I enjoy your ideas, and just want to add the distinction between a catastrophic event for humanity versus an extinction event in terms of justifying space colonization. People sometimes justify our current manned space programs because the sun will boil earth's oceans in 500 million to several billion years. These people have no concept of time.

My impression so far is that a delay of 100 years in colonizing space would make virtually no difference in avoiding random human extinction events, because they happen so rarely. Catastrophes like the ones you mention might happen slightly more often, but they won't exterminate us, and having space colonies won't alleviate the problems.

Yes in the long run we need to get off this rock, but that provides zero justification for manned space exploration in the next few decades. Other justifications are needed.