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00:00Strange things are afoot at the Circle K.
00:06Ever wondered if there could be another version of you out there,
00:09living a completely different life in a universe parallel to our own?
00:12From scientists to philosophers to storytellers,
00:15parallel universes have fascinated humans for thousands of years.
00:19From the implications of quantum mechanics
00:21to the vast expanse of cosmological theories,
00:24the so-called multiverse changes every aspect of traditional reality.
00:28This is Unveiled, and today we're taking a closer look
00:31at 10 Big Questions About Parallel Universes.
00:35Do you need the big questions answered?
00:37Are you constantly curious?
00:38Then why not subscribe to Unveiled for more clips like this one?
00:41And ring the bell for more thought-provoking content!
00:45What is a parallel universe?
00:47By definition, what we're dealing with here is a theoretical universe
00:51similar to our own but coexisting alongside us.
00:54Parallel universes might also be called alternate universes.
00:57The implication being that they could be almost entirely the same
01:00but just a little bit different.
01:02Or, on the other end of the scale, they're almost entirely different
01:06– perhaps with different laws of physics to our own –
01:08but still with at least one or a few recognisably similar characteristics.
01:13As such, parallel universes are, of course,
01:15incredibly popular concepts in science fiction.
01:18Mostly because the creative possibilities are pretty much endless.
01:22Imagine you're flipping through TV channels,
01:24but instead of shows, each channel is an altered reality.
01:27Again, some are almost identical to ours,
01:30while others can be widely different with alternate histories,
01:33different rules of nature, etc.
01:35This higher version of the TV Guide would never end.
01:39The choices available are infinite.
01:41Importantly, though, it's more than just a cool story trope.
01:44According to certain scientific theories,
01:46this really could be the structure of reality.
01:49Our universe really might be just one of many in an expansive multiverse.
01:54For example, in the strange realm of quantum mechanics,
01:57the Many Worlds Interpretation says every quantum event
02:00could feasibly split this universe into two.
02:03Meanwhile, some models of cosmic inflation claim that
02:06parallel worlds are possible through the formation of distinct bubble universes
02:10as space expands ever outwards.
02:13How big is the universe?
02:15Infinite.
02:16How does quantum mechanics predict parallel universes?
02:20Here is where the Many Worlds Interpretation is key.
02:23In quantum physics, particles like electrons can exist in multiple states simultaneously.
02:29It's a phenomenon called superposition, made famous through Schrödinger's cat.
02:34An oft-repeated thought experiment,
02:36it states that if you close a cat in a box with a particle of radioactive material
02:40and a flask of poison linked to the decay of that particle,
02:44then the cat is, in effect, both alive and dead until the box is opened,
02:49and the state of the particle is observed.
02:51One interpretation is that a particle, any particle,
02:54is only ever what it is once we view it.
02:57One implication, then, is that there could be other states happening all the time
03:02outside of what we view, as though behind the scenes of reality.
03:06And this is the basis for Many Worlds.
03:09Many Worlds models claim that when a quantum particle collapses into a state,
03:13instead of discarding all other scenarios,
03:16the universe splits into multiple versions.
03:19In each new universe, the particle takes on one of its possible states.
03:23So, two possible outcomes will always create two universes,
03:26and so on and so on, for every single quantum state, ever.
03:30On a higher level, it then figures that every decision and random event
03:34should also spawn an entirely new universe,
03:37with a different outcome and timeline from then on.
03:40If you flip a coin, the theory suggests the universe splits into two,
03:44one where it lands heads and one where it lands tails,
03:47or maybe even three, with one where it bizarrely lands on its side.
03:52Apply the same thinking to every single random event in the history of everything,
03:57and you get an unfathomably large cosmos,
04:00with a potentially infinite number of alternate universes,
04:03with every possible scenario happening somewhere.
04:06While that sounds like science fiction,
04:08it's a serious theory that many believe offers an explanation
04:11for the peculiar behaviour of quantum particles.
04:14For some, it eliminates the wave-function collapse,
04:17the process where particles choose a state when observed.
04:20Instead, many worlds suggest that all possible outcomes do happen,
04:24it's just that they all happen in completely separate universes.
04:28Importantly, while it's a captivating idea, it's also currently deemed unprovable.
04:33Like most multiverse theories, we can't interact with the alternate realities that it predicts.
04:38But growing numbers do consider it valid for a lot of further research.
04:42So, watch this space.
04:44Look, I need to know what I stand to win.
04:47Everything.
04:49How's that?
04:50You stand to win everything, call it.
04:52How does cosmic inflation predict a multiverse?
04:56Here, we're jumping from the smallest possible quantities to immensely large objects.
05:00Cosmic inflation is a theory at the other end of the scale
05:03to describe the rapid expansion of the universe as we know it,
05:06immediately following the Big Bang.
