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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.
Given the following conditions:
* Two space stations of insignificant mass (compared to what can affect the transmission of a beam of light) are separated by a distance of 100,000 light years.
* With one exception, there are no other objects of significant mass within a sphere of 1,000,000 light years.
* The exception is a single black hole, midway between the two stations, and having a mass of 10 solar masses.
* The sending station is transmitting "S.O.S." in Morse code. A "dot" is 0.5 seconds long. A "dash" is 1.0 seconds long. The time between dots and dashes is 1.0 second. The time between "S.O.S." blocks is 2.0 seconds.
* The beam's wavelength is 475 nm and its energy at the point of transmission is 1 Petawatt.
* The beam is as narrowly focused as the technology will allow and no effort is being made to specifically take advantage of the nature of black holes to get the signal past it. Tightly focused beam shot straight at the other station, nothing else. (If necessary, assume the beam is emitted from a 1 meter diameter lens and is well enough focused to hit a 1 meter detector with negligible loss. Yes, that's miraculous. But the question is focusing on what the black hole does to light — and the focusing tech should be (and is) irrelevant.)
* Ignore ***all other aspects of physics implied by the conditions of this question.*** Please don't complain that the existence of space stations or their placement in space has anything to do with this question. It's like telling your college professor that the answer to the question is meaningless because he chose to use a spherical horse.
Conceptually, pretend the two space stations are attached to one another by a string and are so far away from the black hole that the information transmitted along the ~~beam of light~~ string is uncorrupted. Then begin moving the two stations toward the black hole, always keeping the black hole mid-way between the two stations.
**Question:** How close can the beam of light get to the black hole before the information transmitted through it becomes corrupted?
* By "corrupted" I mean that the "S.O.S." can no longer be recognized for what it is within a period of ten (10) minutes.
[Answer]
**Your signal integrity might improve!**
Chasly notes this possibly in the comment. I was just reading an article about this.
<https://www.syfy.com/syfywire/why-is-there-a-normal-galaxy-sitting-at-the-edge-of-the-universe>
This exceedingly distant galaxy could be viewed on earth because the lensing effect of a black hole in between pulls the light back together. If it were not for the lens in the middle, this galaxy is so far away that its light would be scattered to invisibility.
[](https://i.stack.imgur.com/8vbnK.jpg)
That said, your SOS is not the light from a galaxy. As I understand it, the track of the light between your stations depends on the coherence of the beam and its width at the black hole, the distance between the stations (known) and the gravity of the black hole and consequent strength of the lensing effect.
A lot of numbers. You can adjust these numbers to produce the effect you want for your fiction. I could imagine that at some distance from the hole the path of the light would be bent so it does not reach the far station. But full on to the black hole, if the signal is wide enough it might be bent around the hole (lensed?) on all sides such that it suddenly reaches the far station, extra bright.
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So, the microstructure of abalone shells is 95% calcium carbonate, such as aragonite, tiles and 5% organic polymer that binds them together. This binding fails in a graceful manner, allowing the shell to take a lot of punishment before shattering.
This composite material is around 3,000 times more resistant to fracturing than calcium carbonate and twice as resistant to fracturing as boron carbide, despite the high degree of mineralization.
Source: <http://meyersgroup.ucsd.edu/papers/delete/1999/Meyers%20211.pdf>
On top of that, thanks to how light is refracted by said microstructure, it also looks cool.
[](https://i.stack.imgur.com/f2fY2.jpg)
Can you imagine how insanely bullet-resistant could scales/osteoderms/whatever be if I managed to replace the material of the "bricks" with something stronger? It would probably be like the [Battle of Ramree Island](https://en.wikipedia.org/wiki/Battle_of_Ramree_Island), though with [even more screaming](https://www.youtube.com/watch?v=Jiupj4PyL4U).
Well, I still have some things to solve, but bullet resistant, lightweight armor is a good start for my apex predators.
However, this is where problems show up. Hydroxylapatite is probably the strongest mineral in the human body, but it still seems fairly weak. I mean, yes, the composition of scales could vary across the creature's body, with the strongest covering their head and chest, but those should be as strong as possible.
Other than utilizing enzymes, another way of attaining certain minerals could be the Kakyoin method (RERORERORERO), basically, [lick it until it's gone](https://en.wikipedia.org/wiki/Limpet#Function_and_formation); mountain goats do it too.
**So, what is the strongest (high Vickers hardness, and a-okay or better fracture toughness) mineral that could be obtained by an animal (either by synthesis via enzymes or munching) and serve as a replacement for the aragonite bricks in the aforementioned microstructure?**
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In essence, if I'm understanding correctly, you are looking for a biological material that exhibits a high degree of toughness. To achieve this, we could look at some very strong materials that could replace (or at least compete with) our standard bulletproofing materials. One of these is [spider silk](https://inchemistry.acs.org/content/inchemistry/en/atomic-news/spider-webs.html#:%7E:text=Dragline%20silk%20is%20around%201.1,strength%20of%203.0%20%E2%80%93%203.6%20GPa.&text=Spider%20silk%20fibers%20are%20not,fiber%20but%20they%20are%20tougher). This could be part of the protein matrix that is layered into the scales. Of course nacre protein could be sufficient here as well.
The other part, the replacement for calcium carbonate is harder to figure out. Polymerization is one of the keys, as it has to survive the impact. Tensile networks distribute the forces without fragmentation, but could be weakened by repeated impact. It could be that some healing process could provide additional strength near damaged areas.
Organosilicon biopolymers could create some incidental silicon carbides, which are also bulletproof. [Organosilicons](https://en.wikipedia.org/wiki/Organosilicon) are naturally absent from organisms found on Earth, so you would have to dig deep into the genetic engineering aspect of this form of life to explain it.
There does appear to be some work that has been done on this for astrobiology using bacteria and mutant enzymes. The researcher said "The mutant enzyme could generate at least 20 different organo-silicon compounds, 19 of which were new to science". Nobody thought to see if these could be used to bulletproof an organism however. The layering of organosilicons and spider silk proteins (or nacre proteins) should allow a fairly good bulletproofing scale which has some work behind it to show biocompatibility, even if somewhat deficient on the organosilicon side of things.
The percentage of [silicon carbide](https://www.syalons.com/materials/silicon-carbide/) that shows up in these scales could be altered either environmentally (by acid or enzyme attack) or internally by a process that selectively expels silicon carbides into the scale structures.
The hardness would be below the charted levels, but the surrounding polymers would add toughness. As to whether the silicon carbide could be sustained in multiple layers, it would depend on how the silicon carbide is enriched in these scales. Process is everything in biology.
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One possibility could be a [Boron Carbide](https://en.wikipedia.org/wiki/Boron#High-hardness_and_abrasive_compounds), specifically cubic-BC5, which has a Vickers hardness of 71 GPa and a fracture toughness of 9.5 MPa m½.
Both of which are higher than the values for hydroxyapatite (5 GPa and 1.2 MPa m½, I. Hervas, *Fracture toughness of glasses and hydroxyapatite: A comparative study of 7 methods by using Vickers indenter*).
I'd imagine that it would also be able to be grown in approximately the same microstructure, to produce the same colour as the shell in your image.
Unfortunately [boron](https://en.wikipedia.org/wiki/Boron) is not a common element, although it can be very concentrated in some dry lakes and mineral deposits. But I'm not entirely sure how your creature could produce cubic-BC5, possibly enzymatically.
Hopefully that helps.
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So, I envision a world that has forgotten it's *en route* to another galaxy -- it's been in transit for only a million years, hasn't even properly left its "home" behind (still stars in the sky, at least behind), but while a million years isn't very long as sublight intergalactic travel goes, it's a very long time for a civilization, even fairly long for a species.
The mode of travel is by Shkadov thruster -- take your star and at least the inner part of your solar system with you, accelerating continuously but at micro-G levels. So, a civilization (Kardashiev level 1? 2?) builds the enormous light-pressure-levitated reflector that makes the star itself into a photon thruster, and over the lifetime of a star, the star can travel (close) intergalactic distances.
Doing this with long-lived stars like G, K, and M class is very slow, but these stars, if reasonably young at the start of the journey, have the potential to live long enough to complete the journey, perhaps even with a turnover maneuver (swap the reflector to the other side of the star, to reverse thrust) to arrive in the destination galaxy at a velocity that will capture, instead of just blasting through on a one-way trip to the next galaxy cluster.
A light pressure levitated parabolic reflector, however, will not be passively stable -- instead, it will (like a ringworld or rigid Dyson sphere) require regular or continuous adjustment to stay in position, so the system doesn't veer off course or the reflector tilt enough to just fall into the star (that would be a bad year -- or century -- for all involved).
I'm no astrophysicist, nor even the ordinary earthbound variety -- I took physics in high school and college, but the non-calculus flavor. It's been forty years since I evaluated an integral, and nothing I've read about Shkadov thrusters suggests this -- but there have been laser pulse propelled technology demonstrators that were passively stable on the pressure wave from air expanded by the focused pulse.
So, is it possible to design a Shkadov thruster's reflector with a shape that would make it passively stable, allowing the "passengers" to continue obliviously on their journey (obviously without a turnover to decelerate)
[Answer]
**If by "passive" you mean not needing to expend mass in the form of reaction thrusters, then yes.**
A Shkadov thruster creates an equilibrium between the outward force of solar winds and the inward force of gravity. As the star goes through its cycles the levitative distance will expand and contract, but as long as the sun never flares up enough to push the reflector off into the orbit of a planet or lets it fall down enough to contact with the star itself, altitude variance won't be an issue. It will just mean that at some points in your journey you will be accelerating at faster speeds than others.
To maintain alignment, your relector just needs rudders and solar cells. Imagine holes in the reflector with rotatable reflectors in the gaps. As the main dish drifts off course, power collected from the solar cells can be used to rotate the rudders. These rudders will exert angular momentum on the reflector allowing it to correct its course. Your mega structure would then just need a basic AI to keep track of where it is going and to align the rudders accordingly.
**Now the tricky part is making a system that will not break down over the period of time in question.**
For this we can look to the concept of [Von Neumann Probes](https://en.wikipedia.org/wiki/Self-replicating_spacecraft). There is no way to make a Shkadov thruster (with or without rudders) that will all on it's own not break over the course of millions of years, but you can create an autonomous system for maintaining the Shkadov thruster using self replicating maintenance drones.
It is like this: Most organisms don't survive more than a few decades, but a species of organisms can survive for hundreds of millions of years. Unlike organisms, Von Neumann maintenance drones can checksum themselves (preferably using a majority rules, long-key hash check) with each replication ensuring that they never evolve; so, the drones made on year 1 are identical to the ones still made on year 10,000,000.
Using a combination of recycling and the resources of the uninhabitable planets, moons, and asteroids in the system, your drones will be able to continuously collect everything they need to keep the engine running without ever having to visit the inhabitable worlds or ask anyone for instructions on how to do thier job.
[Answer]
**Spin the star.**
It takes more energy to change the direction of a spinning object in the axis perpendicular to its rotation. This is [spin stabilization](https://en.wikipedia.org/wiki/Spin-stabilisation) or gyroscopic stabilization, and it is why it is easier to stay upright on a moving bicycle - the spinning wheels act to gyroscopically stabilize the bike. Spin stabilization is used for spacecraft and satellites. Also rifled bullets, which are a great example of passive stability. No-one steers a bullet in flight. Maybe body English but that is it.
To spin your star, you will divert some of your thrust to exert a tangential force. Probably a number of these around the star would make sense to make sure they are not asymmetrical. Your spinning star will resist course changes. A good thing about this - your star is probably already spinning to some degree. Use that!
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Dunkleosteus terreli might be the most well known species of placoderm by general media. Having inhabited the devonian seas, this impressive predator possessed an unique four bar linkage jaw mechanism, which allowed not only for powerful bite, but also for a very quick opening, fast enough to essentially creating a suction force that would drag prey closer to its fearsome Jaws. This creature could fully open and close its Jaws in less than a second, and had a bite force rivaling that of modern crocodilians and the T-Rex in terms of pressure.
Given this prehistoric fish's incredible capabilities, I'd like to use a similar concept to its plated Jaws and four bar linkage system. The issue here is that what allowed the placoderm to employ such a system was the lack of a neck ([skull moves while the body armor stays still](https://vimeo.com/52435226)), which is not the case of my land predator, which is a long snouted, bipedal tetrapod around the size of a deinonychus. To try and solve this issue without making the creature neckless, I tried to make use of 2 bony crests in the back of its head and around it's neck, which would then serve as the anchoring points for the necessary muscles and move along with the lower jaw (they're not directly connected to one another, as to allow for a greater degree of up and down neck articulation, but that can be changed Should it make the system more efficient), as seen in the rough sketch below:
[](https://i.stack.imgur.com/ikyAl.jpg)
*red indicates the location of the main jaw muscles, black indicates the skeleton, green indicates where the tree neck vertebrae would be, the 2 crests are represented in the crude sketch below (Sorry if it's rough, I don't have much experience in drawing and couldn't draw the back facing structure properly)*.
The reason for this landbound animal to need a powerful bite and fast opening is it's planet's wildlife, which, due to the denser atmosphere when compared to earth, is largely composed of gliding and flying creatures somewhat similar to pterosaurs, which mostly live and rest near the top of large trees. The dunkle predator in question makes use of its camouflaged skin to climb the trees mostly unnoticed, approaching its prey. Once it's as close as possible, it extends its 20-vertebrae, relatively long neck like a snake or a heron, performing the Jaw cycle and chopping off a limb or other body part of its soft prey, allowing an immediate amount of food and usually making the victim easier to catch. Due to its bright colored mouth and tongue, used to scare off predators, it usually keeps its jaw closed until the last moment (the atmosphere might be denser, but it's not nearly dense enough for the mouth opening to provide a strong suction).
**My question**: Could this attempted variant of a four bar linkage jaw arrangement still be functional? In other words: could it allow for a similar bite force and opening speed as seen in a dunkleosteus from the same proportions? I'd also be glad if an estimated maximum gaping angle possible for this jaw model was also included, as I couldn't find any information regarding the maximum gape of this fish, making it tough for me to make an estimate (though it seemed from models like it was at something between at something between 70 and 90 degrees).
Note: the reason for me choosing this mechanism lies not in the use of suction force, but in combination of a powerful bite and the extremely fast opening that would result in such auction within the water to begin with. This creature does *not* use a suction mechanism to hunt on land.
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Since it has already existed in history, the structure has a basis for existence. To work on land though, it's suction would have to move a lot more air, as the flying creatures would be able to counter any light suction (they already deal with small pressure variances while flying). Because Air has less drag, the animal would have to move a lot more air if that makes sense. The beast would have to have a supplemental air pocket, sort of like a bull frog's throat, or how many animals have the ability to use stored air to seem larger (often for warding off predators or to attract females) to move vast amounts of air to create the suction.
The maximum gape angle seems to be Allosaurus at 80 deg. but this would require a much larger suction system as it has a much larger area it needs to apply suction to. I would suggest having a gape angle at 43.5 deg, similar to the erlikosaurus andrewsi. Still extremely large, but small enough to accurately direct the suction ability.
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I am interested in world building of a alien biospheres, as is done for example in [Alien Biospheres](https://www.youtube.com/playlist?list=PL6xPxnYMQpquNuaEffJzjGjMsr6VktCYl) series. In this context, I would like to know some rule of thumb how to estimate number of animals living on certain area. I found a great resource to answer the question on the [world-builders.org](http://www.world-builders.org/lessons/less/biomes/SunEnergy_good.html) pages. Their recipe is the following:
1. Different biomes produce different number of kilocalories per year per $\mathrm{m}^2$ in plant production. For rain forrest, we get 9000 kcal / year / $\mathrm{m}^2$, while for example for savanna, we get approximately 3000 kcal / year / $\mathrm{m}^2$.
2. Only 10% of this production is transferred to Tier 1 consumers (herbivores). So if there is 3000 kcal / year / $\mathrm{m}^2$ produced in plants in savanna, there should be 300 kcal / year / $\mathrm{m}^2$ produced in bodies of herbivores.
3. Only 10% of this production is transferred into bodies of Tier 2 consumers (carnivores eating Tier 1 consumers). We can continue in the same way into higher tiers.
What I like about this rule is that is allows answering question like: "What will be average number of bisons in certain area?" and similar. As a cross-check, I tried to calculate maximal number of cows that can live on certain area of a pasture. The pasture is similar to savanna and we therefore can expect approximately 300 kcal / year / $\mathrm{m}^2$ in bodies of cows. Since meat has caloric density cca 3000 kcal / kg and since a cow weighs approximately 700 kg, we get cca **0.6 cow per acre per year**. So far, the rule works very well.
However it fails horribly, when applied fir example to number of rodents on the fields. By the same calculation, with mouse mass estimated to 27 g, I am getting cca 15 000 mice per acre per year. Even for bigger rodents (270 g), I am getting 1500 rodents, which is way too much. The real mice density is somewhere between [15 mice per acre](https://www.researchgate.net/figure/Rodent-density-estimates-D-as-rodents-per-hectare-1-SE-by-species-together-with_tbl5_237725934) and 50 mice per acre. Of course, unlike with the cows, the rodents do not consume all the fields production, but is still seems like a significant over-estimate, since they would need to eat only 0.1% - 1% if the whole production.
My question is: **Why does the model fail for small herbivores and is there a better model which I could use?**
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The comments on your question do a good job of framing the issues with your approach for smaller animals. There are three ways you can look at this question.
**1. Back of the envelope math**
This is your current approach. This can give you rough numbers that should act as a sanity check. You're using the caloric content of an animal, which is closely related to its mass. In a [study of forest mammals](https://www.journals.uchicago.edu/doi/abs/10.1086/284596), body mass accounted for more than half of a species' population density. But that still leaves a lot of room for error. To get more accurate, you can look for studies into the total biomass supported by different environments, e.g. [Equatorial Rain Forest](https://www.jstor.org/stable/5128?seq=1).
**2. Species-specific calorie estimates**
If you want to get more specific, look at the actual data for different species. If you're creating a new species in your alien world, you can base them on Earth species. For example, there has been research into [mice](https://www.ncbi.nlm.nih.gov/books/NBK231918/), [pigs](https://www.google.com/books/edition/_/myQeL_v_i7sC?hl=en), [poultry](https://www.google.com/books/edition/_/bbV1FUqRcM0C?hl=en), [small ruminants](https://www.google.com/books/edition/_/1FZOX5oQ7MUC?hl=en), and other animals.
**3. Count the number of animals in different contexts**
If you want the most accurate estimates, you can look at how many of a given species actually live in different types of environments. This is the least flexible approach, since slight changes in the animal or environment could result in very different numbers. There have been population counts of wild [rats](https://www.jstor.org/stable/3669272?seq=1) and other animals.
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For a book that I'm working on I am plotting out various points in time to make sure my plot is following accordingly. I apologize in advance for the lengthy post. It is a fungus-like infection that spreads in a few ways:
* Animals infected with the disease tend to not display deadly symptoms but instead act as carriers for the fungus, mutating in ways to help the spread of it. Birds with droppings of the fungus, on trees the fungus develops into conks
* Direct contact with the fungus can result in infection, especially through open wounds
* Humans infected with the disease develop fruiting bodies in their lungs, where the disease likes to grow. The fruiting bodies release spores in their breath and in coughing fits, which can infect humans in a relatively close proximity
Incubation Period - 0-1 days and the person is contagious, 3-4 days and the person is symptomatic, 5 - 7 days they are severely ill, 7-8 days they are dead.
R-Naught of about 20. Approximately 0.5-1 percent people are immune.
Symptoms - At first, standard cold symptoms, coughing, sneezing due to nasal passage irritation. Near end-stage, progressing to massive lung inflammation, blue veiny rash on the chest, coughing up blood, organic material like particulates, bloodshot eyes, paranoia in some if it gets into the brain stem. Upon death, the disease continues to grow throughout the body, consuming it for energy and in less than two days the fungus breaches the chest, mouth, etc releasing spores.
Timeline:
* Day 2 - Several people are exposed to the disease in Michigan, Illinois, and Indiana via direct contact with the disease along the coastline. The disease has also infected a group of approximately 20 people in Belarus. Estimated infected 100 - 200.
* Day 4 - Contagious individuals have spread the disease, some are starting to show symptoms of a nasty cold. Thousands are infected, but only a few are showing symptoms at this point that are warranting a healthcare visit. The disease has spread to the West Coast through airfare out of Chicago, as well as Atlanta, New York City. On the European side, several more are infected as families are exposed by the group, mainly in the baltic region.
* Day 6 - Approximately 50 deaths reported throughout the midwest from an unknown disease. CDC is investigating, WHO has been made aware. Concerned with the spread of a similar disease in the Baltic region with 20 deaths.
* Day 10 - Deaths are being reported with increasing intensity (100+), but the CDC / WHO are reluctant to give official numbers. Downplaying the severity to avoid panic. Social media is tweeting about it being more severe than that are letting on and that there are reports that people are getting sick in various locations throughout the country now, but tweets are being deleted. Surge centers for support are being set up in some major cities to assist with the influx of patients. Several locations are closing early due to lack of staff in restaurants and stores.
* Day 11 - Many people are attacking similar to preparing for a natural disaster like a hurricane, grocery stores are having problems keeping things in stock. Video leaks on twitter showing the fungus-like growths on a human body from the morgue of a hospital in Chicago. Twitter blows up, the original tweet gets taken down, but copies have already been made and are spreading. At night the CDC / WHO gives a press conference explaining the leaked video since their hand has been forced. Explaining that the cases are related to a disease never-before-seen, confirming the cases spreading throughout Europe and the States seem to be related. Quarantine measures are being put into effect immediately in several of the major cities (more of a public show of effort because they know it's too late to really try and control this)
* Day 14 - Thousands dead, work has been suspended in the city of Chicago, and in several cities. Riots are breaking out near hospitals and in major cities. Surge centers cannot keep up. Due to the fungus-like nature of the disease several pharmacies are being raided for anti-fungal treatments even though it doesn't really help. The fungus is spreading into several other species at this point, showing up in trees as a lichen style fungus.
That's the detailed timeline as is.
Is this timeline, given the background of the disease, realistic?
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**No, because your R-Naught and Incubation period are not consistent with each other.**
I'll stress here that I am not an epidemiologist by profession and what I know about the topic comes from the research I've done in the past in related fields, but my sense of it is that your R-Naught figure is very high for such a short incubation period and symptomatic phase.
The first thing I need to do is articulate an assumption I am making in this question because it's not explicitly mentioned - I'm assuming a mortality rate of 100% given that you haven't listed one and death is mentioned as the 'final stage' of the symptomatic timeline.
Second, I have to point out that the R-Naught figure you have mentioned is [higher than Measles](https://www.healthline.com/health/r-nought-reproduction-number#conditions) (for example) which is believed to have an R-Naught between 12 and 18. Measles has an incubation period (from initial infection to the onset of rashes) of around 14 days on average and the infectee is infectious to others from around 2 days in. With your disease, your patients are long dead by then. That matters because the extra time means more people you can be around and infecting them without realising it. In this disease, that's much harder to do. Also, you don't need a large R-Naught to still cause big problems in any event. Just look at some of the other truly terrible diseases on the list and you can see that an R-Naught of 2 can do enough damage for people to take notice, especially with such a short incubation period.
Thirdly, it is important to note that with 100% mortality rate, even a highly infectious disease, while devastating, is going to burn itself out once people twig and put in adequate quarantine. The powers may sacrifice a city in the end, but it will be contained by virtue of the fact that the disease acts so quickly that people literally don't have time to get out of dodge and find themselves symptomatic and therefore subject to quarantine procedures too quickly to be able to act in a way that is going to cause massive spread.
That said - If the R-Naught is correct, the numbers you're describing are consistent with that but I just don't see it spreading to the level you describe with such a short incubation window. I do however see it taking out Chicago and a couple of other areas to which it spreads before the lockdowns go into effect but with such a short incubation window a lot would have to go wrong for this to go global.
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**Short question:**
which hormones should high contagious fungi spores produce to make their human host spread the joy and infection (by hugging and kisses) on early stages of infection, and become paranoid, irritable and bloodthirsty or suicidal lunatic on later stages of infection?
**Long story:**
Few hundred crazied eco activists (called druids) tries to fully wipe Victorian England level tech civilization - lets call them Atlantis Confederation - which is located on Europe sized archipelago with one major city spreading 400km on shore of some internal sea, and lot of small, rural settlements on this and other islands.
Islands are joined by bridges, with steam train and ferries travelling from one place to other, and, it can took ~ 1 week to cross Atlantis Confederation from shore to shore by train. So, majority of terrain of Atlantis Confederation is like rural area, where you can pass by 3-4 towns during single day walk.
Crazied eco activists uses biologically engineered (with some handwavium) fungus spore as their main weapon, and their own bodies as vessel for this.
In body of eco activist, fungus slowly breeds, maintaining save (for eco activist) level of toxins and only manifesting in strange dark spots on skin. But, on same time, this fungus maintains high level of virulence, so if you, for example, hug eco activist, you will be 90% infected. Also eco activists has lot of bottles with concentrated fungi solution, they can spill it in potable water sources like wells, water towers, even beer kegs.
Its worth notice, that, fungi survives in beer or wine, but, of course, is killed by boiling water like majority of fungi.
First stage of infection - usually nothing happens, in few rare cases there is fever, headache, insomnia, hallucinations, but, in general, its hard to detect. After few hours, you start to spread infection like eco activists.
Its worth notice, that infected person regains some reasoning, so there is 1-2 people per 10.000 who will try to lock themselves to stop spreading infection, and probably 1-2 totally immune per 100.000.
Second stage of infection - is irrational manic joy, you want to kiss, hug and befriend with anybody, you look like happy drunkard. With happy smile, blank face, clumsy movements. And, on same time, you spread infection with every touch and kiss. On this level, you have drunk person grade mind, you can recall friends, can talk and do things, but, much worse than sober or healthy person. Most important, you don't look dangerous. Eco activists has mystical ability to sing chants for Forgotten Gods to prolong 1st and 2nd stages of nearby infected for extra few hours, but if they stop, next stage occurs in less than few minutes.
After some time (depends on infected condition - at least 24 hours), 3rd stage of infection starts. Terrible hallucinations occurs, depression, paranoia, pain comes. Infected either panics and jump from rooftop while running from their imaginary "friends" or cut away their leg, because this appendage is plotting to kill them, or they fire bullet into their head to silence voices or stop headache. Also, lot of infected kill each other, because they start to be both easy irritable and paranoid.
Some "lucky" infected, can roam for months as savage beasts killing everybody they can, like "28 days later" turbo zombies, but with animal level intelligence enough to eat something to stop hunger, and carry and use clubs as weapons to protect themselves and prolong 3rd stage of infection.
Its worth notice, infected spread disease too, but less efficient.
For the luck of eco activists, and peril of Atlantis Confederation citizens, they have Harvest Day festival - approx one week of gluttony, drinking and raving, with nearly 99% of people celebrating - even convicts in prisons are granted some buzz. So, with celebration happening, people are unlikely to notice something weird happening. See it like mix of Christmas, Black Friday, Woodstock and Octoberfest.
Even if you break in Count Victors manor, who, as Major of South Bayguard town, has high tech Telephone device with direct wire connection to nearliest military fort with 52th Her Majesty Yellow Sharpshooters division, or you even manage to dial Her Majesty Telefonimeister (very noble and important person who answers phone calls for Her Majesty), and scream something like "our beer is poisoned, people are killing each other!!!", they will advice you to go to sleep and stop drinking for today.
**So, question is:**
which hormones should this fungi release (or make it human host release) on each level of infection? 1st phase of manic joy is mandatory. 2nd stage - it can either be primal rage, paranoia, hallucinations - probably variants of "fight or flight" behaviour.
**Some background:**
Probably, its not related to question, but it can give few insights how this fungi can alter behaviour. Probably, 1st latent stage, 2nd manic stage, and 3nd lunatic stage is not the deadliest combination.
Because in plot it will be used like this:
Few groups of eco activists hijacked trains in one day before Harvest Day Festival started, and then, they travel as roaming circus performers (because Guild of Railroad workers has vacation and no trains going), they arrive in city, and lure pretty ones to become good bait and carriers on 2nd stage of infection, and physically fit or capable ones as eliminators on 3rd stage of infection. On the same time, they try to poison all drinkable water and food supply they can. After few hours of roaming circus performance, they gather chosen infected on 2nd stage, and travel with them by train to other town. They repeat it until
all population they can reach is infected. Consider eco activists has few times more bottled fungi solution they calculated they should require. They have good planning, and Atlantis Confederation has good railroads, so its possible every town with more than 1000 people in it has few infected roaming streets for middle of Harvest Day Festival celebration. And, Eco activists do not plan to return from this mission.
**UPD:**, as mentioned by @Wrzlprmft, i'm aware of [Ophiocordyceps\_unilateralis](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis) - real world fungus making zombies from ants, but human is not an ant.
And i'm aware of Clickers and Cordyceps from [The Last of Us](https://en.wikipedia.org/wiki/The_Last_of_Us) game, but i want infected to be much more human and look much less dangerous, to make my setting less boring compared to any other zombie apocalypses ones.
[Answer]
Short answer : [Hormones and Chemicals Linked with our Emotion](https://www.amrita.edu/news/hormones-and-chemicals-linked-our-emotion)
*Everything you need should be found in that link, including any information you need to fine tune your description of the effects .. find the hormones most closely associated with effect you want then adjust your expectations of the pathology & symptoms to match their effects.*
Here's a [Google search](https://www.google.com/search?rlz=1C1NHXL_enGB711GB711&sxsrf=ACYBGNQlE2nqHSiDF14WdMPIGhpaiZOEyA%3A1575607773412&ei=3d3pXaToGKHDxgPhtJy4Cg&q=which%20hormones%20contribute%20to%20which%20emotions&oq=which%20hormones%20contribute%20to%20which%20emotions&gs_l=psy-ab.3...5159.8039..9544...0.3..0.97.1203.14......0....1..gws-wiz.......0i71j33i10.25SDql_Vrbw&ved=0ahUKEwjkyo6tnKDmAhWhoXEKHWEaB6cQ4dUDCAs&uact=5) that should get you other appropriate links to read.
] |
[Question]
[
I have a planet orbiting a red dwarf and, as expected, it is tidally locked to its star. I know that these planets will have a very significant temperature difference between the diurnal and nocturnal hemispheres, but I want to know how different it will be, that is to say, what will be the average temperature of both hemispheres if you take into account the warming of the diurnal side and the cooling of the nocturnal side. Is there any way to calculate it?
---
Keep in mind that:
1. The host star has a bolometric luminosity of 0.01 (Sun=1).
2. The planet's insolation is 4.85 (Earth=1).
3. The planet's semi-major axis is 0.05 AU.
4. The planet has an argon atmosphere, with small amounts of other gases (CO2, CH4, NH3, etc.).
5. The surface gravity is 0.75 (Earth=1)
6. The surface atmospheric pressure is 0.6 atm.
7. The albedo of the diurnal hemisphere is 0.4 and the albedo of the nocturnal hemisphere is 0.9 (Bond albedo).
8. The equilibrium temperature of the planet is 356 K for the hemisphere with the albedo of 0.4 and 228 K for the hemisphere with the albedo of 0.9.
[Answer]
You asked "Is there any way to calculate it?". The answer is yes, but it's not going to be as simple as plugging a few numbers into a simple formula.
You'll need a [general circulation model](https://en.wikipedia.org/wiki/General_circulation_model).
The reason is that the heat transport around the planet involves the atmosphere and the oceans, and these require dealing with fluid dynamics. This is going to bring in dependencies like the topography of the planet (the wind is going to be affected by obstacles such as mountain ranges, likewise the oceans are going to respond to the shape of the ocean basins). And just to make things worse, the oceans and atmosphere are coupled. You'll also need to deal with annoying things that aren't very well constrained, like cloud formation, which affects the albedo of the planet.
Needless to say, this is rather computationally intensive (do you have a supercomputer to hand?), and even if you find an available GCM you'll likely have to do a lot of modifications so it can be applied to a tidally-locked exoplanet, especially if the atmosphere is non-Earthlike as well.
One model I've seen being used for a bunch of exoplanet studies is LMDZ4, as used e.g. for [Proxima b](https://arxiv.org/abs/1608.06827). Not sure if the source code is freely available though and even if it were, I'm not sure whether it would be executable on standard desktop hardware.
Otherwise you could try to fudge it by throwing in a simple redistribution factor and emissivity into the usual effective temperature formula. With stellar luminosity $L\_\ast$, planet-star distance $d$, emissivity $\epsilon$, albedo $A$ and the fraction of energy distributed to the nightside $f \in [0, 0.5]$ where 0.5 means an equal fraction of energy distributed to both hemispheres, equating received and emitted power and you end up with:
$$\begin{align}
T\_\mathrm{d} & = \left[\frac{L\_\ast (1-A) (1-f)}{8 \pi d^2 \cdot \sigma \epsilon\_\mathrm{d}}\right]^{1/4} \\
T\_\mathrm{n} & = \left[\frac{L\_\ast (1-A) f}{8 \pi d^2 \cdot \sigma \epsilon\_\mathrm{n}}\right]^{1/4}
\end{align}$$
Where $\sigma$ is the Stefan-Boltzmann constant. The d and n suffixes represent the day and nightside, and I've allowed for different emissivities of both hemispheres (e.g. due to cloud buildup on the dayside versus clearer skies at night).
But figuring out what the appropriate values for $A$, $\epsilon\_\mathrm{d,n}$ and $f$ are basically requires doing things properly.
---
Derivation of the formulae:
For a planet orbiting at distance $d \gg R\_\ast$ where $R\_\ast$ is the radius of the star (i.e. negligible illumination of the far hemisphere, light rays can be treated as parallel), the fraction of the power output of the star intercepted is the ratio of the area of the planetary disc, $\pi R\_\mathrm{p}^2$, where $R\_\mathrm{p}$ is the planetary radius, to the area over which the star's radiation is distributed across, i.e. a sphere of radius $d$, which has area $4\pi d^2$. The albedo $A$ represents the fraction of this reflected back into space, so the absorbed power is:
$$P\_\mathrm{abs} = L\_\ast (1-A) \left(\frac{R\_\mathrm{p}^2}{4d^2}\right)$$
For the planet to be in equilibrium, the power radiated must equal the power absorbed. Assume the planet has two hemispheres, with uniform properties across each hemisphere. Energy balance gives
$$P\_\mathrm{rad,d} + P\_\mathrm{rad,n} = P\_\mathrm{abs}$$
So representing the fraction of the power transferred to the nightside by $f$, we can write:
$$\begin{align}
P\_\mathrm{rad, d} & = (1-f)P\_\mathrm{abs} \\
P\_\mathrm{rad, n} & = fP\_\mathrm{abs}
\end{align}$$
The next stage is to write the greybody emission law for each hemisphere. The total area of each hemisphere is $2\pi R\_\mathrm{p}^2$, the power per unit area at a given temperature $T$ is $\sigma T^4$, and we scale by the emissivity $\epsilon$:
$$\begin{align}
P\_\mathrm{rad,d} & = 2\pi R\_\mathrm{p}^2 \cdot \epsilon\_\mathrm{d} \sigma T\_\mathrm{d}^4 \\
P\_\mathrm{rad,n} & = 2\pi R\_\mathrm{p}^2 \cdot \epsilon\_\mathrm{n} \sigma T\_\mathrm{n}^4
\end{align}$$
Substituting these expressions into the previous ones gives the formulae in the text above.
] |
[Question]
[
Assume an Earth-Clone, that has an axial tilt of 90°. How would the circulation of the atmosphere look like? Would there still be three convection cells?
[Answer]
So the axial tilt doesn't actually influence the number of convection cells very much, afaik. It *does*, however, [affect their position](https://youtu.be/J4K3H9aNLpE). You might also want to note that a world with a 90° axial tilt would essentially present on side to its star half the year and the other half the rest of the year. That means a long day which is summer and a long night which is winter. This leads to some EXTREME weather patterns that until recently were though impossible to overcome (well, at the very least it was thought to be the case for tidally locked planets, but recent simulations show a fast enough spin can compensate that effect).
In the case of a 90° planet, the spin will have no effect on spreading the extra heat from the day side though, because the axis faces towards or against the sun for roughly half of the year (and it faces perpendicular the other half). This means that half of the year, you'd have heat trapped in the day cycle either on one side or the other depending if you take the winter or summer quarter. This could be mitigated if you have a short enough year but then you'd run into problems of star size with instability that features coronal ejections and lethal rays so… maybe not a good idea ([red dwarves are extremely unstable](https://www.universetoday.com/135945/even-calm-red-dwarfs/)).
What *would* affect the number of cells is [the rotation speed](https://youtu.be/LifRswfCxFU?t=3m56s).
] |
[Question]
[
I'm interested in the introduction of bacteria on Mars. If a small base were set up with attempts to maintain some sort of sterilisation protocols, but all the humans died on that base a) what would happen to the bodies and b) what would happen to the bacteria contained within the bodies themselves?
[Answer]
Mars is a *very* dry place, so the bodies would quickly desiccate. (About the only way this could be escaped is if the bodies just happened to be positioned partway down the equator-facing wall of a crater which happens to intersect water-bearing strata just as they produce some of their rare seepage... In other words, not very easily.)
The desiccation would stop all microbial life and the body would effectively mummify as bodies have mummified in desert areas on Earth when undisturbed by animals -- remember that Mars is nearly everywhere drier than Terrestrial deserts. Desiccation would be very quick: days, not months.
What would happen afterwards? First, some bacteria respond to desiccation by going onto a spore stage. I don't know if any of those are the bacteria commonly found in tissue, though it seems unlikely since tissue-resident bacteria would not need that adaptation very often. But maybe some do.
If the mummy later encountered water -- a rare surface flow or water from a future terraforming project -- some bacteria might re-activate and go on about their lives, munching away on the organics until either the organics or the water ran out. Then they'd go back to being spores with little chance of a second revival.
The countervailing effect is that the Martian surface is dangerous to life in other ways than simple dryness. Highly oxidizing compounds such as perchlorates are [common in the Martian soil](https://en.wikipedia.org/wiki/Life_on_Mars) and these would oxidize the mummy's organics. (I can't estimate how quickly, but probably more quickly than air oxidizes mummies on Earth.) They'd also instantly kill any bacteria or bacterial spores they encountered.
Additionally, UV radiation is strong, and this also would tend to destroy organics on the surface.
Probably the best chance of long-term survival would be if the body was covered by a dune which would shield it from the UV and leave it in unchanging soil so that once the nearby perchlorates (etc.) were used up, what was left would probably remain for quite a while.
But even bacterial spores are not eternal -- DNA degrades from random molecular motion and quantum mechanical effects -- so that there is some limit after which even the most carefully preserved spores would not revive.
The sterilization protocols strike me as more of self-sustaining a bureaucracy than as a needed precaution. (Especially since rocks from Earth probably are thrown to Mars fairly frequently.)
[Answer]
Bacteria will stay alive as long as it receives resources. Like any other organism, bacteria also needs oxygen, water, and resources to produce amino acids. These are necessities. So after using all the resources of the dead body, the bacteria will die.
If you are asking if bacteria can evolve and survive, that would be a topic of research and sci-fi.
] |
[Question]
[
Humans have come and gone. Their aggressiveness and pride have caused their own end. War has torn apart all society, engineered diseases pick them off one by one. The last remaining people have fled to the corners of the world. Some say they still live there, hunting and growing crops in primitive villages in the far-flung lands of Siberia, parts of Canada and Alaska, and Oceania. But as far as the rest of the world is concerned, they are long gone.
And the next ones up for civilization are the ungulates.
Many hooved animals already have fascinating and large social structures, and with the disappearance of their largest predator they have started to take on the task of society. Flocks of sheep rule the empty farms. Deer herds patrol the forests. Mustangs wage war against each other. Everyone is competing against their enemies for food, shelter, and safety. Fighting the huge buffalo and horses would be suicide for the weaker species, so they turn to cunning. The race for survival becomes a race of smarts and inventions start to form. Goats make herbal medicines, buffalo find out how to sharpen their horns. But even with the most advanced of innovations, the question still lingers:
How far can these fingerless ungulates advance? At what point is the limit?
[Answer]
Give enough time they should be able to catch up to humans.
Most complaints i read so far seem to focus on them having hooves and not hands. fortunately hands are not the only prehensile appendage. Ex Giraffe's have prehensile tongues, and horse have prehensile lips.
<https://en.wikipedia.org/wiki/Prehensility>
If they evolve quick enough they might be able to piggyback off or what little human technology is left. Of course they might not be able to use human screwdrivers, but that does not mean they would not create a screwdriver that they can hold.
[Answer]
First thing's first. They absolutely need to lose the hooves on their front limbs. Fine manipulators are essential for technology.
The first species to do this will have such an extreme advantage over the rest that I find it extremely unlikely they will coexist very long. The tool-using ungulates will quickly domesticate or exterminate the non-tool-using ungulates. Even if it is a small species that figures it out first; paleolithic humans dealt with mammoths pretty effectively.
As for things that will be different from human evolution here's a few:
* They may have no/little need for clothes. Most will have enough fur and thick enough hides that it's unnecessary. This will limit some species' ranges a little at first however, until they figure out shaving. Sheep would cook in the desert.
* I have no idea what ungulate furniture would look like. How do they sit, given that their legs bend the other way? This could affect vehicle development.
* Big ungulates like horses will probably have little use for work animals. This might hamper mechanization. Without thousands of years of experience using animals to turn axles in mills and pump-houses, they might never get the idea to use water or steam to turn axles. Technology is a tree, like in the civilization games, except in real life you don't know what is down the branches you've ignored.
* Trade might be reduced a great deal. Ungulates have pretty narrow diets compared to humans. They won't be as interested in eating exotic foods as we are. If they don't need clothing, textile trade won't interest them either. With reduced trade comes reduced spread of knowledge.
* Ungulates all have their eyes off to the sides of their head. This means they have poorer vision, but of a much wider field of view than a person. This means they will likely have difficulty reading, writing, or fighting with projectile weapons.
[Answer]
As others have mentioned: fine object manipulation, and sight are probably the two biggest problems.
I doubt any species would get past stone tools and sharp sticks.
To make a complex spear you have to be able to do small things like split a stick to insert a broken rock, and make and use cordage to bind it. I don't think cordage would be very plausible. Imagine trying to split a stick without breaking it with one eye closed. Try tying a knot in a cherry stem with your tongue.
At most, they'd probably use their natural defenses like you mentioned, or use rocks as hammers, potentially broken rocks as knives, and sharp sticks as spears.
As a general note:
I would suggest you take some time to think through why these animals would have all suddenly evolved to sapience, and why herbivores would suddenly take on predatory habits like war.
Predatory action seems to be a common driving force (not the only, but arguably the most prevalent) for intelligence in the animal kingdom. Dolphins coordinate to trap schools of fish, way more than to evade sharks.
War seems to be a reaction to resource (food) scarcity. You'll need to come up with a plausible reason for grass-fed herd animals to decide to fight each other over the Great Planes, for instance, when they could plant and grow crops of their own(elephants do this). This is especially important to nail down, since humans have already deforested and converted a huge percentage of the world to be viable for crops and grasses.
[Answer]
They could definitely grow to be technologically advanced, in spite of their lack of fingers. You just have to be creative, and think in terms of big objects instead of small ones.
To begin with, they start breaking rocks into various shapes by stomping on them, pushing them with their noses or feet, stacking them, and then stomping them some more. It's precarious work, requiring lots of prior planning to make use of hard, precision blows, but before long they have stone objects that they can either fit around their feet by pressing into them, or the objects might have blades sticking out that pierce the hooves like horseshoes.
Not only that, but they are able to produce furnaces by hollowing out large boulders (by putting rocks on the boulders and then stomping them) and stacking wood inside them. Then they stack flint and stone just outside the furnace and stomp on it to produce sparks, and with a little work, it's a furnace!
Once they have furnaces, they can start producing charcoal and coke, which will enable them to make much hotter furnaces and eventually start melting stones in them. Before long, they are cooking metal in large stone (and eventually metal) cauldrons and pouring it into large, carefully chiseled molds.
Supposing they use this kind of thing to make armor, they may need to help each other get dressed, but dressing ourselves with armor or utilities is a habit that humans take for granted, and isn't a necessary component of an advanced society.
Now they've got metal of any shape, wool, and basically the capacity to start farming. They can melt sand to produce glass, and carefully bend metal and heat it to produce kindof makeshift straws for blowing the glass. Once they start refining copper and glass, they can rub wool against the copper to produce static electricity and then store it in (large again) glass vacuum tubes that they've just blown using big, horse adapted glass blowing stuff.
Leather is, I guess, out of the question, but it's not necessary. We've got electricity now, and it's only a matter of time before they start doping large transistors. They'll never have computers with little keyboards like we have today, but they might eventually have monitors with hoof-adapted stomping-interfaces.
Screws are by no means the only method for joining things together. The hooved society would likely just not make use of them for a very long time, if ever. They'd more likely use wedges and compression to friction-lock things together. Eventually, they might even make sap and horse hooves into glue.
We've seen humans do some pretty amazing stuff without any hands at all. If horses wanted, they could get pretty dextrous with their front limbs. I see no reason they couldn't advance significantly with enough time.
] |
[Question]
[
[Cross-linked polymers](https://en.wikipedia.org/wiki/Cross-link) are vitally important materials used all the time in modern life.
For example, the resins used in composite materials are usually some type of cross-linked polymer.
What type of cross-linked polymers could be made by people with access to pre-industrial technology?
The only one I can think of would be [ebonite](https://en.wikipedia.org/wiki/Ebonite), made by heating natural rubber with sulfur.
[Answer]
Keratin is the main protein comprising hair, wool, and fur. It owes many of its structural properties to the crosslinking between polymeric keratin chains.
<https://en.wikipedia.org/wiki/Keratin#Disulfide_bridges>
>
> Disulfide bridges In addition to intra- and intermolecular hydrogen
> bonds, the distinguishing feature of keratins is the presence of large
> amounts of the sulfur-containing amino acid cysteine, required for the
> disulfide bridges that confer additional strength and rigidity by
> permanent, thermally stable crosslinking[21]—in much the same way that
> non-protein sulfur bridges stabilize vulcanized rubber.
>
>
>
One can manipulate these crosslinks with a permanent wave - crosslinks are relaxed with a chemical and heat, then the chemical is neutralized and the crosslinks reform in a new configuration - curling straight hair or uncurling curly hair. The permanent wave is a recent invention, but people have been manipulating the crosslinks in wool this way for millennia. The tremendously useful product: **felt**.
<https://en.wikipedia.org/wiki/Felt>
>
> Felt from wool is considered to be the oldest known textile.[4] Many
> cultures have legends as to the origins of felt making. Sumerian
> legend claims that the secret of feltmaking was discovered by Urnamman
> of Lagash.[5] The story of Saint Clement and Saint Christopher relates
> that the men packed their sandals with wool to prevent blisters while
> fleeing from persecution. At the end of their journey, the movement
> and sweat had turned the wool into felt socks.
>
>
>
Wool felt is dense, durable, warm and useful to humans in many ways. It is not hard to make. You can make clothes, tents and blankets out of it. Your pre-industrial folks will have felt.
[Answer]
Spider silk is complex and mechanically amazing. The tensile strenght is great.
Otters teeth are mixed with Iron, thus the colour and resilence.
As many animals and plants can create the raw materials, why would your world be bereft of those resources?
] |
[Question]
[
**Closed**. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers.
---
**Want to improve this question?** Update the question so it focuses on one problem only by [editing this post](/posts/113011/edit).
Closed 5 years ago.
[Improve this question](/posts/113011/edit)
**I have edited the question, and it is no longer too broad. My one and only question is the one shown in bold below. If you agree that it is not too beoad in this state, a vote to reopen would be much appreciated.**
Imagine that, somewhere, people start breeding seals for as companions, in the same way we did with dogs. I know that there are dog breeds for hunting, herding, fighting and others, but nowadays most people just get dogs for the fun of it.
Anyway, this civilization lives largely on a vast coastal network of waterways like this, except with more solid ground:
[](https://i.stack.imgur.com/UhKQ8.jpg)
In this environment, water not only exists as an ocean, lake or river, but winds everywhere through cities and towns, so that, in some regions, you would rarely be further than 100m from a body of water.
Since large areas of water are readily accessible here and seals are relatively common, they took the place of dogs in our society.
However, this was millenia before the time I have in mind now, and by now seals have been bred into a myriad of breeds for every conceivable purpose.
[](https://i.stack.imgur.com/yrpZd.jpg)
The ancestral species of seal is the harbour seal, *Phoca vitulina* (shown above). What I want to know is, **after thousands of years of selective breeding, what would othe domestic seals look like?**
That is the only question I am asking currently. This question encompasses morphological, pelage and other kinds of visual aspects. I know that the appearance of a domestic animals depends on what it was bred for, and these seals have **breeds for fishing, aesthetic appeal, swimming ability, fetching sunken objects and personal protection while at sea.**
I know this may seem broad, but what I mean is: **After breeding for those specific purposes, what changes might the seals experience and would there be any genetic obstacles to them achieving this?**
If you have any critique, complaints or suggestions for this question, please do say so, and I will amend it promptly.
