Krista Tippett, host: Theoretical physicist Lisa Randall started out seeking answers to questions in Standard Model physics and ventured into pondering extra-dimensional worlds. Now she’s moved into illuminating what she calls “the astounding interconnectedness” between fields which have previously operated more autonomously — astronomy, biology, paleontology. She’s pursuing a theory that dark matter might have created the cosmic event that led to the extinction of the dinosaurs and hence, humanity’s rise as a species. We explore what she’s discovering, as well as the human questions and takeaways her work throws into relief.

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Lisa Randall: It’s OK to be aware of our limitations as human beings, that these are things that make it harder. It doesn’t make it impossible. And that’s the beauty of science, is that we can go beyond these prejudices, if you like, these intuitions that we have built on our ordinary, everyday experience that allows us to think about things that seem obviously wrong. They’re not obviously wrong, they’re just not obvious to us.

[music: “Seven League Boots” by Zoe Keating]

Ms. Tippett: I’m Krista Tippett, and this is On Being.

[music: “Seven League Boots” by Zoe Keating]

Ms. Tippett: Lisa Randall is the author of bestselling books for non-scientists, and she is the Frank B. Baird, Jr. Professor of Science at Harvard University. I spoke with her in 2015.

Ms. Tippett: It was interesting for me to read that you grew up in Queens and that you’ve said that as a young girl, you were more entranced with books like Alice in Wonderland than the scientific books you came across.

Ms. Randall: I actually don’t think I came across that many scientific books as a kid. Basically, I went to the library and read what I could. I just enjoyed reading. I liked the sense of adventure and play. But yeah, I can’t say that I’m really one of those people that said I really wanted to understand the stars. We didn’t actually see that many stars where I was. I think it was later on that I really came to appreciate nature more, really starting, probably, in graduate school, when I started hiking and exercising more.

Ms. Tippett: I have to say, looking at the website at Harvard — it’s The Center for the Fundamental Laws of Nature, the High Energy Theory Group. [laughs]

Ms. Randall: So I am totally not responsible for that name, which I find really arrogant and obnoxious. And I don’t think we’re responsible for the fundamental laws of nature. I think we’re responsible for the laws of nature that we can understand.

Ms. Tippett: Yeah — it is very lofty.

Ms. Randall: It’s not just lofty, it’s misleading. I think it’s misleading, because I think it gives this nature of science as ‘”We have this starting point, and then we derive everything.” But really, that’s not how it works. We try to find the starting point; we conjecture some theories. But we also try to work backwards, seeing what we observe and trying to see how those pieces fit together. So it’s really a push and pull. It’s not just one.

Ms. Tippett: That’s such an interesting way to state it. Here’s something you wrote: “Our world is rich — so rich that two of the most important questions particle physicists ask are: Why this richness? How is all the matter that I see related?” And I just wanted to ask you to explain what you’re describing there. What does “richness” mean in the context of what you do — in that sentence?

Ms. Randall: Well, I think part of what I’m referring to is simply the fact that we really don’t know how to explain why certain particles are essential to the world we live in. We know, for example, that nuclei have what we call up and down quarks inside them. But there are heavier versions. What role do they play? We know there are electrons, but there are heavier versions of the electron known as the muon and the tau. So there’s particles beyond what seem essential to nature or us or life, and we don’t really understand why they’re there. There doesn’t necessarily have to be a reason, but we’d like to see, is it somehow essential to getting us to this point in the world? So that’s part of what I’m referring to there.

Ms. Tippett: So richness is just that variety of particles and qualities that’s known and unknown.

Ms. Randall: I mean there is, of course, also the richness of how the pieces fit together, which is the wonderful stuff that we observe in the world. And we can see how that fits together and then how that came about and try to understand that with science, over time. So it’s kind of twofold. It’s sort of the richness at the fundamental level, but it’s also the richness of the complexity that derives from that, those simple ingredients.

Ms. Tippett: And it seems that the period in which you have been a scientist, these last few decades — when did you get your Ph.D.?

Ms. Randall: [laughs] I hate having to answer that, because it gives away my age. But I got my Ph.D. in ’87. But I will remind you that I took three years as my undergraduate and four years as a graduate student.

Ms. Tippett: [laughs] All right, all right. But what I’m getting at is just how it’s a short — let’s just call it a very short period of time. You’re young. It’s a handful of decades. But the scientific understanding of that richness that you were just describing, even in this period, has been so revolutionary.

Ms. Randall: It’s true, it’s been a very exciting time to be a physicist. I kind of joke that I’ve kind of lived in the optimal time. I mean I think some guys might say they would have liked to have been around earlier, but I think I’m at a very good time, because not only is science exciting, but it’s also a time that allows you to be a woman physicist a little more easily. So I feel like I live in the optimal time for me being a physicist.

But I think, also — in terms of physics, I think the last century has just seen amazing developments. I mean cosmology wasn’t truly a science until the last century, until Einstein developed his theory of general relativity, and observations improved to the point that we could actually see what’s going on and make predictions. Particle physics really only developed — nuclear physics — all the physics I worked on is a product of, basically, the last century.

Ms. Tippett: It just occurred to me — I’m kind of embarrassed to ask this question, because I feel like I should understand it. But I feel like the word — the language of cosmology and physics gets interchanged, at least in non-science circles. I mean how do you distinguish between those things?

