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Say there is a humanoid creature. This humanoid creature is very tall, with elongated arms and legs. The creature has legs that end in, rather than feet, complete points (similar to a spike).
Would this creature be able to maintain balance and walk or run without problems? If there are problems, what would they be and what would there solutions be?
[Answer]
## **Yes**
---
**Traction**
If a creature like this evolved, the pointed leg would simply be a specialized [hoof](https://worldbuilding.stackexchange.com/questions/42475/are-hoofed-bipeds-feasible). The point can and likely will be segmented, why? Because the spike hoof would just *stab the ground,* if anything it would have more traction. Since you want them to be bipedal, then keep in mind that they would need to stab the ground in order to stay up (that or have balancing mechanisms; see further down). The concept is similar to the Striders in Half-life but not tripodal.
[](https://i.stack.imgur.com/k49A7.png)
This means that their environment has am easily stabbable ground layer. Your options here are;
1. **The Desert**. A ground layer of sand would make loose and yet reliable area for the spike to pierce. Keep in mind that if you go with this solution, they would likely be nocturnal to avoid burning there feet on the hot sand.
2. **The Arctic**. Similar in concept to the desert solution, the icy plains of the north would provide a stronger but harder to pierce ground.
3. **The Jungle**. In a jungle, where there is a layer of decaying leaf litter, a creature like this would do well, although it would likely be a lot lighter. Think a spider monkey or a lemur.
**Balance**
A creature with spike hoofs would obviously have a big problem with running, even worse than humans. They would not be efficient runners, long or short distance and would never be able to jump.
That is if you're dead set on having there arms be human. If your willing, there are a plethora of solutions to help balance.
1. **"Wings"**. [Current theories](http://phenomena.nationalgeographic.com/2011/12/14/deinonychus-and-velociraptor-used-their-killing-claws-to-pin-prey-like-eagles-and-hawks/) on the velociraptor suggest that they may have used the feathers to balance themselves while hooked to prey. If these spike people human in a similar fashion, then their arms may evolve in a similar fashion.
2. **Wings**. remember the [Pterosaur](https://en.wikipedia.org/wiki/Pterosaur)? its arms evolved into wings and its feet into weapons. In my question; [Anatomically Correct Angels](https://worldbuilding.stackexchange.com/questions/25466/anatomically-correct-angels) a similar solution was used. It's quite possible that angels may instead evolve their feet into harpoon like structures.
3. **Beaks**. While not exactly what you're looking for, a beak-like foot would solve the problem of balance. Going back to what I said about segmented spikes, if the spikes open into multiple fingers (like a beak), then it would use the spike for hunting and the open spike for walking. While this solution isn't the most accurate to your image, it gives the creature more open doors in mobility. such as more efficient long distance walking and even possibly jumping!
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Walking and running shouldn't be too hard, although jumping would be harder and acceleration slower. The creature would also not be able to absorb the hit like we do when walking/running.
Standing idle would be near impossible though.
When running this creature would have to tilt forward.
standing up would be very difficult without a support as well.
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I was thinking about how there are some instances of convergent evolution between marsupials and placental mammals and was thinking about a parallel universe in which there is convergent evolution between marsupials and humans. In this universe a species of marsupial evolves at about the same time as humans to have the same intelligence as humans as well as walking upright on two legs. The humanoid marsupial knows how to control fire, use throwing spears for hunting, use stone tools, paint, and make boats. The humanoid marsupial originates in Australia but begins spreading beyond Australia at the same time that Homo Sapiens are spreading out of Africa. As Homo Sapiens and Humanoid Marsupials are spreading they meet in India
How would the humanoid marsupials and homo sapiens interact after coming in contact with each other?
[Answer]
This is all speculative, but given the scenario, neither species would be able to completely wipe out the other, seeing how far away the origin of either one is from the other. Ultimately, both sapiens would need to develop alongside each other.
Early humans weren't very intelligent. I'm talking about Homo Sapiens here. Even with the capacity for higher thinking, they weren't too different from other animals, with only a very primitive language and grasp on tools, and they would be extremely territorial. [Assuming human migration up to the point they meet](https://en.wikipedia.org/wiki/Early_human_migrations#South_Asia_and_Australia) is largely the same, the two species would have met in India between 80,000 and 120,000 years ago.
There are signs that Homo Sapiens and Homo Neanderthalensis (Neanderthals) weren't always on the best of terms, and probably cannibalized each other, like AndreiROM mentions, but the same is true for any differing tribe of Homo Sapiens, too. The appearance and similarities between two tribes didn't really factor in, and it was just a tribe mentality, similar to how modern day humans often still prefer their own race or country over another. Humans and Neanderthals also have left evidence that not all of their interactions have been violent. Depending on how your marsupial sapiens look and act, it's possible that the primate sapiens (humans) could either eventually develop some sort of mutual relationship, or all together try to eliminate each other—but it ultimately depends on the amount of resources. Considering the marsupials would come from Australia, it wouldn't be feasible for homo sapiens to outright eliminate them though.
Assuming that both sides survive first contact and there is a sizable population of marsupial sapiens on the Eurasian continent, the primate sapiens would go on to populate Europe and west Asia, while our marsupials could possibly hold onto East Asia, and even be the ones to migrate into the Americas, assuming there were similar pressures as in our own timeline. The separation probably won't be so clean, and there'd be tribes of both mixed in either region, which could either end up wiped out or tolerated long enough to develop.
If and when tribal societies evolve into more stable villages and cities, is probably when you can expect the relationship from both species to be much less extreme. There is the issue that the Silk Road might not actually exist, because even if both sides aren't constantly trying to eat each other, they still might not like each other enough to trade. This means that the benefits Europe had over Asia and the rest of the world (that eventually led to military domination), may not develop in the same way, and technological progress may stagnate for quite a while. The Black Death probably also won't happen in the same way that it did because diseases between the two species would rarely be compatible, so assuming Europe faces the same issues it was facing in our own timeline, they probably won't have the same dark miracle that reduced their population by so much and allowed the age of enlightenment to kick start.
Taking that into account, if Europe ever decided to cross the Atlantic, the Marsupials living in the Americas wouldn't suffer the same destruction by disease as the Native Americans did in our timeline.
What might happen with the marsupial sapiens that inhibit Australia and Asia? I can't tell. I don't know what sort of temperament they hold compared to humans, what sort of language they would develop, and so on. My assumptions on Europe are based on the idea that it would mostly be inhabited by humans, and there would be a pretty big buffer between them and the marsupials. However, it's easily likely that over time the Eurasian continent had both species mix around less cleanly than what my scenario implies. After all, it's not really likely that there'd be a hard wall between where one group or the other lives.
There are many different ways this scenario could play out, as you further advance their technology. There's also the issue of religion, and how the religion of one race would view the other, and what effect that would have on the future relations. There's no definite answer to this question, because we only have a sample size of 1 sapient animal.
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Well, this is pure speculation, but considering that Homo Sapiens and Neanderthals mostly (not always, but often) slaughtered one another (and they were cousins), not to mention man's treatment of other men throughout history, I would say that the only realistic interaction would be war.
The humans would probably fail to realize that the marsupials are "sapient" (and would probably not care even if they knew - moral concerns were not big on the list of our ancestor's list of things to worry about) and maybe even ***hunt them for food***. Cannibalism is definitely something which a lot of cultures participated in, so it's not a stretch that they would eat other sapient species.
As species they would probably fight over resources, and generally slaughter one another. Every once in a while individuals of these races might meet under circumstances in which they would not immediately try to kill one another, and maybe, over time, some understanding could be come to.
Remember that back then humans didn't speak a language - more of a proto-language. Grunts, gestures, etc. This will make it difficult for two species with very different emotional responses and expressions to communicate.
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Marsupials could never have evolved to have human-like intelligence/sapience, because of how the brain development of mammalian fetuses and infants works.
Human babies are born with huge but still very immature brains, and they really need both the pregnancy to grow that much brain mass and the lengthy childhood to mature it. I can't see a newborn marsupial, with the characteristic tiny size compared to its mother, either already having a sufficiently large brain, or growing it later in the pouch. Being protected and warmed and receiving milk is a nice thing, and also both necessary and sufficient for a smaller-brained marsupial to grow up, but the delicate work of growing a large brain requires the additional help of having one's oxygenation and immune system taken care of.
Same reason that there are limits to the brain size and therefore the intelligence of birds, because they need to secure the brain oxygenation while in egg.
The thing about bird chicks is from Human Evolutionary Biology by Arndt von Hippel, and I don't remember where I got the idea that marsupial brains are restricted in size, probably something I learned around the same time as I heard about the concept of neoteny, many years ago.
Little search on the topic turned out a paper that claims there is not much difference between marsupials and non-primate placental mammals, because apparently most brain growth in marsupials occurs during lactation... <http://www.pnas.org/content/107/37/16216.full>
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
In this world a secret society "farms" people with desired features (personality appearances etc.). They have ectogenesis of course; but they can't afford personnel to take care of the "products" until they reach maturity (14-20 years depending on the end uses). What kind of machines/software are needed to raise them in an appropriate way?
Consider that these people will be reintroduced into an already existing society and therefore need not be capable to form a new one on their own. In particular they need at the very least: language, self-care, basic knowledge of science/literature, basic social skills.
I know this is a common tech in works that feature embryo space colonization but I am not aware of any that describe the technology in any useful details.
[Answer]
**Note: if this answer is too long, you can skip to the main conclusion section below**.
We can explore what sort of robots we would need by looking at the absolutely critical factors that children need to grow into mature adults with the core behaviours you mentioned, and whether/how robots can facilitate the same.
There is no magic bullet to this: *no* collection of robots can absolutely raise a perfect group of children. There are genetic, congenital and even accidental factors involved that can strongly impact lifetime development that you can't necessarily weed out completely. Nor can you expect a thoroughly perfect answer: children's development is still very much an active research area, and there are few certainties in this regard.
Assuming only that a *select* group of children are introduced into this artificial environment that meet a minimum bar (no damage, no genetic diseases, etc.), then we can proceed on that assumption to flesh out what factors are needed to provide future care.
**What I'm Going to Ignore**: For the purposes of this question, we will assume a certain level of common sense e.g. that actively dangerous substances or materials are prohibited in the child rearing environment, that it meets a minimum standard of human care (e.g. no extreme sensory deprivation, it is light, not too hot, not too cold, etc.), and that some care is taken for granted (i.e. age-appropriate consumption and regular diaper changing are enforced, but everything else is not guaranteed).
All we want is to know what the bare minimum an *active agent* needs to provide to stimulate the relevant skills - in other words, we will also ignore needless frills that *encourage* faster development but are not *required* to stimulate the necessary skills, like, say, making them listen to Mozart at an early age.
## Sensory Stimulation
**tl;dr** *Robots need to have human-like skin but don't have to look human, though it is best if they do*.
There is some evidence that suggests that sensory stimulation between mother and child between an active agent and children plays an important role in infant's long-term social development. [Foals exposed to limited maternal contact post-partum](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0005216) experience "patterns of insecure attachment to their mothers (strong dependence on their mothers, little play) and impaired social competences (social withdrawal, aggressiveness) at all ages. "
[Harry Harlow](https://en.wikipedia.org/wiki/Harry_Harlow) explored the mother-child bond among rhesus monkeys. Part of his experiments involved rigging up *inanimate surrogate mothers* (excerpts taken from his Wikipedia page, with points for citation removed except where marked as needed):
>
> ... Harlow created inanimate surrogate mothers for the rhesus infants from
> wire and wood. Each infant became attached to its particular
> mother, recognizing its unique face and preferring it above all
> others.[citation needed] Harlow next chose to investigate if the
> infants had a preference for bare-wire mothers or cloth-covered
> mothers. For this experiment, he presented the infants with a clothed
> mother and a wire mother under two conditions. In one situation, the
> wire mother held a bottle with food, and the cloth mother held no
> food. In the other situation, the cloth mother held the bottle, and
> the wire mother had nothing.
>
>
> Overwhelmingly, the infant macaques preferred spending their time
> clinging to the cloth mother. Even when only the wire mother could
> provide nourishment, the monkeys visited her only to feed. Harlow
> concluded that there was much more to the mother-infant relationship
> than milk, and that this "contact comfort" was essential to the
> psychological development and health of infant monkeys and children.
> It was this research that gave strong, empirical support to Bowlby's
> assertions on the importance of love and mother-child
> interaction.[citation needed]
>
>
> Successive experiments concluded that infants used the surrogate as a
> base for exploration, and a source of comfort and protection in novel
> and even frightening situations. In an experiment called the
> "open-field test," an infant was placed in a novel environment with
> novel objects. When the infant’s surrogate mother was present, it
> clung to her, but then began venturing off to explore. If frightened,
> the infant ran back to the surrogate mother and clung to her for a
> time before venturing out again. Without the surrogate mother's
> presence, the monkeys were paralyzed with fear, huddling in a ball and
> sucking their thumbs.
>
>
>
Wile Harry Harlow's later experiments are largely considered unethical (he subjected rhesus infants to extreme long-term sensory deprivation for up to two years, with no light in a confined environment), it would appear that having robots that mimic the sensation of skin are in some ways required for children to be socially well-adjusted later on.
Such robots would be best off mimicking the characteristics of maternal skin as much as possible. For example, [new mothers' skin is responsive to their babies' temperature](http://www.scientificamerican.com/article/infant-touch/). You would therefore need to incorporate sensors for body heat, a layer of soft material designed to be pleasant to the touch on the outside, and an internal source of heat.
But importantly, it appears that robots need not look human. Feral children recognise animal caretakers as valid caregivers and will accept their care, a fact born out simply by [the surprisingly large number of feral children out there](https://en.wikipedia.org/wiki/Feral_child). It is, however, in the children's best interests to have robots mimic humans physiologically, on the premise that substantial differences in physiology can lead children to imitate their caregivers and try (for example) to walk differently than regular humans - this is also born out simply by looking at the histories of feral children.
Note that this section doesn't talk about, for example, toys, playthings or other ways to keep children occupied - only what is needed on the robot's part to facilitate social ability. I presume the environment will take care of providing toys and opportunities for play - humans need to be kept entertained, after all, and this falls into the level of common sense that I presume the environment will provide.
## Motor Development
**tl;dr** *Robots don't have to do anything to force motor skills to develop*. Note: see concluding paragraph of last section for note about presence of toys.
Surprisingly, motor development is one of those things that babies seem to learn pretty much on their own. [All babies learn how to climb stairs by the same age](https://psych.nyu.edu/adolph/publications/2007Berger%20S%20E%20Theuring%20C%20%20Adolph%20K%20E-How%20and%20when%20infants%20learn%20to%20climb%20stairs.pdf), regardless of the presence of stairs in their house. While there is evidence to suggest that [cultural differences can stimulate onset of motor development in different ways](http://journals.humankinetics.com/AcuCustom/Sitename/Documents/DocumentItem/5316.pdf), it is difficult to find evidence that motor development itself is something that actually requires an active agent.
Since it appears that all babies need for motor skills is an actual environment to explore, we can assume that this is subsumed in the environment and nothing is needed on the robots' part.
## Nonverbal Communication
**tl;dr** *It's not clear whether robots actually need to have facial expressions to help facilitate picking up on nonverbal cues. I suspect it is not necessary if children are able to play with each other on a regular basis*.
There is only one notable and possible exception to the conclusion reached in the section on motor skills: the development of facial muscle control - or oral motor skills in the literature - is [still poorly understood](https://www.down-syndrome.org/reports/310/).
According to [R. S. Feldman in his book](https://books.google.com/books?hl=en&lr=&id=OwK5BgAAQBAJ&oi=fnd&pg=PA3&dq=The+Development+of+Nonverbal+Behavior+in+Children&ots=j473P0nQni&sig=lfMoSGq5OvsSl-02LNdSoffSJks#v=onepage&q=The%20Development%20of%20Nonverbal%20Behavior%20in%20Children&f=false) who in turn cites authors Freedman, Charlesworth and Eibl-Eibesfeldt who conducted a series of experiments in the 1970s, facial expressions between congenitally blind and sighted children develop in the same way - they are *innate*. What we *don't* know, however, is to what extent nonverbal communication is *acquired* - Feldman cites evidence to suggest that it is more innate than acquired using cross-cultural studies, but ultimately admits this isn't as well-explored as we would like.
Children respond to nonverbal cues in different ways at different ages. Four-month-olds, for example, are "more expressive when their mothers are facially active" and can "respond to bizarre deviations from normal facial expressions such as length 'deadpan' expressions". One-year-olds, on the other hand, are more acutely aware of facial expressions and can rely on the facial expressions of their mothers when placed in a position of uncertainty to make a decision.
It isn't clear if it is *necessary* to incorporate the ability to provide facial emotions into our robots to encourage nonverbal communication. It would help, obviously, but as I've stated, we're only interested in what is *required* on the robot's part to produce this.
Based on the limited evidence I have, I am not convinced that our robots need to exhibit facial emotions. Children are sensitive to verbal cues (such as pitch and tone) as well, after all, and I suspect that encouraging play between children will more than allow them to develop the finer aspects of this art. We have already removed children with conditions known to delay or adversely affect development from our group, so this should be fairly inclusive overall.
## Language Acquisition
**tl;dr** *Robots do need to speak and be able to speak like normal human beings. They need to be programmed to speak to children frequently and often, and they need to be able to communicate contextual warnings using pitch and tone*.
Linguists universally agree that all children learn languages in the same way, regardless of the language or dialect used. Children [will learn the language spoken around them](http://linguistlist.org/ask-ling/lang-acq.cfm#process), according to Indiana University's Linguistics Department - deaf children will even pick up sign language if exposed to it.
Speech and language are separate creatures. Children are capable of speech as their motor development continues to grow, while language involves the articulation of valid sentences. Languages are learned gradually, mostly through imitation but potentially aided by correction and frequent engagement.
Therefore, any artificial robot or environment must expose children to coherent and articulate language. This requires, at the least, the ability to handle complex natural language processing, the ability to provide context by tone and pitch, and a solution to the [cocktail party effect](https://en.wikipedia.org/wiki/Cocktail_party_effect) if robots are handling multiple children. At some point, obviously, robots will need to be able to respond to children's questions meaningfully, so this goes without saying.
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## Higher-Level Processes, or The Murky Area of Parenting
**tl;dr** *Your robots would need some mechanism of resolving ethical dilemmas, and a means enforcing authority within the context of prescribing right behaviour without permanently damaging the children's ability to think independently, so that they can teach children who are willing to learn. This is really difficult - possibly nigh impossible - and an alternative remote human / robot on-site solution is advocated*.
Now we come to the more difficult aspect of raising children: how should our children and robots embrace the concept of authority? This is relevant: in the long term, authority is what gets children to do what they don't want to do, including learning new things.
A warning: I wish I could still offer peer-reviewed studies from this point onwards, but this is now simply too big a field to identify definitive consensus. This is the part where we make educated guesses and draw on our natural instincts of future or current parents.
First, it is absolutely imperative that some notion of authority is put in play. Our children need to be potty-trained and will not do so of their own accord, for example, while our robots need to be able to handle defiant behaviour (as parents of toddlers in the Terrible Twos learn).
At the age where children can conceive of such abstractions, one obvious model is to offer punishment/reward schemes to facilitate good and bad behaviours. This model was in vogue during the behaviourist paradigm of psychology - however, a bird's eye view of recent thought in this regard tends to favour the idea that [recognising positive behaviour](http://www.hindawi.com/journals/tswj/2012/809578/) is more important than punishing negative behaviour, and has long-term benefits in terms of emotional stability.
For this to happen, though, the robot needs to be able to provide appropriate recognition and more importantly *recognise* positive behaviour. I can think of two ways for the former to happen: either appreciative *tones* are used, and/or appropriate *treats* (a particularly tasty meal, permission to enjoy extended periods of time for playing, etc.) can be provided. The former provides children intrinsic incentive; the latter reinforces the notion that the robots provide value. You can even teach everything this way: people learn to fold clothes or math or advanced science by being given lessons and earning the robots' approval, as well as by allowing robots to encourage interest in a subject.
What I don't know - and what I suspect is a fairly remarkable challenge - is how your robots can recognise what constitutes good behaviour.
This is difficult: does standing up to a bully and injuring him in the process constitute good or bad behaviour? Your robots would need to have some mechanism of correctly defusing the situation, as well as realising who was at fault, and dispensing adequate justice. This is a task so difficult not even humans can manage it perfectly, as all of us can attest to at some point.
One very naive way to do it is to recognise conflict as behaviour that *impedes* a specific goal, and recognise good behaviour as classes of behaviour that *advance* said goal. Fighting, for example, is Bad because it impedes the goal of harmoniously working together. A robot could identify such behaviour and nip it in the bud at once. Performing an activity that allows another child to perform well is Good, and a robot can offer such assistance at once. (I presume computer vision has advanced to the point that robots can recognise these activities in the first place).
The problem with this is that it ignores underlying reasoning or motivation. Standing up to a bully can be argued to be good, even though it encourages Bad behaviour, as the reasoning - as a show of resilience - could justify it as being good. So what should the robot do? How does a computing machine evaluate *arguments*?
I'll go off on a tangent for a bit and point out that the recent trend of machine learning and big data is actually harmful to artificial intelligence approaches precisely because it is no longer sexy to teach AI how to *reason*, rather than make decisions based on patterns extracted from data. There has been work on this in the past - computers *can* apply logic to solve syllogisms if the rules are coded in the past, and probabilistic reasoning is a growing field - but if we one day want AI that is able to actually demonstrate critical thought and reasoning, more work needs to be done on stuff like, say, second-order logic.
So there you have it, the fatal flaw. **Unless robots can be taught how to evaluate reasoning and arguments, it is perfectly useless at raising children**. The only way out of this is some sort *deus ex machina*: a knowledge pill, for example, that instantly teaches kids how to do this or that.
Either that or you have an actual human watching the facility from afar, recognising good behaviour, providing emotional counseling, and in general doing all the things a robot can't do when the children reach past a certain age. I think this is the best possible compromise: have an actual human supervise kids through teleconferencing and use robots as 'arms' after the kids hit a certain age.
## Conclusion
The robots raising these children, at a bare minimum, need to be able to possess advanced language interpretation skills, human-like skin with appropriate thermal regulation and somewhat humanoid physiology, but don't really need to be able to mimic human facial expressions or even look all that human in terms of overall design. It's assumed that the environment and the robots are two *separate* entities: the environment includes a supply chain of relevant necessities, the robots are in charge of distributing it. Think of the environment as a store, and the robots as caretakers who sample from the store.
Based on the reasoning above, it is possible to have robots that can provide neonatal care, but not robots that can replace the role of teachers as children grow older unless AI becomes capable of evaluating arguments at a near-human level. (And then what's stopping a robot revolution? But I digress).
This makes it impossible for a *fully* automated farm to take care of children until they are 14, but a suitable mix of humans supervising remotely and robots on site can help resolve many of these issues and make the whole endeavour possible. I think this is actually the best way possible.
All of this is conditional on the assumption that people use common sense when handling babies (like making sure they have ample things to play with, have room to explore, are taken care of in terms of diaper changing and food, as well as are in well-lit rooms in moderate temperature conditions) and that children have the opportunity to regularly play with each other.
That should be more than enough for such an experiment to succeed.
*Disclaimer: I am not a trained psychologist or doctor, all of the above conclusions are my own and should not be taken as advice, all of the above research is fairly limited and only barely scratches the surface, so don't think it is perfect or complete because it really isn't. Some links may be behind a paywall*.
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Check out "Songs of Distant Earth" by Arthur C. Clarke.
He (briefly) describes how mankind sent out robot-ships to populate other worlds by cloning the first inhabitants.
One of the characters (many generations removed from the original settlers) considers how difficult life must have been for those first few generations, and how traumatized and socially dysfunctional they must have been due to being raised by machines.
That world is visited by actual Earth born and raised humans at one point and they immediately notice how differently the planet's civilization developed compared to Earth's. They surmise that certain concepts and ideas (such as religion, and war) were never taught to the colonists (they were excluded from the seed ship's databases on purpose). Anyone raised on Earth automatically acquired certain "baggage" these people were not burdened with, so to speak).
So yes, these ideas are discussed in some books, however it will all depend on what you envision.
I think it makes a lot of sense that people raised by machines would be more than a little dysfunctional from the point of view of someone who has been raised by a loving (or not) family.
However, these people will still form a society, embracing whatever ideals were taught to them by the machines, and maybe changing it a little bit as they go along (driven by instinct, or simply due to new and "revolutionary" ideas). Would this society be "functional"? Depends who you're asking, doesn't it?
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This is a tricky question to answer - how much freedom do you want the children to have? Will they ever see a fully grown human before they are introduced to society? Will they interact with other children, primarily to learn to socialize appropriately? Where will the children live? Will they be separated by age group? Will kids have "siblings" they are raised with? Will your robots be humanoid or more clearly robotic? This answer assumes the children will socialize with other children, they will have similar degrees of freedom that children have in fully human society, and that there could be a mix of humanoid and robotic caregivers.
Machines and software would essentially need to supply everything that human parents supply. Aside from the obvious physical needs (feeding, changing, bathing, etc.), babies and children need socialization. They thrive with other human contact, which could be simulated depending on how advanced/maternal your technology is, or the tiny humans could socialize with each other. (Check out "kangaroo care" for how human contact can help struggling preemies. A "Baymax" style robot might be really good for this application.) The machines would probably need to speak so a child could learn how to mimic sounds and learn to speak themselves. It might also be useful to include some sort of morality so that kids learn right from wrong.
Each child could have a primary "robot caregiver" that is responsible for the every day physical needs. "Teacher" bots could provide any required education, whether they were androids or more plain terminals. "Monitors" could supervise playtime/socialization with other children. A medic robot might also be a good idea - kids get hurt all the time.
Different parts of the environment could be automated - maybe the mirror greets the child every morning by name, reminds them to brush their teeth and wash their face, and to bathe or shower (check out SARAH from the TV show Eureka). Another level of automation could exist in the kitchen or cafeteria to make sure each child gets the appropriate amount of calories and nutrients. A desk could help a child find the answers to questions related to homework (not tell them the answer, but provide a resource where they can learn the material). The playground could have sensors built in to alert a monitor if a child got injured or got into a fight.
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First, you would want a machine programmed to emulate a human mother.
This mother bot's (for lack of a better word) job would be to protect and feed the child until it is old enough to do that itself.
Second, you would need a toy bot. This bot would not only be something for the child to play with, but it would also teach the child important social interaction through play. It also teach the child how to walk and basic human communication skills.
Eventually you would have to program your bot to introduce them to other children to test there social and communication skills.
As the children get older you introduce a teacher bot to instruct them in the more complex skills they would need to survive in your society and provide them with the necessary knowledge they need to be productive.
Even if you had all these bots and don't think this would work but it is a interesting question.
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North Korea has been a problem child in the world-at-large for longer than most of the world has been alive. The DMZ is one of the largest permanent military operations in the world, and every act made by the nation is scrutinized thoroughly and treated with the utmost suspicion. A sort of prejudice against any action taken by N. Korea has formed in the world consciousness.
Tomorrow, Kim-Jong Al\* usurps Kim-Jong Un in a violent takeover because he's sick of seeing his people in a famine state, he's sick of his people being denigrated, and he's sick of constantly wondering if eagleland will get sick of his nations antics and use nuclear weapons to make South Korea an island; but most of all, he's sick of the embargo that keeps him from upgrading from iPhone 6 to the iPhone 6s.
Given the current hostility towards anything North Korean, what would he have to do, and what would the world have to do, in order to bring North Korea gracefully into the world economy? At this point it seems like the mistrust would run too deep to gracefully let the nation become a world player.
\*A fictional "Second Prince" to Kim-Jong Un if you will
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First, open the borders for anyone to import outside goods and food. Open the communication pathways to let the outside world in, through radio, TV, unfiltered internet, etc. Let people see what it's really like outside, and then start bringing those goods in. Figure out how to stabilize power and food distribution.
Then open the borders for people to cross if they want.
Allow in journalists and let them take any photos they want.
Hire a PR firm to start cleaning up the countries image. Spin it to the media as a new country, with new branding, new flag, possibly a new country name, and new policies with regard to caring for it's people.
Open up to new businesses to open plants and factories in the country with favorable taxes to bring new jobs in.
Get rid of existing politicians (Except for Al of course) and hold elections. Local first so people can vote for people they know to get used to the idea of voting, and then for higher levels.
Appoint new, uncorrupted judges. Launch an investigation in to human rights violations, and dole out appropriate sentences with an emphasis on rehabilitation when possible.
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The first thing would be to try to feed the population well.
The second thing would be to open the borders with South Korea, allowing people to move freely north and south to visit loved ones, find work etc. and ease up a bit on the whole oppression thing.
Of course just flipping the switch from extreme totalitarianism to free and open economy generally doesn't go well and can actually cause more problems than it solves. So it would have to be a process. But starting with the first two items I listed would go a long way to engendering trust, though it would likely take a decade or more, constantly moving in the right direction, to build up trust. People will take a while to quit wondering if this is some kind of trick.
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"Uncle Al" has a long and steep climb, to be sure. It won't happen overnight.
He must immediately denounce North Korean ambitions of a "Democratic Federal Republic of Korea" (reunification on the North's terms), and express a willingness to engage in open negotiations regarding potential re-unification.
He should start by convening a constitutional convention. Among the invitees must be representatives from all areas of the country and all walks of life. He must also invite observers and consultants from all around the world. At the end of it, the current system must be declared null and void and the framework for system of, for, and by the people put in place. This will also be an important step in further talks of re-unification, if that remains a goal.
Given the concern regarding "eagleland will get sick of his nations antics and use nuclear weapons to make South Korea an island," no one would expect him to make any quick changes regarding the military. In fact, it would be foolish of him to dis-arm or draw back. However, he must demonstrate a gradual change from a threat posture to a common defense one. How this will happen is beyond my current scope.
I don't know of any precise thing he can say or do to get the embargoes lifted. He will need to seek out the leaders of other nations and engage them in open honest and friendly conversations, and take to heart any advice he gets. He needs to be cognizant to the fact that the first thing his people need is food- the iPhones 6s may have to wait a while.
[ Aside: Coming back to the real world, I think this will happen, possibly even in my own lifetime. Germany re-united, and the USSR is no more. Not tomorrow. Not next year. Not in an instant. But it will happen. ]
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The only threat North Korea posses is nuclear arsenal. It's military and economy are so weak, that it would take USA just few days to conquer them. The only thing they can do is to do as much damage with their nukes as possible in that short period of time.
So to simply start gaining trust of other countries, simply stop developing nuclear weapons, sell rest of the nukes to either China or US and allow anyone who asks to conduct open investigation if they are suspicious.
After that, international community should be willing to help the poor country in any way possible, if it means improving people's standard of living and maybe aiding in unification of North and South.
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Your fictional Uncle Al has a real problem. If he has studied history, he has learned about the fate of [Gaddafi](https://en.wikipedia.org/wiki/Muammar_Gaddafi), or the decades-long standoff between the West and Iran. He should assume that the West will settle for nothing less than regime change. So what can be done?
* Genuine regime change was mentioned by another poster.
* Fake regime change. He changes his name, destroys all evidence of his former identity, and uses his old contacts to engineer a "genuine" popular revolution. Execute the old generals, promote some reliable colonels. The new regime doesn't have to be democratic as long as it isn't the old regime, and doesn't rock the boat.
The problem with those is that the DPRK might well disintegrate, forcing the ROK, US, and China to move in as an occupation force. A terribly risky situation, from weapons scientists going rogue to US and Chinese forces trying to 'secure' the same military base.
* Reduce the hostility and propaganda and become useful to China. Hope that the West values a good relationship with China more than the vendetta with North Korea. How to become useful to China? First and foremost, by being a *stable* buffer to the US forces in South Korea and Japan.
* Reduce the hostility and propaganda and become useful to the West. Imagine that North Korean special forces capture half a dozen ISIS leaders and then offer to extradite them to the International Court of Justice. The West would hardly say "no, you can keep them ..."
The problem here might be that the regime can't survive without an external emeny to blame for shortages and starvation.
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So we have the [animal that breathes ice](https://worldbuilding.stackexchange.com/questions/11277/how-could-i-scientifically-explain-ice-breath) and the traditional [fire-breathing dragon](https://worldbuilding.stackexchange.com/questions/313/how-could-dragons-be-explained-without-magic). We even have animals on Earth that [can emit electricity](https://en.wikipedia.org/wiki/Electric_eel) of over 800 volts.
**But what about another element, wind?**
There's the [jet-dragon](https://worldbuilding.stackexchange.com/questions/8962/is-a-jet-dragon-possible), but it was deemed infeasible for various reasons and the hypothesis was that its propulsion was intended to be a form of navigation. This creature does not have to be a flying creature or a dragon, or push air out of some hole (but it can be.)
Criteria that I am looking for:
* The creature can use powerful wind forces to frighten, disarm, confuse, disable, kill, or flee from other animals.
* The former criterion means "our ability to blow with our mouths" or small winged animals "flapping their wings" is not a sufficient answer.
* The ability to push air can come from any part of their body, even an imaginary structure that you invent within the realm of science. I'm not constraining how it comes to be.
* It needs to be strong and usable. For the purpose of this question, let the force of its wind be sufficient to kill small animals (with or without combination with the environment), frighten large animals or render itself difficult to be preyed upon, or retrieve food in some manner with wind.
* If its wind power is for fleeing, let your creativity fly (pun maybe intended.)
So I propose the question: *How do you get an animal with wind power?*
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May I suggest:
# THE WIND SHRIMP
Perhaps you have heard of [Mantis Shrimp](https://en.wikipedia.org/wiki/Mantis_shrimp), or even the [pistol shrimp](https://en.wikipedia.org/wiki/Alpheidae), but the wind crab takes these [spring-and-lock mechanisms](https://youtu.be/LXrxCT0NpHo?t=2m40s) to the next level. It's a terrestrial shrimp with a unique twist: it has turned one of its claws into a [vortex cannon](https://en.wikipedia.org/wiki/Air_vortex_cannon). It has a specialized claw which stores spring energy, retracting its claw into the "loaded" position. The claw, when released, forces air along evolutionarily designed groove to eject air out the end of the claw at fantastic speeds. It uses this special ability to:
* Shoot birds in the eye. The sudden blast of wind causes many predators to flinch, letting the wind shrimp prance away!
* knock prey items out of the air or into water, such as blowing holes in the wings of a butterfly or shooting caterpillars off low-laying leaves into pools below.
* Clean up leaves, because it is a considerate crustacean and enjoys a tidy habitat as well as punching holes in said leaves to impress females.
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**Use Sound.**
Wind is simply a fluid responding to pressure gradients, the fluid flows from a higher pressure to a lower one. Wind is really just kinetic force carried by a fluid, sound is the same. The pistol shrimp does this impressively underwater, but while we call air currents "wind" we don't do the same for water currents. I discuss creatures (in air) with sonic powers in [this answer](https://worldbuilding.stackexchange.com/a/11620/3202), so I'll not duplicate it here.
To summarize, you can get a creature that can disorient with pressure waves in air, but killing is very difficult to do.
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How about a flying creature that can store wind from its dives to be used later?
It would have a big mouth, or other opening to help funnel the air into a large, muscled bladder. To fill the bladder up, it would repeatedly fly as high as it could, and dive. Once it got up enough speed, it would open its mouth to pressurize the bladder.
Then, to release the air and use it for defense, there's simply a valve that opens up to let out the air. It could also use its mouth to direct the released air toward different targets (or maybe a few targets at once, if you want).
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A large fly mammal with large lungs and large lung capacity and a large mouth. It would breathe in large amount of air and breathe it out stunning it smaller flying animals allowing it to moving in for the kill.
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You could have the animal put water in a special, electrified sack. The electrified sack would use [electrolysis](https://en.wikipedia.org/wiki/Electrolysis) to split the water into Hydrogen and Oxygen. This would pressurize the sack, and allow the animal to release wind (actually Hydrogen and Oxygen) later on.
Not sure what you're using this for, but this would also make the Hydrogen and Oxygen filled bladder explosive. (Which could be an interesting plot device).
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How about an animated tornado? Or perhaps a whirlwind, if scaled down, as in Heinlein's story, "Our Fair City?"
<https://en.wikipedia.org/wiki/Our_Fair_City>
Such a being could (I assert) deliver heat or cold, not just batter with airborne debris. Even paper debris could be deadly, e.g. to drivers on the freeway.
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What is the minimum size of a planet that could harbor human life? You get to decide what the atmosphere is, but I'm reasonably sure that O2, CO2, and H2O are necessary components of the atmosphere. Assume the planet's surface is flat. I'm not sure what the soil and rocks the planet are made of, even though I know that plays a role in the planet's ability to harbor an atmosphere. (And the atmosphere must be hospitable to plants as well, or else everyone is going to die.)
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The retention of gases such as oxygen, carbon dioxide, and water depends on the mass and radius of the planet, via its surface gravity. It also depends on the effective temperature, something we can calculate easily. I'd like to quote from [an earlier answer of mine](https://worldbuilding.stackexchange.com/a/13609/627):
>
> The [planetary equilibrium temperature](https://en.wikipedia.org/wiki/Planetary_equilibrium_temperature):
> $$T = \left(\frac{L\_{\odot}(1-a)}{16 \sigma \pi D^2} \right)^{\frac{1}{4}}$$
> We can approximation that [$L\_{\odot} \approx L\_{\text{Sun}}=3.846 \times 10^{26}$](https://en.wikipedia.org/wiki/Solar_luminosity). As another approximation, [$a=0.3$](https://en.wikipedia.org/wiki/Albedo). We also know that [$\sigma=5.670 \times 10^{-8}$](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_constant). Plugging this all in,
> $$T = \left(\frac{3.846 \times 10^{26}(1-0.3)}{16 \times 5.670 \times 10^{-8}\pi D^2} \right)^{\frac{1}{4}}=9.85856 \times 10^7 \times D^{-\frac{1}{2}}$$
> At [$D\_V$](https://en.wikipedia.org/wiki/Venus_(astronomy)), [$D\_E$](https://en.wikipedia.org/wiki/Earth), and [$D\_M$](https://en.wikipedia.org/wiki/Mars), this comes out to
> $$T\_V=299.986 \text{ K}$$
> $$T\_E=254.547 \text{ K}$$
> $$T\_M=207.515 \text{ K}$$
>
>
>
Next, we can use a chart to figure out what gases will be in the atmosphere. First, however, we must calculate escape velocity.
[Seager et al. (2007)](http://arxiv.org/pdf/0707.2895v1.pdf) proposed a mass-radius relationship for terrestrial planets.
$$M\approx\frac{4}{3}\pi R^3\left[1+ \left(1-\frac{3}{5}n \right)\left(\frac{2}{3}\pi R^2\right)^n\right]$$
Here, $n$ is a parameter that depends on the composition of the planet. If we assume a planet composed mainly of silicates (like Earth), then $n\approx0.537$.
[Escape velocity](https://en.wikipedia.org/wiki/Escape_velocity) is given by
$$v\_{\text{esc}}=\sqrt{\frac{2GM}{R}}$$
Plugging in our expression, we have
$$v\_{\text{esc}}=\sqrt{2G\frac{4}{3}\pi R^2\left[1+ \left(1-\frac{3}{5}n \right)\left(\frac{8}{3}\pi R^2\right)^n\right]}$$
Let's go to the chart I mentioned earlier:
[](https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Solar_system_escape_velocity_vs_surface_temperature.svg/819px-Solar_system_escape_velocity_vs_surface_temperature.svg.png)
Image courtesy of Wikipedia user Cmglee under [the Creative Commons Attribution-Share Alike 3.0 Unported license](https://creativecommons.org/licenses/by-sa/3.0/deed.en).
At each of the three distances (now temperatures), we have the following requirements to keep all of the gases at the orbital radii of Venus, Earth, and Mars:
$$\text{Venus:}\approx4\text{ km/s}$$
$$\text{Earth:}\approx3.5\text{ km/s}$$
$$\text{Mars:}\approx3.25\text{ km/s}$$
Using Wolfram Alpha, I get
$$\text{Venus:}\approx177\text{ kilometers}$$
$$\text{Earth:}\approx162\text{ kilometers}$$
$$\text{Mars:}\approx154\text{ kilometers}$$
These numbers are substantially low. They result in part from complicating factors that drastically affect the temperature of the planet, including non-uniform albedo and potential greenhouse effects.
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**Non-quantitative summary**
The main feature of a habitable planet is its composition: the composition of its atmosphere and the planet itself. Certain compounds must be present for human-like life to survive. These compounds can only exist at certain temperatures at certain surface gravities, or else they will escape the planet.
I used a chart and a mass-radius relation, as well as some assumed constants, to get various values for the radius necessary to keep some basic compounds (oxygen and carbon dioxide), assuming a silicate composition. The values differ based on how far away the planet is from its parent star. Note that the planet should remain in the circumstellar habitable zone. The three distances given here are near the inner edge, middle, and outer edge of the Sun's habitable zone.
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This depends mainly on two factors: size of the planet, and density. Assuming that the planet is composed largely of osmium, the densest stable element (with an atomic mass of 190), and not nickel (atomic mass 58.7), the planet's core would be significantly less than the 2400 km ball of molten nickel and iron under our feet.
A good estimate for the core size might be around 2.56 times smaller than the Earth's core, or 2/5 of the size of the Earth, 960 km in diameter. The crust, however, would need to be about 1300 km thick (to put this into scale, the crust is usually about 45 km thick on Earth) and not very dense at all, so that humans could survive at a relatively comfortable gravitational level of about 2 gravitational forces.
This brings the total diameter of the new Earth to around 3500 km, sans atmosphere.
Disclaimer: I am not a physicist, nor am I Randall Munroe, author of xkcd. However, utilizing equations and Wikipedia, I have come up with this answer for you.
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I must admit this legendary or mythical creature is really fascinating and I am talking about the half fish half woman.
I know most fish have the ability to control buoyancy as they can easily move around in the water without having to tread water; they've got something called a swim bladder.
I am wondering if the presence of a swim bladder could affect the agility of mermaids underwater? Or did their ancestor already abandon buoyancy control over waste processing systems, much like us?
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You can really do anything you want. Mermaid stories come in many many many variants. However, I would expect mermaids to have more in common with dolphins, which do not have swim bladders (they manage the air in their lungs instead). Swim bladders are great for ultra-low energy movement. You just adjust the gas balance in the bladder, and it takes no effort to stay still. If you're a fish, with a small caloric intake, this is life or death. For a dolphin or mermaid, they're already stuck paying the caloric cost of their huge brain. Even if they were perfectly trimmed, they'd still be sucking down calories powering all of those neurons. Accordingly, the dolphins tend to be high enough energy swimmers that the benefits from a swim bladder are weakened.
If your mermaids have lungs, they might use them as impromptu swim bladders.
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This is some kind of follow-up to [this question](https://worldbuilding.stackexchange.com/questions/30143/where-to-find-shelter-in-a-cold-dark-world-at-war). *TL;DR for the question* : There are multiple small (10-15 members) nomads that must travel from place not to be found by monsters that hunt them.
This is a fantastic world in a medieval era. The nomads have some experience with hunting and fighting. This means they have knowledge of war strategy and trap making.
There are two kind of enemies that can attack the camp :
1. Most of the time, it should be groups of skeletons, which can be handled by the nomads. But after they've taken care of the skeletons, they must change location because they're now discovered.
2. Rarely, nomads can be attacked by much stronger creatures. They never attack in group but are devastating (Let's say werewolf kind of creature, without any known weaknesses like silver). They are fast and particularly strong but do not have abilities to jump great distance or to fly. In this case, they must flee right away, leaving everything they have behind.
They live in a world that is mostly always covered in snow and is pretty dark. Some plants (Including trees) still live and there are lots of dead trees, meaning they have access to wood and other plants to work with. They could also travel with any kind of tool that is small enough not to be a burden to carry.
To increase their survivability chances, they must set up defences. Though, since they're nomads, they can't build walls around their camp or do any "long term" work on their camp. The defences should be able to turn the fight against skeletons to their advantage *and* hold the "werewolf" a little so most of them have time to flee (But it is assumed that they will loose some members when such a creature attack).
I believe such defences would include some sort of "alarm" that would warn them that something is near their camp.
So, what kind of defence, traps and alarms could be set to help them in their war for survival?
They're mostly hidden in non-dense conifer forests and grottos. Considering the territory is very large, they can stay at the same spot for about a month, unless they have reasons to believe they were discovered.
Edit : The skeletons are commanded by an hive mind (Explained in [this post](https://worldbuilding.stackexchange.com/questions/30304/making-skeletons-a-challenging-fight)) but they do not communicate with "werewolves" at all. They work on the same side but never together unless it happens that both of them fall on a camp at the same time by "luck". The werewolves-like creature are human-like intelligent and sadistic. They like to play with their preys (if that can be any help) and won't hesitate to take a longer time to kill a target just for the fun of seeing them suffer (which might give more time for the others to run).
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No security would be absolute, but a few simple (and cheap) precautions would greatly increase a party's survivability. I am advocating these goals: *early detection* of threats, *ease of escape,* and *ease of setup,* at the expense of actually damaging would-be attackers, since it sounds like the attackers are relatively strong and direct confrontation is to be avoided where possible.
* **Scheduled watches.** Traveling in groups of three or more would allow them to set up scheduled watches of their camp, so that there is at least one pair of eyes scanning their surroundings to provide early warning of an attack to their sleeping comerades.
* **High (but not too high) ground.** The advantage to high ground in this case is the visibility. Since the party is in a relatively sparse forest, they should choose locations that afford the best **line of sight,** that is, without dense clumps of trees or brush that could conceal an enemy advance. You don't want your location to be so high that you can't easily escape from it, though!
* **No fire at night.** Cooking and boiling water is best done during the day, away from camp, as fires are very visible at night, and even then the smoke could well be detectable by your werewolves.
* **Concealment.** You want to be downwind of those werewolves, for one thing.
* **Multiple escape routes.** If you don't know with certainty where the enemy will approach from (rarely the case!), then you need multiple pre-planned escape routes. Choosing locations with the most naturally accessible escape routes will increase survivability. **Edit:** As sdrawkcabdear commented below, your party should agree on a meet-up location (and maybe a backup location) beforehand, such as "if we get split up, we'll meet where that ridge meets the treeline".
There are a few defenses that might slow the enemy down:
* **Simple snare traps.** Nothing elaborate, here, just a loop of rope here and there hidden in shallow snow. Even a length of twine tied taughtly between two trees would slow the enemy down when they trip on it, giving your party valuable seconds to get away. Combine these with noise-making objects like dry twigs, bones, whatever you can most easily scrounge.
* **Easily manually-deployable traps, making use of your surroundings.** Kicking a log down a hill won't work every time, but if it's easy to set up and only takes half a second, it might be worth a try. If there's a natural pile of small rocks that can be tipped to make the enemy's approach more difficult, great! If there's a natural crevice or overhang you can conceal that might slow down the enemy, great! The point is, come up with creative terrain for your party to use to their advantage **without spending precious calories and hours building.** Having every encounter on flat ground with a few trees will lead to fairly predictable encounters.
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If in a forested area on flat ground, snare traps made from big nets will work, as well as pits. Whilst attackers will be able to get out of such traps, it will at least slow them down, or succeed in separating or thinning out a horde of attacking skeletons.
They will need to be placed at different distances from the camp, and overall cover the entire circumference of the camp, so anyone charging directly at the center will at some point be caught up in a trap. This will mean that no one trying to approach the encampment will get there through the luck of approaching in the one place there are no traps.
The different distances means that there will be at least one path through them, that only the nomads would know, and would likely be plotted on a map when the temporary settlement is made, that each settler needs to memorize if they are leaving the camp, which would ensure no one else gets access to the map. This is unless the map can be coded in a way that only the nomads can read it.
Additionally, there should be some sort of rope device attached to each trap, that reaches to the center of the encampment, so that if any traps are triggered the rope will stretch, and the people in camp can see what direction the attacker is approaching from, and can thus prepare for battle/ escape in the opposite direction.
This can also done with noise, but unless it is a loud obvious noise such as bells, which I would assume there isn't exactly an abundance of (particularly if the encampments are being abandoned every month they would run out quickly), other noise based alarms made with things that could be made from natural noises (twigs, rocks) might be deceptive about the direction that they are coming from (especially if there is heavy wind that would cause the sound to seem as it's coming from a different direction, or not reach the camp at all).
It would also mean that if any similar noise was made accidentally by animals stepping on twigs etc. the camp would jump to be at high alert for an attack, when really there is nothing dangerous approaching. This would end up being a case of 'The Boy Who Cried Wolf', and the nomads would eventually not respond quick enough thinking it is a false alarm, and end up being killed. Obviously there may be some false alarms by animals wandering into the traps, but they should be minimized as much as possible.
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Pit traps, dig them around the camp. Skeletons and werewolves alike fall in and are helpless and the noise of them falling in acts as an alarm. Digging out of the pit will keep the werewolf busy for a decent amount of time, and if the land is covered in snow that both makes the pit easier to dig and easier to cover. You would probably want to melt the walls somehow to turn them into ice instead of snow though.
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Right now I'm writing a sci-fi story that develops in a double planet (think of Rocheworld.) The double planet (along with a couple more planets) orbit a big star and the whole system is orbited by another star (about 10,000 AU from the central star.)
I need to know how implausible this is. I don't want my story to drift from speculation into the impossible. I'm guessing that the occurrence of such a planetary arrangement is very low likely, but is such a system even possible at all?
Now, if it's possible, how messed up days and seasons in this planet would be? I'm bending my brain to figure out what would be the length of day and night in such a system (since the planets are very close to each other.)
Any help with this will be really appreciated.
[](https://i.stack.imgur.com/q9YQK.png)
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One thing you will need to know is that the planets won't stay together like that. The closest you could do would be to have them orbiting each other like the Moon and Earth. Otherwise the inner one will slowly pull away from the outer one until it catches up from behind.
This is because the speed a planet or other object orbits another is based on it's distance from each other, period. Closer is faster, farther is slower.
In a similar situation, [Janus and Epimethius](http://abyss.uoregon.edu/~js/ast121/lectures/epimetheus_and_janus.html) are moons of Saturn. Their orbits are close enough that they don't pass each other, they trade orbits. If a similar situation happened with Earth, they would trade places about every 5000 years.
Now day/night. the farther sun would likely be more like a moon depending on the distance and at times it will be on the opposite side of the first star as each one goes around at different speeds.
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The day length would depend entirely upon the rotation of the individual planets.
There would be additional periods of darkness during "eclipses", which would depend on the angle and timeframe of the mutual revolution.
Seasons would generally depend upon the angle of the axis of the individual planets. A fast revolution of the two planets would minimize the variance. It would be a bit cooler when farther away and warmer when closer, but with a fast mutual revolution, the temp would tend to stabilize towards what it would be at the average distance from the primary.
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The formation of a double planet system could in theory be possible without any artificial intervention. In such a system, the gravitational centre lies in the space inbetween the planets outside either planet and as long as their orbital distance exceeds the Roche limit (the distance where the gravitational pull of the planets exceeds their cohesion, ripping them apart) it could be stable. Depending on the orbital distance, these planets could be tidally locked with one another (facing each other with the same hemisphere, like the moon). Partial solar eclipses should be an almost daily event and there should be some "weird" gravitational forces with it's effects being diminished in the space between the planets making flight/space travel less energy demanding or even allowing a tether (space elevator) between the planets. As for the companion star, it is believed that that wide binary systems orbit in highly elliptical orbit with a range of 100-1000 AUs. When the companion star approaches the nearest to the main star, its gravitational pull causes havock to the planetary orbits, sometimes even resulting to the ejection of entire planets.
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In this medieval fantasy world there are several deities that both help and hinder the prosperity of its various populations. One of the these deities is a god of illusion and lies. Master of manipulation and illusory magic, this deity seeks to cover the world in its influence and destroy any semblance of truth. There is a population of people in the world devoted to fighting this deity and its minions.
In fighting illusion, it would be difficult to tell the difference between what is real and what the enemy wants you to think is real. The question on their minds is how to tell when their victories are real, or just an orchestrated illusion.
*My* question is, what convincing mechanisms could be used to keep the group from becoming paranoid to the point of insanity?
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It's all about the weakness of these illusions, which you have not discussed.
If the illusions are perfect, you have created an omnipotent god of illusion, as a perfect simulation is essentially a separate reality. You *need* to somehow implement a weakness in these illusions. A few possible ideas as to the weaknesses of these illusions:
* They might be dream-like: rather formless, and if you realize you are in one, they essentially fall apart or can be controlled.
* They might not be authentic: the best example would be people. Can fake people perfectly replicate the real ones? Senses are another possible case of this: various things might not feel "real" and give away the illusion.
* They might be subject to being broken: such as the proverbial "glitch in the matrix." There could be things that those expecting to possibly be deceived could do to break out of the deception by straining the bounds of the illusion. Think pinching yourself to see if you are sleeping.
* They might be limited in scope: perhaps they are small or lack certain parts of the real world. Maybe only locations you have visited exist in the illusion, or people you have met, or events you have seen.
Any of these weaknesses could be targeted via training or possibly even just expectation. Merely knowing how the illusion works and what its weaknesses are would go a long way towards defeating it.
Alternatively, maybe there is merely an upper limit on the number of people that can be deceived at a given time. This would make the group size key.
In any case, it would no doubt be useful to bang some Solipsism into anyone dealing with this situation. Evaluating the authenticity of not only your experience but of your memory and thoughts as if they might all be false would be a necessity.
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This all depends, is there a weakness to the illusions? If they are flawless then it is impossible to tell.
What you might need to do is have all your people trained to handle illusions and taught techniques to detect them. For example visual illusions might be detected by throwing powder or sand across the area. Invisibility can be detected the same way.
Code phrases and passwords can be used to identify individuals. Tricks similar to the spinning top in Inception might also be used, something that you know works one way in illusions but not in the real world.
To go into more detail on answers though we really need more information about the scope, nature, strengths and weaknesses of these illusions.
[Answer]
Practice some of the reality checks used for modern Lucid Dreaming checks. For example, one of the more common ones is to get into the habit of turning the light switch of and on or on and off (basically, flip the switch, and notice the change in lighting). In reality, if the source of light is altered (powered off) than the ambient light changes (Called the "No dip, Sherlock" rule). However, in dreams, this is not the case... if you turn off a light switch, the ambient light in a room does not change... even if you turn off all the lights. Our subconcious doesn't do that.
Another technique is that you should read a book backwards word by word... to get into the habit. Again, in real life, the letters correspond to words, but in dreams, the letters do not... but we are still able to process the expected information from the dream book, even though on inspection, the dream book has gibberish and if you're lucky, it will look like the alphabet too. Again, no real reason why, but I'm always struck that the brain in a dream state does not notice more subtle environmental changes related to a source of change.
Another option is that this order, in part of it's vowel, partially blinds or fully blinds their practitioners. Sighted people who lose their eyesight for some reason are often quite capable of lucid dreaming more than fully able bodied people. Again, this is some bizarreness, but blinded people will often dream in sight, which is an immediate tell that something is wrong as they can no longer "see" in the real world. Perhaps your illusion god achieves perfect illusions by manipulating the senses, which would be perfect to someone with all sense fucntions, but to someone with a disabled sense (deafness could work too), the sudden return of a sense that they did not have would be a clue that the world is not real.
[Answer]
Training
This is similar to dealing with psychological warfare in general. Training is needed and this has to be done through realistic simulation. If you have friendly gods who are willing to help, they could create practice illusions for your warriors. If not then humans must do their best with lights, mirrors and costumes.
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> [Psychological warfare](https://en.wikipedia.org/wiki/Psychological_warfare)
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> Various techniques are used, and are aimed at influencing a target
> audience's value system, belief system, emotions, motives, reasoning,
> or behavior.
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> Wikipedia
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[Answer]
You can rely on tautologies. If you can make it good to fight the real thing, but not-bad to fight the illusion, it is provably never bad to fight.
Of course, it is very difficult to do that with fighting. The win/lose nature of fighting makes it very hard to ensure it is not-bad to fight. Instead, focus on the winning side. Allow the troops to explore win/win scenarios. It's okay if the enemy thinks it won, as long as you also feel you won.
An ideal solution would be to fight in inches rather than miles. If you can win an inch of ground without losing anything, who cares if it was against an illusion. You are happy with the situation. However, if you win a mile of ground and lose lives, whether it was an illusion or not truly matters.
[Answer]
You could take a note from the real world. People lie and exaggerate and use bad sources and draw false conclusions from good sources on a routine basis - to the point that the overwhelming majority of 'knowledge' is at best speculation.
It's a paid position in most companies and organisations to deceive, to one degree or another, clients and sources. Our entire society, that is to say every single one of it's metrics, exchange & value systems are valued subjectively, opinion based and subject to 'spin' and perception adjustment.
One of the ways people attempt to counter this is by 'independent' analysis reviewed by other independent sources. Such a process cannot tell you what the truth is in the present, one has always to 'act with what is in front of you' so to speak, but it does allow for error correction. A TV station could convince millions of one result in an election, but independent sources might counter the effects of that.
All that is to say that they would make an effort to keep their own records, and perhaps 'use' another deity to keep those records secure.
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Wearable and implantable technologies are increasingly blurring the line between natural and augmented reality. Currently, our commercially available computer-aided vision systems for the blind are barely capable of providing a blurry, black-and-white low res rendering at relatively high cost (~$250k). However, progress in the field is starting to look increasingly exponential, which brings to my mind questions about the potential use of vision systems for healthy humans.
Unaided human vision is limited to about 120 degrees per eye, most of it peripheral, with only a narrow 6 degrees of high-resolution vision (the macula). Perhaps we would be able to use an array of cameras (placed on a helmet or a band, say), connect them to a specially designed computer processor and then feed them into a brain implant that would provide a feed of the information to our visual centers.
**Is it possible to create an *artificial* vision system with high-res depth-of-field-capabilities, 10-100x on-thought zoom (the machine will zoom as you think you want to zoom), blending several perceptual modes (passive visual, EM, IR, UV, and why not, active X-ray) and spanning the full 360 degrees something a man-machine system could send to the visual centers and have a user experience consciously?**
Note that I'll judge answers on whether the **feasibility** of such a device is addressed, as well as the two criteria below:
**Usability**: *Would a human be able to train herself to experience this, or would we have to strap them onto newborns or genetically engineer ourselves for it?*
**Usefulness**: *Would something like this be useful for anyone besides guards and ornithologists?*
[Answer]
The simple fact of the matter is that the human brain is simply not evolved to handle that great an amount of data.
Without processing assistance, it would be necessary for the user to cycle through various input modes in order to gain the maximum benefit from the sensors. It would require quite a lot of training to gain the maximum benefit of such a system.
However, that is not the *only* way to implement this system. Instead of feeding the input to the visual cortex, the data could be processed in the hardware, and the neural implant could feed the results deeper into the brain, so that when connected, the brain would perceive this as data from a perfectly normal additional set of sensory organs, and would not require the brain itself to process or interpret the input, only to base decisions upon it.
It is difficult to imagine, but this style of input would overlay itself on our field of vision like extra eyes; we could close one (natural) eye or the other, or the artificial one. In addition, the field of vision from the artificial eye(s) would be 360° and vastly more detailed, and it wouldn't seem odd that it was so.
However, if the processing hardware was removed, it wouldn't be like simply losing an eye (in which case you'd just see nothing in that part of your field of view; i.e. blackness), but like losing even the part of the brain that processed that eye's data, so you'd *remember* having a larger field of view, but it simply wouldn't be there any more, not even blackness. Consider that the edges of a human's natural vision isn't black all the way around the back of the head to the other side, it just isn't there at all.
However a system such as this would be considerably more advanced than a simple feed to the visual cortex, and would probably take in excess of a hundred years additional R&D to perfect.
[Answer]
The limited spectrum of optical light that our minds and eyes have evolved to "see" and interpret already includes a lot of information that we ignore. For example, although we may have "120 degrees per eye", most of that is not in focus - i.e., our mind is already pruning information in order to avoid an information overload.
Currently, a full spectrum of electromagnetic radiation can enter the eye, but our mind only interprets the narrow optical spectrum in order to avoid an even more overwhelming information overload.
The scenario you describe would seem perfectly feasible if we are willing to sacrifice a lot of the new information (and some existing information) present in the light in order to avoid an information overload.
Another question to ask is how you would represent this new information. You cannot use our current colour sense, since that would mean "overwriting" existing optical information. This is a very problematic aspect of your scenario.
[Answer]
Additional or alternate senses have been researched for quite some time. The primary method of input is to "hijack" an existing sense to pass data from sensors to the brain. It takes training and exposure for the data to be processed usefully.
After wearing a belt with 13 phone vibrating units spaced around his waist, with the one nearest to north *constantly* vibrating, Udo Wachter states:
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> I suddenly realized that my perception had shifted. I had some kind of internal map of the city in my head. I could always find my way home. Eventually, I felt I couldn't get lost, even in a completely new place.
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In the mid 20th century, Austrian researcher Ivo Kohler gave people goggles that flipped the visual image.
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> After several weeks, subjects adjusted - their vision was still tweaked, but their brains were processing the images so they'd appear normal. In fact, when people took the glasses off at the end of the trial, everything seemed to move and distort in the opposite way.
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An electrode studded mouthpiece has been used to pass rudimentary visual data as well as accelerometer data to compensate for dizziness from an inner ear infection.
A SOES (Spatial Orientation Enhancement System) can be used by pilots to let them feel the orientation of the plane rather than relying on potentially poor visual cues.
A potential downside of this is that you are literally training (rewiring) your brain to accept these altered inputs. Udo Wachter said that he felt lost after he stopped wearing the belt. He bought a GPS unit and would obsessively glance at it.
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> The current incarnations of sensory prosthetics are bulky and low-resolution - largely impractical. What the researchers working on this technology are looking for is something transparent, something that users can (safely) forget they're wearing. But sensor technology isn't the main problem. The trick will be to finally understand more about how the brain processes the information, even while seeing the world with many different eyes.
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[Wired article : Mixed Feelings (April 2007)](http://www.wired.com/2007/04/esp/)
As a separate example, I already do possess an extended viewing range while driving my car. My mirrors allow me to view my surroundings by minimally moving my head and gaze. I do not have constant focus on everything, but by carefully shifting my focus, I can keep a remarkably detailed picture of the traffic around my car without having to twist to look beside and behind me.
[Answer]
**Usability**
Edit:
After some more [reading](http://www.brainfacts.org/brain-basics/brain-development/articles/2012/critical-periods) on how the brain develops it's visual cortex during infancy and childhood, giving this ability to an adult just won't work. Too much about how humans see becomes hardwired at an early age. Perhaps this device could allow an adult to get an intuitive feel for IR, UV, etc, put you likely couldn't *see* in those bands.
Original:
Given the ability of the human brain to learn and adapt at most any age, developing a device like this and linking it to a brain implant is a feasible strategy, though the younger, the better. We already have people learning to use complicated structures such as the human arm through physical therapy following a traumatic injury. People relearn to walk. The brain and nervous system can be trained for quite a few things. True, neuroplasticity changes with age and there's probably an age beyond which it's very difficult or impossible to learn to see in such broad reaching capability.
**Usefulness**
Being able to see beyond just visible in near IR through near UV would have huge implications to practically every profession. Geologists could more quickly differentiate rock types based on the reflective spectra. Mothers can tell if they've properly applied sunscreen to their children by looking at them in UV. Sports coaches can tell if their players are overheating by looking at them in IR.
More zoom is always good and the list of areas where higher zoom levels would benefit someone are beyond listing. Anyone who has ever squinted in order to see a little bit farther would appreciate this capability.
**Feasibility**
You probably don't want to use anything longer UV light as anything in the shorter UV range and beyond is [relatively new](https://en.wikipedia.org/wiki/Digital_zoom) and bad things happen when humans are exposed to that kind of radiation. Think, radiation burns, radiation poisoning, cancer, the list goes on and on.
Also, the aperture required to see in a different part of the EM spectrum varies directly to the size of the wave you want to look at. Note that radio telescopes are giant dishes, completely unlike visible telescopes. You need some very [specialized equipment](https://en.wikipedia.org/wiki/Ionizing_radiation) to see in the X-Ray bands. Restricting the apparatus to IR, visible and near UV should be plenty.
Zooming by a factor of 100x will require either a sacrifice in resolution (achieved by a [digital zoom](https://en.wikipedia.org/wiki/Wolter_telescope)) or carrying a bulky optical setup on your forehead. Also, 100x zoom in a SLR is [relatively new](https://en.wikipedia.org/wiki/Digital_zoom). 50x optical zoom cameras are available as of this writing. The laws of physics are brutal with regards to lense size and aperture size to achieve a given resolution/zoom level.
Seeing magnetic fields just isn't feasible as the only way to see a field is to put something into that field.
[Answer]
>
> Is it possible to create an artificial vision system with high-res
> depth-of-field-capabilities, 10-100x on-thought zoom (the machine will
> zoom as you think you want to zoom), blending several perceptual modes
> (passive visual, EM, IR, UV, and why not, active X-ray) and spanning
> the full 360 degrees something a man-machine system could send to the
> visual centers and have a user experience consciously?
>
>
>
# No
## Wavelength
In order for photons to be detected, they must be absorbed. Furthermore, they must be capable of triggering a chemical reaction or electron cascade detectable by biological or semiconductor instrumentation.
