W It must have happened before

 

If you go far enough, you’ll get back home

The idea of Level 1 parallel universes basically says that space is so big that the rules of probability imply that surely, somewhere else out there, are other planets exactly like Earth. In fact, an infinite universe would have infinitely many planets, and on some of them, the events that play out would be virtually identical to those on our own Earth

We don’t see these other universes because our cosmic vision is limited by the speed of light — the ultimate speed limit. Light started traveling at the moment of the big bang, about 14 billion years ago, and so we can’t see any further than about 14 billion light-years (a bit farther, since space is expanding). This volume of space is called the Hubble volume and represents our observable universe.

The existence of Level 1 parallel universes depends on two assumptions:

• The universe is infinite (or virtually so).

• Within an infinite universe, every single possible configuration of particles in a Hubble volume takes place multiple times.