[Answer]
Breeding of animals can result in changes that are both intentional and unintentional. Intentional changes are pretty straightforward. If you breed for a long-haired seal, you’ll get a long-haired seal. Presumably you are looking for information about how unintentional changes can occur as a result of breeding for other traits. This will happen and there are two primary mechanisms by which it will occur.
The first is that by selecting for certain traits you will also be selecting for unrelated traits controlled by the same genes. This is called [Pleiotropy](https://en.wikipedia.org/wiki/Pleiotropy). Many genes play multiple roles in an organism in different places and at different times in the body. Additionally, due to the complex nature of living systems changing one thing can often affect other seemingly unrelated things. An example would be that in the process of breeding for friendliness you might also breed for lower intelligence as perhaps those things might be correlated in the seal. In this way some related and potentially unrelated traits will be found with increased frequency in your domesticated seals.
The second mechanism is that selecting for certain traits also effectively selects for traits encoded by nearby genes. This is because when we inherit genes they aren’t all randomly shuffled. There is a [genetic linkage](https://en.wikipedia.org/wiki/Genetic_linkage) between genes near to each other on the same chromosome. Seals who inherit the gene you are selecting for are also more likely to inherit nearby genes on the same chromosome. So, if one of the genes for friendliness happens to be next to a gene for [Tyrosinase](https://en.wikipedia.org/wiki/Tyrosinase) and by chance the most friendly version of the gene happens to be linked with a non-functional version of Tyrosinase then breeding for friendliness will also breed for albino seals. Depending on just how strong the linkage is between these two genes you will get some proportion of crossovers that separate them and so could breed a seal that was not albino if you so desired. But the concept remains that by random chance some completely unrelated traits will be linked with the traits you are trying to breed for and so will show up in your domesticated seals.
So the answer to your question is that we can’t predict any specific phenotypic traits that will change in response to domestication, but we can predict that almost certainly some phenotypic traits will change.
[Answer]
They would definitely take on some morphological changes. After thousands of years of breeding that is inevitable.
You asked about the attempt to domesticate Foxes. Although the foxes in that attempt had unpredictable coat colors, that attempt to domesticate was not active nearly as long as "thousands of years". A chaotic gene expression would certainly be smoothed out and predictable after thousands of years of breeding.
On a meta level: What is the purpose to making your story so accurate in this way? Nobody except a few experts has memorized knowledge about the specifics of Seal genetics. You can really do whatever you'd like with seal genetics and no one except those few experts will have their immersion broken. If you want to have problems with the genetics in your story, that's fine. If not, that's fine too.
I should also mention that Harbor Seals are not very agile on land. They could be bred to have better land mobility, but there is an alternative critter that is already well adapted to both land and water: The Sea Lion
[](https://i.stack.imgur.com/rnI0l.jpg)
] |
[Question]
[
I've decided to draw maps, on these maps, I planned on drawing regions which already have determined areas (ex. Region 1 has 30.000 km²), the problem is, how would a measure a region's area on a map? Some territories have some pretty wild shapes, with many islands, which makes it very difficult to measure its area by common means. So I resorted to (bear with me) pixel counting, needless to say, that didn't work out too well, especially on bigger maps.
So I came here to ask if there's any program, app, or technique at this point, to draw lands whose size's have already been established?
Edit - I plan on drawing multiple territories, each with set areas, on the same map, so I can't draw one region and calculate it's area (on the map) then change the scale of the map so it would fit that one region's (actual) area, because it wouldn't fit the other ones.
>
> **EDIT (from JBH):** The "duplicate question" does not address the question of cartography software at all. This isn't a duplicate question, but it's closed, so it can no longer be answered. However, it's worth providing a simple link to help out people interested in software for drawing maps. Visit the [Cartographer's Guild list of mapping software](https://www.cartographersguild.com/showthread.php?t=1407), where you will find a great many pieces of software both paid and free. Cheers.
>
>
>
[Answer]
Download free AutoCAD or ArchiCAD - these will allow you to have free trials or demonstration versions which will allow you to import an image such as a scan of your countries.
Trace over the country and islands with a polyline (Autocad) or zone (ArchiCAD) and use the measure command (AutoCAD) or simply Get Properties (ArchiCAD) and it will calculate and give you the area. In ArchiCAD you could even give each zone a name, and it would automatically collate the areas for you in a list to get each countries total area.
Modern CAD programs are 'unit flexible', so you could use Kilometres, or millimeters or any unit of measure. Prior to doing the above, put a 'scale bar' on your sketch that is a certain length, so you could proportionally scale the image on the CAD program to give you the correct figures.
These programs are adept at handling tens of thousands of shapes, to any level of detail, so no matter how complex your map is it is possible to get an accurate result. As an example:
[](https://i.stack.imgur.com/HSSfs.jpg)
] |
[Question]
[
I have a crew that need to spend a couple years traveling via spaceship.
Because it's inefficient to have to provide every passenger with living-space and rations, I'd much prefer if it were possible to put them in some sort of stasis for the duration of the trip. Though not by means of cryonics. I'm not fond of replacing people's blood with antifreeze.
I was thinking more along the line of artificially inducing a state of extreme hibernation. The crew's metabolisms would be suppressed as much as possible and that way they'd only need a pods-worth of room and we might not even have to carry any food onboard at all. Stranger still, perhaps the aging process would almost entirely cease. This would be a good thing, because many people might object to wasting 2 years of their lifespans onboard a spaceship.
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So I'm wondering, **are these ideas plausible?**
* Can you slow an individual's metabolism to the point where they wouldn't need to eat for 2 years?
* Would doing so circumvent the normal aging process?
[Answer]
### Can you slow an individual's metabolism to the point where they wouldn't need to eat for 2 years?
Humans do not hibernate. The closest you can get to that is [medically induced coma](https://en.wikipedia.org/wiki/Induced_coma). This is not without adverse effects:
>
> Induced coma usually results in significant systemic adverse effects. The patient is likely to completely lose respiratory drive and require mechanical ventilation. Gut motility is reduced. Hypotension can complicate efforts to maintain cerebral perfusion pressure and often requires the use of vasopressor drugs. Hypokalemia often results. And the completely immobile patient is at increased risk of bed sores as well as infection from indwelling lines.
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Also notice that a person in a coma requires medical monitoring. Each subject would in the very least require a fully automated [intensive care unit](https://en.wikipedia.org/wiki/Intensive_care_unit). Alternatively, some of the people in the trip could forgo such suspended animation, so as to care for the ones in induced coma.
### Would doing so circumvent the normal aging process?
Probably not. There are some studies claiming that caloric restrictive diets (such as one would get while in a coma) slow aging in humans, [but those studies are disputed](https://www.sciencedirect.com/science/article/pii/S0891584914002317).
However, any civilization advanced enough to send humans in such a long trip to space should have more advanced science than we do in the real world. That could include better knowledge of how we age, so you can just handwave the part about people not aging significantly while in suspended animation.
[Answer]
There are quite a number of examples on earth of animals using hibernation to survive adverse environments.
* The polar bear is one for example: it buries itself under snow for a considerably long period.
* There are many insects which can do the same. The grasshopper is one example. It can survive subzero temperature for more than a year and fly right after the snow melts. It can even reproduce successfully after that.
What I mean by quoting these examples is that there are specific proteins that can help preserve cell architecture & form even after freezing below subzero temperatures. Human bodies could hibernate if injected with one of these proteins before sending them off to another planet.
Repeated injections may be needed as a foreign protein will degrade. Obviously, that protein must be stabilized against degradation and be safe from elimination from the body, which could be handwaved using nanotechnology.
I remember hearing about a laboratory in Italy that was experimenting on using proteins like I've described on rats — but I don't know the details or any outcome.
[Answer]
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> Can you slow an individual's metabolism
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It's not only plausible, it's in use today. It's called [Therapeutic Hypothermia](https://www.americannursetoday.com/therapeutic-hypothermia-after-cardiac-arrest-what-why-who-and-how/), and it's often used after cardiac arrest. The patient's core body temperature is reduced to around 89°F. It reduces heart rate, blood pressure, and brain function, while maintaining enough metabolism to keep cells alive. This has the effect of slowing or preventing cell death from oxygen starvation while still allowing healing to go on.
There are [theoretical plans and designs](https://futurism.com/a-real-life-hibernation-chamber-is-being-made-deep-space-travel/) out there for hibernation systems that could keep astronauts in a state of extended hypothermia for the duration of an interplanetary flight.
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> to the point where they wouldn't need to eat for 2 years?
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It would still be necessary to wake astronauts occasionally for exercise periods and ship operations. At present, therapeutic hypothermia is only used for periods of about 24 hours or so, but in theory, with proper medical maintenance and monitoring, it could be continued almost indefinitely.
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> Would doing so circumvent the normal aging process?
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It's unclear at present. As mentioned, it's only normally used for 24 hours or so; theoretically, however, an extended period of hypothermic hibernation *might* reduce aging to a degree.
Aging is a combination of wear and tear on the body's systems with a reduced ability to repair them as our DNA's protective telomeres are worn down. Reduced metabolism would affect both of these, with the body's systems not having to work as hard and cells not dividing as much.
[Answer]
I note from the question you're not asking "how" it would be achieved but I think you probably need some gene editing / therapy for someone to be able to hibernate, the biological processes involved need to be identified first (because I don't think they have been yet?), the genes responsible for those identified & where to insert them in the human genome without causing undesired effects.
That aside lets look at what you did ask.
* Can you slow an individual's metabolism to the point where they wouldn't need to eat for 2 years?
Based on the limits you place on the question (that it's some sort of hibernation & cryogenics is off the table) the answer has to be no.
The longest period of hibernation I can find any mention of is 344 days for a bat in captivity so it would seem two years may be pushing it.
While you hibernate biological processes are slowed rather than stopped & the animal survives off it's body fat, your crew are going to starve to death while they sleep if you keep them in hibernation for two years.
I think it's unlikely you can beat the bat & slow a persons metabolism sufficiently for them to need no food for two years while they hibernate.
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> Clarification / Rationale: if you want to reduce body temperature during hibernation so far that cellular activity is negligible enough they'll need (practically) no food (metabolized body fat) or oxygen then you'll be on the very cusp of freezing them.
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> The smallest temperature fluctuation might freeze them, then ice crystals form & they're dead.
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> It's far too delicate a balance & the best way to mitigate against an accident is to just saturate their tissues with a bio-antifreeze. Once you've done that (if you can) there's no point not going the whole hog & just freezing them for the whole trip.
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> But then you've got cryogenic freezing, which is not hibernation.
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Best case scenario, you have to wake them after a year & feed them a high calorie diet for a few weeks to fatten them up again then you can put them back in hibernation. They need less food & oxygen on the journey with a slower metabolism but these needs won't be completely negated.
Or you can (as Ynneadwraith suggests) drip feed them intravenously while they sleep so you don't need to wake them, which means they're being fed so the answers still no of course.
* Would doing so circumvent the normal aging process?
No it wouldn't, hibernation only slows the metabolic processes.
Small rodents that hibernate are known to have longer lifespans in general than similar species that don't so it's reasonable to extrapolate that aging is slowed a little, which is expected anyway due to the lower body temperature during hibernation & the slower cellular activity that produces.
If you want to stop aging you are going to have to freeze them.
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I'm continuing to work on my [map](https://worldbuilding.stackexchange.com/questions/103879/could-i-get-some-guidance-on-this-map-in-progress), and one thing that's giving me difficulty is figuring out the geology of a region that I wanted to be similar to the Ethiopian highlands and African rift valley. This area is marked dry highlands on the map below. (It's otherwise a little outdated now, but gives a solid idea for this question.)
According to [wikipedia](https://en.wikipedia.org/wiki/Ethiopian_Highlands) the highlands are, well, high, because magma pushed up the surface of Earth, forming a mountain range there and in the nearby Arabian peninsula. This appears to be the reason you get legendarily massive plateaus on top of tectonic plates that are separating, and creating the rift valley. (Or that and some more volcanic activity and erosion.)
**My question is pretty simple: Is rising magma and separating tectonic plates adequate to create a region like the Ethiopian highlands in the area marked on the map above, or is there an important context I'm ignoring? If so, what should I do to justify it?**
[Answer]
The answer is a simple "yes".
The Ethiopian highlands are the product of [flood basalt](https://en.wikipedia.org/wiki/Flood_basalt) forming plateaus with repeated or sustained eruptions for thousands (or millions) of years. Similar events created the [Deccan Traps](https://en.wikipedia.org/wiki/Deccan_traps#Theories_of_formation) in India, the Siberian Traps and Iceland, and others (shown in purple below):
[](https://i.stack.imgur.com/nDWL9.jpg)
All of these formations are associated with rifts or seafloor spreading, and mantle plumes. Your map indicates the same combination of features, so yes, you have the recipe for a stepped highland as found in Ethiopia.
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Basically I'm considering the physiology of eyes and camouflage might look like on an eyeball planet; tidally locked to the sun so the sun is stationary in the sky. At any point on the habitable twilight-zone the sun would therefore be stationary somewhere near the horizon. The eyes might also be slightly different in the twilight-zone slightly nearer the sun-facing side than closer to the shadow-side of the planet, the sun being slightly higher in the sky or right on the horizon, respectively.
**Research:**
The Functions of Different Pupil Shapes
<http://www.koryoswrites.com/nonfiction/the-functions-of-different-pupil-shapes/>,
Eyeball Planet <https://en.wikipedia.org/wiki/Eyeball_planet>, <https://www.space.com/20856-alien-planets-eyeball-earths.html> Camouflage <https://en.wikipedia.org/wiki/Camouflage> <http://animals.howstuffworks.com/animal-facts/animal-camouflage.htm>
The shape of the pupil doesn't seem to be directly related to the direction of light, unless there's anything I've missed. I'm looking for any good reason for slit-pupils and such rotating 90° because of the near-horizon sun, if there is any. If slit-pupils even would be as useful if the light is always the same.
Maybe some watchful grazing animals could evolve with one eye adapted for facing the sun and one for facing the shade? Something I'm considering. If anyone knows about eyes adapted to facing direct sunlight I'd love to hear it.
I've considered corpora nigra, like horses have, could be common to reduce glare; maybe positioned on the outwards side of the pupil rather than above.
I could not find any information regarding the brow ridges having to do with shading the eyes from the sun. If that is at all likely, perhaps brows ridges could evolve on the side of the eye-socket as well as above.
If anyone knows of any research regarding eyelids being horizontally over and under the eyes rather than vertically, I'd love to know that because I haven't been able to find any regarding light. It seems to mostly be about protecting the eye from dust and dryness and such, but maybe vertical eyelids could evolve if that depends on the direction of light. Let me know if you know of anything that could justify it.
Then there's the camouflage to hide from the aforementioned horizontal-light-adapted eyes.
Maybe some way to capitalize on the eyes' different physiology, ways to sneak up on something while constantly casting long shadows, sneaking up on something while facing the sun without being blinded, or being covered in patterns that take advantage of the sun consistently casting long shadows. Would stripes be the go-to pattern, or is that pattern for other reasons?
I guess regular countershading wouldn't work, unless it would be viable having the sides countershaded rather than the bottom? What colors would be best in perpetual dusk/twilight? Please share if you know!
Any examples of animals that accomplish any of the above would be great!
ANY related information you have would be greatly appreciated.
[Answer]
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> Maybe some watchful grazing animals could evolve with one eye adapted for facing the sun and one for facing the shade?
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I am not a biologist, so I can not provide you with an definitive answer about this. But I recently read (in [1]) about Anableps anableps, a fish, which has four pupils in two eyes. Each of his eyes is constructed with one underwater pupil and a "abovewater" pupil.The underwater pupil is adapted to the different optical properties of water. The interesting thing for you might be, that light rays of both pupils are then bent to one retina thus saving the brain from handling the input of four eyes.
So I propose, that your animal has two eyes with two pupils each. One pupil per eye is suitable for looking into the sun and one for dimmer lightning. It may close one of each pupils separately and thus be able to adapt to the current view direction of the eye.
[1] Land, M. F. and Nilsson D.-E.; Animal Eyes; Oxford Animal Biology Series; pages 118 to
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I am not a writer nor an artist but I am creating a video game and I am looking for a realistic imaginary world based on science. I am looking for realistic data to support the strategical framework of the game that follows:
It is based on a company that wants to select $p$ locations among a set of $m$ possible sites for constructing polluting plants in a contemporary world. The $m$ candidate sites are located on a territory containing different cities. We have:
* $d\_{ij}$ the distance between city $i$ and site $j$
* $P\_i$ the population (in thousand of inhabitants) of city $i$
I imagined experts that thought that a city was threatened if there was a polluting plant located less than 2 km from it.
There are two different factions :
1. The authorities' point of view that wants to minimize nuisance. They
want to minimize the number of inhabitants threatened by the $p$
selected plants.
2. The company point of view that wants to minimize the transportation costs.
They take into account the volume of goods transported between the $p$ plants and the $n$ clients. The transportation cost from a plant $j$ to a client city $i$ is $1.5€$ per kilometer and per $m^3$ of transported good. The annual demand of city $i$ is $V\_i$ (in $m^3$). It will be needed to transform the first model so that :
* At most 5% of the population of $n$ cities are threatened (constraint imposed by the authorities).
* The demand of a city is delivered by a single plant
* The company minimizes its total transportation cost
I'm specifically looking for data, real or fictional, that would support this game framework, for instance the number of city in a given environment that would make it realistic in a given context (for example: are 10 sites for a population of 60 million people in 36,552 cities realistic? What would be the distances in this case?)
[Answer]
The main issue you seem to be neglecting are the carriers of pollution. Flows of water and air and even the local rotational velocity of the earth (higher closer the equator) are vital factors in determining your answer.
Air and water flows are mostly governed by climate and geographical features (which all in turn also influence each other, of course. Nobody said this would be simple).
Interestingly, in real life many factories have smokestacks SO high that it is no problem at all for the communities they are serving, but the pollution actually comes down hundreds of kilometers away to cause smog.
If your climate, flows and geography are relatively neutral and we ignore friendly-neighbor-policy smokestacks we can (greatly) simplify our models by assuming all plants pollute in a perfect circle with quadratic fall-off based on distance. At this point the model is so simple, unfortunately, that real-life data simply fails to accomodate. This does lend itself to heatmapping the area, and you can still use recorded smog and water polution levels in real life cities as reasonable benchmarks for tolerance.
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I am designing an alien species of organism (not necessarily intelligent, in fact, probably not). My current settings are these:
The female is very large (bigger than cattle, smaller than elephants), have strong, pointed mouthparts for skewering prey or enemies and are capable of sudden bursts of speed. The males can fly, and are around the size of vultures or other large birds. They also have somewhat dexterous claws for gathering edible vegetables or processing meat.
The dynamic of the sexes is so: one adult female is followed by numerous males (perhaps 5 or 8). The males try to do the female favours, such as scouting for prey or gathering food for the female (both sexes are omnivorous, but prefer meat when it is available). As a reward, the female will become more intimate with a contributing male, and when sufficiently intimate, will mate with it.
I want to know if this system will be evolutionarily stable, as in whether or not some new system will take its place spontaneously as time goes on. For example, will more docile and sex-prone females become more successful than their more demanding counterparts, and hence push the latter out of the gene pool? Or perhaps some kind of sexual selection, similar to those that caused the appearance of peacock tails and the like, cause more "charismatic" male to be selected over diligently contributing males and hence destroy the system?
(I am also leaving out some details like what method of reproduction the organism uses (i.e. egg-laying versus live-birth) in case these variables can be set to stablize/disrupt the system)
[Answer]
Sure, this all seems quite feasible. The mobility of the males means that the 2nd fittest can go looking for other females elsewhere. Therefore the gene pool diversifies and positive genes are spread around the world.
As for "peacock syndrome", if the male is primarily responsible for hunting, and they don't feed females who shun them, then the best hunters will succeed. Females who choose "flashy" males will die of starvation. Keep in mind though, this assumes getting food is hard enough that only fit males can do it well. If flashy males or females can gather adequate food you get peacock syndrome.
Finally, the females will probably be focused on defending the young, hence the spikes. They also have a huge incentive to be picky with their mates as they have lots of options available, and a bad choice means less food for them and the young. Therefore females need to be picky with mates and tough with predators, though once they've found a suitable mate they of course have an incentive to "put out", as it were.
I'd advise egg laying for this setup, as it means the female has a huge incentive to guard the nest, and therefor relies on the male to gather food. This would avoid peacock syndrome. And, if there are predators it would explain her decenses. Maybe the nests are somewhat inaccessible and that's why the males need to fly, to get in and out?
**Edit**: It's been pointed out that the females described in the OP did the hunting too. The above still applies though, just swap "hunting" for "scouting" in the list of male duties. Also, if the female is hunting, then eggs are a bad call, as the nest would be left undefended.
[Answer]
There is no problem with this idea. Insects have been doing this sort of thing for a very long time. Males often give females nuptial gifts, and the quality of the gift is used to determine success. This is the abstract from [one paper](http://www.annualreviews.org/doi/10.1146/annurev.ento.53.103106.093423). This article and the articles that it cites will provide a wealth of possible scenarios.
Edible and seminal gifts that male arthropods transfer to their mates range from important material donations to items that provide little direct benefit. Recent reviews and research have emphasized the negative effect of gifts on female fitness, suggesting that male donations reduce the female's re-mating rate below her optimum or even that nuptial feeding is a net detriment to her fitness.
However, comparative, experimental, and natural history evidence reveal that most edible gifts of prey or glandular products provide direct benefits to females. Gifts clearly supply nutrients when females compete for them or increase mating rates when food from other sources is limited. I point out the difficulties in determining that female re-mating rates are sub-optimal and suggest several alternative hypotheses for the apparently low female mating rates in some gift-giving species. With regard to seminal contributions (absorbed from the ejaculate), I discuss how to separate hormonal (potentially manipulative) and material-benefit effects of male secretions on females.
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This question is not a duplicate of [this question](https://worldbuilding.stackexchange.com/questions/43958/what-would-happen-to-life-on-earth-if-the-planet-had-total-cover-of-permanent-cl). They're similar, but this one has one very large difference: only a large area has permanent cloud cover, not the whole planet.
If low clouds or even fog completely cover a large area (let's say 100 miles sq, about 161 km sq), what would be the effects on the climate? Could people still live there? (Disregard for the moment whether they would want to.)
*Notes:*
* Assume that light can get through, just as light does on a rainy day. The sky and sun cannot be visibly seen though.
* Beyond where there are clouds, the climate is normal and similar to that of Earth.
* I don't know if it matters or not, but the area directly below the clouds is a vast swamp.
[Answer]
I imagine you would end up with an ecosystem akin to a [cloud forest](https://en.wikipedia.org/wiki/Cloud_forest), but with a few differences. Given that the light would be constantly diffuse and scattered you would probably end up with more mosses and smaller leafy plants than you would larger trees with their larger and fairly directional leaves. Such an environment may be favorable for [Carnivorous Plants](https://en.wikipedia.org/wiki/Carnivorous_plant) due to the acidic soil if you are looking for entertaining settings.
As already mentioned, Vitamin D deficiency would be a hazard to those living in such an area due to the low amount of UV penetrating the clouds. If this area has persisted for long enough for evolution to go to work you will likely see things that cannot tolerate UV for long and have polarized vision to see better in the scattered light.
On the whole, everything would be perpetually cool and damp. I wouldn't expect there to be many large animals; but you may get a handful of apex predators and a whole bunch of prey. Plenty of things like insects and rodents.
Geologically speaking you would get methane and tar seeps from the accumulated biomass (again if the environment has persisted for a very long time). If there is some means for water to move and the correct underlying rock layers the acidic soil would create runoff that could hollow out caves.
[Answer]
Well it sounds interesting and here is your answer.
If an area is permanently under cloud cover then a few things will be affected. First of all we can say about the vegetation of that area that the vegetation will get affected because we know that sunlight is vital for Plant growth. So vegetation of that area will most probably die or to some extent get reduced below an adequate level.
The second thing is that the people will suffer from vitamin D deficiency as sunlight is needed for the production of vitamin D.
Third , if the clouds are filled with water or if they are rain clouds, there might be a heavy downpour and this may cause floods and block all the communication channels which might lead to a very critical condition in regards to the communcation with the rest of the world.
The general temperature of that place will also decrease at an annual rate.
The last thing is that this place will turn into *Forks*, which is a city in the USA. You might have seen it in the movie twilight. üòâ
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I have done research on blood and in particular the component adding color and transferring oxygen.
Hemocyanin is directly dissolved into the blood. This works for an octopus, but not a reptilian alien. Hemoglobin however is contained inside RBCs and very little is directly dissolved into the blood. This could work for a reptilian alien but it seems too earthlike to me.
So I figured that maybe I could have the Hemocyanin compound inside globin proteins inside cells and these cells would be BBCs or blue blood cells.
Each Hemocyanin has 2 copper ions that can bond with 1 oxygen per ion so per molecule that is 2 oxygen molecules transported, double the capacity of hemoglobin. Other than that it is similar to hemoglobin(each protein has 4 subunits and each subunit has 1 Hemocyanin molecule.
Now, arterial blood with Hemocyanin looks blue because it is blue. Venous blood with Hemocyanin however is colorless. So the only way you could see veins is by seeing the tissue itself and that is pretty much impossible without an incision. So the only blood vessels you would ever see with the naked eye are arteries.
**Is cyanoglobin a plausible way to have oxygen transported in a reptilian alien who most likely has a totally different evolutionary tree from ours?**
[Answer]
The simple answer is no.
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> > No, it's just too big to fit inside the cells and retain functionality at its lower binding potential. Hb forms tetramers of 64
> > kDa, while Hc subunits start at 75 kDa and often form massive chains
> > exceeding 1500 kDa, depending on species.
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> On a molecular chemistry scale, that's flipping massive - for
> comparison, the largest protein known (titin) is ~3800 kDa.
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Source: [hemocyanin blood using humanoid alien](http://www.giantitp.com/forums/showthread.php?357106-If-my-body-used-hemocyanin-for-oxygen-transport&s=b63845b5ab73bf7cd7279e46ed81d880)
Also, hemocyanin (Hc) is limited in its oxygen carrying capacity.
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> > Unit for unit, Hc carries about 25% of the oxygen compared to Hb but achieves saturation at much lower partial pressures of oxygen, so
> > technically it's more efficient at binding oxygen, just less efficient
> > at carrying it.
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> As I said, a fix would be to have a higher Hc concentration (~4 times
> to be precise), resulting in very intensely blue blood (oxygenated) or
> colourless (deoxygenated), much like our blood is bright/dark red,
> only more extreme.
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> Reading up on it some more Hc appears to function better at cold
> temperatures (spiders and scorpions in the Tropics aside), which could
> be another characteristic of our Hc humanoid (lower body temperature).
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Source: *ibid*
Higher concentration of Hc suggests the fluid blood itself needs to be saturated with Hc, rather like the blood of an octopus only more concentrated.
However, Hc blood does work better at lower oxygen levels than hemoglobin blood. So if your reptilean alien existed in a low oxygen atmosphere, then Hc blood might be an advantage. But, fortunately, cynanoglobin seems to be out. Pity really the idea of blue blooded aliens is rather nice. Another beautiful hypothesis slain by an ugly fact (to paraphrase TH Huxley who called it the tragedy of science).
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On the other hand, I have some information suggesting that Hc isn't quite as dire as it seems. If O2 concentration *and* temperature are correct, i.e. what you might find on a near Earth mass exomoon orbiting a giant planet 3-6 times the size of Jupiter, there might be a narrow window where complex life could evolve despite the seeming disadvantages and/or less iron due to depletion in that system forcing evolution down a different path.
Think horseshoe crabs here, a plausible evolutionary tree would be life starting in deep ocean(s) near black smokers and the resultant life forms eventually adapting to climatic change by evolving into land dwellers.
Over time pressures similar to on Earth may lead to intelligence and eventually consciousness.
I further defined the properties below.
"Blue skin, copper based hemocyanin (i.e. similar to horseshoe crab) and capable of seeing mid infrared to low visible light, 930 to 681nm but otherwise very much like us. 41.17 LY distance, around an M dwarf with three large exoplanets and one Earth-sized exomoon, 1.22G units.
Height: a little under 0.9 metres, bilateral symmetry and capable of limited photo-mimetic abilities."
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My WB society's motto is: **Education is paramount for the advancement of society.** A group of pharmaceutical companies have perfected a drug for children to young adults, ages 6 to 16, that allows for nearly side-effect free, extreme mental acuity, focus and accelerated learning. This society has chosen to mandate that all school children during those ten years be on the medication in order to finish our current day education process from kindergarten to doctoral thesis with elevated comprehension and retention.
Up until age 6, children stay with their parents and are not required
to be in school. After age 6, they begin the process of "hyper education" and are required to stay medicated during the entire time period. After age 16, the drug's effect quickly taper off and the child returns to a normal level of mental acuity and focus (Whatever levels they were predispositioned to have)...no longer term or permanent effects from the drugs exist...however, the knowledge and understanding acquired during the previous 10 years remains.
The drugs have the advantage of making the children docile and obedient. Juvenile delinquency all but disappears, and when any child does act up, they are immediately tested and if found to be off meds, they are pulled away from the parents to be kept in camps until they turn 16 where they can "Focus on their education."
For a society that places a huge emphasis on education...what kind of resistance might this be met with? If there was little emphasis placed on individual liberties, would this be easier to push through? Or what attributes about society would make this justifiable?
Would it be more tolerable if the age range was say 10-20? Thereby allowing children to have more of a childhood before the transition into productive adults?
**EDIT**
No brainwashing, just an honest desire to push the bounds of learning and education for the betterment of the society. The society's motto is the motivation.
The drug would only be effective between certain ages. There are plenty of drugs currently that have the opposite effect on kids that they have on adults. There has been no break through in using the same drug on adults....as stated, the effects taper off at a certain age.
Children on the medication are not zombie like...just not hyper active, they are non-disruptive. The increase in learning piques the normal curiosity and the children also do their own research.
I had originally thought of it as a version of the *Limitless* drug NZT-48...but with the 'limits' of an age range...and no side effects. If you knew you could learn almost anything....but only during a certain time window...it would focus you even more.
[Answer]
That's an interesting question. I think for the children it would be a lot less unpleasant than current educational regimes - especially if your parents are tiger-mom types. My impression of your drug is that it would create monomaniacal focus, submission to authority, contentment and perhaps even happiness when studying, and an intense curiosity about the world.
One important question to consider is why administration of this drug is not continued with adults? Any nation with hyper focused, obedient adults would have a GDP growth rate that would be the envy of China. This drug would also increase the effectiveness of the military tremendously. Most importantly, a leader who instituted a policy of administering obedience drug to all citizens would never lose his position of power.
Assuming there is some mechanism which makes administration of the drug to adults impossible, individualism-oriented societies (like the USA) would generally find the administration of the drug to children abhorrent, despite it making for objectively happier childhoods. I suspect it would be more popular in societies which believe that childhood should be a period of very hard study such as China and Singapore.
There would of course be a massive race for the development of a similar drug which works on adults. Billions would certainly be spent on that. It would be a dream drug for say, North Korea.
The use of this drug would kick off a technological singularity of a sort. Any generation given this drug would be vastly better educated than unaugmented peers. For a variety of reasons, this increased education level would appear to casual observers to be a significant boost to intelligence. There is currently a large cultural gulf between people with high and low levels of education. They vote differently, worship differently, consume very different media, and do different things with their time. People with more education are healthier, wealthier, and live longer.
What I'm trying to say is that I don't think people who had drugged childhoods and people who did not would have much in common. This would create huge societal divisions. In particular, the first generation to have the drug would not be able to identify very well with anyone older than themselves. This would be a generational rift like we have never seen.
People who had to skip parts of their childhood often maintain an increased level of playfulness and interest in childish things for the rest of their lives. I would expect this to be the case for the adults who were drugged as children. This would also be a nice twist on the expectation that these kids would be over-educated automatons as adults, but instead are often found playing with toys or playing tag with each other.
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What kind of resistance might this be met with? Today, despite clear and overwhelming scientific evidence to the contrary, there are those [who believe the earth is flat](http://www.livescience.com/24310-flat-earth-belief.html). There are those who [refuse to immunize their children](http://www.motherjones.com/environment/2016/08/there-are-more-anti-vax-parents-doctors-offices/) for various reasons. There will be many who refuse just to refuse. There will be others that will worry about the long-term effects of the drugs. still others will resist due to moral or religious grounds.
The government need not be heavy-handed. Those who refuse will be horribly disadvantaged. This will create a great deal of social pressure to submit to the drugs. The government can cite the grievous disadvantages the undrugged children will endure as a way to encourage parents to agree. I would say about 1% or less would elect to avoid the drug.
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**How could a civilization create a dangerous autonomous mechanical ecosystem that will not be overly dangerous to its creators?**
Militaries are expensive; military research doubly so. So what's a small colony from a small civilization supposed to do to defend itself? It needs all the resources it can get to bootstrap its own industrial base, so it can't create much more than a token defensive force unless it wants to cripple its own growth. Nanofabrication and robotic mining can help, but everything you produce is going to be inferior to the high-end military technology of the people who might invade you.
So why not evolve new threats? Organisms can reproduce and evolve without your direct involvement, crating new and completely unexpected threats. It's hard to engage a conventional military when strange monsters are swarming your position. Biological organisms probably won't do: they're too vulnerable and unsuited for war. Claws and teeth have limited use against combat armor. You need something that can't be easily handled with fire or chemical weapons, and can do real damage.
So let's make the organisms artificial. A [mechanical ecosystem](http://www.orionsarm.com/eg-article/480a4cff25c2e) of autonomous (<https://en.wikipedia.org/wiki/Self-replicating_machine>) robots that uses [evolutionary robotics](https://mitpress.mit.edu/books/evolutionary-robotics) to become ever-better killing machines.
Now we're getting somewhere: armor-piercing guns and diamond-toothed saws beat keratin shards and teeth any day, and robots evolve much faster and with more purpose than organic life ever could. Programmed evolutionary imperatives and and behaviors mean that this 'mechology' can devote itself to the destruction of intruders without endangering the colonists or engaging in wasteful perpetual war against itself.
A simple ecology will suffice to start. Plant-equivalent robots mine for materials and convert them into refined forms and power sources. Animal-equivalent robots prey on them and each other. Their AIs are simple neural networks. Their genetically-specified controllers ensure that they are evaluated based on military suitability, and ensure that the least fit don't get to breed. All are designed with an artificial version of chromosomes which are merged and mutated during reproduction. The resulting template is then assembled into a robot and set loose. All elements of the robots are subject to mutation, to ensure that preconceived notions don't limit their evolution too much. The only thing that's immutable is instructions not to attack colonists or their infrastructure.
Now comes the tough part: making sure it stays safe to you. Sure, you can enforce behaviors and try to direct the evolution as best you can, but evolution has a nasty habit of doing the truly unexpected, so sooner or later you'll discover that your safeguards aren't as safe as you think. And while an uncontrolled militarized mechology that indiscriminately kills everything in sight is great if you want to make an uninhabitable death world, it's significantly less great if you're trying to live there.
So what can you do to prevent this dangerous mechanical ecosystem from evolving out of your control and becoming a danger to you? How can you create safeguards that are strong enough to not be subverted while still not being intrusive enough to force your new army to evolve predictable traits and tactics? Or is there no way to reduce the risk to an acceptable level?
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## It will come down to how to decide 'Friend or Foe?'
After handwaving away the complexities of evolving machines and the supply chain required to enable the kind of evolution the OP describes, you're still stuck with a fundamental and difficult question "How do you figure out who's a *bad guy*?"
On Earth, this problem has been "solved" a number of different ways. Most applicable to spaceships are the [Friend or Foe Identification](https://en.wikipedia.org/wiki/Identification_friend_or_foe) systems used by militaries and civil air traffic control to identify friendly ships. Note that:
>
> Despite the name, IFF can only positively identify friendly targets, not hostile ones.
>
>
>
This makes sense since you know that you can trust ships that have strongly authenticated themselves as friendly. A ship that does not or cannot identify themselves as friendly is either neutral or an enemy.
## Fire Control Policy
**Not Blue, Shoot It** [(NBSI)](https://eve.fandom.com/wiki/Not_Blue_shoot_it) and **Not Red Don't Shoot** (NRDS) are two approaches to handling neutral or enemy contacts. For NBSI, any unknown ship is considered hostile and will be fired upon. NRDS takes a more generous approach to neutrals by allowing them free passage as long as they take no hostile actions. Which policy you pick will depend on the capabilities and paranoia of the star base occupants.
## Making Evolution Safe(r)
You can't ever be absolutely sure that this weapons system is capital-s Safe. Evolution is a long series of adaptation to pressure. Many of the pressures on this weapons system will be beyond the colonist's control such as local resource constraints, frequency of attacks, weapons used in attacks, tactics used in attacks, attempts at spoofing colonist identification measures, etc, etc.
Further, there may be any number of system characteristics that are beneficial at small scales that completely fail at large scales or cause er, unhelpful feedback loops. For example, it's handy to have the system mine its own resources and this works as long as the material mined doesn't impinge on the colony's general economy. However, what happens when the military grows to consume a significant portion of available mining capacity and crowds out the colonists ability to make money off mining?
## **Making this safe for the colonists**
Depending on the hostility policy, the requirements to make this mechanical immune system safe for colonists will depend on proper identification of colonists. It's up to the author to determine which mechanisms to use.
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You're trying to treat machines as you would living things, but they're not. Machines require maintenance depots, spare parts, and trained technicians, not to mention fuel and ammunition.
Furthermore, machines are *built*, not birthed. That implies having all the advanced raw materials to do so on hand. Nano bots are awesome, but they still can't turn dirt into a tank.
And so, if your technology is able to overcome all that anyway (aka you're hand-waving it), then it's relatively trivial to assume that the bots are also programming their creations to stay far away from your faction/species.
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There have been a few questions on mobile plants on this site and even more on their intelligence, but one that has not been asked so far is related to the lifeblood of creatures: blood. Inside of Earth plants, the circulatory system is less complex, as the organism does not need to move. But surely if they were mobile they would have a need for an effective circulatory system? What would the botanic equivalent to the animal circulatory system be?
My current thought is that the hydraulic fluid that a plant's vegetal muscle uses would be the closest thing to blood.
Next question
[Muscles](https://worldbuilding.stackexchange.com/questions/59194/what-is-the-botanic-equivalent-to-muscles)
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Odds are it would be like the more advanced circulatory systems already on our planet. More movement means you need more resources available to cells, which means you need something better at carrying those resources than just water i.e. blood, and/or something to hasten the circulation i.e. a heart or other form of pump.
Both of these are feasible. Plants already contain sap, resin, and other fluids used for various tasks. And any plant that has developed more extensive movement would therefore also be able to move a "heart".
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This is a pretty simple question, but initial research only seems to provide the opposite end of the spectrum. What I'm wondering is if there are any known side effects of living in an environment with an increased amount of air pressure.
Say, for instance, humans colonized an Earthlike planet which had twice the air pressure at sea level than we have here (disregard whether or not this is possible, that may be a subject for a separate question), or say humans wanted to build an underwater facility and decided to save money by equalizing indoor with outdoor pressures.
I know there are limits to how much you can compress a gas, but I assume humans wouldn't feel too good as they approached those limits. My question is **what pressures would cause problems for humans, and what would those pressures/problems be?**
Assume any pressure would be achieved gradually, so no worries about explosive compression or anything like that.
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## Don't breath pure oxygen and they will be okay
How "deep" a human can descend into a high compression atmosphere will depend completely on the gas mixture of that atmosphere. [Diving gas composition](https://en.wikipedia.org/wiki/Breathing_gas#Common_diving_breathing_gases) is a well understood science on earth and offers information on how a human would adapt/survive in a high pressure atmosphere.
[Oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity) is real and it can kill you. [High pressure oxygen](https://en.wikipedia.org/wiki/Oxygen_toxicity#Mechanism) is more reactive than usual leading to the creation of free radicals that damage cell structures.
Nitrogen poisoning mimics the [effects of alcohol](https://courses.kcumb.edu/physio/adaptations/diving.htm) on a person's nervous system.
Despite the dangers associated with high compression atmospheres, there are [significant therapeutic effects](http://www.mayoclinic.org/tests-procedures/hyperbaric-oxygen-therapy/basics/why-its-done/prc-20019167) to be had (if carefully managed). Hyperbaric chambers are currently used for treatment of diabetic and radiation injuries; wounds that typically have great difficulty healing.
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Effect of entering an atmosphere of 1 Bar is that gases dissolved in the body will increase and eventually be double the amount of gases dissolved at atmospheric pressure. This change occurs without any discomfort to the man provided the increase in pressure is not too sudden and present no problem until he returns to atmospheric condition when the pressurized gases in the body expand and seek to escape.
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It is near future, Portland, Oregon, and the residents and neighboring farmers are sick of everyone moving there now that climate change has made it a (even more) fabulous place to live. In an extreme gesture, the entire city decides to build a wall around the city and neighboring farms, and (hand-waving) the governments involved are agreeable to it.
**Their intention is to be self-reliant. What would they have to do to get to that point?**
Note: this is specifically about logistics; I'm handling the government and people's attitudes. This is for a young adult short-story, so high-level is preferred. Assume no trade is occurring.
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This all depends on what standard of living your inhabitants want.
I mean are they going to watch TV? Turn on their lights? Eat canned food? Read Stack Exchange?
You have about 2 and a half million people living in Portland and the surrounding area. That's a huge amount of food, energy, and waste to deal with.
Do you have energy generation for that many people?
Waste disposal and sewerage is probably fine as that's already distributed although it does depend on where your treatment plants are.
Water supplies? That depends on whether the reservoirs are in your area. The taps may run dry.
Food you may be able to grow enough to live on if you have enough farm area. The diet is going to be much reduced in variety though as you lose all imported foods.
The problem you have is that the modern would is so inter-connected and everything depends on everything else. Your factories are going to shut down as they can't get components they need, and they can't sell their products to enough people. With all the people out of work there no longer spending money the rest of the economy also collapses.
Equipment is going to break down as you can't get spare parts. Do you make any cars in Portland? If not everyone is going to be walking soon.
Do you have oil wells or other sources of fossil fuels and the refinery to process them? If not people are going to be walking even sooner.
The good news is that with 90% of your population unemployed and no power for heating or food to eat that 90% are all going to die. The remaining 10% can then settle down to a simple agrarian subsistence farming existence that will let them survive for a while.
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It is sometimes said that a city is only 3 days away from starvation or revolution. Cities are complex environments which require massive connections to the hinterlands to supply food, water, and energy, as well as places to dispose of the wast products. Cutting off the inflow or outflow would be similar to plugging either end of your digestive tract.
The other issue is that most of what happens economically in cities depends of being able to access markets outside of the city. While large cities have internal economies and can do import substitution to a certain extent (as per Jane Jacobs), this is still only a fraction of the external markets that cities serve. Without access to external markets, the city will have no source of income for their food, energy or waste disposal.
The end result of attempting autarky will be to diminish everyone's standard of living inside the city, and most of the people surrounding the city will also suffer a loss.
Edit to add:
Several cities are embarking on this experiment now, without walls. Adopting laws which require business to raise minimum wages to $15/hr, adopting hostile regulatory regimes against small business, trying to drive out new services like Uber and AirBnB, forcing parents to use public schools by preventing charter or other alternative schools to open or operate and very strict zoning that eliminates new suburbs and drives up the price of remaining housing stocks are some of the policies which "Progressive" cities like Seattle or NYC are adopting. Entry level jobs and small business are being shed rapidly there, and people are moving away if they have the means, or avoiding settling there in the first place. If you want to see the end result, there is always Detroit...
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You're in a group of colonists, headed to your new home on [Tau Ceti e](https://worldbuilding.stackexchange.com/questions/15364/resources-to-justify-long-distance-space-mining-missions). Due to some crazy accidents aboard the ship, the diverse flora that was brought aboard (for food during the journey and for agriculture at the colony) is at danger of being lost forever.
You have the opportunity to save three species of plants before the doom takes them all. **Which plants do you save in order to best ensure the survival of the colony?**
Things to note:
* Of course there were plenty of vitamin supplements brought on board! Unfortunately, these will also mostly be lost in the accident :(
* Once you get to base camp at Tau Ceti e, you can start thinking about bio-engineering GMO foods. The equipment to do that aboard the ship was also conveniently destroyed.
* You have to survive for about 10 more years aboard the ship, and feed about 20,000 people. Assume that there are enough food stores to sustain this population until the three saved crops are completely cultivated and ready to harvest.
* **Edit 1:** The colony on Tau Ceti e will mainly be in an [arcology](https://en.wikipedia.org/wiki/Arcology) designed to imitate Earth ecology as close as possible.
* **Edit 2:** Obviously, the immediate need for food is at the time of the accident. However, the colonists should also plan on how they can survive once they get to Tau Ceti e. Once they get about 2 years away from their destination, they can send a message back to Earth, at which time Earth will launch an unmanned supply ship to provide new seeds, equipment, etc. This can travel much faster than the colonists did, but they should still plan on living off the three crops for 10 years on the ship and a few years on the planet.
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Ignoring some of the more complex aspects this question contains (atmoshpere on TCe, etc.) corn and wheat are the most obvious things since they are high in protein and easy to grow. Potatoes are also a good choice since, although there "protein-to-labour" ratio is lower than corn and wheat, they contain many essential nutrients for human survival. Finally, soybean is a must due to its extremely high protein content and quality, ease of growing, and nitrogen fixing ability.
To directly answer the question, I would say the best crops to take are corn, potatoes, wheat, and soybean.
I see you said three things. In that case I would take only corn, potatoes, and soybean.
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Um, seeds can last for generations, and anything that can seriously damage a seed store would be dangerous to all the people on the ship as well. As such a bucket of seeds of each type of plant saved somewhere safe would go a long way to being able to generate any seed stock.
* You have to survive for about 10 more years aboard the ship, and feed about 20,000 people. Assume that there are enough food stores to sustain this population until the three saved crops are completely cultivated and ready to harvest.
Most crops are planted and can be harvested in 3 months and if the crops are not needed for immediate consumption, the entire harvest can be turned into seed stock for the next growing season allowing for a much larger store.
Now if they are growing these on the planet, while they live in the ship, they likely would have two growing seasons, north and south, to double their production output in a single year.
If the question is for taking the time to get food plants to grow on the planet, that is big difficult issue independent of the available plant stock.
However, the plants that would likely be the most useful to ensure a large starting stock would be (IMO), Potatoes, since they are easy to grow, and have many of our needed nutrients in one plant, Clover, because it is both a nitrogen fixing plant (to help reduce the need for fertilizers and also is a very nutritious for the livestock brought along, is fast growing and easy to grow. Final would be a grain, I would lean toward wheat or oats, but the actual conditions on the planet might favor a different one.
As said a small bucket of seed (or even a handful) could go a long way in saving the species for the long haul, though maybe not enough for the first decade or so.
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Related to the [this question](https://worldbuilding.stackexchange.com/questions/6335/how-to-avoid-objects-when-traveling-at-greater-than-75-light-speed-or-how-not) about not going SPLAT. That one was for conventional travel through space at high speeds.
Now I want to know about how things would work with an [Alcubierre drive](http://en.wikipedia.org/wiki/Alcubierre_drive). I'm trying to understand how this will work and how it will affect other objects. I know that it is supposed to work by distorting space in front and stretching it out behind.
Now, is this little bubble of space moving with the ship inside? If so does that mean that the ship is actually stationary relative to everything inside the bubble and so isn't likely to run into anything? Does that mean the 'warping' affect pushes things aside and around the bubble? What about large objects? What size gravity wells will start to affect the ship and pull them off course?
Or does the ship move the bubble at slower speeds and matter can flow through the bubble? Would matter coming into the bubble leave time to 'maneuver' around it or would that depend on the size of the bubble?
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For the person travelling? Yes. The craft is fairly stationary with respect to its local spacetime. Effectively, there's a tiny bubble of spacetime in which everything is stationary. The drive warps space around this bubble to move the craft forwards.
Any particles in the path of the moving spacecraft get swept into the warped regions in front of and behind the spacecraft. This, however, does lead to a problem. When the spacecraft comes to a stop, and un-warps the space around it, all of these particles are released. Explosively. [Here's an article talking about it.](http://www.universetoday.com/93882/warp-drives-may-come-with-a-killer-downside/)
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**Background**
I have considered rotating space habitats of various forms for my worldbuilding projects (i.e. cylinders, rings/torii, spheres) and recently discovered this intriguing design by physicist Pekka Janhunen <https://arxiv.org/abs/1806.09808>
To summarize, the habitat is a squat cylinder that is passively stable in its rotation. It is fairly large (10 km in diameter) to optimize for a number of variables such as structural and shielding requirements, and material expenditure per inhabitant. The cylinder is open on both ends; its inner volume is exposed to space, with two low-g docking ports and tubes that connect them to the cylinder. The equatorial region has substantial volume for "urban block space", which I imagine would be structured as a sort of arcology.
