[philwelch]

> But I have a hard time seeing the scales he's talking about. Those colonies would not be able to hold billions of people.

It entirely depends on how many of them you build. You could also achieve much higher densities than Earth with no real loss of quality of life, since you wouldn't necessarily build massive oceans or deserts or mountains. (Though I would really love to live on an O'Neill cylinder that was laid out as an archipelago!)

[DennisP]

Also, if we get to a point where we can build them from carbon nanotubes, we could make them the size of continents.

https://en.wikipedia.org/wiki/McKendree_cylinder