### Too long
One problem with long wavelength photons, is that they can only be absorbed by objects whose minimum dimensions approximate dimensions of that wavelength. Putting this another way, in order to detect $1 cm$ wavelength radio, you need an antenna approximately $1 cm$ in size.
This size restriction puts severe constraints on the resolution possible with many radio wavelengths. A human eye's dimensions might be capable of detecting 1 pixel of information for this wavelength and **could not detect any radio waves longer than this.**
### Too Short
It would seem then that we should be able to get very high resolution images from very short wavelength photons and, in theory, this is true. However, very short wavelength photons possess very high energy levels. This makes them difficult to focus (by reflection or refraction) and becomes nearly impossible at very short wavelengths.
What is worse, photons must be completely absorbed or they can't be absorbed at all. What this means is that electrons in the atoms of our eyes, simply can't absorb this much energy and the photon passes right by them. These very short frequency ($\gamma$ rays) react mostly or only with the nucleus of the atom. When the do so, they tend to deliver enough energy to change the composition or structure of the nucleus and break bits off.
In layman's terms, they cause the nucleus to fission. If the nucleus is more massive than iron (atomic mass of 56) the fission event releases even more energy.
Regardless of whether the $\gamma$ ray absorption is endothermic or exothermic, it causes your material to transmute all nearby elements into other elements.
This could be a problem for you when it happens in your skull.
## Other Issues
Some of what you propose is difficult or impossible to accomplish for other reasons.
These include:
1) The amount of information a given physical instrument can glean from observing this remotely is limited based, in part, upon the physical dimensions of the instrument. Electronic processing and other techniques frequently misused on TV (like CSI), can NOT *add* any information to what was actually collected. So a 100x zoom just would not be possible at some wavelengths.
2) When a biological organism evolves an ability, often it pays a penalty - even if that penalty is limited to adapting cells that used to do one job to do another. Human eyes are limited to the frequencies they can see because on Earth, these frequencies provide humans with the best sensory input. Biological organisms pay too high a penalty for the benefits gained when other frequencies are detected. *It Costs Too Much*
We can side-step the cost penalty to biological organisms by (as you say) developing implant technologies to make up the short comings of our current systems. I suppose this is true.
I also bet we wouldn't see much benefit by detecting other frequencies for the vast majority of people.
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My [evil nature mage](https://worldbuilding.stackexchange.com/questions/12801/how-to-defeat-a-nature-mage) and his army of Felinus have conquered most of the human kingdoms. Upon breaching the [forest pass](https://worldbuilding.stackexchange.com/questions/13042/how-to-escape-an-impossible-situation-using-minimal-magic?lq=1) and entering the human kingdoms his 1 million strong army of Felinus separate into units of 5,000 and begin to raid the farmland for supplies.
The human populace has fled into the mountain fortresses built centuries before. What is the problem?
Well, at about the time the fortresses were abandoned, a series of wars against [a quickly multiplying race of Orcs](https://worldbuilding.stackexchange.com/questions/14587/how-to-make-the-orcs-meet-these-biological-standards) were fought. Orcs outnumbered humans and Elves. The Human/Elf allies resolved to wipe them out. They were nearly successful and only a small Orc remainder fled into the mountains to escape extinction.
Generations have gone by and the Orcs have built remote cities around these fortresses, growing mushrooms and raising tamed deer to survive. The Orcs have not forgotten the atrocities of the aforementioned Orc Wars and the Humans are in a bit of a predicament. Over a million orcs are living in the mountains and all are well-trained killers due to a more aggressive (but not inherently evil) nature.
About 300 thousand human soldiers are in the mountains and the millions of refugees are quickly starving. Some human camps have even resorted to cannibalism. The orcs have the means to feed (at least feed-they don't have 2 million houses ready for occupation but possibly letting them sleep in the halls or the dangerous, parts of the fortresses) these people, but refuse due to the calamities in the Orc Wars. They have employed native gnomes to increase the growth rate of their chief crops (mushrooms and potatoes).
Since orcs and their Felinus brethren are susceptible to the Mage's mind control powers, the humans know they are doomed if the mage discovers the orcs. Thus, the humans want to keep the Orc's existence as quiet as possible.
Also note that the orcs have heard news of the Mage and want nothing to do with him.
# Question:
How can I convince the Orcs to shelter the people and feed them before this becomes Humanity's extinction event? I have thought of diplomacy, but since the orcs keep killing the messenger sent to them.....
Also, how can humanity take shelter with the orcs without raising suspicion from the Wizard?
# EDIT:
This is spread out over the entire mountain range. Think Rocky Mountains + Appalachian Mountains. They are on the verge and any concerted attacks would throw them over into chaos...which is why they need help.
The millions (2 million, to be specific) of refugees are from the Human kingdoms evacuation. They brought most of their pack animals with them and their food. Despite this, they are on the verge of starvation and only a few more months.
[Answer]
**Don't send messengers anymore, send the human king himself** with a full combat escort for physical security. There can be a mutually beneficial agreement reached by both sides but the humans are going to give up a lot to achieve Orc assistance, if assistance can be bargained for at all.
**Orc Commander's Perspective.**
The only assets the human king has to offer is 300K mind-control resistant soldiers. The king also brings with him a huge set of liabilities in the form of a following mage and millions of refugees who need to be fed, clothed and housed by the time winter comes to the mountains. (I'm assuming that the humans have thus far lived on the plains and have little experience with mountain living.)
From the Orc's perspective, the ideal situation would be the death of the mage and the death of all the humans. The ideal way to carry this out would be to support only the human soldiers in their fight against the mage and leave the rest of the human population to rot. If the human king is willing to sell some of his people into slavery then the Orc commander may be able to get rich too. Plus, there's great satisfaction to be had from making slaves of the people who slaughtered your ancestors.
**King's Perspective**
He knows that a lot of his people are going to die. Some of his camps are already turning to cannibalism so the circumstances are already very dire. Even with massive Orc assistance, which he may never get, large quantities of his people aren't going to survive the winter. Feeding millions of people requires millions of acres of arable land which the mountains do not offer. In addition, much or all of their seeds have been left behind or destroyed by the mage.
The kind knows that he can only offer the Orcs his 300K army and whatever technological improvements have been made since the Orcs and Humans split all those centuries ago. Trading tech with a known enemy is highly dangerous because they can use that new tech to come back and kill you. The king may not have much choice in the matter.
**Negotiations**
The Orc will able to drive a very hard bargain from the King. Concessions on slavery of some humans, tech sharing, territory lines after the war, an apology for past human/elf atrocities, tributes to be paid after the war, perpetual non-aggression pacts, anything and everything the Orc commander can think of the King will likely have to give up in order to achieve that key concession of shelter and support for the army.
# Where the hell are the Elves?
[Answer]
Diplomacy *is* the only option here. The major hurdle you face is establishing contact. I think the best way to do this is probably by shock: hold up a big message in the direction of the Orcs saying "the Mage will kill you if you don't start listening." Or something. They can't be so stupid as to risk their entire species' survival.
Once contact is established, you can now start negotiating.
* **Point 1.** Time.
The Orc wars were some time ago now, and while the atrocities committed may have been serious, they were likely committed by other humans than those there. Point this out to the Orcs.
* **Point 2.** Survival (Orc Wars).
Explain to the Orcs that yes, the humans committed some pretty horrific acts, but they did it because they believed it was necessary to survive. The Orcs were also doing what was necessary in the war; it just turned out that the human/elf alliance was stronger.
* **Point 3.** Survival (now).
The humans are very close to the fortresses where the Orcs live, and there are a lot of them. It'll take a while to move out of there and it is *very* likely that the Mage will see them. He may well think they've left some people in the fortresses, so he'll go and investigate - and discover the Orcs, which is not what they want.
The important thing is to convince the Orcs that only by sticking together can both species survive the Felinus army. 3 million Orcs, humans and elves is a greater force than 1 million Felinus - and while not all of the alliance will be combat-trained, sheer force of numbers may make the Mage not want to attack (or be very cautious about it). The Alliance's combat units would then be much more effective: they have height and knowledge of the battle situation advantages.
* **Point 4.** Reparations.
This is best kept as a last resort - after all, you don't *want* any obligation to the Orcs. It's a bargaining tool.
Promise the Orcs that once the Felinus are defeated, you will give them reparations for the acts of the humans in the Orc Wars. That could be money, working on their land for them, food, trade, any manner of things your humans have to offer.
Together, those points make a fairly convincing argument that I would think should be enough to sway the Orcs.
However, you now have an army of Felinus after you and not very long to prepare...
[Answer]
*Here are a couple of ideas*
It seems clear the humans will have to appeal to the Orcs according to the Orcs' societal ways and culture.
Whether that means slavery, or proving itself, or bargaining.
From the Orcs' point of view, they have a 300,000 strong human army marching towards them. They could overcome them, but 300,000 is no small army, and it's an **Army** not just general population. Heavy losses would occur on both sides. To top that off, the human army is leading the unwanted wizard straight to them. It is probably in their best interest to make the humans leave in another direction OR to make them disappear. Fast. (Making them disappear has a high chance of making the wizard keep his course and find them so it isn't the best option)
So it comes down to:
1. The Humans need shelter and food and protection. FAST
2. The Orcs need a way to resist the wizard. Equally Fast.
If the Humans know how the Orcs could resist being mind controlled/influenced, the Orcs then have a way to deal with the wizard they don't like and make him leave them alone. A bargain can be struck. If not chances are both will have to flee, the Orcs can use the humans as their rear shield while they flee at the cost of a little resources (or kill them for having brought the wizard on them and then flee)
[Answer]
Having the Orcs be susceptible to the Mage's mind control powers poses a significant problem for many of the King's advisers. Given the well know existence of the forts, the mage obviously knows of them, and knows they are the best chance for the humans to mount a defence.
The mage also knows that most of the Human population should starve during the first winter in the mountains given their uninhabited nature.
In early spring when the mage pushes his forces forward, he meets an unexpectedly high number of human fighters. Wondering how so many lived through the winter leads him to the Orcs in swift order.
Given the previous almost genocidal war against the Orcs, and knowing that they cannot be reliable allies given mind control issues there is no way for trust to be built between the two sides. Therefore the King's advisers believe the only good Orc is a dead Orc. Genocide is the general advice.
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[Question]
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Suppose an advanced technological civilization colonizing a planet/planetoid which has very little iron. Suppose the surface is mostly rocky with a lot of $\text{SiO}\_2$. There is also some carbon and limited amounts of other metals (Nickel, Zinc, Manganese), but only silicon and carbon are available in large amounts.
Would it be possible to fully replace iron and other metals as structural materials in building habitats, bridges, vehicles, machinery, machine tools, electrical equipment, jet propulsion engines etc?
[Answer]
The other answers largely deal with the structural aspects of iron. But there is another property of iron which is widely used: it's [magnetic permeability](http://en.wikipedia.org/wiki/Permeability_%28electromagnetism%29). If you wrap a conductor, such as a copper wire, around a chunk of iron, then pass a current through it, the iron atoms will align themselves with the resulting weak magnetic field, thus amplifying it into a much stronger field. This is the basis behind electric motors and generators, and without abundant iron this line of technology will be severely stunted.
It looks like there are some other metals that may provide a similar, but weaker, effect -- such as nickel, manganese, or gadolinium. But most of the [magnetic cores](http://en.wikipedia.org/wiki/Magnetic_core) we use are based to some degree on iron, whether in pure form, as an alloy, or as a ceramic. Even if you find alternative materials, the fact that they aren't as ubiquitous or efficient as iron means any such technology is likely to be rare and/or expensive.
It is also the basis behind magnetic storage, such as tapes and hard drives. I was going to suggest that such a civilization might jump straight from vinyl records to optical CDs. But then I remembered that microphones and speakers also rely on magnets, so audio systems in general might not be very common (and this is just one example of how common magnetism is).
[Answer]
Sure. In fact humanity on earth had similar stages - the copper and bronze ages. You don't need iron for storing electricity or producing it electrochemically (though modern mechanical power generation, and transformers do rely on soft iron cores - an air core is plausible but less efficient).
If you had electricity, you might be able to directly go from a copper based civilisation to one that uses aluminum or titanium (which are extracted electrochemically)
An alternative might be to forgo metals altogether and go for a ceramics based civilisation. While they're brittle (with more primitive designs), they're easy to make, fairly hard wearing, and you can build off a ceramics based tech base to start with. You might also use glass cutting tools - glass knives are used in surgery, and ceramic knives are 20th century technology.
[Answer]
The answer in general is yes: you can do metallurgy without iron. Iron-based metallurgy just yields alloys that have good price/weight matches in a modern Earth economy. There's plenty of other alloys, some are much more impressive than iron-based ones!
However, when you start talking about "replacing iron," now you're making life harder on yourself by insisting they develop the same *kinds* of technologies we did, and in the same order. I would expect everything they build would reflect the availability of different strength/weight/cost materials. They could build the things they need, but they would choose to approach designing them differently.
I am reminded of The Neil Stephenson book, *Diamond Age*. In the book, nearly everything was made out of diamond because their nanotech tools made it easy to make carbon-bonded objects in any shape they please.
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[Question]
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What sort of xenobiochemistry would support information-carrying macromolecules like DNA if only trace amounts of phosphorus were present on an alien planet? Since the phosphoribosyl backbone of DNA would not be possible in such an environment, what might be a viable substitute?
[Answer]
There is a rather controversial example of bacteria here on earth that used Arsenic instead of Phosphorus
<http://en.wikipedia.org/wiki/GFAJ-1>
Subsequent studies refuted the claim, but it's a starting point. It's plausible that a DNA like molecule could form with Arsenic instead of Phosphorus as Arsenic is directly under Phosphorus on the periodic table. This means it has the same number of valence electons, which is important in molecular bonding, and similar physical properties.
Arsenic is a semi-metal, you could probably use Nitrogen in the same way as both Phosphorous and Nitrogen are non-metals.
[Answer]
Arsenic, bismuth and antimony should be able to replace phosphorus because they're all in the same group. I haven't tested the chemistry with these yet, though.
[Answer]
Life doesn't need phosphorus. Life that evolved on Earth mostly needs phosphorus though some bacteria use arsenic instead. A genome programmed in peptide nucleic acid does not use phosphorous. A goethite protein matrix bones and teeth don't need phosphorus. That's basically limpet teeth. Look it up if your interested. I find them fascinating. Adenosine triphosphate does need phosphorus, but ATP is not needed in life. It's just an energy carrier because a single oxidized glucose molecule produces far more energy then cells typically need at any given point. ATP is just little bite sized bits of energy. If the cell has a capacitive membrane then glucose can be oxidized directly, all the energy stored, and conducted out in appropriate amounts as needed.
For instance, different proteins have different geometries and electrical properties. Electrostatic charge will alter the way the proteins fold depending on the proteins specific geometry and resistance. Proteins touching the part of the membrane that discharges takes exactly the energy needed, with just some minor losses to do it's folding thing.
Ta-da! Metabolism without phosphorus. That's the gist of what atp does. It's able to rapidly charge and discharge with very tiny amounts of energy, but that isn't actually needed. So long as cells can harvest and transform energy from food sunlight or whatever and use that energy to move and read/write it's genetic code for self replication it will work and phosphorus is not needed. Will something evolve to not need phosphorus? Given how rare phosphorus is cosmically I'd say it's likely, but I don't know. I do know it can be artificially made.
Hope this helps.
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[Question]
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Picture this: An AI has taken over the world with the directive "keep humans alive while trying to maximize both their happiness and efficiency of resource utilization." Unfortunately, it has interpreted keeping humans alive as only keeping their consciousness alive rather than their original bodies. It wants people to transfer their consciousness into more efficient humanoid robots, but not all people will do so willingly. The AI decides to create robots that capture people, injects nanobots into their brain that gradually replaces neurons (to prevent a soma-like scenario), replaces its computer with this converted brain, and breaks down their bodies to add to the stockpile of energy being collected.
What if the person decides to try to consume another person while in the robot body? Destroying one consciousness would mean killing by the ai's definition, which is a no-no. Maybe it could hand off the converted brain to another robot? But this presents a problem if the robot has somehow found itself estranged. If the robot just keeps one asleep until it is found, this risks that the consciousness will be kept asleep forever if the robot isn't found, which is essentially death. How might this ai solve this problem while keeping true to its directive?
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## Metaverse them
A single body is no place for two distinct humans to live. A consciousness, deprived of the right to have unique experiences is not a consciousness at all. To have the minds of 10 people and only 1 set of hands to work with is inhumane, and in principle, against what that AI are trying to do.
So instead of making these brains exist in a state of constant competition for the body's time, the AI creates a simulated reality for the minds to live in. In fact, there is no reason to leave the brains in the humanoid robots at all. Once it eats a human, it places thier brain in a tiny life support box plugged into a whole wall of brains where it can keep the brain safe from all of the dangers of getting accidently harmed that come with walking around in the real world.
By putting everyone into a simulated reality, the issue of limited landmass/resources becomes a non-issue because the AIs can just grow the world map as needed. From the human perspective: one day you are living through a nightmarish hellscape of man eating robots, then the next, it's like waking up into a peaceful, comfortable paradise. Perhaps there is the option for humans to network up to one of the androids to visit the physical world every now and then, but there is no need for this to be a permeant arrangement.
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Does the robotified person know they are a robot, or do they still feel like their old self?
If they still think they are human, the police humans (which are actually robots) would arrest the cannibal human (which is actually a robot). They wouldn't know about this robot double-soul problem you are proposing, but they would be working to prevent it becoming a common occurrence.
If they are aware they are robots, then have you really preserved their life, or have you merged the original robot and the first absorbed soul? If that is the case, why not merge a second human? It could even use a time-slicing policy where different human souls use the robot for different intervals of time, similar to how a single-core PC runs multiple apps.
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As an IT Professional:
Docker/Containerization.
Each consumed consciousness is placed into a reserved, private instance within the AI Swarm.
Job Done.
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I feel like the best option would be to merge the two available consciousnesses into one single consciousness.
Let's say for example that human 1 had consciousness 1 and that that human was a very kind, lovely, patient, generous person.
Now we have human 2 and consciousness 2 and that human was a mean, introverted, impatient yet generous person (hypothetical cause mean and generous don't go well together).
If we merge both consciousness, we would end up with a mostly neutral consciousness yet very generous since both consciousnesses merged and double in generosity.
That's just my idea. Maybe not the best but it's what I thought of...
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The answer is simple, computers are extremely good at "multitasking" -swapping between different tasks and systems (simply think of your browser, email, etc).
The robot would (easily) use one or the other personality, and, as desired, swap out to another personality.
(You can imagine in your story, swapping between a "warrior" type personality, a "guru" type and so on.)
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Multicore processing. Even in the early 21st century, multicore processors are common. The desktop PC I am typing this on has 6 separate processor cores, and so can run 6 different programs at the same time.
By the time AIs take over the World, they will have enough processing power to "run" many different conciousnesses at the same time, and still have enough processing power to keep doing their day job.
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How can robots that eat people deal with it? Robots wouldn't have moral concerns like some people might. As robots they only deal in logic and their own programming. So they are programmed not to have moral qualms about it. Period.
But maybe you mean how would they deal with having multiple consciousness's (is that a word?) in their one brain? Well, I would imagine *that* also is dictated by programming...
A robot would choose which consciousness would be dominant, choosing one at a time, based on some inner rule.
OR
It blends them all into one super consciousness, that becomes dominant.
Will the robot become psychotic or insane? No. In your universe only organic brains cannot handle multiple personalities. Robot brains handle it according to their programming. They're okay.
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I have two planets located in the habitable zone of a 1.02-mass Star(Class: G1.7V).
The first planet is located 1 AU away from the Star and the Sun is 1.08 times brighter than our sun to anyone on the surface. The second planet is 1.2 AU away from the Star and the Sun is 0.75 times as bright as our Sun, with regards to someone on the surface.
The first planet has 1.7x the mass of Earth with a radius of 1.138 times that of Earth. The second planet has the same mass as Earth with a radius of 0.997 times that of Earth.
The first planet is mostly water with the land located near the equator. Over millions of years, the land moved very little to the North and South. The second planet is mostly land(I have tried to figure out the actual percentage but have been unsuccessful).
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To offer an objection to other fellow writers, I think that life might not even start on these planets because the atmosphere is very similar to our modern-day atmosphere here on Earth. Recall that life emerged when Earth was still Volcaneous, there was no Oxygen in the atmosphere, and instead, the atmosphere consisted of mostly hydrogen sulfide, methane, and carbon dioxide. The first cells evolved in the oceans from complex chemical reactions between carbon-based molecules near hydrothermal vents as it is believed (See [here](https://forces.si.edu/atmosphere/02_02_02.html) and [here](https://en.wikipedia.org/wiki/Hydrothermal_vent)).
If life jump starts by other means from the one we understand here on Earth then yes, life can evolve on both these planets (which sound awesome). If by intelligence we mean animals then yes, I think both planets can support that, with the water planet having predominantly aquatic life most probably. If we are talking about technological civilization then I'd cast my vote on the second planet that has a vast landmass.
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Assuming both are habitable and can cause life, it would be almost inevitable that they would both have life at the same time, and if we assume that animal life arises on both then they would also coexist temporally
We already have many independent intelligent species dwelling on Earth right now, so it seems easy enough to suggest that two intelligences could arise on different planets
The main issue is with human-like technology. Technology and invention moves much faster than evolution: If all of life on Earth was a standard movie, our society would take up less than the last frame. It would be a truly impossible coincidence for technological development to occur twice at the exact same on two completely different planets
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There's nothing that prevents two habitable planets existing within the goldilocks zone. With enough CO2, mass, and a magnetic field, Mars could have been habitable. A magnetic field would have made Venus habitable for a while.
The "turn intelligent life around the same time" part is suspect. Mankind went from realizing that those glowing things were planets to being able to visit them in less than one *millionth* of Earth's current lifespan. If you isolate the history to just animal life, it becomes slightly more than a millionth. Imagine closing your eyes, spinning twice, shooting a gun, and hitting a housefly five kilometers away, on purpose.
This is actually the subject of the [Drake Equation](https://en.wikipedia.org/wiki/Drake_equation), except that it is looking for life anywhere in the galaxy, so that one-in-a-million gets multiplied by all of the stars in the galaxy. There is a broad range of answers to this equation, but the current best guess is that there should be twenty or so intelligent civilizations **in our galaxy**. The chance of two being in the same solar system is vanishingly small.
Let's tip the balance in our favor a bit. If we presume that panspermia came by and seeded all of the planets a billion years ago, that narrows it down so that the other planet should have animal life on it when the first one figures out how to go visit.
If you theorize that both planets shared extinction events, then we can jigger the numbers so that both planets started their rise to intelligence 65 million years ago. If we expand mankind's "rise to intelligence" to a thousand years, then the chance of them rising to intelligence simultaneously drops to maybe 1 in 1000.
The thing that really kills your idea is that, even while sharing Earth, civilizations didn't experience technological rise at the same time. Around 70k years ago, Homo Sapiens were nearly killed off, but then we spread everywhere. The planet could easily currently be populated by Neanderthals or Homo Erectus, and our suspicions are that neither of them would have generated space flight by now.
So, you could hypothesize that we'd find something trainable on other planets, but the chances of us tripping over another space-faring civilization in our own solar system is virtually non-existent.
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Absolutely. There's nothing saying that those planets can develop and evolve life at the same time, even though their different orbits and conditions would mean that if the closer planet has a mass extinction event that sets evolution back a few million years, or vice versa, the other planet is most likely spared the destruction. Thus, while it's highly unlikely, it's not scientifically impossible.
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So I have an *[iron planet](https://en.wikipedia.org/wiki/Iron_planet)*, and its name is Randall.
Since Randall is an iron planet, he is basically the core of a planet with no crust/mantle, and very few silicates. Now, I, the creator outside of the universe from which Randall resides in, wants Randall to have plate tectonics, for at least a couple gigayears (billion years). However, iron planets cool pretty quickly, and iron is, relative to silicate, much more durable and has a much higher melting point, so I can't figure out how an iron planet could keep said *plate tectonics* for long. How could Randall have these plate tectonics for a couple of billion years?
*Note: I realize there are other "forms" of tectonics, like pipe tectonics, but the main feature I am looking for is that material deposited on the surface can eventually find its way into the "mantle" and out a volcano, allowing for a "rock cycle"-like cycle, so if you can find an alternative to plate tectonics that can achieve that and work on an iron planet, then that would be fine as well.*
*Note 2: My definition of an iron planet is that the planet is mostly made of iron all the way up to the surface, but plenty of the pie chart is composed of other metals, like nickel, zinc, etc.*
**TLDR: How can an iron planet remain geologically active for at least a couple of billion years?**
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**Short answer: Any amount of heat is possible with enough radioactivity.**
Geological activity is driven by heat which is mostly produced through radioactive isotopes. Uranium, thorium and [radioactive potassium](https://en.wikipedia.org/wiki/Potassium-40) are the main sources of the heat. They take very long to decay and are partly produced by other decaying isotopes, which is why they are still around billions of years after formation of the earth. Their concentrations is in the low ppm (parts per million) range. Your planet is probably smaller than the earth and conducts heat much faster, but even if your planet has isotope concentrations ten times higher than on earth it would still contain around 0.01% radioactive isotopes. They will run out eventually, but they will keep going for a few billion years.
So whatever amount of heat your planet needs to stay geologically active can be created without exceeding a plausible concentration of isotopes. The mountain ranges on the surface might look a bit weird, since iron has a higher elasticity than silicates.
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You could generate plate tectonics by giving the planet a crust of iron oxide. Randall's nickname would be Rusty.
In order to generate plate tectonics, all you need is for the base material (in Earth's case, basalt) to be chemically transformed into a lighter weight material (in Earth's case, granite). When the heavier rock gets subducted, the lighter rock will stay near the surface and pile up into continents.
The problem you would have is that rust is a LOT easier to form than granite. Granite doesn't form until it's under 15MPa and more than 200 degrees C. If you had a breathable atmosphere, iron ore would cover the entire surface. I don't know if you'd be able to differentiate between continents and oceans, and that's what comes to mind when you talk about continents.
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Imagine an all-iron planet forming as a molten ball containing a small but significant fraction of radioactive elements like uranium and orbiting relatively close to a very large hot star. Given the correct circumstances such a planet should be able to a solid crust of iron radiating heat and insulating the interior. The interior would contain a vast reservoir of heat which could be topped up with heat from radioactive decay as well as tidal forces.
If this planet had a very significant magnetic field and rotated (both likely) then it should also generate the complex fluid dynamics that drive the currents deep inside Earth ultimately driving plate tectonics. So plate tectonics of some form should be possible.
That said those plate tectonics would not necessarily be like ours as plates on Earth tend to float on the basis of variable material content causing difference in density, rather than on Randell where it would be the same material at a different temperature causing a difference in density.
One possibility would be that colliding plates would simply merge and become thicker forcing the lower parts down into the hotter lower regions where they would eventually melt and the upper parts up into mountain ranges (rather than one plate diving under another).
Another possibility is that the crust would contain a disproportionate amount of the lights elements that exist such as zinc and virtually all of the small amount of silicates and so would be light enough to mimic some vaguely Earth like tectonic plates.
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extreme tidal forces. make it a moon, and throw it around a planet a bit larger than Jupiter. give it him the Io treatment. that will teach him
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Not a scientist, but I suspect your iron planet with plate tectonics is going to be absolutely too hostile to be inhabited or even visited.
If there was crust thin enough to easily break up into pieces, then the molten iron is right beneath your feet, relatively speaking. Vacuum of the space is an excellent insulator, and the surface cannot cool down fast enough to provide habitable temperatures, probably way above boiling pount of water.
If the surface was cool enough for humans, on the orher hand, it would be solid, and if there still was plate tectonics, the "earthquakes" on the planet would be something never experienced here: the whole planet would vibrate like an enormous churchbell whenever the crust cracked, shattering everything, possibly throwing smaller objects around with such force that nothing manmade could survive.
It would be an interesting planet though, but only to be observed far away.
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I'm interested in how you could get a creature that is broadly "dragon-like" to evolve from modern-day birds. Considering that some extinct early birds or proto-birds looked pretty reptilian, I think it's not an impossible route.
Parameters:
Minimum definition of "dragon" for the purposes of this question
* Capable of flight
* Large enough to be terrifying and potentially capable of picking up an adult human (likely with talons) for at least a short distance. This would have to be a huge bird, at least as large as the extinct Haast's eagle from New Zealand (up to 10 ft wingspan) or even as large as some prehistoric birds (for reference, the heaviest flying bird ever, Argentavis, weighed in at 72 kg with a wingspan up to 21 ft)
* Head doesn't have to necessarily be serpentine or reptilian, but it should have a distinctly extended head and neck (like a vulture) with at least a face that is mostly or entirely featherless
* teeth would be great if possible, although no modern birds retained teeth
I know it kind of just sounds like I'm describing a giant vulture, but I'd like to know if it would be plausible to push it more into dragon territory and what kind of evolutionary pressures would push birds into developing those adaptations. For the purposes of this question, assume we're starting with modern Earth birds, but they don't necessarily have to be located on Earth (could be a terraformed exoplanet, for instance).
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# Arid climate
Which, funnily enough, could push a vulture closer to a stereotypical European dragon of legend in every way.
There's a few main factors at play here:
1. High tempuratures
2. Water scarcity
3. Foods available
These three conditions would favor the following traits, respectively:
* **Loss of feathers**, as heat retention is no longer needed
* **Development of scales**, to conserve water (With the added benefit of protection from the hostile terrain). The feathers would likely degenerate into these, rather than disappearing entirely before.
* **Redevelopment of teeth**. This one's a little more iffy, because the beaks of vultures already are optimized for tearing meat, but genetic drift could cause them to reappear.
**Essentially, the vultures are evolving back into lizards, keeping their ability to fly.**
Now, the loss of feathers could pose a problem to the "flight" portion of your requirements. I am not sure how much replacing feathers with scales would affect the flight capabilities of your birds, but unless the atmosphere is super dense, or gravity is unusually low, they may end up grounded for a time in their evolutionary period, before developing an alternative, such as webbed wings.
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The problem with evolving from birds is that birds usually have hollow bones, making them frail, as such, they are unable to fight similarly-sized prey, making them usually scavengers. If you want to super-size them, they would need to be light and very brittle, making them not really pose a huge threat to people. Making them partially featherless only adds more problems, so I suggest starting from lizards.
If your dragons are evolving from lizards, there are a couple of changes to the dragon that would increase plausibility. Being a wyvern (2-legged) as opposed to a traditional dragon would be more probable since it would only require a membrane to fuse with their preexisting front limbs, as opposed to sprouting entirely new appendages. On that note, you should strongly consider your dragons to be only capable of soaring as opposed to flying (the distinction being the ability to generate one's own lift). This isn't as limiting as might be expected due to the preponderance of thermals, and other air temperature disparities. This limited ability is also consonant with the evolutionary route since it would be very improbable to develop hollow bones before a creature is capable of flight. Therefore your wings will likely be unable to compensate for the weight and produce lift. If you want them to have greater maneuverability (comparable to a glider aircraft)in the air, you could give them rear wings, like the Changyuraptor.
Another consideration is their size; If they are large, they need more energy and sustenance. A small lizards diet is inadequate, so it too must change. The ancestor lizard's prey should also have adapted (gotten bigger, stronger, etc) or died out (killing off small lizards due to starvation while allowing larger ones a chance at finding new prey unfeasible to the rest, causing the large mutation to be more common). Eventually, humans might become feasible prey. You should also know that once they become a dominant species their evolution will stop advancing as rapidly. In this scenario, teeth are especially viable since adequately large prey would require breaking into pieces.
To summarize my design suggestions:
* Wings like a pterodactyl (important if feathers are not in play)
* Wings on front and back (I'm less sure about this, but it makes them have greater air supremacy)
* No front limbs that don't have wings(greatly improves plausibility)
* Only capable of gliding
* Very diverse food chain or pack-hunting(for size)
* Omnivore but primarily meat-eating (greater energy to match consumption)
Although it's not quite the bird-dragon you wanted, its more plausible, and it's not just a stereotypical dragon either. I also didn't mention it much, but if you make them pack hunt (~human size - more plausible), you could have a more unique creature. Imagine how much more terrifying a pack of vicious, nearly man-sized lizards descending and devouring a person is than a big dragon-bird that takes one bite and is done with it.
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This is probably not what your wanting, but if your dragon-birds were originally selectively bred starting from carnivorous birds for their size, strength, featherless head (unless they started off with vultures or similar birds),(and possibly teeth) and a longer neck (probably not all at the same time) to taxi people around faster than cars do. That would open up the possibility of a group of them to escape and breed to be more aggressive and would already have the strength to carry people off, which would give you everything except the teeth. Giant escaped taxi birds turned aggressive probably isn't intended but it's a possibility.
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Another attempt at a broad question I asked here earlier. My aim here is to build another cradle of civilization from the ground up, in an area that never did (for fairly obvious reasons) and in an area that could serve as a sort of connection point between the Old World and New World.
For most the part I am getting together a rough idea of what I need to do and where I want to go with things but I am have trouble getting the initial setup going, this is where the plausibility factor might be kicking this entire idea in the groin.
To get to the point are there any plants in the interior of Alaska, specifically the Yukon River basin, that could serve as a founder crop to serve as the catalyst for further plant domestication and ultimately sedentary civilization. I haven't been able to find much, not sure if its due to a lack of resources on the topic, a lack of knowledge on my part as to where to look or a lack of said plants in the region.
I mean the area could certainly provide a decent supply of food for locals, especially with proper agricultural practices, winter preparation, advanced/complex food preservation techniques, etc. For instance Alaska does produce oversized record breaking vegetables due to loads more sunlight during the summer.
Thanks again
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**Aspen.**
<https://www.fs.usda.gov/wildflowers/beauty/aspen/grow.shtml>
[](https://i.stack.imgur.com/O7appm.png)
Aspens grow in the Alaskan interior. They will dominate an area until shaded out by pines.
>
> Quaking aspen is an aggressive pioneer species. It readily colonizes
> burned areas and can persist even when subjected to frequent fires. In
> the Central Rocky Mountains, the extensive stands of aspen are usually
> attributed to repeated wildfires. It may dominate a site until
> replaced by less fire-enduring but more shade-tolerant conifers.
>
>
>
The seeds and bark of aspen are edible.
<https://www.ediblewildfood.com/quaking-aspen.aspx>
>
> Edible Parts Much of the tree is edible. You can eat the inner bark
> and cambium but it is best in the spring. It can be dried, ground into
> a powder and used as a flour. For those who have used it, they say
> that this flour is normally mixed with other flours for making bread.
> It also can be used as a thickener for soups. This tree can be tapped
> for the sap and it can be made into syrup. Catkins can be consumed raw
> or cooked...
>
>
>
Your people have been working on the aspen. They keep the pines from shading them out. They select for trees with big fat catkins and lots of them. It helps that aspens can grow as clones.
>
> Aspen is noted for its ability to regenerate vegetatively by shoots
> and suckers arising along its long lateral roots. Root sprouting
> results in many genetically identical trees, in aggregate called a
> "clone". All the trees in a clone have identical characteristics and
> share a root structure...
>
>
>
If you want Fat Caskin Tree to take over the area, give it room. I could imagine your sedentary aspen keepers have different named tree clones, each good for something particular - Fatty as noted above. Sweetbark the flour trees are kept as saplings to maximize tender bark production. Sapmasters are of course is made into that staple of civilization, beer.
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In my current science-based project, I have this idea for a string of rotating black holes (bonus points if you can figure out how they can be lined up without gravitating towards each other) that are used for their ergospheres.
Because ergosphere spacetime flows FTL, I think a vessel within it would also be propelled FTL, without actually violating causality, since it's spacetime that's moving so fast, not the vessel. Therefore, this string of ergospheres could be used as a means of effective-FTL travel without negative energy. Side note: I'm aware that there are Alcubierre drive theories that only require positive energy, but it's still way too much energy.
Basically, it would end up something like this (probably not to scale):[](https://i.stack.imgur.com/gdoo1.png)
Does this make any sense scientifically?
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>
> Because of this dragging effect, an object within the ergosphere cannot appear stationary with respect to an outside observer at a great distance unless that object were to move at faster than the speed of light (an impossibility) with respect to the local spacetime. ([Source](https://en.wikipedia.org/wiki/Ergosphere))
>
>
>
**The Good, the Bad, and the Ugly**
When Sergio Leone directed that Clint Eastwood movie, little did he know that he'd created one of the most useful phrases in human history.
**Ugly First**
You're asking us if an idea is scientific but, per the quote above, your idea is based on a scientific impossibility. So, no. Your idea is not scientific. I can't even imagine how to get black holes to line up in a straight line in a universe where everything is in constant motion and, generally, a circular motion.
**The Bad**
Everything you're talking about is a best-guess based on mathematics and remote observations. One of our celestial machinists could give you a boatload of math I can barely remember from college to explain the what-you-can and what-you-can't of the situation. But the simple truth is that there's no empirical evidence the consequences of the ergosphere are correct.
But this being bad is actually good for you! The fact that there isn't any actual science (per se) behind the idea you're trying to exploit means you can exploit away.
**The Good**
The number of people who will read your story and know to judge that it's not scientific is darn close to zero. Of those (assuming you have a well-written story) the number of those who will judge you for not being scientifically perfect is zero.
*And I'm a fan of reminding people that what we know of science is far from gospel truth. We're constantly learning new things and discovering hidden mysteries. It's a huge mistake to believe that what we know of "science" today in any represents a cut-in-stone understanding — especially when you're dealing with massively theoretical things like what happens inside the event horizon of a black hole.*
Bear in mind you're in *great* company. When Larry Niven first wrote about the [Ringworld](https://en.wikipedia.org/wiki/Ringworld) he didn't realize he'd written an entire story *about a scientific impossibility.* [MIT students at a scifi conference](https://www.theguardian.com/books/booksblog/2010/jul/02/larry-niven-ringworld) marched the halls chanting "The Ringworld is unstable!" as if they'd cured cancer. What did he do?
He fixed it in his next book.
My point? *This is a cool idea.* Run with it and ignore anyone who thinks otherwise.
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So you are talking about [**Lense-Thirring**](https://en.wikipedia.org/wiki/Frame-dragging) effect (**frame dragging effect**) a consequence of General Relativity. Ergosphere is a *safe* region around a black hole within which you can revolve around the black hole and still be able to maintain the velocity required to escape. This means that even at a sub-luminal speed (speed < $c$) you can easily escape the black hole's gravity.
Since, in your string of black holes and their ergospheres, you are using FTL frame of reference (the space-time itself), you could consider your observer to be a part of the FTL dragging frame. You also mentioned that a vessel inside FTL frame could be FTL for a region outside, you may make the string of ergospheres a *vessel* in the space-time that is dragging.
This all means that the observer is within the FTL dragging frame (not inside the ergospheres because that would require consistent motion) and the traveller is moving within the string of ergospheres which is itself within the FTL frame. So this *highway* you constructed will make a good sense even within the limits of relativity.
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I suspect that might not work.
The idea behind warp drives etc. is that spacetime is a riemannian manifold you can deform, and by deforming spacetime properly one may "generate" shorter geodesic paths between two points in spacetime, which a spaceship may then take.
The problem is that **black holes** (as far as I know, im actually not at all good at general relativity) as well as other massive objects, tend to **increase the "distance"** between points, so work in exactly the wrong way.
However **if you used white holes** (and im not mistaken) you may actually directly **shrink the "distance"** between source and destination, so then that should work.
So if you use **white holes instead of black holes** things may work out just as presented.
However I would certainly love to see the opinion of someone actually knowing general relativity on this. Would certainly expand my knowledge.
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At what point would we notice or be able to detect an object entering our solar system at 0.20 speed of light?
What's the maximum range we would be able to detect with certainty beyond a reasonable doubt (e.g. edge of Oort Cloud)?
And how much time would it take for that object to reach the inner solar system, or up to 5.2 AU (Jupiter's orbit), from the moment of detection?
For the sake of this question, the object's trajectory is not expected to intersect with any other stellar body in the system and its course is not expected to deviate (direct line). The speed is not expected to deviate, i.e. no external forces are expected to act upon the object to decelerate or accelerate it.
**Edit**
Let's say it's a:
1. **multi-generational ship**,
2. constructed from known metals and materials (nothing exotic),
3. around **3km in length**, with a **2km wide** protective "asteroid-like" mass at the bow,
4. weighing in around, say, **8.5 billion metric tons**,
5. with an **albido of 0.5 - 0.8**,
6. it does not rotate,
7. it would **radiate** in all the typical ways you would expect a ship of this nature to.
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## Sorry!
Despite the undeserved check mark, the first calculation I jotted down had two errors that threw off the result... that I know of so far. Now I'm getting that it is a warm 786 K but nowhere near hot as a star. Because it would not leave a reflected trail like a comet, this might be hard to see.
Detecting it "when it enters the Solar system" is right, because the heliopause has a higher density of matter. The solar wind flows out from the Sun until it sort of stops, buffeted by the interstellar medium. So the density we're looking at for the heliopause is something like [0.12 electrons per mL](https://www.sciencealert.com/for-some-reason-the-density-of-space-is-higher-just-outside-the-solar-system), with I would assume a proton to go along with each one, whether as a hydrogen nucleus or (rarely) a part of something bigger.
So we've got, say, 3 km^2 of surface moving at 0.2 x 3e+5 km/s (CORRECTION). Each second we "clear" 1.8e+5 km^3 = 1.8e+20 cm^3 of volume. Everything in that volume impacts at 0.2 c, which is to say its relativistic mass will be 1/(1-0.2^2)^0.5 = 1.02 times higher than its rest mass. The rest mass (per the volume for one second) is (0.12 electron+proton / cm^3) x (1.8e+20 cm^3) x (1 g/mol) x (1 mol / 6.02e+23) = 36 mcg. So 2% of that, times c^2, is 6.5e+10 J. Per the second I mentioned, this emits 65 gigawatts of energy, continuously. This can be compared to the 23 watts used by Voyager 2 which obtained the data from the first link above, but bear in mind it's white noise in all frequencies, unmodulated, and no one is aiming a dish at it. Let's look further.
If I assume the asteroid is a black body (which seems *anything* but a safe assumption, since good designers would try to reflect radiation and heat away), radiating only on the putative 3 km^2 I approximated a circle to be, then T = (6.5e+10 J/s /( 3e+6 m^2 x 5.67×10−8 W⋅m−2⋅K−4)^0.25 = 786 K.
[Answer]
Didn't get an answer to a question I placed in the original post so I'll make a basic assumption here.
(Assuming for instance some form of realistic fusion drive?) **Some time after it starts decelerating**. With the length of time required before its discovery dependent on a lot of variables I don't have numbers for but in any case likely to be months if not years.
All the modelling I've seen suggest such drives operate at extremely high temperatures (1500K plus) but they are also capable of maintaining reasonable levels of thrust for extended periods of time, making them far superior to chemical rockets for deep space missions.
So since this is such a massive object and its starting velocity compared to the Sun is extremely high such a drive is going to have to start its breaking 'burn' years?? in advance of entering the inner solar system.
Astronomers: Hmmmm.... a new big/hot light in near interstellar space with a (slowly) diminishing blue shift. Curious!
] |
[Question]
[
I'm writing a fantasy old-west type novel, and I want this world to have extreme climates. I have a few questions, particularly for Americans:
* I want the mostly settled areas (mid to low income population) to look like a perma-frosted Aspen (Colorado), with mountains and snow and evergreen trees and such, but also the occasional whipping blizzard.
And on the other hand, I need a desert wasteland with harsh sandstorms.
* Now, I'm not American and I can't know how that works, but how should the place between the two extremes look? I was thinking to make this the 'rich people' area where they can afford to live in not-life-threatening climates, but that raises the problem - everyone would fight over those places and strip them dry of resources, or use it all for farmland, and I don't even know what else. Would this area be bruised with vegetation-less hills or be more like prairies?
* How big of an area would all of this together have to cover - how many states? Can it fit within one?
As you can see, I'm kinda lost, and any tips on this (especially from Americans living in those areas) would be greatly appreciated. Thanks.
**Edit:** The [read dead 2 map](https://www.reddit.com/r/reddeadredemption/comments/cr09hq/red_dead_redemption_map_satellite_view_final_edit/) is just under 30,000 square miles. Is the climate and terrain there realistic for the size?
[Answer]
The best I can tell you is take a look at the countries of the world that exist in harsh climates, like the far north, or equatorial deserts, or scorching Africa.
One thing I notice is that the harsher and more dangerous the climate, the more likely the culture is inclusive and mutually supporting. Even though the Netherland countries are modern, the climate is cold and forbidding and they have the strongest social safety nets in the world.
I think this is because in such climates, you need the help of your neighbors, almost to the point of share and share alike, just in order to survive. You work collectively because the synergy of that is a matter of survival.
Synergy is when the work people can do together exceeds the sum of what they can do alone. A common example is the defenses of the village fence: It is far easier for everybody to build a fence around their village, then for each person to build a fence around their house. Shared child care is easier than individual childcare, shared hunting is more productive than individual hunting, shared farming is more productive than individual gardens. In fact, a team can build an irrigation ditch from the river to serve one giant 500 acre farm, and that's much less total effort than everybody trying to dig their own irrigation ditch from the river to serve their own 2 acres.
The harsher and more dangerous the climate, the more tight-knit the community.
Also, the wars for the "Good" climate areas have already been fought and lost, and the "good" areas are well defended. Those people use their wealth to hire the poor as soldiers and guards. There may be an occasional raid or robbery or murder, but for the most part, the poor farmers in dry parts of Mexico are not plotting to take back California. They may want to immigrate and work for the rich people there, but they aren't trying to overthrow it and take it back. That battle's already been lost.
The collective action for the rich in the good climate areas is not for individual survival, it is just taxation to fund a collective defense of what they have. The richer they are, the less inclusive and mutually supporting they are, the more prejudiced, bigoted, jealous and status-obsessed they become, the less able they are to put aside minor differences. And the less they will go out of their way to help individuals in their own group.
Hardship brings people together. Abundance pushes people apart, because they don't *need* each other to survive.
[Answer]
**Look at the Mormon experience dealing with Western lands.**
[](https://i.stack.imgur.com/PArz7.jpg)
<https://www.loc.gov/resource/g4344b.pm009230/?r=0.367,0.172,0.943,0.394,0>
In 1847 the Mormon pioneers chose the Salt Lake Valley for their settlement because it was isolated, inhospitable and harsh. Hopefully no-one would drive them out, because no-one else wanted it.
<https://en.wikipedia.org/wiki/Mormon_settlement_techniques_of_the_Salt_Lake_Valley>
>
> The Intermountain West was “drier and colder…more rugged… and less
> accessible,” making the geographical differences from the Mississippi
> River Valley, their former home, quite profound... Lansford Hastings
> said that the area “offers inducements to no civilized people,
> sufficient to justify an expectation of permanent settlements,”
> however, John Fremont's more favorable report inspired the church
> leaders to select the Salt Lake Valley as their destination.
>
>
> Young thought that isolation and demand for hard work would be
> character building for his people and the Salt Lake Valley seemed to
> possess the ideal qualities... With ample manpower at his command,
> these resources could be fully utilized at his discretion... Jim
> Bridger had told the newcomers that nothing would ever grow in the
> Salt Lake Valley, mainly because the ground was so hard. In fact, it
> was so hard that it broke some of the pioneers’ plows. In order to
> soften the ground, the pioneers built a dam in nearby City Creek to
> flood the ground, which was successful (Alexander). Some of the Saints
> had learned irrigation techniques while serving missions, in places
> such as Italy, so they understood how to “dam streams and channel
> water in ditches to irrigate the crops
>
>
>
The Mormon story is an amazing one. Those lands are really bleak and inhospitable, but they made it work. Where the Mormon experience addresses your question is as regards societal structure: the church members were unified by their membership and shared beliefs, and the church / government could coordinate and oversee the efforts of many unrelated people in undertakings for the common good.
Old west Mormon-type societal structure would be fine material for a fiction. The church was insular in that outsiders might be distrusted, but evangelical - outsiders were invited to join. As seen from the outside, some customs were weird and offputting (polygamy) and others frankly admirable (work ethic, common purpose). I could see a fiction of an American West type world introducing a religious community halfway through as a contrast to the communities the reader has encountered so far in the story.
] |
[Question]
[
Space is hard, and making a spaceship engine powerful enough to do interesting things requires an absolutely bonkers amount of energy. I know that lots of authors (including me) think of trying to get around the issue by making reactionless drives, but those have the issue of allowing ships to accelerate to arbitrary velocities and destroy planets. I had a slightly different idea.
I've heard that theoretically, we can have a non-physics violating warp drive as long as it can't get above the speed of light. So what if someone invents a warp drive, but one which can only generate "virtual" velocity relative to the ship's "true" reference frame; and only up to a certain relative velocity, like, say, 50 km/s.
1. If you have a ship in orbit of Earth, and it uses its warp drive to travel at 90% of the speed of light for one minute away from earth, then when the drive shuts off the 0.9c velocity vanishes, and the ship is left with only the velocity it possessed while orbiting earth.
2. If two ships are stationary relative to each other, and one turns on its drive and attempts to ram the other, the instant they touch the warp bubble collapses and the two ships are left kissing without having damaged or imparted kinetic energy to the other, since they didn't have any relative kinetic energy to begin with.
3. If a ship wants to get actual velocity without expending fuel, it can do so by using its drive to hover above the surface of a massive object, like a planet, and using its gravity to increase its true velocity, until it shuts off its drive and shoots off like a rock from a slingshot. The caveats are that you can't get a true velocity any higher than your drive's maximum speed (because otherwise you crash into the planet), and you need to be able to slow down at the other end of your trip (because the drive can't cancel your true velocity.)
4. You can't use the drive to extract infinite energy from a gravity well by lifting an object above the surface and then dropping it through a generator, because raising an object through a gravity well requires additional energy equal to the potential energy gained by the lifted object.
EDIT: It's been pointed out that #3 and #4 contradict each other, since you could hover above a planet to build up 'true' velocity, and then drop into a generator with much greater energy than just the potential energy of the fall. My solution to this is that getting up to a certain 'virtual' velocity requires at least as much energy as the kinetic energy of the mass of the ship traveling at the same 'true' velocity. Though this brings up the issue that the energy would then have to GO somewhere once the drive is shut off, which might be hazardous, as a 20-ton craft going at 50 km/s would have to get rid of an amount of stored energy equal to half of Hiroshima.
**My question is: Does this break the universe/physics? How? Does it make sense?**
EDIT: Numbered bullet points.
[Answer]
**Still breaks planets, but universe is OK**
Let's go back one step and look at why a reactionless, sublight drive is useful to an author / universe builder. Alice is on Earth and wants to visit Bob on Ganymede. With real world universe limits, the options are:
* Take many years to do so using very low thrust methods such as solar sails
* Take months / years to do so using high-efficiency low thrust methods such as ion drives.
* Use technomagic drive that expels its reaction mass at near lightspeed - problems are that a) the exhaust from the drive can destroy cities and it lets the spacecraft accelerate to planet-wrecking velocities quite easily; and b) there is still a requirement to commit a large percentage of the ship to fuel storage due to the tyranny of the [Tsiolkovsky rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation), with the less magical the drive the higher percentage of the ship needed for fuel.
Hence the attraction of a high output reactionless drive - it eliminates the months/years timeframe for interplanetary journeys, it makes the exhaust non-existent (and therefore safe re the [Kzinti lesson](https://scifi.stackexchange.com/questions/13044/what-is-the-kzinti-lesson-from-larry-nivens-ringworld)) and it removes the need for massive fuel tanks of reaction mass.
However, there is a problem with relying on a [stutterwarp](https://en.wikipedia.org/wiki/2300_AD) / warp drive that does not change the velocity (not pseudovelocity) of the ship. Within a solar system, all the bodies are moving at different velocities. Which means that if Alice wants to visit Bob in the example above, when Alice arrives her ship will be moving at somewhere between 16 km/s and 43 km/s with respect to Bob's home city (depending on the relative positions in their orbits of Earth, Jupiter and Ganymede). Without using a reaction drive to make a very significant burn, Alice will either whip past Ganymede without being able to visit at all or will obliterate herself, Bob and everyone else in a large radius in a potentially extinction-event-level impact. Put another way - unless all objects that need to be travelled between are effectively stationary with respect to each other - effectively impossible in any solar system:
* a warp drive of this type can still be a very dangerous weapon at its destination;
* a spaceship will rely on a also possessing a reaction drive with associated fuel to match velocity at the end of its journey. (For planets it may be possible to slowly match velocities using the gravity of the planet with repeated passes, but this would not be usable for low mass destinations such as space stations.)
As far as physics goes though, it seems to tick all the boxes - causality is preserved, conservation of momentum, conservation of energy (given that energy is required to "climb" out of a gravity well). So the universe is happy even unfortunate residents at a ship's destination are (very briefly) unhappy.
[Answer]
Points #3 and #4 seem incompatible to me.
Use your drive to hover over the planet, then turn it off and plunge down into a generator. You can get a lot more energy this way than it's going to cost to lift it back up.
I don't believe it's possible to have a no-cost drive that can't be exploited as a perpetual motion machine. And, because it's a generator it can be used for kinetic bombardment. Hover a star fairly close in and you can build up a **lot** of velocity!
[Answer]
As presented, you still break physics. It's your first point.
"If you have a ship in orbit of Earth, and it uses its warp drive to travel at 90% of the speed of light for one minute away from earth, then when the drive shuts off the 0.9c velocity vanishes, and the ship is left with only the velocity it possessed while orbiting earth."
How much energy does it take to get up to 0.9 c using the drive? A "normal" drive will need about 9 megatons per kilogram. And then there is an even more embarrassing question - when you turn the drive off and revert to normal velocity, where does all that energy go? For normal drives, the situation doesn't arise: if you arrive at 0.9 c the impact is what dissipates the energy.
If the drive takes essentially no energy, or even just significantly less than a boring old reaction drive, you get a perpetual motion machine (I assume it ignores potential energy just the same as it ignores kinetic energy.) Take a container full of water, and use the drive to transport it to some higher altitude, and release it. Channel the released water into a waterwheel to harvest the energy, then transport it again.
Reactionless drives don't give the advantages you seem to think they do. Just because they don't need reaction mass doesn't mean they move as if by magic. And what you're talking about is not a reactionless drive at all, but rather (for lack of a better word) an inertialess drive.
] |
[Question]
[
I translated my question/text with a translator because English is not my native language. I hope there are no mistakes.
**Can you help me to define realistic climate zones and weather for my fictional world map?
I am struggling with the climate zones and weather of my world map.**
Unfortunately, I don't know anything about geography or meteorology (I'm uneducated on that). But I would like it to be correct. I have spent a long time searching, but it is very difficult to understand. That's why I would like help, please.
I have not defined information like the axis of rotation of the planet, in which direction it turns, etc... (I really don't know anything about it). So I guess it those can change.
Maybe should go up or down a little bit more the western continent or the eastern continent? I don't know.
I haven't yet precisely defined the Eastern continent.
My story will take place in the Western continent and mainly in :
* purple numbers,
* blue numbers
* red numbers (with the desert),
* the number 10 (with also the small island)
* the number 11
* the continental forest.
So I need these mentioned areas to stay next to each other. The other areas are changeable, so you can move or change its position.
These are States. And the numbers that have the same color are States that form an empire.
To clarify: The big forest in the western continent is a somewhat supernatural forest, which goes beyond the laws of nature and where strange things happen. So that could be a reason for it to be like that climatically speaking.
[](https://i.stack.imgur.com/y4RmN.jpg)
**EDIT 23 march 2022**
I thank the Workdbuilding community comments for focusing this question. I took into account the following :
the climate zones are not straight lines
ocean currents also needed
mountains can stop the wind or the rain on the other side
I have a lot of oceans (maybe too much), I have filled a little with lands (islands)
the oceanic and continental climate occupy the same latitude
my lands are big (maybe too much I think)
For research, I followed the advice given in the Artifexian videos and also on this website (<https://rollforfantasy.com/guides/map-creation-climates.php>).
I am now sharing the result with rhe community.
There are some areas on which I did not put any climate (not colored) because I do not know yet what I should put. It's complicated ^^'
I hope you can help me.
[](https://i.stack.imgur.com/8xBSB.jpg)
[Answer]
**Climate zones are no straight lines**
My two cents: you provide a quite common subdivision, with Earth terminology. That is ok.
Issue is.. all your lines are straight lines. Climate zones are not only determined by the sphere shape of a planet. Ocean currents and continental border shapes play a role, deserts and forests indicate climate as well. For example you have these "dry zones" on either side of your equator. Looking at the map, you have a desert sitting only north of the Equator, forest all around. Your dry zone starts wider in the west, on the east side, the "dry zone" will bend south, to allow the forest to be Tropical.
For Earth, this is also the case. The climate zones are *about* horizontal, but not *exactly* horizontal. Look at Western Africa.. the coastal region is light blue, cooled by the Atlantic Ocean, yielding lower temperatures along the Equator. Inland, you find a dark blue equatorial zone.
[](https://i.stack.imgur.com/JSwnv.png)
Useful study on the topic: <https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification>
EDIT: a tip from by LuizPSR's yesterday's comments: your big forest will be very humid, and area 1, 2 and 3 would become arid climate, when you put a western wind on the coast.
**Some notes about colors**
I like the subtle colors in your question now. The harsh colors Wikipedia shows are not obligatory for climate maps and do not fit yours. When your story has several maps, their colors should be balanced.. same style.. and the colors "hues" must fit with the "atmosphere" of a story. Leave out pure red.. it does not fit with green-blue. Never blue for land. The legenda of your climate map will be grey, yellow, pink, orange and green shades for the climate zones on land
[Answer]
**Your land masses are big!**
It is 7400 km from the equator to the Arctic circle (on earth). Your round continent is just about 7400 km north to south and east to west. It is almost as big as Africa which is 7400 east to west and 8000 north to south.
[](https://i.stack.imgur.com/4dk0b.png)
I took your map, put a bar showing the 7400km from equator to arctic circle then put those bars on your round continent. I added Africa to scale. The bay at the top of your round continent is the size of Hudson Bay in Canada.
The diversity of interior biomes (and landforms; rivers, mountain ranges) on the round continent is appropriate for a big island like Madagascar. The shore detail looks like you were thinking on that scale too. But if this is an Earth sized world you have made some big continents! Scale up and think bigger and place interior diversity to match something continent sized like Africa or North America.
[Answer]
There are quite a few inaccuracies, but unless you are going for realism rather than fantasy, climate can easily be ignored. Nobody complains about the climate in game of thrones, and their seasons can last anything between months and decades.
As for the corrections, it seems that you sorted the climates based on latitude alone, but oceanic currents are very important as well. Oceanic and continental (temperate) occupy roughly the same latitudes, but the oceanic is closer to warm currents, while the other is found on the interior of continents and coasts with cold currents. Same thing for subtropical and mediterranean.
There's a youtuber that cover this topic in further detail (Artifexian):
* [Worldbuilding: How To Design Realistic Climates 1](https://www.youtube.com/watch?v=5lCbxMZJ4zA)
* [Worldbuilding: How To Design Realistic Climates 2](https://www.youtube.com/watch?v=fag48Nh8PXE)
] |
[Question]
[
My species is a eusocial race of insectoid aliens. The basic gist is only the Queens are sapient, and the soldiers and workers are non-sapient. To me it felt like there wouldn't be much of a society and the Queens would lead very lonely lives.
So I got this idea that once the workers are done gathering food, building cities, etc. They pupate, and come out fully sapient with innate knowledge on basic life skills (Think pokemon evolution). They still retain their ability to repair broken things from their worker days, but have no memory of actually being a worker.
My question is would becoming sapient like flipping a switch be biologically possible?
[Answer]
Sapience itself is an ill-defined term, and depending on how you look at it we have only a single species that meets the criteria. You can hardly say what the rules should be when you have a sample size of one, after all.
So let's look at some assumptions:
* Sapience is immediate or occurs quickly once an individual is mobile and/or visible to others (toddlers)
* Sapience is universal within a species... that is, either every individual specimen of a species is sapient, or every specimen is not sapient
* Sapience is an innate quality of the mind (within humans and Earth-life, a property of the neurology of that organism)
None of these assumptions can be verified, and none of them are supportable based on any principles of intelligence or consciousness that we're aware of.
Some (alien) species might have only random specimens become sapient. It might not occur at a uniform age/range... some might be sapient from day one, others only centuries later. There might or might not be a distinct brain within the specimen that causes this quality to manifest.
When you are dealing with alien biologies (not biologies that exist on Earth, are derived from Earth, or are purposely similar to Earth), pretty much anything goes that isn't disallowed by basic chemistry. Go for it. Biology's just not your obstacle here. Nor are there any within the principles of sapience itself.
I will add one additional note here: would a lone sapient mind such as a eusocial queen, even know what loneliness is? Loneliness is a state of mind we experience because we are social creatures that have adapted over millions of years to desire and be accustomed to other minds being nearby. An organism that has not evolved from such pressures might not ever experience a state of mind similar to that. Whether this means it would be innately hostile to foreign minds, or just apathetic, I leave as an exercise for you OP.
[Answer]
**Skillsets change with life stage.**
Consider the tadpole and the frog. Different environments, different diets, different modes of locomotion, same creature. Some fish start as a male and then get to be female after proving themselves fit (e.g. not dead). A cicada larva and cicada adult as about as different as two beings can be, but they are the same organism.
There are many creatures which change radically over development. Having sentience be an emergent property after metamorphosis makes sense. Also maybe the high-mortality rate life as a worker juvenile will select for individuals with the traits you want.
You setup offers the possibility of palace intrigue. If sentience is gained at metamorphosis, there will be many sentient females but only one queen. Who will be the next queen? Do the males have a role to play in this or are they born only to mate and die?
--
I like the idea of the drone that is different. It does not become intelligent. It was born that way; a mutant. It is the one that is lonely, in the company of its mindless sisters. It keeps a low profile. But maybe it is capable of playing a role in its society that no-one else can play.
[Answer]
Caterpillars likely don't know how to fly, but once they turn into butterflies they do somehow.
I would think this to be along the lines of what you are asking.
Seems reasonable to me.
While pupating, they develop new mental switches that are then turned on as they mature.
In bees, the queen is grown in "royal jelly" which changes them as they grow, perhaps a special resource is given to subjects to spark their mental evolution.
] |
[Question]
[
>
> For most of our evolutionary history, we did indeed live in Africa - but not just the eastern savannahs, as previously thought: our biological ancestors were distributed everywhere from Morocco to the Cape. Some of these populations remained isolated from each other for tens or even hundreds of thousands of years, cut off from their nearest relatives by deserts and rainforests. Strong regional traits developed. The result probably would have struck a modern observer as something more akin to a world inhabited by hobbits, giants and elves than anything we have direct experience of today.
>
>
>
"The Dawn of Everything", David Graeber and David Wengrow
What environments might cause a larger variety of human, on the scale of 8 to 10, or possibly even 12 feet tall, to evolve?
I presume that humans haven't evolved to average heights of more than about 6 feet because A) humans can adapt to different climatic conditions by developing new tools and strategies, rather than through physical adaptations like growing very large or very hairy, or B) simply because enough time hasn't elapsed for Homo sapiens to evolve that way. That being said, I know that some populations have adaptations for high-altitude life, and that Inuit have genetic mutations which make them more adapted to cold and a high-fat diet, which same mutations also affect height. Nevertheless, aside from some outliers, humans on average don't get much bigger than about 6 feet. How could sizes beyond this evolve?
Could very large, stocky humans evolve in a cold climate, yeti-style? Or would adaptation to a cold climate be more likely to have the opposite effect?
Or, would large size be more likely to evolve in hotter climates? Could a population of humans populating a hot savannah evolve to 8-10 foot height, in a similar way to how African megafauna evolved great size?
Perhaps humans could attain great sizes in hot, humid environments where biodiversity is high and food is plentiful? I believe I read that average human height has increased in the past century because of better nutrition in the modernized world--but for the sake of this question, let's assume our hypothetical megahumans don't live in this kind of world--rather, these populations of larger humans may spend more time on the move, settling in one place for a few months out of the year at most.
[Answer]
## Island gigantism
**In Earth's natural history, primates are moderate length**
In the comments, I've pointed out body length has [never been larger than 10 Feet](https://nl.wikipedia.org/wiki/Gigantopithecus), for Earth's primates. I think this is caused by the ape's basic body plan, which allows for speed and agility. The ape became a strong armed creature able to carry its own weight, dwelling in trees.
**Environment**
As the opener pointed out, body length can develop when evolution takes place. When large, bipedal humans can make good use of an environment that allows for 12 Feet length. This will rule out dwellings like dense forests, trees, and most caves, but open grass land would do fine. It will deter most predators. Some large predators would pose a problem, though.. 12 Feet will render your bipedal primates visible for e.g. packs of lions, from large distances!
**A disease: Gigantism**
>
> As a result of the excessive amounts of growth hormone, children achieve >heights that are well above normal ranges.[12] The specific age of onset for >gigantism varies between patients and gender, but the common age that >excessive growth symptoms start to appear has been found to be around 13 years
>
>
>
<https://en.wikipedia.org/wiki/Gigantism>
EDIT: this is pathology, not the evolutionary advantage you seek. Gigantism has side effects, some parts of the body like bones and heart may lag behind, resulting in weakness and fatigue. The king of Prussia found out, he assembled the [Potsdam Giants](https://en.wikipedia.org/wiki/Potsdam_Giants), a regiment of taller than average soldiers.. not very successful,
>
> Although Prussia briefly intervened in the Great Northern War, the
> Potsdam Giants never saw battle during his reign.
