We're 100+ years away from solving physics: Why a theory of everything is so hard to find

本站添加: 2026-05-30

[00:00:02]There's this dream of the grand unified theory, the GUT, that is a step towards the TOE, theory of everything. So, can we talk about the GUT first? So, what what what's what's entailed in the GUT? So, the GUT is short for grand unified theory. We talked about that there were four known subatomic forces, the electromagnetic force, gravity, the strong force, and the weak force. And electroweak symmetry unification merged the weak force and electromagnetism into the electroweak force. So, what GUT hopes to do is to merge the electroweak force and the strong force into one grand unified force. Now, that leaves gravity outside because gravity is seemingly fundamentally significantly different. Then subsequently, it is hoped that a higher energy we will be able to blend the theory of everything together with all of the known subatomic forces, the strong, weak, and electromagnetic forces, and then gravity. But, so as you say, GUT is sort of a a way station along the way. That's the goal, and uh at this point, I would have to say that I do not see a fast progress in the immediate future. I think we're a ways away from that at this point. You mean on the gravity front? Maybe we'll come up with something really cool. We certainly had some ideas back in the early '80s that we tested, and they didn't pan out. Uh speaking of which, string theory is the thing you're referring to. Mhm.

[00:01:36]So, string theory posits that particles are tiny vibrating strings, and by tiny we mean extremely tiny at the scale of a Planck length.

[00:01:46]Uh then there's there's other leading candidates like loop quantum gravity.

[00:01:51]Uh maybe there's some alternate theories in the works. So, can you uh linger on that a bit more?

[00:01:58]Do you think a theory of everything exists?

[00:02:01]So, I hold personally that there are rules that govern matter and energy, space, time, and they probably are rules that I don't know. There are probably phenomena I'm not aware of, but I do believe that something there are is a rule that governs reality.

[00:02:19]And so, in that sense, once we understand the rules that govern reality, the fundamental rules, that would be a theory of everything.

[00:02:27]You know, there are things that are unknowable like, for instance, inside black holes. We don't know what's inside there, but that doesn't mean that there's not something inside there. So, there's a distinction between what we can know and truth. So, I I I do believe that there are the rules.

[00:02:44]And I do believe that with sufficient time, technology, effort, we will be able to figure this all out. Now, this isn't a thing in my lifetime.

[00:02:52]It's not a thing in my grandchildren's lifetime or even their grandchildren's lifetime.

[00:02:57]>> Whoa, whoa, whoa. That's a pretty strong statement, right? That's a pretty strong statement saying we're >> [sighs and gasps] >> we're 50 to 100 years out from finding a theory of everything. It took 200 years to go from unifying gravity to unifying electromagnetism. It took 100 years to go from unifying electromagnetism to unifying the electroweak force. Now, you could say, "Well, gee, that's went from 200 to 100, so it's getting faster."

[00:03:23]But, it's also getting harder because the unification scale is of order 10 to the 15, which we can do the math, that's a quadrillion times higher than the highest energy accelerator we can build today.

[00:03:38]And it was one thing to you know, we are reaching diminishing returns. We get something like a factor of seven increase in particle accelerator energy every 20 years. And so, we have to get to a quadrillion times. Now, you know, if you really did believe a factor of seven every 20 years, then that's we're talking like 500 years.

[00:04:03]But, you know, this is like Moore's law that it doesn't continue forever. We're not going to every seven year I mean every 20 years get another factor of seven. So yes, I I think it's a very long time. That's my prediction.

[00:04:15]You know, some people are far more optimistic and we can talk about that.

[00:04:19]>> We should also I should mention that I guess your intuition behind that is not just the part where you come up with a theory that's beautiful and seems to be internally consistent, but you have to have a theory that's making falsifiable testable predictions.

[00:04:38]>> Correct. And you have to have a a feasible engineering construction, a methodology for creating an experiment that tests that prediction. So I think a lot of your this is 50, 100, 200 years from now intuition is maybe about the second part of that, which is like you need to have an experiment. Yeah, yes. Yes. But, you know, let's say I mean you alluded to super strings. I haven't answered that question. I'll table that for a moment. Super strings is a fascinating idea. I don't believe it, but I love it. I hope it's true. And there's a real, you know, aphorism and it says you should absolutely never believe what you think. So even if you think super strings is true, you shouldn't believe it because it hasn't been tested.

[00:05:25]Now, let's say super string is correct.

[00:05:29]I mean, hypothesis it's correct, 100% correct. I don't know it's correct. So I don't care. I mean, you know, it could be correct, but I don't, you know, until it's validated, it's just a wild ass guess. You know, so I we have to have a way of validating it. So yes, the the the empirical side of it is important. I mean, you could wake up tomorrow and have the theory that is the perfect theory, but if I can't prove it, I don't care.

