Instant Genius - Professor Fay Dowker: What is the problem of quantum gravity?

Episode Date: March 2, 2020

This week, we’re going on a search for the theory of everything. The two main theories of physics are at odds with one another. Einstein's general relativity explains gravity, but it contradicts quantum theory: how we understand matter, atoms and particles. Theoretical physicist at Imperial College London Professor Fay Dowker has been working on a solution to this quantum gravity problem, and tells us why the theories are incompatible, and how she plans to bring them together. If you have a burning science question you want an expert to answer, send them to us on twitter at @sciencefocus, and we may answer them in a future episode. Subscribe to the Science Focus Podcast on these services: Acast, iTunes, Stitcher, RSS, Overcast Let us know what you think of the episode with a review or a comment wherever you listen to your podcasts. Listen to more episodes of the Science Focus Podcast: Dr Erin Macdonald: Is there any science in Star Trek? Dr Becky Smethurst: How do you actually find a black hole? Kathryn D. Sullivan: What is it really like to walk in space? Hannah Fry: How much of our lives is secretly underpinned by maths? Robert Elliott Smith: Are algorithms inherently biased? Monica Grady: What is the future of space science? Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Hello, I'm Alexander McNamara, online editor at BBC Science Focus. This week, we're going on a search for the theory of everything. The two main theories of physics are at odds with each other. On one hand, you have Einstein's general relativity theory, which explains gravity, but it contradicts quantum theory, which explains how we understand matter, atoms and particles. theoretical physicist at the Imperial College London, Fay Dauke, has been working on a solution to this quantum gravity problem and tells her editorial assistant Amy Barrett why the theories are incompatible and how she plans to bring them together.

I am working on the problem of quantum gravity, and it's a problem and not a theory because we don't have a theory of quantum gravity yet. So the problem is the challenge is to find one, And it's a problem because our current two best fundamental theories in physics are not compatible with each other. It's a strong statement to say that they're contradictory, but I'm not afraid of saying that, actually. I think science, it advances by looking at contradictions between our current different people. pieces of our understanding, and it focuses on those contradictions in order to make progress.

So science actually, it tolerates contradictions, but not forever. So at any particular moment in history, there will always be contradictions. Well, there have always, let's say, in the past, been contradictions between different pieces of our understanding. And those contradictions are exactly where we want to focus on in order to do better, to try to unify, our understanding. So what are the contradictions involved in quantum gravity? So our best theory of gravity currently is general relativity, and that was largely formulated by Albert Einstein.

And according to this theory, gravitational phenomena, such as the motions of the planets around the sun, black holes, the motions of galaxies in the universe are manifestations of the geometry of a fabric that we call space time. Space time is four-dimensional and it's dynamical. So it has a life of its own. It is governed by laws of physics. It bends and it warps and it ripples and it carries energy. It is a physical entity in our current understanding of gravity. And the way that it bends and warps and ripples is governed by the matter in the universe. So depending on what matter there is, then space time responds to it.

So if two black holes, for example, are in orbit around each other, in spiraling, and towards each other, then that will create ripples in this spacetime fabric that we call gravitational waves. But the contradiction arises because our very best and most fundamental understanding of matter is quantum mechanical. And one of the essential features of quantum mechanics is that quantum mechanical events are unpredictable. They're inherently unpredictable when a quantum mechanical event happens, we don't know in advance what the outcome will be. We'll know what the possibilities are, but we won't know which one will happen. So it's like a horse race. You know that one of the horses will win, but you don't know which

one in advance. And that is ignored, that feature of matter, that quantum mechanical feature of matter is ignored by general relativity. General relativity assumes that matter behaves, in a predictable, entirely predictable and deterministic way. So there's the contradiction. Quantum mechanics says that matter behaves in a stochastic or random way, but general relativity assumes that matter behaves in a predictable way. So what are some examples of a quantum mechanical event? What could those be?

