Betting on the Cosmos (2012) - Nobel prizewinner Robert Laughlin is passionate about experiments. He challenges the students in this film, and laureate David Gross, to come up with ways to test our big ideas about the Universe.

David Gross is a theorist. He works on string theory which hopes to unite everything in physics in one grand mathematical model. Robert Laughlin is passionate about experiment. He challenges Gross and the 3 students they meet to come up with ways to test their ideas about the universe. Robert Laughlin: I wonder if you folks could talk a little bit about falsifying early universe models. Is there more than one of them that will account for facts as you see them now? Diego Chialva: It depends exactly what you want to falsify. So inflation so far I would call it paradigm because it’s still looking for a fundamental theory, a more developed theory to be embedded in. Inflation is an early phase of evolution of the universe in which the universe expanded exponentially rapidly. Noam I. Libeskind: Inflation essentially is for the layperson what the Big Bang is. When the layperson thinks of the Big Bang, actually what they’re thinking about is this moment of incredibly fast expansion of the universe. I guess Laughlin was saying, you know: “Is it really falsifiable in that, you know? Do we have a series of models that we can pick out one from the other due to certain experimentations?” David Gross: It’s an incredibly predictive theory but with very few parameters which fits the data very well. Noam I. Libeskind: What are the alternatives to inflation? David Gross: There are no sensible, that I know, alternatives to inflation in the sense that I described it of saying that the geometry underwent inflation. Diego Chialva: Maybe you would be interested in knowing that actually some of the competitors, they have failed the test, these observations, really can falsify models. There have been for example bouncing universes beyond inflation scenarios. So it seems that there are really valid tests. Robert Laughlin: Well, let me be devil’s advocate. The cases I know of explosions are unstable. They’re hydrodynamically unstable. When things are changing scales as a result of a phase transition, which is what we’re talking about, you get structural instabilities in them. Adapting example would be popcorn. Now, in the case of popcorn it would be very difficult to work backwards from the measurements of popcorn to figure out what the popcorn looked like before you popped it. You can make some models and certain models will fit the popcorn better than others but they all might be completely wrong because you didn’t have enough backwards time to see the kernel of the popcorn. Now that’s sort of what I’m getting at when we talk about falsifying models. Do you really have enough experimental constraints to really tell anything? David Gross: Inflation is not a phase transition. Inflation is not... Robert Laughlin: It absolutely is. Diego Chialva: Can I maybe try to answer what you say? Robert Laughlin: It’s an enormous amount of heat coming out of that background, it’s a phase... David Gross: It’s not an explosion. Robert Laughlin: David you’re completely right. It’s not an explosion because it’s not hydrodynamical. But there is energy pushing the thing outward coming from the equation state of the matter of the vacuum. David Gross: Bob this is very different. In general relativity you can sit on the top of a hill and you’re pushing the universe outward. Nothing, it’s a totally, in a sense stationary… Robert Laughlin: David you know perfectly well this is a card trick. What it’s actually doing is blowing up, ok. Noam I. Libeskind: Are you arguing against the Big Bang? Robert Laughlin: I never argue. The first rule of theoretical physics is never argue with David, ok. The question is constraining models. And one of the things that I’ve become very worried about in modern physics is the tendency to underconstrain models of experiment. So we say we’ve got the model in situations where there are many that would give the same experimental result. And in this subject as far, as I can tell as an outsider, the models that I’ve seen are all highly underconstrained. So we’re on task here. So the thing I was trying to bring up here is the issue of the interaction of ideas with experiment. David Gross: So experiment plays a dual role for theorists. It gives them essential clues and hints and partial information on which they can construct a solid foundation for their theories. And then it tests the predictions they make and which is the way we’ve learned to discard bad ideas. So it’s absolutely essential. After the Big Bang and the initial expansion of the universe, inflation, matter cooled down and radiation escaped. The afterglow of this radiation is all around us. It’s known as the CMB, or cosmic microwave background radiation. The CMB is a snapshot of the universe in its early days when it behaved like what physicists call a black body. A black body emits radiation in a characteristic spectrum. Measurements of the CMB show that it matches the black body radiation spectrum