Here are 3 ways a Multiverse could exist.

hey crazies is the Multiverse actually possible given the success of everything everywhere all at once it's certainly a popular storytelling tool right now but physics has a lot to say about multiverses and these stories only tend to focus on one kind and there are three [Music] I've invented a machine to help us out with this whole Multiverse thing but I'm no engineer so it's a bit delicate we're gonna need to be careful what's this thing no no don't touch the Multiverse is not a new invention the idea has been around for thousands of years early versions were just cyclical these many universes didn't exist at the same time they were more like one Universe caught in a repeating series of creation and destruction then again maybe you don't think anything like that should be called a Multiverse well somewhere around 2000 years ago we started to see a change in thought according to the ancient Greeks it is in the highest degree unlikely that the Earth and Sky is the only one to have been created and that all particles of matter outside are accomplishing nothing and of course we all know the ancient Greeks were the pioneers of human philosophy yeah no the ancient Indians had similar writings who will search through the wide Infinities of space to count the universes side by side we don't know exactly when statements like these were written because history is full of fairy tales and ancient history is sparse but we do know this idea stuck around it's something philosophers Now call Cosmic pluralism though for a while this concept was intertwined with religion in 1584 former Dominican Friar Giordano Bruno would famously say he is glorified not in one but in countless Sons not in a single Earth a single world but in a thousand thousand I say in an Infinity of Worlds the he in that statement is the Christian God as you can imagine this idea wasn't very popular in the Roman Catholic Church things did not end well for Giordano Bruno are we back I think we're back where was I right the Multiverse the actual word Multiverse wouldn't enter scientific conversation until about 1896 in a debate between Ludwig boltzmann and Ernst cermello they weren't actually discussing cosmology though they were trying to decide if statistical mechanics was sufficient to describe the laws of thermodynamics of course any conversation about entropy quickly grows to Cosmic proportions pun intended anyway we have two models on the front line of physics general relativity and quantum mechanics and both of them have something to say about the Multiverse when you hear the term Multiverse you probably think of one particular example and it has to do with people's choices say you're I I don't know trying to decide which flooring to put in your house your partner wants easy to clean hardwood while you want that glorious soft carpet eventually you decide on the carpet because you're not a monster but what if there was another version of you that decided on the hardwood instead what if that decision split the universe in two in one reality your house has carpet in the other there's hardwood this exact concept has led to some fantastic stories in my lifetime everything everywhere all at once is just the latest iteration before that there was the Marvel Cinematic Multiverse before that there were the two universes in Fringe before that there was the quantum mirror in Stargate before that there was Star Trek the Next Generation where Warf was married to Troy for a hot minute but the writers abandoned it almost immediately stupid writers are you done yeah I guessed before Wharf and Troy there was the infamous Mirror Universe from the original series in the late 1960s my point is this Trope has been around probably as long as the hypothesis has been around so let's take a look at where that comes from oh no not again this idea that our choices split the universe in two comes from quantum mechanics Schrodinger's equation says wave functions evolve deterministically over time but our observations show this isn't always true say a photon's wave function passes through both of these slits as the photon moves forward it will be in a superposition of many locations determined by the interference pattern of the waves from each slit however when it reaches the screen we'll only see it at a single location the wave nature of the photon is gone we call this wave function collapse and it happens suddenly and randomly in stark contrast to the smooth Behavior described by Schrodinger's equation wave function collapse was problematic to say the least but it was unavoidable that is until 1957 when a physicist named Hugh Everett proposed the many worlds hypothesis he asked a simple question what if the wave function never collapses what if the screen just becomes correlated with the wave function all possible locations for the photon could still exist just in different universes at the time Hugh Everett suggested his many worlds interpretation Nation it seemed extreme it was controversial and it had a share of problems what was keeping observers in each of these worlds from being aware of the others these problems wouldn't be solved until 1970 when a type of censorship was discovered We Now call decoherence make it stop okay so honestly the many worlds interpretation could be a whole video all by itself but you're not here for the gruesome details here's what you actually need to know one these Quantum realities are not some vast distance away they overlap at the same location your house with carpet occupies the same space as your house with hardwood they just don't interact so you're completely unaware of each other it's not actually as crazy as it sounds consider these two waves traveling toward each