So, for example, in a... At the moment, there is a huge amount of experimental work being done in the realm of optics and quantum optics in particular. And that's very exciting. A lot of my colleagues at Imperial College are experts in quantum optics. I really enjoy going down to see their experiments. And quantum optics, one of the fundamental pieces of equipment that they use are called, interferometers. And in quantum optics, they can reduce the intensity of the light that they use in their

experiment so that one particle of light called a photon is moving through the equipment, the interferometer at a time. And when they use certain components of their equipment, This photon, when it passes through something called a half-silvered mirror, it can decide to do one of two things. It can either go straight through the half-silvered mirror, or it can reflect off it. And for a given photon, you cannot predict which way it's going to go.

It will either go through it or reflect off it, and there's a 50-50 chance of it doing either of those two things. You can't predict in advance which one it's going to do. It will do one or the other, but you can't, you, and over time, the average will be that roughly half of the photons will go through and roughly half of the photons will reflect off. So that's something that it's inherently unpredictable, which way the photon will go.

Right. And why doesn't that match up with generality? see? So it's a feature of matter at large scales that this inherent unpredictability washes out. So what we see at macroscopic scales, the behavior of matter, is that this quantum uncertainty is hidden by the statistical properties of the, the statistical properties of the, matter as a whole. I mean, these are very, this is a sort of rule of thumb, a sort of broad brushstroke description of how classical behavior or deterministic behavior, predictable behavior arises from a quantum theory. Actually, the precise theoretical understanding of how that classical behavior arises from quantum mechanics is, in my opinion, absent. We don't, we, we, we can give this

rule of thumb heuristic explanation, but is actually there is no procedure within the, within quantum theory, to explain why this, this classical behavior arises or how it, how it arises, in my opinion. That's one, another problem that I work on in my research program, which is to try to understand how classical behavior arises from, from quantum behaviour. And how does your research, like how do you go about your research, what does a day look like for you? I am a theoretical physicist, which means that I don't have a lab. I'm not tied to a lab. So I can do my research pretty much anywhere. I use a computer a lot, so I'm often sat at a desk reading papers on my computer.

I find it hard to think without a piece of paper in front of me and a pen in my hand. So I'm doing calculations, scribbling notes down on paper. I'm often, so when I'm teaching, I'm interspersing bouts of thinking about research and doing research with my preparation for teaching, meeting students. So, yeah, typical day will involve perhaps a lecture, preparing for a tutorial, talking to my PhD students about their projects,

sitting down, reading an interesting paper that's just come out. So it's, yeah, it's very varied, and that's one of the great things about my work. In terms of working on this problem of quantum gravity, is there any simulations involved or is it really just hard math? It's both. My colleagues use a lot of computer simulations. Computers are incredibly useful even though we're doing theoretical physics. People use computers to simulate the systems. that they are, that the mod, simulate the models that they are creating. Also to solve hard equations, it's often, often computers can do it, can do what we can't do.

So people use computers to solve, for example, differential equations. For example, the equations that govern the geometry and structure of space time are Einstein's equations. They're very difficult to solve analytically just with pencil. and paper. And so people are using enormous amounts of computing power to solve those equations to tell us, for example, what the form of the gravitational waves coming from black hole collisions will look like. So yeah, computers are a big part of theoretical physics today. Right. And so there are lots of other physicists working on this problem currently? There are. It's a global community of people working on.

on quantum gravity. There are different approaches. It's a strange situation at the moment, historically, in which the experimental evidence pointing us in one direction or another in quantum gravity research is very, very scarce. because the two realms in which both gravitational phenomena and quantum phenomena are rather extreme in themselves and when you put them together, the sorts of realms in which they become really relevant are very extreme. So, for example, at the time of the Big Bang, which is...

