No universe, no Earth, no humans. So if you want to develop a timeline of human evolution, it starts with the universe. And scientists know that it all started 13.8 billion years ago because they measured how fast space is expanding. That’s thanks to astronomer Edwin Hubble, who discovered a century ago that distant galaxies are moving away from us. (Probably a good thing they aren’t moving toward us and with Earth as the bullseye.) By running the film backward, so to speak,