Physicist Lisa Randall On Cosmology And The LHC
IRA FLATOW, Host:
Next up, last week, physicists reported that they've seen evidence for subatomic particles - neutrinos - zipping through the Earth at speeds slightly faster than the speed of light, which is considered the speed limit of the universe, according to Einstein's theories. How is that possible? Could it just be an error in measurement? We are after all talking about just billionths of a second. But if those measurements are correct, might time travel be possible? And is there an alternative theory to explain this?
A good question for my next guest. She's an expert on the subatomic world, the tiny building blocks of matter, like neutrinos and quarks and bosons, and how these things interact with each other - or should, at least according to theory. Her new book "Knocking On Heaven's Door" gives an update on some of the latest ideas in cosmology and particle physics, including a look at what's going on at the Large Hadron Collider and the search for the Higgs boson.
But it's not all that teeny tiny stuff she's talking about. She takes a deep look back at scientific thinking, how scientists, like herself, decide which questions to ask and why they often disagree and how science itself plods ahead one study at a time. Dr. Lisa Randall is the author of "Knocking On Heaven's Door" and a professor of theoretical physics at Harvard University in Cambridge. She joins us from Minnesota Public Radio. Welcome back to SCIENCE FRIDAY.
LISA RANDALL: Thank you. Thank you for having me here.
FLATOW: How are you?
RANDALL: Oh, I'm quite well. Thank you. It's been an interesting time. These new stories do kind of raise a lot of curiosity as to just hearing about what's going on in science today. It's pretty exciting.
FLATOW: You know, today is actually a landmark day in science and physics. Today, the Tevatron in Batavia shuts down.
RANDALL: Yeah. It's so sudden...
FLATOW: Tell us about what was so important about that machine.
RANDALL: Well, the Tevatron was the premier high-energy particle accelerator. What does that mean? Well, I do theoretical particle physics. We're trying to understand the most basic structure of matter. And the way you do that is you have to look at really small distances. And to get to small distances, you need high energies. So, basically, the Tevatron reached the highest energy of any machine there was until the Large Hadron Collider in - near Geneva started to run. And it was really was the premier machine. It got to very high energy. It discovered the top quark, the heaviest quark and completing in some sense the standard model of particle physics, telling us that matter is the most basic...
FLATOW: I'm Ira Flatow.
RANDALL: ...element's interaction.
FLATOW: I'm sorry. I'm Ira Flatow. This is SCIENCE FRIDAY from NPR. Talking with Lisa Randall, author of the new book "Knocking On Heaven's Door." Let's talk a bit about this new neutrino going faster than the speed of light. Do you believe it?
RANDALL: I don't think I believe it and probably most physicists don't believe it and probably even the people who presented the results were rather uncertain, and they presented it in a very fair and balanced way in the sense of saying, look, we don't know what's going on. We'd like to see if anyone else can verify this or figure out what's happening. I think it's really part of the story. I mean, it's interesting in the context of the more general story of how science develops.
You have principles. You test them as accurately as you can. Eventually, they might break down. And so people presented a story a lot of the time in the context of Einstein's theory of breaking down. But even, even if this result turned out to be true, I mean, Einstein's theory has been very successful over a large range of parameters, and it clearly will still be a useful theory. The question is whether when you do a sufficiently accurate measurement, you can see something where it breaks down.
In this case, I do think it's very unlikely, but I also think that the interpretation that's been given to it of time travel is probably the least likely interpretation, even if it does turn out to be right. It would probably - more likely mean that the underlying assumptions of Einstein's theory, the underlying fundamental assumptions break down at some level.
FLATOW: That would be...
RANDALL: And at that time...
FLATOW: ...pretty major, would it not?
RANDALL: Of course, it would be very major. But, again, it doesn't mean that everything we've done using Einstein's theory is wrong. It doesn't mean it wouldn't be a useful theory. It would mean, if it were true, that there would be these extenuating circumstances when you get to these limits of precision where a new theory might take over. And there's nothing that says Einstein's theory will be the ultimate underlying theory for - that applies to arbitrary accuracy. We know it applies over a large range, and that's pretty good.
FLATOW: As Carl Sagan used to say, extraordinary claims require extraordinary evidence. So...
RANDALL: I don't think anyone disagrees with that.
RANDALL: I think most people are looking at it pretty skeptically, but it's been interesting, because even among the physics community, it's, you know, had us think about things we wouldn't otherwise think about and to consider how such measurement would be made.
FLATOW: What about the failure to find the Higgs boson so far at the Large Hadron Collider?
