The Infinite Monkey Cage - Episode 1

Episode Date: December 8, 2015

It's 100 years since the publication of Einstein's great theory, and arguably one of the greatest scientific theories of all time. To mark the occasion, Brian Cox takes Robin Ince on a guided tour of General Relativity. With the help of some of the world's leading cosmologists, and a comedian or two, they explore the notions of space time, falling elevators, trampolines and bowling balls, and what was wrong with Newton's apple. It's a whistle stop tour of all you'll ever need to know about gravity and how a mathematical equation written 100 years ago predicted everything from black holes to the Big Bang, to our expanding universe, long before there was any proof that these extraordinary phenomena existed.

In our new podcast, Nature Answers, rural stories from a changing planet, we are traveling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcasts. This is the first radio ad you can smell. The new Cinnabon pull apart only at Wendy's. It's ooey gooey and just five bucks with a small coffee all day long. Taxes extra at participating Wendy's until May 5th. Terms and conditions apply.

This is a download from the BBC. To find out more, visit bbc.co.uk slash Radio 4. Hello, I'm Robin Ince. And I'm Brian Cox. And we spend most of our time on Radio 4 presenting the science panel show The Infinite Monkey Cage, but today we're doing something different. We're presenting a documentary

about one of the most wonderful ideas to come out of a human mind. So like all documentaries, we are going to take you on a journey. Though in this case it's quite a short journey, falling down a lift shaft. Or more correctly, according to Einstein's theory of general relativity, a journey floating in an inertial frame of reference waiting for the bottom of the lift shaft to hit us. frame of reference waiting for the bottom of the lift shaft to hit us. Ground for perfumery, stationery and leather goods, wigs and haberdashery, kitchenware and food.

Are you being served is and was always meant to be, I think, a tutorial on general relativity. Good. So, ten years ago, we celebrated the centenary of special relativity, which is E equals MC squared, the most famous equation to exist in the history of human civilisation. Which gives me some hope, actually, for popular culture, because the fact that there is a most famous equation means that we're not floating in an all-enveloping darkness of trivia. See, that's the problem, though. It's very easy. When you get one of those shows, the countdown of the top ten equations, we always know E equals mc squared is going to be number one,

but no-one knows the position of any of the other equations. F equals ma. Oh, that probably would be number two, wouldn't it? Anyway, so E equals mc squared. Brian, what does that mean? Well, it really means that energy and mass are interchangeable, but it comes from special relativity, which is a theory of space and time. Space and time are no longer to be considered separate entities.

They're merged together into a structure called spacetime. So 10 years after E equals mc squared, now we celebrate what? General relativity. General relativity. I think the majority of people wouldn't necessarily know the equation for general relativity, so that is...

Well, the equation is g mu nu equals t mu nu, with a few pi's and Newton's gravitational contents scattered all over the place. But essentially, what it means is that space-time can curve. And in the immortal words of the great physicist John Wheeler,

matter and energy tell space-time how to curve, and space-time tells matter how to move. So, g mu nu equals t mu nu, but why? Why was this? 8 pi g over c to the 4 t mu mu. Nu mu. Mu nu.

This is, it's lovely, isn't it, when it has one moment it's Einstein, the next moment it's Edward Lear. But what is it? What is it about this particular idea that makes it so admired by physicists, cosmologists and, indeed, failed physics students? Because it's right, primarily. Yeah, no, but there's lots of other physics that's right,

but you don't get people going on about it as much as... I mean... Which bits? It's the first time the universe appears in an equation. It's the first time that mankind attempts to

write down some maths that describes the entire universe and everything in it. The general theory of relativity is the most beautiful physical theory ever invented. I think that that's a very, very defensible statement. And there are some pretty beautiful physical theories out there. But the way that it's self-contained and elegant and very, very compact and precise and how difficult it is to mess with it. You know, like every time we try to fix it or make it better, we end up making it worse.

What he did with general relativity is of such a different scale, it's almost impossible to describe. He gave us a fundamentally new language and a totally, totally different way of thinking about the world. I can't really parallel it with anything else in the history of knowledge that I know of. The reason generation is beautiful because it was one of the great genuine eureka moments where somebody through sheer brainpower realized that we were looking at the universe the wrong way. And that actually the relationship between what's in there and what space around them and all that

is completely different to what we thought. Please don't do the journey. The journey through the equations is really long. But the results, oh, the results are beautiful. So we've been warned by Dara not to go on the mathematical journey so would you say that perhaps two half hours on Radio 4

won't manage to be quite enough to cover what is normally done in three years of undergraduate physics? No, because the story of what the mathematics tells you is explicable and understandable as we hope to show Let us see if we can achieve that. We will return to the cosmologists. But first, we set a just-a-minute task for three physics students who were wooed away from physics by show business.

