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[Question] [ In my near future of manned Mars exploration, NASA/ESA/etc have a dozen or so rovers spread out around Mars. For scientific purposes, the rovers 'talk' to each other via low and high gain antennae bounced off of several orbiters. The rovers are similar to ours today and far enough away that they will never be near each other. NASA could look up these communications (likely in data form of course), but pretty much don't look into them: so largely autonomous. Backdrop/storyline - one of our intrepid Astronauts uses this capability to spy on what another Astronaut is doing near a separate rover far away. In a light sense: Mikey: "Curiosity, tell Spirit to take pictures of Mikey2." **What would be the most practical scientific purpose for having rovers communicate to each other without NASA's management?** I'm looking for a scientific reason that they're programmed to routinely communicate just between each other. [Answer] ## Geological Planetological research. [Electrical resistivity tomography](https://en.wikipedia.org/wiki/Electrical_resistivity_tomography) is a short ranged (apparently couple hundred meters) imaging technique. Seismology gathers and analyses data from seismic waves. It allows mapping of subsurface layers. [Reflection seismology](https://en.wikipedia.org/wiki/Reflection_seismology) goes further, and instead of waiting for natural tremors to occur, it uses explosives to cause short ranged seismic waves when and how geologists want them. Because of those reasons, you really want your rovers to be able to coordinate at up to ~2km ranges - for active research with explosives, and at global ranges for passive detection of natural seismic events. It's nearly certain that at some point, some areas would be deemed especially interesting and rovers would be deployed to map them for resources, interesting geological formations, water or any other reason. If you want single spot done by single machine, it would have to carry a lot of detachable detectors which could be laid down and later picked up, or it could be done by couple of rovers, including specialised carrier, deployer and perhaps recharger (and entire group designed to be mobile upwards to hundreds of kilometres). **Whichever works for your story, but either way, you want your rovers to be able to warn others of incoming natural, global event, so they can lay down detectors and gather more data.** Better yet, for reflection seismology your rovers have a real need to carry explosives, if you ever want your story to have danger on top of those normally associated with space exploration. EDIT: As for part about not looking into data. That one's easy in scenario outlined above. Data regarding rover coordination and warning isn't really important as long as system works. Scientists will want to look at data gathered AFTER, but communication leading to data gathering (one rover telling other that something global is on) will be analysed a first few times to test and benchmark the system and most likely ignored most of the time later on. Until someone decided to look into it to try to upgrade it, verify something or repurpose for another mission profile. [Answer] **Redundancy.** Sending data from Mars is no picnic. Sometimes the data will not get through and at times it will take up to 24 minutes and getting a confirmation would take another 24 minutes. While you may say 48 minutes of data is not very valuable, but during these times, the Sun will be in between two planets which may cause communication problems. Thus, to make sure all data is secure, the best strategy is to duplicate it on multiple devices. While orbiters could be the best idea, they are even more fragile than the rovers on the ground. Thus all devices should be able to communicate and share information for backup. Spying could have done similar to how most systems are cracked on Earth, using a flaw in coding to inject arbitrary code for execution. This could allow Mikey to take control of all devices running the same bugged version of the software. [Answer] They all use a common network, with circuit boards and software as used normally on Earth. Mars and the exploration consortium have their own isolated network, but things inside it behave just like normal IoT nodes. The rovers can talk to each other because the software stack and network fabric supports it; not from any deliberate need. This could be extra sneaky if the person being monitored didn’t think that the rovers *did* talk to each other, while the spy realized they *could*. In this case, if rover A were programmed (on the sly) to send a packet to rover B, it would *just work*, much like two computers in the same company but different subnets. It would send it to whichever orbiting platform was first available, which would see the address and send it back down when in range, and never bother the folks on Earth or inform anyone that this happened. [Answer] Some reasons off the top of my head: 1. I encountered danger, here's what it looked like. 2. I saw something worth exploring but it is too far away from my mission objective. 3. My long range transmitter is broken or there's a mountain in the way of the transmission. 4. I'll take this half of the crater, you take that half. [Answer] # To maintain research independence Each of these rovers have a job to do, so if the same rovers in different locations are replicating work too much (and in effect wasting money), one of them should move onto another task. So, the rovers are aware of the main mission aims and redistribute tasks between them to get the most done in the shortest time. # Multi-band Communication Sand storms on Mars could interfere with radio transmissions, resulting in lost or garbled messages. The rovers routinely re-broadcast mission directive instructions to each other (if you get the same message from two sources, it must be correct). # Plot So, point one gives you the reason, point two allows you to "hack" the system in a plot-driven way (control two or three rovers and you gain control, lose a rover and you lose control). [Answer] **Martian Data-Subsystems Intranet** When NASA humans are actively driving the Rovers around, having them take specific pictures, and taking soil samples, etc. you can bet they want all the high-res images and everything bouncing off the nearest communications satellite and back to Earth as close to real time as they can. When the little guys are in autopilot or sleep-mode a lot of useful-but-boring information like current battery power, weather conditions, etc. are going to be a much lower priority for bandwidth. It would make a lot of sense for these sorts of mundane subsystems to communicate on a low-power local intranet. Essentially, current Rovers (and likely future Rovers) have high-powered antennas for blasting information directly to Earth, but they also have (relative) low-powered antennas that can communicate with satellites that are in-Mars-orbit. In the future, with more Mars-orbit comms satellites in orbit, it makes more and more sense for rovers to save power by using the little antennas by default. Furthermore, if future Rovers are relatively close together (think walkie-talkie range) it might make sense to have direct rover-to-rover communications rather than beam every single datapoint out to Mars-satellites or Earth in real time. Imagine all the Rovers have this local walkie-talkie short distance communication system. What would they want to talk about? The short answer is: nothing exciting. Data backup (for failure redundancy) is probably the main thing. If every rover backs up a copy of every other rover's data, then no data is irretrievably lost even if a meteor or harddrive failure takes out one of your fleet before it uploads its data to the next orbiting satellite. When everything is functioning properly (i.e. no failures), there's no reason\* anyone at NASA is going to open the hood and look at how much bandwidth is being used bot-to-bot (\* other than nerdy curiosity or someone doing an audit for routine systems maintenance). Luckily for your snoopy Mikey1 character, sending backups of video data back and forth could be relatively high-bandwidth (depending on how much is being recorded at any given time) so his own data usage is likely a drop in the bucket. Furthermore, if the cameras of Rover2 are constantly recording Mikey2, then Mikey1 only has to issue a command of "Rover2 push real-time video data to Rover1 for backup." which is basically as innocuous as manually telling your computer to backup your photos now (to an external drive, or the cloud) instead of waiting for the scheduled backup time. [Answer] **Redundancy.** Each rover echos it's findings -- images, raw instrument data, weather data, etc. -- to at least 2 other rovers, chosen randomly from the rovers that are online. Every time an instrument or camera is ready to send a load of data out, it sends it back to Earth and to another rover, so if a rover goes offline or if something prevents data transmission (weather, solar, mechanical failure), the data isn't lost and the mission can continue despite the failure. **Pings.** Each rover pings the other rovers as a "heartbeat." If one of the rovers doesn't respond to the ping, then there's a problem, and the rovers report this back to NASA. **Duplication of effort.** The rovers send each geolocation data. If two rovers happen to accidentally be on converging paths, they warn each other off and stop until NASA can assign new paths (or their internal AI can assign new paths). **Warnings.** If rover 1 detects an oncoming dust storm, it sends out warning data to other rovers with wind speed and direction. Downwind rovers in the path of the storm can then plan accordingly to go into an automatic shutdown to save energy, prevent system damage, etc. during the storm. By having the warning, they can safely stop in-progress testing before the storm hits. **Distributed computing.** If one rover is analyzing data and needs more processing power, it can offload some of the data to another rover that indicates it is (somewhat) idle. This effectively makes the rovers a "cloud computing" system, since some rovers might be at lower system utilization than others. Faster processing means faster delivery of results back to NASA. **Geolocation.** By sending timing packets between rovers and between satellites, each rover can get a better fix on their current position and heading. This means fewer satellites are required to provide the Mars equivalent to GPS. **Local network.** By having constant communications, there's the Mars equivalent to "wifi" for astronauts on the ground. This means the rovers can be the access points for smaller, lower-powered, robots or machines. This way, every machine on Mars doesn't have to pack the weight of a dish and battery capable of reaching satellites or Earth. They just have to be able to reach the nearest rover, which can then relay data to/from orbit or earth for that device. This allows more machines with smaller mass and lower power requirements. [Answer] Say the capability is there for reasons of redundancy, as pointed out by ShadoCat. **Any human on Mars can override orders from Earth or self-directed robot decisions.** This is a safety feature for the humans. If something goes wrong, some scenario nobody thought about, the humans can use any and all robots without waiting for permission from the back office. You need to get a rover stuck in a crater so it is in position to relay medical telemetry? Give the order, the rover obeys. You want to a rover to travel dozens of miles so you can scavenge the batteries for your habitat? Give the order, the rover obeys. [Answer] They are autonomous, maybe they use some kind of self learning AI like neural networks to navigate and find interesting rocks to examine. To maximize learning capabilities they all exchange their inputs and decisions. But every rover still has its own AI because they have different instruments and research goals and to still be able to continue roving and doing science even if connection is somehow lost. Maybe by a defect in an orbiter or an dust storm which can last weeks on Mars. [Answer] They are cataloguing the planet, trying to get new information. Their job will be more efficient if they can tell each other what they have already found, thereby avoiding repeating each others' work. If they wish to explore the entire planet, they will need to share information on where they've already explored again to avoid overlap and waste resources. NASA can't plan their individual territories in advance, because they don't know in advance what they are going to find - one rover might end up spending the entire mission exploring one very interesting 1km^2 area while another may come across a huge featureless expanse and therefore cover a much larger area more quickly. Better to have an AI coordinate the exploration on the job. Additionally, if a rover finds something that, for whatever reason, requires more than one rover to investigate, they'll need to be able to call others over. Maybe one rover has many different types of cameras and its job is to take pictures and send them to another rover with high data processing power to analyse. [Answer] **In Preparation for War!** Right now, exploration of space is a fairly international venture with everyone cooperating for the betterment of all. Sometime in the future, that may change and in preparation for that day, the rovers have been designed to interact with each other without the need for fragile satellites and jammable interplanetary transmissions. They have and use a planetary communication system for the same reason that they all have empty gun mounts on their retractable arms. So that if war ever reaches Mars, they will be ready to defend their owner's claim. [Answer] ## The worst problem of the space probe control is that they can answer a command only hours later... Thus, as it will happen, it will be around the same commands. I write it on human language: * "Here is your new firmware. Install it to yourself and reboot. If everything went well, then upload it also to your pal and say him to do the same." * "Upload half of the new photos from this interesting rock to your pal. Say him to start their sending to us. If he says everything is ok, delete them by you and make a lot of new photos in the free space." ]
[Question] [ In its wandering through the Milky Way, the solar system is getting close to a solitary neutron star. The neutron star will "fly by" above the plane of the ecliptic and its closest distance from the Sun will be 10 AU. The neutron star belongs to the Milky Way too, therefore its orbital velocity is comparable to that of the Sun: they cross each other path. How and when could we possibly detect the neutron star during its approach? We have our present technology. [Answer] # Depends on the type of the neutron star [Neutron stars](https://en.wikipedia.org/wiki/Neutron_star#Mass_and_temperature) that can be observed tend to put out lots of energy. Pulsars in particular would be pretty easy to spot from literally a galaxy away. Young neutron stars may not yet have developed into pulsars, but would still be powerful x-ray sources. However, if a neutron star is young, then it is likely embedded in the cloud of its supernova, which would be another pretty big giveaway that there is a neutron star around (other than the massive x-ray source). In any case, a neutron star shouldn't be able to hide for long. # If a neutron star couldn't be detected (for some reason)... The solar system would be thrown into chaos. A neutron star will have a mass greater than the Sun, and up to 3 solar masses. Therefore, its gravitational attraction will be greater than the sun at the same distance. The semi-major axis of Saturn is 9.5 AU, Uranus is 19.2 AU, Neptune is 30.1 AU. Thus, if a neutron star passed 10 AU above the plane of the ecliptic, it would be exerting more gravitational pull on those planets than the sun. I don't know exactly what would happen, but its a safe bet by the time the neutron star passed, there would be no more planets in the solar system. Given this, the advance warning of an un-detecatable neutron star (which is basically a black hole) would be the objects of the Oort cloud and then Kuiper belt being flung willy-nilly throughout the solar system and out into the galaxy. A massive increase in comets would certainly be detectable to even amateur astronomers. Who says comets aren't harbingers of doom! [Answer] A dead neutron star could probably be detected long before it entered the solar system. Before the general consensus was reached by cosmologists on modern cold dark matter and dark energy cosmology, a viable candidate for dark matter making up galactic halos were known as MACHOs: Massive Astrophysical Compact Halo Objects. Neutron stars are one of the prototypical examples of a macho. MACHOs in general don't emit enough light, radio, or x-ray to be detected directly, but because they are so compact, they can be detected by gravitational microlensing of background stars as they transit in front. The [Wikipedia article on MACHOs](https://en.wikipedia.org/wiki/Massive_compact_halo_object) has a decent summary. EDIT: I don't have enough rep to comment yet, but to address the question of transit time: The sun's peculiar motion (i.e., it's motion relative to the average rotational velocity of the local segment of the milky way) is about 13 km/s [reference](http://iopscience.iop.org/article/10.1088/1475-7516/2009/09/036/meta;jsessionid=E09616A29A30C7EB56A0716A841F33FF.c3.iopscience.cld.iop.org) . The neutron star could easily have a similar order of magnitude, so let's call the relative crossing velocity 20 km/s. From wikipedia, the solar system is about 50 AU in radius, so about 15 billion km in diameter. This gives a transit time of about 20 years. [Answer] It will be ***terribly*** easily detected IMMEDIATELY. There could be 3 or four possible types/stages of a neutron star. A [pulsar](https://en.wikipedia.org/wiki/Pulsar) or [magnetar](https://en.wikipedia.org/wiki/Magnetar) would be immediately detected far, far before it reaches 10 AU to the sun in any direction. The magnetic field would be so powerful, it will probably affect *all* the magnetically sensitive devices on Earth, considering their magnetic fields are hundreds of billions of times stronger than the magnetic field of any planet in our entire solar system. If it is an active neutron star, with powerful gamma bursts, we might never detect it at all: we would all be dead already. This would happen if Earth is unlucky enough to be in line with the poles of the neutron star. Even if it is a *dead* neutron star, no longer having the unimaginably powerful magnetic field or surface temperature of billions of degrees, it would still be immediately detected due to its extremely strong and devastating effect on the planets in our solar system. Considering that the mass of a neutron is 1.4 to 4 times the mass of our sun, it will absolutely wreak havoc at 10 AU from the sun. The orbits of the planets will initially be elongated irreparably, and then some of them might go swirling into the neutron star, or get slingshot out of the entire solar system. At the very least, the orbits of the middle planets (Jupiter, Saturn) would be irreparably elongated. Before getting to 10 AU, the neutron star will wreak disaster on the objects in the [Kuiper Belt](https://en.wikipedia.org/wiki/Kuiper_belt) and far, far before that, it would pick up a whole gang of [Oort Cloud](https://en.wikipedia.org/wiki/Oort_cloud) comets and planetesimals, bringing them inwards with it. Long before the neutron star reached 10 AU, the comets and planetesimals of Oort Cloud and Kuiper Belt will be raining down on the planets (including Earth). We would probably all be extinct several years before the neutron star reached 10 AU from the sun. So in a sense it would be impossible to detect the neutron star entering our solar system. --- **In response to Morning Star's comments** > > I am not sure that the magnetic field would be so strong. Yes, it is extremely strong on the surface. But it decreases cubically with the distance. I think it may be a similar misunderstanding as it goes with the black holes: yes they have a very strong gravitational field, but an 1 Solar mass black hole from 1 AU would have the same gravity as the Sun. > > > You might not be sure that the magnetic field would be so strong, but a quick internet search tells me otherwise. Try this: *These magnetic fields are hundreds of millions of times stronger than any man-made magnet, and quadrillions of times more powerful than the field surrounding Earth.* - [Reference](https://en.wikipedia.org/wiki/Magnetar#Magnetic_field) In order to stay on the safe side, I refrained from quadrillions of times and stayed with hundreds of billions of times. About the gravity of black holes, where did I claim that a black hole of mass $x$ will ever have a gravitational field more massive than that? > > The change on the orbits of the outer planets would be easily visible and permanent, but it wouldn't have a major effect to us. > > > In fact the inner planets would be affected more severely by the gravity of the neutron star. It is simple pythagorean theorem scenario calculating the distance of the intruder to the planets. Here, let me help you: [![enter image description here](https://i.stack.imgur.com/QDjck.jpg)](https://i.stack.imgur.com/QDjck.jpg) Try and work out the relative distance of the planets from the neutron star and figure out which ones would be affected more. Furthermore, the neutron star's gravity and the sun's gravity will partially assist each other, not only pulling the planets out of the solar system's plane, but also bringing them closer toward the sun. It is a matter of trignometric ratios and angles. Work it out. > > About the gamma bursts: Not all neutron star produces gamma bursts and even they don't do it always. > > > Where did I state that **all** neutron stars produce gamma bursts? And when did I state that a GRB source remains active for a long time? Here, I am quoting myself to help you better understand what I meant: ***If** it is an active neutron star, with powerful gamma bursts, we **might** never detect it at all: we would all be dead already. This would happen **if** Earth is unlucky enough to be in line with the poles of the neutron star.* The meaning of my statement(s) becomes clear now. Yes? > > The surface temperature of the neutron stars is some hundreds of thousands, at most some million K, and not billions. Which is still high, but their whole radiation is not catastrophic. It wouldn't be surely visible with free eye. > > > Let me help you about the surface temperature of neutron stars. Here: *"The temperature inside a newly formed neutron star is from around 10$^{11}$ to 10$^{12}$ kelvin. However, the huge number of neutrinos it emits carry away so much energy that the temperature of an isolated neutron star falls within a few years to around 10$^6$ kelvin."* - [Reference](https://en.wikipedia.org/wiki/Neutron_star) OP never mentioned that the neutron star entering the solar system is an old, *cold* one. Once again I refrained from stating trillions of degrees and stayed on the safe billions figure. Furthermore, notice that even after losing most of their heat, neutron stars still get to a temperature of about a million, an order of magnitude greater than "hundreds of thousands". Also, where did I state that ***all*** of the radiation of the neutron star would be disastrous for us/living beings? And where did I ever mention that all the electromagnetic radiation spectrum of a neutron star lays in the visible range? Quote me. > > A 4 solar mass neutron star from 10 AU has the gravitational force of 1/25 of the Sun. Of course it perturbs the orbits, but not significantly, in the case of the Earth it may be even survivable. Considering that the OP says the NS will go above the elliptic, the majority of the orbit perturbation will change the plane in which the Earth orbits. This part won't affect the weather on the Earth. The remainder, yes. > > > As I mentioned earlier, considering that the intruder star and sun are not perpendicular **from the reference point of Earth**, they will have a combined gravitational effect on all the planets, pulling them up (as in, away from the solar system's plane) AND toward the sun. [Answer] First, it's important to realize how very unlikely this is. Even coming as close as Neptune the odds are many millions to one against in a million year period, and billions to one against in a thousand year period. After all, neutron stars are much rarer than stars, or white dwarfs, because only the very heaviest stars can becoem neutron stars. [Debunk: Our Sun or Earth could be hit by a rogue planet, neutron star, black hole, brown dwarf or star](https://debunkingdoomsday.quora.com/Debunk-Our-Sun-or-Earth-could-be-hit-by-a-rogue-planet-neutron-star-black-hole-brown-dwarf-or-star) So, this is rather theoretical. But if this is for some science fiction story, a young neutron star or one in a binary system would be easy to spot from its X-ray emissions and likely to be a pulsar too. But unlike white dwarfs, neutron stars can cool down and become dead remnants. Still we'd detect it via gravitational lensing of distant stars especially if it moves in front of the denser parts of the Milky Way in the sky. You are also talking about something heavier than our sun, so it would have a significant effect on other objects in the solar system and we have many of those now that we are monitoring, transneptunian objects as well as several distant spacecraft that we are still in contact with (Voyager I and II, Pioneer I and II, New Horizons). After all, the gravitational attraction would be more than that of our sun for an object equidistant from both. Also, objects from the Oort cloud would likely hit it from time to time, and cause flashes of light as they hit its solid surface, and most likely leave an accretion disk. I'm not sure how often that would happen or how easy it would be to detect, if anyone knows how to work it out do comment! ]
[Question] [ In an event immortalised in [this Google Doodle](https://www.google.com/doodles/new-years-day-2017), at 4 minutes past midnight (GMT) on Jan 1, 2017, the density of Helium suddenly and inexplicably increased from 0.1664 g/L (at normal temperature and pressure) to 1.664 g/L (in the same situations), a tenfold increase of its apparent weight. Other than causing balloons to tumble in comical fashion, this clearly had many not-quite-so-apparent effects. What were they, and what caused the most disruption to everyday life? How did we find replacements for those uses of Helium that were disrupted by this change? What impact did this event have on society? [Answer] Everybody would die. Let's say you have a helium balloon in your house. This balloon, according to the almighty Google, holds 14L of helium. That 14L is 2.289 grams of helium (if it's an aluminum balloon at STP; if it's latex, it'll be more because it's compressed). If suddenly that were to become 22.89g of helium... that mass would have to come from somewhere. *(Hint: it's not going to come from nearby mass.)* So it'll come from energy, courtesy of E=MC^2. How much energy? 2.0573\*10^14 Joules. *(Sidenote: you probably have at least 1000 of these in your city right now. That energy is ~1.2x the amount of energy from the sun that hits the earth in one second. This is a LOT of energy.)* How much of an effect would this have? Well, if you have an 1800 ft^2 house that's, on average, 8ft high inside, you'll have 520.05 kg of air inside it. That 2e14J of energy would cause a change-in-temperature of that air of 5.511\*10^8 K. *(Hint: it's not going to change that much; it, combined with every other balloon, would just freeze the world.)* And that's just the party balloon you still had from the birthday-party last week... Let alone all the other balloons and other uses for helium. The only other place this mass could come from is other mass - meaning either fusing hydrogen into helium *(Hint: releases a ton of energy)* or fissioning heavier elements down to helium *(Hint: absorbs energy)*. I haven't run the numbers, but I suspect these would be more damaging. If you don't want the world to die, don't tag your question as "science-based." You are literally changing a fundamental law of physics *for one single element*, then changing the laws of physics more *to prevent everybody from dying*. [Answer] Depends on how the helium suddenly gains weight, and how far-spread that change is. ## **How** To make helium become denser, you must **increase the weight** of the individual helium molecules. Or you need to employ a special kind of magic that restricts the speed of Helium molecules to a fraction of their normal Brownian motion speed (i.e. **slows them down** and makes it so that they take up less volume for their weight). ## **Where** If it is **throughout the solar system**, then the sun will certainly get problems -- it lives off fusing Hydrogen to Helium, after all. If helium is suddenly heavier, then that mass needs to come from somewhere, and that most likely will disturb the regular fusion process. Additionally, all helium that has already been produced and is massing in the sun's core, will become heavier and so the Sun's gravity will increase suddenly, and disturb its nice equilibrium. If helium is just slowed by magic, its volume will decrease suddenly, and so the sun's core will suddenly shrink. In both cases: There will at the very least be horrible solar flares for weeks, if the sun manages to stabilize. If not, we could be dealing with the sun suddenly going nova. **Earth only**: If Helium is heavier than air, it will sink to the ground. There are 5.2 parts per million in the atmosphere; a rough estimate has 10km of atmosphere, so helium should pile about 5.2cm high on the ground. Since it will flow from higher ground down to sea level, rowing a boat on the ocean might become hazardous, and I am not sure what the fish in the water (and the ocean-dwelling mammals) will do. Helium is used in the industry for supercooling magnets etc. It's got a melting point of -272°C, and slowing down its molecules will certainly raise that melting point by tens if not hundreds of degrees. As a result, any and all technical applications that use Helium for cooling, will suddenly run hot. Helium is also a sideproduct of radioactive decay (alpha rays are helium nuclei). No clue how radioactive decay will be disturbed if suddenly the breaking-off helium cores are fifteen times heavier than normal (that mass needs to come from somewhere, after all). The alpha rays themselves should lose much of their already small penetrating power (can be stopped by a sheet of paper), but since they are a lot heavier they will probably cause a lot more damage when something like Iodine-13 is ingested. Additionally, whereever alpha decay takes place in an enclosed room, you are in serious danger of suffocating (it can't get out, so it will pile up like carbon monoxide). Tumbling balloons like in your doodle will be the most harmless side effect of heavier helium by far. And, since many DIY youtube instructions for floating balloons all produce Hydrogen from a redox reaction (DO NOT DO AT HOME -- hydrogen is highly flammable, see the Hindenburgh!), there will be many balloons still afloat. Unless you suddenly make Hydrogen denser, too. [Answer] **A ten-fold density increase will kill helium cooled nuclear reactors.** Helium is used for buoyancy, low boiling point (superconductors) and heat transfer/working fluid. In the latter capacity, helium's monatomic nature and especially its low molecular weight are vital. The only way (under our physics, via the ideal gas law) to increase gas density (at same conditions) is to raise molecular mass. A 10x increase in helium gas density would make nuclear reactors using gaseous helium fail. The increase in density would make the key heat removing mechanism ballpark 10x (it might be a square root effect (but still sqrt(10) ~= 3,16..., my statistical mechanics is hazy) less effective. I wouldn't want to be downwind! It will also wreak other devices using gaseous helium for as either a working fluid (some Stirling engines) or as a heat transfer fluid in non-nuclear applications (some chip packaging, or was that technology {IBM, I'm pretty sure} abandoned?) ]
[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/58013/edit). Closed 7 years ago. [Improve this question](/posts/58013/edit) I'm building a world where humans reproduce by machine, not by sex. Two or more individuals submit their DNA together to a breeding company. This company has pods that take multiple people's DNA, combine them in the most advantageous way (based on an algorithm), and turn it into egg and sperm, which become an embryo. The pod then feeds the embryo all the way through its development until it becomes a human baby, which then grows up to become a member of society. Individuals have the option to pay extra for DNA from someone who is well-known for having a certain advantageous gene, such as the ability to run fast, sing well, have photographic memory, etc. So when the child grows up, he/she has the DNA of its parents, plus a part of DNA that is supposed to give it a certain biological advantage, which its parents paid extra for. My question is this: when this child with extra DNA grows up and wants children of his/her own, does he/she have to pay extra for the part of their DNA that was paid extra for? Or, because it's already a part of them, can they just pay for the DNA combining at regular price like everyone else? Who owns the gene? Is it solely the person who sold that part of his DNA for other humans to use, or is it also those people who now have that gene too? [Answer] You can go many different directions, depending on **what you want for plot and flavor**. All of these have precedents in the history of intellectual property. * The lucky person with the photographic memory gene (and his/her heirs) get perpetual royalties. * You only pay for the gene for the first generation, then your children get it for free - but they can't re-sell it. * You only pay for the gene for the first generation, then your children get it for free and they can re-sell it. * The government can seize certain gene lines by eminent domain and distribute them to everybody/members of the military/members of the ruling party/... [Answer] What you describe is very much a social contract, so the answer is 100% dependent on your story. You pick the answer you want, and you can build a society that leads to that answer. This is especially true since, given the way reproduction is done, this society has little to do with modern society. *Edit: So this answer is popular, so I'm loathe to delete it, but the comments below point out that I was misinformed. What's left after I strike that misinformation is minimal. However, I do think my misinformation may still have value for development of fictional worlds, so I'm leaving it here, struck out.* If you wish to stick close to US law, you could consider taking lessons from Monsanto, who makes genetically modified seeds. When they did so, the seed naturally bred with nearby fields and those nearby fields picked up those modified genes. Monsanto sought to sue those farm owners for copyright infringement, but the courts decided that they couldn't claim a copyright on their DNA product. Monsanto's new solution is to make the crop sterile. In this way, all of their seeds are good for growing one year's crop, but the crop itself consists of seeds that themselves cannot foster a next generation. Thus, now farmers must buy new seed every year from Monsanto with their latest genetic modification. [Answer] The way you ask the question makes it sound like you think that necessarily some one must own the gene and that there is some unique way to determine who. But patents are just government granted monopolies, they aren't some inherent property. Have you considered the possibility that no one owns them? Especially since you are building the world yourself, it could be in your world that the laws are such that no one can own any genetic code whether it is naturally occurring or synthesized. Even in the US, naturally occurring gene sequences have been ruled as public domain. The company who developed and spliced the gene can still get paid for the service of placing that gene in a zygote and incubating it to term without needing to be paid specifically for a patent on a gene. And if literally no one is having babies the old fashioned way, then they can even amortize some of their gene-sequencing costs over people who don't elect for gene-modification. (Of course they will still charge a nice premium for the service of modifying any genes. It's just they might have some market competition on that front) [Answer] This is, ultimately, a question of law and legislation. Intellectual property law enables persons and companies to hold rights over things they invent and create. However, things that are discovered cannot be patented or owned as intellectual property. For example, scientific discoveries cannot be owned. Otherwise Peter Higgs could be the owner of his boson. NASA might have to get a licence from the Estate of Sir Isaac Newton every time they launched a satellite. These examples are a bit silly, but they are for the purposes of illustration. The real question is whether finding genes is a matter of discovery or of invention. if a company had invented a gene, perhaps building a completely new of a kind that had never existed before in nature, say, by using the techniques of synthetic biology, then they might be able to make a good case for owning it. However, if the same gene as discovered existing in nature, then their case for ownership is weakened and could be liable for a challenge in court. A recent challenge over the ownership of a medical gene test kit was found in favour of the gene in question being a discovery and not an invention. This resulted in the test kit being able to be used widely without having to either get a licence to do so or have to pay the owners. Since the test was for a type of cancer there were a number of cancer patients who wanted the test kit being made readily available. So they felt it was in their interests to free the test kit from commercial restrictions. On a similar topic, the ownership rights to oil and minerals in land you own aren't vested in the land owner. If a mining company takes out mining rights to pluvidium ore that might under your property, once they find the ore there the mining company owns the mineral and has the right to mine it. You may have been the land owner, but you never were the owner of any oil or minerals under it. Similar arguments have been applied to the genes in your body. They may be there, and part of your flesh, but that fact doesn't give you ownership of them. If it did, then possibly your parents (and even their parents) might also have a claim on the ownership of your genes. It is remarkable that Monsanto has a legal claim over the ownership of its genetically modified seeds. The genes involved in engineering the seeds would have been found through a process of discovery. Possibly, their ownership is vested in the art they exercised in creating the modified seeds. It is also possible that the court decisions that enabled them to claim ownership over their GMO seeds were based upon a misunderstanding about how science is conducted and the judges in question may have been dazzled by the genetic engineering techniques themselves. There are no absolute criteria to determine who knows genes. It is a matter of legal precedent and practise, relevant intellectual property legislation, and the accumulated body of case law and court decisions. Ownership of genes will be refined and decided as more genes are discovered and more claims are made about whether they can be owned or not. People make the laws, ownership is only a matter of law. When people change their minds about how something can or should be done under the law, then the laws change too. NOTE: Pluvidium is a purely fictious mineral. Anyone who thinks they have discovered it or who claims ownership of it, needs to brought back to reality. ]
[Question] [ [Recently, a planet around Proxima Centauri has been found](http://news.nationalgeographic.com/2016/08/earth-mass-planet-proxima-centauri-habitable-space-science/). It is in the habitable zone, in the sense that if the planet was a black body, it would have a surface temperature of −39° Celsius. The planet is very close to its star, which has a number of implications: * Radiation is very strong (additionally, Proxima Centauri is a [flare star](https://en.wikipedia.org/wiki/Flare_star)), and probably has stripped the planet of its atmosphere. * The planet is probably in a tidal lock, with one side facing the star constantly and the other pointing into cold space. I'm therefore assuming that the planet has no atmosphere, but can support liquid water somewhere on the dawn area, where the star shines at a steep angle. *What life forms with the greatest similarity to life on earth are possible on this planet? In what points do they have to differ from earth life?* [Answer] There's really no such thing as a planet or moon with *no* atmosphere. But as it so happens, the object in our solar system most often pointed out to possibly harbour life is Jupiter's moon Europa, atmos$=0.1\mu Pa$, which probably has oceans under a thick layer of ice. There are creatures in Earth's ocean which live without any interaction with the sun, so if Europa has a molten core like Earth, this could provide jets of lava for light and energy. [Answer] The answer to the top question is a likely yes...as we are starting to discover, life seems to exist in a far greater variety of conditions than we could have ever imagined capable of harvesting energy in a large variety of ways. First, there is no surface liquid water on this planet...without an atmosphere, it would "boil" away exceedingly quickly. Which means all life on this planet is relegated to underground / under ice conditions. Answer to the remaining questions is purely speculative...but my answer would be kinda. In the far depths of the oceans on Earth exist some creatures that we would be hard stretched to even call earth like. For the most case, what we consider 'Earth like' all finds it's energy roots from the sun (either directly from the sun as in plants, or animals that consume the plants or each other). However in the vast depths, sunlight is no longer available and life relies on some creative techniques to get it's constant supply of energy. If you are willing to extend the title of 'Earth like' to some of the alien looking creatures at the bottoms of our oceans, then yes...the life on this planet could be 'earth like'. However it's far more likely that this life will be completely alien to us in quite a few manners. [Answer] The [primary reference](http://www.nature.com.proxy.readcube.com/nature/journal/v536/n7617/full/nature19106.html?token=jPA+q2fxWtVhxrlxNGBk0ymazPGlX3K5P7A/pAaQ4yTztjJf4M+NvfQvbKtvNIrq&referrer_url=http://www.nature.com/articles/nature19106.epdf?referrer_access_token=9s4esoS1OnvMMy6UCIh3WNRgN0jAjWel9jnR3ZoTv0OdUoq9A3uBXkywxDHxtCZYsVV2XI9EWh9geyBhzqFKNbbzjutuH5JENrhERg3eqP4VgL-zlkdAeKQcnM25p_JJCBhgEAMGiZBSlC5JG4RGOm6sxm07VWUhOfQuIj3fn68gJ0DElmW3mT2EC0UUkx8F5MnV00gw_u-E_YiWww3nw7-oz5-fcxMCq1KT0qzF9JMNxZFDfhrrdA6IM88Ix0uN86MVhw0efg-j8Zk-4kG9kklecMD0AvGbAgEeEHLbaPM%253D&tracking_referrer=news.nationalgeographic.com) states > > Tidal locking does not preclude a stable atmosphere via global atmospheric circulation and heat redistribution [21] > > > as part of a section devoted to possible habitibility. So I suggest you go beyond the “popular press” digested wimpy version and read the original paper. Indeed, it answers your other bullet as well: > > Because of its close orbit to Proxima, Proxima b suffers from X-ray fluxes that are approximately 400 times that experienced by Earth, but studies of similar systems indicate that atmospheric losses can be relatively small [25] > > > You can follow up on the references cited in this *habitibility* discussion for details that you can use in your world-building case. I’d also like to point out that a tight orbit does *not* imply tidal locking as is commonly assumed. Look at the case of our own planet Mercury! As [this lecture explains](http://www.seti.org/weeky-lecture/patterns-sunlight-extra-solar-planets), having an odd half multiple for spin/orbit resonance is a more stable situation and now thought to be the common case. This is especially favored for an eccentric orbit, and large planets farther out will *drive* that eccentricity. In addition, orbital inclination will cause north-south movement of the sun in the sky. (And the paper points out that even with tidal locking it could very well have enough of a magnetic field to tolerate the flares.) So in your story, you can be faithfull to all known details of the planet and have an atmosphere and have sunrise/sunset cycle every 22 days, with twilight periods in the arctic and anarctic regions. [Answer] Very interesting question, yet seems to be slightly obvious for me: oxygen, or at least, gases are much more important for sustaining life than water. Water acts as a material within which basic biochemical reactions occur; oxygen is the *fuel* that ignites said reactions. Also, water stays in the body for much longer time than oxygen does. The only proper consideration we may have is underground or aquatic life forms, with little or no needs, or different ways for acquiring oxygen, or other "fuel" substances. This way, it should work, as it's definitely not unusual for life to evolve in such environments. I would have a pretty strong assumption that the way life appeared on Earth was not *directly* depending on the atmosphere. (Of course, indirectly it was, but that's another question) [Answer] In a well covered ocean the cheap energy of the star might not be directly available, but [other](https://en.wikipedia.org/wiki/Radiotrophic_fungus) sources might be. Our kind of like has pretty well covered this planet, including the places humans are just getting capable of checking. But there are still two qualms I have about saying we have neighbors like us: 1) Has any life spawned there at all. We are only certain of one abiotic life event, it happened pretty early on for our planet but appears to have happened only the once here. 2) If some long hydro carbons start organizing I find it unbelievable that RNA is the way they do it. It's the only way we do it here, but there are many "that's just the way it is" answers in biology that might not be our way somewhere else. All well and good, but whether it's written in java or perl the app still runs, and I might not be able to tell the difference. I recently couldn't pick some real sea creatures out of a lineup of dreamed up CG ones, so it's quite possible something that lives in water will be at least as familiar as some of our locals. [Answer] There are certainly niches available to life I'd look to the McMurdo Dry Valleys and the deep sea geothermal vent communities to see what organisms can and do survive in the kinds of extreme climates you'd be looking at on such a world. ]
[Question] [ In Pokemon, there are many different creatures. Nearly all of them will, at one point, reach a level of experience where they evolve into a more advanced creature. These evolutions are much more drastic than what human evolution is like. One minute an animal could be an average sized turtle, and the next they are huge and have water cannons on their backs (Wartortle to Blastoise). **How could an evolution like this be possible? Is there any way that science could explain this?** I am more hoping for something that explains a bit less drastic of an evolution than Wartortle to Blastoise, hopefully something more like a small bird turning into a big bird really fast (Pidgey to Pidgeotto) or a bug growing wings (Venonat to Venomoth). [Answer] # Pokémon "evolution" exists and is called metamorphosis Real world animals do this. However, it's not called evolution because it is not in any way evolution; it's metamorphosis, and rather than "experience", it is food (or sometimes just time) that must be gathered to begin the process. The caterpillar $\to$ butterfly is pretty much exactly like pokemon evolution (which is probably why this real life metamorphosis inspired Caterpie $\to$ Metapod $\to$ Butterfree). More examples would be Tadpole $\to$ Frog Maggot $\to$ Fly There are huge numbers of examples of metamorphosis, although caterpillar $\to$ butterfly is one of the most extreme. Generally, they include 4 stages: egg, larva, pupae, adult. # Why is this not evolution Evolution is change in heritable traits of biological populations over successive generations resulting from a selection pressure in their environment (where "environment" can take a very large definition). ### Heritable? > > Baby Pokémon are the lowest stage of Pokémon evolution. The concept > was introduced in Generation II, along with breeding > > > <http://bulbapedia.bulbagarden.net/wiki/Baby_Pok%C3%A9mon> So we can see that Pokémon evolution is not heritable, baby Pokémon are always born at "the lowest stage of Pokémon evolution". ### Selection pressure? Equally Pokémon evolution always follows a set "plan" (of one of a small number of plans) so the "design" itself cannot be driven by a selection pressure in their environment. ### Successive generations? Finally Pokémon evolution occurs for a single individual so is not over "successive generations" ]
[Question] [ I'm writing about a human community (all immigrants or descendants of) in what is basically an elfin city. The main political question facing the community is isolation versus assimilation, but I think it needs some other controversies as well (and this could go for other communities in the world, such as the city at large). Problem is, most of the potential issues and controversies that spring to mind are those from 21st century America, but those would not all apply to this community. Different sexual orientations are completely accepted. Women are politically and socially equal to men. The community is mainly middle class and doesn't have large income inequalities. Racism isn't common - they have far more in common with the other humans than the elves. What sort of topics would be debated politically? What areas should I be looking at to figure out their hot button issues? I've already come up with a few, but it'd be good to see if there's any obvious ones I'm missing. [Answer] Fictional controversy needs to be familiar to readers/users of this world otherwise at best it doesn't seem controversial or at worst is convoluted and confusing...I could probably switch best and worst there without it mattering...anyway, moving on. Some commonly controversial topics: * Religion * Political System * Individuals or groups that stray beyond social norms * Power hungry individuals and organizations (just because everything is stable doesn't mean it will stay that way) * Laws that specify anything racially specific (Jim Crow laws, Anti-Jewish WWII era laws for example) * Introduction of external players, this can create new conflict where it may not have existed before. * Really any form of inequality * Boredom. Lives with no conflict can be felt to have no value. When I hear everything is perfect is usually a clear sign that things are not what they seem. Notes. In standard fantasy humans tend to be far to impetuous for elven tastes and that can lead to conflict. Perception of the world is greatly impacted by longevity and many readers may find it hard to accept that humans and elves live together in such a Utopian way. [Answer] So you need some snakes for an elfin eden... If not racism, how about speci-ism? Do the elves resent the human and vice versa? Do either species approve of mixed marriages? Perhaps the opposite is the case. Perhaps half-elf children are so beautiful and bright, that purebreds of both species are in decline numerically. Purists in both camps could be highly resentful of their diminishing role in the City and might even join together to fight the growing hybrid majority. Ageism is always an easy solution. Some of the elves might be centuries old while the oldest humans have at best, one century of experience. Perhaps 150 year old adolescent elves have trouble calling 60 year old humans with honorifics such as Sir and Ma'am. Maybe they object to the humans holding any seats on the city council, because none of them are old enough for the job. Perhaps the humans consider even the youngest adult elves are old fashioned and tradition bound. Maybe the heart of the conflict is resource management. The elves dislike the wasteful slaughter of trees while the humans think nothing of it. Now all of these conflicts are between the community and the surrounding city. If you are looking for conflict within the all human community, that is easy too. They are human. Conflict is what they do best. Religious beliefs, Clan rivalries, Land ownership disputes, arguments over the details of major historical events,... put any two humans in a room and they will find a reason to hate each other. [Answer] One way to create realistic conflicts is to make them analogous to real world conflicts. For example, mutant superheroes can be used as a substitute for homosexuality. They are different, special. They are born that way. They did not choose to be the way that they are. They are rejected and feared by humanity because of what they are, not who they are. Doing this can allow the stories to engage people who would otherwise reject the story outright. This allows the author to show the difficulties of being the recipient of homophobia to someone who is homophobic and would simply not read or watch a story about homosexuals. You also have the possibility of making your fantasy issues real. One of the advantages of the superhero metaphor is that a rogue superhero really can be dangerous. It takes the unreasonable fear of the homophobe and makes it reasonable. This can allow an author to explain homophobia to the tolerant in a way that slips past *their* prejudices. A specific example for a human/elf society: perhaps elves are immune to demonic possession while humans aren't magical enough for the possession to last long (demonic possession burns out their bodies and kills them). The half-breeds could lose their immunity but remain durable enough to be possessed for long periods of time. This makes a half-elf dangerous. So there's a real reason to avoid interspecies romance. The obvious replacements in a human/elf world are speciesism and ageism, as [Henry Taylor noted](https://worldbuilding.stackexchange.com/a/7234/2113). Another possibility is anti-magic prejudice versus pro-magic chauvinism. That's interesting in part because it may cut across the human/elf divide. Or maybe it doesn't. Perhaps all elves are a bit magical while only some humans are. Are the magical humans more like elves or other humans? Perhaps they are rejected by both. Note that even if you pick a particular human prejudice on which to model your fantasy prejudice, you don't have to tell the reader which one. This can give you more freedom to explore the conflict than you would have had with the human prejudice. You aren't as bound by people's preconceptions as you would otherwise be. And of course, you still have an obvious real world analogy to explore. The humans are immigrants. Presumably they are poorer than the more established elves. If not, they probably used to be richer (they are poorer now than they used to be). How do the elves feel about that? How do the humans respond? You'll be more trapped by the real world here, as there are obvious analogs. You can fill this out though with other reasons for prejudice, which can make the results different. You don't mention why the humans became immigrants. Are the elves afraid that the humans will involve the elves in human problems? Do they wish that they'd left the humans to their fate? [Answer] Why not begin with the fact that elves are in fact superior to humans in many aspects? Think about it: elves are much more long-lived than humans, are more agile than human, their craft skills are vastly superior to our, and not to mention the fact that their society is politically perfect compared to our. Humans are mortal, their skills are crude, they are politically unstable, and divided among themselves, and in terms of purely physical they are less agile than elves. Racism can arise from these differences that can never be filled. Humans can do their very best in order to achieve something that and elf do just like that, but in the end they will fail. Try to imagine the trade between these two races: what could humans offer to them? If humans traded luxury goods (you say they are all middle-class, so I think that they could be craftsmen) elves would difficult buy their products, given that they can craft them better than humans. If humans traded normal goods same thing. If humans traded raw material, obtained through heavy work (think about mines, sawmill, etc.) it would not be long that humans would see their social status lowered to the height of the working class, and friction would born between the “rich” elves and the poor humans. The political and social system could then be affected by envy of the humans against the elves. This would not be racism, but of specism, and would also be justified by the fact that it is not a bizarre idea, but it is the reality of things. [Answer] adaptation of technology! 'Elf' races are hard to write, if you make them too perfect the audience starts to dislike them. Take away all of our common issues, racism/sexism etc, and they start to become a little to perfect. You need real controversies, things where they may *not* be in the right, to show their still human and relateable. The best, in my mind, example of this is adaptation of technology, because it's a great [screw you elves](http://tvtropes.org/pmwiki/pmwiki.php/Main/ScrewYouElves) answer. Classic elves are 'more in touch with nature' and thus have less technology. The thing that people forget is that we use technology for a reason, not only does it make our lives easier, it saves lives, lots of lives. people who imagine 'rural simplicity' forget how much we benefit from technology in subtle ways, like nutrition and food, time to peruse leisure activities, and medication. So, I think a perfect controversy could be adaptation and use of technology. Perhaps your elves have lived a simple traditionalist life with close contact with nature, but the lack of use of technology is starting to make it hard to provide for food for everyone. There could be a great debate between use of technology to improve lives and how it goes against their traditions, or even the concerns about it's harm to the enviroment. Take this a step further and you can merge it into the isolation debate quit well. Maybe the non-isolated people have technology that the 'elves' don't use. They debate about using foreign technology would be closely connected to the debate to opening up to foreign communication. The same traditionalist view may exude both. Some though may be okay with using the new technology, while still wishing to be isolationist, or vice versa. The two debates are closely linked while still be different, and can nuance each other. I personally would go a step further by showing the harm that the lack of technology does, but this is admittedly partially because I'm so frustrated with literature trying to claim those 'in touch with nature' are inherently better while also showing a lifestyle that is impossible without the modern technology they don't use. Show some food shortages that come from lack of using designer foods (long before genetic engineering we designed food by 'breeding' it; banana and corn did not look like what they do today when we first got hold of them). Show death from infection because basic anti-biotic aren't used. You don't have to show the 'elves' as stupider or less advanced then others of course. You could show the 'elves' having better technology in other areas, while still making the debate about using the foreign tech very real. Other then that two standard go-to options would be classism and speciesm (being unfairly bigoted against the foreigners they have been isolated away from, look at some of the anti-Hispanic bigotry). However, these 'controversies' are so overdone I find them a bit tedious to have come up yet again. [Answer] One of the things that tend to happen in a perfect society is that young people with too much testosterone and too little life experience tend to get bored, unruly and eventually violent. The political conflict that might arise could revolve simply around "our young are bored and agressive and we need to pacify them" vs "our young need to get it out of their system, we need to enable them". Life thrives on conflict, and in its absense usually has no problem creating its own. [Answer] I read this, and see a utopia. History can be a wonderful tool for exploring the attempts humanity has endured in the pursuit of utopia. My first thought, is the pursuit of Communism by Lenin, followed by Stalin. I say this not to demonize a political system, but to illustrate a potential avenue for you to explore. It may also be a good point of reference, as you are citing issues prevalent in 21st century America. A look at other nations, and at history may get that creative spark going. The author, Ayn Rand, born Alisa Zinov'yevna Rosenbaum in 1905, had lived through the establishment of Communism in her country, and later managed to immigrate to America. Her novels explore the dangers, as she saw them, in America migrating from a Democratic Republic, to a Communist system via selflessism, or as she viewed it, the use of guilt to deprive one who is successful, in order to supply one who is not, or chooses to remain idle. Instead, she preaches the virtues of selfishness, and throughout her life, maintained that selfishness as she meant, was not as it is defined. Igor Gouzenko was an author and defector, known for the book, The Fall of a Titan, which depicts a Soviet man and his life, in the height of Soviet Russia. Igor Gouzenko had the unique perspective of having lived through the era, and policies of Stalin's Russia. These two authors paint a wonderfully rich image of Communism, it's policies, it's ideals, and the real effect that it had on the people, and in doing so, provide an equally rich avenue for you to explore in terms of potential conflict. Not just from within the constraints of your Elfen and Human city, but from outside sources as well. The history of Fascist Germany and Italy may serve many useful as well. Closer to home, and on the topic of racism, or what may be in your case, speciesism, the topic of war makes a lot of room for controversy. Consider how African American soldiers were treated during the Civil War, WWI and WWII, or how Native Americans were viewed during WWII. Consider how many Japanese Americans were relocated in what equated to American concentration camps during WWII, and how many ended up losing their homes in the process. Further, consider how the Japanese Americans who enlisted into the military during WWII were treated, in comparison to the Native American "Wind Talkers" and what their return from war may have been like. Ira Hayes would be one example. These bring up a wealth of social controversies (on both sides of the table) that don't necessarily have to stem from war. I think if you look to American history, and to the history of other nations, you will find a veritable cornucopia of useful controversy that you can use. [Answer] I was thinking of a controversy in the ancient world that seemed alien to me. I had read about the importance of chariot racing factions or *demes* in Byzantine Constantiople. From Wikipedia on the [Nika Riots](https://en.wikipedia.org/wiki/Nika_riots): > > The ancient Roman and Byzantine empires had well-developed > associations, known as demes, which supported the different factions > (or teams) under which competitors in certain sporting events took > part; this was particularly true of chariot racing. There were > initially four major factional teams of chariot racing, differentiated > by the colour of the uniform in which they competed; the colours were > also worn by their supporters. These were the Blues, the Greens, the > Reds, and the Whites, although by the Byzantine era the only teams > with any influence were the Blues and Greens. Emperor Justinian I was > a supporter of the Blues. > > > The team associations had become a focus for various social and > political issues for which the general Byzantine population lacked > other forms of outlet. They combined aspects of street gangs and > political parties, taking positions on current issues, notably > theological problems or claimants to the throne. > > > Your citizens could ally themselves with a sports team in a spectator sport played by humans and elves both. The activities of the team could be proxies for larger issues. It seems unbelievable to me that an activity for which the closest modern parallel is football hooliganism could destroy half a city and cause the death of tens of thousands but that was the case for these Nika Riots, which were only the worst of the sort of conflicts these *demes* produced. One hazard of keeping the public occupied with bread and circus: the circus piece can get out of hand. [Answer] "Women are politically and socially equal to men. The community is mainly middle class and doesn't have large income inequalities. Racism isn't common - they have far more in common with the other humans than the elves." How are the norms enforced? This could be a great plot twist. How is it that their is no rich or poor, middle class? Are 100% happy with men and women being equal? Racism isn't common, but is it hidden? If these norms are forced upon people, by whom? Is there a government/leadership issue? Are the elves better off. Never underestimate envy. Most people at some level judge by comparison. I may have a Bentley, but the guy next door got a Mercedes and now I'm angry... Is the government/leadership doing enough to assimilate or isolate? Who elected them anyway? Can I break out of the 'middle class' by creating a little strife? Strife is usually not about our conditions, it is about our perceptions. ]
[Question] [ Assuming interstellar travel, and self-sufficient colonies in other star systems, what are some methods of destroying the Earth while leaving minimal impact on the colonies? **Context** I would like to keep Earth-based culture and languages intact, without having to deal with "modern" (modern being relative to the story being told) baggage of maintaining Earth's politics and needs. In short, I'd like to keep things like English, without forcing the inhabitants of the universe to be concerned with resources on Earth, or protecting Earth, or revisiting Earth, etc etc **What I've Considered:** I think the most probable way to knock off Earth is to wipe out the local Solar system with it. In my limited scientific knowledge, this would probably require knocking out the Sun. Waiting for the Sun to die naturally could leave too much time for colonies to advance, significantly changing the technology, culture, and a myriad of other things. The question then became, how do I make the Sun kick the bucket early? Perhaps collision with another body, perhaps another Star, or planet? What are the repercussions of such a collision? [Answer] I'll take a cue from Lois McMaster Bujold's Vorkosigan novels' planet Barrayar. You mentioned interstellar travel but not the means. If you want a series of colonies that preserve modern culture, that would seem to prefer **wormhole travel** over near light velocities and constant accel/decel, etc. That allows rapid enough travel of culture to minimize isolation. So you've got a web of wormholes connecting systems that give you a reasonably quick path to most colonies. Earth is in a little cul de sac with a single link to this web. **Then one day the wormhole closes.** Reasons why are a grab-bag of possibilities. Or a one-way wormhole, allowing colony expeditions for some span of time, then a sudden collapse of civilization on Earth, and that's it for new colonization. [Answer] # [Near Earth Objects](http://en.wikipedia.org/wiki/Near-Earth_object) This will likely be the easiest way to destroy earth, or at least make it uninhabitable, which seems to be your primary aim. It seems pretty likely that, at some near point in the future, we will be hit by something big enough to alter the environment of earth. Many people assume that a sizable impact on earth would make it not so nice for us living on it, including those who survive the initial impact. Asteroid and Meteor impacts are a big enough threat that [people](http://en.wikipedia.org/wiki/Asteroid_impact_avoidance) are dedicating real resources to prevent it. Even small celestial objects can cause things like the [Tunguska Event](http://en.wikipedia.org/wiki/Tunguska_event#Description), and larger ones can cause dramatic climate changes, which can lead to [terrible extinctions](http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event#Chicxulub_asteroid_impact). If you really want overkill, you can use a [rogue planet](http://en.wikipedia.org/wiki/Rogue_planet). Those also have the potential to destabilize the orbit enough to make Earth a rogue planet, or send it to the sun. [Answer] How about a plague? A genetically engineered weapon that is impossible to cure or contain could wipe out Earth just as effectively as any larger apocalypse. Everyone on Earth would be dead and the entire planet could be completely quarantined so you don't have to worry about anyone going back. If the weapon was designed to remain dormant in a different reservoir species then it would never be safe to return. One advantage of this apocalypse are that you don't have to rely on some extremely unlikely astronomical event. Additionally, the genetically engineered weapon could have been created by a small terrorist group, and so you don't need to write in some massive war or anything like that [Answer] For my money you can't beat a swarm of self-replicating nanobots. This has, of course, been tried once already here on Earth, with only partial success. A molecule got thrown together that happened to have the physical property of being able to create copies of itself. That in itself is already a fairly promising recipe for disaster, and indeed to start with that's what seemed likely to happen: the copies, and the copies of copies, multiplied exponentially, threatening to dismantle the entire world and turn it into more copies. The process stalled when it turned out that these replicators were not endlessly versatile in the types of raw material they could use, so all the immediately available usable stuff got used up, limiting the rate of replication. So, the copies turned on, and attempted to dismantle, *each other* for raw material. Random variation in the copies led to a situation where the best-equipped copies won and replicated, crowding out the less-well-equipped copies. This led to a de-facto arms race, externally unguided but effective because of the consistency of the selection pressures that determined the winners. It caused the resulting entities to grow more and more sophisticated, and to gain more and more abilities. A few billion generations later, the copies had got so sophisticated that entire colonies of them could move around coherently and exchange information with other colonies. The colonies themselves got progressively more sophisticated, until they were able to invent the internet, and to use it to ask each other how the job of destroying the world could be done more efficiently the second time around. Sorry if you had different ideas about how we got to this point. But by examining the mistakes made the first time around, the answer should be clear by now, and it is in two parts. First, design a self-replicating nanobot that's more versatile in the raw material it uses, so its exponentially multiplying copies *can* effectively eat the whole world without being contained in the bounds of their own ecosystem. Second, don't let them turn on each other: rather, get them to cooperate so that they make way for each other to spread outwards in search of more raw material. (This is where [a bit of foresight](http://xkcd.com/865/) is required in the design of the communication system.) Stick to this recipe, and we'll have the Earth teeming and homogenized before you know it. [Answer] This method seems a bit extreme... if you want to destroy Earth's politics but keep their culture, there are far easier methods. However, some solutions anyway: ### Nova Bombs In *Andromeda*, all Commonwealth warships [carry Nova Bombs](http://en.wikipedia.org/wiki/List_of_planet_killers#Andromeda). These are bombs powerful enough to cause a star to nova by negating its own gravity, thus causing a nova due to the pressure and a lack of gravity containing it. According to [the wiki](http://andromeda.wikia.com/wiki/Nova_bomb#Science), this nova causes an explosion of hydrogen undergoing fusion, which obliterates everything in its path, destroying the entire solar system. There is a [theoretical way](http://archive.wired.com/wired/archive/6.03/antigravity_pr.html) to do this, using a rotating ceramic disc above powerful electromagnets, although whether it could be done on stellar scale is doubtful. Scaling down... ### Planetary Destruction There [are plenty](http://en.wikipedia.org/wiki/List_of_planet_killers#Star_Trek) of fictional weapons capable of destroying entire planets, most notably in the Star Trek series. For example, the Xindi superweapon was a directed energy beam capable of collapsing entire planets. However, my personal favourite idea for destroying planets is a [Doomsday device](http://en.wikipedia.org/wiki/Doomsday_device), which would kill all life and render the planet uninhabitable for a few centuries at least, but it leaves the option to re-settle the planet later. ### Keeping Culture Alive If you want to keep Earth's cultures, you need their people. There's no doubt about that. So perhaps you should take a few (say 5) people of each culture you want from Earth to survive the annihilation and come with you. You could even select these people by posing as a human for a few years and running a high-tech selection program on Earth's inhabitants. [Answer] How about that uranium in earths core accumulate to a critical mass, in such a big size such that the earth rips itself apart? Such feedback-loops of uranium has happened on earth, and there are even serious scientists that propose that the moom was formed by such a rupture. [Natural fission reactor](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) [ArXiv Preprint with theory](http://arxiv.org/abs/1001.4243) [In the media](http://www.technologyreview.com/view/417259/moon-may-have-formed-in-natural-nuclear-explosion/) [Answer] Humans have been having a hard enough time keeping themselves from destroying Earth since nuclear weapons were developed. They could fail in the future. If all you need is for the place to become a nuclear wasteland, nuclear weapons will do that. There could also be some sort of research experiment which does something that starts some sort of reaction that wipes out the planet and makes it uninhabitable. Scientists have been somewhat concerned about accidentally discovering how to do that when they tested the first atomic bomb. Some people were worried about this recently with certain particle accelerator experiments (CERN Large Hadron Collider), though in that case, we were assured by scientists that there was no actual danger. Some of those independent colonies might do it for political reasons, especially if Earth's government was trying to control all of them, and that could lead to a history of factions and distrust between the colonies. [Answer] **Don't address the question** I like many of the other answers given but the problem with all of them is that they will impact what your world is like outside of Earth. I suggest that you can get away with *simply ignoring the question*. Just take whatever it is from Earth you want and never even discuss what happened to Earth, why it's not there or whatever. You can get away with a few premise details like this being left unanswered; your audience will not be overly concerned. [Answer] ### A black hole (or neutron star) Now of course that one colliding with the eart/sun would be just too easy. But what about it passing by? Its gravitation will play billiard with the solar systems planets, making them crash into the sun, into each other, leaving the solar system etc. ### A gamma ray burst In the right distance, this will wipe out a whole sectors life out of our galaxy, leaving behind just a big toast ball formely known as earth. ### A scientific experiment about something like FTL travel, or the suns fusion, that horribly went wrong, causing the earth to implode into a black hole, or causing massive disturbances in the fusion reactions of the sun, which then causes massive flares/CMEs, or even ejection of its outer shell, toasting the earth or even removing it from its current orbit. [Answer] Let's look at what you want: you want a set of colonies away from Earth, which don't care about Earth and have no influence anymore with Earth. The easiest solution is just to let your story take place thousands of years after the colonies have been formed. Earth will slowly have turned into this mythical place that the young generation has never heard of. This is a major plot point in Battlestar Galactica and is implied to have happened in Star Wars and Starcraft. You say you want to keep English though, which does not go well with this. However, barring any major breakthroughs in interplanetary or interstellar travel, it will already take many years for humanity to get to the point that a colony can exist. Languages evolve anyway, so you can have a sort of futuristic version of English. [Answer] You could always go with the Firefly/Serenity route. Earths natural resources are used up, so the two most advanced countries, the US and China, send colony ships out to a nearby system to start teraforming and colonizing. There is no FTL travel so its a one way trip. Earth becomes a myth of sorts and considered uninhabitable by everyone in the new colonized system. If you do a google search on the 'verse you can find some images of what it could look like, smaller star systems that are part of a larger system. The layout is very similar to Alpha Centauri, with each star having its own planets. [Answer] In Charles Stross's *Iron Sunrise,* one side in an interstellar war is defeated and launches a doomsday weapon at the enemy. This is described as an R-bomb (for "relativistic"), basically a huge bullet launched on such a course that it will hit its target (decades later) at a large fraction of the speed of light. IIRC this is done, at least partly, by slingshotting around stars. That's an option for any civilisation that can launch large objects reasonably fast, and you can just find the mass and speed numbers that will do whatever you want to do to the Earth. For total destruction, knock a big chunk off the side so the wreckage tumbles and flies apart like a rotten peach hit by a rifle bullet. *That'll show my ex who's unreasonable.* [Answer] There is a way without any unlikely physical phenomena. Suppose Earth created a colony somewhere. It's quite likely that it took most of the Earth's resources to create that colony, and though the mission is a complete success, they are physically cut off from Earth, sending out new colonists or even a supply ship is out of the question. Maybe it was a penal colony (stroke guinea pig farm) or maybe for a different reason, the inhabitants don't want to remember where they came from. They start a new life there, advancing technology and creating colonies themselves after a couple of hundred/thousand years, while Earth goes into slow decline, eventually losing the ability to even contact the colony. Of course New Earth will also inevitably fracture politically but it will fracture whichever way you want it. [Answer] Convince other races in the Universe to use the sun as a dumping ground for all their centuries of waste - the growing mass of the sun would require each planet's linear orbital speed to be faster in order to remain stable. Because planets can't just speed up this way, all the planets would start to spiral into the sun, and eventually be consumed one by one [Answer] A few easy steps to destroying Earth: 1. Get hold of a fairly massive celestial body. It could be a star, a rogue planet (as PipperChip mentioned), or something completely different. 2. Put it in a position so that it is orbiting the galaxy at the same rate the solar system does - except much higher up or lower down perpendicular to the galactic plane. 3. Propel the thing in a direction perpendicular to the galactic plane. Perhaps you could accelerate it using a black hole. (This happens to stars near the supermassive black hole at the center of our galaxy. Unfortunately, the supermassive black hole isn't directly above or below the solar system, but we can make do with a smaller one.) 4. Make sure the thing hits Earth - or passes by it on the side, perturbing it enough to chuck it out of the plane of the solar system. Alternatively, you could (well, not in *our* universe) do what Hactar did in *Life, the Universe and Everything*, the third (but not final) book in the [*Hitchhiker's Guide to the Galaxy*](https://en.wikipedia.org/wiki/The_Hitchhiker's_Guide_to_the_Galaxy) trilogy: Create a junction connecting the heart of every star, turning the universe into a supernova. In this case, you could simply connect the Sun to another star, or - even better - the Earth to another star. [Answer] There are limits to how fast one can travel. In order for frequent interstellar travel to be physically possible, the story would have to be set in a region of the galaxy where stars are closer to each other (probably closer to the center of the galaxy). It would have taken humans several generations to get there. To colonies among a number of stars in that region of the galaxy, Earth would be mostly irrelevant because no human would be able to travel between Earth and the colonies within one lifetime. One could imagine that before the first humans had left Earth to colonize those systems, we had already detected the presence of terrestrial planets in the habitable zone around most of these starts located closely together. And this was sufficient for some very adventurous people to set off on a multi-generation trip to colonize those planets. [Answer] Enter a pact with all countries, equip all our nukes with rockets, fire them all and start an interstellar-global-thermo-nuclear-war with our sun to accelerate its dying process. ]
[Question] [ In my story, I have a character who travels back in time to Africa just after the [Youngest Toba supereruption](https://en.wikipedia.org/wiki/Toba_catastrophe_theory), about 74,000 years ago in order to collect genetic samples from the human survivors at the time of the most pronounced human population bottleneck. During her time in the past, she drops an empty polypropylene microcentrifuge tube (similar to <https://www.eppendorf.com/au-en/eShop-Products/Laboratory-Consumables/Tubes/Eppendorf-Safe-Lock-Tubes-p-0030121023>) that she has been using to store her samples, but as she is in a hurry, dismisses it, rationalising that it won't survive until the modern age where it might be discovered, and won't cause a paradox even if it is discovered. Would my character be correct in her supposition that her missing plastic microcentrifuge tube wouldn't survive to the modern age and be discovered, or are there circumstances that would allow the object to be discovered sufficiently intact 74000 years later that it could be identified? To be clear, I'm looking for either "There's no way it would survive, because...", or a plausible scenario in which it *could* survive. [Answer] It's organic, so it *might* fossilise if it found itself in ideal conditions for the fossilisation of soft tissue, i.e. being rapidly buried in stagnant, anerobic mud, which later becomes part of a sedimentary rock. However, even if such a fossil did form, the chances of it being dug up and noticed in the main character's own time are essentially zero. If it happened in a story I would find it really frustrating, as it would be so unrealistic. The reason is that someone would have to look at the exact right rock at the exact right time. In this case that's especially unlikely, since there would likely be nothing special about the rock at all, except that if broken apart in the right place a faint impression is visible that to an expert's eye *might* appear suspiciously similar to the outline of an Eppendorf tube. But even if it was a bigger object it would be unrealistic. For a fossil to be discovered it not only has to be formed in the first place (which itself is a rare occurrence), but geology also has to contrive to bring the rock back to the surface for someone to find it. The vast majority of fossils will either stay in the ground forever or eventually be subducted back into the mantle, or come to the surface and erode away before anyone ever lays eyes on them. Digging up a fossil is a relatively common experience - I've found a few myself, just in our garden as a kid - but you have to remember that those fossils were laid down over millions of years. They're common not because it's common for an animal to become fossilised and dug up again, but because *so many* animals have lived and died over Earth's history that despite how unlikely these events are they've still happened enough times for us to notice. The reality is that entire species of dinosaur have come and gone leaving us only a fragment of a tooth to know they were there, and many more must have come and gone without leaving even that. So story-wise I would definitely drop the idea of the tube being found. It would just be one of those annoying coincidences that pull you out of the story because there's no reason why that specific thing should have happened at that exact time. **Edit:** Other answers suggest having the tube be found with the remains of a human. That would make it much more likely to be noticed - but it's still potentially an unrealistic coincidence, because as far as I know we don't currently have fossil humans from 74,000 years ago, and it would be very surprising if we did, since there were so few humans around at that time. However, if you work it into the story in the right way it might be ok. For example: how does the main character know where to even find the humans, if there are only a few humans on the whole planet? Perhaps it's because such remains have already been uncovered, before she travels back. If that's the case then it's much more likely someone would be carefully examining them at around the same time. [Answer] Polypropylene fully degrades in a few decades, so unless she dropped it in the equivalent of a lab environment it will be long gone 74,000 years later. One circumstance which would fit into your story and cause quite a stir is if it was dropped right by a corpse or body part that then fossilised and was found 74,000 years later. This is because scientists now will analyse the soil around a fossil to help determine it's age and many more things they can find out. The decomposition of polypropylene often leaves some nasty traces in the soil, cadmium and some other things I don't recall, it's rarely pure polypropylene. Which if found would be thought strange and would elicit some niche study. [Answer] **Frame challenge: I'd rather be bothered with modern microbiota introduced into the aged ecosystem** Humans evolve, and whatever other symbiotic or parasitic bacteria we have on or in our bodies also evolve, their composition and adaptation changes to human diet or atmosphere composition or whatever. Since your scientist would certainly spend more than a single day in the past, and would not go everywhere in a biosuit (also keeping all her dumps with herself), any bacteria she has on herself have chances to be transmitted to the populace she'll be in contact, and also to the wildlife (hey you touched a tree, there goes a dead skin eater, etc). This could lead to all the various outcome to the populace, starting from their total extinction (the bottleneck was really small, and a person transmitting sickness agents to the entire populace would spell doom) and up to their unexpected acquirement of new symbiota, allowing to say transit to agriculture faster than unaltered, thus accelerating civilization deployment by hundreds of thousand years. Collateral damage also could happen, in case some modern version of our parasites would meet a suitable host in the forests of old, leading to *their* unexpected evolution, hello domino effect. PS: the girl should also undergo heavy biohazard checks upon return, probably she'll catch some nasty air-transmitting disease back then, and accidentally wreck *current* humanity together with the past one due to us losing immunity to that thing! [Answer] I just don't see what is the problem if a small plastic item is found somewhere in Africa. I cannot say for sure, as I have never been there, but I believe that they do have plastic ballpoint pen caps in Africa? (The item looks very much like the cap of a Bic pen.) But anyway, polypropylene is one of the least resistant plastics to environmental factors, with degradation due to natural factors happening in decades not centuries. I would be very surprised if a small polypropylene ballpoint pen cap dropped on the ground would have survived since Roman times, and really very surprised if it made it through 70 millennia. Are there circumstances where the small ballpoint pen cap would survive in a recognizable form for 70 millennia? Of course there are. After all, we have fossils of *humans* who lived 70 millennia ago, and human bodies are normally even less resistant to environmental degradation than polypropylene. But I would say that overall its chances of survival are very very small... [Answer] For a serious scientific look at the problem of ancient civilizations in the geological record read [The Silurian Hypothesis](https://pubs.giss.nasa.gov/abs/sc07600p.html). The paper can be downloaded for free and has speculation by NASA Scientists about what might remain from the distant past, to quote from the summary: > > If an industrial civilization had existed on Earth many millions of > years prior to our own era, what traces would it have left and would > they be detectable today? We summarize the likely geological > fingerprint of the Anthropocene, and demonstrate that while clear, it > will not differ greatly in many respects from other known events in > the geological record. We then propose tests that could plausibly > distinguish an industrial cause from an otherwise naturally occurring > climate event. > > > [Answer] Frame challenge: Don't bother answering how it survived: There are plenty of artifacts where we don't understand their provenance. Instead, take it for granted that it survived, then have it match a real-world [Out-of-place artifact](https://en.wikipedia.org/wiki/Out-of-place_artifact). Optionally, it was disguised as a failsafe against discovery by the natives. ]
[Question] [ A federation of alien spacefaring nations is doing basically the opposite of prime directive: they are jamming the Solar System, preventing us from leaving it. They are doing so by placing some devices right outside the Solar System, and these are the cause of special relativity and the speed of light problem. Without jamming, in normal conditions, light speed is instantaneous, and there's no limit to the speed you can achieve. How pseudo-plausible is that? I can use handwaving of course, but I'd rather use as few as possible. What other effects might this have? Like nuclear weapons no longer working? (I don't think so, but I'm not sure.) [Answer] ## The Copernican principle As L.Dutch pointed out, this would violate the [Copernican principle](https://en.wikipedia.org/wiki/Copernican_principle), which essentially states that there's nothing special about observing the universe from any one place. Granted, this is not easy to test, as we humans only sit in one tiny portion of the cosmos. However, it's possible that the Copernican principle is incorrect, and tests have been devised and, in some cases, carried out: * Observing distant supernovae can tell us whether we live in a large underdensity ([Clifton et al. 2008](https://arxiv.org/abs/0807.1443)) * That same underdensity would influence our observations of the cosmic neutrino background ([Jia & Zhang 2008](https://arxiv.org/abs/0809.2597)) * Unexpected changes in the Hubble constant at different redshifts would indicate that we on Earth are privileged observers ([Uzan et al. 2008](https://arxiv.org/abs/0801.0068)) * Future radio telescopes could test our assumptions of cosmological homogeneity and isotropy ([Schwarz et al. 2015](https://arxiv.org/abs/1501.03820)) . . . and so on and so forth. Most of these are not related to the problem at hand, but any positive result would indicate that the Copernican principle may be wrong. It's still quite possible that this is the case. I don't think many astronomers subscribe to that view, but it's not yet out of the question. ## Consequences I'm going to stick to the cosmological effects of this sort of change, and what we'd see on Earth. The immediate consequence is that the night sky would, for a short while, turn mostly black. Consider two photons from a distant star, traveling towards Earth. One is emitted just before the jamming begins, and therefore reaches Earth instantaneously. The other is emitted just after the jamming begins; it travels instantaneously to the edge of the Solar System, but then takes a time $\tau=r/c$ to reach Earth, where $r$ is the radius of the jamming region. The Solar System is large (the Oort Cloud is arguably a light-year or two in radius), so it would take about a year or two for the second photon - or any other photons emitted just after the jamming began - to reach Earth. But in that intervening time, there would be no stars in the night sky on Earth. We would also notice that light from all sources outside the Solar System would arrive at the same time. That is, light from a source 10 parsecs away would arrive at the same time as light from a source 100 parsecs away. This is because it only takes them a time $\tau=r/c$ to reach Earth; outside the Solar System, the light travels infinitely fast. We'd have [many of the astronomical consequences](https://worldbuilding.stackexchange.com/a/3658/627) we would get in a universe where there's no speed limit: * No redshift of sources beyond the Solar System, as $z=0$ when $c\to\infty$. * As a consequence of the above Olber's paradox would no longer hold: the sky would be bright, as it would hold light from all of the objects in the (presumably infinite) universe. * We would see distant galaxies as they are, not as they used to be. * Gravitational waves would travel instantaneously fast, as they travel at the same speed as light - which is now, outside the Solar System, infinity. * Spectroscopy is either out the window or severely modified. I'm not sure if you could build a self-consistent model of electromagnetism, let alone electronic or molecular transitions, so spectral lines are likely right out. * Even in the event that lines are produced, most broadening mechanisms (e.g. pressure broadening, thermal broadening) and line diagnostics wouldn't exist because of the aforementioned lack of redshift and therefore the Doppler effect. What this means for science, from an observational perspective: * We can no longer use distant supernovae to measure the expansion of space. * We can't use the radial velocity method to detect exoplanets. * Determining galactic rotation curves would be exceedingly difficult, if not impossible. * Early-universe cosmology is suddenly almost impossible, as we can't see protogalaxies in the earliest stages of formation. * Without spectroscopy as we know it, determining the composition of celestial objects is extraordinarily difficult, if not impossible. All of this is just the tip of the tip of the tip of the iceberg. In other words, you can throw the majority of astronomy and cosmology right out the window - that is, if the infinite speed of light doesn't make things like stars and fusion impossible, and there's still an outside universe to observe. [Answer] The basic assumption behind our constant effort in producing physics theories is that they are valid in every place of the universe. This assumption has never been disproved so far, and if it was as you say, we would observe some hint of this jamming. For example we would observe a discrepancy between the distance of galaxies estimated via the Cepheid method (which uses only the magnitude of some stars) and the same distance estimated via the red shift (which is due to the spacetime dilating while the light travels at c through it). It would also be difficult to keep order in the light reaching Earth: the deeper we look in space, the further back in time we are looking in time, so we observe different stage of the universe life. The jamming should take that into account. Even if handwaving might be used to explain this, a space probe observing the deep universe away from Earth but still in the solar system would observe something different. [Answer] [**Refraction**](https://en.wikipedia.org/wiki/Refraction) Refraction is based on light moving at different speeds through different materials. As soon as light travels everywhere instantaneously, *all* of optics goes out the window. Lenses, prisms, filters, lasers - it all doesn't work or is radically different. Which means that the aliens outside our system are operating under a completely different set of physical laws. Light may travel instantaneously, but the aliens may not be able to see it because it cannot be focused by eyes or instruments. The idea that special relativity was fundamentally wrong was used as a throwaway comment in explaining the aliens' interstellar travel in [The Legend That Was Earth](https://en.wikipedia.org/wiki/The_Legend_That_Was_Earth), but the author was smart enough not to explore the massive impacts on physical laws inherent in this idea. [Answer] **And God saw the light, that it was good: and God divided the light from the darkness** Our keepers have produced a habitat for us where physics works in a way that keeps things running and keeps us alive. Things we perceive as coming from outside our bubble must be simulations of some sort, like the distant ocean background pasted up against the back wall of an aquarium. The fish cannot explore that distant ocean background. [Answer] Not plausible at all, *unless everything we see out there is faked*. The aliens would have built a "bubble" all around the Solar System (or a good part thereof - there is something like that in *Giant's Star* by James P. Hogan, and in [*The Crystal Spheres*](https://en.wikipedia.org/wiki/The_Crystal_Spheres) as well), and the inner wall of the bubble is a sophisticated "screen". Appropriate emitters simulate a relativistic universe. This *solarpsistic* Truman Show includes, for example, the fact that some stars such as [T Pyxidis](https://en.wikipedia.org/wiki/T_Pyxidis) or [T Tauri variable stars](https://en.wikipedia.org/wiki/NGC_1555) emit a distinct time-dependant light signal (such as a nova explosion or a luminosity variation), and then we may see the light from this event reflected back towards the Earth with a measurable delay of weeks or months, as the "flash" illuminates e.g. a large nebula, the nearest parts first. Were *c* infinite, the nova flash would illuminate the whole nebula at once. Also, other phenomena relying on relativistic physics and gravity traveling at the speed of light (e.g. a star orbiting a black hole) would evolve differently were *c* different and practically infinite. This endeavour would need to have been initiated some eight or nine billion years ago, since the Sun's very existence, let alone our biochemistry, relies on the speed of light being more or less its known value. The barrier might have to take into account mass and thermal exchange (haven't done the math). Over billion of years, with a star and its solar wind locked inside, effects on orbits and ecosystems might be significant. [Answer] > > Without jamming, in normal conditions, light speed is instantaneous > > > The universe outside of the illusion would be unrecognizable to us. Time and space in it would not exist as we know them, if they even existed. [Tachyons are hypothetical particles that travel faster than light](https://en.wikipedia.org/wiki/Tachyon). A few excerpts from the wiki: > > As noted by Albert Einstein, Tolman, and others, special relativity implies that faster-than-light particles, if they existed, could be used to communicate backwards in time. > > > And > > (...) in the case of a hypothetical signal moving faster than light, there would always be some frames in which the signal was received before it was sent so that the signal could be said to have moved backward in time. Because one of the two fundamental postulates of special relativity says that the laws of physics should work the same way in every inertial frame, if it is possible for signals to move backward in time in any one frame, it must be possible in all frames. This means that if observer A sends a signal to observer B which moves faster than light in A's frame but backwards in time in B's frame, and then B sends a reply which moves faster than light in B's frame but backwards in time in A's frame, it could work out that A receives the reply before sending the original signal, challenging causality in every frame and opening the door to severe logical paradoxes. > > > It's like people from all times and eras being able to communicate with each other. This, with the causality violations, means time makes no sense outside the bubble. If you handwave that, there is still the problem of light being very fast. We've had another question, which was specifically about that: [What would happen if the speed of light was fundamentally faster?](https://worldbuilding.stackexchange.com/q/47401/21222) Remember the formula $E = mc^2$? If you increase the value for $c$, it means converting mass to energy gives you more energy per unit of mass. This means all nuclear reactions are way more energetic. If $c$ is infinite, then a single particle undergoing such conversion can cause the universe to collapse on itself, maybe generating another universe in the process. In the words of the immortal Douglas Adams: > > *There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.* > > > *There is another theory which states that this has already happened.* > > > [Answer] Let me try and answer this question from a very theoretical point of view. But first, we need to set up some assumptions. The principle of relativity is a good assumption to start with. Now, as the OP mentions, the aliens have set up devices just outside the solar system to *jam us* and prevent us from leaving. Fair enough. But can we sit inside our solar system and observe this? Probably not, because the aliens would not like us to find this out. So they might set up a system where these *devices* they have placed is basically a sphere around us (we are inside a Matrioshka brain?) , and *they simulate the outer universe*. Possible? [Maldacena](https://en.wikipedia.org/wiki/Holographic_principle) would like to agree with you. There is a theory that intuitively states that the description of a volume of space can be encoded on it's surface. Given the ability for instantaneous communication of the device outside our solar system, it can have a number of parallel processing components anywhere in the universe if required to fine tune a simulation for the tests that humans do. This means that no observations that we do without going outside the solar system (if possible) would not reveal the actual structure of the universe. But what about local observations (observations withing the solar system)? No changes from our known results. Standard relativity applies, so all's well. Fine, so the aliens can hide themselves till we venture outside. But all of this was deduced *assuming that the aliens exist* and *can jam a bounded region*. Let's talk about the second assumption fast. Looking at the structure of the universe right now, it's like this [![Structure](https://i.stack.imgur.com/YNnJY.png)](https://i.stack.imgur.com/YNnJY.png) where I would like to stress that this is a projection of the universe onto a 2-D plane, and that the outer universe might not be flat as shown, but may have a different structure.. The space inside the circle (region $R\_1$ is our solar system), and the rest is obvious from this observation. Now, if there are any inconsistencies in a universe with a closed and bounded region having a different light speed than the rest of the universe, then it's bound to occur at the intersection as it is the point of discontinuity. To that end, how can two points, say $A$ and $B$ on the boundary communicate? Since the region bounded is convex (had it been concave, there would still be points that will lie in a locally convex region), the straight-line-communication would have to go through our universe, but then they would be limited by the speed of light of our region and also have a chance of giving themselves away. To avoid such things, they can use a external point $C$ and since $A\to C$ and $C\to B$ is instantaneous, $A\to B$ is also instantaneous. This solves the problem as to what would be the speed of light on the boundary (if it makes sense, like using continuous refraction to keep it on the circle or something like that). How? Define a relation $\sim$ on the set of points $R=R\_1\cup R\_2\cup R\_3$ (where $R$ is the whole universe) such that for $x,y\in R$, $x\sim y \iff x$ and $y$ can communicate instantaneously. Observe that the relation is trivially reflexive and symmetric ($x\sim x$ and $x\sim y\Rightarrow y\sim x$) and by the argument in the above paragraph, $x\sim y,\ y\sim z\Rightarrow x\sim z$ and thus the relation is transitive. This shows that this an equivalence relation and hence $R$ is partitioned into 2 subsets $X,Y$, the former where all points can instantaneously communicate, the latter cannot. Since $A,B\in R\_3$ can communicate instantaneously and since $A,B$ was arbitrary, $R\_3\subset X$ and thus $X=R\setminus R\_1,\ Y=R\_1$.Thus light speed is infinite (in a mathematical sense) on the boundary. So far, no inconsistencies. Now we ask the following question. How will two particles, one in $R\_1$, the other in $R\_3$ communicate? We first look what happens if they are electrically charged. This won't be a problem because of [electromagnetic](https://en.wikipedia.org/wiki/Electromagnetic_shielding) [shielding](https://en.wikipedia.org/wiki/Faraday_cage). The aliens can hide any traces of them, electrically. But what happens if one looks at gravitational effects? Can these devices *hide* geometrical distortions in spacetime? Hard to say. If there is a particle in $R\_3$ that bends spacetime in a way that we can detect using the particle in $R\_1$, then the detectors might take in account the effects and simulate a visual program for us to *see* to validate our observations but giving no information about the outside universe. Possible I suppose, but very very difficult. Might be closer to impossible, but here I run out of maths in this regard. So let's take it that they can keep us in the dark even though we try to measure outside stuff via things that are globally affected. Then, is there any known theory that stops them from doing so> The Copernican Principle? Not so much a problem, because it's a local issue and happens in a closed and bounded region (I can say compact, but let's go with this). Because suppose you throw out $R\_1$(mathematically). Does $R\_3$ have a problem with that? No, because all points in $R\_3$ can communicate instantaneously and hence communication-geodesics (the line of fastest communication) can circle round the hollow region without any problem. There might be some physical issues, but none fatal enough. This does break homogeneity though. But one can characterize the hole as a singular region, akin to a black hole and shut physically it out by not communicating with it. There will be residual information leakage and other effects, but nothing inconsistent that would cause a logical collapse. One might observe that no information about $X$ ever reaches $Y$ and hence $R\_3$ is a horizon, and hence there should be a radiation quite similar to Hawking or Unruh radiation (random particle emission), and we can observe this to know that something is wrong, and there exists a horizon. This line of argument does not work, because we can't observe this, as we would be living inside, roughly speaking, an inverted black hole. The leak would be outside, into $R\_2$. Think as I may, I cannot see any reason why the aliens cannot jam a bound region and not give themselves away. This leads us back to the assumption that *the aliens exist*. The existence of the aliens is an extension to the question of whether a self-consistent universe with an infinite light speed exist. Possibly... yes. Well, at least, the following provide evidence for such a universe to be consistent. Assuming the principle of relativity, and that the universe is isotropic and homogeneous, [Sir Palash B Pal](https://arxiv.org/pdf/physics/0302045.pdf) tells us that two kinds of relativistic systems are consistent. One with a constant $K=0$ and the other with a constant $0<K<\infty$. He argues that the first case arises from the assumption that time is absolute, which is basically a universe where Galilean invariance works ($X$)and the other is basically our universe $Y$. Until we go poking around $R\_3$ (when we will obviously detect the presence of a sphere), $R\_1\cap R\_2=\phi$, and $R\_1$ is closed and bounded and hence is consistence. How shall the dynamics of such an universe work? Pretty much just classical mechanics, non-relativistic QM, and the like. Electromagnetism is inherently relativistic, but non-relativistic electromagnetism, the so called Galilean electromagnetism, [exists](https://web.archive.org/web/20161021014416/http://fisica.unipv.it/percorsi/pdf/jmll.pdf) and is consistent with instantaneous light speed. Interestingly, spin-orbit coupling goes out the window in such a universe. A rather boring set of atomic orbitals. What about gravity? Gravity in $Y$ has a geometric structure, which can be explained by General relativity. But in $X$? Fortunately, there is a consistent geometric formulation of geometric Newtonian gravity, called [Newton-Cartan theory](https://en.wikipedia.org/wiki/Newton%E2%80%93Cartan_theory). Again, the geometry in $X$ and $Y$ has to agree (and be differentiable) at $R\_3$, which the devices probably will have to do if they want to avoid detection. Is it mathematically possible? Yes. The reasons are involved, but it works. Can such a universe have a beginning? Hard to answer, possibly yes? But the birth of stars and everything would have to be modified. The existence of mass-energy equivalence is purely relativistic, but strictly speaking, such a thing cannot be said to be inconsistent with classical physics. One can insert such a term and get away with it because all it would do would be to shift the energy scales from 0 to some other value. But would it have any physical meaning? No. An example to why this is so is simple. Take a particle of some mass. Let it radiate two photons, one to the left and the other to the right, both of equal wavelength. Let's see what $X$ and $Y$ can deduce. First in $Y$. The center of mass frame of reference says that the particle stays at rest because both the photons carry equal momentum. But in a moving frame, one of the photons would have higher energy, and hence higher momentum and thus the body would have lost some momentum. To reconcile both the observations, they deduce that the body has lost some mass. But in $X$, wavelength does not make sense. All radiation are instantaneously propagated and hence the word loses its meaning. Both the photons have the same energy (it it makes sense) and hence same momentum in whatever frame they are observed and hence makes no deduction about the particle's mass or energy. In other words, *stars possibly cannot exist*. First line of thought that can produce an inconsistency found! If no stars are formed, then no higher elements as there would be no nucleosynthesis, and hence no life. I do not believe life can be formed with just the lower few elements, and pure consciousness is not something that can be defined with current theories that we have. Is this enough to kill off the aliens? Highly probable, but there can be one way (more than one way) the aliens can still crop up in such a bleak desolate universe. A stabilized rotating Kerr black hole! Or something similar. Let's suppose the aliens are a Type-III or Type-IV civilization (likely the latter) residing in a universe similar to ours. Maybe something similar to the extraterrestrials in Arthur C. Clark's 2001: A Space Odyssey. They have discovered a theory of how to *jam* regions of spacetime in a Galilean universe to induce a *Einsteinian universe* in such a place. They also have the technological know-how, only no way to test. They also have the potential to open a portal and pass on their information to other universes in the multiverse. One such *thing* reaches a universe that looks like $X$, a Galilean universe. They see no life, just bleak primitive elements and compounds spread across a desolate, barren and dark landscape. The aliens reconstruct themselves in this universe, and then start constructing their device, on a large scale, which, according to them, would encompass several thousands of galaxies in their universe. Once done, some of them stay inside the structure, and the rest leave the universe for other work.They generally don't disturb the device, except to look at what the situation is on different places inside the region. Due to relativity now doing it's work, stars form, heavier elements arise and a miniature Einsteinian universe starts. Ages pass, and life births on several planets, one of them being Earth in the Solar System (their names are different to the aliens, but we call them so for easy identification). After several million years, intelligent life starts on Earth, none of the others being fruitful. The aliens are happy with their simulation, and they construct a similar device just around the solar system. After completion, they deconstruct the outer device. This obviously puts us in the situation the OP has right now, albeit not the process the OP was probably thinking. I don't have anything to add right now, but if I do find anything else, I would add them up. [Answer] Not really One of the key observations Einstein made when developing Special Relativity is that electromagnetism and Newtonian mechanics are invariant under the action of different transformations. Individually, each theory lets you run through your lab at whatever (constant) speed you like and still produces results that are consistent with those you'd get if you'd stood still, but, because the results transform differently between the two theories, when put together they produce contradictions Einstein solved this by making the smallest corrections to Newtonian mechanics necessary to bring it into alignment with electromagnetism (essentially replacing the Galilean transform of Newtonian mechanics with the Lorentz transform of special relativity) We don't want special relativity to be true so, what if we instead try to adjust electromagnetism in the smallest way to make it compatible with Newtonian mechanics? Well this is kind-of what the luminiferous æther was trying to do and, unfortunately, Poincaré and Lorentz eventually showed that, in order to make it compatible with our inability to measure our movement through the æther you end up getting identical predictions to special relativity (just with some additional theoretical overhead and in a form that extends less easily to include gravity) For special relativity to be the result of outside influences, either Newtonian mechanics or electromagnetism needs to be entirely faked That means your aliens need to be able to control every interaction between every particle in the zone they're jamming. This isn't just micromanagement, or even nanomanagement, this'd be more like femtomanagement (electrons living at the femtometre scale) and would require your aliens to be essentially omnipotent and incredibly dedicated Alternatively, you could go for the simulation hypothesis and have us just be a program running inside a non-relativistic universe but that's arguably a more drastic separation from the external universe than a bunch of obssessive gods messing with us for kicks ]
[Question] [ I was inspired by Dead Space which had cloned organ banks for transplants due to mining accidents. I honestly found this idea intriguing so what I'm wondering would it be practical or do better alternatives exist? The "clone" would be a rapidly growing organism that takes the appearance of a bloated infant. The organisms have been cloned to not feel pain and if possible be virtually brain dead. All in all they would be basically a big sack of organs that, due to the human genetics used, takes the vague shape of an infant. The process would be simple: a patient in need of an organ would either be put in cryo if it's a critical organ or simply wait a few days to weeks while the organ is being grown. Once the operation is complete, the rest of the organs are frozen and used for other transplants. Would this be a practical/feasible organism or am I looking in the wrong direction? [Answer] It would be more practical with nonhuman donors. This is **xenotransplantation.[![xenotransplant schematic](https://i.stack.imgur.com/ZdMxm.jpg)](https://i.stack.imgur.com/ZdMxm.jpg)** <http://sitn.hms.harvard.edu/flash/2015/xenotransplantation-can-pigs-save-human-lives/> Human donor babies raise ethical concerns. Also practical concerns: humans grow up so slowly and are so dependent. Pigs grow up fast and a lot of the work of growing up large numbers of piglets to adulthood has been industrialized because we like pork. A genetically engineered pig can feed itself and fend for itself. When its organs are needed the rest can be meat. --- This is strictly coming at it from a practical viewpoint. For the tone of your fiction you may be digging the bloated baby / DeadSpace / H.R.Giger horror scifi angle. You could riff on pigs and keep it weird by making bioengineered aliens. Perhaps the aliens have no rejection barrier and can be genetically forced to grow multiple organs like tumors all over their bodies to maximize yield per alien. Other organs can be grown on these aliens as well depending on what your purposes are and how hard your NC-17 rating is going to be. I can imagine halfway through the story that the (not unexpected) twist is aliens growing human brains. The more unexpected twist is aliens growing several human brains, and other things... [Answer] **There is a far better way**. Really if the can age an organ form infant to adult in a few weeks then they can just start the clone from a single cell in a similar length of time. Or more realistically just grow an individual organ without anything else. Being able to rapidly grow one organ is easier than rapidly growing an entire body of organs. But most likely making an organ will proceed like this. 1. A bio-printer prints a non-cellular matrix matching the correct organs extra-cellular matrix complete with signalling proteins. That's not a cell printer BTW but a biological molecule printer. 2. Another machine fills it with un differentiated or partially differentiated stem cells, which respond to the tags forming the correct cellular layout. Ideally this would be a cell printer. likely both machines would be working at the same time with the latter slightly behind the former. 3. differentiating cell produce a working organ likely with some trimming and testing steps before implantation. The entire process would likely only take a few days and have little waste, we are getting close to this today, I expect to see it in use within the next few decades. [source 1](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5006370/) [source 2](http://schen.ucsd.edu/lab/papers/paper134.pdf) [Answer] ## Yes With an If, No With a But Other answers have suggested that live, fast-growing, barely conscious, human infant clones are not worth doing, because there are better methods which are less ethically fraught, better targeted to the required need, and less wasteful of resources. Speaking practically, however, yes it could be done. But from a story-telling perspective, you might want to explain why it's done this way. You might have to explain that scientific advancement is at this very specific level where they can clone entire humans but [choose to?] not clone individual organs or use donor animals. (I don't know if one is "easier" than the other.) ## Let's Do This Maybe you could say your society is better at other bio-sciences than genetics. E.g., Maybe the "clones" are actually twins, created at the parents' request (or by the State, or by their employer) by splitting the "original" zygote into one or more separate zygotes, and one grows normally while the other(s) is harvested and given the "clone treatment." Maybe the fast-growth is done using synthetic hormones instead of gene-manipulation. Maybe the insensitivity to pain and low brain activity is done by lobotomy on the fetus, or chemically induced partial-coma. ## Don't Look Here On the other hand, your audience might not question the premise. E.g., on Star Trek TNG, Lt. Cmdr. Data cannot use contractions. He just can not. Trekkies ask why but then just figure "Oh it's complicated" and move on (or keep ranting till they die lonely). But if you're going to explore all the dilemmas that arise from your particular type of organ bank, audiences may wonder why we are doing it this way instead of all the other better ways suggested in the other answers. But you might side-step the sci-fi dilemmas by re-directing attention to more legal and philosophical problems. E.g., is the clone property of the patent holder who invented the cloning process? Why would parents or individuals permit clones or even care? Etc. But then we're back to where we've started: what issues are highlighted by *these* clones, which haven't already been explored by androids, replicants, zombies, sentient AI, and yes, clones? I'm not saying there aren't any such issues, I'm just saying that if you're going to set up a highly specific premise, then it should ideally be for a good specific reason. So, from a story telling perspective, it's hard to tell how practical this would be. [Answer] The impractical part is that you would need to grow an entire human being (or all the pieces of one in a single unit) just to get one organ. > > A patient in need of an organ would either be put in cryo if it's a > critical organ or simply wait a few days to weeks while the organ is > being grown. Once the operation is complete the rest of the organs are > frozen and used for other transplants. > > > Why grow an organ to order (requiring the patient to wait for days or weeks and possibly die or deteriorate..."cryo" is not foolproof) if you can just pull a ready-made organ out of the freezer instead? If it's necessary to customize each organ, then who will use the extra frozen ones? It doesn't make any sense. Either patients use "off the shelf" organs (with perhaps a waiting period for rare histologies) or everyone gets a custom one. You'd be better off finding a way to grow single organs. Ethically it's a *much* better alternative (and probably easier than ensuring your "bloated baby" isn't a real person with rights). If not single organs, then perhaps organs in natural groups. Like heart and lungs or kidneys and bladder. [Answer] # Some yes, some no. **There are alternative pathways laid out below:** If you're going to grow a clone for replacement parts, you need stem cells. These can be found in one of a few ways: * Day 2 or 3 [after egg fertilization](https://en.wikipedia.org/wiki/Prenatal_development#Development_of_the_embryo) (prior to implantation and cell differentiation), a few cells would be shaved off and preserved. Unless you have some kind of nano-search tech, the egg will be hard to find and get at this stage. **Would be tough to do now with a high failure rate of re-implantation.** * The Placenta and umbilicus at birth. **We can do this now.** * The epithelial cells (ie cheek cells in the mouth taken by swab) taken from the adult. These will need to be specially treated to bring them back from cheek cells to stem cells (known as [induced Pluripotency](https://en.wikipedia.org/wiki/Cell_potency#Pluripotency)). We can do this now, the downside is that the cells would be old (think [Dolly the sheep](https://en.wikipedia.org/wiki/Dolly_(sheep)), dying of old age before her time). **We are working on this and are confident of a manifest solution within a few years.** Then you have a few ways of growing the person/replacement organs. * Surrogacy, a human accepts an embryo, brings it to term. **We can do this now — it takes 9 months, and the baby still has its full brain function. Lobotomy would be required and body maintenance. Presumably an option for the rich. The major organs would not be capable of sustaining adult life until at least two years after birth - [kidney function of neonate](https://www.pediatriconcall.com/calculators/normal-values-of-gfr-calculator) is 14% of [adult's](https://www.kidney.org/atoz/content/gfr), liver function even less than that, heart too small etc..** * An artificial womb brings the embryo to term, the baby is disconnected and lobotomized. **We can't do this, except to reproduce a few cells in a flask**. * Genetic engineering to prevent higher functions from developing, [Anencephaly](https://en.wikipedia.org/wiki/Anencephaly) is known, and life support could maybe be provided. **We can't produce this condition yet and causes are disputed, give it a few years of research though.** * A scaffold is made/printed (as per other answers, impregnated with appropriate growth factors) then colonized with cells. **We can do this now with very simple structures - skin, blood vessels smooth muscle like bladder, single nerves (note: not nerve bundles). We're working on kidneys, pancreas, liver, these are decades away. Heart muscle presents its own problems regarding electrical waves that we've not solved yet.** *So as the OP will see, the answer is some yes, some no. The OP is free to figure out how future research will find solutions.* ]
[Question] [ A scenario in the far future -- The moon has been successfully terraformed. All problems have been worked-out, from flinging volatiles into collision course with the moon, up to creating and retaining a stable and breathable atmosphere. With state-of-the art technology, an artificial magnetic field shields the atmosphere from solar winds, and additional shielding retains it despite the moon's low gravity. While deploying lunar orbiters, astronomers had to take [mascons](https://en.wikipedia.org/wiki/Mass_concentration_(astronomy)) into account. The mascons create fluctuations in the surface gravity. Along with the moon's low gravity, the changes are sufficient to disturb lunar orbiters and kick them out of orbit, if the right orbit was not chosen. Here is a map of [gravitational distribution affected by mascons](https://en.wikipedia.org/wiki/GRAIL#/media/File:GRAIL%27s_gravity_map_of_the_moon.jpg). (View source [here, from the GRAIL mission](https://en.wikipedia.org/wiki/GRAIL)). I did not find information on how noticeable the anomaly would be to an astronaut standing on the surface. **The question** -- One (among many) of those anomalies happens to be under the ocean's floor. Given the relatively high anomalies (did not find the exact figure in percentage compared to average), would the anomaly cause some water to "pile-up" and create a "hill" noticeable from some distance? Would that be a significant "curve" of the water's surface to make a tourist attractions for colonists and visitors alike? [Answer] [This article](https://science.nasa.gov/science-news/science-at-nasa/2006/06nov_loworbit/) gives us some useful numbers: > > The mascons' gravitational anomaly is so great—half a percent—that it actually would be measurable to astronauts on the lunar surface. "If you were standing at the edge of one of the maria, a plumb bob would hang about a third of a degree off vertical, pointing toward the mascon," Konopliv says. > > > So the "water hill" would essentially be a plateau, hundreds of kilometers in diameter, with a slope of a third of a degree at the edges. It wouldn't be prominent enough to be noticeable, or distinguishable from the normal curvature of the Moon (where 1/3 degree is equivalent to 10 km). Kicking satellites out of orbit might seem impressive, but keep in mind that this happens over time, after the satellites passes over the mascons many times and is nudged a tiny bit each time. And an orbit is a rather delicate thing. The local effects of a mascon are not really that impressive. [Answer] What you ask already happens on Earth, where gravitational anomalies influence the ocean level. These hills and valleys are not visible to the naked eyes, but can be detected by satellites. The first attempts of measuring G were actually done measuring gravitational anomalies close to large mountains. I guess the same would happen on the Moon. There would be hills where gravity is lower than average and valleys where the gravity is higher than average, but they would hardly be noticeable to the naked eyes. Or even be perceived by the unaided human body. [Answer] [Here's a similar question](https://astronomy.stackexchange.com/questions/10422/how-much-do-the-mascons-on-the-moon-affect-surface-gravity) which has an answer talking about the relative field strengths of Mascons compared to the regular surface gravity of the moon. The short answer is that mascons produce tiny fractions of a percent of difference and you wouldn't notice the difference as you walked through them. I would not expect that a Mascon would produce enough effect over a small enough area to be noticeable. Gravity as a force has a pretty shallow dropoff curve compared to the other fundamental forces, the International Space Station for example still receives about 89% of normal surface gravity at 250 miles up. ]
[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/131272/edit). Closed 5 years ago. [Improve this question](/posts/131272/edit) In my SciFi book, 400 years from now, humanity has expanded throughout the solar system and managed to survive the death Earth. In their history, Earth fell during the third world war in 2093 CE and the five existing colonies in the solar system (Luna, Mars, Venus, Callisto, and Titan) were all that was left of humanity. Fast forward 336 years and humanity refers to WWIII as the "Earthfall", the next 49 years as the "Schism" until the five colonies and rogue fleets were united under a single unified government, which is then referred to as the "Formation". Now with that general background in mind, **what would the people of that future refer to our current time period as?** (e.g. Middle ages, Renaissance, Industrial Revolution,...etc) I don't intend for this to be an opinion based question as I am looking for terms that actually might already be used if there are any. Please site a source if it isn't a term that should be easily recognized and I have somehow completely forgotten it. I am discounting terms like "The Digital Age" and "The Modern Age" as everything in the future is likely to continue to be digital, and "modern" means now, which obviously won't be the same for people in the future. Also, if this has already been answered or is too opinion oriented please let me know in the comments. [Answer] We already refer to it as the **[Information Revolution](https://en.wikipedia.org/wiki/Information_revolution)** The use of computers has revolutionised not only the way we collect data and how we use it, but how we think and solve problems. I grew up in a time before Google, and actually learned how to break down a problem into constituent elements, look for keywords, then look them up in encyclopedias. This is a skill that people don't need anymore, like shorthand or even handwriting in some cases. Our ability to analyse data and derive insights is based on the fact that computers don't need to keep all the moving parts of a puzzle in mind as we do to solve it; they simply follow a set process blindly, allowing us to make key decisions along the way and derive insights from data holdings that it would be impossible to interrogate manually. Ultimately, information will become the most important asset and resource to many companies (it is already for some) and how we allow those companies to interact with us has already changed massively. The idea of terms and conditions that deal with aspects like privacy, data disclosure and rights in case of a breach were simply unheard of 50 years ago, and given that we now hear job titles like Data Scientist really tell you everything you need to know. The more interesting question is what the next era is going to look like, and what it will be called by historians. [Answer] Very many names could be devised by future historians for the two century period of massive technological advance (and social devolution). No names have come to us from any future time period, so there are no terms that are already being used. Since there is a devastating war in 2093, the **Antebellum Period** comes to mind immediately. (Yes, "Antebellum" also refers to the early to mid 1800s in the US, but 400 years from now, no one is even going to know what the US civil war was about or why it was important.) The great advances in technology might earn this period the moniker the **Great Leap** or the **Second Renaissance**. The general decay of culture might earn this period the name **Neo-Medieval Period** or the **Great Decadence**. [Answer] I think elemtilas is on the right track with his first suggestion. If the people you are concerned with see WW3 or the Earthfall as the **BIG** turning point in the history, and they certainly would, they would see the preceding period in terms of the war. I am not sure why you are talking about Third World War. Maybe it arises from the tensions left by the second world war in the same way the second arised from failure to properly resolve the first world war. Maybe it is just big enough that it must be called a world war and is called the third because there already were two wars called world wars. The difference would matter in the naming. The time between the first two world wars is often called [the Interwar period](https://en.wikipedia.org/wiki/Interwar_period) because it was the time between the two world wars. (duh) So if the third world war is somehow logically connected to the first two ones it could reasonably be called **the second interwar period** or **the long interwar period**. More reasonably the name would be derived from the Earthfall moniker that seems to imply a pretty crucial difference from the first two world wars that would matter to people when thinking about the preceding period. **Pre-fall period** would be fairly obvious alternative. Another alternative would be to look at the preceding period as the wasted last opportunity to avoid what follows and derive the name from that. But I (obviously) do not actually know the causes for the Eartfall and so cannot speculate on that. Period of some sort of foolishness or blindness for sure. But even the causes for the first world war are still debated. While it is fairly easy to see that political leaders post-Bismarck messed up the system, it is not really simple to name what they did wrong and who the "they" specifically were. But in general the bad news is that elemtilas is probably right about in which direction the naming happens the unknowable future names this period based on what it considers important which will almost certainly differ from what matters to us. Because of, you know, that huge war that pretty much destroys everything our age built. [Answer] **The Stupid Ages** This wasn't coined by me, this a brainchild of Matt Groening... <https://theinfosphere.org/Stupid_Ages> [Answer] # The Deforestation Age or The Desertification Age In hindsight, the key factor might well be what happened to the tropical rainforests, and the [follow-up effects of that](https://en.wikipedia.org/wiki/Deforestation_and_climate_change). Or perhaps other names related to climate change. The problem with that is that we already had severe [climate impact on history](https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse) and it didn't rate a name. # The Global Age Trade and investment patterns are integrated to an unprecedented degree. To go with the *Age of Exploration*, the *Age of Mercantilism* and the *Age of Imperialism*, trade patterns might name the age. # The Chinese Hegemony At least that's what the Chinese would like to see. Other peoples have different ideas, and countries rarely get things entirely their way. Perhaps the Pacific Age. ]