roughly 13.7 billion years ago, when the matter in the universe was in a very hot, dense state, that realm is where both gravitational and quantum effects will be important. But it's very far from us in time. So it's difficult for us to probe that era, to get experimental evidence of what quantum gravity should be like. So because of this situation where the evidence for different approaches to quantum gravity is scarce, there's a wide range of different approaches. So the community is a vibrant and large community. We're divided into different approaches. So some people will focus on one heuristic motivation and some others will focus on a different, a different. starting point, if you like. And at the moment, the experimental evidence is scarce, and so it's hard to be

guided by actual observations at the moment. Right. So we don't see this happening at the moment. Like we can't look out into space and see this happening? We can. So cosmology, which is the study of the universe at the very largest scales that we can observe is a place where we can look for evidence for different approaches to quantum gravity. And I think it's probably the most promising area that we can look to for evidence of different approaches to quantum gravity. And I am actually hopeful that more and more cosmological data will, in the the will in the not so distant future start to distinguish between different approaches and we'll be able to be guided by that cosmological data in our research in theoretical

in quantum gravity. So what are the different approaches going on at the moment? I could divide them roughly into two. I mean, there's overlap between them and there are scientists who work on more than one approach, but very roughly speaking, they can be divided into two rough camps. There's one approach which is, roughly speaking, motivate, it comes from a tradition of particle physics, the physicists who have been focused on trying to understand matter at the most fundamental level. So working on the standard model of particle physics.

And that tradition in theoretical physics has given rise to the approach to quantum gravity called string theory. And in that approach, the fundamental particles are conjectured to be different modes of vibration of a fundamental substance, which is one-dimensional. So that's why it's called string theory. So string is one-dimensional. So that tradition, that particle physics tradition has given rise to an approach to quantum gravity, which would call string theory.

The other tradition, roughly speaking, is to take space time, this fabric, this four-dimensional fabric of space time as the starting point. So to try to think about it as having a quantum mechanical nature. And so, again, roughly speaking, that it's a tradition of physicists working on general relativity, on gravitational physics. And from that has arisen different approaches, which are more focused on space time than they are on matter. So that's a rough description of two different approaches to the problem. Wow. So, I mean, I know nothing about space time nor string theory. are you able to just, you know, my public ask to explain what string theory is, but can you?

I, interesting, interestingly, string theory has grown, I think, hugely beyond its original, well, let me say, so string theory was, it originated from, actually, directly from particle physics as a, in that people, were trying to understand the standard model. And in particular, they were trying to understand the strong nuclear force, which binds together the nucleons in the nucleus of atoms. And string three arose from trying to understand that. It broke out of those constraints

when it was realized that in the that string theory contained within it gravity and that was it was not designed to do so so it was a very dramatic development that a theory that was developed to try to understand the understand matter

to understand the particles fundamental particles actually contained within it gravity you could see gravity in there and that was that was, I think, very, very motivational for a lot of particle physicists to start thinking about string theory as something that could be the theory of quantum gravity that we know we need. Now string theory is, there are many physicists who work on string theory for many different reasons.

gravity is just one of them. So string theory is sort of it's broken its boundaries again and many physicists work on it because they find it very very attractive, very beautiful. It has a lot to say about quantum field theory, which is the area of physics that particle physics is based on. And the Yeah, it's a theory which is really rich. And from its roots, it's grown to be something in which people have found more and more interesting things to look at. And quantum gravity is just one of them. And you mentioned four-dimensional space time. Yes.