Ms. Randall: So the other thing that gets confused is astronomy, so let me try to distinguish all of them. So physics I think of as the fundamental laws of nature. So for me, physics is elementary particle physics, but there’s all sorts of physics, which are sort of the rules by which things work. Cosmology is a specific science. It has to do with how the universe itself evolved. It has to do with the Big Bang theory, the theory of cosmological inflation, all of which I talk about in my latest book. But it has to do with just how things evolved to where they are today. Astronomy is more, in a sense, looking at stars and looking at the actual objects, how they develop, putting together. So what I like to think is, physicists are looking for sort of fundamental ingredients, astronomers are putting them together in a particular way to describe what we see today, and cosmology tells you how we got to this point. And of course, they all intertwine. They’re not completely disconnected. But someone will usually identify as an astronomer or a cosmologist or a physicist.

Ms. Tippett: That’s really helpful. Thank you.

Ms. Randall: Good that you asked.

Ms. Tippett: Well, I just suddenly realized that…

Ms. Randall: I always get mislabeled, actually, so it’s pretty funny.

Ms. Tippett: Yeah, so — well, let’s just leap in. Let’s just go to dark matter. And this book you’ve written this year also has this wonderful title: Dark Matter and the Dinosaurs.

Ms. Randall: Thank you.

Ms. Tippett: And let’s do some definition of terms, up front. I mean dark matter is, we now believe, perhaps 85 percent of the matter in the universe. Just start there. How would you talk about…

Ms. Randall: So people get very disturbed about the idea of dark matter. They say, “How could there be all this matter that we don’t see?” But there’s a lot of stuff that we don’t see. If the history of physics has taught us anything, it’s — or biology or any other field of science — it’s how much we don’t see. And dark matter, I would have — if it was up to me, I probably would have called it transparent matter. It’s matter that doesn’t interact with light. Dark stuff, as you know, absorbs light, so you see it. But dark matter, it’s matter. It interacts with gravity like the matter we know. It clumps. It’s around here, in our galaxy. But it doesn’t interact with light, so we literally don’t see it. We see its gravitational effects, but we haven’t seen other effects. We know it’s there because of the many gravitational influences of large amounts of dark matter, but an individual dark matter particle has so far eluded detection.

Ms. Tippett: I mean let’s clarify what ordinary matter — when we usually say “matter” — non-dark matter is…

Ms. Randall: So it’s the stuff that’s all around us. It’s all matter. It’s all part of what we’re made of. It’s part of Earth. It’s people. It’s the galaxy. But there’s also dark matter surrounding us, it’s just a lot less dense in our vicinity. Nonetheless, there’s billions of dark matter particles going through us all the time.

Ms. Tippett: Right now, even.

Ms. Randall: Yep, right now. But we don’t see them, and they don’t interact with us. We don’t feel them. We don’t smell them. They don’t interact with our senses. People are trying to devise very clever ways to look for very subtle, small effects, but so far as we know, the dark matter is not interacting with us a whole lot. It’s interacting via gravity, but gravity is actually a very weak force, at a fundamental level. That’s why you need large amounts of dark matter to observe its effects.

Ms. Tippett: And you say that while dark matter is mysterious to us, it’s not necessarily such a mysterious thing. I think what you’re saying, it’s not necessarily such a mysterious thing that it exists.

Ms. Randall: Well, I don’t think so. I think it’s rather egocentric to think all matter should be just like the matter that we’re made up of and that looks just like our matter. I find it in some sense remarkable that the matter we know about is as significant a fraction as it seems to be. About five percent of the energy in the universe is ordinary matter, whereas 25 percent is dark matter. I find that remarkable. I mean why isn’t it a tiny, tiny fraction? And the fact that we don’t see it — I mean why should everything interact with light? The fact that we interact with light — it’s the kind of mistake people make all the time. We think we overcame that with the Copernican revolution, we have a more open perspective. But we still have to get it knocked into our heads every time, that things are not just the way we see them in our daily lives.

[music: “Movement III: Linear Tableau With Intersecting Surprise” by Sufjan Stevens]

Ms. Tippett: I’m Krista Tippett, and this is On Being. Today, with theoretical physicist Lisa Randall. Her latest book is Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe.

[music: “Movement III: Linear Tableau With Intersecting Surprise” by Sufjan Stevens]

Ms. Tippett: You have spun this speculative scenario, which is based on real science, in which dark matter might ultimately have been responsible for the extinction of the dinosaur, 66 million years ago. [laughs] Describe that scenario and how you came to it.

Ms. Randall: So it’s actually really fun for me, because I mean it’s one of the reasons I decided to write a book, because I do work on very fundamental, very abstract science, the Higgs boson or an extra dimension of space or fundamental particles. But there was this fun thing, that dark matter actually does contribute to the structure of the galaxy, ultimately is responsible for the fact that things get dense enough that we can form stars in our world. So I liked taking those connections.

But in the science itself, we came at this somewhat indirectly. And I should mention my collaborators, Matthew Reece, Jiji Fan, and Andrey Katz. We were actually trying to explain how you could get a signal that matched some data. We knew the data actually might be spurious; I will confess that right from the beginning. But they saw a lot of photons at the same energy, and there was no standard dark matter explanation that seemed to do this well, that explained why you’d have photons and not other things, including the charged particles. So we were trying hard to say, how can we make a model, a conjecture for what dark matter could be, that could explain the signal? And then we turned it around, and we said, maybe it’s just that dark matter is a lot denser than we thought it is.