[Question] [ ## Information: After eating my [Khorne Flakes](http://forums.kleicdn.com/monthly_2016_04/v3ovmXE.jpg.be46e441ef9f0d95be92ca93b99003be.jpg), from a sudden idea and playing too much Minecraft, I wanted to make a monomolecular obsidian edged weapon (not just throwing knives and arrowheads). * I have nanotech and patience at my disposal. * I don't mind if my weapon is "living". * I just want it to have a nice little obsidian edge, that can be quickly replaced, repaired or just make it cut through [a material that is made soft enough, to not shatter the edge](https://worldbuilding.stackexchange.com/questions/74240/plasma-assisted-cutting-weapons). ## Question: What's the most convenient way of achieving this, and I don't want to carry dozens of swords to the battlefield as "replacements". [Answer] I don't understand why you need nano to make things out of obsidian. Make your cutting edge out of obsidian. If you have a metal cutting edge you sharpen it when it gets dull. If your edge is a fracture plane (as with obsidian) then when your edge gets dull you make a new fracture plane with a sharp edge. Your cutting implement will be smaller in proportion to how much you fracture off (glass) or file away (metal). Ideally not too much. Does nano help with making tiny fracture planes? If so, great - bring your nano with to the battlefield. I am sure people with metal blades brought sharpening stones. [Answer] Replaceable cutting edges. These things are going to break, so you'd need a lot. But along the lines of razor blades, all you need is the cutting edge, so have weapons designed to just fit a new edge. Best to have multiple replacements within the weapon itself. Like a mechanical pencil, press a button and a bit more edge extrudes itself. Press another button and the edge retracts into the weapon. In fact this could be a very nasty weapon if it could also fire the edges. Imagine a thrust into the torso or even arm or leg, press a button and edges are expelled into the body causing all sorts of grief. It's a weapon with multiple possible uses. If fighting armour retract edge and bludgeon, if no armour, extrude edge, if you score a thrust, expel the edges in the body. If you force it into a chink in the armour, expel the edges inside the armour. [Answer] Natural obsidian is a pretty terrible substance to make a durable weapon with, but there are other "obsidian like" materials that could work. "Obsidian like" being glass with impurities... Consider: <http://www.popsci.com/technology/article/2011-01/new-metallic-glass-toughest-strongest-material-yet> > > The glass, a microalloy made of palladium, has a chemical structure > that counteracts the inherent brittleness of glass but maintains its > strength. It's not very dense and it is more lightweight than steel, > with comparable heft to an aluminum or titanium alloy. "It has > probably the best combination of strength and toughness that has ever > been achieved," said Robert O. Ritchie, a materials scientist at > Lawrence Berkeley National Laboratory who is one of the authors of a > paper describing the new glass. "It's not the strongest material ever > made, but it's certainly one of the best with a combination of > strength and toughness." > > > This material seems like it would work well, fairly light weight, strong, and tough. [Answer] Obsidian breaks because it is extremely rigid. You need Flexi-Obsidian, add a little springiness and you should have a more durable weapon. When the weapon experiences a severe shock and starts to shatter, the nanites along the fracture point react by kicking out enough heat to re-melt the glass a little bit. Once it cools, the weapon is back in business. Better make sure the first swing counts. Extended duels won’t go well for this blade. But I could see a team of people in a combat situation, where the person with the obsidian blade makes one mighty chop and then ducks behind some teammates for a second while the blade cools down. Or maybe it’s only used when it’s snowing. I don’t believe this is a practical blade, but if you MUST have obsidian, this solution might be somewhat believable. [Answer] You put a science-fiction tag on the question, so that opens the door on a rich history of great works and greater writers from whom we can borrow ideas. Stasis - Larry Niven suggested the idea of a [Stasis Field](http://larryniven.wikia.com/wiki/Stasis_field), within which the passage of time and all subatomic motion ceases. The arrangement and energies of the particles within a stasis field cannot be changed or rearranged while the field is in effect. If the blade of your obsidian sword is permanently sealed within a statis field, it will remain sharp and unshattered through the end of time. From there, you simply need to find a method of swinging it with adequate force to cut through armor... Which much to wolverine's embarrassment, is a lot more force than any human arm can provide. ]
[Question] [ In traditional fantasy battles, you have 2 large armies charging at each other while magic users on both sides throw out various spells for whichever side they are on like supernatural artillery. But in more modern times we really have pitched battles. In addition to that we already have powerful ranged weapons so using magic in its traditional role isn't necessary. So how would you would use magic users in modern-day battles? Suppose you have a war with both sides having modern weapons and using modern tactics. Both sides also have access to magic users. The magic users powers include: > > 1.summoning a storm ranging from a small drizzle to a super storm. > > 2.summoning a magical creature like a dragon, sea serpent or elemental. > > 3.banishing magical creatures. > > 4.the ability to increase the probability of a certain outcome, such as changing the probability of winning the lottery from 1 in 100000000000 to 1 in 10. > > > My question is, how would this power be used in modern war tactics and against modern weapons? Or are they too impractical to be used at all? The power of an individual magic user depends on his emotional and spiritual state at the time he is using magic. Some people are more spiritually inclined to use magic than others and the more you use magic the easier it is to use it; like any muscle, the more you use it the more powerful you get. I'd say for storm summoning apprentice-level magic users probably summon a powerful storm including lightning and tornadoes but they probably wouldn't be able to make a storm the size of a hurricane for example. At mid-level you might see a magic user summon a storm the size of Hurricane Katrina. At the supreme level you could probably summon a super-storm several times larger than Katrina (there aren't that many supreme level magic users, I'd say less than 10 for each nation.) Distance is also a restraint on a magic user. An apprentice would only be able to summon a storm where he actually is. An intermediate might be able to summon a storm that is several miles away although he would still have to be fairly close to where he wanted it to appear. At the highest level you can summon storms from just about anywhere on Earth. But even at the highest level it would take a long time (maybe a couple days to a week) to summon a storm beyond 100 miles from where you are. Of course this may vary because an apprentice for example might for some reason find himself in the heightened spiritual state which case he would be significantly more powerful than normal. Or for example a magic user at the supreme level who is still mourning the death of a loved one might himself temporarily reduced in power. The same goes for the rest of the abilities. It's magic, not science so I can only really give you generalizations. Ok, let me explain how the system works. The magic users here are people with a special spiritual connection to an higher dimension. While they are capable of doing all of the powers listed above they usually specialize in one, maybe two. Most start learning from a young age. So there is a fair amount of skilled magic users on either side. As far as rules go there are just 3 simple ones. 1. The farther away you are from where you want to use magic the more time and/or skill and power it takes to perform it. 2. Your spiritual and emotional state can also decrease or increase your connection to the higher realm and therefore your power. 3. The more a magic user has practiced, the stronger the connection is to the higher plane and the stronger the power is. 4. Using magic requires spiritual energy. It's not physical energy so it's not going to make you tired or hungry, but using too many spells in a row decreases power slowly until the user is unable to use magic for a short period of time (a couple of days to week); however, intermediate or higher level magic users can use a special form of meditation to shorten that time (fully recovering the magical energy in a couple of hours). The amount of spiritual energy that a person has depends on the overall power level. 5. Magical creatures, while still physical, come from completely different dimensions than ours, which means that they cannot be killed with conventional weapons. However they can still be injured and incapacitated with them. They can also still feel pain. To put it in more practical terms, if you shoot a magical creature in the face you won't kill him but he will probably retreat and heal for a while. When he does come back here he will probably try to avoid attacking you again because being shot in the face really hurts. The only way to permanently get rid of a magical creature is to either banish it or kill the magic user who summoned it. [Answer] Based on the OP's conditions of magic here's how I see the magic being used in the battlefield. First some considerations. 1. There are only a few magic users available - at least a few really competent ones. Thus they will be integrated in higher level headquarters. You won't see magicians in fire team or even squad level, for instance. Magic users will be attached at Brigade (the lower level ones) or Theater. The reason for this is the available counters the enemy has. If a squad in contact requests tactical magic support (i.e. summon a fire breathing dragon at these coordinates, NOW, in order to suppress enemy fires), and the enemy happen to have a dispeller in hand, then that is an effort wasted. Artillery, on the other hand, just slams into the target without much the enemy can do about it. 2. The powers that the military will use will be strictly regulated. Wide ranging weather powers (like summoning super storms) will not be very useful as it will affect everyone involved (including your own people). The weather powers used will be highly localized events. 3. Because of this, planning and intelligence are keys to proper magic deployment. Knowing that you only have a very short windows to achieve good effects on target, you plan your magical deployment to the nth degree in order to support brigade/theater wide operations. 4. Since magicians do not require special rations, equipment, supplies, logistically their deployment will not be a problem. They're just specialist personnel attached to headquarters. So how will magic users be deployed in this setting? First of all, they will be organized into magic units, attached to the theater chain of command under the Theater Commander. The Theater Commander may assign magic task forces to Brigades that need them based on the submitted Operational Concepts plan that these Brigades submit. The assigned Task Force will be there in order to support a specific operation, and not be part of the garrison/day-to-day units. The Brigades will use these units as force multipliers in addition to its own artillery, aviation, and attached SOF assets. While the SOF and Aviation assets prepare the battlefield and provide direct support to their attacking forces, for instance, the magic users will summon highly localized storms at specific locations in the enemy's rear areas in order to prevent reinforcement and resupply (or at least impede them). Since this can affect multiple fronts in a theater, the Theater Commander may want to use this deployment to order other Operations to occur in conjunction in order to maximize the effects achieved. This will all be planned as much as possible to achieve strategic surprise. Rest assured, however, that enemy magic users will immediately react to dispell the weather effects, and as they are detectable per the OP's explanation, the enemy will immediate order counter fires (say artillery/missile/air strikes against the location of the magic users), so using these magicians will also mean deploying security units composed of other magicians, ADA, and Fire Detection radars, etc. It's an expensive proposition. The military will not be summoning elementals/magical beings offensively and tactically in land warfare because of the risks involved for little gain. Whatever a dragon can do (fly around, hit stuff with its claws/tail, breath fire at things), a strike aircraft can do better, with more flexibility (you can't order that dragon to, say, drop cluster munition, or crater a runway, or breach a deeply buried bunker for instance). And this is before the enemy spellcasters manage to dispell the dragon (best case scenario) or a stronger magician manage to wrench control of the dragon to their side, strip it clean of any information it may had (the location of its initial summoner, for instance), and turn it against your own side. Instead, Theater Commanders will use these summoning for strategic interdiction of - say - enemy leadership or assets. An example would be: A highly reliable intelligence is received that a certain enemy commander will be traveling in a convoy from City A to City B without adequate escorts (magical or otherwise). He may order his magician to summon a dragon and condition it so that the dragon materializes right there on the road at a specific time, then engage a specific vehicle - before the defending magician can react, then is dispelled immediately to prevent it from falling into enemy hands. So basically, these magical beings will be strategic precision weapons. The probability boost is likely the power the military uses the most - in order to improve the effectiveness of its planning. Intelligence is all about probability. "Based on these observations, these documents, these intercepted communications, and these gossips at the local bar, there is a high probability that the enemy will redeploy these units to here, most likely to support a planned attack that may or may not occur against these objectives at this date and time." So, the theater commander uses the boost to improve the probability of this actually being true, so that the plan he makes to counter this move has a higher chance of actually doing what he intended it to do. See the paragraph above for another application of this power. The probability booster will also work well in national level missions and/or international level politics. However, since the adversary also has probability booster, they will most likely cancel each other out. So, in conclusion, having magic will provide certain force multiplier options for Commanders to deploy, but with similar capabilities in the adversary's hands, they may not have as wide effect as we'd initially think. Edited to add: Magic specialists will, due to their powers, be high priority targets for both you and the adversary. There will be cells in the Theater staff dedicated to targeting and interdicting enemy magic specialists with their own assets (personnel, aviation, artillery). They will also be afforded a high priority in case they have to call upon shared assets like air strikes. In addition, specialist magic users will be employed tasked exclusively with detecting, countering, interdicting, and suppressing enemy magical activities. [Answer] # Weather Assuming that each warring faction is bound by some rule preventing them from constantly counteracting every one of its opponent's moves, then controlling the weather would be highly beneficial for many reasons. ## Whole new use for Kamikaze and spies In WWII certain disposable airplanes and people flew into enemies for one sole reason: to cause mass damage. They had no intention of getting out alive. This could be used to any armies advantage if they had spies who was also a weak apprentice. The spy could, in essence, summon tornadoes on top of enemy bases/barracks. A [PT-76 tank](http://extremeplanet.me/tag/heaviest-moved-by-tornado/) weighed upwards of 14.6 tonnes(32,000 pounds). The heaviest object lifted by a tornado was about 81 tonnes(180,000 pounds). Given than a non-experienced magic user probably can't create that powerful of a storm, a tornado right in the middle of a military base would still create some serious damage. ## Tactical Advantages According to [Global Security](http://www.globalsecurity.org/intell/library/policy/army/fm/34-81/appb.htm): > > Low visibility is beneficial to offensive and retrograde operations and detrimental to defensive operations. In the offense, it conceals the concentration of maneuver or friendly forces, thus enhancing the possibility of achieving the element of surprise. Low visibility hinders the defense because cohesion and control become difficult to maintain, reconnaissance and surveillance are impeded, and target acquisition is less accurate. > > > Given that the *wizard*, a low level magic user in a dry area could *easily* create wind gusts causing sand/dust storms to hide their movements from the enemy. Strong wind gusts could also make radars malfunction and damage surveillance equipment. Just those two combined could at best cause a little delay in advancements or at worst allow the enemy to sneak bigger more powerful weaponry into good positions for attack. ## Defense The same things go for defense. Good cloud cover and fog could hinder an enemy who is trying to advance. A very good wizard could create small storms on top of advancing enemies. The tactical advantages are endless if you can control the environment of a battle. ## Missile and NBCs(Nuclear, biological, and chemical weapons) Sudden changes in weather can throw off important calculations which can make weapons of mass destruction very unstable and hard/dangerous to try to use properly. Sudden gusts of winds can throw off the trajectory of a nuclear warhead. Even though magic is possible NBC weapons would still be very deadly, but it would give some hope to defenses because even for fighter jets, flying in storms is hard. Overall, war as we know it would be over and it would be even harder to try and gain an advantage against another magic wielding nation. The Global Security(link above) outlines most of the things I talked about and much more. # Magical Creatures In my opinion the magical creatures would be impractical to use in war because of the easy counter by another wizard. Unless a very powerful wizard made a magical creature in a military base and it killed all the wizards that could help, the magical creature would quickly be banished. # Probability Unless you are in a long range gunfight not many things in battle are left up to chance. At a time when any calculation no matter the complexity is possible by means of supercomputers most variables are found and accounted for before it can cause real harm. Guidance systems for missiles and bombs are extremely accurate and most problems are caused by human error. # Side Note If magic was suddenly discovered by more than one nation at a time the war would probably be over before it started. The nation who gained control of the first magician would wield the power to take over/attack other unsuspecting countries with magical creatures and powers that they had never seen. Just like the use of nuclear weapons, the use of magic in war would have to be monitored and controlled very strictly to prevent hostile nations from doing anything crazy. Supreme wizards would be extremely powerful and even overpowered. A storm twice as large as Katrina would cost almost a quarter of a billion dollars which would cripple, if not bankrupt a poorer country. An out of control supreme wizard would devastate economies. *And they say that corporate espionage is bad...* **Edit:** > > Prior to the Geneva Convention, the United States used weather warfare in the Vietnam War. Under the auspices of the Air Weather Service, the United States' Operation Popeye used cloud seeding over the Ho Chi Minh trail, increasing rainfall by an estimated thirty percent during 1967 and 1968. It was hoped that the increased rainfall would reduce the rate of infiltration down the trail. > > > This is a perfect example of the effects of weather on war. All from the wikipedia page for [Weather Warfare](https://en.wikipedia.org/wiki/Weather_warfare). [Answer] Affecting the weather and changing probabilities are HUGE. The weather can make a huge difference on a battle field. Changing the probabilities of weapons hitting their targets can also make a big difference. However, like in any military campaign, if both sides have similar abilities it comes down to the general in charge, the weather, and luck. So while things might be done differently, the end results are likely going to be similar. If one side is improving the chances of a successful hit, the other side will be increasing the odds of them making the same shot. So the better magic and generals controlling can make the difference. [Answer] Essentially the magic users would counter each other out. If only one side had magic then that side would easily win. It comes down to who has more/stronger wizards and who has better tactics. For example the probability power: a magic user could make all their enemies shots miss. Eventually the enemy would counter by making all their shots hit and it would go down to who is stronger. The same works on all spells. The only way it would change is if one team has more power or they thought of a weird new way of using magic. Then they might be able to use it before a counter spell was invented. [Answer] I'll look at this in a different way. Military forces, as constituted in the Western world since ancient times, requires discipline and the ability to work as a team in high stress situations and follow orders. So magic users in the military will require just as much, if not more, training and shaping in order to actually work in a military environment. Consider a magic user in a tactical setting. He is a fairly new wizard with limited power so he needs to be brought close to the front to get in range for his magic to work. He needs to follow the orders of the Sergeant in charge of his squad (I can't see new wizards moving around the battlefield on their own, they need a close protection squad as a minimum) to get around without being shot, and he won't even be allowed to unleash his magic until the proper orders are received (or the conditions set in the orders are achieved). You simply won't be allowed to unleash random magic on a battlefield. Effects need to be synchronized (a lighting bolt without a following infantry assault is just wasted), and secrecy preserved (unleashing magic will be rapidly detected and countered in the most violent manner possible. A modern wizard isn't going to be happy about being the target of artillery, airstrikes or a Predator drone with Hellfire missiles). Basic training is going to involve a lot of psychological conditioning in order to allow the wizard to focus and maintain a level emotional state during high stress in order to actually work his magic. Wizards might have to go through the equivalent of SoF training like Navy Seals "Hell Week" or SAS "selection" in order to demonstrate their basic suitability, and then receive some pretty heavy duty follow up training to become effective on the battlefield. Senior wizards will have already survived this sort of training and will also need to become trained as staff officers in order to effectively plan and integrate magic into the overall scheme of manoeuvre. This is the same reasoning as not letting junior wizards unleash magic on their own transposed onto a bigger scale. Command posts will have operational cells for the use of things like intelligence and tactical aviation, so we will see an extra cell for magic, and a wizard with LCol rank to plan magical integration and brief the senior commander on the plan. Magic on the modern battlefield will certainly be much different than in a fantasy setting... [Answer] > > 4.the ability to increase the probability of a certain out come such as changing the probability of winning the lottery from 1 in 100000000000 to 1 in 10. > > > That seems quite strong. If you fire a rifle into the air, what are the chances that the bullet is going to hit the enemy commander? If you aim a sniper rifle with a scope, you should be able to do much better than 1 in 100,000,000,000. Battles would be very hard on leaders and wizards. The abilities to summon and banish monsters would seem to cancel out. That shouldn't be worse than an artillery exchange. Presumably both sides could control the weather, so they would tend to cancel out as well. If one side is dominant though, that could determine a battle. You might think that ability to change the probability of outcomes would cancel as well. The problem is that sniping is something that you do with surprise and which takes effect immediately. If you summon a monster or storm, it does damage over time. If you banish it, it stops doing damage. An accurate shot may be instantly fatal. There are other outcome related things that can be done. For example, what are the odds that a spark will flare up in the ammunition tent and trigger an explosion? What are the odds that a bomb will fall in the perfect location? This seems strong and without a counter in the system. You'd need to know the right time and location in which to counter. How would you? [Answer] Likely, the magicians would do one of three things. Case 1) They all band together and become supreme dictators of the world. This shouldn't be too hard, seeing as they can create magical creatures and make super unlikely things happen. Case 2) They all band together to create world peace(cynics, feel free to skip this part). This also shouldn't be too hard, if they could combine their power to create some sort of spell that would cause every single weapon aimed at a human (or that would damage a human) to malfunction and turn into a raspberry pie. Case 3) WWW erupts(World War (between) Wizards). Eventually, either one will prevail or the world will be destroyed in the war. Seeing as the beings that we are talking about can effectively turn anything (or anyone) into pillars of salt, the world caught in the crossfire would likely be destroyed. *Side note: depending on the amount of control the wizards in this scenario have over their magic, a spell gone awry could potentially destroy all of Earth and leave the magicians floating in empty space guiltily pointing at each other and saying "He did it"* Now, the battlefield aspect. Friendly fire becomes a **HUGE** issue. Say the magician releases a spell saying something like "May all mine enemies turn to toads", but mispronounces and says "May all turn to toads". *WAM* and all of the soldiers on the battle field turn to toads. In the end, the magicians might be more trouble then they are worth. The battles will turn into two things: a) everyone protects the magician and b) everyone cowers from the firepower of the enemy magician. It's like bringing a nuclear silo to a knife fight. [Answer] At some point if you're talking about probabilities, you could argue that if you have a supreme user affect the probability that you would win the battle with one person from 1:100000000000000000 to 1:1, then what would the restrictions be on who wins if two supreme wizards head it off? This also begs the question on whether or not there are any sort of magical items that disrupt magic, or if another magical user could change the probability that another could never use magical user's ability to 0. Perhaps I don't quite understand the limitations, but there seems to be a strong probability (see what I did there?) of a perpetual stalemate in any war whatsoever. ]
[Question] [ Many of us regret that if human lifespan were longer we could learn more from the minds like Einstein and Alan Turing. Lets assume that the human race is evolved in such a way that the average life span is, say, doubled. Now can we assume that the advancement in knowledge and technology would be more than what we are seeing right now? lets assume these constraints: 1. The longevity is not spread uniformly during the human development, rather it kicks in after the teenage. (*I think this assumption is not necessary*) 2. The reproductive rate is less since we don't want to see a overpopulated world. (*Is it necessary?*) [Answer] I think you would see **less** advancement, not more. First of all, fewer geniuses would be born (or raised/educated/self-made). The rate might be better than half, but not by that much. Second, scientific paradigm shifts would overtake the aging scientists. After 50-100 years developing in a certain paradigm (i.e. classical Newtonian physics), the bulk of scientists would not accept a shift anymore. This would hold the geniuses, and their work, back. Quantum mechanics was not adopted quickly or easily in our world, and it would've been much harder if the authoritative scientists had been older and more conservative. Third, education counts for a **lot**. Each generation after Einstein, Bohr and friends got a much better start in Quantum theory, learning the latest theories in their prime learning age, enabling them to build on that. New paradigms would develop much slower with fewer students starting out fresh each year. The combination of these factors would slow down scientific advancement seriously. --- Note: This answer concerns our current level of advancement, where the leading edge of science and technology features large teams of scientists, engineers, and rapidly changing computer technology. An individual could spend 50 years perfecting a theory, only to emerge and find that some computer had proved it 25 years earlier by simply brute forcing the math. I don't want to disparage the value of experience or years of diligent work, but when it turns into numbers, half the smart people living twice as long is a bad fit for modern science. In Newton's age, and even Einstein's, advancement would probably have been quicker with longer lifespans, but that would only have led to the current situation a bit sooner. [Answer] I would tend to say that yes, somethings would speed up. Only because it HAS. Wiki has a chart showing the average life [expectancy of humans](https://en.wikipedia.org/wiki/Life_expectancy#Variation_over_time) over the last several thousand years. Up through the 1800's world life expectancy was 31 years, in 2010 it was 67.2. So we have more than doubled life times. Looking at the chart, ages of enlightenment the life expectancy of the top tier tended to be longer as well. As more people live longer, technology seems to be speeding up, (and the same technology is helping people live longer!) So I think longer life spans could speed up tech development to a point, since longer lives would also tend to slow down social change. My observation is most major social changes come from new generations growing up pushing change, not old generations spontaneously changing their world view (usually). [Answer] There are a number of approaches to this, the first has been given, that science advances would decrease due, in essence, to plasticity of thought processes and statistics of intelligence. The other way to look at it would be that extended lifetimes may promote advances in different directions. Firstly, you're essentially looking at the difference in advancement between two 25-year old researchers and 1 50-year old researcher. The younger researchers may explore different paths, and develop new ways of thinking, while the older researcher is more experienced, and may be able to get more done in their field, albeit without as much chaotic expansion. You'd see less "breakthough" changes in direction in fields, but the existing systems would be more refined and efficient. The other aspect would be collaboration. If the lifespans of geniuses was increased, there may be a greater chance of highly productive groups forming and doing more than the individuals would be able to. Additionally, you may go along the road that such individuals are made, not born, and living longer gives them the opportunity to increase their productivity by learning from more people. It's probably also worth considering the ramifications of extended lifespans on politics and direction of science. If staving off immediate demise is not the primary motivation, medicine may advance into areas of increasing the productive lifespan (particularly if the elder generation are around for twice the amount of time). [Answer] Yes, almost certainly. The idea under discussion here comes from Max Planck: > > “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” > > > This is a pretty ridiculous idea that reeks of sour grapes, to be honest. And it's more than a little ironic, since several years later some researchers with the benefit of hindsight discovered that many of the most important discoveries of Planck and Einstein *would almost inevitably have been discovered approximately half a century earlier*, if it hadn't been for James Maxwell's untimely death of cancer. (And just imagine what Planck and Einstein might have been able to discover then, if Maxwell's death hadn't held progress back for decades!) This isn't specifically a longevity example, but dead is dead. When great scientists die, they tend to take a lot with them, no matter what it is they specifically died from. [Answer] Strongly, yes. Double longevity with half reproductive rate means we have the same proportion of geniuses, the difference is only their longevity, so they last that much longer. So, in essence, the question boils down to a few questions: what progresses technology more, new minds, or more experienced minds, or some combination of the two? Is a genius' productivity measured merely in years, or is quality a factor? There's two forms of technological advancement: paradigm shifts and incremental development. On the whole, most technological advancement is incremental, paradigm shifts are incredibly rare and, even then aren't necessarily 100% novel and may still be seen as a foregone conclusion in the eventual advancement of the field, even if the results are game changing. If paradigm shifts are truly novel, then they might require a healthy supply of new minds, but that doesn't really seem to be the case; certainly the extreme version of this is absurd as it suggests that the only way to make progress is for everyone to know nothing. Also, the idea that the existing community are 'stuck in the muds' and resist novel change really isn't the case: the resistance to new ideas is far more down to the fact that new ideas require that much more testing and examination to be fully considered. Ideas that build heavily upon existing work that is solid simply have far less to prove. Again, this suggests that longer lifetimes give people more time to finish their own work rather than having to pass it on to those less familiar with it. However, the biggest change is based on sunk costs: even ignoring childhood, due to the predominantly iterative nature of progress, there always will be a large body of education involved in both understanding the depth of a field and generalizing with other fields. As technology progresses, this volume grows. Longer longevity will always offset these sunk costs advantageously even if we only measure a geniuses productivity in mere years- twice longevity is more than twice productivity. If we accept that longer lives mean more experienced, higher quality geniuses, this multiplies even further. [Answer] Some progress depends on people who patiently assemble bits and pieces of knowledge into a whole. Living longer gives more time for more puzzle pieces. Some progress depends on the breakthrough idea of a genius. This might be a [paradigm shift](https://en.wikipedia.org/wiki/Paradigm_shift). Living longer means that scientists who have build their academic reputation on the *old* paradigm will block those young upstarts even longer. Too broad to answer. ]
[Question] [ Imagine a medieval society in which dragons are domesticated for military use. When they are young and still able to fly, they're ridden into combat. Very few make it to an old age, but those who do are unable to fly because of their size and they are discarded, put to other lesser uses. The knights riding them have to be svelte. The attacks resemble acrobatics more than combat: the dragons have to strike fast and retreat before their wings get transpierced with arrows. It follows that the great warriors of that time are short and thin, wear no armor but a thin boiled leather attire. Horse-mounted lesser nobility are seen as grotesque in their heavy armor. Would that setting be enough to influence the standards of manhood into a different path from the rough-type-warrior one we know? What about other standards of aesthetics? Would the build of castles, churches, ships... also change (even though a thick castle would still be more efficient in protecting its people)? [Answer] Well, I'm seeing something different here. Dragons must be raised, taken care of, and controlled by the thinner and shorter riders that you have. You must have, so, someone that is, at the same time: * Not heavily muscled. * Shorter than the regular male, on average. * Lighter than the muscle-bound regular warrior-type. * Apt to take on nurturing roles, taking care of the dragon-babies since they hatch and nurture them to become fierce warriors. You need no bulky male. You need some *dragon-riding girls*! What I see is a world with far more *equality* between the sexes. While on non-dragon riding countries the major advantage of the troops is the raw muscle power of the regular army man, the dragon-riding people would experience something new - the people best suited to ride those giant beasts are actually women. This won't change architecture much, but it will probably put the ladies on a more important scenario - depending on how long this dragon-riding thing is going on, your would could even be a matriarchy, ruled by the ones that can handle the most powerful weapons of war. I don't see any of this changing the aesthetics of anything, however. Architecture is (mostly) gender-neutral, and *if* it would change to something different, it would be something more dragon-themed to reflect the iconic beasts of this people. What is "manly" wouldn't change. What would change is how important being "manly" is to this people. Probably they wouldn't see "being manly" as something even related to gender, anymore. Since there are guys and girls on the army, the standard gender roles are throw by the window and people just stop caring what you do anymore. This is more-or-less what's happening on the world today - with the help of technology, we are each year less dependent on the natural raw power of the males and females, once trapped on less muscle-intense jobs, are now basically everywhere, even in the army. The reflect of this is that people are more and more less concerned to fit stereotypes and more concerned in being happy. So, the way to go is *equality* between sexes, if not a bit of favouritism to females. [Answer] most images of manliness come down to evolutionary pressures, we are trained to see strength and health as mainly because we litterally evolved to be partial to that. I don't think that a few generations of dragon riders will change the entire culture when it's combating evolution. Strength will be regarded as mainly still, though perhaps not the absurd bulking up of museles at the expense of *real* strength some do now. However, since the majority of men, and perspective mates, will be non dragon riders they will be the norm with which cultural views of manliness are set upon. I think that this would not remove the current culture of mainlines, at most it would add another body type, that which works for dragon riding, to potential preferred types. Some will like the big bulky men who can plow the fields, some will like the lean agile fighters. Of course dragon riders will look down on the people on big bulky horses. Every group or faction looks down on the others, the more elite they are considered the more so. It's human nature, look at the rivalry of marines for army for an image of what you may get between dragon and horse mounted carvery. [Answer] War will be like modern warfare with planes and tanks. Powerful kingdoms may have an army composed of dozens of dragons. Land units will be only used for occupying cities once they have been attacked by dragons. Dragon riders look like pilots in the world wars: svelte and without vision problems. The armor is not important as fire will kill them. They may use bows to shoot accurately in the weak parts of enemy dragons or even its rider. However, medieval war values like honor do not fit with this kind of combat. There is no place for heroes, history will only remember the great strategists. Although some dragon rider may become famous as Manfred von Richthofen did in the first world war. Main fortifications should be dug in mountains as they offers more protections against air attacks, so becoming bunkers, and avoiding wooden buildings. ]
[Question] [ I'm cooking up a city populated more or less half and half by humans and halflings (with a scattering of other races). My first thought was that halflings would generally have more or less human-sized houses (to allow their human friends and neighbors easy access), while humans would have a bunch of stepping stools around the house (to allow the halflings to use the human-sized furniture). My second thought was that that might be a bit too humanocentric. What are other ways that the two species might live side by side? Note that I'm not thinking that there are any conscious integration. This is simple two species that have lived side by side for a few hundred years, and learned the best way to do so. [Answer] If there's no *conscious* integration I would expect that many halflings will have accommodations unsuitable for humans and vice-versa. I say this because I observe in real life that most buildings that aren't consciously intended or adapted to be wheelchair-accessible, aren't accessible. Same goes for very short people: they aren't all that comfortable in a typical kitchen. Of course nothing like 50% of the population is in wheelchairs (or under 4 foot high), and if they were then house-builders would take more efforts to build for both. But they'd still have to do this consciously. It won't happen by accident because a human can always save some space by shelving to the ceiling and not having any step, whereas a halfling can always save *loads* of space by building small. Publicly-used buildings (including shops, theatres and so on) would be designed for both unless you want to lose half your potential visitors. Buildings for governmental purposes might be *required* to accommodate both, assuming there's no particular discrimination against one or the other. Therefore techniques will be known, how to design for both without offending the dignity of either. I would expect some human-bias just because (other than shelves) it's somewhat easier for a halfling to make do with human-sized stuff than it is for a human to make do with halfling-sized stuff. However there are plenty of things that could be designed for both in interesting ways: * Large staircases can be shallow and deep (to permit halflings to take an extra pace on each step). Where space doesn't permit that, perhaps staircases could have double the frequency of steps on one side: in effect build a half-step into the right-hand-side of every human-step. Or just do whatever: a half-height human can in fact climb a normal-sized staircase and vice-versa, it's just harder. * 6 foot or lower ceilings aren't all that uncommon in very old English houses, even though some people were taller than that (not so many as today). Therefore a halfling family building on a budget at a low tech level would surely use 3-4 foot ceilings in either some or all rooms, according to whether they feel that entertaining humans is essential or not. You might have halfling houses with one tall room and the rest short. Rich people (with typical human psychology) will in any case build ceilings and doors far taller than they are. So unless your halflings are agoraphobic, luxury buildings will suit both. * Halflings would require windows to descend lower than humans require them to, or they can't see down out of them. Humans require windows to ascend higher than halflings require them to, or else light doesn't come down onto them. So a mutually-accommodating style might tend to tall windows. For buildings with small windows you might see a square at 5 foot above floor level, and another at 2 foot above floor level, with wall in between them. For buildings that have tiny windows for cost reasons you might see a compromise: windows at a height that's convenient to nobody. * Door-handles and similar fitments. Humans like them at their waist-height, which is usable to a halfling but not as comfortable. Reaching much below waist-level is probably more inconvenient than reaching at head-level, so I'd expect handles to be at human-waist-height or slightly below. * Chairs make some assumptions about how tall you are in order to seat you comfortably. A human can barely sit in a halfling-chair at all, and a halfling would perch on the front of a human chair with legs dangling. Therefore, low chaises-longues! If everyone expects to sit with feet raised, or to recline, then everyone can use the same furniture (long enough for a human) and end up closer to the same height than if the chair-base is matched to their leg-length. Failing that, a mixture of furniture would be the way to go for those who want to entertain everyone. * Work-surfaces are difficult. Perhaps they wouldn't be built-in to kitchens, pantries, butchers, offices, workshops, etc. Rather, put in sturdy tables of the appropriate height for whoever is there. If built-in, then you'd just re-fit the place when the new owner is the wrong height. Unless the ceiling is low, in which case you can be sure the user will always be a halfling and build accordingly. * Storage, aka "what can you reach?". I think things like stools and [library steps](https://encrypted.google.com/search?q=library+steps&tbm=isch) will be common. That's what humans use anyway when they shelve beyond their own reach, so I don't think it's as humano-centric as you fear. Of course, a host doesn't expect a guest to need to reach every shelf in the house, so won't necessarily have one in every room. Humans employing halfling servants might, though, and halflings employing human servants had better live in tall houses rather than short ones. Hanging-rails for clothes are probably difficult, since anything high enough to hang a full-length human dress/cloak/code/robe is too high for a halfling to reach. Therefore perhaps a dual-use wardrobe has a removable lower rail or a fold-out step. * Real-life shops often have shelves out of reach to some or all of their customers and employees (to a lesser extent in the last 50 years now that so many shops are self-service, but find someone 5 feet tall and ask them how they get on in a typical supermarket -- they can't reach the top shelf and the store doesn't care. If all else fails they can summon a tall staff member to help them). Ladders aren't that difficult, it's only health and safety that prevents them being offered to customers. Sliding ladders attached to the shelves are awesome. * Cutlery, crockery, glasses and so on could be kept in a wider variety of sizes. In real life I have side-plates and dinner-plates. In your world (and assuming halflings eat less than humans, contrary to Tolkien) I might have three sizes of plate, with the middle one doing double-duty. Mugs/cups/glasses could respect the sizes of people's hands. Alternatively, perhaps society decides that the polite thing is not to discriminate. Pick a size both can use, and this becomes the standard size for everything. It's rude for halflings to use smaller settings while humans are present, or humans to use larger. It's *extremely* rude to assume a halfling only wants half a beer ;-) * In fact, on the subject of rudeness, how come the halflings are called "halflings" rather than the humans being called "doublings" or something? If the species speak the same language and have always been regarded equally in that language, then the words for the species would probably not express one in terms of the other. Of course if the language they speak was originally a human language then it might well call halflings that for historical reasons. If the language was originally halfling then the word for them shouldn't have "half" in it, they might be called "humans" and "giants". * I don't know what your tech level is, but re-designing a real-life car to be driven by either a human or a halfling would be a bit tricksy. Probably best never to use pedals in the first place: perhaps provide acceleration and breaking handles more like a motorbike. And of course you need to either provide enough window for everyone to see out of, or else height-adjustable seats. With a matching footrest, assuming halfling buyers don't want to dangle their legs for hours. Or give up on the idea of making them dual-use and sell two configurations out of the factory. Being cynical, one might expect that halflings can live more cheaply than humans (less square footage and less height), eat more cheaply (less food), but can do less manual labour (smaller and weaker). Therefore they might well *not* be economically equal to humans, no matter how friendly everyone is. They could afford to work for lower wages, and in some jobs are less valuable to employers since they chop less wood per day or whatnot. Do what you like with the economics and politics of this! But if there is a difference in subsistence earnings, then the species wouldn't be fully interchangeable as employees. There would be some jobs that it's too expensive to feed a human to do, whereas a halfling is cheap enough. There would likely be some jobs where a human does more work per unit pay than a halfling, so the situation is reversed and only a human is cheap enough. It might turn out that the species start to separate by profession/industry, but I think that by tuning the parameters you've got some freedom to decide which species is best in which industries. The reason I talk about subsistence earnings, is that once you can demand more than that for your labour/services, it no longer matters so much how many calories you need or how tall your house needs to be, you meet those basic requirements with a smaller and smaller proportion of your expenditure. [Answer] * Instead of western-style tables and chairs, everyone has low tables where you sit on a mat instead of a chair. Perhaps something like the japanse Kotatsu for instance. This allow halflings, children and adult humans easy access to the table, with no chair-complications. * In shops, the shelves stand in pairs in the middle of the room and each shelf is open on both sides. In between two shelves is a scaffold which let halflings retrieve goods on the higher shelves, while humans retrieve goods from the outside. * Combined shelves and stairs like the one below, is an ubiquous part of the city's interior architecture. * instead of our horizontal door handles, the typical door has a long vertical handle, which is twisted sideways or pulled down to open the door. The humans and halflings grab the higher or lower half of the handle and it doesn't feel like it's designed for just one particular race. * Instead of everyone having tall roofs, most buildings have sloping roofs. When sold between the races, the new owner simply re-decorates to suits his/her height, with humans storing things in drawers in the low end and halflings setting up book-case stairs in the tall end. When a human and a halfling shares a meal around an indoor table, the human sits at the tall-roof end. * The door in people's homes are under the roof ridge and so can be a tall one. However, some halflings have halfling-sized doors, with the area over the door for a glass window, to let in more light. The window is flush with the door and can be opened with a clasp, so that a human may enter the house without stooping. * Beds at inns are oval in shape and can accompany both races. One human sleeps along the long axis or two halflings across the short axis. ![enter image description here](https://i.stack.imgur.com/iU0L5.jpg) Ergonomic bookshelf shared by humans and halflings. [Answer] I would expect that for the most part there would be communities where like stays with like. Most halfling homes would be in the same neighborhood, most humans would be together as well. Humans do that all the time and we don't have such differences. How many cities in the US still have a 'Chinatown'? France's Muslim community seems to be mostly separate. How many Jewish quarters have there been? Now that doesn't mean that there won't be conveniences and traditions for mixed race gatherings. As pointed out in the comments, Japanese style tables might be one way, or just lounging couches like the ancient Greeks had. People who host others would more likely own some furniture more suited to them. Sitting rooms would likely be designed for the comfort all. Maybe a halfling couch but up on a dais so that it is level with someone sitting on a full sized couch. A halfling sitting room would likely have a vaulted ceiling, etc. But in general I think it would be extremely cost prohibitive to design homes that could cater to everything for both races even if it took setup time in between. To begin with a halfling home could be quite a bit smaller over all and still have the same relative space. Half as tall could use 1/4 the space to get the same amenities. [Answer] The biggest consideration here has little to do with the population but what level of development is your community? A city developmentally similar to 13th century Paris or somewhere in central Africa today might not change much regardless of the height of the individuals. It hardly matters when sleeping on rush mats on the floor and cooking over an open fire while there is hardly any furniture to be concerned with. If presuming a fairly well developed wealthy/modern community, housing which accommodates both scales of people would be highly inefficient and considerably more expensive - dwellings and private areas would be specialized to be most comfortable for one size or the other. Public areas like restaurants or government offices could be adapted with accessibility in mind, but the added expense is hardly worth it otherwise. The difference in height between the typical halfling and typical human is considerable - there is very little functional overlap. Think of how well a 3 year old (average height at that age is around 3 feet) functions in a normal house - it simply isn't sized for their comfort. We don't care so much for kids, as they grow quickly and don't seriously do much, but adult halflings need functional furnishings to go about their typical daily lives. The idea that buildings would all be human sized and often remodeled to fit the needs of different dwellers very much depends on how wealthy your society really is (a significant added expense to the cost of housing would encourage segregation). Halfling dwellings would be scaled down appropriately, saving massive costs in materials and labor, not to mention significant structural differences to accommodate greatly reduced needs. Building to human standards would constitute gross over-engineering of everything. Even modern levels of wealth would likely find that highly wasteful for half the population. Cultural differences in design would likely be significant, simply due to different perspectives and functional considerations. Do halflings like a cozy atmosphere of ceilings just above their head, or a reaching distance above like we tend to (which would be rooms only 4 feet high for them compared to the typical 8 foot ceilings where I live), or would they enjoy having what is in effect very high cathedral ceilings in every room? Personally I'm only comfortable with such high ceilings in entry-halls or grand dining-rooms (had I such a thing), but not so much in my bedroom, toilet, or study. These kinds of comfort considerations will determine what kind of housing they will tend to use. Being half the population, and families being one or the other so it isn't a matter of accommodating an individual with a disability in an otherwise normal household, facilities would be built to suit their particular comfort. I don't see much overlap between species of such great differences in scale on a daily living basis. In terms of working relationships, such diversity would likely be very useful, but probably going home at night to a home built for their own species (after a night out in the pub with their friends of all sorts). [Answer] Ramps instead of stairs for public areas, otherwise you will have problems giving access to halfling children going to school. Take, for instance, this reference picture of a generic fantasy setting: ![](https://i.stack.imgur.com/phoFZ.jpg) For public drinking fountains might need to lower the third one for Halfling children ![enter image description here](https://i.stack.imgur.com/Y8993.jpg) Houses that give easy access for 5 year olds is a good starting reference for design. Except when it comes to Halfling children. [Answer] Typically old cities grew from smaller villages growing up until there was no longer empty space between them. As such the city would originally have been composed of human villages, halfling villages and whatever made the area attractive enough for a city to be created. A market place, a harbour, a ford, a keep, a religious or political center... whatever. However eventually the villages would start working together for defense, handling relations with local ruler, and administering the focal resource. They'd set up a method for settling disputes. Eventually these would combine to give the city a common identity. However to society would still be based on those original, probably almost entirely single race, villages. That would be where people would live and spend most of their time in. With their friends, relatives and family. This would be the group they'd identify with first, with the city second, and maybe their race or guild after that. The reason these districts evolved from villages would be single race is because people did not really move that often. They'd have a family house built next to the house of their relatives by great-grandfather few hundred years ago. Or by their uncle after the last great fire. The point is people would live next to their relatives, who'd probably be of the same race. There would probably be mixed race districts for transient workers or the destitute, who'd have no meaningful relatives to live with in the city. Even there it would be easier to have separate halfling houses and human houses. Most businesses would also be single race because they'd be local to the district. The exception would be any businesses or services so specialized you would need relatively few of them in the city or that needs to deal with travellers. So while a halfling district might deal with common legal issues itself within the halfling traditions, anything rare or serious would be bumped up to mixed races courts of law. I doubt this would cause significant friction between races absent some political or religious agitation. People do not feel close to their own race, they feel close to their neighbours, friends and family. A stranger is danger even if they are of the same race. ]
[Question] [ Many science fiction books invoke a naval combat paradigm when describing space combat: sensors and battleships with batteries, carriers with fighter-bombers, etc., usually over a distance of lightseconds. Sometimes, they might even use something akin to submarines: "stealth" craft which may try to intercept communications, or conduct submarine like attacks. However, would it be possible for space craft to really be "stealthy" or invisible to *any* degree in space, given that they must release some heat, but space is in general, utterly cold? Would there be regions (apart from commonly invoked nebulae) which may mess with sensors? What would stop spaceships from engaging in combat over the distance of lightyears, rather than lightseconds, if they are readily detectable from distances on the scale of lightyears? I assume no major deviation from today's known science, in particular no faster-than-light communication or travel. [Answer] Some useful discussion and links can be found on projectrho.com, I mentioned these in comments before the question was migrated but they were deleted in the migration, so I'll repost here. First of all, in the [Space War](http://www.projectrho.com/public_html/rocket/spacewarintro.php) page, at the top there are various links to posts on the "rocketpunk manifesto" blog which have good discussions of issues relating to space combat. And here are some other good pages from projectrho.com: [Detection in Space Warfare](http://www.projectrho.com/public_html/rocket/spacewardetect.php) (most relevant to your questions about stealth) [Defenses in Space Warfare](http://www.projectrho.com/public_html/rocket/spacewardefense.php) [Introduction to Space Weapons](http://www.projectrho.com/public_html/rocket/spacegunintro.php) (mostly just devoted to classification, but has a link to [this site](http://www.arclight.net/%7Epdb/hammer-lightnings/index.html) which has a lot of interesting ideas) [Conventional Space Weapons](http://www.projectrho.com/public_html/rocket/spacegunconvent.php) [Exotic Space Weapons](http://www.projectrho.com/public_html/rocket/spacegunexotic.php) [Space Warship Designs](http://www.projectrho.com/public_html/rocket/spacewarship.php) [Combat Theater](http://www.projectrho.com/public_html/rocket/spacewartheater.php) [Planetary Attack](http://www.projectrho.com/public_html/rocket/planetaryattack.php) You can find some other semi-relevant pages if you google site:www.projectrho.com and "space war" (in quotes), but the other pages I saw are almost entirely devoted to describing how space war was depicted in various science fiction works rather than discussing how it would "realistically" work. (edited to add that I recently came across another good article about realistic space combat, [The Physics of Space Battles](http://gizmodo.com/5426453/the-physics-of-space-battles)) Since your question is mainly about whether it would be possible to "hide", definitely look through the "Detection in Space Warfare" page, the author is of the definite opinion that none of the proposed solutions would work. For example, here's the discussion of just channeling exhaust and waste heat in a narrow beam going in the opposite direction of where the enemy is located: > > Glancing at the above equation it is evident that the lower the > spacecraft's temperature, the harder it is to detect. "Aha!" you say, > "why not refrigerate the ship and radiate the heat from the side > facing away from the enemy?" > > > Ken Burnside explains why not. To actively refrigerate, you need > power. So you have to fire up the nuclear reactor. Suddenly you have a > hot spot on your ship that is about 800 K, minimum, so you now have > even more waste heat to dump. > > > This means a larger radiator surface to dump all the heat, which means > more mass. Much more mass. It will be either a whopping two to three > times the mass of your reactor or it will be so flimsy it will snap > the moment you engage the thrusters. It is a bigger target, and now > you have to start worrying about a hostile ship noticing that you > occluded a star. > > > Dr. John Schilling had some more bad news for would be stealthers > trying to radiate the heat from the side facing away from the enemy. > > > "Besides, redirecting the emissions merely relocates the problem. The > energy's got to go somewhere, and for a fairly modest investment in > picket ships or sensor drones, the enemy can pretty much block you > from safely radiating to any significant portion of the sky. > > > "And if you try to focus the emissions into some very narrow cone you > know to be safe, you run into the problem that the radiator area for a > given power is inversely proportional to the fraction of the sky > illuminated. With proportionate increase in both the heat leakage > through the back surfaces, and the signature to active or semi-active > (reflected sunlight) sensors. > > > "Plus, there's the problem of how you know what a safe direction to > radiate is in the first place. You seem to be simultaneously arguing > for stealthy spaceships and complete knowledge of the position of > enemy sensor platforms. If stealth works, you can't expect to know > where the enemy has all of his sensors, so you can't know what is a > safe direction to radiate. Which means you can't expect to achieve > practical stealth using that mechanism in the first place. > > > "Sixty degrees has been suggested here as a reasonably 'narrow' cone > to hide one's emissions in. As a sixty-degree cone is roughly > one-tenth of a full sphere, a couple dozen pickets or drones are > enough to cover the full sky so that there is no safe direction to > radiate even if you know where they all are. The possiblility of > hidden sensor platforms, and especially hidden, moving sensor > platforms, is just icing on the cake. > > > "Note, in particular, that a moving sensor platform doesn't have to be > within your emission cone at any specific time to detect you, it just > has to pass through that cone at some time during the course of the > pre-battle maneuvering. Which rather substantially increases the > probability of detection even for very narrow emission cones. > > > Then the page gives another quote from Ken Burnside: > > "The problem with directional radiation is that you have to know both > where the enemy sensor platforms are, and you have to have a way of > slowing down to match orbits that isn't the equivalent of swinging end > for end and lighting up the torch. Furthermore, directing your waste > heat (and making some part of your ship colder, a related phenomena) > requires more power for the heat pump - and every W of power generated > generates 4 W of waste heat. It gets into the [Red Queen's Race](http://en.wikipedia.org/wiki/Red_Queen%27s_race) > very quickly. > > > "Imagine your radiators as being sheets of paper sticking edge out > from the hull of your ship. You radiate from the flat sides. If you > know exactly where the enemy sensors are, you can try and put your > radiators edge on to them, and will "hide". You want your radiators to > be 180 degrees apart so they're not radiating into each other. > > > "Most configurations that radiate only to a part of the sky will be > vastly inefficient because they radiate into each other. Which means > they get larger and more massive, which reduces engine > performance...and they still require that you know where the sensor > is. > > > "The next logical step is to make a sunshade that blocks your > radiation from the sensor. This also requires knowing where the sensor > is, and generates problems if the sensor blocker is attached to your > ship, since it will slowly heat up to match the equilibrium > temperature of your outer hull....and may block your sensors in that > direction as well. > > > **Update:** Some commenters have been asking about the possibility of having a sort of "heat battery" which absorbs waste heat generated by propulsion and other systems on the ship for the period of time where it needs to be stealthy, and is well-insulated so as not to give off detectable [blackbody radiation](http://en.wikipedia.org/wiki/Black-body_radiation), or to leak its energy to other parts of the ship as heat, so that from the outside the ship would not give off radiation due to heat. I found some useful equations relevant to the feasibility of this, so I thought I'd post them. Suppose we want to have enough fuel for some set of maneuvers during the period the rocket needs to be stealthy, such that, if the same amount of fuel were spent just accelerating the rocket continuously in one direction, the rocket's change in velocity would be $\Delta v$. Then if the final mass once all this fuel is spent is $m\_1$ (which will include both the mass of the weapons and other useful systems, like life support if the rocket is manned and computers and sensors if it's not, as well as the mass of the heat battery), and the initial mass *including* fuel is $m\_0$, and the effective exhaust velocity of the propellant is $v\_e$, then the [Tsiolkovsky rocket equation](http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) relates these quantities: $\Delta v = v\_e \ln \frac{m\_0}{m\_1}$ A related equation is the amount of *energy* the fuel must supply to the rocket in order to achieve this $\Delta v$, given the effective exhaust velocity $v\_e$ and the final mass $m\_1$ that should be left over once the fuel is used up. As given in the "energy" section of the [spacecraft propulsion](http://en.wikipedia.org/wiki/Spacecraft_propulsion) article on wikipedia, "If the energy is produced by the mass itself, as in a chemical rocket", then the energy would be given by this formula: $E = \frac{1}{2}m\_1 (e^{\Delta v / v\_e} - 1)v\_e^2$ The "internal efficiency" $\eta\_{int}$ of a rocket is the ratio of the actual increase in linear kinetic energy delivered per unit time to the internal chemical energy used up per unit time, as explained [here](http://books.google.com/books?id=pFktw0GYSX8C&lpg=PP1&pg=PT56), so if the the fuel delivered an amount of linear kinetic energy $E$ to the rocket while it was burned, the original chemical energy must have been a greater amount $E / \eta\_{int}$, and thus the energy lost to heat must have been approximately $(E / \eta\_{int}) - E = E( \frac{1}{\eta\_{int}} - 1) = E\frac{1 - \eta\_{int}}{\eta\_{int}}$ (Note that this isn't exact, because some of the loss of efficiency is not due to energy lost to heat, but rather due to exhaust particles having some kinetic energy that isn't parallel to the direction the rocket is traveling. Also I'm assuming below that the heat battery is somehow absorbing *all* energy lot to heat, the calculations would be somewhat different if heat couldn't be channeled away from the exhaust trail, but only the heat that would be added to the ship itself, see the chart [here](http://books.google.com/books?id=pFktw0GYSX8C&lpg=PP1&pg=PT57) for estimates of about how much fuel energy is lost to each. Maybe the best way to be stealthy would be to avoid chemical rocketry with hot exhaust trails, and instead use something like a [mass driver](http://en.wikipedia.org/wiki/Mass_driver#Spacecraft-based_mass_drivers) that could fling a stream of cooled pellets backwards at high velocity.) So using the above formula for $E$, the heat generated $Q$ would be approximately: $Q = ( \frac{1 - \eta\_{int}}{\eta\_{int}}) \frac{1}{2}m\_1 (e^{\Delta v / v\_e} - 1)v\_e^2$ If the heat battery has mass $m\_b$ and specific heat $c$, then rearranging the formula [here](http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html), we can see that absorbing heat $Q$ will cause a temperature change $\Delta T$ of: $\Delta T = \frac{Q}{c m\_b}$ And in the equation for $Q$, we can replace the final mass after fuel is expended, $m\_1$, with $m\_b + m\_p$, where $m\_b$ is again the heat battery mass and $m\_p$ is the remaining payload mass (weapons etc.). Then combining the equations gives: $\Delta T = ( \frac{1 - \eta\_{int}}{\eta\_{int}}) \frac{1}{2 c m\_b}(m\_b + m\_p) (e^{\Delta v / v\_e} - 1)v\_e^2$ With some algebra you can solve this for the ratio of the heat battery mass $m\_b$ to the remaining payload mass $m\_p$: $m\_b / m\_p = \frac{( \frac{1 - \eta\_{int}}{\eta\_{int}}) \frac{1}{2 c } (e^{\Delta v / v\_e} - 1)v\_e^2 }{\Delta T \, - \, [( \frac{1 - \eta\_{int}}{\eta\_{int}}) \frac{1}{2 c } (e^{\Delta v / v\_e} - 1)v\_e^2 ]}$ The part to note is the denominator, which goes to zero if $\Delta T = [( \frac{1 - \eta\_{int}}{\eta\_{int}}) \frac{1}{2 c } (e^{\Delta v / v\_e} - 1)v\_e^2 ]$, which would make $m\_b$ infinite; and since $m\_b$ can't be negative either, that means for a physically realistic solution you *must* satisfy $\Delta T > [( \frac{1 - \eta\_{int}}{\eta\_{int}}) \frac{1}{2 c } (e^{\Delta v / v\_e} - 1)v\_e^2 ]$, which can be rearranged as: $\Delta v < v\_e \ln [(\Delta T (\frac{\eta\_{int}}{1 - \eta\_{int}}) \frac{2c}{v\_e^2}) + 1]$ You can plug some numbers into this equation to get some sense of the limitations it puts on any such system. For example, say our heat battery starts off at 0 K, and its temperature can increase up to 1000 K before the insulation can no longer keep a system that hot hidden from the outside, so $\Delta T$ = 1000 K. And say the specific heat $c$ is 0.9 kJ/(kg K), the same as that of the tiles on the space shuttle at 400 K according to [this](http://forum.nasaspaceflight.com/index.php?topic=1561.20;wap2), which converted into [SI units](http://en.wikipedia.org/wiki/International_System_of_Units) becomes 900 J/(kg K). And suppose $\eta\_{int}$ is 0.8, which would be extremely good according to the table [here](http://books.google.com/books?id=pFktw0GYSX8C&lpg=PP1&pg=PT61) ($\eta\_{int}$ = 1 would mean no energy lost to heat at all), which would make $(\frac{\eta\_{int}}{1 - \eta\_{int}})$ equal to 4. Finally, suppose the effective exhaust velocity $v\_e$ is 2,500 m/s, about the same as a typical solid rocket according to the table in the "[examples" section of the specific impulse wiki article](http://en.wikipedia.org/wiki/Specific_impulse#Examples). With these numbers, the formula tells us that $\Delta v$ cannot exceed 2500\*ln(1000\*4\*(2\*900)/(2500)^2 + 1), plugging that into the calculator [here](http://keisan.casio.com/calculator) gives a maximum $\Delta v$ of about 1916 m/s, just slightly under the amount of fuel needed to achieve escape velocity from the moon, and equivalent in fuel use to about 196 seconds of 1G acceleration. That doesn't seem like nearly enough for hitting a target in space that may be making unpredictable changes in its own velocity to confound possible pursuers even if it can't see them yet, and with the distances involved being very large. You can change some of those numbers and plug the altered formula into the calculator to see the effects, though. [Answer] Space combat in the "real world" is akin to a gun fight in a bull ring. Lethal weapons, no cover. One shot, one kill. The ranges will be determined by "Minute of Maneuver". In shooting, rifles tend to have their accuracy measured by "minute of angle", which is a unit of degrees (circles have 360 degrees, degrees have 60 minutes). By "Minute of Maneuver", I mean putting the shot in to zone where the target will be. For (a contrived) example, when hunting, say, a deer, the vital area is quite large (say, 6 inches across). A rifle with a 1 MOA accuracy, can put a bullet within 1" of the aim point at 100 yards. So, with a 6" vital area, a deer could be shot with such a rifle out to 600 yards. With a 2 MOA rifle, it would be 300 yards. When shooting at an airplane, you "know" how fast the plane is moving, you know how fast your bullet travel, so via ballistics, you have an idea how much to "lead" the aircraft to get your bullets on target. But that doesn't consider the airplane changing direction. The farther away you are from the target aircraft, the more opportunity there is for the plane to simply move out of the way. In WWII, anti aircraft worked for things like bombers, because they flew in straight lines at steady speeds. They didn't work so well with dog fighting fighters. So, you can see that the ranges will depend highly on the types of weapons involved. Because "range" only applies to ballistic weapons. A guided missile has "unlimited" range in this case. It can continually adjust its impact point. Now consider the simple case, an asteroid flying through space. Here, the minute of maneuver is very small. The asteroid simply does not maneuver. So, it's "easy" to ballistically hurl an object that will impact the asteroid. Consider the recent comet landing. Yes, there was some actual maneuvering done, but most of the "attack" was ballistic. A very complicated orbit, but ballistic nonetheless. The error wasn't so much the comet, but rather the limitations of the precision of place the probe in to it's proper orbit in the first place. Error tends to add up over such long distances, so corrections were inevitable. For a ship that can maneuver, you have to be close enough to overcome such maneuver. If you shoot a big warhead at, say, 10km/s, and the target is 5km away, the target has .5s to react, and maneuver the craft "out of the way". In space, maneuver is expensive. On an airplane, you budge an aileron, and the plane quickly changes direction. In space, you have to apply thrust to maneuver. You can't rely on aerodynamics to provide "free" maneuvering. How much thrust does the ship have? How long does it take to apply such thrust? All these factor in to the combat range. If a ship takes 10s to maneuver, then you can see that with a 10km/s warhead, you have an effective engagement range of 100km. Now, of course, all these numbers are made up. And also, 100km sure seems REALLY CLOSE for "space combat". But see how these numbers change with light speed weapons. In space, LASERs are, effectively, "ballistic weapons". With our previous example, your LASER "flies" at 300,000km/s. With our slow target before, that puts effective range at 3,000,000km. That's, (very) roughly, 10 lunar diameters. That seems like a more "realistic" "space range". Of course, getting a LASER powerful enough to do damage at 3Mkm is a different problem. You also start running in to limitations of accuracy. A 1000 foot ship (i.e. USS Nimitz) at 3Mkm is .006 degrees large. Can you imagine controlling a device with enough power to do damage with 6/10000 of a degree of tracking accuracy? Difficult to imagine. So, "real" space combat. Is probably going to be pretty close. It's going to be extremely lethal. There will be no cover. Like I said, rifleman in a bull ring. [Answer] Targeting becomes harder with distance. At lightyear distances, even directed energy weapons are far too slow to possibly hit something (remember: a lightyear is the distance light travels in a year, so you'd be pointing a flashlight at where the thing was 2 years ago). As distance decreases, maneuverability becomes more important (ie., quick fighters can dodge better than slow dreadnoughts; they dodge directed energy by seeing where the gun is pointed and being somewhere else). There's a point, though, at which maneuverability no longer matters: the fighter absolutely cannot outmaneuver a missile, because the pilot wouldn't survive the G-forces. Directed energy basically can't miss. At lightyear scale, it's also pretty easy to cloak: energy power level drops off with the cube of distance, so even the "brightest" ships we could build today are likely invisible from even a few lightminutes off. As to what might affect sensors, that depends heavily on how the sensors work. Visible-light sensors can be blocked by black paint at extremely close range, for instance. And, a side note: it's theoretically possible for a ship to go stealthy for a time by sinking most of its heat into some internal store, or by directing it away from the thing they're trying to avoid. [Answer] My first thought is: The question is almost impossible to answer, because we have no idea what technology will exist. Suppose you asked someone in 1492 what the maximum range was at which naval ships in 1900 would engage. Even if he was imaginative enough to consider radical advances in technology, it would be awfully difficult to predict what would actually come about. That said, a few random thoughts: A guided missile should be useful at ranges comparable to the range of your star ships. If you have ships that can travel hundreds of light-years without refueling, then it seems likely you could make a guided missile that would do the same. Laser weapons (or phasers or whatever equivalents) would be limited by the dissipation of the beam. By definition lasers are highly focused, and presumably in the future they would be more focused still. But they must have SOME spread over distance, and eventually this will result in the beam having too little energy per square meter to be effective. Are there theoretical limits to how tightly focused a laser beam can be? At long enough distances, aiming a laser would be an issue. If it takes minutes (or hours) for the beam to reach the target, then a ship could just make random evasive maneuvers to render beam weapons worthless. I say random maneuvers because, if your laser beam travels as fast as any signals from a sensor, there would be no way to detect the laser beam before it hit. In 21st century combat, a missile travels a whole lot slower than light or radar waves, so you can bounce a signal off a missile and detect that it's coming. But how would you do that with a laser? Even if you could bounce some sort of signal off a laser beam, that signal would have to be faster than the laser or you wouldn't get the signal that the laser was coming until the same instant it hit, which wouldn't help much. As to stealth ... the way modern stealth aircraft work is by, (a) reducing the amount of heat they give off, (b) being made of materials that absorb radar waves, and (c) having shapes that bounce radar waves off in directions other than back to the radar transmitter. I'd think similar things would work in space. Of course it all depends on how their sensors work. But if they're transmitting a beam that gets reflected back when it hits something, then presumably you could have technologies that absorb that beam or reflect it in a different direction. If they have passive sensors that detect heat or other emissions, you could have techniques that reduce those emissions to the point where they are below the sensitivity of the sensors. It's difficult to say how hard that would be to do without knowing how the sensors work, and what sort of equipment has to be aboard the space ships for them to operate. *Additional thought* Several folks on here have stressed the difficulty of hiding a spaceship's heat. But that all depends on how hot the spaceship is, how sensitive the other guy's sensors are, and how far apart you are. If someone put a nuclear reactor in orbit around the Sun at the same distance as Pluto, how difficult would that be to detect from Earth? I don't think there is any detection device that exists today that could sweep the sky and instantly find such an object. I suspect it would take a long and meticulous search. Even if there was no attempt to hide the reactor at all, the amount of energy from that reactor that would reach detectors on Earth from such a distance would be tiny. Ah, here's a way to think of it. Energy received is going to fall off with the square of the distance. So if the energy from your spaceship divided by the square of the distance is less than energy being received from stars divided by the square of the distance, then your ship would not stand out against the background noise of the stars. How much heat would a spaceship put out compared to a star? If it was, just to make up a number, 1/10,000 as much, then if the ship is more than 1/100 of the distance away as the star, the sensor would receive the same amount of energy from each. That wouldn't make it undetectable, I suppose: You could have a map of all the stars and any other known energy source and have a computer search for anomalies. But even a very hot spaceship would not stand out brightly. [Answer] Space is really big, and almost any star ship would be really tiny compared to everything else out there. A few light years is a distance at which we can't consistently detect *planets*, let alone a space craft. Even one light second is really far away. For reference, the moon is just over a light second from earth. At this distance, a carrier would be half the size of Neptune in the sky. An X-wing would appear smaller than Pluto. Spotting something that looks smaller than Pluto in a reasonable time at that kind of distance might be possible if it's not trying to stay hidden, but it would be quite easy to give it a stealth coating and fling it towards your target at a relativistic speed without any active propulsion. Combat at a a few light minutes away would be akin to shooting at people on earth from the surface of Venus or Mars. While it's possible that some technology could one day exist to allow such combat, the constraints and distances that such combat would occur under would be entirely dependent on that supposed technology. [Answer] > > Sixty degrees has been suggested here as a reasonably 'narrow' cone to hide one's emissions in. > > > You don't need a cone of that size. Shoot molten pellets that're insulated and covered in ice. Eventually they burn through the insulation, and before that have melted the ice (insulation isn't perfect). Firing those in all directions might be a convenient deterrent vs. heat-seeking missiles (like chaff or flares). Or, another solution to the cone problem is to use a refrigerating laser. I don't see why a radiator needs to 'snap off', there's no air resistance - max force you'd apply would be your own thrust operating in reverse direction (if you didn't rotate your ship). However stealth is hard to get in space. In normal space, you're visible against the background, even if you're black - especially if you're moving (you start occluding more stars). You could try for a chameleon effect, but you'd need to know where your observer is, in order to calibrate your brightness (falls off with cube of the distance, and you're a lot closer than the star... to get the same output at his location, you'd need to know his location, and hope he doesn't have a sensor net up. There are some bending light solutions which might work for this. I've not investigated them fully, but they're int he popular science press - I've seen them in the last couple of months. If those actually work, then it'd make life a lot easier for a moving ship. You can, however, hide behind things. And you can use micro-drones, micro-missiles, and micro-sensors to remain undetected at closer ranges. I expect that you'd end up with remote networks doing much of the fighting, and ships with bio-crew to be so far apart that they're hard to hit with direct energy weapons - probably usually hidden behind chunks of matter in the system (which are hopefully not mined), and moving other chunks of matter to create more hide-behind spaces; Maybe with lots of remote-operated tugs. -- An aside/comment on the deleted answer: I don't see what's wrong with answering a question with questions; it'll help OP firm up the details, or at least pick some things or offer a range of solutions so they can get a better answer from all of us (ie: it can improve the original question). But yes, answer is worded pretty snidely. ]
[Question] [ I'm writing a book to redefine the horsemen of the apocalypse. My first book concentrated on a new "Death", who reveals that there are in fact 7 "horsemen", not 4 - war, death, pestilence, famine, mania, nature and rot. I have War as an vibration which travels through vibrations, sound waves etc. I'm slowly introducing nature, and want one of her abilities to be the control or manipulation of carbon into other forms. I also want her to be able to control natural disasters (or start them) and add to that a couple of new things. To that end, is it possible to effectively negate a person's gravity, to make them "fall" off the planet? The how of it is important because I will be detailing the perspective of the first victim as they experience what will happen to them. Thank you for any thoughts on this. I need the planet not to explode, I have been told that messing with the gravity of the planet, in specific areas, causes a planet wide catastrophe - so that won't work. Thanks for your time! [Answer] > > To that end, is it possible to effectively negate a person's gravity, to make them "fall" off the planet? > > > Using magic? Sure, anything is possible. Without using magic? No. > > The how of it is important because I will be detailing the perspective of the first victim as they experience what will happen to them. > > > In the real world [inertial mass and gravitational mass](https://en.wikipedia.org/wiki/Mass#Inertial_vs._gravitational_mass) are indistinguishable and inseparable, but that doesn't need to be a problem fdor you. Magically set their *gravitational* mass to zero, so that gravitational forces can't act upon them. Their *inertial* mass must remain the same, or they'll instantaneously accelerate to lightspeed with all the badness that entails. When their inertia stays the same, all other forces act upon them as normal. Some magical material that shields from the effect of gravity would also work (the classic example would be [cavorite](https://en.wikipedia.org/wiki/The_First_Men_in_the_Moon), of course), but being put in a death-box is perhaps less dramatic than simply flying up into space. Once gravity has ceased holding them to the Earth, there are various things that will fling them into space: the rotation of the Earth about its axis, the rotation of the Earth about the Sun, and the victim's bouyancy in air. Obviously they can also push themselves off the ground (eg. by trying to run away) which will speed things up a bit, but I'll ignore that factor. The effect will be to ultimately fling them into interstellar space, but initially they'll just appear to rise slowly from the ground, and accelerate slowly into the sky where they'll freeze to death or asphyxiate after a short period of time. --- [Centrifugal acceleration](https://en.wikipedia.org/wiki/Centrifugal_force) (which I'd originally and mistakenly called "centripetal", thanks for the correction by Nuclear Hoagie) is a [fictitious force](https://en.wikipedia.org/wiki/Fictitious_force) that appears to push an object in a rotating reference frame (eg. on the surface of the Earth) away from the centre of rotation (eg. the Earth's axis). Centrifugal acceleration can be calculated using $a\_c = \omega^2r$ where $\omega$ is the angular velocity of the thing in question. At Earth's equator, $\omega$ is 2π radians per day, or ~7.27 x 10-5 radians per second. $r$ is ~6378.1km, giving an apparent upward acceleration of 0.034m/s2, or about 3 milligees relative to your point of departure. I say "apparent" because they're not *really* accelerating upwards, but shooting off the surface of the Earth at a tangent at about 460m/s, but because their point of departure is curving away from them as Earth rotates it will *appear* that they're accelerating upwards. There's a worked example at the end showing the effect and the difference. As you approach a pole, the apparent acceleration will reduce (proportional to the cosine of the latitude) and the direction will be more towards the horizon. At my latitude, ~52°N, the force will be reduced to ~62%, or ~2 milligees, and the victim would appear to be taking off at an angle of ~48° from vertical, pointing towards the south. Their tangential velocity will also change... $v\_t = \omega r \cos{\lambda}$ where $\lambda$ is the latitude, 0° being the equator. There's an additional centrifugal effect caused by the Earth's rotation about the Sun, where $r$ is 1AU and $\omega$ is 2π radians per year. This will ultimately manifest as a 26km/s trajectory out of the solar system and into interstellar space, but its immediate effect is small: at midnight on the equator it gives you an apparent upward boost of 0.006m/s2, and at midday it will reduce your apparent acceleration by the same amount, but in either case its contribution at the beginning is small. It will have the same magnitude regardless of latitude, though, and add or remove about half a milligee. At other times you'll need to do a vector sum, but for a first approximation you can ignore it. The final effect will be bouyancy (well spotted Qami!) as although the volume of the person has not changed, there's no longer any opposition to their bouyancy in air, so they will rise as if they were a vacuum balloon. The acceleration exerted by bouyancy in the air is $a\_b = g\frac{\rho\_f}{\rho\_v}$ where $g$ is the acceleration due to gravity, $\rho\_f$ is the density of air around the victim (~1.2754 kg/m3 at STP) and $\rho\_v$ is the density of the victim (say, 1000 kg/m3). This gives an initial ~0.013m/s2 vertical acceleration regardless of time of day or latitude, and decreases with altitude as air density decreases. That's another milligee and a bit. Lets assume then that this is occuring on the equator (for maximum centrifugal force) and we're ignoring the effects of Earth's orbit. You'd get an apparent initial acceleration of about 4 milligees, which is pretty sedate. Bouyancy forces will accelerate them straight up, and their tangential velocity will carry them up-ish. The victim will rise up, and can reasonably be assumed to be dead by the time they've passed 8000m altitude, the conveniently named [Death Zone](https://en.wikipedia.org/wiki/Death_zone), where they will asphyxiate if they haven't already succumbed to hypothermia (and if they took off from the equator, they might not be dressed for freezing temperatures). The exactly rate of climb is awkward to compute, but you can reasonably assume that in about 10 minutes (give or take), they'll be dead or dying. In the immediate short term though, the acceleration is surprisingly slow... after 10 seconds, they'll have risen less than 2m, and so could be caught by a friend. They'll be experiencing free-fall as soon as their gravitational mass goes missing, so they might be sick. The vomit will experience the same forces, so unless it was expelled quite forcefully it'll stay with them on their way up. Peter LeFanu Lumsdaine suggested that it might be possible to swim back down to the surface, which I suspect would be impossible for someone not equipped with suitable things to flap... the possibility exists though that someone with a couple of big fans or suitably stiff, lightweight boards might be able to fly back down and grab on for safety. Interesting thought though, certainly! --- For anyone who cares, you can see that the centrifugal force, whilst fictitious, isn't wrong, and you can approximate your flight path by using the intial centrifugal acceleration. Here's a slice though the Earth at the equator. The Earth's axis of rotation is the centre of the circle, and the Earth is rotating clockwise. [![Tangential trajectory from a planet, and altitude](https://i.stack.imgur.com/iEqQQ.png)](https://i.stack.imgur.com/iEqQQ.png) $T$ is the trajectory that the victim will be travelling on, neglecting bouyancy effects. $R$ is the radius of the earth, and $A$ is the altitude of the victim, who is assumed to be at the far apex of the triangle. The length of $T$ will be the tangential velocity $v$ of the victim (~460m/s at the equator) multiplied by the flight time, $t$. You can compute $A = \sqrt{R^2 + v^2t^2} - R$. After 700 seconds, the victim's *actual* altitude will be ~8123m above where they started, but using the initial centrifugal acceleration $c\_a$ of 0.034m/s2 and $A = \frac{c\_at^2}{2}$ you'd get more like 8263m which is close enough for government work. As $t$ increases, the less this lazy approximation works, but the victim will be dead by then so it doesn't really matter! Similarly, the rate of altitude gain (or vertical speed) done using $\frac{dA}{dt} = c\_at$ gives you a speed at 700 seconds of ~23.6m/s, whereas the correct derivative $\frac{dA}{dt} = \frac{v^2t}{R^2+v^2t^2}$ gives you ~23.2m/s. Including the bouyancy acceleration vector (which always points away from the centre of the Earth and reduces in magnitude with altitude) and drag (which you can't really neglect after a couple of minutes, and acts in opposition to the velocity vector whose direction continually changes with time and also reduces with altitude) is left as an exercise for the reader. [Answer] If you completely negate someone's mass, then the only thing keeping them on the ground is air resistance. And not for long. For the sake of argument, imagine not someone that has zero mass, but someone who has so little mass that it approaches zero. That person will have very high buoyancy, even in air. Remember when [Lawnchair Larry](https://darwinawards.com/stupid/stupid1998-11.html) gained altitude "as if shot by a cannon"? That person would go up faster than that. Might already become a meteor in the way up to the stratosphere. And I say meteor in the meteorological sense, i.e.: something burning up in the atmosphere as it moves really fast. --- Now let's really nerd this up. A consequence of special relativity is that [massless particles must move at the speed of light](https://en.wikipedia.org/wiki/Massless_particle#Special_relativity). As soon as Nature takes away someone's mass, they will move at $c$. That is five orders of magnitude greater than both the Earth's escape velocity at sea level, and the Sun's escape velocity at Earth's orbit. The person will immediately start leaving the loving solar system. If they don't move up straight away they will just bounce on the ground and then go up anyway. Also all the particles in the person's body will each go their own way, so you don't really have a person anymore. Regardless, the only visible effect for regular humans is that the victim seems to disappear instantly. Along with everyone and everything around them. And an instant flash many times brighter than the Sun. Also if done in an atmosphere, you will see a mushroom cloud. As some colleagues mention in comments, turning mass into photons would likely release amounts of energy measured in the way we measure the output of nukes. If you want something less fatal, have Nature reduce someone's mass instead of removing it completely. [Answer] **Replace "fall" with "sink" or transition to another realm.** > > To that end, is it possible to effectively negate a person's gravity, to make them "fall" off the planet? The how of it is important because I will be detailing the perspective of the first victim as they experience what will happen to them > > > The effects on the person of "falling" off the Earth will be dependent on what exactly "falling" means. I think you mean "lifting", whereas I would suggest another approach is **sinking**. The energy required to lift someone is not enormous - we're talking flying here - it's hot air balloon territory. So, yes, you can make them *fly*. The problem is getting them to keep going past the atmosphere. You are now moving into escape velocity territory which require a lot of energy. Also it is not clear to me why you need that. At about the 10,000 feet mark the air density drops to the point that humans die, pretty quickly (minutes or seconds) from [hypoxia](https://en.wikipedia.org/wiki/Hypoxia_(medical)) (no air is bad !). They will not experience *anything* after that, whatever happens their bodies. Planes have rather a lot of equipment dedicated to preventing this, but an unprotected human without an air supply is dead quickly. So after 10,000 feet (or a bit before if you want them alive and alert !) you can have them transition to another realm (Hades, Disneyland, whatever). They are now out of the picture. Pushing them up to 10,000 feet is relatively small potatoes on the energy front and can be done gradually so they do not suffer injury from rapid acceleration (so just terror). Another possibility is burial. Let's open a hole in the ground and just drop them in and cover them up. They won't be coming back. What happens when they are out of view is up to you. > > is it possible to effectively negate a person's gravity > > > Not strictly speaking, but we routinely fly so finding a method to apply force to someone and push (lift) them up is easy. Your basic creature from beyond should have no problem magicing this without actually doing much damage to local physics on the way. No magic (well, modest amounts), no weird breaking the laws of physics (kind of), just a few writhing tentacles and a portal up there at about the 10,000 feet mark. Practically the same as any day in the Bermuda Triangle. :-) Maybe the realm "above" (or an entrance to it) drops down tentacles to drag the lucky traveler up. Can't go without tentacles in a story like this, IMO. [Answer] ## Just use this warp drive I have lying around (some assembly needed) You probably think I'm kidding, but [here's the paper](https://arxiv.org/abs/2006.07125)! It actually passed peer review and was published in *[Classical and Quantum Gravity](https://iopscience.iop.org/article/10.1088/1361-6382/abe692)*. You just expand space under the mark and contract it on top of him and before long he has free fallen right out into space. True, it takes an amount of energy equal to a tenth of the mass of the sun, but he thinks he can cut it down by 10^30 (yes, to the 30th!). He just needs some computer simulations ... and maybe some security protection against hostile aliens from the 27th century. [Answer] For a pseudo-science and handwavium answer without outright calling it magic, you could have the power's target no longer interact with gravitons from any distance over 10 feet or so. So, only being attracted to the portion of Earth within 10 feet, gravitational attraction is now minimal, allowing the target to push themselves away from the ground with their next footstep. I'll leave it as an exercise to the reader how this person would interact with air, wind and jetstreams, and whether he would be able to rise above the atmosphere. [Answer] ## Anti-gravity is hard, but LIFT is quite easy Birds, planes, balloons, and rockets fall upward all the time. As far a physics is concerned, the sum of two forces is essentially the same as a single force. So, instead of making G=-9.8m/s^2 you can leave G=9.8m/s^2 and add a second force that is 19.6m/s^2 in the opposite direction. To send an average sized man falling upwards at the speed of gravity, you simply need to exert a constant force of 1,215.2 N. The hard part is doing this with your mind, but you already seem prepared to handwave this part anyway. So while your horseman appears to be reversing gravity, he/she is really just pushing the victims up into space using telekinesis. They will accelerate upwards very quickly at first until they hit their terminal velocity, and then as they get higher and higher air resistance decreases allowing their terminal velocity to increase. Once they hit about 10km in altitude, the air with start to thin out very quickly causing them to die of hyperthermia and/or asphyxiation pretty quickly. Once they get high enough, you can stop lifting them and let them start falling again. The atmosphere will make sure nothing is left of them to return to Earth. [Answer] Gravity is a distortion of the fabric of spacetime. Spacetime is distorted by all objects with mass, especially dense objects with a lot of mass, such as planets. Gravity as we experience it is a result of our planet’s immense mass tugging on our own bodies’ masses. So no, it is not possible to negate an individual’s gravity, as the tug of the gravity we all feel is that of our planet’s immense mass and the gravity well it creates. The only thing that wouldn’t feel gravity is something with zero mass. Humans can’t have zero mass without some sort of magic that turns them into pure light or something, and somehow keeps them alive. tl;dr nope, you need magic. [Answer] This is something I only looked at very briefly in undergrad, so, if you care about scientific accuracy, double check everything. However, there is something called anti-matter which \*I think" has negative mass. This means it would do exactly as you say - fall away from a planet. Another way to say it would be that the gravitational interaction between anti-matter and (normal)-matter is a push rather than a pull. This is convenient in that you can get the effect you're looking for but (1) you don't have to change anything about earth's gravitational field and (2) if you want to weaken the affect, you could just stick a person with some anti-matter that has less mass than them. If the anti-matter is 1/2 the target's mass, but is, say, stuck to them, then they will only be accelerated upward 1-1/2=1/2 times as fast as we normally fall down, for instance. As far as how this would be experience - the matter/anti-matter relationship would be almost identical to the interaction between positive/negative ends of a magnet except that opposites repel in this case. In fact, the mathematical descriptions of (Newtonian) gravity and electromagnetic forces are strikingly similar. The actually motion would be like any other acceleration - think of falling or accelerating in a sports car. [Answer] **Swap the victim's gravitational mass to negative.** A person's weight is the result of Newton's formula for gravity: f = GMm/R^2. If one of the masses has a negative value then the force will be negative also. If the person's inertial mass remains positive then this will act to repel them from the planet, accelerating them upwards. This is of course impossible under known physics, but is at least a logical way for you magic to work. ]
[Question] [ Qui-Gon Jinn has finally realized he is an idiot and that everything is his fault. Everything that has happened (fall of the old Jedi order, rise of the empire, the rebellion, the First Order, etc.) can be traced back to his decision to train Anakin Skywalker. If he had just listened to the green troll, none of this would have happened and the galaxy would be at peace. Realizing that he is the retardant-supreme of the series, he has set upon an ambitious plan to correct his past mistakes. The force is pure energy, which runs through and is made up of all living things. When a person dies, they become one with it; their consciousness being subsumed by its presence. There is no past, present, or future in the force, as time is not truly linear. A strong enough force-ghost who has retained their consciousness can therefore appear and act upon the material world. Qui-Gon has decided to go back in time to before he made that decision about the brat. Instead of training him after meeting him on Tatooine, he plans to kill him, his remaining family, as well as anyone who traveled with him to the planet. To do that, he must take over and possess the bodies of living victims in order to get there. Unfortunately, he soon realizes that possessing a individual leads to its inevitable decay. The body begins to rot not long after possession, despite the fact that it is still living. This forces him to body-hop from person to person, leaving behind desiccated, withered corpses in an attempt to stay ahead of time. Why would something like this happen? [Answer] When a spirit possesses a body, it controls its movements: legs walk, hands grasp, eyes blink at the whim of the possessor. Each movement is a conscious act. What most people forget is that the body has completely lost control of everything, so it is up to the spirit to keep the heart pumping, the lungs breathing, and sphincters closed. Besides the fact that the spirit is probably unused to these things due to being not alive for so long, we generally suck at continuous body control. Don't believe me just because I said, experiment with it. Find some friends and say to each one: "you are breathing on manual now". Some will immediately take a deep breath and breath awkwardly for a few seconds as they become conscious of their own lung movements. By the way, you are breathing on manual now. Don't worry if you are affected, it resets in very short time. Back to possessed bodies without a blood flow - anoxia starts after several minutes of the blood not refreshing oxygen for the brain. Some quick googling shows the amount of time needed for its onset varying, but it is usually between four to six minutes. It may vary with general health conditions, and in a Star Wars setting may also vary by species. After ten minutes you may expect permanent brain damage, and after thirty you might be quite sure of brain death. Other tissues die as well due to lack of oxygen. The corpse may be seem fresh for a few hours. If you want it to stink after a few minutes of possession just say that midi-chlorians accelerate the rotting process. That is even cannon for the series, seeing as they did exactly that with Episode 1. [Answer] **Perspective shift**: the body *is not* alive. Once a body is possessed, it dies. It remains a flesh and bone puppet to the possessing entity. The entity can mimic life signs such as breathing and heartbeat but it's not much different to [applying electric stimuli to the correct parts of a cadaver](https://en.wikipedia.org/wiki/Galvanism) - it only *appears* living. So, a dead body will naturally start decaying. There are few other problems the possessed cadaver might face. No wounds would heal, for example. Nicks and cuts and other wounds would keep leaving scars on the body and might force the possession to end early, as it becomes increasingly conspicuous. Another problem is warm temperature - you would need to keep the body *reasonably* cold to prolong the time before it becomes unusable. Maintaining the humidity and other environmental factors might mean the possessed body could be kept operational for a very long time. To maintain the cover, an old person can be a good target. First of all, people don't pay *too* much attention to the elderly. An old person who lives alone with no other family and not much contact with others for a long time is something people will notice but not immediately think "it's a possessed body". And old people are given a large berth for their eccentricity. So what if the older gentleman lives alone and doesn't exit his home? And he prefers his home *very* well r̶e̶f̶r̶i̶g̶e̶r̶a̶t̶e̶d air conditioned? It can draw comments, sure, but is within what society is willing to turn a blind eye to. Maybe the older eccentric gentleman is a doctor from a foreign country, too. At this point all the strangeness can be easily accepted. Until one night the cooling system fails and the dead body falls apart by the time it could be repaired. > > Post contains allusions to [a short horror story](https://en.wikipedia.org/wiki/Cool_Air) that you can read [here](http://www.hplovecraft.com/writings/texts/fiction/ca.aspx). It kind of spoils the twist but...then again, the twist can be seen coming from very far away. > > > [Answer] What you describe might generally be called "localized necrosis." As suggested in comments, gangrene is one form of this. Something similar happens with certain spider bites (though it's often possible to avoid infection in that case because of the small affected area), in Hansen's Disease (colloquially known as leprosy), and necrotizing fascitis ("flesh eating bacteria"). This happens when a limited portion of the body dies while still attached to the living flesh. If unchecked, and in a form that spreads, it's usually fatal. In some cases, (where the dead flesh can be excised) it may only lead to amputation or scarring. Why would this happen when force-possessing a living body? Qui-Gonn's force isn't complete (because he's dead). Some of what was once the essence of Qui-Gonn has taken a wrong turn in the essence of the Force -- and if the body is partially animated by a force ghost, while some fraction isn't so managed, and the original owner's "ghost" has been forced out, the parts that aren't under direct control start to die. [Answer] In general, the idea that when the spirit of the dead possesses a body, the body starts to decay, is so narratively consistent, you do not need any explanation at all. The setting being the Star Wars is an additional factor that simplifies matters. As far as the force users are concerned, it strongly runs on 'good is beautiful, evil is ugly' principle. Using the Dark side makes force users get saggy pale skin, red eyes and so on. Necromantic possession seems very much a Dark side power, so there needs to be no other explanation that the Dark side corrupts the possessed bodies, burns the life out of them and generally makes everything messy, ugly and stinky. Possibly, more detailed explanation could be that the bodies lack biological mechanism to channel the force from outside (if you believe in midichlorians), so they run for some time on the inherent force every living being has, but they burn out, especially if the possessing spirit tries pushing them to use any force abilities. Force is life, if you loose force, you get dead - as simple as that. UPD: by that logic it means that if your force spirit manages to capture a force user body, it may go all Palpatine-ugly on him, but won't decay. If your setting is not Star Wars, but it was merely an example, other explanations proposed here work nicely too. [Answer] **The force ghost does not feel any pain** As such, the host effectively catches a non-congenital version of [Congenital Insensitivity to Pain](https://en.wikipedia.org/wiki/Congenital_insensitivity_to_pain), a horrible real-world disease whose sufferers tend not to live very long. It turns out pain is important for continued survival. Most people have experienced forgetting they have keys in their back pocket, sitting on them against a flat surface, felling pain, and immediately getting up. Well, if there's no pain, they tend to not immediately get up, instead leaving their full weight on the keys for an hour or three and really hurting themselves. There's a million such hazards for those who feel no pain. The ones who live the longest do so through discipline and awareness. The force ghost can go arbitrarily long without even knowing what the issue is. Body parts start to [necrosate](https://en.wikipedia.org/wiki/Necrosis) without warning, and eventually the host dies and the ghost has to seek a new one. Eventually there's a big epiphany. Depending on the format, it may be nice to leave clues for the audience. E.g. in a book, they "put the keys in the back pocket". A few pages later, they "sit down on the hard wooden floor" for a long conference. A few more pages and couple days later, they notice their leg is blackened. [Answer] Every soul is meant to have only one body, and every body is only meant to have one soul. When Qui-Gon's soul enters another body, the original soul is pushed out, meaning the death of the original person. Their soul is gone, and their body naturally begins to decay. The Force, or the fact that Qui-Gon's soul is in the body, enables the body to move and act like a living being, but it is in reality dead. [Answer] Thats easy, **possession destroys the immune system**, without an immune system the body will begin to rot, disease will spread consuming the flesh in rapid order. The only thing stopping your body from rotting now is your immune system. There are more than enough diseases that can rot the body even with an immune system. ]
[Question] [ So this question, [Designing a Carnivorous Plant](https://worldbuilding.stackexchange.com/questions/73220/designing-a-carnivorous-plant), talks about animals being attracted to a plant, at first by a sweet scent, and then being drugged by an unspecified toxin which renders them 'euphoric' enough to not want to move. The plant then digests them and uses their biomass for nutrition like a Venus flytrap does a fly. My question is similar but different (Captain Obvious I know but hear me out): Could a plant use pheromones which sexually attract humans to achieve its purposes? This can be a carnivorous plant or one which wants to attract humans for the purposes of spreading its seeds - or even, strange as it seems, pollination. Clarification: I'm working with current human biology here. By 'pheromones', I'm referring to anything chemical which humans use to signal sexual availability. [Answer] # Short Answer Probably not. Pheromones, even in species that react strongly to sex pheromones, are like an on/off switch or a volume switch that triggers the strength of an existing impulse. But, pheromones don't do anything as complex as changing the basic template of the species (or even family or order or phylum) of what someone has a capacity to see as a sexual object. That would involve reprogramming lots of different areas of the brain, not just adjusting the flow in one or two biochemical pathways in the body as pheromones do. # Long Answer A plant that chemically triggers direct dopamine release a la the Greek myth of the [Lotus Eaters](http://%20thought%20only%20professionals%20like%20medical%20doctors%20or%20CPA's%20only%20be%20personally%20liable%20for%20their%20professional%20liability?%20OK,%20let%20me%20make%20one%20clarification.%20If%20I%20did%20some%20handyman%20level%20work%20(negligent%20work)%20which%20doesn't%20require%20licence%20by%20law,%20will%20I%20still%20be%20personally%20liable%20for%20the%20casualty%20my%20work%20caused%20in%20the%20capacity%20of%20an%20former%20LLC%20employee?) (producing an effect similar to Oxycontin) wouldn't be explicitly sexual, but can be transmitted in gas form (people can smoke heroin, for example), and would trigger feelings of euphoria and trust. Basically, it could skip the sexual arousal phase and go straight to the afterglow. But, even if any existing pheromones have only a slight effect (and count me among those who think that [the evidence supports very mild pheromone effects in humans](https://en.wikipedia.org/wiki/Pheromone#Humans)), I don't think that anyone seriously disputes that sexual arousal has a strong biochemical element to it. [Sex pheromones](https://en.wikipedia.org/wiki/Sex_pheromone) do have powerful effects in many non-human species, and while humans have greatly degraded olfactory capacity, that doesn't mean that the biochemical pathways that sex pheromones trigger in other species don't exist in humans. It just means that the way that those pathways are triggered in humans is different. Find the right trigger and you will get the desired effect. Like pretty much anything else that has a strong biochemical element to it, it would probably be theoretically possible in principle to hijack the relevant biochemical pathways with a gaseous form perfume from a plant, even if that isn't something that happens in nature. A plant could have an even more powerful and plausible impact on the biochemical pathways involved in sexual arousal if it accessed these pathways not through a gaseous form perfume, since humans are particularly insensitive to smells, but instead through some sort of contact poison (think poison ivy that made you horny instead of itchy), perhaps in tendrils extending far beyond the main plant, or spores (the nettle and burr examples are good ones), or pollens. [![enter image description here](https://i.stack.imgur.com/OCng6.png)](https://i.stack.imgur.com/OCng6.png) The real problem with a plant triggering sexual arousal is that even if the plant does successfully achieve this perfectly, in some way or another, leveraging that cue into an attempt to have sex with the plant that in turn causes the plant to be able to eat you is an entirely different matter. Sexual arousal merely makes someone highly receptive to other perhaps otherwise substandard cues that there is an opportunity to have sex (the technical term is [beer goggles](http://www.urbandictionary.com/define.php?term=beer%20goggles)). Someone really aroused and far gone might even try to copulate with a dog or a cow or a goat. But, even extremely sexually aroused drunk people do not generally try to copulate with plants. A plant that did this might cause animals in its vicinity to have inter-species and other varieties of sex that they might not otherwise engage in, like certain plants in the Xanth novels of Piers Anthony, but would probably not lead to someone trying to have sex with the plant itself. Changing the cues in other senses that cause a person's brain to identify a potential sexual partner to the extent that they would be attracted to a plant when they were sexually aroused would be far, far harder (maybe virtually impossible) than merely causing someone to be sexually aroused in general. A more plausible strategy for a plant that could tap into the biochemical pathway that leads to sexual arousal would be to have a chemical trigger that has that effect when ingested, causing people to eat the plant to get the effect and in the process to spread the seeds and encourage humans to cultivate them. [Answer] I can imagine a sexy smelling plant that obtains biomass from humans. Specifically: male humans. [![enter image description here](https://i.stack.imgur.com/s98Ow.jpg)](https://i.stack.imgur.com/s98Ow.jpg) Males aware of the properties of the plant might choose to make a donation. Repeat donations are definitely possible. Probable. I can imagine cultivation of said plants, and possibly even selective breeding for desirable characteristics. [Answer] Carnivorous plants probably aren't going to happen. As AlexP points out in the comments, the great apes are not heavily dependent on pheromones for our sexual interactions. Sure, we have some scent based compounds which appear to indicate immune system compatibility by exposing information about our [major histocompatibility complex](https://en.wikipedia.org/wiki/Major_histocompatibility_complex), but they're a rather calm force. Certainly not something which would generate enough euphoria to snare a meal. If they could develop a chemical of their own which somehow hijacks the signals in our brain in a yet-undiscovered way, they might be able to do something. It is known that our intelligence is substantially taken offline when we're aroused (it's been argued that this is one reason for a lack of condom usage). However, now this plant is stumbling into one of the greatest battles of all time: the battle between the intellect and our base desires such as reproduction. If it were to suddenly be unsafe to get within 100m of such a plant, you can be guaranteed that the human culture would quickly develop intellectual reasons to stay at least 150m away from any such plant (and likely burn it with bombardment fire from that distance). We're a really smart animal to use as prey. However, if you merely want to use humans, there may be more options. If you were a plant and had a more mild euphoria toxin, you could attract humans to you. If you didn't harm them, they'd have no reason to avoid you. In fact, they'd be attracted to you! You could then use them in many ways to help you spread seeds or pollen all over the world. And yes, there's plenty of X rated ways to interpret that sentence, but there's also plenty of mild ways as well. Consider the synergy between bees and plants for distributing pollen. The bees pick up pollen simply by being around the flower and going after what they want. I'd point out that it's known that the human body is designed for long distance travel better than any other land creature out there. These humans could make quite the little bumble bees, carrying your seeds and pollen to the far reaches of the savanna! [Answer] Your question immediately reminds me of this particular scene on this manga: **Dungeon Seeker**. The next page of this image is particularly disturbing, so I refrain from using that, but you can follow [this link](http://www.mangatown.com/manga/dungeon_seeker/c012/13.html) to read the chapter to get the idea. [![Dungeon Seeker, Chapter 12](https://i.stack.imgur.com/d3N1c.jpg)](https://i.stack.imgur.com/d3N1c.jpg) Although this manga setting is magical, I think the idea of using **hallucinogen** to achieve what you are after is possible. The plant may smell nice at the beginning, but that's the hallucinogen starting to fool your brain. The area of effect should be pretty large to allow the hallucinogen to work, then a sweet aroma stimulate your hunger and draw you to the vicinity of the plant. You can imagine the fate of this poor fellow. The hole in this scenario, though, is that human's sense of smell is not as good as dog, and thus not always be able to determine where the smell came from. [Answer] If you are trying to create a plant that attracts people to it then it could be a suggestive shape or motion that would pull us closer since we are more visually stimulated than smell stimulated. That would get them to come investigate but not likely to slow them down enough to get digested by a plant. Another thing that may work is that the pheromones it produces make humans euphoric and they go and hang out around it for the trip until they collapse and become food. Maybe it has a symbiotic relationship with some predator that kills and drags its prey over to get eaten. maybe the predator wears it like a hermit crab and it feeds off the remains. ]
[Question] [ If someone successfully located and mined all the remaining unmined gold on Earth and released it into the global economy within one day how bad would the inflation be? If the inflation isn't much would it still be able to damage the economies of individual countries? [Answer] # Overall - it's unlikely An article on [phys.org](http://phys.org/news/2011-09-gold.html) makes this interesting claim: > > There are enough precious metals in the core to cover the entire surface of the Earth with a four metre thick layer > > > So, if you really mean all of it, gold would become as worthless as dirt is. Most gold nowadays is used in manufacturing (particularly electronics and jewellery) rather than as reserves thus its impact on the world economy would be *fairly* limited. The main place it would have an impact is if a major economy had a recession - during recessions and uncertainty, many traders move to gold as a safe haven. It's more likely though that some other commodity - something like oil - would become more commonly used as a safe haven instead. # Electronics as a counter-case On the note about electronics, something very interesting happens. Computer chips would likely be entirely made from gold, or at the very least, all the traces would be plated in gold as they are on a [typical satellite chip](https://en.wikipedia.org/wiki/IBM_RAD6000) or in a [quantum computer](http://www.digitaltrends.com/features/dt10-quantum-computing-will-make-your-pc-look-like-a-graphing-calculator/): [![A radiation hardened chip designed for use on satellites](https://i.stack.imgur.com/5pVbA.jpg)](https://i.stack.imgur.com/5pVbA.jpg) *A radiation hardened chip designed for use on satellites* [![A quantum computer making heavy use of gold](https://i.stack.imgur.com/ph7aj.jpg)](https://i.stack.imgur.com/ph7aj.jpg) *A quantum computer making heavy use of gold* This is to primarily make use of its excellent contact conductivity as well as its non-corroding properties. Gold is a great conductor and is also very durable so it's currently used where a reliable connection is vital to product performance. This is why the pins of e.g. a USB port are very literally gold. Consumer chips made using a lot more gold would be more reliable. The modern world economy deeply depends on computing so it might even create a mini economic boom thanks to better electronics for everyone. There would possibly be a huge crash in satellite prices considering the [extensive use of gold](http://www.geek.com/news/geek-answers-why-does-nasa-use-so-much-gold-foil-1568610/), increasing the chances of space becoming commercialized and therefore boosting the economy too. # However.. Rather than releasing it into the economy, maybe it could all be ejected into space. *Get rid of it* instead of creating too much of it - that way it can't boost those functional use cases. This route would have more of an impact (particularly in the short term where the rapid cost rise disrupts multiple industrial practices) but ultimately industry would just swap to some other metal instead. [Answer] The function for [money demand](https://en.wikipedia.org/wiki/Demand_for_money) is the following, the equilibrium condition between the demand for real money and the [liquidity preference](https://en.wikipedia.org/wiki/Liquidity_preference) function: $$\frac{M}{P} = \operatorname{lp} \left ( r^-, Y^+ \right )$$ Rearranging this to yield a function for the price level, or the variable of which inflation ($\small \pi$) measures long-run growth (i.e. $\small \pi\_{t+1} = \frac{P\_{t+1} - P\_t}{P\_t}$), yields: $$P = \frac{M}{\operatorname{lp} \left ( r^-, Y^+ \right )}$$ The price level is therefore dependent on three factors: 1. Money supply ($\small M$), as more money supply will lead to higher prices, something we can clearly see in the equation above. 2. Output ($\small Y$), as higher output shifts the level at which prices fall given some constant money. Mathematically, we see this in that growing income leads to a larger denominator, and therefore, a lower price level. 3. Real interest rates ($\small r$), as one must consider that the real determinant of inflation is really the demand for money, which is itself determined by the interest rate. Higher real interest rates would lead to lower real money demand, as people want to hold assets instead. Now, let us examine the change in those factors given some massive change in the amount of gold. First, the **money supply**. This is going to be constant given a massive influx of gold, because nobody is on the gold standard anymore. If you want an increase in gold to affect the economy, you would have to set your story in a world with the gold standard — where the amount of money a government can issue is tied to the amount of bullion it possesses. Second, **output**. This is going to increase, marginally. While it would marginally increase due to cheaper inputs, which would then lead to a fall in price levels, the impact of this is *very* small. From the US Bureau of Economic Analysis's [commodity-by-industry direct requirements](http://www.bea.gov/iTable/iTableHtml.cfm?reqid=52&step=102&isuri=1&5206=7&5205=sum) table, around 1.8% of the computer and electronic products sector's output is derived from all primary metal products. As a back-of-the-envelope calculation of the cost savings, I am going to pretend that gold makes up 100% of primary metals, ignoring the fact that there are other metals like rare-earth metals which also go into production (or aluminium, which is increasingly used in laptop cases, etc). I am going to then pretend that transportation costs do not exist. This massively overstates the size of the impact. Even so, as 1.2 per cent of the economy is derived from the entire [computer electronics industry](http://www.bea.gov/iTable/iTableHtml.cfm?reqid=51&step=51&isuri=1&5114=a&5102=15), this optimistic estimate of cost savings would be somewhere around 6.7 billion dollars. That sounds like a lot, but recognise that is across the entire industry. 6.7 billion dollars in cost savings is somewhere around one-tenth of Intel's gross revenue. Then recall that Intel is *one* firm in an industry of thousands of firms. I cannot overstate how minimal the cost savings are going to be in a major economy. Third, **interest rates** are also mostly unchanged, as changes in the amount of gold don't really affect global credit markets. However, another answer did talk about the fact that people who have their savings in gold will have their savings wiped out. However, this effect is also going to be quite small – the Census [reports](https://www.census.gov/people/wealth/data/dtables.html) that the majority of people's net worths are in their homes and interest bearing accounts, not bullion. --- *Mathematical note:* I use the Keynesian theory of money here mostly due to its helpfulness in explaining issues with liquidity preference and the liquidity trap. However, similar conclusions can be derived from the more basic relationship used in classical economics $\small MV = PY$. This yields the following expression for $\small P$. $$ P = \frac{MV}{Y} $$ Thus, it is still clear that (1) increases in money supply affect prices at a positive proportional level $\small \frac{V}{Y}$, (2) increases in total output decrease the price level, and (3) increases in [money velocity](https://en.wikipedia.org/wiki/Velocity_of_money) (V) lead to price growth, basically some measure of how frequently people change [Answer] A sudden huge increase in the supply of gold would not be inflationary except to things bought with gold. I.e. you'd need an awful lot of gold to exchange for anything else. A bit hard on someone trying to sell an inheritance of gold jewelry, but not something that would impact most people. If anything, this would be deflationary. Gold would be cheaper and easier to obtain. Also, people wouldn't be able to sell jewelry for significant cash. So those people would be poorer. Both effects would be deflationary. However, I don't think that gold is a big enough part of the economy for that effect to be large. Prior to Richard Nixon taking the United States off the gold standard, this would have been problematic. Gold rushes often did cause inflation. But not so much now. If there are any gold standard countries left, this would probably kick them off it. But certainly none of the United States, the countries in the Euro area, Japan, China, nor India would have that kind of problem. [Answer] Release into the *economy* is not really how it would work. Gold is a good and the market would quickly establish a new price and you could not move it all in one day. For the most part gold is not used as a currency. Gold coin would lose value. Any gold stores backing currency would be nearly worthless. Most countries are not on a gold standard and those on a gold standard would quickly come off the gold standard. Gold has many desired characteristic in manufacturing and jewelry. You would see gold used (more) in circuit boards and many other devices. Smart investors would buy gold up and hold it. Since all the gold has been mined it will eventually become a more scare good than it is today. Day by day gold will become more scarce. [Answer] It would cause the price of gold to crash, making your pile of gold essentially worthless. Others would gobble it up and then slowly filter it back into the market as the gold price stabilises, making a killing. Which is what you should have done yourself in the first place of course... This isn't limited to gold, it goes for any commodity. The question is discussed in some detail in discussions about the viability of asteroid mining, where it is sometimes suggested that the haul in precious metals from a single large asteroid would quickly be able to pay for the cost of the entire operation by just dumping it on the market. For all the reasons already mentioned, that's not how it works. You'd rather have to release those tons of rare materials (platinum for example) in small batches, say a few percent of the yearly demand, unless maybe you were to at the same time introduce a new and highly lucrative use for those materials, which would increase demand to the point where a high market price can be sustained despite a greatly increased supply. [Answer] There are major differences between `inflation` and `destroy(ing) the economy`. It's very hard to predict whether inflation or deflation might result. However, the worldwide economy would be seriously disrupted. A significant number of nations would probably be effectively bankrupted, as might numerous banks and other financial institutions, not to mention serious effects on many large and small individual investors. But as @LukeBriggs points out, this shouldn't be an issue of `all the remaining unmined gold on Earth`. If that happened, where could it even be put? Worse, there'd likely be enough of a disruption of Earth's inner dynamics to make thoughts of a disrupted economy trivial. Another good article on "all of the gold" is [How Much Gold is Left on Earth?](http://www.westcoastplacer.com/how-much-gold-is-left-on-earth/) But what about only "all of the currently known and accessible deposits"? Well, that'd likely be more than enough for serious disruption; but it's pretty implausible given how deposits are scattered across numerous nations, and most are not likely to allow very-large-scale illegal mining. Then again, since this has neither a [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") nor [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") tag, some soft, hypothetical science might be okay. The distribution of gold in the Earth's crust is reasonably randomly distributed. What that gives us is a good 71% of the Earth's surface that hasn't even been explored for gold mining much less seen any significant mining attempts. It might be only near-future that undersea gold-mining could be done successfully and economically with robotics. Simple 'random' extrapolation could result in more than twice as much gold as has ever been mined. Now, about "destroying" the economy... Although no world currencies are currently on a gold-standard, gold is still used by central banks of nations around the world for investments and for various important inter-governmental transactions. The largest amount of this physical gold is stored deep underground in the vaults of the [Federal Reserve Bank of New York](https://en.wikipedia.org/wiki/Federal_Reserve_Bank_of_New_York). Transactions between central banks of various nations are done by moving bricks of gold from one central bank's "bin" to another's. (That Federal Reserve Bank is contracted to perform that service. It apparently charges "a $1.75 fee (in 2008) per bar to move the gold.") Anyway, reasonably current estimates (2011) put the [world's total holdings](https://en.wikipedia.org/wiki/Gold_reserve#World_holdings) at approx. 171,300 tonnes with central banks accounting for (only?) 29,500 tonnes. (The Federal Reserve Bank of New York's vaults are reported at [approx. 7,000 tonnes](https://en.wikipedia.org/wiki/Federal_Reserve_Bank_of_New_York#Move_to_33_Liberty_Street).) Amounts held world-wide for investments are around 33,000 tonnes. It doesn't take much imagination to see the likely huge economic disruptions that would come from making 100,000-200,000 tonnes of gold suddenly available. Any inflation/deflation would result from the disruptions rather than from any clear relationship between currencies and gold, in the absence of gold-standard currency. The international valuations of holdings would drop significantly. Any number of investment institutions would effectively be bankrupted since value of holdings would no longer match up with debts. Plenty of individual investors would suddenly find that they'd lost maybe half of what they had, perhaps almost wiping out their planned retirements. The same things happen when stock markets drop. Perhaps harder to gauge would be economic effects on various industrial processes. With a big drop in cost of gold, plenty of products might be produced more cheaply and with better performance. Rapid shifts in costs and prices by themselves can be disruptive to different industries. Beyond any of that, it can depend on where and to whom the new gold is made available. Top "dollar" might be paid by one of two nations, the U.S.A. and China. I suspect that China could be top bidder. There seems to be various rumblings about [China's intentions in the world of finance](http://www.washingtontimes.com/news/2015/aug/18/l-todd-wood-day-china-says-its-currency-backed-gol/). They can afford more gold than anyone else and seem likely to want it. If they can achieve actual linkage of the yuan to a gold-standard, they can replace the US dollar with the yuan as the world's premier reserve currency, though they'd probably be satisfied simply with it being one of them. The threat of that alone could be enough to send shock waves through world financial markets. [Answer] **It would destabilize international politics somehow**. For reasons I don't understand, various small countries pay their superiors for [gold custodian services](https://www.forbes.com/sites/oliverwilliams1/2020/05/20/venezuela-takes-bank-of-england-to-court-over-1-billion-gold-stash/), only to find it has been held up over some political falling out. It seems analogous to sending a son to be a hostage at an overlord's medieval court. If you make these reserves valueless, then either all the small picked-on countries are suddenly more free to do as they wish ... or would-be superpowers have to quickly send in their armies to seize a little chunk of their land as a bargaining chip instead, like Russia in the Donetsk People's Republic. But such small wars could get out of control, leading to the imminent death of all life on Earth... ]