[00:05:57]If we were to think, this is going back to the great courses on the evidence for modern physics, we're talking about energy levels and tiny particles to the degree where the kind of prediction we would be making is not accelerator type predictions.

[00:06:16]So, it's probably going to be impossible to build an accelerator that detects something like a string.

[00:06:25]So, you have to make predictions about macro scale behaviors. That's another alternative. It's a different kind of prediction. Sure. Do we even have intuitions about what kind of predictions they would be? So, what what Of course, one of the lines of intuitions has to do with black holes when you're in the singularity.

[00:06:46]The physics of black holes combine certain elements of general relativity and quantum mechanics. So, there you could see some kind of predictions you could make.

[00:06:57]Uh but you can't really mess with a black hole. It's not like you can create a black hole in the lab.

[00:07:02]>> And the energies that you're talking about, the sizes we're talking about, are inside a black hole, which you can intrinsically never see. Yeah.

[00:07:10]So, you know, you can only see the outside of a black hole, not the inside of a black hole. So, what you said You did say something that was incredibly important and incredibly correct, and probably won't happen, but that's still good. Okay. So, we have two choices when you talk about superstrings. Either superstrings are correct and they're making predictions up at the Planck energy scale, at which point we have to somehow build facilities that can generate Planck Planck energies. That's possibility one.

[00:07:38]Possibility two is this theory, which is currently only applicable at Planck energy scales, someone figures out a way to take those equations and solve them in a way that say predicts the mass of the electron.

[00:07:56]Mhm. Right? And that is a tricky business. Um I am not a string theorist, so I can't tell you that that's likely, but I can tell you that they've been working on it since the '80s and they haven't gotten very far.

[00:08:09]Furthermore, if I uh I think it's fair to characterize that string theory is still a a vague idea, and that's unfair, but let me tell you why I say that. Because what they have are approximate solutions to approximate equations.

[00:08:28]And that is already saying that we're a ways away from really getting a handle on that. So, yes, if there could be some bright young lad or lass out there, someone listening to this podcast right now, who figures out a way to take superstring theory and solve them in tractable ways that makes predictions from the scale at which they currently apply down to measurable scale today.

[00:08:53]And if that happens, well, then I might retract my my question or my my concept.

[00:08:59]There's a reason why I think that probably isn't true. That's probably not valid. So, let let let let me I love this, all right? So, let's back up. I'm going to pitch. I wrote this book for Oxford, Einstein's unfinished dream. And Einstein's unfinished dream was to come up with a theory of everything. It was unfinished because, well, it's unfinished.

[00:09:19]And so, the the second part of the tagline of that book is practical progress towards a theory of everything, with the emphasis on practical.

[00:09:26]Because when you read books about theories of everything, when you see podcasts, when you listen to YouTube videos or whatever, they are often written by theorists. And theorists are they're big idea people. They're very, very smart.

[00:09:44]But but there's a pragmatism that is often missing in the sense that they say, "Well, super strings, look, they you know, they have these little vibrating things and wouldn't it be cool and you know, but you got to get to the do you know it? So, let's pretend super string theory or something like it is correct. The energy scale at which um that should occur is of order um 10 to the 15 times higher, 10 to the 19 GeV.

[00:10:12]We can currently do things at 10 to the fourth GeV, give or take. So, that is 10 to the 15, that's a quadrillion times higher energy.

[00:10:21]So, what we are doing now is we are looking at the world with our very best measurements and we are trying to project out a quadrillion times higher and figure out a theory that explains everything.

[00:10:35]Now, I I I have this I have a couple of analogies, but I like this. Suppose that you were some, you know, Joe Australopithecus 2 million years ago or something in Africa wandering around somewhere in Kenya. Mhm. All right?

[00:10:49]You're about a meter in size. So, you can walk a meter. Meter scale is like your scale. Mhm. You can walk 10 meters in every direction, that's 30 feet, no problem. You can walk 100 meters, 300 feet. You can walk 1,000 meters, that's half a mile.

[00:11:03]You can walk 10,000 meters, that's 60 miles. 100,000 meters is 10 to the fifth and that that's unlikely.

[00:11:11]But the distance that we need to go from what we can see to the Planck scale, it's not 10 to the fifth, it's 10 to the 15th.

[00:11:19]So, that means in my analogy, think about this guy who's walking around Africa. Now, if he walks, you know, 100 feet or something, it looks a lot like what it is now. He can make a prediction about what what sees and when he goes to that new place it's probably going to be okay. But if he starts walking 500 miles east, well, he walking around the center of Africa has no concept of, for instance, the Indian Ocean.

