Planet artsci Episode 11: How Lego Batman explains String Theory Transcript

Planet Artsci – Episode 11


Physicist AW Peet


PLANET ARTSCI: How lego batman can help us understand string theory on this episode of Planet Artsci.

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PA: Hello. Hi. Welcome to Planet Artsci, the official podcast of the Faculty of Arts & Science at the University of Toronto. Each episode we’ll chat with faculty members, students and alumni who are coming up with incredible ideas and innovations. My guest today is physicist Amanda Peet, who will teach me all about string theory and what it can tell us about those gravitational waves created by colliding black holes that were recently discovered. Now, the sum total of my understanding of string theory comes from watching the TV show The Big Bang Theory. So basically I know nothing about it, except that it sounds really cool and really complicated. Thankfully, Amanda takes me by the hand and leads me into a whole new way of looking at the building blocks of the universe. And it turns out that they look an awful lot like the Lego Movie. Ok, they don’t look anything like the Lego Movie, but I promise you that Lego does play a role. And if that’s not enough to grab your attention, our conversation also includes references to Monty Python and Yahoo Serious. Yep, Yahoo Serious. And if you don’t know who that is, you should google him. This is Planet Artsci. So stick around.

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PA: Big question. What is string theory?


AW Peet: So string theory is a part of modern theoretical physics and a lot of people would say it has its home in subatomic theoretical physics. People are tempting to understand the structure of subatomic particles and their interactions. String theory is actually a remarkably simple idea. It posits that the fundamental Legos or building blocks of the universe are not small infinitesimal tiny atomic particle but instead they’re one dimensional strands of energy. They’re different kinds of Lego blocks that are more versatile than particles and allow us to achieve a few more theoretical goals than particles. And a present string theory is a theory in the sense that there isn’t any direct experimental evidence for the idea. Another thing string theorist like to point out is that there have been millions of experiments don’t to date which haven’t ruled it out either, so…


PA: You can’t prove it exists but you can’t prove it doesn’t exist.


AWP: Well, yeah. But like any theoretical idea in physics, the idea itself can be very attractive but we judge it by its utility in solving physics problems. So string theory was actually invented back in the late 60s, around the same timeframe I was invented, and it was an attempt to understand the strong force that holds the nucleus together. And as such it turned out to be a failure as a theory of the strong interactions; we later on built a better theory called quantum chromodynamics. So string theory sort of lay in the waste basket of history for a while and part of the reason was that it had some features that made it highly unsuitable for a theory of the strong interactions. In particular it had one particle in the spectrum that has no mass and has a spin of two and this actually describes the particle that transmits the gravitational force. But it wasn’t realized when string theory was initially invented that it could actually describe a quantum theory of gravity and so that was a discovery that was then put together and really solidified in about 1984 when people figured out how to do string theory for real not just have some vague ideas an idea about how to do some of the physics that was when people figured out how to do the quantum theory of strings properly, so then it sort of became a subject that people could study and work with and try to use to describe the real world. So it had its origins humbly in particle physics and then tried to expand itself to be able to describe perhaps all of the forces and perhaps all of the particles in the universe under one rubric. You know string theorists are interested in peeling back the onion layers to fossick and understand that the very fundamental level what is the structure of matter and force. So matter is stuff and forces if the forces that they feel between each other between them. And so string theory is a cousin of particle theory and that’s the idea that we’ve all probably heard of in high school that the fundamental indivisible constituents of matter and force are point particles that’s what we were taught about electrons and the quarks inside protons and neutrons. Actually my high school teacher lied to use when they actually told us protons and neutrons were indivisible subatomic particles, turns out they’re not. They’ve got three little quarks inside them and some gluons that bind them together in this nucleus. But you know the story had been that those fundamental constituents the Legos of the universe were point-like. And string theorists are people who were rude enough to say I question that assumption. Are you just assuming it’s a particle because you haven’t got glasses to be able to see deep into the structure of things when you peel off those onion layers. And perhaps the reason why you think everything is made of subatomic particles is actually that it’s made of strings but if you could put on a really good pair of glasses you would see that underneath those fuzzy particles are actually very finely focused little strings. So that’s the advantage of string theory that it borrows many of the ideas of particle theory if you can’t resolve the structure of a string if you look at it with blurry glasses you’ll think it’s a particle. So all of the things that you previously that were true about particle physics they’re still true but string theory says well if you could put on very fine glasses kind of like a neurosurgeon does when he’s doing brain surgery or she’s doing brain surgery that if you could put on those super fine glasses then you be able to see underneath all those elections and quarks and gluons and gravitons and Higgs bosons and all those ones, inside them you would, according to string theory, see that there were little tiny vibrating one-dimensional strands of energy. And they’re not made of anything else they are the things out of which things are made, so strings of string theory are different than cat string. The string that your cat plays with is made out of molecules, which are made out of atoms and inside those atoms there are electrons and quarks and all the gluons and all those things. So that’s at the basic level when you peel away all the layers string theorists would say that’s what you’ve got left are the strings – those are the elementary constituents out of which everything else is thought to be made. So the beautiful utility of string theory, you have to accept more complicated ingredients to start with. Strings can vibrate, they can vibrate in different ways, a string can play different musical notes, much as the cords in my voice box can play different musical notes as I’m talking to you on the audio, so the notion is that as string although its more complicated its more versatile and in the sense of string theory, different vibrations of that same underlying string produce the different subatomic particles that we see in nature, so that’s one sense in which people talk about string theory of a symphony in nature in poetic terms. So we think that the one type of underlying string that it can vibrate in different patterns that are then identified as different subatomic particles with different mass and different spin and different charges, and that’s why string theory is so versatile and allows you to do all of the forces that are handleable in string theory under one rubric. Sort of like you only need one Lego set, you don’t have to have a different set of Legos to build gravity and yet a different set of Legos to build the nuclear forces, it’s that if you accept that your Lego are more complicated to start with, you can build anything that you can see for yourself in the universe and a lot of things that we don’t see besides. So then the embarrassment for string theorists is to describe why the universe turns out to be this way rather than something different that we might have been able to build. So that’s one of sort of the key problems a string theorist has to deal with is we could build many different universes for you than the one that we can see starting from our string theory ingredients, so the almighty puzzle if you will if why this universe rather than one of the others we might have been able to build for you. And that’s one of the gigantic problems that we still haven’t solved in subatomic physics. Why is it that our universe turned out to have four-dimensions in space and time, back and forth, up and down and side to side and the dimension of time is tick tick tick? Why were there four dimensions? Why weren’t there more or fewer? Why are there four forces and not 17 or eleventy billion? All those sorts of why questions are still on the table. They haven’t yet been solved. So string theory is probably not the final story of the constituents of nature, but it might be. There are hints within the structure of the theory itself that it indicates there may be no more onion layers to peel. Once you’ve peeled down to string theory, we think that’s probably it. So my investigations are about using those ideas of string theory to address gravitational questions and the questions I’m most interested in answering are the ones which are the analog of extreme sports like Canadian athletes who fling themselves off hills and do loop-the-loops on their bicycles or fling themselves off doing ski jumps and amazing configurations, string theorists are a bit like trying to do that kind of physics. We’re trying to do the most extreme sports that you can imagine gravitationally speaking, which is why we gravitate, ha-ha, towards black holes, which are the most extreme objects that can form when a star runs out of gas and literally collapses on itself gravitationally. And the other really totally extreme situation in the universe was the birth of the universe itself. So we need a theory of quantum gravity to be able to explain what happens in those regimes because we know that Einstein’s theory falls over on its face when it tries to describe big bangs or black holes, the centre of a black hole, so I don’t know what the eventual answer will be for the kinds of questions I’m interested in like what happens to the information that falls into a black hole? But I think string theory is a really good bit at present. It’s got a big enough tool box that is versatile enough to answer some of the really big questions that we’ve kind of been avoiding because we didn’t have the technical sophistication to answer them. We sort of said well maybe you can sweep those problems under the rug and just hope for the best. But then sometimes what you’ve swept under the rug maybe it’s a cigarette butt and maybe it starts a fire and the fire becomes an emergency and you have to put out that fire. And in some ways some of the problems we’ve been encountering when thinking about black hole information in the last small number of years have been that somethings on fire and we really need to fix it. And so there’s quite a lot of enthusiasm and energy in the field. And it’s not easy to become a gravitational string theorist with a job and a pension, but I think a student who really wants to be given a serious try should be given the support and the opportunities to give it a go and to see where they land in the grand scheme of things. So some fraction of my PhD students have gone on in the field and some have gone into other areas with their string theoretic PhDs and I think that’s a good thing to have people out in the world who have done very specialized research who then go and do other things as well as becoming academics. The more science and physics trained people in the general population the better as far as I’m concerned. If I can I’ll sneak a little bit of physics education into everybody before they leave the walls of U of T but you know we’re only one person, we can only do so much.


