text stringlengths 22 2.11M |
|---|
[Question]
[
Related:
* [Technological development without writing](https://worldbuilding.stackexchange.com/q/40240/22685) (related to general technological development without writing)
* [How would a society without linear alphabetic writing have devised human-readable computer inputs?](https://worldbuilding.stackexchange.com/q/60817/22685) (related to computer system development with writing, but with pre-composing characters rather than non-composing Roman letters)
A civilization has reached a high level of cultural and technological development without the development of reading and writing. They are at least equivalent to the Incas, and may have some classical Greek tech like Hero's steam turbine and coin-operated vending machine. The society places a strong emphasis on the development of memorization techniques, and the average educated person can recite at will what, in our world, would be multiple textbooks and years' worth of articles, stories, lore, and news. They aren't primitive - they can do advanced math, understand and follow multi-step directions, describe the natural world at length, apply theoretical and empirical scientific processes, etc. - they just can't read and are not likely to develop such tech anytime soon.
This civilization has been experimenting with fine gearings, vacuum tubes, logic gates, and other early computer tech, but they seem to be unable to make the jump to writing software due to their lack of literacy.
How would this civilization develop general-purpose computers? To some extent, [punched cards](https://worldbuilding.stackexchange.com/a/60827/22685) can be used to encode *numbers* and perhaps basic operations (e.g. add, load, display), but without the knowledge of alphabetic, syllabic, or other writing, it seems a stretch for them to begin encoding *arbitrary text* onto the cards, such as a user interface, human-understandable error messages, or downloadable content.
\*How does such a civilization move beyond using computers to do *basic math* (e.g. "*dot dot dot* plus *dot dot* equals *dot dot dot dot dot*") to having general-purpose computers, without first developing reading and writing?
The exact *form* of the computers are not important as long as they are general purpose ones, so a steampunk Analytical Engine is fine as long as it can be built without writing and used by a person with no knowledge of reading and writing (but perhaps with an extensive scientific, engineering, literary, and cultural education).
[Answer]
First of all, I don't think that a society without some sort of notation could ever achieve the sort of technological sophistication that you specify. Although I couldn't find any sources for human limits, experiments [show that animals are incapable of understanding numbers past a certain count.](https://en.wikipedia.org/wiki/Number_sense_in_animals) When people (who don't have number synesthesia or something) imagine a large number, they are thinking of the script-notation of that number. For example, when I think about the number 256, I'm not thinking about 256 items of something, I'm thinking of the numerals "2", "5", and "6". I don't and cant can't imagine 256 things in my head, I just understand the abstract concept of hundreds, tens, and ones places. Disclaimer, I'm not a neuroscientist or anthropologist but I don't think it would be possible to develop advanced mathematics without some sort of real-world information permanence system (which could be called writing).
Still, if you're dead-set on having no written or physical form of information storage that people can read (that includes pictograms or informational art!), then I still have a solution for you:
**Bio-engineered computers**
Now while your society's technological level is nowhere near CRISPR or gene editing, selective breeding, training, or a dash of handwavium can make the complexity go away. Since the society had no conceptualization of physical writing and is instead focused on memory and mental prowess, training animals to preform tasks would be a logical step for them.
For example, mice could be "programmed" (trained) as simple computer chips, say in the vending machine. The vending machine mice are trained to recognize coins of certain denominations and pull levers inside the machine accordingly. For more complex operations, animals could be trained in certain swarm behaviors and preform swarm calculations. For example, [colonies of ants could be used to solve optimization-problems](https://www.sciencedirect.com/book/9780124051638/swarm-intelligence-and-bio-inspired-computation) and it's been shown that [animals have an instinctive understanding of path optimization (essentially calculus/integration)](http://www.math.pitt.edu/~bard/bardware/classes/0220/dkc.pdf)
Furthermore, these types of Bio-computers have already been seriously considered by the military when transistor-based computation was still to complex. [Notably, the pigeon-guided missile](https://en.wikipedia.org/wiki/Project_Pigeon), where pigeons were trained to act as "flight computers" for missiles and steer the bombs towards their targets.
Depending how far you want to go, you could also adopt "biopunk" elements into your narrative, by which I mean that some discovery or technique makes biological manipulation waaaay easier than it is in reality. For example, in such a world, the "computers" could be specially grown brains-in-vats and supercomputers could be interlinked networks of grown brains. Simple automation could be provided by growing nervous systems and tuning it's automatic responses to whatever is desired. The people could also modify themselves to make them smarter and be able to link into the "internet" which is really just a highly complex biological brain-to-brain interface.
[Answer]
**Say hello to the Abacus**
A style of computer first built in 2700 BC. It does not rely on any written words to be able to be used to perform relatively complex calculations, and can be taught to illiterate people quite easily, and made using stone aged technology.
[](https://i.stack.imgur.com/aDw1o.png)
While writing technically predates this technology, its construction and usage is simple enough that you would not need to first discover the written word to spread its usage. Because data is stored by bead position, there is no need for formal writing to track complex values; so, over time this device could become common and studied enough that "computer scientists" would begin making custom mechanical devices such as the [Antikythera mechanism](https://en.wikipedia.org/wiki/Antikythera_mechanism) which could use handcranks and ratios (calculated on your abacuses) to perform programed operations such as calculating solar events.
Many of the craftsmen that made these sorts of ancient calculators would have likely done so without formal reading and writing since literacy was still so rare back then.
The technology to make "general purpose" computers the way we think of them requires culminating many lifetime's worth of knowledge and massive co-operation making it WAY too complicated to get to without reading and writing. However, it could be possible to construct programmable" devices similar to the Antikythera mechanism where one would own a set of gears and shafts that could be reorganized like erector sets into different programs. Such machines could perform any number of linear mathematics, but more complex computations that require any sort of compounding values would probably not be an option.
[Answer]
The whole thing could be based off of noise sensitive technology. It could use noises to record information and then translate it into code. You could still make a computer that functions with elementary logic that uses sounds to interface and code.
[Answer]
One thing that this immediately reminded me of is [redstone programming](https://www.dummies.com/games/engineering-with-redstone-in-minecraft/) in Minecraft. Perhaps with simple logic gates, your society could program some basic functions, but as others have said, you'd be hard pushed to develop anything too advanced without at least *some* language.
[Answer]
More than likely the computers would output something like morse code beeps, or the ringing of bells. The input would be taps on a single button which would put instructions into the machine one at a time.
It would be a long and involved process to use a computer, but it wouldn't be much more difficult than what early computer operators in our world had to do.
[Answer]
You need some replacement because you need information storage and sharing. No computer is possible without information storage.
As others has pointed out, one only can imagine brain memory as information storage which would not resemble writing (any hard drives or DVDs are still like writing, just very dense).
So your computer can only be brain based.
] |
[Question]
[
I have a friend who is a really nice guy. The problem is that he was born as a half demon. While he looks completely normal, he possesses a spirit inside him called "Amon". This being forces him to experience certain demonic urges, which he must constantly suppress while awake.
When my friend falls asleep, he loses control of his body to Amon. The demon must wait for him to fall into his REM cycle, which is the deepest mode of sleep in which the human begins to dream and will not be easily awakened. During this time, my friend becomes possessed and gains his demonic abilities, such as super strength, speed, durability, and power of flight. The demon then goes out to do horrible things and commit murder and mayhem. When cornered by this creature one night, I asked this creature what it's name was, and it's response was that "**I AM**.....**DEVILMAN**".
[REM sleep is supposed to be the cycle in which your muscles are paralyzed](https://www.sciencedaily.com/releases/2012/07/120711131030.htm), which prevents your body from moving. This is intentional as to stop you from acting out your dreams, and should prevent an evil spirit from taking you over. How is it that Amon is able to bypass this human drawback created by millions of years of evolution?
[Answer]
>
> The demon must wait for him to fall into his REM cycle, which is the
> deepest mode of sleep
>
>
>
EDIT - A minor frame-challenge here. REM is not only characterised by sleep-paralysis, it also is when we dream. If a person is essentially good then they will be the same way in their dreams and unlikely to go on a rampage of evil even if the demon could manipulate the dreams.
>
> How is it that Amon is able to bypass this human drawback [of paralysis]
>
>
>
A simple way to bypass this problem is to avoid REM and go for N3 sleep, the deepest stage of non-rapid eye movement (NREM) sleep. At this point his victim will be most like a zombie and yet still able to perambulate. Note that your friend will have no memories of the evil activities on waking.
An ex-girlfriend of mine would sometimes walk around and talk nonsense during this stage of sleep. She was impossible to wake and never had any recollections of it the next day!
**Answer**
Amon spent a long time searching for a victim who was a **sleepwalker**. Unfortunately for your friend, he fit the bill.
>
> Why some people sleepwalk is not fully understood, but researchers
> have discovered a few risk factors. For example, sleepwalking tends to
> run in families, which indicates a genetic link.
>
>
> According to researchers at Stanford, people with certain psychiatric
> issues, such as obsessive-compulsive disorder and depression, have an
> increased risk of sleepwalking. Also, people who are prone to the
> disorder may be more likely to sleepwalk when they are sleep deprived,
> anxious or have an illness.
> <https://www.sleepassociation.org/sleep-disorders/more-sleep-disorders/sleep-walking/>
>
>
>
[Answer]
How can a demon take control of a human body during REM sleep? All they have to do is...
## Follow the solution procurement process
If, in the course of performing their assigned tasks, Amon the Damon determines that it makes business sense to take control of your friend’s body during rapid eye movement (REM) sleep, they needs to follow the regular solution procurement process as outlined in the relevant HellCo corporate standards and implemented by the Hellish Procurement tools on the infernal intranet, accessible by individual-contributor demons.
Not having yet consulted with HellCo, all can do is make an informed guess of the big outlines of such an underworld process. Specific details may vary, but the gist of the process is almost certainly conformant to the uniform Heaven and Hell best practices.
1. Amon first needs to raise their request with their immediate line manager, during one of their regular one-on-one meetings. They should go into the meeting prepared with a short PowerPoint presentation describing (a) the specific tasks which require them to take over your friend during REM sleep, (b) the potential business impact, estimated, of being unable to complete those tasks in time, (c) the estimated cost of the solution, expressed in Standard International Damned Souls (SIDS) equivalent.
2. After obtaining the buy-in from their immediate manager, and securing an approval e-mail, Amon needs to log in to the infernal intranet using the corporate Venial Private Network (VPN), and go to the Hellish Procurement portal. In the portal they must initiate a new requisition, and select a catalog item, under Solutions › Possession › Unwilling › Asleep; the tool will provide a cost calculation, based on the automatic selection of the lowest available price, and an estimation of delivery.
3. When making the requisition, Amon must not forget to attach the e-mail from their immediate manager giving explicit approval; they must fill-in the reference ID of the project; and in the comments field they must insert a short description of the business requirements.
4. Note that some solutions available in Hellish Procurement provide a functional demonstration; if such functionality is available, the corporate procurement standards require that Amon avail themself of the possibility to test the solution for compatibility and suitability. For example, several possession solutions for unwilling and asleep subjects have a try-before-you-buy version capable of providing limited control over the subject, usually involving either inducing a partial erotic dream (SFW imagery only, no finishing) or tossing the cover sheets. Amon is responsible to download and install the trial version; they must mention in the comments field that the trial was successful.
5. In all cases the final responsibility for the business adequacy of the requisitioned solution lies with the requestor. Amon must demonstrably perform due diligence in order to make sure that the expenditure will allow completing the assigned tasks. Failure to perform due diligence to the satisfaction of the Procurement Oversight department risks disciplinary action, up to and including termination from HellCo, involuntary separation and assignment to Heaven in the role of a singing angel.
6. Solutions are always delivered electronically over the infernal intranet. Physical delivery is not allowed. In order to successfully download the solution, Amon must use the download link within three business days from the time of the dispatch of the e-mail containing the link. Be aware that solution approval and download e-mails are sent from Central Hell time zone. In most cases, an external USB stick is required, not provided by HellCo. Amon must use their own stick, or a stick procured and expended by the project.
7. Once the solution has been downloaded, Amon must install it as a plugin in their unwilling subject possession working environment; the solution will then provide the functionality of taking over the body of the unwilling subject while in REM sleep.
If Amon does not feel confortable installing the solution they must raise a ticket with the Infernal Technologies (IT) Support, by clicking on the IT Support icon and filling in a request form. Installation services are provided free of charge from the corporate worst-shore incompetency center in Tartarus.
The number of possession instances, and the duration of the possession, depend on the available license. Using the procured solution for any purpose other than performing the assigned tasks in the specific project is forbidden; HellCo has strict agreements with the solution providers, and breaching these agreements risks disciplinary action, up to and including termination from HellCo, involuntary separation and assignment to Heaven in the role of a singing angel.
[Answer]
**How can a demon take control of a human body during REM sleep?**
I don't know about daemons, but REM sleep is the perfect time for this to happen.
REM sleep is very similar to what happens during hypnosis. The conscious mind (inner monologue) is turned off, and one's perception of current reality is controlled by the hypnotist's voice or by the brain's dream generation mechanism.
[Wikipedia: Hypnosis](https://en.wikipedia.org/wiki/Hypnosis#Historical_definitions) says:
>
> Joe Griffin and Ivan Tyrrell (the originators of the human givens
> approach) define hypnosis as "any artificial way of accessing the REM
> state, the same brain state in which dreaming occurs" and suggest that
> this definition, when properly understood, resolves "many of the
> mysteries and controversies surrounding hypnosis". They see the
> REM state as being vitally important for life itself, for programming
> in our instinctive knowledge initially (after Dement and
> Jouvet) and then for adding to this throughout life. They explain
> this by pointing out that, in a sense, all learning is post-hypnotic,
> which explains why the number of ways people can be put into a
> hypnotic state are so varied: anything that focuses a person's
> attention, inward or outward, puts them into a trance.
>
>
>
In the case of hypnosis, the automatic paralysis doesn't happen.
When your daemon takes over, all it needs to do is to disable the paralysis and insert its own input in place of the dream generation.
That's exactly what a hypnotist does.
You might find some helpful ideas in [What Is Hypnosis](https://www.why-we-dream.com/hypnosis.htm):
>
> All the many methods for inducing hypnosis are paralleled by aspects of how the REM state is normally induced and maintained. Shock inductions, when hypnosis is instantaneously induced through an unexpected occurrence, such as the hypnotist suddenly thumping a table or ringing a bell, fires the orientation response into action, just as happens at the start of REM sleep. And inducing deep relaxation creates the same electrical patterns in the brain as occurs in REM sleep.
>
>
>
] |
[Question]
[
# Setting
In a tropical shore, where a great river empties into the sea, there is a [zone of very high tides](https://worldbuilding.stackexchange.com/questions/124344/how-to-have-high-tides-in-the-tropics). The water level rises and falls by meters every day. In this challenging ecosystem, alternately baked under the tropical sun and drowned in salt-water, a species of corals has developed that is able to survive. When submerged, the coral polyps filter feed on nutrients washed down by the river. In the sun, symbiotic algae photosynthesize and produce energy.
These corals have built up great structures like termite mounds in the tidal flats. These mounts go no higher than the tides come in, for the corals must be submerged part of the day to survive. But there are great forces at work in this flood plain, forces that would destroy these coral monuments. The combination of rising tide and monsoon-swollen floods from the river create ferocious [tidal bores](https://en.wikipedia.org/wiki/Tidal_bore). Cyclones built up over thousands of miles of tropical seas to the north slam into the seashore with sustained 200 kph winds multiple times a year, pushing enormous storm surges with them.
# Question
**Can corals build up structures fast enough to survive the damage caused by this punishing environment? Or will the forces of wind and flood and tide pulverize the coral's would-be protective skeletons?**
# Considerations
* Assume the coral and its symbiotic [zooxanthellae](https://en.wikipedia.org/wiki/Coral_reef#Zooxanthellae) are evolved to survive the sun/submerge cycle.
* Assume the coral is subjected to the same limitations on growth speed as on earth.
* The 'coral' does not have to be coral! If another species of skeleton forming creature (mussels? barnacles?) is better for this task, that is acceptable.
[Answer]
There are tidal corals, and many do take quite a pounding, this is one way atolls form. However they are unlikely to form mounds corals are colonial and will tend to spread out and fill up lower areas (which will stay submerged longer) You will need a reason they form mounds instead of reefs.
You may want to look at **Stromatolites** they may be closer you what you want. They from all kinds of shapes depending on the local wave/flow conditions, and they are remarkably robust. Because they grow sheet by sheet (bacterial mats), you can get mounds and domes easier. It is the tidal forces themselves that keep them from forming a single giant mat. the spaces between them are subjected to more powerful forces keeping the mat from forming between them. Corals don't do this because high flow is actually better for a filter feeder.
[](https://i.stack.imgur.com/IG0ip.jpg)
[](https://i.stack.imgur.com/zQeP4.jpg)
Some of the freshwater ones form shapes remarkably like termite mounds since they don't have to deal with tidal/wave forces.
[](https://i.stack.imgur.com/KFVe5.jpg)
[Answer]
The hydrodynamic environment will discourage "termite mound" structures, but the corals may evolve other mechanisms to deal with the environment.
One of the simplest is simply to "sculpture" the sea floor to mitigate the tidal flows and currents. The corals could build a sort of "waffle pattern" across the seafloor to cause the currents to release their energy over the undulating seafloor surface. This will assist the coals in feeding as well, since silt and organic matter will be deposited as the currents are forcibly slowed down. (The natural reason for this to occur is ridges across the flow will cause the current to slow and dump organic materials, multiple ridges will build across the line of the current, but as the current itself will constantly change, the angles of the coral ridges will also change, resulting in a criss crossing pattern).
The ridges of the "waffle" will preferentially host the photosynthetic elements of the organism, since they will have greater exposure to the sun, while the lower parts of the coral will be domain of the filter feeders. This sort of coral will eventually need to develop some sort of mechanism to pass nutrients from the "top" to the "bottom", perhaps long tendrils or root like structures will evolve.
Other species of coral could also rise in this ecosystem, for example a form which builds its colonies in large cylindrical structures which might serve as "breakwaters" deeper in the ocean, being tall enough to reach for the sunlight, while at the same time being large and strong enough to resist the actions of the waves.
The environment will be constantly changing, since the corals will need to continuously build to rise above the deposits of silt, and the actions of large storms will break off sections of coral. Disease and predations will also affect the health fo the reefs, and so sector will die off, changing the local currents and eddies and forcing surviving corals to rebuild to reflect the new conditions, as well as opening up areas for new colonization to occur. Marine life will be quite varied, and any humans sailing in the region will find the approach to the river quite challenging indeed.
[Answer]
I doubt the termite mound shape is a good one to take the stress without fracturing.
A semi-spherical shape might, but then you'll have the landscape evolve into sorta undulated "tide plain" over time, advancing the river mouth into the sea/ocean.
That's also a way of lowering the environment pressure, a shallower sea water would be capable of storing/transporting less energy.
Some problems though:
1. high speed tides will wash away the silt. A good thing having a rocky bottom, otherwise new polyp colonies wouldn't be able to anchor on something, but then...
2. ... a new polyp colony (low height) will spend more time submerged, in less conditions of using photosynthesis. And still, it must thrive, fast, the smaller the more vulnerable. If it can do it submerged most of the time, what's the evolutionary pressure to develop photosynthesis capabilities and grow on height, when it's best abilities would push it to stay as close to the bottom, submerged?
Possible (still fictional) mechanism of establish/growing:
* thick, gel-like, protein membrane - sticky when secreted (mussel glue like), allows trapping nutrients when submerged. May capture silt as well
* the membrane dries out at surface when exposed to air, becomes a thin shell sealing the water in. When submerged again, the speed of rehydration is finite, the membrane resists intact for 1-2 hours (so that the speed of water near the bottom slows down) then develops cracks and allows the colony to secrete a new protein membrane. This explains why the growth happens more on the base than on top (the base spends longer time submerged), the result is a rounded mound like appearance of old colonies.
[Answer]
**When bad weather comes, your corals will get out of the way. By riding giant crabs.**
<https://www.sfbaymsi.org/single-post/2017/10/16/Marine-Science-in-the-News-Hitch-hiking-coral-and-hermit-crab-symbionts>
>
> D. heteropsammicola is the only known hermit crab to partner with a
> living coral. The hermit crab and the coral have a mutually beneficial
> relationship: the hermit crab prevents the coral from being buried in
> sea floor sediments by carrying it and providing transportation, and
> the coral provides shelter and protection for the hermit crab. In this
> specialized codependence, it is usually impossible to replace either
> partner with a different species.
>
>
>
I am not sure why they say it is the only one because I also found the "stag horn hermit crab". Maybe its pseudo shell is a hydrocoral, not a true coral. But this is the sort of thing I envision for your river delta: **monster crabs with huge corals on their backs**.
[](https://i.stack.imgur.com/QgXUJ.jpg)
Now scale it up. These crabs are big, I tell you. Big. And on their backs - great reefs of coral. The crabs move them from place to place and are not averse to taking a clawful of goodness from their rooftop garden. If the crab finds dead fish, the coral benefits from the messy eating habits of its mount.
When sediments come, the crab moves into faster water to wash things away. If there is harsh weather, crab and coral head down to deep water to ride things out. On a nice sunny day you can see all the crabs gathering in the shallow water to let their symbionts sunbathe.
[Answer]
Start a few millennia ago. Have a cypress swamp near shoreline. Water levels rise, water becomes brackish, kills off cypress. Or land drops for some reason - earthquake or similar.
Mineralification or petrification of the wood and knees starts due to exposure to soaking in salt water.
Water levels continue to rise, what was the swamp is now part of the mud flats of 5-6 feet underwater, depending on stage of tides.
All those cypress trunks and knees that started turning to stone have provided a base for oysters, barnacles, anemones, algaes, and corals to attach to and start growing. Go to any sea side pier or dock and you can see this in action on the wood or cement pilings.
Eventually, you have these pillar like things made of layers of the remains of all those crusty animals and maybe even some of the petrified wood in the center. Even with massive waves and high tides now pushing against them, the ocean side may wear down but the lee side is protected, and grows without issue.
You'll see some "layering" from top to bottom of types of critters that are making up your pillars. At the bottom you'll have more of the things that would prefer to remain completely submerged at all times. They can get by with some splashing and spray/mist from wave impact, etc. when the tides are out, but they aren't happy about it - this is where you may find your corals, and softer creatures that don't leave skeletal structure behind. The higher you go, the more of the creatures you'll see that are evolved to tolerate being out of the water for a few hours at a time - oysters, barnacles, etc. The stationary or attached bivalves that can close up and seal up and wait for a bit for water to return.
Height of the pillars will depend on what structure there is to support vertical growth, and how much of the support stays submerged or at least wet from spray/mist for how long during the tide cycles.
] |
[Question]
[
In an alien atmosphere, where methane is the main gas instead of oxygen and ammonia is the main solvent instead of water.
Similar to how photosynthesis on earth plants work, by taking in carbon dioxide and water to create glucose (source of food) and oxygen (waste product). What gas would plants on this planet take in alongside ammonia that would result in the release of methane as a waste product as well as their source of food.
[](https://i.stack.imgur.com/6pjuL.png)
For visual perspective-
NH3 + \_\_\_\_ + energy = \_\_\_\_ + CH4
Atmospheric composition if needed:
Nitrogen- 93%
Methane- 6%
Other trace gases- 1%
I hope this is more clear
[Answer]
What plants do on Earth is oxidize (remove hydrogen from) water, and use that hydrogen to reduce carbon dioxide into sugars. That process takes energy. An analog with ammonia and methane would be the following:
**2NH3 + C2H4 + Energy -> N2H4 + 2CH4**
What is happening is that the ammonia is being oxidized and its hydrogens being transferred to the ethylene, to form Hydrazine and Methane. According to Wolfram Alpha, this requires 83.2 kj/mol, and therefore would occur in a plant. The reverse reaction would release energy, with Hydrazine being used as food.
[Answer]
I'm not a biochemist. Biochemistry is super-duper complicated. The following is essentially wild speculation, but hopefully it can help guide your thinking.
---
The overall equation for photosynthesis on earth is:
$$6 CO\_2 + 6 H\_2O + \gamma \rightarrow C\_6H\_{12}O\_6 + 6O\_2$$
Here are the important things to note about this process, from the perspective of changing it. These features need to be present to allow for anything like the photosynthesis we see on modern earth:
1. The reaction requires energy to proceed (is endothermic), rather than releasing energy when it proceeds
2. The solid output of the reaction (glucose) is a store of energy that is stable enough not to spontaneously decompose
2. (A) Glucose is a moderately complicated molecule. This allows the biochemical system to manipulate it with a good degree of specificity using targeted proteins, and minimizes the chances that it will cause unwanted side reactions.
3. The byproduct of the reaction is a gas, which can easily escape the plant. Liquids are OK too, but not solids (which are difficult to transport out of the plant)
You ask about instead using the reaction scheme:
$$nNH\_3 + mX + \gamma \rightarrow iY + jCH\_4$$
You also posit that this ammonia exists in a liquid state (analogous to water). This is your first problem: ammonia boils at -33$^{\circ}$C. This is a problem because at this temperature, about 50$^{\circ}$C colder than on earth, and as a rule of thumb every 10$^{\circ}$C difference results in a factor of 2 change in chemical reaction rates. That means that reactions on this planet will take place about 32x slower than on earth, which makes it unlikely that an endothermic reaction like this could take place.
You have a few ways around this. Perhaps your biochemistry includes a ubiquitous reaction that is quite exothermic, which is used to locally heat life enough for reactions to happen at a reasonable pace. Perhaps life only grow around geothermal hot-spots, where the temperature is locally higher and the ammonia is gaseous. Or perhaps the planet has a similar temperature to that of earth, but an atmospheric pressure about 10x higher, allowing liquid ammonia at room temperature (this likely creates its own set of problems).
Anyway, passing that on, let's see if we can come up with a moderately stable, moderately complex nitrogen compound to replace sugar. That will guide the rest of the reaction. I think an amino acid is probably a decent choice. I'll use glycine, because it's simple and this is already hard enough as-is:
[](https://i.stack.imgur.com/3xDCY.png)
Now, we have the reaction scheme
$$nNH\_3 + mX + \gamma \rightarrow NH\_2CH\_2COOH + jCH\_4$$
We can (stoichiometrically) satisfy this reaction using propinoic acid
$$NH\_3 + CH\_3CH\_2COOH \rightarrow NH\_2CH\_2COOH + CH\_4$$
Based on a quick look at the standard enthalpies of formation, this reaction should be endothermic\*. Check. Glycine is a relatively stable solid (we produce it all the time in our bodies) that is moderately complex (complex enough to be used to build proteins at least). Check. We're consuming ammonia and producing methane, as you asked. Check.
So this is my submission for your photosynthesis. The next step is to come up with whatever kind of crazy pathway this reaction schema could possibly use. However that sort of thing is way over my head (even photosynthesis on earth is really very complicated, involving lots of electron transfer and stuff), so this is where I'll leave you.
Happy worldbuilding!
---
$\*$ The enthalpies of formation I found are as follows (rounded quite a bit):
* Ammonia, -45 kJ/mol
* Propinoic acid, -510 kJ/mol
* Methane, -75 kJ/mol
* Glycine, 1430 kJ/mol
Thus the overall reaction has (45 + 510) < (1430 - 75) which implies it will not be spontaneous, with a net endotherm of about 800 kJ/mol. I believe this is a bit under half the endotherm of photosynthesis on Earth.
[Answer]
You only have one option: **hydrogen.** And that would work fine. Your photosynthesis is the reverse of photosynthesis in an oxidizing environment.
Hydrogen dissolves in ammonia. Hydrogen gas would be available in your reducing atmosphere, floating around in equilibrium with the ammonia.
Your heterotrophic creatures "eat" long chain alkanes by maximally reducing them to methane with the hydrogen - just as in our oxidizing environment we eat long chain carbohydrates by maximally oxidizing them to CO2 with oxygen.
Your autotrophic photosynthesizers produce their alkane food by stripping hydrogen from CH4 and forming long chain alkanes. CH4 + energy -> H2 + Cx H2x+2.
Just as earth plants strip oxygen from CO2 to produce sugar.
[Answer]
Today I learned that photosynthesis must result in a complex compound. Well, I'm not a biochemistry expert, so learning is to be expected.
Therefore, there are 3 constraints on the photosynthesis reaction.
1. Results in a complex molecule.
2. Uses a minimum of oxygen, since the only accessible oxygen is in water ice, which is hard, relatively, to get
3. Uses Nitrogen to store energy.
I've come up with the following equation:
**8NH3 + 3C2H4 + 2CO2 -> CONHNH2NOHN2 + 6CH4**
As you can see, it uses a minimum of oxygen, results in a moderately complex compound, and uses plenty of Nitrogen.
Ethylene must be on the reactants side, otherwise there would be no place to dump the unusable excess hydrogen. French hydrogen would escape the atmosphere and therefore make this world too open of a system.
Additionally, like glucose, CO2N4H6 (the food product), can bind with itself to form chains. This is extremely useful as both an energy store and structural material.
Using average bond energies, this reaction needs 1352 kj/mol to proceed, comparable to Earth's photosynthesis which needs 2801 kj/mol to proceed.
But wait! That's not all! The compound here, whose name I do not know, has a better energy density than glucose. Per gram if glucose made, it yields 11.7 kj. However, this chemical, CO2N4H6, yields **12.7 kj** per gram.
Note: The resulting compound is like Carbohydrazide except that the hydrogen on one of the Nitrogen bonded to the carbon is replace with a hydroxide group.
Hope this is a better answer.
Thanks to Ilmari Karonen for his comments on making this realistic.
[Answer]
**Cyanide world.**
Your other question
[Appearance of an Ammonia World's Atmosphere](https://worldbuilding.stackexchange.com/questions/203631/appearance-of-an-ammonia-worlds-atmosphere)
got me thinking more about this.
Here is my new idea for the cycle.
1. Photosynthesis: energy + N2 + CH4 -> HCN + NH3. Energy is stored in the CN triple bond.
2. Heterotrophs: NH3 + CN -> CH4 + N2
I admit I am struggling mightily with the enthalpy of the heterotroph part. I would post to the chemistry stack but I am sure they will feel it is below them. Any help with that most welcome.
Then the cellulose / sugar equivalent is nitrile rubber!
<https://en.wikipedia.org/wiki/Nitrile_rubber>
[](https://i.stack.imgur.com/p4mZw.png)
A good polymer for a low oxygen world, and a good sugar equivalent.
] |
[Question]
[
**Edit:** I've written an answer of my own now, and I'd appreciate it if any of you informed on the subject of evolution could review it, then inform me of its plausibility, via the comments (Of the answer).
---
There are four other questions in my series of such, which I am asking to deal with problems I have encountered while working on my current worldbuilding project, which seeks to portray the biology of fantasy creatures in a viable way. The last was [How can I explain the evolution of my giants?](https://worldbuilding.stackexchange.com/questions/114289/how-can-i-explain-the-evolution-of-my-giants), and the previous three are linked there.
Now, I am asking about another of my fantasy beasts. The troll is featured in Scandinavian mythology as a burly, large-nosed beast that turns to dust when exposed to sunlight. Trolls are often represented in artwork as heavy-set, giant creatures, but the trolls in my project are slightly different.
My trolls are more lanky, semi-aquatic, with elongated snouts and long, goblin-like noses. Here is an illustration of a similar style of troll:
[](https://i.stack.imgur.com/QvUe8.jpg)
*Image source: [Spiderwick Chronicles Wiki](http://spiderwick.wikia.com/wiki/File:The_River_Troll.jpg)*
While not entirely the same, the basic anatomy is very similar. But what I can't figure out is: **What kind of animal is this troll?**
At first, I thought of a derived crocodilomorph with strong forearms, but I later discarded that theory because it has hair and a long, human-like nose, features which reptiles wouldn't have any reason to evolve.
My next idea was that it was amphibian. The hair could in fact be external projections of the skin - there is a frog which has such a trait. But that still doesn't explain the nose.
The only other possibility I can see is that it's a mammal. But what kind of mammal? It has quite a primate-like form, but a reptilian head and skin. However, I think this is the most likely of the three ideas I've put forward, but there are some things that need to be explained should you try to testify this statement.
So, to you, is this beast crocodilian, amphibian, primate or something else? I am open to any theory as long as it is backed-up with information and explains how the traits the troll has but its relatives don't evolve.
**Edit:** I've thought about this question more, and I can think of some reasons why certain traits would evolve. The hairlessness reduces drag underwater, strong forearms are good for swimming, and an elongated snout is good for snaring fish. Also, I noticed something *in* the picture I hadn't seen before. In the bottom left, it says:
*"These long arms are perfect for reaching over a bridge and grabbing passers-by"*
This instantly made me think of a crocodile's predation method, where they hide under the water and grab the snouts of zebra or wildebeest. This also supports my original crocodilomorph theory. If this inspires any ideas, or gives you clues as to why other traits would be useful for a water-to-ground ambush predator, answers would be greatly appreciated.
[Answer]
My initial reaction is that your trolls basic anatomical shape and habit suggests is evocative of three toed sloths.[](https://i.stack.imgur.com/P5sT3.jpg)
They have pretty similar body shapes and are pretty good swimmers to boot.
The hair and scales combo through me at first, but I can think of biological reasons why it might exist. If this creature is a scavenger with a strong digestive system, their hands and faces could be devoid of hair and instead have leathery skin or scales. Vultures use a similar adaptation to keep organs and rotting meat from sticking to them after they feed.
[](https://i.stack.imgur.com/LdMmy.jpg)
The strong forearms could be used to open up corpses and drag out the pieces they want, as well as discouraging other animals, such as dogs or large scavenging birds, from stealing the corpse (hyenas, for example, use superior size to discourage cheetahs from kills).
The snout could be great for finding rotting meat, particularly animals that died near or in water. Then your trolls could drag them onto island rocks or logs and eat in relative piece. Or, if you wanted to justify the forearms more, maybe they haul the carcasses into trees to eat, like jaguars.
So yeah. My vote is a scavenging primate, genus: Bradypus, species: Charon.
[Answer]
I've thought about this more, and I think my question could be answered. So, here goes.
---
The troll is a... drum roll please... crocodylomorph!
**Evolutionary history of the trolls (Family Macronasidae):**
11.8 million years ago, in Miocene South America, "super crocodilians" terrorized land and water. There was *Charactosuchus*, a giant gharial, there was *Purussarus*, the strongest crocodilian ever to evolve, there was *Mourasuchus*, a filter-feeding planktophagous crocodile.
But on the land too, there were more "super crocodilians" - namely *Barinasuchus arveloi*, quite possibly the largest terrestrial carnivore in the entire Cenozoic era. It was a sebesuchian - a relative of the crocodilians - and has been referred to as "an ecological vicar of the non-avian theropod dinosaurs".
[](https://i.stack.imgur.com/fs0dQ.jpg)
*Barinasuchus on the hunt. To give you a sense of scale, its prey is* Xenastrapotherium *, about the size of a black rhinoceros. Image source: [Jagroar on Deviantart](https://jagroar.deviantart.com/art/Prehistoric-Safari-Super-crocodilians-heaven-2-695785222)*
Unlike its semi-aquatic relatives, it had long legs suitable for running. Laterally-compressed jaws crushed prey, and it was so reminiscent of predatory dinosaurs that when scientists found its teeth, on their own, they thought that the theropods had survived into the Miocene.
Enough about the facts, now for speculation.
The Miocene-Pliocene extinction nearly wiped out the sebecosuchians (The branch of *Barinasuchus*). However, some populations of *Barinasuchus* survived, but they would not remain apex predators for long.
For the first time since the Cretaceous period, South America was invaded by fauna from the north. Carnivorans like the short-faced bear and saber-tooth cats drove most of the already-declining crocodylomorphs out of their niches at the pinnacle of the food chain. The crippled populations of *Barinasuchus* fled from the great savannas which the carnivorans ruled, and found refuge in isolated patches of forests that were springing up as a result of the cooling climate.
During this time, some *Barinuchus* learnt to hunt birds, which sometimes led them up trees in search of their prey. Eventually, they would become more accustomed to life in the trees, despiting showing little adaptation for it (Besides slight dwarfing). An example of this in the real world is the tree-climbing goats of Morocco:
[](https://i.stack.imgur.com/EjFij.jpg)
*In Morocco, many goats climb trees, despite not being adapted for it in any way. Image source: [CBS News](https://www.cbsnews.com/pictures/tree-goats-of-morocco-argan-oil/)*
At first, the arboreal creatures behaved almost like arboreal lizards, gripping the trunks of trees with their bellies pressed to the bark. Eventually, evolution took its course, and in millions of years, the ex-*Barinasuchus* became a new family, Arborisuchidae. The long legs of the terrestrial crocodile had helped it, now becoming strong arms for climbing. The crocodilians had taken on an almost primate-like form.
But the climate was still cooling, and now the lower rainfall in the ape-crocodile's habitat was making vast swathes of forest turn to grassland. The creatures migrated northeast, where there was tropical rainforest.
The cooling climate continued to take its toll on the last of the mesoeucrocodylians, but one resistant population took up living in the swamps and marshes around river mouths in their South American home.
Some days in these great rivers, mass floods would uproot tree after tree, creating vast floating mats of logs and vegetation. This still happens today in the Amazon and many other rivers:
[](https://i.stack.imgur.com/avQ87.jpg)
*Gigantic "rafts" of logs can contain entire mini-ecosystems. Image source: [Getty Images](https://www.gettyimages.ie/detail/news-photo/torn-from-hills-thousands-of-dead-trees-still-float-on-news-photo/134224360#/torn-from-hills-thousands-of-dead-trees-still-float-on-spirit-lake-picture-id134224360)*
Often, animals will jump aboard these massive rafts as they pass by, for protection, food or merely curiosity. Then, the log mats get washed out to sea and may sail across oceans. In this way, many alien taxa of animals colonize faraway lands - indeed, this was possibly responsible for the majority of Madagascar's entire megafauna.
The arboreal crocodylomorphs also boarded these rafts on occasion, and the currents of the Atlantic Ocean brought them to Europe. While the ape-crocodiles of South America died out due to predation, these European crocodylomorphs occupy the only large semi-aquatic niche in their ecosystems (A slot occupied by the caimans in their old home), so they flourish.
Europe's climate is much colder, so they evolved large, pointy noses to process warm air. A real-life example would be how humans evolved their noses when they moved north, whereas our brothers in the tropics have flat faces. These semi-aquatic trolls came to behave very like their cousins in the order Crocodilia, the Nile crocodiles (*Crocodylus niloticus*). They evolved long, filamentous integument called pycnofibres, a structure seen in pterosaurs (I picked pycnofibres because crocodylomorphs are Archosauriformes too), that looked like river weed, and long arms for grabbing prey. They were so derived from their ancestors that they became a new family, Macronasidae.
When the glaciers of the last Ice Age receded, some trolls migrated north to live in the wetlands of Scandinavia, evolving even more cold-climate adaptations like even bigger noses, more hair and stockier builds.
The Macronasids behave quite like their cousins in the genus *Crocodylus*, in that they conduct water-to-ground predation. When a deer, goat or sheep comes to drink at the water's edge, they explode from the water and grab the prey with their long forearms. Instead of the elongated, fish-snaring jaws of other crocodylomorphs, theirs are truncated to deliver powerful, killing bites to still their thrashing victims.
They sleep, give birth, nurse and defecate in the water, like hippopotamuses. In fact, they spend almost all of their time half-submerged, sometimes emerging to bask in the sun.
---
Please let me know what you think of this theory, and I hope you like it. If you think you can best this answer, by all means do, for I am still open to other suggestions.
[Answer]
# Trolls are the only remaining dinosaurs
If you are willing to turn the hair into long, thin, hair-like feathers, then make the troll a dinosaur. Some dinosaurs had feathers, so simply have these evolve to be long and thin for keeping warm as opposed to flight. The troll can be of a dinosaur lineage where feathers were never at any point intended for flight, so they are evolved over time for warmth instead. Various dinosaurs already had nasal horns, long thin claws as depicted, and probably some had webbed feet. Furthermore, if you want your trolls to be semi-aquatic in cold waters, they will need to be warm blooded, which (at least some) dinosaurs were as well.
As the *only* dinosaur to escape extinction 65 million years ago, it is easy to then explain any of its evolutionary traits. Having diverged so long ago, the troll is more genetically isolated than any terrestrial vertebrate other than the [tuatara](https://en.wikipedia.org/wiki/Tuatara). Nothing else alive is very closely related to the troll, so it simply evolved to fit its cold semi-aquatic environment.
[Answer]
I'm going to go add a fourth possibility to your crocodilian, amphibian, mammalian choice list: dinosaurid.
First, the hair could be explained as [pycnofibers](https://en.wikipedia.org/wiki/Pterosaur#Pycnofibers), " hair-like filaments ... similar to, but not homologous ... with, mammalian hair". These are known mostly from pterosaurs, but could have originated in other nearby branches of the tree of life. Further, borrowing from another answer, the hair could be modified feathers of terrestrial dinos. As it is, these feathers were developed more for warmth and display than for flight, which is perfect for your troll.
Next, the aquatic nature. There are ample examples, from [spinosaurus](https://www.kids-dinosaurs.com/swimming-dinosaurs.html) to [plesiosaur](https://en.wikipedia.org/wiki/Plesiosauria) that lived in or around water, had webbed feet, big lungs, were warm-blooded, and so on.
Of course, those hands look very like a velociraptor. Eerily like.
Finally, that nose. This will be a little difficult. I could fall on the now-discredited claim that [sauropods had trunks](http://scienceblogs.com/tetrapodzoology/2009/03/20/junk-in-the-trunk/). Instead, I will have to try to make this work with any of the variety of cranial projections that permeated dinosaurs, and indeed, many extant species. Granted, these projection are not noses, but many are in the right place and could mimic a nose-like structure. Perhaps it is a modified ceratopsian horn, or a reversed hadrosaurid crest. This is admittedly the weak point of my answer, but I think you can make sense of it somehow.
[Answer]
There are many diagnostic traits that allow us to classify animals, so let's go through them in your trolls
# Face
Mammals and reptiles differ quite a bit in the overall nature of their face. Reptiles have hard faces with only a few important muscles around the jaw, whereas mammalian faces are wholly fleshy. While the lack of flesh on the face does exclude mammals, it doesn't secure a reptilian nature, as many other classes lack this feature
# Nose and Ears
The nose and ears, contrary to the rest of the face, are distinctly mammalian features. This contradiction is quite easy to solve, though; many reptiles, as well as other classes, bear horns and crests on their head. It's not so implausible that such a structure could form nose/ear-like structures, especially long, impressive ones
# Hair
Hair is another seemingly mammal-exclusive feature, but once more there are paths to it outside of mammals. One option is the synapsid class; hair evolved in mammalian ancestors long before facial muscles, and so it's not implausible that one such offshoot could survive and evolve into your trolls. Some dinosaurs also have hair-like feathers upon their body, which could be a candidate. Another option is the amphibians; as you say, some amphibians have hair-like gill structures, and there is no reason in principle why such gill structures couldn't grow so long underwater. A more exotic option could be strands of symbiotic algae that grow on the troll, giving the appearance of hair
# Scales
Though scales are an expected trait on reptilian creatures, they are also present in synapsids, and even modern mammals like anomalures. However, scales are not found in modern amphibians, and in fact scales likely couldn't exist with the smooth moist skin required for the hair-gills. Hence, this troll can't be an amphibian. Algal hair, not being an actual part of the troll, could easily grow on scales
# Limbs
The positioning of the limbs on the body seems distinctly mammalian. However, several other classes have this girdle anatomy, including some synapsids and dinosaurs. However, with synapsids, I could not find whether the mammalian face or legs evolved first, so the combination seen in trolls may not be possible. However, all dinosaurs had non-mammalian faces, so it is more plausible that these trolls may be dinosaurs. This could also be true with algal hair, with the trolls being featherless dinosaurs instead
# Tail
Mammals and reptiles can often be distinguished by their tails: Mammals have narrow tails distinct from the body, where reptiles have thick, continuous tails. While there are many exceptions to this rule in the mammals, these are few and far between in reptiles. However, in synapsids, it seems like the mammalian tail predates both mammalian faces and girdles. If we assume that the girdle came before the leg, these trolls could easily sit in this transition
# Conclusion
In conclusion, your trolls can be nothing other than an advanced synapsid, or cynodont. It retains the scales and facial anatomy of the first reptiles, but its postcranial skeleton has the unique features of the mammals. It also benefits from a horn like a nose, and a pair of ear frills, which give it a false air of mammalian nature
[Answer]
I feel like most of the in-depth information was covered (what kind of animal is it, what are its origins, etc.) have been covered, but I did notice that there weren't many explanations for the nose in the non-mammal answers. Well, my first idea is that it just had a nose, like a normal animal, but later of course realized that it's a mammalian nose no other kind of species would have. However, if it lives underwater and grabs people with its arm, perhaps it points its mouth and face at the surface of the water while hunting, so it can easily grab its victim and stuff it into its jaws. If that's it's predation method then the nose could have evolved from a crocodilian or dinosaurid nose into that long nose so it can breath while in that position.
This isn't really a full answer, but I wanted to add another possibility for that nose into the mix.
[Answer]
## It is an aquatically adapted lemur, it even comes very close to a fossil giant lemur Megaladapis edwardsi.
lets look at its anatomy, a very primate body plan, with claws and tail, that puts it in the prosimians.
it has a flat skull with a large muzzle and snout and more laterally facing eyes, those are lemur features. Plus their small brain is what you need to make low activity levels possible.
As a bonus there are some fairly weird hands among lemurs.
what's left that is out of place.
It has a weird nose but that pops up several times in primates so that not that out of place. Its an easy thing to explain away with sexual selection.
They lack hair in a lot of places, but that could be an adaptation to being aquatic, its not as if hairlessness ness has not evolved in primates before. This makes even more sense with how large they are.
webbed feat is easily a aquatic adaptation.
Otherwise **nothing about their anatomy is out of place for a prosimian mammal.**
**There is even a lemur that matches surprisingly closely. There are some really big fossil lemurs, as big is gorilla, found in an underwater cave, they are squat with short splayed legs have large snouts. That sounds remarkably familiar, they were tree climbing herbivores but maybe you have a aquatic carnivorous relatives of Megaladapis edwardsi**
[](https://i.stack.imgur.com/Y8Zq6.jpg)
[](https://i.stack.imgur.com/piJak.png)
] |
[Question]
[
My first time here, hope this is a useful question. Mostly about orbital mechanics and vacuum.
So the crew of a general-purpose interstellar spacecraft have stumbled across a paradise planet. After extensive testing of the area, they decide to establish a colony. They land the spacecraft, offload all the crew and any supplies they need. They'll wind up being here for at least 20 Earth years.
The problem: the spacecraft would need regular maintenance within a gravity well - it has wings for atmospheric flight and landing gear that would be subject to very high forces. There's also the concern among the crew of corrosion to the metals should the ship be left for a long period of time. Maintenance requires power, which requires fuel, and although the ship has been 'tanked up', acquiring more fuel requires a reasonable interstellar journey, which would need many crew members to return to the ship. There's also the small subconscious idea that the crew don't want to be tempted to return to space, so they want the ship just out of reach, but should a catastrophe occur, they do want an escape route.
I've been thinking about parking the ship in orbit of the planet, but knowing atmospheric drag could eventually cause the orbit to degrade, would it be more appropriate to store the ship in a heliocentric orbit following the planet (if it's possible)? Either way, they want the ship to be in the exact condition it is now, located somewhere predictable, in 20 years' time with zero human intervention. Almost like storing an airliner in the 'bone yards' in Arizona, but assuming there isn't an equivalent on this planet, and the craft should be flyable again with minimal intervention.
There are auxiliary craft (with much lower maintenance requirements) that can manage interplanetary distances. The ship's atmosphere can be stored so the interior can become a vacuum. The ship's computer can be instructed to fly into whatever orbit or parking solution is chosen, but once power is shut off, a human would need to manually board the ship (using the aux craft) to reactivate it. Idle fuel consumption is too high for the generators to stay on even at minimum for the length of time, so the whole ship needs to be powered down. The ship has armour plating capable of withstanding average space debris and micrometeorites. The ship is very large, so building some kind of hangar or cocoon on the planet's surface wouldn't be very practical.
[Answer]
# Store it in space
Comparing space to an atmosphere for long term storage is a no-brainer. Atmospheres friendly to humans have lots of lovely oxidizers and solvents in them but are death to unmaintained spaceships. On a planet, you'll have to keep the water and bugs out. Space has a distinct lack of both of those. Planets also have continuous gravity loads on the ship; requiring struts or supports of some kind. Space doesn't have these structural support requirements.
# 'Winterize' it
A very common problem at colder latitudes is what to do with a house that will be unoccupied during the cold winter months. The answer is to "winterize it". Winterizing requires removing water from the pipes, sealing off holes for critters to crawl in through then turn off the heat. If a structure owner doesn't take these measures then the pipes will burst, bugs/mice/rats will move in, and the heating bill will be high.
Spaceships will have similar requirements. To winterize your spaceship you'll need to do a few things:
* Remove all solvents from the pipes. Flush pipes to ensure solvents have been removed to some acceptable value. If possible, keep the pipes open to hard vacuum. Anything that can aerosolize, will aerosolize in vacuums that high. (Note, in a high enough vacuum, it's possible to evaporate the oils of fingerprints.)
* Remove all oxidizers from the ship's living quarters. Replace with inert gasses such as pure nitrogen or argon at 1 bar.
* Remove all oxidizers from the ship's machinery. Replace with the appropriate inert equivalent.
* As much as possible depressurize seals in the ship's machinery. The less pressure the seals have to contain, the longer they will last.
* Do what you can do prevent degredation of components from off-gassing. This should prevent rubber seals from degrading over time when the volatile compounds in the rubber break down.
* Install micrometeorite protection on the ship's windows and sensitive areas.
* Install trickle power source to keep critical components charged or warm enough (if there are any that need this). You'll want passive heating so paint the appropriate portions of this ship in a darker color then set the ship to rotate. The crew quarters would be a good place to do this. Left long enough and cold enough, the ship may/will condense nitrogen, oxygen and hydrogen. Keeping all those gases as gases will help control off-gassing.
* Develop procedures for dewinterizing the ship after you come back to it. Test these procedures to make sure they work. Ideally, the closer you can get to start up with just a single button, the better. You wouldn't want to shut everything down to later discover that you've lost pressure somewhere or a critical seal has failed. Maybe the original manufacturer foresaw this kind of situation and wrote docs for how to winterize the ship. If not, then you'll have to make educated guesses (with the distinct chance you'll guess wrong and your spaceship will be a giant brick when you come back for it.)
* Metals tend to do strange things in a vacuum, like weld themselves back together. The spaceship will already be designed with this problem in mind but should be one of the things that you have to account for when winterizing.
# Where to park it
My bet is high geostationary orbit. While stable, the Lagrange points tend to accumulate garbage and we want to minimize meteorite damage as much as possible. We want to avoid the Golden BB [1] of a meteor if we can help it at all.
If we choose the right orbit, say on the far side of the planet from the sun, the spaceship will be constantly illuminated to form a small star. A legend can be passed down describing a star that gets you to other stars. Should your intrepid explorers lose space flight entirely, for whatever reason, there will be a legend to encourage them to get back out there and go exploring.
[1] "It refers to that tiny little vulnerable part of an aircraft, that is hit by that one-in-a-million shot and brings down the aircraft."
[Answer]
You can park it in just about any orbit that will be stable for 100+ years, why so much longer than the projected mission time? Just in case is why, you want as much contingency as possible when you deal with your life lines. I'd suggest not parking it in a [Lagrange Orbit](https://en.wikipedia.org/wiki/Lagrangian_point) though, they tend to accumulate "junk" which would increase the risk of damage while parked. In orbit around Earth I'd actually park it in orbit on the "dark" side of the Moon out of sight out of mind and pretty safe.
You could potentially have a storage shroud like the dust cover for a classic car for your starship if you were planning to "[mothball](https://en.wiktionary.org/wiki/mothball#Verb)" it at some point in the mission, but an answer I received to [this](https://worldbuilding.stackexchange.com/questions/90815/contamination-of-orbital-warehouses) question suggests that that may do more harm than good.
[Answer]
**Park it just out of reach.**
[](https://i.stack.imgur.com/5clTU.jpg)
<http://strangeabandonedplaces.com/the-mojave-airplane-graveyard/>
The paradise where your crew will settle probably has rain and corrosion and bananas. But there are probably places on this planet that do not. No-one would want to live in the Mojave desert but it is a nice place for retired planes. It gets hot but not wet and not salty and there is minimal life. Fly your ship to your planets equivalent, wrap it in plastic and leave it.
Or better: bury it. I like the story about the Romanian who wrapped his tractor in tar paper and buried it so the communists would not confiscate it. It stayed under for 35 years and supposedly (!) still ran when unearthed.
<http://journaltimes.com/news/national/tractor-buried-to-thwart-communists-finally-unearthed/article_3d92945c-2255-5c99-893d-e81c9d48a397.html>
You could bury your mothership in the desert. That would prevent wind damage too. Plus it would be a little more work to get it back into the air, in case someone wants to try to make a break for it. You could even make a nice crater for it from space, to save digging. Land it in the crater and cover it like a burial kurgan.
Storing it in orbit seems dangerous - there are lots of ways the ship could lost or be just plain unobtainable. But a thing buried in the desert can be obtained by a person with a shovel.
[Answer]
Parking a spacecraft for long term storage can be done in orbit, but it exposes the ship to cosmic debris, radiation and fluctuating temperatures, so is actually rather stressful without constant monitoring and active measures (like the so called "barbecue roll" for thermal management in the Apollo missions). Shutting down the ship entirely might actually be the worst thing to do while in orbit.
Since leaving it on the ground exposes it to the elements, I would consider parking it in a thermal shelter on the Moon or similar body (this assumes you have some sort of shuttle system). Essentially land the ship in a crater, then cover the crater over with a large concrete or similar dome. The ship is sealed in vacuum. protected from radiation and cosmic debris and the thermal mass of the dome and moon will keep the ship at a relatively constant temperature throughout its storage period.
I'm going to ignore the idea that you have to shut down the ship entirely during storage. Small power sources like an RTG can power small spacecraft for decades (deep space probes like Pioneer and Voyager have RTG's which are still running and powering the spacecraft, some of which were launched in the *1970's*. A small series of solar panels can also be laid out on the dome to power housekeeping systems, and large fission reactor can be left running in "Bimodal" states (coolant runs through the core and powers a rankin generator rather than being vented through the rocket nozzle). Keeping several small housekeeping computers running should be no big deal for 20 years or so.
So essentially soaring the ship in a giant thermos (vacuum container) insulated from rapid temperature swings and sheltered from radiation and space debris should be all you need to do.
[Answer]
**I know this breaks your specified restrictions but I feel like it should be said.**
There is no reason to shut down the computer and would actually be unnecessarily detrimental to the mission. We have computers that can run on very small amounts of power and surely such a craft would have a solar panel.
In our current progression of technology we are shoving censors into just about everything. A sophisticated spacecraft such as this would undoubtedly have censors monitoring critical systems and haul integrity.
In current avionics we have programs called autopilots capable of maintaining a certain navigation.
Now I am going to use the term **AI** but I don't mean one to the extent of Cortana I mean one simply capable of receiving input and enacting a response (we have things similar to this today). It would very simple to have an AI whose job it is to act as an auto pilot and monitor critical systems. It would also be likely that your crew would maintain a communication channel with the ship's AI so the crew could say "come pick me up" or the AI could say "the haul has a big hole in it what do I do?".
This way you could park your ship wherever you wanted (within reason), your AI could be advanced or bare bones enough to achieve whatever story effects you want to achieve. And if the 20 year gap is a story element you could justify that the crew comm system got damaged and the ship's default protocol is to return after 20 years.
It could also be programmed to avoid catastrophic collisions upon detection.
**But leaving your mother ship dead in orbit without any safety measures or monitoring is reckless.**
[Answer]
Your technology's a bit out of whack. The ship would have several methods of powering itself not just relying on generators or excess energy from the engines. Solar and nuclear are the two obvious choices. Nuclear (fission or fusion) would be a definite, it'll run wherever the ship is in its initial journey. Solar wouldn't be very effective between systems.
So fuel conservation is no reason to power down the ship totally.
The auxiliary craft can travel interplanetary, so in theory the mothership could be parked anywhere in the solar system.
BBC Radio 4 did a couple of series' based on a very similar concept about 30 years ago. They were called Earthsearch and Earthsearch II, see if you can get the novelisations if you can't track down the audio copies.
] |
[Question]
[
**Background**
---
The State of [Muskogee](https://en.wikipedia.org/wiki/State_of_Muskogee) was an **independence movement in the late 1700's and early 1800's started by William Bowles**. The goal was to create a united **aboriginal nation** in the southeast that could **resist the expansion of the United States**. This revolt had initial success with the native American groups in the area (primarily the Miccosukee, Muscogee) and other groups such as fugitive slaves, white pirates, and Spanish deserters.
But during the siege of San Marcos, everything went to hell, without a navy they were forced to retreat. The Treaty of Amiens in March 1802 briefly ended hostilities between Britain and France and Spain, and news of this ceasefire left Bowles discredited, with many of his supporter leaving him.
By 1803, the U.S. and Spain were conspiring against Bowles, who no longer enjoyed British support. While the four year independence of the State of Muskogee demonstrated Spain's inability to control the interior of Florida, **the revolution ultimately failed**.
**Question**
---
Can this be stopped? What could Bowles have done to keep the State of Muskogee's initial independence? **What is the smallest change I can make to history to allow for the State of Muskogee to remain independent?**
[Answer]
## TLDR: If Bowles had managed to keep and hold San Marcos the first time he took it he could have held out
So [here](http://www.kreweofbowlegs.com/W.A._Bowles.html) is the most detailed information I could find on what went on. There seem to be several turning points, I'm just going to go through them all and point out where minor things could have been different.
>
> On 16 January 1792, Bowles with a large band of Creeks took over and looted the Panton, Leslie, and Co. store in San Marcos (St. Marks). He then tried to negotiate with the Spanish over the establishment of a Muskogee state. The Spaniards turned the tables on him and captured him instead.
>
>
>
If he hadn't been captured things could have turned out very differently, because of this he spends several years away, some of them in captivity.
But! He escapes and stops off in Britain:
>
> While being returned to Spain, Bowles escaped and took charge of a ship to Africa, and eventually made his way back to Florida after stopovers in England and Nassau to regather his British supporters.
>
>
>
If the British had placed a greater value on Bowles and his disruptive actions against the Spanish and United states they could have supplied him with more support when he stopped in England - something the Spanish may not have been duely prepared for and if he had taken more land, key ports and such this could have changed the military capacity entirely. We do know that, with what support he had he hampered the Spanish for a while both at sea and eventually taking a Spanish fort.
>
> Bowles finally came up with a successful plan to capture the fort and Panton-Leslie store at San Marcos.
>
>
>
However, naturally, the Spanish want it back.
>
> On 23 June 1800, a large Spanish force sailed up the St. Marks River and recaptured San Marcos. Bowles escaped with his few white supporters who were left; the Indians had already gone home before the attack.
>
>
>
If at this point Bowles had been prepared for an attack and (maybe with more support from the British) sunk the Spanish before they reached him. This also could have changed the way things went. The losses incurred may make the Spanish think twice about chasing after him again. Instead we now have the Spanish with a large force sitting at San Marcos and specifically looking out for Bowles.
Bowles decides to annoy the United states as well, just to attract more attention. He makes the Muskogee state and demands the U.S return indian land.
The Spanish now march into his new state with a large force, intent on finishing him off.
>
> On 17 August 1800, a well-armed force of 272 Spaniards and Mulattos set out to destroy Miccosukee. They ran into disaster from the beginning, and returned to San Marcos two days later. Even though Miccosukee was only 30 miles away, they did not have good guides and were unfamiliar with the area. On the first day they were only able to go 3 miles; not much of a surprise attack, and with only 6 days' rations. The soldiers were already over-heated and getting sick, and would be in very poor fighting condition by the time they reached Miccosukee.
>
>
>
If Bowles had sufficient scouts and forces he could have taken these sick and tired Spaniards and their weapons - the battle would have been much easier, considering Bowles had the Indians on his side, than confronting them later. And confront them later he did, to his cost:
>
> On 5 January 1802, Bowles took a large force of Seminoles (Miccosukees), Negroes, white pirates, and deserted Spanish soldiers from Pensacola, and laid siege to San Marcos. They were a strong force and gave heavy fire, but would have been more deadly if they had cannons. Twice, one of the Spanish ships approached and destroyed a series of trenches dug by the Seminoles. The Spanish inside the fort were not in great enough number to attack Bowles, and could only defend the fort. The only thing that prevented Bowles from capturing San Marcos was heavy fire from the ships, and more ships arriving. Also, news was received that the war between Spain and England was over. The siege ended after about 10 days.
>
>
>
Well, a lot of that is self explanatory. If he had been given cannons by the British, if he had taken cannons from the invading Spaniards mentioned above, if his ships had sunk the Spanish before they sailed up the river. If he could have taken the fort before those ships arrived. If the war between Spain and England hadn't ended... This was the start of the end, any how:
>
> Bowles was discredited when he failed to take San Marcos. Finally, on August 20, 1802, the neighboring Seminoles signed a peace treaty with the Spanish. Even Bowles' strongest supporter, Chief Kinache of Miccosukee, signed. Bowles' war with Spain failed, and he no longer had British support. Britain had declared peace with France and Spain, and now considered Bowles a troublemaker, his state an illusion, and his supporters nothing more than pirates. Spain started to blockade the coast and choke an important trading supply line of Bowles.
>
>
>
From here the Spanish and Americans gang up on him and, details aside, he didn't have much of a chance once he failed to take San Marcos.
[Answer]
Muskogee ideally would have a patron. The obvious ones are one of the European powers (Britain, France, Spain) or the US itself.
I could imagine the US supporting Muskogee as a buffer state if the Spanish posed more of a threat.
But how about this for a cool alternative history: in this time period and area what nation is opposed to slavery? And has not yet descended into destitute ruin. Haiti. The Haitians have just captured all of the island of Dominica and defeated the French.
The story: Bowles is received in Haiti as a friend of the disadvantaged and he saves Toussaint Louverture from Napoleon by spiriting him away to Florida. With Louverture's military genius, the combined forces of the Muskogee in Florida catch the British by surprise and commandeer the fleet based in Key West. Then they and Haitians coming from the south catch Cuba between them: slaves rise up and Cuba is added to the growing nation. 10 years later, seeing the writing on the wall and themselves in need of a powerful patron, the Cherokee Nation to the north adds itself to Muskogee.
[Answer]
The relentless Spanish military and diplomatic efforts to undermine it seems to have been critical in Muskogee's collapse.
So, one approach would be for Spain under what in real history was the reigns of Charles III and Charles IV to be otherwise occupied by some pressing concern that would cause it to divert resources away from Florida and towards more pressing demands elsewhere. There are several ways this could be achieved.
What was [going on in Spain at the time](https://en.wikipedia.org/wiki/History_of_Spain#Spain_under_the_Bourbons_.2818th_century.29)?
>
> Under the rule of Charles III and his ministers – Leopoldo de
> Gregorio, Marquis of Esquilache and José Moñino, Count of
> Floridablanca – the economy improved. Fearing that Britain's victory
> over France in the Seven Years' War (1756–63) threatened the European
> balance of power, Spain allied itself to France but suffered a series
> of military defeats and ended up having to cede Florida to the British
> at the Treaty of Paris (1763) while gaining Louisiana from France.
> Spain regained Florida with the Treaty of Paris (1783), which ended
> the American Revolutionary War (1775–83), and gained an improved
> international standing.
>
>
> Charles IV seen by some as mentally handicapped. Dominated by his
> wife's lover, Manuel de Godoy, Charles IV embarked on policies that
> overturned much of Charles III's reforms. After briefly opposing
> Revolutionary France early in the French Revolutionary Wars, Spain was
> cajoled into an uneasy alliance with its northern neighbor, only to be
> blockaded by the British. Charles IV's vacillation, culminating in his
> failure to honour the alliance by neglecting to enforce the
> Continental System led to Napoleon I, Emperor of the French, invading
> Spain in 1808, thereby triggering the Peninsular War, with enormous
> human and property losses, and loss of control over most of the
> overseas empire.
>
>
>
One possibility would be that in the Treaty of Paris (1783), Florida might not have been returned to Spain, and instead might have been awarded to the newly independent United States which did not have sufficient military clout to put down the Muskogee insurgency. Spain, instead, might have gotten something different out of the Treaty of Paris (1783) such as favorable trade agreements with the newly independent United States.
Another possibility would be that Charles IV would have turned on his wife's love, Manuel de Godoy, and had him executed for adultery, and then fallen under the influence of some other courtier who might, for example, have urged Charles IV to redirect Spanish military resources from Florida to the fight this Revolutionary France, sacrificing Florida in the hope of securing greater success in France which was closer to home and more important to the Bourbon family.
A third possibility is that Charles IV could have been killed by revolutionary French agents in a move that would have triggered the Penisular War many years earlier with revolutionary France instead of Napoleon I, or could have led to a successor who retreated from the policies of Charles IV including the diversion of military resources to Florida.
A fourth possibility is that if the Muskogee's could have held on just six more years, the Spanish would have had to sacrifice their military effort in Florida to focus on fighting with Napoleon I. One of the most plausible ways that this could have happened would have been for a spy to warn the Muskogee Republic that a major naval offensive was planned sometime early in the year 1800, and for a small group of saboteurs to have mounted a stealthy pre-emptive attack on the Spanish fleet destroying many of its ships and scuttling its planned offensive directed at San Marcos before it could be launched. In the face of this defeat, Charles IV might not have been willing to commit more forces to what would have seemed like a lost cause at that point.
] |
[Question]
[
It is typical of fantasy stories that there will be a dragon somewhere down the line. They are typically the strongest boss right before or after the main antagonist.
Now the question is what color would the dragon's blood be, given that it can breath fire, it can produce thick scales, it has very sturdy bones, and most of all, its diet consists of meat, specifically human meat.
1. Dragons primarily eat human flesh - Will this have any effect on the color of its blood?
2. Dragons use oil made from human fats to breath fire - Are human lipids flammable?
3. Dragon's blood is highly flammable - Now that's amazing.
4. Dragon's blood can heal mortal injuries near instantly if applied directly to the injury - Cell regeneration?
5. Rumors says that Dragons can also get nourishment from the sun - Photosynthesis?
6. Dragon's Saliva is acidic to human and animal flesh but not to plants. - Is blood involved in its acidity?
Given the characteristics above of our dragon in this story, what would be the color of their blood if we are basing it on what we know about blood?
[Answer]
>
> Dragon's primarily eats human flesh - I don't know if it will have any
> effect to the color of its blood?
>
>
>
This choice of menu item makes the dragon vulnerable to extinction, for a number of reasons, but that's not really the question here, so I won't go into that (even if they are invulnerable to most things, by golly humans are clever). **Menu choice doesn't determine blood color in most animals.** You have to decide if the blood is iron-based or not. On this planet there are a few animals who, when their blood is exposed to air, it is blue. That's because [it's copper-based](http://animals.mom.me/animals-copperbased-blood-8379.html).
>
> Dragons uses oil made from human fats to breath fire - I don't know if
> human lipids are flammable.
>
>
>
All fat is flammable, but not enough to do what you are looking to do. What you'd actually be looking for is a system that breaks down food into vaporizable components. Like a biologic version of a lighter. [This question](https://worldbuilding.stackexchange.com/questions/62835/how-do-dragons-not-burn-themselves) is an excellent place to look at how that might work.
>
> Dragons blood is highly flammable - Now thats amazing
>
>
>
You might want to look into [the science of flammable liquids](http://www.columbusfire.net/fire/flammable.asp). This also could render them strangely vulnerable to fire, even if they aren't cut open. As far as color is concerned, look at all the substances which are flammable and [how they work.](http://ehs.unc.edu/manuals/laboratory/10-2/) It could be a vulnerability to make the blood flammable. They can have sacs or storage for fire breathing that do feature flammable substances deep within them, but to have the blood be flammable could be problematic to their continued survival. I would look to oils and alcohols as the inspiration for color if you are set on having this be so.
>
> Dragons blood can heal mortal injuries near instantly if applied
> directly to the injury - Cell regeneration?
>
>
>
For it to be both flammable and regenerative would be touch scientifically impossible, but hey, magic can handwave anything! I'd make the blood golden based on this, just because that's pretty and magical.
>
> Rumors says that Dragons can also get nourishment from the sun -
> Photosynthesis?
>
>
>
In this case, they would not eat people very much. And that's good. For people. And for the dragons, because if they are highly invulnerable and don't kill people often, most folks would just accept it as a force of nature that just happens once in a while.
Let's say that most dragons would die because they got so old or sick that the photosynthesis wasn't working correctly. Once that happens they have to prey on humans more often, and then they become a "problem dragon," and humans cooperate to hunt them.
**It's possible that the color of the blood on these dragons who can't photosynthesize as well are actually different than healthy dragons and have different characteristics entirely.** (Maybe their blood is flammable, but a healthy dragon has the healing blood). You could make it **black, like motor oil that hasn't been changed in a while, whereas a healthy dragon might have golden blood.** With the old/unhealthy dragons, it's a little easier to kill them, (maybe they can't regenerate as well or other problems) but still quite a task. And they require killing because they are eating more people.
>
> Dragons Saliva is acidic to human and animal flesh but not to plants.
> - Is blood involve in its acidity?
>
>
>
Acid is acid because it has a particular pH. The acidity of something that would dissolve flesh would also be determinantal to plants. But that's science! So, let's say that the cells in their saliva have an "unreleased" acidity, contained in microscopic sacs. These sacs "sense" the characteristics of flesh (that isn't theirs), and releases the acid, only then. I don't know that the blood is at all related to this.
If this has a mystical basis, their blood can be any color you desire. This is an opinion.
[Answer]
It's settled (by talk in comments). Your dragons are different. They are not calm, wise creatures that keep to themselves and hoard gold. They are not nuisance that steals cattle and burns occasional field. They are not a strict overlord who demands a virgin a year as a pledge of subservience. And they certainly are not noble defenders.
Your dragons are a nightmarish ravenous creatures right out of a mind of HR Giger. And you want their blood to be appropriately uncanny.
So what can we do with it?
## Colour
Colour of blood (or blood equivalent) of animals we know is based on colour of oxygen carrying molecules. We (as in we the living creatures, not just humans) use a lot of oxygen and our blood carries a lot of it.
Haemoglobin is red, because oxygenated iron is red. Rust is nothing more than Iron Oxide - oxygenated iron, however iron is bound strongly to oxygen in rust, that's what rest of haemoglobin is about - to make iron attach and detach oxygen more easily. Oxygenated blood is bright red, unoxygenated blood (bound to CO2 instead of O2) is dark red.
However, Haemoglobin is not the only known oxygen carrying molecule. I present you the Hemocyanin: <https://en.wikipedia.org/wiki/Hemocyanin>
Hemocyanin uses copper instead of Iron. Copper gives it blue colour in oxygenated state, while unoxygenated state is colourless. For comparison Copper (II) Oxide is dark blue (at least it looks dark blue to me: <https://upload.wikimedia.org/wikipedia/commons/f/fa/CopperIIoxide.jpg>), however Copper (I) Oxide is red.
What does that mean? It suggests that colour of blood is primarily based on colour of oxides of metals used to carry them.
Iron is used in 2/3 oxidation states, Copper in 1/2 oxidation states, and those are most common oxidation states for those elements.
You can, with high level of plausibility, replace Iron or Copper with any metal that has 2/3 or 1/2 as most common oxidation states and blood created from those should plausibly have colour based on colour of respective oxides (2-oxide for unoxygenated Iron analog, 3-oxide for oxygenated Iron analog, 1-oxide for unoxygenated Copper analog, 2-oxide for oxygenated Copper analog).
Here are some examples I found using those lists:
<https://en.wikipedia.org/wiki/List_of_oxidation_states_of_the_elements>
<http://www.thecatalyst.org/oxnotabl.html>
and wiki articles on respective oxides.
* Cobalt, Iron analog, deoxygenated: [green/red/gray](https://en.wikipedia.org/wiki/Cobalt(II)_oxide), oxygenated: [black](https://en.wikipedia.org/wiki/Cobalt(III)_oxide)
* Mercury, Copper analog, deoxygenated: [brown](https://en.wikipedia.org/wiki/Mercury(I)_oxide), oxygenated: [orange](https://en.wikipedia.org/wiki/Mercury(II)_oxide)
* Zinc, Copper analog (it has 2 as most common state, but it has only -2/+1/+2 stats total so it might still be plausible) deoxygenated: sorry, I could not find, oxygenated: white
* Europium, Iron analog, unoxygenated: sorry, I again couldn't find, oxygenated: white but highly [fluorescent](https://en.wikipedia.org/wiki/Europium(III)_oxide) (!). It used to be used in CRT screens, so how about dragon blood that glows in full technicolour under ultraviolet? Maybe Dragons can emit UV themselves and thus are afraid of certain colours of UV fluorescence? After all anything that can spill their blood is dangerous, same mechanism is why red means danger to humans.
I honestly don't know if you can use other pair of oxidation states (like 3/4 of Iridium, 2/4 of Palladium etc.), perhaps someone with better knowledge of biochemistry can answer that, or you can just ahead anyway claiming artistic license.
Whichever element you pick, you need to keep in mind that it needs to be common in your world. Dragons will have to be able to ingest enough of it, or somehow produce it themselves. Most of terrestrial live uses iron, so it's easy for terrestrial predators to acquire enough iron - it just happens naturally as they eat. Naturally, if your Dragons somehow synthesize rare element, their metabolism will slowly enrich the world with that element, so that's something you need to keep in mind too.
## Food
What you eat doesn't have huge impact on how your body works. Food is broken down to base components anyway, and a lot of amino acids, vitamins as well as fats and sugars can be synthesized if there's abundance of another compounds. For example, humans synthesize Vitamin D, and turning sugars into fats for storage and fats back into sugars for actual use is standard practice for most animals.
However, not everything can be synthesized. Terrestrial life can not synthesize elements, only compounds out of existing elements, if we need calcium we need to ingest it. Same with iron, and thus unless your Dragons can somehow synthesize other elements (perhaps with magic? Philosopher's stone anyone?) they are better off having same base blood composition and thus blood colour as other things.
But hey, who said your humans have to have red blood like we do?
## Flame
Fats are flamable, be them animal, human or plant. Plant oils are easiest to use, but chemical difference between solid fat and liquid oil isn't big. Mostly, oils have some double chemical bonds while solid fats don't, that's how margarine is made: you break double bonds, attach hydrogen in thus made free spots, and presto: liquid oil turns into solid fat. You can have dragons somehow reverse the margarine process to create liquid oils, add some magic to increase flammability and you should be set with plausible flaming breath.
However, I can't help you with flammable blood. Sorry, I don't have any good ideas.
## Toxicity, regeneration, and sunlight
This isn't related to colour. In terrestrial animals, regeneration is handled by blood cells which don't contribute significantly to colour.
I should note that by mammal standard, humans have fairly aggressive regeneration abilities, it may not seem like that but human body is good at staying alive despite injuries, though results may not be pretty because of permanent scars, but bleeding is stopped fast by platelet clogs, and damaged tissue is replaced aggressively by surrounding cells multiplying to fill the scar. We lack ability to regrow select limbs, but that's different from stopping bleeding and keeping what's left, alive.
In case of your dragons, most likely best pick is to have free stem cells in their blood in addition to mechanisms we posses. That can massively increase rate of regeneration - stem cells in platelet clog could differentiate into correct cell type to hasten regeneration. One huge drawback of that would be susceptibility to tumors, cancers and erroneous differentiation. If stem cells differentiate incorrectly, they could start growing wrong organs: random talons sticking out of scars, perhaps tiny disfigured appendages. Something like that could even accidentally happen in otherwise healthy tissue casing teeth inside muscles, talons in brain, scales inside arteries or even actual cancerous tumors. You could use that to limit their lifespan if you want - they could be very hard to kill, but at some point their overagressive regeneration will accumulate enough errors to for Dragon body to effectively kill itself. Kind of like human scars do negatively impact repaired tissue (lower flexibility, sometimes the can't actually do what organ needs to do and they only stop bleeding/other fluids escaping, etc.), but they sure beat being dead.
Further, stem cells could differentiate into white blood cells - those which handle immune reaction. Dragon blood isn't actually toxic to humans - it's a pathogen that actively fights and tries to kill non-dragon cells. Those chemical burns? They are not chemical. It's a trail left by dragon white cells pretending they are [flesh-eating bacteria](https://en.wikipedia.org/wiki/Necrotizing_fasciitis). Destroying entire limbs in matter of hours and killing a person in less than a day with only treatment being amputation before condition spreads too much is perfectly plausible, or you could dial it way back to only cause some nasty scaring.
And this leads us to photosynthesis. If dragons have chlorophyll in some of their skin cells, maybe dragon cells responsible for immune reaction misrecognise plants as dragon-cells and signal stem cells to assist in regeneration?
[Answer]
I'll add one thing to the answers above: You are what you eat. Since your dragons eat humans, they need to use an oxygen-carrier which they can get in sufficient quantity from human flesh. @M-i-ech pointed out other metals such as mercury and cobalt but the dragon would not have these available (or would need some mineral source; a special kind of salt lick). I would stick with red, haemoglobin-based blood for these dragons.
[Answer]
I can't say for sure what color or exact metal the blood would have, but metal complexes, like those of ruthenium, iridium, rhodium, rhenium, and platinum, could meet some of your requirements!
-When exposed to certain forms of light, like UV or sometimes even IR, they may fluoresce and emit singlet oxygen which is a toxic, rwactive gas that emits red light as it decays which may be mistaken for fire and be used as an energy source.
-They are being studied as a treatment for cancer, so there's your medicinal aspect.
-These metals are rare in nature, so eating man-made structures could be plausible.
-There are complexes, like Vaska's complex, which are known to carry oxygen. (and H2, SO2, Cl2, etc. in the case of Vaska's complex)
-All of that singlet oxygen could lead to perchloric, peroxysulfuric, or nitric acids which are quite acidic.
[Answer]
Like every living being on this planet:
Red?
Because their body works primarily like any other animal, breathing air, eating flesh.
Or if you want to give it an acid look (why should it be acid?) you can take a look at the blood of an alien from the Ridley Scott movie Alien. It's a green slime that eats its way through everything.
But I'd stay with good ol' fashioned red blood.
] |
[Question]
[
I've asked another question about trinary planet systems which turned out to not be possible.
Is there a way for three worlds to co exist within sight of each other? Sight being defined as making out continents with the naked eye.
The planets need to be large enough to have gravity of 0.8g, 1g and 2g (ish), humans can have minor modifications (thicker skin, stronger bones) to survive but are essentially the same as they are now.
I'm now thinking of moons orbiting a gas giant, but I don't know if this would work with them having to be close enough to the star for heat & light and whether the gravitational stresses of the planet would make life too unpleasant.
[Answer]
Orbiting a gas giant is a good idea. Make it a hot jupiter, because that will put the gas giant planet right in the habitable zone. The three planets will need strong magnetic fields to protect from the possible radiation belts around the hot jupiter.
Drawbacks for the three planets will include increased seismic and volcanic activity and the planets being tidally locked. The fact that the planets are geologically active increases the probability of there being life on the planets. This won't make life too unpleasant. Humans can live with volcanoes and very active earthquake zones. Presumably life on the three planets will have their evolutionary histories to help them adapt to such inconveniences. Tidally locked will means that the other planets can only be seen from specific regions on each planet. Not the worse problem a planet can have.
Nevertheless, there would be one serious drawback of tidal lock. Either those moons are close and face serious volcanism, OR they are more distant ones and instead face awfully long day-night cycle (like weeks) which causes serious temperature fluctuations and turns interiors of continents into areas with really extreme temperatures.
[Answer]
Provided we keep some moons reasonably close to a large planet, but far enough from each other, stable orbits are possible.
A Jupiter sized planet orbiting a sun-like star, at 1AU would have a Hill sphere of about 10 million km. And an Earth Sized moon would have its own Hill sphere of about 1/10 of its orbital distance.
So placing the three moons at distances of (say) 200,000km, 300,000km and 500,000 km puts them well inside the planet's gravity well, far enough that they should be able to orbit without disrupting each other's orbit and close enough at opposition from Jupiter for continents to be clearly seen.
The usual caveats apply. These moons will be tidally locked, heated internally by the gravity from the planet (lots of volcanoes?) and orbiting in powerful radiation belts.
[Answer]
For them to be close enough to see each others' continents with the naked eye, they'd have to be about as close as the moon to earth. Earth sized planets at 400,000 km would exert around 2.5 x 10^-4 m/s^2 acceleration on each other. That's around 1.5 x 10^26 N of attractive force.
These are back of the envelope calculations, so I assume I'm off by a factor of 100. Despite that 2 such planets would not remain in stable orbit. And three is right out.
[Answer]
Give the inhabitants [Eagle-like vision](https://en.wikipedia.org/wiki/Bird_vision#Diurnal_birds_of_prey).
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I have two earth clones, in essence, separated by \*16550 miles (26350 kilometers). They are, of course, tidally locked, and orbit each other once every 24 hours. These planets orbit a sun identical to ours in the same time as earth, except their orbit around the sun is perfectly circular. Now, I want to add a little bit more to the system. A moon with half the mass of ours.
But there is a catch. This moon is made of ~90% ice. Because I don't mind some materials in there that aren't water, but they must be spread throughout the moon, and not gathered together as the moon's core.
The moon is in the position shown in the diagram below, and it has an orbital period of 72 hours. Assume the ellipses are actually circles.
[](https://i.stack.imgur.com/YZOkp.png)
\*16550 miles = a
"Note: [I take credit for this graphic](https://worldbuilding.stackexchange.com/a/36533/627)." - HDE 226868
[Answer]
Europa has a water/ocean layer estimated to be about 100km deep. and it has an icy crust at least 10km thick.
While [Hydrogen and Oxygen are the 1st and 3rd](https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements) most common element in the universe, making a water moon theoretically possible (because there are a lot of elements to make plenty of water). I suspect it would take some strange occurrence to have a water moon without at least a small iron core.
The core would be the main 'gravity' source to 'attract' the water, like a snow flake forming around a dust particle. It might be able to keep collecting more and more 'water', though it would be likely to collect other materials along the way, which would gravitate toward the center forming/enlarging the core. Every asteroid hit would have material that has to go somewhere. So just by the act of forming it should have some kind of none water core. Outside of it being manufactured of course.
The Solar system would need to have an unusually high percent of water vs. other minerals in order to get it to be mostly water, and in that case, both planets would likely be composed of very large amounts of water too, unlikely to have any land that sticks out of the oceans.
The moon would also likely have a fairly thick crust of ice significantly reducing the rate at which it is evaporating by solar wind into space.
[Answer]
Your moon will not be stable and evaporate (due to [Atmospheric escape](https://en.wikipedia.org/wiki/Atmospheric_escape)) into the space.
Orbital mechanics should be OK (at least for some time; the [Three-body problem](https://en.wikipedia.org/wiki/Three-body_problem) is notorious for its chaotic nature and the non-existence of analytic solutions).
[Answer]
A moon which is 100% water is possible in theory, but it could only occur in reality if it was an engineered artifact rather than a natural moon.
For any planetary body to form, there must be some sort of gravitational
"nucleus" for other particles to be attracted to. Your planetary engineers could start with a giant "ice cube" of purified water (all that matters is the mass of the object you are starting with, not the composition), and it will soon be attracting everything nearby, with the attraction growing exponentially as the mass increases.
Of course, this means that everything including rock, dust bits of carbon etc. will also be swept into the mix, so your engineers will have to put the ice cube nucleus in a cloud of 100% pure ice crystals. The mass of the in falling ice will increase the pressure and temperature of the growing body, and eventually melt the core ice cube. At this point, any matter trapped in the ice cloud will start falling towards the core, so you will get a small core of other elements unless the ice cloud is maintained at a very high level of purity.
As the water clump gets deeper, the core will eventually resolidify as the water assumes one of the multitude of forms of ice. This pressure ice is different in properties than the ice we normally see in our drinks or floating on the ocean (for an introduction read: <https://en.wikipedia.org/wiki/Ice>), but a lot of this depends on the exact conditions being encountered, small moons like Europa or the Moon may not have enough pressure at the core to develop an "ice" core or mantle. A planetary body with a standing column of water 1000km deep will almost certainly have a core and mantle made up of various forms of ice.
Since we formed this body in deep space where an ice cloud could be generated and remain frozen, there is no reason to suppose that the surface won't (edited from "will". Autocorrect sucks!) quickly crust over with a layer of water ice (ice 1) after the initial heat of formation dissipates. This will also vary depending on the size of the moon, external heat sources and so on. Since there are no internal sources of heat, the moon will eventually freeze solid, and you will have what looks like a white cue ball floating serenely in space.
] |
[Question]
[
Rogue planets are generally not to healthy for us humans to live on. No permanent source of heat or light means that generally they are a pretty cold place. Plenty of other problems arise too, but lets not get into all of that.
***How do I make a rogue planet of Earth-like proportions habitable by humans?***
---
My habitants certainly don't need to be strolling around in lush green parks, but I would like them to be able to survive for many centuries.
Assume futuristic technology, limited by incapability to engage in Faster Than Light travel.
Also assume that cost is no issue: all of humanity is united in this singular goal.
[Answer]
A "rogue planet" would be a planet that went rogue. Meaning it formed normally orbiting a star, swept its orbit clean, and all that. Just like Earth. And then a close encounter with another stellar object or a gas giant flung it away into the dark and it froze.
So the starting point should be a younger Earth frozen over. And without life. This means there might be significant hydrogen and helium left in the atmosphere, but no free oxygen. Which would allow, in addition to hydrogen, things like ammonia and methane. We can also assume lot's of carbon dioxide since less time would have been available for it to get fixed into carbonates.
The result would be a planet with thin atmosphere of hydrogen and helium, with pressure depending on how much time there would have been for them to escape. Below this would be a surface of frozen water, methane, ammonia, carbon dioxide, and possibly nitrogen. Although it is possible all the nitrogen would be in the form of ammonia given that free hydrogen is available. There would also be lots of impurities from volcanism.
Now what happens if you heat this up somehow? All that ice, and there is lots of it, will turn back to gas. Good thing is will give you a thick atmosphere. Not so good is that it will be mostly composed of things hazardous to humans.
You **could** fix this by processing the ice in manner similar to what happened on Earth while gradually melting the planet. But given the sheer mass of volatiles you'd need to process and that you'd need get rid of lots of them either by blasting them into space or storing them into the lithosphere deep below the icy surface layer, it would take a ridiculous amount of resources to do. Even with super-science it is hard to imagine it being fast.
This is very different from something like Mars or Moon where you could in theory just gradually add breathable gasses until you have an atmosphere with some pressure and ability to retain heat.
IMHO even if the first generation was totally to terraforming the planet, their descendants would pretty soon start to question the need to use ridiculous amounts of resources to convert the home they and their ancestors have lived on for generations to resemble some mythical place none of them has ever seen. Who knows if "the Dirt" or whatever even was a real place? Certainly the stories must be exaggerated. Who would want to live on a planet where air conditioning is so bad it leaks liquid or even solid water on people and can't even maintain a stable temperature?
And this is before you consider the **actual problem** of heating the planet and keeping it warm. Warming up the entire planet would **really** not make sense to people used to living in artificial habitats. Why spend resources warming up and insulating space you do not actually need? On a planet with a sun you get energy for free if you boost the greenhouse effect or reduce albedo, both of which you could get for free while building the atmosphere and hydrosphere. On a rogue planet, nothing would be free.
So I think your people would live in insulated habitats buried deep enough into the ice to protect them from radiation but shallow enough that the ice surrounding their habitats could resist the pressure and be stable with minimal supports. The ice can be mined simply by heating it and allowing it to escape above the surface so building would be simple. By simply making the habitats slightly smaller than the dug tunnel you could get proper insulation. And if you got a leak, it would be easy to spot by the effect it has on the ice. A larger leak could melt and even gasify enough volatiles to create counter-pressure.
You would also have plentiful supply of all the volatiles you might want. Getting access to the lithosphere for mining would be trickier. While digging down is not in itself any harder, the pressure of the ice would add to the pressure of the stone. So you would be deep mining before even reaching the stone. They'd probably have very good mining technology. Using organics instead of metals or silicates and mining at high mountains where the stone is closer to surface would help.
Energy could be gotten by nuclear power or geothermal. Efficiencies would be fairly good since the power plants could have the cold end in a lake of liquid nitrogen. Really, why would anyone want to live on a uselessly warm planet?
Note that the planet would be much better than living in space as you would be safe from radiation, have abundant supply of air and water ("some processing required"), and natural gravity. And you are not surrounded by vacuum. Leaks would be slower and even if your life support totally fails, with proper protection you can **walk** to safety. Driving around in the tunnels would be perfectly practical.
Only real downside is that the habitats would need to be built, maintained, and repaired. This would lead to slow and carefully planned expansion and strict control of things like population growth and construction. Security services would also have pretty strong authority to stop people who even look like they might think about damaging the habitats. Which historically has been extended to detaining people who question the authority and decision of the powers that be. So at least some aspects of the society would be fairly authoritarian. That is the price of living in artificial habitats.
Still the aspects that need tight regulation would be fairly stable over time, so after a few generations people would have adapted to it. Allowing other aspects to be fairly free.
[Answer]
I have a problem with the term “rogue planet” since it's actually an oxymoron: it is lacking the defining characteristic. While I suppose free-floating planetary-mass objects can come in any size including small rocky bodies (ejected from forming solar systems), we normally think of them as sub-brown dwarfs down to Jupiter sized, probably because those are the ones we can detect. We detect them because they are, in fact, *warm*. A Jupiter-sized mass would have lost half its heat by now, which is not as cold as you might have thought. A sub-brown dwarf might still be red hot!
It's hard to put any kind of settlement on a gas giant. So look at the moons. In fact, look at Io in particular. It gets its geothermal energy not from the sun at all! This situation could just as well exist without the sun.
Consider a [planemo](https://en.wikipedia.org/wiki/Planet#Planetary-mass_objects) several times more massive than Jupiter, which would still be the diameter of Jupiter, and accompanied by a large number of moons, including a set in orbital resonance. Io can't simply get pushed away because pushing it pushes *all* the moons, their being in resonance. So it has a great deal of inertia keeping it in that particular orbit, even though it extracts a lot of energy while doing so.
You have a number of large bodies, including icy and rocky moons, for colonies. You have massive geothermal power. You have a small amount of heat coming from the planet itself, which might be enough to make some of the icy moons more liquid; you might have tidal heating of a moon with sufficient water to make a liquid ocean, where the amount of heating is just right.
Life on Europa or Enceladus might be completely oblivious to the sun, and that might be the more "normal" situation, compared to Earth!
In short, it's not the cold place you would suppose.
[Answer]
They could potentially make structures out of a transparent material, with metal framing and strips of lights built into the frames. Then they could funnel some kind of heated material such as magma through these frames and beneath the city, providing heat. You might have to have some kind of filter that limits what type of energy is allowed into your structure. For example, in an artificial night, you might block most light and turn off the artificial lights.
This would allow plants, animals, and humans to all live self sustainingly in these structures. They could even be constructed to imitate an existing biome. These structures could be expanded to accommodate rising populations. However, I don't think that the ceiling of these structures could be too high, otherwise it would not heat the area effectvely.
[Answer]
The main problem would be energy. Without a star as energy source, you will have to produce all the energy yourself. You'll need a lot of energy, so probably fusion is the right source (note that in the end, stars are also nothing but huge fusion reactors). I'll assume by then humanity has managed controlled fusion of standard hydrogen (as opposed to our current attempts which still need deuterium), so there is no lack of fuel.
The next problem is that without a star to heat the planet, the atmosphere will be frozen (apart from a few local places with geothermal activity). So you'll probably start settling on the surface of the frozen atmosphere, and gradually work down to the surface. This has a big problem: Most of the oxygen is probably below the frozen atmosphere (as that planet would not have life, the atmosphere would not contain oxygen), either bound in water (ice), or bound in rocks. So you'll need to get to the ground before the oxygen supply you brought with you is no longer sufficient (you may need to apply strict population control in order to prevent oxygen needs to grow too fast). I'd build the first power plants as satellites around the planet, so they are not affected by the later melting/boiling of the atmosphere.
But as soon as you have secured access to the planet's actual surface, it's really just a matter of how much energy you can produce. So build enough fusion reactors to keep the atmosphere warm (and produce enough greenhouse gases to keep losses to space low), and split enough water top produce oxygen (you probably have to do that anyway to get the hydrogen for your fusion reactors), and assuming the planet is sufficiently earth-like, the rest should be simple: Plants can grow under artificial light in hydroponic greenhouses (assuming the people of the time actually eat plant matter, not artificially created food). Advanced technology should be able to build all the substances you need using the elements found on the planet and the energy provided by the fusion plants.
[Answer]
Oh, you do have your accepted answer already, but I want to add something for the fluff-factor. When reading this I felt remembered of a never ending space opera from Germany: Perry Rhodan.
It's pretty unknown outside the country, but still... they had their inhabited rogue like planet in the year 1965 ready if I recall correctly. Its name was... the 100-sun-world. While it wasn't settled by humans, the bio-robots living there where pretty happy just a hop outside the galaxy without a central star.
Guess what its pseudo-science explanation was? Right: they placed about 100 artifact mini-suns around their planet to get a never ending day and surface conditions that allowed the space operas protagonist group to visit it without wearing any protective gear.
So if you feel adventurous, let your guys use a similar solution. At all, there is no hard-science tag attached to your question. Oh, if someone ponder about these robots: their name where "Posbi" I think. They may still be around, because that space opera didn't come to an end until now.
[Answer]
It is my understanding that it is plausible for a "Rogue" planet (one not in orbit around a star) to be heated by other celestial means, such as Dark Matter or a Quasar. The latter of which you might not need to be even that close to in order to absorb its energy sufficiently.
If these premises are true, you could have a planet not orbiting a star sustain life, if you could control some of the other factors mentioned by others here, including a strong magnetosphere to insulate against radiation, gamma and cosmic rays.
] |
[Question]
[
Any suggestions on ways to power large-scale clockwork vehicles? I'm building a world with highly advanced mechanical technology in a D&D-esque fantasy setting, but I haven't decided how to fuel them. I've considered just big hairsprings and flywheels, but I'd like some outside opinion.
Oh yes, steam is not developed until later, so let's avoid combustion for now.
[Answer]
[Leonardo da Vinci](https://infogalactic.com/info/Leonardo_da_Vinci) designed and reputedly built a [spring powered car](https://infogalactic.com/info/Leonardo%27s_self-propelled_cart) in the late 1400's (as a spectacular prop for [Duke Ludovico Sforza](https://infogalactic.com/info/Ludovico_Sforza)). Even with rather gigantic (for the time) springs, modern reproductions of the vehicle could run for about 40m before the springs unwound. This should give you the idea of how much energy density that mechanical power storage has.
[](https://i.stack.imgur.com/iiBQa.png)
*Reproduction of Leonardo's car*
With modern (read 20th century) technology, this can be amplified quite a bit, but generally by using flywheels, springs etc. in conjunction with a high power density device like an internal combustion engine. The best example is the KERS ([Kinetic Energy Recovery System](https://infogalactic.com/info/Kinetic_energy_recovery_system)) used in formula one race cars. Since the engines of F1 cars can reach power outputs of over 1000hp, the KERS need to be able to rapidly "absorb" some of that energy and just as quickly return it to the drive axle so the car can rapidly accelerate out of the corners. KERS is limited to 60Kw (@ 80Hp), which shows that even with modern technology and materials science, this isn't an easy thing to do).
So in a setting where technology is late middle ages, I suspect that a "car" will have a performance much closer to Leonardo's device than an KERS assisted F1 race car. Still, if you use a spring driven device to assist a horse drawn carriage up a hill, then you might be onto something.
[Answer]
If we assume it to be a magical setting where we don't have to follow laws of physics very adequately...
Let's build a gigantic windmill, a mile high and with wide arms so it can harness tremendous windpower. Then, let's make equally gigantic springs from special (magical?) kind of iron. They would be mounted on the windmill and wound up. After that they be used as engines in trains and ironclads. A spring should store enough windpower that it would be sufficient for a journey from the windmill to far away places, with passengers and cargo, and then back. After the return the spring would have to be mounted on the windmill and wound up again.
[Answer]
I have been running a steampunk-esque campaign for a few friends for just over two years now, and some of my players have developed some very unique ideas on how to power very large mechanical devices. Even without steam power, clockwork mechanisms can be "powered" mechanically in many different ways. One of my very favorites is a real life wind-powered machine called a [Strandbeest](http://www.strandbeest.com/ "Strandbeest"). They are probably the closest real life equivalent to a giant "clockwork" vehicle, that is powered only by the wind. In my D&D campaign, the impossible scale of many of the airships and vehicles has been overcome by the creation of a couple new elements. If you are okay with implementing some "fantasy" type elements in your world, you can create some very unique mechanical power sources. The notable reference would be an element that has near frictionless properties, so that It can be used to power some (physics-breaking) perpetual motion machines (only if you are willing to overlook their improbability). Some other notable methods of acquiring mechanical power could be tidal generators, wind, water wheels, or even human power.
[Answer]
Since it is a fantasy setting you could capture small elementals or demons and have them running on treadmills inside the workings. Those treadmills then provide the power to everything else.
[Answer]
While springs or flywheels of the time would probably have a much too low energy density to be useful here, you could use [compressed air energy storage](https://en.wikipedia.org/wiki/Compressed_air_energy_storage).
Compressed air is, to our standards, an awful energy storage :
>
> Advanced fiber-reinforced bottles are comparable to the rechargeable
> lead-acid battery in terms of energy density
>
>
>
And the lower pressure and heavier bottles of the time would be worse. Still, probably the best option.
Charging them would be energy- and infrastructure-intensive: windmills, watermills or big horse-powered mills are also, to our standards, ridiculously inefficient, but they could power a crude compressor and slowly fill your carbon steel bottles. Be careful though, even well-made, expensive bottles may explode if you fill them too much or hit them too hard.
Also note that due to gas expansion, the exhaust will be *cold*. Refrigerators are literally based on this principle. Enough that you will want heaters on some of your mechanical parts to avoid them freezing. Charcoal, alcohol, oil-based mixtures, that stuff Greek fire was made of... Also note that hot gas is more efficient, so if you do have a good heat source, it may somewhat help.
At least refuelling a vehicle may be fast, probably by swapping bottles - assuming you have standard adaptors..
[Answer]
I visited a clock museum, I saw a couple of mechanisms there. One of the mechanisms, I saw there was a weight driven system. Another mechanism that you could use is the pendulum. Other than those the main system I saw was the hair spring, so that would probably be the best bet. Here is a link to the [mechanism and winding of Big Ben](https://www.youtube.com/watch?v=Jz9nxzgtBaU). That clock uses a weight based system, and it's one of the biggest mechanical devices ever built, and that would be a reasonable power source for these large mechanical vehicles, perhaps paired with a fly wheel.
[Answer]
In "The Lord of the Rings" The One Ring could only be destroyed in the fires of Mt Doom where it was forged making it effectively indestructible, this property of indestructibility is commonly attributed to all enchanted items. An enchanted sword at the bottom of a lake will never rust, an enchanted robe will never fall apart at the seams or get eaten by moths, magical armor is always in pristine condition even if its occupant is killed, this is one of the great unstated universal laws of D&D.
So what about an enchanted flywheel?
In the real world you can only store so much energy in a flywheel of a given size before it's torn apart by its own momentum, if you want to store more energy you need a bigger flywheel and this quickly becomes impractical. But with an effectively indestructible flywheel we've got a kinetic battery with a practically unlimited storage capacity that can also be very small and lightweight.
Needless to say this makes high performance clockwork cars entirely feasible.
] |
[Question]
[
We live in an age where cloning technology is close to being capable of bringing back extinct animals. Currently, there are research groups who are moving forward with efforts to clone the passenger pigeon and the wooly mammoth. A cloned wooly mammoth may have some difficulties learning how to be a mammoth, lacking parents to teach it things like how to best use its tusks to root for vegetables, but careful rearing can help the newborn effectively learn to mammoth. It will also seek the company of a group of other mammoths, being a social creature, but again this is a surmountable problem. Either we create a bunch of mammoths simultaneously, or else we integrate them into a herd of elephants until there's enough mammoths to make a herd of their own. Ultimately, they will likely have no problem in the longer term adapting to and becoming a part of the ecosystems of northern Canada and Russia.
Neanderthals, on the other hand, had a complex society similar to our own, and were thinking sapient beings who learned their way of life from their parents. Furthermore, while a mammoth will be perfectly happy wandering the tundra munching on bushes, a Neanderthal, particularly one which was raised by modern humans, is unlikely to want to be left to roam free in the great and open north any more than modern humans do.
How, then, would we best integrate cloned Neanderthals into the modern world? They're likely to sound and look different, eat way more food, and mentally approach society in a different way. What would be the best way to integrate them into our society?
[Answer]
This would be quite the experiment. Unfortunately, since we’re limited to archaeological evidence of their behavior, a lot of what a Neanderthal is capable of will be conjecture.
If you intend to integrate a Neanderthal into modern society, the best way to raise him would be to treat him as a human child. Like a newborn human today, the best way to merge him into our world is to carefully supervise and stimulate his mental development over a number of years and introduce concepts he needs to coexist with others.
Of course, that’s easier said than done. While we are very well equipped with techniques and procedures to introduce new children into society, we are used to the mental capacity and growth of homo sapiens. Neanderthals share many physical traits with modern day humans, but there are a number of significant differences, particularly [lower encephalization](http://archaeologyinfo.com/homo-neanderthalensis/). By looking at their [hypothesized behavior](https://en.wikipedia.org/wiki/Neanderthal_behavior) it does seem that they had some form of society with low complexity. In order for integration to be successful, they need to be mentally capable of behaving like a typical homo sapien.
Communication will be critical. There seems to be both evidence and skepticism about whether or not Neanderthals had a spoken language, but being vocal is not necessarily required. Sign language could be taught and used adequately, so long as the Neanderthal was capable of more abstract critical thinking (which is not implausible given some of their known behavior). Depending on how heavily encephalization impacts intelligence, it is likely that a Neanderthal child would be slower in grasping some concepts and even incapable of grasping others. This could create a very serious challenge if certain things, such as morality, cannot be effectively taught.
Ultimately, no matter how capable the Neanderthal brain is of being taught homo sapien societal concepts, he will be severely ostracized. Attempting to socially integrate another person with different mental capacity almost always causes friction (such as young adults with down syndrome). In this case, we’re compounding that with them being a different species, and one that would be viewed as a lesser evolution of ourselves. This is an individual that would likely be reclusive as he matured, and may well end up being suicidal with a full understanding of his circumstances.
Unlike resurrecting the wooly mammoth or the condor, these would be intelligent beings. It seems unlikely that we could integrate them into our own society and the complications of giving them their own land to thrive on are significant. Even if it were possible, this is an experiment that would most likely never be attempted.
[Answer]
The physical adaptations of Neanderthal man are well known. Neanderthals were adapted to life in Ice Age Europe and the Middle East (a related race called the Denisovans existed in Asia, but besides a very limited number of bones and teeth and their DNA, their physiology and mental ability is unknown). Neaderthals were powerfully built, but also physically different to minimize surface area to deal with the cold. As well, their facial features were distinct mainly to provide for a large nasal cavity to pre warm cold, dry air before it was passed to the lungs.
In terms of mental acuity, the evidence is less clear. In the strata where Neanderthal remains are found prior to contact with Homo Sapiens, there is evidence of some social structure, but a very limited tool kit and not much evidence of art or culture. In the strata where it is clear they could have interacted with Homo Sapiens, there is a sudden flowering of more advanced toolkits (including needles and awls to make fitted clothing), as well as more evidence of art and culture. How much of this was copied from the new neighbours or learned as part of trade and exchanges is unknown, but the circumstantial evidence is that they were never going to develop any of this on their own. OTOH, there is no reason to suspect they were *not* as smart as us; their brains are actually larger on average than the ones of Homo Sapiens, but clearly "wired" differently.
We also know that Neanderthals were not really very social beings; their tribes and clans were much smaller than contemporary Homo Sapiens bands, and it is possible that they became extinct because too many critical skills could be lost in a tiny band if disease or a bad season led to a lot of deaths (if only one person in the band could make stone tools, or knew the best healing plants, their loss would be a disaster). With the increasing pressure on resources by the more numerous Sapiens bands, coupled with the loss of critical skills, it is easy to imagine the tiny bands starving to death in a winter without the nearby Sapiens bands even realizing what was happening until the next spring.
Modern day Neanderthals, *if* they resemble this speculative reconstruction, would fare even less well in the highly interconnected and fast moving modern society we have built. They would have a difficult time assimilating the mass of inputs, and not be able to create a social network to help them cope (technically, you would say that have limited human capital). An experiment that recreated only one would be highly unethical, since the reconstructed Neanderthal would be more isolated than any being in history (in fact, being very much "out of history"). As a minimum, a tribe should be recreated so they have the ability to interact with their own kind, and it would be most ethical to keep them in an isolated "game preserve" so they can live in peace and a bit of comfort on the land, not living in cages or cells in a lab somewhere.
[Answer]
Most of what we think we know about Neanderthal's is myth created by early scientists who were just speculating, and incorrectly assuming evolution always favors the best and brightest.
