SF author Charles Stross crunches the numbers and explains how difficult space colonization is.
The long and the short of what I’m trying to get across is quite simply that, in the absence of technology indistinguishable from magic — magic tech that, furthermore, does things that from today’s perspective appear to play fast and loose with the laws of physics — interstellar travel for human beings is near-as-dammit a non-starter. And while I won’t rule out the possibility of such seemingly-magical technology appearing at some time in the future, the conclusion I draw as a science fiction writer is that if interstellar colonization ever happens, it will not follow the pattern of historical colonization drives that are followed by mass emigration and trade between the colonies and the old home soil.
He also looks at colonization in the solar system and comes up with a similarly gloomy outlook. Based on my back-of-the-envelope fact checking, his reasoning and conclusions look solid. The comments are long and involved, but bear Charlie out as well.
The most entertaining bit of the comment thread are the people saying that he’s wrong, not because his math is wrong or his reasoning is flawed, but because science fiction authors shouldn’t be so pessimistic and should believe whole-heartedly in the colonization of space.