05:08It's said that the expansion happened in the first few fractions of a second
05:12after the Big Bang moment, at a rate beyond the speed of light.
05:15All in all, it's a moderately successful theory
05:18and has been included in the standard cosmological model.
05:21Inflation does suffer from some issues, though,
05:24including that it's unclear where inflation ends.
05:27One solution to explain this is the bubble universe theory,
05:30otherwise known as eternal inflation.
05:33It's another that's only hypothetical at the moment.
05:35Broadly, it claims that the cosmic inflation
05:38suspected to be at the heart of everything
05:40didn't stop everywhere at the same time.
05:43Instead, it stops at different times in different regions.
05:46And when this happens, it creates closed-off, separate structures,
05:49aka bubble universes.
05:52Our home reality just might exist in one of these bubbles.
05:55But it isn't alone.
05:57Not by a long shot.
05:58So, the theory goes, if we were to break beyond our bubble,
06:01then we should find countless others like it,
06:04although their insides – their laws of physics,
06:07rules of time, their nature of reality, etc. –
06:10would likely all be very different.
06:13Outside of these bubbles, inflation continues eternally,
06:16implying new bubble realities are constantly being created as well.
06:20But for us, detecting bubbles is a serious challenge,
06:23primarily due to the inflating space-time
06:26that's separating ours from all others.
06:29Some researchers wonder if the cosmic microwave background radiation
06:32could provide an answer,
06:34perhaps giving some kind of indirect evidence of the multiverse
06:37via certain patterns or anomalies in the radiation.
06:40But as yet, it's another picture of what true reality might look like
06:44that hasn't yet been proven.
06:46Einstein says that time is not the same for all of us,
06:53but different for each one of us.
06:56Can black holes connect us to a parallel universe?
06:59It's no stretch to say there's nothing in the known universe
07:02that we know less about than black holes.
07:05Yes, they're spectacularly dense regions of space,
07:07with gravity so strong that nothing, even light, can escape them.
07:11True, many of them form from the remnants of massive collapsed stars.
07:15And yes, the event horizon is what we term the point of no return,
07:18the boundary beyond which our black hole is final.
07:21But once passing this point, it's wholly unclear what happens next.
07:25There's spaghettification, the somewhat vague and definitely terrifying process
07:30of stripping matter back down until it's just a long line
07:34of its most fundamental particles.
07:36And then, at the heart of a black hole lies its singularity,
07:39where gravity is infinitely strong,
07:41and all the laws of physics break completely.
07:44But broadly, that's as far as currently confirmed mainstream science goes.
07:48Nevertheless, in the significant gaps of black hole science,
07:52many have mused about potential routes to a multiverse.
07:55For some, the singularity could be crucial.
07:58At this most unknowable of points, it's before been suggested
08:01that it could actually connect to other points in space,
08:04perhaps with the black hole's theoretical opposite,
08:07a white hole, at the other end of the connection.
08:10But more than that, if we accept there being some form of hyperspace
08:13in whichever guise, then the singularity might just as well bridge
08:17other universes in a multiverse.
08:19It's an idea in part inspired by what's known as the information paradox,
08:23which questions where information goes after entering a black hole.
08:27There ought to be something very special about the boundary conditions
08:32of the universe.
08:34And what can be more special than that there is no boundary?
08:40Are wormholes pathways to a multiverse?
08:43Although not the same as black holes,
08:45or potential black hole-white hole tunnels,
08:47wormholes do often come up in similar conversations.
08:50And understandably so.
08:52Wormholes, also known as Einstein-Rosen bridges,
08:55are theoretical passages through spacetime.
08:58They're certainly considered to be physically possible,
09:00and are believed to represent a potential method for creating shortcuts
09:03between distant parts of our universe.
09:06It could be that wormholes actually represent the very best chance
09:09we have of breaking the local speed of light,
09:12thereby managing to achieve intergalactic space travel.
09:15But, in terms of parallel universes, it again makes just as much sense,
09:19particularly if you accept the Eternal Inflation-style multiverse,
09:23that a wormhole could punch through reality to link separate universes as well.
09:27Naturally, there is a major problem with the plan, however,
09:30as we've never actually observed a wormhole.
09:33And we can't seem to make one.
09:35Were one to appear and remain stable,
09:37it's thought likely that it would require exotic matter
09:40with negative energy to operate correctly,
09:42both of which we have very little understanding of.
09:45The more optimistic researchers, though,
09:47tend to point to the monumental jumps in knowledge
09:50our species has made in the past,
09:52as a reason to believe that wormholes might one day be realised.
09:56It wasn't so long ago that we thought the sun circled the Earth,
09:59or that we were wholly unaware of other galaxies in the wider universe.
