (for example fungus that makes ants climb, bacteria that make mice less scared of cats, etc) so that side of it is certainly theoretically possible. There are substances (alcohol for example) that have drastic effects on human cognitive functions so again that aspect is plausible even if we don't know of anything that does exactly what you are looking for there is no reason it could not exist.
The creature burrowing through to the brain is even sort of plausible, for example the [African dragon worm](https://en.wikipedia.org/wiki/Dracunculiasis) which is a pretty horrific little beast. In fact that would be a better starting point than your leaches since it already gets inside people and burrows around.
Physical damage from the burrowing combined with release of chemicals could explain the "zombification". The life cycle of the creature would probably also involve it extending egg layers through into the mouth of the victim so that when they bite people it injects eggs into them. The real reason to make them hungry is so they bite people.
The main weakness though isn't the creatures themselves. It's the fact that humans are smart. We'll find them, we'll work them out, and we'll develop the means to stop them spreading.
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**Definitions**
>
> Hamada: A type of desert landscape consisting of high, largely barren,
> hard rocky plateaus, with very little sand because this has been
> removed by deflation. -- From Wikipedia
>
>
> Desert: A region defined by arid climate, little rainfall and supports
> only sparse and widely spaced vegetation or no vegetation at all. --
> Dictionary.com
>
>
> Polar Region: Also known as Earth's frigid ones, are
> the regions surrounding it's geographical poles. These regions are
> dominated by Earth's ice caps. -- From Wikipedia
>
>
>
**The Question**
In a sleep deprived state, I've managed to place a hamada desert immediately adjacent to a coast in the polar region of my world, as well as a river (opposite the the northern coast, filtering in from the western coast and slightly below the polar region), and a series of mountain ranges. After getting some rest, I've found that I rather like the overall look of this arrangement, but I am wondering as to how plausible this would be. Currently I am using the work of Erwin Raisz (Cartographer best known for his physiographic maps of landforms. March 1st, 1893 - December 1st, 1968) as a reference while I work out the map, attempting to emulate his style and detail.
So, just how plausible is it to have a hamada situated between two glaciated mountain ranges, in a polar region? Are there any real locations that could be used as an example?
**Visual References** For anyone who is interested.
[Experimentalcraft blog: Raisz Map Symbols (Plains and Plateaus)](https://experimentalcraft.files.wordpress.com/2012/02/raisz-map-symbols-physiography-1.jpg)
[Experimentalcraft blog: Raisz Map Symbols (Mountains to Glacial Deposits)](https://experimentalcraft.files.wordpress.com/2012/02/raisz-map-symbols-physiography-2.jpg)
[Answer]
This is perfectly plausible. Greenland is cold, and it is relatively mountainous due to the volcanic activity that used to occur there. As long as your area is a cold desert like Antarctica, your geographical structures will not suffer from very much erosion. Your valley could be the result of a colder age when a gigantic glacier covered the area.
[Answer]
Not counting ice as desert.
The most northern desert in North America is Ashcroft, British Columbia 50° 43′ 32″ N, 121° 16′ 50″ W. I think this is the desert closest to a pole. Obviously not counting Antartica but let's say that wind patterns were such that a section of Antarctica was free of ice it would have to be a Hamada right?
I am going to say that I think it is possible but I can not find an earth analogue.
Here is a picture of the San Rafael Swell in the Great Basin high cold desert there is no sand in the picture. Is it a Hamada?
[](https://i.stack.imgur.com/LDs98.jpg)
[Answer]
The only way that I can think you could get it is to have a large plateau deep inside Antarctica.
Being deep inside Antarctica, precipitation will be almost zero (air will have been "freeze dried" way before it reaches your plateau).
Being high will mean that most of the snow being carried from the surface of Antarctica will not reach high enough to be transported inside the plateau, and the little snow that is transported will be removed quickly also by the wind (you could have some snow accumulated in depressions and other features that protect the fallen snow from wind, though).
[Answer]
Do you mean an area that looks like this?
[](https://i.stack.imgur.com/dcz3l.png)
Or this?
[](https://i.stack.imgur.com/HBjdI.jpg)
Maybe this?
[](https://i.stack.imgur.com/Hzrcp.jpg)
Welcome to Devon Island, the largest (Permanently) uninhabited island on Earth. Perhaps best known to the world because of this:
[](https://i.stack.imgur.com/QyXOm.jpg)
The Mars-Houghton Project, located in Houghton Crater.
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[Question]
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I am aware of biological constraints to our size, such as the issues presented by Vsauce in this [video](https://www.youtube.com/watch?v=DkzQxw16G9w).
However, letting the biological factors aside, what is the perfect size for a technologically advanced species? There are some benefits to being small: materials are stronger, more abundant and the world is a bigger place. However, they might be harder to procure and process. Also, scientific exploration might be an issue.
Note that the question refers to the size of one species on Earth, considering that everything remains the same (e.g. the size of trees).
Later edit: The main point of the question is about the technology itself and the manufacturing process (e.g. if we had been 1cm tall, could we manufacture laptops of appropriate size?) and what can we and cannot build anymore?
[Answer]
**Want to improve this answer?** Add details and include citations to explain why this answer is correct. Answers without enough detail may be edited or deleted.
Given the rather small sample size we have on Earth, Human beings seem to be the "ideal" size for intelligent and technological creatures.
Dolphins and other Cetacea are probably very intelligent, but live in an aquatic environment (meaning they cannot discover and use fire), and have no hands or other manipulating appendages. A marine creature of similar size and composition might be able to become both technological and intelligent if it had hands, and would almost certainly do so if it was also amphibious to the extent it could work for long times on land.
Other creatures on Earth do seem intelligent, and some have some ability to manipulate the environment around them, including elephants, and some birds like crows. squid and octopi and of course our cousins, the chimpanzees. The primary issue that seems to hold them back (besides a terrifying competitive species *Homo Sapiens* invading every ecological niche) seems to be the "brain-body mass" ratio. In essence, the size of their brains, while large compared to other creatures of their order and even in absolute terms, is still small in proportion to their bodies. Since Homo Sapiens is the only example of a fully developed technological species that we know of, that suggests the modern human brain size sets the lower boundary of how large a brain needs to be able to process abstract thought, manipulate objects and language and become fully technological.
So assuming a similar architecture of the brain, then a technological species existing on an Earth-like planet will probably be similar in size to modern humans and have a brain proportionately sized to the body. I suspect that (with certain allowances) this ratio might even remain true for hive creatures, so long as the assembled "intelligent" hive achieves a similar brain-body mass ratio. If you are postulating a different brain architecture or a different sort of planet and biochemistry, then all bets are out the window.
