The Infinite Monkey Cage - Episode 2

Episode Date: December 15, 2015

Brian Cox and Robin Ince explore the legacy of Einstein's great theory, and how a mathematical equation written 100 years ago seems to have predicted so accurately exactly how our universe works. From black holes to the expanding universe, every observation of the universe, so far, has been held up by the maths in Einstein's extraordinary work. So how was he able to predict the events and behaviour of our universe, long before the technology existed to prove he was right, and will there ever be another theory that will supersede it? Brian and Robin head up the iconic Lovell telescope at Jodrell Bank to explore Einstein's theory in action, and talk to scientists who are still probing the mysteries hidden within General Relativity.

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. Now, usually we present the Radio 4 show The Infinite Monkey Cage, but last week Ryan very kindly took me out to the studio to celebrate the 100th anniversary

of Einstein's theory of general relativity. Now, to be honest, as anyone who listens to Monkey Cage regularly knows, I didn't have a great deal of hope of teaching you very much. But I and others tried. What did you learn, Robin? Well, it all starts with thinking about falling down a lift. General relativity follows on from special relativity. That's E equals mc squared. This means space and time is really space-time. You can't have space without time or time without space.

They're inextricably linked, and gravity is the curvature of space-time. Gravity is not a force. And that g mu nu equals t mu nu, that is a tip-top equation. If anyone from another universe wants you to sum up your universe in just a few letters with one equation, well, that's the one to go with. All in all, my head feels like it is spinning. I think I have vertigo, and I don't know whether I should have vertigo anymore

now that I've found out about the geometry of space-time, but that's the way it went for me. That is not bad, actually, Robin. I'm quite surprised we're beginning to get somewhere. G mu nu equals T mu nu. Now that I know it, I'm not going to skimp on any opportunity for saying it over and over again. No. Well, you missed a few things out.

There's an 8 pi g over c to the 4 in front of the T mu mu, and you could put the cosmological constant in if you wanted. So what's the longest version you think I can get away with? Oh, the longest version? Yeah, yeah. I can get away with, not a physicist, me. Just say that g mu mu equals 8 pi t mu mu, about 25-ish. Yeah,

so a factor of 25. You can set g and c to 1. Oh, I'll stick to that, that's fine. So last week we talked about the equation itself. Now, what about the practical uses of that equation? How, over the last hundred years, it has been used? Well, we're going to look at what understanding the geometry of space-time means for our understanding of the universe, its origin and evolution, and the contents of the universe, from pulsars and quasars to black holes. Also, this gave us an excuse to climb up a radio telescope,

in this case the Lovell Telescope, and if you've never had a chance to stand in the dish of the Lovell Telescope, find a chance, somehow get in there. I highly recommend it. It's the best holiday I've had in the last ten years. But before that... We asked cosmologist... And science advisor on the film Thor, Brian.

We always have to remember that. Indeed we do. Sean Carroll, what general relativity means to his work? If you're going to be a cosmologist like me, looking at the expansion and evolution of the universe, general relativity is the first tool in your toolbox. If you're studying astrophysics and the evolution of neutron stars and black holes, then you absolutely need general relativity.

If you want to know about dark matter, even if here in the solar system, if you want to know how to tune your GPS system to figure out where you are in your car when you're turning left and right, general relativity is a tool that everyone must use. Improviser and former physics student Richard Ranch sees general relativity in art as well as science. Oddly it was Freddie Mercury I think who summed up the whole problem with his line, is this the real life, is this just fantasy? And in a sense that's what physicists are trying to find out, what's real, and it turns out that real is pretty weird. Look up to the skies and see It's not just Brian May who has a grand understanding

of the nature of physics and our universe in Queen. Look up to the skies and see. Thanks, Freddie. Little high, little low and our universe in Queen. Look up to the skies and sea. Thanks, Freddie. Back in October, we went to one of the UK's great scientific instruments, the Lovell Telescope. A hundred years after Einstein's theory, the Lovell Telescope is still testing general relativity to its limits. You see, a theory like general relativity is no good at all,

