00:00Imagine if somewhere, you know, trillions of light-years away from our world,
00:05there's another version of you watching this very video right now.
00:09Not as crazy as it might sound.
00:11The multiverse theory is having its time of the day,
00:14from Marvel's movies to Spider-verses,
00:17to the recent famous hit Everything Everywhere All at Once.
00:21But it's not just some wild sci-fi concept.
00:25Physicists have been talking about this theory for decades.
00:27Let's see what they say.
00:29Do parallel worlds exist?
00:32If they do, let's hope that this is the reality where you click that subscribe button before diving into the video.
00:39Now everything starts with the Big Bang.
00:43Before the Big Bang, the universe, with everything we know,
00:47was crammed into an unbelievably tiny, super-hot, and mega-dense point.
00:52Our universe is about to burst into existence.
00:55And then, boom!
00:56The most colossal event you can imagine happens.
01:00In an instant, this tiny point expands with indescribable speed.
01:05It's the beginning of everything.
01:06Time, space, and all the galaxies that surround us.
01:10Then, like an extremely hot balloon,
01:12the universe started stretching out in all directions.
01:16Which sounds logical, but what's curious is that this inflationary epoch
01:20lasted for an incredibly brief time, in less than a blink of an eye.
01:24It's like the universe hit the fast-forward button, and then everything eventually slowing down over time.
01:31After this speedy phase, the universe kept growing, but at a more normal pace.
01:36This rapid expansion is called inflationary cosmology.
01:41It explains some big mysteries about our world.
01:43It tells us why it looks the same in all directions.
01:47Why the background radiation is evenly spread.
01:50Why galaxies are where they are, and so on.
01:53The details of how this cosmic inflation works are still a bit mysterious.
01:58But scientists are on it, and the theory itself is universally accepted.
02:02But it wasn't always this way.
02:05To scientists, this idea sounded like insane sci-fi at first.
02:10However, it explains so many things that the scientists just had no choice but pay attention to it.
02:16However, its initial weirdness was just the beginning.
02:20Now, according to this theory, inflation might not be a one-time thing.
02:24It could be happening repeatedly, maybe even endlessly.
02:28Picture the universe as a never-ending cycle,
02:30with each burst of inflation creating its own bubble universe.
02:35And the most important thing is that these bubble universes might not play by the same rules.
02:40Some could be totally weird, where the laws of physics are going crazy in ways we can't even fathom.
02:47Which means, there might be a whole constellation of bubble universes out there.
02:52However, we can't directly see these other bubbles.
02:54They exist beyond the edge of our spotlight.
02:57That's where the multiverse theory comes into play.
03:00People have been chatting about the idea of multiple universes for a long time,
03:05like way back in ancient Greece.
03:08Now, back in the 1990s, people got really interested in this idea.
03:12And this concept started popping up in books and movies.
03:16As a result, scientists began talking about it increasingly in scientific discussions and journal articles.
03:22And nowadays, many scientists and philosophers are into it.
03:26Now, the problem is, there's no solid proof or evidence that these other universes really exist.
03:33It's not a proved or confirmed theory.
03:36It's not even a theory at all, just a hypothesis.
03:39A bunch of interesting thoughts put together.
03:42Before we draw any conclusions, we need much more in the way of clues and evidence.
03:47And unfortunately, it's hard to find the evidence of parallel worlds when we can't live or look past our own.
03:54Which is why many scientists believe that it might not be real.
03:58But not everybody agrees with that.
04:01While critics say that we can't observe the multiverse and therefore can't test it,
04:06some physicists suggest a different approach.
04:09Instead of trying to find these parallel worlds, we could try to look at ours and its history.
04:14Around the 2010s, researchers took a closer look at data from a space gadget called the Wilkinson Microwave Anisotrophy Probe.
04:24Yes, that's a mouthful.
04:25They thought they found signs suggesting that our universe might have bumped into other universes in the past.
04:32Like sort of a collision.
04:33But then, scientists used an even fancier satellite, which had three times better resolution,
04:39looked at the data more thoroughly, and didn't find any strong proof of these universe collisions.
04:45Plus, there was no evidence that other universes were tugging on ours with their gravity.
04:51However, an interesting discovery happened in 2015.
04:55One scientist checked out radiation left over from the Big Bang.
04:59He claimed to see something super bright.
05:024,500 times brighter than expected.
05:05Well, at least based on the stuff, like protons and electrons, scientists think existed in the early universe.
05:12So, he and some others assumed that this might be our first evidence of our universe crashing into others.
05:20But let's assume that it does exist.
05:22The multiverse wouldn't be about human decisions creating alternate timelines.
05:27In quantum mechanics, it's not human decisions that split everything into parallel worlds, but the measurement of subatomic particles.
05:36So, if we look at this theory scientifically, other worlds would be billions of light-years away.
05:41And what's happening to them wouldn't have anything to do with our daily choices.
05:46So, what would it look like?
05:48Well, Max Tegmark, for example, talks about four levels of universes and multiverses.
05:54Level 1 is the extension of our world.
05:57Our universe is a big place.
05:59And in an infinite universe, there would be infinite chunks like ours, each with its own story.
06:05Most of these chunks might look different from ours.
06:08But because there are so many, some might look just like ours.
06:12But they'd be really, really far away.
06:15Level 2 is a universe with different physical constants.
06:18This idea says that our universe is part of a much bigger space where bubbles form.
06:24Each bubble might have its own set of rules, like different laws of physics.
06:29Level 3 is the many-worlds interpretation of quantum mechanics.
06:33This one's a bit tricky.
06:35In the quantum world, things can be weird.
06:38Imagine rolling a dice.
06:40Each number that comes up might create a separate universe.
06:43So, if you rolled a dice and got a 3, in another universe, it would be a 6, and so on.
06:50Yeah, my head's spinning.
06:52This idea suggests that every possible outcome in quantum events creates a whole new universe.
06:58And level 4 is the ultimate ensemble.
07:02This level gets super abstract.
07:05It says that everything, every possible universe or reality, can be described using math.
07:11Hmm, I wish now I hadn't fallen asleep in algebra.
07:15Imagine all the different math equations describing every conceivable way the universe could be.
07:21This level says that every math equation that can describe a universe actually exists.
07:26And they're all real in their own way.
07:29Stephen Hawking was a proponent of the level 3 many-worlds interpretation.
07:34It was one of his last theories before he passed away.
07:36He predicted that the universe is finite and far simpler than many current theories about the Big Bang say.
07:44According to Hawking, the universe is like a giant quantum system, a sea of possibilities and probabilities.
07:51In this view, every outcome of the universe's history plays out in parallel existences.
07:57And we, as observers, play a crucial role.
08:00Our existence and what we observe, according to Hawking, actively shapes the universe we see.
08:07In simple words, the universe is a canvas and we're all painters.
08:12Sounds very cool and insane.
08:14But hey, many things in science were considered crazy before they turned out to be true.
08:20So, is there another copy of you somewhere watching this video?
08:25And who just pressed the like button?
08:27Who knows?
08:27If there are infinite copies of us, scientists assume that we might be like identical twins,
08:34sharing the same origins and starting from one thing, but then developing into separate different people.
08:40And if these worlds exist, perhaps we can even visit them one day.
08:45There could be some connections between us, something that could allow for interdimensional travel.
08:51For example, wormholes.
08:53Well, whatever the truth may be, let's hope that one day we'll discover it.
08:57Until then, stay curious.
09:01That's it for today.
09:02So hey, if you pacified your curiosity, then give the video a like and share it with your friends.
09:07Or if you want more, just click on these videos and stay on the bright side.
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