Do We Live In a Multiverse?

Astrophysicist Paul Sutter explains

Transcript

00:00Do we live in a multiverse? No. I mean, yes. I mean, uh, maybe. Look, it's kind of complicated

00:11and we're not exactly sure. I'm Paul Sutter and this is Paul Explains, the show where I,

00:18you know, explain. First, let's define what we mean by multiverse. We have the universe,

00:26which is by definition all the things. It's all the stars, all the planets, all the people

00:33and aliens. It's all the bits of fluff just floating around in the void. It is the entire

00:39thing. It's all the stuff. So in one sense, there's no such thing as the multiverse because

00:46the universe is already defined to be all the things. But maybe there are patches of the

00:55universe that have different physics or different realities. They have different forces or different

01:03particles. And this is what we refer to as the multiverse. Now, do we live in a multiverse?

01:12Maybe, maybe not. One of the most promising ways physically to get a multiverse is through

01:21something called inflation. Inflation is our model of one of the earliest and most momentous

01:29events in the history of the universe. In the inflation model, when our universe was barely

01:36getting started, when it was a billionth of a billionth of a billionth of a billionth of a

01:41second old, it became very large. It went from the size of, say, an atomic nucleus to around the size

01:49of a baseball. And this event has the possibility of never ending, of inflation of the universe just

01:59always getting bigger and bigger and bigger all the time. And what we call the universe is just one

02:07small pocket of that much larger volume of the true universe. And in our little pocket, when inflation

02:18ended for us, we ended up with one set of physics and one set of forces and one set of particles and one set of

02:25reality. But past the confines of our little bubble, the greater universe is still going, still doing its

02:34thing, still inflating, and different pieces of it pinch off on their own with their own physics.

02:40Now, it's possible that inflation can lead to a multiverse. We don't know if inflation really

02:50happened. We suspect it did, but we're not entirely sure. And we're not sure if inflation demands the

02:57existence of a multiverse. It's possible that inflation just happened once and did it throughout

03:04the universe and that this is it. Or not. We've looked for evidence for multiverse and have come

03:12up short. Like if another neighboring universe intersects with the bubble of our universe, we might

03:19be able to see signals of that. And we haven't seen anything. That doesn't rule it out yet, but there's

03:26no conclusive evidence for it. Even if there were a multiverse, we would never ever be able to access

03:34any of those other universes. We won't be able to visit them. They wouldn't be able to visit us. For all

03:40intents and purposes, they wouldn't exist. So when it comes to multiverse, whether it exists or not, just

03:48just focus on our universe because really, it's the only one we got.

03:56you