PA: Okay lets unpack this a little bit because all I know about string theory I learned on The Big Bang Theory, and I’m pretty sure they got most of it wrong. Smaller than the smallest particles that we know exist – protons, neutrons, electrons – string theory is this theory that there’s actually energy.


AWP: Yeah, so strings is just a different kind of building blacks than particles. When you were told in high school that if you peeled off the onion layers you would discover as you get further and further down that you would get down into molecules if you kept peeling off the layers you would find atoms and if you kept peeling off the layers you would find electrons going around a very hard dense little tiny subatomic and atomic nucleus and if you peeled off more layers and layers you would find quarks and gluon particles that bind them together inside things like protons and neutrons and the idea of string theory is to ask well what lies beneath that? Is there anything more to discover under those onion layers or is the particle physics that we see, for example in the large hadron collider, is that it? We actually haven’t discovered much of what the LHC has to teach us yet because it’s a relatively new machine by experimental particle physics standards. But the idea of string theorists is kind of a bit cheeky really. It says well who said that everything had to be about particles? We could instead propose that the fundamental Legos the building blocks of the universe are tiny one-dimensional objects rather than zero dimensional objects. Now of course complicating the issue by starting with more complicated Legos, well why would you other with that. That sounds like a lot of hassle for not very much benefit and that was how it was for several decades. Particle theories of subatomic physics were perfectly enough to be able to address many and all the questions that we were really interested in asking. But eventually when people started asking really hard questions about particles and their interactions including the gravitational force then the limitations of particle theory began to become a bit more clear. And so string theory stepped in and said well we have a set of more complicated Legos so you have to have more technical facility to start building with these kinds of Legos but the benefit is we can provide unification of gravity within the other forces all within the idea of string theory.


PA: Can you explain why the theory of gravity isn’t unified without bringing string theory in. What was missing?


AWP: What’s different about gravity? Well there’s one very big thing that’s different about the gravitational force as compared to the other three forces we know about in nature – the electromagnetic force, the weak nuclear force that is responsible for radioactivity and some of the fusion that goes on in the sun, and the strong nuclear force which holds the nuclear together. By the way did you ever wonder why the atomic nucleus doesn’t explode? You learned in high school about static electricity and how if you have charges that are the same then they want to repel each other like your hair if you suddenly take your hat off in winter all the pieces of hair want to repel each other and they stick up, but if you have positively charged particles inside an atomic nucleus, why wouldn’t it want it to just push apart? So why doesn’t the nucleus explode? And the answer is that there is another force that is stronger than static electricity that at the short ranges only inside the nucleus that strong force overwhelms the electric repulsion of the protons in the nucleus and pulls them together and binds them inside the atomic nucleus.


PA: So there’s a force that’s also within the nucleus. It’s not a pressure from outside that’s forcing them together.


AWP: No, it’s a force that only operates only on very short ranges associated with the atomic nucleus. It’s always operating at those tiny tiny scales but if we operate on much bigger scales it’s like we’ve got a pair of blurry glasses on and we can’t see what going on at those very tiny distance scales. So to get back at what string theorists were trying to drive at they said well is there a reason why gravity is not like the other forces?


PA: How is it different than the other forces? What’s…


AWP: Well there are similarities but there are differences. And the primary difference is in what particle, the messenger particle, transmits the force. To get across the idea of how a messenger particle could possibly transmit a force, let’s imagine you and I were standing on a freshly Zamboni-ed ice rink with super sharp skates on and there’s was just you and me and a heavy ball. I don’t know if you’ve ever had to do physical education class in school and you had to throw these….


PA: Medicine balls


AWP: Medicine balls we call them. So let’s imagine that I’m an electron and you’re an electron and the medicine ball is the messenger particle of the electric force. I throw the ball to you. What happens as I throw the ball to you? Which direction do I move?


PA: You’re going to move backwards away from me.


AWP: Because of recoil like when a gun fires a bullet of when a canon fires a cannonball. So okay let’s follow the photon, the messenger particle, what happens when you catch it? Which direction do you move?


PA: Well I’m going to go backwards in the same direction the ball was travelling.


AWP: Right for the same reason to do with momentum conservation. Okay so now what happens if you throw the ball back to me and we keep throwing the ball back between each other?


PA: Well, we’re going to keep moving further…


AWP: If you could see the ball what would it look like?


PA: We’re going to look like we’re moving further and further apart


AWP: Right so that’s the particle physics version of repulsion of forces. So that repulsion of electrons or the static electricity in your hair or the protons inside the nucleus, that electric repulsion is called, in a particle physicist’s language, by exchanging a messenger particle. Okay now I get to the punchline. The messenger particle for electromagnetism is massless and it has spin one. The messenger particle for the two nuclear forces they’re also spin one.


PA: What does spin one mean?