[Question] [ The dwarves in my world are humans who starting digging caves in the Maumturks and Twelve Bens in Ireland during the Iron Age, and eventually connected the caves via tunnels rather than trudge across the bogs that surround the hills. The rough timeline I have is that the caves start during the Iron Age, and by the 1500s the connecting tunnels are a well-established continuous network. Ignoring the fact that Iron Age humans would have very little reason to do this in the first place, I have the following problems: 1. The Maumturks and Twelve Bens are a mix of quartzite and granite, both of which are very hard rocks. 2. The *length* of the required tunnel network. For the sake of reference, [here's a map](https://www.google.ie/maps/@53.5275281,-9.6890897,11.5z/data=!5m1!1e4?hl=en) that I've centred on the Maumturks (running from Leenaun down to Maum Cross, west of what's now the R336). The main network along the Maumturks would be approximately 20km long - and that doesn't include branch tunnels, or multiple levels going in the same direction. So, could humans do this with hand tools, and if so, how long would it take? [Answer] Another approach is to ask how much volume a miner can remove per day. Let's take 1 cubic meter as a starting point. This is only possible since you've specified Iron Age mining. Roman tunneling in softer rock used bronze or copper tools, so their experience is not terribly applicable. Assuming standard tunnel dimensions are 2 meters by 2 meters, with 2 miners working on the face at the same time, this will give a progress of 1/2 meter per day. 20 km will take 40,000 days, or about 109 years. Cut the average output by a factor of 3 and it still only takes about 330 years, which seems well within your time budget. And, of course, you've missed a trick in overlooking motive: gold. Gold ore is commonly associated with quartzite, so following gold veins might well give some economic motivation to the miners. ETA - My assumption of 1 cubic meter per day is, I grant, probably optimistic, which is why I added a second estimate of 1/3 that. There is undoubtedly historic information which can be used, specifically output rates for 19th century hard rock gold miners. I suspect that someone, somewhere, wrote about this at the time, but I'm unable to find such data with a cursory search. If anyone has access to that information, by all means present it. Further edit - Gary Walker has pointed out that I mischaracterized Roman mining technology. Apparently I was wrong about iron tool use. My apologies. Take what conclusions from my mistake that you wish. [Answer] **I say the answer is definitely yes.** The Romans built an [even longer tunnel](http://www.spiegel.de/international/world/rome-s-tremendous-tunnel-the-ancient-world-s-longest-underground-aqueduct-a-612718.html) through rock, though not as hard as quartzite. The Gadara Aquaduct was probably an even larger engineering challenge given that the longest underground span was 106 km / 66 miles. This project took 120 years to complete. Given dwarven miners, it would certainly take less than 120 years to complete. EDIT. Actually I am assuming the average hardness of the rock was less, as this detail is not included in the article. Though granite is abundant in Palestine, it is almost certain some softer rock would be included in the rock excavated for the Gadara Aquaduct. [Answer] According to [Mohs Scale of Mineral Hardness](https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness) Quartzite has 100 absolute hardness, making it 1/16 as hard as diamond. The tunnel you want to build is about as long as [The London Connection](http://www.abb.com/cawp/seitp202/9C1D698E86B2F7ED8025700C00539EFB.aspx) a 20 km tunnel through slowly permeable, seasonally wet, acid, loamy and clayey soils. This 3 meter wide tunnel took 3 years to build with modern tools in an easily diggable area. Now I'm assuming that your hand dug tunnel is as wide as a person. A simple amount of math implies that a tunnel of the same length but human size will take a year (plus 70-ish days) to dig with modern tools in the same area. But you want tougher ground and simpler tools. Give or take clay is 6 times weaker than Quartz, being lower than 1 on the Mohs scale, so even with modern tools the tunnel will take 6 times longer (around 7.2 years). There is no solid math rule I can find for mechanical tools versus hand tools so I am going to assume that they are about 20 times weaker (heavy drills vs pickaxes, seems fair). This will give me around **52416 days or 144 years**. [Answer] Bashing away at quartzite is one helluva bitch. I'm a geology student and have tried doing that a few times with a sledge hammer and chisel and it can take dozens or even hundreds of swings to break off a fist sized piece of rock. Going at it with a pick axe would be a bit faster but still really slow. It's a completely different ballgame from digging in soft rock like this. <https://www.youtube.com/watch?v=Uf6iqub5Lk8> But sounds like you're giving a couple thousand years to build this 20km tunnel so in that time frame it's do-able. My guess is with a pick axe it would take about 20 years per km. You would need to build ventilation shafts though at pretty regular intervals, and you could use those to work on the main tunnel at many different points simultaneously which would cut the time down from hundreds of years to tens of years or even less. Still seems pretty pointless though, you'd be spending years to build the tunnel, not to mention a lot of labour building not only the main tunnel but ventilation shafts every 50 meters or so, and fixing/replacing thousands upon thousands of broken pick axes... The stone mined out would be difficult to shape for construction because it breaks into irregular shapes compared to other rocks and is very hard, and would probably come out in small pieces anyways. Quartz veins are a good rock to look for gold/minerals in but not quartzite which is one of the worst rocks to look for minerals in. They're made of similar material (quartz) but formed rather different, one is metamorphosed sandstone, the other is formed by hot underground fluids. Realistically speaking it's definitely a lot more practical to just drain the bogs or build boardwalks over them. [Answer] The Incas dealt with stone by making small holes and filling them with flamable material. Once this was lit, rock would fragmentate, much like a glass full of hot water when you place it upon a very cold surface. This dispenses with explosives, but is a better technique than attacking very hard rock with only picks and axes. [Answer] You might consider the military tunnels during WWI in the Alps. Since it was difficult to attack up a mountain, the opposing armies would dig tunnels and fill them with explosives to blow the mountaintop positions away. [Wikipedia article](https://en.wikipedia.org/wiki/Mining_%28military%29#World_War_I). [German-language source](http://www2.uibk.ac.at/downloads/c715/geoalp_11_14/06angetter_schramm.pdf) which claims 4 to 5.6 metres per day (more than one km per year) with the aid of *some* explosives. ]
[Question] [ I have a city in space that will have a local population and a lot of travel in and out (center of commerce). Should I place it out in open space or near a planet? Being near a planet obviously involves gravitational forces that affect both the station and travel; my gut feeling is that that's a positive thing but I'm not strong on the relevant science. It also seems like placement near a *suitable* planet would provide resources the inhabitants might need -- food, water, raw materials. If it should be situated near a planet, what is the best positioning? Should it be in line with a pole, in the direct line that runs from star to planet, something else? How far out should it be, with respect to the planet's gravitational influence? (I assume it has to at least be as far out as a Lagrange point or it'd fall to the planet, but they're sometimes depicted as seeming much farther out.) Does the placement decision interact with the [shape of the station](https://worldbuilding.stackexchange.com/q/4444/28), or are these orthogonal decisions? How does the mass of the station affect things? What other factors do I need to take into account? [Answer] ## Near a planet. A planet's orbital path will provide a clean bit of space, a star for energy, a way for people to reference the location, and other minor benefits. Put your city in very high orbit around a planet. In the plane of the solar system and in the direction of planetary rotation will work well (may as well be going the same direction as most of the mass, smaller relative velocity). You'll get minor gravity well and all the benefits. **Clear Space** Planets, by definition, clear their orbital paths of debris. If you don't want to be bombarded constantly with large solar system debris, a planet's orbital path is a good place to start. **Energy** Being in a star system will provide energy for your city. Most species develop in star systems [citation needed], so a star system is somewhere they can feel at home. You get free diurnal cycling if you rotate your city. *Besides, what's life without a sunrise?* **Reference** If you have a city in space then presumably the navigational equipment of visitors is good enough to determine how to get to any coordinates by looking at the stars and a watch. A human won't be pointing their ship at the second star to the right and cruising at warp two until dawn, the most complicated navigation they will have to do is to your web page to look up the coordinates of the city. The computer will do the rest. So, being in a star system near a planet doesn't matter one bit for interstellar navigation, but being able to say "*Oh, this place has the best Korblian Ale, it's around Howsian-4*" gives the place a natural language reference. If your city is called New Portland, it will be hard to find unless you've got a planet and star system (State and Country) to reference it by. Space is a big place, and Portland is an awesome place, obviously there will be a lot of New Portlands out there. *Oh, the New Portland around the fourth planet of Howsian? Yeah, I know where that is.* **Other Benefits** If the planet you're orbiting is an uninhabitable gas giant, then great! No one will ever live there! Guess where that radioactive-toilet-water is going? If it's habitable/near-habitable then it can be used as a rendezvous in an emergency or the city grows into a space port (a high class one, where droids *are allowed*). It's something to look at. Space cities should be beautiful, put it above the rings of a Saturn like planet you will make a killing on the real estate. You can build your city in a captured asteroid. Free solid ground, cosmic ray protection, minor gravity, and micrometeor defence? Yes, please. Minor gravity alone is enough there, make it a health spa, *come here and you'll literally weight 10% of your original weight!* So, yes, around a planet. [Answer] This was originally a comment; so I apologize in advance for anything that got too stream-of-consciousness: Think about what the original purpose of the city was - towns aren't often founded in the middle of nowhere, but tend to spring up around something and then grow into cities from there. So this space station/city will need an original purpose around which the economic growth adds population (which could have been planned for, or happened dynamically, depending on how you want the station/city to be put together). Some examples: 1. **Gas-mining Jupiter** - the city would probably be orbiting the planet for easy access. Core population would be working-class. 2. **Deep-space/nebula research** - station would be away from planets/solar systems to reduce interference or inside the nebula for easy access. 3. **Pit-Stop** - What was originally just a way-station grew until it was a city - this could be just about anywhere, but is more likely to be in *inconvenient* locations as far as resources and purpose. Most of the city's populace is likely to have a space-commute to another space-city/planet for work. If you wanted to build near a planet you would probably want it in orbit so save energy - since it'll be easier to get pulled alongside the planet than if you tried to keep it stationary at one of the poles. See our own international space station. This part is more of an educated guess - but the bigger the objects involved (planet and city station in this case), the further away it should be from the planet's center *OR* the faster it should go. See ISS vs Earth's Moon. Too close means you crash into the planet, too far and you lose too much gravitational pull to stay in orbit - just stay out of the way of other orbiting moons/debris (and don't let the citizens dump their garbage out the airlock or you'll come around the planet and smack right into it!) As for raw resources - you *can* ship it from another planet but building above one that has the resources already there (or on a nearby moon) would make it easier to build. Once built I think you'll have a pretty heavy emphasis on recycling the resources they use (especially water) - even with regular shipments it would be an economic benefit since you wouldn't need to ship as much of it. As far as shapes - anything with a clearly-defined relatively-consistent (accounting for the things/people inside) center-of-mass will make things a lot easier on you fictional designers when determining how to get this thing into a proper orbit. Away from a solar system this isn't really a concern - so beyond that, shape will be determined by a few other factors... 1. **Safety** - What happens if there is a major breach? You need an easy way to seal off the affected section(s) - which means you may even build sections to have their own airlocks between one another - possibly even built physically separate from one another to minimize potential tearing across sections, although that can make determining a consistent center of mass more difficult. If above a rocky planet, it might contain emergency-landing-struts or something similar in case it gets force out of orbit in that direction. 2. **Purpose** - A city-station with a lot of mining ships will need a lot of docking bays (or really big ones) for the mining traffic. A city-station that favors research will have a lot of researchy-looking things (antennae and satellites - big telescope domes and the occasional geodesic dome). 3. **Planned vs Dynamic Growth** - A planned city would likely be modular and easy to expand. But one that springs up dynamically would tend to have a lot of *growths* - additions that come out randomly. An older growth-city would probably have the older sections remain ramshackle while the newer additions would fit together better as people realize what the city-to-be is becoming. 4. **Aesthetics/Architecture** - this is going to depend on what the population likes. Lots or parks and statues and windows is going to look a lot different that the cramped spaces a military culture would probably favor. The last major things to consider are: Communication Import/Export (Resources and Entertainment) Off-hours activities (Theater/Carnivals/Bars) But these are relatively minor or more dependent on culture/technology, so I'm not gonna touch them. After that, you can do a lot with your space-cities to achieve the *feel* you're going for. How open is it? Are there a lot of places where you can see out into the great unknown or is your city more of a cramped borg-like space? What kind of people inhabit the city? Is its original purpose still active? (A city mining gas on Jupiter would have to shift if the gas stopped being used, for example - either collapsing as people left or adapting to a new purpose entirely). Most of the above assumes the entire city is contained within a single structure - or structures that connect to one-another, as opposed to a "The Jetsons"-style city where everyone wears helmets and jetpacks. [Answer] **Location location location** On Earth, cities developed along harbors, fords and defensible strong points (forts). These are their space equivalents: 1. **Home world start point star port**. This Lagrangian point station is where the landlubers from the planet first get started off towards great new adventures. These will likely be the largest space cities, since for the near foreseeable future, the industrial and population capacity of the home world will be many orders of magnitude higher than all of the off-world put together. So these stations will likely act as a trading-house between the home world and the spaceheads, through which most of the planet-space trade will flow. Bonus points if it is a termination point for a planetary space elevator. 2. **Asteroid belt resupply**. For all those miners out there, looking for a good time after 6 months supervising diggers and manufacturing plants on Ceres and other rocks. The population here will be transient, think more Wild West gold rush town than anything else. 3. **Saturn ramscoop and electrodynamo stations**. All the system-outgoing ships must acquire reaction mass from a gas giant, or have sails pushed by laser beams powered by the giant's magnetosphere, so likely space stations will arise to supply the crew and the reaction mass, and maintain the giant lasers. Major spaceship construction centers will be here, far out from the sun's deep gravity well, or perhaps as far out as the Oort cloud. If large colony ships are being sent out, these areas will be intermediary staging grounds and could more permanently host those that decide not to go out-of-system after all. 4. **Military outposts**. Early warning, radar sweeps, mass drivers, can be found here. With a small fleet, you might need pilots or drone overseers. Technicians for complex repair work, nano-factories for spare parts, etc. If distances are such that soldiers will only accept the posting if stationed there with families, could easily grow into full-scale settlement. 5. **Research installations**. Dangerous but very valuable biological organisms that could wreak havoc on a planet if unchecked will likely be in deep space, with atomics for vaporization and escape shuttles. This could grow into a larger settlement if the output is particularly valuable or labor intensive to cultivate. 6. **Mercurian power stations**. Close to the stellar power source, these gigantic solar panels send microwave power to other stations further out in the star's gravity well. Many energy intensive processes will take place here, so likely the supercomputers hosting the most advanced AIs with the largest power consumption will likely reside here. So this will be a major technological center... [Answer] This is something that doesn't seem to be mentioned yet, and I'm not sure if it's a problem, but here's what I'm wondering: **If the city is alone out in deep space, how would you find it?** This is why I commented that it should be near a star: you can see stars from just about anywhere (within reason), often with the naked eye under clear conditions. This will make it incredibly easy for ships around the galaxy to get to your city, kind of like a free lighthouse that can be seen from anywhere in the entire ocean. Once you're in the solar system of your city, you're again going to need a landmark to get you where you're going. At these distances, since I'm assuming you have FTL travel I can probably also assume you can find a space city with ease. However, if you instead look for a big ol' planet, maybe even a gas giant, no matter what technology you're using I'll bet it'll be faster and easier. Other answerers have shown the benefits of gas giants for spacefaring ships, I just think they're easy to find. On the planetary level, I'd think most space navigators could either use their knowledge of the city's orbit in relation to the planet to get to the destination, or simply send out a docking request and wait for a reply with coordinates (since now we're within light-seconds of the city). Long story short, space is full of giant signposts, you might as well use them. Oh, also, unless you're next to a nebula it'll probably look prettier to be next to a planet. You can charge more for apartments if they get a view, and the city'll look better in travel brochures. [Answer] ## Lagrangian Points A Lagrangian point with what? There are ten different Lagrangian points associated with the Earth, and four of them are stable. The most likely places to get early colonization are the Earth-Moon L4 and L5 points (trojans). Those are the closest stable orbits to the Earth. They may require some adjustment though, since they aren't stable against the sun. If you want an orbit that doesn't require regular intervention, there are the Sun-planet trojan points. Obviously the Sun-Earth points are closest to us, but the Sun-Neptune points seem to be the most stable. 3753 Cruithne has what seems to be a stable system composed of two orbits. You might be able to build a city there. ## Why near a planet? Why not near a planet? Cities tend to arise in places where it's natural to have traffic. On the Earth, this is often at the intersections of waterways. Pittsburgh is at the intersection of the Allegheny and the Monongahela and the Allegheny with the Ohio. Cleveland is at the intersection of the Cuyahoga with Lake Erie. New York City is at the intersection of the Hudson River with the Atlantic Ocean. In our solar system, the obvious destination is the Earth. It seems likely that space cities would arise near to Earth first. Start with the Earth-Moon trojans. Then the Sun-Earth trojans. Perhaps 3753 Cruithne to provide easy access to the Earth, Venus, Mercury, and Mars. Also as a jumping off point for further out in the solar system. The Sun-Neptune trojans may serve as natural stopping places for interstellar travel. If that ever became common, perhaps one or both would become a large city. Power might be a problem though. Not nearly as much sunlight there as closer to the sun. Of course, you can make the panels of arbitrary size. The planets are already in the most logical places for stable orbits. The next most logical places are the Sun-planet trojans. It's unclear if any of the planets are interesting enough to attract space cities of their own. Perhaps if we terraform Mars or Venus. You could locate a space city somewhere like the asteroid belt. There may well be a stable orbit there. But would you? We could build a floating city in the middle of the Atlantic Ocean, but we haven't done so. These are certainly possible places for cities, but they seem unlikely. ## Why in space? Why put people in space rather than on the nice, cheap ground? Presumably because you want to do something in space. It's expensive to lift people from the ground to space. I'm also not convinced that space will be more expensive than the ground in the long term. Once we get self-replicating robot miners powered by solar energy, space construction is effectively free. ## Shape As I said [last time](https://worldbuilding.stackexchange.com/a/4455/2113), I think that the most likely shape for something we'd call a city would be a cylinder. I still think that. [Answer] I think it depends on what 'near' is. If we can travel to Jupiter in a couple days, then almost anywhere in between will be reasonably close. If it takes 6 months to travel to Mars then being in some kind of orbit around the Earth, moon or a populated planet would be a much better idea. it would be possible to orbit the Earth even outside the moons orbit. A very large city orbiting say just outside the geostationary orbit would be able to cause effects in the tides. The further out it is the less it will interfere with tidal systems. Orbiting the moon should have very little affect, unless it's large enough to make it wobble in it's orbit. The shape of the city would likely be in a torus or tin can structure in order to easily provide some kind of gravity to those residing inside (unless you discover how to generate gravity/antigravity fields). [Answer] The distance from planets would basically depend on its purpose. What I can imagine, however, is that a future civilization might see things completely inversely: for us space is tough terrain, and it takes too much energy and resources to frequent places out there very often. In the future, it may be the other way around and people might consider descents to planets as *unusual, maybe even unnecessary efforts*. It is completely possible that the far future will see a civilization that has managed to upload itself to computer networks ;) We're not too far from that, are we? In that case all we care about is energy availability. Places look different if you're a bunch of electrons. A city in space in cyberspace has fewer constraints. As an aside, I immediately remembered the movie 'Elysium'. In the movie, an artificial city-state had been built for wealthy super humans, away from all the pollution on Earth. A class metaphor. It appeared to be not too far from Earth (maybe roughly Earth-ISS-distance). But that's more a digression than an answer... [Answer] Converting my comments into an answer: *where* the city is should flow from *why* the city is. Real-world cities exist where transportation and geography intersect. Seaports are places to transfer between ships and road vehicles. Airports transfer between planes and road. Also, waypoints form at oases of habitability along important but difficult travel routes, such villages on the silk road. In a space civilization, there are two good breakpoints: ground vs local space, and local space vs interplanetary/interstellar. 1. If your ships are FTL-capable but cannot land, space cities should be in planetary orbit. There you use short-range methods to transit the gravity well. The outer end of a space elevator would be excellent. 2. If your ships are sprightly (e.g. zero-point anti-grav) but do not have self-contained FTL, stations should control jump points. Make up some law of nature that requires them to be off-planet and limited in number (e.g. natural alderson points and/or expensive star gates). The city grows there. 3. If your ships can lift off, escape planetary gravity, go to warp independently, and come back down to another planet, then spaceports would be ground-based. A space city would require some other reason to exist. Next to an uninhabitable planetoid rich in rare elements? A deep space safe haven amidst light-years of otherwise-impassable dangers? ]
[Question] [ No, this is not not about courtship displays or dominance figths. (even thought I know that that is also part of mating) This is more of "What their genitalia would look like" and how they would "do it". Think on your typical smaug-sized, extra armored, four-limbed, fire breathing dragon (let's ignore the fact the their fligth would be impossible.). The females are slightly bigger than the males, and due to their spikey spiky backs, I think mounting (like birds) or intertweening (like most lizards) would result in castration. So... Nope. Now here goes my especulation (feel free to prove me wrong, and give me a more "correct" anatomy. This is the point of this question...hehehe...) Like reptiles and birds, dragons have cloacae, and due to the "agressive" mating behavior dragons seem to portray in fiction, I belive their genitals would be similar to those of ducks (corkscrew-shaped, the male's in one direction, the females in the opposite one.) As I studied dinos for this matter, I found that Stegossaurus had sort of a away around this: The female would lie down on her side, but I don't think that would work too well on winged beings (the female would have to squish one of her wings for it to work, and expose the soft, vulnerable plating on it's belly), and besides, a dragon's tail is about 2 thirds of it's body, so it would just get on the away. If dragons do it like the T-rex, then also, their tail would get in the way (and I belive that the female would not be able to raise her tail hight enougth, nor crouch properly (the wings would get on the way), and I doubt that a many tons male dragon will be able to main precise equilibrium wilhe standing on his hind legs to get it done. In my opinion, the less-troublesome position would be if they faced away from each other (think moths and butterflies), but still, their long, heavy spiky tail seem to get on the way. So, is there a much more accurate method of dragon sex than the ones above? (cuz, honestly, I think none of those would work ) How? [Answer] ## Have a look at Whales reproducing Whales are awkward shapes. However they have found a way: extremely long penises. [![enter image description here](https://i.stack.imgur.com/ISxHW.jpg)](https://i.stack.imgur.com/ISxHW.jpg) These penises are 4m long, and weigh up to one tonne. They need this not just because of awkwardness, but their huge size means their momentum and velocity are commensurately large and ponderous, they cannot be precise, yet the copulation must last long enough for reliable travel of semen to the recipient. Your dragons would encounter similar problems because of their scale. Copulation could then occur in a variety of positions, not limited to just a single configuration. [Answer] **how about belly to belly?** I'm assuming your dragons are more like whyverns (2 wings working as limbs, hind limbs). In this situation, let's take a look at bat reproduction, even if your dragons lack the "classic" mammalian genitalia. You'll see many species stick their bellies together, doing their breeding. Your dragons could try something similar in giant cave galleries if they had strong tails and hind limbs, using them to support themselves while keeping their bellies close to one another. That way, not only they'd have their underside protected by the mate, their cloacas would be close enough, I assume, to do the deed. This can be also done if, being smaller, the male lays belly up and lets the female conduct the process, in a sign of submission and trust, vital in case they're monogamous and take care of their young like t-rexes and raptor birds like the harpy eagle. At the end she could help him up if he couldn't turn around on his own, solving the problem and cementing the trust in the partner, as she could just leave him to die or kill him herself. While your aggressive females might indicate the males would need to be like ducks, a similar behavior was seen in t-rexes, and the male's only choice was to please the female or get eaten by her, so it's not too crazy to believe your dragons could show similar, if not greater submission In males (notice that with this process you could change your dragon reproductive structures to resemble more that of snakes, with the male cloaca being longer and extending outwards to do the connection, as there'd be less resistance from the female) [Answer] they have wings, why not use them? they both fly in the air so there is no need to worry about anything getting crushed. And this means only good fliers can reproduce so natural selection is taken care of. it seems kinda obvious. also welcome to worldbuilding SE! [Answer] The male releases spores into the wind, the female collects them on her crest, and they migrate into the ovarian tubules around her neck, of course. How else would you do it? You think too narrowly by wanting to impose mammalian sexual organs on creatures that are inherently different. [Answer] Perhaps they might have their genitalia on their tail, like turtles do, allowing them to mate while simply standing with their tails intertwined [Answer] Mate the same way pterodactyls do. Anyway, they were the inspiration for the dragon in the first place, so why don't make them mate the same way. [Answer] They do it like scorpions do. [The male leaves a puddle of seed somewhere, then the female rubs her parts against that](https://en.wikipedia.org/wiki/Scorpion): > > When the male has located a suitably stable substrate, such as hard ground, agglomerated sand, rock, or tree bark, he deposits the spermatophore and guides the female over it. This allows the spermatophore to enter her genital opercula, which triggers release of the sperm, thus fertilizing the female. A mating plug then forms in the female to prevent her from mating again before the young are born. The male and female then abruptly separate, and the male never calls her again. > > > No draconic version of Kama Sutra required. [Answer] Actually, dinosaur reproduction methods are entirely theoretical - soft tissue is poorly preserved, so even if a fossil represented two individuals in the act, none of the relevant cues would be present for interpretation. Ducks and other waterfowl are quite rare among birds - most birds simply perform a variation of the 'cloacal kiss,' no specialty member required. Many can do it impressively fast and with very little yoga required (...which I know because thinking "oops, don't wanna watch those birds that are clearly about to do -" happens to be about the time span required. "Thanks", local hawk pair...) Belly to belly is also fairly plausible, especially while lying on sides or partially supported by water. However, ultimately, "Carefully" is going to be a sufficient answer to explain most mounting positions, spikes and all - after all, there are *plenty* of baby porcupines making their way out into the world on the regular. [Answer] My female dragons lay clutches of eggs with soft shells. The males fertilize them which triggers the hardening of their multicolored armored shells. ]
[Question] [ In Greek and Roman mythology, the Astomi, also known as the Gangines, are an ancient legendary race of people who had no need to eat or drink anything at all. They survived by smelling apples and flowers. Is something like this possible? I mean, we smell things by inhaling particles, and we judge what we should eat by smelling them. i.e. Can a human-sized species get all their nutrients from the particles they smell? [Answer] # Yes. But you need an appropriate environment. Your human-sized species might make do with as little as 1000 kCal per day (if they had a fully human metabolism that would be in the neighbourhood of 2000 kCal, but you can posit a slower metabolism). So we're left with two requirements: **nutrients**, and **energy**. Human food supplies both, but here we need some more flexibility. **We can supply energy using suitable vapours**. Gas and alcohol would supply more than enough energy, but that would mean living in a potentially detonating atmosphere. Not recommended. **Heavier carbon chains are less reactive**, so you could imagine a heavy "fog" of, essentially, heavy Diesel fuel droplets. This could be produced by tree analogues with some equivalent of the Fischer-Tropsch process, and dispersed in the atmosphere, either ubiquitously or in special "feeding ponds". By inhalation, our creatures could easily fulfill their energy requirements; instead of compression, their lungs would simply absorb the fluid and distribute it in the "blood", and the cells would oxidise it much like ours oxidise glucose. Efficient hygroscopic management and sufficiently humid atmosphere takes care of the drinking needs. Energy requirements having been taken care of, **the quantity of required nutrients will go *way* down**; excepting the growing youngs, pregnant females and those healing from wounds, the adult specimens would need little to no extra mass. By making growth and healing lengthy processes, we can work around both problems. Our creatures would inhale somewhat more air than a human would, let's say around 20 cubic meters per day; a possible, if very high, concentration of dust in the air is one full gram per cubic meter (the human COSHH limit is 10 mg/m³ for inhalable dust, but densities up to two orders of magnitude higher have been reported in dust storms and inside containers of specific substances such as flour, maize and sawdust). These densities aren't sustainable for long periods (dust will precipitate and I can't seem to come up with a sensible mechanism to keep it aloft), but the young might romp in the "sawdust", or maybe simply *snort* it. Twenty grams of matter per day isn't very much, but **that's only for those chemicals that can't be supplied in gaseous form** - the "ashes", so to speak. An average adult *human* being is about 3 kilogram "ashes", and that quantity can be easily inhaled in a couple of years (or as little as five months, if passive inhaling is all that it takes). Our people might be less reliant on heavy and uncommon elements (and be thinner to boot), and only require maybe *one to two* kilograms of solids. Having the bones made of carbon compounds (lignin, etc.) would get rid of most of the calcium, which is the large majority in weight of human ashes, and carbon we can absorb from the atmospheric fuel. Of the main building blocks of organic matter - CHONPS - we can easily supply the first four through respiration and suitable chemical reactions. The relative quantities of Phosphorus and Sulfur are small, and both exist in gaseous form as phosphane, organophosphorous compounds, and hydrogen sulfide. We only need dust for the remainder. Of course, at this point the "air" your people breathe is not air anymore, it more closely resembles smoke from a tyre deposit fire mixed with insecticides or nerve gas. [Answer] I am afraid it's not possible. Adults cannot breathe and eat at the same time. So, strictly speaking, whatever we smell ends up in our lungs, not in our stomachs. That would be a first showstopper. But let's say that these creatures are adapted to this sort of nutrition mechanism. What is the amount of food we need to take into account? I have found [this reference](https://www.precisionnutrition.com/what-are-your-4-lbs) which states > > Interestingly, research shows that most humans eat between three to five pounds of food per day. Indeed, as we approach four pounds of food intake for the day, most of us are feeling pretty satisfied. > > > I have the feeling that 1.2 kg of food per day is quite a lot, but let's take the ballpark figure of 1 kg just as a reference. When we smell something, we are usually talking about micrograms or even less of substance, dispersed in the whole volume of the environment where we are in. The lowest [odor detection threshold](https://en.wikipedia.org/wiki/Odor_detection_threshold) is > > Odor threshold value (OTV) (also aroma threshold value (ATV), Flavor threshold) is defined as the most minimal concentration of a substance that can be detected by a human nose. Some substances can be detected when their concentration is only few milligrams per 1000 tonnes, which is less than a drop in an Olympic swimming pool. > > > Let's say the food of this species is not as rare and to be present in the dilution of 1 gram in 1 cubic meter (1000000 times more concentrate than the quoted example). To get 1 kg of food, the creatures would need to breathe 1000 cubic meter of air a day, which are 1 million liters. Considering that on average [a human exchanges](https://en.wikipedia.org/wiki/Tidal_volume) half a liter of air per breath, it would take 500thousand breaths a day, roughly 6 breaths per second, to inhale all that food. The normal respiration rate for an adult at rest is 12 to 20 breaths per minute. Wrapping up, no, it's not possible. [Answer] ## Regular breathing no, but sniffing is a destinct possiblity. Because these creatures are smelling things actively (not just sitting in normal air conditions), they could be sniffing much higher pollen concentrations than one would just hanging out near a tree. During a major pollin bloom, you can see pollen counts in excess of 1000g/m^3; so, your sniffer animals could conceivably "graze" on pollinating plants at that density by sniffing it up at the source. As L.Dutch points out in his answer, a human sized mammal can live off of 1.2kg of food per day which means the animal only needs to breath in 1.2m^3 of air under these conditions to sustain itself. That is 2400 half liter breaths which would take a normal human about 13.3 hrs per day to breath in at a normal respiration rate, but an animal adapted for inhaling lots of air for purposes other than just breathing could probably do it much faster. While this is mathematically feasible, that means your animal would need to have a constant supply of blooming pollin year around... if it is a mammal. Luckly, there are animals that can live off of way fewer calories than mammals: reptiles. Reptiles need ~7.2 times fewer calories than mammals. Reptiles can also survive for months on end without any food at all. The way I would solve this problem is that your creatures are reptiles that actively go around sniffing flowers for about 2 months during spring when everything is blooming kicking off enough to reach these really high pollen counts. During these months, your reptiles can breathe in enough calories to sustain themselves for the year, then the other 10 months, they sit around like sticks in the mud conserving calories waiting for the next bloom. Reptile physiology works out especially well here because they can be just as active in spring as mammals without nearly the calorie cost because they are not spending the energy on regulating body heat. This means they can move from flower to flower as needed. A hibernating mammal might be able to pull this off as well, but mammals generally can not hibernate for more than half the year; so, it would either need to be very specialized or live in an environment with plants that have spread out heavy pollen blooms. [Answer] A tablespoon of bee pollen have around 40 calories. 50 000 of those and you're set for a day (assuming requriment of 2000 kcal a day). Adult human, while resting inhale around 11000 litres of air per day. So you would need 4,5 teaspoon of bee pollen in one litre of air. With each breathe we inhale around 0,5 litres of air. Imagine breathing two tablespoons of fine powder. Remember cinnamon challenge? The problem was the amount of particles that could clog the lungs. I think this could exist in those middle ages books about "far-away" land where people were made out noses entirely. So the surface to filter and somehow consume particles was much bigger and easier. [Answer] Think about it more creatively. Consider if this being was a plant instead of an animal. On Earth, we think of plants as generally being non-mobile, but I don't think that is a requirement. Remember that some orchids live without drawing nutrients from their roots. "Nutrients for epiphytic orchids mainly come from mineral dust, organic detritus, animal droppings and other substances collecting among on their supporting surfaces." ]
[Question] [ I am considering the possibility of having massive cephalopods evolving on my world and having them fill the niche of whales. I've heard about how whales have evolved to increase in size for the purpose of obtaining more food. I've also read about the giant and colossal squid, so it doesn't seem too outlandish for a squid to evolve to the size of whales. The reason why whales can grow to such ridiculous sizes is that they don't have to support their own weight. For locomotion, I'm thinking of elongating their mantles to allow them to swim in the same manner as whales. As for feeding, I'm considering two main ideas. They are able to repurpose their siphon to take in water, and then keep some sort of baleen like mechanism that filters out krill, small fish, or whatever else is small and form schools on my world. My other idea is that they have webbed arms that close onto food and guide it into their beaks, which have been redesigned as a mechanism to trap large amounts of prey. They play an important role in the ecosystem, similar to that of whales, but more stable. They reproduce faster and are more fertile when young. Instead of birthing single helpless calves, the create long chains of eggs. Whaling would be more sustainable on these creatures. They are fed upon by sharks and other smaller predators, as well as larger sea monsters. Their ability to consume smaller creatures lower on the food chain makes them more numerous and thus a more sustainable source of food. Does anything about this sound implausible? Let me know. [Answer] <https://www.livescience.com/54870-giant-squid-may-be-school-bus-size.html> suggests that existing giant squid could reach 20 meters in length. Given a lack of whales and the biological variations you've listed it seems entirely plausible for squid to reach the sizes you describe. [Answer] > > I've heard about how whales have evolved to increase in size for the > purpose of obtaining more food. > > > Well, partially, but it's also for thermoregulatory purposes, and for defense against now-extinct "megatooth sharks" like the various *Carcharocles* species, *Isurus hastalis* and *Hemipristis serra*. > > I've also read about the giant and > colossal squid, so it doesn't seem too outlandish for a squid to > evolve to the size of whales. > > > No, not all. Although it should be noted, there would still have to be some significant increase in size, as squids are not very dense for their length. For comparison, a giant squid can be as long as a humpback whale, but the largest recorded individual was a hundredth of a humpback's mass. > > For locomotion, I'm thinking of elongating their mantles to allow them > to swim in the same manner as whales. > > > This I find unlikely. Modern cephalopods move using jet propulsion, sucking water in and expulsing it backwards through their siphons. Meanwhile, cetaceans move by undulating their spine up and down (because of their mammalian vertebrae - consider that mosasaurs and icthyosaurs had tail paddles which beat from side to side). These are very, very different methods of locomotion, and the latter is very difficult without a flexible spine (a gladius wouldn't cut it). I'd advise you just have them use jet propulsion, perhaps beating their wings for extra boost. > > As for feeding, I'm considering two main ideas. They are able to > repurpose their siphon to take in water, and then keep some sort of > baleen like mechanism that filters out krill, small fish, or whatever > else is small and form schools on my world. > > > This sounds a lot like the "baleen squids" of the [Speculative Dinosaur Project.](https://speculativeevolution.fandom.com/wiki/Speculative_Dinosaur_Project) These animals (one of the greatest creative triumphs of the project) have two modified tentacles ending in a feather duster-like cluster of filaments which they use for filter-feeding. [![enter image description here](https://i.stack.imgur.com/EQNVO.png)](https://i.stack.imgur.com/EQNVO.png) I would recommend a filter-feeding lifestyle over your other idea. However, rather than copying the idea from the baleen squids, you should probably put your own spin on it. My suggestion is that they use their *gills* as baleen; if you look at a squid gill on an anatomy diagram, you could see how it could be repurposed as a filtering organ. This would also be consistent with your siphoning-in idea. > > They play an important role in the ecosystem, similar to that of > whales, but more stable. They reproduce faster and are more fertile > when young. Instead of birthing single helpless calves, the create > long chains of eggs. > > > Sounds good. William J. Sanders actually linked the large brood size of sauropods to their large size; the more offspring you can have, the higher the reproductive rate. a high reproductive rate means that there's a reduced extinction risk, and thus an opportunity to grow large. (Also, the more offspring you have, the smaller they will likely be - in other words, the more different they'll look from the adult form. This means that they'll probably undergo an ontogenetic niche shift, where the young occupy a different niche to the adults. This also reduces the risk of extinction.) > > Does anything about this sound implausible? Let me know. > > > Except for the locomotion bit, it all checks out. Welcome to WB.SE, by the way. [Answer] I was pondering giant molluscan filter feeders in the context of the giant nudibranch I proposed for this question. [Anatomically Correct Mesopelagic Aves](https://worldbuilding.stackexchange.com/questions/142680/anatomically-correct-mesopelagic-aves/142722#142722) Really, specifically gastropod (slugs) or cephalopod (squid) filter feeders - bivalve clams are mollusks too and of course they are all filter feeders. How to change the feeding plan of a cephalopod or gastropod to filter feed? Of course there is one that does. Fortunately for the rule of cool, it is super cool too. Your giant creature is a cephalopod filter feeder, but not a squid or octopus. **It is a giant vampire squid**. [![vampire squid with feeding tentacle](https://i.stack.imgur.com/xGddz.png)](https://i.stack.imgur.com/xGddz.png) <https://www.sciencedaily.com/releases/2012/09/120926133239.htm> > > Hoving soon found that if he placed bits and pieces of microscopic > animals into a tank with a vampire squid, the food particles would > stick to one of the string-like filaments that the animal sometimes > extends outward from its body. The vampire squid would then draw the > filament through its arms, removing the particles from the filament > and enveloping them in mucus. Finally, the squid would transfer the > glob of mucus and particles to its mouth and consume it. > > > So cool. These things live in the abyss. There is no reason they could not get huge because they live a low energy lifestyle. Maybe they do. They have long filaments which capture plankton and detritus and that is what they eat. I could imagine something like this in an Ordovician world. Probably the jellyfish had been living in essentially this same way for eons but the giant Vampire Squid outdoes the jellyfish at their game, its molluscan body plan allowing larger size than a jelly could accomplish. Its feeding tentacles would be great for pulling in jellyfish as well as the rich broth of those ancient seas. [Answer] I see nothing inherently wrong with this idea. In the absence of whales and other sea mammals something would fill the niche. Prior to mammals there were very similar reptiles, so why not squid. [Answer] <https://www.nationalgeographic.com/science/phenomena/2015/03/10/newfound-fossil-octopus-and-squid-were-giants/> seems to indicate that larger ancestors to squid may have lived in the past: "The other fossil beak sat in the mouth of an even larger cephalopod. Named Haboroteuthis poseidon by the researchers, the creature was a Cretaceous member of the lineage that contains modern squid. And from its jaw size, it was quite an impressive invertebrate. Measuring a ridge that runs up the front of squid beaks, Tanabe and coworkers found that Haboroteuthis had a “crest length” of about 2.4 inches. A 25-foot-long giant squid caught off New Zealand, by contrast, had a crest length of only 1.8 inches, and a Humbolt squid with a mantle length of almost five feet had a crest length of 1.9 inches. Haboroteuthis was at least comparable to these modern heavyweights. We may never know for sure exactly how large Haboroteuthis was, but, if its jaw is anything to go by, it was as big as some of today’s undersea giants." ]
[Question] [ During an ice age, would it be possible for a great lake to be frozen while a relatively nearby river was still running? To help illustrate my point: **Would it be possible for Lake Michigan (or parts of it) to be frozen up to ten meters deep? All the while the Missouri River was still running around Kansas City? Or would all surrounding bodies of water necessarily be frozen solid?** Are such varying temperatures and conditions feasible in any way? What should be taken into account? [Answer] Sure, and it did. While there was no Lake Michigan during the Last Glacial Maximum, the Laurentide Ice Sheet was up to a 1500 meters or more thick around the Chicago area, while it never reached as far south as Kansas City, which means rivers would be running during the summer. A sufficiently large river could run all year (albeit frozen over). [Answer] It sort of depends. Rivers rarely (if ever) have a single source for their headwaters. Rivers are a collection of hundreds of smaller tributaries. Sealing a single source, even a major one in ice would certainly reduce the flow of water downstream, but unless you remove the majority it will still flow to some degree. *So the real question I think we need to ask is, what all is frozen?* Once you define that I think you will be able to answer it yourself. A few things to consider: * Is the glacial area spreading or retreating? + If it is expanding you can expect the flow of the river to continue to dwindle + If it is retreating (end of the ice age) you'd likely see larger flows. + If its just sort of stable the edges of the glaciers will melt, providing a regular flow, probably heavier in the summer months and lower in the winter months...possibly turning off completely in the winter. [Answer] I think I can realistically say that the Glacial Ice was, in fact far far deeper that a handful of meters. Most estimates range from the mile-thick to only a couple of thousand meters. In most cases, it is considered that the Missouri river's current location is a direct result of the glaciers depositing earth, rocks, etc at the terminal edge. Prior to the Ice Ages, it is thought that there simply were no 'great lakes', they were scraped from the earth by ice over long periods of time. [Answer] Perhaps quickly-moving water would keep better-mixed and a more uniform temperature, and thus you wouldn't have some parts (e.g. the surface) freezing while other parts are significantly warmer? I wonder if the movement also warms via friction as water molecules rub against the banks and bottom, or against other water molecules? [Answer] the physics of water is unusual, in that as it approaches freezing point, it becomes less dense - thus ice forms on the surface. Below the Ice at the North pole is sea water. Now - bring this down scale a bit. Yes you can have water below metres of ice. Inland though - where does it come from and go to? If the surface (think air temperature) is frozen, then rain will fall as snow or ice, and not penetrate the ground to provide water to flow beneath the ice, or, indeed, to support the ice above it. You will have some water below the ice, but it won't be in a hurry to go anywhere because there is no new water collecting (until spring, if you have one) Depending on the length of time you are projecting, whilst the river will continue to run because it is warmer than the ice, so will 'melt' it's way out by hydraulic pressure, eventually it will cease. A ]
[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. My question is pretty basic, would square thrusters and RCS ports have any real drawbacks over round ones? I know that angles on windows for airplanes is a problem because of the pressure, so I don't know if the pressure of a thruster would have the same problems. I ask this because I am hoping to illustrate my ship designs and I love squares on spaceships. Also I feel it would make the ships more distinct. [Answer] **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. Short answer is yes, they would. Longer version as follows. I've filled out more detail to accommodate the hard science tag. A rocket engine basically works through gas expanding and being thrown out the back of the engine at high speed. What that means in practice is that as the gas expands as a result of the fuel being burned, it pushes out in all directions pretty much equally. What the bell housing on the back of the engine does is give the gas one direction to escape in, pretty much pushing the engine forward. Now, as it turns out, this is nowhere as simple as it sounds, and there's an issue called [Optimal expansion](https://en.wikipedia.org/wiki/Rocket_engine_nozzle#Aerostatic_back-pressure_and_optimal_expansion) that defines the efficiency of the rocket in terms of how the rocket expels its gas, thanks to the nature of its cooling down immediately after the reaction. The nature of that effect means that the most efficient design of nozzle is going to be the [Bell Nozzle](https://en.wikipedia.org/wiki/Bell_nozzle), which is a parabolic curve that caters for the expanding gas, the fact that some of the gas doesn't escape in exactly the right direction, and correctly 'shapes' the exhaust. These are the hardest nozzles to fabricate (and the most costly), but are used on anything where weight is a factor, meaning large rocket engines like the Saturn V, Space Shuttle, etc. What the bell housing does is shape the exhaust as it escapes, guiding all the angled releases so that they go backwards in pretty much a uniform direction, even accounting for change in the exhaust temperature and pressure. As such it keeps the engine thrust directed cleanly and increases the efficiency of the engine by minimising the amount of gas that pushes in an oblique direction to the desired thrust angle. A square housing won't do that. The simplest answer as to why is that if the gas is expanding and being released in a common direction, the gas will expand *radially*, forming (in essence) a circular impulse wave. In effect, that means that the pressures on the inside of the square housing are now uneven, causing pressure to build up, especially in the structurally weak corners of the housing, greatly increasing the possibility of failure just like in aircraft windows. Because all gas escapes from the centre of the bell housing, a round housing just automatically shapes the errant vectors in all cases. A square one will only do so in some instances, namely in the middle of the sides and in the corners. In all other cases, the side of the housing is tangental to the oblique gas vectors, creating inefficiency and (potentially) misaligned spurts of thrust from the engine output, making it less accurate as well. The reason this is a problem is because of the [chamber pressure](https://en.wikipedia.org/wiki/Rocketdyne_F-1#Specifications). On the Saturn V, the F1 engines had an operating chamber pressure of 70 Bar, or 70x the pressure of the atmosphere at sea level. That may not sound like much, but then you have a massive amount of gas wanting to escape, and that goes out the nozzle, and into the bell housing, putting pressure on the internal walls of the nozzle. As has been pointed out by Mark, when you have tangental vectors being generated is that the the gas can be directed into those corners in slightly higher concentrations, and corners are a natural stress point as you highlighted above. This means that your thruster is less likely to survive the stresses of engine burn than a round bell housing is. As a final point, as has been documented in comments there is a 'kinda' square engine possible in the form of [Aerospike Engines](https://en.wikipedia.org/wiki/Aerospike_engine) which may well fit your bill. These are often described as 'inside-out' engines because of their design, but they may well be a solution to your need for square looking nozzles. Certainly, from a hard science perspective, you could simply declare your ships use this type of engine and move on; they are a real thing (although not in active use as yet) and they have as close to the shape you want as I suspect you'll get. [Answer] **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. **If your thruster is not containing high pressure it can be any shape you want.** [![ion thruster](https://i.stack.imgur.com/UEgX5.jpg)](https://i.stack.imgur.com/UEgX5.jpg) <https://www.nasa.gov/centers/glenn/technology/Ion_Propulsion1.html> Depicted, an experimental ion thruster. As opposed to lots of hot propellant expanding out at a moderately fast speed (like a jet), ion thrusters use very small quantities of ions moving at extremely fast speeds. These are not scifi. Real spacecraft are being designed that use these. It is nice in that propellant is heavy but energy is not, and thrust increases with the square of velocity so faster and smaller is better. ]
[Question] [ I would like to know how close two planetary systems could be without having an adverse effect on each other. My goal is to drastically improve the chances of having habitable planets near enough that humans having the technology of today could realistically send manned spacecraft to other planetary systems and even have useful communication and trade. I'm thinking specifically about our own solar system, and to reduce the guessing, let's assume the other system is identical to ours: same sun, same planets. Their "Earth" could be lifeless, I don't think it affects anything. More difficult to define is what it means to "adversely affect" our own system. I have a few ideas, but these are not 100% set in stone: * The other sun should not be brighter in our sky than Venus at its brightest. * It should not be possible to detect any gravitational effects on our outer planets due to the presence of the other system using the best instruments to date.1 - No stealing of planets. * There should be no weird electromagnetic effects like auroras from the other sun other than the visible light and whatever else is expected from observing another star. * I do *not* care about the Oort cloud, simply because I hope that the distance will be less than 1 ly. * I also don't care about any effect on human mythology. Early astronomers would likely find that this star is special and much brighter than the others, which is fine. A bonus question: Would it change if we imagine a number of these systems packed in a [sphere-packing](https://en.wikipedia.org/wiki/Close-packing_of_equal_spheres) formation? If I understand correctly, it would amount to 12 neighbors equidistant from the Sun. --- 1. I admit having no clue how much we can detect, so this is one requirement that may have to go. [Answer] > > The other sun should not be brighter in our sky than Venus at its brightest. > > > This is your tightest constraint. Astronomers are even now doing searches for Planet X and even for brown dwarfs out in the Oort cloud, *and have not yet concluded that nothing is there*. This shows that current technology can't with certainty even detect the gravitational effects of a Sun-like star at lightyear distances. There are certainly not large gravitation effects (other than the discounted Oort cloud disruptions) from a sun-like start 1 light year away. OTOH, Venus peaks out at -4.9 magnitudes while Alpha Centauri i at -0.3. So Alpha could get 4.6 magnitudes brighter before it was brighter than Venus. 5 magnitudes is a factor of 100 (a difference of one magnitude is a change in brightness of the fifth root of 100), so if Alpha got about 73 times brighter it would be as bright a Venus. 73 times brighter is 8.5 (the square root of 73) times closer, which is about a half a light-year distant instead of its current 4.3 ly. So a half light year is probably the limiting distance for a Sun-like star appearing no brighter than Venus. Dimmer stars (which are still capable of having life-bearing planets) could get closer and still not be brighter than Venus. I very much doubt that having twelve of them would be significantly different than having one -- though the sky would be pretty spectacular! [Answer] I Agree with Mark Olson that having the nearest star appear no brighter than Venus in the sky is the main factor setting a minimum distance for the neighboring stars. And I think that half a light year away is not a very great distance improvement. That would allow the nearest star with the same absolute magnitude as the Sun to be 8.6 times as close as Alpha Centauri, or 11.62 percent as far as Alpha Centauri, which is very helpful, but still heart breakingly far for current space travel technology. It would be a much better improvement to make the nearest star one percent as far as Alpha Centauri, or 0.1 percent as far as Alpha Centauri, or 0.01 percent as far as Alpha Centauri. If all the neighboring stars are very dim red dwarfs, or if it is permissible for them to look many times as bright as Alpha Centauri, they could be much closer than 11.62 percent as far as Alpha Centauri, and it would be much easier to reach them. Note that the planets in our solar system have stable orbits despite being 4.37 light years or 1.339 parsecs, from the nearest star system, Alpha Centauri. So it is obvious that 4.37 light years or 1.339 parsecs is larger than the minimum separation between stars necessary for planets orbiting those stars to have stable orbits. There are many double and multiple star systems in which two or more stars orbit each other. And if two stars in a binary system are far enough apart they can both have planets orbiting in stable orbits around them. For example, Alpha Centauri C, or Proxima Centauri, is probably part of the same star system as Alpha Centauri A & B. The distance between Proxima and Alpha Centauri A & B is 12,947 plus or minus 260 Astronomical Units (AU), or 1.94 plus or minus 0.04 trillion kilometers. A planet was discovered orbiting Proxima Centauri in 2016. Planet Proxima Centauri b is estimated to have at least 1.3 times the mass of Earth and orbits at a distance of about 0.0485 AU with a period of 11.186 Earth days. Proxima Centauri b orbits within the habitable zone of Proxima Centauri. Since there are approximately 206,264.806 AU in a parsec, and Alpha Centauri is about 1.339 parsecs or 276,188.56 AU from the Sun, the distance from Proxima Centauri to Alpha Centauri A & B is about 0.0468773, or 4.68 percent, of the distance between Alpha Centauri and the Sun. And that distance is great enough for Proxima Centauri b to have a stable orbit around Proxima Centauri within the habitable zone of Proxima Centauri. (Proxima Centauri is a flare star so there is doubt whether Proxima Centauri b could be habitable) Alpha Centauri A, or Rigil Kentaurus, and Alpha Centauri B, or Toliman, orbit each other at distances ranging from 11.2 AU (1.68 billion kilometers) to 35.6 AU (5.33 billion kilometers), or from about the distance of Saturn from the Sun to about the distance of Pluto from the Sun. A planet of Alpha Centarui B, Alpha Centauri Bc, was announced in 2013. If it is real it orbits at a distance of about 0.10 AU and a year about 12 Earth days long. It is closer to Alpha Centauri B than the habitable zone and probably has lakes of molten lava. This indicates that two stars can get as close as 11.2 AU without disrupting the orbits of their closest planets, though obviously planets orbiting at the distance of Saturn or farther out would have their orbits disrupted. It has been calculated that the habitable zone of Alpha Centauri A would be about 1.25 AU out and the habitable zone of Alpha Centauri B would be about 0.7 AU (100 million Kilometers) out. It has also be calculated that planets in those habitable zones would have stable orbits, though none have been discovered yet. If two stars can get as close as 11.2 AU to 35.6 AU without disrupting the orbits of their inner planets, then two stars can get within 0.0000405 to 0.0001288, or 0.00405 percent to 0.01288 percent, of the separation between the Sun and Alpha Centauri without disrupting the orbits of their inner planets. The Wikipedia article Habitability of Binary Star Systems says: > > In non circumbinary planets, if a planet's distance to its primary exceeds about one fifth of the closest approach of the other star, orbital stability is not guaranteed.[5] > > > <http://www.solstation.com/habitable.htm#sthash.UNS47OKi.dpbs>[1](http://www.solstation.com/habitable.htm#sthash.UNS47OKi.dpbs) This implies that if a planet's orbital distance is less than about one fifth of the closest approach of the other star, its orbital stability should be or might be guaranteed. So if Earth was part of a binary star, and the nearest approach of the other star to the Sun was farther than about 5 AU, the orbit of the Earth would remain stable and almost unchanged. However, these observations and calculations are for planets orbiting stars in binary systems where the two stars have elliptical orbits around their common center of gravity and thus travel at the correct orbital velocities. Two stars separately orbiting the center of the galaxy that happen to pass close to each might have significantly greater relative velocities. And that might mean that they would have to pass at distances many times as great as 5 AU to avoid disrupting the orbits of planets in their habitable zones. Anyway, such close passes would certainly disrupt the orbits of small bodies in the outer solar systems of the two stars which might result in multiple extinction events caused by asteroid and comet impacts on any habitable planets. [Answer] Not difficult at all. Here is an artist's concept of what noon look on Pluto (about 30 AU away) [![enter image description here](https://i.stack.imgur.com/e35Vf.jpg)](https://i.stack.imgur.com/e35Vf.jpg) If you go out a few light weeks away (1 light week is ~ 1200 AU) you can easily have a Sun-like star appear as bright as Venus. As gravitational effects go - the force of gravity is inverse of the square of the distance, so it's fades very quickly. Sun's gravitational pull at 1 AU (the average Sun-Earth distance) is tiny portion of Earth's gravity ( <https://van.physics.illinois.edu/qa/listing.php?id=184> ) but obviously that's enough to keep Earth orbiting around it. Stealing of planets could still happen, but if it does, it will at galactic speed - over hundreds of millions of years. We'll still be able to detect it - we use the gravitational effects to detect exoplanets hundreds of light years away, but it won't have any practical effects on our planet. This far out there won't be any auroras, the solar wind of the other sun will be way too dispersed for that and the solar wind of our Sun will keep it out of our solar system. This all assumes that the neighboring star is similar to the Sun. However, the Sun is bigger than your average star, it's G2V star, so you can easily postulate that the other star is smaller, less luminous star. So in short - a few light weeks will probably be enough to keep the visible effects to a minimum. As for having a cluster of such solar systems close by - also not a problem. The Solar system is in a region of the Milky Way known as the Orion arm, which is not very dense - the solar systems are on average 3 - 4 light years away. If we were in the galactic center, we would have a lot other solar systems that are a lot closer to us. If you want a bunch of neighbors that are close, just place the Solar system in a denser part of the galaxy. <https://en.wikipedia.org/wiki/Orion_Arm#/media/File:OrionSpur.png> [Answer] It Depends. Two stars may be gravitationally bound, or not. If bound, they may remain a binary system for billions of years, and orbits of all planets and comets will get adjusted to having two heavy bodies in the system. If not bound, the stars are going to pass away from each other in a few tens of thousand years. While passing, they will definitely disturb each other's Oort's clouds, sending number of comets into the inner systems. Possibly, planet's orbits will also be disturbed, and some asteroids will be set on collision course with inhabited planets - but this will likely take longer time (100,000s, maybe millions years) to play out, so doomsday will come long after stars had passed each other. As far as the distance go, Sun-like star needs to be about **0.4 light years** away to look as bright as Venus ([calculator](https://www.omnicalculator.com/physics/luminosity)). For a smaller K-type star, distance can be shorter, like **0.2 light years**. This is probably enough for the stars to be gravitationally bound, forming a stable binary system. ]
[Question] [ Series Premise Made Short: For reasons that I'm not allowed to describe here (confidentiality), Earth's deciduous and tropical plant life largely dies off. A hardy and oxygen-hungry microbe infests the dying soil and mankind starts to suffer from oxygen deprivation and CO₂ poisoning. This is projected for year 2062, so tech has improved. What are simple theories for how people can survive on the surface without taking shelter in climate-controlled environments with fancy equipment? Basically, I'm looking for oxygen supplementation that the layman can get a hold of. And, of course, the level of oxygen deprivation that they can reasonably handle and still survive indefinitely. EDIT: Thank you guys for the detailed feedback. Because of the level of implausibility in the premise for the show, I've gotten permission to rework it, and even to share some of the details. I will obviously be registering with WGA to protect the premise of the show, but I'm making a new thread with more details and less BS. Thanks Again! [Answer] First of all, the premise is a bit off. Something like 70% of the oxygen generation on Earth is done by plankton in the oceans, so a blight which kills land based plants will be somewhat inconvenient in terms of O2 production, the real problem in that case is people are going to get pretty hungry pretty fast with the destruction of the terrestrial food chain. However, I'm going to pretend I didn't read the question fully and only got "blah, blah blah, O2 production is in rapid decline", which leads to this answer. The issue of lack of oxygen really does not become a problem for life until the level drops considerably below the current level of 20%. Exceptionally conditioned people can actually climb to the top of Mount Everest without supplementary oxygen (although I certainly would not reccoment this for the vast majority of people), and large populations live at high altitudes in locations as varied as Bolivia or Nepal where the partial pressure is lower (the actual percentage of Oxygen is still @ 20%, it is just the air is so much thinner. By the time you get to the top of Everest, it is like having 33% less O2 per breath....). Translating this to your fictional scenario, this would suggest that we would not get into trouble until the percentage of oxygen in the atmosphere is reduced by 6% (from 20% to @ 14%). This is going to take some time given the massive amount of gases in the atmosphere, so people will not suddenly drop in the street gasping for air. Even at lower partial pressure, you can still get along so long as you are supplementing the O2 intake. Carrying around bottled O2 is the current solution, but only works for limited amounts of time. To supplement your breathing Oxygen intake, I would suggest a zeolite filter with internal pores sized to permit the free flow of Oxygen molecules, but rejecting other, larger molecules like CO2 or Nitrogen. Since pulling air through a filter requires energy, and a super fine filter sized to discriminate against molecular species will need considerably more energy to use than simply breathing hard against the filter. You will need a small electric motor to power a compressor to force air through the filter (or create enough suction to pull air through the zeolite) and from there into a facemask for you to breath through. The canister which contains the device may be small enough to fit in a backpack (with solar cells covering the back, and a battery backup for nights and rainy weather), and will need an air intake, and exhaust port to eject the deoxygenated air and some sort of air hose to connect it to the facemask. How the production designer chooses to do this is up to him, but this should not actually be really large or heavy, and would mostly be in a backpack to ensure everything is protected, the weight is centered on the body and solar cells have relatively free exposure to the sun. A Fireman's air pack might be a suitable model, with the tank replaced by the apparatus. Let us know when production starts..... [Answer] Humans can deal with fairly low levels of oxygen, but a raised level of CO2 is of concern. On space stations, fluctuations in the O2 level are routine, but fluctuations in the CO2 level would be an emergency situation, as that would indicate the failure of the CO2 scrubbing system. Pre-industrial CO2 was about 280ppm and now it is about 400ppm (with significant local and seasonal variation). At over 1000ppm the raised CO2 level starts to interfere with gas exchange in our lungs, and we start to get tired easily. Over 2000ppm and you start to get ill. 5000ppm is the work place limit, although by then, sensitive individuals may already be drowsy and nauseous. 40000ppm (4%) is a level that would lead to brain damage and death. [source](https://www.kane.co.uk/knowledge-centre/what-are-safe-levels-of-co-and-co2-in-rooms) At these raised levels the Earth's greenhouse system is going to go haywire, there would be significant warming. CO2 can be removed from air by bubbling it through an alkali solution, for example limewater (a solution of calcium hydroxide), unfortunately the production process for limewater requires large amounts of energy and produces even larger amounts of CO2. Raised CO2 isn't nice, but in your scenario my first worry would be the collapse of the food cycle. Without crops people are going to get hungry real fast. [Answer] # How low does oxygen level have to be? Altitude.org has a lot of information on oxygen levels in the blood stream at different altitudes. First, [this page](http://www.altitude.org/oxygen_levels.php) with charts shows the effects of 4000m altitude. 4000m is significant because this is about the highest that people regularly live at. There are very few permanent settlements above 4000m. Oxygen partial pressure at sea level is about 21 kPa, corresponding with the 20% oxygen content in the air (since air pressure is about 101 kPa). At 4000m, oxygen partial pressure is 13 kPa, which means you only breather in about 60% as much oxygen in each breath at sea level. This second page shows [hemoglobin saturation](http://www.altitude.org/hemoglobin_saturation.php) plotted against oxygen partial pressure. At about 13 kPa partial pressure of oxygen saturation is still about 100%. At 8848m (the height of Everest), oxygen partial pressure is down to about 6.5 kPa. Looking at the hemoglobin saturation curve, hemoglobin saturation is down around 80 percent. I would consider a permanent year-round oxygen supply of 6.5 kPA to be fatal or close to it for most of the human population. # How to explain your problem The shape of the hemoglobin saturation curve suggests a solution. If oxygen levels get into the part of the curve around the 4–6 kPa range, then most people on earth would die. However, that means that you need very little added oxygen to induce a significant improvement in your health. Let us say that oxygen partial pressure is 5kPa in your depleted earth. Since nitrogen partial pressure would stay constant at about 80 kPa, and nitrogen and oxygen are about the same sized molecules, the air is roughly 60,000 ppm oxygen. In order to get people to survive, lets say you want 10 kPa oxygen partial pressure; that corresponds to about 110,000 ppm oxygen. Now here comes the math. A person's tidal volume (the amount of air taken in each breath) is about 0.5 liters, so to increase oxygen concentration of each breath from 5 kPa to 10 kPa, takes 0.5 × (0.11 - 0.06) = 25 mL of oxygen for each breath. You take 14 breaths per minute, so that is 0.35L per minute. Oxygen has a density of 1.49 g/L; so now you need 0.5 grams of oxygen to breath for a minute. 12 gram CO₂ cartridges cost about [50 cents a pop](http://www.gas-depot.com/12-gram-non-threaded-co2-cartridges-50-pack.html?gclid=Cj0KEQiA7K7CBRCrwt26v5uHs98BEiQA0JzsZ4o_m9LuwCX9Du9ZKB8tAb0utE5pkm81EJ2i7sTMUocaAmNt8P8HAQ); pretty cheap. They are also small and lightweight. One of those, filled with oxygen, will be enough to breathe with for 24 minutes at the above calculation. # Solution A simple breathing mask, not gastight, but equipped with a valve designed to release a small amount of oxygen every time a breath is taken, with three 12 g cartridges plugged in would be lightweight (could be less than 1 lb), and provide enough oxygen for about an hour. A scuba tank has about 2180 liters of compressed air, and thus would provide about 100 hours of oxygen at the needed rate. Because of the way the hemoglobin saturation curve is shaped, a small increase in oxygen can make a big difference between survival and death. If the world's oxygen levels are at one of the high slope parts of the curve, then a very modest oxygen supply can make a big difference. # Unfortunately... This still won't work. If you are writing popular sci-fi (or a TV show) hand-waving the inconvenient truths is probably just fine, but the fundamental problem is: where does the oxygen go? If you want to drop oxygen partial pressure from 21 kPa to 5kPa, you have to remove about $7.5\times10^{17}$ kg of oxygen. That is a lot. There is essentially no conceivable metabolic process for your oxygen-eating microbes that does not turn oxygen into carbon dioxide. The only other possible molecule that is likely to soak up so much oxygen is water. Unfortunately, water needs hydrogen to make it, so to convert a a lot of oxygen to water, you need something with tons of hydrogen and no carbon (otherwise carbon dioxide will form). There is one substance I can think of that is common, and fits the bill: ammonia. So great! These microbes react ammonia and oxygen to make water (and nitrous oxide) and make energy! Except that there just isn't that much ammonia on earth. If we were to add that much ammonia to earth, that would represent a comet made of solid ammonia about 50km across. Since the dino-killing asteroid was about 10km, adding 50 km of ammonia will cause many more problems than lack of oxygen, such as vaporizing the oceans. So really, the only way to get rid of oxygen is to turn it into Carbon Dioxide. But if we turn rougly 3/4 of the Earth's oxygen into Carbon Dioxide, then now the atmosphere is 15% CO₂ (or 150,000 ppm). This is a problem because a. I can't think of any animals bigger than bacteria that won't die of carbon dioxide poisoning, and b. if you think global warming is bad at the current 400 ppm, wait until you see 150,000 ppm. I can't think of a solution to your 'remove oxygen without extinguishing life on earth' problem, but if I do I will let you know. [Answer] ## Respirocytes and Oxygen Chambers [Respirocytes](https://en.wikipedia.org/wiki/Respirocyte) are hypothetical, microscopic, artificial red blood cells that are intended to emulate the function of their organic counterparts, so as to supplement or replace the function of much of the human body's normal respiratory system. Respirocytes were proposed by Robert A. Freitas Jr in his 1998 paper ["A Mechanical Artificial Red Blood Cell: Exploratory Design in Medical Nanotechnology"](https://www.foresight.org/Nanomedicine/Respirocytes4.html). [![enter image description here](https://i.stack.imgur.com/9Chn5.jpg)](https://i.stack.imgur.com/9Chn5.jpg) In Freitas' proposal, each respirocyte could store and transport 236 times more oxygen than a natural red blood cell, and could release it in a more controlled manner. Such respirocytes would allow an adult human to sprint at top speed for at least 15 minutes without taking a breath. ## Oxygen Chambers (Refilling Environments) So, with the respirocytes, people can survive in an oxygen depleted environment for much longer than they could otherwise. In order to refill their respirocytes, people could harness the [oxygen-producing properties of algae](https://www.scientificamerican.com/article/origin-of-oxygen-in-atmosphere/) to fill sleeping and working areas with plenty of oxygen. The algae could be given the excess CO2 and the resulting oxygen could be pumped throughout the facilities. Once people have their respirocytes filled, they can then go back out into oxygen deprived areas. [Answer] ## Implement New Genetically Engineered Human Organs In this idea, two new organs are developed via genetic engineering for human use. One is an oxygen producing organ, and the other is a carbon dioxide removing organ. Depending on what feeling you want your show to have, you can either genetically engineer human DNA to produce these organs from birth, just like all other organs. This new strain of human DNA could be delivered to people via a [retrovirus](https://en.wikipedia.org/wiki/Retrovirus). This scenario could give the human society a feeling of extreme mastery of science, thereby setting a kind of "human greatness" theme for the show. However, if you want a more desperate, dystopian feel for the show, you can simply have these organs [grown](http://www.huffingtonpost.com/entry/lab-grown-organs-transplant-technology_us_562122cee4b08d94253ee660) or [printed](https://en.wikipedia.org/wiki/Organ_printing) in labs and surgically inserted into humans at birth. This gives a less masterful feel to our grasp of science. Bonus: This scenario could also give rise to plenty of drama revolving around haves/have-nots (who can afford the surgery/organs), babies being born where organ implants are not easy or affordable, desperate "beat the clock" scenarios of getting the organs to surgery in time, etc. It also appeals to the "medical crisis" show demographic. ## The Oxygen Producing Organ [Human hair follicles already produce hydrogen peroxide naturally](https://www.sciencedaily.com/releases/2009/02/090223131123.htm). So, genetically engineer an new organ from hair follicles that produces a large amount of hydrogen peroxide. This hydrogen peroxide can then be decomposed in this organ, releasing oxygen. The oxygen can then be integrated into the bloodstream. ## Blood Doping Perhaps [blood doping](https://en.wikipedia.org/wiki/Blood_doping) could be used by everyone so they always will have more oxygen in their blood stream, thereby making them less susceptible to oxygen deprivation during daily activities. ## The Carbon Dioxide Scrubbing Organ Perhaps a human cell can be genetically engineered to produce [carbon dioxide absorbing amines](https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber#Amine_scrubbing). This organ's structure should be such that the blood flows directly next to the amines so that the CO2 is absorbed through the blood vessel walls. Once the amines are saturated with CO2, they can be excreted via the normal eliminatory methods (urine or feces). ## Disclaimer *Do not try this at home unless several scientists are present.* [I'm not a geneticist, but I play one here on Worldbuilding](https://m.youtube.com/watch?v=ts0XG6qDIco). So, the hard science part of this may need some tweeking, but perhaps it can be better plausified by someone who knows more science stuff than I do. Good luck with your show! [Answer] Read the masters. In 1980, the great hard-SF writer Hal Clement tackeled this very subject in [The Nitrogen Fix](https://en.wikipedia.org/wiki/The_Nitrogen_Fix). The story takes place well after the catastrophe and has people using certain devices and procedures to survive. Later they explain in more detail how these were developed as an emergency incentive to prevent extinction, as civilization was falling. As I recall (it’s been a good many years), they had breathers based on biotechnology. The oxygen tanks are filled with tissue that can be grown even by the more primitive society that’s lost most technology. It acts like our red blood cells, grabbing oxygen from the air when the concentration is above a threshhold, and releasing it when the surrounding concentration is below a lower threshhold. When “inside” they just have to hang up the tanks and they recharge themselves. Now in more recent years I’ve seen reports of materials that absorb huge amounts of oxygen. Any sort would provide safe compact storage, but the two-threshhold thing makes it *easy* to just use, without regulators, a complex rebreathing apparatus, and concentrators for recharging. Hal (actually Harry) also had a good explaination for the lack of oxygen which was revealed over the course of the novel. It didn’t break the hard-sf vibe or seem just plain stupid like so much TV, and was beleivable in the story. But it didn’t go into how much energy it would take, how much heqt would be released, and how much time it would take. The “metabolism” idea was kept vague enough to evade these questions, but still stays far away from things that knowledgable SF fans would “know” is nonsense. [Answer] I suggest they use solar-powered electrolysis to break apart the hydrogen and oxygen molecules in water to produce free oxygen. The hydrogen produced can then be used as fuel. [Answer] ## Where Did All the Oxygen Go? Kinglidion brought up a point wondering how to get rid of all the oxygen without dangerously increasing the carbon dioxide in the atmosphere. So, here are some alternative oxygen-loss scenarios: 1. **Divvying up Resources:** Corporations begin off-world colonizing (either on planets, moons or space stations) and they must get their breathable oxygen from somewhere. Perhaps they are faced with a drastic problem: Earth is dying, so we must make a viable living space elsewhere, so people in all places (off-world colonies and on Earth) must share the oxygen, thus leaving one or more places oxygen deprived. Bonus: this could give rise to drama around who needs oxygen more, how to justify who gets it, will we run out if too many off-world colonies die and lose their oxygen, etc. Maybe also for some reason it's not cost effective or effecient enough to split water into oxygen and hydrogen. 2. **Theft:** People start to steal oxygen for their own colonies' use. Perhaps a wealthy colony decides to take as much oxygen from Earth as they can. Perhaps a group of hardened thugs takes more for their living space. There could even become a black market specializing in oxygen theft & smuggling. Bonus: Appeal to the crime show demographic. 3. **Torn Away:** A huge meteor passes right through Earth's atmosphere, missing the ground, but tearing away a huge chuck of our atmosphere, leaving us with just enough to survive. Perhaps many meteors from a meteor shower pass through once, or perhaps many meteors tear away atmosphere multiple times during the show. Bonus: drama around when the next devastating tear will be and how much more oxygen will be lost *this* time? 4. **All of the Above:** Oh boy are people in trouble now! Every worst case scenario has occured and now drama descends from all angles onto every demographic available! [Answer] How about genetically engineered humans who use anaerobic respiration instead of aerobic? They could sweat ethanol instead of sweating water from aerobic respiration. The ATP energy gained for the mitrochodira (cells battery) would be much lower though. I might therefore suggest photosynthesis alongside anaerobic respiration. They could be genetically modified with chloroplasts which live in their skin through a symbiotic relationship. The nice thing about the photosynthesis bit is that oxygen could be put back into the atmosphere! [Answer] ## Bioreactor Put a tank full of green algae out in the sun and bubble CO2-laden air through it, and let the algae convert it back into delicious, delicious O2 for you. You will need some method of preventing the microbe from infecting your tank, but that shouldn't be too tricky. You'll also need a power supply. A [US Navy research paper from 1970](http://aem.asm.org/content/19/1/76.full.pdf) estimated that "approximately 2 ft^3 [of growing medium/culture] and 30 kW would be required to provide the oxygen needs of one man." Now, 30 kW is a *lot* of power, but that's using 1970s tech -- i.e. a big incandescent bulb. There's a [1994 paper here](https://deepblue.lib.umich.edu/bitstream/handle/2027.42/37932/260441002_ftp.pdf;jsessionid=8B62E915EEBF504BB8992EE99BCF1FDF?sequence=1) that investigates using LEDs to do the same thing. Their end result produced 10 mmol O2 per liter of culture per hour. Which more-or-less works out to about half of what the Feds got in 1970, but using a tiny fraction of the power. The downside of a bioreactor is that you're basically looking at a tank of water surrounded by as many LEDs as you can pack in, along with a power supply, so it's not exactly the most portable technology. As I said, the 1994 team produced 10 mmol/hr per liter of culture. Unfortunately, people use more like 1350 mmol O2 per hour (sourcing from [here](http://www.molecularproducts.com/pdf/technical-library/A%20Guide%20to%20Breathing%20Rates%20in%20Confined%20Environments%20Technical%20Article.pdf) and doing some unit conversion), so we're looking on the order of 135 liters (~35.6 gal) of growing medium, plus LED arrays and power supplies. That's fishtank-sized, and not a little desktop one. I'm sure that we could improve the efficiency and production of the system with some system improvements and some selective breeding of algae, but you're always going to be looking at a bulky, water-filled system. So that's your static home solution. For portable use, you want a ## Rebreather [Rebreathers](https://en.wikipedia.org/wiki/Rebreather) for diving and for work in hazardous environments are already available commercially today. The technology is well over 100 years old at this point and very mature as a result. Modern backpack-sized units for diving allow several hours of operation, although they're more finicky than your standard open-circuit SCUBA set. However, given another 40-odd years of development and a *very* pressing motivating factor (like, say, atmospheric O2 being depleted to the point where it won't sustain life), I would guess that rebreather tech would be even more streamlined and reliable by the time period of your setting. Alternately, there's ## Handwavium Technology has advanced a *lot* in the past forty-six years. What's to say that ten years from now someone might invent a catalyst that allows for CO2->O2 conversion in a low-power, compact package? You'd need to find some way to get rid of the excess carbon, but on the whole it's certainly possible. Just as a starting point, there have been several recent developments in [artificial photosynthesis](https://en.wikipedia.org/wiki/Artificial_photosynthesis), but those are focused more on solar-to-fuel production. If that tech is adapted to focus on CO2->O2 production, you could find yourself with a compact gas exchanger that is easy to manufacture and maintain. Which I suppose is basically a rebreather, but with product improvements such that you're not toting around a fickle canister of caustic chemicals. [Answer] Here is a crazy idea for conserving a few watts of oxygen/sugar metabolism: A nuclear powered artificial heart! Why the heart? [The heart does the most physical work of any muscle during a lifetime, at a steady 1-5 watts.](http://www.factretriever.com/human-heart-facts) Think about the kind of nuclear power we sent to Mars aboard the Curiosity rover: The [plutonium-238](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Criteria_for_selection_of_isotopes) fuel lasts a lifetime (half-time of 87.7 years) and its very pure alpha radiation can be shielded by just 2.5 mm lead, they say, so you shouldn't die of cancer too quickly. There is only enough plutonium-238 in the world for a few select superhumans and spacecraft, so we wouldn't want to waste it on 5% efficient thermocouple technology as NASA is currently doing. A [stirling engine](https://en.wikipedia.org/wiki/Stirling_radioisotope_generator) equivalent has been made that is over 20% efficient. We just need to scale it down about 50 times, and use blood for cooling, but let's say we also maintain 20% efficiency. Say we aim for 3W at "the beginning of the mission", letting a battery take the peak load (since the rate of plutionium decay can't be controlled); that would require 15W of heat input to the engine, or **90g** plutonium-238. Even today, a nuclear heart should make you ideal for space exploration, and certain sports like freediving. ]
[Question] [ My world has an upper atmosphere similar to Earth's, and a lower atmosphere compromised of Sulfur Hexafluoride and water. In between is a layer of clouds. Massive treelike sulfite structures stretch to all three layers of the atmosphere. The bottom layer of the atmosphere is very hot since SF6 is a powerful greenhouse gas, so the water here is gaseous. As far as I'm aware, Sulfur Hexafluoride is NOT conductive, so **what would happen to the building static charge?** [Answer] Sulfur Hexafluoride may not be conductive under normal circumstances, but subject it to a sufficiently high voltage differential, and like any other gas, including those in *our* atmosphere, it will become ionised, and its electrical resistance will drop significantly, allowing a bolt of lightning to pass through it regardless. However, the presence of the 'Massive treelike sulfite structures' that 'stretch to all three layers of the atmosphere' may provide an alternative path for lightning, depending upon the relative conductivity of the atmospheric gases and the sulphite tree-structures. The lightning will follow the path of least electrical resistance. That usually means that lightning travels to the nearest solid object. [Answer] Lightning happens when a charge is built between two locations to the point where the gas in between breaks down. In order to have lightning, there needs to be a way to generate a charge separation. On Earth, that happens due to wind generating static electricity as hot air near the surface is drawn up into the clouds. A key point is the ionization around ice particles. <https://www.noaa.gov/jetstream/lightning/how-lightning-is-created> Lightning happens between the two places of charge. It can happen within a cloud (and is quite pretty on a dark night). It can happen between a cloud and the ground. It can happen between a cloud and the upper atmosphere (sprites). The first question has to be how to generate a separation of charge that involves the sulfurous lower atmosphere. Sulfur Hexafluoride is inert and is poorly soluble in water (<https://en.wikipedia.org/wiki/Sulfur_hexafluoride>) and is considerably heavier than air or water vapor. That means that you will have very little mixing. Sulfur Hexafluoride is used as an electrical insulator and can insulate the ground from cloud electrical interactions. It is very likely that this world will not have any lightning that would involve the Sulfur Hexafluoride. The lightning will stay up in the clouds. If this planet had other sulfur compounds in the air, then there might be lightning interactions such as happen on Venus. <https://www.nasa.gov/vision/universe/solarsystem/venus-20071128.html> [Answer] ## *Air* is not conductive The visible part of lightning is the superheated plasma you get when a sufficiently large voltage causes the air (primarily Nitrogen) to break down into a plasma. Sulphur Hexafluoride will also break down under sufficiently large voltage. Strangely, both air (understandable) and sulphur hexafluoride (weird) are in [this](https://en.wikipedia.org/wiki/Dielectric_strength) very short Wikipedia list. Air has a dielectric strength of 3 MV/m3; sulphur hexafluoride is 8.5-9.8 or roughly three times higher. In any event, more than 90% of lightning is cloud to cloud, not cloud to Earth. If your clouds are above the SF6 layer, the lighting strikes to the ground will be substantially reduced. Also, lightning is just a rapid discharge of static charge. Before the lightning, the cloud held a charge; if the lightning doesn’t happen … the cloud holds a charge. It will either rise until it overcomes the dielectric breakdown potential of the gas or it dissipates non-rapidly. ]
[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/242581/edit). Closed 10 months ago. [Improve this question](/posts/242581/edit) In this Sci-if project of mine, bioengineering is now a highly advanced science, nay an art form, and humans are able to enhance their biology using injections of nanomachines which alter their genes. There are myriad genetic enhancements, or genehancements, available to the modern human in this universe. I would like to design a genehancement that increases the “luck” of the user; naturally I don’t wish to imply there is a single gene responsible for psychic luck in humans, like in *Known Space,* but I was wondering whether there are certain physiological/mental traits that could make a person more prone to seemingly lucky incidents. (Note the patron’s use of the term “seemingly”). [Answer] ## The was a [study](http://www.richardwiseman.com/resources/The_Luck_Factor.pdf) done to see what made lucky people lucky, the consensus and conclusion was the thing that united lucky people was **the ability to recognize unique opportunities.** So what does "the ability to recognize unique opportunities" mean. Well you can break it down into 4 parts mechanically 1. high perception to spot opportunities, other people were getting the same opportunities but often they were not noticing them or not recognizing them for what they are. 2. Thinking quickly enough to recognize that it IS an opportunity and one unlikely to come again. 3. Being intelligent enough to figure out how to exploit said opportunity. 4. The wherewithal to carry out their plan, being able to ignore or not have anxiety was an important aspect of being lucky. . So you actually can make your people luckier. Is it a prefect definition no, but it as least precise and falsifiable and gives you a place to start for someone being "lucky" [Answer] Okay - what do you mean by 'luck'? If we are talking about pure random chance - then the answer would be 'nothing'. However, if we re-frame what 'luck' is, we might have some interesting possibilities. 1: **Subconscious perception** Let's assume that what 'luck' is technically, is the ability to subconsciously perceive the world and make better informed decisions without conscious thought. For an example - you see someone sprinting through a Mine field at full tilt and they don't get blown up - an outside observer would go 'Wow! That person is super Lucky!' However, the person doing the running, their brain has evolved/mutated to be able to pick up tiny differences in the dirt *without them consciously thinking about it* and so they *naturally* avoid stepping on the displaced dirt of a landmine. I'm thinking enlarging certain areas of the brain, perhaps a bigger brain stem? I'm not 100% sure of what region of the Brain you would alter - but that's something for you, the writer, to come up with. 2: **unnatural abilities in high-stress situations** Another interpretation of what 'Luck' is - being able to hit a Million-to-1 baseball throw (for example). In this interpretation, when someone is in a high-stress situation e.g. they have activated the Fight or Flight response, along with Adrenalin, they also produce a hormone/chemical/macguffin that temporarily increases their dexterity and muscle control. This allows them to do things that are otherwise considered 'impossible' or extremely difficult. Bonus world-building points - elite level athletes (in your world) train themselves to produce this effect naturally, without the Fight/Flight response. 3: **Unconscious preparation** Throwing an unusual tool in your car, forgetting about it, then needing that exact tool to help a stranger fix the specific fault in their car that said tool is for - well, that's very lucky. Here, you could again enhance the part of the brain that deals with future planning - whereby the individual without thinking has a number of items easily on-hand to address some of the most likely scenarios. Kinda like the old-school Batman TV Show(s) where when facing a particular villain, Batman always had just the right 'tool' on the Bat-Belt to deal with said foe. Those are the best I got. [Answer] If you're talking about the ability win the lottery unreasonably often, you're hosed. That's an example of "luck" where no attribute of the participant (short of the prophetic ability to know the future) can influence the outcome of an otherwise random event. If this kind of luck is part of the question, then it's likely a duplicate of a large number of questions on this site about altering probability. Otherwise... **Absolutely** Maybe you've heard of a phrase that corresponds to "you were lucky," it's "you dodged a bullet." Humans literally cannot dodge a bullet. *If they don't know the moment the trigger is pulled,* they can't move fast enough to get out of the way. But that point about the trigger is relevant. It reflects the idea that a human can be *observant.* Combined with reflexes, strength, and focus, what you have is the recipe to appear lucky. Ergo, some luck could realistically (and is realistically) attributable to circumstances where human attributes can and do influence the outcome of an otherwise random event. * Observation: enhance eye acuity and a mental disposition to "notice" or, for lack of a more medical phrase, be distracted to a degree by something. Such a person is inclined to notice deer grazing along a highway while driving or that a child has wandered into a situation that is unsafe. We've all noticed people driving on the road who appeared to be oblivious to what's happening around them (and we're sure we're not like them, am I right?). They're the folks who lack this ability. * Focus: Focus doesn't mean blinders. It means the ability to rationally and calmly think during a moment of chaos and crisis. You've heard of fight-vs-flight? It's not that simple. Some people freeze (flight). Others panic (fight). What we're looking for are the very scary people who don't appear to be phased during moments like this, who can calmly think through it. You know, Bruce Lee types (the movie version, not the real life version.) You could describe this as enhanced brain control over the adrenal response. * Intuition: is the ability to make the right decision based on limited information. It's benefited by observation and focus. It allows a person to take advantage of a situation, to reasonably "predict" (e.g.) the stock market by noticing a pattern, realizing the potential, and calmly reacting to what's observed. Intuition is an enhancement of the brain's associative memory. It's the mental version of... * Reflexes: or the ability to "spring into action" (or out of danger). The ability to bring muscles to bear very quickly for a short burst of, well, for lack of a better term, super-human action. * Strength: If you really want to improve what appears to be enhanced luck, add a slight boost to strength so you can pull someone aside or pull them with you. Nothing says "that was lucky" like one person saying it to the other out of disbelief that they're still alive. * One more, multi-tasking: The ability to process multiple lines of thought at once so that you're not distracted from your current task when the moment of crisis requires that concentration/focus to resolve it. While there would be all the medical details that must be dredged up to formally explain how all this can be enhanced, I think that's merely an exercise left to the reader. [Answer] **You can't improve on nature (or can you?)** Every person and every living creature that is alive today is here because all their ancestors, from when life began to the present day, were lucky. The unlucky ones died before they were able to reproduce. You may counter by saying "survival of the fittest" or some such. Yes that is of course important. However, given any two organisms with identical genes, one will be luckier than another. How can we explain this? Well, of course it's down to pure luck! Or is it? Firstly luck has to take into account the environment. If we take a batch of identical clones and place them in different environments, then some will survive better than others. Clearly an organism should seek out the 'best' environment. Yet we know that some species end up in very inhospitable environments indeed. Why are there humans living in icy deserts (the Inuits for example). Are they 'lucky' because they can survive in unhospitable conditions, or are they 'unlucky' to find themselves born there? **How to proceed** First of all, you must define precisely what sort of luck to wish you increase. If it is psychic ability then of course you must combine genes from successful psychics. For example, if you consider luck to apply to people who have won the lottery, then you should selectively breed lottery winners together. **Conclusion** Carefully select your desired type of luck and set in action a selective breeding program. When you begin to notice an improvement in luck for that population, it is time to examine their genes and see what they have that is not there in the general population. Implement your gene-modification program to introduce these genes (perhaps by injection) to those you wish to be more lucky. [Answer] If you can identify a person who is 'lucky', then you can at least attempt to breed for it. This may require government control of 'breeding licenses' or some such, or perhaps most adults are limited in allowed offspring, but a lottery allows more. Niven's Ringworld had a plot point with this. A character was the descendent of multiple generations of winners of such a lottery. The downside is that what is 'lucky' for one person may not be 'lucky' for anyone else. [Answer] If you define 'luck' as: ``` An ability to regularly accomplish goals way beyond one's capability. ``` Then this you can do most easily not by having luck *yourself*, but by having other people willingly help you. Basically, what you're looking for is a genetic modification which makes it easier to make (and keep) more friends. [Answer] From a pure genetic perspective, I would give the following descriptions of "luck" : (this is simply a brainstorming, don't take these thoughts as scientifically proven pls... also most of it breaks down to intuition because there are different types of "luck" if you will) 1. Intuition and pattern recognision. This one is hard to grasp but ultimately comes down to how many experiances you made as a child / young adult. Can u call forth patterns you did in mathematics in the 8th grade? If you can gene-engineer your humans it would probably be wise to enable some kind of light autism. Like aspergers. If somebody has an inherit way of remembering the way they went inside a maze / forrest, it's not really luck but more intuition. 2. Sixth sense. This one can be made via "bioresonance" to define a sci-fi word. People can "read the air" if you will. Either by having an enhanced sense of pheromoneal recognision in others ( which will unintendately "hint" clues to get the correct answere in a social situation like a quiz show ). Also maybe a kind of geomagnetic resonator, like pigeons. If somebody always knows the way north, they can maneuver through a cave system by sheer intuition. 3. People could have specific features and pheromones which make others likely to show them mercy or find them non-threatening. ( for example if 3 out of 10 men should get executed - which one is really "lucky" and which one looks just like a threat to the one that's choosing the men for death sentense ) 4. neural co-processor: a kind of ai-powered cpu implant in the brain. it might calculate bullet trajectories in the background, forwarding a roughly ideal shooting angle so that somebody just has to follow. Or the ideal angle of cover in a firefight. Or go even further and calculate f.e. approximated chances in a memory game or the like. The key here is that the wearer of such implants would not need to spent own brain capacity for calculating these values and just makes them up as they go. Whether they know if it was really their own idea to look under memory cards #2 and #345 or if a co-processor simulated many outcomes before hinting them to the person is up to you. But it could, maybe even combined with muscular implants, explain how somebody can hit a basketball in the ring over the head in first try. ( the more expansive the ai is, the better it works ) ]
[Question] [ Piggybacking off this question: [Shallow sea world - plausable geology?](https://worldbuilding.stackexchange.com/questions/4301/shallow-sea-world-plausable-geology) what would we need to have a world covered in reef? An entire world of this: [![enter image description here](https://i.stack.imgur.com/gT2Ug.jpg)](https://i.stack.imgur.com/gT2Ug.jpg) If I understood them correctly the previous questions answers suggest that the planet would need deep oceans as well, so its not all shallow. And that it might need volcanic activity to shed heat. So how about mostly shallow and some volcanic venting? [Answer] **Time.** It is an old, old world. The core has frozen and plate tectonics have stopped, although fortunately for this world's atmosphere the nickel-iron [core has become a large ferromagnet](https://ui.adsabs.harvard.edu/abs/2002AGUFM.P11A0344B/abstract) which continues to protect from the solar wind. Weather continues. Over the eons, rain washes the mountains down into the sea until there is nothing left to erode. Under the surface, mass action causes high points to fill in low points. Now several billion years later the work of the plates has been undone. There is no more land. Rain falls on the surface of the water and underwater the ocean floor is shallow at all points. [Answer] Coral reefs can only exist in warm, shallow seas. High gravity will work to even out the terrain, and you want oceans that are on average no deeper than 200 m. A large planet will be more volcanically active, as well as having higher gravity, so it’ll work out. As for getting energy from its sun, the corals can survive water temperatures between 291 and 313 K, so we want that as our temperature range. Water is a greenhouse gas and has a low albedo, so it should work to keep the planet warm. Get a good axial tilt, and an decently-long day, and it should work for a predominant coral reef biome. [Answer] ## A few thoughts: This isn't a guarantee of a world with NO deep parts lacking reefs, or NO islands, but it may help to explain a lot of the gaps in your worldbuilding. A couple of these might be mutually exclusive, so pick and choose as desired. * I agree, geology would need to be different. Either the world would need to have had a long time to erode, or the plates formed/didn't form in such a way that there are no continents & mountains. * Some kind of combination of highly destructive organisms have been digesting the land, and have found energetically favorable ways to corrode exposed rock to nothing. The land, when it occurs, or even Up-thrust reefs, are degraded by these aggressive land species. * You have species of beaver-like organisms combined (and/or) with corals that form terrace-like structures on the land. They have favorable growing/feeding conditions in these pools, like rice paddies. Everywhere there is land, you have large grown/cultures lakes with thin dam-like structures for every elevation change. So all your land is covered in an endless series of pools filled by the perpetual rains. Thus the land becomes a stand-in for reefs. * Consider a semi-buoyant version of a reef, able to float in the deep ocean over areas without a bottom. These structures have plants at their base that stay afloat to stay on or near the surface for sunlight. They may be in a symbiotic relationship with the the coral-analogs (these might be made of lighter materials), providing the corals with habitat in exchange for protection from predators. These floating reefs slowly agglomerate to form a mass of reef-like structure over the ocean, only occasionally disrupted by large storms or geologic events. So your deep oceans are coated in a blanket of organics that fix the surface and shift with sea levels. [![enter image description here](https://i.stack.imgur.com/0Belf.jpg)](https://i.stack.imgur.com/0Belf.jpg) [![enter image description here](https://i.stack.imgur.com/yhyoN.png)](https://i.stack.imgur.com/yhyoN.png) [Answer] You need some source for minerals for nutrients for those reefs. If there is no exposed landmass to erode, this becomes a bit of a bother. You need to explain why you have large areas of shallow-ish water, with sufficient nutrients for abundant life. And you need to explain why your reefs do not form coral Island that protrude out of the water. As for having vast reefs but no coral islands: no problem. Your coral-equivalent grows at any depth from several hundred meters down, up to *but not reaching* the surface. Something as simple as the local star shining with severe UtraViolet light, that sterilizes the surface but is absorbed and neutralized by a few meters of water. This will allow the coral to grow towards the surface, but stop it from *reaching* the surface. Add that to a world that has smaller tides, so there is no great sloshing of the waters to expose the coral, or to wash coral sand into piles that become islands. As for not having real landmasses, with mountains etc.. You just need to not have active plate tectonics. Your planet is Old, the crust is many hundreds of km thick, and locked in place. Anything that pokes out of the water is already eroded down. As for the nutrient source...hmm. Maybe your thick crust is being invaded by the ocean, causing multiple persistent but non violent geothermal vents all over the place? Or.. a bit radical but picturesque: You planet **HAD** a medium sized moon, in a *very* low orbit. The ridiculous tides from this is what scoured the landmasses down to sealevel, and also filled in most of the ocean deeps. Now, this moon has passed below the Roche limit of your planet, and has broken up into a very dense ring system. Very pretty rings, their even mass distribution has completely stopped the tides allowing your reefs to form, and the continual drizzle of dust falling from the rings seeds the oceans with ample nutrients. [Answer] It's fairly easy. You just need two things: very little continental crust and slightly less water, both of these can basically be handwaved. Both are the results of minor fluctuations in the starting makeup of the planet. You can just say both are true and no one can really say anything. You will have a few small continents, some volcanic island arcs and some trenches, but most of the world will be a mix of ocean of varying height, much of which will be shallow enough for coral. You can make it easier by having a larger variety of coral like organisms, perhaps ones that make skeletons of silica and/or iron oxide. This is an alien world coral which does not need to function exactly like earth coral. It could be more photosynthetically efficient or have more filter feeding varieties. This can drastically widen the depths suitable for "coral". If you can blue shift the star a little or move the planet a little closer to it, it will help with light penetration. Just like on earth, coral islands may get exposed due to geologic changes, but exposed coral will die so you will not get noticeable amounts of dry land that way. Much more coral will be pulled down into deeper water leaving dead or dying reefs in deep water. Expect an entire ecosystem build around this. Expect such a world to have between 1/3rd to 1/2 of its surface area to be suitable for coral. [Answer] The deep sea has pretty much no light reaching it. Deep sea corals do exist, but a big reef in the deep sea has not been discovered. According to Wikipedia and the source listed on Wikipedia, the biggest deep sea reef is only around 35 km long and 3 km wide. All the articles I looked at said that the reef was different sizes, but both the .no websites (the top domain for Norway) said it was 35 km long. That reef is only a couple hundred meters down. That is above the midnight and abyssal zones, where no light reaches. I would say it is very unlikely that a reef covering the entire planet could form, unless Earth is a very weird planet, and future discoveries prove us wrong. A large shallow ocean, covering most of the planet MAY exist, but a large deep sea reef wouldn't be viable, even with volcanic heating. Also, a rogue planet would not work, as a majority of corals need warm water, which, on a planetary scale, will need a nearby star to warm the surface. [You may need to translate this](https://forskning.no/bakgrunn-havforskning/bakgrunn-korallrev-sakte-og-skjort/1084504) [Wikipedia Article](https://en.wikipedia.org/wiki/Deep-water_coral#cite_note-15) ]
[Question] [ In my story one faction in the past used it's Dyson Spheres (they have several) to make a Nicol-Dyson beam (Basically you temporarily redirect a significant portion, or even all of it, of the star's energy output in the general direction of whatever you want to urgently stop existing) to roast one of their neighbors. The attack decimated and vaporized everything that was smaller than several km in radius in the target system, and completely liquefied the crust of rocky once inhabited planets in there. [X] time later the protagonists stumble upon the system during their investigation of the faction with the spheres, and with horror and ave they note that the remains of the planets are still glowing on the nightside despite it's been [X] centuries/millennia since the attack. My question is, how long a liquefied planet has until it will cool down too much for glowing in the visible spectrum? What's the [X], and how can I maximize it? (I don't want the attack to be too recent, several centuries is the minimum) [Answer] # About 24 years How long for a hot planet to cool down. Assuming: * Earth type planet, no atmosphere (if there was any, the superzap would have ejected it to space) * Surface at 1500C, all the way down until the normal mantle temperature is 1500C, thus about 60km. * Surface temperature needs to cool down to 525C (draper point, where visible incandescence begins). * Assuming your starzapper kept its beam on target for several months. Otherwise it would have just ablated off the top layers.... On second thought, this does not matter. Might as well just assume the cold rock got vaporized and blown off-planet, the 1500C surface left is actually the top of the mantle not the remains of the crust! Exactly equivalent for out calculation, and allows a more impressive SuperZap! So we have a planet with very hot core(normal), but the surface terminating at the 1500C level, that needs to cool down on the surface to 525C in a state of near-equilibrium. Kelvinize everything, degrees C is not the best scale: 60Km of mantle material, specific heat of about 700 (J·kg−1·K−1). Starting temp of everything: 1773K. ending temp of surface: 798K Each square meter of surface needs to lose (0.5 \* 60km \* heatcapacity \* density/m3 \* (1773-798)) Joules of energy, for the surface to stop glowing. This is total of : 0.5 \* 60000 \* 700 \* 2200 \* 975 = 45045000000000J (4.5e13 J) The only way to lose heat is via blackbody radiation. Assume emissivity of the magma is about 0.65 (rhyolitic magma) (all figures below are per m2 of surface area) In first second, heat loss per m2 is 364216 J In the first day, the heat loss is 3.15e10 J, the new surface temp is 1772.3K By day 100, the temperature is down to 1711.4K, and the heat loss is way down to 2.73e10 J per day By day 1000, the temperature is down to 1373K, and the heat loss is down to 1.13e10 J per day **By day 8649, the temperature is down to 798K, the heat loss is down to 1.29e9 J per day, and the surface stops visibly glowing.** Sorry, your target will only be visibly glowing for 23.7 years. Erroneous approximations used for this sim: * assume the molten stuff is rhyolitic magma, with heat capacity at 700J per kg per K, density of 2200, and emissivity of 0.65. And that all of these parameters remain constant constant regardless of temperature. * Assume no outgassing, no atmosphere, zero cooling other than Blackbody Radiation following Stefan Boltzmann laws. Any outgassing that does occur gets banished to space due to...reasons. (maybe because you also toasted the sun, and its solar wind is still going nutz?) * Assume that our surface mantle material follows the same heating-per-depth rule as for normal Mantle material once a reasonable equilibrium is achieved, with a temperature gradient of 25C per km depth. * Built a spreadsheet to calculate iterative time periods. Saw less that 3% deviation between running first day as one day chunk rather than per second, so ran the sim in day periods. P.S. Making it hotter does not help much, due to that Temp^4 term in the radiated heat. It you fully double the energy needed before cooling enough, heating it to 2747K (2474C) then it cools to the same level in only 9282 days (25.43 years) P.P.S. There are many assumptions and guesstimates in here. The answer derived is definitely a ceiling value, the true answer may be close to it, or significantly shorter. Longer is not likely unless something really weird happened. To OP's later added question: You ask about > > " I would like an answer that factors in atmosphere. Also interested in difference between time to cool to nonglowing, and time to cool below boiling point of water so oceans can fill." > > > Sorry, but the model I use only models conductive and radiative heat loss, thus no atmosphere. And the conductive heat loss undergoes a transition when the material's radiative heat transport drops below its conductive heat transport. Even the 798K glowing limit is a bit below this point. Going cooler, the temperature drop *drastically* reduces, leaving the surface rather hot for many thousands of years. Basicaly a thin non-glowing layer floating on a deep magma sea. 100C would be achieved on the rough order of 2 million years+, or thereabouts. You are effectively recreating the Earth crust, which took 100 million years the first time around(delayed largely due to a severe case of meteorite pimples re-mixing the surface all the time) [Answer] ## Surface cooling depends on many factors, but even 100 years seems very unrealistic. Lava flows typically start at to 700-1200 C. Yet, because lava has poor thermal conductivity and does not really have much in the way of convective currents, it is often cool enough to walk upon with 15 minutes - forming a surface crust that is much cooler than intuition would suggest. Unsurprisingly, much of the earth's crust is composed of materials similar to lava, and would be conducive to rapid cooling. The real unknowns are how much the lower and hotter layers would be able to break through to the surface and heat things up again due to convection currents. Lava flows that are 10 or 30 meters thick are well known, and cool off very quickly. One formed a pool that was [85 meters thick](http://volcano.oregonstate.edu/how-long-does-it-take-lava-cool), and drilled into 29 years after it flowed, and what discovered to be quite hot at depth even though the surface cooled quickly. Lava cooling is different than entire planet cooling because the cool atmosphere conveys heat away from the lava more rapidly than would occur as a result of a Dyson beam, but given what I know of heat and mass transfer, I don't see any way to justify surface cooling that is millions of time slower than what we observe in lava flows. At most, the planets would have local hotspots where volcanic activity persists over the course of centuries or millennia. To heat the planetary crust to the degree that it is molten to a depth of hundreds of meters is way overkill to sterilize any typical life, much longer heating to turn the crust molten to a depth of kilometers would not significantly change the situation, the molten surface would still cool quickly because the resulting lava surface does not maintain equilibrium with the deep hot layer. ]