The landscaped part of the habitat housing its biosphere is under a transparent roof 50 meters high, to save on the amount of nitrogen required for the atmosphere. But this layer is itself enclosed within the "light channel", the most novel aspect of the design. The outer layer of the cylinder, half of which will be facing the sun at any moment, is a vast array of parabolic concentrators which funnel light into the channel. The inner surface of the channel is composed of a highly reflective material, such that light fills the volume, even the half that is anti-sunward. Semi-toroidal mirrors at the equator deflect the light by 180 degrees so that it fills the volume directly "above" the rural, landscaped part of the habitat.
Here are a couple cutaway diagrams from the paper to help visualize the habitat as a whole:
[](https://i.stack.imgur.com/XmSgQ.png)
[](https://i.stack.imgur.com/LD4PC.jpg)
The amount of light that reaches the surface is regulated by an array of blinders positioned along the transparent roof, so that diurnal and seasonal cycles can be simulated. The actual design of blinders used is not specified in the paper. This is where my problem arises, and it is a problem I've run into with other habitat designs as well, when mirrors are used to redirect and scatter sunlight.
**Question**
Essentially, I'm having difficulty visualizing what the sky would look like to a person standing in this rural space, and the ways this could be adjusted using various types of blinding mechanisms and/or different transparent materials for the ceiling 50 meters overhead. The theoretical builders of such a habitat would want to provide a proxy to normal skies for the psychological well-being of inhabitants, and particularly in this case where the roof is only 50 meters high, they would want to prevent a sense of claustrophobia. I know the sky would not have a point source of light as we do with the sun, so I imagine all light would be diffuse, like an overcast day but perhaps much brighter?
I am also unsure as to the scale of blinders that would be preferable to the builders—they could be meters across, or centimeters, or even smaller, perhaps built into the transparent roof itself [in theoretical settings where space habitats are being built I always assume that material science has advanced significantly]. If they were too large I'd suspect that inhabitants could perceive them visually, giving the sensation of being inside a large room, unless the intensity of light was great enough that you couldn't look at the sky directly, which is something I think would be avoided. Small blinders might allow for variations in brightness that feel more natural, like clouds passing overhead, but depending on the size used you're left with anywhere from hundreds of billions to hundreds of trillions of individual blinders which require monitoring and maintenance. In any case, my problem is that I don't have an intuitive sense as to the behavior of light when it is being reflected and scattered in this context.
Hopefully that didn't come across as directionless rambling; I wanted to provide some of my thoughts. To boil it down to the question itself: **What would the sky look like in the habitat described above, particularly with regards to illumination, and how do these conditions change when you adjust the size of blinders, or method of blinding?
[Note: this is my first question posted on this site. If necessary I will edit it, or add more information]**
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If the interior of the radiator wall is a diffuse reflector, then it will just look white / gray. The image of the sun will be thoroughly scrambled by the outer-hull concentrator array (its job, after all, is to let light in and not let it out, not to maintain any sort of image), and diffuse white light light will then be projected at a shallow angle onto the ceiling to be dispersed into the living area below. If the ceiling is colored something other than white, then... it'll look like that, but matte white would be the optimal finish.
If, on the other hand, the ceiling on the interior of the radiator wall is a specular reflector--i.e., a mirror--then the sky will mostly look like a reflection of the ground, except in a narraow band where you actually see the reflection of the toroidal reflectors that direct light into the "rural" zone, with most of the illumination in the habitable area being indirect. This seems like a suboptimal option.
How this changes if you change the size of blinders or method of blinding depends on exactly what method of blinding you change to! You could make it look like pretty much anything you want with appropriate choice of light-interrupting options--a perfectly uniform reduction in ambient light levels, a band of night travelling radially, a band of night rotating around the cylinder, ambient dimming caused by distinct visible dark patches on the ceiling, etc.
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**The sky is the limit**
**Or: Most results are possible with enough creative engineering**
Collecting light in a tunnel for uniform spreading is a great idea. The parabolic concentrators use the directionality of the incoming sunlight to create a one way barrier, much like a diode in electronics or a valve in fluid dynamics.
From the inside of the tunnel the light will be received as a field of small dots or as stripes depending on whether the parabolic mirrors are circular or linear respectively. In the tunnel light can be directed with mirrors or scattered with diffuse materials like panels with small crystals.
With some creativity any light pattern can be created, but what can't be done is create a single very bright sun like object in the sky. Once light is scattered it cannot be 'unscattered'. But early in the reflective chain some local directionality is still available and that can be used to reflect the light to photovoltaic panels at night or further down the tunnel at day.
One question I have with this design is why the collector part of the cylinder needs to rotate with the habitat part? They do not need to be structurally connected. Only the light needs to have a path to follow. That also reduces the need to put parabolic concentrators 360 deg around, only put them at the sun facing side and rotate it once a year. This also eliminates a lot of structure, because now all those mirrors are effectively weightless.
Some practical options:
1. The blinders could also be LCD's like we tend to put on some buildings to keep intense daylight out.
2. The 'ceiling' can be made of small round tubes in a honeycomb like structure. This means that light going straight down passes unaltered. And light at an angle must reflect at the sides of the holes. Those sides can reflect, absorb or scatter the light. This will create a sky that is bright above, but darkens at an angle.
3. With a grid of small rotatable LED's that project light at a tight angle a sun like object can be created. Nothing in intensity like the real sun, but enough to cast a shade. Our eyes like some shade effect to sharply define objects. A totally cloudy day always feels a bit disorienting. This assumes enough solar panels elsewhere to generate the required electricity.
4. Some transparent materials can are also transparent in the infrared and/or UV spectrum. Like Magnesium Oxide and Magnesium Fluoride and many more. With mirrors from these materials larger parts of the spectrum can be directed inwards. At your discretion. Infrared will add warmth.
Note that every structure that does not reflect 100% of the light will heat up and needs to be cooled. This might add to much detail to the story, but is a very real thing if you want to build it in RL.
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Okay, the time machine itself is science fiction. I've got some handwavium about transformation of Einsteinian equations and unconventional polarization of electromagnetic frequencies and so forth. Here I'm trying to conceptualize the support equipment for it and I want to keep that strictly true to known science and engineering as it existed in 1962 (as a tip o' the hat to *BTTF* my protagonist had his flash of insight in November 1955 and it took him seven years to develop a workable prototype). Here are the rules I'm following:
* The time field generator requires an "activation energy" proportional to the mass involved. The activation energy works out to 260 ft-lbf of energy per pound-mass, or 778 J/kg in SI units (Australian character in 1962; uses SI and EES units interchangeably but his consulting engineers use mostly EES). This must all be delivered to the device in approximately two seconds or a 5th order decay reaction overcomes it and the time field "fizzles". (Another hat-tip to *BTTF*: This is exactly the energy needed to accelerate a mass from a standing stop to 88 miles per hour...)
* The time field generator also requires a sustaining energy input proportional to the volume of the field. This is much less but needs to be delivered continuously. The "slope" encountered within the time continuum is proportional to the frequency of the energy input. During my hero's first time jump he is using a 400 Hz aircraft alternator and inadvertently jumps back in time some four centuries earlier than he planned! (A little difficult to get petrol in Western Australia in 1519...)
* Upon loss of the sustaining energy the object exits the time continuum, randomly displaced in position by up to 500 or so feet, and with an imparted kinetic energy from the decay of the activation energy. This manifests as a velocity vector (summed with the object's initial velocity, if any), in an entirely random direction with a normal distribution centered around 58 feet per second and extremes of 36 and 80 fps.
* If an object emerges from the time continuum superimposed on a solid object, its structure merges with that of the solid object. (With, need I say, fatal results for the occupant!) However, the process of emerging takes a few tenths of a second and gases, and to a lesser extent liquids, can 'get out of the way'.
* Aside from the displacements in both time and speed due to the decay of the activation energy, the object emerges exactly where it originated with its initial velocity vector regardless of how much time has elapsed in either direction. The time continuum is affected by gravitational fields and planetary rotation and objects within it follow them in a stable manner. Of course, I'm not touching the question of a planetary impactor...
* Simple molecules, especially gases, have a multidimensional presence and are present within the time continuum. There is breathable air at normal pressure within.
* The preceding rules, save for the frequency relation, were "discovered" by my character (a professor of Physics at a fictional Perth college) during lab bench tests between 1955 and 1960. He also served as an RAAF pilot during the Pacific War, and he hits upon the idea of building his contraption into a DC-3.
* To supply the activation energy he uses a pair of counterrotating 830 lbm (each) 60" diameter flywheels designed by the college's engineering department. Rotor windings are built into the flywheel rims and stator windings surround them. Except for the windings, the rim of the flywheel is built of martensitic steel and the hub, bearings, and counterrotation transmission are lightweight titanium. The flywheel spins at 5000 rpm driven by titanium alloy turbine rotors (direct drive) which are in turn driven by bleed air from an AiResearch GTCP85 APU unit.
* To activate the contraption, while in the air at a safe altitude he shifts the APU from max bleed air to max electrical output to energize the sustaining field, then energizes the rotors through slip rings to supply the activation energy. With a flash of blue light, the DC-3 disappears from our skies...
...and emerges over Western Australia in the year 1519 (or so). Which leaves me with a couple of questions: First, how is he going to find out when he is and navigate back? Full disclosure: I posted this on astronomical SE and they directed me here. If you want to answer that specific question you can go there or, if comments suggest, I'll make it a separate question here.
The more important specific question I have is that, as I said, he takes off using a 400 cycle alternator and overshoots his destination...badly. He was misled by his lab tests which seemed to indicate that the time displacement decreased with increased frequency; what was actually happening is that he was supplying power from outside the field as he had not yet assembled a suitable self-contained apparatus and it took longer for the lower frequencies to be affected by loss of input power.
Once he realizes that, he "detunes" the alternator as much as possible. So, not being well versed in electrical engineering, **I'd like to know how much a 400 Hz alternator frequency could be lowered without overheating and blowing the windings.** Let's say, for purposes of the exercise, it's a 40KW maximum capacity alternator being operated at 20KW output and that he has the tools with him to bypass/alter the settings of the (mechanical, 1962) governor. Presuming that the contraption is able to handle voltage variations, **could the ability of the alternator to handle frequency changes be increased by making voltage adjustments?**
Although I want him to have to make some stops along the way, I'd like for him to finally blow the 400 Hz alternator in 1943...just in "time" to get a fill-up of petrol and paraffin (kerosene) and to find a 25 Hz alternator which can be adapted to his APU, courtesy of a wartime buddy who wonders why he suddenly came back to the base he was transferred from six months ago but who welcomes him with open arms. My, those six months really aged you....
P.S.: I should also ask those knowledgeable whether a flywheel such as I described (60" diameter, martensitic steel rim, spinning at 5000 rpm) is compatible with 1960-era technology. I've worked out the energies and needed moment of inertia, but I'm not up to computing stresses at the rim.
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You might find this [document interesting](https://theaviatornetwork.com/wp-content/uploads/2019/01/GTM-Complete.pdf) it has the schematics and training information for the Douglas DC-3. I couldn't tell is your APU was ever used on DC-3s, but seems to have been used on DC-9's. I don't know much about planes, though so just a comment.
If it is a synchronous alternator I think you could lower the frequency quite a bit. The output frequency unloaded is just related to speed that you are turning it. I am assuming it is not having to synchronize with another bus that has to be at a certain frequency. For your case, it seems you would have options.
If for some reason, there was another bus at a higher frequency that you were trying to connect to, then you could have a problem since your would have a lagging phase and you could have a large current. So it would depend on your story details.
Since it is 1962, you might have some options for some other kind of problem. For example solid state inverters to convert DC to 400 Hz or 400Hz to DC - since silicon power electronics were pretty new perhaps they were somewhat unreliable, or easy to blow up with a transient. Before the silicon rectifiers and switches were used for inverters there would have been other methods available in the 1940's
In your alternator if it was to charge the batteries for example one of the diode could go bad and there could be a some why to have to rig some kind of mechanical relay or other rectification method.
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I want to create a world for a story: Charybdis - a world of high tides. Very high tides.
Tides that drag whole ocean around the world - or most of it - in a long cycle. It must lasts at least several months, if not longer. I want to make regular cycle of deluges and dry seasons to be dominant force on the planet.
Basically I want this to look like this: there is dry cycle, where things hunker down in torpor, underground or sheltered by thick shells. Then ocean comes, tidal waves smash everything that is not secured and oceanic cycle begins. Fish comes, kelp forest sprout, everything frantically eats and reproduces. Then, after several months ocean leaves, leaving behind small remnant seas that slowly shrink. Meanwhile salt resistant savanna grows and land animals migrate from not submerged areas to graze. Everything slowly dries, awaiting new high tide.
Charybdis is flatter than Earth, so there is less water to be dragged around but it covers much larger surface. The same source that creates tides fuels tectonic activity and it’s a good thing, because something has to raise new land as it is under constant erosion by tides. It also makes new volcanoes for the tidal deluge to pour in.
Now there is question. Can I have this? Is there some way that Charybdis can orbit some other celestial body (no Black Holes, please), that can raise such high tides in a long cycle?
I tried to imagine some orbital configurations but as I see there are problems with everything:
Moon-planet configuration - both Charybdis and its partner body would have to be tide locked to each other. Stationary tide bulge stays forever in one place on the “visible to each other” hemisphere.
Star and planet - that would mean very long day and night cycle, that would climatically and thematically dominate the Charybdis - not tidal deluges. Also star would have to be very big or very close.
So, the question is - is there some reasonable way for my world to have long tidal cycles?
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Good choice on avoiding neutron stars and black holes. I'm pretty sure the planet in Interstellar would have been roasted by x-rays given the time dilation they specified.
The short answer is "no." You have conflicting priorities. If the two bodies are tide-locked to each other, then the wall of water wouldn't move. It would always be right under the other body. That's the definition of tide locking.
If we loosen up that requirement, we could theoretically give it a month-long day with a 45 degree tilt, so that the object it orbited would be above a shifting patch of planet. Now we run into problem #2, which is that the wall of water would exist both on the near and far side.
Which is where we run into our third problem, the thing it's orbiting. There's no way you could do this with a moon. As you run up the scale of sizes, the near parter couldn't both have a month-long orbital period AND be close enough to cause those tides.
Think about it. The current Earth/Moon configuration has an orbital period of a month, and tidal variation of around 16 meters. My guess is that you're looking for a couple of thousand meters. Only the peaks visible at high tide. If I understand my math right, that would require a secondary mass close to that of the Sun. The orbital range would increase with the mass, but you'd be **inside** the Sun.
There is a solution. Not a black hole, not a neutron star, but a trillion year old white dwarf. Actually, that would make it a black dwarf. A reject from the heat death of the universe, thrown back in time by some cataclysmic event. Basically a lump of diamond and ice, held by gravity at just above the electron degeneracy pressure, with nothing left to fuse.
It would be dense enough that you wouldn't be inside of it, and cool enough that it wouldn't make the existence of water impossible. It would make the planet very, very tectonic. The planet would actually have a one-month day, orbiting the dwarf at whatever period you chose. The dwarf would need to be a binary system, orbiting an actual star so that the planet wouldn't suffer Mercury's fate, with one side being fried while the other freezes.
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## [Higher Order Spin Orbit Resonance](https://worldbuildingpasta.blogspot.com/2020/12/an-apple-pie-from-scratch-part-ivd.html?m=1#othersynchronousrotators)
Tidal locking is inevitable if you want that much tidal forces involved. However, tidal locking doesn't automatically mean a 1:1 spin-orbit resonance. 1:2, 3:2 (Mercury), 2:1, 5:2, 3:1, 7:2, and so on for every half-integer ratio of rotation period to orbital period are possible. In fact, as the eccentricity of the orbit increases, as 1:1 resonance becomes impossible. Highly eccentric orbits work best if there are few planets in the system and if there is a bigger planet in mean-motion resonance that stabilized the eccentric arrangements (think Neptune and Pluto).
Probably best to put this around a small star. Note that your days will be wild, but habitable (check the link for further information) additionally, you will have eccentricity induced seasonal variation.this is actually a good thing, since the world's axial tilt will tend towards zero due to tidal effects.
If you want a more complex setup, this would also work if the central body were a huge gas giant or brown dwarf orbiting the star in turn.
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Movement is relative, but I've read that an ex-NASA scientist has quantified the speed of Earth hurtling through space to be 1.3 million mph, using the Cosmic Microwave Background as a frame of reference ([link](https://www.businessinsider.com/earth-screaming-through-space-nasa-animated-video-2019-10?op=1)).
I'm working on a story where a scientist has invented a propulsion method that can reach 20% of the speed of light, and intends to travel to the exact location where Earth was 30 years ago.
I'm aiming for soft sci-fi so a certain amount of handwaving is acceptable, but even then, is it plausible that my scientist would be able to calculate where Earth was in relation to the CMB? What about calculating the exact location of a specific human-scale location on Earth 30 years ago?
As a secondary question, given the velocity and the time frame, how long would it take for the scientist to travel back?
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This is an interesting question, and how you approach it can vary. One issue the precision you need. The other is what you consider the rest frame, or reference.
The precision you need is interesting because even determining the location on the earth to very high precision is difficult. For example the Terrestrial Reference Frame which is the center of mass of the earth, and is determined by taking the data from laser ranging to satellites moves around in small but measurable ways that drifts over time.
For the choice of reference frame, I think Astronomers also define a local standard of rest (LSR), and for objects in the solar system that is good enough, but that point is moving with respect to the center of the milky way as the solar system rotates the around galaxy at a couple of hundred km/s. The LSR is probably defined as the mean motion of mass as it rotates around the center of mass of the galaxy.
Astronomers can also define a Galactic Standard of Rest, or a Galactic Rest Frame. For example using quasar data there is an International Celestial Reference Frame (ICRF) that astronomers also use. This works because the quasars in galaxies are so far away. Of course those galaxies are also moving....
So in the question saying that the rest frame is defined by the cosmic background radiation, I think the assumption is that it is a snap shot of the distribution of mass at the origin of the big bang. Then by doing the survey the astronomers, essentially got a map of everything. Once you have that map, you have information at very long distances with which to define your reference frame. This paper on [Plank 2018 results](https://arxiv.org/pdf/1807.06205.pdf) goes on to explain that with this kind of mapping one can obtain the motion of the solar dipole with respect to the cosmic background, and also the movement of the galactic dipole with respect to the cosmic background.
Editing to actually try and answer the question...
I think then the problem becomes a math problem of how well you know the different orbits: Earth around sun, sun around galaxy etc. This is non trivial over long time periods since it is a multibody problem. So in addition to the movement of the solarsystem and planets with respect to the Cosmic Background Rest Frame there are probably errors with that, depending on the precision you want. And then several calculations between the different reference frames, since you want to perhaps land on a particular spot on the earth.
As an engineer, if you had the technology, it might be simpler to send a series of probes back and forth, and have them tell you how far your calculations are off. The probe could essentially just use a camera to take pictures of the stars, find the location and them perhaps you could move to the location you want, or refine your calculations to get the accuracy you want.
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For the story that I am writing currently, it is set on a colonized planet thousands of years after machines wiped out most of the human colony that were established there, and would go on to form an ecosystem with other organisms since they depend on biomatter as fuel. The machines themselves have evolved to take on the forms of predators such as big cats or theropod dinosaurs and ultimately have driven most other apex predators to extinction.
My question is what would be the largest possible organism to exist in an ecosystem with these types of predators. The ecosystem mostly comprises of herbivorous machines but these predatory ones need prey themselves. **What types of animals would be large enough to cleanse the hunger of let's say a tyrannosaurus sized machine without going into direct competition with possibly more efficient plant-eating machines?**
The planet itself was terraformed through a combination of future tech and ancient magic to make it as earth-like as possible. The planet as a result has numerous dynamic biomes ranging from forests, swamps, tundras, deserts, etc. Each of these ecosystems would be occupied by different types of machines, speciallized to specific lifestyles and options for resources.
The robo-herbivores that the herbivorous animals would be competing with would be different based on each biome as a result of this. Certain machines would adapt to browsing or grazing specific foods, and would have to niche partition in order for the organic herbivores to survive.
To be specific, I'm talking about **grassland**. I wanted the humans in this world to have horses as mounts but not sure if that's unrealistic.
The animals would be competing with a number of robo-herbivores that have adapted to life on the grassland. Many of the machines resembled hadrosaurid/iguanodont dinosaurs in their physique and behavior as herding animals, each species only being separated by food preference (different grasses and bushes) and appearance. These robot-herbivores are around 20-30 feet in length and about 1 ton each. There are also large bulky animals similar to elephants and ceratopsians with each individual possessing a long tentacle like appendage designed for grass collection and browsing. These measure around 50 feet long and 3 tons. Although all these species feed off of mostly the same kinds of plants, they tend to feed at different times and different regions of the grassland.
Our largest organic species (probably an herbivore) would need to partition in similar ways to these robo-machines to avoid direct competition.
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I basically think if there is no considerable human civilization anymore and the whole eco system consists of grassland there would be enough plants for herbivorous roboters and natural animals of any size to coexist, as long as they take slightly different leaves- maybe the elephants have evolved to draw nutritiens particularily well from a plant the robots don't quite fancy, or maybe sheep have developped the ability to eat some mice when times are getting all to rough because of robo-sheeps eating all the grass in the west. However I think the T-Rex predators pose a far bigger problem than the food in the grasslands- I assume with overpowered electronic predators herbivors would have to evolve to escape those predators else they'd go extinct for that reason. So I feel fast and small animals that are good at escaping and hiding would be dominating and pretty robust animals that are maybe even able to counter attack a robo-T-rex.
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Considering that humans are involved with this, domesticated animals (such as the horses you mentioned) would be involved as well so it is possible that the robo-predators would be feeding on the descendants of cows and sheep. The cows would probably resemble aurochs since time would have allowed them to become more wild then before.
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**This question already has answers here**:
[What would be the energy requirements to run a world with an artificial sun?](/questions/207041/what-would-be-the-energy-requirements-to-run-a-world-with-an-artificial-sun)
(2 answers)
Closed 2 years ago.
Suppose there is no sun, how much total energy is required to grow food, recycle air, water, and waste for a single person. I want to know how large of a reactor would be needed to keep alive a civilization of a million people who are totally isolated.
I know that humans need a certain amount of calories a day but what I don't know is what the inefficiencies are for converting joules of electrical power from a reactor into food are. Similarly, I don't know how much energy is needed to recycle waste.
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Look at your households monthly electricity bill... specifically the number of watt-hours used. Divide that number by 720 (30 days x 24 hours per day).
That will give you ONE "AVERAGE" HOUR of household power consumption.
Assuming there are four people per household, multiply that number by 250,000.
Now you know approximately how much energy a million people need.
Next, you have to multiply that number by at least 3, OR 4 to supply the city lights, the electric vehicles, entertainment centers, etc. That number might need to go even higher, lets say by a factor of 10.
That might be a rough estimate of how many megawatts to rate your reactor.
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While looking about for references on how to make a strong, prehensile tail, I found [ProjectApex's answer to that exact question](https://worldbuilding.stackexchange.com/a/213191/87100). The solution is to make the tail a [muscular hydrostat](https://en.wikipedia.org/wiki/Muscular_hydrostat), a bodily structure/limb/appendage/etc. that has no skeleton at its core (unlike a conventional limb) and no fluid core (unlike a [hydrostatic skeleton](https://en.wikipedia.org/wiki/Hydrostatic_skeleton)). As Wikipedia so succinctly put it:
>
> A muscular hydrostat, like a hydrostatic skeleton, relies on the fact
> that water is effectively incompressible at physiological pressures.
>
>
>
>
> ...a muscular hydrostat is composed mainly of muscle tissue.
>
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>
Instead of the muscles acting upon a core of some kind, such as a fluid or a skeletal bone, the muscles act upon one another. This means that, since there's nothing solid to exert pressure on, it's exceptionally hard for a hydrostat to exert sideways force - i.e. lifting something at a right angle to itself. However, they can compress, pull, and push with *incredible* strength relative to their weight; [octopi can break a shark's spine](https://www.youtube.com/watch?v=p9A-oxUMAy8), and [an elephant can lift nearly a third of a *ton* with its trunk](https://www.treehugger.com/extraordinary-facts-about-elephant-trunks-4858665).
Additionally, hydrostats are significantly more flexible and precise than bony limbs. After all, they can bend to their heart's content - there are no bones to get in the way. Moreover, since each component of a hydrostat is muscle, regulating that muscle by making a joint in it further up the hydrostat lets elephants do things like [picking up tortilla chips without damaging them](https://www.facebook.com/ScienceMagazine/videos/watch-an-elephant-pick-up-a-tortilla-chip-with-her-trunkwithout-breaking-it/2669900239965910/).
So, halfway through this wall of text, the question: - **how long and heavy can a muscular hydrostat used as a tail get, relative to the size of the organism it's attached to?**
Now, one of the first problems you might run into is blood flow, since it's hard to pump enough oxygenated blood into an exceptionally long (relative to the organism it's attached to) limb or bodily structure. I've cooked up a couple of ways to alleviate this.
For starters, you can wrap the blood vessels in the hydrostat with their own, small, [toroidal](https://en.wikipedia.org/wiki/Toroid) rings of muscle, which help the main heart pump blood, and function in a fashion similar to [peristalsis](https://en.wikipedia.org/wiki/Peristalsis), or a blood pressure cuff; they squeeze the blood vessel in waves, resulting in the blood being forced down it. Additionally, you can implant a line of [ventricles](https://en.wikipedia.org/wiki/Ventricle_(heart)) - severed from their parent heart - along the length of major blood vessels in the hydrostat, to act as [booster stations](https://encyclopedia2.thefreedictionary.com/booster+stations) keeping the flow moving. Given that [the smallest heart in the world is microscopic](https://kids.frontiersin.org/articles/10.3389/frym.2020.540440#:%7E:text=The%20world%27s%20smallest%20heart%20belongs,needed%20to%20see%20its%20heart.), finding ones that are the right size for this task will not be a problem.
Balance is another problem; when you strap a 20-foot-long tail onto a tiger-sized animal, or a 3-foot one onto a chameleon-sized one, you'll find that said animal may have issues remaining stable. Assume that the organism this tail is attached to simply wraps its tail around itself when it is not in use, and that this renders the question of balance irrelevant.
Essentially, assume:
* that the specific problems of blood flow and balance are not relevant to this question
* that this tail is operating under Earth-standard conditions; a 78-21 nitrogen-oxygen atmosphere, 1 atmosphere of pressure, 9.8 m/s^2 gravity, etc.
* that this tail needs to operate on land.
On top of that, while it's biological (i.e. made of meat, not plastic or silicon or metal), it's also artificial - this is something that's being fabricated in a lab, which is why it has features that seem unlikely to evolve in nature - like muscles around its blood vessels and miniature hearts along its length. This means that it is not limited by evolution; it is limited by the designs of [mad gods](https://worldbuilding.stackexchange.com/).
**I'm not interested in pondering what evolutionary pressures would lead to such a thing, nor am I interested in what it might be used for. All I'm interested is how big a muscular hydrostat used as a tail can get relative to what it's attached to.**
I've researched this myself, but, so far, it seems that there's no upper limit to it - the largest muscular hydrostats, a whale's tongue and an elephant's trunk, have simply evolved in response to evolutionary pressures, rather than been designed by humans, and they're pretty big.
Answers should be grounded in reality - no magic, no theoretical physics, etc. I don't need hard science for this to be answered (hence the lack of that tag), but the best answers will explain what the limit is in terms of the tail's weight relative to the animal's weight, what the limit is in terms of the tail's length relative to the animal's bodily length, and do so in a fashion that's rooted in real biology.
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If you want an animal with legs then 1/3 the total mass. At 1/3 of the total mass one such tail can still be articulated by the animal to do things. If it is between 1/3 and 1/2 the weight then it becomes so cumbersome that a part of the root of this tail gets used to extend the torso. With a weight of more than 1/2 the animals weight your animal would have some serous trouble with supplying the tail with energy.
If you don't mind having other organs (stomach, mouth, intestines, etc.) in the tail then there is nothing left to limit it from being universe spanning. Just make sure that it is under roughly the same gravitational force throughout.
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There's nothing stopping a tentacle from being 100% of the animal: see worms and snakes. Worms tend to be pretty small in absolute terms, but snakes can get to be [42 feet and 2500 lbs](https://en.wikipedia.org/wiki/Titanoboa#:%7E:text=The%20only%20known%20species%20is,previous%20record%20holder%2C%20Gigantophis%20garstini.).
I'm not sure if this difference is a size advantage of internal skeletons. Giant squid have tentacles almost that long, they just also have non-tentacles.
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Basically, assuming you have all of modern human knowledge about smelting iron/steel, and the technology level you have is approximately bronze age, what would be the most effective approach to turn iron ores into usable iron tools? Specifically, the approach that would result in the highest quality result, as well as be as easy as possible to do at a large scale (if these don't conflict).
You can assume the technology available includes clay or adobe bricks, pottery, copper and bronze tools, and anything else a later bronze age civilization could be expected to have, in addition to whatever knowledge is needed for the process (this is handwaved, there doesn't need to be a plausible reason they'd know how to do it).
From what I've read, bloomery furnaces with charcoal as fuel were almost always the first ones to be used when civilizations entered the iron age. However, since we now know about all sorts of methods of making iron and steel, I'm wondering if that knowledge could be exploited without today's existing infrastructure. For example, using coke instead of charcoal, or preheating the air used in the furnace, or even using a blast furnace immediately instead of starting out with bloomery furnaces.
I'm not too knowledgeable about this sort of thing, but it's important for a story I'm writing. Any ideas?
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IIRC China went to blast furnaces with waterwheels and windmills to power bellows very, very early. I don't know much about metallurgy but I do know ceramics, and their high-T furnaces were hollowed out earth mounds or hillsides that generated really powerful draughts as well as having excellent efficiency and top temperatures. They were able to produce tens of thousands of items at a time in medieval times, something only matched by the Europeans in the late 19th century.
The Europeans basically only reinvented porcelain with solar furnaces using big lenses, and then had to figure out how to make furnaces for actual production. I expect the layout and scaling-up of your steelmaking facility will be important and I'd look to China for how you'd do it with premodern technology.
If a very limited amount of steel is all you need, e.g. for demonstration purposes, there's also the possibility of asking the locals about if they know of any places with crashed meteorites....
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How long could a planet or moon survive if it had an Earth mass black hole within it?
Hypothetical primordial black hole formed soon after the Big Bang, or low mass black holes formed later by some other hypothetical process, could have masses lower than stellar remnant black holes which should have at least three times the mass of the Sun.
The lower the mass of a sub stellar mass black hole, the faster it would evaporate via Hawking radiation, and the shorter the time it would last before exploding at the end.
It has been calculated that primordial black holes with a mass of about 1 times 10 to the 11th power kilograms would last for about the current lifetime of the universe before exploding.
The mass of Earth is about 5.9722 times 10 to the 24th power kilograms, which is about 5,972,200,000,000 times the minimum mass of about 1 times 10 to the 11th power necessary for a primordial low mass black hole to survive to the present.
Thus a world with an Earth mass black hole inside it would survive for much longer than the present age of the universe before the shrinking black hole evaported. And the black hole would probably not lose a signficant precentage of its mass within a few billion years.
But how long would a world with an Earth mass black hole inside it survive before it was swallowed up by the black hole?
Atoms and molecules and sub atomic particles of the world would be constantly falling inside the event horzon of the black hole, increasing its mass. As the mass of the black hole increased, its gravitational attraction on moleculesa and atoms outside its event horizon would increase, pulling them in faster. And As the mass of the black hole increased, the diameter of its event horizon would increase, and thus the surface of its event horizon would increase.
Those two processes would casue the rate of inflow into the black hole to increase exponentially, and the amount of matter left to the world outside the black hole to decrease exponentially.
So the Schwartzchild radius of the event horizon of a black hole with the mass of Earth would be about 8.87 millimeters, or about 0.3492 Inches. Thus the suface area of the event horizon of a black hole with the mass of Earth would be 8,769.6115 square millimeters.
That is a very small surface ara, but a very vast one compared to the sizes of molecules, atoms, and sub atomic particles.
So can anyone calculate how long an Earth mass black hole could remain inside a planet, moon, or other world before the rate of infall of the world's matter caused disasters on the surface of the world. Or can anyone point to a source of such calculations?
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### Billions of years
**Assumptions:**
I'm overlooking the "How did it get there" implied by the question. One moment it was suddenly there and the previous moment it wasn't.
I'm assuming your planet is also the size of Earth - so when the blackhole is "done" it's mass has doubled. The blackhole is in the exact centre so there's no orbital shenanigans - perfect equilibrium.
**This is really a fluid dynamics question:**
The blackhole is sitting in high pressure molten iron and consuming it, the upper bound of it's rate of consumption is going to be determined by high pressure liquid metal fluid dynamics - the blackhole swallows all the fluid it intersects, how quickly can the liquid attempt to replace the gap?
We don't know - these ultra high pressure ultra high temperature fluids don't get a lot of testing because we don't have lab equipment that can replicate these temperatures and pressures. There are papers and research on the topic (eg for metal casting) but they're multiple orders of magnitude below what we need. Liquids work towards filling the container, and they propagate the "information" they need to share to do that at the speed of sound in that liquid. To the best of our knowledge, the liquid iron will cross the event horizon at no faster than that rate.
The speed of sound in liquid iron is [3.8km/s](https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/93JB03111).
**Doesn't gravity somehow "outrank" fluid dynamics or something?**
When looking at this problem - it's really easy to mistakenly think that gravity plays a big part here. **[Gravity is the weakest of the fundamental forces](https://en.wikipedia.org/wiki/Fundamental_interaction#:%7E:text=Gravity,-Main%20article%3A%20Gravity&text=Gravitation%20is%20by%20far%20the,scale%2C%20where%20electromagnetic%20interactions%20dominate.).**
With the pressure at 3.6 million atmospheres accelerating the iron, we can essentially ignore gravity as a rounding error, but - If pressure, gravity or some other force tries to accelerate it faster then 3.8km/s - the fluid dynamics will fight back and the accelerating iron will collide with its neighbour atoms and and form turbulence patterns slowing it down, you'll also maybe get cavitation with pockets of gaseous or supercritical iron mucking up the flow. The spherical nature of the blackhole makes this effect much more pronounced - the flow chokes.
The Electroweak force causing the choking interaction is roughly $10^{25}$ times as strong as the Gravity accelerating the iron towards the hole. Gravity looses the battle against fluid dynamics by 25 orders of magnitude.
Put another way - the number of iron atoms at any given distance from the event horizon isn't constant - all atoms are accelerated to the blackhole by pressure / gravity but the increased density gradient approaching the event horizon as even more iron tries to accelerate into such a tight space deflects most of them away into eddies and turbulence.
3.8km/s is an upper bound from physics. Because of these fluid dynamic effects; I expect it to be lower instinctively due to inefficiencies in the motion but can't begin to prove it. I'd suggest reading the [obligatory xkcd](https://what-if.xkcd.com/147/) on the topic of forcing fluids through tiny holes at speeds faster than the speed of sound.
**So how fast will the core go into the hole:**
You've mentioned the surface area is 8,769 square mm. I calculate that's for a sphere of radius 26.42mm - the black hole will not get that big before destroying the planet. I've calculated it as 966 square mm from $4 \cdot \pi r^2$.
Your black hole has a surface area of 988 square mm, each square mm of surface area is consuming liquid iron at 3.8km/s, which is 3.8 litres per second per mm of surface area. 3.6kL of liquid Iron per second.
[Wikipedia estimates](https://en.wikipedia.org/wiki/Earth%27s_inner_core) that the core has $10^{23}$ kg of iron, and it's average density is about 12.9kg/L. So from this you're blackhole is consuming 46.4 tonnes per second of liquid iron, and it's got $10^{23}$ kg to get through before the core is gone. The core is 1/60th of the earths mass, so the blackhole will only grow by 1.6% from the consumption of the entire core - this is small enough that it can be effectively ignored for the purposes of this approximation and we can use the same consumption rate for the entire process and still be accurate to 2 significant figures.
This works out $2.1 \cdot 10^{18}$ seconds to consume the entire core, or $6.4 \cdot 10^{10}$ years - 64 trillion years to consume the entire core.
**And when do we notice this on the surface?**
How much of the core needs to disappear before we notice? That's hard to answer, as it'll be on a geological scale and difficult to differentiate from normal tectonic activity. 0.01% of the Earths core will be consumed in 6.4 billion years, shrinking the circumference by a few km over that period, but that's a rate slower than continental drift by 4 orders of magnitude. So as a rough approximation, for every 1 earthquake the blackhole causes, 1600 earthquakes are caused by tectonic plate activity.
**Is there one in the Earth Now?**
If the black hole had appeared 6.4 billion years ago in the middle of the Earth, I'm not sure we'd be able to detect it yet. We have some very precise measurements of things like Earth-Moon distance, but we don't have 500 years of these accurate records to compare and note a trend. All our precise time and distance measurements would include the existing blackhole effects in their calculations, and our estimate for the earths mass would be off by a factor of 2 - we'd just assume higher density in the core to explain the extra mass.
**If one appeared today, would we notice it?**
If it appeared today, we'd notice the time dilation pretty quickly (GPS would be off by 10s of meters almost instantly), and clocks in space would get out of sync and orbits would change - moon would change orbit noticeably - but we wouldn't be able to blame it for anything geological for at least 100 million years ("Hey that magnitude 3 earthquake last night that jiggled the glasses in the cupboard? 66% probability it was the blackhole!").
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Let's say there is a sapient species around the size of an t-rex, they weigh on average 6000-8000 kg and are omnivores whose diet is mostly composed of plant matter, but with some meat. They are around as advanced as late neolithic or early bronze age humans.
Would a village populated by 100 of the creatures be sustainable in the long run? Are there any ideas for agricultural methods efficient enough to meet their energy needs to settle permanently in an area or would they have to be nomadic in order to prevent overtaxing the environment?
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TL;DR: probably not: they need a lot of calories, and it isn't clear how much farming they could usefully do compared to a group of humans with similar calorific demands.
You might be able to handwave away some of the difficulties if they had access to particularly good crops... things like potato, or sweet potato or perhaps [sugarcane](https://en.wikipedia.org/wiki/Sugarcane#History), but it bears remembering that quite a lot of agricultural tasks really benefit from having human-sized [prehensile appendages](https://en.wikipedia.org/wiki/Prehensility) and giant sloths seem likely to be ill-equipped in that regard. Nomadic pastoralism might be the only practical solution for them (and even then, they probably ain't gonna be making many dairy products!).
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For convenience, lets compare your neolithic giants (which sound a bit like [megatherium](https://en.wikipedia.org/wiki/Megatherium)) to large modern day mammals in the form of African elephants.
Elephants are smaller, of course, and not omnivorous, but they'll do as a point of comparison. Somwhere like [Zakouma](https://www.nationalgeographic.com/animals/article/wildlife-watch-chad-zakouma-elephants-poaching) can sustain a herd of several hundred elephants, which means that your 100-strong group is almost certainly sustainable *as hunter gatherers*.
If your peeps had a similar diet to elephants, they'd be expecting to eat about 5% of their bodyweight a day as uncooked plant matter... that'd be 35 tonnes of food per day, or the best part of 13000 tonnes per year. According to [San Diego zoo](https://animals.sandiegozoo.org/animals/elephant), that's the equivalent of 140000 calories per day or 586MJ. We know that [cooked food yields more calories](https://www.discovermagazine.com/health/why-calorie-counts-are-wrong-cooked-food-provides-a-lot-more-energy) though we're not entirely sure how much... somewhere between 10 and 50%, perhaps. That halves the amount of *food* crops that need to be grown but non-trivially increases the amount of *fuel* crops that are required, and I bet that while the poop of ruminants [can be used as fuel](https://energypedia.info/wiki/Cooking_with_Dung), the poop of animals fed a cooked and processed food diet will be less calorie-rich and therefore less useful as a fuel.
I was unable to find useful food-energy-yield estimates for bronze age farming, alas, but I suspect such figures do exist somewhere.
By analogy though, we can see that the largest cities in the [bronze age middle east](https://en.wikipedia.org/wiki/List_of_cities_of_the_ancient_Near_East) had upwards of 30000 people. If those people managed at least 1500 kcal per day, then the total food-energy requirement of the city would be ~190GJ/day. The equivalent for your giant village would be merely 60GJ/day,
Clearly sourcing that much food is *possible* with bronze-age technology and organisation, but a city of that size like ancient Memphis was the capital of a relatively large and prosperous society with a total population well in excess of [a million people](https://en.wikipedia.org/wiki/Old_Kingdom_of_Egypt). Feeding a city without such a large agricultural system around it would be a tough proposition. I can't find a hint of how big the agricultural population needs to be to feed a city, but it ain't gonna be small
Your giants seem like they'd be able to do large-scale agriculture more efficiently than humans (they're their own draught animals, after all) but how much this would help is unclear... you haven't given us anything to work with, and I'm not sure how to go about estimating it. If they were substantially more productive than the equivalent number of humans with the same calorific demands (eg. could one of your giants do the work of 70-100 or more humans?) then it is possible they'd be able to farm for themselves.
What might be easier though is some form of pastoralism where the giants practise a certain amount of land management, but have mobile settlements. As (or *if*) their agricultural techniques improve they might be able to move more slowly or even settle down, but generating enough calories without some particularly good crops seems like it would be difficult.
[Answer]
**Assuming Your Species has Mammalian like Metabolism:**
A T-rex is about the same size as an elephant, and [this](https://globalelephants.org/space-much-enough/) elephant sactuary has a range of 2700 acres for 5 elephants, or 540 acres/elephant. However, majority of that space is actually needed for psychological reasons. The initial estimate that sanctuary used was 110 acres/elephant, so we know at that is at least enough space to provide enough food. Judging by the photos, I looks like the majority of the sactuary is grassland. Conveniently, [this](https://reducing-suffering.org/net-primary-productivity-land-type/#NPP_per_unit_area) site claims that grasslands have the same net primary production as agricultural lands. In addition, grasslands have the lowest NPP than any other ecosystem your species would realistically be living in. Whether the species is nomadic or agricultural, a population of 100 individuals needs at most 11,000 acres.
**Assuming Your Species has Reptilian like Metabolism:**
[This](https://what-if.xkcd.com/78/) analysis by a former NASA researcher concludes that 80 hamburgers/day can sustain 15 T-rex. Conveniently, 80 hamburgers is about about [12lbs](https://www.wolframalpha.com/input/?i=80+beef+patty+to+lbs) and a cow beef cow weights about [1,200lbs](https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1167344.pdf). Using the latter resource's handy formula, one cow needs ~1.8 acres. That means that 100 T-rex can be supported by [184 acres](https://www.wolframalpha.com/input/?i=100%20*%201200%20*%200.04%20*%20365%20%2F%209500).
But you didn't ask about T-rex; you asked about T-rex sized omnivores. The vast majority of energy is lost when you go up a tropic level. In fact, ~10% is accepted as a reasonable estimate for how much is preserved. T-rex ate herbivores, which ate plants. This means 1% of the energy produced by the plants makes it to the T-rex. The herbivores however, get 10%. By having your T-rex sized species be omnivores who specialize in plants, you have effectively cut the land requirements to sustain an individual ten-fold! Now, the land required for your village is only 18 acre.
You may be wondering why the first estimate is so much bigger than the second. The simple answer is that mammals are warm-blooded while reptiles are not. Being warm-blooded offers a lot of [benefits](https://www.scientificamerican.com/article/first-warm-blooded-fish-discovered/) (e.g. greater temperature tolerance, faster muscles, better senses), but the energy costs are **huge**.
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what can they eat? while I do find it hard to push away from the concept of making them nomadic or at least seasonally migratory, opening up more exotic food options might help them a great deal. Some sources of food might be trees, grass, decaying plant matter. grass and trees are full of cellulose so for they most part they would be pretty sedentary as they don't get a ton of energy fast out of that route, decaying plant matter might be a bit easier on them and their size should help them avoid any major poisoning as well as just things they've evolved. either route however its worth considering giving them a complex or multiple stomachs. Decaying matter would have a lot less cellulose and have the added nutrition of things such as beetles and termites but obviously be lacking else how as a lot of it would be digested by the things breaking it down. You could also take the leaf cutter ant approach and have them farm a fungus that consumes otherwise difficult to break down cellulose. Another interesting Idea might be for them to control large herds of mega fauna herbivores like cattle and follow them to greener pastures, however this proved unsustainable even with things as small as humans so to avoid this they would have to either be able to maintain a really strong population or perhaps have a domesticated version that wastes less energy and nutrition on things like horns or tusks allowing for faster growth with less resources.
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It would depend on the size and abundance of everything around them. If their food sources, etc. are as big as them or incredibly abundant, then they probably could.
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I was thinking of a universe with 3+1 dimensions, in which the spacetime near a massive body is curved. If this universe was empty of energy and matter then the spacetime geometry would reduce to that of Special Relativity, but even in the limit as the distance from a massive body increases and the speeds decrease the spacetime curvature never reduces to Newtonian Gravity.
Could this universe be self consistent?
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Assuming the laws of physics are the same as in our universe, we just need to look at the conditions under which general relativity reduces to newtonian physics.
Since under "normal" circumstances (those we are used to) physics almost always behaves newtonian, it seems easier to list possible conditions for *non-reducibility*:
* relativistic relative speeds (v>0.1c)
* extreme gravity differences (relative accelerations of thousands of earth gravities)
* extreme energy densities (eg. the mass of the moon in the volume of an apple)
While such conditions will exist in many places in a normal universe, one that consisted solely of such extreme environments seems very unlikely. Since the significant distinction of non-newtonian environments is a high *relative* velocity/curvature, there would have to be no large (relative to the perception of the observer possibly concerned with newtonian approximation) region within which all relevant objects were moving slowly (<0.1c) and that had no significant curvature change.
One possibility to prevent regions with a consistent curvature from existing would be permanent gravitational disruptions - gravity waves - with a easily perceptible magnitude. However, I find it difficult to believe that life (as we know it) could exist (or develop) in a universe where all structures were permanently exposed to significant spatial fluctuations.
Another possibility would be a universe where almost all relative movements were close to the speed of light. While this seems even more problematic for the existence of life, a lower speed of light might not necessarily have a big impact on the cellular processes essential for life. Observers in such a universe would constantly experience relativistic effects, though information transfer would obviously be limited to a pace that would seem glacial to us.
Whether our kind of life would really be able to exist in such a universe (an extremely low speed of light would influence things like thermodynamics (movement of molecules), blood flow and nerve signal transmission) seems still doubtful, but such a universe would certainly be self-consistent and should allow for the development of observers (without observers, the question of whether a newtonian reduction can be locally useful seems to lose meaning).
If you are not at all interested in the existence of observers, a universe disturbed by high-frequency, high-amplitude gravity waves would also be consistent and globally non-newtonian (except on the smallest scales, where due to the laws of differential geometry every part of space seems flat).
If you want to have a universe where even on the smallest possible scales movement looks utterly non-newtonian, my only idea is to postulate a phenomenon generating gravity waves according to the [Weierstrass Function](https://en.wikipedia.org/wiki/Weierstrass_function). Since that function (and therefore the shape of the gravity waves) isn't differentiable anywhere, no region of space would look in any way newtonian.
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First post (reposted and more focused). Thanks in advance. I'm working on an epic fantasy series where our future-Earth has gradually stopped spinning about its axis (though still about the sun). Assume magic/future-tech to allow for these assumptions: (1)Assume humans/animals/plants survived and are now thriving. (2) **Assume 6 months of sun followed by 6 months of none**; therefore we are NOT in a tidally-locked situation. (3) Assume one equitorial continent and a northern ocean and southern ocean. (4) Assume 4 "seasons" of dawn twilight, full day, dusk twilight, and full night.
My one focused question is what would the seasons be like weather-wise (along the equitorial continent)? Precipitation, temperature, etc.
Thanks.
[Answer]
### I've never seen the word "Hellish" in so many academic papers.
Side note: **The Earth will start spinning again:**
[The moon will start the rotation again](https://webcache.googleusercontent.com/search?q=cache:n4nYx_H-wS8J:https://io9.gizmodo.com/xkcds-creator-explains-what-would-happen-if-earth-stopp-1625068208+&cd=1&hl=en&ct=clnk&gl=au). It will be slow, takes thousands of years, and wont get up to full 24-hour speed, but it will save us from the 12-month day, which, as you've probably guessed, is going to be hellish.