very closely. And this says Gross is compelling evidence for our Big Bang theory of the universe. David Gross: We have direct evidence that that microwave background is the most perfect ever measured black body radiation, ever, any laboratory on earth. Robert Laughlin: Really? David Gross: Absolutely. Robert Laughlin: Nobody can get better than 10^-4. David Gross: Absolutely, absolutely. Diego Chialva: 10^-5. David Gross: 10^-5, nobody can, absolutely. It is the best black body radiation curve ever. Noam I. Libeskind: The aerobars on the curve are usually smaller than the curve itself. David Gross: It’s 10^-5. There is nothing on earth that has ever been a better black body radiation. Robert Laughlin: I have a hard time with that but I haven’t looked so I don’t know, maybe you’re right. David Gross: By I think 2 or 3 orders of magnitude. Robert Laughlin: Let the record show that I do not believe this man until I look it up. David Gross: Make a little bet? Robert Laughlin: Yeah. David Gross: Ok, a bottle of wine? Robert Laughlin: One bottle of wine it is. Oh wait a minute, who gets to choose the wine? David Gross: Let’s see… Robert Laughlin: If I lose, I’ll give you a good bottle. So you're all witnesses. So what is it? No table top experiment has ever gotten a uniformity of black body radiation better than…? David Gross: The CMB. Noam I. Libeskind: 10^-5 Robert Laughlin: 10^-5. Ok, I’m happy to do that one. David Gross: Was it a case of wine? David Gross: So he was surprised I think by that claim and he thinks that in the laboratory one could do as well. It’s my understanding that one can’t even come close in the laboratory. Noam I. Libeskind: And they had this bet where he said, you know: “I don’t believe that it’s possible to make a black body which is, you know, more fine than the CMB?” Which is of course a bet that he’s going to lose because it’s the finest black body in the world. Ulrika Forsberg: I had never heard that before. That was something completely new to me as well. Noam I. Libeskind: It shows experimental kind of verve that he says, you know: Robert Laughlin: Let the record also show that whenever I lose a bet I pay. I trust the same is with... David Gross: Well the record can’t show that yet, that would be… Robert Laughlin: No, I have lost bets before David. David Gross: Oh ok. Robert Laughlin: If you haven’t lost bets you're not betting hard enough. David Gross: I have. David Gross: I have a lot of bets on supersymmetry. Robert Laughlin: Oh, that’s too bad. Robert Laughlin: Very, very bright people can easily delude themselves. It happens a lot. So you have to learn the skill of how to tell yourself no, that the experiments are not agreeing with me and that even though I’m very proud of myself and I’m an egomaniac because we all are, I have to say I wasn’t right and we had to go back to the drawing board and get it right. You want to propose things that can be proved wrong or you're not the real thing. Diego Chialva: So what you are saying is that until we don’t take the experiments, we should not produce models that may be in the future will be falsified or not? Robert Laughlin: No, people are perfectly free to spend their time the way they want. Diego Chialva: No, but I mean do you think it’s useful to do it or not? Robert Laughlin: Thinking about what might be is always useful. All of us do it, it’s part of a discipline. I mean I’m one of the worst offenders. And I have the thrashed papers to prove it, ok. But this has to do with your desire to find what's fundamental. And one of the lessons you learn here is that you sometimes just have to wait until a good experiment comes even though you might have figured it out. Diego Chialva: Sure, I would agree. Robert Laughlin: Sometimes there’s more than one answer. And there’s just no way you can figure it out by pure logic because things aren’t constrained. Ulrika Forsberg: I would like to return for a brief moment to string theory. As an experimentalist of course I would like to know: How can I test it? When will there be a proper test? David Gross: Part of the problem is that string theory isn’t a theory yet. Ulrika Forsberg: Yeah, no it’s a set. David Gross: It’s the framework. The existence of extended fundamental objects that are stretched out by the universe is the only direct signal of string theory I can easily imagine at this point. It would help to have a theory. And we’ve learned that string theory and quantum field theory are really the same thing and we don’t understand them. And so we’re learning a lot about the theoretical structure but it’s still, unfortunately still a framework and not a specific theory. Ulrika Forsberg: What I would like to hear from string theory and very soon is these are the experimental things; this is how it manifests itself in our world. Because that’s when I think it turns into real physics. So I would have preferred an answer saying that, yeah, we’re on the verge of finding it within a couple of years we will present you with a recipe on how to do an experiment. That would have been the ultimate answer of course. Noam I. Libeskind: Sure, who wouldn't? David