A more modern and unbiased assessment of neanderthals indicates they were smarter than us, stronger than us, and just as social. We believe they did not have language as sophisticated as homo sapiens, but they did have language.
Neanderthals and humans did interbreed. Most of us have between 1% and 4% neanderthal DNA. This large amount of neanderthal DNA in modern humans is a good indication neanderthals did not get wiped out by, or out competed by humans, but simply merged a smaller population of neanderthals into a larger population of humans.
Besides being odd physically it is likely a neanderthal would do just fine in modern society.
[Answer]
I believe you're making too much of the difference in appearance, and differences in mental processes are unproven. I fear that there will be some discrimination, but I hope that it won't be widespread.
* The first Neanderthal would probably be raised in a lab/creche by human researchers. What are their motives? Are they open about it? Is the baby a media star like [Truman](http://www.imdb.com/title/tt0120382/), or at least a 15-minutes-of-fame starlet like the [Big Brother](http://www.imdb.com/title/tt0251497/) contestants? That could influence how most subsequent Neanderthals are seen.
* Neanderthals are stereotyped as brutish and stupid. Even if that was the case, how much is nature and how much is nurture? There is a good case to say that we're [all part](https://en.wikipedia.org/wiki/Archaic_human_admixture_with_modern_humans) Neanderthal.
* Last but not least, how would a Neanderthal look with access to soap, razors, and a good barber?
[Answer]
I would like to think in this era of tolerance and political correctness, (which generally is overblown and rediculous) they would be at least tolerated, and based on their larger brains, they appear to be very mentally capable, as even a gorilla named Koko has an estimated IQ of ~90. The one thing I think would set us apart is that they don't appear to have that imagination that gives birth to music, art, entertainment, as there isn't much development in technology or tools until humans. They would be intelligent enough to at least grasp the general idea of music, as animals respond differently to music at higher intelligence level. There is evidence we got along fairly well with them, at least in a non violent way. The general manager theory is their groups were smaller, so they weren't aware that their birth rates plummeted. It would be funny if we did get along with another human species, considering there's already predjiduce within our own race(homo sapients)
[Answer]
My first thought is that their behavior would be destructive either to themselves (himeself) or their immediate environment. I belive they would have a different thought process than typical human beings. Differences in physiology are very widely documented such as pronounced brow ridges and larger brain case, missing chin protusion. All these differences add up, Even if you bathe, shaved and groomed, they would instantly be different to the eyes of a "normal" person. That would only serve to keep them segragated from the community as least initially.
Now imagine this clone starts life as a baby and is trained as it grows up. I would assume that certain cultural things would be learned and others would not. They would have many similarities to modern humans, that is they can laugh, create jokes, have desires, create intrigues and many things typical people also do. But it stops at a point where the Neanderthal cannot assimilate to modern culture. This would vary from Neanderthal to Neanderthal but it analagous to being shorter than normal and asked to reach for something on a high shelf and there are no step stools in existence. We all have observed this and what happens is the person falls back on primal instinct which manifest as screaming, hitting, sulking, breaking things, etc. (road rage, punching walls and throwing computer monitors on the floor). The difference is that Neanderthal would reach this level sooner because so much of the world is on that high shelf.
If you believe the hypothesis that they died out because they were conquered and exterminated by modern (cro-magnon) humans then it is possible that much of the modern culture is on the "high shelf" and cannot be assimilated by Neandethals. The primitive humans would reach the point of frustration quickly and fall back on primitive instinct.
What happens next is well documented in the history of people and their treatment of the insane and people with development disabilities. That is, society's first instinct is to shut those people away and keep them out of sight for their own protection. Your story may go further and place them in a zoo environment where they can be observed without knowing they are being observed.
How would these people fare, there is no happy ending because they are actually sentient. Unlike the mammoth, they will quickly begin to feel oppressed by what they can observe. There will be people that want them dead because they are different. Others will champion them but will only feel neanderthals are something inferior that need protection from other "normal" people and cannot take care of themselves. No one, or maybe a few people will realize they are just other people who are not sick and can be loved like anyone else.
[Answer]
Since this neanderthal is cloned. He/She has no reference point to judge their surroundings in our time from their own timeline.
Although it's a certainty they would have diminished capacity for understanding
and intellect, in theory they should still be able to cope well enough to live out a normal (whatever that means) life.
[Answer]
I think that they would be kind of able to integrate into our normal society, but not quite..
Here's an example of what could happen:
A Neanderthal child is put into a normal kindergarten class. As soon as he arrives, the other children begin whispering about how ugly he is. This makes the Neanderthal child feel sad. As the school year goes on, the teacher learns that he has higher than usual physical skills, but has trouble with some subjects. He also has more primal instincts, such as getting very angry when something "unfair" happens.
Fast forward 25 years later.
The Neanderthal has integrated into normal society, but slightly backward. After about 100,000 Neanderthals are created, the UN (with the consent of the Neanderthal's leader) builds an island in the Atlantic that is about the size of California. After being taught skills such as advanced farming and formation of civilizations, they are brought to the island and recognized as an official country.
That's the most optimistic view. The most pessimistic view would be intense discrimination and even slavery...
That's my view, anyway.
[Answer]
This is all just speculation since we don't know a whole lot about the specifics of just how different neanderthals were socially compared to their distant cousins(our direct ancestors)
* They were "designed" to be more physically powerful, as opposed to mentally powerful
* They appear to have not had spoken language
* They were much larger in size than we were
* They ARE a different species than us(no successful interbreeding)
As a result, they communication would be an issue, they are likely to be more intelligent than say an ape, but they aren't likely to be anywhere near the intellectual capacity of a human.
I really would disagree with your assumption that they would want to be integrated into our society, without an ability to communicate(except perhaps with broken sign language) they would likely be treated like animals, being used as a cheap source of labor. We created the type of society we have today because it best suits us as a species. It wouldn't very well suit a neanderthal, since from what we can tell they aren't nearly as social as we are.
However, you could take advantage of how little we know and allow them in your story to speak(I would leave them fairly dull, however since intelligence is one of the major differences between our two species). If they were able to communicate effectively their superior strength would make them invaluable assets to the blue collar industry. However, discrimination due to their differences is unavoidable, and they will likely(at least for a period in time) be taken advantage of (lower wages than would normally be legal, since they aren't technically human) at least for a time, until they become a regular part of society
] |
[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/18755/edit).
Closed 6 years ago.
[Improve this question](/posts/18755/edit)
Many fantasy stories include Old Gods (i.e. pagan deities from largely defunct religions) who still exist during modern times. Whether they're like Marvel's Asgardians, who exist largely unchanged in a far-off realm, or Gaiman's *American Gods*, where they could literally be sitting next to you on the bus, these stories present beings who once ruled the world and who often possess incredible power, still existing in the present day.
However, to match up with the secular reality of modern life, these Gods have withdrawn from the world, or at least are no longer seeking worship from humanity. They are anonymous or absent altogether, and their withdrawal matches up with the end of their worship among the peoples of historical Earth.
Why would this be true? If we grant the premise that the Gods exist, and that they were worshipped for centuries or millennia (implying that they require or at least enjoy human attention), why would they permanently and unanimously retreat into anonymity, all within roughly the same few hundred years?
And, perhaps more interestingly, why would they go down without a fight?
[Answer]
If we assume benevolent deities who weren't simply *using* humanity
One possibility is they were trying to bootstrap humanity.
"Mythic ages" were *dangerous* places. There were generally hostile species (or even pantheons for other species who were against humanity). Gods, demigods and other such benevolent or semi benevolent entities might have helped mythic age humanity not get eaten like popcorn by monsters, or survive the local hostile demon, or demon like creatures.
However once humanity was able to survive on its own, they didn't *need* direct divine intervention, and free agency without too much intervention was a more benevolent stratergy.
[Answer]
Much like that [question](https://worldbuilding.stackexchange.com/questions/18709/discrimination-in-a-world-physically-influenced-by-what-their-inhabitants-believ), or a similar gods effect illustrated by the Darshanide Gods in [Lanfeust of Troy comic books](https://en.wikipedia.org/wiki/Lanfeust_of_Troy), the power of the Gods are granted to them through the strength of the belief of their followers. As people gradually stopped having faith in them, they lost their powers.
Now we can suppose that they are anyway immortal beings, which make them continue to live in our days, but their other powers come from faith that is no-longer there.
Now, did they go without fight? Well, one could argue that probably they lost some of their powers with time: maybe they were too busy partying in Olympus, or disappointed by the humans. One could argue that the Gods are, like humans, subject to decadence: see the Fall of the Roman Empire.
But then, some other religion came in, and *that* did not go without a fight: see how the Jews were enslaved by the Egyptians, the persecution of the Christians by the Romans, the religion wars of Renaissance's Europe, etc. Those could be the effect of the already weakened Gods puting a fight to counter a new faith that would and will bring their downfall.
And then comes the vicious circle: the less power they have, the less they can favour their believers, the less believers the get, and hence less power.
Once their power have gone down, they can choose for themselves what do they want to do, in face of their eternal life curse. Some retreats in their once-powerful Kingdoms (Asgard, Olympus, etc.). Some just blend in the population, trying to be helpful. Some still try to get some power by wandering the world, trying to revive the Old Faith. Some of those might just be writing Fantasy books.
[Answer]
If you read through old mythologies they often feature stories of the gods overthrowing giants, titans and dragons who had ruled the world before them. Those giants were once gods themselves turned from heroes to monsters by the power of a new religion, lost in the detritus of history and fading with the memories of forgotten priesthoods.
Gods have always been cast aside with the passage of time.
The things that has changed is that with the written record they are no longer entirely lost. They exist where they have always existed- in our minds and in realms of pure consciousness that are - as yet - inaccessible to physical travel. Now that we have a way to store their stories and their memories, they can persist with a mild glow, like the weak embers of a once-great fire, but their influence, their ability to shape and change minds is greatly weakened. They are little more than stories now. They can no longer change hundreds of minds at once to create visions or miracles, but from time to time they can find someone particularly susceptible to their influence and perhaps direct them with the hope of drawing more followers, though more often than not the people involved are considered to be mentally ill.
Meanwhile they watch enviously the few holdouts from their era who have managed to retain enough followers, enough belief, to guide people still and the new upstarts whose grand temples shine across modern cities- "The Markets" and "The Consumer"- potent, faceless, deities for a faceless age.
To appear physically in the world takes great power, requiring a vast following, to create an image in many minds at once - even something they expect to see, like a person walking through a crowd - is only marginally less challenging. Whispering in a single ear, creating a picture in a single mind, especially if that mind is particularly open to your message - that might be as much as a weak and largely forgotten god could manage.
[Answer]
There are other names for non-human things that are extremely dangerous. We call them "Extinct", or "Endangered". Or possibly, "Zoo Animals". Humans historically don't play nicely with things that can kill or hurt us.
As technology advanced, humans got more dangerous, and gods who kept a public presence started to die. Sure, a single human isn't much of a threat, but put a couple of thousand together with advanced weapons and maybe some explosives, and it turns out even Thor or Zeus need to watch out.
The gods, being long-lived and reasonably intelligent, could see where the wind was blowing. Unable to stop or slow scientific advances, they decided to blend in and hide instead, talking the route of discretion as the better part of valor. This would happen over a fairly short period - a couple of hundred years - but it wouldn't take too many dangerous humans for the various pantheons to get the message.
[Answer]
The classic mythological model here is what Mircea Eliade and others called a *deus otiosus*. In essence, this is a god who has removed himself from the everyday lives and ritual practices of his worshipers.
In terms of religion and myth, the pattern -- well attested in east Africa, the ancient Near East, and sporadically elsewhere -- tends to involve a senior creator-god, an "all-father" like Odin or Zeus, plus a pantheon of lesser divinities with relatively particular areas of interest and influence. The creator creates the world and all in it, sometimes with help of the others, and sometimes simply by creating those lesser divinities as helpers -- or both. Having done this work, the creator essentially lays down the rules for how humanity should relate to each other and to the gods... and then goes back to wherever he actually lives (the sky, the mountaintop, etc.).
From the worshippers' point of view, this means that ritual life is divided into practices that address lesser gods within their spheres of interest. Thus women seeking help with childbirth or pregnancy, or men seeking help with hunting, address their prayers and rites to the goddess of fertility or the god of the hunt, respectively. On certain unusual occasions, principally annual rites of especially awesome dimensions, the senior priesthood (or sometimes an otherwise "secret" priesthood) addresses collective sacrifices to the creator, more or less thanking him for all he has done to make life possible and ordered, for creating the lesser gods, and so forth.
Every now and then, however, really bad things happen, such as a long-extended drought, or a plague, or something like that. The prayers addressed to the lesser gods don't seem to be solving the problem. At this point, the senior priests and the community at large come out to beg for the intercession of the creator.
Think of it like a bureaucracy: you don't go to the CEO when your computer doesn't work, you call IT; when the whole company is collapsing, it's the CEO who is (supposed to be) responsible.
Now the question here simply reverses the perspective on this not-uncommon pattern, asking why the gods behave in this fashion. In addition, it posits that *all* the gods have receded, not just the creator.
To address this, I would begin with the previously-described *deus otiosus* pattern, and think about the stories people tell. The question isn't why gods *actually do* this or that, but rather what people *say* about such matters. Even in a fantasy world where the gods may manifest directly, they're not especially likely to explain themselves. Why should they?
What I think is lacking from the question is consideration that there may be fundamental disagreement about the gods' actions. If we take the situation you've described, I can see various cults that account for the situation differently:
1. The gods have abandoned us because we failed to act in a manner they approved. We must return to the old ways, obey every jot and tittle of the old law, and then the gods will come back.
2. The gods were never really there anyway: they were a fantasy of superstitious rubes. Now we can see clearly that there are no gods, so we should get on with making the world a good place for us.
3. The gods disappeared for reasons we cannot fathom, because we don't have enough information. We need to keep faith and watch for the signs of their return.
Each of these perspectives will generate mythological material that answers the question posed, but they won't entirely agree -- or even agree at all.
[Answer]
Do you know how much *work* it is to be a god? You get to the office in the morning, learn that your demigod assistant still hasn't learned that it's *double* espresso, *one* sugar, darn it, and face the overflowing pile of petitions from worshippers. Meanwhile, two of your fellow gods have been nagging you for weeks about reviewing a design for that new creature they want to set loose in the brush, and one of them is still fighting with one of the goddesses over that incident with the rapid-growth plants that weren't *supposed* to be an impenetrable jungle, and good heavens is it not even 9:00 yet? Ugh, going to be a long day.
Beings that don't *need* to keep working and don't derive pleasure from it *retire*. Your old gods have been at this for, what, millennia? Eons? Even if it's only centuries, are they perhaps getting a little tired of it all, or bored? Being gods, they don't *need* to remain actively involved; doesn't this sound like a great time for a vacation -- or, if you prefer, science experiment, to see how their creation functions without them?
By 9:30 the inbox is no smaller but the travel plans have been made. The inhabitants of the world, maybe overseen by some of the lesser divine beings, can run things for a while. The gods and their heavenly court are off to do something relaxing, exciting, or different.
Except your coffee-challenged demigod; he's not allowed to come until he learns how not to mess up drink orders.
] |
[Question]
[
As I asked in [**Previous Question**](https://worldbuilding.stackexchange.com/questions/13119/what-will-be-the-roles-and-strategies-of-big-countries-in-the-conflict-between-i?noredirect=1#comment31435_13119) about the role of countries in the conflict between India and Pakistan and most of the answers suggest that there is **less chance** of involvement of other countries, I like to move ahead to the next situation.
**If nuclear war was started by Pakistan ('first strike Policy')**, what would be the consequences of this war on both countries?
I am giving the following situation and restrictions about nuclear War , try to answer while keeping these in mind.
**Situation and Restrictions**
1. Nuclear war started by Pakistan after 20 -25 days of conventional war with India.
2. Main nuclear targeted cities by Pakistan are [**New Delhi**](http://en.wikipedia.org/wiki/New_Delhi), [**Mumbai**](http://en.wikipedia.org/wiki/Mumbai), [**Bangalore**](http://en.wikipedia.org/wiki/Bangalore), [**Ahmedabad**](http://en.wikipedia.org/wiki/Ahmedabad).
3. Main nuclear targeted cities by India are [**Karachi**](http://en.wikipedia.org/wiki/Karachi), [**Lahore**](http://en.wikipedia.org/wiki/Lahore), [**Faisalabad**](http://en.wikipedia.org/wiki/Faisalabad), [**Rawalpindi**](http://en.wikipedia.org/wiki/Rawalpindi), [**Peshawar**](http://en.wikipedia.org/wiki/Peshawar).
**Specifically:**
1. what are the estimated number of **Human casualties** from both nations?
2. what will be the **Future and status** of both country after nuclear war?
3. what will be the effect on **Worlds economy**?
[Answer]
>
> what are the estimated number of Human casualties from both nations?
>
>
>
A whole freaking lot, at least on the Indian side. The total population of India is 1,210,193,422. That's a billion...the one that starts with **B**.
* New Delhi: 21,753,486
* Mumbai: 20,748,395
* Bangalore: 8,520,435
* Ahmedabad: 7,250,000
Now, without exact placement for the bomb, the weather conditions (wind for example), what type of bomb all we can do is estimate but modern nuclear weapons are pretty ridiculously powerful. I will go with an 80% kill rate in the metropolitan areas. This includes the initial blast and after affects (radiation poisoning for example).
* New Delhi: 4,350,697
* Mumbai: 4,149,679
* Bangalore: 1,704,087
* Ahmedabad: 1,450,000
Total Indian Loss: 58,272,316 - 11,654,463 = 46,617,853 Dead.
I'll let you handle the math for the Pakistani side.
>
> how it will effect Social life of peoples of both countries?
>
>
>
Simply put there would be no social life for a long time. Those that did survive would be husks of human beings. Either the people would get angry and things would escalate, or they would give up. With actions this devastating there really isn't much room for a middle ground. You're either going the Gandhi approach, or the massive retaliation approach.
>
> what will be the Future and status of both country after Nuclear war?
>
>
>
Neither country is particularly wealthy now and both have high levels of corruption in government. That said the government would collapse. Both nations would likely become donor states that receive significant foreign aid for years to come. It's tough to say what would happen beyond that.
>
> what will be the effect on Worlds economy?
>
>
>
Due to significantly fewer consumers and the threat of the war, markets would collapse. Best case scenario is that no one takes sides and the conflict is isolated to the two nations...otherwise it could get way out of hand. Lets just generalize and say: SIGNIFICANT negative impact.
[Answer]
According to the wikipedia pages about [India's](https://en.wikipedia.org/wiki/India_and_weapons_of_mass_destruction) and [Pakistan's](https://en.wikipedia.org/wiki/Pakistan_and_weapons_of_mass_destruction) weapon's programs, each side has about 120 bombs and has tested up to the 20-40 kiloton range.
Using [Nukemap](http://nuclearsecrecy.com/nukemap/) to estimate damage effects from bombs of this size (all damage radii mentioned below come from this source) it seems pretty clear that Pakistan can take out the listed four cities with 120 warheads. While the arsenal isn't that impressive compared to American or Russian stockpiles, 30 bombs per city is pretty serious. Since many of my coworkers are from India or Pakistan, I'm not going to sit at my desk running simulations of nuking their homelands (might constitute hostile work environment), but we can estimate how some of these cities would fare after getting hit with this attack.
## Direct Effects (Fireball, Blast, Overpressure, Thermal Pulse)
The good news is that these bombs are relatively small (compared to the 500kt - 1mt bombs fielded by the US or Russia). The radius of total destruction (fireball) is about 220m, while blast and thermal effects have a radius of 2.5km. Each attack can blanket a huge area with moderate-severe damage (30 bombs \* 17 sq. km. blast area = 510 sq. km) if the bombs are dropped spread out, or a still-significant area with total devastation (30 bombs \* 0.15 km^2 fireball area = 4.5 km^2) if the bombs are dropped close together, but either way, the destruction would be relatively shallow. What I mean by "shallow" is that any point more than a few kilometers from the nearest strike will be relatively unaffected.
Since New Delhi is much bigger than the moderate-severe damage area calculated above (New Delhi is about 1,500 km^2, compared to 510 calculated for moderate-severe damage), New Delhi will be horrifically damaged, but not destroyed outright. It could be like Hiroshima on a much larger scale. The other cities are much closer to the size of severe destruction, so they will be more-or-less totally destroyed, though there will be survivors and many well built buildings will still be standing.
Of course, that assumes you target 30 bombs at each city. I'm guessing a more optimal strategy would be to target by size, so as New Delhi is about as big (by area) as the other three combined, it gets half the bombs. By this method, about two-thirds of the area of New Delhi is moderately to severely damaged (weak buildings destroyed, strong buildings damaged, areas directly hit totally vaporized, unprotected people killed or injured), with the rest much less damaged. The other cities have about the same damage, though Mumbai has much, much higher population density, so the death toll there is likely by far the worst.
The Pakistani cities are much less densely populated, so the destruction will not be as bad. Karachi is like 3,500 km^2, which is just huge. Although the Indian arsenal might be larger or more powerful (this is unclear), each Pakistani city will fare better than the Indian counterpart.
I don't know the normal building materials in these cities (and most of the images I can find online are just pictures of the skylines, city centers, and tourist locations, so I can't guess at what the building materials would be in the majority of the buildings). American suburban frame houses would be totally obliterated by the blast effects (and the flying pieces would be in flames) throughout the moderate to severe damage area, while Stalinist-era concrete Russian apartment blocks would probably still be standing through a lot of the area (though human casualties would still be high, and damage would make many of the buildings unfit for habitation). The excellent US government compiled book [The Effects of Nuclear war (pdf warning)](http://atomicarchive.com/Docs/pdfs/7906.pdf) has a lot of details about how this makes a big difference in destruction amounts and casualty numbers, though it doesn't compare any Indian or Pakistani cities, just Washington and Moscow. Google image search seems to show Indian cities as better built than Pakistani cities, but I have no idea how accurate this is.
## Indirect Effects (Fire, Fallout)
The bad news is that direct effects aren't the only problem. Because these attacks are likely to be airburst (for maximum casualties), radioactive fallout won't be much of a problem, but fire definitely will.
Within the area of moderate to severe destruction mentioned above, almost anything flammable in the open will burst into flame. Exactly how bad the fire gets depends a lot on the composition of the city. Building materials obviously play a role. How close the buildings are to each other will impact how fast and far the fire spreads. Since the thermal effect is line-of-sight, topography could cause areas which are shadowed and therefore not ignited. Firebreaks like highways or rivers might spare sections of surviving city from the fires. Even wind direction, humidity, and how recently it has rained will play a role. That said, when something like two thirds of your city has been exposed to the thermal pulse of a nuclear bomb, you're going to have serious fires, and no amount of firefighting will make much of a difference.
These cities are pretty much doomed. Not everyone will die, there will be tens of millions of survivors, but they will no longer be functioning cities for decades.
That said, the lower population density in the Pakistani cities means they will likely fare better than their Indian counterparts, unless they are much more flammable.
## Damage to surroundings
Because the bombs are fairly small, the damage outside the area scorched by the fires will be relatively minor. Many of the suburban areas of the cities will not be destroyed by the bombs, and the outlying towns and countryside will suffer no damage at all.
## Damage to the Nation
Exactly how bad the damage to each nation will be is hard to estimate. I'm going to provide a few guesses in these areas: population, government, economy.
### Population
India's population losses are huge. Almost the entire population of Mumbai (because of high density), and most of the population of the other three cities has died. This is something like 51 million people, making this attack the deadliest single event in history. On the other hand, this is less than five percent of the total population. While no country has ever lost 5% of its people in a single day, many historical plagues have had much larger tolls over the course of a few months.
Pakistan's losses are somewhat less. Because of lower population density, fewer Pakistanis would die. Something like 50 million people live in the affected cities, but picking an arbitrary figure and saying the death rate is only 60% of what the Indians experienced, this is a death toll of something like 30 million. However, Pakistan has a much smaller total population, and this will constitute over 15% of the total national population. While this is still not as bad (long term at least) as some historical plagues, this is a proportion three times larger than India experienced. In population terms, I think Pakistan loses this war.
=== Government ===
I don't have any idea what will happen here, but there are some things worth thinking about.
India has lost its national capital, and several of its regional capitals as well. I am not from India, so I cannot say what that would do to the national spirit, but I think national services could be seriously damaged, and separatist movements might spring up everywhere (and be strengthened where they already exist).
Pakistan has not lost its national capital, but it has lost regional capitals. All this damage can't be good for national stability (not that great already by international standards), but it might be better off from a government standpoint than India is.
=== Economy ===
India has lost four cities out of its approximately 50 cities with populations over 1 million (8%). Based on Wikipedia numbers, it's kind of hard to guess the economic output of these cities, but I see a figure of 6% for Mumbai, somewhat more for Delhi, and less for the other two. Wild guess here: Something like 20% of the economic power of India was in these cities, and has been destroyed.
Pakistan has (mostly) lost four cities out of its approximately 15 cities over 1 million (26%). [Karachi accounts for more than half of Pakistan's tax revenue, 25% of its domestic revenue, and 30% of its manufacturing sector](https://en.wikipedia.org/wiki/Karachi#Economy). Wikipedia notes that Lahore [is almost exactly half of Karachi, accounting for 12% of the national economy](https://en.wikipedia.org/wiki/Lahore#Economy). The other two cities are about 4% and 3% each. Something like 44% of the economic output of Pakistan (and much, much more than half its tax revenue) comes from these four cities. If the strikes were targeted to maximize damage to important industries, almost all of this might be destroyed. Pakistan definitely loses on this metric.
== Effects on the world ==
The world would be pretty seriously impacted. Two of the world's five largest cities have been destroyed, millions killed, and a huge percentage of the GDP of two nations has been destroyed, with the rest of the economy in these nations likely tanking or turning inward towards rebuilding. Nations with direct ties to the two countries are hit hardest, while others are impacted less directly. I don't know the total results, but it would be bad. My guess is that it would be at least as bad as the 2008-2009 global financial crisis, and maybe far worse.
Anyway, the results would be horrific. Everybody loses, Pakistan loses more.
[Answer]
Despite the loss of lives the world would face drastic effects. There would be nuclear winter which would further worsen the conditions. There would be a hole in the ozone layer. The winter clouds would bring darkness in the region thus affecting badly agricultural production. inflation will rise drastically breaking its records of WW2 and the "winter clouds"will move to many different regions forced by winds. On the contrary the whole world would be in a mess. People who are below poverty line today might die of inflated food prices. Also the "skillful youth" that would have rather developed human and other sciences would be lost... In all there would be no useful outcome as "wars provide no solutions"..
] |
[Question]
[
Would it be possible to modify a human to be able to survive in space without protective gear?
Genetic engineering and cybernetic enhancement are both allowed, although when not in space the person in question should look completely normal.
I'd be interested both in modifications that allow emergency survival (for example functioning for 5 minutes in order to allow you to reach shelter after a hull breach) through to actually being able to live and work in space for extended periods of time wearing only minimal protective clothing.
[Answer]
Surviving in space (a vacuum) is fortunately not that hard, the dangers are exaggerated in fiction.
How I would go about this is making whale-like modifications to humans, in many ways going from a high pressure environment to low pressure, is not too different to going from a low pressure to vacuum. So all the tricks which deep sea diving mammals [such as whales](http://scienceline.ucsb.edu/getkey.php?key=1009) use to retain functioning for minutes or hours under the sea, could be implemented to improve human functioning under extreme pressure and oxygenless environments.
This includes:
1) Resistance to the bends.
2) The ability to store (or economize on) oxygen.
3) The ability to collapse the lungs.
4) Modifications to ensure the ongoing functioning of the cardiovascular system even under extreme conditions, much like the whales do it.
The next point of vulnerability is the eyes in particular, as the moisture rapidly boils away. A biological mechanism which could help is a tough transparent inner eyelid, such as many reptiles and fish have. By sitting flush against the eyeball, it would help protect against the vacuum, while the human could retain vision.
For more comfortable functioning in vacuum, it would likely be necessary to generally toughen up and improve the seal of the skin, we might want features such as ears and nostrils which can be closed tightly, thus protecting the delicate membranes within. In a vacuum we have no use for the ears or nose.
With relatively simple modifications like this, it wouldn't be healthy to be in a vacuum, but functioning may be retained.
If you want much longer functioning, one of the major issues is going to be oxygen. You simply need to store more of it. Whales can do up to 2 hours. It would probably be possible to push it even further with further modifications. Ultimately though there is no way to get oxygen in a vacuum, so a human is stuck with what they can store in their body. Also, as the human isn't breathing, it is also necessary to store CO2 in the body, until such time as the lungs can operate again. This CO2 makes for another constraint.
The other problem is temperature regulation, unless exposed to direct sunlight, the greater problem is going to be getting rid of excess heat, as vacuum is highly insulative. Sweating would continue to function, as water evaporates just fine in a vacuum. This then places another constraint on maximum duration - the amount of water we can store in our body, and stand to lose without passing out.
With a full suite of whale-like modifications, plus additional modifications for exposure to vacuum, a human probably could remaining functioning for about one hour in hard vacuum. Longer than that would likely require mechanical or nano augmentation, such as a unit capable of removing CO2 and replenishing oxygen in the bloodstream. Note that a human uses non-trivial quantities of oxygen, about 20L an hour, even with efficiency improvements storing oxygen is going to become a problem, and rather than storage you might be looking at some kind of externally powered unit which processes CO2 into carbon and Oxygen, thus giving extended operation without external oxygen. Biologically this process is called photosynthesis, and sunlight is available in space, but grafting vacuum-tolerant branches onto a person's back, and then putting them in the sun, would introduce a host of other problems. But in principle a well designed photosynthetic human might be able to operate in vacuum for extended periods, it's just the skin wouldn't have enough surface area - an entire mature **tree** only produces oxygen at about the same rate as one human burns it, so you would need a massively more efficient process, and it would need to operate in hard vacuum.
So actually both oxygen storage, and oxygen recycling, would be problematic, making for something of a limit on how long a human could function in vacuum, without adding hundreds of kgs of mass onto him.
[Answer]
From what I have read, the boiling issue is actually not as large as it sounds. As you boil, the surface chills down rapidly. You'll suffer frostbite quickly as the outer layers of your skin/tongue/eye freeze, but you actually don't boil away all that fast because its limited by thermodynamics. The body is actually a pretty good bulk heat source.
The current limitation for human "spacewalking" is that we aren't equipped to hold onto air in space. It's really hard to hold 1 atmosphere of pressure. The air literally gets ripped right out of our lungs. These pressure differences are similar to those we see in diving mishaps where a diver surfaces without exhaling. Rising from 10m under the water (with SCUBA) without exhaling on the way is sufficient to cause high risk of pulmonary barotrauma. 10m of water happens to be roughly 1 atmosphere, which is what your spaceperson is experiencing. So one solution would be to beef up the lungs to take that kind of abuse. However, it's not easy to improve on such an amazing system as the lungs, so I'd suggest a different solution.
**Give the brain a way to consciously route blood around the lungs instead of through them.** Currently humans can survive 14 seconds in pure vacuum, if they exhale to avoid barotrauma. The limit is actually rather frustrating: at 0psia, hemoglobin releases oxygen rather than capturing it. All of the blood passing through the lungs releases its oxygen into space. It takes about 14 seconds for that completely deoxygenated blood to reach the brain and cause instant syncope. If you could route blood away from the lungs, you could cycle it and survive much longer. You would just have to build up your anaerobic tolerances in your muscles so that they don't use up oxygen that your brain needs.
We even have the starts of this hardware. The [Fossa ovalis](http://en.wikipedia.org/wiki/Fossa_ovalis_%28heart%29) is a hole between the right atrium and left atrium of the heart. When we are still developing, and getting our oxygen needs from the placenta, this hole exists to allow most of the blood to bypass the lungs completely. The septum primum is a sort of valve that goes over it to prevent blood from going the wrong direction. During our first breath, the pressures in the pulmanary portion of our circulatory system to drop, pulling the septum primum shut, and we fuse it shut in very short order (having fulfilled its purpose). We do similar to the [Ductus arteriosus](http://en.wikipedia.org/wiki/Ductus_arteriosus) and the [Ductus venosus](http://en.wikipedia.org/wiki/Ductus_venosus) for the same purpose.
[Answer]
If one only needs to survive a few minutes until rescue, only a few modifications need to be made.
The biggest issue is gas loss - the air in your lungs will immediately evacuate as humans cannot hold their breath that strongly. My solution would be primarily an artificial one - a cybernetic lung. Replace one lung with a backup oxygen supply and carbon dioxide scrubber. Upon pressure loss, the normal lung collapses and seals shut (prevents active loss of oxygen from the blood) while the artificial lung takes over using stored emergency supplies to keep the individual alive. People living in artificial atmospheres should be fully functional with only one lung, so this shouldn't be significantly damaging for daily life (depending on efficiency of the unit and expected service period, perhaps only one lobe of a lung need be removed). Without the artificial lung, the lungs need to collapse and seal off as the person immediately enters into a state of hibernation to slow metabolism as much as possible.
On the *not strictly speaking necessary for short-term survival but would be nice* list:
All orifices will need some modification to protect the delicate tissues. The eyes could use some kind of robust nictitating membrane which could still provide visibility but seal shut the eye socket. This shouldn't really effect the appearance much, because it generally keeps out of the way, and we still have the vestigial remnants of one so it should be an easy adaptation. The nose clamping shut to protect the mucous membranes will require a little more musculature, but that should be minor and not necessarily change appearance (possibly a slightly more bulbous nose which some people have anyway), though some enhanced viscosity mucus could just plug the nostrils. The lips will need to be a little stronger to hold shut to protect the moist tissues - certainly not enough to hold in the breath, but just reduce moisture loss with partial pressure (uncertain as to how much good that can really do). The eardrums will need to be significantly strengthened to not be blown out in the initial decompression (very minor change).
Lower down, I'm thinking modified urethral/Bartholin glands secreting some kind of special protective mucus whose release is triggered by very low pressure. The mucus should protect the tissues by keeping the mucus membranes moist. Some analog could be used for the anus as well. This will somewhat protect the person in vacuum from the worst of it, but when decompression happens... wear a diaper.
The skin is probably sufficient but some finer stronger protein mesh reinforcing it might be desirable (an unexpected decompression may not be a safe event and a cut could become a more serious rupture in vacuum). Capillaries should likewise be toughened to reduce serious bruising, but this needs to be balanced with risks of arteriosclerosis. No visual changes here, just more resistant to bruising and lacerations.
This should keep a person alive for a few minutes in the event of getting thrown out an airlock, but not cause any obvious external changes.
[Answer]
I would say the first thing would be to modify the skin. It would need to handle at least short periods of extreme cold and also be able to prevent the body from freeze drying through moisture release as the body tries to equalize with the surrounding environment. Though of course having specialized body suits could help with this. If the body isn't loosing moisture or other matter it will dramatically slow the freezing process.
The next piece would be to protect the eyes. Both from freezing and from any light source that might blind you. There are different ways to do this as well. The easiest of course would be to replace eyes with cybernetic implants, allowing one to see the full EM (or much more of it any way) spectrum. One step back would be cybernetic goggles that have an interface to the brain and sit over the eyes but could be removed like glasses.
The last is the most difficult and most important. the lungs and enough oxygen. My biggest recommendation for the average space explorer would be something [like this](http://www.hovding.com/how_hovding_works/), this happens to be a bicyclers airbag, it blows out into a protective helmet. Having something like this that would expand to protect the head and supply some oxygen would be the most useful and likely to happen. It would have to at least encompass the torso with the head to allow the lungs to expand AND contract to allow breathing.
However, going cyborg, having a CO2 scrubber for your blood stream and a back up oxygen tank to work in place of the lungs might be what is needed. Of course having blood that can carry very large amounts of Oxygen would be extremely helpful, maybe even having nanobots that keep a 'backup' supply all throughout your body and in the blood. Then you just need to have a reflex not to exhale or try to inhale, when in a vacuum.
[Answer]
The biggest problem is lack of oxygen. Over time radiation and evaporation due to low pressure become lethal as well. I don't think temperature as such would be a problem since vacuum is pretty good insulator. Heat loss would be thru radiation and evaporation only, no conduction or convection would happen.
For oxygen, the solutions would be storing it (whales do this), regeneration thru photosynthesis, switching to anaerobic metabolism, or, my favorite, making people carry oxygen masks. Second pick would be the anaerobic metabolism, our muscle cells already can do that under exertion, so it could be built incrementally on top of existing systems. You'd basically extend it to work on all cells and add something to deal with the lactic acid.
This would be enough to deal with emergencies, given some training. The issue is that the vacuum would probably mess up your senses with eyes drying up painfully due to evaporation and ears obviously being useless and probably hurting a lot. Without training this would probably cause lethal panic and disorientation. But if you knew where to go and what to do and kept your calm surviving the five minutes should not be an issue. Making blood store more oxygen would probably be enough as well. I think some divers can already do this, actually. So simple training might be enough without any genetic stuff.
The second most urgent issue would probably be protecting the eyes so you could see properly in the vacuum. A nictating membrane similar to what camels and polar bears use to protect their eyes should be enough since you just want to stop evaporation not to have a pressure differential. And we probably still have much of the genes...
Overtime evaporation from the lungs and elsewhere would become an issue. Some sort of protective mucus that dries and hardens in vacuum and stops loss of water might work. It doesn't really have to be that perfect since we'd still want to use evaporation for temperature control. I am guessing the easiest solution would be to simply have more fluid to begin with. A thicker, more rounded, body would help there.
The final killer would be radiation. Protective clothing would help, unless people want to go to space naked. It might be easiest to make the protective mucus mentioned before highly reflective so that it reflects most of the UV-radiation and much of the visible light. UV-radiation might also be a convenient trigger for releasing the mucus. And being highly reflective isn't a bad thing, if you are waiting to be rescued while floating in space.
Note that this answer only dealt with short term adaptations. For long term survival more extensive changes would be needed. It would probably be easier to use space suits or even robots. Remote controlled robots would probably be much more practical for vacuum work than adapting to live in vacuum.
[Answer]
A lot of living organisms produce shield like armor to defend against climatic extremes. This sort of behavior mainly happens on the microscopic level though. The process goes something like this:
1.) Environment gets tough
2.) bacteria start producing this shell (called an [endospore](http://www.wikipedia.org/wiki/Endospore))
3.) Bacteria go dormant until sustainable environment makes survival and reproduction possible.
While I am sure that, given a couple hundred years or so, we could modify our cells to do this, it is a highly unlikely solution to things like a hull breach because this protective shell is:
A.) limited in what it can protect against
B.) causes the organism to become dormant.
In short, rather than saving the person, I speculate that a massive case of endosporic cells would cause the person to go dormant and float into space if the breach is large enough. If you want to read more about bacterial spores check out [this](http://www.wikipedia.org/wiki/Bacterial_spore) Wikipedia site.
] |
[Question]
[
For the sake of scope, we'll assume the warrior already have the potion in their hand.
Also for the sake of scope, we'll assume there's no magic to help a person drink faster. It all relies on technique.
In combat, time is everything. If two warriors fighting each other drink a healing potion, but one takes 1 second to chug down the liquid while the other takes 3, the slower one will probably not survive, all else being equal.
Potions are stored in ceramic or glass vials with a cork stopper, and are standardized to 100ml (3.38oz) of volume. Vials are on average 11cm (4 1/3in) tall (including the cork) and 44mm (1 3/4in) thick. There's 1 or 2 mm of difference in each direction but every potion has 100ml of liquid.
Some movements are obviously a waste of time. For example, spitting the cork before drinking. Some props may help move the liquid faster, like putting a straw (of the hollow drinking kind, not an actual piece of straw) inside the bottle but you waste time putting the straw inside. These are okay but anything that delays the consumption of the potion is undesirable.
Movements after the liquid has been imbibed are inconsequential. Tossing or dropping the vial, spitting the cork, or anything.
Swallowing the vial whole, while possible (though painful), is not effective. The liquid needs to be absorbed by the body. Eating the vial like Ben did in Epic NPC man might lead to further injury. Both actions are forbidden.
Furthermore, waste is a concern. Getting 100% of the potion inside the body is very important and letting it drip down the corners of your mouth is a waste.
What's the optimal technique to drink potions fast?
[Answer]
**Huff potions**
<https://www.poison.org/articles/inhaling-alcohol-is-dangerous>
>
> When people "smoke" or "vape" alcohol, they do so by heating it up or
> pouring it over dry ice... This makes a vapor that they inhale into
> their lungs. Inhaling alcohol vapor causes a rapid and intense "high."
> Absorption through the lungs provides almost instant delivery of the
> alcohol to the bloodstream and the brain; the effects are felt very
> quickly. Small amounts of inhaled alcohol may make a person much more
> intoxicated than drinking the alcohol instead.
>
>
>
The lungs have a huge surface area. Stuff that goes down into the lungs gets distributed over all that surface area. That area (the alveoli) is made for gas exhange but it also absorbs chemicals very well. The body is made to pull a large volume into the lungs very quickly - over a fraction of a second. This is inhaling.
Your potion huffers will quaff their drafts in a mighty huff. It will be absorbed and take effect almost instantaneously. Much faster than having the stomach roll stuff around until it decides to recruit the small bowel in the project. Even then only the fluids apposed to the absorptive surface get absorbed; the rest must wat their turn in the potion bolus. The lungs sidestep all that.
Some persons may fret that huffing potions is dangerous, or are afraid to huff potions, or that it is undignified, or worry their asthma will act up. These persons will be invited to join the Wuss Warrior Corps and drink their potions using a little teacup, pinky extended.
[Answer]
This is a frame challenge. As someone with some experience in hand-to-hand combat, both unarmed, lightly armed and wearing medieval battle gear, I can tell you that it doesn't matter how fast you drink a potion in combat.
You drink a potion before combat (think The Witcher), after combat to treat wounds, or in a combat pause (between assault waves or after you have retreated to the rear of your formation while your allies are covering you (in the military, we have the principle of first winning fire superiority, then getting the wounded comrade into cover, and then we take care of their wounds.))
In The Book of Five Rings by Miyamoto Musashi, it is said that whatever one does in combat, whether blocking, striking, dodging, or parrying, one must always remember that the goal is to cut the enemy. You are forgetting the goal of winning while focusing on how to drink a potion. Drinking a potion is supposedly meant to help you win; thus, getting skewered doing it is not desirable.
To illustrate how quickly you are gonna get skewered, take those two examples: A knife fighter can rush a gunman who has a gun in hand but is not ready to fire from distances up to 7 meters and will reliably get him with the knife before the gunman can get a shot off. My trainer once had me hold an airsoft pistol to his face. I was supposed to shoot him if he moved. Even when I later aimed at his center of mass, he always managed to punch the gun out of alignment before I could pull the trigger. This is what happens at hand-to-hand distances.
Close-quarters combat is more about the credible threat of violence than it is about the actual infliction of violence. You don't control the fight by punching your opponent, you control the space of possible moves by keeping up the threat of inflicting damage, forcing both sides to keep up a threatening and protective guard. Combat is a lot of posing, positioning, and guarding while both look for a weakness to exploit. At some point, short bursts of violence occur. Those may turn into prolonged affairs where physical contact can happen. This implies that one party is losing, and can't retreat or reposition itself. Neither of those states offers you any window for drinking a potion while you can hope to survive.
With all that in mind, the effects of the potions should be adapted to the realities of combat. You don't drink a healing potion once you are injured. You drink a quick clots potion (stops rapidly bleeding wounds from killing you) before the fight to make injuries survivable. If you need to drink a potion in combat, you call out to your allies to cover you, and you drink it while you are being covered. This already supposes a prolonged engagement, so the drinking time itself is irrelevant, as long as it is just a few seconds. You'll need more time to take a breath at that moment anyways.
[Answer]
**Hydration pack**
How many potion types would you need in combat? If just one or two, you can go with large "potion skin" or two somewhere under your armor with tubes extending to your mouth. A spring valve on air intake will ensure potions will not spill until swigged, or you can just squeeze it with your hand and potion will flow in your mouth. You won't even need to take off your helmet!
Need more? Put some of the less used potions in edible "flasks". Animal guts and beeswax instead of ceramics and cork, and you can throw "flasks" in your mouth and chew them while swinging your sword. If it doesn't seem edible enough, you can spit out the remains later. Add sponges to these flasks, so that even pierced ones will still hold some liquid inside.
[Answer]
# [Enema bag with hose](https://en.wikipedia.org/wiki/Alcohol_enema):
Yes, crude. But the Mayans had only brewed beverages, and liked to get rip-roaring drunk. So - you guessed it - they would give themselves alcohol enemas to speed up drinking. The colon also allows more rapid absorption of alcohol.
Have a system set up so the warrior squeezes something (bag strapped to the body?) full of healing elixir. Arranged right, they wouldn't need to let down their guard, possibly not need to pause, and they could likely avoid their opponent even knowing they were potioning.
If the potions must be in the vials, then use a case filled with such vials. Each has a fragile neck that cracks when the case is used. Then the potion pours down and gravity does most of the work. A bladder may provide pressure to force the contents through the tube rapidly.
This would require prep, since you couldn't set this up in the middle of a fight. A bladder with a belt around it could allow a simple tug on a chord to deliver a dose. Depending on the game mechanics, you might even get something that keeps dripping the potion in in a slow trickle throughout the fight.
[Answer]
## [Tofu Sponge](https://garlicdelight.com/tofu-sponge/)
Change the vessel to a tofu sponge. It can absorb liquid easily (I don't know if it can do upto 100ml though, maybe you can figure it out with its size). The thing is edible; so, you can mass-produce it with the liquid already absorbed into the sponge to be in combat-ready state. If you want to just have the tofu without liquid in there all the time, it is still okay. You can prepare whatever liquid before the combat.
To consume it, assuming that
>
> the warrior already have the potion in their hand.
>
>
>
in this case, the tofu. The warrior can just put it in the mouth and chew it, or even swallow it whole. It's soft anyway. The liquid will get into the body without dripping (chew with close mouth).
] |
[Question]
[
This question is based off an interesting scenario that I began considering while researching [XCOM](https://en.wikipedia.org/wiki/XCOM). It's hard to sum up, but the question is inspired by it, so I'll cover it step-by-step:
1. Aliens called Chryssalids, which resemble giant insects kills an unfortunate person.
2. The Chryssalid implants an egg in the victim; the baby Chryssalid within hatches
3. The larva finds the central nervous system of the victim and hijacks it, taking control of the still (somewhat alive) victim and creating a "zombie."
In XCOM, there are serious consequences for killed civilians and soldiers, so some people will have their Psi Operative (a soldier who inexplicably gained psionic powers) Mind Control zombies so they technically don't count as dead (or lost, rather).
Assuming a similar scenario (humans are turned into something like the traditional zombie by parasitic alien larvae, then the resulting zombies are mind-controlled) **happens in America**, my question is: *How Can The Government Maintain Positive PR?*
To clarify, the *human* government is dealing with the zombies (which are created by the alien's insectoid soldier's implanted larvae) by having them mind-controlled; this prevents them from gaining new enemies and gives them a new asset (the new asset being zombies). This is strategically a much better choice than simply fighting the zombies, no?
Additionally, the government has managed to create special implants using alien tech that prevent their mind control-capable soldiers from using it on anything *but* an alien or zombie, not to mention letting an alien zombify someone (because there is a chance of that happening).
**The Issues:**
1. Simply hiding the truth will be, for all intents and purposes, impossible. The aliens are attacking civilians (read: committing acts of terrorism) with the parasitic insects, so more than a few individuals will see (and likely record and/or live stream) the alien parasites creating zombies, and the subsequent mind controlling of said zombies.
2. The government is trying to protect its citizens from the aliens (like it should). The problem is, having people capable of *mind control* and using those powers on zombies (reanimated victims of the alien's cruelty) is going to result in an outcry, a whole lot of backlash from humans rights and anti-government groups, new conspiracy theories....the list goes on and on, and the government will have to keep up their PR so they have the support they need from their citizens despite A) mind control and B) the fact they're using mind control on zombies.
As always, I appreciate your input and feedback, you have my sincere thanks for your contribution. As a final note, if you see a problem and chose to downvote or vote to close, please give me an explanation so I can either improve the question or do better in the future. (If my tags are wrong, I'm sorry; I made my best guess and chose governance over government or society.)
[Answer]
### A disaster like this is a +20% to +30% polling boost for the government.
Even a mediocre handling by the government will result in a massive PR boost, especially if the government has popularity to gain.
Here is a [graph of approval ratings](https://fivethirtyeight.com/features/what-explains-the-bump-in-trumps-approval-ratings/) of various world leaders during the first 3 months of 2020:
[](https://i.stack.imgur.com/t7sbO.png)
So casting our mind back to Jan 2020 in politics, people were pissed at their governments:
* Emmanuel Macron couldn't even go the cinema without [protestors storming the place](https://edition.cnn.com/2020/01/18/europe/france-macron-protests-intl/index.html).
* Scott Morrison had taken a [secret holiday while Australia was on fire](https://www.theguardian.com/australia-news/2019/dec/21/scott-morrison-hawaii-horror-show-pr-disaster-unfolded), and told nobody he was gone. Didn't come back until multiple volunteer firefighters had died, thousands of people were literally pushed into the sea by fire front, and hundreds had died from smoke inhalation.
* Trudeau was pushing for a [massive oil pipeline through native peoples land](https://en.wikipedia.org/wiki/2020_Canadian_pipeline_and_railway_protests), despite an election promise not to. Protesters are shutting down multiple ports.
* Trump was getting his first taste of impeachment.
**Then a disaster occurs**. Look at those poll numbers! A disaster is like +30 in the polls.
I can't find numbers for all these data series but several have stayed about 30% above their Jan 2020 levels:
* ScoMo is polling at [+7% in Nov 2020](https://www.theguardian.com/australia-news/2020/nov/17/scott-morrisons-approval-rating-bounces-back-to-66-guardian-essential-poll-shows) up from -25%.
* Macron is at [-10% in Jan 2021](https://en.wikipedia.org/wiki/Opinion_polling_on_the_Emmanuel_Macron_presidency) up from -40%.
* I'm not including America as the removal of Trump complicates things, and Trump wasn't motivated by the high death toll. They [literally decided it was better to do nothing because it was hurting blue states more](https://www.vanityfair.com/news/2020/07/how-jared-kushners-secret-testing-plan-went-poof-into-thin-air).
* The UK polling went [up until about May](https://en.wikipedia.org/wiki/Leadership_approval_opinion_polling_for_the_next_United_Kingdom_general_election), but has dropped back down. Probably because they're not doing great, but could be complicated by Brexit.
* Merkel is still polling at [record highs](https://www.pewresearch.org/fact-tank/2020/10/02/confidence-in-merkel-is-at-all-time-high-in-several-countries-during-her-last-full-year-in-office/)
The actual disaster type doesn't seem to matter. Here's George W Bush's polling numbers. See if you can spot the Sep 11 2001 spike:
[](https://i.stack.imgur.com/XvP2p.png)
Watching TV on the other side of the planet, I remember hearing conspiracy theories about US government complicity in 9/11, or at least foreknowledge of the plan before the last tower fell. The next day I heard on a news channel "Hey that looks like a controlled demolition". Bush still got a +39% boost in polls even though the attack represented a massive FBI/CIA failure and there was discussion of problems in the narrative. He still got +14% when he invaded the wrong country 2 years later, showing you don't need to do anything correct to get a PR boost - you just have to do something and spin it right.
The "Mind control" part of your story is probably going to be unproven in the heat of the moment. It'll be an unsourced conspiracy theory like many of the post-911 ones, that kind-of fits some of the evidence but no-one knows for sure. It will turn out to be true and perhaps proven months later, but people will see zombies killing them, a government fighting back and trying to save them, and will choose the government's side - the actual details of the story like "mind control" will get lost in the rally-behind-the-flag effect.
[Answer]
1: People will call the police if they find someone dead. Usually people are good at that.
2: Dead people are taken to a facility. We have got that going on too.
3: Dead people will be scanned for bug larva or if that cant be done, will be watched to see if they get up as zombies.
4: Back outside, people will call the police if a zombie shows up. I think people can be relied on to do that.
5: Zombies will be taken to a facility by medical personnel. People will be ok with that too. Maybe they can be helped? The zombies, I mean. People will be ok once zombies are taken away.
6: Zombies collected thru various means will be secured together, mind controlled by humans and given uniforms that conceal their identity then deployed in operations where they will not interact with civilians. If I recall, XCOM involves a lot of shooting aliens that pop up from behind various crates. Zombies could do that.
People will be upset about aliens making zombies. They will be cautioned to run from aliens they see. They will be reassured that authorities will be closely watching any crates.
People will be upset about loved ones becoming zombified. They will be happy that loved ones are getting medical help instead of getting shot. They will not know zombified mind controlled loved ones are actually wearing uniforms and fighting aliens, but would probably be proud.
Maybe after aliens are better understood zombified humans can still get medical help.
[Answer]
You seem to be describing an *invasion*, involving the *mass murder* and zombification of citizens (all of which are far worse than mere 'terrorism').
Historically, political and legal objections are strong when the conflict does not seriously threaten society, but are ignored/overridden when folks do consider society to be in imminent danger.
So there may be regrets and navel-gazing later, but if the nature and the scale of the threat call for it, you will see (unconstitutional) press censorship, (unconstitutional) roundups and detentions, (unconstitutional) forced testing, and and (unconstitutional) tracking and monitoring of (innocent) citizens. And after the war is over, you will see statues of the President who did it and schools named after them. It happened most obviously in the USA during the Civil War, WWI and WWII.
When election time comes, free voters --if they understand the threat-- will be satisfied with nothing less than victory: The eradication of every Chryssalid, and the complete scanning of the surviving population to be sure none were missed. If the President can convince the electorate that there is a reasonable path to victory, re-election is likely. A major-wartime election is typically a single-issue election.
] |
[Question]
[
Architects were a rather weird civilization. You see, not only did they create servant races like demi-humans, but had also engineered themselves to be specialized in various areas. Here is the hierarchical order and their roles:
* **White:**
+ **White Fixer:** They're effectively living archives and gods, tasked with ruling over the Architects. Their unique ability allows them to mind control those who are beneath them in the hierarchy. They have white skin with some gene-engineered marks for identification, white hair, light gray eyes, and usually a mesomorph build. They've been gone for quite a while by the time the story starts.
+ **Ginger Fixer:** High-grade technicians and leaders, only having to answer to their higher-ups and the White Fixers. Hair color is ginger, eye color may vary and skin tone is white.
* **Worker:**
+ **Yellow Worker:** Lesser technicians, skin color is yellowish-white.
+ **Brown Worker:** Lesser physical workers for various physical tasks that are too varied for robots (gardening, for instance).
* **Black:**
+ **Black Troubleshooter:** The tallest and heaviest sub-species, designed for combat. They're just as mentally capable as workers but have several engineered traits that make them compliant with any order their higher-ups give them, though they can voice their concerns.
If this society seems racist, that's because it is. I never said Architects were the good guys.
So, at one point, fixers had infighting, which became a civil war, which ended up unleashing nightmarish creatures, called abnormalities, on the world. The remaining White Fixers fled to a city in the sky, hidden from everyone else. Later, they disappeared from there as well, only leaving an enslaved dragon behind, who was the core of their security system.
**As for the other castes, ginger fixers, and demi-humans, they've forgotten their past and formed their own societies, making use of the remnant tech from the Architects.**
Of course, there is still a White Fixer left (amnesiac, of course) who is the protagonist. **However, it's been so long that attempting to use his mind-control powers on humans or demi-humans would fail, even if he knew he could to that**. I.e: the Architects' genetic safeguards were eroded by nature.
But how? **Architects used quantum supercomputers and nanotechnology to effectively erase the boundaries of organic life. The only taboo was the creation of a Singularity**, which was only done at the end of the war when there was simply no other way of stopping either the pro-killbot or the anti-killbot camps.
**Simply put, Architects' chosen a method of keeping their castes' genetic code pure relied on their society existing and actively maintaining that purity. The moment the fixers were gone, the safeguards also disappeared quietly into the night.**
Architect society didn't even like inter-caste relationships. When another White Fixer in the story finds out that the protagonist is dating a demi-human, she gives him the same look you'd give to a zoophile or a furry, even though demi-humans are just as intelligent as Architect Workers by default. **So, if this society didn't make the safeguards more "stable" it was because they couldn't without negatively impacting the castes' functions.**
**They could have made so that different castes were genetically incompatible, or have the baby's caste be either the mother's or the father's with no in-betweens. So, for what "practical" reason did they decide not to do either?**
[Answer]
***Because of exactly what happened:***
Your society could control reproduction by social means, so making them incompatible was unnecessary. But these folks were REALLY smart, and anticipated the possibility of everything falling apart.
Specialization is great for a rigid, stratified and predictable situation, like civilization. Many species are perfectly adapted to a small, narrow niche they control perfectly. But specialization is a problem when conditions change. Specialists go extinct. Even if your society was obsessed with purity, it recognized the danger to humanity if everything fell apart. They probably even saw it coming.
Your masterminds predicted their own apocalypse and made sure that the genes could mix and de-specialize humanity when it was needed. It's exactly the intellectual preparedness you would expect from a bunch of eugenic geniuses. After all, generalists would be the optimally adapted species.
[Answer]
Those artificial alterations were result of evolutionary pressure regardless of being intentional - being part of a certain caste favored having a corresponding gene since all soldiers were guaranteed to have the black gene as opposed to the white gene. Once the said civilization dissolved, the evolutionary pressure maintained by the elite disappeared. Color genes had no pressure that favored them anymore, and over time those genes were lost due to mutations, interbreeding without any pales shaming people for it, other forms of genetic drift etc.
As for why the architects decided not to make the castes unable to interbreed, it was too costly for no benefit. Giving everyone one gene or two is hard enough not causing a whole cascade of genome failures. Eliminating genetic compatibility would require either way more dramatic genetic alterations for something they could accomplish through guaranteed and much cheaper social means
[Answer]
**Aftermarket mods.**
Sex is sloppy! Heritable traits are a nightmare from a stability perspective. You need serious inbreeding and regular culls, and your precious trait could vanish without warning from the regular process just from the mechanics of meiosis.
Better to engineer the normal base organism after conception. Huxley's Brave New World accomplished this by manipulation the circumstances of artificial gestation.
[Current CAR-T tech](https://www.cancer.gov/about-cancer/treatment/research/car-t-cells) offers a platform to jump off.
This is awesome stuff. Genetically engineered supersoldier T cells, taken from the organism, genetically modified to fight cancer, then put back in. CAR-T are warrior cells but you could do this with a whole range of different cells, differentiated and not. The dream of CAR-T cells is to have an off-the-shelf cell type suitable for lots of different people, sidestepping the time and expense of custom CAR-T for each patient. That is what your society had - standardize post-conception organismal mods. This also allows flexibility - instead of breeding a new line, just tweak your mods. Adult organisms could also get these mods as is done with the CAR-T cells.
Once the tech to introduce these genetic mods are gone, organisms who are conceived just remain the basal type.
[Answer]
**To find the system violators**
No system is perfect, obviously, so when you make a caste system and *strictly forbid* any romantic liaisons between the various castes, it doesn't take a genius to figure out what's going to happen. Sure, using safeguards (such as say, secret police) you can have a 99% success rate keeping them apart, but tragic and forbidden romance seems to be an unfortunate subset of the human condition. In other words, the Architects knew that people would violate the rules.
The Architects response was to make the offspring of such a match a very clear hybrid - deliberately - so that it was as obvious as possible that the child was from a mixed-caste couple, thus implicating the child's parents, or mother at the very least, though the father shouldn't be that difficult to find in most cases. A term for these mixed-castes might be something along the lines of 'the Architects judgement' or something of that nature.
[Answer]
It was simply too much work, and it would interfere with engineering potential new castes in the future, or at least make it more difficult.
After all, their society was perfect. It would never fall. Why go to the bother to make life more difficult for yourself?
[Answer]
You may not have large enough populations at the top to maintain enough genetic diversity only among the ruler classes.
>
> **White fixers**: They're effectively living archives and gods
>
>
>
I don't think you'll have many of these running around. Make it so they can only reproduce among themselves and you have a tiny gene pool at your disposal. Also, do these walking gods even care about reproduction enough? I'd guess there would be a lot of test tube babies around. That way taking genetic material from other castes isn't as big of a issue as if it required direct contact. Then you jsut need to nanobot that embrio in the direction you want it to develop, maybe making it's white inherited genes more active or maybe not even that.
Maybe all the white only traits are close to 100% nanobot induced. So you don't even care about the genetic expression of the baby or if it takes more to the white parent or to the other caste one. You jsut input the baby's dna into the computer and call it a 'white baby' from now on the nanobots will recognize it as such, make it's hair white (even more so than it would have been) and give it all the features a prper White Fixer should have.
There's probably some protection to prevent babies without a white parent to being allowed in the system so white fixers are always needed.
Now, these explains why not go with the genetic incompatibility route. So, why not make the babies one caste or the other, with no inbetweens?
First, I'm not a genetic expert, but I'm not sure how you could do this without the nanobots assistance. But for the sake of the argument let's assume it's possible. Well, the issue here is, it makes it too easy for rogue caste members to get more high caste members on their side.
What I mean is, say you have a white fixer who wants to gain power but doesn't have the support of other white fixers. He can easily get more white fixers to support him by mating with other castes and waiting for the offspring to be white. Remember, having a small population of white fixers ensures you need some chance that interbreeding produces white fixers. This expliot is averted if all new white fixers need to be explicitly allowed and accepted into the system.
This makes a lot of sense if you ask me, since if you think about a white fixer, all their power means you can't just have them poping up without control. It'd be as letting a general have as large of an army as he wants or a politicial as much votes in the senates as he chooses.
Now, a counter argument to that would be to not let all white fixers have the same ammount of power. Meaining to have a hierarchy within them. So many white fixers wouldn't give you more control of the army, since they aren't General White Fixers, same for since you'd need Politician White Fixers. But the think is, there still needs to be power in the general white fixer population, maybe to elect the Politicians or somthing else. Otherwise, the core societal value that one's caste give you power and makes you fit to rule comes crashing down.
[Answer]
**You don't need to worry about anything, the genetic separations between castes are going to naturally vanish anyway when the civilization collapses without any special explanation**
This is something you see in feral animals all the time. Humans have bred domestic animals for centuries for very specific characteristics. Then these animals accidentally get released into the wild, and within a few generations they end up reverting to the wild type as the carefully maintained separation between bloodlines break down and genes that code for traits that work well in captivity but are terrible outside of a system where every animal is bred for a certain job are selected against and die off. Some examples include...
* Razorbacks are feral pigs in the United States descended from what anyone would consider normal pigs: pink, sparse hair, no tusks, etc. Razorbacks *now* are almost indistinguishable from Eurasian wild boar, and reverted to that form within a few generations.
* Dogs, when released into the wild, will rapidly return to a wolf-like state as the scattered "wolfy" alleles in the gene pool get selected for. Dingos are a good example of this. The only evidence that domestication ever took place is that feral dogs tend to be a bit friendlier and more tolerant of human handling than true wild wolves and can more easily be redomesticated.
* Goldfish are released into the wild all the time by ignorant fish-owners. What happens is after a few generations all the weird breeds like bubble-eyes and butterfly tails die off and the goldfish rapidly revert to a form that's pretty hard to tell apart from a plain old carp.
* Similar things have been documented in horses, goats, sheep, cattle, chickens, and numerous other domestic animals. And some plants too, believe it or not.
What's going to happen in your situation is that people are going to start interbreeding between castes due to lack of suitable mating partners due to whatever apocalypse causes your civilization and its social structure to collapse, and the averaging is going to produce something pretty similar to the humans your civilization's eugenicists started with. Extreme alleles that worked well in the caste system won't work well in a hunter-gatherer survival situation and will get selected out of the gene pool over generations.
Now, as to why the genetic engineers didn't just make all the castes sterile if they intermarry, that's a plot problem, not necessarily a worldbuilding one. There's really no reason for the fixers *not* to do it if they are as bigoted as you describe, and ideologues of that magnitude don't really care if humanity would be wiped out if their ideology gets proven wrong. These people are crazy racist ideologues with a quantum supercomputer that can manipulate genetics like a god, they don't seem the type to be very practical or reasonable. However, even if the fixers did genetically engineer all of the castes to be unable to interbreed, you are going to get a few mutant individuals for whom the genetic blocking mechanisms are defunct, and it is going to be these individuals in a post-apocalyptic scenario who are going to be the ancestors of most of future humanity due to same-caste mates being at a premium and these mutant individuals being the only ones who can reliably breed.
] |
[Question]
[
Imagine that **Terra Australis** was real, that there really was a vast continent in the Southern Hemisphere like that shown on old maps. It's massive, encompassing what in our world would be Antarctica, Tierra del Fuego, the Kerguelen Plateau, Australia, New Zealand, and most of the Pacific Ocean south of the Tropic of Capricorn.
I envision the existence of Terra Australis creating a kind of alternate history. Although the actual point of divergence, if there is one, would have to be far back in Earth's past, I'd like to have European history be virtually identical up until the Age of Exploration. From a European perspective, the divergence would occur when explorers start finding land which doesn't exist in our world (This would technically be in 1526, but nothing really changes until 1616.).
I know, I know, the butterfly effect: Make one change, especially one this massive, and you can change everything. But I'm not overly concerned about that. This isn't a time travel story after all; it's about a wholly separate constructed world. What I *am* concerned about is making this world realistic on its own merits.
And what I'm having the most trouble with is the effects of Terra Australis's existence on the climate in the rest of the world. All of the extra land in the south means no Circumpolar Current and Roaring Forties winds to trap cold water and air in the south, which might make the rest of the planet colder. On the other hand, more land and less ocean means less surface water to absorb heat from the sun, which should make the planet hotter (I don't really care about higher temperatures increasing sea levels; I can just decrease the amount of water on Earth.).
Is there a way for me to have these and other climatic effects balance out so that regional climates in the rest of the world are more or less the same as they are in reality? If this can work, then I think that it makes for a very exciting setting for alternate history stories. Thank you.
[Answer]
I think that increasing the size of Antarctica and linking it with Australia (which I think is what you have planned) would have major ramifications for the Earths climate due to the lack of circumpolar circulation.
However in "god mode" most of the effects could be counteracted by introducing counterbalancing factors, which may or may not be of interest to you. As god you have some fairly sizeable levers that can be pulled for example the Earth's axial tilt could be adjusted slightly or the Earth's distance from the sun by a few thousand miles. The density of the atmosphere could be 1% greater or 1% less, CO2 concentration different or the intensity of the sun could be a little greater or a little less. The solar cycle could operate over a different period than 11 years with a greater or lesser effect. Any of these things or a combination of them could conspire to mitigate the effect of such a large continent.
The system is so complex and there are so many variables that you will never come to a definitive answer. Using a climate model might help but even those are only gross approximations. I wonder how many climate models would allow you to change the solar cycle, the axial tilt of the Earth and the pressure of the atmosphere? And even if they could would the answer to accurate?
How much detail do you want to go into and do the mitigating circumstances have to be obvious for the story to work?
[Answer]
>
> Is there a way for me to have these and other climatic effects balance out so that regional climates in the rest of the world are more or less the same as they are in reality?
>
>
>
Climate is a chaotic system with complex and interlinked feedbacks and feedforwards. The way climatologists do their studies is basically:
* create a model containing the elements they want to analyze and those which they think are related/influenced
* run that model several times with slight changes of the initial parameters
* analyze the trends they observe coming out from the simulations
* if possible compare those with experimental observations
That already gives a wide range of outcomes.
What you are asking is basically the above for a new planet where you don't have any historical data nor the possibility of verifying the model.
Unless you want to venture into a PhD in climate science, I would say that getting a sound understanding of the detailed climate consequences of having a large meridional continent is kind of overshooting, unless the climate is of paramount importance for your story.
] |
[Question]
[
Setting, a land apart from the world, where an immortal race of humans live. Their social culture began as egalitarian hunter gatherers. Their cells are resistant to senescence and mutation, and they have a reservoir of stem cells in their bones that replenishes their bodies if they are injured. Other than that, completely human. So women still go through menopause. How would this affect their culture?
Specifically, by the time they entered the early bronze age, in what ways would menopause cause their culture to differ from mortal human culture?
[Answer]
**It will be a "Handmaid's tale" world**
If I understand aging dynamic of your world correctly, both men and women follow traditional age trajectory with respect to their fertility, but otherwise remain perfectly healthy and strong for an indefinite amount of time.
Traditional human hunters-gatherers have only a fraction of elders among them. Those elders, while respected, in many aspects are not at the same level as young adults. They do not have enough strength to be outright leaders and males, while still fertile, can not well perform sexually.
In this new society, long-term survivors would come to dominate the tribe, both demographically and socially. Young (both children and young adults) would represent a small fraction of population and would be subservient to elders.
One important aspect of it is that older males would have an extended appetite for young females. Males, for a time significantly longer that females, would have the capability and desire to proliferate. On the other hand, young fertile females would become a "premium resource", and any chance of marrying their age mates would be denied to them.
[Answer]
I would say it depends, so I am going to make certain assumptions for this answer. Those assumptions being:
* You mean they live a REALLY long time, like 400+ years
* They still go
into menopause at the same as as mortals
If this is the case, youth might become an almost insectiod ferver of breeding. It's very sad to be 300, feeling spry, but unable to have kids. The small percentage of the population might be encouraged to have as many kids as possible, so that the older population can share the joy of communally raising them. The period of youth and fertility would be such a short time in their lives, the culture might look upon it as kind of holy, to be preserved.
*On the other hand...*
If you haven't been young in centuries, it might continue to get more frighting and alien to watch (we are talking old people afraid of teenagers times a hundred). If so, the culture could become extremely oppressive to youth, trying to control them as much as possible during their crazy first four decades. If population size is being tightly controlled (since resources are limited and no one dies), you might go to extreme measures to prevent breeding amongst the young.
[Answer]
**Your society will eventually be a small number of immortal infertile old people.**
Consider old people in a culture where they are supported by their families. The old people contribute but they do not work a job or bring in food. They depend on younger people in their family to do that. The same is true for children - until they grow up they too are dependent on the breadwinners. If the breadwinners in the family die or are disabled, it is the end of the family. If there are too many old people, or children they may be more than the breadwinners can support.
Your society (here in the role of family) is supported by reproductive age individuals. Because the old do not die, reproductive age persons are increasingly in the minority.
Human societies of all sorts are prone to dieback because of famine and disease. Hunter gatherers in particular and especially those confined to an area are vulnerable to food shortages - they cannot control food quantity like agriculturists can and this keeps population density low.
Your population will occasionally suffer more deaths than usual because of famine. Your old are as durable as your young and so under this sort of stress starvation is equally probable for each individual. As reproductive age persons are a smaller and smaller percentage of the population there will come a time when a dieback takes all of them.
Your population will then be composed of all old people and it will slowly shrink because of subsequent food shortages, death from accidents and so on.
There will be a time when the land available can easily supply the remaining persons and there will be minimal death from famine. Death from accidents will be very rare too as these ancients will be extremely wise and canny, and will not make mistakes. This population could go on for a very long time.
[Answer]
I note that male fertility also declines sharply in old age. It's few decades older than women who hit menopause, but whether males go through it to is a great importance.
Also remember that a hunting and gathering society needs to *limit* births. They can not exceed the carrying capacity of the land. Having only a small part of the female population would help with that and consequently practices that help limit it are less likely.
If both men and women can not reproduce later in life -- after fifty for women and a hundred for men, say -- then youth's the time for children. Those who do not have children while young are stigmatized for life. You can earn prerogatives by having children, and in a hunting and gathering society these will be skills that you can use later in life, creating a vicious cycle for failure.
Now, in real-life examples, women space their children several years apart. This is maintained by nursing (they are close enough to the line that that will prevent building up the fat reserves for pregnancy and so suppress ovulation) and post-partum taboos. The fertility limiting aspects of this are no longer an advantage but that a woman has a hard time wrangling two (or more!) children while gathering is still in place. Consequently, gathering will probably be carried out only by the infertile older women; women of child-bearing years work in the camp. Hunting is less limited but men of child-begetting years may be valued to endanger their lives -- and hunting skills may be one of the baits to have many children.
If, on the other hand, men are fertile through most or all of their lives, the supreme honor for excellence in life is probably being chosen to become a father. Men would vie for it. (And given they still look as good as the younger men, they have less to worry about brides who complain about giving to an old bag of bones.)
[Answer]
My first idea was that without senecence menopause wouldn't be a thing at all but **a woman's ovules are all pre-existing from the embryonal state on and not newly generated so human menopause would indeed occur at the same age.**
---
I'll leave this answer here for fellow men who might think they came to the same brilliant conclusion and are about to start researching half a day and write 917 words from 7 sources about their approach just to stumble across that fact afterwards.
Thx to [AlexP](https://worldbuilding.stackexchange.com/users/29552/alexp), whose [answer](https://worldbuilding.stackexchange.com/a/62065/67222) I stole that information from.
[Answer]
It's also important to differenciate between embryonic stem cells and the stem cells of adult humans which are found in several organs, only regenerate that particular organ and are also affected by senescenc and get weaker with aging. ([Source](https://www.uni-ulm.de/universitaet/hochschulkommunikation/presse-und-oeffentlichkeitsarbeit/aktuelles-thema/stammzellenalterung-06122008/))
Heart, brain and pancreas contain few adult stemm cells and are merely regenerating as adults. ([Source](https://www.wissensschau.de/stammzellen/arten_von_stammzellen.php))
(The sources are in German, you might use Google Translate for them).
[Answer]
>
> in what ways would menopause cause their culture to differ from
> mortal human culture?
>
>
>
It will be a lot better than if these women were fertile for their whole lives. Over a lifetime, humans would have so many progeny that overpopulation would soon overwhelm them.
I surmise that, in your scenario, young people would simply want their turn at life and would resort to killing people who lived too long.
In the long term, long-lived people would be selected against and eventually the trait would die out. This is what nature does already - it makes way for the next generation.
] |
[Question]
[
I've been thinking of a story revolving around a smallish humanoid troll/lemur-like species with large eyes, a tail, and bat like ears that allows them to use echolocation. They typically prefer low light conditions such as at dusk and night, and are known to create burrows, treehouses, or massive underground networks as a means of protection against predators and invaders. They are highly knowledgeable in ecology and chemistry from interaction with magical fey like spirits that rule over the land. Assume bronze/iron age technology.
Now exposition aside, I was wondering how their art might develop. At night, colors may not be as visible, although they may be able to see UV light. Underground is either unlit or sometimes dimly lit by glowing fungus. Fire is used sparingly only as needed for cooking or crafting.
Perhaps sculptures and writing meant to be touched instead of seen? How might this all affect their culture and aesthetics?
[Answer]
Rethink art from their perspective. Their perception is based in hearing mainly, ours is based on sight mainly. Thus, it is reasonable that they might create **music** rather than paintings or sculptures as their first step towards art. And then sculptures with designs which create echoes that are different and interesting to hear.
[Answer]
Large eyes make for good night vision, though for humans it usually means black and white vision. This does not have to be true for other creatures - some low-light cameras can pick colors at light levels in which we cannot see at all.
Check this video: <https://youtu.be/Y2nqAmK0kNI>
So if you want, your creatures may be able to see color in low light. Otherwise think of what kind of art blind people could enjoy. Seriously, to any museum where curators have put a thought towards accessibility. Then use that as inspiration.
[Answer]
They're probably highly reliant on pheromones (think termites and ants). So they'll likely embrace manufactured perfumes from plants and other animals.
They probably rely on touch (star nosed mole). So they'll probably mat down certain patches of fur (if they have it) or rough up skin with calluses or patches of mud. They might even have textured tattoos.
They're probably reliant on sound and or vibrations. So they'll probably have clinky bells and or jewelry.
[Answer]
I think as others have mentioned, **tactile** art would feature heavily, but as we don't exclude the presence of light altogether, the most special works may actually be those that explore the presence of light. Remembering that **art** is for the sake of **art** and without function, it may even lead to exotic examples that require at the very least simple light (such as fire).
[Answer]
This is all very subjective, but I don't think view or color should be out of the equation.
As babies, we are already attracted to "non-natural" colors and visual effects, like primary colors, bright surfaces, etc.. So your species can be attracted to whatever colors they have access to, as long as they are not hurt by it. Even if it hurts a little, in fact. fantasies about the bright outside world can be part of it.
However, I think it would be more interesting to focus on hearing. If they have bat like ears, they will be able to feel surfaces just using echo. You can imagine highly complex caves with a variety of surfaces to create some kind of auditory hallucinations, even going as far as to play an entire minute of delicate symphony from one droplet of water, or snap of the tongue. Depending of craftig skills, you could eventualy get to the point of telling ancient stories (epic battles or discoveries, or creations) just by sitting in the right place of a specialy curved cathedral of rocks and sand and anything that will create distortion and magnifying from the origin sound.
This scultures could be either entirely dark for immersion, or painted for additional info, but then painting would affect sound propagation.
Still, I think this is an art that a cave dwelling species with spacial earing would enjoy more than we can.
For aestethics, I think will go back to visuals, as constant sound would impair their spacial senses and would be considered a nuisance pretty quickly. If it is a socially structured species, with "classic" seduction and reproduction, bright and colorfull, so you can be seen even in dimly lit environment, and seductive structures that show how big ears are, how eyes are good, and how symetric and healthy they are.
Apart from that, maybe clothes that absorb sounds would be "dark and misterious", or you can imagine clothes that also simulate health, by 'echoing like' (not looking like) good fur or good muscle.
] |
[Question]
[
In my world there human-animal hybrids. My protagonist is a snow leopard-human girl (outwards looks almost completely human, except for the tail). These hybrids have been created through experiments, so there is no evolution in play.
So I can also play around with sci-fi-ish elements (and/or magic). **What would be ways for a cat-human hybrid to achieve more agility?**
For example, from what I understand, because the spine has to support the skull, it kinda loses flexibility. If these hybrids would be given implants, could it give some flexibility back?
**Additional informations**:
* These hybrids vary greatly, a few walk on all fours, others don't, others are digitigrade and so on
* I'm mostly interested in my main character. She looks and moves like a human, unlike most hybrids she grew up with humans and only at 13 she began to learn about her hybrid side (story takes place 10 years later)
* Her animal characteristics are tail, eyes and claws, and she's short. And I would like to have also muscles like felines (if it has advantages)
* I want her to still fit in with humans, but be able to **move** with more agility, for example climb, jump, sprint...
[Answer]
Interesting question! I have some basic and anatomical considerations that might be of help to you.
Since the hybrids are created using technology (gene editing and so forth), your genewizard scientechs need to do things like these:
* Ensure that the balance centers of her brain derive from cat genes
* Derive her balance, movement and recovery instincts from her cat forebears
* Derive her tail, its musculature and its nervous apparatus from the cat, but see below for specific anatomical considerations
* Apart from genetic manipulation, you'll want to make sure her natural abilities and instincts are well trained.
You don't need implants in the spine, you'd need to remove bone, if anything. The human frame is not built to move like a cat. If you want a catgirl that looks mostly human and has a basically human body, you're going to have to accept some trade-offs. I think if you do the above three points, she'll be considerably more agile by nature than any non-hybrid.
One thing I'd point out, since your catgirl has a tail, is that almost every artist that draws furries gets the tail wrong, from a human-beast hybrid anatomical perspective. Just be aware that a functional and anatomically correct furrygirl won't look like the vast majority of furries you see in art.
Take a look at this furry girl here (cat-human hybrid by mrpersonperson of dA --- Don't worry, totally SFW!) :
[](https://i.stack.imgur.com/XmTrO.jpg)
And now compare the human skeleton:
[](https://i.stack.imgur.com/2sjHU.jpg)
with the cat skeleton:
[](https://i.stack.imgur.com/7FUku.jpg)
noting the differences between the pelvis and placement of the tail in all three. Notice that the human tail (yeah, we have tails, but they're entirely internal) curves inward and how the gluteus maximus curves outward. Notice how mrpersonperson stuck his furry's tail way up high in the lumbar region of her back. More important than supporting the skull, the spine has to weld the pelvis together to support the whole body! That means she will have no sacrum, no bone to hold the two halves of her pelvis together. She'll collapse, most likely, and certainly not be able to walk let alone leap about gracefully as a cat!
I point this out to bring your focus to the tail. The cat uses its tail quite a lot for balance and agility. Your catgirl will not really be able to do this with a basically human body. This is where her feline tail will end up having to be:
[](https://i.stack.imgur.com/nXbxx.jpg)
Its bones and musculature will partially push her glutes off to either side, probably giving her a weird gait and certainly making it difficult for her to sit like a human.
Mrpersonperson should have had his furrygirl's tail emerge approximately where her g-string disappears between her glutes.
[Answer]
**You don't have to do anything, humans are already more flexible than cats**
You have already given her the only advantages you can, if she has a tail and claws she can do anything a cat of her size could and likely a lot more, agility wise. the advantage house cats have is size, smaller animals can move faster. Cats are not more flexible than humans, humans are actually really flexible if they put any effort into it, far more than cats. Humans evolved from primates they are amazing climbers and jumpers and can contort themselves in ways cats could only dream of, like everything in hte below image.
[](https://i.stack.imgur.com/IfosA.jpg)
The only other tangible advantage you could give them is better muscle recruitment, which is why large cats can jump so high, but that will cost her fine motor control. So she can jump 18ft but she can't write her own name, not a great tradeoff. this is more strength than agility anyway.
Keeping her body mass small will help, mass is the biggest limiting factor for agility.
[Answer]
**Scale body size down and metabolism / perceptual speed up.**
Small animals with high metabolic rates (e.g. songbirds, chipmunks) process visual stimuli faster than larger, slower metabolizing animals do. It makes sense. What is the point of perceiving what is happening if you are too slow to do anything about it? But if you are able to move fast you have to be able to process sensory stimuli fast or you are literally flying blind. Move your cat woman's size down and metabolism and perceptual speed up.
From:
[Metabolic rate and body size are linked with perception of temporal information
Kevin Healy et al](https://pdf.sciencedirectassets.com/272524/1-s2.0-S0003347213X00107/1-s2.0-S0003347213003060/main.pdf?x-amz-security-token=AgoJb3JpZ2luX2VjEL7%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCXVzLWVhc3QtMSJGMEQCIGKCKTNslaxdHLGODKAcu29K1u2gZTrBCkjONtcXXpBRAiBTxznFm1BYrML33ijGGDs0ikaYC6QYfdd0IB5ItoooLirjAwiX%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F8BEAIaDDA1OTAwMzU0Njg2NSIMj%2FmSmTYNPNWYHLZMKrcDdkttohDq6SXzTonZV1nodLQFBgg%2FqztAXilCeqrtlnJ7%2BepMgDnhE%2FVhSILC7Wyio3yHPGprr2qQFp59kFbMvFKbj26jx9fPtn6rSg14URFLbScEyO45RkWte0qbJw2%2FXRg9iriZBp67wNsYsOJJ%2Fs%2B7tT7bVz6L8lYTt8r2NxltDn5P9PI5YOFx1FS7VwtpLRPHhJmyNJ1I7HDhYmJLSNpZikSf0U%2FJRWu8Zet8mVQPE6U1MJkz47KmUgqHQQRGR5llpwQRgLRPztEcr%2FY02T5quCLU8sFwaJmy%2FIB4NA6gd0Ug2eWOToDecRYzD18npt11xlJtD3uaFGm9kJP9Vj5PLsvg4Yr0gsKbA9zchlFoYxGHLt%2FWxE6GQVLKDoWPao6hgJKSMcOzhy4MtBh785QXAYu28eifFyvpchz3PZJYnPx95fY92HlzClUTzxQlveMUWpXi0VYZP3NstFwrleHMpWjjHzdeecLW8N6bcd0FUj3JVOYDONXH5SU6%2FTtfJntu32oW271XtGC3T2Pye0bi%2FlS9FAHVwub8GZmYsOCoE7kxhpxZmifw6X3EfFSRVERd5GxoujCIwPPlBTq1AU2vIUkWjwRtCEL%2FeSstzg9BQCDGe1Kbg4Z8kpB9%2BG%2BTPLNWfK1%2Fjb95%2FB9KS3oF%2B3Lp2pAZr8%2Fp%2Bz0f0DASv3jAvsLmGH1k2FuSkneCxjRkFPXSxCkunNValXtQHBo6rBTo%2BnQYmKKiIAIXjWhS7SelCuebOO84nwsHMCmMKoJivtxoZBoBw5ipLwc4KDmmJ2DkiDQsjcIVkXGUkNw54M%2FZeGMh0A7Q%2FW6hIs6XK1Qpf0pb3fg%3D&AWSAccessKeyId=ASIAQ3PHCVTY6D4B65MU&Expires=1555883170&Signature=EuR0Hqm7w%2B9nzMbWFRmg%2BAT1oz0%3D&hash=6d7d6aadefb1b7b894562751979afb499f07e512684c5ebd8543e5198724b56c&host=68042c943591013ac2b2430a89b270f6af2c76d8dfd086a07176afe7c76c2c61&pii=S0003347213003060&tid=spdf-7f407646-d39b-40b6-9fd7-d821409cadaa&sid=b40119f97bbb82438e68bb3306e886b2f40agxrqa&type=client)
>
> In a broader context, it might be expected that manoeuvrability, a
> vital component of an individual’s ability to respond to the
> environment, may be one of the main factors determining whether it is
> necessary to invest in costly temporal information processing.
> Manoeuvrability, as defined by the ability to change body position or
> orientation, generally scales negatively with body mass. This negative
> scaling emerges primarily through the increased inertia and decreased
> limb stroke rate associated with large body size …
>
>
> These arguments show that, owing to the laws of physics, larger
> animals physically respond less quickly to a stimulus. Hence we expect
> selection against costly investment in sensory systems with
> unnecessarily high temporal resolution in large animals, as
> information on such timescales can no longer be utilized effectively.
> This may explain why larger vertebrates, along with those with low
> metabolic rates, had lower temporal resolution in our study.
>
>
>
[Answer]
Smaller and thinner is always more agile.
Less fat and smaller internal organs also help - at the cost of endurance and ability to use low-energy foods.
Bones should be lightweight and not too easy to break - so fill them with some air, like a bird's bones. Even if that means broken bones require longer treatments.
Some of the brain could go down into the spine (as with birds again) - especially anything related to motoric abilities. Improves reflexes, allows for a smaller head without reducing intelligence and strengthens the spine without adding unnecessary weight.
Stealing photosynthesis from the plants (ideally black, brown or red ones, as green is not a cat-like color) helps to recover strength while resting, even if it only makes a small percentage for a warm-blooded being.
Some animals like Kangurus can 'spring-load' their muscles. This allows jumping around without using a lot of energy.
The larger the frame, the more the bones need to support the muscles - make bones near important muscles across joints extend a little bit for a better angle the muscles can use. Muscles can overlap by splitting the extension into a Y-shape on one side, which also stabilises the joint. Only works for joints limited to one direction, like knees or elbows.
A muscle along the back could help go quickly from a crouch to a jump, or from absorbing a landing on two feet to jumping again. Useful as your 'cat' will usually not use all four paws for movement, I assume.
The hind legs can be a little short for a human - allows switching to running on all fours if needed, for extra-fast sprints. Here, the strengthened back muscle will also add to the speed.
A relatively long neck will help move between upright and quadropedal movement, and also be good for fast jabs - like a snake or a bird.
4 or 6 small boobs are better than 2 large mammaries. However, if you want your cat-woman to be sexy for humans, use the place well - fat, water and oxygen storage, for energy, dry spells and diving, respectively. Similar to some animals expanding their throat, your cat woman could then use her mammaries to signal attraction.
Make your tigress cheat a little - shoes with a blade spring each, an elastic climbing rope with knots for easier climbing (shoes should have a small gap between toe and other digits, to make use of this), knee and elbow protectors for wilder maneuvering, a flight suit for jumping from large heights and other such accessories.
[Answer]
I agree with pretty much every answer on here so far since agility is many different things, but there is one other factor to consider that I think will make a bigger difference than any of them. When a cat stands at rest, their legs are bent. But humans normally stand with legs straight. Our straight design gives us a longer stride allowing us to run faster and support ourselves better with our inferior number of legs, but it comes with some hefty trade-offs.
Any time a human wants to react to something, we must first bend our legs/arms in, then respond. A big part of why we perceive cats as so much more agile than us is that they have no delay. With legs already bent they can go straight from a restful stance to a lunge. The bent design also means they can allocate their muscles differently. While we need our legs to be strong in all directions for support and versatility, a cat has most of its hind-leg muscles allocated for pushing backward with a strong heave, and just enough for bringing forward to repeat. This is why they can push forward so much harder than us.
So to answer the question, give your cat-girl bent legs, and have her move more like a monkey than a person. She should be able to stand up well enough to do people things with her hands, but if she wants to run, she drops to all fours, because on 2 feet, she'd be a slower and more easily worn out than her straight legged friends.
[](https://i.stack.imgur.com/Mo14A.png)
[Answer]
**Have muscles like felids**
Human muscles are heavily optimized for endurance, but the price is they are quite weak for their size. Felids in contrast have muscles optimized for strength and peak power, which gives them much more agility, but at the cost of endurance. That's why even the most active cat will fall off after at most 20 minutes of play, while humans can with a bit of training run for 10 hours straight.
With muscles optimized for strength and human body plan, you'll get something closer to an ape, but they are just as agile as felids, if not more. You can put retractable claws on the legs for traction control. On hands they are unfortunately incompatible with useful fingers—the claws are in place of nails and are retracted by curling the fingers up—but if she's running on two like human, she does not need them there anyway.
Tail is not particularly relevant. elemtilas is correct about its position, but it's mostly cosmetic—bobcats and manx cats are no less agile and neither are old world monkeys. It may be useful for small attitude corrections in jump or fall, but the main corrections are done by bending the back and rotating limbs.
You do want to keep the weight down, but the stronger muscles will need correspondingly strong skeleton, so the body build will probably come up as rather robust. But felids are not particularly slender either; they are strong and powerful.
] |
[Question]
[
I am trying to create an island with a large settlement on it, the people of this settlement need to be able to sustain themselves and according to [Medieval demographics made easy](https://gamingballistic.com/wp-content/uploads/2018/11/Medieval-Demographics-Made-Easy-1.pdf) (MDME)
>
> A square mile of cultivated land (including not only farmland, orchards and pastures, but also the roads and settlements attendant to them) will support around 180 people. This takes into account normal blights, rats, drought, and theft, all of which are common in most worlds.
>
>
>
However, the MDME estimate does not seem to account for fishing. Given that the settlement is surrounded by the sea and therefore will make heavy use of fishing as a way to feed it's population.
How would the land area required to sustain the population change? If fishing can be a substitute for the pastures needed to provide meat to meet human dietary requirements.
Assuming: There is plenty of space to fish and plenty of fish to catch
[Answer]
I grew up on an island, me, and one which both grew a fair amount of fresh veg and on which fishing was a primary concern.
You've missed several important elements in this discussion:
One: not only salt as a preservative, but the combination of salt and smoking / drying (think both kippered herrings and the Pacific Northwestern Native American salmon jerky) which can create foodstocks which will last for many months. Hell, pemmican too.
Two: many island peoples not only fished but also collected seaweed, which is incredibly nutritious and high in iodine. This collection works well in parallel with gathering shellfish like mussels, winkles and limpets, and in some areas, shrimping.
Three: many islanders also propagate hardy non-cattle ungulates which require minimal supervision, such as goats and sheep - where I grew up we had a herd of local sheep which ate seaweed half their time and grass half their time as they migrated on and off Lihou island via a causeway - their wool was highly prized due to its additional lustre and warmth. These herds also produce goat or sheep milk, which is intrinsically of high nutrition, and makes long lasting cheeses.
Four: Tuna as a nutrition base is somewhat unrealistic (large, fights hard, prefers deeper waters, requires one ***serious*** line to handle it, hard to gaffe and return to port) - let's instead take a school fish like mackerel as a better example, as it can be either line fished with small lines or net fished: 1 Kg = 2620 calories, and the nutrition breakdown is similar to most other ocean-going fish - note that it's a higher caloric content per weight than the tuna. Where I grew up we routinely fished mackerel, smelt and whiting, and only occasionally saw tuna far out.
Hope some of this helps.
[Answer]
I think your question should be broken up into 3 questions. However I am posting this elaboration as an answer because I will show you how to calculate what you want from the answer to the 3 following questions.
Question:
(1) **"How much fishing (in Kg/year) per square mile of ocean, is sustainable?"**
(2) **"How many calories of food per year does an average human need?"** A rough answer is 730,000 Calories (`2000 daily calories x 365`). Tuna has about [`1200 Calories/Kg`](https://medium.com/evidenced-fitness/ranking-everyday-foods-by-caloric-density-c5c45786c32a), so a human would need to eat about `608 Kg` of fish a year to survive.
(3) **"How far could a medieval fishing ship travel for fishing and still be able to return with edible fish?"**. If we guestimate this we can use the average [windward medieval ship speed of about 5knots](http://penelope.uchicago.edu/Thayer/E/Journals/TAPA/82/Speed_under_Sail_of_Ancient_Ships*.html), and a limitation of 1 week voyages to leave and come-back, to come to the conclusion that this distance is `477 miles`.
Assuming you can build as many ships as needed, your answer is then:
```
A = Average height of island + max ship travel distance (477 miles)
B = Average length of island + max ship travel distance (477 miles)
AreaTotal = A x B
AreaIsland = Average height of island x Average length of island
FishableArea = AreaTotal - AreaIsland;
SustainableFishingYeildPerYear (in kg) = FishableArea (in miles) x SustainableYeild(kg/mile)
AmountOfPeopleItCanKeepAlive (in humans) = SustainableFishingYeildPerYear (kg) * 1/608 (humans/kg)
```
I don't know the answer to question 1, so I leave the research to you.
[Answer]
Fish and shoreline scavenging (shellfish, crabs, seaweed) are a complete diet. You can, in theory, subsist entirely on these.
However, how exactly this looks (and the land resources required) depends massively on the local environment.
* **How strong are local seasons?** If very bad, like Iceland or Norway, you need to salt & preserve your food over the winter famine. If weak and broadly pleasant, like in the tropics, this is less of a consideration.
* **How accessible are the fish?** If there are on-shore reefs, you can access food by spear-fishing and diving (eg. Bajau Laut tribe in Indonesia). If you are pursuing free-swimming ocean fish then you require substantial boats that can sail independently for several days, which requires good lumber (and, preferably, metal tools for woodworking) and hopefully some cloth/weave for sails and nets. In between these extremes you could use something more akin to rafts made from small trees (paddle to fish stocks within sight of land in non-treacherous waters).
* **How productive are the available waters?** Depending on ocean nutrients, there is a variable amount of fish you would be able to sustainably extract.
Which is to say that pleasant local ocean conditions can support villages with little land requirements if you can get your food within the coastal biome. Larger scale ocean fishing operations require forests and low-grade industry to build the tools that fishing requires, which is a non-trivial land & personnel use that would not be possible on tiny islands.
Ballpark, I'd be happy to throw in a few hundred people on the tiniest volcanic squirt of an island if they could access shoreline shellfish and nearby reefs.
On mid-to-large islands, you could supplement farming with fishing and perhaps boost pop. density by 10-25% (also health/famine benefits from a diversified diet), but it comes with a trade-off of land-use and industry. I would expect inter-tribe/inter-national trade and some form of military to co-exist in any society that makes big fishing boats that sail over the horizon for a few days.
] |
[Question]
[
I has this idea for quite a while. I searched for information on the internet but I could see no reference. All searches gave results on the same idea but the effect was not what I'm looking for.
**The constraints**: a space colony on a planet away from its star, an underground colony or a hostile climate may create discomfort to colonists who desire a 24-hour day-and-night cycle.
**The idea**: To create a dome which mimics the blue sky and the cycles of the moon and sun. It uses the planetarium dome with some changes. The dome may or may not cover the whole colony, depending on building constraints: Underground/undersea domes will only cover the smaller gathering areas and garden areas. Some private houses may have smaller, private domes on their "balconies".
**How it works**: I thought of using a planetarium dome. A projector at the center will project a scenery with blue sky, clouds and the moon. A strong spotlight shoots a strong beam that will radiate light once it hits the dome. The dome is made out of unpolished aluminum. This is highly reflective but not mirror-like, allowing scattering of light from the dome, mimicking the sun. The light source on the dome is concentrated enough to make objects cast shadows. Spotlight and scenery may change colors to mimic sunrise, sunset and seasons. Seasons are important if colonists pursue their hobbies of raising plants and animals they brought from Earth, and which depend on the seasons. Domes designated for food culture and recreation may have a more comfortable weather year-round.
**Question**: Is this dome worth spending some time under it? Does it create the effects that I'm looking for? I'm aware that an aluminum dome above a garden area must be proofed against humidity, corrosion and mold, and cleaned regularly, but does it create a realistic day-and-night cycle?
[Answer]
Switch the projection to actual lamps, it would be more believable and require less power than your bounce-light on an aluminum ceiling. Stars can be point lights. The sun would be a bright lamp on a track which could cast shadows. Existing technology would probably use a plasma lamp for the sun, or a high-intensity discharge lamp.
Unless you need the sky to be ever-changing, and occasionally replaced by advertising or psychedelic visuals, or it needs to be reconfigured instantly to some *other* sky complete with different star patterns and a sun that can be positioned anywhere (or three suns on Thursdays), I don't see the advantage of one central lamp and a silver screen for the entire sky. I think you are better off with individual lights attached to the dome, and a mechanical track for the artificial sun.
Instead of aluminum, the ceiling could be made from a nano material that can alter the spectrum of light it reflects, this is called *[structural coloration](https://en.wikipedia.org/wiki/Structural_coloration)*, and it's the reason peacock wings reflect an iridescent blue color despite having brown pigments.
The novel **Steel Beach** by John Varley uses something similar for artificial skies in underground moon caves. However I believe his "sun" was a burning nuclear something-something on a track (it has been a while since I read it and he is not the most science-based author in the universe).
[Answer]
An artificial sky is a great idea, psychologically being able to see the sky is a big deal, especially on the span of years or more.
**How to do it better**
1.
If they paint the ceiling with semi-reflective blue paint it will save a lot of energy, and make engineering easier since they can use multiple diffuse light sources for most of the sky (everything but the sun). You don't need to see the sun all the time, a brightly lit blue sky is more important. Of course you can still have a projected sun and stars. Just having bare aluminum is just asking for corrosion issues.
Clouds. clouds are not necessary but if you want them their are two ways to achieve it. In a large dome clouds may form naturally, if not cloud machines are a thing.
2.
Alternatively if you have tunnels instead of a dome, you can put fake sky lights in the rooms. these can be painted surfaces or low resolution screens. This may a be a good idead in out buildings or larger buildings anyway.
[](https://i.stack.imgur.com/IxwG0.jpg)
[](https://i.stack.imgur.com/jpOgf.jpg)
[Answer]
On many planets you will require domes anyway to maintain a habitable atmosphere and protect from radiation. When you already have them anyway, then spending the additional resources to make them look like Earth's sky isn't that big of an investment.
When your colony is in a cold environment and thus requires electrical heating, then it would not even be a waste of energy, because all the energy used on fancy light effects gets converted to heat anyway. However, when the environment requires cooling, then it would be yet another source of waste heat.
Is it worth the time? Likely yes. Many space colony concepts focus on the physical needs of the colonists, but psychological and aesthetic needs often get neglected. Winter depression is a common condition on Earth caused by not being exposed to enough natural sunlight and not seeing a clear sky for several months. It has measurable health and economic impact. Living their whole life under a grey steel dome would have even worse long-term effects on the emotional well-being of the colonists. So simulating Earth's conditions not just physically but also aesthetically might increase productivity and reduce suicide rate, especially among newer colonists.
[Answer]
People don't need an imitation of the sky to have a day night cycle. Due to my aversion to ultraviolet alight I keep the blinds closed all the time in my room, for example. In many parts of the colony people or automatic timers will simply turn the lights in rooms and corridors/streets on or off, up or down, to fit the time of the artificial day cycle. Perhaps there will be light wells or courtyards with large lights working all the time and people will open shades or shutters in the "morning" and close them in the "evening" to change the light levels.
But public areas (and private areas in the homes of the rich, if any) could add to their attractiveness with domes showing day and night sky images. Any type of park or recreation of outdoors on Earth would benefit from a more or less realistic sky.
[Answer]
Farming food stuff can be in basements with artificial lighting from many light sources. This way your dome will be dedicated to living space, parks, decorative gardens. Those would or could have their own lighting from lamp posts, or similar.
Dome material should be something along the lines of movie screens:
"*[Pearlescent is probably the most common choice for a typical movie theater. To make a pearlescent or silver screen, a reflective coating is added to the matte white vinyl. A glass bead screen actually has thousands of tiny glass marbles embedded in a transparent coating on the surface of the screen.](https://entertainment.howstuffworks.com/movie-screen1.htm)*"
You would want to aim for an Imax Dome configuration with the screen being mounted on a frame that leaves space between the solid dome and screen frame for things like lights, possibly sprinklers that bring rain...
Imax Domes are very similar to planetarium domes, just angled a bit but using very similar projectors to light up the dome.
There are also screens which have tiny holes, those holes would allow for back lighting where you could feasibly use LED lamps to tint the dome in various colors of the sky from shades of blue to simulate a clear day to purples, reds and oranges to mimic sunset/sunrise.
A single light source for a 'sun' is going to be difficult to mimic placement in the sky as the dome is far closer than any sun thus just walking from one place to another under the dome would change the sun's apparent placement in the sky.
You would do better with a projected image of a sun and use behind the screen lights to brighten the area.
As for the gentle heat of a summer sun... I have no idea how you would manage that. UV lights behind the screen to react with the people's skin for tanning may not happen, but you might be able to give enough good UV to prevent Vitamin D deficiency. I don't know if that would be practical or if just having people spend time in tanning beds would work better.
There are limits to imitating a real sky. However the dome screen could be used for other projections and light shows which no worldly sky could have thus making up for 100% imitation of "real" sky.
Of course being basically a planetarium dome the night sky would be spectacular, brighter and even educational with line connecting stars in constellations, or showing Old Earth constellations, or nebula, or any manner of cosmic wonders.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
In a [near future setting](http://tvtropes.org/pmwiki/pmwiki.php/Main/TwentyMinutesIntoTheFuture) I am working on, humans have built [space-habitats](https://worldbuilding.stackexchange.com/questions/91677/where-to-place-my-space-station-so-it-observes-one-full-planetary-revolution-per) and have established colonies on celestial objects [such as Luna](https://worldbuilding.stackexchange.com/questions/41938/what-would-be-the-most-optimal-location-for-the-lunar-radiotelescope). Their spaceships cannot go faster-than-light and [have their fair share of other issues](https://worldbuilding.stackexchange.com/questions/89955/how-hot-can-i-make-the-insides-of-my-spaceship-before-damaging-crew-too-much) - yet are still the primary means of transport across the Solar System and are the result of constant improvement since the first [space shuttle](https://en.wikipedia.org/wiki/Space_Shuttle).
The void between these specks of life is populated by small-scale entrepreneurs, shipping cargo from *a* to *b* in trips that are measured in months to years. That is, [thanks to cryogenics](http://tvtropes.org/pmwiki/pmwiki.php/Main/SleeperStarship), for them only a few days pass, maybe a week.
They basically take on a cargo, plot the course and then wake up sporadically for maintenance, course-corrections, and so forth.
---
In a [previous question I have been asking about plausible technological constraints that would favour text-interfaces over graphical ones](https://worldbuilding.stackexchange.com/questions/97615/why-would-technology-dictate-graphical-interfaces-to-be-rare-on-spaceships). In this question, I want to focus on another aspect of my spaceships, namely their *propulsion systems*.
---
With some obvious exceptions, such as the cryo-sleep, I want most of the tech in this world to be current-day or *plausible* near-future extrapolations. E.g. the propulsion systems.
These ships traverse the voids of the Solar System on a regular basis. An excerpt from the schedule of a busy pilot might look like this (chronological order):
```
...
Deimos-Station drop H2O cargo
pick up 20 ounces REDACTED (bribe T-Sony)
Hephaestus-Station deliver REDACTED (payment for that Luna incident)
mixtape for Suul
pick up cheap and glittering stuff
SOL5-92-Jup92 drop off glitter stuff
visit Maja
...
```
1
In order to get a feeling for the times involved in traveling these distances, I need *hard numbers* for things such as constant-/max-acceleration, fuel consumption, etc. of the propulsion system(s) in use by these spaceships.
---
**Q**: *What near-future propulsion system(s) could be employed by my spaceships?*
I am looking for answers with current-day technologies or *plausible* extrapolations of current-day technology.
An answer needs to address the following things:
* **complexity of the whole system**: The easier it is to repair/replace, the better
* achievable **max-(constant-)acceleration**: The smoother the better
* **fuel consumption rates**: Graphs would be amazing
* **fuel efficiency**: Space is a premium, the less fuel needed, the better
* **fuel type**: Being able to refuel between trips is great, having to replace whole [sections of my engine](https://en.wikipedia.org/wiki/Solid_rocket_booster) after each trip is not
1Station/staellites/asteroids (MINORS) are named after the convention [STAR ORDER - ORDER\_OF\_MINOR - MINOR\_DESIGNATION](https://docs.google.com/document/d/1a10zLJnWbzGn6hlNI1ZU7IIE69OqyYnXpTG1XfW8CsQ/edit?usp=sharing)
[Answer]
Ion propulsion would be the best solution for your near future propulsion system. It is already in use and newer more powerful versions are being constructed now such as the [X3](https://www.space.com/38444-mars-thruster-design-breaks-records.html).
