Science fiction movies like the "matrix" suggest the possibility of a simulated world were people exist - not an original idea of course. If we existed in a simulated universe, how would we be able to detect this?
Within our admittedly limited local knowledge of how things work, perhaps we could assume some similarity between our "inner universe" and this "outer universe", were such a possibility so. For example, we have software programs such as "second life" that we inhabit with animals and structures similar to our current experience. We also define them to follow similar physical laws, such as obeying gravity, requiring food or eventually experiencing death.
We could hypothesis that such inhabitants, in our simulated creation, would not be able to think, have free will, possess a soul etc. Is this a fair comparison though? After all, we are not experts in all matters of technology. If we were inhabitants of a simulated universe created by others, would they not also consider the same of us?
The question I pose is how could we tell? What experiment could we perform to discern the difference between a "real life" and a "simulated life"?
Again, perhaps we can imagine some correlations between both "lifes" exists. Also the manner of simulation may also have similarities. For example, we consider our "real life" to flow continuously in time whilst (computer) simulations use "discrete time steps". It follows therefore that a discrete time universe would behave differently from a continuous time universe.
To illustrate, we know how to implement discrete time implementations of analog filters using "Digital Signal Processing" or DSP technology. This requires the time step between samples to be small relative to the time between (significant) changes in the signals being processed. If this condition is violated, we get "alias" responses.
How does this relate to the speed of light "c". It is said that we cannot exceed this velocity, or at least transfer information across a distance faster than that which could be achieved using light or radio waves traveling at c. Does this effect seem similar to that expected from a discrete time sampled system? Would the velocity limit implied by "c" corroborate, to some degree, the possibility of our universe being a simulation?
If we were simulations, how would we know ourselves? Perhaps the best analogy comes from Hitch-hiker's Guide To The Universe in the chapter where the "mice" that secretly run the earth required Arther Dent's brain to "complete the ?matrix"
Mice; We want Author Dent's brain
Arther; You can't have it!
Ford Prefect; You can have a mechanical replacement
Zaphod; A small one should do the trick - you wouldn't know the difference...
Arther; I'd know the difference!!!
Ford Prefect; That's just it - you'd be programed not to!
Inside a simulation, we would not be able to prove one way or another but we might have observations that could cause us to consider the possibility. For example, entities in the "outer universe" could arbitrarily fiddle with events inside the simulation. They could make anomalous outcomes occur. People, for example, often report "flying saucers" that sit uncomfortably with our current understandings of the universe. Further we have "abductions", "shadow people", "ghosts", remote viewing", crop circles", "dark matter", dark energy", to name a few. Are these potential evidential categories for life inside a simulated universe?
If we were a simulated species, then how would the god concept now be interpreted? Would the entities that created the simulation be, by definition, our god(s). Certainly they could "create" a "Jesus actor son" to enter our simulation and perform "miracles" as many Christians believe. This intervention might have been motivated by simple curiousity - "what if we introduced this new character and watched what happens"?
Alternatively would we redefine "god" as some entity further removed from the "outer universe" and its inhabitants, so that they too were reportable to him (or her or it). If so, could it be construed as arrogance on our part to presume that we could have superior religious knowledge inside a simulated universe whilst our designers did not? Or could it be that our designers "speckle" our simulated universe with hints of an outer deity?
Unless we can test the difference between "real" and "simulated" we cannot simply state that the suggestion is impossible, and therefore hope the questions evaporate. It seems reasonable to speculate that the knowledge of inhabitants within a simulation would be inferior to the knowledge of those outside. We could therefore not claim that, because our (internal) technology could not accomplish such an arrangement, that it therefore follows that inhabitants in an outer universe would be so equally limited.
Further, if no possible method could theoretically be construed to test the difference (s) then perhaps these questions are untestable and in a "Popperian" sense, not useful. Even so, can we devise such a proof to support such claims of non dis-provability when suggestive observations of limitations and commonly witnessed anomalies as I describe might point towards our existence potentially inside a simulated universe?
According to Carl Popper, theories cannot be proven but they can be dis-proven. Even though religion is based on faith rather than measurement, followers of most faiths still use their minds and attempt to construct consistent frameworks. What would become of god though, if what I suggest could be true?