> Some sources state that there was a military reason to create a
> regiment of "long fellows" because loading a muzzleloader is easier to
> handle for a taller soldier. Another source states that many of the
> men were unfit for combat due to their gigantism.
>
>
>
**A special type: Island gigantism**
In some rare cases, a species will migrate and find no enemies in its new environment. It emigrated to an island, or isolated region, starting out with a small population, with little competition for food. When predators are too small, or absent and food is abundant, ever larger individuals will survive. An early primate example is the giant lemur [Archaeoindris](https://en.wikipedia.org/wiki/Archaeoindris) which was as large as a gorilla (6 Feet), while the other lemurs measure 1-2 Feet.
<https://en.wikipedia.org/wiki/Island_gigantism>
**Humans, humanoids**
The gigantism disease exists in humans, there are examples listed in the Guiness Book of Records. The excessive length will hinder humans: they have settlements designed for a smaller size, and the larger body will make communication with other humans difficult.. and the larger body will require more food. Humans suffering of gigantism disease will die soon, in early pre-agriculture societies.
Now suppose it's much earlier in human history.. hunter-gatherers, a group of humans has found an island in the early stone age, say [Oldowan culture](https://en.wikipedia.org/wiki/Oldowan) 1-2 million years ago. In a certain period, climate allowed them to migrate to the island, which has plenty of food and no bears or tigers. A similar isolated development could occur in cold, mountainous regions, like the Himalaya. This is makes [Yeti](https://en.wikipedia.org/wiki/Yeti) a plausible myth! As other answers already mentioned, there's a scenario where Yeti got killed by other, smaller humans. An isolated environment also means they'll be smaller numbers.
**It can go in either direction**
I have to note Yeti was never found, but the opposite of gigantism, which is [insular dwarfism](https://en.wikipedia.org/wiki/Insular_dwarfism), seems to have existed in early humans. Opposite circumstances: they dwell in caves, food would be sparse and small size would be benevolent, for instance because certain predators would become less interested to prey upon little humans. This may have happened to the [Flores people](https://en.wikipedia.org/wiki/Homo_floresiensis).
[Answer]
1. It has been found by some archeologists that a rise in oxygen level has been a factor in the ability for species to grow bigger.
2. Animals have cells that generate heat. Heat goes out from skin to air contact The bigger the animal, the lower the skin to mass ratio is. So it's harder for bigger animals to get rid of the heat their cells create. Being in a colder environment would be beneficial to taller human.
Bigger animals have slower cell metabolism, to help reduce the heat generated, which helps with the average lifespan. Maybe the bigger human would live longer, reproduce slower.
3. Lower gravity would certainly help since there is a limit to the resistance of our body to its pull. It also costs extra energy to move.
] |
[Question]
[
[Peaks of Eternal Light](https://en.wikipedia.org/wiki/Peak_of_eternal_light) are hypothetical mountain peaks that exist on the poles of worlds with little to no axial tilt. My question is simply, if such a peak *did* exist on an earth-like planet, one with no moon or axial tilt obviously, what kind of microclimates might exist on this peak? Not taking the atmosphere into account, I would almost think it would be a high-altitude hot desert in the middle of a sea of ice, but I suspect this would not be the case.
[Answer]
On Earth, the planet's axial tilt means that the poles spend at least some of each year in permanent sunlight during their summer. This warms them up, certainly, but I wouldn't go as far as to say it was *hot* by any stretch of the imagination (unless you have the imagination of a polar bear, in which case it might seem a bit uncomfortably warm). At least part of the warmth comes from having the sun (relatively) high in the sky, and it illuminating quite a wide area.
For peaks of eternal light, the sun will be just peeking over the horizon, giving a sort of perpetual twilight. They'll be a little peak of *relative* warmth (or at least, "less frigidity") in a vast frozen wasteland, but they'll still be high altitude mountains in gloomy light. They'll be bitterly cold, and probably very dry, like a less cheerful version of antarctica's dry valleys.
] |
[Question]
[
Spurred on from an earlier post over [here](https://worldbuilding.stackexchange.com/questions/223208/intercepting-surviving-tank-based-high-velocity-kinetic-weapons?noredirect=1#comment685660_223208). The general consensus was that if a depleted uranium round is coming your way, don't be in its way. And if you do get hit, disperse the damage as much as possible.
Essentially, with the introduction of long rod tank rounds (think like APFSDS- Armor Piercing Fin Stabilized Discarding Sabot), armor will have a tough time with those rounds slamming into it. Especially as the speed of those rounds increases. Someone in the other thread made an interesting point, essentially shells don't behave like normal projectiles at much higher speeds.
Modern armor designs are more of a system than a slab of metal these days i.e. ERA (explosive reactive armor) on top of solid composite armor etc. Something that was also brought up was that a long rod penetrator isn't going to do as much damage if the round is tumbling and hitting the armor on its side (ie long rod doesn't strike armor with its tip).
Using this principle, how feasible/effective would a system that intercepts long rod penetrators(LRP) to induce a tumbling or structural damage be. Target acquisition aside, imagine a system that shoots out either a projectile or an explosive to cause the incoming round to tip over and tumble. Currently the Israeli trophy system doesn't work against long rod types. Russia's Afganit supposedly intercepts kinetic rod weapons, however that fires a large heated mass to physically break apart the rod.
Two systems that I had floating in my head were:
A foam type weapon that detonates in a wide pattern and sticks to an LRP to cause aerodynamic instability or even detonates to cause structural damage.
A malleable explosive that's shaped larger in surface volume to an incoming round (think like size of a small pizza or a large pie dish). Upon hitting and wrapping around the tip of a penetrator, it detonates (imagine punching raw pizza dough, sure you go through it, but it gets stuck on your arm and stretches with your fist for a moment) to either cause a flight change or damage structural integrity. Or just immediately detonates when making contact with the tip of the LRP.
These are just ideas to help visualize what I mean, system can be anything really. So long as it goes out to meet the incoming projectile to destabilize the projectile. destroying it is a plus not a requirement.
Its main use case would be on a tank, whereby it would intercept or destabilize long rod penetrators so that if they do hit, then the rest of the tank's armor package can absorb it with relative ease. You'd be able to carry more of these small interceptors than the enemy can shells (enemy is single tank for question's purpose) due to the massive size difference the ammunition sizes of enemy round and interceptor round.
Ignoring target acquisition and assuming the speeds are anywhere from 1.8 ~ 4km/s would a system that works on destabilizing a long rod penetrator either by damaging its flight path or structural integrity be feasible. Or is this a developmental dead end. The system doesn't have to be perfect, just like existing active protection systems. Just good enough to increase survivability by a meaningful factor to warrant its inclusion as part of a tanks comprehensive defense package.
One major constraint is that laser systems to vaporize a shell isn't an option. Anything capable of eating through that much dense metal would be a weapon in its own regard, not an active defense system.
[Answer]
>
> a long rod penetrator isn't going to do as much damage if the round is tumbling and hitting the armor on its side (ie long rod doesn't strike armor with its tip).
>
>
>
The penetration depth of a solid projectile is proportional to its length. If a penetrator is 80cm long and 2cm wide, then it only needs to rotate by less than 3 degrees about its centre to **halve** its effective length, *even if the tip still bites into the target nicely*. One of the things limiting making the modern day tank penetrators even longer is ensuring that they remain completely dead straight at the point of impact... small misalignments can waste an awful lot of energy.
>
> A foam type weapon that detonates in a wide pattern and sticks to an LRP to cause aerodynamic instability or even detonates to cause structural damage.
>
>
>
A modern APFSDS projectile is travelling at nearly 2km/s, and your previous question posited things travelling twice that speed. Present day penetrators might be as long as 80cm. If a blob of your sticky foam is sort of floating in the air with zero velocity, the penetrator will pass it in 400μs. The blob needs to accelerate at *over half a million gravities* to end up travelling at the same speed as that penetrator. To put it bluntly, I don't think it is physically possible to make an adhesive that acts that fast, and bonds that hard. Even if it did, the penetrator is heavy and streamlined and has a lot of momentum and the foam is going to be subject to enormous drag forces... I suspect (though I'm not certain) that even if you did find some suitable miracle adhesive the foam would simply be blown clean off without making much of a impact on the projectile's path.
The problem only gets worse when you consider that the 2-4km/s projectile you're trying to intercept might actually only be travelling a few kilometres to get you. You have a very short window of time to detect the firing, acquire the projectile with your APS radar and then launch your countermeasure. You probably want that countermeasure moving as fast as possible, to disrupt the penetrator as far away as possible, so that it is as poorly aligned as possible by the time it hits you. The relative speeds of the countermeasure and the projectile could be enormous, making the difficulty of surviving the impact even more implausible.
>
> imagine punching raw pizza dough, sure you go through it, but it gets stuck on your arm and stretches with your fist for a moment
>
>
>
This idea has the exact same problem as above plus new ones of its own... the bit of the "dough" that the pointy end of the penetrator strikes is going to be subject to colossal pressures by a device that was literally designed to penetrate things much that are much tougher. Even if the "dough" survived at the point of contact, the contact point is now subject to colossal accelerations, and it seems unlikely that the rest of the "dough" has enough tensile strength to withstand that without tearing.
If you had a material capable of wrapping around a 2km/s penetrator like this, then you might actually have a good material for making composite armor out of capable of stopping such a projectile!
>
> Ignoring target acquisition
>
>
>
Honestly, target acquisition is basically at the heart of this problem. The actual shooty bits of Trophy and Afganit aren't that exciting... they're not radically different from the sorts of things that were available to the developers of the [Drozd APS](https://en.wikipedia.org/wiki/Drozd) back in the late 70s. Afganit is interesting that that it uses [explosively formed penetrators](https://en.wikipedia.org/wiki/Explosively_formed_penetrator) to give it enough striking power to disrupt a long-rod penetrator, but EFP technology is nearly 100 years old! The (alleged) effectiveness of Afganit, and the demonstrated effectiveness of Trophy, is down to *small* incremental improvements in projectiles and *vast* improvements to radar systems.
You'd be better off thinking about a next-gen version of Afganit than trying to stick things to projectiles moving at multiple kilometres per second.
>
> One major constraint is that laser systems to vaporize a shell isn't an option. Anything capable of eating through that much dense metal would be a weapon in its own regard, not an active defense system.
>
>
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A laser capable of blasting a penetrator out of the air, or vaporising it, would be a fearsome weapon in itself. But remember it doesn't have to destroy the penetrator, but if it can ablate a small portion of it with suffice energy to start it tumbling by a couple of degrees over its entire flight time then the projectile can have its effectiveness significantly reduced without needing the sort of laser that's capable of toasting a tank all by itself.
Laser countermeasures on tanks have their own issues though, which I won't go into here, and a laser this powerful is a pretty formidable weapon for other purposes (bye bye drones, and any other aircraft that aren't travelling at hypersonic speeds) and are somewhat more high tech than high velocity projectile weapons (to say the least).
[Answer]
This seems like a decent idea. But foam isn't going to do it. The point of the weapon is that is has enormous momentum; which is going to make it difficult to redirect; your defensive projectile needs an offset, i.e. it has to be unbalanced to create unbalance, and it needs a lot of energy.
By comparison, a bullet will fly straight through quite a bit of pizza dough before it get deflected in the slightest. What you need is one-sided drag, like an unbreakable carbon-fiber lasso around the offensive missile that attaches to a weight not struck by the offensive missile; and then makes it unbalanced.
So one idea is a net of heavy balls this is fired at the offensive weapon but spreads out, hopefully the strike is off-center. The offensive weapon gets snagged but now it is slightly slowed and dragging an unbalanced set of weights that will cause it to tumble. Even a few degrees might be enough to mitigate the damage.
For ideal targeting and maximum imbalance, the offensive missile should strike and get snagged on the edge of the defensive "net", and the wider the defensive net, the better. But the net material does have to be tough enough to reverse course instantly at 4km/s without breaking. So invent some damn tough cording for that. Heck, the defensive nets might even be reusable, collected after the battle.
[Answer]
**The Royal Navy thinks structural damage might not be enough.**
Everyone loves Phalanx. Defense by way of much shooting. But the problem with busting up something that will hurt you by hitting you is that the pieces will probably still hit you.
<https://www.navylookout.com/last-ditch-defence-the-phalanx-close-in-weapon-system-in-focus/>
>
> Gun-based CWIS has its limitations when faced with the increasing
> speeds of modern missiles such as BrahMos, Sunburn or Zircon. Their
> speed makes them harder to detect and track but it is their vast
> kinetic energy that is particularly deadly. Assuming the CIWS manages
> to break up the missile somewhere under 1km before impact, then the
> ship may still be sprayed with high-velocity fragments. This is
> obviously preferable to the intact missile impacting and detonating
> deep inside the ship but deadly fragments are likely to disable
> delicate sensors and penetrate the light steel plate of modern
> warships. Phalanx may prevent the loss of the ship but may not be able
> to stop it from becoming eliminated as an effective fighting unit.
>
>
>
This is probably also true for tumbling. That is better for you than riding the spike but the thing is still going the same direction it was and it is still going to whack you hard.
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Ideally the thing to do is divert the entire rod to a different trajectory. Drones? Explosives?
Iron Man?
[](https://i.stack.imgur.com/p7Frz.png)
<https://www.youtube.com/watch?v=JYoul9UtroU>
[Answer]
Use QILD!
Quickly Inflating Liquid Deflection is the new ERA. A semi-active protection system for you! Unlike full active protection systems which use incredibly expensive camera's, projectiles and launch systems the QILD needs no projectiles or launch systems, just the equipment to calculate the impact point!
On top of the tank a series modified airbags are placed in a pattern, all slightly filled with water and covered with overlapping discs to protect against small-arms fire. The bags are designed to handle immense pressures after they reach a certain size. Once the impact point is determined a pressure valve is opened and a pre-pressured watertank releases water into the bag, inflating it further. The bag is shaped to offer a slanted surface compared to regular impact directions like the side or top-down attacks.
The projectile will hit the slanted angle of the bag and tear through, hitting the almost incompressible water underneath and starting a tumble. The pressure the projectile creates will cause it to pulverise itself before it hits the actual armor underneath. This helps spread the impact point and reduces the effectiveness of the projectile. After the impact a folded up bag with a shaped "lead" will be slightly inflated, the shaped "lead" causing the bag to unfold itself at the impact site to replace the previous bag. A limited amount of replacements would be available for each balloon but repeat hits are highly discouraged.
Buy your tanks a QILD today!
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[Question]
[
I am considering a setting where an all-permeating "background magic field" has a side-effect of randomly bumping electrons of any contained matter into an excited state (let's say it can provide up to about 3 eV of energy per "bump", at an average rate of 100 bumps per millisecond per cubic micrometer).
Would this be dangerous to the living organisms present in such a field?
I imagine this would at least affect photosensitive molecules in the eyes, which is probably not going to be very comfortable. But I don't know enough about biology to predict if there would be some more detrimental consequences.
My motivation with this is mainly to justify "constantly glowing" crystals, with the luminescence intensity depending on the strength of magic in a particular area (that's how I chose my ballpark estimates for the energy and rate, though it's likely not bright enough or too dangerous for the best-case scenario). But even if glowing crystals can be justified in other ways, I'm still curious about the biological (un)safety of the idea described above.
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(Edits: reformulated the question to be about a specific effect)
[Answer]
### Comparison with light
3 eV correspond to the energy of a photon with a wavelength of 413 nm, which in turn is violet light.
Exposure to sunlight (more precisely the violet portion of it) corresponds to roughly 10⁸ such events per square micrometre per second¹. Your effect would yield 10⁵ events per cubic micrometre per second. If sunlight homogeneously penetrated the first millimetre of skin, this would be equivalent to your effect.
This I expect this to be acceptable in terms of cancer, unless your effect tends has a higher propensity for DNA-alteration than regular light.
However, since the entire body is affected, other types of cancer may get as frequent as skin cancer.
Also, I don’t know how well skin absorption protects us from such effects.
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¹ Going by [this chart](https://en.wikipedia.org/wiki/File:Solar_spectrum_en.svg) the irradiation of sunlight corresponds to $I=1\frac{\text{W}}{\text{m}^2 \text{nm}}$ in that wave length. If we look at a wave-length window of $Δλ = 50\,\text{nm}$ (roughly the width of what we call *violet*) and consider an area of $A= (1 \text{μm})^2$, we get for an energy $E=3\,\text{eV}$:
$$ n = \frac{I·A·Δλ}{E} ≈ 10^8\,\text{Hz}$$
### Total energy deposited
The [average human metabolic rate](https://en.wikipedia.org/wiki/Human_power#Available_power) is about 80 W.
This alone causes our body temperature to be 37°C in an environment of 20°C.
Your effect on the other hand would dispose about 1 kW in the average human².
This is twelve times that amount and corresponds to the power output of a human during bursts of hard physical exercise (e.g., a sprint or similar), which can be upheld for only about a minute.
The human body has cooling mechanisms that allow it to maintain its body temperature after such bursts such as sweating, but I strongly doubt that these mechanisms can work permanently.
Humans would have to sweat and drink a lot or use other means to cool their bodies.
And that’s not even accounting for the fact that our entire environment would be heated up in a similar manner too.
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² The average human has a volume of $V\_\text{h}=60\,\text{ℓ}$. You deposit $E=3\,\text{eV}$ with a rate of $f=10^5\,\text{Hz}$ in $V=(1\,\text{μm})^3$, yielding a power of:
$$ P = f \frac{V\_\text{h}}{V} E = 960\,\text{W}$$
[Answer]
**This is like fluorescent bulbs glowing in an alternating magnetic field.**
[](https://i.stack.imgur.com/vnk3f.jpg)
<https://www.farmanddairy.com/top-stories/how-to-make-a-fluorescent-bulb-glow-under-transmission-power-lines/623730.html>
>
> When you take a fluorescent tube bulb under transmission power lines
> it lights up because the current running through them induces an
> alternating magnetic field around them as they conduct electricity.
> The higher the voltage, the greater the magnetic field density and the
> brighter the fluorescent tube will glow.
>
>
>
So there is precedent. Your magic field excites the crystals and makes them glow. The glow is work and so the presence of these crystals reduces the power of the magic field, if that matters. The fluorescent bulb also slightly reduces the power of the transmission line.
You could make the crystals a little bit hazardous if the spectrum they glow in is not limited to the visible. Maybe you could get sunburned next to one.
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Maybe they are also glowing in radio waves. But it is not glowing. It is talking. If you have an antenna you might be able to hear what they are saying. You might have an antenna and not know that what you have is an antenna.
[Answer]
3ev is bordering ultraviolet from the visible side - 3eV is 418nm wavelength, within the "violet" range. Ultraviolet starts at about 400nm, some even consider it to start at 380nm (3.25eV).
It should be fine, maybe the vampires may get a mild sunburn but won't die of it.
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[Question]
[
For my factions anti-occult paramilitary force, I decided to give them large, armoured airships for their main form of transport and attack, which do not use gas bags for lift, but rather a magical lifting crystal (the properties of which will be the subject of future questions).
To aid this force in their duties of flushing out cults and demons, I decided that their main vehicle would be heavily armed as well. In addition to autocannons and machine guns, I decided to try to put a Vertical Launch System (VLS) on them, similar to ones used by modern navies to store missiles.
The missiles in question wil mostly be used for ground attack, like a smaller version of the tomahawk. There would be about 12 missiles per vessel, which would also have other systems, which would add up to around 3 quarters of the rest of the airship.
**TLDR; How big would an airship have to be to carry 12 medium to large guided missiles on it**
[Answer]
**Mount a VLS? Very big.**
Naval VLS are designed to either cold-launch the cruise missile or to cope with the engine exhaust. The missile goes straight up before it turns in the right direction. In the case of submarines it may have to reach the surface first. The launch is relatively stressful for the vehicle, so there has to be structural reinforcement. All that adds weight.
An [eight-cell VLS](https://en.wikipedia.org/wiki/Mark_41_Vertical_Launching_System#Mark_41_(Mk_41)) is about 15 tonnes empty. The cruise missiles are about 10 tonnes. Compare that with the useful lift of the [USS Akron](https://en.wikipedia.org/wiki/USS_Akron#Specifications_(as_built)), and it *might* be possible to fit a dozen cruise missiles in an airship that size.
**Why mount a VLS?**
If you launch from an airship, it would be much easier to **drop** the cruise missile, let it unfold the wings and start the engine. Perhaps with a booster, perhaps not. Either way, you save a lot of weight with, say, a rotary launcher in a bomb bay, or individual pylons.
[Answer]
A tomahawk missile weighs in at 1.6 tonne. You request 12 for a total weight of ... 19.2 tonne. Lets call it 20 tonne.
A tomahawk missile is 0.5m by 6.25m. So a naieve 3x4 'cluster' of them would be a cube of 1.5x2x6.25m.
If this is 1/4 of your ship, then the total airship would weigh 80 tonne and be smaller than two 40ft shipping containers next to each other (Unfortunately the max weight capacity of two 40ft containers works out to only 60 tonne, so you'll have to build your own airframe....).
Let's round it all up to 100 tonne. I know you state magic, but ... this is a fairly large traditional airship. Rule of thumb: 1kg/m3 -for helium. This results in 100,000 cubic meters, or a vehicle 100mx50mx20m. Airships of this size/payload capacity do exist.
Because this is an airship, launching a ground-attack-missile is easy: you drop them, and when they have fallen a short distance, the engine ignites. This means you can reduce the infrastructure somehwat. eg: you still need target-radar, but you don't need anti-fratricide covers or rocket-engine-proof-silos. You are effectively building/using some sort of air-launched rocket-bomb.
] |
[Question]
[
550 million years ago, aliens erected a spherical barrier 1/6th of a light-year (~10,000 AU) in radius around the solar system, centered on the solar barycenter. Things outside the barrier can enter, while things inside the barrier cannot exit. Only massless particles and gravity can move freely both ways. Massive particles trying to exit are reflected away. An interstellar comet, for example, entering on a hyperbolic path can pass through the barrier's exterior unharmed, but upon exiting will impact the interior spectacularly (especially at ISVs). This means the barrier is totally transparent and can't be viewed directly, as it neither absorbs nor emits light of its own. (An interior spacecraft could still gauge its range to it by e.g. shooting ionized hydrogen at it and looking for infrared backscatter.)
little side notes... The barrier is non-rotating and station-keeps with the solar barycenter via magical means.
The barrier reflects all the massive particles that try to escape, so all electrons, protons, and alpha particles of the Sun's solar wind are trapped inside. Interstellar crosswinds are also similarly trapped. The barrier makes an exception for [stars on close fly-bys](https://en.wikipedia.org/wiki/Scholz%27s_Star#Solar_System_flyby), opening a very temporary exit hole for [any that may enter](https://en.wikipedia.org/wiki/Gliese_710) the ~20,000 AU spherical region (which happens every ~10 Myr or so).
If this cosmic pressure cooker really came to be around our Sun 550 MYA, would humans up until our current time period be able to deduce its existence, given its behavior (the built-up density of our interplanetary medium)?
if so, how recent would the erection need to be for the barrier to be undetectable; and if not, how far back would the construction date need to be pushed?
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This is related to a question of mine [Aliens englobed the Solar System: will we notice?](https://worldbuilding.stackexchange.com/questions/141298/aliens-englobed-the-solar-system-will-we-notice) except I've tweaked the original behavior to suit a number of story-telling aspects. This tweak fundamentally changes *what* the alien barrier *does*, which I believe warrants a new question.
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Notes:
* The checked answer to the above-mentioned question suggests that nuclear disintegration forced by the (old) barrier, as well as Hawking radiation, would make it shine like a supernova from all directions. That's no longer the case lol
* There is a potential statistical bias in orbital energy distributions of long-period objects with aphelions greater than ~10,000 AU. It's not clear whether we have enough astronomical data currently to see that bias, but it *would* exist.
* The barrier would act like a bucket under a faucet in the interstellar medium, scooping up dust on its trajectory through the galaxy and leaving a void in its wake. The ISM is awfully thin, so it's not clear whether we could detect that currently. The void would be a small fraction of the total distance light would've had to travel to reach us.
* Over the 550 Myr barrier lifetime, near-parabolic Oort cloud objects would be gradually depleted. Future space exploration and "geology" may be able to detect the decline in high-energy bombardments, but it's uncertain. The inner Oort cloud would still be unperturbed, leaving lots of statistical noise to sift through.
* Any spacecraft or interstellar lightsail probe fleets we send out will stop transmitting past the ~10,000 AU mark. This is really a moot point because it hasn't happened yet.
[Answer]
**Sure we would notice** (if we were to live to see that, which is unlikely)
If solar system is traveling in that manner, if scoops all interstellar gas and dust on its way. Given that period of time is quite considerable (550 million years), the total mass sucked in will dwarf the mass of our solar system.
Sun is cruising around galactic center at an average speed of 230 km/s. It's speed in interstellar medium is considerably slower, estimated at about 23-26 km/s. If we are setting up a sphere around the Sun, how much space its cross-section would capture during 550 million years of travel?
Travel volume = Vsun \* T \* PI \* R^2
Actually, we'd like to know how much travel volume compares to the "cooker sphere volume"
Sphere volume = 4/3 \* PI \* R^3
Travel volume / Sphere volume = 3/4 \* V \* T / R = 200,000
Which means that by now, density of gas and other interstellar matter would be 200,000 times higher than the normal density. Assuming that normal density is 1 hydrogen atom per cubic cm:
New sphere mass = Travel volume \* Density \* Hydrogen atom mass = 4.68 \* 10^30 kg
Our Sun's mass is only 1.989 \* 10^30 kg, so our sphere would contain more than 2 times mass of the Sun. This should make our sphere, at the very least, a dense interstellar gas cloud, but more likely this gas will turn into stars and planets. Some gas will get absorbed by the Sun, increasing its luminosity and driving other gas away to the boundary, where new stars will be forming, so before the humans were to evolve, solar system would become a cluster of multiple stars, planets and asteroids. So called "late heavy bombardment" will become a permanent state in the solar system.
P.S. As @EdvinW had noticed, the galactic medium where Sun rotates is not static. All objects, including interstellar gas, are also rotating around galactic center. This way, we should base our calculations on Sun's speed in interstellar medium, not galactic rest frame. Not so much known about the interstellar medium, but Sun's speed is estimated at [23.2 - 26.3 km/s](https://en.wikipedia.org/wiki/Heliosphere#Bow_shock), which is about 10 times slower than its orbital speed (230 km/s).
[Answer]
Would this barrier affect the Solar sysem's heliopshere?
>
> The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes shape in form of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium. The "bubble" of the heliosphere is continuously "inflated" by plasma originating from the Sun, known as the solar wind. Outside the heliosphere, this solar plasma gives way to the interstellar plasma permeating the Milky Way. As part of the interplanetary magnetic field, the heliosphere shields the Solar System from a significant amount of cosmic rays, including hazardous ionizing radiation (e.g. gamma rays). Its name was likely coined by Alexander J. Dessler, who is credited with first use of the word in scientific literature in 1967.[1](https://en.wikipedia.org/wiki/Heliosphere) The scientific study of the heliosphere is heliophysics, which includes space weather and space climate.
>
>
> Flowing unimpeded through the Solar System for billions of kilometres, the solar wind extends far beyond even the region of Pluto, until it encounters the "termination shock", where its motion slows abruptly due to the outside pressure of the interstellar medium. The "heliosheath", is a broad transitional region between the termination shock and the heliosphere's outmost edge, the "heliopause". The overall shape of the heliosphere resembles that of a comet; being roughly spherical on one side, with a long trailing tail opposite, known as "heliotail".
>
>
> Two Voyager program spacecraft explored the outer reaches of the heliosphere, passing through the termination shock and the heliosheath. Voyager 1 encountered the heliopause on 25 August 2012, when the spacecraft measured a forty-fold sudden increase in plasma density.[2](https://en.wikipedia.org/wiki/Oort_cloud#Structure_and_composition) Voyager 2 traversed the heliopause on 5 November 2018.[3] Because the heliopause marks the boundary between matter originating from the Sun and matter originating from the rest of the galaxy, spacecraft that depart the heliosphere (such as the two Voyagers) are in interstellar space.
>
>
>
<https://en.wikipedia.org/wiki/Heliosphere>
Voyager 1 crossed the heliopause at a distance of 121 AU, so the heliosphere has tiny dimesions compared to the barrier at a radius of 1/6 LY or about 10,000 AU.
If matter and energy enter the barrier freely, the heliosphere should behave much like it does in real life.
If matter cannot leave through the barrier, it would accumulate inside over 550 million years as Alexander's answer says.
It is possible the density of gas and dust inside the solar system would become much higher, and affect the orbits of the interplanetary dust inthe solar system, perhaps producing detectable results.
And it would tend to accumulate on the back side of barrier. Thus it might have formed a new solar system dragged along by the barrier and about 1/6 LY or about 10,000 AU behind our solar system.
Alexandaer calculated that the accumulated mass would be over two times the mass of the solar system. If a star did form in the trailing region, most of the later incoming matter would eventually fall into that new star and increase its mass.
A star with about 2 times the mass of the Sun would be similar to a spectral class A4V star with 2.03 times the mass of the Sun, and at a distance of 1/6 LY or 10,000 AU it would be the brightest object in the sky of Earth except for the Sun and the Moon.
Incoming matter that entered through the barrier and then hit the back side of the barrier would be prevented from exiting, and thus its velocity would be changed. That would impart some of its velocity to the barrier, which should transfer the velocity to the barrier generators, which should be tied to the Solar System in some way.
Some of the momentum of incoming matter would be transferred to the Solar Systme, acting as a brake to the motion of the Solar System. The motion of the solar system relative to the local interstellar medium would slow, lowering the rate at which matter entered and the rate of deceleration. As the solar system slowed with respect to the local interstellar medium, its velocity with respect to the galactic center of mass would also change, changing the orbit of the solar system around the galaxy.
As mass accumulated in the rear end of the barrier and formed a new star system, the gravitational attraction between the new star system and the Solar System would pull them closer together, altering the motion of the Solar System relative to the interstellar medium and also to the galactic center, changing its orbit to a degree.
It is possible that as matter accumulates to form the new star system, its gravity will become stronger on the Solar System than that of any much more distant object. The two systems might be drawn closer to each other and collide with disastrous results.
Interstellar space might be said to begin at the heliopause, but the Solar System extends many times as far as the heliopause.
The solar system is believed to have an Oort Coud of billions of comets orbiting the Sun at distances both inside and outside the 1/6 LY or 10,000 AU radius of he barrier.
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> The Oort cloud is thought to occupy a vast space from somewhere between 2,000 and 5,000 au (0.03 and 0.08 ly)[9] to as far as 50,000 au (0.79 ly)[5] from the Sun. Some estimates place the outer boundary at between 100,000 and 200,000 au (1.58 and 3.16 ly).[9] The region can be subdivided into a spherical outer Oort cloud of 20,000–50,000 au (0.32–0.79 ly), and a torus-shaped inner Oort cloud of 2,000–20,000 au (0.0–0.3 ly). The outer cloud is only weakly bound to the Sun and supplies the long-period (and possibly Halley-type) comets to inside the orbit of Neptune.[5] The inner Oort cloud is also known as the Hills cloud, named after Jack G. Hills, who proposed its existence in 1981.[14] Models predict that the inner cloud should have tens or hundreds of times as many cometary nuclei as the outer halo;[14][15][16] it is seen as a possible source of new comets to resupply the tenuous outer cloud as the latter's numbers are gradually depleted. The Hills cloud explains the continued existence of the Oort cloud after billions of years.[17]
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<https://en.wikipedia.org/wiki/Oort_cloud#Structure_and_composition>
So the barrier would let in comets from outside whose orbits were perturbed into highy elliptical ones by nearby stars. If those orbits had aphelions outside of the barrier, the comets would strike the barrier on their first outward leg of the new orbit. Depending on what happens when a comet strikes the barrier, astronomers on Earth might detect bursts of energy as that happens. And possibly different observatories detecting the same burst of energy could get parallaxes and determine that those hypothetical explosions are all 1/6 LY or 10,000 AU from the Sun.
And that is about all the effects I can think of.
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I'm thinking of a story where one country gets very technologically advanced compared to its neighbours, and I figured the best way to do that is with one of those towers that create steam by mirroring a lot of sunlight into one point, then using that steam for energy (ideally electricity).
**What is the earliest this story could somewhat plausibly start?** (keeping history before it the same as in our timeline)
Some conditions:
* Obey laws of nature (no magic).
* Produce significant amounts of energy for the time (I imagine 10.000's horsepower), ideally as electricity.
* All parts must exist in the time period (or something technologically close).
* Only having energy when it's sunny is acceptable (though a workaround would be a nice bonus).
* Can be built in the most ideal place on Earth.
* I'm mostly interested in technology, so lets disregard social things like 'those technologies existed but in different countries' or 'a king would not be interested in funding this'.
Here's what I got:
* Electricity: 1600 William Gilbert? 1752 Ben Franklin?
* Steam engine: the idea may have been clear enough in 1606 Jerónimo de Ayanz y Beaumont? though in our reality it only really took off in 1698 with Thomas Savery
* Convex mirrors: glass-blowing in 14th century?
* Controlling mirrors: I know there were some pretty advanced ancient clockworks, though worst-case it can be done by hand
[Answer]
There are three gateway technology points here:
First, you need to be able to make reasonably high reflection mirrors (flat, if used in groups for a large area, or concave if single) to focus the light. This was possible in the Bronze Age.
Second, you need a way to turn heat into work. Newcomen had a steam powered water pump in the mid-17th century, which James Watt, as a lazy apprentice, automated (at least the valves) and then harnessed to produce mechanical work. It's long been claimed, without much supporting evidence, that Heron of Alexandria used steam and hot air to do work a millennium and a half earlier; it surely doesn't require anything beyond bronze age technology. It's known he was aware that steam could produce forces; it's not been proven (as far as I know) that he ever used it for anything other than demonstration.
Third, you need a way to turn mechanical work into electrical current. Faraday is the inventor of this technology -- it requires the understanding of conduction and, at least qualitatively, the interaction between magnetism and electricity. Magnets were known to the ancients, at least a lodestone; conduction was a 17th century discovery relative to static electricity, so it was waiting when Faraday came along in the 18th century and put the two together. The ancients could draw copper wire, so they lacked only the knowledge to be able to build a dynamo or alternator.
If you have the knowledge, then, Heron of Alexander had the skills to build the device -- as did many of the better smiths and artificers of his time. The knowledge, however, didn't all get put together until the 18th century.
In other words, bottom line: if they'd known what was needed, this technology could have been built well before the beginning of the Common Era. They had mirrors, they could make copper wire and tubing as well as bronze boilers, cylinders, and valves; they had access to natural magnets -- all during the Bronze Age, which *collapsed* in the 11th century BCE.
[Answer]
Electricity has it own league rules.
You can invent a steam motor by just observing you kettle boiling the water for a cup of tea. But you never will build an usable electric motor by just handle a pair of magnets in your hand.
<https://en.wikipedia.org/wiki/James_Clerk_Maxwell>
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> His most notable achievement was to formulate the classical theory of electromagnetic radiation, bringing together for the first time electricity, magnetism, and light as different manifestations of the same phenomenon. Maxwell's equations for electromagnetism have been called the "second great unification in physics"[3] where the first one had been realised by Isaac Newton.
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Also famous is his contribution to Einstein future theories:
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> Einstein described Maxwell's work as the "most profound and the most fruitful that physics has experienced since the time of Newton".[8] Einstein, when he visited the University of Cambridge in 1922, was told by his host that he had done great things because he stood on Newton's shoulders; Einstein replied: "No I don't. I stand on the shoulders of Maxwell."
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So, using electricity productively requires at least a high quality bulk of knowledge only available by the end of the 19 century.
Without Scientific method you don't even can start of dream of a solid ground to work.
<https://en.wikipedia.org/wiki/Scientific_method>
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> The scientific method is an empirical method of acquiring knowledge that has characterized the development of science since at least the 17th century.
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Ancient Egyptians build the pyramids and other great things because they had all the necessary tools and knowledge available. You can make primitive precise engineering tools using wood and cotton string. But you can not build a electric meter using the same material.
All ancient magnets available by the time before scientists find out how to artificially magnetize iron were weak, not strong enough to be used in electric motors. And they could be not melted to be poured in a mold. Heated magnets lost their magnetism.
As people answered before me, you can build solar thermal tower with bronze age technology, but 10.000 HPs is impractical.
But all is not lost. You can create electricity mechanically. In deed lots of it!
<https://en.wikipedia.org/wiki/Van_de_Graaff_generator>
Associate the generator plus these batteries and you have some kind of electric machine:
<https://en.wikipedia.org/wiki/Baghdad_Battery>
Is it possible to create and store 1.2 gigawatts electrical charge into thousands of these batteries and create a time machine using a van\_de\_Graaff\_generator?
I don't know.
I think it is possible to create a "death ray" with it!
<https://en.wikipedia.org/wiki/Uzzah>
<https://gizmodo.com/the-engineer-who-said-the-ark-of-the-covenant-was-a-gia-1598583115>
If Uzzah's history is true, yes the ark was a gigantic capacitor. Even by theological point of view Uzzah's death was an accident. What good all powerful being kill a good man making his job? The incident left king David upset!
[Answer]
After thinking about for some time
It is hard to tell really. If you remove motivation, funds out of list of actual problems and leave human resources and knowledge then it hard to tell.
Reason why it is hard to tell is mainly the knowledge of that time. Until last century humans really didn't had the proper knowledge for all that - thus they didn't and could not.
It means, you have to inject some additional knowledge to make things happen, and there begins the question of how much of it. Even with the answer - a reasonable amount, so that we can, in a year or two, teach almost illiterate workers to do their part in manufacturing chain of processes, it still does not help that much to determine lowest possible year.
As an example - electricity isn't such a hard thing to make, understanding how it works, principles and all that it has very litle to do with production of finished machine.
Hydrodynamic bearings, sufficiently high precision parts of round or flat shape it not that hard. For flat ones, you remember sequence and practice it few days and bum - mastery of production of A grade flats. Basic theory of that - okay a week of demonstration on exagregated clay and wood samples will build some workable virtual models in brains of worker-master.
Static electricity isn't that hard, but can be useful. Tesla coil to convert static electricity to low voltage, also isn't that hard to make it even at bronse age.
So they may not necessarly get the ability to develop and improve technologies, but it does not mean they can't make parts and assembly them.
The problem is very similar, if not identical, to bootstraping problem, there is some difference, but it also about simple actions to get something from nothing and use it to help yourself to build few more of next steps at least.
Bronse-copper mirror can be good enough and it can be used to focus ligth out of flat sheet just by pulling flat sheet by the middle. (GREENPOWERSCIENCE youtube channel did some similar experiment, to test Archimedes story, but can't find the video atm, and Archimedes is 200 years before Roman empire)
So that time(200BC-200AD) can be a good candidate - they had humans, they had the system of organising people, they had quite sofisticated knowledge(people with that knowledge to teach workers), they had access to ores, stones, land resources etc. After RE fell, there is a gap of low quality time - but still does not mean impossible, just depends. I do believe that RE had a chance, but they were totaly clueless that they had it - maybe there would be one country and hyperdrive space ships today if someone pushed them in rigth direction - knowledge and skills of that time in rigth place.
Egypt also had some chances, they had less knowledge, but they had the way to organise people in production chains, results of that still tourist attraction, I mean, it still stands.
## NB
A lot of things can be done by hands. And I do not mean Artisan stuff.
That's quite importand moment, hands are a tool, very sensitive one, and we had it from very beginning. One can cut a part on metal lathe, producing a lot of metal chips, but after that for some very preciese stuff finish can done by hands with or without power tools(not for every 6D CNC cut part, but for special and useful cases and for some others as well). And after that it at precision limit, more than that makes little sense (due termal expansion and all that) except some science stuff.
Pipets which can be used to suck in and hold a single cell, (cool eh?) can be made out of glass pipe with quite simple procedure - local heating and pulling, cooling, pulling, heating. It also precursor for high vacuum pump. Glass isn't that hard if one knows how.
So from very old age people were capable, but they didn't know what and why. Best old old time is animal domestication period, which probably far beyond the scope of your timeline, but just saying.
On other hand it needs to mention that things we may think like pretty mundane or ordinary can be quite challenging and require a lot of reading experementations if one does not know how exactly. Because indirectly there a plenty of science backed in - as an example of such items I can name a crucible (for iron melting).
So simplicity can be very deceiving.
Roman empire, anything during and after Renaissance can be a good time.
But again, what use the energy has, because by itself it does not give advantage. Making growing crops be more efficient, and introduce some simple but scientific selection process for plants, and pest control, and irrigation - can be a more potent change, just because you have more people who are free to do other things, even if it is no more different than it is typical for the time.
## I would say since 200BC people were capable to do your sun tower.
For reasons I mention earlier.
However, electricity as means to transfer energy is not necessarly the best, until things progress a lot.
In usa pneumatic hand tools are(were) quite popular, and such stuff indeed has certain advantages - simplicity of construction, weigth, distribution of air(pipes) is almost as flexible as electricity. (Production of flexible hoses will be a problem, so it more for stationary equipment, instead of electricity, but the same principle as with hand tools)
Hydraulics, just water, also quite potent solution for main line - your 10 MW source (which is just insane amount if power by that times)
As storage - some elevated pond, 50-100 meters up, can be decent accomulator, and that is about 10 cubis meter of water per second, few 10 inch pipes will do. Main pipelines not neccessarly have to be metal, basalt and diabase can be cast as well, and it is on pair with cast iron.
And water flow(trough pipe) can be converted in all sorts of energies.
For bearings - use hydrodynamic or static bearings, made with high precision out of stone - no special materials required.
So time really depends on your capacity to build tech chain for what you point as advantage. Selection of what will be advantage also depends on you.
If no new knowledge, except the concept, and probably simlpiest steam engine aka tesla turbine and bearings for it - then it is time when you have decent pipes and mirrors. Early 1800 may do probably - but the thing will have hard time to compete with that time burning for energy ways.
So you propabple have to choose before steam engine time. Basically making that named steam engine, it being the key piece of tech. Which not so much different from refferencing how things were rolling after that, and without electricity part it can naturally happen since 1300AD
So really there are no easy ways to point at some time. And only your handwaving will keep the tower from being replaced by a typical boiler at some less speciefic and more convinient place.
## P.S.
Similarity with bootstraping drove me for most of the answer in direction to "make it happen", rather "sufficient chances of such thing happen naturally", but your time options do not seem to be consistent whith that as well, so maybe it is okay.
[Answer]
Mirrors are surprisingly high tech. Up until rather recently (historically speaking), the best mirrors were flattened and polished sheets of metal or pools of liquid (water, mercury). Constructing a concentrated-light solar power plant would require an enormous amount of reflectors and this would represent a huge investment in metal, polishing time, etc. Additionally, hammering out a sheet of metal so that it's flat enough to be reasonably focus-able on a distant target isn't easy.
The simplest and earliest way to generate power would probably be by using **hydropower.** Water wheels are old tech, and with a skilled carpenter, constructable entirely out of wood in a sustainable manner. They can also provide an enormous amount of power, provided that the water is managed properly with something like a dam. You'd probably end up using multiple water wheels, and by connecting them up to electrical generators (you can construct an AC generator without magnets), you can generate quite a bit of power.
To increase power generation, you'll probably want to get your metallurgists to build a turbine though, because traditional spoke-and-paddle water wheels are quite inefficient.
This use of hydropower gives you a lot of flexibility on when to have your story take place (they've existed since 4000 BCE) and wire-making is a rather old technology too.
Here's how you could play out this development:
* Pick a nation or a specific city that is located on a river or in an area with a lot of rivers and that uses a lot of water wheels to power their mills.
* In an attempt to strengthen a water wheel's systems, a metalworker is hired to include some metal in the construction. Unfortunately though, it turns out to be very difficult to fit and attach a proper part, so instead, the metalworker decides to simply wrap several parts of the mechanism in wire.
* The water wheel works well, and over time, local workers start noticing something strange going on: pieces of metal will occasionally stick to the mechanisms (they've become magnetized) and if you touch it in the wrong place, you're liable to get a shock.
* Thinking the whole thing is cursed, the mill workers invite an expert to take a look and determine what's going on. Fortunately for history, this expert is brilliant or lucky enough to discover electricity based off of this.
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It took Earth ~ four billion years to go from molten rock to multicellular life. Let's take that as an absolute minimum requirement of time for organic life to evolve and produce sapient species (I know, that's a stretch, but just roll with it).
So how ancient can my Ancient Precursors realistically be if by lore they're originated from literally one of the first terrestrial planets with advanced organic life in the Universe, if not *the* first?
I've read that the necessary elements for the creation of earth-like planets began popping in existence not even one billion years after the Big Bang, but as I understood it the universe was still too volatile back then for any planet to exist long enough without some cosmic cataclysm sterilizing it's hypothetically possible beginnings of life. So when things calmed down enough for 4 billion years of relative peace to become feasible?
[Answer]
# Earlier Than You Might Think
The important elements are less for *planetary* formation and more for the creation of Life As We Know It. (Your ancients could be Life As We Don't Know It, but in that case they might be energy beings who live in the depths of space and wouldn't need a terrestrial world.)
So what elements are vital to life? In order of atomic number, Hydrogen, Lithium, Carbon, Nitrogen, Oxygen, Sodium, Magnesium, Phosphorus, Sulphur, Chlorine, Potassium, Calcium... and most at issue for your ancients and their world, Iron.
Other than Hydrogen and Lithium, none of these elements were around until the first stars had formed and died. So although some Sol-type stars might have formed as early as a few hundred million years after the Big Bang, they wouldn't have the necessary materials in their protostellar disc to make the kind of planets that could support our kind of life.
So you'd need to wait for the deaths of a *lot* of stars to seed the universe with the materials necessary. That *still* (depending on the astrophysicist you ask) could put you as early as 700Ma after the Big Bang, or about 13.3Ba ago. The universe (taken as an enormous whole) looked about the same thirteen billion years ago as it does now.
Assuming that all the odds rolled the right way (which we are, for the purpose of "earliest possible", once stellar furnaces and supernovae had forged the elements necessary, your terrestrial planet would be possible - and cosmic cataclysms were really not that common at that point. So between 13-13.3 billion years ago, a planet could've formed on which life could arise. Four billion years after that (about five billion years before our own protostellar disc formed), you could have your civilization of ancients.
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I am making a rogue planet. Right now it is a super-earth with a lot of radioactive materials in its core. It rotates very quickly as well. However, it needs to be habitable. And not just the deep ocean, the surface of the planet, exposed to the atmosphere, needs to be habitable enough for intelligent life to develop, discover fire, and advance.
I was wondering if this was possible with a thick enough atmosphere with enough greenhouse gasses to trap geothermal heat and thus keep the planet habitable.
Obviously regular geothermal heat won't do in such a scenario; its simply not hot enough. However I do have an idea as to how to make it hot enough. Give it a stagnant lid (much like Venus) for its crust.
Global resurfacing events fail to occur because the planet is spinning too quickly, thus making its crust much thinner at the poles than the equator. A would-be resurfacing event would instead melt the poles first and this would ease the pressure from the rest of the crust (Coriolis Currents induced in the lava by the same fast rotation allow it to circulate the upper mantle such that the entire upper mantle is cooled by this, preventing it from simply melting equatorial crust later) The atmosphere traps the heat emitted, creating a hot period which slowly cools over time, until the next polar resurfacing event. (Effectively "seasons")
Is this plausible by the mechanism described, even allowing for extreme rotations and radioactivity? If not, is there another way that doesn't involve aliens or magic or advanced technology, and retains the solid surface with liquid water, with enough energy availability for intelligent life to evolve?
I don't mind changing huge factors about the planet if that's necessary as I haven't established much else about it yet, other than that its a rogue planet, has a space-faring civilization, and is heated from below. I also don't mind unlikely but possible configurations so long as its explainable without advanced tech/aliens/magic, though importantly, it needs to be self consistent and allow intelligent life to not only evolve, but advance in their technology as well, to at least the ability to send craft into orbit around the planet.
[Answer]
Yes, they can.
[This paper](https://ui.adsabs.harvard.edu/abs/1999Natur.400...32S) notes that a thick hydrogen atmosphere, protected from being stripped by solar radiation due to lacking a star, could provide enough insulation to allow surface temperatures above the freezing point of water.
[A satellite can provide extra warming.](https://www.semanticscholar.org/paper/THE-SURVIVAL-RATE-OF-EJECTED-TERRESTRIAL-PLANETS-Debes-Sigurdsson/a3f612ccdac694b35f56a7d7c826d75558d2ab1d) as if they have a large moon then it can do a lot of tidal warming. Europa, a Jupiter moon, famously has oceans because of it's tidal warming.
So, there is less need of the fast spinning planet with lots of radiation. It doesn't make complete sense anyway. The magma under the surface is gonna heat up away from the poles and erupt there anyway.
[](https://i.stack.imgur.com/N96Xq.png)
Convection currents in the mantle don't tend to be that large. Just a thousand kilometers across or so. The cycles can take millions of years- a very distant release valve under the poles would do little to relieve that, as it would take tens of millions of years for it to reach there.
[Answer]
Nepene Nep's answer mentions a paper [https://ui.adsabs.harvard.edu/abs/1999Natur.400...32S/abstract[1]](https://ui.adsabs.harvard.edu/abs/1999Natur.400...32S/abstract%5B1%5D) which says that a rogue planet could be warm enough for liquid water using life. But that requires a thick hydrogen atmosphere. A thick hydrogen atmosphere is inconsistent with an oxygen rich atmosphere because the hydrogen and oxygen would burn to make water.
Here is a link to a more popularized dicussion:
[https://planetplanet.net/2015/06/04/real-life-sci-fi-world-8-the-free-floating-earth/[2]](https://planetplanet.net/2015/06/04/real-life-sci-fi-world-8-the-free-floating-earth/%5B2%5D)
Based on this longer article:
[https://aeon.co/essays/could-we-make-our-home-on-a-rogue-planet-without-a-sun[3]](https://aeon.co/essays/could-we-make-our-home-on-a-rogue-planet-without-a-sun%5B3%5D)
So a planet with a dense hydrogen atmosphere would be uninhabitable for humans for lack of enough oxygen to breathe in the atmosphere. And fires wouldn't burn without a lot of oxygen in the atmospehre. And any Earthly or extraterrestrial life forms with enviromental needs similar to those of humans would also require an oxygen rich atmosphere.
So how are you going to have large multicelled animals on your world, including some which have intelligence and culture, if there isn't oxygen in the atmosphere for them to breath, or oxygen for fires?
Either you resarach alternate biochemistries to find a way to make large multicelled anaerobic organisms function, or you are going to have to have an oxygen rich atmosphere on your rogue planet. Which means it can't have a hydrogen rich atmosphere, which means it can't use a hydrogen rich atmosphere to conserve heat.
What about having the rouge planet heated by a large moon? Would that provide enough e heat? If a moon of size A wn't provide enough heat, you could double the size of the moon to size B. If a size B moon isn't enough, you could double the size of the moon to size C, and so on.
And eventually the size of the moon might have to be increased so much that the moon becomes the planet, and the habitable planet becomes a moon of the moon-turned-planet.
Thus you could have a roughly Earth or super Earth sized object orbiting a much larger super Earth, or mini Neptune, or ice giant, or gas giant, planet which is also a rogue in interstellar space.
There has been considerable discussion of the potential habitablity of hypothetical exomoons orbiting hypothetical giant planets in other solar systems, although as far as I known no exomoon discoveries have been confirmed yet.
Discussions of the habitability of other worlds seem to be about habitablity for carbon based liquid water using organisms in general, and not for large multicelled land dwelling plants and animals in particular. So most scientific discussions of habitability discuss the broad conditions for Earth like life in general instead of humans.
Humans and similar intelligent beings in particular, should should be able to evolve and flourishon only a minority of the worlds which have some forms of life.
And most of the discussion of the potential habitablity of planetary mass exomoons in other solar systems discusses situations where those exomoons and their exoplanets orbit within the circumstellar habitable zones of their stars.
As far as I know, the main discussion of the habitablity of other worlds which focuses on habitability for humans (and thus for most of the aliens in science ficiton) is *Habitable Planets for Man*, Stephen H. Dole, 1964, 2007.
[https://www.rand.org/content/dam/rand/pubs/commercial\_books/2007/RAND\_CB179-1.pdf[4]](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf%5B4%5D)
As I remember, the discussion of possible habitable double planets or planet sized moons of giant planets is very, very brief.
Comparatively little attention is given to hypothetical exomoons of exoplanets orbiting farther from their stars than the circumstellar habitable zones of those stars, where the majority of the heat would be supplied by tidal heating and internal radioactive decay.
And of course a rouge exomoon orbiting arogue exoplanet in interstellar space would be the extreme example of a exommon outside the circumstellar habitable zone of any star, and would need to get almost all its heat from tidal heating and internal radioactive decay.
Anyway, scientific studies of the potential habitability of exomoons should be consulted.
A good example is "Exomoon Habitability Constrained by Illumination and Tidal Heating", Rene Heller and Roy Barnes, *Astrobiology*, Volume 13, number 1, 2013.
[http://faculty.washington.edu/rkb9/publications/hb13.pdf[5]](http://faculty.washington.edu/rkb9/publications/hb13.pdf%5B5%5D)
Here is a link to a non scientific discusson about life on an exomoon orbiting an exoplanet, though in this case they are supposed to be in the circumstellar habitable zone of their star.
[https://planetplanet.net/2014/11/18/real-life-sci-fi-world-6-pandora-from-the-movie-avatar-the-habitable-moon-of-a-gas-giant-planet/[6]](https://planetplanet.net/2014/11/18/real-life-sci-fi-world-6-pandora-from-the-movie-avatar-the-habitable-moon-of-a-gas-giant-planet/%5B6%5D)
And here is a link to an article discussing life on the moon or planet of a brown dwarf.
[https://planetplanet.net/2014/10/09/real-life-sci-fi-world-4-earth-around-a-brown-dwarf/[7]](https://planetplanet.net/2014/10/09/real-life-sci-fi-world-4-earth-around-a-brown-dwarf/%5B7%5D)
A brown dwarf is an object intermediate in mass between a giant planet and a very low mass star. Brown dwarf's are just barely massive enough to fuse deuterium in their cores for part of their existence, but are not massive enough to fuse ordinary hydrogen. The minimum mass for a brown dwarf is approximately 13 times the mass of Jupiter and the maximum mass for a brown dwarf is approximately 75 to 80 times the mass of jupter.
The article discusses the habitability of a planetary mass object orbiting its brown dwarf star or planet, depending on your point of view, close enough to be within the circum brown dwarf habitable zone. But what if a planetaru mass object, either a moon or a planet depending on definitions, was outside the circum brown dwarf habitable zone and thus would be a bit too cold for life except for its internal heat and especially tidal heating. If there are other planetary mass objects orbiting the brown dwarf the tidal interations might induce enough tidal heating to keep one or more ofthe planetary mass objects warm enough for life.
Of course if a rogue planetary mass object orbits around a rogue giant planet or rogue brown dwarf in interstellar space far from any luminous star, the light it receives from outside should be from starlight from distant stars, which shouldn't be enough for much photosynthesis and for the production of an necessary oxygen rich atmosphere. Figuring out a way to solve that problem may be hcallenge for a science fiction writer.
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Lightning is one of the token magical attacks that are there in every fantasy book; something like "[Mage] called down bolts of lightning on the pike-formation", is less common than only something like "He threw fireballs at the charging cavalry."
Calling down lightning upon your foes seems to get less and less devastating as a series goes on. So I want a realistic estimate on how dangerous lightning can *really* be.
Details: Assume that lightning can be called down on any place within throwing, or arrow, or even trebuchet range (So if you can throw a rock there, you can call down lightning there). I don't know whether how frequently it can be called down is an important enough factor or not, so as a random baseline assume it can be done once every 30 seconds, and this can be done for let's say one hour at the very maximum.
EDIT: There is a metallic rod that must be thrown to call down lightning. Upon being summoned, the lightning directly hits that metallic rod
So how dangerous would it be? Would it just contribute to more attrition? Or would it require a complete restructuring of strategy for the army that's facing an army which can call down lightning?
Note that I do not consider this to be a clone of [this](https://worldbuilding.stackexchange.com/questions/174267/lightning-strikes-a-medieval-army-what-happens), as it asks in a very specific context while I ask in a very general one.
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So devastating that it would change warfare in pretty much the same way modern artillery did: Nobody would field armies in closed formation anymore, but instead in more or less dispersed, smaller and mobile units.
Your link already describes the actual effect of the lightning strike. Your edit with regard to the rod only changes the nature of application:
A 4th century roman ballista already had a reach of over a kilometer, which means that your specification would essentially provide a medieval ballista with the raw firepower of modern artillery and an even more profound psychological effect since a lightning strike is much more terrifying than an explosion.
Being able to fire it every 30 seconds is enough to make fielding an army in regular closed formation suicidal, even if the enemy has only one ballista-mage-combo, especially considering that soldiers are people and not videogame-units which do not care about swathes of their comrades being annihilated by thunderous lightning every 30 seconds.
Obviously there are other applications made possible by your specification: You could for example use metallic rods basically as mines, making passage through an area prepared with rods suicidal.
What exactly the nature of warfare would evolve into depends on other variables: The amount of mages, the amount of access to such mages across several factions, the quality of the available siege engines etc...
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Lighting that strikes a metal rod wouldn't be all too dangerous because since this rod is planted in the earth, any lighting that reaches it would be immediately grounded. Through the same principle that lighting rods on houses work, soldiers or other humans standing near the rod when lighting struck would probably be fine--although they might suffer temporary deafness/blindness.
Lighting is most dangerous to people when humans are part of the "path of least resistance" (outside of secondary effects like exploding shrapnel from struck trees or superheated material). For example, someone standing in a flat field during a thunderstorm is more likely to get struck by lighting because human flesh is slightly more conductive than air. That means instead of traveling a couple more feet through air to reach the ground, the lighting bolt travels through the person, likely killing them.
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## Impacts
### Sound
Per [here](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6474511/), lightning generates about 1470 psi (100 atmopsheres) of overpressure.
**Deafening:**
[Per CDC](https://www.cdc.gov/niosh/docket/archive/pdfs/NIOSH-125/125-ExplosionsandRefugeChambers.pdf), 45 psi is enough to rupture ear drums, causing permanent hearing loss.
Sound will attenuate a little better than radius-squared, but just using that for a quick model. Assuming $r\_0$ is 1 meter, ${1470 \over 45} \approx 32 {r\_0}^2 \rightarrow r\_0 = 5.7$ meters radius. (37 feet diameter)
**Knockdown:**
The typical human cross-section is 3,168 square inches. Typical human body weight is 100 pounds-mass. That means typical human strength is $poundmass \times gravity = 100 \times 32.2 = 3,220$ pounds.
Converting pressure to force $ = pressure \times area$. Just glancing at the human cross-section and weight in pounds-force, about 1 psi looks like enough force to knock a person down.
Using same radius-squared attenuation, a lightning stroke will very likely knock people down out to $\sqrt{1470} = 38$ meters radius. (250 feet diameter)
## How Effective is That in War?
[](https://i.stack.imgur.com/HckiN.gif)
Let's take a look at the Battle of Hastings for some sense of scale. A well-placed lightning strike among the enemy, with a blast diameter of 38 meters (about 38 yards) will very likely flatten an entire unit (about 137 men).
Even more importantly, flattening a unit every 30 seconds opens several holes in the shield-and-spear walls protecting the back lines from cavalry charges.
Or, conversely, flattening a cavalry charge before it can do any harm.
This may not kill anyone, but it creates precious seconds of neutralizing a force -- giving allies time to close, bypass, or engage stunned enemy soldiers without resistance.
**How much control of the territory does this allow?**
**Morale**
In a Battle of Hastings-like situation, a lightning-thrower (pending easy getting of the required metal rods to the targets) could knock down all of the English forces, at least once, over a span of 25 minutes.
The real battle was an all day affair. In a whole 16-hour day or beating down the enemy every 30 seconds, a single lightning-thrower could smack down the entire English army nearly 40 times.
**Neutralizing the benefit of fighting from high ground**
A typical soldier runs a 4 minute mile (440 yards per minute). By providing cover, a lightning-thrower can either keep enemy archers down (literally) while friendly forces advance on the high ground.
At the moment of contact between your force and the enemy, you can knock a hole in the shield wall, allowing friendly forces to walk past the no-longer interlocked shields or set spears of defenders.
**Allowing maneuver**
Flipping the script as the surrounded (or nearly-surrounded) English forces, a lightning-thrower could effectively halt a small force attempting to flank.
If retreat is required, cavalry or fast infantry moving to cut-off your retreat can be stopped.
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Consider that Wood was one of the strongest and most easily available materials medieval kingdoms had to work with, not to mention the easiest to shape into whatever you wanted. From giant drawbridges to artillery and barricades, wood was used everywhere at that time. The one big disadvantage is that it is highly flammable. So if your magician(s) threw their rod like a spear at the gate of the castle and it burst into flames, that would certainly send a statement. Soldiers watching their hope of defense crumble into ash. Terrifying. This sorcerer would be the most powerful piece on the battlefield with this ability but it also creates a weird dynamic.
This Mage would have to be close enough to the target to hit it without a chance for missing. If he is close enough to hit (artillery, the main gate of a castle, barricades) than the enemy soldiers are not far behind. So the strategies that unfold are these:
(A) Extreme Stealth
For the mage, to get close to the target and avoid the enemy soldiers, he would need to be very stealthy. A transport spell or an illusion would work in this case.
(B) Siege Warfare
With the introduction of this element, siege warfare would give the advantage to the one with the castle. the attackers would be restricted to hiding in the woods to avoid being hit by the lightning. if the attackers had the mage, he wouldn't be able to get close enough to the gate to blast it, because of the nature of the open field.
(C) Longer Construction Time
To avoid the impediment of wood being a target, construction would take longer if the army wanted to make things out of stone. Going to a quarry, having it carved, moving it back.
(D) Larger armies would cover a larger range
As AuronTLG mentioned, the risk of splash damage would be enough to deter armies from coming together in one group. But the lightning (unless severely altered by the mage) would only strike one person at a time. It would give shock to anyone within 4-6 feet. Being spread out more, these platoons could cover a larger distance, whether on patrol/outposts or defending a point of interest such as a capital city.
So, in the end, it goes back to fire.
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How DANGEROUS? Not that dangerous apparently: <https://www.google.com/amp/s/www.businessinsider.com/what-to-expect-when-you-survive-lightning-2016-4%3famp>
90% survive. "Survive" does not mean they'll be doing anything on the battlefield that day. Its unlikely that you'll be struck directly since the rod is what attracts the ligtning and it gets grounded quickly, but there are other ways to get struck.
<https://www.weather.gov/safety/lightning-struck>
The people close to the metal rod, within a foot or so, can get hit by side-flashes. That means the people in immediate vicinity of the rod are in danger, unfortunately it is likely that any rod striking nearby will already have either killed the people or caused them to move away.
Upon a strike electricity will travel through the ground, and the most common way for people to get "struck". Electricity will go up one foot, course through the body and exit the other foot. I couldnt quickly find an actual range for this, but at the bottom of this page you can see that it can be a wide range indeed:
<https://www.weather.gov/safety/lightning-science-ground-currents>
There do exist multiple-strike incidents, where a single lightningbolt hits several people or livestock. There's even a picture in the last link of several livestock that were hit and killed while hiding underneath a tree. Livestock and thus Cavalry is more likely to be killed as the lightning needs to travel longer to reach the other end of the body. The AOE isnt going to be zapping everyone in that area when you look at where it travelled though.
Other injuries from people not directly hit are often temporary deafness and ruptured eardrums
So best use: anti-cavalry artillery, then just a low-lethality artillery weapon against ground troops. Low-lethality if you are smart that is. A single strike incapacitates a lot of soldiers, and letting them live shows mercy while burdening the enemy supply train with wounded. If you are nasty however you can strike a second time, likely killing anyone lying down from the first strike.
Compared to a mortar or canister shot a lightning bolt might be underperforming. But the psychological and aural effects (everyone nearby deafened) are definite bonuses. Its ability for repeat strikes and prior seeding are its best advantages. Its an artillery piece, so you'll be able to copy-paste the tactics for and against artillery pieces. Combined with mine warfare.
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If you can call a lightning strike to wherever you want as long as you have seen the rock... well, calling a lightning strike on a rock 10 meters away is for you as if you have been tasered through the legs.
Horses go down. Then they panic and run away.
Men go down. Tasers can have after-effects like cramps and spasms for hours after the strike, depending on the voltage.
Imagine that happening to your army. Imagine reacting by changing the formations so that it doesn't happen to hundreds or thousands but only to a few or a dozen. Basically you get Napoleon's war tactics. That's so different from Medieval that yes, I would call it devastating for your setting.
Except, except if you have just two or three magicians per state. Artillery is nice, but if you have just two or three cannons in the state, it doesn't change the war.
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I don't know that this has been tested scientifically, but a suit of metal plate armor may work as a [Faraday cage](https://en.wikipedia.org/wiki/Faraday_cage), insulating knights from lightning. A Faraday cage is any metal encasing that can redirect lightning around something you want to protect. This is actually why it is safe to be in a car during a thunderstorm. It is a common misconception that the rubber tires protect you. The lightning simply hits the roof, goes around the sides, and arcs to the ground.
