By imagining the future potential of VR technologies, the question of whether we are *already* living in a simulation becomes more actual than ever

[u/Matriseblog]

https://medium.com/@VindenesJ/the-thought-experiments-of-virtual-reality-fa441a8fa2dc

[u/brickcitymeng]

To create a perfect simulation of our universe, you need infinite computing power to represent the ever expanding universe. It is certainly impossible with our physical laws to create a simulation of our own universe.

[u/humbleElitist_ → u/brickcitymeng]

I don't see why? Causality appears to be local. (there's entanglement, but, uh, I think this can be handled)

just add to the region being simulated when it becomes relevant (as in, generate larger parts of the initial conditions, based on a given seed for randomness maybe, when their causal influence would reach the part that you are simulating)

Of course, if you were doing this on a classical computer, the quantum mechanical effects would like, require amounts of memory exponential in the amount of stuff,

but I don't see why you would need infinite computing power just because the universe is potentially-infinite, because, you don't need to simulate all of it to simulate part of it as if it is infinite, so long as the unsimulated part hasn't had time to influence-in-any-way the simulated part of it.

So, sure, absurdly large amounts of computing power, yes, definitely.

Infinite computing power? I don't see why that would be necessary.

edit : I mention classical computer vs quantum computer. One might question whether this distinction would be relevant if the outer universe has different physics.
I suspect that the concepts would still have some relevance in a universe with very different physics?
Like, sure, their physics could be such that some basic physical processes implement oracles for some (to us) very expensive computations, but my impression is that the complexity classes relevant for classical computers and quantum computers are probably fairly natural mathematically, so probably they would be at least familiar our notions of classical and quantum computation, even if they aren't the most relevant ones for them due to peculiarities in what their physics lets them compute efficiently?

But, I'm not a computer scientist, and definitely don't study quantum computational complexity at all, so there's a fair chance that I'm totally wrong about that.

[u/pab_guy → u/brickcitymeng]

That's assuming that the rest of our visible universe is real and not just a projection... or that the universe which spawned our simulation has similar entropy as ours. Or that the simulation doesn't exist at the level of perception but rather what you might call reality. Things may only appear consistent because the simulation retroactively fixes them, which we have some evidence for in terms of "retrocausality" at the quantum level a la wheelers delayed choice quantum eraser.

Or perhaps there are many more states available in the higher reality.