Just wondering, as my husband says.
Why are people afraid an asteroid or comet or anything else will mean the end of the world? Things would change a lot, but even a war everywhere on the planet with the worst weapons would not mean a stone age unless they were used everywhere and not just the countries that have them.
Progress would almost stop because there would be so few people, but computers and the internet are everywhere, and probably most of what is important would not be gone.
If only a million people survive around the world, they would probably find each other in a couple of years, and even though almost no progress would happen for a while, people could pick up where they left off as the number of people grow.
But this is just guessing. It would still be a terrible thing.