Seth Shostak takes a look at the simulation hypothesis, the idea that we are in a computer simulated reality: Is Life an Illusion? | Seth Shostak.

…a future historian (or curious teenager) wielding programming skills and access to a honking big computer could construct SimEarth on steroids. They could, for example, run a simulation of 15th century European society to see what it was like during the era of the Black Plague: a so-called ancestor simulation. Unlike Keanu Reeves in The Matrix, the people in the simulation wouldn’t know that their lives were merely code running in a machine. Now if it gets this far, you can bet that the coders won’t run merely one simulation. Someone who has Grand Theft Auto on their machine doesn’t play it just once. They play it a gazillion times. In other words, if ancestor simulations are possible, then they will greatly outnumber real societies. Consequently, it’s very probable that all humanity is in a simulation — that we didn’t get one of those rare lottery tickets that would make us a real society of real beings. Everything you do today (and have ever done) could be just an illusion coded up by some clever Klingon.

Shostak list two possible alternatives to the probability of us being in a simulation. The first is that societies rarely progress past our current state of technology to the point of being able to build these simulations (implying that our civilization is probably on borrowed time), and the second is that most societies don’t bother with simulations, which he finds implausible.

I’m not a big fan of this type of probability reasoning. There’s just too much about reality that we don’t understand, and when I hear that calculations show that reality is probably an illusion, or that we’re all probably Boltzmann Brains, or anything along those lines, I’m much more inclined to think the calculation is simply flawed due to our ignorance.

That being said, I think there is at least one other possibility: that all encompassing simulations are much harder to do seamlessly, or will be much more expensive in resources, than we currently imagine them to be. The idea of a proliferation of universe simulations assumes that computing power will continue to increase indefinitely. I’ve noted before that this isn’t guaranteed. Silicon performance may be within a decade of its performance limits, and quantum computing isn’t guaranteed to rescue us from those limitations.

Of course, there is the possibility that our universe actually is a simulation. If it is, what does that mean for us? Well, I think it would mean that our reality has a purpose, something many have hoped for, although that purpose might not be a comforting one. It also means that the intelligence behind this simulation would effectively be our God or gods, again with no guarantee that they would be benevolent ones.

The problem is, if we are in a simulation, is there any way to detect it? Shostak discusses attempts to see calculation grids in the cosmic microwave background, but I think the only real hope we might have of ever detecting a simulation is if it has any defects. Of course, if we do find a defect, we might never know whether it is an actual defect or just an attribute of our universe. For example, is our inability to reconcile quantum mechanics with general relativity due to a defect in the simulation, or to us simply not understanding the universe well enough yet?

If we are in a simulation, there is probably little we can know about the outside universe, at least without the intelligence behind the simulation communicating with us. That outside universe, and the beings in it, may be unimaginably alien. They may be incomprehensible to us. They may also not even be aware of our existence, or if they are, they may regard us as an unwelcome complication in their experiment, vermin gumming up the works. Worse yet, if the whole universe is being simulated, we are such a minor player in it that we might be irrelevant noise.

If we are in a simulation, then this simulation is our reality. And the simulation appears to have stark consequences for failing to take it seriously. As entities within the simulation, we have little choice but to continue playing the game, and hope the controlling intelligences don’t end it.

Another interesting question is if we do start bringing up simulations, at what point do the characters in those simulations start to be deserving of rights? It seems like we should be careful about our attitudes toward those characters, since our own simulation owners might be watching and judging how we treat them.