Now, we have a lot of evidence that dark matter is spread out in a diffuse spherical halo in the galaxy — but, we said, maybe some of that dark matter is like ordinary matter. Ordinary matter is not spread out in a spherical halo. Ordinary matter sits in the Milky Way plane. So it’s much denser than it would otherwise be, and the reason is that ordinary matter can radiate. It can cool down. And because it can cool down, it’s in some sense making smaller excursions, so it gets concentrated in this sort of pancake-shaped region at the mid-plane of the galaxy. So we said, maybe dark matter — not all the dark matter, just a fraction of the dark matter — does the same thing: Maybe a fraction of the dark matter can radiate and also form a plane in the galaxy. And in fact, we realized this remarkable thing: that if dark matter particles are heavier than the proton — I realize this is getting somewhat technical — but it would be a thin disk in the Milky Way plane.

And that would be extremely exciting and interesting. First of all, it would have observational consequences. But second of all, what would happen is that — as the solar system orbits around the galaxy it bobs slightly, up and down, it weaves slightly, up and down, as it goes around in its mostly circular path. And so what we proposed is that every time it passes through this dense, dark matter, just the tidal force is strong enough that it could dislodge comets that are weakly bound. Now, comets are, in fact, very weakly bound in the distant Oort Cloud, which has been in the news lately, so maybe people have heard of it. But it’s 50,000 times further away than the Earth is from the sun. It’s very far away. And for that reason, the force of gravity is much smaller than it is for us here on Earth. And so that means that it’s weakly bound, and if you have a strong enough tidal force, it could dislodge a comet. So our proposal is that every 30 or 35 million years, there’s this extra tidal force that dislodges comets from the Oort Cloud and explains the periodicity of large comet hits. This is not completely established. The statistical evidence isn’t extremely strong, but there is some evidence that this happened. Large hits happen on a periodic basis of around that time. And since the one that killed the dinosaurs happened 66 million years ago, maybe it was one of these comets. It was an enormous, 10-to-15-kilometer object coming speeding down on the planet and caused the extinction. So we propose, this is what triggered it.

Ms. Tippett: So now are you working with this hypothesis and investigating it and trying to solidify it?

Ms. Randall: Well, it’s very hard. I mean the evidence for the periodicity comes from craters on the Earth. There’s a great thing — you can look at the Earth Impact Database and see all of the ones that have been found. There is now something called the Gaia satellite that’s measuring the position and velocities of a billion stars and that will essentially create a 3D map of the galaxy. We’ll learn more about the galactic plane. So if, in fact, there is this dense, dark disk, there should be evidence for it in this data, which will be really exciting.

Ms. Tippett: Wow.

Ms. Randall: In fact, it was an amazing thing, because when we proposed this, we weren’t astronomers. We didn’t even know about the Gaia satellite, and we were so excited to realize that the measurement we would have asked them to do is actually going to be happening. And it launched the fall that we had actually proposed the idea, so it was very nice timing.

Ms. Tippett: When do you expect that data to be there?

Ms. Randall: It should be coming in the next few years. It’s probably a five-year mission.

Ms. Tippett: That’s exciting.

Ms. Randall: Yeah, and one thing that I’m doing now with a student is actually analyzing similar, but not as accurate, data from the old Hipparcos satellite, which is similar in spirit, and trying to see what kind of constraints you get from that.

Ms. Tippett: I would like to talk — I’m sure we’ll come back to dark matter. I would also like to talk about the way you’ve worked with and thought about extra-dimensional worlds, which — one of the things you say is that, again, kind of clarifying for laymen, that imagining other dimensions is not probably like our favorite sci-fi dramas — which I love, where my lifetime is happening somewhere else, with other endings and other pathways. It’s that they would just be very different, different realities. Is that your understanding?

Ms. Randall: Well, I think that’s certainly what I imagine is — you could have — I mean the kind of things that I talked about in extra dimensions, where particles and forces we know about are stuck on an object called a brane, which is like a membrane-like surface in a higher-dimensional space — the particles and forces that are stuck here could be different than particles and forces that’s other places. And it’s not entirely different from what I’m saying about dark matter, just to tie together, because what I’m saying there is that there could be different forces. There could be a different kind of electromagnetism, could be a different type of charged particles. I mean the fact is that if there are other worlds, even if they’re in the same place, there could be other universes, in some sense, right here with different particles, different matter, different interactions, just like there can be different forces and particles in other places, along an extra dimension.

Ms. Tippett: I loved in your — what was the book that had “warped” in the title?

Ms. Randall: Warped Passages.

Ms. Tippett: Warped Passages, yeah. There’s a quote at the very front of the introduction from the Beatles song: “Got to be good looking, ’cause he’s so hard to see.” [laughs]

Ms. Randall: [laughs] Getting permission for all those quotes was a pain, and probably the Beatles one was probably the most painful, but I just love that quote. But I just love that quote.

Ms. Tippett: Yeah, it’s good.

Ms. Randall: I loved, actually, abusing all the song lyrics. It was really fun.

Ms. Tippett: [laughs] Yeah, you had others. One thing that you say that I experience again and again in my conversations, I think especially with physicists, is that physics is more creative and fun than people would possibly guess, on so many levels. I mean there’s actually a joy in it. There’s kind of a whimsy that you bring in with quotes like that that still make sense and, also, this speculative leap that you’re making in order to investigate in a kind of hard-scientific way.

Ms. Randall: Right. What I like to think of — the most interesting kind of creativity is constrained creativity, where you have some rules. I mean it’s not just true in science, it’s true when you’re making a movie. I have friends who make movies. There’s certain formulas that you have to stick to, at some level, but within that framework, can you make it interesting? Can you see how things fit together in more complex and surprising ways?