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RANDALL: Yeah. People really focus in on it as a failure to find it. So what really - if you would ask people, say, a few years ago, before the Large Hadron Collider was running, what is the most likely - and when I say people I mean theoretical physicists. If you ask them what they felt was the most likely value for the Higgs boson mass, it would be a value that has not yet been ruled out. It would be a value that has not yet been tested. It might be tested within this year, but it has not been.
So basically, what the experiment has done - and it's very impressive. We have to keep in mind the Large Hadron Collider is not running at full capacity yet. It's only running at half energy, and it's not running at full intensity. Yet it's put significant bounds on what the Higgs boson mass could be, if it is a simple single-particle Higgs boson. And so what it's done in some sense is remove some sort of cushion of saying, well, we think it's this value, but maybe it's all of these.
I mean, now, we know it's in a very range if it is this fundamental Higgs boson that people have assumed it is. It could be, though, that - I mean, really all we know - and when I say know, there's pretty strong theoretical evidence that there's something called the Higgs mechanism. Higgs is, by the way, refers to Peter Higgs, the physicist who had the idea of how particles acquire their mass. And the thing is we want experimental evidence of this mechanism, other than the fact that particles have mass. And that evidence in the simplest version of the theory would be this single Higgs boson that we can make predictions about.
FLATOW: And the...
RANDALL: If, however, it turns out to be something different, it means that there's another more complicated Higgs factor. And actually, I talk about what possibly it might be.
FLATOW: Yeah. It's quite interesting. I'm talking with Lisa Randall, author of "Knocking On Heaven's Door," which you wonder why lyrics from a (unintelligible)?
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FLATOW: We'll ask...
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FLATOW: ...we're going to take a break.
RANDALL: Everyone wants to know about the title.
FLATOW: The title, yeah.
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FLATOW: Well, our number, 1-800-989-8255. Maybe she went to a concert (unintelligible). 1-800-989-8255. You could tweet us at @scifri, @-S-C-I-F-R-I. Or go to our website at sciencefriday.com/scifri or on our website and leave us a note there. Don't go away. We'll be right back with Dr. Lisa Randall on talking about her book "Knocking On Heaven's Door" after this break. Stay with us.
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FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.
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FLATOW: You're listening to SCIENCE FRIDAY. I'm Ira Flatow. We're talking this hour about physics, cosmology, particles, all kinds of great cool physical things with Lisa Randall, author of "Knocking On Heaven's Door." She's also a professor of theoretical physics at Harvard University in Cambridge. Our number, 1-800-989-8255. And because she's been asked the question so many times, why did she name her book "Knocking On Heaven's Door," I'm not going to ask that question. No, of course, I'm going to ask that question to you.
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RANDALL: Well, I'll explain anyway. So what I really wanted was to somehow convey how science advances. We have this core of knowledge, this body of knowledge that's pretty well-established. We have this very clean picture of science, you know, these well-established rules with which we make predictions. But when you're really doing science, when you're doing research, you're at the edge of what we know. And so what I wanted to convey was something that sort of said how do we get beyond, how do we get to the sort of things that are tantalizing us but just beyond in the edges both technologically and theoretically of what we know today.
So - and as anyone who read my first book knows, I have song lyrics that go around my head, which I can't help sometimes when I think about something. So these are the ones that came to my head. So - but I thought it conveyed the idea very nicely...
FLATOW: If you...
RANDALL: ...if you interpret it the right way.
FLATOW: Yeah. Do you think scientists have a responsibility to speak out when science is trashed?
RANDALL: Well, I think no one - I mean, every individual can make their own choice. I mean, we certainly want people who are just doing science if that's what they want to do and if that's what they're good at. But I do think there is an overall sense that it is important. I would say it's important for scientists to speak out when they can and when they can be listened to. I think that it's not just when science is being trashed. I mean, I think the more general point that I'm trying to make in my book is that the kind of thinking that scientists do has even broader applicability just in ways of thinking about problems and asking questions.
They can just be very useful. And, of course, there's all sorts of other considerations that come in, political and otherwise. And it will only be listened to a little bit in many cases. But I do think it's important that some people are out there just saying what they know.
FLATOW: Yeah. You actually get into a bit of Wall Street there, talking about how that might benefit from doing things more with critical thinking in mind, science (unintelligible).
RANDALL: Well, I'm sure some people think I overstepped, but really, when I was writing this book, you know, this crisis was unfolding. And, you know, there was this kind of irony of people worrying about black holes that they'd all like to see. When, you know, we're pretty well-established. I mean, it's perfectly fine to ask the question. But we've pretty well-established there's no problem there. But, meanwhile, all these other risks that are surrounding us, and I really was trying to think how could it be that these are being missed when, you know, there seemed to be some pretty obvious indicators.
