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Parallel Universes -

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Parallel Universes

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What makes our universe just right for our existence? It could be that the universe we call home is
one of many, just a small part of a huge multiverse. Graham Phillips looks into various multiverse
theories and highlights the difficulty in proving the theories. However, there are high hopes that
CERN's Particle Accelerator will turn those theories into reality.

Dr Graham Phillips

Here's a great mystery: imagine you could vary the laws of physics. You can make gravity a bit
stronger or a bit weaker, or say, change the mass of the electron. Because everything in the
universe is connected to everything else, there'd be flow-on effects. The bottom line is, complex
life, like you and me, wouldn't be able to exist. Begs the question - has the universe been set up
for us?

Professor Lawrence Krauss

It looks like the universe is fine-tuned for our existence, because any small change in any
fundamental constant would mean we wouldn't be here. Now for some people, that sounds religious,
but in fact, it's kind of a version of, of cosmic natural selection if you want, cosmic evolution.

NARRATION

This cosmic evolution requires the very sci-fi concept of parallel universes, where our universe is
just one of many. Collectively, they're called the 'multiverse'.

Professor Lawrence Krauss

Each different universe within the multiverse could have different laws of physics, and that's
really interesting, because it could mean in that case that the laws that we see here are not, are
not fundamental at all. They're just an accident, an environmental accident.

NARRATION

In our universe, the accident was just right for life like us. That's the theory of cosmic
evolution.

Dr Graham Phillips

So, mystery solved, you might say. But what's the origin of this multiverse? Well, it could have
been there wasn't just one big bang. Maybe there were many, each giving rise to a different
universe.

Professor Lawrence Krauss

Our current best idea of what happened in the early universe is this idea called inflation that
says our universe expanded very, very fast in a very short time. But in fact, as a result, that
means there could be other regions in the universe that did the same thing, and are forever beyond
our horizon, we'll never see them. And in fact, there could be an infinite number of different
universes that are causally disconnected.

NARRATION

To imagine this multiverse, think of boiling water.

Associate Professor Charley Lineweaver

It's kind of like a pot of water, and you're heating up the water, and then you get these bubbles.
And so inflation acts like to get this bubble at the bottom of a pot of water and go, 'brrmp',
really big.

NARRATION

Each of these bubbles grows into a separate universe.

Professor Lawrence Krauss

The other possibility for a multiverse comes from recent ideas from particle physics which suggest
perhaps that there may be extra dimensions in nature. And it's possible that there could be other
universes, literally a millimetre away in an extra dimension, and we wouldn't know about it.

NARRATION

Remarkably, the atom-smasher at CERN could find them. Physicists would go wild.

Professor Geoffrey Taylor

Absolutely amazing. That is a massive discovery. I mean something beyond any of our dreams right
now.

NARRATION

These extra dimensions would explain a mystery about that force that holds the universe together -
gravity. Why is it weaker than theory predicts? Because we only feel a fraction of its full force.

Professor Geoffrey Taylor

So it may well be that gravity that we're seeing appears very weak because it's just a leakage from
higher dimensions into our world.

NARRATION

If the higher dimensions theory is true, many black holes will appear in the collisions at CERN.

Professor Geoffrey Taylor

We may be able to create black holes because we connect with those higher extra dimensions.

NARRATION

Now let's get this straight. We're not talking about earth-eating black holes, like these. Rather,
miniature ones that evaporate as soon as they're created.

Professor Geoffrey Taylor

We should be able to create these mini black holes and they'll have a fairly distinct signature in
the detector.

NARRATION

Find that signature and there might be other universes hidden in those extra dimensions.

Professor Lawrence Krauss

There could be an infinite number of three-dimensional or four-dimensional universes like our own
embedded in that larger space. So not far removed in our three-dimensional world, but far removed
or maybe even close up in a little extra dimension, just above your nose.

Dr Graham Phillips

Now if what you've heard so far is threatening your sanity, I've got some bad news. This next
multiverse theory is the strangest of all - the many worlds interpretation of quantum physics. It
is bizarre.

Professor Ray Volkas

When I first became aware of this, I didn't like it.

Professor Geoffrey Taylor

Yeah, it's very whacky, no doubt about it. Very difficult for us to, to really get to grips with
how, what it means.

Professor Ray Volkas

It seemed to me to be superfluous and even kind of, kind of shocking and frightening.

NARRATION

In the many worlds theory, for every one of us, there is a multitude of duplicates.

Professor Lawrence Krauss

So there are an infinite number of other universes, quantum universes, but I pick the one I live in
by observing it.

NARRATION

Confused? Well maybe an analogy will help.

Dr Graham Phillips

When you toss a coin, conventional thinking says it lands on either heads or tails. But imagine
just before it lands, the world splits in two. In one world, the coin lands on heads, and in the
other, it's tails. That's the essence of the many worlds interpretation.

Associate Professor Andrew Greentree

Any time there could be multiple outcomes, different measurement results that we can observe, then
both of those results actually occur.

Professor Ray Volkas

And so in a sense, we also split into different versions of us.

Associate Professor Andrew Greentree

Then there must be other copies of you. Other copies of me, having this conversation in slightly
different ways.

Professor Lawrence Krauss

There could be an infinite number of Graham Phillips. There could be an infinite number of me.
There could be a universe in which I'm interviewing you.

NARRATION

Could we ever meet our double?

Associate Professor Andrew Greentree

This is something that everyone thinks about. We don't talk about it very much in our lectures. We
don't tell our students about it. Um, but it is something that we think about.

NARRATION

Excitingly, it can't be absolutely ruled out, and in case you're wondering, quantum physics is no
fringe theory.

Professor Ray Volkas

It's an incredibly successful theory, and quantum mechanics has never been falsified.

Associate Professor Andrew Greentree

What gets me, the more I've gotten into quantum, is the fact that it actually makes sense to me
now.

Dr Graham Phillips

So there's no shortage of multiverse theories - in fact, an embarrassment of riches, really. How
can we prove these other worlds exist if we can never visit them?

Professor Brian Schmidt

So the problem with this idea of the multiverse is it sounds great, but you've got to be able to
test things. So you know, we have science, we have metaphysics. So metaphysics is sort of, you
know, it seems good, but we have no way of testing it.

NARRATION

But soon, we may be able to separate the multiverse from the metaphysics, by coming up with a brand
new theory that explains our universe very well.

Professor Lawrence Krauss

Maybe it explains everything that we can see, but one of the predictions is also that there are
other universes that we can't see, we probably say it's physics. Because we say it explains
everything we see, so the predictions we can't see, we're willing to believe.

NARRATION

Then the mystery of why our universe seems to have been set up for us would have been
scientifically solved.