Wolfram Physics Q&A

None. It is just following certain rules that we can think of as computational. There is no underlying “substrate”. The universe is just doing what it does, and we are describing it in terms of computation. When we think about Newton’s laws describing the motion of the Earth using equations, we are also imagining the equations describe what the Earth is doing, not that the Earth itself has a mechanism inside that is solving the equations as Mathematica might.