Look up. Do you see a thought bubble? Of course you don't. But zoom out a bit and imagine someone was watching you from his computer screen, seeing a thought bubble above your head indicating that you are reading this right now. It's the ultimate philosophical nightmare: we're not real, we're just a series of electric impulses darting about who think we're real. The old we're-just-brains-in-a-jar argument.

What are the chances of such a philosophical blackhole? Dr. Nick Bostrom, a philosopher at Oxford University, is quite specific on the number: "My gut feeling, and it’s nothing more than that, is that there’s a 20 percent chance we’re living in a computer simulation."

Such a thought is not foreign to us who have played the Sims and watched "The Matrix". Paranoia aside, isn't it possible for us to be part of a program and not be aware of it? The tastes and smells, the joy and pains, all sensation is just electrical impulses in our heads. It's entirely possible that all these electrical impulses are done inside the processes of a super computer.

That's exactly what Bostrom suggests. An advanced race of "posthumans" have built a supercomputer that simulates their ancestors, ie, us:

I think it’s highly likely that civilization could endure to produce those supercomputers. And if owners of the computers were anything like the millions of people immersed in virtual worlds like Second Life, SimCity and World of Warcraft, they’d be running simulations just to get a chance to control history — or maybe give themselves virtual roles as Cleopatra or Napoleon.