[Question] [ ## Deceleration as a weapon --- In a very interesting [question](https://worldbuilding.stackexchange.com/questions/185802/proper-combat-distance-scaling-for-a-sci-fi-space-opera-tabletop-setting/185944#185944) about the scale of distance useful for a space opera game, I was inspired to consider the use of deceleration as a weapon. Considering humans have a certain threshold of G's of acceleration/deceleration, is it possible to use **sudden deceleration as a lethal weapon/trap in space combat**? Specifically, we want to ambush a ship is traveling at fast speeds, higher than, say, the voyager 2, at 15.2 km/s. (Originally was asking about sub/near light speeds, but realize that even a droplet of water would pulverize the ship). *If one could predict the exact location an enemy ship will pass through, and some materials are left locally at rest (0 velocity) at that location as a blockade to ambush them*, **is this 'Space Speed Bump' capable of incapacitating the enemy crew through impact deceleration alone**? The best answer would ideally have some form of calculations or citations to back it up (rough calculations are fine). ## Hull Materials --- After using the equation for [armor penetration](https://www.alternatewars.com/BBOW/Ballistics/Term/AP/AP_Pen_Formula.htm) with a ball of 3g of sand (with the same F-coefficient as an armor penetrating bullet) traveling at 15,000m/s, it was found that against a Chrome Nickle Steel Armor plate with a perpendicular (head on) impact, it would penetrate 87m of steel armor. This is far beyond the limits for modern armor on hulls. As such, the question needs to involve some theoretical materials, either being equipped with about 0.15-1.5 meters thick of [carbon-fiber strength or nanotube hull](https://www.nasa.gov/vision/space/gettingtospace/16sep_rightstuff.html), which can be up to 600 times stronger than steel. Or assuming that a ship can have at least 100 meters of self-healing, steel-strength plating. Without at least this level of hull strength, any random collision with a 2-3mm large spec of dust will cause a hull breach and kill the entire crew. ## Assumptions --- * We do not care about the state of the ship after, just that what incapacitates the crew is the deceleration. * The ship and blockade share the same reference frame, perhaps velocity with regards to the center of the universe, factoring in ([space's expansion](https://en.wikipedia.org/wiki/Cosmic_microwave_background)). * In regards to @JustinThymeTheSecond's questions about relative velocities, assume the ship will collide into the blockade at 15,000m/s (1/20,000th the speed of light), as the blockade and ship share the same reference frame (whichever frame is picked). * The ship does not detect the obstacle in time to greatly decelerate or change course * The basic ratios (using a space shuttle as reference): a shape like a cylinder, with cone diameter of 6 meters at the front, and weight of 120,000 kg. Scale as needed. * Assume the blockade material has a similar density to water * The ship hull is at least as strong as 100m of composite steel, or 1.5m of nanotube armor * The hull will protect the crew from dying to a hull breach by grains of cosmic dust while flying in normal operation. On a tangent, would it be possible for the deceleration to not cause heavy damage to the ship and its cargo, while still being deadly to the crew? Would we need a special material or setup to best spread this impact throughout the entire surface of the spacecraft? [Answer] Way out in left field answer number two. So far, most answers are looking at something that the ship 'runs in to'. Instead, **A sticky solution**. How about magnets? Every ship produces an EM field around it. This EM field is traveling at extremely high velocities. So, feed the area with a gadzillion ball bearings. When a ship with a high EM field passes through, eddy currents will be induced in these ball bearings. These eddy currents are proportional to the speed of motion of an inductor in a field - i.e. very strong at spaceship speeds. These eddy currents will generate a very large magnetic field around the steel balls, which in turn will be attracted to the ship hull, or indeed the EM field around the ship itslef. ([Lenz's law](https://en.wikipedia.org/wiki/Lenz%27s_law) - an induced magnetic field will oppose the field that prodced it). The ship does not have to HIT the ball bearings, they will be attracted to the ship (accelerate on their own) and all of this energy will be subtracted from the ship's forward momentum. Like the electric brakes on an electric car - the motor is turned into a generator and the power returned to the battery). There would be a sudden deceleration jolt in the target spaceship, from three factors. One is the ship actually hitting a stray ball bearing, but I am sure the ablative shield could withstand it. Second, the mass of the ball bearings attaching magnetically and probably non-destructively to the ship, increasig its mass, and thus lowering the speed. But third, the induced back-EMF field opposing the motion that created it in the first place. This force, given the speeds involved, would be the strongest force, and not dependent on the mass of the ball bearings. Of course, the target ship could avoid this by shutting down all sources of EM radiation, but this would potentially shut down all navigation and sensors. Also, I suspect even a ship traveling through background radiation would produce some induced EM field around it. However, an alternative would be for the ball bearings to be somewhat intelligent. Upon sensing an approaching ship, they would generate their own EM field. They would not only be attracted to each other, but collectively to the approaching ship. The effect would be like encasing the approaching ship in a magnetic fishing net. Apart from a defensive move of a ship laying in wait, it would produce an effective speed-limiting measure around a space station. Only vehicles approaching at a very low rate of speed relative to the station would not be 'braked' by the system - a true 'speed bump' the purpose of which is to slow down the driver. **Edit Example** [Here](https://en.wikipedia.org/wiki/Eddy_current_brake) is an example of how eletric induction brakes are used to stop, for instance, trains and roller coasters. > > An eddy current brake, also known as an induction brake, electric > brake or electric retarder, is a device used to slow or stop a moving > object by dissipating its kinetic energy as heat. Unlike friction > brakes, where the drag force that stops the moving object is provided > by friction between two surfaces pressed together, the drag force in > an eddy current brake is an electromagnetic force between a magnet and > a nearby conductive object in relative motion, due to eddy currents > induced in the conductor through electromagnetic induction. > > > **EDIT Food for Thought on 'stickiness'** Water, or in fact, most liquids, can not exist in space. With the almost nil (atmospheric? non-atmospheric?) surrounding pressure, the molecules of almost any liquid in space will boil off almost immediately. But it boils off, not in individual molecules, rather in 'clumps' of molecules. When the clumps, or particles, get very small, they will now 'freeze' (turn into a solid) - they have lost so much energy in breaking the molecular bonds in 'reverse boiling' (boiling not because external additional energy is added, but boiling because the pressure is lowered so that the existing energy causes boiling) that they now [solidify into a very fine mist of crystals](https://www.forbes.com/sites/startswithabang/2016/12/23/water-in-space-does-it-freeze-or-boil/#8d5d84a5f919). However, the property of a liquid would be useful in this case - liquids are deformable (wet) and can wrap around an object when impacted. This is a 'sticky' property of liquids. They 'pour' over an object, covering it, without necessarily 'impacting' the object at high velocity (first contact would be an impact, but when the remaining liquid surrounds the object, no catastrophic impact). Nevertheless, it requires energy to do this - energy that is taken from the speed of the object. So how to replace the molecular bond of a fluid with another 'fluid-type' but non-molecular bond? Yes, of course, electromagnetism. With no current flow, there is no magnetic attraction. All of the ball bearings remain 'at rest' with respect to each other in a disjointed cloud. (Eventually, of course, gravity would clump them together.) But as soon as eddy currents are induced in the ball bearings, the eddy currents produce a magnetic field, and the particles now attract each other. One will follow the other in a fluid motion. Even if they connect, they will still act like a 'fluid', due to their roundness. They can move over each other. Thus, they can surround another object without forcefully impacting it. But here is the thing. Inducing a current in these ball bearings takes energy. The stronger the induced current, the more energy is 'expended'. This energy comes from the forward momentum of the inducing object. But the faster the ball bearings move in the field, the stronger the eddy currents. [Here](https://www.toppr.com/guides/physics/electromagnetic-induction/eddy-currents/) is a good primer on induced eddy currents and energy conversion. They are so powerful, as I have stated, eddy currents induced in the wheels of a train can bring the train to a stop. To clarify why I think there would be an EM field around a space ship, they have been proposed as a ['shield'](https://physicsworld.com/a/magnetic-shield-could-protect-spacecraft/) to protect the ship against cosmic radiation and such. EM fields could conceivably be standard fare for space ships in the future. **TL:DR** To clarify, the idea of using induced electromagnetic fields in ball bearings, is not to use the impact energy of a 'stationary' ball bearing on a moving space ship to destructively cause a loss in momentum of the ship, but to use the momentum of the spaceship to induce a magnetic field in a stationary ball bearing, **causing the ball bearing to impactlessly accelerate to the speed of the space ship**. It is this acceleration of the ball bearings that in part creates the drag on the ship, that results in slowing it down, not any destructive direct impact. Another factor in the loss of forward momentum in the ship is the loss of energy as it is converted into heat in the ball bearings, from the induced (short circuit) current flow. **The greater the induced current flow in the ball bearings, the more heat generated, the more energy taken from the ship's forward momentum.** The induced eddy currents in the ball bearings are created, in the first place, by the **forward movement of the EM field around the ship**, relative to the stationary ball bearings. [Answer] I'm fond of a scene from the movie *The Hunt for Red October.* > > Can you launch an ICBM horizontally?Sure! Why would you want to? > > > > > We learn from [here](https://hypertextbook.com/facts/2004/YuriyRafailov.shtml) that it's not just deceleration, but the time during which a body is exposed to the deceleration. So, we either need a lot of acceleration for a short period of time or a little bit of acceleration for a long period of time. So, assuming some averages and guessing a little bit, we need either 5G for 60 seconds or 50G for one second. Reference scenario: * Your ship and my ship are indestructible. * [According to Wikipedia](https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier) a fully-loaded Nimitz-class air craft carrier has a mass of approximately 91.8 million kg. When you really think about what it would take to move a ship and cargo/weaponry through space, I think this is a great starting point. So, the mass of ***both ships*** (for convenient math) is 108 kg. * We're sub-light. Let's assume 0.1c or about 30,000,000 m/s. The target ship is gliding at that velocity. So, kinetic energy = $\frac{1}{2}mV^2$ or $45e^{21}$ joules. * My ship is already *nose to nose* with your ship. And I turn on my engines to accelerate at 5G for 60 seconds. Everybody's dead, but let's ignore that for a moment. $$F=mA$$ So I just applied 16 billion newtons of force for 60 seconds for 960 gigawatts of power. You need to create that much power *in friction* with, I'm assuming, some agent (like sand) that you're carrying with you. Here's your problems: 1. We started with an opposing mass equal to the oncoming mass. If you're going to use a disposable mass (i.e., you want to live through the encounter), then you need to either bring that much mass with you (that's your 108 kg ship hauling a 108 slug with it) or you need to be traveling *in the opposite direction* with a velocity higher than your opponent's (how much higher depends on how much mass you can haul with you). Since kinetic energy scales by the square of velocity, if you can move against your opponent at the same initial speed (a total of 2X delta-V) then you can haul 25% of the mass. But that means you're moving at 0.2c (in my example). 2. Remember our stipulation that the ships are indestructible? Author Larry Niven circumvented some unpleasant realities in his stories by declaring that General Products hulls were indestructible ("an artificially-generated giant molecule, with the inter-atomic bonds artificially strengthened", causing the hull to resist "any kind of impact, and heat in the hundreds of thousands of degrees." C.F. *Flatlander*). If that's OK with you, it's OK with me, but if your ships are destructible, then a 5G deceleration for 60 seconds would be devastating. Remember, the back end of the ship wants to decelerate more slowly than the front end. That's the reason cars that hit walls look like crushed beer cans. 3. Friction causes, among other things, heat. Some of the kinetic energy lost through deceleration will go to pushing away the mass that's in your way. But some of it will be converted to heat. A lot of heat. Now, to be fair, fighter jets capable of 9G turns don't burn out like an old flash bulb — but they're not sustaining 9G for 60 seconds, either. Nevertheless, one would hope that issues #2 and #3 were part of the design process for the ship. BTW, there isn't a lot of difference using the second deceleration speed (50G for 1 second). It's about the same amount of force. The biggest difference is how much you need to spread the mass out (along a path of 1.8 million km or 30,000 km). **So, the real problem is issue #1** Can you slow a ship down via friction such that only the crew dies? Yes. Is it practical? No. * You need to haul either mass equal to the mass of the target ship, or be traveling substantially faster than the target ship. It's a trade-off. * At low-A, you're forced to depend on your opponent's reaction time. In my example, 60 seconds is a long time and your opponent can "pull up" and exit the debris field. If you're bringing enough debris to keep that from happening, you're substantially increasing the amount of mass you're hauling. * At high-A, you're forced to depend on really accurate timing to drop the load. You get one shot, then you're a month turning around (and have to go pick up another load of sand). **One more thing...** Before we leave, note that there's two ways to look at this. One is the pirate ambush where they happen to see the target ship and act to go get it. That's unlikely given the size of space and the speeds involved. The other is the planned attack where you know your enemy's path before the attack and can lay a trap. Why am I mentioning this? Because the friction idea is a one-off solution. You get one chance. Then you're out of abrasive material (or you're hauling so much that you're a big, slow whale that's easy to out-accelerate or really easy to lob missiles at). There's also the question of just how far ahead (in time) you can detect an incoming vessel? Lots of ugly in that situation. But as a planned attack where the target's path is known... then you have the time to spread out the abrasive — and the longer the field the better as it would be harder (lower mass-per-cubic-meter) to detect (theoretically, there's some arguments to be made here). This is the Titanic-hits-the-iceberg solution. And in this case, I think it's a cool story/world idea. [Answer] Throwing something in their way would create more of a problem owing to their hitting something at such high speeds than through deceleration, though the deceleration itself. The use of *water* as such a danger has been exploited as a plot device by such writers as Larry Niven and David Brin. (Owing to its apparent innocuousness, and its ease of transport in dense form, and piping out when needed.) To actually get only deceleration damage, you would have to put the danger out far enough that they can detect it, but only far enough that their options to avoid it are limited to hard deceleration. [Answer] **TL;DR** You need to bring a 17 km/s ship to a complete stop in ~~0.035~~ just under 35 seconds to kill the crew. Most space ships are actually pretty fragile, and bumping into something could be very bad. A google search shows that the [minimum thickness of the ISS](https://www.google.com/search?q=minimum+thickness+of+the+iss&rlz=1cahlqr_enus870&oq=minimum+thickness+of+the+iss&aqs=chrome..69i57.3998j0j7&sourceid=chrome&ie=utf-8&safe=active&), which although probably is not the best answer, is 4.8mm. Even if you had this deceleration technology, it would probably be much easier to poke it with a needle and let the air drain out, killing all the crew inside and leaving the cargo a little cold but mostly okay. Anyway, severe deceleration COULD work, but it would have to be pretty fast deceleration. If your target ship is going too fast, it could end up destroyed and then your speed bump is pointless because you can't capture the cargo. You say you want it to incapacitate the enemy crew, which I interpret as 'dead, unconscious, or unfit for combat', but that's just me. One thing you might run into is that you need to stop them really quickly. Car crashes and drag races have severe deceleration, and most of the time the people are alive, and mostly in the case of drag races, people are up on their feet relatively quickly. But this is SPACE, there is no gravity, so even if their legs are broken, they can grab a rifle and hold onto a wall. To have an effective stop sign, you need them knocked out or dead, which will be hard to do without breaking the ship unless it is designed for getting punched around or your world just has really strong ships for no reason. But let's say the ships is immune to breaking, then we need to stop it quickly. If we assume your craft is going the same speed as Voyager, then it's going 17 km/s, or just over 38,000 mph. This is way faster than a car could ever go, so you can't exactly test the point where you black out or die. The most gs anyone has taken before is about 42 gs, but your crew is probably trained for this so we can round up to 50 gs. So let's see how fast we have to stop to get to 50gs! So let's work backwards from 50gs. I'll be using metric, so we multiply by 9.8 m/s to get 490 m/s as the deceleration we need to get. Now we need a start speed, end speed, and time it takes to slow down. As said before, I'll be using 17 km/s for initial speed, and for an end speed I'll use 0 km/s so we bring it to a complete stop. Time is the variable we'll be changing until we get the desired result. After I did some calculations, time ended up being about ~~0.035~~ just under 35 seconds to get 490 m/s deceleration. How you stop it is up to you, this is how long you have to stop it if you want the crew incapacitated. I know this is kind of a half answer, but my knowledge as to HOW it would be stopped is none, and I just googled most of this stuff here. You should probably check this yourself in case I did something wrong, but I'm pretty sure this is right. [Answer] I'm going to point out — because no one else has mentioned it — that a conventional 'speed bump' doesn't decelerate a car at all. A speed bump introduces an extremely unpleasant *vertical* motion: one orthogonal to the direction of travel, but proportional to the speed of movement. Cars decelerate because drivers want to avoid that jolt, not because the speed bump does anything to slow the car itself. One can drive over a speed bump at 60mph if one wants, and it won't slow the car; it will just make the car buck like a bronco, and give the passengers a taste of free fall for a second or two before the front end crashes down. With that in mind, it might be wiser to consider a precision orthogonal push — a kind of space PIT maneuver — designed either to send the craft into a spin (push aimed at the head or tail), or jolt it severely sideways (push aimed center-of-mass). This could be done with jets of water of gas, possibly with a magnetic field, but the point would be to force the pilot to decelerate as soon as he is aware of the 'bump' in order to keep control of the craft. I'm sure someone else can work out the maths; I'm not up to it today. [Answer] ## **Yes, a Speed Cloud made of sand** --- **Disclaimer: Answering my own question for reference purposes, but accepted answer came up with a better setup**. This answer relies on the spaceship having enough hull strength to survive hits from grains of sand. If we assume that the sand won't pulverize the hull (as by ensuring they are in a cloud, rather than a condensed block), we still have the question of whether the actual deceleration can be done with a reasonable amount of sand. From some resources and inspirations from other answers we can do some calculations: Assuming a very normal space shuttle, moving at about 15,000 m/s (1/20,000th the speed of light), weighing in at 120,000kg. It hits a 4000kg block of material of similar density to water, say, [sand, which is 40% denser](https://civiljungle.com/density-of-cement-sand-and-aggregate/) spread into a cloud. The sand would be very easy to store, fitting into a condensed 1.4x1.4x1.4m cube when not in use. We throw this into a [conservation of momentum calculator](https://www.omnicalculator.com/physics/conservation-of-momentum): [![enter image description here](https://i.stack.imgur.com/DXRIW.png)](https://i.stack.imgur.com/DXRIW.png) **The important point to look out for is the delta-v for the spaceship, sitting at 500m/s.** From the resource provided by @JBH, [50gs in one second, or 4-6gs in more than a few seconds](https://hypertextbook.com/facts/2004/YuriyRafailov.shtml) is enough to kill most people. For reference, car crashes take fractions of a millisecond for delta speed change for objects equal in weight, but even if we assume it takes a much, much longer length of 5 seconds, **we arrive at 10gs of deceleration over 5 seconds, or 50gs over an entire second, enough to kill pretty much any human.** (Thanks @NuclearWang for pointing out the previous mistake in calculating G's). **Essentially, a cloud the width and height of the space ship (6m), stretched over the length of 0 to 1 to 5 seconds of travel or less (~0-15km-75km) should be enough to incapacitate the crew.** If we assume a massive ship maintaining a slow 15,000m/s, it will take no more than 3400 cubic meters of material, being stored in a 14x14x14 meter cube. *It can be seen than the amount of sand needed scales linearly, due to momentum transfer being the considered factor in delta-v.* [![enter image description here](https://i.stack.imgur.com/o9MaH.png)](https://i.stack.imgur.com/o9MaH.png) **Thus, a collision with a cloud made up of a mere few cubic meters worth of sand is enough to kill most spaceships' crew members with deceleration alone.** This means that by using a cloud of sand, or a 'speed cloud', we could avoid destroying the spacecraft as long as the sand is not in large clumps. By using a cloud, the deceleration will happen along the entire front surface of the spacecraft coming in. This would cause less damage to the spaceship itself, but still be enough to lethally injure the crew with the decelerating force alone. [Answer] I am going to go way off on a tanget in this answer. It seems to me that what you are after is some form of '**friction in space**'. That is, something that will slow down the ship without actually impacting with it. Like a boat going through water, where the water changes density (through, say, seaweed), or a car changing from the road to sand. Not a speed bump (that would take a sudden strong and very local change in gravity), but a sand trap. But space has no friction. Except that it does. The **Higgs Field** is so new, that it has not yet infiltrated sci fi writing. We just don't know enough about it, so it isn't used, or even speculated on. We use every other field (EM, gravity, for instance) but not the Higgs Field. This field has been described as a sticky field that gives everything inertia, and is present everywhere in the entire universe. It also seems to be uniform in 'density' throughout the entire universe. Makes it hard to get going, hard to stop, but when it is going at a constant speed, it offers no resistance. Since there is essentially no such thing as something having 'absolutely no velocity', the Higgs Filed is actually influencing everything, inertia wise, except that it exhibits its effect only on **changing** velocity. So here's the thing. What happens if either the Higgs Field, or the number of Higgs bosons, changes in density? It would be like trying to accelerate or decelerate an object. In fact, I posit it would cause acceleration or deceleration, if inertia changed. If somehow a weapon is designed that can modify the Higgs Field by, for instance, creating a blockage of a huge number of Higgs bosons, then anything entering this altered area would experience a dramatic change in 'inertial resistance'. It would be like a car changing from driving on a road to driving on sand. The spaceship would experience sudden deceleration, without actually hiting anything. As long as the ship could withstand the inertial change through inertial dampening, it would be relatively unscathed. However, if the g forces created by deceleration were great enough, the humans would suffer very substantial effects, due to changes in blood and bodily fluid flow, load on the heart, probaly suffer embolisms and blood clots from pressure changes, and probably even concussions. This is not hard science, but it is certainly speculative science, within the realm of what is known about the Higgs Field, with a bit of handwaving. [Answer] I think you're overthinking this. Lets take a simpler weapon: A spacegoing "mine"--it's a missile that doesn't try to go after it's target, just tries to get in the way. (Think of the goalie in soccer.) They're seeded around in space, if they sense (or are told about) an enemy ship that's going to pass close enough they get in front and stay there if it tries to maneuver. All of the deceleration will be delivered at once, producing the maximum damage for the mass involved. Nothing gets wasted being too far to the side--any mine that's too far to the side remains a functional mine and can engage another ship or be picked up and moved at a later date. It will also punch through far more armor than any of the light things you are thinking of. Assuming your ship (120,000kg @ 15,000m/s), a 100kg mine half a meter across I get a peak deceleration of 45 GN--for a tiny fraction of a second you're looking at 38,239g. If you're in a General Products hull you're very, very dead, with something more sane the ship is going to flex it's as if you fell 8 meters on Earth. Not a certain kill but the crew is definitely not functional at that point. You also have a boom equal to 2.5t of TNT (but far more destructive as the energy is entirely directed inwards.) This will be a much more effective weapon than any small dispersed matter. Furthermore, dispersed matter is the equivalent of WWII torpedoes--defeated by zig-zagging. [Answer] ## Edit Frame Challenge: In comments moved to chat, the OP insists that a "stationary" object is the answer to crippling a crew, but keep the ship intact. It is argued in the question that it's not astronomically impossible for some ship to wander into this trap without it being completely massive in size. It is also assumed that a 15k m/s hit isn't going to completely destroy a ship. Space is so large that 2 ships being in the same solar system and notice each other is pretty low on the probability scale, unless it's a known inhabited system. **Having a "sand trap" of any material or sized particle would have to be massively large.** It would be so large that it wouldn't be economically feasible to make it happen. And if it was done in an inhabited system, whatever authorities that happen to be around would either try to warn ships away from it or try to clean it up. As for the forces involved in a 15k m/s hit, a hit of 1 ton of material, even in 3g pellets, would have a 10^11 Joule force impact. That would completely shred nearly anything. A kiloton of TNT is 4.184×10^12 J, but most of that is dispersed away from the target. Think about that being a shaped charge where only 10% is against the hull of a ship. That's a massive amount of force for a ship to be built to handle. [And 1 ton of material is a tiny fraction of the material needed to make a trap like this.](https://en.wikipedia.org/wiki/TNT_equivalent) And because it's so large and has so much mass, any reasonable ship is going to have sensors to notify the crew to avoid that part of space. Unfortunately, this "stationary speed bump" idea just doesn't hold water. There are just too many reasons why it won't work, and that doesn't even get into celestial mechanics or gravitational effects by nearby planets or other bodies. It also ignores the gravitational effects of itself, if it's supposed to be a distributed mass of small particles. And a liquid like water would either freeze or sublimate, so that changes how it impacts the ship, but not it's ability to be detected by ship sensors. The OP should reconsider the question frame to be more feasible in terms of real physics and astronomical laws. **End Edit.** What you and most of the other Answers are thinking about are on the order of depth charges. These are thing that hit the target and either do direct damage or try to slow down the vessel. There's a couple of problems with that. The first is that an exploding device would have to be fairly close to do damage when it detonates, as only the shrapnel and some gasses are expelled, which dissipate fairly quickly in a vacuum and don't propagate a blast wave. And even with a lot of shrapnel and a large explosion, it would have to be a significant percentage of the target vessels force to have any real effect to slow it down. Even a nuke might not have enough power to slow it down, unless you also want to rip apart the vessel. The second problem is the difference in speed of the vessel and the material launched at it. In order to make much difference to the pursuing vessel, you have to eject the mass at a high speed, otherwise it's just floating between you and them in a relative lack of motion. There's no wind to slow it down for you, so you have to do it yourself. And that might include explosives, which could damage your own vessel. Just letting decompression happen likely won't be enough, nor will it likely keep things concentrated enough to mean much. And when you run out of material, explosives, or air, you don't have any defense left. Part 2 of the second problem is that if you launch material at a following vessel is that you are also launching yourself forward at the same force. Since you are trying to force your pursuer to slow down drastically, you are also speeding up drastically. Sure, the mass of each vessel depends on how much each happens, but a large vessel probably doesn't have much to fear from a smaller vessel in interstellar distances. Part 3 of the second problem is the fact that the following vessel isn't likely to be following directly behind, so the force of this mass hitting them will need to much higher, or it'll only cause them to be off course, rather than slow them down. Also, they will be able to dodge the mass, unless the mass is spread out, which means even more mass is needed to slow down the chasing vessel. This gets mass-expensive fast. And with the chaser being not behind you, you'll still need a computer to calculate trajectories to make every hit at least try to count. Besides all that, the equation for kinetic energy is weighted for velocity to matter more than mass. KE = 1/2 mv^2 What this means is that if you double your mass, you double your force, but if you double your speed, you quadruple your force. <https://www.calculatorsoup.com/calculators/physics/kinetic.php> Let's do some math. Here's some simple examples: M = 1, V = 1; F = 0.5 M = 2, V = 1; F = 1 M = 1, V = 2; F = 2 M = 2, V = 2; F = 4 M = 4, V = 2; F = 8 M = 4, V = 4; F = 32 M = 10, V = 10; F = 500 M = 20, V = 10; F = 1000 M = 10, V = 20; F = 2000 M = 20, V = 20; F = 4000 I showed this without units, since that doesn't really matter at this point. As long as you use the same units, the differences are still the same. (If you just can't get past the whole "unitless" comparison, the mass is kg, the velocity is m/s, and the KE is Joules.) So what does this mean? Use high velocity, small mass rounds to try to slow down your adversary. Sometimes these are called railgun rounds, but these usually do more damage directly than actually slowing down someone. Also, you're still having to deal with Problem 2.2, which is Newton's Third Law of Motion. <https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion> ]
[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/123672/edit). Closed 5 years ago. [Improve this question](/posts/123672/edit) July 20, 1969, Neil Armstrong sets his foot on the moon surface. He declares : "*That's one small step for [a] man, one giant leap for mankind*". But what history books don't mention is that, as he gazes at the desolated landscape, he notices, a shining intriguing structure close to the horizon. When Buzz Aldrin joins him 10 minutes later, Neil points out this direction but, light has changed, and Buzz, thinking that Neil shows him the landscape, declares "*Magnificent desolation*". They walk back to the lunar module and Neil stops thinking about it. However, when he does his debrief at the NASA center, he mentions this intriguing structure, which arouse the curiosity of the scientists and the military. As matter of fact, one of the objective of Apollo 12 mission was to understand what Neil Armstrong caught sight of. Incredibly, the astronauts of Apollo 12 mission ( Charles "Pete" Conrad & Alan L. Bean) discovered the remains of an ancient advanced civilisation. This information is classified and all remaining Apollo missions true objective is to explore those vestiges. * My question is : what are the possible reasons which pushed the US government to keep secret this amazing discovery ? * **Bonus question** : - For what reasons did US government stop the Apollo program and thus the exploration of the vestiges as soon as 1972 ? [Answer] > > what are the possible reasons which pushed the US government to keep secret this amazing discovery > > > The US Government at this time was INCREDIBLY paranoid, and totally committed to trying to protect the status quo by whatever means necessary. Discovery of proof of intelligent alien life would, if nothing else, be incredibly destabilizing and for these people, keeping it absolutely secret would be a no-brainer. Allowing the discovery to go public would cause massive social and political upheaval, and would likely spur the Soviet Union to double down on their own space program to ensure they weren't left out. > > Bonus question : - For what reasons did US government stop the Apollo program and thus the exploration of the vestiges as soon as 1972 ? > > > Easy: They didn't. Instead they took the entire lunar program and put the entire thing under the tightest secrecy possible. Remember: The US Government's primary objective at this point is to keep the Soviets as far away from the moon as possible. The best way to do this is to make the moon look BORING. So. They finish out the Apollo program by using the subsequent missions to gather as much information about the artifacts as possible with the technology possible. Then they shut it down, at least publicly. The USA is Done with the Moon, and the Soviets chalk it up as a Loss and move on to new things. In the meantime, a massive secret program launches to analyze all the images and artifacts returned from the moon. Many of the spectacularly sophisticated and expensive Keyhole reconnaissance satellites are actually put into Lunar orbits rather than taking pictures of Soviet missile sites. The United States put up a desperate front to convince the USSR that the entire attention of the United States scientific and military establishment is still focused on the prospect of confrontation with the Soviet Union, while instead those resources are entirely focused on the moon. In 1973 NASA launches Skylab. Ostensibly a primitive attempt to explore the challenges and possibilities of orbital space stations, Skylab is actually intended to be an orbital launchpad and refueling station for a new series of lunar expeditions. The technical challenges associated with trying to SECRETLY get the second generation lunar modules into orbit and launched into lunar trajectories prove to be insurmountable however, and in 1978 the program is shut down. In 1983 the deployment of the Space Shuttle finally gives NASA the tools they need to quietly return to the moon. Contrary to popular opinion, the stealth programs headlined by Lockheed's Skunk Works have had the primary objective NOT of developing stealth aircraft, but rather the creation of stealth SPACECRAFT that can be carried into orbit by the space shuttle to come and go from the moon in secret. Completely unbeknownst to all but the inner circle, every third shuttle launch actually carries a stealth second-generation Apollo module outfitted with Radar Absorbent Materials and ECM. Once in orbit the new "Hermes" modules quietly make their two-week journeys to the moon and back with mixed crews of astronauts and specially trained scientists. The moon program is shut down along with the shuttle after the Challenger disaster results in the loss of not only the publicly acknowledged shuttle crew, but also a fully crewed lunar probe with six more astronauts and scientists, including the project lead. Missions continue, although at a reduced frequency, until the loss of the Columbia in 2003. The grounding of the shuttle fleet immediately afterwards required an emergency re-entry procedure to be executed a week later by the returning crew of the final second-generation lunar mission, as the shuttle mission that had been scheduled to ferry them back down to earth had been cancelled. This marks the end, at least for now, of manned exploration of the moon, although over the two and a half decades a massive trove of detailed examinations and artifacts have been collected that will keep an army of exo-archeologists busy for a generation. EDIT: In a moment of extreme irony, NASA **themselves** conceive and propagate the idea that the moon landing was faked, adding another layer to the smokescreen and helping support the idea that the moon is Boring. [Answer] I came up with some quick ideas that may help get your creative juices flowing. **Reasons for Keeping secrets** *Advanced Technology:* The space race was at the height of the cold war with the USSR. The careful balance achieved during that war was (in the opinions of those involved) largely reliant on the policy of mutally assured destruction through the use of nuclear arms by either side. However, The apollo missions discovered some serious hardware on the moon, things that would tip the balance of power so far in favor of the USA that the USSR would likely feel compelled to respond. For this reason, the files were sealed away. *Dangerous Space Organism:* The apollo program discovered a potentially dangerous organism on the moon and brought it home. Apollo 13's mission was actually to bring home a sample and as such, they had problems when it "breached containment" on the way home from the moon. The cover story to this was that they had "trouble" in space, thereby detracting from the truth if it were to ever come out. Since it was common practice at the time to quarantine apollo astronauts, no one was the wiser when oen of them slipped the sample phial to the CIA operative in the recovery party at sea. **Bonus Question:** *Soviet Encroachment:* The americans realized by 1972 that they were starting to "leak" information to the USSR. This was of grave concern because of the advanced technologies and potential discoveries on the moon. As a result, the public exploration of the moon was halted by order of national security interests rather than the desire to stop, this was to ensure the soviets never felt "extra compelled" to go to the moon like the americans had. IT was essentially a bluff. For good measure, and as a sign of good faith, the US space agencies shared their moon dust and moon rock samples with the soviets. Nothing to see here. *A darkness lurks on the moon:* Apollo missions left behind some rudimentary remote controlled robots (possible with the era's technology) to explore the ruins on the moon. One of the robots was designated to investigate a section of the city deamed a bit too dangerous for entry by astronauts at the time (to be visited later when they could smuggle space soldiers into an apollo launch instead) but the remote robot ended up going dark minutes into its run. The second (and last) robot left on the moon tried the same but managed to relay the image of "something in the shadows" before it lost contact. Minutes after both of these incidents, mission control received the same , cryptic radio message, an unknown sequence of noise that at the time was considered undecipherable, at least for now... EDIT: For some spelling mistakes. [Answer] # The human ego is fragile America was at its technological peak, new worlds were being explored, the excitement was there for the future and what could be done with this new technology. The last thing needed was clear evidence that someone had got there first. Given that this was the height of the cold war, people would immediately assume it was the Russians, the space race had been lost, and all hell could break loose. It could be the end of the American way of life. Better to say nothing and let it be for the duration. The best way to let it be is to find a reason to shut down the whole programme and for nobody to set foot there again for 50 years. [Answer] Since they didn't fully understand what the shining structure was, they had several reasons to keep it secret. * It was still in the middle of the Cold War. Whatever there was on the moon, the US government did *everything* in their power to keep the knowledge from the Soviets. That included keeping the knowledge from as many people as possible, as almost everyone could have been a spy. * They needed time to examine and study their findings. there's only so much oxygen you can transport to the moon, so they needed several missions to have enough time to study the structure and bring objects back to Earth. * Of course they wanted all technology and knowledge for themselves. Again, the Cold War was still waging on. What did they actually do? Obviously, they couldn't excavate anything in a big scale because that would be visible from Earth. So they cut a hole in the structure and found a maze of corridors, but not much else. They brought anything small enough to be transported back to Area 51 (and some worthless stones as red herrings to keep the Soviets away) and are since investigating these objects on Earth. Why did they stop the Apollo missions? Because they *still* don't understand the objects they brought back from the Moon. In order to keep this a secret, especially in modern times, you can have only a *very* limited number of people knowing of and working on the research. Obviously, you cannot simply plug a battery into an alien object and expect it to light up. Contrary to popular TV shows you cannot plug a USB cable into them and interface our technology. It took them years to realize how to interact with these objects and they simply don't understand the output of them. They haven't got any tangible results and there was neither any death ray gun nor a mind reading device among the shiny souveniers from the Moon. Without results, no money. That was the end of Apollo. [Answer] I liked YElm's answer until he came to the end of the missions. Genuine alien relics in Area 51, and the government **stops** the investigation? No way, not even for a good story! * They found something and Apollo 12 returned with samples. * The focus of the Apollo missions changed completely, overnight. Unfortunately they couldn't get more rockets and more trained astronauts overnight, so the rate of launch did not increase. The urgency and the readiness to take risks went up, causing Apollo 13. * Apollo 14, 15, 16, and 17 poked at *things man was not meant to know.* Apollo 17 entered an alien base and accidentally activated the defense system. They got away while the weapons dug themselves out of the regolith, but space has become much more lethal. Remember those lost Mars missions? Same cause. * There are conspiracy theories about a Soviet moon mission. Weave them into the story. Alternatively, a computer or the like **told** the astronauts not to come back, and made credible threats. ]
[Question] [ This question is inspired by a premise from the video game *Batman: Arkham City*, in which a portion of Gotham City has been closed down by the public to be reserved for prisoners from such places as Arkham Asylum and Blackgate Penitentiary. Unfortunately, that was only a temporary environment, as the real agenda, codenamed "Protocol 10", was to cull Gotham's excessive population. The context in this scenario is different. In the near-future, some global or near-global disaster has forced the construction of multiple Shimizu Megacity Pyramids, Ultima Towers and X-Seeds 4000, arcological structures that are supposed to support great populations with minimal area space. Which means that any of the old cities, like New York, Tokyo, Beijing, Sydney, Houston, Detroit, Chicago, London and many others, would be viewed as undesirable by the public, thus converting these old cities from public settlements to extra-extra-large prison colonies. Provided that extra security measures be done--like filling the outside spaces with walls--could converting a large, metropolitan complex into a prison be feasible, much less wise? *For further clarification, **physical feasibility** is the only target in this question. Whatever happens inside--gang wars, survival struggles, other kinds of social unrest--is not the point.* [Answer] Define prison. A lot of electronics these days is manufactured in China. Some cities are practically industrial compounds where people work [34-hours shifts](http://www.dailymail.co.uk/news/article-1285980/Revealed-Inside-Chinese-suicide-sweatshop-workers-toil-34-hour-shifts-make-iPod.html) for minimal pay. Steel wire meshes are fitted to buildings to prevent suicide, because enough cases happened for it to be a thing: [![Sadness](https://i.stack.imgur.com/glVCa.jpg)](https://i.stack.imgur.com/glVCa.jpg) The workers don't own their own houses. They sleep in dormitories that belong to the factories: [![More sadness](https://i.stack.imgur.com/q9v7d.jpg)](https://i.stack.imgur.com/q9v7d.jpg) [![Even more sadness](https://i.stack.imgur.com/056LQ.jpg)](https://i.stack.imgur.com/056LQ.jpg) The article in the link claims there are no luxuries such as air-conditioning. I will let you imagine other things such as bathrooms. They have no money to pay for groceries nor anything. Food is part of their payment. They eat what the factories give them to eat, at rigidly stablished times: [![Yet more sadness](https://i.stack.imgur.com/TvfDU.jpg)](https://i.stack.imgur.com/TvfDU.jpg) All in all, they spend their life in the factories. They don't leave on weekends, they don't choose what they eat, they don't choose when and where they sleep... I see no difference between this life and the life of an inmate. --- All this was just to show that a penal city is not only feasible, we practically have the infrastructure for those. Shenzhen gets its food and water from outside, and "imprisons" people by mixing economical hardship with an oppresive government. In a fictional world, all you have to do for a penal city to be sustainable is to choose its residents based on criminal conviction rather than economical need. [Answer] ## It depends on where the guards are **If the guards are in the city, then that's a big prison.** You can expect to see the same kinds of prison riots that humans have observed in all kinds of actively oppressed populations going back to antiquity. Expect this kind of situation if the arcologies are actively trying to punish the prisoners. Oppression rarely works out well. Given the scale of the penal institutions, it will be very difficult for the prison's security apparatus to enforce uniform control. Expect to see the emergence of [no-go zones](https://en.wikipedia.org/wiki/No-go_area) where the prison authority cannot exercise full control. Personally, I think this is the least likely option since it costs so much to hire and equip guards. Also, if this is a true prison population then the arcologies are on the hook to provide food and medical care for the inmates. If you're populating New York purely with inmates that have to be supported, your arcologies are either wealthy beyond reckoning or this program won't last long. **If the guards are around the arcologies to prevent the prisons from getting back in,** then it's possible that we'll get an Australia style penal colony. When given a chance to start new lives, the former prisoners started businesses, married, had children and built a civilization in the middle of nowhere. I think this is the more likely as it's cheaper to just eject people you don't like from the arcologies and make them fend for themselves. Given how well humans are at surviving, the inmates/undesirables will find a way. If you did it right, these ex-arcology people would be a useful source of trade and "off-shore" labor for the arcologies. [Answer] # What is the goal? As I understand it, the people in your story plan to build walls around the cities and put undesirables inside. Is the goal to get rid of *most* of them, without getting their hands dirty, or do they consider it necessary to keep *all* inside? Building those walls is feasible. Consider the [Berlin Wall](https://en.wikipedia.org/wiki/Berlin_Wall#Structure_and_adjacent_areas) and the inner-German border during the [Cold War](https://en.wikipedia.org/wiki/Inner_German_border#1967%E2%80%931989:_the_%22modern_frontier%22). What happens inside a surrounded city *without* resupply and government services is going to be ugly. Again going to history there are the [Jewish Ghettos](https://en.wikipedia.org/wiki/Nazi_ghettos) in Nazi-occupied countries, but note that those were intentionally genocidal. But even without such intentions, simply cramming people together in an *urban* area without surrounding countryside won't work because they can't feed themselves. That brings up questions of escape attempts. The Communist regime had police and secret police "inside the prison" trying to prevent [escape attempts](https://en.wikipedia.org/wiki/Republikflucht), yet those ranged from [tunnels](https://de.wikipedia.org/wiki/Liste_der_Fluchttunnel_in_Berlin_w%C3%A4hrend_der_deutschen_Teilung) to [home-made balloons](https://de.wikipedia.org/wiki/Ballonflucht) (German links, but glancing over them shows the scale of attempts). Would the people guarding the wall have agents inside to detect such activitiy? [Answer] Yes - although a custom built structure would be way more efficient as it would have less pre-existing escape routes (sewers, railway lines, exterior windows) to secure. You would need to seal off the perimeter so a surrounding wall would be essential. Beyond this there are a few issues to consider: * **Access** Does anybody need to access the confined areas? In a close historical analogy, during the sealing off of ghetto cities by the Germans during the Second World War local populations entered to trade with the confined population. This made it much easier for people, information and goods to be smuggled out. * **Security** How likely are the confined populations to try and escape? No wall is going to be solid enough to keep a determined population in for ever. If people are going to attempt escape then border guards will eventually be required. * **Health and Resources** Are there sufficient resources within the enclosed area to keep the residing population alive and healthy? If there are there may be less will to escape leading to a diminished need for external security. On the other hand, if they are literally zones of slow starvation there will be a strong incentive for incumbents to penetrate the exterior barrier. Further, if any 'outsiders' live near the camp then their health is an issue. Disease will not stop at the barrier and plague could easily spread from poorly fed or treated prison populations. However, there is no practical reason why this wouldn't work and the physical sealing off of cities or districts has often been carried out in history. [Answer] Cities are an intense area of study - from Urban Design to town planning, transport and economic development. I used to study in the field of Urban Design, and early on you realise the complex nature of cities, they are incredible objects that defy comprehension often as they are so integrated with culture, engineering, architecture, and urban planning. From a practical point Planners struggle even today to deal adequately with infrastructure and to cater for growth and development. Development is unpredictable, land uses can be regulated but in the end people would want to do what they like and inhabit the city as they see fit. Cities also evolve to suit economic and political situations at the time - these are perhaps the largest factors affecting a modern city. So a city as a prison? Well you can start off that way... but wait and see what would happen in a couple of decades. Have a look at the following cities: * SINGAPORE: An island city, isolated, no resources, import all goods, but still an economic powerhouse. Why? Because it is an ideal trade mid-point from the Indian Ocean to the Pacific, Asia to Australasia. * SYDNEY: Started out as a penal colony! Full of criminals. But now it is one of the most liveable cities on Earth, highly regarded, and a defacto capital of a peaceful nation. Obviously didn't end up the way it started. * MUMBAI: Slums and more slums, full of the poor. Yet now it's development scale is off the planet - there is a massive amount of money and money flowing into India, and many are now reaping the benefits. Next to slums are new Millionaire condominiums. * BERLIN: West Berlin was surrounded by the most fortified wall at the time, surrounded by East Berlin. Yet the wall was to keep people OUT, not in, as so many caught in Soviet society wanted to 'escape' to the 'walled city'. This was a prison, yet strangely in reverse. The above is not to really define a simplistic idea of a prison city, but merely to demonstrate the complexity of situations and cities make oversimplification impossible. A wall around a city is the least influencing factor of what the city actually becomes, it is more what it represents. The city will grow, shift, 'break it's banks', evolve and change, and it would be difficult to predict what its destiny will be. ]
[Question] [ There's a pariah country in your neighborhood that is in war with one of your enemies. Officially you condemn the war and support the UN resolution for peaceful settlement, which presents yourself as an enlightened peacemaker. Unofficially it's in your best interest to provide clandestine support to their war efforts as long as it's done discreetly and doesn't end up on the front pages in the media. The longer the enemy is busy with them the better. How to maintain unofficial diplomatic relations if you didn't have an embassy and opening one would be very bad for your image? [Answer] You can use a "man in the middle". Country A doesn't have an official relationship with country C, but both A and C have a good relationship with B. Through B, A and C can have diplomatic contacts. It was done between during WW2 between Italy and UK using Vatican City, if I remember correctly. [Answer] There are lots of possibilities, ranging from official bureaus just not called embassies (and not enjoying the special protected status of embassies) to clandestine contacts maintained by some secret services. Delivering support and weapons to them secretely is somewhat more difficult, because a weapon can fall to hands of the enemy and may be traced to its origin. But in real world there are shady weapon dealers around selling surplus weapons from old conflict zones and failed states, so you can organise a delivery of former Yugoslavian kalashnikovs without revealing the sponsor to the public. [Answer] You use corporations as a front. Business men meet in a third country. Perhaps both sides happen to be on vacation. Neither of them is official tied to the goverment so not under any embargo. This way you keep your hands clean and only the people directly involved are aware. Another would be Phone calls, phones exist and I doubt the country is completely cut off from the world's cellular network. Again you could use a man in the middle set up to keep distance. It's less discreet but as hard to track down for the media. They can't legally tap any phones. ]
[Question] [ I'm working on a sci-fi/fantasy world set in a solar system with a few habital, currently-being-colonized planets. Most of the action will be taking place on the surface of one of them, but I want background detail to add to the setting and give me info for future developments. I was wondering if a solar system could exist with massive amounts of natural debris and dust, such as asteroid belts and the like, that affected space travel in such a way that ships couldn't accelerate too fast for fear of losing maneuverability and hitting something. I'm talking **dense.** This would also add an element of uncertainty and surprise to space battles, as normally you would be able to see your opponent from far away using sensors, but in the dust and debris, stealth would be much more feasible. On another note, I want a Star Trek or Mass Effect kind of ship handling, and to me, imposing this sort of speed limit will help with that. Any suggestions along that vein would be most appreciated too! EDIT: Wow, didn't expect so many helpful responses, especially on my first post ever! You guys are making my life a lot easier. I'm leaning toward a debris disk/field right now, as that seems perfect for what I had in mind. For additional info, the reason that there are people in this solar system is that that's where life appeared, and as they haven't developed FTL tech, they're basically stuck there. I think I'll call the system and the star Apex. The 'homeworld' colonizes a couple other planets in the system, and after a civil war between the colonies, one of them suffers orbital bombardment, plunging the few survivors into a post-apocalyptic mess hundreds of millions of kilometers from home. [Answer] What you described looks just like **very young** solar system, where planetary formation is a process still in progress. Your dust and asteroids is simply a [protoplanetary disk](https://en.m.wikipedia.org/wiki/Protoplanetary_disk). Planets are on the small side, still clearing their neighborhood. Probably no native life there, but easier to mine. This might be a reason to go there at all. Can't find source, but I remember reading somewhere that thickness may be about 19% of diameter. That's quite a lot - and interesting stuff is inside. Also, you seem to care about stealth. Risk of being attacked may outweigh risk of traveling inside stealth-able environment. Or not, but you still need to get in and out. [![An artists rendition of a proto planetary disk from the wikipedia article](https://i.stack.imgur.com/EAiV7.jpg)](https://i.stack.imgur.com/EAiV7.jpg) [Answer] # Give it a [protoplanetary disk](https://en.wikipedia.org/wiki/Protoplanetary_disk): ![](https://upload.wikimedia.org/wikipedia/commons/e/eb/NASA-14114-HubbleSpaceTelescope-DebrisDisks-20140424.jpg) Image in the public domain. Protoplanetary disks are circumstellar disks that form early on in the life of a planetary system, from the original protoplanetary nebula around the star. They can survive for over 10-20 million years (see [Mamajek et al. (2009)](https://arxiv.org/abs/0906.5011)), meaning that life likely could not develop, but you could have loads of protoplanets and related bodies around while still retaining plenty of dust. I would recommend a [debris disk](https://en.wikipedia.org/wiki/Debris_disk), but they're not necessarily as dense. Additionally, they won't necessarily have bodies as large as protoplanets inside them - although even asteroid-sized bodies can be hazardous to space travelers. What will the densities actually be like? They can vary quite a lot over time. Here's a graph of surface density $\Sigma$ vs. radius $R$ from [Dullemond et al.](http://web.gps.caltech.edu/classes/ge133/reading/ppv_preprints/sec6-6.pdf): [![enter image description here](https://i.stack.imgur.com/pmEpd.png)](https://i.stack.imgur.com/pmEpd.png) Initially, there are maximum surface densities in the order of 10,000 grams per square centimeter; after 3 million years, this peak has gone down to 100 grams per square centimeter. We can use Equation 5 from [here](http://www.ifa.hawaii.edu/users/jpw/ism/reading/williams_disks.pdf) to find the spatial density: $$\rho(R,Z)=\frac{\Sigma(R)}{\sqrt{2\pi} H}\exp\left(-\frac{Z^2}{2H^2}\right)$$ At an elevation of $Z=0$, and assuming a scale height consistent with that of [Chiang & Goldreich (1997)](http://iopscience.iop.org/article/10.1086/304869/pdf), then at a distance of about 1 AU, $H\sim0.045$ and at a time of about half a million years, the density is . . . quite substantial. --- [Sean Raymond's suggestion](https://worldbuilding.stackexchange.com/a/53038/627) of a debris disk might be better than my answer, for a few reasons that he pointed out: * Debris disks aren't so short-lived. * They can contain large rocky planets; the debris disk I suggested only holds small planetesimals You should strongly consider that. [Answer] It's not plausible to invoke a protoplanetary disk: they are too short-lived. There's a ton of dust floating around in those disks because it's where planets are forming. If your planets are already formed (with non-molten surfaces) then the disk is gone. What you need is a "debris disk". In astronomer-speak, debris disks are belts or disks of rocky/icy leftovers of planet formation that produce enough dust that you can see them directly. Here are a couple of famous examples (note that debris is usually inferred from spectra rather than seen directly; these are prime examples): [![enter image description here](https://i.stack.imgur.com/8JX0Y.jpg)](https://i.stack.imgur.com/8JX0Y.jpg) Most debris disks are relatively cold, made of bodies on very cold (think Neptune-ish) orbits. But a few do have warmer belts closer to where terrestrial planets live. The trick is this: very dense belts don't last long. The best way I can think of to have a super dense debris field is to make your story take place during a late heavy bombardment-type event. Like the Solar System's bombardment (<https://en.wikipedia.org/wiki/Late_Heavy_Bombardment>) but much heavier. This is totally plausible from an astrodynamical point of view. [Answer] That solar system is just a slag pile from some Type 2 Civilization's strip mining operation. We thought it was natural when we arrived. Some kind of young solar system or a late-blooming proto-planetary disk; but its sun turned out to be too old for that. Also, most of the expected heavier metals were missing. It was a real mystery for a while. Then we found the first of the artifacts. No more than a thousand Earth-years ago, some very advanced miners reduced most of the system to dust and rock fragments. They left a couple planets intact. Probably used them as their mining camps. They even took most of the primary star's mass. It didn't used to be a dwarf. They left just enough mass to keep all this junk from floating away and causing havoc out in open space. This place would be a wasteland, except those ancient strip miners left some of their tools behind; mostly broken bits and warn-out parts. Probably junk to them, but precious artifacts and technological wonders for us. That whole solar system has become a technological boom town. It is the center of the 24th century gold rush! [Answer] Such a system wouldn't be colonised in the first place. In a protoplanetary disk, there's a lot of debris floating around, which is what you asked for. But that large amount of debris crossing planet orbits also means lots of impact events. These tend to do bad things to real estate values. Really bad things. Most sensible colonists would avoid this as way too likely to get a rock dropped on you from orbit. Unless there's some reason why you can't just go to the star next door. [Answer] You could make your solar system filled with a combination of frequent clouds of gas and frequent asteroid belts. This could potentially force slowness and allow stealth while still allowing for an inhabitable solar system. [Answer] There's an example of this, a later stage star with a crap ton of debris. The suspicion is that two planets within it collided. <http://articles.latimes.com/2014/mar/08/science/la-sci-sn-beta-pictoris-star-planet-gas-collision-comets-carbon-monoxide-20140307> Even if we're pretty far away, if Mercury hit Venus, we'd have a lot of junk floating around. Not sure, how long we'd live. [Answer] You can place an ancient megastructure on this system, like a Dyson sphere. Due to his abandonment, the structure collapsed long ago, creating numerous remains. Over time, theses remains started to collide at high speed, creating smaller remains. At last, you obtain a system with a lot of debris on various size, from dust to country-sized part. Any advanced civilization can easily and logically create such kind of structure. [Answer] I'm going to more or less disagree with everyone here. I don't think the option of [protoplanetary](https://en.wikipedia.org/wiki/Protoplanetary_disk) disk would work. If it's ***proto***-planetary, planets are not yet formed or still in the stage of big ugly magma balls, incapable of hosting any life. When a planet gradually cools down and terraforms itself to be capable of hosting life, several billion years would have passed and the debris would have been cleared by the planets. You could have another planet in the system to have collided with a [rogue planet](https://en.wikipedia.org/wiki/Rogue_planet) recently (i.e. few million years in the past). That will give you a nice debris field. But it would mean that planet would be frequently and heavily bombarded with asteroids. It would not be suitable for life. If somehow you were able to have a debris field and have a thin debris free strip for the planet, the debris would not affect spacecrafts. Because they need not to fly in the planetary plane, they can fly out of it and get out of the system. [![Weeeeeeee!](https://i.stack.imgur.com/QcoPS.png)](https://i.stack.imgur.com/QcoPS.png) So the alternative for you is to have your planet in a debris free zone, but give some incentives for the spacecrafts to go into a dangerous zone full of debris in another part of the system. --- Look at this breathtaking animation of Jupiter herding the asteroids: <https://www.youtube.com/watch?v=yt1qPCiOq-8> I got an idea from this. Have a star larger/hotter than Sun, where your habitable planet is around 5-8 AU from the star. Have a gas giant closer to the star. And then have an inner planet collide with a rogue planet few 100,000 years ago. The gas giant will herd the debris so your planet will not be affected much. And oh, the rogue planet was *crossing* the planetary plane, so the debris is not a disk, but a big mass ball of dust, sand, and rocks around the star. [![enter image description here](https://i.stack.imgur.com/cz5kr.png)](https://i.stack.imgur.com/cz5kr.png) And maybe your spacecrafts need to go near the star to recharge like [Rama](https://en.wikipedia.org/wiki/Rendezvous_with_Rama), or there's a valuable mineral that could be mined in the asteroid field. ]
[Question] [ I feel like this is the most noobish question ever. Anyway, imagine an asteroid hits Earth and the atmosphere is now full of particles, successfully blocking the Sun from Earth. There are people still alive on the planet. Assuming the sun isn't 100% blocked, enough for people to see their hands in front of their faces in "daylight" at least, does this affect electricity and how? **\*Further Clarification:** I'm referring to the electricity we use on our day to day lives from light bulbs to televisions and so on. So if the sun is blocked, will our homes still be running on electricity - that's the electricity I'm referring to. [Answer] Atmospheric dust **by itself** shouldn't have any major impact on generation or distribution of electricity. **The two are unrelated.** **However,** a fraction of the Earth's electricity production is based on current solar input, either directly or indirectly. There is the obvious: photovoltaic electricity production, [which globally amounted to a total of 41.4 TWh in 2012](http://www.energies-renouvelables.org/observ-er/html/inventaire/Eng/conclusion.asp). While this is a tiny sliver compared to [global electricity production](http://data.worldbank.org/indicator/EG.ELC.PROD.KH) ([also here](https://yearbook.enerdata.net/world-electricity-production-map-graph-and-data.html)), the global photovoltaic electricity producting sitting at almost exactly 1% of the US electricity production of 4,310 TWh, [some countries have significantly higher proportions photovoltaic electricity production](https://en.wikipedia.org/wiki/Solar_power_by_country) than others. You will also face indirect effects due to changing weather patterns. I would expect wind patterns to change, which may or may not have an impact on wind turbines, and you may very well see changes in other energy generation techniques as well. Blocking out such a large amount of the sunlight as you describe is going to cause global temperatures to plummet, which in human societies would lead to an increased need to provide heating in buildings (wild animals would also suffer, obviously). In summary, electricity supply from photovoltaic generation will obviously be directly impacted by sunlight being blocked (at this scale probably to the point of providing only negligible amounts of power, if indeed any at all), and other power sources may be affected as well as exemplified above. There is of course also the risk that the power grid has been damaged, but I would expect such damage to be primarily local or *possibly* regional in nature following an asteroid strike; the power grid is normally designed to be able to deal with failures without triggering [cascade failures](https://en.wikipedia.org/wiki/Cascade_failure#Cascading_failure_in_power_transmission), but whole areas may be cut off from the larger grid to protect the rest of the grid. You may also see secondary effects from the strike itself, but that won't be about electricity per se. The combined effect of all the above may be to force power rationing techniques in areas where affected power sources make up a noticable fraction of the total power mix. [Rolling blackouts](https://en.wikipedia.org/wiki/Rolling_blackout) is a power rationing technique that has been used in practice, and likely would be employed in such a scenario, assuming enough people surviving the immediate effects for society to continue to function at all. Rolling blackouts were done [in Japan after the 2011 Fukushima Daiichi disaster and more-or-less immediate shutdown of almost a quarter of Japan's nuclear reactors](http://www.bbc.com/news/world-asia-pacific-12731696) which led to a severe short-term power shortage. [Venezuela is doing something similar in 2016](http://www.bbc.com/news/world-latin-america-36108295) in response to drought. Generally speaking, if you can't service everybody all the time, then it might be better to simply tell people that until further notice and for defined periods of time during the days they will simply have to make do without electricity service; the alternative may very well be grid overload, which at best is going to lead to a total shutdown and automatic reset, and at worst may very well cause severe equipment damage. Backbone electricity grid transformers, isolators and so on is not something you can just walk into a store and buy; such parts often need to be manufactured to order, and delivery times of months is far from unheard of even at the best of times. Even if things are otherwise good, this is a scenario the grid operator is going to want to avoid at (almost) all costs. With modern, "smart" metering, it *might* even be possible to reprogram the meters such that power (watts, not watt-hours) draw above a certain threshold for a given period of time shuts down service for that user for a period of time, to reduce the peak load on the grid. Even if such provisions aren't normally allowed for, I'm sure in such a situation *someone* would *very* seriously consider the possibility. It's also worth remembering that even though electricity can be transmitted relatively easily over short to medium distances, moving electricity over large distances is a non-trivial problem, and one mostly avoided by having reasonably local power production. So for example, having enough electricity production in South America doesn't do much to help Canada cope, and the same goes with transmission across [Eurasia](https://en.wikipedia.org/wiki/Eurasia). [Answer] Nope. The dust in the air may generate a static charge, which in turn may increase lightning (even in the absence of storms), and blocking the sun will of course limit the effectiveness of photovoltaic cells (solar panels), if not render them outright useless. However sunlight has no bearing whatsoever on the movement of electrons through conductors, most of which are shielded from sunlight anyway (not because the sunlight has any effect on them, but because we tend to do silly things like wrap conductors in insulators to prevent people being electrocuted or circuits being shorted). This can also be seen in the fact that you can turn on your lights when the sun sets below the horizon, and up north here we can still turn on our lights, even when the sun sets and doesn't rise again for 3 months! Now, with such a catastrophic event, the power grid is very likely to have been disrupted if not outright destroyed. So while the physics of electricity remain unchanged, it's not merely plausible but almost a downright given that most people won't have power in their homes after this (if their homes even survived); even those far enough away from the impact to not have any direct impact on them likely suffered massive earthquakes that damaged or destroyed critical infrastructure, though those furthest from the impact are more likely to still have power or more easily repair their power grids. [Answer] A complete answer to this question needs to consider both electricity supply and demand. As far as I can see the existing questions only cover supply. In terms of supply, the main kinds of generation which will be affected are those which depend on weather but no form of generation will be unaffected. # Electricity Supply * **Solar Power** is obviously going to be directly impacted. Photovoltaic deals quite well with diffuse/scattered light, if the intensity of light is halved, then it generates about half the power. However solar thermal, which involves concentrating sunlight, requires bright direct sunlight and won't generate at all with a badly hazed atmosphere. Fortunately nearly all solar is photovoltaic. * **Wind Power** is likely not going to be impacted much at all. Wind has multiple causes, but as a rule wind is caused more by the rotation of the planet than by the sun. The cold outer planets have very high wind speeds. Wind turbines could still be damaged by dust or freezing temperatures (in locations where these weren't expected environmental hazards). * **Hydro Power** is ultimately dependent on patterns of rainfall, snowfall and snow melt. Reduced temperatures will reduce evaporation, reducing rainfall and snowfall. Snow melt will also be reduced. Some hydro dams can store sufficient water for several years of power generation and such large lakes will also resist freezing so if they are full when the asteroid strikes their output will not be immediately impacted. Hydro power plants without enormous reservoirs could be more quickly impacted, and might stop producing altogether if their river completely freezes. * **Thermal and Nuclear Power** may be badly affected where the lake or river which they rely on for cooling completely freezes, although it may be possible to use the hot water from the power station to maintain an artificial lake of tepid water. In the cases where the river dries up from lack of rain/snowmelt power generation will be halted. Distribution of fuel may also be disrupted by storms snowing in railways and roads, and ports freezing over. * **Electricity distribution** will also suffer badly. In cold climates blizzards can down power lines, sometimes leaving houses without power for weeks at a time. Areas which previously were not subject to snow or icing, suddenly will be, and the power grid will suffer extensive damage during blizzards and storms. # Electricity Demand The impact on demand is going to depend a great deal on the climate and the proximity to the asteroid strike. In some areas nearly everyone will be killed, which will dramatically reduce demand for power. Of course in those areas the power stations will also be be badly damaged or destroyed. In areas where most people and infrastructure survived demand might be either increased or reduced. * In **hot climates** the electricity required for air conditioning will be reduced which will reduce power demand during the middle of the day. If the temperature drops sufficiently that actual heating becomes necessary then the demand is likely to be severely increased. Reverse-cycle air conditioning can be used for heating too which is quite efficient. However in hot climates buildings tend to be poorly insulated and poorly sealed, and many people will suddenly require heating just to stay alive, and electric heaters are the quickest and simplest way of heating rooms - unfortunately they are also the least efficient. Furthermore, when air conditioning drives demand the peak demand is during the middle of the day, but the peak demand will shift to the evening/night. In some locations this wont matter a great deal, but in desert climates where extensive solar power is used to cover daytime demand there may not be adequate supply for night time heating. Also in sunny climates solar water heating is used extensively, with the sun blocked these units will fallback to electricity. * In **cold climates** the impact is also likely to be severe. In cold climates buildings will be better insulated and rely less on electrical heating, instead using heat pumps, gas, oil or wood. Electricity demand will still be increased however, as temperatures plummet far below the normal minimums. In locations where it is already difficult to supply peak winter demand, it will become impossible to satisfy demand, resulting in brownouts or blackouts. With disruptions to the grid caused by storms it will be a good time to have home heating which does not depend on electricity. Fortunately, more people in cold climates will have such heating options, but those who rely exclusively on electricity might be badly affected. [Answer] The only electricity it affects directly is solar power generation because it takes sunlight and converts it to electricity. Now there are plenty of secondary affects that could cause issues with electricity generation and distribution. Difficult to burn coal, or get coal to the power plants, same with oil etc. Power lines might fail or start sparking and grounding with all the 'stuff' in the air. But if the power plants (coal, nuclear) can run and the transmission lines are still operational then it would not affect electric power. [Answer] > > "We don't know who struck first, us or them, but we know that it was us that scorched the sky." > > > -- Morpheus, *The Matrix* > > > Electric power generation works by converting other forms of energy into electric power. Depending on how long sunlight is blocked, many of these other forms of input energy will likely run out. * Reduce insolation for minutes, and photovoltaic and solar thermal plants produce no useful power. * Reduce insolation for weeks, and weather patterns change, interfering with wind and hydroelectric power. * Reduce insolation for months, and you block plant growth, interrupting the supply of corn for ethanol and soy and algae for biodiesel. At this scale, you start to get human starvation too, as the supply of food is likewise interrupted. Without humans to monitor generators, they start to fail within a week to six years, as illustrated in the speculative TV series *Life After People*. (See [Life After People Wikia](http://lifeafterpeople.wikia.com/wiki/Category:Power_plants) for more info.) * Reduce insolation for thousands of years, and you block plant growth enough that decaying plants and algae cannot renew fossil fuels. Coal is essentially compressed peat, and petroleum and natural gas are algae that have been buried and pressure-cooked in anoxic conditions. * In theory, tidal and nuclear power would be less affected, so long as humans remain around to staff the generators. [Answer] Well, it might. But only a little, for now. As others have pointed out, we only get a small portion of our energy from solar power. However, the Sun is indirectly related to other methods of producing electricity: * **Wind power:** The Sun heats air, which can produce currents that cause [wind](https://en.wikipedia.org/wiki/Wind). We can capture some of this energy using wind turbines. * **Hydropower:** The Sun also heats water, causing some to evaporate. It's responsible for the water cycle. Without the water cycle, places filled with water that aren't filled by water from springs won't receive as much water. This can be troublesome for rivers, which means that hydropower will be less effective. ]
[Question] [ In this context, I will define a Roguelike RPG world to be a world where a lone adventurer fights scores of monsters who drop magical weapons, armor and artifacts that the adventurer may pick up, use, and sell. The specific games I am thinking about are games like Nethack, Sword of Fargoal, Dungeons of Dredmor, Dungeon Crawl Stone Soup, and some others that have deep dungeon diving and little territory above ground. **Consider these points.** Usually there is only one person in the whole world who travels around fighting monsters. These monsters may drop items that sometimes do not make sense in the context, either due to the items size or the monsters typical eating habits. An example would be a bat dropping an Iron Sword or a Wizard dropping a suit of Iron Armor. All the other characters in this world just stay in the relative safety of their town or towns. Somehow they are able to survive in an economy based entirely on the loots of the lone adventurer. There is an infinite amount of loot in the world. Typically the deeper you go underground, the more likely the magically enhanced loot will be dropped by the monsters. Those monsters also get tougher and more fantastical the deeper underground you go. There are other aspects of Roguelike worlds that could be considered, but I will leave them for another question. --- I know this might be a silly question, but I am hoping that the answers will be interesting or imaginative. There are so many Roguelike RPGs these days that I think the depth of their thematic potential is worth considering. **Is there any plausible explanation, whether fantastical or scientific, that could describe how a Roguelike RPG world could exist?** [Answer] The basic assumption of such games is that the hero can visit only the locations interresting for them. The rest of the world with working economy and people living their ordinary lives is not important, so this is not on the map. This doesn't have to mean that it doesn't exist. Perhaps there are other ways, but I understand it as something like [Mythago Wood](http://en.wikipedia.org/wiki/Mythago_Wood), where some magic overrules ordinary laws of physics. Some dark, mysterious power lies in the bottom of the dungeon; perhaps another plane of existence connected to ordinary reality, making the border (dungeon and perhaps some area around it) twisted. The monsters could be solid, physical, and than everything would be as [DonyorM](https://worldbuilding.stackexchange.com/a/219/95) wrote. Or the other world might be "spiritual", and they appear physical due to the contact with solid reality in the area of "mixed physics". The deeper in the dungeon, everything is closer to the essence of the other plane, allowing the monsters to "project" their true being into more potent forms. As the hero goes down dungeon levels and up character levels, they become more and more imbued with the essence of this strange world, and thus more capable of hurting the monsters. They become more and more "solid" for the inhabitants of the other plane, who otherwise regard us as soft "spirits". SO the hero doesn't even notice that the world ressembles the "ordinary world" less and less and that it is less and less solid to ordinary world's standards. As they return, they return back to their normal nature, getting more real - again, no reason to notice it. The loot is nothing the monsters carry with them. A monster can have a giant maul and drop just few coins, or a swarm of insects can drop halberd - there is no or very vague connection. So the weapons the monsters use are just part of their "body", which vanishes when it is destroyed and they cease to exist, or return to get a new "body" somewhere. The loot is something given by whoever or whatever enforces laws of the strange reality of the other plane - who defeats another being, gets some reward, that's simply how that world work. These rewards belong to their new owner, and get imbued to ordinary reality as they leave the depths of the dungeon (becoming useful for selling to ordinary merchant, who will use them in ordinary economy). My world is "ordinary fantasy", but I have already created few dungeons acting almost like this (well, upper levels only, and halberds didn't fall from dead animals) in my RPG campaign in it, and everything was fine and even the most inquisitive players were happy. [Answer] Anything is possible. First, let's start with the economy. Scientifically, I doubt a whole world economy could be sustained on one "lone-adventurer." But it's unlikely that any of these worlds are actually like that. Each town is likely self-sufficient. They probably have their own economy, with blacksmiths, farmers, and merchants. Now as for loot and monsters, oversized loot is a little difficult scientifically, but under fantasy rules, there are possibilities. For example, monsters are magic. They can carry an infinite number of things in a hidden "flap" or pocket. Whoever created them gave them this power. As for the infinite loot, it's just that the game takes place after the world has fallen too monsters. Countless towns have been destroyed and looted. In the space of one game, no one can collect all the loot. Whatever created the monsters is underground. So from underground the monsters come. The monsters on the surface were the first monsters created, the experiments. They moved to the overground when they were driven out by the new monsters. The newer monsters are stronger, but stick closer to their creator, underground. So there you go, Rogue-like RPGs possible in a nutshell. :) [Answer] Personally, I've always thought of Dungeon Crawl Stone Soup as an allegory for the special purgatory of an obsessed being whose personality became so fragmented that he endlessly sent pieces of himself into the depths of a horrific death trap only to pursue some fabled thing for no rational reason. In his many incarnations, he acted out a fantasy of slaughtering everything around him while subsisting on their raw flesh, often even finding his death at the hands of his own specters. Ultimately, the Roguelike story is a horror story about the madness of obsession and, like all good horror, derives its impact from the psyche of the one who consumes it and, therein, becomes consumed. In such a sense, Roguelikes are implausible only in their packaging; once unwrapped by the player in playing, their reality is made manifest. Have 'Fun'. [Answer] Basically, **NO!** . . . unless many things were changed. > > Usually there is only one person in the whole world who travels around > fighting monsters. > > > Maybe the player almost never runs into any such person, but one of the more interesting features of *Nethack* and others is that you can encounter the bodies and/or ghosts of your (or on a shared computer, others') previous characters. Also, although you didn't list it specifically, in *Dwarf Fortress* you can (with difficulty) retire and then rejoin your characters to form a group of adventurers. Also the background text. character class descriptions, hall of fame, and the shopkeepers etc all acknowledge the existence of adventurers as a class, even if during gameplay, there are pretty much not multiple adventurers running around at the same time, and certainly not wiping out the dungeon ahead of you. That being said, some aspects of this I feel are reasonable, and others not. Certainly adventurers may be rare... they probably would be. And, given what happens to the world when an adventurer goes out and doesn't get killed right away, there HAS to be only a very rare number of such adventurers, or the world would have been purged of monsters long ago. Which leads to one of the most implausible things to me, which is simply *Dungeons & Dragons*-style hierarchical character improvement power levels. The conceit started with that game and copied by huge numbers of games, is that trained human warriors start out slightly better than minor opponents, but hopeless against medium monsters, and that by killing a dozen or a few dozen monsters (and healing amazingly quickly between each battle) they can become ever more powerful on a very steep power curve until eventually a hero is about as powerful as Superman, but the world is full of still more super-monsters, etc etc. Which is basically ridiculously implausible and unsustainable, at least in the way it is typically implemented in such games. However, if those mechanics (which involve killing hundreds of foes and somehow gaining a superhuman ability to sustain injury) were replaced by something involving skill and intelligence (where characters learn how to survive by being smart and avoiding combat and injury almost always), there might be some hope for an actual world with highly-experienced adventurers not requiring superhuman powers nor annihilation of hundreds or thousands of victims per hero. > > These monsters may drop items that sometimes do not make sense in the > context, either due to the items size or the monsters typical eating > habits. An example would be a bat dropping an Iron Sword or a Wizard > dropping a suit of Iron Armor. > > > This is a good point but is less sloppily done in Roguelikes than it is in their action derivatives such as *Diablo*, *Dungeon Siege*, *Torchlight* et cetera, in which animals drop human equipment. I think the best explanation here is that usually this should not be taken to mean that the handless unclothed monster actually had a suit of armor or whatever, but that such loot were nearby to where they were encountered, and is only findable after the monster is slain... possibly again items lost by victims of the monster. However I feel this is a concession to sloppy game implementation. Often in Roguelikes the loot is just lying on the floor near a monster, which makes more sense. As for world plausibility, it would be realistic if the treasure found were all remains discarded and scattered from previous adventurers or original inhabitants of magical strongholds... but the way these and other games tend to have so much treasure lying randomly everywhere... no, that seems almost impossible unless a dragon hoard, battlefield aftermath AND a wizard's guild storehouse were distributed by a few years' scattering by the Bat monster from Atari 2600 *Adventure*. The weapons and tools are far more plausible than consumable magic items such as potions and scrolls. To see what would be plausible, play through a dungeon and then wander back the way you came, looking at what you left behind. Of course, there would also be more stuff left behind if the game didn't allow the player to carry an implausible amount of junk with them. > > All the other characters in this world just stay in the relative > safety of their town or towns. > > > That sounds extremely plausible to me, and is what most people do on earth all the time, and especially is what most people did during the corresponding time period. > > Somehow they are able to survive in an > economy based entirely on the loots of the lone adventurer. > > > It never occurred to me that the adventurer was keeping the village alive with his loot - in which game did you see this? It seems clear to me that the villagers in these games get their requirements from non-adventuring activities, and that economy in the modern sense has very little to do with it, let alone the adventurer. The adventurer in a Roguelike can usually join them by leaving the dungeon or adventure area, at which point they generally get a hall of fame entry saying they retired or whatever instead of that they died. i.e. In our plausible Roguelike world, they would farm and hunt and fish and craft in safe places that might or might not be shown in the game (which tends to omit or downplay safe places to focus on the adventure). > > There is an infinite amount of loot in the world. Typically the deeper > you go underground, the more likely the magically enhanced loot will > be dropped by the monsters. Those monsters also get tougher and more > fantastical the deeper underground you go. > > > I was about to say that it wasn't really infinite, but then I considered that not only do some Roguelikes have some regenerating Infinite Dungeons (e.g. some places in *ADOM*) but practically all such games do have randomly generated monsters that appear as the hero wanders around, and they do generally have a chance to drop more loot. I would say that the thing that is *most* implausible about that infinite regeneration, is the *rate* at which it occurs, as well as the general absence of any findable path by which the newcomers could appear. The most plausible way I can think to explain that is they must be entering from passages the player has no access to, or they are being teleported in by dark magic. It might be seen to make some sense that the more powerful monsters would be lower down and have more valuable loot, especially if it were provided by previous dead adventurers, the better ones making it further down before dying and leaving their gear. However that doesn't help explain why newly-arrived monsters, particularly ones with no way to carry anythings themselves, result in usable equipment such as a suit of armor or magic book when slain. What WOULD make more sense, sort of, would be: 1) If the better equipment was actually appropriate to and being used by the better monsters. The Death Knight probably does have some interesting weapons and armor, some of which might still be usable after beating him. 2) The reason for this dungeon existing and having monsters might be some wizardly alliance or demon sect or something that intentionally populates and equips the dungeon, putting more common beasts up top to stop intrusion without raising too much attention, while the lower levels are filled with more serious creatures with supplies that they are supposed to use on intruders. However these should be more organized than the random distribution in most Roguelikes, and they should tend to mainly be using that equipment against the intruders, rather than leaving it unused for the intruders to prosper with. > > Is there any plausible explanation, whether fantastical or scientific, > that could describe how a Roguelike RPG world could exist? > > > Again, I think the only real way to explain the type of world, would be to change the mechanics as presented in the games. The time scales are all wrong, as are the power scales, the carrying capacity of players, the usual layout and monster/loot distribution, and so on. I think though that you *could* correct many of those things and still have a world that is fairly similar to many aspects, but be much more self-consistent, sustainable and even almost plausible. I think one really needs to fix the holes in cause and effect before one could get anywhere. Why are there underground complexes? Some make some sense - there are mines and temples or even underground cities created by magic. That's no so bad. But what's living in there, why, what are they doing, how do they interact with each other, and the villagers survival makes sense - what are a random mix of monsters doing that has them manage to co-exist underground and have enough food and water and air and shelter? There can be good answers to those things, as seen in more thoughtful/realism-oriented RPG published adventures (generally NOT D&D, but some are better than others even there). [Answer] Here's an explanation... The dungeon is a window into multiple dimensions. If someone enters a room that is empty, there is a chance it will close the door, stopping time until an adventurer in some other dimension reopens the room and tries to kill you for loot. So in this model, there are no monsters at all...just all the greedy adventurers being trapped for others of their like to discover and kill. Like a Venus Fly Trap for Dungeon Delvers. [Answer] Loot is what they took off the body of the last adventurer to get that far.... ...loot gets better as you get deeper as adventurers that get that far have better gear... ...monsters get stronger as they don't want to be bothered by adventurers poking them all the time so stronger ones live as far away from them as possible....and then steadily weaker monsters are pushed out towards the higher risk edges. A bigger problem is the ecology of the area (how do all these monsters eat for example - each other would be a short term solution) and how the mines/caves/whatever got formed in the first place. Neither of those is easy to explain. [Answer] Kind of a razy idea, but maybe the monsters are just "spirits" that need a physical *anchor* to our reality, and that need to possess a physical object; they seem to favor possessing metallic objects, like coins and metallic weaponry (like, say, an iron sword); when they are slayed by our hero, they revert to the physical form they had before. Maybe the magic weapons are the remnants of the "spirit" of especially powerful creatures. ]
[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/139839/edit). Closed 4 years ago. The community reviewed whether to reopen this question 1 year ago and left it closed: > > Original close reason(s) were not resolved > > > [Improve this question](/posts/139839/edit) Let's say through some unexplained (and largely irrelevant) phenomena, an alternate timeline has suddenly "collided" with ours. The specifics don't really matter besides the idea that the two timelines are now connected. Perhaps it's only possible to send messages from one timeline to the other, perhaps there are portals that allow people and objects to travel from one to the other, perhaps even the two timelines have somehow "merged" to form a sort of patchwork earth with some geographic regions from one timeline and some regions from the other. Again, doesn't matter. Let's also say that our timelines split a few centuries perhaps in the early 1800s. Now obviously this is major, major news. There are now potentially hundreds of new nations with which to forge alliances and make war. Regardless, the various world leaders are definitely going to want to have a bunch of UN type meetings to discuss the new paradigm. Now one of the first things I'm sure they'll approach is the nomenclature that should be used to refer to things from one timeline and from the other. --- For instance, since the split happened in the 1800s it's more than likely there are a bunch of countries that have the same name now. You might have two sets of the united states for instance. They might even have the same flag (apart perhaps from a different number of stars). So what language should you use to differentiate between them? Well, the "traditional approach" has generally been to talk about timeline A and timeline B, so you'd be able to say A-USA and B-USA for instance. However, there's a problem with this: which timelines get to be A? Which one gets relegated to being B? It might seem like something childish and trivial to care about, but you should never underestimate a nation's willingness to engage in pointless posturing: "If we let them be A, then we'll be marked as weak! We have to make a strong first impression!" Another idea would be to look to the point where the timelines split and use whatever events did and didn't happen there to label the different versions of history. So, for instance, you could have the "No-napoleon timeline" and the "Napoleon timeline", except of course this might not be such an easily identifiable splitting off point (perhaps the split was a Vietnamese peasant eating breakfast an hour later or earlier which then butterflied its way into radically altering history). Also, going back to the Napoleon example I doubt people would appreciate having to refer to their timeline as the one where some random European dude they had never heard of *didn't* rise to power. --- Here are some criteria that any adequate timeline nomenclature system would seem to have to meet, at least to me (if I'm wrong feel free to correct me and explain why): * Not arbitrary. Things like timeline-square and timeline-circle are confusing and would probably get too easily mixed up. * Not too specific. This would be a convention that applies to the whole world (the whole two worlds) so it can't only be meaningful to a subset of it. * Not preferential. The naming convention can't imply that one timeline is the default, normal or "first" timeline. Things like timeline #1 and timeline #2 are out. As are "normal-timeline" and "bizarro-timeline". **So, what naming convention could be adopted to refer to the two different timelines and the entities they contain?** [Answer] # Named by History Look for a specific, major divergence in history, and name them by that. For example, one timeline has the North Atlantic Treaty Organization. The other, instead, has the Pacific Defense Conference (formed in the 1930s by the USA, Canada, Japan, Korea, and Australia to oppose the Axis powers of Germany, Italy, and China). So the first timeline is the NATO Timeline, and the second is the PDC Timeline. # Named by Science A common fiction trope is that alternate timelines and parallel universe resonate on a different frequency. Having an actual, connected example might allow scientists to detect the difference, proving the concept. The two timelines could then be referenced by that value; Timeline 92 nHz and Timeline 83 nHz. # Named by Futurama In one episode of the show Futurama, there were two parallel universes that interacted (more actually, but it was mainly the two). It was suggested that one be Universe A and the other be Universe B. As you stated in the question, Universe B was not happy with that, so they decided to go by Universe 1 instead. You could do the same thing, or at least something similar, like Timeline α and Timeline あ. [Answer] **Colors.** When assigning teams or groups, a value neutral way to do it is by color. Red is not intrinsically better or worse than blue, or green. One could make a case that black, white and brown have attached values but if you stick to the established primary and secondary colors you are usually safe. I like the idea of naming according to sky. The visitor exclaims "Your sky is so red!". Perhaps it was a spectacular sunrise that day or some random event related to dust, but the name sticks: Red Sky. The other timeline is Green Sky, which started as a joke in a newspaper opinion article and caught on. Of course both timelines usually have regular blue skies but sky and color are neutral, and the color labels can be easily adapted to other things. For example, when I visit, I wear my green Hawaiian print shirt to distinguish myself from my red sky counterpart who wears a red Izod. He is also a little heavier than me, and his teeth have suffered more misfortunes than mine. But he is pretty funny and I have some grilling skills to learn from him. [Answer] ## Pick some significant point of divergence, and label the timelines according to the way they went If the timelines are truly different, then there are going to be things in each timeline that aren't in the other one. So you could name the timelines according to these things. There are any number of possibilities, depending on what people in each timeline know about the other. For example, perhaps Picasso had a purple period instead of a blue period. So people might refer to the "Blue Picasso" universe and the "Purple Picasso" universe. Of course, bigger and more obvious differences than my siily example are very likely to exist, and be better candidates for labeling the timelines. The only limit is your imagination. [Answer] I am not so sure your question is far-fetched. It could be posited that there have always been divergent timelines within human history itself. Consider the American Civil War, as an example. There are now two divergent time lines in America. One believes that the Civil War never ended, that the fight still continues, and they have their own heroes, their own version of history, their own concept of a legal system, their own version of reality, their own culture, their own moral code, and in fact in many areas their own judicial system (if you accept that there are Democratic Supreme Court Justices and Republican Supreme Court Justices). The other believes that the end of the Civil War was definitive, that the issues were resolved, and that the legal system resoundingly supports a progressive liberal socialist stance. These two timelines, in fact, have become ideologically dichotomous, to the point where they are incompatible with each other. And the timelines are infused throughout American society and geography. There are Red states and there are Blue states. Each has their own reality, and their own version of history. The main difference, in your scenario vs this one, is that your timeline has been completely temporally/spatially separated for a period, and then merged back together. This scenario has always been contiguous. Is this separation/non-separation relevant to the result? I posit that it is not. The ideological divide between the two timelines would be just as pronounced, either way, weather they somehow merged after being separated or were always together. My point is, there is not just one nomenclature for these two divergent timelines. One could just as easily call them "Confederate' vs 'Yankee', 'Democrat' vs 'Republican', 'socialist' vs 'conservative', 'Northerner' vs 'Southerner', and so on and so forth. There would never be just one designator, one label, one set of terminology. It would depend on what particular aspect of the divide you were looking at. **EDIT** Now, let's go one step further. Suppose, during the Civil War, there actually WAS a split into two spatially/temporally distinct time lines. One is the timeline we live in. In the second, the South won the civil war. In this timeline, events would have unfolded pretty much along the lines that the 'Confederates' in our current timeline would have liked it to, and who already live to some extent in that reality. Would the factions from each timeline be much different in outlook to their compatriots in our timeline? So, let's merge the timelines. There are an abundance of people in OUR timeline who would rejoice, and identify with the merging timeline. And there would, undoubtedly, be those from the other timeline who would identify with the prevailing views of people from this timeline. Would there really be a fundamental difference in the ideological divide? Perhaps just more pronounced? Wouldn't the desinators applied in our timeline just be transferred to the factions in the other timeline, and vice-versa? The same expletives? The same pejoratives? **END EDIT** However, there would be, and is, one commonality between both scenarios. In both cases, the interactions really coalesce into the differentiation 'US' vs 'THEM'. That seems to be absolutely consistent throughout human history. [Answer] Name the lines after one of the first differences a visitor sees (in the case where material transportation is possible) or after something different about the format of official messages. The first-discovered portal on one end is located in a park, and that is the Local Parks Director or Famous Parks Architect timeline. This portal connects to a cavern in the other time line, and that is the Cave Explorer or Prominent Cave Feature timeline. In one time line, the Comic Sans font is universally loved. In the other, the first entity to make contact uses Garamond font for all official communications. These names will have history associated with the contact itself and will be items that are obviously related to the travel or communication experience. They have less of a 'judgment on an entire collection of civilizations' character compared to trying to identify the divergent event. And hopefully whoever the landmark or message characteristic was named after has a name that is both catchy and easily pronounceable. [Answer] **Give them both names that will be equally flattering** "Grand marshal Sikolov of the awesome timeline USA, I'm president Freeman of the kickass timeline USA, I would like to talk to you about collaborating to beat those damn commies...". [Answer] For good examples see the novelettes and novels of H. Beam Piper's Paratime series. In his world, timelines are splitting all the time. One primary time band has developed a means (Paratime transporter) that can move across time to other bands. The base concepts don't withstand too close a scrutiny. It never made clear how a multi-furcating timeline can be assigned a number and a distance from the home line. Nor how the home line copies themselves don't keep colliding on trips. But the result are good tales of adventure and mayhem. Anyway: Early timelines are often named after some great migratory event. E.g. Aryan Trans-Pacific when the Aryans went east... Mongol Europe, where the hoard just kept coming. China Lake, where the Chinese kept up their exploration and became the dominant culture throughout the South China Sea/Indonesia/India More recent ones by who won some critical battle. E.g. the Reich band where Germany's third Reich didn't collapse. --- A simple labeling system won't work unless you have a mechanism to reduce the number of different timelines to a manageable size. While at present you only have two timelines in your universe, you want to have the mechanisms thought out for how this may increase if your world has legs. One such idea is that timelines are created all the time, but most of them collapse, and merge together again. This will explain why sometimes you find something exactly where you left it, but it wasn't there at the start of the search. In a timeline that split yesterday, you left your car keys by the phone instead of on the hook. This also explains why your memory of an event may be quite different from someone else's. Criteria for a timeline splitting have to be nailed down. Perhaps in addition a small event that had a even chance of going either way, the consequences of that event have to be fairly quick. Often a battle will be a split when some critical player is/isn't taken out. You may also do some furious hand waving to create pre-conditions: Temporal Pressure -- Timelines only split once every 50 years or so. This would still give you 2^40 timelines in 2000 years --roughly a trillion, an inconvenient number. Perhaps all timelines merge again, given time, as the past recedes enough that it doesn't matter to the present. [Answer] > > However, there's a problem with this: which timelines get to be A? > Which one gets relegated to being B? > > > That is going to depend a lot on the details of your portals. If one timeline developed the technology which produced the portals, they get naming rights. Or not, maybe. If, for instance, the discovered timeline was better militarily and invaded and conquered the portal developers, the conquerors would impose their own nomenclature. If portals just started popping up like mushrooms with no one to blame, then it's a free-for-all. [Answer] ## Name them By Mass If this is a natural phenomenon, and if it happens often, it is nearly guaranteed that the mass of the two universes is not precisely equal (because one or the other has had people and material cross over to another timeline). If this happens a lot across the whole universe, the universe's probably have different masses. ## Name them By U-235 Amount Similarly, one timeline (with more joins) may be longer or shorter compared to a peer. A "representative" sample of rock from the two timelines would have different amounts of naturally-occuring U-235 decay products (it would geologically "date" the rock to a slightly different time). ## Name them By Unusual Astronomic Geometry If there are joins in space-time naturally occuring, one or more constellations may look slightly differently (fewer stars, extra stars) than another. You could use the naming convention for isotopes to distinguish Cassiopeia-5 from Cassiopeia-8. ]
[Question] [ So recently there was this interesting [theory](https://arxiv.org/abs/1804.04727) -the paper itself is quite readable, but here's an article [link](https://www.universetoday.com/139052/the-challenges-of-an-alien-spaceflight-program-escaping-super-earths-and-red-dwarf-stars/) that expands on it. Basically, it states that aliens on those very habitable but massive super-earths might not be able to escape their planet's gravitational grasp with chemical rockets. Well in theory they could, but it would require a rocket design with preposterous weight requirements on the order of an ocean battleship just to launch a satellite. The most obvious alternative -to our mind- would be nuclear propulsion, but this made me wonder: what are the long-term effects of repeatedly blasting regions into wastelands while sending such rockets into space? Is it possible to re-use a lap of land already annihilated by what is really a nuclear bomb, or would the aliens have to resort to using other fertile launch pads? [Answer] You do not need to create a nuclear wasteland to have a nuclear rocket. All you need is heat and propellant. If you need more propulsion you need more heat, and you deploy more nuclear power. One idea about how to do this would be a **nuclear ramjet**. It turns out they exist. <https://en.wikipedia.org/wiki/Project_Pluto> > > The principle behind the nuclear ramjet was relatively simple: motion > of the vehicle pushed air in through the front of the vehicle (ram > effect), a nuclear reactor heated the air, and then the hot air > expanded at high speed out through a nozzle at the back, providing > thrust. > > > The notion of using a nuclear reactor to heat the air was > fundamentally new. Unlike commercial reactors, which are surrounded by > concrete, the Pluto reactor had to be small and compact enough to fly, > but durable enough to survive a 7,000-mile (11,000 km) trip to a > potential target. The nuclear engine could, in principle, operate for > months, so a Pluto cruise missile could be left airborne for a prolonged time before being directed to carry out its attack. > > > Nuclear ramjets do not shower the area they fly over with nuclear waste. Probably the remnants of the nuclear engine are deposited at the impact site, but their effect is lost in the larger nuclear explosion. Back to your heavy worlders: for the last piece of the trip outside the gravity well, there is not enough atmopshere remaining to use as propellant so your nuclear ramjet will need onboard propellant to be heated and exhausted out the back. Something which expands greatly on a phase change would serve - like rocket fuel. Or water. [Answer] There was a [detailed exploration of launching from heavy planets in the Space Exploration Stack Overflow](https://space.stackexchange.com/questions/14383/how-much-bigger-could-earth-be-before-rockets-wouldt-work); I think it's a better explanation of the problems with conventional rockets than the cited paper. Nuclear engines get around the problem because they can give more energy, hence a higher velocity, to the exhaust stream than a chemical reaction can. Unless they have an accident, they don't make the exhaust stream radioactive in the process. So the keys to reducing the radioactive contamination of the launch site are (1) fewer accidents and (2) less radioactivity from accidents. Fewer accidents is hard. Starting a space program without accidents is almost unbelievably hard. There are likely to be some. But reducing the radioactivity has some promise. What makes a reactor dangerously radioactive is, well, the *reaction* in the reactor. The original fuel load isn't so bad, particularly if the fuel is encapsulated in rods or pellets. The radioactivity builds up as the fuel "burns" because it's (mostly) the fission products. So the nuclear engine starts as not so dangerous, but becomes more so as it runs. You'll want to get it launched and on its way. If you can get your experimental rockets headed out over an ocean, you'll also minimize the problems from eventual explosions. Big chunks will sink, and smaller dust will be dispersed. Oceans are *big*. We ended up blowing up a lot of equipment, infrastructure and people getting to space. If there was an easier way, we would have taken it, but there wasn't. So long as a culture on a heavy planet thought getting there was worthwhile, using nuclear rockets isn't *that* much harder than our progression from throwing things, to firework rockets, to modern chemical rocket engines. It's just one more step. [Answer] You could repeatedly use one piece of land for take-off/landing operations provided you had good shielding and/or remote systems for permanent structures and transportation equipment bringing rockets and supplies in. You have a much bigger problem though; the atmospheric radiation pollution from launching volleys of nuclear powered spaceships would start to kill the planetary ecology in short order. [Answer] Project Excalibur was a "Star Wars" plan to use satellites that would explode atomic bombs and use lasers to focus the X rays to destroy incoming satellites. <https://en.wikipedia.org/wiki/Project_Excalibur> Thus it seems possible for a somewhat similar system to use mostly underground nuclear explosions to power powerful ground based lasers used to power rocket launches. Nuclear pumped lasers can also use the energy from nuclear reactors to power ground based lasers, which could be used to power rocket launches. <https://en.wikipedia.org/wiki/Nuclear_pumped_laser> Other methods have been suggested for transmitting energy from ground based generating systems to launching rockets. If and when fusion power generators become practical they can be used to generate power that could be transmitted to launching rockets. [Answer] Assuming that the biology of the aliens is not very different from ours when it comes to dealing with radiation, it is straightforward that the place where a nuclear explosion took place is barren for access. The only solution for reusing a launch spot a la Cape Canaveral or Baikonur would be to have remotely operated machinery to execute most of the operation needed for site and launch preparation. Astronauts in the ship would be protected by the shielding of the ship itself. I mean, if you can survive a nuke exploding below your buttocks thanks to the shielding, you are not going to worry about some radioactive nuclei scattered on the ground. To further limit fallout it would be good to use a sort of potato cannon, with the explosion taking place underground. Few hundreds meter more to rise won't be a challenge for a nuke, but the subsequent collapse of the ground around the detonation site would prevent most of the fallout of a surface explosion. Not all, as some would exit following the ship. ]
[Question] [ If Age of Sail era Ships were to come into regular contact with Polynesian outrigger and Catamaran ships like the [Hōkūleʻa](http://www.hokulea.com/vessels/hokulea/), and the people using the ships did not start using the foreign design of ships, how could they adapt their ships to compete in an age of sail setting including naval combat with things like cannons? The design of the hulls and would likely have to be changed drastically to suit so how could they make the required changes while still staying true to the original design? [Answer] ## Firepower is the key The other answer is saying that you can take advantage of upwind speed and manoeuvrability. It is true, but it will not compensate for the enormous firepower of larger monohull warships. Let’s take an example: The galleys were able to move fast even when there was no wind, they were able to go straight upwind if needed. They were much more manoeuvrable. However, in the battle of Cape Celidonia, 5 Spanish galleons (big mono-hull sailing ships) defeated 55 ottomans galleys. This is typical from this period, when large sail-only ships started to replace galleys on the seas. Basically, during late sail-era, the more fire power you could carry, the more likely you were of winning. ## Your case You are not talking about galleys, but light multi-hulls. I believe however that the problem will be similar: your vessels are small. It is difficult to build a large catamaran or outrigger, because of their shape. A monohull warship is basically a big cylinder. Catamaran are two smaller cylinder with pieces attached between them. So the limitation that you have are: * Less cargo (food, men…) for a similarly sized vessel, so you cannot go so far away without ressuply * Probably more delicate * Less guns, very important * Guns closer to water * Lower freeboard and bulwarks, making it easier to be boarded. (or harder for them to board bigger ship) The advantage were already covered in another answer: * Faster upwind * Better manoeuvrability ## Classic war In an open war between well-defined opponents, larger boats, even if they can't catch your catamarans, can come in range of cities and gun them from the sea. They could occupy harbours. They can go further in the open sea. They can carry more men and resources, in a safer way. My guess is that the catamarans are going to lose, not because they are sunk, but because the large ships are going to cut their harbours, resources and so on. ## Hull design solution You ask if anything can be done in terms of hull design. I believe that the only way is making it bigger. But probably, while trying to make them bigger, they are going to lose some of the advantages (think weight and structure fragilization). Maybe the architects are going to reinvent mono-hulls? ## Adaptative solution : Guerilla war So, as these boats won’t stand in front a large mono-hull vessel. Their strategy, in order to exploit their advantage at the maximum, is to play it guerrilla style. * Approach quickly, discretly * See if you have a chance * Attack by surprise, or only smaller boats * Run away and hide * Repeat This strategy is close to what were (and are) doing a lot of pirates. [Answer] A lateen rigged mulithull vessel such as Hōkūleʻa have straight advantage over the square rigged monohull designs the European powers used. # It's faster and it can sail closer to the wind Choosing when to have your combat is one of the most important factors in "random encounters" in the period. Many of the Hornblower type stories include statements about larger and faster vessels and the risks of encountering one. They also spend a lot of their time trying to gain the controlling position upwind of the vessel they're chasing. The lateen rig of the Polynesians on a catamaran hull with appropriate leeboard/centerboard can sail 10 to 15 degrees closer to the wind than a square rigged monohull. In this case, even when smaller, it's still faster, and sailing closer to the wind, you get to choose your opponents, and when and where to fight or not. Under normal (modern) circumstances I would say that a multihull vessel is slower to turn, but in this case you're again comparing a schooner-lateen rig with a square rigger. If you maintain this difference in rigging then you maintain faster maneuvering as square rigs lose all speed to tack and can end up going backwards. It's entirely valid to scale catamarans up to quite large sizes without having to change the rigs all that much. If you have the people and you have the timber you can build them up to galleon scales. However one of the key differences you'll notice when scaling up a multihull when compared to a monohull, apart from the significantly higher complexity of construction, is that monohulls have larger holds relative to deck size. Multihulls have much larger decks but can't haul as much cargo. This leaves you in a situation of having greater naval effectiveness close to your home ports but limited ability to project power at greater ranges. [Answer] ## Attack Head on, then Pivot In classic "Ships of the Line" combat, the two forces formed two parallel lines, and then battled it out. This was driven by the reload time of the cannons - it took a fair amount of time to reload, so you wanted many cannons to maximize your firepower. You generally did not want to approach your enemy head on - they showed you their side, which had many guns, and you showed them front of your ship which had few. But (!) an outrigger is highly maneuverable and has a VERY small cross section when seen from head-on. An outrigger would be very hard to hit when it was a approaching head on. So a potential modification could be: take a note from modern catamarans and place a platform between your main hull and your secondary hull. It only needs to be strong enough / large enough to hold your guns. This platform can be utterly destroyed by enemy fire, and all that happens is you loss the use of the guns on it. Now, load up as many guns as you can fit on it, mainly arranged to face forward. Charge at the enemy. Your hull has a very small cross section, and the enemy has a large cross section - you should score many more hits, on average. Once you've fired all your forward facing guns, use your maneuverability to turn about, and steer away. The non-forward facing guns provide some cover fire for your retreat. You reload at your leisure, outside of firing range, while another outrigger rushes in to take your place. This creates a steady stream of accurate fire against your enemy, who often misses due to your small target size. You probably want to keep this fight at the end of cannon range - it maximizes your advantage in target size and avoids downward shots onto the broad "catamaran deck" you've created. A good volley from a Ship of the Line against a smaller ship from close range would be devastating. [Answer] Gunboats have been used [well into the Napoleonic era](https://en.wikipedia.org/wiki/Gunboat_War). An outrigger canoe could, in principle, [function the same way](https://commons.wikimedia.org/wiki/File:Gunboat_battle_near_Alv%C3%B8en_Norway.jpg). * Those gunboats were used in the constrained waters of the Baltic. How they will cope with the Pacific, even between islands, remains to be seen. * The [larger](https://commons.wikimedia.org/wiki/File:Shallop_gunboat_Gunboat_War.jpg) gunboats were bigger than most outrigger canoes. ]
[Question] [ Working on my world, I'm reminded of ice mages that can instantly freeze their opponent using an *Ice Ray*. That got me thinking if this is possible in the real world. The most promising method of instant freezing is using an ice pack, which immediately absorbs heat when the chemicals are mixed. However, I'm skeptic of the freezing part. The best I guess such mixture can do is sort of frostbite in an area around the wound. That is fine to me. What I'm asking is whether utilizing an instant cold pack **as a melee weapon** to achieve that effect is possible or not? If yes, in what form can such a weapon can be effectively used? --- Right now I'm thinking about something similar to a poisoned dagger, but using a dagger with ammonium nitrate wrapped in plastic. On a successful full stab (the blade fully penetrates the flesh), the ammonium nitrate will dissolve and cause endothermic reaction, hopefully enough to cause the intended effect of frostbite to surrounding tissues. [Answer] In short, no. A human body is sitting at something like 300 Kelvins (K). A flamethrower might reach 1000°C, or 1270K - but the coldest an icethrower can ever get is 0 K. Even that flamethrower, which while very damaging isn't by any means the hottest flame we can make, has a higher temperature differential than the freezer. If you can get your victim to breathe in ultra-cold air, you can freeze the lungs and kill them that way. If you can immerse them in an ultra-cold fluid, that'll work. But the frostbite you'll give them by spraying even liquid helium on them, while it will be nasty and maybe eventually fatal, is nothing like as effective as the damage from a heat weapon that weighs the same and is easier to use. [Answer] You're talking about hitting someone with an instant cold pack. [WebMD](http://www.webmd.com/first-aid/tc/using-ice-and-cold-packs-topic-overview) recommends keeping a cloth between the ice pack and the skin and limiting exposure to 15-20 minutes. As a weapon it's not going to be very effective. I'm not sure why you'd want to in the first place. Even if you dumped a dewar of liquid nitrogen on someone you'd be looking at some added [frostbite](https://en.wikipedia.org/wiki/Frostbite). This will be unpleasant to whomever has been stabbed, but the stab wound itself is of much greater and more immediate concern. [Answer] What you're talking about (seemingly, correct me if I'm wrong) is supercooling a blade to the point where contact with human skin would cause some kind of Ice Burn or other lasting cold damage. Unfortunately, while it is possible to supercool something like a dagger blade by dipping it in liquid nitrogen, the process makes the metal incredibly brittle, so using a dagger wouldn't be practical. It would break apart into splinters if you struck anything with force. However, you could press the flat side onto someone's skin and apply pressure to force the supercold metal into them (This might be easier with a larger block of metal on a stick, like a hammer). However, as mentioned previously, you wouldn't be able to actually strike anyone with it, because it would just break. It would work quite well as a torture device, but not as a melee weapon, I'm afraid. [Answer] **TL;DR**: This is possible. ## Damage from skin conduction (no penetration) Ignoring real-world compounds for a moment, what *could* work is a really cold solid with a high specific heat capacity so that it can absorb a lot of heat energy without significantly reducing the temperature gradient, which would cause the cooling rate to fall more than it would otherwise. To simplify calculations, let's assume that our ideal solid has a temperature of $0 K$ (absolute zero) and an infinite specific heat capacity, i.e. will suck heat away as fast as possible. According to [this tabulation](https://users.ece.utexas.edu/~valvano/research/Thermal.pdf) (which has a lot of useful values for other tissues and organs), the epidermal layer of the skin has a thermal conductivity of $0.209 W/(mK)$ (watts per metres per Kelvin). The dermis has a thermal conductivity of between $0.293 W/(mK)$ and $0.322 W/(mK)$ - I'll assume $0.308 W/(mK)$. The tabulation doesn't have information on the subcutaneous layer but [this page](https://www.training.seer.cancer.gov/melanoma/anatomy/layers.html) says that this layer is mainly fat and collagen, so I'm assuming a value of $0.209 W/(mK)$. Assuming an epidermal thickness of $0.2 mm$, a dermal thickness of $2.5 mm$ and a subcutaneous thickness of $1mm$ (I have not found information on the latter value so it's a complete guess), the total thermal conductivity of the skin is: $$\frac{0.209 W/(mK)}{0.2mm} + \frac{0.308 W/(mK)}{2.5mm} + \frac{0.209 W/(mK)}{1mm} = 1380 W/(m^2K)$$ (I initially got the units wrong for this - [this Physics SE answer](https://physics.stackexchange.com/a/76570/105169) helped to straighten this out.) Assuming that the internal tissues of the human body are constantly at $310 K$, the energy loss through the skin is: $$(310 K - 0 K) \* 1380 W/(m^2K) = 427800 J/(m^2s)$$ $427800$ joules per second per metres squared of contact surface. However, this is not taking into account that melee weapons generally cut or stab, not press against the skin of the opponent. Also, they tend not to be theoretically perfect energy vacuums. This value means, given a surface area of $10 cm^2$ (flat of a blade) and a contact time of $0.25 s$, the heat transferred through the skin is: $$427800 J/(m^2s) \* 10 cm^2 \* 0.25s = 107 J$$ Given [a specific heat capacity of $3470 J / (kg K)$](https://www.engineeringtoolbox.com/human-body-specific-heat-d_393.html), $$\frac{107 J}{3470 J / (kg K)} = 0.0308 kg K = 30.8 g K$$ This is starting to look promising. Of course, this is spread out across $10 cm^2$ of skin. To work out how much this skin weighs, the density and thickness of the skin can be used. I couldn't find a value for the density online, but [this page](http://www.protocol-online.org/biology-forums-2/posts/26245.html) suggests that it is less than that of water - I estimate $0.95 kg / l$. First, the conversion factor between skin area and mass needs to be determined: $$0.95 kg / l \times (0.2 mm + 2.5 mm + 1 mm) = 0.95 kg / dm^3 \times 3.7 mm = 3.51 kg / m^2$$ Combining this with the energy loss through the skin and specific heat capacity, this gives: $$\frac{427800 J/(m^2s)}{3470 J/(kg K) \times 3.51 kg / m^2} = 35.12 K/s$$ Note that this is *through the skin*, assuming that the specific heat capacity of whatever is under the skin is $3470 J/(kg K)$ and has no thermal capacity. As the threshold for ice crystal formation in cytoplasm is ~4°C, or a difference of $41 K$, this gives a contact time of $1.168 s$ for third-degree frost-bite. This is *without penetration of the skin*. Contrary to some other answers, **this is possible**. [Answer] This type of melee weapon would have some odd effects in terms of the wound it would inflict. As discussed in this question: [Sealing a wound: ice or fire?](https://worldbuilding.stackexchange.com/questions/51195/sealing-a-wound-ice-or-fire) The ice treatment would cool and possibly freeze the blood and tissues around the wound. If the wound itself is not fatal, the extreme cold at the wound site would act to limit the initial loss of blood, possibly allowing the injured person more time to get medical treatment than they would otherwise have had from a non-freezing weapon. Of course freezing tissue damages that tissue, so when the area around the stab site thaws, the bleeding and infection would likely be worse than from a normal stab wound. So definitely a mixed bag in terms of lethality. [Answer] This would do some damage. This is just a theory, but the “ice pack” would destroy surrounding tissue, which would slow down healing of the wound. It would also hurt a LOT, maybe disorienting the target enough for you to hit them again. I’m thinking you just leave the dagger in, not pull it out. The constant pain would hurt more, and tissue damage would be accelerated. While the victim is distracted, pull out another dagger and stab them again. [Answer] **Can an ammonium-nitrate ice pack be used to instantly freeze an entire average sized human? Possible, yes. Feasible, no (It would take hundreds, or have to be huge, and it would take a very long time).** Assuming an [average sized male weighing 62 kg](https://en.wikipedia.org/wiki/Human_body_weight), and [an average specific heat capacity of 3470 J/kg•K](https://www.engineeringtoolbox.com/human-body-specific-heat-d_393.html), the minimum amount of energy required to completely freeze them is: $q=mC\Delta T = 62kg\cdot 3470\frac{J}{kg\cdot K}\cdot\left ( 37-0 \right )\approx8000 kJ$ How much energy could be absorbed by an instant ice pack? The molar heat of solution is the amount of energy released or absorbed per mole of solute being dissolved, and is typically found experimentally. [One source](http://www.sciencedirect.com/science/article/pii/0040603178851132) lists the molar heat of solution of ammonium nitrate as: $\Delta H^o=25.41 \frac{kJ}{mol}$ With a [molecular mass](https://pubchem.ncbi.nlm.nih.gov/compound/ammonium_nitrate) of 80.043 g/mol, how much ammonium nitrate would be required to achieve that much cooling? $m\_{NH\_4NO\_3} = 8000kJ \cdot \frac{1}{25.41\frac{kJ}{mol}}\cdot 80.043 \frac{g}{mol} \cdot \frac{1}{1000\frac{g}{kg}}\approx 25kg $ That's a big cold pack, and that doesn't include the mass of water required to dissolve that much ammonium nitrate. Furthermore, this is a lower bound on the mass and doesn't incorporate heat flux, or how long it would take. A [typical](https://www.enotes.com/homework-help/ammonium-nitrate-mr-80-used-cold-packs-give-439672) instant ice pack contains 40 g of ammonium nitrate and enough water to make 200 g of solution. (Means we're looking at ~625 ice packs to freeze a human in an perfectly insulated environment) This also doesn't account for the extra amount of heat being generated by the human - on the order of [100-120W](https://physics.stackexchange.com/questions/116960/how-much-energy-in-form-of-heat-does-a-human-body-emit). --- **Can an instant ice pack cause localized tissue damage due to cooling?** Yes, but it takes a while. An icepack can lead to [serious burns and frostbite](https://www.burn-injury-resource-center.com/2012/01/ice-packs-can-cause-serious-burns-frostbite.html) depending on duration of contact, size of contact, blood flow, and other factors like wind. The primary mechanism of injury is freezing the water in the blood cells. Secondary injury can be caused by lack of blood flow to an area of tissue. Ice pack burns usually results from [minutes of contact](https://www.ncbi.nlm.nih.gov/pubmed/10450486) (e.g., 20 minutes), not the fractions of seconds that may be involved in a melee attack. --- **Is an instant ice-pack sword feasible?** Possible, maybe. Feasible, not really. See @wizzwizz4's analysis. Melee cold damage requires large amounts of heat to be transferred quickly. This has two parts: how much heat can be transferred (heat transfer), and how quickly that heat can be transferred (heat flux). The heat transfer depends on the mass, specific heat capacity, and temperature differential. The heat flux depends on conductivity, and gradient. As tissue freezes, heat conduction is reduced. The frozen tissue tends to insulate deeper tissue from being frozen. Relying solely on conduction (e.g. direct contact) for heat transfer is going to be limited, since any heat removed from the tissue is going to warm up the weapon, reducing the temperature differential. This means a massive weapon. --- **What form could an instant ice-pack weapon take to maximize damage?** Maximize heat transfer * increase mass of weapon * increase specific heat capacity of weapon * reduce mass of tissue * increase temperature differential * increase contact time Maximize heat flux: * increase the surface area in contact * increase temperature differential In a melee context, maximizing the amount of time in contact with the tissue could be achieved with a blade that penetrates and stays, or something that is wrapped around a part of the target (like a whip). To maximize the temperature differential between tissue and material, the weapon needs to be extremely cold (as close to 0K as possible). This needs to be balanced with the fact that many materials become more brittle at lower temperature. Conduction could be increased on the weapon side if it was made of a material with high thermal conductivity (e.g. metal). This could be implemented as a hollow sword, with the instant ice pack material inside. Local freezing could also make a penetrated blade more difficult to remove if it was frozen to the tissue. --- EDIT: The original answer was based on super-cooled liquids as an alternative mechanism to get instant ice. A volume of super-cooled liquid could be nucleated and crystallized/frozen into the shape of whatever container it was in: basically an instant icicle. This could cause localized tissue damage using the same mechanism as an ice burn, especially if it was stabbed and remained in place. ]
[Question] [ England, 1208. The Pope declares an Interdict on England because the King would not agree to the Papal choice for Archbishop of Canterbury. In our reality, King John tried to tough it out and to get clergy to support thim, but he was not very aggressive about it. Eventually he failed and surrendered the Kingdom to the Pope, resulting in a rut that had to be resolved 500 years later. But what if he were to act boldly and to open the churches by the sword, declaring himself Supreme Governor of the Church in England, basically doing a Henry VIII and founding Anglicanism 300 years earlier? There is no Luther nor Calvin to supply the doctrinal stuff but the King could, for example, send out feelers to Constantinople. And then he remains allied with Raymond VI of Toulouse. And he has lands in Aquitaine. And Toulouse has a powerful ally in the Albigensian Wars... Would this work, or would this fail? What would be the big obstacles to overcome? [Answer] [King John](https://en.wikipedia.org/wiki/John,_King_of_England) the Much Maligned actually did resist admirably to the Papal pressure, and, more importantly, England backed him up to the hilt; the Papal Interdict of 1208 is probably one of the best examples showing that although medieval people were deeply religious they didn't actually care all that much about the Church with capital C and its hierarchy. The context is that the Pope of that time, [Innocent III](https://en.wikipedia.org/wiki/Pope_Innocent_III), consecrated [Stephen Langton](https://en.wikipedia.org/wiki/Stephen_Langton) as Archbishop of Canterbury (and head of the Church hierarchy in England) without the King's consent; the regular procedure was that the King would propose a candidate (or a short list of candidates) and the Pope would confirm and consecrate the candidate (or pick one of the list); in case of disagreement it was expected that the King and the Pope would negotiate. That the Pope consecrated a head of the English church without Royal consent was a hostile move; the King responded by refusing to allow Stephen Langton to enter the country, and, for good measure, seized the lands of the archbishopric. The Pope escalated the conflict by placing the kingdom under the Interdict. The Interdict, in the mind of the Pope, was the ultimate deterrent, the *nuclear option* as we would say. In principle, priests were prohibited to perform any religious service other than the baptism of the young children and the confession and absolution of the dying. No Mass was to be celebrated, no communion, no confession, and most importantly, *no marriages* could take place. This would put the country under enormous pressure, hoped the Pope, and the King would have no choice but to submit. What happened in reality was quite different. Essentially, both King John personally and England collectively chose to ignore the Interdict. Churches remained open, marriages were celebrated, life continued as before; those priests who manifested excessive obedience to the Pope and tried to enforce the Interdict found that life had become quite hard: their lands were seized (as were the lands administered in the benefit of the Papal See itself), they were driven out of the country, their mistresses were arrested and held until the sinful priest payed a hefty fine. Seeing that placing an Interdict on England was one thing, but having it enforced was quite another, Pope Innocent excommunicated King John (in 1209), with no effect other than (a) determining the King to consider seriously the possibility of a war against the Pope and (b) reinforcing the King's determination to redirect the revenues of the Church; Wikipedia says that *"around 14% of annual income from the English church was being appropriated by John each year"*. The King's revenues increased, the country carried on as before: what's not to like. And the King and the Kingdom continued in this happy state until 1213, when a compromise with the Pope was sought. The issue was [King Philip II](https://en.wikipedia.org/wiki/Philip_II_of_France) of France, *Philip Auguste* as the French call him. King Philip saw the excommunication of King John as a very convenient pretext for going to war against England, and was busy building a fleet and gathering an army; whether he had the consent of the Pope of not is not clear, but he definitely did not have any material support from the Pope. King John performed an admirable show of contrition, declared himself a humble vassal of the Pope and agreed to pay annual tribute -- which was about one tenth of the annual income he had collected from the lands of the Church during the years of the Interdict, and which both parties tacitly forgot after three or four years anyway; in exchange, he got the Pope to allow *him* to make war upon France. And here comes the actual interesting point where history did truly lay balanced on a fine point; for John's campaign proceeded quite well initially, or at least not worse than any other medieval military campaign, despite the growing reluctance of the English lords to support John in foreign adventures; the English took [Anjou](https://en.wikipedia.org/wiki/Anjou); their ally Emperor [Otto IV](https://en.wikipedia.org/wiki/Otto_IV,_Holy_Roman_Emperor) of the Holy Roman Empire attacked from the north. All seemed to go so well. But then came emperor Otto's defeat at [Bouvines](https://en.wikipedia.org/wiki/Battle_of_Bouvines) (today on the border between France and Belgium, at that time in [Flanders](https://en.wikipedia.org/wiki/Flanders)), which in the real history ended all hope of restoration of the [Angevin Empire](https://en.wikipedia.org/wiki/Angevin_Empire), sealed the fate of King John (who not only acquired the nickname *Lackland* for losing many of the possessions on the mainland, but also ran out of money and had to accept to sign the [Magna Carta](https://en.wikipedia.org/wiki/Magna_Carta)), and launched France on its way towards becoming a superbly centralized state (which it still is). But the outcome of the battle of Bouvines was not preset; on the contrary, it is believed that the Allies (the Holy Roman Emperor, England, Boulogne and Flanders) had the advantage of numbers. The fortunes of the battle fluctuated during the day; at one point King Philip himself was "unhorsed and narrowly escaped death" (words from the Wikipedia article). In the real history the French won and the Allies lost. But if Philip had been killed or taken prisoner, if [William Longespée](https://en.wikipedia.org/wiki/William_Longesp%C3%A9e,_3rd_Earl_of_Salisbury) ("Longsword") had succeeded in taking the bridge instead of being taken prisoner, history would have been different. The English crown would have kept the Angevin lands (Normandy, Brittany, Anjou, Touraine), would have kept Aquitaine -- about the one third of France! France would be much smaller, while England would be just one of the provinces of an Empire spanning the Channel. ]