AWP: Spin is a thing that we use to characterize subatomic particles. There’s actually three ways that we characterize a subatomic particle we say what mass does it have, so that would tell you its weight if it was in a gravitational field. And we also ask it, how much electric charge do you have? Or other kinds of force charges, so are you positive or negative? And we also ask it what amount of intrinsic spin do you have? And you can think of it as a tiny version of a spinning top but it a little different than the spin you can produce by whirling a top around or on the top of your desk in that this spin is intrinsic. This is why I keep calling it a intrinsic spin ‘cause it’s a small amount of spin that the particle has that is associated with it being that particle. And you can’t dig it out of the particle or remove it or slow it down with our changing the identity of the particle so it’s sort of like you know a person might call themselves transgender, well this particle has called itself I’ve got a spin half or I have a spin two or I have no spin at all like the Higgs boson or if I spin one those are the messenger bosons of most of the forces. Three out of the four forces have a messenger boson with spin one. Gravity is the odd one out. It has a messenger particle with a spin two and that makes it qualitatively and quantitatively different as a force in terms of how subatomic physicists see it. So it’s got quite a lot of similarities with electromagnetism. Gravity it’s a long range force. It can operate over long distances the nuclear forces are short range that’s a way that they’re different from the gravity force, but electromagnetism is also a long range force and so there are some similarities between gravity and electromagnetism and there are differences. But the main difference, the one that really impedes your ability to understand it, is the fact that it’s a spin two messenger particle.


PA: And so where does string theory come in. You said you know we’ve got this other set of really complicated ideas around…


AWP: More complicatedly goes if you accept a more complicated Lego set you can build cooler things. So perhaps an analogy is the difference between the more technical Legos and the more simple types.


PA: So the Legos when I was kid compared with the Legos today where you’re building like entire star wars sets.

AWP: Well, maybe. Yeah. Yeah. Accept one aspect that’s not quite good with that metaphor is that Lego has got sort of more corporate and more specific. Rather than so now you can build a star wars set but could you build anything else out of the same pieces? The Lego sets when I was a kid was sort of like you can build anything in your imagination out of them as long as you had enough bricks. So that’s a better metaphor I suppose.


PA: So what does string theory helping us understand?


AWP: Well trying to understand how to put together this theory of gravity you may have heard that last week there was a huge announcement in the gravity community that there had been a discovery by LIGO of gravitational waves and I played the press conference during my graduate class that day because it was such a momentous announcement that I couldn’t possibly bear to be teaching them about some sort of aspect of subatomic physics while this wonderful press conference was happening. But yes the gravitational force is one of the things Einstein managed to come up with a pretty good explanation of. So I like to describe what string theory helps you to do as marrying tow things that seemed like they were separate and conflicting pillars of twentieth century physics if you like. So one of the great discoveries of the 1900s was Einstein’s discovery of his theory of relativity but specifically in very late 1915 and early 1916 the world was learning about his general theory of relativity. And this theory has withstood the test of time over a century and things that were being calculated almost 100 years ago finally saw experimental discovery just the announcement was just last week. So there’s this beautiful ways that Einstein’s theory of gravity has successfully described a lot of phenomenon in the universe – solar system tests, galactic tests, cosmological tests on all of the link scales that people can imagine testing out Einstein’s theory of gravity there hasn’t yet been an experiment that showed it to fall on its face and be unable to describe the real world. So we sort of had built a huge amount of confidence that Einstein’s theory of relativity, or GR for short, was a really great way of describing the physics of very big heavy things like planets and stars and galaxies and whole universes. But there was this problem that there was also an entirely different set and also very beautiful experiments and theoretical development from the 1900s called quantum mechanics that was invented in the 20s and 1930s people were starting to learn about it more broadly and its worrying about the physics of very small scale things which is what quantum mechanics does led to revolutions like semi-conductors and iPhones and the internet and other cool stuff like that. That’s a little bit of a stretch but the general idea is there. So quantum mechanics was one of the pillars of twentieth century physics with you know millions of experiments had shown how powerful quantum theory was this way of thinking about the microscopic world and on the other hand we had general relativity describing the physics of very big heavy things. The problem is that if you try to marry together or try to merge quantum mechanics and general relativity together there’s a big explosion. They can’t live under the same roof. They’re warring parties. They can’t possibly make a peace treaty between them.


PA: One makes sense of one thing one makes sense of the other, but together they don’t make sense at all.


AWP: That’s the problem that people are facing that if you assume that Einstein’s theory of gravity is true and you treat it like any other particle theory on interaction and subatomic physics, it blows up in your face and it gives you nonsensical results like if you ask Einstein’s theory of gravity, what’s the curvature of space time at the heart of a black hole? And it says, infinity. You ask Einstein gravity, what’s the probability for there to be a whole bunch of electrons next to the singularity of a black hole? Infinity. What’s the probability of something else happing at the big bang? Inifinity. Infinity. Infinity. And you get the feeling that this theory might be a bit broken. So the way I like to describe it is that building theories of the world is a bit like upgrading yourself to a new version of an operating system. So Newton taught us how to build the very first theory of gravity, Newton’s theory of universal gravitation, and that was supremely important 300 something years ago because his ideas about gravity have unified celestial physics with terrestrial physics. The way that suns and moons and baseballs moved was explained by the same general ideas and the precision of Newton’s theory of gravity was good enough to get us to the moon. You don’t need Einstein’s fancy theory of relativity from 100 years ago even to successfully put humans on the moon. I mean that’s pretty cool.


PA: That’s pretty impressive.


AWP: Yeah so in everyday regimes where we can’t go very fast when compared to the speed of light and gravity fields are relatively weak compared to a black hole, then Newton’s theory is pretty great. But people discovered that it was limited and in particular it doesn’t describe the gravitational waves that were just the discovery was announced last week. So you know Einstein’s theory of gravity is like an upgrade on Newton’s theory of gravity that made it more able to handle more experimental situations and we grew in confidence about it. But then we realized it has limitations that if you try to compute at extremely high energies, what is the probability of a couple of gravitons to interact with one another? You can get nonsensical answers like probabilities of 5000 percent, which we know can’t be true. Probabilities only can go between zero and 100 percent. You could get 98 percent probability of something but you don’t get 5000 percent probability of something happening. That’s sort of a nonsensical answer. So people realized that even Einstein’s beautiful upgraded theory of gravity still had limitations. So that’s where string theory steps in and says well I have a proposal for how to unify gravity and quantum mechanics together. The price you’re going to have to pay to bring those two warring parties under the same peace treaty is to accept that maybe the Legos of the universe are more complicated than point particles. Perhaps the Legos that describe everything if you peeled off all the onion layers and you could look close enough with equipment we haven’t quite figured out how to build and may never figure out how to build, but the notion is that maybe if you could peel off enough layers what you would see would be vibrating string underneath instead of a point particle.


PA: Well it did take us to go 100 years to go from Einstein in 1916 to last week’s announcement about gravitational waves. I don’t think you know 100 years or 200 years of however many years to figure out whether string theory actually is not just a theory. I don’t think that’s too much to ask.


