Originally Posted by Narzon
They're on an artificial ring using made up alien "Forerunner" technology to simulate conditions virtually identical to those on Earth. Very similar to the world in "Ringworld".
Then Soggy_Popcorn is right and wrong. He is correct that, if it were real, you should be able to see stars, and the atmosphere would not be as thick, thus producing a sky that is not as blue, and more transparent. But, they are chocking it up to the "forerunner" technology to make conditions the same as Earth, meaning that somehow the atmosphere would be as thick, and the sky would be blue, and not be able to see stars. So, I guess everyone is right, but at the same time everyone is wrong.
But this also raises a further question as to why the aliens made the conditions on the ring identical to Earth instead of identical to their home planet, unless their home planet has the same properties as Earth, which would be even less likely.
Maybe we should just stop delving into the atmospheric conditions of the ring, because it just keeps getting more and more confusing...