Welcome to the vast and infinite realm of
the multiverse. There’s nothing quite like it in all of science, physics, space,
or theoretical thinking. It’s a concept that essentially laughs in the face of most
mainstream models on how the world works, and provides us instead with an endless, glittering,
constantly regenerating expanse… of potential. By now, thanks in large part to
various works of science fiction, we of course know that the multiverse is
multiple universes. A web of realities that’s in some way entangled to form the true,
wider, total physical structure that we are but a tiny part of. It’s parallel dimensions and
alternate realities; it’s bridges, wormholes, quantum phenomena and time travel.
It’s thrilling and it’s disconcerting. Thankfully, then, some have at least tried to make
even a little bit of sense out of it all. And, today, we’re moving through the many levels of
one explanation of the multiverse, in particular. This is Unveiled, and today we’re
taking an in-depth look at the nine types of multiverse, according to the
theoretical physicist Brian Greene. Do you need the big questions answered? Are
you constantly curious? Then why not subscribe to Unveiled for more clips like this one? And
ring the bell for more thought-provoking content! Brian Greene is a US physicist and mathematician.
He was born in New York City, graduated Harvard and Oxford, he’s a professor at Columbia
University, and he founded (and chairs) the World Science Festival. He’s also deeply integrated
in the modern history of the multiverse. In 2012, Greene released his book, “The Hidden
Reality: Parallel Universes and the Deep Laws of the Cosmos”. In it, he outlines one of the most
comprehensive attempts to explain the multiverse, in full, dividing it all into nine more
specific categories. While variations of the categories had been seen
(and debated) before, by others, Greene pools them all together in a bid to
finally nail down the true nature of reality. #1: The Quilted Multiverse In general, this is the simplest of all Greene’s
multiverse types. The quilted multiverse only really requires this universe to be infinite
- which many believe that it is. From there, all manner of arguably “parallel” worlds are
possible. It certainly works in theory because in an infinite structure, everything should be (and
happen) an infinite number of times - including all possible variations of physical matter.
Greene suggests that it’s only due to the universal speed limit - the speed of light - that
we’re wholly unaware of the multiverse we’re in. If true, one of the implications is that not only
do we share this universe with other life forms, but we share it with other versions of ourselves.
Naturally, we know that life the like of which we find on Earth is possible… because we’re the
proof of it. So, in the quilted multiverse, somewhere beyond the catchment of lightspeed,
life as we know it should happen again. And again. And again, an infinite number of
times. On a larger scale, the same should be true for planets and stars. Meaning that,
in this quilted reality, there should be other instances of Earth and the sun, of our entire
solar system, exactly as we know them. And, in fact, there should be an infinite number
of other solar systems, just like this one. The other implication is that if we could
only find a way to travel beyond lightspeed, then we would eventually discover this
multiverse with our own eyes. In simple terms, it should be only a matter of traveling in any
direction for long enough before we inevitably encounter ourselves, again. As to all of
the other variations of life, matter and energy that we might find along the way… it’s
a patchwork of yet more infinite possibilities. #2: The Inflationary Multiverse Sometimes referred to as the bubble
multiverse, this rendering asks us to take our first major step away from the
conventional cosmos, as we typically know it. The inflationary multiverse is born out
of eternal inflation theory… which says that, at the highest level, our reality is
always expanding, and that an event such as the big bang could actually be caused by that
expansion, rather than being the cause of it. Along our own timeline, we know that there
was a period of extremely rapid expansion that occurred fractions of a second after our
universe began. During this fleeting moment, space-time grew faster than light speed. A
subatomic speck was transformed into a sprawling expanse teeming with energy and potential. And
this initial burst set everything in motion. But, in the higher, wider inflationary
multiverse, it didn't happen just once. Such inflation wasn’t an isolated event, but
was (and is) an ongoing process occurring in different regions at different times - like
popcorn kernels popping endlessly in a vast, cosmic popper. Each kernel represents potential
universes within bubbles that are expanding within higher-dimensional space. But, no one piece of
popcorn pops at exactly the same time, nor in exactly the same way. Scaled up to multiverse
level, this means that every bubble universe that’s created isn't just separate; but should
also have its own unique laws and parameters. The laws of physics that we know are universal,
yes, but perhaps they aren’t multiversal. Every bubble stands alone. One might have stronger
gravity, for example, or no electromagnetism. Another could be teeming with forms of
matter that are fundamentally alien to us. #3: The Brane Multiverse With its roots in M-theory - an extension of
string theory that requires eleven dimensions to work - the brane multiverse model also suggests
that everything we know exists as just one of many on another, higher plane. This time, however,
the universe is a three-dimensional membrane, floating in a higher dimensional space -
sometimes called the bulk or hyperspace. Brane cosmologists also suggest that the
