German scientists say they've found a way to tell whether or not our universe is a giant computer simulation - and that there's evidence to suggest that it is.
The basis of the idea is that, if the universe is a simulation, then it would have certain observable constraints.
The laws of physics, which appear continuous, would have to be superimposed onto a discrete three-dimensional lattice which advances in steps of time.
This lattice spacing, says Professor Silas Beane of the University of Bonn, would impose an otherwise unnecessary limit on the energy that particles can have, because nothing can exist that is smaller than the lattice itself.
And, he says, precisely such a a cut-off in the spectrum of high energy particles exists: a limit to the energy of cosmic rays known as the Greisen–Zatsepin–Kuzmin (GZK) cut-off. High energy particles interacting with the cosmic microwave background lose energy as they travel across long distances.
And there's something else to look for that could, perhaps, confirm things one way or the other. If we're living in a simulation, 'the angular distribution of the highest energy components would exhibit cubic symmetry in the rest frame of the lattice, deviating signiﬁcantly from isotropy."
In other words, the cosmic rays would have a tendency to travel along the lines of the lattice, so that they wouldn't show up equally in all directions. And this is something that can be checked using current technology.
There are a couple of caveats. First, this technique would only identify a certain type of simulation - and we could be living in one that's constructed completely differently.
Second, the preferential travel of cosmic rays would only show up if the lattice cut off is the same as the GZK cut off. This occurs when the lattice spacing is about 10^-12 femtometers; if it's much smaller than that, there's no way of knowing.
The team's paper, Constraints on the Universe as a Numerical Simulation, is here.