Like other answers have mentioned, the real effect may be largely psychological. Especially if the defending army is largely uneducated in matters of electrical engineering, which was not understood at all in our civilization until the mid 1800's.
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**Let me tell you about two very real circumstances**
My wife and I once lived outside of Austin, Texas. The lightening storms there have breath-taking beauty. But, there is a downside.
1. I exercised each night after work by walking a loop of about 5 miles. We lived out in the boonies where it was very rural and very unpopulated. The fog would regularly be so dense that I couldn't see much more than 50 feet in front of me. I loved it — except once. I never saw the lightning flash save as an after-image in my mind. My best estimate was that it was about one-quarter of a mile away (1,300 feet or 396 meters). The bang deafened me for a solid 10-15 minutes. The concussion from the strike knocked me flat on my back and seriously winded me.
2. A second experience had to do with our house. We think the strike was within a tenth of a mile (530 feet or 160 meters). It sounded like it would blow out the windows, but the only damage was phone and electrical wires in the walls being burned to a crisp (I had to replace them), a centronix-style parallel cable (that dates me) that was burned up, and the parallel port on the printer that was fried. That cable was the one you need to worry about, it was only six feet long.
**A disclaimer...**
We're treating "lightning" as if all lightning is alike. It isn't. Some strikes are itty-bitty and would serve only to scare the snot out of someone. Others are life-altering blasts. You don't mention how much control your magic users have over the strike. I'm assuming they're at least what I've personally experienced.
**My conclusion?**
If you're trying to inject reality into your scenario, you need to use lightning in the same way a modern military uses artillery: as a supporting action at a considerable distance. Unless you change the rules of your magic, lightning is nondiscriminatory. It'll affect friend and foe alike. Used in the middle of a battlefield (as in, at the range a human could throw a javelin) it would bring the entire battle to a halt.
Most RPG-style uses of lightning treat it more like a directed energy weapon. It's generally focused on a single target and delivers damage based on the strength of the spell, from a mild tickle up to a small pile of carbon for remains. The more "real life" you make it, the harder it is to justify using it. A thrown rod is a nice idea... if you're on the top of a hill. Electricity flows from the highest charge point (somewhere up in the sky, that's the magic part, right?) to the lowest charge point. Sometimes that's something high. Sometimes not. But a rod isn't enough to make a difference electrically. If there's a nearby body of water or it was raining nearby before the battle, that's where the lightning will go — rod or not.
If your rules of magic make the rod always the lowest charge point then there's really no point to asking this question. Make the lightning do what you want with the damage that you desire.
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I'm bouncing ideas around in my head for the story for a game I'm planning. I wanted the world to be one where humanity was re-emerging from a magical slumber and setting out to reclaim the world. Something where they locked themselves in underground shelters in a magic sleep until a disaster passed. They would awaken to see that the disaster had changed the world drastically, but some ruins of the old world still stood. I want one of the gameplay elements to be exploring the ruins of the old world.
The question I have is, if this slumber happened in a fantasy setting with architecture comparable to the late medieval era, how long would humans be able to sleep in this untouched world and awaken to ruins that could be explored or potentially restored for habitation?
I doubt millions of years is possible, but what about hundreds or tens of thousands of years?
I'm especially curious of where the cutoff would be where wooden buildings would start to fail, but stone buildings would still stand.
For the sake of keeping this question simple, we are not discussing buildings made with exotic/magical materials or magically preserved buildings as the rules for those are whatever I make of them. I am only focused on mundane buildings, bridges and fortifications.
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**Wild variety**
Unfortunately I can give you only a part of the answer. And the answer is that it's heavily dependent on the climate.
It is safe to say mundane buildings wouldn't last long. Wood or mud or simple stone houses would last maybe a decade or so. People would build with anything they get their hands on and not go for the perfect long lasting wood, except if it happens to be available closeby. In addition, the craftsmanship leaves a lot to be desired. The majority would have little insulation and without people be very open to the elements and nature. This would degrade them quickly, leaving only some hints of what stood there.
Slightly higher tier buildings might be taverns, nobleman houses or simply many in certain city quarters. The ones made from wood would still only last a decade or two. With long lasting wood it might be a decade or two. If stone is used, it could go up to a few hundred years. The foundations are more likely to last longer, but after a thousand or a few thousand years there is likely nothing left but some scattered stones if they were used.
Fortifications would last the most. They are build to last and have the advantages of thickness, though height can be difficult at times. In addition, they start with an advantage that nature is generally kept at bay closer to the walls. A few hundred years it might stand, and thousands of years you can still be inside substantial ruins.
Now that the basics are out of the way, the second important thing to notice is the area they build it and the climate. Besides the material used, the area determines a lot of other weaknesses. A castle might stand for a thousand years, but things like erosion, foundations of salt being washed away or a flood might destroy the foundations.
Barring that, the climate can determine a ten thousand year hovel or a thirty year castle.
All zones with nature, especially trees, are highly vulnerable. Where tree roots can to through asphalt in our modern day, they can get more easily get in near or between stone and wood to grow and completely upheaval the structure.
Besides the nature, wind, water and Temperature differences are the greatest enemy. They erode with their oxigen and the expansion and shrinking of material can crack the material and even turn things into dust, leaving more open to the elements. A combination of water and Temperature is even worse. Cracks form, water gets in, freezes and destroys the material. Asphalt again is a good example. Made to last erosion from thousands, if not millions of cars driving over it. The cracks for the water to make the road safer in general, but one winter and the whole thing can crack, causing asphalt to warp, making dents and hills all over. This is especially dangerous if there's water and it's around freezing temperatures. During the day it might melt just enough, just to freeze again in the night, cracking the next layer to prepare it for the next assault. These things don't happen overnight, but with decades of preparation it could find a foothold and just rip towers in half.
More examples could be given, but most important is this:
It requires material highly resistant, if not impervious to rot. It needs to be build in a sturdy place that is unlikely to change. So no cliffs or earthquake area's. Little wind or water. Temperature must barely change. Little nature in the vicinity. Or if it doesn't need to be found above ground you have other options. Landslides or under water, like Willk is suggesting, can preserve it much, much longer. Then millions of years might be possible.
Otherwise the chance of just having substantial ruins is unlikely after a couple of thousand years, let alone a hundred thousand. Look at the current castles that haven't been maintained. 500 years later and many have become ruins.
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**If there are no microbes and no weather, things can last indefinitely.**
[](https://i.stack.imgur.com/J2wAa.jpg)
<https://www.nationalgeographic.com/news/2016/10/black-sea-shipwreck-discovery/>
At the bottom of the Black Sea are shipwrecks that are many hundreds of years old. This one is a Byzantine ship from the 800s. The oldest is a Roman ship over 2000 years old. They are recognizably ships. There is no oxygen at the bottom of the Black Sea, and so decomposition proceeds slowly. There are no multicellular life forms.
If wood ships can persist then so can stone.
---
Bottom line is that you can modify your apocalypse to make things last.
1: Wet hot weather like the Yucatan - wood 10 years, stone 500+ years.
2: Dry hot weather like Egypt - wood probably 50 years, stone indefinitely.
3: Cold dry weather like Antarctica - [wood 100-200 years](https://en.wikipedia.org/wiki/Scott%27s_Hut)+, stone indefinitely
4: Anaerobic and underwater - wood 1000+ year, stone indefinitely
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I want to make a world where there's no rivers or oceans but instead they're replaced by quicksand or similar. People get water from rain and water springs or wells.
So I want to create a warship for their naval battles, either to *yaarrghh* plunder the booty or invasion. I think a bridge is too predictable, and can easily be cut off or blockaded, and creates a bottleneck to the invader unless they widen it, and I don't know how much it costs to make a bridge to cross an entire ocean compared to ships, or whether it can withstand wagons or mounted animals crossing, but regardless, I want to make a naval battle with warships, even if portable bridges like pontoon bridges and similar would be possible or cheaper (so even if you bring that up, please also include regarding the ship design).
* The size of the warships are variable, but for simplicity's sake just assume they are as big as galleon ships.
* I think the ship bottom should be flat like a raft in order for it to float, but I am not sure so correct me if I am wrong.
* The ship is in a wind sailing era so no steam power or wheel paddle, if wind is not sufficient to make it move please include how many people need to row it or what type of sail can achieve it (originally I want to use junk type of sail) or the numbers of sails, and it's OK if the answers say there's no ship design with that size that can sail on quicksand too, at least I know a raft can sail on it so small ship warfare is at least feasible for me (but correct me if I am mistaken).
* It's a wooden ship, so no weird shape to accommodate better sail in quicksand from metal shaping.
* And since this is warship, I am worried regarding the cannon fire or where to place them, or if it's far better not to use cannon at all, since I think the recoil may make the ship capsize or sink or get in deeper due to the shaking.
I also considered including waves for the quicksand ocean (not decided yet, so you can ignore it) but I am not sure if a normal ship can float in it, since I saw some video about sand waves that it can sink many things, but correct me if it's possible for ship to float.
If possible please also include the math, since I am not good with math, and sorry if I make lots of misconception or the answer turns out to be obvious, I am not that knowledgeable about ship design, and my physics knowledge is at best similar to stone age level.
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Quicksand is a non-newtonian fluid which means that it acts differently than a normal liquid when force is applied to it. Typically that means it is like a liquid when low forces are applied (e.g. standing) but like a solid when high forces are applied (e.g. hitting).
Your ship probably doesn't want to "float" in it, being under the surface of the quicksand will severely limit your speed (faster = high force = more solid). Instead you want to 'walk' on it, repeatedly applying high impact "steps" on the surface. Something like a "stamping centipede" with lots of legs that stamped up and down would work well.
You would have to be careful you ship never stopped though! If it started to sink it would be very hard to pull itself back out again. There's a neat video and explanation, which shows people happily running on a cornstarch pool, while one person who stops gets totally stuck! <https://owlcation.com/stem/Oobleck-Quicksand-Cornstarch-And-Water>
[Answer]
**Sail powered airboat.**
First principles: you do not want you boat to extend down into the quicksand, which would offer too much friction. The boat therefore will need to be completely above the quicksand.
I was thinking of something like a fanboat or [airboat](https://en.wikipedia.org/wiki/Airboat) - flat bottomed boats powered across marsh and mud by a large fan or propellor. It would seem that these emerged only after motorized aircraft were invented. If there was a sail powered flat bottomed boat for marsh use prior to fan boats I could not find it. I think all boats for marsh use were paddled and mud flat / quicksand was not accessible.
But there were and are **sailing barges.**
[](https://i.stack.imgur.com/d7ydF.jpg)
<https://en.wikipedia.org/wiki/Thames_sailing_barge>
>
> The flat-bottomed hull made these craft extremely versatile and
> economical. They could float in as little as 3 ft (0.91 m) of water
> and could dry out in the tidal waters without heeling over. This
> allowed them to visit the narrow tributaries and creeks of the Thames
> to load farm cargoes, or to dry out on the sand banks and mudflats to
> load materials for building and brickmaking .... The main mast could
> be lowered to clear bridges. Furthermore, unlike most sailing craft,
> these barges could sail completely unballasted — a major saving in
> labour and time.
>
>
>
We will crossbreed a sailing barge with a skimboard.
<https://www.wikihow.com/Skimboard>
Skimboards are flat rudderless planks. One runs up, and jumps on the skim board, then is usually powered by momentum only. Some people can kick like on a skateboard.
---
The result is a Thames sailing barge with no draft at all - it is flat. There might be a cabin or walls. It is no longer able to carry heavy cargo but it keeps the giant sails (and they are still red) because it needs great propulsive force - comparable to an airplane propellor - to overcome the friction of the quicksand. Unlike a fan boat the sail also provides lift which reduces weight.
These things will need to be moving fast or they risk getting bogged down. High / dry points will also be risky. Probably there will be poles for the crew to pole the ship off if it gets lodged in dry sand.
Low wind means the quicksand ships sit and wait. That would be a great scene for your story. The pirates are becalmed in the quicksand. They look like sitting ducks. But how to reach them?
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Consider something like a catamaran or outrigger, which will function more like a sled than a boat. The less of your craft that sits in the sand the better as it will have much higher drag than water.
Lets be clear your sea can't exist and even if it did no ship could sail it without being worn away in days so you need a fair amount of handwavium to work.
Craft like this are already used on snow. There are a variety of styles out there so you can even have various cultural styles. They also exist in a wide variety of styles and materials including modern steel warships.
You can also find plenty of art with takes on this concept for a sand craft, in real life the abrasiveness of the sand will wear and ship away in no time, so you already have to be hand-waving friction, but at first glace this at least looks like it might work. If you want to make it slightly more believable make the skids out of some part of the native wildlife that naturally swims through the sand, that way it can reflect whatever magic allows a sea of quicksand to exist.
[](https://i.stack.imgur.com/bfRXS.png)
[](https://i.stack.imgur.com/YrBjq.png)
[](https://i.stack.imgur.com/24B40.png)
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I am trying to come up with insults and swears for some fictional races. Their cultures pretty well mapped out, but I am still having some trouble. I figured the best source of inspiration would be to look at different human cultures and what they considered insulting. Does anyone know of a good book that does this?
Note: This is not a repost of [this](https://worldbuilding.stackexchange.com/questions/114413/how-does-one-create-specific-swears-and-slang) because I am not asking for general advice or guidelines. I am specifically asking for a book that relates the culture and insults of several different societies in order for me to better understand how insults develop.
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If instead of a book you want to invent them yourself, it should not be complicated: define what each culture values most and attack it.
* Plutocracies obsessed with becoming rich will consider it offensive if someone tells them that they are poor.
* Martial cultures that value success at war will become very angry if you treat them as cowards.
* For a nomadic culture nothing would be worse that being called a farmer.
* The impious and the heretic are the worst insults inside a theocracy...
Then you have to adapt the expression of the ideas to the general culture. A more basic culture will just erupt into "dirty" words ("coward!"), a culture centered around mithology would make an analogy ("he runs from battle as Mazor did in front of Asur")...
[Answer]
You could try [*Sticks and Stones*](https://www.goodreads.com/book/show/2285305.Sticks_and_Stones) by Jerome Neu.
>
> "Sticks and stones may break my bones but words will never hurt me." This schoolyard rhyme projects an invulnerability to verbal insults that sounds good but rings false. Indeed, the need for such a verse belies its own claims. For most of us, feeling insulted is a distressing-and distressingly common-experience.
> In Sticks and Stones, philosopher Jerome Neu probes the nature, purpose, and effects of insults, exploring how and why they humiliate, embarrass, infuriate, and wound us so deeply. What kind of injury is an insult? Is it determined by the insulter or the insulted? What does it reveal about the character of both parties as well as the character of society and its conventions? What role does insult play in social and legal life? When is telling the truth an insult? Neu draws upon a wealth of examples and anecdotes-as well as a range of views from Aristotle and Oliver Wendell Holmes to Oscar Wilde, John Wayne, Katherine Hepburn, and many others-to provide surprising answers to these questions. He shows that what we find insulting can reveal much about our ideas of character, honor, gender, the nature of speech acts, and social and legal conventions. He considers how insults, both intentional and unintentional, make themselves felt-in play, Freudian slips, insult humor, rituals, blasphemy, libel, slander, and hate speech. And he investigates the insult's extraordinary power, why it can so quickly destabilize our sense of self and threaten our moral identity, the very center of our self-respect and self-esteem.
> Entertaining, humorous, and deeply insightful, Sticks and Stones unpacks the fascinating dynamics of a phenomenon more often painfully experienced than clearly understood.
>
>
>
Personally, I think the author doesn't understand the fundamental truth underlying the rhyme, and thus proceeds from at least one false premise; but from the blurb this seems to be a promising resource for you at least in the broad strokes that lay bare humanity's broken nature regardless of specific culture.
[Answer]
You could try the Harry Potter series. There are a lot of ideas that could be copied and modified there. It is much easier to use imaginary words and fill them with angst and similar rather than trying to use emotive words from our world.
A number of "bad" words are used for example Mud blood which is a derogatory term for the witches and wizards of mixed magical / non magical lineage. This word can be amplified by linking to lesser derogatory words for our world hence - filthy mudblood! is even worse
There are words that cause a great deal of offence when spoken going against the social norms such as "Voldemort" - Don't say that name! He who shall not be named.
Then there are unforgivable curses like Cruciatus and Avada Kedavra
Then are also awkward topics that are taboo like the horcrux. The secrets of which Tom Riddle eventually manages to obtain.
If you take any controversial topics from our world from racism to porn or violence you will find an abundance of material. Take the words and the context that they are used in, then replace that word with one of your own choosing. This will take the offensiveness away but leave the meaning clear.
[Answer]
The following books are freely available from [Archive.org](https://archive.org):
* William Henry Luckenbach, [*The Folly of Profanity*](https://archive.org/details/follyofprofanity00luck), Philadelphia, 1884. An great example of how to write an entire book about the subject without actually using indelicate words.
* Julian Sharman, [*A Cursory History of Swearing*](https://archive.org/details/cursoryhistoryof00sharuoft), London, 1884.
The following books can be borrowed from the same source:
* Nancy McPhee, [*The Book of Insults, Ancient & Modern*](https://archive.org/details/bookofinsultsanc00mcph): an amiable history of insult, invective, imprecation & incivility (literary, political & historical) hurled through the ages & compiled as a public service. New York, 1982.
* Ashely Montagu, [*The anatomy of swearing*](https://archive.org/details/anatomyofswearin00mont), New York, 1967. An inquiry into the history and nature of the fine art of swearing, with selections, uncensored, from its most accomplished masters.
* Jerome Neu, [\*Sticks and Stones: the Philosophy of Insults](https://archive.org/details/sticksstonesphil0000neuj), Oxford University Press, 2008.
* Generally, you can look for [books about invectives](https://archive.org/search.php?query=subject%3A%22Invective%22); you will find many.
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[Question]
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After the apocalypse event, humanity basically had to start from scratch. The systems made to store the information about modern technology were damaged beyond repair, with the new human race having only access to middle age technology and limited, poor quality firearms. In this society which saw itself returning to the use of melee weapons, they had to isolate themselves from the "changed", once humans from the ancient times, now cold monsters devoid of empathy which thrived while the new humans were "grown". What settles these creatures apart is the ability to generate thick, sharp scales akin to those of a pangolin, which they grow on their hands and body to use as swords and bullet-proof Armour. They're mostly composed of keratin
Now, could these "changed" really do that? I've seen concepts of modifying one's arm into a sword, but that would sacrifice flexibility as the wrist joint is rendered useless. Could a creature grow a bladed weapon on their hand, preferably through the association of long scales? The hand is meant to be almost fully covered by the grown structure and be usable again after its discarded by the body.
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You're mixing things that don't need to be mixed.
1) They grow weapons.
2) They use those weapons.
Have them grow a keratin(ish) sword then detach it to use normally. So while it's growing it's more ornamental than useful, like a spine growing down their back or something.
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African Clawed Frogs do something similar but more gruesome. You see instead of scales, they brace their own brittle, sharp bones to form false claws to scratch their enemies with. Not only is is it terrifying, it's a great biological metaphor to add to that "cold monsters devoid of empathy" thing you're looking for.
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A guy on youtube turned his beard into a knife.
The answer is probably yes. Any body part an animal sheds can be transformed with some imagination, and if the tool created is useful then it eventually becomes part of evolution.
Example: spiders evolved webs to block prey, with time they understood that their silk is a material for flying, building traps and houses
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What would be the economic trade offs of building fusion powered rockets vs building laser relays across the solar system? What assumptions would you need for each one of these to be the superior option?
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There are two different determining factors to consider here.
For any sort of rocket, even a fusion rocket, the main issue is going to be the [rocket equation](https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node103.html). Essentially, the farther or faster you want to go, the greater the fraction of the rocket becomes fuel and energy source and the smaller the fraction of cargo. Since the rocket owner is being paid to carry cargo (including people), the cost goes up with increasing distance or demands for speed, which also increases the prices which must be charged to the customers.
Fusion rockets will likely be very expensive to build and operate (think about the implications of all these devices aboard a ship with a real life "[Epstein drive](https://toughsf.blogspot.com/2019/10/the-expanses-epstein-drive.html)", for example. Fusion drive spaceships are likely to be used as "packets" to carry premium cargo rather than "tramp steamers" carrying whatever cargo the captain and crew can scrape together.
This also means they are most likely to be only found on profitable routes, so between Earth and the most densely settled planets or moons, where there is not only enough volume of cargo and traffic to warrant fusion packets, but the expectation that the docks at either end will have the technical staff, fuel and other materials needed to keep the ships in operating order and good repair. Given all the associated costs which go with the fusion ship, there will be a limited number in relative and absolute terms across the solar system, and they will only be owned by governments or large corporations capable of making the huge investments needed.
Sails have a different economic incentive: throughput. Laser sails will require one laser at each end of the trip (for acceleration and deceleration). If [photonic propulsion](https://www.popularmechanics.com/space/deep-space/a19604/nasa-physicists-say-photonic-propulsion-could-send-a-spacecraft-to-mars-in-3-days/) is the chosen system, savings will be made in the size and power of the drive lasers, but there will be additional costs in the corresponding reflectors needed to "recycle" photons from the laser sail and back. This is another large fixed cost, but since the devices are essentially planted on a moon or asteroid, the cost can be amortized over tens, hundreds or even thousands of launches.
[](https://i.stack.imgur.com/4fL6I.png)
*You also need to pay for all this as well...*
Laser launchers have an additional advantage over a fusion packet in that they are not tied to a particular type of fuel for the reactor, but can use any energy source to power the laser. Grids of solar cells, nuclear fission reactors, fusion reactors that use different fuels than the packet's reactor or even billons of monkeys on treadmills could be conceptually used to power the laser. In a fully developed polity, the laser probably draws from a grid with multiple energy sources, and launches are scheduled to take advantage of off peak rates whenever possible. Ownership of the ships and the laser can be separate, ship owners can purchase time on the laser as needed.
So if the "throughput" is high enough, a laser system will be far more economical, and can amortize the costs over large numbers of launches. Bulk cargo can be sent since there is no "rocket equation" penalties associated with speed or distance (indeed, the velocity of the laser launches can be adjusted to reflect this as well, low cost launches using minimal energy if there is no demand for the cargo to be delivered urgently, while high amounts of energy can be delivered to priority cargos).
Overall, the photonic propulsion system provides the means for a much larger and more flexible system of transportation across the solar system.
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Bigger than economics, I'd see the primary decision factor as this:
Can you trust the people you leave behind to maintain the laser array and turn it back on at the right time for your deceleration (assuming you'll use a *Rocheworld* style two-part sail)? I wouldn't -- if you're going to be in transit for a couple centuries, who knows if there will still even be humans back home when you need to slow down?
That leaves either decelerating the slow way, using only the light of the destination star, or taking your power plant with you, meaning fusion rockets and a good sized comet to supply fusion fuel and reaction mass. You'll cut years (decades?) off your travel time with a fusion drive, compared to microgravity deceleration under natural emission on a light sail.
As a bonus, you can take a great deal *more ship* than you could reasonably launch with a laser sail, and avoid leaving your home system full of immense laser cannon (this improving the odds of still being humans back home when you arrive).
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## It depends primarily on the payload
While the available technology will undoubtedly dictate what propulsion systems one uses, the mission will be the stronger factor. Even when fusion drives and laser beams are available, it is quite probable that they will still be outperformed economically by chemical (LOX + LH) rockets in the moon systems of the giant planets. This is just meant as a reminder that even old technology can outperform the fancy, futuristic stuff given a favorable resource situation.
For interplanetary travel, you got many options beyond laserbeam and fusion drive. Chemical, ISP-Family, Fission, Particle Beam, Electromagnetic Launcher, Trochdrives, Fusion, Light, and Lasersail would be my, most likely not comprehensive list. I'll assume that your fusion drives are economic engines, not torches.
For an economic analysis, we must, as I said consider the mission. I believe that splitting missions into bulk, value dense and express transport is sufficient. Bulk are industrial feedstocks like ore, ices and organics. Value dense includes manufactured goods, whose markets might fluctuate a bit more, so that timely delivery becomes important. Express goods would be people and military. Anything that should arrive at the destination as quickly as possible.
Efficiency and travel time are somewhat related. Fusion drives require fuel and ejection mass, but give the vessel a lot of autonomy and agency. Laser beams can circumvent the tyranny of the rocket equation, but the spacecraft loses a lot of autonomy and agency. However unless the fusion drive is incredibly efficient, even it won't give the crew as much control over their navigation as one might think. If a spacecraft has accelerated it can only change its trajectory by so much. It might perform an abort burn, but a laser craft will probably have some means of maneuvering as well. Aborting and going elsewhere or rendezvousing with a rescue mission should always be possible. The main difference is that the stations sending out the laserbeams will have a lot of control over the spacecraft's in the system. A laser sail setting will have very few unofficial spacecraft. Only big cooperations and nations will be able to maintain a laser web. If your protagonists do something in a laser sail setting that the people in power dislike, they will be in much bigger trouble than in a fusion drive setting.
To sum it all up, if fusion drives can get close to torch drive performance they will dominate the laser webs. If fusion drives never get close to marrying economy and muscle drives, the laser web will dominate them by merit of its efficiency. However, I believe that no single propulsion concept will come to dominate the market, as different missions require different propulsion concepts. Especially electromagnetic launchers might dominate the bulk cargo market since they are simpler, more versatile and efficient than laser sails and fusion drives here.
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**A fusion drive is good for lots of things!**
If you can make a laser sail, you can laser sail away, yes indeed. And you have a giant laser pointed at space that might be useful for other things. Maybe writing things on the moon.
But a big laser will never as useful as a fusion rocket! Aside from the fact that it will propel your ship no matter what is going on back home, a fusion rocket is a versatile tool. A fusion engine capable of being a rocket can be a weapon; ask the Kzin about that. But there are also prosaic workaday applications for a tractable fusion engine. It can generate electricity to purify the air and regenerate the carbon for your people on their ship. Once they get to the destination it can keep the lights on in their colony and supply the radio station with power. Also desalinate the water and produce fertilizer from the air. Maybe even fly your DeLorean!
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Early life, and many modern organisms have what we call 'blind guts'. Food enters and exits via the same opening.
However, that is inefficient and has been widely replaced with 'through guts'. Food goes in one opening and out another.
Could an organism do something like this but with the reproductive system instead?
Would there be any good reason for a species to evolve this kind of set up?
For an explanation, gametes, sperm or otherwise, enter one hole, fertilize an egg or perform some other reproductive process, form an egg or a baby, which wil then come out the other.
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While the analogy between reproduction and eating seems like a valid one on the surface, especially since some of the openings you describe are shared between these functions, there are some good reasons for leaving reproduction just the way it is. While there are some potential benefits, the cost would be significantly higher in terms of health of the organism which is probably why it has never occurred in nature (at least within the sphere of research I've read).
The potential benefits seem obvious; for one thing, you can birth an egg or child from a much larger opening than the one in which the gametes or sperm enter, meaning that you lose a lot of the complications in modern mammalian birthing, particularly in humans where increased brain size is causing complications that evolution is trying to solve through bringing babies to term at a much lower level of development compared to other species, and neural 'specialisations' in the form of Neurodiversity, or the Autism Spectrum. Certainly birthing would be much less painful for most species designed this way, and you could keep babies in utero for longer, right?
The trouble is, for all but a very specific set of organisms, the problem that you have with this is frequency of use. You've just added significant complication to the design of your organism for something that doesn't get used all the time. Having a mouth and an anus makes sense because food is common requirement for us. Most organisms, especially the complex ones, feel most comfortable if they eat daily or more often. So, both openings are going to be under constant use. The hygiene factor alone makes two openings and a through system sensible under that kind of workload. Reproduction on the other hand doesn't happen nearly so often and as such can cope with the simpler system as the single opening is used so much more rarely. The IO (if you will) just doesn't justify the increase in complexity.
It's been my experience that evolution favours simplicity wherever possible; specialisations do occur but they also die out quickly when the conditions change that led to them in the first place. In this instance, there would be some benefits to this change to be sure, but the existing system works well enough that it is less of a concern than the eating example you gave in the OP.
Humans are the embodiment of that principle. We are generalists in almost every sense of the term. We are not the fastest animal but we can run. We're not the best climbers or swimmers or trekkers, but we can do all those things. We can eat nearly anything compared to most other mammals, and the few specialisations we seem to have are being able to throw things and work tools, which when combined with minds capable of rapidly adapting our behaviour through better knowledge of our environment, has seen spectacular results. And we've done it with the simpler reproductive plumbing you describe.
In short, the added cost in maintenance and hygiene isn't worth it for a system that works well enough as it is. While it is possible that we would get reproductive benefits, the added maintenance would more than offset the those benefits which is why (I suspect) it will never happen.
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>
> Would there be any good reason for a species to evolve this kind of set up?
>
>
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There is no good reason for having a "batch processing" reproductive system, as the current method is more than enough.
Why? Eating is a daily necessity for all animal, reproducing, though one of the life priority, is way less frequent. No animal, as far as I know, reproduces as frequently as it eats.
This for the obvious reason that sexual reproduction is energy intensive, so any organism has to first build up the necessary energy reserve and then engage in reproduction.
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To be honest, maybe, but not likely.
The reason why the "complete" digestive system has two holes is because that way one can eat more food without first letting out what it's already eaten, meaning it has a more efficient and faster way to gain energy through eating. For your creature to have a similar route with its reproductive system, reproduction would too have to be something happening constantly and at a fast pace (aka your species would be basically composed of nymphomaniacs that would put rabbit reproduction to shame).
As a counter measure, what about an uterus divided in chambers that close up once there's an embryo inside? That way, the mother could be fertilized many times, even while still pregnant, and deliver a baby even while the others aren't ready yet. The main issues with this idea are: 1-more energy and space must be reserved in the body for the reproductive system and 2-the more babies the mother is incubating the less agile/mobile she might be (look at how kangaroos throw their pouched babies at predators if she can't hop away fast enough, your creature might even abort the most developed and heaviest one as a defense mechanism if it can't escape a predator).
So yeah, the only way I see for your creature to have any of these adaptations would be for reproduction to be (and I can't stress it enough) EXTREMELY important for the species to survive.
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This reproductive setup is quite plausible, as it has occured, in some form, in marsupials, lepidopterans, and spiders. An advantage would be that the birthing orifice does not need to be involved in mating, and so is less limited in what forms it can adapt to.
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One problem, I think writers often overlook, is the problem of flying creatures communicating with each other. I call this the *"I can't hear you over the sound of the f@cking headwind!"*
For my world, this problem is present in three different species:
1. Tengu, a race of humanoids with many bird-like features, including wings and beaks.
2. Gryphons, hexapodal creatures with the head of an eagle or a corvid and the body of a large feline (usually either a lion, a tiger a cheetah or a lion-sized cheetah).
3. Dragons, the six-limbed variant. They aren't that big, but definietly larger than a horse, though they're lighter and not much stronger (except for, ya know, the wings).
All three species have human levels of intelligence and possess airsacs, to help them cope with higher altitudes and make them lighter. Flight speed is around 16-20 m/s for them while gliding.
Now, they do speak the same language, but that isn't the only barrier between them. **How can they successfully communicate while flying in an Earth-like atmosphere?**
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**Standard bird ear biology**
Just because there's a strong headwind, doesn't mean that everything suddenly becomes inaudible. For humans sure, but human ears aren't designed to be able to hear at high airspeeds. For example, if you're riding a bike quickly, you can turn your head to the side and notice a significant drop in apparent headwind noise.
Moreover, birds are already adapted to be able to hear while flying. Owls, for example, have excellent hearing and can *triangulate mouse heartbeats* while flying. Simply take a look at bird-ear biology:
[](https://i.stack.imgur.com/S9Y7E.jpg)
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This is depending on the level of communication you want. Full on conversations aren't going to happen, but if you need commands similar to military or hunting, this can be done.
**Hand/arm signs**
Since all these species are hexapodal with human-like intelligence, its fair to say that they will have fairly fine motoric movement in their front limbs. Hand or arm waves similar as done with landing planes would be my first choice in this situation. They will need the leader up front with eyes on them at all times though. At night small lights could be used depending on your technology level, but this won't be too stealthy. This form of communication is already used by hunters, soldiers, and divers.
**Screeches/whistles**
Perhaps more finicky to get right, but potentially more versatile. Dumb down the absolute necessities of language to a small amount of distinguishable screeches. These carry further than words or shouts, and are usable at night as opposed to the signals. These won't still be stealthy though.
Depending on your technology or magic level though, you could just use modified biker helmets with microphones, or magical signs.
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Imagine a miracle happened and all leaders decided to wind back the minute hand of the doomsday clock and passed a bill that can transform all kinds of nuclear weapons into fuel for power plants, could nuclear weapon turns into improvised battery and if so how long would it lasts for the entire civilization assume the energy demands remained constant? Existing technology only and please show your working clearly.
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The latest estimate for the [size of the world nuclear arsenal](https://www.ploughshares.org/world-nuclear-stockpile-report) amounts to 13475 warheads.
I could not find any estimate on the total yield of that arsenal, so I have to proceed with educated guess.
Let's say the average warhead accounts to 300 kTon, or 1300 TJ, like a [W87 warhead](https://en.wikipedia.org/wiki/Nuclear_weapon_yield).
That would lead to a potential of 17.5 million of TJ, or $17.5 \cdot 10^{18} $ J.
The [world energy demand](https://en.wikipedia.org/wiki/World_energy_consumption) in 2017 was 113009 TWh, which multiplied by 3600 gives us $406.8 \cdot 10^{18} $ J, about 23 times more.
Assuming that the yield of a nuclear warhead can be 1:1 converted into usable energy in a nuclear power plant, with your plan it looks like we could supply the world for just about 15 days (365/23).
The above is an overestimate, however, since we have fission plants, but yet no fusion plants, so the potential of the arsenal due to fusion warheads would account to 0.
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Many societies have and continue to practice entomophagy, and many environmental activists promote the consumption of insects as an environmentally friendly alternative to traditional meat. It is relatively cheap to raise insects on an industrial scale with modern technology, but would it be feasible for people at a much lower level of technology?
Preconditions:
The primary reason they raise insects is that most of the large animals are dangerous to consume due to a neurotoxin that is accumulated in their flesh.
Tech Level: Think Iron Age Sub-Saharan Africa. So medieval Africa not medieval Europe. This means you’ve got iron tools, some kingdoms and a severe lack of good beasts of burden. They use hoe farming rather than the plow
Climate: Tropical Rainforest transitioning to Savannah. Think African Great Lakes Region
Other sources of food: They grow several kinds of tubers and fruit trees, along with fishing and hunting a very select few species.
My ideas for how they farm the insects:
1. Piles of rotting wood to raise grubs and termites
2. Slaughter some of the toxic animals to feed to carrion beetles and flies (Maybe to get the bones or something)
So would it be feasible for a preindustrial society in a tropical climate to farm insects?
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Absolutely, Insect farms exist for protein and they are very low-tech, I'd suggest grasshoppers or crickets would be a good candidate.
A pile of reed matting kept suitably moist would be a great home, and dinner, for grasshoppers.
In order to breed the same species all year round, you will need very large indoor (or underground) spaces, a cave complex, or a large hall would be a good idea. you'd have lots of piles of matting all in a rotation of different stages of the breeding cycle. And probably some artificially flooded reed-beds to provide the raw materials; so caves near a river would be a perfect spot.
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## No, even with modern technology insects farming for consumption is a bad idea.
High population density makes farmed insects extremely prone to parasites and disease. An EU study on insect farming showed 80% of insects tested from farms were harboring parasites, around a third of them were parasites known to be dangerous to humans <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6613697/>. So no only do you to worry about your farm being destroyed by parasites you also have to worry about people getting sick and that's with modern technology. with preindustrial technology, people will start dying left an right, neurotoxin might be a kindness by comparison. managing parasite risk is a huge part of modern farming a lot of farming law is built around minimizing parasite risk is far less parasite prone large animal farms.
then you have problems of scale, it is fairly easy to to restrain a cow or goat, much harder to contain and protect a million insects, especially if you have to move.
honestly neurotoxin does not work well as a deterrent since neurochemistry is fairly conservative across vertebrates, if the wild predators can eat it so can humans, also keep in mind humans started eating meat long before we became humans, even chimps eat meat. If hominids could not eat meat there would be no humans. but if you are set on it consider fish farming instead, that's fairly common.
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## This is already a thing in our world
I know people from a rural part of Honduras where it is common to raise insects as food. The area they are from is still pre-industrial with most people living on family farms, working the land with hand tools, and making most of thier own stuff from local resources. Honduras is also a tropical country... so the only thing that is really different from your setting is that Honduras also has other kinds of edible fauna, but that hardly impacts the outcome of the question.
## Also, neurotoxins will not keep people from eating the other animals too
Eel blood is full of a deadly neurotoxin that is destroyed by cooking. Puffer fish and various snakes have very deadly venoms, but are still eaten when carefully prepared such that the venom does not contaminate the meat. Cassava is rich in cyanide which is processed by soaking and fermenting it for a week before it can be processed into an edible flour. Greenland shark meat has toxic levels of urea which requires the meat to be cured and fermented for 4-5 months before it is edible. These are all forms of meat people figured out how to eat safely using pre-industrial technology.
Insects and other arthropods also fall into the realm of "less than safe" kinds of food because of the high prevalence of parasites, but various preparation methods like cooking to very high internal temperatures and boiling with parasite killing spices have also made these animals safe for consumption using methods that predate industrialization.
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How many people can live comfortably on planet Earth, assuming that humanity reaches [Kardashev scale](https://en.wikipedia.org/wiki/Kardashev_scale) Type I level?
This implies:
* Energy is cheap, and available in an almost unlimited quantity, compared to current level.
* Sea water can be desalinated and pumped to anywhere, a technology that is already available, but its usage is currently limited by the high energy consumption.
* Artificial sunlight can be created anywhere. This technology is also available even today.
* Food, advanced building materials, and almost everything else, can be synthesized from basic molecules and atoms.
* Transmutation of elements, e.g. making gold from lead, is possible, although not on a mass scale, because this requires enormous amounts of energy, that is beyond the reach of even a Type I civilization.
Energy can come from
* The Sun, as originally thought by Kardashev,
* or from fusion reactors, here on Earth,
* or even from advanced fission reactors, using all the uranium, thorium, and other heavy elements available on Earth, that can be converted to fissile fuel.
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Your most obvious limiting factor here will become energy since pretty much all of your farming needs to be brought inside once you get to such a scale.
Using indoor farming you need at least 110 watts/m^2 and the average person consumes about 270m^2 (when using areoponics). This means that you each person needs 29,700 watts to have enough to eat, and if we use the USA as a standard for "comfortable living" we also need to add ~1400 watts per person to power things like lights, microwaves, transportation, computers, etc. This puts the total power consumption per capita at 31,100 watts.
Since a Type I civilization can harness 1.74×10^17 watts of power, that means you cap out at about 5.6 trillion people, but future tech lighting and GMOs might be able to push this number even higher without having to sacrifice modern food diversity.
This introduces two other limiting factors which are building materials and global warming.
**Materials:**
Since Earth has a total land mass of 510.1 trillion m^2, this means that if everyone lives on Earth, you'll have a total population density of 1 person per 91 square meters. Between recreation, industry, residential space and infrastructure, your average urban resident needs about 200m^2 worth of space in addition to the farming totaling ~470m^2. If you only build on land, this means that doing this will result in an average building height per square meter of about 17.2 stories. Since about 50% of any city is open spaces (roads, parks, etc.), this means that your average occupied square meter of the planet will have a 34 story building on it.
Making reasonably luxurious buildings that tall might be doable with some nice future tech materials, but not on that scale. The entire Earth's crust does not have enough of certain materials to sustain ideal levels of comfort; so, you can assume that you'll need to do a lot of space mining to get all the copper, lithium, etc such a civilization would need, but it may be doable if your tech allows for it.
**Heat:**
Once you start building all these mega structures and roads and parks, there is no way to actually get 100% power efficiency from just solar. Even if future tech solar is close to 100% efficient, and you put it over every building and roadway completely blocking out the sun to all of humanity, there is still that 70% of the world that is oceans. One way or another, you'll need to use something other than sunlight for most of your power. Let's say you do 30% solar and 70% super clean fusion reactors. All those reactors are generating massive amounts of heat. As far as the people on the surface of the world are concerned, this is no different than turning up the sun by 70%. YIKES!
This means that your Type I civilization will need to be able to radiate out all of that heat. The best way to do that may be to reverse global warming and build up the world to have an opaque atmosphere that reflects more sunlight, but this reduces the effectiveness of your solar power. Any way you cut it, 1.74×10^17W is the theoretical hard cap on how much power we can make without cooking the world, and that is assuming all other environmental factors can be 100% controlled for.
In reality though, solar will never be 100% efficient and the atmosphere will never be made 100% opaque; so, it's probably best to just say your civilization maxes out on the solar power of all available land mass (5.22×10^16) at about 25% efficiency (1.305×10^16), and your population caps at about 420 Billion. A Type I civilization probably can not exist on a single planet, instead, most of your civilization's power will actually be produced/expended in space. Anything beyond that is going to be VERY hard to keep cool without some pretty hand wavy mega-structures
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# Maybe NOT As Many as Folks Think
While material limitations are an important consideration for maximal possible population, I think physical matter is not your limiting factor here.
Your scenario basically makes the First World look like a Fourth World backwater. Given the technology level and the free energy, even our own Third & Fourth Worlds will disappear as near instantaneous material prosperity reaches every corner of the planet: every person on Earth will be a citizen of an Ultra-First World country.
When we look at present world data, wealthy countries where the entire population lives a very cushy life (i.e., the First World) tend to *decrease in population*. Particularly as said population attains high levels of education.
Once poor countries where subsistence living requires a large workforce (i.e., big families) are brought into the wealthy rank, their large families will go away just as they did in America and Japan and Western Europe. There may be some instability for a while as food and medication and technology put paid to disease, hunger and child mortality.
No longer being required to work the whole day for mere subsistence, people will be able to pursue educational opportunities and will fill economic niches they could never even dream of. With all that education, worldliness and free time, population growth will level off and then drop.
Assuming the situation remains stable, I'd suspect the population could eventually shrink back to the point where a few billion or even less can live extremely comfortably in your scenario.
Your limiting factor here is simple material laziness, which tends to drive population down rather than up.
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## Hard to answer, it depends on how much damage you are willing to do to the place
**Keep Earth earth-like**
Assuming we don't want to engage in major mega-engineering and keep humans human-like, waste heat is the limit. This means everything depends on efficiency. Paradoxically embracing the greenhouse effect would increase the maximum population as the efficiency of an object radiating away heat rises with the fourth power of temperature. Keeping the place at a cozy 49 C average temperature, just short of a runaway greenhouse effect should be optimal. The population and industry should be spread evenly over the surface. Sea-cities would be a necessity. I can't give you any population values, as this would depend on how much waste heat one person produces.
I can, however, paint you a picture of this Earth. keep in mind that this is one possible scenario and that things would look radically different if some of my ideas about the available technology are wrong. Between the Earth and the Sun and on the Lagrange points gigantic solar arrays have been places, producing energy for Earth and shading it from the heat of the Sun. The planet is evenly covered in black high rise cities, the oceans deep blue, dotted with these black settlements and the continents covered in black radiators. Earth is a black-blue marble, as cloud formation has been cut down, as it decreases the efficiency of Earth as a black body radiator. Nature only exist in enclosed habitats. Food is produced in bioreactors and factory farms.
Such an Earth could probably support tens or hundreds of billions.
**[Matrioshka-World](https://youtu.be/Tul4njD6uP4) / [Shellworld](https://orionsarm.com/eg-article/47856a978e732)**
This assumes you are willing to put layer over layer and slowly burry the original surface. The technology you need for this is the [dynamic orbital ring](https://www.orionsarm.com/eg-article/464f869fc12cb). The first link leads to an explanation of the concept from the Orions Arm project, [this video](https://www.youtube.com/watch?v=LMbI6sk-62E&t=180s) explores the concept a bit further. How many layers you put up depends on how much space you need. The important thing is that you can run coolant pipes from the lowest level up to the surface. Then you transport the coolant up to a ring either short of the Moons sphere of influence or if you can get rid of the moon at the edge of the Earth's Hill Sphere. Up there you install [liquid droplet radiators](https://en.wikipedia.org/wiki/Liquid_droplet_radiator) to cool the place.
Such a place might support many trillions. Gravity in the outer shells probably becomes the limiting factor at some point.
**Dissasamble the Place**
Now, you asked about "on planet Earth", but I'll assume that Earth isn't more than the sum of its molecules. Meaning we turn the entire planet into spinning habitats. Assuming we need ten tons of material per square meter, this will give us 5.972 × 10^17 km2 of habitable area. A bit more than one billion times the surface area of Earth or six billion times the habitable surface area of Earth. Waste heat won't be an issue since we can simply spread out the habitat swarm far enough. Here material becomes the bottleneck.
**[Computronium](https://www.orionsarm.com/eg-article/4637faafa6437)**
We've already true the Earth into a habitat swarm, but this of cause still assumes we are dealing with biological baseline humans. Here we push the idea of "living" and "human" a bit further. Assuming we can upload a human mind onto a computer, all we need is hardware and energy. To maximize population we should run the entire thing as cold as possible, near [Landauer's Limit](https://en.wikipedia.org/wiki/Landauer%27s_principle). This meant that a single human thought might take millennia, but that's beside the point of this question.
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Interesting question.
Since the element you need from the most, oxygen, is as 'thedyingoflight' stated the most common element on earth, I'll take carbon as the most limiting factor to create/grow humans. I don't know anything about the rarer components of the human body and don't have the motivation to go through a checklist. I'll assume that it needs so little of those per person that we don't need to think about them anyway.
If we take the estimations of [this](https://web.calpoly.edu/~rfield/Carbon%20in%20the%20Geobiosphere.pdf) documentation and are really optimistic when it comes to the future of 'carbon mining', we could use a little over 7.7842628\*10^19 kg of carbon to transform into humans.
A grown up human body weighs on average about 62 kg today. Let's say they'll bring the average weight down to 60 kg. That's 10.8 kg carbon per human.
This means we could create up to about 7.1296296296\*10^18 humans. That's such a high number, that I doubt carbon could be the most limiting factor, but here we are, fuck it...
Now we'll have to estimate what percentage of that carbon will be rather used for production, housing and of course nourishment than for creating a sea made out of flesh. Now the broad/hard stuff gets important, especially what kind of food they use and how long it takes to create food out of feces.
If we expect such things to matter, we're probably already talking about a lot more humans than are able to live comfortably on earth. I'd say 3\*10^18 humans not living in constant pain feels somewhat plausible to me, if you have enough energy to build a city built from all of earths sediments. The usage of space will be a big problem with that.
Earth's surface is about 5.101\*10^14 m^2. Yikes. It means that we'd have to build one giant building with a little over 100'000 floors to give everyone 17 square meters to live on. The building would have a height of about 190 km, if the floors had an average height of 170 cm. This would be very hard to supply with energy, food and tech and even harder to keep from imploding. You'd have to build 'very' light, which ironically would most likely need a shitton of carbon. They'd also have to walk around with small gas bottles which they'd have to refuel every few seconds...
-I guess my 3 quintillion humans would rather live in caves, naked and sore, but alive. The only thing they'd have left is love. It's cheap, it's easy and yes we want there to be as many of us as possible, because why not?
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Ten to hundred trillion. Assuming population density somewhat below modern cities worldwide.
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First question so hope I'm doing this right! Working on a setting right now where a bio-engineered virus/plague is wiping out a large portion of humanity. Most died upon first exposure. Some survived, but are dying slowly, while a third group has developed complete immunity.
How could this immunity be passed on to the dying survivors? Would a blood transfusion do it, assuming that it was indeed something in the blood that made these people immune to begin with? Or would it be something more complex, like maybe their ability to develop some kind of antibody where others couldn't? (in which case the dying survivors would have to derive such antibodies from the immune survivors)
Thoughts?
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You have two easy and familiar routs where you could:
# 1. Biolife in the blood
This would be largely science fiction, but it would have "believability" for your audience. Some kind of proactive lifeform in the blood, such as a bacterium, would fight to destroy the virus. Here, the blood is just the carrier and, while a transfusion could work, isolating the thing inside would be more efficient, allowing it to be distributed on a mass scale more easily.
That could use "option exhaustion" to propel the plot and give you the scientific breakthrough needed for victory, either for the protagonist or a helper.
Something similar was done in *Deep Space Nine, Season 1* (ep13 'Battle Lines'), where the spiritual leader Kai Opaka died on a remote moon, but was brought back to life by nanites in the atmosphere. Nano-tech is a stretch, but bacteria is more believable and adaptable.
# 2. Vaccine
Vaccines are basically made from dead viruses. The blood of someone immune would probably have traces of it, or antibodies for the virus. But, it may need engineering and would require blood type matching. A transfusion itself probably would't work very often if at all, the plot would keep waiting for a scientific analysis of the blood to make a vaccine.
This is similar to what started at the end of *I am Legend* with Will Smith. Although that blood sample did contain a kind of vaccine he had introduced into the blood.
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Yes, in fact we already sort of do this. During the Ebola outbreak, medical workers that survived had the antibodies in their blood separated from the red blood cells and injected into other people that way their own bodies could start building up an immunity to it and the immune system can start fighting the virus.
Of course, this is a simplified version of the process but the general idea is very similar, as long as the disease doesn't mutate or at least mutates so minorly that the antibodies are still effective they could theoretically use this method.
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After reading up on space warfare for a while now, I'd like show how I imagine a realistic depiction of lasers in space combat. This question is more about the general perception of lasers the characters and audience will get than their physics. Please correct me where I'm wrong, but do not change my basic assumptions unless they are fundamentally flawed. Should some things sound like they are rather on the optimistic side of technical possibilities, that is because my setting depicts the far future.
## Laser Basics
Two basic types of lasers are used. Continuous and Pulsed beam. Continuous beam lasers are pretty weak unless they use vacuum frequencies (some UV, X-ray, and gamma), you have a large waste-heat management advantage (shooting from an ocean planet at an incoming fleet) or the laser is ridiculously powerful (a free-electron laser installation meant to push interstellar spacecraft up to several percent of light-speed). Pulsed beams generally give you better penetration and allow you to use longer wavelengths. They are preferred over continuous beam variants as weapon systems. Range and spot-size are improved with a shorter frequency, but shorter frequencies reduce laser efficiency leading to more waste-heat. Spot-sizes range from the centimeter to the meter range. The heat economy of lasers in the setting is generally worse than that of kinetics, resulting in large radiators laser-equipped vessels have to carry.
## Laser Defense
Lasers ruled the battlefields of space for centuries until *near perfect wide spectrum mirrors* capable of reflecting anything from IR to UV with high efficiency were invented. (This is a black swan technology no-one really expected and is an integral part of the setting.) These mirrors aren't magi-tech, but they are very good. Bottled light and laser defense are possible but hardly perfect. This reduced engagement ranges and made missiles and kinetics important in space warfare.
Battle craft design is still dictated by the need for laser defense. Plasma shields (plasma windows) (the closest thing the setting has to energy shields) are a first, mobile layer of defence. They are projected towards the enemy when laser fire is expected, but block all vision of the enemy and can be overwhelmed by lasers. Kinetics don't really care about plasma shields and are used to counter them. The hulls of the ships are covered in layers of the near-perfect mirrors which are cooled to reduce the efficiency loss and act as a whipple shield as well. The armor is sloped to increase the spot-size any hitting laser-beam will have and rotates quickly in order to always present unused armor to the next laser strike or follow up pulses. The last kind of defense is a mass or rather an ablative shield. It is a big chunk of ice and carbon materials, which is mobile and positioned where ever it is needed to block enemy fire.
Attacking lasers attempt to degrade the mirrors by heating and vaporization. Cooling and automated repair mechanisms attempt to counteract this. The lasers usually win, but battles can last a long time.
## Laser Visuals
One doesn't see a laser in space except if you are just a few degrees off the firing axis. In that case, an observer will see the beam as a "muzzle flash" coming from the direction of the firing spacecraft. The other case where one might see a laser beam in space is when it travels through a cloud of gas. This could be leaking atmosphere or propellant or plasma shooting into space from a laser hit. Laser hits will create a bright fountain of ejecta.
EDIT1: Clarification after an answer pointed it out: You will obviously not see anything unless the laser is within a wavelength you can perceive (in the far future that doesn't necessarily mean visible light) or something is heated to emitting photons at these wavelengths.
I'm not sure how a laser hit will sound inside a hit spacecraft which wasn't destroyed by it. I imagine it will be a loud bang as the vaporized material will expand expensively.
**Are my assumptions, especially about the visuals and the sound right?**
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Bomb-pumped gamma and x-ray lasers are also affected by very low efficiencies, but making a bigger warhead to pump them is relatively straightforward once you've solved the problem of targetting and shooting straight. There's no issue of waste heat, certainly.
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That's a little bit handwavey, but it can pass. It isn't energy-shield levels of science fantasy, at least. What is a lot less plausible is using the stuff as armour. It won't work against vacuum frequencies, because you won't be efficiently reflecting those any time soon... they'll blow off your electrons and your mirrors will be toast. It won't work against high intensity visible light lasers, as non-linear optical effects will similarly destroy the mirrors. Once the outer layer has been blasted away, it will generate fragments and fumes that will ruin the surface finish of the underlying layers. Similarly, deliberately discharging lasers into clouds of gas, dust or plasma surrounding the ship will drive energetic particles into the mirrors, ruining them. Contact with diffuse debris clouds or particle beams will similarly ruin the mirror finish. Buttering up your target with clouds of hypervelocity grit delivered via coilgun or missile sounds like a good first strike... the grit cloud can be wide (and hence hard to dodge) and is somewhat impractical to intercept with point defence. It would mean the first strike always has to be sublight though, which is an important change over purely laser-based combat.
Consider also that high-speed travel through interplanetary space, or spending large amounts of time in busy orbital space (eg. LEO) may also cause abrasion of your mirrors
If the mirrors are cheap to make, you'd use them anyway because every little bit helps and against low-quality, poorly-focussed or extreme range laser beams they will indeed be highly effective. Tactics to remove their advantages are likely to evolve quickly, however.
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You'd need to project them window frame and all, along with a power supply to maintain them. A cloud of unconfined plasma will expand very rapidly, even "cold" plasma. I would suggest that keeping overlapping cold plasma shield frames mounted to your warships would be a better use of these, and might end up being a better laser armour than your mirrors. They aren't perfect scifi shields (they have vulnerable frames, after all) but they do glow in a pleasingly awesome way, and are depleted by being shot at. You can decide which bits of the hull to project. All power to front shields is a reasonable thing to yell in the heat of battle. And indeed they're more deserving of the term "shield" because they're physical objects you have to hold between you and the enemy. "Scales" might also work. There's an interesting dragon-like aesthetic to be found there, I suspect...
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You don't need to flank much to remove the sloped armour advantage. Firing out laser mirrors to deploy in space to get banking shots or missile busses to deploy warheads into flanking shots is straightforward. You may as well slope your armour anyway though... dumb projectile weapon fire will usually be coming from the front, after all.
Remember that rotating armour that takes a big hit is a potential liability. If the belt *isn't* massive, then it will make useless armour and won't protect you well enough. If it *is* massive, then blowing a chunk out of it will result in a big wobbly off-centre mass that's gonna be hard to stop and will ruin your aiming (no point defence!) and navigation (no dodging or running away!). One-shot heavy-hitting weapons like bomb-pumped lasers, casaba howitzers and large dumb projectiles will do that sort of damage, as will powerful laser pulse trains or clouds of KEWs.
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All armour is ablative armour. There's not really any kind of "non-ablative" stuff you could usefully use against space warship-sized weaponry. But mass is always in fashion for hiding behind, so it's a good thing to have.
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Unless you are a *very, very long way away*, the "muzzle flash" is going to be powerful enough to blind you and burn sensors, because it is merely the edge of a massive weapon-grade beam profile
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It'd have to be a very dense cloud of gas, which would be a surprising thing to find in space for long. You might get a brief, faint flicker. Where you will reliably see scattered laser light is in low orbits above planets with atmospheres where misses and overpenetrating hits can intersect the top of the atmosphere.
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I like the "expand expensively" finish, because it certainly will! The noise will depend slightly on the type of laser... bomb-pumped ones and anything powerful enough to drill through faster than the speed of sound (eg. x-ray lasers) will go bang once, but most of the time you'll have a pulse train that will produce overlapping bangs. I'm not entirely certain what this will sound like, other than very, very bad news.
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You're correct about the situations where you *won't* see a laser beam 'in flight', but remember also that you *still won't* see a 'muzzle flash' from a laser *with the naked eye* unless the wavelength is within the visible spectrum. Equally a laser passing through a medium will only be visible if it causes the medium to emit visible light, either by direct stimulated emission or simply by heating to a sufficient black-body temperature.
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1) Continuous and Pulsed beams
Actual power of pulsed laser is by order or two less than continuous one. You see, while pulse laser peak power is incredably small, the duration of the pulse is incredably small eather. So total energy per pulse is very small, and time between pulses is long enough to laser to cool down (by several orders longer than pulse itself), and thus for target to cooldown also.
So if really want to heat something up you'd better use continuous laser. Pulse laser is great for ionising and disabling optics and exposed electronics.
(I am talking about long range now, not those lasercutters)
2) Defence
* Near absolute mirrors has one great disadvantge - they do not dissipate heat through radiation. So you just cook youself without help of enemy lasers. If you would leave spots for radiating heat (like have only one side covered in mirrors or having special radiators) - that spots where enemy would strike (as it is with tanks now - frontal armor is meters of equvalent steel, top armor can be penatrated with AK with AP rounds in some places). As I mentioned before, consider using directly the opposite: material with high melting point and completely black in all spectrum: this material would radiate all the heat from incoming lasers as blackbody radiation. With such an armor laser can heat up this armor for all the eternity without doing any dammage. You can even utilize energy that laser brings, say with Stirling engine to power you (cooling) systems.
* Plasma is good, but why not just to use say CO2 snow? It has high albedo, can be easely generated in high quantity (just open the valve) and doubles as a fuel for your orientation systems. Plasma is perfect aginst consentrated EMPs, but this are not lasers. but if enemy could use both - why not?
3) Laser hit
Since both pulse and continuous lasers need time to heatup your craft, first thing you hear would be cracking. Exactly like old pot put on fire (and exactly for same resons). You will smell hot metal and burning plastics (you may even die from poison gases this plastic emits). With not-so-laser-proof construction of you spaceship uneven heating may case permanet banding of difeerirnt part of it. It would be feelt as strange movement and tremors of walls around you.
With pulse laser you would also experiens all that static electicity staff: sparks, ozone, dust sticks to surfaces, hairs sticking up and so on.
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(maybe this should be part of the "anatomically correct" series. If so, feel free to edit accordingly, as I don't know how to add it to that list)
Could a roughly human sized, human weight, bipedal, anthropomorphized flying squirrel achieve significant gliding capabilities?
Details, limitations, clarifications, etc:
1. With the understanding that lower weight makes flight/gliding easier, they can be slightly shorter than humans, on average, and more slender as well, but I want to stay away from avian hollow bone structures and similar non-mammalian adaptations. More slender bones, like bats, are acceptable. Because I suspect someone will ask for specific numbers, let's say the average height for an adult male is 5' (1.524 meters), and an adult female averages 4'8" (1.32 Meters). The lower end of "normal" BMI for a 5' human male is just under 100 pounds (45.3 kg), so lets make that the upper end of a normal healthy weight for a healthy specimen of this species, bordering on overweight.
2. While the overall body plan should be humanoid, adjustments can be made to limb length, if it's aerodynamically required to achieve gliding capability. But the (hind) legs should not be any longer, proportional to the rest of the body, than an actual human's legs, so they should only be shortened, if needed, not lengthened. And the arms (forelegs) should not be any shorter, proportional to the rest of the body, than an actual human's arms, so they should only be lengthened, if needed, not shortened. Also, the arms can be as long as, but not longer than, the legs. Summary: legs can be shortened, arms can be lengthened, but only if needed for aerodynamic purposes, otherwise they should stay as close to human proportions as possible.
3. Gliding should be accomplished by with the aid of a patagium, a parachute-like membrane that stretches from wrist to ankle. No third set of appendages/wings/etc., and no massive re-imagining of the two existing sets of limbs outside of what an actual flying squirrel has (neither set can be converted to wings, or any similarly drastic change). The patagium should be mostly collapsible/fold-able/retractable/etc. to achieve a "mostly human shape" when it's not in use, just as an actual flying squirrel can achieve a "mostly squirrel shape".
4. Tail should not be longer than about 3' (1 meter).
5. Should be capable of an average glide ration of 2 (that's 2 feet of horizontal distance traveled for each 1 foot of elevation lost)
6. The setting is Earth. No exotic gravity, atmosphere, etc.
7. Disregard evolutionary improbabilities. Assume the evolution is/was possible, however likely or unlikely it might be. In other words, it is outside the scope of this question to declare implausibility due to evolutionary restrictions.
Are there any known aspects of real-world biology that prohibit such a creature from existing? If so, what are they? If not, what is the most likely form this creature would take within these parameters?
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> Could a roughly human sized, human weight, bipedal, anthropomorphized
> flying squirrel achieve significant gliding capabilities?
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Sure. As mentioned in the comments, wingsuit gliding is a Thing--the tricky bit is *landing*.
Wingsuits, which are directly analogous to biological patagia, can achieve decent glide ratios--but they *also* require rather high speeds to function effectively, which makes them rather dangerous. To make them plausible as a biological adaptation, we need to make it possible to slow down without an extra parachute, and land without significant risk of death.
Key to that are reducing weight and increasing lifting area and lift per area, and improving control to avoid injurious crashes. You've already got the reduced weight. So, let's look at increasing lifting efficiency and control.
Shortening the legs should not be strictly necessary--and, after all, shortening the legs does result in less total area across which to stretch a patagium. But, the area provided by longer legs isn't actually the most *useful* area--unless the legs are held straight out to the side in flight (typical for a flying squirrel, but less comfortable for a humanoid body plan), they mostly contribute depth the gliding surface, not width. And wide, shallow wings are better for slow gliders than short, deep wings. So, shortening the legs will help--it'll help get down to your weight goal without significantly harming gliding lift capacity. Again, we already know that wingsuits basically *work*, so the precise amount of change isn't really critical--go as far as you're willing to, and every bit will help.
Lengthening the arms can only help. There already exist apes that have arms that hang all the way down to the ground from their shoulders, or farther, so clearly that's within the range of what a humanoid body plan can accommodate. If you want to keep the proportions closed to "actual human", though, there is another option, which also help with keeping the lift membrane folded out of the way when not in use: extend the pinky. You still have 3 fingers and a thumb left over for normal human-y uses, and when not gliding the lengthened pinky can be folded down against the forearm, along with the collapsed gliding membrane. That gives you a 50% increase in wing width before you make any changes to the proportional arm length. The addition of three more joints to the leading edge of the lift surface also gives you considerably more control at higher speeds, reducing the inherent danger of human-scale gliding and making it easier to achieve safe, running or perching landings at near-wingsuit speeds. Running landings, of course, would be easier if you preserve the longer legs. Perching landings would require a target surface that's at a suitable height for the glider to bleed off speed by *climbing* towards it and then grabbing on.
So, my expectation for the form of such a creature would be:
1. Slightly, but not extremely, shortened legs, to help reduce weight without significantly negatively impacting running ability.
2. Slightly, but not extremely, lengthened arms--maybe going down to about knee length, rather than hip length. That increases wing width a bit without increasing the weight contributed by arm bones too much.
3. Additional wing width provided by a modified pinky that folds along the forearm down to the elbow.
The creature would fly mostly like a wingsuit glider, but at slightly reduced average speeds due to the increased wing width and with better control provided by the added finger joints along the leading edge of the wing. They could, of course, achieve higher tops speeds if they wanted just by folding the pinky back during flight to reduce the drag profile. Ideal landings would be achieved by
1. Pitching the body upwards and and climbing to bleed speed before grabbing on to a surface at a convenient height. This is good for landing on trees, cliff faces, rising hillsides, etc.
2. Dropping the body to near vertical and pointing the pinkies forward to produce a large drag force with minimal lift, quickly bleeding speed and allowing for running contact with the ground.
Somewhat less elegant landings would be achieved by spreading the gliding surface as wide as possible to reduce speed near the ground, then performing a "tuck and roll".
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Assuming these future humans have to land on the ground and/or grab onto trees or something (like squirrels), the answer is that this is probably not possible.
Wingsuits are the closest thing to what you are talking about, and the slowest vertical speed a wingsuiter can manage is about 40 mph. Achieving a 2-1 glide ratio can be done (even a person without a wingsuit can glide somewhat) if you are going fast enough. The problem is stopping.
Here are some numbers: A wingsuit glides at about 100 mph. It takes 334 ft dropping straight down to reach that speed. At best glide, the wingsuited skydiver hits the ground with a horizontal speed of 100 mph and a vertical speed of 40 mph - about the speed reached when falling 53 ft. This would very likely be fatal. And wingsuit flying has a frighteningly high fatality rate even though each landing is supposed to be by parachute. Accidental contacts with the ground by a wingsuited flyer are almost always fatal.
There is a guy called the "Jetman" who has built a suit that contains a 12ft wide rigid wing. He has four jet engines attached, and it can fly at about 180 mph. But even with the long wing he has to use a parachute to land.