infinite nature of reality should mean that there are endless other membranes out there,
all also suspended in the same broader structure. One key implication, however, is that it
might be possible for separate membranes to interact. And for those interactions to then
have a profound effect. From our point of view, perhaps our membrane - our universe - has before
collided with another. Or maybe we’ve spent our entire 13.8 billion years overlapping with
a nearby membrane - another reality - which has then in some way shaped this
reality in a fundamental sense. The brane multiverse also triggers all new
considerations when it comes to potentially moving through the multiverse. Whereas in the
quilted and (to some degree) inflationary models, traveling the multiverse may only ever boil
down to reaching (and breaking) light speed… in the brane, a would-be traveler would need to
physically cross over from this world to another. #4: The Cyclic Multiverse This grade of multiverse is closely
related to the previous brane model, but it rests on one idea, in particular. In
the cyclic multiverse, membrane universes certainly do interact with each other,
and in the most profound way possible… because collisions between branes are
here what double up as big bang events. Now, the multiverse assumes a more dynamic
and even more eternal regenerative trait, as the membranes in the bulk also become the
birthers of other universes, just by being there. The precise mechanics of how a membrane
collision could cause something as dramatic as a singularity cascading into life… are unknown. But,
if true, it’s a model that repaints hyperspace as being something like an easel, upon which a chain
reaction of creation is constantly unfolding. Of course, this is hardly the only cyclic model
in cosmology, in general. The big bounce theory has fallen in and out of favor over the years,
suggesting that universal expansion will one day halt, and everything will contract back
inwards from that point… until such time as it’s all compacted back down into a singularity,
and the big bang happens again. At that moment, it could be said that the universe will
have been bounced back out into space. The cyclic multiverse, by comparison, employs
a similar logic, but on an even grander scale. #5: The Landscape Multiverse Next, and we’re heading full tilt into string
theory, probably the most well known attempt at a “theory of everything” there is. It
posits that the fundamental constituents of reality are one-dimensional, vibrating
"strings" rather than point-like particles. And one (of many) things that this would
affect is the makeup of the multiverse. In general, string theory allows for many
different ways in which its strings can vibrate, and each mode of vibration corresponds to
a different elementary particle. Meanwhile, and as a result of that, reality is really
divided into many more dimensions than just the three space plus time that we’re familiar
with. There are then many possible shapes that all of those extra dimensions can take,
when they’re compacted down. In fact, there could be an effectively
endless number of shapes possible, each leading to an all new universe with
its own distinct set of physical laws. The landscape of the “landscape multiverse”,
then, pitches these different universes as though they exist along a never ending series
of hills and valleys. Every universe of the multiverse… appears somewhere along this
structure. Some are more stable than others, but none are identical. All are unique. In this
view, our universe just so happens to reside in one valley within this broader landscape created
by the fundamentals of string theory. And our particular set of physical laws corresponds
to just one way in which strings can vibrate. But, all the while there are infinite
other valleys and environments out there, to represent all other universes with
different laws derived from their own unique vibrational patterns. And their
own unique shape, taken as a result. #6: The Quantum Multiverse Along with the quilted multiverse, this
is probably the most widely known and discussed of all Greene’s nine types.
The quantum multiverse suggests that at every moment when a choice or diversion
is made, a new universe is created along with the one we inhabit. It works
on both the micro and macro levels, and is best laid out by the famed Many
Worlds Interpretation of quantum mechanics. On the quantum level, due to various phenomena
including the observer effect and wavefunction collapse, we know that particles can
be one thing or another - until they eventually settle down into what they ultimately
become. But the quantum multiverse imagines that nothing is lost as reality takes shape;
that all possible outcomes take place, just along an endless mesh of different
timelines. These timelines (or what some refer to as parallel worlds) are constantly
branching off from the one you’re in right now… which, in itself, has branched
off of uncountable others in the past. It’s perhaps more satisfying to visualize
at a larger scale, though. Consider all of the choices you’ve already made today. What you
had for breakfast; what you said to a colleague; how many YouTube videos you’ve watched; whether
or not you scratched behind your left ear, switched your alarm to snooze, or tripped on
your own doorstep. You might think of some of your actions as being more consequential
than others, but in the quantum multiverse they’re all equally valuable… because they all
spawn parallel worlds of what could have been. Apply the same thinking to every single quantum
fluctuation that’s happening all around you, countless times, during every single second
of your existence… and the sheer density of this particular multiverse becomes clear. Some
strands of it will be almost indistinguishable from the one along which you’re currently living.
