NOVA

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Narrator

We usually think of our universe as a vast nearly endless expanse, that contains every galaxy, star and adamant existence. But is it? What if our universe is just one of many? Could we live in a multiverse, one with parallel universes, containing other galaxies and possibly other earths? This isn't just the stuff of science fiction. Physicists are starting to take the multiverse idea pretty seriously. Here are four real models of what parallel universes might look like and how they could form. The Inflationary Multiverse. You know, how you learned in school, that the universe started with the big bang? Well, what if that big bang wasn't the only one, in The Inflationary Multiverse model big bangs are happening all the time. The idea is that, there's an endless sea of energy, where universes is pop up like bubbles in the ocean. Each new bubble universe, is created during a rapid period of expansion called inflation. And these other universes the physics could be strangely different. There could be universes where gravity is weak and objects seem to almost float around, or universes where electromagnetism is strikingly different. The Quilted Multiverse, in this model there's really just one universe, but it's not just big, it's truly infinite. So infinite that if you could search through the infinite space, search the infinite galaxies with infinite stars, you'd eventually find a number of planet earths, just like our own. And on some of those earths, you'd even find someone identical to you. But you aren't likely to ever meet yourself because that other you, probably lives in an unreachable patch in our infinite Cosmic Quilt. Even if you started flying through space at light speed right after the universe was born, while you could travel tens of billions of light years away, you could never escape your small local patch, in the endless quilt of space. The Quantum Multiverse. When things get really small, they get really weird. Quantum mechanics rules, the behavior of small particles, like this electron, as it moves along, where exactly is it? Quantum mechanics would say that it could be any number of places, but take a picture it's right there. But how did it decide where to go, when you took the picture? In the Quantum Multiverse hypothesis, fickle particles don't have to decide where to pose for pictures. Each of those possibilities would live in its own universe. And the crazy thing is that any time you take a picture or observe something, you split the universe. You can't see all the universes because you just live in one of the many possibilities. So as you move along your life, observing particles, people, puppies, the universe is constantly splitting and you're just traveling along, one of the many paths in The Quantum Multiverse. The Brain Multiverse. Sometimes people talk of parallel universes as alternate dimensions. We live in three spatial dimensions, front to back, side to side and down to up. Are there more dimensions though? In The Brane Multiverse, the answer is yes. Because The Brane Multiverse, comes out of a type of string theory, where our three-dimensional universe, lives on a membrane or brane for sure. That is actually embedded in 10 dimensions. But our be wouldn't be the only one. There could be other branes with other universes. It's like how a three-dimensional book, has many two dimensional pages but our multi-verse book is 10 dimensional. And our universe is on one of the many three-dimensional pages. So could we find hard evidence, that any of these four Multiverses exist? Scientists working on telescopes around the globe are searching the sky, to confirm the existence of a sort of fingerprint leftover, from just after the big bang. It's a pattern of polarized light, resulting from our universe's brief period of rapid expansion called inflation. And if inflation happened here, it could have happened elsewhere too. Implying the existence of a vast Inflationary Multiverse one with endless bubbling universes, each with its very own big bang and inside they'd probably be infinitely big, which would be evidence that The Quilted Multiverse is also possible. So do we live in a Multiverse? We may know very soon. So the next time you look up at the sky just remember that what you're seeing, may just be a patch in a bubble in an endless Multiverse. (soft music)