Tuesday, August 25, 2020

Is It Computation All The Way Down?


edge |  We're now in this situation where people just assume that science can compute everything, that if we have all the right input data and we have the right models, science will figure it out. If we learn that our universe is fundamentally computational, that throws us right into the idea that computation is a paradigm you have to care about. The big transition was from using equations to describe how everything works to using programs and computation to describe how things work. And that's a transition that has happened after 300 years of equations. The transition time to using programs has been remarkably quick, a decade or two. One area that was a holdout, despite the transition of many fields of science into the computational models direction, was fundamental physics.

If we can firmly establish this fundamental theory of physics, we know it's computation all the way down. Once we know it's computation all the way down, we're forced to think about it computationally. One of the consequences of thinking about things computationally is this phenomenon of computational irreducibility. You can't get around it. That means we have always had the point of view that science will eventually figure out everything, but computational irreducibility says that can't work. It says that even if we know the rules for the system, it may be the case that we can't work out what that system will do any more efficiently than basically just running the system and seeing what happens, just doing the experiment so to speak. We can't have a predictive theoretical science of what's going to happen.

The question that I'm asking myself is how does the universe work? What is the lowest level machine code for how our universe works? The big surprise to me is that over the last six months or so, I think we've figured out a path to be able to answer that question.

There's a lot of detail about how what we figured out about the path to that question relates to what's already known in physics. Once we know this is the low-level machine code for the universe, what can we then ask ourselves about why we have this universe and not another? Can we ask questions like why does this universe exist? Why does any universe exist? Some of those are questions that people asked a couple thousand years ago.

Lots of Greek philosophers had their theories for how the universe fundamentally works. We've gotten many layers of physics and mathematics sophistication since then, but what I'm doing goes back to these core questions of how things fundamentally work underneath. For us, it's this simple structure that involves elements and relations that build into hypergraphs that evolve in certain ways, and then these hypergraphs build into multiway graphs and multiway causal graphs. From pieces of the way those work, we see what relativity is, what quantum mechanics is, and so on.

One of the questions that comes about when you imagine that you might hold in your hand a rule that will generate our whole universe, how do you then think about that? What's the way of understanding what's going on? One of the most obvious questions is why did we get this universe and not another? In particular, if the rule that we find is a comparatively simple rule, how did we get this simple-rule universe?