[Answer]
I'm assuming an alternative Earth in the following. Same physics, climates, DNA based life, fish as common ancestor to all higher land based life. No centaurs or superintelligent insect colonies.
Maximum size is quite easy. Something like a gorilla. Much larger and falling over becomes a hazard to life. But an elephant doesn't have hands and can't evolve into a centauroid because it's body plan was set by its fish ancestor. I don't think a trunk is a sufficient substitute for hands for developing technology.
Now the interesting direction. Smaller. The basic physics is that surface area goes as length squared but volume as length cubed.
A creature 10% the weight of H.Sap. couldn't support a human sized brain. Is that necessary? I think not. There have been people with anomalously small brains which were discovered at post mortem of a "normal" person. And there's Alex the parrot who approached chimp intelligence on a walnut sized brain. So I'd deduce that a brain one tenth human weight might evolve to support human equivalent intelligence. One hundredth, I'd doubt. Not least because a third or more of our brain is dedicated to vision processing.
A half-scale human has one eighth of the brain volume. Such a biped would average around a meter tall. I've fudged upwards a bit because it would not need to be proportionally as thick set as a human. Smaller limbs can be more slender and a smaller body falls less hard.
Now given the necessary intellect and hands could it access technology? Consider some key developments.
Coming down out of the trees ( only environment that encourages evolution of hands?) Proto-humans could stand to see above the prairie. Is three feet high sufficient? There's no obvious route to using fire if you keep living in trees. OTOH meerkats exist.
Fire. Making fire by friction is not easy. The creature has to dump sufficient muscular energy into a dry stick in a short time window. Like most kids I have tried and failed. Could any creature with one tenth human average arm muscle mass succeed? Perhaps, especially if it had theropod dinosaur ancestry rather than mammalian. Birds are from that branch of the tree of life and can support a higher metabolic rate. Otherwise are natural fire sources sufficient to attain technology?
Weapons. A tribe of humans with spears can defeat any predator often enough that the predator learns to leave humans alone or becomes extinct. Could a one-tenth human-mass creature become the top predator? Also could they develop bows and arrows? A scaled down arrow rapidly becomes non lethal.
Agriculture. Could these creatures domesticate oxen and horses? If not then ploughing becomes problematic as does keeping large wild herbivores away from the crops. Also the wheel works better for ox-carts than llama-carts or human-carts. The Incas didn't get to the wheel.
I hope this is food for thought. Technology would clearly be harder to attain for a creature with human intellect but one tenth our body mass. It feels like a lower limit even if you bless it with dinosaur genes.
[Answer]
TLDR: Smaller is more ideal
Well, Homo floresiensis were tiny, measuring only about 3 feet in height. They were not midgets or dwarfs, simply a much smaller version of Homo sapiens. In an alternate universe they very well have been the norm for our planet, but I think much of our size has to do with competing against predatory animals, which tend to be larger than their prey. If you had a non-meat eating race with only limited exposure to predators it could be smaller since it doesn't need to out-chase or fight for food, or defend itself.
Coincidentally, the Spartans were the fiercest and most efficient fighters of their age, and Greeks tend to be much smaller than Germans or Nordic based people. I mention this because weapons are what really blossomed technology through the ages. Being small has a lot of advantages as you need fewer resources to survive (less food, less material for clothing, smaller structures for housing, etc.). This means those same resources can be spread out over a greater number of people, which means more minds working to create new discoveries.
In summary, the smaller you are the more densely you can live, the less food you need, the lower the impact you have on the world... there's also a study that shows that shorter people live longer than taller people. This leads me to surmise that smaller is in many ways better, but due to circumstances of who won which war, population growth, etc., we are on the larger size these days. Our size has not affected our intelligence, and there's no current evidence that we would have had more/fewer technological advances had we evolved smaller.
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[Question]
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I have a planet with two moons. I want them on opposite sides during the equinoxes and together during the solstices. The seasons are a little lopsided, with spring and autumn having 90 days and the other seasons having 126 days. Thus, there are 108 days between equinox and solstice.
What function would describe this relationship?
[Answer]
To describe two functions which are equal every 216 days and opposite every 108 days after being equal, you simply need two sinusoidal functions properly scaled and shifted.
Moon 1: $\sin({{1}\over{216}}\pi \times days)$
Moon 2: $\sin({{1}\over{216}}\pi \times days - \pi)$
Overlaid, the functions look [like this](http://www.wolframalpha.com/input/?i=plot%28sin%281%2F216+pi+t%29%29+plot%28sin%281%2F216+pi+t-pi%29%29+from+0+to+864) (shifting sine by $-\pi$ is the same as −sine):
[](https://i.stack.imgur.com/JnUSq.png)
Starting at day zero, the moons are at the same point in the function, 108 days later they are the maximum distance apart, after another 108 days (216 total) they are back to being at the same point.
---
If as SJuan76 points out, you want to have more realistic orbital periods (non-identical, but still line up as requested) you can just use a multiple period, like this:
Moon 1: $\sin({{1}\over{216}}\pi \times days)$
Moon 2: $\sin({{1}\over{72}}\pi \times days)$
[](https://i.stack.imgur.com/as152.png)
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[Question]
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What would the most advantageous alternate thumb orientation be? I.E. on the underside of the hand, in the middle of the wrist, or in between the fingers (replacing the middle finger). Would there be a strong advantage to having multiple opposible thumbs (i.e. one on each side of the fingers or even two next to each other)?
And how would this orientation affect things like weapons and key interfaces (positively or negatively)?
[Answer]
Two thumbs, one in the same place ours always is, and a second coming out of the opposite side of the hand, still opposable in the exact opposite way as our current thumb. This, so you can still use the hand to lay flat against an object, but you can also grasp objects that much better, or even in the case of weak broomstick shaped objects, break them easily with one hand. Most existing human weapons and hand tools would be fully compatible with such an appendage, with some gaining usefulness, and almost none being negatively impacted.
Full fingerprinting recording and matching systems would have to be changed to add the two additional potential prints, but most biometric security systems could remain unchanged. Most biometric locks only rely on a single fingerprint to unlock.
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[Question]
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I've a creature that can focus CO2 laser through the len of the unique eyeball as means of self defense mechanism via natural selection. Now using the same natural selection process how can such creature prevent the laser from overheating the eye? Kindly use magic sparingly else face the wrath of my creature, it likes to put on a cape which do little to lessen the build up of heat. As usual answer that enables the species to shoot laser the longest duration wins.
