# Tag Info

## Hot answers tagged moons

98

Immunity to Disease Your lunar citizens live in a perfect environment! They have all the food they need, they have recycling that, frankly, removes most bacteria from their lives. Atmosphere is constantly recycled, which includes scrubbing. Water, too, is recycled, scrubbed and clean for use. In fact, the colony has been disease-free for, well... ...

84

Given Sweden has a latitude of 60° N and south Africa of a bit over 30° S, you can never see one from the other no matter how high one is and no matter how small the planet is (as long as it still is big enough to allow you to neglect the distance between your eyes and the surface). The Sweden simply rises further away in the hemisphere invisible from South ...

53

There is no atmospheric height any object of any size can be, perpendicular to the location of Sweden, that could be seen by anyone standing anywhere in South Africa. I don't need math to prove this. Just take out a piece of paper, draw a circle, and use a ruler to start drawing lines. That combination cannot be done. Alternatively, visit maps.google.com,...

48

Materials exposed to vacuum for extended periods often become brittle and/or literally lose mass over time. Outgassing, cold-welding, decomposition of alloys back to their constituent materials, coronal arcing due to ionization from exposure to ionizing radiation, acceleration of outgassing and decomposition again due to ionizing radiation exposure are all ...

41

A non-obvious loss area would be Genetic diversity. After several thousand years of carefully controlled plant growth, and several thousand years of inbreeding, unless care was taken to maintain genetic diversity in plants and animals (including humans), a single mutated bacteria could take out a key component of the self sustaining ecosystem.

28

Volatiles like hydrogen, carbon, nitrogen, and noble gases. These elements are necessary for life and useful for industrial processes, while being difficult to replenish. Hydrogen, carbon, and even nitrogen can be used as rocket propellant which will consume these elements without any chance of recycling. They are also liable to loss through slow leakage. It ...

24

The will to live Survival on a lunar colony is a lot harder than here on planet earth. You are tired at the end-of-day, and the time to have and raise kids is just a little more than you can take. Population decreases until there is just not enough left for the colony to be viable/

16

Computer chips. Computer chips are an interesting case. You can pack millions of high-end microchips into a single 1-ton storage container. Conceivably you could store enough to provide spares and replacements for thousands of years of maintenance in a fairly small space. Yet to actually produce more takes a huge industrial base. Chip fabs are vast ...

15

Light and thus Energy. This probably will happen as a result of natural phenomena involving Earth's magnetic cycles. The current dust storms on the moon - referred to as "Moon Dust Fountains" that occur as a result of electrostatic levitation of tiny particles of regolith (as a consequence of being stripped of electrons by the solar wind), are due to get ...

12

Something we didn't know we needed, because we always had it. The people who built this colony were not fools. They would know plants need boron and humans need sodium. There would be provisions to tap lunar water and generate building materials and oxygen from regolith. Carbon is precious and would be carefully conserved. There will not be holes in ...

11

Electronics Electronics manufacture require a vast and complex industrial base. There is no way the Moon Base has what it takes. They have a large store of spare parts, and things don't break all that often, but there is a limit. Some things can be replaced in non-electronic ways. Solar panels is probably the hardest to replace. It might be possible to ...

10

The short version is that it depends entirely on the manner in which the moon disintegrates, or more specifically the energy thus imparted on the resultant fragments. I'm assuming here that the mass remains roughly the same, so nothing like matter-antimatter annihilation. I'm also assuming that the moon is large enough to begin with to become roughly ...

9

Let's establish some notation: The star is labelled $S$, the giant planet is $P$ and the moon is $M$. The diameter of the star is $d_S$, the diameter of the planet is $d_P$ and the diameter of the moon is $d_M$. The radius of the orbit of the planet is $r_P$ and the radius of the orbit of the moon is $r_M$. At a distance equal to the radius $r_M$ of the ...

7

Your initial configuration, with the two moons orbiting perfectly out of phase, is not a stable one. Over time their orbits will change very slightly as the result of various random effects, such as asteroid strikes, which will not affect both moons identically. The moons will tug on each other in surprising ways. Just read up on the three body problem and ...

7

It's not about what gets out, but what gets in. To survive that long, mankind will make many many trips out into the Lunar landscape to gather and process lunar regolith so that they can replace lost air and water supplies. However, regolith is extremely hazardous to human life. It's highly abrasive, nearly impossible to filter, and it builds up in the ...

