Earth occupies only a very small space and a minuscule mass within the Solar System.
If the sun were considered a building, then Earth would be about the size of an apple.
This "apple" is several kilometers away from the "building".
Compared to celestial bodies, "basically nothing" is what makes up the vast majority of the universe.
Therefore, in this era, more humans are born in space cities.
Staying in space for extended periods leads to a significant loss of calcium in human bones and muscle atrophy.
But this is not an issue at all for Cybermen.
Two hundred years ago, David Klein vigorously promoted national space programs for this very reason.
Benchmark Man gene modification surgery and human cyberization technology have nearly resolved most of the issues involved with human interstellar migration.
However, space cities across different universe regions each have a completely different look.