[Answer]
**The creature's eyes are completely transparent to infrared light.**
Perhaps the creature can also see far into the infrared spectrum, thus eyes which are transparent in infrared light would be selected for. The CO2 laser is coherent light in the infrared spectrum (it can't be seen by humans), that light is not absorbed by the eyes, so no energy is absorbed, and the eyes don't heat up.
[Answer]
How about having large balloons around the eyes that contain some sort of liquid with low vaporization temperatures? The vapor can then be pumped through a biological equivalent of a condenser, and fed back to do more cooling work.
[Answer]
**Radiator Fins**
Blood, lymph, or some other liquid is pumped around the ocular lasing organs to absorb waste heat and then through a radiator fin, where the heat is radiated off through the high surface area.
Weather and temperatures would have an affect on how much the laser could be used without maxing out the radiator efficiency.
It could also work similar to a bat wing, where it extends out when needed to provide a large surface area, and then folds up to conserve warmth when it's not.
It's liquid cooling for the eyes.
[](https://i.stack.imgur.com/r3fnj.jpg)
[](https://i.stack.imgur.com/g1vj8.jpg)
[Answer]
It **generates many little lasers in it's lung**,
wich is **cooled by the air** it breathes, (also, there is **good oxygen supply** in the lung at all times)
and uses **optical wave guides** to **bundle and transport them to the eyes**,
where **they only pass transparent parts**.
the creature
[](https://i.stack.imgur.com/kRirq.png)
optical wave guides
[](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQahL6pQWjvv5uWphXupslMDK49Fn-42tddTzLf0tuVLuWcV8dcWg)
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[Question]
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In this scenario, the American British Colonies never revolted against Great Britain. Therefore, GB still has many of its colonies.
Now, imagine that it is 1938, and the Second World War is right around the corner. Germany is about to invade Poland, and Great Britain and France are about to declare war on Nazi Germany. You, a British minister, are confident in your country's success in the war, sure that you will crush Germany just like last time.
Now fast forward to late 1940. In real life, Britain was being crippled by the Nazis, and the U.S. was debating sending aid to Britain, their ally in mainland Europe. But, for the purposes of this question, Great Britain controls the 13 original colonies. However, it controls *only* those 13. The rest is under the neutral control of the Native American Indian tribes.
The question is: How would Great Britain controlling the 13 original colonies have changed the outcome of WWII?
I recognize that this is an extremely difficult question to answer because the U.S. played a huge part in the history of the world before World War II. Nevertheless, I would like to have an idea of what would have happened to GB if it still controlled the 13 colonies.
To make this question clearer, you can look at the circumstances like this:
Everything has happened up to the beginning of WWII as it did in our real history. The difference is that in this scenario, suddenly at the beginning of WWII, everything is exactly the same, except that GB controls part of America and the U.S. does not exist. The change is only at WWII; the time before that is totally unaffected.
If anybody needs any clarification, which I am sure will be needed, I implore you to please tell me in the comments.
Thanks in advance.
[Answer]
Yes, Britain would still win WWII. Simply put, British are one monster nation (or at least ***used*** to be. no disrespect intended) and it is next to impossible to beat them in war. What of their investment in technological advancements and what of their supreme skills in diplomacy and conspiracy. Not to mention their extremely practical approach towards practical matters, no matter what the cost.
OK, so you aren't satisfied by my simple answer. So I think I must break it down to pieces, starting from 1789 ...
**The American Colony**
As British control 13 of the American states (I am assuming all states are near-equal in area and natural resources, as implying otherwise would put this question into unnecessary detail of *which* states the British control), they have to make the necessary investments in this region so as to cultivate a good tax reaping every year. Railways, telegram (later upgraded to phone lines) and canal irrigation system are the first areas of investment. The locals would first be persuaded and then *forced* into cultivating more of the cash crops which the British can sell in the international market and earn huge profits (we are talking cotton here). Of course direct access to international markets is strictly forbidden to the locals.
Militia is another primary area of investment. Hiring local populace to serve for The Crown makes sure there is very less chance of a rebellion as the most war-worthy males are already paid to fight for the The Crown.
After a while (some 10-20 years of installing the railways network and "persuading" the locals into cultivating cash crops), the area would start giving output in terms of tax returns. In colonial India, the ratio of tax was --hold your breaths-- 50% of the total agricultural yield. A similar percentage would be implemented for the American cultivators too. Now I ask you to stop here, do some math and calculate how much would the British be earning annually from American Colony? I am saying 7-8 million pound sterling annually would be the tax return while 2-3 million annual would be the expenditures (paying the militia and the management employees etc). So the Brits would be making an annual profit of 4-6 million pounds from their American Colony.
Profitable? Yes, very much indeed! We are talking about the currency value of late 1700s early 1800s here so don't assume 4-6 million are worth as less as they are today!
**World War 1: Lessons Learned**
After world war 1, the British have understood that if ever there is a second such war in the future with advanced technology and more gun-fodder, they will have to rely heavily on their colonies for fueling the war, both in expenditures and hiring a mercenary army to fight the war for the British.
What does it mean? It means that the size of militias kept in India, America and other colonies would be increased. Ammunition factories would be set up fortnightly in those regions. The British management officers would show *slightly* less egotist behavior when dealing with a local.
**Mid 1930s. World War II Hovers On The Horizon. What Now?**
Immediate preparations! Here are the steps taken by the British to prepare for war:
1- Increase the training level of the local militias so they can last longer in front of German and Japanese machine guns.
2- Increase the tax ratio. Immediately! From 50% to 70%. These are times of war. However, to persuade locals into joining the military, a family having 2 men registered in the military would pay only half the tax.
3- Start stockpiling the food reserves in the colonies. We are going to need that if Hitler goes at it again!
4- Employ the power of media (newspapers and radio stations) and make it look like the Germans would crush the British colonies if they win the war. (Yeah, they did that in India after they realized local Indians are more enthusiastic in getting rid of British, than fighting their war for them, back in late 30s and early 40s).
**War Proceedings**
\*- 1938. The British are fully prepared for the upcoming war.
\*- 1940-42. Instead of looking for potentially strong allies to assist them, the Brits successfully employ their colonial militias for serving gun-fodder.
\*- 1943-1946. Indians serving in the British in eastern regions (Africa, Japan etc) while Americans and native British forces stopping Hitler on the western and northern regions (Europe).
