Wolfram Physics Project
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I Never Expected This

It's unexpected, surprising — and for me incredibly exciting. To be fair, at some level I've been working towards this for nearly 50 years. But it's just in the last few months that it's finally come together. And it's much more wonderful, and beautiful, than I'd ever imagined.

In many ways it's the ultimate question in natural science: How does our universe work? Is there a fundamental theory? An incredible amount has been figured out about physics over the past few hundred years. But even with everything that's been done — and it's very impressive — we still, after all this time, don't have a truly fundamental theory of physics.

Back when I used do theoretical physics for a living, I must admit I didn't think much about trying to find a fundamental theory; I was more concerned about what we could figure out based on the theories we had. And somehow I think I imagined that if there was a fundamental theory, it would inevitably be very complicated.

But in the early 1980s, when I started studying the computational universe of simple programs I made what was for me a very surprising and important discovery: that even when the underlying rules for a system are extremely simple, the behavior of the system as a whole can be essentially arbitrarily rich and complex.

And this got me thinking: Could the universe work this way? Could it in fact be that underneath all of this richness and complexity we see in physics there are just simple rules? I soon realized that if that was going to be the case, we'd in effect have to go underneath space and time and basically everything we know. Our rules would have to operate at some lower level, and all of physics would just have to emerge.

By the early 1990s I had a definite idea about how the rules might work, and by the end of the 1990s I had figured out quite a bit about their implications for space, time, gravity and other things in physics — and, basically as an example of what one might be able to do with science based on studying the computational universe, I devoted nearly 100 pages to this in my book A New Kind of Science.

I always wanted to mount a big project to take my ideas further. I tried to start around 2004. But pretty soon I got swept up in building Wolfram|Alpha, and the Wolfram Language and everything around it. From time to time I would see physicist friends of mine, and I'd talk about my physics project. There'd be polite interest, but basically the feeling was that finding a fundamental theory of physics was just too hard, and only kooks would attempt it.

It didn't help that there was something that bothered me about my ideas. The particular way I'd set up my rules seemed a little too inflexible, too contrived. In my life as a computational language designer I was constantly thinking about abstract systems of rules. And every so often I'd wonder if they might be relevant for physics. But I never got anywhere. Until, suddenly, in the fall of 2018, I had a little idea.

It was in some ways simple and obvious, if very abstract. But what was most important about it to me was that it was so elegant and minimal. Finally I had something that felt right to me as a serious possibility for how physics might work. But wonderful things were happening with the Wolfram Language, and I was busy thinking about all the implications of finally having a full-scale computational language.

But then, at our annual Summer School in 2019, there were two young physicists (Jonathan Gorard and Max Piskunov) who were like, "You just have to pursue this!" Physics had been my great passion when I was young, and in August 2019 I had a big birthday and realized that, yes, after all these years I really should see if I can make something work.

So — along with the two young physicists who'd encouraged me — I began in earnest in October 2019. It helped that — after a lifetime of developing them — we now had great computational tools. And it wasn't long before we started finding what I might call "very interesting things". We reproduced, more elegantly, what I had done in the 1990s. And from tiny, structureless rules out were coming space, time, relativity, gravity and hints of quantum mechanics.

We were doing zillions of computer experiments, building intuition. And gradually things were becoming clearer. We started understanding how quantum mechanics works. Then we realized what energy is. We found an outline derivation of my late friend and mentor Richard Feynman's path integral. We started seeing some deep structural connections between relativity and quantum mechanics. Everything just started falling into place. All those things I'd known about in physics for nearly 50 years — and finally we had a way to see not just what was true, but why.

I hadn't ever imagined anything like this would happen. I expected that we'd start exploring simple rules and gradually, if we were lucky, we'd get hints here or there about connections to physics. I thought maybe we'd be able to have a possible model for the first seconds of the universe, but we'd spend years trying to see whether it might actually connect to the physics we see today.

In the end, if we're going to have a complete fundamental theory of physics, we're going to have to find the specific rule for our universe. And I don't know how hard that's going to be. I don't know if it's going to take a month, a year, a decade or a century. A few months ago I would also have said that I don't even know if we've got the right framework for finding it.

But I wouldn't say that anymore. Too much has worked. Too many things have fallen into place. We don't know if the precise details of how our rules are set up are correct, or how simple or not the final rules may be. But at this point I am certain that the basic framework we have is telling us fundamentally how physics works.

It's always a test for scientific models to compare how much you put in with how much you get out. And I've never seen anything that comes close. What we put in is about as tiny as it could be. But what we're getting out are huge chunks of the most sophisticated things that are known about physics. And what's most amazing to me is that at least so far we've not run across a single thing where we've had to say "oh, to explain that we have to add something to our model". Sometimes it's not easy to see how things work, but so far it's always just been a question of understanding what the model already says, not adding something new.

At the lowest level, the rules we've got are about as minimal as anything could be. (Amusingly, their basic structure can be expressed in a fraction of a line of symbolic Wolfram Language code.) And in their raw form, they don't really engage with all the rich ideas and structure that exist, for example, in mathematics. But as soon as we start looking at the consequences of the rules when they're applied zillions of times, it becomes clear that they're very elegantly connected to a lot of wonderful recent mathematics.

There's something similar with physics, too. The basic structure of our models seems alien and bizarrely different from almost everything that's been done in physics for at least the past century or so. But as we've gotten further in investigating our models something amazing has happened: we've found that not just one, but many of the popular theoretical frameworks that have been pursued in physics in the past few decades are actually directly relevant to our models.

I was worried this was going to be one of those "you've got to throw out the old" advances in science. It's not. Yes, the underlying structure of our models is different. Yes, the initial approach and methods are different. And, yes, a bunch of new ideas are needed. But to make everything work we're going to have to build on a lot of what my physicist friends have been working so hard on for the past few decades.

And then there'll be the physics experiments. If you'd asked me even a couple of months ago when we'd get anything experimentally testable from our models I would have said it was far away. And that it probably wouldn't happen until we'd pretty much found the final rule. But it looks like I was wrong. And in fact we've already got some good hints of bizarre new things that might be out there to look for.

OK, so what do we need to do now? I'm thrilled to say that I think we've found a path to the fundamental theory of physics. We've built a paradigm and a framework (and, yes, we've built lots of good, practical, computational tools too). But now we need to finish the job. We need to work through a lot of complicated computation, mathematics and physics. And see if we can finally deliver the answer to how our universe fundamentally works.

It's an exciting moment, and I want to share it. I'm looking forward to being deeply involved. But this isn't just a project for me or our small team. This is a project for the world. It's going to be a great achievement when it's done. And I'd like to see it shared as widely as possible. Yes, a lot of what has to be done requires top-of-the-line physics and math knowledge. But I want to expose everything as broadly as possible, so everyone can be involved in — and I hope inspired by — what I think is going to be a great and historic intellectual adventure.

Today we're officially launching our Physics Project. From here on, we'll be livestreaming what we're doing — sharing whatever we discover in real time with the world. (We'll also soon be releasing more than 400 hours of video that we've already accumulated.) I'm posting all my working materials going back to the 1990s, and we're releasing all our software tools. We'll be putting out bulletins about progress, and there'll be educational programs around the project.

Oh, yes, and we're putting up a Registry of Notable Universes. It's already populated with nearly a thousand rules. I don't think any of the ones in there yet are our own universe — though I'm not completely sure. But sometime — I hope soon — there might just be a rule entered in the Registry that has all the right properties, and that we'll slowly discover that, yes, this is it — our universe finally decoded.

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