I'm sure everyone that has watched the Matrix has experienced that moment of panic when they realise that they might not be in the real world. In fact, they might not even be real. I'd been thinking along these lines for quite some time when the Matrix arrived on the scene, so I was rather amused at the reactions some people seemed to have when they realised that they had no way to tell whether or not what they saw around them was the “real” world.

Anyway, you might say, that makes me pretty strange, but why am I telling you about this? Well, BBC2's excellent Horizon programme this evening was about time machines. The universe, it seems, has something of a love/hate relationship with time machines; it may be possible to build them (whether you use rotating black holes, pairs of cosmic strings or just very large rotating cylinders is up to you ;->), but it appears that even in the solutions to the equations that allow such ridiculousness, you would be unable to travel to a time before such a machine was built. Which seems rather pointless.

OK, so what has this to do with whether or not I'm real? I mean, that was the title of this piece, right? Well, in rather an interesting twist, it appears that the easiest way to get back to the past may well be to simulate it. Yes, that's right, simulate it. If you assume that Moore's Law continues to hold, then it will eventually be the case that we will have a computer powerful enough to simulate (at the very least) sizeable areas of our universe. Furthermore, assuming Moore's Law still holds at the point at which such simulation becomes practicable, then within a very short amount of time it will be possible to perform it routinely; indeed, within a few tens of years, there would be billions of such simulations. Given that our descendents have an interest in the past, it is reasonable to assume that some of these billions would be detailed replicas of our time. Including us, or at least, models of us that insisted 'til they were blue in the face that they were conscious, and replicated our behaviour down to the finest detail.

The stunning conclusion of this intellectual exercise is that there will be more simulations and hence more models of us than the single original version, and that is before you start counting simulated simulations and so on. That is, the chance that we are real is actually vanishingly small. It is much, much, more likely that we are not!

I have to confess, I would not be the least bit surprised if the scientists and philosophers responsible for these intellectual acrobatics are correct. Indeed, I wonder whether we may already have stumbled across the evidence with which to back-up this bizarre claim; as we investigate the sub-atomic depths of the universe, it seems we keep running across strange phenomena, things like uncertainty, quantum tunnelling etc., many of which strike me as rather convenient properties if you wanted to simulate the universe… that is, they generally appear to be artefacts that would allow the universe itself to hold less information than it would otherwise have to, whilst providing a high level of overall accuracy.

So, perhaps, the real universe is the only one without unusual quantum effects. If so, then we are certainly not in it.

Perhaps this is also the reason that it is so hard to unify quantum physics with Einstein's relativity… perhaps it is the case that the simulation simply isn't consistent.