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ever look up at the night sky and just feel like there's gotta be more out there.

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What if our universe is just a tiny piece of something way bigger and, I don't know,

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more complicated?

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Welcome to Cosmos in a Pod, Space and Astronomy series.

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So today we're diving deep into the multiverse.

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The idea that maybe there are tons of other universes out there, each with its own laws

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of physics and maybe even different versions of us running around.

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It's an idea that's been around for a while.

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Scientists, philosophers, sci-fi fans, they all love it.

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And the thing is, it's not just like a made-up story.

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The idea of the multiverse comes from some pretty serious physics.

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Yeah, that's what I find so cool about it.

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There's actual science behind it.

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But before we get too deep into the theories, can you kind of explain what we're talking

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about when we say multiverse?

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Like paint a picture for our listeners.

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So imagine our universe right.

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All the galaxies, stars, planets, everything.

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Picture that as just one bubble.

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And this bubble is floating in this giant cosmic foam.

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And each bubble is a separate universe.

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Maybe some are similar to ours, but some could be so different we couldn't even imagine them.

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Whoa.

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So we're not just talking about like a few extra planets or stars.

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We're talking entirely different realities.

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Yeah.

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And maybe like an infinite number of them.

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Yeah, that's the thing.

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It's a massive concept.

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It's kind of hard to wrap your head around.

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It is.

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It makes you rethink what's real, what's possible.

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And like I said, this isn't just imagination.

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It comes from some really important physics theories, things like quantum mechanics, cosmic

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inflation string theory.

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OK, let's start with quantum mechanics.

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How does that connect to the multiverse?

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So one of the weirdest parts of quantum mechanics is this thing called superposition.

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Basically a particle can be in multiple states at the same time until you observe it.

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And there's one interpretation of this called the many worlds interpretation.

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And it says that every time a quantum measurement is made, every time a particle picks one state

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up, the universe splits.

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It creates a new branch of reality where the other outcome happens.

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So like every decision, every tiny quantum event creates a new universe.

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Exactly.

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And each of those universes keeps branching out with every other quantum event.

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So you end up with this crazy complex multiverse that just keeps growing.

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That's wild.

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So there's a universe out there where I picked a totally different job or like have

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a different family.

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It makes you think about all the what ifs.

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It does.

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And that leads to another cool part of the multiverse, cosmic inflation.

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OK, hit me with it.

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What's cosmic inflation and how does it fit in?

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So the theory of cosmic inflation says that right after the Big Bang, like a fraction

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of a second after the universe expanded incredibly fast, like way faster than the speed of light.

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And during this crazy expansion, different parts of space time could have expanded and

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separated.

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They form their own distinct universes, each maybe with different properties.

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So it's like the universe had a growth spurt.

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And during that spurt, different parts kind of butted off to become their own universes.

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Yeah, that's a good way to picture it.

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And each of those bubble universes could have totally different physics, you know, like

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different gravity or even a different speed of light.

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So you could have this crazy variety of cosmic environments.

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OK.

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And what about string theory?

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That's another one I've heard supports the multiverse, but it's super complicated.

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Can you break it down?

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Yeah, string theory is definitely complex.

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So basically it says that the smallest billing blocks of the universe aren't particles,

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they're these tiny vibrating strings.

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And the way these strings vibrate determines the forces and particles we see.

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Now the thing is, string theory says we need more than the three dimensions we experience.

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Like extra dimensions.

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That sounds like sci-fi.

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It does, but the map of string theory needs them.

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And here's the connection to the multiverse.

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String theory says that different universes could be created by different arrangements

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of these extra dimensions.

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Think of these extra dimensions curled up in these tiny crazy shapes.

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And each shape could be a different universe with its own unique laws of physics.

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So each universe is like a different musical note played by a different vibration of the

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strings in those extra dimensions.

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Yeah, that's a cool way to think about it.

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And it shows how string theory could allow for like a huge variety of universes.

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OK, so we've talked about some pretty mind blowing theories and they all seem to point

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to this idea of a multiverse.

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But is there any like actual evidence for it?

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Can we ever really prove or disprove that other universes exist?

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That's the tricky part about the multiverse.

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Actually seeing other universes, that's, you know, beyond what we can do right now.

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But it doesn't mean we have no clues at all.

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There are some pretty interesting things that might hint at the multiverse.

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OK, I'm listening.

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What kind of evidence are we talking about?

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Well, one thing is cosmic inflation itself.

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The predictions from inflation theory, they line up really well with what we see in the

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cosmic microwave background radiation.

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That's like the afterglow of the Big Bang.

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And this agreement between the theory and the observations, it gives us some confidence

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in inflation.

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And if inflation is right, then multiple universes could totally come from it.

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So because inflation seems like a solid theory, it makes the multiverse more likely.

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What else is there?

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Another piece of the puzzle is this thing called the fine tuning problem.

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It's the idea that the fundamental constants of physics, you know, like the strength of

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gravity or the mass of an electron, they seem incredibly fine tuned for life to exist.

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If these constants were even a little bit different, the universe wouldn't be the same.

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So it's like the universe hit the jackpot with all the right settings for stars and planets

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and, you know, eventually us.

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Exactly.

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And the multiverse could explain this fine tuning.

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Think about it.

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If there are tons of universes with different constants, then statistically, at least one

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of them would have the right conditions for life.

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And hey, we just happen to be in that one.

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I see.

