We might not know if the universe is a simulation, but we know enough about the properties of the universe to put some constraints on its properties. For instan

We might not know if the universe is a simulation, but we know enough about the properties of the universe to put some constraints on its properties. For instance: We know about entropy. We know that there is an upper bound on the amount of information that can be contained within a given space, and it is proportional to surface area of that space. (The upper bound is realized when the space becomes a black hole.) These values constrain any simulation of the physics of our universe in any universe which has the same physics. We know that in the case of accurately simulating the entire physical universe, you're going to need a LOT of space and energy.