Do We Live In a Multiverse?
Astrophysicist Paul Sutter explains
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00:00Do we live in a multiverse?
00:04No.
00:05I mean, yes.
00:07I mean, maybe.
00:09Look, it's kind of complicated, and we're not exactly sure.
00:14I'm Paul Sutter, and this is Paul Explains, the show where I, you know, explain.
00:21First, let's define what we mean by multiverse.
00:25We have the universe, which is, by definition, all the things.
00:30It's all the stars, all the planets, all the people and aliens,
00:34it's all the bits of fluff just floating around in the void.
00:38It is the entire thing.
00:40It's all the stuff.
00:42So, in one sense, there's no such thing as the multiverse,
00:46because the universe is already defined to be all the things.
00:50But, maybe there are patches of the universe that have different physics or different realities.
01:01They have different forces or different particles.
01:04And this is what we refer to as the multiverse.
01:09Now, do we live in a multiverse?
01:12Maybe, maybe not.
01:15One of the most promising ways physically to get a multiverse is through something called inflation.
01:24Inflation is our model of one of the earliest and most momentous events in the history of the universe.
01:32In the inflation model, when our universe was barely getting started,
01:37when it was a billionth of a billionth of a billionth of a billionth of a second old,
01:43it became very large.
01:45It went from the size of, say, an atomic nucleus to around the size of a baseball.
01:51And this event has the possibility of never ending.
01:58Of inflation of the universe just always getting bigger and bigger and bigger all the time.
02:05And what we call the universe is just one small pocket of that much larger volume of the true universe.
02:15And in our little pocket, when inflation ended for us,
02:19we ended up with one set of physics and one set of forces and one set of particles and one set of reality.
02:26But past the confines of our little bubble,
02:30the greater universe is still going, still doing its thing, still inflating,
02:35and 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.
02:47We don't know if inflation really happened.
02:50We suspect it did, but we're not entirely sure.
02:53And we're not sure if inflation demands the existence of a multiverse.
02:59It's possible that inflation just happened once and did it throughout the universe and that this is it.
03:06Or not.
03:08We've looked for evidence for a multiverse and have come up short.
03:13Like if another neighboring universe intersects with the bubble of our universe,
03:19we might be able to see signals of that.
03:22And we haven't seen anything.
03:24That doesn't rule it out yet, but there's no conclusive evidence for it.
03:30Even if there were a multiverse, we would never ever be able to access any of those other universes.
03:37We wouldn't be able to visit them. They wouldn't be able to visit us.
03:40For all intents and purposes, they wouldn't exist.
03:44So when it comes to multiverse, whether it exists or not,
03:48just focus on our universe because, really, it's the only one we got.