12600 years ago a comet wiped out all of civilization and most of living things if you want to learn more about this topic go to Joe Rogan's YouTube channel and look for the podcast with Graham Hancock

The point is that we are ready for another strike by either asteroids or comets and last time they completely destroyed civilization this time we have the technology to prevent such devastation

But just in case we can't then some people are going to live underground and that's probably what Elon Musk is working on