Can you explain? I mean, getting my head around four dimensions and space time is quite difficult. Yes. Yes, it is. it's a new it's a new world view a new way of thinking about the universe how do you how can you get your head around three dimensions yeah three dimensions is something that we're all familiar with right yes good exactly so and what does that mean exactly well what it means is that you can think of a thing let me say okay what have i got in front of me i've got um my tea-cats

right? So my teacup, I can think of that thing. And to say where it is, I have to give you three numbers, three coordinates. I can tell you how high it is above the floor, how far it is from the front wall, and how far it is from the side wall. So I can tell you, I can pinpoint its position in three-dimensional space by giving I can pinpoint it's position in space by giving you three numbers and that's what we mean by space being three-dimensional so for example

a map of of Bristol consider to think of a map of Bristol and you want to pinpoint your position in Bristol right now on that map you only need to give two numbers which is the two

coordinates of the coordinate grid on the map. So the map of Bristol is two-dimensional. The space in in this room is three-dimensional. I need three numbers to pin pin down where something is. And the idea of four-dimensional space time is that you need four numbers to pin down not just where you are, but when you are. And what I mean by when you are is not you, because you persist for many moments of time, but a particular instance of you. So I mean you now. So to say where that event is of you and now,

you need to say, give four numbers, three where you are in space, roughly speaking, and one, when that moment is, what time it is at that moment. So four-dimensional space-time is the collection of all these events. Everything that happens needs four numbers to pinpoint it, roughly speaking, three of space, where it is, and one of time when it is. And if you collect together all of these events, they form this four-dimensional fabric of space-time. But how does that relate to quantum gravity?

Well, first of all, it relates to gravity. So it relates to quantum gravity because it relates to gravity. So if you take all of the events in the universe, then they form this four-dimensional fabric. And the four-dimensional, and the structure of that four-dimensional fabric gives us, it manifests itself as gravitational phenomena. So this four-dimensional fabric of space-time is gravity.

It explains gravity. It tells us why the planets orbit the sun and why the galaxies behave as they do, why black holes exist. So this four-dimensional fabric of space-time is gravity. So to understand quantum gravity, we have to understand quantum space-time. So space time has to do with quantum gravity because it is the fundamental way that we understand gravity. And so why is it important that we solve this problem of quantum gravity? It's the epitome of what science is to try to better our understanding of the universe.

And as I said, the science tolerates contradictions, but it doesn't tolerate them forever. So science advances by resolving contradictions between different parts of our current understanding. So the scientific drive to understand better is what motivates our attempts to find, our quest to find a theory of quantum gravity. And because quantum gravity, the problem of quantum gravity is so fundamental, space time is, it is the arena in which everything that happens happens. It is our universe. And so understanding that better at a fundamental level is bound to have consequences, which we can't foresee because we don't know what quantum gravity is yet. it's bound to have consequences in every part of our lives,

although, as I said, it's hard to predict what those will be. And, I mean, from your opinion, how far away are we from understanding that? That's, yeah, that would be, if I knew that, then, yeah, I just don't know. I think, as I said, a lot depends on, A lot depends on what happens in cosmology in the future. What sort of new data will come in? At the moment, so for example, at the moment there's a tension. Some people would even say, now call it a contradiction between our best theory of cosmology.

It's also confusingly called the standard model. So it's, but this is a standard model of cosmology. Between that best standard model of cosmology and our, our observations, in particular, our observations of the expansion rate of the universe. So the universe is expanding, the galaxies, our galaxies are getting further and further away from each other, and we can measure the rate at which that is happening. and that rate is now in contradiction, that measurement of that rate is in contradiction now with,

well, let me say contradictions are strong. Experimental physicists are very conservative. They don't want to announce a contradiction until they're really, really sure. But there's now a growing tension between our observations of the expansion rate and today. the expansion rate of the universe today and our standard model of cosmology. I think that that is going to show that our standard model of cosmology has to be reformed, and I think that that's going to be a clue to quantum gravity.