However, lets assume you've magic'd away the moon, then what:
### Crippling hot summer. Very stormy.
The hot side gets very hot. Very very hot. The [calculation is on Wikipedia](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law#Effective_temperature_of_the_Earth) but your day time temperature will peak at about 102 degrees Celsius (in the shade).
For those preferring freedom units, that's 215 F. You can boil water without a stove.
That temperature will evaporate water extremely quickly. That moist hot air will hit dry hot air and create extreme storms around the "midday" area. Those storms will block the sun in nearby areas, dropping the temperature, but creating more of a temperature gradient. I lack the imagination to predict how intense these storms will be, but "Hellish" seems like a safe bet.
Rocky or concrete ground that holds a lot of heat will get hit with rain, it will immediately evaporate, and fall back down again in a constant cycle. This cycle will make bigger and bigger hailstones each cycle. Basketball sized hailstones will probably result.
But fear not, some microbes will survive the heat, as well as any humans in deep underground bunkers.
The hottest temperature plant life has survived is 72 degree C, so no plants survive the summer.
### Extremely stormy sunset
I lack the skill to predict exactly how stormy this will be. All the papers I read just say things like "hellish" rather than give a calculation of wind speed.
The wind will be strong enough to knock you over even if you're braced for it. Strong enough to blow over anything except reinforced concrete and very flexible things.
The rain will be intense and sudden, and then hail will fall. I don't think you'll get much nice puffy snow, the water will just fall to earth as chunks of ice.
### Freezing cold winter
The moon and stars gives just over a million times less power than the sun, and it keeps getting colder over all 6 months. The equilibrium point works out to (~0.0006/5.6E-8)^(1/4), or 10 Kelvin. (-263 degrees C), it will never get there (heat will be sucked from the ground and ocean for all 6 months), but expect about -100 C. We could get "hail" made of carbon dioxide.
Petrol will freeze. Oil will freeze. Antifreeze will freeze.
The ocean will freeze down at a rate of about 5cm per day. By the end of winter the ice over the ocean will be about 8m thick.
### And a hurricane, earthquake and flood all at once for sunrise.
Same intensity storms as sunset, but this time the frozen ground (which is frozen solid to a decent depth, below most existing foundations) now rapidly thaws. Water tables which had frozen will now thaw. This will destabilise the ground, structures will move, sink, and fall over.
All water has frozen, and starts thawing, however all the small creeks and streams will thaw before the big rivers - entire countries will be flooded by thawing water that can't fit into the frozen lakes and rivers.
Also the oceans will thaw top-down, so the rising ice will push thawed water up onto the land.
### Oh, and the planet will be totally flat in a few centuries.
The freeze-thaw cycle is one of the best ways nature has to flatten landscapes. Water seeps into a crack in a rock. Freezes and expands, cracking the rock. The equator and tropics are usually free of this process.
However now you have a planet wide deep freeze and thaw cycle, every mountain will be reduced to gravel, and that gravel will be blown around the planet. The planet will eventually form a boring, uniform, sphere.
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I'm writing a story about the supernatural, except with as few "explained by magic" elements as possible. In the case of vampires, I want them to look as similar to humans as possible while being able to see at night as well as we can in the day. This rules out slit or hyperenlarged pupils. A taptum lucidum would be cool but it blurs vision. I read that maybe quickening the protein reaction in cones would work, but it wasn't explained whether that would negatively affect vision clarity.
Also, I thought it would be interesting to change the cone frequencies so vampires can see red light more intensely, and also UV light. I believe uv vision in vampires would be beneifcial in warning them of the approaching dawn before its too late. If this means sacrificing some color vision between the two spectrum extremes I am perfectly alright with that. But that then raises the question of how the uv light will pass through the cornea and lens.
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The human eye is very optimized to do what it does and that is detect various levels of light that you might find throughout the daytime; essentially dusk till dawn (pun intended). The frequencies that are eyes detect (visible spectra of colours) are not random either and are very in tune with sensing relevant information about the world which aids in survival. Likewise the light levels the eye can detect are very optimized for conducting business over the same period of the day.
Starting with the frequencies:
The reason that our eyes cannot see ultraviolet light very well is because these frequencies and are energetic enough to damage our eyes. So the eye contains an internal lens which filters these frequencies out; there are people who are born without these filters or lose them due to surgery report higher sensitivity to short wavelengths including the ability to see light ultraviolet sources, however, these people are at a higher risk of losing their eyesight due to cataracts. For vampires, I'm guessing they would want to avoid sunlight so it might be beneficial to be more sensitive to ultraviolet light, but I wouldn't see why this would necessitate an external change in appearance of the eye.
Infrared detection is a bit of a different case. Infrared wavelengths interestingly enough tend to be absorbed by materials to which visible light is transparent. For instance, Water and Glass allow visible light through, whereas these materials tend to strongly absorb infrared wavelengths. This of course is a general trend and differs on the exact composition of the material in question, but it is important because the eye is filled with water-based fluids which absorb most near-infrared wavelengths of light.
Some animals, like some snakes, can sense mid-Infra wavelengths to detect sources of heat, but these organs do not even remotely resemble an eye and are very short range (within a few meters). There are many reasons for this, part of this is because short wavelengths require extremely small apertures to focus the light, severely restricting the anatomy of the organ, and also because there are much better ways to see (eyes for example).
So while detecting near-ultraviolet may be a useful fairly practical thing for your vampires, without too much of a visual give-away, I do not see much use nor feasibility in detecting near infra-red.
Now to the question of seeing in low-light environments:
This is difficult because the only ways to enhance the ability to see in low-light environments is to either increase the amount of light allowed into eye (larger pupils) or to increase the light reflected within the eyes (taptum lucidum). Both these method will require visual changes to the eyes.
Increasing the concentration of rods over time to adapt to low level environments, would likely work without resulting in a significant change to the visual appearance of eye, but would still be far short of true night vision. Of course this would likely also affect colour vision and possibly visual acuity to some degree.
[Answer]
How about taking an example from cats? Their pupils get very small when there is lots of light, and get much larger when it is dark. The structure of their eyes also helps them see prey better, which could be an advantage for your vampire.
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Respirocytes are an artificial analogue of red blood cells. Tiny sapphire capsules that can absorb oxygen in the lungs and release it in the capillaries. From the capillaries to the lungs, they, in turn, deliver carbon dioxide. Only respirocytes are hundreds of times more effective than ordinary red blood cells - each of them is able to carry much more oxygen molecules. An injection of fifty cubic centimeters of solution is enough to replace the entire volume of human blood (5 liters) in terms of transport efficiency. If you replace one liter of blood with a solution of respirocytes, the subject will be able to forego breathing for up to four hours.
Here's a page on Ray Kurzweil's website talking about them as a link and explaining where these numbers come from:
<https://www.kurzweilai.net/respirocytes>
( More detailed description of respirocytes: <https://foresight.org/Nanomedicine/Respirocytes1.html#Tab2> )
My question is: how can I biologically create the above-mentioned "respirocytes" as another type of red blood cells (completely replacing them)?
That is, is it possible to grow biological analogues of respirocytes by means of certain biological mechanisms ( similar to the formation of bones)?
Yes, most likely, sapphire and diamond can not be used as a building material for respirocytes of biological origin, for a number of reasons. Therefore is it possible to replace sapphire with some other more affordable material, but still able to withstand high pressure (more than 50-70 atmospheres)?
It is also interesting to learn how to create "clottocytes" biologically. Clottocytes, for example, replacing the "native" human platelets achieve bleeding cessation (artificial fast-acting hemostasis) in 1 second, and the bleeding can be quite extensive (physical tissue damage) or small internal. At the same time, the concentration of artificial platelets is 100 times less than natural ones. That is, clottocytes are 10,000 times more effective than the natural analog, since the time of normal thrombogenesis varies from 5 to 17 minutes.
[Answer]
Looking at the two referenced articles: I think they qualify as science fiction, or even fantasy. The proposed respirocytes are gas storage tanks at the nano level, with many atmospheres pressure. One minor flaw in one of them, and the patient might explode!
Having said that, I think that it is possible one could build something better than a red blood cell for oxygen transport. I think with work, one might achieve an order of magnitude improvement ... but I wouldn't expect it until nanotechnology has been in general use for *centuries*.
I expect the big problem to be telling the synthetic when to acquire oxygen and carbon dioxide, and when to release it.
I suspect that red blood cells just balance the levels, releasing the $\mathrm{O\_2}$ and $\mathrm{CO\_2}$ when they have more than the surrounding tissue, and absorbing when they have less. I think this is comparable to osmosis.
Being significantly more efficient would probably require being more aggressive, but this requires two things: a mechanism for knowing which to do, and power to do it.
Strangely, I can conceive of a way to work on this. If these nano-machines could receive power through a small electromagnetic field, field generators could be placed on each heart exit to power and configure them.
While you might be able to biologically grow the nano-machines, I doubt the field generators could be, especially as they need power too.
If you don't need that much more efficiency, one might just design a molecule like hemoglobin and a molecular construct to hold them, that could serve as an efficient red blood cell replacement. And like a red blood cell, it would not need power. (I suspect there is a lot of inefficiency in the red blood cell because it had to start as a cell.)
This could almost certainly be built biologically.
It might also have a longer lifespan than the 90 days of a red blood cell.
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For my project there is an environment with a very rapid fire regime due to the usual stuff like a dry seasonal climate and dragons. While most animals escape the flames by running, burrowing, or flying away; there is one that simply takes the heat.
It’s a massive Xenarthian that looks like the love child of a Megatherium and a Pangolin ! 
It’s fire specific adaptations:
•Covered in Keretainious scales that are heat resistant and have a gloss to them that causes the burning venom sprayed by dragons to simply flow off like the water off a duck’s back so that it can clobber the puny lizard to death (dragons weigh like 200 pounds in this setting)
• Sweats a bunch when it gets super hot, maybe natural flame retardant.
• Can close its nostrils and hold its breath for a considerable amount of time due to a very slow heart rate and big lungs.
Is this feasible?
[Answer]
The answer is a qualified yes. Adaptions would certainly help an animal survive fire, but only to a point. Big animals can get overheated very quickly so the problem is more one of temperature control than fire resistance.
If the soil was loose or sandy it might pay for the animal to dig itself a hole or at least a hollow in which to lay so that only the top half of its body was exposed to the flames. In addition if the excavations were pushed back in the direction of the fire they might smother nearby combustible materials.
Another advantageous feature would be a thick fire resistant and insulating hide at least on the back. One that could regrow after fire damage a bit like hair or nails.
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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.
Does anyone know an equation or something along those lines for calculating how many and the locations of atmospheric circulation cells for a planet?
Also, does the planet's radius and atmospheric content affect it?
This is my first question on here so I am open to constructive criticisms!
[Answer]
Firstly, you would need to define 'circulation cells'.
If you're talking about, say, low pressure surface systems, these are considered 'synoptic scale', and tend to be on the order of 1000km+ of horizontal distance. These surface lows circle Antarctica, for instance, riding the upper atmospheric river of air known as the jet stream. As wind exits troughs within this jet stream, this creates upper air divergence (a vacuum). This pulls air from the surface, thus creating low pressure at the surface. This is the primary driving engine for middle latitude and sub-polar weather in the southern hemisphere.
Moreover, from a planetary perspective for earth, these synoptic scale systems (circulation cells) are driven from a planetary scale by cells - the Hadley Cells, Mid-latitude or Ferrell Cells, and Polar Cells. Please see below a diagram. This is what creates high pressure at the poles and in a band at roughly 30 N & S latitudes (think where you find the majority of earth's non-orographic deserts). This also drives a global equatorial band of rain called the Intertropical Convergence Zone (ITCZ). This band of rain basically bounces between the two high pressure belts around the equator seasonally.
Included is a diagram of the planetary cells. I've also included a picture of the Antarctic low pressure systems circling the continent (Antarctica is actually the largest desert on earth!). Coriolis (spin of the earth) also plays a role in determining circulation of high and low pressure systems by hemisphere.
So I suppose you would have to start by: (a) determine the thermal driving mechanisms for your planet (for earth it's the heat differential between the poles and equator); (b) determine the behavior of the upper atmospheric flows (the atmosphere behaves very much like a fluid); (c) come up with a basic weather modeling scheme from this (a VERY complex and difficult process).
I hope this helps.
[](https://i.stack.imgur.com/ozMmc.jpg)
[](https://i.stack.imgur.com/fSX3Q.png)
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Inspired by [this answer:](https://worldbuilding.stackexchange.com/a/150920/16987)
Suppose there is an enormous dragon sleeping underground (let's not worry about the biomechanics of how such a creature could exist). One day, it wakes up, shakes the earth off its back, and takes off, leaving the planet and flying into space, to destinations unknown. In the linked answer, @elemtilas demonstrated that a dragon the size of Asia would destroy the planet, returning it to a ball of molten rock and stripping most of the atmosphere. My question is, how large could such a dragon conceivably be, to be able to take off without eradicating all life on the planet?
EDIT: Okay, let's get some devastation scale definitions. Using [this](http://www.openthefuture.com/2006/12/an_eschatological_taxonomy.html) classification of end of the world scenarios, the dragon in the previous answer caused a class 5 event, close enough. What would be the largest dragon that could take off while staying below, say, a class 4? Biosphere potentially damaged, but not destroyed, and wide-scale diverse life will recover and continue on Earth.
(By request, the listed classes from that site)
0: Regional Catastrophe (examples: moderate-case global warming, minor asteroid impact, local thermonuclear war)
Global civilization not eliminated, but regional civilizations effectively destroyed; millions to hundreds of millions dead, but large parts of humankind retain current social and technological conditions. Chance of humankind recovery: excellent. Species local to the catastrophe likely die off, and post-catastrophe effects (refugees, fallout, etc.) may kill more. Chance of biosphere recovery: excellent.
1: Human Die-Back (examples: extreme-case global warming, moderate asteroid impact, global thermonuclear war)
Global civilization set back to pre- or low-industrial conditions; several billion or more dead, but human species as a whole survives, in pockets of varying technological and social conditions. Chance of humankind recovery: moderate. Most non-human species on brink of extinction die off, but most other plant and animal species remain and, eventually, flourish. Chance of biosphere recovery: excellent.
2: Civilization Extinction (examples: worst-case global warming, significant asteroid impact, early-era molecular nanotech warfare)
Global civilization destroyed; millions (at most) remain alive, in isolated locations, with ongoing death rate likely exceeding birth rate. Chance of humankind recovery: slim. Many non-human species die off, but some remain and, over time, begin to expand and diverge. Chance of biosphere recovery: good.
3a: Human Extinction-Engineered (examples: targeted nano-plague, engineered sterility absent radical life extension)
Global civilization destroyed; all humans dead. Conditions triggering this are human-specific, so other species are, for the most part, unaffected. Chance of humankind recovery: nil. Chance of biosphere recovery: excellent.
3b: Human Extinction-Natural (examples: major asteroid impact, methane clathrates melt)
Global civilization destroyed; all humans dead. Conditions triggering this are general and global, so other species are greatly affected, as well. Chance of humankind recovery: nil. Chance of biosphere recovery: moderate.
4: Biosphere Extinction (examples: massive asteroid impact, "iceball Earth" reemergence, late-era molecular nanotech warfare)
Global civilization destroyed; all humans dead. Biosphere massively disrupted, with the wholesale elimination of many niches. Chance of humankind recovery: nil. Chance of biosphere recovery: slim. Chance of eventual re-emergence of organic life: good.
5: Planetary Extinction (examples: dwarf-planet-scale asteroid impact, nearby gamma-ray burst)
Global civilization destroyed; all humans dead. Biosphere effectively destroyed; all species extinct. Geophysical disruption sufficient to prevent or greatly hinder re-emergence of organic life.
X: Planetary Elimination (example: post-Singularity beings disassemble planet to make computronium)
Global civilization destroyed; all humans dead. Ecosystem destroyed; all species extinct. Planet itself destroyed.
[Answer]
**Working backwards from your specified end results, a class 3 event**
First we'll assume this is not a man-made dragon, so it's a class 3b, not 3a.
In the examples of a 3b event, as cited in your reference site (and transcript), one item listed is a "major asteroid impact", and while reading the cited answer (especially phase V) I was reminded heavily of what I would imagine a "dwarf-planet-scale asteroid impact" might look like, which happens to be another citation from your reference site, matching the class 5 event you mentioned as well. And the dragon itself, in that answer, could reasonably be considered to be "dwarf-planet-scale".
So, I suggest treating this new dragon as a "major asteroid" scale, in terms of destruction.
The dwarf planet dragon was probably on the lower end of the spectrum, as far as mass and speed are concerned, for dwarf planet impactors go. But it made up for it by concentrating its force on 4 small points (each foot), poking narrower and deeper holes and releasing energy from VERY deep in the Earth.
However, since the major asteroid scale dragon won't be poking it's feet in to the mantel, it will have to increase its devastation capability, either by being on the higher end of the size spectrum for asteroid impacts, or by taking off at a speed that is faster than average for asteroid impacts, or some combination of the two.
How big of an asteroid is that? I suggest using the Chicxulub asteroid (the one cited to have caused the mass extinction of dinosaurs about 65 million years ago) as a reference. It's estimated to have been between 11 and 81 km in diameter.
Since asteroids are generally more spherical than dragons, we'll take this 80-ish km long asteroid (we're going for the large end of the spectrum, remember) and stretch it to Dragon-shape. Depending on the specific body style of this dragon (long thin eastern asia versions vs shorter stockier european, etc.) this will make it well in excess of 250 km long, maybe reaching 500 km or more. Wingspan will be even greater, say, 500 km to as much as 2500 km
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[Question]
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So, in my setting, telekinesis is divided into two sub-fields:
* **Soft telekinesis** allows for precise manipulation of objects but doesn't pack a punch. Newton's third law is negligible for this type.
* **Hard telekinesis** is a quick burst of force that can accelerate an object in a certain direction, but also creates an "opposing force" of the same magnitude in the opposite direction.
+ Because of this, hard telekinesis "force bursts", usually originate from the side of the wizard, not the wizard directly, save for a few examples.
+ Force bursts dissipate over longer distances, at around 50 meters,
the opposing force dissipates much faster.
+ The burst itself is invisible and can only be detected through the air turbulence, it generates and its mechanical interaction with other objects.
+ The burst has a "recharge time", but doesn't **seem** to consume material components, and can be cast as long as sufficient energy is available.
+ Though somewhat scalable, the only time Anon (the strongest wizard in the setting) used hard telekinesis at its full potential, it sent an adult human male, weighing 89 kg, flying for 4 meters before crashing into a rock at 3.5 m/s (I guess. It may have been faster). The guy survived, but his spine was done for, and now he has to spend the rest of his life in a wheelchair.
+ Note: [Hosch250 did the math](https://chat.stackexchange.com/transcript/message/49381540#49381540), and it came out to be at around **610 newtons**.
Notes:
* **Magic**: Magic is a mysterious art, that involves robots, chemistry, physics, and is nearly synonymous with science.
* **Telekinesis** is the basis of so-called spells. Despite the word's origins, it doesn't involve woo, nor is it the sole doing of the mind. The mind commands an unspecified type of robot, or groups of robots, to execute its will. It's that you can't really see them, that's why it appears to be classical telekinesis.
**You're free to use nanomachines, superconductors, and even James, as long as the laws of physics aren't violated.**
**How could my hard telekinesis work? The rules have been established, but I don't know what mechanism should I use.**
**How can I generate that much force?**
*How can I keep it concentrated?*-In the next question
[Answer]
Assuming you are wanting to use an existing force within the realms of known physics today, I can think of two ideas.
The first idea uses your soft-telekinesis to rearrange the electrons in two objects or areas -- like a knight and the air in front of her or him. Or between the wizard and an arrow|bullet|club
Assuming I have two things A and B separated by the distance d, then IF you concentrated a fraction of the electrons in A and B you would create a coulombic force that would repel A and B from each other by the equation
$F= k\frac{Q\_a\*Q\_b}{d^2}$
where k is coulombs constant
${Q\_a}$ is the charge on A
${Q\_b}$ is the charge on B
the trick is d can be arbitrarily small. The smaller the gap between A and B for constant values of charge on A and B, the greater the force.
There is a real-world limit since high charge densities seek out low or opposite charges. Examples are lightning and static zap from touching a doorknob wearing your socks.
And another real-world limit would be that things made out of metal would be "easiest" to effect with this method. Things like wood and stones would be harder. It's because of how free electrons are to move around in the object.
The other mechanism would be to base it on the Lorentz Force, the interaction between magnetism and the flow of electrons. Its a lot more abstract so I'll give you refer you to the Wikipedia link [Lorentz force - Wikipedia](https://en.wikipedia.org/wiki/Lorentz_force)
I am sure there are other ideas, but those are two that occurred to me.
[Answer]
I’m not sure how well my answer will apply to your system but, rather than violating the laws of physics, i suggest merely side-stepping Newton’s third law as i have in mine.
In my magic system, magic is another type of energy, like kinetic or chemical energy, that a magic user converts into other kinds of energy (in keeping with the conservation of energy). For example, if you wanted to push someone across the room, you would convert magical energy into kinetic energy while pointing your hand at the target.
The way i side-stepped Newton’s third law is by ‘cutting out the middle man’ in his second law. Rather than getting an object with mass and accelerating it to get some amount of force, magical energy has been directly converted into kinetic energy. So, because we are directly generating the energy rather than generating it via f=m\*a, there is no equal and opposite force acting on the caster. The energy is directed and generated facing away from the caster and no energy is directed towards them. Its a strange technicality admittedly but i don't feel any laws are being violated, whilst we have kinetic energy, i don’t think we have force until that kinetic energy connects with an object with mass (such as the air or a person).
This allows us to side-step Newton’s third law without violating it and although force is not being generated via traditional means, this method still conforms to the conservation of energy and works from a theoretical stand point. Both Newton’s second and third laws are intact and still apply to everything in the world. When the kinetic energy we generated touches something with mass, it accelerates it and generates force (thhough still conforming to the conservation of energy).
Applying this to your setting, these nanobots you’re using could be designed to convert magical energy into kinetic and the level of force generated is determined by the caster’s thoughts (in the same way you could light tap someone’s shoulder or try and push them into the floor).
[Answer]
Since **anything** goes... And for the record I fully expect my suggestion will still be too far.
1. Build a mecha of appropriate size.
2. Make it "self-driving" and give it "face lock" and gesture and voice input.
3. Give it telescoping legs that can kick targets within reasonable range with significant force.
4. Give it **really** good stealth.
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[Question]
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2 informational references for Alcubierre fields can be found at the end of this question.
Warp-lanes aren't a novelty in science-fiction. Space ships can use a specific route to go through a Galaxy at often superluminal speeds. Alcubierre found a way to use current physics of relativity by Einstein and create a possibility for FTL travel in the Alcubierre drive. One of the disadvantages of this drive is that you lose the negative mass that you require for the field. The solution to this is to send a subluminal ship with the negative mass and this ship creates a lane of negative mass that can be used and re-used by ships afterwards to travel faster than light.
A problem that I expect to occur is that everything is spinning. Mass of a planet spins around an axis, the axis spins and wobbles around a sun, the sun spins around the center of the universe. Building a warp-lane from one solar system to another could simply have "seasons", where during a certain season the enter/exit point of the warp-lane is farther or closer to the solarsystem's center. But it could also mean that you need to build and re-build warp-lanes every so many years to keep a proper lane open.
My question is: What is the most efficient way to lay down a warp-lane in a way that it requires the least amount of new warp-lanes for a given time? Say 1 Galactic rotation.
If necessary, two scenario's are considered:
* A warp-lane from Earth to Alpha-centauri.
* A warp-lane from Earth to a system at 50.000 lightyears from earth, at the other end of the Galaxy (Earth is approximately 25.000 lightyears from the Galactic center).
For an answer, it is allowed to simply keep extending the warp-lane if it drifts off, so long as it does not extend the warp-lane length more than 20% of the original length.
For some background information you can watch this: <https://www.youtube.com/watch?v=94ed4v_T6YM>
More information can be found here: <https://www.researchgate.net/publication/258317793_The_Status_of_the_Warp_Drive>
Notable are the advantages in this paper:
* Benefit 1:
Removal of interstellar distance barrier, as
no longer restricted to subluminal speed limitations. Get
faster than light travel, as measured by distant observer
outside of disturbed region. This will allow missions to
the nearby stars and closer examination of astrophysical
phenomena than is possible today.
* Benefit 2:
It is a conventional transport scheme, in that
it requires no ‘tearing’ of space or non-trivial topologies
(i.e. wormholes) and does not require the transmission
of copies of objects across space as a means of getting to
the destination (i.e. teleportation).Warp drive is a simple
transport from origin to destination through space.
* Benefit 3:
No time dilation effects, as usually expected
with other space propulsion schemes due to special
relativity. This is because the vehicle could be moving at
subluminal speeds so that clocks on board would remain
synchronized with the origin and destination.
* Benefit 4:
No relativistic mass increase of vehicle,
since ship is at the centre of warp bubble is at rest with
respect to locally flat space.
* Benefit 5:
No requirement for rocket type propulsion to
achieve near light speed, which usually restricts the
maximum speed attainable due to special relativistic
effects such as infinite thrust for infinite masses.
* Benefit 6:
Technological and economic benefits to
mankind.
(1) (PDF) The Status of the Warp Drive. Available from: <https://www.researchgate.net/publication/258317793_The_Status_of_the_Warp_Drive> [accessed Jan 29 2019].
[Answer]
If the lanes themselves don't move through space along with the galaxy they're in, then the whole system is a wash. But if they do (and from your description, it sounds like they do), then under the parameters you've laid out, you may not actually have the issues you're imagining you might have.
Remember that a galaxy doesn't just rotate, but moves through the universe, as well. As you describe them, your warp lanes are fixed with regards to the galactic center. If this is so then that means they are traveling along with the galaxy at large; if not, then they'll be sitting alone in deep space as the rest of the galaxy quickly leaves them behind. So, if they're traveling along with the galaxy, why can they not also orbit the galaxy just like every other occupant?
Now, at first glance, that may not seem to solve your problem entirely, since star systems all orbit a galaxy at different rates. But, since you mention leeway of up to 20%, you probably don't have to worry about this at all, since it would take many thousands of years of relative drift between systems for a warp lane to "stretch" past this limit. Alternatively (or additionally), you could set up multiple endpoints in advance to supercede older ones as planetary systems shift in distance to each other, but that would be planning *way* in the future.
Also, as a much more minor concern, keep in mind that a solar system's orbital plane doesn't necessarily line up with it's parent galaxy's plane. Our own solar system's orbital plane is at roughly a 60 degree angle to the Milky Way's orbital plane. As you design your warp lane systems, angles more favorable or more extreme to each other may have some impact on the ideal/optimal endpoints for your lanes on a case by case basis. (E.g., one lane might be able to line up essentially connecting one inner planet to another inner planet, whereas in another case, a lane is better suited exiting on the outskirts of the system.) But even then, the angle between systems would need to be quite close to 90 degrees for this to be an issue.
Update in response to comment concerning "twisting and turning" of the warp lane:
Such a twisting motion doesn't need to occur. The factors affecting an object's position don't equally influence its orientation. To use a very simplistic analogy: if your warp lanes are like "tubes" through space, they don't need to be tied down at their endpoints, they just need to reside (orbit) at their desired positions.
Theoretical warp lane constructs like you're describing would have, by necessity, some measure of "tension" to them. So, continuing with my extremely simplistic analogy: imagine a hose dipped into a basin of water (on the surface of the Earth). If you let a hose sink down partway into the water, and then you start rotating the basin, then sure, that hose will be subject to the influence of turbulence you've just created, but the dominant forces affecting it's position will be hydrostatics and gravity, same as if the basin were at rest. If we performed this experiment at the scales you're concerned with, the effects would comparatively be even more negligible.
It's not a perfect analogy, of course, but this is a lot like how the dominant gravitational forces affecting the endpoints of your warp lanes would exert themselves. The endpoints aren't relatively "glued" to their locations, they're in orbit at their locations. The rotational influence of nearby bodies (i.e., the "turbulance") won't be enough to disrupt the stability of your warp lane so that they'd start to twist in disruptive ways. Rather, it's the overall gravitational influence of the nearby objects (i.e., the "hydrostatic equilibrium") interacting with the mass of the lane itself that exerts the most influence.
Granted, these descriptions are relative depending on the perspective of an observer. But the overall notion that stable warp lanes don't necessarily exhibit catastrophically destructive twisting effects is maintained, regardless. The simple reason for this is, if they were so easily affected by such forces, they wouldn't be stable enough to exist in the first place.
[Answer]
Construct a web of warp-lanes with fixed points in space relative to a predetermined galactic "center of commerce". So, with respect to that point in the universe, the warp gates are immobile (not spinning with the rest of the universe). Arrange the network so that there will always be a way to get somewhere close to where you want to go, granting that some places will (with the seasons) be more or less difficult to reach. In this scenario, the "seasons" won't require rebuilding the warp-lanes, but will require travelers to pick different routes through space in order to get where they want to go.
Economically, this implies that whoever owns the center of the web has an advantage over the whole network of warp gates. But there can be more than one web of warp-gates, with different relative-centers. This means that routing of traffic between two far-removed places in the universe can get very complex, but not infeasible at all. If your ship-computer has all the information it needs to simulate the motion of these webs, then it can generate the best path between any two points on-the-fly.
So, you'll need a lot of warp gates to start, but changing distances between two gates won't be a factor affecting gate maintenance.
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[Question]
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I've been working on [a system with a habitable moon](https://worldbuilding.stackexchange.com/questions/127226/feasible-star-planet-moon-combo-did-i-miss-anything-that-makes-this-system) (Moon A) for a story, and I'm now trying to populate the other moons around the parent planet. I'm considering placing one (Moon B) in a co-orbit, horseshoe configuration, with my habitable moon.
While I understand the concept of these orbits, the actual calculations of the orbital times is beyond my mathematical capabilities.
I understand that on a horseshoe orbit there is an inside section and outside section where Moon B is catching up to, or falling behind, Moon A, respectively.
I understand that if the 'inside ring' is nearer the parent body (the 'planet' in the case of co-orbital moons) than the L1 Lagrange point of Moon A, then Moon B will escape the horseshoe orbit and just start orbiting the planet directly. And, similarly, if the 'outside' ring is outside of L2 Lagrange point of Moon A, Moon B will escape and orbit the planet directly. And if either ring is too near the actual orbit of Moon A, it will be a tadpole orbit(never passing the L3 Lagrange point of Moon A before returning to Moon A from the same direction it left it), instead of a full horseshoe.
What I can't figure out (again, math skills limitation) is **How long it would take (longest and shortest possible times) for Moon B to make one complete cycle of the horseshoe?** And so I can't decide if I should use this type of orbit or not. For example, 3753 Cruithne takes about 770 years to complete it's horseshoe cycle relative to Earth, far too long to be useful for my story. But I don't know how to calculate ho long my co-orbit scenario would take. I'm confident it could be made significantly shorter than 770 years, but exactly how short it would be is still a key factor in the decision.
I would like to know how often the two bodies would approach each other at the two extremes of possibilities, the longest possible time between complete cycles, and the shortest possible time between cycles.
For this question: Planet mass is 477 Earth masses, Moon A's mass is 0.11 Earth masses, Moon B's mass is 0.01 Earth masses. Moon A's semi major axis is 4 million kilometers. (please let me know if any other variables or details are needed)
To re-word the original question: **By adjusting the semi major axes of the inner and outer rings of Moon B's horseshoe orbit, either closer to or farther from the semi major axis of Moon A, what are the longest cycle time, and shortest cycle time possible for a horseshoe orbit in this system?**
[Here](https://upload.wikimedia.org/wikipedia/commons/d/d6/Lagrange_Horseshoe_Orbit.jpg) is a visual representation of the types of orbit changes I'm referring to. The contour lines inside the highlighted one (nearer L3 L4 and L5) are what I'm referring to when I mentioned adjusting the horseshoe orbit Axes nearer to the semi major axis of Moon A. And the contour lines outside of the highlighted one are what I'm referring to when I mention moving those axes farther from the semi major axis of Moon A. When I refer to a complete 'cycle', I mean the time it takes for Moon B to go from Point A on that image, through Points B, C, D, and E and back to A.
[Answer]
The direct calculation of the orbital times is beyond just about *everybody's* mathematical capabilities. This is an example of the infamous three-body problem, for which there is no analytic solution in the general case (and it's not one of the few special cases that do have analytic solutions, either).
In order to get accurate results, therefore, you will have to resort to numeric simulation, and just sweep over a range of orbital parameters to simulate until you find the inner and outer edges where the system no longer displays horseshoe behavior.
To get a very rough approximation, though, we can just compare the keplerian periods of each orbit. Orbital period $T$ is proportional to $R^\frac{3}{2}$. The period of a horseshoe cycle will be the time it take the small world to lap the large one on the inner track, and vice-versa when the small world is on the outer track. The lap time $T\_L$ is given by $T\_L = \frac{T\_O T\_I}{T\_O - T\_I}$, where $T\_O$ and $T\_I$ are the orbital periods of the outer and inner moons, respectively. We can also make the simplifying assumptions that the large world will have its orbit changed only insignificantly, and the small world's orbit will differ from the larger world's orbit by the same amount in either direction.
Putting those all together, we first get the cycle time in terms of individual orbital periods to be $C = \frac{T\_M T\_i}{T\_M - T\_i} + \frac{T\_M T\_o}{T\_o - T\_M}$, where $T\_M$ is the period of the larger moon, and $T\_i$ and $T\_o$ are the inner and outer orbital periods of the smaller moon, respectively. If we then sub in $R^\frac{3}{2}$ for $T$, using $r$ for the difference in orbital radius between the large and small moons, we get
$C = \frac{(R (R - r))^\frac{3}{2}}{R^\frac{3}{2} - (R - r)^\frac{3}{2}} + \frac{(R (R + r))^\frac{3}{2}}{(R + r)^\frac{3}{2} - R^\frac{3}{2}}$
This is obviously not a good approximation for the longest cycle time, because it tends towards infinity where $r$ approaches zero (and you end up with a fixed-separation Trojan orbit), by which time you will long have left the horseshoe regime behind. It also won't tell you how much separation you can have before the worlds are too far apart to exhibit co-orbital behavior anymore, but if you can establish that independently, it should be reasonably accurate (within an order of magnitude, anyway) for the fastest possible cycle times.
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[Question]
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I have already reviewed a few questions about the feasibility of a radio communicating creature. Like these:
* [How would organic EM transmitters/recievers be different than our mechanical ones](https://worldbuilding.stackexchange.com/questions/4474/how-would-organic-em-transmitters-recievers-be-different-than-our-mechanical-one)
* [Anatomically correct radio communication](https://worldbuilding.stackexchange.com/questions/123462/anatomically-correct-radio-communication/123511#123511)
But this is a different particular case. I have this creature I am designing (*Volutus sapiens*). It is basically a meat roll (literally).
[](https://i.stack.imgur.com/CBKlc.jpg)
They live on an Earth-like planet and they are carbon-based.
Besides their standard circulatory system, they have a secondary circulatory conduit of ferromagnetic fluid.
To communicate, they use their muscles along that conduit to move a bulge of ferromagnetic fluid in circles (as shown in the second picture). The creatures can move the fluid at will, altering the speed and rotation pattern as they wish.
[](https://i.stack.imgur.com/VWMWT.jpg)
And they receive the electromagnetic signals through a circular nervous system with a high concentration of iron to make it more sensible to the electromagnetic signals. (third image).
[](https://i.stack.imgur.com/NKhtv.jpg)
the question is: **Is this specific way of radiocommunication possible?**
[Answer]
Instead of rolling around a ferromagnetic fluid I think it would be more effective for the organism to utilize triboluminescence or piezoluminescence to produce electromagnetic radiation. These are physical/chemical processes that are already at work in existing lifeforms.
The receptive organ would essentially be an eye that was sensitive to whatever frequency the sending organ produces. Since radio frequencies are more penetrative than light the receptive organ could be safely internalized (an eye on the inside).
If the receptor and sending organs were combined in the same structure this organism could utilize back scattering to see in total darkness.
[Answer]
## I don't think so.
A conductive loop must move within a magnetic field, or vice versa, to create a current, which is needed to create radio waves.
In *Tortamque sapiens*, though, as is currently constructed, the conductive loop **is** the magnetic field.
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What characteristics (compare those of a mountain goat foot: good grip on rocks, doesn't slip off, etc) would the foot of a dog or a wolf need to have to be useful in rocky settings such as mountains (but not very steep ones) and rocky deserts? What about the pads, claws, general roughness?
This creature relies on chasing its prey, rather than being an ambush predator.
Thanks a lot.
[Answer]
[Mountain Dog](https://en.wikipedia.org/wiki/Mountain_dog) breeds are typically working dogs - built and adapted for protection of flocks. So I don't think they are a good reference point for your needs (a predator who chases its prey).
The species which would make a better reference point for a "prey-chasing rock dweller" I think is the snow leopard. Although it would prefer to ambush, it certainly [does chase prey across rocks](https://www.youtube.com/watch?v=Uj0EVT-Ekog).
[Some of their adaptations](http://www.discoverwildlife.com/animals/mammals/6-ways-snow-leopards-are-adapted-their-habitat). Specifically - large paws, short forelimbs and a long thick tail, all to help balance. Also - extremely powerful rear legs - ability to leap crevices etc is crucial for navigating rocky environments.
They also have [thick paws](http://snowleopardadaptations.weebly.com/adaptations.html) to avoid cutting themselves easily on sharp rocks.
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[Question]
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Is it possible to use thermal byproduct of daylight operation to power night time operation of volatile computer storage?
In my setting, a moon-like moon with almost no atmosphere has one of its sides (the far side) populated with nodes powered with sunlight (solar flux of said planet is around $1247 W/m^2$), and day-night cycle is 27 days long. The computer storage on this node is volatile, meaning it needs continuous power supply to keep it from losing its memory. The node's storage requires constant power at $4\times10^6 W$.
Each node operates at $2\times10^7 W$ of power, easily powered by sunlight during 13.5 days long daytime. About $4\times10^6 W$ of it is deposited in flywheel energy storage during daylight, that is 13.5 days. Naturally, each node radiates $2\times10^7 W$ as thermal energy, so I equip them with radiators that operate at 600K temperature, with coolants exiting at 400K, radiating at a rate of $7656 W/m^2$ according to equation on this [answer](https://worldbuilding.stackexchange.com/a/58756/7974).
As mentioned above, at daylight the radiator outputs coolant at 400K temperature, and this heat is stored on water reservoirs, for the sake of this analysis assume that the reservoir is near-perfectly insulated. This reservoir stores $3.52\times10^8$kg of water, that stores about $1.87\times10^14J$ in the form of heat.
Now, at night the node is allowed to operate at lower temperature, let's say it could be as low as 273K, and with hot reservoir at 400K, this is 127K of temperature difference. Again as in linked answer, the temperatures of the hot and cold reservoirs of your power generation system define Carnot efficiency, and in this case it is ideally at 37.5% efficient. But let our heat engine works at 35%, this means from the stored energy only ~$5.6\times10^6W$ of usable work could be extracted for the entire night time (13.5 days).
Flywheel energy storage charged from 13 days of continuous operation at $4\times10^6W$ during daylight is now extracted, and due to limited conversion efficiency at around 80%, only $3.2\times10^6W$ of power could be extracted.
In total, energy from heat engines and flywheel energy storage provide us with $8.8\times10^6W$ of usable energy during night time, enough to power our computer storage, and some energy is left for node maintenance.
Now, this system also radiates energy at around ~$2\times10^7W$ (heat from reservoirs and from energy generated by extracting the flywheels). The radiator at night time took 400K coolants and outputs it at temperature of 250K, according to linked question the radiator would radiate heat at a rate of ~$1400W/m^2$.
My concern is that although the configuration appears realistic enough to be workable for me, this results in total of constantly radiated heat of $2\times10^7W$ during day and night, despite the fact that each node is powered by $2\times10^7W$ of sunlight only in daylight. At first I thought it is possible because of different working temperature, 400K during daytime and down to 273K during night time, but I can't be sure.
Therefore, I came up with this question: **Is this configuration of utilising thermal byproduct to power night time operation possible?** If it is not, then where is my error?
---
*[This question was on [sandbox](https://worldbuilding.meta.stackexchange.com/a/5649/7974)]*
[Answer]
1. Why at night the system dissipates 2E7 W when it is only powered by 2E7 W during the day?
Because during the day it doesn't dissipate any heat. During the day, the OP says, the waste heat of the data processing subsystem is used to heat up water.
2. Does it work?
No it doesn't, not as such. The bewildering array of numbers in the question fails to take into account the energy necessary to operate the radiators (coolant pumps, heat pumps, etc.) Otherwise it's fine, except that it's overly complicated. Why radiate heat as electromagnetic radiation just to capture it and heat some water? Instead of this strange detour, the system should heat the water directly using a [countercurrent a heat exchanger](https://en.wikipedia.org/wiki/Countercurrent_exchange).
If the pilot installation finds out that the energy stored as hot water is not enough to power the data processing subsystem at night then some more solar panels should be added to heat the water directly. [Thermal energy storage](https://en.wikipedia.org/wiki/Thermal_energy_storage) is quite well understood and it's one of the proposed solutions to the necessity to have solar power plants work at night.
On the other hand, [static RAM](https://en.wikipedia.org/wiki/Static_random-access_memory) is a thing, and [static CPUs](https://en.wikipedia.org/wiki/Static_core) are not unheard of. The data processing subsystem can simply halt in place at dusk and resume operation at dawn with no power requirements during the night, or at least with minimal power requirements to maintain air circulation and avoid deep freezing.
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[Question]
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When I was a kid, I conceptualized a post-apocalyptic story entirely starring Barbie dolls. One idea I had about how they would live and get around involved transmission towers, or power towers. Imagine something like [this](https://en.m.wikipedia.org/wiki/Transmission_tower#/media/File%3APylon_ds.jpg). Note: By the time they started living there, the power lines had long since stopped working.
These dolls would be as smart as humans, but can only lift about 5-10 pounds. They're functionally immortal, since only way to kill one is to completely destroy it by setting it ablaze. They eat, drink and sleep to maintain their energy levels and keep their strength up. Not doing it won't kill them, but will make them very tired and weak.
The idea was that somehow they were able to live in different parts of this tower (with branch platforms or nets and hammocks) and get to different floors with stairs or an elevator up the side or down the middle of the tower.
However, the main benefit to living in this power tower that I thought of was to create a system of Gondola lifts or Cable cars to travel from one tower to another with the power tower's wires. Looking back I don't see how I thought that was supposed to work. But that's where you come in!
How could a society of Barbie dolls build and maintain a system of Aerial tramways connecting a bunch of power towers?
[Answer]
Most cable cars and gondolas tend to use moving cables, although designs with a static cable are possible and some are actually used by Nation Grid for inspection and repair.
But unfortunately the biggest problem is that power cables are connected to pylons by large insulated connectors like this
[](https://i.stack.imgur.com/HgXwn.gif)
This would make using them as a cableway difficult.
[](https://i.stack.imgur.com/jM1Zq.png)
But some would still try it...
(she was later rescued)
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A year ago, I asked a couple questions about a world I was building where the all the ecosystems in a planet were designed from scratch by a galactic consortium of species ([1](https://worldbuilding.stackexchange.com/q/39059/6270), [2](https://worldbuilding.stackexchange.com/q/39117/627), [3](https://worldbuilding.stackexchange.com/q/39183/627)). I'm revisiting that world, and trying to dig deeper to look at some of the issues the scientific group would have to deal with.
In particular, I'm interested in how the group could model evolution (though I'm not asking about that). To try to better figure out what methods they could use, I'd like to do some simulations of my own. I know that computational evolution is an active field, and I've seen [a Stack Overflow question](https://stackoverflow.com/q/396938/6535830) about simulations that have been done, and some packages available to people wanting to do things themselves. However, I'm more interested in planet-wide (or at least continent-size) simulations - because, after all, the alien experiment involves an entire planet.
What programs or resources are out there that can be used to simulate evolutionary processes across an Earth-like planet? I'm looking for things along the lines of [SimEarth](https://en.wikipedia.org/wiki/SimEarth), although I don't know how good that particular one is - and it seems more like a game than a worldbuilding tool.
[Answer]
The game SimLife attempts such a thing. However, it uses a laughably simplified model for evolution. And even so, keeping track of enough members of just a few species winds up straining home PC resources to the breaking point. The best ecosystem I ever got it to simulate stably was a very simple predator/prey world. Probably it would have been able to do much more if it hadn't been so graphics-heavy.
The problem is, you need LARGE populations of predators, interacting with 100x as many prey, interacting with 100x as many plants. And that's just for 1 species apiece, in one biome. For an entire world, you'd need a computer as large as an entire world. (Don't panic.)
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I'm imagining a situation that we can see a star change color periodically:
1. A star and Earth orbit around a black hole
2. The star is very near to the black hole so that it has high orbital speed, while the Earth orbits the black hole at far away
3. As the star has a high orbital speed, when the tangential direction points towards the planet, it causes blue shift and appear as a blue sun, and when it moves away from the planet, it looks like a red sun due to red shift.
Is such a system possible?
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Please correct me if I am wrong, I just did some back-of-the-envelope calculations without thinking everything through. I do not know how humans would perceive the shifted spectrum, but let's assume it's a linear relationship which I think is the best we can hope for:
Doppler effect: (f/f\_0 - 1 ) \* c = v .
So if you want to notice anything, let's say f/f\_0 = 0.8 ~ yellow to red, you need speeds close to light speed, in that example 0.2 \* c.
How fast is your star? <https://www.space.com/20303-black-hole-star-speed-record.html>
2 million km/h. That means: 555,555 m/s = 0.001853 \* c.
Unless you are ok with very subtle color changes ...
Oh, yes, maybe in theory a star could rotate faster, but would an "Earth" exist there? Calculating under which circumstances a faster rotating star could exist and a planet and so on is I think beyond this forum, I would go with what kind of data we have
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You may use the relative speed between Earth and star, whether the star is moving toward Earth, to determined the color people on Earth see.
According [Doppler effect](https://en.wikipedia.org/wiki/Doppler_effect), if the light source (in this case, light also wave) move toward Earth, then on Earth, people will see the light with higher frequency (toward violet). But when the star move away from Earth, people see the star orange or red (low frequency)
You may refer to [Visible spectrum](https://en.wikipedia.org/wiki/Visible_spectrum) to define it based color, a color a person can see the star if they are on the spaceship which relative station to the star. A color when star move further earth (reduce base freq) and a color when a star move toward earth (increase base freq)
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The short version: yes, but you might need a *really* big black hole.
In order to get a large spectral shift, you want as high an orbital velocity as possible for the star. To get the highest possible orbital velocity, you want it to orbit the black hole as close as possible. For a rotating black hole, you can actually set up stable circular orbits at arbitrarily small distances from the event horizon if the BH's angular momentum is large enough, but to keep things simple we'll just consider a basic Schwarzschild BH with no angular momentum. In that case, the innermost stable circular orbit occurs at a radius of $R = \frac{6GM}{c^2}$ - twice the radius of the photon sphere, and 3 times the radius of the event horizon. Calculating the proper orbital period and velocity is a bit trickier, but it turns out that for an external observer (which is what's relevant for the view from the planet), close circular orbits around a non-rotating black hole still obey Kepler's laws exactly, so the orbital velocity is given by $v = \sqrt{\frac{GM}{R}}$. Substituting in the previous equation for $R$, the factor of $GM$ cancels out, and we get $v = \frac{c}{\sqrt{6}}$. Thus, the maximum orbital velocity that the star can attain around a non-rotating black hole is independent of the black hole's mass! And it's a little bit more than $0.4c$, which is enough to shift yellow light way off into the infrared or ultraviolet. Half that velocity, at double the minimum orbit radius, would be plenty to produce obvious visible effects, with a yellow star shifting between red and violet over the course of half an orbit (assuming that the observer is in or near the star's orbital plane).
Now, we just need to make the black hole big enough to make these fast orbits wide enough that a star will fit, without overlapping the black hole or being torn apart by tides. For that, we can use the fluid satellite approximation for the Roche limit, $d = 2.44R\_{BH}(\frac{\rho\_{BH}}{\rho\_S})^\frac{1}{3}$ We need that value to be smaller than the orbital radius, so $2.44R\_{BH}(\frac{\rho\_{BH}}{\rho\_S})^\frac{1}{3} < \frac{6GM}{c^2}$. We can then simplify that to get:
$2.44\frac{2GM}{c^2}(\frac{\rho\_{BH}}{\rho\_S})^\frac{1}{3} < \frac{6GM}{c^2}$
$2.44(\frac{\rho\_{BH}}{\rho\_S})^\frac{1}{3} < 3$
$2.44(\frac{3c^6}{32\pi G^3M\_{BH}^2 \rho\_S})^\frac{1}{3} < 3$
And then solve for the mass of the black hole:
$2.44(\frac{3c^6}{32\pi G^3 \rho\_S})^\frac{1}{3} < 3 M\_{BH}^\frac{2}{3}$
$2.44\sqrt{\frac{3c^6}{32\pi G^3 \rho\_S}} < \sqrt{27} M\_{BH}$
$2.44\sqrt{\frac{c^6}{288\pi G^3 \rho\_S}} < M\_{BH}$
If we plug in the average density of the sun ($1410 kg/m^3$) for $\rho\_S$, we end up with $M\_{BH} > 1.07e38 kg$, or about 54,000,000 solar masses, with an orbital radius of about 5.5AU.