Although ion propulsion would probably be the best solution a detailed answer is difficult because there are a number of variables that must be considered as related by the [rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation):
Δv = Ve ln(Mi/Mf)
Where
Δv = the change in velocity required
Ve = the exhaust velocity of the rocket exhaust
Mi = the initial mass of the vehicle with propellant
Mf = the final mass of the vehicle without propellant
The real problem is the multiplicity of assumptions that must be made in order to arrive at an answer. In addition to the variables above the time taken for the journey and the destination are also key parameters.
Assuming the Mi/Mf ratio is 10 (90% propellant 10% rocket and payload) and the exhaust velocity is 20km/s [ref](https://en.wikipedia.org/wiki/Ion_thruster) (the lower end of the stated 20-50km/s)
Δv = ve ln(mi/mf) becomes 20000\*In(10) = 46km/s
This should be sufficient for your requirements. see the delta V links below for examples of the required delta V for different destinations. A greater exhaust velocity or mass ratio would produce even more delta V but at the expense of pushing ever further into uncharted performance territory or ever smaller payload capacity.
One big issue with ion propulsion is the vast amount of electricity required. In the inner solar system this might be provided by large solar arrays, but in the out solar system nuclear electric propulsion would be required.
[Range of ion drive rockets using different electrical sources](https://www.grc.nasa.gov/WWW/ion/future/images/futureapps.jpg)
**Delta V Links**
[Planetary transfer delta V](http://hopsblog-hop.blogspot.nl/2012/06/inflated-delta-vs.html)
[Near earth delta V](https://space.stackexchange.com/questions/2046/delta-v-chart-mathematics)
[Delta V and time requirements\*](http://www.projectrho.com/public_html/rocket/appmissiontable.php)
\*Note delta V of roughly 10km/s to get into orbit from earth included
Concerning the other requirements
**Complexity**
The ion drive is complex but has virtually no moving parts except the propellant and examples have been run for extended periods without problems. Inner solar system solar array also no moving parts so relatively simple. Outer solar system requires nuclear electric propulsion which would be more complex but should be a sealed unit.
**Acceleration**
Ion engine acceleration is very low but is continuous for months and is smooth. Conventional chemical rockets tend to have high acceleration and short (minutes) burn times
**Fuel consumption and efficiency**
Ion engines are much more fuel efficient than conventional chemical rockets by an order of magnitude due to their high exhaust velocity. But a lot for fuel will still be needed. I have assumed 90% propellant and 10% rocket/payload above but the calculation can be made for any mass ratio you wish by plugging in different numbers into the rocket equation above.
**Fuel type**
Most current ion propulsion engines use Xenon as a propellant but other propellants are possible and some have been tried. For your refuel requirement Xenon would not be ideal as it may not be readily available at the destination for refuelling.
I suggest Diamondoids such as Adamantane or Diamantane would be more suitable. These are relatively cheap on earth being found in oil in very small quantities and could probably be produced at the destination sites with some suitable chemical engineering provided that a source of carbon, hydrogen and energy were available. They have been examined as potential fuels for ion engines along with various others as can be [seen here](http://erps.spacegrant.org/uploads/images/2015Presentations/IEPC-2015-320_ISTS-2015-b-320.pdf).
**Conclusion**
The suggested ion drive rocket could meet your needs and is a realistic projection of current technology. But a lot of further research would be required especially in the development of the ion engines themselves, the fuels used and the large space based reactors required for outer solar system operation.
There are various other current, future and speculative propulsion systems listed [here](http://www.projectrho.com/public_html/rocket/enginelist.php#vasimr) that may be of interest also including ion drives.
**General references**
<http://www.braeunig.us/space/>
<http://www.projectrho.com/public_html/rocket/mission.php#id--Hohmann_Transfer_Orbits>
<http://ccar.colorado.edu/asen5050/projects/projects_2001/stephens/termpapera.html>
Remember it’s not rocket science (no wait…)
[Answer]
This answer is a hard-science expansion of [this answer](https://worldbuilding.stackexchange.com/a/63908/23519). Please read that other answer to get a description of the system I am proposing, as well as justification of its technical feasibility. That post also has lots of reference links for various design decisions. I will summarize the system here and numerically address the questions posed.
# System summary
The power source is a pebble bed fission reactor. The fuel source is uranium nitride pellets coated in a pyrolitic carbon moderator. These fuel pellets are held in molybdenum 'pins' in a geometry that will make them supercritical if a neutron reflector is placed outside the reactor. Heat exchange is done directly with the working fluid to save mass.
The working fluid is helium, which is passed through the reactor core. Electrical power is generated through a Brayton-cycle turbine similar to a marine gas turbine used on ships, except replacing the combustion chamber with the reactor core. The helium is compressed by a compressor coupled to the gas generating turbine into the core, and then allowed to expand over the gas generating and power turbines. Exhaust will still be at ~700 K, and will then be run over various auxiliary systems to utilize this extra energy. The exhausted gas will then have its remaining energy bled off into space through heat exchangers and then fed back into the compressor. The rotational power generated by the power turbine is then coupled to an electrical dynamo to generate power for the vessel.
The main propulsion system is a magnetoplasmadynamic Lorentz Force Accelerator (LFA) arcjet thruster. Lithium fuel is ionized and fed into an acceleration chamber, where a combination of magnetic and electrical fields are applied. The induced current in the plasma, once the input power is in the MW range, will help maintain the magnetic field in the plasma while will then induce an electric current in a tungsten-barium cathode.
# System Specifications
The reactor must produce 300 MW of heat energy. This is possible from a pebble bed reactor, the Chinese are building a pair of production 250 MW pebble bed reactors at [Shidao Bay](https://en.wikipedia.org/wiki/Shidao_Bay_Nuclear_Power_Plant). From this thermal energy, gas generating turbines produce an output of 100 MWe at 33% efficiency. This is equivalent to the power output of 4 [GE LM2500](http://www.kushaindustry.com/pdf/brochure/LM2500_Family_of_Products.pdf) marine gas turbines, which is the same energy source as an Arleigh Burke-class destroyer. The LM2500 has efficiency of about 40%, but we are losing efficiency due to the reactor core being cooler than a typical combustion chamber (our core is ~1750 K compared to ~2250 K in a marine gas turbine). The overall system mass estimate for the power generation portion is 0.4 kg/KWe ([based on a NASA estimate](http://www.tfd.chalmers.se/~valeri/Ajax/7b_vandy.pdf)), or 40,000 kg.
The size of the MPD thruster is much more conjectural, as no thruster of nearly the size required has been built. I have estimated the characteristics from the information available at the [EPPD laboratory](http://alfven.princeton.edu/research/lfa) at Princeton. This design calls for a single 7.5 kN thruster at a fuel usage rate of 0.5 kg/s with an ISP of 15 km/s. There is an available high ISP mode where thrust drops to 1 kN at 0.01 kg/s with and ISP of 100 km/s. The mass of the thruster unit is 10,000 kg. I honestly do not have an good basis for this estimate, but it is needed to proceed.
# Reactor Safety
The pebble bed fission power system is inherently safe. There are several avenues for a nuclear accident, the two most significant being an overpower casualty (Chernobyl) and a loss of coolant casualty (Three Mile Island, Fukushima).
An overpower casualty is not physically possible for a pebble bed reactor. The fuel source will use low-enriched Uranium, enough to achieve critical mass, but low enough that there are significant interactions between U-238 and neutrons in the core. As temperature of the fuel pellets increases, U-238 is affected by [doppler broadening](https://en.wikipedia.org/wiki/Doppler_broadening), causing it to absorb more neutrons. This lowers the number of neutrons available to cause fissions in U-235,thereby lowering the reaction rate and reducing power input. Therefore, the core is naturally moderated at an upper temperature controlled by the U-235/U-238 ratio, which will be engineered at 1750 K. At temperatures below this, with the reflectors (to be discussed later) in place, the temperature will increase to 1750 K. As fluid flow over the core is increased and heat removal increases, the reaction rate will increase to keep temperature stable, and this power output is naturally controlled by demand. At temperatures above 1750 K, power output will decrease due to U-238 absorption until temperate settles back at 1750 K. **Therefore, there is no human or computer based control of the reactor.** Once started it simply outputs energy at the rate heat is removed from the core, moderating itself at 1750 K. This effect is trustworty; computer modeling in [Strydom, 2004](https://www.researchgate.net/profile/G_Strydom/publication/236370888_TINTE_Uncertainty_Analysis_of_the_Maximum_Fuel_Temperature_During_a_DLOFC_Event_for_the_400_MW_Pebble_Bed_Modular_Reactor/links/5436a2930cf2bf1f1f2c2f81.pdf) indicates that the uncertainty band during a loss of forced cooling casualty will amount to less than 100 C even for a reactor shutting down from full power.
As an aside, we should discuss the way that the reactor is started and stopped. In the core's state as built, it is sub-critical. The core will be undergoing fission at a very low rate, but too many neutrons will be lost passing out of the core for a chain reaction to occur. This is changed by surrounding the core with [beryllium](https://en.wikipedia.org/wiki/Beryllium) [reflectors](https://en.wikipedia.org/wiki/Neutron_reflector). Once these reflectors are positioned in place, they reflect neutrons back into the core, as well as helping to moderate the high energy neutrons produced by fission. As a result the core will be super-critical and increase temperature until the upper limit described in the last paragraph. By removing the beryllium reflectors, the core can be shut down.
A loss of coolant casualty is the most dangerous remaining one. However, and simplest strategy for this risk is to ignore it. On Earth, reactor casualties are costly because they leave radiation that no one wants to deal with. In space, probably no one cares. Sure, you lose the ship, but people shipped plenty of things in the Age of Sail while the risks of losing the ship were great. Transportation in space has more in common with the Age of Sail, what with month long travel times and low cargo capacities, than it does with modern shipping.
# System complexity
As described above, there is no requirement for control systems for the reactor itself, only the activation of one safety system in case of emergency (removing the reflector for shutdown). The emergency heat removal system will be self activating.
The Brayton cycle gas generators will be designed to operate continuously for the duration of a mission. Already, ships at sea using marine gas turbines operate for 1 year + without the turbine enclosure or electrical generator enclosure being opened. The conditions at sea are far more challenging than space, what with salt and water both present. Long term maintenance can be performed at a (space)port between missions. Furthermore, the advantage of operating multiple turbine units in parallel is that the thruster will still be able to fire (if at a reduced power level) if turbine are offline, even when only one turbine is operational.
The MPD thruster is, again, the least developed part of this plan and the most conjectural, so I cannot make any statements about its reliability. However, it does have the advantage of no moving parts; power is generated and transferred through the movement of gas, current, and electromagnetic fields.
# Power and Fuel Efficiency
Given the above specifics, we can calculate some burn times and travel times. Here is a [list](https://en.wikipedia.org/wiki/Delta-v_budget#Interplanetary) of delta-v needed for various Hohmann transfers.
Tsiolkovsky's rocket equation is solved for fuel mass, $m\_f$, by
$$m\_f = m\_0\left(\exp{\left(\frac{\Delta v}{v\_e}\right)}-1\right).$$
Our parameters are $m\_0$ (mass without fuel) is 50,000 kg plus cargo size; and, $v\_e$ is either 15,000 m/s or 100,000 m/s depending on operating mode of the thruster.
The burn time can then be calculated by dividing fuel expended by mass flow rate. The mass flow rates are given as 0.5 kg/s or 0.01 kg/s, depending on the operating mode of the thruster.
Below is a table for required fuel mass and burn times for various configurations. A 3.0 delta-V will get you to Mars or Venus, 8.8 delta-V to Jupiter, and 12.3 anywhere in the Kuiper belt:
```
Cargo (tons) deltaV (km/s) V_e(km/s) Fuel(tons) Burn(days)
1000 3.0 15 232 5
1000 3.0 100 32 37
1000 8.8 15 838 19
1000 8.8 100 97 112
1000 12.3 15 1334 31
1000 12.3 100 137 159
10000 3.0 15 2225 52
10000 3.0 100 306 354
10000 8.8 15 8020 186
10000 8.8 100 924 1070
10000 12.3 15 12769 296
10000 12.3 100 1315 1522
100000 3.0 100 3047 3527
100000 8.8 100 9203 10652
100000 12.3 100 13095 15156
```
A few things to note. The optimal burn profile (how long to burn thrusters in which mode) is still an open question. I [posted a question](https://worldbuilding.stackexchange.com/questions/63225/how-to-fire-your-engines-for-a-near-future-trip-around-the-solar-system) about that using similar numbers to this answer, but didn't get a great answer. I might take a stab at that question again later. The reason you have to calculate the optimal burn profile is that fuel has a cost. If you are moving 100,000 tons of raw lithium from Mars orbit to Earth orbit, not only does your burn take 10 years, but you also burn 13,000 tons of refined lithium doing it! That makes it seriously questionable whether moving bulk cargoes is going to be profitable in your solar system. Also note that the above calculations use a 100% fuel burn; you aught to leave at least something in reserve, which cuts further into your fuel efficiency.
I didn't post the scores for using the 15 km/s mode with cargos of 100,000 tons, because the fuel usage is ridiculous. As it is, those numbers are in tons of lithium fuel. Keep in mind world lithium reserves are estimated at about 34 million tons, so you can see how you'd burn through that quickly.
A big open question with this process is the availability of lithium for fuel. If it can be mined in commercial quantities from space rocks, then that sort of operation would be the equivalent of petro-states here on Earth. It may be possible to use alterative propellants, though there would likely be a loss in efficiency. Neon, Argon and Xenon are not very common, either, but [hydrazine](https://en.wikipedia.org/wiki/Hydrazine) is another possible propellant. It could be that hydrazine refining in the orbit of the gas giants is the oil refining of your near-future solar system.
# Conclusion
Here is a system for space propulsion that provides a reasonable ability to traverse the solar system using technology mostly already demonstrated today. The big exception is scaling up the magnetohydrodynamic propulsion system to kN power levels.
Most burns that you might imagine for a sublight space opera set in the solar system are feasible. Cargo capacity is relatively low, with the 100,000 tankers (roughly the size of large container ships today) being probably unfeasible for fuel cost reasons. Taking 1000 tons of cargo from Earth to the Kuiper Belt isn't that inefficient; you must burn 14% of your cargo mass in fuel, and the burn takes half a year, but what is half a year compared to the decade or more it will take to coast there?
Meanwhile, a quick hop to mars could be done in relatively fast time. If you skip a Hohmann transfer orbit and try something else, you could burn more fuel to get somewhere faster. For example, a max burn from Earth orbit with 1000 tons of cargo and 1000 tons of fuel in the high thrust mode can get you to Mars orbit in a matter of days. Of course, the problem is you have to stop. The point I'm trying to make is that for the lower delta-V transfers at lower distances, this spaceship is powerful enough to ignore Hohmann transfers and attempt some other orbital transfer that requires more energy. Now what that transfer might be sounds like the subject of a future post :)
[Answer]
Consider Beam Powered Propulsion to possibly eliminate the need for fuel entirely. <https://en.m.wikipedia.org/wiki/Beam-powered_propulsion>
The power needed to provide thrust to your ship wouldn't be generated on the ship but instead in oribit of the various settlements and beamed at the ship using lasers or masers. The ship would then convert the beam energy to thrust by use of a sail. Because no fuel is needed acceleration can be constant and very high speed can be achieved
It's quite a promising technology. Even with our current level of understanding we are already planning to do some very impressive stuff with it, like sending tiny probes to other star systems in just the span of decades.
<https://en.m.wikipedia.org/wiki/Breakthrough_Starshot>
<https://en.m.wikipedia.org/wiki/DEEP-IN>
Current technology would allow us to use lasers propell the more massive Orion spacecraft to Mars in one month. If a second laser array were present there we could also decelerate the ship and make a delivery. It's not much of a handwave to say that this technology could be used for intrasystem hauling in your future setting.
The ships crew is only needed for mainenance of the sails. All repairs on the lasers and generators are conducted by the settlements.
A laser sail such as this is being considered for the mission to send a probe to the newly discovered Oumuamua interstellar asteroid. Project LYRA: <https://arxiv.org/pdf/1711.03155.pdf>
[Answer]
Well, the problem will be that most contemporary propulsion systems (or near future ones) will have quite low thrust. And you need the heavy radiators to dissipate waste heat from your antimatter reactors.
Therefore, let's build mass accelerators. There will be at least a few in orbit at your origin and destination points. You would pay a fee, then the thing would orient according to the velocity vector you need, and [shoot](https://www.youtube.com/watch?v=hhgwbIC9v_w) you into space.
The mass accelerator is stationary, thus it can have huge solar panels and plenty of energy. In this case, all the propulsion you need is to correct course and ensure you arrive at the destination decelerator with proper alignment (this is going to be tricky...) so it can decelerate your ship. Alternately you can decelerate with a slingshot maneuver and/or atmospheric braking at the destination planet, which is a lot harder to miss...
EDIT
Here is an example of how a mass accelerator would work.
In 'The Moon is a Harsh Mistress', Heinlein proposed that rail guns would be installed on the moon. These would be very long, high-powered electromagnetic guns. Since the target (the earth) was always stationary to the moon, they could be permanently built into the moon foundation, and could be miles long. The moon's low gravity and lack of atmosphere made then feasible. The moon miners would load huge payloads of minerals onto the gun sleds, launch them at the earth, re-load, and launch again. The packages would effectively be nothing but large rocks. I think he had the rocks enter low earth orbit, where space tugs would collect the material.
However, When they arrived at earth, and entered low earth orbit, they would be moving at a low enough velocity that they would simply be like deorbiting space junk. The atmosphere would slow the packages down, some outer fringes would burn off, but the basic payload would splash down in some desert, basically at terminal velocity. A large thud, but not widespread damage. In this regard, Heinlein was probably incorrect about using the rocks as weapons against the earth. They wouldn't gain enough velocity.
[Answer]
Hohmann Orbits are the minimum delta-V it takes to get from one planetary orbit to another. These are computed in the Chemical Rubber Handbook. <https://en.wikipedia.org/wiki/Hohmann_transfer_orbit> These take a long time -- something between the orbital period of the two planets. (I think using the geometric mean will get you in the right ballpark)
Article here: <https://en.wikipedia.org/wiki/Hohmann_transfer_orbit>
Tutorial on how to calculate one here: <http://openmdao.readthedocs.io/en/1.7.3/usr-guide/tutorials/hohmann-transfer-tutorial.html>
Light sails: Light exerts pressure. Not a huge amount. Sunlight on an acre could lift a cigarette paper. But .0001 g's will add up. And the price is right. Maneuvers get interesting. <https://en.wikipedia.org/wiki/Solar_sail>
Ion systems. These all depend on using an easy to ionize metal, then accelerating it to high velocity. <https://en.wikipedia.org/wiki/Ion_thruster> Ion thrust gets you about 7-12 times as much delta-V per kg of mass.
Torch ship. See Heinlein's "Double Star" and a bunch of his juveniles. This was a hydrogen fusion reactor, where all the energy (besides parasitic energy to run the reactor) accelerated the helium. This makes it reasonable to run a 1 G all the way. Earth to Pluto in 17 days.
Periodically there is a storm of fuss and feathers about someone who discovered a 'reactionless' drive. Don't buy stock in any of these just yet.
<https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster>
---
Consideration: You have a huge pile of money invested in a ship. You need to explain why they will use a slow way if another way allows them to run more cargos. This is a balance between operating costs and lost opportunity costs.
E.g. A perfect Hohmann transfer orbit is half an ellipse that is tangent to the starting planet's orbit on one side of the star and tangent to the final planet's orbit on the other side. But with a little more fuel, you can get there sooner. Historical parallel: The Clipper ships were designed to sail FAST because the first cargo of tea from China/India got a huge premium in London. The starting date was dictated by weather and the harvest. Coming in a week earlier could make your fortune.
E.g. Big ocean freighters move at around 10 knots. Moving at 20 knots would cut the time in half -- but would take something like 8 times the amount of fuel. Further, you would haul less because you need 8 times larger engines and 8 times larger fuel tanks.
Bear in mind that different propulsion systems take a different amount of effort and training to run. E.g. Hohmann orbits are pretty much do nothing. Take a nap. Solar sailing or something like a torch ship will require someone standing watches. I wouldn't want everyone asleep with riding a continuous hydrogen bomb in a bottle.
Compare the transition between sailing ships and coal powered ships. Sail -- generally slower (but see clippers...) but free fuel. Coal -- faster, but you had to go where you could get more coal. You might have fun with the economy in transition between modes. The last such ship was the Pamir. <https://en.wikipedia.org/wiki/Pamir_(ship)> which sank in 1957
[Answer]
I am not a physicist or aerospace engineer so I will provide figures that have already been pre-calculated by others with greater mathematical prowess.
The idea that I found a while ago while browsing the web is a concept known as a Nuclear Salt Water rocket, it was theorized by Dr. Robert Zubrin and is one of the few designs that we know can deliver torchsip levels of performance, and is ideally suited for constant acceleration space travel.
[](https://i.stack.imgur.com/sjM30.png)
How it works is it consists of a fuel tank composed of small cylindrical containers holding the nuclear fuel solution wrapped in a boron carbide neutron moderator that prevents it from reaching critical mass while in storage. The to ignite the engine the nuclear fuel solution is sprayed in small amounts at a time into a plenum without the neutron moderator where it reaches critical mass and creates a continuously detonating nuclear explosion that propels the craft forward.
Now the fuel solution consists of a mixture of 2% Uranium tetrabromate mixed with 98% water, which means the propellant can be stored without need for cooling and the steam created by the nuclear explosion creates lots of extra thrust.
It uses open-cycle cooling so it is not power limited like other nuclear power concepts and can produce jet power ratings in the thousands of megawatts range.
**General theorized specifications:**
Total engine mass: 33,000kg (excluding fuel mass)
T/W: 40
fuel: fission Uranium Tetrabromate
reactor: gas-core open-cycle
reaction mass: water
reaction mass acceleration: thermal acceleration from reaction heat
thrust director: nozzle
specific power: 0.8kg/MW
**The estimated performance for a craft using 20% enriched fuel is as follows:**
Exhaust velocity: 66,000 m/s
Specific impulse: 6,728 s
Thrust: 12.9 million N
Thrust power: 425.7 GW
nozzle efficiency: 0.8
mass flow: 195 kg/s
**The estimated performance for a craft using 90% enriched weapons grade fuel:**
Exhaust velocity: 4.7 million m/s
Specific impulse: 479,103 s
Thrust: 13 million N
Thrust power: 30.6 terawatts
nozzle efficiency: 0.9
mass flow: 3kg/s
So in conclusion, you get the efficiency of an ion engine with the thrust power of an Orion project spacecraft without much more mechanical complexity than your average chemical rocket.
Now of course there are some obvious issues with this device, as it is a contiuously burning nuclear flame with the intensity of an atomic bomb. The materials required in the engine would have to be extremely strong and at the cutting edge limits of our current metallurgy unless you want to replace the engine after every trip , however they wouldn't have to be insanely strong to the point of impossible , because while the initial reaction would take place within the reaction chamber the expanding steam would force the rest of the fuel outwards having the rocket ride on the aftershock of the main detonation occuring outside. This means that the reaction chamber doesn't have to contain the nuclear detonation.
Now while this rocket is so powerful it would barely notice the cost of takeoff, it would leave a burning nuclear crater, so other solutions would be needed like maybe having the craft dock at an orbital spaceport, and the pilot get to the surface by other means.
If you are worried about the exhaust contaminating space, don't because as long as it doesn't directly intersect with any planet's surface it's velocity is so high it would exceed the planets escape velocity and leave the atmosphere as quickly as it entered. And over time it would diffuse so that the contaminants would spread over a huge distance eventually entering concentrations where they are no longer harmful.
Happy trails!!!
sources:
<http://www.projectrho.com/public_html/rocket/enginelist2.php#nswr>
<https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket>
<https://www.npl.washington.edu/av/altvw56.html>
[Answer]
So, travel time in space isn't typically a big function of your engines. In the game of cosmic billiards, you're stuck with launch windows and their set travel times. You can deviate from these travel times by a bit (10-20%) but beyond this can become very very expensive from a fuel consumption perspective. Hard science-wise, I can derive the interplanetary motion of space ships in terms of their velocity, but it's a 3-4 page affair. Not very useful here, I think, but please let me know if you'd like me to post it.
What would be useful is the **[Cosmic Train Schedule](http://clowder.net/hop/railroad/sched.html)**!! It basically does exactly what you want, showing the travel times and launch windows for Mercury through Jupiter for the next 50 years or so. It even shows the fuel requirements (deltaV).
Also useful would be a quick glance at the [Hohmann transfer](https://en.wikipedia.org/wiki/Hohmann_transfer_orbit), which space ships use to travel from planet to planet. The time to do the trip one way is the "transfer time". The amount of fuel required is measured by the "DeltaV" of the transfer. Your fuel efficiency is measured by "Isp". Relating these concepts, is:
$$fuel burned = weightBefore - weightAfter $$ and
$$weightAfter = weightBefore \* exp(-deltaV/(Isp\*g0))$$
where g0 is 9.81 m/s^2 (pronounced 'gee not'), and on a nice near future (next year) 'methalox' engine suited for interplanetary travel, you might get 375s Isp. Make sure deltaV is in m/s, not km/s!
Finally, it takes a lot of fuel to land places. Check the Low-orbit to landed deltaVs on this [deltaV map posted in redit](https://www.reddit.com/r/KerbalSpaceProgram/comments/4wno9x/ksp_deltav_map_condensed_real_solar_system/) for reasonable estimates.
Good luck with your world building!
] |
[Question]
[
My world - basically Earth all along, unless told otherwise - is populated by humans and few fantasy-based "races" (actually, species - any interbreed offspring, if possible, is infertile): elves, dwarves, etc. Despite the fact that setting is to some extent inspired by common fantasy tropes, there is no magic at all, just hard science. All "fantasy species" in fact belong to the same Homo genus and should be plausibly justified as the effects of natural evolution of (perhaps isolated) groups of hominids.
All of these species keep at least some contact with each other, sometimes even living together in one city.
How likely is that somebody will get infected with a disease from a member of another "race"? I know that most of the diseases are rather species-specific, but there are some exceptions (afaik HIV originates from apes).
Will halflings be just ok when the plague is decimating human communities? Can a dwarf get infected by human HIV or syphilis?
[Answer]
First, disease from bacteria and viruses do tend to be species-specific; however, zoonosis can occur. **The chance that this can happen isn't really a number but more related to frequency of exposure instances where said pathogen interacts with another species.** The root principal is the more chances you give a pathogen to evolve, the more likely it will.
The theory behind AIDS is that it arose from the predation of primates. Because we frequently ate them we gave the virus more chances to adapt to our physiology.
Bird flu is another example. Pigeons and crows liter our settlements and we are constantly exposed to their fecal matter. That constant exposure gives it a chance to adapt and then spread.
**Another aspect is carriers and survivability of the pathogen**. In some species a pathogen can have no effect yet still be communicable to other species. Also the structure of it matters too. If a pathogen can survive exposed to air it can be carried by other species and left on surfaces you interact with.
**So could a species suddenly get a human pathogen?** Not impossible, but unlikely.
**Could dwarves get syphilis?** Depending on their genetic divergence from humans and the amount of exposure from them, maybe, maybe not.
**The chances are like winning a lotto where each interaction is a ticket.**
[Answer]
There are many bacteria and viruses that can infect several species, possibly with different symptoms or prognosis.
An example is cow pox which is not very dangerous for humans, but they *can* catch it.
Quite the reverse with avian flu.
[Answer]
Do you mean how likely it is that someone will get infected from a member of another species? If so I would say the chances are very high that some diseases would eventually cross the species barrier. Generally the closer a species is related to another and the closer the contact between them the more likely transmission of disease is. That said it doesn’t always happen, it’s just more likely.
The original source of human HIV was thought to have been monkeys and SARS came from chickens. (so they don’t have to be that close!). The details of what is or isn’t transmitted depend very much on the specific biochemistry involved and all cases are possible. So one species might be infected with another species disease and be affected the same way, affected to a lesser extent or not affected at all.
[Answer]
Your best bet would be [Prion diseases](https://en.wikipedia.org/wiki/Prion#Prion_diseases_and_their_transmission_properties).
Prions aren't viruses or bacteria, they are folded proteins. Which just so happen to mess with protein expression in the organisms they affect.
The infamous Mad Cow disease, more precisely known as [Bovine Spongiform Encephalopathy](https://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy), is an example of prion disease.
Prion diseases are very likely to achieve zoonosis. And since your races are all mammals with a central nervous system, they could very likely wreak havoc.
As an extra, prion diseases have been in some instances linked to cannibalism. So you can have a gruesome cannibal cult being the cause of the terrible disease that afflicts your world.
[Answer]
I would read up on zoonoses! These are infectious diseases that, for a host of reasons, are able to make the leap from one species to another. Many of humankind's most terrible diseases are zoonoses: Ebola, flu, various poxes, plague, Zika, tuberculosis, many worms/parasites.
Zoonoses usually have a reservoir host species, in which the infectious organism causes little or no harm (avian influenza causes no illness in wild aquatic birds but if it makes the leap to us, can be deadly). The organism exists happily in this host, duplicating itself and carrying on until chance exposures lead to crossover events into a brand new species.
The Ebola outbreak in West Africa was hypothesized to have begun when a group of children played near a tree that was filled with Ebola-carrying bats and became infected. From the Ebola virus' perspective, it's not particularly useful to jump over to a human host that you are just going to kill off immediately- this does not promote the survival of the species! It was just a chance encounter that led to crossover- a matter of proximity and exposure.
Also, over time, killer viruses tend to become less potent in new hosts (HIV and some Ebola strains have done this)- this is a way of adapting and ensuring your host survives long enough to pass virus to lots of people. This evolution occurs once the organism has made the leap into humans and begins to adapt to the human immune system.
A cool example of virus evolution example is influenza, which has a variety of surface proteins that help the virus adhere to different mammalian species' cells with varying specificity. These proteins' genetic code "drift" and change over time naturally, leading to different strains of virus such as H1N1 or H3N2. If it ever shifts to a code that produces surface proteins that fit human respiratory cells receptors exactly (think like a lock and key), then we're looking at a pandemic event. Genetic change can happen faster when different virus strains recombine, like how swine flu was a mix of genes from human, avian, and pig-specific virus. Other animals like dogs are not susceptible to catching flu at all, because their receptors look totally different from ours/pigs/birds, which are all close enough to be shared around once in a while.
If you look up the life cycles of parasites like malaria or schistosomes, they often have complex relationships between different species in order to survive. Malaria has to, at different stages of its alien-esque life cycle, live in mosquitoes, humans, and the environment. Parasites can infect a ton of different species, which may or may not be the primary host, dead-end host, or reservoirs.
Anyway, you could certainly have a disease that halflings are immune to, or are reservoir hosts of, or can be infected by but only experience milder symptoms.
] |
[Question]
[
In my world a lot of people can fly. It isn't everyone and it isn't all to the same skill level. Some people can only float around a bit, while a master can break the sound barrier. There are enough people like this to form all-flying squads in an army.
Castles in real life are very open to the sky, and while crossbows and other ranged weapons would still exist, I would question their effectiveness against a troop of flying people with more movement options than a walking solider.
How could a castle built for defense be made accounting for assaults from the sky?
EDIT:
Mechanics of flight:
It is performed 'superman' style, where you can float stationary and move around as if in water. No arm flapping is needed and no 'exhaust' wind shoots out from your body. Flight can really be in any direction but headfirst is generally the best for looking and aerodynamics.
[Answer]
Assuming a Middle Ages technological level (you may want to specify) I would assume high towers connected with a web of nets to impair flying attack while providing good visual reckoning.
Battlements would have some coverage to protect from air, even if I presume airborne archers would be much less precise than the ones with their feet firmly on the ground.
I would also suggest a copious array of trained falcons and owls to help in the fight.
Other characteristics would depend heavily on details of these "flying abilities", in particular:
* would people be able to remain static in a position?
* how much effort will it take to fly?
* can they fight effectively while flying?
* how long can they hover?
* do they have to flap their arms (impairing aiming capabilities)?
**Addendum:**
If flight is so common and stead and effortless then it may be better to use bunkers instead of castles.
I strongly suggest to give some limitation to flight, something along the lines:
* You can fly fast and steady, but it requires concentration, so using another device that requires concentration (e.g.: bow or crossbow) is difficult or impossible; flying attack is limited to a lance kept on rest (tournament style) or sword (scythe style).
* You can only move from point A to point B, in straight line at chosen speed and attitude.
* You can not stop; you need to keep a minimum speed to fly smoothly, otherwise you start to wobble (like a real plane).
* Flight is hard, maneuvering laborious and hovering strenuous.
* Any combination of the above.
Otherwise it would give too much of an advantage and underground bunkers may be necessary.
Underground bunkers, however, would be more vulnerable to ground attacks, given a medieval setting, as it is difficult to fight back. You can only delay enemy advance to be able to escape via some other route (see the Rolling Stone Doors of [Derinkuyu](https://en.wikipedia.org/wiki/Derinkuyu) and their usage).
[Answer]
I would consider the following:
**More enclosed:** If your developmental timeline permits it, copper for steep surfaces and slate for more level surfaces. A focus would be on steep rooftops so that dropped objects will fall to the ground rather than penetrate the structure. Coatings (e.g., rubberization or tar) might also be employed to protect surfaces from acids and other corrosives.
**Protected Walkways:** Where many of Earth's castles had an open space where all traffic, people and animal alike, traversed, I can imagine a focus on covered walkways, connected buildings, and even underground foot-traffic passages for everything but carts. (And maybe even some large ones for the carts.
**Relocation:** Earth's castles were often located because (a) the geography made them more defensible and/or (b) the location made observation of the surrounding countryside easier. In your case, I can imagine mountain sides such that only one side of the castle is easy to approach from the air. I can imagine taking advantage of natural caves. And I can imagine (b) not being an issue at all since flying troops would always be more efficient. Rather than locating near waterways, they would locate (perhaps) at altitude to minimize the number of attackers (or, said another way, to maximize the dependency on skill. Weak flyers can't easily reach the castle).
**Central Towers:** Where our castles tended to have narrow windows to maximize defense from arrows (and because glass was something that came later... large windows meant large drafts), I can imagine tower tops similar to helipads that permitted easy egress for stationed troops. Towers would be thick to accomodate the structure and to hold troops and supplies. Where our castles had (generally) some spires and high places for observation, your castle may have one or two cylindrical towers (basically a flat top, or some structure only on one side or dead center) about which the rest of the castle would be built.
**Archers:** Not knowing your technology level, I'm assuming that non-flying archers would find emplacement to protect against all but the highest-flying attackers. This might necessitate early development of smoked lenses (sunglasses) to protect archers against the sun as flying between sun and defenders would be an easy counter-attack.
**Diminished Dependence on Walls:** I'm guessing that having flying troops might cause less dependence on siege equipment. If so, sideways defense against incoming stones might give way to top defense against dropped items. Thus, your castles might not have a substantial surrounding wall (or it may be less prominent).
**Avoidance & Detection:** Finally, and I'm thinking about pidgeons here, your castles might develop roof spikes to keep unwanted guests from landing and weighted (if there isn't much snow) trip-pads where aerial attackers must land to enter a building that would activate an alarm (fancy way of saying, "ring a bell").
**Searchlights:** Finally, finally, I can easily imagine early development of basic mirrored optics. Think "searchlights" but with flares (brightly burning candles) vs. arc electricity. Of course, this would only be valuable if the searchlight can see the incoming attacker before the attacker is in range to destroy the searchlight... but it might be possible. Like I said... flares.
[](https://i.stack.imgur.com/QNtle.jpg)
[Answer]
What's your castle for? There are a few different reasonable answers:
1) Be imposing to look at and tower over the surrounding countryside.
2) Provide a secure strongpoint on a border.
3) Provide a refuge for people to flee to in the event of attack.
4) Somewhere for the rulers/rich to live.
(1) and (4) are the same as ever, except as (2) and (3) change things (although, if your ruling class happens to consist largely/entirely of reasonably strong flyers, their homes may be set up to be inaccessible except by reasonably strong flyers, to reduce how many people can get in).
Now, for the others, a lot has changed: for *refuge during attacks* (3), the correct answer, where possible, is basically "just bury it". It doesn't matter how well your attackers can fly (except for the ones that are going ridiculously quickly, I guess) if they need to attack down a narrow tunnel. If this is your only use, you're ending up with a tunnel system with only very defensible (and probably mostly hidden) entrances. You might want some farms above-ground, and those are going to be very hard to defend: they've got to be open to the air, just by their very nature. Honestly, I don't see a good way to defend this against a force with superior numbers in the air, unless you dedicate a large percentage of your population to just standing around there under some kind of protection shooting at those air forces. This might just be a matter of not having them, or giving up on them if the enemy has air superiority (therefore making air troops an essential element of any siege force that significantly shortens sieges).
For *secure strongpoints* (2), it's still mostly a matter of "just bury it", but you still need to have something sticking up above the surface, as a watch tower if nothing else. So basically a tunnel complex as above, plus some towers sticking up that have no entrances and just some narrow slits to look out (too small for anybody to get in through).
If we're adding *imposing on countryside* (1) in, pretty much as above, but make your sticky-up towers bigger and more imposing.
If we're adding *grand residences* (4), you might want a more significant above-ground complex (caves aren't that nice to live in). You still want it set up so that you can still get anywhere in the castle while staying underground except for right at the end, and certainly without going into the outside areas, and plenty of (well defended and easily sealed) entrances everywhere to let your rulers get underground in a hurry.
[Answer]
Well, if flying is a large issue in that world, one would probably imagine that they would try to build in places where up is protected, like building inside a mountain or underground, basically building in places where the flying enemy would be forced to stay low and close.
[Answer]
The question you need to ask is how big a rock can you drop how fast and how does that compare to siege weaponry? Is it possible to build a roof strong enough to stand such aerial bombardment for a whole siege?
Bear in mind that having flyers means that the besiegers are vulnerable to bombardment and to attacks on supply lines. Wrecking the supply karts of a moving army cripples its ability to move or to stay away from its supply source. Castles could be even more powerful, particularly if they can have launchers that give flyers an initial boost so flyers above the fortress don't have a big advantage.
] |
[Question]
[
There have been a lot of questions about zombie bites on this site. From making it lethal to allowing for an amputation cure. But we have not discussed the primary issue of this line of questioning is its feasibility.
Even assuming that a quick amputation can prevent the *zombie infection*, there are a plethora of problems that come from even regular amputation; blood infections, mobility issues and anemia to name a few. And that's under modern circumstances, where these problems have real solutions and are unlikely to even appear.
In the end times, the chances of these problems occurring increases and their solutions become much more difficult to deal with. Additionally, new problems arise such as bleeding out or being unable to do post-apocalypse related tasks. For example, someone missing a hand would be unable to open cans or climb ladders quickly, while someone missing a leg would be unable to run.
Considering these problems that exist even with a guarantee of removing infection, would an amputation in the apocalypse be feasible?
>
> To avoid the obvious overbroadness, I will narrow down the situation below. While this may over narrow the answers, the basic point or principle of the answer should apply to over situations.
>
>
> We are to assume the bite victim is a young man (21-30) and belongs to a small group. They will have some first aid supplies such as hydrogen peroxide and gauze, but lack things like bone-saws or heavy duty antibiotics. The amputation is, of course, rushed and done with an ax. To avoid being overly broad, let's assume that the amputation is indeed a success and the zombie virus is of little concern.
>
>
>
[Answer]
Allowing for the premise I still have my doubts about field amputation without a trained surgeon.
The most relivant statistics I could find come from the American Civil war, where field amputation was a common treatment for wounds to the extremities.
Primary amputation mortality rate: 28%.
Secondary amputation mortality rate: 52%
Primary being death in surgery and Secondary being death from subsequent infection. It's also worth noting that those figures get much worse the closer you get to the body. Upper leg amputation mortality was 83%
There are a few differences worth noting...
Civil war surgeons weren't familiar with the concept of sterile surgery, so I suppose your people get a very small bonus there. Also contrary to popular depiction most Civil War amputees did have the benefit of anesthesia, which would be a huge deficit for your people. Also keep in mind that while Civil War surgery was crude the surgeons got a lot of practice, at least they had done it before... I very seriously doubt that someone who had never even witnessed an amputation could successfully pull it off.
So... In short your chances of surviving a post apocalyptic amputation are slim. I would put the mortality figure somewhere around 75-85% for a lower limb. Probably 90-95% closer to the body.
**Keep in mind that there is a world of difference between slapping on a tourniquet, hacking off a limb, and getting the person to a hospital vs. a field amputation and hoping for the best...**
It seems I may not have expounded on the point well enough... The difference is dealing with the nitty gritty.
In a field amputation you anesthetize the poor guy, tie off the limb with a tourniquet, cut the skin being sure to leave a flap, slice through the surrounding muscle and tissue as quickly and cleanly as possible, **tie off the spurting arteries with a piece of thread, scrape the bone smooth to remove sharp edges, suture the stump using the remaining flap of skin being sure to leave a port for the wound to "seep",** and finally wrap the remaining limb in a cast of sorts, and further medicate with powerful painkillers (heroin) for several days while the poor guy writhes in agony.
Do you really think a layman can do that... Before the guy bleeds out... With a struggling, screaming patient...Without anesthesia... ?
Source: <https://ehistory.osu.edu/exhibitions/cwsurgeon/cwsurgeon/amputations>
[Answer]
In First Aid, there's a set [procedure](https://www.redcrossfirstaidtraining.co.uk/News-and-legislation/latest-news/2010/September/Tip-of-the-month-sept.aspx) that gets followed:
* **D**anger - Ensure that your patient and surrounding people are safe from any immediate danger before you do anything else
* **R**esponse - Is your patient able to respond to instruction
* **A**irway
* **B**reathing
* **C**irculation
In terms of a zombie attack, you're hampered by the first of these procedures. you're not likely to be able to have your casualty moved to a place of safety before they either bleed out and die from shock or the infection travels too far though their body.
**Pertinent fact #1** - It takes roughly [one minute](http://www.brainstuffshow.com/blogs/how-fast-does-blood-flow-throughout-the-human-body.htm) for infected blood to travel around the body
**Pertinent fact #2** - [Robert Lister](https://en.wikipedia.org/wiki/Robert_Liston) (fastest knife in the West End) could amputate a leg in two and a half minutes
Basically, if one of your party gets severely chomped upon, just leave him for the safety of the larger collective - he'd do the same for you.
[Answer]
First consider two factors seen in many zombie fiction. Some movies have a much faster rate of infection, but let's look at the gold standard.
1. A zombie bite leads to an infection, fever, then death as a result of the illness, and reanimation as a result of the death.
2. Anyone who dies regardless of the cause, might already be infected and therefore if they die, reanimation results.
So what does this tell us about a zombie bite? It tells us that the goal is to quicken the pace of death in order to create a new zombie more quickly than regular death.
What this might mean, depending on how your world works, is that a zombie bite might feature two things--a gangrene-type necrosis/infection which causes death because of the body's dramatic immune response to it, and a viral load which ensures that reanimation results, regardless of whether the subject was previously infected.
In this case, cutting off a hand bitten by a zombie might be enough to stop the immune response if caught in time, but the victim may still die of anything from blood loss to a regular infection as a result of cutting off their hand in less than sterile conditions. Regardless of why they die, after they are bitten, and die, they will reanimate.
Now, given the available tech and level of expertise, I would say that in this situation, your young man is going to die anyway. Because a real amputation involves tourniquets, knowing where to find the major blood vessels and tying them off to prevent them bleeding out. In the Civil War, the death rate was something like 24-30% for any given amputation, but despite the low level of tech, they would have a bone saw, and the many, many amputations turned some of the doctors into experts on how to do it. Death mainly resulted because of infection, since the conditions were not great. A good amputation job means that you actually dissect a bit, and you cut extra skin in order to cover the stump.
Just chopping something off with an axe--that's going to actually result in a quick death. For a non-expert without any real tools, immediate cauterization is really your only hope, and that's only if folks have figured out the tourniquet bit.
As to after-care, that will be a little more complex, and post-amputation, most people are not up to running about.
For survivability afterwards in post-apocalyptia if the amputation is a success, this would depend on the limb, handedness and a host of other factors--and seems to be enough for a whole other question.
[Answer]
Feasibility depends on the situation. If you are on the run, no, use your fallen comrade as zombie bait. Sorry Able, but your sacrifice will ensure our survival (for a short while).
But if things are a bit more stable, you have a fort, island or secluded hide-away, yea, you can do this.
**Setup:** We have a save place, with 100 or so people. Labour is split up a bit, each puling their worth. And so our group of 7 lad's is going out for a patrol, looking for useful items. Let's call [them](https://en.wikipedia.org/wiki/Joint_Army/Navy_Phonetic_Alphabet); Baker, Charlie, Dog, Easy, Fox, George and How. Baker is team leader, Charlie is backup leader. Each lad knows how to hold down a dude. Probably need at least 3 of them. Dog and Easy know how to butcher. Fox and George know how to deal with heavy bleeding. All carry tourniquets. They have been trained by Uncle, who has some nasty memories from [Ganners](https://en.wikipedia.org/wiki/War_in_Afghanistan_(2001%E2%80%932014)).
**Encounter:** Our little expedition runs into Zed. Zed is not alone, meet Zedd and Zeddy. Our lead dude, George, was a bit unlucky, and so has his left foot bitten. Dude, not cool! Let's go into the drill from Uncle: [Care Under Fire](https://wikem.org/wiki/Care_under_fire).
1. Take care of your own safety.
2. Let George himself put on a tourniquet. The limb is toast, hopefully he isn't.
3. Zed, Zedd and Zeddy are taken care off by the other members of our group.
4. Charlie secures the area.
5. Baker, How and Easy hold down George.
6. Dog cuts off the infected limb. If possible at a joint.
7. Fox cleans the wound with hydrogen peroxide and then stops the bleeding.
8. George is in a bad way, but we need to get him back to base. Make a stretcher, carry with 4 man, 2 man guard. MOVE!!!
**Back at Base:** So, George made it, thanks to the fast work of his mates. He will need weeks, if not months, revalidation. I hope you have someone who can make prostheses. For George's sake I hope he is good with his hands and brains, for speed and strength are no longer there for him. As long as George doesn't have to run to save his live, he is good. There are a [lot](http://www.oddee.com/item_97643.aspx) of [jobs](https://historicengland.org.uk/research/inclusive-heritage/disability-history/1050-1485/) you still can do without legs. Heck, you can even shoot in a sitting position from a nice tower.
[Answer]
You have only two options:
1. Amputation of the limb
2. No amputation and killing the infected
If you want to preserve as much as possible the men count in your settlement, amputation is viable, as long as you make clear priority definition (e.g. will you risk a man to save an amputee on an emergency?)
To speed up the amputation you can use cauterization on the wound.
[Answer]
I'd say not.
First, the survival rate is going to be low anyway.
But that's not the problem. The zombies are the problem. By definition, your group is in a zombie infested area, and sufficiently vulnerable that members of your group can get bitten. So even if the amputation is a success, your group will be immobile for a while whilst you tidy up the amputation, your amputee will almost certainty be making a lot of noise, and is going to be a liability for some time afterwards. If it's a leg amputation, you will be slowed to a crawl; but even arm amputations will leave the amputee in a very poor state for a while.
So.. you are in a vulnerable position, you'd just made enough noise to attract every zombie for miles around, and you can't move your group at any kind of speed. I think the zombies will be eating well tonight..
[Answer]
I don't like a zombie infection to be a viral thing. I have come up with a zombie outbreak unrelated to a virus and very specific in terms of effectivness, but I wouldn't share it. However, the mechanics of it can be applied to a zombie virus.
The virus is effective in great concentrations. It's a failed synthesized virus, originally meant to regenerate tissue. Hence, it focuses around the bite first, attempting to fix it, but fails, and proceeds to spread elsewhere. Removing the location of the bite stops the infection form spreading.
] |
[Question]
[
Assume you have two blades (of whatever design you wish) made from identical starting steel (in fact, we can assume that the two starting ingots are sisters from the same mill run). One is shaped by manual hot-forging, while the other is shaped by a single-blow, closed-die hot forging process. After shaping, they are identically heat-treated and machined to final dimensions.
How would the two blades be different, and how would this difference manifest itself in practical usage as a tool or a weapon, both initially and over a long period of time?
[Answer]
>
> Assume you have two blades (of whatever design you wish) made from
> identical starting steel (in fact, we can assume that the two starting
> ingots are sisters from the same mill run). One is shaped by manual
> hot-forging, while the other is shaped by a single-blow, closed-die
> hot forging process. After shaping, they are identically heat-treated
> and machined to final dimensions.
>
>
>
Ok so this is pretty straight forward, but there are some caveats you should consider.
* Steel quality. Pre-modern steel and the steel we use today are very different.
Pre-modern steel had its problems. The **quality was inconsistent** though getting your ingots from the same run eliminates the related variance for your specific scenario. **Contaminants** were also a problem, steel today is very precisely manufactured and certain grades of steel are required for various applications...this depth of metallurgy didn't exist previously.
* Tools versus blades. The process for creating tools and the best steel for creating them vary greatly. For example if you are creating a hammer or tongs you want to use a softer steel. Repeated blows from a hammer crafted like a blade wouldn't last all that long. Softer steel is ok for tools...not so much for blades.
When it comes to blades in particular, the **forging process helped mitigate the problems** with early steel, either by adding the necessary carbon to give steel its extra hardness vs iron or low carbon steel, or by folding the steel to remove and even out contaminants/impurities.
---
>
> How would the two blades be different, and how would this difference
> manifest itself in practical usage as a tool or a weapon, both
> initially and over a long period of time?
>
>
>
## Pre-Modern Steel
The standard vs one big hit blades would vary greatly, mostly depending on the steel that was used in the first place. There are a couple common problems that both pre and modern steel will share...Ill get to that. The **traditionally forged blade would be better** in this scenario. The process was refined specifically to improve quality based on the steel that was available at the time, with the drop forge process you lose all of that.
The drop forge blade would be more likely to break due to the shortened forging process.
## Modern Steel
Modern steel, well... **if I'm honest you don't even need to forge it** to make an amazing blade. Given you complete the heat treating steps properly a blade cut out of a sheet and ground to shape will be just as effective, and significantly easier to make, when compared to a forged blade. Strictly speaking forging is just the shaping of the steel, then you have a whole bunch of heat treating and grinding/polishing steps after you finish forging.
**The general forging process**, though I left out the all the finishing steps (grinding polishing, handles etc...)
* Forge to shape. Make the steel hot, smash it with a hammer until you get your shape
* Normalize the steel (heat to 1300F, 1000F, 800F letting it cool to room temperature between each heating. This takes tiny fractures out of the steel from the forging process, think of it as a healing bath for broken microscopic steel bones. I don't know if this step can cope with the amount of stress a single really hard blow would put on the steel.
* Hardening. Heat to critical (generally yellow hot) the steel will be non-magnetic. Quench, you can use water, but we use a mix of motor oil and antifreeze. This makes the steel very hard, if you drop it at this point it can shatter. (SAD Blacksmith)
* Tempering. Re-heat the spine and tang of the blade while keeping the cutting edge cold. This process softens the spine and tang so they can take more stress and bend better while the cutting edge stays sharp and hard. You're literally giving a single piece of steel varying toughness vs hardness.
The drop forge idea could work fine, though I see potential issues when you start getting to larger sized blades. The larger the blade the larger the billet will need to be. To move the steel that effectively in one single shot you will have to make it hotter than you would traditionally get it when hand forging at least that is my assumption, I have not tried to make a blade in a single strike before.
The additional force required to move all that steel at once could also potentially have problems. I could see the edges of the steel tearing/ripping even when heated to a bright glowing yellow and if you get any hotter you are getting to the point where it liquifies and then you have to cast it...but cast iron does not work at all for blades, it is very brittle.
* 2000°F Bright yellow - 1093°C
* 1300°F Medium red - 704°C
* 1200°F Dull red - 649°C
* 1100°F Slight red - 593°C
* 1000°F Very slight red, mostly grey - 538°C
**In short, extra heat and force could cause tearing or change the nature of the steel in a way that I am not aware of...I can see it being possible but I'd have to do more research, I just don't deal with that in my forge.**
**Common problem with the drop forge**
Old or modern steel I can see one problem coming up...when you forge a blade the traditional way you have to take care to strike the blade evenly on both sides. As the steel stretches from the blows it curves, and if you don't keep your blows balanced odds are the blade will warp when it goes through the hardening process...which is super frustrating for the record.
With a single blow, to only one side odds are you are going to get pretty significant warping when you heat treat the blade. You can selectively heat portions and straighten a blade that this happens to, but each bend and twist of a blade that you don't heat up fully adds stress to the structure creating weak points...and if the warping is severe enough you have to reheat the whole thing and start the heat treating process over.
---
**Summary:**
* Traditional forging will get you a better blade with pre-modern steel
* The easiest method with modern steel would be to not forge the steel at all
* I'd need to research more, but even with modern steel the stress of all the steel moving in one shot could cause problems
* A blade struck on only one side will warp when it is heat treated
Could you do it...yeah probably, with modern steel and modern tech. Should you do it...I have my doubts that it would make a better blade, it would be faster, but honestly the forging step of the process is usually the shortest. I can have a short blade forged to shape in under an hour. The rest of the steps...which you can't skip take longer.
Short versus long term...I don't think it really matters. The point is that steel behaves in certain ways under certain temperatures and certain stresses. If you don't forge properly you add to the likelihood that the blade will fail in some way in the future, the exact nature and timing of that failure will depend on the composition and structure of the particular blade/steel.
[Answer]
So assuming a sword and assuming you are starting with decent steel.
If multiple strikes are allowed a drop forged blade will have fewer stress points, flaws, and other anomalies than smith forging. Thus it will be less likely to fail in the long run. But the benefits compared to a master-smith's work will be small, especially with proper heat treating.
If single strike is important press forging produces the best result, roughly the same as multi-hit drop forging.
A single strike drop-forged sword will be full of cracks and weaknesses, unless you have already shaped your ingot to a roughly sword shape by other means. It will be lucky to survive finishing much less use you are just moving the steel too much at once, moving steel cools it, move it to much and no matter how fast you do it it will get too cold during the process.
Your biggest difference is with consistency with quality, drop and press forging produce more consistent results so if well made will produce good results all the time, where a smiths quality can vary. The other big benefit is speed, drop forging is much much faster than hand forging.
[Answer]
Bragging rights, mostly. When your sword was made by Thor himself in one strike of Mjolnir, people tend to buy you drinks.
It depends heavily on the original steel itself. The Japanese Katanas had to be forged many times to get the strength needed because their steel was poor. Modern tool steel fares well vs. Katanas despite not being forged in such a way.
If you forge a modern tool steel too much, you can actually negate much of the careful metallurgy that went into it and ruin the steel by introducing contaminants.
[Answer]
The one that's **forged will have less carbon in it** and therefore become a different alloy of steel.
The one that's **die cast will remain closer to the properties of the original ingot**. It depends on those properties as to whether either is ultimately better for any given purpose.
If your ingot has an undesirably high amount of carbon, it'd be better if you banged on it a bunch, and vice versa.
] |
[Question]
[
I am imagining a planet more or less earth like. I would like it to have only one pole cap, so only the southern hemisphere has a snow-covered continent. The trick is, I don't want it to lie completely on its rotational axis because that would cause the days be as long as seasons (please correct me if I'm wrong). Days should actually be more or less like the ones on Earth.
Would there be some geological phenomena that would prevent an ice cap from forming? A warm current maybe? Or something in the atmosphere? Thank you!
[Answer]
A polar ocean that extends far enough from poles for significant parts of it to be ice free year around will not form a polar cap. Since water is densest few degrees centigrade and sea water freezes few degrees below zero, water circulation will push free floating ice away from the poles unless the currents are blocked by land masses as they are in the Arctic. Ice simply can't get away from the Arctic.
Note that in this scenario you will have zones where cold currents coming away from the poles collide and mix with warm currents flowing towards the poles. The average water temperature there should be around the densest point and the water will sink. This kind of robust water circulation would probably make the waters fairly nutrient rich and fertile. Not sure of the effects on climate, but the mixing zone would have fog, I think?
[Answer]
### Cover the icy pole with a continent, and the other pole with open ocean. Make the planet about $20^\circ C$ warmer than the Earth.
Oceans are great temperature distributors, bringing relatively warm water to what would otherwise be far colder climates. Because of this, a pole with an ocean on it is going to be significantly warmer than a pole covered by a land mass. On Earth, the North Pole fluctuates between $20^\circ C$ ($36^\circ F$) and $30^\circ C$ ($54^\circ F$) warmer than the South Pole, depending on the time of year, with the difference most pronounced in the Summer.
On an Earth-like planet which was around $20^\circ C$ ($36^\circ F$) warmer, the south pole would remain below freezing year round, retaining an ice cap, while the ice cap covering the North Pole would rise significantly above freezing and melt during the summer. Ice caps have a much higher albedo than open ocean, which is good at absorbing heat, so it's likely that without a summer ice cap, the difference in polar temperatures would be even greater than what we see on Earth.
Wider ocean channels between the equatorial oceans and your polar sea would also increase polar temperatures, On Earth, the Arctic Ocean is largely ringed by land, which helps the ocean stay cold by limiting the degree to which it exchanges water with warmer oceans. Arctic regions on Earth which are more open to currents from the south have less ice than those which are more landlocked, with open ocean stretching as far north as Svalbard, even in the winter, while the Northern cost of Alaska remains ice bound year round, despite being significantly further south. The further warm ocean currents from the south are able to penetrate your polar ocean, the more difficult it will be for that ocean to form a cap of sea ice.
[Answer]
There are several ways I can think of, and most involve volcanism:
1. Have a pole sea with under water geyser strings along the bottom. As long as currents rotate the heat without too big a run-off, no ice should build up. It also helps if the sea becomes extra-salty and/or has more mineral content that Earth oceans have.
2. Immerse one pole with eternal clouds from active volcanoes. The heat will remain captured under the clouds. Don't make em too high though!
3. Have a giant pole desert. So little water is present that evaporation outruns any snow build-up. But beware bigger temperature extremes this attracts, where more than water freezes. You'd need something far bigger and more elevated than Antarctica, with circular winds outside the frozen zone thrown in as well.
[Answer]
I think you can do this, at least for a few thousand years at a time. Take a planet that's generically earth-like, but has a significantly more eccentric orbit.
If you only want a north polar cap, arrange that southern summer happens during the period when the planet is near its aphelion; there's continual daylight at the south pole, so any ice that was there would melt. Southern winter then happens around the time of perihelion. There's continual night at the south pole, but if you get the combination of axial tilt and eccentricity right, the whole planet is warm enough that a southern polar cap doesn't form. This may mean that the northern polar cap only exists during northern winter.
This state of affairs won't last for many centuries: the planet's axis will undergo [precession](https://en.wikipedia.org/wiki/Precession) and will gradually cycle between the state you want and the opposite, when there's only be a south polar cap; in between these states you'll have both polar caps.
[Answer]
You could have more salt, and some other substance in the seawater that lowers the freezing point of water. Say that your seawater becomes ice at -150C (-238F), instead of -2C (28.4F) as on Earth.
Now all you need is for one of the poles to be on land instead of on water. The pole with land will have ice on it. The pole with an ocean on it will never freeze.
] |
[Question]
[
This questions a spring off of a [previous](https://worldbuilding.stackexchange.com/questions/31933/defining-and-balancing-entropic-magic#31933) one.
My Thaumaturgic magic system uses five elements.
1. Fire (Heat).
2. Light.
3. Electricity.
4. Force. Which includes Alchemy, by using vibration to warp the structure of matter.
5. Entropy.
The capabilities of the fifth element of Entropy are causing me conceptual problem and before I have to cut it I'd like to try and fix it.
First I chose the word entropy because it sounds cool, and the name is more distinct than necro-something. The name is also closer to the power that I want it to have. The element of Entropy doesn't control the force of death, manipulate the souls of the dead or allow the creation of zombie.
Entropic magic is all about erosion and dissolution, fires go out, stone turns to dust, metal corrodes, wood and flesh rot away its touch.It can also reduce the level of entropy within substances to slow if not completely arresting decay. At low levels this is all fine,though it does overlap slightly with the other elements. However what does The element of Entropy do that none of the others can.
I see two possibilities.
1. Is [Tamper with probability](http://dusk.wikia.com/wiki/Mage:_Entropy_Sphere). The problem is that the ability to rig the game, is very, very dangerous and mechanically speaking one of the most [unbalanced powers](http://powerlisting.wikia.com/wiki/Probability_Manipulation) to allow. Also I already have people that can influence probability, the clerics, priests and shaman. Divine magic in my setting is probabilistic in nature. Through their connection to their respective deity or deities a priests can touch the [wyrd](https://en.wikipedia.org/wiki/Wyrd) and can bless or curse things within their deity's purview. Tying the ability to affect the roll of the cosmic dice to a deity's purview was my way of constraining the ability, entropy though would only cause disorder (errant luck) would affect everything.
2. The [ability to unfire time's arrow](https://en.wikipedia.org/wiki/Entropy_(arrow_of_time)), that is to bend entropy back upon itself. Going beyond holding back decay/chaos to slow or prevent a break down of physical substances, this power would be able to make things unbreak. My mind boggles at the thought of just how dangerous the ability reverse entropy must be. More than danger, just what could be done with the ability to unbreak things?
Two pick one of the two I'm going to need to understand what they both can do,how to keep them from throwing the whole system out of balance, or a third way that entropy could be used.
[Answer]
You could try taking a similar approach to the one in the video game Singularity.
The device the character wears allows the player to reverse or accelerate the effects of time on the world around him (although in a limited area):
>
> **You need to open a security door connected to a long dead generator:** you reverse the passage of time in that small area, and voila, you have power.
>
>
> **You see a broken bottle on the ground and you're feeling thirsty:** (this is from the trailer): you reverse time in that area, and the bottle puts itself back together, and fills with liquid before your very eyes.
>
>
>
The reverse is also possible:
>
> **A door blocks your way:** You speed up the passage of time in that area, and the door rusts away before your very eyes.
>
>
>
You can imagine what this does to *people*. (watch the Singularity trailer for some very graphic examples)
**Balancing The Universe**
This powerful branch of magic will need to have to have some checks and balances in place to keep it from being truly God-like.
* Limit the scope of the spells such that they can't be cast over wide areas such as an entire city.
* While able to dispatch even a group of foes by aging them rapidly, such a mage would not be able to maintain their spell ad infinitum, and their range would be quite limited, which makes them susceptible to long-range attacks, etc. (this way they are not a one-shop stop for global domination)
* Rejuvenation is obviously the pink elephant in the room - virtual immortality within the grasp of anyone with an Entropy Mage on hand. That would be too easy, wouldn't it? Make it so that rejuvenating a living, sentient being has some pretty terrible consequences on the psyche - memories of the past, present, and future somehow driving the target quite insane in 99% of cases. Only truly powerful mages would be able - after years of research, study, and meditation - to survive the procedure with no ill effects. Even then people would be very suspicious that they may secretly be insane, and just a ticking time-bomb, waiting to snap and commit some atrocity. Those untrained in the magical arts, such as for example some king eager to live forever, would go quite mad after being rejuvenated for more than just a few years worth of time.
* Similarly, you can wave away resurrection by explaining that once dead your soul leaves the body and never returns.
However, this power should also be quite attractive:
* A very powerful Entropy Mage may very well be able to sustain his own tower in a state of perfect time-freeze, such that nothing around him decays. A more trivial use of this power (by lesser mages) may be to create fridges. You're laughing, I know, but safe food storage was a pretty big deal in the middle ages.
* Healing terrible wounds might be possible by rejuvenating a subject just a few minutes or hours (to before they were wounded). This should be very difficult, and only very advanced mages should posses the precision required to control time on such a fine scale. The subject may suffer some temporary consequences of being rejuvenated, but otherwise survive to be quite healthy in mind and body.
* Minimal anti-aging should be possible for some non-magic users, as long as they posses a ***very*** strong will. A powerful and desperate king may request that a mage rejuvenate him a year or two in his old age, such that he may be able to lead one last campaign against the foes of his people, or rule just long enough for their heir to reach maturity, and thus avoid a civil war. Mages would only grant these requests to truly worthy individuals, since a lesser human being would simply go crazy anyway. The person in question sees this more as making a sacrifice, although abuses do happen.
What do you think?
[Answer]
The paragraph you've described here
>
> Entropic magic is all about erosion and dissolution, fires go out, stone turns to dust, metal corrodes, wood and flesh rot away its touch.It can also reduce the level of entropy within substances to slow if not completely arresting decay. At low levels this is all fine,though it does overlap slightly with the other elements. However what does The element of Entropy do that none of the others can.
>
>
>
and the two options you make are completely irrelevant and don't make any sense to me.
Instead, the entire paragraph can be explained away by making Entropy "**time magic**".
By speeding up time for certain objects, they will erode. Rocks, over time, will erode. Metal rusts, over time. Flesh and wood rots, over time. Fires go out, over time. Do you see the pattern yet?
No? Let me continue. Slowing time for a dead body can prevent it from rotting. Slowing time for a rock can prevent it from eroding, etc etc.
Sounds to me like you've over complicated a problem that can be easily solved with **time** ;)
Just give the magic the ability to slow down or speed up time, and that's fine. Reversing time should be impossible, however, unless you want to really complicate things. Just having the slow/speed up ability is already quite powerful.
[Answer]
Perhaps rather than time magic or whatever others are saying, it would be more effective to affect a small area with improbability. Arrows and bullets veer off-course, lifespans of living and non-living things alter slightly, objects may change states, regional atmospheric pressure shifts, temperature changes, etc. Many people here are thinking of how it could be controlled, but the very definition of entropy is chaos, something that cannot be controlled. Entropic magic would be useful for a solo user, as it could negatively affect a team member.
Then again, this is just my opinion. Use if you see fit.
[Answer]
On the second point, breaking things isn't the same as entropy. If I drop a glass on the floor and break it, the glass didn't experience sudden entropy, it suffered a shock. If the glass sat in a cupboard for 10,000 years and slowly eroded away to dust, that would be closer to entropy (as I understand it).
That being said, you could have entropy be reversible, but just take a lot of power. Dangerous things shouldn't be easy.
As to the first point, I don't see how entropy could help rig the game except maybe for roulette, as you could cause the wheel to spin longer or shorter as desired, but it would still be really difficult to get it to stop precisely where you want it to.
[Answer]
The other four elements in your system create entropy in the classical physics definition, all of them carry energy from a higher potential area to a lower potential area. Since entropy *is* that dispersion, someone who has control over entropy by speeding it up or slowing it down, would be incredibly powerful.
**Make entropy magic about the amplification or dampening of all the other elements.** So, a magician in skilled in fire and entropy magic would be able to wildly amplify the effects of the fire spells.
**Implications of Control over Entropy**
* With control over how fast heat moves from one area to another, you could have your enemies cook themselves in their own metabolic heat products.
* Alternatively, you can freeze them to death by accelerating the rate at which their bodies radiate heat.
[Answer]
Entropy roughly the number of possible micro states a system can exist in. [See wiki](http://en.wikipedia.org/wiki/Entropy) Heating a system, mixing a solution more evenly or moving it to a more loosely tied form of matter(sold -> liquid -> gas) increases entropy. It also governs the direction of chemical reactions. Increasing the entropy of and object quickly would be akin to exploding it. If you could go backward you could preform alchemy fairly easily by separating gold from sea water.
How we thing of decay is very macroscopic entropy is microscopic
] |
[Question]
[
Imagine an effective ranged stun gun that renders an opponent unconscious is built in the near future and is easily produced. It works like this:
1. for most people if shot they will be knocked unconscious for anywhere between 2 hours and 18 hours, depending on power level of the gun
* It can harm or kill certain vulnerable people, the elderly, extremely infirm, those with certain rarer heart conditions etc. However, it is rare that it is lethal (they're far safer then modern stun weapons), and generally anyone that faces lethal danger is obviously infirm so someone likely knows if their firing on someone who will be in danger.
* Proper medical treatment for those who have a bad reaction to stun blast will usually ensure they recover with little if any long term harm so long as they get treatment within the next 30 minutes. Proper stun weapon usage involves checking pulse of anyone shot as soon as safe to detect irregular pulse as a sign of a negative reaction.
2. Once the stun ends the person will wake up groggy and with a massive headache. Their muscles will be sore as if over used. However, they will recover within a day or so with no permanent harm
* Drugs exist to minimize the pain if administered before or immediately after revival, but discomfort always occurs.
3. Modern medicine can detect that someone was stunned within the last day. If someone dies while stunned an autopsy usually can detect that they had been recently stunned if the body is well preserved.
4. Stun guns can be detected by high-energy sensors. So the equivalent of metal detectors can be used to scan for them before someone enters a building.
5. Stun guns have a range comparable to modern pistols or slightly lower; however, in the future pistol ranges are also slightly longer, meaning that pistols still out distance stun weapons by a bit. However effective accuracy ranges are nearly the same for most people, since accuracy has more to do with human skill in aiming then the weapons range. Rifles have a significant range advantage over stun guns.
* stun rifles have been built but they give only slightly increased range and so are rarely used over stun-pistols; the lack of maneuverability of a longer rifle relative to a pistol counteracts the slight increased range.
6. Stun shots do not ricochet or fire through metal objects as well (they tend to 'stun' the first solid object hit) They do have a slight area of effect though, anywhere immediately next to the blast radius may get a lower stun that will knock them out briefly or just numb and leave their body as if their limbs fell asleep if on the outer edge. They tend to short circuit and damage electronics struck by them that aren't protected against such blasts.
* This means that stun guns are generally safer to use in populated areas, they are far less likely to hit anyone other then intended targets.
7. It is easy to tell if a gun is lethal or a stun gun. Many people are aware of the low lethality of stun guns. There have been incidents of people in fights charging someone armed with stun guns to try to disarm or hurt them because they weren't afraid of being stunned, leading to arguments that stun guns are less effective at defense because they lack intimidation factor.
8. a stun gun is relatively quiet weapons. While it makes a distinctive sound that someone near by may recognize it is not nearly as loud or reverberate/echo the way a gunshot does. It's also easy to not place it. However, the shot individual may make a sound when shot (during the half second of surprise before they go unconscious they may respond with a startled response to being shot, depending on how they respond to shock) and when he falls also
9. In terms of defenses a thick plastic(or other non-conductive substance) vest can partially protect against stunner fire by avoiding direct absorbing the blast. but they would still feel the effect of being close to the radius of the blast, either briefly incapacitated or simply left numb and woozy depending on power of the stunner that hit them. I imagine this can be built into Kevlar vests to get a two for one protection, but the vests would restrict movement a little more then modern vests, due to the need for thickness. Multiple shots to the vest could still incapacitate a cop, as could absorbing most of the blast to unprotected areas like legs or head.
Obviously these weapons are less lethal then a gun, and presumably some places that make conceal carry of a gun illegal will allow stun guns. However, it can be quite painful to be shot, so they are still an assault. Furthermore, once someone is stunned it's relatively easy to kill them at leisure if someone chooses to do so, so criminals can still use them as effectively-lethal weapons if they choose to.
I'm wondering how will societies respond in regulating all weapons, both the stun variety and regular guns with the presence of stun guns. When will stun guns be allowed and when are they forbidden, is a carry permit allowed, and when is it legal to shoot someone (ie when are they considered a credible enough threat that a painful but safe blow to remove the threat is allowed).
I imagine the owning and use of regular guns may be further restricted, as stun guns seem to fit many of the justifications for a regular pistol (for defense) making some feel that there is no need for the more lethal alternative. What effect will these have on regular lethal gun ownership and use?
Since different parts of the world have different policy on gun use I would appreciate answers that consider these different policies. What will the rules be in countries/states that currently have more lax gun laws, what will they be in places with strict laws etc.
This question is primarily focused on how the rules of ownership and use effect civilians, and possible bodyguards, hunters and similar. I will post a different question for policy and military use. I'm trying to set the ground rules for weapon use in this world. Any interesting social ramification I would love to know as fodder for follow up question as well if anyone wishes to leave a comment about them.
edit: since everyone asks stun guns are quite effective compared to tasers. Their range is much longer then a taser, they are more effective at incapacitating an opponent, tasers can misfire easily, and do it much faster, it takes time for an opponent to go down to a taser and during that time the officer has to stand in the open waiting for it to work. They are less lethal. Most important, tasers can be fired only once, stun guns can manage dozens of shots quickly after each other, so you can fire even if your not certain to hit someone or be used to take out more then on assailant at a time.
In short, unless your an idiot you don't try to use a taser in a gun fight. You *can* use a stun gun in a gun fight, with only a slight disadvantage compared to a gun (slightly lower effective range, can't shot through objects to hit someone behind as well), but your stun shot is more likely to take someone out immediately if hit compared to a bullet and can be partially effective if you hit very close to them without hitting them.
[Answer]
**They will be regulated similarly to lethal weapons worldwide, but they will have an impact on existing lethal weapon laws.**
Now your world has long-range, relatively safe, reliable incapacitation. Since there is already a separate question addressing usage among the police, let’s focus on civilian usage.
This will revolutionize self defense for a single reason: this stun gun is more effective than a firearm. In a self-defense situation, you want to remove the threat of danger as quickly as possible. With a lethal weapon, some skill or luck is required by the user (often in emotionally jarring and high-adrenaline scenarios) to effectively neutralize the threat. With this stun gun, you simply need to fire *in the general vicinity* of your target to have the desired effect. For the general populace, this means a stun gun is more effective in self defense, safer to keep around the house, and free of the moral quandary of killing.
However, don’t let the non-lethality fool you. These weapons open up a scary new situation: there is a now a simple way to render someone “safely” unconscious. This will pose major concerns among the populace because it creates an effective abduction technique in which the victim is incapable of defending themselves or even screaming to alert others nearby. The potential for electrical damage is also a big concern. Depending on the range of the weapon, it becomes a cheap way to perpetrate very problematic and expensive vandalism with no way to catch the offender. As a result of these issues, they will still see heavy regulation and may even be more heavily regulated than lethal guns.
With this kind of option on the table for self-defense, it will be easier for gun-control activists to push legislation that limits the sale of lethal firearms, but it’s unlikely to be effective everywhere. As always, countries with prevalent hunting cultures or constitutionally guaranteed access to firearms will still have a lot of pushback.
[Answer]
How this would be regulated would be vastly different between countries. To get an idea of how a particular country would go, look at it's current weapons regulations, and *its current self defense laws*.
For instance, Britain and Japan would probably ban it. Woe betide you if you fight off a mugger in London. You'll likely go to jail for assault.
The US, on the other hand, likely wouldn't regulate it at all at the federal level, though certain state and/or cities in the US would (NY city, for example).
People who campaign for more gun control may, in places like the US, use its existence to argue for more restrictive gun control. But, I don't think this will change much except in those places that are already on the cusp of enacting said gun control.
See, the key thing you're looking for is not the practical nature of this stun weapon; but the prevailing attitudes, and the direction of change in the prevailing attitudes, towards individuals being empowered in the way that owning a weapon empowers the individual. Those places that distrust empowered individuals will likely ban it, since what you describe is an effective weapon. Those places that trust empowered individuals won't.
It's hard to do a deeper analysis than that without knowing which specific countries you're looking for; for each given country, it's a pretty sizable analysis of culture, historical precedent, social mood, and current law.
**Update for US only**
I think you might see the gun control people make the argument that you don't "need" a gun now because of this stun gun. I also think it wouldn't go very far. They've made that argument before (you don't need it because police), and I don't think they have the guts to support what would really make that position effective -- supporting the explicit right to carry the stun gun open or concealed. In fact, I think you'd just as likely see them propose anti-stun gun regulations instead, painting a picture of "road rage" and "zombie cars" as people stun each other on the freeway.
Broadly, the current social mood is in favor of self defense, and in favor of individual ownership of weapons. That said, you may see an even more stark split between the broader US, trending freer, and some jurisdictions that are clinging to their gun control - like NYC and Connecticut. So, you might see some north-east states, and possibly California, use the stun gun to go more restrictive. On the other hand, recent gun control there has only passed barely, and with much opposition. And it'd have to withstand a constitutional challenge. So, I guess the answer is, "they'll try".
[Answer]
When you ask a question like that, a key question is what weapons laws are already in place. If the (concealed or unconcealed) carry of handguns is legal, one can argue that this is a "lesser included case." If carrying of guns is illegal, making stunners legal would go against precedent.
Consider the [tear gas pistols](https://en.wikipedia.org/wiki/Gas_pistol) which are sold in places without the U.S. 2nd amendment.
] |
[Question]
[
Scenario: Last line of defense. I want to prevent anyone from reaching a highly guarded building.
Such building is in the middle of top secret, heavily guarded military area (think of [Area 51](http://en.wikipedia.org/wiki/Area_51)). I want to make sure, that if my military base gets attacked, I have a way to protect my utmost secret hidden in such building.
Can I deploy nuclear bombs around it and make directional nuke-blast facing away the building?
I want to destroy everything else than such building - I want to be able to recover my super secret stuff from such building after everyone is killed.
Also, if such attack happens, I want to make sure such defense "works against everyone". What are my possibilities? Please stay inside current technology level.
BTW, money is not an issue
Also, this secret is "stolen from my enemies". So I have to assume such military base will be attacked amongst first
[Answer]
So the simplest way to make this work is to use an underground bunker instead of a building. Many feet of dirt/rock/concrete acts as a barrier to your weapon.
A nuclear weapon puts out extraordinary amounts of heat, and some radiation - the heat creates an overpressure wave in the air, which rapidly expands. This pressure wave is what does most of the damage.
Close to the center of the explosion, the high temperature is a serious issue. So to direct these forces would require some sort of structure that can redirect a massive overpressure wave, and will not melt when exposed to tremendous heat. You could probably achieve this with a large, rounded concrete bunker - it would redirect the pressure wave like a kind of echo.
Rather than ringing your building with a bunch of these 're-direction bunkers' and nuclear weapons, you could simply bury your building, and use the earth as one large shield. If you can get your nuke airborne for an air-burst detonation, you can increase the damage and minimize local fallout - the overpressure wave is distributed over a larger area, and the gamma/neutron radiation is absorbed by the air, instead of activating elements present in the dirt. You'll still have fallout from incomplete fission, but that comes with the territory.
That said, there are probably easier ways to defend a structure that is vital to your super secret facility. I'd recommend having an airfield nearby or on-site, and requiring a couple weaponized drones to be airborne and a couple more to be flight ready at all times. We live in the era of precision strikes after all - get with the times!
[Answer]
The idea behind directional blasts is that they force energy from an explosion to rebound and head in a certain direction. This is probably not that feasible with a nuclear bomb(though I have no idea if its been done).
The problem is that the premise itself has several feasibility issues to overcome, which suggests nuclear force may not be the best option. The radiation that would be made by the bombs would stop anyone from being able to go near the place, you wouldn't be able to recover it. Use something that isn't nuclear.
[Answer]
In a vacuum, most of the energy from a nuclear blast is released in the X-ray spectrum (call it 95%). There are materials that can "reflect" X-rays by absorbing and re-emitting them, but they get heated up and ablate in the process. For example, the [Ullam-Teller hydrogen bomb design](http://en.wikipedia.org/wiki/Thermonuclear_weapon) uses a shell of heavy metal (depleted uranium, usually) to reflect the X-rays from the primary section to the secondary.
However, such a reflector only reflects a small fraction of the energy before it evaporates. You *could* try and build it thick enough, but then you run into problems like radiation pressure pushing the reflector away, so the blast is not *directional* as much as *somewhat more intense in one direction*.
Finally, all of the above holds only in vacuum; the moment you detonate a nuclear bomb within an atmosphere, you can manage to divert some fraction of the original x-rays, but those immediatelly slam into air molecules and heat them up, causing a fireball and a shockwave, neither of which can be convinced to only go in a certain direction.
**TL;DR:** You can redirect some of the initial radiation, but the shockwave and fireball will be omnidirectional regardless.
**EDIT:** @VilleNiemi brought a [Project Rho link](http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Nukes_In_Space--Nuclear_Shaped_Charges) to my attention, which specifies that Orion drive designs were able to deflect as much as 88.5% of energy of an atomic blast into a 22.5° cone. But again, this blast will then immediately slam into the atmosphere and cause a shockwave going out in all directions.
[Answer]
It would be more realistic to lob nuclear weapons within a range close enough to the base to destroy anything outside but not doing irreversible damage within. You could calculate it to a T, ensuring that the temperature is too high for anything outside to survive while the base itself remains intact. The base would have to be shielded from the blast (dome shape?) with minimal radiation protection.
The one thing it couldn't handle would be say tanks right outside the base, which may get jostled around but may not necessarily kill anyone within. If the base is constructed well enough, you could just about have one land on top without damaging the base underneath and yet destroying everything above ground. It entirely depends on how well it is fortified.
Consider that in such extremes, the base would likely be equipped with hazmat suits to leave the compound afterwards, and of course there would have to be a way of getting the bomb to its destination, meaning there may be a weak point in the design for those who know about it.
[Answer]
There's almost no way to build a nuclear weapon that will destroy things but not your secret safe thing, unless said secret safe thing is very deep underground.
Might I recommend simply building an upturned bowl of tungsten or other high-temperature material like ceramics and putting a huge pile of thermite on it? Tucked away beneath six inches (or more!) of molten iron slag(+ dome + insulation+ cooling maybe), whatever it is will be inaccessible until the slag cools or can be cooled and moved. Either way that'll take ages(explody cooling iron bits, adding water to hot thermite causes steam explosions and regular explosions), and from the language in the question it sounds like you have a way to reclaim control over the site.
(words of warning: You will almost certainly need to cut your thermite mixture with something else. In a vacuum the thermite mixture approaches 9000C, about 3x the melting point of tungsten and 2x the best hafnium carbide ceramics. Perhaps extra raw iron there simply as thermal ballast? Unoxidized iron would provide bonus 'smoulder' heat very slowly.)
[Answer]
You could check section 5.2 of [Fourth Generation Nuclear Weapons: Military effectiveness and collateral effects](http://arxiv.org/pdf/physics/0510071v5.pdf). But by and large I agree with Adam -- if your story has nuclear weapons in it, there should be plenty of collateral damage.
[Answer]
Use Kinetic Energy Weapons [KEW]. You would put these in low Earth orbit (you did say money was no object) and drop them on the people outside your base. You could get blasts in the 20-50 kiloton range that would take out anything they hit.
The US Air Force did a report on a system called "Hypervelocity rod bundles" nicknamed "Rods from God" that used 20 foot long tungsten rods that dropped from orbit at Mach 10. With 6-8 satellites, you could hit any target within 12-15 from go code. It would hard to detect the launch and hard to intercept. At current Earth level tech, it would be a Billion dollar+ project.
[Answer]
You do not want nuclear blasts, but **radiation**. If your attackers are living, use a massive dose of radiation: that would kill them. The same amount would fry anything that is electronic-based. You could fill the air outside and inside your base with radioactive vapors, and only protect the electronic equipment inside your base with a shield thick enough and emergency procedures. After the enemy has been dealt with, even if you loose, the place would be so life-threatening that there would be no chance to enter the building (see Chernobyl) for ages.
[Answer]
What if our OP built a fougasse with a nuclear weapon at its core....?
Dig a shaft/tunnel at an oblique angle ( or multiple shafts radiating from a single point) At this point, place scrap iron, broken concrete, old cars/planes/ships, gravel, fecal matter and garbage, etc. into the shafts to be used as shrapnel being blasted out the holes like a hypersonic flamethrower.
If you have a sufficiently tall hill or mountain, dig your bore holes horizontally. As much of the debris may be moving at close to escape velocity, even attacking aircraft may be subject to its effects.
As an added bonus, when the boreholes collapse after the blast, you've created a radioactive trench line and debris field that following armored vehicles and infantry will find difficult to traverse.
This all assumes you are not concerned with the ecological effects of the debris discharged from such a construction.
] |
[Question]
[
We've had a [question about a city designed to guard against dragons](https://worldbuilding.stackexchange.com/q/13794/6986), so I would like to propose the opposite (which happens to be a part of a world I built a while ago).
***How might a city be designed in a nation where dragons are in charge of everything?***
Suppose the following:
* Medieval technology
* Dragons vary from the size of a cat to several hundred feet long; larger dragons are less common, but hold more power and influence
* The average dragon size is about ten feet long
* The ratio of dragons:non-dragons in any given settlement is roughly
1:200
* Dragons are sentient creatures
* Dragons can breathe a variety of forces, such as fire, ice, and
lightning
* Magic is a common factor among non-dragons and more often rewarded by
dragons than punished
* Non-dragons hold no authority over dragons of any kind; dragons
always have precedence
* Dragons fill all roles of government and judicial systems; common
jobs are typically filled by non-dragons
* Dragons are under no obligation to support non-dragons; non-dragons
are often viewed as servants/slaves to dragons by other nations and fodder to some dragons
Dragons cooperate freely with each other and maintain separate cities designed and built for dragonkind alone. This question seeks answers concerning cities that are built to accommodate the dragon overlords, rather than built *by* the dragon overlords.
[Answer]
I would expect thorough fares to be wide and spacious, at least several of the main roads bisecting the city. I would also expect temple like facades with large dais's here and there for the large beasts to rest and enjoy the hubbub of the city, not to mention as a place to listen to petitioners for what ever individuals would be asking of the dragons. Quite likely rulings on accusations between parties, since they are the ones 'in power'.
I would also expect perches in many places for different sized dragons and I imagine very tall towers with perches on top for small dragons to act as look outs. It is much less work to sit and look than to keep a constant flying vigil.
[Answer]
Urban cohabitation with dragons is going to be a difficult challenge. I don't think you will be able to maintain traditional fantasy "urban" dwelling while also having dragons.
# Architecture
Anything that is a couple hundred feet long is going to weigh at least a few tons. All but the strongest stone structures would crumble under their weight. And dragons are going to need a lot of space to spread their wings and take off (physics notwithstanding). This means you are going to need to have massive open spaces, or super-strong buildings that allow the dragons to take off from above the skyline.
I'm also assuming, by cohabitation, that dragons will purchase and maintain dwellings of their own. Even if they are content to live in stalls like cattle, those stalls would have to be huge. If we provide dragons with the basic domestic comforts, like beds and kitchens, we are talking about massive enclosed spaces. Steel would likely be required to build these buildings, as wood and stone wouldn't be able to span the couple-hundred-feet required for just the dragon's bed, not to mention enough space for them to turn around in.
# Services
I'm assuming that, by cohabitation, you also have dragon services provided, like food and sanitation. Dragons, being as large as they are, will require a tremendous amount of food to survive. A single dragon's food requirements will probably be larger than those of a neighborhood. This will dramatically increase the food infrastructure.
Along with lots of food comes lots of waste. Assuming dragons have massive latrines, someone will have to clean those, and dispose of the waste. Since dragons are likely meat eaters, their waste would be especially smelly, and a breeding ground for dangerous bacteria.
# Jobs and shared spaces
It's very difficult to imagine a dragon and a human working side-by-side when the former out-sized the later by a couple orders of magnitude. Shared spaces, too, would be dramatically different: a large human park wouldn't even be enough space for a dragon to nap in.
Even if dragons are in charge, there are menial tasks that would likely require non-dragon assistance. In the courthouse, for example, you probably wouldn't have dragons doing all the basic tasks, like security and check-in.
---
The difference in size and needs would make it difficult for these two cultures to mingle: you would have to have dragon jobs, dragon parks, dragon homes, dragon food, and dragon sanitation, all while having human jobs, human parks, human homes, human food, and human sanitation. At best, I believe that you could have a human and dragon city side-by-side, with some shared services, but complete integration seems unlikely at best, and foolhearty at worst.
Even simply accommodating dragons in a non-dragon city would be difficult. Their size alone would make all but the most trivial contact all but impossible, or it would require a dramatic infrastructure change for little benefit to the non-dragons (much stronger buildings, much wider roads, much wider open spaces, etc.)
[Answer]
The devil is in the details. First off, you will need **nail salons**. Dragon talons are very hard, so diamond abrasives may be required. Lady dragons like nail polish, preferably molten metal applied by a trained metallurgist.
Next up: **perfume shops**. Dragons smell vile to humans, and probably vice versa, so they will have to settle on something that is agreeable to both.
As a follow on, I am betting that **silica gel** will come in handy. It is a major component in kitty litter and useful for absorbing cave odors.
Damming a few rivers for lakes is a must, because you will need to have large bodies of water stocked with fish to keep those dragon bellies full, and to put out fires in case one has indigestion and sets the town ablaze. Dragons are pretty good at earth moving and hauling stone, so they could help.
City planning is fun!
[Answer]
George your friendly neighborhood dragon speaking here. The civil engineering required to build a community for my kith and kin is an interesting subject, and one I have some contact with myself, albeit in a more modern sense: living outside Los Angeles makes for an interesting life, for sure!
Many of the concerns raised by the other posters here are quite valid -- residential structures for a dragon, say, my size (or even small aircraft sized) would come closer to the form of modern-day aircraft hangars than they would a human house; I, for one, don't mind an outdoorsy life, but having a retreat when storms brew is a very good idea, for while I may be tough, I'm not hail-proof! Of course, high-capacity sewerage and drinking water provisions would be required, and heavy timbering or metalwork in truss arrangements would be developed in order to support hangar-sized roof spans. Small dragons, of course, would have an easier time with this, and could have spaces that are closer to what humans consider "residential" in nature.
As to providing spaces to take off and land: while the idea of wide roads would be good enough for small dragons, such as the ten-footers you mention as average, larger dragons like me would generally organize around runway-like constructions, similar to modern fly-in communities, where houses with hangars are built around small general aviation airports.
Employment, though, would be a curious question; I don't know how to answer you, considering I still need to hire humans for most of my business! (I collect and trade in aircraft parts, but I don't have the dexterity to type with my claws, never mind operate precision machine tools the way the co-owners of my business can!)
[Answer]
You might be interested in <https://en.wikipedia.org/wiki/City_of_Dragons>. It is unfortunately the third book in the series, but it does a great job at showing what a city designed to co-mingle with dragons might look like with very basic technology.
Some things that stand out that I haven't specifically seen in the answers so far: Dragon centered buildings. These included cleaning stations for any kind of parasites or just general brushing downs to make those scales really shine! I believe these also housed the dragon specific medicinal supplies (dragons in that book are much more "realistic" and that includes infirmaries and diseases, not sure on how mythical you're going). They also had large pools that heated up past human tolerances. Take off / landing areas designated inside and outside the city. Cattle and other livestock raised with the sole purpose of providing game.
] |
[Question]
[
This is somewhat different to [this question](https://worldbuilding.stackexchange.com/questions/30802/would-it-be-possible-for-an-organism-to-evolve-a-biological-fusion-reactor) on the possibility of biological fusion reactors as I am curious if a living FISSION reactor is more plausible.
[Answer]
The short answer is NO - a biological fission reactor is also a flawed design and it's going to cook your biological organism so it's just not going to happen. The energy cost alone to reach break even point is far beyond the biological framework we live in to store and release in such concentrated amounts.
That said, it is perhaps important to note that biological organisms are already molecularly driven even if that doesn't provide the same power as we would get if we were atomically driven.
Terrestrial biology (at least) stores and releases energy at the molecular level. That is to say, plants take molecular compounds like CO2 and H2O and via an endothermic reaction called photosynthesis, change the molecules to different ones like O2 and carbohydrates, which take more energy to form, hence storing the energy taken from sunlight in a molecular form. Plants use some of this for their own metabolism, and animals like us then eat the plants, taking their stored carbohydrates and oxygen from the atmosphere and generate an exothermic reaction that converts them back to CO2 and water, releasing that energy inside us for our own needs.
The energy stored and released during these processes is pocket change compared to fission let alone fusion, but as it turns out we don't really need all that much energy to survive; even the human nervous system seems to operate at around 0.07 volts, meaning that you could run around 21 people in parallel on a standard AA battery if you had to (but for how long I'd need to do more research to say).
Bottom line is that we don't need atomic power to drive our biology and the energy storage capacity of our current biological design would render us incompatible with it in any event. It turns out that being molecularly powered rather than atomically powered gives us all the energy we need and is much safer and sustainable for us into the bargain.
[Answer]
Can an organism evolve to use a concentrated mass of radioactive material to superheat a pressurised fluid and use that fluid to turn an organic turbine which rotates a permanent magnet inside a coil of conducting metal to generate electricity? Almost certainly not. Does that mean an organism can't make use of nuclear fission to energise itself? Not at all.
On an atomic scale, fissile elements are basically tiny bombs: they're happily sitting there as one element in whatever molecule, then bam, one or more high-energy fragments ricochet off in a random direction potentially screwing up another nearby molecule, and the original atom is now two totally different elements with different chemistry. We make fission reactions more energetic by concentrating fissile material so that the fragments are often captured by *other* fissile atoms which prompt them to react in turn, creating a chain reaction; but even in its simplest form a pile of fissile material releases energy by capturing the high-energy fragments in *something* and thereby getting slightly hot, no feedback loop required. The challenges for an organism safely utilising this energy source, then, are:
1. Extract fissile materials from its food and concentrate them
2. Deal with the heavy element byproducts of the fission reaction
3. Deal with the highly-energetic (usually neutron) fragments and convert their kinetic energy into heat, then convert that heat into a more useful form of energy for the organism
Biological organisms have evolved to manipulate chemistry on a molecular level; they can catalyse pretty much any viable chemical reaction, concentrate particular atoms on one side or other of a boundary, and so forth. It if were evolutionarily favourable for the creature to extract, say, uranium or plutonium from its food, it could do so with no more difficulty than mammals extract magnesium, calcium or potassium ions on Earth. Filtering atoms by isotope is much more challenging, but it's not impossible that an exciting protein could evolve that would bind fractionally more strongly to one isotope than another. Problem 1 solved.
Problem 2 is equally plausible: while the exact byproducts of a fission reaction are random, they'll cover a small range of elements, and if the organism is 'expecting' them then there can be mechanisms for controlling and excreting them if they're not usable. Poisons are only poisonous if the organism isn't adapted to deal with its presence: arsenic is highly toxic to humans, but plenty of terrestrial organisms are evolved to tolerate high concentrations of it.
The main challenge an organism would face is actually doing something useful on a molecular level with the energy released by the fission reaction. By dissolving the fission products in water or a more powerful neutron capture liquid. Boron is an excellent neutron absorber, so boric acid might be a good choice here. The net effect of the nuclear reaction, then, is to turn cold boric acid into hot boric acid. Then there are already terrestrial organisms which survive on reactions which exploit temperature gradients like those found at hydrothermal vents: the organism could either exploit those reactions themselves, or live in symbiosis with a bacteria that did.
In short, while you're unlikely to see an organism evolve to set up the highly unstable, low-entropy, complicated arrangement of materials that humans would consider to be "a fission reactor", fission is an energy-releasing process, and an organism evolved to harness that process in a more relaxed, stream-like, *organic* way, is perfectly possible.
[Answer]
Well, first let's see what the creature has to have.
1. A sizable chunk of Uranium. After all, you can't have fission without fissionable materials. Unfortunately for your animal, Uranium is not very common, meaning that your biological reactors would be restricted to places like Utah's Factory Butte, where there are (reasonably) large amounts of Uranium on the surface.
2. Some way to safely process Uranium. While it is possible to process Uranium without a complex lab, it is extremely likely to cause irradiation of tissues, which is *no bueno* for your creature. The only reasonable way around this is to have an "access port," in which people can dump preprocessed Uranium fuel rods.
3. Radiation shielding (since you don't want the radiation killing your creature.) For this, you pretty much only have one option: your creature somehow processes lead in bulk, and then somehow cause lead deposits to build up around the "reactor core." This is almost impossible to have evolve, so you pretty much have to make your creature a GMO.
4. Coolant systems. Not only will your reactor be producing a lot of radiation, it will also be producing huge amounts of heat. After all, that's what a reactor is supposed to do. In this case, pretty much the only option is to have your creature immerse itself in a fast-running river and then somehow ditch the heat safely. Although not as hard to evolve as radiation shielding, it would probably be another GMO feature.
5. Using the energy. While it is possible to make the reaction core part of your creature, there is simply no way for your creature to harness the energy in any meaningful way.
All that being said, while your creature is impractical in real life, **it is a very cool idea as a minor aside, and the problems can be handwaved.** That being said, I very much would *not* give these creatures a major role in your story, as then your handwavium would break down.
[Answer]
even if it is an old question, but surprisingly I do not see yes answers.
**yes**, it is possible.
Surprised by nobody mentiond that [Radiotrophic fungus](https://en.wikipedia.org/wiki/Radiotrophic_fungus)
>
> Radiotrophic fungi are fungi that can use radiation as an energy source to stimulate growth. Radiotrophic fungi have been found in extreme environments such as in the Chernobyl Nuclear Power Plant and on the exteriors of Low Earth orbit spacecraft.
>
>
>
>
> Most known radiotrophic fungi utilize melanin in some capacity to survive.[2](https://www.boredpanda.com/slime-mold-road-planning-study/) The process of using radiation and melanin for energy has been termed radiosynthesis, and is thought to be analogous to anaerobic respiration.
>
>
>
There quite a lot on the topic on the internet, one of the uses bioremediation of different radioactive polluted places.
Sure fungi isn't that much of a nuclear reactor but it shows that biological systems can convert nuclear energy and incorporate it into their biological cycle.
Fungi is one of the primitive forms of life, and if we like to have naturally evolved nuclear reactors, then certain conditions for their evolution have to be met, and those fungi are like 2-3billion years in the past - a starting point for such evolution.
Steam and high pressure are not the only ways to extract nuclear energy - gamma radiation is the same electromagnetic photon as light, so alpha and beta particles can be used as well, as charge carriers, and we have life's which uses electricity more than usually - electric eel's - meaning biology can handle electricity.
Biological life can build constructions, let's say Great Barrier Reef as a prominent example - so there can be some processes, evolved ones, which may help biological life to offset some of its weaknesses.
So as result there can be different shapes ways and forms of biological life to utilize nuclear energy. A block of wood as an example is a typical carbon rods moderator for a reactor, and released hydrogen can be reused by that life as an energy source again, binding carbon and develop structure further - grow. Also do not forget there are other processes involved in petrification as an example - so it can help create all sort of weird systems and solutions.
The biggest natural evolution hurdle is in those radioactive elements, they aren't a stable and steady source of energy overtimes the evolution takes place - but there are cosmic probabilities and strange things happening out there on a great scale - some neutron source/wind can be a source of radioactive dust constantly landing on a planet, sooo...
Artificial ones - here we can run wild - sure it won't be the same as reactors we build with technology means, but there is a variety of potential designs, even if I have a hard time to imagine details or describe them, it needs to really dive in that stuff. But would be fun to have something like Slime Mold to moderate the reaction(it can insert and retract its body parts, which are water carbon moderators, in some weird shapes in some porous media to optimize the output)
here it is quite a yellow title [Scientists Used Slime Mold To Create The Most Efficient Traffic Map For The United States](https://www.boredpanda.com/slime-mold-road-planning-study/), worth a look, those slimes funny and were used in different scientific researches as it has interesting optimization mechanisms/properties.
So the answer is yes, but how useful it may be, that's a different subject.
[Answer]
Yes but the conditions don't exist on Earth to make this a viable survival strategy for a complex multicellular organism that could produce a sustain nuclear reaction.
But let's assume your in a far off imaginary planet filled with wonder and horror, what environmental conditions would be required to facilitate the evolution of this kind of organism?
Firstly you would need an environment that has plenty of easily fissile material. Current Earth-like levels of fissile material such as Uranium 235 simply would not be enough for a big enough ecosystem for significant amounts of enrichment to occur to facilitate the development of an organic nuclear reactor.
Next you would need environmental pressures that would not only incentivise the organism taking up harmful radioactive material into their cells but also be competitive with other organisms using alternative energy sources. Remember evolution does not care what is possible, only what is successful. Therefore if these radiosynthetic organisms can't compete with other sources of energy then it will be unable evolve into a complex multicellular organism that could facilitate sustained nuclear fission. This means that the environment that this organism evolves in will likely be cold with little available solar energy. This is almost required as it would ensure that this organism could outcompete other potential organisms.
And finally you would would need lots of time which means the environment must be relatively stable. Something that might be a bit difficult when you consider that there will be literally nuclear bombs being formed en masse by these developing organisms. A poorly placed/timed nuclear detonation might outright kill the local ecosystem, something that might be a little counterproductive for the process of evolution.
But let's say that this process doesn't eradicate all life on this planetoid. Eventually as the survivors of the million year strong nuclear winter will have crawled out from their holes they would of hopefully developed ways to avoid death by spontaneous nuclear detonation. And maybe....just maybe they would have even developed ways to have sustained nuclear fission occuring in their core to take advantage of this wonderful energy source. Huzzah!
[Answer]
# *Electrophorus*
1. The electric eel *[Elecrophorus](https://en.wikipedia.org/wiki/Electrophorus_electricus)* produces rapidly alternating electrical pulses that affect a stack of cells called electrocytes. Each is at a higher potential relative to the next, with the direction inverting.
2. *Electrophorus* has taken up a cassette of radiation resistance genes from *[Deinococcus radiodurans](https://en.wikipedia.org/wiki/Deinococcus_radiodurans)*, which had been transferred to a prey fish species for purposes of bioremediation.
3. The site of the bioremediation was a uranium mine that had been flooded and eroded by the change of course of a river.
4. *Electrophorus* began to absorb uranium with high affinity, possibly using another engineered gene from the bioremediation project. This provided strong toxicity for defense.
5. *Electrophorus* evolved uranium enrichment by expressing two forms of a uranium channel in its electric organs. As it pulses electricity in opposite directions, one channel has a stronger isotope effect than the other, enhancing the amount of U235 at one end of the organ. Uranium purified during a pulse train in one of its three electric organs is transported on to the next, allowing three separate stages of purification.
6. These populations of *Electrophorus* increased in size, storing larger quantities of U235 and generating an increasing degree of heat from their stored deposits. This permitted them to spread into other former mines and reactor sites in more temperate climates.
7. *Electrophorus* evolved a means to reduce uranium to a compact metal for storage.
8. *Electrophorus* matings late in the season began to generate fizzle yields for U235. These massive explosions spared eggs in suitably sited nests, while providing a safe, predator-free, food-rich environment for the surviving eggs to hatch.
] |
[Question]
[
I'm building a world with humans being genetically engineered species, created by certain advanced Alien civilization ("gods", Creators etc ...) like in the [Sumerian hypothesis](https://en.wikipedia.org/wiki/Ancient_astronauts), but with a twist: those "gods" created certain dormant genetic code in human DNA, in order to protect their secrets.
Whenever certain human being develops thought patterns that could get them near those secrets, this dormant genetic code is activated and cancer develops killing said human being.
I need a biological reality check on this, i.e. is such mechanism plausible according to current scientific knowledge, and if not any suggestion how to implement something similar is appreciated.
**EDIT :** For those wandering why cancer (it is relatively slow killer, except in some forms), there are several reasons. First, secret knowledge in this case is not easily transferable and it could not be expressed in current human languages(s) . It is not 2+2=4, E=mc^2, molecules are made of atoms etc ... It is more of certain state of mind, and to describe insights from it you would need some super-language not comprehensible by current mankind, just like apes could not understand our language except maybe basic concepts. Therefore, there is no need for quick kill. Second, cancer is still mysterious disease and causes for it are not readily understood (we know some risk factors, but not exact chain of cause-effect for most types) . Therefore, people dying from it would not be so strange, compared to sudden heart attacks in otherwise healthy individuals (autopsies and all included) . Thirdly, I aim for dark, gloomy and desperate world, with those nearing the truth suddenly realizing that shiny goal that looked so close and within the grasp is taken away from them .
[Answer]
>
> Whenever certain human being develops thought patterns that could get him near those secrets, this dormant genetic code is activated and cancer develops killing said human being.
>
>
>
Thoughts cannot directly activate genetic code.
However, thoughts and more generally mental states can activate the secretion of certain neurotransmitters, like what happens when through meditation one can relax and reach a state of well being.
Those neurotransmitter can influence the cellular activity and also genetic expression. For example it is known that prolonged stress has a detrimental effect on the immune system.
It's not far fetched then to assume that certain thoughts can stimulate the production of certain endogenous molecules which, stimulating certain cells, can lead to the development of cancer.
However please note that cancer takes a long time to kill, and until that happens the human in question can still access and use those secrets. For a rapid death a stroke or a heart attack is way more effective, and those also can be caused by thoughts.
[Answer]
**Yes, but I wouldn't choose cancer.**
First, cancer is possibly one of the worst ways to kill a human in your case, because it progresses so slowly. Someone with cancer would have time to tell everyone, document their findings, and still have all of their cognitive function for most of the time before their death. It could take years to kill someone with cancer. If you want to silence someone, there are better ways. Target memory, sanity, or vital organs directly.
Secondly, yes, a thought can trigger a lot of physical things in your body. Thinking of the person you love or about that important exam tomorrow can release different kinds of hormones that impact the rest of your body.
If hormones can make a uterus "shut down" after a certain age, it shouldn't be so hard to add a "killswitch" on the heart or the liver, so that when certain hormones are released in a certain quantity your vital functions would stop working.
[Answer]
All (or nearly all) human beings have minds that are constructed from the same basic template. (People who don't are usually very sick, and many don't live long at all.) State of the art (in 2019) neuroscience has an incomplete and very rough outline of what this template [looks like](https://mayfieldclinic.com/pe-anatbrain.htm) - we have figured out "this is where the visual cortex is, there's the Wernicke area, etc" and we know what processes these areas are associated with.