The outcome? British win the war much ***easier*** than they did in real history. With Indians and Americans having to cope with the greater part of casualties, the British can go home merrily, making demands to Germans and Japanese for stopping the war.
Result. Brits win. Colonies cope with casualties and even stricter tax terms. Japanese and Germans crushed by war loss and damning war fines.
[Answer]
>
> Everything has happened up to the beginning of WWII as it did in our real history. The difference is that in this scenario, suddenly at the beginning of WWII, everything is exactly the same, except that GB controls part of America and the U.S. does not exist. The change is only at WWII; the time before that is totally unaffected.
>
>
>
So we assume the US east coast is under British control, while the rest of the US is a patchwork of neutral, maybe Spanish states and colonies trading with anyone and helping no one.
Being held as a **colony** is not as productive as being a free and democratic country. While the east coast is probably quite rich and can muster their own military, it's not the powerhouse it is today with the backing of the entire 51 states. We can safely assume this colony can handle it's own protection with regular troops as well as send some money, elite forces and navy to help Great Britain wherever it's needed.
Great Britain itself has always been an **Empire**. Another colony will not change that much. It will **improve it's strengths** a bit because of additional income and manpower, but it's organisation, political actions or general world view would remain unchanged.
So there we are, at the brink of another war. Would it have started? Most likely yes. The Nazis did not start the war with a great master plan in mind. "World War" was a risk they took when expanding eastwards, not their actual goal. Hitler was a gambler and would have taken the risk anyway, even if it would have been greater. After all, there is not much greater risk than the "World War" he was risking already.
In terms of **military**, Great Britain would be slightly better in what they were already great in: Navy. They'd have more ships and better ships. They already had planes and tanks that were good, if not even better in a plane-by-plane or tank-by-tank comparison than Germany's. With more resources, they might have been even better. However, the tactics lacked. And when it lacks with a colonial Empire with X colonies, there is no reason to assume a colonial empire with X+1 colonies would improve significantly.
Germany won their first campaigns not by being superior in weapon design or even superior in absolute numbers. It won it's early campaigns through superiority in organisation, focus and tactics. "Blitzkrieg" was not about having the coolest tank. It was about ruthless use of combined arms effects, concentration of power, daring leaders and a few elite troops.
Chances are, the **campaigns** against Poland, Denmark, France, Yugoslavia and Greece, even the Soviet Union **would not have changed much**. The campaign against Norway relied on seaborne transport. It was clear from the start that the German Navy would have losses and with even more British sea power, more German ships would have been lost. Maybe, **Operation "Weserübung"** would even have **failed**. Or never been started. But again, it had been a gamble from the start, and I think it's safe to assume that gamblers will continue gambling even at higher risk.
The battle in the **Atlantic** would probably have been turned in favor of Great Britain quickly. Being able to protect the **convoy routes** with their own ships end-to-end using air cover and without the help from a non-combatant that had to hide all their actions as to not be drawn into the war would be an enormous advantage. The convoy battles elsewhere, for example later on the route to Russian ports would have been easier also, with more navy and maybe even Norway free of enemy occupation.
However, while the convoys would be safer, they would also either not transport as much or transport goods at a *much* higher cost. A lot of the goods that went by convoy either to support Britain or the Soviet Union was **lend lease**. Without a US, those goods need to be *paid for*. Assuming the colonies can easily support Britain itself and can also be taxed into oblivion in wartime, that still leaves the goods transported to the Soviet Union.
So in **Europe**, the course of the war will be **slightly altered**, with Norway maybe not occupied and Great Britain free to put less resources into convoy raid protection and maybe more into bombing the Reich. With more resources, maybe that tactic would not have been abandoned. However, although not directly involved, with the US and it's economic power out of the equation, not much would have changed. The advantages for Britain would probably be on par with the disadvantages that not having the other US states on their side impose. If you look at who actually suffered the losses of the war and who actually killed the most soldiers and defeated the Wehrmacht, then a change in UK power would not matter much. The Soviet Union did a majority of the fighting, killing and last but not least dying to bring down the Axis.
With Europe only changed in details, the whole conflict in the **Pacific** would change radically. With the US out of the picture (that would probably include the Philippines, maybe still a Spanish colony or independent then), Japan would rule supreme. Being locked in a land war with China, there would be a huge *what if*. What if Japan, not threatened by a US embargo, simply decided to conquer China and live happily ever after? Great Britain and the Soviet Union would defeat the Reich more easily. But what if not? In reality, Japanese Ships butchered almost any allied fleet presence but the US navy. With Pearl Harbor a free trading port, the Japanese Navy would be free to chase down any remaining navy in the Pacific and Indian Ocean. Instead of invading the Philippines, they could conquer New Zealand or Australia. They could certainly harass India enough to neutralize it in terms of help for GB in Europe. However, both options are purely speculative. Unlike with Europe, the situation would be so different, we could only guess.
So the bottom line is:
**Not much would change in Europe, but the changes in Asia would impact Europe. And the changes in Asia without a US presence are hard to project. It may have went either way. Use whatever fits your story best.**
[Answer]
TLDR; Japan would start WWII.
I think there is more to Japan. In 1930s Japanese imperialism would be free'd from dispute on northward versus southward expansion. Note that in 1937 Japan was already at full-blown war with China. Nanking Massacre happened in 1937 in real world. But lack of large U.S. Navy in the Pacific would direct Japan even more to naval expansion. It would *also* antagonize Britain more, as they would see Japan as their *main* adversary in the Pacific.
So I think the Second Sino-Japanese War would just transform itself into a World War, and that it would be remembered that WWII started in 1937. United Kingdom would aid China in 1938 or 1939. This would promptly cause Japanese naval attack on British fleet and colonies. Historical Khalkin Gol (probing other expansion routes) wouldn't make sense in this setting and would be obviously replaced with taking of Phillipines, a colony with a weak Spanish presence, as well as other Pacific islands being a power-vacuum without United States.
In this setting Hitler would be even more encouraged to expand eastwards. He would invade Poland even sooner, at the beginning of 1939. With UK war effort already concentrated on Pacific/Indian Ocean, Germany would likely succeed with blocking British Isles, cope better with the aerial war and try the naval invasion (in 1941).
Soon after German invasion on Britain, the USSR would attack Germany (Suvorov scenario) and become formally an ally of UK, but they wouldn't progress more than 200-300 km. Germany would need to withdraw from Britain. In 1942 Germany would launch a counter-offensive on USSR, which would progress similarly to real-world Operation Barbarossa.