[00:11:44]He would never predict sperm whales or kraken. He would never predict what it's like the bottom of the ocean is. Going north, he's he's in Africa. He would never ever have a clue about the Alps or Antarctica. Going even smaller distances, going a mile up, things wouldn't be very different. But if he goes 10 miles up, he wouldn't breathe and he'd freeze. If he goes 100 miles up, he would die. If he goes 2 miles down, he would roast. The point being is we are like that Australopithecus. We have a realm that we can study, and we can even predict to some validity what would happen if we go some distance away. But the farther away we go, the less and less our local prediction really represents the reality of those more distant times. And so, basically, his theory about the the world would be totally bogus. And so, even if he had the best theory, his theory would not have anticipated the Alps. It would not have anticipated penguins.

[00:12:52]Right. Flamingos, not there, you know?

[00:12:55]>> And that is just the case. So, now, that's what we're doing. We are taking something and we have reason to understand what we know, and we can predict a factor of 10 or 100. But I think it is the absolute the pinnacle of arrogance to think that what we can do, given the understanding that we have from what we've measured now, and predict it out a quadrillion times higher than we can see now. So, my opinion, and this is partly because I'm an experimentalist, the correct way to make progress, practical progress towards a theory of everything, is to look around at the things that we don't have answers to right now. For instance, are there something smaller than quarks? I don't know. Is dark matter real? I don't know.

[00:13:43]May- If it's real, what is it? I don't know. Is dark energy real? Yes, probably, but I don't know. What is the nature of space and time? I don't know.

[00:13:53]But these are questions we can explore.

[00:13:56]And I would expect, and this is my prediction, that all right, we're going to figure things out at a factor of 10 or 100 times better than we can do now, and we might be able to do that in my kids' lifetime or something like that.

[00:14:07]But in order for us to predict a quadrillion times higher, I'm pretty sure superstring theory is wrong, not because people aren't smart, but because something new is going to happen. I mean, if you were talking about chemistry, you would have never predicted nuclear physics, and that's a small increase in energy, right? The idea that there is something in the nucleus of atoms that causes the sun to burn, there's a reason why people didn't believe, you know, they they calculated how old the sun should be, and it should only be 10 million years old, because otherwise it would burn out. Well, that's clearly wrong, and it's wrong because of nuclear physics. That is why I feel fairly confident to say, while someone could think, well, superstring might be right or something. Maybe it's right, and I hope it's right. It would be awesome if it's right. But what are the odds when you're making something with that tiny lever arm, predicting it out a quadrillion away, and say, oh yeah, we got it right. What are the odds? And my answer is, you got to be kidding me.

[00:15:09]Now, I could be wrong, and I admit that I could be wrong. But that's why I I think the real issue is not the brilliance of humanity, it's the stuff we haven't found.

[00:15:20]For We don't know, I mean, simple one, I'm in the I'm say it's simple and it's not, but what is dark matter? We don't have a freaking clue.

[00:15:30]Not a clue. We know a lot of what it isn't, but we don't know what it is. And so, you know, talk about super strings. All right, well, maybe dark matter fits in super strings or maybe dark matter is governed by a physics that is completely diametrically opposed to the super string concept. And allow me a bit of a thought experiment here, a brief thought.

[00:15:50]My intuition says that when you propose a theory of everything, the kind of prediction you want to make involves a kind of leap of conceptual understanding that Einstein did. So, for example, you want to come up with something like space-time and that gravity bends space space-time.

[00:16:11]So, it's not merely that you have this beautiful mathematical framework, but that framework allows you to rethink how you see reality enough to make a prediction that's about the macro world. I mean, just come up with something like space-time. You know, there's one idea for instance to say that space and time aren't real. They they emerge from from entropy. Yeah, that's a way of a new way of thinking and maybe there's some validity in it. I want people to think about it.

[00:16:45]But in the end, it's just an idea.

[00:16:49]And that's the real key thing. And And as you say, it has to tie to a macro world. You have to validate. If you don't validate, it's a crazy idea.

[00:16:57]Theorists are incredibly creative, smart, wonderfully interesting people, but I don't care. I want a measurement that validates the idea because there are so many I mean, if you read the the journals, there are so many theoretical papers with all these nifty ideas that die.

[00:17:18]You know, one that was recently I liked and and might still be true was um that dark matter that, you know, our simple model of dark matter is that there's a subatomic particle out there that's heavy and it's floating around and it's causing gravity. But someone said, "Well, you know, maybe there's complex dark matter, which means there's a whole dark sector. So there are dark atoms and they interact with one another." And that is a nifty idea and I love it.

[00:17:44]And that was all the rage for a while and we looked at it and it may still be true, but the simple ideas have been mostly invalidated because we've tested it and it doesn't work.

[00:17:55]Same thing, there was a talk about um large extra dimensions. The reason that gravity is so much weaker than the other forces was, "Well, maybe gravity can sneak into more dimensions than the other forces. It leaks into those dimensions.

[00:18:07]>> That was a cool idea. I mean, and but that's the point is you have these lovely cool interesting ideas that constantly die.