Elizabeth Kolbert writes in “The Sixth Extinction” that 100 million years from now everything we see will be compressed to the thickness of a cigarette paper. Earth is 4.5 billion years old. A billion is a thousand million, so there are ten cycles of 100 million years in each billion years, or forty since the Earth’s beginning. And we have another forty cycles left before the sun goes nova. That’s eighty times something could rise and fall and be squashed as thin as a cigarette paper. Maybe we’re the first to get this far, but how can you be sure?