[Question] [ So in this scenario our character is just a regular man in his 30's. Multiverses exist, and our character exists in countless other universes, each variant of himself having different life experiences. A powerful entity has merged these countless life experiences into our character's one mind, giving him composite memories and skills - so in one universe he learned martial arts, in another he learned advanced engineering, etc. The function of this is that he seems naturally talented - he can intuit how to solve most problems, MacGyver his way out of sticky situations, etc. The thing is, he isn't aware of any of this - it's all muscle memory skill, with the actual retrievable memories being buried deep in his subconscious (probably so he doesn't go insane). He isn't a genius, he doesn't have eidetic memory or anything like that, he just has the equivalent of all the mastery of skills one would have built up over multiple lifetimes. However, over time, he starts to have conflicting memories of his past, to the point where he can no longer tell which is the "real" one, so he goes to the hospital. **How would modern medical equipment detect a person with composite memories? What would the signs that something is abnormal look like?** Although this is clearly science fiction, I'd like to keep the medical science as realistic as possible. My best guesses are brain imaging technology to detect [concussions](https://www.sportssafect.com/blog/when-is-brain-imaging-ctmri-needed-for-a-concussion), possibly an advanced MRI like an [fNCI scan (functional Neurocognitive Imaging)](https://www.cognitivefxusa.com/blog/can-an-mri-detect-post-concussion-syndrome). The conflicting memories may be explained as [proactive interference](https://en.wikipedia.org/wiki/Interference_theory#Proactive_interference), or the interference of older memories with the retrieval of newer memories. The closest thing in a work of fiction I can think of is how in the film [The Butterfly Effect](https://tvtropes.org/pmwiki/pmwiki.php/Film/TheButterflyEffect), an MRI shows that the character's brain has signs of age-induced scarring of someone twice as old as he is. I also considered how Dissociative Identity Disorder could be detected, but it [doesn't seem like it's very easily detected by things like MRI](https://www.quora.com/How-do-MRIs-of-people-with-dissociative-identity-disorder-compare-to-others?share=1) (and also, he doesn't have Dissociative Identity Disorder, he has his own memories buried in his subconscious). My only other thoughts of how it could be detected are a sort of lie detector test where all memories are equally valid/true, heightened neural activity, more neural connections than an average person, or a brain at its capacity (centuries of information) so it's overwriting old memories with new ones - but again, how would medical equipment detect any of these things? [Answer] Modern medical equipment could not identify the specific situation. fNCI, fMRI and the like cannot "read memories" in any way. If you were generalising from stories where that was possible in the present day, I have to tell you that the authors were making stuff up for the sake of their story. fMRI might notice that there was an unusual *amount* of activity when memory recollections were happening, but this would be interpreted at first as some interesting new kind of brain problem. This increased activity seems plausible because an unusually large number of memories would be found in response to any stimulus. The likeliest way in the present day for this situation to be correctly identified would be for a psychologist or psychiatrist with an interest in history to realise that all the memories they learn about are suspiciously plausible. That would be very unusual in their experience, and might prompt a systematic investigation. [Answer] # By seeing brain areas not be active fMRI and EEG is probably your best bet. Let's take martial arts as an example. Because it is both about the experience and skill, we know that both the temporal lobe as well as the motor cortex are changed. However, it seems unlikely that the brain can handle the amount of connections made if every single skill is added. It could lead to mingling of many concepts and skills. This is akin to a kid making a ton of connections in the brain during learning. The amount and wrong connections can lead to them mixing words for example, resulting in the personal child speak people find endearing. Even if such things wouldn't happen it is unlikely that the brain can function. Transport of waste and nutrients would become impossible. Not to mention that the brain would get much heavier in neurons and connections, probably not fitting in the skull anymore. It is safe to say that these skills and menories are somehow processed in the other dimensions. That gives us the option to *not* see the brain in action. Our brain is good at mimicking things we see or hear. Fantasising moving your arm to grab a ball will activate the motor cortex for that exact moment. Seeing it happen on a screen can do the same. With fMRI or EEG we can check the activity in the relevant brain areas. When showing martial arts, something he hasn't learned himself, his own cortex will not respond. One somewhere else will. Memories are the same. Thinking of the own memories will activate some brain areas. Thinking of memories from alterative versions would not. As it starts with the experiences of the person in question, like seeing martial arts happening, we can see strange artefacts. He is responding to the visual stimuli, but at a certain point things start to disappear as they are rerouted to the appropriate brain. These are signs that something is very definitely off, but might not give rise to the right conclusions. That looks more like a plot related issue to me. ]
[Question] [ I need a plausibly scientific explanation for how an alien species could "transmute" a skull from bone into a glassy or crystalline substance. It doesn't need to to be too hard-science-y, just enough to be a surface level explanation. I know organic to mineral is pretty much an impossible transition, short of magic. But something that fast-tracks the fossilization process, maybe turning it into diamond more than crystal, could be achieved through a chemical bath and/or some kind of radiation treatment. Does this seem plausible? Edit: the main purpose is to preserve skulls of ancestors for veneration. [Answer] **Opalized.** [![opal bone](https://i.stack.imgur.com/266w7.jpg)](https://i.stack.imgur.com/266w7.jpg) <https://www.opalauctions.com/learn/did-you-know/australian-dinosaurs-opalised-bones> Fossils are created when the organic matrix from a creature has a mineral containing solution soak into it. The organic parts rot away and the mineral containing solution turns to rock. Or to crystal. Opalized fossils are rare but not vanishingly rare. The mineral containing solution is soluble silica and the crystal formed by that is opal. Your aliens could use soluble silica to produce opal skulls. It takes quite a while to make an opal but maybe the aliens have tech to speed it up. Or maybe the aliens take quite a while. [Answer] [Already done by the scientists at Caltech.](https://www.caltech.edu/about/news/bare-bones-making-bones-transparent-54837) > > First, the researchers removed calcium from the bones: calcium contributes to opacity, and bone tissue has a much higher amount of calcium than soft tissues. Next, because lipids also provide tissues with structure, the team infused the bone with a hydrogel that locked cellular components like proteins and nucleic acids into place and preserved the architecture of the samples. Finally, a gentle detergent was flowed throughout the bone to wash away the lipids, leaving the bone transparent to the eye. > > > This builds up on old technology that renders corpses translucent (though not completely - you could see a lot of the insides). I thought of including some images, but it might be uncomfortable for some, so if you wish you can google for "translucent mice". Anyway, since you can do this to bones, you can also add your own colorants to make the transparent bones seem reddish, greenish or whatever glassy color you wish. [Answer] Since you put "transmute" in quotes; perhaps it isn't the actual skull, but a 3-D printed exact copy of the skull; in crystal. Accurate to the molecular level, after being rapidly but destructively scanned. They were using it as a model to study, and it is the alien custom to make such models durable enough to remain unchanged for many thousands of years; even if they only wanted it for a brief period of time. This can be so accurate it cannot be distinguished from an actual transmutation. that is why you see no casting marks, carving marks, etc, even under a microscope. Why you can even see, say, the beginnings of a tooth cavity, or a crack in the root of a tooth, or reknit bone from an injury. ]
[Question] [ In a pre-industrial human culture on Earth with slightly altered flora and fauna, where rivers and canals are the major ways of transport, how would an ideal and realistic animal replacement for horses look like? * Grown River Horses should be able to draw swimming carriages (i.e. boats or floats). * Humans should be able to mount and ride them, even if that’s not the preferred method of transport. * They don’t have to be mammals, but should breathe air. They don’t have to have legs and feet. * Ideally, they would sustain short routes through salt water as well. I cannot make up my mind whether to base them mostly on dolphins, seals, manatees, hippos, crocodiles or something else. [Answer] **Giant Newfoundland** A [Newfoundland](https://en.m.wikipedia.org/wiki/Newfoundland_dog) is a kind of dog. For dogs it ranges between big and colossal. They were bred for rescuing people in the water and can do so on long distances. They can even go into rough seas, but likely they aren't used to stay in rough seas for extended periods. They have webbed feet, long lasting lungs and won't get cold thanks to their thick fur. Even on land they are strong dogs. They are very intelligent, easy to train and very loyal. In your altered flora and founa, a giant version of the Newfoundland is created. It can haul large weights on the water, including in teams. A giant version might have the spine to allow riders both in the water and outside. Their high trainability helps for a huge amount multiple roles. This can range from land riding and hauling to hunting and guarding. Dogs are highly "customisable". We've been breeding them for many wildly varying results. Improvements in breeds like better stamina, lesser fur for warmer climates, faster or stronger versions. Smaller ones can be better for hunting, *herding* and companionship, while bigger ones can draw the water carriages and a whole slew of multipurpose roles in between. They are carnivores, which might be a problem if not enough fish or other meat is available. Compared to horses they require food to be brought with you. On the other hand, the long trecks with Huskies are working and we've been living with dogs for a long time now while being able to feed them. That being said, it's a slightly altered Earth. Dogs have omnivorous characteristics already, so we can expand them to being true omnivores. I would think of a wide range of these dogs to help you both in the waterways and outside. Huskies of the river, fish-herder dogs and companions. There's a lot of possibility here. [Answer] # Teams of dolphins Believe it or not, [there was a study](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6778436/) that assessed the ability of dolphins to work together to pull a rope. > > ...bottlenose dolphins learn to coordinate their behaviors via trial > and error and recognize the necessity of performing simultaneous > actions with a partner to successfully accomplish cooperative tasks > > > With generations of careful breeding and a little handwavium, you could have teams of dolphins working together to pull barges just like oxen pull wagons. [Answer] Horses and other animals like Oxen were used extensively to haul barges along rivers. In quite a few areas were environmental preservation is good, the towpaths along the river banks still exist today or their former existence is still visible in the landscape. There is no problem with the idea of land animals towing barges. From an energetic point of view it is more effective to use land animals for towing. They are independent of a river current and walking on ground, being more rigid than water, needs less energy than swimming in water. One can easily hold a heavy boat in a moderate current, but doing so while swimming is more streneous. Of course, if there are river creatures strong, willing and intelligent enough for such a task, and they don't dabble on every occosion, I doubt people would refuse their services :-) [Answer] **Ignore implausibility-mini whales** Why? A few reasons. First dolphins are smart to a degree that such a thing as having them haul without pay or any kinds of reparations is arguably slavery. So that's not an option unless that's what you where looking for, Whales themselves are intelligent, but that's halfway due to their large size. If they had a mini cousin, in all likelihood it wouldn't be anywhere near as smart due to the relative volume of grey matter. Whales end to consume a larger variety of foods than some other aquatic creates, with whales consuming krill, fish, crustaceans, plankton, and a variety of plants, which is most important as it allows for cheap feed for livestock.Further, as some whales consume far more than plants due to their large size this makes more complex lifeforms an inherent part of their diet, those with biomass more dense in terms of energy, with the size removed a diet consisting of mostly plants actually becomes feasible. Or, to repeat what I said exactly again, but in a different format * Not slaves due to small size and so less brain * Can subsist on a diet consisting primarily of plants due to small size, * and further * Varies, but a large percentage of a whales body consists of muscle mass enough to be viable as a practical method for hauling cargo * You're gonna need some deep rivers * Hippo's might also be fine, but that was an entire question, with a link [here](https://worldbuilding.stackexchange.com/questions/89434/how-does-a-society-domesticate-the-hippo) Hope that helps some. This answers not very good. You might also be better of with something like walruses [Answer] **Giant (small horse/donkey-sized) otters** [![A close-up of a sea otter, taken in Morro Bay, California in 2016.](https://i.stack.imgur.com/oWjXJ.jpg)](https://i.stack.imgur.com/oWjXJ.jpg) (A close-up of a sea otter, taken in Morro Bay, California in 2016., Marshal Hedin from San Diego) (CC BY-SA 2.0, [source](https://en.wikipedia.org/wiki/Sea_otter#/media/File:Sea_Otter_(Enhydra_lutris)_(25169790524)_crop.jpg)) I remember reading (before I got bored of the novel constantly repeating itself over and over and over again only to add a small tidbit and move on to repeating something else) a web novel called Savage Divinity, where the author created a community of almost-nomadic barbarians riding giant otters. Those otters were very smart, pack-based, and very, very mobile. They can take care of their own food if you release them to hunt in the ocean or nearby forest/river. The otters regularly pulled carriages and could pull a boat, even if they were not the fastest either on land or in the sea. [Answer] **Humans.** [![swimmers pull boat](https://i.stack.imgur.com/zIGRx.jpg)](https://i.stack.imgur.com/zIGRx.jpg) <https://www.guinnessworldrecords.com/news/commercial/2019/1/dubai-police-swimmers-pull-355-tonne-boat-for-as-part-of-fitness-challenge-556599> Humans are good draft animals. They understand what they are supposed to do and humans have great endurance. Humans are also pretty decent swimmers. In your world there are human swimmers who pull boats. They are called water horses. Like other old style jobs it is a hereditary thing. Boat pulling is an endurance affair, not a strength thing and so men and women both pull the boats, starting when they are teenagers. The women take a break to have kids and then come back to it when they are old. --- The cool thing about this is that there can be water horse characters. It is a different world they live in, the water horses. They have a different outlook. They are happy for the work but in their private lives they might be less friendly to outsiders. [Answer] Gaelic "Each-uisge" or water horse is one mythological version that's quite widely reported. It lives not so much in rivers (where the kelpie lives), but fresh water lochs and sea-lochs. Never having seen one, I can't comment on what they look like... but [(inevitably!) Wikipedia](https://en.wikipedia.org/wiki/Each-uisge) reports sightings on Skye, that had a beak like a sea turtle! Which, if they are related, would give them a good broad back for riding on, should you manage to tame one. ]
[Question] [ I'm new to this and my scientific knowledge is massively lacking in this area (so please take it easy on me!) I'm writing a historical science-fiction novel. Parts of it set in the past (1977) and some of it set in the not so distant future. I need to create a planet that has a layer of silver dust (not necessarily the element/metal silver, but silver in appearance) that covers the entire planet's surface. From a distant solar system, does not need to be similar to our solar system. I would also like to include rivers/lakes of mercury on the surface of the planet. Is it possible for a planet like this to exist and what would its chemical make-up be? Humans do not need to be able to survive there or even visit. Just two metal robots/spacecrafts... one is from Earth (launched 1977, Voyager) and one is from another planet (Robot, very sophisticated). [Answer] A world with very large amounts of mercury seems improbable as mercury is so much less common than the lighter elements. Perhaps large amounts of mercury could have been gathered by an alien race for some unknown purpose, but rivers of mercury are sadly very unlikely to occur naturally in the vast quantities that you need. Should such a world be hand waved into existence and remain intact I would expect the vast majority of the planet to be composed of metallic elements. Many non-metals would react with mercury forming a range of salts that would spoil the appearance with a white or coloured crust. Many metals also form amalgams with mercury so there would be a great deal of erosion of any metallic landscape. That said some metals are more resistant to forming amalgams such as iron, platinum, tantalum and tungsten so these elements might be more useful in constructing any landscape on the surface. As an additional issue a world the size of the Earth built from heavy metals would have a much stronger gravitational field than the Earth, so it would be necessary to accept the higher gravity or specify a smaller planet. [Answer] **Your planet is a construct.** [![CIRCUIT BOARD PLANET and moon](https://i.stack.imgur.com/v1mK9.jpg)](https://i.stack.imgur.com/v1mK9.jpg) Liquid gallium rivers are its superficial circuits / arteries. The powdery surface is its skin, intended to slowly ablate as our skin does to protect from radiation and particle impacts. This construct can be integrated into your story. Maybe it is of the same provenance as your advanced robot and they are part of a package. Maybe that robot built it, or found it and modified it for its own use. [Answer] I'm not sure of the viability of this: Your planet started life as a jovian or superjovian world. It spiraled in towards it's parent, eating everything it encountered (and this was far more material than comprises our inner solar system), but then it got so close to it's parent that it was vaporized--but it's gravity was enough to hold onto the heaviest elements (at that temperature there are no compounds) anyway. It then moved back out and cooled. You're left with a cinder that's mostly heavy metals. I do not know how to keep the mercury from reacting with the other heavy metals, though. ]
[Question] [ A spacecraft enters an unnamed system and spotted a gas giant with a pulsating planetary ring, it glows bright intermittently. What natural phenomenon could be responsible for such brilliant display? It would be better if you can explain why the glows only occurs within certain range of the electromagnetic spectrum. [Answer] Io and Jupiter have a very special relationship. Io is a volcanic moon, which ejects charged particles. Due to its relatively low gravity (~0.18g), the particles escape, but they get trapped by Jupiter's immensely powerful magnetic field and form a plasma torus. The density of the plasma is higher close to and ahead of Io. ![Jupiter and Io](https://i.stack.imgur.com/gtQzE.jpg) Saturn is like a smaller Jupiter, but with huge rings. It has shepherd moons - moons that orbit between rings. Now combine both: a gas giant with saturnian rings, a volcanic shepherd moon and a jovian magnetic field. The plasma shines (in specific wavelengths, even!), and the glow is reflected by the rings. The plasma glows and dims as the moon orbits the planet - it seems stronger when the moon is on the same side of the planet as you, and diminishes when the moon is on the other side. For reference, the orbital periods of Prometheus and Epimetheus, two of Saturn's shepherd moons, are approximately 0.6 and 0.7 Earth days, respectively. ]
[Question] [ How do underwater cities (with aquatic human-like citizens) handle sewage? What type of technology would be possible to use underwater in order to take care of the mess? [Answer] In treating sewage, you're going to have two distinct problems; number 1 and number 2 Proper treatment will leave you with 'gray' water and sludge. The gray water is not suitable for drinking (ick), but can be used to do things like irrigation. Your number 2 problem is the sludge, and that's more problematical. Once it's dried out it can be burned, it can be used as compost/fertilizer, it can be used to produce methane. The main problems with the sludge are that it generally has to be dried out before being used in one of these ways, and that takes time or a source of heat (preferably both). If they're not concerned about the ocean around them, they can just pipe the sewage out into the ocean itself and let dilution solve the problem. Alternatively they can run a pipe to the surface and drop the sewage on the land, much like humans used to do to the ocean. If they don't want to go with that idea, a society with a similar tech level to our own will have options for sewage treatment. It's not a very simple process, but it's definitely better than spraying the area you live in with feces. Current technology for us can make use of various forms of algae to chew through undesirable bits and produce gray water. You don't necessarily need high tech to treat sewage, though. If you can construct an artificial wetland, that will act as a phenomenal filter for the sewage. You'll still have the problem of sludge, but probably not as much, as some of it will go into helping the plants in the wetland grow. [Answer] **Upwards flush tornado.** [![underwater tornado](https://i.stack.imgur.com/s0tO3.jpg)](https://i.stack.imgur.com/s0tO3.jpg) The Atlanteans are masters of current manipulation. By channeling currents, they can produce an underwater vortex like this one caught on video off Aruba. Perhaps by pushing a lever that opens a valve, the current comes in and the vortex starts. This vortex carries waste material deposited in the vortex chamber up and away from the deep sea abode of the Atlanteans. Like other large water creatures (e.g. manatees, whales) the Atlanteans produce liquid wastes and once these have been wafted upwards to the uninhabited upper realms, dilution and biology take care of the rest. --- from comments @StephenG - ""what goes up must come down". The Atlantean system is much like the system terrestrial cities use when they deposit their wastes in a river. The wastes go elsewhere and break down by environmental action during the trip. So too the poopnado: wastes go up and then are carried off by winds and surface currents, breaking down along the way. If they come down, it is not in Atlantis. [Answer] Move the stuff out of the city and then let little helpers do all the work. By little, I mean microscopic. Bacteria in all of their various forms can break down almost anything. Get the solid waste to the outskirts of town and turn your little helpers loose. Use the results to fertilize the kelp beds or whatever. You will have to worry about bacteria getting loose, since they will probably get everywhere, but I would hope it would be something that doesn't harm the locals. [Answer] They would recycle the liquid waste, since it is closer to drinkable water than saltwater. Solid waste - that depends on how Atlantis gets its food. If they import it, they can just fluh it outside. The ocean has an almost unlimited capacity to absorb this kind of waste. If they grow their own food, they would use it for fertilizer. [Answer] I would look into "survivalist" grey-water systems. In general you might be interested in researching survivalist culture. The idea being to create homesteads that are entirely self-contained. You'll likely find many of the ideas transferable to an Atlantis-style environment. [Answer] Some variation of an Aerobic Treatment Unit <http://www.nesc.wvu.edu/pdf/WW/publications/pipline/PL_SU05.pdf> Once the effluent is treated sufficiently, the rest could be take care of (or even used to farm) fish and other critters. edit: To add to the tech/magic level of your Atlantis, you could also include some kind of biosolid sonication <https://sonotronic.de/technologies/ultrasonic/sonication-of-bio-solids> Could be done by magic dolphins or high tech equipment, but it is a real thing. ]
[Question] [ By saying giant, I mean something roughly around 2-3m long from nose to rear legs (not including tail) and 1m tall at the withers. **How would such a creature fare as a mount used by humans/humanoid to travel in the desert?** (both Sahara-like and something like the Outback in Australia or the Grand Canyon) Specifically, how would it probably compare to horses or camels regarding: * The creature's own survival and resistance to hot and arid weather * Speed and suitability for the terrain * Food and water needs And a bonus (optional): * Ability to pull a sand sledge **If the general answer is on the lines of "it would suck!", is there any simple change that can be done to its nature to make it more suitable?** (e.g. longer legs? inner water storage like that of camels? being an endotherm rather than an ectotherm?) Central bearded dragon reference: [![Central Bearded Dragon](https://i.stack.imgur.com/CfIw0.jpg)](https://i.stack.imgur.com/CfIw0.jpg) [Answer] **Reptiles lack aerobic endurance.** I thought this was because they were cold blooded but apparently it is an artifact of how they use their spines - excellent excerpt below. <http://reptilis.net/myths.html> > > It is true that many reptiles today lack aerobic endurance, that this > is caused by their "cold-bloodedness" though, is blatantly false. The > lack of aerobic endurance in most reptiles is due to their anatomy. In > most reptiles, locomotion follows a sigmoid (S shaped) path. This > movement was inherited from the undulations of their fish ancestors. > Now while gills work fine with this movement, it doesn't translate > very well into terrestrial locomotion. In most reptiles, respiration > is controlled by the costal (rib) muscles. Unfortunately these muscles > are also used in locomotion. Furthermore this sigmoid movement > alternately compresses each lung, thus making it a real chore to > breath and walk at the same time. For many reptiles this means holding > their breath as they move and evolving a high anaerboic capacity. This > is why lizards often take breaks inbetween walking; to catch their > breath. > > > You want your mount to be able to go along at a steady pace and the lizard will struggle with that for any prolonged ride. Additionally these bearded dragons are bellydraggers. If it is big enough to carry a human it will have a weighty belly and it will get bellyburn from all the dragging. [Answer] # Maybe ### Pros (relative to a camel) * **Long life span**: The life span of creature tends to increase with size. While you can get 20 years out of a domesticated horse or camel, a Komodo Dragon, which is significantly smaller, has about 20 years between sexual maturity and average lifespan in the wild. Life expectancy would go up in captivity and go up again once you increase the size of the lizard by a factor of 5-10. * **Doesn't need much water**: A general advantage of reptiles. However, it is hard to determine what exactly the water requirements might be once the lizard is scaled up to half a ton or so. More to the point, it is hard to tell if it would really have better water efficiency than a camel. We will tentatively put this in the pro category. ### Cons (relative to a camel) * **Low carrying capacity**: Look at a camel's legs. They are directly under it. Now, look at a lizard's legs. They are splayed off to the side. In fact, the lizard uses its stomach for a lot of ground contact, to reduce the work done by its legs. As a means of locomotion, this has superior efficiency if you do a lot of stopping and starting, like if you are chasing bugs around. But if you plant to walk 400 km across sand dunes, a camel will carry weight more efficiently, and moreover, can carry more weight with its legs directly under it. * **Eats meat**: A bearded dragon doesn't strictly eat meat, but I understand that they need some animal protein. Pet guides online indicate that they should be fed both fruits and bugs. This will be harder than feeding a camel, which can live on the barest scrubby vegetation available in the desert. Now, the lizard has the advantage of ectothermy, which means it in general needs fewer calories. So this might be an advantage of sorts; but if you expect it to carry large loads long distances, most of its caloric intake is going to be expended in locomotion, so a camel and lizard's calorie intake will be more similar. * **Overheats**: Camels endothermic regulation helps to keep it from overheating. Lizards can generally run at hotter body temperatures than a camel can, but once it gets hot enough, the lizard must seek shade or die. * **Not all deserts are hot**: Even nights in the Sahara, especially in winter, can freeze. In these conditions, a wooly camel will do well; a lizard will barely be able to move. # Conclusion Can a bearded dragon work as a mount? Sure, so long as it is properly domesticated. Is it better than a camel? Probably not. [Answer] A few other components to consider (other answers catch the main items) 1 - Salmonella. Lizards carry Salmonella. The standard defence is to wash hands after handling...might not work if you're sitting on the beast for a long duration. Your mounts may cause disease in your riders. 2 - Brumation. Not sure if you're aware on this one...but Bearded Lizards do hibernate, usually into fall and winter as a reaction to changing light cycles. I'm sorry, you'll have to walk as your mount is hibernating for the next few months' is probably something nobody wants to hear let alone suffer through. 3 - Little more out there...but one of the leading causes of death in pet Bearded Dragons is from eating excessively large items. The result is the stomach contents put pressure on the creatures spine and ultimately paralyzes it. I'm not 100% if sure if putting any form of weight on the creatures back would allow it to digest properly (IE, there might be a biological reason why you can't actually sit on your mount here...maybe the duration of a combat scene?...but not for prolonged journeys). This is very much a product of its belly already being in contact with the ground...any weight on its back just squishes it's innards a bit. [Answer] It's already been answered, but if you're determined to have a reptilian mount, you would be better off looking at a varanid, agamid or massive snake as a mount than a bearded dragon relative. Willk didn't name the exact reason why the S-shaped movements limit breathing, it's called [Carrier's Constraint](https://en.wikipedia.org/wiki/Carrier%27s_constraint). Varanids (goannas, perenties) use gular pumping to help force air into their lungs as they move. Gular pumping expands and constricts the throat to force air into the lungs as the monitor moves so they can maintain a relatively active lifestyle. (A paper to look up would be 'Contribution of Gular Pumping to Lung Ventillation in Monitor Lizards'. There's a free pdf of it available on google scholar) Agamids run bipedally so avoid the constraint entirely and snakes can breathe and move at the same time (sidewinding would the preferred Sahara movement method and the serpent could likely employ similar tactics boas use to climb trees to maneuver in a Grand Canyon type setting) Also, if you want to be really different, consider looking at the family tree of the Crocodylomorpha, there were armadillow-like crocs (Armadillosuchus) and crocs that could gallop on land (Pristichampus) to scratch at the surface. In comparison to camels and horses, your best option is a camel really. They are completely adapted for desert living, are capable of high rates of activity regardless of the temperature swinging between hot and cold and due to their herbivorous diets would be easier to feed than a reptile (where a camel can immediately eat any available vegetation, your reptile would need to be fed on animals that are eating vegetation, in a desert life is relatively scarce so needing to feed a massive mount on primary consumers would be difficult to do in a way that would maintain more than a few such mounts at a time). And a camel beats a horse because their feet are better adapted for traveling on sand or rocky ground (no hooves to pick up stones, split, crack or sink into soft sand), their humps and thick fur are combination food stores, metabolic water store and insulation against the sun's heat, which horses lack. Horses also have higher water requirements than camels. [Answer] I just wanted to throw it out there that we imagined flying lizards that spit fire and also people mounted on them, mounting a giant bearded dragon (that doesn't actually exist, obviously) wouldn't be that far fetched. [Answer] bearded dragons are mad spiky though so it would probably be really uncomfortable. ]
[Question] [ Stars are born through the fusion of light atoms and the star's nucleus. So let's say that as a star is being born, the nucleus split and creates two stars. Could this even happen? If so, would the stars be considered twins? [Answer] Although astronomers have considered this phenomenon in the past, the data indicates that this isn't how stars are born. That said, yes, your premise works. Here's how you make a star, in a nutshell: 1. Take [a big cloud of gas and dust](https://en.wikipedia.org/wiki/Molecular_cloud). 2. Have the cloud grow until it reaches roughly [the Jeans length](https://en.wikipedia.org/wiki/Jeans_instability), at which point the cloud is unstable. 3. Let some perturbation - perhaps a shock wave from a supernova or radiation from other stars - create a change in density and pressure. 4. The cloud should collapse into a [protostar](https://en.wikipedia.org/wiki/Protostar), a giant blob of gas that isn't quite the finished product. 5. Let the protostar contract via the [Kelvin-Helmholtz mechanism](https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_mechanism) until it gets hot enough to fuse hydrogen. Voila! A star is born. Binary star systems do exist. The [leading theory for how they form](https://www.astro.princeton.edu/~eco/AST541/Mary_Anne_Peters.pdf) is that fragmentation happens during the collapse of the cloud, meaning that it splits in two before a star begins to form. Each smaller collapsing cloud then forms a star, creating a binary system. Therefore, you can indeed have your "twin stars". The idea you're talking about resembles the so-called *fission hypothesis* ([see section 2 here](http://www.phys.lsu.edu/astro/nap98/bf.final.html)), where one protostar, early on, splits in two. There are quite a few problems with the idea, including features of the gas's compressibility. The fragmentation hypothesis is much more commonly accepted. If you're looking for a more detailed overview of the topic, you may find [this paper](http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1988ComAp..12..169B&defaultprint=YES&filetype=.pdf) illuminating (pun intended). [Answer] No, not *after* the star is born. But this is happening all the time during the star formation - this is called a binary star. However, there is no guarantee that binary system will consist of two twins - typically one star is bigger, and the other is smaller. [Answer] Maybe if a white main sequence star was hit by a red dwarf, you might be able to get two orange stars out of the deal, but that's just off the top of my head. I don't have any specific experience looking at these collision in simulations (or papers on the same) to back up that idea (conservation of angular momentum might play a key roles). <https://en.wikipedia.org/wiki/Stellar_collision> ]
[Question] [ Do clones have fingerprints? Are they the same as their original? Fingerprints are based on your genes but are influenced by your birthing environment. Identical twins don't even have exactly the same fingerprints! So would clones? If you have a dna sample of someone, you can't work backwards and get their fingerprints! My [previous question](https://worldbuilding.stackexchange.com/questions/44981/how-do-you-produce-fast-grown-working-clones) about how to grow clones has lead me to question how to tell them apart from each other and the original. Fingerprints seem like an easy low tech solution. I would imagine that it might depend on the method of cloning. * Clones that were 3D printed might have the same fingerprints. * Clones grown in some steamy tubey coffin shaped device would probably not have fingerprints much different to their genetic disposition. * And clones grown in a watery gooey uterine bath could possibly have fingerprints but would they be the same? [Answer] Yes, clones have fingerprints. No, they wouldn't be exactly like their original: fingerprints are influenced by [in-utero and epigenetic factors](http://www.todayifoundout.com/index.php/2011/02/identical-twins-dont-have-identical-fingerprints-even-from-birth/), not just by the DNA. A clone's fingerprints would be very much alike its progenitor (and *some* features *would* be nearly identical), but [not the same](https://books.google.it/books?id=pnrSBQAAQBAJ&lpg=PA29&ots=QgKZKmlBo1&dq=fingerprints%20epigenetic%20factors&hl=it&pg=PA36#v=onepage&q=fingerprints%20epigenetic%20factors&f=false). *Copies*, i.e. identical living beings created by some kind of duplicating machine, (faulty) transporters, and time loops, would have of course the same fingerprints - unless the machine for some reason is designed to do otherwise. Even though the two beings would not be *identical* since they're exposed to different stimuli and environments (so that they would immediately start diverging mentally and biochemically), and in the end it would be possible to tell them apart, still having only one of them at hand one could not say whether it's the original or the "copy" (indeed, even the concept of "copy" gets a bit murky). If the two beings started with the same set of fingerprints, barring accidents, wounds and similar more or less intentional alterations, they would go on having the same fingerprints; that alone could not be used to tell them apart. Accurate chemical analysis of said fingerprints possibly would. # Telling identical fingerprints apart Several chemical and hormonal contaminants exist that might end up in fingerprint grease in detectable amounts (given sufficiently advanced technology). Also, the isotopic composition of said grease might yield valuable clues. For example living long enough in different solar systems would alter the relative isotope abundance in finger grease (which is mostly CHON), and that in turn could allow to tell the fingerprints apart. Different Population I stars might sport different ratios of some elements (e.g. 14N and 15N). Living, breathing and eating proteins on such a star's planet would slowly alter an organism's isotope proportion to reflect that of the host planet. Also, a young star's planet should experience less cosmic ray activity, therefore the abundance of 14C in the atmosphere would be lower. Planet climate, as well as [the latitude at which the clone lived](https://en.wikipedia.org/wiki/Rayleigh_fractionation), also affects [relative abundance of 18O](https://en.wikipedia.org/wiki/Oxygen_isotope_ratio_cycle). [Answer] Clones have fingerprints but do not have the same fingerprint. Fingerprints are not genetically created so even if they both had the same DNA they would have different fingerprints. The fingerprint is determined by the environment around it was created it and also many other things can alter it. [Answer] A 3D printed clone would have whatever fingerprints were designed into it. A grown clone, or one assembled from separately grown tissues, would have fingerprints, but they wouldn't be the same as the original. [Answer] I don't even have the same fingerprints I was born with. I cut my thumb and my fingerprint changed to absorb the wound. The environmental variables outweigh the DNA in this case. The swirl patterns 'may' be the same, but the individual print would be different. ]
[Question] [ What would a galactic Empire based off Plato's Utopia be like? The government of [Plato's Utopia](http://plato.stanford.edu/entries/plato-utopia/) was designed for a city-state at the time of the Bronze Age. But what if you upscale it to a galactic Empire, made up of humans capable of faster then light travel? For those of you who haven't read "Republic" and "Laws" let me give you a run down of their core principles: 1. The State should be run by special people who have been trained and bred for it. 2. These people will be called Guardians and will have no families and own nothing. 3. The Guardians will be protected by a special warrior class. This class will be bred and trained to protect Guardians. They will be indoctrinated to be completely loyal to the Guardians and to not take power for themselves. Now for my questions: First: Is this form of government practical for a galactic civilization? Second: If not, what changes can be made to make it more practical? [Answer] Like so many Bronze Age ideas, Plato's idea of a utopia doesn't really work so well in the modern world and beyond. The world has changed too much in the past 2500 years for it to work now, and even more changes will make this system even less viable. The crux of the issue is that in Plato's day, basically everyone had the same life. The vast majority of people were focused merely on making sure that they had enough food to last the winter. His system worked then because it wasn't as large of an issue to have a few people (say 1% - it's been a while since I've read Plato, I can't remember if he went into detail on how many people would be needed to be Guardians and the warrior class) work for the good of the state in matters of diplomacy, rather than working for the good of the state by working the fields. Now, however (and in the future, presumably), we aren't focused on survival. We have amounts of food unimaginable to someone in Plato's day - I have four pounds of almonds in my desk at work so that I can have a snack if I get hungry between meals. There are entirely different problems faced by today's world, and the world of the future. And the problem is that someone raised to be a ruler likely wouldn't have any firsthand experience with many, if any, of those problems. (Note: using problems of today as concrete examples, as I won't pretend to know what the problems of the future will be.) If they're raised from birth to be a ruler, they wouldn't have student loans, wouldn't know what it's like to live paycheck to paycheck. Why would such a ruler care about fixing the economy when they've never known the pressure of trying to find a job in order to be able to pay rent? How can they effectively make laws regarding new technology when they own nothing and (presumably) have never used it (a modern analogue would be, how could they rule whether Apple should help the FBI unlock the San Bernardino shooter's iPhone when they've never owned an iPhone)? Coupled with that is the problem of scale. For a Bronze Age city-state, a ruler would only have to know about a small area of land. Scaling this up to a galactic empire? Let's say it's a small empire; they "only" have to know about a hundred planets. How can they possibly know what's best for all of these worlds? In order to fix this problem, you'd essentially need many layers of government. Have a set of rulers for each major city/area on a planet, who report to a set of rulers for the entire planet, who report to a set of rulers for a region of space (and the planets therein), who report to the "over-rulers" who rule the entire empire. Each set of Guardians has their own group of warriors, and any higher authority can call on them (eg the rulers of a region can call on the warriors of all planets in their region if they need to quell a revolt). Judicial appeals can be escalated to the higher levels, if so desired, similarly to the current US judicial system. Laws themselves work the opposite way - more local laws override empire law, except in certain situations (murder, rape, etc can't be legal, period, but something like drug use is down to the local administration), to ensure that the laws accurately represent the local culture, customs, etc. There would need to be rules in place dictating how the next set of rulers is chosen. Honestly it's starting to look like a medieval society, but in space - kings rule counts rule dukes rule mayors rule citizens, and the higher levels don't really care what the lower levels are doing so long as they pay their taxes. Just with groups of people acting as the rulers, rather than individuals. And that hasn't worked out too well historically. And even with those changes, you don't fix the problem of the rulers being out of touch with the real world, with what the general population is experiencing. [Answer] There's actually a couple movies about a "Republic" like the one you describe: > > 1. The State should be run by special people who have been trained and bred for it. > > > [Jedi](http://starwars.wikia.com/wiki/Jedi/Legends) > > 2. These people will be called Guardians and will have no families and own nothing. > > > Like the [Jedi](http://starwars.wikia.com/wiki/Jedi_Code) > > 3. The Guardians will be protected by a special warrior class. This class will be bred and trained to protect Guardians. They will be indoctrinated to be completely loyal to the Guardians and to not take power for themselves. > > > The [Clones](http://starwars.wikia.com/wiki/Clone_trooper)! And it looks like a city-state thing [[citation needed]](https://xkcd.com/285/), with the city called: [**Coruscant**](http://starwars.wikia.com/wiki/Coruscant) In these obscure movies when they try to turn the [Republic](http://starwars.wikia.com/wiki/Republic) it into an [Empire](http://starwars.wikia.com/wiki/Galactic_Empire/Legends) it all *kinda* goes to sh\*t (empires have a history of doing that), but the same still pretty much applies, change *Jedi* for [*Sith*](http://starwars.wikia.com/wiki/Sith) and *Clones* for *Stormtroopers* ## Answering your question: > > Is this form of government practical for a galactic civilization? > > > You can judge by yourself looking at the material for the perks and drawbacks of both the Republic and the Empire. You could also check the [Old Republic Era](http://starwars.wikia.com/wiki/Old_Republic_era), which wasn't depicted in the movies but also kind of follows the same structure. And **if you want to submerge yourself on it**, to soak up the ambiance and people and government of the setting, you can try the [*Knights of the Old Republic* RPG game](https://en.wikipedia.org/wiki/Star_Wars:_Knights_of_the_Old_Republic). [Answer] This system assumes all the actors will be well behaved but is they behave badly or greedily it will fail. **You can't enforce number 2** **These people will be called Guardians and will have no families and own nothing.** Whose job is it to watch the Guardians and keep them impoverished and alone? If you give them power to rule they will use it to benefit themselves. Stable government systems are build on the assumption that every one is greedy and nasty, that is why they work. In modern democracies this power is balanced by giving everyone some power to choose representatives, on the assumption that they will pick whoever will benefit them the most, and kick out the ones who get too greedy. Different branches of government all want power and benefits and fight each other. The constant completion and fighting establishes a balance. In oligarchies or dictatorships it is assumed that those at the top will get what they want and then use force, or the threat of force to hold the rest of the country in check. **You can't enforce 3** **They will be indoctrinated to be completely loyal to the Guardians and to not take power for themselves.** Who will force the guards back into line if they turn on the guardians? If the indoctrination is effective, what do guards do if the guardians start fighting each other? Who ensures sure they were indoctrinated to guard all guardians, and not just a few? [Answer] I do doubt your special warrior class would consider exploring the rest of the world, planet etc else since their entire existence is for the Gaurdians. I don't mean for this answer to seem critical but I've read your first comments - No slavery gives me the picture of sustainable but isolated, no emotion or opinion from these warriors. Yet this state does sound peaceful, but aren't imaginative like we are with astronauts, hikers and soldiers [Answer] Neal Asher's Polity is a galactic utopian empire controlled by artificial intelligences, the AIs rulers employ lesser AIs and human agents as their warriors. The AIs tend to let people do as they please and the vast majority of people are quite happy living in ships/colonies/stations/etc administrated by the AIs. [Answer] Jo Walton has published a [series of novels](https://en.wikipedia.org/wiki/The_Just_City) based on an attempt to implement such a society, in ancient Greece, with Athena and Apollo driving the project. It isn't an answer for this exact question, but it's worth a look. ]
[Question] [ I just finished Isaac Asimov's novel [*Foundation*](https://en.wikipedia.org/wiki/Foundation_(Isaac_Asimov_novel)), the first book in the [Foundation series](https://en.wikipedia.org/wiki/Foundation_series). Its premise relies in part on one character, Hari Seldon, planning the future of a scholarly world by using [psychohistory](https://en.wikipedia.org/wiki/Psychohistory) to help figure out on what timescales civilizations will rise and fall, and when crises happen. He then leaves messages for the times when these crises will occur. Is it at all plausible to use psychohistory - the prediction of large-scale future events in a civilization - to guide a civilization through the future by leaving it time-capsule-like messages when major crises will emerge? I'm interested in a galactic civilization, meaning that small fluctuations aren't as important. The crises that I'm thinking of would affect a substantial portion of the galaxy - like a severe economic depression starting on several star systems that threatened to ruin the galactic economy, or warfare between two small interstellar alliances that could bring the entire galaxy to bloodshed and fighting. Note: If your response is that psychohistory could never work, that's fine. Just justify your answer. [Answer] If I remember correctly, Hari's predictions moved farther and farther from actual as time progressed. Part of this was because the original course set was actually a blind. Then he was trying to 'guide' history along. Heisenberg anyone? However, given a large enough data set people ARE predictable. Kind of like ant colonies, they are much simpler to observe and predict. You can't predict any single ant, but have a pretty good idea what the colony as a whole will do. But even there we observe some incredible behaviors based on a small set of reactions. So finding the key elements to group reactions is paramount in having a chance at good predictions. Adding to that, I expect different societies and cultures to have different reactions to the same stimuli. So while you might be able to predict how a culture would react, it is not the same as an individual in that culture. Just like any other statistics. Stats are useful as long as you understand what you are measuring and the variables that change it. That is all pyschohistory really is. Super-advanced stats, on a race. I think we would need to be able to have an algorithm that can predict the stock market 3 days out using world events as a precursor before we have much luck with predicting humanity with an algorithm. And ultimately successfully predicting the future, will cause people to either try and change it or capitalize on it, changing it. So you can predict it and watch it come about, or try and change it and have no idea what will actually happen. [Answer] Fernand **Braudel** talks about the [**Longue Duree**](https://en.wikipedia.org/wiki/Longue_dur%C3%A9e) (the long view), i.e. thinking about history structurally, usually through an economic lens. Certain developments tend to occur in order. You get stone axes before you get agriculture. You get metallurgy before you get cannon, etc. Opening one area of progress creates new challenges and the theory is that once you adopt a high-level view, the "froth" of event history gives way to the smooth flow of inexorable trends. In many ways, the **Marxist** view of the world is similar, with historical trends leading to changes in the means of economic and industrial organization, that supposedly have predictable and unavoidable consequences. Others would argue that ^**this is all bunk.** Chaos theory (developed later by more mathematically gifted people) suggests that large deviations in outcomes can result from seemingly minor differences in initial conditions. So, who is right? It would be mulish of me (wink!) to try to adjudicate this debate in here, but it is undeniable that there seem to be large scale trends in human history that seem impervious to actual events. World War 2 was doubtlessly a big deal, and our history would be much different without such a cataclysm, but I challenge you to find it as more than a minor blip on the charts below. [![enter image description here](https://i.stack.imgur.com/Qlm84.png)](https://i.stack.imgur.com/Qlm84.png) [Answer] I think that looking at history many things make sense in "hindsight" which were very difficult to predict at that time, let alone hundreds of years in the past. Thus, my answer is a firm **No**. I'll elaborate: One major aspect in the way the world ticks along is technology. It's not reasonable to know exactly what tech will be developed, and how it might influence society, politics, or the world. The perfect example is nuclear power. When the nuclear bomb was first employed many people either: * Predicted the end of the world * Predicted that we will all be driving nuclear powered cars in just a few short years (Fallout universe style) * Thought that energy shortages would become a thing of the past (the list goes on and on) None of those things really came true. It impacted our lives, sure, there were major implications, but nuclear technology is not quite as widespread as people back then would have thought. But ***if*** a brilliant scientist ***had*** miniaturized nuclear reactors, and made them super-safe to use then our history would be quite different. Next we have ***the internet, and social media.*** On one hand some experts argue that we have sacrificed our privacy and given major corporations / power hungry politicians the tools to control our lives. Others believe otherwise: that we now have the tools to communicate and spread information such that "the evil government" will never be able to control us completely again. That the "cat's out of the bag" as it were. Both points of view are valid, but which will ultimately prove to be the end result? Complete domination by power hungry corporations, or a society in which we can communicate freely and openly, and in which governments and corporations fear the voice of the people? (The outcomes above are a little extreme, but you get my point) [Answer] **Tl/Dr;** Yes, I think it is possible. However, it is not easy. In fact, its hard to even pin down the exact requirements on the question. The real key is that you have to model the universe with yourself in it, which encourages solutions that are self-similar, fractaline in nature. Given that questions like these are the subject of the rest of the Foundation series, I'm going to consciously deviate and consider another character which predicted the future: the Paradash Emperor Duke of House Atreides, Paul Atreides, aka Muad'Dib. For those unfamiliar with the name, he is a character in Frank Herbert's *Dune*. The theories one may apply to Paul certainly apply to Hari Seldon. By switching to a different universe, I can talk about common issues they may face using details and word choices which hopefully will not lead to spoilers. This answer is *long*. Perhaps too long, but I find it actually ties into real life applications well enough to put it on paper. We humans do too many things that look like miniature versions of psychohistory to leave the concept to fiction. The first part discusses what to do with the chaotic systems that wreck typical predictive algorithms. The second part explores why working with other humans could be a very wise path. The final part gets to the real crux of the issue, of why psychohistory could work, or why it couldn't. The first step to a question like this is going to be defining some basic assumptions. The first thing needed to really make any headway on fantastical theories like Psychohistory is compatabalism. Modeling the freewill of a human being is tough. In fact, its a major sore point in Western philosophy. Compatabalism claims that the freewill we have is compatable with a physical world: we do not observe anything which *requires* a metaphysical world above. In Dune, Frank Herbert never relies on anything supernatural which could not be explained using physics. The great mythos of Shai Hulud is explained as the result of centuries of gently prodding by the Bene Gesserit and efforts in planetary ecology. The place the Bene Gesserit cannot go is highly spiritual in its description, but the explanation for what it is and why they cannot go there is defined within the bounds of physics. As a result, it is possible to simplify the problem at hand by transforming the world we live in to a world which is identical in every way, except every living being with freewill is replaced with a p-zombie, a philosophical construct which has no freewill but acts exactly the same as though it had it. If one can find a solution to the problem in this world, it is trivial to show that it must work in this world, but this is only true if one starts from the assumption of compatabalism. Without that assumption, the possibility of things like miracles really limit the ability to predict the future. The second assumption I want to make is a limitation of scope. Saying "is is plausible that psychohistory works" is reasonable, but to come to a consensus on whether or not it is actually plausible, I think it's helpful to pin it to more strict wordings. There are two requirements that I believe make sense here. The first is that the the theory must yield *admissible* results. "Admissible" is a statistical decision theory term which basically states that there is no rule which is always better than it. This is a low but essential bar. Playing the lottery is an admissible decision because there is a possibility that you will end up richer than any other decision you could have made. It is a good rule because it handles the case where you simply don't have the cards in your hand to save the universe. You don't have to "win" the game, you just have to play a hand which isn't provably worse in all cases than a different play. The final requirement I add is a minimum threshold for utility. You want to accomplish more than just doing nothing. In our real life, this can be hard. There's a lot of amazing stuff out there that doesn't require our hand at all. However, in both Paul's world and Hari's world, that isn't the case: * In Paul's world, the genetic essence that makes us "human" is becoming too dilute to sustain itself. Failure to do anything could result in the end of all humanity. * In Hari's world, the dark ages are coming, 10^30 years of darkness are at risk. Needless to say, the future is dark indeed. In both cases, we see that there's a lot of room for improvement. The darker the world is without intervention, the easier it is to argue the value of such intervention. It will also help because you are going to have to make some very tough calls along the way. If the world could turn out just fine on its own, it may be very hard to justify acting in a way which can harm the structure you're trying to create. Now the key to this puzzle is trying to figure out what sort of thing we're trying to construct. We know it needs to be able to do predictive modeling on a large scale, using small scale resources. From an information theoretic standpoint, this likely means the need to aggregate large amounts of state information from the world around us into small scale information. We want to be able to play with numbers like "GDP of the United States," not "a list of the GPS position of every dollar bill, by serial number." Obviously, if we had such an aggregation system in place, it would be easy. However, that's handwaving a mighty thing. Consider what *anyone* would give for a tool that could predict the things that matter in their life. We can't just handwave away the construction of this system, it has to at least be plausible to create. The system also has to deal with chaos. It is currently believed that the world contains chaotic systems, such as weather. They are unpredictable, by definition. The obvious solution is to try to ensure no chaotic system's behavior matters in the great scheme of things, but we run into a self-referential problem. We have to treat ourselves as a p-zombie, if we want to be consistent, and thus our unpredictability and chaotic behavior would need to be squelched like all others. A smooth laminar universe awaits! 'Tis a horrible idea no? Okay, lets work on a far harder answer: embracing the chaos. How can we accept chaotic systems into our tool and let them help us? The secret lies in [these metronomes](https://www.youtube.com/watch?v=Aaxw4zbULMs). We can entangle ourselves with these chaotic systems to predict and affect their state. This is similar to entangling photons so that their states are the same at great distances, except it will be done macroscopically, and has to be done without the help of Quantum Magic. The goal is to create a chaotic system within your tool whose state is coupled to the chaotic system outside of you by continuous interaction. Over time, you can build up a feedback loop such that the behavior of the two systems is linked. If one of them is perturbed, it rapidly transfers the information to the other, keeping the two in sync. Its hard to do, but fundamentally very similar to what one has to do to balance a broomstick on one's hand. So now we have a few useful tools: * We can synchronize with chaotic systems, allowing us to predict information about their state. * That synchronization also allows us to know the lowest energy way to affect the state of the chaotic system outsides. The second half is key. Efficiency of energy utilization is going to be a big deal. The Chinese martial art Tai Chi has a saying, "Use four ounces to move four tons." We're going to use perhaps 4kg to move 10^52kg! Sheesh! We're going to have to be super efficient! Of course, there's still the question of the systems which are not chaotic. They are well described by classical mechanics, so we can actually measure their state directly rather than having to entangle with them. However, there's a question of storage space. There would be far more data than you could possibly store in your head, and its clear any one bit of it could be useful. We're going to need more storage. Fortunately, we have somewhere to store it -- all of the chaotic systems we entangled have plenty of state data which we aren't 100% correlated to. Unfortunately, chaotic systems are a terrible place to store information. We're going to have to work on that next. We're going to have to enlist chaotic systems to store and process data for us. That's right, enlist chaos. If you try to skirt around the issue of chaos by damping it out, psychohistory is impossible. You will likely find some chaotic systems more helpful than others. For example, your fellow compatriots, or at least their p-zombie representations, can help. They are very chaotic systems that have arguably been bred for observation and data processing. We've got a kilogram of squishy wrinkly material in our head dedicated to the task! This shows up in Dune with Paul's choice of companions. The Duke, and later Emperor, is always surrounded by people who are observing the world, processing information, providing it to him, and acting on his orders (which includes guarding his life). It was intuitive to see that your best friend is going to be of more help for psychohistory than a gust of wind, but why? If we understand that answer, we may be able to better choose which people/p-zombies to bring close to us. I think part of the intuitive answer is trust. You need to be able to trust these people to act as an extension of yourself. You need to be able to trust that they are holding onto the key information about some system, and are monitoring it for any changes that you might need. You need to be able to trust them to act on their own. What sort of system might we be able to trust in this way? One of the key facets of trust is that it is built through repetition. You prove your trustworthyness by being predictable and reliable. Of course, the ground beneath your feet is predictable and reliable, which demonstrates that the trust we need also needs to be flexible, or else you're treating your best friend like the dirt beneath your feet. The simplest structure which is trustworthy is one which polices itself. If you can trust someone's "inner self" to police their "outer self" and keep it in check, maybe even report to you when the outer self is misbehaving, then you can trust the person as a whole. Of course, this is a chicken and egg problem. You have to be able to trust the "inner self", which could involve trusting an "inner inner self" and so forth. In an ideal world, such as one where psychohistory might come about, this process could continue as deep as one needs. In our world, we know eventually there's going to be something unpredictable at the core of this structure. We'll address this in a moment, but there's an important and convenient detail here. We mentioned earlier that our plan needs to include the effects of our own actions. This means a sub-plan of the plan needs to account for whatever we choose to do. Thus means a sub-sub-plan of the sub-plan needs to account for how we plan for our choices, and so forth. We need the same structure in ourselves as we need in those around us! This is very important, because it permits *us* to be part of someone else's psychohistory while we strive to be part of our own! We see this in Dune. Paul's closest compatriots, such as Gurney Hallack, Stitgar, and Paul's own mother and father, are all striving to shape the world to their goals, and all have this deep self-within-a-self structure. Each of them encourage Paul to develop his own structure deeper, both helping them with their goals and helping Paul achieve more control over his own future. This can be contrasted with the Baron Harkonen. Under the Baron, depth is only encouraged as long as the Baron maintains control. He takes care to make sure none of his servants gain more control over his life than he has over theirs. Now with all of this, we can start to put the pieces together. We can see how we can entangle ourselves with chaotic structures, including our p-zombie friends. We can see how to use these friends to keep track of the huge volume of valuable information we need for our psychohistory. And we can see how we can work together, even if there isn't a strict hierarchy of who is in charge. The lack of a strict hierarchy brings up an interesting question: whose psychohistory is it anyway? Did Hari Seldon really create it out of the blue, with no external muse guiding his way? In Dune, Paul Atraedes clearly admits he's following some greater scheme that he does not fully comprehend up until the moment where he does, and crowns himself Emperor of the Galaxy in the aftermath. So we clearly have to consider two patterns. One is that there were already forces at play trying to solve the dark ages problem of Foundation, or forces at play leading towards the unraveling of the dangerous web the Bene Gesserit wove. In such a case, psychohistory or one's status as the Kwisatz Haderach is really just the culmination of a much larger effort. It may seem magical, because nobody can see the undercurrents. This would suggest that it is no accident that Hari took the secrets to his grave. The other pattern is that your Hari or Paul is actually the first ripple forming in an avalanche that follows. In this case, Hari or Paul may have undergone tremendous inner searching, and found everything revolved around one small nugget... the part of themselves they could not see into. They brought it to the surface, and it happened to be more effective than any other approach anyone else had. If someone else had an effective approach, Hari may have believed psychohistory works, when it in fact does not. In Dune, a similar thing happens when Paul's son actually disrupts Paul's vision of the future by doing something Paul never thought someone would do. In this case of a small influential nugget, it might expand with the flow of time like a smoke ring, until it is entangled with everything of importance. Then, it may turn inward and find a Hari or a Paul to be its harbinger. However, what kind of idea can behave this way? The more divisive the idea, the more rapidly it devolves into Baron Harkonen's style of thinking. The more unifying the idea, the more it can be upheld by those like Paul's gang of highly conscious individuals. In fact, the most unifying ideas would be those which so strongly resemble the status quo that nobody realizes anything changed at all! The most powerful ideas may be no more than just a whisper. [Answer] If we go by Asimov's explanations, the answer is clearly **no**, since Psycohistory is a statistical tool used to model the actions of masses of people (the Galactic population, in fact) and leadership is defined as actions taken to get people to carry out the leader's intent. Think about this in terms of insurance, a real life product of statistics. using masses of data, actuarial tables are drawn up demonstrating the likelihood of death within certain age groups. Qualifiers can be added to take into account productive and counterproductive behaviours (for example smokers in any age group will have a much higher chance of death than non smokers). So the amount you pay in a premium is determined by statistics on the historical death rate per thousand of people in your age group (adjusted for factors like smoking). However, this information has nothing at all to say about when you will actually die. Making a change like quitting smoking can shift your position inside the table (death of ex smokers per thousand/age group), but other than making a general shift in your position, the actuarial tables still don't predict when *you* will die. Quitting smoking is perhaps a weak analogy, but since psychohistory is predicted on modelling the behaviours of a giant mass of people, then the actions of individual leaders will be much like convincing people to quit smoking, there may be subtle shifts in the actuarial tables over time, but few dramatic changes. Statistical tables and prediction are based on most variables being stable over time. Later in the Foundation series, > > psychohistory broke down when a wild card was introduced in the form of a mutant with psychic powers. > > > Later in the plot it is revealed that > > galactic history is not merely predicted, but actively managed by a protagonist. > > > Similarly the actuarial tables use to calculate insurance premiums could be overturned by some sort of large scale natural disaster, or even the after effects of something like a limited nuclear exchange in the Middle East (every group is ow affected by radioactive fallout, so all tables after the event need to be recalibrated, but this is no longer accurately predictive since the effects of fallout or natural disaster could be changeable each year. A year with high dust storm activity spreads more fallout and creates another spike in deaths years downrange of the windstorms). This sort of reasoning means that the sort of "leadership" needed to change the predicted outcomes of psychohistory is going to be of the operatic "Grand Guignol" type capable of changing the statistical outcomes of millions or billions of actions in a very short period of time. Asimov himself understood how unlikely this was, hence the introduction of a unique and totally off the charts individual in the stories. [Answer] It seems to me that Asimov's premise would have been more plausible if, rather than fixed messages opened at fixed times, his psychohistorian had left behind a computer program. The program would read the galactic news feeds, gleaning information from current events. When certain conditions were met, the program would release messages tailored to solicit the desired change in behavior among the leaders. As the story stands, it suggests a "Rube Goldberg" level of machination. We now know from chaos and game theory that accurate long term forecasting in highly complex systems is inherently impossible. [Answer] No, never. Small random events can have huge unpredictable consequences, as predicted by [chaos theory](https://en.wikipedia.org/wiki/Chaos_theory). Example from recent history of USA: In 2000, [Butterfly ballot](https://en.wikipedia.org/wiki/Ballot#Design) flipped USA election results from Al Gore to W Bush. As consequence: * USA spend 3 Trillions USD on wars in Afghanistan and Iraq, destabilized the region, which sent refugees to Syria and destabilized it, which sent 1M refugees to Europe. As a result, there are 20M of people in Middle East who have a cousin in Europe, who is (according to tribal laws from original country) required to help that cousin, feed him and help him to find a job, if only s/he can get to Europe somehow. So for 20M people in Middle East, getting smuggled to Europe is best shot on decent life they have. 1 M per year for foreseeable future. Open liberal democracies like in Europe have no decent way to protect themselves from such influx without radically change how they think about their own society (to be less open). So old open Europe is over, one way or another. * W Bush election in 2000 also significantly changed US domestic politics. Parties became more polarized. It allowed W Bush to shift Supreme Court balance to the right, and after [Citizens United](https://en.wikipedia.org/wiki/Citizens_United_v._FEC) unlimited private money to influence (buy) election results. Koch brothers spent millions to battle scientific consensus about climate change, and as result less people trust the scientific consensus than in 2000. Which slowed down the necessary and inevitable transition to low carbon economy, which will likely change Earth's climate for millenia. Situation is so polarized right now that I expect to have as many (or more) downvotes as upvotetes for this answer, because personal position to climate change today is not based on scientific consensus, but on personal political preferences. All this as a result on obvious design error on a voting ballot in one county in Florida in 2000. Not predictable by any statistics. Asimov has another novel well wort reading dealing with similar problem from other perspective: [The End of Eternity](https://en.wikipedia.org/wiki/The_End_of_Eternity) where scientist do careful "minimal reality changes" to change the flow of the history and minimize the suffering of humanity. And again, such changes have unpredictable consequences. So even Asimov was not 100% sold on the feasibility of psychohistory. Funny fact: Economic Nobel laureate Krugman was so hooked up on Foundation that [he decided to study macroeconomics](http://www.wired.com/2012/05/paul-krugman-geeks-guide-galaxy/) - this was the closes he could get to psychohistory. [Answer] For psychohistory to be a possible theory, and for it to be used in time capsules, there are several criteria that humanity as a dynamical system must meet. First of all, this system must be non-chaotic. The reason is simple, if it is chaotic, it is fundamentally unpredictable, because infinitely close initial conditions will lead to diverging results, if enough time pass. Since we can now the universe only with finite precision, that will lead to any prediction to fail at some point. That is not a definitive problem with psychohistory itself, since on short time scale relative to the system (which can be seconds, days or millennia for what I now) the prediction may be accurate. But to keep them accurate on long time scale, you need to update them, and you can not do it with a time capsule. Second, the system must be stable. It means that an external (small) perturbation will not leads to diverging results. It is important since most of physics, for example celestial mechanics, has been proved to be either random or chaotic. Since you can not predict these facts, if they can disrupt your system, your predictions will diverge from the reality. So the picture we can have at this point is that psychohistory predicts a trend in the future, which is disturbed by perturbations that are not sufficient to make the system jump from one trend to another. Now we have to ask ourselves an important question : are the big crisis mentioned in the question a consequences of the trend, or a perturbation of it ? As an example, lets examine world war 2. The clear trend is that before the major powers were Europeans, and after they faded and USA and USSR raised as superpower. But does this switch happen *because* of the war (making it part of the trend), or would it has happened *anyway* making the war a perturbation of the trend ? It is clear that if crisis are perturbations of the system, you can not predict them. So the third criterion is that crisis are part of the trend. That is still not sufficient. Because you not only want to now *what* will happen, but also *when* (because you want to use psychohistory in time-capsule). If world war 1 is generally though as having been inevitable due to the social and political context, it is also admitted that the assassinate of Franz-Ferdinand in Sarajevo speeded up the process. However for you psychohistoric time-capsule to work, you need the system to be stable in its rate of change, to be able to now when your time capsule should open. ## Conclusion Psychohistoric time capsule, to work, needs the galactic civilization system to have the following features : * Being non chaotic * Being stable in his behavior * Having crisis as trend and not perturbation * Being stable in its rate of change Not that these must be feature of the *system* and not of the *psychohistory*, thus being independent of its implementation. Judging if with all that the use of time-capsule for psychohistory is plausible is let as an exercise to the reader. [Answer] I think it is possible, but not always. Meaning of psychohistory is : > > "while one cannot foresee the actions of a particular individual, the > laws of statistics as applied to large groups of people could predict > the general flow of future events." > > > It reminds me the way meterologists predict the weather. If I remember it right, Hari Seldon needed the historian and full history of galactic empire to create his mathematic methods to perfection. And this is my theory based on psychohistory: If we would be able to have full access to history data, and offcourse the true history data, not just something that winner writes, we could use that to search for patterns according to some events and if we find some, we can try to confirm with another part of history where the same event became and if the output is the same, we may very well have a pattern! And I believe that, if we have enough of these patterns, we may very well have a good way to predict output of every event, the real cause and effect! Of course, my theory have a few problems like,where to get real data, with enough precision and detail, and how to create search pattern code. ]
[Question] [ Loosely based on real life, what single event either man-made or natural can cause communication either to or within governments on a global scale to fail? Can be fictitious, just not totally unrealistic e.g. zombies, aliens, we all turn to dust for no reason at all and so on. My main focus is on cities that become lawless or left to civilians to survive since the official governments are no longer in control or are unable to be of any help. But I need to understand the quickest way to collapse a government, and from the answers thus far, since governments are systems, and information is critical - that would provide a key hint on how to make governments fail. Hopefully that clarifies the question so it's taken off hold. Thanks in advance! :-) [Answer] There are a lot of options here. **Natural Disasters** * Large Meteor Strike: This option is obviously pretty dramatic. Reference Question: [A giant meteor, balancing destruction and life sustainability](https://worldbuilding.stackexchange.com/questions/788/a-giant-meteor-balancing-destruction-and-life-sustainability) * Volcano/Earthquake: Major tectonic activity can wreak serious system wide havoc. * Super storm: Ever see 2012 or any other super storm movies? Just like that. **Biological Disasters** * Out of control pathogens, bacterial or viral, doesn't matter. These can be sourced from all sorts + Government Program: anthrax maybe + Naturally occurring: ...Ebola anyone, imagine if it were airborne. + Supernatural: A deity of death and disease got bored or angry perhaps. + Space: Aliens bombing us with bad...stuff + Food shortages **Man Made Disasters** * War: I hope this doesn't require elaboration. * Nuclear conflict or accidents * Climate changes: Yep... + I put this in because it has the potential to cause large shortages of food and water etc in time. * Ran out of fuel, natural resources * Economics * Food shortages ## The Point The point of this isn't the lists it's the ideas behind it. * Governments generally don't collapse overnight, generally it is a drawn out process that takes time. Admittedly the end can culminate very very quickly (military coups, mass protests for example). These types of situations are usually a long time coming and the snowball gets faster so to speak. * It is a **system**. You have to overload a system for it fall. Governments can be good at stretching but not breaking. Taking into account what the system depends on is usually the best route to define what could cause it to collapse. Governments rely on a few things to function * Communication networks. Ironically our system is far less flexible in this regard than it used to be as we are totally reliant on powered communication. If you eliminate electricity a government will shudder to a halt. * Information, this goes hand in hand with communication but you can also think of very oppressive governments not getting good information because they are hated and/or feared. * People. You kill off the people you kill off the government's ability to function. This would tend to be more localized. Its tough for emergency management to function when the emergency manager and his staff got wiped out by a storm. * Supplies, be they natural resources or food or fuel or raw materials, a shortage or embargo can bring a state down. You can talk about food shortages/riots, or any other combination of stressors. Take into account the strength of a nation/government, find weaknesses and hit them with a disaster they can't handle things snowball, government gone. [Answer] Any situation which could instantly render the bulk of out technology useless. Personally I prefer the scenario of a massive solar flare, but targeted nuclear strikes designed to massive Electro-Magnetic pulses could fit the bill as well. Individuals could even simply seek to take out key parts of the electical grid in major countries, idealy destroying power plants first. Our current society is extremely reliant on electrical devices, and more importantly most of our communications would be destroyed. In many places the most basic utilities would be disrupted, and in many places clean water would not be available after a few hours to several days. Individuals with wells or towns fed off a well system may be better off as long as a non-electrical method could be used to retrieve the water, however there would be many areas where food stocks would be depleted in a matter of weeks. If power could not be restored quickly, and especially in the case of a solar flare; where most vehicles would cease to function, Many areas would fall to basic anarchy in a matter of days. [Answer] Lawless and collapsed government are not quite the same thing. Government also operates on several levels (municipal, state/provincial, and national)...I'd assume you are going to want something that drops all three levels. Viva La Revolucion! First method of dropping a government to its knees is the people themselves. Let's say the powers that be behind the Anonymous movement get what they want (anarchy)...you'd see coordinated anarchy on all levels (the idea here is that lack of government does not equal lawlessness). Not so sure if this will fit the bill for what you want though, committed anarchists believe in no government and not committed to lawlessness. I'm assuming you are looking for more of a disaster that makes the government incapable of functioning. For this to work, you need something to affect the populace heavy enough that there is no longer enough people to maintain the current government (which is actually a pretty large number of people, the bureaucracy will expand to meet the needs of the expanding bureaucracy after all). Plague / sickness is my first choice here...a government cannot operate if the employees of the government are too sick (or dead) to keep it functioning. Radiation / nuclear war. If you want to empty major cities fast, put the threat of a nuclear strike on it. A global event that causes a catastrophe that damages nuclear reactors and causes them to meltdown worldwide (Fukushima for all!). Even a super villain that managed to detonate the majority of nuclear arms in their silos would work here. Entirely irradiating a nations food source would probably work to the same extent, cities need large amount of food to survive, a mass shortage of food can empty them and reduce it to lawlessness as we compete for the remaining food supply. Even a worldwide food shortage/disaster could have this effect. Neutron war. Maybe I'm off in this theory, but there is a 'neutron bomb' idea that has a bomb that is relatively 'weak' when it comes to causing damage to buildings, but absolutely devastating to the population in those buildings. This would be a far more instant version of a ghost town. Drop enough of them and you'll have your anarchy. The options above allow for a ghost city where the city is relatively unharmed (radiated maybe?) but the population has mostly disappeared. I've got some other options, but they don't really leave cities behind. [Answer] One most physically possible and under-reported would be **[massive solar flare](http://en.wikipedia.org/wiki/Solar_flare)**. Like [Solar storm of 1859](http://en.wikipedia.org/wiki/Solar_storm_of_1859), whith auroras as far south as Caribbean and so bright you can read newspaper. Depending on intensity of such flare: * power grid would collapse for weeks, * GPS satellites would be destroyed (it could take years to restore satellite network to guide planes and ocean transports) * huge transformers would be destroyed - and would be hard to manufacture replacement without available electricity * computers would be destroyed, obliterating everything from banking (how much money I have in my account?) to car computers (how to resupply after food got spoiled with no refrigeration) * diseases spread by unclean water would become common (typhus, cholera) and hard to deal with without modern transportation and healthcare * food factories and farms would collapse without electricity. They can run on generators for few hours, but without electricity you cannot make fuel to power generators. Refineries cannot refine without electricity. Mad Max world. * global unrest of hungry and desperate people all over. * and so it goes. We spend more than hundred years to build infrastructure for managing power. If it was destroyed, **it will take years to rebuild it** even if we have some remnants of manufacturing not destroyed. The country which avoided complete disaster (if any) would be next superpower. I am not afraid of plagues or other natural disasters - we survived so far so it is good chance our own nature can deal with it. Solar flare is different - we cannot depend on nature to help us, and our own technology is inadequate to deal with the scope of disaster. Nuclear war, green or grey goo - we can avoid that if we are smart enough. We cannot avoid next coming flare, it is out of our control - only thing we can do is to prepare to deal with it. Which we don't do, too much to bother. Let's make a movie about it! [Answer] One example to answer for a single city as the last part wants: Nuclear threat - I am currently using this but I will likely never get published or finished. If 3rd party publicly announces that the city will be attacked by a nuclear warhead and it seem believable for some reason, said city will be agressively evacuated. Limited military forces will likely remain within the area. Those who know better, are unwilling to leave home in the required time frame so hide, or break through defenses would find a largely uninhabited city with plenty to loot. This fits better as a "no mans land" as few people would be there. [Answer] A fast spreading virus that renders its victims blind and deaf at the same time for several months should do the trick. Let say travelling diplomats and diplomatic agents or couriers spread the virus among their social circles (which consist of other government people mostly). Also that virus is genetically engineered to spread but stay silent for a while then attacks your specialised neural circuitry (visual and aural). The virus is not lethal, much like a like cold sore virus (herpes simplex). It infects you, renders you deaf and blind (for a while) then vanishes. [Answer] An extremely powerful solar flare. As said many times before, enough energy in an electromagnetic pulse will generate a very high strength electromagnetic field, causing Eddy currents, and heat, burning up wires. Satellite control via radio will also be destroyed as the waves can deflect radio signals. The onboard electronics controlling the thrusters of the satellite are also melted, leading them to slowly spiral into earth, one day creating disaster. All communications are reduced in a day, when every side of Earth has had time to be exposed, though the Poles may be spared. ]
[Question] [ Could a star system exist where a body orbiting the star has an inhabited planet moon orbiting it instead of the sun? And the inhabited planet moon has its own smaller satellite. I have very little experience with this kind of world building, so thank you in advance. --- *Edited for terminology: In a nutshell, if it [orbits the star and it is large enough](https://en.wikipedia.org/wiki/Definition_of_planet), it is a planet. If it orbits a planet, it is a moon. A planet does not have to be inhabitable and a moon does not have to be uninhabitable.* [Answer] Yes, it is possible for a star to have an orbiting body (a planet) which has a habitable body as its satellite (a moon), and it is possible for such a habitable body to have its own satellites (the moon's moon). It is even possible for the *satellites* to have their own satellites, though rather unlikely. The more satellites of satellites a system has, the more unlikely it is... though consider that technically a star may be the satellite of the super-massive black hole at the centre of its galaxy. If the star is the largest body we are considering, the body orbiting the star will be the next largest (discounting other bodies in orbit around the star), the habitable body will be smaller again, and the body orbiting the habitable body will be yet smaller still. If bodies approach the same mass, it can no longer be said that one orbits the other, but rather that they orbit each-other, or more specifically, they orbit a common [barycentre](https://en.wikipedia.org/wiki/Barycenter_(astronomy)). Thus, the difference in mass between primary and satellite must be sufficient that the barycentre is within the primary for it to be considered to be truly orbiting the primary. [Answer] A moon orbiting a moon is called a **submoon**. It's possible for them to have a stable orbit, but it's more constrained than for a normal moon. None have been observed so far. The conditions for stable orbits and observations are discussed in [Orbital Stability of Exomoons and Submoons with Applications to Kepler 1625b-I](https://arxiv.org/abs/2005.06521) (2020) along with a lot of relevant references. I don't think any of the conditions for a stable submoon orbit preclude habitability. [Answer] There are many scientific articles discussing the possibility that large enough exomoons orbiting giant exoplanets can be habitable. Looking up such articles would be desirable. It is possible for a moon to have a sub moon or a moon of a moon orbiting it. However, there are more dynamical problems and restrictions with a giant habitable moon having its own moon of a moon than there are for a planet having a moon. So possibly you might want to ask for the help of someone expert in orbital dynamics to help design your fictional star system. ]
[Question] [ In a nearby star system to Earth, there lies an... interesting planet. Thirty thousand atmospheres of pressure, "surface" temperature of 5,500 kelvin, an atmosphere made of gaseous sillicates and vapourised *iron*, it makes Venus look like a paradise. So let's give it an appropriate name, like Hell. Now, due to Alien Space Magic a portal 5m wide opens on the surface of Earth connecting to the surface of Hell at the present day. What happens to the area around the portal on Earth, and could we send a probe through to Hell that would survive long enough to send back data? [Answer] ## Looking for [Choked Flow](https://en.wikipedia.org/wiki/Choked_flow) $\dot{m} = C\_d A \sqrt{\gamma \rho\_0 P\_0 ({2 \over {\gamma + 1}})^{{\gamma + 1} \over {\gamma -1}}}$ * $\dot{m}$ is the choked mass flow rate, the value we are looking for * $C\_d$ is the discharge coefficient. Let's go with 1.0 for space magic * A is the area of the portal. A 5m diameter circular portal has an area of ~19.6 $m^2$ * $\gamma$ is the [heat capacity ratio](https://en.wikipedia.org/wiki/Heat_capacity_ratio) of the gas. For gaseous silicates we'll use 1.29 * $\rho\_0$ is the gas density. We'll need to figure that out. * $P\_0$ is the upstream pressure. 30,000 atmospheres, or 3.045 gigapascals (GPa). ## Calculating Density of Death World's Air The equation for density is $ P = \rho R\_{specific} T $ * P is 3.0 GPa ($3 \times 10^9$ Pa) * T is 5,500 Kelvin $R\_{specific} = {R \over M}$ * R is the gas constant 8,314 ${m^2 kg} \over {s^{2} K mol}$ * M is molar mass. For silizate ($SiO\_2$) gas, it's Si (28) + O (16) x 2 = 60 $g \over {mol}$ $R\_{specific}$ = 138.6 $\rho\_0$ = $P \over { R\_{specific} T }$ = 3,995 $kg \over {m^3}$ ## Final Flow Rate Inserting Variables and Solving : * $\dot{m} = C\_d A \sqrt{\gamma \rho\_0 P\_0 ({2 \over {\gamma + 1}})^{{\gamma + 1} \over {\gamma -1}}}$ * $\dot{m} = (1.0) (19.6) \sqrt{(1.29) (3,395) (3,045,000,000) ({2 \over {(1.29) + 1}})^{{(1.29) + 1} \over {(1.29) -1}}}$ * $\dot{m} = 19.6 \sqrt{(1.29) (3,395) (3,045,000,000) ({2 \over {2.29}})^{{2.29} \over {0.29}}}$ * $\dot{m} = 19.6 \sqrt{(1.29) (3,395) (3,045,000,000) (0.87)^{7.89}}$ * $\dot{m} = 19.6 \sqrt{(1.57 \times 10^{13}) (0.34)}$ * $\dot{m} = 19.6 \sqrt{5.34 \times 10^{12}}$ * $\dot{m} = (19.6) (5.34 \times 10^{6})$ * $\dot{m} = (4.53 \times 10^7)$ $kg \over s$ The average velocity of that gas is $\dot{m} = \rho v A$. Which is 577 $m \over s$. ## Expansion and Cooling After exiting the portal, the iron-laden silicate gas is expanding and cooling from 5,500 Kelvin and 30,000 atmospheres. The speed of sound for this expanding death world gas is $a$ = $\sqrt{ \gamma R\_{specific} T}$. $\gamma$ has a different meaning here. It's the adiabatic index, and for diatomic gasses it's 1.4 (not quite the tri-atomic SiO2; but using this for now). T is in Celsius instead of Kelvin. * $a$ = $\sqrt{ (1.4) (138.6) (5,500) }$ = 1,032 $m \over s$ The death world gas is initially expanding from the portal at the it's speed of sound, 1,032 $m \over s$, or about Mach 3. Which would mean there's plenty of sound, noise, heat, and toxic vapor jetting out of this thing, but most of it is the higher-temperature, higher-pressure air expanding and cooling. ## Limits Where does the expansion end? ${P\_1 V\_1} \over {T\_1}$ = ${P\_2 V\_2} \over {T\_2}$. $P\_1 \over P\_2$ is 30,000. $T\_1 \over T\_2$ is ~ 200. The volume at which the gas reaches Earth temperature and pressure $V\_2 \over V\_1$ should be 150 times the exit volume. For a portal 5 meters wide, I'd estimate you'd need a grid 750 meters on a side to keep people clear. ## Heating Some folks have asked about how much the portal to the death world starts to heat up the surrounding environment. The heat passing through the portal is related to the mass flow rate, specific heat properties of the gas (glass), and the temperature difference between the portal and the environment $\Delta Q = \dot{m} ( \Delta H\_{vap} + \Delta H\_{fus} + c \Delta T )$ * $\dot{m}$ was calculated above. $4.53 \times 10^7$ $kg \over s$ * $H\_{vap}$ is 0 ([according to this source](https://www.physicsforums.com/threads/how-much-heat-energy-in-molten-glass.789170/)) * $H\_{fus}$ is 0 (same source) * c is 0.8 ${kJ} \over K$ * $\Delta T$ is (5,500K - 300K = 5,200K) Solving: * $\Delta Q = 4.53 \times 10^7 ( 0 + 0 + (0.8) (5,200) ) = 1.88 \times 10^{11}$ $J \over s$ = 188 $TJ \over s$ If I've done that right, $\Delta Q$ is 188 ${TJ} \over {s}$. Or 188 terawatts. For scope, 80 terajoules is the amount of energy released by the first atomic bomb test. ## Sound Like the whistle of tea pot, or the rumble of an explosion, the portal will generate a sound that will carry for miles. I'd like the equation to figure out the frequency at the nozzle, but it escapes me at the moment. ## Visibility Iron and silicon dioxide (glass) are both solids at Earth pressures and temperatures. The cooling dome of gas would project nearly 1 kilometer up, and look something like the ash clouds over erupting volcanoes. ## Survivability of a Probe At 5,500 Kelvin, the atmosphere of the death world will even melt the most temperature-resistant material, [Tungsten](https://en.wikipedia.org/wiki/Tungsten). Additionally, the ground beneath the gate is a gas at death-world temperatures. You shouldn't take it for granted that the gate is not now floating inside a crater of it's own making. However, electronics that can survive the forces of being fired from a cannon [are now a real thing](https://maritime-executive.com/article/darpa-develops-smart-bullet-for-deck-guns). [![enter image description here](https://i.stack.imgur.com/1cZ2I.jpg)](https://i.stack.imgur.com/1cZ2I.jpg) The main gun of an M1A1 tank has a muzzle velocity of ~1,600 meters per second. From the safe zone, it could propel a saboted sensor package across the gap and into the gate in under half a second. The sensor package would capture as much as it could before melting. However, there's another problem. The cloud of iron and glass gas is an effective block to radio and optical signals for the probe to send back. Sonic is unlikely to be effective either. Thankfully, some nice fellows have [invented neutrino communication](https://physicsworld.com/a/neutrino-based-communication-is-a-first/), which can communicate through solid rock. ## TL; DR The portal would be incredibly hot, with an explosive blast spreading at Mach 3 from the portal area into the surroundings. [Answer] Based on James McLellan's excellent, if (as of the moment I write this) slightly flawed answer, when this portal is opened, 5,000K, 30,000ATM iron-glass gas is going to erupt from the portal at a rate of around 600,000 metric tons per second. At standard pressure and temperature (1 ATM), this gas would have a density of $0.1385kg/m^3$. However, at 30000 ATM, its density would be around $4155kg/m^3$. Dividing the mass flow of $600,000,000kg/s$ by the portal's area of $19.6m^2$ and the gas's density, we get a velocity of $7368m/s$, or approximately Mach 7. Then we must consider that Silicon Dioxide has a specific heat of around $0.7J/g/K$, so each second we're adding $2×10^15J$ of energy to the surrounding area. That's on the order of a 476 kiloton bomb every second... or 2 petawatts of power... ten times the power output of the most powerful hurricanes. This jet of superheated ultra-high pressure gas is going to ablate anything in its path in a roughly conical volume with its point within the portal, the centerline of the cone aligning with the centerline of the portal. Eventually, the Earth's atmosphere and crust will absorb the momentum of the gaseous iron-glass, and it will also cool enough that it will condense as a liquid iron-glass mixture, which will behave rather like lava. Initially, I expect that this iron-glass gas will cool rapidly as it expands into the earth's relatively cold atmosphere, probably before it loses its kinetic energy, with the result that it will condense into a liquid iron-glass spray that still retains a significant velocity. It may even cool sufficiently in order to solidify before it loses its kinetic energy. At this point, there may well be sizeable droplets of iron-glass, but it is likely that there will also be a significant amount of finely divided material much like volcanic ash, that will remain suspended in the atmosphere for some time. As the event continues, the earth's atmosphere will heat up, slowing the rate of cooling while still absorbing kinetic energy, meaning that eventually molten iron-glass will begin to rain down upon the landscape. However, things don't stop there. The erupting gas will impart its kinetic energy to the earth's atmosphere, resulting in an accelerating hot wind in the direction of the jet cone. This will distribute hot iron-glass ash - and as the atmospheric temperature increases, molten iron glass - around the world. The global temperature will rise to the point where the entire earth is blanketed in a pyroclastic cloud, until the heat from the jet of superheated gas begins to melt the ash deposits around it, resulting in a flood of molten lava advancing toward the portal. Until the weight of molten glass around the portal is sufficient to counter the outflow, the outflow will not stop. If we consider a planet big enough to have an atmosphere such as this, it will have way more atmosphere than Earth. There is practically no way that it will run out of atmosphere before the earth is covered in a thick life-extinguishing layer of hot iron-rich glass. Alternatively, the portal will fail at some point, saving the planet. Whatever continent it was on is probably completely wiped out. As for getting a probe through the portal... without a railgun, there's probably next to no chance, and even with one, no projectile will survive more than a fraction of a second in such a hellish environment. The probe would have to be launched toward the portal at the instant or even before the portal opened to have any chance of making it through... and it is likely that if the scientists in charge weren't aware of exactly to where they were opening a portal, any probe and recording device is unlikely to survive long enough to be launched, let alone return any data. [Answer] I believe it can be probed, but the probe will be very limited in what it can do. Start with James McLellan's idea of firing a large gun into it. He's got the wrong gun, though. We want a large caliber artillery piece, not a tank. (Yes, most artillery pieces can be fired horizontally. You don't see it because it's a last ditch defensive move, not something they want to do.) The propellant is calculated so that after passing through the gas streaming out of the portal it doesn't have much velocity left. When it goes through the portal it opens up like a flower. You now have an object with quite a surface area in a hypersonic wind, the wind is going to grab it and throw it back through the portal. To be flung back through the portal it obviously can't go too far from it and it can't survive the heat for long--the data package is insulated as well as possible, the instruments have a very short lifespan before being destroyed. The recorder is as light as possible, it needs to be blown by the wind far enough from the portal to survive and be recoverable. [Answer] **Yes, but no probe. Map it from our side.** 1. Cap the portal. You will need to approach it with the cap mounted on a bulldozer. The bulldozer can be remotely driven. 2. Cap will of course need to withstand heat as well as pressure but pressure is constant, and so will not need to withstand sudden shocks or impacts. 3. Ideally cap would be in the shape of a dish and could be used as a radar dish. If not (antenna not durable in hot atmosphere?), cap should be able to allow radar waves through it. A refractory ceramic would work. 4. Map the far side thru the capped portal with radar. Sonar might also be useful; high pressure gases on the far side will probably transmit sound well. ]
[Question] [ In a world I'm constructing the sun, the moon, and the stars are not visible but there are tower that stretch from the ground to, roughly, low earth orbit. Each one is around 200 meters in diameter with a unique design (colors, materials, decorations, etc). Over an area the size of Europe there are maybe 12 or so of these towers spread out randomly so they are quite sparse. The people of my world did not build these and are actually at roughly the late middle ages in terms of technology (basically your standard fantasy technology level). I want to figure out how people in my world navigate across large distances over both sea and land. My idea was that the towers would be used as guides instead of the sun and stars but I don't think people would be able to see them at large distances. Maybe making them glow would work but since people live near them I'd rather not blind anyone who looks at one up close. **Question:** How do I modify my very very very tall towers so that people of a standard fantasy world can use them for navigation? Bonus points if your solution makes the towers look cool(er). Solutions may use any form of technology or magic as long as it is a property of the towers not the inhabitants of the world, who are normal humans. Edit: To address how the planet is actually lit up, the thing that blocks the sun and the stars is pretty much a Dyson sphere. The entire inside of it glows uniformly during the day and it turns of at night. Note: All other problems caused by there being no sun or how the towers stay together have been solved through generous applications of sufficiently advanced technology and are out of scope of this question [Answer] The function of the towers is easily solved by turning them into lighthouses where the light is emitted at or within the cloud line. Perhaps the towers were intelligently designed to accomodate the cloud cover such that the illumination is always 200 meters or so below the cloudline. Your real problem is visibility. Assuming nothing else is impeding your view, Mt. Everest (~9 km above sea level) could be seen from approximately 370 Km away. If you're standing on a beach, the horizon is only 5 Km away. Now, your towers go up a long, long away, but you can't see them from just anywhere, meaning your count of towers might be very low to make this practical — especially if there are things like mountain ranges in the way. Here's the equation for an unobstructed (that's *really important*) view to an object on the horizon on Earth (that's *somewhat important*) from [Wikipedia](https://en.wikipedia.org/wiki/Horizon) $$d \approx 3.57\sqrt{h}$$ > > where d is in kilometres and h is height above ground level in metres. The constant 3.57 has units of km/m½. > > > ***You do not identify the height of the cloud cover. The height of the towers from the perspective of this question is irrelevant. They need only be as tall as the bottom of the cloud cover. Clouds can be, generally, 2 Km to 6 Km above sea level ([Source](http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml)). But, to make it easy, let's assume the bottom of the clouds is really high, almost the height of Everest, such that your maximum sighting is 200 Km away.*** * If your people have no better navigation than to look at the towers, they need to average 400 Km apart. * If your people have better navigation, perhaps they could average 1,000 Km apart. The U.S. is about 4,300 Km in width. So you'd have 4 towers across that distance and the need to use a good compass and potentially a clock. **but what about the cool factor?** My vote is to have the towers emit a regular *pulse* just beneath the cloud line, so that the light travels outward from the tower in an expanding ring, illuminating the clouds. That *pulse* could travel, say, 400–500 Km (the distance really depends on how easy you want navigation to be in your story) and the *pulse* can be a specific color or pattern, distinguishing each tower. The regularity of the pulse would be useful, too, since the pulses from two towers would only meet at the same moment when you are exactly half-way between the two towers. Thus, by measuring the difference in time between the two pulses, you can reasonably estimate where you are between the two towers (or three, or ten, depending on the maximum range you set for the pulses in your story. A simple ground-based GPS system.) Of course, that previous paragraph assumes the towers are evenly spaced. But even if they are not, it's just a bit of math to achieve the very same effect. This would lend to the idea of a *navigator's guild* where the secrets of that math are closely protected. *Just keep those navigators away from the [spice](https://www.youtube.com/watch?v=AGqdE1NdMTg).* [Answer] The towers are like a benevolent Eye of Sauron. 1. Some humans have a palantir compass. These artefacts are incredibly valuable and hard to come by. When you look into them there is a pointer pointing to the nearest Eye. 2. As above but each Eye has a name. You speak the name into the palantir as you peer into it. 3. Using mind-waves an Eye detects when a human is searching it out. It projects a pulsing multi-coloured narrow beam of light directly towards the person making sure that the intensity is adjusted to the distance and the visibility to make it safe. If the person is nearby the light comes from low down. If they are over the horizon, the light comes from further up. If they are very far away the light may come from the top of the tower and appear like a bright star in the sky but flashing different colours. [Answer] I remember looking into something similar with landmarks when I was working on my Thesis Topic. This is a simple localisation problem. As long as you can see Two landmarks and know your previous position, you can estimate where you are (assuming the landmarks aren't right next to each other). I can't put any equations or diagrams in as I'm at work, but here is the basic gist of it. Firstly you need to know the height or size of each tower. Depending on how high the tower appears to you, you can determine how far away you are from a single tower (or landmark). This creates a circle around the landmark where you can be. If you can see two circles (draw two intersecting circles on a piece of paper) then you can pin your location down to two different points. In the best case scenario, the circles only meet once and you know where you are. In a normal scenario, the circles meet twice. Using your previous location, you can then determine where this is (as long as the landmarks are far apart so the intersections are clearly identifiable). The worst case, is that you have incorrectly Identified a tower and the circles don't intersect at all (or the landmarks are right next to each other and they intersect the whole time). With 3 or more landmarks you will always be able to locate yourself. This is similar to the way GPS works, where you will need roughly 3 satellites. The more landmarks, the more accurately you can determine your position (Due to uncertainty, its not like a nicely drawn circle, but more like a blurry circle drawn with a sharpie). Now the biggest issue in this case is if you only have 1 or no landmarks, but since your towers are so tall, I dont think this will be an issue. You can many different forms of landmarks as well. Unique coastal formations, Villages or islands. Ships which only operate in a certain area. As a Note: The position of the sun can also serve as a landmark. While its not good for measuring distances, it does allow you to use it as extra information with a tower, Aka you could figure out the relative positioning and your logical position as a result, and it will help you identify the orientation of the tower which further lets you narrow down your position. (E.g. if there is a door on the front of the tower, and I can see the door, I must be infront of the tower). This can be combined with the land around the tower (the coast) and should also lets you pinpoint your location based on the distance from the tower and the orientation of the landscape that you can see. So ideally, with just 1 tower in sight, you should be able to determine your rough location (assuming the towers are different from each other in either shape, height or surrounding terrain) [Answer] People were navigating before GPS, by using mountains as directional beacons, or following coasts, rivers and mountain ranges. If people in your world can **climb a tower**, they can plan their journey, e.g. by realizing that they can get to the next tower by following that one river, and then going left at river's fork. Alternatively, if the **benevolent ancients have anticipated this problem**, they could have put a powerful laser on top of the tower, to shine a concentric grid on the clouds around the tower. Or just to have a light spot moving through the clouds towards the tower. Finally, if the beacon (or the sun) is above the clouds, you can use a certain natural stone that acts as a polarizing filter to find direction to actual light source, and thus navigate: <https://en.wikipedia.org/wiki/Sunstone_(medieval)> [Answer] Each tower is a pole of a giant magnet, as strong as the dipole within the Earth's core. Compasses will point to (or away from) the nearest tower. A little triangulation tells you where the towers are. Couple it with known landmarks and you have a quite descent positioning system that peopoe in mefieval ages can use. [Answer] Part of the answer to this has to be determined by what you define as 'large distances' but Low Earth Orbit is pretty high; anything between 160 - 2000km. Your original idea of using triangulation on the towers would probably work in the Mediterranean at least. But, unless there are even more towers interspersed around the globe, they're unlikely to help you around the Cape of Good Hope, for example. That said, there is actually a [research paper](https://www.researchgate.net/publication/269524633_The_Coverage_Analysis_for_Low_Earth_Orbiting_Satellites_at_Low_Elevation) on the coverage of low earth orbit satellites that looks at the problem from the opposite direction, but could be useful. My advice? Read the paper in detail, reverse engineer the coverage angles to show where on the earth you should still be able to see the top of the tower, then subtract 50% for atmospheric visibility, potential cloud cover, need to see at least 2 towers, etc. then distribute your towers on the surface of your planet accordingly. It's actually a pretty neat idea - an optical, low tech version of GPS. The other advantage is that your fantasy world inhabitants may get to space earlier than we did because they learn to use the towers as space elevators, eliminating the need for 1, possibly 2 stages of your regular Saturn V rocket in order to get to the moon, just from launching from the top of one of these towers. [Answer] I can think of one clever solution. Breed lots of ravens (e.g. Game of Thrones) in the easternmost tower and wrap a silver wire around one leg, so that they can only get food from that one tower. If they fly to one of the 11 other towers they get no food. Then caravan leaders and ship captains can purchase some of those ravens for their journeys and watch which direction they fly when released. Most likely that would be the eastern tower. Repeat the process for Southern Tower ravens with gold wires on their legs. Once you have two vectors you can figure out where you are on the global map. Some super smart but expensive ravens can be trained to selectively fly to any of the 12 towers but then return to the caravan after one hour if they haven't been fed enough to make that journey, so this way the caravan navigator can watch one raven's flight direction back and forth towards selective towers for a few hours to make sure the caravan is heading in the right direction. [Answer] Make them some kind of lighthouses, but instead of just emitting light they start some kind of energy pulse in regular intervals, causing something like aurora polaris. Those energy pulses could travel much slower than light, so you could actually see the rings getting bigger and bigger. Over the distance the light would change color/intensity so you could estimate the distance to the next tower and you will clearly see where the pulse is coming from. Also this solves the issue with clouds/mountains obstructing view, as you only need some free sky above you to navigate and there is no issue of the signals traveling below the clouds. Maybe you want mountains slowing down the signal, creating a nice effect of not perfectly round signals - creating additional information for navigation. ]
[Question] [ I'm working on a sci fi story which heavily integrates themes of varying alien configurations and how they shape society, culture and language. As part of this theme, I want to have some of the human characters using a variety of different methods of communication, rather than falling into the "all humans communicate through spoken language and aliens have variations" trap. I decided to have a main human character who primarily uses a signed language, and have decided to 'make' her Deaf as a part of this. (Capitalized intentionally, see below.) One thing I really want for this character is for her to come from a cultural background of heavy signed language usage. It's important to the themes and the character to have her come from a Deaf cultural background, and I'm looking for things which would cause and maintain a population with high stable rates of Deafness/hearing impairment as a result, which would still apply outside of her place of origin, as that is where much of the story is set. I've also decided for other reasons that I want her to come from a space colony near the setting location rather than from Earth itself. The idea I have come up with is that this settlement is one of the earliest human settlements outside of the solar system, coming from an intergenerational starship with a minimal staff and a wide variety of frozen/preserved embryos meant to establish a human population upon arrival. The idea I had is that for whatever reason, those embryos happened to have a high frequency of Deafness, and as the years passed resulted in an established human settlement which mostly uses a signed language. I do not need an explanation/justification as to why they wouldn't all use technology to become hearing. I have that covered. My question instead is: what sorts of causes might result in a population with widespread generational Deafness such as this? I had originally conceived of this as purely biological reasons and been looking for something which would specifically affect Deafness rates in the population, but some other suggested explanations have suggested environmental factors which could cause Deafness to be specifically created or selected for. These answers are also appropriate. I am not sure how to update the tags for this to reflect this. The best answer will have a plausible genesis (such as a specific genetic syndrome and/or something which could cause stored embryos to be susceptible to it, or a reason for the starship to be originally crewed by Deaf folks) and a reason why it would be stable many generations down the line. Scenarios should be consistent with a culturally Deaf background and a signing background, rather than suggesting alternate means of communication technology. EDIT: Okay. I was cool with the edit which removed some other plot details for clarity, but ever since it was made I've been getting "what if instead of Deafness you did [x]" answers, and that is not what I'm looking for. I specifically am looking for a Deaf culture here. [Answer] Genetic manipulation/augmentation can often have consequences that extend to offspring, whether they affected the target of the augmentation or not. Perhaps this generational deafness came from some initial genetic augmentation targeting something else that had unforseen consequences in the offspring. [Answer] First, I'll say that it would be a lot better to have your characters descend from or be raised by capital D Deaf people. This way you get an established Sign Language (which can morph like any language will) vs having to spontaneously create one. I've actually seen a first generation Sign Language (wrote my undergraduate thesis on it) and it's not as grammatically complex as an established language (though it for sure had grammar) and the vocabulary wasn't very big either. Plus you have consistency issues. In this case, the language didn't start up until the children were old enough to go to school, and there were strong influences from visitors and of course the native spoken language. While doing it this way can make an interesting story, if you want to honor Deaf culture, preserve an existing language with native users. There's a terrific short story in this anthology: <https://www.goodreads.com/book/show/23129839-octavia-s-brood> Octavia's Brood: Science Fiction Stories from Social Justice Movements Earth transports babies deemed unacceptable due to their disabilities to a space colony. Which turns out to be a pretty awesome place. While of course a lot of deafness is acquired, for those born deaf, even existing technology can diagnosis it (all newborns in hospitals get the screening tests and there are further tests for those who "fail"). Another way to get a Deaf community is to have a colony come from a group of workers or settlers chosen for their deafness. Because it was advantageous for that location or the work. As they raise families, many of the children will also be deaf, since some deafness is genetic (you can even screen for that initially). And everyone will grow up signing. Depending on what's around, people born hearing might not thrive, or might live with whatever noise there is, or the noise could be gone by then, or they might choose (or their parents will choose) to make them deaf medically for their own comfort and health. I can imagine all the hearing readers gasping right now. But the reality is that our society routinely removes someones ability or even bodypart that is not deemed important, because there are other benefits. Extra fingers? who needs those? A quick clip of the auditory nerve could save a lot of children in this colony. [Answer] **Your colonists have Waardenburg syndrome.** [![waardenburg syndrome](https://i.stack.imgur.com/ZZ48d.jpg)](https://i.stack.imgur.com/ZZ48d.jpg) <https://healthjade.com/waardenburg-syndrome/> <https://en.wikipedia.org/wiki/Waardenburg_syndrome> > > Waardenburg syndrome is a rare genetic disorder most often > characterized by varying degrees of deafness, minor defects in > structures arising from the neural crest, and pigmentation changes. > > > There are a lot of other images of folks with this syndrome on the web. They characteristicaly have a white forelock, bright blue irises and wideset eyes. The Wikipedia article states that about 1 in 30 students at schools for the deaf have this syndrome and so they can be cognitively normal. For your story, there is some tremendous benefit conferred by Waardenburg syndrome as regards living on your space station, such that all available Waardenburg embryos were chosen to grow up. You will need to invent this benefit or read more about the syndrome than I have. An easy one is that for reasons beyond control, your space station is irrevocably loud such that inhibitants are driven to deafness anyway, and having Waardenburg's is an easy way to ensure deafness without also having more debilitating congenital anomalies. Or you could give them something extra - for example an abnormal accumulation of neural crest cells in the pituitary (the vestigial "third eye" in the center of our brain) give that organ back the powers that it lost during our evolution [Answer] **Perhaps your colony was designed to be deaf.** This isn't as far-fetched as it may seem at first glance. Today there are [many known instances](https://motherboard.vice.com/en_us/article/ypwa5j/how-reproductive-tech-could-threaten-or-preserve-deaf-culture) of parents intentionally having children with a “disability”. Using preimplantation genetic diagnosis parents can choose the traits of their children. While generally, we assume that parents would choose to have “healthy” children many parents are using these services to have “disabled” children, generally in the same way they themselves are “disabled”. Your use of Deafness with a capital D suggests you already are aware of this, but many "disabled" communities, Deafness perhaps chief among them, think of deafness as less of a handicap and more of something like a culture. Advocates of this idea feel that being deaf isn’t a significant impediment to their everyday lives and rather enriches their lives in various ways. New colonies are often formed by those dissatisfied with their current environment or who are being persecuted for one reason or another. Perhaps your Deaf colony arises from a Deaf community fleeing laws outlawing their continued existence or otherwise seeking independence. [Answer] You might want widespread **congenital cytomegalovirus (CMV)** infection. Most of the medical terminology on a cursory search is well over my head here, but to pick out the dramatic highlights: > > [Cytomegalovirus](https://www.cdc.gov/cmv/index.html) (pronounced sy-toe-MEG-a-low-vy-rus), or CMV, is a common virus that infects people of all ages. **Over half of adults by age 40 have been infected with CMV**. Once CMV is in a person’s body, it stays there for life and can reactivate. Most people infected with CMV show no signs or symptoms. However, CMV infection can cause serious health problems for people with weakened immune systems and for unborn babies (congenital CMV). > > > And also: > > [The diagnostic rate](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3490478/) using combined genetic deafness test and CMV DNA detection test was determined to be 46.4% in bilateral profound sensorineural hearing loss (SNHL). > > > At first blush it looks like it has some promise. [Answer] > > 2.What sorts of causes might result in a population with widespread generational deafness such as this? > > > First, in the case of generational colony ships and genetic mutations, this is highly unlikely as both the populace would be prescreened for such defects and likely trained to be selective in their breeding. Mutations could still happen, its just unlikely that it would propagate to the whole population. **But here is a plausible idea:** **Over Exposure to Loud Noises** During the generational voyage a component was damaged beyond repair. That component was responsible for dampening sounds generated from [insert loud machine component like the engine]. Thus the populace self mutilated themselves so as to not need to hear so they can sleep. The society then adopted sign language as their official means of communication. Fast forward to the colonization, after generations of the above situation the populace both forgot how to speak the spoken word and are use to and prefer sign language. [Answer] An alternative approach with non-biological causes: The generation ship was prone to catastrophic loss of air pressure. Automated systems and rapid response from the staff meant pressure loss didn't last more than a few seconds each time (and people can survive that, it's just uncomfortable), but the air pressure loss was significant when it occurred. Thanks lowest bidder contracting! Most of the negative effects of brief exposure to near-vacuum conditions are unpleasant, but not long term. But unfortunately, your sinuses are bad at venting pressure quickly; when the pressure drops rapidly from 14.7 psi to less than 5 psi, [your eardrum is almost guaranteed to rupture](https://hypertextbook.com/facts/2007/ShemikaWhite.shtml). Now, any given rupture generally heals within a few months, but unfortunately, the steady drip of air pressure problems means they usually got reruptured over and over before the healing completed, and eventually the scar tissue stiffened the eardrums to the point of deafness. So after a few decades of this, your skeleton crew arrives at a new planet stone deaf, having long ago discarded spoken language in favor of text and sign communication as they all went permanently deaf. As it happens, all the embryos have perfectly functional ears. Unfortunately, no one thought to send along recordings of the language, and everyone who knew how to speak it is decades out of practice (or dead, if the original crew died en route to be replaced by children born in space), and can't actually hear what they're saying; the newly decanted babies simply don't have any consistent model for speaking the language. So they learn sign instead. And it works. And reinventing spoken language from scratch is not that easy, and when it happens, each local group does it independently, ending up with mutually unintelligible spoken language, so sign becomes the lingua franca. Even if the occasional group speaks aloud amongst themselves, they have little choice but to fall back on signing (which *everyone* inherited from the original skeleton crew) when dealing with outsiders. Add on some additional motivations for signing (e.g. the planet itself has a low pressure atmosphere or constant high winds which reduce how well sound carries and/or require respirators that muffle your voice, or have dangerous critters that attack noisy folks), and the system can end up self-sustaining for quite a while. [Answer] The statements > > "...a wide variety of frozen/preserved embryos" > > > and > > "those embryos happened to have a high frequency of deafness" > > > seem to be a statistically very unlikely combination. Any sensible expedition would be sure to have plenty of genetic diversity and that is implied by 'a wide variety'. However if the embryos were all planted by a mad scientist (probably all his/her own offspring) then massive inbreeding would occur. It would be very likely that a genetic defect such as deafness would arise. Alternatively, perhaps many of the embryos were destroyed in transit. Again inbreeding would be a serious problem. [Answer] If you are looking for a plausible reason behind everyone being able to sign, we need look no further than the vacuum of space. For a space traveling culture a language immune to radio failure and decompression would be invaluable. On a generation ship, it would be taught equal to spoken language, to maximize the odds of survival. [Answer] In your universe, people should already feature brain-to-brain, brain-to-machine and machine-to-brain full-duplex efficient communication. This means that communicating through verbal means is something outdated and inneficient. Even typing things is inneficient. Further, in that scenario, many people do not even need to develop or learn spoken languages. Space is quiet. If you live your whole live in a spaceship, you aren't going to hear anything from the outside. If your spaceship is quiet, there should be no need to hear anything. Things happening inside the spaceship could be detected by machinery installed into the spaceship itself. If needed, sounds could be captured with microphones and transmitted to humans via a machine-to-brain mechanism. This also have the advantage that frequencies that are way out of the human biologically-hearing ranges can be heard perfectly. This means that hearing through the biologic hear is not needed anymore. Talking isn't needed either. Now, let's suppose that the ship is not so quiet. That damn reactor produces a very loud awkward sound! That combustion chambers produces horrible echoes around all the ship! Couldn't we be better if we just choose to not hear them? If those sounds are captured by a biological hear, then we can't filter them out and they bother and hurt too much for being tolerable. So, it would be better to be biologically deaf and hear things only via the machine-to-brain interfaces. The machine is responsible to filter out unpleasant or irrelevant noise. [Answer] The other answers are quite detailed, but if you're looking for a quick 'n easy solution, just handwave *Cosmic rays*. Make 'cosmic deafness' due to space radiation a known occupational hazard for early colonists, before the cure was developed. Even worse, for some areas (colonies in the Oort cloud for example) it's genetic and affects offspring. [Answer] **Maybe they can hear but not speak?** If your objective is a human society using sign language instead of spoken communication, you may wish to consider the flipside of deafness - a population that can hear but is dumb (in the medical sense). To quote from an article on the [Australian ABC News website](https://www.abc.net.au/news/health/2018-11-08/paleo-fantasy-return-to-simpler-times-evolution-constant/10470044?section=health) > > Our ancestors, as well as modern apes like chimpanzees, didn't have a > space between the horizontal tube that leads into the jaw and the > vertical tube that leads to your throat, the way modern humans do. > > > But the space, which makes it possible for us to choke on food, also > allows us to do something else: speak. > > > Speaking is a huge advantage and choking on food is a low order risk in our current situation on Earth. However, there could be a combination of environmental factors that make the choking risk much greater for a population on an offworld colony somewhere. As a result, the ability to speak was removed through genetic and/or surgical manipulation in order to remove the choking hazard. This may have been intended as a short term solution but gained cultural inertia due to other situations where sign language was advantageous and/or speech was a liability. As an alternative or addition, if the critical requirement is Deafness rather than sign language use, have some parasitic lifeforms akin to a tick in size that target the human ear as an entry point into the body. The parasites require still air, so they do not target the nose or mouth where respiration is almost constantly occurring, but the ear is ideal for them. As per the above scenario, the ears needed to be sealed in order to remove the entry point by surgical and/or genetic means. [Answer] They all work in the engine section of the ship. The permanent high noise means ear protection is worn at all times and people communicate using sign language to the extent that after multiple generations in that environment it's just what they always use. [Answer] You don't need deafness to suppress speech. Space is vacuum, space ships/stations are bunch of vessels with different pressures separated by vacuum. Voice communications are unreliable in such environments without intercoms (which could be made unreliable via other means). Eardrum damage due to sudden pressure changes reinforces the drift away from voice toward more reliable means. You can easily have a population that uses dominant sign/body language because of entire life spent in ship environment. It becomes part of space-dweller culture, retained when raising the settled-down generation. Much like a hearing kid raised among deaf people, they can be capable of vocalizations and hearing, but for them every spoken language would be a foreign language. ]