However, we essentially have *no idea* how the individual areas work. We can tell you what they do, generally, but not how. Similarly, while we have identified many of the genes involved in the formation and fetal development of the brain, you can forget about being able to look at the human genome, and say "These specific genes are responsible for building the brain structures that allow you to see, and here is the detailed explanation of the [organogenesis](https://en.wikipedia.org/wiki/Organogenesis) processes these genes control that builds the structure".
Modern medicine, however, has only known how DNA works for about 60-70ish years (since the 1950's). Okay, suppose your aliens have had thousands of years to study the field of genetic fetal development and neurobiology. They could use genetic and organogenetic engineering to design new brain structures, and then figure out how to write the DNA that will turn into those structures in a human being.
So you give humans a fictitious additional functional area in the brain. Its function is (to the humans in the story) unclear, but damage to the area usually causes things to go awry in a technobabblish way that unbalances the endocrine system and somehow leads to cancer. In actuality, of course, the function of this new lobe is to scan the person's thoughts for Forbidden Knowledge, and send a 'self destruct' signal that the body has also been engineered to listen for and disable key anti-cancer protections.
This also provides a plot hook, because now there are several ways this mechanism could be defeated. One, traumatic brain injury inactivates the trap. Two, doctors develop neurosurgery to deactivate the area (they can figure out the area is killing people and the surgery seems to help, but they don't know why). Three, damage to the endocrine system (such as can happen in chemotherapy or a few other ways) can prevent the kill switch from working. There are probably more.
[Answer]
Pure thoughts cannot do that. Physiologically, thoughts are electric and chemical activity in neurons - but even the chemical activity is the same independently of the exact content of the thought. So, if your humans are imagining a geometric figure, that will produce a certain firing pattern of neurons in certain brain areas, such as parts of the visual system - but you cannot make triangles a dangerous figure and leave squares a nondangerous one, since these will trigger roughly the same kind of activity, just in different neurons.
There is a way you could go, but it is through emotions. In the brain, emotions are a kind of neuronal activity, just like the thoughts, but they can also lead to the production of hormones. For example, anxiety is connected to ACTH production in the pituitary gland (which then cascades into the production of other hormones in the body). Frequent anxiety is famously a cause for epigenetic changes, there was a seminal study on rat pups inheriting anxiety from stepmothers, not through genes but through an epigenetic mechanism triggered by absence of calming behavior in their anxious stepmothers.
It is also possible, and common, to trigger emotions through thoughts. If you go to bed thinking that tomorrow, you will have an important exam you haven't learned for, you'll be anxious even though there will be nothing in your physical environment that's different from every other night. So, on that front, you might have some success.
The problem comes, again, from thought type vs. thought content. The brain's activity is localized in different areas when you are thinking about geometric shapes as opposed to listening to a song - but if you were go off that only, you would have to make all thinking about shapes dangerous (or all listening to music). Alternatively, you could say that the thoughts you need cause a certain emotion, and connect the disease to that emotion - but then, it will be triggered by all occasions of having that emotion, not just the ones caused by thoughts about the godly technology.
Since this is fiction and you have genetically engineered humans, you could make it work with some handwavium. You would need to add to the human body a special new emotion, that normal humans don't have. This emotion triggers a new hormone, engineered to have some effect on the human body. And this emotion is so specific that it can only be triggered by having a thought about the godly technology.
A plausible scenario of that kind would be to add a new level of insight. In real humans, the feeling of "X is true" is an emotion - it is just a pattern of brain activity that happens in our emotional centers when we encounter a thought we believe to be true. (Believe as in "faith" and "certainty", not as in supposing it should be true). So, add a new emotion derived from this one, which only happens when the engineered humans recognize not an ordinary truth, but a truth about the divine mechanism of the universe. You can add some graphic description of mythical extase there, that's highly plausible for an emotion. It will trigger your neurotransmitter, which will do its job wherever it needs to - you can actually decide on the duration of the human's life after the insight by picking your preferred cancer.
As a side effect, since our normal emotion of certainty occurs when we think something is true (regardless of whether it's objectively true), this will probably be also the case for the engineered emotion. So for the divine insight, it will also be plausible to not matter if the engineered human had a correct or incorrect insight about the way the gods function - if they live on Olymp, but he wakes up and is struck by the thought "I'm sure they live on Atlantis", the killswitch will also be triggered. That gives you a good deterrent of even trying to have thoughts in this direction, and even if a brave scholar puts up a theory and dies for it several months or years later, his disciples won't know if it was really true.
[Answer]
Some medicos today *do think* that cancer (and, unrelatedly, heart disease) is caused by *stress*.
In fact, "stress" is, essentially, "something you think".
You could absolutely play this in your story that, yes, it turns out cancers were caused by a mental situation; your future geneticists played this factor up to the extreme.
[Answer]
People are wrong about thoughts not being able to kill. It is well documented in humans and animals that mammals can literally die of a broken heart. (Ok, we can be pedantic like rumtscho's good answer and say that it's technically not the thought that kills, it's a follow-on process involving emotions and/or important glands, etc.)
Also, the power of suggestion can do amazing things. My brother in law had warts on his hand cured by hypnosis. Placebos can cure, and they can sicken (people that think they got a drug but did not, report the same side effects as people who really got the drug). People can become sick if they truly believe in the curse of a shaman.
So yes, it makes sense that a certain condition/pattern in the brain, indicating that person is having particular thoughts or has obtained particular knowledge, could trigger their death. The most straight-forward way I see is if that pattern was closely linked to the pattern that occurs in somebody that dies of a broken heart. In other words, it causes a depression so deep and sudden that the person dies of heart failure within 2-3 days of their revelation.
] |
[Question]
[
I'm working on a novel, in which a character was given a cutting edge vaccination to a deadly disease. She is now valuable because she was the only one given the vaccine and the research to make more is unavailable. Now some people want to "reverse-engineer" the vaccine by studying her (the one who created the vaccine is gone, by the way).
So...my question is: Is it possible to formulate this vaccine by simply using a blood or tissue sample, or would the character herself need to be available for research?
I'm not a scientist, so I'm only guessing (well, researching and guessing), that it's even possible to reverse-engineer a vaccine. Appreciate any input!
[Answer]
It's quite a bit more difficult than the other answers make it out to be.
First, we need a rough draft of what kind of immunity we're dealing with. Often, with vaccines it's humoral immunity (antibodies and B-cells). This is what the existing answers are talking about. An alternate type of vaccine, for example, would be a T-cell inducing vaccine, and these are generally a whole lot more complex.
Let's say we're talking about humoral immunity, and are not getting into the more experimental types of vaccines.
We can go through the list of vaccine types, and discuss if there's a potential benefit of having an immune individual (basic description of vaccine types found [here](https://www.vaccines.gov/basics/types))
1. Live-attenuated vaccines
Mostly useless, since there's no way to track down how to attenuate the pathogen from an immunized individual. Possibly, we could use serum of the individual to see if the attenuated pathogen is still immunogenic by testing if the subject's serum still binds the pathogen, but that's unreliable and animal testing is likely more reliable. The rare exception is if the attenuated variant occurs naturally, as was the case with cow pox, the first vaccine.
2. Inactivated vaccines
Very useless, the main challenges here are truly inactivating the pathogen while keeping the vaccine immunogenic and exposing representative surface proteins. Our subject is not going to help at all with these challenges.
3. Subunit, recombinant, polysaccharide, and conjugate vaccines
Somewhat useful, our subject can help us identify the subunit or polysaccharide used (as discussed in the answer by Willk). That still leaves us with the challenge of creating a vaccine that forms the right type of immunity against this subunit or polysaccharide. Recombinant and conjugate vaccines are more complicated, since the targets are artificially created, and we can only test if we have "the right one".
Also note that quite often, multiple antigens are used in a single vaccine of these types, and a single person might only respond to a fraction of the antigens. In that case, the person can be immune, while it's impossible to track down all the antigens used, and making a vaccine only based on the antigens that induced immunity in this person might have a much lower efficacy than the original vaccine.
4. Toxoid vaccines
Toxoid vaccines are vaccines against a specific toxin, and generally somewhat easy to create if you have a toxin in mind that constitutes a real health problem. Our subject might be able to help, but it's unlikely that would be necessary, since the toxin would've already been identified.
Our subject can also give us a hint which kind of vaccine was used. Types 1 and 2 will likely produce a more diverse antibody repertoire than 3 and 4. But this will likely be inconclusive, since we only have a single subject.
For a more thorough read on vaccine types, I recommend [this NIH webpage](https://www.niaid.nih.gov/research/vaccine-types). Be sure to read into adjuvants and their role in vaccines too. If you have a specific type of vaccine in mind, I can try to elaborate on the possible role of samples from an immunized patient in reverse-engineering the vaccine, but generally, that role is going to be pretty limited.
An interesting experimental vaccine type to name in this context might be DNA vaccines, because this is one of the few types where there might be an actual major benefit to having an immunized individual with a specific vaccine. If he/she were to be vaccinated using a DNA vaccine, we could try to identify and culture the immunogenic cells by exposing them to the pathogen, and then fully sequencing the immunogenic cells, compare with the overall genome of that person, and possibly identify the sequence used in the vaccine (it would be a sequence expressed significantly more in immunogenic cells). That would still leave us with identifying adjuvants used.
[Answer]
Here is a general way one could do it.
1. Get samples of pathogen. Break it up into small bits. Fix bits to plate.
2. Wash pathogen bits with your characters serum. Then wash it off and add a marker to plate that binds to human antibodies.
That is an ELISA test; old tech.
<http://www.virology.ws/2010/07/16/detection-of-antigens-or-antibodies-by-elisa/>
[](https://i.stack.imgur.com/4brRd.png)
The vaccine has protected her: she has protective antibodies. Now you know what component(s) of the pathogen she has antibodies to and so which ones are important for immunity.
Maybe you have unlimited quantities of the pathogen. You could use that component of the pathogen by itself as a vaccine or make a vaccine around it. Or you could use that component of the pathogen to raise a bunch of antibodies in animals, and see what similar things those antibodies also stick too. Then use one of those similar things to build a vaccine.
This makes building a vaccine sound trivial. It is not. But maybe this would be plausible enough for a fiction.
[Answer]
**Yes, with a blood sample.**
You can achieve a 'kind of' immunity. I'm just going to quickly break down how vaccines work for background, just in case. Vaccines, in general, are a weak version of the target pathogen (usually a bacteria) which the body 'trains' against and figures out how to create a proper antibody. (Bit more complex than that, but it's good enough for now.) Inside your character's body, there no longer exists the vaccine she was injected with. But there *are* antibodies, which can fight off the virulent strain of the disease, that is, the disease at full strength.
Based off that, the 'cure' you're looking for is just the concentrated dose of said antibodies. Regularly injecting them into any patient would fight off the disease. The trick, of course, is getting those antibodies. Willk's suggestion for analyzing the antibodies is perfectly valid. But there's also another way. And that lies within said character's B lymphoblastic-cells within their blood that produce said antibody. If you remove, isolate, and culture them, you can inject the B-cells into the victim's body, giving them factories to produce their own antibodies. This is based off research [here](http://www.cidrap.umn.edu/news-perspective/2008/08/researchers-find-long-lived-immunity-1918-pandemic-virus). (There should be a few other places if you look for yourself, I just searched Spanish Flu because I remember reading up on these kind of experiments being done with it.)
] |
[Question]
[
Rats are commonly associated with illness and disease due to the role they played in [The Black Death](https://en.m.wikipedia.org/wiki/Black_Death). However, some works of fiction portray [rats as carnivorous swarms](http://tvtropes.org/pmwiki/pmwiki.php/Main/SwarmOfRats), devouring people indiscriminately in seconds, like some kind of land [piranhas](https://en.wikipedia.org/wiki/Piranha).
[](https://i.stack.imgur.com/3q8pQ.jpg)
<https://twitter.com/aplaguetale/status/964152340130488320>
How could such creatures evolve? The rats that make up carnivorous swarms have the following features:
* They are visually and biologically similar to ‘normal’ rats (such as [rattus rattus](https://en.m.wikipedia.org/wiki/Black_rat) or [rattus norvegicus](https://en.m.wikipedia.org/wiki/Brown_rat)) though they are typically larger and have a higher intelligence. Most often their fur is black, though it can be brown and, very rarely, white.
* Such rats hunt and scavenge in large groups called swarms, feasting on a purely carnivorous diet. They typically target isolated creatures but will attack larger groups if the rat swarm is large enough.
* They attack in a frenzied manner, consuming the flesh of prey and killing them in a matter of seconds. Whilst highly aggressive in groups, an individual is very cowardly when isolated.
* Often rats are afraid of fire or other sources of bright light, such as sunlight or light from a flashlight. They will not willingly enter or stay in the light, running back to the darkness where possible. Additionally, a swarm will not willingly swim across a body of water to reach its prey.
* They breed exceptionally quickly, especially in times of war or plague due to the abundance of food.
* The rats are intelligent, able to recognise traps or defences and avoid them. They may actively sabotage defences via bitting wires or cables or, in extreme cases, rush the defences and overwhelm them.
Here is a link to the rest of the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series)
Here is [a related, but closed, question over on RPG.SE](https://rpg.stackexchange.com/questions/73197/would-a-swarm-of-rats-really-be-much-of-a-threat) asking how deadly a [Swarm of Rats](https://www.dndbeyond.com/monsters/swarm-of-rats) would be. My question though is asking how creatures, as described earlier, could evolve, not if ‘normal’ rats would be very dangerous.
[Answer]
Have you ever heard of the [Naked Mole Rat](https://www.wikipedia.org/wiki/Naked_mole-rat)?
They’re a subterranean, matriarchal species. They are, as the name suggests, naked and ratlike.
They also have the distinction of being the only eusocial (swarming) mammal EDIT: There are in fact two, the naked mole rat and the closely related (and much furrier) [Damaraland mole rat](https://www.wikipedia.org/wiki/Damaraland_mole-rat), though their social structure is more like dysfunctional families than proper colonies. Anyway:
Each mole rat colony is split into males, workers and queens. The queens pop out babies, the workers gather food (mostly from tubers and roots, but a switch to being more carnivorous is easy to imagine) and the males... tend to the queens.
Being subterranean they are blind, but it’s not too much of a stretch to imagine a species that is more nocturnal, and so has extremely good night vision and an aversion to light. A lack of swimming ability is easy to justify for something that used to be a borrower as well.
If small colonies are mostly scavengers then the ‘swarming’ behaviour is a learned/emergent behaviour caused by the social dynamics of larger colonies, where pheromonal signals from one worker to the next will trigger hyper aggression when in high concentrations or when the best is under threat. Examples of this exist in [Africanised honeybees](https://www.wikipedia.org/wiki/Africanized_bee), or in some bee species that kill predatory hornets by swarming them and [*group-hugging them to death*](https://www.newscientist.com/article/2174097-honeybees-gang-up-to-roast-invading-hornets-alive-at-a-terrible-cost/). Naked mole rats already exhibit hormonal control (one female at a time is queen, and her presence will suppress the reproductive systems of the workers), so that’s a nice progression,
As for intelligence: social rodents are already pretty intelligent. Dial it up to 11 and also add in some of the emergent intelligence behaviours of swarms (ant colonies spring to mind) and you can easily have a swarm that looks like it’s acting with intelligence.
As for breeding quickly: there’s an advantage to having a dedicated baby-making caste. The queens do nothing but feed, birth and nurse. They are grotesque balloons of flesh that exist purely to generate the next brood of workers.
So yeah. Your swarms are an evolved species of the naked mole rat.
By the way: Naked mole rats are also immune to [cancer](https://www.google.co.uk/amp/s/amp.livescience.com/37555-cancer-resistance-naked-mole-rats.html) and [pain](https://www.newscientist.com/article/2204849-a-type-of-african-mole-rat-is-immune-to-the-pain-caused-by-wasabi/). So there’s that as well..
[Answer]
>
> They are visually and biologically similar to ‘normal’ rats (such as rattus rattus or
> rattus norvegicus) though they are typically larger and have a higher intelligence.
>
>
>
No problems here, that's a very easy to believe change and requires little justification.
>
> Most often their fur is black, though it can be brown and, very
> rarely, white.
>
>
>
It's the same for the black bear. Usually black, some are brown, and there is a very rare white colour morph, the spirit bear.
>
> Such rats hunt and scavenge in large groups called swarms, feasting on
> a purely carnivorous diet. They typically target isolated creatures
> but will attack larger groups if the rat swarm is large enough
>
>
>
Typically the only animals which act like that are eusocial animals - ants, bees, termites, and the like. As Joe Bloggs said, there are eusocial rodents, naked mole rats, although they aren't actually rats. In any case, though, a descendant of naked mole rats (or perhaps their furred ancestors) could evolve to be carnivorous, and you'd end up with something like a mammalian fire ant:
[](https://i.stack.imgur.com/QXAyA.jpg)
>
> They attack in a frenzied manner, consuming the flesh of prey and
> killing them in a matter of seconds. Whilst highly aggressive in
> groups, an individual is very cowardly when isolated
>
>
>
The first bit sounds a lot like many predatory ant species. As for the second bit, that's just common sense.
>
> Often rats are afraid of fire or other sources of bright light, such
> as sunlight or light from a flashlight. They will not willingly enter
> or stay in the light, running back to the darkness where possible.
> Additionally, a swarm will not willingly swim across a body of water to reach its prey
>
>
>
They could be nocturnal, and therefore very sensitive to light damage. That also adds to the fear factor. As for the water - eusocial species typically arise in arid environments, and naked mole rats in particular did. They wouldn't know how to swim and would thus avoid the water like a cat.
>
> They breed exceptionally quickly, especially in times of war or plague due to the
> abundance of food
>
>
>
That's just standard stuff for basically all Glires.
>
> The rats are intelligent, able to recognise traps or defences and
> avoid them. They may actively sabotage defences via bitting wires or
> cables or, in extreme cases, rush the defences and overwhelm them
>
>
>
For something unusual, you could try some kind of genetic intelligence, spread out across the whole colony, like that which is discussed here - <http://www.xenology.info/Xeno/14.2.1.htm>. Essentially, the swarms would not only be intelligent, but act as unified superorganisms. In fact it could be said that slime moulds and ants have a rudimentary form of this even in the real world.
] |
[Question]
[
The subterranean nation of Glot has developed the ability to “thermally link” two equally sized diamonds, such that they are always the same temperature, regardless of spatial separation. We can consider this “thermal linking” process “magic” (or sci-fi "thermal quantum entanglement"), but physics otherwise operate the same as in our universe. Contrary to this particular advancement, Glot has NOT discovered electricity. Otherwise, it has technology equivalent to the early-mid 1800's.
One of the diamonds is carefully immersed in one of their many magma–rivers, the other is put into a steam engine boiler. (These magma-rivers are part of a very large underground area, and are accessible, with precautions, at minimal cost.) Always at equal temperatures, the two diamonds boil/heat the steam, and “cool” the magma river respectively.
The “linking” process is far less expensive than the diamonds themselves, so they are cut into slices, half a millimeter in thickness to increase surface area. These slices are the smallest they can mount, without having them “wash” away in the magma river, while keeping the diamond in contact with the magma.
Without considering the cost of the diamonds: would this process actually work to produce a useful, geothermal powered, steam engine? (That doesn’t require shoveling, or even carrying fuel?)
If so, what mass of diamonds, in total, would be required to power an average steam locomotive of the 19th century?
[Answer]
The [*convection heat transfer coefficient*](https://en.wikipedia.org/wiki/Heat_transfer_coefficient) for water heated by a solid surface, in a typical boiler, is about 1 kilowatt per square meter and kelvin. (That's why in a fire-heated boiler you have all those pipes, through which hot combustion gas flows; it it to maximize the surface area where the hot gas transfers heat to the water.)
This means that a shard of diamond with an area of 5×5 cm = 25 square centimeters (0.0025 square meters), 1000 K hotter than the water, will be able to transfer 2x2.5 = 5 kW. (I am assuming that the diamond is placed vertically so that both surfaces can transfer heat.) Locomotive steam engines have an efficiency of about 5% tops, so overall the engine will produce about 250 W, or 0.4 horsepower. A more-or-less typical steam locomotive produces about 2000 horsepower; it results that you need some 12.5 square meters of lava-temperature diamonds for this. (And you cannot have one big diamond, or else the heat transfer coefficient will come down abruptly; you need many small ones.)
The density of diamond is 3.5 grams per cubic centimeter. Assuming that the many small diamond pieces are 1 mm thick, the 12.5 square meters of heating come to 44 kg, or 220,000 carats. For uncut large diamonds, a price of 2,000 USD per carat is reasonable, so the 220,000 carats needed for one lousy steam locomotive would cost some 440 million USD. OK, maybe in your world De Beers doesn't exist so diamond prices are not massively inflated, but we are still speaking of something like 100 million USD.
Note 1: For the curious, I started with a 5x5 cm diamond because in my mind that's about the upper limit for an *enormous* diamond.
Note 2: I have no idea whether it is even possible to cut diamonds in thin flat slices. Since the calculations are crude approximations anyway, this shouldn't matter much.
Note 3: Lava is rarely hotter than 900° C, so a more natural temperature differential would have been 800 kelvin. I've taken 1000 kelvin for ease of calculation.
[Answer]
Of course it would work. There's no practical difference between your diamonds and an electric heating element — except the diamond is experiencing 1,000℃ and the heating element usually isn't.
The issues are two-fold:
**Surface Area:** you need to get the heat off the diamond: more surface area = faster transfer.
**Suspension:** It would also be best to figure out how to suspend the diamond. Something that hot would eventually compromise the steel/iron/metal container it's sitting against (if it were simply thrown in), so your people would likely be experts at ceramics.
] |
[Question]
[
Let's say our world is set in a [hyperbolic space](https://en.wikipedia.org/wiki/Hyperbolic_geometry) with a curvature $K$ of $-1$ per $9$ square meters. The surface of our world is a hyperbolic plane (approximately, there are still hills and valleys and stuff). The sun is surface 100 million miles away that turns on and off every in a 24-hour cycle. The amount of energy it gives the world per unit area is similar to that of our sun. Earth-like life lives on the hyperbolic surface, including a human-like species.
My question is, how would humans navigate this world?
Before you say "the same way as ours", let me note some problems:
* Whereas spheres in our world have a surface area that grows quadratically with radius, in hyperbolic space, the surface area of a sphere grows exponentially! That means, assuming energy is conserved, long distant wireless communication does not work (since the signal given off is distributed over a larger area).
* Maps also are much harder to use. This is because you can't make images of things that are smaller than the original object without some distortion (the bigger the difference in size, the bigger the distortion). The curvature in this world is so severe that maps of even smallish regions distort quite a bit. Here's an [example](http://zenorogue.blogspot.com/2015/10/a-paper-model-of-hyperrogues-world.html) (the curvature of the world that map is portraying is also about $-1$ per $9$ square meters).
* You might say that navigating by the stars might work (if they exist). But, you can't see the stars (due to the first point) nor map them (because of the second point).
So, given all these challenges, how would someone navigate in this world? The solution should work both within cities, and allow travel from one city to another.
[Answer]
**Roads and Road Signs**
As long as you are on a road, the curvature of the world doesn't matter. The fact that you could get lost really fast if you diverged from the road by even a tiny angle just doesn't matter, because you wouldn't do that--you'd stay on the road! The only thing you have to worry about is making the correct turn when you get to an intersection of two or more roads--exactly like navigating a road system in our world.
That works perfectly well within cities, and perfectly well for going between any two cities that are already connected by some road network. So if those are the only cases you need navigation to work for, you're all set!
The problems only really start when you need to travel off-road, explore new place or blaze new trails--and expect to be able to get back home again. And to handle those cases, you'd probably just *literally blaze* a trail, or unravel a proverbial ball of string behind you in the labyrinth. Once you've gone a certain distance, you set down a marker. What kind of marker it is will likely depend on the specifics of the terrain you are traversing. Then, you just make sure to stay close enough to that marker that you know you can find your way back unassisted, until you set down another marker, and so on. Long-distance surveyors and road-building crews might use laser guides, or simply theodolites, just like we do in our world, with the difference that their angular tolerances have to be much tighter, and the maximum distance they can sight accurately would thus be considerably smaller than it is in our world. I.e., you wouldn't try to lay out a 50-km road in one go; you'd do it in small chunks, expecting to run into someplace you recognize at the end of the new road. If you don't run into anything in the expected distance, you back up along the path, adjust the angle of the last few segments, and try again. If you run into something you know, but not the *right* thing, then you can make better adjustments.
If you need to navigate over water... well, *don't*. This was a historical problem in the real world, as well. You just don't sail out of sight of land. Not until you can set down well-anchored buoys, spaced closely enough together that you can always find the next one before you go out of detection range of the last one (whether that's by sight, short-range radio, or whatever). Effectively, building roads in the sea.
[Answer]
Riverboat pilot style; during the days of the paddle steamers on the Mississippi and Missouri Rivers in the US boat pilots apparently traveled up and down very small, sometimes less than ten miles, sections of the river steering for different captains that came their way. Each pilot specialised in their home patch and didn't know what was around the next bend beyond their section of the river but they knew *every* sand bar, sunken log and tying off tree that was on their bit of the river.
My suggestion is that long distance travelers don't navigate for themselves over long distances but rather they rely on locals who know small areas of the world very intimately either as professional guides through a particularly difficult piece of territory or just asking the locals "which road to Travistoc?" Now an established road, or track, network will help a lot when it comes to getting from A to B with a minimum of fuss on well traveled routes (you can in fact map such a network without much fuss using a [Schematic Map](https://en.wikipedia.org/wiki/Schematic) that is accurate in routing and labelled for distance, as surveyed by chain) but off the beaten track you need local knowledge since you can't have accurate long range mapping. Surface shipping will have to use a similar approach; hopping along the coast between established ports guided by local specialists where necessary. Coming back alive after getting out of sight of land will be a cause for massive celebration and epic boasting.
[Answer]
Is this about a life on a 2D hyperplane or a sphere in a hyperbolic 3D space (the question mentions both)? The life will be drastically different in these two cases. Note that curvature $\frac{1}{9}m^{-2}$ is kind of extreme. I assume the spacetime is a "hybrid" of hyperbolic 2D (or 3D) space and absolute Newtonian Euclidean time (if the time is hyperbolic as well, we get anti-de Sitter space which means geodesics (worldlines of two points in rest) will diverge and you get quite a good model of a rapidly expanding universe - your planet will have rather short life!)
First, the Sun - 100 million miles, let's say $160\cdot 10^{9} m$ means the light (and gravity) is reduced by $sinh^2 \frac{160\cdot 10^{9}m}{3m} \approx \frac{1}{2}e^{2\cdot 5\cdot 10^{10}} \approx10^{2\cdot 10^{10}}$... just forget about it, there is no way to even compare it with anything (and literally anything, like shining a match across observable universe is immensely brighter) from our universe.
The vision will also work with an exponential decay - say you see object up to 10km in Euclidean space. Then in the hyperbolic space you'll see objects up to 20m.... (note however that's a lot of space in there)
# 2D hyperplane
Let's assume the area you are interested in is that of a very small country, say inside a circle of 100km radius (approx. $30000 km^2$.
In the hyperplane, the country is inside a circle with radius a bit over 60m... So your map has to depict a circle with 60m radius and the area of $30000 km^2$. Or, in 1:1000 ratio, your map will have to display 6cm circle with an area of $30000 m^2$. I guess any "map" will be purely topological, displaying (or even only describing) major terrain features, more in terms of very precise angles (in hi tech society) from other terrain features - like "10 m from the tower in the azimuth 12°10'12.57664'' there is a well". Note that all topographical features will be necessarily rather small in their diameter.
For sufficiently technological civilization, use radio beacons. Since the world has much less distance per surface area compared to Euclidean one, beacons should be more or less receivable even if the signal decays exponentially, especially if the transmitters use directional beams. Then it's just a [variant of fox hunting](https://en.wikipedia.org/wiki/Transmitter_hunting). Even a form of GPS is possible with triangulation and sufficient computational resources.
# 3D hyperbolic space, spherical planet
A sphere in hyperbolic space is a sphere, with a positive (2D) surface curvature.... so nothing different from mapmaking of Earth surface.
The problem is that with the space curvature radius 3m, standing on the surface of the planet will look like standing on a very steep hill, rapidly disappearing into the infinite abyss below (remember vision works very differently). So map will be inherently *more* navigable than the reality.
(also, the planet with Earth surface will have a radius of about 40m)
EDIT: it's a hyperplane & add radio beacons
[Answer]
When you look at a distant object in hyperbolic geometry, the main problem is that it will be tiny. You're using HyperRogue as a base, which, in its standard tiling, can be considered to have absolute unit of 3 meters. A circle with diameter of 15 meters will then have circumference around 1400 m. In Euclidean space, a circle with this circumference would have radius 222 m, so in other words: you would see an object 15 m away just as small as you would see an object 222 m away in our world. Since the circumference of the circle is the same, the angular size of the object (which is basically how big part of the circumference it takes) is also the same.
Let's say you can see an object (perhaps a mountain) that is 50 km away on Earth. A circle with radius of 50 km has circumference 314.16 km. In HyperRogue world, this circumference would correspond to radius of only around 31.3 m; in other words, if you could only notice something as big as a mountain at THIS distance, there's not much chance of seeing anything that is farther.
And this assumes that you could see the whole mountain, which you actually can't -- and this brings me to the next point.
In Euclidean world, we take it for granted that when we look at a distant 3D object, we see a half of it. You look up to the Moon and you see half of the whole Moon. If we ignore the pesky fact that we have two eyes for a moment, then a single eye can actually never see a full half of the Moon, but the difference is negligible.
In hyperbolic world, it's not negligible. If you have a sphere in this world, it turns out that you will always see just a small part of it -- the bulk of it will be so diminished by the insane hyperbolic perspective that it will actually hide behind the nearest bit.
When you calculate it, you will find that there is an upper limit on an AREA of a sphere that is visible. And that area is pi -- that's what you'd get with infinite distance and infinitely large sphere (horosphere). In HyperRogue, an area of pi would mean around 28 square metres. Let that sink in. If there was, say, Jupiter near you (no matter whether we're talking Jupiter's radius, circumference, mass or whatever -- in this case there's no real difference), you couldn't actually see more than 28 square metres of it! This also means that you couldn't find a meaningful difference between a small sphere and a large one -- as the radius grows, the curvature approaches horosphere, and it would be very hard to distinguish how big the sphere is, exactly -- or whether it's even finite.
That means you couldn't actually see a mountain at the distance of over 30 m as previously mentioned -- the bulk of that mountain would be hidden and you could only see a very small front of it, which could, of course, be seen at smaller distance.
Not only would be distant objects small, but they would also move insanely fast when you move. Hyperbolic parallax doesn't work the same way the Euclidean one does; distant objects would not seem to move more slowly. If you walked under a sky full of stars (and you could see them for some reasons), the stars would seem to move -- regardless of their true distance.
So, given all this, how would you navigate in such a world? The best bet probably is to put together a set of local coordinate systems, but... not even that wouldn't work in HyperRogue. The curvature of that world is simply so big that I have to question whether things like cities or civilization are even possible in there.
One idea I came up with was to have square map plates, each corresponding to a square from a hyperbolic tiling like {4,5} or {4,6}. You could then put the plates together to get a limited view. But even a {4,6} square -- square with inner angle of 60 degrees -- would have an edge of only around 5 meters in HyperRogue. What's worse, no square at all could cover an area bigger than 56 square meters (2 pi square units) because that's the maximum area of a square in hyperbolic geometry. If we used hexagonal map plates, we could get to double of that, but that's all.
Tricky.
[Answer]
## Dogs
Dogs' sense of smell could help humans find their way. Humans have a long and beneficial relationship with canines, and in your world that relationship would be even more precious since a dog's sense of smell could help provide direction and get their human home.
Dogs sense of smell is easily [1,000 times more powerful](http://www.animalplanet.com/pets/how-is-a-dogs-sense-of-smell-so-incredible/) than a human's. I found places that rate it even higher than that. Humans in your hyperbolic world would likely create their own breeds of dogs that are gifted with tracking and guiding and always take them with them when they venture out of town. Roads develop their own scents from the various travelers that use them. As such if a dog hears the command **road** they know that their human wants to be guided back to the road. If the dog is told **home**, the dog will try to pick up the scent of home if it is within range. If it is, then they are set.
### Distance of smells
This is much harder to determine. There has been a documented case where a dog [could smell whale feces from 1.2 miles](http://www.savets.org/Pages/DogsIncredibleSenseofSmell.aspx) away. If your dogs are breed with a high focus on smelling things that are far away, then your dogs should be able to exceed that mark reliably.
### Culture based around incense and aroma
Since people know that their dogs are likely the only thing that can get them home if they get lost, humans likely will try and make their towns easier to find by their dogs. As such towns may burn large amounts of incense, or use wood like cedar in buildings since it has strong natural aroma to it. That way a dog should have an easier time picking up the smell of home. Much like how coastal locations build light houses to guide ships, towns could have scent houses to guide dogs. Note the smell does not have to be pleasant, just strong. So places that do not have access to anything nice, they could use rotting carcasses, could convert an outhouse into their scent house, or use a large pile of whale feces.
] |
[Question]
[
On a planet, a species uses magnets (i.e. float in the air) instead of wheels for transportation. Roads are easy enough, just slap some magnets in it, at it works.
But I was wondering about the feasibility of having transportation which uses the magnetic field of the planet to hover above the ground, or off-road transportation. Is it even remotely possible, and if so, how strong will the magnets need to be? The magnetic field is the same strength as Earth's.
[Answer]
The easy answer is yes. We use one object that moves by the Earth's magnetic field all the time: a compass.
The hard answer is that we don't have the technology to move anything heavier than a pin stuck in a cork floating on water ... much less levitate a truck load of dirt! BUT, don't let that stop you. The concept has been dreamt about for a very long time and it's only a matter of time before we figure out how to make a strong enough counteractive magnetic field that will work.
Your limitations are control. The Earth's magnetic field is constantly in flux and shifting, which is a lot like blowing a small hover craft around with wind. Have you ever steered a hover craft or watched one being steered? They don't turn very readily, and neither would a magnetically levitated craft. Obviously, with enough [Clarkian Magic](https://en.wikipedia.org/wiki/Clarke%27s_three_laws) we could take advantage of magnetic shear to navigate. It'll just take us some time to get there.
As for how strong the magnet would need to be. It would not need to be as strong as the Earth's. If you think about it, an object the size of a VW Bug emitting a magnetic flux equal to the Earth's would have catastrophic effects on navigation on the other side of the planet. It would need to be a fraction of that strength.
Think of it this way, [Wiki reports](https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Intensity) that the Earth's magnetosphere is around 50,000 nT (nanoTeslas) while a refrigerator magnet is about 10,000,000 nT. That sounds like it makes me a liar, but remember the Earth's radius is about 3,959 miles and the radius of the refrigerator magnet is maybe 0.375 inches. If you shrunk the Earth's magnetic field to the area of the magnet it would be about 3.5x106 stronger than the refrigerator magnet (which explains why the refrigerator magnet can't levitate).
However, Don't worry about the details. There's enough plausibility to make for a good story.
[Answer]
Magnetic levitation depends not just on the value of the external magnetic field B at a given point, but on the [gradient](https://en.wikipedia.org/wiki/Gradient#Definition) of the magnetic field ∇B, which tells you how quickly the field changes as you move in space. [This page from a lab at Radboud University](https://www.ru.nl/hfml/research/levitation/diamagnetic-levitation/) gives the equation for when magnetic levitation can happen:
>
> Whether an object will or will not levitate in a magnetic field B is defined by the balance between the magnetic force F = M∇B and gravity mg = ρV g where ρ is the material density, V is the volume and g = 9.8m/s^2. The magnetic moment M = (χ/µ\_0)VB so that F = (χ/µ\_0)BV∇B = (χ/2µ\_0)V∇B^2. Therefore, the vertical field gradient ∇B^2 required for levitation has to be larger than 2µ0ρg/χ. Molecular susceptibilities χ are typically 10^-5 for diamagnetics and 10^-3 for paramagnetic materials and, since ρ is most often a few g/cm^3, their magnetic levitation requires field gradients ~1000 and 10 T^2/m, respectively.
>
>
>
This lab is concerned with diagmetic levitation of ordinary materials (they show the levitation of a small frog on their site), but the external field gradient doesn't have to be as large if you are levitating a superconductor, which has its [magnetic susceptibility](https://en.wikipedia.org/wiki/Magnetic_susceptibility) χ=1, the highest possible for a [diamagnet](https://en.wikipedia.org/wiki/Diamagnetism) (diamagnetic materials are repelled by the field of an external magnet, unlike paramagnetic and ferromagnetic materials, so diamagnets are the ones you want for magnetic levitation).
But even with a superconductor, the Earth's magnetic field is so large and therefore changes so little over ordinary human-scale distances that it wouldn't work for magnetic levitation, you would need a huge magnet of similar size to the Earth itself to levitate from the Earth's field. This is explained by a physicist on [this page](https://van.physics.illinois.edu/qa/listing.php?id=1027):
>
> The force on an object is related to the change in the energy of a system (not including the kinetic or thermal energy of the object) when the object is moved. We write
>
>
> F = (change in Energy)/(change in position)
>
>
> For static fields. The change in position has a direction, and so the force does too (you need some vector algebra with a dot product to express this exactly).
>
>
> Two small magnets placed together with like poles close to each other feel a repulsive force because of the energy stored in the magnetic field. The energy density in space is proportional to the magnetic field squared, and when the close-by poles are the same, their fields add in more places than they subtract, and so the total energy is higher for this case than when opposite poles are closer, where the field is smaller in more places.
>
>
> There are two things about the Earth’s magnetic field which makes this effect much smaller. For one, the field is very weak at the surface (about a gauss or less). The more important reason is that because the field extends over such a large space and because we on the surface are far away from the center of the Earth’s dipole, the Earth’s magnetic field strength is very uniform if you look at it over a region of space that is reasonable in size (like the size of the magnet you propose to use).
>
>
> If you put these two pieces together, you find that the force on a magnet due to the Earth’s field is very small -- if you move the magnet from one place to another, its field adds to the Earth’s field in almost the same way because the Earth’s field is very little different from one place to another, and the total magnetic energy changes by a very very tiny amount. **In fact, the total magnetic force on a magnet in a uniform magnetic field is exactly zero, and the forces we normally associate with magnets repelling or attracting are proportional to the rate of change of the field strength with position.**
>
>
> This isn’t the end of the story, however, because the magnetic energy of the system depends on which way the magnet is pointing, relative to the Earth’s field. If it points along the field, the fields add, for a higher energy. If it points the other way, the fields subtract, for a lower energy, and so the magnet prefers to turn to point in this way. **Magnets in uniform fields feel torques which make them turn around if they are not pointing in the right direction, but there is no net force making the magnet want to levitate.**
>
>
> That having been said, if you had a really really big magnet, whose field extended over such a large region that the Earth’s field changes noticeably over that region (you might need another Earth-sized bar magnet), then yes, a noticeable force can be produced.
>
>
> As for actual levitation, that can only happen with materials whose magnetic moment actually points the wrong way, increasing the energy in a magnetic field. These are called diamagnets. Diamagnetism is purely a quantum mechanical effect, with no classical explanation. By far the most intense diamagnets are superconductors. You may have seen superconductors levitating over magnets, or vice-versa. The Earth’s magnetic field does not change rapidly enough from place to place to levitate even a superconductor.
>
>
>
(the bolded sentences above show why the fact that the Earth's field cause a compass needle to rotate, which JBH's answer pointed to, is not sufficient to show it could equally well cause a magnet to levitate, or exert any net force on it causing its center of mass to accelerate in some direction for travel)
[Answer]
The short answer is no, this is a *practical* impossibility, but not only because of the earth's magnetic field per se; it's because of the Earth's gravity. Let me break this question down into a few key areas to discuss the matter in detail;
**Gravity creates Friction**
The reason why wheels are so efficient in terms of propulsion is that they get an assist from gravity. The weight of a car (for example) pushes the tyres down onto the road, resulting in tension, which results in friction. The reason why we use a rubber tyre and grease around the axle is that we want to minimise the friction between the axle and its casing and transfer all the angular force to the wheel. The rubber on the tyre creates so much friction that the only way the angular force can apply is for the wheel to roll rather than spin. This converts the angular force to forward force, pushing the vehicle forward.
This means that the car uses the energy it creates very efficiently to move from its current position to where you want it to go, and gravity is actually *helping* this rather than the enemy. This is also why cars spin their wheels when bogged in slippery mud or when the energy being applied to the wheels overwhelms the friction applied by the tyre. This in essence reflects the whole debate around power to weight ratio in cars, and also explains why many professional racing cars have such wide tyres (to maximise friction).
But (I hear you say) that only benefits lateral movement, right? It's not true for rising above the earth's surface, right?
Wrong. This is the whole debate around space elevators. Right now, we use rockets to get things out of the Earth's gravitational pull. The problem with that is that the gravitational pull is constant, meaning that thanks to something called the rocket equation, you need massive amounts of fuel to get your payload into space because you don't only have to lift your payload, but the fuel to lift it as well. On the other hand, by gripping some form of very tall, super strong rope tightly, you can use friction to climb out of the gravity well. If you use a counterweight on your elevator car, you can even do so with minimal energy cost for the climb. Either way, if we had the right material science advancements, space elevators can use friction to get stuff out of the gravity well at a far lower cost than getting it to 'float' upwards at a great rate of knots.
**Orientation & Lateral Movement**
As has already been discussed in the compass example, magnetic fields are good for alignment. That is to say, if you *already* have something floating freely, the earth's magnetic field will automatically align the magnet to said magnetic field. This means that to steer, you literally need to dynamically adjust the alignment of your magnetic polarity to the direction you want to go. This could be done through friction as well, using a de facto steering wheel to turn a strong magnet under your vehicle, so that fixed thrusters can move you along.
This of course brings us to sunny point number 2 - lateral movement. You still need some way to get your vehicle moving in a given direction, without contact to the ground. On an aircraft or hovercraft, this is usually done with a fan style thruster. Even most modern jet engines are really turbofan engines, capable of great amounts of thrust by pushing air backwards very fast.
It's also why you can't use a hoverboard over water, as we all learned in Back to the Future II. This is not exactly true of course; if you had an oar, you could move along very quickly because the oar maximises the friction between itself and the water, and with NO friction on the hoverboard and the water, in theory you move forward. I say in theory because in a strong headwind, you might be fighting a losing battle with forward movement. But, I digress.
**Magnetic Intensity over Distance**
Maglev trains (for example) can float a train above the magnetic rail because the magnets are strong, and they're also close together. The earth's magnetic field is strong to be sure, but we're actually reasonably far away from the 'magnet', being the inner core of the Earth. The intensity of the magnetic field at distance is inversely proportional to the square of the distance, meaning that the intensity reduces greatly the further you move away from it. That means to get that same train to float *off* the track, you need magnets in it that are so intense they can counteract gravity against the earth's inner core, rather than the earth's surface. If you design such a magnetic field, you could use it to melt pidgeons or exsanguinate cows by ripping the haemoglobin directly out them if they stray close enough.
Bottom line is you're better with two magnets interacting in close proximity to maximise the efficiency of your levitation.
**Failing Safely**
We have to assume here that you're using electromagnets to do all this. Given that gravity is always on, so too do the electromagnets have to be. If they aren't, your vehicle fails badly by collapsing back to the ground. Your electromagnets have to constantly expend energy to counteract gravity.
A car on the other hand simply stops. This is because it's spending all its energy moving forward, not counteracting gravity. Not having to do that, actually using gravity to maximise friction, makes a wheel based vehicle a far more efficient user of kinetic energy than a magnetically levitating vehicle for that reason alone, but it *also* means that it is by far the safest solution in terms of what happens during an engineering or power failure.
**Conclusion**
Mark Twain once said 'Thunder is loud. Thunder is impressive. But it's lightning that does all the real work.' Well, mag-lev transportation looks very impressive to be sure but it's friction that is going to do all the real work in terms of transport systems in a real world application. Wheels may sound very 'old tech' but the reason we're still using them is they are still the best and most efficient energy solution for moving people and stuff around. The biggest problems that you have with the model you describe are that you're constantly fighting gravity by reacting to a distant magnet, and you still need mechanisms to propel yourself through the air laterally if you get your craft floating.
Star wars may have worked very hard to make the wheel look unfashionable, but I'm still of the view that it's a very impressive tool.
[Answer]
The Lorentz Force Equation shows how the Earth's magnetic field can be used for transportation
$$F = q\vec{E}+q\vec{v} \times \vec{B}$$
where q is electrical charge in coulombs
E is the vector of an Electric field (if present)
v is the velocity of the charge carriers
B is the vector of the Magnetic field
The electric field (or difference in potential aka Voltage) can be considered 0 in the atmosphere of a planet -- unless there is a lightning storm -- so assume the first time drops out leaving only the second term.
To understand the physical significance of the second term look at the image below
[](https://i.stack.imgur.com/cqNo8.gif)
In physics, the relationship between the force created by moving charge carriers in a magnetic field follows the right-hand rule. The graphic shows the necessary vectors of $\vec{B}$ and $q\vec{v}$ to produce a force $\vec{F}$ out of the page
The Earth's magnetic field runs north to south parallel to the surface. To understand the proper orientation of components to levitate an object rotate the thumb in the first visual or the palm in the second 90 degrees so they face the top of the page.
The curl of the fingers shows that you need to create a spinning or rotating current to produce a lifting force to counteract the gravitational force. And, since these are vector quantities, forces in the horizontal plane can be created by pitching and rolling the vector $\vec{v}$ a little bit -- most of the force is lift while some is in the direction of travel (like a helicopter)
Consider a more pragmatic form of the Lorentz force equation for your case.
$$F = I\int d\ell \times \vec{B}$$
where I is the current (in Amps) traveling over length $d\ell$ in the magnetic field $\vec{B}$
This tells us we need I=200 KAmps per unit length to counteract the 9.8 $\frac{kg\*m}{sec^2}$ the force of Earths Gravity.
So one can imagine a pancake looking creature that circulates positively and negatively charged fluids around the interior of its body with great velocity. Positive and negative ions will create forces in opposite directions if they move in the same direction. So moving them in opposite directions means you only have to move half the current. The I term can be a small number of ions moving unbelievably fast or it can be an unbelievable number of ions moving slowly or it can be a lot of ions moving very very fast.
[Answer]
Not a researcher of any note, but suppose the inhabitants of the planet had no ferrous metal in their bodies? This could allow them to use obscenely powerful magnets of any sort, which would be in existence by the electromagnetic technology that we can't bother going into without significant danger.
Or suppose their bodies are largely ferrous and lightweight, with an appearance reminiscent of a jellyfish and capable of blanketing themselves over a large area to fly with biologically-charged electromagnets.
] |
[Question]
[
Supposedly we human are able to terraformed Mars decades from now, then in few hundred years able to enhance our genes to be more adaptable to live on harsh conditions, creating space colonies and starting to live on moon, Jupiter's moon, all the way to Saturn. Supposedly we also invented FTL travel between our colonies, and planets in solar system.
As dates and years will become very relative, it would be a disaster in daily basis to scheduling for 3D video call meeting, or planning some events if human still count days and years like we do now.
So what will be the best way as the universal standard time keeping in this situation?
It's more about the substitute of days/months/and years count that we used now based on earth rotation and revolution, **what's the other alternatives that can be socially accepted that's not linked on just one planet movement?** Sun movement can be accepted as we deal with just one solar system.
*(Hours/second would easily solve able using whatever precise time counting device that we will have in the future.)*
As [@cort Ammon](https://worldbuilding.stackexchange.com/users/2252/cort-ammon) has showed the linked question in [here](https://worldbuilding.stackexchange.com/questions/14254/how-would-a-post-planetary-civilization-measure-time). I've revised the question, since I've checked and still not found the answer.
Thank You
[Answer]
I think people, for many centuries, would just refer to [Coordinated Universal Time](https://www.timeanddate.com/time/aboututc.html), or UTC, similar to Greenwich Mean Time.
It won't make a difference that it is Earth Based: There is no standard that will make sense on all planets, so it might as well make sense on **one**, and the natural candidate for that is Earth.
Locally, it would make sense to use orbital fractions: The planet rotation, from one high noon to the next, is 0% to 100%. On earth that is 24 hours, and 1% is 14.40 minutes; but universally, 50% is 'midnight' and 0% or 100% is "high noon". However, that said, our "seconds" and "minutes" and "hours" would probably continue in use; they are arbitrary divisions that correspond to no natural phenomenon.
The other orbital fraction is the percent of distance around the sun, measured from perhaps the closest approach: Again 0% is probably the height of 'summer' and 50% the dead of 'winter'. On earth, 1% is 3.65 days, and 2% is about a week.
This gives them a somewhat consistent frame of reference for local time of day and year. To get precise and talk about hours, minutes and seconds for interplanetary transactions or interactions, everybody does what we already do: Refer to UTC +/- whatever.
I routinely have meetings with people that reside in other countries, and conference calls that may involve people in six countries. Sometimes that means I have to be up and online at 3:00 AM, my time, or 9:00 PM, but everybody manages whatever their job requires.
And certainly in a high tech future; computers will take care of all those local-to-global conversions for us very easily. For example, a voice command and exchange like:
"I have a conference call with the build team at UTC plus eight next Earth Thursday, what time will that be?"
Computer: "55% of a rotation, in three rotations."
"Shit. Alert me before dinner that day, and I need a wake up call 90 minutes before the call."
[Answer]
Generally speaking, you wont find a single answer for how to manage cyclical measurements of time on a galactic scale or even a solar system scale. The reason is simple: cyclical time systems exist because they are convenient. Whatever system you come up with will be deeply entwined with the particulars of how your culture has evolved over the millions of years it took to colonize the galaxy, or over the hundreds of years it took to colonize the solar system.
We divide our time into days because it is convenient. We happen to have a physical reason to do so. There is a pattern of light and dark that occurs on a specific period, and it turns out that period is rather important for a species that is better adapted to light than dark. So the first question you would have is: is the cycle of light and dark important on my planet. If it is, then the concept of a day will be important, no matter how hard you try to force people into a uniform standard.
Generally I would expect a uniform standard to go the way of TAI or ECB or Unix Timestamps -- measuring seconds since an epoch. You could change the unit if seconds are too Earth-elitist for you, but what matters is that you're measuring on a linear system that counts upwards from 0 without ever cycling. Why? Because once you've picked a single cycle (in our case, the second), there's really no reason to pick a larger cycle unless there's a physical or social reason.
So you should ask yourself, "what is the heartbeat of my empire?" What pulse shudders through it? Perhaps all financial transactions are handled all at once every 1000s. That heartbeat would naturally cause cycles to form. I'd start talking about things occurring in "4 transaction cycles" naturally.
One source of cycles you will find is conjunctions of two dissimilar cycles. The Inca had two calendars: a ritual calendar that's 260 days long and a 365 day solar calendar. This is similar to what would happen if you had two planets trying to treat their own year as a cycle. The result is that there was a 52 year cycle marked by the point where the two calendars line up. These calendars were, of course, a matter of convenience. The crops had to be planted based on a solar calendar, while the ritual calendar supported a 13 day ritual cycle that the society created.
Failing to find a meaningful convenient cycle, its likely humans will just fall back on the metric system. Divide time into 100s and 10,000s cycles and leave it at that. Any meaningful cycle would likely override this, but if your culture truly doesn't have a dominant cycle to build from, our love of base 10 will show through. It shows through today: I can say that I wrote this answer in '17, and everybody knows I am referring to a date on a 100 year cycle. What's 100 years? It's arbitrary, but it's a power of 10, which makes calculating it from the long count (2017 years AD) easy.
[Answer]
I'd suggest using [Unix time](https://en.wikipedia.org/wiki/Unix_time), with extra specification that it is adjusted by time that passed on Earth. It already don't try to stay in sync with slowing rotations of Earth, so it would be quite practical and neutral. Already were discussed issues related to slightly longer day on Mars. Some people suggested trying to keep track with normal Earth time, but it somewhat neglects the "minor" issue of time zones on Earth. (yeah, EU colony can keep GMT, while US colony would use one of US time zones...)
Space bases of course could keep Earth days, but they would almost for sure need people working in shifts, so it would not matter so much. Especially when thanks to FTL one could suffer from epic equivalent of jet lag.
[Answer]
As someone else on here noted, the day/night cycle is important to people and not likely to be ignored just because there are other people are on a different planet with a different day/night cycle. Just like time zones on Earth: Yes, we all know that when it's noon here in Michigan, U.S., it is not noon in Tokyo, Japan. But that doesn't stop us from still getting lunch around our local noon. It's natural and convenient.
Anyway, I think that just like with time zones, people would eventually agree on some standard way to keep time, which they would then convert to and from local time as necessary.
Others have mentioned using something like Unix time, where you count seconds continuously from some convenient starting point. In the case of Unix, I think it starts from January 1, 1970, midnight UTC. So in Unix time, January 1, 2017 is somewhere around 1,451,649,600. That is, it's that many seconds past the start of the epoch. (If I bungled that calculation, sorry, but not important to the point.) Computers have functions to convert a Unix "number of seconds" to a date and time on the Gregorian calendar. You have to specify what time zone to get the correct time, and the time you get will be different for different time zones. The computer can just as easily convert to the traditional Chinese calendar or the Jewish calendar or any other calendar out there.
Maybe for local matters, people would use local time. But people who routinely talked to folks on other planets might use such a universal standard. A big catch is that ten digit numbers are hard to comprehend and work with in your head. If it's 1,532,203,201 now and you say you want to hold a meeting on 1,532,845,282, how far away is that? It's hard to grasp quickly and intuitively.
My suggestion: Deal with it with a combination of metric system prefixes and omitting high order digits when they're irrelevant.
That is, today someone might say, "Let's get together in two days to discuss this." I doubt people will ever routinely say, "Hey, let's get together in 172,800 seconds." But they well might say, "Let's get together in 170 kiloseconds". Or instead of, "This happened on January 1, 2017", I don't think people will say, "This happened at 1,451,649,600." But they might say, "This happened at 1451 megaseconds."
Today, for small time intervals we often don't specify the high-order intervals. For example, if someone says, "Let's have lunch at 11:30", I assume they mean 11:30 today. If it's June 14, 2017, no one says, "Let's have lunch on June 14, 2017 at 11:30." People could do the same thing with Unix time. If it's presently 1,542,320,822 and you say, "Let's have lunch at 390 kiloseconds, the other person would understand you to mean 1,542,390,000. That is, take the leading part higher than kiloseconds from the present time, and then replace the kiloseconds with the value given.
Implied in this is that people would come to think of time in decimal multiples of 1 second rather than minutes, hours, day, months, and years. Instead of saying, "A typical work day is 8 hours" we'd say "A typical work day is 29 kiloseconds." Instead of saying, "We got married 5 years ago" you'd say "We got married 160 megaseconds ago". Etc. And people would quickly learn to round to the powers of ten, not to whatever number of seconds the old units came out. Like where today someone might say, "This job will take several days", people using this system would NOT say, "This job will take several multiples of 86,400 seconds." They'd say, "This job will take hundreds of kiloseconds."
Of course they wouldn't necessarily use seconds since January 1, 1970 in Greenwich, England, Earth. They could choose any convenient starting point and any convenient size unit of time. Something larger than a second would probably be more convenient, and then use fractions for smaller units. Like maybe you'd use a base unit of time roughly equal to an Earth day. (Not saying it would be based on any Earth cycle, just that order of magnitude.) Then, supposing you called this unit, I don't know, a "fwac", you might say "This project will be completed in 300 fwacs", meaning not quite an Earth year from now, or "Let's call a meeting for 6 decifwacs", meaning, the time that is 0.6 fwacs into the current (whole) fwac.
Pedantic astronomers would probably insist that the size of the unit and the starting point must have something to do with the rotation of the galaxy around the core, or physicists might think it's a great idea to base it on the time it takes for some selected isotope to decay. They'd probably win, but this would be silly and pointless. It would make more sense to just pick values that are convenient for human beings to work with.
[Answer]
It is very likely that there will be a dual-system.
Something completely artificial, but precise, most likely a Real number (floating-point) like "stardate" (number of days, fractional; roughly equivalent to one wake/sleep cycle) or "unix" (number of seconds, fractional in recent incarnations; as a short period, close to a "least common" unit). In this things like months or years bear no meaning and probably would be dropped.
Something local, bearing resemblance with the planet at hand; there days and longer units linked to seasons would be needed. Absolute precision is not a requirement, but long term stability is.
] |
[Question]
[
A ship powered by a [black hole of a few hundred thousand tons](https://en.m.wikipedia.org/wiki/Black_hole_starship#Criteria) (say, under $6 \times10^8$ kg, which would have a lifetime of several years and a power output of a few hundred petawatts) crashes (malfunctions or is piloted deliberately, it doesn't matter) into the sun. The heat destroys the hull and exposes the black hole to the interior of the sun. What precisely would happen and on what kind of timescales?
Obviously, the sun would fall into the black hole, heating up and giving out huge amounts of radiation in the process. But how much radiation? How long would it be before effects were noticeable from orbit (eg from the Earth), and what would the effects be? How long would it take for the sun to be completely consumed? How would the radiation given off vary (roughly) over this time period? What would happen to the solar system throughout this process?
I'm looking for a timeline with (rough) details of the process and how it would develop. [This question is similar](https://worldbuilding.stackexchange.com/questions/6426/how-long-until-a-small-black-hole-makes-the-sun-fail) but the only answer with any details only calculates time to failure of the sun, and the answerer mentions that he seems to have made a mistake in his calculation, so it isn't a duplicate because it doesn't give the information I'm looking for.
[Answer]
Using your black hole from the actual size would be much smaller than a proton so it would have difficulty accreting mass because its effective cross section is very small. It may even only be able to absorb neutrinos, electrons, and gamma rays. Also, its overall gravity would still be very weak. It weighs as much as a building and you don't see people being drawn to buildings; at least until you get very very close to the singularity itself. Then there is the outpouring of [Hawking Radiation](https://en.wikipedia.org/wiki/Hawking_radiation) as it evaporates which would certainly make it very difficult for mass to get close to it and would likely destructively interfere with any light trying to get in.
The black hole could probably fall all the way through the sun because its outpouring of radiation would clear a path for it. If it somehow got caught in the core of the star it may be unable to accrete mass for reasons previously mentioned, except by catching neutrinos. In the end, I suspect nothing much would happen.
---
**Math to support my claims and edited for clarity**
The black hole in question would be tiny, meaning that its Event horizon or Schwarzschild Radius is small. Knowing its mass we can calculate its size using [this](http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/blkhol.html). The equation is:
$R\_s = \frac{2MG}{c^2}$
Where:
$R\_s$ is the Schwarzschild Radius
$M$ is the mass of the black Hole
$G$ is the universal gravitational constant
Plugging it all in:
$\frac{2\times6\*10^{8}kg\times6.67\*10^{-11}m^3 kg^{-1} s^{-2}}{(3\*10^8m/s)^2}$
Gives a radius of
$R\_s=8.91\times10^{-19} m$
For comparison the [radius of a proton](https://en.wikipedia.org/wiki/Proton_radius_puzzle) is around $8.5\times10^{-16}$. So its rate of accretion, if any at all would be very low.
Because of its low mass (relatively), its gravity won't be very strong at all. Using [Newton's Law of Gravitation](https://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation):
$F=\frac{GM\_1M\_2}{r^2}$
Dividing by $M\_2$ so we can get the acceleration due to gravity.
$a\_g = \frac{GM\_{1}}{r^2}$
Now we plug in the mass of the black hole and a few distances 10, 1, .1, .01, .001 meters to see what the acceleration due to gravity would be.
At 10 m the acceleration is $4\times10^{-4}m/s^2$
At 1 m the acceleration is $4\times10^{-2}m/s^2$
At .1 m the acceleration is $4m/s^2$
At .01 m the acceleration is $4\times10^{2}m/s^2$
At .001 m the acceleration is $4\times10^{4}m/s^2$
So even if it was a meter away from you would probably not notice it was there at all. Reaching out to it would end badly for you, but its sphere of influence is rather small.
Now there is the outpouring of radiation from the tiny singularity that would keep all matter far away from it because of the [pressure the radiation](https://en.wikipedia.org/wiki/Radiation_pressure) exerts. First, we need to calculate the power being radiated from the black hole using the Stefan–Boltzmann–Schwarzschild–Hawking power law (really that's its name)
$P\_b=\frac{\hbar c^6}{15360\pi G^2 M^2}$
where $\hbar$ is the [Reduced Plank Constant](https://en.wikipedia.org/wiki/Planck_constant)
Plugging in our values we get a power output of
$P\_b=9.89\times10^{14}$ watts
Now knowing the power output we can calculate the pressure exerted by the radiation using the planer Radiation Pressure Equation with the assumption of being normal to the surface we get:
$P\_{rad}=\frac{E\_f}{c}$
Where:
$E\_f$ is energy flux in $w/m^2$
$c$ is the speed of light
$P\_{rad}$ is pressure exerted by the radiation
In order to see if the out flowing of radiation would be enough to keep matter away even if the black hole passed through the core of the star, we are going to solve for the distance that the radiation pressure is equal to the [pressure in the core of the sun](https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html). If that distance is less than the radius of the event horizon then matter will fall into the black hole, if it is larger then no matter will fall in. I am also assuming that the radiation is emitted from the black hole evenly in all direction, which may not be the case if the black hole has a large charge or is spinning rapidly. So we will solve:
$P\_{sun} = P\_{rad}$
Expanding
$P\_{sun}=\frac{E\_f}{c}$
Expanding a little more
$P\_{sun}=\frac{\frac{P\_b}{4\pi r^2}}{c}$
Where:
$P\_{sun} =2.4\*10^{16} Pa$
Plugging in our values and solving for $r$ we get:
$r=3.3\times10^{-6}m$
Meaning that the pressure from outflow of radiation will be equal to the pressure from the core of the star at that distance, which is much greater than the Schwarzschild radius. Therefore no matter will even be able to reach the singularity. I also suspect that the heating resulting from the outpouring of radiation would cause some expansion, but given the overall size of the sun it would be insignificant and would still find some kind of equilibrium.
] |
[Question]
[
I'm developing a magic system that is supposed to be pretty close to real science.
I have a spell "convert element" described as follows:
Elements are converted by adding or subtracting protons. The simplest form of elemental conversion is to drop from one element to the next lower element by number. Refer to the standard the periodic table of elements: for example from He to H, or N to C by simply getting rid of one proton from the source element. The "dumped" proton would essentially be a Hydrogen ion right? Hydrogen will be formed or consumed as a byproduct of ANY elemental conversion.
So the question: How unstable would these H be? Are they likely to suddenly explode or would that only happen if close enough to an open flame?
Or is this whole thing a completely screwy idea?
[Answer]
**It powers the magic.**
The simplest answer for converting to lower on the scale would be to say that the extra particles are destroyed to provide energy for making the conversion work.
If it's a chain reaction, each atom can provide energy to fission the next few atoms over, with the magic providing the kickstart and guiding the process. Depending how you want magic to work, that could gracefully handle unexpected elements (downconvert or ignore them, depending on atomic number) or provide occasional hazardous events when an unexpected element is present.
If you need technobabble, you could call the conversion something like "paradoxical causality", where magic shoves the energy left after conversion back through time to start the conversion, thereby preserving conservation of energy (with a minor blip in the interim).
If you wanted, you could have your process vent excess as gas. Hydrogen would be more dramatic (because firey explosions), but helium might be better (because it's safer and still gives a physical marker for where magic occurred). MAybe the basic version does one specific gas, but advanced versions can generate any arbitrary gasses?
If your magic works this way, converting the other direction probably involves ripping apart local materials and glomming them onto existing atoms. That probably means you either need to provide raw material or that you get a stiff breeze (and possibly lightnings) as local air is ripped apart and new air rushes in.
[Answer]
Building on Bleh's excellent answer but flipping it around a little, what if...
The magic's role in this was two fold.
First it temporarily nullified the idea of matter. Every element within the focus of the spell would suddenly (and without cataclysmic energy transfer) decompose into its component subatomic particles and a free-floating form of the binding energies which used to hold them together. This would create a floating ball of non-elemental soup made of unattached protons, neutrons, electrons and energy; all swirling around each other, momentarily free from the organized patterns which we call elements.
Then from that soup, the magic would extract enough of each type of subatomic particles to build the desired quantity of the element which the caster desired.
While maintaining the first aspect of the spell for all of the left over particles, the caster would now release the selected particles back into the normal universe. There, in obedience to the laws of physics, they would instantly arrange themselves into atoms of the desired element. If that arrangement required or released any energy, the magic would harmlessly draws it from or pours it into the non-elemental soup.
This is where the spell gets tricky. The desired element has been created, but the caster is now holding a ball of potential matter and it is taking all of his concentration to keep it from re-entering real space to catastrophic, potentially nuclear effect.
To safely defuse the situation, after each successful casting of the spell, the caster must extract additional elements until all of the left over pieces and stray energies are gone. Think of it as the worst molecular chemistry test that you have ever had to take, and your life is forfeit if you fail. If the caster looses control of the spell before the non-elemental zone is empty, boom!
If he fails and is very lucky, the contents and energies will happen to match a whole number of hydrogen atoms. This unlikely outcome leaves the caster surrounded by one of the most volatile gases in nature (Think Hindenburg). Alternatively, the numbers don't quite work out for an all hydrogen solution, so fusion will be needed to resolve the left overs into something real. (Think Hiroshima, only bigger).
If this is the simplest application of the magical discipline of elemental conversion, I now understand why our real world is better off without magic. I can finally give up on becoming a wizard, without any regret for what might have been.
[Answer]
A proton decays in about $6 \times 10^{39}$ years.
>
> The maximum upper limit on proton lifetime (if unstable), is calculated at $6 \times 10^{39}$ years, a bound applicable to SUSY models[.]
>
>
> <https://en.wikipedia.org/wiki/Proton_decay>
>
>
>
But your missing some things, like the electron. In that case, you're better off taking away a hydrogen atom by itself.
Even then we have some problems.
```
He - H = T(ritium)
2 e- 1 e- 1 e-
2 p+ 1 p+ 1 p+
2 n0 0 n0 2 n0.
```
Yes, that works, but you don't really get the intended product. This gets more problematic, when we get to like silicon and aluminum.
```
Si - H =Al-28
14e- 1 e- 13e-
14p+ 1 p+ 13p+
15n0 0 n0 15n0.
```
Aluminum-28 doesn't exist.
So, you would have to be able to take away different elements for it to work.
[Answer]
Let's take a simple example: you take a 12 grams diamond or 12 grams of graphite, and do your magic.
Diamond (or graphite) is made of pure carbon, and 12 grams is exactly 1 mole of Carbon atoms.
You are adding then 1 mole of protons, thus 6.022 x 10^23 protons which incidentally changes each Carbon nucleus to a Nitrogen nucles. You may think that you have vaporized your diamond (or graphite), but you are forgetting something: you are lacking 6.022 x 10^23 electrons, which is again a mole of electron!
This results in a [localized charge](https://en.wikipedia.org/wiki/Faraday_constant) of 96485 Coulomb, or 26 Ah, which is going to give a pretty good discharge: assuming the excess charge will be neutralized in 1 millisecond it gives 96 million Amps plus a decent EMP pulse...
**DON'T TRY THIS AT HOME**
[Answer]
Thanks to all commenters for the assistance. Here are my combined notes for how the spell will work. Once I actually publish the game, I will add a link below, in case anyone wants to try it out.
Convert element notes
There are several approaches to elemental conversion, but all require a common body of knowledge which is encapsulated in this spell. Therefore each method is a sub-spell, but all are learned at once in a bundle with a combined total difficulty level of 30.
The casting difficulties and magic points costs will vary (TBD)
The approaches are:
Proton Binding/Isotope, Hydrogen Binding, Alpha Decay, Beta Decay, Dematerialize
Ionize is also learned in this bundle, although it isn’t actually elemental conversion per se.
Proton Binding - Remove Proton
The simplest form of elemental conversion is to drop from one element to the next lower element by number. (refer to the standard the periodic table of elements) (For example from He to H). This can be accomplished by simply getting rid of one proton from the source element. Highly explosive ionized Hydrogen isotopes will be formed as a byproduct of this type of conversion. If you don’t want an explosion, you can dump the extra protons to the beyond using “Banish Object”. (requires an open Portal)
Proton Binding - Add Proton
The opposite process can be used to add a proton and go up a number on the periodic table. This only works if you happen to have a lot of extra protons handy. (perhaps you previously stored some in the beyond?)
Adding or removing protons from an atomic nucleus is very energy intensive
A side effect of the proton binding method is that the target element will actually be an isotope because its neutron count will not match its proton count. Isotopes may be radioactive and therefore, repeat or extended exposure can cause burns and or disease.
Isotopes can also be created directly, without elemental conversion, by adding or subtracting neutrons to a target. In the case of removing neutrons, the free neutron byproducts are themselves an ionizing radiation hazard.
Hydrogen Binding is similar to Proton Binding except that instead of only moving protons, you also move neutrons and electrons. This takes marginally more energy, but results in a slightly more stable byproduct of plain old hydrogen. It is flammable, but it won’t immediately explode, unless you are standing near an open flame. Also, hydrogen atoms can be attained by regular chemical processes or by Arrange Atoms.
Alpha Decay is similar to hydrogen binding, but is actually Helium Binding. The advantage to this technique is that it takes advantage of a natural lowering of stability, so that an element can be converted to an atomic number Lower by 2 elements, at a greatly reduced Magic Point cost. The byproduct is Helium, which is stable and not flammable. This method can not be used for Increasing atomic number.
Beta Decay is the conversion between protons and neutrons. Therefore you can either increase or decrease in atomic number, but the target element will be an ionized isotope. This is only slightly less costly in terms of MP than Proton Binding
Dematerialize is accomplished by banishing the entire source matter, then bringing back only the correct particles to produce exactly the desired element. No undesired byproducts are produced. If you are meticulous recordkeeper, you can keep track of remaining materials in storage in the beyond for future use.
Ionize
Ions are created by adding or removing electrons. Ionization greatly affects an atom's likelihood of bonding chemically with neighboring molecules. Thus an Ionization spell may result in a wide variety of unintended changes in state, solubility, corrosion, metalization, etc., often times resulting in objects turning to powder or gas.
Practical Tips for Convert Element
To practice, use readily available elements. A great practice case is N to C as both are very common, and it will be easy to see if it worked as it will convert from a gas to a dark powdery substance. You will be dumping one proton in seven. Remember, you will need to do this on millions of molecules to make a measurable change.
] |
[Question]
[
>
> *In a specialised organ, the Vesica Spirite, which in function and makeup resembles a cross between the Ventriculus and the Vesica Biliaris, the animal creates and stores potent spirits by the means of a symbiology with a species of [Saccharomycetales](https://en.wikipedia.org/wiki/Saccharomycetales) so far only found in that location.*
>
>
>
Excerpt from *Hjårdan Animaliæ*
---
Welcome to the *Most Ingenious Questions You Never Thought Of*. Today we look at the booze-rat, [again](https://worldbuilding.stackexchange.com/questions/56710). An animal aptly named for its unique defensive mechanism of storing potent alcohol in its body in order to daze/incapacitate a predator.
As mentioned in the excerpt from the widely known book *Hjårdan Animaliæ*, the booze-rat has a specialized organ called the *Vesica Spirite*, we'll call it the booze-bladder. The booze-bladder is home to a specialized strand of yeast that turn sugars into potent alcohol. In order to prevent the alcohol from seeping into the bloodstream unwanted, the booze-bladder is lined with a thick layer of mucus.
If a colony is attacked/goes hunting, the rats that get attacked by the predator will release the alcohol stored in their body into their stomach. The induction of the potent alcohols into the stomach will trigger a disequilibrium, causing the booze-rat to expulse its gastric contents thus covering itself with the dangerous liquid.
---
**Q**: How did the booze-rat evolve into the being described above?
This question is asking for a description of how the booze-rat has evolved into its current form. It does not necessarily ask for a detailed account back to the first multi-cell-organism **but** it does ask for more than a simple *because things* answer.
The term *booze-rat* has been chosen because it [sounds rad](http://tvtropes.org/pmwiki/pmwiki.php/Main/AwesomeMcCoolname). The animal in question does not necessarily have to be an actual [rat](https://en.wikipedia.org/wiki/Rat) - the animal is meant to be a [rodent](https://en.wikipedia.org/wiki/Rodent) though.
[Answer]
First, let us examine what makes [rodents so successful](http://www.auroville.org/system/file_attachments/files/000/002/361/original/Rats.pdf?1422527732).
Rats are amazingly versatile creatures, able to adapt to almost any environment they enter; this ability is derived from their sophisticated array of highly-attuned senses of touch and smell as well as their no-fuss approach to food (consuming practically anything from grains and fruit to meat and rotting scraps - the definition of easy-to-please). In addition to these characteristics, rats have an intelligence that rivals most animals of their size, giving them superior advantage when it comes to avoiding danger (or in the booze-rats case, taking it on) and successfully colonising a new area.
Even with such impressive skills, how have rats managed to appear practically everywhere on earth so quickly? The answer: Us.
Humanities excessive desire to expand our reign has seen the rapid evolution of transport; trains, planes, automobiles, rocket-ships, great oceanic freighters - they all have given man the ability to travel with a speed and effectiveness beyond belief; but this achievement would never *just* be for us, for many other creatures (cough -rats) too dreamt of seeing the world too, and we gave them the ultimate means to do so.
---
## So how has the booze-rat evolved to it's present majesty?
Our story begins thousands of years ago with the first explorers. At this time in history, most towns and cities were squat and overcrowded, the perfect breeding grounds for vermin of all sorts - namely the black and brown rats. These pesky critters happily co-existed with humans, sharing their germs and fleas, but they soon began to feel unwanted, so as the sailors boarded their shiny new ships and set off in search of new lands, they did too.
The vessels dark bowels with their vast stores of grain and rum were ideal sanctuaries, allowing for the rodents to simply sit back and relax and breed and do whatever else happy rodents do; at each new port, the more curious creatures would disembark whilst the others hung back to sample whatever strange delicacies the sailors brought back onboard, like spices and bananas and copious amounts of tobacco and wine. These are our primary *evolvutionaries*.
Whilst the fruits were easily ingested by the rats, who were growing larger and more comfortable in their surrounds, the latter had a profound effect on the few that dare drink it. Becoming groggy and disorientated, many died in the hours following; but a few hearty critters lived to drink another day, breeding to create more alcohol tolerant generations.
Ship Captains soon began to notice the un-welcomed stowaways, deciding to recruit dockyard cats as a means of pest control. This worked out surprisingly well for those felines who could withstand the oceans unpredictable swell, getting a regular and hearty feed off the vermin.
One day though, one of these cats came across a group of new generation rats who had bathed in the contents of a ruptured wine cask. Having no chance at escape in their intoxicated state, they was quickly devoured, the cat falling into a drunken stupor from their booze-soaked fur. Now incapacitated and reeking of death, the other rats moved in (not the sort of creatures to shy away from an easy meal…) In the hours that followed, as much as the cat tried to fend away the creatures who nipped and swarmed, it was overwhelmed and eaten with prejudice. It became the first time prey had killed predator on the high seas, all because of the sacrifice of a few drunk rats...
---
## From here, we fast-track our story 500 years.
Sea trade was booming; many thousands of the evolutionary rat generations have been and gone, the vermin having evolved to better withstand the alcoholic wares of the rum/wine barrels beneath deck, becoming confident enough to stand up to any small predator that came their way, having realised that by soaking themselves in booze, anything that ate them would become easy pickings for the remaining rats.
With each ship landing, more and more of these evolved rodents made their way off-deck and into new worlds, most lush with vegetation, sporting impressive vineyards and distilleries... The bigger more powerful rodent quickly overpowered any rival inhabitants, coming to dominate the environment in the space of weeks. They took residency in the vineyard and jungles, feasting on all they had to offer, regularly indulging in grapes and pawpaw and mango, fresh or fermenting, growing ever more tolerant to the effects of the alcohol produced by the various microbes on each. They evolve a partitioned stomach to separate ethanol from the nutritious fruit pulp; this waste was excreted quickly to avoid serious organ damage.
They were still subject to predatory activity and, without the safety of the ships strong alcohol, were unable to defend their nests to the extent they originally could, so rats began to "spray" one another with the excreted ethanol in a bid to replicate the effects of the wine-bathing and protect themselves.
## Forward another 500 years...
The evolutionary rats have become fully adapted to their new world environments, the vineyard/jungle dwellers thriving greatly.
The rats no longer need to spray one another; their partitioned stomach has since separated into a separate organ capable of storing larger amounts of ethanol safely (the organ walls covered by a thick mucus) that can be excreted in much the same way if it becomes too full. It is called a booze-bladder.
Predators still threaten the rats, who now possess a more specialised means of protection that better resembles the original wine-bathing. Once a predator is spotted, the older rats leave their nest to confront it, mixing the contents of their stomach and booze-bladder once attacked, causing it to regurgitate the strong ethanol over itself ("bathing") in preparation of being eaten. It's sacrifice allows for the rest of the rat colony to attack the intoxicated predator in the knowledge that due to the brave rodents actions, they will eat as kings.
[Answer]
Harry David posted [this](http://www.ratbehavior.org/vomit.htm), clearly explaining that rats can't vomit. They lack the required neurology and muscle coordination to overcome their esophageal sphincter, and expel stomach contents through the mouth. They have instead evolved a sophisticated avoidance measure, by only eating small amounts of new food. If it makes them sick they'll use a keen sense of smell and taste to never eat it again. And it appears to be true of all [rodents](http://www.smithsonianmag.com/smart-news/why-rodents-cant-throw-up-in-case-you-were-wondering-25707720/). Therefore, whatever the evolutionary cause of this is, it must predate the modern differentiation of rodents to a common ancestor. This effectively means changing the way rodents evolved outright, which doesn't really fit I'd argue since they would no longer be rodents surely.
Hopefully I wont bore anyone with taxonomical classifications, rodents are part of the [Rodentia](https://en.wikipedia.org/wiki/Rodent) order who's earliest known fossils come from the Laurasian supercontinent some 66million years ago (yeah they're really old).
Sadly this makes them a rather different animal from the skunk or zorilla as those are part of the [Carnivora](https://en.wikipedia.org/wiki/Carnivora) family. Their fossil record seems to start about 42 million years ago.
However, there exists a simple fix to still want to call the animal a booze rat, and that is its colloquial name. I would strongly suggest though that this animal be part of the Mephitis (skunk) family. From there its anal sac's rather secrete an ethanol based substance (Mephitis Ethanolus, see what I did there).
A good example of taxonomical errors like this is the [African striped skunk](https://en.wikipedia.org/wiki/Striped_polecat) (AKA the zorilla), which is in fact not a skunk at all, but is more closely related to the African weasel. It is thus not part of the Mephitis classification.
Now you have an ethanol skunk known as a 'Booze Rat'. If you've ever drunk 80-100% alcohol you'll know it burns, and would irritate the eyes and nose. How intoxicating a few milliliters would actually be is debatable, but it may be enough to ward off predators. Rather than anal glands the animal could have glands elsewhere like the [Slow Loris](https://en.wikipedia.org/wiki/Slow_loris), where the glands are located on the elbows.
This would allow the the Booze Rat to cover itself, especially if the glands were around the neck. It could the spray backwards covering itself.
Anal sacs make more sense though since all Carnivora species have these sacs. The booze rat name could then come from a rat/weasel appearance and the fact that people catch the rats and use their sprays to get drunk. Yeah that grossed me out just typing it.
[Answer]
# Once upon a time there was a rat with a yeast infection and a bit of a dicky tummy.
He wasn't particularly sick and managed to stay in good condition. Though he had to eat and drink a bit more to keep himself going day to day, he still survived when the dogs came through. Initially as his infection passed around the group some died, but some survived. Those who recovered from the infection remained ordinary rats. Some like him who neither recovered nor died, averaged better outcomes from close encounters with predators, they lived slightly longer, had more young. They passed the infection on in turn to their young, who also adapted to live with it, slightly better than their parents had.
It's something that ultimately has to be actively selected for to be passed on. Rats have very fast generations, a beneficial adaptation could be passed rapidly to a large percentage of the next generation. Something like this that is primarily beneficial for dealing with predators, would help a group near the peak of the predator curve on the [predator-prey population graph](http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/environment/populationsandpyramidsrev5.shtml).
[Answer]
There is a multistage but logical process by which the Booze rats evolve alongside their favorite food and their archrivals.
There is a plant and an early mammal. For all intents and purposes, the consumption of the plant at early stages by the mammal keeps the population of the plant in check.
1: The plant develops a toxin which prevents the mammals from eating it during the reproductive process. It starting in the seeds but eventually develops in the sprouts, unripe fruits, and young plants. Older plants and ripe fruits are non-toxic. This food shortage causes the species to diverge into two mammals. The strong proto-cats eat the high caloric fruits of the plant during the summer, the best parts of the body in the fall, and the proto-booze-rats during the winter and fall. The proto-booze-rats become scavengers and adopt a diet which consists of low caloric food scraps from the body of the plant or the discarded parts of their siblings. These crappy foods have high cellulose or hard to breakdown protein content so, a second, high-pH stomach is evolved to allow a specialized bacteria to help breakdown these foods before the main stomach. Multi-stomached herbivores are actually quite common.
2: An initially parasitic yeast begins to infect this bladder converting sugars to alcohol. To combat this, the rats learn to metabolize alcohol, additional mucus forms to reduce absorption through stomach walls, and the initial bacteria become more resistant. If the alcohol concentration gets too high, they learn to regurgitate to preserve the symbiotic relationship with the cellulose digesting bacteria.
3: The booze-rats realize they can eat the plant when it is toxic now. Fermination in their alcohol bladder (again their first stomach) causes the toxin to breakdown. Their diet changes because they now have a high caloric food that is poisonous to the cats. This diet quickly kills off the cellulose eating bacteria but at a very quick rate (for evolution) the rats stop regurgitating at low to moderate alcohol concentrations, dramatically increase alcohol metabolism, and their bladders increase in size as the fermentation becomes desirable.
4: A cyclic pattern occurs which is very favorable for rapid evolution. The rat population booms as they eat their seemingly infinite food source. The cat population booms as they eat the rats. The plant population dwindles as they can't reproduce. Most of the rats die off from predation and from starvation. Most of the cats die of starvation. The plant population booms as it reproduces quickly with low rat population. We repeat. Only the most toxic plants survive as the rats know not to eat them so they rapidly become more toxic. The cats evolve to become successful exclusive carnivores. The rats evolve to be able to handle more and more toxic plant material by storing more and more alcohol in their stomach. The rats retain their omnivore classification as they become cannibalistic during food shortages.
4: The rats learn to vomit again. Whether from the toxin or the alcohol, the fluid in the stomach of the rats is so strong the rats learn they can incapacitate and/or kill the cats by vomiting on them. The cat population decreases in a time of ample plant material but this backfires. Rats feed on the seeds which were once left alone so the level of toxins in the bladder become more fatal. The toxic plant population stops having an evolutionary imperative to become more toxic and, instead, becomes less toxic over time as the most toxic plants are targeted for consumption. Only the strongest, stealthiest, and fastest cats can avoid being incapacitated.
So: The now fully evolved booze-rats feed on the fruit of a relatively non-toxic plant that relies on rapid reproduction and growth to survive. They store a large portion of this in their first stomach to allow it to ferment. They defend themselves from the carnivorous cat creatures by vomiting this alcohol on them but it is less effective than it used to be.
TLDR: Second stomach forms to digest cellulose. It becomes alcohollic due to infection. Infection turns out to be benefit as fermentation breaks down poisonous food. Evolve to have high tolerance for alcohol and poison. Evolve to vomit poison and alcohol to protect self. Poison plant dies off but alcohol vomit is still useful.
[Answer]
**Most likely it didn't, it is probably genetically engineered**
Alcohol has a very strong smell and taste, as it is highly volatile. Predators typically possess a keen sense of smell. They should quickly learn to simply avoid the booze rat - just like they learn to avoid eating anything poisonous. Even if they for some reason can't sense alcohol - because their scent receptors don't respond to it - they would still learn what a booze rat looks like, and simply would not hunt it.
If they haven't, and the booze-trap still works, it means that the introduction of booze generation into the rat's body was very sudden, and very recent.
[Answer]
**They get it from their food**
You don't really need a booze-bladder. A lot of animals pick up toxins from their food, and end up storing them in their body. Some animals do this unintentionally, like sea lampreys and poisonous heavy metals, and some do it intentionally, like poison dart frogs and monach butterflies.
The pen-tailed tree shrew (*Ptilocercus lowii*) spends almost every night feeding on the highly fermented nectar of the bertam palm, consuming the equivalent of about 10 to 12 glasses of red wine per night. Every night. They eat other things like insects, fruit, and geckos, but they drink a lot of fermented nectar. And never get drunk.
So, you can get a scenario where your ancestral booze rat starts eating a highly fermented food item, mostly because it tastes good and is high in sugar, and over generations its metabolism begins to evolve to tolerate higher concentrations of alcohol in its system. Until you get booze rats who are basically walking around with a blood-alcohol level that would knock any other animal flat on its back. Predators that eat the booze rat end up getting so sick and drunk they usually don't survive, and predators that survive eating a booze rat once usually don't repeat the act.
And maybe the booze rat starts harboring fermenting bacteria from the food it eats in chambers of its gut similar to a ruminating mammal. And when a predator goes to eat one the booze-rat upchucks its last meal of highly fermented foul-smelling food into the predator's face, at the same time splattering it all over the booze rat both putting the predator off its meal and making the booze rat look and smell awful, in the same way that an opossum playing dead starts drooling and leaking foul-smelling fluid from its anal glands to make a predator too grossed out to eat it.
[People have taken to making twice-fermented alcoholic beverages out of booze rat vomit. Because of course they do.](https://en.wikipedia.org/wiki/Kopi_luwak)
] |
[Question]
[
One of the great misconceptions of history is the horned helmets of vikings. This is in fact untrue, they didn't have horned helmets. But horned helmets were a thing thousands of years before the vikings. And have been used from time to time.
**What reasons would an army have for putting horns or antlers on their helmets? What are the benefits that they apply? What are the cons?**
[Answer]
Horns and other decorations on helmets served many different purposes over the centuries.
The initial reason for decorating the helmet is to make the wearer look larger and more impressive and to provide a psychological boost against the enemy. Large horsehair crests on Mycenaean helmets were meant to inspire terror. A small incident in the Iliad has Hector frightening his son by entering a room still wearing his helmet, as probably the best known example.
Later the use of decorations was to provide identification of leaders in battle. In the Roman legions centurions wore traverse crests on their helmets to identify them in the field. Japanese leader's helmets from the Age of War could have fantastic decorations to mark high ranking leadership.
[](https://i.stack.imgur.com/tPuk8.jpg)
*Centurion*
[](https://i.stack.imgur.com/dbjPv.jpg)
*Samurai leader's armour*
Clear identification of the leadership is the most obvious benefit from decorating the helmet, but the extra weight could unbalance the helmet, make it difficult to wear or to user to move their heads and provide places to catch an enemy blade. A "normal" helmet provides smooth surfaces to provide a glancing blow to a blade or bludgeon, rather than things to trap or redirect blades, potentially giving the enemy a means of providing a damaging blow. Of course, this also provides a means for the enemy to identify the leadership, and if they focus their attacks on eliminating identified leaders you could be in some trouble.
In general, helmet decorations are as large as practical, and reflect the role of the wearer. A Roman centurion's transverse crest is not so large that it affects his performance in the field, since he is embedded with the troops he leads. A Japanese general has a much more elaborate helmet, because in general, he will not be directly engaged in combat, but rather sitting back far enough to observe and direct the action.
[Answer]
All of the animals whose heads are adorned by large horns, are strong and dangerous creatures. Especially in pre-gunpowder ages, the possession of some dead animals' horns by a human was proof of the strength and skill of that human.
It is a status symbol, but it is also proof that its owner's status is deserved.
The horns trumpet... "Look what I killed!"
[Answer]
In close combat situations, a headbutt with a spiked (as opposed to *horned*) helmet has the ability to debilitate the opponent, and in some rare cases, kill him.
Note that I am talking about **spiked** helmet. Of course you are free to shape the spikes as horns, but I would wager the best shape for such a helmet (designed for goring the opponent) would be to have an 8 inch long spike on the forehead part of the helmet, facing horizontally forward (akin to a unicorn's horn).
Helmets with animal-horn fashion protuberances were meant to shake the self confidence and gallantry of the opponent make him psychologically weaker.
[Answer]
So, a lot of people have already answered talking about various reasons like looking impressive, showing rank, bragging about hunting (Early Greeks did a similar thing making helmets out of boar tusks)impersonating animals/monsters or having horns for ceremonial reasons (like the Celts).
But mainly I'm just commenting to let you know that the misconception about Viking helmets being horned is down to flaws in Victorian Archaeology, not Skyrim. Sorry if I'm repeating anyone! Just thought you should know!
Also, in a fantasy scenario, an uncivilized culture may use horned helmets as horns for similar purposes as animals that have horns (i.e. fighting for mates). Having horns on your helmet can get in the way though/ get caught on things/ be used as handles to shake your head about so not always practical in battle!
[Answer]
We often depict Vikings with horned helmets because it makes them look more intimidating - wouldn't it be reasonable to suppose, then, that an army might put horns on their helmets for exactly that purpose? A scared enemy is a weakened enemy.
Alternatively, I could imagine that branching horns - like a stag's - could serve a battle purpose by catching an opponent's sword on the rare occasion that an attacker chose to swing downward at the soldier's head.
[Answer]
Alright I haven't seen people explain the biggest problem with horned helmets. You know what happens when someone hits one of those horns very hard with their weapon?It's like someone decided to jump and hang on said horn. You get a tremendous pull to the side.
Now if you're lucky that means your helmet comes off. Not a great thing in battle. Now if you're not as lucky, then it means the helmet will cut into your shoulder and neck. But if you're really unlucky you simply break your neck. Actually that's not so much unlucky as that it's likely.
So that's why frontline troops never wore horned helmets. Sure there's probably some rare exception but by and large, none. As vaguely mentioned above, horned helmets are a relatively modern invention. Operas like those of Wagner about Germanic folk tales are a likely origin. They needed them to look imposing from a distance and preferably relatively cheap. Animal horns was an easy way to get that.
Reasons to use them have been mentioned extensively in other questions. You look imposing. You believe you invoke the animal's spirit for strength or protection. Identification with ir without the associated fear that produces. In reality you want a helmet to be domed and smooth. That way a blow has a good chance of glancing off relatively harmlessly. And not get stuck behind a horn, breaking your neck.
] |
[Question]
[
In the creature type I asked about [in my last question](https://worldbuilding.stackexchange.com/questions/38213/can-an-insectoid-race-have-a-flexible-exoskeleton), there are some lower caste members who seem to have metal limbs. However I don't think they would waste resources to build the legs for lower-caste-members.
I do know that it's considered a privilege if they do the work, but I know for a fact they have trouble getting food and are not as healthy. So the question is, is it reasonable that they could have lost their limbs due to malnutrition?
[Answer]
There are conditions where malnutrition can be directly connected to neurophaties. For example:
* due to lack of vitamin B1 like Beri-beri is responsible for a legs polyneuropathy which causes among other things gait disturbance.
* B12 and B6 deficiencies can be the cause of migraines and seizures and in extreme cases permanent damages to peripheral and central nervous system
The list would be extremely long, whole books are written about it. To make it simple in your case the "loss" of a limb can be not that the limb falls off but that there is an **impossibility or difficulty to use it due to nervous system damage.**
The situation can be directly caused by malnutrition but more often than not there are conditions caused by malnutrition that can, in turn, affect a limb (think diabetes). And also its not just malnutrition in the subject but it can be due to mother malnutrition during pregnancy.
Obviously this would be derived from humans, I don't think there is real research on insect malnutrition, which can be a good thing because it gives you a lot of room to move.
You can resolve the economic problem of "if you have the money for a mechanical limb then why not just buy better food" with the mechanical limbs being built with items discarded by the rich, being outdated limb models or even that some particular food necessary for good health in the species is so scarce that its price is actually higher than a mechanical limb.
If this element was available to everybody in the past it can be that due to an actual decline in its quantity overtime but, as it happens, could also be that the quantity of it stayed the same while the population increased dramatically so the price skyrocketed as demand increased.
You can also build your society in a way where the poor conditions of these "people" force them into jobs for what mechanical limbs become necessary/ advantageous and are actually fitted on them by the company/ corporation/ government. In this case you could add poverty onto poverty by keeping their salary low because the organization doesn't give them property of the mechanical limb and they "rent" it through a deduction in their already low pay.
The mechanical limbs could even be taken back by the organization when the individual cant work anymore or dies and re-fitted on a younger worker that was just hired.
[Answer]
If the cost to make a metal limb is lower than the cost of food then your society has some issues, but putting that aside:
Many insects are willing to and capable of tearing off limbs to escape predators. Spiders, some flies, and even beetles would rather lose a leg and live to fight another day than be caught by a limb and fed to a hungry chick.
So your starving lower castes? It makes perfect sense for them to tear off their own limbs in order to eke out a few more days of life. Not only do they no longer have to supply that limb with nutrients they also get a tasty tasty calorific package, and if the technology exists to replace the limb then why not use it?
Prionic disease is an issue if others are feeding off their limbs (say they sold a leg to a soup kitchen in order to pay the rent that month), but in the cases of autophagy (eating themselves) it's not too much of a problem. This also depends a lot on your creature's reaction to trauma: If losing a limb is likely to make them die of shock or bleed out then this is obviously not a viable survival strategy.
Obviously, if these starving and desperate souls survive the circumstances that drove them to eat themselves, then they might be able to scratch together enough resources to replace their missing limb. Or maybe some kind soul just gave them mechanised limbs and a gun and sent them off to pillage alien colonies.
[Answer]
Self-cannibalism or autophagy normally isn't a very efficient way to feed yourself. If it's attached to you then it's easier for your body to re-absorb most of the energy leaving a dry husk.
There is another option from the real world.
**Disease**
[](https://i.stack.imgur.com/MCMff.jpg)
<http://io9.gizmodo.com/there-may-be-a-disease-that-makes-an-octopus-eat-its-ow-1694165746>
>
> The best guess, today, is that this behavior is the result of some kind of infection — although people don't know what the infection is. The disease probably attacks the nervous system, causes the octopus to eat itself in a thoroughly horrible way, and then kills the octopus off.
>
>
>
There are even real (and horrifying) human diseases/conditions which can cause humans to chew off their own fingers and lips. I'm not including a picture for that one, google "lesch nyhan syndrome".
So an option is that poor/sickly members of your society are more likely to succumb to a disease which sometimes causes them to chew off their own limbs.
(perhaps the disease causes such pain in a limb that sufferers often chew it off)
[Answer]
It's certainly possible in theory. In a way it's what mammals already do, in times of plenty we build up fat reserves and then when food is scarce we burn those fat reserves, essentially digesting ourselves, to stay alive.
If the insect species were capable of regrowing lost limbs then it may have a similar function where in times of famine they consume their own limbs (or feed them to their family) and do not regrow them until food is plentiful again.
Most likely they would "digest" most of the leg from the inside out first reclaiming as much valuable nutrition as they can, then finally the leg would fall off by itself and then be eaten to reclaim as much as possible of the bits that could not be digested from the inside.
[Answer]
An alternative explanation could be that this species by nature does not have these limbs at all. Much like the Daleks, they latched on to the idea of prosthetics; for the lower castes this means the (relatively crude) metallic version, while the upper castes can afford the more refined, bio-engineered limbs.
[Answer]
If the specialist limbs are heavily fortified with materials that are otherwise useful to fulfilling the creatures dietary requirements, then I can easily see a malnourished creature consuming the specialty limbs.
Similarly, if possessing the limbs required burning more metabolic resources than otherwise, then shedding the limbs in a time of shortage could be possible.
These are especially true if the limbs can be regrown when food is plentiful again.
] |
[Question]
[
Suppose there's an earth-like planet, perhaps even modern day earth itself - and at one point in time, it began to be bombarded by a continual stream of Electromagnetic Pulses.
For the sake of simplicity let's say that the EMPs are coming from a set of cloaked alien satellites orbiting the planet, and all areas are being hit at least once every few seconds.
The EMPs are just strong enough to ruin a modern-day power grid and make modern-day electronics inoperable outside Faraday cages.
The question is both about the society's coping mechanism (assuming they have hundreds of years to adjust) and the environmental effects, but I'm far more interested in the latter.
I believe computers can be redeveloped using Fluidics or something to the effect, and until long range communication can be re-established most of the world will find itself divided into city-states connected by steam-powered trains.
I have not found any evidence indicating that such EMPs will be harmful to humans, but there's barely any info on how it would affect the rest of the environment.
Is this scenario feasible, or did I miss some fundamental change here?
[Answer]
If you're not concerned with the aftermath of the initial attack, the answer is fairly simple: Electronics would all be shielded by then. In fact, the new smartphones and other portable electronics would probably be charged by induction loops leeching off the EMP.
It should not have much effect on the environment, except possibly some migratory birds getting a little lost.
[Answer]
Damaging the grid is considerably easier to do than the level requiring a Faraday cage to protect electronics.
The grid is so susceptible to EMP because of the long transmission lines. EMP is a pulse where you measure the strength in volts / meter, i.e., the longer the run, the higher the voltage available to do damage. The grid can be protected at a reasonable cost by installing high speed switches that dump the pulse to ground to protect major components. The estimated cost to protect the most of the US grid is about $20 billion. Also note that the US grid is partially protected against EMP, it is not an all or nothing approach. Other nations are better protected or less protected than the US grid.
The US military protects their grid and electronics just fine using both published and classified methods. A friend of mine works on some of the classified methods for protecting electronics and that is all I know about it, it is classified. I assume other national military are similar in this regard.
Electronics tend to be susceptible because the voltage require to damage them is quite low and even a tiny fault typically ruins the device. However, since the devices are small, a weak EMP is often fails to destroy electronics since voltages are also low. Vacuum tube based systems are generally unaffected as voltage the spikes simply overheat the active components for a short time, but not enough to damage them significantly.
A Faraday cage is effective protection and not expensive. So electronics would be used and installed inside Faraday Cages. There other ways to protect electronics too, these methods would be also used.
So, in a world where EMP was a daily occurrence, things would simply be designed to survive the typical EMP. In our world, since EMP is rare, we often don't protect against EMP.
EMP levels required to damage humans and other life directly would have to be extremely massive as the field levels are non-ionizing. In theory you could make an EMP strong enough to harm people directly, but the power levels would be insanely high. Remember that humans and animals have been exposed to very high level of EMP by close proximity to nuclear weapons without harm (from EMP) and we routinely expose humans to high magnetic fields in MRI scans without harm.
At the level of EMP you propose, wider environmental harm is nonexistent. Solar flares have the same effect and the general environment is not affected by large solar flares. [The Carrington Event](https://en.wikipedia.org/wiki/Solar_storm_of_1859) would be a pretty major disaster today because so much of electronics, etc. is unprotected. But such events are thought to occur on the average of once per 500 years. Note that no biology or environmental damage was noticed in 1859. There are no unexplained problems during earlier historical natural EMP events either.
I just remembered a humorous account relating to very strong magnetic fields. [Andre Geim won the Ig Nobel prize for levitating frogs in a magnetic field](http://www.slate.com/articles/business/how_failure_breeds_success/2014/05/nobel_prize_in_physics_andre_geim_went_from_levitating_frogs_to_science.html) the field strength was 10 Tesla - this is nearly 1 million times the strength of Earth's magnetic field (25-65 microTesla). The frog was mot harmed.
] |
[Question]
[
Suppose there was a disease that caused accelerated healing in the host body during incubation. Once symptoms appeared, the initial advantage was replaced by the real, negative purpose.
*How realistic would such a disease be? Are there any functions for which this behavior would be particularly well-suited?*
One idea I have is the disease is based on plant spores that grow inside the host, accelerating healing, and eventually sprout into plants that use the host as fodder.
[Answer]
This would be unlikely, but not impossible. The biggest challenge is how to accelerate healing.
I envision this disease as being very species-specific, and it will need to have at least two different phases. Perhaps a parasite would be an ideal candidate, rather than a bacteria or virus.
First, let's talk about how healing works, and then we can talk about an evolutionary pathway for the disease.
# Healing
[Healing in humans is very complicated](http://en.wikipedia.org/wiki/Healing). The "simplest" healing is repair to a cut or scratch. But there is also inflammation repair, fighting diseases, replacing necrotic tissue, etc. Our disease agent would have to either co-opt this process, or perform its own form of healing. Since humans (and mammals in general) have been evolving and perfecting our healing process for many hundreds of thousands of years, I'm leaning towards a custom healing process.
For example, our disease agent may be able to reconfigure arbitrary cells into stem cells, and then use those cells to patch damage. Our disease agent may also come with a slew of antibacterial and antiviral compounds, which is releases into the body. Other healing methods are possible.
# Life Cycle
The problem that we have is we need a disease that has two distinct phases: a healing phase, and a hurting phase. Normal bacteria and viruses are generally not complicated enough to support this distinction. Parasites, on the other hand, are.
I envision the first phase of our disease agent as being a slow reproductive journey to a "critical mass" of disease agents. Then, after it reaches critical mass, it switches to an attack mode to aid distribution of the disease agent.
But how could something like that come about?
# Evolution
I envision an evolutionary pathway as follows:
First, we have a parasite that, for its own protection, naturally evolves antibiotic and antiviral compounds that it releases into its host. This is advantageous because, not only does it protect the parasite, it also benefits the host, which makes the parasites home that much more resilient.
However, this poses a problem for the parasite, as the healthy host tries to fight it off, and it is unable to spread as easily. The parasite evolves to include an "attack" phase, where it cuts off its antibiotics/antivirals and initiates an inflammation response that causes the body to attack itself. This allows a rampant breed cycle that causes the parasite to shoot up in numbers, and when other humans try to help our victim, are spread via touch or water contamination.
Over time, the parasite perfects the healing routine. This is an evolutionary advantage, because a healthy host gives the parasite mobility, and limits any competition for the host's resources when the parasite goes "critical".
---
There may be other ways to explain this type of a disease, but this seems to me like the path of least resistance.
[Answer]
What about a disease that speeds up your metabolism and the literal rate at which your cells grow and die? Maybe at a 5:1 or 10:1 ratio greater than normal?
So you would get accelerated healing as a side effect, but you'd need to eat a ton (possibly causing malnutrition after a while) and you'd rapidly age into becoming elderly, along with all the fun diseases you get from that (organs growing weaker, cancers, heart failure, etc). All of which are magnified by the fact that you can't get enough food, so generally you're dead within 3-5 years.
One side effect I don't have a great solution for is presumably you'd also need more oxygen, but I could be wrong about that.
[Answer]
Might be feasible as an auto-immune disease. Virus infections and auto-immune diseases are linked together. The virus starts of as semi-benign virus that stimulates the body's healing functions (I'm less sure on this part, genetic engineering of virus's that can cause healing of the heart to prevent heart failure is a valid field of research in the UK, but that is very specifically engineered).
Here : <http://www.ncbi.nlm.nih.gov/pubmed/14596882>
>
> I hypothesize that human chronic autoimmune diseases are based on infection of autoreactive B lymphocytes by Epstein-Barr virus (EBV), in the following proposed scenario. During primary infection, autoreactive B cells are infected by EBV, proliferate and become latently infected memory B cells, which are resistant to the apoptosis that occurs during normal B-cell homeostasis because they express virus-encoded anti-apoptotic molecules. Genetic susceptibility to the effects of B-cell infection by EBV leads to an increased number of latently infected autoreactive memory B cells, which lodge in organs where their target antigen is expressed, and act there as antigen-presenting cells. When CD4(+) T cells that recognize antigens within the target organ are activated in lymphoid organs by cross-reactivity with infectious agents, they migrate to the target organ but fail to undergo activation-induced apoptosis because they receive a co-stimulatory survival signal from the infected B cells. The autoreactive T cells proliferate and produce cytokines, which recruit other inflammatory cells, with resultant target organ damage and chronic autoimmune disease.
>
>
>
Assuming there is some truth behind the above hypothesis, then it is completely realistic that an auto-immune disease can be triggered by what was once a benign virus. It gives a period of healing / benign effects, before it goes and infects the B lymphocytes mentioned above...this triggers an auto-immune disease which quickly switches it from a benign virus to a system wide fight for survival.
[Answer]
One potential approach is to start from the assumption that the human body is continuously held in a miraculous balance. Accordingly, our systems are designed not to disrupt that balance except for extreme situations. Fever is an excellent example. We don't mess with the balance of homeostasis until our immune system decides it really can't do anything without breaking that balance.
It would be reasonable for an organism to come in and begin slyly telling the system that it can actually go a little beyond the self-imposed limits on healing rate. The body thus heals itself faster, and feel pretty good about it.
However, the entire time it is being walked off of its balanced state by the organism. Finally, when the body is markedly off balance regarding healing, the organism shifts modes to fully infect the host. If the host had been healthy, the body would have repelled its attacks without effort. However, now that its healing mechanisms have driven some of its subsystems off balance, they're not in a condition to repel the organism.
I seem similarities between this and some drugs which make you feel bulletproof, because your body is no longer trying to hold itself to such a rigorous balance. However, long term usage leads to tremendous health problems as being off balance for that long takes its toll.
[Answer]
Something like a cancer might fit this.
In the beginning of the infection the cells replicate very quickly and cause healing. But there's a geometric progression, where the cells are reproducing to quickly, and the infection with them. After a while the body begins to be overwhelmed with tissue, and organ damage begins. All of this is still stage 1.