other along a string they won't Collide instead they'll combine into one composite wave for a Time eventually they'll pass through each other entirely and return to their original shape as if the other one wasn't even there the same thing happens with waves on the surface of a pond Schrodinger's equation is what describes the quantum world and its Solutions are waves so it's it's not that crazy to think the quantum world might behave this way each Universe being a different Ripple in some four-dimensional pond two this is not about human choices well I mean sure if you subscribe to the many worlds interpretation of quantum mechanics your choices would be splitting universes but that doesn't make you special this splitting would be happening for every Quantum interaction that releases information to the environment your brain just happens to also be made of quantum particles three it's not the entire universe dividing this is a local event a superposition just splits into measurable States at that location that separation happens here and only here the rest of the universe is fine all the information is still there too you just can't see the whole thing anymore and finally four this isn't like a tree that branches continuously and gets larger over time other Quantum events might bring them back together so it's not necessarily permanent it's more like a big messy web of events than a tree full of universes fictional stories like everything everywhere all at once can be fun but they're not real it's important to look at the science behind these things too we've figured out over the last century that the Universe has been around for about 13.8 billion years and is currently 93 billion light years across but that's just the observable universe we know the whole thing is at least 20 times larger than that but it's probably infinite and our finite part is really uniform sure on the smaller scale you've got interesting collections like planets stars and galaxies but if the smallest piece you look at is about a hundred million light years across the observable universe is basically the same everywhere there's no reason to think that's gonna suddenly change beyond the observable Edge so oh come on I just got into a rhythm today we're going to be estimating how many universes there are can you actually calculate that uh yeah I mean well we can do a very crude estimate okay so let's let's let's take a look our observable universe has a finite size let's say this is our observable universe it is 10 to the 27 meters across there's a lot it's a lot of meters but it is finite as far as we can tell this observable universe is inside of a larger space that is infinite in size probably we don't know that for sure but all of our data suggests that it is infinite now if our observable universe has a finite size with a finite number of particles in it and if those particles can have a finite number of configurations which stands to reason if the observable universe is finite then in an infinite space those patterns should repeat eventually we'd expect them to repeat and so the next natural question here is how many particles are in the universe now that's something we call eddington's number and it's an estimate we've had for a while it is 10 to the 80 there are 10 to the 80 protons in the observable universe but are there particles other than protons there are neutrons and electrons but those don't actually affect this estimate all that much see most of the matter in the universe is inside of stars it's mostly hydrogen or ionized hydrogen which is just protons neutrons don't show up until you make larger elements on the periodic table and so uh there aren't nearly as many of them but even if there were even if there were exactly the same number of neutrons in exactly the same number of electrons you would just end up with 3 times 10 to the 80. which in this case and the way we're doing these estimates that's still just 10 to the 80 that would round down to 10 to the 80. we're doing very very aggressive estimations here something we call order of magnitude estimation so we're only interested in the powers of 10. something else we know is we know the diameter of a proton so this thing has a diameter it does take up some space because it's made of smaller particles and this size is something we call one femtometer which is 10 to the negative 15 meters it's a very small amount of space but again it is a finite space if we want to know how many possible spaces they could exist in we need to know how many we could cram in there like to the brim we want to cram it full of protons how many protons would there be and that's actually not that difficult of a calculation so all we have to do is divide the two sizes 10 to the 27 the diameter of the universe and divide it by the diameter of a proton and we get something like this now this will tell us how many protons we could fit along the diameter of the observable universe but what we want is the entire volume and so all we have to do is cubit now sure you might want to put like a four-thirds pie out front or something but again that's a fraction or a number outside of the power of 10 and so it doesn't actually matter we don't actually need to know the four thirds Pi for a spherical volume it does all we need is the powers of 10. this fraction cubed comes out to be 10 to the 126 spaces and so this is how many spaces are available for protons to exist in in order to figure out how many different configurations these protons can have again we're doing rough estimates we're not going to worry too much about how they collected atoms or anything or to put this another way we want to choose 10 to the 80 out of 10 to the 126 and that's very specific language it's called