If we use double the innermost stable circular orbital radius, still producing plenty of Doppler shift, that cuts the necessary black hole mass down to a mere 19,000,000 suns, with an orbital radius of 2.25AU
For subtler color changes, you could get away with an even smaller black hole, and a smaller orbital radius for the star, but it's still going to be in the supermassive range.
We also need the distance between the event horizon and the orbit to be larger than the radius of the star, but that's pretty well covered. The sun's diameter is *much* less than 1AU. :) For reference, current estimates of the mass of the supermassive black hole at the center of the Milky Way are around 4,100,000 solar masses, but the SMBH at the center of Andromeda weighs in between 110 and 230 million solar masses, so this sort of object is well within the capabilities of our universe to produce.
Arranging for that star to be the primary source of life-giving heat and light for a planet would be pretty tricky, though, seeing as how the distance between them will vary by between 5 and 11AUs, and the minimum distance between the orbits of the star and the observing planet would likely need to be greater than 1AU to ensure the planet's orbital stability. Much more feasible to make the color-changing star a bright light in the sky, comparable to the Moon (which also exhibits cool Einstein-ring lensing effects when passing behind the BH), and provide another star for warmth.
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Rana sylvatica, the only amphibian found north of the arctic circle, has a very unique survival strategy: it pumps its body full of glucose and hormones just before freezing so that ice crystals don't cause irreversible damage to the creature's body. Then, when it comes time to thaw, the frog thaws slowly. The membranes around the heart begin to stretch, somehow causing a sort of energy discharge that constricts the heart muscles in an odd twitch that "wakes up" the dead frog.
I recognize that humans are far more complex than frogs, but perhaps the frogs' innovation is in the right direction. What is keeping the frogs' approach from working on more complex organisms?
[Answer]
The use of [Cryoprotetants](https://en.wikipedia.org/wiki/Cryoprotectant) such as ethylene glycol is already part of the cryopreservation of humans. These chemicals are used to protect tissue from damage associated with freezing, primarily the formation of ice crystals.
Preventing the formation of ice crystals is only one of many [obstacles to success](https://en.wikipedia.org/wiki/Cryonics#Obstacles_to_success) of cryonics.
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Something that isn't quite like a thesaurus. For example when writing fantasy it would be nice to have a list of established fantasy terms, partly so that I don't plagiarize other writers (words that are common enough to probably have been used before like dragonborn or fel magic) and partly to become inspired by others' creations. Another aspect is to be able to become a better genre writer such as looking up the "best" word to use in a fantasy setting when describing everyday objects that need a "non-modern" flair like saying "looking glass" instead of "mirror" (bad example I know).
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I'm not sure if this helps but you might try to go in the opposite direction, instead of looking for a fantasy thesaurus simply look up a name generator. Most name generators produce original names not found in most common fantasy or sci-fi. This is what the reverse of what you're asking for but I think it would help. You can also download medieval or fantasy insult generators or find a list of words from the early 19th century to describe things that we have today using words that have fallen out of fashion (use early nineteenth-century terms instead of words from the Medieval Age because it will make it easier for your readers to understand what you're talking about without needing a dictionary.)
[Answer]
None that's immediately obvious, however there are multiple compendiums of various aspects of fantasy worlds. A quick google for 'dictionary of fantastic places' brings up a [book that is just that](https://en.wikipedia.org/wiki/The_Dictionary_of_Imaginary_Places), for example.
Googling for terms you are thinking of using should quickly bring up references to places they are used, and this [horrendous time sink](http://tvtropes.org) is an excellent way to check plot devices you may wish to incorporate in your world for sanity/overuse.
Aside from that: [Wikipedia](https://en.wikipedia.org/wiki/Fantasy) is easily navigable and contains a great many examples of world building that you can use for inspiration/to avoid similar worlds.
If you're looking for an easy way to turn words like 'old man living in the city of Quarn' into 'The Venerable Seers of The Magnificent Quarn', then I'm afraid you'll need to do three things:
1: Read a lot.
2: Grab an actual thesaurus.
3: Use your imagination.
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## Setting
A [binary planet](https://en.wikipedia.org/wiki/Double_planet) system consisting of two terrestrial planets (hereafter Alpha/α and Beta/β). The system [barycentre](https://en.wikipedia.org/wiki/Barycenter) (C) is between the two planets; for the sake of this question the exact position is variable as long as it remains in the space between the two, but *closer to Alpha than to Beta*. They are tidally locked to each other.
[](https://i.stack.imgur.com/maixI.png)
Alpha is a continental planet comparable in all aspects to Earth (i.e. within 20% of size, mass, surface gravity, etc), with tectonic activity at least as active as on Earth (e.g. global average tectonic plate speed is no less than ~7 cm/year).
Ideally Beta is similar, but consider its dimensions and features as variable (so long as it remains a terrestrial planet) as needed.
## Which – *if any* – of these scenarios is the most plausible?
α: Planet Alpha
C: Barycentre
Grey Triangle: hypothetical area of barycentric influence
Thin Grey Line: Lighter [continental/felsic](https://en.wikipedia.org/wiki/Continental_crust) plate
Thick Black Line: Denser [oceanic/mafic](https://en.wikipedia.org/wiki/Oceanic_crust) plate
[](https://i.stack.imgur.com/aaDES.png)
A dense ocean plate becomes fixed below the barycentre in its area of influence. The plate may drift or rotate within this area.
[](https://i.stack.imgur.com/Kbsoz.png)
A thick and mountainous continental plate becomes fixed below the barycentre in its area of influence. The plate and its mountains may drift or rotate within this area.
[](https://i.stack.imgur.com/K24SC.png)
A [hot spot](https://en.wikipedia.org/wiki/Hotspot_(geology)) or upwelling from the mantle becomes a fixed feature below the barycentre in its area of influence. Plates drift freely, causing a chain of volcanoes. The oldest volcano attributed to this hot spot is no less than 100 million years old.
## Before you say *none of the above*...
(And I'm completely open to that answer.) Would positioning the barycentre directly on the surface of Alpha make a difference?
[Answer]
I have problems to find a good formulas, however:
1) For geologically active planet (like Earth).
Theoretically continent plate and continental plate remain in hydrostatic equilibrium, so none of them would be specially preferred over the other. Earth, because of rotation has got geoid shape. Here, because of slow rotation (tidal lock) of this gravitational interaction, instead of "squeezed" sphere, you'd get a "stretched sphere", something similar to Earth with tide, but tide would not only affect hydrosphere but in the long run the whole crust. [](https://i.stack.imgur.com/OHCMX.png) In the same way as such not perfectly spherical shape has not influenced location of land masses on Earth, same would apply to your planets.
2) For geologically dead planet (like Mars or the Moon).
A bit more tricky, as it would no longer be able to return to equilibrium shape. If a tiny planet first become geologically dead, then lose significant part of hydrosphere and atmosphere (possible, no protection from magnetic field, plus it had lower gravity at start), then the most stable position would be showing some big continental crust both towards the other planet and in the exactly opposite direction.
[Answer]
I agree that it’s none of the above. There is no mysterious “barycentric influence”. The planet will take the shape based on gravitational potential so it will be out of round. But given that shape, features can be present anywhere with the same effect: it is “sea level” everywhere and objects are not attracted or repelled because the **sea and crust already form the right shape**.
Now if the world were not in hydrostatic equilibrium but was cold and solid and fairly small, and it was slightly off balance due to its history, then it would prefer o face the heavy side away from the partner. But that's not the case you described.
If you want to find something special about the point below the partner, try looking at the [Coriolis force](https://en.wikipedia.org/wiki/Coriolis_force). Since the planet is rotating about a point outside of itself, it will behave rather strangely from our point of view. Besides weather and ocean currents, this may affect mantle convection, biasing the plate tectonics in ways we don’t see on Earth.
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This answer is to add some basic background data. Since this is science-based, I wanted to provide this to keep answers from getting too out of hand.
Earth:Moon has a ~100:1 mass ratio. The moon is tidally locked to earth, but not earth to the moon. The Earth will eventually become tidally locked too...it will just happen after the sun eats the earth so its a moot point.
Pluto-Charon has a ~10:1 mass ratio. Pluto and Charon are both tidally locked to each other; they are both in synchronous orbit around each other. This is the situation for planets A and B.
The Earth-Moon barycenter is 4671km from the earth's center, or about 2/3 of the way out from the core.
The Pluto:Charon barycenter is 2110km from Pluto's center, which is about 1000km above the planet's surface.
Now I'm off to research plate tectonics.
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In the movie [The time Machine](https://en.wikipedia.org/wiki/The_Time_Machine_(2002_film)), humans drill the moon and destroy part of it.
[](https://i.stack.imgur.com/7KxlW.jpg)
So this made me wonder, if we destroyed the moon like this...
* How would it affect the Earth?
* Is it possible to achieve such a view as seen on the picture above?
* Also, if we completely destroyed the moon, would life still be sustainable?
[Answer]
**How would it affect the Earth?**
First, what will happen to the Moon is that the remaining mass will slowly start to form a new sphere, creating a new, smaller Moon. This is due to gravity of the mass.
Second, what will happen to the Earth depends very much on how do you destroy the Moon. If you use great force on one side of the Moon, it will move the Moon from its orbit. So depends on the direction, it might even send the Moon towards the Earth. In this case, it is apocalypse part II (Apocalypse part I was when a meteor obliterated the dinosaurs).
Third, upon destruction of the Moon, debris would fall on to Earth.
Suppose that you destroyed part of the Moon in a way that it doesn't change its orbit, then [the remaining mass of the Moon would form a sphere and continues orbiting the Earth](https://anime.stackexchange.com/questions/20758/how-did-koro-sensei-prevent-the-moon-from-falling-onto-the-earth). Since it is now much smaller, then tides won't be as high as now. Night would also be a lot darker since Moon is the main 'source' of light during night. It won't affect metropolitan though.
**Is it possible to achieve such a view as seen on the picture above?**
To destroy even a part of the Moon would require a lot of energy. The best thing to achieve that is by explosion. However, explosion tends to be spherical since they push from the central point of the explosion outwards in all direction. So the result would be something like this.
[](https://i.stack.imgur.com/WtmEx.png)
Of course if we talk about fiction, I don't see why it would be impossible to achieve what you want. You can use Squall's Blasting Zone, or have Sephiroth cut the Moon into two and then destroy the cut half in a hyper battle.
**Also, if we completely destroyed the moon, would life still be sustainable?**
If the Moon goes bye bye, then the greatest effect would be that there won't be high and low tides due to the Moon anymore. While it is debatable whether the Earth would still be habitable or not, one thing for sure is that the destruction of the Moon would affect many ecosystems along the shore and the sea. Without tides, the sea would be so calm, animals and sea plants that relies on tides to spread would possibly be dead.
Since the Moon also acts as a protective shield against asteroids, then with it gone we will see more falling stars.
[Answer]
## We could survive, but:
* The moon affects the oceans on Earth, without the moon we would have tides that are a third as high as now.
* We would have much much more darker nights and shorter days - 6-8 hours.
* A lot of asteroids would crash into earth - the moons gravity catches a lot of asteroids.
* The force used to make such a hole into the moon would affect the moon in any possible way, but I cant really say what would happen.
* The stones moving around the moon would either crash into the earth and the moon destroying a lot of life, or the moon would get a ring like on Saturn.
* We wouldn't really see flying rocks around the moon, they would have to be super large and stones this large missing on the moon would make the moon cave in.
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I was thinking I would have a race and at the most basic level it is a ground covering moss. As it encounters other colonies of itself they will join together to form one contiguous colony while keeping the genetic diversity of both colonies. Once any given colony of moss reaches a certain (probably large) size it will achieve limited sentience and as it grows larger it grows smarter though it itself is only able to determine things that it is in contact with.
This moss is capable of choosing to grow any of three types of flowers, the first of which when fertilized it will form into a spore pod that, when mature, ejects large amounts of spores high into the air to be taken by the wind to grow new colonies. The other two types of flowers when fertilized will produce a pod that will grow either a worker or a soldier.
Both workers and soldiers contain live colonies of the moss inside them and if they remain still in a colony of moss long enough the colony will join with the moss in their body and allow them to "talk" with the colony of moss. Drones and soldiers communicate to each other using speech.
Workers are Humanoid in form with one head, two legs and two arms that end in hands, range between 2-4 feet tall and are on average about as smart as a human. Their main function is gathering resources and building structures that aid the moss in spreading or resisting the forces of nature. They do not use photosynthesis despite being plants because moving and thinking take up a ton of energy so they are omnivorous eating anything they can get their hands on. They do not store excess energy as fat but they have a bladder of calorie and nutrient rich liquid that they store excess energy in. This bladder can expel this liquid into their mouth which they can then swallow and digest for energy or pass off to another worker or soldier who might need it.
Soldiers are four legged creatures that are 1-6 feet at the shoulder and share roughly the same proportions as wolves. Soldiers have large claws and teeth for their size and are intelligent enough to use speech, but their vocabulary is lacking. Soldiers are generally subservient to workers and will take orders from them with larger soldiers often being drafted to be beasts of burden. If left alone soldiers will attempt to bury themselves in the moss and stay still allowing itself to connect to the moss. These stationary soldiers will be constantly alert looking for creatures that might harm the moss and if they are alerted to hostiles then they can have the moss they are connected to relay it to every other soldier connected to the moss to raise the alarm before trying to defend the area. The added benefit of being attached to the moss most of the time is that they can act like access points for all mobile workers and soldiers to talk to the moss through. Soldiers do not eat anything, save for the high energy liquid produced by workers, this allows them to have a very low energy cost digestive system and have more room inside to pack everything they need for murder.
Workers and soldiers do not grow after being "birthed" by the moss, and when they die the live colony moss they have inside of them consumes them to either join with the colony of moss that the creature died on or create a new colony wherever the creature died. The moss can also select for traits it wants in the next generation/group of workers or soldiers by choosing to only flower in the places with the moss where the workers and soldiers with the traits it wanted died.
So my question is, Could this setup possibly work without things like magic or technology so advanced it is indistinguishable from magic, and what could make it better?
[Answer]
I'm not certain this will work as it is without some form of magic but a few changes might make it work.
The moss growing and absorbing smaller colonies is probably fine and a similar thing happens with cells absorbing smaller cells/viruses in the real world.
I have no idea if a moss achieving sentience is possible. I would think it is impossible or highly unlikely. On the other hand I don't know this and I think many people would believe that a moss could become sentient.
A moss could definitely create different types of flower. Most animals can produce two varieties of offspring (male and female) and some plants have separate male and female flowers.
I don't think a moss could create what are essentially animals. Your only feasible option is a symbiotic relationship between the moss and an ant-like species. This would work pretty much as you describe except the creatures would not be birthed from the moss.
Some explanation is still be required to explain how creatures communicated with the moss and how the soldiers send their long-range communications, possibly pheromones.
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I'm currently planning for my own new story, and in one point in time there will be a city somewhere on the Atlantic Ocean which has to have the space resources necessary to sustain for around 1 billion people, the survivors of a global catastrophe. There is no possibility for people to live elsewhere, as this city (which has no final name yet) is the only safe place. How should the city be designed in terms of housing, growing food, transportation and overall look of the city to support that much people in the smallest volume possible without lowering the live standards below basic levels (everyone has food, water, a place to sleep and some entertainment)?
* Assume current technology, or technology which comes likely in the next decade, with a few exceptions: every basic work, including growing food and maintaining every part of the city can be done by robots. You have no energy problems, because if you need more power you build more fusion reactors (which are completely safe in this universe). Also you have super strong and super light building materials, so building structures which are 4 km tall is no problem.
* The whole city should be air-locked. There should be no damages or deaths if the city was suddenly transported to a vacuum. So it has to clean it's own air if the atmosphere is not available.
* Government is a dictatorship of a single long-living trans-human, which controls every system of the city and cannot be removed. Assume this dictator does only good and will do no harm.
* Population can be controlled by contraceptives in the food and water. The inhabitants have no control over this.
* The city should not be impacted by tsunamis, storms or freak waves.
* There don't have to be enough ships, planes or other means of transport to the land, because leaving the city is not intended.
* Water and air have to be cleaned of bacteria and viruses, because there exists very harmful types with could infect the whole city. There exists a 100% reliable test for such pathogens, but no cure, so every infected has to be burned.
**PS:** Please be gentle, I have been following Worldbuilding SE for quite a while now, but this is my first question :)
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[Very Large Floating Structures](https://en.wikipedia.org/wiki/Very_large_floating_structure) is an active field of Research and Development. There are quite a few experiments such as the [Mega Float](https://www.mhi-global.com/company/technology/review/pdf/e382/e382039.pdf) in Tokyo bay (a country used to natural disasters such as the ones mentioned by you).
[](https://i.stack.imgur.com/QETy6.gif)
The technology seems feasible and stable although some of your requirements are though to follow. I doubt a structure of this size would be able to do well in vacuum. It's not just about full isolation from outside but also about pressure difference. In the sea the biggest pressure would be exterior (so it floats), in the vacuum would be interior.
For the current state of this technology I would advise documents such as the following:
[Very Large Floating Structures: Applications, Research and Development](http://www.sciencedirect.com/science/article/pii/S1877705811010848)
Having one billion people inside is hard to achieve since it would necessarily be crowded. In any case I think a modular approach to such a construction would be the best one deal with all the characteristics you've mentioned (so several constructions connected by bridges or tubes, etc.). Each module could have it's own specifications on temperature, humidity, hull strength, and so on. For a current use of this technology today check, for example, [Assembly of the International Space Station](https://en.wikipedia.org/wiki/Assembly_of_the_International_Space_Station):
[](https://i.stack.imgur.com/3HPNJ.jpg)
As for survival in a closed environment I would suggest taking a look at concepts such as [Close Ecological System](http://Closed%20ecological%20system) such as [Biosphere 2](https://en.wikipedia.org/wiki/Biosphere_2):
[](https://i.stack.imgur.com/rr3Xl.jpg)
Obviously you would need to tackle each of the problems on a one by one basis (after all no such project exists) but using current technology I think you can explain most of your structure if you follow good architecture and engineering principles.
[Answer]
A floating city possible would by using a material with an incredibly strong electric field able to float a city in the sky but this way your citizens would not be able to use anything made of metal because it would be destroyed almost instantly and the city has to be made of an incredibly light material ,because the heavier is the city the stronger the electric field must be to support it's floating and if the field is too strong it could kill people due to the iron in their blood
About purifying water from viruses the easiest and cheapest way is to simply boil all the water to 1000 Celsius degrees in order to kill every single virus in it , then get the Vapour and cool it down to liquid state in a clean container while all the dead bacteria and viruses will be left in the container where water was first boiled
-Edit
I correct myself , there's also another option but I'm not really sure about it, it's called Aerogel or also known as solid Air , I know it's lighter than air and can support x1250 times its weight remaining at the same height but due to its incredibly lightness it would be transported by the winds
[Answer]
Here is a city all floating in China.
[](https://i.stack.imgur.com/7M85Y.jpg)
I would imagine like solar farms that are on water it would have to be calm water most of the year to work.
[](https://i.stack.imgur.com/KRYXK.jpg)
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This question has to do with the same storyline I proposed in [How would government change if everyone died by the age of 25?](https://worldbuilding.stackexchange.com/questions/29199/how-would-government-change-if-everyone-died-by-the-age-of-25) (although now that I've written a few short chapters, the name of the land has changed, as have other things). Basically, a virus killed every over the age of 25, and whenever someone reaches 25, they die suddenly. At this point in time, things have descended to a tribal hierarchy as warriors-in-training took command, although there may be a push to socialism, [as suggested by James](https://worldbuilding.stackexchange.com/a/29204/627).
What I'm exploring is the fate of another group of people who were unaffected by the virus. I'm not yet finished with the details, but here's what I have so far:
* They were highly dependent on the Xenquans (my old name for the main group), who were somewhere between overlords and governors (as in the colonial sense).
* Their infrastructure and economy were inextricably linked with the Xenquan economy.
* Their tech level was a bit worse than the Xenquans, who had medieval-level tech.
* Their self-government was minimal; local leaders reported to Xenquan governors.
* The land of the people is about . . . say, half the size of Switzerland. It is mainly forests and fields. The population was about several hundred thousand people.
After most of the Xenquans die, these people have to start society anew. This will first entail forming a government. Given that they only have experience governing locally, what is the most likely (and effective) form of government for them?
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Given the fairly low tech level, and the familiarity with local governing, I suggest that something like a [city state](https://en.wikipedia.org/wiki/City-state) would be the first logical step.
Basically each city would control itself and everything within a days march, maybe a little more for larger cities or if the terrain is favorable.
Each city would likely have a community of villages around it to make better use of resources: Farmers would want to be close to their fields, miners to their mines, etc, and having to commute from the city would not be practical.
The villages would rely on the city for defense if needed.
Cities would trade and have alliances, and over time a central government could be formed to control the land between them and to help coordinate armies.
Or one of the cities might become powerful enough to force control over the others.
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### Relationship with the Xenquans
It really depends on the feelings that your "Swiss" had towards the Xenquans:
* was it a colonial relationship as we have seen in the first part of the 20th Century: some of the indigenous participate in the colonial system, but the majority are not much more than slaves?
* was it a somehow protective relationship, where the colonees are feeling relatively well in general?
* was it a purely commercial relationhsip, where the "Swiss" have a relative feeling of political independence?
In the last two cases, it is likely that the political structure will continue, with a stronger independence from the Xenquans, or even a reverse relationship will establish itself.
### Weaken Colonial Powers in Modern Times
I will now concentrate on the first case from before. Seeing a weaken Xenquans, it is likely that members of the overall populations, bitter from the difficulties with the colonial power, seize the opportunity to get rid of them completely. Some members of the colonial structure will also jump in to try to seize the power for themselves.
Of course, due to the effect of the virus, the Xenquans can't oppose anything. So it would not turn into some form of independence war as was seen, e.g. in [Vietnam](https://en.wikipedia.org/wiki/Indochine_War) or [Algeria](https://en.wikipedia.org/wiki/Algerian_War). But most probably there will be three groups to oppose:
1. those close to the power circles of the colonial administration, who want to seize the power for themselves, but otherwise leave the global organisation unchanged.
2. those not close to that power circles, who want to change the system entirely (revolutionary circles)
3. those who don't want to throw down the complete system, but want to make a transition to a better human/economical/etc. situation.
and a large majority of people just wanting to live their lifes and get some food every day.
Then again, it really depends on the relative power of each groups and the culture of the country. Let us consider the following possibilities.
* **1 >> 2**: possibly by being linked to the army, the people in power during the colonial administration keep it, and prevent any attempt at organizing a revolution. This would probably lead to some form of **dictatorship** as the power is controlled by the army force. A number of African regimes, or possibly Argentina or Chile's dictatorships come to mind. It does not have to be extremely harsh, it might be "just" extremely corrupt.
* **2 >> 1**: there, you get a proletarian revolution. The population arms itself, parts of the military/police join them. The people of the first group, flee or are arrested and often executed. Examples stem from the already cited Vietnam, or Algeria, but as well as the Russian and French revolutions. The outcomes may vary as much as the revolutions presented here. It can eventually lead to new **Emperor** (even if somewhat sympathetic of the "base" population) or to a **proletariat dictatorship**. But it can be a bloody business.
* **1 $\sim$ 2** you might get into a **civil war**. And that could be a very bloody business. It can lead to the total destruction of the political and law enforcement systems, economy, and a high number of victims. What comes later is hard to predict. If it goes on badly enough, you might see some form of tribal groups appearing. Where locally people unite, with as many forms of political organisation as there are tribes.
### Case of early medieval world
I just wrote the previous part forgetting you have a medieval setting. And thought it could just stay in as illustration of how modern political ideas would be.
Considering that your "Swiss" are in an early medieval tech and culture (?), back then the military power was the almost direct source of political power. There are many possiblities, but I will explain the most likely ones.
The "Swiss" have a King or some form of leader, who was dependent on the Xenquans power.
* He was responsible for the inequality of the relationship with their overlord. And a member of his family profit from the weakness of his relative support to make an attempt for the throne. The perceived weakness and surprise makes the plot successful. The new leader gets crown, and make sure the protests against the coup get somewhat limited.
* He was born in that system but was himself unhappy at having a liege lord above him. When the Xenquans disappear he takes a firmer control of the power and establishes himself as independent ruler.
Either way, when their positions get secured they get on reforming the economy (which might entail trying to conquer parts of the Xenquans lands).
Note on Post-Apo. Due to the fact that they aren't affected by the virus, there does not necessarily occur an apocalyptic desaster throughout their land. So the political system is likely to be some transition from the previous situation.
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It seems (in the relative short term) that a totalitarian "Big Brother is watching" government would be the best. By exercising such absolute control, crime can be reduced (also temporarily) and production increased. Now, it's true that in the long term this (conventionally) would not work out and would end in revolution, but the fact that you can only stay alive for a very short time means that that probably won't happen. If you set the minimum age to be elected at 22, the leaders would only stay in power (and live) for 3 years. Because of that, there would be a regime change every few years, so nobody could start taking advantage of their absolute power. This will also prompt the leadership to prioritize the cure. Also, short term benefit will be **extremely** important in this scenario, as the society needs to rebuild and become richer.
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The most probable outcome may be some free for all wars, followed by a theocratic gerontocracy.
When the domination of the Xenquians collapse, the local leaders will want to keep they (limited) power, and probably to extend it. This will most likely results in wars, but this also means that the local governments will mainly remain the same.
However it will not last too long before the information that Xenequians now all dies young spreads (economic links means exchanges, also exchanges of informations). So the people will connect the dots : Xenequians die young, but they don't, and it is what make the Xenequian domination end.
It must be a divine intervention !
Somebody at some point will have this reasoning, and conclude that the gods are in favour of them, that they are some king of chosen people. Since it is an easy reasoning and that it is seducing, the idea will spread.
All local leaders will be united around the idea that they are all part of a chosen group of people gifted with long lives. The religious people will use that belief to pacify the region and extend they powers.
The next step follows quickly : they are gifted with long lives, but that also means that they are gifted with old people capable of accumulating experience. Thus older people will gain a new respect, since they are missing to the Xenequians.
Even more, as soon as Xenequians lost their old people, they were unable to keep their domination (of course the immediate and massive deaths also count, but it will be easily shadowed). Old people are the key to success, and only us are gifted by the gods with them !
Now all ingredients are there. Religion strengthened, increased respect for the old ones and some efforts to unite the local leaders... well this results likely in some sort of council of the oldest local leaders under the supervision of religion.
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In the historical period associated with your technology level *almost* everyone had **some form of absolute government**. Usually hereditary monarchy.
**Despotism has its advantages.** The key one here is that things can be done quickly, there's no bouncing around between two elected houses who care primarily about being re-elected, something is said and it is done.
Life in this period was nasty brutish and short, there wasn't time to drag a decision out for 5 years.
The advantage of hereditary monarchy is that when the leader for life inevitably dies, there's theoretically no doubt about who is the next leader.
**Disadvantages** You're very dependent on how good the leader is. A bad leader can get the whole country into a lot of trouble and lead to civil war, some thing that almost never happens to a democracy. A democracy also filters out most of the worst decisions that an individual could make. The worst comes when a leader dies and there's doubt over the next incumbent, this is almost inevitable civil war.
**Theocracy** or **Who died and made you king?**
>
> **King Arthur:** The Lady of the Lake, her arm clad in the purest shimmering samite held aloft Excalibur from the bosom of the water, signifying by divine providence that I, Arthur, was to carry Excalibur. THAT is why I am your king.
>
> **Dennis:** [interrupting] Listen, strange women lyin' in ponds distributin' swords is no basis for a system of government. Supreme executive power derives from a mandate from the masses, not from some farcical aquatic ceremony.
>
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Kings were appointed by god and ruled in gods name. There were no atheist kingdoms, they're almost impossible without constant military suppression of the population. It's much easier to suppress the rebellion in their minds by saying that god appoints kings and they rule by right.
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If you're careful, you'll be able to create small elected councils at local level, probably based in a small town, this sense of local democracy can be culturally inbuilt as it is in Britain. Cities can also be republics though they're often subject to military conquest by (someone who wants to be) a prince (*see Machiavelli*).
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Surprisingly some sort of military construct might be needed.
To maintain civilization, the people should constantly be teaching their offspring everything they know. Probably some sort of hierarchical society would be suitable with something like military ranks that signify levels of knowledge. Also, because of the short lifespan, there is no time to sit in schools, you'd have to be doing what you can for the society as soon as possible.
Learning would probably be much like in the military, where the time between theory and practice could be really short. The first assignments would be easier and more forgiving in sense of errors than those you'd get to do with higher rank.
Government would be some sort of decentralized construct, because there would be no time to establish a 'heavy' government before the terminal age. Continuous changes in central government would cause instability if the power is not distributed to several persons. Politics would probably be more impulsive than those in today's world, because of the lifespan issue. Ambitious persons would be quite ruthless, like in the ancient times. Foul play would be common among the high-rank citizens.
In all it wouldn't be easy to maintain a government. People would have barely survived the onslaught of teen hormones when they reach the terminal age. But probably that would make a good story.
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If everyone died at age 25 (or was killed when the jewel in their hand turns black), that would put the world in the hands of people at best in their early 20's. When I was in my early 20's, there was only one thing I was interested in, and it wasn't government.
Assuming this virus hit in the current day, one can assume that the current knowledge base would not be wiped out. As such, any governments would probably not be based on theocracy, as the need to explain the unexplained with religion doesn't exist today, to the degree it did in pre-scientific times.
If you're writing a story about this, it would be interesting to not follow a formula on older adult ideas on government (which is what we have today) or modeling it after pre industrial/dark ages ideas on government (with a limited scientific knowledge) but a simpler, more idealistic, and probably more hedonistic ethos. That approach would have the added benefit of seeming to be more realistic, because it didn't follow existing formulas.
After all, if you're going to die at 25, you may as well have fun while you can.
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Let's say I have a roughly humanoid race (similar size, form, activity level, etc.) that spontaneously generates any energy that they need via Magic. However, they still need to eat some materials in order to grow and repair their bodies.
Assuming that their biology is mostly the same to humans, other than the energy generation, how often and how much would they need to eat, and what would be good sources of food?
Their biology has not yet evolved the ability to create matter, and there is an upper limit to the amount of energy they can generate in a certain amount of time.
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It sounds like they need everything except calories for their normal diet. That implies their body chemistry would lack processes for absorbing and storing carbohydrates and to some degree fats (fat is essential to human brains, would likely hold up).
It's up to you whether that means:
* They could safely eat the same stuff humans do, with all the carbohydrates and superfluous fats just passing through untouched
* Those things (especially sugar) are toxic to them and they need to get their proteins, minerals, vitamins etc from specific pure foods.
* They evolved their magic only recently and their bodies still store all calories, causing permanent weight gain if they eat any at all.
In any case, things like mineral clay, plants (unripe fruits?), and select protein-rich parts of animals or other are likely foods.
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A mutation or virus (we do not know) has suddenly modified humanity by making people live indefinitely though cycles of aging (to 70 yo) and then rejuvenating (to 3 yo).
* This does not make people immortal: they are still vulnerable to typical accidents, we just rule out the death by aging and illnesses. The birth rate had homogeneously dropped worldwide so that it compensates these accidental deaths. This way the world stays at today's ~7 billion inhabitants.
* People are spontaneously aware of the change (an alternative could be to have them discover this as they go, I believe this would just be an initial perturbation leading to stability equivalent to them having been made aware of the change spontaneously).
* People keep their memories through the cycles (their experience is cumulative across the cycles).
How would that change our world?
This is an idea I had under the shower so feel free to make reasonable assumptions on what I could have missed
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People would be a lot more careful!
There's a lot of things that you can't regrow at 3yr old. Many anatomical structures grow in the womb, and are very hard to reproduce after the fact. Everything you develop before you are 3 would be considered remarkably essential to preserve, so people would be very careful not to lose it.
Assuming they magically are brought back to "what they were at 3 yrs old," with perfect regeneration, the pattern of lifecycles may be dwarfed by the mere ability to live as long as you like. Depending on how you manage that one in your storyline, the actual lifecycle may matter little at all, or you may be able to make it an essential part of how people go about their existence.
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I've wanted to work out a world where summers are extremely hot except for two weeks in the middle of summer. Winters would be extremely cold except in the dead of winter when there would be two weeks of spring like weather.
Can a planet have unusual weather changes due to its interaction with other astronomical bodies?
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Sure. The Earth already sees these. Tidal forces can cause shifts in the major air currents causing weather events like rain, snow, etc. Because these forces are caused by movements tied closely to the revolution of the Earth, there's a day-night pattern to most of it, slightly offset because the Moon rises and sets on a different schedule than the Sun.
You might have a habitable moon of a gas giant orbiting its star at a distance that provides an Earth-like climate for the moon (let's say the star's a bit hotter but the gas giant orbits further out to compensate). The weather on this moon would be more closely tied to the orbit of the moon around the giant; when the moon's between the giant and the sun would be the planet's summer, and quite a hot one as the orbit of the moon around a large planetary body would also place the moon at perihelion. Then, the winter, when the moon's on the dark side of its gas giant, would be fairly cold. A one-Earth-year orbit of the moon around the gas giant would not be implausible especially if the gas giant takes ten to fifteen years to get around the star.
The interruption of this normal pattern for two weeks might be the orbit of another moon of the giant in the same plane, which causes a long-lasting total solar eclipse for two weeks. That would explain a cool period in summer. The warm period in winter would be harder to explain, perhaps an elliptical orbit around the gas giant which puts the world close enough to this heat-absorbing and radiating mass that it acts as a proxy sun during perigee.
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Here's a 'simple' solution which doesn't require extremely complicated assumptions about the planetary constituents, etc.
So to have a cold winter and a warm summer you just have a eccentric orbit, so the gas giant orbits closer to the star in the summer and further during the winter.
Now for the cold 2 weeks in the summer. Let's make it easy and say there's another planet in a polar orbit, with the same period as our gas giant, every year, once a year, it pulls in between our gas giant and the sun until blocking some percentage of the sunlight for a few weeks.
Making a hot 2 weeks in winter is *a lot* harder. Heating a planet is unbelievably hard, because planets are big. You can't heat them through some friction processes because then the planets orbit would decay. In fact in space there's really only one thing that heats a planet - a star. So lets just say we have a binary star system. The second star can be smaller than the first, only just reaching enough mass to actually turn lighter elements into heavier elements. Let's put it in a pretty far away orbit as well, let's say double the distance of our planet to the sun. Certainly enough to affect the amount of energy the planet receives, but not enough to cause any significant tidal forces. Remember the temperature difference between the hot and cold extremes can be due to a small (1% variation in the relative position of the planet when at apogee and perigee).
These types of system are somewhat uncommon. Typically most bodies orbit in the same plane due to some rather complex physics. But it's easy to imagine a system where a rogue star was captured by the primary star's gravity.
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The 4 seasons on Earth are caused by our tilt. This affects the angle at which the light from the sun hits us.
If another body were to affect this tilt because its orbit interacted with us, you get different patterns. If the orbits were set up in a way that they affect the tilt in a regular way then you could absolutely get odd weather patterns.
Heck, you don't even need another body involved if you want. You could have a very fast procession. That's the time it takes for earth to wobble on its tilt. This would affect the angle more often and cause even weirder seasons.
Besides seasons tho, any massive body could affect the planet enough to cause issues. Similar to how the moon affects our tides. The problem is that anything massive enough and close enough would likely cause much more severe problems than simply weather. Massive earthquakes and such.
A second star could cause very odd weather patterns by our standards also. 2 Summers, 2 Winters a single fall and spring and so on.
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A highly elliptical orbit will give us a start, with a very hot summer and very cold winter. For this set-up, seasons will be worldwide, with distance from the sun being the determining factor instead of the tilt of the axis.
Now we need a way to warm up the planet when it is in apogee and to cool the planet when it is in perigee. Please note that these solutions may be closer to *science-sounding* rather than *science-based*.
To cool the summer: a moon of the planet is generally stable, but as the planet's perigee is approached, the heat and gravitational stresses is enough to trigger volcanic activity on the moon, which sprays out enough material (chemical make-up to be determined) which dims the sunlight enough to drop the temperature for a couple weeks until the moon settles down as the planet moves farther out.
To warm the winter: the planetary system includes a dust ring of volatile chemicals whose inner edge is at the same distance of the apogee of the planet. Chemical reactions between the atmosphere and the in falling dust generates enough heat in the atmosphere to mitigate the winter for a couple of weeks.
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It occurred to me that part of the problem is answered by a *circumbinary* planet. In this configuration, the planet warms up as it approaches the two binary stars, but cools off when one star passes in front of the other.
Unfortunately, that doesn't explain the increase in temperature during winter. I could throw in a third star, maybe a red dwarf, that was also in a circumbinary orbit. Our intrepid planet would approach it just as it happens to be closer in its own orbit.
For this sort of arrangement to occur, there would have to be some kind of orbital resonance going on. Does anyone have the math and the desire to try that out?
Another possibility is that one of the binary stars (a white dwarf stealing mass from the other star) erupts in a supernova while the planet is furthest from the pair. This is a condition that might last just long enough for life and intelligence to arise on the planet and realize that the white dwarf is about to go kerblooey for good.
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Bob escaped from his exploding spaceship in the world's most ghetto escape pod - an airtight metal box, with only some respiratory gear ($\text{O}\_2$ tank, $\text{CO}\_2$ filter) as company. Now he's floating in open space, awaiting rescue. Disregarding that people die *fast* in space due to exposure to the vacuum.
* How long can he stay alive in this situation?
* Can he do anything to maximise his survival time?
* What eventually kills him?
More details:
* Assume a 1x1x2m box, constructed of sheet metal. (If this isn't strong enough to resist a vacuum, then have the sides a bit thicker.) If it makes a giant difference, then maybe a slightly bigger box could be used, but remember it needs to fit in an airlock at the end of the day. In universe this is a small cargo container.
* Earth orbit. Bonus pts if you can describe other locations, but Earth orbit is most important.
* Bob is mentally strong.
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You said not to worry about this, but for grins and giggles I attached a link to [what would really happen during explosive decompression](https://scifi.stackexchange.com/questions/2628/what-would-really-happen-if-you-were-exposed-to-space/85118#85118).
I think @Mikey is correct about the water and food situation:
* However long your have $O\_2$ supplies and $CO\_2$ scrubbers for
breathing (hours to days?)
* days to a week before dying of dehydration
* weeks to a month before dying of starvation
## In Shadow
I think @Mikey is incorrect about temperature exposure. [This question on Physics Stack Exchange](https://physics.stackexchange.com/questions/159590/heat-transfer-from-a-spaceship-in-deep-space) has useful information.
Using the radiative heat transfer equation for a pod *in shadow*:
$$ \frac{Q}{t} = e \cdot \sigma \cdot A \cdot \left( T^4\_{skin} - T^4\_{ambient} \right) $$
and plugging in the numbers:
$A = 1.2 m$
$e = 0.97$
$\sigma = 5.67\times 10^{-8}$
$T\_{skin} = 304 K$
$\frac{Q}{t} = 2000 \frac {Cal}{day} = 100 W $
and solving for $T\_{ambient}$ yields an ideal ambient temperature (minimum food consumption) of ~$290 K = 17 C = 69 F$ (not surprisingly this is the temperature of temperate locations on the surface of the Earth).
If you flip this around and figure out the amount of energy needed to burn to stay warm in deep (3K) space (and using all the numbers shown above), you learn Bob has to consume 11,600 Cal / day for his body to generate enough heat to stay warm (this assumes no heaters in the craft).
If we limit ourselves to just doubling Bob's Calorie consumption in a day to stay warm, we need an ambient temperature of about $273 K = 0 C = 32 F$
This answer is different than I thought, I thought the pod would be *less* sensitive to external temperatures than it is. I was wrong, without pod heaters, the pod is far more sensitive to ambient temperatures.
## In Sunlight
Having the escape pod in sunlight makes a big difference to the heat equation. A human body might produce ~100 W of heat but Sunlight at Earth's orbit on the sunward side of a human body sized object generates **800 W** of heat.
Equilibrium temperature for this configuration will be a scalding
* At Earth, $344 K = 71 C = 188 F$
* At Mars, $308 K = 35 C = 109 F$
* At Asteroids, $237 K = -36 C = -47 F$
* At Jupiter, $210 K = -63 C = -107 F$
## Summary
Ideally you'll be near a large body. This allows you to cycle between shadow and heat. It should help moderate your temperature tremendously.
In general though, it'll be easier for the pod to stay warm through heating than to provide active cooling when exposed to direct sunlight.
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If pressure and air are taken care of, the next major risk is temperature.
The [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature) of an object at equilibrium is given by
$$T = \left(\frac{L(1-A)}{16\pi\sigma D^2}\right)^\frac{1}{4}$$
Assuming the Sun (luminosity L = 3.8\*1026 W), a reasonably reflective box (albedo A = .75), and three escape situations (Earth orbit D = 1.4\*1011 m, Mars orbit D = 2.2\*1011 m, and Saturn orbit D = 1.4\*1012 m), we get the following equilibrium temperatures for the box:
* Earth: 212K (-60C)
* Mars: 169K (-104C)
* Saturn: 67K (-205C)
In Earth orbit, Bob might live long enough to be rescued: vacuum is a pretty good insulator, and the equilibrium temperature isn't that far below body temperature -- a *very* rough calculation says he's got about four hours before going hypothermic, and maybe 12 hours before dying of cold. In Mars or Saturn orbit (or deep space, for that matter), the same calculations give one to two hours to hypothermia, and three to six hours to death.
Note that if his box isn't tumbling to even out the heating, he runs the short-term risk of burns if he's in Earth orbit, as the sunlit side of the box heats up. If his clothing provides sufficient insulation to avoid burns, he might be able to use this to extend his life expectancy.
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Setting aside thermal issues, and assuming a limitless (or large) supply of air:
1. After [two to three days](http://www.livescience.com/32320-how-long-can-a-person-survive-without-water.html) of dehydration, Bob would perish.
2. So Bob has water and disposal of water; after two to three unpleasant weeks without food, Bob will perish.
3. So Bob has water, disposal, and food... it's up to him how long he can bear to be with himself in a breathing/eating/drinking/poop/pee apparatus.
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Does he have a light source? Anyone to talk to? In a weightless environment, no visual stimulation, no sound other than his own voice... How long would an average human-being mentally survive while held against their will in that environment? He would be driven insane by his own thoughts. He would be sorry he brought an oxygen supply. he would WANT to die.
So there is a limit to how long someone can live in the absence of each of his physical needs. In order of priority:
Air pressure
Breathable air
appropriate temperature
clean water
hygienic enviroment.
nutritious food.
Is the metal container in the sun? His environment would cool to 4 degrees Celsius, which is survivable in winter clothing. What is he wearing? If the container is between galaxies then the environment could cool down to negative 270 degrees Celsius and he would be frozen solid in a few minuets regardless of what he is wearing.
But again, supposing all of his physical needs were met for a few weeks, he would probably find a way to commit suicide before then.
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A bit of background to the question. Vampires are rare in human kingdoms and are hunted down, and the technology level across the world is around the 17th century level in terms of our world, since magic stunted scientific development.
Vampires need blood because human blood contains complex chemicals called succulents which attract and hold natural mana present in the atmosphere. They cannot make them by themselves. Vampires are composed of part flesh part magic, making them more adept at doing magic and also making them faster, stronger and more durable, basically magic holds them together like glue, if they don't get the succulents the need, they'll fall apart like legos. (Note: they don't burn in sunlight, don't know if this is useful or not however)
So back to the question, there's this kingdom of purely vampire citizens, and each one needs atleast 1 liters of human blood (per month) to not die. How would they be able to farm blood at such a large scale? (note: the number of vampires in the kingdom is around 2 million, humans in captivity are around 10-ish million)
Edit: Changed the two litres to one liter, per month (I forgot to write 'per how much time') and there are more humans now (at a ratio of 2:10).
Seems the question has been closed because I haven't given enough detail or clarity. I don't really know *what* detail to give, but I'll give anything that's important:
The kingdom can either breed humans, or, they can use their military might to force nearby human kingdoms to forfeit thousands of citizens in return for the kingdom not getting absolutely rampaged. Space and time magic do exist, but how to perform them have been lost to time, so that's a no-go.
My question is really just asking about how vampires can harvest human blood at such a scale, and how and where would these captive humans be kept, when there's 10 damn million of them. Are they in giant fortresses? Or are in villages where they would be forced to work the land, give food to their overlords and also keep some for their own sustenance, along with a tax of blood. How efficient would that system really be? How can it be improved?
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Perhaps and an addendum to any other answer here: Afflict your "donors" with [Polycythemia vera](https://en.wikipedia.org/wiki/Polycythemia_vera)
>
> In oncology, polycythemia vera is an uncommon myeloproliferative
> neoplasm (chronic leukemia) in which the bone marrow makes too many
> red blood cells[1](https://en.wikipedia.org/wiki/Polycythemia_vera) as well as white blood cells and platelets.
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How you afflict them, and if the thicker blood is of benefit to the vampires is another question and up to the OP :)
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### Quick Math
Today, people can generally donate 0.5 l of blood every 56 days.
This means, that per annum, a singular average adult human donor can contribute about 3.5 liters safely. Now, granted that this is aligned with modern health and safety guidelines, so you could probably squeeze more out of them, especially if you tailor the diets of your donors towards blood-production, but still. Not a lot. To supply the 12 l a single vampire needs, **you'd need between 3 and 4 healthy adult humans**. The problem is that not all humans are the same.
For example, a short adult woman can sustain significantly lower blood production than a large adult male. Similarly, if you want these healthy adult donors, then you need to have healthy children that grow up into healthy adults. Especially with how "pyramid-shaped" demographic curves used to be historically, this means that you'd need even more people on a per-vampire basis.
With infant mortality, larger families, lower life expectancy, and the adults constantly donating blood, it is not unreasonable to say that about half the population would be under 18 years old, so **the total number of humans required to sustain one vampire would probably be between 6 to 8 people.**
This means that in order to get 2 million vampires fed, you'd need another 8 million or so humans who need to supply blood, create progeny, and feed themselves. With how little caloric surplus was available at the time with agricultural techniques of the time, you'd probably need to increase the human pop. even further to support people when they're weakened after giving blood, so maybe stack on another couple million humans.
Also, this isn't considering that some vampire aristocracy might want more than 12 l per year, because they feel like extravagantly bathing in a bathtub of blood for kicks. Consider how many people are employed by the "luxury goods" sector, even historically (pearl divers, gemstone miners, gold, etc) and you can again slap another couple million to build up a bit of a surplus.
### Making it work
With your vampires requiring this much blood, the most attractive option I see is simply running an empire. The largest empires of the 17th century were those in Asia with the Qing Dynasty at approx 100m or, a bit smaller, the Ottomans at maybe 30m. Your vampires simply form their own kingdom where they are the aristocracy, and instead of taxes, the peasantry simply tithe blood to their local landlords.
In order to prevent blood-logistics issues, you'd distribute the vampires.
For example, a small farming hamlet of 100 inhabitants might have a single family of four or five vampires acting as their local lords. The peasantry farms and provides with blood, and in return, the vampires act as local law enforcement, protection, and maybe lend their magical aid to make the people and fields fertile.
In general, the best way to play this situation from the perspective of the vampires is probably to get the humans on their side. Offer tangible benefits like protection (bye-bye local bandits) and healing magic (reduced infant and mother mortality) alongside perhaps painting the vampires as rightful religion-supported rulers and presto: the deal is so sweet that your human peasantry is even willing to fight against foreign human invaders when necessary because they think they've got a sweet deal (giving a pint of blood every two months isn't so bad).
[Answer]
## You need *a lot* of willing or captive humans
Humans can only sustainably generate so much blood, specifically 1 liter every 24 days. That's the base replacement rate. If you could somehow capture all of (and only) the old blood cells that each human body would have recycled, you are left with a *minimum* vampire:human ratio of 1:48. That's assuming such a process is even possible.
More realistically, the safe maximum blood donation rate is 1/2 liter every 56 days. Maybe you can fudge that a little to 1/2 liter per 50 days, leaving you with a likely sustainable ratio of 200 humans per vampire. And maybe you can fudge that a little further with a special diet and magical supplements that increase the rate of blood replenishment. Maybe you can get down to 42-45 days.