And that’s where the creativity comes in, trying to figure out — you have these elements, but how can they be connected? Is there some link that we’re missing? And then, once you have that, you have to be creative about figuring out, how will we know if this is true? What are the predictions that you would make that we wouldn’t be making otherwise? And how can we test them? So I definitely think there’s a lot of creativity. I mean there are certain kinds of physics where you’re just working things out, but there’s certain types of physicists who are thinking about new ideas a lot. And that’s what I like to do.

Ms. Tippett: I was just thinking about a neuropsychologist I interviewed who’s studying creativity and the brain and creativity as distinct from intelligence. And one of the things they measure, one of the measures of creativity is actually humor, because it is, in fact, about making unexpected connections.

Ms. Randall: I think that’s totally true. In fact, I have a movie reviewer friend who had actually talked about Robin Williams in this context and talked about the amazing connections he made. And that was part of his humor, was this incredible wordplay. And I do find that a lot of math-y people I know really enjoy wordplay a lot, too, because it’s also these bizarre connections that you might not have anticipated.

Ms. Tippett: Making those unexpected connections, and then I think about leaning into them with joy, leaning into them.

Ms. Randall: And I’m certainly guilty of that, too. [laughs]

Ms. Tippett: [laughs] I know. Actually, I think we’re going to get to that in a little while.

Dr. Randall: I get accused of making nerdy jokes a lot.

Ms. Tippett: You write that once or twice in your life, in the course of your life, when you’ve told someone what you do, that you’re a cosmologist — and they’ve had no idea what that is — they thought you meant cosmetologist. [laughs]

Ms. Randall: [laughs] That’s actually happened.

Ms. Tippett: But then you go on to make this wonderful — you investigated the fact that those words both actually come from the Greek word “cosmos,” and then you say, “Like a face, the universe has both beauty and an underlying order.”

Ms. Randall: Yeah, thank you. I actually was thrilled by that, that that is why these words are related. And it does have to do with the kind of order and beauty that they’re associated with, both of them.

Ms. Tippett: I wanted to just — I do sense that that search to find that order — just that sense of adventure, also, about finding that underlying order — is in all your work.

Ms. Randall: I know. Despite all evidence to the contrary, I insist that the world should make sense in some ways.

Ms. Tippett: [laughs] Yes, but you also say we shouldn’t be obsessed with the theory of everything.

Ms. Randall: Well, that goes back to what I said earlier about fundamental laws. I don’t think so. I mean I think we make advances. Making advances doesn’t mean that we have the fundamental answer. It doesn’t mean we have the ultimate answer. Even if we did have a fundamental theory, it doesn’t mean we would have everything worked out. It doesn’t mean we’d understand life, because we have the fundamental equations. You’d still have a long way to go to understand a lot of the science that follows from those equations.

So there’s two places where I think it’s a problem. One is, do we even have the fundamental equations? And second, once we have them, what are all the consequences? So I prefer to think of it in terms of sort of working backwards, step by step. As we understand more, as we study more, trying to make connections, we have a chance of really solidifying, seeing if they’re right. That doesn’t mean we can’t play around with fundamental theory, see what the consequences are. But I don’t think we want to do that to the exclusion of the kind of science that’s more traditional science.

[music: “Brace Brace” by Bonobo]

Ms. Tippett: You can listen again and share this conversation with Lisa Randall through our website, onbeing.org. I’m Krista Tippett. On Being continues in a moment.

[music: “Brace Brace” by Bonobo]

Ms. Tippett: I’m Krista Tippett, and this is On Being. Today, I’m with theoretical physicist and author Lisa Randall. We’re exploring her discoveries and, also, the human questions and takeaways she reveals in her writing on subjects from dark matter to dinosaurs to extra dimensions.

Ms. Tippett: As I was reading through your various work, I wrote down some ideas, quotes, that seem to kind of epitomize some of the interesting ways you think about science or that you make science somehow explicable.

Ms. Randall: Thank you. What a lovely thing to do. [laughs]

Ms. Tippett: [laughs] Well, and that you clarify in ways for non-scientists that I think are unusual. So here’s one: You talked about the research that led to the dark matter and dinosaurs book, that there were some inspiring lessons from that research. And you said the first inspiring lesson was that the earth has a love/hate relationship with its environment. So talk about that, what that means for you.

Ms. Randall: Well, I think one of the amazing things about the fact that we can have life on Earth are just the amazing — you can call them coincidences, but whatever — the amazing conspiracies that have to happen. I mean we want to be close enough to the sun to be warm and have energy. We don’t want to be so close that we’re just going to be zapped out by all these cosmic rays or whatever — not cosmic rays, but just radiation. We want to be protected from cosmic rays from the outer solar system; so the outer planets, maybe, help us. We need a carbon cycle here on Earth.

One of the amazing things is that the fact is that plate tectonics are contributing to the carbon cycle. And plate tectonics are driven by nuclear energy, in some sense. There’s nuclear decays inside the earth that’s heating it up, and the plates can rotate. I mean there’s just an astounding number of amazing connections that led to the fact that all these things can happen.

But like I said, we need to be protected from all the dangerous things. And not only rays, but there’s comets and asteroids that hit us. If we were being bombarded all the time, that would kill any life that was formed. So we also have to be protected from stuff that’s falling in. A lot of the environment would kill off life, but some of it is obviously essential. And so that’s what I’m referring to.

