These are from Gerard O'Neill's book, The High Frontier, which described how such colonies could be built and outlined their engineering parameters. I first read it as a boy and it's always stuck with me.
Essentially, with the technology of the 70s he argued that it was plausible to build the "Island Three" design, a tube 8kms in diameter and about 32kms long. Each would be paired with a second such tube and both would rotate in opposite directions to create gravity. Such habitats could hold millions of people.
McKendree[2] later speculated on what might be achievable with mature carbon-based nanotechnology, expanding the possible size to 460kms diameter and 4600kms long -- almost as much surface area than Russia -- and in any basic climate configuration desired.
Essentially, with the technology of the 70s he argued that it was plausible to build the "Island Three" design, a tube 8kms in diameter and about 32kms long. Each would be paired with a second such tube and both would rotate in opposite directions to create gravity. Such habitats could hold millions of people.
McKendree[2] later speculated on what might be achievable with mature carbon-based nanotechnology, expanding the possible size to 460kms diameter and 4600kms long -- almost as much surface area than Russia -- and in any basic climate configuration desired.
[1] http://en.wikipedia.org/wiki/The_High_Frontier:_Human_Coloni...
[2] http://en.wikipedia.org/wiki/McKendree_cylinder