## Time-dilation chamber?
If time magic is possible, you may be able to make due with your 2:1 vampire:human ratio by placing your humans in a chamber where time passes one year on the inside for each day on the outside. But that runs into more issues because now you have to deal with the fact that they age 365x faster as well, and therefore die every 60-75 days. Plus you'd have to drain each human once every few hours (according to the clock outside the chamber), ensure they keep breeding, etc...
That might be possible, but it has the same nutritional requirements of a massive farm of 3.65 billion humans. That's almost certainly not possible at 17th century technological levels, even with magic.
## Workarounds
Consider the following:
* Make your vampires *a lot* less thirsty
* Have some sort of nutritional supplement that sends human blood production into overdrive
* A reliable way to synthesize blood with alchemy, perhaps one that uses real blood as a seed or catalyst.
* Have a lot fewer vampires
[Answer]
The numbers here need to be reversed. You can't farm an animal less numerous than your own species and expect everyone to eat. In our own world, humans account for about 36% of the mammal population, while livestock accounts for 60%, and meat only makes up a small portion of our very varied diet. Imagine how much worse it would be if we were obligate carnivores who could only derive nutrients from one part of one slow growing species that they don't even produce that much of? Vampires are solitary apex predators, and, as such, have nutrient requirements that stand at odds with large populations. There aren't that many tigers because each tiger needs a lot of space with a lot of prey roaming around to support itself. Vampires would likely work the same way. Even getting them into a position where they could form cities would be a challenge, and would require massive captive human populations. Vampires would need to be the minority even in their own cities, with at least 2 or 3 captive humans to every vampire. This isn't all that unusual. There were more slaves than citizens in the Roman Empire. Historically, minority populations lording over much larger majorities has been a thing we have seen often. Those recognized as citizens by a given society have often not been the most common people in that society. A nation of vampires, likewise, need not have a majority vampire population.
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Multiple large moons around a terrestrial planet is something that is seen in science fiction a lot, but is not really easily possible. An alternative is to use smaller moons but have them orbit closer.
With this in mind, I wanted to get the exotic look of multiple moons with large angular sizes but without the orbital instability. I decided to recreate the Galilean moons but to scale with Earth's mass as the host planet. I scaled down the mass of Io, Europa, Ganymede, and Callisto so my 4 moons would have an equal mass-ratio with Earth as the real moons do with Jupiter. This puts their masses in the range of very large asteroids like 4 Vesta and 2 Pallas, which depart from an equilibrium shape only due to rotation.
It's a bit of a handwave as to how a rocky planet could form multiple moons like this, as they are not thought to have planetary accretion discs like gas-giants but I'm assuming a collision happened like with the case of our moon, only it was more of a glancing collision that smeared the body into a large disc, out of which clumps formed into resonances in place.
I reduced the semi-major axis of my "Io" by 10, down to 42,170km and coincidentally that puts it just outside of geostationary orbit where material would be pulled down to Earth rather than recede. From there, another 2 moons follow the laplace resonance of the Galilean moons, so their semi-major axis is calculated from the orbital period for a 1:2:4 ratio. Finally, we have a Callisto, and I wasn't sure how that should be scaled to make it gravitationally equivalent, so I just made it the same ratio as Ganymede's orbit is to Callisto's.
I tested this in an N-body simulator, with these characteristics:
[](https://i.stack.imgur.com/onD0E.png)
My goal is to get impressive sci-fi moon sizes so I thought copying(ish) the Galilean system would be a good starting point, and as a visual aid, I made this, using 4 Vesta as an angular size model:
[](https://i.stack.imgur.com/ZhCdT.png)
(If you sit at the right distance from your monitor that you can cover up the moon with your thumbnail, you'll get a reasonable picture of what it would be like to see such moons in the sky).
So ultimately, stability wise this doesn't seem to be a huge problem. Earth even has enough orbital real estate for 4 Ceres sized moons (so nearing twice the diameter of my case), when they are separated by 12 mutual hill radii.
The issue is tides. The moons are going to be pushed further and further away over time, just like our moon (in this case the resonance may or may not break). However, it is true that smaller moons would raise a smaller tidal bulge on Earth and so recede less rapidly than a larger moon would under equal conditions.
Here's my question given this information: how much angular size are the moons likely to lose after 4 billion years? As a ballpark, given their size, are they going to recede a very great distance or only a small amount?
[Answer]
An earth size planet can’t sustained that many large body in its ration because of the continuous pull of the each moon pulling on each other as well as the planet being pulled by the moons and vise versa. They moons would rapidly destabilize and either get slinged shot out of orbit, some possibly colliding causing large debris that would be hazardous to life if the planet as well as pulling the planet out of it own orbit causing it travel further from the sun and increase the chance of be pulled by another large body and getting slinged shot out of the solar system or collision with another large body of planets. Or when the smaller moons started forming they would could quickly get absorbed by the not yet completely formed planet or one of the larger forming moon resulting in 1 moon to the planet. Or if some how they did all form the bodies would also heat each other due to all the friction causing them to oceans of lava on the surface where at some point they would rip each other apart.If you are wanting to build a world that has multiple large bodies in its sky the best scientifically accurate scenario would be the planet that has life is simply a large moon orbiting a gas planet with other large moons as well. And the gas planet was in a orbit close to the sun but it mostly likely would still have dramatic climate changes from life friendly to freezing temps were complex life would mostly never evolve unless the gas planet is positioned just right in a binary star system that would allow for the moon with life to have more stable conditions while it travel around the giant gas planet were it receive plenty of light regardless of which side it’s at around the gas planet and the other large moons that are in close orbit would still show in the sky.
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Assuming the skies are clear of suspended particles, what color should they be at mid-day if viewed with human eyes?
The planet is larger and twice as massive as Earth, with a nearly identical atmosphere composition but a far higher surface pressure. This implies a thicker atmosphere with more scattering, which could produce light, warm-toned skies rather than blue ones. I watched [some](https://www.youtube.com/watch?v=9-j_JOWPLj8&ab_channel=Artifexian) [videos](https://www.youtube.com/watch?v=L9MNC45Jr6Q&ab_channel=Artifexian) by Artifexian on the subject, and used the spreadsheets and sources he had provided to determine what color they should be. However, I wasn't able to come to a solid conclusion based on some gaps and conflicting info:
* The [two](https://docs.google.com/spreadsheets/d/1cW7BIWlBUscqS9MVqs5gSbPH0OGzyE-j2cz6ADBSVzE/edit#gid=0) [calculators](https://docs.google.com/spreadsheets/d/1YhSapw5xSUli1H321JSM2JqMfbmuzqwJp5Iba6DxuWs/edit#gid=0) generally point towards a light, warm-colored sky. This is based on two things: first, the approximate height of the tropopause. This isn't provided in the first calculator, but I roughly extrapolated it from the height at which air pressure is between 70-400hpa (~15591.61-30545km.) This probably isn't the best way of estimating it, and the margin is wide enough to go either way in terms of color.
* Next, I compared this and the planet's actual surface pressure (2.43atm) to the results from the second sheet; it calculates the required properties for a sky, with 1atm of surface pressure and the same scale height, to become warm-toned (tropopause at 21453.68m, ~2.36atm.) The tropopause is based on the scale height and angle of twilight. I was unable to calculate this based on my planet's radius, making the results somewhat inaccurate. It also does not take into account the density of the atmosphere, which would increase scattering at the surface.
* These results conflict with [a source](http://panoptesv.com/SciFi/ColorsOfAlienWorlds/AlienSkies.php) he cites in [another spreadsheet](https://docs.google.com/spreadsheets/d/1AML0mIQcWDrrEHj-InXoYsV_QlhlFVuUalE3o-TwQco/copy). This guide suggests my skies will have a bluish tone at 3atm and even 10atm, given the spectral type of the parent star. It mentions that planets with higher gravity can achieve more surface pressure with a thinner atmosphere, and will appear thinner than they actually are, further pointing towards blue skies.
Planet Stats:
* Mass: 2.0MEarth
* Radius: 1.25REarth
* Average Surface Temp: 25ºC
* Sea Level Pressure: 2.43atm
* Atmosphere Composition: 78.19% N2, 20.45% O2, 1.23% Ar, 0.08% CO2, .05% Trace Gases
* Star Type: K6V (.64MSol, .168LSol, Peak Wavelength ~619.94nm)
Sources:
1. [Designing Earth-Like Atmospheres](https://www.youtube.com/watch?v=9-j_JOWPLj8&ab_channel=Artifexian) / Artifexian
* 1a. [Habitable Pressure Chart](http://www.projectrho.com/public_html/rocket/images/worldbuilding/atmograph04.jpg) / Project Rho
2. [SKY & PLANT COLOR ft. Worldbuilding](https://www.youtube.com/watch?v=L9MNC45Jr6Q&ab_channel=Artifexian) Notes / Artifexian
* 2a. [Script w/ Sources](https://docs.google.com/document/d/1LxroJkoyy02A2yWra2z8fmcvYJMbX54X3Tl0Jv33poE/edit) / Artifexian
* 2b. [Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization](http://www.xenology.info/Xeno/5.4.2.htm) / Robert A. Frietas Jr
* 2c. [Earth: Portrait of a Planet](https://www.amazon.co.uk/Earth-Portrait-Planet-Stephen-Marshak/dp/0393111377), p697 / Stephen Marshak
* 2d. [Atmosphere of Titan](https://en.wikipedia.org/wiki/Atmosphere_of_Titan#Composition) / Wikipedia
* 2e. [Sky turns orange across UK](https://edition.cnn.com/2017/10/16/health/orange-sky-uk/index.html) / Judith Vonberg, Brandon Miller, CNN
* 2f. [Why isn't the Martian sky blue like the Earth's?](https://web.archive.org/web/20040810170442/http://humbabe.arc.nasa.gov/mgcm/faq/sky.html) / Dr David Catling
* 2g. [The Sky on Alien Worlds](https://www.orionsarm.com/xcms.php?r=oa-page&page=gen_skyonalienworlds) / Stephen Inniss, Steve Bowers
* 2h. [Activity 1: Exploring Spectra](https://skyserver.sdss.org/dr8/en/proj/basic/spectraltypes/studentclasses.asp) / Sloan Digital Sky Survey
* 2i. [Sky Colors for Exo-Earths](https://epod.usra.edu/blog/2009/02/sky-colors-for-exoearths.html) / Ivan Gonçalves
3. [Earth-Like Atmospheres 3.0](https://docs.google.com/spreadsheets/d/1cW7BIWlBUscqS9MVqs5gSbPH0OGzyE-j2cz6ADBSVzE/edit#gid=0) / Artifexian
4. [Sky & Plant Color Calculator](https://docs.google.com/spreadsheets/d/1YhSapw5xSUli1H321JSM2JqMfbmuzqwJp5Iba6DxuWs/edit#gid=0) / Artifexian
5. [Colors of Alien Skies](http://panoptesv.com/SciFi/ColorsOfAlienWorlds/AlienSkies.php) / Panoptes
6. [The Worldsmith v3.04](https://docs.google.com/spreadsheets/d/1AML0mIQcWDrrEHj-InXoYsV_QlhlFVuUalE3o-TwQco/copy) / Artifexian
7. [Colors of the Sky](https://aapt.scitation.org/doi/10.1119/1.2341808) / C.F. Bohren, A.B. Fraser
**EDIT**: Accidentally linked the wrong videos, corrected.
[Answer]
You have to take both the star type and the atm into consideration. On the Atmosphere Spreadsheet it shows that the visible wavelength will be a red color. Then on the Sky Color source it shows the sky looking like the image for worlds with a K5 star and atm of 3.
[](https://i.stack.imgur.com/Z3QrQ.png)
I would say your world has a hazy blue sky with a tint of reddish-orange during midday and as the sun sets it will get more red and orange. Dusk and dawn will appear kinda brownish with a tint of reddish-orange.
[Answer]
well as far as I remember the sky's colour is based on the chemical composition so with that in mind the colour would be blue, just like our old earth. the addition of a K6V or a orange dwarf star would not make any difference during the day, however sunrise and sunset would certainly make the sky dip into deeper orange and reds
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Suppose you have what it takes to build a Ringworld, or at least a Culture Orbital, but instead you make a tiny scale model of Earth, with a neutronium core to make the surface gravity match, a membrane to prevent atmosphere loss, and whatever else it takes to make surface conditions (other than curvature) match those of Earth.
If this toy world is small enough, wind and water carry heat quickly enough to make temperature mostly the same all over. So: How big must it be to prevent that, so that latitude makes a noticeable difference in climate?
A comment justly says ‘noticeable’ is too vague, so how about this: the world must have icecaps (or at least permafrost) and tropical lands where ice is unknown.
[Answer]
The nice thing about having the technology to create a small planet is that it will let you build in methods of controlling the climate. The builders would need to add heat pump technology to the right areas to compensate for the spreading of heat. The polar regions would pump the heat out to cool it. That heat would be sent to the equatorial regions to heat up that location. If you have the energy to build a planet, you have the energy to move heat between two (or more) areas on said planet. You could do this as a way that mimics underwater hydrothermal vents. These vents would not only allow you to move temperature around the planet, but also to add nutrients into the ocean which would be lacking due to the absence of geothermal activity.
[Answer]
## Your [neutronium](https://en.wikipedia.org/wiki/Neutronium) core is already cold.
In order for your nutronium core to have the desired effect you're going to have to pack a lot of matter in there. That's not a problem because neutron matter is nicely compressible as it is not electrically charged.
That said, it is not infinitely compressible, and your really tiny world might need more than you can fit inside it with compression alone. We need to get colder.
Since your world has neutronium based toys, I think it would be safe to say that extremely energy efficient little freezers could plausibly exist.
You could recycle this coldness and have it physically connected to the poles of your tiny world, causing water already there (and maybe actual water molecules in the air to condense) and form ice. The method of transfer could be passive or active. Passive would require less energy, but an active system (live valves etc) would allow you control over it enough to make seasons. Bigger ice caps in winter vs summer?
Unfortunately you would also need a heater connected to the equator, depending on how tiny the world was. If it's room sized you probably wouldn't - but if it's marble sized you definitely would. A heater would add the benefit of actually making the equator hot, rather than just a little colder than room temp.
That said - I have made a little leap from neutronium core toys to tiny kitchen appliances - so my answer may not be in scope for your world.
TL;DR - control the temperature using technology within the little earth.
p.s. lots of toys run on batteries.. Put a hinge somewhere on it and the worlds smallest star head screw.
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What would be the specific long term and short term outcomes of slashing wounds in microgravity?
The scenario is that a normal adult is slashed with a knife in a microgravity environment. Assume standard atmospheric pressure and normal atmospheric composition. Assume that the injury cuts through skin and moderate amounts of muscle. Assume the wound is taken on a thigh (ample musculature).
For instance:
A lack of gravity experienced during space flight has been shown to have profound effects on human physiology including muscle atrophy, reductions in bone density and immune function, and endocrine disorders (<https://www.frontiersin.org/articles/10.3389/fcell.2020.00096/full>).
Weightlessness is associated with blood flow stasis in internal veins. Blood flow stasis could lead to a lack of clotting materials and nutrients for normal healing ([https://www.google.com/amp/s/www.syfy.com/syfy-wire/human-blood-acts-weird-in-zero-g%3famp[][1]](https://www.google.com/amp/s/www.syfy.com/syfy-wire/human-blood-acts-weird-in-zero-g%3Famp))
Microgravity has been shown to be detrimental to wound repair. Astronauts injured in space have a harder time healing. The cells cultured in microgravity and the cells cultured on earth will differ in gene expression. Blood vessel development will be impaired in cells cultured in microgravity (caution pdf) (<https://www.google.com/search?q=wound+healing+in+micro+gravity&oq=wound+healing+in+micro+gravity+&aqs=chrome..69i57.17574j0j4&sourceid=chrome-mobile&ie=UTF-8>)
[Answer]
So, this is a bit of postulation based on what we know from the real world...
First off, despite *a certain television program's* insistence that gravity is part of the healing process, the effects still happen in an environment where you're neutrally buoyant, e.g. weightless. If you're swimming, a cut will still clot, even though you are neutrally buoyant. Gravity is not a trigger for clotting factors or healing in general.
As to what happens to the blood you bleed, blood is considered a Newtonian fluid, [so I imagine it'd behave quite like water](https://www.youtube.com/watch?v=o8TssbmY-GM). Thank you Chris hadfield for your [water experiments].(<https://www.youtube.com/watch?v=P36xhtpw0Lg>)
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I have a character who cannot smile, frown, express anger on their face, or make other expressions but can still move facial muscles to blink, eat, blush, puff cheeks and still feels emotions like happiness. Aside from the expressionless face they are completely normal and able with no other issues. I've found "moebius syndrome" but that seems to commonly come with other effects such as troubles with eye movement. Any other conditions or disorders?
[Answer]
## Not as written
Facial expressions are controlled by several different cranial nerves. There is literally nothing that could damage them all without destroying the nervous system or entire front of the skull. The only way for a person not to be able to make any facial expressions would be to be complexly non-responsive (a.k.a. a vegetable) or to not have a face.
If they have no face, if they literally have no musculature anywhere on their face, say from a severe burn, such an injury would also render them blind and and unable to eat. Not being able to make facial expressions would be the least noticeable thing about them.
There are conditions that can drastically reduce emotional expression in the face, if that will work I suggest re-asking a modified question.
[Answer]
**too much clothing**
They can make facial expressions all day, voluntarily or involuntarily, without any repercussions. It's just nobody will be able to tell, because nobody can actually see their face.
As to why would only very few individual in the entire population wear a face mask? There are some options. One option would be that there's an ongoing pandemic of an airborne disease, and most people simply don't care, but that's too unrealistic.
Another choice would be they are a prominent member of a religious group that isn't too common in that country or only adorns its prominent members with face masks. They could doff it at any time, if they don't mind the shame it brings to their family, eternal damnation, your pick... or maybe it's one of those groups that perform more ... fundamental ... modifications to the face, while being careful enough to not disrupt functionality.
A medical condition is an option for sure. Not one that prevents muscle movement - but one that makes exposed skin a real problem, or just unsightly enough that full-body cover is the lesser evil. Pick one of those diseases that wreck your skin if too much UV light touches it, and crank it up a little.
Or perhaps they do it to hide their identity for a legitimate (or illegitimate) reason, or they really like someone who does.
[Answer]
**Parkinsons disease.**
[](https://i.stack.imgur.com/18vWX.jpg)
<https://www.nydailynews.com/life-style/health/ali-face-struggle-parkinson-disease-article-1.2660640>
One of the symptoms of Parkinsons disease is [facial masking](https://www.medicalnewstoday.com/articles/mask-face-parkinsons#facial-masking). Affected persons struggle to move their faces and show expression. Muhammad Ali had Parkinsons for many years.
<https://www.apdaparkinson.org/what-is-parkinsons/symptoms/facial-masking/>
>
> She ends with his face, but no explanation is necessary: he’s remained
> almost expressionless. To the untrained eye, the man appears
> disinterested, even bored.
>
>
> But to Tickle-Degnen, it’s clear that the subject, a Parkinson’s
> patient, is exhibiting “facial masking,” a symptom in which facial
> muscles become immobilized and the patient has what can best be
> described as a blank expression. “The face is the primary way we
> communicate with other people,” says Tickle-Degnen, who has been
> researching nonverbal and verbal communication among people with
> Parkinson’s and other diseases for the past twenty years. “We tend to
> believe the actions of a person more than their words if we feel there
> is a discrepancy between the two. So, a person with Parkinson’s
> disease may be talking about their feelings and saying that they are
> really enjoying life but may not be believed.”
>
>
>
The person with Parkinsons is the same person he always was. He can love and hate and feel grief and feel joy. He can laugh. He can cry and it might surprise you when he does, because he does not look upset.
The other symptoms of Parkinsons might get in the way of other things like walking, or eating. Or maybe not. Parkinsons is not the same for different people. Some people get all the symptoms, some people have symptoms straggle in over the years, and some people have a couple of troubling symptoms but the others not so much. If you want your character to have pronounced facial masking but only a little tremor, that can happen.
[Answer]
**Facial palsy**
Usually this affects only one side or other of the face but it is possible for an unfortunate individual to be affected on both sides.
>
> **Facial palsy caused by brain damage versus Facial palsy caused by facial nerve damage** Facial palsy in non-stroke cases is a result of
> damage to the lower part of the facial nerve. In non-stroke cases the
> damage occurs after the nerve has left the brain and travels down to
> the facial muscles. There are many causes of damage to the lower part
> of the facial nerve. Facial palsy in stroke cases is a result of
> damage to the facial nerve inside the brain. In case of an ischaemic
> stroke, damage to the brain tissue and nerves is caused by lack of
> oxygen. In case of a haemorrhagic stroke, the bleeding puts pressure
> on the nearby tissue and nerves. In both cases, cells are killed
> within minutes.
> <https://www.facialpalsy.org.uk/causesanddiagnoses/stroke/>
>
>
>
[Answer]
Facial [frostbite](https://en.wikipedia.org/wiki/Frostbite) can harm nerves controlling facial muscles and make person have difficulties speaking and smiling.
[Answer]
## Eisenhorn, nerve damage.
The character Eisenhorn experiences this, after being tortured, which leaves nerve damage.
I can't rightly say how well/respectfully Dan Abnet portrays that character, as I've not experienced it myself. But Eisenhorn uses it to his advantage, and it also works against him at least once.
This sort of shows there doesn't need to be a named condition that leads to this, as the majority of the entries in the TV Tropes page [Frozen Face](https://tvtropes.org/pmwiki/pmwiki.php/Main/FrozenFace) (warning for the page image, as it is a little startling if you're not expecting it) are from 'nerve damage', 'muscle paralysis' and 'scarring'.
[Answer]
[Autism](https://en.wikipedia.org/wiki/Autism) is often accompanied by [reduced affect display](https://en.wikipedia.org/wiki/Reduced_affect_display) - which is a technical term for facial expressions being reduced or absent.
People with autism are not [neurotypical](https://en.wikipedia.org/wiki/Neurotypical), and may range from quite impaired to above average. It is possible for a person to have high-functioning autism, and for some neurotypical persons to not notice that anything is wrong with them. They may even be considered to be geniuses.
As a person with autism and reduced affect, I don't show my emotions on my face much, if at all. My daughter is also autistic, and also has reduced affect. However, we both still have emotions, and we are also both capable of making emotional facial expressions... we are as capable as any neurotypical person of smiling, frowning, scowling, appearing afraid and so-on... except that unless we make a *conscious* effort to do so, *we just don't*. We don't smile when we're happy, or scowl when we're angry, we make those expressions when we're *acting*.
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I'm trying to engineer an Earth mass planet built initially out of pure silicon dioxide (silica).
So basically, imagine a glass sphere slightly larger than Earth somewhere in the Goldilocks zone, preferably closer to the outer region.
Keep in mind that this planet has no moon, so there is no tidal heating. The inside of my glass ball is cold (and I want to keep it that way).
The tilt of the planet is something smaller than Earth's, around 15°.
Then, out of the same silica I need to shape the relief (well get back here in a second).
Afterwards, my engineers build an equatorial magnetic ring system, which is basically a conductive ring on tall stilts that circulates current around the equator, powered by solar panels (also highly elevated) that are in the immediate vicinity of the ring, on both sides. The width of this solar panel fields should be enough to power the ring in order to obtain a magnetic field a few times (maybe 20?) more powerful than Earth's (since we have no atmosphere at the start so we need to collect the solar wind at a high rate for hydrogen, oxygen and nitrogen).
So, up to this point we have a smooth glass ball with a planetary magnetic shield generator that can be powered on anytime.
As you might have guessed, I'm trying to make the planet habitable, and as a matter of fact very comfortable (nice and mild temp. range, no extreme weather phenomena).
**Issues/Questions:**
1. Question was moved here: [How to stabilize the tilt of a planet without heating its core from tidal forces](https://worldbuilding.stackexchange.com/questions/193159/how-to-stabilize-the-tilt-of-a-planet-without-heating-its-core-from-tidal-force)
2. Since there is no plate tectonics and volcanism, there is no natural circulation for elements such as carbon, calcium and nitrogen. This is the most important part and the core of this post: **How should I design the topography of the planet** (altitudes in every point, from the lowest point of reference - since there is no water yet), **so that when I add the water** (some will be formed from the captured solar wind, but it will be a very long process, so I'll just transfer an ocean of unsalted water to my paradise in the making) **there will be no "dead zones" in the ocean where the nutrients get deposited and there are no currents to move it in a coastal region or even just the surface so plankton gets access to them?**
**My ideas for the second question were that:**
* I could add a "cone hat" continent on each pole, covering the entire polar circle (here between 75° and 90° latitude) that would facilitate the formation of ice. When it would "slide off the cone hat's edge" (polar cap meets the ocean of fresh water and does the iceberg thingy) the melting of the ice would create a current in the ocean. If it needs to be focused in order to have a direction, then I could make the said continents more horseshoe shaped, so that ice falls off and meets the water predominantly in a certain region.
* I could make the ocean shallow (what was again the maximum depth at which sunlight can reach? 200 meters?) and also flat (so there will be no deposition zones designated by topography)
* I could make the entire dryland areas to be at most Madagascar sized islands equally distributed on the surface and placed in such a way as to not create any calm areas in the water around them (such as deviating a current from the water area between island A and island B - then that area would become a deposition area, which is not wanted).
* I could add genetically engineered species that feed in the ocean but live, die, breed on land, or marine species that commit suicide on the shores so that nutrients would be continually moved from the ocean to the continents.
* I could design the continents/islands with an edge on their perimeter (just a few tens of meters tall, not Km) so that they act as food plates and not spill the nutrients into the ocean too readily
**Notes:**
* I do not want to create a textbook planet, I want to make an engineered resort planet kind of thing
* all the other elements needed for life (iron, sulfur, carbon, phosphorus, etc.) will be added in "perfect quantities as to generate biosphere" (meaning that I don't need a few billion tons of iron if the biosphere's weight is limited by another element [most likely phosphorous])
* I will add mountain ranges on the continents/islands keeping in mind the Hadley cells in order to avoid the generation of arid areas/deserts.
* the end salinity of the ocean would be something along the lines of 0.1%-0.25% - so it will actually be barely drinkable by humans
* once the atmosphere reaches 1-1.2 atm. of pressure, the magnetic shield can be toned down to something similar to Earth, so we avoid gaining any more atmospheric mass.
* I think this is a good thought experiment for when we try to terraform Mars (since the plate tectonics and volcanism are gone) as well as for when Earth will go through a similar state (long after the Sun explodes, but whatever).
**Bonus question:** what would you recommend as a chemical insulant between the planet body and the highly reactive chemistry of the biosphere/ocean/atmosphere? Is silicon dioxide inert enough to leave it unprotected, or I would need to add protection so the planet doesn't get corroded? (I'm afraid of the occasional spontaneous production of nitrous acid, which AFAIK melts/eats glass).
If every issue is resolved then we will end-up with an ultra stable, predictable, and unchanging planet designed with habitability in mind. Which will be preferable to the ever-changing ever-dying planet that we are on right now.
Bottom line: I want to change the paradigm of the concept of a planet from a chemical actor in the surface processes, into just the structural body on which those processes take place (so I want to un-involve/isolate the planet from the water-air-biosphere chemistry happening above, but still make those processes work, although maybe altered)
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There are a few things you can do to ensure nutrient circulation on your planet. First, you can make sure that the continents are evenly distributed and not too large. This will prevent areas of the ocean from becoming stagnant. Second, you can add mountain ranges on the continents to help circulate nutrients. Third, you can add genetically engineered species that feed in the ocean but live, die, and breed on land. This will help to move nutrients from the ocean to the continents. Finally, you can design the continents with an edge on their perimeter so that they act as food plates and not spill the nutrients into the ocean too readily.
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You have a few misunderstandings.
1. Solar wind doesn't deposit elements, it blows them away. That's why the inner planets aren't gas giants. Our magnetic field actually keeps our lighter elements from getting blown away. Without it, we might look more like Venus.
2. You don't need moons for tidal force. If the planet rotates, then the star will create tidal force, slowly turning rotational momentum into heat through deforming the shape of the sphere as it rotates.
3. [Air is circulated due to uneven heating between the equator and the poles.](https://en.wikipedia.org/wiki/Hadley_cell) Hot air at the equator rises and flows towards the poles, then drops down at around 30 degrees latitude. Planetary rotation then makes a chaotic mess of this.
Cool water surfaces don't create updrafts, so the warm tropical air comes down from the Hadley cells over large bodies of water in the 30-60 degree latitude range, which is what makes the west coast of North America warmer than it should be around Washington and Oregon, and warms the Mediterranean and Black seas. If you wanted to evenly distribute heat across the planet, then you'd want to put a ring of maybe six bodies of water across the 50 degree mark.
Not sure how that would translate into water currents, but you'd probably wind up with something that looked like a [Faberge Egg](https://en.wikipedia.org/wiki/Rose_Trellis_(Faberg%C3%A9_egg)).
On the magnetic field thing, the calculations that I've seen suggest that solar power wouldn't be enough to maintain a magnetic field. The back-of-napkin calculation suggests that photovoltaics would need somewhere around 110% of the Earth's surface to power your ring, assuming that the entire surface were laid flat, facing the sun. If your race can create planets, then they might also create a Dyson Swarm to power it, use fusion powered, or just inserting an iron core in the planet and spin it.
The latter would also solve some of your density problems. Glass has slightly less than half of the density of the Earth, so you'd need a much larger sphere to generate 1G.
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Probably this is question is related with things like snakes recovering their limbs or an anatomically correct [naga](https://worldbuilding.stackexchange.com/questions/44703/anatomically-correct-naga/190324#190324) or lamia or [medusa](https://worldbuilding.stackexchange.com/questions/34221/anatomically-correct-medusa).
But now I am thinking other possible form of "snake limbs", the idea arose that snakes could obtain small limbs with those of an arthropod or specifically a centipede from their ribs.
But that was some ridiculous why a snake would need a lot of little legs that will not make the difference between its normal locomotion, so my conclusion was that this new limbs probably just could be useful at specific zones of the body, neither I am sure about the real uses but I have some disperse ideas, for that reason I made a fast drawing:
[](https://i.stack.imgur.com/uQbGB.png)
A cobra hood with arthropod-like limbs, looks some like the facehugger from alien, so I thought that probably could be used to grab on to some unsuspecting prey and feed in larger quantities for days by depleting the prey like a monitor. Other option, maybe being a giant arm (compared with the size), or less possible eventually developing multiple amrs like some representation of a naga.
But finding more possible uses based on some drawings and information about this:
[](https://i.stack.imgur.com/TZVSX.png)
[](https://i.stack.imgur.com/kAdfU.png)
But the showed examples shows the cobra's hood anatomy like a pair of ribs for any vertebrae, with multiple joints and with necesary muscles to make the hood move to behind the head and what I found is not currently possible.
Then my principal point is, is it really possible that new joints come from the ribs developing segmented ribs (related with how animals get new joints)?
Could really work this type of limbs?
Finally I would ask about if this can become to more humanoid arms, at least able to manipulate objects, but I thought this is excesive, they do not have the required structures, shoulder blade, collar bone and breastbone
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**They don't need extra joints to have effective limbs**
having multiple pairs of legs which are each individually mobile would allow the snake to manipulate objects finely withought going through the effort of gaining extra joints and muscle anchors. Even with limited movement the snake could easily catch prey with thickened and strengthended rib bones. It could probably also gain the ability to rotate and finely manipulate objects using the small amount of sideways movement they have in each rib joint.
Instead of thinking of the ribs as arms it is probably better to think of them as fingers. Most tasks can be done (with some difficulty) without using the central joints of your fingers. The full range of human actions and tool use could probably be done using modified snake rib limbs.
Functionally the limbs will be very similar to any other limbs, although they would look very different.
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So I found a question on this site that talked about the possibility of having a habitable planet in a stable trojan position (a planet located at Lagrangian point L4 or L5 of a much bigger object). And I thought it was cool, and decided to make it the homeworld of a spacefaring civilisation of my worldbuilding project.
So I decided to create a planetary system consisting of a central sun-sized star (1.1 solar masses), an orbiting brown dwarf (20 Jupiter masses, distance to the star: 1.45au, quasi-circular orbit), and a small rocky planet of half the Earth's mass at L5 point of the brown dwarf. That's not all but the rest of the system isn't relevant.
Then I started thinking about the planet's details and a few questions came to my mind. One of which I cannot answer at all is the following :
How would asteroids and comets be affected ? The brown dwarf would attract them all even more than Jupiter. Would a significant amount of them (or their debris) be redirected towards the planet, thus increasing the overall amount of asteroids hitting the planet? Or would the dwarf attract all the asteroids coming to the planet, completely protecting it ? Overall, would more or less asteroids collide with the planet ?
My knowledge is limoted on how exactly Jupiter affects asteroids, other that it attracts them and thus protects the rocky planets. In this situation the Jupiter-like object is much more massive, and my planet is much closer to it, and more or less comets and asteroids could affect the habitability and amount of natural resources of my planet, especially by adding water. On the other side, if asteroids regularly hit the planet, it might make it a harsh environment, that would definitely affect the native's culture. Hence my question.
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Well, the full answer to your question is not really possible as mankind doesn't fully understand Jupiters influence on comets and asteroids until now. The newest study regarding the 'shielding by Jupiter'-theory I could find is [this](https://academic.oup.com/astrogeo/article/49/1/1.22/306978) one and I will try to answer your question mainly on its conclusions.
One of the most important core-facts the study accomplished by simulating the movement of more than 100k objects in a period of 10 million years under the influence of different Jupiter-masses was the following:
>
> As the mass of Jupiter is increased, the impact rate from objects moving inwards from the Edgeworth-Kuiper belt first rises to a peak, then falls away again. The end result is that a Jupiter like our own (one Jupiter mass) provides an almost equivalent amount of shielding to no Jupiter at all! More importantly, were our Jupiter smaller, then the impact rate from this Centaur-derived population of objects would have been higher than in either extreme case. In the worst case, with a Jupiter around 0.2 times the mass of our planet, the impact rate would have been significantly higher than at either extreme!
>
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The study used the actual mass of Jupiter as a max for their simulation but the statistics suggest that a significantly higher mass for Jupiter (as your brown dwarf has) really could have a shielding effect for objects in the same or a lower orbit. I conclude that on their following statement:
>
> When there is no Jupiter, then very few objects acquire Earth-crossing orbits (Saturn is much less effective than Jupiter), and so the impact rate is particularly low. As the mass of Jupiter increases, the efficiency with which it places objects onto Earth-crossing orbits also increases, and so the impact rate rises. Eventually, though, as the mass increases still further, Jupiter becomes ever more efficient at ejecting the particles from the solar system entirely, and removes them from Earth-crossing orbits on ever shorter timescales. Thus, even though more objects are flung inwards, they are removed so rapidly as to pose significantly less of a threat. The shorter their residence in the inner solar system, the fewer opportunities they have to hit the Earth, and the lower the risk they pose.
>
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The biggest difference between your system and the study is, that your planet is in the same orbit as your brown dwarf and the study is for planets in a lower orbit than Jupiter, but by the concept of the simulations they made I think it could get similar results for your planet. At least I am sure the planet at your Langrange-Point L5 should not get a higher impact-rate than a planet on a lower orbit around the sun of your star.
Long story short: I think a longtime-habitable planet at L5 within your constellation is plausible.
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**Closed**. This question needs [details or clarity](/help/closed-questions). It is not currently accepting answers.
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The world is infinite in extent (both in area and age), with no large-scale curvature (normal mountains and such exist). The sun is infinitely far away, but has infinite size. The net effect is to appear with an angular size and brightness equivalent to Earth's sun. Its daily path across the sky is roughly what would be seen from Australia: rises in the East, Northward at noon, sets in the West, solar elevation angle changes throughout the year just as on Earth. So on average each unit area of the world's surface receives the same amount of energy as does the Earth's surface around 25 degrees latitude. The seasons (caused by the yearly cycle of solar angle) are simultaneous over the whole world (ie every location has summer at the same time). I have considered having seasons vary by position but haven't come up with an interesting scheme so far.
Under the surface is rock to a great depth. There might be an "undersurface" if you go down far enough, but it's probably tens of thousands of kilometers down if it exists. There are no plate tectonics, but there are creatures of truly enormous size whose burrowings (very) occasionally create mountains.
Ocean salinity is the same as Earth's in amount and general distribution. In the absence of plate tectonics, this is maintained by some process that I haven't yet determined.
At night, the sky is black with many stars, and from most places on the surface there are one or perhaps a few moons visible. The moons are mountain-sized floating rocks that shine independently of the sun. There are no gravitationally significant objects in this universe other than the world itself.
With no Coriolis force and a simultaneous day/night cycle and solar elevation angle across the entire surface, there would be no circulation cells (Hadley, Ferrel, Polar) like Earth has, thus no prevailing westerlies or easterly trade winds.
The question is this: are there any effects that would cause larger weather patterns than the mesoscale?
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Geography.
If you have large oceans and large mountain ranges, they will have much larger effects, through their effects on rainfall. The places near the sources of evaporation will get more rain, and the mountains will get far more rain on the side facing the body of water than the other, which will be part of the rainshadow.
Also, the farther inland you go, the more temperature will vary, both up and down. Water has so high a specific heat that it moderates the temperature need it.
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Being new, this is my first question. I've read some other posts that gave me valuable insight, but I still have some questions.
First, some specifics:
* Star: red dwarf. 80 x jupiter mass. 3 billion years old, after the violent flare phase.
* Gas giant: 7 x jupiter mass (edited from 12, so its not a brown dwarf). Almost white, 0.75 - 0.85 albedo, the more the better. Let me know if this is not possible.
* They orbit around each other. **I want an orbital period of 1 year** for the planet. That would need a distance between them of around 0.45 AU (according to US2).
* 2 earth-sized moons tidally locked to the gas giant with orbital resonance of 2:1. They have water and earth-like atmospheres (maybe a bit more CO2 for greenhouse effect). However, they will probably be frozen.
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So... does the gas giant have a good way to heat up its moons' surfaces to human-friendly temperatures (0 - 30 celsius average)? Like... how close the moons have to be for tidal heating to be a factor without destroying them? Also, the gas giant has high albedo, can it heat up its moons by redirecting star light (planet so big and white that creates a secondary day in the parts of the moons facing it...)? Are there other ways for the gas giant to heat up its moons?
Extra: if all the ways the gas giant have to heat up its moons combined are not enough and the moons just stay frozen... How much more massive does the red-dwarf have to be for the moons to achieve the desired temps? (mantaining all the rest the same, specially the **1-year orbital period**)
If relevant: I want a system that can harbor human life for a much longer time than our system can. That's why I chose a red dwarf after its flare phase and earth-sized moons (to avoid tidal locking to the star), but I want the orbital period to be 1-year... and with a red dwarf that means really cold moons, so the gas giant providing heat is a solution I thought could work. However, I have no idea what the numbers are or if the gas giant actually has a way to heat up its moons. Maybe I need a heavier star, but if it's not as massive as the sun that's still a win for me.
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depends on the technology your inhabitants have available; the quick and relatively easy is mirrors to enhance the sun's energy in concentrated regions; or you might be able to tap the huge electro-magnetic forces of the gas giant somehow. Your gas giant is big enough to give off heat on its own without being a brown dwarf, but if your people have the technology it could be fired to be a false brown dwarf, which overcomes your problems of Roche's limit.
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This question has been asked in similar forms on this site already with some good answers like here:
[What Color Can the Sky Be?](https://worldbuilding.stackexchange.com/questions/13279/what-color-can-the-sky-be)
[How could the sky be orange in a breathable atmosphere?](https://worldbuilding.stackexchange.com/questions/65530/how-could-the-sky-be-orange-in-a-breathable-atmosphere?noredirect=1&lq=1)
[What would make a sky appear purple during the day?](https://worldbuilding.stackexchange.com/questions/17815/what-would-make-a-sky-appear-purple-during-the-day)
but I want to put a special emphasis on compatibility with life as we know it. So the question is: **What possibilities exist to color the sky of an earth-like planet differently from our blue sky under the condition that life as we know it is supported?**
This means:
* The atmosphere consists of about 20 % O2, some N2 (for our dear plants!) and has a pressure of about 1 bar at sea-level
* None of the atmospheric gases must be poisonous for (most) animals and plants
* Photosynthesis must be possible
* All constituents of the atmosphere must be chemically inert with respect to each other (e.g. large amounts of CH4 would combust with O2 at the earliest convenience and set the world on fire)
* The color is seen by a human, so no fancy photoreceptors.
I'm open to suggestions about more conditions I may have overseen.
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Now the possibilities of changing the color are to my knowledge:
* Rayleigh scattering: Since the gases of our atmosphere possess resonance frequencies in the UV region, violet light is scattered more than red light. A quantitative deficiency in violet light (at least percieved by us) leads to blue being the dominant color. Are there gases with different resonance frequencies that could alter the scattering behaviour?
* The sun: Emits a color spectrum according to it's temperature. By changing the temperature a different color *can* be obtained, but would this be possible in an extent that still satisfies the condition of permitting life? A strong red-shift would cause a UV-deficiency (photosynthesis) while a blue shift would increase the UV radiation to possibly hazardous levels for everyone.
* The sun again: Next to the continuous spectrum defined by Planck's formula elements have strictly defined elemental lines. Could an enrichment of a certain element like Ca lead to a strong Ca-line that changes the sun's apparent color?
* Particles in the atmosphere (like on Mars or even in Peking): In this case I am concerned about getting enough light to the surface to let plants live. Are there different colors possible or would it always be something red-ish?
Edit: I really don't know why this question has been flagged as duplicate. The linked question only covers one coloring mechanism and completely lacks the compatibility with life which is emphasis of my question as I clearly stated.
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**Just about anything, if the conditions were just right.**
First, about the color of the sky itself, in general:
The other questions you link to in your own question do a fairly comprehensive job describing factors that affect how we perceive the color of the sky. Insofar as what possibilities exist for an Earth-like atmosphere *specifically,* the basic principles of those answers still apply: the thickness of the atmosphere, the type of star, and so on. In other words, having an Earth-like atmosphere doesn't really change the main considerations, so in large part you can still refer to those other answers. In particular, [there are several answers here](https://worldbuilding.stackexchange.com/questions/65530/how-could-the-sky-be-orange-in-a-breathable-atmosphere) that should directly interest you.
Second, specifically regarding plant life:
Since the atmosphere is going to be hospitable (and assuming they get all the other nutrients and hydration they normally need), the main concern is the amount of light they will receive. Different plants require different amounts of sunlight, so some species may have difficulty flourishing if your planet experiences too much difference in light level.
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So, we've gone off to another star system and decided to build a Dyson bubble--a continuous statite, supported by radiation pressure, surrounding a star--with a surface gravity of 1g to live on.
Now, clearly, the bubble has a total surface area of hundreds of thousands of Earths--plenty of space! Except... we don't actually get to use all of that. Since the ground is held up by radiation pressure, we can't exceed a certain maximum areal density. Colonies have to be built in widely-separated dimples, with unobtainium cables spreading their weight over an enormous surrounding area. So, to figure out what kind of *living* area we'll actually have available, it's not sufficient to just know how much total surface area we have to work with--we need to know how many multiples of Earth's biosphere's *mass* we can support.
And to do that, we need to know how much the ecosphere--or *at least* the portions of it necessary to support human life, if that's less than all of it--actually weighs.
So, if we were to leave all of the mantle rock and metal behind and just strip off the life-supporting surface of the planet, how much would it weigh?
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The weight of the earth's biomass is estimated around 1.8 E15 kg by several sources summarized here <https://hypertextbook.com/facts/2001/AmandaMeyer.shtml>
Bedrock is not very biologically active. Therefore we will set an upper bound to the amount of crust needed by considering soils and sediments. A survey of depth to bedrock is given below
<https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016MS000686>
The world average depth to bedrock is about 13m. Assuming a soil density of 2 g/cm^3 (high estimate) we can estimate a world soil mass of 4E18 kg.
Water is also important to life. Most of the world's water is in the oceans, and most freshwater is frozen. The hydrosphere weighs 1.38E21 kg, but only 2.5% of this is fresh and 31% of that is liquid. This component weighs 1E19 kg. This is almost all groudwater.
<https://water.usgs.gov/edu/earthwherewater.html>
This gives a total "ecosphere mass" upper bounded at 1.4E19 kg for the Earth, or about 93 tonnes/m^2 in intensive units. If we remove groundwater (which mostly doesn't interact with the biosphere) then we have much less. This gives a mass of 4.1E18 kg or 27 tonnes/m^2
I would guess this is still quite high and we could make do with 2m of soil or less. In any case, actual biomass is inconsequential.
For fun, this is 4E13 W/m^2 of radiation pressure to balance. Taking the sun as a point source, we achieve this at 6E-6 AU = 900km which invalidates the assumption. The sun's core is about 100,000 km radius, and thermal pressure dominates here.
Mirror films naively seem like the best support option because they have 1. double the momentum transfer per unit energy and 2. twenty times less radiative absorption than a blackbody. On the outside face, they conduct heat to a blackbody which emits into space. However, reflectance drops rapidly at emitting temperatures, so we're limited to something like 1000K. This allows a flux of 1E6 W/m^2, so you need 10^7:1 support to loaded area. This assumes the film weighs nothing.
However, it turns out the flux is so sensitive to max temperature that a blackbody with higher temperature tolerance is better. If you use something like a high performance ceramic at 2300K, you can tolerate 1.5E6 W/m^2.This however makes cooling the biomass much more difficult.
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Before picking specs, I need to ensure feasibility. Only one of the planets need be Earth-like; in fact, I would prefer if the other planet were rather small and dead, like a moon. The orbits will be eccentric enough to produce tectonic strain. Obviously they'll be tidally locked.
What would the tidal bulge on the home world be like? Would the planet take the shape of an egg? Is it reasonable to suppose that an immense volcanic plateau would form in the shadow of the sister world? Might there be major geological uplift?
I'm trying to create this plateau landform within scientific parameters. The only other necessary condition I can think of is the length of day-- it must approximate the 24-hour cycle (though with some room for variability, as a relatively long day/night cycle may also be an interesting feature of this world).
I basically want a normal world that gets weirder and more alien as you near the spot directly below the sister world. I'm thinking that plateau and/or surrounding environs will resemble Iceland's landscape. I imagine leading up to that you'd find a Patagonia-like desert strewn with what seems like a geographically far-flung "staircase" of strike-slip faults, escarpments, and terraces.
Is this scenario plausible, and, if so, under what conditions?
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## Everything would more or less be the same as on earth in each planet, even the plateau.
Everything you'd want to know is in this video: "Double Planets and Rocheworlds" <https://youtu.be/lgkqbHJczWs> by Isaac Arthur. It even links to an orbital period calculator.
Per the video, the other planet would simply appear 'stationary' in space, while you still have your normal day/night cycles. I would imagine that you would have frequent eclipses. However, the video mentioned that the other planet would reflect sunlight and would be many times brighter than the moon! The animations in the video also illustrate how all parts of each planet would have regular day/night cycles.
Some exceptions:
* If you bring the two planets close enough you can have a "bulge" in both planets. These are called Rocheworlds.
* However, the closer you bring the planets together, the quicker the days must be.
* Also, the bulges are not stable in geological time scales (millions of years I would imagine). They would eventually be drawn to each other and the planets would eventually merge into one (rather destructively, as the narrator mentions).
* The bulges could probably lead to the oceans covering a good part of the planets with continents potentially arising on the opposite ends of the bulges.
The only other primary concern are tidal forces. But these can be minimized with mostly-circular orbits. If you need 24 hour periods then the planets must be far enough away to not have Roche bulges and would otherwise evolve like regular earth-like planets. However, the "dead" planet could have a mars-like or venus-like atmosphere that would explain its dead-like state. The 'weirdness' in the region might be more along the lines of wildlife that has adapted to the unique scenario of having frequent eclipses. Indigenous people would probably worship the dead planet as some kind of deity.
From the video description:
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> ### Orbital Period Calculator:
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> <http://www.calctool.org/CALC/phys/astronomy/planet_orbit>
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> Note: make
> sure to set units of both bodies to Earth Mass and period to hours or
> days if trying to look at double planet cases.
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[Assuming I read your question correctly, Planet A has a spot which always faces Planet B; B still rotates relative to A]
Planet A would certainly have a massive Mountain range or plateau on that spot, as well as having no tides.
The plateau would also be massively cooler since it's the spot that only gets light if the sun is in an angle and therefore always misses "noon"-sun.
I can't say whether there would be Iceland-style volcanoes and seysers, since on one hand it's so far above the rest of the world, while on the other ALL tectonic plates strife there.
