Of all the most bizarre points of research in science, the growing theory of parallel universes
is perhaps one of the most exciting. The idea that our universe, the largest structure we know of,
could potentially be one of many can feel at times almost impossible to comprehend.
But scientists are increasingly inclined to take the topic seriously,
with one physicist even theorizing different levels of multiverse in our wider reality.
This is Unveiled. and today we’re answering the extraordinary question;
what if humanity lives in a Level Four multiverse?
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Physicist Max Tegmark not only believes in the multiverse but has proposed his own multi-layered
structure for it. He argues that the concept of the multiverse shouldn’t be considered a theory
only, but rather a prediction based on other more established theories, such as cosmic inflation.
In whichever way he arrives to the conclusion, though, Tegmark separates his multiverse into
four different levels, each building upon the other in terms of complexity and possibility.
A Level One multiverse, for Tegmark, is the most basic.
It assumes that the universe is both infinite and has a somewhat even distribution of particles,
which are both well-supported claims. From here, it then figures that the universe goes on forever,
repeating any and every particle arrangement allowed by the laws of nature - theoretically
an infinite number of times over. In Tegmark’s Level Two multiverse,
universes have the potential to isolate themselves across another, even higher plain,
which allows for infinite bubble universes that each contain Level One multiverses within them.
As the structure of reality broadens, Tegmark suggests that these bubble universes could then
have different particle possibilities, elements, and perhaps dimensions.
Next, Level Three incorporates quantum mechanics into the equation, and theorizes that each time
a decision is made - any decision - or something random occurs, the (by now already multi-layered)
universe splits into different branches once again. A Level Three multiverse doesn’t allow
for more physical possibilities in and of itself, but each decision - even if it’s a tiny decision -
does get its own version of the universe from that point forwards. And all splinter universes
from every possible moment are equally real. We’ve taken a closer look at the lower levels
to Tegmark’s model in other videos on our channel, so be sure to check them out!
But now, our focus is on Four! A Level Four multiverse is even more fundamentally based
on one of the greatest questions in science - what is reality? For Tegmark, there are
two main schools of thought. The Aristotelian paradigm says that physical reality (and what
we experience of it as humans) is real, but we use mathematics to try and make sense of it…
while the Platonic paradigm takes the opposite stance and sees mathematics as the real truth of
the universe, while our perceptions of it are only limited approximations. More broadly speaking,
Tegmark shows how this question of reality has important implications for general science.
For example, if the Aristotelian view is the right one, then scientists will never find a theory of
everything since our subjective experiences are all different. If the Platonic view is right,
however, if mathematics makes up the universe itself, then there is a theory of everything
out there, somewhere. With regard to the Tegmark multiverse specifically, Level Four sides with
the Platonic view - that mathematics is key. The proposal first draws upon our overriding,
innate reliance on math in just this universe. Mathematic laws seem fundamental to us.
For instance, when humanity launched Voyagers 1 and 2 in the 1970s, we equipped them with a
golden record inscribed with various attempts to communicate with potential aliens through science
and math. Our cosmic position given pulsar locations, what our hydrogen atom looks like,
and various instructions coded in binary - they were all etched into the now-far off golden discs.
The thinking being that math should transcend any possible language or communication barrier
between us and whoever should find the Voyagers. The thinking also being that
the universe is, in essence, made of math. But Tegmark takes the notion further for a
Level Four multiverse, by drawing on ideas such as Robert Nozick’s Fecundity Assumption - which
suggests that if a world is possible then it must exist. Level Four supposes, then,
that all possible mathematical equations (and therefore worlds) must take place somewhere.
Even with the infinite bubbles and endless splinters of the multiverse (as per Levels One,
Two and Three) there must also exist more than just the mathematical world of this universe
(or this multiverse) to contend with. This creates an essentially infinite
degree of versatility and an infinite number of possibilities. Levels One to Three already allow
a huge amount of diversity in terms of dimensions and possible elements, yes, but all must still
conform to certain, natural expectations. Time, motion, thermodynamics, and more, must be adhered
to. However, this isn’t the case at Level Four, as any one multiverse can ultimately have totally
different laws of nature compared to any other multiverse. With only the endless possibility of
math to guide it, there’s really no telling how reality could unfold in any one place.
This creates worlds that are very hard to imagine. There could be universes
where time moves backwards, or in irregular spurts instead of along a dependable line.
There might be places where gravity exerts itself in a wholly different way,
or where thermodynamics work differently, as well. Universes where motion works differently, for
example, could have moving objects that naturally get faster as time moves on, instead of slower… or
perhaps there’d be a place where there were only two speeds: zero and the speed of light - which
can now be anything, too, and not just the speed of light as we understand it. These worlds are of
course so difficult to imagine because we’re so used to the reality we just so happen to live in,
where objects fall to the ground and light travels at a consistent speed. But,
when those laws can vary, anything is possible. Beyond just what’s inside them, however,
every universe in a Level Four multiverse is also a mathematical shape. Thinking about just
our universe, that means that somewhere - at some higher level of understanding - even it
could be described as a specific shape by mathematics. But now, every other possible
shape should also correspond to a universe, too. And herein lies the basic, endless landscape for
a Level Four multiverse. Every mathematical shape imaginable has an accompanying reality.
These aren’t optional, either. Tegmark suggests that if a shape is mathematically possible,
then it must have a real, physical incarnation. He calls this principle Mathematical Democracy,
highlighting that the multiverse isn’t simply allowed to pick and choose which
shapes to represent, and so it must represent all possibilities. There is no cosmic favouritism or
asymmetry in a Level Four multiverse. One final realisation out of all this,
however, is that Level Four would mean once and for all that our universe isn’t special.
Instead, it’s just a mathematical shape in amongst endless other mathematical shapes.
It’s just a ball of complicated equations, in a never-ending mass of other balls made up of
other complicated equations. A Level Four multiverse is, then, the last and definitely
final level of Tegmark’s multiverse model, as it could never be superseded. Because, if we were
to devise some other structure to contain all possible multiverses to this point, then really
we’d have only devised another mathematical shape - another mathematical reality - and so it would
simply be a continuation of Level Four. So, what might the future hold for us?
Will the multiverse ever be officially proven and confirmed? Or will it remain a subject for
increasingly confident scientists to debate, only? Across his various articles, papers,
and presentations, Max Tegmark appears to concede that Level One to his model
remains the easiest to come to terms with, and therefore the least controversial. But, as we
move up through the levels, this bold attempt to explain reality gets more and more exciting.
At the very top of Tegmark’s thinking, even whole universes become really quite tiny things. We’ve
moved from one infinite expanse, to infinite bubbles containing expanses, to the many worlds
of the quantum realm, to the mathematical structures that could encase them all. It’s
been quite a journey… but that’s what it could be like if humanity lived in a Level Four multiverse.
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 and ring the bell for our latest content.