Let me start:
It appears that the universe will die in a state of absolute entropy where nothing at all happens anymore. Forever. But that is a long way off. In fact, it's so many years off that if one were to assigned one atom in the universe to each year of the universe's life, we'd run out of atoms long before reaching the year of absolute entropy. I learned this just now from Wonders of the Universe on the Science channel.
Got an astonishing fact? What is it?