Robert Laughlin - What's Fundamental in the Cosmos?

Bob, I have this desire to know what's fundamental. Sounds silly to some people, but that's what I've been given. My genetic structure is such that I want to know what's fundamental. So where do we start? Let's talk about the constants of nature, physical law. How can we give these some definition? Well, the way I give them definition is you measure them. You want something that doesn't change, that is really fundamental. Well, the simplest definition I know is that you measure something, and it always comes out the same. And there are a handful of such measurements. They're very special, about 20 of them. I won't bore you with the details, but they're neat. All of them are neat. So what does that mean about these universal constants? What are they? You've defined them operationally, that when you do the measurement, it always comes out the same with a certain amount of exactness. What more can be said about it? Well, the short answer is that nobody knows for sure. But there are two points of view. One point of view is that you found the building blocks of nature. The fact that they don't change tells you you've found the fundamental pieces of things. The other point of view is that there's symptoms of something. When you find exactness, it means that the matter of nature has organized itself and become simple. And one of its manifestations, one of the manifestations of this simplicity is this thing that you measure so exactly all the time. So how then can we articulate these two concepts, the exactness of these constants and the so-called physical law that some people just talk about in very loose terms? Can we give it some relationship between them? Well, the only relationship I can think of that would be simple is worldviews. Because ultimately, we're talking about experiments and experiments are experiments. You know, you measure what you measure. The experimental difference between the two things is that the fundamental part doesn't change when you bang it, hit it harder, try to see what it's made of. Whereas the emergent thing, the thing that's a symptom does. It morphs out of existence when you examine it on smaller and smaller scales. So I guess you might answer the difference in those worldviews affects how you would treat these things that you find. One would say, ah, we're done. The other view would say, oh boy, let's try to take it apart and see if it goes away. So let's take some examples that we would call fundamental in the universe. Take Einstein's theories, for example. Relativity, which is two parts, special relativity, speed of light, constancy, and general relativity, which is the theory of gravity and space curvature and all of that. Are these fundamental? Well, of course, per my previous remarks, nobody really knows for sure. What you know is that they work. Now, when Einstein invented special relativity, he had in his mind something fundamental, something that just was. He hypothesized that this thing just was, and then made predictions that were quite astonishing, and they turned out to be true, every single one of them. Why? Well, because the hypothesis was correct. Now, the hypothesis was correct in the physical sense. The reason why it was correct may not have been what Einstein thought, but nonetheless, relativity is true. Now, of course, at the time, it was very revolutionary, and naturally, other scientists didn't believe him. The point now is that the reason we believe in relativity today is not because we had a great transition in our beliefs about what should be so. We believe in relativity because we have no choice. It's true. Measure it to be true. Now, what is beyond relativity? Well, of course, within our ability to measure right now, nobody knows. There don't seem to be any. Although, there are experiments looking for failures of relativity in the motion of very fast particles, for example. So far, all the results have been null. And relativity has stood the test. So far. That's right. Now, is there a difference conceptually between special relativity and general relativity? Oh, big one. Special relativity is based on experiments you can do. It's basically an inference that you draw. And I like to say that we credit Einstein for having thought of relativity, but in a short number of years after he invented that theory, everybody would have been drawn to that conclusion experimentally anyway, because the experiments were coming along, and it was just undeniable. The general theory, on the other hand, is a vastly bigger thing. It's a speculation about gravity based on the relativity principle that most of us suspect is right. The reason we suspect it is that it's so beautiful. It's built on nothing. It's built on two things. The principle of relativity, on the one hand, and something we call the equivalence principle on the other. And then you think about it. Of course, not you, Einstein. Einstein thinks about it and comes up with the answer. And of course, once Einstein has explained the answer to you, it's obvious. So you won't find a card-carrying theorist around who thinks that general relativity isn't right, even though we don't really have all the tests yet, because it would require violating one of those two things. Now, the problem is we get to an astonishing prediction of general relativity that very large objects should form black holes. There, something truly terrible has happened that is so terrible we can't even describe it quantum mechanically. Now, the struggles about gravity that we're having now have to do with that. What's the resolution of that? We don't know yet, because we don't have experiments. But my best guess is that those experiments, when they're done, will show that the relativity principle was emergent. Now, as of this moment, it's just a wild speculation. But those experiments are not going to come until you and I are six feet under. But many generations hence, those experiments will be done, and they'll come out one way or the other. And if they come out the way I say, then it will turn out that the relativity principle was emergent. Now, the significance of that is astonishing, because the implication is that space-time itself, then, is emergent. Well, it's astonishing until you begin to think about the facts as we know them. The idea that space has phases and phase transition is perfectly mainstream. The relativity principle, we think, is on a higher plane, but that's just because there's no experimental reason to worry about it yet. So the idea of the vacuum made of something is not revolutionary at all. Of course, in fact, what we're worrying about in fundamental theories of the vacuum is, what is the stuff? Exactly what are its equations? How do you describe it properly, and so forth? Well, there are two ways to look at that. One is that when the vacuum of space exists, it's composed of stuff. But all of that takes place within the stage of space-time. And space-time is sort of always there. And this stuff, it fills the vacuum. Another way to look at it is that space-time itself is emergent in some way. Yeah, you know, everybody knows it has to be the second thing. The reason you know this is the famous cosmological constant problem. You must be familiar with it. The logic of Einstein allows a whole bunch of different equations, and they are characterized by this number called the cosmological constant. For some miracle that nobody seems to know, this number is very close to zero. But not exactly zero. Well, maybe not exactly zero, but so close it's good enough for government work. Now, that is just too many miracles on top of each other. If you postulate that the vacuum has no cosmological constant, and then throw in this stuff, you find a giant cosmological constant. So in order to get the universe as we know it, you have to start with a negative one that is exactly canceled by all the matter that's in there. To 120 orders of magnitude. Correct. It's a miracle that's inconceivable. And so the fact that the cosmological constant is so small tells you that these two things are intimately related somehow that we don't understand. And does that imply that there's some more fundamental stuff that we... more fundamental than space and time? I'm a scientist, and I believe in experiments rather than speculating. So the truth of the matter is, based on the measurements that we have now, you can't tell. Now, if I'm allowed to put on my speculator hat, my answer would be almost assuredly yes. There's something to be discovered there. Not just one thing either, a whole bunch of things to be discovered.