7

Phosphorus Always a good candidate when you need an elemental bottleneck to life, phosphorus is needed in minimal quantities, but by pretty much all known life. A closed ecosystem will recycle it pretty well, as long as there is no population growth, so the lunar colony could have been fine with small reserves to compensate the inevitable losses that ...

6

Use moon E for interplanetary craft. It is likely the interplanetary craft don't descend into the gravity well at all, but shuttle craft come up and meet them to refuel and exchange the personal and cargo. These interplanetary ships contain the life support equipment for long voyages, which is essentially useless mass when in the giant's gravity well, and ...

6

This answer is fundamentally flawed in that it assumes that the 'horizon' formula is valid for any value of h. Unfortunately, this is simply not true, and as the image shows, it is only a valid approximation when h is much less than RE (RE >> h) If you can see something depends on how high you are, and how high is what you look at: Africa is ...

4

Something similar it is thought to be happened when our Moon formed, as a consequence of the impact of the proto-Earth with a planet the size of Mars, called Theia. There are 3 paths that the fragments can follow: fall on the planet, bombarding it leave the local system, if they have enough velocity to escape the planet gravity well coalesce back into ...

3

Genetic Diversity With the relatively small breeding population, over tens or hundreds of generations minor genetic defects could be interbred into major genetic defects. It's up to the author to determine what kinds of defects are being introduced. Based on those choices, the colony may be in danger of dying out from a single bad virus or defect induced ...

3

There are many things and I would like to list and explain everyone of them (as far as my knowledge goes) Bone density loss. In space astronauts have been found to lose bone density despite intense workout sessions. Your people on lunar colony have been inside a dome for 1000s of years where gravity is 1/6th of what their bones have evolved for. Hence the ...

3

The one with the least gravity Gravity requires fuel to escape thus the lowest gravity requires the least amount of fuel to escape from means more fuel for the journey.

3

Using a completely comparative approach, rather than a direct calculation approach, here's my best answer: Totality of an eclipse involving the actual Sun, Earth, and Moon can last up to 7 minutes and 31 seconds. The orbital period of this moon around its planet takes about 1 1/3 as much time as it takes for the moon to orbit the Earth, so it seems ...

2

The best location for the fuel Depot is wherever most of the people and infrastructure in the gas giant system are. Without knowledge of exactly what the major propulsion system of your interplanetary spacecraft it is very difficult to make recommendations, but there are two major regimes to consider: If the delta-V potential of your spacecraft is low ...

2

Prior answers have focused on the genetic diversity of humans. We have more bacteria in our guts than cells in our bodies. There are many bacteria on our skin. Part of our immunity and well being is due to the interaction of our bodies with those bacteria. Hunter-gatherer societies have far more diversity of bacteria. Losing genetic diversity in those ...

2

Information. All this time they still used the original networked computer system. The centralized datacenter had massive redundancy, but not quite infinite self-repair. During the technological regression, the redundancies failed one by one. Even at recovery, no one wanted to learn the complex system, and there was no case for building another. I had been ...

2

The moon's surface gets very hot during the day - up to 100 degrees C, water's boiling point - and very cold during the night - -173 degrees C, far colder than any natural environment on Earth. The good news is that as long as they are protected from actually touching the surface, they could survive for quite a bit longer than you'd expect in these ...

2

They do it in steps. Very little is known about the Moon, so they need probing. The probing will consist in a small group of the most powerful mages available, wrapped in all sorts of protective spells, that will teleport to the Moon and back for longer and longer times - initially they will stay there for as little as they can, maybe less than one second. ...

1

You have three questions here. 1. How high can a geostationary Sweden be visible from South Africa? Answer: 68,100 km This is a question that humanity has pondered since we first climbed down from the trees. The other answers are correct that if two points are more than 90 degrees apart on the globe, they cannot see each other at any height (unless the ...

1

If you imagine an idealised planet with a star at an infinite distance, how much of the planet can see it? The answer is half: the star projects a cone that rests on an equatorial line perpendicular to the direction it lies in. Those standing on that equatorial line are looking along the tangent to the curve of the surface of the planet. So the basic ...

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