But we'll see that's something that may or may not happen in the next few years as more cosmological data is gathered. So at the moment, we're noticing that the expansion of the universe is happening faster than our standard model, if I got that right? Ah, it's slightly more subtle than that. So you're right. So the expansion rate, what you're referring to is that roughly about 20 years ago now, it was realized that the expansion rate, what you're referring to is that roughly about 20 years ago now, it was realised that the expansion rate, expansion rate of the universe is greater than it would have, than it would have been if the so-called cosmological constant was zero. So the standard model of cosmology has changed over history. And 20 years ago, the standard model assumed that this so-called cosmological constant was zero. And that was shown to be in contradiction with the data, with our measurements of

of the expansion rate today. To resolve that, the standard model was altered to include a cosmological constant. And that standard model then agreed with the, with the, with the agreed with the observations. Now, what's happening at the moment is that these are much more precise measurements of the expansion rate today that are being made. And it's that that's bringing the standard model into, again, into contradiction with the data, because the data is getting better and better. We're able to measure the expansion rate today at a higher and higher accuracy.

And do you think that there's any, you know, I mean, that's just shown I had a misconception, really, because I thought we were still back at, you know, 20 years ago, I guess. Are there any misconceptions out there in the general public about, well, cosmology or quantum mechanics? When I give public lectures, I am amazed at how well-informed people are. I often get questions from the audience when I give a public lecture that are far more astute and incisive than those questions that I get asked by my colleagues. I think it's because people are really, they have a much broader perspective. They want to know, they're much more questioning. They want to know in general why one is interested in this. Why is one doing this?

What are the broader issues here? And that's, I enjoy that enormously and people are very, you know, they're very astute. They can spot an inconsistency in your argument. So when you're talking to your colleagues, often people are very focused on details, they're focused on, that may already be working in that area and are not asking you why you're doing something, but just about a particular detailed calculation. So, yeah, so I really enjoy speaking to, to, non-experts because their questions are challenging, very challenging and often very, very well-informed.

So particularly about cosmology, I think people are very well-informed and I haven't come across anyone who asked the question that I thought, well, they just haven't kept up with the current developments. Quantum mechanics is a different matter because, but that's not the fault of people of interested non-experts, the confusion and perhaps misconceptions about quantum mechanics that abound and that they do abound are because the community of physicists itself has not come to a consensus about quantum mechanics and how to understand it. that is a remarkable situation given that quantum mechanics was created in its in 1925 and has been in the words of Einstein our most successful physical theory

but there's still no consensus on how to understand it what it means what does it mean what picture of the world does it give us so that's it's a different situation from general relativity There is consensus in the scientific community about the picture of the world that general relativity gives us. There is no consensus on the picture of the world that quantum mechanics gives us. There are different points of view.

Different. And one point of view is that even asking that question is a waste of time and we shouldn't bother. But amongst those who think that it is a genuine an important physical question, and I include myself in that category, there are different opinions. So what interested non-experts, people who are just generally interested in science, are picking up, is that there is disagreement, there's controversy, there are different points of view, and there are many different, I would have to say, contradictory statements made

by physicists about the nature of quantum mechanics. And because we think that scientists or science, there's no room for opinion in science. And I think that that's in itself quite confusing to come across conflicting opinions. Yes. I'm surprised that anyone would think that there are no opinions in science. Yeah.

Yeah, that just, I don't, how can anyone get that impression? There's science, you know, there's, science thrives on debate and discussion and disagreement. We have to, yeah, I mean, even an individual scientist, so many, you know, if you, if you look at what they, what they say, their work, I mean, that develops over time, you know, people can hold contradictory views. at the same time and people's later work or statements can be in you know can disagree with their earlier work and statement so so yeah as a community we're constantly constantly debating and arguing um with each other and that's it it's a it's the way science works and also it's it's a it's the it's the strength of science so it individuals can always be wrong. In fact, we're always, we're wrong a lot of the time. But the

community as a whole advances because we can reach consensus. We have to, we have to persuade each other. We have to convince each other that the evidence for something is strong enough that we owe, that we change our opinion. And that's, that's the strength of it. So as a community, we can be right, even though as individuals we are constantly wrong. And what about your own journey through science? How did you get to what you are today? When I was young, a young girl and young student, I was very interested in maths.