[Question] [ ## The Context A few years from now, perhaps around ten years or so, after first contact with star-travelling aliens, humans have acquired FTL and other technology making a new diaspora of humanity to the stars not only a feasible possibility, but given conditions on Earth, a highly desirable course of action for a great many. It stands to reason that the various cultural groups would each set out on their own, to get them away from their cultural enemies and allow them to set up 'ideal' societies. Some would no doubt embrace the new technologies the aliens made available, while others may well choose to eschew high technology. Let us further suppose that we have a cultural group that currently places a high value on body modesty for religious reasons, where going about displaying any more skin than necessary is socially unacceptable - some extremist sect derived from Islam or Judaism perhaps - which might emigrate from Earth with the intention of practising their particular religion and following its requirements with more rigor than possible on earth. Additionally, these people want to abandon the high technology to which the aliens have exposed humans - since many on earth are in favour of the alien technology, they must move to a planet over which they have sole control. This means that there has been no major terraforming effort - that would require using the technology that these people would rather avoid. The environment therefore is a naturally-occurring oxygen-nitrogen atmosphere world in its primary's goldilocks zone, with very roughly 1g of gravity. Of course, to get an oxygen atmosphere, there must be pre-existing native life, and to be able to eschew the unwelcome alien nanotechnology, that life must be reasonably compatible with terrestrial life. ## The Question What conditions on the single particular planet that this group colonises, and/or mishap or miscalculation in the colonisation effort could force them to practise universal nudity, at odds with their beliefs, within a short period of time after arriving? ## Restrictions The reason will have to be either environmental or ideological - these colonists (or at least their leaders) eschew high technology prior to or immediately upon arrival. The more powerful aliens aren't interested in slaves, in fact the whole first-contact was grossly mismanaged, and the aliens are now reluctantly in the same position as Europeans making contact with much more primitive natives, who have got hold of European technology, at the cost of the natives' society disintegrating as they argue about how to use it. The aliens want nothing more than for humans to get over their juvenile societal upheavals and to become mature equal partners in trade. I am looking for a reason for the colonists to want - or at least *have* - to practise nudity across the entire habitable surface of their chosen new world. I don't mind if the change is ideological, as long as it is one that would fit with any current Earth religion that currently practises moderate to extreme body modesty, or if it is imposed for other reasons. Any answers suggesting an ideological change must support their answer with justification for a relevant example real-world religion's followers to make such an ideological change. It would need to be pretty convincing, as many religious people will do the most impractical things because their religion demands it, and these colonists are all pretty fanatical, or at least most of them are, and the rest can pretend to be just as fanatical really well, otherwise they wouldn't have been invited to come along. An ideological change in these circumstances would be pretty unlikely, but if there is very good justification then I'd be interested. Otherwise, that just leaves environmental or accidental reasons, which would be just as good - it would be interesting to explore the deep conflict between religion and necessity or disaster management. I would prefer if the reason was *not* that "The local sentient species insists upon it", as I don't want to introduce yet another sentient species in this context. Finally, if an answerer believes that there is *no* reason that would make the majority of the radical muslims/jews/whatever abandon their clothing in order to survive or avoid extreme discomfort on their new hell-world, or that they wouldn't find some way to cover their nakedness even in the face of extreme shortages caused by accident or mismanagement (like making clothing from food, rather than eating it), I'd like to know that too - it would be interesting to explore a world where all the fanatics either died out or go about in daily torment because of their beliefs. [Answer] **Contagion.** In (the book) World War Z people were stripped naked to look for evidence of bite wounds - which meant zombie infection. In your world there is some contagion or parasite. Infection with this parasite can be concealed under clothes. Clothes come to be viewed with suspicion. Nakedness means your healthy skin is on display - you are uninfected and not to be feared. [Answer] ## Safety One of the primary benefits of clothing is safety. So make nudity safer. Perhaps there are some kind of large, violent, native life form that is attracted to the textiles available to the colonists and are happy to eat them (and anyone wearing them). Or more believably, some microbial lifeform that rapidly consumes the textiles like highly aggressive moths with the munchies trapped in a closet. Perhaps there is some kind of aggressive mold spore or bacterial life form that colonizes and grows rapidly in the textiles and they trigger some kind of allergic or venomous response when in contact with human skin. ## Climate If the climate is extremely hot and humid but the risk of sunburn is relatively low compared to earth, then nudity becomes a more practical response to the climate. Wearing a full garment is no fun when you're hot and sweaty all the time. ## Local Civilization Maybe they discover a local civilization that eschews clothing for any number of reasons. If that civilization threatens violence over the human's use of cloth (again for any number of reasons), then they might have to drop clothing to maintain relations or even survival. ## Disaster Maybe there was a fire on the colony ship or a crash landing, and so the colonists were reduced to the clothes they were wearing; the rest were burned or destroyed. Those clothes, for whatever reason, aren't made to last for a long time. So the colonists are throwing them away as they wear out. There just aren't enough resources yet to start generating new textiles. Food, shelter, and other long-term needs are more important. For now. # Discovery Long shot and would probably cause some serious rifts in your colony. But... What if they landed and stumbled across some evidence to show that their religion was somehow linked to this new world? Some religious iconography obviously shared by their belief system is found, etc.? So there are direct and obvious ties to the basis of their body modesty. And yet... mixed in with that are cues or directives that practically demand that they change those beliefs. Nudity being one of those "new laws," but probably not the only one. From a story perspective, that could be interesting if explored well. Would the colonists split into sects based on whether they accept or reject the findings? Would they begin to question their beliefs? [Answer] Follow Nancy Kress's example from [Beggars in Spain](https://en.wikipedia.org/wiki/Beggars_in_Spain) and modify the bodies of your body-shy colonists to be photosynthetic. Perhaps the planet they have chosen has no edible plant life, and the indigenous is highly competitive keeping imported crops from surviving. Rather than starve, the colonists have allowed themselves to be altered such that they can create their own food from the abundant sunlight. But in order to function, the skin must be exposed. [Answer] A very hot *and humid* climate will encourage at least partial nudity (and/or air conditioning) to maximize heat lost through sweating. A hot and dry climate, however, encourages lightweight but full-body clothing to avoid moisture loss. There's a reason that native cultures in jungles and on tropical islands stereotypically don't go in for a ton of clothes, because they're not practical in that environment. That said, unless the colony is fairly desperate, it shouldn't be hard for them to establish *some* kind of cooling system, so this might be a temporary plot device at best. [Answer] A powerful and advanced native species which takes grave offense at covering up the body and is willing and able to kill colonists who don't strip would do the job. The hard part of answering this question is explaining why the privileged areas of the body (such as the genitalia) must be uncovered, despite having very small surface areas. An angry group of locals fits the bill. [Answer] 1. A widespread deadly bug or parasite that hides itself in clothes, but if naked it's easily and safely brushed off or doesn't attack at all because its afraid of open air or sunlight. Wearing any clothes would guarantee getting bitten or infected, the bug able to hide itself very well and is undetectable by the means they have available, while going naked makes you completely safe. 2. A simple rebellion against the former leader, with being naked having some significance to the rebels (such as one of their own being unjustly punished by being forced to go naked and then killed, or being unjustly punished for being naked and killed) and eventually nudism forming part of the rebels identity, anyone who wears clothes seen as siding with the enemy. The rebels winning the conflict in the end and the practice continues. 3. Swimming and diving for whatever reason constituting a very significant part of their daily activities. Although this wouldn't mean nudism, just less clothing. 4. Just thought of another interesting one. The settlers are hiding out on the planet from the aliens or other humans, and whoever they are hiding from is going (or sending drones) from planet to planet and scanning it for intelligent life and their equipment detects intelligent life by scanning for living beings who are wearing clothing. Being naked keeps them safe from the scans. [Answer] **Boycott** tl;dr: Americans did drink hot water for political reasons. Just translates this to your world. Full version: As this cultural group sets on their own planet, they start to develop an ideal society (in their view) that is much less technology oriented than the neighboring colonies established. They consistently refuse to buy machines from the aliens. Perhaps they instead promote their own alternative form of technology, which is more respectful of their beliefs. In a attempt to pressure them, aliens start a trade war by raising taxes on any of the colony's production and convince the colony's commercial partners to either raise prices or cut ties. Clothes production however has evolved very rapidly when human and alien's societies started to interact. As alien technology was simply incredibly more productive and advanced than ours, clothe industry on Earth has collapsed, and the entire galaxy is now buying from the cheapest provider. Rapidly, the isolated cultural group faces clothes shortage. It is also against their beliefs to kill animals and the economical hardship that the trade war is putting them through impedes them to divide their ressources wisely between feeding the population and defending the planet. In sign of protest, some religious leaders start shirtless marchs in the street. The images of these protests are highly publicized precisely because nudity is such a taboo. The protests organize into a political movement. While the oldest members of the community disapprove their methods, they get widespread support as the feeling of belonging to a nation of its own grows into this community. They symbolize a combination of pride to belong, hate towards the alien and excitement among the youth of the community that lacks a clear cultural reference frame on this new planet. Within a few years, the boycott party takes over strategical positions of power. Showing more and more skin becomes an easy way to demonstrate dedication that is in appearance very courageous but risk-free. Naturally, most politicians go for it. Some more-traditional parties refuse it completely. After some time however, the boycott party finally gets a grip on the ministry of trade and clothes import become formally forbidden. A series of arbitrary arrests are lead on the charge of wearing imported clothes. Most of the time these were imported way before the law came into force, but this is only a pretext as these arrests are really targeted at political oppositions in an attempt to tighten the party's grip on power. Most of the general population agrees with the boycott party, when the others stop wearing clothes too in fear of standing out as subsersive. As time goes by, new history books are being edited where the role of the "heroic shirtless march of [insert date]" is emphasized. The idea sinks in the young minds that nudity is a symbol of bravery. Slowly but surely, the religious discourse reconfigures and reinterprets the sacred texts so as to embed this idea in their teaching [Answer] I probably should have modified the question to a reality check, but didn't have the time before the existing answers would have been invalidated by the necessary change. So, we have a bunch of radical Muslims, tbe type that practise a radical interpretation of the Koran's modesty requirements, with men covered from neck to ankle, and women wearing burkas in any public situation. The technology that they are trying to escape is general-purpose autonomous nanites that for the past few years have been putting people out of work since there is little call for labourers, only people with the imagination ans skills to be able to instruct the nanites. So, amid much fanfare as Humanity's diaspora to the stars begins, these Muslims gather like-minded people to their cause, and set out on an alcubierre warpship, devoid of nanites but stocked with everything else they might need, to their promised land - purchased from the aliens who discovered it, but who couldn't be bothered to develop it themselves. Alcubierre warpdrive is still an emerging technology for humanity, and their journey will take years. However, that technology improves faster than the flighy time of the first ships, and before many can arrive, they are pounced upon by pirates in faster ships. Our unfortunate Muslims are startled when they arrive in their colony world's solar system only to find that people have arrived before them - pirates. Unprepared for an attack by well-armed pirates who even seem to have the blueprints to their ship, they are helpless to prevent the pirates from taking everything they want. Left alive - because a dead sheep can only be skinned once while a live one can be shorn many times - but with minimal resources compared to that which they started with, the Muslims land on their promised land. However, while the world carries non-sentient life that is moderately compatible with human biochemistry, the pirates have stolen all the nutritional supplements that could have made up the deficiencies, along with all the biological samples of any species that may have been thawed, grow & farmed to generate the required Vitamin - Vitamin D. To make matters worse, their system primary is a K-class main sequence star that produces hardly any UV wavelengths. Only just enough UV is present in the primary's emissions in order to allow humans to synthesize enough Vitamin D to avoid deficiencies as long as they have fair skin and spend every daylight hour exposing as much of their bodies as possible to sunlight. This altered habit of (un)dress is made easier by the planet's vast areas with a very warm and humid climate. People with dark skin and/or who do not spend enough time completely nude out of doors in the sunlight are doomed to an inevitable Vitamin D deficiency, especially since few if any terrestrial foodstuffs were left by the pirates and the local lifeforms, while edible and nutritious, do not contain Vitamin D. Anyone not exposing themself to enough sunlight will rapidly develop deficiencies, with symptoms including osteoporosis, osteomalacia and rickets in children. For a new colony where a great deal of manual labour will be required for many years, such bone diseases are a major threat to the colony's future. While many colonists could be expected to refuse to doff their clothing and expose themselves to the new, weaker sun, deficiency-related diseases can be expected to be common, reducing productivity and endangering lives. Religious leaders would be faced with the suddenly conflicting requirements of health and modesty and the real potential for modesty to threaten the survival of the entire colony. ]
[Question] [ First, let's settle the background. We're in a middle of a virus-induced zombie apocalypse. Infected people don't return from the dead, but have their brain capacities cut to a basic minimum and their only urge; eat humans, and only humans. They will grab, they will bite. The virus will suppress any survival instinct, pain or fear from infected people. Meaning they will chase you until their heart can no longer feed their muscles and brain, no matter how badly they are injured (broken bones, vital organ failure, muscle tears...). So two options to kill them: brain injury and bleed them to death. You are a survivor but you have a very hard time dealing with these starved zombies and merciless thugs. You choose to take a dog as a companion to help you to survive. **QUESTION: What breed would be best suited for this environment?** * **It would need to be able to spot enemies** Very good hearing and smell. + Bonus points if it can find food, water and drugs. * **It would need to be intelligent** Can a dog understand the concept of stealth? Is there a breed that can just freeze when it spots enemies and doesn't just bark at it? Would it be possible for the dog to find a secure path by getting around troubles? Can you give it a mission, like staying close to your injured mate in a secure location while you go outside to look for a first aid kit? + Bonus points if it can hide itself during a gun fight. * **It would need to be able to injure a zombie** Since dogs are invisible to zombies, that would be a very good way to bleed to death an isolated zombie. + Bonus points if it can aim for the throat. For example: [German Shepherds were used as scouts in Vietnam](https://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/SP4_Bealock_and_scout_dog_Chief.jpg/762px-SP4_Bealock_and_scout_dog_Chief.jpg) [British Springer Daniels are used as detection dogs for the police](https://upload.wikimedia.org/wikipedia/commons/thumb/1/1d/London_Police_Dogs.jpg/1280px-London_Police_Dogs.jpg) [Dobermans are used as guard dogs](https://upload.wikimedia.org/wikipedia/commons/2/25/Dobermann.jpg) [Answer] Well, I believe we can establish that you'd need a big dog for the purposes listed. A small dog may be a good sniffer and so on, but it just doesn't have the mass and bite force to take on a human. A small dog would not be able to cover as much ground, either. It would need to be intelligent, have good pain tolerance, have a good nose and be attentive. Among the large breeds, there are several who are traditionally used as 'work dogs', and those are a safer bet than other breeds. why mess with an option you know works? First, you can consider the German Shepherd, as you said, or some of its close cousins from the Shepherd family like the Belgian Shepherd (Malinois). As you can see [here](http://dogtime.com/dog-breeds/belgian-malinois#/slide/1), they are very intelligent, very trainable, are used as both service and attack dogs and can be trained for complex jobs. they are also trained as sniffer dogs, so that's a bonus. Their bite is fearsome and they can be trained to let go as well, which is just as important. Another choice is a Husky or an Akita. Both are powerful dogs, are used as attack dogs, hunters and work dogs, and have a powerful bite and tenacity. The downsize is that they are very independent, are harder to train and would probably be more prone to do as they will. You can also go for the power of a pit bull, bulldog or Cane Corso. They have a very powerful bite, very high pain tolerance, they can be massive, they are intelligent and according to [this](http://dogtime.com/dog-breeds/american-pit-bull-terrier#/slide/1) and [this](http://dogtime.com/dog-breeds/cane-corso#/slide/1), are almost as trainable as Shepherds. The only problem would be their prey drive, which means it would be harder to train them to release once they bite, but all in all a Pit might be as good a choice as a Shepherd. A Doberman may be added to the list here. they are very intelligent, sleek, powerful and they are used both as guard and work dogs. My only hesitation is due to the fact they have a lot of energy and may be less tolerant of holing up and hiding for large amounts of time. They can be quiet, though. And, well, I feel they just don't have the mass, that tank look a dog in the described environment would need. Last, I believe a [Rottweiler](http://dogtime.com/dog-breeds/rottweiler#/slide/1) is in the same spot as a Pit or a Corso. They are massive, intelligent, have a powerful bite, are used as guard and police dogs as well as herders and even used to pull carts! they are trainable and have the same prey drive as Pits. Use the site in the links to get more info and browse through breeds. I believe all of the above are good choices, it just remains to be seen which fits your exact needs better. [Answer] **Pugs.** > > It would need to be able to spot enemies Very good hearing and smell, > bonus points if it can find food, water and drugs. > > > This pug earns the bonus by finding a stash of cocaine. [![cocaine pug](https://i.stack.imgur.com/O6uaw.jpg)](https://i.stack.imgur.com/O6uaw.jpg) --- > > Can a dog understand the concept of stealth? > > > No-one knows this pug is here... [![cough pug](https://i.stack.imgur.com/aVyMN.jpg)](https://i.stack.imgur.com/aVyMN.jpg) --- > > It would need to be able to injure a zombie > > > [![pug puppies attack](https://i.stack.imgur.com/RGdFN.jpg)](https://i.stack.imgur.com/RGdFN.jpg) Like a school of piranha. --- [Answer] For hunting zombies with my shotgun, I'd go with one of the various Pointer breeds, since silently pointing at the prey is what they do. <https://en.wikipedia.org/wiki/Pointing_breed> > > The name pointer comes from the dog's instinct to point, by stopping and aiming its muzzle towards game. This demonstrates to the hunter the location of his or her quarry and allows them to move into gun range. > > > The problem is for them to determine *zombie human* from *normal human*, and only point at the zombies. A specific odor given off by the zombies can be the differentiator. As a sentinel, the Lhasa Apso, since it was bred as an indoor sentinel. <https://en.wikipedia.org/wiki/Lhasa_Apso> > > a non-sporting dog breed originating in Tibet.[1](https://i.stack.imgur.com/6Z6DY.jpg) It was bred as an interior sentinel in the Buddhist monasteries, to alert the monks to any intruders who entered. > > > I would *not* want my dogs attacking the zombies, because the blood that gets on the dog's face could cross-contaminate me. <http://www.pawculture.com/uploads/pointerdog.jpg> [![enter image description here](https://i.stack.imgur.com/6Z6DY.jpg)](https://i.stack.imgur.com/6Z6DY.jpg) [Answer] If you have the time and inclination to train them, you could use [Caucasians!](https://en.wikipedia.org/wiki/Caucasian_Shepherd_Dog). The are Loyal, Huge, smart, huge, great guardians, huge, and really really big! And did I mention they are huge? Caucasians can get up to 100 Kilos. That's plenty big enough to deal with infected humans. They were bred to be guard dogs and have some natural aggressive tendencies. They also have jaws that could easily hamstring a zombie or even crush it's head. They have a heavy coat that makes them really resistant to cold conditions. You could also use the shed fur to make felt for a yurt if you are getting really primitive. One of the breed traits is that they tend to be aggressive with strangers, making them good for taking on zombie hordes. It's kind of like keeping a tamed bear. (You might guess I kind of like the breed) For specifics: Stealth. Their coat type lends itself to good camouflage. Humans are sight driven predators, and I see no reason why infected humans would be significantly different. Intellect. These dogs are pretty smart, but they are stubborn. Lots of intensive training would be required. Strength. Should be self explanatory. I mean look at this guy! [![Full grown Caucasian](https://i.stack.imgur.com/HyKFy.jpg)](https://i.stack.imgur.com/HyKFy.jpg) They were bred to guard things. [Answer] Great Danes fill most of your requirements. They can be very protective. I don't know how good of a "sniffer" they are but they are smart enough to tell a threat (zombie or scum bag) from their body language. They are also big and have the body mass and height advantage to knock someone over and pin them. Their jaws are pretty strong if that's needed but I agree with RonJohn that I'd rather not have my dog bring zombie cooties back with him. I don't know if it was just ours or if it is a general breed thing but mine was really quiet. I remember a time when I was in the yard with Puppy (ironic name) when a stranger tried to open the back gate. Puppy just sat himself on the other side of the gate, looked the stranger in the eyes (sitting they almost had the same eye level), and showed his teeth. Not a sound. The stranger decided that he had other things to do that day. Puppy was no longer in a playing mood and spent a while walking the fences. [Answer] Standard poodles are also very intelligent and were used for hunting. I will admit that the silly "snowball" cut for their fur would look ridiculous in a TV adaptation. Though most standard poodles are rough-cut. And they are fairly large dog. The major problem that I see is that poodles don't shed, so the owner would need to trim their fur. [Answer] I do think you're background is quite, EASY TO OVERCOME, SO EASY I can use your Zombies for the next Olympics, Hows that? Your environment said that your Zombies eats Humans AND HUMANS alone, and Basically, You also pointed out that A dog IS invisible, so is a Tiger, Lion, Elephant, Rhinoceros, Bulls, Cheetahs, Hyenas, Cougars, Crocodiles, Alligators, WOLVES, etc... So to make your story short, I'll Go to the wilds in a car, get my guns with tranquilizers, Hunt for a pack of Wolves, Return to the City, Unload Wolves, Repeat(I'll be Wearing a full plate armor for my sake). Or Better yet, go to the nearest Zoo, Open ALL Cages, Sit Back, Drink my beer and be a Hero. But in all seriousness, If you really want to survive YOUR zombie apocalypse, if you can manage to tame a pack of wolves, that's it! Wolves are part dogs, and with a pack of them you're protected in a very large radius. You'll be using your guns for enjoyment perhaps, and as long as you have a good bond with the alpha male, You're set to go. I'm thinking also that this question is a bit easy to answer because it does not indicate how the zombies can differentiate a human and a dog? What if a Human walked using his hands and feet? does your zombie consider them as a dog? ]
[Question] [ Horses are not perfect for war but they are still very good when trained. **How to make a horse better for the following conditions?** * be stronger in the act of charging infantry and other horseman * more resistant against conventional weapons * also faster and stronger in any other way you see fit I know this is slightly opinion-based, but I believe the answers for it to be more effective under these parameters, which can be scientifically answered. The food requirements are not a consideration in this question. [Answer] When it comes to a cavalry charge (in medieval eras), the ability to break a line of infantry has more to do with the weight of a horse being thrown at the weight of a man than anything else. So it would reason that a larger horse (taller and heavier) would be able to charge through a line easier. A horse has a relatively small head and tends to leave it's neck and chest open to attack while at full gallop. A shorter neck and larger head would provide more cover for it's weak spots. In addition, strengthening the neck and skull so that it coud conceivably headbutt would increase it's effectiveness while charging. A horse doesn't add much advantage after a charge outside of its rider now attacking from the height of a horse. A weapon (such as horns) would allow the horse to have some manner of offensive abilities after the charge was completed. A horses skin is relatively thin for a creature of its size and doesn't offer much protection vs attacks. Large size creatures tend to be easier targets for ranged weapons (arrows) as well. Giving the horse a thicker hide that could potentially resist arrow fire (piercing) would dramatically increase its ability to stay on the field (especially vs an opponent such as the mongols that would simply shoot and kill the horse and ignore the knight on it). Fearless. Somewhat like humans, horses are naturally scared creatures (herbivore evolution) and are inclined to run in the presence of danger or unknown (camels, elephants, even snakes will spook a horse). Fortunately horses, like humans, can overcome these instincts through discipline... but a mount that lacks this 'run' attribute would be better as a war mount. I'm starting to describe a buffalo, though it should be noted that a horses speed and mobility is one of its greatest attributes... many of these changes listed here sacrifice these two attrributes for greater strength and size. Everything is a trade off, these changes would suit a European knight decently well, but would be extremely counter intuitive to a mongol warrior that valued the speed and mobility traits. [Answer] I imagine something akin to a rhinoceros would be the best war steed. Small enough to easily mount and control (unlike a gigantic elephant). The entire body, head, and neck have evolved for powerful charges, perfect for breaking an enemy line. They can actually run faster than horses, have thicker hides, and can probably carry more. A medieval knight could adorn the rhino's head and horn with armor and spikes to make it even more deadly in a charge. They're probably tough to tame, but I imagine if they were domesticated over many generations, they would be fine. [Answer] If you really really want to have a mount, use elephants instead of horses. Sure, you don't just find elephants anywhere, but an armored elephant is much more dangerous than a horse. Your riders will mostly have one job; to direct the elephant, as you'd likely have to blind the elephant to stop it from being scared. The armor should protect its limbs as it charges, and a flailing armored elephant trunk is no small threat. If you're asking for raw power, this is as good as it gets. It's slower than a horse by about half, but its significantly stronger and harder to kill, especially when you're limited to medieval technology. If you don't actually care for having a rider and you just want animals in war, send in some grizzly bears. [Answer] Edmontonia , they are big enough to carry a person with no difficulty, heavily armored, the forward facing spikes means we know they liked charging, and since they are extinct you can make up how domesticatable they are. Plus as dinosaurs they will need a lot less water than a horse. [![enter image description here](https://i.stack.imgur.com/84Cih.png)](https://i.stack.imgur.com/84Cih.png) or go with an ankylosaur, bigger better armor, and while they would not be as prone not charging they can defend your flanks fairly well since they basically have a giant mace attached to their tail, so getting surrounded would be far less of a problem. biggest downside is sitting on it is going to be tricky, they are very wide animals. Alternatively Paraceratheriidae gives a wide range of heights of what is basically what you would get if you crossed a horse with a rhino. [![enter image description here](https://i.stack.imgur.com/zFLZi.jpg)](https://i.stack.imgur.com/zFLZi.jpg) If you are willing to go entirely fictional just make a very large horse like thing with ankylosaurus armor. [Answer] In order to have a stronger charge and be more resilient to damage my first thoughts are that your mount should be larger with a shorter, thicker neck. I would suggest some sort of bull or ox to fit those criteria as it is already designed with a thicker skull to make it viable for it to charge in self defense and the bulkier more muscled body offers more protection to penetrative attacks. Of course one of the reasons bulls aren't used for mounts is that they don't have the same endurance as horses and can't maintain charging speed for more than short bursts. If you want to have a faster mount capable of maintaining higher speeds over long term you would want something with longer legs. [Answer] I believe that a camel is described as a horse designed by a committee. Which is intended as an insult. But camels are superior to horses in many ways. So camels or more camel-like horses would be a good bet for improved war horses. Making your war horses more elephant-like, or replacing them with elephants, may also be a good idea. War elephants have been used for thousand of years. Their use in the Mediterranean during Hellenistic times was a minor sideshow to their use in South Asia. And I have been able to think of a number of different uses for war elephants that might have made them more effective than in real life. It should be noted that there were different uses for horses in war. For example, heavy cavalry needed bigger and stronger horses to carry the weight of their riders, their riders's armor, and the horses's own armor, and carry that weight at a gallop. I can easily imagine that reinforcing heavy cavalry with some camels and some elephants might make them more formidable. On the other hand, light cavalry needed fast horses, to outrun fleeing enemies when the enemy army broke and to make fast raids and fast scouts. Since light cavalry horses didn't have to carry as much weight as heavy cavalry horses they could be smaller, but they should be as fast as they could be. It may be noted that in *The Hobbit* and *The Lord of the Rings* orc armies included wolfriders, orcs riding wolves. Most orcs were small, closer to the size of children than men, and the wolves were *wargs*, bigger and stronger than modern wolves. If your armies include members of different species with different sizes, their cavalry mounts might be members of different species with different sizes. And a lot of horses, and related animals like mules, were used for other purposes in war. Pulling travois or wheeled vehicles with supplies, for example, or sometimes carrying supplies on packs on their backs, or pulling artillery. As late as World War II when many armies were largely mechanized, there were still millions of horses used for military transportation. And of course camels and elephants are also useful for military transportation. Some elephants were used for military purposes in World War II, including one that loaded heavy barrels of fuel onto airplanes. In the US Indian Wars in the American west, the various hostile groups and the US army had different strengths and weaknesses. And sometimes the same difference would be an advantage for the Indians in some situations and and advantage for the army in other situations. The difference between Indian ponies and army horses was an advantage for the Indians in some situations and an advantage for the army in other situations. So if your fictional armies have need different types of horses for different types of cavalry and for transportation, you should modify the different types of horses for different purposes in different ways and perhaps make them resemble different types of animals, or replace them with several different species of animals. [Answer] “If I had asked people what they wanted, they would have said faster horses.” ― Henry Ford Build a Tank. This is a "think outside of the box answer." [Leonardo da Vinci already designed a tank.](https://en.wikipedia.org/wiki/Leonardo%27s_fighting_vehicle) So it's entirely plausible. And because you didn't specifically said it had to be an animal that replaced your mount I gave this as answer. Getting "better" horses which are like more durable, tougher then normal horses just leads to [power creep.](https://en.wiktionary.org/wiki/power_creep) [Answer] The real problem with the question is "perfect" is rather situational. A Knight in the Middle Ages would actually have several horses, depending on what he was doing, and each one was "perfect" for the task, being bred for it. Knights would ride [Destriers](https://infogalactic.com/info/Destrier), [Rounceys](https://infogalactic.com/info/Rouncey), and [Coursers](https://infogalactic.com/info/Courser_(horse)), depending on their role on the battlefield and their personal financial situation (Destriers were larger and more expensive than the others). Even within the various classes of war horses, a Knight or Man at Arms may choose to ride a different class of horse depending on the expected role in battle. Rounceys, based on surviving literature seem to have been fast horses which may have been used for scouting or pursuit tasks, while Destriers were very large and aggressive horses used for shock battle encounters. [![enter image description here](https://i.stack.imgur.com/GhSek.jpg)](https://i.stack.imgur.com/GhSek.jpg) *Drestier* [![enter image description here](https://i.stack.imgur.com/QWLfJ.jpg)](https://i.stack.imgur.com/QWLfJ.jpg) *Courser* [![enter image description here](https://i.stack.imgur.com/ggVKz.jpg)](https://i.stack.imgur.com/ggVKz.jpg) *Rouncey* When not actually riding into battle, the Knight and most of his train of servants, squires etc. would be on a riding horse like a "[Palfrey](https://infogalactic.com/info/Palfrey)", due to the more good natured temperament and smooth gait, while various pack horses carried the equipment, food and bedding. Without a clear understanding of what is different in your world, it is difficult to say why giving a Knight a Rhinoceros, Ankylosaur or [Terror Bird](https://infogalactic.com/info/Phorusrhacidae) would provide an advantage over a bred warhorse. Clearly there could be a reason that a different creature would provide an advantage, but without knowing the reason, there is no way to argue for or against anything other than a horse. [![enter image description here](https://i.stack.imgur.com/KH6A7.png)](https://i.stack.imgur.com/KH6A7.png) *Big enough to ride, but you better have a good reason to do so* ]
[Question] [ If cheap and reliable anti-gravity devices (sufficient to allow personal flotation harnesses, flying cars, etc) were developed in the next ten years how would it change the design of cities and buildings? Would we start seeing new and three-dimensional layouts or would people still be more comfortable with the conventional layouts? Essentially we can now control gravity in the same way we control magnetic fields, for example we can place walkways up the side of buildings with gravity pointing towards them, we can have rooms with both the floor and the ceiling able to be walked on. Cars can float or fly, as can people. The technology in question does require some power (so safety is a concern) but is reliable. The larger the area and the larger the effect the more electricity it requires, but still personal flying devices would be affordable for your average person. Flying cars would maybe twice as expensive as a normal one, modifying gravity in buildings would be expensive and probably only used for the very rich or for commercial purposes. [Answer] Things would certainly be different in many ways, but in others they would stay much the same and I think that is a reflection of old versus new. Building new infrastructure is one thing. New infrastructure is expensive to be sure, but it is far more expensive to update existing infrastructure. **Old Cities** Old cities can be broken down into (at least) two parts. Cities we consider old today, and the modern cities of today. When I speak of old cities today I mean places like Athens, Istanbul and the other truly ancient cities. These cities (at least the ancient portions) would likely change very little if at all. Which as a person who appreciates the old and its conservation is something I would whole heartedly agree with. Personal mobility would likely be the only significant change, having what amounts to a jetpack would make traversing the old cities much easier. Personal in home use (as you mentioned walking on ceilings) might change somewhat, perhaps allowing greater population density. Modern era cities would likely change significantly more but it would take a long time for that change to be uniform. As I mentioned updating infrastructure is time and cost intensive. In a similar vein to white flight odds are the well off would move out of major "old" cities to live in new neighborhoods that were completely integrated with the new technology and then the technology would work its way back into the cities **New Cities** As mentioned in the old cities section these *new modern* cities would see the most rapid change and be the most uniformly impacted places. This is your city of the future where the infrastructure and construction were designed with the new technology in mind. This is the simple bit...relative to updating old cities. **Automation** The more commonplace this 3D environment becomes the more automation will be necessary. Managing navigation in a crowded 3D space may well be impossible for humans to manage with any reasonable level of safety. Either you can go the self-driving vehicles connected to a massive program to control them route or you can go with the 2D routes just elevated. So similar to two level roads you could do the same for flying vehicles creating 'lanes' above the street at a fraction of the cost compared to building and maintaining roads. I am picturing a sort of metal frame that the vehicles would have to stay within. This would be complex to design effectively...LOTS of on and off ramps. **Controls** Either route you go you are going to have a controlling agency akin to the FAA. This is particularly relevant in the automated flying cars scenario but I think would be necessary either way. You would likely have to make elevation restrictions based on classes of mobility. For vehicles, express lanes above 100 feet, between 50-100 feet for going to a specific local location, and under 50 feet would be for personal mobility vehicles...i.e. "jet-packs" **Density** If you can get past the biological implications of being upside down...which is not a simple task you could drastically increase population density in city centers by allowing people to live on the ceiling. More practically and realistically it would make movement far more efficient making previously impossible routs available for transport. --- All in all the changes would be drastic and the impacts to industry, transportation and personal life would be nearly as profound as say...electricity in homes in the 1900's it would simply change the way humans live and interact with the world on a very fundamental level. [Answer] You make mention of anti-gravity, but also talk about walkways on the sides of buildings. More than just anti-gravity (reducing the effects of gravity), this implies that your futuretech is actually directional gravity manipulation. Anti-gravity alone would have a great effect on construction. Buildings of far taller sizes could be manufactured with greater ease - you would not need nearly as powerful cranes to lift building materials. If the anti-gravity technology can be built into the structure itself, you could potentially use lighter materials because the load of the whole building could be reduced. Either way, the end result is verticality - buildings would be very, very tall. (The manufacturing implications of gravity control technology is touched on, albeit briefly as it is not the focus of the story, in [David Weber](http://www.davidweber.net/)'s Honorverse.) Assuming the cost was cheap enough, anti-gravity would also drastically improve the capability of humans getting into orbit. As an alternative to tall terrestrial structures, you'd have the capability of building large structures in space. If the technology is truly directional gravity manipulation, you could provide those structures with internal artificial gravity, eliminating the micro-gravity related problems of long term space habitation. Anti-gravity without directional gravity manipulation would still reduce resupply concerns, making living in orbit more attractive. Despite easing the engineering implications, I think the larger concern is the [human factor](http://en.wikipedia.org/wiki/Equilibrioception). The human body uses a combination of what is effectively a gyroscope in the inner ear and visual stimulus to determine where you are and where you're going. Without really having directional gravity manipulation, there's no way for us to test it, but I suspect there would be issue with your proposed walkways - the ear, subject to gravity would be telling the brain one thing (down is towards my feet) while the eyes would be saying something different based on the horizon. In a space habitat, the horizon/orientation problem is mitigated because the environment is presumably small enough that your senses tell you you're inside at all times. TLDR Buildings would get taller and/or leave the planet completely, but the orientation would remain the same. [Answer] As with many situations, it depends. You've specified that these devices are *sufficient to allow personal flotation harnesses, floating cars, etc*. However, it follows logically that the more of them you have, the more mass you can lift. So, as alluded to in the comments, the major factor here is cost: * How much does it cost to manufacture one? * How much (if anything) does it cost to maintain one? This includes energy costs, repair and upgrade costs. If these devices can be manufactured and run cheaply, they will quickly become fairly standard in building and vehicle design. The use of the air allows much more space for driving around in - just make sure you limit altitude so people can't crash into planes. That said, flying cars might even make the aerospace industry fairly obsolete. The speed of integration of these devices will vary fairly linearly with their costs: high costs = slow integration; low costs = fast integration. It also depends, as the comments say, on area of effect: a large area of effect means you need fewer devices to cover a bigger area, thus reducing total cost and speeding up integration. However, society, as always, plays a big role in the speed of *acceptance* of these devices. As with any technological revolution, there are naysayers and yaysayers, and while I don't want to rigidly stereotype, the acceptance is often affected by age. The older generation are more likely to cling to what they've always known; the younger, more inquisitive generation are more likely to want to try this out as soon as possible. You can see examples of this in many new technologies: in my personal experience, I adapt to new technologies and developments quickly, while my parents and older family are happy with how things are. [Answer] I've read this in some Stanisław Lem book ("Return from the stars", I think), so it is not my idea, but I liked it a lot: The antigravity device should be able to dampen any acceleration, not only the gravity. So, you would have a cheap and reliable safety device: in case of any crash the device just nullifies the acceleration, so no damage is taken at all. You could equip the cars and other potentially dangerous objects with this device. You could give this device to people and make it work automatically when, for example, the person fails. I guess, people would be still very cautions at the beginning, but this level of security is quite promising, and, I guess, the technology would be accepted quickly. As the devices would become common, the fear of height or crash would reduce, so, I suppose, 3-d layout would be only a matter of time. [Answer] Having freely-available antigravity would turn the concept of security on its ear. Fences, walls, gates, moats or trenches, and any and all access control devices that restrict movement in two dimensions instantly become obsolete when the average intruder is able to simply fly over them. There are two ways to deal with this, as an author. Develop an entirely new physical access control paradigm, or have someone come up with an anti-antigravity technology that they install on security walls, fences, etc, that projects a field upwards that disrupts antigravity. This, of course, would lead to an arms race between intruders and security people. Maybe parasails or hang gliders become standard equipment for the determined thief, to allow them to glide safely over an anti-antigrav zone, for example... [Answer] **TL;DR - Probably not a lot** Probably the biggest driver of approving new technology for public use is safety. This always involves the question of "What happens if said technology fails?". If the engine on a car dies, you pull over and slow down safely, but what happens if your anti-grav car shuts off? Will everyone have ejector seats and parachutes (not that that would even work well)? What about your vertical walkway on the side of the building? If your anti-grav fails, what will happen to the people standing on the side of the 10th floor? Whatever new technology is incorporated into the public landscape, there needs to be fail-safes for everything. I personally have a hard time coming up with a reasonable way to keep people safe when your anti-gravity systems fail. Unless you can come up with some strong backup systems, there's no way anti-grav would ever be approved for public use, and so your cities of the future would probably look pretty similar to those of today. [Answer] > > ...personal flying devices would be affordable for your average person. > > > I think that alone would change a lot. Most people would own and always wear a personal flying device. Flight controls and safety measures on these devices would become very advanced, as would auto-pilot systems. People would simply fly to anyplace nearby (work, school, etc.), rather than use a vehicle. This would lead to some interesting clothing (bubbles?) with an emphasis on aerodynamics and warmth. > > Flying cars would maybe twice as expensive as a normal one... > > > I think what you would have is independent gravity-control devices that could be attached to *anything*. No need to have a car at all -- people would simply fly with their personal flying device, and put their possessions/luggage in separate container that has it's own flying device, likely set on auto-pilot. > > ...modifying gravity in buildings would be expensive and probably only used for the very rich or for commercial purposes. > > > Due to millions of years of evolution I think people will still be most comfortable with a basic *gravity-goes-down* setup. Besides if people all have personal grav devices, there's not much of a need for a gravity controls *inside* the building itself (kind of like how there are fewer public pay-phones now that most people have cell phones on them at all times). I think there would be some floating buildings though -- although, given the expense, they might be limited to big businesses, novelty clubs/restaurants, and security buildings. I agree with TJL: "Buildings would get taller and/or leave the planet completely, but the orientation would remain the same." Since everyone will be able to fly, this question may be helpful too: [How would an avian city be different from ours?](https://worldbuilding.stackexchange.com/questions/2975/how-would-an-avian-city-be-different-from-ours?rq=1) [Answer] [Why We Don't Have Flying Cars](https://hollyiblogs.wordpress.com/2013/07/22/why-we-dont-have-flying-cars-2/). It's not about technology. It's that most people can barely drive in 2D. Forget 3D. That's why few people get airman's licenses. All kinds of buffering fail in a big enough accident, and pieces rain out of the sky. Skirts are gone, over. You never know what direction your feet are going to be pointing, so trousers, long or short, will be part of public decency. They might remain as fetish wear at home or in places of amusement. So new architecture won't worry about making stair treads opaque. In fact, I imagine stairs will be emergency wells only: you step into the lift and float up or down. I really like the suggestion that as soon as we have personal lift belts, the whole business with passenger vehicles will be over. Freight can be delivered by underground trains and trucks, and never appear on the streets. People in their bodies are much less dangerous than drivers in vehicles. A bubble of antigrav can keep off precipitation and most collisions, I imagine. I think this also does away with fear of heights and fear of falling, as one always wears one's belt. Security is a concern, yeah. It can no longer be just at ground level, but will have to be all the way up an exterior, including the roof. Still, I think flipping directions will mainly be a novelty. It's physically unsettling. It's like glass outside elevator shafts. How many buildings bother? The trick is to imagine in what industries this would be useful. Business rent will be charged by cubic feet, not square feet, because you can put more cubicles on the ceiling and walls, and float the lights between. Warehousing becomes much easier, as does work in shipyards. [Answer] Let's assume that traffic control for flying cars and trucks can be solved. GPS, computers, good training and licensing, whatever. Also assume that they can fly at the speed of a small aircraft, not the speed of a ground car. * Express highways could be replaced by designated air lanes at high altitude. They're both cheaper than ground highways and higher capacity due to vertical stacking, and faster because they don't mix with low-altitude traffic. * The same would happen to major streets in the city on a slightly lower/slower scale. Instead of multiple lanes arranged horizonzally, there could be multiple lanes arranged vertically. No need to worry about a toddler running onto the road if that road is 20 feet in the air. * There is still a requirement for parking space. Either on a reinforced roof or in front of the houses. That could replace all/most city streets with relatively narrow lanes for pedestrians and bicyclists, lined by parking space. Green grass instead of hardtop roads? The increased speed could also allow longer commutes, allowing suburbs to spread out more. The poor can live more in densely packed inner cities, the rich can live on larger estates? [Answer] I would imagine that if you could cast the effects of an anti-gravity device over a large area city design would probably reflect what a space habitat would look like at least in a minimalists form. A spce city would look like this: ![enter image description here](https://i.stack.imgur.com/wzEib.jpg) I would imagine people living in artificial houses resembling this on a much smaller scale. After all, we still need gravity, right? The spin of the house would create artificial gravity and might be auto piloted by a computer to prevent it from exiting the zero-g zone. These zero-g communities would only be available as vacation homes to the ultra rich due to the cost of designing and building a house regulated by a primitive AI and the fuel needed for the thrusters that would be used to keep houses in the zero-g zone. If you want flying cars, I suggest not applying the zero-g field to a wide area, but rather creating a narrow strip of zero-g generated above a certain point. Therefore there are very clear "sky-lanes" and people on the ground can still choose to use ground-based vehicles. I guess the most noticeable way this might effect city design would be the power grid in zero-g area would be better built, better secured, and they might have many fallbacks. If the main grid gets knocked out they would have many more backup generators so that floating houses and flying cars would not.....learn the effects of gravity first-hand if the main grid gets knocked out. As a side note, car design might be effected. If the anti-g drives are as cheap as you imply in your comments and edit, then what is to stop people from putting them in cars? The problem there is that traffic would be less regulated than if using the sky-lane idea. This might only be legal for law enforcement, in that case. ]
[Question] [ What would be the major changes to our bodies if we were herbivores? Would our bodies be weaker because they were not getting any protein from meat? Would we be completely different? (Probably, I suspect). [Answer] As far as I can tell, the major changes would be to the human digestive system, as well as to all body parts involved in processing food. **Teeth** The teeth of carnivores and herbivores differ because they eat different things, which require different techniques to chew. Plant matter is a lot different in consistency when compared to a slab of meat. [Wikipedia](https://en.wikipedia.org/wiki/Tooth#Mammals) has a nice note on the subject: > > The shape of the animal's teeth are related to its diet. For example, plant matter is hard to digest, so herbivores have many molars for chewing and grinding. Carnivores, on the other hand, need canines to kill prey and to tear meat. > > > Our teeth are best suited to eat both meat and plants; if we became herbivores, I would expect that our molars would develop even more, while our front teeth would become less developed. **Stomach** As you mentioned there are conspicuously low levels of protein in plants. Herbivores, as a whole, will most likely receive a different set of [nutrients](https://en.wikipedia.org/wiki/Digestion#Breakdown_into_nutrients) than carnivores. Stomach [enzymes](https://en.wikipedia.org/wiki/Digestive_enzyme) and fluids work to break down different substances; we would see a change in these enzymes and acids as more plant matter was introduced into our diet. If Wikipedia is correct, the major protein-processing enzymes include proteases and peptidases. We might see reduced numbers of these in a group of herbivorous humans. These acids are active all over the digestive system, so other organs would be affected --- > > Would our bodys be weaker because its not getting any protein from meat? > > > Have you ever fought a 400 lb [gorilla](https://en.wikipedia.org/wiki/Gorilla#Food_and_foraging)? Exactly. [Answer] Humans are omnivores, this has resulted in our digestive system evolving as it has. However, if humans had evolved as herbivores, then the following changes would be necessary: **Teeth:** Human teeth are actually fairly well adapted to a herbivorous lifestyle already, albeit herbivory that includes mostly fruit and nuts and soft leaves. Were humans to evolve as leaf/grass eaters (lower quality food), teeth are worn down rapidly by such a diet, and the molars would have to be larger and would either have to be replaced frequently (as in elephants) or be open-rooted so as to grow continuously (as in horses). The incisors may also have to be open-rooted, depending on if they are used to strip leaves off branches, or if they are used to crop grass. The numbers of teeth - and the size of the mouth - depends on the method by which the diet is digested. **Gut:** A herbivorous diet with lower-quality food requires a considerably higher amount of treatment in the gut than human's current diet. There are two ways this can occur: Foregut fermenters (such as cows) have large stomachs in which their food is stored in a bacterial soup which aids its digestion. They are able to regurgitate their food in order to chew it later. They have long intestines to maximise the digestion of the pre-treated fodder. However, if they eat food that is too rich, they tend to suffer from bloat as the foregut bacteria metabolise and reproduce out of control. Hindgut fermenters (such as horses) have normal sized stomachs, long small intestines, and an enlarged caecum (that in humans is the appendix) before the large intestine. Hindgut fermenters must chew their food more thoroughly (and must therefore have more grinding teeth, hence the answer to the question about horses, "Why the long face?") than foregut fermenters. Partially digested food accumulates in the caecum, where it undergoes bacterial fermentation, however, high quality food is not an issue, since the pre-treatment in the foregut would have removed the high-quality components, leaving only the difficult-to-digest stuff. However, hindgut fermenters are not quite as efficient as foregut fermenters. (As a diversion, this is why horses can be fed apples, but cows cannot.) A human-sized herbivore would likely gain more advantage from a foregut-fermentation digestive system, as it would not require as great a change in dentition, however a hindgut fermentation system would allow a greater variety of food. Gorillas, who are primarily herbivorous, are hindgut fermenters. [Answer] OK, it looks like nobody mentioned one major difference. **BRAIN SIZE** Research indicates that human brain sized increased very rapidly as our ancestors switched from a primarily herbivore diet to including meat in their food. <http://www.livescience.com/24875-meat-human-brain.html> <http://www.livescience.com/23671-eating-meat-made-us-human.html> <http://www.npr.org/2010/08/02/128849908/food-for-thought-meat-based-diet-made-us-smarter> <http://www.nasw.org/article/eating-meat-drove-evolution-our-big-powerful-brain> <http://www.berkeley.edu/news/media/releases/99legacy/6-14-1999a.html> **LARYNX** Meat eating means hunting. Hunting means group activity. Group activity means communication. Communication means sending and receiving complex detailed informational messages. Detailed messages in short time mean the need of producing many types of sounds. Many types of sound production means you need a larynx not deep down your throat like the gorillas have, but right up up up at the top of the throat the way we have now. <https://books.google.com/books?id=FgX2wcQXHTgC&pg=PA159&lpg=PA159&dq=meat+larynx+position&source=bl&ots=0NJ45Rkqx-&sig=4dtQt88fPFM1Z4u5CEfebi5VRBw&hl=en&sa=X&redir_esc=y#v=onepage&q=meat%20larynx%20position&f=false> There are several other important changes related to meat diet, but most of them are about the psychology and social structures of early peoples, so I will not mention them here. ]
[Question] [ Some published settings -- such as the Greyhawk 'verse commonly seen in conjunction with Dungeons & Dragons -- treat the prime planet's host solar system as geocentric. How could this be reconciled with what we now know about orbital mechanics and gravitation, though? The only theories I have come up with so far are: ### A heliocentric system that 'fakes' a geocentric system convincingly In this case, Oerth (Greyhawk's prime planet) is a large-ish planet that is tidally locked to a highly luminous host star, so that one side of the planet is permanently in the broiler, and the inhabited side is dark save for what light their star gives them. What the inhabitants perceive as the star, then, is a large, highly reflective moon that orbits the planet; the remaining 'planets' to the inhabitants then become smaller moons, and they'd have a few small rocks to serve as actual moons close-in to the planet (captured asteroids, perhaps?) This wouldn't work, though, if there were gas giants roaming around -- they'd have to orbit the true host star, which'd provide a way for the inhabitants of the prime world to detect what's *really* going on. ### A very large planet and a very small star in a tight binary couplet In this case, Oerth would be an *enormous* rockball with high gravity and inertia, and be orbiting in a tight couplet with a very dim, small star such as a red dwarf. Moons would be as normal as could be in such a deep gravity well, while the rest of the planets would be further out from the star-planetoid (brown dwarf?) binary couplet. However, this raises two questions: 1. Greyhawk's published canon states that the sun there is the *third* object out from Oerth -- with the inner two presumably perceived as planets; they could be very small moons or captured rocks instead, though, and I suspect people wouldn't catch on, at least at first... 2. How do you keep the gravity of this megaplanet from turning the inhabitants into Flat Stanley? [Answer] TimB's answer is basically what I would write, except for a very small loophole that I'll include here. Any celestial body does not actually orbit another body, but a point in space called the system's [barycenter](http://en.wikipedia.org/wiki/Center_of_mass#Astronomy), the center of mass. You can take a look at some of the animations [here](http://en.wikipedia.org/wiki/Binary_star#Center_of_mass_animations) to get a good idea of what I'm talking about. In a system such as the Earth-Sun system (where one body is much smaller than another), the barycenter is inside the larger object, like here: [![enter image description here](https://upload.wikimedia.org/wikipedia/commons/5/5a/Orbit4.gif)](https://upload.wikimedia.org/wikipedia/commons/5/5a/Orbit4.gif) Image in the public domain. In a system where the objects are closer in mass (such as a pair of neutron stars), the orbits will be more like this: [![enter image description here](https://upload.wikimedia.org/wikipedia/commons/7/73/Orbit1.gif)](https://upload.wikimedia.org/wikipedia/commons/7/73/Orbit1.gif) Image in the public domain. Now put a small body in the center of the system (you can use [this](http://phet.colorado.edu/en/simulation/my-solar-system) simulator, accessible directly [here](http://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html)). Use three bodies, with two of the same mass, and put the third - the smallest - in the center. What happens to the planet? > > Absolutely nothing. The forces on it are in equilibrium. > > > This equilibrium would not last forever - in fact, it would only last for a very short while - but in this case, the stars would revolve around the planet. --- There's actually a second possibility I hadn't considered: a binary planet. Take two very massive Hot Jupiters (let's say about 18 Jupiter masses each). put them close together (I mean *really* close together) and set them spinning about one another. Now take a brown dwarf1, about which the stars revolve. Perhaps it's low-mass, around 25 Jupiter masses. Have the planets go in motion around it. In the resulting system, the barycenter will be closer to the planets, meaning that, technically, the star orbits the planets! It'll be more like this system. [![enter image description here](https://upload.wikimedia.org/wikipedia/commons/f/f2/Orbit2.gif)](https://upload.wikimedia.org/wikipedia/commons/f/f2/Orbit2.gif) Image in the public domain. --- 1 Okay, brown dwarfs aren't truly "stars", but they're close enough. [Answer] Unfortunately the answer here is "magic"...or alternatively "sufficiently advanced technology to be indistinguishable from magic". As you correctly point out any known star will weigh massively more than the planet. In order to provide the desired result the sun must be considerably smaller than that and there is no way to get a natural star sufficiently small and light to orbit a planet without the planet being so massive it would crush all inhabitants. An artificial sun would need to be constructed using mechanisms unknown to us. It would have similar size and mass to a moon and could then be placed in orbit around the planet and turned on. It could potentially be fusion powered using something other than gravity to keep the fusion contained. Alternatively something more mystical like a portal to the plane of fire or something more pseudo-scientific like a wormhole connected to the heart of a star. Your "fakes geocentric" option would also immediately fall down as soon as someone moved away from the planet into space (in a magical world that's easy to do) or started exploring and moved around on the surface until they were starting to see the real sun "rise". Even if you had a small continent on the far side of the planet from the sun surrounded by a huge ocean you can guarantee that someone would explore that far. Again magic would make that sort of exploration much easier than in our world. Additionally the tidally locked and super-heating process would generate some really extreme weather conditions that locals would be able to study. While they may not be able to determine what is going on they would certainly know that something is. [Answer] Geocentrism only requires that we be a little bit wrong about gravity. And the atom proves how easy this could be the case. How do we know that heliocentrism is the "correct" view for how the universe works? Quite simply, it's because it predicts orbits better than the geocentric models did. But that only became the case once Kepler discovered that orbits were not circular (as all geo- *and* heliocentric models had assumed until then), and then he applied the results of his calculations (using Tycho Brahe's observations) to Copernicus' heliocentric model. He could just as easily have applied them to Ptolemy's or Brahe's geocentric models instead, though; would have given us a more complex model, but that alone doesn't prove it's wrong. So what does the atom have to do with this? The [Bohr model](http://en.wikipedia.org/wiki/Bohr_model) is still taught today in schools despite everyone knowing full well these days that [it does not accurately represent atoms](https://physics.stackexchange.com/a/114346). What it does do, however, is provide a simple and convenient model that explains covalent bonds, energy emissions and absorptions as electrons "jump orbits", etc. Which is why it's still taught in schools today. Just like Kepler's heliocentric model, it's the simplest explanation of how, when, and why these things will happen. And yet we know it's wrong. We know electrons don't orbit atoms in such neat little circles, but rather dash around haphazardly in a chaotic cloud. *(Thanks, quantum mechanics!)* So the Bohr model proves that you can have a simple model for how things work even though it represents those things completely wrongly; why can't the same be said for Kepler's heliocentric model? Because we also know gravity *does* work the way Kepler's model requires. And our understanding of gravity is observed consistently throughout the universe, right? Well, no, actually -- astronomers have had to "invent" the concept of "[dark matter](http://en.wikipedia.org/wiki/Dark_matter)" (stuff with gravity that we cannot see or touch but trust us it's totally there!) to account for all their calculations about gravity being *wrong!*1 So for the geocentric concept of the universe to be right, we only have to be wrong about a model that we've stood behind for a mere fraction of the time -- the [Ptolemaic model](http://en.wikipedia.org/wiki/Geocentric_model#Ptolemaic_system) was *the* model for the universe for around 15 centuries, and successfully resisted the Copernican heliocentric model because the latter was no more accurate; it was Kepler's heliocentric model that finally figured it all out, and only usurped it around 5 centuries ago. We're wrong about the Bohr model despite it having its benefits, so why can't we be wrong about Kepler's model, too? Depending on your world, you have a couple of ways to go if you want a geocentric universe: 1. A magical force that produces the spheres-on-spheres (actually ovoids, as Kepler's proven) necessary for the Ptolemaic model 2. "Dark matter" is real -- and it's actually the aether that made up the aforementioned spheres-on-spheres 3. Ptolemy was right about the spheres-on-spheres, but not their composition, and they are in fact binary systems of planets/moons/the sun with a companion dark matter body, all orbiting around Earth because... well I haven't quite figured this part out yet... --- Disclaimer before the comments start: I actually do not believe the conclusions postulated above. This is merely an attempt to answer the question as asked by presenting a somewhat plausible explanation for a geocentric universe given modern scientific concepts by first showing how science has progressed in the past and extrapolating that it could continue in the future by disproving what we "know" today just like it's disproven much of what we "knew" in the past. I've treated a few scientific concepts with a certain light brevity that would not fly in any scientific circles solely because presenting what is effectively an anti-scientific model as "reality" requires first putting science in the backseat, at least a little bit. This is, after all, all for fiction. --- 1 This is, amazingly, only a *slightly* simplistic representation of how "dark matter" came to be conceived! [Answer] If you don't have the ability to measure [stellar aberration](https://en.wikipedia.org/wiki/Aberration_of_light), the [Tychonic system](https://en.wikipedia.org/wiki/Tychonic_system) (Sun orbits the Earth, planets orbit the Sun) is indistinguishable from a heliocentric system. A true [Ptolemaic system](https://en.wikipedia.org/wiki/Geocentric_model#Ptolemaic_system) (everything orbits the Earth in circular orbits) is impossible except through magic, or at least [sufficiently advanced technology](https://en.wikipedia.org/wiki/Clarke's_three_laws), because the Sun needs to be sufficiently massive to sustain nuclear fusion. [Answer] I think you can do this in a helio-centric system; as long as everything orbits the 'earth' (Moons) and the 'earth' orbits the sun. In other words as long as there are no planets (well visible ones at least) When you observe planets, in out solar system, due to parallax effects they will seem to [reverse their direction as they orbit](http://en.wikipedia.org/wiki/Apparent_retrograde_motion). This is what led Kepler to work out that the solar system is a elliptical helio centric system. So if there are no visible planets, either too small, or are too far away, to observe; then you would have a pretty convincing geocentric appearing system. The only caveat is, you would not have any (slow moving) planets to hang myths and legends or have astrologers able to assign cause to (blame on) "Mercury/Mars/Venus is in [Retrograde](http://en.wikipedia.org/wiki/Apparent_retrograde_motion)" [Answer] If this is worldbuilding: I like a lightweight (but maybe large? in volume), magically powered sun that orbits a planet (2e: Continual Light, FTW!). I'd make this one of the dark planets, floating thru the interstellar void, brought to life. ie: No sun to muck things up. If we're trying to justify Oerth, then we need all the details. "Greyhawk's published canon states that the sun there is the third object out from Oerth" So, what's the order? Oerth (center), next out are Y and Z, and then the Sun orbits them all? Moons are totally the way to go in this case. Tidally locked Oerth gives tons of problems. The broiler side will have massive effects on your atmosphere. And reflected sunlight is going to be difficult to make the cold side anything but an icebox. Plus the always lit areas near the border, where you can't see the sun directly, but the sky stays lit up... forever. Easiest way to do Oerth, is just to say that gravity doesn't run the orbits. Gravity can weaken a lot faster, and something else propels them in orbit (magic). Which could be used to explain the flying and other anti-gravity spells, and tie in with Spelljammer gravity effects as well. Now, the question is, why is canon correct? Just because someone reports something, doesn't mean they didn't lie, or that they got [stufff] correct. Just retcon away :D [Answer] My first solution *would* be that gravity works differently in this world. Barring that, I'd be inclined to alter physics elsewhere and postulate an element easier to fuse than hydrogen, allowing a lower-mass star.... Actually, that's not necessarily an alteration of physics in itself. We have isotopes easier to fuse than H1. It's just that the natural distribution of elements and isotopes doesn't lead to stars made primarily of something other than H1 and He4. ]
[Question] [ Right off the bat, the world/setting that this takes place in is not the pinnacle of realistic, but I do want to have a bit of realism. Anyway, so in this story, really more of an idea,there is an action-figure named Rina that at times rides around on a talking and human-level intelligence seagull named Lafa she has befriended. And by rides on I mean like flies on, since she can walk on her own. So, putting aside obvious fantasy elements, can an average,let us say male ring-billed gull, still take-off and fly with an average plastic,6 inch tall action-figure mounted on his back? [Answer] **Yes.** [![seagull riding seagull](https://i.stack.imgur.com/vu8CH.jpg)](https://i.stack.imgur.com/vu8CH.jpg) <https://www.youtube.com/watch?v=H8KH_266tRs> This is pretty fantastic. What the heck were these two up to? If this video is faked, it faked me out good. Maybe the ridden seagull is practicing with his buddy so Rina gets a smooth ride. [Answer] Yes it can. Is your world hyper-realistic? No. Is it at least feasible? Yes. Then you have your answer I think, give yourself permission to draw your own lines. ...besides which, I've seen a seagull fly off with a cheeseburger that weighed more than a four ounces. To ratchet it down, you can add some realism by discussing how Rina stays attached... how she stays on, how she limits the impact of her not-aerodynamic form on Lafa's flight capability. [Answer] Birds can typically carry [about half their bodyweight](https://www.askprofessorbird.com/single-post/2017/04/20/watching-bird-behavior), though only downhill. [This six inch action figure](https://rads.stackoverflow.com/amzn/click/com/B08WH2HP2L) weighs 8 ounces, or 0.2 kilos. An average seagull might weigh a kilo to a kilo and a half for a male, or 0.7 kilos to 1.1 kilos for a female. A female bird on the smaller size would probably struggle getting up with an action figure, since they're close to three times as big as an action figure, and so are close to the only fly down weight limit. A male bird on the larger size would have little trouble, weighing 7 times more than an action figure. [Answer] If depends on the species of "seagull", but a herring gull has been recorded as attacking and carrying off a chihuahua dog, weight around 1kg. The usually live in flocks, so if one bird finds a substantial item of food its first reaction is to carry it away to somewhere safe, rather than be forced to share it with the other gulls. Carrying a plastic figure would be no problem at all. ]
[Question] [ So I'm designing an alien race loosely based on the Kafers from the tabletop RPG 2300 AD. These aliens not only become temporarily hyper intelligent as an electrochemical effect of their equivalent to the "fight-flight-freeze" response, but also have permanent increases in fluid intelligence over a longer period of time as a result of being in what are perceived to be threatening situations. This later effect can even be accompanied by slight increases in brain size (which their braincase compensates for over time) if it’s extreme enough. These aliens are initially psychologically similar to humans. If never exposed to stimuli that activates their fight-flight-freeze response, (described above), they generally will maintain an equivalent human fluid intelligence of around 70 IQ, but can theoretically reach a genius-level intellect if they've been having a bad enough time in life. It should also be noted that they don’t necessarily enjoy being in threatening situations any more than humans do. So we would expect a low likelihood of an “addiction to danger” psychological condition within their race. I’m mostly curious as to the psychological and sociological implications of such an organism, say, if you got an ancestral hunter-gatherer population of this species, and let evolution do its thing for about 200,000 years or so, how will this affect their psychology and social structures, especially when they finally start building permanent settlements and advancing past the stone age. Edited: Grammar and some extra clarification. [Answer] ## Evolution by Drama: Despite the fact your species doesn't like being threatened, no evolution is an island. Your species is CAPABLE of being smarter. The real question is, WHY is this only triggered by stress? If intelligence is an unmitigated benefit, then the daily stresses of life would eventually trigger intelligence, and everyone in their society would be smarter. The advantages would just be too great. So let's figure out why they aren't ALL smarter. * **Hierarchical**: Your species has a caste system or ranked leadership system. The leaders are the ones doing the fighting and thinking for the rest of society like in *Brave New World*. The rank-and-file citizen is only happy doing their crappy jobs for angry, overbearing aggressive bosses if they don't think about it too much. So if the alpha citizen dies, their successor(s) takes over and faces immediate stresses that make them smarter - but also dominating and aggressive, so they have more semi-violent stressful situations that push their intelligence up and increase their dominance. * **Caloric restriction**: Being smart is expensive. Your smart individuals consume vast amounts of calories. So you can only have either a small percentage of smart people, have people smart for a short period. If you have the whole society shift to smart for too long, they need to establish a new stable culture with lots of calories. Historically, during disasters, this meant a period of social adaptation where the species carved out new ecological niches for itself. * **Secondary Consequences**: Your species has other BAD things that happen to their bodies when they get smart. Maybe it significantly shortens lifespan. Maybe it causes muscle atrophy so the smart individuals become sedentary like village elders. Maybe the expansion of the cranial cavity comes with a 30% mortality rate. So the "part-time-smart" is an evolutionary workaround to compensate for the physical problems. Like ever-broadening hips for human females giving birth to big-headed kids, this adaptation compensates for the consequences of smartness, while still giving the species access to extra intelligence and the good things that brings. Overall, I would guess from the logic of most of these arguments that your species should actually have less intelligence and smaller brains than humans do prior to boosting. The bulk of their people would be mild-mannered citizens complacent with their jobs on farms and doing manual labor. Social structures would be as stable as possible to maintain the status quo. The rulers would want to keep people happy and stress-free, because the more stressed people get, the smarter and less compliant they get. Eventually, it would lead to revolution, famine, and the establishment of a new social structure that would let people calm down and go back to being simple citizens. An odd consequence of this system is that as their civilization progressed to higher levels of technology, there would be increasing pressures to have smarter individuals to manage the technology. Although the day-to-day tech would be made extremely easy to use, it would need smart stressed people to design and maintain it. So the society would have structural pressures that would favor increased levels of stress as technology made people's lives theoretically less stressful. Social structures with things WRONG with society would generate stress until enough people were smart enough to deal with it, leading to reduced stress. You might find there was a pressure to either have a caste system where a certain group maintained an artificial stress level (like a priest/[Aristoi](https://en.wikipedia.org/wiki/Aristoi) group) or a sexual dimorphism where society gave one gender or another more stress by social role - think either 1950's suburbia or the [Tuareg](https://en.wikipedia.org/wiki/Tuareg_people) culture. [Answer] ### Dunbar Number One of the interesting psychological and social implications of increased intelligence is Dunbar Number. Dunbar Number is often described as increased trust. I think it’s more appropriate to say you “get” a larger number of people— understanding their point of view provided only the broadest strokes of their background. The big difference between trust and this is that you also understand when you may be violating boundaries, or be in conflict. From a utility perspective, Dunbar Number increases the maximum possible size of your tightly knit professional or other organizations before they split into focus groups. It is believed to increase the maximum size of the smallest chunk of “community” (what feels like a small town, your band of brothers, a pack, or a tribe) ### Trust Gap There may be an actual name for this, but there’s been research indicating that there is a band of intelligence within which two or more people can work well together. I’ve felt the metaphor to explain this is reading level. Beyond a certain point, the less intelligent person is increasingly required to take on faith the interpretation of the unintelligible words (reading level) or unfollowable thinking (people). It becomes an increasingly difficult ask. From the other person’s perspective, an increasing amount of information gets lost in translation. The more intelligent partner is increasingly required to also take on faith that the coworker understands whatever the topic is and is making informed judgements. If the gap in your aliens’ intelligence is pretty great, then they probably live as actual aliens among their peers - coping with lives of miserable social isolation, not being really understood but trying to get along. Because of the higher Dunbar Number, they probably “get” that. ### Optimizing Humans try all sorts of practices (education, prayer, “brain games”, exercise, good diet, meditation) and take all sorts of drugs (caffeine, tobacco, chewing on cocoa leaves, industrialized cocaine, British and German experiments with meth, nootropics, hallucinogens) to keep the intelligence performance boosts we can get out of them. This may be a cynical perspective, but I believe your alien society would set the performance benchmark of your people slightly above “natural”. The bottom half of the social band will be taking whatever performance enhancers are accepted by society (smoking, coffee, prayer) just to keep up. The middle band will optionally be doing the same thing for an “edge” at work, and the top tier will be bifurcated with people enjoying themselves as they are, and the most hardcore competitors taking every method available to them to create and keep in top shape constantly. [Answer] They would initially have a much higher mortality. When in the fright/flight/freeze state humans have evolved to go to a lower state of consciousness. This state lets us bypass much of our brains, letting us come up with a solution much faster and then act on it. The phrase "I never thought as fast in my life" is tightly bound to this. The "problem" with this is that you dont make the best solutions, but that doesnt matter in a low-tech environment where the fastest solution is more likely to let you survive than your smartest one. These creatures would be more intelligent but our conscious solution to a problem is often worse than our subconscious solution (again, in low-tech environments). A great example is people who are trapped outside in the cold: a child is much more likely to find a hole to hide in and survive until its found, but adults will consciously assume they need to find help and will walk in circles for hours exposing themselves to the elements and freeze to death faster. The conscious solution in those situations is the worst. So your aliens would have a much higher death rate than the "dumb" humans who immediately create one panicked plan and stick with it. When technology and knowledge increase you will first see a higher survival rate for these creatures. Of you know that something poisoness bit you and you can create an antidote rather than run away in panick you have a greater chance of survival. This all gradually stops as mass-media takes its toll and people get the increasing ability to spread misinformation both on purpose and by accident. Parents of this species will be encouraged to still give their children the biggest advantage as possible, so they would likely invent terror-schools. Schools designed with peaks and lulls in the children's stress levels, scaring them with a "test that will define their life" or tests that will result in severe punishments when you fail (and students who perform too well will be punished for smaller infractions). Followed by healthy low-stress downtime so the children wont be high-functioning PTSD patients (and believe me, school alone is more than enough to get PTSD if you are unlucky). Due to the fluid intelligence that remains for some time after being scared, adults will use this when they need an intelligence boost. From interviews to last-minute crunchtime to finding the solution to that one last question, they'll want to get a high stress level. To ensure they arent getting complacent they can use various methods: fights aimed at leaving nasty physical damage like a broken bone or large cut that you can only get out of if you win the fight, doing things they fear deliberately or risking something that person values which they will lose if they fail. [Answer] ### Some in that race will intentionally self-panic. I believe I would. Would you (the reader, a normal human) rather be **"Dumb and Happy"** or **"Smart and Petrified"**? This choice is not obvious and people pick their own choice for their own reasons. Now if "smart and petrified" made you actually smarter? For me at least the choice is obvious, but this would not be true for everyone. (Happy sounds pretty nice) Projecting myself into your species: * I value my own intelligence + I do not want to be dumber, and will take steps to avoid decline in intelligence if I'm aware of them. + I want to be smarter if theres a way to get it. + I will spend finite time and resources on this. * Danger is my own perception and subjective. + You pull a gun and point it at me I'm freezing up (probably because I've never seen one before outside of a screen) but someone with training can stay cool. + I can look outside and see an orange sky and thick ash from a major bushfire nearby and think "ho hum. Australia's gotta Australia". Had I not seen this a dozen times before I'd flee and die on the road like most panicking people do in these fires. + I once had a panic attack after having a drink spiked. It reoccured every time I thought of the events, and, yes I control what I think about. + So in conclusion I'm part of the process that determines whether my body enters that panic mode. * Danger is all around if you look for it. + One quarintine worker slips up and Covid could get out in Australia again. + Cops who just randomly hurt or kill people if they're having a bad day. Which I've personally witnessed before. + One more random government lockdown and me and my entire house loses their job. Governments have been locking down with hours notice when covid is even suspected to leak. + Climate change is making '1 in 100 year" disasters occur monthly, and it's getting worse, and 51% of our government treats climate change like a fairy tale while in office. + Health, diet and nutrition information is all over the place, but all the simple and tasty foods are probably killing me. * I view unintelligent people who want to live in peace as part of the problem with these long term issues. + Climate change is a hard problem, people who dont want to hear about it - just sit back and cash their coal-backed-dividends - are part of the problem. + Cops killing black people is made worse by the lazy uneducated white person practicing casual racism. + People in places where covid is still spreading are refusing to wear masks. "Oh covids not that bad, it only kills old people, and I'm not old, and Bill Gates made it anyway". + Choosing to live in peace and ignoring long term dangers and subtly making the problem worse is unpalatable to my values. So let's combine this together: If I can control my own mental state to some extent, and one of those states results in me becoming smarter, which I desire, I will enter that state as often as I can. I will stay awake at night panicking about climate change and antibiotic resistant superbugs and animal extinction and other long term perils, because **I value intelligence more than I value serenity**. The choice to stop living in fear and be dumb and be part of the problem would be unfathomable. No I don't like living in fear, but it's better than being dumb and part of the problem. Applying this back to your race, I suspect you'll get a split in your population based on their answer to this question. You society would have 2 extremes: "Panickers vs dumbs", and the differences between the two would be analogous to left v right politics today. [Answer] ## Forget high school, it's Battle Royale! Your race gets smarter from threatening situations. As they get smarter, their threat-assesment gets better, preventing them from weekly horror movie sessions to become a genius. This naturally limits the increase in intelligence for the vast majority of the race. If you know 99.9% of people survive some artificial threat scenario, it's not a threat. Otherwise, they'd become smarter every commute. To still reap the benefits of increased intelligence, some percentage of adolescents is selected to take part in Hunger Games/Battle Royale style fights to the death. The survivors come out significantly smarter and can look forward to leadership positions in society. To maintain the increased intelligence, these leaders are allowed to ascend in position and power by killing and taking the place of a higher-stationed leader. This keeps them permanently on edge, because there are always new threats from lower ranks. Conversely, a strike at lower stationed leaders is not allowed and sanctioned by society and other leaders. When times are good, relatively few members are sent or volunteer to take part in these trials. When resources are scarce or an indirect threat is identified (say climate change), the rate of these deadly trials is greatly increased and survivors tasked with coming up with a solution or taking part in more rounds of Battle Royale if they fail. A direct external threat (alien invasion, war, etc) results in hordes of grunts being sent to fight and the survivors forming the real army that employs actual strategy and tactics. This of course leads to a caste-like division in society, where the vast majority just goes about their routine job and mundane life, while there's a continuous and violent struggle happening over their heads. The leadership is motivated to keep the number of people sent to trials to the minimum necessary to increase their own longevity while still preventing the society as a whole from losing direction and ending up in a truly threatening situation. [Answer] I haven't seen this mentioned in the other answers, so I thought I'd share. ## Don't underestimate the power of familiarity! What I mean is that the first time you encounter a dangerous situation, it stresses you out and you are "in danger". The fiftieth time it happens, it becomes "oh, that again" and there is no feeling of being in danger. As an example, remember the first time you took the drivers seat and started in traffic, and how ten years later it's routine to just grab the car and go on. The danger is the same. All the stimuli are the same, but it has become familiar enough to not warrant any kind of danger response. *As a side note, roller coasters have just become the best thing ever, as if they weren't already!* ]
[Question] [ **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I was in the shower the other day thinking about the sun going Nova, *you know...like you do,* and a thought occurred to me: **Could you turn the sun into a stable, mostly closed system?** Some details of the universe in question: * The actor in this case is a type II civilization * They have colonized 5 planets in their 12 planet system * They have access to unobtanium for the purpose of building any machinery that needs to interact with their star or be used in the process. * The unobtanium is not adversely impacted by the heat of the star or the cold of interplanetary space. For the sake of this question it is also perfectly sealed meaning there is no loss of whatever in your calculations. **The goal:** * Create a system that allows you to prevent a star (identical to our sun) from going nova, or burning out or at least drastically elongates the lifespan of the star (at least 20% more starry life) * Requires the least possible amount of external stellar fusion resources from being space-trucked in to feed the system. **Answers must:** * Identify which solar products must be removed from the star + How would you extract it? (keep the unobtanium in mind) + In what quantities? + How much energy would it require? How does this energy compare to overall solar energy captured? * Identify which elements/compounds must be added to the star + In what quantities? + How much energy it would take to move them from Mars orbit to the sun + For the sake of this question ignore resource availability * Identify what can be recycled from the extracted stellar waste + Ideally most if not all of the required elements could be synthesized from solar waste. + The remaining waste can be dumped on a Mercury like planet nearby, the less the better. * Propose machinery/system to execute the process **Show your work** [Answer] A star's life ends when it can no longer undergo fusion at its core. For massive stars, this often happens when the core is made largely of iron, which can be fused (and is) in small amounts, but only endothermically. The products of nuclear fusion are, at this point, like carbon monoxide: it's not that their presence is toxic to the star, but it prevents the star from getting the fuel it needs - sort of like how CO molecules binding to hemoglobin make it difficult for a human to get the oxygen it needs. They take up space. Therefore, if you could remove those products, hydrogen could take their place at the core, and the death of the star would be offset. I very much agree with Ender Look on one point: convection is key. It allows you to transport heavy elements from deep within the star to its surface, while mixing hydrogen back into the core. This happens in the outer regions of all stars, but in low-mass stars(say, less than $\sim0.3M\_{\odot}$), this convective region reaches all the way to the core. The Sun's convective zone ends in a place called the [tachocline](https://en.wikipedia.org/wiki/Tachocline), which occurs at about $0.7R\_{\odot}$. Below this point, the star is stable against convection. In particular, something called the [Schwarzschild criterion](https://en.wikipedia.org/wiki/Schwarzschild_criterion) is satisfied: $$\frac{3}{64\pi\sigma G}\frac{\kappa LP}{MT^4}<1-\frac{1}{\gamma\_{\text{ad}}}$$ where $\kappa$ is the opacity and $\gamma\_{\text{ad}}$ is the adiabatic index. We can assume that $\gamma\_{\text{ad}}=5/3$. I decided to try to model the tachocline on my own by determining where the following is satisfied: $$\frac{3}{64\pi\sigma G}\frac{\kappa LP}{MT^4}-\left(1-\frac{1}{\gamma\_{\text{ad}}}\right)<0$$ I used [numerical simulations by John Bahcall](http://www.sns.ias.edu/~jnb/SNdata/solarmodels.html) (in particular, [the model designated (BS2005-AGS,OP)](http://www.sns.ias.edu/~jnb/SNdata/Export/BS2005/bs05_agsop.dat)). I calculated the opacity via [Kramer's opacity law](https://en.wikipedia.org/wiki/Kramers%27_opacity_law), including opacity contributions from free-free and bound-free absorption, as well as electron scattering: $$\kappa\_{\text{ff}}=3.68\times10^{22}g\_{\text{ff}}(1-Z)(1+X)\frac{\rho}{\text{g cm}^{-3}}\left(\frac{T}{K}\right)^{-7/2}\text{ cm}^2\text{ g}^{-1}$$ $$\kappa\_{\text{bf}}=4.634\times10^{25}\frac{g\_{\text{bf}}}{t}Z(1+X)\frac{\rho}{\text{g cm}^{-3}}\left(\frac{T}{K}\right)^{-7/2}\text{ cm}^2\text{ g}^{-1}$$ $$\kappa\_{\text{es}}=0.2(1+X)\text{ cm}^2\text{ g}^{-1}$$ Assuming that $g\_{\text{ff}}\approx g\_{\text{bf}}\approx1$ and $t\approx10$, I get the following plot of opacity contributions: [![Opacity contributions](https://i.stack.imgur.com/vyrBl.png)](https://i.stack.imgur.com/vyrBl.png) I then plotted the difference of the two sides of the inequality: [![Plot of convective stability](https://i.stack.imgur.com/R1Qht.png)](https://i.stack.imgur.com/R1Qht.png) This places the tachocline at about $0.82R\_{\odot}$ - an overestimate, but not by much. Notice that for the two major components of the opacity, $\kappa\propto\rho T^{-7/2}$. Therefore, if you increase the density or decrease the temperature, $\kappa$ will increase and the convective region will move inwards. This is what happens during something called a [dredge-up](https://en.wikipedia.org/wiki/Dredge-up), affecting stars that are off the main sequence. Say we cut the temperature to $0.75$ times its current value at all points in the outer half of the Sun. Then we find that the convective envelope can extend to about $0.72R\_{\odot}$ - progress. Now, the core extends only to $0.25R\_{\odot}$, so we would need to dramatically increase the opacity much deeper in the star to further lower the tachocline. [![Plot of convective stability](https://i.stack.imgur.com/5kovs.png)](https://i.stack.imgur.com/5kovs.png) Once we can figure this out, all that remains is to determine how to increase the efficiency $\lambda$ of this artificial dredge-up - that is, how much of the newly-produced heavy elements are cycled to the surface. Ideally, we'd have $\lambda\approx1$, and typical dredge-up efficiencies vary. The solution I've come up with is almost counterintuitive: Add more heavy elements. Notice that $\kappa\_{\text{bf}}$ - the major source of opacity - is proportional to $Z$. This means that by increasing the amount of heavy elements in the *outer* layers of the star, we can extend the convective zone down towards the core. Given that for the Sun, $Z\simeq0.001$, changing this shouldn't change $X$ and $Y$ by a significant amount. In fact, $Z$ is so small that there's only about one Jupiter mass of heavy elements in the Sun. I decided to adjust $Z$ by various amounts, and looked at how deep the convective zone extended. [![Determined convective zone for a variety of metallicities](https://i.stack.imgur.com/MgOVU.png)](https://i.stack.imgur.com/MgOVU.png) It seems that by adding about Jupiter masses worth of heavy elements, we can extend the tachocline to at least $0.6R\_{\odot}$, if not deeper. Remember, of course, that my original calculations underestimated tachocline depth, meaning that in reality, this could be enough to bring the convective zone to the edge of the core. You might notice that around $0.5R\_{\odot}$, it seems that my computations produces a convective region extending to the core even at low metallicities. I believe this zone doesn't exist in those low-metallicity models. So why does it show up? Well, notice how $X$ and $Y$ change deep in the Sun: [![Graph of how X and Y vary with radius inside the Sun](https://i.stack.imgur.com/kXKUR.png)](https://i.stack.imgur.com/kXKUR.png) Inside about $0.2R\_{\odot}$ - and, to an extent, inside $0.5R\_{\odot}$ - there is non-negligible gradient of both $X$ and $Y$, which translates to a non-negligible gradient of the mean molecular mass, which means our stability criterion should actually be something called the [Ledoux criterion](http://www.scholarpedia.org/article/Stellar_convection_simulations#Schwarzschild_.26_Ledoux_criteria_for_convective_stability), which takes concentration gradients into account. If I accounted for this, I believe this supposed convective region would disappear - except in the high-metallicity models. My guess is that adding roughly 30 Jupiter masses (likely less, given that we don't need to increase the metallicity in the *core* - just the region directly outside it) worth of heavy elements would increase the opacity to the extent that the tachocline would reach the core, allowing for mixing and eventually heavy element transport to the surface. The details of how you get all of these heavy elements back *out* further compounds the problem, but I believe that if you could trigger a burst of fusion, that could lead to an artificial dredge-up, as I discussed before. Rinse and repeat, periodically - perhaps every few billion years or so, just to be safe. Honestly, 30 Jupiter masses every few billion years isn't too much to ask of a Type II civilization, is it (depending on what resources are in the planetary system, of course)? [Answer] Of course, it's possible, a Kardashev type II civilization will have it quite easy. This is a healthy star, like our: [![enter image description here](https://i.stack.imgur.com/K8MS4.png)](https://i.stack.imgur.com/K8MS4.png) And this is a super healthy star (even when scientists says it's a failed star!): [![enter image description here](https://i.stack.imgur.com/wf9yf.png)](https://i.stack.imgur.com/wf9yf.png) Our objective is the second image. Now, let me explain everything. # How is a normal star Normal stars, like our star or the star from the first image, **have their elements divided into layers**. Our sun is like the first image, but with fewer layers (2 main layers: 74% Hydrogen and other from 25% Helium, the 1% is scattered around the photosphere), since it's less massive and younger. A young star only has hydrogen in its core but, after some time, helium reserves will be build from the hydrogen, and so they **will stay in the core (displacing the hydrogen)** due to their increased weight. This new helium will replace the main-hydrogen-fusion and create new elements that will perform the same cycle. Our star is quite young, so the main-fusion is made from hydrogen -even when the core has 60% of helium- due the Sun doesn't have enough temperature to fuse helium yet. The problem is that when helium raise in the core, **all the hydrogen (not burned) will be displaced from it to the outer layer**, and because the Sun can't fuse helium, gravity will reduce its size, massively increasing the pressure of the core, causing nuclear fusion of helium that will counter-act the new pressure. So... what is wrong or bad from that? Well, that all the **non-used hydrogen is just discarded**. That precious fuel won't ever be used by the Sun, instead **will accumulate in the outer layer of it**. So, how can fix that? That happens because the Sun transfer all its heat in form of [radiation](https://en.wikipedia.org/wiki/Heat_transfer#Radiation), so the solution is: # [Convection](https://en.wikipedia.org/wiki/Convection) - The solution Basically, convection is this: [![enter image description here](https://i.stack.imgur.com/tIyQq.png)](https://i.stack.imgur.com/tIyQq.png) > > Convection is the heat transfer due to the bulk movement of molecules within fluids such as gases and liquids [...]. > > > An example would be when you boil water in the oven, the water from the bottom becomes hotter and move to the top, forcing colder water to move to the bottom. This is characterized by a [mass transfer](https://en.wikipedia.org/wiki/Mass_transfer) between the hotter zone to the colder one. And that is great! If the molecules of the sun are forced to move by convection all the "layers" of elements get broken, that means that **heavier elements won't be moved to the core nor lighter elements (hydrogen and helium) will be moved outside it**. It will be a homogenous mix! And we need that, so the Sun will be able to **fuse all their hydrogen before start fusing heavier ones** (like helium). Now the problem is: How to archive convection? # Building a convective star - Mass and Size From [Wikipedia](https://en.wikipedia.org/wiki/Stellar_structure#Energy_transport): > > Convection is the dominant mode of energy transport when the temperature gradient is steep enough so that a given parcel of gas within the star will continue to rise if it rises slightly via an [adiabatic process](https://en.wikipedia.org/wiki/Adiabatic_process). In this case, the rising parcel is [buoyant](https://en.wikipedia.org/wiki/Buoyancy) and continues to rise if it is warmer than the surrounding gas; if the rising particle is cooler than the surrounding gas, it will fall back to its original height. In regions with a low-temperature gradient and a low enough opacity to allow energy transport via radiation, radiation is the dominant mode of energy transport. > > > Now, I'll summarize the following paragraph from that link into 4 items. Basically, the mass of the star determines the type of thermal conduction due to its fusion: * Well, the first is special. [White Dwarf](https://en.wikipedia.org/wiki/White_dwarf) don't fuse, so they don't produce heat, their only transfer its remaining heat using [thermal conduction](https://en.wikipedia.org/wiki/Thermal_conduction). We will only use this after the star dies, in order to maintain it warm for more time. * Medium stars (0.3 - 1.5 [M☉](https://en.wikipedia.org/wiki/Solar_mass)), like our Sun, primary fuse hydrogen-to-helium using the [proton-proton chain](https://en.wikipedia.org/wiki/Proton-proton_chain) which doesn't produce enough steep temperature gradient (only 4th power). Thus, convection isn't possible and so radiation is used in the core. The outer portion is enough cold to allow convection. * Massive start (> 1.5 M☉) has cores with greater temperatures, which allows the [CNO cycle](https://en.wikipedia.org/wiki/CNO_cycle) to produce hydrogen-to-helium fusion. This cycle has temperature rates of 15th power, enough steep gradient to make convection effective. The outer portion of the star doesn't have steep gradients due being colder, which force them to use radiation. * Small stars (< 0.3 M☉) have no radiation zone; the dominant energy transport mechanism throughout the star is **convection**. [![enter image description here](https://i.stack.imgur.com/zVOu2.png)](https://i.stack.imgur.com/zVOu2.png) Black arrows are convection and red arrows radiation. Massive stars are difficult to make and since there are bigger they consume more fuel (even using convection), so smaller stars are the best: we need a red dwarf. # [Red Dwarf](https://en.wikipedia.org/wiki/Red_dwarf) - The economical star From Wikipedia: > > A red dwarf (or M dwarf) is a small and cool star on the main sequence, of M spectral type. Red dwarfs range in mass from about 0.075 to about 0.50 solar mass and have a surface temperature of less than 4,000 K. Sometimes K-type main-sequence stars, with masses between 0.50-0.8 solar mass, are also included. > > [...] > Stellar models indicate that red dwarfs less than 0.35 M☉ **are fully convective**. Hence the helium produced by the thermonuclear fusion of hydrogen is **constantly remixed throughout the star, avoiding helium buildup at the core, thereby prolonging the period of fusion**. Red dwarfs, therefore,**develop very slowly, maintaining a constant luminosity and spectral type for trillions of years**, until their fuel is depleted. Because of the comparatively short age of the universe, no red dwarfs exist at advanced stages of evolution. > > > Emphasis mine. Red dwarfs are really small and so they consume a lot less of fuel and remix it constantly avoiding wasted hydrogen. Note that red dwarf produces much less heat and light, so you must (a) bring the planets close to the star (and avoid the possible [tidal lock](https://en.wikipedia.org/wiki/Tidal_locking) or gravitational squeezing) or (b) produce your own artificial light for those habitable planets. But, how we make a red dwarf? # Operating a star: Making a Red Dwarf Make a red dwarf is really simple, **you just need to remove mass from it**. Well, that is extremely difficult but for a type 2 civilization and with a green light for unobtanium use you may do that in just a blink of eyes. Once you finish to remove the unnecessary mass, be sure to keep it in a safe place, free of nuclear fusion (or a new star will be made). After that, you should be constantly checking your star, feeding with more hydrogen when it needs, and removing the heavier elements that disturb the convection (a so reduce its luminosity). After running out with all your fuel reserves, start feeding it with Jupiter, Saturn and the other gas planets from the solar system. After that, I'm sorry but we will have to accept its death... or not. # Maintaining the undead: Blue Dwarf [Blue dwarf](https://en.wikipedia.org/wiki/Blue_dwarf_(red-dwarf_stage)) From Wikipedia > > A blue dwarf is a predicted class of star that develops from a red dwarf after it has exhausted much of its hydrogen fuel supply. Because red dwarfs fuse their hydrogen slowly and are fully convective (allowing their entire hydrogen supply to be fused, instead of merely that in the core), the Universe is currently not old enough for any blue dwarfs to have formed yet, but their future existence is predicted based on theoretical models. > > > Stars increase in luminosity as they age and a more luminous star needs to radiate energy more quickly to maintain equilibrium. Stars larger than red dwarfs do this by increasing their size and becoming red giants with larger surface areas. Rather than expanding, however, **red dwarfs with less than 0.25 solar masses are predicted to increase their radiative rate by increasing their surface temperatures and becoming "bluer"**. This is because the surface layers of red dwarfs do not become significantly more opaque with increasing temperature. > > > Your red dwarf will become blue. Also, the increase in heat will allow you to fuse heavier elements like helium, carbon an so on. You may start feeding it with all that heavier elements (but never with iron or heavier, they consume energy instead of produce on fusion). Be careful to not overfeed it and produce a giant star or worse and go supernova. But finally, it will perish. # The holy corpse: White Dwarf If your civilization still wants to extend its lifespan you should consider making a new religion for it... anyway white dwarf is dead so they don't fuse. > > A white dwarf, also called a degenerate dwarf, **is a stellar core remnant composed mostly of [electron-degenerate matter](https://en.wikipedia.org/wiki/Electron-degenerate_matter)**. A white dwarf is **very dense**: its mass is comparable to that of the Sun, while its volume is comparable to that of Earth. A white dwarf's faint luminosity comes from the emission of **stored thermal energy; no fusion takes place in a white dwarf wherein mass is converted to energy.** > Emphasis mine. > > > Be careful about its size because: > > The material in a white dwarf **no longer undergoes fusion reactions**, so the star has no source of energy. As a result, it cannot support itself by the heat generated by fusion against [gravitational collapse](https://en.wikipedia.org/wiki/Gravitational_collapse), but is supported only by [electron degeneracy pressure](https://en.wikipedia.org/wiki/Electron_degeneracy_pressure), **causing it to be extremely dense**. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the [Chandrasekhar limit](https://en.wikipedia.org/wiki/Chandrasekhar_limit) —approximately 1.44 times of M☉—beyond which it cannot be supported by electron degeneracy pressure. A carbon-oxygen white dwarf that approaches this mass limit, typically by mass transfer from a companion star, may **explode as a [type Ia supernova](https://en.wikipedia.org/wiki/Type_Ia_supernova)** via a process known as [carbon detonation](https://en.wikipedia.org/wiki/Carbon_detonation) [...] > Emphasis mine. > > > But don't worry, they last a lot of time also (as red dwarf): > > A white dwarf is very hot when it forms, but because it has no source of energy, **it will gradually radiate its energy and cool**. This means that its radiation, which initially has a high color temperature, will lessen and redden with time. Over a very long time, **a white dwarf will cool and its material will begin to crystallize, starting with the core**. The star's low temperature means it will no longer emit significant heat or light, and it will become a cold **black dwarf**. [...] the **length of time it takes for a white dwarf to reach this state is calculated to be longer than the current age of the universe (approximately 13.8 billion years)** [...] > > > Emphasis mine. # Defying Death: Necromancy! Now your sacred religion must perform a final ritual, an unholy ritual: necromancy. We can still bring alive the star, but it will not be cheap. In this catalogue we have three rituals to perform. You may choose one of them... of all if you like, it is possible in the correct order! ## First ritual: The Black God (Black Hole) After the white dwarf becomes a [black dwarf](https://en.wikipedia.org/wiki/Black_dwarf) hence a truly dead star, increase massively it mass or pressure (preferably the second one) until the gravitational collapse or pressure is enough to make a black hole. Once you have summoned your black god star feeding it with mass, the [accretion disk](https://en.wikipedia.org/wiki/Accretion_disk) will produce enough light to simulate a star. ## Second ritual: The Army of Hundred of Demons (Tiny Black Holes) In order to perform this ritual, you must make an extremely small black hole from a little portion of the black dwarf mass. In case you already have a black hole, you are ruined, you might split it extracting a tiny piece of it or use unobtanium to force the [Hawking radiation)(<https://en.wikipedia.org/wiki/Hawking_radiation>), which is sci-fi. For being exactly, you need 962.5653 kilograms of a mass black hole to simulate the 384.6 yottawatts of energy produced per second by the Sun (calculated [using this](http://xaonon.dyndns.org/hawking/)) and it will have a radius of 1.429267e-22 centimetres. Note that this black hole will die after 7.497924e-8 seconds... so you need to feed (or replace) it quickly (if you replace be careful with the super explosion produced before banishing). From [Wikipedia](https://en.wikipedia.org/wiki/Hawking_radiation) > > Hawking radiation reduces the mass and energy of black holes and is therefore also known as black hole evaporation. Because of this, black holes that do not gain mass through other means are expected to shrink and ultimately vanish. [Micro black holes](https://en.wikipedia.org/wiki/Micro_black_hole) are predicted to be larger emitters of radiation than larger black holes and should shrink and dissipate faster > > > Basically, black holes produce virtual particles and anti-particles (not confuse with antimatter, this is **completely different**) in its surfaces. These particles are made from nothing but they annihilate themselves very quickly an so any physical law is broken. The interesting thing is that these particles **can escape from the black hole** and **less massive black holes are easier to escape**, so, when one of this two particles escape and the other don't, this "escaped particle" becomes "real" and in order to not break any physical law, the black hole is "obligated to pay the price (in mass and energy) of both particles), effectively reducing its mass and emitting light. If you are a physist, please don't criticize me, it's just a **very** basic explaining. ## Last Ritual: The master of tunnels (Quantum tunnelling) Have you heard about the fascinating [Quatum tunnelling](https://en.wikipedia.org/wiki/Quantum_tunnelling)? Do you remember the Hawking radiation? Well, that was a type of quantum tunnelling. It's difficult to explain because it is related to [Heisenber uncertainty principle](https://en.wikipedia.org/wiki/Heisenberg_uncertainty_principle). [![enter image description here](https://i.stack.imgur.com/ycjkB.png)](https://i.stack.imgur.com/ycjkB.png) Weird, right? But imagine yourself, if you run at maximum speed to a wall, can you move *through* it? Well... yes, I mean, NO! Don't try it! Theoretically speaking *you can* but in real life you *can't*. If you want an explaining, [in this answer I've already explained it](https://worldbuilding.stackexchange.com/a/118530/35041) Using the most refined handwavium techniques with the most exquisite unobtanium, scientists are able to force this quantum effect (for being exactly [proton tunnelling](https://en.wikipedia.org/wiki/Proton_tunneling)), effectively splitting heavier elements into lighter ones as hydrogen. **So you are able to recycle wasted elements into precious fuel for your star!** # A gift for you! These are just fancy animated YouTube videos from *Kurzgesagt – In a Nutshell* that explain some interesting stuff in non-scientific language! And they're last less than 10 minutes! * [Black Holes](https://www.youtube.com/watch?v=e-P5IFTqB98&feature=youtu.be) * [Red Dwarfs](https://www.youtube.com/watch?v=LS-VPyLaJFM) * [White and Black Dwarfs](https://www.youtube.com/watch?v=qsN1LglrX9s). [Answer] **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. Basically, stars lose stability as their ratio of heavy and light atoms shifts. Hydrogen is the primary fuel of main sequence stars, but as the heavy non-fuel byproducts of that fussion becomes more concentrated. This increased the inward force of gravity to outward force of fusion ratio which causes it to burn bigger and faster as the volume where fusion is happening increases from added pressure. So if you want to extend the life of a star, you need to fly in and collect all those heavier elements (iron, aluminum, oxygen, etc) to slow down the fusion. This is especially interesting because your civilization could use those elements to manufacture otherwise impossibly costly structures like the a dyson structure (sphere, cloud, ring, or whatever you prefer) that helped them achieve type 2 to begin with. The one concern is that while this would extend the star's life, it would also cool it down which would limit the power that a type 2 civilization could gather. For this to be truly sustainable, there would also need to be a good way to put more hydrogen back into the star, and that would be best managed by choosing a star somewhere in a solar nursery where hydrogen can be passively added by the environment. (So, if you do a sphere, it would still need enough holes in it to let new gases in.) A Sun sized star fusses about 300 times the mass of Mount Everest every day. This means you would need a truly massive harvester fleet to keep up with it; so, whatever your unobtainium is made out of, you need to be able to produce it on a huge scale. For power requirements, you drop your ship from the dyson structure by just decelerating it by a few thousand miles per hour so gravity takes it into the sun (not a significant power expenditure). You mine what you came for, then you use the power of the sun to get back. (solar sails or something like that) To find the power lose, Hydrogen has a mass of 1.00794u and Helium has a mass of 4.002602u, So when 4 hydrogen nuclei fuse to form one helium nucleus, the difference that’s left over is 4\*1.00794u - 4.002602u = 0.029158u. This fraction represents 0.029158 / 4.002602 = 0.007285 = 0.7%... [EDIT] Since E=MC^2 and v=sqrt(KE/(m\*1/2)), we can find that 0.007kg of mass converts to 6.2913e+14 joules which can move the remaining 0.993kg of mass ~35,596 kps. Now I could not find the exact math, but according to this <https://www.wired.com/2014/12/empzeal-earthfall/> if an object were to fall from 1au into the sun, it's final journey would cover the last 7% of the distance in the final 13 hours. From this we can assume the opposite which is that if you eject from the sun at ~224kps, gravity will pull you to a stop at 1au. (perfect for landing back in the habitable zone where your dyson structure might be with your fresh building materials) so you don't need to reach the sun's full escape velocity of 618kps to get to an Earth like orbit. That means you only need 0.63% of the star's power output to eject fussed matter at the same rate of production to where you can use it to build up your civilization. [END EDIT] ...though actual power usage is probably a bit more or less since the cargo to ship mass ratio is undefined. Also, Heavier materials like iron, oxygen, etc are also fused several times; so, if you target them I believe your star's power generated to mass ratio is theoretically better. On a final note: This would require a round trip of 128 days. The most efficient thing to do would be to have permanent mining stations in the sun, and just spend a day or two loading and unloading your freighters. So if you assume a freight mission is 130 days, this means your total fleet would need to be able to carry ~4.7 quadrillion tons of material per haul. Or in numbers normal people can think about, that is the transport capacity of 8.6 million Triple-E Maersk heavy freight ships. [![Triple-E Maersk](https://i.stack.imgur.com/dfGZp.png)](https://i.stack.imgur.com/dfGZp.png) [Answer] Assuming your unobtanium is stable even within the core of a star, you can do this: * You build a fusion power plant made fully from unobtanium, capable to process hydrogen all the way up to iron. The bigger the power plant, the better. Ideally, it would have the same excess-heat power output as your star, you may even want it to produce some power that you don't use otherwise than dissipating it in form of heat. The power output is just the bonus. * You drop this power plant into the core of the star, and use the generated energy to remove the produced iron from the core. How you do that, it's up to you, but I could envision a gigantic space elevator that moves the iron into a stationary orbit. You'll be building an iron planet out of the star's waste there. * The effect is, that the excess heat from the power plant increases the star's energy production. The star, however, is a self-regulating power plant itself, **so the star will ramp back its own energy production**. You are thus **replacing** hydrogen-to-helium fusion without waste removal with hydrogen-to-iron fusion with waste removal. * Since you are fusing all the way down to iron, your power plant needs less hydrogen to output the same amount of heat. Thus, your supply lasts longer. * By removing the waste, you avoid the star's natural up-regulation of power output as it ages and starts fusing heavier elements. The later stages of a star burn much quicker through their fuel, in a large part because the star's power increases. You avoid this ramp up, so the fuel lasts longer. * Because you are removing the iron, the star shrinks, and will eventually halt its own natural fusion processes. When this happens, it becomes little more than the fusion power plant's fuel reserve and excess heat radiator. Great, now **you** get to dictate how fast (or slow) your star burns through its fuel! * And all the time, you are getting insane amounts of nice, easily usable electric power. [Answer] **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I would imagine the effort and power requirements to keep such a star sustainable would far exceed to energy gained from the star. I the dying stages of a star, it may be more energy effective to begin build the society to prepare for the death of the star. This may be strip mining every world of the solar system to build massive space stations to house what may be 100's of billions of citizens. The problem may be then, without a star, how do you power your civilization? They may harvest the unused nuclear fuel from the star upon its death to build more compact fusion reactor that they can extract closer to 100% from. This may sustain the civilization for a few more millennia until the obtain the ability to reach another star system. By that time, they may just move from star to star to stripe it of Hydrogen, Deuterium or such for their own use. ]
[Question] [ I have a story in a mediaeval setting with no magic. There are elves, but they are essentially just absurdly long-lived versions of humans with pointy ears and somewhat more acute senses. Unicorns are central to the story. They are roughly horse-shaped, though there is no need for them to be equids—in fact, I'm toying with the idea to give them cloven hooves. Naturally, they have long, fluffy hair and elegant spiral horns. I see no issues with any of that. The problem is, they are fiendishly intelligent, on a par with people. That, too, is key to the story, but I just can't convince myself that animals that can't use tools and live fairly standard ruminant lives would evolve this kind of intelligence. Show me that I'm wrong, won't you? [Answer] The problem with this is that we only have humans to go on for human-level intelligence. There are many highly intelligent creatures including but not limited to primates, crows, dolphins, and octopodes. If intelligence on this level is what you're after, then there is your proof that an animal can achieve that level of intelligence. For higher intelligence, we're forced to look at what it is believed to be the reasons behind *human* intelligence. There are several theories regarding the importance of intelligence in humans during evolution. ## Tree life One theory being that in order to sleep in trees without falling out, we had to have higher brain functions. If our ancestors fell out of the trees, they could seriously injure themselves or get eaten by a predator. Bad things happened otherwise. Unicorns don't sleep in trees traditionally (though maybe yours do, but I'll assume that's not your case). ## Tribe Another theory being that it was very much in the interests of survival to make friends and therefore be social. Higher brain functions are required to be able to recognize many faces and have many friends. If you had few friends which took care of you, eventually they may die off leaving you to fend for yourself, and being alone for the type of lifestyle which our ancestors had was a rough life to be sure. There was strength in numbers. Your unicorns may move in packs, but that's not quite the same as being social. They would need to be able to communicate in some fashion, perhaps using a highly sophisticated calling mechanism? Hmm, I'm not honestly convinced of this. ## Tools The traditionally believed reason behind modern human intelligence has been the usage of tools. In fact for a long time, it was believed the use of tools was a unique trait of human intelligence and what distinguished us from other animals. We now know this is no longer the case. [Crows](https://gizmodo.com/watch-a-genius-crow-solve-8-complex-puzzles-in-perfect-1520343494) have been found to use sticks to obtain items out of reach, for instance. Although this isn't a unique trait, it could still be that the need for more advanced tools such as spears and knives meant the difference between being cold and hungry and being clothed and well-fed. Unicorns obviously cannot use tools, so I think we're also going to have to exclude this possibility. ## Conclusion Unicorns don't quite fit the description of these theories, and as such, none of the same conditions exist for a unicorn which existed for our ancestors. Though perhaps it is incorrect to base conclusions on the intelligence of human beings, however this is all we have to base ourselves with. I hate to say it, but I'm in agreement with your sentiment that such animals could not have human level intelligence. It could be quite clever without being as intelligent as human beings, but it could never equal our intelligence without otherwise meeting some of these conditions in my humble opinion. [Answer] Intelligence has a lot of components, and there are driving evolutionary forces to increase them * **Memory** It is argued by evolutionary biologists that the complex fruit-based diet of primates requires a good long-term memory to remember where to find good food sources * **Social structure** Some intelligence is necessary to maintain a complex social structure. * **Hunting** Carnivores are usually more intelligent than herbivores * **Language** Having a language requires a lot of intelligence, but using it is evolutionary very efficient Tools only come as an afterthought. Whatever their body allows, you may detect some tool usage on your unicorns (e.g., a stick handled with the mouth) [Answer] Why not make your "unicorns" carnivorous, tool users? They hide their diet to keep the other intelligent animals from fearing them. They manipulate tools using a long, forked, prehensile tongue (and shake "hands" when they greet each other). [Answer] This is a case of convergent evolution. An isolated population of humans or elves evolved into unicorns. We can imagine a very specific combination of environmental pressures selecting for traveling on all fours, hands and feet becoming hooves (as happened during the evolution of the modern horse), long, fluffy hair, and elegant spiral horns. It took a long time. [Answer] If they aren't necessarily equine, and can have things like cloven hooves, why not have prehensile hooves? Prehensile hooves don't exist in the real world, as far as I know, but then, neither do unicorns. The moveable parts can be the actual hooves, or soft portions protected by the hooves as they walk, or a combination. That being said, if elephants can be very social and intelligent, despite the inability to create or manipulate a lot of tools (sure, a fair bit with their trunks, but not much else)...and if marine mammals such as whales can also be intelligent, why not unicorns? Maybe an ability to really manipulate (or even create) tools will put them above the intelligent animals without that ability. [Answer] You mention you're writing in a no (or low, anyway, depending on terms - given unicorns and long lived human "elfs") magic medieval-like setting. The medieval setting is well known for having a strong component of "magic" in history, in the form of religion (regardless of personal views on religion, it can be called a kind of "magic system" in fairness). You could justify your world's unicorns by claiming that the "spirit" or "soul" is intelligent - the "software" as it were, while the body just provides the brain hardware to run or assist the intelligence. There should be ample room in the braincase for a human-like brain with full equivalence, etc. You'd just have to justify why a) some pre-mortal spirits ended up unicorns and some as humans, and b) why whatever deity or creation method created two species. As other answers have stated, b) is somewhat difficult to justify with the "magic system" (again, sufficiently advanced science and whatnot, regardless of personal stance) of evolution, while with a neglectful creative intelligence you can say "she just likes unicorns and humans" and move on without impacting the story (or even mentioning it overmuch to the readers - the value is that *you* know the underlying causes in your world). Edit: ah, didn't notice the "evolution" tag. Given that that "magic system" is presupposed, my answer might not be useful. ]
