The simulation argument says that IF you:
expect a substantial chance Q of our civilization surviving a long time,
given survival, expect a vast number V of subjective years of experience by future descendants, in total across the whole future,
expect them to spend a substantial fraction F of their per-person-subjective-year resources R running simulations of their distant past, for entertainment, research, or other purposes,
expect a fraction A of such sim resources to go to sim this our current year, 2010, on Earth, and
expect a fraction B of these 2010 sim resources to go to sim fully conscious humans unaware they are in a sim, where each such creature costs on average C per subjective year of experience.
THEN you should expect there will be on average of N = A*B*Q*V*F*R/C sim creatures who assume they are humans living in 2010. If your N >> 1010 (current human population), then unless there is some particular reason to think your life is much less likely than average to be the sort of life that a sim lives, you should strongly expect that you are such a creature; you are a sim. (Of course you should then question how much you know about the sort of universe you live in, which may change your N estimate. Even so that probably won’t drastically reduce your estimated chance you are a sim.)
For example, if Q = 10-2, V = 1030, F = 10-4, A = 10-9, B = 10-2, R/C = 101, then N = 1014; you are a sim.
While I published back in ’01 on how to live your life differently if you might be a sim, it took Charlie Stross pondering the topic recently to remind me that I’ve never fully engaged the argument, by trying to come up with my own best estimate of N. So what do I think?
Let’s break it down by purpose. First, consider entertainment. Even compared to other humans, we today spend record large fractions of our income on tv, movies and video games; we are in the process of reacting to the development of unprecedented hyper-stimuli. Humans in general are also clearly unusual compared to other animals, who spend almost nothing on anything sim-like. And humans are mainly interested in simulations of other humans; we hardly have movies or games about monkey life.
So if our descendants become better adapted to their new environment, they are likely to evolve to become rather different from us, so that they spend much less of their income on sim-like stories and games, and what sims they do like should be overwhelmingly of creatures much like them, which we just aren’t. Furthermore, if such creatures have near subsistence income, and if a fully conscious sim creature costs nearly as much to support as future creatures cost, entertainment sims containing fully conscious folks should be rather rare.
Now, consider academic study of history. Once economic growth and tech innovation slows to a near halt, I expect far less interest in learning new things, which includes learning new history. The little learning that remains should mostly be done to signal future folk good features, and so they’ll much prefer to pay one future person to think carefully about the past, rather than spend similar resources to sim one person from the distant past.
Full scale simulations of the entire Earth over many years should be very rare, and perhaps non-existent. Similar understanding would come much cheaper from sims that only model a few people in enough detail to make them fully conscious. Modeling a few such folks in detail and then having most other modeled folks just act in ways that are statistically similar to those few detailed folks is probably good enough for most purposes. Perhaps there will be other reasons to run sims containing fully conscious creatures, but I expect those to be even more rare.
Bottom line: I expect R/C near one, even if Q=1, and expect A*B*F to be smaller than 1010/V. So, I’m probably not a sim.
Yes. The question of "Are we in a sim?" depends on whether we're in a finite computational space type sim or whether we're in a non-finite computational space (i.e. running on a quantum computer).
In a finite sim where we want it to be as realistic as possible, having a high speed of light would mean we'd have to simulate other civilizations too, thus reducing the achievable complexity of the sim on average.
In a finite sim with a low speed of light we only need to simulate locality with any kind of high degree of fidelity.
In an infinite sim, there could conceivably be no detectable difference between base reality and the sim.
Speculating on whether we're in a finite sim, I'd expect to see lots of attempts to compress unneccesarily detailed information and I'd also expect to see level of detail reduced when we're not looking at it. I'd also expect to see non locality happening faster than the speed of light but not necessarily explained by the physics of the sim.
I agree with whoever said that the simulations wouldn't have to be simulations of historical events (you could argue that simulating a random possible universe would be unlikely to result in this particular universe, but I would shoot that argument down (since you can say that in any universe, provided that the universe exists))
Also, what I took away from the original paper about simulations was not a belief either that we are or aren't simulated. The point, as I see it, is that IF anyone simulates a universe (especially more than one) in the future, it means that we are probably in a simulation.
Also, I have homework to do. The internet is ruining me.