Do we live in the Matrix? Researchers say they have found a way to find out



Any simulation of the universe must have limits, and finding these would prove we live in an artificial reality, physicists claim



If the Matrix left you with the niggling fear that we might indeed be living in a computer generated universe staged by a malevolent artificial intelligence using the human race as an energy farm, help is at hand.

A team of physicists have come up with a test which they say could prove whether or not the universe as we know it is a virtual reality simulation - a kind of theoretical red pill, as it were.

Silas Beane of the University of Bonn, Germany, and his colleagues contend that a simulation of the universe, no matter how complex, would still have constraints which would reveal it.

Is the real world real? Physicists say they have come up with a way of determining whether the world we experience is actually a computer simulation, as imagined in The Matrix trilogy of films

All we have to do to identify what these constraints would be is to build our own simulation of the universe, which is close to what many researchers are trying to do on an incredibly miniscule scale.

Computer simulations have been run to recreate quantum chromodynamics - the theory that describes the nuclear forced that binds quarks and gluons into protons and neutrons, which then bind to form atomic nuclei.

It is believed that simulating physics on this fundamental level is equivalent, more or less, to simulating the workings of the universe itself.

Even operating on this vanishingly small scale, the maths is pretty difficult so, despite using the world's most powerful supercomputers, physicists as yet have only managed to simulate regions of space on the femto-scale.

To put that in context, a femtometre is 10^-15 metres - that's a quadrillionth of a metre or 0.000000000001mm.

However, the main problem with all such simulations is that the law of physics have to be superimposed onto a discrete three-dimensional lattice which advances in time. And that's where the test comes in.

IS REALITY MERELY AN ILLUSION? The question of whether we are actually aware of the real world is one which has been continually asked by philosophers.

One of the earliest articulations of the conundrum occurs in Plato's Republic, where the Allegory of the Cave attempts to describe the illusory existence led by most unthinking people.

Plato, regarded by many as the father of Western philosophy, suggested that the only way to come to a realisation of the real world was an in-depth study of maths and geometry, which would give students an inkling of the real nature of the world.

French philosopher Rene Descartes, pictured above right, whose works are often used as a general introduction to metaphysics, raises the problem again as a thought experiment to lead readers to a position of radical doubt.

By postulating a malicious demon who can keep us trapped in an illusory world, Descartes asks readers to cast aside all the evidence of their sensory experiences in a search for one certain premise.

He famously comes up with the argument 'cogito ergo sum', or rather 'I think therefore I am', which he uses as a indubitable bedrock from which to reconstruct a certain picture of reality.

Subsequent critics of his work, however, say that just because there are thoughts, there is no guarantee there is really a thinker.

Professor Beane and his colleagues say this lattice spacing imposes a limit on the energy that particles can have, because nothing can exist that is smaller than the lattice itself.

This means that if the universe as we know it is actually a computer simulation, there ought to be a cut off in the spectrum of high energy particles. And it just happens that there is exactly this kind of cut off in the energy of cosmic rays, a limit known as the Greisen–Zatsepin–Kuzmin (GZK) cut off.

As the Physics arXiv blog explains, this cut off is well-studied and happend because high energy particles interacting with the cosmic microwave background lose energy as they travel across long distances.

The researchers calculate that the lattice spacing forces additional features on the spectrum, most strikingly that the cosmic rays would prefer to travel along the axes of the lattice. This means they wouldn't observed equally in all directions.

That would the acid test that the researchers are searching for - an indication that all is not at it seems with the universe. Excitingly, it's also a measurement we could do now with our current levels of technology.

That said, the finding is not without its caveats. One problem Professor Beane identifies is that the simulated universe could be constructed in an entirely different way to how they have envisaged it.

Moreover, the effect is only measurable if the lattice cutoff is the same as the GZK cutoff, any smaller than that and the observations will draw a blank.