But, still, take just a short journey through it, and you could very quickly end
up in an entirely alien place. #7: The Holographic Multiverse This wouldn’t be a video about the true
underlying physics of reality without at least a passing mention of black holes - and this
is that mention! The holographic multiverse builds on the holographic principle, which says that
our three-dimensional reality could be encoded on a two-dimensional plane. That everything
we know - from stars and planets to cars and sandwiches - is actually projected from
that 2D structure, to generate our universe. It ties back to black holes as a possible solution
for the black hole information paradox. This is the realization that information is seemingly lost
in black holes that eventually evaporate away, despite that apparently being impossible
as per the conventional laws of physics. Grand cosmic holography isn’t the only -
or even the most well supported - solution, but for advocates it could be that the
seemingly lost information within a black hole is actually encoded
in 2D along the event horizon. Apply a similar model to the entirety of the
universe, and it could well be a process that happens time and time and time again. And
suddenly the multiverse begins to feel like a multiplex cinema, with multiple movies (or
realities) playing across multiple screens (or spaces). Perhaps more than any other model
up until this point, it could quickly make you feel quite… inconsequential. Suggesting,
as it does, that at your root you’re not even a three-dimensional being. However,
and as with all proposed multiverse types, it can also easily be argued that, really,
it doesn’t matter. That, even if life, the universe and everything is a hologram,
nothing actually changes from our point of view. #8: The Simulated Multiverse This is another of the more widely
known multiverse possibilities, given how it’s permeated pop culture in recent
times. Born out of the simulation hypothesis, as proposed by Nick Bostrom, it says
that our universe is first and foremost a product of complex digital code. That everything
we know, see and feel is only ever the result of a program that’s running on some far-off
supercomputer, in a higher dimension. For those in favor, it might even be argued that
a simulated multiverse is inevitable so long as technology progresses. In our own world, we’ve
seen how computer simulated games and virtual reality experiences have become more and more
life-like over a relatively short period of time… to the point that some have predicted it
may be impossible to tell the difference between the real world and a simulated environment, in
the future. Ideas on the simulated multiverse simply approach that line of thinking from
a different perspective. Because, what if, for some other, higher, more advanced civilization
or entity, that line has already been passed… and we’re the ones being convinced (or tricked) by
it? What if our world is just a very good sim? Traditionally - so to speak - it was an idea
that led some to envisage one single controller or player; a supreme, god-like being who’s
watching over our every move, because they’ve designed every single thing about us. But combine
all the potential for a simulated reality with the endless repetition of a multiverse… and
you quickly land on something even bigger. If simulated universes are possible,
and if multiple universes are possible, then all that we know could (even should) be
just one variation of cosmic code in amongst an endless stream. Consider that we, ourselves,
have constructed simulated realities, albeit quite primitive and superficial at present. This would
mean that our controller created us to create and control others. So, why not a creator for our
controller, to control them while they control us, while we control our sims, and so on? Then
consider that comparable chains must surely be erupting an infinite number of times
along an infinite number of other chains, and we again have one of the deepest
and densest multiverses imaginable. #9: The Ultimate Multiverse Finally, to an effectively unknowable
multiverse that represents the most expansive and all-encompassing of
all concepts possible. In this view, every conceivable universe with every possible
set of physical laws and constants exists within a grand cosmic collection. Imagine that
you could lay all of everything we’ve covered in this video out on the table, and bag it
up. The ultimate multiverse is that bag. Sometimes referred to as
the mathematical multiverse, and directly comparable to Max
Tegmark’s level four multiverse, it transcends all possible constraints that
might be placed on any other multiverse version. In this staggering vision, not only are there
universes like ours with slight variations, or even like ours but with radical differences…
there are also universes that are governed by completely different mathematics. This means that
any form of logical or mathematical structure that can exist does exist as a separate
reality somewhere within this overriding, ultimate landscape. In this way, most of
it is impossible for us to even picture, given the limited view that we inescapably have.
It’s a final structure that pushes infinitely far beyond our understanding of physics because it
suggests that our own universe's laws - everything from quantum mechanics to general relativity
- are not uniquely fundamental in any way, whatsoever. Instead, we’re merely cast adrift
in an endless sea of theoretical frameworks. While highly speculative and abstract,
contemplating such a multiverse challenges us to reconsider what we deem as
necessary truths about existence, in general. It opens up profound questions
about reality's true nature and our place within it. It may be, then, that our universe
isn’t just one page in a much longer book, but that it’s one page in an endless library. For
some, the ultimate multiverse could even lead to a multiverse of multiverses, contained only
by the one truth that it cannot be contained. So, what do you think? Which of Brian
Greene’s nine types of multiverse do you think hits closest to the truth?
Or are you unconvinced by the idea of a multiverse in any form? Let us
know your take in the comments! For now, while the prospect of a multiverse is
increasingly covered in contemporary science, it remains true that - at its heart
- there are questions that humankind has always wrestled with and will
always wonder about. Why are we here? What is our purpose? How real
is real? And what does tomorrow hold? Importantly, the multiverse
has yet to be proven. But, it’s an idea that’s very much alive, and
challenging us all to take a higher, wider view. What do you think? Is there anything we missed?
Let us know in the comments, check out these other clips from Unveiled, and make sure you subscribe
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