Ms. Tippett: You point out that there’s kind of a corollary to physics and cosmology being explicable to non-scientists, which is analogous to how we have trouble understanding biological evolution. And Darwin was aware of this, that it’s very hard to talk to people about things that happen in the course of geologic time, that our brains simply can’t go there. And you talk about how the scales of the cosmos and of physics are, on the one hand, so enormous or so unfathomably small, that they’re so removed from our experience that this is one reason it’s hard for us to — for people to take in a lot of what’s — of science.

Ms. Randall: I think that’s true. The distinction I would make is that it’s not unfathomably hard. It’s hard. So I think it’s OK to be aware of our limitations as human beings, that these are things that make it harder. It doesn’t make it impossible. And that’s the beauty of science, is that we can go beyond these prejudices, if you like, these intuitions that we have built on our ordinary, everyday experience, and understand what’s going on in regimes that we don’t usually deal with. And that’s the beauty of mathematics, that’s the beauty of science, is, it allows us to think about things that seem obviously wrong. They’re not obviously wrong, they’re just not obvious to us.

Ms. Tippett: That’s a wonderful way of thinking about the tools, the capacity that science and technology create for humanity.

Ms. Randall: Well, I really think so. And I think there’s just important lessons to be learned. I mean I think we very often think that just what’s obvious is correct and forget that what’s obvious has to do with our senses, has to do with how we perceive the world. And it’s not just a lesson for science; I’d say it’s also a lesson for social interactions too. We’re familiar with our social groups, and we forget that other people’s experiences are different. Or if we remember, we just find them unfathomably difficult to understand, as you would say. But they’re not unfathomably difficult, we just have to make a little bit more effort.

Ms. Tippett: You point out some things that — sometimes, when you speak, there are things we know, and there are things we don’t know, which are really fundamental. I think this gets at your point — that you’re saying that scientific progress is in part about working back. So you’ve said, “We talk about the Big Bang, but we don’t completely know what banged,” [laughs] which is an interesting phrase.

Ms. Randall: That’s right, and we don’t necessarily have to know. But that doesn’t mean we can’t study the Big Bang theory that tells us what happened after the bang happened, whatever that was — how the universe expands, how the universe cools, how structure forms within that universe. All those are questions we can answer, and we can even look for evidence in the formation of galaxies and stars.

Ms. Tippett: And I mean you even point out that it’s not just that we don’t understand dark matter. There’s so much we don’t understand about ordinary matter.

Ms. Randall: Yeah, that’s actually almost a joke. But at some level, we do understand it — we understand that it’s made up of elementary particles, we understand the forces through which it interacts. But what we don’t understand is why the matter has survived to today. We know that matter, what we say, “annihilates” with anti-matter: It turns into pure energy. If you have a quark, it gets together with what we call an anti-quark and can turn into energy. For us to have the universe we see today, there has to be more matter than anti-matter. And we don’t know, fundamentally, how that came about.

And that’s a really important question, and it’s a really fundamental question, because it means symmetries that you might have thought are obvious are violated. The fact is, plus-charge is not the same as a minus-charge. So, the question is, why is this true? What happened in the early universe? And there’s ideas for what happened. In fact, I’m working on some of them today. But it’s still a very important and interesting question.

Ms. Tippett: Is that question related to the question of what banged [laughs] at the Big Bang?

Ms. Randall: Probably not, but it might have to do with what happened after things banged, in the sense that we — in some sense, from a practical level, we can consider cosmological inflation as the effect of Big Bang, something that we’re pretty sure happened, where things expanded exponentially, quickly. And so the question is, what was the temperature at which that happened? What was the energy? And so it could be related to that question.

Ms. Tippett: So many people who work with mathematics across the years have talked to me about beauty, beauty as a kind of litmus test of whether something is true. And you say somewhere — you know, beauty and elegance. You say that for you, simplicity is a better guide than beauty. And I wonder if you’d just elaborate on that.

Ms. Randall: Yeah, well, I have a chapter in Knocking on Heaven’s Door called “Truth and Beauty and Other Fundamental Scientific Misconceptions.” I don’t think that beauty is as much of a guide as we think it is, because, as you know, we all think different things are beautiful. And also, even what an individual thinks is beautiful changes over time. There’s some ways in which Einstein’s theory looks really beautiful, but there’s other ways, if I told you what the equations look like and what the solutions look like, you’d think it was a bloody mess. So I mean you can frame things so that they seem more beautiful than they are or less beautiful than they are. For science to be meaningful, you want to have as few ingredients as possible to make as many predictions as possible with which you can test your ideas. So I think that’s more the sense — I think that’s what people are thinking of. And simplicity, by the way, isn’t always beauty. [laughs] Sometimes complex things are a little more interesting.

Ms. Tippett: But is beauty a factor for you? I mean I experience it to be kind of a motivating force for a lot of people in science.

Ms. Randall: I would say that there’s a sort of fundamental satisfaction that I find when I find connections, when things you thought were separate could be related. Is that a form of beauty? I mean — probably. I mean I could define it that way. [laughs] And there certainly is the sense in which I’ll be sitting in a seminar, and someone will say something that’s technically natural, and I’m like, “Yeah, but it’s ugly.” So clearly, I do care.

I mean look, writing books takes away a lot from my time to do science, but there is a sense in which I kind of do recognize that if I’m going to tell you about this, and you’re going to make faces, it’s probably not a beautiful theory and might not be the answer. When you have something beautiful — on the one hand, we all have different ideas, but on the other hand, there’s some things that we probably would agree on. And so one of the tests of whether something is beautiful is, can I tell it to you with a straight face?