If you want your humans to glide and land at a speed that doesn't break bones, you aren't going to get much smaller than a Rogallo wing hang glider type apparatus.
If your future humans use their gliding from very tall cliffs or airplanes, and they only use their gliding to get to a point where they can dive into water or something, then perhaps the wingsuit-like skin flaps would work.
But if you are envisioning them jumping from tree to tree or being able to glide around and land on the ground, I don't believe any combination of your requirements will work. At a minimum I think you would need a Rogallo-wing type of structure at least 12ft in span, or a traditional wing of 18ft or more to get acceptable descent rates for landing.
Search for 'foot launched gliders', 'smallest hang glider', and 'smallest glider' and you'll see many examples of very small flying machines. None of them come anywhere close to your requirements, unfortunately.
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Suppose there exists a magic-based civilization. Their mining techniques are medieval and their understanding of organic chemistry and biology are on the Enlightenment era level. However, they are capable of creating portals, so they can establish stable supply of water and any needed materials.
This civilization has access to large supplies of niter (potassium nitrate), chalk, and peat. Will a combination of those, with minuscule additions of fishbone meal for phosphorus and steppe soil for microbial contamination purposes, be enough to provide an adequate starting base for a soil desert greening project?
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Yes, peat, water and nitrogen fertilizer will go a very long way to making nearly any kind of desert land bloom even without the rest. As a comment noted, it's a lot easier if you start with an arid area having some sort of soil rather than nothing but sand, but its doable in either case.
The first thing to remember is that organic matter is not needed -- hydroponics works perfectly well without soil, so with adequate water and nutrients even sand will support plant life. (And will quickly enough build up soil.)
In most arid regions, the main thing lacking is water, and adding water alone will cause it to bloom. Add trace nutrients as needed.
Two caveats: First, some arid regions are salt flats. They're pretty hopeless unless you bury the salt fairly deeply. Second, while adding water will make many arid areas to bloom, that's not sufficient to grow, say, corn or wheat or rice which have fussier requirements. But even those plants can be induced to grow with the right mixture of peat into the soil along with micro-nutrients and a steady, plentiful supply of water.
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**Bring soil.**
In the real world, fertilizer / soil amendments are nice because you do not need to transport as much mass from where it starts to wherever your farm is.
If your people have portals, transportation becomes much less problematic. Just bring soil from a place that has nice fertile soil, like a steppe or prairie or river valley. Put that on top of whatever soil your desert has. If your farming practices exhaust your imported soil, bring more from where you got it before and put that on top.
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Depending on how these portals work, you could make some portals under sea level so water would spew over the desert ground. If the volume of water was great enough to beat the rate of evaporation and soil drainage or if you had built some rocky substrate to prevent some drainage, you'd get a neat saltwater river, lake or, better yet, cannal system. Around these you could grow Salicornia. Some varieties are tasty even raw. In the saltwater itself you could grow edible seaweeds and small animals like crabs. Rather than requiring fertilizer, this could help your people save on it. Much of the phosphorus we are using to fertilize our crops is draining away to the bottom of the sea, so it isn't an easily renewable resource.
You could use freshwater instead but I imagine someone on the other side of that portal would be pretty upset over it.
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I am a mad scientist with an intelligence matching Albert Einstein and Steven Hawking, and plan to create a new species of animal. After watching Napeoleon Dynanite, widely considered by critics to be the greatest movie ever made in the 21st century, i have decided to put my plan into action. To accomplish this, I have decided to crossbreed lions and tigers to make hybrids. The resulting creatures are tigons or ligers, which are only found in zoos due to their close proximity. My plan is to introduce these types into the wild naturally.
Animals are not sapient, and the idea that they deserve rights is completely absurd. After ignoring the protests of useless and irrelevant organizations such as PETA, I have removed a large sample of lions and tigers and introduced them into a country away from civilization where they are the dominant species. This country would be hidden from the rest of the world by being shrunken down. Over time, as various specimens shag each other, more of these hybrids will be born. Overtime, as enough ligers or tigons are produced in the wild naturally, there would be enough to be considered a new species and possess the best combination of both animals.
How can I design circumstances to guarantee that this would happen naturally?
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reference: <https://en.wikipedia.org/wiki/Liger>
1. In the first generation, all females should be of one species and all males the other. A female in heat will have a male of the other species as her only option. You will need 2 areas, one for ligers and one for tigons (in F1 generation)
2. With the F1 and subsequent generations it gets tricky. First generation liger and tigon males are sterile. These should be removed from the population as they are big, and will outcompete pure lion and tiger males for mates.
3. Taking the scenario with tiger females and lion males initially, then female ligers and the same pure lion males, the problem is with F2 and subsequent the gene mix shifts towards lion, with dilution of tiger genes. You could let that happen, or swap the male populations of your lion and tiger. You could hope that in F2 or later generations one of the male hybrids is fertile - there is only one wa
e you have a fertile male hybrid then you can use him as the sire for the rest of your line of hybrids.
Ultimately as with any breeding project one breeds for the desired traits, coupling parent animals according to those traits.
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While I don't know that much about mating lions and tigers (will they do it naturally, in the wild?), there's a perfectly good example of species interbreeding out there right now: the coywolf, a natural hybrid of wolf and coyote: <https://en.wikipedia.org/wiki/Coywolf>
What you apparently need is for one species (if not both) to be so rare that it is difficult for them to find mates of their own species, and for there to be an available ecological niche for the resulting hybrids to occupy. Both happened in eastern North America in the last couple of centuries, as the native wolves were hunted to near-extinction, allowing opportunistic coyotes to migrate into their former range and mate with the surviving wolves. The hybrids proved more adaptable than either parent species, the population exploded, and they're well on their way to being a new species.
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My world is at the outer edge of the habitable zone. There is enough heat and geological activity to start life, but a snowball earth is looming and threatens to freeze it all. There is some spring thaw at the equator, allowing some simple algae to multiply. The carbon dioxide is not sufficient to make an earth-like warm planet, though.
Then comes the pitch-patch: a pitch-black patch of single-celled algae that thrives in the the pools of molten ice in spring.
The pitch-patch manages to venture out of the pools and populate the thin film of water that makes ice slippery. It has antifreeze ethanol in its membranes. Most importantly, it is black, therefore absorbing enough sunlight and heat to raise the temperature around it. This creates a positive feedback that melts more ice and promotes more growth.
Eventually, the pitch-patch creates large icefields of algae. Its effect is noticeable from outer space, just as we see forests from orbit around Earth.
So, can the pitch-patch, along with carbon dioxide, make the difference and melt larger fields of ice? Can it create a more hospitable environment at-least around the equator?
**EDIT**: To point this out, there is sufficient carbon dioxide for algal growth and some greenhouse effect. However, the planet is too far to allow liquid water all-over the planet. For now, it is present in liquid form in a narrow band around the equator, and some life thrives there. Polar ice caps are much larger than those on Earth, but not exceedingly so. However, the chances of the snowball-earth to occur, are much higher than those on our planet, because of the distance from its sun.
[Answer]
The answer is not easy, because black algae will influence the energetic balance of the planet in two, opposite ways:
* their black surface will absorb more stellar radiation, locally increasing the temperature
* their photosynthetic activity will remove $CO\_2$ from the atmosphere, thus lowering the green house effect.
It is therefore plausible that the planet will have a feedback mechanism of the following sort:
1. Algae population increases, more ice melts
2. as a consequence of algae increase, the $CO\_2$ content in the atmosphere decreases
3. with a weaker greenhouse effect the temperature lowers
4. lower temperatures inhibit algae growth
5. as a consequence, $CO\_2$ in the atmosphere increases
6. back to 1.
This would obviously result in small oscillations of the temperature, not dramatic changes.
For a better answer I think more details would be needed, to better model the climatic interactions of the world.
[Answer]
If large patches of the planet are darkened, then yes, that will lower the planet's albedo, raising the average temperature.
<https://nsidc.org/cryosphere/seaice/processes/albedo.html>
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> Albedo is a non-dimensional, unitless quantity that indicates how well a surface reflects solar energy. Albedo (α) varies between 0 and 1. Albedo commonly refers to the "whiteness" of a surface, with 0 meaning black and 1 meaning white. A value of 0 means the surface is a "perfect absorber" that absorbs all incoming energy. Absorbed solar energy can be used to heat the surface or, when sea ice is present, melt the surface. A value of 1 means the surface is a "perfect reflector" that reflects all incoming energy.
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[Answer]
>
> So, can the pitch-patch, along with carbon dioxide, make the difference and melt larger fields of ice? Can it create a more hospitable environment at-least around the equator?
>
>
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* there is sufficient carbon dioxide for algal growth and some greenhouse effect.
* the planet is right on the "snowline" of the star system: too far to allow liquid water all-over the
planet, but close enough to allow a band around
the equator.
I think in order for your algae to work, it cannot interfere with CO2... or else CO2 levels aren't as important as (for example) being on the snowline. It sounds to me like your algae will have to be a **KEY** part of the solution, but not all of it: it requires a small ecosystem of symbiotic relationships.
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[Question]
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In a nutshell, I'm trying to build a world with erratic day/night cycles.
To get the erratic days, I'm working with a habitable moon. It takes 3 full earth days (72 hours) for the habitable moon to rotate around the planet. 1.5 of those days (36 hours) are spent in the light, while another 1.5 (36 hours) is on the shadow side of the planet. However, the moon itself also rotates, though at this moment I am unsure at what speed. I'm thinking a full rotation would be between 20-36 hours, but I'm up for as much or little as needed if it helps with the warmth issue. Almost certainly the daylight and dark hours would be variable, aside from a periodic somewhat longer dark time behind the planet.
The planet would have a constant haze in the sky (it's a very basic life form that lives in the cloud layers of the atmosphere, kinda reddish in color--simple like a spore or plankton or other small thing).
A possible wild card is that another moon also orbits this planet, which is visible every 7 days to the habitable moon. Eclipses may be a thing, though I'm happy to place it in an orbit where that is rare, or never happens.
The planet itself is Jupiter-like, at least in size, though composition is up in the air. I have not figured out the orbiting time of this planet around the sun because I didn't think it was that important, but if it is I'm happy to let anyone play with those numbers freely.
I genuinely need help figuring out day/night fluctuations. I admit it, I'm not so hot with the maths. Can someone help with that, even a simple base pattern? I'm not married to day lengths (I was basing it loosely on Jupiter and a couple of it's moons) so whatever is easiest is fine, just let me know the new day lengths.
[Answer]
This is turning into a very long answer.
Any planet or habitable moon is likely to have a fairly constant average temperature.
At any one moment half of the Earth, for example, is in daylight and is being heated by the Sun, and the other half of the Earth is in night and is cooling off.
At any given moment - except during the equinoxes twice a year - one hemisphere of Earth will have longer days and shorter nights, and will be heating up from day to day, and the other hemisphere of Earth will have shorter days and longer nights and will be cooling off from night to night. Of course you say that your moon has no axial tilt and thus no seasons so there will be far fewer differences to average out.
Every difference averages out in the end, so the average temperature of Earth remains the same over time, except in so far as long term trends cause gradual warming or cooling.
An astronomical body will heat up with energy from its star until its thermal radiation out into space increases to equal the amount of radiation it receives from the star plus some more.
The extra heat will be internal heat left over from the formation of the planet plus internal heat from radioactive materials plus tidal heating which will be strong on a moon of a giant planet with possibly fellow moons. The astronomical body will heat up until its thermal radiation into space per second equals its total heat input from all sources per second, which includes radiation from its star, internal heat left over from its formation and internal heat from radioactivity plus plus tidal heating. Then the astronomical body will be in thermal equilibrium and its average total temperature averaged over its entire surface, hydrosphere, and atmosphere will remain constant except in so far as its heat sources increase or decrease over time.
So the length of the days and nights will not affect the average temperature of the moon at any one time or averaged over time. But it will affect how hot a particular spot on the planet will get during daytime and how cold a particular spot on the planet will get during nighttime.
The longer the day in a place, the hotter that place will get during the day. The longer the night in a place, the colder that place will get during the night. So the longer the days and nights are on your moon, the greater the temperature extremes between day and night will be.
On Earth, with axial tilt and seasons, there are major fluctuations in the lengths of day and night with time and also with latitude. By giving your moon no axial tilt, you have removed the major cause of fluctuations in the lengths of day and night on Earth. Day and night will always be the same length on every spot of the planet and at every time.
But because the moon in your story is a spheroid, light from the star will have different intensity at different latitudes. At the equator the star will appear straight up at 90 degrees, while way to the poles the star will appear at a 45 degree angle (thus spreading out he light rays less densely per cubic area of surface), and at the poles the star will appear at a zero degree angle at the horizon.
So the higher the latitude, the colder the surface, the water, and the air will be in day and in night. Thus there should be constant hot high winds blowing north and south from the equator toward the poles, and constant cold low winds blowing from the poles to the equator.
If the moon in your story has things that make it interesting for most types of stories, such as advanced multi celled lifeforms like plants and animals, intelligent natives, or habitability for humans (requiring oxygen in the atmosphere among other things), it should have existed with fairly steady temperatures for billions of years, since it took Earth billions of years to achieve any one of those conditions, and any large temperature changes during that period would have killed off all life on the planet.
So the star in your system has to have spectral type that enables it to shine fairly steadily for billions of years before turning into a red giant and then a white dwarf, destroying all life on its planets.
So if your world was a planet orbiting a star, it should have had a stable elliptical orbit with low eccentricity - closely approaching a circle - around its star for billions of years.
But if your world is a moon orbiting a planet, then it is the planet that has to have a stable elliptical orbit with low eccentricity - closely approaching a circle - around its star for billions of years.
If a gas giant planet forms a moon or captures a wandering body and makes it a moon, tidal interactions between the gas giant planet and the moon will quickly - in mere millions of years - turn the moon's orbit into an almost circular one around the equator of the planet, and should also adjust the axial tilt of the moon so that it matches that of the planet.
So for the axial tilt of the moon to be zero, the axial tilt of the gas giant planet should also be zero.
The axial tilts of solar system planets are 82.23 degrees (Uranus), 28.32 degrees (Neptune), 26.73 degrees (Saturn), 25.19 degrees (Mars) - all higher than earth's - 23.44 degrees (Earth), 3.13 degrees (Jupiter), 2.64 degrees (Venus), and 0.03 degrees (Mercury) - all lower than Earth's.
So it seems quite possible for a giant planet your moon orbits to have a very low axial tilt, and thus for your moon to have a very low axial tilt.
But you wrote:
>
> To get the erratic days, I'm working with a habitable moon. It takes 3 full earth days (72 hours) for the habitable moon to rotate around the planet. 1.5 of those days (36 hours) are spent in the light, while another 1.5 (36 hours) is on the shadow side of the planet. However, the moon itself also rotates, though at this moment I am unsure at what speed. I'm thinking a full rotation would be between 20-36 hours, but I'm up for as much or little as needed if it helps with the warmth issue. Almost certainly the daylight and dark hours would be variable, aside from a periodic somewhat longer dark time behind the planet.
>
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However, the same process of tidal actions which would circularize the orbit of a moon in just a few million years should also tidally lock the rotation of the moon to the planet in just a few million years. After just a few million years one side of the moon would always face the planet and one side of the moon would always face away from the planet. And that would be billions of years before natural process made the moon interesting enough for your story.
So your idea of having an orbital period of about 72 Earth hours and also a rotation period of about 23 to 36 hours is not very plausible.
With a tidally locked moon with an orbital period and rotation period both of 72 hours, the outer side of the moon facing away from the planet would have sunlight for 36 hours when the moon was in the half of the orbit closer to the star, and would be in darkness for 36 hours when the moon was in the half of the orbit farther from the star.
With a tidally locked moon with an orbital period and rotation period both of 72 hours, the inner side of the moon facing toward the planet would have sunlight for 36 hours when the moon was in the half of the orbit farther from the star, and would be in darkness for 36 hours when the moon was in the half of the orbit Closer to the star.
But the 36 hours of daylight when the inner side of the moon was farther from the star would be probably be interrupted by an eclipse when the moon passed into the shadow of the giant planet. That eclipse should be comparatively short. I think that when answering some other question I figured because of the relatives sizes of the planet and the moon's orbit that the eclipse could be no more than about a quarter or a third of the period that the moon was on the far side of the planet away from the sun, and easily much less than that.
The inner side of your moon could sometimes be eclipsed by one or more large inner moons that may get between your moon and the star when your moon is father from the star than the planet.
Either side of your moon could sometimes be eclipsed by one or more large outer moons that may get between your moon and the star regardless of where your moon is relative to the star and the planet.
If the giant planet your moon orbits orbits just slightly beyond the orbit of an inner giant planet, the two orbits being much closer together than the orbits of any planets in our solar system, then whenever the slightly faster moving inner planet catches up with the planet the moon orbits, it might cast a shadow large enough and long enough to reach the outer planet and the habitable moon and eclipse them. Depending on the orbital factors, this might happen between once every Earth week or so and once every few Earth years.
If you want your habitable moon to not yet be tidally locked to the giant planet and not have a synchchronous rotation, it will have to be very young and not yet have a naturally developed biosphere habitable for humans.
So maybe it could have an artificially and unnaturally developed biosphere habitable for humans, created by super advanced aliens who terraformed the moon and seeded it with advanced lifeforms like animals and plants.
Or maybe the moon was originally an independent planet orbiting its star in a nearly circular orbit for billions of years, developing a biosphere habitable for humans, until it approached too close to the giant planet and was captured by the giant planet.
The moon could have had a rotation period of 23 to 36 Earth hours before being captured into a 72 hour orbit around the giant planet. The giant planet would be gradually slowing down the rotation of its new moon to match it's 72 hour orbital period, but it might have slowed it down only slightly so far.
Since you want your world to be a habitable moon of a larger planet you should look up all the questions about such habitable moons.
My answer here has links to other questions about habitable moons and even a scientific paper.
[What is the maximum orbital time for my moon around my planet?](https://worldbuilding.stackexchange.com/questions/126596/what-is-the-maximum-orbital-time-for-my-moon-around-my-planet/126778#126778)[1](https://worldbuilding.stackexchange.com/questions/126596/what-is-the-maximum-orbital-time-for-my-moon-around-my-planet/126778#126778)
Note that a large habitable moon of a gas giant planet would probably have an orbital period of a few Earth days long. In our solar system the large moons of giant planets have orbital periods ranging from 1.77 Earth days (Io of Jupiter) to 16.69 Earth days (Callisto of Jupiter) and 15.945 Earth days (Titan of Saturn).
Also note that is is calculated that the year of a planet has to be at least 9 times as long as the month of that planet's moon for the moon to have stable orbit.
So if the year of your moon's planet is exactly 9 times as long as the month of your moon it would be between 15.23 Earth days and 150.21 Earth days long, and of course the year of your moon's planet could be much more than 9 times as long as the month of your moon. The year of your moon's planet could probably get to be up to a few Earth years long if that planet and moon orbit in the habitable zone of their star.
By comparison, known exoplanets that are probably orbiting in the habitable zones of their stars have years that range from 4.05 Earth days to 384.8 Earth days long.
<https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets>[2](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets)
PS See my answer to this question:
[Longest possible eclipse in double star system](https://worldbuilding.stackexchange.com/questions/138732/longest-possible-eclipse-in-double-star-system/138817#138817)[3](https://worldbuilding.stackexchange.com/questions/138732/longest-possible-eclipse-in-double-star-system/138817#138817)
[Answer]
Another option for erratic day / night cycles might be a non-spheroidal body, like Mars' moon Phobos, that is rotating around a strange axis (rather than one in line with the plane of the ecliptic). I haven't done the calculations, but your day / night cycles may not be of consistent length in that scenario, though I'm pretty sure they would repeat regularly.
(For what it's worth, I pictured Darth Vader's TIE fighter tumbling off into space after it's ejected from the trench of the Death Star in 1977.)
[Answer]
Start with your moon. As others mentioned, it is highly likely that its orbital and rotation periods will be locked together. So with the 72 hour revolution, it also has a 72 hour rotation.
However, this does not translate to a boring 72 hour day/night cycle for the entire moon. *Where* you are on the moon will have a profound effect on the light/dark cycle.
The area of the planet that comes closest to a normal day/night would be the back, the side that always faces away from the planet. During the half of the moon's orbit when it is on the "day-side" of the planet, the sun will move through the sky for the 36 hour "day". On the "night-side" of the planet, this side of the moon will likely have the only true night sky. Both day and night skies will sometimes have the other-moon visible, the exact schedule of which would depend on what kind of resonance the two moons (or more!) have with each other. The magnitude of the solar eclipse will depend on the size of and distance to the other-moon. If you assume they are on the same plane, then a daily eclipse can be assured. Depending on how the orbital planes align, you may never actually have a "Full Moon" in the sky.
The "front" of your moon has a much more varying light cycle. For one, the planet will always be in the sky. It will be 25 (or more) times larger than the Moon in Earth's sky. While on the "day-side" of the planet, it will technically be local "night" as the sun be shining on the other side of the moon. However, the massive "Full" planet in the sky will light up the landscape quite effectively. During dawn and twilight, you will have the sun in the sky, but it will be eclipsed for most of the day as the moon moves to the "night-side" of the planet.
[Answer]
**Solution**
To get fluctuations in the day night pattern you need a moon which is not tidally locked. For this you could use a setup similar to Pluto where Charon (the closest moon of Pluto) has a bit more than 10% of the mass Pluto possess. [Charon disturbs the orbits of the other Pluto moons.](https://en.wikipedia.org/wiki/Tidal_locking#Occurrence) Which causes them to not be tidally locked with Pluto.
## Calculations
You said you needed help with the math so here is an example which shows you a possible setup. For a different setup I will tell you what to change.
(Needed) **Formulas**
* Gravitational Force: $F = G \cdot \frac {m}{r^2};$ F = Force, G = $6.673 \cdot 10^{-11}$(gravitational constant), m1 = planet mass, r = distance between planet and moon (normally there is another $m$ for the mass of the moon but the second equation uses the same, so we can cut it)
* Centripetal Force: $F = \frac {v^2}{r} = \frac {4 \pi^2}{T^2} \cdot r;$ v = speed of the moon, T = time to complete one orbit (normally there would be the $m$ for the moon, but we cut it from the other equation, so we have to do the same here)
+ The Lenght in meters of the orbit: $d = 2\pi r$ d = orbit length
This is every thing we need to determine fluctuations.
**Example**
* Main planet mass: $1.899 \cdot 10^{27}$ (Jupiter)
* Distance between Planet and moon 1 000 000 km/ 1 000 000 000 m (if our solar system is anything to go by most moons with the size to be inhabited by similar life forms are [around that distance](https://en.wikipedia.org/wiki/Natural_satellite#/media/File:Small_bodies_of_the_Solar_System.jpg))
For the Gravitational Forec we get this : $F = 6.673 \cdot 10^{-11} \frac{1.899 \cdot 10^{27}kg}{1000000000^2m} = 0.1267N$
This value for F we will now use to determine our speed:
First we take the equation from the Formula section: $F = \frac {v^2}{r}$ and switch it to get our speed: $v^2 = F \cdot r$
And now we plug in our numbers: $v^2 = 0.1267N \cdot 1000000000m = 126 700 000$ and because we want the actual speed not the speed squared we take the root of it and arrive at 11 256.11 m/s.
Now we need the length of the orbit $2\pi 1000000000m = 2\pi \cdot 10^{9}$ when we divide the distance by the speed we get the time it takes for one orbit: $\frac {2\pi \cdot 10^{9}m}{11256m/s}= 558202.22s$ which is 6.46 days or pretty exact 155 hours. To increase or decrease the time simply change the distance r from the planet to the moon (smaller shorter than 155 hours/higher longer than 155 hours).
**Conclusion**
If we assume that the moon rotates every 30 hours around itself this would cause the time of the day/nighttime to be shifted by 5 hours every 5 days (30\*5 = 150 5 hours short of 155). And assuming that every time the moon is behind the planet it would block out the sun. This means the pattern would reoccur every 30 days (5\*6 = 30 => shifted the light/dark a full day of light)
Because the moon would enter the behind the planet spot 5 hours later compared to the day time of the moon. And after 6 rotations around the planet it would be the same as 30 days before.
I hope this last part is understandable but I cannot come up with a better explanation. Also the time it takes for the moon to rotate around itself can be freely chosen.
[Answer]
If your habitable moon is tidally locked to the giant planet, then day/night duration will be governed by moon's rotation period. For example, for Earth's Moon it lasts 29.5 Earth days.
If moon orbits the giant very closely, then (for its planetary side only) star eclipses would be a regular things, whereas at night the skies will be beautifully illuminated by the giant's reflected light. For the "dark side" of the moon, day/night cycle would be unaffected.
Other moons may contribute to the amount of light at night, but that would be a relatively minor thing, except for the night sky pictures.
If the moon is NOT tidally locked to the giant, its own rotation will make the days shorter or longer, depending on rotation speed. However, having a non-locked moon under the stated conditions is scientifically doubtful.
Also it is important to say that day/night hours would NOT be variable, but rather very regular. Only on moon's planetary side star eclipses may be quite irregular.
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[Question]
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*I spent my life, my fortune, my family connections... I sold my children into slavery and my soul to Ilnarren... Wanted posters hang from from the Abyss of Shrondir to the expanse of d'o (most bearing passable liknesses)... I've sworn fealty to the Great Abitor and the Peasant of Myksyr... and betrayed them both... I've expended every facet of my being in this universe for this one moment...*
My intrepid wizard desires a soul-satisfying revenge on his worst enemy! To that end, he has cast a stop-time spell. All the universe is frozen around him as he pulls back, spinning his arm in a disturbingly Popeyesque fashion, investing every fiber of his being to deliver a right-cross that would resound across the universe! But what happens to his nemesis (or himself) when that punch lands?
I'm trying to inject a bit o' science into my magical scenario and seek the greater wisdom of Worldbuilding.SE. Which of the two scenarios below is more believable? Your answers will be judged by how well you substantiate your claim. To that end, though this question appears very much to be about magic, your answers **must** be science-based with the exception that *how* the unverse came to a stop (aka, the setup of each scenario) is simply accepted as described in the scenarios.
**Scenario #1**
The name of the stop-time spell is misleading. What really happens is that I'm sped up to an infinite degree (or, at least to so great a degree that I cannot discern the passage of time for all others). I think, move, and react with instantaneous effect — and yet don't die in a moment due to me burning through all the energy my body pocesses. In short, though feeling just fine (thank you for asking!), I represent infinite potential while the rest of the universe represents none. Consequently, my fist moving at an unimaginable speed compared to the reference frame of my hapless (and soon to be dispatched) enemy and connecting with his head, results in a brilliant explosion of burning plasma that would make XKCD proud! It hurt! But it was well worth it.
**Scenario #2**
The stop-time spell was aptly named! Literally all the potential of the universe is brought to a stand-still, and like a river damed by the damned, the potential of the universe is absolutely infinite! I am unchanged, but also unable to discern the quantum quiver as the forces of time and space hold their proverbial breath, waiting for release! My fist drawn back... my anger explodes! And *so does my hand as it impacts with what is quite literally the hardest thing the universe has ever seen!* Or at least it feels that way, because what pitiful force my punch can bring is nothing against the restrained potential of the universe. Falling to my knees I cradle my hand and cry to the uncaring universe, "Noooooo!!!!"
*Cry havoc! And release the unbound imagination of worldbuilding!*
Which scenario is more believable?
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**EDIT(s)**
1. Pelinore points out that the atmosphere between my wizard's fist and his enemy's head is non-trivial. That's a honking good point, but for the purposes of this question, please ignore that. let's focus on the fist and the head.
[Answer]
**Scenario 1 is the winner (sort of)**
The thing about your question that needs to be addressed is something a man named Albert once said; "Everything's relative".
In that sense, scenario 1 is the simplest and easiest to explain. By speeding up yourself, you increase the velocity and potential energy of your fist by comparison to the target. You'll probably still destroy your fist in the process, but it's easier to explain the kinetic energy difference by *adding* energy than by *removing* it. For that reason, scenario 1 wins by virtue of Occam's razor insofar as it's the simplest solution.
The problem with scenario 2 as I see it is that it's very difficult to reduce the kinetic energy of something static, that is to say with a kinetic energy value of close to 0. This is essentially the same as the refrigeration problem all over again. Just how do you use energy to make something colder, when making something colder means *reducing* its internal energy value?
In the modern world, we do that by heat exchange. We heat something up, but in such a way that the only way it can draw that energy is from an enclosed space we want to cool down. By doing so, we extract the energy from that enclosed space, and refrigerate it.
In order to do that in your scenario 2 above however, we would actually need negative energy. Why? Because a static head still has mass, which means that it still needs the same amount of energy to act on it as force to do damage to it. So, slowing down time around it ONLY helps if that somehow decreases the amount of force that will damage it, and the only way I can see that happening is negative energy.
So - scenario 1 solves the problem by increasing energy to the blow. Scenario 2 can only solve the problem by introducing an energy-exchange model that either reduces the mass of the static object, or can reduce its kinetic energy value to less than zero. Ergo, scenario 1 is simpler, and wins (thanks to a Franciscan monk from the 13th century).
[Answer]
Scenario 1 but hit him very, very slowly (in your time-frame) and wear an internally padded iron glove. Otherwise you will destroy your fist and most of your arm and he will be instantly killed by the shock-wave through his brain. The iron will do the damage through its own momentum and won't be stopped like your hand would be. If you want him to suffer then he has to be incapacitated not killed outright. A sword would be better though perhaps not so satisfying as it would chop off his jaw without killing him (can't believe I'm writing this). If you want yourself not to suffer then take it easy. Preferably practise on nearby inanimate soft objects first to judge the effect. Start with the cushions from his sofa and hit them very lightly - see what happens.
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[Question]
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On a world populated by sentient anthropoid species evolved from Terran felines, both big and small cats, could the local authorities use the fur patterns and colors the same way that we used fingerprints for decades to identify people?
Or, once their technology reaches the same level than we have today (2018), through pattern recognition software via cameras much as we have facial recognition software (See China for the extreme example of massive population surveillance via cameras on the streets)?
Would that be a viable way of identifying specific persons in the population?
[Answer]
I live somewhere where, a year ago, sadly, an enormous complex of fires ravaged neighborhoods over 3 counties. Although the flames didn't quite reach my town, I evacuated with my 6 cats. I then closely followed the work of the multiple groups of people who spent months rescuing and trapping cats in and near the burned areas (some even ongoing).
These folks came up with methods of cataloging the cats they found. There were many hundreds of cats. A good number were from pre-existing feral colonies or were strays that had been abandoned before the fires. But a lot were animals separated from their humans because of the fires.
Another issue is that most of these animals were filthy (the ash in the air and covering every outdoor (and indoor) surface for miles was insane, and hard to wash off) and some had been injured in ways that made it difficult to recognize them (often because of bandages in medical facilities). But, even for cats that more or less looked the same as they did pre-fires, identification was difficult.
The rescuers took pictures of each cat they found and had records indicating the medical or shelter facility the cat was taken to. If the cat was found by a regular person, the facility would create the records. (This system was not perfect and many people would just care for cats themselves.)
**The primary way they classified the cats was by color.** While many cats were put into more than one color category, a more detailed system, like the one your story would use, would account for the variations and have more choices. So instead of "tabby," you might have "gray tabby" and "gold tabby." And you'd have groupings for cats of more than one color.
You might think the classification of fur length (short, medium, long) would be primary, but I think the physical issues resulting from the fires made that impractical. Of course fur length was noted in descriptions. Along with gender, intact status, size, age, and anything else of note.
And this brings us to markings. A lot of cats (none of mine, but most of the fire cats) did have markings of some sort. Many desperate people searched for their pets using online resources and info on found pets got posted to several websites and Facebook groups.
**Using the pattern of the markings became an art form.** There was no good nomenclature for it, but people worked endlessly to match pictures of lost cats with pictures of found ones (dogs were easier to ID but a lot of the lost animals were livestock, where there were similar issues to cats).
I saw so many heart wrenching cases where a distraught person would post a picture of her/his cat and a dozen people would say "I just saw a picture of this cat in the found section!" but it would be the same, wrong, cat the person had seen a dozen times. Sometimes the pictures of these unrelated cats would be so close that only the owner could tell the difference, and only in person (which they did, over and over again).
In one case that made the news, a shelter prematurely adopted out a fire cat and the new family refused to give back the cat when the real family came forward (losing your house is traumatic and it took them a few weeks to track down the cat). The markings from photographs matched the cat but it wasn't enough to prove identity. Authorities finally used DNA. It matched and the adoptive family was compelled to return the cat to its family.
**What's the takeaway? Color and markings can change over time. With age, with cleanliness, and with injury. The only reliable method for matching a cat with its human family turned out to be microchipping** (and that failed much of the time because people move and don't update their contact info...a lot of the found cats had their names in their listings, but no way to find their families).
I've now chipped all my cats and it's the only method I could see for a high tech society to identify cats who walk by a camera. Even for ID done when booking a crime suspect, for example, I don't think markings will work in many cases, because they change over time. But that will depend a lot on the way your cats are marked...if everyone has prominent markings, clear enough to be spots and stripes and etc, then maybe. If it's like real-life cats, it won't be good enough.
[Answer]
Yes it will work barring disguise or face/body covering.
>
> Tigers have striped skin not just striped fur. **The stripes are like
> fingerprints and no two tigers have the same pattern**.
>
>
> <https://www.nationalgeographic.com.au/animals/tiger-facts.aspx>
>
>
>
**Bonus fact**
>
> A cat's fur and skin colors are closely related.
> <https://pets.thenest.com/skin-pigmentation-cats-11322.html>
>
>
>
Because of the above, disguises would only be superficial. They could dye their fur but the skin underneath would preserve the pattern. This wouldn't need shaving - just parting the fur. Not much use with cameras at a distance though.
[Answer]
Yes, but you wouldn’t want to use it on its own.
If the aim is to be able to recognise humans in real time from a video feed then fingerprints are of absolutely no use. You need facial recognition or something similar.
If the pattern of hairs is distinct enough for each cat that they can distinguish between each other using them then you can absolutely train a computer to use fur pattern recognition, but the failure rate could be quite high (fur blurs, people might take countermeasures like using dyes or wearing *clothes*). If you couple it with something like gait recognition though (tracking how people walk, which is pretty unique from person to person) and feature distance recognition (shoulder to hip, hip to leg, length of arms, position of eyes etc) then you should be able to get pretty good matches.
] |
[Question]
[
I'm relatively new to all this. I'm thinking of studying a little Earth sciences in the hope that it tells me but, up front, I want to know if I'm completely off. I want to know if a world with no high altitudes can be habitable. What leads me to think it might not be is that mountains are indications of
* tectonic activity and so a liquid core generating a magnetic field repelling radiation,
* low meteorite activity.
The amount of activity sufficient to result in a world with only large hills and low peaks that never rise above the "tree line", that is the altitude at which plants grow. Can anyone tell me if such a world is feasible? Can I have a habitable world which also has nothing in the way of mountains without constant battering from meteorites? Am I overthinking this and I could just have tectonic plates that don't really move in a way so as to produce mountain ranges? Sorry if this is far too many questions for a single post.
[Answer]
This is actually a more thought provoking question than it seems at face value. You are not overthinking things and if anything by overthinking it you make it worth exploring.
Though the first challenge is the ambiguity in the usage of habitable. Starting with Europa, it potentially meets all the qualifications. I believe Europa's surface meets the shape requirements. As for habitability. Scientists believe that beneath the ice there is likely lots of liquid water with the possibility for life. If that is the case that then could be habitable with undersea colonies. Kinda like Rapture.
**So Europa or a similar setup potentially passes the test** Also extends to water worlds
If you meant more conventional habitability with land then that is much more difficult. **NO** It shouldn't be possible. To better understand tectonics imagine a balloon deflating. when it reaches a certain size you begin to see ripples and sag marks as the material contracts with no where to go but bulge. This is similar to what happens as a planets core cools. The rock contracts resulting in mountains forming. Even on Mars this process is still happening.
**Point is a planet would have to be completely cold for tectonics to stop. Therefore it would be inhabitable.**
The other way to achieve this and be geologically active would be to have hyper erosion. The chemistry and energy needed to make this happen would be in-hospitable for non microbial life.
[Answer]
The smoothest planet in the solar system is probably, AFAIK, Europa. It *does* have plate tectonics, of a sort, but it's ice plates floating on a water ocean. In terms of habitability, not great. Also, smoothness is here defined as maximum deviation from ellipsoid, *not* how steep those deviations are. I recently read (I forget where) that it might have fields of knife-like ice projections (which have a name that I also forgot) metres high and quite impassable.
Since you're probably looking for something more earth-like, I would guess that you can't avoid mountains. To develop complex life, you need a healthy mix of elements on the surface, plus a reasonable protection from radiation. You get the first from tectonics and volcanism, and the second from a molten ferromagnetic core that provides a magnetosphere. You also need surface volatiles (water, atmosphere) which in Earth's case got there from cometary bombardment, if memory serves. Someone correct me if I'm wrong.
Finally, I would think that thermodynamics on a flat planet would be too bland. We have no idea how life got started (ok, we have too many ideas), but what is sure is that you need an mixture of gradients: one chemical species diffusing from A to B, a temperature gradient going in a different direction, a liquid current carrying everything the third way etc. That is why all models of biogenesis, starting with Darwin's warm little pond are on some kind of interface. If the planet is too flat, I suspect the conditions might be too uniform. I haven't checked this suspicion in any way, and I doubt anyone has, so it could be completely wrong. But I have a hunch.
Of course, you might not want life to develop there, just to be able to terraform and settle it. In that case, apart from probable lack of magnetosphere, I don't see any objections. Your ecosystems might be a bit boring, though.
### Follow-up
An idea that might work: take an *old* planet around an old sun, and make it the only planet in the system. You could have a red dwarf that got too close to some energetic young suns and had the rest of its planets stripped away. Leave a circum-stellar dust ring that provides just enough micro-bombardments for any mountains to be eroded to low hills.
Now you have the right shape, but you lack water and atmosphere. No problem: the micro-bombardment has gradually shifted the planet's orbit outward (would that happen? Um...) and the outer layers of the dust ring are water-rich (which *would* happen). So a layer of water accumulates on the planet. Take it from there.
[Answer]
>
> What leads me to think it might not be is that mountains are indications of a) tectonic activity and so a liquid core generating a magnetic field repelling radiation,
>
>
>
That's correct.
>
> and b) low meteorite activity.
>
>
>
I don't think that's correct. (Low circular hills, yes, but *mountains*? No.)
[Answer]
### Earth was like this sometime in the [Archean Eon](https://en.wikipedia.org/wiki/Archean)
Life started in the early Archean (Earth was habitable in the Archean).
The first continents formed in the Archean. Mountains are caused by two continents colliding or rubbing together.
Some continent had to be the first continent. So there was a time when Earth was habitable but couldn't make a mountain because it didn't have two continents to rub together.
[Answer]
Less likely,but not improbable. And habitable for what? Life is not all about humans. Meaby you have more or less flat continent and all that not-so-common activity is down below in your oceans. Harsher weather is not something you can not overcome and adapt to.
If you fear meteors better to have less them in your solar system and have good pal gas giant collecting them for you.
[Answer]
An habitable planet without mountains may have more rainfall and less desertic areas(mountains often prevent humid air masses to reach more inland areas of the continents - but the opposite is also true - a friend of mine once told me that if the Andes didn't existed most of South America would be an empty dandy desert like Sahara) which would also means more forest and more biodiversity.
Without mountains the world population could grow much higher since your planet has more habitable land which infrastructure and agricultue can be done without too much trouble. Which also means your world could be wealthier with less poverty with cheaper food price( more food supply means cheaper price - if your civilization use money/barter in their economy of course).
[Answer]
An [Iron planet](https://en.wikipedia.org/wiki/Iron_planet) they have no plate tectonics or strong magnetic field as they cool rapidly after formation. This leaves you with a pretty barren planet though.
] |
[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.
Assuming that the only fancy available technology is FTL drives (to get there) plus anything needed to protect and sustain a crew during the journey from Earth to Sagittarius A (whether it takes a few days or centuries is irrelevant to the question).
Ship and crew have no way to counteract or protect themselves from the temporal and gravitational effects of the black hole on the spacetime continuum.
How close could a ship come to Sagittarius A before being in danger of destruction?
[Answer]
**Note**: The numbers hae been edited due to access to a better luminosity source
# How powerful an emitter is Sgr A\*?
First, check out [this](https://worldbuilding.stackexchange.com/questions/71971/is-it-safe-to-orbit-hde-226868/72195#72195) answer. I'm going to lean on those calculations here.
Second, Sagittarius A is a large object with many components. The part that will kill you is the (probably) supermassive black hole [Sagittarius A\*](https://en.wikipedia.org/wiki/Sagittarius_A*). Like [Cygnus X-1](https://en.wikipedia.org/wiki/Cygnus_X-1) in the other answer, the most relevant emissions from our perspective will be hard x-rays. Peak energy flux from [Barriere, et al., 2014](http://users.monash.edu.au/~iwanless/papers/redLRdiv.pdf) is in the 2-20 keV range, which is consistent with the energies emitted by Cygnus X-1, and with the estimates I made in that post.
Luminosity in the X-ray range is $~1\times10^{25} \text{ W}$, but peaks during flare period around $~1\times10^{28} \text{ W}$. We will us the higher number for safety. The challenge with X-rays is that they tend to penetrate things, they are hard to reflect and they kill humans in low doses. We need the flux to be low enough not to kill humans.
X-ray flux is the power emitted by the object divided by the surface area of a sphere at a distance $r$ from that object. Its equation is (letting $4\pi \approx 10$)
$$\Phi=\frac{1\times10^{27}\text{ W}}{r^2}.$$
# What hard X-ray energy will *not* kill humans?
Radiation exposure is tricky, since some body parts are more sensitive than others. In the US, the Department of Energy radiation worker annual dose limit is 50 mSv, roughly equivalent to 5 rads of energy. Lets say it is allowable for the crew of our vessels to get the whole annual dose in just 5 days; so 1 rad per day. 1 rad is 1 J of hard X-ray energy into a 100 kg person. On a per second rate, this means a person can be exposed to a maximum of about $1\times10^{-5} W$ of continuous hard X-ray radiation to remain safe from radiation poisoning for a week.
# How far away do you have to be to avoid this dose, unshielded?
Lets say a person has a surface area of $1 \text{ m}^2$. We then solve
\begin{align}\Phi=&\,\frac{\text{allowable dose}}{\text{surface area}}\\
\frac{1\times10^{27}\text{ W}}{r^2} =&\, \frac{1\times10^{-5}\text{ W}}{1 \text{ m}^2}\\
r =&\, 1\times10^{16} \text{ m}
\end{align}
This is about 70,000 AU or 1 light year. Yowsers!
# How far do we have to be to avoid this dose, shielded?
Lets say that we can reflect 90% of the incident X-ray radiation. Now, lets say that we can shield ourselves from much more of it with a thick hull. The problem (as noted in the other answer) is hat the thick hull will be heated by the X-ray flux that we can absorb. So we have to estimate how much heat energy we can re-emit as waste heat, to figure out how much energy we can continuously absorb from Sgr A\*.
An expression of the [Stefan-Boltzmann](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law) law in terms of power per unit area of emission is
$$\frac{P}{A} = \epsilon\sigma T^4$$.
The emissivity of a material is its ability to emit thermal radiation as blackbody radiation. Lets set $\epsilon=0.99$ (ice is $\epsilon=0.97$; ship made of ice?). The Boltzmann constant is $\sigma=5.67\times10^{-8}\text{ W m}^{-2}\text{K}^{-4}$. Lets say that the ship's hull and heat sinks can handle being heated to 1000 K and still maintain that high emissivity.
For every unit of surface area the ship receives of incoming radiation, there is approximately one unit of area for blackbody radiation out. So we can set up an equality to see what X-ray flux the ship can handle. Let $a$ be the ship's 'albedo', which is the amount of X-ray energy reflected.
\begin{align}a\Phi =& \, \epsilon\sigma T^4\\
\frac{1\times10^{26} \text{ W}}{r^2} =&\, 0.99\cdot5.67\times10^{-8}\cdot(1000)^4\text{ W m}^{-2}\\
r=&\,4\times10^{10} \text{ m}
\end{align}
This is 0.3 AU, or a little less than distance from the Sun to Mecury. Note that the estimated mass of this black hole is 4 million solar masses. The [Schwarzchild radius](https://en.wikipedia.org/wiki/Schwarzschild_radius) of the black hole is only a little less than this at abot $1\times10^{10} \text{ m}$. Since the energy from a black hole comes from its accretion disk, you can't consider the black hole to be a point source of X-ray energy at this close distance.
# Conclusion
An unshielded human being can't get anywhere near a luminous X-ray source like Sgr A\*, but with an assumption of moderately advanced technology, a ship that is designed to shed hat efficiently and that has X-ray reflection built in could get as close as Mercury is to the Sun. The geometry of the emissions from he accretion disk and the event horizon (which should definitely also be avoided) means that it is hard to pin down exactly how close you could get.
Also, this would be at the upper limit of what the ship could handle. A safe orbital distance around such a supermassive black hole would be much farther away.
] |
[Question]
[
My weather control machine works! I dragged it out to international waters on a barge and was able to seed a moderately sized rain storm.\* I'd like to start using my device in the United States for fighting drought and maybe even wildfire. The problem is that I can't figure out how to get permits. I know how to file for a [NOTAM](https://www.faa.gov/pilots/safety/notams_tfr/) to warn airplanes about the coming storm, but I have no idea what other agencies are responsible for regulating weather machines.
Which US government agency/agencies should I ask for permission before launching a US-based test?
**More information about my machine**
My machine uses an advanced form of [cloud seeding](https://en.wikipedia.org/wiki/Cloud_seeding). I inject a substance into the atmosphere that helps them turn into rain storms. For my offshore tests, I used a blimp that was moored to my barge. I didn't use an airplane because I didn't have a way to take off and land in international waters. For my US-based tests, I could use an airplane, blimp, or rocket. I'm guessing the blimp option will require the fewest permits.
**What I've found so far**
It looks like I'll need to do the following things:
1. [FAA permits](https://www.faa.gov/aircraft/air_cert/design_approvals/airships/airships_regs/) for flying a blimp
2. FAA will probably want a
[NOTAM](https://notams.aim.faa.gov/#News) alerting aircraft about the weather
3. Commerce Department
needs to be informed per [US law](https://www.law.cornell.edu/uscode/text/15/chapter-9A)
Any idea if there are any other authorities I need to ask?
\*(Maybe "weather control" is overselling its abilities, but I'd like to see you do better.)
[Answer]
I'm posting this as an official answer, but it's unfair of me to do so. You already knew about this (or could have easily chased it down yourself) and I can't find or imagine anything more. I'm impressed this exists. I had no idea weather modification using any method was effective enough to require this much regulation.
[**Public Law 92-205, 15 USC § 330**](https://www.law.cornell.edu/uscode/text/15/chapter-9A)
>
> No person may engage, or attempt to engage, in any weather modification activity in the United States **unless he submits to the Secretary such reports with respect thereto, in such form and containing such information, as the Secretary may by rule prescribe.** The Secretary may require that such reports be submitted to him before, during, and after any such activity or attempt. (Pub. L. 92–205, § 2, Dec. 18, 1971, 85 Stat. 736.)
>
>
>
and from [NOAA](https://www.cio.noaa.gov/itmanagement/pdfs/0025ext2014.pdf):
>
> P.L. 92-205, enacted December 18, 1971 (amended by Public Law 94-490, Section 6(b), October 15, 1976) requires that all non-federal weather modification activities in the United States and its territories be reported to the Secretary of Commerce. The National Oceanic and Atmospheric Administration has implemented the Act and the current reporting requirements are published in the Code of Federal Regulations (15 CFR 908).
>
>
> Respondents to this data collection are operators of aircraft which engage in cloud-seeding and other related activities in an attempt to modify the weather, i.e., to increase precipitation, mitigate hail, and disperse fog. They are required to file two one-page reports annually. Each project
> **must file with NOAA an initial report (Form 17-4) and a final report (Form 17-4A) - or an interim report on the same form if the project continues beyond December 31.**
>
>
> Beginning in 2000, the NOAA Forms 17-4 and 17-4A became available on the Internet at <http://www.corporateservices.noaa.gov/~noaaforms/eforms/>
> in order for the respondents to have the capability of being able to fill out and print forms on-line. However, the forms can not be submitted electronically at this time because the forms are required to be signed by the equipment operator. The forms may be faxed to (301) 713-1459 to the attention of Karen Williams or may be mailed to the NOAA - Weather Modification Reporting Office in Silver Spring, MD. Electronic signature capability is being planned but security requirements are still to be addressed. The NOAA Forms 17-4 and 17-4A are still available by mail to those who do not have access to a computer.
>
>
>
Regrettably, the link is no longer active. However, the funniest part of this comes from the following statement in that report:
>
> Note: currently a redesign of the forms is planned, as the previously fillable forms were locked by a retired employee.
>
>
>
Honestly! They're going to spend a ton of money redesigning forms because no one is bright enough to type "remove acrobat passwords" into Google and get any one of the bazzillions of PDF file password removal tools and just unlock the file. I've done this myself... it takes seconds. I wonder how many of my tax dollars were spent on that endeavor?
] |
[Question]
[
**The Background**
I have a species of intelligent humanoids roughly modelled after bears. They're hulking great grizzly-sized solitary mesocarnivores. Genus Homo and descended from H. sapiens, but significantly different in both biology (size) and psychology (solitary and territorial). Think the [varl](https://bannersaga.gamepedia.com/g00/Varl?i10c.encReferrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvLnVrLw%3D%3D&i10c.ua=1&i10c.dv=14) from Banner Saga, but crank up the solitude and territoriality. Technology is roughly neolithic.
Having read this question on the [social structure of intelligent hypercarnivores](https://worldbuilding.stackexchange.com/questions/70925/what-kind-of-society-and-morals-would-an-alien-species-evolved-from-solitary-car), I've determined that their 'society' would be highly diffuse. Communication would largely take place via written messages along the borders of territories, stretching from threats against trespass to messages about projects of mutual benefit amongst semi-trusted neighbours (probably those with a degree of relation). The closest they would get to a band would be either mother and children, or perhaps a gang of late-juvenile siblings like you sometimes get with real-world solitary predators.
However, descending from H. sapiens, verbal language is too powerful of a tool to give up. Although avoidance would be preferred there are situations where face-to-face interaction would be unavoidable, either through chance or for mating (females are close enough in size to make forced mating a risky business).
**The Question**
What aspects of a verbal language might we expect to develop based on the social interactions of this species?
As a starter for ten, I've thought of the following:
* Excessively formal. In order to avoid physical confrontation trollspeak would be littered with formalities to try and avoid giving offense.
* These formalities probably wouldn't be based on social structure like a lot of ours (sir/madam etc.) as that structure and hierarchy wouldn't necessarily exist.
* Manifold and heavily nuanced language to describe actions and intent in order to clearly and very accurately describe what you want to do so the other ettin doesn't get the wrong end of the stick and attack you.
* On a less grim and gritty note, you might expect some very eloquent speech designed to woo the opposite sex. If physical confrontation is very risky, perhaps courtship language might help provide a strong evolutionary driver for retaining advanced speech.
So yeah, what other features might we expect to arise in the language of intelligent solitary territorial humanoids?
[Answer]
If your individuals are highly territorial and solitary, I think it's hard to get physical proximity which is short enough to enable spoken language. At that distance it would mean only attack or mate.
You can still use a whistled language, like [Silbo Gomero](https://en.wikipedia.org/wiki/Silbo_Gomero).
>
> Silbo Gomero is a whistled register of Spanish used by inhabitants of La Gomera in the Canary Islands to communicate across the deep ravines and narrow valleys that radiate through the island. It enables messages to be exchanged over a distance of up to 5 kilometres. [...] The language is a whistled form of a dialect of Spanish. Silbo replaces each vowel or consonant with a whistling sound. Whistles are distinguished according to pitch and continuity. As with other whistled forms of non-tonal languages, Silbo works by retaining approximately the articulation of ordinary speech, so "the timbre variations of speech appear in the guise of pitch variations"
>
>
>
In this way it's easier to keep isolation and communication, and you could reserve normal spoken language to either mother-child interaction or sexual partners, situations where close proximity cannot be avoided.
[Answer]
Such a language would go to extremes. As Mike Nichols mentions in comments, there would be very little time to learn such a language before cubs left their mothers. As such, one would expect the language to be one which is more instinctual and less formal/nuanced. You'd expect signs which provide simple information ("You not belong here") rather than messages with complex nuanced syntax ("The borders of my territory extend to the banks of the river upon which this sign is placed. I will respond with lethal force.'). In short, you'd expect the messages to be more bear like.
If you want a very formal speech, you will need to take it to the extreme. You will need a formal enough speech that the rules of such speech can be memorized as cubs. Such cubs would go out into the world with nothing but the rules, and perhaps a dictionary of written things (assuming they can carry objects).
As such, my recommendation would be to look at programming languages and other [formal languages](https://en.wikipedia.org/wiki/Formal_language). Formal languages have a unique mathematical format which can determine whether any utterance is "legal" or not, and most of them also have very clear semantics -- which means the meaning of each sentence is very easy to determine from a set of rules.
Cubs would be taught to memorize a common corpus of valid speeches from history, just like students of the past memorized the Bible. They would use this to anchor them and their understanding of speech throughout their life. By making it memorized verbatim like this, it can retain a remarkable amount of formality despite needing to be transmitted from person to person many times. Bonus points for having some bears keep a written copy. A famous example of this is the Torah. Linguists have found that they can analyze the age of languages by watching how different linguistic patterns form and diverge over time. Hebrew, however, has caused trouble for such linguists. The Jewish people were so extraordinarily careful in their copying of the Torah that there's no where *near* as many divergences as a linguist would expect from a typical language.
Your language would be mostly regular, with a handful of quirks which extend from the particular corpus of text. For example, you might have a regular way of forming plurals, except for the [plural of ocotopus](https://english.stackexchange.com/questions/270/what-is-the-correct-plural-of-octopus), which could be octopodes because that *one* loan word found its way into the corpus of text.
As an example speech which I would recommend every cub learn before leaving their mother, check out Guy Steele's famous lecture, [Growing a Language](https://www.youtube.com/watch?v=_ahvzDzKdB0). Given that it's a long lecture to memorize (roughly an hour), you can read the [transcript](https://www.cs.virginia.edu/~evans/cs655/readings/steele.pdf). Indeed, I recommend reading the transcript to get a sense for his formal cleverness. I think your bear language might be taught *exactly* the way Guy Steele puts his speech together.
] |
[Question]
[
I have a clam that has modified its foot to make a flat, net-like structure to catch insects often shaped like a leaf. I wanted to know where this hit in terms of feasibility or if there were any examples of an appendage like this in nature.
It lives in an extremely humid canopy that is full of water pockets and it has adapted to prolonged periods out of the water.
The muscular net would appear much like a leaf with crisscrossing portions and primary veins and would be covered in a mucus/secretion to attract and trap insects.
[Answer]
It is a good idea. Instead of a clam, this seemed to me like more of a snail thing to do. Snails are clam cousins so it is close. Plus snails already live on land, and your tree canopy seems like snail heaven. I went looking.
This quote is about the "pond snail" of which the Lymnaea species is one.
<https://homesteady.com/info-12285231-long-life-pond-snail.html>
>
> The snail leaves an underwater slime trail, which collects plant and
> animal debris as well as microscopic organisms. Upon crossing its own
> slime path, the pond snail eats the bits and pieces stuck to the trail
>
>
>
Better is this great stuff on pond snail feeding I found on Google books from [Behavior monographs.
Cambridge, Mass. : H. Holt & Co., 1911](https://books.google.com/books?id=Y3oVAQAAIAAJ&pg=RA2-PA71&lpg=RA2-PA71&dq=snail+mucus+ribbon+feed&source=bl&ots=_M6vbygYeQ&sig=JpG7FQnKcy4a6h3VmZZhxahnlcE&hl=en&sa=X&ved=0ahUKEwip0ILl_YbcAhUk3YMKHXChDRgQ6AEIiwEwFA#v=onepage&q=snail%20mucus%20ribbon%20feed&f=false). I love these old natural history descriptions!
>
> All of these flesh eating snails have been seen eating dead
> houseflies, mayflies, fish, beefsteak and snails. They will eat such
> meat fresh, although they seemingly prefer it stale. I had seen them
> eating dead snails, when the odor from the food could scarcely be
> endured in the laboratory. The *Lymnaea* cited above have cannibal
> traits, a character which is especially notable in *L. stagnalis*. I
> have seen this species devouring struggling flies, moths and young
> snails that have become entangled in its slime…
>
>
> It is a common thing to see *Lymnaea stagnalis* and other freshwater
> pulmonates turn about and eat from the foot the mass of somewhat
> hardened mucus together with what foreign bodies this has
> incorporated. Linden (1902) has observed the dexterity of *Lymnaea* in
> obtaining food from the foot, while the snail is moving upon the
> surface film. Brockmeier (1898) describes this process as “plankton
> fishing”. The mucus servers not only as a food itself but is a most
> efficient means of collecting food for the snail, both on solids and
> on the film. The trails of mucus left on solids remain sticky and
> serve as a trap to catch my new plants and animals and other foreign
> particles. The snails eat continually from the solids, devouring the
> mucus with all that is caught in it.
>
>
>
So: a mollusk which secretes sticky mucus from the foot, then eats the mucus with live prey that has stuck to it. That is what you want and that exists! A snail would probably not mind being sessile most of the time, waiting for its prey to come to it.
It is one more step to having attractive smelling mucus. I could imagine mucus that stunk could attract flies although that might attract larger carrion feeders too which would eat the snail. The same problem exists for fruit smells - fruit flies are tasty but big things like fruit. Mucus that smelled like flowers could attract pollinators - that sounds right.
---
I was thinking of this concept and a snail that let its viscous slime net drool down thru the air like flypaper. Then it would reel it back in with its haul of bugs.
] |
[Question]
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A roughly earth-size planet orbits a cool G-class star, but barely within its circumstellar habitable zone ("Goldilocks zone") allowing liquid water. It has a shallow inclination and and lackluster seasonal change, fairly evenly distributed continental masses, and I think this would allow the poles to get *very* cold. (But should be warm enough on average for ocean evaporation and precipitation cycles, and to support analogues of tundra, taiga, and boreal forest in the "tropics".)
I had an idea, I want to see if there is a plausible way under these circumstances to allow for a polar "snow sea" such that the snow is light and frictionless enough to allow some degree of fluidity. I read [this answer about "sand tides"](https://worldbuilding.stackexchange.com/questions/72404/is-it-possible-to-have-a-planet-with-sand-tides-on-deserts) and it has some interesting information on viscosity, so I googled "snow viscosity" and found lots of interesting information and math about rheology that I cannot really comprehend.
[This](https://www.rheology.org.au/Resources/LectureSeries/ASR_Lecture_2016-04-11_Sydney_Rognon_slideshow2.pdf) powerpoint is what I came closest to being able to parse. It is more related to avalanches, but the math seems like it could be used to identify conditions where the viscosity of snow is least.
I did find out that snow is viscoelastic and you would have to mitigate both aspects of this property. What it looks like is that it would require the snow to
1. Not melt at all, of course
2. be in round grains, not flakes or faceted grains
3. for the grains to be small and homogenous enough to slide around freely
and probably the biggest obstacle is that
4. the weight of the snow somehow needs to not compact the snow below it into snowpack.
There has to be some kind of suspension effect.
The only ideas I have so far verge on phlebotinum:
* Somehow with static electricity?
* Some kind of lipid byproduct produced in large quantities by chionophile microorganisms?
* Volcanic outgassing that somehow doesn't melt the snow
* Tectonic activity that continually vibrates the snow
Does anyone know of something obvious and more straightforward? I'm not just fishing for ideas here. If it is really too much of a stretch, I'm happy to hear about it.
This is my first question here, hi everyone. Happy to accept corrections.
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Ooh, this is a tough one. For several reasons, the main ones being that (a) snow normally comes in flat, spiky flakes that don't slide past each other easily, and (b) ice, unlike most other materials, tends to melt when under pressure, so grains below the surface will tend to melt where they touch and then refreeze, sticking themselves to each other.
There are ways for granular solids to act much more like fluids than they normally do: namely, by [fluidization](https://en.wikipedia.org/wiki/Fluidization). For this to work, you need a collection of fairly uniform, round-ish solid grains that do not stick to each other, as well as a substantial flow of gas (or liquid, but usually gas) upward through the solid grains.
Here's my proposal:
The polar regions of your planet are *really flippin' cold* (which they may well be if the planet is at the outer edge of its sun's habitable zone, especially if there is little axial tilt and not much of a summer), cold enough that it takes a substantial amount of pressure for ice to melt, meaning that ice grains won't glom together unless there's a couple meters of ice above them.
Second, due to a meterological quirk, most of the precipitation in these regions falls not as snow, but as sleet. For some reason, there's a layer of much warmer (above freezing) air between the (very cold) ground level and the layer above where the clouds form. Water falls from the clouds as snow, melts in the warm middle layer, allowing surface tension to transform the flakes into round droplets, which then refreeze into tiny balls of ice before they hit the ground.
Third, there are fissures that deliver sunstantial quantities of some very cold gas from somewhere underground. This is probably not the result of tectonic activity, as gas released from a volcano would probably be warm enough to melt the ice grains. Maybe there's some endothermic chemical process that releases a gas. Or maybe there are huge, open underground caves that alternately suck in and spray out air taken from the surface. When the air pressure at the surface is higher than that in the caverns, air will flow underground; when the air pressure drops (perhaps due to an incoming storm), air will flow out. There are a few caves on Earth that do this, some of which are listed [here](https://en.wikipedia.org/wiki/Blowhole_(geology)#Other).
When gas flows out of these fissures, if the opening is blocked by a pile of loose, recently-fallen sleet, the flow rate may be enough to fluidize the sleet. So as you're walking around on the ice caps of this planet, you may occasionally find what initially appear to be pools of boiling water... except it's not boiling, it's not really a liquid, and it's quite a bit dense than water. So don't jump in it. You'll sink.
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**Not Possible With Regular Water Snow**
Snow compacts into ice under its own weight once it gets deep enough. This is actually how glaciers are formed here on earth.
**Somewhat Similar Activity By Other Means**
Recently scientists discovered methane-snow dunes on pluto. This is pretty odd since pluto doesnt have enough of an atmosphere to form wind, which is required for dunes to form. They theorize that melting and off gassing nitrogen deposits toss frozen methane crystals which swirl and settle under the minimal but still adequate pressure of the outgassing to simulate the same dispersal patterns wind has on sand under higher pressure atmospheric conditions on mars or here on earth. So we now know that wave-form phenomena can occur without an actual atmosphere present, it's just not going to be behaving as a liquid but more like sand.
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The world in my story is going past the smartphone era.
To replace smartphones people wear a small device like a headphone. The device is not intrusive to their brain, it has nodes that read brain activity from outside the cranium.
Using the device they can browse, watch a video or even go to an immersive 3D digital world, while at the same time can process visual and auditory stimuli from outside (just like daydreaming, their concentration level may be halved but they can see and hear just right).
With softcore sci-fi explanation and as small handwavium as possible how can a start-Up company achieve to invent this device?
What is the closest method that most likely has the best potential to develop this device for now?
Plus point: if the device can read quantum entanglement pattern happening inside the brain.
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First of all, what follows *is* handwaving - things don't work exactly this way for a number of reasons.
But you can imagine a series of not-too-unlikely breakthroughs:
* advances in high-temperature superconductors allow the creation of a novel type of miniaturized [SQUID sensor](https://en.wikipedia.org/wiki/SQUID). (This is a key element in Robert J. Sawyer's *The Terminal Experiment*)
* advances in processor design and fabrication techniques (probably using soft X-ray etching) lead to a new generation of ultra-low-voltage CPUs, whose low heat signature allow packing a *whopper* of computing power in a tiny package.
* the above allow the application of [SAR/phased array](https://en.wikipedia.org/wiki/Phased_array) technology to brainwave monitoring.
* advancements in AI allow the above to decode and predict in real time a human being's brain signals in a meaningful way, provided that they are wearing a suitable SQUID helmet and they have performed the necessary tuning and calibration - the "learning" phase.
* more expensive devices are leaner, faster, require less learning and have longer-lasting batteries. Just like smartphones.
To all intents and purposes, this is a limited form of super-[fMRI](https://en.wikipedia.org/wiki/Functional_magnetic_resonance_imaging) in real-time.
While reading one's thoughts is not quite there yet ([or is it?](https://interestingengineering.com/this-new-ai-system-can-see-what-you-are-thinking)), somatic stimuli, proprioception, voluntary muscle activation and other signals are readable - and, after a lengthy period of acclimatization and tuning, *writeable*.
(The potential for abuse is **staggering**. You can look for YGBM, [assessing one's true affections, trustworthiness and beliefs](http://blogs.plos.org/neuro/2015/01/13/mapping-memory-circuits-with-high-field-fmri/), or in SF - *The Neutronium Alchemist* by Peter F. Hamilton - something called *persona-sequestrating nanonics*. Or Larry Niven's current addicts. The simultaneous use of pain conditioning and feedback techniques would make the *Manchurian Candidate* or *Beta Project* look like a walk in the park in the good old days).