[Question] [ Let's say an alien species discovered Earth and wants to land here and establish contact, however their homeworld's gravity is only 46 percent of Earth's, Would it be possible for them to be able to walk on Earth? Is it possible for them to adapt to Earth's gravity? They are 1-2 ft tall and walk on two legs. Weighing about 50-60 pounds on their homeworld. [Answer] Short answer: it depends. The anatomy and physiology of your aliens will determine a lot. For instance, their hearts are going to be working much harder to pump blood around their bodies, particularly when pumping upwards. Compare aliens which look like a 2 foot tall dog and aliens which look like a 2 foot tall ostrich or giraffe. The vertical distance between heart and brain in the ostrich-aliens is much greater than the dog-aliens. So the ostrich-aliens' hearts will be under much more strain. Their hearts will be pounding away like they've just run up a flight of stairs, even when they are just sitting watching TV. Similarly, skeletons come with safety factors built in. When those safety factors are exceeded, bones break. For instance in humans, the force your leg bones has to bear when standing still is equal to your body weight. When you walk, that force doubles. When you sprint or jump over things, it is higher still. However, your bones can take all these forces, plus a bit extra for the safety factor. Your aliens have come to a gravity more than double their own. So standing still will be the equivalent of walking, walking will be like jogging, jogging will be like running an Olympic hurdles race, and so on. If their species has evolved to bounce around like gazelles (huge leaps, gaits called stotting and pronking), or is like a monkey species which habitually hurls itself out of trees onto the ground (as opposed to climbing down or jumping tree to tree) then their bones will be designed to take a pounding and have HUGE safety factors. So they may still be able to walk and jog, but should avoid running and jumping. If their ancestors evolved a more 'normal' lifestyle - zebra rather than a gazelle, or a normal monkey rather than a 'parkour' monkey - then walking may be the limit of what they can do without breaking bones, getting sprains and strains, etc. Consider the elephant. Zoos have concrete moats round the elephant enclosure, because elephants are at the limits of the safety factors their bones can take. Elephants can't jump over that moat - they'd break their legs. In fact, elephants can't even run or trot, because their leg bones can't take it. A charging elephant is speed walking! EDIT TO ADD EXAMPLES: at 1g a horse can walk, trot, gallop and jump over fences. The much heavier rhino can walk, trot and gallop but not jump over fences. The Elephant can only walk (partly weight and partly due to not having bones as thick as it 'should' for an animal that heavy - i.e. reduced safety factors). So your aliens may be 'horses' on their homeworld, but 'rhinos' or - if they are really unlucky - 'elephants' on earth. Your aliens muscles will slowly get stronger as they adapt to the gravity. They may lay down some more bone to reinforce their skeleton. But the bone they'll be making is more of the same 'low gravity' bone with low gravity safety factors. Evolution won't have given them the tools to make 1g bone. There will also be a lot of wear and tear on soft tissues. Knee cartilages will be feeling the strain, spine compressing on disks, sole of the foot taking a pounding, and so on. They may spend all their time with bad backs and aching feet. [Answer] Walking for the low-gravity aliens would be like running a marathon. This is something that is best done in small doses. While exosuits are feasible. An alternative is mobile flotation tanks. The aliens will wear a protective suit, and rest inside the mobile tanks in a floating position. With medical equipment in case of "gravity stress" problems and possibly cardiovascular apparatus to take the load off their bodies. One aspect about low-gravity aliens visiting Earth is the fact that their spacecraft, when they land and take-off from planet Earth, will have to be at relatively low acceleration, compared to the kind of rocket take-offs we know, and be for a much longer duration. Unless their ships are propelled by a super-advanced field-drives which either neutralises or considerably reduces the g-forces accompanying the acceleration. [Answer] If their bone structure can withstand the stress, then they can, but it will be exhausting and highly uncomfortable. For comparison, imagine carrying around your own body weight in extra weight all day and night, evenly distributed over your body. Every step will be a chore, lifting your arms and even your head will feel like workout, every breath you take is a struggle. Not even lying down is much comfort because you will be pulled down so hard. You will want only your most able-bodied aliens to ever visit Earth, and even they will require some sort of mechanical exosuit or strength-boosting medication to get through the day without too many problems. [Answer] If the aliens have arrived via a long spaceship journey, and if they knew what was waiting for them when the got here, then they would have been well advised to use the journey as preparation. Their spaceship should have some kind of artificial gravity. Whether by some high tech plating (per Star Trek) or simply the craft revolving (per Space Oddesey), the strength of this gravity could be increased steadily through the journey time to help the travellers adjust to the conditions at the destination planet. A regime of weight training and exercise en route would be necessary as well. Picking suitably strong individuals for the journey in the first place would also be a consideration of course. Weaker individuals would struggle to adapt, but for stronger individuals coming off the ship after a journey helping them to adapt, they should be in good shape to cope with conditions on Earth. There is one other caveat to mention though. Breathing. If the aliens' planet has a lower gravity, then it follows that it also has a significantly lower atmospheric pressure. Even if their air composition is similar to ours, breathing air on Earth may cause them to hyperventilate. They will therefore likely need assisted breathing aparatus of some kind. This will appreciably add to the weight that they need to carry with them, which in turn will make adapting to the increased gravity a bit harder still. [Answer] Assuming they are biologically similar to humans, question boils down to this. Would you be able to carry 117% of your own weight? For me the answer to that question would be no, but for some, this might be possible. [Answer] # 2.2g That is how the aliens experience Earth. Assuming they are otherwise made of flesh similar to ourselves, this should be difficult but not nearly impossible. However, you also have them at only 1-2 ft tall. There are two factors that make high gravity a problem. * everything weighs more, thus needs more muscle power to move effectively. and much **much** more important. * your heart has to pump blood up against the gravity, and your feet need to resist the static pressure of supporting a column of blood as tall as you are. These vascular issues are the main problem with higher (and lower) gravity. For your aliens, this second factor is GREATLY diminished, because they are so short! In all, in my opinion but supported at least a bit by facts, your aliens will be fully mobile just tiring much quicker than normal. They will also tend to be clumsy, as they fall over following an imbalance more than twice as fast. --- # The problem of STAIRS! If your biped aliens are proportioned anything like humans: To a 1-2ft tall, biped, operating in a 2.2g (for them) environment, normal stairs will be IMPOSSIBLE to climb! Even a normal sidewalk with a vertical riser of 6 inches will be a WALL somewhere between knee height and navel height to them. You try climbing a wall that high, while in 2.2g gravity [![enter image description here](https://i.stack.imgur.com/ijnHi.png)](https://i.stack.imgur.com/ijnHi.png) And at 2feet tall, weighing 60lb **on their home planet**, they will weigh 132lb here. That makes for a very short, squat, heavy little alien! Not agile climbers by any concept. ]
[Question] [ I'm trying (failing) to write a story set within the exclusion zone around a nuclear power plant incident set in the near future. The 'incident' that leads to the exclusion zone being set up isn't the story itself, but I want the 'how' to be plausible. Modern (generation 3 and onwards?) light-water reactors seem to have a whole host of safety features that would prevent a meltdown or accidental release of radioactive particles. Containment buildings, automatic control rod insertion, backup generators and coolant pumps all make a Chernobyl-like exclusion zone coming about seem like an unlikely situation. A natural disaster could work, but the area I have in mind as the location of the plant is tectonically stable with no history of earthquakes or tidal waves. Plus just copying what happened at Fukushima seems like being cheap. So I'd prefer to avoid going that route. I was thinking maybe some sort of 'cyber-warfare' attack on the control systems, but I'm not sure how plausible that would be either. A lot of the safety features seem to be independent systems that kick-in with a lack of power. Any ideas? [Answer] Modern reactors are surprisingly stable. They're deemed virtually unstoppable, which is why the earthquake at Fukushima needed to literally shift the entire plant 100m along the ground before it started to fail. The ability to release fallout is considered so unbelievably utterly horribly bad, that it's nearly impossible to get a plant to do it without doing something grand. Politicians have trouble getting re-elected if nuclear power plants release fallout. They don't like that. They'd certainly be hardened against cyber attacks, so if you want a cyber attack to be at fault, look at [Stuxnet](https://en.wikipedia.org/wiki/Stuxnet), which is the first known attack to clear an airgap. Even then, there's *tremendous* incentive to make them fail safe. For example, one medical grade reactor design I am aware of relies on bubbling air through the cooling water to lift the control rods. If *anything* goes wrong with the electronics, the air stops being circulated, and the control rods naturally settle. You'd probably want to study a long term attack. While reactors are typically designed to be tamper resistant, nothing is perfectly tamper proof. With enough physical access over a long time, you may be able to disable all of the computerized safeties, jam all of the mechanical ones (many I presume are in high radiation areas, restricted access of course), and then provide the humans false data so that they don't think to hit the big red button when things go wrong. Even then, you probably want to try to time it around some giant event outside the plant to distract people. People at nuclear reactors are funny... its almost like the unconsciously want to protect the plant, and can smell a cooling motor misbehaving from 3 rooms away. Its almost like we hire them for personality traits like that. Want more information than just vague "maybe" scenarios? Well, the information you ask for would qualify as a vulnerability in our national nuclear power capabilities, so I would expect it to be classified as TOP SECRET//RD, which requires a special "Q" clearance from the Department of Energy to access. Needless to say, if I had access to such a clearance, I would be choosing to not answer even hypothetical questions on a forum regarding my job. *(Sometimes it's nice not knowing the real answers! I can hypothesise more that way!)* [Answer] Just as one option, there are quite a few RBMK-type nuclear reactors (similar to Chernobyl's) in former Soviet/Warsaw Pact nations that are still operating. Theoretically, a similar sequence of events would do much the same thing there. One potential difficulty is that the final nail in Chernobyl's coffin wasn't under human control; the control rods to SCRAM the reactor for the test got stuck in exactly the wrong position at exactly the wrong time. Basically, what you have to do is set the reactor up on a positive feedback loop, where an increase of power output causes a change in reactor conditions that drives a further increase in power. Exactly how you do this depends on the exact design of the reactor; most are designed with several layers of "passive safety", where in the event of something out of normal occurring, the design of the reactor itself will cause a *negative* feedback loop where the reaction mass drops to a subcritical state (no fission chain reactions). For instance, unlike the RBMK design, in many newer designs a loss of coolant renders the fuel subcritical because either the coolant is also the fuel and only goes critical within the specially-designed reactor core (such as in a molten salt reactor), or because the water coolant is also needed as a moderator, to slow the neutrons in order for chain reactions to take place; without the water, as in a loss-of-coolant accident, the neutrons are too fast and leave the core without causing enough chain reactions on their way out to keep the reaction critical. All that said, once a nuclear plant is built and goes online, there's not much that can be done to upgrade any passive safeties developed after it was designed. Most of the plants in service today are 70s vintage, especially in the U.S. where Three Mile, Chernobyl and Fukushima happened at just the wrong times in the discussion about whether to build more nuclear projects here, and no new fission plants have gone online since '77. It's not talked about much, but despite the *extremely* conservative policies towards engineering a nuclear plant, things can go wrong. [Answer] The swiss plant at Beznau apparently is a fairly optimistic piece of work, and there also appears to be a ridiculously long list of fautls this reactor has. If I remember correctly, people even drilled holes through the metal containment bubble to mount a fire extinguisher. You will have to goolge the details, since i can only find german language articles at the moment. And i am pretty sure it is only one of a longer list of sad examples. What I am trying to get at: **In theory**, a nuclear power plant is very safe, with a lot of redundant safety mechanisms. But in the real world it is one of those *25'000 moving parts, all provided by the lowest bidder* things, combined with a lot of politics (or, to put it more bluntly: greed): there will always be weaknesses that should not be there. Provided you find them, you can play with them. Or, for your story: just drop in a side note that they were there and greatly magnified problems that should otherwise not have been catastrophic. What a nuclear power plant really, really needs is coolant. And something else it needs, surprisingly, is electricity. So, if you manage to deprive it of cooling water and sabotage the power lines so that they won't be fixed any time soon, i guess you might pretty soon end up with a situation where your overheated fuel starts melting its way out of confinement and into the environment, providing just the situation you were looking for. [Answer] Control rods are suspended, controlled and monitored very carefully, but any control system can be subverted if you falsify the inputs and/or override the outputs. I cannot and will not give details on how to do this, but rest assured that there is no built in simulator that will just let you fake these. And if you tried it on my old submarine you'd have to kill every last one of us to manage it. And you'd have to bring your own power source, because I will personally destroy every piece of generation equipment before I let you do this. In all cases, a SCRAM is simply the removal of power (or other motive force) from the latching device and allowing it to drop. It is trivial to lose the fuses, smash the controls or axe the cables - all engine room personnel know where they are. The last option is to critically damage the unpressurized side of the rod drivers themselves. All I have to do is make sure there isn't enough wire left to do anything with. In the specific case of slow-fission water moderated reactors, I can also blow all the reactor coolant overboard. It seems counterintuitive until you know that these use water to slow neutrons to the point where fuel will absorb them. The core will probably melt - but you will never achieve criticality, much less the kind of criticality accident this scenario would require. Sources: My training as a former nuclear operator for the U.S. Navy is specifically designed first and foremost to understand and prevent this specific scenario at all costs. [Answer] Is the reactor itself important to your story? Is it important that it was an accident with the operation of the reactor itself? If not, **go for spent nuclear fuel** instead. Spent nuclear fuel need to be stored before being moved to final deposition. This storage can be at the nuclear power plants, or at a central repository. In any matter, at one point, sooner or later, it has to be transported. While there can't be a nuclear explosion, there can still be terrorist attacks, or some other grand explosion that breaches the containment of the transport, destroys the canisters the fuel is handled in, and spreads the material. However, to really create a big exclusion zone, you will want to have some way to spread nuclear material as ash from a fire - this was part of the reason you got so much nuclear material from Chernobyl to spread over such a large area. The initial explosion made a hole, and spread large chunks of radioactive stuff over the surrounding area, and then radioactive ash was spread into the atmosphere from the burning graphite. [Answer] [Generation 4 reactors](https://en.wikipedia.org/wiki/Generation_IV_reactor) (there are currently some experimental Gen 4 reactors around) are designed so that failure of machinery and personnel to enact safety protocols cannot cause a containment vessel breach. Meaning neither hacking, power failure, nor Homer Simpson could cause the reactor to spew radioactive fallout. It would take active physical intervention (e.g. explosives) to cause Gen 4 reactors to spew fallout. [Answer] The plant on Three Mile Island, Pennsylvania, had an incident in '79 in which a small amount of radiation was released (still with a USD $1B cleanup), but what made the difference between what happened and a catastrophic meltdown was, basically, luck. And a meltdown would certainly have necessitated a sizeable exclusion zone. There are several still-operating plants built before TMI: the *Yankee Clipper* plants in Connecticut come to mind. (The TMI plant was only 13 months old at the time.) Basically, a meltdown happens when the cooling stops (for any reason -- at TMI it was turned off), and results in the radioactive core melting through the containment and sinking until it hits groundwater, lots of which is turned into radioactive high-pressure steam, which could come up over a wide area, depending on geology. There's a discussion of this in the movie *The China Syndrome*, which was released the same month as the TMI incident. There's a chapter on just what happened at TMI in Charles Perrow's excellent and very readable book **Normal Accidents**. I highly recommend reading the (whole) book for anyone trying to construct any believable fictional accident or disaster. He was on the commission that investigated the Challenger Space Shuttle disaster, and knows a thing or two about how disasters happen. And he's a sociologist, so he explains the scientific parts for an audience that doesn't know a megajoule from a kilowatt. P.S. If you don't have a culprit, you could make the meltdown the work of a huge Atlanta real-estate developer, since it's the only major U.S. city more than 50 miles from any nuclear reactor. (More plausible than Lex Luthor making Arizona oceanfront, anyway.) [Answer] Look to the Fukushima disaster as an example of what can go wrong, that was a fairly modern reactor. In that incident, the four reactors did not fail. They were shut down as a precaution against the effects of the earthquake. What happened is - even after stopping the nuclear reaction, a great deal of residual heat is still present. Uranium, being a very heavy metal, will retain a great deal of heat, just as brass retains a lot more heat than a light metal like aluminum. Normally, the reactor's cooling pumps are kept running until that residual heat is gone, but that can take several days. However... the tsunami that followed the earthquake flooded the backup diesel generators that were needed to power those coolant pumps, and the electrical grid that could have provided power from elsewhere was also down. Without coolant pumps to take away the extreme heat still present in the uranium core, the reactors overheated, boiling off the cooling water that was present. Two of the reactors experienced internal explosions from accumulated hydrogen gas, and there was also a substantial leak of radioactive water. Fukushima could have resulted in a core meltdown, where the uranium melts and falls clear of the neutron absorbing rods that stop the nuclear reaction. If that happens, there's nothing to stop the nuclear reaction from not only restarting but spiraling out of control. Fortunately, the situation was arrested before full meltdown, but it still made quite a mess. So, if you want to make a disaster around a modern reactor, create some small fault that would result in a precautionary shutdown, and then fail the backup generators so that the coolant pumps can't run. ]
[Question] [ Excluding teleportation, the most rapid way of delivering troops to an operation planeside is by dropping them out of orbit in a steel can. Whether a small QRF or a few thousand marines dropping in to suppress air defenses and establish a foothold, drop pods are a staple of scifi stories. However something they can never seem to agree on is how many people these pods should carry. What are the potential benefits and drawbacks of choosing a larger 2-5 person pod over a small single person pod and vice versa? **In-universe considerations** I'm not going for a particularly hard science fiction approach so some degree of handwavium is acceptable when it comes to technology. Example: An artificial gravity well can be created that will make passengers in a vehicle more resistant to high G shocks, but, you still need to worry about the vehicle itself staying together. Electronic warfare has advanced to a point where highly complex electronics are of limited use in a conventional war this can effect the following: * Robotic soldiers exist but have only basic problem solving capabilities, organics (real people) must also be on the field to direct their mechanical comrades. * AI targeting systems are very accurate but easy to fool, most guided gun and missile systems must have an organic gunner, not necessarily to aim and fire, but to make corrections where needed. Expect late WWII level hit probability on particularly fast moving objects * Wireless communication can be easily jammed, the EM spectrum of a battlefield is ridiculously noisy, whoever has the stronger signal wins in the broadcasting theatre of a battle. QRF: Quick Reaction Force Please let me know if you need any further elaboration or clarification! [Answer] I'd say the biggest driver of drop pod strategies would be the kind of resistance you expect. Ideally you'd have one drop pod (or drop *ship*, potentially) per objective, and you'd load each one up with enough personnel and equipment to achieve their goal. Problem is though, if the objective is defended in any way then there's a risk that a particular drop pod could be destroyed before it landed, with all the resulting loss of life and material that entails. Intercepting hypersonic re-entry vehicles isn't trivial, but remember the existence of things like [Sprint](https://en.wikipedia.org/wiki/Sprint_(missile)) and [Spartan](https://en.wikipedia.org/wiki/LIM-49_Spartan) that demonstrated the ability to intercept ballistic re-entry vehicles using nuclear warheads that allowed for pretty big margins of error. Those two projects used 1970s missile and radar technology, and by the time you're considering mass troop drops from space you might reasonably expect to have improved both of those things somewhat. By using multiple smaller re-entry vehicles, together with what Cold War military strategists referred to as [Penetration Aids](https://en.wikipedia.org/wiki/Penetration_aid) (no giggling at the back) the chances of wiping out an entire task force is vastly reduced. The penalty is that now you need to spread your drop pods over a much wider area (if they were too close to each other, then a big nuke could either destroy them or kill their meaty centers) which makes the contents of each pod much more vulnerable to what it might meet on the ground, compared to the single big drop that's the alternative when there's no risk of hostile aerospace defence. The lower size limit would be set by how widely you were willing to spread out your troops, and how much you were willing to risk individual soldiers (or very small groups) whilst they tried to link up with the rest of the force in potentially hostile and unfamiliar terrain. It is also worth considering that the drop *pod* following the classic [blunt-body re-entry vehicle design](https://en.wikipedia.org/wiki/Atmospheric_entry#Entry_vehicle_shapes) is great for use in a non-hostile theatre, but what you probably want for combat drops might reasonably look a lot more like a hypersonic glide vehicle optimised for unpowered but manoeuvring flight that retains high speeds at lower altitudes, making it somewhat harder to intercept (at least, by modern-day standards). That means it'll probably end up looking more like this: [![Artist impression of Raytheon's hypersonic boost glide vehicle ](https://i.stack.imgur.com/LUWU0.png)](https://i.stack.imgur.com/LUWU0.png) (Artist rendering of Raytheon's Tactical Boost Glide flight system. Image credit: Raytheon) than something pod-like. [Answer] ## It is a tradeoff One big drop ship is cheaper than many small ones. Big pods have a higher volume to surface area, plus there are certain components you need 1 and only 1 of regardless of pod size like navigation computers, landing cameras, etc. Also, one big component is often cheaper to mass produce than lots of little ones; so, making 1 big landing thruster is cheaper than 5 little ones even if both sets produce about the same total thrust. So, it is cheaper to drop a given number of troops in the bigger pods. That said, ever heard the saying "don't put all your eggs in 1 basket"? If you have to drop 5000 men into hostile territory, and the enemy has the capacity to hit 1000 of your pods on the way down with AA weapons, then deploying in smaller pods means 80% of your ground forces will survive the decent, but if you send fewer larger pods, you risk your whole invasion force being wiped out. This makes the question of drop pod size directly proportional to how much your civilization values an individual life. If your civilization sees human life as cheap and expendable, then bigger pods make more sense. If your civilization places a higher value on human life, then smaller ones make more sense. That said, there are also situational factors to consider. If you are trying to deploy a lot of assets into a fully secured LZ, then drop "pods" may not be the way to go at all. A single large transport ship can store a lot more troops, supplies, and hardware if it's not wasting a ton of capacity on drop pods at all; so, your initial "beach head" invasion will probably be done with a swarm of these small pods, but once you have secured a place to land, you would want to bring in full sized landing ships full of not just troops, but tanks, artillery, AA batteries, etc. [Answer] For a given shape, the surface to volume ratio increases with the decrease of the size. Aerobraking is affected by the cross section of the object, while the amount of energy that is has to shed is affected by the volume. Therefore, for a given shape, the smaller it is the more easily it can aerobrake. If you apply this reasoning to the descent pods, a single passenger pod seems to be more efficient than a multi-passengers pod. Then you need to make a trade off with the availability of materials: here the advantage goes in the other direction, with bigger being better. [Answer] **4 person team pods.** The problem with orbital drops is inaccuracy. Your soldiers might be scattered over a large area. It is bad for morale to be a single soldier all alone. A team of 4 persons can support each other and is big enough to get things done. **And 0 person pods.** [![rupert the paradummy](https://i.stack.imgur.com/mc43Im.jpg)](https://i.stack.imgur.com/mc43Im.jpg) <https://en.wikipedia.org/wiki/Paradummy> Here is Rupert the paradummy. Fake paratroopers are good for soaking up bullets. So too empty pods. A lot of your pods will be empty, or might be full of propaganda. They are to divert attention from the pods with people in them on the way down. [Answer] # It's complicated First off there is a good chance steel will be used much less frequent. Polymers (like plastic) will have advanced in a great way, allowing for better drop pods. The reason drop pods are different in size is because each has merrit for a certain kind of attack. Individual ones allow for a greater spread to capture tactical positions, but are more difficult to put into small clusters. They can be no more than a suit, possibly discarded the moment they touch the ground. This allows freedom of movement and near instant deployment. They can evade fire and detection more easily because of the small cross section and higher manoeuvrability. The scatter can also be a detriment, as well as having no cover. In addition, you need a lot of materials if you cover every single troop in the pod, as well as fill it with technology, fuel and whatever. A single hit is more dangerous to the person, but less to the group. A multi transport offers cover when arriving. The troops are also concentrated, allowing for better ground control. The transports themselves can still be scattered, allowing for capturing of strategic positions. The technology and materials to support them are less. Each transport can have a team that is build to support each other. Like light and heavy assault, support, medic, etc. They are easier to spot and shoot down. A hit is less severe on a multi transport, but destruction of the transport offers a higher loss of military power. They can often be reused, salvaged or used to bring manpower back into the air/space. Personally I would have mix. A few single person drop pods to come down in strategic locations, clearing out or tying up the enemy troops. Then multi troop transports come down. I would go for trio transports, each facing a different direction. This will give them a bit of cover as well as 360° firepower each side if they drop right in the middle. These should create a true beach head, allowing the 20, 50 or even bigger transports to land in relative safety. These can bring the heavier equipment, generators and other matetials. At any point you can still drop down the smaller transports where required. The initial wave of one man and 3 man drops are often sacrificial. Though well trained troops their loss is accepted. But a few of these can drop elite soldiers tasked with important missions, allowing them to drop in less detected and less chance to lose them all if a transport blows up. [Answer] # Empty of Flesh ## (Full of tungsten) If you are in a position where you are * involved in a war * against a planet-bound force * the orbitals of which you occupy * with *n* millions of kilograms of matter * that you can selectively de-orbit **You have already won**. You have the ability to selectively devastate any enemy fortifications, cities, industrial areas, airfields, and *spaceports*. Dropping soldiers and equipment is a waste of time. Why drop a 54,000kg tank and its crew when you could just drop 54,000kg of mass moving at orbital velocity on whatever you were planning to have the tank attack? Once you've leveled any meaningful resistance, you can deliver troops to the surface at your leisure, if you still have any reason to do so. [Answer] Drop pods have a specific purpose. They arent as versatile as dropships so you have to emphasise their advantages to use them. Mainly: cheap and hard to hit by using smaller sizes. Drop pods would be for the initial engagement. You want to be able to clear a space and start landing larger equipment as soon as possible, like vehicles and the supplies your soldiers are dependant on. This means that drop-pods arent just for firing straight into combat, a more likely attack method would be to shoot them a few kilometers away from their target where they have a higher chance of landing safely and then assaulting their objectives so dropships can land and disgorge the real assault. This means that the size of the drop-pod is dependend on where it is supposed to land, and the effectiveness of the anti-air defenses in question. The closer to any defenses capable of shooting a drop-pod out of the sky, the smaller the drop-pod is to increase its chances of survival. The farther away the larger the drop-pod can be and land safely. Larger drop-pods also means more volume inside for supplies and heavy weapons, assuming some of the drop-pods dont deploy into small artillery pieces and towable guns. So its essentially up to you. Want to drop the pods on top of the AA defenses? Small Drop-pods are the way to go. Want to do a more intelligent drop? Bigger one's a ways away from the AA defenses are a solid option. [Answer] ### They aren't just for transport - they also turn into kinetic warheads A drop pod has four major components:- * Re-entry heat shield * High-altitude guidance system * Can of meat (ideally not cooked, minced, or otherwise processed!) * Low-altitude braking/landing/guidance system Once you're down to a sensible height and a sensible speed, the first two are simply dead mass when you come to landing. So why not put them to an alternative use? Once re-entry is done but the pod is still a pretty damn long way up (maybe 50,000 feet), the drop pod can jettison the heat shield and its guidance system. Each pod's heat shield then becomes a [rod from God](https://en.wikipedia.org/wiki/Kinetic_bombardment), guided onto targets around the drop zone to clear the area. For bonus points too, the wave of kinetic warheads will swamp anti-aircraft defences and greatly reduce the window where the pods themselves can be targetted. With this in mind, we have a good reason to have lots of smaller pods for assaulting a defended position. The more pods we have, the more kinetic warheads we have. Larger pods are used for dropping on undefended positions where we don't need that bombardment. [Answer] **You have a complex dilemma. Do you use streamlining or atmospheric breaking (AB).** Manned objects entering the atmosphere use atmospheric breaking to decelerate upon entering the atmosphere. Traditionally this is also what SF drop pods have done i.e. rely on AB for their initial deceleration in the stratosphere and higher. And if they have engines at all these are usually just for maneuvering (dodging counter-fire and reacquiring the LZ after having done so) perhaps with a last minute 'kick in the pants' for the occupant to bleed of all but the last dollop of V just before impact. Of course deeper into the atmosphere ailerons can do some of the work as can parachutes. Point is - manned vehicles that do this are not streamlined to resist drag, they depend on it for breaking so they tend maximize the surface area pointed in the direction of their line of flight (think the space shuttle - it came in hull first not nose first) and consequently leave a visible trail behind them. This is because in most manned flights of the grunt work of deceleration is done by AB which means hull temperatures exceeding **1800 degree C** plus a nice long/bright trail of ionized gas. All of which means that despite being able to jam active electronic sensors the capsule are going to scream red on well designed SF style IR sensors. And you'd need massive jamming on the radio frequencies the ionized gas gives off as well. **Second option don't use AB, instead be streamlined.** In this case, like nuclear missiles and hyper-sonic vehicles the drop ship can have have an aerodynamic shape (arrowhead etc) that lets you cut cleanly through the atmosphere like a knife in minimal time and not leave as much of a wake. *Except* you still have to slow down. Which means once your in the lower atmosphere you have to fly around for a lot longer losing speed until you can land or else install some form of handwavium 'inertial dampener drive' that magically kills off all your velocity. So either design strategy entails risks (just at different altitudes) and requires (I think) similar flight times without magic engines to save you. Option 1 (AB) you stand out during the high altitude part of the drop. Option (2) You have a quicker, less visible drop to low altitude but then have to loiter there till you kill of most of your velocity. Neither is ideal for obvious reasons. So if, as you indicate ground defenses are potentially highly accurate the safest answer would appear in the end that lots of small cheap disposable drop pods would be better regardless of the design. They don't have to be one man but you certainly don't want 747 sized pods with a company on board either. Then you just throw them out of your ships like chaff with as many unmanned decoys as possible included in the mix. EDIT: That's for the initial drop anyway. As your forces secure the drop zone and/or gradually neutralize the air defenses around the DZ you can switch over to larger drop pods, especially unmanned ones stocked with food ammunition and other essential supplies ]
[Question] [ In the real world all humans start off as females in the womb and then develop male organs before being born. I'd like to expand that concept further to the humans in my world. In my world, humans are all born females, turning into males later in life. So all younger people would be females and all older people males, with sex being an indicative of age. The result would be that all the people will become males once they get old enough. In this scenario, is it viable for a species in which all organisms are born females but then turn into males after a certain age is reached to survive? Assume that the sex change happens in adulthood around the age of 30-40 years. [Answer] > > In this scenario, is it viable for a species in which all organisms are born females but turn into males after a certain age is reached to survive? > > > Yes. It's very viable, given certain constraints, and there are even certain, although mild, advantages. First, the female stage needs to be for a sufficiently long amount of time, especially if the species is intelligent. Intelligent species tend to wait until later in life to have children - here 'later in life' means sexual maturity after at least a few years of development. Humans in particular take an astonishing long time, which makes sense because of the way intelligence vs instincts works - intelligence is always better in the long term, and the longer you can allow for intelligence to develop, the better the species is. But I digress. You'll need a sufficiently long time of sexual maturity, I'm thinking at least 25 years, possibly longer. (Again, this isn't strictly necessary for an unintelligent species, but it's better for an intelligent species to have a longer span of time.) After that, you'll want a transition phase where the individual isn't sexually mature while they transition and then reassume sexual maturity as an adult. Funnily enough, this requires *less* time within sexual maturity because at this point the species is a mature adult, though obviously, the more time, the better. The lifespan looks like this. 0-15 - development, 15-40 - female stage, 40-45 - transition stage, 45-death - male stage. There are a few advantages to this, namely, that since everyone can perform 'double duty' when it comes to reproduction, they have twice the womb capacity as a fixed race such as ours. That said, I'm not certain female->male is the way to go. True, it has benefits. On the one side, you get much faster access to wombs, which is very important for a developing society. In primitive societies, wombs are really important because those are what you use to get the best of all resources - new offspring. And while you're restricted by the number of wombs, all it takes is a handful of males to fill those wombs, meaning it's better to lose men than women. That's why males are the disposable gender and why they're the warriors. (Among *other* reasons.) Having the species develop first as women so they can give birth to offspring and *then* become the disposable men seems like a good thing. On the flip side, men are also pretty important as the warrior caste, responsible for the hard work and fighting and all that good stuff. If they're busy giving birth to children until 45 (okay, you can play around with the ages, but the thought still stands), then you run the risk of having a male society which isn't really that strong or fit - and that's pretty bad! In evolution, specialization tends to beat generalization, so if you had a tribe of these male/female humans vs a tribe of male humans + female humans, I'd take the latter over the former. That said, there's no inherit problems in this structure. I means, society is going to be very interesting because every marriage is going to contain a 30 year age gap and you'll have to do some nimble footwork to avoid mother/father-daughter incest issues, but it can work. Theoretically. [Answer] ***It already exists:*** About 2% of fish species already do something like this, and it is perfectly plausible. ([Source](https://ourblueplanet.bbcearth.com/blog/?article=incredible-sex-changing-fish-from-blue-planet)) [Answer] The species will survive, but not in the same way we do. You have set up a situation in which, unless the population is rapidly contracting with sub-replacement birth rates for a long time, there will always be many more females than males. First, any given age cohort will decrease in size as it ages, due to accident and disease. So under exact replacement birth rates, when all males are older than all females, the male-age cohorts will all be smaller than the female-age cohorts. Furthermore, if the population is growing, younger cohorts will have a higher base size than older cohorts--which further increases the number of later-born women over the number of earlier-born men. One way to fix this is to simply accept than some people will never reproduce as females. That may work in a modern industrialized civilization, where not everybody needs or wants to have kids, and populations stabilize at replacement levels. But "wasting wombs" is just not a viable strategy for a pre-industrial culture. As a result, polygamy will be the universal default state for this altered humanity. In situations where population growth is slow, so the female:male ratio is less than 2:1, not every mature male will have to be a polygamist, but the most well-off--those who best able to support multiple wives and more children--will be. And when the population is growing rapidly, or when the male population has been depleted--say, after a war or famine or pandemic, all of which reduce population generally but affect males and the elderly more than females and the young--it would be seen as every male's *duty* to take multiple wives. In this instance, polygamy is not a reward for powerful old men at the expense of other males, who are then left discontented and serve as a source of violence--rather, it is the normal arrangement required for social stability, and a duty which some men may find themselves relieved from in times of unusual long-term prosperity. [Answer] Yes, provided that the women develop a means to safely and effectively suppress testosterone production in men once they are no longer needed for reproduction. [Answer] **In this scenario, is it viable for a species in which all organisms are born females but then turn into males after a certain age is reached to survive?** **Yes, but** 1. What if you suffer mass loss of life, you need to have the transition bought forward. The change may not be purely aged based, maybe pushed forward or back depending on environmental conditions. (like the frogs from Jurassic Park) 2. If life expediency is about 30-40 they you don't have enough males. They need to both change to male healthy, and spend time health as a male. 3. It might be advantageous for good female genes to be spread far and wide via male reproduction. Ie genes for a good female is capped with one child every 9 moths; the genes for the men are well dependent on the number of women. I feel like that genes for a good male/female would dominate, like a reward for making it that far. 4. What about the comparative advantage of the female, that turns male early? What stops that gene setting up younger and younger males? Is their fighting? are they too weak to mate? **Modern Society**: Need a pretty hard re-write. its pretty significant. 1. Gender divide now makes no sense. You can't exclude women from careers etc, because they will become men; and all the men used to be women (some had children). This alone would have all sort of impacts that change society. 2. It cuts away partners for life for breeding, as your partners all age into males. Do you have children as the man or women? Would this prevent the nuclear family? A guess communal child rearing still works. 3. Now women may delay children, until they are men. If your left with any disadvantages around this (stay at home disrupt a career) none would would want children as the women. 4. The window of female child birth is very limited in a modern society that needs to delay children (or child care) for additional education, it pushes back childbirth. ]
[Question] [ I have a spaceship that can get to speeds very close to the speed of light. How can this ship measure how fast it is going near the speed of light? I would think one would measure how fast other stars fly by but does this even work if time dilation makes everything faster outside of my frame? [Answer] You can use the [relativistic Doppler effect](https://en.wikipedia.org/wiki/Relativistic_Doppler_effect) > > The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the special theory of relativity. > > > The relativistic Doppler effect is different from the non-relativistic Doppler effect as the equations include the time dilation effect of special relativity and do not involve the medium of propagation as a reference point. They describe the total difference in observed frequencies and possess the required Lorentz symmetry. > > > Before starting the journey, your ship needs to have a set of reference light sources, with known spectra. During the trip, by measuring those spectra, relative velocity can be calculated. In the picture below, taken from the linked page, the top half shows what Doppler shift to expect according to the direction in which the observer is looking at the light source in the relativistic case, while the bottom one shows the Doppler shift in the non relativistic case. [![Doppler shift vs viewing angle](https://i.stack.imgur.com/4XGQP.jpg)](https://i.stack.imgur.com/4XGQP.jpg) [Answer] It is important to note that travelling very near the speed of light is no different from being at rest - it all depends on the chosen frame of reference. Travelling at .999 c in one frame of reference = being totally still in another. You can only measure your speed *relative* to other objects in space. There is no absolute speed. If you are heading towards a star, you can measure your speed relative to that star by the blueshift of the star's spectrum (which has a special signature depending on spectral type). Similarly, if you are moving away from a star, you can measure the redshift of its spectrum. If you aren't heading directly away from or towards a star, you can measure the redshift and blueshift of stars to the side and compensate for the angle. ]
[Question] [ I wonder if a time machine can be the cause of a bootstrap paradox? **Background:** Let's say one day I found in my room a portable time machine. I use this machine to travel to the future, where I realize I am the person who placed the machine in my room. I then travel to the past to drop off the time machine and let my past self use it. The time machine always travels with me. There is only one time machine. **Condition:** Now let's say this time machine has critical components built of iron and, after many, many iterations, it rusts and falls out of order. At some point I won't be able to travel to the future ... but the time machine should be here, shouldn't it ? **Question:** Is something wrong with my scenario, or could this happen? (If so, how is it possible (theoretically)?) [Answer] The paradox only occurs if you assume a single timeline. In which case it is pretty much identical to the 'grandfather paradox'. In the left fig. below, if there is a single timeline then there is a single 'time-path' for you (red line) - that doesn't in itself produce a paradox, but the time-machine also only has a single path (blue line) which by definition must be closed. So the time machine would age further in each loop and result in your paradox - unless time travel itself somehow reverses entropy in the machine in which case you could arm-wave yourself out of the paradox. If you accept a multiverse-like multiple history situation, things are a little more complicated but there is no paradox. On the right below, some initial you (red line) gets access to a time machine, travels forwards and then backwards. On arrival at the end of the backwards step the timeline splits. The original timeline continues (in which you disappeared, reappeared in the future and then disappeared again forever). An alternate you (orange line) now repeats your journey in a first alternative universe,. This can be repeated numerous times until eventually (with the yellow-line you) the time-machine breaks and yellow you, the time machine, and your green-you alternative spend their lives all together in a final alternative. Note that the blue line is open , not closed, so the machine can obey the normal laws of entropy. There is still a potential paradox in answering where the time machine came from in the first place. But a non-paradoxical solution would be that in some 'first' time-line, someone invents the time machine, then someone travels with it back in time and in a 'first' alternative timeline, stops that person from inventing it, so no 'other' time machine appears in any of the observed timelines. [![enter image description here](https://i.stack.imgur.com/NOWeC.png)](https://i.stack.imgur.com/NOWeC.png) [Answer] There is a thought experiment out there that says that time travel is impossible; not because of the physics, but because of what we do with it. Basically it goes like this. If time travel *is* possible, we'll use it to change the past. Eventually, we'll change the past to one in which it is impossible to create or use time travel. Hence, time travel is impossible. Your antiquating time machine paradox is really just a less complex version of this. The loop is infinite. The durability of your time machine is not. The Laws of Entropy state that this loop has to eventually fail because eventually the machine fails. While the Ship of Theseus model can help, the problem is that every time you consume a resource in the past to fix the machine, you're also making a minor change to the past that could (eventually) accumulate to a future which precludes the use of the time machine. Even if you only use parts in the future, or the latest point in your loop, eventually the supply of those parts has to run out also. All things considered, this is not an infinitely tenable scenario. [Answer] > > The Bootstrap Paradox is a theoretical paradox of time travel that occurs when an object or piece of information sent back in time becomes trapped within an infinite cause-effect loop in which the item no longer has a discernible point of origin, and is said to be “uncaused” or “self-created”. It is also known as an Ontological Paradox, in reference to ontology, a branch of metaphysics dealing with the study of being and existence. ([Source](http://www.astronomytrek.com/the-bootstrap-paradox-explained/)) > > > Can the time machine be a necessary component of the bootstrap paradox? sure! A really good example is, IMO, the machine in the movie *[Primer](https://en.wikipedia.org/wiki/Primer_(film))* (2004). Does your scenario describe a viable bootstrap paradox? Maybe. All bootstrap paradoxes focusing on an object have one basic problem: the object never seems to get old. This is because the explanation of the paradox is, IMO, inadequate. Note that the quote above states, "...trapped within an infinite cause-effect loop..." This is NOT a requirement for a bootstrap paradox. In fact, it's almost never the case than an infinite loop exists (at least I've never heard of one where it had to exist, or could even be assumed to exist). Why? Let's look at your scenario. you-before-first-use finds the machine and uses it, causing you to become future-you. Future-you travels back in time to place the machine. And there's the problem. Future-you watches you-before-first-use use the machine ... and then lives out the rest of his/her life in comfort and profit (having sold the rights to your autobiography). The loop only occurs once. The only way it could occur an infinite number of times is for future-you to *always* be the one who uses the machine the first time. Curiously, neither example used in the source I quote above represents an infinite loop, even though the article believes they do. In Heinlein’s short story “All You Zombies” (1959), the protagonist travels back in time to impregnate his/her former self, becoming his/her own parent. OK, the person who traveled back in time didn't disappear. The linearity of time for the traveler is unique with a single loop. It can only be thought of as happening over-and-over if you ignore the future of that aspect of the protagonist (who most likely lived a long and happy life...) The example of Somewhere in Time (1980) involves a pocket watch. But, once again, the loop only can occur once unless you assume that when Christopher Reeves traveled back in time he somehow merged with his future self. **It's easier to answer the question by asserting a single loop — but then you wouldn't have a question.** Since the loop can only occur once in your scenario, there's no issue with the iron components becoming rusted and failing. **What would it take to get infinite loops in my scenario?** Star Trek the Next Generation investigated two possible ways. One is like in Star Trek the Next Generation's *[Cause and Effect](https://en.wikipedia.org/wiki/Cause_and_Effect_(Star_Trek:_The_Next_Generation))*. The ship itself is thrown back in time to a starting point. When tracking the linear history of the ship, there is only one ship repeating the same loop in time over and over and over. The show creatively lets the crew in on the secret by providing means of "communicating" outside the loop. There are never, for example, two Picards. There's only ever one. In this case, nothing can age, and so your iron components would never fail. Said another way, time simply "resets" to the beginning of the loop. The second is STNG's episode *[Time Squared](https://en.wikipedia.org/wiki/Time_Squared_(Star_Trek:_The_Next_Generation))*. In this, a future Picard is thrown back into the past. But this episode cheats the question by never portraying an infinite loop. This is a good example because it shows what to do with the duplicates (Picard and the shuttle craft): they're destroyed in the explosion. So, although the episode does not show an infinite loop, one could be created if Picard took the same actions over and over. But in your case, you-before-first-use always uses the machine. There's no way to create an infinite loop because you need future-you to always make the choice. **Conclusion** Which returns us to the above stated conclusion: your machine will never take more than one iteration and therefore the component will never wear out. If you figure out how to make iterations, it will either always result in a new machine or in the machine never aging. [Answer] *"I use this machine to travel to the future, where I realize I am the person who placed the machine in my room. I then travel to the past to drop off the time machine and let my past self use it."* I am going to assume you mean that FutureYou created the time machine, then went back in time to give it to CurrentYou (PastYou from FutureYou's perspective). That is because the other reading, where you go to the future and then to the past to drop off the machine, doesn't make much sense. The good news is that we can still form a stable time loop given what you have said in the premise. * To start with, you wake up with a time machine in your room * Next, you travel to the future and learn that you created the time machine. This knowledge is the key to the stable loop * You go on merry adventures throughout time, until eventually a critical part of your time machine rusts through and the machine stops working At this point your question is how can you have a time machine if you aren't able to go to the future with it? But we already know that you invented the machine in the future, and it is obviously true because how else would it have appeared in your bedroom? So the only logical solution is that.... **You invent a time machine.** It might take years, or even decades. You might have to wait for new technology to be developed or existing ones to be refined. You will probably need to completely redesign and rebuild the entire machine from scratch (otherwise it would have been old and beat up when you first found it in your room). But, you know that it is possible because you have already done it. After spending however many years on your time adventures you should be familiar enough with the machine to at least have a rough idea of the design of it, and what kind of technology it uses. Even if it is as high a level as "Important Part A was built by Technodyne Industries" and then waiting until that company is founded to see what they build. You can work out the details as you go. The only thing this really requires is for the machine to break down sometime before you create it in the future, and within your life span. If you break down in the 1500s you are going to have a bad time, but if you break down 45 years before you create the time machine you will be golden. There is a little bit of a bootstrap paradox as far as the design and functionality of the machine, but less than you may think. CurrentYou, who is using the time machine, can have only a very high level idea of how it works or what the design of it is. Obviously you will know what it looks like, but you won't know *why*. After the breakdown when you realize you need to rebuild the machine, you can learn more about the theory and reverse engineer your own design. There would need to be some future information which would be right on the line of paradoxical (in my opinion), such as which parts to use and what things look like. But there is also an argument that that information is emergent from the machine itself. If a part is made by a specific company, and then that company comes out with that part in the future, that isn't inherently paradoxical. Knowing that you need their part for the time machine is a little questionable, but you can always say that what you learned while studying the theory drove you to use that part instead of just the knowledge that you used it. The main hangup I think people have with these kinds of stable time loops is forgetting that you still have a personal, subjective timeline you have to follow. Just because you know what you will do in the future doesn't mean you know how you got to that point. If you ignore all of the time travel parts the story is that you find a machine and eventually manage to reverse engineer it. Nothing about that seems unreasonable. [Answer] **The time machine doesn't break down - its condition oscillates.** If there are multiple timelines, then you have no "obligation" to return the time machine. If you do it regardless (perhaps out of belief that you have to do it), then Penguino's answer covers what happens. If there is only one timeline, then when you return the time machine to the past and when "past you" finds it, it will be in the exactly the same condition like when you found it. This is the only logical possibility since these two events are actually the same event. Without time loops, entropy grows and unmaintained things get into worse condition over time, e.g. iron rusts. However, if there is a time loop, entropy can't grow the whole time, because it has to return to its previous value. But that's okay, because there is a non-zero probability that entropy will decrease, although said probability is usually absurdly small. But in a time loop, a decrease (or constancy) of entropy becomes mandatory. The amount of rust on the time machine will also be periodic. If the time machine will rust at some periods of time, then it will also "un-rust" at some other periods of time. The same goes for the condition of any of its components. [Answer] If you're looking for a way to do this, then Ship of Theseus is the way to go. That is, the Time Machine is made up of parts and the parts are gradually replaced alongside this time-travel cycle. Each part is replaceable, but despite that, the ship cannot be completely built from scratch for reason which aren't understood. Of course, this doesn't really help because any time loop (which puts physical objects in the past) generates entropy and these time loops are supposedly infinite, which means an infinite increase in entropy. You're asking 'Is this possible if I don't replace it?' and the answer is 'No', but it's not 'No' because the machine rusts, it's 'No' because it's a self-fulfilling paradox. Time is linear, not circular, the time machine can't be there in the first place. Something cannot come from nothing. ]
[Question] [ You are a traveling across what used to be Colorado and Utah: it may be cold, it may be hot. This is okay, you have caches of clothing and weather gear you can easily pick up. Electricity is sporadic outside of wealthy areas of cities, and water more so due to the scarcity of correct piping. Most people over the age of 30 are dead, less so in the cities. You are not terribly wealthy, and cannot afford many specialised or high tech tools. Manufactured goods are vastly more expensive, so most of your stuff is natural based and durable. What would you carry with you on a daily basis? [Answer] The standard **Post Pockyclypse Traveller's Kit**. Kindly note that this is a list of *essentials*. There are hundreds and thousands of items a traveler could carry and would undoubtedly find useful. Most of those things can easily be stowed away in a cache or supply dump. This kit is simply stuff a traveler should carry at all times. * Knife #1. Not a dainty little folding pocket knife. A proper knife. Gets the job done proper like. Saves on ammo; can save our traveler's life in a sticky situation. Even though this will scare the bejeezus out of anyone facing the wrong end of the thing, it is not for show. It's for doing a dirty job. Yes, those are 4mm thick steel serrations along the back. No, these were *not* made for sawing wood! Ouch. [![enter image description here](https://i.stack.imgur.com/LORRy.jpg)](https://i.stack.imgur.com/LORRy.jpg) * Knife #2. Workhorse, full tang, with sharping stone. [![enter image description here](https://i.stack.imgur.com/l0bva.jpg)](https://i.stack.imgur.com/l0bva.jpg) * Shotgun. Pistols are for pretenders. You need something that can do real damage almost without aiming. Good for hunting & defense. Plentiful ammo to boot. [![enter image description here](https://i.stack.imgur.com/FdWhN.jpg)](https://i.stack.imgur.com/FdWhN.jpg) [![enter image description here](https://i.stack.imgur.com/oqJVJ.jpg)](https://i.stack.imgur.com/oqJVJ.jpg) * Water bottles or canteens. Very handy, especially where you can find good, clean water. [![enter image description here](https://i.stack.imgur.com/AsDiG.jpg)](https://i.stack.imgur.com/AsDiG.jpg) * Water filter. This is the post Pockyclypse: our traveller won't know what kinds of yuck have been spilled into the waters where she's travelling. Industrial waste, chemical waste, animal waste, corpses & carrion abound. Don't want to drink that! [![enter image description here](https://i.stack.imgur.com/lDTd3.jpg)](https://i.stack.imgur.com/lDTd3.jpg) * Some rope. Useful for so many things! [![enter image description here](https://i.stack.imgur.com/OH0OC.jpg)](https://i.stack.imgur.com/OH0OC.jpg) * A good book. Unless you're special forces or a prepper, you probably don't know a whole lot of specifics about post pockyclyptic survival. Read deep. Learn fast. [![enter image description here](https://i.stack.imgur.com/hpl8G.jpg)](https://i.stack.imgur.com/hpl8G.jpg) Other than the above, your standard Boy Scout (back when the Boy Scouts were actually about Scouting and not social engineering) kit will suffice, including things such as: maps, compass, water bottle, poncho, toothbrush, emergency surgical kit / first aid kit, couple interesting trade items, carving or pocket knife, fire kit, survival blanket, pencils, moleskine journals, small camp hatchet. Note: the "Boy Scout Kit" is *not* intended to be an exhaustive list. That's what the BSA Handbook and Field Guide are for! With "most people over the age of 30" being dead, I don't think you can count on any electricity, water, gas or goods of any kind getting anywhere. It's the people who are over 30 (and under 70) who actually know how all that stuff works, know how to fix it and do the actual work. Most of those who are still alive will be the ones who've picked the military surplus shops, gun stores, pharmacies, hospitals and so forth clean while all the 20-somethings are wondering when their e-connections are going to become less sporadic. Your traveller is going to want to move from place to place with some stealth. Away from people who are sick, starving, desperate a/o suffering from Netflix withdrawal. Hitting a supermarket or mom-n-pop shop for some canned goods may be a necessity from time to time. But for the most part, she's going to want to live as much off the land as possible. Hunting & trapping; raiding the houses of the dead; looting the occasional shop. Unless she's got a troop of like-minded individuals with her, she's going to live a very dangerous life and she'll want to stay away from people as much as possible. Find a few good folks in the area she can trust, keep the rest at bay! [Answer] Alas... i would love to give you a list of every item, but doing so would be about a mile long make me sound like a prepper which i'm not. However, if you fill in the various important sections of preparedness then you should be ok... ish Food, Water, Medical, Clothing, Navigation, Fire, Defense, Communication, Trade, lets go through these BRIEFLY!!! many of the things on the list are as much about Moral as they are practical, but moral is very very important in a survival situation Also worth noting that while Shelter is an improtant section, i've not included it as your question stats low funding. most of the below is fairly cheap in the grand scheme of things. but decent shelter is usally expensive unless you amke it yourself, so while its not emtioned below. Rope or and type of Cordage is always worth carrying a decent amount of. **Food and Water** These go almost without saying, you're not going to set out on a long journey without them, but its difficult to carry 1 months worth, on your back, so you'd likely want to bring the long living staples like, Rice, Pasta, then if you find something on route you can add it for flavouring, but these foods offer densely packed calories but need water... Water you would need various forms of purification. Its all fine having a Water Purifying Straw, but if it gets lost, stolen or breaks, you're stuffed, so a couple of these along with some purification tablets and maybe knowing a thing or two about purifying water with VERY small amounts of bleach and then filtering would do you fine. a good line of reasoning is 2 is 1 and 1 is none, if you don't have a backup then you don't have any bascially. **Medical** Now, its unreasonable to carry an ambulance worth of medical supplies, oxygen tanks and a defibrillator with you, but some bandages, gauze, anti septic and some antibiotics are a good start. the important thing to consider is stopping a small injury becoming a big one. research Immediate First Aid Kit or IFAK, for better details. **Clothing** Socks glourious socks! you want to change these every day at least if your hiking a lot. but also some spare dry clothes, nothing will sap your energy and moral then finishing a long hike in the rain and then having to sit and sleep in wet clothes and are unable to get dry. things like Trench Foot can quickly become an issue as well. And of course some waterproof cloths and probably a waterproof poncho for reasons i'll go into later. **Navigation** Maps and compasses, GPS will eventually stop working unless someone is controlling it, o if its 10+ years into the Apocalypses, and yet GPS still works (if you can charge a unit up at least) then someone somewhere is maintaing the orbits of those sateiltes!!! So learn to read a map, and use a compass!!! **Fire** Yay! Fire! the fun stuff! carry a at least small amount of tinder (not to be used for dating or hookups!) with you, and several ways to light it, and at the very very least a fire steel! lighters run out or stop working when wet, Fire steels don't. Then all you need to do is practice and learn how to build a decent fire. and these slides nicely into the next section... **Defense** Drawing attention to yourself isn't that much of an issue today, but in the apocalypse someone *might* want your stuff, so a big smoke trail leading up from your bonfire is probably going to draw attention. whether is good or bad... that's unknown. So to be safe you'll be wanting Knives and Guns and Rocket Launchers and... oh... what do you mean you've been crushed under the weight of it all... There are a million different websites and blogs out there as to the best knife or gun for this situation, i'm not going into it here, all i will say is that being able to reuse ammo is a big benefit, so Bow and Arrow, or Slingshots are genuinely good options if not for a primary defense then as a backup. i don't want the comments section exploding with "why didn't you recommend X, Y or Z gun instead of A, B or C But... This is not just about people, or even animals, this is also about the environment, remember that waterproof poncho I mentioned earlier, open it up and use it as a temp shelter is a very good defense against the wind and rain. a good sleeping bag is good defense against the cold. think along these lines. **Communication** Carrying a radio without anyone to talk to seems pointless doesn't it? well maybe not. think about it, you've come across a small town... can't tell if anyone lives there so you stroll in and get shot... or maybe just robbed and run out of town. OR, you get close, stay hidden, and turn on your PMR radio, the type that uses the same channels that all shop bought PMR radios use, then you just scan through a few times, you might pick up some people talking to each other. its not a given, you could miss it or they don't have radios, but why not take a few minutes to check first. you'd still approach the town with caution but you might get a hint before exposing yourself **Trade** This is an odd one, but cigarettes and small bottles of alcohol are worth their weight, people will trade useful items or food for a pack of smokes if they haven't had any in a while. decent strength alcohol can be used to sterilize wounds but also for trade if needs be. Ok... so this is an INCREDIBLY brief list, and yet its massive hope it helps [Answer] I recommend people check out the great answer by elemtilas, but there is a point in the question that was overlooked there... > > You are not terribly wealthy, and cannot afford many specialised or > high tech tools. **Manufactured goods are vastly more expensive, so most > of your stuff is natural based** and durable. > > > (emphasis mine) I would like to challenge this somewhat, but then to adhere to it after. ## "Too long, didn't read" version The essentials, and how to source them naturally, include... * **cutting tools**, probably made of stone. Break stones apart and use the sharp edges. Look for flint; it can help with fire starting and also can have a very sharp edge. * **containers**. You should try to stay near water as much as possible, but have containers to hold water for when you must leave the river. Make by burning out a hole in wood if you have nothing else. * There are no good natural items I know of that make good shelters which are light and small enough to easily bring with travelers. **Trading for a tent or tarp** will be high priority if possible. * **Rope**, make from plants or plant fibers. * **Either flint & steel or friction fire tools** (base board and either wood drill or wood plough) for starting fires. ## Challenge If this is the same generation of people that lived through the apocalypse and are now facing the post-apocalypse, then there are likely to still be a *lot* of manufactured goods available. Not everything, but enough to get you some items. In my country there are many times more knives than there are humans. There are lots of knives in stores. There are even more knives in the kitchens of almost every house in my culture; many of them wouldn't be the best survival knives, but they are better than nothing. Heck, my father used a knife sharpener on a *butter* knife and made a razor sharp camping knife out of it. There might not be enough axes to go around, ditto for some other tools, but there will be enough that they are not super rare. And everyone who has these things will find them so valuable fast that they would not sell them to the wealthy people unless they were starving and the wealthy provided the food they need. ## And back to your restrictions... The other answers provide reasonable lists, so I'll try to concentrate on their natural counterparts as per your restriction. I try not to go into too much detail or link to tutorials because this question is about a list of essential tools. If you want to go beyond that, Google the terms I use below. Most post-apocalyptic stories I've heard of assume all the tools are scavenged from the remains of society. I like that you've suggested that is possible but not practical and are going for a more primitive, naturalistic feel. It is like jamming the stone age and the space age together and reconciling the two existing in tandem. Almost everyone who gets into outdoor survival and gets even reasonably good at it says this same thing: **if you learn some skills, your brain becomes more valuable than any physical tool.** Using your knowledge, you can make tools or even get by without needing them. **Cutting tools** 1. A knife 2. A secondary cutting tool (ax, saw, hatchet, etc.) if you can manage it. Also these can substitute for many knife functions if you cannot get a knife. 3. If you manage to have iron/steel tools, a sharpener will keep them working better for a long time. A good steel knife would be so useful to survivors in your scenario, especially to the traveling ones, that many people would literally kill for one. You can get by with wood and stone cutting tools. They can get a job done, and you would do well to learn how to make and use them. But they wear out fast. **This is not Minecraft - an iron axe doesn't just have three times the durability and work a little bit faster than a stone axe.** In reality, iron tools are *vastly* superior to their stone and wood counterparts. An iron tool properly cared for can last a lifetime, or even several lifetimes, and it will need to be sharpened a lot less often and will cut through things *way, way* faster than most natural alternatives. If you can manage in your scenario to get an iron/steel tool or two, especially a good knife, then you should go way out of your way to do so. If you cannot get a good metal cutting tool, then you need to resort to sticks and stones to make cutting tools. You better get used to making them, as you'll need to keep making them many times for the rest of your life if you keep needing to cut through things. You can make stone cutting tools by breaking rocks apart to expose sharp edges; that is an overly simplified view of it, but that is the basic idea. You can cut through wood with sharp rocks, and you can even cut through wood with sticks if you work at it long enough. To cut wood with wood, you literally just keep rubbing them together so that the two pieces of wood slowly wear each other away by friction. It takes a huge effort to do this, so what you need cut better be worth it or you might as well forget about it. **Food and water tools** 1. A container(s) to carry water while away from water source 2. A way to boil the water if it could be biologically contaminated There is a reason why many cities are near lakes or rivers. People used to settle near fresh water so they had all there water needs met. Do the same; travel between and along waterways. And use some containers to bring as much water with you as you can whenever you leave water behind. If you don't have a manufactured container, you can make one. * Fold a leave into a cup. * Burn out a deep hole in a piece of wood to make it into a cup. * Scrape clean an animal hide, clean it, and fold it up into a cup. * Use anything you have to hold water even if that is not what it's meant for. Tarp, inside-out rain poncho, plastic bag, anything. * Learn to make clay containers. If you think the water could be biologically contaminated (germs, viruses, or other bio), then boil it if you have something to boil water in. If you have a container that you do not want to put into a fire, then putting a hot rock from the fire into your container can boil the water. For food, that is such a broad topic that you could ask multiple questions about food-gathering tools. **Shelter** If you can get a tent or at least a tarp, great. But since we are concentrating on natural items... If you are going to be traveling, then you really just need to keep setting up tiny shelters out of whatever you find along the way. You really just need to learn the art of making survival shelters. Anything you could make naturally would be either too big and heavy or take a very long time and a lot of skill to make. **Rope** Rope is so very useful. Unfortunately, it takes a lot of effort to create natural ropes in this setting. You need to figure out how to pull off the long, thin, flexible strands of fibers from plants and work them together to form rope. In a pinch, if you just need a short length, lots of plant parts can be used as short ropes: some plant stems, the thin flexible ends of branches, vines, thin roots, and similar long, thin, tough plant parts. **Fire** Very, very good, dry fire-starting **tinder**, and any 1 of the following... * If you can manage to get a manufactured old item: a ferrocerium rod or a magnifying glass * Flint & steel * Friction fire base board and either wood drill or wood plough * Fires are not needed often, so maybe you could cook infrequently and borrow some hot coals from someone else's fire to start yours Learn to find flint in the wild (it does not occur everywhere) and also learn to identify rocks with iron deposits on the surface and try to strike them together to make sparks. However, even if you have a good piece of flint and even if you strike it with an actual steel striker that was designed for striking flint, even then it is still not easy to get a fire started. Your travelers will need to do lots and lots (and lots and lots and...) of practice and have a mountain of patience. If you have natural flint in your area, this is also great for another reason: flint can be used to make good cutting tools as well. The other way your travelers might start fires is by a friction fire method. These methods are also hard. There are multiple different friction fire starting techniques, and I encourage you to look them up. The common names for these techniques (and each one of them is different) is: fire drill, bow drill, fire plough, fire saw, fire roll. Again, a *lot* of practice and patience is necessary. Whatever method is used, you also need very good tinder. Thoroughly dried out grass, or certain plant seeds, or very thin wood shavings thoroughly dried, etc. - but whatever you use to light up, it needs to be very dry. ## Conclusion That covers most of the essentials, and as you can see you will need to learn how to make these things yourself or have something to trade with others who can make them. So really, the number 1 thing you need is knowledge about how to make the things you need. Or, if you can get your hands on one in your scenario, a book that tells you what to do. All of these naturally crafted things will keep wearing out fast. You will need to keep remaking them frequently. If you are in an area of cold, snowy winters, maybe you will spend your winter making tools for the coming year. If not, maybe you stop all other activity every once in a while to spend a week making tools. [Answer] Many of the other answers are fine, but I'd add what I consider to be the most important single item: **a bicycle**. Yes, it's a "manufactured item" but so is almost every other thing presented here. It increases your speed and range dramatically, which reduces every other risk. [Answer] sun glasses, knife, rifle/ammo, compass, topographic map, canteens, binoculars, fire-kit, fish-hooks/line, poncho, thin rope, field guide of edible plants etc., toilet kit, spare socks, sewing kit, tarp, blanket, cooking kit, wrapping plastic, notebook/pencils [Answer] You say you are *traveling*. In hostile territory you would do well to limit your movement to nighttime to avoid being seen. That is counter-intuitive but most creatures including people are scared of the night so that works to your advantage. That is added insurance but it introduces other risks and considerations. For example night trekking without light through broken terrain and brush would make you more prone to lacerations and joint injuries so you'd need added protection, gloves, clear eye protection, skin wrappings, and essential first aid stuff. You'd probably need to boil the water you're able to forage but that would be limited to daytime so you'd need suitable containers to carry all the water you might need for an entire night's trek. Your hunting opportunities would be limited so you'd need packable food. Probably your biggest challenge. You'd also need suitable camouflage to hide yourself during the daylight hours should you be caught in open terrain. Last but not least, you'd need to make sure your affairs are in order and a will is left with your next of kin because there's a good chance you won't make it. [Answer] There is no one right answer, there are dozens of ways to survive and meet your needs and hundreds of tools to solve them. Different survival doctrines will emphasis different things. But there is a good tool to evaluate your answer. Start with the basics work up from there, lets introduce Maslow's hierarchy of needs, not perfect but a good guideline. [![enter image description here](https://i.stack.imgur.com/dvIR4.jpg)](https://i.stack.imgur.com/dvIR4.jpg) Start with what you need to fulfill the lowest tier on a regular basis, and work your way up fulfilling needs, keep travel weight in mind as you fill things in. It is ok to have things from higher tiers but make sure their weight is representative of the pyramids distribution. 1. Most survival doctrines will list 5 things :food, water, source of fire, shelter, and a knife (which is essential for acquiring and maintaining the others) that's the base of your pyramid. People often forget containers make keeping food and water far easier and is essential for someone who want to travel in the region described, water sources can be separated by many days of travel. shelter includes both clothing and the means to make a safe weatherproof place to sleep. So at minimum a *knife, ax, water containers, something to boil water in, a source for fire*, even an empty lighter is better than making a fire from nothing. If you can get a tent and fur blanket even better. And you will need clothes for cold windy and hot sunny weather, in history people in the region often used bone or steel needles to make clothing from local wildlife. A way to hunt or fish is essential, they will not be getting much food otherwise. 2. Next comes security and medicine. Security can be from either animals or people, ideally this can help fulfill other needs as well so a weapon that can be used for hunting or wood working is best, a bow or gun for preference, given how open much of the ground is in the area. Medical means the ability to take take care of common injuries, this can take the form of simple disinfectants and banadages to having antibiotics, sutures, and painkillers 3. Friendship is up to you, but any survival expert will tell you two people have a much better chance of survival than one. Also humans don't do well in prolonged isolation. 4. this seems pointless but there is no society in human history that did no create decorations. For modern people things like grooming and bathing will fall into this. Again multifunctionality is helpful, a pair of scissors and a mirror serves for grooming but also has many other uses, likewise soap has grooming and medical uses. there is no humans society that does not decorate themselves so you should think of how your character does. 5. this should make up the smallest portion of your weight but few humans will not have something for this, this can be as simple as a knife for woodcarving, tools to make jewelry, a deck of cards, or a musical instrument. You need something for the person to do during down time, specifically on days they get stuck due to weather, if there is more than one person this also serves as social capital. Survivalist will tell you even a simple musical instrument like a harmonica does wonders for maintaining the psychological needs of those in survival situations. And remember a tool that can be used for years beats a more effective tool that will only last months. [Answer] If it's Zombies, don't assume dead or tap with your foot/arm, shoot again in the head. Also always check all the bathroom stalls, you don't wanna be left with your pants down. Source: Zombieland My own thought: Some sort of razor trip wire at around knee height might be really nice, sharp enough to cut deep into their rotten flesh, hopefully, stop them from being able to stand up. If you had a roll of the stuff just put around the doorways, rooms, windows, of the area. I think it would provide a lot of peace of mind. Also modern barbed wire like in the picture below has much more frequent barbs. Ouchie. [![enter image description here](https://i.stack.imgur.com/G9euh.jpg)](https://i.stack.imgur.com/G9euh.jpg) ]
[Question] [ 252 million years ago, the worst event in the history of life on Earth occurred. 70% of all terrestrial species and 96% of all marine species became extinct through, according to geological records, a combination of events--flood basalt eruptions in Siberia, runaway greenhouse effect caused by the melting of methane ice, even the formation of the supercontinent Pangaea itself. In an alternate Earth, a reverse Great Dying occurred, one in which 96% of all terrestrial species and only 70% of all marine species became extinct. What combination of factors would create such specified damage? *Just a reminder, this question does not ask how long life would recover, who would fill in the vacant niches, etc. The question is what would cause an extinction event as described in the paragraph above. It doesn't matter when it happened.* [Answer] **Gamma ray shower from a close-by supernova**. [![supernova](https://i.stack.imgur.com/4pD87.jpg)](https://i.stack.imgur.com/4pD87.jpg) The [explosion of a supernova](http://earthsky.org/astronomy-essentials/supernove-distance) close (few tens of light year) to the Sun would bathe the Solar System in a shower of highly energetic gamma rays, which are lethal for life. Moreover, stripping over the ozone layer, it will allow also radiation from the Sun (UV, X-ray, gamma ray) to easily reach the surface. Being shielded by water, the organisms living immediately after the surface layer would get a better protection from such shower, thus explaining why there is an higher mortality on land than in water. [Answer] **Snowball Earth** [![snowball earth](https://i.stack.imgur.com/Z7FNX.jpg)](https://i.stack.imgur.com/Z7FNX.jpg) <https://252mya.com/products/snowball-earth-wallpaper> The Snowball Earth hypothesis proposes that for a period during the Precambrian, the Earth froze over entirely or almost entirely. <https://en.wikipedia.org/wiki/Snowball_Earth> > > The Snowball Earth hypothesis proposes that Earth surface's became > entirely or nearly entirely frozen at least once, sometime earlier > than 650 Mya (million years ago). Proponents of the hypothesis argue > that it best explains sedimentary deposits generally regarded as of > glacial origin at tropical palaeolatitudes and other enigmatic > features in the geological record... A > number of unanswered questions remain, including whether the Earth was > a full snowball, or a "slushball" with a thin equatorial band of open > (or seasonally open) water. > > > For this answer, the Snowball Earth event occurs instead of the Permian extinction, as stated on the question. There would be a thin band of open water at the equator (as in above image). This open water would act as a refuge for the 30% of aquatic species surviving the event. On the ice covered land only 4% of species survive: land based insect scavengers of dead fish washing up, and specialists eating snow algae. How would the Snowball Earth come to be, you may ask? Just as with the Precambrian one - the earth cools because of volcanic winter or some similar event, new ice increases the earths albedo and reflects away heat, and runaway cooling ensues. <https://en.wikipedia.org/wiki/Snowball_Earth#Mechanisms> > > Many possible triggering mechanisms could account for the beginning of > a snowball Earth, such as the eruption of a supervolcano, a reduction > in the atmospheric concentration of greenhouse gases such as methane > and/or carbon dioxide, changes in solar energy output, or > perturbations of Earth's orbit. Regardless of the trigger, initial > cooling results in an increase in the area of Earth's surface covered > by ice and snow, and the additional ice and snow reflects more Solar > energy back to space, further cooling Earth and further increasing the > area of Earth's surface covered by ice and snow. This positive > feedback loop could eventually produce a frozen equator as cold as > modern Antarctica. > > > But how, you may ask, will the Snowball Earth ever thaw? In my proposed scenario, giant burps of volcanic CO2 and microbially-produced methane from the ocean floor increase the greenhouse effect and the earth melts. > > Global warming associated with large accumulations of carbon dioxide > in the atmosphere over millions of years, emitted primarily by > volcanic activity, is the proposed trigger for melting a snowball > Earth. Due to positive feedback for melting, the eventual melting of > the snow and ice covering most of Earth's surface would require as > little as a millennium. > > > [Answer] ## A much less lucky meteor strike. Here's the thing with the K-T extinction event, which is most famous for having wiped out most the non-avian dinosaurs (and actually wiped out most of the avian ones, too: today's birds are descended from no more than five species that survived the strike). ***It could have been much, much worse for land animals.*** Here's a map I made of where the meteor hit, with images from this website: <https://www.businessinsider.com/maps-of-north-american-continent-2012-7#cretaceous-tertiary-65-million-years-ago-32> [![enter image description here](https://i.stack.imgur.com/d9SlV.png)](https://i.stack.imgur.com/d9SlV.png) It doesn't seem very big, does it? And in relation to the continent, it isn't. It also happened to hit a relatively benign spot, geologically speaking - that shallow area, which would become part of the Yucatan Peninsula, was mostly a centuries-old tropical reef and the porous limestone it had formed. Now just imagine a slightly larger meteor hitting harder continental rock, like the granites of a mountain chain. The K-T event killed off about 70% of marine species because species living at lower depths were the least affected by its worst effects - turning the atmosphere into a huge oven, killing off the food chain by blocking out the sun, etc. With a larger meteor hitting harder rock, that advantage doesn't change. However, that slight change in luck makes it that much harder for land-based species. A larger meteor hitting continental rock is going to throw even more mass into the atmosphere, blocking the sun out for even longer, and continuing to bake the surface for longer as it rains back down. It's very likely, and it's all it takes to wipe out life in the ratios you're looking for. [Answer] You need to cool the atmosphere *without* poisoning the oceans. Oceanic life can survive simply cooling better than terrestrials, water is an excellent insulator. What nearly killed the oceans during the Great Dying was sulfur depleting the oxygen from the water. So to cut light without pumping sulfur into the atmosphere you need smoke, lots and lots of sooty smoke over an extended period of time, hitting a large forest with a meteor would be a start but I'd suggest that you actually want to burn a lot of relatively clean coal with very little oxygen. [Coal seam fires](https://en.wikipedia.org/wiki/Coal_seam_fire) can potentially pump out smoke continuously for centuries, probably longer. If you have a reasonably large meteoric impact that burns large areas of forest that's growing on shallowly buried peat and coal deposits then the fire could take hold in those buried carbon deposits. Partial combustion of the deposits, due to poor oxygenation, will pump sun blocking smoke into the atmosphere for years afterwards cooling the world and killing land-based lifeforms rapidly and the oceans slowly, the effect will be enhanced on a super-continent as smoke and fire blankets the continent while leaving the oceans relatively clear. [Answer] The great oxygenation, undone - **Chloroplast virus**. 2050: The ancient enemy of man, genus *Plasmodium* is driven to extinction. [The apicomplexan vestigial chloroplast proves to be a fine therapeutic target.](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166169/). Even the hypermutable plasmodium cannot out-evolve the synthetic virus targeting its chloroplast. Malaria is eliminated as a human disease. 2055 Crop failures are noted in central Africa, followed by similar failures in central and South America. It is realized that not just the crops, but all plants are dying. The synthetic virus has mutated, and all chloroplasts are now potential hosts. 2085 Green plants are gone and with them all terrestrial vertebrates and most insects. Green algae are not far behind. 2095. With green algae and plants gone, oxygen levels begin to drop. Free swimming organisms die when the oxygen levels of the ocean fall below 15% and many of the rest die at 10%. 2096. The lands of earth are left to the fungi, which spread in riotous profusion, subsisting on the remains of the land. Certain robust insects and mollusks survive by feeding on the fungi. As oxygen levels dwindle, so too the number of these survivors. 2097. Coral reefs explode with vigor. Partly it is the lack of predators. More importantly, [the dinoflagellate chloroplast is genetically so distinct](https://www.sciencedirect.com/science/article/pii/S0168952504000769) from that of the plants (and apicomplexans) that the virus cannot target it. These photosynthetic organisms thrive as do the corals, sponges and gorgonians that host them, their symbionts now providing both food and oxygen to their tissues. Outside the growing reefs, the oceans are now ceded to cyanobacteria, which also colonize the empty land. Within a few decades, oxygen levels begin to rise once again. --- The few terrestrial survivors are the fungi which made it through the lean years and soil / detritus dwellers like earthworms and sowbugs. Ocean life does better thanks to the coral reefs, although survivors are heavily skewed towards sessile organisms with photosynthetic dinoflagellate symbionts and (as on land) acorn worms and similar hypoxia-tolerant dwellers in the subsurface. ]
[Question] [ From: <https://en.wikipedia.org/wiki/Multiverse> > > The multiverse (or meta-universe) is a hypothetical set of various possible universes including the universe which we live in. Together, these universes comprise everything that exists: the entirety of space, time, matter, energy and the physical laws and constants that describe them. The miscellaneous distinct universes within the multiverse are called the “parallel universes,” “other universes” or “alternative universes.” > > > And from: <https://en.wikipedia.org/wiki/Many-worlds_interpretation> > > Many-worlds implies that all possible alternate histories and futures are real, each representing an actual “world” (or “universe”). In layman's terms, the hypothesis states there is a very large, perhaps infinite, number of universes, and everything that could possibly have happened in our past, but did not, has occurred in the past of some other universe or universes. > > > I’m using those definitions/explanations here because they put into words my thoughts better than I could right now. So, let’s say we take the above described concepts as real, with those as a jumping off point I am trying to create a place, some point in space/time, where two of the universes from that infinite bunch (ours and another) are blending into one another without either being destroyed. Imagine these two realities are caught in the same space/time but instead of annihilating one another they are “blending”, mixing, and creating something new, something that is a little of both. My sci-fi explanation of this is that an alien race with the tech to warp space time was conducting an experiment that they hoped would take them to one of those other realities. Instead it mistakenly brought another reality closer to ours, but not fully, so there’s “blending” going on at this point of space/time. I want my space explorer characters to achieve some kind of understanding of what might *cause* this to be possible. Any thoughts? I realize that some hand waving will come into play, but I want to give readers something that at least sounds plausible. Maybe something that scientists are really theorizing(?). EDIT: Just adding some food for thought: A) Dark Matter cannot be observed except we know its there because of its gravitational effects. So isn't that kind've like another dimension existing right here within ours without any annihilation? B) Neutrinos can pass through matter because they have little mass and no charge. Couldn't something similar apply here? [Answer] Fundamentally, you're not going to get into the subatomic physics of the blend. In fact, it's almost certain that if you tried, you'd get the physics wrong (since there is no physical version of this). Thus, what you need is something that *feels* right and is useful to the story. Bonus points for physics based and slightly unintuitive. My recommendation would actually be to look at supercritical fluids. Add heat to a liquid, you can boil it into a gas. Refrigerate a gas, and you can turn it into a liquid. Increase the pressure, and this effect happens at a higher temperature. We can draw what is known as a phase transition curve showing this effect at different places. [![Phase diagram](https://i.stack.imgur.com/9u2zs.png)](https://i.stack.imgur.com/9u2zs.png) Here we can see a phase diagram. You can see that, at reasonable temperatures and pressures, if you have a liquid and increase it's temperature, you can make it a gas. But what about that funny point marked "critical point?" This is where something funny happens. If you heat a liquid past this point, its molecules have so much energy that the structure assumptions we get to make about how bonds form in liquids just don't work. It's not a liquid. However, it's still too dense and there's too much intermolecular interactions to be treated as a gas. At this point, we have a "supercritical fluid." It's a phase of matter all its own. It's not a liquid. It's not a gas. It's something else with some hybrid behaviors from both. Weird behaviors. Ever wonder how they make decaffeinated coffee? They raise the pressure on some CO2 until it goes supercritical, then pass it through the beans. I mean that: *through*. Supercritical CO2 can pass right through the solid coffee beans. It then acts as a solvent to pick up all the caffeine molecules, and passes right out. You can add whatever quantum verbage you like. You can talk about resonance or interference, but if you really get into it, those concepts are hard for a reader to grasp. They're hard enough for a writer to grasp. However, the nature of supercritical fluids, and how they aren't *just* a summation of liquids and gases, is much easier to grasp. It also creates room for a natural drama. As the temperature and pressure fall towards the critical point, the material is going to act more liquid like or more gas like, depending on how they fall. There's a natural winner-takes-all feel to this process that is easy to take and weave into some plot. While this supercritical quantum flux foam might be supporting both realities now, as it cools, it may begin to take on aspects of one reality or the other. That should be terrifying. [Answer] It seems like you're trying to bend the rules on [causality](https://en.wikipedia.org/wiki/Causality_(physics)), or rather you're trying to blend two points that have no common cause into one. Paraphrasing the definition of causality: an effect cannot occur from a cause not in it's past [light cone](https://en.wikipedia.org/wiki/Light_cone), and cannot cause an effect outside it's future light cone. A light cone is essentially the cone of all possible paths that a photon can take through spacetime. In other words, a light cone represents all possible effects that a cause can have, because the effect cannot reach outside of the cone without traveling faster than the photon/faster than light. I don't have enough physics doctorates to go into the math on why what you want is physically possible or impossible. However, I can roughly describe what would need to be possible for what you want to happen: Imagine you are looking at the light cone of an event coming toward you, i.e. you are looking at the base of the cone which looks like a circle. If the event that made that cone could have produced a different effect, i.e. created a different universe, and was also coming at you, then the two cones would look like a [Venn diagram](https://en.wikipedia.org/wiki/Venn_diagram). The common parts of each universe are in the overlapping center of the two cones and are already 'blended' because they came from the same event. The edges, however, are the differences between the two universes and are what you want to blend together in your weird non-causality world. Therefore, **the sci-fi alien hand-waving-the-non-fun physics explanation for blending two universes is simply blending two non-overlapping light cones into one, thus bending the rules of causality.** Essentially, things just need to *happen* without any event causing them to happen. [Answer] *Note:* Quantum *anything* is odd. Don't take my word as law. Look to the comments and to other answers for reasons why this is impossible. I'm simply here to describe a possible course of action. Let's look at the base idea: Two universes diverge at a single point, and the differences ripple out at the speed of light. ![Slice through a Minkowski diagram of my life](https://what-if.xkcd.com/imgs/a/140/problems.png "Slice through a Minkowski diagram of my life") Suddenly, these two universes are literally overlapping. The base volumes of space randomly flips between the two universes as they merge. For most of the observable universe, nothing would be wrong. Since each universe has the same contents, randomly flipping between them shows no difference. The issue comes in when you're less than $c\*\Delta t$ from the event. In this case, you're inside the light cone, and are affected by the merger. Suddenly, the basic units of matter are flitting in and out of existence. Affected by the diverging causalities, atoms that would have been in one place are in another place, leaving gross problems occurring all across the light cone. These interactions effect more change, leading to a slurry of the two universes that is completely uninhabitable by standard physics. You can't outrun the growing bubble of problems. You don't even know it exists. It is literally the fastest growing bubble of death that could possibly exist. By the time you know it exists, it is upon you. The only recourse is FTL, with its own host of problems. Inside the problems bubble, though, things begin to settle out. It's still a slurry of probabilities, but with the two universes interacting at the level of the basic forces acting on matter, they eventually resonate into alignment, becoming effectively one universe again. Unfortunately, there's still a giant front of death expanding across the universe as the two universes reconcile their differences. Now, this isn't even remotely possible. We have no real systems that could 'un-collapse' a quantum waveform, and the base tenets of many worlds exclude this scenario. [Answer] I don't really understand causality. Jakob Lovern seems to be suggesting that when it blends, the same matter can't be in two different places possibly causing massive damage(who really knows and I'm not sure I understood his point). Giter seems to suggest that you just need to focuse on differences because the things that are the same can already be considered blended, how you blend the differences, having both, part-n-part or only one is up to you. I wanted suggest a different route where the nothing is blended, everything becomes duplicated (kinda) instead . You can consider this idea is that many universe share the same space and are only seperated by a fragile glass that prevents them from affecting each other. Once the aliens make a hole in the glass, the matter of the two universes start to affect each other through gravity, this puts even more stress on it until the cracks go from the epicenter to all throughout the universe(This could happen fast or slow and the barrier near the center is probably long gone by the time the cracks reaches the edge). This would probably destroy the structures in the majority of the universe but there is possible that some galaxies might not be too affected as they werent aligned with anything on the otherside. Ofcourse as the only survivors would probably be in the places nothing interesting was happening, it might not be the best story setting but I still had to say it. Another reason I like this idea is that it could show that the big bang could have expanded into to each dimension at the same time and not that it existed in both dimension, which could show that the big crunch is only likely to happen if more dimmensional barriers are broken, as one dimension will have more mass. [Answer] The multiple universes are just different simulations. A programming error, or CPU overload could break down the separation memory leak or space leak: <https://en.wikipedia.org/wiki/Memory_leak> Also, it allows use of exploits that would allow travel to other universes [Answer] I'd suggest dropping multiverse and accomplishing your task through another mechanism entirely. The interactions between particles are governed by the fundamental forces. (Gravity, EM, Weak, and Strong are to our knowledge what's going on at room temperature.) The influence of the fundamental forces is goverened by coupling constants, like the electron's charge. Without the coupling, the forces don't do anything. So, let's say that all along there has been an entire other universe (overlayed on the same space), with an extra set of forces, and an orthogonal set of charges. Their positive and negative would look neutral to our electromagnetic force, and our positive and negative would look neutral to theirs (extend this to the other forces). We'd be like a ghost to them, and they a ghost to us. Something happens that causes the charges to start changing: suddenly, a block of matter from our universe acquires their kind of charge and looses our kind of charge. Somewhere else, it happens in the other direction. A naive observer would think that the chunks were "teleporting," between realities, but they wouldn't have to move at all. Extra work: what happens if the matter ends up with *both* universe's associated charges? Neither? (If neither, it would all fly apart as the bits and pieces would have thermal and degenerate energy, but wouldn't exert confining forces on each other any longer!) [Answer] ## Large wormhole? People use think of [wormholes](https://en.wikipedia.org/wiki/Wormhole) as giant doors, but in general relativity, there more like a place that two points in the universe, or even two different separate universes, are "glued" together. In fact, if a wormhole was large enough, you may not even notice is it there (besides all the exotic matter in it, but there will probably be exotic matter outside it as well). So, if you are near the wormhole, some directions naturally "lead" into the other universe. This might lead to blending if someone has blenders in the wormhole. If you just want to connect to different points in time, any [Closed timelike curve](https://en.wikipedia.org/wiki/Closed_timelike_curve) (of which wormholes are just one variety), would work. They allow the future to be near the past in a wide variety of ways. [Answer] Imagine multiple more-or-less parallel tunnels in a cave system, or through a mountain.  The tunnels aren’t perfectly straight; they meander enough that sometimes two of them come very close together. * If the wall between them gets down to 1 cm in thickness, it may be possible for the occupants of one tunnel to hear sounds from the other. * If quartz and/or other transparent / translucent rock are present, it may be possible for the occupants of one tunnel to see events in the other. * There could be a hole in wall, allowing matter to move between the tunnels. Do this in a handwavium mine, and you’ve got parallel universes. You should look at the [“Apprentice Adept” series](https://www.goodreads.com/series/40494-apprentice-adept) by Piers Anthony.  It takes place in two parallel universes that have limited points of contact / overlap.  He doesn’t explain how this came to be; * it’s treated as a feature of the multiverse that has always existed. * magic works in one of the universes, so there’s not a lot of technical exposition. But he does explore the concept of inter-universe contact. [Answer] Imagine the universe as Einstein's trampoline, with each universe being its own trampoline. Go to a point on your trampoline where it's just like the trampoline of your target destination - probably (but not always) a really long way from a gravity well, where both trampolines are almost flat. If there were two identical solar systems, you might be able to do it in a gravity well. Blast off a *shitload* of energy. Like, infinite heat levels of energy, where the rules of physics start to get really weird. You can punch a hole through your trampoline *and* their trampoline. You can even cauterizing the edges to keep it open. Now you can travel between universes. [Answer] Mirror matter: <https://en.wikipedia.org/wiki/Mirror_matter> This is NOT anti-matter. But another set of particles that effectively only interact gravitationally with our visible universe. One of the serious proposals for the missing mass problem. See also John Cramer's novel "Twistor" <https://www.amazon.ca/Twister-John-Cramer/dp/0450551172> It's only a ho-hum novel, and will remind you of the pulps of the 40's. But Cramer is a working physicist. Finally getting back to the parallel universe, take a gander at 'renormalization' in particular. Start here: <https://4gravitons.wordpress.com/2013/01/11/whats-so-hard-about-quantum-field-theory-anyway/> The idea is that for any given quantum interaction there are a multitude of "it could have happened this way" and the actual outcome is the superposition of all the other possibilities. So your parallel universes are constantly in the process of spliting and merging. The length of time it takes to merge is a matter of both balance and scale. This has some explaining power: The car keys that are on the kitchen counter but weren't there 10 minutes ago are the merge of two universes. Some of the times that your memory of an event is totally different from someone else's memory is the result of merging. It also gives you a neat response to one problem of multi-universes: If everything is possible, what is the point of making a good choice? Yes, you need more hand-wavium to make it work. ]
[Question] [ Let's say that a race of aquatic merfolk have managed to achieve sapience, they are basic hunter gatherers, living in relatively shallow waters of up to 100 meters deep. As I have begun designing their culture I have ran into a road block, how does such a species develop agriculture? After all, very few plants exist so deep and those that do grow do not produce fruit or vegetables. I had originally planned on them domesticating schools of tuna or salmon or even prawns or krill, but the amount of such an animal they would need to keep in order to provide for even just a town would be way too massive. How does a culture living underwater develop agriculture? If they cannot develop agriculture, what else can exist for them in lue of it? Let's assume that these merfolk are omnivorous mammals. [Answer] **Agriculture** Do these guys eat some sort of seaweed? Have them plant seaweed in designated locations, just like we do in fields. Due to certain conditions (maybe a warmer current in the area?) I'm sure that some areas of the sea floor would work better than others, thus giving rise to, essentially, agriculture. Furthermore, merfolk could build clam gardens gardens close to the shore, and reap the fruits of their labor (check it out, the north american natives did it in British Columbia). **Taming Fish** Fish are not smart enough to tame - especially not entire schools of it. However, why not corral the fish, and eat them at your leisure? Build large nets, and set them up as domed structures, then simply use your superior intellect, and agility to shepherd schools of fish into them. Better yet, convert the hulls of sunken ships into solid holding pens for all sorts of "snacks". **Food Storage** Your biggest long term problem is actually food storage. Our ancestors would smoke, or salt meat, which will then keep for very long periods of time. Your merfolk will only be able to corral so many fish, and grow *so much* seaweed. Eventually, they will run out of food, as fish migrate with the seasons. At that point they themselves may need to move to a different location, which is essentially reverting back to a hunter/gatherer stage. What you need to establish is either a way for them to keep food from spoiling, or a constant flow of food in their area. Depending on migrations, as opposed to stored food will, however, render them incredibly vulnerable to any sort of environmental upsets (if a migration doesn't take place, or a species is decimated, your merfolk will themselves starve) [Answer] **Farming is not just about planting seeds or herding animals.** A large portion of farming is actually in taking care of the land (tilling, fertilizing, etc.) and also providing care to the things which are growing (pruning, weeding, dealing with insects and other pests, etc.) Even if the merfolk aren't deliberately planting seaweeds, or actively corralling fish, they can certainly change their environment to maximize the production of useful food. For example, perhaps a prized food source likes piles of rocks with lots of nooks and crannies. Or is frequently found in conjunction with certain corals or anemones. The merfolk could then deliberately create the appropriate rock piles, or could attempt to provide the right environment for the corals or anemones. In this way, they "cultivate their fields" in order to maximize their fish production. Additionally, there are likely predators and parasites which will harm their desired foodsources. The merfolk could actively hunt the predatory fish, keeping them away from their "fields" of desirable fish. Or they could "weed" their fish beds by digging out harmful pests (e.g. the [Bobbitt worm](https://en.wikipedia.org/wiki/Eunice_aphroditois)). Or they could "apply pesticides" by capturing cleaner shrimp from other areas of the ocean, and relocating them to their "fields". Additionally, there are many things in the ocean which are sessile, or at the very least not very mobile. These are mostly invertebrates, and include corals, sponges, clams/oysters, and some crabs/shrimp. These either stay put on the surface, or will not move very far from their home burrow. All of these could be "farmed" by providing a good environment for them. One complication here is that a fair number of sessile species in the ocean undergo a planktonic stage, where they young animals are free-floating in the water column. This complicates farming, as the young animals don't stay close to their parents. However, you can still farm these animals, either by providing the ideal environment for the planktonic larvae to settle, or by having the merfolk search for desired young animals "in the wild", and then bring them back to the village fields where they're protected and given a better chance of survival and growth. [Answer] Here is a list of sea things edible to humans and human efforts at cultivating them: <https://en.wikipedia.org/wiki/List_of_types_of_seafood> <https://en.wikipedia.org/wiki/Seafood> <https://en.wikipedia.org/wiki/Seaweed_farming> <https://en.wikipedia.org/wiki/Aquaculture_of_giant_kelp> If mermaids can digest other foods in addition to these, they will have a larger range of diet. In addition to Andrei's fine points, we do have some basis for agriculture. The sea cucumbers, the kelp, the seaweed, and even edible microphytes. Some of these are a good source of nutrients, thankfully, which in addition to fish and other things should make for a stable diet. For cultivating fish, crabs, etc., you will need a few things: 1) Environment, they can't freeze or the like. This can vary a bit with season, depending on the depth on the ocean. 2) Food source, you can't have your food starve or you'll starve. The farm's limit is its food's limit. If you can cultivate your farm's food somehow (I am no expert on how), you will cultivate your food. Note that with migratory fish you rely on seasonally, they have the advantage that they get their food source elsewhere. 3) Control, you need to be able to control this farm to an extent, or else it just becomes hunting. If you could enclose your food into a small environment they're easy to catch from, that works--but you have to keep in mind the possibility of them running out of food in this small environment, or spreading disease if they're too enclosed. Clam and kelp gardens are simple, along with other vegetables. Fish are trickier, most will need quite a bit of space, and good places to lay their eggs, and their full diet. There are various ways you can control this. If you know when the salmon come in and how they get to their grounds, you could set up traps that allow you to capture a percentage of the salmon, and let the rest through to breed. If your mermaids can stand fresh water for a while, they could also wait till most of the salmon have spawned, then swim in to harvest the adults before they die naturally (and some caviar, if they're wasteful). I'm not sure what hunting of post-parent salmon is like. You might even be able to breed the fish to the point where they'll start to have instincts that makes farming them easier. Other than that, dolphins and whales would be good tamable animals for work, defence, and possibly food. Seals might be, as well. Sadly, I don't know enough about the needs of fish, to know how to set up these farms, how much space they need, what places for eggs, how much food and how well you can cultivate it. Real examples of fish farming will probably give a good idea of this. [Answer] I not a marine expert but im sure they could grow sea weed or some other sea plant the way we started to grow wheat. If not then perhaps they could become herdsmen instead of farmers. They could grow algae and feed it to fish who they would then eat like we would feed grass to cattle. ]
[Question] [ I'm putting together a scenario, where a "Sun" and some debris are flung so distant that 14 billion years after the big bang, it has an "Earth" (and maybe some other minor rocky/icy objects), but no stars are observable to the naked eye. I know we can't see anything other than our own galaxy with the naked eye, but this would be a galaxy-less "rogue" star. **Is this possible - if so, how?** [Answer] ## Galactic Collisions This sort of stuff will happen a lot during [galactic collisions](https://en.wikipedia.org/wiki/Interacting_galaxy#Galaxy_collision). In the gravitational chaos, groups of stars, star-forming gas clouds, or even individual star systems can easily get ejected. Like in [@HDE226868's answer](https://worldbuilding.stackexchange.com/a/34554/3510), except in my scenario you could also expect the ejection of regular, sun-like stars with high enough metallicity to have rocky planets. [![enter image description here](https://i.stack.imgur.com/EnUhx.png)](https://i.stack.imgur.com/EnUhx.png) The long tails you see in the picture are streams of stars getting lost into the great intergalactic vacuum. If thrown out in the right direction, such a star could eventually get far away enough from other galaxies that no stars would be visible to a human-level eye. If this sounds far fetched, think about the fact that **our [Galaxy and Andromeda are going to collide](https://worldbuilding.stackexchange.com/questions/29942/what-would-be-the-effects-of-galaxies-colliding) in a billion years or so**. [Answer] **It's totally possible (sort of)!** Such stars are called - not surprisingly - [intergalactic stars](https://en.wikipedia.org/wiki/Intergalactic_star). These stars are often referred to as [hypervelocity stars](https://en.wikipedia.org/wiki/Stellar_kinematics#Hypervelocity_stars), because in order to reach galactic escape velocity, they have to be traveling really quickly. The current theory is that a pair of binary stars encounters the supermassive black hole at the center of their galaxy. One star goes towards the central black hole, while the other is flung out of the galaxy at an enormous speed. [![](https://upload.wikimedia.org/wikipedia/commons/e/ee/HE_0437-5439_mechanism.jpg)](https://upload.wikimedia.org/wikipedia/commons/e/ee/HE_0437-5439_mechanism.jpg) Image in the public domain. This graphic details a three-star system encountering the supermassive black hole, but the same setup works just as well with only two stars. Only one will be ejected, not two. That said, galaxies would still most likely be visible from a planet orbiting the star. [Many galaxies can be seen with the naked eye](https://astronomy.stackexchange.com/questions/1018/how-many-stars-and-galaxies-can-be-seen-by-the-naked-eye), and this would still be the case for planets outside the galaxy. So it's likely that inhabitants of this planet (if there are any) would still see plenty of galaxies. They'd just be very, very faint, for the most part. Additionally, we have to deal with the issue of the orbital stability of the material orbiting the planet. Any encounter strong enough to fling the star out of the galaxy might dislodge the debris from its orbit around the star, sending it somewhere completely different. I would think it unlikely for the star to pick up a substantial amount of planet-forming material on its way out, and certainly not outside the galaxy in the intergalactic medium, but its possible. [Answer] A bit late, but anyway... Building on the comments to the question, since you talk about a rogue star (with a "earth") and objects visible to the naked eye, you have a "simple" option: just put your rogue star about 30/40 million light years away from the nearest object. Or, for example, you can put it in the so called "supervoid", an existing empty area in space (1.8 billion light years across): this way your earth has about a billion light years in every direction without stars/galaxies, which should be enough to have a dark sky without observable objects, at least to the naked eye. As you can read in [this question on Astronomy at SE](https://astronomy.stackexchange.com/questions/2085/whats-the-furthest-object-observable-by-the-naked-eye-from-earth), it seems that the furthest object claimed to be visible with the naked eye is M83, at about 15 million light years. [Answer] It seems reasonable that any solar system that's wandering around without a galaxy would be in an area that is relatively dark, so the relatively-near galaxies would appear as stars do to us. It's likely that we can't see galaxies unaided because of all the "light pollution" provided by the Milky Way. ]
[Question] [ Some scientists discover that plants have humanlike feelings. Now it becomes unethical and immoral to have mass production farms for plants as it is yet for animals. As there are animal-right activist, plant-right activists become a real thing. The Information is every where and the theory proved to be right. > > **So, how would society react and how would the understanding that we misstreated plants such a long time be processed if at all?** > > > *Edits:* * The Scientist presents some patterns to understand the feelings of the plants like there are for dogs. (If tail in the air he's happy something similar.) * All the plants have feelings but the plants which are more complex or larger organisms have more specific feelings. [Answer] Well, some would feel that only eating the 'fruit' of the plant would be conscionable such as apples, or corn. Since that is what the plant is producing it for, as a way to propagate itself. But for most people, it will likely make them less empathetic, since 'everything' we want to eat has 'feelings' so they will feel the need to distance themselves even more, like Nazi prison guards from their charges. They are something 'else' and 'beneath' me. But ultimately we'll get some more nut cases fighting for plant rights that are nuttier than some of the people fighting for animal rights. But people need to eat something and since plants don't have eyes to draw pity from us, will be mostly ignored. Don't they just melt your heart? I prefer they melt butter... [![enter image description here](https://i.stack.imgur.com/c55cF.jpg)](https://i.stack.imgur.com/c55cF.jpg) People saving trees might have a little more umph behind their arguments but it will only slow some things down. You could also point out that 'spiking' trees to 'save' them is a bit of a 'lesser of two evils' choice... [Answer] I imagine that the world would simply go in eating corn as it always has. Unless governments want to deal with starving, desperate, and angry masses, that is. History has shown us many times (do I really [need](https://en.wikipedia.org/wiki/Donner_Party) to [cite](https://en.wikipedia.org/wiki/1972_Andes_flight_disaster)? I mean, [really](https://en.wikipedia.org/wiki/List_of_food_riots)?) that even the most reasonable of people will resort to extremes given a lack of food. Since plants feed much of the world, I theorize that no big changes would happen. Vegetarians and vegans would be viewed worse than they currently are, especially since there would be a considerable group of (even more considerably) outspoken plants rights activists that are ignored as much or even more so than animal rights activists are currently. You specified in the comments that you wanted a more complicated response than "us versus them," but in reality it wouldn't get more complex than that. As @bowlturner stated in his answer, forest conservation organization would have more leverage, but in the end everyone needs a place to live, and trees are coincidentally the perfect building material. [Answer] By and large, facts are much less important to the human species than their conceits, delusions, preconceived notions and comfortable myths. As plants lower in evolution have less precise feelings, most humans will continue to farm and consume plants deemed to be less evolved, just as they consume animals deemed to be less evolved like chickens, cows, lambs etc. but mostly refrain from eating more evolved animals like apes and monkeys, except in some remote areas. A similar situation will eventually exist with plants too. There will still be rampant illegal harvesting of evolved plants for various purposes just as there is rampant poaching of elephants and rhinos. [Answer] The same way we have for animals. Local laws will mandate non-harmful behaviour, and will be followed to a greater or lesser extent depending on local enthusiasm. Plants which make good pets and/or which are visually appealing will get preferential treatment. However you're making the assumption that mass-production is automatically harmful, and this isn't necessarily true. Chickens for instance prefer *not* to be outside on their own - they would rather be in a darkened barn surrounded by lots of other chickens, so you can have rather intensive farming of chickens which is still completely ethical (assuming you approve of the fact and method of slaughter). Grass plants naturally grow surrounded by lots of other grass plants, so it's quite likely that intensive farming conditions would be what would make wheat most happy. [Answer] One thing that hasn't been mentioned is that some people might be driven to try to find other things to eat. For instance, maybe in this 'hopefully' fictional world, mosses or fungus don't have feelings. Or maybe they will only eat some kind of gruel made from plants that had already been cut down before the discovery was made. Or only laboratory organics that have been produced from various chemicals with no natural ingredients like Cool Whip and Cheetos. Just a thought. Also, maybe some vegetarians might swing the other way and start eating meat? [Answer] Many plants have evolved so that they are propagated best by being eaten by higher beings. Humans and animals eat fruits, which sometimes includes the seeds. Later, the seeds are deposited in the waste from the animal, which becomes fertilizer for the seed. The cycle repeats. Certainly a plant that has evolved this way cannot be upset when nature takes its course. Regardless, there are plenty of plants that I hate, such as kale. Nothing is going to change that. I don't care how kale feels about me. Kale and me, we just don't get along. On the other hand, I am immune from poison oak. Most people aren't. Does that mean poison oak likes me and not others? [Answer] Actually, plants DO have feelings. Sorta. The Mythbusters tested this a while back, and actually got a response from both bashing the plant and thinking bad thoughts about it. However, this didn't really mean much of anything for anyone. I see that as a good thing: They can 'sense' and 'output' emotions, but cannot act on those emotions. (Could this mean plants have brains? Dreams?) So, the overall answer is: **society couldn't give a damn 'bout plants, especially seeing as how we raze the rainforests.** Even then, there's going to be some activitsts. [Answer] There's a big difference between feelings like dogs and feelings like humans! And another big difference between feelings like dogs and feelings like sheep. If specific species of plants start showing for example pain when they see other plants suffer, and affection for other plants and their human carers, some people would stop eating those plants. They would become characters in kids' stories. People would start keeping those plants as pets. That would be the real way those plants would stop being eaten - no-one will want to eat potatoes after Sally's potato wags its tail at them. Ultimately, lots of people do eat dogs, so we can't really expect everyone to stop eating these plants. If it's all plants, then we'd be in real trouble. All our livestock eat primarily plants. We'd start investing much more heavily in algae, plankton, yeast etc. (it will become a righteous act to serve Vegemite!), and also fish farming. Some people would pay a small premium for non-sensitive foods. People would probably increase their vegetable consumption once there were enough advertising campaigns about how much corn is factory-farmed to produce one kilo of beef. Where people still farmed plants, there would be efforts to grow them more humanely, with low pollutants, more careful machinery and more spacing between rows so that the plants are not needlessly crushed by machinery, plants only grown in appropriate climates, etc. People would pay more for these humanely grown plants, the same way people pay more for free range eggs. [Answer] The first thing would happen is a counter study that "proves" the first study is a load of rubbish! (Similar to how studies into the environment go IRL) That way, anyone who wants to go on abusing plants can simply believe the counter study and their conscience is clear. ]
[Question] [ Question inspired by movies [You only live twice](http://en.wikipedia.org/wiki/You_Only_Live_Twice_(film)) and [Moonraker](http://en.wikipedia.org/wiki/Moonraker_(film)): I am Evil Overlord at his best: I am super rich person with net worth of 32 billion US dollars. I already own island and I am making money also by selling space technologies to SpaceX and NASA (so I have knowledge about the tech) Suppose, I want to get rid of all humans in Moonraker style: I will build huge space station on the orbit, get people there and then kill everyone else from the orbit. **Can I do it?** * I am willing to spend all my money I have. I am also willing to go into debt, because when I will be True Evil Overlord, current money will be gone forever. So assume I have budget around 50 billion US dollars * I want to go to orbit as silently as possible. Preferably in a way when no one notices * My space station has to hold at least 201 people for at least half a year (Artificial gravity is plus, but not required) * Assume that there are already people working for me in space technology, so at least buying "rocket stuff" will not be considered weird [Answer] Why hiding totally, while you can much easier hide in plain sight? Present the project, present the funding you offer, for a superior successor of ISS, and as a major investor, contribute a lot to the development - experimental habitats to train moon colony crew and test prolonged space travel conditions. Make it an entirely civilian project with stuff like weapons hidden inside construction elements, backdoors in software and so on. On one day your craft delivers the new worldwide atmospheric scanner that would let your ecological efforts better monitor biomass of Earth. You miss the little part about obliterating said biomass selectively. Your part of the crew takes over the station using the weapons on board, you arrive with the rest of the crew by routine flight, and boom... [Answer] At the end of [The Jennifer Morgue](http://www.michaelmjones.com/the-jennifer-morgue-by-charles-stross-golden-gryphon-2006/) is the afterward essay *The Golden Age of Spying* which flows across a few topics, including what a "supervillian" would really be like. (Emphasis mine) > > ... if they really existed, they would instantly be hunted down and arrested by INTERPOL? > > > Careful consideration will lead one to reconsider this hasty judgment. Criminology, the study of crime and its causes, has a fundamental weak spot: it studies that proportion of the criminal population who are stupid or unlucky enough to get caught. The perfect criminal, should or she exist, would be the one who is never apprehended — ***indeed, the one whose crimes may be huge but unnoticed, or indeed miscategorized as not crimes at all because they are so powerful they sway the law in their favor, or so clever they discover an immoral opportunity for criminal enterprise before the legislators notice it***. Such forms of criminality may be indistinguishable, at a distance, from lawful business; the criminal a paragon of upper-class virtue, a face-man for Forbes. > > > When the real Napoleons of Crime walk among us today, they do so in the outwardly respectable guise of executives in business suits and thousand-dollar haircuts. The executives of WorldCom and Enron were denizens of a corporate culture so rapacious that any activity, however dubious, could be justified in the name of enhancing the bottom line. They have rightfully been charged, tried, and in some cases jailed for fraud, on a scale that would have been the envy of Mabuse, Blofeld, or their modern successor, Dr. Evil. When you need extra digits on your pocket calculator to compute the sums you are stealing, you're in the big league. Again, when you're able to evade prosecution by the simple expedient of appointing the state prosecutor and the judges — because you're the president of a country (and not just any country, but a member of the rich and powerful G8) — you're certainly not amenable to diagnosis and detection in the same sense as your run-of-the-mill shoplifter or petty delinquent. I'm naming no names (They have intelligence services! Cruise missiles!), but this isn't a hypothetical scenario. > > > If you develop this capability, you will not be spending all your money but making more of it. Developing an industrial scale capability of *anything* will be visible and expensive. But you will have overt uses for it, and success (in the cover business) is guaranteed because you will not play by the normal rules to find customers. Other multinational companies and governments will be paying you to develop these capabilities, for selfish reasons of their own (so they think) or normal contractor guaranteed-winner through politics and influence in the highest levels. Other industries that you don't control outright will be working on your behalf, guided to that end by the *influence* that defines your power. As Stross indicates, you don't have to hide your *capability*— just your motives and ramifications. --- Alas, a huge space station is beyond your capabilities. The amount of lift needed is far too great for a crowd and their supplies. However, you don't need to get them into orbit: you *need* to sequester them. A portion of the secret base is fine for that. You should think twice about killing everyone to have the world to yourselves, though. Who will maintain the infrastructure and keep you in all the modern tech and conveniences that all of you enjoy? [Answer] 50 billion dollars isn't a huge amount when it comes to space exploration, honestly you would be better off on an isolated island. If that is not possible for some reason though then your best bet would be to get involved in the existing space exploration projects. As a major source of funding for something like the [Orbital Airship](https://space.stackexchange.com/q/6548/11253) you would have a lot of influence over the way technology developed. Unfortunately space elevators are still a bit far away and outside your budget. The reason I suggest the airships is because they are about getting large amounts of mass into orbit cheaply. That would then let you create a floating hotel. When you are ready to unleash your evil plan you just fully book the hotel for you and your minions, fly up on the regularly scheduled flights, and then begin. [Answer] ## There's no secrecy in orbit For historical reasons mainly related to the cold war and nuclear weapons, many governments have been very interested in monitoring space. Multiple authorities have a very good idea of all objects in orbit, multiple countries have satellite networks dedicated to monitoring launches, and it is not possible to get anything in the orbit without "everyone" noticing the location, time and size of the launch. Furthermore, all *large* objects in orbit are visible even to amateurs. ISS is visible with the naked eye, and a station made for 201 people would be obviously noticeable. You can't hide it, in any orbit reasonable for such a station it will be moving over populated areas multiple times per day. You will have to do it not in secrecy, but disguise - everyone will know that the project exists and the size of that project (and it being an order of magnitude larger project than the ISS), you can only hope to disguise the purpose. [Answer] Seeing that you are an evil genius, you should seriously consider launching your space vehicle using the well-researched method of [Project Orion](http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29). For those not familiar with this, you launch your vehicle by using about a 1000 nuclear bombs that you drop below the pusher plate on which your spacecraft rests. There are designs for vehicles in the range of 4,000 tons to 8,000,000 tons — actually there are smaller designs too, be the price of a 4,000 ton launch is so little different from a 100 ton launch, there is no good reason to skimp as you will still need the same amount of fissile material — making micro nukes is pretty inefficient. 8,000,000 tons even more surprisingly still requires about the same amount of fissile material. At 8,000,000 tons, you could launch a city. Add an extra thousand nukes and design your launch vehicle so you can separate the inhabited section from the remainder and you now have the ability to destroy the earth by smashing your vehicle into the earth at high speed — and because of your dramatic launch, everyone will already know you can do it too. Plus, you can just nuke people from orbit when the moods strikes. Orion missions that have been designed include massive launch to LEO, round trips to Mars and Saturn and one-way to Alpha Centauri — all designed in the late 50's early 60 using tech that was considered available near term back then. On your production line, expect you nukes to cost you about 1 million each. So only a billion per thousand nukes, no need to skimp there. Someone is going to have to do some math to see just what your can do for 50 billion or so. Given that a smaller vehicle mission to Alpha Centauri was priced at around 360 billion I think you will have some nice solutions. Though you could raise some extra capital by selling nukes on the black market too if you want to supersize your launch vehicle. Major plus — everyone on the planet will know what a bad-ass you are. You may not even have to actually destroy the earth after all, put them all to work for a mere 10% of GDP to stay on the don't destroy list and you can live the life of fame, power and luxury you deserve. Clearly stealth is not an option using this approach — but you won't need or want it this way. Can I reserve a spot? An evil genius needs qualified minions. ]