Quite the opposite, of course, of your own journey, Brian. My name's Ben Miller. I am a comic actor, and I started life as a physicist. I did a degree in physics, and I did about half a PhD in physics as well. My name is Dara O'Brien. I have a BSc in mathematical physics and mathematics from University College Dublin, awarded sometime in the mid-'90s via a very circuitous route around the department. My name is Richard Vranch,

and although I now work as a comedian improvising at the Comedy Store, I did study physics, and I did a PhD, and I was briefly a fellow of St John's Oxford. I'm a sort of a lapsed physicist, I suppose. So, Richard Vranch, you have one minute on general relativity, starting now. General relativity is a lot more complicated than it looks, but that's true of a lot of physics. Even Einstein's most famous equation, E equals mc squared, contains a lot of hidden treachery. So even in that, it's not quite as complicated. It's much more complicated

than, oh, damn. There we go. A challenge, hesitation or repetition of damn. Dara, you have 33 seconds on general relativity, starting now. The best way to explain general relativity is that it gives a of the view of the universe around us that shows that matter, mass of an object, shapes the space that surrounds it, that the very nature of the surrounding... Oh, I know I said surround twice. But how can you not say space twice? There's no, like, euphemism for space.

Space is space. This is impossible. Dara, you correctly challenged yourself there with repetition. But as challenging yourself, we're actually going to pass it over to Ben Miller. Ben Miller, you have seven seconds on general relativity, starting now. General relativity is a theory proposed

by the physicist Albert Einstein. He finished in 1915. It essentially describes gravity as an acceleration within a higher dimensional space rather than a force which occurs between objects that have mass. Its implications are enormous because it teaches us not only that distant galaxies will have their light red-shifted because they are moving away from us, but also if that light passes through a gravitational field. If you like, the light has to struggle up through the four-dimensional well of space-time to reach our eyes and becomes stretched and crimson as a result. See, I avoided red.

Well done, Ben. But Richard Vranch has challenged the very nature of the time measurement we are using for this particular take on Just A Minute. So, Richard Vranch, you have however long I suppose it's going to take to explain how the nature of time that we're using is in some ways forfeiting the entire conceit. If you did have a minute to describe general relativity and you were travelling quite quickly, the good news is you'd have just over a minute because people looking at you would see your minute clock ticking down slightly more slowly than you saw it, so you'd have longer to say this than you thought you had,

though it wouldn't make it any easier. Oh, we have a challenge there from Professor Brian Cox. Yeah, he's not at liberty to change the rate of passage of time in his own frame of reference. I think that is a correct challenge, though, to be honest, I don't really have any idea, but you have done a lot of study on this thing, so I'm going to give it to you. So, Brian Cox, you win that round.

There is no choice. You get very cross if you don't win things. Now, it's time to regain control of this programme. Rest the tiller back from the showbiz hordes. We are talking about the most celebrated theory in all of physics. So what motivated Einstein to come up with this radical new theory of gravity, which is, after all, a totally different way of thinking about our universe? Sean Carroll is a leading cosmologist at Caltech. Yeah, he was also a scientific advisor on the Hollywood film Thor, so a little bit showbiz-y. It's always very interesting to see how genius physicists do their

work because they're all different. You know, the styles are always different. One thing that actually strikes me about the personalities of many successful genius physicists over the course of history is how stubborn they are. He just got this thing in his mind that he was going to fit gravity into special relativity. And the thing that was weird about it was that there was very little experimental demand for such a theory. You know, we had Isaac Newton's theory of gravity. It did perfectly well, as far as anyone knew. There was like a couple of things here and there, like the orbit of Mercury maybe didn't quite fit. But mostly, Einstein was driven by the demand that all of our different

pieces fit together when it comes to our theories of physics. He was a pioneer of special relativity, and he knew that Newton's theory of gravity, as good as it was, didn't fit with special relativity. We didn't need to make them fit in terms of fitting the data at the time, but this just bugged him, this inconsistency. And so he just, you know, without much experimental input at all, he made conceptual leap after conceptual leap. And to his enormous credit, he didn't get stuck in a rut, you know, like he was willing to change his mind and do different things. And, you know, later in life, famously, people make fun of Einstein for getting stuck in a rut. But, you know, if you have Einstein's track record, I think that you get some credit later on in life no matter what you do because you were so right so many times.