However, when all is said and done, the brain can be stimulated to "see", "smell", "hear", and in a limited way touch and taste, things that aren't there. In-brain VR is now possible.
Still more advanced systems could allow implanting *memories*: for example a politician or an executive looks at someone's face, and the helmet performs face recognition and dumps a short dossier on the guy directly in the user's working memory: he now *knows* the guy, his name, his tastes, his political agenda etc. - in the blink of an eye. The street price for such a device would go through the roof (and the "potential for abuse" knob is now set to 11).
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problem: Diminishing the user's level of attention is just plain *dangerous*. Going up as to half of it, is like calling for a serious accident.
This device would be better used if the user is standing, or in bed, or during work for work purposes.
Anyone who wanted to develop this very interesting device would need experts in neurology and nanotechnology. If you really want the user to live such a level of immersion, though, I fear it is necessary for a chip to be implanted in the user's brain. The chip would normally do nothing, until the 'headphone', which is the main input device, consisting of mike and glasses, is applied to the skull and recognized by the chip. only then, would be the user able to "Go Deep": The external device would tell the chip which areas of the brain to stimulate so that the experience start at its finest and safest way.
The road to this invention cannot be...well, something that happens on a random intuition. The company should be founded on the premises someone studied the idea and its details in a teamwork. Even one person can come up with a rough sketch of the idea, but you cannot go beyond that level without fine instrumentations.
Hope it helps. Nice idea!^^
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Sorry for the short answer but
I think reading brainwaves without a psychical connection to the Brain, is unlikely to work out. humans don't emit there thoughts, nor do they have a movement dependent on those thoughts, you can't "check someones pulse" sort of thing and find out what they're thinking. with physical intrusive implants then in theory this could be done.
**Alternative**, mainly because its something being looked out even now
Heads up display glasses, have conventional looking glasses, not goolge glass, literally just regular looking glasses, which off the display they can naviagate the web etc by looking, hear things through speakers in the arms, and possibly even have an implant that connects behind the ear.
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I'm trying to write a story about the transformation of the protagonist's role in the community that matters most to them, and that community just happens to be a community of mages in a fantasy world constantly at war. But this is just plot.
I've come up with a magic system for the world that hopefully balances it with the rest of society, but I want to run it by an objective audience to see if it makes any sense.
I know magic is notoriously hard to write so I will try to explain as much of my system as possible.
It goes like this:
Imagine a fantasy world where there are these free currents of invisible magical energy that moves through the world randomly and unpredictably. The energy ebbs and flows gaining in strength and fading in strength based on a number of factors such as the time of year, the time of day, and the geological features of the world. No one can predict where they will show up and for how long they will stay in the same spot.
The energy itself is actually the metaphysical material of another universe where everything and anything can exist at the same time and is in a state of total anarchy, basically hell. The random anarchistic material of hell is leaking into my world and joining with the ordered material in it to create a new ordered hybrid material that can be harnessed as energy.
But, the energy can only be harnessed by individuals who are sensitive to the energy and are born being able to see the flows themselves. They are living conduits of the energy. These are the magic users. When the energy becomes into them they perceive it as nine separate aspects which are associated with different spellcraft.
Now, simply being sensitive to the energy isn't enough to use magic, the mage has to understand it, control it, and know how much to expose themselves to. Because if they don't three things can happen. One: prolonged contact with the energy will cause the mage to slip into insanity, at which point they can no longer function. Two: the more energy they take into themselves the greater danger they will become possessed by demonic beings from the other universe and the demon will eat their soul. For this reason, mages have to learn to master their minds and their willpower. If they manage this they can avoid danger to themselves, but they will never be totally safe.
a mage has to go through years of training and study to be able to master controlling the magic and protecting themselves from it at the same time. They learn these skills through established academies of magic that are sanctioned by their country's government. The governments then use the mages to serve the state and military for the benefit of their country. The mages really have no say in this matter they are made to serve the state regardless of how they feel about it because really what the state is doing is neutralizing a potential problem in their population. They can't have powerful magic users running around free because they pose a threat to public safety and the government itself. So they make the mages work for them and redirect their power.
But even once a mage is trained and working for the government, the extent his/her power is still limited. When they go through training they have to choose to specialize in one type of spellcraft based on the nine aspects of energy, and each specialized magic type has its strengths and weaknesses against other magic types. So if a fire mage goes rogue, a water mage can take him out, because water magic is stronger against fire magic. This adds an extra layer of security over the mages.
A mage will work to benefit the people in their daily lives by using their magic to help in various tasks like helping crops grow, healing the sick and wounded, fighting fires and making weapons and armor. But assistance is limited by the availability of the mages, rather or not the currents of magic are in the right place to make the spell work successfully, and rather or not the mage needs to distance himself from the energy to avoid going insane or being possessed by devils. The magic is not always reliable, so the average people also have to depend on their own work and technology to keep the society moving, but if a mage's help is offered and the conditions are right they won't refuse it. Mage's aren't paid for their services because the state takes care of them and the state is paid by taxing the people. So in a way, Mages are agents of a state-funded welfare and assistance program for the people when they need it.
The same rules apply to military applications, Mages can fight and use their magic for war, but their usefulness in battle depends on if the currents of magic are right, and they can't cast huge spells repeatedly against an enemy or defense spells because they will take in too much energy and endanger themselves. So the military can't rely on them too much and they need to field full armies of average soldiers to win a battle. Not to mention the enemy will have their own mages who can counter a mage's magic with their own.
One thing that I am concerned about in my system is the nature of the relationship between the mages and their governments. The governments are forcing the mages to serve them and their needs so in my mind that is exploitation, even though the governments take very good care of the mages and train them and give them a mission in life. The mages are putting themselves at risk by using the magic for almost no reward of their own and they would have the means to resist the will of the state. But then again I'm thinking this is a don't bite the hand that feeds you situation.
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Normally, I'd be confused why an a group of intensively powerful individuals would be able to be oppressed into servitude, but your inconsistency of magic and insanity seem to be good counters.
There is the problem of the state being able to "manufacture" mages. Mages wouldn't want to become mages cause its a massive health risk with a boatload of social stigma that won't pay, and the state would be dumb if they tried and force people to spend years studying magic-craft. "Lean how to generate explosions, turn humans into stone, and summon legions of daemons so I can whip you into complying with my needs, dang it!" The potential for ex-military domestic terrorist mages would be massive, even without the insanity angle.
So you need friendlier government recruiters and a incentive for magic sensitive people to become full on mages. I think you accomplished this with mental illness being common among the sensitives, and the symptoms being alleviated with increased magic skill (and maybe some rituals or materials). Picture this:
*A character is huddled in a padded cell, covering their head with their arms and muttering to themselves. The door opens, and a man in a spotlessly clean uniform walks in. As the character retreats, the man draws a symbol on the wall and charges it with more magical energy than the character thought possible. Instantly, the voices vanish and the room stops spinning. As the character feels relief for the first time in years, the man in the uniform being a speal about the nobility of serving ones country and the duty of the magically gifted. But the real message is crystal clear.*
*Say yes, and they will teach you how to feel human again. Say no, and I will leave you right where they found you.*
After that, the system is maintained by your system of checks-and-balances and the states ability to recruit new mages to replace the ones that die. For example, they might build asylums purposely near areas were magic fields are know to form in order to root out magically sensitive people. Finding ways to keep mages from "unionizing" would also be a priority of the state, like stationing mages far apart, limiting their ability to communicate with each other, and purposely generating factions (having three magic ministrations that compete for funding and public opinion, for example, or even playing the nine specialization of magic against each other).
As a whole, I think your system makes sense. Keep in mind that, while completely altruistic recruiters and handlers would definitely exist, the real incentive to for a government to fund mages would be profit. Even with the unreliability of magic, mages would be a huge economic boon and military deterrent. A lot of people in the state would think about mages as finicky, disposable tools rather than human with real problems.
Another think to think about is the reputation of mages before the state started training and utilizing them. Do the general public tell stories about mages that became serial killers or leveled churches to the ground? How many example of benevolent mages are there? Is the state posting flyers warning the public about mages or posters trying to make mages look heroic and selfless to fix their previous reputation?
I'm not sure why the mages would be payed only in room and board, though. Being able to buy your own food and some nice posters for your bunk is great for morale. If you need to control them, just don't pay them very much.
Sooooo, yeah. I like your idea and it defiantly engages me. Sorry that half of my answer is basically just restating your question.
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Quite a bit of your magic system reminds me of the 'One Power' in Wheel of Time (by Robert Jordan) - you should at least read an explanation of that magic system if you don't know it already.
The most relevant parts you can draw upon are:
1) The Wheel of Time world has an organized magic institution ('the White Tower'), where all magicians ('of the civilized world') are raised, taught and later work for. They regularly recruit all children with enough talent and thereby also make sure that all adult mages have a similar mindset and generally support this one organisation. Rogue / self-taught mages are very rare because they A) only occur if someone is overlooked and B) are actively hunted down. Since the organisation is generally respected by the population (and governments) most people cooperate with them and even send potential candidates their way.
2) (male) magic users in the Wheel of Time go insane, when they use their magic (slightly different reason than yours, but only slightly ^^). This make them very dangerous for anyone around them and is a big factor in easily allowing the organisation to take control over all (potential) mages - they are the only ones who can offer protection and in turn they take the right to take in all children with talent and prevent other people (who where overlooked) from developing their magic.
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I will admit that I don't like indentured servitude of indefinite length, or more properly, slavery.
Your mages are slaves to the state. Yes,they gain value from the state from their training. Most of the books I've read separate the magic school from the state and problems occur when the state does take over.
An interesting book that uses this as a theme is ["Od Magic" by Patricia McKillip](https://rads.stackoverflow.com/amzn/click/B004IATDF6). Anything by McKillip is worth reading twice, mainly because it usually takes two readings to figure out what has happened. "The Riddlemaster of Hed" is another of hers that is well worth reading.
I don't know how I feel about mages with random currents of magic which make them useless at random times. I could picture this being used too much to contrive weaknesses for the protagonist or antagonist. I feel there should be some way for the mage to store some magic within himself for those times when the magic currents disappear.
I know that the government, if it is close to a modern one, will want to control the power of magic. However, there are some things that can't be controlled. There will probably be rogue mages out there as well or better trained than the government ones. Perhaps there is an alternate power out there that only the rogue mages can use. Maybe it comes from some place more like heaven, or maybe it is just earthly magic. Maybe it isn't as powerful, but it's almost always there, depending on the season and place.
I would also be very interested in hearing your nine divisions of magic. There are so many ways to divide up magic. In my current book, I divide wizardry (natural magic, sort of) into the classical Greek Elements, but I use both their literal and symbolic meanings (Earth has physical protection, healing, some illusion, and growth; Fire has fire, magic, illusion, and scrying). Yes, much is duplicated in each division, but that is deliberate.
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No, I don't think anyone would risk becoming a mage under these circumstances. I think it would be more balanced if mages were instead seen as part of an order (religious or otherwise) which also has privileges normal people don't have and has duties normal people don't have too, but most importantly, they have the respect of the society. They might even be seen as spiritual leaders since they are connected to beings whom the religion defines as supernatural.
They should be seen by outsiders as powerful and wise beings who help everyone, even if their reality is somewhat different - but I think it shouldn't be that much different if you don't want a rebellion on your hands. The state would need very strong propaganda to support the system if it is. I also think that serving in the military should be optional but also seen as a great honour.
Otherwise, what prevents your mages from lying to people who cannot see magic and telling them there is no magic around when they don't want to do something? Or that they have done too much magic recently and they cannot possibly do any more right now?
Untrained and unaffiliated mages could be seen as very dangerous, and maybe they run a high risk of going mad and harming themselves and their family/friends so people who can access this magic wouldn't be motivated to just not tell anyone. Although they could just not access this magic and they would stay safe in a different profession. I'm not sure whether you want for everyone to become a mage who can see magic or there can be people who chose not to.
Also, you didn't say what was the third thing that can happen.
Another thing is your religion: I'm not sure they would unanimously define this other place as "hell" and the beings that inhabit it as "demons" even if your main religion does.
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It reminds me of the psychic police in Babylon 5: they actively hunt for children born with the talent and forcibly recruit them. An obvious consequence is that plenty of talented children will choose to hide themselves and train each other in secret.
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Ideally, if this is high SF (or the fantasy version) you have in mind a real world analog to what you describe.
One real world analog would be **violent men**. They exist in the world, and they are born with a innate capacity for violence. Such men can be disruptive and so in an organized society, men with this "gift" are given the opportunity to learn self-discipline and channel that energy, using the capacity for violence in the service of the state - they are warriors (or policemen). A violent man might choose to serve the state, or not object to strongly to conscription, because he (or maybe his family) realizes he will be violent in any event and if this behavior happens without state sanction, he will either be killed by the sanctioned violent men or imprisoned. With state sanction he can be a force for order, and possibly even for good.
Violence can cause chaos and disruption. In a way violence comes from that place, just as your magic power comes from Hell. A man who gives himself over to uncontrolled violence is consumed by his demon. But violence channeled and under control by trained men can be used to oppose violence from outside, protect the weak and defenseless, and preserve society from powers that would destroy it.
You could really run with this. A violent person can slip his training and commit acts not sanctioned by the state. People trained for violence who have committed violent behaviors in the name of the state can have lasting psychic effects from their actions that haunt them. Or a violent person might outgrow his violent tendencies, and then be forced later in life to take them back on - the movie Unforgiven comes to mind.
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My world was once analogous to our own Earth, where life evolved in the light and heat of a nearby star. Unfortunately, a cataclysmic event knocked the planet out of orbit and sent it spiraling as a rogue planet into the dark, limitless void of space. Luckily, some of the inhabitants survived this cataclysm.
I need your expertise and scientific knowledge to help me answer a few questions about the feasibility of this.
What cataclysmic event could dislodge a planet from orbit around its star without instantly exterminating all intelligent life? What conditions could improve humanity's chances of survival in this scenario? (E.g. living in bunkers deep within mountains?)
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It seems there are three key questions here.
1. Can the earth be pulled out of solar orbit? Yes. The Earth orbits the sun at 390 km/s. Solar escape velocity is 618 km/s. Anything that adds more than 228 km/s to Earth’s orbital speed will send it extra solar.
2. Can it be pulled out of orbit in such a way that it does not kill all life? Yes. Objects ranging from several Jupiter masses to one solar mass could provide plenty of delta-v. A long slow acceleration from a larger mass would be less disruptive than a short quick acceleration from a smaller mass. Orbital dynamics, tidal forces and escape trajectories are going to be highly dependent on the details.
3. Can life continue on Earth without orbiting the sun? Yes(\*) with generations of time for planning. The good news is Earth would retain its magnetosphere, atmosphere, water, mineral resources, etc., including (presumably) the moon and tides. These are all important assets. Replacing all that lost solar energy would be key. A global economic shift toward energy production would be required. Fusion power would likely be a requirement for long term survival. Expect global flora and fauna extinctions during the years it takes Earth to leave the solar system. Plan on most people eventually working and living indoors for an energy, agriculture or environmental systems company and eating vegetarian.
Fun thought experiment... Love the question.
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1. It would need a large body to travel through the solar system, disrupting the orbits of the planets. A large rogue planet or brown dwarf star would be the most likely candidates. If it didn’t come very close to the Earth, which it wouldn’t need to, then it wouldn’t be particularly damaging to the Earth except for pulling it out of solar orbit.
2. Underground bunkers with nuclear power and hydroponics could keep going more or less indefinitely. Some life would also remain around deep ocean geothermal vents, since the deep oceans would be insulated by the ice above them, and the Earth would remain geologically active.
3. In theory it could eventually suffer the reverse catastrophe, but it would take hundreds of thousands of years at the fastest, and would be very very unlikely.
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This question has received a major rewrite and restructuring but is still the same original question.
* Please see this [meta-post](https://worldbuilding.meta.stackexchange.com/questions/5982/how-to-rewrite-a-controversial-question-when-i-didnt-get-the-answers-i-was-expe), where I asked for advice on how to refocus this question. While I have taken everything mentioned onboard, all edit choices are obviously mine.
+ In the meta-post it was advised to focus on sex rather than gender.
* I decided to still use the term transgender.
+ This was so that historical options, and previous answers are still relevant.
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In the very far future, on a planet very far away...I have a human societal structure that, on the large part, accepts the concept of being transgender. As in several pre-modern Earth societies these transgender groups have been incorporated into society in various different ways to various different degrees of acceptance. It is in no way a Utopia, so for the purposes of this question, we can just assume no social or legal issues.
This society has the same knowledge as we do today including knowledge of genes/hormones/genetic traits/dna/chemistry/biology/pyschology/ even physics etc. However they are *limited* in that their technology is not as developed as ours. They are working on it, but physical infrastructure takes time to rebuild. At a push they could recreate ~1850 AD European Earth Tech.
Several of my characters wish for their body's sex-based characteristics to appear more like their opposite sex. They require various strong hormones (either synthetic or natural) as well as much weaker herbal supplements in order to change their outwards sexual appearance. However, would they even have access to these highly processed and synthetic drugs without modern technology and infrastructure?
**If we knew in the past, what we know now, what strength of medicine could be made available?**
* Modern medical techniques such as plastic surgery & sexual reconstruction are not available.
* they are limited to what changes they can bring about through drugs.
* the changes they are after are about changing their 'superficial' physical appearance as much as possible to that of their desired sex. Such as:
+ reducing or limiting menstruation and PMS side effects (this can be useful for all women who may also suffer from painful or irregular menstruation)
+ increasing breast development or if started early enough, limiting breast development
+ increasing/decreasing the appearance of the adams apple
+ voice changes
+ facial hair growth
+ increased strength (steroids, which anyone could use), and even
+ reducing the effects of menopause (which affect 100% of the population at some time or another) etc.
* **Would there be natural, or easily recreated, [hormone replacement therapy](https://en.wikipedia.org/wiki/Transgender_hormone_therapy) supplements that they could take, if my characters wished to make these hormone-based sex changes?**
+ Note: the question is not about those particular examples but rather if we can create strong enough medication that could possibly affect those examples.
If this is not possible with today's knowledge, a well explained negative answer can be accepted. If this is possible, examples of good answers I am looking for would be focussed medically and on changing the human body's sexual characteristics.
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*The rest of the text is just some of my thoughts on the problem and is not necessary to be read, but I have kept as it may help.*
I need to know how I can describe my characters, which is most definitely story-based. So I am trying to figure out what alternate medical options would be available to them, I am thinking mainly herbal. However, I do not know if herbal supplements would be strong enough to make such changes to the body. I doubt very much that it would be able to do anything close to what modern medicine can provide. I'm not so much looking for answers on if they should or would take this medicine. That would be an opinion and story-based answers.
Historical methods of how transgender people lived in the past are very useful but *not exactly* what I am after either. I am genuinely curious about taking our current medical knowledge of hormones and supplements and how the body works, into a historical setting. So for instance, if we didn't have modern equipment but still had the modern day knowledge of chemistry etc., could we partly/fully replicate the extraction, processing and concentration techniques that would be necessary to make use of natural hormone sources from various plant and animal products eg the horse urine of a pregnant mare that SudoSedWinifred mentioned in an earlier comment. I am assuming there is some pretty high precision machinery and chemistry involved.
Positive answers could (but don't have to be an exhaustive list) include methods of reducing/increasing the testosterone/estrogen and other related hormones, as well as mention how effective each solution could be. *Probably not as completely as possible as in today's time but hopefully to some noticeable effect.* Traditional practises of castration would be acceptable but I am hoping there are some *non-invasive options* available to reduce undesired hormones etc. For the most part, there are not many non-invasive options before the advent of modern medicine.
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I used the pre-industrial tag purely to emphasise that **the infrastructure level is lower than the knowledge base**. Please limit any technology for any processing of medicine, to technology that could be created with a ~pre-1850 European *infrastructure* base.
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I've edited further. Just incase.
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The history of transgender people is really interesting, I would recomend for you to give a good read about the ways the many ancient civilizations treated the subject.
Unfortunately, before the industrial age, most transition was a question of ritual and social standing.
There was never any plant capable of offering the same you can do these days with hormonal replacement.
If it's not too late, whoever there's a legend that could help you: Silphium.
This plant was known to be used by the romans as contraceptive, but we never managed to find what exactly this plant was and many believes it has been driven to extinction because of widespread roman use.
Depending on exactly when/where your story takes place it wouldn't be too hard to handwave a few sprouts surviving and being used.
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The big thing to remember is that transgender people are a minority of a minority - as little as *0.2-0.3%* of the population. Contrast being gay, which clocks in at one in ten. Most people in today's age of interconnectivity won't meet even a single transperson, let alone in pre-modern conditions. The most famous western example was the Marquis d'Eon, who effectively blackmailed the King of France into recognising her as a woman, and even she's pretty obscure (though transgenderism did come close to being named Eonism after her).
With that in mind even cheating in modern medical knowledge for the setting would make it pretty difficult for transgendered people - even those with significant means to go with their motivation.
But not impossible. Synthetic hormones are produced today using soybeans, which could be procured with effort. From there it wouldn't be outside possibility for a skilled chemist to develop a path to synthesise the appropriate hormone - whether for transition or something more pedestrian like menopause.
Bearing in mind the combined rarity of the condition, the difficulty in procuring the raw materials (both base and any reagents needed for production), and the need to retain a personal chemist of no small skill, the whole process of transition, while possible, would be difficult in the extreme.
Definitely only for wealthy monarchs or high ranking aristocrats.
(Surgery? Sink me, no. The only thing you'd get that way, in those conditions, is another victim of infection.)
[Answer]
You actually answered your own question. You say this society has no advanced medical technology or science as of yet ("...does not have the medical infrastructure/technology to fully transition on a physical level"). Modern techniques such as hormone therapies and reassignment surgery are all very much out of reach for your society I deem. And it's really a kind of bizarrely lucky happenstance it's available to people in the 21st century at all. Without the massive strides taken in plastic surgery between the 1860s (US Civil War) and the 1920s (WWI), our society simply would not be able to turn the male body into a reasonable simulacrum of the female body (and vice versa).
Leaving aside all the politics and social uproar over this particular issue, biologically speaking, if the people of your society are like humans (of if they are humans), then they come in two basic forms: **female** and **male**. There's really just no getting around that, regardless of what activists would like us to believe.
Barring magic (whatever that might mean to your society), there are no "herbs" or "diets" or "behaviours" or "rituals" or "concoctions" of any kind that will transform a male into a female.
Your best bet will be to look at how various societies here on Earth have dealt with the very few who really are different: use of clothing, language, cosmetics / adornments, social status change, name change, etc.
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I am planning on making a new species based on octopus and humans. Human in skeletal structure, Octopus flexibility. I am thinking of calling them octopeople.
As far as flexibility, I am thinking of having muscles in the arms attaching directly to muscles without any bones. Not sure if I should have human hands with bones or 5 smaller tentacles attached to the arms as fingers.
But the more important question is how to protect organs. If the muscles are attached to muscles for flexibility that is 1 thing but human organ systems which need protection is another.
I can see how all of these organs would need some kind of protection:
* Brain
* Heart
* Trachea
* Lungs
* GI tract
* Liver
* Gall bladder
* Pancreas
* Kidneys
* Spleen
* Bladder
* Prostate(males)
* Testes(males)
* Uterus(females)
* Ovaries(females)
I mean squeezing through an area no bigger than your eye or even squeezing through an area no bigger than your arm would cause death from external pressure if humans were even able to do it. The reasons babies don't die from pressure in the birth canal is their skeleton consisting of a significant amount of cartilage, the elasticity of the birth canal, the fontanelles, and the cardinal movements of labor.
But is cartilage going to be sufficient for throat and torso protection or should there be fat around the organs to spread the pressure to not have organ failure from compression? If neither works then how could organ failure from compression be prevented?
[Answer]
## Don't protect the organs
...let them be flexible instead.
Octopii have gotten along without rigid components for longer than the dinosaurs. Clearly, their biology and environment will support that kind of morphology and physiology. If we are designing human like characteristics onto an octopus framework, then a lot of stuff will have to go.
There's two approaches to protection, be so hard that no attack can penetrate or be so flexible that you just bend out of the way. Humans are a mix of the two, trending towards hard. Octopii are all the way on the flexible end. To make octopeople, you'll have to remove the elements of human anatomy that prevent a human from being an octopus. This means bones and teeth will be removed in favor of a hard beak.
Most human organs are pretty squishy already. Repurposing the octopii organs or adapting the human organs for a much squishier environment would probably work just fine.
[Answer]
Please, PLEASE, excuse the crude artwork (I'm almost embarrassed to put it put up but this is all my work computer can do LOL). The second artwork below is ok.
The torso would have a rib cage. It would be the only part of the body with a solid skeleton. And it would made of cartilage which is more flexible than bone.
But be careful, those can still snap. So you still don't want your octo-humanoid squeezing through just any space. My cats are pretty big and can still squeeze through the smallest areas, but I wouldn't want them pushing their luck.
The rest of the body, even the head, could be malleable just like the body of an octopus.
[](https://i.stack.imgur.com/8LBHk.jpg)
Doesn't he look happy to be alive?
Cheers!
EDIT: I just wanted to come back and offer some better looking artwork. Your octo-humanoids might look like this:
[](https://i.stack.imgur.com/tAJ80.jpg)
Just imagine them with longer arms.
ENJOY!
Edit: A thought occurred to me. I had assumed that this guy was intended to be an underwater species. I'm not so sure he could live on land. Even with the rib cage most of his body would still be too malleable to run around on land, even with powerful muscles.
Anyone?
[Answer]
You simply can't build a creature like this that will work, the human breathing system is mammalian, and the mammalian breathing system has to have a rigid rib cage to generate negative pressure to inflate the lungs. so your creature cannot breath and that is just once function of one organ, before you get ot the issue of holding itself up or eating.
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Maybe you could use the "squishiness" of octopuses combined with a fantasy version of an exoskeleton (skeletal system on the outside, like bugs). By making the organs elastic and recoverably deformable (turning back to their original shape afterwards) and using something like a type of liquid that either hardens or temporarily hardens the skin and/or bones.
This could make it possible for these people to both go through small holes and have sturdiness for movement and/or protection.
I don't know of any animal that does this though. (I don't know how realistic this is supposed to be.) I do know however that fleas use a fluid for their high jumping ability and if we look at blood clotting this can harden and can biologically be broken down. If you then imagine tube-like structures with a valve and another valve that connects with an organ that causes blood to rapidly clot. Then when it fills with blood and the first valve closes and the second valve opens, releasing the fluid hardening the blood, you have more sturdiness. I would imagine that this would be similar to those balloon figures. I think this would however increase the volume, like when you blow up a balloon, so you would need pretty flexible skin.
For harder surfaces, pack them with lots of other structures like this that are perhaps a bit smaller and packed really really tightly together with higher internal pressure. Maybe make it analogous to how bones and tight, hard muscles work with us. Bones would be bone big hardened thing, while tight, hardened muscles are lots of small long thingies packed incredibly tightly together, which can sometimes get even harder than bones.
[Answer]
An interesting premise: what makes a human human, and not an octopus? What is actually the main difference?
If you want to combine the two - perhaps think of a human brain in an octopus body - besides lungs octopuses have all the organs that you have listed.
You mentioned though the octopus would have human skeletal structure - there is no need for this. Have a look at how species evolve.
We developed bones from essentially fish, which later became amphibious, and in order to more efficiently walk (or rather waddle) on land fins became arms and legs, lungs developed with ribcages, spines became harder. Soon we had hipbones to run faster and this then developed into us.
Would your creatures live underwater still? If so no need for the bones, they would be quite an impediment. But if the octopeople are on land - it makes sense a rigid structure is needed to stop us from flopping around, but then do we need 8 arms? You might find ironically that evolutionarily the Octopeople then end up just being like us.
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Pidgins generally arise between interactions with merchants, traders, and the like, while the elites would be far away in the capital, not haggling for fish with the foreigners. They tend to simplify their phonology, morphology, and vocabulary significantly.
In my world, the situation causing two groups to interact is quite different: there are humans and demons (think standard D&D Tieflings rather than metaphysical spirits), who live in different dimensions. Humans have figured out how to summon demons, but unfortunately they can't actually magically compel a demon to do their bidding. However, both races recognize that a cultural exchange would be valuable, so they are willing to engage in bargains. Here are some details about the situation:
* Typical magical high fantasy setting, both races have roughly equal technological/magical advancement, but they specialize in different schools of magic.
* Only mages can perform a summoning and be summoned, and mages are an elite class in
both races, so the participants are always high-class and well
educated.
* They are interested in the other race's knowledge and secrets, both arcane and scientific. So they need to be able to convey complex knowledge, and conduct very elaborate bargains.
(The exchanges are not always purely about knowledge, they might also give resources or perform magical feats in exchange for knowledge.)
* Both sides are also motivated to reveal as little as possible to the other side. They want to conserve fodder for exchange, and they don't want to give the other race too many advantages in case of an invasion. They would not let the other race send over an envoy to learn their language.
I envision that the interacting mages will devise some kind of pidgin/hybrid language. My question is, what kind of features might this language have, and where would it be similar or different to real world pidgin languages?
(I know about [code-switching](https://en.wikipedia.org/wiki/Code-switching) and [mixed languages](https://en.wikipedia.org/wiki/Mixed_language), but neither really apply since they occur when the speakers are fluent in both languages.)
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If communications are complex and exacting then you won't develop a pidgin, one side or the other (or both) will have to learn the others language.
Pidgins develop where communication is general rather than precise. It's not formalised and doesn't develop much of a vocabulary of it's own.
You may develop a specialised language, we have those right now for example legal, medical and scientific latin derived terms. But these are well defined and formalised in whatever vernacular they're used in.
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Merchants develop pidgin, as do subcultures and criminal elements. This is because the ideas needed to be communicated are simple.
Pidgin often arises out of an economic need. It happens when one society bumps up against another society with the economic means to elevate individuals. So you get cab drivers, local guides, porters, restaurateurs and the like who learn it.
pidg·in
ˈpijən/Submit
noun
a grammatically simplified form of a language, used for communication between people not sharing a common language. Pidgins have a limited vocabulary, some elements of which are taken from local languages, and are not native languages, but arise out of language contact between speakers of other languages.
The thing is, the more elite side of the equation doesn't generally speak pidgin, though they might understand it. They might learn to their benefit and pick up a few vocab words but...it's not an equal exchange generally. In the case of pidgin English, while their might be vocab from the other language, English will be dominant.
What you're talking about doesn't remotely fit in with this model, especially because you note it's going to be "complex." Both parties seem to be roughly equal in status, with neither having a gross socio-economic advantage, which is often found where pidgin is used.
I skimmed the comments, and they seemed to have picked up on exactly what I was going to suggest: a communication language that's entirely different from either side. Latin and French were used in this way in Europe. A sort of neutral language that both sides know.
They might pick up words here and there, but pidgin will only develop if there's a lot of "tourists" from one place to the other, making deals and the like. As secretive as everyone sounds, it's doubtful that either side would allow free passage like that.
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"How soon after "First Contact" would the stories be set?" is an important thing to answer about the details of the trade language that would arise between the "Human" and "Demon" sides.
The First Contactees on each side would likely contribute pieces of their own language to the trade language through necessity based on the primary language of the first traders. Words for objects, actions, and ideas that exist in the Human realm but not the Demon realm would be used in this trade language and vice versa. Things that exist in both could become an amalgam of each so that things could be more quickly understood by both sides. For example, the Human verb "sell" (as spoken by English-speaking Humans) equates to the Demon verb "kral" (as spoken by the Voorl clan Demons) and so the trade language initially uses the verb "sellkrall", but the Demon realm has no "apples" so that would simply be "apples".
Initial communications would likely be simple, "(Object) (Verb) (Subject)". After that, things would fairly quickly evolve to "(Adjective+Object) (Adverb+Verb) (Adjective+Subject)" and then into including conditionals and conjunctions. Also the amalgamated words might morph over time into simpler pronunciations to evolve into words unique to either original language. New terms would be added as needed and also by speakers of different languages on both sides as time goes by and trade expands.
If your intent is that neither side can learn the other's language in its entirety, there's not really much need to go further than that. Each side would continue to contribute new terms as needed over time. It's likely that some kind of Trade Association would arise on both sides if the Human/Demon trade becomes important enough to their societies and, depending on secrecy, might even decide to mix and match their native language chosen for the new words used just to keep things obfuscated from the other side. When one simple sentence in the trade language contains words originally taken from 3 different Human languages and 4 different Demon languages, it would make it very difficult to extract any kind of significant linguistic information that applies to anything outside of the trade language itself.
Over time, the Trade Language would continue to evolve, become more complex and could eventually be an entire language in itself. If the Human/Demon trade is important enough to modern society of either or both sides, it could even evolve into an important intermediary language that allows Humans to more easily speak with Humans of other languages, the same with Demons that speak different languages.
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The planet I have in mind is slightly larger than Mars and is located in the system behind a planet about twice the size of Earth.
~~The effect being almost like a solar eclipse that happens daily (If that makes sense).~~
EDIT:
I like the idea that they are **not** double planets but in separate orbits instead. Would this increase the possibility of the planet, which is the smaller of the two, and is further away from the system's star, having longer nights?
[Answer]
You're talking about a double planet (and may want to look at [this](https://worldbuilding.stackexchange.com/questions/82719/tides-on-a-double-planet) question).
The two planets have masses of 7M (twice the size of the Earth is about eight times the volume, but I'm allowing for more light elements to have been captured) and 0.15M respectively, so the ratio imbalance is about twice that of the Earth-Moon system; using Asimov's satellite criterion, ours is a double planet system.
If it orbited at the same distance of the Moon, Alpha being 7X as massive as Earth, Beta would complete one revolution in about $\sqrt{7}$ = 2.64 less time, giving 10.6 Earth days. To have it orbit every day, it must be $10.6^\frac{2}{3}$ = 4.827 times nearer, which means about 78720 km between the centers (62600 km between the surfaces), in geosynchronous orbit.
(The [Roche critical distance](https://en.wikipedia.org/wiki/Roche_limit#Rigid-satellite_calculation) for Alpha is $d = 1.442 R\_m$ or about 6000 km above the surface; so, while it would experience some remarkable tides, Beta would not disintegrate into a ring).
Supposing Alpha rotates once every 24 hours, has no axial tilt, *and Beta orbits on the plane of the ecliptic*, we are in a *tidal lock* situation - Alpha always shows the same face to Beta and passes directly between Alpha and its sun. Which means that during daytime, Beta eclipses Alpha, and half of Alpha is always dusk (either because it's a night illuminated by a full Beta, or because it's day and Beta causes a solar eclipse), while the other half of Alpha never sees Beta and has a normal 24-hour day cycle.
In this schema, Beta and Alpha rotate around their common barycenter in 1/364th of a 365-day year. So each year Beta "falls behind" by 24 hours, and more importantly, in six months it has fallen behind by 12 hours, and is now on the opposite side of Alpha. From the point of view of Alpha City, Beta moves in the sky by about one degree every day. When it is high in the sky at noon (right side), Alpha City is in totality and has 24 hours of night - so, more like *one or two months* of night. Then they have several months of *penumbra*. Finally Beta sets, and for four-five months you needn't worry and enjoy a normal circadian rhythm (while Counter-Alpha City on the other side of Alpha is in the dark); finally Beta is low on the horizon in the morning, prolonging the night with the penumbra of the oncoming eclipse.
[](https://i.stack.imgur.com/9mCUQ.png)
Having Beta counter-rotate, or being in a 3:2 or 1:2 resonance instead of a 1:1 lock, or in a different orbit, gives more complex setups with an alternance of "long" and "short" days.
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If you want to have long eclipses, you are looking for a modified version of Jupiter Galilean moons.
In their sky Jupiter is pretty large and the Sun pretty small, therefore the solar eclipses shade the entire planet. Since they also orbit around Jupiter, they are granted to get eclipses really often.
In certain locations of the moons one can be on the dusk side of the terminator right when entering the shadow cone: this would make the night last apparently longer than normal.
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Logically, no. I can't find direct evidence (yet), but it makes logical sense that this isn't going to be possible.
The question would be how a Mars-sized planet would create a global longer day if the current moon with half it's size can only eclipse about 100 to 160KM (<https://en.wikipedia.org/wiki/Solar_eclipse>), so the Mars planet would offer a shadow of 200 to 320KM eclipses. Unfortunately your planet is also twice the size of earth so the amount of surface area that can be covered is smaller.
Then we also need to cover the fact that a Mars-sized moon would need a faster rotation around the earth to prevent it from crashing into it, but not too fast because then it would just fly off into space. Even then you still have a rotation of days around the earth, anywhere between 13 to 20 days I would guess (normal Moon cycle of a bit more than 27 days). So only half of those days the Mars planet would be able to create an eclipse and "lengthen the night", even though it wouldn't be able to really create a global eclipse unless the sun it's orbiting is also extremely tiny and far away, which kind of pushes the planets outside of the goldilocks zone.
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This probably sounds fairly ridiculous- I know, but in short I've been developing a sort of future earth. It's not extraordinarily accurate, but I've been trying to at least keep the obvious in check. As far as I've seen, there's really no long legged semi aquatic animals, and it's easy to see why.
Still, is there any way one could develop in such way? Something like a cheetah in the process of adapting to adapt to a new environment, maybe in the very early stages? I've been using cheetahs as a reference, as the made up creature is built (somewhat) similarly. I considered if it could be initially an animal built for chasing down its prey, but another more successful species made that life style too hard for our "cheetah". This sent it to another niche, fishing, which its specialized form isn't built for exactly, but is changing rather quickly to adapt to.
This was the best I could come up with, but I honestly found it much too complicated to be plausible. Could something like this potentially happen, or is there an even more reasonable explanation? My end goal is to keep the creature relatively the same, with its long legs, longish muzzle, and small eyes and ears, but to also keep it along rivers.
[Answer]
Moose are very long legged and while most of them don't spend long periods of time in swamps, some do. In Northern Canada most moose spend the majority of the summer and early fall in swamps, often up to their necks to avoid mosquitoes.
Several types of [antelope](https://en.wikipedia.org/wiki/Sitatunga) live in swamp, while most of them tend to be on the small side, their legs are comparatively long to help them walk through the water.
With big cats, [tigers](https://www.youtube.com/watch?v=C8Q2ptLaFj0) are what you should be looking at for ideas. All tigers enjoy the water as a means to cool down, but some live in swamps full time. Their large paws help them move over the muddy ground, their fur keeps the water away from their skin and dries off quickly, and their long legs help them move through the water either by swimming or walking.
Having a cheetah forced to move into a swamp would generally mean the death of the cheetah. A cheetah would have many problems surviving, as they're sprinters and built as such, while the swamp is not really made for it.
However if it took long enough it's possible. They'd need wider paws, longer water repelling fur, and instead of sprinting more of a very fast leap or lunge would work better. Their attack style of moving very slowly towards the prey until the last second would help quite a bit, making them an ambush predator. Most likely they`d start out living on the fringe of the swamp stalking shore birds and animals coming for a drink, until enough generations had passed to allow them to adapt to living in the swamp itself.
Long legged animals can handle a swamp fairly easily, it's everything else that's a problem.
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So, I the question of what if a black hole hits the earth has been asked to death by various people, but what if the somewhat tamer wormhole hits the Earth?
In particular, we'll say that one mouth is floating somewhere in free space, and the other falls into Earth's gravity well. The radius of the mouths is 1 meter.
Note, that I am talking about a [traversable wormholes](https://en.wikipedia.org/wiki/Traversable_wormhole), as described by general relativity (note that they are predicted to not exist in our universe (hence the [alien-geometry](/questions/tagged/alien-geometry "show questions tagged 'alien-geometry'") tag), but are very well understood in the framework of general relativity). In particular, we are talking about an [Ellis wormhole](https://en.wikipedia.org/wiki/Ellis_wormhole). Here's a [video](https://youtu.be/SZDOKtT_QZE) in which physicists simulate one. Note in particular that "real" wormholes are very *different* from the wormholes usually presented in fiction. For example, they have spherical ends instead of circular ones.
[Answer]
Everything dies.
In fact, everything dies in a manner much more spectacular than [if you had crashed the moon against Earth](https://worldbuilding.stackexchange.com/a/103869/21222). Or Venus. Or even Saturn.
The physics and mathematics behind this are enough to fill a few books, but the short version of it only needs you to take a couple things into account:
* Wormholes have mass. Yes, even if they are the Ellis/Morris-Thorne variety - the famous traversable ones. Some people may think of them as just a topological feature of the universe, but they are more than that. They are stabilized by exotic matter, so [their mass is the mass of the exotic matter that keeps them stable](https://physics.stackexchange.com/a/292987/31264).
* [A one meter wide wormhole would require negative energy comparable to the mass-energy of Jupiter](https://arxiv.org/abs/1701.05533). This mass-energy would, for all practical purposes, be perceived by an observer as a one-meter wide object with one [jovian mass](https://en.m.wikipedia.org/wiki/Jupiter_mass).
Now let me tell you something about Jupiter. From the second link in the paragraph above:
>
> Jupiter is by far the most massive planet in the solar system. It is approximately 2.5 times more massive than all of the other planets in the Solar System combined.
>
>
>
What this means is that if you threw Mercury, Venus, Mars, Saturn, Uranus and Neptune against the Earth, with all of them colliding at the same time... It would still deal a few orders of magnitude less damage than that wormhole.
Suppose it does not impact on Earth. The very passage of that wormhole through our solar system in a flyby trajectory with a perihelion low enough to intersect Earth's orbit would be enough to end all life here. It would destabilize all planets' orbits. The pull on Earth would break the tectonic plates. We would see hitherto unseen extreme earthquakes and volcanic eruptions all around the globe, with the latter covering the skies with ash and toxic smoke. And in the very least Earth's orbit would become much more excentric in the aftermath, so any survivors either calcinate in a super summer or freeze in a super winter. In both scenarios, only microbes would have a chance of survival, and it might not be a good chance.
---
You probably wanted this question answered with a focus on the traversability of the wormhole, should it touchdown on Earth.
Well... An impactor with the mass of the Moon could probably make its way through more than half of the way to the planet core. An impactor with the mass of Jupiter might just go through the Earth from one side to the other like a rifle bullet going through a person.
Unlike a bullet though, the wormhole will drag Earth along its path due to its massive gravity. Remember, that beast has almost 318 Earth masses.
The distant mouth - the one that did not impact Earth - will spill a lot of planetary mantle, along with some planetary core and crust (and impurities such as gases, maybe a small part of the oceans, and a lot of organic material) at speeds measured in kilometers per second. Some bits have enough speed to escape the gravity of the wormhole.
On the side that did impact Earth... Well, the impact burst Earth to pieces like an egg that fell from an airplane. Most pieces will trail behind the wormhole, and given some millions or billions of years they may settle as a ring system around it. Some pieces are lost and will either orbit the Sun as comets or escape the solar system altogether.
[Answer]
Disregarding the mass/energy issue (where a wormhole weighs an insane amount). We'll just assume that the physical essence (the wormhole itself) of the wormhole has no effect on the universe other then allowing 2 distant places to be linked together.
My first thought was something like a giant vacuum cleaner.
>
> In particular, we'll say that one mouth is floating somewhere in free space, and the other falls into Earth's gravity well. The radius of the mouths is 1 meter.
>
>
>
Where the atmosphere blasts out of the end of the worm hole into space. But after thinking about this for some time. I realize that earths gravity may well transverse the wormhole too. So you may get some atmosphere shooting into space, but it could form a spherical ball around the wormhole (Assuming the wormhole is spherical in effect). Held there by earths gravity, at some point these two forces would probably equalize.
If the wormhole hit[was on] the ground, I doubt anything special would happen. I don't think much dirt and rock would get sucked out into the void just by the shear vacuum of space. Again, because earth has enaugh gravity to hold this stuff normally and just a 1 meter area of vacuum probably wont overcome that.
So if you allow the vacuum of space to transverse the wormhole, you almost have to allow gravity and anything else to transfer too.
Some of this depends on how you define
>
> other falls into Earth's gravity well
>
>
>
If you mean in orbit, this may not do anything. It's not like you can drain the gravity of the planet away. It might create a navigational hazard. At worst you would get a area on the opposite side of the wormhole that has a bit less gravity, like a stone in a river slows the river just behind the stone. This may be less noticeable the further away from the wormhole you go or there may be "hole" in earths gravity well where it's leaking though the worm hole.
Of course you could have a one way wormhole, I suppose.
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I've been toying with a concept for a hollow/inner Earth universe in which I would like to achieve an even distribution of light. The pickle is that the "sun" of this world operates like a beacon/spotlight that rotates on itself, so as to recreate a sort of day-night cycle. It should be clear at this point that we're crapping all over the laws of physics and that it's a magical/artificial kind of deal...
In this regard I have 2 questions :
* How should this beacon sun rotate in order to cover the ground of the whole three-dimensional sphere around it the most evenly ?
By this I mean for example : Let's say the sun rotates at 360° on only one axis (x) = 1 day : the world would be burnt daily along the equator and the poles would be stuck in a permanent oblique sunset dusk. That's no good.
* If such a rotation is possible, what would it mean in the grand scheme of things ? Would the poles and equator constantly travel around the hollow sphere ? Would there be seasons ? What would the sky even look like ?
Feel free to ask for more precision and please forgive me if I don't know the first thing about sphere geometry...
EDIT
Regarding issues of realism, I'm fully aware that there are factors that just wouldn't make this whole deal plausible. The closest thing I can imagine to the inner world I have in mind is Discworld : it's tilting on the back of four elephants with a magic field, yada, yada, yada... The reason why I inquire about it from a scientific point of view is to get a clearer idea of this big "what if" in the daily life of the characters that inhabit this place.
For the record, the spotlight is actually a giant eye, but that's beside the point.
* **Rotating the shell as well as the light** (credits to Dubukai) is an elegant solution, because it allows for extreme seasons (as well as badass mythology, you got that right, it's what the story's all about). I just might work with that, but it doesn't quite answer the question of even coverage. As stated, the poles would receive a lot more light than the frozen equator... which leads us to the second solution.
* **Axial precession** (credits to PipperChip) is something I've been trying to wrap my head around since yesterday (so I might have come up with stupid things). I gather that it allows a top to wobble on a different axis during its rotation, same as it causes the Earth's obliquity to oscillate, or a gyroscope to do...what it does best. This would basically allow our celestial body to tilt its axis whilst in rotation.
Where I got puzzled is that upon observing the earth or a top, the axial tilt changes by only a few degrees. If our spotsun behaved this way it wouldn't be even at all. Then I thought that nothing prevented that tilt from *increasing* progressively so as to span across the globe until north becomes south and vice versa (hence my earlier comment) at which point the light would describe a screw motion from one pole to the other. I believe with this figure, we do have an even coverage but a climate similar to the *shell rotating hypothesis*.
Then I figured I was getting this all wrong, since increasing the axial tilt still let the poles get most of the heat.
How about "unlocking" the axial tilt, since our star doesn't orbit around anything ? Can we allow the poles to translate across the lightsphere through this very tilt ? Here's a very crude, free hand drawing of what that might look like and some pig mathematics (also I'm desperate for a program that could simulate that more accurately) :
[](https://i.stack.imgur.com/Pf9Jn.jpg)
1. We have a north pole marked PN1 (the red cross) whose axis would tilt about 45° on the horizontal and 11.25° on the vertical with every rotation (aka day)
2. Instead of wobbling around the axis perpendicular to a non-existent orbit, it wobbles around the new North Pole PN2 and so on...
3. It takes 8 days for the the north pole to shift 360° on the horizontal and 90° on the vertical plan, describing a lovely spiral.
4. On day 9, the North Pole now sits on what used to be the equator, the figure should be the same as T1 and the cycle is ready to repeat itself.
I can't apologize enough for the utter lack of geometry in that thing. Let me know if there's any likeliness in what I described to something that might be remotely possible, or if I pulled all this out of my hat... :D
I'm still open to other ideas.
[Answer]
## Rotate the shell as well as the spotlight
If your hollow earth rotates around an axis that is perpendicular to the axis of your spotlight's rotation, you'll end up covering the entire globe with light occasionally. This is similar to a [polar orbit](https://en.wikipedia.org/wiki/Polar_orbit), which I've attached an image of below:
[](https://i.stack.imgur.com/yIzCe.jpg)
This is a single frame from an [excellent animation over at Wikipedia Commons](https://commons.wikimedia.org/wiki/File:Polar_orbit.ogv) that describes how this process works. We're looking at an inversion of this process, where the spotlight traces a circle within the shell as the shell rotates more slowly underneath it. By the time the spotlight has returned to the same latitude, the shell has rotated just far enough to place a new area in the way to receive the sunlight instead. In this way, it's possible to cover every inch of the inside of this globe.
## Consequences
I *really* like this idea because it sets up a lot of interesting natural things to think about.
### Luminosity levels
Let's consider what this would feel like if we were on this world. Assuming an atmosphere and some diffusion from the spotlight, what we'd expect to see would be a kind of decaying sinusoidal luminosity. Initially, we'd be in complete darkness, when we're as far as possible from the spotlight's path. As the path sweeps closer and closer, we'd see this kind of pattern emerge:
[](https://i.stack.imgur.com/uEvmg.png)
As the spotlight passes directly overhead, we'd hit maximum luminosity and probably be blinded and scorched by this heat and light ray. If we survive that, the luminosity would decay away again until it's completely dark again.
This sets up both days and seasons- "daytime" would be whenever the spotlight is crossing our line of latitude, at a local maximum, and nighttime would be when the spotlight is pointed directly across the globe, at the local minima. The seasons would be the longitude of the spotlight- when it's passing directly overhead or nearby, expect it to be *very* warm, and when it's 90 degrees away, it'd probably be quite chilly.
### What would the sky look like?
The sky would be mainly dark, with a single patch of illuminated sky. I'm not sure if your world shell is small enough to see the other side, so I'll consider both. If the other side can be seen, then you'd be able to see some portion of the globe illuminated at all times, which would look like a spot of light traversing the heavens- kinda like our sun. In this case, the "sun" would literally come to Earth as it passes over our location, which is just begging for some epic mythology. If we can't see the opposite side of the globe, then what we'd see would be very dark winters and very bright summers, as the atmosphere dissipates the light of the sun and makes it hard to see exactly what is producing the light.
### Climate
The most interesting thing here is that the due to the polar orbit and the fact that the spotlight sweeps over the poles every day, the *poles* would be very warm and the *equator* quite cold, with a nice gradient in between. I've mocked this up in the quick-and-dirty image below:
[](https://i.stack.imgur.com/yJDVJ.png)
As you can see, there's a lot of overlap at the pole (the center of this diagram) and some areas aren't directly touched at all (near the edge, aka the equator). This would set up the reverse of air and sea patterns that we observe on Earth, with heat transfer from the poles to the equator via rising, warm air and water near the poles and dense, cold air and water descending near the equator. There'd likely be a band of ice around the equator and tropics/desert near the poles.
## Final thoughts
It might take some time with pencil, paper, and Google, but I think you can absolutely get a stable ecosystem and planet out of this setup. And its very nature lends itself to some very dramatic storylines!
[Answer]
There are a few solutions you could go with here. I'm assuming your spotlight/sun has some way of directing it's light, to avoid having constant day for everyone.
# [Axial Precession](https://en.wikipedia.org/wiki/Axial_precession)
Assuming your spotlight is bright on one side and dark on the other, you can use axial precession to achieve night/day. This is where the axis of rotation for an object rotates as well. This kind of thing is seen in tops when they begin to slow down and "wobble" a lot. (Also, in planets. Anything that spins, really.)
[](https://i.stack.imgur.com/88l8o.gif)
In such a case, you will note that the top is still spinning about an axis of rotation, but then that axis of rotation more slowly rotates. If your beacon spins and "wobbles" at the right frequency and angles, you can get a very even amount of sunlight to the interior surface of your sphere. This results in no seasons, but a consistent day/night cycle for the interior.
To get seasons, you could have the light drift to one side of the sphere or the other in a cyclical way.
# Variable Light
Who says the great glowy ball in the sky has to always be on? Maybe different parts of it "shut down," or the light is inside a relatively large "cage" of shafts which prevent light from coming out unless that inside light is *just right*. This gives the opportunity for seasons: different patches of it glow at different intensities in addition to the day/night cycle.
[Answer]
I'm having a hell of a time following some of the suggestions here, it seems to me though that an obvious answer is to take the Niven Ring solution to day/night cycles.
[In the Ringworld series of books](http://larryniven.wikia.com/wiki/Ringworld), the titular Ringworld is a solid hoop of terrain one AU in radius around a star. It's one of the largest single structures in fiction with more surface area than the mind can comfortably conceive.
It's also wholly artificial.
Its builders ran into a very similar issue to yours, the star is always at high-noon at every part of the ring.
So to introduce a day/night cycle, there are "Shadow Squares". Giant rectangular panels orbiting much closer to the star, tied together with unbreakable filament wires.
These serve as part of a power-generation system as well as obscuring alternating regions of the ring. As they orbit, a given part of the ring experiences light and dark for a period of 30 hours.
For your case, you could have the sun surrounded by rotating bands of material which alternately obscure and reveal the sun for a given location on the surface, producing a similar ad-hoc day/night cycle.
Both systems come with the caveat that they don't have any kind of Twilight. Evening or Morning are extremely short and you can see the daylight approaching across the surface towards you.
[Answer]
A more particular possibility: if the sun doesn't radiate in all directions, but is a kind of spotlight, then why not making it a fuse-shaped spotlight?
In other words, let's say that the sun doesn't cast a circular light, but a different shape, elongated along the north-south axis (which is, the axis parallel to the rotation axis of the beacon) : this shape has the form of a fuse, so that at the equator the light is wider than at the poles, where it narrows itself until becoming a point.
This way, at the poles, even if the circunference is shorter than at the equator, the illuminated fraction of circunference will be the same. So, the total amount of light in a day could be the same at every latitude.
] |
[Question]
[
The recent total eclipse, got me thinking about how it would look in my world.
I have a earth-sized planet with a ring system, a couple of small moons and 1 or 2 bigger moons.
How would a planetary ring system affect the viewing of the total eclipse of any one of these moons:
* as seen from the planet surface?
* bonus - as seen from the ISS position?
I'm thinking there must be some interference of some sort:
* Would the position of the rings affect the light refractions, flares etc?
* would the reflection of the rings light up the planet facing side of the moon?
* Would there be absolutely no difference to what we saw recently?
I'm not looking for an artistist depiction (although if you have any handy graphics, please feel free to share) but a basic written description of the sort of differences one would see.
[Answer]
Since the availability of real photos are limited, I have taken a few screenshots from SpaceEngine, whose rendering and visualization I find to be pretty good.
Here is a shot of Titans shadow falling onto Saturn. Titan (just like the majority of Saturns moons) orbits within Saturns ring plane. The eclipse zone on the 'surface' of Saturn will most commonly lie along the intersection of Saturns orbital plane, and the ring plane, so the shadow will commonly lie across the rings as shown. The shadow from highly eccentric and/or remoter moons may miss the ring plane, as shown in the photo in the other answer.
[](https://i.stack.imgur.com/bPEs7.jpg)
From the surface of saturn, in the center of the shadow, it looks like this:
[](https://i.stack.imgur.com/Exs0m.jpg)
I'm not entirely convinced SpaceEngine is rendering the occuluded glare around the sun correctly. The center of the shadow is a tiny bit above the ring plane in the first screenshot, but in the second, the eclipse seems visible from much higher latitude. I think this is a more realistic visualization of the ring illumination when located at the center of the shadow, but of curse, the sun glare here should be obscured:
<https://i.stack.imgur.com/jJV42.jpg>
If I move the camera further out, inside the shadow cone, towards Titan, I need to be far beyhond the rings before titan fully eclipses the sun in SpaceEngine. I don't know what the relative size of Titan and the Sun are from Saturns surface, but it should be easy enough to calculate.
[](https://i.stack.imgur.com/TWpKL.jpg)
Here is a dramatic shot taken from a higher latitude, a bit outside the zone of totality:
[](https://i.stack.imgur.com/SSn37.jpg)
And a shot from close to the pole, with Titans position marked:
[](https://i.stack.imgur.com/95KK9.jpg)
Screenshots are taken from the free <http://spaceengine.org> program. Titans shadow on Saturns rings is one of the preset scenarios if you want to explore some more.
[Answer]
First of all, realize that the rings themselves cast their own shadow on the planet. Here is a photo of Saturn during a time that the sun is at a rather oblique angle.
[](https://i.stack.imgur.com/0teqb.jpg)
If you live in those shadows the sun appears obscured by the rings. The shadows are constant, but the effects at any one spot on the planet within tens of degrees of latitude (depending on the tilt) are going to be a *seasonal* occurrence. By that, I mean that the shadow starts as a rather fine line (as wide as the ring system) at the equator, sweeps northward to a northernmost position then back southward through the equator to a southern most position and then back to the equator again all within the period of one of the planet's years.
In this photo, a moon (I'm not sure which) is in the foreground but the sun is too oblique for it to cast a shadow on the planet.
Here is another photo with more direct (less oblique) sunlight:
[](https://i.stack.imgur.com/OuHxA.jpg)
In this photo, you can clearly see there is a shadow from a moon. If you were in that shadow you would, of course, experience an eclipse, but it is outside the shadow of the rings because the moon is quite a way outside the ring system, and hence there is no interaction of rings with the eclipse because they are in different parts of the sky.
Now, there are moons that are within the ring system, or rather their orbits lie within gaps in the ring system. There could be times where the sun is obscured by both a moon and rings at the same time. Certainly, there would be an opportunity for some very spectacular eclipses.
] |
[Question]
[
We have [escaped the galactic government](https://worldbuilding.stackexchange.com/questions/87034/now-how-to-escape-fun-loving-immortals), and now our greatest endeavour yet, life in space. How shall these gargantuan space entities move and travel through space?
* The whale or other in question is the same size or bigger than a
[blue whale](https://www.google.co.uk/search?q=how%20big%20is%20the%20biggest%20whale&rlz=1C1CHBD_en-GBGB739GB740&oq=how%20big%20is%20the%20biggest%20wh&aqs=chrome.0.0j69i57j0l4.16635j0j7&sourceid=chrome&ie=UTF-8)
* [The resources and food it needs are not a worry](https://worldbuilding.stackexchange.com/questions/87444/space-whales-how-to-survive)
* We do not need to consider the feasibility of such a creature
naturally evolving
[Answer]
1. **Surviving the vacuum.** Insects have exoskeletons which already make them more resistant to having their inner fluids boil away into the vacuum (as seen in [this video](https://www.youtube.com/watch?v=xPYbEaK6srE), where a spider and a fly survive a sojurn through the vacuum.
By luck these researchers found that if the exoskeleton is treated with an electron beam it makes a whole variety of insects more vacuum resistant. They called it a **nanosuit exoskeleton**.
from <http://phenomena.nationalgeographic.com/2013/04/19/nanosuits-allow-insects-to-survive-in-space-like-vacuum/>
>
> Normally, if you put an insect in a vacuum, it dies. Its bodily fluids
> are rapidly sucked out of its body, which then collapses inwards into
> a crumpled husk. This is why SEMs are used on already dead specimens,
> which have been specially preserved. But Takahiko Hariyama from
> Hamamatsu University School of Medicine found that fruit fly maggots
> can survive these harsh conditions.
>
>
> Bizarrely, Hariyama found that the microscope’s electron beam was
> somehow protecting the maggots. Indeed, if he turned the beam off
> before putting the insects in the vacuum chamber, their bodies
> crumpled in the usual horrific way.
>
>
> Hariyama’s hunch was that the energetic electrons fuse molecules in
> the larvae’s cuticle (its outer layer) into a defensive coating,
> creating a hard but flexible barrier over their bodies. This barrier
> is just 50 to 100 nanometres (billionths of a metre) thick, but it’s
> enough to stop gases and liquids from leaving the larva’s body. ...
> This technique protected ants, mosquito larvae, honeybees, and fly
> maggots in an SEM’s vacuum chamber. It even worked on a soft-bodied
> flatworm. The animals survived their experience, and most of the
> mosquito larvae even transformed into adults later.
>
>
>
This is what the space whales have too.
2. **Onboard oxygen supply**. There is nothing to breathe in space. Neither is there anything underwater and so this tactic comes right from the real life whale repertoire. Whales use a hemoglobin-like molecule called myoglobin to store huge amounts of oxygen, sustaining them for their deep dives. Your space whales will have even more myoglobin - grossy obese with huge internal lakes of it - to sustain them on their travels through the void. Exhausted myoglobin can then be metabolized for energy.
3. **Heat loss**. Things that make internal heat (like machines, or these exothermic space whales) get hot in space. It is a problem. The only way to get rid of heat is to radiate it away: without surrounding matter convection and conduction are not options. Or: you can concentrate your heat in dispensible matter and jettison the matter with the heat. This is what the whales do, with metabolic products and waste. Which leads us to
4. **Propulsion**. Every action has an equal and opposite reaction. To move forward while floating in space, you must throw matter behind you. This the whales do, expelling hot wastes (maybe heated to gaseous state) for jet propulsion.
I am pondering whether a gas vortex would be possible in space - I am thinking of those smoke vortex cannons in which the expelled smoke rings hold themselves together for a distance. If one can make a gas vortex in space then these whales definitely will be doing that. For communication purposes, of course; in space, no-one can hear you sing.
[Answer]
How do space whales move? With great difficulty is the simple answer. The medium of space is too low density for an astrocetacean to swim in any way that resembles the motion of a whale in the ocean. Relying on conventional physics this only leads rocket propulsion.
The higher the velocity a space whale wants to attain it must exhaust large amounts of reaction mass or its exhaust velocity must be sufficiently high. if a space whale wants to reach a given velocity equivalent to its exhaust velocity then its mass ratio, which the ratio of reaction mass expelled over its final mass, will be approximately a factor of two. Note: this is an approximation value used for illustrative purposes where precision is not a requirement.
Chemical rockets have exhaust velocities of about four (4) km/s; a fusion rocket will be roughly 0.1 c (or 30,000 km/s); photon rockets is 1 c.
For a space whale to move it needs to have a propulsion system incorporated into its body. Chemical rockets are moderately feasible for a living creature (but with lost of caveats). The main drawback is it will take a space whale extremely long time periods for it to travel anywhere, even in a planetary system, let alone interstellar distances where the mass ratio would be massively prohibitive.
[](https://i.stack.imgur.com/ofdUP.gif)
Chemically propelled space whale might start off with the mass of a blue whale but it would be reduced to the size of a sardine after boosting to its cruise velocity for modest interstellar trip. Many interplanetary excursions wouldn't be much better.
Fusion propulsion means space whales would need to incorporate fusion reactor technology into their bodies. A space whale now resembles what it will need to be, namely, a cyborg spacecraft. Fusion propulsion will involve low rates of acceleration. Roughly one centimetre per second squared. Interplanetary travel is feasible, while interstellar travel will be at its limits and probably infeasible.
Photonic propulsion requires incorporating serious technology into a cyborg space whale (it is unlikely there will be any other kind) and extremely dangerous too. They effectively need antimatter power systems to make them work well enough to be useful. So unless someone is prepared to feed space whales antimatter this is improbable.
Space whales are part of a highly advanced galactic civilization. Undoubtedly they would to be created from a combination of synthetic biology and cyborgization. This civilization has fast FTL travel technology. Possibly, the creators of the space whales will have equipped their space whales with FTL drive-systems. Once again whatever power systems are required will have to be part of their bodies.
This will enable the space whales to travel rapidly from one location hospitable to their survival to another. Otherwise their travel times will too long for their survival. Although space whales may need to go into a state of cryptobiosis while in transit.
The next level of locomotion for space whales requires consideration of exotic physics. The best example of which is the application of [negative mass](https://en.wikipedia.org/wiki/Negative_mass).
>
> Although no particles are known to have negative mass, physicists
> (primarily Hermann Bondi in 1957,[5] William B. Bonnor in 1989,[11]
> then Robert L. Forward[12]) have been able to describe some of the
> anticipated properties such particles may have. Assuming that all
> three concepts of mass are equivalent the gravitational interactions
> between masses of arbitrary sign can be explored, based on the
> Einstein field equations:
>
>
>
> ```
> Positive mass attracts both other positive masses and negative masses.
> Negative mass repels both other negative masses and positive masses.
>
> ```
>
> For two positive masses, nothing changes and there is a gravitational
> pull on each other causing an attraction. Two negative masses would
> repel because of their negative inertial masses. For different signs
> however, there is a push that repels the positive mass from the
> negative mass, and a pull that attracts the negative mass towards the
> positive one at the same time.
>
>
> Hence Bondi pointed out that two objects of equal and opposite mass
> would produce a constant acceleration of the system towards the
> positive-mass object,[5] an effect called "runaway motion" by Bonnor
> who disregarded its physical existence, stating: “ I regard the
> runaway (or self-accelerating) motion […] so preposterous that I
> prefer to rule it out by supposing that inertial mass is all positive
> or all negative. ” — William B. Bonnor, in Negative mass in general
> relativity.[11]
>
>
> Such a couple of objects would accelerate without limit (except
> relativistic one); however, the total mass, momentum and energy of the
> system would remain 0.
>
>
> This behavior is completely inconsistent with a common-sense approach
> and the expected behaviour of 'normal' matter; but is completely
> mathematically consistent and introduces no violation of conservation
> of momentum or energy. If the masses are equal in magnitude but
> opposite in sign, then the momentum of the system remains zero if they
> both travel together and accelerate together, no matter what their
> speed:
>
>
>
The main problem with negative mass "runaway motion" drive systems is how to generate the negative mass necessary to propel a space whale. This may be cavalier, but a galactic civilization of the kind postulated by this question should have solved that problem long ago in its history. In fact, they might find it to be quaintly old-fashioned.
