SPEAKER 1: You’re listening to Short Wave from NPR.
REGINA BARBER: Here’s your waiver. Is Regina Barber here. Those of you who have been listening to this show for a while might already know I’m a huge Trekkie. One of my all-time favorite episodes of Star Trek– Next Generation that I want to talk about is called “Darmok.”
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CAPTAIN JEAN-LUC PICARD: Captain’s log, stardate 45047.2. The Enterprise–
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BARBER: In the Star Trek universe, most everyone in space can talk to each other with this futuristic technology called the universal translator. But in this episode, that translator– it fails.
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CAPTAIN DATHON: Rai and Jiri at Lungha.
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CHANDA PRESCOD-WEINSTEIN: So Captain Picard of the USS Enterprise is stuck on a planet with an alien captain, Captain Dathon. And they are, technically speaking, what viewers would understand as English to each other. But the grammar and the sentences don’t quite make sense.
BARBER: That’s Chanda Prescod-Weinstein, another huge Trekkie and a theoretical physicist.
PRESCOD-WEINSTEIN: It turns out that this alien species communicates through the figurative, so they communicate through stories and metaphor rather than directly just stating facts.
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SPEAKER: [NON-ENGLISH SPEECH]
PICARD: When the walls fell.
SPEAKER: [NON-ENGLISH SPEECH]
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PRESCOD-WEINSTEIN: And the universal translator doesn’t know how to deal with translating the figurative.
BARBER: And we’re talking about this Star Trek episode, because to me and Chanda, a lot of theoretical physics and how we share physics uses the language of metaphor.
PRESCOD-WEINSTEIN: Every time I try and explain a concept to you, I need to use a metaphor, because I need to use something that’s familiar to you to invite you into something that’s not familiar to you.
BARBER: This is something Chanda has been thinking about a lot recently, because she just published a new book called The Edge of Space-Time. It starts with metaphors to explain challenging concepts, whether that’s as big as cosmic inflation or as small as quantum mechanics– the realm of subatomic particles, which are even tinier than atoms. So today on the show, we’re talking about quantum physics. How do classical mechanics connect to quantum mechanics? Why are scientists still searching for a grand unified theory of physics? And why does all this matter anyway? I’m Regina Barber, and you’re listening to Short Wave– a science podcast from NPR.
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BARBER: OK, Chanda, I feel like you and I were both very into the idea of quantum mechanics and– and quantum physics as kids. But then we– we go to university, and they’re like, you got to start with basic mechanics– this Newtonian mechanics. And you start the book with this idea that went something like, I’ve begrudgingly agreed that maybe we should start with this, like, macroscopic movement– this Newtonian physics that talks about motion and gravity and how we understand the world we see– before we learn about wild particle physics and general relativity. Why did you begrudgingly come to that realization and– and say, like, yes, we need to learn basic mechanics first?
PRESCOD-WEINSTEIN: I continue to be a fan of when you’re trying to teach someone something or help them understand something, that you should actually make the case to them for why you’re taking the approach that you’re taking. And so I do wish the thing that we said to students is, is it really exciting to think about balls rolling down inclines? Maybe not. But I think one of the things that we’re doing is frosh physics is actually your introduction to physics language. So if we think about this as– as translation work, there are certain concepts that are really important that are going to follow you for the rest of career as a physicist. Energy is maybe the most important concept in physics. And what matters about that course is learning how to think about energy and the role that energy plays in motion.
BARBER: And just learning the terms.
PRESCOD-WEINSTEIN: Learning the terms. I think there’s also an element of it, is we’re just trying to teach you how to put calculus into conversation with the physical world. And the– the math that you need to do it is simpler than what you need for quantum physics. It’s just the baby step way to get you speaking the language. And then once you start speaking the language, you can get more creative with it, and you can try harder things.
BARBER: Yeah, it makes me think of when we teach children how to write. We start with their name. We don’t start with, like, this is how you write an essay. Like, these are the five, like, paragraphs of an essay, right?
PRESCOD-WEINSTEIN: I can make that case for teaching going into the classroom. But also the book is supposed to be fun, and that doesn’t actually sound super exciting, right? I know if I don’t seem excited and if I’m not excited, my reader is not going to be excited. And so I did give myself this challenge of going back to what makes this a set of interesting questions, which is, first of all, where is motion happening? Can I see it? Can I touch it? Can I feel it? How do I think about that? And that turns out to be like a very deep question that actually we don’t spend a lot of time on in the classroom, because there is this imperative of making sure there’s certain material that they know.
BARBER: When students– and you and I– had to learn basic Newtonian physics first, and then we learned quantum mechanics and quantum physics, what did we have to unlearn?
PRESCOD-WEINSTEIN: Well, I think we had to go back to this Newtonian concept of a continuous space and continuous time and motion being continuous and energy being continuous, like this idea of there are no gaps. That–
BARBER: It’s a very calculus thing, you know.
PRESCOD-WEINSTEIN: It’s a very calculus thing. And actually, like, when we’re calculus, everything is about you can take the little pieces, and you can add it together, and then it becomes this smooth line, the smooth surface. There are no–
BARBER: –infinitesimals.
PRESCOD-WEINSTEIN: –infinitesimals. Right. And then you get to learning the fundamentals of quantum physics. And suddenly, you’re challenged with actually there are leaps. There’s no smoothness. There are bunches. These are all different figurative forms that we’re using to try and communicate this thing. And that doesn’t prepare you particularly well to go out and explain next door, what significance does this have? Why does this make your computer go? Because computers all run on quantum phenomena.