[Question] [ Is there any way that a town or city could exist that has interconnecting houses floating on a body of water? I once read in a novel about a small village like that in a swamp, and was wondering if a similar thing could be adapted to a larger scale to exist on an ocean/sea/lake. **Conditions for existing:** * It would be a town/small city of different families living together peacefully, and would travel between different ports to trade. * It is made up of individual houses/buildings that exist on their own floating vessel, that are interconnected with bridges to other adjacent vessels. * Its main source of food is fishing, which it also uses to trade in the port cities for items they require. * Normal towns and cities still exist on land. * There are other towns/cities that are the same, and whilst not having any government that presides over these towns/cities there is a mutual understanding between them that they are civil with each other and do not attack each other (generally). * They can live out at sea for up to months at a time without having to visit dry land. * It exists in a medieval era world. * It can distill fresh water from sea water using sunlight as an energy source. * Children do not necessarily stay living in these towns/cities when they are grown up, but many of them do. Other new families/individuals also sometimes join an existing flotilla, but only if they are trusted. * Whilst there are other fishing boats, they generally stick close to land for shallow water fishing, and do not generally venture out for longer than a day. Deep-fishing boats cannot compete with the capacity that these towns have for getting the fish that do not live close to shore. * Trade and passenger ships still exist to get people and objects from one town to another, as they offer a direct route for delivery. They can also visit the floating towns, but it is unlikely they would find a specific one because they could be anywhere out at sea. **Considerations for existing:** 1. What is the most reasonable body of water such a town/city could exist on? Would an ocean have too volatile weather conditions for it to survive a large storm? Would a lake not offer enough fishing opportunities for it to survive? What conditions would a planet where this type of town exists need to have? 2. To avoid scurvy, would it need its own farm using bought soil to grow vegetables for the long periods living out at sea? Would it be possible to have such farms out at sea to grow vegetables if there is ample fresh water? 3. What is the largest size such a city could grow to? Would it eventually break down as a society? Would it have to split itself into two smaller towns when it gets to a particular size? 4. How would such a floating collection of vessels travel? Would they need to co-ordinate a series of sails, or could they operate from a single large sail? Would they need to use oars? 5. Are there any other considerations that I have overlooked that need to be considered for such a society to exist? I also asked a question [here](https://worldbuilding.stackexchange.com/questions/13780/what-would-be-the-ramifications-of-someone-who-has-lived-their-entire-life-at-se) about what a person would be like if they lived or grew up in such a city. [Answer] Does it help to know at least 15 and probably many more of these already exist? <http://weburbanist.com/2012/08/20/water-worlds-15-real-floating-towns-ocean-cities/> Not sure if all of those qualify for what you are looking for...I'd go with the Thai one built on stilts as it is more independent from land. I think the number would be significantly higher if the Tsunami in '05 didn't wipe a few of them out too. They are not modern cities, nor do they have huge standing skyscrapers poking out. Instead it's more of a flotilla of buildings and ships stuck together. Phuket (Thailand) is another great example and is one of my favorite destinations [Answer] You got a lot a questions about our city, and like any grounder, you'r probably expecting that we've got answers for you. But that's not the way things work out here. Out here on the water, everything's always moving. There are no answers. We just do what we have to, to survive. Let's get the tourist crap out of the way first. Why are we here? We ran from shore to escape the black plaque. Three hundred boats of all shapes and sizes. We travelled together into the ocean's blue water, then waited to see which boats had brought plague with them. The boats with sickness and their crews, burned and then sank, and we've been plague free ever since. Water was our first challenge. We didn't have nearly enough but we couldn't go back for more. So we sent a scout back into the nearest river mouth, to fill up jugs and water bags. That worked for a while, then our merlin created a way to boil sea water with sunshine. The water missions weren't needed anymore. During the winter, when the sun gets small, we bring back the water missions, visiting rivers for clean, sweet water. It's like I said. No answers, but we survive. Storms? Yeh, they'r a problem. It's no fun to be out on the water in a storm. Still, there's usually some warning. Some of the older sailers, our elders, watch the horizon for signs of trouble. We can usually get most of our boats out of the way if we're warned. If a boat isn't fast enough, or the wind is wrong and it has nor oars, that boat's crew will join a faster ship and they'll leave the slow boat to the storm. Are we a city? maybe. We're more a collection of boats or maybe a fleet. But if you like the word "city", go ahead and use it. Only don't be confused. Our homes don't stay at any fixed address. We move around as we need to. Even among ourselves, we are always in motion; just like the sea. How big can we get? I don know. People come and go. Smaller fleets join up and sometimes we splinter up. We always split up when its time to trade with one of the shore towns. A couple dozen boats, some with weapons, others with wares, seperates from the whole and heads in shallow to represent us. Those are the best kinds of separations, because we all know that we'll join up again soon, once the trading is done. Yeh, life at sea has its challenges, but it is a good way to live. No rules, no boundaries and no answers. We just survive. [Answer] As Dustin Jackson said, people are working on it now. A modular city would probably be best. Each block is a separate piece that can disconnect from its neighbors and move off independently. This would be useful during storms, since the bigger something is, the more structure/stronger materials need to used, especially when designing for torquing stress from waves. After the storm the city would reassemble. ![enter image description here](https://i.stack.imgur.com/JvaQ4.jpg) This would also allow the city to grow easily, and be restructured if needed. Need to add more businesses, just build more business tiles and push one of the residential tiles out. Farm tiles could be added as well for produce and vitamin C. The biggest hurdle would be navigation. The currents would be able to push it pretty good, and sails *could* be added, but you wouldn't want to get very close to land if possible. It would eventually be something of a nomad ship, going where the currents take it. Probably not have set trade routes/schedules. However, they could have ships that travel between land ports and the city, which means it wouldn't need to move much. [Answer] Believe it or not we are already working on such projects. [The SeaSteading Institute is working on making a floating city](http://www.seasteading.org/floating-city-project/) that you are looking for. While it will be as expensive as hell to live in one and dangerous as hell with all the crazy whether caused by global warming I see no reason why they **COULDN'T** exist. I do see a practical reason to **not build one.** The main reason is, as stated above, the massive storms caused by warmer, larger oceans will destroy all but the most well-built cities. With no direct avenue inland to escape anyone living there will be, for for lack of a more appropriate term, SOL. **EDIT:** Instead of making them above water, build your cities underwater [like so](http://www.telegraph.co.uk/news/worldnews/asia/japan/11244758/City-of-the-future-sinks-into-the-ocean.html). The underwater cities could house up to 5,000 people comfortably and are nearly totally self-sustainable. They will also fare better against the currents than a city against massive waves. You could also do an in-between and make your city be submersible to handle storms...new hurricane? Let's go to the lower levels and submerge! When the storm passes re-surface. You might be able to genetically engineer a species of grass to use saltwater and survive temporary submersion. Add drains to all of your metallic/stone houses. I am not totally sure how you would protect your furniture but you could in theory install water-proof wrappers of some kind. If you really need your city to be mobile I suggest having a spiral docking bay where your city can connect and disconnect. Hope this helps ;) **EDIT....TAKE 2:** As I missed the Medieval tech requirement I am updating my answer. I do not believe that a floating city is possible. I do however know for a fact that there have been cities founded in swamps that utilize waterways. Take [Venice](http://www.wikipedia.org/wiki/Venice) as your chief example. It was founded in a swamp/Archipelago to escape the cavalry-oriented Huns and other barbarian factions. This gives you both a real-world example and a reason for it coming into being. Another real world example of a civilization doing this is the Aztec capital of Tenochtitlán. To make a long story short the Aztec killed a princess of a powerful tribe, they were exiled to a swampy island, and they build a massive, thriving metropolis. They used a method similar to that in @AndyD273's answer. They had floating sections of wood that they piled dirt onto to farm as well as artificial housing built on wooden foundations. Again, I hope this helps you come up with ideas. [Answer] Since the most plausible way for such a "city" to exist would be a refugee fleet fleeing from some sort of disaster/threat from land, the social structure would be built around protecting the fleet from the threat, and eventually channeling the paranoia/aggression back against the land; you have just created a pirate fleet! Even on the largest semi plausible ships (something like the Chinese "Treasure Fleet" junks), there simply isn't enough room to grow crops, raise livestock or carry a large supply of raw materials such as bar stock for blacksmiths to make the metal fittings for the ships. Life aboard would be very austere, with fairly severe rationing in effect for much of a resident's life. Sighting the shore or strange vessels would be an occasion for rejoicing, since there is now a chance to jump aboard the raiding boats and get fresh supplies of whatever you are short of. The pirates from the fleet will be much fiercer than the sorts of pirates we know from our history, since they don't have a secure base on short to go back to, and their need for "booty" will be far greater than the usual tropes of gold and slave wenches; they will essentially swoop down like locusts. The pirate fleet will send large raiding parties which include engineers, pioneers and other specialists who can rapidly disassemble buildings and machinery, cut down trees and rip apart hiding places to get the most useful items. For the people living on land, life will be much like the Mediterranean Sea after the collapse of the Roman Empire. Most settlements during that time moved inland to escape from the predations of the Islamic raiders, and remaining ports built up impressive defences to keep corsairs at bay. In a world where there are one or more pirate fleets like that on the ocean, the land dwellers will either retreat from the shore and build massive defences where they cannot retreat, or start building fleets to hunt down the pirates if they depend on sea trade (the *Serenìsima Repùblica Vèneta* did both). Eventually the pirates will be overwhelmed, since they don't have the numbers or resources to resist for long periods of time (A ship from a land based power with access to shipyards can be easily replaced, while a pirate ship cannot). I suspect that after a short time, the fleet would develop a sort of symbiotic relationship with one of the land based polities in order to access land and resources, and the bulk of the people will settle back on the shore of "their" new nation. [Answer] I'm not even going to try to address that wall of questions. So I will limit myself to the first half of question #2. > > To avoid scurvy, would it need its own farm using bought soil to grow > vegetables for the long periods living out at sea? > > > Addressing the scurvy issue: [lacto-fermentation produces Vit C](https://bodyecology.com/articles/sauerkraut-is-a-superior-source-of-vitamin-c/). So pickles, sauerkraut, kim chee, etc. It's also a really good way to preserve vegetables in a place where you can't get them fresh. So win-win. It also produces other nutrients the body needs. Looking at the second half of question #2: > > Would it be possible to have such farms out at sea to grow vegetables > if there is ample fresh water? > > > Yes. Boats can have gardens. Ones that produce enough to provide significant fresh produce (not everything one needs, but a good portion of it). Wall containers are an excellent choice on a boat as they don't take much soil (you leave out the soil that is just filler between plants), aren't very heavy, and don't take up much space. Another easy source of produce is sprouts. If kept dry, seeds last a long time. You can make sprouts from seeds in just a few days with nothing but a jar, a piece of cloth, a piece of string, and fresh water. ]
[Question] [ Let's assume a planet like ours, same size and same conditions. My characters live at approximately 60° North, in a boreal forest, with a climate much like the Nordic countries in Europe. They are travelling south and need to encounter a hot desert much like Sahara. This desert has to be placed as close to the boreal area as possible and still be believable as a hot desert. I've done some research and the [Gobi desert](http://en.wikipedia.org/wiki/Gobi_Desert), which is placed at ~45°N, is too extreme with temperatures as low as -40°C during winter nights and as hot as +50°C during summer days. This could be a good starting point, though, if it's possible to have a desert approximately this far north but make it less cold during winter nights (let's say no colder than -5°C). Any factors that is true on earth, like warm or cold air and water currents, could play a part in bringing these biomes closer together. I am looking for: * The shortest possible distance between a boreal area with cold winters and a hot desert that should not be colder than approx. -5°C during winter nights. * The factors that make it possible to place these very different biomes so close together. (I am new and I hope this belongs here and not on the Earth Science site.) [Answer] I can think of a few places where you have desert and forest near one another. You may or may not get the TYPE of forest you want but these can serve as models for you to work from. 1. Basically all of Peru and Chile. ![enter image description here](https://i.stack.imgur.com/bZMSP.jpg) 2. The Black sea's southern coast line. ![enter image description here](https://i.stack.imgur.com/YbTux.png) 3. Basically the entire southern border of Tibet. ![enter image description here](https://i.stack.imgur.com/imcuq.jpg) 4. (and 5) are both from Utah actually. The first is a ten minute drive from Salt Lake. The Salt flats are nasty hot. But I think #5 is the closest for you. The national forest is beautiful the mountains are amazing...as soon as you hit St. George completely desert and dry, and a little further south once you drop through the virgin river basin you hit the desert outside Vegas and that is truly desolate. ![enter image description here](https://i.stack.imgur.com/6oBpX.jpg) ![enter image description here](https://i.stack.imgur.com/q7BFo.jpg) **Notes:** * Elevation will have to play a role, generally a mountain range. Its the only way to get the temperature swing necessary to support the two environments. * Proximity to water. If you want trees you need water. Mountains help make the distribution of that water uneven. These are the two key factors to get what you are looking for. But as mentioned in other answers, the temperature swing in deserts from day to night is larger than in any other habitat, you simply don't have anything to stabilize it (water, trees, etc). Water also helps normalize temperatures a bit. [Answer] **Have them encounter a Pumice Desert** The type of dirt can change the overall environment drastically regardless of weather. I was up in Crater Lake a few years ago and as we drove from the still snow covered Alpine we suddenly found ourselves in a vast Pumice Desert. The otherwise forested region came to an abrupt halt where the soil turned to sand for miles. Nothing can really grow there, as the entire valley had been filled thousands of years ago with pumice rock up to 300 feet deep. [![enter image description here](https://i.stack.imgur.com/c0cjI.jpg)](https://i.stack.imgur.com/c0cjI.jpg) If you are looking for the *ABSOLUTE SHORTEST* way to change a forested biome into a desert, go with a drastic change in soil. And if you want to keep it warmer than the immediate area, change its rock color to something more like the Shasta Lava Beds. And to further increase the temperature there year-round, lower the elevation of this desert to below sea level. [![enter image description here](https://i.stack.imgur.com/zGrY6.jpg)](https://i.stack.imgur.com/zGrY6.jpg) [Answer] But deserts get cold at night, all of them. Even [Arizona](http://en.wikipedia.org/wiki/Geography_of_Arizona) deserts get down to -5C in January. Moving deserts north is going to make this worse. The reason is deserts have so much sand and is an excellent insulator/reflector. It's gets hot when the sun shines and quickly releases it's heat when the sun goes down. The cold is almost as dangerous to those traveling across it as the hot days. I don't think you could get a better example to work with than the Gobi Desert. One idea to make it 'less' cold at night would be to have the sand be black basalt. It would absorb heat all day (making it worse) and take longer to release it at night, so the temp wouldn't get as cold by morning than otherwise expected. [Answer] * Hot deserts: A hot desert need to be quite close to the equator because it needs a lot of heat mainly form the Sun. Most of them are located between the tropics for this reason. The northernmost hot deserts extend to 35° were they become cold desert usually For most of them, the average monthly temperature never go below 5°C. This doesn't mean that the temperature never go below 0°C but just that this is under the average. The farther you are form the equator, the greater the temperature variation between summer and winter. At the tropics, summers are really hot but get slowly cooler as we move toward the poles. I see it unlikely that a desert (hot) could exist closer to the poles because winter and summer would be colder. Being close to the sea would make the winter temperature warmer and could maintain it over 0 but would also reduce the summer maximum. * Boreal forest: Most of the Canadian forests are boreal. Meaning that they extend almost to 45°N. These are mostly located at a somewhat higher altitudes, and this help a lot. * Distance: supposing that your planet is as big as earth: 45°-35°=10° and the distance for each degree is 111,11111.... km. A plausible distance would be 1111km. **How to reduce the distance:** * Make the planet smaller. * Have a high plateau near the hot desert. The temperature will be lower and although it's not really a boreal forest, it may look very similar. The hot desert has an annual temperature of 18° and the boreal forest is around 0°. Increasing the altitude by 1000m reduce the temperature of 6° each time. If the forest is at about 3000m of altitude, it can be close to the desert. * We also need to consider the difference in precipitations. For that, we could solve the issue by placing a mountain range in between. It might not be necessary for the mountains to be very tall because the forest is already on a plateau that is high enough to block a large portion of the precipitations by itself. **Do you really need a hot desert?** Cold deserts can have hot summers too with an average of 26° in Western China for their hottest month. [Answer] How large does the area need to be, are you traveling four days across it, two weeks? A month? I'm not sure I can provide a good answer for a very large desert, but in my travels I have found a small desert (that used to be much larger) in Southern Manitoba. (Latitude = 49.666) It is called the Spirit Sands. It used to cover an area of 6,500 km, now is about 4 km across and took 5 hours to hike on a brisk September morning. 6 am was around -2 (cel) and 10 am was around 8/10 (cel). The surrounding geology is an area known as The Canadian Shield, a large rock mass. It is very diverse terrain, tons of quartz, and as well mostly boreal forest. This boreal forest extends thousands of kilometers north and east, it gives way to the (flat) prairies to the west. *Edit* And the Rockies are further west past that. It was a large river basin that slowly drained giving way to the shifting sands there are there, I think some of what may have given rise to this is further north the land becomes tundra (and permafrost area) and well used to be covered by glaciers. The glacial deposits ran further east as the land experiences greater chances in elevation. The Red River to the east, and near Winnipeg floods seasonally. ![Spirit Sands](https://i.stack.imgur.com/9MMMj.jpg) This picture is just before the rise to go into the larger desert. ]
[Question] [ **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I'm writing a story about scientifically plausible superhumans ( a new genetically enhanced human species that is mentally and physically superior to ordinary humans ), and one of their main features is the ability to hold your breath for a long enough time ( more than thirty minutes), but without lowering your metabolic rate. At first glance, the most obvious solution to my problem would be to increase the volume of my superhumans ' lungs so that when they inhale, they can inhale more oxygen. But in this case, I need to improve the ability of their blood to carry oxygen. After all, blood circulation performs one of the most important functions of transferring oxygen from the lungs to the tissues, and carbon dioxide — from the tissues to the lungs. The oxygen consumption of tissue cells can vary significantly, for example, during the transition from a state of rest to physical activity and vice versa. In this regard, the blood must have large reserves necessary to increase its ability to carry oxygen from the lungs to the tissues, and carbon dioxide in the opposite direction. Hemoglobin is able to capture oxygen from the alveolar air (a compound called oxyhemoglobin) and release the necessary amount of oxygen in the tissues. A feature of the chemical reaction of oxygen with hemoglobin is that the amount of bound oxygen is limited by the number of hemoglobin molecules in red blood cells. Question: how would it be possible to increase the number of oxygen molecules that could be carried by the blood? Note: if you have to sacrifice your hemoglobin for something else, I'll be happy to hear an alternative. [Answer] ## Swimming Like a Seal: I'm not sure hard science is the best fit for this question, but I'll give it a go. I think the key element you are looking for is [aquatic mammalian myoglobin](https://www.bbc.com/news/science-environment-22853482#:%7E:text=The%20team%20studied%20myoglobin%2C%20an,findings%20are%20published%20in%20Science). There is a good set of review articles [here](https://pubmed.ncbi.nlm.nih.gov/10936758/) on the subject. The biochemistry gets pretty technical, so dig in deep to the second link to get the hard science. Basically, cetacean myoglobin is able to reach much higher levels than most mammals, but is structurally a little different to reach these concentrations. It stores oxygen, releasing it in the muscles over time. Seals, for example, can achieve up to two hours of dive time, although this is likely at a much-reduced activity level. But 30 min at a reasonably normal respiration should be achievable. Big brains are also greedy for oxygen, so this will also come into play. [Dolphins](https://seaworld.org/animals/all-about/bottlenose-dolphin/adaptations/#:%7E:text=Depending%20on%20habitat%2C%20most%20bottlenose,of%20diving%20to%20greater%20depths.), for example, get to only about 12 min on dive times. Biology is all about give and take, and I'm guessing there are consequences to having all that atypical myoglobin. It may function differently in non-diving conditions, it may have a very high energy cost (to make/maintain), it might function best at high pressures (like underwater) but the science of "this-is-better-than-that" is always highly speculative and not a good match for the hard science tag. [Answer] **Circulating peroxisomes carrying O2 as H2O2** synopsis: H2O2 is a concentrated liquid source of O2 gas with available O2 increasing as concentration of H2O2 increases. Stores of oxygen as H2O2 could be tapped during long breath holding. All hail the peroxisome, ancient armor of our ancestors! <https://en.wikipedia.org/wiki/Peroxisome> Peroxisomes are tiny intracellular organelles, a 50th of the size of a red blood cell. They handle hydrogen peroxide for us - detoxifying it when it accumulates and producing it when needed for oxidative metabolic functions / offensive oxidative attacks against invaders. So: except for the noneukaryotes in the audience, we all have tiny spaces which are fortified against the corrosive effects of H2O2. In this scenario, H2O2 serves as an oxygen source. Can one produce O2 from H2O2? Yes, and in generous amounts. [A 3% solution of H2O2 will produce 10 times its volume of O2 gas.](https://www.researchgate.net/post/What_does_a_40_Volume_hydrogen_peroxide_mean) So a liter of 3% solution makes 10L pure O2. I am fairly sure that the internal concentration of H2O2 in a peroxisome is less than 3% but let us use 3% - nothing will burst into flame and these are supersoldiers after all. Assume O2 consumption for a breath holding supersoldier mediating is 100 ml/minute and a supersoldier doing squats (like they do) is 2000 ml/minute. Average 1000 ml/minute and one would get 10 minutes of O2 demand from 1L of 3% H2O2 solution. Peroxisomes are the size of platelets. We will fortify the blood with a liter of 3% H2O2 peroxisomes circulating. We will stash another liter in the liver and a third in the tissues. At cost of 3 extra liters volume we get enough O2 for 30 min moderate activity. The peroxisomes can just dump peroxide into the blood and the oxygen produced by endogenous catalase will be swept up by RBC. These researches injected H2O2 into bags of deoxygenated blood, which perked them right up. [THE OXYGENATION OF BLOOD BY HYDROGEN PEROXIDE: IN VITRO STUDIES](https://bjanaesthesia.org/article/S0007-0912(17)52400-9/pdf#:%7E:text=Hydrogen%20peroxide%20is%20a%20highly,saturate%20more%20than%201.5%201.) [![oxygenation by h202](https://i.stack.imgur.com/HXcaW.jpg)](https://i.stack.imgur.com/HXcaW.jpg) I think these folks were using 30% peroxide and so a tenth the volume of the 3% in my scenario. Peroxide packs a lot of O2! [Answer] **Using a blood substitute you could improve this.** [Perfluorochemicals](https://en.wikipedia.org/wiki/Blood_substitute) can carry several times more oxygen than red blood cells. They could be adapted for that. Along with other minor efficiency boosts, this could let them survive longer underwater. [Answer] There was a good article about this a while back: <https://foresight.org/Nanomedicine/Respirocytes.html> Now, this was talking about *artificial* respirocytes, but the general concept remains. Long story short: whereas red blood cells mainly store O2 in solution and/or chemically bound, if you store O2 under pressure instead you can achieve a much higher capacity if you have the materials for it (and the nanotech to be able to actually construct the thing). Major caveats: 1. The pressures required to actually be helpful require extremely strong materials. The above article was assuming diamond walls. 2. These would not fulfill the ancillary duties of red blood cells (clotting, notably.) 3. The complexity required for the control scheme for said respirocytes (when/how to let out/in O2/CO2) is rather high for something that isn't a fully-viable cell. ]
[Question] [ Scenario: Earth's history is 100% equal to reality . It’s the year 2040. First interplanetary cities with 3% total population of mankind. 200 million years ago humans appeared on Venus, developing into a greatly advanced civilization spanning multiple planets (divided into multiple nations) until a catastrophic war killed most of them (rendering Venus hostile to life and destroying all major habitats and cities). The survivors (about 200k people) tasked an AI to make Earth habitable and then went into stasis chambers (my equivalent of cryogenic technology) in which some of them remain until today. Once Earth was habitable the majority of survivors migrated there and became the beginning of modern-day mankind. Then the AI shut itself down. About 20k of those 200k stasis chambers survived (they are different from those survivors used to establish the human population on Earth). Prior to their emergence from stasis in 2040, the chambers were floating in space. **Question:** If the ruins are still standing and technically visible, why they haven’t been seen by modern people (by using telescopes or similar)? What would be the reason for modern scientists' inability to discover any remains (broken ships, space stations, etc.)? **Note**: the ruins are all over the solar system. In modern times there are still remaining ruins (though most don't need to work) and people in stasis that in theory could be awakened [Answer] **We still haven't been able to watch in the good spots** Except for the planets where we have sent probes, we don't know have that big resolution of the surface of the objects in the Solar System (for instance, there is still some debate about the effective shape of Oumaouma). The places where we were able to map in high resolution the surface and we can rule out the existence of some big or medium sized surface structures are (if I remember well): * Mercury * Moon * Mars * Ceres * Eros * Pluto and Charon (not 100% of the surface) The satellites of Jupiter and Saturn were mapped at different resolutions, but, for instance [Europa is mainly mapped at 1km resolution](https://www.planetary.org/articles/0218-mapping-europa), so if the ruins were rare and far apart, it would still be difficult to have an image of them at the current level of technology and exploration of the solar system. About the mentioned planets, they would be the places where the population density was higher, so the places where the war likely brought the most destruction: it is safe to assume that whatever structures existed there would have been completely destroyed during the war (and, particularly on Earth, erosion did the rest). About the chambers, if they are some meters of size, it is likely that we haven't been able to see them (or, if we have, we haven't been able to realize they are artificial objects, since in many cases we were able to only measure the brightness): from the wikipedia page about [near Earth objects](https://en.wikipedia.org/wiki/Near-Earth_object#Number_and_classification) > > The number of asteroids brighter than H = 25, which corresponds to > about 40 m (130 ft) in diameter, is estimated at about > 840,000±23,000—of which about 1.3 percent had been discovered by > February 2016; > > > And it would be even less if these chambers were placed on a far from Earth orbit. [Answer] **Geology and nature** The disappearance of most spaceships, ruins and technology is easy. Earth is relatively benign compared to many other regions of the solar system. In the timeframe you're talking a great many things can and will happen. Sattelites will crash or be trown out of the solar system. Ruins will be eroded, cities will crumble and little will be present to show that there was a civilization at all. Even things like plastics, which few organisms and processes can destroy, will mostly be reduced in such societies and the remainder can be difficult to pick up on unless you're physically there with equipmemt. It's more difficult to have things survive a million or 50 million years than have anything left standing. Seeding ships and such can destroy themselves when their task is finished into pieces small enough that they'll be eroded long before people can detect them. The only problem is the cryochambers. If you want them to survive, you either need a super stable area or constant maintenance, preferably both. Deep underground or the sea is a good possibility, as long as it's stable enough. Even then many will probably not survive due to random movements of the soil. An alternative is hiding cryo in the astroid belt, inside the astroids. They aren't stable, as in the last 100 million years the astroid belt has been reduced with more than 99% thanks to random collisions, but it'll be difficult to detect with modern equipment. Finally you can hide them outside the solar system. They might be small enough and quickly far enough not to be detected or thought of anything else than random debris, if detected at all. It is still not fully safe, but it can explain why only 20 million survive. [Answer] Being buried under Antarctica or under the ocean bed seems as good a place as any to not be found. This holds true on other planets too. Things tend to get buried after 200 million years anywhere there is weather. And if there's no weather, there's probably a lot of meteorite impacts so you would probably want to bury it yourself anyways. You're not going to see any of that through a telescope. 200 million years is also plenty of time for space station in orbit around a planet to deorbit. [Answer] They landed 200 million years ago on a planet with nothing to support their tech. The best they could was to cannibalize their ships and reuse as much as possible for their purpose: why do you keep a space ship when you need a blade to kill some animal and reach tomorrow? You tear it to pieces and reuse it, and since of course you have nothing to maintain the tools you make, they will be tore down to dust and rust. If anything can be found it won't be ships, it will be shavings and fragments. [Answer] They were placed at the [subduction zones](https://en.wikipedia.org/wiki/Subduction) of fault lines, and thus subsequently destroyed as they were buried in magma. 200 million years is more than enough time to subduct anything placed in these areas and leave virtually no trace. [![subduction zone](https://i.stack.imgur.com/8hmcG.png)](https://i.stack.imgur.com/8hmcG.png) So how were they ultimately found in 2040? Perhaps they contained rare elements not typically found in large supply on Earth, and these elements were detected in the discharge from nearby volcanoes? Maybe one or two of them wasn't quite close enough to the subduction zone to be pulled down, but it wouldn't be discovered so easily because it's still buried under the sea floor at the bottom of the deepest trenches in the ocean. Possibly some future deep-sea construction project unearths some surviving relics. Maybe some ancient sea creature found one and dragged it away from the subduction zone before deciding it wasn't edible. There's any number of possibilities. [Answer] **Underground** They built pretty much everything under the surface. While you've stated that Venus was habitable, the other planetary bodies would not be (with Earth being disqualified by your statement that they needed to terraform it). Safety from the natural dangers of radiation and meteor strikes, in addition to the dangers from interplanetary warfare, resulted in subterranean communities. Similarly, any orbital habitats would have a layer of rocks and ice surrounding them, giving them the appearance of asteroids. One large issue that you may need to address, is the dangers of long term cryopreservation. Even if you are perfectly shielded from outside dangers, the radioactivity given off by your own body will end up doing fatal damage. This would be over a timespan of a century or so, so a timeframe of millions of years would require something to counter that. [Answer] **Partial Answer:** Not sure if partial answer works the same way here as over on puzzling, but here we go... ON VENUS (not trying to explain why there is nothing, anywhere in the solar system, as it's generally answered by others / I agree lets hand wave 200 million years is plenty of time as described in other answers - probably is, but no one is really supporting) specifically the majority of the world is an ocean, but it wasn't always. Venus used to be much more earth like with continents spread across it - the original humanoid inhabitants were unable to control sea level rise, or adapt to it, and were pushed to relatively last minute escape measures - most of the planet Venus is well developed by our standards, i.e. like greater Los Angeles across the planet, but taller skyscrapers in many locations. It's still there to this day, but it's all underwater now. The Earthen myth of Atlantis actually stems from the civilization on Venus, not anything on Earth. At least one source for the whole "it's all covered in water now" claim: https://earthsky.org/space/venus-map-with-oceans-on-surface-terraforming#:~:text=And%20what%20does%20it%20show,and%20lows%20on%20Venus%20surface(I had to remove a "'" after Venus for the link to work correctly on SE) And while the time frames are a little off, Wikipedia claims habitability until 700 million years ago-https://en.wikipedia.org/wiki/Life\_on\_Venus#:~:text=Recent%20studies%20from%20September%202019,to%20750%20million%20years%20ago. -doesn't really establish massive sea level rise that hide a far advanced civilization, but we also only have scans through heavy clouds so *imagination* wins here Might be a stretched for science based? Not sure, but it all kind of is, so hope this helps! [Answer] After having been in the cosmos of the solar system for nearly 200 million years, the stasis chambers accumulated dust and were impacted by asteroids and comets and are themselves covered in the collision detritus and they look like any other asteroid or comet in the solar system. Have a closer look at Ceres, Vesta, Triton. There will be other that just haven't been noticed. ]
[Question] [ Wrathful aliens are teaching the humans a lesson by relocating their world from a cosy 1 AU to around 4 AU away from the central Sun-like star. The planet is Mars-sized and covered in a salt-water ocean averaging at 6 km in depth with very little land. The atmosphere is Earth's in both composition and pressure at sea level, but the scale height is greater due to the lower, Mars-like gravity. If no human intervention takes place, the oceans and atmosphere would condense and freeze, turning the world into something resembling Enceladus. The humans hastily cobble together a plan: use a magical device capable of remotely spawning thermonuclear-like explosions at any location to constantly explode the depths of the ocean everywhere around the planet. The heat released into the oceans eventually finds its way to the atmosphere, warming it as well. (The magical device doesn't produce any nuclear fallout.) Is this a viable method to save the planet (meaning, keep the oceans liquid and the air unsolidified)? If so: if the limit of explosive force delivered by the magical device is 10 megatons, and assuming we intelligently distribute the explosions to areas of ocean that need them most, how frequently do we need to detonate? Once a second? A hundred times a second? A thousand? [Answer] **Slight frame-challenge.** I'd suggest detonating them in the highest level of the reaches of the atmosphere, Just outside the limits of the [exosphere](https://en.wikipedia.org/wiki/Exosphere). (About 1000 Km up) The detonations should happen on the side of the planet facing the sun (such as it is, far away). Maths: Each 10 Mt explosion consists of $4.6\*10^{16}$ joules, [35% of which would be thermal and light](https://www.atomicarchive.com/science/effects/energy.html#:%7E:text=Thus%2C%20a%201%20kiloton%20nuclear,4.18%20x%201015%20joules.), and much of which would be directed away from the planet. At the limits of the exosphere, approx 46% would go planet-wards. That's $7.4\*10^{15}$ joules per explosion. The Earth needs (by pre-industrial standards) $1.74\*10^{17}$ Watts of energy delivered incident on the upper atmosphere. (That's joules, per second). That's about 23 or 24 detonations per second delivered above the "midday" point as the sun apparently moves. Fits with the UK frame rate for old terrestrial TV as it turns out, you'd not notice much flicker probably. Half sized ones, at twice the rate to make sure might be better. Say take it down to 21 or 22 per second (\*2?) to compensate for residual solar radiation at 1/16 the normal rate ([inverse square law](https://en.wikipedia.org/wiki/Inverse-square_law)). You can vary it a bit to make seasons. Easy. [Answer] The earth every hour receives [430 quintillion Joules of energy](https://phys.org/news/2015-12-sun-energy.html), where 1 qunitillion = 10^18. The energy from a [1 Megaton nuclear bomb is 4.18\*10^15](https://www.atomicarchive.com/science/effects/energy.html#:%7E:text=Thus%2C%20a%201%20kiloton%20nuclear,4.18%20x%201015%20joules.) joules. Thus, a nuke of 10 MegaTon TNT equivalent releases 1000th the part of hourly radiation of sun. There are estimated around [14000 nukes](https://en.wikipedia.org/wiki/List_of_states_with_nuclear_weapons#:%7E:text=From%20a%20high%20of%2070%2C300,nuclear%20warheads%20in%20the%20world.) in the world. If you burst all of them simultaneously, you will only produce around 15 hours of extra sunlight effect. Of course, the Sunlight is countered by various ions etc in upper mesosphere and thermosphere as well, so you could probably add a couple of hours of extra sunlight to that. But that still won't be enough in the long term to deter aliens. The heat so generated would dissipate away in the atmosphere anyway. Next, total volume of all oceans is [1.3 sextillion liters](https://pubs.acs.org/doi/10.1021/es1012752#:%7E:text=The%20ocean%20volume%20exceeds%201.3,over%20354%20million%20km2.). It takes 4200 joules to raise temperature by [1 degree of 1 liter water](https://www.bbc.co.uk/bitesize/guides/zpjpgdm/revision/4#:%7E:text=The%20specific%20heat%20capacity%20of%20water%20is%204%2C200%20joules%20per,water%20by%201%C2%B0C.). You can do the maths, but all your nuclear weapons blowing simultaneously would not even raise the temperature of seas by 1 degree. Thus I don't think nukes will help you to keep things warm. Rather, you can 1. look into pulling stray asteroid matters of small enough size into the earth's atmosphere. that way, the asteroid constantly burns in the atmosphere, keeping the temperatures high, and the ill effects (ash/gas) etc are not enough to trigger a global cooling on its own. 2. You find a way to increase the amount of green house gas in atmosphere. This keeps earth warmer for longer due to trapping of solar energy. But you've to be careful not to cause more cloudy conditions, as those can trigger cooling of surface. CO2 is thus a natural option, but you can look into increased methane or ozone production as well. [Answer] These hypothetical people might be better off using their magical device to create volcanic eruptions. When a volcano goes off, it releases a significant amount of greenhouse gases as well as ash and lava, so the heating would be more of a cumulative process. You wouldn't just be relying on the heat from the explosions, but using the resulting gases to help the atmosphere hold in more heat. Agitating the planet's mantle artificially would also boost activity at deep-ocean vents, keeping the ocean floor a viable biome. [Answer] ### [Use the nukes to thicken the atmosphere by selective rock shattering.](https://earthobservatory.nasa.gov/features/CarbonCycle/page2.php) All the other answers so far have good maths re energy and warming and such, and I'm not going to repeat good work, but there is one more possibility - greenhouse effects and geological carbon sinks. Detonate your nukes at the bottom of the sea, such that it fractures rock. You haven't specified the lithosphere of the planet, lets say there's a layer that's rich in limestone (which is often under oceans - it's old shells and sediment under pressure). When this is shattered and heated - carbon dioxide is released. This will build a greenhouse effect, heating the planet. Humans will detect the air as bad at about [2000ppm - 5000ppm](https://www.dhs.wisconsin.gov/chemical/carbondioxide.htm), that's an order of magnitude more than Earths CO2 levels in the 20th century, so you can increase the insulation by a factor of ~10 before the air even starts to seem stale. That's 10-fold increase in insulation, enough to make up for the decrease in incoming energy. [Answer] > > The magical device doesn't produce any nuclear fallout > > > I think you're missing something very important with this. You ***want*** the fallout, because what you want to do is ### Strengthen the greenhouse effect using water vapour Water vapour is a major player in the [greenhouse effect](https://en.wikipedia.org/wiki/Greenhouse_effect). We focus on CO2 because that's human-created, but CO2 doesn't directly cause all of its effects itself. It also has has a role in how much water vapour stays in the atmosphere, which causes a further impact on the global climate. Intuitively, we do know that days are warmer when there is cloud cover. Of course we experience more direct heating from direct sunlight, but cloud cover maintains the temperature when the sun is not at its peak by acting as an insulating layer to prevent convection from dissipating that heat, keeping a warmer layer of air closer to the ground. This effect is experienced locally, of course, but modelling suggests that increased humidity will increase global temperatures. This is [still a matter of discussion](https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives/its-water-vapor-not-the-co2.html) and [significant research](https://www.nasa.gov/topics/earth/features/vapor_warming.html), but is well supported by the science to date. So the focus of your nukes should not be specifically to warm the oceans. Instead, it should be to disperse as much water vapour into the air as possible. You don't need to actually boil the water, you just need to maximise the aerosol effect. Note that this is a different scenario to [nuclear winter](https://en.wikipedia.org/wiki/Nuclear_winter) or [volcanic winter](https://en.wikipedia.org/wiki/Volcanic_winter), where soot particles in the atmosphere prevent heat from reaching the Earth. Water vapour passes substantial amounts of heat and light, so whilst clouds and smoke are superficially similar, their effects are different. [Answer] Expanding on @RottweilerOnMarket-day's answer, I've generalized their calculations into formulae. For a given planet radius $R$, altitude above the surface $H$, and approx. kilotonage of "nuclear" blasts $k$,... * ...the fraction of sky occupied by the planet's disk at altitude $H$ is given by the angular diameter: $D = -\frac{{\arcsin}(-R/(H+R))}{\pi}$, * ...the wattage required to maintain an Earthlike atmosphere is about: $W=1.74\*10^{17}\*\frac{4R\pi^{2}}{5.101\*10^{14}}$, * ...the kilotonage of the blasts in joules: $K=k\*4.184\*10^{12}$, We can find the frequency of blasts required to maintain the atmosphere via: $E\_{Hz}=\frac{W}{K\*D}$ --- For a Mars-sized world with radius $3400km$ and 10 Mt explosions at an altitude of $1000km$ we get $E\_{Hz}\approx 42Hz$ ]
[Question] [ So the ideal of solarpunk is obviously that you would not need one, but if not every nation went in a solarpunk direction at the same time, you would likely need a defense against those that did not go in this direction and wanted the natural resources of solarpunk societies that obviously aren't as interested in exploiting their own resources. Politically, the society is somewhat more decentralized than modern capitalist ones, but they still have a degree of quasi-national government for certain things(like a military to defend against a foreign aggressor, keeping electrified railroads between cities active, and monitoring those who might cheat on extremely strict environmental regulations). How might a military be structured for such a society? Starfleet from Star Trek might be a source of inspiration given the shared optimistic focus, but it really doesn't work all that well. The problem is that Star Trek posits an extremely advanced society in terms of technology and especially energy output. Their reliance on starships and orbital/air power is fairly hard to adapt to a society that is deliberately relying on less energy than is required. The closest modern equivalent would be a powerful air force whose fighter squadrons pretend they are primarily for aerospace testing and airshows in support of extremely light ground forces that pretend they do something other than soldiering and thus generally lack the proper equipment to do it. The likely enemy is a more or less cyberpunk nation that heavily uses mercenary companies to back up the government military that is one of the few things more or less funded, but for the sake of simplicity, assume a more or less modern tech level. The tech will probably advance a fair bit, but it is easier to ignore this for now and convert things later. EDIT: The real question I think should be about how to make a military less wasteful overall. What changes would have to be made here? [Answer] **Frame Challenge: Militaries by nature require waste and reducing it reduces your military potential.** **Personnel** In order to have proper soldiers, they need quite a bit of training. This means you can't reasonably put a 1 month trained recruit squad against a SEAL squad and expect them to perform well. The SEALs are trained much more stringently. Reducing the number of available personnel also reduces the chance of military success. Due to the training time, if you don't keep a populated enough military then when the conflict happens you likely won't have enough personnel to send to the battlefield and won't have proper useful personnel added for quite some time. Training troops requires resources. Keeping those troops for extended periods is more resources. Using more resources to keep your military in tip-top shape without conflict could be considered "Wasteful". **Equipment** Just as with your troops, keeping equipment available and ready to go is also wasteful. Additionally, you have to expend some of that equipment in order to keep your troops properly trained. (If I had the link for how long equipment can be operated before replacing vital components I would put it here probably). **However** Potentially you can find a balance where the amount of troops and equipment you have is enough to buy you time to alter manufacturing and recruiting to gather more equipment and troops. Although, exactly what timeframe that would require is a whole question worth asking. [Answer] ### Solar panels on military vehicles wont happen Perfect utilisation of solar power gives about 1kW/m^2 during peak daylight. This is actually a lot of power. However it's not enough for direct use in a military as we know it. An F-35 fighter with 100% efficient solar panels over its skin could absorb a peak of about 70kW of power. That's a lot of power, until you realise that one of its engines is rated at 22MW. You have the same problem with APC's, tanks, etc. They need more power than the sun provides. You need to have batteries on board anyway for nighttime use, but this just results in a poor duty cycle, eg the solar powered F-35 could only fly for 1 hour for every 300 sunlit hours on the ground. Submarines don't get much sun underwater. Ships aren't much better. If the USS Gerald R Ford had solar panels embedded in it's flight deck it would get 26MW of power at peak, its reactors currently give up to 1.4GW. ### But you can have a green, solar powered military * You have a massive field of solar panels, cranking out GWs of power. + Current tech levels you can get 38MW per Square KM, theoretically up to 1GW is possible. * Adjacent to that, you have a [Power-To-Methane](https://en.wikipedia.org/wiki/Power-to-gas#Power-to-methane) factory, which takes power, CO2, and water, and puts out methane and oxygen. * And adjacent to that, you have a [Methane-To-Methanol factory](https://en.wikipedia.org/wiki/Methanol_fuel). That methanol contains the captured solar energy (5.4kwh/L), and is used as a low risk, easy transport fuel, similar to gasoline now. Batteries will probably still be needed, by methanol should be preferred, as they're 25-50 more efficient per kg. Really high power / low weight applications (like the F-35) might be better off just using methane (or liquefied hydrogen / oxygen if we're really getting extreme), but storage of a high pressure gas is much more fickle than storage of a liquid. As an extension; Liquid hydrogen and liquid oxygen can be made from the power to methanol plant. (Basically hydrolysis and then refrigeration). This would allow for a [Green Space Program](https://worldbuilding.stackexchange.com/questions/184568/could-you-actually-make-a-green-space-program) [Answer] **Flying drone avatars.** [![skybot](https://i.stack.imgur.com/PrMGI.jpg)](https://i.stack.imgur.com/PrMGI.jpg) <https://www.space.com/russia-launching-humanoid-robot-into-space.html> Solar power is collected by high altitude dirigibles, floating well above the weather and transmitting power wirelessly. Flying humanoid robots patrol everywhere, and see everything. Perhaps they return to the dirigibles to recharge. These flying robots are autonomous most of the time. They are capable of striking from altitude, like the drones we have now. They can come close for a better look. They can land and interact with persons on the ground - not for hand to hand fighting but for police and rescue actions, and to ask questions. Like an automated answer system which can put a live operator on, one of these robots can be taken over by a remote operator. This might be a paramedic, a person with expertise in car repair or nuclear technology, or whatever the situation warranted. This person inhabits the robot and can carry out operations on the ground. High flying humanoid drones would be flexible and able to help this society in many ways. There is also a hint of Big Brother(s) which could be good for a futuristic fiction. --- As regards military operations, the drones would be very effective. They could demonstrate their abilities from altitude, then a negotiator would come down with one of the drones and interact with insurgents or enemy military. [Answer] Decentralize operations, especially in theater. Smaller, modular, deployable field bases that provide greater opportunities for in-situ resource utilization can help break your dependency on the great weakness of modern militaries, the supply chain. You don't need to rely on shipping tankers of fuel or piles of ammunition from supply depots to the front lines, which means your supplies can't be intercepted or stolen, they're harder to sabotage, and you aren't painting a big bright truck-shaped arrow saying "they're over here!". Actually achieving full resupply in the field is a tall order. You'd need power generation - solar, hydropower in some areas, maybe biofuel generators - and you'd need the ability to convert some of that power into liquid fuel of some kind for vehicles. You would need the ability to recover or create ammunition. (Coilguns would be ideal here because the propellant is electricity and the projectile can be anything ferromagnetic; you could make your own bullets from scrap if need be.) You would need to be able to provide food and medical supplies, either from some kind of field production or from very efficient storage. (Read: military rations will still be unpalatable.) However, even if you still need to metaphorically come up for air once in awhile, anything you can do to reduce the size and frequency of supply shipments will pay dividends in your units' maneuverability and security. Decentralized operations also provide a useful (but potentially very dangerous) political independence for your troops. If you're reliant on Acme Co. or the City of Wherever for your supply lines, you're not going to do anything that could upset them: even if they didn't simply let you starve (for fuel, for ammo, or just literally) the tension between you would invariably result in less efficient supply shipments and thus weakness on the field. But if your supplies are independent, you can go over and put pressure on the city whenever the central government needs you to, without worrying where your next meal is coming from. As I said, dangerous as well as useful - this also means your government can't reign in a rogue operator as easily. Finally, from an out-of-universe perspective, this gives you an excuse (or opportunity, if you prefer) to justify why your group of protagonists are operating without a million forms and constant logistics shipments and oversight and everything. They can go where you need them to go, fight who you need them to fight, without worrying about it. And for a videogame specifically, it's pretty much tailor-made for the conventions of most of your major genres: relatively small numbers of troops, a mobile base that can meet most of your needs, on-site production, etc. [Answer] **Go small, go swarmy, go green** Going solarpunk also meant for your society to go greenpunk. Higher integration of technology with the biosphere. They may be able to control swarms of insects (mosquitoes, hornets, fleas, etc) after converting them to accept hive like instructions. These species may be able to produce special toxins on demand or, as a safer option, to go collect toxins from special reservoirs setup by the army. Integrated hardware in the insects would allow the army to direct and support them (providing food and shelter, integration in tactics together with army squads on the field and so on). They would not be able to destroy an APC but neither would the APC be able to destroy (or detect) them. But they would be able to spy the enemy unseen and report back either with the movements like the dance of the bees or strightforward hardware integration. The enemy would need to resort to chemical warfare against them and there would be an arms race in this field. Of course they should not be the only weapon available to the solarpunk society but more an important asset to be used in combined arms tactics. [Answer] # **Animals.** Humans have been shaping the creatures around us for tens of thousands of years; just because lifeless mechanical equipment has outpaced bioengineering *lately* (with regard to war machines anyway) there's not much reason to expect **biotech** to sit around content with plagues & cyborgs: **Almost any conceivable piece of equipment could be made from living organisms**, largely self-repairing, & reproducible at higher efficiencies than metal & plastic units. [Answer] [Bicycle-cavalry](https://en.wikipedia.org/wiki/Bicycle_infantry) units have found use in war in real life. Bicycles have advantages over alternatives: less fuel than an engine or a horse, cover more ground more quickly than infantry, don't require much of a supply chain (one member can carry parts and tools), etc. [![enter image description here](https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/LTTE_bike_platoon_north_of_Killinochini_may_2004.jpg/640px-LTTE_bike_platoon_north_of_Killinochini_may_2004.jpg)](https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/LTTE_bike_platoon_north_of_Killinochini_may_2004.jpg/640px-LTTE_bike_platoon_north_of_Killinochini_may_2004.jpg) The solarpunk Low Tech Magazine made an argument that [guns could be replaced by bows and arrows](https://www.lowtechmagazine.com/2022/11/what-if-we-replace-guns-and-bullets-with-bows-and-arrows.html). I'll let you decide how convincing it is, but it would certainly be interesting. I like the idea of combining these, and having bowmen on bikes. One interesting thing is that Terran warfare is very noisy, but bicycle bowmen would glide silently – until dey scream. --- **Rules of war**: these already exist on Terra, e.g. no blinding weapons, no chemical weapons, no flamethrowers. The governance of a solarpunk world might be such that this is even greater, allowing only [highly restricted, regulated kinds of warfare](https://en.wikipedia.org/wiki/Flower_war), perhaps even banning guns like Low Tech Magazine wants. Anything greater would be considered a war crime and that would be enforced. [Answer] I don't know if this helps but what I immediately thought of was the setting for 00 Gundam. In this world, all the major countries have access to "Solar Elevators", which are towers that extend past the atmosphere and have solar panels miles in length, to collect energy. The solution for these countries was to focus on single units rather than mass production of jets/tanks/ships. This requires the individual units to have the strength of multiple, smaller units. The amount of materials used to manufacture a single, higher output machine, far outweighs the cost of mass producing hundreds of weaker machines. This is far less wasteful. The GN drive that powers the titular mecha, Gundam Exia, has six times the output of a mass produced mecha, the Union Flag. Incidentally, these GN drives are also known as solar reactors or furnaces. Individual units also have the capacity for one on one combat rather than large scale battles which leads to quicker conflict resolution. For another thing, who prefers a Stormtrooper to Darth Vader? At least in this show, mass-production always gives way to fine-tuned individual units. [Answer] * [Methanol](https://www.nationalreview.com/2011/12/methanol-wins-robert-zubrin/)-[powered](https://doi.org/10.1126%2Fscience.182.4119.1299) vehicles. Alternative and natural fuels can be used to power military vehicles and methanol or some other renewable biofuel that can power anything they wish to ride without having to worry about harming the environment as much as their enemies. Methanol can easily be produced with [anaerobic](http://www.whoi.edu/news-release/major-source-of-methanol-in-the-ocean-identified) bacteria and phytoplankton. * [Laser](https://en.wikipedia.org/wiki/Laser_weapon) weapons. Have [laser](https://www.globalsecurity.org/military/world/dew.htm) weapons and direct energy weapons that can mostly be powered by recharging a battery if energy-efficient enough. * You can have solar-powered drones that [act](https://en.wikipedia.org/wiki/Lethal_autonomous_weapon) [as](https://www.csis.org/analysis/dod-updating-its-decade-old-autonomous-weapons-policy-confusion-remains-widespread) [lethal autonomous weapons](https://doi.org/10.4324%2F9781315591070) being both eco-friendly while allowing them to fight fire with fire if they are battling a cyberpunk nation. ]
[Question] [ Apparently the Biology stack doesn't like theoreticals. :P I'm looking into the sci-fi trope of floating plants via some sort of equivalent of a kelp's [pneumatocysts](https://en.wikipedia.org/wiki/Pneumatocyst/), and the biggest issue to overcome seems to be that of lift gas storage. Methane is a big enough molecule that many organic substances can hold it securely, but produces little lift. Hydrogen and helium provide much more lift, but will permeate through just about anything, including [most metals, polymers and even many dielectrics](https://www.sciencedirect.com/science/article/pii/S2352179119300109). The closest thing I can find would be a naturally-produced rubber via [plant sap and ammonia](https://www.coruba.co.uk/blog/how-is-rubber-made/), but I fear that its permeability would by far outstrip the hydrogen-production ability of [hydrogen-producing algae](https://www.designnews.com/electronics-test/new-approach-derives-hydrogen-algae/127060357758771). Is there a lightweight, naturally-secreted substance that can hold helium or hydrogen more effectively than organic rubber? Note: I am past the needs of [this question](https://worldbuilding.stackexchange.com/questions/103752/could-a-microbe-plausibly-generate-lift-gas-for-manned-balloon-flight) asking about the feasibility of lift gas: science is currently trying to figure out how to ramp it up to industrial scale. Likewise, I'm not asking for the evolutionary pathway to this end product like [here](https://worldbuilding.stackexchange.com/questions/34892/evolution-of-giant-floating-mammals) and [here](https://worldbuilding.stackexchange.com/questions/96644/plausibility-of-floating-whales). Just organic substances that fit my use-case. [Answer] In general, semi-permeability is a necessary aspect of living things. Part of the definition of life is that it needs to be able to grow and metabolize things, and you can't do that without a way of getting things in and out of yourself. Even when biology does create an impermeable membrane, it tends to then take those membranes and fill them full of proteins to make holes through which the things they need can pass. Because lifting gasses like H2 and He are small, symmetrical, and non-polar they can pass through pretty much any protein bypassing the lock and key mechanism that proteins use to filter larger organic compounds. That said, sometimes life secretes things that are not alive such a mucus, hair, venom, and silk, but these things also tend to be made largely out of proteins (turns out you use what you know, and life KNOWS proteins). Your best bet for an organic zeppelin will probably involve resin. Unlike most other biological secretions, natural resin is designed to create a continuously impermeable polymer which is designed to protect plants from wounds by keeping things out; so, your float bladder could be coated with something similar to resin to prevent the escape of gases. There is also the question of how much hydrogen can this organism actually get from water. 1 gram of hydrogen has a volume of 11.12 liters at STP. Since water is about 11% hydrogen by mass, this means that, by splitting a single millilitre of water you get about 1.2 liters of hydrogen which creates about 2.4 grams of lift. This means that your floating flora or fauna will be able to easily adjust its altitudes once neutrally buoyant, but filling up from empty will probably take landing in a body of water. It will also be able to do some re-inflation using it's own stored body water, but will still need to regularly land for more water. [Answer] Actual gas cells in actual airships were made from the outer membrane of the intestines of cattle. Lifting gas is held in balloons or gas cells at a pressure only very slightly above the presure of the surrounding air. There is very very little pressure differential pushing it to escape. *Any* kind of barrier will work, especially if made airtight, for example by waxing. In real historical airships, the gas cells were made of [goldbeater's skin](https://en.wikipedia.org/wiki/Goldbeater's_skin), which is produced from the outer membrane of the intestines of cattle: > > *To manufacture goldbeater's skin, the gut of oxen (or other cattle) is soaked in a dilute solution of potassium hydroxide, washed, stretched, beaten flat and thin, and treated chemically to prevent putrefaction.* ([Wikipedia](https://en.wikipedia.org/wiki/Goldbeater%27s_skin#Manufacture)) > > > Fun factoids: * Around 1912 the Germans realized the advantages of goldbeater's skin for the construction of gas cells, and started using it enthusiastically for their Zeppelins. (It was a British monopoly before that.) A worldwide crisis of goldbeater's skin soon followed, as the amounts required for use in airships vastly outstripped the available supply: a typical small-ish WW1-era Zeppelin required about 200,000 sheets of goldbeater's skin, coming from the intestines of about 80,000 oxen. * A large Zeppelin, such as [USS *Shenandoah*](https://en.wikipedia.org/wiki/USS_Shenandoah_(ZR-1)) or the LZ 130 *Graf Zeppelin*, used about 750,000 sheets of goldbeater's skin, requiring the sacrifice of 150,000 heads of cattle. [Answer] **Let it leak out. But recapture it.** Your lift bladder contains hydrogen. Squirmy little hydrogens do leak out of the membrane. But on the outside of the bladder membrane are vascular channels which contain hydrogen-binding proteins. Escaping hydrogen is recaptured and cycles back to the lift vessel interior. A reservoir of circulation protein bound hydrogen is also handy for quickly adjusting the size of your lift bladder without wasting hydrogen by adjusting the rate of hydrogen capture / deposition. The size of your lift bladder is dynamically regulated. Some hydrogen gets away. That is OK. You can regenerate hydrogen from water to match your losses. ]
[Question] [ My ancient golden dragon has a lot of time, since he doesn't die of old age in my world, and a lot of magical constructs that will tirelessly built a defensive mountain chain for him. This chain will act as defense as well as a testament of his might. It consists of blocks stacked on each other. There don't need to be any rooms in it apart from maybe some small guard garrisons near the top. Other than that it can be solid stone blocks and as wide as need be. The wall will be 3000 km long. Earthquakes shouldn't be taken into account, wind can be a factor. Bricks should preferably be made from materials easily available. As long as it is easy to gather other materials can be used, as long as it's nothing like aerogel. Better ones can be constructed trough magic but then the "reward"/"cost" trade-off should be high enough. One construct would be able to carry 1000 kg (2200 pounds) to the top of the wall in each trip. I would like to know the height available when One side is as close to vertical as possible and the other can be sloped or when both sides are sloped. Presume that simple resources are no problem. Builder constructs created over estimated time frame should be the biggest thing to consider. *Addressing similar question* - [How quickly can I form a mountain chain?](https://worldbuilding.stackexchange.com/questions/73842/how-quickly-can-i-form-a-mountain-chain) This is focused on natural formation, I'm focused on man (construct) made formation [Answer] A quick Google search says that a high-quality brick will have a compressive strength of around 100 kg per square centimeter. A similarly quick Google search says those high-quality bricks have a density of around 0.002 kilograms per cubic centimeter. Simple math says that a brick wall 500 meters tall will be heavy enough to crush the bottom layer of bricks. In practice, I suspect that imperfections in the bricklaying, a desire for safety margins, and similar factors will limit your mountain of bricks to around 250 meters in height. Still taller than the Great Pyramid. [Answer] My search for numbers to support any conclusion to this question that included wind factors led me down a rabbit hole of interesting science. I'll try to keep the following answer as clear and concise as I can. I started with a basic question: What are the limits of a wall? After some finagling of my Google search terms, I found what must be the most authoritative source of engineering formulae I've ever had the (mis)fortune to try to understand. This report on the [Strength of Masonry Walls Under Compressive and Transverse Loads](https://www.govinfo.gov/content/pkg/GOVPUB-C13-cbd9e73eb0ff58cfe671dbd6d5b23c4d/pdf/GOVPUB-C13-cbd9e73eb0ff58cfe671dbd6d5b23c4d.pdf) was both an eye-opener and informative, but incredibly dense to the point I spent over an hour trying to understand the equations and what they were telling me. (I'd relate them here, but there's a simplification later, so you can peruse if you want.) After seeing the term "cavity wall" in that report, I decided to do some digging on what kinds of walls were out there and what their limits were. That led me to a [Study on Stress Performance and Free Brickwork Height Limit of Traditional Chinese Cavity Wall](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=15&ved=2ahUKEwjT0IL0xoHgAhUHilQKHXc1DHsQFjAOegQICRAC&url=https%3A%2F%2Fhrcak.srce.hr%2Ffile%2F277485&usg=AOvVaw18_kkxeXduhibEqvTtAJRu). This report indicated that traditional Chinese cavity walls could survive a 6.0-magnitude earthquake if they weren't more than 12.79 meters tall and they could survive a 20-meter-per-second wind if they weren't more than 7.5 meters tall. (Note: [handy tool](https://www.engineeringtoolbox.com/wind-load-d_1775.html) for calculating wind pressure.) But what about other kinds of walls, like a solid wall? Back to the drawing board. Looking for the limits of a structure, in general, led me to this question on our sister site, Physics SE: [How high can be tower or building?](https://physics.stackexchange.com/q/273260) (sic) The OP's research led them to a simple equation: $$ h = \dfrac{\sigma}{\rho g} $$ The OP did some additional research after asking the question, which produced another equation that for shapes other than a cylinder or cone, $\sigma$ is constrained by $$ \sigma \geq \dfrac{\rho g V}{S} $$ where $\rho$ is the density of the structure, $g$ is acceleration due to gravity, $V$ is the volume of the structure, and $S$ is the surface area. But wait, there's more! From comments on that question, I made my way over to [this answer](https://physics.stackexchange.com/a/44061) to a question about ice walls. There, the answerer indicated that > > [t]he most heavily solicited cross section will be the one at the very bottom, which will be supporting a compressive pressure of $\rho h g$, where $\rho$ is the density of the ice, $h$ the height of the wall, and $g$ the acceleration of gravity. > > > Comparing that resulting value to the compressive strength of the material in question will indicate at which point the wall will fail. However, s/he also noted: > > As an aside note, if you are willing to sacrifice perfectly vertical walls, having a wall with width growing as $A e^{by}$, where $y$ is vertical distance from the top of the wall, will have every cross section of it standing the exact same compressive pressure. > > > This would allow you to make the wall as high as you wanted. [Answer] Even though the footing of the [Monadnock Building](https://en.wikipedia.org/wiki/Monadnock_Building) in Chicago extends 11 feet into the street, the walls of its six foot thick base have sunk 20 inches. It's 197 feet tall. > > The Monadnock's final height was calculated to be the highest economically viable for a load-bearing wall design, requiring walls 6 feet (1.8 m) thick at the bottom and 18 inches (46 cm) thick at the top. Greater height would have required walls of such thickness that they would have reduced the rentable space too greatly. > > > I don't know what the upper limit is, but if you keep it under 200 feet, you can still even go inside it. It is reinforced with wrought iron, but that's for wind loading because it's hollow. [Answer] If you release the "one side has to be vertical" requirement and build a basically trapezoidal wall (a smooth wall with a 60 degree angle is bloody hard to climb) the weight of the top bricks will be better distributed over the lower bricks. If I take the number from mark's answer, the 500m height should be easy, replacing the safety margin with a slope. ]
[Question] [ **What single change(s) in history would cause the Dutch people to be speaking German instead of Dutch?** I understand that German and Dutch are both Germanic languages and share a common ancestry, as German has dialect continuum from the border with Poland all the way to the Netherlands. I'm looking for a change that would **prevent** the drastic, but gradual diversion that happened between the two, so that someone from Berlin could understand a Dutchman just as well as he would someone from Munster or Austria. I do know that people from different parts of Germany and Austria can have difficulties understanding each other, but overall it's still the same language. [Answer] ## The Dutch speak Dutch / the Deutsch speak Deutsch As the famous quip goes, [*a language is a dialect with an army and a navy*](https://en.wikipedia.org/wiki/A_language_is_a_dialect_with_an_army_and_navy). The historical linguistic reality is that south of the [north Germanic languages](https://en.wikipedia.org/wiki/North_Germanic_languages) and east of the [Anglo-Frisian languages](https://en.wikipedia.org/wiki/Anglo-Frisian_languages) there used to be two Germanic [dialect continua](https://en.wikipedia.org/wiki/Dialect_continuum), conventionally called [Low German](https://en.wikipedia.org/wiki/Low_German) (Plattdeutsch, German of the Flat Lands) and [High German](https://en.wikipedia.org/wiki/High_German_languages) (Hochdeutsch, German of the High Lands). Like this: [![The Ik/Ich isogloss, a.k.a. the Uerdingen line](https://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Ik-ich-Isogloss_-_Uerdinger_Lien.svg/527px-Ik-ich-Isogloss_-_Uerdinger_Lien.svg.png)](https://commons.wikimedia.org/wiki/File:Ik-ich-Isogloss_-_Uerdinger_Lien.svg) *The [Uerdingen line](https://en.wikipedia.org/wiki/Uerdingen_line) (the Ik/Ich [isogloss](https://en.wikipedia.org/wiki/Isogloss)), one of the isoglosses separating Low German (to the north and west) and High German (to the east and south). Map by [Slomox](https://commons.wikimedia.org/wiki/User:Slomox), available on Wikimedia under the CC BY-SA 3.0 Unported license.* Low German and High German differ principally in that High German dialects participated to the [second Germanic consonant shift](https://en.wikipedia.org/wiki/High_German_consonant_shift), which is the reason why in Modern German "ship" is "Schiff", "apple" is "Apfel", "out" is "aus", "two" is "Zwei", "wife" is "Weib" and "day" is "Tag". (The corresponding Dutch words, as a Low German standardized dialect, are much more similar to the English words: "schip", "appel", "uit", "twee", "wijf" and "dag".) Berlin is firmly in Low German territory: so how come that today Berliners speak a High German variety and can no longer understand their Dutch Low German close relatives? The answer is complicated, like most answers having to do with European history. The basic reasons are: * The territories which make up modern Germany and Austria were for a long time part of the [Holy Roman Empire](https://en.wikipedia.org/wiki/Holy_Roman_Empire); politically the HRE did not account for much, but the imperial bureaucracy eventually standardized on a common bureaucratese called Sächsische Kanzleisprache, Saxon Chancellery Language, a form of High German which avoids the more extreme characteristics which would have made it utterly incomprehensible and alien to Low German speakers. In time, people first became accustomed to the simple fact of life that official documents used a language similar but different from their daily speech. And then, when modern times came and education became free and compulsory, guess what common language was taught? * The territories which make up modern Germany and Austria (called "the Germanies" in the Early Modern period) have always been quite closely united culturally, whereas the Low Countries were always outside this cultural community. * And finally, around 1870 the nascent German Empire decided administratively that everybody should learn High German in school. * Yes, the famous translation of the Bible by Luther played a role, but it was a modest role. Luther's translation uses a central variety, neither too Low nor too High; it's main importance is that is strengthened the cultural links between the Germanies. ## A simple small change in history Coming back to the question, *what change in history would make the Dutch speak German*, the answer is that in a sense they actually do. Continental west Germanic has two standardized forms, one called Dutch ("Nederlands") and one called German ("Deutsch"); Dutch a standardized Low German dialect, and German is a standardized High German dialect. While I cannot imagine a "simple" change which would have resulted in only *one* standardized form of continental west Germanic, I can easily imagine a relatively simple change which would have preserved the Low Germanicity of Saxony and Brandenburg and Prussia and Pomerania: [Gustavus Adolphus](https://en.wikipedia.org/wiki/Gustavus_Adolphus_of_Sweden) does not die in the [battle of Lützen](https://en.wikipedia.org/wiki/Battle_of_L%C3%BCtzen_(1632)); instead, he continues to lead the northern Protestant side in the [Thirty Years' War](https://en.wikipedia.org/wiki/Thirty_Years%27_War) and establishes the [Corpus Evangelicorum](https://en.wikipedia.org/wiki/Corpus_Evangelicorum) as a polity separate from the mostly Catholic Empire. A political boundary between the northern and western Low Germanic dialects and the southern and eastern High Germanic dialects would have preserved the linguistic separation, which would have, in time, resulted in two standard languages. And who knows? Maybe the Dutch would have adopted the Low German standard of their Deutsch neighbors... [Answer] Well. I have little knowledge on the history of the Netherlands, but judging according to [this Wikipedia page](https://en.wikipedia.org/wiki/Netherlands#Celts,_Germanic_tribes_and_Romans_(800_BC%E2%80%93410_AD)): I think that the changes have to go back to the early middle ages: Maybe the Frisians (who were Saxons, theoretically related to both Anglo-Saxons and the inhabitants of the German region Sachsen) win the [Battle of Boarn](https://en.wikipedia.org/wiki/Battle_of_the_Boarn). If they continue to repulse the West Franks but are instead only defeated by [Otto I](https://en.wikipedia.org/wiki/Otto_I,_Holy_Roman_Emperor), who for some reason happens to be less occupied with Italy and puts the focus of the Holy Roman Empire more to the North, keeping local nobles more under control and the ties to other German peoples stronger... You may ask why it is necessary to go back so much: The [Old Dutch](https://en.wikipedia.org/wiki/Old_Dutch) is related to the Frankish languages while the [Old Saxon](https://en.wikipedia.org/wiki/Old_Saxon) is related to the modern German. It can become complicated in the ethnic chaos of the migration period (the Franks were for example were no single germanic tribe, but rather a confederation of tribes) or in the feudal anarchy of the later times, but I think it's doable with so much explanation. Of course if this is a major plot device, then you are going to need much more research. [Answer] Just to be clear, the *current* differences between Dutch and German is *far bigger* than outsiders would think at first sight. Their vocabulary shares many similarities, but a Dutch person **cannot** go to Berlin and instantly switch to German - Dutch high schoolers study German as part of its middle school curriculum, but even then they'll need to go to university or immerse themselves in the German culture before being considered fluent. You cannot literally translate a Dutch sentence into a German one without sounding like a fool. It will sound like the German version of [Dunglish](https://en.wikipedia.org/wiki/Dunglish). It's hard to pinpoint a definite change that will make the Dutch speak German since the concept of a politically unified Germany is 'relatively' recent. I'd go back far in time for that. Another problem is Belgium (the northern, Dutch-speaking part) which I presume you'll also want to speak German. Historically speaking, the Low Countries were one entity until [1648](https://en.wikipedia.org/wiki/Peace_of_M%C3%BCnster), at which point the Spanish gained possession of what would later become Belgium. That'll require some butterflying. [Answer] Just make the Netherlands be part of Germany, and they can keep speaking the exact same language, but it will be called a dialect of German. It’s no more different from “standard” German than the Scots dialect is from standard English, and if Scotland was an independent country then Scots would be a language rather than a dialect. [Answer] As you correctly point out, even among Germans there are quite some variation is the pronunciation, and Hochdeutsch is about as "fictional" language for Germans as much as ABN is for Dutch: they learn it at school, but there is nobody talking it as family learned language. I have personally heard some Dutchies (rather non conformist ones, I'd say) admitting that Dutch is nothing more than a German dialect. The only way to prevent the divergence between the two modern languages would be to force the common living between the populations and preventing the foreign influxes that moved Dutch away from German. So, to cut it short, have German kingdoms expanding in the low lands until the North sea. [Answer] If the Reformation doesn't start, and if the ruler of the Netherlands isn't seen as a foreign tyrant, the Netherlands might not revolt in the 16th century. Assume that Ferdinand I, the overlord of the Netherlands, instead of Philip II, inherits them from Charles V. Assume also that France is decisively defeated and the Ottomans stopped or even pushed back in the Balkans and Mediterranean by Charles V, and thus there are fewer wars that Ferdinand I needs to tax the Netherlands to pay for, thus lessening the chances of a Netherlands revolt. Supposed that Ferdinand I and his successors divide their time more or less evenly between their wealthy and powerful possessions in the Netherlands and in Austria/Bohemia/Hungary. Then it will be possible that the elites in both regions will start to speak an new dialect that combines features of both regional dialects. And by the time that universal schooling starts, the idea may be that the new dialect is the only proper one and that only country bumpkins would speak regional dialects and thus only the new dialect should be taught in schools. Thus the new dialect becomes the universal versions of German. This has the added advantage that it may be a much more peaceful history than ours. Perhaps millions of people will be killed in European wars from 1500-2000, but that might still total over a hundred million fewer lives lost than in our history. [Answer] Martin Luther’s translation of the bible could have been a pivotal point in history. To address a larger audience, he intentionally picked a south German dialect as opposed to his own, which would have been understandable by his contemporary Dutch. Northern Germans have, to read the Luther Bible, effectively given up their own dialect, while the Dutch have had their own translation. Luther’s attempt was a failure, since the addressed south Germans remained mostly catholic after the 30 year war. If he stuck to his own dialect, maybe the Netherlands would today border on Bavaria and Austria or would have never left the Holy Roman Empire. ]
[Question] [ Body art is an important element in this society. This art is painted on the skin and applied with magic. They are semi-permanent, only being removed as needed by other magical items. It is not mandatory to wear, but very popular and widely used by men and women. They are gender specific and applied like makeup to enhance characteristics of the individual. However, rather than just being an accessory, it is also meant to tell a story about the person and there place in the world. Common uses include: * welcoming in the seasons, a new year, or bountiful harvest * celebrations and festivities, religious holidays * wealth and prestige * accomplishments and successes, number of enemies defeated in battle or children birthed into a clan * rites of passage into adulthood, or applied to bodies representing passage into the next life. These markings are judged by their beauty and intricacy, as well as the story they tell of the individual or the concepts relevant to this culture that they symbolize. A marking may be pretty to look at, but if there is no meaning behind it, it is meaningless and wasted effort. Important clans may even have unique tattoo specific to their family, and are worn with pride to symbolive their place in the community. EDIT:The society in question is matriarchial, with clan descent traced through the female line. Women often use art to emphasize female traits, such as wisdom, strength, fertility, intuiton, intelligence, and power. Men, in contrast, use it to emphasize male traits, such as courage, bravery, physical prowess and brawn, honor, victories in battle, etc. Body art can be applied to a number of places, including face, chest, and arms. How can magical body art be used to designate and judge social status among people? What may be some complications that could come of this and how could they be avoided? [Answer] Does tattoos are used to mark a social status? Yes. [![teardrop](https://i.stack.imgur.com/5tf7N.jpg)](https://i.stack.imgur.com/5tf7N.jpg) The tear is not a sign of a sweat and dedication for hard work. Traditional Ethiopian tattoos are exactly what you are looking for, they are the letters that tells a story [![enter image description here](https://i.stack.imgur.com/7GsJT.jpg)](https://i.stack.imgur.com/7GsJT.jpg) And then you have the "tribal" tattoos, they mean nothing, have no message hidden apart from "I've chosen this from a trendy tattoos coffe book". Problems may arise when somebody use a picture used in one society without realising it meaning, like a dolphin or a lilly. Or they are tourist that have a "delivery on Monday" tattooed in foreign language. [Answer] **Māori Tattoos (Ta Moko)** The Māori are the indigenous Polynesian people of New Zealand. Although the tattoos were mainly facial, the North Auckland warriors included swirling double spirals on both buttocks, often leading down their legs until the knee. The women were not as extensively tattooed as the men. Their upper lips were outlined, usually in dark blue. The nostrils were also very finely incised. The chin moko was always the most popular, and continued to be practiced even into the 1970s. **Moko patterns and meaning** The Moko is similar to an identity card, or passport. For men, the Moko showed their rank, their status and their ferocity, or virility. The wearer's position of power and authority could be instantly recognized in his Moko. Certain other outward signs, combined with a particular Moko, could instantly define the "identity card" of a person. For example, a chief with Moko and at the same time wearing a dog cloak could be identified as a person of authority, in charge of warriors. These were undeniable signs of the "identity card". It would be considered a great insult if the person was not recognized as the chief he was, and this could lead to "utu" - vengeance. The male facial tattoo - Moko - is generally divided into eight sections : Ngakaipikirau (rank). The center forehead area Ngunga (position). Around the brows Uirere (hapu rank). The eyes and nose area Uma (first or second marriage). The temples Raurau (signature). The area under the nose Taiohou (work). The cheek area Wairua (mana). The chin Taitoto (birth status). The jaw Ancestry is indicated on each side of the face. The left side is generally (but not always, depending on the tribe) the father's side, while the right hand side indicates the mother's ancestry. Descent was a foremost requirement before a Moko could be undertaken. If one side of a person's ancestry was not of rank, that side of the face would have no Moko design. Likewise if, in the centre forehead area there is no Moko design, this means the wearer either has no rank, or has not inherited rank. Everyone else has pretty good answers generally. So yeah it can be done and to great effect. [Answer] It's not that uncommon, many groups of people choose to have tattos that represent their association with certain group: **Criminal tattoos** are a type of tattoos associated with criminals to show gang membership and record the wearer's personal history—such as their skills, specialties, accomplishments, incarceration, world view and/or means of personal expression. Tattoos are strongly empirically associated with deviance, personality disorders, and criminality. Certain tattoo designs have developed recognized coded meanings. The code systems can be quite complex and because of the nature of what they encode, the designs of criminal tattoos are not widely recognized as such to outsiders. In **Southern India**, permanent tattoos are called pachakutharathu. It was very common in south India, especially Tamil Nadu, before 1980. In northern India, permanent tattoos are called godna. Tattoos have been used as **cultural symbols** among many tribal populations, as well as the general Hindu population of India. In **military** there are often tattoos that represent if you are from air forces, marines, navy or any other specialized group. Problem could be that not everybody wants to show their social status or association to any group. Not everyone wants to have a tattoo as well. As tattoos are meant to be permanent they would divide people they couldn't just change tattoos as they want. [Answer] This is an interesting concept. Social status has been represented in cultures using a number of ways, primarily wealth. The rich would wear jewelry, expensive clothes and all the usual indicators. So, it makes sense that those in the higher echelons will have better crafted tattoos. Something to also keep in mind is color. Purple was a rare dye in Europe, so mostly only nobility could afford it. This lead to purple being "royal colours". It makes sense that certain materials and designs will be off limits to certain people, e.g. clergymen having specific markings to mark their place in the church. Something to also take into consideration is counterfeiting. Perhaps an assassin murders an ambassador, copies his henna and then impersonates him. This could prove an interesting avenue to explore. Depending on the cost of the henna, the poor may not be able to afford it, making it an impromptu sign of poverty. Criminals (or similar transgressors) may have tattoos applied to record their deeds [Answer] As a fictional example, in FarScape, the Luxan race has tattoos on their chin tenkas (tentacles) to indicate military rank. One of the protagonists, Ka D'Argo, falsely imprints the markings of a general on his chin while only a soldier, so that during capture and interrogation, his injured general would be overlooked; with D'Argo being tortured in his place. Apparently, one adds to the tattoos over time, so that a higher rank is essentially a combination of markings from lower ranks (an `OR` mask). Pretty neat actually. [![enter image description here](https://i.stack.imgur.com/V5Ikd.jpg)](https://i.stack.imgur.com/V5Ikd.jpg) [Answer] Let's break down social status into possible elements, inspired by what people told me about work by [Pierre Bordieu](https://en.wikipedia.org/wiki/Pierre_Bourdieu): **Economic Capital** What do you actually own? The quality of the skin art itself can tell something about how much you can spend on it. Less subtle, major titles to property that you want to advertise - to land, a house, a corporation - might be inscribed. *Possible complication:* If it is expected to wear ownership titels on ones sleeve, this brings about a certain transparency and expectation of transparency. Beeing silent shareholder might be illegal or frowned upon because it does not fit with the norms surrounding the skin art. **Cultural Capital** Meaning aquired knowledge and aesthetic sense. In actually exxisiting societies this is displayed by talking (or not talking) about certain subjects, the classicval noveau riche will fail this test. In skin art, cultural capital will be displayed by tasteful execution of the art and a few hints at activity and education that fits. **Role in formal Hierarchies** CEO, captain (military or mechant marine), secretary of the local chapter of the centrist party or laborer at the local cardboard box factory - each could have a symbol designed be the organization the role is held in. **Family & relationship status** Widows, married folks, preeteen kids etc. could be identified by their specific arts or lack thereof. **Social Capital** typically means whom you know and in what standing you are with them. Maybe this society develops a few types of formalized friendships that can be displayed as skin art - which would likely only happen for exceptional close or important friends. A few complications come to mind: Such a system might enforce some transparency in matters you would rather keep private, at least some of the time. I would expect things like dresscodes or the Hankie Code to persist, for people who want to disclose one spect of their life some of the time and only to those who understand the code. Or skin art symbols with several meanings are used and only insiders understand all of them. The second complication revolves around complexity - if the system hopes to describe a few of the facets above, it will be a complex language in itself. LAnguages evolve, split, etc. Don't expect everyone to be 'fluent' in all organizational, regional etc. varieites of the skin art. Expect skin art section in all dictionaries and travel guides, or in the briefings business travellers receive. Then, changes of social status will only 'count' if they are reflected in the skin art, it will seem not proper to have a strong mismatch for a long time between displayed skin art and role. How much one wears of the skin art expected of one could be a sign in itself, in several directions: Maybe not everyone can afford extensive skin art & the poor will display only the most important aspects. Or the powerful will display very little because everyone imporant knows them anyway and they don'T care about the others. Or both? [Answer] Since you say this art will be applied with magic, that opens up a lot of options that aren't available in real-life examples of cultural tattoos. You could make ones that move, sparkle, emit an aura, make a smell or sound, change with the weather or mood, or dozens of other things. This could make counterfeiting harder and allow for the markings to be a genuine status symbol. For the children example, a woman could get a magical tattoo symbolizing the number of children she has and as she has more it could automatically update. And for ones that automatically update, it would make keeping certain secrets impossible. Also I have read many stories with "soulmate tattoos". It is kind of an overdone trope, but in the right context you could use something like that. And as in other answers the more complex the tattoo the more expensive it is, the wealthier the person wearing it. Or it could be the opposite. What if everyone was born with them, and the only people who could afford to erase them were the rich and powerful. None of the other answers focused on the magical aspect, so it seemed good to point out your options in that regard. Edit: Another thought it utility tattoos. Since they are magical you could make ones that tell time, or can be used to cast a certain spell. For instance in Fullmetal Alchemist, many characters had tattoos that they used to activate a certain power (I know that was meant to be pseudo-scientific). ]
[Question] [ This is a followup to [this question](https://worldbuilding.stackexchange.com/questions/73497/can-a-city-in-a-flood-plain-be-maintained-for-centuries-if-it-is-built-on-stone) about city building on flood plains. There is a civilization that developed along the rich *varzea* flooded forests of an enormous rainforest river, larger than the Amazon. This civilization is dispersed into many tiny villages practicing seasonal [agriculture](https://worldbuilding.stackexchange.com/questions/69100/how-to-build-a-floating-farm) and fishing; almost all transport through the forest is done by boat. There are great trade centers at the crossroads where the rivers meet in the dry season; because of the 15m flood levels, these centers are built on raised mounds so they stay when the wet season turns the forest into a giant lake. The mounds are built piece by piece first by driving logs into the damp earth in a ring and filling with dirt. As cities get wealthier, they can afford to purchase and transport stone blocks from the mountain kingdom to the south. The blocks are used to form an outer ring around the city mound. The Earth inside the blocks is compacted by constant use, and occasionally filled by hammering pilings into it to support new buildings. Available building materials include the basalt blocks from the south, [*Gaudua* bamboo](https://en.wikipedia.org/wiki/Guadua) from the nearby forest, and, most commonly, timber from tall [palms](https://en.wikipedia.org/wiki/A%C3%A7a%C3%AD_palm). Other building materials that can be found in the Amazon or Congo rainforests can be assumed to be present. Bronze tools are not made locally, but can be imported for workmen, and otherwise technology is Bronze Age. Building a mound is obviously time- and resource-intensive. These cities are flourishing, but space is at a premium. The logical recourse would be to build up. My question is, **given the wetness of the foundation and available building materials, how high can buildings on these mound cities be built?** [Answer] The Dutch historically faced a similar problem and came up with a nearly identical solution: [terps](https://en.wikipedia.org/wiki/Terp). The village church would be the obvious building to build on a terp, it can typically house every person in the village (it already does this every Sunday) in case of a flood and is very sturdy (well, the ones that are still around today) to survive a storm. From my experience, I estimate that it's not uncommon for these churches to be around 30 meters (100 ft.) tall, with some well in excess of 50 meters (160 ft.). ([Your average church on a terp. image](http://static.zoom.nl/A21C3C485A02AAEBB37C3243BF9293AF-kerk-op-terp.jpg)) Something that typically happens nowadays, in order to build skyscrapers, is that buildings are built on [piles](https://en.wikipedia.org/wiki/Deep_foundation) that are driven deep into the ground for stability. However, there is some [evidence](https://en.wikipedia.org/wiki/Pile_driver#History) to show that this solution has been around for thousands of years. [Answer] [![enter image description here](https://i.stack.imgur.com/0R2sF.jpg)](https://i.stack.imgur.com/0R2sF.jpg) **Mound Builders.** I am glad this premise is back. I have been thinking about it. @Swier gets the vote for terps, which I had not heard about. But my bedtime reading lately is about the Mound Builder society, which existed in North America approximately 1000+ years ago. Above is a pic of the [Cahokia](https://en.wikipedia.org/wiki/Cahokia) Mounds site and there is the Mississippi in the background. Floodplains are nice and fertile but you need high ground when it floods. I have never read that these mounds might be anything other that analogous to to pyramids. Now it seems obvious: they are terps. The big mound (Monks Mound) is 30 meters tall. There is enough space on top to build as big of a Beowulfy longhouse lodge as your tech will allow. A good thing about this is that you do not need stone at all; you can use wood. The bad thing for your folks is that it floods deep where they live every year and the mounds took years to build. It would be a scramble to get one big enough up during one dry season. 2. **Something underneath.** Here is the last shot from the movie From Dusk to Dawn, which features a seedy Mexican bar that turns out to be loaded up with vampires. At the end of the movie the aerial view shows that the bar is the very top of a buried Aztec pyramid. Best thing in the movie. [![enter image description here](https://i.stack.imgur.com/mP94t.jpg)](https://i.stack.imgur.com/mP94t.jpg) Maybe there is something solid underneath where your folks live. Cyclopean prehuman ruins are always a favorite of mine. They can discover it when a statue of something is seen poking its head up thru the mud - on trying to retrieve it they realize it is attached. In any case - a firm spot, and your people build on top. It is not always safe to build on top of ancient ruins which extend an unknown distance into the ground, as we learn in [Conan and the Flame Knife](https://en.wikipedia.org/wiki/The_Flame_Knife) But with a solid footing of some sort they can build on stone, the ruins serving as the pilings. ]
[Question] [ If humanity discovered peaceful aliens that are truly alien, not just rubber head aliens, but alien in a way that seemingly defies the way evolution occurred on our world. Considering humans have a habit of fearing things they don't understand, mixed with the fact that fear turns to hatred in the human heart, could human culture ever accept aliens into their culture? To avoid being overly broad lets assume that the aliens are members of one of the least human species discussed on this site; The [anthills](https://worldbuilding.stackexchange.com/questions/46962/what-would-a-collective-consciousness-look-like). [Answer] I would say that pretty much any life form will eventually gain *some form* of cultural acceptance, but that whether we would want to have them around will depend on a few things. Terrible body odor, very sharp, pointy (dangerous looking) appendages which could very easily cause harm if someone were to bump into them, etc. would cause people to largely shun them, and rightly so. This is not to say that people wouldn't interact with them at all, or hate them as a species, but mingling with them would be difficult for very real reasons, not just xenophobia. Another big point is whether we would be able to communicate with them openly. A hive mind such as you describe probably wouldn't be interested in engaging any mere human drone in conversation. At that point we might deal with them at the government level, but not necessarily ever even see one in person, let alone speak to them. Accepting them culturally will also tie in with whether we trust them politically and militarily. There's always going to be crazies claiming that an alien ate their baby, or pet, that one of them tried to "probe" them, etc. But if the aliens prove trust worthy and actually engage with humanity at some level then yes, they would be accepted. Consider that hundreds of thousands of nerds such as ourselves would be super excited to meet them. [Answer] Gut reaction: no, aliens cannot become part of human culture. However, it would be possible for both cultures to merge into one shared culture. This would require time (many generations), during which there will be opponents on both sides trying to stop the process or derail it. If it does succeed, the culture will probably be 1/3rd originally human, 1/3rd originally alien and 1/3rd completely new stuff that grew out of the cross-pollination of cultures. [Answer] It depends on a variety of factors. **1) are the aliens truly peaceful?** A truly peaceful race has a lot better chance at being accepted than a warfaring race (though it should be stated that we would probably *understand* a warfaring race better, even if we wouldn't accept them per se). But what if the peace is a fragile one, and one easily able to be broken due to simple misunderstandings? A classic Far Side cartoon has a race of aliens shaped like hands and the bumpkin who they first run into pick up their header and shake him, thus dooming earth to destruction. **2) what are the differences?** are they simply made of different stuff than we, but generally configured the same with a head, 2 arms, 2 legs, and divided into different genders? (for instance a sentient race made of crystal aka diamondhead from Ben 10) The weirder and more outlandish the differences, the more difficult of a time we will have understanding and accepting them. In the original Star Trek there's a creature called the Horta which is, by all appearances a un- sentient monster that's killing the miners, but Spock gets to the root of the problem by communicating with it to their mutual benefit. **3) what are their motives?** In the Twilight Zone episode "To Serve Man" the aliens came and solved many (if not all) of mankind's problems, in order to use us as cattle. **4) Are we able to communicate with them?** any sort of peace needs to be based on mutual understanding and communication. What happens if the form of communication is one that only other animals and not humans understand? What if said communication enrages the animals they come into contact with? [Answer] **Yes, it can happen.** There were always people who said that different human cultures couldn't live together. Germans and French. Japanese and Koreans. Improved communications, easier travel, *and a common enemy* made it possible to recognize common ground. **It will change both societies.** Turkish and Arab immigrants in Western Europe have influenced music, styles of street food, etc. Same for Mexicans in the US. They also show different voting patterns than the old population. **There will be backlash.** Some people simply won't accept the change to their culture, often but not always out of ignorance. There are studies that having an immigrant co-worker makes one *less* afraid that immigrants are taking jobs away from the old population. Xenophobia is most rampant where there are few immigrants. (Of course that could be a chicken and egg problem -- people don't go where they are not welcome if they can help it.) [Answer] The very first question is: Would we even recognize them as sentient beings? Or would we just see an ordinary anthill of a previously unknown ant species? If the latter, we will only coexist peacefully as long as they don't get in our way. You wouldn't have any qualms about fighting ants entering your home and eating your food, would you? Also, would the sentient anthills recognize *us* as sentient beings? Would they be able to comprehend that a single animal, no matter how large, could be sentient? [Answer] **No, it's not possible** If we have a common enemy we can very well become allies and tolerate each other, but for accepting to share our culture they would need more than simply being sentient beings. If we can't interbred, worse, if we can't even share emotions then how are we supposed to fraternise at all? It's difficult enough to accept humans from other cultures (and usually one has to lose his own culture in order to be accepted), so I don't see it coming for non humans beings, ever. Will they be able with their bodies to enjoy our food? We probably won't like the same stuff at all! Will they be able to speak our language without vocal cords and etc.? It will be a pain to talk to them. Will they feel pain the way we do, weep the way we do? Probably nope... Again, we could live peacefully and accept each other if their presence is beneficial to us (and vice versa), and maybe even enjoy their presence, but that's it. [Answer] **Yes, It will always lead to peaceful acceptance of aliens** Before I start I want say that regardless of how much time passes, there will be always a small sect of people who resent, blame and are opposed to aliens. So 100 % acceptance is never possible, it extends not only to aliens but to acceptance of any thing. If humanity (current century) discovered peaceful aliens, I am gonna assume that aliens discovered us, and they visit us. There might be protest, hatred, even some who pray to them and lots of other people who see them in different manner. But most government officials and scientific community would understand the difference in scale of technology (at-least capable of near light speed travel), and would never opt for a animosity. It would be like bears or wolves trying to attack us because we have advanced technology, we would always kill them if we thought they posed a threat. If the aliens were to extend a olive branch, we would immediately accept it and try to learn their technology and improve our own either for creating defense in case of future attacks by aliens or for technological evolution. Regardless of the aliens appearances, as humans more than anything are cunning, (government might spin a different story to public). If after us learning to adapt their technology choose not to go to war with them. (Probably wont, in fear that they may have hidden higher technologies). With new technology, and new improvement to consumers, most humans would accepting for aliens, they might still be apprehensive of direct interaction, but most humans wont hold a grudge or distaste for them. 2-3 generations from the initial meeting, aliens might even partially integrate themselves in our societies. There would be still *racism* against them, but would gradually decrease with generations. A good real life example is *Saudi Arabia*. Regardless of its human right abuses west largely ignores it because oil. [Answer] Probably not. Just think how one human culture accepted another human culture in ou history. And think how the non-hostile citizens ended when discovered by explorers with advanced technology. Most probable scenario will be attack them and wipe them out. Then the humanity will fight each other for the new resources, see very ending of > > [Iron Sky](http://www.imdb.com/title/tt1034314/?ref_=fn_al_tt_1), especiall after the nazi fleet and Gotterdämerung are destroyed. > > > Secon option is, that we'll attack them but will not conquer them resulting in long war. May be, humanity will reach unity, but i suppose not. If humanity and some alien culture shall merge it will take a vast ammount of time and we will need third alien species strong and lethal enough to force both species to join their effort to survive. This threat must also last enough to polish our built-in "pride and prejudice". Play [Conflict FreeSpace: The Great War](https://en.wikipedia.org/wiki/Descent:_FreeSpace_%E2%80%93_The_Great_War) (US: Descent) and its sequel [FreeSpace II](https://en.wikipedia.org/wiki/FreeSpace_2). [Answer] Two factors will determine the outcome: 1. Resources. If humans and the aliens both need (or greatly desire) a resource subject to the rules of scarcity, the potential for conflict is present. 2. Pride. If our rulers decide that their interests are best advanced by conflict, there will be conflict, unless the rest of humanity responds to this by replacing their leadership. [Answer] In the future, we may have posthumans and transhumans. If people are used to transcending their biological existance and eventually uploaded minds and AI outnumber the biological humans, they may be a lot more accepting of intelligences in other forms than we imagine we can be today. It’s just a new style of hardware, well after getting past the notion that the intelligent being is not dependant on what hardware he runs on in order to be a being. Is this common or even universal among star-fairing species? The people that meet in space may be uploaded intelligences running in ultra-low-mass starships. They might get pretty far along in terms of friendship and collaboration before the subject even comes up of “Hey, what did your original phenotype look like?” [Answer] History shows that different human cultures first meet there is mutual incomprehension and misunderstanding. If hostility doesn't get in the way the different cultures start to learn about each other and make mutual adjustments in how they deal with each other. The incomprehension and misunderstanding gap between humans and aliens, in fact, any aliens would be so much bigger. Presumably the time required to develop mutual understanding and cooperation would take longer than between any two human cultures. However, the very alienness of the two cultures with respect to each other means they won't be competing for the same resources, so this reduces the likelihood of conflict. It may also provide greater incentive for them to want to understand one another and to cooperate. Part of this will be driven by the advantages of understanding and cooperating with the aliens. For example, if they arrived on Earth in gigantic twenty kilometre long starships you can be sure there is a lot about their technology we would want to learn and acquire. If for no other reason to reduce any risk and threat they represent. Ease of communication will be one of the major factors to be bridged before easy conversation can take place between members of the two species. Don't expect instant results -- unless the aliens had a lot of experience at dealing with other alien species, then they might be extremely good at bridging the gap between them and us. ]
[Question] [ **Goal:** Just imaging a Star Wars X-Wing fight, and you've got the idea. However, I want to know whether something like that is possible without tons of metaphysical hand-waiving and 'just because'. **What I've figured out so far:** * Sound can be an auxillary computer program to help the pilot process information when he's too busy looking at the radar / sensor read-outs (i.e. the computer creates sound effects according to what the sensors say, kind of like the parking help in cars nowadays). * You could perhaps make use of that technique to make otherwise invisible weapons fire visible (i.e. creating a projection on the screen of the trajectory). * Lasers are out. For one, I want a fight where the opponent has to come within a humanly visible range when they want to make effective use of their weaponry. [This question](https://worldbuilding.stackexchange.com/questions/32549/attenuation-of-a-laser-in-space) gives a ball-park figure that nowadays, a 300km distance is easily within reach of a weapons-grade laser. For another, lasers are instantaneous at such short distances. Even when using the computer-assisted screen rendering, it would look like a solid line from start to end that briefly blinks into existence (= undesired visiual effect, not to mention whether it is even possible to detect a laser not targeted directly at oneself). For another, I do want my pilots to have some warning that they are being attacked *before* they have a nice coin- or football- or ship-sized hole in their ship. **Question** Is there a kind of physically possible weapon that could satisfy my requirements: * detectable by sensory equipment before impact * flies at a speed where human reaction time can save one's bacon from a distance of 1km * does not have any intelligence capability (i. e. no heat-seeking missiles) * can be mounted on single-person space fighters * can actually cripply or destroy another single-person space fighter within a couple of shots Could something as mundane as bullets satisfy the requirements? What about the recoil? **Bonus Questions** Is there a shielding possibility that doesn't involve sacrificing heavy armor plates? Why the frag did my space fighting race not go for lasers in the first place? [Answer] **[JordiVilaplana's answer](https://worldbuilding.stackexchange.com/a/39325/13637) about plasma is flawless, but I would like to extend it some more.** --- In addition to **high speed plasma**, two I can imagine two other kinds of space weapons that fulfill your criteria: **Railgun:** A [railgun](https://en.wikipedia.org/wiki/Railgun) uses an electromagnetic system to accelerate a piece of metal (preferably something quite heavy and durable like tungsten) to very high speeds (from a few thousand km/h to relativistic speeds - *in your case the lower the better*), and during this acceleration the piece of metal gets heated to an enormous temperature, so it's *shining hot*. I think bolts of shining hot metal would very much like blaster rounds from Star Wars. **Regular guns with tracer ammo:** [![tracer ammo at work](https://i.stack.imgur.com/Ne9At.jpg)](https://i.stack.imgur.com/Ne9At.jpg) (You might [watch a video](https://youtu.be/iwCFMh2IBkM?t=64) for better understanding. **Edit:** Here is a [better video](https://www.youtube.com/watch?v=yYQlYocoFzo) thanks to @AndyD273) [Tracer ammunition](https://en.wikipedia.org/wiki/Tracer_ammunition) are bullets or cannon caliber projectiles that are built with a small pyrotechnic charge in their base. They are fired from regular guns and built to leave cartoon-like light traces mid-air. Bonus: why would you use tracer ammo? To ease targeting. You see space is big - I mean really big - and your target is relatively small. If you want to hit it from a km or so with a round that only goes with like 6-800 m/s, you should fire plenty of them and you should be able to track their general trajectory. --- **On shield technology:** I would vote for an SF-solution in this case, namely nanotechnology. With nanotechnology, you can (theoretically) create a diamond-firm layer of nanobots around your vehicle (even a transparent one), which can repair itself as long as you can provide "shield-energy" and replacement nanobots. --- **Why not lasers:** The short answer is that no matter what sf told us lasers suck at space fights. Lasers are electromagnetic radiation, so they lose energy according to [the inverse square law](https://en.wikipedia.org/wiki/Inverse-square_law). which means a laser which is deadly from 100 meter is only a joke from 200m and can barely be seen from 2km, while a physical projectile which causes the most harm using kinetic energy will practically lose no energy with the trip it does. [Answer] **PLASMA CANNONS** Which are, actually, the technology behind the Star Wars blasters. I think it fits all of your requirements: * It is easily detectable due to its "bullet's" high thermal signature. * It can fly at whichever speed you want, even a 9mm gun's bullet will give you about 1s until it hits you if fired at 1km. But you have to see it coming and remember: the faster, the better. * A plasma blast is like a bullet, you fire it in straight line, it has no guidance system. * If technology is advanced and miniaturized enough, you can even build hand guns. * It depends not only on the cannon, but on the target's defenses. Shoot 1oz of carbon plasma to a 1m thick steel shield and you will do almost nothing. Shoot 1lb of iron plasma to a rabbit and you will delete it from existence. Unfortunately, a plasma blast is not like a bullet or a slingshooted pebble, it's not just its kinetic energy what you must worry about. A plasma blast is a bunch of concentrated and ionized high temperature matter, so it can melt your starfighter's hull and make some electromagnetic disorders. Heavy armor plates would be effective against small blasts, but they can still get heat up if hit by many blasts, so I would add two improvements: * **EM shields**: A strong enough electromagnetic field around the space fighter should be able to deflect the plasma blasts. * **Internal Heat Cycle System**: In space there is no air that can cool down your ship, but you need to spread the heat in the hit area to minimize its effects. Place a pipeline of cooling fluid through your hull. For sure a plasma blast requires more energy than a laser beam, but it is much more effective. Maybe your space armies began using laser weapons, and maybe they ended up with fancy mirror hull spaceships. Then some genius tried to fire a plasma blast to a spaceship and earned much more than 7 years of bad luck as the ship's mirror hull gained a not-so-fancy hole. [Answer] For a primer on space combat and weaponry go read [Atomic Rocket's: Space War](http://www.projectrho.com/public_html/rocket/spacewarintro.php) and the follow-up materials on the weaponry. In fact, you should do that before you read any more of my answer. A quick summary of the science is: 1. Fighters are unrealistic 2. Stealth is unrealistic 3. Shields are unrealistic 4. Armor is not practical 5. Weapons all come from 2 basic forms (directed energy or projectile) with lots of variety. I am going to challenge you on your constraints (e.g. no lasers). I think there could be a way to get what you want and keep those in. ## On Weapons There will be two main categories of weapons, directed energy weapons (this includes lasers) and projectile (this includes guns, missiles, and anything else that is not a directed energy weapon). ### Lasers Most of what I have to say about lasers applies equally well to other types of directed energy weapons (e.g. particle beams of various types). Forget everything you've seen in SciFi about space lasers. The most effective laser is one that has lots of power and a large primary mirror to focus the beam at a distance. So a Traveler RPG type "spinal mounted" laser with two pop-up turrets (one on each side of the ship) might be the way this is accomplished. This gives you 1 lasing cavity with two apertures. One can be doing target tracking while the other handles the shooting. The "spinal mount" might be a Free Electron Laser (FEL) so that you can tune the laser to any wavelength (e.g. for beam reasons, this will probably be X-Ray). You might get an effective kill shot on a ship of the same size all the way out to 1 light-minute distance (11 million miles or 18 million km). The beam travels at the speed of light (or for particle beams, close enough that you'd have a tough time telling the difference). The targeting is only as good as the physics allows. Meaning at 1 light minute distance, your target has 2 minutes to get out of the way of your incoming fire. ### Projectile Projectiles actually covers a couple of different groupings. Weapons with propulsion and guidance and those without. You might call weapons with low thrust but high $\Delta V$ torpedoes and weapons with high thrust but low $\Delta V$ missiles. Both would require guidance. To ensure a near miss would still kill the target, most of these will include a nuclear warhead. Note a 1 km miss with a nuclear warhead means no damage to the target. You might even miss by 100 m and not inflict significant damage (depending upon warhead size). An alternative to projectiles with propulsion and guidance would be completely dumb projectiles. All of these (chemical powered ones, gauss/coil guns, rail guns, gas guns, etc.) might be classified as "guns". The problem with these is that they're really only good for close range. Against a maneuvering foe at a 1 light-minute range you have almost no ability to hit a target with them - no matter how good your computer targeting is. ## An alternative to fighters The Atomic Rocket's site states that fighters don't make sense. The pilot actually significantly reduces the survivability of the platform. However, the concept of fighters still makes sense: project weapons into locations too dangerous for your big space cruiser. So they use the idea of a Kinetic Kill Vehicle Bus. It's a "missile bus" that drives the passenger missiles into an engagement envelope so that the missile's on board propulsion and guidance can complete the intercept of the enemy ship. * It's possible the KKV bus uses a low thrust high $\Delta V$ engine while the missiles provide a high thrust, low $\Delta V$ engine for the terminal maneuvers. * It's possible the KKV bus provides extra computing power and penetration aids to distract your target's defensive systems. * It's possible the KKV bus provides telemetry and recon information back to the mother ship. Which makes it valuable in the battle even after it flies past the target ship. * It's possible that the KKV bus may also attempt a target intercept if the target is in the KKV bus engagement envelope. Regardless of what you put on it, the KKV bus is on a one-way journey. The energy costs of getting it to return would be too high. If you read the [Honor Harrington books](https://en.wikipedia.org/wiki/Honor_Harrington), this would be very similar to the ["Apollo"](http://honorverse.wikia.com/wiki/Manticoran_Missile_Types#Apollo) which they launch with their missile salvos as a control node. ### Some advantages A KKV bus has several advantages over "space fighters" and shares all the advantages of a manned "space fighters". The first is that they can maneuver at significantly higher accelerations than any manned craft - possibly up to the 10,000 g accelerations. They don't need to carry any of the life support equipment to keep a human alive. Best of all, they don't need any equipment for recovery, each is expendable with all that means for performance, size, cost, etc. Using a KKV bus to deliver a MITW (multiple independently targeted weapons) instead of just launching those weapons en mass has some advantages. The first is that the vehicle can carry extra equipment to improve the performance of those missiles (sensors, penetration aids, communications, etc.). The second is that for engagements with unfavorable kinematics, the KKV bus can use different (high impulse) propulsion to provide the necessary total $\Delta V$ required for an intercept. This does not make a KKV bus a requirement for such high $\Delta V$ missions - a clever war fighter might provide his side with multi-stage missiles in which the first stage had similar high $\Delta V$ capabilities. However, the KKV bus provides a bit more flexibility than simply extending the range of the missiles. ## The engagement In space combat there are certain advantages that go along with different engagement aspect ratios. ### General A very non-exhaustive list: 1. A tail chase favors the attacker because the attacker can always turn inside the defenders turn radius. 2. A tail chase favors the defender because projectile engagements require less $\Delta V$ to hit the enemy (you can leave mines in your opponents path). 3. Head on engagements favor directed energy weapons over projectile (it's difficult for projectile weapons to successfully intercept). ### Directed Energy vs. Projectile The laser ship (directed energy) will try to get close enough to the projectile ship so that their laser can get a kill and so that the targeting light-speed delay is short enough that the laser can hit the other ship before it moves. While the enemy fires missiles, the beam will be tasked with shooting any missile which looks like it is within an effective engagement envelope. Priority will be given to hitting the KKV bus **before** it launches its payload of missiles. One turret will be acquiring a new target while the other turret is firing. As soon as the current target is destroyed, the beam will switch turrets and the roles will reverse. The projectile ship (kinetic energy) will try to stay outside of the laser ship's effective range. They'll fire a barrage of KKV buses at the laser ship. They will try to saturate the laser ship's defenses. A laser ship will be able to fire more shots than a projectile ship so the projectile ship needs to complete the defense saturation as quickly as possible. After an engagement the projectile ship will need to restock its inventories. ## Weapons Visible to Human Crew Rather than making the weapons visible (especially at the range of 11 million miles!), what the human crew might be seeing is their defensive computers projection of the enemy's aim point. Alternatively, if the enemy ship is directly firing projectiles or missiles are approaching you, then your defensive systems will definitely be tracking those objects and providing the human crew with probable trajectories. For projectiles with propulsion, the result will be a 3-dimensional shape representing the incoming ordinances propulsive capabilities (this is sometimes called a basket but it is usually not basket shaped). [CJ Cherryh provides an excellent treatment of craft and weapon probable locations based upon latest data, known hardware capabilities, and light speed delays](https://en.wikipedia.org/wiki/Alliance%E2%80%93Union_universe) If the enemy is firing directed energy weapons, you obviously won't see much of the beam unless it hits you, but it is possible that if your sensors are good enough, they could detect the passage of a powerful laser weapon based upon reflections from dust and gas. The computer could provide that feedback to the crew too. The crew would have up to minutes to respond to the threats. ## Summary Basically, instead of making the weapons visible to a human's naked eye, the combat information system is overlaying all of its information on the map/screen and providing the human crew with information about probable trajectories, laser misses, aim points, etc. If your enemy is pointing a multi-gigawatt FEL laser at you and their probable aim point is at the bridge, it would give the crew of the ship, the same feeling as if they saw incoming tracer rounds from that same ship. [Answer] As you mentionned, after shooting any projectile you will have to get a recoil. To avoid that you could have your projectiles accelerate by themselves (like rockets). A shot would consist in releasing the projectile and waiting for it to accelerate toward its target, which could take a few seconds and give to the pilot some time to avoid the shot if his ship is nimble enough. Due to the increasing speed of the projectile it would be difficult to anticipate all the parameters and shoot a target at an unusual range. This system could work for any kind of projectile, as long as you can make rocket thrusters of the right size. [Answer] I would envision typical sci-fi "blaster-like" energy weapons as producing unstable damaging particle blasts that decay over time. This decay produces low amounts of non-ionizing radiation as a byproduct, up to and including visible spectrum. The amount of radiation from the particle decay is far too weak to cause significant damage. Over time (and therefore distance), so much of the particle blast has decayed into low-energy photons that it becomes no longer viable. This explains their limited effective range. The initial discharge from a blaster produces a distinct burst of radio waves. All military ships carry readily available equipment that determines the location of the RF burst, translating it into audible noise for the crew or pilot. Different types of blasters have different RF signatures (and therefore produce different noise in the translation software) allowing crew and pilots to determine if the source is hostile or friendly. [Answer] Well, I was with this same question in mind, but I searched for videos about star wars and I found this one: <https://www.youtube.com/watch?v=1po2ut5zi0Y> As it says, a "blaster" (real term would be a "Plasma Railgun") could eject an plasma "bubble" to 200 km/s and reach tempetures hotter than the sun. He explains with more details, you should check it out. ]