The war would end in 1945 with Berlin taken by Soviets and France liberated by British. Soviet Union wouldn't invade Japan as it did in 1945.
Britain would develop nuclear bomb in 1946 and the demonstration would cause Japan to sign a peace treaty. Japan would hold part of China and remain the most powerful navy over Pacific, but it would withdraw from India and Indian Ocean, where British would continue to rule.
[Answer]
**Executive summary:** The military situation is more difficult for Germany and much easier for Japan.
Let us consider the situation at the outbreak of war in 1939. It seems reasonable to assume the following:
* The 13 former colonies have become an independent nation allied to the UK, similarly to Canada and Australia in the original timeline (OTL). Let's call it USEA (the United States of Eastern America).
* Population growth and industry in the USEA developed more or less as it did in OTL.
* The colonies have approximately the boundaries of the following modern units: New Hampshire, Maine, Massachussetts, Pennsylvania, Connecticut, New York, New Jersey, Maryland, Delaware, Washington DC, Virginia, North/South Carolina, Georgia. (These equate to the original 13 plus Maine and Washington DC.) Everything further west belongs to the neutral Native American nations.
According to the 1940 US census, the USEA had a combined [population](https://en.wikipedia.org/wiki/List_of_U.S._states_by_historical_population) of 50 million people. They have no direct access to the Pacific Ocean, so they are not particularly interested in Japan; their main concern is the prospect of a European war.
In 1939, [populations](http://www.populstat.info/Europe/europe.html) of the major belligerent powers in western Europe were:
* UK: 48 million
* France: 40 million
* Germany: 70 million
* Italy: 44 million
In OTL, the Axis powers of Germany and Italy had a combined population of 114 million, compared to 88 million for the Allies of UK and France. With the addition of the USEA, the Allies now have 138 million people. This would make them a significantly tougher opponent for the Axis.
In OTL, Germany and the USSR signed a non-aggression treaty (the Molotov-Ribbentrop Pact). After it conquered Poland in 1939, Germany then had a free hand to blitzkrieg France in 1940 without worrying too much about its eastern border, before turning its attention to the USSR in 1941.
With the participation of the USEA from the beginning, Germany will find it much more difficult to conquer France or enforce a U-Boat blockade of Britain. How this will affect German military and diplomatic strategy is left as an exercise to the reader.
The war in the Asia-Pacific theatre will be very different. With no need to worry about the USA, Japan will have much more freedom of action. It may attempt an invasion of British India via Burma. It is also likely to come into conflict with the USSR much sooner, instead of at the very end of the war as in OTL.
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[Question]
[
If an Earth-like planet was tidally locked to a star similar to [Sirius A](https://en.wikipedia.org/wiki/Sirius), at which distance from the star would the night side be able to have liquid water, possibly with an average temperature of about 10ºC in the night side?
[Answer]
[See also Physics SE](https://physics.stackexchange.com/questions/29293/does-a-tidally-locked-planet-have-seasons) and [Space SE](https://space.stackexchange.com/questions/5026/could-a-planet-that-is-tidal-locked-to-its-sun-be-habitable-to-naked-humans) with the same answer.
A fascinating [presentation on the SETI Seminar Series](http://www.seti.org/weeky-lecture/patterns-sunlight-extra-solar-planets) goes over tidally locked worlds and lays to rest the presumption that the day and night sides are extreme and inhospitable.
The situation can be substantially complicated by
* odd half multiples of spin-orbit synchronization, like Mercury
* eccentricity
* inclination of orbital plane
* axial tilt
In short, *locking* does not mean an unmoving sun; situations like Mercury are in fact the norm, and the presence of other giant planets can drive a close rocky world into a state with both high inclination and eccentricity, and eccentricity causes odd-half multiple rotations to be preferred.
In extreme cases, the overall insolation can be averaged out to the same degree as a non-locked world like ours. And it takes far less to average out the temperature to a reasonable degree.
Sirius A is 25 times more luminous than the sun but less than twice the diameter, and is only 250 million years old.
A planet close in would be baked indeed. *Unlike* the case of Mercury and the trend of figuring out how such planets could be more uniformly lit, you really do want it locked with a permanent night side.
Note that even Mercury has ice in permanent shadows. The key is not having an atmosphere. That means not having liquid water either.
Consider an underground aquifer. If the planet has a permanent day and night side, the place for liquid water does not have to be exactly at the anti-sol point. It can be frozen at the midnight point, and have a "just right" belt some distance between the hot and cold.
The existence of such temperature gradients depends on the composition of the rock, and how it conducts heat. So, you can considerable flexibility in making it (plausibly) come out just right.
I'm more worried that a rocky world would not have had time yet to cool down and form a solid crust. That's more of a hard math physics question.
[Answer]
When discussing the habitability of a tidally locked planet, temperatures are only ONE of the vast array of variables, each of which has a critical role in determining whether long term life sustenance is possible on the planet or not. Here is a list:
**1- Temperature**
As presented in your query, temperature is one of the key factors determining the habitability of a planet (tidally locked or not). The temperature on the night side of the planet would depend on:
a. Composition and thickness of the atmosphere. By "thickness" I mean how far the atmosphere extends above the crust of the planet. By composition, I specifically mean the presence of greenhouse gases. You could say that temperature on the night side = density of atmosphere x ratio of greenhouse gases
b. Presence of active volcanoes on the night side. This should be self explanatory. Volcanic activity does a long term job of heating up the crust of a planet.
c. Presence of large water bodies (oceans) on the planet. Large water bodies do a magnificent job in reducing the difference of temperatures between two zones. If there is a huge ocean that stretches both sides (day and night) on the planet, the temperature difference on these sides would be much lesser than if it were a desert planet (no water).
**2- Perpetual Wind Speed**
Seasonal storms and gales are one thing, but when you have a large temperature difference between two sides of a PLANET, things get terribly messy. We are talking about vortexes, cyclones and dunes in speeds excess of 1000 km/h. For the sake of reference, remember that a hurricane/cyclone with wind speed exceeding 350 km/h would splatter normal concrete houses to bits. Storms exceeding 600 km/h would bend and crush metal structures (we are talking steel here). I don't want to discuss wind speeds exceeding 800 km/h here. The very thought gives me shudders of horror. You should read about the giant red spot on jupiter to learn about what I mean. All these horrible vortexes are generated due to temperature differences.