Gross: In the near future I think the best hope is still the LHC because we have a good chance there of learning a lot of new physics. And any clue, you know, is incredibly valuable. I mean my wild hope would be somebody would see some cosmic strings and we could see the cracking of cosmic strings in the gravitational radiation coming from those cracks. But the real hope is that we will learn a lot from the LHC, from the nature of supersymmetry multiplets and breaking and that that will appear while I’m still around to do something about it. Several days later when the 5 physicists joined a boat trip, they were still arguing over who won the bet. Ulrika Forsberg: Have you settled it yet? Robert Laughlin: Well no, I have to wait till I get home to check but I think he should pay up now. David Gross: We actually have here 3 witnesses. Robert Laughlin: What I say is those 3 constants are measured to 10 significant figures on earth, therefore I win the bet. David Gross: No. Robert Laughlin: You also measure the principle of detail balance to better than the part…in a lots of ways. Therefore I should win the bet. David Gross: No, you should win the bet, of course. Robert Laughlin: I think we understand each other now. And you, you and you know if there isn’t… David Gross: I think I’ll inform my lawyers. Mars Incorporated: Harold Schmitz: It starts with a belief that the problems that we have facing us in the future and the opportunities will be solved through understanding nature. Science is the discipline that helps us to understand nature. It’s great to be here in Lindau because it is literally the only place in the world where we can interact with the brightest minds from Nobel laureates like Dudley Herschbach to the brightest young students. Ralph Jerome: You really want to rub shoulders with the best and the brightest and they’re here in Lindau. Harold Schmitz: If there’s one reason why Mars needs to be interacting with this meeting, it is because agriculture is one of the largest footprints on the world in terms of its sustainability. Ralph Jerome: Yeah, for sure. Harold Schmitz: However. The best minds in physics and chemistry and medicine often don’t think about how to influence that. Ralph Jerome: When you think about the impact agriculture has on the planet and the challenges that are going to be coming forward in the next 10, 15, 20 years, our role being a catalyst to resolving some of those issues is going to be critical. We want to attract people that are really talented but also people that want to make a difference. Sarah Gallagher: My PhD is funded by Mars and I was a bit worried, when I started that being funded by industry, they would be very driven on profit and not looking into basic research or just wanting to learn things. And instead, I’ve realised that they’re really a principled company. And there are many things that they won’t do or things that they will do specifically for the principle of the matter. Ralph Jerome: Well, the Mars fellows are world class talents that then have the access to a world class community and that’s where the collaboration happens. Where the collaboration becomes magical is when the great fundamental science and discoveries in universities are brought into the private sector. Harold Schmitz: What's the hardest question that you would like to ask, that you can think of? No name 1: How are you guys looking at helping those regions which currently support you? No name 2: How do you bring the problem of food transportation? No name 3: What kind of role computation and modelling might play in your research? Ralph Jerome: We don’t have all the answers and some of these solutions are much bigger than us. So, not only do we have to be delighting our consumers, we have to be collaborators and a catalyst for change in a lot of our supply chains. At Mars we fundamentally believe that many of the problems facing us going forward and really the opportunities are going to be fundamentally science based. So people that are scientific entrepreneurs, that want to make, as Steve Jobs used to say, a dent in the universe, this is the place. Harold Schmitz: We believe that collaboration amongst the brightest scientists throughout all the sectors is essential to help address these grand challenges. Leadership matters. And when it comes to collaboration many of you will be leaders in this context. Dudley Herschbach: All of science is collaborative. You can’t do it by yourself. Everything you’re thinking about and methods you use they have a history and you will add your bit to pass it on, that’s the really glory of the enterprise. Applause.

Betting on the Cosmos (2012)

Nobel prizewinner Robert Laughlin is passionate about experiments. He challenges the students in this film, and laureate David Gross, to come up with ways to test our big ideas about the Universe.

Betting on the Cosmos (2012)

Nobel prizewinner Robert Laughlin is passionate about experiments. He challenges the students in this film, and laureate David Gross, to come up with ways to test our big ideas about the Universe.

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