I'm going to give you the slack. So this is where I have the first kind of impasse. So Newton, his idea of gravity, again, one of the most famous ideas in the whole history of science, it's wrong. There's something that doesn't work out when Einstein looks at it. That's right. We now have a more accurate theory. So Newton's theory was that there is a force between massive objects like the Earth and the Sun which pulls them together.

Einstein's radical suggestion, which leads to a more accurate theory, is no. There is no magical force between objects that pulls them together. What we're feeling when we experience the force of gravity is the geometry of the universe itself. So why is my apple falling? Well, Einstein would say the apple isn't falling. The apple is minding its own business with no forces acting on it, travelling a perfectly straight line through space-time and the earth gets in the way. So the picture really is that the ground is accelerating up to meet the apple. And this is where the happiest thought comes in which is it's not often a happiest thought is plummeting to the ground in a lift though here's former physics

student ben miller explaining that happy thought of einstein's what if i was in a lift in space stick with it because it's brilliant so okay now imagine i'm in a lift and i'm so far away from any gravity that there's no gravitational effect on me at all. He said, if I was in this lift and the lift were accelerated, let's say up, you know, he said, I would feel like the bottom of the lift was pushing on my feet. So I would feel like I had weight. And you have to be Albert Einstein to think of this. He said, OK, so if I'm in a lift in space and the lift accelerates,

I feel like I've got weight. What if weight is an effect of acceleration? Can we just ask you, Mr Inman, when you say, I'm free, you mean that very much from the perspective of the forces of the universe? He means, I'm free-falling. That's what he means. I'm in free-fall, which means we're no forces acting. That's what he meant. Mr Humphreys, are you free-falling? I'm free-falling.

So this is just about gravity then. So that's what we're talking about then. It illuminates us in terms of what gravity means to the universe. Well, it's much more than that, which is why general relativity is one of the pillars of 21st century physics, of my 20th century. It's about space and time. And it's also a theory that applies not just to a solar system

or the Earth going around the sun. It applies to the whole universe. Well, that means we need, obviously, to journey further, not only down the lift shaft, but also to Durham. Yeah, you see, it's a segue, isn't it? And we went to see Carlos Frank, who wonderfully, in the reception area outside his office, actually has a bust of Albert Einstein,

which watches you as you walk around. So when he's thinking of ideas, he makes sure that Einstein's looking at him all the time. So here's Professor Carlos Frenk. Everything we know about the universe, it ultimately boils down to the ability to solve Einstein's equation, the Big Bang, the expansion of the universe, the origin of the chemical elements, the existence of dark matter, the formation of galaxies, all can be traced back to this man thinking deeply around 1916. So special relativity, she said 1905,

E equals mc squared, which is the thing that is probably most famous for in the public mind, the most famous equation in physics. But then, so space-time enters that equation, or that theory, as something you can kind of take it or leave it. It's quite nice in special relativity, isn't it? Space-time.

Do you think he had any inkling that that concept could be turned into a theory of gravity and a theory of cosmology, the theory of the universe, back in 1905? Well, I think I'm now second-guessing one of the greatest minds that humanity has produced, but I can see a link between Einstein's thinking in 1905 and then his thinking 10 years later, or a bit more than that, when he developed general relativity.

Because when he was thinking about special relativity, he had objects that were only in constant motion, moving always with the same speed. And then the minute he said, well, what happens if the speed changes? Then that change of speed is called an acceleration. Accelerations are produced by forces. And then at that point, he had to think about forces,

gravitational forces, for example. And he had a certain reluctance to think in terms of forces. So when he started thinking about objects changing speed, he thought, well, how do you accelerate them? And here was the genius. He then said, you don't need a force. You just need to change the geometry of spacetime, and that will cause acceleration. to change the geometry of space-time and that will cause acceleration. So that was, I think, if you have to put your finger on where the genius is in Einstein, is in realizing that you can do away with forces and explain everything in terms of

geometry of space-time. Now the first time you hear this, you'll be traumatized like I did the first time. What on earth? Geometry of space-time? What do you mean space? What geometry? Well, it takes a little while to get used to the idea. So we physicists like to have analogies. So you imagine, for example, a cannonball on a rubber sheet. So the rubber sheet is space. And first it's flat flat then you put a cannonball and it bends so that gives you a kind of feeling for the distortions that gravitational heavy objects can produce on in this case you're the fabric of space and then it takes a further leap of imagination and probably a few years of

thinking about this to add time into the equation and to recognise, well, time is the same as space and gravity distorts not just space like a rubber sheet, but the whole of space-time. There is something, when we were sitting opposite Carlos there, the excitement, the gleam in his eyes, the talk of the fact that he is just, there he is having his Cocoa Pops in the morning and thinking, I'm just thinking about general relativity.