[music: “Pearls” by Helios]

Ms. Tippett: I’m Krista Tippett, and this is On Being. Today, with theoretical physicist and author Lisa Randall.

[music: “Pearls” by Helios]

Ms. Tippett: You write in the Dark Matter and the Dinosaurs book about dark matter debates that you were part of, a conference. And this gets back to, I think, the fun for you in being a scientist. So there’s Occam’s razor, which is the idea that the simplest explanation is probably true, which scientists work with, which, as you say, is not always right, but often is a good guide. And then, so just — would you explain this? So in the course of this conversation — I think it’s a paragraph in your book — you’re talking about some discussions among you and some other scientists. There was Occam’s razor, and somebody proposed “Wilson’s scalpel,” and you proposed “Martha’s table,” as guidelines. And I just wonder if you would share that.

Ms. Randall: Well, I think when people use Occam’s razor, they don’t realize they’ve narrowed the playing field a lot of the time. They focus on a particular problem, and they say, can you solve this problem? And yes, you could probably have a simple theory that solves that one particular problem. But if you can’t fit it into a larger context, that’s probably not the right scientific theory. So I joke about Martha’s table: that you want a complete table setting, that you don’t just want…

Ms. Tippett: And you’re talking — you’re referring to Martha Stewart.

Ms. Randall: Yeah. [laughs] Even if it’s a very complex table, if it’s — it can still look orderly and nice, and you can have the tools to address all the different meals you’re going to be served. And the universe is a complex place with a lot of phenomena you want to explain. So you can’t just narrow down only on one particular problem. Of course, you could do that as a temporary thing. But at the end of the day, you’re trying to explain the larger set of phenomena. And it goes back to what you were saying earlier, that it’s — you don’t want to get so overly focused on one problem that you lose track of the fact that it’s part of this larger world.

Ms. Tippett: I think this also gets at something else you wrote that’s a simple sentence but strikes me as very important, that “We often fail to notice things that we are not expecting.”

Ms. Randall: Yeah, I think that it’s so hard to believe, but I mean — and I think going out in nature helps you see that a lot. Someone will notice some animal that just went by, and they’re like, “How did you not see it? It was right in front of you.” But you just weren’t looking. And I think that’s just true of so many things in our daily lives. I mean I have an apartment in Manhattan, and when you look up, you see all sorts of interesting architectural details that you don’t see when you’re at eye level. You sometimes just have to look around, or you miss things. And I think the world is full of surprises, and we’re surrounded by them. But we often miss them.

Ms. Tippett: And it’s fascinating to think about applying that, then, to this sphere in which you’re working — in particle physics and thinking about extra dimensions and dark matter. And you’re saying that the same holds true.

Ms. Randall: Well, I think it’s not just important for me, but I think it’s important for telling experimenters what to look for. They have very complex experiments. Unless they know to look for something, it’s very likely that they’ll miss it; it’ll get caught up in the background of all the buzz of all of the other stuff that we know is there but doesn’t tell us something new. So you want to really think about the specific things that you’re looking for to make sure you don’t miss them, and that’s one of my roles as a scientist and as a model builder.

Ms. Tippett: So I want to read — and this is kind of a longish passage from the Dark Matter and the Dinosaurs book, just because I think it’s wonderful. And then I’m going to ask you a question.

Ms. Randall: Thank you.

Ms. Tippett: And this research is kind of bringing together insights from astronomy and biology and paleontology, in addition to the things you always think about. And you said, “I was awe-struck and enchanted not only by our current knowledge of our environment — local, solar, galactic, and universal, but also by how much we ultimately hope to understand, from our random tiny perch here on Earth. I was also overwhelmed by the many connections among the pieces that ultimately allow us to exist. To be clear, mine is a deeply unreligious viewpoint. I don’t feel the need to assign a purpose or meaning. Yet I can’t help but feel the emotions we tend to call religious, as we come to understand the immensity of the universe, our past, and how it all fits together. It offers anyone some perspective when dealing with the foolishness of everyday life.”

And so I want to just kind of drill down into that a little bit and ask — that perspective that you have from the science you do, can you just talk a little bit about what form that takes, how being steeped in these ideas and discoveries and questions shapes the way you move through the world of ordinary matter [laughs] that we’ve also been talking about?

Ms. Randall: Well, it’s funny, because — I mean I’m a pretty observant person, but I can also have blinders sometimes and just focus on what I’m interested in, and I think it’s important to do that if you want to make progress in what you’re doing. It’s funny, when I was at MIT, one of the staff people who I hardly knew — I guess she maybe did entries — and she came over and said, “I noticed that you seem to be able to” — because there are obviously issues at any university — she was like, “I noticed you manage to be able to ignore all those things and just focus on what you’re doing.” And I was just really surprised. I was like, “Huh,” because I certainly didn’t feel like I was ignoring them; I was pretty aware of them.

But there is some sense in which you have to have some perspective and say what’s important; and for some people, those details are important, but I like to think that there’s fundamental truths that we might be learning that are in some sense more important. And those are worth drilling down and really focusing on. So sometimes I’ll laugh — I’ll think about, suppose there were creatures in other planets, and they read our newspaper, or they watched our TV? I mean what would they be thinking? I’m not saying they would always have negative conclusions, but it’s just fun to think of someone who’s outside all the details, outside of all of this. I mean will they really be as excited about the new iPhone as people seem to be?

Ms. Tippett: [laughs] Right, yeah.

Ms. Randall: Will they really notice a difference? “That looks pretty much the same to me.” [laughs] So that’s not to say that we don’t all get caught up in it, but I think it is sometimes important to think, what are the really big places where we’re making advances?