**3- Renewable Food Source**
The night side of a planet means no direct sunlight. No direct sunlight means no photosynthesis. No photosynthesis means no green plants. No green plants means no herbivores. No herbivores mean no mutton, beef or chicken. No photosynthesis also means no wheat, rice, maize, barley, pizza, pasta, chocolate cake ... You will need to develop a food chain base. A food chain base is something that generates food for others and makes it food by itself. On our planet earth, it is green plants making magic happen with photosynthesis.
**5- Building Material Availability**
What are you going to make buildings with, on the dark side of the planet? No photosynthesis means that "wood" is out of question.
a. Is there a system of natural caves where people can live in safely?
b. Is there an abundance of easily available building materials other than wood? Iron, hydrocarbons (plastics family), construction grade rocks (granite, hard layered limestone/marble etc). If your people aren't living in caves, you'd certainly need some of these things to build houses for them.
**6- Perpetual Light Source(s)**
Because, you know, you are living on the night side of the planet and your characters would be groping in perpetual dark unless ... you give them sort of giant planet-wide lamp or something.
**7- And yet ...**
The above mentioned 6 variables are the very basic things you cannot even THINK surviving without, on the night side of a tidally locked planet. Having all these does NOT mean you can host an intelligent civilization on that planet. Think about these little things:
a. In the absence of photosynthesis, how are you going to get all the vitamins required for healthy growth? You can't survive on carbohydrates or proteins alone. Where are you going to get the "fiber" in your food?
b. Sunlight is also necessary for skin, eyes and several other things in our body. If you live in an underground well-lit shelter for 2 weeks, you are going to quickly lose your skin freshness and your muscle strength. Thats what sunlight deprivation does to you!
c. For a civilization living in perpetual dark side of a planet, evolution rule states that they will lose the sense of vision rapidly as there will be no use for it. Creatures living in dark caves don't have eyes. You ought to provide a natural light source for your people. It's mandatory if you want them "seeing" things!
d. Besides energy requirements of food, you also need water. Fresh, clean, pathogen free water. At least for complex life on earth, which we are used to seeing and being.
These are the very basic factors determining the habitability of a planet. There are several other "subtle" variables too, which I haven't included here for the sake of refraining from dragging on. For a start, think about gravity, metabolism type (oxygen I mean for earthly life), sensory organs, modes of locomotion, moon systems, cosmic rays prevention system (ozone layer, in case you were wondering) etc etc etc
] |
[Question]
[
For this question lets take a trip to Slyo Dacas:
[](https://i.stack.imgur.com/zaDiJ.jpg)
Slyo Dacas (sil-yo-dak-iss) is a world roughly the *same size of Earth* with a decent *magnetic field* and *no moons*.
The world is a bit *drier than earth*, its seas are shallower and smaller and its land more bit *more arid* on average.
The planet has *plate tectonics*, a *day of 24 hours*, and a *year of 365 days*.
The main difference though is its orbit: ***highly eccentric***.
There are no seasons due to *almost no axial tilt*. However, since the orbit changes the climate so drastically for simplicity sake I will say it has seasons. Summer with the planet's orbit at closest approach to its star, and winter at it farthest reach.
**Winter** features the coolest temperatures where the poles are below freezing and the seas are at their greatest size and coolest temperatures. The planet looks a lot like the above picture.
**Summer** temperatures rise drastically. Most of the water evaporates into the atmosphere and massive cyclones rage across the planet drenching everything in hot rain.
[](https://i.stack.imgur.com/CVadU.jpg)
A lot like this.
Now we know that erosive agents here on Earth help shape just about everything from mountains, coastlines, rivers, even individual rocks.
This planet has most of those processes as well, but in a more advanced pace and on a yearly schedule. The planet is also a bit drier. So taking these details into account my question is:
**What can we expect from this terrain acted upon by rapid changes in climate?**
Example: Would there be more sandy deserts, smoother canyons? No ocean cliffs? Please provide explanations.
*Bonus questions:*
How could plant and animal life adapt to survive the changes during the year?
Where would be the most likely/unlikely places to find that life?
[Answer]
The greatest change would be a much higher preponderance of "chaotic terrain" caused by flash floods.
Consider that the bulk of the planetary water will start forming snow as the orbit moves away from the sun, and by the time it reaches the farthest part of the orbit, there will be a deep, dense snowpack which has been frozen very hard due to the extreme cold.
As the planet approaches the sun in the "spring" part of the orbit, the deep, cold snowpacks will begin to thaw, but this won't be a gradual process; the deep cold of winter will make it take longer to thaw, while each day the insolation will become much greater as the planet approaches the Sun. The snowpacks will melt suddenly and catastrophically, releasing flash floods which will rapidly make their way to the lowest elevations (most of the water will rush into the low oceanic basins.
Huge wadi's, deep canyons and even "chaotic terrain" caused by major water features overflowing and breaching their barriers will be common. There will be huge accumulations of silt in the oceans and large deltas will be found at the ends of rivers. Geologists will delight in the amount of sedimentary rock, and over millions of years, we should expect to find large areas of sedimentary rocks like shale and sandstone being quite common.
The life on this planet will need to adapt to the hydrological cycle as well as the wildly fluctuating insolation, and we should see lots of interesting adaptations, ranging from deep roots to massive migrations, or even life cycles designed to take advantage of this (for example, a creature which might use migratory sea birds to take its eggs or spores inland for hatching and development, then riding to sea with the "spring" floods for the remainder of the life cycle).
[Answer]
I'd say you'd have at least a couple things:
1. Cracks - There would be a lot of cracks in this planet caused by a lot of freeze/thaw cycles. During the fall, there would be a lot of rain. The rain would fill up small cracks in rock/ground/anything. During the winter, the water would freeze and expand, enlarging cracks and generally breaking stuff up.
2. Lots of Sand - When the rocks cracked, they would leave sand behind. During windstorms, this sand would be blown about sand-blasting everything, and making everything smoother. Think smoothed out rocks, plants, etc.
3. Deep Canyons - There would be huge rainstorms and snowfalls on this planet. During the Summer, a lot of the water would evaporate into the air. When the air cools during Fall and Winter, the water will come out of the air in the form of precipitation. During the rain and when the snow melts, erosion would be cutting deeper and deeper canyons into the planet. These would be deeper than Earth's (assuming they're the same age) because rainfall and thawing would involve a lot more water (even though there's less of it than Earth).
4. Short, Low, Well-built vegetation (I'm assuming you want vegetation) - As you said, the drastic differences between Winter and Summer would cause cyclones and windstorms around the planet. Any tall plants would have more surface exposed to the wind, which would probably uproot or otherwise destroy them.
