We've all heard that "life is a game". But what if we are all, right now, actually living in one, designed by someone who is living deep into the future?

It's usually the kind of far-out idea debated in college dorms with the ritual passing of a bong and comprised of equal parts

The Matrix and Star Trek's holodeck. According to the theory, which an academic from Oxford and a scientist from Nasa have put forth separately, there's an almost mathematical certainty that we're toiling inside an intricate simulation created by beings existing anywhere from 30 years to five million years from now. In essence, we're just some future being's hobby, his or her version of a massively multiplayer online role-playing game such as World of Warcraft. I suppose you could say we're living in sim.

Mind-bending, sure, but is it more far-fetched than religion, which promotes the idea that God created the Earth and Heavens? Or less believable than the Big Bang theory, which holds that the universe started out as a speck of matter of incredible density, smaller than a pore on your skin? Ten to 15 billion years ago, a massive explosion began stretching the fabric of space like a balloon, forming a hundred-trillion galaxies in the universe and three-hundred-trillion stars in our galaxy. In the process, it heralded the beginnings of time and, somewhat later, the Earth coalesced from hot gases and, by sheer luck and happenstance, ultimately created an environment from which life sprang.

"Nick Bostrom, a philosopher at Oxford University and director of its Future of Humanity Institute, calls it the Simulation Argument"

Really? Compared to that, existing in a game simulation seems plausible.

Nick Bostrom, a philosopher at Oxford University and director of its Future of Humanity Institute, calls it the "Simulation Argument". An adherent is astronomer Rich Terrile, director of the Center for Evolutionary Computation and Automated Design at Nasa's Jet Propulsion Laboratory. They don't wear tinfoil hats, wander around city parks and spout sci-fi-worthy conspiracy theories.

Their views are shaped by maths, science and history.

Bostrom bases his thesis on an assumption he calls "substrate-independence", meaning that mental states are not solely attainable by humans and other animals -- they can exist in other physical and/or digital phenomena. A conscious, intelligent, self-aware being could reside in an organic brain, silicon brain or magnetic brain. You could say the product remains the same; only the packaging has changed. If he's right, a powerful computer with inordinately complex software could achieve a state of what we know as consciousness and which Terrile claims is no more than the by-product of sophisticated architecture in the human brain.

According to Hans Moravec of Carnegie Mellon's Robotic Institute, a $1,000 (£624) computer in 1980 had the brainpower of a bacterium. But, he says, if computers' processing power follows the same growth curve, by 2030 a computer could achieve a complexity equivalent to the human brain. Terrile seconds the motion, predicting that in the next ten to 30 years artificial consciousness will be embedded in machines. The fastest Nasa computers crunch data at twice the speed of a human brain. Before 2020, we could compute the equivalent of 10,000 human lives, including every thought, in one game controller.

Of course, we won't know we're in a simulation. "If the simulators don't want us to find out, we probably never will,"

Bostrom wrote in a 2003 paper. Terrile finds inspiration in the idea that we may soon have the technology to create our own synthesised universes. Then we, who live in a simulated world, have created a simulated world, whose denizens wouldn't know they're the product of our collective computing imagination. And what if our master designers also lived inside a simulation, and so on, and so on? Potentially, you could have levels and levels of sims, perhaps millions of them.

In that case, Terrile speculates, if there is a creator for our world, it is we, or at least an offshoot of us, hailing from the distant future. Then, "We are both God and servants of God," he says. Now that's what I'd call the ultimate game design.