Ms. Tippett: You are really — you are a scientist’s scientist, in addition to being a translator for the rest of us. But I also really feel like your work is so interwoven with your being, and there’s a joyfulness, there’s such a lightness to it. It’s not all intellectual. I kept thinking of — do you know, Karen Armstrong, she’s a scholar of religions?

Ms. Randall: Yes.

Ms. Tippett: And she’s a former nun. I mean she was a nun.

Ms. Randall: I remind you of a nun. That’s interesting. [laughs]

Ms. Tippett: [laughs] No! Well, OK, here’s what [laughs] — no, here’s what it reminds me of. [laughs] I asked her once — because she had been a nun, but now she’s not a nun anymore; she left the cloister. She’s a scholar, and she’s a thinker. And she said that she thinks of her work now as her prayer, like her scholarship, her thinking, her study. And I don’t know, this may be a real stretch, but I just wondered if there’s anything in that that reminds you of you — not that you would use the word “prayer.”

Ms. Randall: It’s really funny, and I’m so the opposite of that, in the sense that I try not to take myself overly seriously. I mean of course, if you ask people around me, they probably would disagree. But I’m not thinking in those terms. I’m thinking about, like, what is the problem I’m trying to solve? Is there an answer? Is this a credible answer? I mean do I feel satisfaction in doing it?

I’m not trying to label it. I’m not trying to say — I’m not trying to say, “Am I building a cathedral?” I’m just saying, does it work? And the fact that it can add up to something more is fun. And one of the joys of writing a book is being able to take that step back and say, look, this is why it’s interesting. This is why it’s important. This really is saying something about our world.

But in my day-to-day existence, that’s not how I’m thinking about it.

Ms. Tippett: I guess I’m not really thinking about how you think about it, but how it feels, how you carry it. I don’t know. Does that make sense?

Ms. Randall: Like I said, I think there’s some sort of satisfaction in making connections, solving a problem. I mean you finish a crossword puzzle — OK, it’s not like you’ve advanced the world, but there’s a satisfaction in that. There’s a satisfaction in winning a game of chess. We all feel this satisfaction, winning games or solving problems. And it’s somewhat like that. But it’s something that I think has more meaning, something that you obviously are going to be working on for a longer time. You have deeper, more developed connections among all the different ideas. And there is a sense of play in it, in addition to all the seriousness about it, because some of the ideas will be true, and some won’t be true, but it’s fun to figure out how are we going to know what they are? What are the possibilities? Which are the ones that work? Which are the ones that don’t work? And maybe, deep down, I’m taking it as seriously as everyone, but I think as soon as I start saying that to myself, I think I would be afraid. And I think it’s just much better for me to think of it as sort of a little bit of a game.

Ms. Tippett: Yeah, it’s pretty amazing to think about just this one thing we’ve talked about that you’re working on now, the nature of dark matter, and if you do indeed — are indeed able to make a connection between a new understanding of dark matter and this extinction event that has shaped life on the planet…

Dr. Randall: And also, to be clear, it’s not just one thing I’m working on. I mean there’s different possibilities for what dark matter can be. And I’m working on different ones that aren’t even necessarily all consistent. I want to know what the answers are. So it’s fun to think about what the possibilities can be.

Ms. Tippett: There’s something I wrote down somewhere you wrote. Oh, here — I like this: “When it comes to the world around us, is there any choice but to explore?”

Ms. Randall: Thank you. Exactly.

Ms. Tippett: That’s kind of a good mission statement.

Ms. Randall: Yeah, there we go. Thank you. I wish I could — can I get this list of quotes? It’s fantastic. I’m like, “Wow, I said that. That’s great.” [laughs]

Ms. Tippett: I can send you my notes, if you want. [laughs]

Ms. Randall: Awesome.

Ms. Tippett: It was a lot of fun.

Ms. Randall: That would be fantastic. Those would be great talking points. Thank you. [laughs]

Ms. Tippett: Well, and so just my final question. So let me just say this — weren’t you in Brian Greene’s same high school class?

Ms. Randall: No, Brian Greene was in my class.

Ms. Tippett: Oh, sorry. He was in your class. Yeah, got it.

Ms. Randall: No, it’s the same thing. I’m just joking. [laughs]

Ms. Tippett: Yeah, I know, I know. [laughs] So I had a conversation — a public conversation with him once, and I think he was being provocative and playful, but really kind of resisting the reality of all these things that are our intuition that, in fact, are proven to not be true, by science. I feel like you — you’re very clear in saying there’s what science and its objectivity and its complexity can see, and then there’s the reality of how we as human beings are and how we interact with the universe. And these things are just — they’re just different.

Ms. Randall: I would say it slightly differently. I would come back to the notion of an effective theory. Here’s a simple example — or not simple, but just one example: Are Newton’s Laws correct? Well, we know Newton’s Laws are not fundamental. We know that quantum mechanics is more fundamental. We know that relativity is a more fundamental theory. But Newton’s Laws happen to work incredibly well over a large range of parameters. And that is to say, we can send a man to the moon, based on Newton’s Laws. So for that purpose, they are correct.

That doesn’t mean that it’s the ultimate reality, if you want to say it that way. And I think that’s kind of very helpful in thinking about a lot of philosophical questions, a lot of scientific questions. The notion of effective theory — it really adds depth and meaning and helps us understand these questions, because it’s saying: Within this realm that we’ve explored so far, what are the rules that work? And when we go beyond that, what are the rules that work? So that’s more how I’m thinking about it.