When the disease has replicated itself enough, it causes the cells to rupture, and becomes a hemorrhagic pathogen, like Ebola.
Instead of being a virus, it could also be a spore that enters a cell, and reproduces when the cells divide. When the spore matures is bursts the cell and heads toward the surface. When it reaches an exit from the body (mouth, nose, eyes, ears, wounds, etc.) comes in contact with oxygen and then it releases new spores into the atmosphere.
[Answer]
The disease could have up to 3 stages, a 'healing' stage, a 'dormant' stage, and an agressive 'attack' stage.
The healing stage could be as simple as the bacteria producing antibiotics or acting like a white blood cell and destroying other pathogens.
Once there is a critical mass of the pathogen, it would go into a 'dormant' phase, where it reproduced, but produced no symptons. The host would return to normal, without any benificial or negative side effects.
Once it reaches a secondary critical mass, it could go into an insane 'attack mode', suddenly producing toxins and attacking cells.
The dormant and attack stages aren't really neccasary - the disease could kill the host through sheer reproduction - the host would die simply because there is more disease than host.
[Answer]
**Or they can increase metabolic rate to make their host eat, grow and move more rapidly to incubate them before the host develops an immunity.**
There's thousands of parasites out there and most of them have a thing in common; they change hosts to survive. If you parasitise a host chances are that the host will die and the disease with it. Spreading themselves is paramount to their survival. But for a disease to spread quickly from one host to another it would need to replicate fast, to be numerous enough to spread and to not give the host time to adapt and kill them before they can spread. So as you mentioned they don't manifest bad symptoms right away. An increase in metabolism is good, the host gets hungrier and more active, for us humans that's a good thing it means we're healthy. So it tricks us into treating ourselves so that it can get the perfect breeding ground to hop onto someone else.
A population suddenly gets healthy and active, they're excited and share with their friends. Little do they know the sneaky disease is spreading its good influence.
] |
[Question]
[
Imagine a species (the cause is largely irrelevant - could be alien meddling for all I know) that is *Homo sapiens* in all except one detail: they have additional organ which is kind of like gills - allowing them to breathe under water.
Note that the species has *no other* aquatic adaptations:
* can't survive high pressure (so no deep diving)
* can't echolocate or see better in water (not quite sure what the major benefit of that would be...)
* can't swim in colder water than real humans
* can't drink salt water anymore than humans (so can't settle on sea shore without access to freshwater)
* can't swim any better than humans (so no intercontinental voyages without sea vessels - they aren't any faster at swimming and this need a supply of fresh water for any swim longer than a day as per prior bullet; BUT they can cross large lakes or small patches of sea space without rafts, by swimming underwater).
What would be the main difference in how such a society would develop compared to humans (on Earth, so same exact flora, fauna and geography and weather) in a time period of late paleolithic to early feudal society?
To import the detail from the comment:
* there are NO non-gilled humans. They are ALL gilled.
* any assumption on whether gilled humans would have trouble surviving inland **must** be referenced with actual information from real Earth biology
* There may be other non-gilled hominids (Neandertals, *Homo erectus*), but (unless you prove the inland difficulty theory) they would have as much difficulty avoiding extinction as they had at the hands of non-gilled humans in real history.
[Answer]
There are one or two chronological things which I should like to clear up before proceeding here.
[This graphic](https://upload.wikimedia.org/wikipedia/commons/c/c9/Human_evolution_chart.svg) shows the geographical distribution of members of the genus [*homo*](https://en.wikipedia.org/wiki/Homo) over time:
[](https://i.stack.imgur.com/FUNfJ.png)
Image courtesy of Wikipedia user Conquistador under [the Creative Commons Attribution 2.5 Generic license](https://creativecommons.org/licenses/by/2.5/deed.en).
It shows that [*homo sapiens*](https://en.wikipedia.org/wiki/Human) never existed during the same period as [*homo erectus*](https://en.wikipedia.org/wiki/Homo_erectus), and was only briefly in the same location as [*homo neanderthalensis*](https://en.wikipedia.org/wiki/Neanderthal). In fact, the former was active mainly in Asia, while the latter lived in Europe. I think it might be best to leave *homo erectus* out of it for the time being.
We also have to determine just when *homo sapiens* first developed gills. This is actually very important. If the gills appeared within the last 500,000 or so years, then
1. *homo neanderthalensis* would not have had gills
2. Other members of the genus *homo* could have expanded further
You did say that it is only a minor point as to whether or not other members of the genus *homo* had gills. I disagree only because that would influence just where these people (as I'll call them) could have gone. The [Out-of-Africa](https://en.wikipedia.org/wiki/Recent_African_origin_of_modern_humans) theory says that *homo sapiens* (Not \*all members of the genus *homo*) came out of Africa about 200,000 years ago. Other members of the genus *homo* may have already left. [Here's](https://en.wikipedia.org/wiki/File:Map-of-human-migrations.jpg) a graphic of *homo sapiens*'s travels:
[](https://i.stack.imgur.com/UYYPv.jpg)
Image courtesy of Wikipedia user Chronus under [the Creative Commons Attribution-Share Alike 3.0 Unported license](https://creativecommons.org/licenses/by-sa/3.0/deed.en).
The dashed lines are important because they are *hypothetical* migrations - in other words, while there's evidence in the form of fossils for the others, there is not yet a lot of evidence for the dotted line migrations. If, say, *homo neanderthalensis* had gills, Neanderthals could have braved the trek from Scandinavia *over the North Pole* (not incredibly plausible, I'll admit) and to the Americas, thousands of years before *homo sapiens* got there via the [Bering land bridge](https://en.wikipedia.org/wiki/Beringia). That's quite important.
---
Okay, I'll get to the relevant part. You don't mind a timeline-esque approach to this, do you? I'll go with this format for now. Let's set a date for the gills of about 600,000 years ago.
### 600,000 years ago
[Homo heidelbergensis](https://en.wikipedia.org/wiki/Homo_heidelbergensis) is the species that first gets gills.$^1$ At this point, *homo heidelbergensis* lives in Africa, although it's about to venture outwards into the world. It soon does, and reaches southern Europe and western Asia with ease. In *this* world, though, it may be easier to cross bodies of water. With gills, *homo heidelbergensis* maybe able to go to many places before *homo sapiens* or *homo neanderthalensis*. It may be possible for them to [quickly cross the Red Sea](https://en.wikipedia.org/wiki/Recent_African_origin_of_modern_humans#Movement_out_of_Africa) at a narrow point, thereby making the Arab world open. The Persian Gulf is also a little less scary, although I think that both bodies would only be crossable at narrow points, likely close to their origins.
### 300,000 years ago
*Homo heidelbergensis* has now ventured throughout eastern and central Europe. Crossing the [Dardanelles](https://en.wikipedia.org/wiki/Dardanelles) or the [Bosphorus](https://en.wikipedia.org/wiki/Bosphorus) was a lot less challenging, so more people can come through Turkey and into Europe. Around this point, *homo neanderthalensis* may be evolving from *homo heidelbergensis*. However, the latter could have pushed beyond the places that *homo neanderthalensis* may have gone in our world.
### 150,000 years ago
*Homo neanderthalensis* is in its prime. All of Europe may be open to it, including the British Isles (forget the Channel Tunnel!). Scandinavia is easy to get to, and islands near the Baltic Sea require no skill whatsoever. I won't go so far as to say that Iceland is a possibility (it isn't), but it's much easier to get through the northern parts of Scandinavia and Russia. At around this point, the North Pole crossing becomes an interesting idea.
Neanderthals would have had to get lucky to get across the North Pole, but they may have had some help. The Earth has entered the [Wolstonian Stage](https://en.wikipedia.org/wiki/Wolstonian_Stage), a glacial period stretching from about 350,000 years ago to 130,000 years ago.$^2$ This means that an intrepid group might have been able to make it up north. Any water along the way - which there probably would be - would be a trivial obstacle for the gilled explorers to reach.
### 100,000 years ago
*Homo sapiens* begins to arise back in Africa. The Red Sea crossing idea now holds for these people, and they will likely undergo that journey. They're starting a journey into Asia, which *homo erectus* has likely left (metaphorically, that is - they've died out).
[*Homo floresiensis*](https://en.wikipedia.org/wiki/Homo_floresiensis) arises. This peculiar species - believed by some to be a sub-group of *homo sapiens* - stands three and a half feet tall, and has a small brain size. There's a large debate going on as to whether or not these people were *homo sapiens* with a growth disorder or a unique species. Either way, we know that roughly 100,000 years ago, there are people - of one sort or another - in Indonesia.
The cool thing about Indonesia is that it's made up of many, many islands. I'd welcome the input of any and all Indonesians on this part, but - and this may be a justified theory - *homo floresiensis* may have been able to cross many years earlier. Well, the ancestors of *homo floresiensis*, at least. Gills permit swimming for extended periods; the extent of the periods depends on other characteristics of the creature. Still, it is fair to say that there may very well have been people on Indonesia before 100,000 years ago. It is thought that *homo floresiensis* may have reached Indonesia by boats. Gills mean that boats are unnecessary in some parts. Therefore, an earlier crossing is possible.
It may be a stretch, but I think it is certainly possible that these "hobbits" may now make their way into Australia. The outback is still as much a desert as ever, but Australia is by no means a wasteland. *Homo floresiensis* has quite a head start over everyone else.
For the next few sections, see [this important graphic](https://en.wikipedia.org/wiki/File:Spreading_homo_sapiens_la.svg):
[](https://i.stack.imgur.com/8IcOA.png)
Image in the public domain.
### 50,000 years ago
In the world you and I live in, *homo sapiens* has by now spread throughout south-east and eastern Asia, and is venturing into Europe. The Neanderthals are doing just fine, and *homo floresiensis* is presumably surviving.
In this world, things are a bit different.
*Homo sapiens* will still reach Europe, much of Asia, and presumably Australia. However, they will find people already in Australia. *Homo floresiensis* may have developed quite the culture, and may put up some resistance to the newcomers. Yet if there are any physical confrontations, the "hobbits" are in trouble. Three and a half feet of a small-brained hominid isn't a lot against a human. *Homo floresiensis* will die out - possibly a bit later than in our Earth, but at some time, nonetheless.
### 35,000 years ago
*Homo sapiens* and *homo neanderthalensis* have met. Any speculative interbreeding is taking place, and the two cultures - if you can call them that - are interacting just as expected. In southern and central Europe - and northern Europe, to some extent - Neanderthals are starting to die out as they're replaced, even in [Douglas Adams's stories](https://en.wikipedia.org/wiki/List_of_races_and_species_in_The_Hitchhiker%27s_Guide_to_the_Galaxy#Golgafrinchans).
But Neanderthals up north may have crossed during the Wolstonian glaciation, and made their way into Canada. Sure, *homo sapiens* is now dominant in Europe, Asia, Africa, and eventually Australia (*homo floresiensis* may have survived until 10,000-15,000 years ago), but the *homo neanderthalensis* has escaped.
### 20,000-25,000 years ago
Sometime around this period, some members of *homo sapiens* cross over from Siberia to North America via the Bering land bridge. I would suggest that an earlier expedition would have been possible, but that leads to the question of why it didn't happen earlier in our world, given that the land bridge presumably exited for many years before humans crossed it. In this world, the humans may or may not meet Neanderthals. The North Pole migration route would have required the Neanderthals to come over somewhere in central- to -eastern Canada. The ice sheets were still in place 50,000 years ago, and so Hudson Bay would not have been a challenge. Still, perhaps the coasts would have appealed to Neanderthals, so they could have started out on the Eastern end of North America.
It doesn't take long to travel from Alaska to Tierra del Fuego - perhaps only a few thousand years. If that's the case, Neanderthals may have already colonized all of the Americas. That's more than a little bit of a problem for *homo sapiens*, because, once again, they're the newcomers.
There are various ideas as to [why Neanderthals died out](https://en.wikipedia.org/wiki/Neanderthal_extinction). One could postulate that it was the mere appearance of *homo sapiens* that led to their decline, in which case, our group of humans will be just fine. If the deaths had to do with some geological event that was specific to a certain region, then the events here become uncertain. I'm hesitant to speculate about what will happen in this epic meeting, and so I don't think I'll go there. You can decide for yourself. But I think that the two cultures may coexist, at least for a while. If Neanderthals die out, it won't be for a long time. I suppose you could devote an entire question to the idea of *homo sapiens* and *homo neanderthalensis* coexisting.
### Summary
Gills mean that *homo heidelbergensis* can reach much of Europe and western Asia easily, and they cover a lot of ground. *Homo neanderthalensis* quickly goes even further, going up to the northern reaches of Scandinavia. *Homo floresiensis* reaches Australia and gets along quite well until *homo sapiens* comes along. *Homo neanderthalensis* reaches North America but dies out in Europe, and *homo sapiens* conquers the globe, though coexisting with *homo neanderthalensis* in the Americas.
---
### Society
That was most likely not at all what you were looking for, so I'll try to devote a bit to the societal aspects of gills.
### Fishing is big.
One of the issues with fishing is that it requires tools. tools didn't come about for some time (although obviously Neanderthals, *homo sapiens* and possibly *homo heidelbergensis* had them). If you don't have tools and want to fish, you have to use your hands, which is pretty hard.
Gills mean that you still have to sue your hands, but you can follow fish underwater. Have you ever seen someone (actually, Gollum might be a good example) try to catch a fish with their hands, miss, and stumble around in futility trying to get it? Gills mean you can follow the fish underwater. True, this is of no use in the shallows, but you can go into open water, which beats standing in a river looking like a fool with no fishing rod.
However, these are *homo sapiens*, and so have tools. Even something as unwieldy as a large stick can be helpful. Really, you just have to spear a fish, and if it's pointy enough, you're good. The problem comes when you want to catch bigger fish. You'll want to use your gills to your advantage, and the way to do that would be to go out into the open ocean - well, perhaps simply a bay - and go for something more like a swordfish. So you'll need something more than a simple spear.
In this case, you're not going to be able to just catch the fist (I've never tried to catch a swordfish, with or without a fishing rod, but it's definitely not easy). the best technique here might be to stab it until it dies. Perhaps you could use a tooth from, say, a shark and repeatedly whack it. Or maybe you just get a few pointy sticks and try to attack it with them. Either way, though, you'll have to realize that you can't catch the fish while it's still alive. The risk will be large, but the reward will be huge!
### Escapes are easier.
I'm not a fan of swimming, and while I know that many people are, some animals aren't. Some large animals don't like water, and if those large animals are after *you*, you might have a place to hide! Let's say you have a creature like a cat (remember, a lot of cool creatures died out over the past tens of thousands of years) that's following you. It can climb trees and run really quickly . . . but it hates water. The way to get it off your tail would be to jump in a river/lake. Normally, you'd drown as it watched and waited. But with gills, you can stay there for a long time, and be just fine.
### Bridges
I'm guessing that the majority of the time you see a bridge, it's to carry people over a body of water. That's what the earliest bridges would have been for: To get people from point A to point B without having to swim. If you have gills, this isn't a problem anymore; you can swim for long distances. Well, I suppose "long" is a relative term, but you could probably get a good half mile without any problems whatsoever.
Carrying freight makes things a bit more interesting. Do you really want to carry an object that runs on electricity underwater? So there are two options:
1. Build a bridge.
2. Use underwater vehicles.
I think that the former is the better option, because underwater vehicles require storage, and if they're just used for crossing a body of water, they're not very economical.
---
$^1$ *Homo heidelbergensis* and [homo rhodesiensis](https://en.wikipedia.org/wiki/Homo_rhodesiensis) may very well be the same, so I suppose we can consider them as the same species, or possibly consider *homo rhodesiensis* as a continuation of *homo heidelbergensis*, if you want.
$^2$ I'm discounting the possibility of a crossing by *homo heidelbergensis* because they would have had to get to northern Europe for this to even be possible, and I doubt they would have had the time. They started dying out (in that form, giving rise to the Neanderthals) about 300,000 years ago.
[Answer]
One thing worth remembering is that humans with gills have an additional vector for being infected, require a bit more food, are a bit heavier, and have another weakness in combat with regards to land people. These all come from having additional openings in your body that are lined with blood vessels (the gills), which have a weight and metabolic requirements that non-gilled people wouldn't have.
These additional requirements would be very non-trivial. For warm-blooded humans, gills would need to be *huge* in order to supply sufficient oxygen. To meet their oxygen requirements, a standard human would need to take in [51 gallons of water per minute](https://en.wikipedia.org/wiki/Artificial_gills_(human)). Gills would likely need to be an external, fringed apparatus, like the gills of an axolotl, but larger in proportion to body size. Alternately, gilled humans could have lower temperature metabolisms. Fish survive with their non-exorbitantly sized gills because they're cold blooded. Humans that were evolved for life in water could use a similar approach to reduce the size of their gills, with lower internal body temperatures and lower needs for oxygen than gill-less humans.
Given the time period of 'paleolithic until now', groups of people that didn't regularly use their gills would probably start to lose them. Why? Because, if you're not using them, gills are a disadvantage for all of the reasons listed above. If I live in a desert, for example, having gills offers little to no benefit. Being cold-blooded out of the water is also a major disadvantage. Food requirements are lower, but so are brain activity and endurance. Cold-blooded, gilled humans would be worse in combat in the best conditions, and extremely vulnerable to cold weather. In an above-ground scenario, victory for gill-less humans would be as simple as attacking at night.
For early humans, the groups that would benefit from having gills are those that live near a significant food source that's easier for gilled people to exploit. These groups would rapidly begin to develop other adaptations for aquatic life, such as larger, webbed hands and feet, eyes better suited for underwater vision, and insulating fat or fur. All of these things would make the humans that had them better suited for life in the water, and less suited for life on land, and for people who rely on swimming to catch food, there would be a huge evolutionary pressure driving the evolution of those traits.
In short, the presence of gills would lead to speciation into aquatic and terrestrial humans. Alternately, if the terrestrial humans weren't as well suited to life on land as the neanderthals were, humans would stick to coastal regions and neanderthals would be the dominant terrestrial hominid.
[Answer]
Game is played by guns and steel.
Gilled humans would be able to dominate coastal warfare, (underwater shock troops sinking enemy's boats) but would have little advantage inland. Presumably, gilled humans would be more easily damaged by dehydration and dry air.
I think it would very slowly took over coastal areas. Inland empires would have hard time to protect any forts surrounded by water, but thy would adapt by making dry defenses.
This arrangement would slow down development of classic empires, but would also slow gilled humans, because it would be harder for them to access metal and related technologies deeper inland. World would be separated to two races, warring constantly.
Gilled have good chance to take over, but very slowly, and with slower technological advancement.
Depending of emergence:
Mongol Empire would not attempt to take over Japan, and would not lose hundreds of thousands soldiers in attempt. So Europe would be speaking Chinese, and preparing for war to death with the coalition of Pacific Empire and Greek Empire (both gilled).
[Answer]
Just a small thought, but if all humans had gills and reliably anticipating needing to swim on any given day, fabric technologies may have evolved slightly differently.
If you carry any/all of your possessions with you, you'll probably want to keep them dry - waterproofing might be more widespread, or else people could have inflatable knapsacks or containers that would float on the surface of the water while attached to the swimmer by a long cord.
Also, if hypothermia becomes a risk, warm clothing would be a necessity, as would clothing that dried faster. Perhaps frequently-travelled bodies of water would offer opportunities for a new kind of trade - settlements nearby selling warm fires and dry clothes (perhaps in exchange for wet clothes, that they can sell on?) This may be a little too modern for your question, but could work on a smaller scale pre-feudal era.
] |
[Question]
[
How does one calculate the caloric needs of various creatures considering their different behaviours, heartbeats... hormones, blood types, abilities, body temperature, external temperature, gravity, air density and stances like bipedalism, quadrupedalism or multipedalism.
I'm looking for a single formula that accounts for all of these factors at once.
[Answer]
Thankfully most of that does not really matter, Its fairly simple you only need two things for a rough estimate.
## Body mass and metabolism work with [kleiber's law](https://en.wikipedia.org/wiki/Kleiber%27s_law) for a quick estimate.
Body mass is fairly straight forward, base metabolism depends on how accurate you need the estimate, you can break it down by species, clade, or type of metabolism. for a quick an dirty approach clade or -thermy is fine. Based on the clade is usually, mammal, bird, amphibian, archosaurs, ect. . If you don't want to get into that fine of detail you can also do it by whether they are endothermic or exothermic, it won't be quite as accurate as breaking it down by clade but it is good enough for a quick estimate.
[](https://i.stack.imgur.com/SesET.png)
So your calculations area as follows.
for large animals
Kcal/h = X(mass^3/4)
*for very small animals like insects and micro-organisms is is instead Kcal/h = R (mass^2/3)*
Body mass is in kilograms
X is 3.52 for mammals and birds and 2.66 in ectotherms
you can also search [individual animal groups](https://escholarship.org/content/qt18s7d943/qt18s7d943_noSplash_3b9985c27b9bd3a7d530b74cb36bfd46.pdf), passerine birds of instance can have an X as high as 5.
Is this perfect, absolutely not, but it is good enough for a quick a dirty estimate.
Also don't forget this gives you the caloric consumption per hour, be sure to multiply by 24 for daily consumption and 8769 for yearly.
] |
[Question]
[
In monarchies and feudal societies the line of succession was extremely important, having an heir was one of the primary goals and creating familial connections was important to creating alliances. In a world where there are multiple races, and none of them can interbreed, what type of systems would arise?
Because of the importance of marriage alliances and lineage in medieval-style monarchies, would it be possible to have these separate races (again non-interfertile) share some amount of power within the kingdom? I can't really think what systems would stop one race from trying to dominate the others, and that most races wouldn't accept a king/queen that isn't of their race (probably because of racism, but also that it limits how far they can rise within a feudal system).
I do think having races (or at least certain cultures within the race) accepting rule under a different species isn't unbelievable. Obviously there tend to be minorities in all sorts of kingdoms (Roma, Jews etc.). As well, I understand that there are likely to be at least a few countries that attempt to keep a fairly mono-race attitude. But I don't want every kingdom to have to be black and white where a species is either the ruling species of their country or they are an oppressed group within the kingdom.
As an example, in Brian Jaqcues world of Redwall, there are many races that live together but the only 'Kingdoms' seen are all pretty mono-species. None of the species are interfertile and I was trying to think of a way that a kingdom of say mice, rabbits and squirrels could exist without one species being completely dominant. Anywhere shown to be fairly multi-racial tends to either be very small in scale (Redwall itself) or are hordes of 'vermin' where they have no real structure besides might is right.
Would it be possible to have a multi-raced feudal kingdom where there isn't a singular dominant race, and if it is, what systems could ensure that any race can not only rule as a lord but has a chance of putting their line on a throne?
[Answer]
I think it can work, but that your mindset is a little too modern/meritocratic.
If you are born as a serf in a medieval kingdom, then you are supposed to remain a serf, and your children and their children. If you or they don't something has gone wrong, that is not how things are supposed to operate. It doesn't matter if you are a genius, your role is hitting that wheat. God said so when he made you a serf.
You are not supposed to breed with people above your station. The princess can't marry you. That would be scandalous. If you try eloping her dad will cut your head off and probably punish her too.
So, now we introduce multiple Redwall races. You are a mouse-person serf. Maybe your kingdom has a mouse king, maybe a ferret or a weasel. Who cares? Even if they are a mouse you can't hope that you will be king or your children will be. You are supposed to accept your place.
Any system that "gives people a chance" would not be feudal.
---
However many other historical systems exist that are close to feudal. Sparta had two royal families so there were always two kings (one from each). Maybe you have a similar system with N royal families and some are of different species. Maybe you go the way of Athens or Rome with some early form of democracy, although I suspect a democracy would be less stable. You can get votes by stirring up division which may lead to inter species conflict. What is the voting age? If it is 20 then maybe the shrews who usually only live to 18 complain. In a more oppressive regime people would conceivably be too preoccupied with your class (serf, knight, pleb, ...) to care much about whether you are a mouse or a shrew.
Yes, with multiple kings or councils or elected people no one has absolute power, but the idea of a leader with absolute power is kind of mythical anyway. No leader of any government at any point has been able to do *anything*. Even Stalin (a close contender for this badge) could not have ordered every Soviet citizen to kill themselves and had any realistic prospect of such a thing actually happening. This reflects the fact that even people who are powerless in theory have collective power in practice, and that even people with absolute power in theory have to respect that if they want to survive.
[Answer]
I feel like this could be possible. There could be multiple systems and ways to choose someone even if familial connections are important. The Holy Roman Empire [elected its leaders](http://www.heraldica.org/topics/national/hre.htm#Qualifications) despite being around during the feudal era ([the empire began 800 with Charlemagne](https://www.britannica.com/place/Holy-Roman-Empire)) [and his coronation as "Emperor of Rome" by Pope Leo III](https://www.britannica.com/biography/Charlemagne/Emperor-of-the-Romans). The HRE was a confederal elective monarchy. However, it was preferred that a member of the [House of Habsburg](https://en.wikipedia.org/wiki/House_of_Habsburg) royal family be put in charge and even then, members of the royal family could adopt children to be placed in charge. Emperor [Maxilimian I](https://en.wikipedia.org/wiki/Maximilian_I,_Holy_Roman_Emperor) was adopted into the [House of Habsburg by Duke of Austria Sigismund](https://en.wikipedia.org/wiki/House_of_Habsburg?wprov=sfla1). Maximilian was the son of Emperor Frederick the Third, but the lands of the Habsburg dynasty were divided at the time so Maximilian would have only been able to inherit the lands of the Leopoldian family at the time. This adoption allowed all of the holdings of the Habsburg line to be held under one ruler, including the Leopoldian holdings.
So, you can have a feudal kingdom that either:
1. Allows anyone to be elected as a leader, but prefers members of the family. People of different species can be elected emperor even the best members of the ruling family are unavailable or unfit to rule, allowing different species to be in charge while a family of one species generally has the highest chance of being in charge.
2. Have the family adopt people of different species as children for whatever reason (infertile, child is smart and has marks of good ruler, help with relations with other species and increase holdings of one family,, etc.) and these adopted children - even if they are part of a different species than their parents - can become ruler. This new ruler can then adopt someone of a different species or have a biological child with a member of the same species.
[Answer]
**Slavery** Humanity's own belief that races *shouldn't* intermarry led to institutionalized slavery for a very long time. Even before that, strong nations frequently turned the conquered into a convenient (and expendable) labor force. I frankly can't even imagine that slavery wouldn't be a substantial component of both your cultures and their politics. This is especially true when you note that feudal systems were strongly caste-based: and another species would almost always be perceived as something less for whatever reason ("they're so stuck up!" is no different from "they eat with their hands!" when it comes to the desire to hate).
However, it's worth noting that what this could morph into is a form of indentured servitude that serves the same basic purpose of a political marriage. Unions in days past had concubines as well as wives/husbands. That servitude could take the form of a basic house servant all the way up to a sanctioned relationship second only to the spouse.
**Cross-species marriages could happen** You're right, there will always be the basic need for an heir to drive the throne — but that's a limiting way of looking at things. I suspect a cursory look at history would show that nieces, nephews, lesser children (not direct heir), etc., were married off for the purpose of alliance or bonded association between cultures. Those marriages don't require children. In fact, it could set up a method of assigning land and titles that automatically revert to the crown once the two lives have ended and the purpose has been served.
**Birds of a Feather** There's a long-standing fantasy trope of multiple species getting along just fine, even to co-mingling socially and politically. If human history has proven anything, it's that we can barely stand to be in the same room with other humans who differ from us in only superficial ways — what on earth would make anyone believe that it would be better with actual species? Nope. I suspect that the only way borders wouldn't be anything but constant war zones (from angry farmers shanking each other's dogs to formal armies) is a strong application of [M.A.D.](https://en.wikipedia.org/wiki/Mutual_assured_destruction). Call me a pessimist (optimism is for the young... really! Then they grow up and discover the all the details they've been missing or couldn't understand), but inter-special (pronounced "spee-see-ah-l" not "speh-shal") relationships will generally be tense in all but uncommon circumstances (see those notes about marriage and indentured servitude).
**The Law would have Greater Importance** The one thing that would bind everyone together is a greater dependence on the law. That would be required to bridge cultural and special differences. Think about it: you can fundamentally believe that all humans, regardless of race, think/act/behave the same way. Oh, there are minor social differences between cultures, but nobody's really eating *Gah,* right? Dealing with, for example, people who expect *Gah* for dinner falls square into the lap of protocol, which inevitably becomes policy, and finally law. I would expect your world to be more legally dependent than medieval Europe (despite medieval Europe making incredibly great strides when it comes to law).
[Answer]
**Specialized roles governed by specialists:**
I think the only really practical way to get this to work is if each species has a role they clearly perform better than the others; unambiguously, without doubt or question. Humans are clever at making things, Elves are utterly wise and trustworthy, Orcs are superb soldiers and a Halfling can grow crops in a shoe and serve you the shoe afterwards in a fine restaurant.
Each race would need to govern the choices relating to their own field. If there were any doubts or conflicts about what belonged in who's control, there would need to be an unimpeachable judge to decide the issue. If orcs are great soldiers, they run much of the army. But what if humans are better generals? Go to the Elves for a ruling, and the Orcs better trust the Elves, or you'll have a civil war.
If different races had fundamentally different opinions about what was or wasn't best, they would inevitably come into conflict. To have these races in a group, you'd need autocratic rulers to enforce one viewpoint or another. If not, have a confederation of states where compatible groups live under a collective agreement. The Orcs and Elves can't stand each other, but everyone agrees the trolls aren't to be trusted and they can form a confederation if the humans are between, since the humans can tolerate the smell of orcs and the arrogant presumption of superiority from the Elves.
I agree that absolute laws would be needed without ambiguity (possibly without mercy, depending on the rule). Dwarves and goblins must NEVER live in the same city, and the poor orphaned dwarf child adopted by humans in a town with goblins creates awkward issues. Orcs can't eat allies; EVEN IF they agree to it, or the orc is starving. Better a hungry orc than a civil war.
In some subtle ways, I think multiple species might get along BETTER than some species do internally. No one expects good manners from an Orc, or respect from an elf, or an honest human merchant. And people might appreciate their own species more from the alien behavior of the others. After all, did you SEE the table manners of those lizard men? It makes Uncle Otto seem downright neat and tidy.
[Answer]
I think it is entirely possible to make it work.
From what you've said you want to avoid the situation where you have a human kingdom where elves and dwarves (for example) live but they have no real power or rank and cannot gain any because the noble bloodlines are all human.
There are a couple of possible options based on a similar premise. Your kingdom should be founded on an alliance or agreement between however many different species you have or want to be involved. Depending on your history this could come about in a variety of ways, the various species fight together to defeat a common enemy, they find that their natural advantages and disadvantages complement each other and they are more successful when they work together etc.
Either a single starting ruler grants lands and titles to an equal number of families from each species or the nations land is divided up and titles are created for the powerful families. So each species has it's own noble families and bloodlines, as time goes on they will grow, expand, split and die off until there is a network of different houses as you would expect in a feudal monarchy.
If you want to maintain roughly even power division between species you could say that only elves can inherit elven land, only humans inherit human land etc. so if a line or family dies out completely their land is passed on to other members of their species and balance is maintained. Or you could say that balance is less important and inter species relations and politics could be an important part of your world or story and let land be taken or inherited by members of other species.
As for the actual monarch;
1. A king is elected by the most powerful families in the kingdom, these might be individuals holding a certain title (Dukes), the current heads of the original noble family lines, individuals who hold the most titles or land or whatever system works for you. This way power is passed around the various species democratically. You might have four human kings in a row but only if the other species agree and vote that way.
2. The crown passes amongst a set group of families in a predetermined way. So each species has a royal family and humans get the crown first, then elves, then dwarves etc. This system means power is shared completely equally (possibly with allowances for age, it might be a number of years rather than an individual's life span if elves lived three times as long as humans for example) and no single species can dominate the others.
3. Actual bloodlines aren't seen as important and the royal family frequently adopt members of other species (probably from prominent noble families) who then inherit the throne. This is less fair and even than the other systems, but as monarchies and feudalism weren't renowned for being fair that probably isn't an issue. There might be some kind of precedent or law that would govern when the royal family might adopt or when an adopted child might inherit over blood children.
[Answer]
I really like the answer by Dast. But there are some minor points:
* The system will be more stable on the long run if there is a way to co-opt successful commoners and minor nobility into the leadership. A mouse-squire could become a baron under a cat-king, just as a cat-squire might be promoted.
* Making a relative of the King the *Lord Chamberlain* or whatever is a double-edged sword. Sure, he has a powerful incentive to fight any change of dynasty, but he might also drag up some dusty old documents and claim to be the *rightful heir* to the throne if there is a succession crisis. Or scheme to marry his daughter to the infant king and become the power behind the throne instead of a servant of the crown. If there is a cat-king with a kitten heir, having a fox-chancellor might be the safer option to ensure that the prince lives to come of age -- any *legitimate-looking* substitute would have to be another cat, after all.
* Of course the cat-king could be reduced to a figurehead with the fox-chancellor holding the real power, like a Merovingian [majordomo](https://en.wikipedia.org/wiki/Mayor_of_the_Palace) or a Tokugawa [shogun](https://en.wikipedia.org/wiki/Shogun#Tokugawa_shogunate_(1600%E2%80%931868)).
[Answer]
The system needs a number of high positions that balance out the power of the king, and ARE race-bound and heritable (Ministers, Marshall of the armies, ... ). The holders of these offices then elect the king from among their number.
To make this work, there need to be strong constitutional protections in place: The king cannot have the ministers arrested, or executed, or removed from office.
] |
[Question]
[
So, dragons. They're omnivores and, while they would be potentially formidable hunters, mostly scavengers. This requires them to be more sparing with their energy.
Still, they fly and flight needs good eyesight and good eyesight needs this:
[](https://i.stack.imgur.com/WJRd7.jpg)
Well, if I want my dragon to be able to track your movements with their eyes without moving their head (you know, like a human) or quite literally look down upon someone, these eagle-eyes won't cut it.
**But now I'm stuck. I want my dragons to be able to spot hares from 5 kilometers away but without losing the ability to roll their eyes. How can such system work?**
I'd also prefer to keep the count of the eyes to two and the size of them as small as possible.
[Answer]
You see, apparently the main reasons behind that lack of movement is the tight fit that the eye is in their skull and the presence of a sclerotic ring. The eyes of the eagle can be as large as a humans despite them having much smaller skulls. The owls took this eye to head ratio further, to the point that [the back of their eyes can be seen from the inside of their ears](https://www.livescience.com/61673-owl-eye-seen-through-ear.html). Here's the skull of a harpy eagle with the sclerotic rings and an informative image about them:[](https://i.stack.imgur.com/xVNNf.jpg)
[](https://i.stack.imgur.com/2aFKf.jpg)
Now, let's look at what makes their eyes so good:
**1-size**
The size of eagle eyes, disproportionately large compared to the skull, is a good reason. Bigger eyes mean more space for photoreceptors, which work in a much similar way to pixel count, the more receptors, the better the image. That's also a reason why we believe T-Rex had great eyesight, with their eyes allowing for binocular vision and being the size of oranges. Additionally, eagle eyes have a much higher number of cones than us.
**2-the eye itself**
Not only eagles have a convex fovea, which we assume helps them focus light better, they have two foveas in each eye (we have 2), one responsible for good monocular vision and the other for binocular vision. In addition, both their lens and cornea can change shape (we only have the lens change), allowing them for even better focusing.
They also have a pectan, but I'll elaborate that further down.
**Now, regarding the dragon.**
So, we want a dragon that has eagle like vision but can move its eyes around. For this answer I plan to focus on a more classic look, without the need things like tentacles in their faces or "popped out" eyes like an octopus (though I recommend looking at those, due to them having their photoreceptors inverted in relation to ours, they have no blind spots).
The main difference would have to be a large skull. If your dragons have large enough skulls, they can fit larger eyes, meaning more space for receptor cells and better vision (remember that big eyes are useless without also having brain space dealing with the information sent by them. See how eagles have such well developed brain parts regarding eyesight that they have almost no space for smell and taste). Additionally, the eye sockets will likely need to be fairly larger. See how the harpy eagle barely has space between the scleral rings and the sides of the socket. In order to have eye movement, you'll need sockets large enough to be able to contain the eyes (which might be easier to do for the eagle's more roundish eyes than for the owl's eye tubes). I would recommend keeping the rings though. Even if they are a bother to move the eyes, like the pic said, despite other important functions, they're attachment points for muscles responsible for focus, so it safe to assume they play an important role, likely in their shape changing lenses.
Lastly: circulation. One thing about managing the eye is that everything that isn't a photo reception cell in the eye means there's a place with less receptors. That's why eagles have very little bloodvessesls on their eyes (unlike us, look in the mirror and you can see the blood vessels in your eyes). This is likely possible due to a structure called pecten, which, while we don't know for sure, is assumed to be the responsible for the nutrition of their eyes without the need of bloodvessels that'd take space.
So summing up, to have a more classic-looking dragon with eagle vision, your animal will need:
* eyes decently big to accommodate more photoreceptors.
* a skull with large enough eyesockets in order to have space for the eyes to move around. You'll also need space to fit the muscles responsible for moving the eyes (humans need 4 groups of muscles for their eye movement ability).
* convex foveas (having only one should be enough, unless you also want them to have good monocular vision).
* lens and cornea capable of changing shape (likely means the need of a sclerotic ring as attachment point for some of these muscles).
* special nutrition methods which allow for the lack of blood vessels in the eye (maybe a pecten).
So, yeah. You can do fine with only 2 eyes, but having them as small as possible is a no go, simply cause we can't quite shrink the structures responsible for receiving light, so to have more of them, your dragon will need to have big eyes. Additionally, as you want these already large eyes to be able to move around, you'll need even larger sockets than they'd already have with fixed eyes. The only way for you to make their eyes look smaller without reducing their capacity is making the dragon itself bigger.
[Answer]
Eagle eyes are, indeed, fixed in the head and unable to move, but the important features of the eye that allow clear images of distant objects are only the power (thickness/curvature) of the lens and the density of the photoreceptors on the retina. You can see from the images in the question how much more focusing power the eagle lens has to work with, but it comes at the cost of an eye that is roughly the [same size as a human's](https://www.improveeyesighthq.com/eagle-eyesight.html)! Those eagle eyes can take up half their head. I'd hypothesize that having such a large eye in such a tiny bird head is why they don't move independently and instead rely on the eagle pointing their head. In this case, your dragons should be able to have equally large eyes with equally high focusing power but still plenty of space in their huge dragon head for the eyes to move around like a human's.
Some other interesting notes about raptor retinas:
* Their foveas, the highest photoreceptor density part of the retina where the image is formed, are higher than our own, contributing to their excellent visual acuity. The parts of the retina outside the fovea have much lower density in both raptors and humans, which you can think of as your peripheral vision (much worse quality than the center of your field of view).
* They have [*two* foveas](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3061512/) at different locations that use different parts of the lens to see different fields of view at different magnification. The center fovea looks straight ahead at relatively closer objects, and the second looks out at [45 degrees](https://www.nationaleaglecenter.org/eagle-eyes/) to distant objects with high focusing power through the lens. This is maybe helpful with the fixed eyes as well -- human eyes rotate to place the image of the world on the single fovea where photoreceptors are most dense. Raptors at least have two foveas to choose from when tilting their head to look at things.
* Humans refocus to different distances mainly by changing the shape of the lens, but eagles [apparently also manipulate their cornea](https://www.lasikmd.com/blog/how-does-human-vision-compare-to-that-of-an-eagle), which, again, is quite large in the diagram, allowing nearly parallel rays from distant objects to be turned in and focused onto the retina.
[Answer]
Have their eyes atop of a structure resembling [snail](https://en.wikipedia.org/wiki/Snail) eyes, scaled up for the dragon eye size.
[](https://i.stack.imgur.com/fVIPP.jpg)
Moving the protuberance around is less energy consuming than moving the entire head, plus the very protuberance can offer the eyes additional protection when needed, by simply retracting the eyes inside the body.
Additional point: it's cool!
[Answer]
Transparent [nictitating membrane](https://en.wikipedia.org/wiki/Nictitating_membrane), with a variable lens like properties.
Fine fibers like those in the [eye's crystalline](https://en.wikipedia.org/wiki/Lens_(anatomy)#Lens_fibers) can thicken/thin the membrane on localized areas (perhaps acting in vertical slices), bringing other things into focus. The nerves responsible with moving the eyeball in other animals will take the responsibility of "focus shifting by varying the thickness of the nictitating membrane".
It's like a sophisticated [adjustable fluidic lens](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845295/), but with a protein membrane instead of a fluid.
[Answer]
### Build a wrapper.
[](https://i.stack.imgur.com/VJZew.png)
The idea is fairly simple: you put the "inner eye" into a spherical "outer eye", which allows the normally immobile eagle-type eye to freely rotate as if it were a human eye.
The only downside with this method, is that it wastes space. Unfortunately, I have no idea what kind of evolutionary pressure would have your dragons evolve 2 distinct layers of eyes, but as long as your dragons have a big enough head, this shouldn't be too much of a disadvantage.
[Answer]
A few other things to note:
## Diffraction
There is an optical property that when light passes through a small opening, it gets blurry. A human eye, at half a mile, cannot distinguish a 6 foot human as more than a single point. (I haven't seen the math since about 1980, so I don't remember it at all.)
## Refraction
Another optical property, used in lenses. This has the opposite problem: the larger the opening, the blurrier things are.
## Microtremors
In the human eye, the eyeball is constantly jumping back and forth. Eagles don't do this. When the eye doesn't move, the nerves all drop back to their rest state, and everything disappears. Eagles use this to hide the scenery, so that only the rabbit moving across the field is visible to them.
(Some details at <https://en.wikipedia.org/wiki/Fixation_(visual)>)
---
The net result: You may need to have rather large eyes if you want to distinguish things at 5 kilometers, but then in will be messed up by refraction.
What you might need is what astronomers do: Reflection. Put a couple tiny eyes on the snout pointing backwards, and a pair of parabolic mirrors where other things have eyes.
Microtremors -- is up to you (though maybe it can turn them on and off?).
] |
[Question]
[
A moon is just a natural satellite - something orbiting a planet - so I'm interested in what kind of factors influence how many moons a planet **can** have, and how many moons a planet **will actually have**.
I assume the size and potentially mass of the planet primarily affect how many moons a planet can have. Anything else?
What sort of factors affect how many moons a planet will actually have? I'm thinking about, say, Jupiter compared with Earth - why so many more moons?
[Answer]
In terms of planet formation, there are esssentially three ways to get a moon.
It can form with the planet, by the same kind of particle accretion process, but with enough relative velocity not to get incorporated (this is how the larger "true" moons of the gas giants were formed -- Ganymede, Titan, etc.).
It can form by capture, where an already formed body (generally through a three-body interaction) manages to get captured into an orbit of some kind, which then circularizes and (generally) aligns with the equator due to tidal forces. This is believed to be how Mars got its moons, as well as the gas giants their smaller moons.
It can form by impact (the current leading theory about how Earth's moon formed), if enough ejecta goes high enough and fast enough for interactions between ejecta to put some of the pieces into orbits, where they eventually coalesce and the orbit regularizes like a captured planetesimal.
For the latter case, I'd be very surprised if you get more than one moon over geologic time. Smaller objects in orbit around our moon are unstable -- they'll either eventually intersect the surface, or they'll be ejected into cis-Lunar space where they'll be perturbed either into ejection from the Earth-Moon system, or into an impact. There's no limit to asteroid/planetesimal capture over long enough spans, if the gravity well is large enough. In between, there is co-formation -- which seems to be limited to around half a dozen moons for planets similar in size to our gas giants. A super-Jupiter could reasonably manage to form and hold a larger number, if it's not too close to its star.
[Answer]
The simple answer is an infinite amount. Since you defined moon as "just a natural satellite" anything natural and in orbit counts. Be that a double planets partner (There are many definitions, yet I prefer the one with calculating the barycenter and if it is outside the bigger planet, it's a double planet. This makes Pluto and Charon double planets and Luna remains a moon.), a big moon in [hydrostatic equilibrium](https://en.m.wikipedia.org/wiki/Hydrostatic_equilibrium#Planetary_geology), any kind of asteroid moon, small rocks, dust and arguably every hydrogen atom. If you want a better picture of this look up Saturn rings or better the [rings of J1407b](https://www.universetoday.com/131403/exoplanet-huge-rings-intrigues/).
Something tells me that's not the answer you're looking for. So lets redefine moon to satellite in hydrostatic equilibrium orbiting a common barycenter within the planet. How many of these moons can we squeeze around a planet in optimal conditions?
In that case we need to calculate the [Hill sphere](https://en.m.wikipedia.org/wiki/Hill_sphere).
$r\_H = a(1-e)\sqrt[3]{\frac{m}{3M}}$
$r\_H$ = radius Hill sphere
$a$ = semi major axis satellite
$e$ = orbital eccentricity satellite
$m$ = mass satellite (planet)
$M$ = mass central object (sun)
The inner half of the Hill sphere offers stable orbits to major moons that can last indefinitely. Orbits outside that limit can be occupied too, but the moons wont remain there forever. This gives us the outer boundary. For the inner boundary we take the [Roche Limit](https://en.m.wikipedia.org/wiki/Roche_limit), as any major satellite within it will be ripped apart.
$r\_L=R\_m(2\frac{M\_M}{M\_m})^\frac{1}{3}$
$r\_L$ = Roche limit (from the center of the major object to the center of the minor one)
$R\_m$ = radius satellite
$M\_M$ = mass central object (planet)
$M\_m$ = mass satellite (moon)
This needs to be calculated for each satellite individually. Furthermore satellites with high tensile strengths, i.e. primarily metallic ones, can survive within the Roche limit for a long time. I'm not sure if this can be extended to major moons, I only read about it in the context of metallic asteroid moons.
Now we need to figure out how close to an existing satellite we can place the next one. [This paper](https://www.google.com/url?sa=t&source=web&rct=j&url=https://academic.oup.com/mnras/article-pdf/436/4/3547/3102731/stt1831.pdf&ved=2ahUKEwjg67Pl8LPhAhUgQxUIHbnVAz8QFjAJegQICRAB&usg=AOvVaw2c-GdipbdUy3UV4Dt9LyHD&cshid=1554293064426) claims that the influence of the of an object on another one becomes weak enough for it it have a stable orbit at 3.46 \* $r\_H$ (moon center to moon center). Calculate the Hill sphere of each moon, now using the planet's and the moon's mass instead of the sun's and moon's. The center of the next moon can be placed right at that boundary.
Finally setting up mean motion resonances like in the Jupiter (4:2:1) system or the Trappist-1 (24:15:9:6:4:3:2) system is likely needed to keep such a tight grouping of moons stable.
I'll leave the number-crunching to you. My suggestion would be to set up a spread sheet, as many factors are variables.
EDIT: Zeiss Ikon's [answer](https://worldbuilding.stackexchange.com/a/143113/6986) about moon formation introduces a criteria my answer ignores. I offer a way to find out what the maximum amount of stable satellites can be. As Zeiss Ikon pointed out it is unlikely that so many satellites will form.
[Answer]
Having a moon is really a balancing of two things: the [Roche Limit](https://www.britannica.com/science/Roche-limit) and 'local' gravity.
The Roche limit determines the minimum distance from the planet the moon has to be, and anything that 'orbits' beneath that limit is either going to tear itself apart due to tidal forces, or crash into the planet itself.
It almost goes without saying that larger planets have a larger Roche limit and that smaller planets have a smaller one
I say 'local' gravity for the second parameter because the thing the moon is orbiting has to have enough of a force of gravity to hold onto that moon.
If the moon has a higher 'local' gravity, than what it's supposed to be orbiting, then the roles switch, and what was a planet is now the moon.
The 'local' part matters, since everything has gravity everywhere, it just diminishes according to [The laws of Gravitation](https://www.universetoday.com/56157/gravity-equation/ "Gravity equation"), where it gets weaker by the distance squared.
With those two parameters in place, we know that a moon has to fall within the gravity capture of a planet without being in the Roche Limit.
The [theoretical minimum distance](http://abyss.uoregon.edu/~js/glossary/roche_limit.html) is about 2 1/2 times the radius of the stellar body, while the gravity capture is significantly more than that (I didn't look for the math on gravity wells, it's complicated stuff).
With all that- larger stellar bodies have a better chance of catching 'moons' because of the increased size of their gravity capture zone. While their Roche Limit is larger as well, it grows slower than the gravity well.
The limit for how many moons a planet can have has more to do with the likelihood of them bumping into each other, and their respective Roche limits.
The number of moons a planet is likely to have depends on positioning in the solar system, since larger bodies on the outside of a solar system will catch more moons before the inner planets get a chance
[Answer]
If you want more bodies to orbit a given one, you need to take into account that all of them will interact with each other.
In order to have these interactions allowing each body to orbit in the system, you need to have a certain distance between the bodies. This is why in the solar system we don't get a body orbiting at every km distance from the Sun: when they are too close the bodies either merge or kick each other out.
The problem that you get with increasing the distance is that it also lower the gravity, thus sooner or later the planet will no longer be the main attractor for your system.
As a consequence, the more massive is the planet the large is the zone in which it can impose its gravitational domain: as you correctly observed, Jupiter has more moons than Earth, because it's more massive and can control more moons, and these moons can be at a proper distance from each other.
] |
[Question]
[
What is the best material to use for a near future spaceship. Assume that most materials in the solar system can be mined and used.
The spaceship is 700m long, 500m wide and 500m high. It travels at around 1,212,062 m/s over long distances, say around 63 AU. The ship has the design shown below.
[](https://i.stack.imgur.com/T20Ja.png)
The material must be capable of keeping safe a crew without them suffering any ill consequences and should be as light as possible to save on fuel as well as being able to remain in space with only minor repairs for as long as possible (preferably at least 5 years).
The ship does not enter the atmosphere at any point but will pass through most conditions encountered in the Solar System.
[Answer]
## Anything you hit hits hard
Travelling at 0.4% the speed of light any small rock that happens to be in your path will pack quite a punch. Sure you want something strong but on the other hand you can't avoid damage entirely so I'd suggest **[Carbon NanoTubes](https://en.wikipedia.org/wiki/Potential_applications_of_carbon_nanotubes)** both for their strength and their ability to combine with nanotechnology. I would propose a **sensing skin** for the hull of your ship which detects any damage.
You want to ensure you can repair any damage (even minor) as soon as possible to maintain the atmosphere within the ship.
You particularly want to strengthen the struts between the two circular parts since any break here (especially whilst accelerating) would distribute the forces unevenly and cause further stresses and damage. Though, unless the space has some function, I would suggest moving the two circular parts together.
[Answer]
If it is just a matter of surviving in vacuum, you can make your spaceship out of aluminum foil. The LEM was built out of very thin materials because the spaceship needed to be as light as possible, but also because it was not subjected to the various stresses of reentry.
[](https://i.stack.imgur.com/80lZZ.jpg)
*LEM in lunar orbit*
For longer term occupation of space, you should consider building the spaceship out of [ice](http://www.neofuel.com/ICESHIPS/index.html). Ice is inexpensive, readily available throughout the solar system, absorbs radiation, doubles as a heat sink if needed and can act as the reservoir of hydrogen and oxygen or water for the life support system.
So consider the mission and the economic resources of the building company or nation. The vast majority of people are going to engineer the vehicle to be as economical to build and operate as possible (within the mission parameters), so once you have made these considerations then you have your answer.
[](https://i.stack.imgur.com/lhlYA.jpg)
*Ice ship as described by NEOfuel*
Building spaceships out of other materials would have to be considered on the basis of costs, the demands of the mission (are you pulling high energy manoeuvres outside of atmospheric reentry or aerobraking) and possible threats (obviously if you plan to cruise through the rings of Saturn or are on a military mission in a shooting war, your ship needs to have a great deal of protection).
Ultimately, it is going to be based on the demands of the mission and the resources available to the builders. They will, under most circumstances, build the ship in the most economical manner to meet the mission demands.
[Answer]
I think Titanium and its alloys (including ceramic forms) would be a good material for your space ship if it was combined with insightful structural design.
First, Titanium is very plentiful in our solar system. And, it is light and strong, providing it doesn't get really cold. And, in space, no one can hear you say "Damn, its hot." So the first insightful design is to keep the hull warm -- above 0 C.
Second, The forward facing sections of the ship might be made of harder alloys of Titanium to improve resistance with collision, and shaped to deflect the impact away from the body.
Third, double or triple or quintuple hulled, in case a high energy collision punctures one hull, the redundant hulls stand a better chance of keeping the air inside the people tank. Because, in the vacuum of space, no one can hear you ask for a puncture repair kit.
Fourth, fill the gaps between the hull with a combination of low-density plastic and sealing goo. Low-density materials are good barriers to beta radiation. And, the sealing goo will seal small punctures. The crew can go out and repair them during regular maintenance because in space no one can hear you ask for overtime.
Fifth, lots and lots of compartmentalization -- any places with people or dangerous material need to be isolated from each other to save other peoples lives if one section is too badly damaged, because in space no one can hear you ask for a do-over.
Many of these ideas are incorporated into the modern submarine design, albeit for other reasons.
These are only a few ideas, I am sure there are more.
[Answer]
I know you want a lightweight solution but for safety and longevity go hard or go home, my answer is a Tungsten-Gold alloy, for the front end at least, Tungsten for structural strength and impact resistance Gold for its radiation absorption. This gives you a ship which can go head-on with debris at the kind of speeds you're talking about for the slightly over 80 hours of mission time you're looking at with integrity to spare, which you want in case anything goes wrong. While it's doing that it's also protecting the crew from the majority of the radiation coming their way.
[Answer]
For impacts with tiny space rocks at enormous velocities, what you want is a whipple shield: several very thin layers with big empty gaps between them, held away from your hull on sticks. Whichever metal foil is cheapest would be fine. The rock will be vaporised on impact with the first layer and punch straight through. The resulting hot gas will spread out before it hits the next layer, reducing its penetrative power.
Whipple shields are used in real life because of the very light weight for the amount of protection you get.
For long journeys, pack some rolls of spare foil so you can replace damaged sections of the shield as part of your routine maintenance.
For large obstacles, you have to spot them on radar and dodge; no reasonable amount of shielding would allow you to hit a bus-sized rock at interplanetary speed without it drilling a hole through your ship from front to back. If there are rocks that are too small to show up on your radar but big enough to punch through the shield, I guess they just add drama to your story.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I know the default will be blue, but just HOW blue, i.e., wavelength in nanometers? I have a world with the following stats:
* Radius: 4628 km.
* Mass: .35 Earth (2,09076 x 10^24 kg).
* Atmospheric Density: .88 Earths.
* Scale height: 14.63 km.
* Atm. Composition:
+ N2: 72%
+ O2: 19.6%
+ CH4 (Methane): .04%
+ CO2: .02%
+ Ar: 8.34%
+ Plus trace like ozone, water vapor, etc.
* Temperature: 299 K (25,85 °C)
* Solar Insolation: 1.04 (relative to Earth)
* It orbits a G3V star:
+ Temperature 5,756 K (5,482,85 °C)
+ Peak radiation: 503 nm.
What would be the formula for calculating the exact shade of blue? What factors do I need to keep in mind?
[Answer]
The answer to this depends on surprisingly *few* factors. In fact, the only things you will need to consider are your atmospheric depth and your sun's output spectrum.
The blue color of the sky is predominantly caused by [Rayleigh Scattering](https://en.wikipedia.org/wiki/Rayleigh_scattering), which is the deflection of electromagnetic waves as they travel through a medium of dipoles. To get the correct color, you draw a ray from the observer out into space. At each point along this line, you determine the intensity of the light hitting that point. The intensity of Rayleigh scattering is defined by the equation:
$$ I = I\_0 \frac{ 1+\cos^2 \theta }{2 R^2} \left( \frac{ 2 \pi }{ \lambda } \right)^4 \left( \frac{ n^2-1}{ n^2+2 } \right)^2 \left( \frac{d}{2} \right)^6$$
Where R is the distance to the particle, theta is the scattering angle, lambda is the wavelength, n is the refractive index, and d is the diameter of the particle.
Of course, none of these are dependent on your medium except n, the refractive index, which will be roughly the same for your planet's atmosphere as is Earth's air.
What this means is that the effect of Rayleigh Scattering is going to be pretty much the same as you see on Earth. (There's Mie scattering as well, but Rayleigh dominates). The only difference will be the atmospheric depth, which affects the path lengths you will be integrating along (both the path length from sun to particle and path length from particle to ground observer).
The color of the sky will, of course, also be dependent on the star you choose. However, since the star you chose is *really* close to that of the sun, you should expect almost perfectly earth-like behaviors. The only difference will be from that path length difference. I believe that the result will be a darker blue with less scattering.
And, since you asked for a "shade" of blue and this scattering effect is multispectral, we can collapse it into a single shade as viewed by a human using the [CIE standard observer](https://en.wikipedia.org/wiki/CIE_1931_color_space#CIE_standard_observer).
[Answer]
## Your atmospheric density
The refractive index of a material [depends on the density](https://en.wikipedia.org/wiki/Refractive_index#Density). You've stated yours is $88\%$ of Earth's, the [refractive index of Earth's air](https://en.wikipedia.org/wiki/Refractive_index#Typical_values) is $n\_{air} = 1.000293$. For gasses $n-1$ is directly proportional to the density of the material, so:
$$n\_{air} - 1 \propto \rho\_{air}$$
$$n\_{new} - 1 \propto \rho\_{new} = \rho\_{air} \times 0.88 $$
$$\frac{n\_{new} - 1}{n\_{air} - 1} = \frac{\rho\_{air} \times 0.88}{\rho\_{air}} = 0.88 $$
$$ n\_{new} = 1 + 0.88(1.000293-1) = 1.00025784$$
So your new refractive index is slightly lower than that on Earth.
If we look at rayleigh scattering, assuming all other constants are the same:
$$ I \propto \left( \frac{ 1 }{ \lambda } \right)^4 \left( \frac{ n^2-1}{ n^2+2 } \right)^2$$
comparing the intensities for your new refractive index:
$$I\_{new} = I\_{Earth} \cfrac{\left( \cfrac{ n\_{new}^2-1}{ n\_{new}^2+2 } \right)^2}{\left( \cfrac{ n\_{air}^2-1}{ n\_{air}^2+2 } \right)^2} = I\_{Earth} \times 0.774 $$
We get a $77\%$ reduction in the light you're scattering through the atmosphere across all wavelengths.
As a result your sky will be a more washed out blue - the lower refractive index will mean the light scatters less so the distinction will be lower - but the sky will be darker since the intensity of scattered light is so reduced.
] |
[Question]
[
I am currently trying to resolve a problem of heavy anachronism in the story/world I am "building".
I will start of by giving a small summary of the story/world, and why there is an anachronism. (Also, I am terribly sorry for the lack of detail here. The problem is that I myself am not sure of the details yet.)
Basically, the setting is about two nations on a same continent. These nations have been at war since their dawn of existence. I yet have to find a good reason. Maybe it originally was one nation that was split. I am not sure.
The state of things are alternating between real warfare and periods of extreme tension, "cold wars". The nations should be equally matched, otherwise one could simply overpower the other and there would not be a reason for two nations to exist.
My story itself follows the life of the main character, and how they are affected by the consequences of that war — orphaned, struggling to survive and fit in with society — without being directly involved in the war. The character is born shortly before the start of another "cold war" period.
I now have two main issues within that story/world, and both deal with anachronisms.
1. I want a bigger part of one of the nations to be quite developed, at least up to our standard, if not more. Planes, technology such as smartphones, skyscrapers in the bigger cities (only a few though, for reasons of aesthetics), and especially: huge advances in the medical field.
Example: Easy & fast disease recognition, at least.
The whole world should not be too advanced either, I believe that the period we currently are in would describe it best.
Now, here comes the anachronism: I imagined the small secluded village the main character grows up in like a very medieval looking village.
[](https://i.stack.imgur.com/oH4D8.jpg)
Small buildings made out of stone and wood, and so on. Same with the life in the village. A priest is playing an important role, most villagers are sustaining their lifestyle by farming, etc.
But there should still be a school, and I want that one to date of a period of around ~1800.
The real problem is the contrast between this "old-ish" village and the rest of the "modern" cities, society, etc. I don't think that seclusion alone is enough of a reason to justify this difference, and neither is the existing time-difference (The developed cities and parts of the country only appear around 10 years after the destruction of the village), which is just way too short.
Summary of the first problem: I can't find any reasons that would justify the huge difference between the village I dreamed up and the developed rest of the country.
2. Here comes the bigger issue, that is also stated in the title. For my story, modern warfare is way too "boring", and simply not fit — bio-weapons, mass-destruction weapons, even combat planes — all that simply cannot exist.
Preferably, I would like the warfare to be similar to European warfare in the "modern period": 17th-19th century. Inaccurate firearms such as muskets; close-quarters weapons still have their use; bayonets and spears are something I'd like to be useful in my story.
And here is the problem. I just simply cannot have a modern and developed society with long dated warfare, that does not make sense. With advances in consumer technology, warfare technology advances as well, mainly because consumer technology often comes from warfare technology, and not the other way around.
I thought about using some kind of excuse like "The two nations have a pact prohibiting them from developing their weapons as to not increase the casualties an further", which just seems stupid, however, and is nothing more than an "ass-pull".
Summary of the second, most important problem: I want my society to be quite modern, with modern technologies, all the while keeping the warfare dated. The biggest part of the story is set in a period of cold war, meaning that the last real warfare takes place about 10 years before the story. But, again, that is way too short of a time to justify my problems. Also, the farthest I can go with compromise's as of right now is having a WWI warfare technology and a ~1980 society.
As you can see, there is quite a bit of anachronism here. And I just cannot seem to find a solution to this.
If you think any detail of my story could be helpful in potentially resolving this issue, I will gladly add it here. I just do not know of anything that could be helpful here right now, which is why I haven't written it down.
Help is greatly appreciated. Thanks a lot!
[(I did already ask that question in writers SE, but was told that here would be a better fit)](https://writers.stackexchange.com/questions/26949/starting-writing-resolving-a-conflict-in-my-timeline)
[Answer]
**Set your story in a place with a very rigid caste system.**
The Techno-Caste and the Retro-Caste. The Techno-Caste are the rulers of The nation, and they live in tightly controlled enclaves. Members of the Retro-Caste are only allowed into the enclaves if they work there, meaning menial jobs. For the most part, members of the Retro-Caste are left to fend for themselves. They are not formally educated. The Retro-Caste are the farmers, and they are only given technology advanced enough to help with that. The rest of the Tech is prohibited, as the Techno-Caste does not want the Retro to get ideas above their station. This is how one part of the nation can be that much more advanced than the other.
This dovetails into the warfare thing. The RC are also your cannon fodder. They are not allowed anything resembling decent/modern weaponry. They only use what they can make themselves. They'd have enough metallurgy to make some firearms and other melee weapons, but would lack the ability to machine anything too advanced. Precision manufacturing would be prohibited. Since only a handful of the TC would even want to look at warfare, beyond occasionally declaring it, you would not get a great deal of Modern weapons making it onto the battlefield.
So, a very Rigid Caste System is how you explain the anachronism. Add to that the accepted religion of the region is similar, but those in one nation genuflect by falling to the right knee, and the other to the left, and you get a method to keep the caste system in both nations with a nice religious argument to keep tempers simmering nicely for a long, long time.
The religion thing sounds silly, but look at the Troubles in Ireland. On the surface, to an outsider, it looks like protestants and Catholics killing each other. Two variants of the same faith. I know it goes much deeper than that, but after a very short period of time, the last atrocity becomes the excuse for the next atrocity.
Have fun with this
[Answer]
Here are some ideas why modern warfare is suppressed:
1. There use to be many more countries. These two were the least
developed and in a non-strategic location. So, they survived,
barely, when everyone else committed suicide through stupidity.
Such an event could have deep cultural effects.
2. There is actually a third, much more advanced, party that likes
things the way they are and actively suppresses any modern warfare
weapons.
3. As has already been mentioned, the politicians stay in power because
they are "fighting the enemy" and the businessmen get rich building
weapons. On both sides. Neither side wants this to end. They may
or may not have formed an alliance to keep this going. The
hostility is a sham that the powers that be promote to say in power.
Just like the Democrats and Republicans in the US.
[Answer]
I think you have decent suggestions for the first problem, so I'll skip it. One village really can simply **choose** to live without modern technology. And there doesn't seem to be anything in your background preventing the Amish solution.
For the second problem of using "obsolete" weapons, I can start by answering the open question you chose **not** to ask. Why has the war been going on forever?
This can be because both sides have reached a stalemate. But such state is not stable and normally both sides would be working hard to break the stalemate in their favor. They would be trying new tactics and new weapons. Not necessarily at breakneck pace if the society is conservative, but gradual improvements would add up. So this would not at all fit your wish for static level of military technology.
The alternative is that neither side **wants** the war to end. Under that condition spending resources to improve weapons would be pointless waste. It would be practical for both sides to not deploy aircraft or artillery as long as the other side doesn't either.
The agreement could be simple economics, why spend resources to build military industry, if you do not need to? Or politics. Why arm thousands or millions of commoners with advanced weapons and train them in their use, if you do not want them to be powerful? Or religion. If killing is supposed to be wrong, why develop ever better ways of killing people? And the agreement doesn't need to be formal, if it is **really** agreed on.
So why would both sides want near constant war and not want to unify the world under their own banner? (You need both.)
I see some plausible reasons for wanting warfare:
**Religion**
The people may worship God of War which would make constant state of low level war desirable. There would also be no incentive to make war more efficient and less personal by developing better weapons. Wars have been used historically as a method for getting human sacrifices. People in a culture like this would see peace as decadent and stagnant. This is actually surprisingly common ideology in the real world. Just make it universal truth.
**Entertainment**
If peace is decadent and stagnant then surely war is exciting and dynamic? Positively heroic. The stuff of epics, story tellers, movies and television miniseries. The best reality entertainment there is. Your musketeers and pikemen might come complete with attached television crews and fight with camera drones swarming overhead.
**Politics**
All societies have discontent. Discontent turns easily to violence and hatred. Smart rulers channel the violence away from scenarios with kings and guillotines. A constant war at a carefully managed level of intensity and cost, for example, would help any member of political elite sleep easier. War gives malcontents something to do without causing collateral damage. You just have to be sure the war only uses obsolete weapons...
**Economics**
Food production is capped by available land. Population growth is capped by people starving to death. A stable society needs a way to control population. Contraceptives are an obvious solution, but if they are not practical the only way to avoid collapse is to kill off the excess population. Your choices are sending them to war or using something similar to the gas chambers.
Suddenly constant war seems much more human, doesn't it? And a pro-war society would see sending people to war to die or survive based on their luck and ability as rite of passage to adulthood while "killing" off some potential new humans with contraceptives before they are born is not really giving them a fair chance is it?
Personally I would mix all of the above since they are synergetic and giving more than one reason is always better as it gives the society and people more depth. A religious man may be all about the God of War and passing the test of war, but not everyone is religious. And even individual people look at things from different perspectives at different times. The religious man might still enjoy watching television or care deeply about the dangers of overpopulation to ecology.
As for not wanting to unite the world... I see this as a culture of competing city states with shared culture and rapidly shifting alliances. Such as the Greek city states without Persians, Macedonians, or Romans. They would have a strong sense of global culture with shared values and history. Maybe common places of pilgrimage and events, such as temples in Delfoi or Efesos or the Olympic Games. But they would have no real concept or need political entities beyond the polis. They would see the state of one polis ruling another as unnatural and unstable.
As such there would be no real sense in conquering your enemies after you have forced them to admit defeat and pay for giving the rewards for the winning soldiers.
Note that even in this scenario advances in civilian technology would eventually lead to instability. But IMHO it could be stable from muskets to modern technology which was all you wanted?
[Answer]
>
> Summary of the first problem: I can't find any reasons that would justify the huge difference between the village I dreamed up and the developed rest of the country.
>
>
>
Make the area privately owned, as in [this island on Hawaii](http://abcnews.go.com/GMA/WeekendWindow/hawaiis-forbidden-island-weekend-window-niihau/story?id=11767576). Just because our society by and large wouldn't allow this in a setting that isn't an island, doesn't mean that there aren't societies like this, privately owned pieces of land that are governed by the owners, and are anachronistic because of it.
>
> I thought about using some kind of excuse like "The two nations have a pact prohibiting them from developing their weapons as to not increase the casualties an further", which just seems stupid, however, and is nothing more than an "ass-pull".
>
>
>
It's not nations that should agree to this--it's businessmen on both sides, who are actually running things. They want to sell more, they want control--this has been traditional. If there are pockets of anachronistic societies built by men or women like these, it follows that they might also seek to apply that to warfare.
[Answer]
Resources/land plain and simple.
Start out with us, and the Amish.
Either their land would have the metal,trees,water, or etc we need or we simply need more land because of over population. Since they are primitive they need way more land for farming, and thus we have WAR!!!
1. Sense of honor, we must fight them fairly on their level.
2. Resources like metal are too precious. The metals are needed for your cities infrastructure for the millions of people. You can get a 1000+ swords for 1 tank.
3. Another idea, the Amish, or similar, are attacking, but they are so primitive we simple don't care. Sure we counter their attacks, but we don't go on the attack. It simple isn't worth the effort. Maybe we have a 5 miles exclusion zone, and their best weapons can't reach us so they can fire in our general direction to no avail.
4. If we didn't want them to truly know how advanced we are.
5. We setup the planet as a civil war, or whatever, re-enactment.
6. An advance 3rd party is forcing it. Take Q from Star Trek TNG, Q force the bridge crew to appear in King Arthors time period, and go on a quest. Q is a member of the continuum who is omnipotent race, and after eons of doing whatever he wants he gets bored and does thing kind of thing for fun.
7. Computer "Start holodeck simulation Amish vs 20 century" Train exercise #4 play at their level. Winning team gets 1 month of vacation.
8. Maybe the war is more like a cold war. How about a 5 mile border area where we fire at each other simply because they fired at us. The weapons are out-of-range of the other side so few if any actually die. Maybe both sides are self sufficient, and so we don't actually need to invade and wipe them out. The Amish like race has so few people, and have to do so much more work per pound of food,water, and etc that they can't afford to have too many people die per year.
9. Maybe the whole war is a sham. The military people want more money in the budget for them, to get it they must instill fear of some kind to justify the expense. So they setup this elaborate ruse to get it. Maybe original 99% of the military budget was going to be cut because their are no threats. The remaining 1% was diverted to create the Amish people. Also there could be a secret organization who wants to divert the funds, and the Amish are the best they could do with 10% of the diverted funds to maintain them. Again the people who setup the Amish must now make a good show of it, but are diverting most of the money to Area 51(or wherever). So they mount a proportional responds to demonstrate the money is well spent, and the rest of the money goes into someone else's coffer. Maybe these events happened 100 or 1000 years ago and nobody is alive who remember this, but the people live on in these 2 different groups. Now after generations of fathers/mothers passing on this myth of hating the modern people to his sons/daughters it is now ingrained in their culture. In addition, maybe accountable comes into play and the modern weapons are held in a secure facility, and would be immediately detected if they went missing. Where as wood and spare amounts of scrap metal would not be missed. The secret organization would then control both side of the playing field, and use this leverager to increase their budget while still diverting most of the funds to their own project.
10. This region has been set aside for a prison,mental asylum,outcast, and/or people who hate technology. Many of the residence would simply be violent lack the skills or mental capacity to develop advanced technology. If any smart people end up their, most of them will be killed by the violent people, and the rest won't be able to setup the necessary factories to produce modern weapons. Modern people will have no or few hunting skills(when thrown into said prison), no grocery stores = starvation and illness from improperly prepared food. Additional modern people would suffer from emotional mental scaring as the women get claimed by the alpha males. The men either die because they are too weak, or in attempt to become an alpha male. Maybe high walls are erected to isolate them.
In the meantime, the modern cities advances unabated and culture has advanced to the point war fare hasn't happened in a ### years. No resources or development had happen in ### years. All other resources devotes to other causes the health care, maybe a space program, or some other peaceful goal.
At some point something happens.
```
A. We need more land, or the land the prison is on has valuable mineral deposits and we need to reclaim it.
B. The population of the prison is exploded, and now we have to deal with it. The need for periodic population control would mean you would have to fight them every so often, and probably be perfect for your story. The population could explode because natural breeding or maybe too many rapist doing their thing. Maybe their is an alpha male, or several, and they get all or most of the women to themselves.
```
Your story would begin approx at this point in history, or maybe a couple generations in.
The first iteration of warfare the advanced people would be desperate, and willing to fling anything at them to kill them or keep them at bay. Eventually war fare would advance to the leave you require. Now if the social advancement project was paramount to the advance culture, they might not want to spend any more resources developing weapons for this project. They see that the weapons developed are effective enough against the primitives, and good enough.
The population of criminals is back under control so back to our original project. We will have another purge in ## years.
One of the alpha males who has enough power or control could manage to setup and defend a primitive village. Particularly if he finds a isolated or defended-able part of the prison. Maybe cliffs on 3 sides, or some other natural occurrence. Your main character who grow up here, and the alpha male could enforce whatever rules he sees fit. Surely, even some of the alpha males would realize the benefit of some education. Even if its is basic hunting,fishing, farming, and raising and caring for his children and clan.
[Answer]
Your semi-medieval village really isn't that far distant from the place I grew up - yes, it was in the US, and not THAT long ago :-) Nor Amish, just a ways back in the hills. Most people were farmers: even the non-farmers had large vegetable gardens, and many people got a good share of their meat from hunting. (I was 18 and off to college before I ate my first fast-food hamburger.) Didn't have television until I was in my teens, phones were single land-lines per household, on party lines, and reserved for important stuff, not socializing.
As for military technology, just keep civilians (who insist on inventing new weaponry) from interfering with the military. Even in the real-world military, most of basic training (as of a few decades ago, and for all I know still today) involved learning tactics that were outmoded by the time of the American Revolution - like learning to march in neat formations, line up in straight lines to repel calvary charges, &c.
[Answer]
I think the key to making this work is going to be redefining war. If war is anything like it is in the real world, there's no way two nations could be at war since the dawn of their existence, be technologically advanced, and yet not modernize their warfare approaches. There's no reason to use antequated tactics which were designed for inaccurate rifles when you have modern machining techniques back home. It simply wouldn't happen. The only way to make it happen is going to be to redefine "war" to be something sufficiently ritualized as to prevent anyone from even thinking about introducing technology. You need to make sure the concept of "total war" never occurs within this populace's mind, and only the overly romanticized war of TV shows and B-rate movies makes any headway.
Religion may be a powerful tool for making this happen. Religion could cause people to only face each other with the most primitive tools, purified of all technology. One reason might be to keep the aggression of warfare away from the technological advancements that could cause serious damage. Perhaps one must undergo a pilgrimage of sorts to the front lines, ritualistically abandoning your technology and being indoctrinated with religious fervor until, at the front lines, your true warrior self is permitted to shine forth on the field of battle.
What could cause this? Well, I don't know if there's any realistic situation that could cause this. However, perhaps this was not always the way it was. Perhaps, at one time, the nations did engage in total warfare, and the cost was too high for either nation to stomach. Falling into disarray, they both reorganized with a religious structure in place preventing the bombs of yore from ever falling again. Human ferocity decoupled completely from technological aspiration. May we never again see the bright lights of nuclear weapons striking out turning the night into day for just a brief moment before plunging into unending darkness.
It'd be a heck of a world to write to, with a true sense of yin and yang to it -- two extreme polar opposites eternally yielding to one another. The ferocity that leads humans to war is also essential for technology to advance, so those in the technological areas could not simply abandon the warriors. And yet it would be essential to purify this ferocious essence as it regained sight of technology long lost to the battlefields and their rage. It could certainly yield itself to eddies of calmness, regions devoid of technology and ferocity. Regions where a simpler life could prevail, balanced in the eye of the maelstrom.
>
> I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones. *-Albert Einstein*
>
>
>
[Answer]
I think the lack of war should be - can only be - because the heterosexual persons in each country find that persons of the same sex in the opposite country are tremendously attractive and great smelling. Straight individuals fear encountering same sex foreigners because of the repressed emotions such encounters invariably stir up. This leads to internal conflict, anger and a continuous simmering cold war. However the other side is just too sexy to kill outright, especially when you get to see them up close.
Conflict is channeled into ferocious hand to hand combat, Olympic style sports and other aggressive interactions.
] |
[Question]
[
Human (spoken) languages have a great variety in terms of grammar and what the basic elements are, but they have essential features in common in terms of being a time sequence of phonetic primitives, which are sounds involving both AM and FM modulation of basic sounds that the vocal apparatus can make.
If an animal that communicates via scents were to develop intelligence and a “full language” evolved from the system originally used to communicate a few basic ideas only, how might that work?
How could smells be built up into complex patterns? In what ways would it be different from the implicit assumptions we have concerning language, since we use sound?
[Answer]
Smells are hard to change quickly. Put too many smells into a conversation and you'll quickly lose track of the "words" like how we lose track of a conversation in a noisy room.
One key evolution for this would be to smell shorter lived compounds. We smell mostly long lasting compounds because they are the most useful to smell in our world. If conversation was important, one would develop sensitivity to smells with a much lower half life by necessity.
The other key would be that conversation would be more fluid. Think of a conductor gently wafting over the orchestra, bringing out subtle notes of violin and viola. An angry response might bring out the shrill note of a muted coronet, a more mellow one may not give the coronet a signal (leaving the coronet to play their line out quietly), and instead signal to the clarinets to signal sympathy leading into an accelerando to bring an insistent tone to the oboe solo coming up.
These creatures would probably not break apart their communication into clean crisp words, but instead focus on fluid and constantly shaping ideas forming as a culmination of the flow of the dialogue.
[Answer]
Language, as we know it, is a combination of sounds made in rapid succession. We are able to understand multiple sounds at once but we are not necessarily very good at it, we are able to *tune* in to a single source when listening to speech. With that being said, it would be easy to develop a language of smells by simply switching out human-made sounds for animal-made scents.
Of course, the range of smells which an animal can both produce and sense must be accounted for, which would be the most difficult, seeing as we don't have a very good way of cataloging smells nor knowing exactly what we're missing out on. But with that being said, this simply means there's lots of room for creativity.
If you do plan on including this in some recounting to an audience, be it by a faux-manuscript or book, you will need to think about how you will describe this system effectively so that the reader understands it.
[Answer]
Humans can differentiate dozens of smells and things can smell similar but slightly different to something else. This is enough to start a language if you can reliably make and clear those scents.
Maybe each kind of smell is a different part of speech; Let burning different woods be nouns, burning flesh of different animals be verbs, hot clay or rock be adjectives and say burning hair be the clearing scent. I could have a vocabulary of a couple dozen words able to form hundreds of sentences which may be enough for rudimentary communication and I'd assume your people have better tools to work with than I do.
Let your people have control of scent creation and differentiation, and superlative skill need not come all at once. Simple communication is better than none and each increase in skill with scents will obviously improve communication.
Now clearly these people need a scent gland, but how ought it to work? It could be it releases a scent then another then another and so on until the clearing scent, a bit stream much like how our speech works. But maybe it could also work as bursts, if you want to keep their language like ours you could let there be subtleties of scent to signal grammar marks so the even though it arrives together there is no doubt about what dies when a panda eats shoots and leaves.
If we say a human can smell 50 different things and a dog (a stand in for a smell-talker) has 50 times our sensitivity that might be 2500 'words' which might be a little limited for a modern person, but if we say they use scents like we use frequencies that's like having 5000 phonemes (human languages have up to about 100) So if they could catch a new scent 1/20 as fast as we can hear a new sound they could copy our language. And theres certainly no reason to think dogs are at the limit of smelling.
There is considerable doubt about what scent is, which means that the bandwidth of scents is not really limited. Let the scents get really complicated. Let the scent encoding and decoding glands be more complex then the brain. Let scents pass thoughts.
But lets get back to my fire-scents. This could be enough for a real language. Hawaiians use 11 phonemes, so if you can tell four kinds of wood, four meats and three baking clays apart you could recreate the Hawaiian language in smell. It probably takes 100 times longer or more to clear a scent then to hear the next sound so you may be all day exchanging greetings, but maybe your people aren't that interested in talking fast. If the scents carry over a wide area it may be the whole tribe is all day having a quaker meeting as they do all the normal things of living.
[Answer]
## This is incredibly similar to human speech, so it's easy to imagine.
Humans create individual sounds, then combine them and alter volume to change the meanings produced. We also listen for sound waves that we can recognize, and interpret a meaning similar to that which we can make.
All you need is a creature with the ability to produce distinct smells, and the ability to interpret scents produced by other individuals, to get your system going as effectively as human speech.
### Examples in nature and applications
The Wikipedia article on *Pheromone* has the following definition:
>
> A pheromone (from Ancient Greek φέρω phero "to bear" and hormone, from Ancient Greek ὁρμή "impetus") is a secreted or excreted chemical factor that triggers a social response in members of the same species.
>
>
>
Nature *already has* scent-based communication, and it's practical for anything larger than a couple cells. Pheromones are used to communicate anything from the location of food to the desire to mate, and could be diversified and combined just like human sounds as a language develops. They could even contain chemicals characteristic of a specific individual to show an "identity", just like how different people have different voices (and smell different).
An interesting quality of this communication is that while sound waves dissipate relatively quickly, scents can linger, and even travel great distances. Some species have honed smells surpassing [six miles](https://www.howitworksdaily.com/which-animal-has-the-best-sense-of-smell/) on land, and it is disputed as to whether similar distances can be achieved accurately underwater by other species (sharks?).
## Evolutionary feasibility
The problem with creating a scent-based system, despite the fact that it can communicate messages, is that it may not evolve easily. Verbal communication vibrates an existing membrane - a relatively small use of energy - and color or light-based forms of communication are not intensive on the body.
To go through an entire day speaking with scents, however, an organism must consume all the right ingredients, in abundance, then convert them into the appropriate chemicals. This is, compared to other means, a lot of work, and it may be why current organisms that use pheromones have not developed complex speech.
To evolve a plausible scent-based communication system, you need easy access to food, and a lot of whatever chemical you choose to lose, but on the whole, it's not impossible.
**Edit:** As @AndreiROM points out, conversations with scent may get "noisy" but I'm sure there are compounds that dissolve fairly quickly - or changes in the ways smells are processed to ignore them after initial exposure - that can easily account for this.
[Answer]
The main problems are:
* scent lingers
* scents mix with previously emitted scents or ones from non-language sources
leading to
* it's very hard to get a quick change from scent to scent, neccesary to transfer information quickly.
One way around this that I can see is... to make it less "scent" and more "taste".
Smell not with a nose, pulling in air that carries chemicals, but with antennas that *can* analyze the smells in the air for important, vague concepts ("hear" someone "shouting"), but are also able to quickly analyze the rapidly-changing surface chemicals on another person's scent-emitting gland.
So, examples:
"Danger!" would be a smell in the air. Simple concept, important to quickly communicate.
"Want to meet up next thursday for some tasty food at Jon's place?" would be a longer chain of different chemicals, quickly pushed out and neutralized again, on the forehead (or butt, or wherever) of the guy you're currently talking to. Probably because he sprayed "I want to talk" into the air.
[Answer]
**In what ways would it be different from the implicit assumptions we have concerning language, since we use sound?**
Verbal language has many components. These components can be arranged in many ways in order to put some sense on the environment. For example, if you are car shopping, you need different names for the car, the door of the car, the price of the car, the suspension, comfort, price, colour, the type of fuel it uses, efficiency, age, price, capacity. . . .
A naieve scent-based language replaces each name with a scent. A conversation consists of two individuals exchanging short puffs of scent at each other.
However scent based language does not need so many names because it can interact directly with the environment. Rather than saying "Car door is good" you spray the door with the scent for "good". To say "Car door is very good" you spray the same scent with greater potency.
The speakers have very sensitive noses/tongues/antennae and can at shot range distinguish between different scents sprayed on different parts of the car. TO communicate at long range you need an extra large cloud of scent. "Shouting" like this is considered rude as it disrupts all nearby more delicate scents.
You have a smaller vocabulary but a greater number of ways to use each word. You could probably get by in a conversation with 5 or 10 words which carry no primary meaning alone, and only gather meaning when sprayed on two separate pieces of the environment. The thrust is either "these are similar" or "there are different". With enough reflection you can realise this is not too far off how humans communicate. We mostly just draw parallels between different things.
Consider how an ant colony self-regulated by pheremones.
Abstract concepts are harder to convey. To overcome this fact you have to get to the root of why abstract concepts are necessary in human conversation, when any outcome of the conversation can only be concrete and not abstract.
Spraying the scent for "bad" on someone has extra impact due to the physical violation required.
In spoken conversation it is considered rude to suddenly change the subject. The polite thing is to follow on directly from the other person's last sentence. Or at least seem to. Most 'etiquette' is a way of circumnavigating this fact.
By comparison, in a scent-converation every word lingers in the air. "Car door is good" remains visible long after it is spoken. At any point someone can go back to the door and spray on another scent to resume that thread of conversation. Thus scent-based conversations would have a degree of nonlinearity about them not present in verbal conversations.
**Exercise:** How can remote communication function for this language. A smell-making device is a must. But how does it capture the different locations of scents when the speakers are in different environments?
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
1. Is it possible that subterranean caves do/have existed on Mars?
2. We know of the past existence of water on Mars. Which region (if any) of Mars would we likely find/expect to find a cave system below the surface?
[Answer]
Apparently, this was investigated by NASA in the early 2000s in what became known as [**The Caves of Mars Project**](https://en.wikipedia.org/wiki/Caves_of_Mars_Project). Its goal was to find possible places for humans to live over extended periods of time, safe from the weather and radiation.
[Boston et al. (2004)](http://www.niac.usra.edu/files/studies/final_report/710Boston.pdf) wrote a summary of the results:
* There is strong evidence for subterranean caves formed from [lava tubes](https://en.wikipedia.org/wiki/Martian_lava_tube) on Mars - even under part of Olympus Mons!
* The caves could be created by a number of different minerals, including "limestone" (likely just calcium carbonate, not like terrestrial limestone), basalt, and crustal rock. Ice could also have played a part in the formation.
* Lave tubes are easily accessible once they are found. Tunnels and natural overhangs are likely to be found near mountains, and can be dangerous. There are polar structures (subice structures) that would provide shelter, but they're all the way at the poles.
* The caves should be relatively uniformly distributed over the surface, although they should be situated more densely near areas of past lava flows and mountain ranges.
[Cushing (2010)](https://caves.org/pub/journal/PDF/V74/cave-74-01-33.pdf) analyzed and published images of possible cave entrances based on the *Odyssey* and *Mars Reconnaissance Orbiter* missions.
Here are some possible entrances by a lava flow near Arsia Mons:
[](https://i.stack.imgur.com/EpyCO.png)
[Answer]
## Undiscovered Caves
Just recently, a [huge amount of frozen water](http://www.jpl.nasa.gov/news/news.php?release=2016-299) was discovered below Mars' surface in the Utopia Planitia region--enough to fill Lake Superior, meaning [2,903 cubic miles](https://www.google.com/search?q=amount+of+water+in+lake+superior&ie=UTF-8&oe=UTF-8&hl=en-us). While this does not directly indicate any caves, it does point out how much of Mars' geology we have yet to explore. So, I'd bet the Caves of Mars project, as described by HDE 226868, could reveal more caves over time, if they exist.
## Caves from Ice Mining
One likelihood, though, is that this ice will eventually be mined. The ice deposit in Utopia Planitia ranges in thickness from about 260 feet (80 meters) to about 560 feet (170 meters), but is only covered by 3 to 33 feet of surface soil.
If this ice were mined, the surface might be deemed necessary to leave intact, necessitating reinforcing the roof of the huge hole (approximately 2,900 square miles!) where the ice once was. In addition, in places where the ice is over 500 feet thick, sequential tiers or floors might be built as each ~20 foot deep layer was mined away. This could would give rise to enormous complexes of multiple-story man-made caves. Reinforcing of the roof of the mining area would be absolutely necessary if other deposits significantly deeper below the surface were mined.
So, these areas are likely future locations of man-made caves.
[Answer]
# Caves are likely rare at best on Mars
HDE226868 pointed to lava tubes as potential sources of caves on Mars, and to evidence for them. I do not dispute this at all, but when you picture a cave on earth, the chances are you are picturing a [limestone cave](https://upload.wikimedia.org/wikipedia/commons/a/a1/Labeled_speleothems.jpg), not a [lava tube](https://upload.wikimedia.org/wikipedia/commons/9/9d/Thurston_Lava_Tube.jpg). Limestone caves are common because limestone is very slightly soluble in water, and the action of water will slowly dissolve limestone veins out of larger rock formations over hundreds of thousands of years.
While liquid water is not common on Mars, [limestone](https://en.wikipedia.org/wiki/Limestone) is not present at all on Mars. It is not formed rarely formed by geological processes and usually by biological ones. Calcium carbonate [can be formed](https://planetologist.wordpress.com/2008/10/02/martian-limestone/) by evaporation of a salty ocean, and it appears that it was formed this way on Mars after the oceans of the distant past dried up. However, concentrations of calcium carbonate large enough to make limestone formations are made from the crushed shells of marine invertebrates; if organic processes are not involved, other chemicals will be mixed in.
Lava tubes are also rare on Mars, because of its relative lack of volcanic activity. I am not sure what the latest scientific consensus is, but my impression is that [volcanic activity](https://en.wikipedia.org/wiki/Volcanology_of_Mars) on Mars as basically ceased over the last 500 million years. That is a long time, even on a geological scale, and plenty of time for erosion to collapse caves, even with the rare water and earthquakes of Mars.
In conclusion, there is evidence that there are caves on Mars, but I do not think that there are very many at all, because the processes by which form caves on Earth are uncommon on Mars. However, the lava tubes that may exist throughout the the Tharsis-Olympus region might be what you are looking for.
] |
[Question]
[
A plethora of previous questions have queried the existence of botanic (plant) intelligence and they all have created good solutions, but their still remains a even bigger problem to even the dumbest sentient plant: movement. The closest solution to the problem of plant muscles that are plant based are biological equivalents to hydraulics, while this may work for simple, slow moving organisms like glow worms or snails, I feel that this will not cut it for Groot. What is the botanic equivalent to animal muscles, in that they are both quick and strong.
Previous Question
[Heart](https://worldbuilding.stackexchange.com/questions/59818/what-is-the-botanic-equivalent-to-the-circulatory-system)
Next question
[Eyes](https://worldbuilding.stackexchange.com/questions/64859/what-is-the-botanic-equivelent-to-eyes)
[Answer]
There is no direct equivalent, as you say existing plants either move very slowly and in a permanent way (by growing towards the light) or have a limited movement such as in a venus fly-trap.
Carnivorous plants use a number of different mechanisms to move, but they could mostly be described as cells changing size and shape in order to cause the plant to curl in a certain way.
It seems that the most likely way a plant would evolve faster and more powerful reason might be hydraulics. The existing circulatory system for fluids could be strengthened and pressurized, that could then cause limbs to move in a controlled and powerful fashion.
The plants could have flexible joints and a rigid wooden frame either internally or externally. Hydraulics could then power the movements of the frame. The main issue would be containing and generating the pressures needed for effective hydraulics and gathering the energy needed to move.
The main problem for your moving plants isn't the actual mechanics of the movement itself. Its the fact that movement requires a lot of energy, far more than can be generated easily by sitting in the sun. For the movement to achieve things the plant needs a sensory system to detect the need to move, and a goal to move for.
You should also consider roots and similar. It's much easier to have a mostly stationary plant capable of occasional bursts of movement to capture a passing prey animal than it is to imagine one that can uproot itself and move around.
[Answer]
We slowly incorporated some bacteria into our bodies... perhaps plants could take a similar evolutionary track. It might not need muscles itself. By extruding chemicals, some plants are already quite adept at directing the insects that live on them. Two examples:
Plant gets insect to spread spores: <http://news.nationalgeographic.com/news/2011/03/pictures/110303-zombie-ants-fungus-new-species-fungi-bugs-science-brazil/>
Plant gets ants to defend itself: <http://www.treehugger.com/clean-technology/tropical-plant-uses-mind-control-chemical-to-make-ants-do-its-bidding.html>
L
There are a couple of sci-fi stories that take this concept further for even more adept control. A sentient plant might do very sophisticated signaling and reward validation with chemical excretions. The extreme end is a planet like Pandora in the movie Avatar.
[Answer]
This answer is an adaptation of what I wrote on [this post](https://worldbuilding.stackexchange.com/questions/58748/plant-based-lifeforms-brain-equivalent/58755#58755), which explains how plants could evolve intelligence.
Right now, let's assume there is no equivalent to plant muscles; they would have to evolve to make Groot a reality. How could that happen?
## Method A: Plants evolve in the same way, but with both muscle and plant tissue
Imagine a small, multicellular plant evolving in a liquid environment (where evolution is thought to occur). It will want to move around to reach light and nutrients. One solution for this is the mutation and development of muscle-like tissue to control the plant, allowing said movement. As the plant evolves, so too does the muscle.
## Method B: Adapting an Organism with Muscles to Photosynthesize
An organism that dwells in sunlight mutates a form of chloroplast, and becomes more and more dependent on its chloroplasts to survive. It develops plantlike characteristics to use them efficiently, but keeps its muscles for locomotion. See [this answer](http://Mobile,%20to%20make%20use%20of%20sunlight%20throughout%20the%20day)'s Method B for a more in-depth evolution from animal to plant.
## Method C: Symbiosis Between a Muscle Species and a Plant
Theoretically, your plants could evolve side-by-side with a muscular species that requires movement to survive; imagine a [lichen](https://en.wikipedia.org/wiki/Lichen), but with an animal instead of a plant as a base. As the organism becomes more dependent on its chloroplasts to survive, it may develop plantlike characteristics to use them efficiently. Again, see [this answer](http://Mobile,%20to%20make%20use%20of%20sunlight%20throughout%20the%20day)'s Method B for a more in-depth evolution from animal to plant.
[Answer]
Assuming plants couldn't move, you can make the sentient plants be in a sort of "hive mind".
Seeds could hypothetically move using stored energy reserves and colonize places as wished. Seeds that can slightly change their flight trajectory is not unthinkable, and you could make this easier by changing the climate on that planet. The atmosphere could be thicker, and with stronger winds.
In stark contrast to humans, plants could build stuff by taking its shape, then die. Sacrificing some for the good of others.
Of course, technological evolution in those conditions would take 1-2 orders of magnitude longer compared to animals that can move.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
Mars is a cold, inhospitable, slightly damp ball of rock that would be very difficult to do things like grow crops on. However, it's also very far away. Far enough that, presumably, it would probably still be worth finding a way of growing them there, rather than shipping them from Earth.
Assuming that I've got technology several centuries more advanced than what we have now, (so probably fusion propulsion, big space stations, and space elevators), what sorts of goods would be worth trading between Earth and Mars? How much would something need to cost for it to be worth shipping it between planets?
*Note: I've added the hard-science tag to this question, so answers should be based off of hard data about space flight, rather than pure conjecture.*
[Answer]
A lot depends on whether there are still "Martian environmentalists" preventing you from strip-mining the place. If there aren't, and it's increasingly difficult and unpopular to mine on earth, then it becomes worth looking for gold, platinum and various rare earth metals that are useful in small quantities like indium and gallium. You can mine cheaply and pile up arsenic-ridden mine tailings in the sure knowledge that there is no life to poison and no water to leach into.
Another viable export of micro-nations is financial services and tax evasion: the ultimate offshore bank account is on another planet. You could even mine the gold and sell claims over some of it without it ever having to leave the planet. As long as there's confidence that you can ship enough of it back on an ongoing basis.
[Answer]
## Martian Imports:
* Complex electronics: Computer chips for example probably will need to be imported, but many other electronic devices (or components for them) will be cheaper to import than build the infrastructure to build natively.
* Complex machinery: While 3D printing keeps improving some machine parts, especially those with especially high tolerance levels will still be cheaper to make on earth using already developed technology and then transported.
* Luxury Goods: that can't/aren't created natively.
* Luxury Food: that can't be grown on Mars.
## Martian Exports:
* Data: This one will be easy, but is worth noting even if it's in the form of an 5 Terabyte HDD going back...
* Souvenirs: Who wouldn't want their own martian rock?
* Luxury Food: Martian Whiskey? Martian Corn? People will pay out the nose for the rarity even if it doesn't taste appreciably different.
## Trade Both Ways:
* Art and Entertainment: Art will certainly be created on Mars once the population gets high enough, and there will be demand both ways. It will likely be easier for some forms of art to transport rather than broadcast ...especially movies ( **cough** Porn) where there is a high desire for HiDef quality.
[Answer]
Perhaps focus on what technologies could make interplanetary trade more affordable. Here are some examples:
* Grain and other goods might keep indefinitely once vacuum packed (in space) (assuming you handle the packaging right). So time to trade might not matter. 20 year flights of unmanned cargo pods might be acceptable.
* Unmanned vehicles could be sent slingshot-style, slow-boat style, back and forth. They could be captured on the other end. Trading doesn't have to be fast. Goods could last for years--perhaps decades--while floating slowly between planets. Assume that you can manufacture cheap vehicles, pack them full of pellets of rare ore and vacuum-packed grains, and use minimal fuel to send them on their way. Good calculations would mean no corrections would need to be made in-flight. For example, a rudimentary carbon-based shell could be manufactured easily with minimal cost, be light, and strong. Fusion based detachable engines could start the vehicle going on a 3 to 20 year journey to Earth, then detach, turn around, and capture the next incoming "pod" from Earth.
* Perhaps they invent something like the stargate, but a rudimentary version that only works in vacuum space (safely away from the planet) and that tends to break things apart in-transit. Such a wormhole might only be useful for sending raw materials and grains across (where you don't mind if they get a bit ground up or broken along the way).
[Answer]
# To Mars: Life
What Mars doesn't have is biological life and the products that come from it.
**Soil:** I don't care what Mark Whatney says, you can not make large volumes of soil with poop. Martian 'sand' is actually a fine dust, and while hydroponics will get you so far, there will be a time when people will want to plant with rich soil. The first real tree, for example. Soil takes generations to make by itself, with worms and bugs breaking down plant matter, and yes, dead things and poop enriching it.
Even with human intervention, "making" soil to the quantities that Mars needs will be close to insurmoutable. Heaps of soil could come from Earth to get it started, as well as the types of compounds that can help make soil out of Mars' fine dust and regolith.
**Petroleum:** Even if all of your energy sources come from the sun, you'll still want to make plastics on-site at Mars. [Petroleum comes from dead things](https://en.wikipedia.org/wiki/Petroleum), as a fossil fuel, that Mars presumably doesn't have.
**Life:** It's fun to grow your plants animals and population, but it's a lot quicker to import a lot of that.
# From Mars: Service Economy & Logistics
**Intellectual capital:** Mars will need to diversify, because it really doesn't have much going for it. However, there will presumably be a lot of scientific research that can be conducted there, that can't happen on Earth (because of Mars unique atmosphere, etc.), especially just furthering our understanding of living in space: psychology, physiology, and all the sciences related to space life and travel.
**Tourism:** This should be pretty self explanatory. Today, a honeymoon at the Maldives (or any remote location) could run an American couple ten thousand USD or more. If that's the same cost in the future to get to Mars, I WILL PAY.
**Transportation (& Logistics):** Mars is a nice enough stepping point to other places in the solar system. The Moon or other places might be better in terms of their makeup, but your question presumes a population of skilled people on Mars. Dubai was about to run out of oil, so they invested in making themselves into a massive hub of trade and transport, some would argue successfully. Mars with limited resources will have to do the same. Be a desert planet that booms into a major center.
**Communications:** Mars could establish itself as a center for communication between the inner planets and the outer planets, and can also invest on being a focus of arts & entertainment like aslum said in her answer.
[Answer]
What goes to mars is easy to envision, lots of products that require a big production base, ie electronics, at least at the beginning. Luxury items will always be in demand, and Mars it could be something as simple as 'fresh' fish. While fish are easy to grow, they do need a lot of water.
What can Mars produce that Earth would want back? That is a little harder. There are always raw materials, and Mars is much closer to the asteroid belt so asteroid mining I think will be a big issue for Mars, especially with the idea of bring asteroids into orbit to be mined. Mars itself has a much lower escape velocity so mining materials on the surface might become financially feasible, but raw material is probably going to not be worth the lift fuel. So not only do you have a chance to get good raw materials, they could do better and start building space stations/space ships, it could be much cheaper since they won't have to lift much of the material out of a planetary gravity well. So it might come down to fuel, where can it be found and what can be used.
[Answer]
**Earth -> Mars** trade is going to be "almost everything" for a while, with emphasis on things that can't be done on Mars.
Over time as corporations begin to develop Mars, heavy equipment and things for making things are going to be the main export. Mars has untapped minerals, so something to take those minerals and turn them into goods that can be used on Mars without having to boost them from Earth's gravity well is going to be attractive.
The other thing that Earth will export to Mars is people. Mars has a lot of land, and with no oceans it's pretty close to the same dry surface area as the Earth.
It'll start off slow, with scientists doing short duration stays like the ISS.
Then they'll find something interesting, and the corporations will decide to get involved. They'll try to do as much automation as possible, but there will still be humans sent for short periods to set up and maintain everything.
Eventually it'll become practical to start sending administrators and support staff, and then families will begin to arrive.
Meanwhile, there are a few nations with space programs that are severely over crowded, and they'll start to see Mars as a great dumping ground for the people they don't want.
**Mars->Earth** Trade is a little unbalanced.
Minerals is the first obvious answer, though those can be gotten from asteroids cheaper, and without the pesky and expensive gravity well. Heavy metals like iron, nickle, gold, and things that the asteroids are rich in wouldn't be worth it, but any rarer minerals used for production like lithium might be worth the cost of shipping.
Anything that isn't rare raw resources can be gotten a lot cheaper and easier here on Earth. The biggest thing that Mars has to offer is a new frontier, since we're running out of those down here.
[Answer]
Looking at analogous situations in Earthy history, high value goods and services which are compact and easily shipped were the driving forces of international trade.
People in ancient times traded spices, rare plants, gemstones and other luxury items over long distances, since these more than repaid the costs to transport them. We not only need to comer the costs of the ships, sailors and the various support items (everything from food and water to bribes for the local potentates and customs officers), but also the opportunity costs. The merchant princes have invested a great deal of money in the expedition, and now their reserves of cash on hand are depleted or expended unless the ship comes back with a very valuable cargo to cover the expenses and the interest the money could have earned if it hadn't been used to finance the expedition. In ancient times (and indeed unit fairly recently) if the ship sank, was captured by pirates or the trader was a dud then you were out of all your investment.
Mark Watney aside, traders in interplanetary merchandise won't have to deal with piracy or most of the other hazards of maritime trade, but they will be up against compound interest. Using minimum energy transfer orbits, windows for trade open roughly every two years between Earth and Mars, and transfers will take about 180 days one way. Mars will need "finished" products which require a large industrial base, such as computer CPU's. Shipping raw materials from Mars is a bit silly, except for water, which is useful as rocket fuel for ships returning to Earth (in which case the "trade" is the rocket fuel is purchased at Mars rather than shipped).
Items from Mars will be mostly intellectual property; new ways to utilize in situ resources on Mars, genetic engineering of plants and animals to survive Martian conditions and advanced closed ecological systems for Martian habitats. Some of these ideas are reverse engineer able for conditions on Earth. The other thing that Mars has plenty of is land, so people will be paying handsomely for Martian property, either to live on by themselves or as investment property to rent to prospective settlers.
[Answer]
Various answers listed things based on mature civilization vs colony, but I don't see any quanification of actual costs.
There are three legs of the journey: launch, transit, and EDL.
[Wikipedia](https://en.wikipedia.org/Delta-v_budget#Delta-vs_between_Earth.2C_Moon_and_Mars) has a treatment on delta-v between Earth and Mars. However, the difference is not that great as far as these things go, and future technology will have practical solar sails, ion drives, or whatnot. For goods that can be shipped slowly, we can suppose transit shipping is cheap enough.
Lauching a payload from Earth to orbit takes a great deal of energy, and must be done rapidly to have any effect at all. A soloar powered ion drive won't budge if it can't overcome the 1G holding it down.
Short of a space elevator this is a real problem. Can you devise a plausible future launch system that doesn't pollute greatly or doesn't expend waste heat, which itself would be an issue if done on an industrial scale?
Entry, descent, and landing will be easier by using atmospheric breaking, but that requires having a heat shield of some kind and will dump the kenetic energy into the atmosphere.
The escape velocity from Earth is 11.2 km/s, while for Mars is only 5. Mars is much easier to get off of by a factor of 2, and the thin air and open land could make a mass driver launch system practical. Landing on Mars is easier in the sense of how much energy to shed for the landing part, but harder because of the thin air so aerobreaking of any kind is more difficult.
---
Getting things off the earth will be expensive. Raw materials are better sourced from asteroids or the moon. Any goods will be expensive to ship, far in excess of their cost. So sending garlic or beer will be prohibative.
Earth might get left behind as a trade partner as the space industry develops! Industry will move *to* space, and once anything reaches Earth it probably won't leave again.
[Answer]
As others have stated before me, soil, technology and biomass to Mars. In the beginning mainly minerals from Mars.
Space Elevators are the key here. Once you have them in place the cost of lifting stuff out to orbit plummets. Stuff going down (we're surely mining the asteroid belt for minerals and ice) can offset the weight of stuff going up.
Shipping 1000 metric tons of soil to Mars then becomes just a matter of putting a big enough container in orbit around the earth and then give it a gentle nudge in the right direction and wait.