BARBER: Yeah, all bits.
PRESCOD-WEINSTEIN: All bits. And transistors– they’re fundamentally quantum materials objects. And our computers or phones have like a bajillion of them in them. That’s not a technical number, but I’m going with it because I’m a theoretical physicist, and we don’t do numbers.
BARBER: And we talk in metaphors in this episode. So [LAUGHS] so I think there’s this contradiction. There’s been this, like, hunt for a long time for this grand unifying theory that links everything together. Why don’t these two ways of thinking about the universe connect?
PRESCOD-WEINSTEIN: I think the simplest answer is that they are just coming at two very different questions. So quantum physics, at its base, is very concerned with how are particles behaving, how are atoms behaving? How much energy does it have? Where is it physically? Not necessarily always how is it going to be moving, although sometimes it’s part of the conversation. And when we get to Einstein’s theories of relativity, and particularly general relativity, which accounts for gravity, as well as the fact that the speed of light is finite and is constant in a vacuum, that is much more concerned with the– the structure of space and the fact that gravity is actually curvature in space time, and is kind of unlike the other forces in this respect. There is an argument to be made that gravity is not actually a force. It’s an effect of the structure of space-time.
BARBER: I mean, yeah, that is the better way to say it, but it’s like, it feels so wrong.
PRESCOD-WEINSTEIN: It feels wrong, and it’s not what we were taught. Gravity is the first force that we ever meet in a physics education, and it’s the one that we consciously live with in everyday life. So on a level, in terms of thinking about this question of what happens when you try and put quantum into conversation with gravity, these are two different frameworks that are trying to solve two different problems. And then you’re saying, well, what if I think about the problem together? So for example, I want to understand the structure of space-time at the microscopic, particle-like scale. And then you run into some serious mathematical difficulty because the question is, is space-time– does it have gaps? What– what would that mean? How do we write down the math for it? And there’s really a whole universe out there of– of ways that people are thinking about the quantum gravity problem. But I do think it can be helpful to understand that maybe framing them through the metaphor of a clash or a war is not the right way to do it, because they’re not fighting with each other. They really are just addressing different things.
BARBER: Then in that case, we can even take a step back. Why do physicists want this grand theory to exist? Like, what makes physicists believe something like this is possible?
PRESCOD-WEINSTEIN: I mean, certainly for me, I think there’s an element of the universe is out there, and I like understanding how things work. And so I’m curious about the answer to that question for the sake of being curious about the answer to that question. It is also the case that there are so many different ways that my life is shaped by the pursuit of trying to answer that question. And the things that I’ve learned along the way– an example that I talk about in the book is when you get introduced to quantum physics and quantum mechanics, you learn about things like light behaves like a wave and a particle at the same time. And the particle-like version of it is– we call this a photon. And I was still a baby physics student. I was like, wait a minute. Every time I turn a light on, I’m making photons, like, fly out of the light. And like, this light bulb is just, like, throwing off photons. There are some people who really like to go hiking, and I’m not– I’m not a hiker, but I can have that experience of awe with the natural by literally just turning on the light in my office. But it’s a way in which realizing that, like the– the wonder of the universe is actually with you all the time. And physics gives you some entry into that wonder, carrying that sense of awe into your everyday.
BARBER: Yeah. Something you talk about in book is this idea that, like, the practice of science isn’t about what we know. It’s about what we don’t know. Why do you think this is so important, to– to really spend this time figuring out what we don’t know?
PRESCOD-WEINSTEIN: The one thing with doing science and being curious about the world and how the world works is that you actually never know when the thing that you’re just trying to figure out is going to turn out to be massively important. A really good example of this is with Einstein’s theory of general relativity, which is talked about as this very esoteric thing– curved spacetime. Space-time is expanding– like all this stuff. I think most people in the United States anyway use some form of GPS– Google Maps. Maybe you’re one of the few who uses Apple Maps. I don’t know. Waze. These– these different things. And all of them are using the global positioning system. And the global positioning system depends on calculations that use general relativity. It will not give you correct information about your current location and trajectory without these calculations from Einstein’s relativity. Did Einstein sit down to be like, actually, I’m going to make it so that in the future, people have little computers in their pockets that will speak out loud to them and tell them where to turn left? No. But that is one of the products. So I do think there is this element that you don’t know what material benefit is around the corner from the work of basic science, but I also think that you don’t need it to have a material benefit for it to be important, because we are a curious storytelling species. And the story that I tell in The Edge of Space-Time is our cosmic history. This is how we came to be. This is the world that we exist in, the universe that we exist in. This is one of the most important stories that we will ever tell. And I think that’s good enough.
BARBER: Chanda, thank you so much for coming on the show, and thank you for thinking of us. Come back anytime.
PRESCOD-WEINSTEIN: Thank you for having me on.
BARBER: If you liked this episode of Short Wave, please share with a friend. We know, based on multiple studies, that word of mouth is one of the top ways people find new podcasts. So your recommendations really do help out our show. This episode was produced by Hannah Chan. It was edited by our showrunner, Rebecca Ramirez, and Tyler Jones checked the facts. Jimmy Keeley was the audio engineer. I’m Regina Barber. Thank you for listening to Short Wave– the science podcast from NPR.
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