Ms. Tippett: And would you say that at present, there are lots of things about biological life — about our brains, for example, and about the ecosystem that is a human being — that we can’t explain or can’t address? And are you just — you’re OK with that?

Ms. Randall: Of course I’m not. I’m a scientist. I want to understand everything. But what I would say is that — so I just want to make the distinction: So there are some things that we — like we have optical illusions. And they are illusions. We can see they’re illusions. So yes, our senses sometimes deceive us. That’s one thing that happens. Another time, we just don’t have access. So for example, dark matter, we don’t see in our daily lives. Does that mean that we’re crazy to think that we only have real matter? Well, to all intents and purposes, in many ways, we’re only interacting with ordinary matter, so we can forget the dark matter for a lot of the things we do — not for the things I do, but for the things you’re doing.

But I do think the beauty of science is that it can tell us the distinction. It can tell us, when are we really making a mistake when we think our intuition is right? So when does it matter? And again, I would argue that this goes beyond the scientific realm. Things that are obvious are not always obvious. Sometimes they’re just familiar. And sometimes it helps to have objective ways of codifying whether or not those things are true at a more fundamental level.

Ms. Tippett: So what would an example be, just a really standard example?

Ms. Randall: Well, I mean a stupid example is, “All the scientists are men.” There was a time when all the scientists were men, but that’s no longer true.

Ms. Tippett: Right. Right.

Ms. Randall: So it’s just — it has to do with a whole bunch of circumstances, societal circumstances that created that. But if you were observing what it was like 200 years ago, you might have come to that conclusion and thought, “Well, it’s obvious.” [laughs] So it’s not obvious.

Ms. Tippett: Yeah, yeah. So the question I actually wanted to ask you out of this is this question of what it means to be human, how you would start reflecting on that — and the sense of how that’s evolved, as your scientific work and perspective has evolved.

I know, it’s huge.

Ms. Randall: [laughs] Yeah, that’s kind of a huge question. I was like, Oh, just one little question to end.

Ms. Tippett: No, you don’t have to give a comprehensive — just how would you start thinking about that? [laughs]

Ms. Randall: I guess I would think about how I interact with the world, what that is at a fundamental level, what my senses can perceive, and then, how I interpret that information, how I try to form a bigger story. I think the influence of time is really important — how that story changes over time. I think that’s one of the really interesting questions. How does the you today connect to the you that you were when you were younger? I think that’s a really important question. When did you become you, in the sense of, when did your thoughts and memories develop to a point where they’re distinct? So I guess I would try to break it down to smaller questions so that I can compare, say, one time to another time, maybe the way I see something to another human being.

I mean there’s so many fundamental things we don’t know. I mean when I see something blue, am I seeing the same thing that you’re seeing? There’s just so many questions about what it means to be human that I sort of don’t know where to begin, but on the other hand, I would begin at any one of these places, and they probably all could give you some answers.

Ms. Tippett: Yeah. The idea of time — I feel like this is one of the most interesting, profound places where science just — and physicists, in particular — just see the world differently than the ordinary experience that most of us have.

Ms. Randall: Oh, I would just say nobody understands time.

Ms. Tippett: That nobody understands time?

Ms. Randall: Yeah.

Ms. Tippett: I remember talking to Paul Davies a long time ago about Einstein, and he talked about the notion of block time, that essentially, somehow, everything is actually happening at the same time, but we can’t perceive that.

Ms. Randall: Yeah — do you believe that? Doesn’t seem to be true. [laughs]

Ms. Tippett: I don’t know. I mean I think about it sometimes. I try to imagine.

Ms. Randall: It’s awfully deterministic. I don’t know. It seems like to me that there’s a little bit more randomness in the world.

Ms. Tippett: Yeah, so I mean how do you think about — I mean I love those questions you just framed about the me that was then and the me that is now and what time makes possible. I mean how do you think about time as an element of human becoming? Or does that even make sense?

Ms. Randall: Well, I mean there’s sort of a practical element of just how things change over time. I think it’s interesting, as people study aging. I mean this is sort of a depressing idea, but when I think about the question of the soul, it’s just interesting, because when you see someone who’s on the verge of death or has Alzheimer’s or is really sick, I mean is that the same person they were before? I mean so where’s the soul? Is that the person that’s going to survive? I mean it just seems like it shows you how difficult these concepts are to really define in any way, which is why I pretty much don’t believe in it. But I do think it forces you to think about what it means to be a human being and what it means to be about a particular human being.

But there’s time associated with people, and there’s times associated with abstract physical processes. I can talk about extra dimensions of space, but we don’t know how to talk about extra dimensions of time, really, and, certainly, ones that we overlap with. So time seems to be this thing by which we measure progression, but how that got defined in the first place, I think, is a very difficult question.

Ms. Tippett: Is mystery in your vocabulary — the language of mystery?

Ms. Randall: Oh sure. Sure. So is solving. [laughs]

Ms. Tippett: OK. [laughs]

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Ms. Tippett: Lisa Randall is the Frank B. Baird, Jr. Professor of Science at Harvard University. Her books include Warped Passages, Knocking on Heaven’s Door, and Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe.

[music: “Great Northern” by sleepmakeswaves]

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Staff: On Being is: Trent Gilliss, Chris Heagle, Lily Percy, Mariah Helgeson, Maia Tarrell, Marie Sambilay, Bethanie Mann, Selena Carlson, Malka Fenyvesi, and Erinn Farrell.

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