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So if we're saying our universe is just super special, we could say it's just one of many

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and we happen to be in the one that works for life.

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Right.

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But, you know, even though this is all interesting, it's not like we have proof of the multiverse.

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There are also some problems and criticisms to think about.

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All right, let's hear them.

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What are the biggest challenges for this theory?

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Well, the main one is that we don't have direct evidence.

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Like we were saying, we can't actually see other universes, so it's hard to really prove

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they're out there.

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Yeah, that makes sense.

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It's a huge idea and it's going to take some really strong evidence to convince everyone.

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For sure.

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And that leads to another problem, falsifiability.

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For a theory to be scientific, there needs to be a way to test it, a way to maybe prove

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it wrong.

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But with the multiverse, it's not clear how we could do an experiment to really prove

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it one way or another.

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So the challenge is to find a way to test the multiverse to make it more than just a

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cool idea.

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Exactly.

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The other point that people bring up is Occam's razor.

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It's this idea that the simplest explanation is usually the right one.

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And some people say that saying there are infinite universes is way too complicated.

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Maybe there's a simpler explanation for what we see.

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Okay, so it's a debate about finding the most elegant and simple explanation.

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Do we really need infinite universes or is there a simpler answer?

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That's the question scientists are trying to figure out.

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And then, you know, besides the science stuff, the multiverse also brings up some really

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deep philosophical questions.

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Oh, yeah, I can imagine.

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Thinking about infinite universes, infinite versions of ourselves that has to lead to

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some crazy ideas.

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Yeah.

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Where do we even begin with that?

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I think one of the first things we have to ask is what does the multiverse mean for our

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place in the cosmos?

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Like if our universe is just one of countless others, does that mean our existence is less

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significant or does it make it even more special?

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That's a question I think a lot of people struggle with.

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On one hand, it's humbling to think we're just a tiny part of this huge multiverse.

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But on the other hand, it's kind of amazing to imagine how much is out there.

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Exactly.

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And it also makes us think about free will.

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If there are infinite versions of us making every possible choice, does that mean our

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choices don't really matter?

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Whoa, that's a tough one.

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Like if every decision I make creates a new universe where I made a different one, what

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does that say about my choices in this universe?

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It makes you question everything.

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It really does.

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And then there's the even bigger question of what is reality.

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If we're just a small piece of this massive multiverse, what does that mean for how we

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see the universe?

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Like what does real even mean anymore?

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It's like the multiverse series making us rethink everything we thought we knew about

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the universe and ourselves.

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It's exciting, but also kind of scary.

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Yeah.

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So it sounds like the multiverse opens up a ton more questions than it answers.

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But even if it's just a theory, it seems worth exploring, right?

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Like what kind of research could help us understand this whole multiverse thing better?

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You're right.

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It's a journey with a lot of potential.

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And one promising area is to keep studying the cosmic microwave background radiation.

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We talked about how its patterns support cosmic inflation.

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But if we look even closer at its tiny variations, we might find more clues.

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Some scientists think those variations might actually show signs of collisions or interactions

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with other universes, like little fingerprints left over from the very beginning.

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Wow, cosmic fingerprints.

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That's pretty cool.

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Yeah.

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It would be amazing to find those, but it's really tough.

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You need incredibly precise measurements and some serious data analysis.

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But hey, it could lead to huge discoveries.

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Another exciting thing is how string theory and its related theories like M theory are

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developing.

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We touched on this earlier, but string theory naturally leads to the idea of a multiverse,

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with different universes coming from different configurations of those extra dimensions.

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And if we can find ways to test these theories, it could give us more solid mathematical evidence

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for the multiverse.

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So we're on the edge of a totally new understanding of reality.

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What are the researchers out there?

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Well, quantum physics has a ton of potential too.

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With advancements in quantum computing and experiments with entanglement, we might be

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able to explore the limits of quantum mechanics in ways we never could before.

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And some researchers think this could give us indirect evidence for parallel universes.

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We might even be able to catch a glimpse of these other realities.

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Whoa, quantum computers looking at other universes.

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That sounds crazy, but so cool.

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It's definitely an exciting idea.

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And of course, alongside all the science we need to keep thinking about the philosophical

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side of things, philosophers, physicists, cosmologists, they're all working together

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to explore the nature of reality, the idea of infinity, what it means to exist in a multiverse.

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It's a huge effort bringing together some of the smartest people to tackle some of the

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biggest questions we've ever had.

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So basically trying to understand the multiverse is pushing the boundaries of what we know

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and what we can even imagine.

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Absolutely.

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And even if we never actually travel to another universe or meet another version of ourselves,

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just trying to understand it is giving us incredible insights into the cosmos and our

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place in it.

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It really shows that the universe, or I guess I should say the multiverse, is full of wonder

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and mystery and possibilities.

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And even if we don't find all the answers, just asking the questions and exploring is

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what makes it so fascinating.

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I totally agree.

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It shows how curious we are as humans and how much we want to understand the world or

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I guess the world's around us.

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So to everyone listening, if you're intrigued by this idea of a massive multiverse with

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endless possibilities, keep looking up at the stars, keep asking questions, keep exploring.

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We're just at the beginning of this journey and who knows what amazing discoveries are

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waiting for us.

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And don't forget to subscribe to Cosmos in a Pod for more deep dives into the universe

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and check out our YouTube channel for some awesome visuals.

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Thanks for joining us on this cosmic adventure.