I don't think you fully appreciate just how difficult space travel is, especially the kind of space travel where you found a colony that will sustain itself after the Earth is hit by an asteroid. The required scale of technology/economy comfortably puts it in "at least several centuries from now, if we're incredibly lucky and/or devoted".

In this regard, the comment about CO2 is actually much more pertinent than it seems at first. If we manage to screw up the climate in this century (which seems very likely these days), inundating every coastal cities in the world, "sustainable space colony" will have to wait a bit longer. Much longer. If you're worried that an asteroid might hit us 500 years from now, you might want to rethink your priority.

Advancing chemical rockets now is important, but compared to the scale of space colony, it feels somewhat like producing better vacuum tubes to make sure (say) the US is the first to create strong AI. Any sane 50s US leader would have understood that "trying not to have a nuclear war with Soviet" is a much more important goal anyway: you can't fund AI research if your country is a radioactive wasteland.

> The required scale of technology/economy comfortably puts it in "at least several centuries from now, if we're incredibly lucky and/or devoted".

We went from not flying anything heavier than air to going to the Moon in 66 years. If we really really wanted to, we could go to Mars in thirty. This is a problem of priorities, not technologies (although the technological problems are real, they are not insurmountable).

While true, it is also not as direct of a threat. CO2 is affecting us now, whereas asteroids, etc., are (thankfully) only possibilities. Serious ones, to be certain, but not immediately threatening.

CO2 is a direct and immediate threat.

Humans as a species will survive CO2, though, whereas asteroids conceivably can go from "not immediately threatening" to "Earth will be destroyed in a few years" without warning.

> not immediately threatening" to "Earth will be destroyed in a few years" without warning.

Unless the lead time is 50-100 years, years might as well be tomorrow, it's going to kill us all either way. Even that might be stretching it.

> Humans as a species will survive CO2

Maybe, personally I believe humans will cause their own extinction. I'm just not sure yet if we're going to take all life with us or not. Dealing with CO2 is a toss up between making the planet uninhabitable or completely inhospitable to life.

What study has indicated CO2 might make the planet completely inhospitable to life?

"... few days"

I went with years there to be safe as I'm uncertain about what the detection levels are like for planet-killer sized asteroids. I know we discover house-sized ones passing between us and the Moon after they whiz by.

No detection. Who's looking? Many are found by amateurs, as you say, after they whiz by.

CO2 is a very real threat and we should be doing more about it. That said, the threat is neither direct nor immediate.