I wasn't too interested in physics at school, and I went to university to study maths. And then in my third year at university, I learnt about general relativity and I loved it. I've loved it ever since and it's been it's been the rock on which I've rested my

intellectual journey ever since. I still love it. I had the opportunity to teach it to my undergraduate students and it was a joy, a privilege, and yeah, it was my dream teaching experience. I love it. So, yeah, so that's...

I came to physics late in life, I suppose, in the sense that it was only while I was an undergraduate student that I started to be interested in physics. And I came... And quantum gravity always seemed to me to be the most fundamental question that one could ask. So I loved general relativity, but I could see that it didn't accord with our understanding of matter. And so I wanted to know and still want to know how to make that work, how to reconcile the quantum nature of the world with our understanding of gravity.

Can you sort of explain what is general relativity and why did you love it so much? General relativity is our best theory of gravity, and it's also a theory of space time. It's quite mathematical in its technical aspects, but its conceptual features are that we have a new view of the world as being four-dimensional, instead of three-dimensional. So we live in space time. We don't live in space with time ticking away for us. In fact, our world is made not of three-dimensional objects, but of events, things that happen.

So it's a new perspective on reality. So instead of fundamental things being tables and chairs and and, and, and, galaxies and planets. Fundamental things are events, things that happen in space and time. And space time is made of those events. So the events are more fundamental as building blocks for the universe than three-dimensional objects. So this, what I loved about it was this change of perspective. And it's not just a change of perspective that you are allowed to make. Science dictates. takes that you must have this change, must have this change of perspective, because

general relativity is, is empirically, testably, experimentally verified, better than the theory of gravity that came before general relativity, which was Newton's theory of universal gravitation. So this general relativity is a better, it's our best theory empirically, provably, demonstrably and quantitatively better than our previous understanding was. And so this change of perspective that our world, our universe is made of event and not of three-dimensional things is, it's demanded of us as scientists. You have to take this perspective because generativity is better than our Newtonian understanding. So that I, I was just thrilled and challenged and excited by this new perspective.

I just wanted to know more about it and to learn more. And now I want to push the boundaries of our understanding so that it incorporates quantum theory. And the approach that I work on to this problem is one in which space time is fundamentally granular or bity, pixelated, atomic, discreet. There are many words that have the same connotation here. So in generativity, space time is smooth and continuous. It's a fabric. It's a smooth fabric.

But in the approach to quantum gravity that I work on, the conjector is that this smooth, continuous fabric is just an approximation to something which is fundamentally. fundamentally granular, fundamentally atomic. So the word atom means uncuttable. So it's something you can't divide up anymore. You get to a smallest piece that can't be made any smaller. So space time in the approach to quantum gravity that I work on is conjected to be atomic. It's conjected to be made of fundamental events that are the smallest possible events. And you, You can't cut them up anymore.

Wow. It's really hard to get your head around, isn't it? I'd really like to just hear about your PhD and what it was like working with Professor Stephen Hawking. Stephen was my PhD supervisor, and it was an amazing experience being his student. He was a very generous supervisor to me. He involved me in the work that he was doing very generously. He gave me a great problem

to work on, very interesting, and he was very approachable. I was a little, I was a shy person and not good at putting myself forward, but he, yeah, he, he was not standoffish at all. I could he always made time for me, even though it was often, I wouldn't often have to wait a long time before seeing him because he was so busy. But it was, he always made sure that he made it clear that science and his work and his research was a priority. So, yeah, that was an important part of my PhD. The things that he taught me, I still, they're still part of the way that I think about physics. So his focus on space time as being fundamental.

He championed a particular approach to quantum mechanics called the sum over history's approach or path integral approach, which I think is the most fruitful way to think about quantum mechanics. so that's still part of my research. It's part of what my research is based on. And the opportunities that I got from being his student also helped me enormously in my subsequent career. Sorry, what was that approach? Can you just explain that really quickly for me?