And the beauty, that's what he kept stressing when we were sitting in his office, the beauty of the theory. Yeah, I think it's something that everybody who studies general relativity in any depth experiences, because although mathematically, technically, it's a complicated theory, in terms of the basic ideas, it's elegant and simple. See, we already had the idea of space-time. That dates back to special relativity, 1905, 1906. And we had Newton's laws, which tell us there's a force between objects. That's what gravity is, a force between massive objects.

What Einstein does is simplify that and say, no, there isn't a force, a fundamental force between massive objects. There's just space-time and there's the way that massive objects curve and warp and bend space-time. See, that's what I find exciting as well, which is he's made things less complex, which means that I would have to spend even more years studying it to find out that things are much simpler than we first thought. Which is why I went to Imperial College to see Professor of Theoretical Physics, Faye Dowker, where she's doing her introductory lecture on general relativity. Unfortunately, it's an introductory lecture for fourth year physics students. So let's see how long it takes for me to get a little bit lost.

it takes for me to get a little bit lost. I'm currently sitting in the front of a lecture hall to listen to Faye Dowker's introductory physics lecture and this is the first time I've been in a university lecture hall, I think since a lecture on Andrew Marvell, the poet, in probably 1989. And on the blackboard Faye has just put that gravity should be innate, inherent and essential to matter. She hasn't finished writing the quote yet. Ac ar y bwrdd gofyn, mae Ffey wedi dweud y bydd y gwirfoddolrwydd yn unig, yn herenol ac yn bwysig i fater. Nid yw hi wedi di-synnu'r cyfeirio hyd yn oed. Rwy'n mynd i weld sut i fynd i'r cyfan cyn i mi fod yn bwysig ac yn amlwg. Diolch i'r cwrs ar gyfer cyfathrebu cyffredinol. Mae'r GIG yn un o'r trefniadau mawr o wybodaeth gwydnodol, mae GR yn cynnig i'r cyfnod newydd,

ffisigol, dynamig, sy'n ffyrdd ffyrdd dynamig, ffabrig, sy'n ffyrdd, sy'n ffyrdd, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, sy'n gwrth-dwy, and warps and ripples and carries energy. And the reason that general relativity is so fundamental and the reason that it constituted such a great revolution in physics is that this fabric, this four-dimensional fabric, is space-time itself. So you're all right at this point, Robin? I think for the first 20 minutes I'm fine. Even the fourth-dimension stuff, I think we've had enough car journeys with you explaining that to me,

that some of it, some of it has been absorbed. But, well, we're just coming up to the point now. A Lorentz transform set of coordinates. And if we take the Lorentz transformation to be going in the positive x direction, then the Lorentz... So it's there now, and I think if there is a graph which can be made out of my attempts to understand contemporary physics, then there is always a downturn when we get to Lorentz. It is the Lorentz rule of my incomprehension.

General relativity is a difficult theory. I was taught it, actually, by Faye's dad in my final year at the University of Manchester. And I sort of understood it a bit then. But you have to hear it more than once and you have to think about it many more times than once. And actually, it was only relatively recently, talking to Faye, in fact, and having explained for the 15th time

that I began to really get a clear picture of what general relativity is all about. Is this the beginning of a new career for you? Are you going to leave comedy behind and move into the real world? Some people say I left it behind a long time ago and became a performance artist, obviously. But I just found it very exciting to pick up on other people's excitement. Again, this idea at any time where physics is described as some kind of cold pursuit. And then talking with fame, with other people as well, about the fact that this was front page news as well, not 100 years ago, 96 years ago, 1919.

Einstein's theory, there are observations made that go, yep, this is a good theory. Arthur Eddington. But how do you make those observations? Well, Eddington observed the bending of starlight around the sun. And to be able to see stars close to the sun, you need to obscure the sun. So he ran an expedition to observe a total solar eclipse. And the reason for that is that the sun's light is blocked out by the moon so you can see the stars behind it. And he measured the bending of starlight. And that's why I think this was front page news because it's a very simple concept and an evocative concept. The words are that you're seeing starlight bent by the sun.

