Multiverse (noun, “MUHL-tee-vers”)
This is the idea that our universe isn’t the only one out there. Instead, it’s one of many, many universes. How many? No one knows. There could be lots.
In one version of the multiverse, a lot of universes might have formed right after the Big Bang, when our universe expanded very, very quickly. If that expansion continued outside our universe, there might be other universes, ones that don’t have anything to do with us. These are called “bubble universes.”
In another version of the multiverse, other universes have everything to do with ours. In this “many worlds” idea, each universe would be an alternate version of our own reality. In this universe, you wore sneakers today. In another, you might have worn sandals. In a third, you might not exist.
The bubble universe and many worlds idea are only two options. There are other ways to make multiverses. But not all scientists agree that multiverses are real. After all, no one has ever found another universe other than our own. There’s not even consensus on how to find them. One way might be to look at gravity. Other universes might be large, with a lot of gravity. That gravity could pull on our universe. By measuring that pull, it could be possible for scientists to detect a multiverse. But so far, there is no evidence.
In a sentence
In some theories of the multiverse, every time you decide to wear a red shirt instead of a blue one, there’s another world in which you made the opposite decision.
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