AWP: Well yeah except we do have to recognize while I’m the first person to encourage the public to spend taxpayer money on scientific discovery and in particular blue sky scientific research that there won’t probably be a way of commercializing in the near future. Those are the sorts of research that I think we should be doing and they’re important to do and fun and very worthwhile for society. And society deserves to know about what we’re doing with their taxpayer money. But if the question were to have a healthier population of Canadians living in poverty or having more string theory, I think I’d have to choose the former. So it’s super exciting. But what string theorists are trying to do and people who are inventing other approaches to trying to solve this clash between gravity and quantum mechanics is we’re trying to upgrade Einstein’s theory to a version three. If you treat Newton’s version as gravity 1.0, take Einstein’s version of gravity as gravity 2.0, people like me, string theorists and other quantum gravity people, are trying to build gravity 3.0 – a theory that marries together gravity and quantum mechanics and can describe the most extreme gravity situations imaginable in the universe, which is the big bang that created the universe in the first place and the very heart of a black hole. So those are the most extreme kinds of physics I can imagine. A bit like extreme sports.


PA: Why are you fascinated by this and why are you fascinated by trying to explain these things, trying to explain the big bang theory, black holes, gravitational waves, what’s the interest?


AWP: Well I guess I’m a scientist. My parents claim that I always had that sort of proclivity. They would take me to a beach and all of the sudden they would discover me looking at the bugs or the starfishes or whatever it was or the rocks or those kinds of things. And I think many of us when we’re young look up to the night sky and wonder why we see what we see up there and what it all means. I guess science really captivated my interest. When I was in high school I had a very indulging teacher who noticed I was super interested in science. And Mr. H was really one of the only reasons why I got interested in physics. He noticed in his general science class, I guess the equivalent would be about tenth grade in Canada, he noticed that by the second week of the whole school year I had read to the end of the text book and metabolized all of it and that I was going to be a bit of a pain in class if I kept answering all of the questions he kept asking the class. So very early on he pulled me aside and said, I’ll make you a deal, kiddo. If you be quiet and keep your hand down and let the other kids in the class answer the questions and learn in real time and so forth, then I promise once a week you can come to my office and ask me anything you want about science. And so true to his word, he let me see him after school on Tuesday afternoon for about an hour and would completely indulge whatever question I had about science.


PA: Do you remember the questions you were asking back then?


AWP: I was asking stuff about earth’s geodynamo and what SU(5) was and how in quantum mechanics you could have a super position of states, what on earth did that mean and a bunch of other questions. Just little things that I had picked up by reading news articles. I was asking what the top quark was and why they were looking for it.


PA: And was he able to answer those questions?


AWP: He was a very very humble science teacher in that the majority of the questions he was able to answer right off the cuff. Most of the rest of them he would answer the next week if he didn’t have the answer right off the bat. And sometimes he said, you know what I really don’t know and that’s a really interesting question. Do you want to try and find out together?


PA: Sounds like an amazing teacher.


AWP: Yeah. I was very lucky also. I had parents at home who were both scientists.


PA: What kinds of scientists were they?


AWP: So my dad is a retired chemical engineering professor. So when I ended up going to undergraduate at the same university where he was teaching, there was one subject I was very clear I wasn’t going to do and that was chemical engineering. But anything else was on the cards.


PA: Was he disappointed?


AWP: Nah, I don’t think so. I think he understood that everybody in a family needs to carve out a little bit of territory that they can call their own. My mom has taught high school math and chemistry and other subjects, so it was very fortunate for me that when I had a lot of questions about science, there were a lot of answers at home. Very few kids have that kind of home privilege.


PA: I’m picturing rooms full of textbooks and encyclopaedias.


AWP: Well some of the books I remember enjoying reading were called Tell Me Why. I think it was a series of kids encyclopaedias that happened to be sold in New Zealand and probably was imported from Britain or something back then. Now we get a much broader range of literature for kids from a lot of different cultures.


PA: Now when you went to university, did you have a career in mind, what you wanted to do or were you just going because you really loved science and wanted to study more science, more physics?


AWP: That was really why I went. I was just really interested in the subjects and I was quite naïve about careers and what it might take to achieve a career in some area. I suppose I was just super lucky back then that floating into university without having a very good idea of why I was there. The subject ignited me and I found an intellectual home pretty quickly. But the conditions under which I was making that decision is quite different to what I see from my students today. Back then back in New Zealand tuition was essentially free. Now people have to pay thousands a semester to be able to do the same course load as I did, and they graduate with a lot more debt around their necks than my generation did. So that was one of the reasons it was easier for me just to not really know about careers very much.


PA: Indulge your passion.


AWP: Yeah, so I think I would still advise anybody who’s really captivated by science and really interested by it to follow it and to take it as far as you can and see where it goes. Whether or not it ends up forming the primary way that you earn money, that’s something between you and the subject and the universe I suppose.


PA: How did you land on physics? At what point did you decide, you know what I’m going to be a physics major and then a physicist?


AWP: I think it was about in third year at university that I was really convinced by then that I was a physicist. Prior to that I had a delusion that I might have been a mathematician. I did find math and chemistry more interesting in high school than physics and actually when I went to university I went straight into second year math and chemistry and only into first year physics ‘cause I wasn’t feeling very confident about the physics. I had a quite capable high school physics teacher but I didn’t feel super confident about the material and after a couple of years of trying out chemistry and realizing it wasn’t for me, it was the organic chemistry that would have done me in, so that’s the reason why a lot of us who might have been chemists didn’t actually go into chemistry was the organic labs. The subject was just fascinating. I would find myself getting energy from thin air to read about, to do the homework assignments, to learn more and more physics and sort of cascaded on itself I suppose. But I could have gone into different subjects I think if perhaps someone had really encouraged me at some point differently it might have been possible for me to do different things, but the subject was really fascinating. I suppose when I was having conversations with Mr. H about quantum mechanics and SU(5) and all those sorts of things that I thought, wow this theoretical physics stuff is really cool. And the more I dug into it the more I found I loved it. And it was relatively easy for me in the sense that it wasn’t too much of a struggle to do.


PA: It kind of came more naturally to you…


AWP: Yeah, but again…


PA: Than organic chemistry.


AWP: Right, and that could have been a function of character or background or fortune and genetic stakes or God knows what. You can’t control a lot of things in life, but I just found the subject to be completely igniting. It got me carried away and I would always find myself not running out of energy for doing it so I think that’s a good signal that you’ve found a subject that’s likely to be something you can keep doing is if it isn’t too much of struggle to do it. But then everybody who works in any given subject knows how hard they have to work.


PA: Why theoretical physics and not applied physics? For you, how did you delineate between the two and steer in that direction?


