"We are so far from being able to move a good fraction of the population anywhere else. Even if Elon Musk and other private individuals manage to start sending humans to Mars, we may be a few hundred years away from putting any sizable population there—and we have to fix Earth right now. Eventually, if we’ve been irresponsible enough to create problems in our world, moving to a new one won’t necessarily solve the problem because we might do the same thing in the future."