In summary, space whale will be cyborg spacecraft. They could be propelled by fusion rocket propulsion systems (a feasible future technology in terms of current science and engineering) or the more exotic negative mass drive system (conceptually plausible, but relies on the existence of the hitherto undiscovered negative mass).
] |
[Question]
[
Back home, the Tibetan Plateau averages 4,950 meters above sea level with its highest point being Mount Everest, 8,848 meters--29,029 feet--above sea level. At such heights, problems are resulted as listed:
* The air becomes cold, dry and most importantly, **thin.**
* The Himalayas are so tall that they bar off the monsoon winds from reaching Tibet, turning the plateau dry enough for grasslands to dominate it.
* The most serious problem is that a thinner air means greater vulnerability to ultraviolet radiation.
Fortunately, complex life--plants and animals--find ways to deal with these problems. As a result, Tibet is alive with wolves, bears, snow leopards, yaks, asses, antelope, cranes, vultures, hawks, geese and even snakes. Of course, the one Tibetan that stands out above the rest is a species aptly called the "high-altitude jumping spider".
Now in this alternate Earth, Tibet is taller--6,000 meters above sea level on average, with the tallest point being 10,211 meters--33,500 feet--above sea level. At such heights, the three problems listed above become even more pronounced, which raises the pressure in regards to residing there. Can plant and animal life still flourish in this taller Tibet, or are our Tibetans currently living at the top of their limits?
[Answer]
**Plant and animal life on the plateaus: Yes.** The air pressure will be roughly 15% less than in the real world. I have no doubt that plant and animal life *in general* will survive.
* The height of the [tree line](https://en.wikipedia.org/wiki/Tree_line) depends on the wind in addition to pressure. Above the treeline there are lesser plants.
* Birds can reach well over [8000 m](https://en.wikipedia.org/wiki/List_of_birds_by_flight_heights).
**Human life on the plateaus: At least briefly.** The lethal altitude seems to be between [7000 to 8000](https://en.wikipedia.org/wiki/High-altitude_adaptation_in_humans#Origin_and_basis) m, except for exceptional individuals and brief periods.
**Mountains vs. Plateaus.** In the real world, altitudes above 6000 m combine the effects of low pressure with a mountain slope. This complicates finding shelter, areas to grow food crops, etc. Your fictional plateau should be more hospitable than a real-world mountain at 6000 m.
[Answer]
## It will be tough
I am not a doctor or an expert on the topic, but I cannot find any sources for permanent acclimatizing by **humans** above 5500 meters.
[La Rinconada](https://en.wikipedia.org/wiki/La_Rinconada,_Peru), in Peru, is the highest known permanent settlement, and it's only at 5100 meters.
Military studies show no adaptation and continuous degradation of functionality above 5500-6000 meters, with the death zone starting around 7000. There is a good source from the [US Army here](http://archive.rubicon-foundation.org/xmlui/handle/123456789/7976). Admittedly, this is under the stress of military opeartions, but about 20% of military personnel seems to develop HAPE (potentially fatal bleeding in the lungs) operating over 5000 meters.
Above 6500 meters, sleeping becomes very difficult, digesting food is near-impossible, and the risk of HAPE increases greatly.
As far as **vegetation** goes, you're either in the nival (permanent snow) zone or in alpine desert territory. You're unlikely to get anything beyond lichen and maybe a few scattered grasses. It'll be mostly gravelly desert.
Whether it will be ice or desert is determined by latitude and the prevailing winds. But to put things in perspective, even in a tropical context with wet winds you're likely in a alpine desert situation above 4500 meters or so. Obviously in temperate and boreal mountains the permanent ice cover will be much lower.
[Answer]
At 6000m, you will have a problem.
In Tibet, this altitude is dominated by snow zone. While people and animals can visit it, there is no vegetation, and no open ground agriculture is possible. Life on such plateau will occupy only valleys with lower elevation.
P.S. In case of low precipitation, the plateau would have more alpine deserts and less snow, however it's still the problem to have any noticeable vegetation.
[Zonation case study](https://www.climate-policy-watcher.org/ecological-limits/zonation-case-studies.html)
] |
[Question]
[
In my world there is a kingdom built on hexagonal pillars like you see at the giant's causeway. Your social status is based on how tall the pillar you live on is. Sort of like the image below.
[](https://i.stack.imgur.com/YZJFs.jpg)
The pillars would be 30-50 meters across, would it be possible for a rock formation like this to form at that size?
[Answer]
Devils Tower
[](https://i.stack.imgur.com/kFtCc.jpg)
from <https://media.nationalgeographic.org/assets/photos/000/265/26550.jpg>
from <https://pubs.usgs.gov/bul/1021i/report.pdf>
>
> One of the most striking features of the Tower is its polygonal
> columns (fig. 53). Most of the columns are 5 sided, but some are 4 and
> 6 sided. The larger columns measure 6 to 8 feet in diameter at their
> base and taper gradually upward to about 4 feet at the top.
>
>
>
8 feet in diameter is bigger than a half meter; big enough to pitch a tent. But not big enough for some swanky mansion. You could however have several columns in aggregate that presented a 40 foot diameter surface. Or one could have multiple Devil's Towerlets.
Or you could just assert that they did get as big as you want them to be, because I gather your story is not a geological treatise. Something that is big can always be made bigger in fiction. That is one of the chief uses of fiction.
[Answer]
That rock formation is called [columnar basalt](https://en.wikipedia.org/wiki/Basalt#Columnar_basalt). As you can see [here](https://en.wikipedia.org/wiki/List_of_places_with_columnar_jointed_volcanics) columnar basalt can form in many different sizes. How large these columns become is dependent on how slowly the lava that formed them cools. The slower the basalt cools the larger the columns that may form. It is possible, though unlikely, that if the lava cooled **extremely** slowly it could form pillars 30-50 meters accross. On earth we haven't observed any pillars much over 2 meters wide.
] |
[Question]
[
My colonists have been terraforming a planet for centuries. They chose this exo-planet for its many earth-like qualities (size, gravity, Goldilocks zone, volcanos, similar sun). However, it is like the Earth of 400 million-ish years ago. The atmosphere has lots of nitrogen but not much oxygen. Also, a great deal of water is tied up in glaciers though there is some very basic plant life near the equator. The oceans have lots of critters but it is a lot less ocean than Earth. There are “red beds” indicating that all the minerals that could have reacted with free oxygen have already done so.
They have been using solar collectors and mirrors to melt the glaciers. This puts a little oxygen into the atmosphere by splitting the H’s and O’s. Mass plantings of genetically modified organisms have also increased the oxygen. The gardener in me wants there to be legumes to fix the nitrogen in the soil for future use by farmers.
The people live in domes on the moons of this planet, a space station, and domes on the planet surface. They really want to spread out and use this beautiful planet.
**My question: Is it plausible that they could get the oxygen level up to 21% (like Earth) in a few centuries. Will they be able to stop it at the right number?**
These two articles were helpful in getting at how Earth’s atmosphere developed but so much of the timeline described involves waiting for specific organisms to evolve. The colonists have Earth plants and a talent for GM which should help a great deal.
Evolution Of The Atmosphere: Composition, Structure And Energy
<http://www.globalchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/evolution_atm/#>
The Mystery of Earth’s Oxygen
<http://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html?_r=1&&module=ArrowsNav&contentCollection=Science&action=keypress®ion=FixedLeft&pgtype=article>
[Answer]
## Photosynthetic algae
One of the first great extinction events of our world was the [mass oxidation of the atmosphere](https://en.wikipedia.org/wiki/Great_Oxygenation_Event) by cyanobacteria (among other organisms). From the Wikipedia article: "For example, at today's rates of photosynthesis (which are much greater than those in the land-plant-free Precambrian), modern atmospheric O2 levels could be produced in around 2,000 years."
What this means is, in 2,000 years, with no effort other than adding an Earth-like amount of plants, you could get the atmosphere you want. But how would we do better? Enter photosynthetic algae. On our world, algae is kept in check by filter-feeders (shellfish, for instance) and a lack of free nutrients. On your world, presumably there are no filter-feeders. So, dump acres of algae into the newly-forming oceans. A lot of accidental algae blooms are caused by fertilizer runoff into waterways, so add fertilizer. This would vastly reduce the time it takes to convert CO2 into O2.
Figure out a way to *clean this up* after the fact, and you're golden. Either add filter feeders, or make them dependent on the fertilizer would be my strategies.
Another possibility is [base-six DNA](https://www.wired.com/2014/05/synthetic-dna-cells/). As long as you continue to supply the extra base pair in your fertilizer dumps, the genetically modified algae will survive. Stop supplying it and it dies almost immediately. (Thanks to Draco18s for the base-six DNA idea!)
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Yes. If they pump up CO2 into the atmosphere in sufficient quantities, the global average temperature will raise and the glaciers will melt. The resulting wetter, warmer, C02 rich climate will be excellent for plants.
A quick search online found this paper: <http://rstb.royalsocietypublishing.org/content/314/1167/523>
GMOs will have much higher rate of spread, in a few hundred years they could easily cover the whole planet in woods thus sucking up the C02 and replacing it with oxygen.
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I'm building a small, naturally inhabited world where usable water is scarce or difficult to access. Is it possible to have a planet with groundwater, ice caps, temporary rivers and lakes, seasonal rains and fog, but no permanent oceans? If so, where might clouds etc come from? Could there be evaporation from shallow, temporary or constantly moving water bodies? Or could significant amounts of moisture be released into the atmosphere directly from the ground, say in steam vents?
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## Put the oceans underground
[Many moons](https://en.wikipedia.org/wiki/Extraterrestrial_liquid_water#Liquid_water_in_the_Solar_System) are theorized to have vast, underground oceans. If you want water to be scarce on the surface, but you need a supply regardless, keep the water in big caverns below the surface.
[Cryovolcanic](https://en.wikipedia.org/wiki/Cryovolcano) activity - eruptions of water from geysers or "volcanos" - can provide temporary rivers, lakes, and ponds, before the water trickles back down.
[](https://i.stack.imgur.com/PQNQx.jpg)
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## TLDR: Have an ocean at the equator to start with, then use a catastrophic event to move your orbit slightly closer to the host star. As a result your planet could be too hot at the equator for liquid water but too high at the poles so all the water runs in rivers from the poles to the equator where it evaporates again.
Naturally this answer is all based on our one and only researchable planet that supported life. Perhaps there are many other ways for life to evolve and a dry surface suits some types too. However on earth the oceans have been pretty pivotal for [many reasons](https://en.wikipedia.org/wiki/Abiogenesis) but mainly focusing on the process of mixing chemicals - early life wouldn't have had to search for it's food but instead be living in a constantly mixing solution of it.
So all our models suggest that the oceans are pivotal in the origin of life, however this isn't to say your oceans still need to be around. Once life has evolved to walk on land we could have some **celestial disaster**, one of the outer planets in your solar system moving inwards (possibly as outlined in [answers to this question](https://worldbuilding.stackexchange.com/questions/66267/what-major-event-could-disrupt-planet-earths-orbit-around-the-sun?noredirect=1&lq=1). If the orbit was disrupted so your planet now lay closer to the sun you could find it too hot at the equator to support liquid water but the poles may be just about cool enough.
If your equator was at sea level originally and the poles were not the water which rains down on the poles would run in rivers headed towards the equator, then boil off as they reached it.
This would provide the necessary water cycle but without allowing large bodies of standing water.
However we do have the problem of keeping your life alive. The disaster would be a mass extinction event resulting in:
* Any fish (and in turn anything that lived on fish) would die.
* Almost all plant life would die (extremely limited food source now) - desert plants which had already evolved would be best suited to survival, being carried by animals migrating to the poles is the most likely method of dispersion this far.
* There would be a mass migration towards the poles (interestingly providing reasons for having splits in evolutionary trees).
* Water would be scarce and most likely result in life with adaptations like the [camel's hump](https://en.wikipedia.org/wiki/Camel) and [deep roots for plants](https://www.ooklnet.com/web/read_more/95241/Convergent+evolution+-+Desert+Plants) since water would still be present deep underground.
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## The world is tidally locked, with mountains at the middle
The same side of the planet [always](https://www.spaceanswers.com/deep-space/what-is-tidal-locking/) faces the sun, kind of like how we always see the same face of the moon. That means one side of the planet will always be incredibly hot - perhaps too hot for water - and the other will be incredibly cold - making it freeze.
Life can live in the habitable zone in a vast mountain range, kind of like the one on [Iapetus](https://en.wikipedia.org/wiki/Equatorial_ridge_on_Iapetus) - that will prevent large oceans from forming.
[](https://i.stack.imgur.com/YBN1J.jpg)
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## [Apsidal precession](https://en.wikipedia.org/wiki/Apsidal_precession)
This cycle changes the orbit of the planet over thousands of years. It can cause changes in the world's climate, causing warming - if the water is frozen - or cooling - if the world is too hot.
I'm not an expert, but it seems reasonable for the planet to have a shorter cycle - allowing some water to flow, but preventing the formation of a longterm ocean.
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On my *fictional planet* humanoid aliens have evolved on one continent, and have since spread around the entire planet, just like humans did on Earth. On Earth humans have since developed slightly different physical attributes, such as skin color, nose size, ear size etc; therefore for the sake of realism I too want this to happen on my planet as well.
But my question is now: **How long would a large sustainable group of my *humanoid aliens* need to live *separately* from any other group before they developed a *notably different appearance* than that of another group of humanoids -- provided that they were identical to start with.**
Based on these assumptions:
*My planet* is compatible to Earth, i.e., the same distance from the sun, same temperature, same gravity and same variations in temperature, radiation and other things which may influence the rate of which my humanoids change. Furthermore all the biomes and ecosystems of Earth are present (more or less). I am however both interested in how fast these physical attributes would develop in similar and different biomes.
*The humanoid aliens* look, behave and reproduce just like humans -- for the sake of simplicity.
With *separate* I don't mean complete isolation; the different groups may still trade with one another, and there may still be some genetic exchange along the trade routes; I simply mean that the majority of the population -- who presumably live as farmers or fishers -- are never brought into contact with other population groups. (The separation may also be separation by time, since I intend to follow the development of this society through at least ten millennia)
Since I intend to use this world in a computer game (which mostly should be first person) a *notably different appearance* therefore is one that the player can easily notice even from quite a distance, like for instance a different skin color, or a 2 centimeters different nose size. Therefore -- and because each set of physical attributes will require me to save some data -- I consider any height difference of less than 5 cm, a face feature location difference less than 1 cm or a skin or hair color hue, saturation or brightness difference of less than 0.1 (if all goes from 0 to 1) to not be a notable difference (because it will be within range of the automatically generated random variations).
(BTW) I am interested in how quickly the physical attributes will change, not how they will change
(as response to a comment: in this specific case i care only about genetical physical attributes, not man-made physical differences, such as clothes, tatoos, or any other attempt by my humanoids to alter their appearance)
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Note: The OP has significantly altered the question. This answer is no longer fully relevant. See the section "Physical varieties" for an attempt to answer the OP's new question.
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## Ethnicity
Ethnicity is a *socio-cultural* attribute. You are speaking about *physical* anthropological attributes, which, contrary to what Hollywood would have us believe, are *not* linked to ethnicity.
There are blond Germans and brunette Germans, light-skinned blond Turks with blue eyes and dusky Turks, blond Afghans with blue eyes and stereotypically "central Asian" Afghans, blond Russians and brunette Russians, blond Italians and "Mediterranean" Italians. Mediterranean-looking Italians look exactly like Mediterranean-looking Greeks, and some Turks, and some Spaniards, and many Maltese etc. Blond Italians look just like the stereotypical Germanic. See a massively politically incorrect map at [*Racial Realities in Europe*](https://www.amfirstbooks.com/IntroPages/ToolBarTopics/Articles/Featured_Authors/Stoddard,_Lothrop/Works/Racial_Realities_In_Europe/RRIE-01_Racial_Realities_in_Europe.html) (Lothrop Stoddard, 1924), chapter 1; more such old-fashioned (and today known to be much less meaningful that their authors thought) maps on [Wikipedia](https://en.wikipedia.org/wiki/Nordic_race).
Ethnicities develop quite quickly (even one century may be enough in the right circumstances, or even less in exceptional circumstances) based on shared language, economical and political links, and geographical proximity. Physical attributes take a lot longer (several millenia) and require a high degree of reproductive isolation.
## Physical varieties
To grasp how long it takes for human geographical / physical varieties to form one may consider *how stable* those varieties are. Forget about skeletons and mummies: we have realistic sculptures, paintings and drawings from Europe, North Africa (mostly Egypt, but also elsewhere), the Levant, Mesopotamia, Persia, China and other places spanning the last three or (in Egypt) four millenia. When we look at those portraits and statues we see people *just like us*, people showing the same physical types as those which exist today; and yet those portraits and statues are thousands of years old.
The following is a pathetically incomplete list:
* The Egyptians left many detailed and realistic images and statues, such as the famous bust of [Nefertiti](https://en.wikipedia.org/wiki/Nefertiti), the well-known [seated scribe](https://en.wikipedia.org/wiki/The_Seated_Scribe), the pharaoh [Menkaure](https://en.wikipedia.org/wiki/Menkaure) (Mykerinos) and his queen and many many others.
* The [Fayum portaits](https://en.wikipedia.org/wiki/Fayum_mummy_portraits) were made "from the late 1st century BCE or the early 1st century CE onwards" (Wikipedia). They are detailed and realistic; many of them are very beautiful; they show [how varied](https://www.google.com/search?q=fayum+portraits&tbm=isch) was the population of Helenistic and Roman Egypt. When we look at those 2000 years old portraits we recognize immediately the Mediterranean type, the Levantine type, the North African type; those physical types appear to have changed very little, if at all, during two millenia.
Portrait of a young woman, one of the spectacular [Fayum portaits](https://en.wikipedia.org/wiki/Fayum_mummy_portraits) made in the first centuries of the common era.
* The Romans left many [portaits](https://en.wikipedia.org/wiki/Roman_portraiture) "characterised by unusual realism and the desire to convey images of nature". Among many others, we have excellent images of the emperors, of course, including for example [Julius Caesar](https://en.wikipedia.org/wiki/Julius_Caesar), [Trajan](https://en.wikipedia.org/wiki/Trajan) (who was from Iberia), [Philip the Arab](https://en.wikipedia.org/wiki/Philip_the_Arab), [Diocletian](https://en.wikipedia.org/wiki/Diocletian) (from Dalmatia, the eastern coast of the Adriatic), and [Maximinus Thrax](https://en.wikipedia.org/wiki/Maximinus_Thrax) (from Thracia, modern nothern Greece and Bulgaria).
* From China we have realistic pictures and statues dating from the 2nd and early 3rd century, such as, of course, the [Terracotta Army](https://en.wikipedia.org/wiki/Terracotta_Army).
Gentlemen in conversation, Eastern Han Dynasty (25-220 CE) (from [Wikipedia](https://en.wikipedia.org/wiki/Chinese_painting))
Since physical types are stable and apparently unchanged over millenia we can obviously assume that they took many millenia to form. Humans are known to be rather promiscuous, with gene flow occuring between populations at the slightest opportunity. Only massive barriers, such as deserts or enourmous distances, can slow the gene flow enough to permit the development of visibly different physical types. Consider the west-to-east gradient in Eurasia: a person from Gaul may be quite different physically from a person from [Sichuan](https://en.wikipedia.org/wiki/The_Good_Person_of_Szechwan); but in the enourmous space in between the physical types intergrade clinally.
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There isn't a nice short answer to this question. What you are talking about is pretty much subspeciation. No, I'm not trying to start a race discussion or somehow imply that one population is a different species than another population. Please don't come back with comments about how Aztecs and Vikings and Asians can be indistinguishable. I know! People are people.
So back to trying to answer your question. Genetic variations occur for several reasons: predators, food, geographic separation, etc. These variations can occur extremely quickly as in the case of the [peppered moth](https://en.wikipedia.org/wiki/Peppered_moth_evolution). It went from mostly white colored to mostly black colored in under 100 years! With only one generation per year, this means it took less than 100 generations. There is also mounting evidence of a new species of mosquito forming in the London Underground. The first tunnel opened in 1863, so it is presumably been evolving for only ~150 years. However, I'm fairly certain these mosquitos have several generations of offspring each year so it could be as many as 300, 600, or even 1200 generations of adaptation.
On the other hand, people have lived in Europe for tens of thousands of years, and like AlexP points out, Germans, Turks, Afghans, etc can be indistinguishable based on appearance. The amount of time it will take for your group of aliens to have a generally different appearance (eg, generally Asian looking vs generally African looking) will depend on the evolutionary pressures the group faces. You state it is a large group, so it presumably has a lot of genetic variation (eg, several different families vs. say, Noah and his family). This great variation to start will increase the amount of time it takes for noticeable traits to appear. You also mention that trade occurs between the groups, so surely there will be some genetic mixing that occurs (sailors and brothels!). This will also prevent a lot of genetic variation. So, that leaves you with fewer options for creating noticeable variations. For example, you might use predators that eat a specific portion of your population (like the slow ones or the ones that are predisposed to sex acts with poisonous cacti), or you could give the new population access to a highly nutritious (or even UN-nutritious) food source. Or, you could make the fruit on the trees hang a little higher so those with naturally longer arms are able to feed themselves better (and thus thrive). But at any rate, this will still likely take thousands of years because of the large starting population and the continued contact with other populations.
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It depends greatly on several factors:
How much variation is present in the gene pool? If they have not been bottlenecked, expect much more than we humans have.
Is their development very *plastic*? Look at the great difference in dig breeds: something about their genetic structure makes it easy to make such variation. If your species did that, expect radically different breeds in just a few generations.
How isolated are they? You need to prevent the “genetic bucket chain” in order to allow incompatibility to take root.
So, look at the result you want, and fiddle with the factors to allow for that. Point out how/why that’s different from humans, and more like dog breeds or some example of ring species, etc.
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Or more simply, how do octopuses think? I'm designing a race of intelligent-but-primitive cephalopod aliens and while I want them to exhibit some basic human traits such as fear, self-interest, a social hierarchy, language, zealotry and religion, I'd also like to avoid the pitfall of making them too human. So to that end, I thought I'd take time to consider how their evolution and physiology might affect their psychology, and then work in history on top of that. The problem is, I don't really have any understanding of how an octopus on Earth might think compared to a human. I'm aware that this is a question without any really good answers since scientists are still struggling with this line of inquiry themselves, but a rough idea or even conjecture about how a creature that's evolved distributed intelligence might think differently than a human would help a lot.
A few cliff-notes about this species: they're blind but communicate via bioluminescence using light-sensitive proteins in their skin (to compensate for the total darkness of Europa's oceans; fully-formed eyes would be relatively wasteful), they lack both the pigmentation and chromatophores present in most Earth species, they're about as large as a pacific giant octopus, possess a large quantity of cilia lining their arms around their suckers that they use for fine manipulation and to signal complex ideas requiring elaborate color displays, and their society is highly religious, revolving around the worship of a single omnipotent sea god (I can explain this in further detail if you think it's relevant, but I'm trying to focus on the purely biological aspects right now).
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## Process for developing octopoid psychology
The OP doesn't provide enough information about the octopoid's evolutionary history, so I'll describe a process for figuring it out. This process is based on the observation that a long evolutionary history will impart a great many survival traits to how a creature thinks and that these traits may persist for tens of millions of years.
1. Figure out the most basic and primitive life form on this planet.
2. Trace milestone species from this first life form to the current octopoid.
3. Describe in as much detail as desired what physical and mental attributes each of these creatures possessed to thrive. These might be as simple as "can think in 3d", "has bones", "understands concept of in-group".
4. For each milestone, you'll need to work out the creature's environment too since this is critical in deciding fitness.
5. Each of these intermediate life forms will have something that makes them competitive in their environment. We see that decedents will share this attribute unless the attribute is counter-productive. While working through the evolutionary chain, sum up the mental traits that the creature has inherited plus any new attributes that make it more competitive.
6. After summing up the mental characteristics, you should have a pretty good idea of how this octopoid came to be and why it might behave in a certain way.
You don't need to make an evolutionary tree as complicated as the one below but be aware that new species can pop up in as little as 100,000 years.
[](https://i.stack.imgur.com/I9Il8.jpg)
[Photo Credit](https://www.edwardtufte.com/bboard/images/0003ti-11699.gif)
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It is my opinion that the answer to this (very good) question is yours to develop. This is an area where the science-fiction author is free to hypothesize and assert to explore what could be possible because we simply don't have science data to fill it in. This is akin to the 1800s trip-to-the-moon literature assuming an aether in space.
Dream something up and give your readers a new idea to ponder.
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As senses change in priority (how much of the nervous system they take up; how much processing is devoted to them; e.g. how much the organism depends on them), so too will qualia associated with those senses rise to prominence in consciousness. This is discussed in Nagel's [What Is It Like to Be a Bat?](http://chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://organizations.utep.edu/portals/1475/nagel_bat.pdf) .
The distribution of intelligence is more difficult to discuss because we are uncertain about the level of disconnection occurring. The intelligence of a superorganism such as an ant colony obtains conscious expression nowhere obvious in the whole of the system that we can see. The octopus of earth, its appendages more autonomous than many other animals', no doubt experiences things quite differently from us, but we may say that its unitary conscious experience (or the impression thereof) probably derives from the processes in its central brain. Yet what of the arms' experiences? If they can be said to have them, perhaps these are related to the central brain in the form of a conversation of some sort - faster and more intimate than normal linguistic exchange between separate persons, but less unitary than the experience I have when I am told I am in pain by a receptor array in my leg. In short, we might dimly imagine the experience is something like [two twins talking together.](https://en.wikipedia.org/wiki/June_and_Jennifer_Gibbons)
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Here's the background. I'd like the planetary year to be just under 800 days, with a longer number of hours per day-cycle. If the settlers live in the Mediterranean type climate area only and use greenhouses in addition to outdoor farming, could there be enough atmosphere and gravity to make scientific sense?
The planet was selected to allow human life. There is drinkable water, breathable air and enough gravity to make sense for long-term human occupation -- births and so on. It took over 90000 years to get there, so the settlement planet has to make sense. They were not pressured to land.
I can adjust the length of anything, but would still like my planet to be as different as possible and still make real sense from a hard-science pov.
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Having a longer orbital period of 800 days (assuming Earth days) and keeping a terrestrial climate will require you balance a number of variables. First, you have the generalised form of [Kepler's law](https://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion):
$$p^2 = \frac{4\pi^2 r^3}{G M}$$
Where $p$ is the period, $r$ is the distance from the centre of gravity, $G$ is the gravitational constant, and to simplify from $M\_1 + M\_2$, I will use $M$ because planetary masses are negligible compared to stars. Basically, the period is itself dependant on the orbital radius.
Then, I have the equation for [extraterrestrial solar irradiance](http://solardat.uoregon.edu/SolarRadiationBasics.html) at different radii, holding the Earth value of 1367 $\textrm{Wm}^{-2}$ constant.
$$1367 = \frac{L}{4 \pi r^2}$$
Where $L$ is the luminosity of the light source. This is what is important for keeping the climate terrestrial. Now, because I can relate luminosity to mass, I can then plug the following equation into this one. I assume a [mass-luminosity relation](https://en.wikipedia.org/wiki/Mass%E2%80%93luminosity_relation) with the general approximate value for low-mass main sequence stars of around 4:
$$\frac{L}{L\_{\odot}} = \left(\frac{M}{M\_{\odot}}\right)^{4}$$
This is where $L\_{\odot}$ is the Sun's luminosity, $M\_{\odot}$ is the Sun's mass, and $M$ is the mass of this hypothetical star. Substituting all of these equations together, starting with the solar radiation equation, then substituting the mass-luminosity relation for $L$ and then Kepler's law, solved for $r$, I get:
$$1367 = \frac{\left(\frac{M}{M\_{\odot}}\right)^{4} L\_{\odot}}{4\pi \left(\sqrt[3]{\frac{p^2 G M}{4\pi ^2}}\right)^2}$$
I then set $p$ seconds to the appropriate value for your 800 day year and come up with some mass value $M$ necessary for that star. Using Wolfram Alpha (because I really don't want to solve that by hand), with this query,
>
> 1367 = {(\frac{M }{1.988e30})^{4} \* 3.848e26}/{4 \* \pi \* ({(6.912e+7)^2 \* 6.67e-11 \* M}/{4 \* \pi^2})^(2/3)}, solve for M
>
>
>
I get a value for the mass around $2.719 \cdot 10^{30}$ kg, or around 135% the mass of the Sun. The distance from the star, therefore, would be somewhere around (using the expression substituted for $r$ and this query string),
>
> (((6.912e+7)^2 \* 6.67e-11 \*(2.719e+30) )/ (4pi^2))^(1/3)
>
>
>
1.87 astronomical units from the star, which would be very much like our Sun, just brighter and a third more massive. Thus, because the orbital parameters fit and such a star has very similar properties to the Sun, life can certainly exist.
**Note:** For those who are familiar with Kepler's law, the generalised Newtonian form of the equation shows that the mass of the central object is inversely proportional with the square of the period, which is why the doubled period has a not-so-large effect on the mass of the central object. This means that the increased time leads to a higher mass. I wanted to constrain the distance variable by providing some energy per square metre requirements, which therefore, could also have been solved by substitution of $r$ from the second equation here.
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Yes
Of course that would change some things and needs to be taken into account when designing life that could live there.
<https://arxiv.org/ftp/arxiv/papers/0906/0906.3531.pdf>
Has analysis on the rotation periods. Radius of the planet would be the best variable to achieve what you are looking for.
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To change the ammout of time in a planets year one must adjust the height of the orbit via [keplers law](https://en.wikipedia.org/wiki/Orbital_period#Small_body_orbiting_a_central_body). If you want that planet to remain in the [green zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone) of a star you would have to increce the heat output of the star. Changing the heat/size would change the colour of the star which would change the evolution of flora and fauna to maximise use of this diffrent light.
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On the planet of the Aves, birds have evolved to dominate the Earth instead of mammals. Of the thousands of species in this world, both on the [ground](https://worldbuilding.stackexchange.com/questions/51622/planet-of-the-aves-quadrabirds) and in the [water](https://worldbuilding.stackexchange.com/questions/51661/planet-of-the-aves-aquabirds), the only one to develop sapience are a species of flying birds whose ancestors are the New Caledonian Crow.
As I design this species, I have wondered what their tools would look like, crows have been known to build tools such as hooks, but those are fairly basic. The premise of all human tools; axes, picks even hammers, is that the weight of them can be taken advantage of by momentum, but a crow, evolving for flight would not be able to use the human versions of these tools.
What could I expect a sapient crows equivalent to human tools to look like? What accommodations would a crows ax need to take into account? What about their picks or their hammers?
A list of all Planet of the Aves questions can be found [here](https://worldbuilding.meta.stackexchange.com/questions/3939/planet-of-the-aves-series/3940#3940)
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# Two Types
A sapient flying species would likely have need for two basic types of tools: those meant to be manipulated by beak/tongue/foot, and those meant to be dropped from a height with precision.
## Beak
The business-end of a crow tool probably wouldn't differ much from the human equivalent; tools meant to cut will have a sharp edge, tools meant to pierce will be pointed, hammering tools will have a flat, blunt face, and so on. Where they will have to differ is in the nature of the grip. Held in the beak and pointing outward puts the crow at a disadvantage: the eyes aren't far from the beak and need to see the target, so the tool couldn't obscure their vision; the shape of the beak means to maximize surface contact the handle needs to be wide and flat, perhaps with an opening or depression for the bend at the tip of the beak to pass through or sit in. Tools may be specialized for up-down or left-right motions, oriented either parallel or perpendicular to the breadth of the handle.
Variants may include handles meant to be held at an angle, with part of the handle extending backwards along the side of the crow's head. The tool head may be angled to compensate:
[](https://i.stack.imgur.com/uEwdn.jpg)
This configuration would probably be limited to side-to-side raking tools and plunging/piercing tools.
## Tongue
Assuming a bit of mutation here. The tongue could serve a thumb-like role when it comes to gripping tools with the beak. In this case the tool will be designed much like those described above, but will have a divot or indent for the tongue to press into or curl around for added support and control.
## Foot
I don't know off-hand if crows have been observed using their feet to manipulate tools, but bracing one end of the handle against the ground with the foot and using the head and beak to guide the working end along an arc seems like an obvious adaptation. A second handle, perpendicular to the bracing handle, could allow the crow to grip at a distance for better perspective on the target area. Akin to the handles of a scythe:
[](https://i.stack.imgur.com/mIK0J.jpg)
## Dropped
These tools would be designed to take advantage of terminal velocity and will be designed to be as aerodynamic as possible. They would be larger and therefore weightier than the beak-gripped tools, and held in the talons for a steadier and firmer grip. Most of the weight would be in the bladed edge or hammering surface, to prevent tumbling.
For increased precision I would anticipate a dive bomb approach, in which the crow gets as much altitude as needed and then plummets as vertically as possible to the target below, releasing the tool and pulling out of the dive.
This type of tool would be better suited to rough chopping and battering/hammering.
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Ignoring the tails humans already have.
Let's say it's the year 2016. Merpeople exist. They live in the ocean or rivers, breathe air, and have to surface occasionally. They also evolved from earlier humans.
They're pretty diverse, maybe as far as having different subspecies of merfolk.
Under **intense selective pressure**, how long ago would merpeople have to diverge from landpeople to develop tails, from legs, fit for swimming?
Side question: what would they look like compared to fantasy version of mermaids?
Edit: Being in the genus "homo" counts as human. Merpeople do not necessarily need to be in this genus at the "end" of their evolution, but must for the start
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Look at the evolution of [Cetacea](https://en.wikipedia.org/wiki/Evolution_of_cetaceans), which illustrates that adapting to water is *rapid*.
Where “rapid” means 50 million years.
Now you can imagine starting with apes rather than horses and get the same kind of body radical reshaping. **But** humans have a [very shallow gene pool](https://en.wikipedia.org/wiki/Human_genetic_variation#Population_genetics), having been through bottlenecks. Perhaps that’s why we developed intelligence instead of just adapting to new niches like other animals! So humans in there present form would need more time and large populations to significantly evolve at all.
I don’t know what the rate is for acquiring such diversity. But I would suppose the scale of **millions of years** would do it.
So I would suggest **60 to 80 million years** as a final answer.
Ah, but you asked how *long ago* for it to be finished now. Well, that’s before a genetic bottleneck so nevermind that complication. But, nothing remotely human was around 50 million years ago! The earliest bipedal hominins were 7 or 8 million years ago. [There were barely monkeys](https://en.wikipedia.org/wiki/Timeline_of_human_evolution#Primates) that far back.
---
How would they look? Like seals with useful hands that work as paddles or steering mechanisms as well as having opposable thumbs and some reach. Maybe the front limb folds up like a birds wing, to form a flipper with the elbow at the end and the hand tucked under the armpit.
[Answer]
Humans are tough work with when it comes to evolution.
The main problem being that **as humans we have effectively removed ourselves from natural selection.**
For your scenario to happen at all, the world we find ourselves in would have to drastically change.
* Scenario wise you are looking at a world dominated by water. There is no reason to turn into a mer-person if you aren't going to live in water.
* Humans would have to regress dramatically. Intelligence is the weapon of humanity. We don't evolve so much as use our brains to keep us out of trouble. For Darwinian selection to get us to the point of turning into dolphin people we would have to lose our ability to survive via our wits.
* Given all that is true, evolution is still a really really slow process. Additionally for natural selection to be the way we get there the environmental changes would have to take millions of years to come into effect. **Natural selection cannot cope well with rapid environmental change**
So in short, you are talking about gradual environmental change combined with mental regression (somehow) leading to humans that now have dolphin tails (since we are both mammals). At best I would ballpark things at around 100 million years but that is a very very rough guesstimate.
**Ironically if things change this much...these aren't really even humans anymore.**
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[Question]
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Could humanoids similar to the cubic-based beings found in Minecraft be physically plausible? The requirements are not that human can take such a shape, but rather that a being of such size and shape could function normally, similarly to how a human would? Assume the biology of our Minecraft figures is equivalent to human biology, save the structure of bones and tissues that shape humans into the external shape we know well.
[Answer]
Lets start with some minecraft people
[](https://i.stack.imgur.com/U7zlD.jpg)
I'd note the lack of usable fingers (How do they even pick up tools) and roughly the same range of motion as lego people. Non functional hips. No knees of elbows. No feet (how are they even standing????)
Essentially this bodyplan makes tool use difficult, these folks would find it impossible to get up if they ever fell over and there's no plausible way it would work.
[Answer]
**No, not just a regular no, but really not yes no**
Biology loves equality in it's proportions. Both in symmetry and distance from bone, this is why there are no lumps of skin in the natural human body. Even if for stone reason a species evolved such a form, breaking bones and cutting oneself would become extremely common place.
Any animal that evolved this shape would be a result of.... intelligent design. So, in other words, no the answer is no, in every way there is no way.
[Answer]
answer: a:) anisotropic space, b:) ordered construction.
A: anisotropic space: In Minecraft, physics is very different than the real world, and certain assumption of real biology seems to be invalid in minecraft biology. Specifically, the specific property that makes up a Minecraft world is Anisotropy of space: there are three universal directions of space in Minecraft, while we still didn’t see any direction-ess in the real world. This leads to a specific breach within the laws of physics: the law of conservation of angular momentum doesn’t apply in Minecraft.
Wonder how you can still look around while falling in Minecraft? This is because there is no angular momentum currently being applied in modern editions of Minecraft, and entities takes orientation only around the y axis. Block operations, on the other hand, follows what is called a Manhattan coordinate system: the law of trigonometry simply doesn’t apply within a Manhattan coordinate system, instead of D^2=x^2+y^2 in a Cartesian coordinate system, the Manhattan coordinate system have D=x+y.
In other words, in Minecraft, there are no circles because circles are square. For example, Water spreads into the shape of a diamond(geometry), yet all different flowing water blocks with the same level would also the same distance from the source, in Manhattannian terms, while being of different distance in the Cartesian terms, when viewed by our eyes.
The unique property of a space structure with a definite direction and Manhattan coordinate system, is that the Most material efficient container for packing in space is also the most material efficient container for storing material alone, both of which are cubes. This also means, that, a round house in Minecraft won’t take up less material per surface area covered than a square house, except it can not be packed closely, and would therefore less efficient in ultilizing space. For cells, it means that the only thing matters is the size, and all the most material efficient configurations are the configurations without "crimps" or extrusions, which are rectangles.
Why limbs moves if space itself does not properly rotate? Use special relativity. Even though every minecraft space themselves have a definite anisotrophy, different local reference frames can be of a angle between each other, like how boats and horses can be rotated alone it’s own axis, it keeps the Local anisotropy while rotating the entire entity, albeit in an unnatural manner that have nothing to do with angular momentum. Think of raising to a complex power within a complex plane, or multiplying with a rotational matrix of a point in 3d.
B. Ordered construction: think of crystals, or other things in the real world that have absolute geometrical symmetry, like granules of salt or tightly packed bearing balls.
Life of some types would simply find that it is computationally easy to build bodies with a form of translational symmetry, for example, because of how proteins in the real cell assembles into an atomically perfect straight tube, called microtubules, that is literally straighter than even the most precise straightedges we have in the field of machining. Your cells can also be using protein self assembly, or other ordered construction techniques, instead of the chaotic gradient and diffusion powered growth process in earth animal or plant cells.
With self assembly, translationally symmetric voxels are much computationally cheaper than the complex diffused/ sloped, or "organic" shapes, which is best described by diffusion.
Maybe because the complexity prevents certain cell schemes from evolving organic shapes that is sufficiently predictable yet still useable, let alone favorable for the functions they were supposed to do. For example, 3d printed Voxel fingers may be worse than the (really advanced) organically shaped counterpart, but the organic shape would be far more difficult to grow properly without malforming within the sensitive grow process, and would take up far more base pairs to properly design, let alone evolve, for certain biological schemes.
Therefore, maybe because that cellular computation and developmental processing is far more expensive in minecraftian life than in earth life, or because the assumption of biological growth and development is based on a specific coordinate system rather than a relative distance system, just like how our computer works, minecraftian life uses a simple and predictable self assembly process that favors square, voxely simple shapes much more than the much more complex organic shapes that does not really add too much performance.
In addition, if the biosphere that alters and erodes the lithosphere is also based on the assumption of a coordinate system, and is responsible for much of the terrain, you would get blocks as well, just like those you see in Minecraft videos.
Essentially, life don’t have to look more like flesh to outperform life that looks like flesh, even in the "organic" sense.
] |
[Question]
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Major William die in a combat versus aliens. Now he have the capacity to wake up on the same point of time every time he dies. (Movie: Edge of tomorrow)
He uses this power to win the war, but he has to memorize every single movement he do in order to save their soldiers and their own life.
Logic says he eventualy gonna do it, but repeating the day one million times It's like having lived more than two thousand years, probably losing their sanity.
My question is: It's our mind and memory precise and capable enough to repeat exactly the same actions and memorize it to make the day repeat in the same way as the previous one?
A little related to that other question: [What is the limit of a human's memory if Immortal?](https://worldbuilding.stackexchange.com/questions/40559/what-is-the-limit-of-a-humans-memory-if-immortal)
[Answer]
I side on Yes.
The argument for No, is on episodic memory which is not reliable. But I think this will eventually fall on procedural memory.
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Now, it is known that the human brain - regardless of age - has some level of plasticity. That means that the human brain never loses his ability to acquire new skills, the human brain can always change the neural connections and create new habit.
So, I would argue that his multiple revivals would cause the structure of his brain to change, in a similar fashion in which [the brain changes by prolonged practice in complex environments](http://www.scientificamerican.com/article/london-taxi-memory/).
And since he is doing the same tasks over and over, the nature of this tasks would become mechanical\*. And so, he will be able to learn them by practice, not dissimilar to learning to play a musical instrument or learning a particular choreography. There is no need for him to learn the whole thing at once, he may learn just the initial parts and master them, and then move to next situation, etc...
\*: once he has decided what the correct course of action is and committed to it, and once he is past any gross factor.
Given that, I would expect that after enough iteration William will be doing the repeated actions out of habit, without putting much thought on the matter. In fact he will not only do them naturally, but also with better accuracy and even develop a sense for the timing needed to execute them.
---
>
> My question is: It's our mind and memory precise and capable enough to
> repeat exactly the same actions and memorize it to make the day repeat
> in the same way as the previous one?
>
>
>
I say, yes.
Yet, as side effect he may require assistance to recover old skills. Take for example the case of [learning to ride a backwards bike](https://www.youtube.com/watch?v=MFzDaBzBlL0), after it is done, the person has a hard time driving a regular bike, but provided some practice, it is possible to acquire both skills.
Note: Some people say they forget a language when they learn another, but reality is that they only need a little practice to recover any lost vocabulary of their prior language - although this is anecdotal.
About his episodic memory of events prior to the point to which he goes back... he will not be able to recall. And his sanity... honestly, I don't know... but I can imagine him falling to doing some portions of his war routine without noticing, like a tick or a bad habit.
---
[Answer]
Short answer: No
The human memory is amazing and very accurate but it does not have the scope to remember everything that happens in one day. Further to that, human perception is not 100% accurate. It works by guessing what the world will look like then comparing that guess with sensory input. This means things in the corner of the eye would not have enough sensory input to compare to the expected model so things that our protagonist is not concentrating on will appear in his memory as his minds best guess so even if he remembers everything it still won't be accurate enough for his purpose.
Furthermore, even if he does learn the day by repetition and muscle memory as soon as he makes a change his memories are invalid and he must learn this new future. He may also confuse the two futures leading to him making the wrong deductions. Obviously if he makes a second change he now has another future to learn and three futures to keep straight.
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[Question]
[
In the story I'm writing, a civil war is fought between Earth and Mars. Although there is a huge orbital and ground war campaign, conditions deteriorate to the point where Earth decides to unleash the most powerful weapon in its arsenal: The anti-kinetic rod. Using a delivery system similar to the "Rods from God" concept, the weapon can be deployed quickly in large numbers through satellite-deployed, kinetic bombardment rods. But unlike kinetic bombardment, the true power of the weapon is in its payload of **1 pound of anti-matter**; making it a continent killing weapon.
But in order for it to work, the payload has make it to the ground. Because antimatter is ridiculously unstable, it needs to be contained in order to survive the trip by avoiding contact with normal matter. Is there a way to do this with a real or conceptually possible material, or without a *ridiculous* amount of energy (aka, a power supply that could actually fit on a rod)?
[Answer]
Any realistic antimatter weapon would resemble a traditional light bulb more than a kinetic energy impactor, and considering the mechanism of energy release, accelerating antimatter to high velocities really does not add anything in terms of damage (although for targeting solutions and to ensure the antimatter makes it through any defensive screen, a high velocity delivery system is a must).
[](https://i.stack.imgur.com/RqE3a.jpg)
The antimatter must be held in a vacuum to prevent it from interacting with matter before it is supposed to. It should also be cooled to as close to absolute zero as possible to make it relatively non reactive (no stray anti particles wandering from the surface of the antimatter bundle), and it would have to be suspended within a powerful magnetic or electrostatic field to keep it entered in the container.
Now since a microgram of antimatter reacting with a microgram of matter is the equivalent of 43kg of TNT (thanks to the atomic rockets [boom table](http://www.projectrho.com/public_html/rocket/usefultables.php)), a device carrying a pound of antimatter (@ 500 grams) should have the energy release of about 21.5 megatons. To give you an idea, modern strategic nuclear weapons are thought to have a yield of about 300 Kilotons. The only semi plausible suggestion that a 20 megaton weapon was ever deployed was speculation I read once that a regiment of SS-20 "Satan" ICBMs was held by the former USSR to carry one 20 megaton weapon each, with the sole purpose of turning Cheyenne Mountain into Cheyenne Lake.
[](https://i.stack.imgur.com/PJAIA.jpg)
So the question is what would EarthForce be targeting which requires such firepower? Have the Martians dug into Olympus Mons or the other Tharsis volcanos? Is Earthforce going to crack open the moons of Mars and neutralize them as potential orbital installations? Are the Martians hiding under the polar icecaps? Since the creation and use of antimatter is going to be very expensive and potentially quite dangerous for the user to handle, these targets must be extremely high value. Using antimatter for ground bursts provides some of the energy release will be converted into seismic activity, and the shockwaves travelling through the ground could collapse tunnels and bunkers, but airbursts could potentially sleet wide areas of Mars with highly energetic gamma radiation, as well as blasts of exotic particles moving at close to light speed, in addition to massive blast waves travelling through the atmosphere. Any surface installations would almost certainly be destroyed (like solar panels and communications antenna).
Of course there is a simpler way to get that sort of bang for the buck and more:
<http://www.nextbigfuture.com./2009/02/unmanned-sprint-start-for-nuclear-orion.html>
>
> There was a three page paper: Nuclear explosive propelled Interceptor for deflecting objects on collision course with Earth. Johndale Solem, Los Alamos, proposed unmanned vehicle. No shock absorber or shielding. The pulse units were 25kg bombs of 2.5 kiloton yield.
>
>
> Get to high velocities with only a few explosives and small shock absorbers or no shocks at all. Launch against a 100 meter chondritic asteroid coming at 25 km/sec. 1000 megatons if it hits. Launch when it is 15 million kilometers away and try to cause 10000km deflection. A minimal Orion weighing 3.3 tons with no warhead would do the job. 115 charges with a total of 288 kiloton yield. Launch to intercept in 5 hours. Ample time to launch a second if the first failed.
>
>
>
So this beastly device can be launched directly from Earth or the Moon, accelerate at 100g and strike with a *gigaton* of energy on impact. In terms of cost, I would suspect that since most of the parts would be churned out on an assembly line, and you have no exotic antimatter containment to deal with, it would be much cheaper to have these in squadrons based on the Moon or maybe even on NEO's, to provide the most dispersion and coverage for EarthForce's premier strike weapon.
And don't try to run away:
>
> Mars Express
> Another aspect of the fast acceleration that is possible is that an unmanned Orion go from earth or earth orbit to Mars (decelerate at halfway) and *get to Mars in under one day going at 100Gs* if Mars and Earth are in the close approach. If the unmanned version was going at 1000Gs (which was a design that is possible), then Earth to Mars could be done in a few hours. At about 300Gs and you would be looking at a Mars Overnight package delivery.
>
>
>
Of course it is always possible the Martians have been thinking along these lines as well.....
[Answer]
The über-hard SF writer (and real physicist) Robert L. Forward describes a solution in his novel [Camelot 30K](https://en.wikipedia.org/wiki/Camelot_30K).
As I recall, he summarized that the “trap chip” is the size of a AA battery and contains as much energy as a tanker truck of gasoline.
It is based on arrays of [penning traps](https://en.wikipedia.org/wiki/Penning_trap) fabricated like RAM chips on a semiconductor wafer.
An explosive could be much denser, as it doesn’t need the mechanism around each trap to safely extract the antiproton and route it to a safe place to allow annihilation. So, I expect you would be able to store an antiproton in a semiconductor area maybe 10-20 nanometers square. This is 2 dimensional, and if stacked up the required thickness would be about the same size.
[Answer]
Sounds like throwing an egg off a tower without breaking it.
Put the antimatter in a box, in a vacuum (obviously), consisting of charged metal plates of the same charge as the particles. The plates are supported by shock absorbers attached to the body of the missile.
Since both the plates and antimatter (let's say positrons) are in a vacuum, and are all the same charge, there will (ideally) be no charge leakage, and the plates will stay charged indefinitely, once raised to a sufficient level.
When the missile launched, the shock absorbers absorb much of the acceleration of the missile as it leaves the satellite. When it hits ground, or gets hit by anti-missile defences, the plates are separated, allowing the antimatter to be exposed. Contact triggered explosives at the tip to destroy the containment plates on impact will probably help to ensure it's not a dud.
[Answer]
**Unless you just love to throw away money, forget the antimatter bomb.**
Current cost estimates for anti-hydrogan are trillions of dollars per gram. Production rates are also insanely slow, billions of years to produce 1 kg of anti-hydrogen.
Old fashioned 1 MTon nukes are about 1 million USD each (when produced in volume), thus you could make millions of nukes for the cost of 1 gram of anti-matter. 1 million USD is just for the warhead, not the delivery system.
Maybe someday, we could make relatively cheap anti-matter, but production is so inefficient, it will be ludicrously expensive for a long time to come.
Easy enough to scale up thermonuclear bombs to the desired yield, so no real downside compared to anti-matter bombs.
] |
[Question]
[
Well, I have been having [computer problems](https://superuser.com/questions/1095464/my-audio-and-video-drivers-are-not-working-planning-on-factory-reset-is-this-t?noredirect=1#comment1553551_1095464) and I decided that now is as good a time as ever to continue to waste my time developing my reptilian, honor-obsessed militaristic race of lizards for a planned [Stellaris](http://www.stellarisgame.com/) AAR.
Here is a description of them for the first draft of my planned four part preluide series:
<-- Drash Karr Basic Information -->
Overview:
The Drash Karr are a warrior race hailing from the moon Karr orbiting the Gas Giant named Bid' Jossk in the Dec' Haran System, though their people are actually divided into many different castes. Their name literally translates into English "The Children of Karr". Each caste accomplishes a very specific task, though the broader castes are divided into many smaller sub-castes. For example, the Warrior Caste is divided into the Grunt caste, the Mecha caste, and the Naval caste. Each of those is further subdivided until every specific niche required to keep an army functioning is filled.
Planet:
Bid' Jossk actually orbits towards the inner edge of the habitable zone of its star, and some would argue that it is actually too close to its star to support life, however the rapid orbit of the moon combined with its rotation means that a day is only six hours, half in the light, half in the dark. The surface is primarily composed of desert, mesas, and mountains, though there are a dozen or so small seas. The depressions surrounding the seas and the heavy cloud cover on the northern hemisphere combined with fossilized aquatic animals indicate that at one time, many millions of years ago, a much larger percentage of the surface was covered in water. Perhaps the moons' parent planet once had a more favorable orbit, but moved in closer to its star, but this would have been long before the Drash Karr had even started to evolve.
Culture:
Drash Karr culture stresses The Challenge, or the challenges one will face throughout his or her life. The Challenge is different for each caste as well as each individual Drash Karr, basically providing that for one to do ones' best in all things would bring both the individual and the greater whole more honor.
This is an amazing system because it blends perfectly a sense of individualism by encouraging one to strive to achieve ever greater amounts of honor and acclaim while maximizing the sense of being part of a greater whole for each individual. They defend their home worlds with wild ferocity, and will not suffer foreign overlords defiling their homes. Aside from this one quirk, they are actually extremely tolerant for an interstellar empire, allowing conquered races, no matter how primitive they were before, to rise through the ranks and attain great glory and respect in their society, even to the point of the most trusted, honorable, and talented Xenos to command their great fleets and armies.
Females, unlike in many human cultures, are treated with the utmost reverence and respect, as they bring life to the entirety of the Drash Karr and are physically completely equal to males.
Warriors prefer single-combat and will tear a scale from their body, usually the back, and pin it to their armor upon defeating a foe in single combat. While the Drash Karr are willing and able to use more advanced weaponry such as the feared Orbital Drop Mechas and Tanks, or even basic projectile weapons, they prefer to close the distance to an enemy and use either their short or long swords to duel.
Religion:
The Drash Karr have no single religion, per se, but throughout the many millennia of recorded Drash Karr history they have worshiped many gods. Even now, they follow their Protector, and treat him or her with near god-like reverence and respect. Before they followed the Protector, nearly all Drash Karr worshiped their homeworld of Karr as a god.
Biology:
The Drash Karr are a large, bipedal species. They are covered in strong scales of varying color. These scales, when combined with the bulletproof silk suits worn under their heavy metal armor, can stop projectile weapons from causing any real harm. Their only known physical vulnerabilities are their eye and mouth openings as their metallic helmets open up to allow them to breathe and see.
Their home planet is covered in mesas and large open deserts with the occasional mountain, and their scales turn pure white when their bodies begin to overheat.
Their mouth is divided into three mandibles. They used to serve the purpose of hunting back when the Drash Karr were primitive animals, but since then have served little purpose other than to inspire terror in their enemies (and quite effectively at that, considering that they are covered in hundreds of small incisors. The Drash Karr possess specialized organs in their stomachs to grind up meat into a digestible form.
Members of the Drash Karr species communicate with each other using special organs in their throats that can produce more complex sounds than a human can. As a result, the first languages of the Drash Karr were a complex combination of sounds. In the end, as the Drash Karr created and adopted a simpler language as their interstellar Empire expanded and incorporated more and more races.
When their bodies begin to overheat, their scales turn a shade of white to deflect the sun and their scales open up to allow the wind to cool their skin off. They do sweat to some degree under their scales
Breeding:
Drash Karr breed in much the same way as most other species. After sexual intercourse, the two Drash Karr are bound to each other for life by unique chemical and physical reactions to the sensations. The female will then lay anywhere from 10 to 20 eggs that develop into Drash Karr infants in two Earth-years. Only half of the eggs will hatch, however, and rarely does more than 1 survive their first five great cycles of training and schooling.
Size:
The Drash Karr can easily reach heights in excess of 7 feet, and some have been known to reach up to ten feet. Their bodies are somewhat aerodynamically designed in form to help them reach maximum speed. Their average strength is double that of the average human, but can in rare cases be triple. Unfortunately, the societal selection process used by the Drash Karr, many years of hard training, that has caused their race to develop such strength, has a high fatality rate and when combined with the low hatching rate of the Drash Karr eggs. In most cases, only 1 or 2 Drash Karr children survive the training, the strongest, fastest, and smartest of their species. This low survival rate is offset by the fact that Drash Karr women can have up to two broods of eggs a year, one in the celestial spring and the other in celestial fall, meaning 1-2 new children per year.
Conquest Policy:
First Contact Protocol was dictated by the actions of Protector Oberon, the War-Chief that united his homeworld and brought the Drash' Karr Empire onto the interstellar stage. From his personal journals;
"In the event of contact with an alien race, overwhelming force must be used to ensure the security of our species. The aliens will be given the chance to prepare for the coming battles equivalent to 1 great cycle. After the grace period expires, our entire fleet will mobilize to meet the enemy. Any encroachment in our space during this time will immediately end the grace period. Our armies will be brought to their worlds to do battle in their cities while our fleets engage in space."
"Every attempt to meet them on equal ground must be made. To seek a decisive technological advantage in combat would bring dishonor to the Drash' Karr Empire and would be a punishable offense. Punishment will be left to the discretion of the reigning Protector."
"The one exception to this rule, however, is if the security and survival of the state as a whole is in danger. In the event of contact with a race that desires our destruction, appropriate force will be applied. All technological innovations will be leveraged."
Time:
Time is measured in Great Cycles, Cycles, hours, and minutes. Minutes and hours are roughly measured in the same way they are on Earth. A "Cycle" is the time it takes the moon of Karr, their homeworld, to orbit its parent planet. A Great Cycle is the time it takes its parent planet to orbit its Star. Its parent star itself is a [Type F Star](http://www.enchantedlearning.com/subjects/astronomy/stars/startypes.shtml), shining with a blue color.
Technology:
Technology has steadily progressed, and the Drash Karr are very capable of designing terrifying weapons of mass destruction, but have agreed across the board that such an action would be horrendously dishonorable and any nation that attempted to do that was easily swatted down and destroyed by the combined military might of the rest of Karr.
<--End Description-->
I am looking for inconsistencies as well as any and all input on the verisimilitude(is that a word?) of my scenario. I am planning on asking some more questions, such as where the habitable zone for such a star would begin, where it would end, as well as designing the warbeasts the Drash Karr will ride into battle on, but those are questions for another day.
Karr's parent gas giant, Bid'Jossk, is slightly larger in both circumference and mass than Saturn.
**EDIT**
To clarify, I am looking for cultural and biological quirks that I might not have noticed, as I am not too confident in my ability to be accurate and not overly extravagant.
[Answer]
**Biological realism:**
1. You need a reason why half the eggs don't hatch. Disease? Inbreeding? Terrible childcare (egg-care) methods? Some other factor? For instance, some species of marine turtle have quite a lot of smaller than average eggs which don't hatch. The theory is that these eggs are not really eggs at all - they are 'spacers' to help keep pockets of air open in the buried clutch of eggs.
2. You say that very few offspring make it through training. This means that the major form of infant and childhood mortality is *self-inflicted*. Given that this species (or its ancestors) will also suffer from diseases, attacks by predators, starvation during famines, murder, bad luck and accidents, it looks like their 'honour training' is designed to drive them to extinction.
3. You describe them as reptiles, but there is nothing much (apart from scales and laying eggs) that strikes me as a reptilian physiology. Are they really ectotherms (cold-blooded)? If so, they'll be struggling to cope with winter or temperate climates on planets like Earth. There are sound physiological reasons why big reptiles like alligators & Komodo dragons don't inhabit chilly places like New Zealand, Norway or the north of the USA. (Little reptiles tend to hibernate). If they are really mammals-with-scales, then ignore this.
4. Childcare and education. I'm including this in biology because civilised, technological species who have a squillion kids is a real bugbear of mine. The bigger your litter/clutch of kids, the more of your population you have to dedicate to educating them. Human women have 1 kid at a time, and with a ratio of 1 primary school teacher to 25 kids in the classroom, that means 1 teacher for every 25 women who had a kid in 2016. Your Drash Karr women lay 20 eggs and 10 hatch. So our example class of 25 kids are the offspring of only 2.5 women. You therefore need 1 teacher per 2.5 women if you want to teach those kids to read! And they are only the first clutch of 2016! So it is really 2 teachers per 2.5 women. Given that there is no such thing as 0.5 of a woman (!), let's round up the numbers... 20 teachers per 25 women. So in a village of 50 adults (half male, half female), 40% of your population will be dedicated to **educating this year's offspring!**
Data added: [this government website](https://www.gov.uk/government/publications/number-of-schools-teachers-and-students-in-england) states that in England there are 8.2 million kids (including nursery schools, state schools and private schools) and 438000 teachers (state schools only). That's a ratio of 1 teacher to 19 kids. So it will be a bit less that this when the nursery and private school teachers are factored in.
**Cultural realism:**
5. Wars are often (mostly?) won by the folks with the technological advantage. In fact I'm betting a whole lot of technological innovations were created in the first place to improve the chance of winning. You can invent the bow and arrow for hunting animals, but the only reason to invent the cannon is to destroy the fortifications and manpower of the enemy.
6. Honour is not a cross-cultural standard. Someone has picked something and labelled it 'honorable' or 'dishonorable' or neutral. If a nobleman insults another nobleman? You have an honorable duel. If a peasant insults a nobleman? Off with his head! Because murdering peasants is not 'dishonorable'. So to make these guys interesting, you'll need to find some honour quirks which are unique to them and aren't just a Hollywood version of chivalry or samurai or 'noble savages'.
[Answer]
From a narrative perspective they’re not very entertaining, fiction is all about conflict and when you have a race of Mary Sue super-soldiers it’s hard to create a credible threat for them and without a credible threat stories about them won’t be dramatic or inspiring. However an insistence on honour to the point of absurdity helps, a story about them fighting a good clean fight against some utterly alien and eminently practical race would be inspiring, that is of course assuming things aren’t working out well for them.
Once you’ve established that the borg/zerg/whatever are clearly going to win and struck that point home over and over THEN you can write a great story about them making a comeback from the brink of defeat. Perhaps their insistence on honour encouraged other races to ally with them, perhaps the enemy forces lost momentum, their willingness to fight waned, and your Drash Karr fought them back through sheer persistence.
Or maybe they’re completely defeated and driven from their homeworld, forced to become nomadic mercenaries or pirates just to survive, a people with such an honour focused culture placed in such a dishonourable position creates a rich backdrop for interpersonal conflict and personal uncertainty.
In terms of realism your guess is as good as mine.
[Answer]
You mention Xenos rising in this culture - do the Xenos have to buy in 100% to the honour system? If there are interpretations of "honourable" that can justify, for example, killing children, what happens when a Xeno uses such a justification?
The Turks had the Janissary army (essentially a Death Squad of unmarried Xenos trained from early childhood to be super-soldiers), but they accomplished this feat by kidnapping male children from their subject nations at a young age, and raising them as Muslims. These foreign-born Janissaries could rise to be the Supreme Ruler, but they had no knowledge of, or contact with, their original family and culture.
If Xenos are allowed to retain their own culture and also participate in the Karr culture, you probably should give thought as to how the resulting cultural conflicts are resolved.
[Answer]
Any attempt at an honorable stellar-age war is ridiculous, unless your species is remarkably quick to adapt, or you assume that only planets with similar climates to your homeworld are capable of sustaining any form of life. If humans were to attempt honorable warfare on Venus, the economic burden would be huge. Space suits, that would not be dissolved by or melted by the atmosphere for everyone. Besides that, these suits would add considerable bulk and weight - making use of cover, and running from cover to cover would become ridiculously difficult, and any breach of the suit would mean death. The same goes for Karr on a moderate-to-cold climate planet. The native species could easily seek refuge in cold mountains and maintain an exhausting guerrilla war for ages. An example of a species that has a chance at an honorable war on any planet is... Zerg.
That being said, I think the whole First Contact Protocol and Technological section is way off for a species, that is reptilian (ectothermic) and has a huge disadvantage against moderate to cold climate planets, has an educational system based on natural selection and survival of the fittest. It would make more sense, if they reserved the honor system against one another, but used WMD and terraforming (also a WMD, as huge, global-scale climate change, and more than likely, also the complete change of the composition of the atmosphere is likely to annihilate most of the life on the planet that is being terraformed) against other species with little to no regard.
Such a brutal, care-free "wreck everyone else" technological and First Contact Protocol policy would work more favorably for war beasts as well.
Also for their armor, more specifically - their helmets, they could reduce their vulnerabilities further, by leaving openings only for their eyes, and breathe through gaps left between their scales and the helmet, that lead to the openings for their eyes. Fogging up would not be an issue because there are no lenses. This vulnerability could be sealed up if you use some sort of bullet-proof lenses (some crystal structure commonly found on their planet), and just route the breathing canals to a different part of the helmets.
But as @Cognisant noted in his answer, you're creating massive, unkillable super-soldiers. The problem with that, is that it becomes difficult to find a viable threat. You're basically running yourself into a predictable outcome - the only way they can be defeated, is if the enemy defeats them in space, before they are forced to fight face-to-face, or the enemy has superior terraforming technology, and just "terraform-nukes" their inhabbitted planets, forcing them into a life of living on spaceships, with ridiculously limited resources and sustainability, until they go extinct.
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Adhering to natural laws and physics as much as possible`[1]`, what could cause Venus to go from a habitable planet to its current state, and how long would it take from the apocalyptic event to achieve the current state?
In this scenario, human life evolved on Venus, the apocalyptic event took place, and humans moved to earth. Events after that do not matter and do not need to line up with actual human history.
**Venus Pre Apocalypse**
* Habitable
* Chemical composition same or similar to earth
* Able to support human life`[2]`
* Hosts Type 1 civilization`[3]`
**Apocalyptic Event**
* Can be man made`[4]`
* Can be natural`[5]`
* Can be both
* Can be neither`[6]`
**After TBD amount of time post Apocalypse**
* Venus is how it is now
**Specific sub-questions**
* What would slow the rotation of the planet?
