By BBC – The idea that we’re all pawns in a simulated universe isn’t a new one by any means. In his famous Allegory Of The Cave, the Greek philosopher Plato illustrated how what we assume to be real can so easily turn out to be an illusion. Some 2,000 years later, the French philosopher Descartes speculated about the existence of an evil demon who is constantly deceiving us with a fabricated reality.
But if we really are living in a simulation, how could we ever find out? In cult sci-fi film The Matrix, the main character Neo is presented with two pills. His dilemma: take the blue pill and remain in the artificial reality forever, or take the red pill and escape into the real world.
Sadly for us, it’s not quite that easy. But a team of physicists, including Silas Beane at the University of Bonn in Germany, have announced that they have found a way to prove once and for all whether we’re all actually living inside a simulation.
BBC Interview with Silas Beane – theoretical physicist at the University of Bonn!
Who first suggested that we might be living in a simulation?
There have been variants of this idea going all the way back to Plato, but my collaborators and I are interested in the work of a Swedish philosopher at the University of Oxford called Nick Bostrom. He came up with an interesting argument: if computers keep growing in power as they’re growing now, then our descendants will be able to simulate reality.
And if our descendants don’t have any qualms about simulating reality, then they’re probably going to perform a lot of simulations. So we should ask ourselves the question: what are the odds that we’re in the one true reality, and not one of these many, many, many simulations?
How does this relate to your own work?
About eight years ago my colleagues and I started to use high-performance computers to simulate a fundamental force of nature called the strong nuclear force. We decided we may as well call ourselves ‘universe simulators’ because that is indeed what we’re doing – we’re simulating the strong nuclear force within these little boxes, which enables us to calculate the properties of matter.
What is the strong nuclear force exactly?
It’s one of the four fundamental forces, along with the weak nuclear force, gravity and electromagnetism. We know the equations for this force – they describe the interactions between fundamental particles called quarks and gluons. The problem is that although we know the equations, their solutions are very complicated. That’s why we need the world’s most powerful supercomputers to carry out our simulations.
Not quite. The box sizes that we’re currently simulating are roughly the size of a proton – more or less 1 femtometre [one millionth of a nanometre] across. So it’s still a very, very small number. But if you extrapolate into the future, then if technology keeps progressing, there’ll come a point when the box sizes are large enough to contain microscopic objects such as cells, and then even macroscopic objects such as you and I. Eventually, with enough computing power, it’d be possible to simulate an entire Universe.
How could we find out if we’re living in a simulation?
British physicist John Barrow pointed out that if we’re being simulated, then we might expect to see glitches on the part of the simulators. This was something that resonated with us because when we do our calculations, we’re always worried about glitches and work hard to remove them.
How could we spot these glitches?
We only know one way of simulating the strong nuclear force, and that’s to use a grid – a kind of framework that divides up space-time into a lattice structure. We use that as a fundamental assumption, that whoever’s simulating the Universe is also using a grid. And if we’re being simulated in a box with a finite grid size, then by the rules of quantum mechanics there’s a maximum energy that particles can have. As particles get closer and closer to this maximum, they probe smaller and smaller regions of space. So for large enough energies, you’d see the lattice structure. That’s the glitch we’re looking for.
So we could see the grid by looking at high-energy processes?
Yes – one place where you would see these effects is in the very high energy range of the cosmic ray spectrum. In our work, we consider collisions between extremely high-energy cosmic rays and extremely low-energy photons left over after the Big Bang. Our calculations show that, in the presence of a grid, the stuff coming out of these collisions should direct itself along certain axes, not equally in all directions. So if you could detect these directions with sufficient accuracy, you could determine if our Universe is indeed built on a grid.
Could we measure this in the ‘real’ world?
In principle, yes. We’d have to detect these cosmic ray collisions along different angles in the sky to try to figure out if there’s some preferred direction. These events are extremely rare, so it’s not clear to us exactly how we’d go about doing that. We’re theoretical physicists, after all!
If the Universe is an illusion, what could we do about it?
I think if we knew we were in a simulation, then it’d become interesting to communicate with the simulators. There are also arguments to suggest we wouldn’t be the only simulation, so it might be possible to communicate with others.
For me, it seems likely that our simulators would be interested in simulating many universes, varying different parameters to see how things turn out. For instance, if they changed the fundamental constants of nature or the masses of particles, maybe silicon-based life would emerge instead of carbon-based life like us. I think they’d be interested in observing the evolution and ultimate fate of these universes.
Do you think we’re living in a simulation?
I find Bostrom’s argument compelling -and quite depressing, too. To me, the crux of his argument is that the only way we can conclude that we’re not in a simulation is if we’re going to destroy ourselves in the near future. Or alternatively, maybe when the technology arrives, humans will decide not to simulate universes after all? Maybe, but humans will do whatever we’re capable of doing… right?