And so one of the things that science teaches you is how to ask questions and how to categorize by different scales. So one of the issues that comes up is just when you're asked about risks, for example, it matters the scale of who you're asking about risks for and on what timescale are you asking about it.
FLATOW: 1-800-989-8255 is our number. What is the state of theoretical physics today? Give us a brief thumbnails sketch of what we're - what are the big questions that we're still wondering about?
RANDALL: Well, there are sort of two different categories of questions. There are questions that we think we have a real chance of answering immediately, you know, in the next few years with experiments. And there's some sort of deeper questions that might take a long time to unfold, that are more purely theoretical. The state of particle physics is that we have something called the standard model of particle physics, which really does describe matter's most basic elements and interactions.
It works really well. It's been very well tested. And - but there are some clues that it is not the whole story. One is that we actually don't know this question I mentioned earlier, how particles acquire their mass. And although that sounds odd, you think of mass as an intrinsic property. It turns out that if you - particles just had mass from the get-go, you would make nonsensical predictions, like interactions, probabilities greater than one. So we know there has to be something around that accounts for it.
And that's probably this Higgs mechanism. So one of the questions is what is it that provides this Higgs? What is it that accounts for particles' mass? But there's a second question that comes with that, which is why do particles have the mass they do? It seems like if you actually just made a prediction for what they should be based on the theoretical principles we know using quantum mechanics and special relativity, you would think they should be enormously bigger than they are, 16 orders of magnitude bigger.
So it's only by - if you don't have anything else in the theory, it's only by a - what we call fine-tuning that you can account for masses. Now, we don't believe that. But then when you actually go down that rabbit hole and try to solve that problem, you find really amazing things that could be the - account for it. It could be an extension of symmetries of space, time, extensions of, say, rotational symmetry, which says physics looks the same in every direction.
It could even be an extension of space itself, another dimension. So it seems that the answers to that could really lead to deep insights on both into particle physics and maybe even to the nature of space.
FLATOW: And those are the questions you don't think we'll answer in the near future?
RANDALL: Those are the questions that I do think - I mean that's what's so exciting about the Large Hadron Collider. I'm sorry if I didn't make that clear. What's so exciting is that it really does have the energy which we think those questions should be answered. Another thing we should be able to answer, hopefully, is the nature of dark matter. That depends on if it interacts in certain ways. But there are indications that dark matter could even be produced at the Large Hadron Collider or in dark matter experiments today.
The kinds of questions that are more theoretical have to do with distances that are even smaller. The LHC, the Large Hadron Collider, is studying 10 to the minus 19th meters. It's questions that have to do with many orders of magnitude smaller than that, 10 to the minus 33 centimeters, where you start getting into questions about quantum gravity and the nature of gravity itself.
FLATOW: And how do you answer critics who say, why should we spend our money building these things? They're even talking about building the next collider, right, that might go out - go back to Batavia, a linear collider - and could cost billions and billions of dollars?
RANDALL: Well, you know, these are difficult questions to answer, and it is difficult to evaluate. But if you do look at places where we have invested in science, we've always come out ahead. We've come out ahead, not only through reasons that we could predict. And it could be even very theoretical research. I mean, what's so amazing to me is even quantum mechanics, which seems like the most theoretical type of idea we've had, actually, entered into semiconductor industry, which is responsible for the electronics that we have now, I mean, when people found electricity.
So it's very, very hard to say this is what will come out of it. What you know you do get is, first of all, information about the universe and the world we live in. You get an educated populace. You get interested. You get technology. So it just seems, overall, the benefit is great. And when you think about the savings, you have - I mean, although billions of dollars sounds like a lot, I mean, it isn't really that big a fraction of a budget. And that's not to say we should take it lightly. We should choose our projects wisely. But I think of it as an investment in the future. And it is not clear. It's not a clear investment, but that's why it's so important. It's a long-term investment in sort of education, but also science and knowledge.
FLATOW: Hmm. Let's go to the phones. To Jeff(ph) in Jacksonville, Florida. Hi, Jeff, welcome to SCIENCE FRIDAY.
JEFF: Thank you very much.
FLATOW: Hi there.
JEFF: Pleasure to talk to you. I got two questions, actually, one I started more than the initial one. One, how does it did you know, can you describe how they actually measured the neutrinos? What was the detection method that they used? And second question, about five or 10 years ago, I was reading an article on the quantization of space. And I - has anything been done with that? Just the actual - that space itself has a quantized size to it? And I'll take my answer off the air.
FLATOW: OK. Thanks for calling.