AWP: I like the abstraction, the mathematical aspect of it. I think the fact that I had a flirtation with mathematics but ended up sticking with physics is part of the reason why I’m a theoretical physicist rather than a experimentalist. Right up until I graduated as an undergraduate I had to do the labs just like the other physics specialists and majors, and it honked many of the experimentalists tending people off that I was actually quite good at it. But I think now I would be a liability in a lab: I don’t know my way around equipment, I don’t know how to use the machine shop, all those sorts of things. Years ago it used to be professors of any description were allowed to use the machine shop facilities in physics but after a long period of time presumably unfavourable incidents, they learned some of the more theoretical inclined professors couldn’t be trusted with the equipment to not damage themselves and break things, so I would have to do significant amount of training to be useful in a lab. So yeah I love the mathematical aspects of it and mathematics turned out to be the language of theoretical physics. It wasn’t preordained that this should be so. Sometimes people speak of this philosophically as if it’s completely obvious that advanced mathematics would be the language of theoretical physics the way that we explain the universe, but I don’t think it’s all that obvious. And it’s wonderful the way that so many things that are invented if you like for fun and for abstraction reasons in mathematics, turn out to be practically useful in doing physics. String theory is a little bit more mathematical than some parts of physics in the sense that some of the things that physicists invent to solve physics related string theory problems, push the developments of mathematics and vice versa. So physics is always a heavy user of mathematics but its not always contributing a lot in the other direction to the development of mathematics. I’m not one of the people who write string mathematics papers but we have a post-doc in the group who works on more of that kind of stuff and there’s plenty of real string theorist who are more mathematicians than I am.


PA: What was the appeal of string theory when you first came across it?


AP: I think its versatility is a thing that seduces a lot of people to get interested in string theory. That it’s a bit of an all singing, all dancing set of tools that you not only describe the nuclear interactions in electromagnetism and perhaps any other forces that lie waiting to be discovered at future colliders or the LHC but the versatility of string theory to be able to describe the gravitational phenomenon as well under the same theoretical rubric that’s what really got me interested in it. So when I first went to Stanford in 1990 it was a grand adventure. I didn’t have much of an idea of what I was going to leaving New Zealand for America. I was pretty naïve. I’d only seen pictures of America on the TV. When I was a kid, I don’t know if you remember, there was a California motorcycle cop drama called CHiPs. There was John and Ponch and whoever it were who would go around exerting justice in their corner of California or whatever it is, that was my image of what California was going to be like when I flew into San Francisco airport and was going to enroll in Stanford for my PhD. So when I got there I discovered one of the subjects people were really interested in was black hole physics and some of the theoretical people in the theory group at Stanford in the physics department and the people that I was trying to get in with, hopefully working with for my PhD, were interested in a number of these topics, so I got really interested in using black holes and string theory had a flurry of activity in the mid-late 1980s that meant there were a bunch of tools lying around. But at the time in 1990 when I started my doctorate, people were like, well maybe string theory has kind of played itself out. We don’t think there’s much left to get from there. Maybe you should think about doing something else. And they gave me good advice to go and do something else ‘cause it didn’t seem like string theory had very much of a future. But a few years later the superstring duality revolution hit in 1995 just a year after I finished my PhD and all of a sudden there was a ton of activity going on and there was a really exciting set of tools that for the first time were being used to do things like compute the black hole entropy from first principles.


PA: Okay.


AWP: This is the thing I had been so excited to see happen in my career that when I started in 1990 people were like so down on string theory and it’s like ugh you know it’s a flash in the pan and it’s probably not going to pan out more generally. You really should go work on something else, Amanda. Go and work on particle physics at SLAC. And so I tried and I tried valiantly to go down that path and maybe that might have worked in the end but I got electrified by the idea of whether or not string theory might be able to solve some long-standing puzzles in black hole physics.


PA: And this is the superstring duality aspect?


AWP: Yeah, so the string theory had another sort of a mini revolution or some people call it a major revolution in the mid-90s that was distinct from the one that had been sparked in 1984 when people figured out how to really do the quantum physics of strings. Before then we couldn’t really say we had a believable theory of quantum gravity, but when Greene and Schwarz proved this thing called anomaly cancellation in 1984, that was when people realized, we actually understand how to do quantum physics for strings now. In ’95 there were new things discovered about the structure of string theory and extra dimensions and things called branes and m theory and the really exciting thing about these new tools that were invented around then is that they allowed us to build analogs of black holes sort of toy models, Lego versions of black holes, simplified versions of the black holes that we would really like to understand in nature but sufficiently well understood and well controlled that we could actually calculate some things about them. And one of the things people were able to do for the first time in 1996 was to understand the origin of the entropy of a black hole. And I can explain entropy is and why you would care…


PA: Please.


AWP: If you like but it was sort of there had been this long-standing puzzle that people figured out that black holes must have this entropy and they were able to describe something about its properties but they weren’t able to give a description of where it came from, what was the entropy counting for you. And string theorists were able to do this for these Lego versions of the black holes and it made a fairly big splash and towards the end of the 90s that was the reason why there were a few people like me who got hired because of some of the advances that had happened using the new tools of string theory.


PA: Where do you see string theory going? I know that’s a big question, I know that’s a huge question, but when you look at you know in 1984 and that development, 1995, ’96, it seems like every 20 years, 15, 20 years…


AWP: It’s really hard to say. I think if I could bet what the future of string theory was going to be, I would already be a billionaire. Well, not quite. I would have millions of dollars in research grants. So don’t trust my prognostications. Anybody who says they can predict the future of what’s going to happen in an academic discipline is probably dying. But I’m not probably famous enough to have a really long term view of what the future might hold in string theory. But it’s certainly not all over. There’s a lot of activity that’s still yet to be done and a lot of exciting questions to ask. And I think that a lot of people have thought of it, especially after Brian Greene’s excellent books for laypeople came out like The Elegant Universe and there was a Nova documentary series by the same name and so forth that it got into the popular consciousness and people began to think it was something that you either believed in or didn’t or it was like a girlfriend according to the big bang theory or a religion or something. You know analogs are made, but really we don’t use it because it’s some sexy belief that has no basis in fact. Honestly if people could come up with a simpler theory of gravity to do all the things that string theory currently does, we would totally be into that. And if somebody were to invent another approach to quantum gravity that didn’t have holes as big as a sieve through it and so forth if somebody came up with a superior theory of quantum gravity tomorrow, a very large fraction of us would drop our tools and go over and learn how to use the other tools and start writing papers about that. It’s the best tool set available with the fewest bugs and that why I choose to use it for my research. I don’t mean to say that string theory is the only approach to marrying together quantum theory and gravity together. There are other ways of doing it.


PA: Let’s talk about your research. What exactly are you doing as a researcher?


AWP: So I’m interested in using string theory to investigate, illuminate, puzzles about black hole physics mostly and in using string theory to describe other aspects of the real world that it might be able to do. So I’m not an expert in using string theory to model particle physics to say, well this particular string theory and this calabi-yau produce that sort of stuff that’s the kind of thing that people like Brian Greene do and other folks. I’m interested in using string theory to solve gravitational physics problems and so there’s two rather related but distinct branches of my research that I’m interested in. And one of them as I mentioned is solving some of the long-standing puzzles about black holes. What is the origin of the black hole entropy discovered by Bekenstein and Hawking all those years ago? What’s the resolution of Stephen Hawking’s 40-year-old information paradox about black holes? Those are the questions that most keep me up at night. And those are the ones I would dearly love to solve. Ideally I would love to solve it a few years before I die.


PA: As opposed to a few years after you die?