And the reason that the starlight curves around the sun is because space and time themselves are curved by the mass of the sun. And that's an easy thing to write headlines about, even if the mathematics is extremely complicated. I love that image there as well of just the fact the front page news, a man picking up his Times newspaper as he's dunking his toasty soldier into a runny egg and going, I told you, Molly, I told you it is curved. I was right all along.

Anyway, we asked cosmologists John Eleven and Brian Green, why was this headline news? Well, I think there's probably two reasons. One reason is scientifically it was just opened up an entire world, completely changed the way we viewed everything. There were consequences of general relativity that even Einstein didn't foresee. And so it is incredibly exciting to follow a theory to conclusions you didn't foresee. And that's quite thrilling. But I think there's also was kind of a political reason that the world was in trouble. And there was a lot of strife and a lot of nationalism and coming out of

World War. And I think Einstein represented something else to people that transcended that kind of nationalism. That was a gift from humanity. It was a humanity's accomplishment in some sense. Yeah. The other part of it too is that Einstein was described as having toppled Isaac Newton, right? So you had this giant of science who had given the world an understanding they thought of the theory of gravity. And here comes Einstein to give a radically distinct picture that went head to head with Newton's approach in these eclipse observations of 1919. And when the eclipse observations showed that Einstein was right and Newton was wrong, that's when the New York Times, that's when the Herald Tribune, that's when the London Times, that's when the papers around the world blared out these headlines that Einstein had toppled Newton, and that's when the world took notice. The wonderful thing about general relativity is we've heard throughout this program

about this complex theory you only begin to learn about in the fourth year of a physics degree describes the whole universe, and it's an act of genius. Undoubtedly all those things are true but at its heart there are very simple concepts and essentially what general relativity says is that we can dispense with this force of gravity and we can replace it with just the way that objects move around in curved space. And it's something that's easier in that sense than the Newtonian theory. Well, I asked Faye if there was a way of kind of comprehending it without having to wait for an eclipse.

You can have the experience which tells you that there's no force of gravity pulling you down. So the idea that there is a force of gravity pulling you down is at odds with your experience, your actual experience, which is that your chair pushes up on you. It's pushing up on you right now. You can feel it. You do not feel any force acting on you, pulling you down. What you feel is your chair pushing the pressure of your chair upwards on your bottom right now, as you're sitting there in your chair. And that's totally in accord with general relativity,

but at odds with the Newtonian theory. The Newtonian theory says that there's a force pushing up on you from your chair, but also a force pulling you down, the force of gravity pulling you down towards the centre of the Earth. Sorry, stop for a moment. I want everyone just to think, because the people are sitting there now. Yes, yes. And they need to feel that.

They do need to feel it. This is, for me, a perfect example, probably the best example, of the power of physics and the power of thought. I mean, we have a theory that came essentially from Einstein's head, a remarkable theory, which makes extraordinary predictions about the universe. It predicts the existence of black holes. It predicted the Big Bang. It describes the orbits of planets around stars. It describes the orbits of neutron stars, of pulsars around other pulsars, of pulsars around black holes, the behaviour of the most exotic objects we've yet discovered in the universe. And indeed, the behaviour of the universe itself is predicted with accuracy,

as far as we can tell, by this single, simple theory. So hopefully, even if you haven't fully grasped what g mu nu equals t mu nu necessarily entails, you have got perhaps a little bit of a change of the sense of the feeling of gravity around you. And next week we look to the

future of general relativity. I think they're going to keep it going for a while, aren't they? As a system of running a universe. It works. What is the future, John Relativity? They got rid of it. It just... They've got new universal rules. And do remember, there's no unique definition

of past, present and future in relativity. Without your trousers In the infinite monkey cage Right, I think we'll just sit here and just feel our chairs. For nearly 90 years, BBC Radio listeners have been there for thousands of homeless and vulnerable people across the UK by supporting the work of St Martin-in-the-Fields.

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The new Cinnabon Pull Apart, only at Wendy's. It's ooey, gooey, and just five bucks for the small coffee all day long. Taxes extra at participating Wendy's until May 5th. Terms and conditions apply. In our new podcast, Nature Answers, rural stories from a changing planet we are traveling with you to Uganda and Ghana to meet the people on the front lines of climate change we will share stories of how they are thriving using lessons learned from nature and good news it is working learn more by listening to nature answers wherever you get your podcasts.