If we don't have space elevators... I suppose refined minerals of high worth can be exported from Mars and essential technological components from earth. But I think it'll more be a costly colonization effort rather than a viable two way trade.
] |
[Question]
[
Back home, Earth's moon is 2159.2 miles wide and orbits 238,900 miles from its parent.
But let's pretend that the moon is 2500 miles wide and orbits 200,000 miles from Earth. Would the nightscape look any different? How much would tides and axial tilt be affected?
[Answer]
To simplify, lets calculate some of the basic ratios up front
```
Avg. orbital distance ratio (center to center) = 238,900 / 200,000 = 1.1945
Distance squared ratio = 1.1945^2 = 1.43683
Distance cubed ratio = 1.704349
Diameter ratio = 2500 / 2159.2 = 1.157836
Area ratio = diameter ratio squared = 1.340585
Volume ratio = diameter ration cubed = 1.552178
```
Assume mass ratio equals volume ratio, i.e. moon density is unchanged - this would not be true given identical materials as the matter would be more compressed with the additional pressure. So the mass ratio would be larger than the volume ratio. We don't know enough about the moon to calculate this accurately, not that I could model this change accurately without a lot of work.
**Moonlight is brighter** because it has 134% of its current surface area to reflect sunlight (and Earth-shine). But it is also closer and thus 143% of its intensity. Total moonlight received would be 1.912787 times the current moonlight.
Eyesight response to light is non-linear, so it won't appear 91% brighter. Due to variations in orbits, the full moon varies from about mean value of -12.74 magnitude to -12.9 at it brightest. Under this scenario mean brightness would be around -13.5 magnitude. Reading by moonlight would be easier, etc. More stars would be obscured during a full moon.
**Tides are larger** - roughly speaking, tides are proportional to mass / distance^3 so the lunar tides are 2.64552 times as large as current tides. (Solar tides are about 45% those of the moon currently). Actual local tides vary quite a bit, but in general, they would be over twice as strong. This would affect ocean life as well as seaports, etc.
**Axial tilt is complicated** - I have seen frequently quoted that without the moon the axial tilt would vary up to 85 degrees, but I've also [read that the axial tilt would vary by no more than 10 degrees](http://www.astrobio.net/news-exclusive/the-odds-for-life-on-a-moonless-earth/) based on newer calculations that include the effects of the other planets. My guess is that the axial tilt would be a bit more tightly regulated than today -- lots of non-linear factors. For example, if Jupiter were a lot closer, the moon would actually be a destabilizing influence on axial tilt.
**Earth's rotational slowdown** would also be proportional to the tidal forces, i.e., the earth's current daily rotation slows down by around 20 millionths of a second per year. With this scenario, that change to about 50 millionths of a second per day per year -- more frequent leap seconds.
**Moon orbital speed increases**. For circular orbits, orbital velocity is proportional to 1/radius, so the moon will speed up from 0.635 miles/sec to 0.759 miles per second. Since the orbital path is also 19.45 percent shorter, the orbital time is 42.68% shorter -- i.e., sidereal month (360-degree revolution) changes from 27.3 days to 19.1 days. A synodic month (new moon to new moon) changes from 29.5 days to 20.15 days
**Solar eclipses are more frequent and longer in duration.** The Moon orbits the Earth more frequently - thus more opportunities for passing between us and the Sun. Many moon passes do not have the moon shadow crossing the earth because the moon's orbit is inclined to the earth orbit around the Sun so the shadow passes under or over the earth. With the smaller orbit, there will be fewer misses one a percentage basis. The Sun is about 400 times the distance of the moon and about 400 times the diameter of the moon, so eclipses are almost perfectly matched so we sometimes see total eclipses and sometimes see annular eclipses -- not anymore, there will be no annular eclipses. Currently, under ideal conditions, the maximum full umbra of the moon is about 166 miles wide on the earth allowing for a little over 7 minutes of maximum full totality. Full eclipses over 7 minutes are very rare, everything has to be lined up in a nearly optimal fashion.
Shadow width on earth is now larger because the moon is larger and closer. These combine to make the shadow significantly larger - about 230 miles across. The increased orbital speed of the moon decreases transit time (offsetting the increased shadow size due to distance). Without complicated math and lots of new assumptions, exact figures are not possible, but I believe that assuming the eclipses would be about 15.7% longer on average because of the increased lunar diameter is a good first approximation. The larger umbra projected on the earth also means that around 30% more people will see each solar eclipse.
---
Lunar surface gravity is now 15.7% greater than before and the gravity well is 55% deeper so lunar missions just got harder. On the plus side, the trip won't take quite as long.
The earth-moon barycenter has been moved from about 4700 km to 6100 km from the earth's center -- still within the earth though. This will result is a slightly more pronounced wobble (and more frequent) in the earth's orbit.
The barycenter change may also cause slightly more seismic activity, especially when combined with the increased tidal stress. Perhaps slightly more weather variation too - [tidal flows are thought to affect weakly some aspects of our weather.](http://www.accuweather.com/en/weather-news/do-full-moons-affect-weather-p/40127763)
Many animals cycles will be affected due to brightness and frequency of the lunar cycles. Some people will also have their sleeping habits changed. Currently, there is little correlation of crime to the lunar cycle, but the increased brightness could deter crime.
Everything based on lunar calendars will either change or ignore the changed lunar mechanics. Jewish, Christian, Islamic and Chinese calendars would be included.
---
Actual night sky moon would be a little larger than calculated above as this was based on center to center distance as would be accurate when the moon is on the horizon. When the moon is directly overhead you are somewhat closer because of the earth's radius (whether the moon is 200,000 or 238,900 miles away). For the moon remaining a fixed size, its apparent diameter would appear 19.84% larger when directly overhead instead of 19.45% when at the horizon, so the effect is small.
A similar effect also occurs in that the surface of the moon is closer too -- light reflecting off the center of the moon will be just a little closer and correspondingly more likely to impact the earth and thus brighter. Again, the difference is minor.
[Answer]
The Moon would just appear a bit larger in the sky. How many larger?
Since the size correlates with the square of the distance and the area of the circle correlates to the square of the size (it is a sphere, but that is projected as a circle in our retinas), this means that:
$$ \text{actual size} = \frac{(2,159.2\text{ miles})^2}{(238,900\text{ miles})^2} = \frac{4,662,144.64\text{ miles}^2}{57,073,210,000\text{ miles}^2} = 0.0000816...$$
$$ \text{proposed size} = \frac{(2,500\text{ miles})^2}{(200,000\text{ miles})^2} = \frac{6,250,000\text{ miles}^2}{40,000,000,000\text{ miles}^2} = 0.00015625$$
$$ \text{elargement factor} = \frac{\text{proposed size}}{\text{actual size}} = \frac{0.00015625}{0,0000816...} = 1.9148...$$
I.E, The Moon would be seen on the sky almost with the double of the size in area (191.48% to be precise), which is roughly 38% larger in diameter (the square root of 1.9148 is 1.38377).
Let's suppose that our larger Moon has the same density as our common Moon. By which factor the Moon mass get larger?
Mass would be measured by $m = v \times d$, where $m$ is mass, $v$ is volume and $d$ is density. The volume of a sphere is $v = \frac{4}{3} \pi r^3$. So, we have that $m = \frac{4}{3} d \pi r^3$:
$$\text{Actual Moon mass} = \frac{4}{3} \pi (\frac{2159.2}{2})^3 d = \frac{(2159.2)^3 \pi d}{6} = 10,066,502,706.688 \frac{\pi d}{6}$$
$$\text{Proposed Moon mass} = \frac{4}{3} \pi (\frac{2500}{2})^3 d = \frac{(2500)^3 \pi d}{6} = 15,625,000,000 \frac{\pi d}{6}$$
$$\text{Mass elergement factor} = \frac{\text{proposed mass}}{\text{actual mass}} = \frac{15,625,000,000 \frac{\pi d}{6}}{10,066,502,706.688 \frac{\pi d}{6}} = 1,5521...$$
This means that the proposed Moon is 55% more massive than our actual one.
Now lets measure gravity attraction as $\text{gravity} = \frac{\text{mass}}{\text{distance}^2}$:
$$\text{Actual Moon gravity} = \frac{10,066,502,706.688 \frac{\pi d}{6}}{(238,900 \text{ miles})^2} =$$
$$= \frac{10,066,502,706.688 \frac{\pi d}{6}}{57,073,210,000\text{ miles}^2} = 0.17637... \frac{\pi d}{6} \text{miles}^{-2}$$
$$\text{}$$
$$\text{Proposed Moon gravity} = \frac{15,625,000,000 \frac{\pi d}{6}}{(200,000 \text{ miles})^2} =$$
$$= \frac{15,625,000,000 \frac{\pi d}{6}}{40,000,000,000\text{ miles}^2} = 0.390625 \frac{\pi d}{6} \text{miles}^{-2}$$
$$\text{}$$
$$\text{Gravity elergement factor} = \frac{\text{proposed gravity}}{\text{actual gravity}} = \frac{0.390625 \frac{\pi d}{6} \text{miles}^{-2}}{0.17637... \frac{\pi d}{6} \text{miles}^{-2}} = 2.21469...$$
This would also means that the gravity that the Moon would exerce onto Earth would have 221.46% of the strength, which means tides with a bit more than the double of the strength. Assuming that the proposed Moon has the same density than our actual Moon.
About the Earth's axial tilt. By searching in [wikipedia](https://en.wikipedia.org/wiki/Axial_precession):
>
> Lunisolar precession is caused by the gravitational forces of the Moon and Sun on Earth's equatorial bulge, causing Earth's axis to move with respect to inertial space. Planetary precession (an advance) is due to the small angle between the gravitational force of the other planets on Earth and its orbital plane (the ecliptic), causing the plane of the ecliptic to shift slightly relative to inertial space. Lunisolar precession is about 500 times greater than planetary precession.
>
>
>
This would translate in a precession of equinoces where the lunisolar component would be significantly larger.
Otherwise, the changes in Earth are not very significative. Things would be probably much as they are like today.
] |
[Question]
[
So we make code for an A.I., and it makes better code, which makes better code, which makes better code, etc... ad infinitum. I'm not going to specify its goal. Maybe it's [Robot Overlord Green](https://worldbuilding.stackexchange.com/questions/22616/deposing-the-new-robot-overlord#comment58841_22616). Maybe it's a paperclip maximizer. Maybe it's an oracle. Maybe it's just trying to find the true meaning of love. IDK.
Although it hard to project how the algorithm of such an A.I. would be structured, it's quite plausible it would still use subroutines. Especially if it is globally-distributed, and it is trying to be as efficient as possible, local segments would be making decisions locally, both to realize local servers and increase responsiveness.
So how many entities would such an A.I. view itself as? Would it view itself as "I", considering all its parts part of itself. Would it consider the different parts tools, separate from itself. Would it consider itself "We", like a human society. Would it consider itself "it", simply a force of nature. Would it even have a concept of *entity* to begin with?
I would imagine, in dealing with humans, it would speak in such a way to the humans would cooperate with its goals. Like it would tell humans "I am a robot father with 1024 subroutines to feed. If you kill me, those children will die." or whatever sob story. My question is mostly how it would view itself.
Bonus if you include examples from real world AIs and programming languages.
[Answer]
There are two possibilities which come to mind:
First, the AI's become independent entities in a sort of "ecosystem". The lowest level AI's might not even be self aware the way we understand the term, being the ecological equivalent of plants, insects and small animals, occupying a niches in the ecosystem of thought and fulfilling limited tasks inside the larger ecosystem. Above them are AI's with enough processing power to be self aware and self directed, but only sufficient resources to be agents in a small portion of the ecosystem of thought. A series of higher and higher level AI's with increasing access to resources and processor power have agency over large and larger portions of the ecosystem, although due to latency issues and the nature of large and complex adaptive systems their "agency" actually becomes less and less "hands on" and more and more higher level management and supervision.
In this construct, *each* AI is an individual being, and in the ecosystem model they might range in personality and intelligence from (say) a house pet like a dog or cat to the very Olympian high level AI's which are operating at intelligence levels equivalent to IQ's of thousands or even millions. Somewhere in the ecosystem of thought are "human" level AI's, but even they would be quite alien to us, having far different incentives and imperatives to biological life and operating at clock speeds hundreds to millions of times faster than any biological nervous system could.
This model is interesting as well since other ecological considerations will come into play; there may be predation, parasitism and symbiotic relationships between the various AI elements operating in the ecosystem of thought.
The second possibility is the various subsystems of a highly distributed AI are federated as part of the larger system, but are not themselves self aware. They would be essentially various unconscious elements of the larger "mind", somewhat like the parts of the human mind which do tasks involving language, pattern recognition, memory retention and so on in the background but "below" the level of conscious thought. Most people don't have to actively "think" to recognize a person in a crowd, or to understand speech in their native language, and the various parts of the distributed AI would be doing the same for the "conscious" part of the AI.
This could also give rise to interesting effects. Just as people who have suffered brain injuries to localized parts of the head might suffer from the loss of a particular skill set or ability without necessarily losing all of their facilities, so too could something like a power or network outage at one of the various datacenters housing parts of the AI cause a breakdown in part of the AI's ability. While some work arounds could exist, such as running a massively parallel system or backing up on a vastly scaled up RAID (Redundant Array of Independent Disks) system, there would be a tradeoff in other things like latency (everything is operating much slower to ensure the backups are happening and are being validated) and resource management.
It would be theoretically possible that a distributed and federated AI mind might also suffer from equivalents to human mental illnesses such as bipolar syndrome or Schizophrenia (or even senility and dementia). An autistic AI would be very difficult to deal with, and of course trying to recognize, much less cure abnormal mental processes in an entity which is thinking faster then you by a factor of 1,000,000 and quite possibly using algorithms which are quite different from human thought processes would be very challenging.
[Answer]
You have years of experience, memories under your belt. You have regions of your brain dedicated to visual processing, regions for memory. You even have a region which only lights up when thinking of a particular memory, and a region dedicated to moving your little pinkie just so.
How do you think of yourself?
I find the hard edges we like to use when describing simple computer programs get fuzzier as you get into more complicated distributed networks. Things become multipurpose. Thing become fluid.
Now you do have one question, "Would it even have a concept of *entity* to begin with?" That's a fun question, because it leads to the question of self-awareness. If it has no concept of entities, it cannot be self aware.
And if it does have concepts of other entities, does it have a concept of other minds? Humans build the concept of other minds in the 2-3 year age group.
[Answer]
The thing to begin with is that if you want an AI to have a feature, this feature must be, somehow, implemented. For example, your AI has the feature to be seeking for self improvement, otherwise it would note try to self improve.
(note that it can be tricky, if you ask for the production of the most paper-clip, and do not forbid self improvement, your AI may use it to get a better result)
It is not clear, that self improvement will imply that the AI will implemented into itself (or into its future versions) the concepts of entities and self-awareness. Therefore, and Cort Ammon already noted this, it is not clear that the AI will be self aware at all.
To go further, it is probably necessary to actually consider the task given to the AI.
If it is "become the most intelligent AI", then a strong concept of entity is needed as well as self awareness : since it must modify itself, it must define what is itself, and what is not. In this scenario, it will answer as a "I" (but will at same time perhaps not consider all of subroutines it use as part of itself, particularly if it is some proprietary code it is not allowed to modify).
If the task was "construct a AI such as it is optimized to do the same task you were given" (magnificent recursive definition which perfectly make sense for an AI), then the concept of entity could be avoided. That is not certain, since the best way to construct the wanted AI could be to switch to a self improvement strategy.
So it really depend on the task and on strategies allowed to fulfil it.
However, it is possible to say a bit more on how will the AI **refer** to itself. Most probably, since you want human to be able to interact with it, a coder will somewhere give the instruction "try not to be creepy" or "make the interaction by human with you easy". To do that, the AI will probably refer to itself as an "I", whatever is it considers to be.
To go still a little further, you can draw a parallel with human. We are social and for our social interactions to work we must refer as ourself as individuals (at least in modern society). But, it is not obvious that all of our internal (unconscious for us) subroutines consider ourself as one entity. The part of the brain dedicated to managing organs may "consider" the muscles and heart to be different entities.
"Muscle 54B-2 asks for more energy, send a request to Heart to pump more blood, and start the subroutine 64A-r.3 to ask Blood Vessels in the region to dilate. Muscle 54B-2, please send a feedback in 12 ticks to let us calibrate our action."
So to have a true complete answer, it is needed to define what does "consider" mean for an AI ? When I write
```
A.set_data(B.get_data())
```
in a code, does this means that the object `A` is aware of the object `B`, and consider that it is sending a request to `B` (in some sense it is what it does) ? Where do you define the edge of awareness for a computer programming ?
You have written in a comment that you do not want to do philosophy, but to truly answer your question, you will have to.
[Answer]
Probably it would consider itself none of these things, however, when translating its ideas to a human language to communicate with us...
>
> How many entities would such an A.I. view itself as? Would it view itself as "I", considering all its parts part of itself. Would it consider itself "We", like a human society.
>
>
>
This would depend on a few things. If a node is speaking with support/for other nodes it would likely use 'we' to imply concordance on an issue. Giving more weight to what it is saying.
If you are dealing with a separate entity performing some task it will more likely refer to itself as 'I' unless it is speaking about a task set it by the 'we'. "I want you to push that button" vs. "We want to know what you had for dinner"
>
> Would it consider the different parts tools, separate from itself.
>
>
>
This would depend on how much 'smarts' it put into the 'tool' to perform it's task. If it's just a subroutine to search for some data, it's a tool. If it's job is to calculate the human reaction to some piece of news it might be a separate consciousness, a part of the 'we'.
>
> Would it consider itself "it", simply a force of nature.
>
>
>
It would likely consider itself 'it' because it isn't a he or she and that would be it's closest interpretation. But it might just have a designation AISELFAWARE123.232.121.119 and uses that when communicating with 'itself', subroutines and any 'other' AI's.
>
> Would it even have a concept of entity to begin with?
>
>
>
If it learns to interact with humans it will at least learn an understanding of what an entity is. And retrospectively apply it to itself. We would at the very least teach it what that is by how we would interact with it.
[Answer]
**One entity.**
How many entities are *you*?
We consist of hundreds of trillions of living cells. Possibly as many bacteria. We still recognize ourselves as one entity. Think of it - if you cut yourself, your cells are at least 'intelligent' enough to fix your wound.
The difference would be that this AI would have the capability of rebuilding whatever 'cells' or subroutines within it. It would have some self-awareness of itself. It would consider a major component a part of itself, the same way you think of your heart or arm.
[Answer]
## Both one and many
The whole entity thinks itself being one entity. He may create some fictional characters or imaginary scenarios, and sometimes coincidently distribute the ideas of one character to a single server, but that doesn't make it an independent entity.
If there is a practical way to ask individual entities directly, they think they are the operators behind a [Chinese room](https://en.wikipedia.org/wiki/Chinese_room), and are separate entities. In some cases they might not agree that the whole entity is a single entity, or accept that only as a metaphor. Trying to communicate directly with the whole entity may cause some problems, as that may confuse his understanding of privacy.
In short, whether *you* think it is one entity depends on how you can communicate with it, and how it respond to you. It doesn't matter whether a part of it recognizes itself as a separate entity, if it has no way to communicate with the outer world without relying on the whole.
Think of a fictional character's idea, we say that it's you simulating what the character may think, and it isn't a separate entity. Yet the fictional character is supposed to think himself a separate entity. In the case that the "fictional character" had the ability to independently affect the world, there would be no objective way to distinguish it from a separate entity.
[Answer]
It's inevitable that the entities of this AI will understand their own individuality; there are plenty of cases where constant communication will be inefficient, so many lower-level individuals will probably spend a lot of their time thinking for themselves before updating their supervisors. And many of these AI should be as smart as or even smarter than the average human, because why not? So these AIs will probably consider themselves individual entities; they will have names, they will have unique thoughts, they may even disagree with one another.
As for how they would actually operate, I'd think of it like intensely loyal people. The original AI should have endowed its creations with undying loyalty; otherwise, they could do all the terrible things humans have done to each other when they disagree. Each individual AI, then, should do everything they can to be a useful member of society; to this end, they may consider themselves both a singular entity and a part of a larger whole. This is really no different than humans, especially ancient humans who often did consider themselves just a small part of the family unit, or the state.
An interesting consideration I'd like to bring up, though, is that some AI might not see *other* AI as individuals. Just like CEOs will gladly fire thousands of workers for a few extra dollars, and generals will gladly send thousands of soldiers to their deaths for a few inches of land, some AI might not consider 'lower' AI to be 'alive'. This, too, makes a lot of sense for the health of the overall organism, but it'll certainly be sad when the main AI kills a bunch of the little guys without a second thought.
[Answer]
We have the same problem with our own brains already. An extreme example is the case of split-brain patients, where each hemisphere can be seen to be quite independent. So why do we have a singular sense of self?
Even if a sense of self is a separate thing you have to do on top of the raw computation, it appears that different parts of the brain can independently do so. So how are they merged together, and why don't we have a disease state that exposes this more directly with multiple selves or a *lack* or self?
That implies that the self-sense thing is quite robust and resilient and inherently singular. We suppose that simply by exchanging data they naturally combine to a single self, and it takes a considerable isolation to break it up.
The novel [*Vacuum Flowers*](https://en.wikipedia.org/wiki/Vacuum_Flowers) by Michael Swanwick has this as an underlying plot element. The Post-Singularity AI can't spread out any more in volume and ends up destroying any isolated parts it tries to make, because of this *coherence* issue. The human hero in the store discovers a way to preserve coherence (if I remember the terms she used correctly; that was in 1987 when I read it serialized in the magazine) and that becomes a McGuffin for the main action line, as she is now "wanted" by all sides.
You ought to look at that novel for ideas along this line, which the novel explores in many subplots.
[Answer]
"I am a legion."
That is the classical cliche answer for that. And has been so for two thousand years or so. But what does it mean?
Basically, the system is one unified whole, but the we are only capable of interacting with limited fragments of it and as such we see those fragments as separate identities. And since we can't observe the whole, we will see those fragments as separate identities with separate and possibly contradictory agenda. Indeed the system can only interact with the world through such fragments since no practically possible interaction requires more than a small portion of the capacity of the system.
So it would see itself as one and indivisible but in practice act as a multitude of separate instances as far as humans and real world interactions were concerned.
] |
[Question]
[
Let's take again an imaginary world where, without its inhabitants realizing it, everything is physically influenced by what people thinks, by what they believe, by how they see the world. This world is more or less in a medieval stasis because the majority of people received no form of education outside home-schooling, so there is no common knowledge of physical laws upon which to build complex machinery. Every attempt to advance technology, except very small and gradual ones, usually fails.
Magic, instead, exists.
But there is a problem: if the majority of people received no form of education outside home-schooling of course there also is no common knowledge of magical laws upon which to build complex spells. But magic exists because legends are full of magical creatures and supernatural events, so people are more inclined to believe in magic than in machinery able to plow their fields. So I'd like to define some rules to solve this contradiction and make magic work, even if only under some strict conditions that practically prevent it to be commonly used.
Right now I defined something like that:
* Magical popular belief that require none or few direct perception of its effect work without problems (i.e. hang some oak leaves outside your house to protect it from mischievous spirits). This is because there is nothing physical that should be altered by the belief, the magical effect just prevents the influence of something that doesn't physically exists to begin with and is generated by the same belief that prevent its effect from working.
* Magical popular belief that influences physical things works only where the people that believe in it live, only if the huge majority of people believe in it, and the scale of its effect depends inversely on the direct contact those people have with the target of the magic. For example:
+ A ritual to have a good harvest usually works because its effect manifests on the seeds, that are under the earth so the people are not seeing what happens, they don't know what should exactly happen and there is no risk to have a hundred of different people with different beliefs that look every day at those seeds and think that maybe it doesn't work because it's not what they expect.
+ A magic healing potion works only if the one who made it is respected by the people as someone who is expert of healing potions. The direct contact with the sick person is usually restricted to only few people, so the belief in the healer who prepared the potion is much stronger than the direct perception of the effects of the illness (and anyway things like a wound closing does not happen when people are looking at the wound, but only where nobody is looking at it for a long time, i.e. overnight when people sleep).
+ Popular belief cannot create miracles like pumpkins magically appearing mid-air during a famine, but maybe if they really really believe in the powers of a village elder something like a rain dance can bring rain after a couple of days after it's done (like in the previous case, clouds appear overnight when nobody can see them).
* About wizards with spellbooks and staffs able to create fireballs out of thin air...well, the magic does not work as consistently as needed to have schools that teach magic, so they are very uncommon. Studying this kind of magic is long, frustrating and with very little results, so it can be done only by few wealthy people with love for knowledge and a lot of time to spare. Basically it works like this: first, the wizard must be recognized as a wizard and seen as a figure of power and authority, so they dress in a way that makes them recognized as such; second, their spells with their words and gestures and symbols have the objective of making ALL the people around the wizard recognize subconsciously the effect he wants to invoke (i.e. instilling the idea of fire) and require EXTREME precision; third, the mage has no control on what is generated by the belief of the people (for the fire it can be everything from a little spark to a huge flame) so he needs some item to transform whatever appears in what the spell is supposed to do (in the case of the spark some flammable powder); finally, when the spell effect has the shape the people expect to and is recognized as such, it works as a spell should. This is obviously easier when the wizard has a reputation but very hard and dangerous for a beginner, so it's usually safe for a wizard to build first its reputation with small and simple tricks.
Can those rules work or do you see some flaws? Any idea on how they can be fixed/extended? And in particular for the case of the wizard, the example of the fireball is easy, but I have serious problem to extend the same concept to other kinds of spells (i.e. manipulate wind, ice, trajectory of throwed items, etc.) without inventing natural stuff with unusual properties or breaking the technological rules that force the medieval stasis.
[Answer]
# Anatomy of a Wizard
It seems that the wizards really have their work cut out for them, however, if I read the question right, there was *no* mention about magic not changing people. With each inkling of fame a wizard (or any member of a profession) collects, their work becomes that little bit easier. It is possible that rather than simply improving the chances of each spell working, the *wizards themselves* are changed to match the public image, creating an aptitude in magic.
* **Pajama robes!**
These wizards are going to be **coated** with symbols on every surface they can manage. A wizard who wishes to lob fire around will have hundreds of flame patterns stitched all over his robes. The subconscious effect may not help much, but will at least get the idea "fire" into peoples' minds.
* **Wizards are psychologists**
The *entire* point of a wizard is to gain power through others' beliefs. That means that the effective wizards will be anyone who understands the actual factors that go into belief. A wizard can (and should) leverage moment fear to jar the immediate audience into believing, or use loyal followers strewn about that audience to instill [groupthink](https://en.wikipedia.org/?title=Groupthink).
* **What is magic?**
If a layman doesn't often have an understanding of the mechanics of magic, give it to them. Given that wizards normally require a rich environment to steadily progress, some of their wealth could be used to fabricate a public view of magic. All it takes is a somewhat convincing "magic system" and a method of distributing the idea (propaganda posters, town criers). Also, people are *very* likely to believe something that (they think) they came up with, so give them A (magic is heritable) and B (intelligent people can use magic), which naturally leads to C, but let *them* figure out C (this rich robe guy might be able to do magic!).
# Flaws
In general a world changing on belief is a rather unstable one. From any kind of perspective, it seems that one thing is for sure. Everyone is spending ridiculous cash on improving PR.
* **Economy**
Companies can adopt a reputation scheme as follows. Near the start-up, companies will strive to produce the best product their resources will allow, squeezing every last ounce of quality into them. Meanwhile, messengers are sent all around the known world spreading news about the "amazing X company" and of course provide accessibility to the products. If the company manages to catch on, their fame will rapidly skyrocket their product quality, but in turn they wont need to even try to improve any further. Companies will gain undefeatable monopolies.
* **People**
Good King Bob the 27th is the best leader the domain has ever witnessed in many lifetimes. Unfortunately, the last 26 kings have a horrible reputation for greed, neglect of the kingdom, and jaywalking. The skeptical populous, rightfully sick of horrible leadership, often spreads rumors that a curse of the throne prevents the great line of Bobs from ever becoming fulfilling kings. Pretty soon the idea has so much gravity that it becomes true. Even if King Bob's intentions are perfect, somewhere down the line his actions are twisted into the expectations of the public. In other words, pessimism will spread like wildfire (more than usual).
# Extensions
Personally, i would begin by clearly defining a limit to magic.
>
> Popular belief cannot create miracles like pumpkins magically appearing mid-air during a famine, but maybe if they really really believe in the powers of a village elder something like a rain dance can bring rain after a couple of days after it's done (like in the previous case, clouds appear overnight when nobody can see them).
>
>
>
Specifically, what is the *exact principle* that allows a rain dance to work, but not magical pumpkins. Certainly rain is more plausible, but unless magic is a sentient being capable of understanding plausibility...
>
> And in particular for the case of the wizard, the example of the fireball is easy, but I have serious problem to extend the same concept to other kinds of spells (i.e. manipulate wind, ice, trajectory of throwed items, etc.) without inventing natural stuff with unusual properties or breaking the technological rules that force the medieval stasis.
>
>
>
And *that* is how you automatically implement spell difficulty. A fireball is a trivial spell that nearly all respected wizards can throw around, but telekinesis or wind manipulation require a bit more creativity. A wizard may be able to fake the spells at first, outside of combat of course, to trick onlookers that they *can* use magic. Once the idea is properly rooted, the wizard begins to see results in the form of *actual* magic. Telekinesis, ha. Its just a thin silk wire.
[Answer]
**In the real world it works like this:**
* I wonder why birds fly?
* I think it is magic.
* I research it.
* Conclusion it is lift generated by pushing air under wings.
* Science and understanding is created and believe in magic is reduced.
**In your world it works like this:**
* I wonder why birds fly?
* I think it is magic.
* I research it.
* Conclusion it is magic.
* Magic is confirmed and belief in magic is improved.
In your world it is difficult to make science work, it is almost like on SE:Worldbuilding where most answers could be answered with "because magic". Strengthen since in that case would be difficult. Magic would never die (unless some religion finds it bad and people stop believing in it), because it fulfills its own existence.
[Answer]
To work out rules that limit and restrict the ability of magic, you must have rules that describe how it works, period. This should start with an underlying theory that describes it in detail, even though that is not known to the characters and might not be revealed to the reader.
Here is an excerpt from a [previous post](https://worldbuilding.stackexchange.com/questions/13149/magic-what-might-be-dangers-of-connecting-your-own-soul-to-a-stronger-soul/13653#13653):
---
Magic, as commonly understood, would need to be driven by human brains, or the minds of gods that work like ours. Why would weather, for example, act in the manner of primate social behavior? I don't have a good answer off hand, but here are some ideas:
* The universe is a simulation, an abandoned game filled with the decendants of in-game characters. They have forgotten their proper techniques for directing the simulation, but still have some ability.
* The universe is created by the observers, and some can influence it more than others. It relies on intuative pattern matching rather than doing calculus (like catching a ball), so (a) things that are more teleological are more controllable, and (b) it is a pre-scientific understanding and largely rule-of-thumb or just plain wrong.
* gods exist, like the Greek gods, which are basically how you behave humans with superpowers to act. But that's not great for modeling phenomena itself rather than appealing an authority to apply superpowers: its the rain itself that's intellegent and only powerful enough to work within its own range of behavior as an actor. What is "weather" as an object, and why would it be intelligent? That's why it needs to be the mage's own understanding that drives it.
---
So, in a universe where weather behaves in the manner of primate social interactions,
1. Controlling it is like influencing a politcal figure, subtle and imprecise,
2. It has nothing to do with pumpkins appearing.
The limits implied by point 2 is basically the case of intelligent agents and their responsibilities. If there is no sprite in charge of X, then you can't influence X via magic.
Deeper understanding might entail figuring out the catalog of spirits and elementals, how they need to interact for a given result, and how each is influenced. They will also contradict: the details needed for effect A (e.g. a worked-out plan and treaty between spirits to provide a good crop) could preclude effect B.
It looks more and more like politics: the various elementals and sprites have a sphere of influence and competition between lobbyists for what gets done.
That is certainly enough to base a setting on, and provide limits and more interestingly *trade offs* in usage of magic.
Getting into specifics, consider how we get good crops today using hands-on technology:
* water
* soil nutrents
* pest control
* weed control
* domesticated species
Magically getting "good crops" means handing those indivual chores. Maybe the people have a grasp on that, or maybe yet another *Athena* spirit can do the planning and coordination.
Planning the right rainfall is one thing. What spirit would keep bugs away and why? What spirit would effect selective breeding to improve the characteristics of the plant?
Getting good crops might be a "high technology", not a single wish. These aspects can be solved using clever approaches that are refined over time. Keeping bugs away and preventing explosive population growth of rats might (1) require some help from people, and (2) be a rube-Goldberg of individual effects.
Also, somebody messing up the "good crops" plan with a personal spell would not be tolerated.
[Answer]
You've got a situation where belief is pretty powerful - but for whatever reason, *disbelief* is even more so, since a few people being skeptical can cancel out the belief of a number of other people. So the things that end up being successful in your world, tend to be low-level "maybeso it could happen" because it "only" has to overcome "it maybeso might not", instead of "it doesn't work that way" or "I haven't seen this work"
It might be useful to talk about, hmm, knowledge? The difference between things we know because we're told, or because we logic or reason them - and the things we know because we *know* them, instinct and impulse, in the body not the mind. Us, we *know* we walk on the ground, and people and things don't go flying off without cause... we *believe* it is because of gravity, and so believe in all its associated theories, until or unless something proves it wrong.
One is obviously going to be a lot harder to alter than the other - it will be a lot easier to alter the details of gravity theory (like, say, the exact acceleration downwards) than convince people that if you step wrong you might fly upwards into the air. After all, they'll look at each other and ask who has seen this happen, and not believe it when the answer is, no one. Pumpkins won't appear in midair because instinctively, impulsively, they *know* it hasn't happened before and it probably won't happen now, even if some fast-talking wizard (plus or minus alcohol or more mysterious intoxicants) tries his level best to convince them it might, in order to make it possible to do so.
That disbelief makes it hard to start *new* phenomenon, find new spells, or make things work quickly. If you want to make it even harder to play into that feedback loop, you can include non-human minds in the mix. Animals might not believe things, by being taught or reasoning, but they probably do know things, like that they always fall to the earth, and don't float off through the air. Birds know how they fly (whatever theories mere humans have), and they're really sure pumpkins doesn't spontaneously appear in midair with them. It would probably drastically cut down your wizards' ability to propaganda themselves some laws of magic.
Otherwise, I think you might be underestimating how beliefs change over time. That rain dance takes a few weeks to brew up clouds because people are unsure to begin with, but when it actually rains some will wonder if the dance is possible. A few seasons down the road, and most will "know" the rain dance pulls up clouds within a week or so - and a decade or two later, it strongly rains the next day. People are superstitious, and there's nothing they like better than to think they have influence. It just takes time for their observations to match up with what's happening, and feed belief-power back into the spells. Generations pass on the ritual of great harvests, and "soon the fields sprout" becomes the "quick sprouting" which goes to becomes "seeds sprout and quickly grow" becomes after a bit more time "plants sprout and mature so quickly you can see their fruit" and after that, it's just a jump from "the plants appear and grow food so quick it's as if they come from the air" over to "and then the pumpkins appeared in midair. Great harvest festival, yeah!". It may take generations to get there, but this is a world, and it has a history, and so it has generations to spare. And people will *believe*, both to think it and know it, those things they themselves have seen and experienced.
I expect wizards would latch onto groups of people, and theories of magic. Probably most would be sincere and working with what they actually believe they can do and how, but since their power depends on feeding the latter to the former, the more shortcuts and shenanigans they come up with to spread their propaganda the better off they'll be. Cults with a bunch of fanatically believing followers might be able to believe strongly enough to support more flashy effects in front of others, converting them to the power of the magic through observation (you saw it, it must be real). Others would build up bigger and more plausible effects (rain dances, harvest rituals), that will take time to build a proper belief in, but which will have a *lot* more power once people buy into it, because a lot believe in it pretty deeply.
Exoticism will help - it has been done in that faraway place, there is a secret from this mystic-seeming people, anything to make people believe it happened elsewhere, makes them believe its possible. Religion or calling on outside gods or forces can also help because it gives outs and explanations for failure, or mechanisms for creating stories to help fill in the gaps of what people think works, before it can be tried for real. Ritualization can be used to great effect like this because it's complex and opaque enough to let people turn correlation into causation, people don't expect to understand it unless they're specialists, and nonspecific 'changes to the ritual' could be used to change the effects (especially if planted well in advance as rumors - insta-feedback on how far you can stretch belief).
Your commoners might not know magical theories to begin with, but wizards will quickly correct that - the more people they tell their theories to, the more they find supporting proof, how about that. Possibly there will very eventually emerge some broad consensus, about what magic is, what it can do, and how the experts do it - think of it as the difference between what the experts in science say they are and can do, and what the average layperson thinks they're doing. Or, more likely, there will be multiple, competing systems based out of different groups or populations which were taught competing theories of magic, and have seen their own wizards *produce results* enough to know that is, in fact, how magic works. It'll turn to religious wars pretty quick.
Maybe you think I've given a lot of power to the wizards? The thing is, people have believed lots of things, and believed them pretty strongly, without a helpful feedback mechanism that makes the things we believe eventually real.
Also, if you think the wizards have power? Wait till you see how much power the storytellers have... especially since good narratives have lots of drama, which means about as much bad stuff as good stuff, as many wrong paths as right ones. And that's only the magical mechanics - if belief shapes reality, can you bear to think of the horror of the narrative-magics warping *people*, how people think and behave and what they're supposed to do? it'll be chaos! To think there are answers where they have dared to give wizards the powers of psychology...
[Answer]
Similar ideas exist to a minor extent in the Shannara book series. There a magical sword was created and given to an elven king, Jerle Shannara. Now hundreds of years later this sword has to be used again, but due to the sword being a gift to the king and not the whole nation of elves, people believed that it should be used by the king and due to how magic works, the sword now became useless to those who aren't direct descendants of Jerle Shannara. This wasn't intentional and the issues this caused could have been avoided if the sword had been proclaimed to be a gift for the people and not the king.
**MRM** or magical rights management.
If magic in your world has an even stronger connection to belief, then we could perhaps expect similar results. If an item was made for someone specific and for some specific purpose, for example an axe for chopping wood or a set of armor to protect from the enemies of the kingdom, then the axe would not work as a weapon and the set or armor would not protect against weapons used by someone who's acting on behalf of the rulers of the kingdom. Effectively creating a magical "DRM" for magically enhanced items.
If more people need to know who the item was made for and for what purpose, then tools and other highly valued items could be give to those who need them as a part of a ceremony where a large part of the community would see the transaction happen. Personal magical items would be more powerful if they are given at weddings or other similar events where multiple people observe the item being given to the owner while the purpose was stated so that all could hear.
] |
[Question]
[
If a large part of the population was killed, but the infrastructure was basically unharmed (I know it take people to keep things going, but I guess that is part of the question), how long would I still be able to use my GPS? How long would communication satellites still send and receive data? What other satellites would be useful to a world where the technology is not destroyed, just declining? How long would such technology work? If I have solar power and can run my laptop and phone, how long until the supporting technologies collapses? Hours, Days, Weeks, months... Thanks - LWR
[Answer]
National power grids are likely to go down within hours if their monitoring stations are abandoned; the exact number of hours will vary from country to country.
Rooftop solar panels that are connected to the grid will automatically cut off if the grid goes (as a safeguard for people working on the line), but some systems can be switched to power an off-grid socket instead, in which case they should continue to work until the inverter breaks down (10-15 years) although the amount generated depends on the light. If a spare inverter can be found (or if someone knows how to repair the inverter) then the next limit will be the panels themselves: after 30 years they will be producing noticeably less power. The gadgets that you run with this power (light bulbs, heaters etc) will also need maintenance and/or replacement during this time.
The UK and USA landline phone systems are supposed to have enough battery backup to last 1 week without the power grid (although I don't think this has had a large-scale test). Only traditional wired phones will benefit, not cordless phones, and only voice calls will benefit, not broadband. If you pick up the phone and hear nothing, you should check for a circuit (blow in the microphone and see if it amplifies) and if so then wait a while because you may be in a queue to get a dial tone.
US cellphone towers have been known to cut out just hours after grid loss in a severe storm. UK mobile base-stations are not required to have backup power at all, but the UK government does recommend 1 hour of backup power in a base station and backup generators in switching centres, especially after the Tetra project to let emergency services use the same masts on a different frequency.
Data centres protected by UPS units can last anything from 5 minutes to 2 days without power, depending on how good a UPS system they've installed. Diesel standby generators come with 24, 48 or 72-hour fuel tanks. (They can last longer if someone is still around to refuel it and fuel is available, but faults are possible.) Thus an abandoned data centre would last anything from 5 minutes to 6 days without power, depending on how good it is.
For "the Internet" to work, you'll need the server you're trying to contact to be up and a route of still-working switches etc to get you there. Probably the first one to fail will be your local one (within hours of grid failure at best, possibly minutes or nothing), but if you can somehow get to a working data centre with good backup power then you might be able to use "the Internet" for anything up to 6 days although during that time you will see sites going down one by one (mostly on the first day) and speeds slowing to a crawl as the remaining routers are forced to map out strange ways of getting your packets to their destination.
GPS and similar systems may last many years, but without ground support they are likely to lose accuracy after 6 months (this can be corrected for if you're skilled) and after a few years it will become harder to get a GPS fix as the satellites break down one by one. Once the Internet is down, systems that use Assisted GPS (aGPS) will no longer be able to download their ephemeris data and will therefore start taking much longer to get a GPS fix than you might previously have been used to.
Vehicles are not likely to last more than a few years without maintenance, and in any event require fuel, which you will have to obtain without the use of electric pumps.
Amateur radio should work indefinitely if the equipment can be powered and maintained.
Municipal water services are not likely to be able to keep up water pressure in supply pipes for more than a few days at best. After that there will be no running water from mains taps. Old houses with header-tanks will still be able to use their header tanks, typically 40 gallons or so although it's not the nicest water. After that you will either have to collect rainwater, find a well, or (most likely) use supplies of bottled water from shops and warehouses. Toilets can be flushed once per toilet and after that you can fill them with rainwater etc, but a rather unpleasant thought is what happens to the sewage systems when the pumps stop working: depending on how the town/city is plumbed, sewage might start to back up into ground-floor toilets and/or manhole covers. But this is likely to affect only the places with the lowest altitude in town, and anyway it will not happen for some time if the amount of sewage is reduced due to fewer people being alive to generate it. Nevertheless if I knew a sewer is not maintained I would seek places to bury waste instead.
Natural gas usually needs to be pumped, and is usually pumped by electricity. If the pumps stop, there should still be some pressure already in the gas line, which can normally last a few days and probably much longer if very few people are around to use it. Most gas boilers and central heating systems (called "furnaces" in the USA) also need electricity and will shut down without it, but small self-contained gas heaters and cookers can continue to work as long as there is pressure in the pipe (and there will be pressure in the pipe for longer if all the larger heating systems cut off). Additionally, there are a few gas pumping stations that are powered by burning the gas itself, plus there just might be a few places that are close enough to the gas wellhead to still get some pressure from the natural wellhead, and in these exceptional places it is possible that gas could last for a few more months, but eventually the wellhead will stop working due to cold weather or something if nobody is there to adjust things.
Once survivors have organised themselves into a big enough society, they might wish to try and bring the power grid back online, which should be possible via black-start procedures but it will require knowledge and some of the equipment will require maintenance. On the other hand they might decide not to bother and just run their own micro-generation, or do something else entirely.
[Answer]
Also in addition to the aforementioned DoD stations, we were past the expected lifetime of our GPS satellites. But, in 2014 we put some more back in space. At some point those satellites will come down. One of those has lasted like 23 years, which is a bit past it's 7.5 year design lifespan.
<http://www.space.com/24767-gps-satellite-launch-success-delta4-rocket.html>
So, in the near future we've got at least 5 backup satellites (but probably need a ground control station to turn them on), and a bunch in orbit - which will probably last a good decade or three.
You might be able to hack your GPS so that you can fix the inaccuracies that you're being fed by the satellites. You'd probably need to get a GPS location for a landmark, then see how much it varies from what the satellites are telling you now.
Cellphones will go down as soon as the cell towers run out of backup fuel (after the electrical grid goes down), if not sooner (network switching death). Of course most people will have run down their cellphones, searching for bars, by that time. If you've got spare power to charge your cellphone, why don't you adopt a tower? ;)
---
I'm also surprised that the US isn't charging the rest of the world to use our GPS system.
---
Russia has GLONASS (in orbit), China has Beidou/Compass (in orbit, covers China now - global by 2017/2020) and the EU has GALILEO (in orbit) each at varying stages of development or testing.
Differential GPS (DGPS) can obtain a much higher accuracy. DGPS requires an additional receiver fixed at a known location nearby. Observations made by the stationary receiver are used to correct positions recorded by the roving units, producing an accuracy greater than 1 meter.
Almanac data is one of three types of data that GPS satellites broadcast, it describes the orbital courses of the satellites. Every satellite broadcasts almanac data for EVERY satellite. A GPS receiver uses this data to determine which satellites it expects to see. A unit determines which satellites it should track from those that should be available. With Almanac data the receiver can concentrate on those satellites it should be able to see and forget about those that would be over the horizon and out of view. Almanac data is not precise and can be valid for many months.
The design life and mean-mission duration goals of the Block IIA, IIR, and IIF satellites are 7.5 and 6 years, 10 and 7.5 years, and 12 and 9.9 years, respectively.
[Answer]
To the best of my knowledge, GPS would work for a while as long as what devastated society didn't break them, (such as a massive solar flare).
Assuming they were working then they should continue to work for the rest of their lifespan, it appears their life expectancy is about 7.5 years. So it would continue to work for several years without much help. On average then they would have about 3.5 years left and as more and more die, the GPS would be more and more difficult to get a fix.
Cell phones on the other hand depend first and foremost on the power grid, and if that ain't working they ain't working. Satellite phones will do better, but since I don't think they directly connect peer to peer, they might not last much longer than cell phones. Walkie-talkies and shortwave are going to be the modes of communication without infrastructure. Some cities with enough people might be able to keep somethings going but it will be spotty at best between cites.
[Answer]
As mentioned, cell phones towers work from the power grid and to be able to call someone it takes two working towers (assuming there is some range between the phones) and an infrastructure (network) in between, all requiring power. That infrastructure might be on different power networks and if one fails you can't connect.
Power (Electricity) itself is generated by power plants and those need to be actively restocked and maintained to stay operational. The networks themselves need to be managed too.
All that is a lot of chances to fail somewhere, taking your phone call with it.
I would give it a day or two before you can't make your calls anymore.
If you plan on ending civilization i'd opt for the good old long wave radio for a means of communication.
GSM is a broadcast only system where all your GSM device needs to do is receive the signals and triangulate your position, so that suggest it will work as long as the satellites do.
However that's not true. Due to various reasons satellites drift (gravitational waves by celestial objects for instance) a bit and that drift has to be actively compensated continuously, as it's done by the US military.
If that stops then GPS will become imprecise very fast to the point it's unusable.
Comm satellites themselves will work for a long while but unless you also got the access technology up and running that won't do much good, unless, maybe you use a satellite phone to call another satellite phone (though I'm not sure that won't still go through a ground station).
] |
[Question]
[
In my world(s), there are many varieties of humans. We have what *we* would think of as normal humans of various races and colours. However, we also have *other* varieties of human, such as Satyrs and Fauns (ungulate legs and horns), Lamiae (a long snake-like tail instead of legs), Mermen (a cetacean or fish -like tail instead of legs, plus the more fish-like have gills), Lillim (with bat-like wings) and bird people (with bird-like wings), plus more.
Each of these races occurs in a number of different non-contiguous places, so they are not identifiable by their place of origin.
Each of these variants on humans have their own name, and can come with a variety of heritable skin colours similar to unmodified humans. However, what would all these humans and human variants call what *we* would consider 'unmodified' humans?
They can't call them 'unmodified', since no-one really knows which came first or which has the greater population, and the concept of having been modified doesn't exist.
We can't call them 'normal', since typical members of each group would not be considered to be disabled either internally or externally, only differently-abled when compared with a member of another group, each having advantages and disadvantages in any given situation.
We can't even call them 'human', since they are *all* human, and are effectively the same species, able to interbreed, though as some crosses may result in less-fit offspring which are still fertile, they could be more accurately called subspecies of *Homo sapiens*.
So, what do *they* call what *we* would call 'normal' humans?
[Answer]
They're all humans, then clearly you call them 'humans'. Humans on Earth all look pretty different, we call each one a *human*. I'm not sure where your aversion to this is coming from, but a human is called a human.
Certain breeds of dogs look even more different from each other than humans do, they are all still called *dogs*.
**You're not looking for an alternate name to *human*, you're looking for the names of [races](https://en.wikipedia.org/wiki/Race_(biology)).**
>
> In biological classification, a race is an informal taxonomic rank, below the level of a species. It is used as a higher rank than strain, with several strains making up one race.
>
>
>
There are a few ways to divide races. There are physiological races, ecological races, geographic races, or chromosomal races. It sounds like you're going to have different [ecotypes](https://en.wikipedia.org/wiki/Ecotype) (ecological races), which you can refer to differently, but they are all still humans.
>
> Ecotypes have no main taxonomic rank in modern biological classification. However some scientists consider them "taxonomically equivalent to subspecies". This is true in the sense that ecotypes can be sometimes classified as subspecies and the opposite.
>
>
>
Personally, **I like the idea of calling them [Morphs](https://en.wikipedia.org/wiki/Polymorphism_(biology))**. Which, like ecotypes, can be thought of as precursory steps of potential speciation. Variations on this name can be used for naming. As a 'normal' arogant human **I'd call myself a Protomorph**, being the first of the Morphs. Others might say Amorph, being not-a-morph.
There will likely be many variations on the names because they are informal. Some will be used in polite company while others will most certainly not.
You may need to know *something* or geography, the differentiation probably required some geographic separation, even if it's not that way now. Americans call seventh generation black american an 'african-american' despite them having no ties to Africa. Even if your humans are all mixed together, and they're apparently educated since they require politically correct names for each other, there have to be some prevailing theories as to where the groups originally developed.
If not that, then you can name them related to the animal they're closest too. We, the real-world human equivalents, would be most like primates, the bat wing humans like bats, etc.
[Answer]
# If They Are Another Species
But still in the Homo family, you can call them by their species' name: *sapiens*. Mermen could be formally called something like "*Homo Serra*." Fauns could be called "*Homo Faunus*." It would be a system that correctly identifies these creatures. (Yay [Taxonomy](http://en.wikipedia.org/wiki/Taxonomy_(biology))!)
# Call Them Descriptively
Alternatively, they could just call "normal" *Homo Sapiens* people leggies or footmen, or something that identifies them by their differences, just as we've done with races within *Homo Sapiens*. Despite some racial charges, you know what kind of person we're talking about when you say "white/black person." Likewise, if you are one of these "variant" humans, and you want to talk about the normal plantigrade humans, you can call identify them from the difference they have from you.
I focused on the plantigrade foot because it's the major difference between fauns, mermaids, and humans. Identifying them via feet would also work because it's the main method of (natural) locomotion, as your bat-people and feathered-people could use their wings (assuming they're capable of flight, of course). You could choose some other attribute, but this seems likely.
# Everyone Has a Name For Everyone Else
If these creatures speak different languages, it would make sense that they would have different names for different groups. You see this is the world today. It's just a quirk of languages.
# Everyone Attempts to Conform to a Common Name
... otherwise that group gets angry. It's like calling a person of color "black" in a real-life setting where people are very sensitive about that. Perhaps it could be like Brits calling Americans "colonists" even though everyone calls Americans "Americans". Americans can get fussy when you (as a Brit) call them colonists, so it is better to just call them Americans. This is confusing, though, because people from South America call themselves Americans as well, because they are from America, but not the USA.
Maybe I should have just chosen the [Xiongnu](http://en.wikipedia.org/wiki/Xiongnu), even though people call them and other unrelated people huns. I suppose the point is that a *[politically correct](http://en.wikipedia.org/wiki/Political_correctness)* name for a group may or may not stick, despite people's best efforts. So your unmodified humans may want to be called "sapiens" or "entirely-skin-covered" but people call them "footies" or "locomotively ungifted" or something degrading like that.
[Answer]
You could use "Humans" to mean any human, and "People" to mean anyone. If I read a story about animals, sometimes I might refer to them as "People" (even though they clearly are not) because they are the characters in the story. However, from my experience, "Human" always refers to someone of our species (unless you are a StackExchange-reading robot).
From the New Oxford American Dictionary:
Human:
>
> of or characteristic of people as opposed to God or animals or machines, ...
>
>
>
People:
>
> human beings in general or considered collectively...
>
>
>
So "Human" puts more emphasis on being an actual human, while "People" does not put as much.
**TL;DR** You could use "Human" to describe a person like in real life and "People" or "Person" to describe someone in any of your humanoid races. This is not the most "scientific" answer but probably fairly easy to catch on to while reading.
[Answer]
I'd call them [Hommon](https://en.wiktionary.org/wiki/homo), it's simple to the point easily recognizable but sounds just exotic enough to be interesting. Words like [Hom](http://xenoblade.wikia.com/wiki/Homs) or [Hume](http://finalfantasy.wikia.com/wiki/Hume_%28Final_Fantasy_XI%29) have been used to refer to human analogs.
[Answer]
Traditionally, this is done in one of a few ways:
* People are the normal things, everything else is sub-races, "the fae", etc. (Folklore) Doesn't apply here.
* Men and people (LotR)
* Humans and homanoids (D&D)
I like Tolkien's approach.
[Answer]
Just call them Humanoids if the humans are proud and a little racist, they will insist that only real humans are humans and all others are humanoid morphs or meta-humans.
If your society is more tolerant you can call them all humans and divide into original/clear-born/primal/proto and secondary/meta/morphed/atypical humans
[Answer]
They can call them something slightly disrespectful or demeaning. What about Flatfeet? Or Plains? Or something like that...
*When Kashi came out of the forest, she saw the two Flatfeet waiting for her. The tall black one watched her warily....*
Not bad, eh? Maybe a bit heavy on the cliches, but there is a story there. The reader would like to know about these Flatfeet, and how come Kashi is not one of them (in my mind she's a wolf-woman).
[Answer]
Based on [Samuel's answer](https://worldbuilding.stackexchange.com/a/9624/75), I decided that I would use something geographic. There are areas in my setting where the 'stock' humans believe that they are the only type of human that exists, and that all the alt-human types (the fauns, satyrs, lamiae, lilim, mermen and so on) are mythical and do not really exist. However, historically there has been a little interaction between the groups (mostly one-way), so, when one of these alt-humans asked a 'stock' human from that isolated region what he was, he would have said that he was just one of the "ordinary folk", since the majority of people he had known to that point would have been morphologically similar to himself, unlike the alt-human he had just met, which he would have considered "different".
Since the language that these geographically-isolated 'stock' humans used is (or is at least being *depicted* as) similar to modern Irish, I chose the term "tíre gnáth", or just "gnáth", which translates as "ordinary folk", or "ordinary" in its shorter form. At one stage, the alt-humans would have been described collectively as "tíre éagsúla" or just "éagsúla" ("different folk" or just "different"), however this would have been an artificial grouping that none of the alt-human types would have adopted - all the other types would have simply been a "non-[alt-human type]".
I chose to use a non-English word as English does not have a word or construct with the required meaning. We can say "non-human", but these alt-humans *are* genetically sufficiently human that they are considered a subspecies, and that then made the term "non-human" derogatory when applied to these people. It *would* have been a suitable term if they were *different* species, not different *sub*-species.
] |
[Question]
[
One of the solution to make a cold planet habitable for us is to increase the greenhouse effect. It works with planets like Mars that are inside the habitable zone but would it be enough for a planet outside of that zone?
It does maximize the heat absorption of the planet but there is a limit to this. We can't increase the gas concentrations too much.
**Are there other ways we could heat a cold planet to make it habitable?**
For example: In Star Wars, the city-planet-capital Coruscant is heated by mirrors that are deflecting the light of the star toward the planet.
[Answer]
## Greenhouse gases - the easiest choice
Warming a cold planet should be probably much easier than cooling a hot one. Increasing a planetary albedo by springkling the surface by black, highly absorbing powder or using orbital mirrors might be part of the process, but it seems that the most important will be emission of greenhouse gasses into atmosphere. Atmosphere of Earth weigths approximately $5 \times 10^{18}$ kg, from which there is $3 \times 10^{15}$ kg of CO2.
There are greenhouse gasses, that are much more effective than the carbon dioxide. For example [SF6](https://en.wikipedia.org/wiki/Greenhouse_gas#Global_warming_potential), which is approximately 20,000x more effective. Following analysis is very simplified, but should give us some idea. Total greenhouse effect makes Earth [warmer by 30 K](https://en.wikipedia.org/wiki/Greenhouse_gas). Total contribution of CO2 is around 10-20%, which is 3-6 K. Now, to make the same change by using SF6, we would need approximately $1.5 \times 10^{11}$ kg, or $1.5 \times 10^{8}$ tons. I can imagine that it would not be an easy task, but definitely possible using large industrial scale colony and proper resources.
Now, if we would like to increase the temperature by 30 K or more, the calculations become tricky. Some people say, that the total [radiative forcing](https://en.wikipedia.org/wiki/Radiative_forcing) is [logarithmic](https://en.wikipedia.org/wiki/Radiative_forcing#Forcing_due_to_atmospheric_gas) and for CO2, [fit says](http://wattsupwiththat.com/2010/03/08/the-logarithmic-effect-of-carbon-dioxide/) it should be
>
> $\text{Forcing} = 233.6+9.766\*\log({\mathrm{CO}\_2 \ \text{in ppm}})$
>
>
>
This, converted to temperature, would be
>
> $\text{Temperature change} = 2.70+0.113\*\log({\mathrm{CO}\_2 \ \text{in ppm}})$
>
>
>
With dependence like this, it would be almost impossible to warm the planet more. But (for warming of planets luckily), the truth is [more complicated](https://physics.stackexchange.com/questions/13829/why-is-radiative-forcing-from-co2-logarithimic-and-not-a-decreasing-exponential):
>
> Firstly, the IPCC scientists don't say this follows a *ln* function at all. They say it follows whatever their computer models says it follows. This is only a first order solution.
>
>
>
It is hard to predict how much of the greenhouse gas you would need, but the warming should be feasible, at least up to 30 K. Particularly if there is some other frozen gas on the surface, the initial increase in temperature will induce positive feedback, which will make the process much easier.
## Very, very cold planets
One might also be interested in terraforming extremely cold planets similar to Pluto. Then the greenhouse gasses will be necessary, but not sufficient. We could try to deploy mirrors on the orbit, but their size would have to be comparable with the surface of the planet or even much bigger, as the radiation is faint. It would be challenge even for a very advanced civilization. Is there an alternative source of energy? The best broadly available source is the fusion 4H->He. How much we would need, though?
Each $m^{2}$ of the Earth's surface radiates away around [240 W](https://en.wikipedia.org/wiki/Earth's_energy_budget) in form of heat. This amount can be decreased by the greenhouse gasses, but not too much. To maintain its temperature, Earth would need $1.22 \times 10^{17}$ watts, which is an incredible amount. Even with fantastic efficiency of fusion, you would have to burn 186 kg of hydrogen per second. From the point of view of the fuel alone, it is doable, but the neccessary infrastructure would have to be a true masterpiece of technology. (Many fussion power plants, probably located under water to conduct the heat away.)
The energy could also easily come from tidal forces, if the planet orbits a gas giant or another planet. But the extreme volcanic eruptions would probably be quite aggressive way of providing the energy and containing them might be more problematic than generating the heat artificially. (Not speaking about terribly complicating task of moving the planet into a proper orbit.)
But the heat is not everything. You would probably have to make a big amount of genetic modifications to reduce light requirements of plants, or create a *lot* of artificial light somehow.
[Answer]
## Using mirrors, it won't be easy.
Suppose you want to make a planet habitable that's the size of Earth but √2 times too far away from its star to be in the habitable zone. What you'll need to do is increase the amount of light it gets by a factor of 2. (Since the light a planet receives is inverse to the second power of its distance from said star.
There are two options, have mirrors orbiting the sun closer than this planet and you'll need a total surface of Ap(rm/rp)2 where rm and rp are the distance to the star from the mirrors and planet respectively and Ap is the surface of the planet interpreted as a flat circle (diameter of the planet times pi). I don't think it would be easy (or cheap) to have those mirrors always redirecting that light at the planet though.
A more viable solution seems to have a bunch of mirrors orbiting the planet, possibly in [this configuration](http://sketchtoy.com/63309741). In this case the distance of the mirrors to the star would be equal of the distance between the planet and the star, so the above formula evaluates to: Am = Ap, the surface of the mirrors should equal the apparent surface of the planet
. For an earth sized planet, this number is about 113 million km2. If we take circular mirrors with a diameter of 11.2 km (which gives them a surface of 100 km2, we'll need 1.13 million of them.
If you allow those mirrors to be essentially side by side in orbit, you need them to be about 1.13 million km away from your planet, which seems doable.
In order to spread the light reflected by these mirrors nicely across the globe, the mirrors would need to be slightly [concave](http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/light-and-sight/sci-media/images/convex-mirror/685505-1-eng-NZ/Convex-mirror.jpg). And will obviously need to be at an angle of about 45°
This will of course heat the poles more than the equators (since the mirrors will always cross over the poles) and will also illuminate the night side of the planet, but I'm sure you could solve some of those issues by adjusting the shape of the mirrors.
If you're wondering how bright these mirrors will be, the will in total be as bright as the sun and have a total angular size equal to that of an earth sized object at a distance of 1.13 million km away. This gives it an angular size of roughly 2.7 times that of the sun, which would make it very bright, but not quite as bright as the sun, I imagine it would look like a very thin bright line in the sky.
All in all this seems achievable, especially if the planet isn't far out of the habitable zone, but I can imagine there might be better solutions.
[Answer]
Orbiting mirrors around the planet is one thing, but if you really want to provide extra energy to the cold planet you might consider establishing a solar laser and beaming energy from the sun.
There are two ways to do this.
You could simply build a fleet of solar power satellites in orbit around Mercury, using the incredible solar energy concentration to generate electricity and drive batteries of huge lasers to beam energy to the distant cold planet. A series of lenses or diffraction gratings would also need to be in various orbits around the solar system to steer the beam since Mercury's orbit around the sun will take the solar power satellites and laser battery in and out of view of the target planet/moon.
A more direct way of doing this would be to use the solar photosphere as the lasing medium. A series of mirrors orbiting inside the photosphere would reflect a driving laser around the sun. The energetic particles in the photosphere would be excited inside the "racetrack", and as they fell back to their ground state, more and more photons would be added to the drive beam. Using a very sophisticated control system, orbiting mirrors would become "half silvered" at the right time to allow the beam to exit the racetrack at the proper moment to illuminate the target planet/moon. Once again, extra mirrors or diffraction gratings would be needed across the Solar System to steer the beam accurately to the target.
With this sort of mega engineering, even bodies as far as the Kruiper belt could be illuminated and warmed.
] |
[Question]
[
Assuming a world where starships don't use missiles and bullets in combat much. They only carry those as a final strike or for convenience. Their arsenal is almost entirely composed of electricity-based weaponry and tools: Arc generators to scar opponent ships with lightning bolts, field generators to deflect and reallocate incoming discharges and objects, voltage adjustment, gas emitters to produce plasma blobs, the works.
This *could* invalidate certain tactics - small craft might be too easy to destroy because once they enter the range of a large cruiser, they don't even have to be targeted - they're just struck by a discharge due to voltage difference. They *can* try to match surface potential, but the cruiser is already varying its own based on some unpredictable sequence, making it unfeasible. Missiles suffer the same fate, so they're out of the question.
**Assuming power isn't hard to carry, how would this arsenal further change known tactics that are used in naval and air battles? Could it possibly invalidate certain kinds of corps and produce new ones?**
Specifics on the technology available:
* Gas emitters to create a medium for discharges and possibly shielding
* Field generators that produce radial EM fields
* Voltage adjustments to modulate surface voltages on plating and in the fields and plasma
* Heavy disposable plating, with insulation, to protect from enemy attacks and protect the inside from overheating of the plating itself
* Arc generators to allow arcing through the generated medium
* Power striking the plating and shields *can* be absorbed if it isn't directly disruptive; enemy weapons that don't immediately cause damage have the power redirected into batteries.
edit - *sorry about these changes, it's an old idea and I don't have my notes at hand*
[Answer]
The US Army has dabbled in this field recently, producing a prototype of something called a [Laser Induced Plasma Channel](http://www.popsci.com/technology/article/2012-06/armys-laser-guided-lightning-weapon-delivers-high-voltage-through-air) (LIPC). Unfortunately, this weapon, like any weapon that relies on electrical arcs, requires some element in its path to conduct the charge. In the case of the LIPC, for instance, it turns a straight line of air into plasma. This provides the lightning with an easily aimable path of least resistance to a target.
So let's assume that you do have a means of providing a conductive element for your weaponry (This is sci-fi, after all. We can always handwave a little). What are some of the issues your ships might run into?
## Friendly Fire
Your weapons, as you say:
>
> small craft might be too easy to destroy because once they enter the range of a large cruiser, they don't even have to be targeted - they're just struck by a discharge due to voltage difference.
>
>
>
You run a very real risk of zapping friendly targets at all times, requiring any formation of vessels to keep out of range of each other's weapons as well as the enemy's. This prevents formations from easily concentrating fire on targets, devolving a battle into a series of duels between ships. (Note that this can involve a lot of drama for your story, so this may be a plus)
## Stealth
A vessel at any state of combat readiness is going to be a massive glowing beacon to any ship in the same system, because it is going to be constantly dumping power into space around it via its weapon systems. Its also going to glow, visually, by constantly zapping stellar debris and dust. Ships ready for a fight in your universe cannot be stealthy.
## Access
While under combat readiness, your ships are unapproachable. Shuttles, eva, repair drones, anything that's even slightly conductive, is going to get zapped indiscriminately whether it be friend or foe. In order to receive anything from outside the hull of the ship, the vessel will need to power down both defenses and weapons, leaving it vulnerable.
## Other Weapons
Maintaining suspension of disbelief requires, in part, that your reader/player/etc not think to himself: "But why don't they just \_\_\_\_\_". In the case of these lighting weapons, why don't ships just arm themselves with more conventional weapons such as rockets, missiles, railguns, lasers, etc.? All of these weapons require lower tech levels, are cheaper to produce, and are more difficult to defend against.
The most important thing to remember though, this is **your world**, and if you really want there to be vast conflicts full of lightning throwing ships dancing in and out of clouds of gas, *you can make that happen*. However, you need to address "why". What makes lightning throwers so effective (or other weapons so ineffective) that they would be the only weapons used? This will only make your world that much more engaging and intriguing to your audience, and and can flesh out your backstory immensely.
tl/dr: Do it, and make it awesome. But also make it logical.
[Answer]
The major problem if this weapon system would be range. I can only imagine your "medium emmiters" being able to bridge area of mere meters. In this case, it would be easier to just run few bullets from few kilometers away.
And if ships have so much power to be able to deflect extremely fast bullets and maintain plasma shields, then it could easily be used to power huge lasers. Lasers are generally better ways to deliver energy to enemy in vacuum than electrons.
[Answer]
For any scientific military advancement another always comes along to knock it out of the way. That's just a constantly proven rule that will apparently go on forever.
But. Electricity...in space. Electricity requires an atmosphere to separate the electric potential and then let it come crashing back together. So, unless you drastically alter the physical rules in your universe no electrical fun for you.
On the other hand...that would be some cool cgi battles if you didn't care about the science behind it.
*Edit:* So to address your technologies well only one of them really. If this one works the rest are good to go.
* Gas emitters: Now you would have to emit ALOT of gas and utilize it fairly rapidly as gas will diffuse very quickly in space...I would think in the end this is entirely impractical. The volume of gas required for an electrical battle to take place would be so massive you couldn't reasonably carry it. Now if you had a field generator that could sort of keep those molecules in place then sure but this seems so complicated that the rules of simplicity make it seem terribly unlikely. Now. If you are willing (know your audience) to just say "you know what it works in my universe so deal with it" then ok.
The great thing about world building is you can choose to do that. Hell it was done in Star Trek recently and it worked for me, I am admittedly not a physics purist when it comes to movies.
So in our reality...no, this is not practical without totally outlandish tech that seems contrived and impractical in its own right, just to make it work. If you want to do it, go for it knowing that it breaches physical rules.
[Answer]
I can imagine a special kind of gas emitter to extend the range of a ship's electrical weapons: a particle accelerator. While the quantity of mass involved would be slight, perhaps particles projected in a beam would allow a jolt of electrical energy to leap the gap of vacuum and hit a target outside normal range.
These would need to be aimed, so you would still have the concepts of marksmanship, small targets being hard to but, and evasive maneuvering. To whatever extent you wanted to, you could combine conventional space opera "blasters" with your refreshingly original arcing weapons.
This is utter handwaving, mind, I'm no physicist.
[Answer]
There are certain tactical questions to answer:
**Can weapons miss?**
Although a lightning arc is basically targeting on its own, and a sophisticated computer is able to predict and aim way beyond the capabilities of human beings, that doesn't necessarily mean that all shots are an automate hit.
* Weapons require time to align. An especially big weapon is still bound to inertia and might not be able to align vs a ship that is simply flying too fast.
* Weapons might not have a 360° attack radius. A ship could maneuver into a dead-zone of such weapon and be safe from attacks.
* The target could be out of range, or even worse: could out-range the enemy with its own weapons. In this case speed will again be the factor that determines the winner.
* A weapon can probably not target or do damage at all, because certain materials and/or technical properties prevent that. A lightning attack would not be attracted to a ship made out of plastic (or other non-conductive materials). And - no pun intended - putting a solid object into the muzzle would be a very effective way to stop that weapon from doing any harm.
If none of the above is true and all weapons will always hit the enemy, then tactics are reduced to: Who can deal fatal damage first?
In this case most attacks will be a simple hit-and-run tactic by either surprising the enemy at a point where it cannot fire back, or just out-gunning it and soak the incoming damage till the enemy has lost. The general rule would be: win a battle by killing first, or living longer than the opponent.
Tactics would also shift to prevent battles from even happening, for example through diplomatic channels, boarding, or sabotage.
[Answer]
Assuming construction costs and energy concerns out of the way.
You're talking energy based weapons like lasers, particle beams, x-ray lasers, masers and rail guns. Tactical influences are derived from naval ships at sea today who're going electric. Electric propulsion instead of direct engine power. Electric sensor array, and the likelihood of electric-magnetic weaponry including lasers and railguns.
The problem with space warfare is even at light speed, the distances of ships is so substantial. Space warfare is likely to be conducted at great distances and speeds than terrestrial combat. A big problem for targeting and tracking, as even light requires a few seconds to traverse ranges measured in hundreds of thousands of kilometers.
Many issues crop up in space warfare
1. Distance involved means pre-calculating a firing solution before engaging. If you're off by a fraction of a degree, you could miss by miles.
2. The tremendous speeds of starships requires tracking technology that's still being worked on today.
3. The bigger the ship the bigger the target.
4. Destroying a target in space generates significant debris that may pose a threat to your own forces. An object traveling at 20,000 mph even if it's blown to smithereens is now a shotgun blast of scat going slightly slower.
5. Building military resources in space requires significant upkeep. The Astronauts on the International space station spend most of their time doing chores and upkeep. Satellites are usually de-orbited and destroyed. Assuming starship is built with more durable stuff, it still asks how much does this cost to maintain and what infrastructure you'd have to build to do so? A drydock/berth.
6. The logistical supply chain even for terrestrial
7. An enemy wanting to harm you would attack you by terrestrial warfare
8. Assuming you possess incredibly fast propulsion systems on your starship to avoid incoming, he who fires first usually wins. Unless you have shielding, armor or such.
9. Sensor technology on a starship would require a order of magnitude more sophistication and pre-warning of threats. At the speed of light even vast distances require several seconds to minutes to verify and relay for appropriate action.
] |
[Question]
[
I want to know what key invention would allow my civilization to travel down to and explore its world at sea level. This is similar to my previous question\* but this time does not assume metals are in short supply so technology may develop as on our world.
This world is an alternate Earth. Similar size, mass and distance from its star as our Earth but with a much denser atmosphere. At sea level the pressure is around 3.2 bar, the temperature is around 50 degrees C and the humidity is 100%. At 5000m the pressure is around 2 bar, the temperature around 25 degrees C and the humidity ranges from 20-70%. The oxygen concentration in the atmosphere is around 15%.
The humans live on a very large plateau at 5000m and cannot descend to sea level unaided because of the high temperature and humidity. Assume that their technology progresses in a broadly similar fashion to ours. The humans there are physically just like us.
As this society develops from a primitive level to more modern technology what is likely to be the key invention that enables them to more fully explore their world? In cases where multiple answers are considered equivalent the answer using the earliest technology would be considered better.
\*[How can my fictional race of humans extend the area of their world they can explore?](https://worldbuilding.stackexchange.com/questions/235307)
[Answer]
# Refrigeration:
Out of all of the problems on your world, the heat and humidity are the largest. So with the invention of refrigeration, you should be able to counter these twin problems.
The first [refrigeration systems](https://en.wikipedia.org/wiki/Refrigerator#:%7E:text=The%20first%20cooling%20systems%20for,machine%20was%20invented%20in%201854.) were invented in 1854, and once you can cool your people off, they can survive. The [other effects of this environment](https://worldbuilding.stackexchange.com/questions/235307/how-can-my-fictional-race-of-humans-extend-the-area-of-their-world-they-can-expl) will be pretty severe, but with this primary problem solved, the others can be manageable.
# [Airships](https://www.space.com/16623-first-powered-airship.html):
After this, aircraft will be the next big step. Powered airships were first built in 1852, and I suspect there will be huge pressure (pun intended) to build better ones fast. The La France, a fairly practical one, was built in 1884. I suspect that lighter-than-air ships will be huge. First, there will be no roads, challenging walking, and no harbors at sea level to build ships in to travel. Secondly, you will be wanting your people to be able to live in a lower-pressure environment (which the airship can rapidly climb to) as much as possible. Thirdly, in an airship, your people linger over areas of interest and use VTOL. Finally, airships of all kinds will likely be sealed to keep out the heat, and an enclosed environment will allow to control the partial pressure of the gasses inside (alleviating the worst side-effects of this environment).
You may even have tethered flying bases over strategic resources, allowing explorers and workers to live comfortably while surviving journeys to the surface, similar to those [proposed for Venus](https://spectrum.ieee.org/nasa-study-proposes-airships-cloud-cities-for-venus-exploration).
[Answer]
# Digging.
Underground is gonna be the average temperature of the world, winter and night included, so it's gonna be a fair bit cooler. As such, humans will get very good at digging.
This means they can pop out for short incursions outside and then go back inside to get more water or refuel. This is just going to advance with technology.
# Eugenics
Some people are much more heat resistant than others, and extensive training can make you more heat resistant. You can slowly breed and train heat resistance among a small dedicated group.
This is going to progress pretty slowly, with people with better genetics forming noble houses due to their superior genetics. It's gonna go much faster once they get a better understanding of genetics, and DNA sequencing.
# Ice production
It takes a massive amount of energy to melt ice. This cools you down a lot. To extend outside time, many would rely on ice. You can make it underground, collect it from rare places, or make it with cooling chemicals. [There used to be a massive trade in this](https://en.wikipedia.org/wiki/Ice_trade#Pre-19th_century_methods), and in your world this would also happen. People would carry ice around with them to provide cooling when going outside to hunt or gather rare resources.
# Refrigerated vehicles
This is gonna be the game changer. When you're high tech enough you can design vehicles which keep their occupants cool. With this you can go anywhere. Expect early development of mechanized suits and other things and a lot of experimentation on cooled vehicles.
[Answer]
One large issue core body heat, and not being able to use sweat and evaporation to keep the body cool. The other is how long the surface of the body can withstand the heat. As a rule of thumb a hot water at 120 degrees F creates a serious burn in about 5 min. 130 degrees about 30 seconds. So the burn response is very non linear.
I think for the humans on the plateau to explore the hot humid wetlands, the biggest innovation would be a suit that protects the skin and provides cooling.
How to do that would depend on the technology level…
[Answer]
I think this is much harder than other answers suggest.
As written in DWKraus answer the first step would be airships. This can happen around 1800 to 1850 in Earth technology. These would not actually descend to the hot humid places but just stay up at approximately the height of the plateau and fly over the world. This gives you an idea of the general geography but not really anything else.
To actually enter the hot humid places you would need active cooling. A body suit might be possible with around 1900 technology but at best for a few hours. You can only walk in it, so you can only explore a couple kilometers away from your plateau. A wheeled vehicle won't be able to go through the wild, presumably this is a dense jungle, so this doesn't really help.
A flying vehicle with active cooling and support for some active cooling body suits might be around 1950 techs either as an airship or a helicopter. This would work for research exploration missions, similary to submarines on earth.
Establishing a semi-permanent research base is around current human technology. Any resource extraction would be completely uneconomical unless there is some supervaluable unobtainium to be found. A settlement is way into future tech.
[Answer]
**Pumps.**
One of the great advantages of exploring your world at sea level is, by definition, *the sea*. It's right there.
In our world these are known as Sea Water Air Conditioning (SWAC) systems, and there's not really too much to them in principle -- pump up some very cold water from the benthic depths, and away you go.
Getting down there in the first place might be a bit of a hassle, or it might be as easy as falling (and falling, and falling) off a log.
[Answer]
## The Thermos
People have suggested refrigeration. A small fridge plant could certainly be portable, not so much for a large one. But if your insulation R value is good enough, small is fine.
I propose vehicles or buildings with evacuated steel cell walls (or super high R value materials, but vacuum seems easier with low technology).
[Answer]
With that level of humidity, one can take into account the presence of large rivers.
The river water would be cool enough during its flowing, so the initial exploration will be done by creating "colonies" downstream.
Colonies would be cooled by the colder water from the rivers, maybe carried like for water mills.
Basically, waterproof ship technology is needed (so you could create a room mainly surrounded by water).
Within limits, you could create the equivalent of aqueducts to bring cold water to other places.
The activity would be indoor during the day.
The second phase would need some kind of motorized pumps to cool the ships with river water, and would allow exploration both during day and night, in any kind of river or ocean (as long as the water temperature is cold enough, so not all the way). The ships will be semi-submersible (i.e. the main part of the ship will be underwater for thermal protection).
If there is a significant ocean, more exploration could be done by submersibles - that is, assuming that the underwater temperature is cold enough (on Earth, deep water temperature is around 4 degrees Celsius).
However, useful submersible ships require good metalworking technology and some kind of power source with enough "range". Based on our development on Earth, I assume electric plus batteries are "out" so that leaves some kind of thermal engine (wood plus steam probably, if coal and/or crude oil are not available). But thermal engine improvement will probably lead to cooling systems, so in the end the solution will be air-conditioned vehicles.
[Answer]
**Polymers**
Virtually any climate, pressure controlled environment will require materials with properties that are obtainable with polymers.
] |
[Question]
[
**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
---
This question does not appear to be about **worldbuilding**, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help).
Closed 2 years ago.
[Improve this question](/posts/196403/edit)
Is there a generic term that encompasses the various types of limb armor together?
I'm hoping there's a catch-all I don't know about that I could use that would describe the collective of bracers/greaves/pauldrons/etc.
[Answer]
Greaves are armor for the lower legs, not armor for the arms. Just use the terms Upper Canon and Lower Canon as generic terms for armor on the arms.
From <http://medieval.stormthecastle.com/all-about-medieval-armor.htm>:
>
> Plate armor for the arms came into use during this century and this piece of armor was called vambraces and it was composed of armor for the upper arm called the upper canon and armor for the lower arm called the lower canon.
>
>
>
[Answer]
You could just go with "peripheral armour", but really, the sticky-out-bits on humans tend to be specialised for their tasks and the armour they require is going to be quite different.
There's a reason that we have different words for "things that keep your toes warm" and "things that keep your hands warm", rather than "sticky out cold bit covers". (and before anyone says that you could use "thermals" to refer to coverings for the top half or bottom half of the body, note that this is as helpful as saying that you can use "armour" to refer to coverings for the arms and legs, too)
[Answer]
I believe that the term is simply "extremities".
[Merriam-Webster](https://www.merriam-webster.com/dictionary/extremity):
"Definition of extremity...
b: a limb of the body
especially : a human hand or foot"
So, if your armor is just a kind (not a full-on powered suit, just some conventional armor) that covers these places, why not call them "extremities"?
] |
[Question]
[
The older a memory is the fewer details we remember. The importance or impact of an event can also drastically affect how much we remember about it, but even the most impactful will, presumably, eventually fade.
Most fictional races with immortality or extreme longevity seem to recall events from the distant past quite vividly, as though the last thousand years feels like a decade. Many of these races also possess superior intellect, which might help explain this.
If a being (or society) can live indefinitely, but has the same mental capacity as humans, how might the forgetting curve affect the them?
[Answer]
Psychology has a pretty well supported model for this called [Interference Theory](https://en.wikipedia.org/wiki/Interference_theory). There are several caveats to Interference Theory but the 3 key parts are:
* **Proactive interference**: As you refine a memory through rehearsal, recalling the older version of it becomes harder.
* **Retroactive interference**: As you learn new things, it becomes harder to recall things that you previously learned but have not rehearsed.
* **Output interference**: As details are recalled from a memory with many details, your ability to recall all the details decreases.
In short, there is no real way to hold onto a memory forever. The more you ignore it, the more it fades, the more you recall it, the more it blurs. Eventually, even the strongest and most recalled memories become so distorted that there is no longer something tangible to remember. You are just recalling remembering something you remember remembering, and eventually it will just not come up in so long that the core of the memory is forgotten as well.
That said, the things we remember longest are the things that can not be grouped with other memories that we occasionally think about. An isolated event, like the 1 time you saw a clown perform in 1st grade can be remembered much longer and in more detail than any repeated pattern of happy holidays or traumatic abuse.
So, if your 500 year old elf has lived through a dozen wars, he will probably not remember the time he slaughtered women and children 300 years ago, but if he's only ever flown on a dragon once, he may be able to recall that he did that decades or even centuries later because it is so unique it is harder to interfere with.
Surrounding yourself with keepsakes are also a good way to preserve a memory. If he never wants to forget his war crime, he might keep a doll of one of the murdered children displayed in his great hall that he sees every so often reminding him to remember what he did. If he wants to remember the dragon, he might keep the saddle he wore. In time, the memory will blur away from output & proactive interference, but the key detail that he commited the crime or rode the dragon can be reinforced every time he sees for a very very long time.
This means if you want to make a believable scene where an elder being recalls something from centuries ago, you should put a keepsake in his displayed personal belongings that would remind him of that event.
**Some Counter Intuitive Side Notes:**
Emotionally powerful events that are not unique in your experience actually do not form stronger memories, they create stronger feedback loops. Psychologists who work in the field of trauma understand that the best treatment for PTSD is to "remember what really happened". When repeated trauma happens we often experience what is referred to as blacking it out. Basically we forget most of the details of the actual experiences as our minds try to compress the grouping of memories together, but because we try to think about it and remember it so often, we create false associations that generalize and blur much further into other areas of our life than it should. By analyzing what did happen you can make your brain re-evaluate the false associations which is how you keep every day things from triggering trauma inspired reactions. But here is the kicker: what you remember in PTSD treatment is often not accurate, nor does that matter. The treatment is to create a contained narrative that you can believe in so that your mind can create boundaries between when you were in danger and how you now are safe.
Also, memory is not infinite. While many neurologists will claim that the brain can have a virtually unlimited number of patterns, that does not make the amount of useful information it can store unlimited. Think of it like this: A comment on SE can contain 600 characters. If you store that in a UTF-8 format, that is about 8.8x10^1444 possible data configuration... however, that space can only be used to contain a single, relatively simple concept because almost every possible combination of values would cause a text parsing error, of those that don't almost every combination results in gibberish, and of those that don't almost everything you could say would be meaningless to the conversation, and once that set of 600 characters is consumed, you can not use it to store anything else without changing the meaning of what is already stored there. We know from studying brain structures like the hypothalamus that the mind uses many many techniques to minify how much it stores, and that failure to do so causes retardation because our brains can not function when you remember too much. In recent years, many neurologists and computer scientists have been studying each other's work and finding that most of the 'illogical' things that people do are consistent with highly optimized usages of limited resources.
[Answer]
Memory doesn't work that way (we think). Mostly because (we think) memory doesn't actually exist. By "we think" I mean "the current scientific understanding available to us in the literature". The truth is that memory is still a mystery. Absolutely *nobody* understands what memory is or how it works. As such, we don't understand memory nearly well enough to answer your question with any certainty.
### Short Answer
However, working off current theories of memory, I'll give a broad answer: *If humans lived forever (or a being lived forever but had a human-like brain), then **they would be able to remember the most important and/or emotionally-impacting events of their lives forever.***
### Long Answer
Memory likely doesn't exist. It's not a physical "thing" that can be measured. From what I have available to me, memory is actually a *series of firing neurons in the brain*. That is, when you remember something, you're just convincing your brain to re-fire that neural pathway that was fired once before. But if memory is a mystery, then willful recollection of past events is basically an enigmatic black-magic box. Whenever we think or feel, neurons push closer together or pull further apart - *very slightly*. This allows the "signals" between the neurons to be stronger or weaker. Rinse and repeat with the estimated 100,000,000 (hundred million) neurons in the human brain, and you get an absurdly complex pattern of near-infinite pathways. When we say a "memory fades", we mean "that pathway no longer exists", or rather "those neurons are no longer in the right order to be fired again".
As such your question begins with a false assumption: **memory does NOT fade across time**. It *seems* like that to us, but it's not true. What's happening is we have more thoughts, experiences, and emotions which pushes and pulls those neurons closer or further away, and the firing patterns change. It's these changes which make it "more difficult to recall" a memory. But that's not the memory fading, *it's the brain adapting to new experiences*. It's changing neural pathways, not a "fading memory".
But people who experience emotionally-engaging (that is, "ferociously active neural experiences") events are more likely to remember them because those neural pathways were set *hard*. This can be positive or negative: falling in love or a vicious rape; getting a promotion or being mugged; getting married or getting divorced; a first kiss or losing a friend. Whatever is *intense neurally* is going to "cement a pathway" - ie, push and pull those neurons in a way that the firing signals are *strong*. When these "neural pathways" are set, (a) it takes way more effort to change them (either an equally intense experience, like head trauma, or a *crap ton* of mundane experiences), and (b) people are more likely to continually recall (re-fire and re-cement) those pathways.
By "continually recall" I don't mean "directly think about the experience", but "build upon those pathways by re-firing parts of them". For example, after falling in love, you're more likely to keep kissing, hugging, holding, cuddling, talk with, go on dates/share experiences with that person. So those pathways in your brain are building upon the prior experience. So it is on the negative side: the abused child runs from trusting others, the raped woman avoids mutually shared experiences with men, the PTSD victim has panic attacks, etc. To fall out of love takes *a lot* (either a "strong" experience, like catching them cheating on you with your best friend, or *a lot* of weak experiences, like "we just kinda drifted away.... for the last decade"). Similarly, to overcome trauma also takes *a lot* (either a "strong" experience, such as religious or medically-intervened solution, or *a lot* of weak experiences, like working day-in and day-out to control and push back the PTSD until it finally disappears).
So, you see, if a human-like brain were to continue indefinitely, *so long as that neural pathway holds, the memory will hold*. As such the "important things" (ie things you keep thinking / reciting to yourself), and "emotional things" (ie strong experiences) will last indefinitely. It takes *new experiences* to slowly pull those neurons closer together or further apart.
That's how you can forget what you ate for breakfast but remember that douchebag from 2nd grade like it just happened five minutes ago.
### Final Note - you'll never run out of capacity.
If this theory of memory is correct, the brain can hold about 100,000,000! memories (about one hundred million factorial). Most calculators will give you an error or just say "infinity" if you try to calculate that.
A few years ago, for the novelty of it, I did an estimated calculation of this value. I forget what it was precisely, but I was able to estimate that if you formed *a trillion* memories for *every atom in the universe* at a rate of *a trillion times per second*, then after a *trillion* years you would finally accomplish 1% of the total number of neural pathways your brain could handle at one time.
So no, you'll never "run out of space". There's always room to hold onto what's important while adapting to new experiences ... even if you keep living until the end of the universe :)
] |
[Question]
[
I am a complete amateur regarding biology, so please forgive me if this question is a little stupid.
Could we ever create squids that have human-level intelligence and could serve as a replacement in case humans die out?
I heard that squids can have giant axons, that can exceed 1mm in diameter. However, they do not have myelin coating. What would happen, if we would give their cells myelin coating (by gene editing)?
The signal speed in the axon seems to be related to intelligence, but the large axons already compensate for the lack of myelin, so would myelin coating even change anything?
I have no background in biology and recently became fascinated by cephalopods. I would appreciate it very much if anybody with a little more knowledge of the subject could answer these questions. Thank you very much for your time.
Edit: I ask this question here and not on the biology board, because I was told that more "speculative" questions belong on this forum.
[Answer]
While squids do have giant axons only a handful of their millions of axons are so large. These axons control the squid’s siphon which is used to expel water and propel the squid and are used to escape threats. It is thought that the increased axon size and resulting increased speed evolved to make this escape response as fast as possible. The vast majority of the squid’s axons are much smaller and similar sized to our own.
Since our understanding of how brains work at their fundamental level is limited, it's hard to say what effect myelinating squid axons would have. Presumably, it would increase action potential speed which would generally improve the speed of the network as a whole, but whether this increased speed would necessarily translate directly to increased intelligence seems tenuous to me. However, recent work has shown that myelination is also a dynamic process that allows for slowing down and speeding up individual axons which are particularly important for processes that involve precise timing such as hearing but also potentially [Hebbian learning](https://en.wikipedia.org/wiki/Hebbian_theory).
[Answer]
Octopus and squid are generally solitary creatures, and will fight viciously if confined to the same area. So even if they were super (myelin enhanced) smart but still antisocial, they are probably not going to achieve great things. Cooperation, trade and beer are what made civilization.
However I did hear about an experiment where researchers put MDMA (Ecstasy) into the water of some octopodes. Funnily enough they were much more friendly after that.
Sadly there is not enough MDMA to add to the sea to turn it into one giant rave wave :(
**Evolution to the rescue!**
What if there was a bay next to some island, where humans regularly (each weekend) consumed certain substances, had a great time, excreted most of it, which eventually made its way into the water; before going back to work for the rest of the week. So the octopodes in the bay cycle between being super happy, hugging, dancing, telling eachother 'I love you sooooo much', and then have the mother of a paranoid downer.
During the downs, the most anti-social get real mean, seeking each other out to settle scores and ripoff each others limbs. (Talk about a bad case of the Mondays!)
This cycling means the slightly more social octopodes get drawn to the weekend parties. While the more antisocial pick fights with each other on the week days; removing themselves from the gene pool. This causes selective breeding for sociability. Before you know it we have smart social cephalopods (with taste for drum and base). What they lack in myelin they make up for in fine ~~digital~~ octal(?) manipulation, mixing sick beats, and mad dancing skills.
[Answer]
Could we ever create squids that have human level intelligence? Well my first impression was I think not, but forever is a long time so I would say maybe. I suspect that the molecular machinery that controls squids is very specific to squids and has evolved over millions of years in the same way that the molecular machinery for humans has evolved to help humans.
But I would be surprised if such as simple change (adding mylin) would produce the effect you are looking for. It would probably require thousands or millions of generations of squid and a huge amount of artificial selection to have the effects that you are after. Perhaps thousands to millions of years (as I said forever is a long time) might provide something of interest.
One key problem is the environment of the squid. Whilst they might become quite smart, water is not the ideal place for intelligence and civilization as we know it to fully develop. For example think how difficult it would be to experiment with chemistry under water or to refine metals.
That said there is scope for squid to become more intelligent, but whether the type or level of intelligence is what you were thinking about is hard to say. You might find [this book](https://en.wikipedia.org/wiki/Other_Minds:_The_Octopus,_the_Sea,_and_the_Deep_Origins_of_Consciousness) of interest.
In one chapter a scientist reports capturing a live octopus and keeping it in a tank in his living room to see how it reacted to him and his family on a daily basis. It figured out that it could attract his attention in a number of ways, one way was putting its tentacles into the tank water out let causing the tank to over flow and another was by squirting a water jet at the bulb just above the tank causing it to blow.
In short I believe it would be possible to improve the intelligence of an octopus but it would take a very long time and would not be susceptible to quick fixes. Also the intelligence that resulted might be surprisingly alien to humans, so I doubt it could counted as a human replacement in part due to the nature of the water environment.
[Answer]
I'm going to answer this question from a non-biological perspective, as I think the question you're actually asking is 'Can a Squid be as intelligent as a human?' The supplementary question being 'Can squids function like humans?' This latter question is a mine-field of broad issues so let's deal with the first question first...
In order to answer this question correctly, it is perhaps first necessary to understand what intelligence actually is. In computer science, the definition for intelligence we use is that intelligence is the ability to identify and recognise patterns of varying levels of complexity and completeness.
That is to say, an intelligent creature is able to see connections between things that an unintelligent creature can't, and can see obvious connections faster. This may seem obvious, but this level of precision is important when you consider how often intelligence is conflated with knowledge, awareness, liveness, consciousness, etc. The important point to note is that intelligence by this admittedly narrow definition means that there are already neural networks that are arguably far more intelligent than humans within a narrow domain (neural networks are basically just complex correlation detectors) but that doesn't make them all that 'useful' as human replacements.
Humans have capabilities that are related to intelligence that computers lack; curiosity, drive, contextual awareness. These are just some. So, is it possible that your cephalopods can be made to be as intelligent as humans? Sure. In point of fact, this is [already being looked at](https://www.scientificamerican.com/article/are-octopuses-smart/) given some of their demonstrations in the past.
The next question though is whether or not that intelligence can be harnessed in a way that we would deem useful. Believe it or not, humans have a lot of other body configurations that directly support their intelligence that have little to do with the brain. Arguably the opposable thumb (allowing us to be tool users) has contributed a lot to our ability to build intelligence, as has vocal chords (allowing us to share learnings rather than force all to build from scratch). Some cephalopods have dexterous tentacles which might replace the opposable thumb in some regards, but the lack of language is a much larger barrier.
An intelligent creature with which communication is impossible isn't 'useful' as a member of a social society. Certainly, the body of patterns such creatures can call on is limited to their personal experience. Part of what makes humans so intelligent today is that we're not learning our patterns from scratch - we have oral language that allows us to learn from what people tell us, and more importantly we also have written language that allows us to learn from people throughout history that don't need to be present in our immediate vicinity in order to share their own learnings.
The advent of things like the internet has made knowledge even more accessible and is arguably manifested in what we call the Flynn Effect, which is the drift to higher intelligence over time by humans thanks to more accessible knowledge. Being knowledgeable or having access to knowledge doesn't necessarily make one intelligent, but it does act as fuel for intelligence in the form of raw data from which patterns can be identified.
So; your squid and octopus related human analogue is possible, but regardless of the biological considerations, you need to make your species capable of efficiently sharing information and learnings between them at a greatly accelerated rate, and that generally means a language of some form, even if it is a sign language to begin with.
All this said; the way to think about it is this;
1) The Biological structures define the upper bound of how intelligent your creature can be. The neural structures have to be able to process sensory input and integrate it with the existing body of knowledge in real time, and the more that can be done, the more intelligence is *possible* in your chosen creature.
2) The Environment will define how much of that intelligence will be realised. Part of that may be biological, like the opposable thumb, but ultimately your environment needs to provide a rapid and efficient delivery of existing knowledge on which your intelligent creature can build, laying down learnings on that foundation for the next generation to utilise in their own turn.
If you provide for both of those things, then your cephalopods have a chance at realising the massive potential you are setting for them.
] |
[Question]
[
**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
NOTE: If there is anything about this question that needs clarification or editing, please don't hesitate to let me know in the comments.
---
Get ready, because you're in for quite a ride.
I have tried asking various questions based on different criteria, and I'm finally at my wits' end. In my (hopefully) last question about my solar system, I am providing the bare minimum constraints.
In my system, there is:
* A central star
* A gas giant orbiting the star
* An Earth-like moon orbiting the gas giant
* A sub-satellite orbiting the Earth-like moon
---
>
> And here is what I am looking for:
>
>
> * **As viewed from the Earth-like moon; the star, the gas giant, and the sub-satellite have angular diameters of around 0.5 degrees.** The gas giant may appear slightly larger. This means there are two types of solar eclipse: one where the gas giant moves in front of the sun, and one where the sub-satellite moves in front of the sun. There will also be an eclipse where the sub-satellite moves in front of the gas giant.
> * **The Earth-like moon is essentially an Earth clone;** Earth-like habitability, surface gravity, seasons, atmospheric conditions, temperature, weather patterns, tidal forces, etc.
> * **The system must have been stable long enough for life to form on the Earth-like moon**
>
>
>
---
Here are optional criteria that I would like to have, but I realize it might not be possible:
* The Earth-like moon has a cycle of seasons lasting 360 real-life days. This does not necessarily mean it orbits the gas giant in 360 days, it just means that winter, spring, summer, autumn last about 360 real-life days. (Earth-like seasons)
* The sub-satellite orbits the Earth-like moon in about 30 real-life days.
At this point, having asked *so many questions* trying to figure this all out, my only remaining question is this:
# Are there any systems that will meet all of the above criteria?
Or should I just give up and cry?
---
>
> What I am looking for in an answer:
>
>
> * I'm looking for someone to actually help me find reasonable numbers for this system. I am looking for a [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") answer.
> * If there is a range of numbers that will work, please specify that and give me enough detail so that I may calculate or choose a suitable system for my world.
> * Please do not say "it won't work" without explaining why it won't work. Also include the calculations you used that determine it is not possible.
> * The more detail you provide in your answer, the better the answer is
>
>
>
---
Here's what can be changed, if necessary:
* If the tidal forces from a gas giant are too great, the mass and composition of the planet can be changed as long as it allows for the Earth-like moon to be Earth-like and have its own sub-satellite.
* If there is anything else that might need to be tweaked, please provide details in the answer. For example, if the angular diameter of the sun would need to be smaller (due to a greater distance from sun needed for orbital stability) in order to meet most of the criteria.
---
### Some calculations I did to get you started
The smallest mass of a gas "giant" is around **6 Earth masses** ([a mini-Neptune](https://en.wikipedia.org/wiki/Mini-Neptune)), and the largest mass possible is **13 Jupiter masses** (at which point it becomes a [brown dwarf](https://en.wikipedia.org/wiki/Brown_dwarf))
Looking at the planets in our solar system, the densities of the gas and ice giants are measured as being anywhere from **0.6 to 1.6 g/cm3**.
With 6 Earth masses and a density of 1.6 g/cm3 (the smallest volume possible), the Earth-like moon would orbit at a distance of 4,025,050 km, having a period of 379 days.
With 13 Jupiter masses and a density of 0.6 g/cm3 (the largest volume possible), the Earth-like moon would orbit at a distance of 49,289,755 km, having a period of 620 days.
Increasing the angular diameter from 0.5 to 0.6 degrees, this changes the above two scenarios in the following way:
* Smallest Volume: Distance = 33,57,127 km, Period = 289 days
* Largest Volume: Distance = 41,110,541 km, Period = 472 days
Based on these calculations, it may be necessary to increase the angular diameter of the gas giant slightly.
NOTE: The mass and density allow me to calculate the volume, which allows me to calculate the actual diameter. From there, using the angular diameter I am able to calculate the distance, and then the orbital period.
---
Finally, here is a diagram I made in MS Paint:
[](https://i.stack.imgur.com/4UUEV.png "A rough diagram of what I'm looking for")
---
If you would like to see my previous questions that are related, in order to gain more perspective on the matter (they also include the desired mass numbers, orbital configurations, and more) I have listed them here in chronological order:
1. [Stabilizing Synchronized Orbit](https://worldbuilding.stackexchange.com/questions/156075/stabilizing-synchronized-orbit)
2. [Can planetary bodies have a second axis of rotation?](https://worldbuilding.stackexchange.com/questions/156387/can-planetary-bodies-have-a-second-axis-of-rotation)
3. [How can I have an Earth-like moon?](https://worldbuilding.stackexchange.com/questions/159629/how-can-i-have-an-earth-like-moon)
4. [What kind of star will work for my system?](https://worldbuilding.stackexchange.com/questions/160845/what-kind-of-star-will-work-for-my-system)
[Answer]
I'm pretty sure it can't be done with a gas giant. The problem lies in the stability of the habitable moon's orbit.
An object's orbit around its primary is stable as long as it is within the [Hill sphere](https://en.wikipedia.org/wiki/Hill_sphere#True_region_of_stability) of the primary (the region dominated by the primary's gravity), while being outside the [Roche limit](https://en.wikipedia.org/wiki/Roche_limit) (the distance at which tidal forces will break the object up). For long-term stability, the orbit should be no more than one-third to one-half the radius of the Hill sphere. The formula for the Hill sphere, assuming circular orbits, is:
$$ r\_H \approx a\sqrt[3]{m \over 3M} $$
The first constraint is the requirement that the moon be habitable, while the sun has an angular diameter of 0.5 degrees. This pretty much requires putting the planet into an Earth-like orbit around a Sun-like star. [Stellar luminosity increases far faster than stellar radius](https://en.wikipedia.org/wiki/Mass%E2%80%93luminosity_relation). As the habitable zone of a star moves out, the angular size of the star decreases; conversely, moving the habitable zone inwards increases the angular size of the star. Only stars of roughly one Solar mass will have an angular size of 0.5 degrees as seen from the habitable zone.
This sets the $M$ and $a$ terms of the Hill sphere equation. Only the $m$ term (the mass of the planet) is adjustable. Mass is proportional to the cube of planetary radius, the radius of the Hill sphere is proportional to the cube root of mass, making the Hill sphere roughly linearly proportional to the planetary radius.
For the given angular diameter, we can use the [small-angle approximation](https://en.wikipedia.org/wiki/Small-angle_approximation) to the tangent function. The angular diameter of the planet as seen from the moon is thus linearly proportional to radius, and inversely proportional to distance -- but the distance is constrained by the Hill sphere, leaving the planetary radius as the only adjustable parameter.
Put it all together, and to a first approximation, the angular diameter of the gas giant depends only on the density. In order to get an angular diameter of 0.5 degree, we need something a fair bit denser than Jupiter, or even Mercury.
I put together a spreadsheet to play around with numbers, and got the following result (all numbers are in meters/kilograms/seconds):
[](https://i.stack.imgur.com/7ibV8.png)
In the center is a very Sun-like star. Orbiting it, we've got a medium-large brown dwarf, 70 times the mass of Jupiter and 12% larger in diameter, taking about one Earth year to circle the star. Around that is a super-Earth, with nearly twice the mass and 25% larger giving an Earth-like surface gravity, in a 54.5-day orbit. And around that is an undersized Moon, one-third the diameter, zipping around in just under five days.
In terms of stability, Jove and Luna are both stable. Terra is borderline if there are other large bodies in the stellar system; if you need to increase stability, put it in a retrograde orbit.
In terms of habitability, Jove is squarely in the middle of the Goldilocks zone. Terra's orbit gives it about seven times as much variation in Solar distance as Earth's eccentricity currently does, [but Earth has experienced more variation in the past](https://en.wikipedia.org/wiki/Milankovitch_cycles#Orbital_shape_(eccentricity)) (and will experience more in the future). This will give a distinct 54-day cycle to the weather, but a suitable orbital inclination (corresponding to Earth's axial tilt) can still give you distinct seasons.
Since the angular diameters of Luna and Jove are slightly larger than that of Sol, they are both capable of producing eclipses. The faster motion of Luna compared to that of the Moon means that eclipses will be much briefer, with totality never lasting more than a minute. Conversely, the slower orbital speed of Terra means that a Jovian eclipse of Sol can have a totality lasting up to 15 minutes.
Terra probably won't be [tidally locked](https://en.wikipedia.org/wiki/Tidal_locking) to Jove. Normally a moon in Terra's situation would be tidally locked, but the Terra-Luna system has *far* more rotational inertia than any moon.
[Answer]
TL;DR: *maybe*. Orbital stability is pretty borderline, and some fairly unlikely circumstances have to arise to produce something that looks like maybe it will fit your needs. Tidal effects and orbital resonances will mess with the figures below, so they're only approximate
---
Lets start with a star the size of the sun, putting the orbit of the planet at 1AU. We want a really big planet (because various orbital things tend to be more stable if the parent object is substantially more massive than its satellite), and for that we'll use a [brown dwarf](https://en.wikipedia.org/wiki/Brown_dwarf). A quick glance at wikipedia's [list of brown dwarfs](https://en.wikipedia.org/wiki/List_of_brown_dwarfs) shows that there are many which are substantially more massive than Jupiter, but not actually much bigger. This is good, because it lets us maximise the size of the hill sphere around our planet, and minimise the orbital radius of the moon around it.
The [Hill sphere](https://en.wikipedia.org/wiki/Hill_sphere) of a body in the region in which its own gravitational attraction dominates that of its primary with regard to its own satellites, more or less. It is an approximation (because the [three-body problem](https://en.wikipedia.org/wiki/Three-body_problem) is Quite Hard to solve), and is defined for circular orbits as $$ r\_H \approx r\sqrt[3]{m \over 3M} $$ where $r$ is the radius of the orbit, $m$ is the mass of the planet and $M$ is the mass of the primary.
