October 19, 2020
It is impossible to tell the difference between living in a real universe and living in a perfect simulation of one. If you cannot tell the difference between two models of reality then is no difference.
Since there is no difference between living in a real universe and living in a perfect simulation of one, we can treat our real universe as it it were a simulation of our universe running on a computer. I will call the computer's sysadmin "God".
It is natural to think of God's computer program as a procedural system. It starts by simulating the first moment of time, then the second, and so on. But time in a deterministic universe is symmetric. God could just as easily work from the end of the universe and runs His algorithm backwards.
From God's perspective, the multiverse is a stateless system. In programming terminology, God's universe is functional software.
God need not even run a simulation of the whole universe. If you are born at time $t_i$ and die at time $t_f$ then there is no subjective difference to you whether God runs the computer outside the interval $[t_i,t_f]$.
Spacetime is local. God could further optimize His simulation by not simulating any of the universe except you. There is no way for you to tell the difference.
You do not actually experience your whole timeline $[t_i,t_f]$ simultaneously. You can only experience one instant $s_0$ of local spacetime—the moment you are experiencing right now. There is no way for you to find out whether God simulates anything outside a ball of radius radius $|s-s_0|<\epsilon$. Since you cannot tell the difference, that means there is no difference, to you, between God simulating just this instant of local spacetime and God simulating an entire universe.
The universe is materially reducible. The word "conscious" describes some—but not all—large-scale organizations of matter.
It is easy to think about people as numbers or computer programs. When you dig down to the deepest levels of theoretical physics, reality dissolves into group theory. It is more accurate, from the perspective of theoretical physics, to describe macroscopic organizations of matter as group representations. You can think of the universe as a group and macroscopic phenomena like consciousness as a subset of the group's macrostates.
Macrostatic phenomena like consciousness are not bijective group representations of the universe. Macrostates are strictly surjective and consequently degenerate. Time is an emergent property of conscious macrostates' degeneracy.
Consider a consciousness at point $m_0$ in the multiverse. What we describe as "time" is a continuous path through spacetime. This path tends to flow towards increasing entropy because on the microstatic scale all adjacent points in spacetime are equally likely to become the next subjective instant. But on the macrostatic scale, some points have higher degeneracy than others. In particular, the points with higher entropy have much higher degneracy. Macrostatic time travels in the direction of increasing entropy even as microstatic time flows in all directions without prejudice.
If this is true then you would expect every point of single-universe spacetime, both classical and quantum, to flow in the direction of maximizing proper time. And that is exactly what we see both classically and from the perspective of quantum field theory.