no matter how beautiful, unless its predictions agree with observation. And to observe the universe, you need vast instruments like the Lovell telescope. So we did really need to go there, didn't we? We should make this clear. It's not just an excuse to go up a telescope. I mean, we couldn't have made this programme without going up the telescope and having that brilliant day. Well, it's not far from my little house in Oldham. Well, that was my first visit there, and it is a remarkable and beautiful steel structure

right in the midst of the countryside. Not Brian's first visit there, as I often tell people, because he's used his connections many years ago to abuse the dish of the telescope by recording a D-REAM video there. That dish can only get better. many years ago, to abuse the dish of the telescope by recording a D-Ream video there. See, that's beautiful, because that is like Tom Baker in Legopolis, who, of course, he falls off the Lovell telescope, I believe, at the end. In the same way, what happened was,

the meeting of your keyboard world with... It was like, Brian, do you want to come down for the telescope? No, you keep being in a band. I'm going to stay here and observe the universe. It's a beautiful story, you regenerated. Handing the baton of knowledge to me, which I grasped with both hands and stayed, staring at the stars rather than topping at the pots. And things can only get better.

They can only get better Can only get better Tim O'Brien, Professor of Astrophysics and Associate Director of Jodrell Bank, has the keys to the telescope, so he unlocked the gate and took us into the meadow that holds one of the world's greatest instruments for interrogating the universe. What I find... You've spoilt this actually in some ways because I think this is an incredible human

made structure and yet now I've immediately had a flashback to you doing a pop video with D Ream where you misused your connections to sit in the middle of that, didn't you? Put that out of your mind. Look at this, this is a thing. This is magnificent,

but it's been besmirched by physics pop fools using their power to sit in the middle. I look at it, I don't know what Tim thinks about this, I look at it another way. I would say that this is one of the iconic architectural structures in Britain, as well as an iconic scientific structure.

Oh, I would agree with all those things. It should take its place as a valued cultural icon, and we should not pigeonhole it as merely a scientific instrument. We should say that it's part of our cultural heritage. Even if it was just a structure, you'd go, that's pretty good. Oh, and it works as well. This is really now getting incredible images, which are putting together our understanding of the universe.

One of the things I find remarkable about these precision scientific instruments that are also vast because how how precisely can you position this uh structure that what's the mass of the level 3200 tons 3200 tons of steel how precisely can you position so we measure its position to to a thousandth of a degree, its position. But the problem with that, of course, is that it's a real thing. The steel bends and flexes, and so you do get things we have to model out on that. And in fact, the whole ball of the telescope sags under its own weight. So as you tip it to a different angle, it sags and moves away from its real shape.

So all these very pragmatic, very real things that you need big spanners to deal with, all those sorts of things come into play in order to test Einstein's general theory of relativity. And you can keep it pointed at an object that's, what, three-quarters of the way or further out to the edge of the observable universe? Yeah, 12, 13 billion years the radio waves have been travelling

from some of the things we look at. So right to the edge of the observable universe, and you could do that with 3,200 tonnes of Scunthorpe steel. So how high are we going to climb and also be taken up? So the big bowl is 76 metres in diameter, 250 foot in old units. So the top edge is somewhere like 90 metres off the ground. It's actually within about a metre of the same height as the very top of the spike on the top of the Big Ben clock tower.

If you could imagine that sitting next to the Houses of Parliament, the little telescope's as high as the top of the Big Ben clock tower. This is a pearl. I've never known if I have vert tower. This is a pearl. I've never known if I have vertigo. This is a test, isn't it? This is brilliant. Going through this door is the test as to whether you've got vertigo, because that's the point at which you realise you're now a long way above the ground.

Right, OK. You see down. So now we're going to find out if this is also going to be a special with Claudia Hammond about how I cured my vertigo. Here we go. We've got intellect. Oh. Oh, there we are. Oh, listen to that.