combinatorics to get our final crude estimate we need three things the formula for combinations Sterling's approximation which is a way to find factorials of large numbers more easily and the fact that 10 to the 126 is much larger than 10 to the 80. when all is said and done we get a formula that's very simple now all we have to do is plug in the numbers so assuming space is infinite we get approximately 10 to the 10 to the 82 unique universes unique verses anyway this is a stupid big number and believe it or not this is the easiest Multiverse to understand these universes aren't in some other plane of existence they're just a ridiculous distance away if the expansion of space wasn't accelerating we could actually reach them if we were patient enough it's just a numbers game but that expansion of space comment has me thinking there was this era in the early Universe called Cosmic inflation where space was expanding at a rate oh crap hey science Asylum Nick here what is the fastest thing your first thought might be a cheetah which can reach speeds up to 59 miles per hour Usain Bolt is the fastest human and his highest recorded speed is only about 27 miles per hour slow poke but that's not the fastest humans have ever gone according to the Guinness Book of World Records the fastest speed humans have ever traveled is 24 800 miles per hour aboard the command module for Apollo 10. if you know a little physics though you know the universal limit is the speed of light travels at 670 million miles per hour in a vacuum so that settles it light is the fastest thing or is it the endless chain of cause and effect puts an upper limit on how fast things can move in space but it puts no such limit on how fast space itself can move the space contained within the universe has been expanding since the beginning but not always at the same rate right now at this very moment most galaxies are moving away from us faster than light because the space between us is expanding faster than light however shortly after the big bang it temporarily expanded exponentially faster it had to otherwise the universe would not have been as uniform as it is today this begs the question why did this period of cosmic inflation stop but that begs an even better question did it stop remember some infinities are larger than others there could easily be an infinite space inside of an even larger Infinite Space Cosmic inflation began when the observable universe was a trillion times smaller than an atom it occurred shortly after the big bang it lasted only for a decillionth of a second that's a billionth of a trillionth of a trillionth of a second this period of inflation stopped as quickly as it began leaving the observable universe about the size of your fist its volume expanded by a factor of 10 to the 78th power to expand that much again the universe would take another 13.8 billion years we know Cosmic inflation stopped in our observable universe otherwise it wouldn't be here but cosmologists soon realized something interesting inflation doesn't have to stop everywhere all at once our observable universe might just be an infinite bubble inside of an even larger space a space experiencing inflation eternally what implications does this eternal inflation have that's coming up right now foreign okay let's try this again infinite multiverses inside of other infinite multiverses is going to be a bit confusing so let's call the larger thing in Omniverse it's a space that contains multiverses different multiverses within this Omniverse are just regions where inflation has stopped but in the voids between those bubbles inflation is still ongoing and no matter can exist there that inflation is so fast that even though a Multiverse like ours is expanding it may never collide with another Multiverse each Multiverse bubble would be unreachable by the others they would be completely separate which gives us an extra degree of Freedom see the many universes in our own Multiverse may have started with a different set of initial conditions but all the fundamental constants are still the same this is still the gravitational constant this is still the fine structure constant this is still Planck's constant this is still the mass of the electron every one of those universes has the same matter in it and it all obeys the same rules that doesn't necessarily extend to the other multiverses in the Omniverse here every bubble is a separate Multiverse each expanding at a different rate each with a different number of Dimensions with its own types of particles with different kinds of structures made from those particles our Multiverse may be uniform but there's no such requirement for the rest of the Omniverse the only constant across the Omniverse are the fundamental physical relationships whether you think the quantum realities from the many worlds interpretation are real or you believe that space itself goes on forever and repeats or even if you think this is all just bogus philosophy which you know Fair opinion they might not be real but no matter how you feel about this we should all agree that everything is described by two theories general relativity and the standard model those relationships are what hold the Omniverse together and until next time remember it's okay to be a little crazy Arthur was wondering if Brown dwarfs could account for dark matter what's nice is that would no they can't the number of brown dwarfs you would need is ridiculously larger than could possibly exist if you want more info I actually have a video about this Link in the doobly-doo anyway thanks for watching

Channel: The Science Asylum

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Id: -cfN-QxJkjU

Length: 19min 15sec (1155 seconds)

Published: Sat Apr 01 2023