I wont try to present the entire field in any way. Instead I’ll just leave you with a nice video.
This is all very much related to the field of Digital Physics.
Is this Universe a simulation?
I don’t think this is a question we can answer with any certainty. So I won’t even try to speculate right now since there is what I would consider to be a far more interesting question with much more practical implications:
Is simulation possible within our Universe?
Many types of simulations are run every day by scientists, engineers and even casual gamers. The simulation of basic Newtonian physics is simple enough to be done by a high school student with a computer. But as we know, the universe is not actually Newtonian, and that complicates things. A better question might be: How realistic simulations can we make in the universe we have?
The universe is estimated to contain about 10^x elementary particles. All of which would obviously be unfeasible to simulate directly. But would we really need to simulate them all in order to give the impression to an in-universe observer that it actually contains 10^x particles? That leads us to an interesting solution to making a simulated universe feasible:
See the star in the night sky? You know that it’s a fiery ball of gas with ~10^x particles. But what if it isn’t really? What if that star is at that moment, just a bunch of photons hitting your (and possibly others) retinas. If we’d look at it with a telescope, we’d see it in better detail, what if that was actually generated for us? The simulation might only keep track of the high-level details of the simulation, and fill in with lower levels of detail as necessary.
This is very related to the old question: If there is no one in the forest hearing the tree fall, does it make a sound? The relevant counter-question to this would be: Does it need to? If it isn’t, how much easier would that make the simulation?
Simulations with other laws of physics
What if we could create a simulation that contained “conscious” beings yet had vastly different laws of physics?
One might ask: Why does the universe have 3 spacial dimensions. Could the same amount of complexity be feasible in 2 or 4? If so, why isn’t it? I suspect a 2D simulation would be far more limiting. And perhaps 4D is just unnecessary. 3D might actually be the best compromise between computational complexity and simulation sophistication.
Ethics of simulation
One might ask: Why should we embark on this quest to simulate a universe? Doesn’t simulating the universe also simulate all the pain and suffering within it?
I don’t have any good response to this question, but I’ve thought a lot about it and will hopefully explore my thinking in writing at a later time when I’ve done more reading.
Much of this is in the realm of unprovable knowledge. And while attempts to simulate a universe might be possible, verifying that our Universe is a simulation seems to be impossible. The simulation hypothesis trilemma formulated by Bostrom is an interesting attempt which attempts to show that if simulation of universes is possible (and desirable, see the section on ethics above) within our universe, our universe is very likely to be a simulation. But I have some doubt it’s actually that simple.
It’s safe to assume we still know relatively little about the universe, so to consider this anything else than wild (but interesting) speculation is probably a mistake at this time. In short: Don’t lose any sleep over this stuff.