Are you for real?

Are you a hologram? Do you live inside a computer? Is this the only universe? Physicist BRIAN GREENEtells us why the questions matter and why maths may have the answers

IN THE LAST issue of

Bang

we had a short piece on the theory that you and the world around you is actually a computer simulation. We were so fascinated by the idea that we got in touch with the bestselling author and physicist Brian Greene, whose latest book

The Hidden Reality

is about the various types of “multiverses” – parallel or other universes – there might be.

Greene works in an area known as string theory and his book is full of incredible theories, including the idea that we may just be holographic projections and that there may be other versions of you somewhere out there in the universe. What’s more, these odd ideas not only have groundings in maths but may ultimately be provable some day.

The massive “atom smasher”, the Large Hadron Collider, for instance, could deliver visible proof that ours is not the only universe.

He explained to us how these ideas work and how they might be proved. These are strange, sometimes difficult ideas, but incredible and fascinating ones that scientists are taking seriously.

The idea that we might all be living in a computer

"This comes from two things that many of us are familiar with: from something like The Matrixyou can at least imagine that the reality we know about may be simulated in some way, either by stimulating the brain appropriately, as in The Matrix, or just by creating a fantastically realistic computer simulation where beings like you and I may exist but think it's real.

“The interest in this came from Nick Bostrum over in Oxford. He made the simple realisation that if it is possible to make these simulated worlds in the future they are so much more easily created than a real one. So you’d expect, over time, there would be many more simulated realities than real ones and by the sheer numbers involved there’s an overwhelmingly probability that if you’re experiencing a reality it’s probably a simulated one.

“But frankly the real reason I brought this up in the book is not so much to argue that this is really what’s happening – it may or it may not, but take that with a grain of salt – what I find fascinating is this possibility that it provides a wonderful way for allowing a reader to understand how mathematics can relate to reality.

“Often people say, ‘you keep talking about maths but how can these mathematical calculations be related to the world we see?’ This potential of a simulated world helps get the idea across because if you and I are right now in a computer simulation, it certainly seems real. But if we’re in a computer and you were to open its hood and look inside you’d see a bunch of ones and zeros dancing around inside in a manner dictated by mathematics.

“So in that sense everything we are experiencing would be the result of mathematical manipulations. Whether it’s happening around us is irrelevant, it helps gives us a sense of how maths and reality can come together.”

We might just be holograms

“The idea is certainly one of the strangest we’ve come upon in recent times. It goes like this: various investigations to do with black holes and string theory are coming to the conclusion that all we see in the world around us might be a kind of holographic projection of more fundamental processes that take place on a distant thin surface that surrounds us.

“It’s much like an ordinary hologram, which is a thin piece of plastic that, when you illuminate it correctly, yields a realistic three-dimensional image. We may be that realistic 3D image. And the thin piece of plastic may just be laws that exist on a thin surface that exists on the edge of the universe.

“That is a profoundly strange idea but if I give you just one more piece of information on it, it makes it clear where it comes from. There’s been a puzzle about black holes in space for a long time: it is that if you throw something into a black hole what happens to the information it contains? If I throw in an encyclopaedia or your iPad, what happens to all of the data? The original idea was that it would just be gone, destroyed.

“The problem with that idea is that it runs into a conflict with a fundamental feature of quantum theory which basically says that information cannot be lost. So people struggled with it for a long time: black hole says it’s gone, quantum theory says it can’t be gone.

“The answer people have come to is that the information thrown into a black hole seems not to be gone. It seems actually to smear itself around the surface of the black hole, which means that information on the surface of the black hole can be adequate to describe a 3D object like an iPad or an encyclopaedia.

“People have concluded that the notion that seems to be true for a black hole might be true more generally; that all the information needed to describe the world around us, the 3D world we see, actually can be encoded on a two-dimensional surface that surrounds us. And in fact the 2D surface might be the primary place where that information really resides.”

There may be other versions of you in the universe

“This comes out of the most mild of assumptions: that space goes on infinitely. We don’t know if it does but it’s just one of a couple of viable possibilities. Either it goes on forever or it doesn’t.

“If it doesn’t, then maybe if you go out into space far enough you double back on yourself rather like the surface of the Earth. Or maybe you just go on forever, and that’s a possibility scientists have taken seriously for a while. And if you couple that with the mathematical laws we know about here, that apply everywhere – we don’t know if that’s the case, but it’s a reasonable assumption – you get to this rather startling conclusion that matter can only arrange itself in a finite number of ways, in any finite region of space.

“The shuffles of a deck of cards have to be repeated because there is only a finite number of orders. Go through space far enough and the order of the particles has to repeat.”

If he had to bet on one multiverse theory being proved

The multiverse from string theory is called the “brane universe”, this idea that all we think we know about may be on this giant membrane – I like to think of it as a giant slice of bread – with the possibility of other universes, other slices of bread out there, populating a grand cosmic loaf.

“I like this idea because it may be testable in the not too distant future at the Large Hadron Collider. If that picture’s true, violent collisions between protons can create debris that would be ejected off our brane, off our slice of bread, off our universe. So there would be less energy left in our detectors after the collision than before. So people will be looking for these missing energy signatures and, to me, if they’re found that’s a nice and strong piece of circumstantial evidence that there might be other universes out there.”

Our universe may not be special

“I took my son, when he was four years old, to a shoe store, and the guy measured his foot for a shoe, and we tried it on and bought it. And when we left, my son said, wasn’t it amazing that the shop happened to sell just his size. Of course, I explained to him that the shoe had all sizes but that’s a bit like our view of the universe.

In the last 500 years we’ve gone through a series of cosmic demotions. First we thought the Earth was at the centre, then the sun, and the sun as one of many stars and the galaxy as one of many galaxies. If this idea is correct then you take this one step further: not only are there many stars and many galaxies but there are many universes and it’s not that ours is particularly special it’s just the one in which the shoe fits, the one in which the conditions allow us to exist.”