5. Animals would either hibernate, or live underground - Any animals outside during Fall or Spring would probably not survive the giant storms on this planet. Animals living underground would be able to eat the roots of plants and other animals living underground. Other animals would find a safe place to hibernate during dangerous transition periods.
Some other things to think about: The oceans would probably settle without the moon constantly mixing them. (see [Tidal Forces](https://en.wikipedia.org/wiki/Tidal_force))
[Answer]
>
> What can we expect from this terrain acted upon by rapid changes in climate?
>
>
>
I suspect that the terrain won't be much different from Earth, other than because of no moon to help keep the mantel and crust a little more active, mountains will likely be lower, balanced by a bit less water and no moon for less erosion leaving things surprisingly similar to earth features. Smaller and fewer lakes rivers and oceans etc.
>
> How could plant and animal life adapt to survive the changes during the year?
>
>
>
Plants handle winter pretty easily now, many plants also go dormant in desert climes until the rains come then burst into life. Many will also live in what lakes and oceans exist while they exist. Some plants change quickly between a wet and dry environment, and these would be even better adapted to such, likely absorbing large amounts of water like cactus's. Now if the clouds actually obscure the sunlight during the summers, it will help keep the worst of the scorching away, but it will make it harder for photosynthesis. So plants will have to store food during the 'spring', to help survive the 'summer' and produce 'fruit' in the 'fall' before 'winter' comes back.
>
> Where would be the most likely/unlikely places to find that life?
>
>
>
Anyplace that water will puddle as rivers lakes and oceans. Likely will stay much closer to the equator since that will have the longest 'unfrozen' seasons, since the poles are going to warm up the slowest because of the angle of the sunlight hitting it. A couple years of the poles not thawing out could quickly lead to a lot more of the available water being trapped in polar ice.
Land animals would likely be in foot hill type areas, near places that lakes will fill up but with enough upland to stay 'dry'.
] |
[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.
Setting: we have a fantasy world which is a planet with much of the same conditions that can be seen on Earth, but with the difference that it is orbited by a moon with a mean diameter of 3 500 km. The moon has an albedo of 0.12 and its distance from our planet is 20 000 km at perigee.
The moon/planet system orbits a star that has an apparent magnitude of -27, when observed from the moon/planet system. Assume that we have the same atmospheric conditions as on Earth, and - if other parameters have to be taken into account besides the atmosphere - assume those are equal to Earth's as well.
I would like to learn two things here:
1. What would the apparent magnitude of the moon in question be to an observer looking up at the night sky from the planet it orbits, when the moon is at perigee and in its full phase?
2. What does the equation that gives you the solution to this problem look like?
[Answer]
There's a relatively easy way to calculate this number. Compare your moon's parameters to ours and multiple those differences
**Size**
Start with out Moon (diameter 2,156 km) and compare to your moon (diameter 3,500). This means that the size difference in moons makes yours $ \left( \frac{3500}{2156} \right)^2 = 2.6 \times $ brighter due to the size difference.
**Distance**
Your moon is ~ $19 \times$ closer than ours, which would make it ~$ 19^2 = 361 \times$ brighter due to its distance.
**Albedo**
[Luna (our Moon)'s albedo runs around 7%](https://the-moon.wikispaces.com/Albedo?responseToken=80e4d2ec87958b71af29394e3521a46f), while yours comes in around 12%. Your moon comes in around $ \frac{12}{7} = 1.7 \times $ brighter due to its reflectivity.
**Sun's brightness**
Your world's star has an apparent magnitude of -27, while [Sol's (our Sun's) apparent magnitude runs around -26.7](https://en.wikipedia.org/?title=Apparent_magnitude#Example:_Sun_and_Moon). The difference in brightness from this is negligible.
**Combined**
When you combine these factors, you get the following:
$$ 2.6 \* 361 \* 1.7 = 1631 \times \text{brighter than our Moon, Luna}$$
[$ m\_{Luna} = -12.6$ (Moon's magnitude)](https://en.wikipedia.org/?title=Apparent_magnitude#Example:_Sun_and_Moon)
$ m\_{Moon2} = \text{Unknown} $
$ \frac{F\_{Moon2}}{F\_{Luna}} = 1631 $ - Ratio of the two moon's brightness
The equation looks like this:
$$ m\_{Moon2} - m\_{Luna} = -2.5 log\_{10} \left( \frac{F\_{Moon2}}{F\_{Luna}} \right) $$
Plug in the numbers:
$$ m\_{Moon2} - -12.6 = -2.5 log\_{10}\left(1631\right) $$
Simplify
$$ m\_{Moon2} = -2.5 \times 3.21 - 12.6 = -20.6 $$
So, **the visual apparent magnitude of your Moon would have is about -20.6.**
**NOTE**:
My above numbers were performed using our Moon as a comparison and factoring those differences. I did **NOT** derive the value directly from your Moon's values. You can do that as an alternative method of getting the same answer.
] |
[Question]
[
During the Permian and Triassic periods, all the continents had joined together to become the supercontinent Pangaea. Its size means that the majority of terrestrial life might have been confined to the coasts, away from the large, unforgiving desert, and its pole-to-pole position means that with no exchange from warm water to cold, the oceans were anoxic.
But if all the continents centered around either the North or the South Pole, what would the climate and ocean circulation be like?
[Answer]
**Ocean circulation:**
The surface currents would flow following the dominants winds. They would circle around the whole planet if there is no landmass to stop them. [It looks like this](http://etc.usf.edu/clipart/62600/62680/62680_ocean_circul.htm) except that, without the landmass, there is no curving arrows. It's just like the Antarctic circumpolar current.
The continent, starting from the pole would probably extend to the mid latitudes: 40-45. At this latitude, the surface currents and the dominant winds are normally going eastward. I said normally because such a large landmass will cause some perturbations.
**Winter:**
The large continent will become very cold in winter. Probably as cold as Antarctica is during winter. Temperature below -50 and even below -60 Celsius would be very common over large areas. Looking at eastern Asia during summer, the temperature could be close to -10 or -15 near the coasts, close to 40 degrees of latitudes.
The interior would be excessively dry during winter. The coasts could receive some rain but again, by looking at rainfalls in Eastern Asia, it would not be a lot.
**Summer:**
The interior of the continent become much hotter than in winter but large parts would probably remain under the freezing point. Taking Antarctica as an example, the 0 degree isotherm is close to the polar circle. Meaning that the areas under it have an average temperature under 0 even in their hottest month. Closer to the coast, temperatures could reach 15 degrees making it possible to practice agriculture.