10:03So, perhaps it's not quite so far-fetched to believe that at some point in the future,
10:07wormholes won't only be known, they'll be common.
10:10It's infinitely complex.
10:11They have access to infinite time and space,
10:14but they're not bound by anything.
10:16They can't find a specific place in time.
10:20They can't communicate.
10:22That's why I'm here.
10:24I'm going to find a way to tell Murph, just like I found this moment.
10:27How does string theory relate?
10:29As one of the leading contenders toward a theory of everything,
10:33could it be that string theory holds the solution for parallel worlds?
10:36In short, it aims to unite nature's four fundamental forces into a single, cohesive model.
10:41These are the strong and weak nuclear, electromagnetic and gravitational forces.
10:46Gravity is the weakest of all,
10:48which means that it's also the most difficult to incorporate into quantum mechanics.
10:52Which is why a working model of quantum gravity
10:55doubles up as all that's still required for a theory of everything to work.
11:00So, how does string theory propose to solve the riddle?
11:03It says that the cosmos' most basic building blocks aren't exactly particles as we'd usually imagine them.
11:09Instead, they're tiny, vibrating strings.
11:12At the smallest level, according to string theory, we don't have point-like particles,
11:16but instead one-dimensional strings.
11:19And it's the frequencies at which they vibrate
11:21which determines the particles and forces that we observe at our higher, macro level.
11:26One of string theory's most intriguing qualities, however,
11:29is its requirement for extra-spatial dimensions
11:32beyond the three of space and the one of time that we're all familiar with.
11:35Even at its most conservative, it says there could be up to ten or eleven in total.
11:40As to where they are, it's said that they're compactified, curled up
11:44and basically much smaller than we can detect or comprehend.
11:48And here's where various multiverse scenarios perhaps naturally arise.
11:52Some claim that it's in how these extra dimensions are compactified
11:56that could ultimately result in different types of universe.
12:00With each compactification corresponding to different rules of physics.
12:04And before long, the wider structure creates a vast, multiversal landscape
12:09commonly referred to as the string landscape.
12:12Now it's as though our reality is but one specific stitch
12:16on this new and rich tapestry of strings.
12:19And what's more, it could be that string theory has a role
12:22specifically to play in the bubble multiverse idea as well,
12:25with all of its extra dimensions wielding unknown influence
12:28over the processes of eternal inflation.
12:31Groupings of tiny energy waves bound together.
12:34By what?
12:35Forces of attraction strong enough to convince us that matter is solid.
12:41It's not my body passing through yours.
12:44What are brain worlds?
12:46To another offshoot of string theory,
12:48as brain worlds are another potential answer to the puzzle of the multiverse.
12:52Here the word brain is short for membrane.
12:55And in this context, membranes are multidimensional objects
12:59existing in a higher dimensional space.
13:02Some varieties of string theory lead us here,
13:04modelling our universe as a brain, a three-dimensional brain,
13:08embedded in a much broader structure known as the bulk.
13:12Now it's the bulk specifically that proponents claim
13:15has more than our four familiar dimensions,
13:18and again, potentially as many as ten or eleven.
13:21So, while we're confined to our home brain,
13:23there may be other brains existing alongside ours,
13:26each with the potential to harbour universes.
13:29Perhaps even with the potential to host multiverses of their own,
13:32of, say, the bubble universe variety.
13:35With brain cosmology, there's the potential to really up the ante.
13:39In some ways similar to the lower-level bubbles of eternal inflation,
13:43it could then be that these brains are right next to each other,
13:46in the bulk, and yet entirely inaccessible to us.
13:49It could be that they never meet, or link, or merge…
13:52although there are some theories that they, again,
13:55may wield indirect influence over one another.
13:58It's been suggested, for instance, that fundamental phenomena such as gravity
14:02could somehow leak throughout the bulk, permeating our membrane at least,
14:06and thereby dictating what is and isn't possible here.
14:10At the same time, there is discussion surrounding the follow-on question
14:13of what would happen if brains were to collide.
14:16Such collisions may give rise to new universes, or alter existing ones.
14:20Some cosmologists go as far as to suggest the Big Bang might have been a brain collision,
14:25spawning our realm alongside the untold others that could also be out there.
14:30This is still a topic of debate, and various, perhaps less radical ideas
14:35have been proposed to explain the Big Bang.
14:37There's arguably no strong evidence for any position, however,
14:40with the prospect of colliding brains therefore just as valid as any other.
14:45I have to show you that our friend has proven that time, indeed, has a beginning.
14:50Not only that, how the universe was born, and how it will end.
14:54Bang!
14:57Crunch!
14:58Do we have direct evidence for the multiverse in any form?
15:02Given all of the ideas that we've discussed, it's a kicker, but it's important.
