Are we actually living in a computer simulation? I'm not. But you might be. This idea was explored most famously in the films The Matrix and The Thirteenth Floor. (I actually thought the second of these was a better treatment of the topic). But surprisingly, philosophers and scientists have also taken this idea seriously.
The Oxford philosopher Nick Bostrom has proposed that we are more likely than not to be living in a computer simulation. (Bostrom maintains a web page covering this and a variety of other fascinating ideas). His argument, roughly speaking, is that any sufficiently advanced civilization will produce millions or billions of computer simulations, at such a high level of sophistication that the inhabitants of these simulations would be unable to distinguish them from reality. Unless we occupy a very special place in the universe, the odds are a million to one, or a billion to one, that we are actually living in a computer simulation instead of in the real world. (Of course, a similar argument suggests that I am more likely to be Chinese than American, but let's not go there...)
How could we test this idea? Physicist John Barrow has pointed out that all computer programs require periodic upgrades to prevent software failures -- if our software got "upgraded" we might see small, sudden changes in the laws of physics. For instance, the speed of light might suddenly jump by a fraction of a percent overnight.
But more importantly, how could we prevent out digital overlords from pulling the plug? Economist Robin Hanson wrote an entire paper on this topic. He suggested that if our world exists (like most of our own simulations) to entertain the programmers, then the obvious answer is to try to be as interesting as possible. I, on the other hand, recommend shameless groveling.
In fact, I don't find the simulation argument very convincing, because I don't think there is any evidence that machine consciousness is even possible. But that didn't stop me from writing a story about it shortly after I encountered Bostrom's argument. I'll post it next time.
Update: the short story is here.
Update: my main blog site is www.cosmicyarns.com.