[Also,if this constellation is older, the side facing away from B would have noticeably fewer land, if even any, due to all tectonic plates moving away]
B in contrast would be a nightmare to live on.
Volcanoes everywhere, 24/7 earthquakes, and tides in the range of kilometers high (speculative), as well as horrible storms because of that.
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Assuming the wars of the far, far future aren't either fought exclusively by unmanned spacecraft/robots/drones or in ways so incomprehensible to us that comparisons are meaningless, the only foolproof way to increase the power of an infrantryman's weapons are to make the switch to laser and energy weapons, which can produce a theoretically arbitrary (or at least very high) muzzle energy. But the problem with man-portable energy weapons, especially those in excess of a few megajoules or (dare we dream) gigajoules is how to power them. Presumably the people of the future will have perfected the means of creating antimatter cheaply and efficiently to the point where it can be miniaturized and even weaponized.
But is it safe?
How would the soldiers, commanders and generals of the far future prevent their antimatter batteries from turning into antimatter warheads, and how would they prevent their antimatter warheads from turning friendlies into casualties when their Penning traps are breached in an attack by the enemy? Is there a way to render such devices inert in the event of damage to their EM containment fields or does the very nature of antimatter make any device utilizing it for power one stray laser blast away from a bomb?
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I don't think there's a way to safely store antimatter in a world made of matter. Maybe you could produce it at the moment through Hawking Radiation from a very small vaporizing Black Hole?
Actually an interesting source of energy could be the last phase of a Black Hole evaporation. For very small BHs the evaporation time is tiny (Wiki cites 10^-40 s for a Planck mass BH, see also Micro\_black\_hole on Wiki) and the BH temperature constantly increases producing a final burst of Gamma rays. The problem could be the creation of a micro BHs without a huge accelerator like LHC but the use of some exotic particle could be a way (someone said "Dark Matter accumulator"? ;)
While the technical problems to use this power source for civil use are huge their application in a military context could be reasonable.
[Answer]
Ok, so I'm no physicist and can't give you a lengthy explanation here.
Why not put your Penning trap into the muzzle of your weapon? Creating your energy bolt immediately before firing seems to be to be safer than having it buzz around in a backpack waiting to be punctured by a stray (or not so stray)round.
Your fuel would then be a lot less angry and need less energy to contain it prior to firing.
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I have a different proposal, if anti-matter is not essential to your story, use matter annihilator. A device that would convert matter into energy without the use of anti-matter. This is a safe way of producing energy and will net the same amount of energy per gram as anti-matter storage. Obviously one of the biggest advantage is that you can use *any* matter. And the conversion rate is out of this world, 1 gram of matter will net you 90 TJ of power (Hiroshima bomb was 63 TJ).
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The point is, if you are using a weapon that can shoot five laser beams per clip, with each laser beam carrying around 1 gigajoule of energy...
Then your clips have, *at least* and assuming 100% efficiency, five gigajoules of energy.
That's a ridiculous amount of energy to carry. Doesn't matter if you are using anti-matter or not, high-powered batteries *are* dangerous. Modern batteries have several self-regulating mechanisms that *work really hard* to keep the energy inside it stable. The energy on a battery wants to go out, and wants do so explosively, most of the time! With such an amount of energy, it becomes almost impossible to make a stable, safe battery that is to be carried around by a soldier on the battlefield.
Laser Weapons are fancy and really interesting from a sci-fi point of view, but really, they are really, really hard to explain in a hard-science way.
My suggestion to you is that, if you want to keep you laser weapons, don't try to explain the power source. Handwaving the source of the pew-pews worked for Isaac Asimov and Arthur C. Clarke, it may work for you too!
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I'm trying to work out some really basic biochemical details for cold-world aliens whose bodily fluids are based on liquid methane rather than water. I figure they have to be hydrogen breathers, because you won't get free oxygen on a world with methane oceans! But that means that their metabolism would produce water and ammonia as waste products- and both of those are very solid at liquid methane temperatures.
Additionally, although the solubility of water in liquid methane is apparently unexpectedly high according to [Nature](http://www.nature.com/nature/journal/v305/n5933/abs/305412a0.html), it's still extremely low on an absolute scale. It seems this would be a bit of a problem for anything larger than a microbe that needs to expel metabolic wastes- or for "plants" that need to consume water and ammonia to get oxygen and nitrogen supplies for synthesis.
So, how might a methane-based alien go about transporting waste water and ammonia in its blood? I imagine special transport molecules would be required, but is there something relatively small and simple that could act like a reverse-soap to dissolve these polar solids in methane, or would it necessary require something large and highly specialized, like the hemoglobin we use to transport oxygen?
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Ok basically you want a bio version of a chemical membrane that's resistant to methane. So, let's start with the materials what we know on this planet used to resist or keep methane contained.
Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. Aluminum is also used as part of the membranes used to keep methane products out of the soil. Basically, plastic and aluminum. [Here's link to a waste disposal site which uses this in methane situations](http://www.cordek.com/products/mb420-gas-membrane).
We make plastic industrially, but who is to say that an alien body couldn't make it, in conjunction with aluminum to hold water and other waste products. Or it could just be aluminum, an important part of the aliens' diet. I would say it would have to specialized and "large" like hemoglobin, and that it would dump the waste in a "holding tank" made out of much the same materials, that would then be expelled out of a specialized tube, like the anus.
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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Closed 7 years ago.
* 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).
* This question does not appear to be about **worldbuilding**, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help).
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Don't ask me why, but my story's come to a race of zombies coming to blows with a race of skeletons.
**The Zombies**
The zombies are able to infect *live* non-zombies. They wander about aimlessly, moving no more than about a mile per hour (roughly a third of normal human walking speed). When they see any non-zombie, they run (that is, two miles per hour) directly toward their target, not taking into account obstacles on the ground. (Note that all of their prey will turn into humanoid zombies, regardless of its original species.) That said, they have claws to climb over that sort of thing. They do have the ability to swim, but it's the same proportions as above: one-third the speed of humans when "inactive" and two-thirds when "active." They have normal blood circulation and are warm-blooded.
Zombies are unable to reproduce; they're comparable to viruses in that they infect hosts with their genetics to create more of their species. They can die, but only if their head is detached from the rest of their body.
They can use weapons (read: anything they can pick up and whack something with), but they only attack in this method if they can't bite their target without rendering them unconscious. Oh, and by the way, the zombies have a mind hive: they can all communicate with each other mentally. They're not your garden-variety braindead zombie; to the contrary, they have excellent brain capacity.
Now here's the catch. Zombies are able to turn themselves into humans for about thirty seconds, after which they turn back into zombies. There's a half-hour cooldown on this ability. When posing as humans, they have normal human capabilities, though most notably the fact that they can move significantly faster than they could otherwise.
**The Skeletons**
The skeletons, on the other hand, can move at normal speed all the time. Unlike the zombies, who take no defensive measures while scouring for *live* prey, the skeletons are able to hide. They can see infrared waves as well as normal light waves. They have their own "chatter" language to communicate, and they are able to strategize to capture their prey. Because they can communicate and strategize so effectively, they can give each other boosts over walls.
They are able to deconstruct the bones in their body and use them as weapons or tools, but they can only control the bones directly or indirectly attached to their skull. They cannot die, but cutting off every bone from the upper skull essentially takes away any method of attack. They cannot reattach lost limbs.
Skeletons are able to reproduce, but they are also able to infect non-skeletons. (Unlike the zombies, though, the prey will retain its original species. Thus, many skeletons are able to fly, and many are forced to swim.)
**The Big Question**
Assume that these species live on a planet exactly like ours today, and they fight in the middle of a big city where there's lots of prey (say, NYC). Their primary goal is to defeat the enemy, and if they have the option between attacking the enemy and attacking a nearby human/pigeon, they'll attack the enemy.
Which species has the upper hand? What are each species' dominant strategies? (I'm an aspiring mathematician; bonus points for identifying Nash Equilibria under these circumstances.)
**Why this is on-topic**
For those who voted to put this on hold, this bit is my response. [From the help center](http://meta.worldbuilding.stackexchange.com/questions/3300/why-is-my-question-too-story-based-and-how-do-i-get-it-opened):
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> Capabilities of characters...are on-topic, but questions must focus on what is *possible* or *likely to develop*, not what someone *would or should do*.
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That is exactly my question. Given the capabilities of my characters, what is "likely to develop"?
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All those zombies and skeletons in NYC, but no one sees them ? ;)
Lets consider these two scenarios:
1. *They all fight it out in a big open field*
The zombies already have the advantage because they are stronger (durability wise, don't know about the zombies and skeletons strengths) than the skeletons. Bones are brittle, and will break from one strong smash. Even if skeletons all armed themselves with weapons beforehand, it will be hard to cut off a zombie-head with those weapons. Not to mention using *bones* as weapons, as they are blunt weapons - and not particularly strong ones either. The zombies (if smart enough) can even wear some armour while it will be hard for skeletons (they won't fit properly). **Hence, the zombies will definitely win here.** No Nash Equilibrium over here, just plain old charge-and-kill.
2. *They have time to prepare*
The zombies may have a hive mind, but the skeletons have their own language. So, I think the skeletons are smarter. A particularly smart one will start to convert everything it can into skeletons - birds, small animals, humans, etc. The zombies don't realise because they are staying away from the skeletons and are dumb anyways. Then, after a while the skeletons can release their army of skeleton rats and birds to attack the zombies :) . Imagine if a bunch of skeleton-hawks are carrying something heavy and drop it on those zombies. Even if all the original skeletons are killed, the zombies won't be able to hit those flying skeletons, who will stay away and continue to drop things on the zombies. **The skeletons probably won't win outright, but they can continue to chip away at the zombies until they are weakened enough to fight openly (ALL zombies vs. ALL skeletons). If the skeletons prepare, by stocking up on weapons and armours, then they definitely win. Otherwise, they just have a (big) advantage (depending on how much they reduce the zombies)** Nash Eq, the zombies probably won't figure out the skeletons plans.
The skeletons can use all sorts of scenarios - they can use some expendable skeletons (small animals) to lure the zombies into one place, then the humanoid skeletons can drop heavy stuff on them. (Assuming they get up into a building and kill/convert all those people and drop all heavy stuff from the balconies onto those zombies below).
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Let's look at the strengths of both armies, (I assume that both armies are the same sizes)
## Zombies
1. Have a hive mind
2. Will never have to worry about miscommunication
3. Among the troops the whole army will react as one to every attack.
## Skeletons
1. Cannot die
2. Can hide
3. Can run.
4. Can repair themselves
So my money is on the skeletons. In a straight fight they will last longer, they are also unable to die, but the zombies can die to blow to the head. And because the skeletons can hide they can also set up an ambush. And if all else fails, at least they can run away unlike the zombies in order to regroup and arm themselves with more weapons.
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Those who have read my recent questions posted here will have noticed that my questions are often related to hardcore biochemistry, atmospheric processes etc. While I have had some good answers to parts of these I would like to solicit suggestions as to what other Q+A sites and/or forums might be better equipped to handle the highly technical and scientific aspects of my xenobiology queries.
My generally weak areas of knowledge tend to be in biology/biochemstry, geology and astronomy. I find that the answers on this site relating to astronomy/planetology/geology are pretty high quality and sufficient for my worldbuilding needs but I think I need somewhere more specialist for the xenobiology questions.
Can anyone recommend where to take questions about the metabolic capabilities of dimethylsulfonium proprionate, for example? It would need to be a site that is comfortable with fielding questions about hypothetical xenobiology from non-practitioners (e.g. non academics). I realise there are other stack exchanges that might fit the bill but want to take input from those that have used them or other resources.
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Best resource I know of (contains lots of useful related other stuff too) is actually a book called **[Xenology](http://www.xenology.info/Xeno.htm)**, by Robert A. Freitas Jr. It has been posted online in full by the author. A little bit is dated, but a very thorough walkthrough regardless.
Look to
Chapter 6. A Definition of Life,
Chapter 7. The Origin of Life,
Chapter 8. Exotic Biochemistries,
Chapter 10. Alien Bioenergetics.
Hope it helps!
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Another resource is [Speculative Evolution](http://speculativeevolution.wikia.com/wiki/Main_Page). It's a website where a bunch of people collected resources for Xenology over the past few years.
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So I want to send a ship to Alpha Centauri very quickly - by this, I mean less than 5 years. This means that the ship will have to accelerate at 50-100 $g$ or even more. But we don't want to turn our astronauts into pancakes, right?
Is spending long time periods in perfluorocarbons saturated with oxygen (or similar stuff) actually healthy or does it pose risks? What are the side effects? Does it neutralize the $g$-forces? How does it feel swimming or sitting in tanks filled with perfluorocarbons while your ship is accelerating at 1000 meters per square second?
Can this only be used on spaceships or can you use that in habitats on high-gravity planets too?
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**You probably can survive heavy acceleration while breathing liquids** though keeping tabs on infection and ventilator function over longer periods will be definite concerns.
**Breathing Fluorocarbons**
The [Biology SE answer](https://biology.stackexchange.com/questions/23074/what-are-the-effects-of-long-term-liquid-breathing) indicates that it's possible for animals (very little human testing has been done) to survive for extended periods while immersed in and breathing fluorocarbons. Animal diaphragms aren't strong enough to move fluids so a ventilator must be used. Due to the dearth of research on the long-term effects of adult humans breathing fluorocarbons for weeks, months or years, everything is speculation though, given the inert nature of fluorocarbons, it would probably be okay.
**Suspension in Fluorocarbons**
* Density of water is 1 gl/ml.
* Density of FC-75 is [1.75 to 1.79g/mL.](https://www.fishersci.com/shop/products/perfluoro-compound-fc-75-acros-organics-3/p-179920)
* Density of human body is between [1.04 and 1.08 g/ml](http://ajcn.nutrition.org/content/20/4/305.full.pdf) (page 307).
So without a weight belt/suit, a human will tend to "float" towards the top of the tank. Under 1$g$ acceleration, a simple weight belt is sufficient to maintain buoyancy because the strain induced by differences in buoyancy between the human body and water is negligible. *However, under 50 to 100$g$ the strain will be considerably more and will need to be accounted for.* A full body weighted & pressure suit will be best because the less dense portions of the human body will want to float up and must be restrained.
There is also [this article](http://onlinelibrary.wiley.com/doi/10.1002/cphy.cp040240/abstract) (paywall) about adaptation to acceleration environments.
*Yes you probably could suspend a crew in a fluid for the crushing accelerations required by the OP but it doesn't take a ton of handwaving to do so.* The only people you're going to really annoy are the buoyancy scientists.
**Older Answer:**
From the Biology SE answer:
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> Kylstra, the first pioneer introducing the idea of land animals breathing liquids (Kylstra et al., 1962, found mice could withstand 4 hours of 160 atmospheres of pressure.
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So how much acceleration is equivalent to 160 atmospheres?
```
100kpa is one atmosphere.
100kpa * 160 = 16000kpa
P=F/A
F=P*A
F=16000000 Pa (N/m^2) * 1.7 m^2
F = 27.2 MN
```
While 27.2 meganewtons seems like a lot, remember that this is across the entire surface of the body and from all directions so the pressures equalize. Free gases in the gut will diffuse in the surrounding tissues so decompressing/decelerating will need to be done slowly to avoid a lethal case of the bends.
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Does it neutralize the g-forces?
Being immerged in and breathing a liquid with a density close to that of the human body can aliviat damage from g-forces because in such an environment the forces are applied evenly. However Perfluorocarbon fluids are a bad choice, as they are far too dense - The density differentials in this case is as big as they are when you are immerged in and breathing air, you just change the sign.
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I want to create a world set on our Earth but with humans shrunk down as much as possible to allow a huge population.
As the population increases they genetically modify their bodies to be as small as possible while retaining human intelligence. They do **not** [replace their bodies and minds with machines](https://worldbuilding.stackexchange.com/questions/1290/maximum-earth-population-by-wiping-out-biological-life). As a result each shrunk human requires considerably less food and water, allowing the population to increase beyond what Earth could otherwise sustain.
The shrinking is limited by the need to remain mobile. I don't want the humans shrunk down to a brain in a jar. They still have arms and legs and can move around (albeit more slowly).
If they make use of the entire surface of the Earth, collecting as much solar power as possible without overheating the Earth beyond what they can survive, and maximise efficiency by not eating meat, what is the maximum population that could be sustained long term? Assume that they drive other creatures to extinction and only sustain life that they use for food.
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Looking at ant hills, the biggest ant colony ever found housed about 300 million ants on a 2.7 km² big area. for comparison, that's basically everyone living in the USA packed together in 2/3 of central park.
If we assume that an ant colony of that size needs 10 square miles to sustain, that means we can fit 15 million ant hills on the land surface, assuming the earth was flat. However, if we only take arable land, that's 1.4 million ant hills, or about 428,400,000,000,000 humans.
However, there are some problems with this.
first: lifespan scales linearly with size, while energy requirements scale less than linear. This means that humans will live far less long, but require far more energy in comparison.
second: no other living creatures means that the entire ecosystem is ruined. I assume that everything larger than us is completely destroyed.
Third: at such small sizes, technology would be far more difficult to work with, because basic molecular physics fail at that level.
Fourth, and very crucial: It's really, really hard for something as complicated as the human brain to be made smaller without affecting mental acuity. One of the reasons we're smarter than our close cousins chimpanzees is that our brain is so much bigger. I can only see 2 outcomes: either we don't shrink the brain as much, which results in implications for our spinal column, or we change the location of our brain in a way that can sustain growth. Either way, at an actually quite early point, we cannot shrink anymore without serious medical issues.
So the question is not just "what is the maximum population possible?" but "how small can you make a human before we encounter basic biological, medical, mechanical and ecological problems that would cause the population to decrease again?" I think we first need to figure out what size you are aiming for. Also, if it's a world with futuristic tech, you can basically make them as small as you want and handwave the downsides through the technology.
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Right, maths for this question too! We'll be using the US as a basis for the maths.
The US has 9,629,091km2 of land, of which 16% is farmland and if farmed correctly we will assume could support them all (on a vegetarian diet). It's population is 316,000,000, meaning if you remove farmland, comfortably you could fit 39 people per 1km of land.
The Earth has a land mass (minus water) of 149,000,000km2. Taking off our 16% for farmland, this gives us 125,160,000km2 of land.
Now, if we say humans were shrunk to 1/10th their size, so we could fit comfortably 390 people per 1km, you'd be looking at 48,812,400,000 people. But you notice how I keep saying comfortably? Earths current population is 7.125 billion, that's 56 people per 1km. With our shrinking, that'd be 70,089,600,000 people. But maybe 1/10th size isn't enough? How about 1/100th size? We would have room for 700 billion people.
But as stated in Nate's answer, this is assuming they eat the same portion of food (scaled down), if they have to eat more due to a metabolism trying to compensate, you would need a higher percentage of farmland, which would cut that figure down dramatically.
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The main point is that we want to keep the same level of intelligence. Shrking beyond a certain point would affect our intelligence.
Looking at the real world, shriking our size by a factor or 2 or 3 and keeping our brainsize seems achivable. We would basically all be dwarves.
Through some genetic manipulation let's say that we manage to make our brain more compact while retaining the same efficiency. Realistically I don't think we could shrink it more than the size of a child's brain withouth affecting it's functionality.
So I think that we could biologically shrink ourselves to have the size of a 6 year old child while keeping our intelligence but we ll never be able to shrink ourselves to the size of smaller mamals like cats or hamsters.
I disgress a bit but I really think that we can feed way more than our current population using more advanced farming IF we find a way to produce cheap renewable energy.
The solution would be soilless vertical farms. If you have energy you can mosly do anything.
-make freshwater out of saltwater
-create artificial lights to simulate sunlight
-extract minerals from seawater
You could build 100 stories skyscrapper on a 1 square KM plot of land and feed an entire city with it.
It s not scifi and is already exprimented in Singapore and Dubai. The pb is that electricity is still too expensive and it s not profitable.
However in 100 years if we crack fusion power solar power that becomes feasible.
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[](https://i.stack.imgur.com/Zsx3H.jpg)[](https://i.stack.imgur.com/2a4cn.jpg)
This world’s average surface temperature is 42°c. Has a day length of 12 hours and 5 minutes. Has an obliquity of 87°. And, has a mainly oxygen/nitrogen atmosphere that is 4.76 the pressure of Earth’s atmosphere at sea level. Also, this world has a diameter of 0.704x that of Earth’s and a gravity 0.672x that of Earth’s.
The brown patchy areas on the map represent highland/mountainous areas. Nothing too extreme but enough to have climate differences and cause rain shadows.
Based on this information, could someone tell me how many circulation cells per hemisphere this world would likely have or even help make a köppen climate map for it?
My current assumption is that the equator would have tropical Af, Am and As/Aw climates along with Cfa in higher elevations. The mid latitudes would have Csa (with the summers being particularly severe) and possibly Cfa climates. Closer to the poles it would be inhospitable desert (BSh and BWh) surrounded by tropical savannah As. The coasts of the equator next to the large northern ocean would be battered by severe hurricanes (perhaps it could be even called the ‘Sea of Hurricanes’).
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In my setting, the characters live at the bottom of a gas giant's metallic hydrogen ocean, just above the rocky core. There the dense metallic hydrogen acts as the ‘air’ and the core as the ‘ground’ for them, because they have alien ‘biochemistries’ that allow them to live in such condition. Metallic hydrogen is opaque to light, but the characters have some exotic sense that allow them to ‘see’ through it as if it's clear air or water.
The problem is, what kind of sceneries and natural phenomena will they ‘see’? As far as I know, the ‘air’ is magnetically convective, so there will be magnetic ‘winds’. The ‘air’ may also [change phases from superconductor to superfluid vice versa](https://en.wikipedia.org/wiki/Metallic_hydrogen#Possibility_of_novel_types_of_quantum_fluid) depending on the magnetic field strength, although I'm not sure if it will produce quantum vortices or not. But how will superconductivity affect things between ‘air’ and ‘ground’, such as the ‘weather’?
Also, apparently [there will be no diamond there](https://www.nature.com/articles/nature.2013.13925), as the carbon gets dissolved in the ‘air’. But I wonder if there could still be ‘rain’ of carbon or other materials near the core's surface (helium-neon rain should be out of question, since it forms thousands kilometers away from the ‘ground’, but is it possible that the rain falls on its surface, since helium and neon are immiscible in hydrogen)?
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This question does not appear to be about **worldbuilding**, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help).
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I'm new to worldbuilding, so it would be good to find more experienced people who can help me build my first world. I know this isn't a discussion forum, so where would I go to find the support that I'm seeking?
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I have the two largest towns of this smallish Kingdom's populations, but the first place the protags of my story are going to encounter is going to be village or hamlet sized. Most of the resources I am coming across seem to focus on the big cities, which is nice, but not needed for another few chapters. (Also, MDME seems to give very high population numbers ...)
Stuff I have already come across:
[Medieval Demographics Made Easy](https://gamingballistic.com/wp-content/uploads/2018/11/Medieval-Demographics-Made-Easy-1.pdf) (and [the donjon calculator](https://donjon.bin.sh/fantasy/demographics/));
[Worldbuilding Mega Tutorial](https://www.reddit.com/r/worldbuilding/comments/4byhle/megatutorial_on_worldbuilding_medieval_towns/);
[Notes on Medieval Population Geography](https://medium.com/migration-issues/notes-on-medieval-population-geography-fd062449364f)
Some particular notes about this particular country is that it is the home to Fairies and their longer lifespan (and also been around for about 2000 years, maybe, max), but I am probably going to need this answered again once the protags come across a human (Been around longer but shorter lifespans compared to the Fairies.) based kingdom and some of it's villages.
[My World Anvil Entry for the Fairy Kingdom](https://www.worldanvil.com/w/estoria-fangirlshadow/a/fair-folk-kingdom-settlement?preview=true)
Update: The Village in question is situated in between two rivers with a mountain range to the north. This village is the northernmost village on this side of the kingdom, but it's not against the mountain range itself. The region is somewhere in the temperate zone. Fairly Straight north of the capitol of the tiny kingdom. One of the youngest villages, Tiny lake to the south where the two rivers meet. Closest village is southeast. Capitol is also a port. The entire kingdom is set in a forest. The equivalent of an Earth element Deity resides in the capitol.
The village's story purpose is more of a first encounter for the protagonists who have lived in said mountains their entire lives.
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Thanks for the extra info, FangirlShadow, and I apologize that you're not receiving better support.
A town is a [larger and more complex place, which includes structural achievements like castles and walls](https://www.medievalchronicles.com/medieval-life/medieval-towns/), but you're asking after a young village, which will be small.
Any community in a fantasy medieval setting has or may have...
1. Government (including law enforcement and taxation)
2. Trade/Crafts (skilled people such as blacksmiths, farriers, etc.)
3. Trade/Merchants (supporting city activities)
4. Trade/Commerce (supporting import/export)
5. Artistry
6. Entertainment
7. Education (possibly, fantasy stories often follow the apprenticeship model)
8. Religion
9. Banking/Financing (possibly, it depends if there's monetary currency or if you're using barter)
So, working with this and what you've told us...
* You said your capitol had something akin to an Earth Element Diety residing within it. Let's assume there's a process of worship, which always means a basic bureaucracy. A village could be expected to have a priest or adherent of that worship. Though he/she might double with another task (e.g., they might also be a fisherman), such people were often local counselors and leaders. So, population +1. We'll say no family, either an older person or celibacy.
* Two close rivers mean fishing as a staple industry. This means we can use supporting specialized trades like net manufacturing and repair. Fishing as an export was easier than other proteins because they were easily [smoked for preservation](http://aquafind.com/articles/Smoking_Fish.php). (You can jerk red meat, too, it's just easier with fish.) So if you want an export, you can export fish, and that means supporting workers for preservation, packing, transport, and security (hungry people and hungry animals). This sounds bigger than it really is. How many is based on other rolls, but with a small village, let's say 10 fishermen + families, another 15+families for all the supporting trades and commerce. An [estimate of the average family size in medieval England](https://www.shaddock.ca/english-heritage/study-of-the-family-in-the-middle-ages) is 3.5 people. So, population = +87.
* There are basic needs in any village: entertainment (often just a pub, but it can be more), blacksmiths, thatchers and carpenters. (Larger towns need masons and a host of other things.) And, of course, their families. Let's say two each for population +28.
* You have a diety living in the capitol, which would suggest a reasonably well formed bureaucracy, meaning taxes and law. Your village will need a leader and sheriff for law and order. Our village is getting a bit large and there's those wild animals to consider, so the sheriff has two deputies. Population +14. (BTW, it's true that not everyone has a family, but the average statistic does well for giving us a starting point.
* I mentioned before hunters and farmers. Agriculture was well established at any point during Medieval Europe's years. As the northernmost village you'll likely favor hunting over farming (more settled areas tend to have an element of being over-hunted). We don't need a lot of farmers because [a square kilometer can support approximately 2,000 people](https://worldbuilding.stackexchange.com/a/9601/40609). However, I'm a bit wary of that answer because it assumes a top caloric output and medieval farming was rarely that efficient and it does depend on your climate (length of growing season) and the quality of your soil. Let's assume your village can achieve half that. So far we have 130 people in your village, suggesting we need .13 square km (130,000 square meters), *but that was just the people.* You also have horses, goats, cows, dogs, cats, sheep, pigs, chickens, and who knows what domesticated critters needed for everything from food sources (e.g. milk and bacon) to lowering your blood pressure (pets). There's also the need for a little future planning, so you want some excess that's stored against the proverbial not-rainy day (drought). Animals often outnumber humans by many:1, but it's a village. Let's assume 3:1. So our "population" for the purposes of calculating supporting farmland is closer to 400 for about two-fifths of a square kilometer or about 49 acres. About a person per acre or 49 farmers/work-hands and another 10 for supporting activities + families. Population +206, but now you need more farmland. let's avoid the calculus. Population +300 to support the community's people and animals.
Total basic population: 430 people.
From this point you can adjust the size of your village to suit the needs of your story. The largest population variable is your group of farmers, just remember that as you adjust that count, your other counts need to adjust with it. Cut your farming in half and the rest of the town must cut in half, too, or there won't be enough food to feed everyone.
***Note***
There were medieval villages as small as a couple of dozen people all the way up to formal cities with tens of thousands (the [population of London in 1200 is estimated to be 20,000-25,000](http://www.demographia.com/dm-lon31.htm)). Remember that Europe was feudal, so there really weren't many (if any) independent villages, towns, or cities. There would have been a manor with a knight or other peer to whom everyone was basically answerable. But when you got away from the central manor and into the land controlled by the manor, those villages were on average [250-300 people in size](https://ludusludorum.com/2014/10/28/get-medieval-the-village-in-the-middle-ages/), so my estimate isn't far off (bit on the high side).
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I'm going to break with worldbuilding tradition here and say it doesn't matter. Find the purpose of the city/village/location and populate it accordingly. Ta daa! Done.
Except you're not done, you need to make sure that every thread you pull on connects to something. So if it's a hamlet there's PROBABLY not going to be a bank there. If the protagonist needs to visit a bank they have to go somewhere else. Maybe it's the distant city of Poombah (no relation) which is a thriving port city, which also means it's on a trade route, which means it's not just a native population, but there are also itinerants, which means higher crime, which means a legal system designed to mitigate it and guards to enforce it, which means a local governor, which means taxes, which means unhappy citizens who will move away because the burden is too high, which means the population is continually in flux.
In nearly every case, the population of a city isn't as important to a protagonist as all of those other factors in addition to size and population density, which are all up to you.
If you DO run into a general population question, like how large a military can this city/country field, it's also up to you but you have to have a reason for it. The size of the army is important to the story. If you need to put 30,000 soldiers on the battlefield, you have to assume at least 60% of the population is at home, and that's if it's a desperate struggle and you're shoving every able body you can find into a boiled leather shirt and handing them a sharp stick. Maybe 5-10% of any given population in a hostile area would be directly involved in the military. During peacetime, that number would be closer to 2-3%. But you know what else? That's also up to you because it will depend on the local culture - do they value military prowess? Are they nationalists who are proud to fight? Or are they conscripts who do it only reluctantly? Are they warmongers looking for an excuse to die in glorious battle?
Realizing I didn't really answer the original question very well except to say "it depends" ... a small village would probably max out between 1,000 and 2,500 if there's a residential area with outlying farms.
[Answer]
Since people seem to be having trouble reading the entirety of my previous answer, let me paraphrase.
The population of a city is less important to a protagonist than population density, access to goods or resources, or local government.
The actual population would require access to a number of factors that are decided on and weighted by story and plot, so no calculator or formula is going to provide you with an easy answer. The simple (and in my opinion lazy) answer is anything between 30 and 150 people per square mile, and that number is nuanced by the reasons people have for being in that location. See the mention above on what's important to the protagonist because they're also important to everyone else in it.
It will also depend on an endless number of mitigating factors - for example, does the region have access to people with the skills to construct buildings higher than 3 stories?
If you want to use real-world metrics to define your fantasy world, then a medieval hamlet, defined as a small settlement, would be anything between 1,000 and 2,500 people. The same location in the early renaissance would be considerably smaller (depending on the exact region) since the Black Plague cut the population of Europe as a whole by 1/3.
Pull a string, see what it tugs on, make a decision, pin it down.
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My primary question comes from a fledgling animator's perspective. I'd like to capture the general look and feel of a lot of South Florida's cities, while also combining it with my urban-fantasy/science-fantasy's quirks. What I'm not sure about... is what sort of balance to strike between clear real-world inspirations (especially when it comes to road/city layout, the look of buildings, the arrangement of residential, industrial, and business areas) and the purely fictional designs (especially with the alternate history in-mind). Forgive me if this question and its context are a bit wordy... I've been building on this idea for a few years now, and am finally at a point where I want to, and can, make something concrete about it.
***To add a bit of context:***
The primary setting of many of my stories is set in an alternate South Florida (one that was separated from the rest of North America sometime in the 1830's, about 170 years before the series' present day... a channel was carved through the middle of Florida through abnormal means, turning Lake Okeechobee into a colossal river that allows water to flow from the Atlantic Ocean into the Gulf of Mexico... turning South Florida into an partially flooded island). The new river is about 40 - 50 miles wide, North-to-South, and cuts through the peninsula, creating some very rough coastlines.
To speak of the alternate history, this is one where the United States, as we know it, does not exist. Britain, as we know it, is a different animal. Its monarchy was effectively wiped out during the tyrannical reign of a "god-king" (ruling from 1356 to 1556, until he was destroyed), and the concept was dissolved following a period of instability and uncertainty (between the 1560's and 1650's). Fast-forwarding a bit to the 19th century... I'd like to imagine that this alternate Britain has some colonial hold on North America (made a bit difficult by the Spanish Empire, American Natives, and the supernaturally vigorous flora, fauna, and geography). This, somewhat haphazardly, leads us to the Sionna-Seminole Wars (1810's - 1850's), when Florida was bifurcated (conflicting contemporary reports point the finger at both the Seminole and Nature itself, as both Europeans and Seminole received substantial casualties from the event). The Seminole were eventually subjugated, the island colony of St. Sionna was established (the alternate Southern Florida).
St. Sionna would achieve independence in 1930, following a catastrophic war. And now, in an alternate 2006, we have a modern island nation in the midst of a strange, hazardous world.
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Ok your 'Florida' is kinda a caribbean island now.
So make your base architecture like that of Cuba. Because well Cuba is cool.
However for the more fantastic aspect have it that for whatever reasons the [Família Basilica](https://en.m.wikipedia.org/wiki/Sagrada_Fam%C3%ADlia) never gets approval to go ahead. So [Antonio Gaudi](https://en.m.wikipedia.org/wiki/Antoni_Gaud%C3%AD) doesn't die, and moves to Florida getting a job as a city planner architect.
One thing leads to another and boom fantastic Florida.
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If you're talking about cities in USA I would say there cannot be any similarities to "our world modern" cities. If you look on map of Manhattan (or Fort Amsterdam) from 1640 you will notice that althought it was kind of straight it was also very organic. A map from 1660 embelish it even more [Fort Amsterdam on Wikipedia](https://en.wikipedia.org/wiki/Fort_Amsterdam). A clean, easy to read grid of streets and roads showed in the second half of XIX century. In Europe Barcelona is only city I can think that look that way.
What more, cities in USA lack a need to wall themself. That need had very strong impact on European and Euroasian cities. You could differentiate beetwen villages with "Main street" that had buildings along it and towns that grow from a circle. A castle, bailey, market etc.
In your world the need to have a palisade is still there. And that dictate how cities grow. European cities are not so close and tight because they didn't had space to grow. It was just more convienent to be close to gate that could be closed and provided security. Best if you were living inside that gated community from the start.
For example, maybe, Fort Harvie would never be abandoned. "Ok the war is calming but there is no reason to leave this post because we might need it soon". Which, if you mention flora and fauna the "soon is now".
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A common trope in fiction is the "life debt," wherein two characters become "bound together by a bond of oath" because one has saved the other's life.
* Often the two characters are strangers when the lifesaving incident occurs
* Often one of the characters comes from a primitive culture wherein the tradition of a "life debt" is an unavoidable consequence
* either the person who gets saved feels indebted to the savior, and thereafter swears allegiance
* or the person who is the savior prevents the saved person from "meeting his fate" and thereafter must take responsibility for changing fate by watching over the person who was saved
* the story then may include a role-reversal scenario that absolves the subservient person from further responsibility
We consumers of media have seen this concept of a "life debt" haphazardly bandied about... from Gilligan's Island to Star Wars.
What is the determining cultural factor that governs which person becomes indebted, subservient or responsible?
(Wikipedia defines the "life debt" as a purely "literary phenomenon" - but can you think of any real-world cultures that are **known** to have this tradition?)
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I hesitated to ask this question, given the acute sensitivities engendered by current events. But since the fortnightly topic challenge is religion and I would like to include a British Muslim character in my future world, I decided to go ahead.
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The setting is London 50-70 years in the future.
For background, this question refers to the same world as in [this question](https://worldbuilding.stackexchange.com/q/15089/9207), in which a repressive regime has forced the regression of technology to mid-twentieth century levels. The takeover and regression occurred some forty years before the time in which the story is set. The top people in this regime are actually alien magic-users inhabiting human bodies but, since they are few in number and magic is fairly weak, that makes little difference to ordinary people's lives. In fact many people still refuse to believe that they are anything other than human frauds. The alien rulers are probably no worse than most human rulers throughout history. Most people accept the situation.
Among those who don't are quite a few religious people. I think I can explore the very different ways in which various types of Christians would respond to the "compatibility issues" caused by probable existence of - and rule by - magic-users and aliens from my own background knowledge. Ditto for the somewhat simpler philosophical situation of atheists. I am much more in the dark about how Muslims would respond to this scenario.
The Muslim character I am concentrating on is a female, mid-20's, lower middle-class, unmarried member of the Resistance with a mostly South Asian ancestry. She wears a headscarf but not a veil and works outside the home. Her beliefs are not shared by all British Muslims of her time, but she is meant to arise from a significant current of opinion. In the Resistance she is part of a fractious but functioning coalition of humans of many different religious and non-religious beliefs.
Would she be willing to believe in magic or aliens at all? or would she be one of those who think it is a bunch of humans cooking up a technological fraud to keep themselves in power? What would she take from the Koran about the possibility of magic and/or aliens? They clearly are not either demons or angels, but morally mixed creatures like us. If she does accept their genuineness, does she see their rule as something that needs to be opposed on the grounds that magic is evil, or rule by non-humans is evil, or would her resistance be purely political? It is relevant to state that the regime permits religions to be practised so long as they stay in line. Decades ago risings against the aliens in Muslim countries were savagely put down, but Islam is not seriously persecuted in Britain at the time of the story.
What words would she use to describe her own beliefs as a member of the resistance? Jihad seems an obvious one, but are there other concepts from Muslim thought that she would apply to this situation? What suras, ayahs, and hadiths would she quote?
The aliens generally exhibit mild disdain for all Earthly religions and political theories, although a few express a rather condescending interest. Would she think it obligatory to make the probably futile effort to convert any she meets?
Moving away from this one character, what other types of Muslim response would there be? What religious justifications might those Muslims who choose to collaborate with the aliens put forward? Or those who resist, but not in cooperation with the officially pluralistic general resistance movement in Britain?
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What would be technological impact to our every-day world, if we suddenly have room temperature super conductors ?
Specifically, what would be the major areas of change in the immediate future (one or two years)? In other words, looking for immediate primary effects, not longer term effects such as changes in social order. Assume they would be mass producible, cheap and flexible.
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What are the ways in which resources can be distributed in the society other than the use of money or the barter system, so that unequal or unfair distribution of resources can be avoided? If a society like that were to exist, how would it function (with technological development like the one we have now)?
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I started thinking about Alderson disks. They are usually portrayed with large uninhabitable sections on either side of the habitable zone.
Why not just build the habitable zone, and save materials? (As if that were really a concern for Alien Space Bats building a freaking Alderson Disk....)
Well, the thinner the annulus is, the less well any local area approximates an infinite plane, and thus the less stable it is against radial collapse. *But*, [toroidal planets](https://en.wikipedia.org/wiki/Toroidal_planet) are physically possible, so we could just have a toroid encircling a star with inner-facing surfaces being habitable... *but again*, toroidal worlds are subject to gravitational bead instability when the aspect ratio exceeds 3, and a torus just thick enough to produce Earth-like gravity and wide enough to encircle a star will have an aspect ratio *way, **way*** larger than 3! (For all practical purposes, it locally approximates an infinite cylinder.)
"How exactly would one counter bead instability in such a structure?" is probably too big of a question; I expect it will require [Clarketech](https://tvtropes.org/pmwiki/pmwiki.php/Main/ClarkesThirdLaw). But perhaps we can address something more tractable:
**What is the magnitude of geologic forces that would need to be actively countered to control bead instability in an "Alderson Torus"?**
Just how much suspension of disbelief would I be asking people to accept here?
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>
> Just how much suspension of disbelief would I be asking people to accept here?
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**A lot**, but you can probably go away with it, as audience is unlikely to consider the different points of the settings separately, but more as a whole.
1. The quasistable toroidal planet hypothesis makes the assumption that the structure behaves *fluidly*, which can be accepted for typical rocky planets, but
less so for a rigid structure. Shifting from planet-size to a solar system size adds some order of magnitude to the mechanical constraints of said structure.
2. Such toroid structure is metastable. Bead instability are the issue here, but if the structure is already rigid, you can just get away with it.
3. A rotating toroid structure will create local tidal force pulling matter from the inner part toward the external one. Using a ring-shape solves the issue, but as your rigid structure is there, you can as well stick with it.
To sum-up: the structure will face forces orders of magnitude above anything mankind can deal with today. The weakest item above involves energies comparable *at least* to continental drifts, requiring a fair share amount of suspension of disbelief to go through. An audience accepting any of the premises is unlikely to refuse the other ones just because it implies the structure being a few orders of magnitudes better.
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"Life could exist on either side of the disk, but the direction of gravity (the direction of "down") at any given place on the disk would be toward the center of mass of the overall system."
Any practical hypotheses based on this theory, would end up wanting.
Just how much suspension of disbelief would I be asking people to accept here?
Too much. If presented as a ground truth, the rest of the framework must be presented as fact.
Suspension of disbelief, only carries for plausible solutions within the perceived world.
Anything maybe possible in a magical, fantasy, or sci-fi worlds, but unless otherwise reasonably defined, The reader is bound to their interpretation.
Alderson disks in their nature defy logic. The missing logic must be provided.
Alderson disks were portrayed successfully in the movie "Upside Down" in 2012.
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Start game
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You wake up in a forest, naked and lying on your back.
As you stand up you realize something has been watching you, it seems to be a dog, a very big f\*\*\* dog, a wolf!
The wolf, bigger than you'd ever expect rushes in eager to attack you.
6 meters between you and the wolf is the line separating you from a one way ticket to eternal sleep.
You've got one chance, running is not an option, you've gotta endure through the pain as the wolf bites into you and meanwhile hurt it really badly in a weak spot.
What weak spots in a wolf can be severly damaged without weapons and cause the wolf to run away or be defeated?
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An unarmed, unarmoured, unprepared human against a large apex predator? That can be expected to hunt in packs? That's a fairly clever hunter? That eats things that are substantially bigger, stronger, faster, tougher and more dangerous than humans?
Your best bet is to offer it a limb you don't need as much... your off-hand, perhaps. If you're lucky, it won't like the taste of you very much, and will give up. If you're *really* lucky, it'll choke on some of the splintery little bones, but I wouldn't pin my hopes on that. It is at least slightly more likely than plan B, which is hope that a tree falls on it.
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> What weak spots in a wolf can be severly [sic] damaged without weapons and cause the wolf to run away or be defeated?
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The same weak points that any predatory mammal has. Realistically though, you will simply not be able to hit them... you are a naked ape, with limited capacity for resisting teeth and claws, you have no useful natural weapons, and you're trying to go one-on-one with an actual killing machine. You know how you don't hear many stories about people kicking bears in the balls, or poking tigers in the eyes, and escaping to tell the tale?
There's a reason for that. Don't fight apex predators on their own terms. You gonna get et.
(also, even if you *did* somehow manage this miraculous action, this is a pack animal, and do you really think you're gonna pull it off more than once? against multiple opponents? nope)
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Consider though, it might not actually attack you. You're a funny shape, and a funny smell. You aren't much like its regular prey. Wolves aren't stupid. It isn't going to just charge in and attack immediately like a computer game random encounter. If it has rabies, it'll behave as you're asking, and then you're SOL (and even if you did survive, you've probably just contracted a deadly virus, yay!)
Your only hope is that it reacts like a normal, healthy wolf, and you're able to back away, take stock of the situation and start equipping yourself with the tools you need to survive. Cos without them, you won't.
[Answer]
**This is a game. You aren't going to get killed in the first 10 seconds.**
[](https://i.stack.imgur.com/BmEqo.jpg)
<https://www.airbnb.com/experiences/924806>
If you attack it will kill you. If you run it will chase you and then if you turn and attack it will kill you.
The wolf has been there. It could have killed you in your sleep but it did not. Why not? Now it is rushing in because you woke up. It is excited that you woke up.
If you stand your ground it will watch you. If you talk to it and look at its tail, it might wag its tail. If you hold out your hands it might come get a scratch. If you throw a stick it might go get it and crunch it up.
This is a game. A dire wolf sidekick will be cool.
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Using examples of people attacked by dogs and jaguar, ram your fist down its throat.
Your hand is large enough it can't bite down effectively once it is far enough in, and it will choke. This will be hard to do but not impossible, even if you are bit drive your arm deeper, no predator is ready for that, prey tries to escape it does not push deeper. Other wise ideas are to kick, punch, and grab, a human easily has the strength to rip a wolf's ear off or gouge an eye. Pin it if you can, humans are much better wrestlers than wolves.
Even better kick or try to pin the wolf first, lettings yourself get bit is stupid, a wolf is unlikely to let you go if it has your arm because it can drag you to the ground. Stay on your feet and hurt it first, predators are not movie monsters if you are strange and dangerous they will leave you alone.
Before it even gets to you grab rocks or soil and throw them at it, humans have defended themselves form predators by throwing things since forever, most predators are confused by projectiles, and a human can throw rocks HARD, hard enough to crush its skull. The mixture of
oddity + pain + aggression = get out of there to a predator.
Even if it does not run away it will be far more cautious, which buys you time to find a better weapon or tree o climb.
If you successfully injure the wolf, it may leave you alone, animals are not movie monsters, they generally ty to avoid dangerous fights. If you are aggressive you are automatically a threat, if you do things that have never happened before then you are a strange threat to be left alone.
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Just like sharks. The eyes. Creatures are psychologically inclined to avoid permanent damage (except eusocial creatures or a few outliers like badgers). Poking its eyes is your only chance of really threatening to deal permanent damage enough to at least let it back off. If it backs off permanently is the question though.
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Maintain eye contact.
Look as big as you can make yourself look.
Back away slowly while maintaining eye contact.
That is, treat it like a wolf.
However, if you can, see if there are any large branches in convenient grabbing position, or trees you can climb. Use your ape advantages! With a branch you can go for its eyes. Rocks can do damage, and dirt can blind.
Note that the leafless branches low on trees often break off with no more than hand pressure, so be careful if you use them for climbing, but hey -- the other way gets you a club.
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### Be more Brian Blessed
As [famously reported by the man himself](https://www.youtube.com/watch?v=S9c05bvN6Z0) and [illustrated by Jim'll Paint It](https://jimllpaintit.tumblr.com/post/62917608703/brian-blessed-punching-a-polar-bear-in-the-face-as), Brian Blessed once punched a polar bear when it invaded his tent. Apparently clocking the bear on the nose and loudly shouting at it to f\*\*\* off (and we know how loud Brian Blessed can be!) was enough to make it want to be elsewhere. When it comes to apex predators on land, polar bears are well in the running for top place, so if it works on a polar bear then it'll work on anything.
Predators, by definition, want to eat prey. They also want to not get injured in the process. If you look aggressive enough, regardless of size, there's a decent chance you can make it decide that there are easier meals out there.
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**First, don't get bit.**
Wolves (Dire or not) will go for the throat, this would be instantly fatal. If they grab your arm, the canines will pass straight through, they'll then (once you're crippled with pain and shock) seek a better grip on something vital. Don't let them bite you.
**You'll need to be fast and bold.**
Hold your forearm out horizontally as a point of aim for the attacker, then at the last minute (impossible to practice the timing, just go for it) drop it a few inches, then thrust it upwards with full force. This will have the effect of knocking the D-wolf's mouth closed and their head up.
Wrap both your arms around it's neck pressing your head against its and holding on as tight as you can. At this time the animal will try to bite whatever it can reach - ear, scalp. Ignore the pain, the growling, the claws raking your chest and stomach.
**Groundwork.**
The thing will be jumping, snarling and writhing, trying to free itself, you must wrestle it to the ground. Your objective is to wrap your legs around its waste, cannids are not well protected there. Cross your ankles and using the strength in your quads - kick away with all your might. You might lose grip with the ankles at first, but lock them and kick again crushing it's gut up into its diaphragm. With any luck you'll have the strength to rupture the membrane and muscle between it's abdomen and its chest - thrusting its guts into the space it needs for its lungs and make it impossible for the creature to breath.
Keep kicking hard until you're sure that it's not going to put up any more fight, then pick yourself up and seek first aid for your missing ear, lacerated chest and half a face.
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One friend got attacked by a [Karakachan like dog](https://en.wikipedia.org/wiki/Karakachan_dog) because he patted a female dog of its interest. While dog was not super aggressive in general, it was a real attack. His quick reaction (before he could think about it) was to give it a uppercut which caused the dog to fly back whimpering.
So a strong man can scare off a predator giving a few real-strong punches and not letting the predator byte. So a strong punch and like John's answer - throwing rocks and sand at it, can realistically scare off a large wolf.
