The thing that would surprise me the most is if we don't find the Higgs particle, which is responsible for endowing mass to all the other elementary particles. Our whole universe is permeated with the Higgs, but we still haven't seen this particle. And that's what one of the big goals of the LHC will be. I think, for me, the big problem is understanding, is the Higgs fundamental? Is it something that parameterizes some yet unknown new physics? You know, if we find the Higgs, or if we don't find the Higgs, it will tell us about what that new physics could be. If we could probe a theory beyond this model that we have that describes all of physics except for gravity at a quantum-mechanical level, the first thing that would go through my mind is a quote by Albert Einstein, in which he said, "the most incomprehensible thing about the universe is that it's comprehensible." But if we don't know, if the experiments tell us something that comes from left field, and we're like, "What's going on here? The standard model works so well, but now it doesn't work at all," then it's not gonna stop us from trying to figure that out. But we'd need to go back to the drawing board and think all over again about how particle physics is connected to the cosmos.
The way I think about the Large Hadron Collider—imagine that you lived in a world where you could only see with red light, like a photographer's light. And you could see a lot of things. Some things wouldn't be very distinct, they would look black under the red light. You would be completely missing certain things, because you simply couldn't see them with red light. And then imagine that we suddenly turned on a full spectrum light. And now you see all of this detail that was looking black to you before, plus you see a lot of objects that you weren't able to see before. And I think turning on the Large Hadron Collider works very similarly. We've had a lot of time to think about what might happen, so there's a lot of predictions, there are a lot of theories out there. But what is so great about nature is that nature isn't elegant. Nature is incredibly complicated and doesn't do things in the way that we actually expect her to do things. And so what I really hope is that we turn on and we see a whole set of new phenomena that is not described by any of the present theories. If we're completely off the mark in the way that we understand physics today, I think that from the point of view of history it won't be such an incredible surprise. It's sort of hubris to imagine that our description is absolutely right, right now. And we just need a few more clues and suddenly there'll be a big breakthrough, and we'll see the world very differently. And that's what I hope LHC will give us is those extra clues.
The goal of high-energy physics is to understand the smallest things. How small is small? So there are molecules, there are atoms. Inside the atoms, there's a nucleus, inside the nucleus there are quarks. What's inside the quarks? Is there anything inside the quarks? And that connects with the picture of the universe, because by looking at smaller and smaller things, we understand the biggest thing, which is what the universe looked like, looks like now. But after 101 years of tremendous intellectual achievement and a lot of hard experimental work, we've come to the conclusion we don't understand 97 percent of the universe, which is, I think, a big shock. And kind of a reminder of how puny we are. Now, the 97 percent breaks into two parts, dark energy and dark matter. Dark matter, there's some kind of credible ideas that it could be particles. And the new experiments at CERN may be able to tell us something about those particles. But dark energy, no clue. None. Nothing. That leaves a few percent which we understand very, very, very well. And that's the stuff in this room and on the Earth, and we have a very good theory for that. So I'm doing a dark matter experiment. I'm actually going to look for the dark matter that's around us. And what I'm really excited about is that we make a big step forward in the big picture. Because ultimately you want a picture of the whole universe, everything—the history, the future, now. And in the next 10 years, all of this is going to come together, I hope. So that's why I'm excited.
What would make my day completely is absolute confusion—such as existed in the field way back in the 1960s when new particles were being found that didn't seem to fit into any well-recognized pattern, and one had no idea of what was going on until the concept of the standard model developed. The standard model is a theoretical construct that gives a very good description of physics at energies that have been studied so far. But it doesn't answer all our questions by any means. It leaves unanswered such simple questions as, Why are there six quarks in nature? And why is the muon, a silly particle that was first seen in the 1930s, why is the muon 200 times heavier than the electron, and indeed, why is it there? Who needs the muon? Who needs the strange quark, etc.? And we'd like to have a unique theory of physics, a theory of physics that has to be the way it is, and the question is, Will there be such a theory? And this will be crucial to the field, because if it happens that the Large Hadron Collider, which is soon to open, sees nothing, that would mark the end of what has been a very exciting enterprise in particle physics. Either there's something new and exciting, or the game is done. That would be the natural end to our discipline, and perhaps it's an end that we're approaching.
The LHC will give us that evidence needed to really understand what the state of the universe was after the big bang. Right now, there are a lot of theories about how the mass of the elementary particles came about. However, they are all over the map. There is no very clear direction from the theoretical perspective. Everybody is just brainstorming. Do we have the entire particle spectrum, or is there something more out there? It's a completely unchartered [sic] regime, you know? With the LHC energies, we will be able to find if there are heavier particles, which we have not found yet, which existed at the beginning of the universe, and we may be able to rule out a whole bunch of theories right away. And then we may be able to look at our data and say, "What exists?" and brainstorm with our theoretical colleagues and try to understand how all this came about. Try to build a model of the theory from there. We are explorers and adventurers as we are going into the LHC. That's how I view myself.
I think it would be incredibly exciting to find evidence of extra dimensions. I think it would be exciting to find any of the things we've thought about or even something beyond what we've thought about. There are questions about the cosmos: What is the dark matter? Even more mysterious, what is the dark energy, the 70 percent of the energy that permeates our universe that doesn't seem to be associated with any known form of matter? So these are all big, driving questions. But I think the idea of extra dimensions in space is just such a fascinating notion. If there were extra dimensions, you could find mysterious particles, such as a particle that has a property called "spin-spin two." It's a particle that would be associated with a graviton, the particle that communicates gravity, but travels in extra dimensions. That would be something that you just don't expect in most other theories, that has grand implications for how the universe evolved in its early stages. So I would be very excited if that would turn out to be the right direction to go in.
The LHC, in some sense, is just pure exploration. In the LHC, we'll be able to bang particles together harder than we've ever banged them together before. So in some sense, the LHC is just a pure leap into the dark. Now, of course, we all have our guesses as to what we'll see. So what I hope personally is that we'll find the Higgs boson, this thing that gives mass to all other particles, but then I hope we find something completely bonkers besides that, because we have so many unsolved problems. There are as many models of what we will see as there are theorists writing papers. In fact, it's worse than that. There are as many predictions of what we will see as there are papers written by theorists, which is sort of 10 times the number of theorists times the number of years since they came out of graduate school. So we really need to find something completely unexpected to show us the way, to give us a push, to point us, you know, how we can get around the wall and stop banging our head against it. You know, we always fear that the really interesting physics may be hidden from us, not, you know, by "we're not clever enough" or not by, you know, "we can't come up with a good enough model." They could just be hidden from us by sheer brute force, that the interesting physics happens at some enormous mass or some huge energy that we'd never be able to create on Earth. Einstein was fond of saying that nature is subtle, but she's not malicious—but, you know, that would be an example of nature just being downright mean. Taking the good physics and hiding it way off, out of reach. And so I would really love to be in a situation where this interesting physics was at low energies where we could get at it.
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