We're guaranteed to find an identical copy of our whole universe, as well as countless
variations where things are similar to here but still different.
Multiple universes now are a genuine possibility, which begs the question:
Now, it probably doesn't surprise you that studying parallel universes was once
considered completely bonkers in the scientific world and even alienated people who
decided to pursue it.
When I was a grad student, I used to secretly print out my multiverse related papers.
This job was the only job I was ever interviewed for.
I was on the verge of having to drive a taxicab.
Now, theoretical physicists have realised that parallel universes are possible,
mathematically at least
Now, one of these reasons comes from the weird world of quantum physics.
The important thing to remember about quantum mechanics is it's weird.
It really is weird.
It's the study of subatomic particles, the building blocks for every single thing around
us in the universe.
And what it tells us is that these particles can be both particles and waves,
but crucially, they can be both at the same time, which splits our reality, giving us multiple
different universes.
The idea here is that when you make a measurement of a particle
that's here and there at
the same time and you find the particle over here, then there's a you which finds a
particle over here in this world.
But at the same time, there's another world over there where another you has found
the particle over there.
And both of these worlds are equally real.
So the quantum multiverse is not separated from us by distance.
It's not someplace very, very far away
It's some place effectively here in space
But the complexity of the quantum dynamics prevents these different branches
from talking to each other.
Whether you like it or not,
the fact that we live in a multiverse is the dominant scientific paradigm.
Suck it up.
Another theory is one of mathematical inevitability
if our universe is made from a finite
amount of simple matter, then it follows
that other universes are made in a very similar way.
Just as this house is made out of fundamental building blocks that we call Legos,
everything in our world is made of fundamental building blocks
we call elementary particles.
And if you have some random process arranging elementary
building blocks in a
finite volume, there are, of course, very, very many different ways in which it could do this.
And that means that if this process repeats and an infinite number of other volumes
of the same size, then we're guaranteed that eventually it's going to create every
possible arrangement.
We're guaranteed to find an identical copy of our whole universe, as well as countless
variations where things are similar to here, but still different.
Even a Max over there who's identical to me, not just in his physical appearance, but in
that he actually feels that he is me.
Another theory called Inflation describes how the universe expanded exponentially in the
very first tiny fraction of a second after the Big Bang.
But with some areas of space expanding faster than others, creating bubbles or pockets of
spacetime where other universes could have formed.
If this idea turns out to be right, then it could mean these pocket universes
developed with the very own laws of physics
so there could be another you in those universes that's able to walk through walls or fly
through space.
So if our universe is not alone, the question remains:
According to quantum theory
there's a new version of you and a brand new universe made with
every single decision you make.
So every time I flip a coin, say, heads or tails, that is just some little quantum accident.
The universe is splitting into two worlds every time it comes up, heads or tails.
So our experience of the splitting is like the experience of walking through a
garden of paths that fork
When we come to a fork in the path, we take one or the other heads or tails.
But both forks exist at the same time.
We only experience one of them.
There are literally gazillions of universes out there, of which ours is only one.
Then there's the patchwork model and near identical copy of our own universe just made elsewhere.
In this kind of parallel universe
there's another you that's very similar, just with subtle differences.
We're guaranteed to find countless variations where things are similar to here, but still different.
The dinosaur killing asteroid that was our lucky break
missed Earth so there are no humans, just dinosaurs in Winchester today.
There's another one where I didn't make it as a physicist, but I'm actually enjoying life
working as a bartender.
Then there's a whole bunch which are very similar, where I just chose to dress a little
bit differently.
These ideas all point towards multiple weird and wonderful universes existing out there
but with scientists not able to see the entirety of our own universe
Scientists think that they might be getting a little bit closer.
Truth goes through three stages.
First, it's ridiculed, then opposed strongly and finally becomes self-evident.
Perhaps now we are reaching the stage of self-evident.
Scientist Laura Mersini-Houghton found
something really weird.
She found evidence for what appeared to be two universes crossing over.
The detection of the cold spot, which was one of the signatures that we predicted by tracing forward the
quantum entanglement of our universe with all the other surviving universes.
We predicted that there should be a large area in the sky of about 10 degrees.
And indeed, that's what was observed about seven months after we made the prediction.
Recently, there's also been a big leap forward for inflation theory, which predicted that
if this rapid expansion of the universe happened, it would send ripples out into the universe.
We call these ripples gravitational waves.
We'd never detected anything like this until 2015 when two experiments called LIGO and VIRGO
managed to detect gravitational waves coming from the merger of two black holes.
With that detection made, it makes it more likely that we might be able to detect
gravitational waves from inflation.
But why should we really even care about figuring out if multiple universes exist?
Well it actually feeds into the age old question of what is our universe expanding into?
If other multiple universes exist, perhaps our universe expands
as neighbouring ones contract.
And this could actually tell us more about our own universe and especially how
our own universe will end.
Perhaps eventually we will expand until those other neighbouring universes also then have a
big bang and start expanding into us, which means that we then start contracting and
perhaps our universe will end in a big bang, but in a big crunch.