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1. Snout
2. Eyes
3. Dewlap
4. Groin
1, 2 and 4 hit hard, 3 is caine specific, if You grab and hold then is posibility that wolf surrender and find You alfa male. But need a lot of strengh and agility to do that.
Can try to put arm in to jaw and rip throat from inside but that is so much risky.
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Only option I see is to make like Ryan Hall. Dive for an ankle, wrap your legs around its upper limb, and use your entire body to put enough torque into its joint that it snaps.
It probably won't work though.
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The user can manipulate fire in many ways, and to a certain extent, he can also manipulate electricity. The fire he uses is special and can reach temperatures above sun, but the average temperature reached by its flames is "48 times hotter than normal fire." He can increase his power gradually over time and is very resistant. Although it has a lot of resistance, his own flames can burn him, so he uses technologies to prevent this from happening, such as power armors. Its very resistance makes it always need the power armor. His manipulation of electricity is very weak, so he uses it very little. One of his weaknesses is that he can't spend much time in the water, and it makes him weak.
I wanted to know if there is any way to defeat him using technology and science. It doesn't matter if the technology to be used is futuristic. Like a power armor or something.
[Answer]
# Shoot Him In The Head
You haven’t specified that he has any kind of supernatural senses, so a well placed sniper shot from well out of his visual range, (3km has been done but let’s make it 2km for safety) will neatly take care of the problem.
[Answer]
The tech and science I use will be
**A BREWERY!**
[](https://i.stack.imgur.com/iTnu3.png)
And I will say "Dude, you must be thirsty. I very much am. And I have some beer from that new brewery! I am going to have one. Would you like one?"
then I will add the ancient tech of the Chickpea!
[](https://i.stack.imgur.com/I9J0b.png)
Because the beer made me hungry, and him too. And I have those pita chips and some hummus! And some more beer for when we finish the first ones.
I have not defeated him, but he is not my enemy. It turns out that in addition to fire power he can play guitar and knows a lot of songs I know too.
Eventually the neighbors hear us and come over.
[Answer]
# Hot stuff:
Most of what you need is off-the-shelf tech available in Menards, a fire station, or somewhere similar. Start with a fire extinguisher, and go from their.
* **O2 deprivation**: If you get up to sun level, the pyromancer will probably induce fusion and blow himself up. But at more manageable levels, flood spaces with CO2, nitrogen, or similar inert gasses that can't burn and deprive a fire of needed oxygen. At the lowest levels, this can be a simple CO2 fire extinguisher. At the upper levels, sophisticated fire suppression systems exist for just this purpose. And a pyromancer who can't breathe is just as dead.
* **fire suits**: Ever see those guys wearing the fancy silver suits walking up to volcanos? The gear of fire fighters is more basic, but the idea is to make a heat-resistant non-flammable barrier. At lower tech levels, asbestos has been a thing for centuries. Cancer in 20 years is better than burning to death.
* **Choke on it**: When does a pyromaniac fear lighting a fire? When they're standing in a pool of gasoline. One of the quickest ways to stop a fire is to use up all the oxygen and fuel. Or maybe they can shape fire, but if you overwhelm their capacity to control, it's out of control. A fuel source that is really something else (like dynamite) will cause the pyromancer to be [hoisted by their own petard.](https://en.wikipedia.org/wiki/Hoist_with_his_own_petard)
* **Do you smell smoke?** Perhaps the pyromancer is detectible because they are generating a smoky signature around themselves. Perhaps they make a readily trackable heat source with their powers and don't even know it. But they could easily have a tell that broadcasts their location or even their intentions. Devices as simple as a smoke detector or as complex as thermographic cameras allow observers to always know when and where things will heat up.
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This is Bob the cop. He's going to arrest the pyrokinesis user for some crime he apparently commited.
If the pyrokinesis user kills Bob, then DanielB's answer will likely soon follow. If the pyro keeps Bob alive and "just" hurts him to keep him away, for example by reaching for the electricity in Bob's taser and using that to tase Bob, then friendlier methods to arrest him and place him in an asbestos cell somewhere will be taken.
The pyro has to take on society. Is he going to steal his food every day by force? Or the money to pay for his house and livelyhood? What is he doing for social interaction? Even if he just gets a job and does the normie thing, as long as he's wanted enough that he comes into contact with the law, he is screwed.
So sending Bob didn't work? Ok the police can simply hire someone to change the locks on his house while he is away, and if necessary empty the house and use that as a bargaining tool to get him to cooperate with justice. Doesn't work? Ok next time he turns the corner to his house he gets blown down by a watercanon, by the time he knows what is going on he's in handcuffs with a hood on, cold, wet, disoriented and halfway to a cell. Or maybe the police does the time-honored act of lifting him off his bed in the early early morning, since this is a powerful individual they might also send some teargas inside every window just in case. Or maybe they just wait for him at his commute where they tase him (cant control it if it happens before he reacts), pepperspray him, fire tear gas and a rubber bullet or two into his chest to incapacitate him as he rounds a corner and arrest him...
Unless the pyro is a hobo who keeps moving and tries to stay out of sight, there just isnt a good way the pyro can truly stay ahead of the law.
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If we talk futuristic, then any type of sonic canon or any sound-based weapon should be able to deal with the pyromancer. While he/she can reach temperatures above sun, the sound is still able to travel through the plasma. Some way to send them to vacuum could also be a solution, as well as anything gravity-related.
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Well - treat it like any other fire. Just keep dumping water on him. A water cannon is going to keep him off balance, and super heated stream will at least block his visibility. It might damage power armour, and force him to keep working to keep the temperature up.
Evaporating water also would shield the surroundings from the heat, and while you can't *shoot* him as effectively through the water and steam, it still lets you contain him at a relatively low cost.
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This will be a question that I am fine with having less realism in. I was thinking of a weapon, like a spear, that can go at FTL (*faster than light*) speeds. To be clear, the spear is FTL due to propulsion (*that is where the realism fades*) rather than being a miniature **Alcubierre Warp Drive** (*that creates a space-time bubble that eats matter around it*), so when the spear hits someone, they are still being hit by a solid object (*that is, if the spear does not get destroyed immediately*).
The thing is, I have little idea of the ramifications of being hit by something going FTL. I know that an object that is moving at speeds nearing that of the speed of light can already have enough power to create earthquakes and rival nuclear weapons in terms of devastation. But what about beyond the speed of light? Can kinetic energy even be used anymore for such a weapon?
EDIT: Since you want to know how the FTL was supposed to work, I was thinking of using concentrated Dark Energy as a propellant, expanding space behind the spear to make it look FTL.
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I'm not sure on what happens when the spear reaches its FTL speed, but you're going to have issues while the spear is accelerating *to* FTL speed. Because it is constantly hitting something, namely "the air", and just the force exerted on the air itself is going to be bad news for anything in the vicinity of this weapon speeding up.
I'm not sure if you're familiar with the [**What if?** series on XKCD](https://what-if.xkcd.com/1/), but the very first one handles the effects of an object suddenly going relativistic (a baseball, in the example) and they're.... catastrophic to say the least.
Basically the spear turns into a nuclear explosion nanoseconds after it starts accelerating and obliterates the wielder, the target, and anything within a mile or so of the event, before it even manages to reach the speed of light.
So unless your weapon is operated in the vacuum of space (not a good place for spears) or accelerates to FTL speed instantaneously, there's probably no serious difference between stabbing someone with it and detonating a briefcase nuke you're carrying around.
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Kinetic energy quantifies the momentum imparted to a particle from an interaction. Current physics is restricted to four classes of interactions (forces). Since all interactions in current physics are mediated at or below the speed of light, there is no theory that describes how the FTL object would impart momenta, and thus such an event cannot be described in terms of well defined physical quantities such as kinetic energy.
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An object moving at the speed of light would destroy the universe.
[](https://i.stack.imgur.com/nsDnu.jpg)
Kinetic energy under relativity increases to infinity, so everything in the universe that could be hit by a sphere of energy moving at light speed would be destroyed.
This would likely kill your enemy, your enemy's world, and their galaxy.
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I don’t think it could hit anything at all, in the sense that you mean. When two objects hit each other, they are affected because of the electromagnetic forces between their component atoms. But those forces are mediated by virtual photons travelling at the speed of light, and so can’t affect something travelling faster than light. Your FTL spear is going to effectively be dark matter, not interacting with regular slower than light matter.
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So far it seems all these answers rest on misunderstandings of relativity
Relativity does not actually preclude objects moving faster than light, only objects travelling at the speed of light. As such, relativity prohibits objects accelerating from sublight speeds to superluminal speeds, but if we wave our hands around when we break the light barrier, and only consider the object once we already have it travelling faster than light we get pretty reasonable physics out again
A few starting points (working in natural units where *c* = 1):
The energy of a relativistic object (including its rest energy, which is just *m*) is:
The momentum of a relativistic object is:
Because both of these equations feature a factor of  you will sometimes see a concept of "relativistic mass" invoked, which is equal to this factor. Such a concept is generally considered deprecated in physics these days, because as soon as you start doing anything more complex than basic kinematics, it starts making things more complicated rather than less, and leads to some unhelpful intuitions
As an object approaches the speed of light (from either direction),  and so both . This is known in the business as a Bad Thing, and means something unphysical is happening. This is why relativity predicts no objects can cross the lightspeed barrier. Luckily for us, the spear is made of handwavium and has a way around this
Unfortunately now we have a different problem. Because we now have *v* > 1,  is imaginary. In order for a bunch of other physics to make sense, we need Energy to be a positive real number, and so any tachyons in the universe (including our spear) must have negative imaginary mass, so the factors of i & -i in  cancel out
Again though, our spear is made of handwavium, and so as part of crossing the lightspeed barrier, its mass becomes negative and imaginary
Now we have a spear travelling at faster than light speed. The first thing to note is that it will emit gravitational Cherenkov Radiation. Cherenkov Radiation is normally encountered around nuclear reactors and is why they seem to glow blue, and is roughly the electromagnetic equivalent of a sonic boom. The normal sort is electromagnetic and occurs when a charged object travels through a medium faster than the speed of light in that medium. Gravitational Cherenkov Radiation is the equivalent with gravitational waves instead of electromagnetic waves, and will occur whenever a massive (gravitationally charged) object travels faster than speed of gravity in that medium (as we are in space, this is just the speed of light here)
As such, our spear will be emitting a bunch of weird, high energy gravitational waves, causing it to rapidly lose energy
Looking at the equation above for energy, and ignoring the pesky imaginary factors that we're cancelling with our handwavium, we see that whereas we're normally used to energy increasing as you speed up, energy *actually* increases as you get nearer the speed of light. As such, superluminal objects lose energy by accelerating, and so, as our spear loses energy by Cherenkov radiation, it accelerates. As this causes it to move at an even greater speed, it starts to lose energy even faster, and its speed rapidly heads towards infinity, and its energy heads back down to its rest energy *m*
Now this is where it gets interesting. From quantum mechanics, we know that the wavevector (essentially a vector consisting of the wavelengths in each direction, with a slightly different normalisation), and substituting our expression above for the momentum **p**:
As *v* > infinity, this goes to 0 in all directions
The reason this is interesting, is that from studying interactions in particle physics, we know that a particle will only interact with an object if it's wavevector is of a similar scale to that of the object. As the wavevector rapidly goes to 0, and any real object has non-zero size, the probability of the spear interacting also goes to 0
So where does that leave us?
The spear itself is not the danger, as the probability of it interacting will be essentially 0 shortly after it breaking the lightspeed barrier
What is dangerous though is the burst of Gravitational Cherenkov Radiation. This circular blast wave (perpendicular to the velocity of the spear) centred on the point at which the spear crossed the lightspeed barrier will carry almost all of the energy that went into accelerating the spear. Depending on how much of the crossover the handwavium applies to, this could be an astronomical amount
So, the spear allows you to concentrate the energy you build up propelling the spear into a circular blast wave where it breaks the lightspeed barrier. With a long enough run up, that's a lot of energy in a very concentrated burst and, because it's gravitational radiation, won't be able to be effectively blocked in the same way electomagnetic radiation might be able to. As such, it will get around shields, or physical armour. The downside is that gravity is comparatively weak and so you'll need to put more energy in the burst to do the same damage
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It's impossible to say what the effects might be as we have nothing to go on. We can't use the existing scientific framework which would normally be used in such a circumstance (relativity) because such FTL travel violates relativity. All we can do is to invent some new science and try to explain it with that.
Edit: Following from comments made by Razor I would add that although relativity does not preclude objects from being brought into existence traveling at speeds faster than c, such objects would have imaginary mass and would violate causality and remain beyond the existing scientific framework.
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FTL is essentially magic (Clarketech). It could vary from destroying the universe, to doing absolutely nothing, to turning the target into a confused sperm whale or a pot of petunias.
You want to do it *without* magic though. That's just not possible. The question of what it would do is meaningless. Pushing something to make it go faster than light is like slowing something down to slower than not moving at all.
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The problem with this is that relativistic mass is given by the following formula:
$$ M = m \times \sqrt{1 - \frac{v^2}{c^2}} $$
Where $M$ is the relativistic mass and $m$ is the rest mass.
At speeds higher than c, your relativistic mass is your rest mass multiplied by the square root of a negative number, which is imaginary. That is kinda impossible to imagine though.
Yes, I know. This is [science-fiction](/questions/tagged/science-fiction "show questions tagged 'science-fiction'"), not [science-based](/questions/tagged/science-based "show questions tagged 'science-based'"). So the first thing that comes to mind is that an FTL projectile would become a beam of high-energy [tachyons](https://en.wikipedia.org/wiki/Tachyon). They would have to be focused on a point in time and space in order to be effective. You will shoot at some time and it will hit a target in the past and another in the future. Then it will keep causing some damage going in both directions in time. Could make for a nice sci-fi story.
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Two things to consider:
1: at orbital speeds (not even relativistic speeds!) Metals impacting each other will act like liquids rather than solids. Going faster will just mean more materials will act this way as by the time the surrounding matter can react, the impacted molecules are already pushed much farther away. So there is no "solid impact" possible.
2: mass and energy are connected. Light is massless, but if you concentrate enough light energy on one point they can create a black hole we call a Kugelblitz and these suddenly have gravitational attraction!
That gives us a problem: when you approach the speed of light you have to put in increasing amounts of energy to speed up, but you'll never reach the actual speed of light unless you find a way to put in infinite energy. Going FTL means adding infinite energy+1. Even without impacting anything your projectile would turn into a black hole that expands at the speed of light to swallow the whole universe forever, only the parts beyond the visible universe (due to universe expansion) are safe. And that is assuming the black hole wont remain traveling at FTL speeds in its original direction which it probably would.
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**Frankly, as with all kinetic weapons, it depends as much on the size of the slug as it does the speed of the slug... maybe...**
I'm all for ignoring relativity — which is a ***requirement*** if we're going to examine an FTL object from a purely classical-physics point of view and ask "what if?"
So, what ~~does~~ ~~would~~ might happen?
**1. I'm standing on my world, minding my own business, when [Skeletor](https://www.denofgeek.com/wp-content/uploads/2014/06/skeletor.jpg) unleashes his FTL spear at me...**
Between Skeletor and I exists an atmosphere that, at this moment, can only be described as *inconvenient.* Referencing what is perhaps [the most referenced XKCD in history](https://what-if.xkcd.com/1/), we discover that mere moments after the spear is unleashed, the friction/compaction between the front of the spear and the atmosphere causes fusion. The resulting explosion would certainly defeat me, [Skeletor's nemisis](https://cnet4.cbsistatic.com/img/XXcdNB7DdPtlycVyYN2jBFeKtAQ=/2019/12/19/a3a6ed4e-5670-4125-b2bb-b19cc686c767/twitter-in-stream-wide-heman-mattel.jpg), but it would also defeat Skeletor, which is *no bueno,* and a good chunk of the kingdom, too. So, in this condition, long before we even got to FTL speeds, everybody dies. And I didn't even get hit by the spear. In fact, I can't be hit by the spear, which means the only *practical* answer to your question for this condition is "nothing." I love this site.
**2. I'm floating in intergalactic space, lowest particle-count-per-square-mile possible, minding my own business,1 when Skeletor unleashes his FTL spear at me...**
Now we're cooking with gas! The spear actually has a chance of hitting me at full speed! What happens? Well, per that previously linked XKCD, as the spear pierces my space suit and the atmosphere between the space suit and me2 that inconvenient fusion problem happens again and without my ever having even *noticed* that Skeletor threw the spear3 I convert into a mass of energy that on a galactic scale wouldn't even be worthy of describing with the word "burp." So, once again, I was never hit by the spear. And despite the certain presence of a lot of drama, once again the answer is, "nothing." Oh, yeah. I love this site!
**3. Skeletor spent a depressed weekend binge-watching *Mythbusters* where he learned that a [bullet will go through a hat rather than knock it off!](https://mythresults.com/episode79). Convinced that he finally figured out how to kill me, he found me sitting in a public restroom,4 minding my own business, reading about the latest conspiracy theories concerning infectious disease and U.S. politics via the [world's best investigative journalism](https://youtu.be/qTFfthVy_pA), when Skeletor unleashes his FTL needle bullet at me!**
OK, *technically* the FTL object *actually touched me this time.* But the proverbial millimeter inside my skin... fusion... bang... burp. You get the picture. BUT! At least this time the answer is, "bad honking things happen, Cyclopscore! *BAD HONKING THINGS!"5*
The unfortunate truth is that most objects with mass traveling at high speeds welcomed by classical physics don't generate substantial heat due to friction as they pass through ~~the victim~~ something. In most cases, unless a really big, flat surface is involved, the object just passes through the target, leaving a big hole.6 The bigger the object, the more it will simply push the target aside with enough *[NCIS](https://en.wikipedia.org/wiki/NCIS_(TV_series))*-quality blunt force trauma to make a good Halloween horror movie.
But when you bring speeds even approaching light speed (much less beyond light speed) into it, friction becomes a *serious problem.* I'm not going to bother with the math, but I doubt a 1mm pellet could get through the human body without the fusion-burp result.
*But if you throw $600,000,000 of Hollywood's best special effects at it, it'd look cool, wouldn't it?*
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1 *Actually, I'm on the verge of peeing my space suit because I'm down to 1% oxygen supply in the middle of intergalactic space. But your question doesn't consider the circumstances of the victim... thanks for asking.*
2 *If there is any atmosphere. I can imagine a space suit that only requires oxygen near mouth and nose, the fabric over all other parts of the body being skin-tight, providing heat and capable of wicking away oil and sweat, and otherwise maintaining pressure through elasticity. but let's assume something more traditional. Big honking space suit full of combustible atmosphere!*
3 *This is an interesting question. What would I see? Skeletor rears back, and then maybe my mind imagines a naunce of forward motion. I begin to say something clever like "You Ba...." ... and that's it. I'm not convinced Skeletor would do this. He's all about making sure **I know he brought about my doom!** But hey, we're suspending certain rules of reality. So maybe Skeletor's happy with proverbially shanking me in the back. It's not like he could ever win in a fair fight. Right?*
4 *In the vacuum of space, of course, I didn't really need that space suit in the last example. I'm He-Man, after all.... You should have known I was just making this up the moment I led you to think anything would cause me to pee the suit. Sheesh.*
5 *I love this site.*
6 *A quick word about kinetic energy. Most of the other respondents are answering as if all that energy would somehow be absorbed by the victim... or in one case all of space-time. That's not really how kinetic energy works. Otherwise shooting a bullet through a piece of rice paper would cause it to burst into flames from the raw infusion of energy. The ability of the target to absorb that energy vs. simply being pushed aside (whether it be a hole in the body or really being pushed aside) has as much, if not more, to do with it. Civil War soldiers were found with holes in their sides 8 inches or more in diameter where cannon balls simply went through them — and they had plenty of kinetic energy left over after passing through the victim. It takes a really large really flat surface (or a really hard really difficult-to-pierce surface) to not simply punch a hole through something. Or that something must be incredibly brittle. I'm not sure the universe is that brittle. Or that wall nailed down.*
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### How much kinetic energy exists in 1kg of matter in FTL?
Sci fi doesnt seem to conserve momentum in FTL. For example: every time a ship leaves FTL and is immediately in a high orbit around a planet with the planet visible from the bridge. (Wow - how lucky they were that the velocity was precisely correct). There is a plot-driven creation or destruction of energy in this process. Putting a value on this arbitrary energy interaction helps work out how your FTL spear works.
With no true 0 speed and varying frames of reference (the systems are orbiting the galaxy centre at dozens of km per second relative velocities) maintaining your relative speed is pretty unhelpful. You pop out in one system with the kinetic energy of the previous system and you'll be flying extremely fast. If you're able to adjust your speed after exiting FTL then your ships will be overpowered in maneuverability. This isnt ideal.
If ships exit FTL at c, there'll be huge g forces and a long deceleration run. In atmosphere till be like a nuclear bomb going off. This would make a great FTL spear.
However for the spear to work every other FTL exit needs to decelerate to shed the energy that would otherwise go into the bomb. This isn't great for plot purposes - after an FTL jump every ship needs to spend 3 weeks slowing down in order to enter orbit.
If you do commit to this FTL dynamic - then yeah, an FTL spear is basically a death star blast.
If you don't commit to this dynamic - equivariant mass as a meteor I guess.
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FTL is not possible with our current model of how the world works. That leaves you with two possibilities:
* You need to either abandon the theory of relativity and, for example, simply stick with Newtonian physics: There is no relativistic effect of speed, no absolute speed limit, kinetic energy continues to grow quadratic with speed etc. This leads to a host of fundamental logical problems, but those may not be apparent or visible in your story, so ignore them. This is, implicitly, what a *lot* of space opera does.
* Or you enhance/modify the theory of relativity so that FTL (or something which has the *effect* of FTL) becomes possible. If you don't want to bend space and time (you said "no Alcubierre drive") then you'll need wormholes or the like. The spear would essentially travel close to c in order to be dangerous and not waste too much time on the first and last light seconds (a bit like walking to and from the subway used to make up a lot of our commute before Corona) but take a shortcut to the target so that your story can continue, which is the whole point, I assume.
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AT light speed, an object would have an infinite mass. The formula for kinetic energy is 1/2 Mass x Velocity^2. So it would pretty much destroy everything.
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When it comes to FTL impacts, I think the [Holdo Maneuver](https://starwars.fandom.com/wiki/Holdo_maneuver) is an interesting metric. ([Video link](https://www.youtube.com/watch?v=X0pNaImGfbs))
The funny thing is that they actually down played the effects of the Holdo Maneuver. Apparently a ship that big aimed at a planet becomes the ultimate budget planet killer.
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In my story's world, witchcraft is a respected institution, with the most powerful practitioners being at the top echelons of society. Due to this, society traces its lineage through matrilineal lines. Witchcraft is exclusive to the female line. Ritual magic involves using the mana of the world and directing it in a way to suit you (altering terrain, changing the weather, erecting barriers, etc). It requires chanting, numerous ingredients, and a group of people depending on the spell. Society is divided up into covens, with the most powerful witches being top leaders in their covern. Ritual magic is essential to society, so logically the more witches a coven has, the more powerful and influential it would be. However, this matriarchal system has more males than females in these covens.
There is a spell that allows one to choose the sex of their offspring. This is a simple spell requiring only the individual , some incantations, and a number of ingredients. Why would this civilization choose to have more boys than girls If they lack access to magic? What would be the benefit?
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Inheritance is matrilineal. Having multiple daughters means that there is some controversy over who inherits. And even without controversy, there is complexity. Primogeniture might give the bulk to the firstborn, but how to provide for second-born and later daughters?
Sons are outside inheritance. Have as many as you want. Their purpose is to make good marriages or to support their sister. Perhaps the occasional dark magic ritual sacrifice to increase power. Sons increase the family power with less concern about splitting it.
One daughter makes it clear who the heir is. A second muddies those waters. And can become an aunt who might claim precedence over a niece.
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Males can be used as unskilled labor, and you need more unskilled than skilled workers (at least with medieval technology). Or males are used as cannon fodder in wars, or as internal police force, which increases their mortality.
More female offspring:
* Require more teaching effort from mother. B/c untamed magical powers can be very destructive. Magical powers are inherited, and mother is responsible for destruction caused by her child (if she survives, ofc).
* Will fight more between themselves, especially is magical power is limited or shared within a family.
* Are more likely to rebel against the mother. More children mean weaker bond between mother and each child, and higher chance than any one child starts feeling that mother favors other child more than them.
Finally, witchcraft will likely extend life, but only for the witch herself. So to keep gender the ratio constant, you have to have fewer female newborns.
PS For modern science, it is a lot easier to pick gender of the child on conception than to change gender of a growing fetus. If the witch can do same things with her magic, she might as well choose to clone herself rather than mix genes with some male.
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**Witch offspring sap mana from their mothers.**
You can have a witch baby but when she emerges she takes some of mother's magic with her. If you want to be at the top of your magic game you do not want to share your magic with your offspring. The uberwitches might have only boys - but then their lineage dies. Middle powered witches might opt to share with their daughters because the lineage benefit outweighs the power loss.
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The bodies of men collect and concentrate the manna of the world (making more potent spells possible), but they have no ability to control or direct it. A woman will therefore become more powerful herself if she has a few sons before having daughters as she will be able to use their concentrated manna to power her spells.
Please note that a civilization can't make choices, only the individuals in the civilization can, so the choice has to make sense in a per person context.
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**Untrained witches are dangerous to everyone. And you can train only so many at once.**
Every daughter of a witch has magic. But it is training that makes a witch out of a girl. Without training, magic is still there, but it is spontaneous, wild, bursting out at random. None wants to be around an untrained witch, as you have to maintain strongest protective charms at all time and still won't be completely sure if that would be enough.
On the other hand, the training involved is long and deeply personal. One full-fledged witch can train only one apprentice at a time. And the training up to the moment when she can be graduated and the next apprentice gets accepted takes two decades. Thus, it is extremely rare for a witch to mentor more than two girls over her lifetime (she would graduate the second one in her sixties at the earliest). And many elect to train only a single designated successor.
Of course, basic control gets taught early on, and you can have a non-volatile girl just a year after her magic manifests. Yet, without further training she wouldn't contribute much to the coven, and it would be such a waste (especially for her mentor) to just cut training short there. And if an unclaimed girl comes of age for whatever reason (say, her designated mentor met an accident), then either someone free (and unwilling) has to teach her, or someone has to halt teaching their current apprentice to deal with a new menace.
Thus, it's not that boys are preferred. But there is a hard limit on how many girls are acceptable, and everyone else has to be boys. Assuming witches aren't too chaste, yet don't use contraception, this will be a natural consequence.
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Magic is sex-based, so the power is based on the amount of sex. A woman can have more sex than a man can, so having more men increases the total power.
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**Lineage**
Men, though unable to use magic, inherit the greater party of parental power.
Thus boys will be used for arranged marriages against dowry.
This would allow the greatest witch families to easily perpetuate and increase their power from one generation to the next.
Introducing the notion of nobility and lineage.
In the same way arranged marriages will allow to enrich the family, to rise up the ranks of society.
Moreover, a line that has "lost" its power could rise by marrying a girl to a young boy of a famous lineage
In conclusion, to answer your question: it would be advantageous to have a single daughter with several brothers, since a boy could be ~~sold~~ married to other families. Boys married or not will not be a burden because they would find work (crafts, soldiers, finances, etc.)
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Males born of witches can't access magic, but they are **immune** to magic by virtue of their lineage and a quirk of how magic works.
Thus, they're good -- and devoted -- warriors in the internecine battles between covens.
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A witch’s time is incredibly valuable. Every minute she’s not casting spells or performing rituals or experimenting with new magic is wasted.
So men do everything else. Not just the traditional “man’s work” chores like putting up the shelves, but also the traditional “women’s work” chores like cooking and cleaning, and the specialized work like raising the newts and harvesting their eyes, and dealing with the world outside the coven, and even jobs that we’d consider prestigious like engineering that in their world are still not worthy of a witch’s time.
It’s not about keeping the men down; in fact, “everyone knows” that men are better at cooking and cleaning, as well as math and singing, That isn’t actually true (any more than it’s true that women are better at sweeping and men are better at doctoring in our world), but everyone believes it any way (just as people did in our world until the last century or so).
The one thing the men can’t do is teach new witches, which is a very time-intensive task. Schooling can only do so much; magic is highly personal, and much of it has to be passed on directly from mother to daughter. If you have four daughters, that quadruples the time you have to spend teaching them, which is time as you have to take away from actual witching. (What happens if a mother dies? Her nearest female relative with no daughters is expected to adopt and raise the girl instead of having one of her own.)
But if you have one daughter and three sons, that’s three extra people that can be useful to the coven without needing to be trained by a witch, so you’re wasting a lot less time.
Why couldn’t there just be women who aren’t witches, so they can divide the labor between men and mundane women? Well, you *could* have a daughter and not raise her to be a witch, but it would be considered horribly uncouth. People would think you’re being unconscionably cruel to your daughter, not to mention depriving the community of a witch.
Maybe there are some cultures that did develop that way, but every major civilization today traces its descent to a handful of cultures (like the Greek, Hebrew, Indus Valley, and Yellow River cultures in our world) that don’t, so as far as everyone is concerned, this is the way things have always been. The different major civilizations can be different in major ways (e.g., westerners are polyandrous, centralians encourage male homosexuality, easters expect women to be serially monogamous and men compete to be a woman’s last baby-daddy, the one who gets to stay with her through menopause and into eventual retirement), but they all have no place for non-witch women in their sexual politics. The ones who did are thought of like the Philistines or Barbarians of our world.
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### [Eugenics](https://en.wikipedia.org/wiki/Eugenics).
In a medieval setup they will not have access to DNA sequencing or even knowledge about DNA but the witches know (by methodic observation and deep knowledge of nature) how the genetic inheritance work.
Sperm have more variety in [genetic recombination](https://en.wikipedia.org/wiki/Genetic_recombination) than egg cells ([spermatocytogenesis](https://en.wikipedia.org/wiki/Spermatogenesis#Spermatocytogenesis) result in four cells while [oogenesis](https://en.wikipedia.org/wiki/Oogenesis) produces only one) so the genetic content from sperm is valuable for eugenic process.
So, witches are told by their coven leader to give birth to males and with whom to mate, only chosen witches are allowed to give birth to females.
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In the end, all of us know [where this setup leads to](https://en.wikipedia.org/wiki/Bene_Gesserit)...
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The Iroquois Confederacy had a rather unique gender role system. Women had more political power, but men were vital to society as well. Generally, Men were used in matters of foreign affairs - Diplomacy and War. When the confederation formed, Men were sent to the confederation council (the Sachem or Grand Sachem) to represent the local tribe's female exclusive council. The local councils had more power technically, because they had the right to recall their representative (called Horn Knocking due to ceremonial importance of deer horns in the headdress among the male leadership). Both men and women councils had to reach a 75% consensus for a decision to pass.
In the home front, the women owned the property and it was passed down matrilinearly and men were adopted into the family of their wives and was considered on the level of his wife's brothers in the household. Men were also exclusively warriors but only women had the ability to declare the war. This lead to a rather unique war philosophy called "Mourning Wars" which sought captives to replace deceased members of the family and tribe (often the war dead from a prievious attack or raid). Thus, the goal of wars for the Confederacy was to capture as many people and bring them back alive to be adopted into the tribe, not territorial gains. Thus slaughter of the enemy was seen as a bad tactic as it decreased the success of the war, and the war could be a failure if the number of war dead on their own side was not offset by the captives taken, so the Iroquois were quick to retreat.
Those that did not go to war were declared cowards by the clan mother and it was taboo for women to marry men declared as such. Thus, men went to war to prove they were worth of marriage. Typically, a male War Chief was declared who would have authority on the battle field but not much authority at home.
All of this existed due to the creation myth, which held that women were stewards of the land and must be respected in their decisions. Men traditionally hunted game while women tended to the farm and the land the clans controlled, and thus had greater importance. Thus their ability to name leaders of the tribes and clans. While men would be the face of the Confederacy to outsiders, women were often the power behind the throne. This could translate into a matrilinear society where the magic of women was such that it was better for them to remain close to the home and not participate in the day to day management of the government by traveling to meeting bodies or court favor from the courts, but the men worked for them, not the reverse, and if they didn't like the outcome, they could remove the offender from office.
(It should be pointed out that Iroquois aren't considered a Matriarchal society... both Genders had political power and were quite important in governing the nation.).
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**Out of kindness**
Because there is somehow a great psychic/psychological burden to witchcraft that it is, in itself, some kind of great curse or scouring: the greatest curse the witch can craft being to induce witchcraft in another. This can be the case despite external benefits. There are many stories where supernatural gifts are a burden to the beholder.
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It's a matriarchy, so women are elites that have all the power. Lots of men all compete to be the best man to produce the next generation of witches, so more men equals more choices.
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The society allows for witches to have multiple husbands, so you have lots of male children to **marry them off to other covens in order to cement alliances**.
Marrying off daughters would weaken you, so use sons.
Also, everybody has magic - they don't need any particular material good, so you can't "buy" allies the same way you otherwise could. But what's the one thing a sensible witch can't make herself? Men that are safe to have children with. So you trade those.
As a final bonus, men can be pretty useful if you don't feel like casting spells to fetch water, build walls, and do other simple tasks.
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Human sacrifice is required for more complicated spells. The women certainly would not reduce the magic from the gene pool by sacrificing females/witches. That leaves those mostly worthless men as fodder for their dark spells.
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While in theory only one man is needed to get offsprings for good large willage of females, probably (if virginity is not required) powerful one (females) would prefere to have at least choise from man (not only one god or bad) eventually have even each ones harem.
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## Marriage as Business
In the first minutes of [Netflix's Explained](https://www.netflix.com/title/80216752) chapter about monogamy, the narrator states that some historians believe that marriage was invented as a way to have a "gain" for your family - a means to join forces with another "clan". They give several examples as to how marriage was used to join powerful families and mantain control over the ages (Cleopatra and the romans).
The reason for men to exist could be linked to that. If powerful witches have a high social standing, it would be only natural that a certain witch would have a male son to join two powerful "witch houses".
## Women are Rare
Women already play a central role in society without magic powers. They have children and thus, are the only ones capable of perpetuating society.
But what if having a female child was really hard?
Since they manage to control mana and be very powerful, there could be some magical BS that made women really hard to come by - to the point that witches would actually rely on magic to try and shift those odds for a better chance for a girl to be born.
Some people have already said here in here that maybe a newborn witch draws a portion of the mother's power. Maybe that's true and, therefore, only the most powerful witches could have a chance to give birth to a girl - and that would certainly take a toll on the mother.
Maybe it could even be a death sentence to try and give birth to a woman!
## Seventh Son of a Seventh Son
I don't know where [this saying](https://en.wikipedia.org/wiki/Seventh_son_of_a_seventh_son) originated, but it has something to do with great power.
Suppose all witches have to be the seventh children - after an unbroken line of six male sons - of a mother who, in turn, is a seventh children herself.
This would fairly explain why are there so much more men than women and also why they would rely on magic to have a lot of male children before a woman is born.
## An Unorthodox Magic Component
Having a male children could be a magic component for some desired spell - like eternal life.
Suppose there's a ritual that gives you 10 more years to live. Witches would certainly cast this spell multiple times through the years in order to live for centuries.
Of course it would have to be a high level spell and, therefore, require a lot of time and resources - and a male children could be one of these resources. In [this question](https://worldbuilding.stackexchange.com/questions/119171/what-would-be-a-good-metaphysical-component-for-a-spell), I tried to make a silly game where people would come up with crazy magic components for spells. For this particular spell, one of the main components could be "being pregnant with a boy" or "giving birth to a boy".
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The amount of mana available to use for magic is divided among the current witches. Too many accessing it's powers will diminish the powers of them all. Having more males ensures that the witches in power stay powerful. Have another female born when a witch is retiring (dying) or has died already in order to bring it back to balance.
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## Dowry, which actually caused a gender imbalance in China.
Men are expected to perform all of the non-magic chores. This includes gathering things needed by the household, feeding the family members, cleaning the home, and taking care of children and the elderly. Women can therefore focus their efforts on their magic. Although the practice may seem outdated to us, everyone does benefit by it, and it is the norm of that culture.
When a couple marries, the husband is expected to care for the wife's aging parents. This means the husband is no longer available to care for his own parents. At the time of marriage, the wife's parents compensate the husband's parents by paying a dowry. The practice is very common in various real-world cultures, although the roles of gender are usually reversed.
Something is causing couples to have fewer children. In China it was the One Child policy, but you can make up any reason you want. Supply and demand causes the cost of dowries to radically increase, which favors couples with sons and penalizes couples with daughters. Couples therefore choose to have more sons than daughters.
This actually happened in China, which now has 30 million more males than females.
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There could be a number of reasons,
1. Hierarchical Limits: If only women can practice witchcraft then daughters = power. If the covens live in a society, then they are most likely organized and their power is restricted. The most powerful covens are allowed to have the most daughters, lesser covens fewer. The main question with this though is why would they get pregnant if they were 'full' on the number of daughters they could have. Which leads to the next possible reason.
2. Maximizing Potential Members: So let's assume that the coven can only support so many members, either from the above scenario, or for some other reason such as available magic or resources. Logically they would want the best and the brightest. Let's suppose The coven can support 9 members but only has 8. Each baby born is examined, only daughters with the highest potential are carried to term, the rest become boys. This leads to an excess of male children.
3. Breeding Stock: In this world only women can use witchcraft, but what if the potential to use witchcraft is mostly inherited from the male side? In this scenario then some males might be extremely valuable, and some well, might be more expendable.
4. Cannon Fodder: Every army needs foot soldiers. Though from the description of the world Covens would already be on top. Perhaps as muscle to keep the non coven people in line and handle mundane tasks?
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**Economics and Resources**
Economics and the availability of resources has a huge impact on real world geopolitics and socials structures no matter which period you are looking at, you could use it in your world to explain at least in part the wanted behavior.
This point match with the "numerous ingredients" in your post. If resources aren't infinite in you world, there is probably a competition for resources between witches.
Witches would have a huge requirements of ingredients for several reasons :
* Casting spells
* Training in spells : how can you get better at magic without *actual* practice ?
* Increasing your own magic power : for example through regular consumption of elixir made from expensive components
* Building magical tools if they exist in your world (alchemy, wands, golems, magic jewelry, ...)
For all the reason listed above, the confirmed witches would already have a huge everyday cost in resources consumption and the training of new witches would also be extremely expensive. It would then be obvious it is better to focus the resources on a select few rather than share them along a lot of witches who will end up half-trained.
Chinese wuxia/xianxia novels use this mechanism a lot to drive competition between cultivators (people who train to become immortals like in Chinese myths)
If you combine this struggle for resources with other reasons that make it unacceptable to leave women untrained in magic, you get a mechanism to explain the imbalance in the male/female population.
This reason could be social stigma as suggested in another answer.
Or a stronger practical reason : every woman is born with magic whether trained or not and untrained, and if left unchecked accumulate mana over time, releasing surges of wild magic randomly (maybe only once a certain age threshold is passed).
These women would basically be walking time-bombs and witch training for young/teenage girls could easily be made compulsory (at least in civilized parts of the world, I'm not sure how medieval or modern your world is).
Combine the mandatory magic training with the limited resources and it could make giving birth to a female child a matter to plan ahead for most witches, making them use the sex choice spell to have male offspring most of the time as males would provide mundane workforce without the resource strain.
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The Witch tax.
Witches are dangerous. Local governments fear nothing more than rogue covenants. Every girl born must be entered into the system. This is expensive. There is a tax collected from every girl's parents. This tax pays for school, social education and frequent visits from the "caretakers". This tax is not cheap.
If the parents can't pay the tax the child is drowned. Any attempt to hide a girl is punished by death.
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How about aging? If a witch is able to prolong her life for hundreds of years, each female offspring represents potential direct competition. If a witch has 2 daughters and in 20 years they are a match for her power what happens if one of them decides they really don't want to wait for mom to die off before grabbing that inheritance. What if they rebel against mommy and join a competing coven? Males, on the other hand, have no chance of affecting mom's power base so are much safer.
Additionally, males though not able to directly use the magic still share half of their genes from their mother. Powerful witches could create alliances in an attempt to improve magic bloodlines by marrying off their male descendants to other powerful witches.
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I wonder why no military from history *wouldn't* make their spears and swords barbed. If the point of thrusting is to damage vital organs and cause massive blood loss, wouldn't it make more sense to design your blades to be hooked in such a way that it can tear open an exit wound and still be able to be removed with enough ease?
Would the advantages of this outweigh the downside of your fighting ability possibly getting hampered for a second or two?
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War is not a turn based game, where you can take all the time you need to make your move, nor is a movie or an anime where the enemies politely attack one at a time.
Once you have hit an enemy with a blade/spear, you want to have it available again as soon as possible: having to struggle for pulling it out, as it would be the case for a barbed weapon, will make you tired much sooner and will let you exposed to attacks from other enemies. Even during World War I the soldiers quickly learned that when using a shovel as a weapon it was much better to use it to hit "flat" with it and not with its edge, because the edge would have gotten stuck in the enemy.
Additionally a barbed blade would need to be used with tip attacks and not with slashing attacks, which would make the blade much less versatile on the battlefield.
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The point (so to speak) of a thrusting attack is to concentrate as much force as possible on as small an area as possible. Greater concentration of force means it's easier to sunder armor, break bone, and rend muscle. So it follows that you want your point to be as keen and narrow as possible (while also not being too structurally weak) so as to impact as small an area as you can.
Barbs, however, *spread out* the impact. As soon as the barbs touch the enemy, they're distributing your carefully mustered force over a much larger area and the attack becomes much less potent. No armor split, no bones broken, no muscle torn.
One of the major purposes of body armor is to distribute the force of a blow across a wide enough area to make it harmless. You don't want to *help* your opponent do so. You'll have a hard enough time overcoming their armor as it is!
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# Cripple versus Kill:
Certainly if you only have one opponent, then barbed weapons are fine. But if you kill your opponent with a thrust, you gain no advantage from tearing at his insides. In war, you either want to kill many opponents quickly or injure many opponents and make them ineffective soldiers.
# Melee:
The guy in front of you with a melee weapon is a hazard to you as long as he can fight. It is much better to kill or cripple him quickly so he can't kill or cripple you. You can stab him and damage a vital organ - at which point, you will need to withdraw your weapon and do the same thing to the next guy - or if armor doesn't permit, you hack and crush him to death (in which case, you don't want your weapon stuck in a wound because you need regain velocity to apply more energy to him).
Adrenaline is a funny thing, though, and your opponent will likely keep fighting until you are dead or crippled - and then collapse from slow blood loss. A Pyrrhic victory is a little too late for my tastes.
The point of impact of your weapon should be tiny for a thrusting weapon to maximize penetration of armor and depth of the wound, maximizing the likelihood of lethal organ damage (or massive tissue trauma from cutting or crushing, in the case of maces, axes, etc.).
# Missile weapons:
In a missile attack, the rules are a bit different. You are trying to get him first. Here, if he is injured, he stops being a threat to you because he is likely to retreat. So at that point, the value of maiming him permanently goes up. **You DO see barbed arrows for this reason**. Additionally, you are not typically re-shooting an arrow right away that is stuck in an enemy somewhere. Your enemy MIGHT shoot your own arrows back at you, also increasing the value of barbing the arrow (it's harder to reuse). Roman spears, for example, would bend after being thrown so they needed to be repaired to re-throw.
But even here, there is value in un-barbed arrows. If you have lots of time for your opponent to bleed to death and die in agony, barbs are great. By all means, they are perfect for sieges where attrition needs to be maximized. You might be BETTER with a wounded soldier than a dead one in a siege - he needs to be cared for and fed, but is useless. But the chief way the arrow *kills* is in a deep, penetrating attack. Barbs don't help with that, and *may* even reduce effectiveness. If you anticipate winning the battle, you are likely to want to reuse your arrows later, a task made much easier without the barbs making the arrow extraction difficult or impossible. (the tip of many an arrow has been found in the bodies and bones of dead soldiers).
* All the hunting arrows I've ever worked with were designed with a mix of tiny razor blades (to maximized cutting) with a very narrow point (to optimize penetration). Unfortunately, through most of history you could only make an arrow that did one thing or the other really well.
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The problem with a barbed weapon is that if the enemy is armored (very likely) or even just has bones (practically certain) the weapon may get stuck and be impossible to withdraw in a reasonable time (= 1-2 seconds in battle, *at most*). A common spear head can still lodge (between ribs or in the skull, for instance), but isn't anything likely to do so as a barbed spear point.
The same is true for why heavy piercing weapons like picks weren't used much in combat: too prone to getting stuck enough to take time you won't have to retrieve.
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## Real war
Real wars tended to be 99% marching and 1% battles. Then it's just politics. A side breaks and flees, you hunt some, get prisons, and get a favorable agreements with the other state. GG.
Point is that it's not about min maxing your army. You just want to achieve a particular goal. Weapons are just tools, if anything all of war is just a tool.
Whatever works good enough and checks all the boxes wins.
## Handling
Imagine a baseball bat with razor blades sticking out everywhere. Terrifying, for sure. But how you gonna be marching kilometers daily with that thing?
A spear has just one sharp and dangerous end, I know some had two. You can easily march with it in your hand and have little danger of sneezing and getting a dissection as a result.
You can throw a bunch of spears in a cart and still not worry too much.
A sword has a scabbard. Also swords in particular are both a side arm and a daily carry self defense, or statues symbol, weapons. Civilian life and defense would be effected by military practices. You have a rapier and a war rapier, some changes but it's practically the same. Instead of having a war rapier as a war weapon and a quarter staff as a self defense weapon, it changes too much.
But back to just the practical side of things. Being able to easily and safely handle your weapon is not a small consideration. Obviously it's a bit different but ammunition and its safe handling is an important part of all armies. Also protecting storage ammunition in stuff like tanks and so on, but that's a bit different.
Barbed wire spears, a flail with a lot of heads...etc are just too challenging to even move around with. And nobody wants to burden themselves further with creating scabbards to safely handle them not just because of the money but also just practicality. It burdens the army more, costs more, and slows down the time it takes your individual solider to be ready for combat.
## Armor & shields
This is a very broad subject. But generally speaking that type of weapon is terrifying against naked human flesh. But even with bronze swords you have not only shields but also body armor. Anything from mail to some sort of hardened leather to just padded stuff to even layering your clothes.
It's just not effective at all. Sure. If you corner a half naked or lightly clothed human and swing a barbed and sharpened metal thing. But when you are facing armored humans with shields and spears it's just not as effective.
## How combat works.
Think of a spear. A one handed spear with a thrust and cut head. Now think of the most common battlefield tactic: shield wall. Now think of what part actually has contact with the enemy?
Yes. A very small part when you thrust, or a bit more when you cut.
Now think of the formation. You have a spear and a shield, your unit is not a Hollywood movie where the 100000 combatants battle ends up being 600 having fun 1v1 fights.
Real war is not a video game. You don't just have room to jump, roll, dodge...etc. You are part of a formation and limited in space and movement. Roman legionaries for example where trained in how to draw their sword with their right hand and in a reasonable movement that did not take space.
Having 6 barbed heads for your spear has no benefit if you are not able to contact them with the enemy, we already established limited in space. You just can't run around an individual enemy and contact their body with your weapon.
You have a limited window to attack and a spear, or similar weapons, are perfect for that. Anything is useless weight and materials, really.
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Good answers already. My addition is that barbed melee weapons take more training and skill to use. I train with Polynesian weapons which have multiple projections. They can catch on you or your own people if not used properly before they ever hit an enemy.
Likewise, in actual combat they can be used against you if the opponent can hook into them with their weapon and rip yours out of your hands. I have a specialised weapon designed in part for this exact purpose. Difficult to use, but feared because once it captures a weapon, they either drop it immediately or lose the use of their hand forever.
[](https://i.stack.imgur.com/zMXYJ.jpg)
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Interesting question. I personally think that building a barbed spear with crude, stone-age technology would be a lot more difficult than just making a normal spearhead. Even with more advanced techniques developed in the Middle Ages, it would still be easier to construct a normal spear or sword--and keep in mind, these 'normal' weapons are deadly as well. If you receive a direct hit with a sword or spear in a vital organ, barbs won't do much: you'd be dead either way. It is only when you receive a glancing blow (say, in the arm or leg) that barbs would exacerbate injuries.
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## Humans are Pretty Easy to Kill
Inflicting "more damage" was generally not required with melee weapons. A three inch deep stab wound in the gut is fatal without rapid, modern medical attention.
So a Roman gladius would be plenty deadly with a very shallow stab. Doing "more damage" might have the advantage of killing the enemy faster (because they bleed out more quickly), but that's probably not necessary. A mortal wound is likely to put the enemy in shock, and blood loss makes it hard to keep fighting, even if actual death takes many minutes.
A barbed weapon is much harder to build/maintain, harder to train, more likely to get stuck in the enemy, etc. and thus the simpler stabbing weapon - which is "good enough" - has historically been the accepted answer.
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