RANDALL: So let me talk about the first - the second question first. The quantization of space - so that's sort of the end of the story of scale. I mean, I talk a lot about scale in physics in my book, in part because I think it's very important to categorize sort of where we are and to get some intuition for these different things, but also to realize how we've advanced in scale. So this limit - there's probably a limit to distance scale, and I say probably because we actually don't know, even in principle, how we would study distances smaller than what's called the Planck's length, this 10 to minus 35 meters that I mentioned a moment ago.
And part of the reason is if you had enough energy to probe it, you would actually be making a black hole. And then you add more energy, it gets bigger. So it really does seem that space might break down, the notion of space that we have, might break down. We don't know that for sure, but there's theoretical arguments that say that. But again, this is well beyond what we can do for (unintelligible)...
FLATOW: What do you mean the notion of space might break down? It's hard for us to wrap our mind around that idea.
RANDALL: That's right. And it's happening at a scale so distant that it really doesn't matter to us. I mean, 10 to the minus 35 meters, it's not a scale that we encounter, and it's a scale that we're readily averaging over all the time, which is really how physics proceeds. So you don't need to know the most fundamental. You don't need to know if space is ultimately quantized. It works pretty fine to say the smooth space and general relativity applies to it. But it could be that at very distant scales, scales that are not affecting our daily lives, scales that aren't even affecting experiments at the highest energies we could do, there could be more radical and remarkable things that happen.
FLATOW: So space would not be smooth. It would be a little quanta of particles of space?
RANDALL: Space is almost certainly not smooth at those scales. You just work out what quantum mechanical fluctuations would be. It's very unlikely that space is smooth the way we are familiar with it at those scales. But, you know, that's the kind of thing that we see a more immediate example, where we see classical physics going over to quantum physics. I mean, the laws of physics that apply in an atom look very different than Newton's laws, but that doesn't mean Newton's laws break down, and it doesn't mean we have trouble predicting where a ball will land when we use Newton's laws.
Even though there is this more fundamental structure, it doesn't matter the level at which you can make measurements when you're doing, where you're saying where a ball lands. And in that same way, it could be even something like space might break down. But it's, again, instead of very distant scale where it doesn't matter to kinds of things we're doing today.
FLATOW: Call the space tow truck once it breaks down.
RANDALL: Although, of course, it's a really important theoretical question.
FLATOW: 1-800-989-8255 is our number. What about - you mentioned dark matter. What about even spookier dark energy? Do we have any idea what that might...
RANDALL: Dark energy sounds like a spooky name.
FLATOW: Start bringing the "Twilight Zone" music when I say that, but...
RANDALL: Dark energy is mysterious. The dark matter - let me just put it context. I mean, first of all, people know I think at this point that the matter we see, the matter we experience is only about 4 percent of the energy in the universe. So another basically 25 percent is dark matter, and another some - around 70 percent is what's called dark energy. Now, dark matter isn't that hard, I think, to wrap your head around. I mean, people get very disturbed by this first, but really it's just matter that doesn't interact with light. It's matter. It clumps. It interacts gravitationally. It's stuff.
And so, you know, it's not so presumptuous to - it would be a little presumptuous to think everything in the universe was just like us and interacted just like the stuff we're made of. So it's not that crazy to think that there could be other forms of matter out there. What is actually really interesting, and one the things I'm researching these days, is the fact that the amount of energy in dark matter is actually so close to the amount of energy in matter. In principle, they could have been very, very different.
FLATOW: And dark energy (unintelligible)...
RANDALL: So the (unintelligible). But then, dark energy - I'm getting there.
FLATOW: Well, I'm running out of time, so (unintelligible)...
RANDALL: So dark energy is not matter. It's just energy that's permeating the universe. It just fills up space. It doesn't clump. It just fills up space. And the real mystery about dark energy is, again, I mean, there's no reason it shouldn't be there. It's perfectly allowed. But why is it so similar in size to the other energies we know about? What is it that sets it - and in that sense, we don't know where it came from.
FLATOW: And some people say there should be a lot more of it if it's going to be there, right?
RANDALL: That's right. And in fact, 120 orders of magnitude more, so that's the real mystery.
FLATOW: Wow. And there are a lot of great mysteries in Lisa Randall's new book "Knocking On Heaven's Door," little song going around in our head when she wrote the book.
RANDALL: It's very cheering.
FLATOW: It is.
RANDALL: It's not a cheering song, but it is very cheering, the lyrics there.
FLATOW: And it's got - it covers the whole waterfront, if I might call, the universe: "How Physics and Scientific Thinking Illuminate the Universe and the Modern World." Lisa, thank you for taking time to be with us today. And good luck, as always.
RANDALL: Thank you very much.
FLATOW: Lisa Randall, author of "Knocking On Heaven's Door" and a professor of theoretical physics at Harvard University in Cambridge. I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.
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