15:06As things stand, we don't have any direct evidence that parallel universes exist.
15:11The multiverse and parallel worlds are much more theory than fact,
15:15but it's also a field of research that's really still in its infancy.
15:18As we've already seen, finding evidence for parallel universes is particularly challenging.
15:24The simple nature of alternate realities makes them inherently difficult to prove.
15:28By definition, they exist independently from one another,
15:32and therefore independently of literally everything we know.
15:35We're living, working, thinking, and existing in a separate and self-contained world
15:40as is every other world that may or may not be out there.
15:43It's unclear whether it would ever even be possible for contact between parallel worlds to ever take place.
15:50Even observation of them might be a step that's inevitably too far.
15:54All of the above applies for almost every conceivable parallel universe model,
15:59from bubbles to brains, quantum splits to pulsating strings.
16:04Nevertheless, many of the leading theories in support of parallel universes
16:08are based on strong scientific principles with intriguing possibilities.
16:13Optimists within the field may well hope that unknown future advancements in science and technology
16:19will one day make it possible to identify evidence.
16:22What's your opinion? Let us know in the comments.
16:26So, what next?
16:28Prove it.
16:30How do parallel universes affect our understanding of the cosmos?
16:35Philosophically, even contemplating parallel worlds requires a major shift in thinking.
16:40The concept challenges long-held, deeply entrenched views about who and what we are.
16:45Our traditional view of reality comprises space, time, matter and energy, all contained within our universe.
16:52But casting our net wider out into a multiverse suggests that for all the unknowns we already have,
16:58we've only ever been observing a tiny, tiny pocket of existence as a whole.
17:03In almost all proposed forms, an alternate reality could have different physical laws,
17:08different physical constants and multiple extra dimensions.
17:11Our safe and comfortable 3D plus time just doesn't cut it anymore, and the impact is profound.
17:17One of the most famous potential applications of the multiverse is that, in some versions,
17:22it could mean that there are multiple versions of you somewhere out there.
17:26So, how should we feel about that?
17:28Would the multiverse lessen the importance of our own lives?
17:31Or does it matter?
17:32Could it be argued that parallel worlds ultimately prove that free will is an illusion?
17:36Or are we still in control of what some may call our destinies?
17:40Looking deeper into parallel universes, it challenges any assumption towards us living in a single, objective reality.
17:47Instead, it thrusts us into an indescribably complex, multi-layered existence.
17:52And that's pretty exciting.
17:54Or maybe it's just quite scary.
17:57It's a probability storm.
18:00Every choice you could make, existing all at once.
18:03What's he saying?
18:04You're inside Schrodinger's box, and you're the cat.
18:08That doesn't make sense.
18:09What does the future hold for parallel universe research?
18:12To put it mildly, there is a lot that's in the pipeline.
18:16In the field of quantum mechanics, we're already seeing major advancements in quantum computing,
18:20which could enable us to control the subatomic realm like never before.
18:24In astronomy, our technology is constantly improving,
18:27with the James Webb Space Telescope recently becoming our single greatest and most powerful piece of observational equipment.
18:34It and its successors will provide unparalleled world of the universe, and perhaps beyond, for decades to come.
18:40Meanwhile, we have a growing network of particle accelerators like the Large Hadron Collider,
18:45which are continually revealing new bits of information about nature's most fundamental processes.
18:50Even higher energy colliders are reportedly coming.
18:53Which could probe even deeper, potentially taking us much closer to major advances in string theory or the brain world.
19:01What's clear is that right now, science is only just getting started.
19:05While science fiction has its fun dissecting all that could happen if parallel universes were real,
19:11science fact is busy chipping away at the concept in real life.
19:14But regardless of the specific findings, that can only be a good thing.
19:20Now it's your turn to deal with the consequences of your achievement.
19:28Parallel universes push the boundaries of modern science, encouraging us all to think outside the box.
19:34Quantum mechanics, cosmic inflation, string theory, and brain cosmology all incorporate it, in general,
19:41to potentially explain certain phenomena which might otherwise be unexplainable.
19:45But in the meantime, the entire endeavour encourages interdisciplinary, collaborative research.
19:51Thinking about parallel worlds is to blend physics, cosmology, math, and philosophy in a wholly fresh and unique way.
19:59It's big picture thinking, but on the grandest scale imaginable.
20:03And along the way, multiverse research is sure to trigger countless breakthroughs.
20:08But perhaps more than anything else, it's a line of thought that humbles us.
20:12Even the fact that parallel universes exist as an idea already represents a dramatic alteration to our perception of reality.
20:19If they ever were to be proven, then humankind will have truly entered into an all-new age.
20:25Steven.
20:30I'm glad I fell into your universe.
20:34So am I, kid.
20:37So am I.
20:38So am I.