AWP: Well, yes. So I’d get the chance to enjoy it, to know that it was right or something. But also that I would have a chance to work on a lot of interesting problems before it’s all sewn up and tied up with a neat little bow. And then we’d have to move on to working on something else and developing other aspects of science.


PA: Okay what’s black hole entropy?


AWP: I guess the first thig to try to explain is why would anybody care about something called entropy in the first place? You may have heard of entropy. An approximate human description of entropy is how messy something is. So if a teenager has a very neat bedroom with all the clothes exactly in the right place that would be a low entropy situation. Whereas if all the clothes were messed and all over the place and all sorts of configurations then that would be a high entropy situation. And people were interested in entropy to begin with when they were trying to build heat engines, things like steam engines, and they wanted to try to figure out why is it that when you try to use heat, like you heat up some coal and make steam and then try to use the steam to push pistons, why is there always some heat that’s lost as waste? Why can’t all the heat go into producing work like moving a piston so the train can move along the railway tracks? And it turns out there are some fundamental rules about heat transfer that means you always have to waste something when you’re producing something. So it’s a little bit like the statement that there no such thing as free lunch. And it’s also the same reason why there no such thing as a perpetual motion machine that you can’t have something where you have a perfect conversion of heat into work with no waste. And it takes quite a bit of effort to show why this is the case but there was a story developed even in the 1800s called thermodynamics, which was about the dynamics, or how things change over time through space, of thermal physics, in other words heat transfer. So people had come up with the idea of entropy and they were able to use it to describe losses for steam engines and why certain engines couldn’t be more efficient than a certain percentage and all those kinds of questions. That was all nice and fine and dandy but people hadn’t realized there was such a subject as black hole thermodynamics until quite a lot later. So it wasn’t until the 1960s and 70s that people started working out that black holes seem to have an entropy associated with them. And it was proportional to the horizon to the event horizon of the black hole. Not the event horizon is the place at which if you are near a black hole that if you go closer than that distance away from the centre pf the black hole, you’re inevitably going to fall in. if you stay outside of the event horizon or even a bit further out, then you can by judiciously firing your rockets in the right direction, not fall into the black hole. In fact, if you sun were suddenly to be acted on by a magician and become a black hole, our orbit wouldn’t change but the lights would go out and it would be very cold. But what I was trying to get across was so people had figured out that black holes had entropy. It seemed like if you threw stuff into a black hole then it should grow fatter and that corresponds with the entropy increasing so people had discovered through this thermal physics steam engine stuff that in any process that you would see happen in nature, the entropy would always tend to increase or it wouldn’t spontaneously decrease. You don’t suddenly see a teenager’s room getting clean. If it suddenly has become clean you suspect it’s been visited by a cleanliness fairy who went in there and expended a lot of heat and worked and wasted some entropy tidying up that bedroom so that it would be a low entropy bedroom. Generally things tend toward more entropy. People wondered if you could explain the entropy of a black hole the same way as thermodynamics experts had been able to explain the entropy of a box of gas. They were able to say, well if you’ve got a piston that’s this many centimetres across and that many centimetres along that I could tell you how much entropy that box of gas has and if you half the volume of the gas then I could tell you how much the entropy is changing, those sorts of things. And they figured out that if, this is the really key thing, that if you knew something about the individual molecule, you could use something called statistical mechanics to compute the thermal entropy of the box of gas. So people learned using quantum physics and something called statistical mechanics to be able to calculate from first principles if all you knew was about the physics of one gas molecule then you would be able to work out the entropy for the whole box of gas molecules like you know millions and billions of molecules in one little piston. So people once they had discovered there was an entropy and two very famous names that were involved in developing this entropy of the black hole were Jacob Bekenstein, who died just last year I think a very very big figure in theory of black holes and black hole entropy and so forth, and Stephen Hawking was another person involved so it was called the Bekenstein Hawking entropy of the black hole. So there was this thing that people knew was an analog of the thermal entropy but they didn’t know the quantum statistical mechanics to be able to calculate that entropy from first principles to say, I know about an individual ingredient of the black hole therefore I can compute the entropy of the whole black hole. And so two Harvard physicists Andrew Strominger and Cumrun Vafa were able to do that first in 1996 using brand new tools from string duality discoveries, particularly about things called d-branes. So they were able to build a Lego analog of a black hole, analogs are the ones that gave the gravitational wave signal to LIGO, and they were able to calculate from first principles using string theory ideas quantum string theory fancy mathematics to be able to calculate that entropy of the black hole. And they got all the coefficients exactly right. They didn’t have to wave their hands at it. Previous people had come up with some sort of hand waving arguments about why the Bekenstein hawing entropy came from something more fundamental but they could get the coefficient right. They had to fake that part of it, hope for the best that eventually one day we would understand where that came from. But then these upstart string theorists came along and said, well look we can actually compute it from first principles. Unfortunately, the black holes for which we can do it are not the ones that we see in the real universe in front of us but we got really excited by it and thought, well maybe we can work towards explaining the entropy of the realistic black holes by starting with our relatively unrealistic Lego black holes. It’s not as good as being able to do it for the black hole directly. If we were smart enough to be able to do that, people would have written those papers already, but what I and other people, many of whom are much more famous than me, have been working on developing is how far you can push this idea of using quantum string theory ingredients to model what might make up a black hole so that you could calculate things about it and in particular we would really dearly love to resolve a paradox that Stephen Hawking posed about 40 years ago called the black hole information paradox. And this is what my thesis advisor set me to working on when I signed up to be his graduate student at Stanford. So Lenny Susskind is one of the big names in black hole information paradox literature far more famous than I will ever be, but he taught me a lot about how to think about black holes and why string theory is an exciting set of tools to address many of the questions that we might have about gravitational extreme physics. It’s a chapter of theoretical physics that hasn’t finished yet so that story about the black hole entropy and the black hole information problem is the stuff that really keeps me awake at night. So what’s the information problem? Well you may have heard that Stephen Hawking managed to find out that black holes, even if they were alone in the universe and didn’t have anybody to eat or make friends with, they would give out a faint radiation. The radiation that these black holes give off, it was thought that black holes only absorbed things. The caricature that we hear about black holes is that they’re kind of like giant vacuum cleaners that suck up everything near them. Only if you’re foolish enough to fall through the event horizon are you dead. They’re sort of these big things. Hawking calculated that the radiation that comes off the black hole, only knows a very limited amount of things about what fell into the black hole. It only knows about the mass and maybe the spin and the charge like we said before you characterize a subatomic particle by its mass and its spin and its force charges. Turns out you can also characterize black holes by the same properties. So the Hawking radiation that comes out of black holes, suppose we just said that it just had mass to keep things simple. So let’s do a thought experiment where I take a black hole and I throw a 1kg book into it. It’s a book on thermal physics and statistical mechanics. And the radiation that then comes off of the black hole knows a little bit about what fell in. it only knows about the mass of the book. Now let me think about a different thought experiment, thought experiments are cheap real experiments are expensive, so that’s why theoretical physicists think Einstein is a bit of a rock star because he introduced us to the gedanken experiment or the thought experiment. Anyway, the second thought experiment, imagine instead of you throwing a 1kg textbook into the black hole that you threw a 1kg fish, an orange roughy from New Zealand for example. Then the Hawking radiation that would come out after you had chucked the fish in would be exactly the same.


