I worked with simulation (ECAD and beyond) from the 70's. At one point the concept of demand driven simulation was derived for more efficient simulation.

"Where traditional event driven simulation propagates signal values forward through a circuit in response to input pin events, demand driven simulation propagates requests for simulation values backwards both through the circuit and through time. In this manner, only those evaluations required to obtain “watched” signal values are performed."

Being of philosophical bent, I made the connection that the (known) universe could certainly be some sort of simulated "virtual reality" and that in fact quantum observability was an efficient method of doing the simulation if it was one. Stanislaw Lem in very early Sci Fi broached the idea that what was "virtual reality" for one universe was reality in another. Chinese philosophers dating back thousands of years, made the similar connection that dreams were a kind of reality that could not really be distinguished from our "real" reality. Dreams in a sense are just a simulation with a different set of rules for its universe.

I've come to believe that the "known" universe is still an extremely (to the nth degree) limited piece of whatever we want to call the absence of nothing. One window to this is the simple concept of mathematics and the consistent discovery that mathematical concepts seem to eventually map into "reality." I can't remember the name, but there is an excellent book exploring the concept of infinity and in its way it exposes the reader to the levels of how conceptually you create bigger and bigger numbers and numbers that race faster and faster toward "infinity." When you get your mind around some of these "large" numbers, the "finite" universe actually seems very small indeed. Numbers like the number of particles in then known universe are simply stated with a very finite number of zeros. So when physicists started bringing up theories like "brane universes" and parallel universes and more dimensions, I was ready to keep an open mind and believe certainly that there is much more than our "known" universe.

If you really want to get way out there, our universe could be a single thought from the mind of a "god." On a different scale it is the same as the universe that is created by our dreams. It is unfortunate that tests to determine the "truth" are hard to come by and even if possible take large time scales (minimum seems to be decades). I hope we can test the brane theory of the universe in my lifetime (some ideas are out there on gravitational interactions between multiple universes).