Yes, of course. Part of my work on quantum gravity involves trying to understand quantum mechanics itself better. I said that there is no consensus in how to understand quantum theory. And again, within that and within that, there are different approaches, different opinions. So one approach to the foundations of quantum theory, this is not specifically to do with gravity, but just quantum theory itself, quantum mechanics and quantum field theory, is one approach is called the sum over histories approach, and that's due, it's associated very closely with the particle physicist Richard Feynman.

So it's often called Feynman's sum over histories, although it dates back previous, I mean, it's older than Feynman, so it was actually initiated by Paul Dirac in the 1930s. But it's closely associated with Feynman. And in this approach to quantum mechanics, the same sorts of concepts as arise, that general relativity is based on are fundamental in the path integral approach to quantum mechanics. And those concepts are the concept of event, something that happens, something that happens in space and time. and the concept of history. So a history is a detailed way in which an event can happen. So, for example, an event could be it's raining between 1 and 2pm in Bristol.

That's an event. It either happens or it doesn't happen. and a history would be a very particularly detailed way in which it can be raining. So the exact number of raindrops, a particular pattern in which they fall, whether it's windy or not as well as raining, all these details would be a history. So in the sum overhistory's approach to quantum mechanics, you think about a quantum system in terms of those concepts,

things that can happen, events, and then histories which are very detailed ways in which that thing can happen, that event can happen. And Feynman sum over histories is a way of making predictions about those events. So there are rules for how to calculate the probability of an event happening. And the Feynman sum over histories gives you a way of calculating those probabilities. And we, my colleagues and I are trying to base an understanding of the physical world, of the quantum physical world, on this sum over histories. And that's, it's a work in progress.

We haven't, we haven't, it's not complete, but it's a, it's a direction in which we are trying to, trying to go in understanding the nature of the quantum world. And I wonder, thank you for spending so much time with me, but I wonder just quickly, is there anything about your experience with Professor Holking that has impacted the way you work with your own PhD students today? There are so many things that let me pick out a couple. I went with Stephen to a workshop at the University of California in Santa Barbara. at the Institute for Theoretical Physics there.

And it was an amazing experience. I was just a PhD student. I met so many people whose work I knew. And Stephen made me give a talk. I didn't want to. I was scared out of my, I was just scared out of my skin. It was terrifying. But he wouldn't, he simply made me.

me do it. He said, well, you're going to do it anyway. And I did do it. And it was, although it was really very difficult, I'm really glad that I did. And he, yeah, he, he was like that. He just expected, he treated his students as intellectual equals in the sense that he listened to what we had to say. And obviously he was just vastly more experienced. So he knew that we didn't know that much, but he did, you know, he treated us. He listened to us as he listened to his colleagues. But he also expected us to do these things that, to embed ourselves in the community. So I do try to encourage my students to take every opportunity to speak about their work, to to get comfortable talking about their research and to take, yeah, absolutely take every opportunity

to present their work when they can. And not, even if they're worried, afraid or, or don't want to do it, I encourage them to do it. I'm probably not as dictatorial as, as that. I wouldn't absolutely insist if they were, you know, really, they really didn't want to. So that's, yeah, that's, that's one thing that's influenced me as an advisor. And also the fact that he just expected us to be involved in whatever he was doing at the time. So for me anyway, he had a research program and I was just expected to be part of it. And I think that's very encouraging for a young scientist to feel that they're part of something bigger, part of a program, a program of research.

That was theoretical physicist Faye Dauke on the problem of quantum gravity. Do let us know what you think of this podcast with a rating or a review wherever you listen to your podcasts and be sure to pick up a copy of the latest issue of BBC Science Focus magazine. Inside we have even more mind-bending science and try to find out what our consciousness really is this month. As ever, there's loads more inside. Now we have a message from our sister magazine, BBC Sky at Night. Back Garden Astronomy Week is back from the 2nd to the 9th of March. If you've ever wanted to get into astronomy but not known where to start,

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