PA: ‘Cause it’s still 1kg.


AWP: Right. Now the fish was different. It was made of different molecules perhaps, and it had a different shape and it might have had other different properties, but the Hawking radiation, at least that Hawking calculated in the mid-1970s, only cared about the mass. So if some of the information that goes in doesn’t come out, well, hell isn’t that a bit of a problem? I mean if we’re calling ourselves quantum physicists and we’re supposed to be interested in peeling things down in onion layers to the most fundamental level, we shouldn’t be losing track of information in our universe – that would be really embarrassing. It would be like we totally failed in our mission as physicists to be subatomic theorists if we didn’t keep track of all the information that was out there in the universe. Stephen Hawking even proposed that black holes eat information. He said that information is not sacrosanct anymore. You can lose information if you have black holes in your system. And this caused enormous consternation among the subatomic theoretical physics community because we had thought that we were the ultimate muscular people in tracking information and being able to keep track of all those little microscopic degrees of freedom. All of the sudden here Hawking was presenting us with an idea that maybe our tools were incomplete and that if we are not wanting to understand where that information went and if it was ever going to come out of the black hole again, would we ever see it again? Would it go off into another universe? What would that even mean? All those kinds of questions. So people like me are trying to use the tools of string theory that had the success with the Bekenstein-Hawking entropy explaining and were able to explain some of the spectrums of Hawking radiation that comes out of black holes using string theory techniques. But we still haven’t resolved that information puzzle yet. And there’s been some pretty big arguments in the literature over the last few years. New techniques being brought to bear to destroy old solutions to problems we thought we had a resolution of the information puzzle and then some people pointed out well maybe you don’t, there’s some things wrong with it solution so we need to work harder. So I don’t know how long it’s going to take for people like me to resolve the black hole information problem, but I probably think it’s not going to be next year. And probably not five years from now. It’ll probably take longer than that, but hey if I could predict, as I said, I would already be a billionaire making tons of money in the stock market.


PA: I’ve got just a couple more questions. The gravitational wave discovery – how significant is that? It’s been all over the news. We’ve heard all about it but from inside the world of physics, how big a deal is it?


AWP: It is a freakin’ huge discovery, to use the language of Monty Python. It’s a gigantic enormous terrific fantastic discovery that physicists have been waiting for for decades. The first proposal to get started with doing this was back in the early 70s I think what they said at the press conference and the first funding form the national science foundation in the US towards LIGO was secured in the early 90s while I was a graduate student at Stanford. And to finally see this cone to fruition and detect a gravitational wave at such a great degree of statistical significance its giant. It’s super exciting. And the way that we feel about it is people had known for a long time that there should be these gravitational waves but all we had had was indirect evidence and this came from things like binary pulsars, which is when you have a neutron star that has a very strong emission that we can see and these things are so strongly interacting that the time scales are very short. They might be winking at us from somewhere on the sky at millisecond timescales, and people had noticed that these pulsars, the one that was winking at us in a binary system, was gradually slowing down, winking at slightly less winky frequency. And people calculated from Einstein’s theory of gravity what you would have predicted if it was losing gravitational radiation from the stresses and strains on the gravitational fabric from these two bodies accelerating madly around each other in this gravitational embrace. It’s super amazing that people were able to actually detect these things from real actual binary merging black holes. It was electrifying. Everybody was so excited and I told my graduate students, well today is a day for celebrating science and remembering the joy of why you went into the field in the first place. It helped people have confidence that Einstein’s theory of gravity is a really good theory. The LIGO results from last week were really the first strong field test of Einstein’s general relativity. Einstein’s GR had a lot of other tests that had wildly successfully done like predicting the bending of light by the sun in 1919 that’s what made Einstein a rock star in his day. He didn’t win the Noble Prize for that incidentally. He won the Noble Prize not for general relativity but for explaining the photoelectric effect, which is an aspect of quantum physics that explains why, for example, you should not fear the so-called radiation from your cell phone or wifi transmitters. So if you have a kid and you’re worried about the condition of their brain, having a wifi transmitter at school won’t do them any harm and Einstein proved why and won the Noble Prize for that explanation. There are things to worry about with protecting your kid but wifi’s not one of them.


PA: You saw that on Facebook today, didn’t you? ‘Cause I did.


AWP: No, really. I have been giving this spiel for years.


PA: There’s a meme going around on Facebook and I saw it on my newsfeed today that’s from I don’t know if you know that site.


AWP: I do. I have a very good Twitter feed.


PA: And it’s why you shouldn’t fear wifi signals, and I went to it and that’s what it talked about. And I was like okay I didn’t know whether I should or shouldn’t.


AWP: I explained this in my first year physical mathematical universes 199 course. I helped students in fact I was just explaining it last week in my lectures last Wednesday. An analogy, just super quickly, is you might wonder why cell phone or wifi radiation, why that isn’t dangerous. Whereas why is the x-rays that we go and get at the hospital, why are those said to be dangerous. The difference between all of the forms of electromagnetic radiation all the way from gamma rays and x-rays down through visible light and infrared, which we know of as heat and radio waves and microwaves and all that stuff and TV and so forth, it’s all made of the same stuff, these little subatomic particles called photons which transmit the electromagnetic force. So the little particles of light that strike your eyeballs, the only difference between them and the x-rays that they use to image your bones in the hospital is the energy of the photons. Of the photon, the little particle of light, you can think of it as a little lump of light if you wish, the only way that that can damage DNA in your body is by actually kicking electrons that were in orbit around the atomic nucleus – kicking them into different energy levels or kicking them out of the atom entirely. The difference between radiation that’s dangerous and radiation that isn’t is determined by how energetic it is and that’s determined in turn by the wavelength of the photon. If the thing has a long wavelength much longer than an energy required to kick an atomic electron out of orbit, it’s totally not dangerous. Whereas if it is strong enough to be able to kick an atomic electron out that’s called ionizing radiation and that is dangerous. Anything that’s in the ultraviolet of the visible spectrum just the every bluest end of the spectrum that our eyes can detect, if you can get a sunburn from it, then it can do DNA damage, which is why you should absolutely wear sunscreen. But the reason why you don’t have to fear your cell phone, you might think, if I had say a photon that was one millionth of the energy required to disrupt an atomic electron, well what’s say I got really sneaky and organized a million photons all of which could do one one millionth of the kicking. Suppose I tried to line them all up and get all million of them to kick exactly the same time and exactly the same way and kicked the butt of the electron, would it come out of the atom? People had thought before Einstein’s explanation pf the photoelectric effect that this would happen, but when they did the experiment, didn’t happen. So confused. And then they realized that it actually would take an incredibly improbable thing to get them all lined up to be able to do that and you can calculate using quantum physics what’s the probability that a million high jumpers that could only jump a few micro metres. Suppose each high jumper could only jump one micro metre. Would we say that they won the high jump if we got two million of them to jump a micro metre together? That wouldn’t be enough to clear a two metre hurdle or over two metres and win the Olympic gold medal. Similarly with atomic electrons, if you actually had a million tiny energy photons, even if you could line them all up, it would be so improbable that you could do that that on average it never happens in the lifetime of the universe. That’s why you can be confident that radio frequency photons coming from your wifi, you microwave, TV or you cell phone or whatever it is, those things as long as they’re not producing ionizing radiation, they’re not dangerous to biological tissue as far as we know. There’s no known biological mechanism using interactions of subatomic particles that could damage the DNA in the body. And the body has very very good DNA repair mechanisms. On an average day, your cells undergo a lot of DNA repair on the basis of all sorts of things, some of which is ultraviolet photons coming in from the sun and doing damage to some little cell in your body. So not every incoming ultraviolet photon will give you skin cancer. It has to give rise to DNA disruption which then has to give rise to cell damage which then has to give rise to tumor growth and all those sorts of things. It’s not very probable but if you live long enough, you’ll eventually probably get cancer somewhere. So that’s why you should wear sunscreen, and I can tell you that based on quantum theoretical physics.


