[JakubTyl (OP)]

I am interested if human could live (not with modern technology), in different planetary environment, for example planet with two moons or closer/further from the earth. Lets assume that humans were able to somehow got in to that environment or they evolved somehow the way they are in different environment. I am asking how much that environment could be different from the one we have and what would surely not lead to human evolution. I mean, some environmental changes would surely change the environment that much that human could not ever evolve there, but there must be some environmental changes we could still stand.
Would our environment become human friendly if there would be no moon, multiple moons, or we would be closer, further from the sun (not too much)?
Our planet would be smaller or larger?
What effect has existence of other planets in our solar system on our planet? Would be our planet different if it would be the only planet in the solar system? or some different number of planets then we have now?
Would be life possible if some neighbouring planets were much closer to our planet?
Would be human life possible if there would be different size of sun (assume that our planet would be closer/if smaller and further/if larger)?
And what about multiple suns? Could planet with human life take multiple suns in some proper distance and placement?

[chris]

Bump! I discovered this lonely, but thought-provoking question lurking somewhere in the sitemap;

I thought it would make for a nice debate du jour...

[Kryptid]

Assuming that you could transport humans to a different planet which had all of the necessary food and water, the planet itself could indeed be fairly different from Earth and let humans survive. Humans that go down in the deep ocean are subject to pressures much greater than at the surface and can survive them pretty well (up to a limit). I recall that a group of people were spending time at ten times atmospheric pressure in some underwater habitat somewhere (and were killed when explosive decompression caused the pressure to suddenly drop to one atmosphere). Humans can survive low pressures as well, just so long as there is enough oxygen in the atmosphere. The lower limit should be somewhere around 20% of normal Earth surface pressure, since an atmosphere composed of 100% oxygen at that pressure would have a similar oxygen content to our current atmosphere.

We don't directly require the Moon to live, but some organisms do. Assuming that this new planet already had life which was adapted to a world without a satellite, we'd probably be just fine there ourselves. I may come back and add more later when I have more time.

[evan_au]

Some astronomers believe that plate tectonics is necessary for life on Earth. It recycles material from the land into the sea and back to the land via volcanoes.

If the Moon had not formed, taking much of Earth's crust with it, Earth's crust may have been too thick to support plate tectonics.

Mars appears to have a crust that was too thick to support plate tectonics (but it was also too light to hold onto a thick atmosphere).

See: https://en.wikipedia.org/wiki/Theia_(planet) [Links inactive - To make links active and clickable, login or click here to register]

[Bill S]

Lets assume that humans were able to somehow got in to that environment or they evolved somehow the way they are in different environment.

There appear to be two quite different scenarios here. 

In the first; humans are transported to a new environment, in which case their survival would be linked to the relationship between their native environment and the new one.  They would probably soon discover if they could survive.

In the second, “humanoid” beings have evolved in this environment, so they must be able to survive and thrive in it.

[jeffreyH]

Planet atmospheres are not directly related to the size of body they adhere to. Mars has a very thin arms sphere whereas other bodies in the solar system that are smaller than mars have more appreciable atmospheres.
http://www2.astro.psu.edu/users/rbc/a1/lec29n.html [Links inactive - To make links active and clickable, login or click here to register]

[jeffreyH]

Mainly it appears to be a matter of luck as to whether or not a planet would be habitable to humans. Whether or not it is in the goldilocks zone. What the initial atmospheric composition was. How the particular solar system has acted to modify the atmosphere.