> Having a tiny fraction of humanity on a different world, which is entirely dependent on shipments from home for the foreseeable future, is an irrelevance to the problems we're facing on Earth.
I agree. Which is why I think the fanciful idea of a Mars colony is nothing more than a hand-wavy distraction at this point, designed to propagandize a billionaire's other projects to gullible sci-fi enthusiasts.
Having a tiny fraction of humanity on a different world, which is entirely dependent on shipments from home for the foreseeable future, is an irrelevance to the problems we're facing on Earth.
> Moreover, the whole justification for colonizing Mars is supposed to be if a disaster struck Earth. So in a sense you have moved all of humanity to Mars if humans on Earth go extinct.
Sure, but those disasters are entirely unrelated to any of the problems we're facing right now. Nobody is claiming Mars is a refuge from, say, man-made climate change. It could be a refuge from, say, a gamma-ray burst crossing Earth's orbit in half a million years.