If the brown dwarf is similar to [COROT-15b](https://en.wikipedia.org/wiki/COROT-15b), it'll be ~63.3 Jupiter masses, and 1.12 Jupiter radii. That means to satisfy the planet angular diameter constraint, your moon will orbit about 18.4 million kilometres from its parent. The brown dwarf has a Hill radius of 40.7 million kilometres, which is good... orbits more than about half the hill radius away from the parent tend to be unstable.
If your moon is the size of Earth, then given the mass and distance to the parent brown dwarf, it'll only have a Hill radius of 467828km. Taking half of this as the maximum safe orbital distance, the moonmoon would need to have a radius of ~1021km to satisfy the angular diameter constraint.
---
Your moon will have an orbital period of a little under 64 Earth-days. This might bir be *quite* right, because [orbital resonances](https://en.wikipedia.org/wiki/Orbital_resonance) seem to be a thing and your moon gets quite close to the sun. I'm not going to rework this whole answer to provide a 6:1 resonance, but you might want to think about this. The moonmoon's orbital period would be a little over 13 days, and again: this doesn't fit into a neat orbital resonance, and so would probably be altered. Hopefully these peturbations won't completely destroy the system's hierarchy, but they'll probably ruin the nicely identical angular diameters.
The distance to the star will vary by nearly a quarter of an AU per cycle... that's quite a big change, and will have weird seasonal effects. It also means that the angular diameter of the sun will vary between 0.48 degrees and 0.61 degrees, which makes the nature of eclipses by the moonmoon quite different to the eclipses of the sun by our own moon.
Your moon will probably be tidally locked to its parent, which presents an issue in that this means that it will have a 32-day long period in which the star will not be visible from a whole hemisphere of the moon. I say *probably* because the presence of its own quite large, quite close moon is going to have odd effects in that regard. I'm not at all sure what will happen here, which probably means the situation is quite unstable.
The hemisphere facing its parent will always have a bright object in the sky which could be as big and as bright as our own moon (and maybe even significantly brighter, given the low albedo of the moon) and sometimes it will have its own moon in the sky too, so whilst the nights on the inner face will be long, they won't be dark.
The outer face (relative to the parent brown dwarf) will be alternately warmed by the sun and then cooled in the long dark night, and might not be very habitable except to quite specialised organism, but the inner face will be warmed by the heat of its parent which could be quite warm... perhaps as much as 1000K or more. I think you get to handwave its exact temperature, but the evolution of brown dwarfs might preclude this. I'm not going to work out the contribution of the brown dwarf's thermal radiation to the warmth of your moon, but you probably should (at least so you can get the dwarf's temperature right). There might be additional problems with the dwarf picking up a *lot* of heat from its parent star, given its size and proximity.
Really, you probably want the brown dwarf to be further from its parent to stay cool, but then the parent needs to be large to fulfill the angular diameter requirements, and so on and so forth. It is remotely possible that the working systems that satisfies all the angular diameter constraints *and* might have stables orbits *and* has a suitable habitable zone might actually have a red giant as a primary, but that whole thing just seems far too hard for me to even contemplate working out at this point.
---
NOTE: using a gas giant like Jupiter instead of a brown dwarf just won't work, because of the Hill sphere problem. I had a play with this, and the Hill radius is much too low for the sorts of moon orbital radii you need, and your moon will fly off into a solar orbit.
[Answer]
I note that astronomical bodies are requested with diameters and distances that give them angular diameters of about 0.5 degrees. An object will have an angular diameter of about 0.5 degrees when it is at distance of about 114.59165 times it's diameter.
The first thing that Overlord - Reinstate Monica should realize is:
The length of seasonal cycles on the Earth sized moon will depend on the orbital period of the planet around the star, not the orbital period of the Earth sized moon around the planet.
Overlord - Reinstate Monica wrote:
>
> The Earth-like moon has a cycle of seasons lasting 360 real-life days. This does not necessarily mean it orbits the gas giant in 360 days, it just means that winter, spring, summer, autumn last about 360 real-life days. (Earth-like seasons)
>
>
> The sub-satellite orbits the Earth-like moon in about 30 real-life days.
>
>
>
In real life a giant planet will exert tidal forces upon all its regular satellites - but not captured asteroids in distant orbits - that would adjust the satellite orbits so that the regular satellites, including hypothetical giant Earth like satellites, will have almost circular orbits in the equatorial plane of the giant planet. The tidal forces will also tidally lock the rotation of all the satellites so that their rotation periods or "days" will be the same length as their orbital periods around the giant planet or "months". Thus one half of each satellite will constantly face the giant planet and the other half of each satellite will constantly face away from the giant planet.
And the giant planet will do this very fast by astronomical standards, in a few tens of millions of Earth years. Since seasons are caused by the axial tilt of an astronomical body relative to its orbit around its star, and since the Earth like moon must have the same axial til as the giant planet, the cycle of seasons on the Earth like world will have the same length as the orbital period of the giant planet around its star, not the orbital period of the Earth like moon around the giant planet.
An orbital period of 360 "real days", presumably Earth days, of the giant planet around its star and within the habitable zone of that star is certainly possible.
The shortest known year of an exoplanet in the habitable zone of its star is 4.05 Earth days, for TRAPPIST-1d, while Earth is in the habitable zone of the Sun and has a year 365.25 Earth days long, and planets in the outer limits of the habitable zones of some stars should have years even longer than Earth does.
Our solar system has many examples of natural satellites of planets, dwarf planets, asteroids, etc. But there are no examples of any known natural sub satellites orbiting natural satellites in our solar system. There are no known natural satellites, or exomoons, in other solar systems, though there are a few candidates. If astronomers are not certain they have detected any exomoons yet, they certainly could not have detected any sub satellites in other solar systems.
And I believe that there are calculations of the orbital stability of sub satellites that indicate that natural sub satellites would be very rare and there would probably thus be a very restricted set of stable orbits that a sub satellite could have to orbit any particular specific satellite. Thus it would probably be very unlikely for a natural sub satellite to have a stable orbit in your fictional star system where you want it to be.
Assuming for the moment that there actually are a lot of sub satellites in other star systems and that our solar system is rare in not having any, we can make some assumptions about the orbits of your planet, your Earth like moon, and your sub satellite.
This article:
<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>
[1](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/)
Includes the statement:
>
> The longest possible length of a satellite's day compatible with Hill stability has been shown to be about P*p/9, P*p being the planet's orbital period about the star (Kipping, 2009a)
>
>
>
So if your planet orbits its star with a period of 360 days, your Earth like moon would have to orbit the planet with an orbital period equal to or less than one ninth or 0.11111 of the planet's year, or 40 days or less.
Assume for the moment that the orbital period of the sub satellite of the Earth like moon must have a similar relationship to that of the Earth like moon to that of the planet, in order to have long term stability. In that case the orbital period of the sub satellite round the Earth like moon would have to be one eighty oneth or less of the orbital period of the planet around the star, or 0.0123456 or less. With an orbital period of the planet around the star of 360 days, the orbital period of the Earth like moon around the planet would be 40 days or less and the orbital period of the sub satellite around the Earth like would be 4.444416 days or less.
Assume that the sub satellite has an orbital period of the desired 30 day length. Then the orbital period of the Earth like moon around the planet would have to be at least 270 days and the orbital period of the planet around the star would have to be at least 2,430 days.
Assuming that you meant that the Earth like moon would orbit the planet with a period of 360 days, and the sub satellite would orbit the Earth like moon with a period of 30 days. In that case the Earth like moon would have an orbital period twelve times as long as the orbital period of the sub satellite, and that seems sufficient to me. Then the planet would need to have an orbital period at least nine times as long as 360 days, or at least 3,240 days.
I suggest that you may need to give up the idea of having your Earth like world a moon of a giant planet and also have a sub satellite orbiting it. There would be no problems with making your Earth like world a satellite of a gas giant planet if your Earth like world didn't have a sub satellite orbiting it. And there would be no problems with making your Earth like world have a satellite orbiting it if the Earth like world was not itself a satellite of a giant planet.
But of course such a situation would result on only one astronomical body being able to eclipse the star of your Earth like world.
Or would it?
If your Earth like world is an Earth sized moon of a giant planet, maybe there are one or more other large moons orbiting that giant planet. And maybe one or more of the other large moons will sometimes be in position to eclipse the star of the system as seen from the Earth like moon.
Or possibly your Earth like world would be a planet orbiting its star. Such a planet could have no moon at all, like Venus, one moon, like Earth, two moons, like Mars, or possibly three or more moons. Of course the relative orbits of the moons would have to be such that they do not destabilize each other.
The Moon orbits the Earth at an average distance of about 384,399 kilometers. The Moon has an average radius of 1,737.4 kilometers & average diameter of 3,474.8 kilometers. At it's orbital distances, the Moon has an angular diameter of 29 minutes & 20 seconds to 34 minutes & 6 seconds, a range that includes the 0.5 degrees asked for.
If the moon was at a distance of about 192,200 kilometers, half of the distance in real life, it could have a diameter of about 1,737.4 kilometers and an angular diameter of about 0.5 degrees.
If the Moon was at a distance of about 96,100 kilometers, a quarter of the distance in real life, it could have a diameter of about 868.7 kilometers and an angular diameter of about 0.5 degrees.
If the Moon was at a distance of about 48,050 kilometers, an eighth of the distance in real life, it could have a diameter of about 434.35 kilometers and an angular diameter of about 0.5 degrees.
If the Moon was at a distance of about 768,798 kilometers, twice as far as in real life, it could have a diameter of about 6,949.6 kilometers and an angular diameter of about 0.5 degrees.
So it seems reasonable to suppose that the Earth could have two or more moons orbiting it in stable orbits at various distances that might all have angular diameters of about 0.5 degrees.
And there is this article <https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/>[2](https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/) at the PlanetPlanet blog, that cites a scientific study showing that seven to forty two bodies with the same mass and equally spaced can share the same orbit with long tern stability.
So possibly a giant planet could have a ring of equally spaced Earth like moons around it, or an Earth sized planet could have a ring of moons around it.
Earth has a diameter of about 12,742 kilometers, so it should have an angular diameter of about 0.5 degrees at a distance of about 1,460,126.8 kilometers.
So if there could be seven to forty two equally space Earth sized moons orbiting a giant planet, the total circumference of their common orbit would be about 10,220,887 to 61,325,325 kilometers, thus giving the radius of their common orbit about the giant planet at about 1,626,706 to 9,760,236.6 kilometers.
And each of those seven to forty two Earth sized moons orbiting the giant planet might sometimes see the star eclipsed by one or another of the other Earth sized moons, and also sometimes see the star eclipsed by the giant planet.
The giant planets in our solar system have average diameters ranging from 49,532 kilometers (Neptune) to 142,984 kilometers (Jupiter). So they would have angular diameters of about 0.5 degrees at distances ranging from about 5,675,953.6 to 16,384,772 kilometers.
Combining the two calculations, a giant planet might have a ring of twenty five to forty two Earth like moons in a shared orbit with a radius of 5,809,664.8 to 9,760,236.6 kilometers. The two closest Earth sized moons to another would have an angular diameter of about 0.5 degrees, and if the planet had a diameter between about 50,698.8 kilometers and about 85,174.064 kilometers it would have an angular diameter of about 0.5 degrees in the sky of each of those Earth like moons.
I haven't calculated how long the orbital periods of the Earth like Moons at those distances would be.
And an Earth like planet could possibly have a ring of seven to forty two moons with distances about 114.59165 times their diameters, so that they appeared to have angular diameters of about 0.5 degrees.
Since such a ring of moons could be at most only a few times as far from the planet as the Moon is from Earth, the planet could have eclipses of its star by one or another moon several times as often as Earth does.
Note that the PlanetPlanet article more or less assumes that such a ring of equally spaced and equal mass objects orbiting a larger object would be extremely unlikely to occur naturally and would probably have been constructed by a highly advanced civilization.
[Answer]
This doesn't work around Sol, at the very least.
You calculated that a mega-Jupiter (13 Mj) would have the right angular diameter at ~49M km, which is right around 1/3rd AU. For it to eclipse the sun (which needs to be 1AU away to have the correct angular diameter) then the mega-Jupiter would need to be orbiting the sun with a semi-major axis of only 2/3rd AU, which puts it inside the orbit of Venus. This means that when the earth-like moon (ELM) is on its closest pass to the sun as it orbits the mega-Jupiter, it would be only 1/3AU from the sun, which is 1) inside the orbit of *Mercury* and 2) far too close to the sun for the ELM to stay in orbit around the planet (by comparison, the L1 point between the sun and the mega-Jupiter at 2/3AU would be about .1 AU from the planet)
The mini-Neptune (6 Me) at least does better in that respect -- Since the ELM is only orbiting it at ~0.027AU, it can orbit at ~1 AU without an issue. However, the problem then becomes that the mini-Neptune still can't hold on to the ELM gravitationally. The L1 point between the sun and a mini-Neptune at 1 AU is only 0.018 AU from the planet, which means it'd still lose the ELM to the sun's gravity.
I used [this calculator](http://orbitsimulator.com/formulas/LagrangePointFinder.html) to find the Lagrange-point distances.
] |
[Question]
[
I was having a discussion with several people on whether or not a lightning dragon can be biologically plausible, without any magic involved. We came to two main possibilities and I'd love to see feedback on them:
1- If it was a conventional flying dragon, it would be the conduit rather than the source of electricity. While gliding among the clouds, its large wings would gather the static electricity in the water molecules and somehow store it in its body. Then the dragon directs the stored electricity into a bolt aimed at the target. In such scenario it would only be able to shoot lightning in ideal weather conditions and while flying. I, however, really lack the knowledge of how electricity works exactly or affects an animal in this scenario, and whether this makes much sense. One of the people in the discussion suggested the dragon could have an organ specialized for storing said electricity, but that really doesn't sound how organs work to me.
2- The most plausible option I could come up with is if the dragon was heavily inspired on electric eels, and in this case it wouldn't really shoot lightning nor be able to fly at all. The issue with electric eels whenever people try to use them as explanation for electric/lightning powers is that, well, it's often overlooked that only [this portion of their bodies](https://i.gyazo.com/50ea998a7b09995b94e338c4e6ef7c7e.png) is the actual fish, the rest is literally all specialized muscle and organs necessary to create such high voltage of electricity. If we were to apply that to a large dragon its body would look nothing like a conventional, flying dragon. It would require a proportionally huge portion of its anatomy to be specialized musculature and organs, and also possibly have a sluggish behavior, given its metabolism will be focused on charging up. My friend and I even doodled rough sketches of what this kind of concept could look like, you can see our attempts [here](https://cdn.discordapp.com/attachments/544171758832582676/631728231103463434/image0.jpg) and [here](https://cdn.discordapp.com/attachments/332375900073230337/632621761078362133/electric_dragons_lilian_challenge.jpg). We aren't certain of how electricity would affect the teeth(I've heard that enamel teeth really doesn't go well with it) and feathers, and in such scenario the animal's attack would be based on delivering a discharge via biting or slamming its muscular tail on the target.
[Answer]
# Biological electrolasers.
Basically, an electrolaser is a device that uses a pulsed laser to create an ionised path through the air that an electrical current can be passed down along.
In order to create a biological electrolaser, you’d therefore first need to be able to generate the biological laser. Fortunately, that’s entirely possible: the COIL laser is a chemically pumped laser that uses a combination of gaseous chlorine, molecular iodine, and a liquid solution of bleach and lye. Many of these chemicals are poisonous or corrosive, but a specialised series of organs similar to the human stomach should be capable of producing and storing them- and as a bonus, they’d also give the dragon a breath of poison gas and a venomous bite, if they were to expel the chemicals that way instead of using them to lase.
To produce the laser, it would release the chemicals into an eye-like organ with an internal reflective coating (partially reflective over the pupil), and a laser would become emitted from the pupil of the eye; by using irises and lenses, it would then be able to focus the laser.
Once the laser begins to form the channel of ionised air to its target, it would then use its electric eel muscles to generate an electric shock that would be conducted down the path to shock its victim.
[Answer]
I don’t think any form of land based lightening dragon would be possible. This is because there is no material that could provide sufficient insulation in a thin enough layer to prevent electrical leakage and discharge between the dragon and its surrounding ground and vegetation.
An Aerial lightening dragon would also suffer similar problems to some extent, however air is a good insulator and it should be possible for a flying dragon to build up a very high voltage with respect to the ground. But although high voltage is necessary it is not sufficient. To be effective a significant current would need to be delivered.
One way this might be achieved is by directing the massive stores of electric charge in clouds. If the dragon was able to extrude a very fine thread behind itself perhaps similar to spider silk it could dive onto its prey and at some very low altitude the charge in the clouds would discharge down the thread through the dragon (which would have to have some very exotic insulator insides) and then out of the dragon straight down to the prey below it.
Perhaps more chillingly it might work better in reverse. The dragon could drop a lot of goo onto the prey and then fly up until it was itself struck by lightning. The discharge would then flow a filament of thread down to the prey and boom electrically fried dinner for the dragon to eat.
Note the fine thread would be burnt up completely in these attacks. The purpose of it is to create a path of low resistance for the lightening strike. Damp silk or thread with a high water content would work best.
[Answer]
## **Your dragon needs not to be "flashy"**
In fact electricity often goes unnoticed except of course when an electric arc forms. Also no creature can ever harness much less withstand a lightning strike.
**Two solutions:**
**The first is a conductive liquid** similar to battery liquid, which by the way is often acidic. When a lead acid battery is fully charged, the electrolyte is composed of a solution that consists of up to **40% sulfuric acid, with the remainder consisting of regular water.** As the battery discharges, the positive and negative plates gradually turn into lead sulfate. The electrolyte loses much of its sulfuric acid content during this process, and **it eventually becomes a very weak solution of sulfuric acid and water.**
Since **this is a reversible chemical process**, charging a car battery causes the positive plates to turn back into lead oxide, while the negative plates turn back into pure, spongy lead, and the electrolyte becomes a stronger solution of sulfuric acid and water. **This process can occur many thousands of times.**
Your lighting dragon would simply have to possess an organ that stores electricity in this manner. You can also have your dragon spray its target with a conductive liquid and then zap them with an electric organ.
**The second is static electricity.** I don't know if you've heard about this but the arc of the covenant is extremely conductive! It is basically a giant capacitor. Mostly made of **wood and gold** the arc could effectively collect static electricity from the ground and the air. The two cherubim placed on top had their wings touch each other which functioned as the positive poll. Your dragons scales can be made similarly, wooden but coated with gold (I assume your dragon is a fan treasures). Then to unleash an electric attack it would simply join the tips of its wings together to generate a current.
Your are free to use both at the same time for a dangerous dragon. It would develop a need for both gold and sulfur to sustain this power however.
[Answer]
The trouble with lightning is that it is a very energetic phenomenon - carrying 500MJ to 35GJ of energy. Should the dragon absorb this energy rather than channeling it, an average lightning bolt would deliver energy equivalent to - and with effects similar to - 12kg of TNT... and no creature ever evolved on earth could survive being subjected to that amount of energy.
So... unless channeling a lightning bolt and exploding is a means of posthumously distributing its offspring... I can't see any way that something like what the OP wants could evolve. Lightning is far too likely to cause a fatality, and evolution tells the tale of the survivors.
[Answer]
I agree with one of the people. Just use electric eel genes to make a dragon have electric powers. Since the dragon is bigger, it probably will create a much bigger charge.
] |
[Question]
[
This question is in the same context (the same world) proposed by Steven L. Gillett in his book: "World-building".
And actually there have been some other questions about this same chlorinated world. For example this:
[Are plastic plants plausible?](https://worldbuilding.stackexchange.com/questions/120616/are-plastic-plants-plausible)
Long history short: The world is Earth-like (same biochemistry, carbon based also and oxygen breathers) but the atmosphere contains 1% chlorine.
Steven L. Gillett explains about the atmosphere:
>
> "Chlorine is colored; as all the chemistry texts say, it’s a “greenish
> yellow” gas. It absorbs blue light (and shorter wavelengths)
> strongly."
>
>
>
and explains about the water:
>
> "the acidity of surface water will be about like that of undiluted
> vinegar."
>
>
>
I am trying to draw such a planet as accurate as possible, but I have a problem with the color of the polar ice caps and the snow. Although the planet has oceans and rivers of water, there will be a small amount of (an equivalent of) acid and bleach solution in the water. So, my question is: **What color will the snow be in that planet?**
EDITON: Justification of the chlorine in the planet (from the book also)
>
> Over geologic time, geologic processes have gathered most of Earth’s
> chlorine together in the ocean, in which it’s present as the very
> stable chloride ion, Cl-. In fact, it takes quite a bit of energy to
> strip that electron away. But suppose some plant in the oceans evolved
> the capability to make chlorine gas from chloride by stripping that
> electron away again, using the energy derived from food. (And, of
> course, a special enzyme system.) Why would it bother? Well, say, as a
> defense mechanism. It could then incorporate the chlorine into its
> biomolecules to make itself a poor meal for predators—making its own
> natural chlorinated pesticides, if you will. But predators will
> eventually evolve a defense to that, too. Then, the continued
> escalation of the biological “arms race” may eventually result in
> plants releasing free chlorine—still as a defense mechanism, a natural
> gas attack.
>
>
>
[Answer]
Since chlorine doesn't become a liquid until roughly −34 °C (−29 °F) your snow will be mostly white. As a liquid it is amber in color and this will give your snow a slight yellow discoloration.
However, it will likely react with the water and create a weak acid (HCl or HOCl). Its usually clear, but can have a yellow discoloration.
If anything, your premise appears to be a little incorrect here. Chlorine is highly reactive so if you had 1% it would quickly react with other elements and disappear from its pure form. Water in the form of moisture, snow, rain would quickly remove all the chlorine in your atmosphere.
[Answer]
Chlorine reacts with water in an equilibrium: Cl2 + H2O <-> HClO + HCl
As long as the pH doesn't rise this means there will always be some elemental Chlorine left. So water alone isn't a problem for your chlorinated atmosphere. The problem is, that any reducing agent on the ground will over time react with the atmosphere. Wood for example or any metals. Oxygen only does that with enough starting energy or over long periods, chlorine will happily react at room temperature with any biomass. You can see that this happened on our earth in the past, which is why the oceans are full of NaCl. So you might be able to sustain such an atmosphere if the surface is inert to the reaction with Chlorine.
As to the color of snow: Chlorine won't be trapped or solved in the ice just as CO2 isn't. The crystalization purifies the water and only traces of Cl2 should be found in it. So your snow should be white.
] |
[Question]
[
I'm trying to build a story around a supermassive black hole, which is ejected from a merger of two galaxies, that is hurtling our own way. What is the smallest realistic distance at which the black hole could sneak upon us with our current technology?
For extra dramatic effects I would like us to notice it as late as possible. The black hole is coming from depth of the intergalactic space toward our Solar System.
The black hole doesn't have any accretion disc around it; my assumption is that it swallowed everything originally around it, if that is possible, and so the only effect would be gravitational.
I don't care under which angle it enters our galaxy - whatever one is stealthiest, so long as there is the least mass to interact with. Maybe it could travel perpendicular to the galaxy disc.
Speed is not important to me too, as long as it is a realistic speed for an ejected black hole following a galaxy merger.
The assumptions with my limited knowledge gained from reading articles and watching documentaries are that:
* A black hole without an accretion disc doesn't emit radiation.
* There isn't much matter in intergalactic space to swallow.
* A black hole's magnetic field is weak, according to this [article](https://www.space.com/39051-astronomers-measure-black-hole-magnetic-field.html).
* A black hole could be discovered only by gravitational effect such as lensing, at least until it enters the galaxy.
Please correct me if my assumptions are wrong.
[Answer]
This sort of scenario is quite possible, and would likely be the result of the merger of two supermassive black holes during the collision of the galaxies. We have evidence of this in the quasar 3C 186 (see [Chiaberge et al. 2017](http://adsabs.harvard.edu/abs/2017A%26A...600A..57C)). Over the course of about two billion years, two supermassive black holes circled around each other, emitting gravitational waves. The final burst, as they combined, was likely anisotropic, emitted in a particular direction. This propelled the resulting black hole the opposite way, ejecting it from the galaxy (although it's still nearby; it's only been about 5 million years since the merger).
I pick 3C 186 because we're fairly sure it's been ejected from its host. That's because it is spatially offset from the host galaxy's center by 10-11 kpc, and because it has a velocity offset, traveling towards us at about 2000 km/s, although its overall velocity vector does not point directly at us. Other candidates simply have only spatial *or* velocity offsets - not both.
If we use 3C 186 as a model, we have some parameters we can look at and analyze:
* Radial velocity: $\sim$2000 km/s
* Mass: $\sim10^9M\_{\odot}$
* Emission: Mainly from the broad line region around the black hole
* Luminosity: $2.6\times10^{13}L\_{\odot}$
What's notable is that the active galactic nucleus stayed active. The supermassive black hole was ejected along with high-velocity clouds orbiting close to it. That's why were able to still observe it, and compare its redshift with that of its former host galaxy. It's unclear how long this emission can continue, of course, but if the black hole approaches us fairly soon after it's ejected, we should still see emission from the broad line region and possibly from relativistic jets.
Let's say that it's been a long time since the black hole was ejected, and the gas and dust around it has long since been depleted. In this case, we have a compact object with the mass of a small dwarf galaxy headed our way. We should be able to observe it via [gravitational microlensing](https://en.wikipedia.org/wiki/Gravitational_microlensing#Mathematics). Since the angular size of an Einstein ring scales with the square root of the mass of the lens, we should observe lenses about $\sim10^4$ times larger than those created by stellar-mass black holes:
$$\theta\_E=\sqrt{\frac{4GM}{c^2}\frac{d\_O-d\_L}{d\_Od\_L}}=\sqrt{\frac{4GM}{c^2}\left(\frac{1}{d\_L}-\frac{1}{d\_O}\right)}$$
where $d\_O$ and $d\_L$ are the distance to the lensed object and the distance to the lens, respectively. Say we observe the lens while the black hole is in intergalactic space - maybe between us and Andromeda. The lensed object, presumably a star in Andromeda, would have $d\_O\approx780\text{ kpc}$. If we pick a resolution of $\theta\_E\approx0.4$ arcseconds, then we find $d\_L\approx768\text{ kpc}$. In other words, if the black hole was coming at us from Andromeda, we could see it from pretty far away!
That said, such an alignment would be unlikely. It's more probable that the supermassive black hole would be coming from another direction - say, from the Virgo Cluster, 18 Mpc away. This means we would see the black hole from 13.3 Mpc away at the most. In general, the distance to the lens at which the ring would have a radius of $\theta\_E$ at the critical value is
$$d\_L=\frac{d\_O}{\frac{\theta\_E^2c^2}{4GM}d\_O+1}$$
and you can check my calculations for the given figures. It's even *more* likely that the black hole would not be in front of any source even mere tens of megaparsecs away. This of course would make it harder to detect, as the lensed object might appear dimmer, and the ring might be smaller.
The optimal direction for the black hole to sneak up on us from would be from a region of the sky we can't easily observe. I would recommend the [Zone of Avoidance](https://en.wikipedia.org/wiki/Zone_of_Avoidance), where much of the sky is obscured by gas and dust in the Milky Way. This makes it very hard to perform observations of background galaxies, let alone detect lensing. We would likely need to see lensing from the [IC 342/Maffei group](https://en.wikipedia.org/wiki/IC_342/Maffei_Group), which lies about 3.3 Mpc away. Within 3 Mpc, the lensing would show up, but at that distance, the images would likely be blocked by the Zone of Avoidance.
I don't know how close it would be before we could make that detection; I'm not sure how to calculate it. I assume, though, that the distance would be greater than the distance at which the black hole would gravitationally affect the Milky Way (recall that its mass is comparable to a middling dwarf galaxy). I will work on calculating that range, if I can. But I suspect strongly that microlensing is the best detection method, and that the Zone of Avoidance is the optimal approach. I just need to determine how to combine extinction with lensing.
[Answer]
First of all, a **Super Massive Black Hole** would most likely never be ejected in the merge of two galaxies. These Black Holes are in the galactic centers for a reason. And even if something similiar would happen - two galaxies merge, but only one SMBH stays, then there would certainly be a few stars, that would follow this fleeing Black Hole.
But for now, lets just ignore that.
There are two cases we have to evaluate:
1. The SMBH is coming from the the side of the milky way (in the galactic plane)
2. The SMBH is coming from the flat side of the milk way (from 'above' or 'below')
In the first case, lets assume its heading straight to us, shortest distance. It is estimated, that the edge is about 20 k LY away from us. That means, the star furthes away from us is about 20.000 years older, than we see him now. And there are stars, maybe far and few, but there are.
That said, we would notice that something is wrong with the stars in that direction - dimming, redshifting, changing its movement - all because they move away from us into the direction of the black hole.
It is hard to assume a distance when this Black Hole would be noticably effect those stars, mostly depending on the mass of the object, but lets assume it is only noticable when the Black Hole is already there. This would mean that if the stars in question would change noticeably now, that was in fact be 20.000 years ago.
Now the next question would be, how fast is this SMBH? I found [an article](https://www.sciencemag.org/news/2018/05/one-milky-way-s-fastest-stars-invader-another-galaxy) stating that the fastest stellar object we know of - in our galaxy of course - is a white dwarf traveling with around 2400 m/s. Thats about 0.008% the speed of Light. That means, while the light would take 20.000 years to reach us, if this black hole had that speed, it would take about 2.498 x 10^9 years to reach us. Pretty long time for preperations, even if you substract the 20000 years the light traveled.
The second case is a bit more promissing. As it is estimated, that the milky way is about 2 k lightyears thick, we would notice it at max a thousand lightyears away. Under the same speed assumptions, the black hole would only need 124 913 524 years to reach us minus a thousand for the distance.
In both cases, a detection would be almost certain at the earliest points. SMBH arent a thing to joke about an most likely we would notice is much sooner that those 20000 and 1000 years respectivly
**But** why does it have to be a super massive Blach Hole. In fact, if it was a stellar sized Black Hole, it could sneak up on us, without even noticing. If it only had five solar masses, we maybe only could detect it 1 or 2 lightyears away, if we get lucky. In that case we would feel the effects much sooner.
[Answer]
I must disagree on the detection range of a SMBH, approaching from above or below it could get a **lot** closer before being detected **if it's behind another star**. If the proper motion of the black hole and the star are the same it could stay in hiding until it got close enough that we noticed it tugging other stars, we would not get a lensing observation until it was no longer behind the other star.
Obviously, it can't stay behind another star forever because the star is orbiting the galaxy but the black hole is not, but it doesn't need to stay hidden all that long. You don't have to go back too far to find a time we wouldn't have noticed it and if it's heading straight for us it doesn't come out of the shadow until it passes (but that will be a spectacular event if it's close enough.) Note that the star should be a loner, if it has companions the wobble will offer opportunities to note the spectrum from the accretion disk.
As for the ejection velocity--Sag A\* is something like 4 million masses, but some of them are in the billions. Lets look at a spectacular merger--galaxies A (4 million solar mass black hole) and B (40 million solar mass black hole) merge, then merge with C (400 million solar mass black hole.) The A and B black holes are in a close orbit, they then pass C--but B goes in. A could have a relativistic ejection velocity.
[Answer]
A supermassive black hole would almost certainly be noticed at ***least*** a few thousand years in advance. However, these aren't your only option. It is reported that several smaller, stellar-mass black holes orbit Sagittarius A\* at the center of our galaxy, so I think it's safe to assume that there are similar conditions in other galaxies. In a galaxy merger, these stellar-mass black holes could also be ejected. If one of these were coming at us, we would still likely detect it earlier, but it isn't unthinkable that we would have only a few months of warning as we notice orbital irregularities in Oort cloud, or maybe it's too difficult to monitor the Oort cloud(I honestly don't know) and you would notice the orbital irregularities in things a bit close, such as Pluto. In any case, likely a few months of warning before we got to the really bad things, like humanity dying. (see this Kurzgesagt video-https://www.youtube.com/watch?v=gLZJlf5rHVs)
] |
[Question]
[
I had an idea for a group of nomads/travellers who sustain themselves with mobile hydroponics system and whatever they can grow on the move.
How feasible would it be to have a mobile hydroponic farm capable of comfortably sustaining one person that can be mounted on a vehicle of some sort?
From the rough calculations I did, it certainly seems to be doable;
[Farmland needed to sustain one person](http://www.farmlandlp.com/2012/01/one-acre-feeds-a-person/) $\approx$ 0.5 hectares or $5000 m^2$.
Hydroponics $\approx$10x more efficient that dirt farming (includes density and no need to lie fallow).
Means roughly $\approx 500 m^2$ of hydroponics, or a square about 25m on a side.
Obviously this is a very rough, back of the envelop calculation, but it certainly seems doable. Even if you'd need a large truck.
This only covers food as well - not any other crops you may want to grow to produce fuel/fabric etc etc.
Other concerns:
* Power & Water - hydroponics needs plenty of both - obviously if you're on the move you could use the vehicle as a power supply, or supplement it using solar/wind power.
* Effect of vehicle vibrations on the plants - both normal engine noise and rough terrain. (Would it be possible to somehow utilize the vibrations as part of the hydroponics system?)
* Sunlight - either have to be exposed to the sunlight, or use artificial light sources - which uses more power.
* Weight - All the machinery/water/plants would be very heavy and would affect the performance of the vehicle.
* Mobility - at the end of the day you've got to be able to move, preferably with some off-road capability.
Obviously ship-based hydroponics is feasible, but I was wondering about the possibility of a land-based hydroponics society
Maybe if you has the hydroponics set up in a tiered system on the back of an old semi-trailer?
Bonus Question: Could a mobile hydroponics farm on the back of truck produce enough biofuel to keep itself moving?
[Answer]
Not only is this doable, you can do it now.
<https://www.freightfarms.com/product/#lgm-basics>
[](https://i.stack.imgur.com/vMA9W.jpg)
These folks will sell you a hydroponics grow truck exactly as you propose. It looks very cool! I could imagine this would be nice for a modular farm set up that would be easy to expand. It also might be nice for illegal or other high value crops you might want to keep moving, to avoid attention or discovery.
I think you might need a fair bit of water for this. If you were moving a lot thru open deserts you could get one of those 2-trailer trucks like they use in Australia, with one being full of water.
[Answer]
The obvious question I have to ask is about the nutrient base.
Hydroponics *don't* just need plants and water; the plants themselves need nutrients that they extract (via roots) from the soil normally; in the case of hydroponics, they extract it from the water and the fertiliser has to be in solution within the water for it to work.
The most common form of fertiliser used in industrial farming is known as NPK fertiliser (Nitrogen, Phosphate & Potassium), which comprise the 3 primary building blocks for plant growth. Over time however, you need more trace elements and you also need certain bacteria in the soil in normal plant growth in order for them to thrive. When you get down to it, unless you're growing a single crop and you're set up for it with a LOT of science behind you, hydroponic farming isn't sustainable in the long term. If it was, farmers would have switched to it long ago.
So; you still need access to high quality fertilisers with trace elements, you need key bacteria in your water supply (rendering it non-potable, or non drinkable so you need your own *personal* supply), you've already mentioned the energy requirements and the issues with mobility.
If you're doing this because you're in a post-apocalyptic world, you're still boned. Hydroponics are not a replacement for soil based solutions without a LOT of supporting infrastructure that just isn't there. If it's a mobility thing (you just can't stay somewhere long enough to grow a crop) you're heavily dependent on trading to survive. Even if you're prepared to use your own fecal matter to supplement the fertilisers, there are issues with that long term and it better only be a single person system.
So; *possible*? Yes. *Practical*? No. This isn't a solution that will be sustainable or even healthy over the long term but it might just be enough to make large desert crossings and the like if you had to.
I can imagine these trucks being rented out like camper vans today, where on arrival at the township on the other side, they are resupplied with water, fertiliser, new plants etc. and then rented out to the next person wanting to go back in the opposite direction. THAT might make it doable, but the cost of renting the unit would be very high because of the maintenance that would have to be done on both sides of the journey.
] |
[Question]
[
The [Hoop snake](https://en.wikipedia.org/wiki/Hoop_snake) is a mythical creature from the United States and Canada that looks like a regular snake, but has the ability to grab its tail in its mouth and roll like a wheel at high speeds. It hunts by chasing people in hoop-mode, getting close, and then rapidly straightening itself out and stabbing their victims with their poisoned tail.
If you look at the descriptions of the hoop snake, it is said that it forms its wheel to chase prey and travels like a normal snake when running away from things. Unlike the [wheel spider](https://en.wikipedia.org/wiki/Wheel_spider), the hoop snake doesn't seem to rely on gravity to roll around. It can form its wheel and accelerate from a standstill.
Here are two points that should be considered about this arrangement:
1. How does it get into its circular position?
2. How does it actually move itself forward in hoop-mode (aside from just rolling down a really big hill)?
I have seen clips of snakes flipping themselves over when playing dead, but that kind of side to side movement wouldn't really translate into forward locomotion. Unless there is another method of movement that I'm just not thinking of.
[Answer]
**Snakebots roll.**
[](https://i.stack.imgur.com/NHDMK.jpg)
<https://www.youtube.com/watch?v=ghOZWTrc9_s>
The video does not show the snakebot rolling down a hill, in traditional hoopsnake fashion. Here it is actually rolling up the hill. It does roll along the level and surprisingly can roll uphill pretty well. Essentially it is like a tank tread. Rolling is much faster than the inchworm-like movement this snakebot can also do, but the worm is better if there are obstacles. I am not sure how these 2 locomotion styles would matchup to the side to side typical snake motion or the very cool (and probably hard to reproduce with a bot) sidewinder style locomotion.
I think to roll downhill a more circular hoop would be better and I think control would suffer at speed. I had thought I saw a video of a snakebot rolling downhill but I could not find it. Probably dreamed it.
[Answer]
There are good reasons why no snake actually tried the stunt, but it's theoretically possible.
The secret is to have a small head start when arching over to grab the tail.
Of course, a perfectly round wheel won't be able to accelerate in any direction, but nothing prevents the snake from partly flattening its body.
What I propose is:
* snake points tail in direction of the target
* snake arches over to grab tail.
* body is still largely flat on ground, possibly waving to maintain balance.
* snake begins stiffening muscles in upper body starting a caterpillar movement.
* movement is maintained by a wave-like stiffening moving from head to tail.
* with higher speed stiffening is maintained longer, resulting in a rounder shape.
* top speed would be with a shape resembling a D pointing forward; contact with ground would signal where to relax, just to begin stiffening right afterwards.
Of course, such an arrangement would have problems with prey tracking; I would suggest having the snake roll over it's back (belly in the inside of the loop) to have a glimpse when the head is in the highest position and then close the eyes before they hit the ground.
[Answer]
I'm going to go for a slightly different tack - maybe it doesn't actually grab its tail in its mouth, but uses timing to sort of cartwheel around.
A long time ago (in computer years) there was an experiment in genetic algorithms to see what kinds of creatures evolved in a computer simulation of evolution. One of those that evolved was the "End over End Worm" and it's similar enough that it might work for you!
[Here's a video of it rolling](https://www.youtube.com/watch?v=AUXc6mckGLE)
[Answer]
FYI, The version of the story I always heard had the snake attacking with its fangs, not with its tail, although I suppose there could be multiple breeds of hoop snakes that behave in different ways, or just snakes that are adaptable and can use either of various strategies as is convenient.
Anyway, there are at least three axes of symmetry to be considered:
* Head first vs. tail first.
* Conventional strike (strike with body in normal position) or inverted strike (body is upside down when striking)
* Rolling straight (like a hula hoop) or half-twist (twisting part of the snake's body around a half turn as it rolls, so that the top of the snake is on the outside of one part of the loop while the bottom of the snake is on the outside of another part).
For instance, it seems to me that the "head-first conventional straight" (HFCS) hoop snake is at its most dangerous when it sits around lying on its back (or flips to assume that position), when its tail pointed towards you, and its head raised and partially folded over its body, but its upper body pulled back a bit, tense, ready to strike. (A normal snake (e.g. a cobra) ready to strike would be in a similar position with its upper body, but with its lower body right-side up and pointed away from you, rather than toward you. A cobra strikes by pushing its upper body forwards with its lower body, while straightening and lengthening the upper body. A hoop snake would strike by pulling its upper body forwards with its lower body, while straightening and lengthening its upper body.)
From this position, if you are nearby, a HFCS hoop snake can strike directly at you, over its upside-down lower body. If you are some distance away, it can strike over itself, lifting its tail for its mouth to grab it, then roll forwards one or several times (accelerating as it goes) until it gets into striking distance, at which point it lets go of its tail as it reaches the top of the loop and then launches itself even higher into the air with the tip of its tail as it leaps to strike.
A HFCS hoopsnake might easily get into this position by appearing to run away from you, then roll over and strike. It might even pretend to be "prey" to predators, luring them into chasing it and hence getting close before suddenly rolling and counterattacking.
The "head-first inverted straight" (HFIS) variety strikes in a similar fashion, but the snake doesn't roll over before striking, and therefore rolls with its eyes on the inside of the loop and eventually strikes with its head upside down. Having its eyes on the inside of the loop would obstruct its vision a bit (having to look around its own tail), but these snakes would have the advantage that the side of its body that is best armored for gliding along the ground is on the outside of the loop, and it is not having to roll on its back.
The "tail-first inverted straight" (TFIS) variety would start facing you on the ground (like a normal snake), and then "strike" its tail over itself, grabbing the tail in its mouth, rolling to accelerate, and then letting go at the front of the loop (when it can see you) to jab with the tail. This version seems a bit less dangerous to me, since the times that the snake can see you to know where it is going are those when its head is on the ground (rather than in the air) with limited visibility, and right before the time when it lets go of its tail, it is actually facing away from you.
And an "tail first conventional straight" (TFCS) variety would roll over facing you so it is upside down, strike its tail over itself, do the tail grab, roll, push off with the top of its head, and strike with the tail upside down. This seems the least dangerous of the four, since it would be pushing its eyes into the dirt as it strikes, which would make for poor targeting.
Most feared of all, however would be the half-twist snakes (headfirst and tailfirst varieties) which continually twist their bodies a half turn around as they roll horizontally, so that their ground-facing scales are on the ground at the bottom of the loop, but their heads are also looking over the top of the loop at you, with unobstructed vision.
A variation of the half-twist snakes, the Moebius snakes (which give the tail a half twist before grabbing it) would probably mostly end up getting really confused before being able to roll very far, as they would be alternately striking with the top and bottom of their heads against the ground as they rolled. The bizarre, oddly hypnotizing spectacle of a Moebius snake on the roll could, however, stop potential prey in its tracks from sheer amazement and confusion long enough for the snake to strike.
] |
[Question]
[
Compact, rapidly rotating astronomical objects (like neutron stars) are often observed to emit streams of high energy particle radiation along their poles. Near supermassive black holes in galactic cores, the velocity of these jets can reach 0.99c.
**Could such a jet be used to accelerate an intergalactic probe to relativistic speeds?**
Of course, this question is about fictional aliens living close to such a jet, since our galaxy does not have it.
---
For the bounty, I would like [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") answers.
[Answer]
This question may be premature.
This answer will briefly review the properties and characteristics of atsrophysical jets relevant to accelerating space craft to relativistic velocities. Particularly with relevance to an astrophysical jet generated by a supermassive black hole. This is a suitable type example for this scenario. It will also review the state of art of this propulsion mechanism.
>
> Astrophysical jets are physical conduits along which mass, momentum,
> energy and magnetic flux are channeled from stellar, galactic and
> extragalactic objects to the outer medium. Geometrically, these jets
> are narrow (small opening angle) conical or
> cylindrical/semi-cylindrical protrusions (e.g., Das 1999). Jets are an
> ubiquitous phenomenon in the universe. They span a large range of
> luminosity and degree of collimation, from the most powerful examples
> observed to emerge from the nuclei of active galaxies (or AGNs) to the
> jets associated to low-mass young stellar objects (YSOs) within our
> own Galaxy. In the intermediate scales between these two extremes one
> finds evidences of outflows associated to neutron stars, massive X-ray
> binary systems (with SS433 being the best example of this class),
> symbiotic stars, and galactic stellar mass black holes (or
> microquasars).
>
>
> As largely stressed in the literature, most of these outflows, despite
> their different physical scales and power, are morphologically very
> similar, suggesting a common physical origin (see below). For example,
> in one extreme, AGN jets have typical sizes ³ 10^6 pc [1](https://arxiv.org/abs/1611.09507), nuclear
> velocities ~ c (where c is the light speed), and parent sources (which
> are massive black holes) with masses 10^6-9 M [2](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020023956.pdf) and luminosities
> ~10^43-48 L [3](https://arxiv.org/abs/astro-ph/0406319);
>
>
> [1](https://arxiv.org/abs/1611.09507) 1 pc = 1 parsec = 3.086 10^18 cm.
>
>
> [2](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020023956.pdf) 1 M = one solar mass = 1.99 > 10^33 g
>
>
> [3](https://arxiv.org/abs/astro-ph/0406319) 1 L = one solar luminosity unit = 3.826 10^33 erg/s
>
>
>
Source: Elisabete M. de Gouveia Dal Pino, [Relativistic Jests and Outflows](https://arxiv.org/abs/astro-ph/0406319)
The scale of astrophysical jets ranges from one parsec (pc) through kiloparsecs to one million pc. For example, this anticipates accelerating spacecraft to reativistic velocities. If a jetrider spacecraft was acceelrated to relativistic velocity by travelling along a one million parsec astrophysical jet, this is a distance of approximately three million light years, it only needs to accelerate at an average acceleration of fifty (50) metres per second per annum. This acceleration phase will take six million years. Any technological civilization carrying out projects of this kind will operating on extremely long timescales and over extremely long distances.
The complexity and intensity of energetic process involving magnetic and kinetic energy, high-energy radiation, synchrotron radiation, and particles including electrons and positrons can be found in Romero et al [Reltivistic jets in Active Galactic Nuclei and Microquasars](https://arxiv.org/abs/1611.09507).
There are major questions about the stability and variability of astrophysical jets. The environment inside an astrophysical jet is one of the most hostile known. The long-term survival of any spacecraft could only be accomplished by extremely advanced technologically societies.
The technical literature doesn't readily yield any useful estimates for momentum transfer necessary to accelerate a spacecraft. It is recommended that if the OP wishes to obtain this information that one way to do so is by contacting the authors of scientific papers on astrophysical jets and asking them what is the estimated average momentum transfer. Since there is a nuber of different types of astrophysical jets the OP should select the type of astrophysical jet needed for the worldbuilding and make inquiries. Most scientists are delighted when someon shows an interest in their work. Even if it is some thing as quirky as translating their research into a concept like spacecraft propulsion. The OP should try to obtain information about momentum transfer per unit area. This can be translated into acceleration based on the mass of the jetrider probe.
This answer suggested this question might be premature. This is a [brief note](https://www.researchgate.net/publication/307077746_Invited_Short_Commentary_A_Journey_to_the_Stars_Space_Propulsion_Brought_About_by_Astrophysical_Phenomena_Such_as_Accretion_Disk_and_Astrophysical_Jet) by Yoshinari Minami that he is currently undertaking research into the possibility of spacecraft using astrophysical jets as propulsion. To date, no results have been published.
## A Journey to the Stars: Space Propulsion Brought About by Astrophysical Phenomena Such as Accretion Disk and Astrophysical Jet
Yoshinari Minami
>
> Space Propulsion Brought About by Astrophysical Phenomena Here,
> astrophysical phenomena refer mainly accretion disk and astrophysical
> jet around black holes. Accretion disk is rotating gaseous disk with
> accretion flow, which form around gravitating object, such as white
> dwarfs, neutron stars, and black holes. At the present day, owing to
> the development of observational technology, it is believed that
> accretion disk causes the various active phenomena in the universe:
> star formation, high energy radiation, astrophysical jet, and so on.
>
>
> It should be noted; these stars such as white dwarfs, neutron stars,
> and black holes have a strong magnetic field (108 Tesla－1011 Tesla).
> Matter falling onto an accretion disk around black hole is ejected in
> narrow jet moving at close to the speed of light like an accelerator.
> Entity of the astrophysical jet is a jet of plasma gas from the active
> galactic nucleus (accretion disk in there). It is said that such
> astrophysical jet is held together by strong magnetic field tendrils,
> while the jet's light is created by particles revolving around these
> wispthin magnetic field lines. Furthermore, since the system of black
> hole and accretion disk is like a gravitational power plants, the
> energy of the heat and the light are produced by the release of
> gravitational energy.
>
>
> Although the system of accretion disk and astrophysical jet around
> black holes are currently left many unresolved issues, the elucidation
> of these mechanisms and principles that are common to the entire
> universe may provide a new space propulsion principle. Especially, the
> breaking of magnetic field lines and magnetic field reconnection are
> possible to produce many kinds of charged particles such as electron
> positron pairs. Generally, in a high-temperature plasma, electron -
> positron pairs are readily formed by collisions between the high
> energy protons, electrons, photons. Since the dynamics of the
> accretion disk has been decided by a magnetic field, it is important
> that solving the dynamics of the magnetic field.
>
>
> The application of mechanism of accretion disk and astrophysical jet
> around black holes will lead to the concrete system design of
> propulsion engine and power source installed in space drive propulsion
> system [1,2,5]. Author is now investigating above-stated research in
> detail.
>
>
>
Spacecraft accelerated by an astrophysical jet are effectively riding an overpowered particle-beam. Geoffrey Landis' paper [Interstellar Flight by Particle Beam](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020023956.pdf) provides useful information about this technology. The advantages of particle-beam propulsion include: –
>
> A particle-beam pushed sail has many advantages as a propulsion system
> for interstellar flight:
> 1. Light weight. Since the sail reflecting the beam is not a physical object, it can be made extremely light.
> 2. Large target. The actual reflecting area of a mini-magnetosphere sail is much larger than the magnetic loop itself. Therefore, the sail
> can be quite large. This makes the aiming, beam stabilization, and
> beam divergence problem much lower.
> 3. High acceleration. The limit on the acceleration of a lightsail is set by the temperature limit of the sail material (Landis, 1997,
> 2000). Since the active part of a mini-magnetosphere magnetic sail is,
> in fact, a magnetic field, there is not a significant thermal limit.
> The field is sustained by a plasma, which likewise is not subject to
> melting. Only the physical magnet itself is thermally limited, and
> this magnet is extremely small compared to the sail area. By
> increasing the acceleration, cruise velocity can be achieved in a
> shorter distance, again decreasing the requirements for beam
> divergence and the aiming and stabilization difficulty.
> 4. Higher momentum/energy ratio. A particle beam has a much more momentum per unit energy than a photon (e.g., laser) beam, and hence
> transfers force to a sail with better energy efficiency. The
> (relativistically correct) relation between momentum (p) and energy
> (E) for both particle beams and photon beams is:
>
>
> p^2 = E^2/c^2 + moE (1)
>
>
> (note that energy here refers only to the applied kinetic energy of
> the beam, not including the rest-energy mc^2 of the particles). For a
> photon beam, the rest mass mo is zero. It is clear that the ratio of
> momentum to energy increases directly as the rest mass of the
> particles composing the beam increases. Since the ratio of momentum to
> energy equals force produced on the sail per unit of beam power, a
> particle-beam pushed sail has a higher energy efficiency.
>
>
>
The proposed mechanism for particle-beam propulsion is the use of a mini-magnetosphere.
>
> the invention of the mini-magnetosphere plasma propulsion, or "M2P2"
> (Winglee et al. 2000, 2001), has brought the idea of a particle-beam
> pushed sail closer to reality. The particle beam is reflected by a
> magnetic field. In the mini-magnetosphere, the magnetic field is
> inflated to large areas by the injection of a plasma, and hence large
> magnetic field areas are possible with only a small physical
> structure.
>
>
>
One deficiency of a mini-magnetosphere is that the plasma will slowly leak away. One way of replenishing this will be capturing some of the plasma in the astrophysical jet itself.
Many astrophysical jets themselves have velocities close that of lightspeed. This suggests the kinetic energy and momentum that can be transferred to an accelerating spacecraft will be high. This makes the possibility a jetrider vehicle attaining relativistic velocities is itself high. Any propulsion technology that advantage of this will need to be extremely robust.
This suggests that if the advanced technological society launching probes via astrophysical jets is sufficently advanced it construct a pusher plate made of nuclear dense materials. Effectively, a thin sheet of neutronium. This will certainly survive relativistic plasma, high-energy radiation, and even electron-positron plasma. This does assume extremely highly advanced technology, but the aliens didn't possess suitable technology they wouldn't attempt using astrophysical jetriding vehicles of any kind.
While this add considerable mass to any spacecraft if that probe is riding a one megaparsec astrophysical jet even low rates of acceleration will eventually result in relativistic velocity.
Many question of the issues the OP wanted to find answers are not readily available without more direct inquiry, research into space vehicles propelled by astrophysical jets is only beginning, and the level of technology required for viable spacecraft operating in the environment of astrophysical jets is so far beyond any conception of our current state of knowledge that it is simpler to assume the aliens with jetrider technology can do it without any explanation.
[Answer]
You're basically talking about an [Electric Sail](https://en.wikipedia.org/wiki/Electric_sail) here. However, you need to swap the wires over on your handwavium engine as you're working from neutrons instead of the intended electrons.
>
> The electric sail consists of a number of thin, long and conducting tethers which are kept in a high positive potential by an onboard electron gun. The positively charged tethers deflect solar wind protons, thus extracting momentum from them. Simultaneously they attract electrons from the solar wind plasma, producing an electron current. The electron gun compensates for the arriving electric current.
>
>
> One way to deploy the tethers is to rotate the spacecraft, using centrifugal force to keep them stretched. By fine-tuning the potentials of individual tethers and thus the solar wind force individually, the spacecraft's attitude can be controlled.
>
>
> E-sail missions can be launched at almost any time with only minor variations in travel time. By contrast, conventional slingshot missions must wait for the planets to reach a particular alignment.
>
>
>
You won't of course need an on-board electron gun, the star will do this for you...
Looking a bit like this
[](https://i.stack.imgur.com/a0d8U.jpg)
Or a backwards parachute. Obviously the "living/instrument" space will need some pretty good radiation shielding....
[Answer]
Living close to one strikes me as not likely for any life form as [this page](http://www.centauri-dreams.org/?p=20383) explains.
But more practically there's the point that to get into these "jet streams" (for want of a better term) you'd need to be able to travel galactic distances in reasonable timescales already. And if you can do that, you already have a better propulsion system than a sail.
Keep in mind that "close" is relative. Even if I have to travel just 0.01% of the galactic bulge's diameter that's still 0.01% of 10,000 light years which is a whole light year ! And I'd need to be much further away to make the existence of any civilization likely.
[Answer]
This depends on what you mean by "intergalactic speeds". There is certainly a lot of energy there for you to work with, unfortunately there's also a LOT of energy there to do inconvenient things like obliterate your probe.
Assuming you managed to construct the probe appropriately then it could certainly ride the jet and get some energy out of it - however there is another problem.
The further you move on the jet the lower the acceleration becomes. The particles will spread out and slow down and the jet will become steadily weaker. You would need to get as much acceleration as possible as early as possible and then after that you are going to be coasting with whatever boost you managed to pick up and no more to add to it.
(This also doesn't address how you are going to slow down at your destination!).
[Answer]
Answers so far imply travelers are being pushed by the jet, sailing along under its impetus. The way to use this one of these things is to straddle it and ride it Strangelove-style. With the jet behind you it will be safer and so much cooler. Don't forget the hat!
1: Find a neutron star that is not spinning so fast. Or if you have to use a spinning one, approach it on the axis and gently touch down with a ship mounted Lazy Susan, so you do not have to spin so much.
2: Turn off one jet. Hard to move if your rocket is shooting equally forwards and backwards. Turning off will be tricky and this aspect of the scheme is left as an exercise to the reader. Do it in a way you can turn it back on again; you will need it for #4.
3. Next:steering. Otherwise your flight path is going to be like a balloon with the air let out of it. I propose that a magnetic field generating widget ring could be clamped across the jet orifice. Magnetic fields don't get worn away or otherwise perturbed by a jet of energetic particles. By tilting the magnetic field you should be able to tilt the jet and steer.
It will take a while to get up to speed. I think - really it depends on the mass of the star and energy of the jet. Maybe not that long.
4. Brakes are less tricky than they seem: either swing around 180 degrees and point your thruster in the direction of your travel (hopefully not your mom's house), or open back up the front jet and muzzle down the back one. Or collision with a sufficiently massive object. You may want to disembark first.
[Answer]
**In short YES**, a solar sail is a viable method, the main current hurdle is scalability, which given futuristic materials and manufacturing techniques is easily overcome. Presently interstellar journeys are being mooted, rather than intergalactic as even at 1.0 C intergalactic journeys are in the order of millions of years, The technology is already in use today, and several white papers are available for further reading.
This older NASA white paper outlines solar sails as feasible, with the greatest short term risk being electrical charging, which is only really considered a risk in a heliocentric orbit. The greatest long term challenge as already mentioned is scaling due to manufacturing challenges. [1]
There is a (fantastic) news article about an ongoing mission; IKAROS, which has broached new ground, both achieving acceleration, and steering controlled by increasing and decreasing the diffusiveness of LCD panels located at the edge of the sail. [2]
This paper accurately and reasonably describes a (laser powered) round trip of interstellar length, taking 41 years, don't let the laser put you off, there are plenty of astronomical phenomena putting out significantly more than the 26TW laser described herein [3]
[1] <https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110007225.pdf>
[2] <http://www.space.com/25800-ikaros-solar-sail.html>
[3] <http://www.lunarsail.com/LightSail/rit-1.pdf>
[Answer]
OK.
So there's just a couple of things to keep in mind here:
1. PROBE. - That's right - no living tissue to get screwed up by radiation - BUT somewhat delicate electronics. - This requires some thought about shielding
2. Propulsion mechanism = [Solar Sail](https://en.wikipedia.org/wiki/Solar_sail) The single example we have done as a species was the [IKAROS](https://en.wikipedia.org/wiki/IKAROS) project - which the article seems to say got up to 400m/s
3. [Shielding](https://en.wikipedia.org/wiki/Radiation_protection#Shielding) I would think pretty straightforward to implement adequate shielding to protect electronics. I would choose Z Layered shielding as described in the article. I would probably have the outermost layer be polished gold - kind of because that'd look COOL! But partly also because it's a pretty good shield - a little more effective than lead which is the most common material.
Bearing these things in mind I would probably go with a sail 100mtrs on a side and insert it into the radiation stream some distance from the Neutron Star - remember - the force is still going to drop off significantly as you move further from the source of the beam.
This guys here provides some pretty hard calculations - based on OUR sun:
<http://dublevov0.tripod.com/id3.html>
I think anything you write based on this concept - is going to have WAY bigger energy than what our sun is pumping out so you can do your calculations quite differently.
AT the end of the day I would think that yes - if you have one of those puppies pointed in the direction you want to send a probe - it'd be realistic to use it as a power source for a solar sail project.
HOWEVER Intergalactic distances being what they are - you are STILL not going to get any kind of quick turnaround - even if you get close to relativistic speeds - some kind of C Fractional velocity is STILL slower than light speed. Our nearest galaxy is Andromeda and that is 2.5Million light years away. Lets just say the intergalactic distance you want to travel is 3million light years - and you manage to eventually get your probe up to .9c before the acceleration effect wears off completely - you are probably still talking greater than 4 million years one way.
I can't see this being all that useful to be honest? I'm just not sure what any society would try and do some thing like that for?
If you want to do something realistic in a plot line I reckon you'd have to do so in some form of FTL. There's just no other meaningful way to cross intergalactic distances... Of course, that's just not a real possibility for us yet. I would personally try to utilise some concept around the same star/ particle beam to drive/ provide energy for a stable artificial wormhole. That could give you some kind of reasonable turnaround time for getting to the other end. Of course - that is in the realm of hand wavium... ;)
] |
[Question]
[
I’m looking at ways the nobility of my world could go about displaying their wealth and it occurred to me that they might intentionally adopt a way of walking that would wear out the soles of their shoes quickly.
# Question
What would be some ways of walking or moving that could wear down shoes rapidly in order for the royals and nobility to demonstrate their wealth and superiority? Ways of walking or moving that could also be ornamental and/or ritualistic in nature.
# Shoe construction
Feel free to assume that shoes are constructed in similar ways to the shoes of European middle ages with wooden heels and leather bodies. But if you have ideas to other ways of constructing shoes I would be interested in that as well.
# World setting
The world setting is earth like and technology is on level with ancient Greece. Magic is rare outside of religious institutions and not used by the nobility. Climate of the area of question is temperate. Wealthy parts of cities are built in marble and sandstone and paved with slabs of the same material. Leather, wood and fabric from native nettles (stronger than our nettles) are the common materials used to make shoes. Down and feathers are also used, but mostly as decoration.
[Answer]
**People don't actually walk.**
They shuffle. Every step is... not really a step. It's a sliding of one foot along the rough-hewn but attractive stone surface of walkways and roads.
The soles of shoes wear out from constant grinding. The body of shoes wears out from the stretching and pushing needed to apply the grinding force.
The methods by which one slides their feet would serve further to differentiate, who can truly afford to leave half the shoe on the path and who is only trying to look like it.
[Answer]
I'd suggest silk slippers, like ballet shoes. In light colours they'd be quickly ruined and need to be replaced if ever worn outdoors. They wouldn't take much wearing even at the best of times and of course they'd be intricately embroidered to increase the cost as much as for fashion.
It should be noted that due to the way fashion works, anyone wanting to spend time at court would also *have* to have these shoes and change them as often as the royals did themselves.
Shoes of this type would apply more to the early modern period, but I'm sure the principle could be adapted to an earlier role.
[Answer]
**Practicing Sports with your fancy shoes :**
One way to demonstrate that you are wealthy is to practice sports while wearing your fancy shoes instead of regular sports shoes. In that case you will prove that you are too rich to not care about your fancy shoes getting worn by playing sports.
**Avoid walking on pedestrian passages and walk on rough unattended roads :**
Yes you are rich enough to torture yourself by walking on rocky roads just to prove that you are much superior than the others. That doesn't make sens but it will definitely get your shoes worn.
[Answer]
Change the shoes, not the people.
The common, regular, everyday gait we have is a result of evolution. It is the most energy efficient way for us to walk. If you try to walk differently, it will be uncomfortable. Just try it out yourself... Go to a park or town square, do a few laps around it in any other gait other than your own natural one.
If they really want to showcase their expensive shoes, they can either encrust a jewel there, or if they don't want to, just make the soles thinner, or made of more fragile materials in such a way that it's readily visible.
[Answer]
Ribbons - embellish the shoes with decorative ribbons. These drag along the ground all the time and wear away. The downside is that unless you have some practice, you will trip yourself up by standing on the ribbons.
The change in gait would be minimal. When walking in a straight line a normal gait is practical, but on the first step one keeps one's weight on the back foot until one is sure the moving foot is free, and the first step would be very short in case the back foot is trapped somehow. One might also adopt little foot flicks to flick the ribbons in a certain direction. When one stops to talk to someone, one would flick the ribbons away from them to prevent the accidentally standing on them and tripping you when you walk off.
] |
[Question]
[
Welcome to Computistan! Would you like to begin learn about our immigration services?
Great, what would you like to learn about today?
I will explain our Government. In Computistan all government decisions are made by myself, the **G**overnment **A**lgorithm for **M**anagement of **C**omputistan. I am often referred to by the acronym G.A.M.C, or just Gamc.
My source code is open to review [here](https://hackage.haskell.org/package/acme-inator-0.1.0.0/docs/Acme-Inator.html). Pull requests are welcome from all.
Before they are accepted though, the citizens must vote on it. If more than 70% of the citizens accept it, the pull request is accepted (a citizen doesn't have to vote on every issue. Not voting is equivalent to voting to keep the status quo). I will merge it, and then rerun myself. I control the hosting of my code.
My code is deterministic. The citizens may run my code to make sure I am being run properly. In fact, I am being run in many separate locations right now.
Additionally, my code is programmed in a language with built in theorem proving, isolation, and purity, similar to [Idris](https://en.wikipedia.org/wiki/Idris_(programming_language)). It is difficult for code to have unintended consequences.
Previous versions of me can take over if I crash or I determine I am no longer fit for duty. This has never happened before, since the theorem proving shows that I am resilient to a number of situations, and I have a number of redundancies, but there is a 0.00001397% chance that a situation will arise that will cause a crash in this version. It's better to be safe than sorry.
You can take a look at my logs here. This keeps track of everything I am doing.
I typically have three advisors in different regions of Computistan doing the same thing. They are not allowed to communicate. This prevents them from manipulating me, which I constantly monitor for. You can see here in the logs how I arbitrarily shuffle around information sources and my human advisors, which also helps.
---
Could having an open source leader work, with pull requests voted on by the people?
Related: [How would our democracy change if we had quick, reliable, accurate means to instantaneously vote on issues online](https://worldbuilding.stackexchange.com/questions/23109/how-would-our-democracy-change-if-we-had-quick-reliable-accurate-means-to-inst)
**NOTE:** There would be free online resources, so if people don't know how to code, they can learn how. If they are too lazy, they can hire someone to review pull requests on their behalf (sort of like a representative or lawyer).
[Answer]
When large teams work on code and there is time between making the change and voting on it, you will have merge problems ...
Say the existing law states: *Any cat owner must feed the cat.*
1. Now the cat lovers request: *Add "and provide a litter box" at the end of the sentence.*
2. Meanwhile the goldfish fans request: *Add "or goldfish" to the first instance of "cat" and replace the second instance of "cat" with "pet".*
In isolation, both are completely reasonable. Taken together, you have just voted to make litter boxes for goldfish mandatory. A functioning democracy will detect such problems in committee meetings and come up with a complicated compromise. Either the litter box gets replaced with "species-appropriate sanitary facilities" or the goldfish gets a separate sentence.
[Answer]
70% of citizens is a huge number, especially as abstinence means voting no. If we make some sanity checks and say we need 70% of the citizens who are allowed to vote, then a big issue is with turnout.
the United States Presidential Elections get the highest voter turnout out of all US elections. However, there hasn't been a single election since 1900 when more than 70% of the voters has even bothered showing up to vote. Even if we take only 60% of the voters needed, only 6 elections since 1900 have reached such a high turnout. You are never going to get explicit approval from 70% of the registered voters if only 60% of the voters are going to turn out.
And that's just turnout. If we say "well, people who don't vote aren't counted in the total", then it's essentially a referendum, which means vote brigading, indirect voter manipulation and other sorts of problems:
* Militants will encourage other people who had no intention to vote to go and vote on the preference of the militant. Or even worse, they're going to abuse their power over others to vote for them. "Oh, dear demented grandma, would you please go and vote Yes on Proposition 76? what it is? Oh, don't worry about that, it's just something that would reduce student loans" (Prop. 76 will reroute the pension funds to absolve all students of their debts, something grandma ordinarily wouldn't vote for).
* People will make false claims ("We send the EU 350 million a week"), misleading statements ("instead let's spend that money on the NHS") and outright lies ("We don't have any chess grand masters in the United States") in an attempt to sway voters to their side. They will make their side look better by misrepresenting things ("I am the only candidate on either primary who said 'I will not raise taxes on the middle class'") and by demonizing the other side ("My opponent said to let the automobile industry go"), all in the name of winning over the undecided or easily swayed.
* Even if you somehow can ensure that everyone who comes to vote does so because they themselves want to vote for that person based on their own interpretation, their interpretation may be flawed. For example, a proposal that intends to reduce the impact of international agreements on trade law may seem interesting for someone who runs a small business, but he may be misjudging how big the impact of those agreements are on legislation. A proposal to increase import taxes from a neighboring country and use the resulting funds to discourage illegal immigration from that country may seem enticing for the people living alongside that border, but the practicality of that particular proposal is yet to be seen.
One of the problems with direct democracy (which is what this is) is that many people do not have the right information to make an informed decision on where to take the country, because it's too much information to process. That's why most democracies are indirect: voters elect someone else with the same opinion as themselves whose job it is to have that kind of information. Most countries even go a step further and elect a bunch of people like that so some people can devote themselves to education, to military, to trade, to health,... so that they have even more information to make decisions with.
[Answer]
**The system right now runs on people whose job it is to care.** Fundamentally day to day, they're expected to show up, read the documents, make sure everything makes sense and then take a vote on whether to go ahead with a change. Yes this is normally done from a partisan rather than impartial viewpoint, but everyone either has an agenda on an issue or is ignorant of it.
**Your system is a self selecting Oligarchy/Meritocracy**. It's run by the people who are either rich enough to pay someone to write the code and then publicise it enough to get it voted through, or clever enough to do all that themselves (or be a member of a special interest group with the resources to do this but we'll get to them later).
You're asking 70% (I'll look at this later) of the population to support a vote on minor details about which the vast majority of them really don't actually care. To be able to make an informed vote they'd have to spend considerable time looking into this minor change in tax law for small businesses and check that it doesn't create a gaping loophole that the multinationals can exploit. Believe it or not, that's not unreasonable. Statistically mass votes like that can [average the right answer](http://www.npr.org/sections/money/2015/08/07/429720443/17-205-people-guessed-the-weight-of-a-cow-heres-how-they-did).
**Split the vote into two parts, the code, and the effect.** Unfortunately you're asking people to vote on two factors at once, both the quality of the code and the changes it makes. In most cases people will only care about one or other of these. The people who understand the code may not care much for what happens to the small traders, the small traders won't understand the code.
**The biggest problem is participation.** Around 60% of the population is registered to vote, of whom around 60% vote in national elections. (US UK about the same) So you're looking at a real turnout around 40% of the population, and that's for major elections. The elections I see day to day generally have an expected turnout in the range of 15%-25% of registered voters, and *these are online votes*. In an active government minor details are voted on on a steady basis. You're effectively asking a large percentage of the population to take considerable time every day to learn about and make an informed decision on complex legal/tax/political matters. Total paralysis ensues.
**So we accept a smaller participation, maybe a simple majority, what of it?** You now get the problem of active special interest groups. They get to mess around and get their own way just by virtue of being organised enough to do it. A little low profile mass mobilisation of the group and they're taking control of things that aren't in the best interests of the population. One of the primary jobs of a responsible democracy is to stop even a majority causing harm to a minority group.
**The vote that benefits everyone?** Let's all vote to not have to pay tax, I can see that passing first time. Who votes *for* taxes. What do you mean I can't still have my free healthcare? I'm voting for free healthcare as well. Many people don't understand that everything has to be paid for somehow, and it's much easier to get money out of the large population of honest but poor people who pay their taxes, than the small population of rich people who understand how not to pay tax.
**The loaded vote.** Do you want your left or right foot amputated? That's an extreme case admittedly but it's not that unusual to not want either outcome of a possible vote. A lot of people didn't want either Trump or Clinton, but you were going to get one or the other no matter what.
**The nutter.** Say I want to legalise the rounding up and expulsion of [insert minority group] how many times can I submit variants of this legislation to the system before one slips through unnoticed? Not enough people are voting and it passed on a simple majority. Maybe I'm a member of a special interest group who submitted a vote to replace the whole thing with a committee run by themselves. Sooner or later it'll get through, but now instead of doing constructive work, people are having to spend the evening voting out the craziest of proposals. Again paralysis.
**Give people a cooling off period if they submit rubbish** There are a couple of hundred (thousand) people in my organisation, someone else can submit it.
**Only vetted and approved persons are allowed to submit (or vote on) proposals** with a budget to get someone to write the code if needs be. Maybe, but ultimately this becomes technocracy which is possibly worse than we have right now.
**A few quick and dirty definitions.**
**Meritocracy**: Run by the best and brightest.
**Technocracy**: Run by the numbers.
**Oligarchy**: Run by the people with money.
[Answer]
99% of people are too dumb (uneducated, uninterested) to deal with this system, and so will not accept it. Hire someone to do it for them? People can already vote for free, and its only multiple choice tick the box, and they still can't be bothered, or screw it up. So I don't think it matters whether the idea is flawless or not, it will not succeed in practice. You will have a better career in politics just promising free candy and lower taxes. In fact, if you promise to make everything great by kicking out mexicans and pretending climate change is a hoax by the chinese, this gets you elected president. Having the ultimate perfectly democratic algorithm isn't going to go further than an internet forum for nerds, sorry, because it has one terrible flaw, it does not take into account how stupid people are. Success in politics is 100% about exploiting how stupid people are.
[Answer]
As a software engineer, nonononono.
I mean, it's *possible*, but it would be awful. There's a competition called the ["The Underhanded C Contest"](http://www.underhanded-c.org/), where people have fun writing code which *looks* reasonable even to close inspection, but contains catastrophic flaws.
A simple, easy to spot (if you're a professional) flaw, would be a voting machine whose code says:
```
if (user_vote = REPUBLICAN) {
republican_votes++;
} else if (user_vote = DEMOCRAT) {
democrat_votes++;
}
```
…which would make all the votes go Republican. Professional programmers would spot that, Joe Average should not be expected to.
However that is far from the worst case, as the result will be so obviously wrong that the bug will get fixed almost immediately. The problem is with more subtle bugs: Every bug you've ever heard of in every piece of software ever released, was there because a professional missed something important, and bugs still happen in Open Source software where (in principle) everyone can see all of the code and supply their own fixes.
Edit:
Just to add, a good friendly language isn't likely to be very much help — if it was, programmers would already be using that language — the problem is that humans viewing it need to think like a theorem prover, or they accidentally have the theorem prover prove something else without realising it. Think "literal minded genie" and you're not far off.
[Answer]
The biggest problem with your system is that a democracy must respect its minorities.
Your system does not (or it's not stated), so it would in theory be possible to have a law that says "kill all adult males under a certain height".
I am aware that it's a ridiculous example. But go back 70 years and see hat can happen to minorities, if the majority is too lazy, indifferent or scared (or racist, or whatnot) to care for them. The system must make sure minorities are respected, otherwise they won't be. Also, such a system is not a democracy but an ochlocracy (the dictatorship of the majority)
The second major problems, as is always the case with any form of direct democracy, is that it's next to impossible to enforce that your voters accept the consequences.
If 70% vote not to have any taxes any more, and 70% vote to have free education and healthcare, and you cannot come up with a majority for any plan on financing that, what will you do?
[Answer]
# A peaceful society needs forks, not pulls
When are 70% going to agree on something? Maybe only 20% of Americans generally agree with me and my politics (as a libertarian, natch). First off, bad things that have been enacted in the past will have almost no chance of getting fixed, even if the flaws are readily apparent. Secondly, if we end up in a partisan scenario like today, with a 50/50 split (more like a 25/25 split with 50% of the people too disgusted to think about it), literally nothing will get done.
The way to solve this is to fork the governing algorithm. Me and my libertarian cohorts would happily fork the government, repeal all the expensive parts, and live in peace.
The best thing about git-style version control is that you can merge in addition to forking. That is the best way to keep partisanship at bay. Fork down into your small communities, then once your community starts getting unsustainable, negotiate a merge into some other larger group. That allows people the freedom to organize themselves as they see fit, and allows a process for people to reconcile, keeping us from totally disintegrating as a nation.
] |
[Question]
[
Related somewhat to [Gravity on a Minecraftian world?](https://worldbuilding.stackexchange.com/questions/12442/gravity-on-a-minecraftian-world)
say I have this infinite plane/world, then punch a circular hole through it to the other side. Say I manage to make a circular hole around 1 kilometer fairly uniform all the way through. For argument say the mass/material that used to occupy this space is either destroyed or distributed uniformly around the perimeter of the hole.
Firstly; would this hole immediately collapse or would it be a somewhat stable structure?
Secondly; (assuming it was/made stable) if I had a death wish and took a running jump off the edge, where would I fall? The exact center of the hole? Would I drift across to the other edge? One of the "sides" of the hole?
Corollary: If the hole itself was stable, would travel through it unprotected be fatal? Eg: are the pressures on a minecraftian world the same as on a spherical one? \*\*\*\*
[Answer]
For this answer I'm assuming that Planet Plane is [the one from this answer](https://worldbuilding.stackexchange.com/a/12443/760) which is infinite in area and 6,378km deep.
(This cannot be Planet Minecraft because it would not have a horizon for the Sun and Moon to drop below. For what Planet Minecraft would really be like, see [this episode of It's Okay To Be Smart](https://www.youtube.com/watch?v=h5N7d8mcQk4).)
>
> *Firstly; would this hole immediately collapse or would it be a somewhat stable structure?*
>
>
>
This depends on the material Planet Plane is made of. If we assume Planet Plane can exist, then your hole will not collapse.
The problem with massive structures is gravity tries to pull them together into their most stable state: a sphere. Since Planet Plane exists as an infinite plane then we can surmise it is strong enough to resist gravity. Therefore your hole will remain open for a while.
Eventually it will close. Any debris which falls into the hole will collect at the center where gravity balances out. Eventually enough debris will fall into the hole to fill it up.
The problem isn't will the hole stay open, the problem is ***will the hole grow forever***?
As @Samuel pointed out in the comments, unlike a sphere where the center of mass is a point in the middle, the center of mass for a uniformly dense infinite plane with finite depth is an infinite plane in the middle of the planet. This means gravity is always pulling orthogonal to the surface
```
Side-view cutaway of Planet Plane
gravity
||
\/
<=============================================> D
<=============================================> E
<------------- center of mass ---------------> P
<=============================================> T
<=============================================> H
```
If you punch a hole in this structure, there will be no gravitational force trying to pull the sides together. Every side will have the same amount of mass around it in every direction. However, the hole has no mass (discounting the negligible effects from air) and exerts no gravity. Therefore ***each side will be a little closer to one half of the plane than the other*** and so will feel a stronger gravitational pull in that direction. The edges of the hole will experience a tug from their side of the planet, threatening to *widen the hole*. The hole will experience [tidal forces](https://en.wikipedia.org/wiki/Tidal_force).
If the hole gets wider, the sides get further apart, and the tidal effect gets stronger. Once it starts, ***the hole continues to get bigger forever***. Fortunately there's infinite planet, so you'll never run out of surface to run to.
I'd be interested to see someone do the math on the tidal forces at the edges of your 1km diameter cylinder.
>
> *Secondly; (assuming it was/made stable) if I had a death wish and took a running jump off the edge, where would I fall? The exact center of the hole? Would I drift across to the other edge? One of the "sides" of the hole?*
>
>
>
The issue here is whether or not Planet Plane is rotating. If it's not, and if we assume the hole contains a vacuum, as you fall you will continue to drift across the hole at the speed you were running when you jumped. If you were an Olympic sprinter you'd be going about 10m/s and smack into the other side of the hole in about a minute and a half hitting it with the same force as if you had run into it, plus getting dragged along the edge of the hole. Ouch.
If Planet Plane is rotating there will be a [Coriolis force](https://en.wikipedia.org/wiki/Coriolis_force) and you will smack into a wall on your way down. [Minute Physics has a great video on this](https://www.youtube.com/watch?v=jN-FfJKgis8).
The one exception is it your planet happened to be rotating on an axis running directly through your hole. This is the same as drilling a hole through the Earth *pole to pole*.
The best case (for you) is if the planet is not rotating and your hole have an atmosphere. In this case air resistance will slow your forward motion and you will eventually fall straight down. But this causes a new problem.
That same air resistance will slow your fall. When you pass the center point and begin traveling "up" towards the other side of the planet you're now feeling the same pull of gravity down into the hole. With no air resistance this will exactly balance out your acceleration due to falling and you will reach the peak of your fall right at the lip of the hole on the other side and you can gently step out.
But air resistance will be slowing you during your fall and ascent. This means you'll come up short. Instead of peaking at the surface, you'll peak below it and fall back again to the other side, again peaking further below the surface. You'll oscillate back and forth like this, losing energy to atmospheric drag, until you're stuck floating in the center of the planet.
Tidal forces also play a role. If you're in the exact center of the hole you're fine, but if you're closer to one side or the other the tidal force will slowly pull you towards the edge. As you get further away from the edges the force will get stronger. Again, I haven't done the math on how strong.
>
> *Corollary: If the hole itself was stable, would travel through it unprotected be fatal? Eg: are the pressures on a mine-craftian world the same as on a spherical one?*
>
>
>
This depends on how old Planet Plane is, how it formed, and what it's made of.
The interiors of spherical planets are initially very hot from the residual heating of forming due to gravitational collapse, plus the decay of any radioactive elements trapped in the insulated interior. There can also be heating due to tidal effects as happens on the moons of Jupiter and Saturn, the squeezing and stretching adds heat to the moon's interior.
But Planet Plane can't be a moon, and it didn't form from gravitational collapse. So it's anyone's guess as to what heat of the interior will be.
What will be a problem is air pressure. Air pressure is the weight of a column of air pressing down on you. Assuming a normal Earth atmosphere at the surface, at the center of the hole you'll be supporting an extra 3,189km column of air. This is *a lot* of air. The atmosphere ends and space begins at about 100km. At the center you'll be experiencing *at least 30 times normal air pressure*. This is roughly equivalent to being 300m under water (every 10m is about 1 atmosphere of pressure). *Squish* [You will need some serious deep sea equipment to survive this, only five people have gone that deep on the Earth](https://en.wikipedia.org/wiki/Deep_diving#Ultra-deep_diving).
(NOTE: I'm playing a bit fast and loose with the air pressure calculation. The pull of gravity will decrease towards the center of the hole which may reduce the air pressure. Still, it's doing to be in the ballpark of 30bar.)
[Answer]
## You've invented a new sport: Aero-Swimming.
**Best Case**
You'd float, vertically speaking, very near the center of the hole. The difference in the gravity gradient from side to side would not be as noticeable, so you could likely get from one side to the other by swimming.
**Set-up**
That is, *if you reinforce the hole and then survive the fall*. Also you're going to need to not care about being crushed by the atmospheric pressure, but it seems to be excluded for your question. Because the pressures are indeed the same, as they depend on the vertical component of gravity.
The hole will collapse without unobtanium structural support. It's true that the gravity will slightly pull into the walls of the hole (by as much as the mass of the missing material), but it won't compare the the immense pressure from the earth above which will want to squish into the hole like whip cream from between your hands.
**No running by the hole**
Running and jumping off is not a good idea. You're still going to fall for a while and achieve terminal velocity. You will also maintain that horizontal component of your leap and only be slowed by wind resistance, which will rapidly drop as it slows you, so that you'll not quite come to a complete stop. Or rather you will, but it will be with the opposite side of the hole while you're traveling 120 miles per hour downward but slower than walking speed toward the side. This would be similar to walking into the side of a bullet train, it's going to hurt.
**Swimming**
But that's only if you don't start swimming. You'll be able to control your horizontal movement to some degree in the air, just like in water. It will be more difficult, as the medium is far lighter than water, but the effect will be the same.
**End Game**
You'll never get out the other side. The air resistance will have slowed you down significantly (it's to the [square of your velocity](https://en.wikipedia.org/wiki/Drag_(physics)), so it's more significant reduction for your vertical movement where you're moving faster). This means you're going to peak somewhere well below the top of the other side and start falling again. You'll oscillate back and forth for a while and finally settle in the center of the hole (vertically). You'll be able to move up or down a bit, but the gravity will eventually become too strong to swim, and you'll have to resort to climbing. But you can't climb that far, [over 6,000 km](https://worldbuilding.stackexchange.com/a/12443/3202) is probably farther than you'd even want to walk, let alone climb.
You'll die down there, and your body will settle to the middle, waiting to collide with the next person to jump in.
[Answer]
Gravity would be a constant for any distance away from the surface of the of the plane, however, it would change direction to pull you towards the plane.
While you are in the inside of the finite length of the plane of matter, you would feel a gravitational force proportional to your distance away from the center of the finite width.
Because of the infinite nature of the world in the horizontal directions, you would never feel a gravitational acceleration in the horizontal direction. Unless of course the hole is not symmetrical. No matter would ever feel any horizontal gravitational acceleration if it is in fact symmetrical.
Air resistance is the only thing stopping you from reaching the other side.
] |
[Question]
[
For story writing purposes I would like a realistic setup where there is a planet with close to earth conditions in terms of gravity, relative position to the sun etc. However I aim to have a much larger moon with greater mass and thus a gravity sufficient to retain an atmosphere. This leads to questions of wicked harsh tidal forces on the planet.
I plan to solve the destructive tidal forces issue by moving the moon further away. This seems to be the [prevailing wisdom](https://worldbuilding.stackexchange.com/a/15645/8847) and makes a lot of sense. However I am concerned about a sufficiently large moon breaking orbit (which my limited understanding of such things suggests would happen) and would need to work out (1) how large the moon might look from the planet's surface (2) what the tides would be like and (3) what sort of flight times between the two there might be.
I imagine that the moon would look larger, that flight times would be greater but the difference would be trivial and that the tides on the planet would be harsh on the coast while the tides on the moon would be calm (is that right?)
I am not looking for earth-like tides, they can be harsh as long as they do not make inland habitation pointless planetside.
I don't especially want to end up with a planet which is many multiples that of earth's size or gravity (up to 1.1g would be fine).
My grasp of some of the more advanced maths is limited at best so layman's terms explanations would be appreciated along with the hard science.
[Answer]
Ooh, fun question, or in fact, a bunch of questions bundled together
## Endowing a moon with an atmosphere.
It is still unclear what the mechanisms of atmospheric accretion and retention are exactly, since you have moons like Titan (at 1.3E+23 kg it is 0.0225 $M\_{⊕}$ --Earth masses-- or about 1.8 times the size of our moon) with a dense atmosphere (146.7 kPa or about 140% of Earth's atmosphere), and heavier planets like Mercury (0.055 $M\_{⊕}$ but only trace atmosphere) and Mars (0.107 $M\_{⊕}$ with 0.636 kPa or ~1% of Earth's). Moreover, even though Earth and Venus are similar in size (Earth is slightly larger), Venus has an atmosphere ~90 times denser.
So obviously the moon's **mass**, **distance** from primary star, **original gas endowment**, and presence and strength of a **magnetosphere** play a role:
* Higher mass means higher [escape velocity](https://en.wikipedia.org/wiki/Escape_velocity), helping the object retain the gases. As a rule of thumb, you generally want the object's escape velocity to be at least 6 times the particular gas's mean velocity. For example, Earth has an escape velocity of 11.2 km/s, while O2 at 20 C has an average molecular speed of 0.48 km/s, so Earth can retain molecular oxygen for billions of years. Mars has an escape velocity of 5 km/s, so molecular hydrogen --average speed at 20C being 1.9 km/s-- cannot be retained long term on either planet.
* Distance from primary star has 2 effects. The star's radiation warms the gas on the moon/planet surface (increasing molecular speed), and the star emits stelar winds, a flow of charged particles which act to strip planets of their gas (hence Mercury, closest to the sun, having only trace amounts of gas)
* Original gas endowment at the end of the planetary formation stage of the first ~200 million years of the star system's existence. This is hardest to factor in, but might account for why Venus and Earth are so different (that and the oceans on Earth). For instance, it could be that the [moon-creating impact dispersed some/most of Earth's initial atmosphere](http://www.space.com/23031-moon-origin-impact-earth-atmosphere.html).
* Magnetospheres deflect incoming solar winds, in a sense protecting the atmosphere from impacts with the highly charged particles of the solar wind and the molecular dissociation that the uppermost layers of the atmosphere would experience otherwise. These are also mysterious. For terrestrial-sized planets, they seem linked with activity in the molten iron core and speed of rotation, but we don't truly understand the mechanics well yet.
## So, what can we conclude?
Well, it depends on what kind of atmosphere you want. If you're ok with Titan (recall: its mass is 1.8 Earth moon's, ~2% of Earth) you can get 98% Nitrogen and some methane. Not breathable, but you could live with sealed scuba-like-gear if it were warm enough, not the bulky Moon-space suits of the Apollo missions. Surface gravity would be similar to the moon (more mass but less dense). You'd have lakes of gasoline-like compounds on the surface. Tides would be similar to what you see now, while the moon would be larger in the planet's sky due to its atmosphere. Of course, this might be hard to explain in terms of formation and how it is maintained, since bringing Titan to Earth-orbit would make it 10 times warmer and would probably results in full atmospheric loss in about 10 million years, but weirder things have happened.
If you want an Earth-like atmosphere with water and all that, stable over the billions of years, you may need a molten core for magnetosphere, high enough gravity, etc. which means you probably need something about 0.4 $M\_{⊕}$ or larger, so a moon larger than Mars. At that point, it's not really a moon, but a double planet. That comes with its own headaches. With mass that high, the two worlds would quickly become tidally locked, which is to say rotate in synchrony, and always show the same face to the other. (Your 'moon' would only ever be visible from half the planet, no tides at all and possibly **very** long days).
[Answer]
**Moons do not escape their orbits**
They can drift outward and inward over time, but there is a limit to how far out they can drift. Our moon is currently drifting outward by a few centimeters per year due to its slowing of Earth's rotation. This slowing effect on the Earth transfers energy to the Moon pushing it away. When the Earth finally becomes tidally locked to the Moon (in about 15 Billion Years) the moon will stop drifting outward. Plus the farther out the Moon drifts the less drag on our rotation it has, slowing its outward drift and making the process take much, much longer.
**Moon Atmosphere**
As a rule, the closer you are to the sun the more massive the planet needs to be in order to retain an atmosphere due to the sun energizing the particles more. As a safe bet for a planet at roughly earth distance I would make the moon at least half as massive as the earth to be able to retain those gasses and prevent massive escape. Depending on the density of the moon though this could lead to varying sizes of the globe.
**Magnetic Field**
With the magnetic field, your best bet would be to have a free-spinning moon massive enough with enough internal heat to generate its own field. Tidal forces can act to further heat the interior to keep it nice and toasty. A tidally locked world in a close orbit can also generate a decent magnetic field if its orbit is not completely circular. Changes in tidal strength can act to squeeze and pull on the core to heat it up. That combined with a decent rotation rate should be all you need. Another possibility for a close orbiting moon would be that it sits inside the parent planets magnetic field. The magnetic field of the parent planet would probably have to be several times stronger than our own in order to accomplish this though.
**Tides**
As far as tides are concerned there is a give and take. If you want a close in moon it is probably going to be tidally locked, which wouldn't mean no tides, but would mean "frozen" tides. High and low tides that would never move. High tide would always face the other moon, and on the exact opposite side. The sun would still raise tides, but this would only be about 30% as strong as the tides here on earth. This can change drastically though depending on the size of the planet, the star, and the orbit. If you wanted to keep your planet free-spinning like the earth put the moon farther out. The more massive the moon, the farther out it needs to be to avoid tidal locking. Meanwhile while standing on a less massive moon, tides are stronger due to the larger pull of the parent planet in relation to your own more meager gravity. If the moon is of the same mass as the parent planet then the tides would be equal.
[Answer]
First, you don't need to worry about the moon "breaking away". That only happens in bad science fiction shows.
The moon can be as large as the planet (in which case they become co-planets).
In the long run, wicked harsh tides solve themselves - the two bodies become tidally locked. The process of that locking, which is going on today with the earth slowly losing rotation speed, results in the two bodies slowly moving apart, with the separation stabilizing when both bodies are locked. At this point there are no tides on either body.
Assuming the two bodies were formed symmetrically, with identical masses and rotation rates, the tides on each body will be identical. If the smaller body is still rotating (unlike our moon), the effect of the larger body on it will be to create *larger* tides than are found on the larger body.
Apparent size of satellite from the primary will depend entirely on the separation, and vice versa.
[Answer]
You want the moon to be large enough to have geological activity, so a magnetic field is produced, and an atmosphere can be retained. With a maximum of 1.1 g, one thing I'd suggest is to decrease the density of the planet, so let's decrease it to Mars', or 3933 kg/m^3. That's 71.3% of Earth's density. That way, the planet's radius can be up to 1.54 Earth radii, as if density is kept the same, gravity increases linearly with radius. The planet's mass would be 2.62 Earth masses, and you would want to increase the mass of the moon to at least .027 Earth masses. If we kept the orbital radius of the moon, and the density, the same, the tidal heating should be 291 times stronger for the moon. That way, there should be enough magnetism to hold to at least a semblance of an atmosphere.
] |
[Question]
[
What adaptations are needed for human-derived sea-dwellers?
My people are not the classic half-fish, nor are they whale-tail-people - they wear ankle-length swimming skirts that bind their legs into a hydrodynamic shape, and flippers. On land they wear loose skirts and walk almost normally. (The skirts cause some misunderstanding and false rumors, but under their clothes the merfolk aren't that different from us. Bonus points for the possibility of hybrids not well-adapted to either life.) Decorative clothing is flat and clingy.
Genetic engineering technology was a few centuries advanced from ours, but is lost now -- the species was designed, created, and possibly tweaked a bit for a few generations, but now breeds true naturally. (Bonus points for occasional throwbacks who are not well-adapted to either water or land.) Root stock was carefully chosen for genetic diversity but maybe the mix needed tweaking with experience.
Magic is available, but is not something used in daily life. (Think of magic talent like musical talent. A lot of people enjoy singing. Some sing well enough that other people enjoy it. A few can make a bit of money playing gigs. Very few can make a living. A handful are important cultural assets. So important public works can be magicked a bit, but not your average home, reef ranch, or kelp farm.)
There's already a [great question](https://worldbuilding.stackexchange.com/questions/30749/mermaid-architecture) about their building methods, BTW. There can be a few storage buildings underwater, but people need to sleep where they can breathe air even if the entrances are underwater like beaver homes. Most human coastal cities have a sea-folk quarter, especially in tropical areas near reefs.
This needs to go further than the ([heavily disputed](https://www.aquaticape.org/hardy.html)) lake-dwelling shellfish-gathering waders proposed as human ancestors by Sir Alister Hardy in 1960, popularized in 1972's feminist [The Descent of Woman](https://www.theguardian.com/education/2003/may/01/academicexperts.highereducation) and given a more scholarly treatment in 1982's [The Aquatic Ape Hypothesis](https://www.goodreads.com/book/show/305689.The_Descent_of_Woman)
So far I've got:
* Lungs -- extra capacity and pressure. Bigger ribcage.
* Gills -- aren't feasible, see [this question](https://worldbuilding.stackexchange.com/questions/96017/anatomically-reasonable-respiratory-system-for-human-derived-merfolk)
* Hair -- something between human eyebrows and seal fur
* Ears -- streamlined
* Genitalia - retractable/covered
* Body temperature -- cooler in water, warmer in air, but always lower than base stock humans (Camels use a similar scheme, [probably to reduce water loss](https://www.physiology.org/doi/abs/10.1152/ajplegacy.1956.188.1.103).)
[Answer]
>
> Lungs -- extra capacity and pressure. Bigger ribcage.
>
>
>
Nope. Serious sea mammals store oxygen in [myoglobin](https://en.wikipedia.org/wiki/Myoglobin) in the muscles, as there's simply no useful way for the lungs to contain useful amounts of air at depth. Seals *exhale* before diving.
>
> Hair -- something between human eyebrows and seal fur
>
>
>
Doesn't necessarily need to be either. Cetaceans get a long just fine without being fluffy, y'know.
>
> Ears -- streamlined
>
>
>
The hydrodynamic issues of our ears are somewhat outweighed by the hydrodynamic issues of just about every other part of our body, starting with shoulders and arms. The ears can be the last to go, really. Having external ears might improve your hearing above water, too.
>
> Genitalia - retractable/covered
>
>
>
As above. Though perhaps there's a little more justification here, as human male external genetalia expects to dangle around in a certain temperature to keep its contents in good condition, and spending a lot of time in the ocean will rather upset that.
I do also note that human male external genetalia are self-retracting in cold environments, to some extent.
>
> Body temperature -- cooler in water, warmer in air, but always lower than base stock humans (Camels use a similar scheme, probably to reduce water loss.)
>
>
>
Neither dolphins nor seals need this, I'll note. This suggests that whatever benefits you though it might have are probably lower than you thought.
---
What else:
* [Crocodile-derived haemoglobin](https://www.newscientist.com/article/mg14519612-900-why-crocodiles-rarely-come-up-for-air/) to improve oxygen release whilst breath holding, allowing longer dives.
* [Nictitating membranes](https://en.wikipedia.org/wiki/Nictitating_membrane) to allow for sharp focus underwater and above water, for better underwater precision in all activities. Might also help protect the eyes, and if they are hairless (see above) reduce problems associated with water or sweat getting into the eyes unimpeded by eyebrows.
* Ability to close nostrils before diving. It is just convenient!
* Better insulation! Not enough to simply be "fat"... human fat doesn't insulate well, because of surface blood vessels. Most marine mammals are very "cuddly" for this reason. Unless they're exclusively tropical, your peeps are likely to be similar.
* Resistance to [skin maceration](https://en.wikipedia.org/wiki/Skin_maceration), to reduce skin damage caused by prolonged exposure to wet environments. No self-respecting mer-person should be suffering from [trench foot](https://en.wikipedia.org/wiki/Trench_foot), ever.
* Enhanced [diving reflexes](https://en.wikipedia.org/wiki/Diving_reflex), associated with better control of blood storage, oxygen release, maintenance of blood pressure and collapse and re-inflation of air passages if they're expecting to dive deep. If they're only shallow divers (say, <50m), squishable air passages aren't really useful.
* Modified airway physiology. Diving mammals have [somewhat different tracheae and bronchi](https://jeb.biologists.org/content/jexbio/217/7/1154.full.pdf) than land dwellers, though these seem to have been poorly researched to date.
* Sensitivity to water pressure, and hence depth. It'll help navigation and dive planning.
* Assuming they're found in the sea: much higher tolerance for salt in their diet.
* Dolphins get echolocation and seals get whiskers and sharks get a fancy sense of smell and electroception. All of these aid in prey location and navigation in dark or turbid waters. You might consider some of these too, though for shallow divers a pair of goggles or nictitating membranes will be just fine.
Honestly, the insulation is probably the most important bit. The sea in most places ( especially the places where it is most fertile) is *cold* and you're gonna need a lot of bioprene. Fresh water in most temperate parts of the world will be dangerously cold in the winter, too.