The coastline would receive a good deal of rainfall since it would be located under the unstable polar front but the still cold temperatures from the interior will not pull the moisture toward the interior. Precipitations would be similar to those of Noway : over 1000 mm per year but would gradually diminish as we move inland. The precipitation on the pole would quite likely be close to those of Vostock : 22 mm per year. That info comes from Wikipedia but I think it's likely to be much lower than that.
] |
[Question]
[
I imagine that if we could transform [the Moon](http://en.wikipedia.org/wiki/Moon) into a beautiful [planetary ring](http://en.wikipedia.org/wiki/Ring_system_%28astronomy%29) around [Earth](http://en.wikipedia.org/wiki/Earth), wouldn't it be spectacular! Problem is the feasibility. Are there any practical solutions?
**Option**
I think blowing up the Moon is the only viable option but wouldn't it also spell [disaster for Earth, too](http://www.dailymail.co.uk/news/article-2238242/Cold-War-era-U-S-plan-bomb-moon-nuclear-bomb-revealed.html)? With all the debris from the leftovers of the Moon they will eventually form a ring around Earth, will they?
**Objective**
Transform Earth to look like Saturn. I couldn't care less about the Moon as long as it does not obstruct the planetary ring.
[Answer]
No need to blow it up, just give it a gentle push to the edge of earths [Roche Limit](http://en.wikipedia.org/wiki/Roche_limit). The gravitational pull will slowly tear it apart and create an awesome ring. I've grown tired of the moon anyway, so I endorse this plan. Risk of huge chunks of the moon crashing into the earth is a minor concern.
[This article](http://io9.com/5931098/using-the-roche-limit-to-put-a-ring-around-earth) covers your question quite well
[Answer]
Blowing up the Moon would create quite enough debris on orbits steep enough to fall on Earth and end all life. Leave our Moon alone.
Let's develop a good, strong drive and fetch a plenty of *small* asteroids into Earth orbit, somewhere between LEO and GEO because the satellites are very useful.
Crash them into each other *gently*, to break them apart into multiple meteorite-sized chunks, without spreading them by much. There, you have your ring.
Alternatively, decelerate the Moon gradually, until tidal forces are strong enough to overcome its gravity, tear it apart and let it form a ring.
Easy mode: Get the Chinese to launch four-five more of their anti-satellite rockets. (yes, even 2 should suffice; we're close enough for that!) This should increase the amount of space junk past the chain reaction threshold, as satellites hit by space junk explode into more space junk, very quickly turning the Earth LEO into a massive, shiny cloud of debris, and preventing all space travel for a next century or so.
[Answer]
Converting the Moon into a ring would quickly make this world uninhabitable. Unbeknownst to most people, the Moon performs a function vital to mortal life on this planet--it churns the ocean, preventing trillions of tons of defunct organic matter from becoming a floating morass of stagnant foam--a rotting biohazard--emitting hundreds of quadrillions of cubic feet of toxic fumes, which would kill nearly all land-based and aviary life, in addition to making the sea unlivable for nearly all life forms except for some hardy detritivores. Instead, the ocean tides exerted by the Moon's concentrated mass making daily cycles around the earth performs a tremendous and necessary service by waterlogging that organic detritus and sinking it to the bottom of the ocean, where it is converted into useful petroleum in great quantities daily.
Even if one could gather the destructive force necessary to cause the disintegration of the Moon, it would make this planet unlivable within a matter of days.
] |
[Question]
[
I am working on a survival suspense story, where a sizeable group of surivors is trapped in a tropical island (somewhere in the [Ring of Fire](http://en.wikipedia.org/wiki/Ring_of_Fire)) by a volcanic eruption. They find shelter from the erpution in an old mansion built in a high-rise cliff on the edge of the island.
The cliff is sturdy and the mansion is [stonemasonry](http://en.wikipedia.org/wiki/Stonemasonry), so there is little danger of fire from cinders or a collapse.
[The eruption](http://en.wikipedia.org/wiki/Types_of_volcanic_eruptions) I am visualizing would have a **[Volcanic Explosivity Index](http://en.wikipedia.org/wiki/Volcanic_explosivity_index) of 4 to 5**. Most of the inhabitants and tourists of the island died because of the [pyroclastic flow](http://en.wikipedia.org/wiki/Pyroclastic_flow) and other eruption hazards. Only the few that climbed the hill leading to the cliff survived because the pyroclastic flow goes downhill, and there is a sizeable valley between the volcano and this hill.
They are cut off from rescue for a long period of time (so I can play with isolation, food shortage and so on), so I need the mansion to survive the eruption and remain in the extreme end of habitable (temperature, etc - almost inhospitable). Sickness from inhaling ashes and heat strokes are hazards that will claim some survivors, but a handfull must survive to the end.
The lava flow would reach the ocean before climbing the cliff, but isolated the group from the rest of the island, and is too close for confort, but they can still venture outside the manor for short periods of time.
How close can I put the mansion from the lava flow and/or the volcano caldera so not to push the suspension of disbelief?
[Answer]
It depends first on the eruption. Mt. St. Helen's type eruption is devastating for many miles in whichever direction it blows.
Hawaii type is mostly medium to slow lava flows making the island bigger is another matter. They could easily have some fast flows and cut off the people in the mansion. If it was a little bigger and went in other directions too, then any emergency response would be focused else where leaving the far reaches to fend for themselves for a while.
Lava flowing through someone's backyard
EDT: Taking into account the size of the eruption, you might want to have an uneven one, like Mt. St. Helens. The main resort side is in the direct path of the eruption and most of the flow, leaving the other side (more of a remote location) to be 'safe' and anyone who was staying there or just touring the 'back' of the island would be the survivors.
[Answer]
Looking at a variety of VEI 5 eruptions throughout history, I think 20-30km is often immediately survivable, regardless of terrain. That's not to say the house might not catch fire or collapse in the resulting earthquake. Another factor that might let you get closer is that not all eruptions are directly upwards. To take Mt. St. Helen's again, that blast was most severe towards the north, where the mountain sloughed away a 27km landslide, followed by a pyroclastic flow in that direction that covered an area 37km by 31km.
The biggest problem your hapless tourists are going to face is asphyxiation from the immense ash cloud that is the very definition of a VEI 5. That, and the searing heat of the potential shockwave. You might consider going for a smaller VEI number, as that has much less to do with the amount of lava as the total amount of all ejecta combined.
] |
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