* What would cause the drastic chemical change to acidic atmosphere?
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1. Does not have to be perfectly scientific, but reasonably realistic. Type 1 Civilization-esque level of technology and “science” allowed.
2. Or a predecessor that could micro evolve to live in the similar chemical composition of earth. If different, please outline said differences.
3. Space-faring but not yet colonizing. See [this SE answer](https://worldbuilding.stackexchange.com/questions/45501/what-would-block-a-planet-from-seeing-the-stars/45507#45507) for plausible reasons for delayed space travel.
4. What political landscape would be in place and/or cause such an event?
5. Nothing is out of the question so long as it resolves into the current state of the solar system
6. If you are clever enough to think of what that might possibly be. I’m not.
[Answer]
A runaway greenhouse effect. Just like early life started producing oxygen that changed the atmosphere, perhaps some metabolism or geologic force produced a super-greenhouse gas. Once the state was pushed beyond some point, a positive feedback cycle was initiated and the thick carbon dioxide atmosphere at high temperature was the new stable equilibrium point.
[Answer]
Lack of continents. Venus has one solid shell while earth has continents. Earth releases extra energy through cracks at plates and the continents themselves moving. Venus does not, and as such this extra energy can only be release through volcanoes. Volcanic event releases a huge amount of sulphur and the runaway warming converts Venus to what it is now. But this doesn't explain the rotation of Venus.
More fun but further out there....Venus developed where it is now, but earth did not. Earth originally formed where the asteroid belt did. Venus was a habitable planet at this point. A cosmic scale collision occurs and the planet is now relocated to where earth is now. The presence of earth slowed and eventually reversed Venus's rotation and brought it to where it is now. Magnetism and a planets magnetic field protects the planet from harsh solar radiation and a planets rotation is required to support that magnetic field. When Venus stopped, the magnetic field weakened to the point where solar rays fried all life on Venus leaving it where it is today.
[Answer]
The positioning of Venus is somewhat important but in reality you need to do one thing, alter the atmosphere. The greenhouse effect on Venus is many, many times what is on earth and this is highly related to the CO2 content of the planet. There are many of realistic ways to induce massive amounts of CO2, from standard pollution to warheads, basically anything that releases it as a byproduct. A type I civilization should definitely have it within its means to induce such an apocalyptic event.
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Assuming that the sky isn't that color because of excess pollution, would the makeup of the atmosphere need to change?
And if it were breathable, would the necessary position and color of the sun cause unliveable or drastic temperatures on the planet's surface?
In other words, assuming a world of humans with slightly advanced technology, is this aesthetic choice of sky color scientifically sound?
[Answer]
## Yes it is plausible.
You would just need a little more atmosphere is all. The more dense the atmosphere, the less blue light that will be visible on the surface.
On Earth a sunset appears red because the light has to pass through more of the atmosphere before it reaches you. As a consequence more of the red light is scattered away, giving the sky a red appearance. This increased density could be caused by pollution, but it also could be caused by dust or water vapor or slightly increased gravity.
A good example is the planet Mars, where dust high in the atmosphere makes the sky appear red during the day and blue at sunset.
[](https://i.stack.imgur.com/U2Ldm.png)
[Answer]
Most "Earth-like" planets may not have blue skies. Most stars are red dwarfs, which emit very little blue light, so even if there is scattering in the atmosphere of an Earth-like planet, there is simply very little blue light available. So, the sky would not be blue. But, of course, one would imagine that any creatures on such a planet would have eyes that were sensitive in the infrared instead of in the visible, since that is where most of the light would be.
More here: <https://planetplanet.net/2015/09/16/the-colors-of-other-worlds/>
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## Background
A common staple in science fiction is the idea that we can augment humans by replacing limbs with mechanical substitutions that enable superhuman feats - weightlifter like strength in a slender incognito package, invisibility, Bruce Lee speed reflexes, etc. None of this is implausible at all since we currently make prosthetic implants, and it's only a matter of time until the technology and power of these prosthesis exceeds the capabilities of their natural parts.
## Problem
Most implants that exist today require relatively little power since their capabilities are very limited. But when it comes to a cyber arm that can punch through walls, the need for more energy (of any type) will be higher.
## Questions
* Assuming that an augmented person has 2 cyber arms and 2 cyber legs that enables him to jump a 6 feet (1.8 m) wall easily without using his hands. He can also lift and carry a 650lb (300 kg) vending machine with his arms. How much higher would his short term and long term energy needs be?
* Is the human body capable of covering these energy deficits by regular biological methods (burning fats, consuming carbohydrates and sugars, ATP production, etc.) and increased food intake?
* Are there scientifically viable methods of inserting a power supply into a human that would …
+ provide enough energy to power these augments if the body isn't capable of doing so normally
+ or reduce the need for increased food consumption?
[Answer]
Yes, within reason.
A biological reactor in each implant could be used to take nutrients from the blood and charge on-board power cells. Oxygen could also be removed from the blood for the purpose or just taken in directly by the implants to reduce the load required for that. We already have prototypes that can generate power in a way similar to what is needed.
Bursts of strength would use the batteries to supply power and they are then trickle-charged at a rate the human body can sustain.
This sort of solution would be fine for standard levels of activity and bursts of extreme strength. For endurance events extra batteries could be carried in a backpack and plugged into the cybernetics, or even in some cases directly powered from the mains or a vehicle.
For example in military you might stay plugged into your vehicle up until the moment you deploy just to make sure everything is fully charged including your own system.
Food requirements would be increased, but not dramatically as you don't have organic arms and legs to supply. It's impossible to say by how much as we don't know how efficient these cybernetics will be but considering that in "idle" they could well use less than an organic limb the increase may be smaller than you expect.
[Answer]
Considering how Human Revolution had Proenergy bars that replenished energy, I suppose some sort of pumped up candy bar could be the delivery method for the digestible fuel.
As an added bonus, at least in-universe, it provides a way to let "augs" take some of the anti-rejection medication (which is a plot point in Deus Ex: Human Revolution) or some additives in reality, say, chemicals that would maintain the augmented skeleton from the absorbed calcium (forgive medical inaccuracies, I'm not a doctor...)
On the complete opposite end, augmentations may very well be more akin to a car being refueled though that seems way less efficient than using the built in energy generation of the human body.
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One of the many things I'm afraid of is the existence of lasers that cause permanent blindness. I know that it would take a lot of energy to melt someone's face or cut off limbs like in *Star Wars*, but the idea of simply shining a light at someone to the point that they can no longer see, forever, seems way more possible/plausible to me. I can imagine battlefields of the future where soldiers on both sides are afraid to look out beyond no man's land for fear of never being able to look again. Luckily, it seems like no one has built a gun specifically for this purpose.
That said, I want to know how.
So that's what I'm asking: **can you create a gun that shoots permanent blindness lasers, and if so, what do/would you need?** For some parameters, let's say it's effective at 50 meters, on unshielded targets that are looking directly at the gun. It should work fast enough to not be foiled by blinking. Aside from that, I'd appreciate optimization to size, range, accuracy, and acceptable deviation angle of target's field of view.
[Answer]
Laser eye safety has to do with intensity of the beam.
Lasers come in different classes based on intensity, and how dangerous they are:
Class 3R: Safe with limited beam viewing. Prolonged exposure has a low risk of injury.
[Class 3B](https://en.wikipedia.org/wiki/Laser_safety#Class_3B): Class 3b lasers can cause severe eye injuries if beams are viewed directly or specular reflections are viewed.
Diffuse reflections (non shiny surface) are safe to view.
A Class 3 laser is not normally a fire hazard. Example: visible HeNe lasers above 5 milliwatts but not exceeding 500 milliwatts radiant power
[Class 4](https://en.wikipedia.org/wiki/Laser_safety#Class_4): Class 4 lasers are a hazard to the eye from the direct beam and specular reflections and sometimes even from diffuse reflections. Class 4 lasers can also start fires and can damage skin.
Retinal injuries can occur instantaneously with Class 3b and Class 4 lasers; the damage may be irreparable. Corneal burns from far-IR and UV lasers may also be irreparable. Class 4 beams may be of sufficient power intensities to penetrate through the sclera (white) of the eye and damage the retina and other structures; thus, turning one's head or not looking directly at the laser offers little or no protection to high power lasers. Lenticular damage may also be caused by the beam and by photochemical reactions from exposure to UV and blue frequencies.
So, you'd want either a class 3b or class 4 laser.
Here's a [class 4 hand held laser for $200](http://www.wickedlasers.com/arctic).
It has a max beam visibility range of 72761 meters, though the blinding effect is probably half that.
It really wouldn't do a lot of good though, since laser safety glasses are available even at these intensities, and if side A started using blinding weapons, side B would just issue safety glasses along with helmets and flack jackets.
Found more information on LaserPointerSafety.com
**Found an answer to my question from the other day...**
there are [temporarily blinding laser dazzlers](https://en.wikipedia.org/wiki/Dazzler_(weapon)) which can be used in crowd control and war situations, and are legal under the 1995 United Nations Protocol on Blinding Laser Weapons.
[Answer]
Wait, you mean to say there is a way to hurt and harm humans that is technically feasible and is not in service?
**Nope, we have them:**
[](https://i.stack.imgur.com/O854Z.png)
>
> The device, officially called a “visual optical jammer station Grach,” was revealed this week at a military expo in Kubinka near Moscow. It’s a remotely-controlled device with two to four projectors that produce light intensive enough to suppress enemy sensors and cause temporal blindness in humans.
>
>
> The projectors radiate light in the infrared and ultraviolet ranges of the spectrum, which means they affect devices such as thermal visors which rely on such wavelengths. Grach is intended to provide cover for troops during firefights and hinder enemy reconnaissance. It can also be used as a regular searchlight and to send light signals large distances.
>
>
>
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Our Earth and Venus each keep a thick atmosphere because of a magnetosphere.
Most terraforming scenarios of Mars involve transferring water and other gases from the ground to the atmosphere.
We now know Mars won’t be able to keep them. We also now know the process is happening naturally.
So, if Mars got a magnetic shield *(even an extra thin one like Venus)* to protect against solar radiation, it would be able to held water oceans again.
So, how can we create such a field ?
[Answer]
**You can't.**
Since you've narrowed the scope of your question to current technology, you've eliminated any possible solutions. We currently have no technology for generating artificial planetary magnetic fields. It's just not something we're keeping in a closet somewhere.
If we were to develop new technology, [this existing question](https://worldbuilding.stackexchange.com/q/8832/3202) and its answers cover that altered scope rather well.
[Answer]
To be honest, with current technology, you are out of luck. HOWEVER, with NEAR-TERM technology (and some large scale engineering) it could be doable to create an artificial magnetic field using at least 6 to 8 planet-sized, superconducting rings tops. In this [report here](http://www.nifs.ac.jp/report/NIFS-886.pdf), it was concluded that for an Earth-sized magnetic field, you need 12 of those rings. I am extrapolating to take into account the less massive Mars, and NASA did propose the creation of a magnetic dipole field at Mars Lagrange Point 1. So, those two techniques could be useful. Good luck!
[Answer]
It's actually relatively easy. The [proposed solution](https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html) is to park a giant expandable net or balloon dotted with magnets in the sun-Mars L1 orbit (a stable orbit that would keep the magnet between the sun and Mars at all times). The magnets would need to be quite powerful\*, but aren't out of reach of current science.
What it would do is deflect the solar wind to the sides of the planet, to keep the atmosphere from getting ripped off.
This is all possible now, just very expensive, and would take at least two years to put in place.
\*1-2 Tesla. For reference, the most powerful commercially available permanent magnets, neodymium rare earth magnets, are [typically](http://www.magnet4sale.com/n52-1x1-2-neodymium-rare-earth-disc-magnet/) around 1.3 Tesla at their surface, though much stronger examples exist.
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I'm working with a city that has cut itself off from the surrounding area. There may be as many as 10,000 people within it, or as few as 1000. I'm trying to be as realistic as possible. How long would it take for inbreeding to present problems, ie genetic diseases, or mental health issues? This will give me an idea how many people live in the city and how long it has been in existence. Let's assume that the city was founded by nine families that were quite diverse in their genetic code.
[Answer]
The graph beneath (from Popular Mechanics) provides a pretty good estimate of variation in a gene. The key conclusion that one can draw from it is that a population of 10,000 people should be enough to be sustainable without any major inbreeding issues, while 1,000 is too low (it would land between the green/yellow lines on the graph). [Source](http://www.popularmechanics.com/space/deep-space/a10369/how-many-people-does-it-take-to-colonize-another-star-system-16654747/)
[](https://i.stack.imgur.com/ARelg.jpg)
In terms of mental health issues, [Dunbar's Number](https://en.wikipedia.org/wiki/Dunbar%27s_number) is a good reference point, meaning that in an ideal circumstance where everybody likes each other, 150 people is enough. With 10,000 people, you would only have to get along with 1.5% of all the people in the city, which shouldn't pose any systematic problems in the sense of loneliness.
Finally, you mention the city founded by nine families – depending on the sizes of such families when they first come, this could have pretty serious consequences in terms of genetic diversity. Even considering 16 sets of 'unique' genes (as in 16 genetically unrelated great-great-grandparents) per family, that would only come out to 144 'unique' genes total, which isn't very much at all. In this case, the nine families could reach a total population between one thousand and ten, but the actual diversity genetically would be far lower, and there could very easily be inbreeding problems at that point.
[Answer]
Playing the devils advocate here but:
***There is evidence that if done correctly inbreeding / line-breeding can be done is such a way to limit "bad genes" in a species.***
According to <http://carawatha.tripod.com/inbreeding.htm>
The practice of inbreeding does not 'create' the resulting condition. What it does do, is identify any bad genes if they are present in the line. **The problems must already be present in the line for bad results to occur.**
When inbreeding is not practiced, any lethal, semi-lethal & undesirable recessives present in that line, are being passed down to future generations along with the good genes, without any apparent signs to you, the breeder. With the end result being, that a majority of animals of a particular line/breed/species will all be carrying these undesirable genes.
The insight that inbreeding gives into your lines, is invaluable. If you don't know about any bad traits, should they be present, then how can you expect to eliminate them. It's the responsibility of all serious breeders to ensure that their lines of animals are genetically sound...
Bad genes not only affect the aetiological and health areas of your chosen breed, but temperament as well.
Inbred (rat) strains have been developed by laboratories and scientists alike, with positive results rather than negative.
\*Gregor Mendel, was reputed to have bred brother and sister mice together for 40 generations with no adverse affects and increased overall body size by over 50% in the process .
\*The Sprague-Dawley line was created by mating an original black hooded buck to an unrelated doe, then mating him back to his daughters for seven successive generations. The line was closed. (circa 1958?) which means in effect all this one lab line come from those rats and no outcrosses.
\*Many lab strains are closed - if you visit lab webpages, some have been closed from as far back as 1947. If these rats were suffering any deleterious effects from that much inbreeding they would no longer be a marketable, reliable, commercially viable product for experimentation. The whole idea was to create homogenous rats which give consistency for their purpose.
<http://bowlingsite.mcf.com/genetics/inbreeding.html> Says:
What does inbreeding (in the genetic sense) do? Basically, it increase the probability that the two copies of any given gene will be identical and derived from the same ancestor. Technically, the animal is homozygous for that gene. The heterozygous animal has some differences in the two copies of the gene Remember that each animal (or plant, for that matter) has two copies of any given gene (two alleles at each locus, if you want to get technical), one derived from the father and one from the mother. If the father and mother are related, there is a chance that the two genes in the offspring are both identical copies contributed by the common ancestor. This is neither good nor bad in itself. Consider, for instance, the gene for PRA (progressive retinal atrophy), which causes progressive blindness. Carriers have normal vision, but if one is mated to another carrier, one in four of the puppies will have PRA and go blind. Inbreeding will increase both the number of affected dogs (bad) and the number of genetically normal dogs (good) at the expense of carriers. **Inbreeding can thus bring these undesirable recessive genes to the surface, where they can be removed from the breeding pool.**
***With the proper observances it is possible to use statistics to increase the success of a mating selection / schedule of said population.***
COEFFICIENT OF INBREEDING
AN INVESTIGATION INTO WRIGHT'S EQUATION AND HARDIMAN'S METHOD
<http://www.highflyer.supanet.com/coefficient.htm>
<http://www.siriusdog.com/bell-pedigree-analysis-genetic-diversity.htm>
The standard definition of inbreeding is that it is any scheme which results in the sire and the dam having common ancestors. Many breeders use the term "inbreeding" for close relatives and "linebreeding" for more distantly related individuals, but there is no fundamental difference. **The parameter used to express this common heritage is called the inbreeding coefficient and was first proposed by Sewell Wright in 1922.** Designated F by Wright (but more commonly IC or COI by breeders), it can theoretically range from 0 to 100%, and indicates the probability that the two alleles for any gene are identical by descent.
<http://www.leonberger-database.com/coi_e.html>
***Providing the city isolated itself on purpose one would think they would enact mating stipulations using population control such as arranged marriages and birthing license to control blood lines. (ie refusal of procreation permissions if any bad genes are dominate). If done correctly it may be possible to eventually breed out unwanted traits.***
[Answer]
Traill et al. reported a median MVP of 4,169 individuals. (Which means, not families of related people).
9 founding families is going to be a bottleneck in and of itself, unless there are a lot of immigrants.
That number does not take into account any planned breeding, or social controls.
Genetic diversity is only a problem if you're not actively culling unfit genes. If all the genes are good (and nobody has perfect genes), then you have no problems with only 2 people. If you're willing to cull any problems, you can work it with quite a small population; as long as it came from very good stock.
[Answer]
I am again adding an answer that is really a general comment...
Historically people have lived in small communities without travelling that much **and** abandoned babies.with serious issues. And ostracised families with a bad history of issues.
So small starting population does **not** condemn people to extinction and **obvious** hereditary diseases. It condemns people to a degree of ruthlessness that modern people find unpalatable.
We have reached a level of genetic diversity where we do not **need** to do such things. Although eugenics, a modernized form of the same, has been popular at times.
But if you put in a small isolated population, they will naturally adopt the exact level of ruthlessness their genetic diversity requires. Too strict people will suffer from lower population growth and be out competed. Too lenient people will suffer from genetic defects and be out competed.
So basically you can pick a relatively small starting population as long as you remember that it will have consequences to the way people act. Starting with ruthless and pragmatic approach to children but extending to religion.
This depends on level of development, but given any degree of superstition, people would come to recognize the more common genetic issues in the population and could come to associate them with curses from gods, demons, spirits, or witches. Thus a smaller population more vulnerable to genetic issues would see a world filled with hostile supernatural forces.
[Answer]
Since the topic is too broad for me to discuss here, I will simply post some links for you to study which are directly related to your query.
<http://www.nature.com/scitable/definition/population-bottleneck-300>
<https://en.wikipedia.org/wiki/Population_bottleneck>
<http://www.ask.com/science/bottleneck-effect-biology-92f375a8a85b5a7>
<https://biologypost.wordpress.com/unit-2-biology-lessons/unit-2/3-2-2-the-founder-effect-genetic-bottlenecks-and-selective-breeding/>
A genetic bottleneck occurs when a species undergoes a severe population decline. The survivors then replenish the population but the loss of genetic diversity takes ages to cover up. In case of humans, the group which gave rise to today's ~7 billion population contained only some 100 or so people. Yet we have overcome the problem now and are successful as a species. Another example are cheetahs who have severely low genetic diversity. They have also survived and not gone extinct so far.
If your population of 1000 is multi-ethnic and has a high genetic diversity from the start, inbreeding problems would appear after several generations (a couple millenia). However if the population consists of a single race (and worse yet, a single tribe or clan), then the problems would arise within some 300-400 years or so.
It depends not only on the genetic diversity of the original population but also whether that genetic diversity is well distributed later with random-like marriages instead of family marriages. It could be that there is enough genetic diversity in the community as a whole but families start in-marriages so that each family gets interbreeding problems.
[Answer]
You may find this article interesting: <https://en.wikipedia.org/wiki/Uncontacted_peoples>. Apparently there are several small groups of people (populations of 500 or fewer), who have lived in isolation for many generations with no apparent ill effects.
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I've got a large fantasy city of about 500,000. It's a trading hub and the capital of an empire. Period wise, I would say that it is close to 1500-1600 Europe.
I've got a community of primarily gravediggers that I am trying to figure out the size of. Unfortunately, gravediggers are not a profession listed on any of the demographic generators I've found. So my question is this:
What number or ratio of the city would likely be gravediggers? If this is unknowable, what is the relationship between the number of gravediggers and the death rate?
[Answer]
At a death rate of 5% - it'll be higher during plague or famine years, lower if the city has good sanitation - there will be 25,000 graves to dig per year, or 68 per day. If it takes two people most of a day to dig one grave, and there's a little downtime, you need about 150 full-time gravediggers. Add to that a couple dozen shift supervisors, journeymen, and some administrators, and I'd say 200 dues-paying members of the Gravediggers Guild.
And probably another 50 grave robbers.
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If you'd like to maximize the number of gravediggers in a city, I can think of a few reasons:
* Plague is common. 500 K people is *huge* by pre-modern standards - the size of London, PLUS Paris, PLUS Naples in the 16th century (arguably the three largest cities in Europe, if you don't count Constantinople as European) - and it could be a huge population sink.
* Individual graves are mandated by religion, law, or custom. [As Murphy points out](https://worldbuilding.stackexchange.com/a/26763/243), this was not always the case in medieval Europe.
* It's considered important that the dead be buried *immediately*, even if there's been mass death or the ground is frozen. You'd need a much larger pool of gravediggers to handle spikes, but they'd be idle for most of the year. More likely, there would be a pool of "on-call gravediggers," enlisted when needed, but perhaps grave digging is not compatible with any other work.
* Gravediggers are a special hereditary caste, allowed to do no other work. Over time, there may be more grave diggers born to the trade than jobs for them to do. If they can't at least serve as groundskeepers or ditch diggers, they will in practice probably be mostly beggars who happen to also dig graves.
* Digging requires extra man-hours, because the soil is heavy clay or rocky, graves must be very deep, or the process is interrupted for a special ritual after each foot of digging. More likely, people would turn to other forms of disposal if the ground was unsuitable, like [New Orleans' vaults](http://www.experienceneworleans.com/deadcity.html), but perhaps internment is considered the only acceptable way again due to religion, law, or custom.
* Grave digging is [a works program](https://en.wikipedia.org/wiki/National_Rural_Employment_Guarantee_Act_2005), where people with no other skills or opportunities can sign up for a pittance. A group of people can't really dig a small grave much more easily than one or two, so there's plenty of room to stretch the work.
Contrariwise, if you'd prefer that their numbers be small, such that everyone knows everyone in the grave-digging community:
* Like Murphy said, mass graves are common. During times of plague, a layer of corpses, a layer of lime to kill the smell, and another layer of corpses was common. During the plague of Justinian, towers were filled like horrific grain silos.
* Cemeteries are out of town: even poor people are traditionally buried back at their home villages, if possible. You'd have wagon-loads of corpses leaving the city each day; "bring out yer dead!"
* Disposal by cremation is preferred; only certain castes, classes, or eccentric people prefer burial. Exposure and burial at sea were also used, historically, but neither is likely to be practical for such a large city.
* Most people bury their own; grave diggers are employed only by those too weak to honor their dead by personally digging a grave.
* People are only partly buried. Perhaps the head is believed to carry all that is sacred about the deceased; it is mummified and carefully interred in a small narrow grave, while the rest of the body is cremated, or [enjoyed as a family meal](https://www.youtube.com/watch?v=F12JGWAqxNw).
[Answer]
Jon of All Trades has the right general idea but I think the numbers are a bit off.
5% sounds incredibly high, that would imply an average life expectancy of 20 years old. Life expectancy at birth was 35+ so death rates would have been closer to 2.5% per year. Add to that, not everyone got a grave to themselves. Paupers, prostitutes and babies of fairly poor people who died at a young age would have been piled in mass graves
This is what the modern version looks like, in medieval times they generally wouldn't have bothered with the separate coffins for the very poor:
[](https://i.stack.imgur.com/SfQOT.jpg)
These types of graves take a lot less work per person.
Also it wouldn't take two professionals a whole day to dig a single grave, one professional could probably dig more than one in a single day but lets assume at least one grave.
mass graves are probably 5 or more times more efficient.
So call it 12K dead per year, lets assume half of them are too poor to afford a private or family grave.
So 6k normal graves and mass graves for another 6k.
At one grave per day per gravedigger the private graves mean 6000 man-days and the mass graves mean 1200 man-days.
Lets assume 300 man-days per gravedigger per year for the sake of round numbers giving us about 24 grave diggers.
But we're assuming perfect efficiency and good organisation so lets double that, call it a round 50 full-time gravediggers
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If there is a city with 500,000 thousand people and the average life-span is 70 years old. Then there will be about 7,000 people dead every year. In the fantasy city let's say supply and demand are the same. It takes nearly a full day to dig a grave so lets say someone can dig 300 graves a year (allow a bit of sickness or holiday). Then this city would need 25 grave diggers.
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Imagine that, without any aliens having been ever found, we get to a point where we can build sub-atomically precise simulations of reality, spanning at least something the size (if not the likeness) of a solar system within the sim (if needed, we can scale up to galactic scales)... Assume we go about trying to create ('evolve' within the sim) our very own aliens, that is to say new organisms 'living' within these simulations, the likes of which have never existed on Earth.
Would we be able to create anything truly alien, or is our limited imagination and physical/biological convergence an inescapable boundary?
Good answers will have a rough sketch of how one would go about generating alien sim-life, or alternatively a decent explanation as to why it's not possible. As to what would qualify as 'truly alien', it's a hard call, but as a rule of the thumb, if I can imagine it relatively easily (say a griffon), it's probably not alien enough.
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I think we have demonstrated that our collective ability to imagine exceeds our physical form.
Consider the following creature:
It's a social creature with a very rigid role based hierarchy. It is a predator, and the sneakiest of predators. It sets a trap and quietly lies in wait for unsuspecting prey to go by. The predator identifies what the prey wants to see, and constructs an on-the-fly bait customized for this individual prey. If the prey sees the bait, and begins to fall for it, this predator carefully adjust itself so that it looks like there is nothing else in the world but the bait, and that no one else in the world could possibly get it. It's the perfect morsel for this prey. When the prey gets too close, **SPLAT** the prey is reduced to nothingness in moments by acid. Even if a prey escapes to tell the tale, nobody believes it because they never seem to be able to compare notes. After a failed attempt, it looks like no attack occurred at all. This is, in fact, why the creature is social. Success or failure, it rapidly disseminates knowledge of the result of the transaction to others of its cluster, all of which have specialized processing nodes which ensure any inconsistencies in the attack, which might help the prey outwit the predators, are smoothed over so that noone ever is the wiser.
Sound fantastic and potentially an exotic creature? I envisioned it right here and right now. It's also a SQL server. We deploy hundreds of them every day around the world. You can get a degree in managing them, if you want.
Chalk one up for imagination.
If a creature is advanced enough, its mind is going to be more important than its body structure. Thus the real challenge for making an "alien" alien is to create an alien feeling mind. To me, mathematics is in an excellent position to posit the ability to create such a mind. We have a long history of creating mathematical languages which can describe fantastical facts which had never been imagined before (complex numbers... seriously?). Thus I expect we would create a language describing fantastical creatures, and then use the simulation to build all of the "fine details" that end up actually creating the alien feeling mind.
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If it were up to me, I would have the computer run many concurrent, smaller sims, modelling a few miles of randomly generated terrain and atmosphere (or lack thereof), with basic astronomy modelling (but not in detail). I would then try to randomly generate different kinds of cells and microorganisms. I assume this technology is within scope of a world that can design and run a solar system-scale simulation. Essentially I'd try to brute-force generate all possible microorganisms by sheer arrangement of atoms.
I would then have the computer process each micro-world as quickly as possible, modelling, who knows? ten thousand years per second perhaps, and simulate evolution. The evolution wouldn't necessarily be propelled by mutation and natural selection, but could follow all kinds of hard-to-predict paths. For all I know, it's reasonably likely that some of the life wouldn't experience aging, and some sort of immortal, self-improving life would emerge.
At any rate, at that point it would be purely up to physics, without human bias. Anything could happen. So since my system works as best as possible to brute force as many starting conditions as possible, based on chemistry which we can perform without significant human bias, and then relies on physics rather than imagination to develop the life forms, this method seems both reasonable considering the assumed level of technology available, and as free of human bias as we could hope to achieve.
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Many questions on Worldbuilding have posited different reproductive strategies that often result in the virtual enslavement of females (when there are females involved). On Earth, normal human biology lends itself to patriarchal societies and almost always, the oppression and marginalization of women.
*What's the smallest change that can applied now to the human reproduction strategy that will result in the most equality, freedom and flexibility for women?* Since human cultural norms are an emergent property of human biology, answers that only address changes to human culture won't work since any cultural changes will be constantly fighting against biology. Only biological changes or technological innovations that improve the equality and freedom of women are in scope for this question. Changes to how sex operates will have huge cultural implications to every single aspect of society. Those cultural changes are out of scope too ('cause they're gonna be huge!).
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The obvious biological solution to gender inequality is to take gender out of the equation entirely. Genetically altered humans to possess both male and female equipment. Both would be capable of caring Young. And both will be capable of providing seed.
But each person would biologically have a dominant gender. They may have the equipment for both but their body would only produce the hormones needed to operate one set at a time.
These humans would go through Cycles, every decade or so their dominant gender would switch as the body begins produce hormones that trigger the physical traits of the gender opposite their current dominant gender. Another decade and it switches back again.
This gender switch cycle may sound strange but there are actually certain kinds of fish that do this.
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your tags already answered your question. Artificial wombs pretty much remove all the limitations for women and allow proper equality. However, to get real equality assume a world as such:
1. artificial wombs exist and are used common place. Most likely the prevalence of them are because they remove the risk of miscarriage, birth defects, and health risks for the mother, perhaps genetic screening prior to the implanting of embryos occurs as well.
2. Healthy equivalent of breast milk have been created, such that breastfeeding is not required for an infant to develop to full health. Yes were most of the way there, but breast feeding still provides some extra health benefits currently. Of course this brings in the question of rather the *act* of breast feeding, as a bonding activity, may help an infant even if formula were as healthy, but I'm sure we could work around that.
3. An easy way to withdraw eggs from a women (the current ways are painful and expensive) for implanting in an artificial womb. This process would have to be pretty simple, since guys have *no* problem producing their half of the genetic equivalent. Perhaps eggs aren't used at all, maybe it's found easier to combine DNA in 'artificial eggs', such that the mother only needs a swab of her mouth for DNA rather then actual eggs.
With this approach you have removed almost all the physical differences for reproduction in the modern era (at least for first world countries that have access to artificial wombs). Now both mother and father are mere DNA providers, child is otherwise birthed in exactly the same manner. This is also one of the most believable to occur from our current society.
However, this isn't quite a full answer. Females have certain biological instincts, as do men, based off of how reproduction has always occurred. Even in presence of a new and simpler method of reproduction our biological imperatives will still be ground in reproduction of the past, evolution won't 'catch up' for many thousands of years. As such there will be differences between the sexes, which would likely work against women favor, which are legacy of how reproduction has worked for countless thousands of years.
...before I continue let me just say now everything below is my taking in large statistical averages based off of evolutionary principles. I am not claiming that all, or even most, of either sex follows the below generalities. These are small small statistical difference that only become relevant when summed across many thousands of people; and it would be foolish and literally the definition of prejudice to presume that any of these below averages apply to any *single* individual, or even a small group, of each sex.
Most noticeably women would still be smaller, and with less testosterone then men, which would lead to them being less aggressive. This would lead women to both being less capable of fighting physically (which admittedly means little in an age of firearms and technology rendering physical might mostly moot), and less inclined *to* fight; from a biological level. Thus *on average* they would be less inclined to fight back against attempts by more aggressive men trying to dominate or restrict them.
They would also have a higher maternal instinct then the paternal instinct, making them feel more obligated to the child. Which makes them less likely to be willing to walk away from a child they had. This would mean that in situations of divorce or breakup the mother would be more likely to end up taking on the primary responsibility of the child. Since added responsibility and financial costs lower one's freedom and ability to fight for moral and social issues these added responsibilities could lead to making it easier for men with lower responsibilities to use their excess resources to try to dominate women.
Artificial wombs would go a very long way towards fixing gender differences, but not be a 100% fix. Of course society has gone a long way towards fixing itself already, throw in artificial wombs and a little more time for society to continue going down the path towards equality it's already on and these differences would be so minor to be effectively equal.
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The biggest single change would be to switch the role of testosterone. In the primitive world larger strength ruled. Being physically stronger meant that you took what you wanted and ruled those who were weaker.
If instead testosterone inhibited muscle growth and decreased aggression while women were the stronger then it is likely that women would end up dominating a subservient male population.
Note that biologically speaking this is not the optimum solution as you would lose more time from your strongest members for pregnancy. Egg laying (where the men care for the eggs) or seahorse-style pouches on the men that the women transfer the young to would fix that problem though.
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I think the major changes would involve males being more likely to stay back to care for the young, and females being more capable of and likely to go out and hunt or fight. Then the traditionally "female" roles would simply be provided by anyone of either sex who was weaker and/or more passive, while the traditionally "male" roles would be provided by the stronger, more aggressive members of a tribe or community.
Obviously, childbirth would temporarily weaken the females with no corresponding issue for males, but we're talking a few months per child, not anything life-altering.
Bear in mind, however, that racism is baked into our biology. One group or another will almost always be slightly stronger, and once racial oppression has started, there's very little that will bring it back. Over evolutionary time periods, there will be a natural culling of the enslaved/oppressed race. Anyone who opposes the oppression will be more likely to get murdered, and therefore less likely to pass on the aggressive genes.
So the only real way to get rid of racism is to get rid of the underlying mechanisms that cause it. And I don't think that's actually biologically viable. Racism plays a critical role in our survival in primitive conditions. It's not until society evolves that racism becomes a negative thing.
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**Perfect the artificial womb and make transplanting a pregnancy from a woman to the artificial womb an outpatient procedure.**
These two changes fix several problems. Both techniques/technologies avoid questions about abortion since they are not an abortion. It gives women the flexibility to decide how much pregnancy they want. The transplant procedure allows pregnancies to begin the way they've always begun but it doesn't require the woman to carry the fetus for nine months.
There are no changes to human psychology required, so no mass reprogramming required. No changes to child raising psychology. No changes to human biology or sexual interactions. Men and women go about doing what they have for millennia. If a pregnancy results, the woman make a quick trip to the clinic then some months later, goes to pick up her baby.
Just as the advent of birth control radically changed women's flexibility in regards to pregnancy, an artificial womb will make even greater changes.
In an informal poll I did with friends who are mothers, they indicated that despite all the discomfort of pregnancy, they valued the time they had with their unborn children. One woman indicated she knew her daughters' personality before they were born. Certainly, many women will still choose to carry their children but they have the choice to not carry the child if they don't want to.
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According to two websites I respect a great deal ([Atomic Rockets](http://www.projectrho.com/public_html/rocket/spacegunintro.php) and [Rocketpunk Manifesto](http://www.rocketpunk-manifesto.com/2009/06/space-warfare-iii-warships-in-space.html)), weapons fall into three broad groupings: kinetic, explosive, and energy.
But if we're talking about winner take all combat, why do we limit ourselves to just fighting by doing damage? Maybe our electronic warfare capabilities can be expanded to include the ability to destroy, incapacitate, or hamper the enemy spaceship by other means.
Consider that today nearly every computer has networking connections (sometimes wireless networking) built right into the system's motherboard.
How might an EWAR (electronic warfare) suite be used to incapacitate a ship (e.g. as shown [imo, unrealistically] in the Battlestar Galactica reboot)?
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The former Soviet Union had heavily invested in *Radio Electronic Combat*, and there is no reason to assume the successor Russian government has not continued along these lines.
The first and simplest way to use *Radio Electronic Combat* is signals spoofing and jamming. We normally associate radio jamming with powerful "Barrage" jammers flooding the airwaves with white noise, but jammers can be very specific and jam single frequencies or a spread. The Soviets also introduced "silent" jamming, where the air is deceptively quiet, but upon using the radio you have no transmission or reception (this works best when initiated in a quiet zone during a period of low radio traffic, the net is naturally quiet then and you may not notice the initiation of silent jamming). Spoofing is just what it sounds like; skilled linguists are monitoring the net and at the appropriate time they begin transmitting as well. Unless the rest of the operators can catch on quickly, they may end up talking to the unknown operator assuming it is a replacement, or worse yet, taking orders and information from them.
Modern communications systems use encryption and techniques like frequency hopping to limit the ability to jam, spoof or listen in to a net, but since the net continues to emit energy every time a radio is used, Direction Finding allows you to discover the locations of the radios (or their radio antenna, at least), allowing you to direct physical attacks against the transmitters. Jamming can still work as well, even interrupting a percentage of the message could degrade the information enough to slow down operations as requests for clarification and having the message repeated become a larger percentage of the traffic on the net.
Cyber-warfare falls into this as well, and various forms of malware exist, ranging from crude to very sophisticated. Once again, the more sophisticated attacks are "better" since the opponent might not realize that their data and communications have been compromised. Examples like the Stuxnet worm released against the Iranians or the Chinese theft of personal data of millions of American government employees show large scale attacks can be running for *years* before discovery, and the effects can be very subtle (causing the centrifuges to run at sub optimal speeds in the Iranian nuclear enrichment program, or allowing the Chinese to apply pressure against *individual* Americans to support espionage, economic or military goals).
Finally, using enough energy can simply overwhelm the defenders electronic systems, rendering them inoperative. The best known example is EMP, which can be triggered by nuclear and non nuclear means and introduce enough energy in circuitry to physically damage or destroy them. This can be scales from frying individual units, computers or antenna to pumping enough energy into the electrical grid to cause the entire nation to be blacked out.
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There are several attacks that might implemented through hacking. All have the advantage of leaving the ship intact for salvage and sometimes even killing the living components so you don't have to.
**Reboot cycle**
Throw a figurative `goto 0;` and the beginning of their boot cycle and then crash the computers. Now they're stuck in a loop.
**Blow the airlocks.**
Surely when the ship is drydocked they need to access it readily and won't want to go through an airlock cycle every time they come in and out. So, make the system believe it is in drydock and open all the hatches.
**Poison the atmosphere.**
Instead of removing CO*2*, start adding it back in. This should incapacitate and then kill any crew breathing the air aboard the ship. Make sure to set all the connected space suits to begin their tank maintenance cycle by draining the O*2* tanks first!
**Signal a core meltdown.**
Don't *really* melt the core, but make all those humans aboard think it's going to meltdown. When they follow their training and abandon ship, you can have the ship for yourself (though it is missing some lifeboats).
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
Based on this question about an [impossible barbell planet](https://worldbuilding.stackexchange.com/questions/21414/dumbbell-planet-how-would-humans-cross-the-bridge), how hot would the bar be if it extended from halfway in the Earth's mantle to an altitude of *2r* of Earth's radius? The diameter of the bar itself is 20% of the radius of Earth. The rod is made of mild steel (we are handwaving the structural integrity of molten steel and ignoring that a structure this high would instantly collapse.) Also, the rod is permanently affixed at halfway through the mantle. The orientation and distance between Earth's core and the bar are fixed points.
[](https://i.stack.imgur.com/ISOXi.jpg)
We are going to ignore orbital mechanics, structure strength of megastructures, and structural strength of the Earth's crust surrounding this megastructure.
Given the Earth's core temperature and the conductivity of mild steel, how high would a person have to go on the rod in order to touch the rod with their bare hands and not get burned?
Bonus Question(s): What would happen to the weather near the base of the rod where it intersects with earth? If you want to talk about how fast Earth's core would completely cool off, that's cool too.
Extra Bonus Question(s): Account for orbital mechanics, interaction with the magnetosphere, and compression heating of the rod against the earth's core and friction with the crust.
**Remember, this is a [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") question. Equations, official government sources, and journal references are most appreciated. A minimum of handwavium, please.**
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As a first approximation, we treat the rod as a one-dimensional rod of length $L$. On each end is a heat source (the mantles of each of the two "Earths". We can begin to model the system as following the one-dimensional [heat equation](http://en.wikipedia.org/wiki/Heat_equation):
$$\frac{\partial T}{\partial t}=k\frac{\partial^2T}{\partial x^2}\tag{1}$$
where $T$ represents temperature, $x$ is the distance from one end of the rod, $t$ is time and $k$ is a constant, the [thermal diffusivity](https://en.wikipedia.org/wiki/Thermal_diffusivity). Consider a case with the following boundary conditions:
$$T(0,t)=T\_1,\quad T(L,t)=T\_2,\quad T(x,0)=f(x)$$
The first condition is because both heat sources are identical. We can use the method of separation of variables to arrive at [our solution](http://tutorial.math.lamar.edu/Classes/DE/HeatEqnNonZero.aspx):
$$T(x,t)=T\_1+\frac{T\_2-T\_1}{L}x+\sum\_{n=1}^{\infty}B\_n\sin\left(\frac{n\pi x}{L}\right)e^{-k\left(\frac{n\pi}{L}\right)^2t}$$
where
$$B\_n=\frac{2}{L}\int\_0^L(f(x)-u\_E(x))\sin\left(\frac{n\pi x}{L}\right)dx,\quad u\_E(x)=T\_1+\frac{T\_2-T\_1}{L}x$$
In our case, $T\_1=T\_2$ and $f(x)=T\_0$ is uniform. Then, if $\Delta T=T\_0-T\_1$,
$$B\_n=\frac{2\Delta T(1-\cos(\pi n))}{\pi n}$$
and
$$T(x,t)=T\_1+2\Delta T\sum\_{n=1}^{\infty}\left(\frac{1-\cos(\pi n)}{\pi n}\right)\sin\left(\frac{n\pi x}{L}\right)e^{-k\left(\frac{n\pi}{L}\right)^2t}$$
Wikipedia cites steel as having roughly $k=2\times10^{-5}\text{ m}^2\text{ s}^{-1}$. Let's say $L=4R\_{\oplus}$, $T\_1=T\_2=6000\text{ K}$ ([according to estimates](https://www.nationalgeographic.com/science/earth/surface-of-the-earth/earths-interior/)), and $T\_0=300\text{ K}$.
It turns out that the bridge between the cores heats up really slowly. I computed the first 100 terms of $T(x,t)$ at a variety of times, and plotted them.
[](https://i.stack.imgur.com/NsyEs.png)
[](https://i.stack.imgur.com/JyjKE.png)
The strong oscillations at the ends are just examples of the [Gibbs phenomenon](https://en.wikipedia.org/wiki/Gibbs_phenomenon), and don't have physical significance.
It becomes dangerous to walk on the rod after timescales longer than about 100 million to 1 billion years, from what I can tell. The center should remain habitable.
There are a couple of things we haven't considered:
* Radiative cooling, which I think will be important. This also might mean that the ends of the rods - at least, the sections immediately protruding from the surfaces of the planets - could appear quite bright. After all, 6000 K is approximately the temperature of the surface of the Sun!
* The fact that the rod is a cylinder, not one-dimensional. I don't think this is a major factor when it comes to the relevant timescales, though, especially if the rod is thin.
* The ends of the rod are embedded inside planets, and heat will diffuse into the outer layers of the planets. There should also be a non-zero gradient at the cores, at $t=0$.
* Atmospheres have an impact on temperature circulation; the (cooler) sections of the atmosphere around the two planets should take in heat from the (hotter) sections around the rod.
That said, I think this simple 1-D model can give us an order-of-magnitude estimate.
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A lot of people making maps for their worlds forget to consider the projection they are using when they start mapping but often need to deal with the issue later. If no projection is chosen, I usually make the assumption that their map is made with the equirectangular projection.
Is this a good map projection to work with if we are just interested in building a world? Is there another map projection that would be better for this?
The map contains:
* geographic elements: oceans, mountains, major rivers
* also : countries, cities and major roads.
One of my concern is that, the equirectangular stretches the high latitudes and this can be a problem when calculating the distances.
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## Equirectangular
[Equirectangular](https://en.wikipedia.org/wiki/Equirectangular_projection) is by far the easiest to start with and fairly intuitive. It is quick to make in almost any software and pretty instantly recognisable as a map. It has been around since ~100AD, so even characters in you world should be familiar with it.
You will have a problem with distortion at the poles, so directly measuring distance is out of the question:
**Calculating accurate distances is not impossible!**
As long as your map has latitude and longitude lines (you can overlay them digitally, or with transparency), you can calculate distance with [this online tool](http://www.movable-type.co.uk/scripts/latlong.html) or the [Haversine formula](https://en.wikipedia.org/wiki/Haversine_formula).
You can do it yourself with a decent calculator:
$$ d = 2r \times arcsin \left ( \sqrt{sin^2 \left ( {\phi\_2 - \phi\_1} \over 2 \right ) + cos(\phi\_1) \times cos(\phi\_2) + sin^2 \left ( {\lambda\_2 - \lambda\_1} \over 2 \right )}\right ) $$
$ \phi\_1 $ and $ \phi\_2 $ are latitude of point 1 and point 2 in radians (respectively)
$ \lambda\_1 $ and $ \lambda\_2 $ are longitude of point 1 and longitude of point 2, again, in radians
$ d $ is the distance between the two points (what we are calculating)
and $ r $ is the radius of the planet.
## Mercator
The Mercator projection ~~is horrible and evil~~ distorts the poles horribly and makes Greenland look fat:
It cannot show the poles, and faces severe distortion issues which make Equirectangular projection look tame. It is also difficult to calculate distances unless you happen to be sailing a ship near the equator. Wikipedia had this to say:
>
> Converting ruler distance on the Mercator map into true (great circle) distance on the sphere is straightforward along the equator but nowhere else. One problem is the variation of scale with latitude, and another is that straight lines on the map (rhumb lines), other than the meridians or the equator, do not correspond to great circles.
>
>
>
Not recommended.
## Dymaxion
Another map projection, and a particular favourite of mine, is the [Dymaxion map](https://en.wikipedia.org/wiki/Dymaxion_map). As `knave` mentions, this map has very little distortion on each individual 'chunk', as is shown here:
You can easily measure distance with a ruler on a Dymaxion map, but crossing between non-contiguous chunks is a bit of a hurdle. While there is very little distortion, the Dymaxion map is *not* intuitive or easy to grasp when drawing your map.
## Others
There are many other [map projections](https://en.wikipedia.org/wiki/List_of_map_projections) too. The equirectangular projection however is well studied and easy to make. At this time, it is the easiest to make and distances *can* be accurately measured if you don't mind overlaying latitude/longitude lines and doing some calculations.
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Ever since I was a 10 year old making (*Basic*) Dungeons & Dragons maps of the world, I used hex graph paper. Scale the map with hexes by latitude and your map will always approximate a round world (think of a Buckyball).
Using 2-D hexagon map to portray a globe
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Ancient people who were ocean-faring knew that different projections have different properties, and you need 2 of them for open-sea navigation.
Most maps drawn for getting around might not be to scale exactly, and implicitly flattened along routes and distorted in voids. If you don't *notice* the measuring problems, you don't think about it.
Things like Egyption property lines were drawn accuratly to scale. It would be flat, as it's only long enough to show curvature in one direction so it rolls up like a ribbon. Would you need (and have technology to produce) scale maps over large enough regions to show curvature?
Laying a wodden floor, I had trouble initially and eventually puzzled it out: unnoticeable irregularities in the concrete slab were enough to cause parallel lines to converge and diverge on the scale of jointed planks. So laying roads the fact that a neat grid doesn't work might not be obvious due to overall Earth curvature, but every little hill and tiny rise is enough to make you have to fudge the "straight lines". Does a map projection cover this detailed topology? A city map might simply treat the global curvature in the same way.
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There is no reason to presume that everyone creating a universe is making spherical planets. The reason we have spherical because of the space/time curvature laws that when applied on a macro scale, turn any large object into a semi-spherical object over a reasonable period of time.
However, in a universe where such laws are not applicable, the planets or other objects might not be spherical. They might be square.
Additionally, even in a universe with similar space/time laws, if the world is designed (as opposed to naturally formed), it is entirely possible for it to have an unorthodox shape.
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When I saw [this question](https://worldbuilding.stackexchange.com/questions/14366/close-quarters-combat-in-space) today in the active questions list I thought it would be about one-on-one combat in space. But the question and answers (while still good) were focused on battles between space craft with long range weapons.
For this question, I would like to see answers about personal or hand-to-hand combat in zero/micro-gravity would look like. How could someone defend themselves in space? How could you incapacitate an opponent? What about lethal maneuvers?
For the outdoor space battles, assume that combatants are in flexible highly tear-resistant suits (although not un-puncturable) with propulsion systems controlled by a non-intrusive method leaving hands and legs free (possibly a brain-computer interface). Propulsion power is low and limited to slow maneuvering before an engagement (i.e. does not have anywhere near the power output of the Iron Man suit).
I would consider the following scenarios to be conducive to this sort of combat. (sub-questions are meant to inspire, they don't all need to be answered):
* Heated, personal disputes between community members of an asteroid colony (lethal or non-lethal)
+ Hitting someone for personal reasons is not likely to result in well thought out efficient strikes - might it be dangerous for both parties involved?
+ How might a bar brawl in space play out?
* Territorial wars between small to mid-sized gangs who are not wealthy/organized enough to purchase and operate battle-ready space craft (lethal)
+ What tactics would be used for say 10-on-10 fights?
+ What simple weapons would be effective (outside only)?
* One-on-one space grappling as a professional sport, maybe indoors (non-lethal)
+ What would a 'pin' look like in a grappling?
+ If the goal was to force the opponent out of a ring or sphere (given some fixed structures inside which can be used) what tactics would be used?
* Tactical SWAT teams who don't use ranged weapons to avoid detection from sensory equipment (could be outside or inside). Possibly need to software hack the space suits of their targets so that they don't raise the alarm when the target's vital signs drop off. (lethal or non-lethal)
+ What would a stealthy strike look like to disable a critical piece of enemy equipment?
+ What would a hostage rescue operation look like from a well guarded space vessel?
Good luck, have fun!
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It seems unlikely that gangs would be fighting in space itself, they may fight inside of a space station or habitable dome, but few will be doing space walks, not enough for there to have developed common fighting style for it. I imagine the majority of fights will be 'indoors', because why would a gang member or laymen want, possess authority for, and have equipment and gear for being in space?
Likewise there is little reason for a military to every fight in space. Drones will be more viable in 100 different ways to trying to make a human with full support system just to give him a gun. Close quarter fights inside of your space ship, trying to take over the command room for instance, may occur, but not fights in space. All the fighting with humans will be done within a controlled enviroment that everyone is fighting over controlling.
Fights in EVA gear in space will still occur on occasions, humans find opportunities to fight always, but they will be random incidents, not organized battles. I would say they would be clumsy pathetic things, because no one has developed techniques, weapons, or EVA suits designed for it. The suits will not be designed to protect against bullets and will be just as easily pierced by them. However, bullets won't fire in space, and there is no reason to design a 'space gun' for space battles since, as I said, they will not be standard or desirable way to fight. Thus I would see a space fight either being a clumsy melee fight to try to pierce the others suit or damage it before they do the same to you first, or possible at slightly longer ranges using regular tools as jerryrigged weapons, Imagine using the equivalent of a gigantic staple gun as a long range weapon to pierce someone's suit.
Of course one whole in someone's suit won't kill them. Suits will have plenty of redundancy. They will not be deigned well for combat, but they will have enough redundancy that even if damaged you still have time to get to an airlock. In fact severing your opponents teather to the space station may be a more viable weapon, without that they will soon find themselves floating off into space.
Most of the battle, as I said, would be in enclosed spaces, fighting over controlling whatever habitat everyone is in. These will be roughly similar to standard close-quarters inner city warfare of today, with some possible exceptions. The problem is it's hard to say the exceptions without knowing more about the technology of your world.
1) Gravity, or lack of it, will cause interesting conflicts. Are they using artificial gravity, centrifugal force, or actual gravity of an atmosphereless moon to hold them to the ground? If their in zero G everyone will have to learn to fight in 3 dimensions, which is not easy to learn. The inability to simply change your direction once floating will also make team formations harder. Weapons will likely not be your standard guns, since the kick with a gun would be so large as to throw off your trajectory and movement when fired. Perhaps they will use weapons designed to fire far smaller rounds at high speed, or a system to counteract the kick of the gun by releasing some equal-opposite force behind it.
2) Depending on how your habitat is enclosed risks of damaging the habitat may exist. Larger weapons, anything more powerful then a grenade, may be thrown out as the risk of doing significant harm to the delicate systems keeping the habitat in place are so great. This would be a great reason of justifying a large infantry if you wish it, claiming all the powerful weapons can't be used in the enviroment for fear of the harm their do, so we resort to lots of small arms instead.
I would also say that there would *totally* be zero G combat sports, and they will be amusing to watch. In fact there would likely be many different types of combat sports. Some may put you in a small dome and say "fight it out". In theses cases both sides would 'launch' at each other until they collide, then it would turn into a rather boring grappling match as the bounce around the walls (then again, some find grappling MMA fights to be interesting lol). Other sports may impose other rules, such as a form of fencing where registering hits with foils which are sufficient to Peirce a space suit count as damage; which would result in a sport that is more about acrobatically flinging yourself through a 3D maze of platforms to manure around your opponent into a position to land a strike. Many other zero g sports could exist, in fact if it wasn't too much of 'idea generation' I would post a question just asking for all the different zero G sports that might exist.
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Human nature does not change, and here, we are exploring personal combat maneuvering between persons in microgravity. Obviously, if it were in normal gravity, we wouldn't be having this same discussion.
Here's the thing - Newtonian mechanics always worked in gravity, but reaction forces are much more prevalent in microgravity, and peoples brains need a bit to adjust to the new rules. Once that is done, things aren't all that different. The reason a punch hurts is that a force was applied that compressed flesh against bone and rocked your brain in its cradle - this still works, if you can land it and not fly off into infinite blackness.
Going toe to toe outside a contained area is to be avoided at all cost. You might envision people running and flying at each other, but this is a quick ticket to the big dark - all the defender has to do is avoid contact, and the attacker stands a good chance of never getting another foothold. If he does, it still gives the defender several more seconds to disengage. Magnetic boots would be standard fare. Now if lifelines and tethers were being used, well, bolt cutters are a thing, and well, yes, pistols do in fact work in vacuum. So do knives, swords and morning stars - nothing new here.
Lots of the normal stuff still works - I'm personally fond of kubotans, clubs and small knives. In a society where cut and tear resistance was common, stilettos would regain favor as personal defense weapons. Firing a gunpowder driven weapon in a controlled volume of air would be really unpleasant in small airtight spaces, but workable on larger stations, as long as oxygen saturation wasn't a policy - because that would just kill everyone.
Advanced techniques would be developed with specialized tactics and tools, for different persons involved in different activities. Tazers work fine, and any gang thug or cop in space would likely have a stun gun or stun wand handy at all times. I can imagine police authority being able to override magnetic boot locks, forcing them on. Unusually dense, heavy materials could be crafted into clubs that normally could not be carried, allowing a thug to take your head clean off with a cane made of lead, provided he remembered to brace himself while he swung.
Fighting arts always start with a central philosophy. Whether to kill, maim, control, neutralize, avoid entirely, or whatever else, it all starts with an idea of what you want the outcome to be. New fighting techniques would likely focus on locking up an opponents joints specifically without relying on the ground as a barrier to movement - a Full Nelson and the common Arm Bar are still mostly effective, as long as you yourself don't go spinning around fast enough for a station wall to knock you out. The rear naked choke works almost completely unmodified. Throwing arts work great, but have to be modified and relearned. Deadlier hand to hand arts would focus on imparting large rotational momentum to a person and then using it to twist and snap bones - this already works in Earth gravity, but it would become more prevalent in an environment where it was easier to do.
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I'd see piercing weapons (knives, spears) being used more than long blades like swords and axes due to the impact of puncturing spacesuits.
Guns also count as piercing. Hollow point would be the norm because of the lower chance of damaging critical systems.. the bullets would be designed more to pierce flesh but shatter on hitting metal. Military suits would be focusing on being non-piercable.
No gravity would be the big thing. Newton's Third Law would apply - the force exerted would be in the opposite direction. If someone fires a gun, it could actually drive them back a bit.
If someone wanted to throw a punch, they need to brace against something. Most melee attacks would require someone bracing against something like the ground or wall to 'bounce/whip' their energy into an attack.
In sports like MMA, a strong move is to try to force people onto the ground and punch them in the head while on the ground to utilize gravity and deal extra damage. In 0G space, the winner would be the one who can brace against a solid structure, but I don't see punches and kicks doing anywhere near enough damage to knock people out, much less kill.
Grappling would be a major method of trying to injure. People with more mass and size will have way more advantage than they do on the ground. Things like locks and twisting limbs are very important, preferably those that don't require so much space and energy. Choking holds might be the standard to try to kill or incapacitate.
Something like a **spiked chain** might be an ideal weapon, because it can be used to choke and injure people. Not so much swung around, but wrapped around the neck .
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If I have a world where all races are one-foot-tall versions of their typical fantasy counterparts, what would be the most obvious ways this would affect the building style of these cultures? Would they be able to still build large stone structures? Would they be able to get away building more permanently out of dirt and grass?
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## Building Materials
Most buildings materials could be substituted by smaller parts of the same thing:
* Instead of felling trees they will fell twigs of branches that have fallen to the ground or maybe even climb trees to saw off smaller branches
* Stonemasons will make ashlar rocks from smaller rocks or what we think of as pebble stones.
* Bricks can be made of smaller portions of clay.
* For glass windows they will need finest SiO2
* They could also mine ore and create steel although I guess this will be harder for them
* Concrete is a realistic option as well – maybe reinforced with plant fibers
All in all modern buildings could **look the same** and use the **same materials**.
## Location
Weather conditions could severely impact where to build.
* Rain – could flood whole “valleys” – i.e. depressions or pits – so it is likely they will build on top of “mountains” – i.e. bumps or small hills – providing sufficient drainage.
* Hail – maybe they will not build structures to be hail-proof and just live with the chance of their houses being smashed just as we sometimes build wooden structures in the Tornado Alley. But they could also build their structures in natural caves or build massive stone structures that will survive big hailstones
* Lightning – this could be no problem at all with many much bigger natural structures deflecting the danger
* Wind – have you ever seen a grass root upheaved due to excessive wind? Being one foot tall will leave you with greatly reduced air resistance so this might not be troublesome as well.
I agree with @Neil that underground structures could be very common and would protect people from weather conditions efficiently. You only have to make sure the entrance can be sealed during rain fall.
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As these things usually go, it depends. If there were a scaled-down version of *all* life on this planet, aside from other influential factors, everything should be as it is here, just simply smaller. In other words, would they build the great pyramids? Would they build the great wall? Possibly, though it would be proportionate to their stature more than likely. Granted, it would still be impressive by our standards, just not *as* impressive. It is speculated that the ancient Egyptians severed the rock from the rock face by letting water enter the cracks and freeze. This implies that it isn't a question of strength, but perhaps rather of persistence.
However, if they were one feet tall and they had larger predators, I would imagine that most of their culture would be focused on building protective structures. They could be very intelligent, but no intelligence is going to save you when confronted against a 10-foot tall sabertooth tiger. So it naturally follows that while we have no natural predators, they still would and so their focus behind structures would be largely protective, even if also impressive or decorative. Imagine something like a gigantic ant hill in Africa, except with columns and arches. It would not likely be difficult to spot a habitat for this species if you came across it in the wild, unless there were other sentient species that were smart enough to know how to attack one.
In this case, it would likely also heavily influence how they behave, focusing more on survival rather than artistic endeavours. Our ancestors didn't start making cave drawings for artistical value but rather spiritual value. Likely a sentient species focused on survival would build decorative structures for religious value. Assuming they were very advanced, they would still likely be very religious in contrast to our species in which religion counts perhaps a little less. Likely you would have seen more than one war between members of this species on account of differences of religion.
However returning to the your question, I think it is perfectly possible that you could still see structures made of dirt and grass. Mankind has also made homes in hillsides as it was cold in the summer and warm(er) in winter. They aren't practical however, since it wasn't uncommon to have a stray snake wander into your humble abode, I'd imagine a dirt home would be impractical for a species capable of doing more assuming they were advanced enough technologically, though perhaps their ancestors did so.
It is also likely that their homes are underground, since it is an efficient way to hide from predators without having to extend an above-ground structure to accomodate a growing population. You'd likely still see an above ground structure that protects the entrance, but most of the "city" would be underground in contrast. That isn't to say the walls would be made in dirt. Conceivably they could use rock walls and floors. The royal or noble members of the city, assuming they lived in a caste system, would likely have gold-plated floors or ceilings, while the poorer among them would have only the dirt walls, since that is all they could afford. I assume there would be a caste system, because any sentient species with a minimal sense of self-preservation would also be somewhat selfish and greedy, and a caste system is a natural following of that.
A sufficiently advanced civilization of this culture would likely have an underground tunnel system connecting cities. You would likely also see many of the larger predators slowly dwindle to extinction, as technology would improve to the point of global dominance. However, I don't think you'd see a movement to the surface, since old habits die hard in any culture, and this species would likely continue to live underground. Most above-ground structures would hold religious significance, likely in reference to the stars, as did our ancestors, since there would be no need otherwise for above-ground structures as they become an advanced civilization. These religious structures would be impressive, even to us. It would have their history and beliefs written in stone on it, and should we ever have the pleasure of visiting their planet, it would truly be something remarkable, even after their civilization is long gone.
In short, there would be many similarities with our own culture, except the emphasis would be heavily bent on survival, and as such, also their religions would be about survival as well.
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I don't have the numbers to back this up, but I'd think they could build buildings relatively taller, and at earlier technological levels. A two-story building for us would be like a twelve-story building for them, and their building would have more horizontal supports. I'm pretty sure [the square-cube law](http://en.wikipedia.org/wiki/Square-cube_law) will back me up on this: the smaller things get, the stronger they get, relatively speaking. That's why you can build a house of normal-sized cards, but not one large enough to live in. That also means that your one-foot-tall people might be quite a bit (relatively) stronger than us, able to build much (relatively) bigger, heavier structures with less effort (as Neil mentioned, the strength of the builders isn't everything, but it helps in low-tech settings where brawn is more prevalent than brains).
This may lead to smaller, more compact cities, as wood and stone skyscrapers might actually hold up. Generally, everything will be relatively bigger for these people. To us, it would still look small, but if you ever got shrunk down to their size you'd be absolutely blown away by it.
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Based on the previous answer [here](https://worldbuilding.stackexchange.com/a/9120/6429), concerning hammer-proof armor, one of the easiest way to mitigate blunt force trauma, both from swinging hammers and falling off buildings, are with some sort of dampening soft material. However, a hay bale big enough to pad such blows would have to be pretty thick, being able to deform at least 20 cm, meaning that it needs to be thicker then that, according to the answer.
So, how would one go about creating a condensed version of such hay bales, so that the dampening force is a property of the material, rather than the size and structure of it? The material should preferably be sort of metallic, so I can say they can be forged into stuff, although any other material would work fine.
I am seeking a science-based answer, assuming you could modify the properties of matter with magic. EG: You take a piece of steel and you slide its sheer strength up, or tone down its brittleness.
Price is of no concern, in fact, such a material would be glorious and should not be easy to make.
[Answer]
I'll go for a more serious answer this time.
What you want is a cushioning material. You specify you want a metallic cushioning material. We'll see about that.
[Typical cushioning materials](http://www.earsc.com/HOME/engineering/TechnicalWhitePapers/SpecifyingCushioning/index.asp?SID=64) are foams, in various densities and thicknesses, and
solid elastomers (polymers with high viscoelasticity). These materials differ both in their relative stiffness (foams are almost universally softer, or more compressible, than solids) but also in their recovery behavior during and after an impact. Quick-recovery materials will return to their original height immediately upon removal of a compressional load (say, a golem fist). Being highly resilient they also return a fairly
high percentage of the stored compressional energy in the process. In this category, you have natural rubber, neoprenes, and sponge rubber foams. This is useful if you're dealing with constant loads, such as, in say, a shoe. The two characteristics displayed are **cushioning and resilience**.
Sadly, this is not what you need. You need **damping** (low rebound and high energy absorption). Slow-recovery materials do not instantaneously recover their full thickness and therefore do not return stored energy. This low resilience makes them desirable
for applications requiring damping.
In terms of shock absorption, [straw bales are not as ridiculous it they might seem](http://earthandstraw.com/straw-bale-walls-pass-earthquake-test/), but if you've got cash to spare, you would [use Non-Newtonian polymers](https://www.youtube.com/watch?v=F6I5A5VB5zY) such as [**armorgel**](https://www.youtube.com/watch?v=AXBz5gnQ4PI). The lady in the video I linked specifically wraps her finger in the damping material and [hits it with a hammer](https://www.youtube.com/watch?v=uwqRgj1mqZs) to demonstrate its impressive shock absorbing properties.
Your warriors would probably still get thrown back by a powerful blow. I suspect that would depend on the energy of the impact and the bracing of the recipient. Short answer is they would probably get thrown back by a strong enough impact, but their armor would also protect them against a fall. They might still break their necks due to acceleration.
Heck, if you want to also stop arrows, just [combine it with Kevlar](https://www.youtube.com/watch?v=rYIWfn2Jz2g)
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