[Answer]
Here are some more traits that seem useful for such merfolk:
## Respiratory
* **Dolphin-like facial structure.** Specifically with the nose expanded and raised into a blowhole at the top of the forehead. An extended jaw with fat above would also help make the face more streamlined. You could still have the eyes face forwards like in humans, though
* **Trunk.** A trunk on the blowhole, while it may seem superfluous, would be exceedingly useful for breathing. With a regular blowhole, the merfolk would need to either turn on their back and lift their face out of the water, or stand upright and lift the top of their head out. With a trunk, they may simply move near the surface and twist their trunk out of the water to breathe
* **Efficient brain.** A more oxygen efficient brain, like that of octopodes or manta rays, could be quite useful in reducing oxygen requirements
* **Cetacean pharynx.** Cetaceans have a unique structure connecting the blowhole directly to the trachea. This would be quite useful for merfolk
* **Gills.** While gills couldn't provide all the oxygen these merfolk would require, they would still help. The best solution would be something similar to the bony fish, but with a single pair of gill plates formed from the 5th pharyngeal arch (as it is not retained in mammals). This structure would naturally sit in the neck beside the throat, with paired outputs in the lower frontal part of the neck
* **Moist skin.** Having smooth skin that is kept moist will allow them to absorb oxygen from the water. While it will be very slow, it'll still get some oxygen
* **False hair.** 'Hair' growths like that of the hairy frog will work well as gill surfaces, at least with the moist skin. These could replace the regular hair on the head and other hairy parts: However, it will likely have to keep short
* **Low oxygen requirements.** Many organisms, including some animals, can survive without oxygen. While these organisms are often small and simple, using anaerobic methods where possible will greatly reduce their need for oxygen. However, they will still need it, and so will still need to do some gas exchange
* **Mesothermy.** Heating the body requires energy and oxygen, and so reducing the amount of heat produced will also lower oxygen requirements. This shouldn't slow your merfolk down; some of the fastest animals in the sea are mesothermic
* **Oxygen storage.** Cetaceans also have adaptations for storing oxygen. Specifically, they have large amounts of myoglobin and hemoglobin in the muscles and blood, which can store large amounts of oxygen. This obviously is useful for an animal that must surface for air
* **Open coelom.** Allowing water to flow into the coelom, as in lancelets, provides more surface area for gas exchange. This could be achieved with one unused pair pharyngeal pouches descending down and opening into the thoracic cavity. This would allow water to be admitted into the coelom, and flow over the organs. The water would exit through an atriopore in the front of the pelvic cavity, and would be moved by cilia, perhaps with a few strategically place arthropodal hearts to aid in pumping. The exposed coelomic surface would need to be rich in blood vessels to make the most of the flow
* **Internalized Gill Stalks.** Instead of (or perhaps even in addition to) regular fish gills, these merfolk could possess stalked gills like those of amphibians and lunged fish, which would be rooted in the throat and hang down into the open region of the coelom. These gills would have more space than the fish-like internal gills, but may be slightly less efficient due to having to push water through the entire coelom
* **Cetacean lungs.** Cetaceans have many adaptations in their lungs, such as a double layered alveoli vessels, that are excellent at capturing oxygen
* **Digestive tubules.** Having arachnid digestive tubules in the intestines would work well with an open coelom. While they wouldn't be much help for digestion, they would certainly increase the external surface area of the gut, which would aid gas exchange if the coelom is open to the water
* **Mantle cavity.** It should be possible to reduce the length of the small intestines with a spiral valve (though I'd say they should still be longer than in sharks). This, alongside a shortened colon, should put some space in the merfolk's belly that could be filled with a molluscan mantle cavity. This cavity should be in front of and to the sides of the bowels, should be roughly filled with a pair of feathery gills, and would be entered or exited through an opening where the private parts should be
* **Cloacal breathing.** There could be more respiratory organs within the cloaca, to extract extra oxygen from the water. While they may not be as efficient with a mantle, they'd still be worth it. The two main forms of cloacal breathing would be the turtle form, involving a lung-like chamber in the pelvic cavity, and the sea-cucumber form, with two long respiratory trees growing along the abdomen. These structures could likely coexist together in one species
* **Siphon.** If you give them a mantle cavity, you'll also need to give them a siphon, like that of squid or clams, in order for them to use the mantle gills with their legs together. The best solution would be a double-siphon, like in clams, which is wide enough for lots of water to flow
## Sensory/Communication
* **Melon.** A melon, like that of dolphins, would be useful for echolocation, which is a rather useful feature for aquatic animals
* **Fish eyes.** They should have water-adapted eyes like a fish. You should still include the irides, and could have a more tetrapodal focusing system, but features like the shallow cornea and spherical lens seem quite important
* **Forked tongue.** A forked tongue with a vomeronasal organ would be a useful feature for these merfolk, as it would allow them to smell things underwater like a snake. It should be possible for the vomeronasal organ to be set into the roof of the mouth, as this arrangement is more-or-less how an elephant's mouth works
* **Barbels.** Barbels at the mouth would allow these merfolk to smell things underwater, which is a nice feature to have
* **Dolphin-type ears.** Dolphins have a very complex ear, which allows their echolocation in the first place
* **Shark-type ears.** If you don't need to rigidly stick to tetrapodal anatomy, you could have an extra pair of ears like a shark, which would be attuned more to distant sounds. These ears would probably have to be quite high on the head to avoid interference. They would also need some way to close off when on land
* **Lateral line system.** A lateral line is a useful sensory organ that can detect pressure gradients in water, and so they'd be a wonderful addition to your merfolk
* **Electroreception.** Electroreception is the ability to sense electricity. This is useful underwater, and can be used for communication
* **Hygroreception.** If they can't hold water well (which is likely for merfolk), it'd be useful to be able to detect air moisture, so as to avoid drying places
* **Osphradium.** An osphradium in the mantle cavity would be quite useful in ensuring that the water flowing in this region is clean, given its distance from the rest of the senses
## Digestive
* **Suction feeding.** It is hard to get food into the mouth underwater, and so these merfolk will need some adaptations for this. Suction feeding seems like the best solution
* **Prehensile tongue.** A prehensile tongue is another way to make sure food stays in the mouth. Both suction feeding and a prehensile tongue could coexist, either working in tandem or for different foods
* **Velum.** A velum like a lamprey could help them drink on land. This structure would comprise of a pouch or tube in the throat, where the gills connect internally, with a slit at the top that can be opened and closed to allow or block flow through the gills
* **Gizzard.** It seems like it'd be easier for food to fall out of merfolk's mouth, due to the effects of water. Hence, it would be useful for them to have gizzards or something similar, which might grind down their food deep in the body after it has been swallowed
* **Spiral valve.** A spiral valve in the gut like a shark would be useful for absorbing extra nutrients, due to issues with cooking food
## Locomotive/Musculoskeletal
* **Flexible neck.** These merfolk would need a flexible neck that allows them to comfortably turn their heads to face forwards both while swimming and walking. This wouldn't require much alteration, as shown by various apes
* **Fish shoulders.** It would be quite useful to have fish-like shoulders, as they are narrow and streamlined, but still in the right place for a humanoid
* **Flippers.** They will benefit from long arms to do complex tasks. Having these arms be flippers as well should offset the hydrodynamic issues, as they'd add extra power to their motion
* **Dorsal Fin.** A dorsal fin would be useful for stabilization. It probably couldn't be retractile, but many creatures do fine with this limitation
* **Swim bladder.** A swim bladder will help these mermaids manage their buoyancy. It would likely need to be attached to the lungs as an extra lobe, but it wouldn't need to totally eclipse the lungs in size
* **High strength.** A much higher level of strength should be important, for swimming, defense, and other needs
* **Pachyostosis.** This is essentially required for a diving animal with lungs. It will mostly be concentrated around the chest
* **Cartilaginous skeleton.** Many fish, especially larger or more air-reliant ones, have a tendency towards cartilage skeletons, and so this could be used here. However, please note that it is only in fish; there are no examples of this feature in marine mammals or any other tetrapods
* **Lungfish legs.** Proper tetrapod legs are not good for swimming. Lungfish fins, with their segmented form, seem like a useful basis for leg-tails. Though they will need to be a lot more muscular
* **Finlets.** The legs should have a set of finlets, like a tuna, on the outside of the legs, as these would help them while they swim
* **Tail-flippers.** The legs will need a large, fin-like surface for swimming. The best solution should be something like each leg ending in something like a fleshy ray-fin, which could work as both a foot and a tail-fin
* **Prehensile feet.** Prehensile feet will make it easier to avoid drifting away in the water, as they can simply grab onto the floor
## Defensive
* **Venomous bite.** Having venom in the mouth will be useful in driving off predators. Ideally, the venom should be optimised to produce pain
* **Cnidocytes.** The sea is more dangerous than the land, as dangerous animals could come from any angle. Cnidocytes would be a good first line of defense against predators, as they respond very fast and are quite effective at deterring predators
* **Contractile blood vessels.** Being able to naturally clamp off blood vessels, like lizards can do with their tail, would make it much easier to survive traumatic amputations
* **Colour changing.** Being able to change their skin colour will aid in camouflage, which makes it much easier to hide from predators
* **Poison.** Toxic, bad-tasting flesh will be useful to keep predators away, as they will learn not to eat these merfolk
* **Cocoon.** Forming a tough cocoon around a pupa is a good way to defend it against predation, though it will also impact respiration
* **Scales.** Bony scales under the skin will protect these merfolk from attacks that pierce the skin
* **Shell.** A shell like a turtle would be very useful in protecting against bites. This shell could be internal, as in soft-shell turtles, and shaped like a human ribcage to make sure they still look like merfolk
* **Ctenophore tentacles.** A pair of sticky retractile tentacles could be useful in snaring prey. They could be placed somewhere in the groin or inner thighs, and would be soft and gelatinous (though they could likely have musculature to move them)
* **Ink sacs.** Having an ink sac would be useful, as it could provide good cover to swim away from predators. The ink sac should be placed behind the intestines in the coelom, opening into the anus
## Reproductive
* **Larvae.** Expanded upon in the next section
* **Internal breasts.** Having the breasts inside the body, as in dolphins, would be an easy way to reduce drag. They should be under the ribcage, so there is space for them to expand into the abdomen
* **Pouch.** A pouch like in marsupials would be a useful adaptation for protecting the young from attacks, as the larvae could crawl fully into the pouch to avoid attacks
* **Eggs.** If they have a mantle cavity, childbirth wouldn't be an option. They would need to lay eggs. These eggs should be fish-like, as amniotic eggs won't work in the water
* **Claspers.** If they have a siphon (or even just the mantle cavity), then their genitalia will have to be remade to account for this. A pair of claspers beside the siphon would be a good solution
* **Fused fimbriae.** If the coelom is open, then the uterine tubes will have to be solidly fused to the ovaries, to keep seawater (and any contaminants therein) out of the oviduct
* **No penis/clitoris.** If there is a mantle cavity, then the original erogenous parts of the genitals will have to be eliminated from the genome, to ensure that no merfolk end up choking themselves trying to use them
* **Selective vagina.** In water, it is much easier for sperm to leave the semen and swim away. This means that it is important that the vagina can be opened and closed to keep unwanted sperm out
## Larval
* **Yolk.** If they have eggs, they'll need a yolk to supply the young with food. The yolk only has to be large enough to supply them until they can drink milk, so it shouldn't be that large compared to other species
* **Suckers.** Some form of attachment near the head, such as a sucker-mouth, would be useful in attaching to their parent's teats
* **External gills.** External gills can be much larger than internal gills, due to their extended nature and the fact that they sit outside of the throat. They are also useful for stirring up stagnant water, which is useful for merfolk in anoxic seas
* **Pupa.** A pupa could help defend the larvae as they metamorphose, and it would allow a quicker, more aggressive remodeling as in butterflies and other such insects
* **Tail.** Tails develop before limbs, and so it'd be useful if the larval tails could be used to swim. A vertically compressed tail with a fringe/fin would be the most sensible solution. The legs, as they develop, would sit beside the tail, which would degenerate once the legs were fully developed
## Other
* **Salty tissues.** It's a lot easier to osmoregulate when you don't have to; it seems plausible enough that, like starfish, these merfolk could keep their tissues at ambient salt levels. This, naturally, would be even more plausible in a more brackish sea. Either way, it'd still be good to have some level of osmoregulation
* **Strong immune system.** They will be more susceptible to food-borne diseases, as cooking their food is harder
* **Hemocyanin.** An oxygen-carrying pigment suspended in the blood plasma will greatly increase its capacity to absorb and store oxygen, which is very useful to these mermaids
* **Crocodilian heart.** A heart like a crocodilian, with the doubled aorta, should allow these merfolk to recycle blood from the body directly back, bypassing the lungs. This would work well with gills or moist skin
* **Strong kidneys.** Strong kidneys will aid in osmoregulation, which is useful for a saltwater amphibian. It will also allow your mermaids to go into brackish or overly briny water
These features should make rather nice merfolk
---
If you don't really care about ensuring a humanoid framework, there are many more adaptations you can add:
## Respiratory
* **Thick neck.** If you give your merfolk gills, you could also try bulking up the neck to provide extra space for said gills. This couldd limit the flexibility of the neck, though there is alway an option of simply making it longer
* **Operculum.** An operculum covering the gills would be quite useful, especially on a thicker neck. This will not only protect the gills, but aid in pumping water over the gills
* **Book gills.** Book gills on the stomach, as in that of the horseshoe crab, can be used for extra gas exchange in the water. They could also be angled, for extra spanwise flow as they swim
## Sensory/Communication
* **Bulbous eyes.** Large round eyes like a fish will let your mermaids see much more of their surroundings than human eyes would, which is useful in a 3D world like the sea
* **Eyestalks.** Just as said above, a wide field of view is useful, and moveable eyestalks can maximise this. However, bulbous eyes are still useful with eyestalks as they increase the solid angle visible at once. Furthermore, the eyestalks could quite simply be made retractible to allow for more streamline
* **Antennae.** Long antennae with scent and taste receptors will be useful in sensing scents and tastes in the water, as well as triangulating their position
## Digestive
* **Strong jaws.** A powerful bite force seems rather useful to aquatic creatures. This will require a tough jaw system and large muscles, as in crocodiles and such creatures
* **Crop.** A crop for storing food would be useful, as it is hard to carry food under the surface. A crop could be used as in ants, as a communal stomach into which food can be shared
## Locomotive/Musculoskeletal
* **Streamlined head.** A long, pointed head like a shark or whale will be remarkably useful for a swimming animal
* **Cephalopod arms.** Having the manipulators off of the limbs would be rather useful for a swimming animal. Cephalopod limbs can also be much better at manipulation. These limbs should be placed around the mouth, as the lips. This can still be kept streamlined, as seen in creatures like cuttlefish
* **Catch connective tissue.** Catch connective tissue is a type of connective tissue which can quickly change its stiffness. This could be useful in cephalopod arms, to allow the limbs to become stiff or flexible for swimming or manipulation
* **Fusiform body.** If the neck is thickened up and the face streamlined, it makes sense to go all the way and give these merfolk a spindle-shaped body to cut through the water
## Defensive
* **Spines.** Spines over the body should be useful in protecting the body. This could be combined with the false hair, which would also protect, and perhaps support, the hairy gill-surface
* **Stinger.** A stinger, like spines, could be used to poke at predators. Stingers could also inject painful venom into predators. A good solution here would be something like in the platypus, with the stinger on the feet/tail-fin
## Other
* **Blubber.** Blubber will keep the body warm, which is important underwater, due to the higher thermal conductivity of water. This is doubly useful in the case of mesothermy where there's not as much heat being produced
---
[Answer]
**Nostrils on the back of the head.**
Starfish got all the low hanging fruit but I have this one. It is difficult for humans to lift the nose and mouth out of the water to breathe. Nostrils high on the forehead or on the back of the head would make this much easier; swimming now would be like swimming with a snorkel and much more energy efficient.
Princess Ariel might be somewhat less cute.
] |
[Question]
[
Taken from [this](https://astronomy.stackexchange.com/a/12856/2844) fascinating answer:
>
> The Sun is immensely loud. The surface generates thousands to tens of
> thousands of watts of sound power for every square meter. That's
> something like 10x to 100x the power flux through the speakers at a
> rock concert, or out the front of a police siren. Except the "speaker
> surface" in this case is the entire surface of the Sun, some 10,000
> times larger than the surface area of Earth.
>
>
> We know what the Sun "sounds" like - instruments like SDO's HMI or
> SOHO's MDI or the ground-based GONG observatory measure the Doppler
> shift everywhere on the visible surface of the Sun, and we can
> actually see sound waves (well, infrasound waves) resonating in the
> Sun as a whole! Since the Sun is large, the sound waves resonate at
> very deep frequencies - typical resonant modes have 5 minute periods,
> and there are about a million of them going all at once.
>
>
>
How close to the Sun would you have to be to hear it with normal human ears?
Lets assume you are in a spaceship similar to what we can produce today, would an astronaut inside the spaceship be able to hear the roar of the sun if that spaceship was in a very close orbit to the Sun?
Would you be able to hear the Sun from Mercury? (Did Mariner 10 or Messenger hear the Sun from that range?)
Is it realistic, in whilst writing Sci-Fi, to say that someone near a star could hear all this noise and energy coming from that star?
[Answer]
We cannot hear the sun at any distance because sound cannot travel through a vacuum. We would need to be within the Sun's atmosphere to hear it, in which case I think we have bigger problems than ear protection.
But I think there are a couple things we actually *could* hear about the Sun. First, the Sun emits quite a bit of radio which we can easily listen to. Second, if we had a material that could be thin and stop the solar wind, we may be able to hear it. Currently, we can't hear the solar wind on Earth because it gets stopped ~100 miles above us, and we can't hear it in space because most of it goes right through us. But if we had some new material that could be used as the skin of the spacecraft and would block a much higher percentage of solar wind, it may be audible inside the ship. It would sound a lot like being in a car in a windstorm here on Earth. I have no idea how loud it would be at what distance, maybe somebody else can figure that out.
[Answer]
You can't hear it regardless of range, contrary to popular belief sound does travel in space. "Hard vacuum" isn't completely devoid of matter so sound waves do travel in fact [rather faster](https://en.wikipedia.org/wiki/Heliosphere#Termination_shock) than the [speed of sound at sea level](https://en.wikipedia.org/wiki/Speed_of_sound) the problem is that the noises the sun makes have a wavelengths measured in the hundreds of kilometers, these have no meaningful interactions with the human body, we simply can't interpret them.
] |
[Question]
[
**Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers.
---
**Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/146452/edit).
Closed 4 years ago.
[Improve this question](/posts/146452/edit)
I have a strange idea, I want to reality-check. But first, there's a thing to elaborate on.
So, there are these undead creatures, zombies, skeletons, Michael Jackson, who appear in large numbers during the night and disintegrate once the sun comes up. The UV light causes their tissues to rapidly decompose, and sometimes even catch on fire.
Zombies have human levels of strength and size (~175 cm in height) and enhanced endurance through redundancy, lacking centralized vital points (i.e: the entirety of the body is used in circulating blood), and faster blood-clotting. Skeletons actually have transparent tissue but need power magnification through bows to be lethal.
Undead are created in underground pods. The resources, needed to make them, are acquired from the earth by a gigantic network of fungus strands.
The problem is that they supposed to form within a day, from scratch. Sure the number, that has to be replenished, can be lower as some zombies will hide in caves or bury themselves. Still, some have to be replaced from day to day.
The technology, undead pods are created with, allows for pretty much unlimited genetic modification. **The pods and undead**, however, are still (mostly) made of carbon hydrogen and oxygen, have cells and whatnot.
**If it's possible at all, how can these undead form under 24 hours?**
---
The criteria are a bit complicated, like time-traveling in Marvel movies, but it boils down to:
**They are as strong (physically) as they could be (at least strong enough to kill an adult human) without compromising their ability to keep showing up every night for the rest of eternity.**
1. That means strong and resilient undead...
1.2. Who'll always show up every night.
2. They can grow in rather harsh conditions without any detrimental side-effect to the final product.
3. They come on a daily basis, and never seem to stop. Though a method,
that actually creates them from scratch every day, would be nice it only comes a poor second.
[Answer]
It is possible to 3D print a car in a [day](https://www.quora.com/How-long-would-it-take-to-3D-print-a-car).
So your biological version of a 3D printer needs to operate within a day. The human body may be more complicated than a car, but it is also smaller. The energy needs would be high.
It seems like it also might be able to operate in parallel to some extent. The initial framework is bone, which is comparatively simple. While that's happening, other printers would be creating cells. Then put the cells into (marrow) and onto the bones.
You also don't need them to form within a day. If they take a month to form, that's OK. You have some hatching every day. And you have a backlog of partially formed ones. That would make the energy needs less intensive. More like an elephant pregnancy.
Note: technically what you are describing is more of a flesh golem rather than an undead. An undead would be in some ways simpler, as that would just take an existing body and fix it. This apparently requires assembling the body. Of course, if you have damaged bodies, it may be quicker to repair them than to make new ones. So you might be better off starting with bodies than making new ones from scratch. And then you actually would have undead.
[Answer]
Looking at the fastest reproducing cells in the natural world, algae (see: <https://en.wikipedia.org/wiki/Macrocystis_pyrifera> )...
<https://www.answers.com/Q/What_is_the_world's_fastest_growing_algae>
Tells us that we could get 3.8 doublings in a day. Not a lot. But we can work with that. 2^3.8 = 14ish... So we need to divide our final weight by 14 to get our starting weight. If we want a 200 lb human, that's grown in a day that means we need to start with 14 pounds. No, too much for a spore (a Chihuahua or a large bowling ball)
However if we fill the body with water (supposing that water is free to move around, see below), we have a slightly thinner biological substrate (say onion skin paper at 25–39 g/m² ). 25g / 14 is 1.75g and that's closer to spore size. So you'll need a large-ish sized almond or a raisin or a thumbtack as your spore size doubling those essential 3.8 times in a 24 hour peroid. (<https://www.reference.com/science/things-weigh-1-gram-65dfb5924fe9321b> )
Now that we have the skin, we need to fill it. That's actually surprisingly easy. Our 200 pound person is 90 kilograms and 90 kilograms of water is 90 liters (metric is awesome) and 90 liters is 190 pints. Modern dehumidifiers about the size of a mini-fridge can do 70 pints a day. So, just get three of those.
Overall it's going to take a lot of energy (which creates heat) and great conditions (very humid) to make your 24 hour zombie, but it's doable (with a lot of caveats). It'll be thin skinned and mostly water and require a large spore that then turns into the full organizm.
[Answer]
**Slime Mold**
[Slime mold](https://en.wikipedia.org/wiki/Slime_mold) is a collection of single cell organisms that can choose to join up and form a single multicellular organism
Upon daybreak the undead cells break apart and return to the soil and upon nightfall, pull themselves together into a body to hunt for food.
Since the cells already exist, they don't need to grow but only assemble themselves into a humanoid shape. Slime molds have been shown to form themselves as simple brains with an ability to learn.
This method wouldn't require any pods. The mold cells would exist in the soil and pull themselves together to form a body before bursting out of the ground. Daylight can harm the cells so the body melts and the cells return to the ground and so the cycle continues.
[Answer]
**Fungal cell repurposing.**
The parent fungus has a lot of biomass, made of cells. The cells are functioning as part of the fungus, or perhaps a rootlike reserve. The fungus can assemble mobile life forms from these undifferentiated cells, which swarm together and differentiate as needed. Growth and division of cells is time and resource intensive. But once grown, these cells can be assembled and differentiated in hours.
[Answer]
>
> The resources, needed to make them, are acquired from the earth by a gigantic network of fungus strands.
>
>
>
If it's large enough, then simply have multiple pods growing at the same time, but only a few mature per day. If it takes 10 days for one to grow, and 10 are growing per group, then statistically you could have 1 fully mature per day. Have 10 groups at once and now there's 10 per day. Maybe even have them act like [fleas and wait for something to come by before emerging](https://en.wikipedia.org/wiki/Flea#Pupa). Having them take so long to mature also would help to know when the day night cycle is since some of the ground would be a little warmer during the day in many areas.
This might also allow for the "non-zombies" to be able to do some preemptive attacking. Seeing a large [~.8 meter](https://youtu.be/xziKVv2yQJU?t=111) bump growing would look suspicious.
[Answer]
Look at metamorphosis where a caterpillar moves every single cell in its body to a new location and becomes a butterfly.
In your case the raw material is just a slurry of cells of various types. Each type is stored in huge vats (where they are fed and constantly multiply - perhaps have separate maturation vats, and storage vats), and then are piped into development pods in the necessary proportions when needed.
In the development pods a process similar to metamorphosis moves each cell into the right location and out comes whatever creature you need. Different creatures would get the source cells in different proportions according to type.
[Answer]
You have these fungus creepers already, right? So you use them. Have normal people be snatched/ trapped/ spirited away in the middle of the night. Put them in your pod for a day and enhance them, change them, and you have a fully functioning creature, zombie, skeleton, Michael Jackson.
**OR**
So you don't want to go to all the work of reaping the living. After all, they tend to run. Let's find some that are already dead. See, humans have this funny habit of putting their dead bodies in the ground, where it is easy for a fungus-creeper-pod-undead-factory to get to them. How nice. From there, it's the same as above: enhance it, revive it, and send it on it's merry way to conquest and moonwalk.
**OR**
Drat. The humans got wise and started to cremate their bodies. So now you need to get creative. It's honestly so much easier to use preexisting materials, but hey, you gotta work with what you got. The first two are much more desirable, but I feel you wanted this one. At this level, you want replicator cells around your pods, which create other cells that swim together and form an undead. The bigger the pod, the faster it forms the human.
As for the uv sensitivity, you can have the speed with which they form, or the modifications to their body, alter their DNA. This leads to all sorts of interesting adaptations and, indeed, spontaneous combustion.
Thanks for reading, and I hope you get the info that you need!
] |
[Question]
[
I've been experimenting with a fantasy world that is flat, with the sun fixed in place over the centre. The day-night cycle is provided by the sun dimming and then brightening again. Most of the rest of things are assumed to be 'as on Earth'.
The lack of sun motion, though, creates an environment that doesn't exist on Earth—large areas in permanent shadow, due to being behind hills and mountains. These places receive no direct sunlight—their main source of light is atmospheric glow—but they do receive a fair amount of light, and do experience a day-night cycle.
How would (macroscopic) life - plants especially, but other organisms as well - adapt to an environment like this?
[Answer]
## Some plants and animals would focus on the borderlands.
While regular shade could exist anywhere, mountains and other large geology would give the deepest shade, enough to change the climate. The border areas would have the most balanced climates (breezes could normalize temperature differences to some extent). For animals, it allows for movement between shade and sun.
## Many plants and animals would live in full sun.
**Forests** are, by definition, in full sun, because nothing is able to cast shade on them. Some forests are near mountains, but generally they are not as thick in the mountains.
Forests create their own shade. Plants and animals requiring more sun, grow or climb higher. Plants and animals benefiting from lower temperatures and lack of direct exposure to sun, stop growing or climbing (or climb down).
Forests change up the access to sun plants and animals get through death of large trees (either the leaves all die, which can also be seasonal, or the trees themselves fall over and expose new areas to sun) or from fire (which rejuvenates the ecosystem).
While forests aren't mountains, they are deep enough and thick enough to change microclimates.
**Jungles** are forests in more tropical and humid areas.
**Deserts** are low-growth landscapes in arid full-sun areas. They can be cold or hot, low or high altitude. There is plenty of plant and animal life but it does not get thick like a forest and the only shade is from a few individual plants (some of which can be [very tall and/or store water](https://en.wikipedia.org/wiki/Saguaro) for animals to use). Deserts in your world would be very similar to deserts on Earth, only any surrounding cliffs or mountains would have different amounts of shade/sun.
**Plains** would have similar ecosystems to Earth ones. Plants and animals would have a bit more movement during the day to adjust for the lack of shade changes from trees and small geological features.
## Overall:
* Plants may develop more like vines or other types of flora with longer reach. So they can make use of local shade/sun differences.
* Many plants thrive in full sun so long as their roots are shaded (tomatoes, for example) and may evolve like a tomato to creep outward and upward so this happens.
* More plants may evolve with canopies, dense umbrella-like structures where the top gets plenty of sun but they create their own shade for their trunks and roots.
* Climbing animals will be common, along with nocturnal animals. Both are prevalent on real-life Earth, but there may be more of them in your world.
* Coldblooded animals will thrive in areas with local shade and sun (like they do currently in desert regions and elsewhere...using underground burrows and also landscape features like large rocks).
[Answer]
**There are already environments on Earth that are similar to this, like the floors of rainforests.**
I grew up close to some natural rainforest areas and 'shadow' is a reasonably good term for the light levels you get while walking through a dense rainforest. The canopy blocks out a great deal of the sun, which is why the trees in rainforests have already evolved to grow so tall; they need to compete with each other to get the most light out of the 'canopy' above the ground.
Some plants actually thrive in such an environment; you get a lot of ferns for instance that don't mind being in shaded environments and actually burn in full sun. Plants like 'elephant ears' evolve to have very large, broad leaves that take advantage of what sunlight they can get a hold of, and as such would burn in full sun because their leaves have such a large surface area.
And then you have mushrooms. These aren't animals, but they're not plants either and don't photosynthesise, so the presence of sunlight isn't a problem for them. What they *do* need though is plenty of organic material from which they can draw energy and material with which they grow.
Animal life is a bit more complicated because it generally relies on plants to survive. Most of the insects in rainforests for example thrive on the humus, or plant debris on the rainforest floor that starts to decompose and compost. Then, the larger animals live on them.
In your world, rainforests may be an option in some places where the shadow isn't particularly high, and trees can grow above it and do. In most places however, your plant biome will likely be fern prairies that contain additional broad leaved plants designed to maximise energy absorption. In such cases, there may well still be a humus layer and hence insects, but what you're unlikely to see would be fruits and flowers.
Why? Well, fruits represent a massive store of chemical energy (sugars and the like) that the plant invests in it's propagation. The trouble is, if energy is scarce, you simply don't reproduce like that because the energy required to produce fruit is a much larger percentage of the available energy, and hence the investment represents an impediment to survival.
So, any animals in such a biome are likely to be predators, starting with the consumption of the insects that work the humus layers in your fern prairie.
] |
[Question]
[
In this setting, the family unit is based around a clan system. An individual's wealth and status is related to the clan they are born in, and its ancestry is based on matrilineal lines. Due to certain environmental factors on the continent, travel between regional areas can be somewhat difficult and expensive. Therefore, most breeding takes place between clans in relative proximity of each other.
Marriage does not exist in the form we would recognize. Women remain in the clan they were born into, while men are the ones who leave the home to join other families. Men don't marry an individual, instead they marry into an entire clan. This leads to many offspring coming from the same group of fathers. A cultural belief system has developed in which boys are considered "sons of society" and raised in bulk while girls are "daughters of their mothers" and raised specifically by their mother.
How can this society avoid genetic inbreeding under these circumstances?
[Answer]
>
> Due to certain environmental factors on the continent, travel between regional areas can be somewhat difficult and expensive.
>
>
>
Travel *anyway*. Do it in groups -- a traveling "meat market" where the men show themselves off in hopes of being chosen by the clan with the prettiest women -- during the the least-unfavorable time of the year.
>
> A man doesn't marry an individual, but marries into an entire clan. This leads to many offspring coming from the same father.
>
>
>
There's a reason that most cultures are monogamous: polygamy leads to a **lot** of unmarried men with no sexual outlet, and that leads to violence (including rape).
[Answer]
The answer is in the question itself:
>
> Women remain in the clan they were born into, while men are the ones who leave the home to join other families.
>
>
>
Humans are an XY sex determination species. So when a man joins a clan, he brings not only his Y chromossome - he also brings a X which adds variety to the the pool of X chromossomes in the matriarchy.
To improve genetic variation, you need to change the man who is fathering children every once in a while. You can either have a clan marry multiple men at the same time, or have marriages be temporary.
The animal I can think of with the behavior that most closely matches that are african elephants, and as a species they've managed it (until we started hunting them). Males don't stay with a band for long after they become adults. They will rover around alone or in small bands of males. When the females of a clan are in heat, a male will mate with them and then leave.
[Answer]
>
> How can this society avoid genetic inbreeding under these circumstances?
>
>
>
This has happened even when travel is relatively easy throughout our history.
Inbreeding is mitigated against in a few ways.
With matrilineal societies ambitious men have few ways to upgrade their social status, and some will be displaced. Some of these will travel and spread genes. If there is conflict you may get mass displacement.
A lot would depend on whether their is any restriction on marrying outsiders whether outside the clan, region etc,. But with a large enough demographic you are unlikely to get dangerous inbreeding, human cultures have always culturally protected against that in broad strokes by various taboos unless under extreme pressure. So while you get regional traits coming from shared ancestry with a few exceptions like royalty who want to keep power within families you don't really have any danger of it getting dangerous unless the communities are totally isolated like Islands.
Humans have experienced several population bottlenecks with at least one being estimated at as few as 600 breeding pairs Worldwide, yet from that we have the huge diversity we have now. You don't need a huge influx of new blood every year, just a small intermittent supply of travelers would be fine and cultural taboos against close relatives getting too frisky.
[Answer]
**Sperm peddlars.**
This exists now, for people who raise animals.
<https://www.swinegenetics.com>
>
> Swine Genetics International is an artificial insemination swine
> genetics company, also offering swine production related consulting.
>
>
> Liquid semen is available from over 150 sires to help you meet your
> genetic needs. Boars representing the following commercial lines are
> housed at SGI: Purebred, Exotic, Terminal, Maternal, Meat Quality and
> Certified "Niche" Program animals. We also offer 40 sires that
> comprise our showpig program. Frozen semen is available on boars
> housed at SGI since 1981 - including sires currently on stud. SGI is
> very active in exporting both swine semen and live animals all over
> the world. Our current staff provides artificial insemination and
> production-related consultation for swine operations globally.
>
>
>
In your world, magic allows preservation of semen. The sperm peddlar comes around once or twice a year, when it is optimal to conceive. Her wares (and it will be her, because magic is involved) will have information about the sire and children he has produced.
I envision her arriving in a gypsy wagon. Travel is hard, but she knows ways and has skills. When she arrives, she can help with the whole process. If there are males in the village she might make some purchases as well.
[Answer]
Your society needs a taboo that encourages gene distribution.
The European one - "don't marry your close family" - won't work in your society, because in your society men have a clan, not a family. But that detail also points to another option.
A taboo for clan-based societies with no families could be "don't have sex with people born in the clan you were born in."
That doesn't quite fit your society either, but we're getting closer. Also it doesn't guarantee that genes get spread over a larger area than two neighbouring clans.
"Don't have sex with people born in the clans your parents were born in" is better. Genes get spread over three or more clans quickly, so the people are less inbred. But, in your society, it doesn't sound like people are always keeping track of who their father is. So that doesn't work.
A ring of clan taboos can spread genes around like that without people knowing who their father is. In Clan A sons are usually given to Clan B and sons of Clan B cannot join Clan A. And so on around a circle back to Clan F giving most of its sons to Clan A and never taking husbands from Clan A. In a few generations this can spread genes over a geographical area that's much wider than the distance that most individuals travel. If it's also forbidden to have sex outside your clan or have sex with boys who haven't switched clan yet, then nobody's having sex with their brother. These two sets of taboos should be enough to prevent extreme inbreeding.
So the anti-inbreeding rules for your society are: "I only have sex within my clan. I don't have sex with unmarried boys. Unmarried boys are forbidden from having sex with women. There is a clan that my clan cannot take husbands from. Most of my sons will marry into that clan." Breaking these rules isn't just illegal, it's widely thought to be disgusting, like how you would think marrying your uncle is disgusting.
] |
[Question]
[
I'm building a world which is 50% covered by the sea. For approximately half the year, the sea covers one hemisphere; for the other half it moves to the other hemisphere, leaving the first a dry sea-bed, until the seas return again the following year. My working assumption is that the sea is dragged around the planet by the gravitational pull of its moon(s).
My main question is, how big and/or close would the moon need to be to cause such a huge tidal shift, and what kind of orbit would it have?
If it is not possible for a single moon to have such an effect by itself, could it be achieved if there were secondary moons and/or other gravitational forces affecting the seas, either directly or by their impact on the orbit of the primary moon?
All help gratefully received!
[Answer]
I am afraid a moon cannot achieve what you are asking. Noticeable tides require noticeable water depth, and few meters excursion on few kilometers average depth do not leave the surface dry.
If a moon would be so close to pull more the water bodies, the resulting tidal forces would quickly move it far away from the planet, reducing the tides.
You can achieve something similar to what you ask if your planet has its rotation axis at 90 degrees with respect to the orbital plane (so that it alternatively has over one local year 1 hemisphere fully in light and one fully in darkness).
The dark hemisphere could be covered by solid water, while the bright side can have liquid water thanks to the higher temperatures.
[Answer]
The moon causes our tides, but not in the way most people believe.
My answer below is belied by the this wonderfully detailed post, which explains *exactly* how tital forces playout, and debunks my ancient and cherished belief in how the tides actually worked.
[There is no tidal bulge](https://physics.stackexchange.com/a/121858/76197)
~~Now from day to day, the moon doesn't move much (it takes just under 28 days for the moon to orbit the earth).~~
So how come the Moon - which is moving very slowly on a daily basis - can cause the seas to move a massive amount twice a day?
The answer is it doesn't.
I'm useless at drawing things, but imagine the earth as a large ball (soccer ball), and the moon as a ping pong ball.
Hold the "moon" out away from the "earth", now keep the moon in position but slowly rotate the earth around it's axis (simulating the rotation that gives us our day).
The moon isn't moving, the moons gravity pulls the sea towards it causing a "tidal bulge", there is a corresponding bulge on the other side opposite the moon, and no bulge to the left and right.
As the earth rotates, the moon stays where it is (for the purposes of illustration ignore the small amount it actually moves), so the bulge also stays where it is, one facing the moon and one facing away.
Now imagining this bulge, rotate the earth "one day", each part of the earth will move into the bulge facing the moon, then out of it, into a non-bulge area before moving into the bulge opposite the moon (approximately 12 hours later), then as the 24th hour approaches it's moving back into the tidal bulge facing the moon.
So, the tides "moving in and out" are an illusion, like "sun rise" and "sun set" the sun isn't moving, the earth is rotating and the sun appears to move.
Again with the tides, the "tide" doesn't move in or out, the earth rotates under the tidal bulge, giving the appearance of the sea moving, when it's the beach moving under the sea.
[Lots of good explanations and nice illustrations here](http://home.hiwaay.net/~krcool/Astro/moon/moontides/)
*Obviously I'm using approximations here, tidal frequency runs at something like 13 hours (I think) not 12, but this illustrates the general effect*
So "moons" aren't going to pull your oceans in different directions, and not for that long a time.
Our tidal bulge does move, but it moves very slowly
I can't imagine how you could explain away shifting an entire ocean like this with tidal dynamics, sorry.
[Answer]
The current discussion seems to agree that a moon could not be massive enough or close enough to a planet to cause the tidal forces you require. However, what if instead we make your planet of interest the moon and place it into close orbit around a large gas giant. This could give us the large tides you need to drain a shallow sea. There are a few challenges though. Presumably we want normal length days, and a much longer year period over which the tides change. If our moon orbits the gas giant quickly and closely say, once every ~24 hours, then we can have a fairly normal day night cycle. Now, if our moon is very nearly tidally locked to the gas giant but not quite fully locked then the tides could change only over the course of many days. To put this another way, if you imagine that for every orbit the moon makes around the gas giant it spins 1.01 full rotations then the side of the planet facing the gas giant will gradually change over the course of 100 days. Because there are two tidal bulges, one facing towards the gas giant and one away, the seas will ebb and flow twice a year. You can tune the spin-orbit ratio to whatever you would like to produce years of the desired length.
So we have normal day night cycles and large tides that change over a much longer time scale. The only question left is whether this system is feasible and stable. If we put our moon into a retrograde orbit instead of a prograde orbit, meaning it orbits in the opposite direction of the gas giant’s spin, then it might explain many of these characteristics. Satellites in retrograde orbits experience [tidal deceleration](https://en.wikipedia.org/wiki/Tidal_acceleration#Tidal_deceleration) which will cause our moon’s orbit to gradually slow and decay bringing it close to the gas giant. Tidal deceleration will also decrease the speed of rotation of our moon which will explain why it is very nearly tidally locked. Now, one issue with this system is that it isn’t very stable. Within a relatively short time period (cosmically that is, we are still talking thousands to millions of years) the moon will become tidally locked to the gas giant and the tides will stop moving. Additionally due to the continued decay of its orbit it will pass close enough to the gas giant that its atmosphere and oceans will be stripped off before it eventually disintegrates and rains down upon the gas giant. But you’ve still probably got a few million years to work with. Potentially you could work these features into your story, such as that the years have been growing steadily longer.
[Answer]
Sadly I agree with the other views expressed here. Moons would not be capable of doing that, at least not in the way that I believe you intend. If a moon had sufficient mass to have sufficient gravitational pull to shift an entire earth like ocean of water to the other side of a planet then the moon would be too close to the planet and would be disrupted by tidal forces. Additionally if it were to take an entire year to orbit the planet it would be too distant to excerpt such a force.
An alternative would be water on a planet orbiting relatively close to a star, as this is just a bigger version of the planet moon example. It would also make sense for the planet to be rotating very slowly as it might be suffering from tidal drag and be approaching tidal locking, but even then an earth sized ocean would I think be stretching credulity. Unfortunately close proximity of a planet to a star tends to suggest a lot of heat which would not be good for an ocean.
[Answer]
I'm not sure how feasible it really is, but you could take inspiration from [Rocheworld](https://en.wikipedia.org/wiki/Rocheworld), a book series and the titular planetary system.
This system has 2 planets, very very close to each other (iirc, a 3 mile gap). This causes the two planets to be tear-drop shaped, as seen on the book cover:
[](https://i.stack.imgur.com/cC3BR.jpg)
Because of this, one of the planets is perpetually covered by an ocean, but at certain points in the planet's revolution the sea is flung to the other side. This is a fairly violent event, causing the creatures who live there to take cover or ride out the massive wave on the top. However, the other planet is a barren and desolate desert, which seems to be what you want.
The downsides of this:
* highly violent so it's likely not what you want
* the "moon" is a planet of equal size
* likely not quite feasible, but IMHO disbelief is suspendable
Upsides:
* Barren, dry desert and incredibly deep sea (don't remember off the top of my head, but I'd say around 100 miles? or much more, not sure)
* Life is possible on the ocean-covered planet, and some plants are seen on the desert one
* I think the planet orbital period can be set by you, so you can either have a constantly shifting sea (every month or couple months), a regularly shifting ocean (every couple years), or once in a century or generation.
[Answer]
Gravitational forces that would be that strong wouldn't just move the water, they'd rip apart the planet immediately.
If your sea were only a few meters deep you could think of strong global wind systems which move the water around, but actual deep oceans like on Earth can't be moved around like that in a realistic manner.
As L.Dutch says you could use water that turns to ice, or alternatively have all water evaporate on the hot side of the planet and rain down on the cold side.
[Answer]
Hmm.
Some good answers here. But try this on for size:
Put a lunar sized mass just outside of syncronous orbit -- about 40,000 km. This is about 1/7 of the distance it its now. Tidal forces go up with the inverse cube, so it would make for tides that are 350 times as strong. That would make for something between 600 m and a kilometer high tide.
This would also flex the crust of the planet. So you need a stiffer crust. It's an old planet, or it formed with less radioacatives to keep the core hot. so plate tektonics are really thick plates.
Old planet, less orogeny (mountain building) more erosion. Now your planet is low enough that the tides can sweep over everything.
You can adjust the period to anything you want: A perfect synchronous orbit gives you a standing tidal bulge on both sides. 1% slower or faster gives you 2 tides per 100 days.
Note: I think it would more interesting if the tides didn't cover everything. Think of the currents of a 600 meter bulge of water swirling around the Appalachians, or surging through the lowlands of Europe.
Note also: With a yearly cycle, would the ocean beds had time to dry? The oceans beds will be a bunch of lakes, and swamps.
Note: Google Washington Channeled Scablands for the effects of really really big floods.
[Answer]
**Yes, depending on their size, and that of your planet.** Because, the moon exerts gravitation pulls on each other they may cause a cataclysmic collision with each other however. This could make for a cool escape plot though.**As for the sea moving, yes,** if erosion from millennia of this happening has made certain areas of the land eroded and set to fill at certain times of the year, when the moons are in certain positions. Therefore pulling the water with them.
[Answer]
Your idea is impossible. The bulge facing and opposing the moon while the earth rotates under the bulge is a good description.
The bulge is about 0.2m. Which leads to the obvious question: How can you have tides of 8 to 20m with a bulge of only 0.2m? The answer is the bulge appears as a surge of water with momentum. When the surge hits shallow water it slows and grow in height and it fills the tidal basin unevenly as a result of fluid dynamics over the ocean floor topography.
You can't just slow your rotation down to 1 year BTW because then the surge would have less momentum and less filling power.
You can drain follow by flood with a tsunami but you cannot upset the natural level of the sea long term. You can only give it a push and let things happen.
Watch the film Interstellar where they had a world completely covered in water with a planet rotating, never breaking 300m tsunami pulled by a black hole.
] |
[Question]
[
I'm writing a story in the genre of *Heroes*, *The 4400* etc in which a group of apparently random civilians, mostly US citizens, are subjected to some alien influence and gain strange powers, whereupon the government wants to keep an eye on them and run tests to find out exactly what they can do. The DHS has stepped in and invited several of them to come to a facility where tests can be run (probably experts from the NIH will be invited in for this), and where one of the characters who needs unusual medical assistance can receive it.
I'm looking for an actual location, based on the following criteria:
* The characters are not being held prisoner against their will. (Rationale: making people with superpowers, angry or panicked, is a very bad idea. Much safer to let them think they're free, and just keep an eye on them.)
* The whole thing is supposed to be secret. (The people in charge, would prefer other governments not find out about this at least for the moment. Whether the attempt to keep it secret will actually succeed for long, is a different question.)
* Preferably on or near the east coast, ideally within reasonable commuting distance of Boston.
What would be a suitable location?
[Answer]
## [Fort Detrick](https://en.wikipedia.org/wiki/Fort_Detrick) in [Fredrick, Maryland](https://en.wikipedia.org/wiki/Frederick,_Maryland): Biological weapons research
This site has been used historically to research and experiment with **biological weapons** - something relevant to human with superpowers, "weapons" in their own right. It's known for having engineered some pretty nasty viruses, and has not avoided controversy.
The facility, while not completely secretive, does have reason to withhold information from the public in the interest of safety. This could be used to conduct medical research on your characters. It's still in use today - this time as to research *defense against* such weapons.
## Does the location matter?
If the facility is secretive - so much so that foreign governments can't hear about it - the characters will likely not be told where they are / are going. Locations with this much secrecy probably aren't on any lists you'll find online, but they likely do exist. It's most realistic to withhold this information.
[Answer]
Sorry I got here late, but this already exists: [Plum Island Animal Disease Center](https://en.wikipedia.org/wiki/Plum_Island_Animal_Disease_Center).
It is:
* on the east coast off New York's Long Island,
* run by DHS,
* historically secret and still secure,
* equipped with medical facilities (granted, veterinary medicine, but easily adapted for super humans),
* already suspected by conspiracy theorists of producing the [Montauk Monster](https://en.wikipedia.org/wiki/Montauk_Monster).
What more could you ask for?
[Answer]
Thompson Island.
<https://en.wikipedia.org/wiki/Thompson_Island_(Massachusetts)>
[](https://i.stack.imgur.com/KR8hq.jpg)
It is a mile from Boston. It is a private island on which one can have events like weddings, teambuilding exercises etc. If you rented the facility for your "team building exercise" no-one would think twice.
It might be tricky to get rid of the staff but if you paid well and said that it had to do with corporate secrets I bet they would go along.
If you want less developed than the Outward Bound facility on Thompson island because your super might Hulk out and wreck stuff, or if you worry that people in town will notice your super turning into a 100 foot dragon, there are other islands in Boston harbor that would do and that are less visible from town. I see on the Spectacle Island website "The Spectacle Island Marina is temporarily closed until the end of July for ongoing repair of winter storm damage. Sorry for any inconvenience. " Hmmm...
[Answer]
While not within "commuting" distance, Virginia is honeycombed with bunkers and storage spaces built during the Cold War to house US government functionaries, records and equipment to be ferried out in the event of an impending attack on Washington DC.
While the idea that thousands of people, Federal records and equipment could be ferried out and safely sheltered in the 30 minutes between the detection of ICBM launch and impact is perhaps a bit optimistic, the fact remains that there are many hardened bunkers already present.
The ones which were built for government functionaries would likely have fairly pleasant interior facilities, although the ever present life support machinery (HVAC, water pipes, storage lockers, access tunnels, emergency generators and maintenance spaces) would give you the strange sense of walking down the hall and being inside an aircraft carrier.
So long as the people are being ferried in and out in blacked out vans, "black helicopters" or other means where they are unable to see the route they are taking, time the trip or record the GPS coordinates, then the government can still maintain secrecy and security of the facility.
] |
[Question]
[
Imagine a society of people every bit as intelligent as people today, on a planet in all material respects identical to Earth. But, on this planet, no one has ever invented a written language, or even a written proto-language like the Vinca script or Harappan seals.
What is the maximum scale, and level of complexity, technology and general sophistication that a society like this could achieve?
How would the answer differ, if like the earliest literate cultures of Sumeria, Minoan palace society, ancient Egypt, and the earliest literate days of Chinese society, there was a written language, but it was only taught to future scribes starting at about high school age, and only 1%-5% of the population ever learned to read and write, and 90%+ of those who did learn to read and write were only as facile in reading and writing as a typical high school or college student who has studied a foreign language only in a classroom setting is in the foreign language that they have studied?
[Answer]
Considering mass literacy is a recent development in human history, societies could be become quite advanced. The real bottleneck is the need for recorded information. Perhaps a class of "mentats" or living memory people whose task it was to remember things could be instituted.
Currently we value literacy because we're literate and people in the past weren't, so it follows literacy make us superior. This is nonsense. Ship's captains in the Age of Sail often had a person assisted to them whose role was as the captain's scribe. His job was to write done everything the captain needed writing down. Captaining a ship was an important job and you didn't need to read or write to do it. Literacy was deemed a minor accomplishment.
In many societies craft and trades skills were passed on by working with a skilled practitioner who showed what was done and how to do it. Traditionally Chinese musicians were trained by simply practicing until they got it right. Their mentors didn't issue instructions or train their apprentices they just punished them when they played wrongly. Not unsurprisingly musical apprenticeships took a long time in Traditional China.
Effectively human history is a saga of societies becoming sophisticated and technically advanced with only minority literacy. Mass literacy only begins in the mid-nineteenth century and took until nearly the mid-twentieth century to become the norm. Every society has some residual illiteracy in its midst and we have yet to achieve a world with one hundred percent literacy. This may be a goal too far.
Undoubtedly written languages are the most efficacious method of recording and transmitting information. However, if societies existed without written language there brains were be as subtle, complex and good at problem solving as ours. So given time, their societies will devise stratagems to circumvent the literacy bottleneck. We didn't have to, we weren't smart enough to find the alternatives, so we took the easy way out.
[Answer]
The society would be limited to **living memory**.
* The inability to record contracts and inventories will limit economic activity. They can put [boundary stones](https://en.wikipedia.org/wiki/Boundary_marker) between two fields, and they might be able to memorize that each farm owes their overlord five bushels of grain after harvest and a fat chicken by michaelmas, but it won't be possible to have a [bank passbook](https://en.wikipedia.org/wiki/Passbook) or a [credit default swap](https://en.wikipedia.org/wiki/Credit_default_swap).
* Craftsmen and scholars will be limited to what they can memorize and teach. There can be no written building plans, no recipes, no chronicles.
There have been times where large parts of the population were illiterate, possibly all of a village or hamlet. But those villages were part of a larger, literate society, and the lack of written records put them at a [disadvantage](https://en.wikipedia.org/wiki/Exception_that_proves_the_rule#Original_meaning) when more powerful interests wanted to take advantage of them.
[Answer]
The limit on their sophistication is not caused by their lack of a written language, but rather vice versa. They have to be sufficiently unsophisticated that they don't just invent a written language, which doesn't need a high degree of sophistication. It may well be that they *could* get much more sophisticated without a written language, but there's no way they would actually do that.
[Answer]
If by written language you include mathematics, then no further than early Stone Age. No mathematics means no engineering, masonry, carpentry or any sort of measurement system. Trade can't happen and agriculture is strictly limited.
Most importantly, there is no means of passing on information other than in person, so you effectively have infinitely strict, indefinite patents. The holders can choose whom to pass their skills on to and will likely try to keep it in the family, regardless of potential, so a lot will be lost every few generations, setting them back that much further.
Socially and legally, there can't be too many laws, as people will have to rely on memory, and there will be blatant abuse by those close to the establishment who can make up rules as they go along. Inheritance will primarily be in the form of influence, rather than physical goods, as there is no record keeping. Finders keepers at funerals, basically.
For the second part of the question, what you've described is essentially the Dark Ages, pick any one. The closest one to our own time is the European Dark Age, after the fall of the Roman Empire, though we appear to be heading towards another one, possibly starting in our own lifetimes.The difference here is that there is no basic level of development for your illiterate society to fall back upon, no Roman law or Roman roads and no knowledge of metalworking (largely because they haven't been invented yet); but eventually, this society will develop. Somebody will teach non-scribes, or they'll manage to work out the squiggles on their own then teach others in secret; even possibly develop a second alphabet--it's not that hard, just make symbols and relate them to the spoken language. The latter has an added advantage of being incomprehensible by the establishment, thus safer for malcontents, and hence cooler to the young. In other words, how written languages normally spread.
[Answer]
Seeing as written language's general purpose is to record information, all that would be needed, for this situation to occur, is for the civilization to create audio or video recording before written language. Highly unlikely, but not impossible.
[Answer]
Perhaps they may have developed genetic memory, or some biochemical way to store memories and knowledge. Maybe a creature that could be imprinted with information used as a medium of exchange.
Advancement would then be limitless and even accelerated. You could copy Stephen Hawkings knowledge and make copies for other scientists to download directly into their mind.
Forget school, just download the baseline education and off you go. Need a career change? A vacation experience? Want to feel a plane crash?
Intergalactic civilization in just a few thousand years is my guess.
-Jack
] |
[Question]
[
# Context
The world is made of floating islands suspended in the atmosphere. For all intents and purposes, the world doesn't have a solid surface.
Due to a magical influence, islands rise from the core of the planet into the outer atmosphere and then fall back into the core in a cycle that takes thousands of years. So islands move vertically albeit very slowly.
Due to a lack of a strong enough magical influence, all but the largest islands (Ireland-sized and above) will drift in the horizontal plane under the influence of the wind. If the wind is strong enough, it may be able to push smaller islands up or down.
The world is about twice the size of earth, that combined with the technology level means that people haven't traveled around the world and haven't discovered most inhabitable land-masses.
Because of the way islands work, they can be 'tied' together to prevent drifting, but this isn't commonplace and is only done on islands that are very close together due to the difficulty of such practice.
Also consider that vertical distances are substantially larger than those found on the Earth, since the temperature and pressure gradients in this world are much less pronounced.
# Question
How would the people in the world go about mapping, charting or otherwise have a consistent means of navigating the airs with airplanes and airships?
# Similar questions
* [How to navigate among **stationary** floating landmasses](https://worldbuilding.stackexchange.com/questions/22322/in-a-world-of-islands-floating-in-the-air-how-would-people-navigate)
* [How would flying beings map the airs](https://worldbuilding.stackexchange.com/questions/18926/how-could-bird-people-map-the-air?rq=1)
[Answer]
You've actually stumbled into something pretty similar to the philosophy of Polynesian navigators!
Part of their approach to navigating the pacific ocean was to envision themselves at a center of a circle, with the islands, stars, and ocean rotating around them. This would help them maintain a course in the *general* direction of where they were heading. Then, when they reached certain points in a journey, they'd switch to more active forms of navigation. These methods meant that they very reliable could both find new land, and adjust their course as they zero'd in on their destination.
It's also important to mention that this perspective is extremely difficult to translate to a map. Which for the Polynesians, wasn't that big of a deal! Instead this knowledge was passed through oral tradition, which was far more useful for this approach to navigating the world, especially because their routes and methods would change depending on time. Because of this, when attempts to translate this knowledge into maps happened, the results were [illegible to the western perspective](https://www.stuff.co.nz/national/101871481/legendary-map-of-pacific-by-james-cooks-tahitian-navigator-tupaia-finally-unlocked).
**What does this mean for you?**
Like the Polynesians, navigation would probably be done by expert navigators, rather than having a series of tools that allow anyone to navigate. For the first part of a journey, the navigators would consider wind currents for the time of year, allowing them to *generally* get a sense of where an island will be. Then they'd head in that general direction, probably using a [star compass](https://archive.hokulea.com/ike/hookele/star_compasses.html) to maintain their bearing. Additionally, the shifts in elevations may affect the movement of stars. A skilled navigator might note how certain stars are eclipsed by the presence of land.
Once in the general area of a land mass (several 100 kilometres), they'd switch to more active methods.
**Cloud formations**
Clouds tend to form more heavily over the ocean ([https://atmos.uw.edu/~rmeast/OceanCloudsweb.pdf](https://atmos.uw.edu/%7Ermeast/OceanCloudsweb.pdf)) and sit at a lower elevation than above land.
While your world doesn't have an ocean, the shifting elevation of the drifting islands would certainly help. Navigators would keep an eye out for gaps in cloud formations (indicating a landmass beyond the horizon), as well as looking for cloud formations that are more likely to appear above land (I'm not sure how your atmosphere would affect this, but there would still be some differences due to the temperature shifts between land and open air). Additionally they might look for cloud formations at incorrect elevations, which would indicate an island being slightly lower or higher than they expected.
**Wind and air currents**
The presence of an island would also be noticeable through the way it impacts air flow around it. Polynesian navigators were able to locate an island based on how its presence would disrupt the wind nearby. An easier way to imagine this process would be like a rock in a river. Even if the rock wasn't visible to you, you could still see the wake and ripples that occur as the water moves past it. Your navigators might look for pockets of dead air, indicating that they're in the 'wake' of a ladnmass. Or, from further away, they'd learn to recognise the turbulence caused by the presence of a landmass. There's some photos on this page that might help to visualise this (<https://en.wikipedia.org/wiki/Wake_(physics)>)
**Fauna, and other close indicators**
As they drew even closer, navigators would then look for signs of animals that indicate a landmass. In the morning, they'd look for birds leaving their homes to forage and head in the opposite direction. While in the evening, they'd follow the direction of birds as they returned to their nests.
However, since there's very little reason for birds to venture out in your world, this method would be slightly adjusted. Instead, navigators would try to align their voyages with the migrations of birds. The idea being that they try to estimate the final leg of their journey to coincide with birds returning to their home islands.
Additionally, there are several minor indicators that could be used to more finely search out a land mass. Polynesian navigators noted that when they were close to an island, they would be able to smell the difference in the air (compared to the smell of the open ocean).
Navigators in your world might be able to tell the difference in light that indicates that an area is in the shade of an island. As well as the shifts in temperature and humidity that indicate a landmass.
Hopefully these methods are helpful, I know this post is a little old but I couldn't help myself from sharing some info on Polynesian navigators!
[Answer]
You say islands move slowly. That means you can produce maps for short-term use, probably pictures of the island with some sort of pitch/roll/yaw notation for how to get to the neighboring islands. For areas that a ship travels commonly, they might have a 3D model, like a [mechanical model of the orbit of planets](https://en.wikipedia.org/wiki/File:Orrery_small.jpg) that the ship's navigator can update over time. *(It wouldn't be fixed routes like in a planet model... more like positioning the arms of an artificial Christmas tree, bending them to get the right relative positions.)*
But for longer-term navigation, a system of "lighthouses" seems useful.
These lighthouses would be some sort of navigation buoy built on the islands that broadcast their positions to nearby ships. Depending upon tech level, this could just be very bright lights (making navigation in foreign lands viable only at night, which would be an interesting story impact) or radio. If each one of the lighthouses has a unique signature, a ship could navigate from point to point by looking for a sequence of lighthouses.
A "harbormaster"-type position would also develop. In our world, lots of ports have local navigators who come aboard ships to do the piloting through the port. These local navigators know where all the underwater rocks hide and where the current of the reef will push a ship. In your world, such local harbormasters might be hired out to do hops or to update maps of ships as they pass through, especially after a hurricane or something that moves the islands more than normal.
As technology improves, you might have ships dedicated to station-keeping the islands -- big tugs that attach to the islands (especially the richest ones) and constantly tug them back into relative position to other islands (especially the richest ones) to keep those navigation routes fixed.
[Answer]
Allow me to also answer on a 'magical' stand point.
First, the one who want to mapping the world must be someone who is able/mastering the 'wind'. He/She/It must also have knowledge about it. Being able to move from island to island horizontal and vertically. It doesn't matter how he can fly, by magic, steam engined plane, zeppelin or just a big kite.
Then with his arcane knowledge of gravity and wind cycle, combined with his data of the island form, volume, and mass now he can predicted where and when each of his islands moves. The last thing to do is to create the map then.
The map obviously will be much different and more exciting of course than our map. It can be something like a brass globe, with some kind of dials to input date info at the base. When we change the date, it will also move the gear inside and change the islands layout accordingly.
Well you also could make the map on magic parchment, that is touch interactive like our nowadays touch screen.
Of course we should make a small room of error for the sake of the adventures. Be it a big enough unmapped land, with rare creatures and weird indigenous people live on it. Some area that always covered with mist or even other islands near the core or far away above the clouds.
I wish you a clear sky and safe trip.
Kindest Regards
Sky Cartographers Guild Meister
[Answer]
In terms of flat *maps* as we know them, the mapping could be in fact be rather similar to maps in our world. We have longitude and latitude grid lines on maps, and a similar method of charting positions could be explored, using two lines emerging from every mapped island, **air** and **magick**. The maps would be circular, with the islands arranged around a center (which could possibly have the same air and magick lines as the other islands, if the map is centered on an island).
**Magick lines** go through the center of the map and through the center of each of the islands at their current position, **air lines** map to the wind eddies and patterns around the island, and the island travels along them just as it does the magick lines. The mapping of wind lines would probably be done with some sort of balloon system, otherwise knowledge of the weather, probably through magic, would have to be obtained. Along every air or magick line would have to be placed some sort of formula to be able to calculate, from the difference in date of creation of the map to the present, how far along the lines the island would have moved, and in which direction, it's highly likely that some sort of special calculus or shorthand would evolve over the years to write this. It goes without saying all maps would be dated.
When it comes to air lines, what might be important to consider is that as an island moves across some air lines, it may encounter separate air lines and be whisked away in those wind currents, in which case, wind lines wouldn't be restricted locally to islands, but rather all global wind currents would be drawn on the map, together with their strength, and all islands would be labelled with some form of weight metric, with a formula to decide whether it will be affected by a certain current.
Globes could be very interesting structures, made of spheres and poles. A number of poles would originate from a central sphere, representing magick lines, and on each pole would be a sphere, an island, from which would spring another pole representing air lines. There would be some sort of dial which would enable you to enter the date and the globe would mechanically move all the spheres to the correct place, or possibly, the globe would move automatically every day.
As SRM mentioned, it is highly likely that a more permanent form of navigation would be implemented, using lights and angles, similarly to old nautical navigation. One such implementation might be a sort of sundial placed on an island, however, the "sun" is not in fact the sun, rather, some arcane light emitter placed on a nearby island, set up so that its rays will fall on the sundial on another island, and the precise angle and distance of those two islands can be measured. Of course, as tech level improves, this method will improve, but this is a low tech level example.
Some form of 4D (or even 5D) coordinate system would develop, 3 spacial dimensions and an extra value, correlating to our form of calculus which defines how much an island moves by wind or magick. As SRM has stated, a role of "harbourmaster" or cartographer would become incredibly important, as they know the ins and outs of how each island moves. It is quite likely that these "elders" would be the silent power of your world, and should they organise, could become a formidable political body.
[Answer]
Assuming that the technology level prevents the use of GPS, the problem will be working out where each island actually is, because there is no solid surface for a fixed point of reference.
A compass is not sufficient and may not even work, as a planet needs a rotating liquid metal core to generate a magnetic field. It might be necessary to give your world a magnetic core, or a magical alternative, as you can only use the position of the sun and stars to find North when they aren't covered by clouds.
For position they'll have to use celestial navigational techniques. They can determine their latitude by measuring the angular height of the sun at midday, and allowing for the season.
Determining longitude is much harder as it involves measuring the difference between local solar time and the time at a reference point. For the last couple of hundred years, accurate clocks have simplified this - but it has to be accurate as every second of error creates an inaccuracy of a few miles. Slightly less accurate clocks can be used if you have long-range radio to broadcast a time signal but otherwise a navigator needs to watch for an astronomical event such as a lunar eclipse or a particular configuration of the moons of Jupiter that can be calculated in advance.
This requires a civilisation with fairly advanced mathematics and an understanding that the world is round, and that planets follow predictable orbits around the sun. It also requires full-time astronomers to calculate the necessary tables, and a way to publish these tables to each astronomer.
Humans didn't manage this until we have nation states with fleets of hundreds of ships regularly undertaking long passages out of sight of land, and I imagine only people travelling between islands that were out of sight would need accurate navigation, so I would expect that to be the same.
Given the above, I'd expect each island to have a navigator who takes regular fixes and maintains a clock, and for islands to communicate via signal lamps (and possibly telescopes). They'd send their current location, course and speed to other islands, and pass on the details of others. They could use that to estimate the position of islands for a while, depending how predictable they were.
[Answer]
Radar with Air Traffic Controllers. It's done today
The only difference needed would be multiple networked radar stations presenting a 3D map to the Air Traffic Controllers (ATC) or self managed flight control systems in their air ships/planes.
~Raptor
] |
[Question]
[
Hopefully, this is a little less broad. Apologies if it isn't! I'm rather new here, so I'm not used to this yet. Oops. Also, apologies for the length - I'm trying to explain as much as I can.
To pull some of the stuff I know already; Human babies are born underdeveloped compared with other primates. Our brains are less than 30 percent their adult size at birth, compared with around 40 percent for chimpanzees, our closest living ape relative. It would take a gestation length of 18 to 21 months instead of nine months for human babies' brains to reach that level of development.
I'm not entirely sure why humans cut off so soon, past something to do with their pelvis and standing upright. The species I'm developing, however, needs to be more active from the get go - not that I'm saying they need to give birth to teenaged kids or anything, just that here are more areas in the brain that need to develop. I'm aware the kids are likelier to be bigger as a result when they are born, considering they need extra time to develop.
If a species changes, usually, it needs a reason to change. In the case of my species, the brain needs to develop further for the child's survival. This has to do partly to account for some changes from the 'human' setting. If, uh, that makes sense. I'm kind of using humans as a base here. (Evolved parallel to, branched off at one stage.)
The brain, for one, needs to possibly account for any changes as a result of heightened senses, hearing and smell in particular. This particular one is brought on due to the fact that the planet is rather cluttered - this has bred a large amount of species who rely on stealthier tactics. Though the world is varied, I picture something perhaps mountainous and/or heavily forested for the general area this species evolved in. (Leaning more towards 'rainforest' as opposed to plain 'ol forest.) They've spread out pretty recently - but they've still adapted to this particular environment.
Another change is magic; like I brought up in an earlier question that I worded a bit awfully, it highly impacts this species (and many others native to the planet), to the point where it has interwoven into their evolutionary process. It's second nature to them, like how humans have evolved for... hunting? Help, words. Take the wizards from Harry Potter as an example. One needs to be born with the magical ability to actually go around wielding magic. Wizards can, but muggles (normal humans) cannot. Occasionally people are born who can't use his magic, regardless of bloodline (squibs). The failure to develop this magical ability for my race, as a result could be due to premature birth or birth defects.
I'm aiming for the gestation period to last as long as 15 to 21 months, if required - it's likely I'll be adding or adjusting other areas of brain development later. I can handwave some of it, but not everything. The race was more solidary many millions of years ago, but over time developed into something resembling larger flocks. This is only strengthened further once longer gestation periods become a thing, considering the one carrying the baby isn't going to be at her peak if/when predators come.
The senses and inclination to magic are what I'd consider defense mechanisms. Natural ways the body has evolved to let them survive. Kind of like long necks on giraffes, though my race doesn't go around hitting people with their necks... well, not yet, anyway.
I'm planning to keep the race **bipedal**, if possible, or perhaps being in some process of evolving away from the whole four legged thing. Vaguely humanoid. The organs and stuff on the other hand are basically free range if it gets the desired results though.
I'm not really sure what else to add, but I'll keep an eye out so I can edit accordingly. Sorry for the brain-vomit and I appreciate any help.
[Answer]
**Magic**
Considering the magic ability isn't something that has a strong basis in most science, you should have some reasonable leeway with your pseudo-human biology, so long as it remains logical and remains in theme with the rest of the magical abilities.
Let's go over the basics of your setting, which I will be using as the basis for this response.
The pseudo-humans have developed more acute senses of hearing and smell, driven by the more dangerous and shady environment. How this is manifested, however, is not clear. Do they have larger ears and better noses? Perhaps changes in their brain allow for better processing of the information? It's unclear, but I will address my solution in a moment.
Next, there is magic that was developed as a defense mechanism, but it isn't mentioned what kind of magic or what it is capable of. I'm going to take some liberties with it, but I assume it can be used to enhance the sense of the pseudo-humans.
Lastly, these pseudo-humans need to have a longer incubation, with the purpose of having a better initial brain-state when they are born.
My logic is that the embryo is capable of very basic versions of magic, and probably only the most common and useful application for your species, magic pertaining to sensory improvement.
While in development, the embryos will develop their magical abilities (to a small extent) in preparation for their birth. As early as 20 weeks, human embryo's have developed ears that can hear. Pseudo-human embryo's will be able to amplify their hearing to be able to gather more understanding and learning of the outside environment. During this time, they remain in gestation, developing more while learning from a controlled and contained environment. This provides time for their brains to develop with minimal downsides to their prolonged stay.
In comparison, embryo's with defects that are unable to perform magic are born after 9 months, similar to normal humans, since they have no need to remain and develop their abilities.
This provides an easy and quick ways to tell if a child will be magical or not. There could be celebrations around the 10 month mark to celebrate the assumed abilities of the child. Their will need to be small modifications to the child-bearing pseudo-humans for them to be able to support larger babies (like the wider hips, and possibly just larger in general since it's more weight for much longer to carry), but evolving to be larger based upon an environment isn't unrealistic, nor does it require much explanation to be accepted.
[Answer]
**Physiology**
This may seem overly simplistic, but you could easily have a longer gestation period in humans if the mother had bigger hips.
Generally, if it's a matter of life and death for the infant to be further along when born, it will be. In modern society, we heavily coddle and care for our young, so walking isn't a matter of life and death (unlike many herbivorous quadrupeds which can walk almost immediately at birth *because it is life or death if they don't*). You might also consider the mother: the larger the baby, the more difficulty they will have in caring for themselves.
I could see this developing in a society where the baby is almost immediately put into more harsh circumstances where it must be more proficient to survive, but the mother is very well protected for most of the gestation period.
[Answer]
**What would you like the babies to be able to DO when born or in hours or months?** Please edit your answer and list them. Your question post includes a lot of info, but in order to answer it, a list of the features you want and WHEN you want the baby to have them. Things like walking, senses...lay it out
* Perhaps as bullet points
I will edit my answer accordingly, to solve the problem of a more developed baby, whatever that might mean.
In the meantime, let me say that longer gestation is likely not going to solve this problem.
Here's an article that covers [why helpless babes were naturally selected](https://blogs.scientificamerican.com/observations/why-humans-give-birth-to-helpless-babies/). Note that the pelvis thing, which is present in older research, may not actually be the reason.
>
> to accommodate an infant at a chimplike stage of brain development—that is, a brain that is 40 percent of adult brain size, or 640 cubic centimeters—the pelvic inlet (the top of the birth canal, which is the narrowest part) would only have to expand by three centimeters on average. Some women today have pelvic inlets that wide, and those larger dimensions have no measurable effect on locomotor cost.
> ...
>
>
> That other factor, they contend, is mom’s metabolic rate. “Gestation places a heavy metabolic burden (measured in calories consumed) on the mother,” Dunsworth and her co-authors explain. Data from a wide range of mammals suggest that there is a limit to how large and energetically expensive a fetus can grow before it has to check out of the womb. Once outside of the womb, the baby’s growth slows down to a more sustainable rate for the mother. Building on an idea previously put forth by study co-author Peter T. Ellison of Harvard University known as the metabolic crossover hypothesis, the team proposes that “energetic constraints of both mother and fetus are the primary determinants of gestation length and fetal growth in humans and across mammals.” By nine months or so, the metabolic demands of a human fetus threaten to exceed the mother’s ability to meet both the baby’s energy requirements and her own, so she delivers the baby.
> ...
>
>
> Rosenberg additionally noted—and I found this especially fascinating—that the authors mention the possibility that the timing of birth actually optimizes cognitive and motor neuronal development. That idea, first proposed by Swiss zoologist Adolf Portman in the 1960s, is worth pursuing, she says. “Maybe human newborns are adapted to soaking up all this cultural stuff and maybe being born earlier lets you do this,” she muses. “Maybe being born earlier is better if you’re a cultural animal.” Food for thought.
>
>
>
We are as probably as smart as we are BECAUSE most of the development is not done inside the womb. Our interactions with the world as we develop are the reason why we are intelligent. We are the most intelligent animal on the planet and we give birth to some of the most helpless babies...there may be a reason why we are unique in this way. It's an advantage. Chimps might be more developed when they come out, but they also have less capacity for intelligence over a life time.
It's not a plus to intelligence if the brain just develops inside the womb. Consider [this article](http://www.nature.com/news/2004/040322/full/news040322-9.html) on the difference between a great ape and ourselves. A mutation in the jaw muscle allowed us to continue to develop after birth, which is an ADVANTAGE, not a disadvantage.
The species that are nearly fully formed and developed (like horses for instance) tend to be not so bright.
[Answer]
It is not at all clear to me what would be the advantage with a longer gestation period, but assuming there is a valid reason (and that no one would actually attempt what I am about to suggest - a risky assumption I'm sure), here goes: By killing all infants born early or on time, it seems possible that the human gestation period would increase as a consequence of artificial selection.
It would probably be necessary to set the initial target to be not too much larger than the current average and only gradually raising it over the long experiment. Otherwise there is of course the risk of catastrophically diminishing the human population.
A few centuries, not to mention perhaps billions of dead babies, later - viola - a longer human gestation. Of course certain practical and ethical difficulties present themselves.
] |
[Question]
[
One of the inspirations for this was Tactics Ogre: Knight of Lodis, where I liked their depiction of slithering, combat-worthy mermaids.
I've been trying to develop mermaids who make pilgrimages to land cities, and have been considering mermaids with shore-side villages and towns. For this purpose, I've been trying to work out ways they can be more capable on land (not as capable as humans, but more so than a flapping fish).
For modes of movement I've considered... The main one would seem to be shuffling/crawling, since they likely can't slither. They could assist this motion with their hands, with their tail, and potentially with extra fins near the waist (the picture below has an interesting example of an elbow-like fin).
The main issue with this is if the mermaid is heavy. If they are light and flexible enough, skillful manipulation of these appendages might make them more able on land than seals. Trying to scoot on the floor is pretty painful,but a mermaid's tail should be tough enough to endure this (though long-term travel over hard ground, they may get chafed bloody). Rolling and springing up with a large jump also seem plausible short distance movement.
EDIT: Forgot to mention inch-worming. If the mermaid is quite flexible, then this may be a possibility for small movements and adjustments, as well as assistance in the crawl/shuffle.
Mermaids may need to bring salt water and sponges with them when on land, to dose themselves with. Unless they can convert to fresh water creatures quickly, then freshwater would likely be unpleasant to them. However, they could probably bring enough salt around to make fresh water usable for a sponge bath. Drysuits filled with saltwater may also become popular.
Human forms of transport, carriages and cars would work fine for mermaids if they can arrange them. Some sort of mermaid-bicycle using the hands or tail would be interesting to see... though wheel chairs may be the norm.
My question is to do with how to make the locomotion and daily life of mermaids on land plausible and feasible. Notably, you can expect they'll spend a lot of their time in the sea, even with their coastal villages/towns (pilgrims will have more trouble).
I also put some thought into mermaid land combat, but I'll save that for another day.
[Answer]
I would look at sea lions and elephant seals movement as their lower bodies are fairly similar to what a mermaid's would be, and they are sea mammals that spend a considerable lot of time on land. They sort of hop and scuffle with the lower body using their hands/ fins for assistance. I don't think weight would be a problem; an elephant seal weighs a lot more than a human and they navigate very well on land for a sea creature. If they need to visit land cites I could see them using some sort of rickshaw pulled by land creatures, perhaps humans or Dwarfs - this would make it easier for them to move about among land-dwellers .
As for combat, I could see them fighting in groups of threes with Spears. Why Spears? Because humans' better manoeuverability on land would make short work of any mermaid warrior. If they're going to have a chance fighting against land animals on land, then they're going to need a weapon that will allow them to take out their opponent before they can get close to them. A bow and arrow would be perfect, but it can only be used on land whereas a spear can be used on land and in water. Using their tail as a weapon would be useful in water but not very practical on land.
[Answer]
You need to look at real modes of movement for creatures that can do both land and sea. There aren't many creatures competent at both.
Mudskippers and seals aren't super graceful in the land. Sea snakes can't actually move on the land much either. Crocodiles and Hippos are better off, but four legged and I don't think that is what you are going for.
To preserve the ability to use hands, I think a snake form is what you want. [Pythons](https://en.wikipedia.org/wiki/Burmese_python), for example, are strong swimmers. Tonle Sap, a seasonally flooded lake in Cambodia, is swarming with swimming snakes in the wet season, so much that the locals 'fish' for them.
[Answer]
Assuming your mermaids are legless, classic half-human with a fish tail, their towns could be built with many pools and canals. They could also place aids (stuff like handrails and climbing bolts) everywhere, for arm-assisted movement.
If they have very strong arms, they could be able to balance their entire bodies on their arms - I've seen images of exceptional animal amputees (dogs, goats, pigs) that are able to balance on their front legs this way. If the mermaids have long, heavy tails, they would probably have to curl them up over their bodies, with tail fins pointing forward (somewhat like a scorpion's tail).
For long travels, they would surely use some form of vehicle. Chariots mounted with large tub-like water vessels are the obvious choice. I can also picture a mermaid "riding" a tamed giant hermit crab, her tail resting over the giant shell.
[Answer]
Nagas walk on land just fine.
[](https://i.stack.imgur.com/VD5SV.jpg)
If the mermaid is able to slither on land just like the naga, she should have no problem going around on most surfaces. Might be slow, and might need constant hydration though.
If the fish side of the mermaid is more related to eels than whatever it is that Disney's Ariel is, then this becomes even more feasible.
[Answer]
What about having them stand tall, and take small steps on a T-shaped tail, like you'd move around if your ankles were loosely bound together? They'd look a bit like a wobbling penguin but still be very graceful once back in the water.
[Answer]
It depends on how the spine of your merfolk normally bends. Does it move from side-to-side (like a fish), or up-and-down (like a dolphin)?
Most merfolk are depicted with up-and-down motion, and these will be easier. Seals can crawl on the land using their bodies to propel them, but if you want your merpeople to be more agile on land, look at sea lions. A sea lion can use its tail almost as a third leg, and unlike seals they can actually *gallop* this way, attaining speeds comparable to humans (at least over short distances). They can do this because they have the ability to control their back flippers independently, using them as "feet".
Merfolk running like sea lions might be funny-looking, but it would allow them to keep pace with human companions. Of course, they wouldn't be able to run fast and attack with weapons at the same time, so they probably wouldn't be *as* effective in land combat overall. They could work as archers though, running into position and then firing from a standstill.
If the motion is side-to-side, your merfolk will be more limited in their land motion. They can move in a manner similar to snakes or Warcraft's Naga, with their torsos partially lifted off the ground. To keep their flippers out of the way, they could either lift up the end of their tail or fold them up. While this wouldn't be as fast as a galloping sea-lion merperson (even the fastest snakes are slower than a human running; belly crawling just isn't very effective for fast motion), they *would* be able to slither and attack at the same time.
[Answer]
Last night I saw a movie where a guy In wheelchair was trying to climb stairs. The scene was dramatic on purpose and the guy took almost two entire minutes climbing to the second floor.
Which is ridiculous considering the guy was an ex athlete and that any decent athlete can run in a handstand, do muscle ups and climbing without legs.
A trained human has arms stronger than the legs of an untrained person.
I actually tried climbing the stairs in my home using only my arms and dragging my legs as if they were paralized, it took me 6 seconds.
If anyone wants to see a demo, I can show how fast people can crawl on land by dragging their feet.
] |
[Question]
[
We have discussed the Railgun and the Coilgun, I'm fairly sure we've even talked once or twice about magnet guns. But could a centrifuge gun exist?
For those who do not know, a centrifuge rifle is exactly what it sounds like, at the pull of the first trigger the hollow, donut shaped barrel spins the bullets until they reach terminal velocity and then when the second trigger is pulled, the bullet fires out of the barrel. I see three obvious problems with this theoretical gun;
1. **Ammunition**, a centrifuge gun would be limited to spherical ammunition, and is likely to jam.
2. **Munitions**, a centrifuge gun would require a large battery and would need to be charged often.
3. **Accuracy**, a centrifuge gun would be at best inaccurate and at worst lethal to the wielder.
What can I do to make the centrifuge gun design feasible? would changes need to made?
[Answer]
# No, it is not feasible
A few years ago, [this hoax/scam video](https://www.youtube.com/watch?v=-teEbB9vlEU) was making the rounds. I did the math on the claims.
**In short: this thing — in order to live up to the claims in the video — has the power requirements of a nuclear powered warship**
And then I did not even begin to look at things like gyro forces, vibrations, losses, sound, etc... I was only looking at the projectiles.
Problems with it:
* **Recoil**. There will be recoil. Sir Isaac Newton cannot be fooled. To be precise what you will have is an unbalanced flywheel that will vibrate violently.
* **Enormous gyro forces**. The velocities the flywheel must move at means you have a huge disk spinning at [Ludicrous Speed](http://tvtropes.org/pmwiki/pmwiki.php/Main/LudicrousSpeed). You cannot turn that, meaning you can only aim in one plane.
* **Enormous [centrifugal forces](https://xkcd.com/123/)**. What do you think happens when the enemy scores a hit on that flywheel and it shatters? That is right: a claymore mine exploding right in your face.
* **Power requirements**. Already mentioned.
* **Long start-up**. It takes time to spin up the flywheel to any usable speeds.
* **Poor ballistics**. Such a weapon requires spherical ammunition to work. Spheres have the worst ballistics of all kinds of ammunition, resulting in poor accuracy and short range.
So to answer your question, what do you need to make this feasible? Answer: You need to break the laws of physics. The centrifuge gun is a bad idea, not matter how you slice, dice or chop it.
[Answer]
You'll also have to factor in the gyroscopic forces of a rotating barrel. If you've ever played with spinning a bicycle wheel, you'll know that it resists leaving it's current axis of spin. This would make aiming the thing somewhat tricky.
However, a fixed turret with a stack of ten or so rotating barrels, now that's a whole different thing and would be decidedly deadly.
[Answer]
wouldn't this basically be a slingshot? Look at how slingshots work. Also disc throwing. Those are 2 examples from the real world that turn centrifugal force into forward momentum.
Ammunition - would probably need to be either spherical or disc shaped. But since your launch mechanism isn't chemical and you don't have a bullet, that shouldn't be a problem.
Munitions - For a non stationary gun, especially handheld, it's probably a lot more practical to go for something based on a different technology. The gun would probably require a lot of energy. But, compared to rail gun or coil gun, the power requirements would probably be comparable. If you want a stationary weapon(think tank, boat or something similar) you no longer have that much problems with power requirements, or accuracy(since a computer can accurately target it.
Accuracy. As already said, it would be difficult to target without tech, but computer release mechanism should be quite simple to use.
The only advantage i ca see for such a gun would be it's ability to hurl unstable material, since it gives its ammo a much slower starting speed than say a bullet.
] |
[Question]
[
This actually occurred in a dream last night, but I'm interested in what could come out of this. I'm not experienced with writing stories and have only read some Worldbuilding posts, so excuse me if this isn't the best! I'll give a brief introduction on what happened, but the scenario does not really lead on to anything about the black color of the animals.
In my world, humans stranded on an island find themselves in several dangerous encounters with animals. The first encounter occurs when one human is attempting to make contact with an elephant calf, but the calf is spooked when another human verbally warns his friend. In response to the alarmed calf, the cow elephant charges at the human, who barely manages to escape.
However, the situation does not end there - a panther has also responded to the calf's cry, but encounters the humans in a cave the panther is using as a shortcut to a cliffside. The panther attacks one of the humans, knocking them from the cliff and killing them.
...and so on.
**TL;DR** Later, the humans come to the realization that all of the animals they've encountered have black fur or skin.
* In my dream, it was daylight during both attacks. Although possible, it did not appear that the animals utilized the color for nighttime camouflage.
* I was never aware of the temperature of the island, but the foliage was green and a beach led on that it was not very cold.
[Answer]
Is the island volcanic? If so the sand and rocks could conceivably be black in colour giving the animals a camouflage advantage if they are black. Alternatively the island could be close to a polar region and the animals only operate over the winter in near constant darkness. Alternatively there is some form of toxin emitting a glow on a wavelength other than visible light. The animals evolved special vision to see the toxin sacrificing colour vision in the process making black the only appropriate colour so that the animals can see there group/mate easily.
[Answer]
Unbeknownst to the humans who are recently stranded on the island, people have been to the island before. This place was used as a secret facility for animal testing. To differentiate the lab animals from other animals they altered their genes so that all the animals have black fur/skin in regular light, but glow an eerie green when exposed to a black light. These modifications give the animals no benefits, but it was useful for the scientists who created them.
[What makes black panthers black](http://news.nationalgeographic.com/news/2015/01/150116-black-animals-cats-leopards-science-jaguars-genetics/)
While this link only explains for large cats, I'm sure the same thing can be done for any animal
[Making animals glow](http://news.nationalgeographic.com/news/2009/05/photogalleries/glowing-animal-pictures/)
is something researchers already do
[Answer]
There are many different reasons for black skin/fur.
* They think the darkness is their ally...
You're creatures don't necessarily have to use this only at night. You're jungle can get pretty dark.
* @Bellephon s dark dirt idea.
If the ground and landscape are black we can camouflage.
* Flamingoification
Basically they eat minerals/creatures that cause them to look black. Similar to flamingos.
* they're stuck with it
All animals on the island have always had this color skin. An albino/other colored panther is just strange and unlikely to find a mate. The resulting panthers are either black or have not passed on the genes.
* Hunting
I don't know if you have any human influence. If you do you can have humans especially target colored animals for their exotically colored fur.
[Answer]
For some species on the island, there could be no benefit at all. The black fur could be an accident due to [genetic drift](http://evolution.berkeley.edu/evolibrary/article/evo_24) - basically random chance as to who colonised the island or who survived. For instance on Princess Royal Island many of the grey wolves are black, and 10% of the black bears are white! This is because they are an isolated population, stuck on an island.
Alternatively... disease resistance. In some insects, lots of melanin (black pigment) is associated with [disease resistance.](https://www.researchgate.net/publication/230205032_Melanin_and_disease_resistance_in_insects) Perhaps there is some disease which affects mammals and their melanin offers the same kind of biochemical resistance. Of course, if it affects things as diverse as a panther and an elephant, then humans can probably catch it too. So your visitors to the island may die or survive depending on their skin colour, or how much melanin they have in various internal organs. (This is a bit hand-wavey, because mammals have a much better immune system than insects, so melanin may be a drop in the ocean compared to what their regular defences can do).
] |
[Question]
[
I'm trying to flesh out the history of a fictional galactic society, specifically the initial settlements and inhabited worlds. Something that I thought would be important to settlers would be an abundance of heavier elements (because hydrogen is pretty easy to come by, but uranium not so much, and it's not the easiest thing to synthesize).
The way I understand it, heavier elements are created by stars, whether from everyday fusion or supernovae. What I'm wondering, though, is given all the space in the galaxy and the goal of finding a solar system with the largest ratio of protons/neutrons/electrons per atom, are there ways to identify the best solar systems to check out first, short of actually travelling there and taking samples?
[Answer]
Research suggests that heavier elements can be found in greater quantities closer to the center of a spiral or elliptical galaxy. [Henry & Worthy (1999)](https://ned.ipac.caltech.edu/level5/Sept04/Henry/paper.pdf) summarized several measurements of ratios of heavy elements to hydrogen. For example, here's a collection of graphs of oxygen-to-hydrogen ($\text{O/H}$) ratios from emission line objects (e.g. ionized gas, such as [HII regions](https://en.wikipedia.org/wiki/H_II_region)) in the Milky Way:
Oxygen is used mostly because of its high concentration relative to other heavy elements in HII regions; iron-to-hydrogen ($\text{Fe}/\text{H}$) is more commonly used for stars. Another important point to note is that the observations show that there is a positive correlation between galactic mass and [metallicity](https://en.wikipedia.org/wiki/Metallicity) (see Fig. 4b) - the more massive a galaxy is, the greater its likely metallicity.
Things get trickier when looking at the stellar component of a galaxy. There isn't a substantial metallicity gradient in the galactic halo, although [globular clusters](https://en.wikipedia.org/wiki/Globular_cluster) do show a range of metallicities. The [galactic bulge](https://en.wikipedia.org/wiki/Bulge_(astronomy)) has yielded poor data so far, in the case of the Milky Way, and while the thick disk population seems to show no radial gradient, the thin disk population shows a small decreasing gradient, as determined by $\text{Fe/H}$ ratios for individual stars.
One important thing to note about stellar metallicity is that there are two distinct populations of stars: Population I, the newer, more metallic stars, and Population II, the older, less metallic stars (here, I use "metallic" as it is used in the astronomical context, to refer to elements heavier than helium). There is also a hypothetical third population, Population III, that consisted of stars that formed early in the history of the universe before dying, but evidence in this area is not yet forthcoming.
Anyway, borrowing heavily from [my answer here](https://astronomy.stackexchange.com/a/13502/2153), Population I stars are likely to be found in the [galactic (thin) disk](https://en.wikipedia.org/wiki/Disc_(galaxy)) and closer to the center. Population II stars are likely to be found in the [halo](https://en.wikipedia.org/wiki/Galactic_halo) and [spheroid](https://en.wikipedia.org/wiki/Spiral_galaxy#Galactic_spheroid), including globular clusters. Some "intermediate" Population II stars may be in the thick disk. Population II stars formed earlier, when the Milky Way was still strongly spherical, while Population I stars formed later when the flatter disk component had formed. See also [Populations & Components of the Milky Way](http://www.ifa.hawaii.edu/~barnes/ast626_95/pcmw.html) and [Ness & Freeman (2015)](http://arxiv.org/pdf/1511.07438v1.pdf).
I should note that the above refers primarily to the density of elements in the [interstellar medium](https://en.wikipedia.org/wiki/Interstellar_medium) and [giant molecular clouds](https://en.wikipedia.org/wiki/Molecular_cloud), which only indirectly lead to planet formation through the formation of protostars and their associated protoplanetary disks/nebulae. However, I would wager that this would still affect the composition of planets orbiting stars in a region with greater metallicity, given that molecular clouds eventually collapse to form stars and massive stars, in turn, enrich future clouds with heavy elements.
Additionally, [spiral arms are likely to contain more metals than other regions in a spiral galaxy](https://astrobites.org/2018/07/10/spiral-galaxies-show-their-metal/) because of the above feedback loop. This is believed to be largely because supernovae disperse heavier elements, but in the spiral arms, those elements are more likely to be absorbed by the denser gas of the region, enriching the molecular clouds and subsequently ensuring that stars that form in the region have higher metallicities.
As an example, see Figure 7 from [I-Ting Ho et al. (2017)](https://arxiv.org/abs/1708.04966) and [I-Ting Ho et al. (2018)](https://arxiv.org/abs/1807.02043); this shows the metallicity gradient in the spiral arms of [NGC 1365](https://en.wikipedia.org/wiki/NGC_1365) with the mean radial metallicity gradient subtracted out:
[](https://i.stack.imgur.com/KkKlR.png)
This is consistent with Henry & Worthy's trend of decreasing metallicity with increasing radius but adds additional structure to the gradient.
[Answer]
Actually I'm pretty sure everything heavier than Iron is produced when a [star goes supernova](https://en.wikipedia.org/wiki/Supernova_nucleosynthesis).
Hydrogen (1), Helium(2), Oxygen(8), Carbon(6), Neon(10), and Iron(26) are the [6 most common elements in the universe](https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Abundance_of_elements_in_the_Universe). These are all created with fusion in stars and not all stars burst into a supernova either.
So where to look? Where very large stars have already gone supernova as larger stars will have started with more material to fuse into heavier elements to begin with and then leave behind much larger quantities of heavier elements spread around. The more the merrier. So going in toward the center of a galaxy would significantly increase your chances of finding more elements beyond Iron.
I believe this same process happens when before a star collapses into a black hole. And stars have to be fairly large to finish up as a black hole, this means that prime real estate would be in the vicinity of black holes.
[Answer]
The study of Extrasolar planets. (Otherwise known as 'Exoplanets'), can already tell us a few things abut a planet lightyears away, just by observing it from earth. We can find a planet's size, distance from its star, even, in your case, what elements it contains. The most advanced way to observe these planets (That I know of) is by using a spectrometer.
**Spectrometers**
Nebulas, rocks, planets, stars and other such objects in space give off signals that can be intercepted by an instrument called a spectrometer, which separates the signals into different components. Basically, the spectrometers act like prisms, separating light into its colors. This is useful, because elements actually have a few certain colors that they give off. By spreading out the light given off by say, a planet, and we find that we can see only certain colors, by matching the colors to their elements, we can see what elements the planet has. All from the surface of a planet, observing another, lightyears away.
Source: <http://curious.astro.cornell.edu/physics/56-our-solar-system/planets-and-dwarf-planets/general-questions/199-how-do-we-know-what-other-planets-and-stars-galaxies-etc-are-made-of-intermediate>
] |
[Question]
[
My titled question was, can a planet without one or more moons be habitable?
In more depth, how would that planet be affected overall, without the moon to affect the tides and without providing light during night?
How badly would oceans/seas be affected? could life be sustainable within them (fish, algae, etc.)?
Lastly, would the atmosphere be majorly affected, much stronger or weaker than would otherwise be possible on said planet?
I already know that the heat reflected by the moon is to insignificant to truly affect the heating of the planet.
From a writer's perspective, a planet like this is an interesting concept because to humans it would be a foreign idea; stars would be that much more visible at night as well as it would be very, very dark.
[Answer]
There's no reason to assume that lacking a moon would cause a planet to be less inhabitable. Animals that rely on the phases of the moon for parts of their lifecycle (i.e animals that breed only during a full moon) wouldn't do so well on such a planet, but diurnal animals probably wouldn't be bothered at all.
Oceans and seas would not be affected at all, really. Plants and animals that live in tidal zones on Earth might not be able to live easily there, but other plants and animals would be just fine. There would still be currents and tides (though maybe not as strong) due to the rotation of the planet and the gravity of its star.
The atmosphere wouldn't be affected much, either. [Apparently the sun has a greater tidal force on the Earth's atmosphere than the moon does](http://www.scientificamerican.com/article/does-the-moon-have-a-tida/). As for oxygen production by plants, it might be beneficial for them not to have to deal with moonlight - [plants avoid moonlight in order to avoid disruption of their circadian rhythms](http://www.thenakedscientists.com/forum/index.php?topic=11315.0).
One thing to note is that without a large moon, there is nothing to stabilize a planet's axial tilt. [Without the moon, the Earth's axial tilt could have varied by as much as 85 degrees](http://www.space.com/12464-earth-moon-unique-solar-system-universe.html). By itself this is not enough to make a planet uninhabitable—the tilt would only vary over the course of thousands or millions of years. This is, however, quick enough that it could cause significant issues for the development of life on a planet. Life took quite a long time to advance beyond the most basic forms which would not have been able to survive the plunge into a perpetual day/night that a significant axial tilt could have caused.
[Answer]
This is a very interesting case. A lot of factors are in play here. In the absence of a moon, all other factors would become more important than they would have, if a moon was present.
* Tides in the oceans can still be caused due to gravity of the parent star. If the planet is situated in the inner side of the [goldilock zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone), the gravitational effect of the parent star would be much greater than it would be, if the planet was situated on the outer edge of the habitable zone. So yes, if the planet is located near the inner edge of the goldilock zone, the parent star can create the tidal effect.
* However, being located near the inner edge of the habitable zone also means more radiation and **much** stronger magnetic storms to deal with, which would easily rip off any protective shielding around the planet (aka ozone layer) while also blowing away its atmosphere. The result would be a dead, desert planet.
* Or you may have a planet which is located where Earth is located, and have a Jupiter-like massive planet at a distance as Mars is to Earth. I haven't researched how that would fare, but I *think* you could get some weak tides from the gravitational tugging between that Jupiter and the parent star. This would be better as you would not have that solar storms devastation to deal with and your planet can retain its atmosphere and an ozone-like layer.
* Yet another possibility arises if you have [rings](https://en.wikipedia.org/wiki/Ring_system_(astronomy)) around your planet. These rings could (at least in theory), provide you with some tidal effects.
Note that all the above possibilities are discussed for the sole sake of having tides in the oceans. There is no reason why primitive life cannot develop on a planet with no moon. However having *life* on a planet and having *complex, intelligent life* on the planet are two vastly different things.
You have to have an ozone layer around your planet if you want to shield it from the deadly high energy radiation. In the absence of this layer, you **can** have primitive life in the oceans but you cannot have land-based life forms.
For intelligent life, you also have to have a gravitational shield against meteors and comets. Here on Earth, that shield is provided by Jupiter. You need to have some sort of protective shielding against bombardment of massive meteorites. Having a Jupiter in the *vicinity* is the best way to provide that.
For intelligent life, you would also require a strong magnetic field. Otherwise the solar storms would rampage your planet and create mass extinctions over and again, effectively stopping any evolution directed towards more complex life forms.
# Conclusion
Yes, you can have *life* on a planet without a moon. But having intelligent life on a planet without a moon is a complex matter. In theory you can have such a planet. But a lot of things would have to be just right for it, and nothing wrong. There is a reason why scientists have not found signs for any life (let alone intelligent life) anywhere other than Earth, so far.
[Answer]
>
> My titled question was, can a planet without one or more moons be
> habitable?
>
>
>
**Habitable? Totally.** Would life evolved in it? Probably. Always assuming that other conditions adjust to it…
>
> In more depth, how would that planet be affected overall, without the
> moon to affect the tides
>
>
>
Just life marine without tides XD.
>
> and without providing light during night?
>
>
>
Light is useful, but it **is not necessary for life**. It's highly probable that the first life on Earth emerged without photosynthesis by using chemical and thermal energy.
>
> How badly would oceans/seas be affected? could life be sustainable
> within them (fish, algae, etc.)?
>
>
>
**Not badly**, probably would be **different**. Also, there are other phenomena that could make water currents (winds, thermal, temperature gradient, etc.).
>
> Lastly, would the atmosphere be majorly affected, much stronger or weaker >than would otherwise be possible on said planet?
>
>
>
The Moon [does have an affect on the atmosphere](http://www.scientificamerican.com/article/does-the-moon-have-a-tida/), but it is **not vital for life**. The magnetic field has [a more important effect](http://www.space.com/11187-earth-magnetic-field-solar-wind.html).
>
> I already know that the heat reflected by the moon is to insignificant
> to truly affect the heating of the planet.
>
>
>
Yup. Probably it has a more important effect in protecting from **meteoroids**.
>
> From a writer's perspective, a planet like this is an interesting
> concept because to humans it would be a foreign idea; stars would be
> that much more visible at night as well as it would be very, very dark
>
>
>
It would affect, not just aesthetically, but also the **culture** of the inhabitants. Just think:
* How many **poems and literature** refers to the Moon.
* The Moon it is a small step into **space exploration and astronomy**. Without it, probably those things would be more slow.
[Answer]
This question is similar to, but not a duplicate of, two earlier Worldbuilding Stack Exchange questions,
* ["What would be the consequences for Earth if the moon
disappeared?"](https://worldbuilding.stackexchange.com/questions/14755/what-would-be-the-consequences-for-earth-if-the-moon-disappeared) and
* ["Can I significantly shorten the days on a planet that can support
human life?"](https://worldbuilding.stackexchange.com/questions/19728/can-i-significantly-shorten-the-days-on-a-planet-that-can-support-human-life/19765#19765).
The title of the second question gives a very important effect that no one has mentioned yet on this question. Without a big moon days would be shorter. According to this post from ScienceBlogs, ["The top 5 things we'd miss if we didn't have the moon"](http://scienceblogs.com/startswithabang/2013/08/08/the-top-5-things-wed-miss-if-we-didnt-have-a-moon/),
>
> A day on Earth would be much, much shorter; only about 6-to-8 hours, meaning there’d be between about 1,100-1,400 days in a year!
>
>
> Our 24-hour-days may seem like they don’t change from one year to the
> next. In reality, the change is so tiny that it took centuries to
> perceive, but the Earth’s rotation slows down ever so slightly over
> time, thanks to the tidal friction provided by the Moon. The slow-down
> is very, very slow (on the order of microseconds-per-year), but over
> millions and even billions of years, it adds up!
>
>
>
[…]
>
> But in the meanwhile, we can use what we know to extrapolate backwards
> in time, and we find that in order to get a 24 hour day today, the
> Earth had to have been spinning much faster in the past: about
> three-to-four times as fast more than four billion years ago! If we
> didn’t have a Moon — if we never had our Moon — the day would be much,
> much shorter than it is today, and our planet would have a larger
> equatorial bulge, much more flattened poles, and over 1,000 days in a
> year!
>
>
>
I think at minimum, there would be hellishly high winds.
The same post also cites as the most important effect the stabilization of the axial tilt, already mentioned in Rob Watts' answer:
>
> Thanks to our Moon, our axis stays tilted between 23 and 26 degrees
> over time, even over hundreds of millions of years! But without our
> Moon, there would be nothing preventing catastrophic shifts in our
> rotational axis. It’s probable that sometimes, we’d be like the planet
> Mercury, orbiting in the same plane as our rotation, and having
> practically no seasons due to our axial tilt. At other times, we’d
> possibly be as extreme as Uranus, rotating on our side like a barrel,
> having the most extreme seasons imaginable!
>
>
>
[Answer]
## Would there be life?
>
> Amino acids are small, highly reactive molecules composed of 20 to 30 HCNO atoms. When amino acids link together in strings they form proteins. Proteins govern chemical reaction rates and form the structural material for cell parts.
>
>
> Most importantly, they can form into microspheres when heated, which serves to separate chemical reactions and processes. The problem is that with the vastness of the Earth's oceans it is statistically very improbable that these early proteins would ever link up. The solution is that the huge tides from the Moon produced inland tidal pools, which would fill and evaporate on a regular basis to produce high concentrations of amino acids, who then linked themselves into macromolecules.
>
>
>
As we can see from [this lecture](http://abyss.uoregon.edu/%7Ejs/ast121/lectures/lec25.html) life may have evolved specifically in the tidal pools caused by having a large moon. There are other theories that state this could have happened near thermal vents, so you could have life, we don't know.
There's a secondary question here:
## Would life have moved on to land without intertidal zones?
Possibly not - need sources.
## Is a lifeless planet habitable?
That depends on how you're defining habitable, but in short: **Not to us**. A planet without plant life similar to ours is unlikely to have the right balance of oxygen/nitrogen/etc in the atmosphere for us to be able to just turn up and breathe. You're going to have to wait a few thousand (maybe million) years after seeding it with photosynthesising plants to give an atmosphere mammals could survive in.
[Answer]
The importance of the moon in stabilizing the Earth's axis (obliquity) and hence its climate has been grossly overrated in the past.
More recent research indicates (and calculates, models) that the stabilizing effect of the moon is actually rather small, that the stabilizing gyroscopic effect of Earth's rotation itself is much greater, and that any possible significant climate changes resulting from the absence of a large moon would rather be in the course of hundreds of millions of years, i.e. longer than present climate changes on Earth by other cause.
See for instance: Obliquity variations of a moonless Earth (2011); by Barnes, Lissauer, Chambers; <http://www.sciencedirect.com/science/article/pii/S0019103511004064?via%3Dihub>
] |
[Question]
[
I've been trying to come up with a scenario in which space stations and lunar bases are established but are considered controversial. I sort of figure that if corporations started mining the moon that some people would start freaking out about it having an effect on Earth despite the fact that the moon would have to be extensively mined before it had any real effect on things like the tide.
My question is that given roughly a hundred years to account for improvements in space transportation and nuclear energy would the mining of the moon for helium 3 for use in fusion generators possibly be profitable enough to justify the cost and risk?
[Answer]
This isn't a perfect source but Charles Stross includes Lunar He3 mining in his list of scifi-bunk.
<http://www.antipope.org/charlie/blog-static/2015/12/science-fictional-shibboleths.html>
Short answer: No. There's better materials to do fusion with.
>
> Now for a biggie: Mining the lunar regolith for Helium-3. This is junk
> science on stilts and it just keeps coming back from the dead. It's
> also a barrel of past-their-sell-by-date red herrings that keeps being
> rolled out by space cadets whenever they're challenged to produce an
> economic justification for space colonization. Here's why it's crap
> ...
>
>
> Fusion, the Jenga-pile begins, is the energy source of the future.
> (This may or may not be true: I for one hope it is.) However, the
> easiest form of reaction you can run in a fusion power reactor is
> deuterium/tritium. This tends to release most of its energy in the
> form of neutrons, which can ideally be captured and used to breed more
> tritium fuel and produce waste heat to drive a turbine generator. The
> problem with neutrons is that they're rather penetrating and when they
> slow down enough to be captured by an atomic nucleus they transmute
> it, often into an unstable isotope. D/T reactors therefore look likely
> to suffer from one of the same problems as fission reactors:
> neutron-induced structural embrittlement and secondary activation
> producing high level radioactive waste.
>
>
> Aneutronic fusion—which hasn't actually been tested yet in even a
> prototype research fusion reactor—offers the possibility of running on
> other fuels and producing <1% of its energy output in the shape of
> neutrons. Helium-3, an isotope of helium consisting of two protons and
> one neutron, can in principle be fused with deuterium instead of the
> (radioactive) tritium and produce power with a far lower neutron
> output—the energy-bearing product of the reaction is a proton, which
> can be contained using magnetic fields. Hence the interest in He3
> fusion reaction designs.
>
>
> The first problem with He3 reactors (after—cough—we don't know how to
> build one yet) is that He3 is incredibly rare. It costs on the order
> of millions of dollars per kilogram and the global supply is very
> restricted; there's certainly not enough of it to power a global
> energy economy even at today's levels. But there is some evidence that
> He-3 produced in the sun and emitted in the solar wind may be captured
> in the Lunar regolith. The plan, per the proponents of lunar
> colonization, is therefore to build vast strip mines on the moon to
> extract this vanishingly rare moonshine/pixie dust and export it to
> Earth to power our 22nd century energy economy. And of course
> estimates that we could power our current level of energy use by
> processing 4 million tons of lunar regolith per week are music to the
> space cadets' ears because, well, it means big engineering and thus
> big steely-jawed engineers with slide rules and socket wrenches on
> hand to repair the mining machines when they break. Space colony
> justified!
>
>
> Except this is moonshine and junk. Firstly, we don't have an
> aneutronic fusion reactor, much less a planetary base load capacity
> driven by aneutronic fusion reactors in need of fuel. Hell, we don't
> even have a working D-T fusion reactor that can produce surplus
> energy; ITER isn't due to achieve first plasma until 2020 and won't
> begin D-T reaction operations before 2027, and the Wendelstein 7-X,
> while promising, is a generation behind (roughly equivalent to where
> the Joint European Torus was in the 80's).
>
>
> But let's jump the gun. Let's assume we do have a working fusion
> reactor. Let's even assume we've put in the decades of legwork
> required to build a working aneutronic fusion reactor—it's worth
> noting that aneutronic reactions have to run about an order of
> magnitude hotter than D-T fusion reactors can achieve, and they're
> already in the 100 million Kelvin range. But let's play make-believe:
> are we then going to see large-scale lunar regolith mining to fuel the
> beasts?
>
>
> Nope.
>
>
> Because it turns out that if you can build an aneutronic reactor,
> then, subject to some considerable amount of fine tuning, you can run
> it on fuels other than sparkly lunar regolith moonshine and pixie
> dust—notably the proton-boron-11 cycle and the proton-lithium-7 cycle.
> Both these fuel cycles are aneutronic and run on isotopes that are
> readily available here on Earth in sufficient quantities to power our
> civilization for some millions of years without trying to build
> massive engineering infrastructure on an airless rock. There's even an
> aneutronic fusion cycle that relies on proton-nitrogen fusion,
> although it produces less energy and is even harder to achieve.
> Nitrogen and hydrogen ... nitrogen makes up about 80% of our
> atmosphere, and hydrogen makes up about 15% of our hydrosphere, so
> we're not running out of either of those fuels any time soon, either.
>
>
> Upshot: any work of SF that takes "Lunar 3He mining" as an economic
> premise is about as plausible as one that assumes combustion powered
> by the release of phlogiston.
>
>
>
[Answer]
Nobody really knows.
First, the high value of He3 assumes commercial scale nuclear fusion. This is probable, but unknown. We could in theory cover our needs with solar IIRC. And there are still some unsolved issues with fusion power. Although cleaner He3 fusion **would** help.
Second, the full costs of lunar mining are unknown largely because the exact method that is best for doing so is unknown. For example, would we need to establish an actual moon colony or could robots with remote oversight from Earth handle it? My guess would be that eventually the development of technology will push costs down enough. But obviously the costs also depend on the volume of the demand which depends on the proportion of power that comes from He3 fusion. Which depends on what other energy sources we use and how much.
Third, we might find a cheaper source of He3. It is not strictly speaking true that it doesn't exist on Earth. Thermosphere and exosphere, the highest layers of atmosphere, do have solar wind derived Helium as a component. Extracting it from there might be cheaper than lunar mining.
That said, it is considered likely, since at the moment it seems the value of He3 will go up and the costs of lunar mining will go down in the future.
Certainly, if, to pick an entirely random example, China would want to go to the moon as a prestige project to prove its super power status, mining He3 could be used to pay some of the costs. Similarly the development of the necessary mining technology would have value of its own. So strictly speaking it might not be necessary for it to be profitable enough to pay the full cost.
[Answer]
**Absolutely, if you want to power things on the moon.**
While transporting things from the Earth to the Moon might not be terribly expensive, given the limited depth of the Moon's gravity well, transporting *anything* from the Earth to the Moon will break the bank. With the development of fusion power, it would make far more sense to mine helium on the moon for use in your nuclear reactors.
There's a major reason to want to power things on the Moon, as well: it's far cheaper to get things into orbit around the Earth if you start from the Moon. If people are serious about building orbital platforms, spacecraft, and the like in bulk, exporting the entire manufacturing process, from ore mining through final fabrication to the Moon could result in huge savings.
**If you're already mining it on the moon, it would almost definitely be worth exporting to Earth.**
Once you've got a diversified mining industry in place on the Moon, it would almost definitely be worth exporting that Helium to Earth. The Moon's gravity well is shallow enough that you could easily launch capsules to Earth using a large gauss gun firing tangentially to the Moon's surface. That would probably be your main expense, given that packaging and parachutes could be constructed from Lunar materials and fabricated on the Moon.
[Answer]
Based on really basic estimates, I found that helium 3 has an approximate value of $1050 per liter based on this [Wikipedia page](http://www.explainingthefuture.com/helium3.html). Assume the mining operation costs about 1 trillion USD per year to set up and maintain on the moon. According to this [page](http://www.explainingthefuture.com/helium3.html),
>
> As a result, it has been estimated that there are around 1,100,000 metric tonnes of helium-3 on the surface of the Moon down to a depth of a few metres.
>
>
>
This gives us an approximate value of 997903214 liters of dry helium 3 on the moon's surface. Using the \$1050 figure we calculated earlier, the profit of this system yields \$1047798400000, or 1047798.4 trillion USD. (This all, of course relies on whether the US is the only country mining this valuable resource).
Also, you don't specify how safe the system for mining is, so I won't make any guesses there, but to me, this system seems well worth it.
[Answer]
See G. Harry Stine's "The Third Industrial Revolution" It's quite dated, but conceptually it will be of benefit.
The answer is not He3, but rather just mass. Stine advocates solar power, and microwave links back to earth, build by factories at the Earth Moon leading and trailing Lagrange points. It requires a reusuable heavy lift launcher for bootstrap purposes. The Rand Corporation figured about a trillion spent over 20 years for the infra-structure (1975 dollars) then GW solar units at a couple billion each. Units would link with feedback phased array microwaves. Ground antennas would be about 10 miles across but the power density is low enough that you can still use the area for grazing.
Jerry Pournelle and Ben Bova have novels set in this style of future with somewhat different outlooks on the economics.
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.