PA: You mentioned earlier you don’t spend much time in labs, in workspaces. I don’t know if you’ve been in the workspaces that are downstairs, here the new ones, the new labs…


AWP: The new first year lab spaces that we have? That’s a really exciting innovation that we’ve done over the last small number of years. We didn’t have them when I first came to U of T as a faculty member in 2000 and there was a development spearheaded by people in the department who are more experts at physics education research that informed a real overhaul of the first year lab courses so that they were more in tune with the curriculum that we were teaching in the classes and made them more brains on, hands on, active learning style…


PA: They’re really cool pod-like…


AWP: Little pods and there’s even accessible aspects so that if you happen to be a person using a wheelchair then you would be able to use one of the accessible stations and that was something that I was really clear should be in the design. Of course, it’s the law also. When you build new things under the Accessibility for Ontarians with Disabilities Act, you have to be inclusive of people with disabilities. I’ve been really excited about it. I’m not one of the people who was one of the leaders in the development of this, but I’m super proud that our department was doing that. I think it was about time we upgraded the learning experience for first year students and that’s eventually working its way through the higher aspects of the curriculum as well. People are looking at modifying second year courses to bring in more of these research motivated innovations into the way we teach undergraduate curricula, so I think it’s fantastic for young students to consider physics as an option nowadays. Many times you ask an average student could they think about making a career in physics. What would that be useful for? There was a movie a long time ago called Young Einstein and one of the famous lines from it is “what do physicists grow, son?”


PA: Wasn’t that Yahoo Serious?


AWP: Exactly. It was Yahoo Serious. Indeed and it was set in Australia. It was one of the reasons I saw it as a kid in New Zealand. So what do physicists do that is useful? Well, people worrying about quantum physics back in the 1920s and 30s gave rise to iPhones today. The payoff isn’t always immediate. You can’t necessarily go into scientific thing knowing how it’s going to be technologized or commercialized or whatever else –ized. But I think it’s a wonderful time to be considering going into physics. if you look on for example the Canadian association of physicists website or the American physical society, a number of professional societies of physicists around the world have put together information online that you can find out about all the careers. The doors can open if you take physics as an undergraduate subject. Ideally I would like a lot of people to be physics educated, even if the vast majority of them never become physicists or not even scientists. I think it’s super important that researchers try to bring an understanding of what we do to the public who pay for it. That’s kind of like the reciprocity deal – the taxpayer agrees to put some funding to funding curiosity driven blue sky research, or the kind of thing that I do, and our reciprocal obligations are to try to get young people excited about it, to try to explain what we do to the general public. Sometimes we fail, sometimes we don’t do a too good of a job explaining things or making it comprehensible. We need to keep trying and to keep working on it because we owe that to the public. If some of their hard earned taxpayer dollars are going to fund our research, the least we can do is try to explain what we do and get people excited about it.


PA: Now just to go back, in those first year physics labs there are photographs at each work station, each pod, there’s a framed photograph of a physicist. And I’m wondering, do you have a favourite physicist?


AWP: Oh dear. Well that’s a very difficult question. It’s a bit like saying what’s my favourite colour. I like a lot of colours.


PA: That’s my next question.


AWP: To be honest, I don’t have one. I like to think of heroes as fallible, so I don’t hole any one person to a impossible standard that they must be a fantastic physicist and a fantastic human being and a fantastic all the other things. I will say that there are a number of very famous physicists that I have met in my day during the course of my 25-ish year academic career who are just really spectacular and amazing. Some of them are wonderful people, some of them are jerks…


PA: Who’s the jerk? It’s Hawking isn’t it? It’s Hawking.


AWP: No, actually in any group of people you will always find some really interesting characters some of which will be famous jerks, some of which will be famously generous. I will say the people that I admire not only have done great science, but when they look down on somebody it’s because they’re helping them up. Those are the kinds of people I put up in my pantheon of heroes. People who have inspired me aren’t necessarily in that same category. Certainly Stephen Hawking is one of the people who’s been a heck of a role model for a lot of us. I wouldn’t consider my disability to be anything like what Stephen has, I am a person with disabilities, but to see him at a conference even struggling to get breath and a few people were saying, it’s so cold why don’t we close the door? The answer comes back, well Stephen needs the breeze in order to be able to breathe properly, so everybody’s like, okay we don’t mind being cold. He’s an astounding human being. I have an aunt who died of the same thing that disables him amyotrophic lateral sclerosis or Lou Gehrig’s disease…




AWP: ALS. Or motor neurone disease is what the UK and some in New Zealand and Australian people call it. Most people are taken from us much more quickly than Stephen, and he’s extremely unusual among people with ALS for having survived so long. He’s not an easy person. When you have that degree of disability and the structural rubbish around you that makes your life so difficult just to live and sometimes even to breathe, I think that you get a pass for being a jerk sometimes. I know that I’m sometimes cranky when my pain is really spiking and it can make it difficult when human aspects of life intrude on our ability to do science. But I admire Stephen singularly for his ability to keep doing the science and to keep having immense joy from doing the science and appreciating the science and hearing of other scientific discoveries by other people. And if I can have anything like one percent of his joy level and his obstinacy at continuing to do physics, even under the most awful of circumstances, that’s a heck of a role model for people who feel like they’ve got burdens to deal with. Lots and lots of people that I’ve met in my career Edward Witten is one of the most famous string theorists on the planet and I’m nothing like him. I don’t think I can ever be anything like as smart as he is, but if I am able to contribute even a small amount then I think that’s worth doing.


[theme music]


PA: That’s another episode of Planet Artsci in the books. Thanks to my guest, physicist Amanda Peet, for helping understand string theory. Planet Artsci has been brought to you by the letters A & S at the University of Toronto. I’m Barrett Hooper. Thanks for listening.