"Let's move to"... time would have already run out for us centuries before reaching the technological level enough to us being able to move a significant portio

"Let's move to"... time would have already run out for us centuries before reaching the technological level enough to us being able to move a significant portion of mankind elsewhere. And far more time will take to significantly terraform (at the level of being able to stay outside any tightly closed construction) any other planet. And if we will live in a totally manufactured environment, the space itself (around Earth or Sun). Asteroids may provide the base materials for that kind of space habitats. But, again, we might have run out of time already. Survival in a world with diminishing food (because compromised agriculture or fish resources by global warming and environmental destruction) will become a priority, and the civilization may not be able to sustain a strong enough space program able to do that kind of colonizations. We must try to fix what happens here before thinking in going (in such scale, at least) elsewhere.