Oh, that is... So what is, I mean, this, the original dish, what is it made of? It's just steel. The key thing about it is it's the right shape. We have birds living in here as well. So it's the right shape. So it's a paraboloid

in the shape of a parabola and it collects, reflects all the radio waves and brings them to a single focus which is where you put your radio receiver. So the shape's the key thing. It's not a cliched use of the word dizzying. This is the thing that gathers information about

the distant reaches of the universe and it's all focused in here onto the radio receiver up reaches of the universe and it's all focused in here onto the radio receiver up there on the tower and it allows us to tell the story of the origin and evolution of the universe. I think it's a wonderful thing. And test this theory, this hundred year old theory.

Wouldn't you have loved to show Einstein round the level telescope? Yeah, absolutely. He only just missed it in fact. It would have been under construction. When did he die? He died in 1955. Yeah, it would have been, actually, yeah. It would have been rising up already from the Cheshire Fields,

poking up above the hedgerows. So it started in 1952 and finished in 1957. Yeah, so it just overlaps with the end of Einstein's life and then 50 years later keeps proving him not wrong. That's right, yeah, yeah. You don't really know whether he's right. How's your vertigo, Robin? There's no where I can go down.

I just remembered, as a kid I was able to climb but I wasn't able to abseil. So this is where I'm living now. I don't know if you could just drop tinned meat on me every now and again. It's very peaceful up here, actually. It is. It was very peaceful up here, actually. It is. It was till I got here.

While we were up there, I think we were so awed just by the surroundings that perhaps we didn't talk as much as we should have done about general relativity. But pulsars are a vital part of understanding general relativity, aren't they? They're essentially clocks. General relativity is a theory of space and time. And pulsars are collapsed stars, perhaps the size of a city, 10 kilometres across, but with a mass one and a half times that of our sun.

And they spin many, many times a second on their axis. So they keep perfect time, which means it's like throwing a watch into some strong gravitational field and watching how the watch ticks. So when they first started monitoring pulsars, I mean, what were they observing? Telescopes like the Lovell telescope

can observe the regular radio pulses that are emitted from pulsars, which tick the most accurate watches or some of the most accurate watches in the universe that allow you to probe the structure and curvature of space and time. Open your eyes, look up to the skies and see. So we're currently in Jodrell Bank. We're actually in the control room of Jodrell Bank.

Lovell Telescope is behind us. But why are we here? This is the first thing that we're doing. We're joined by Tim O'Brien and Sarah Bridle. And for a lot of people, they might think, well, general relativity, that's pretty much dealt with by equations, isn't it? You don't need to create a really big telescope.

Now, possibly, I think, still currently the third biggest in the world, but soon maybe the fourth biggest in the world. It's a magnificent human-made structure, and many people will probably think that general relativity, well, that's just maths, isn't it, Einstein? It just scribbles down equations. Why do you need a great big third or fourth biggest telescope?

I think Robin's thinking of sort of a pseudo-Feynman story. You're imagining Einstein walking into this control room, aren't you? And looking up at that thing and saying, don't you trust me? Yeah, I've done the equations. Why have you built the thing? Yeah, I mean, we obviously use this telescope for lots of different things. So it's a real multi-purpose instrument. So it looks at radio waves coming from space that will tell us lots of stuff about stars forming, stars dying, distant galaxies. But there's a few key areas in which general relativity is applied.

One is pulsars. Another is gravitational lenses, so how space-time is distorted by mass. And we can see the effect of that in these observations. In fact, the very first gravitational lens ever discovered was discovered from observations with this telescope back in the 1970s. So what is gravitational lensing? I mean, I've seen posters all round this building on gravitational lensing.

Sarah, gravitational lensing. Yeah, so basically in gravitational lensing, the space-time gets distorted by the presence of heavy stuff, lots of dark matter, for example. So space-time gets curved and then light travels towards us and the light rays get bent by this curved space-time. So it's a bit like if you look, say, through your bathroom window and the objects behind that bathroom window you see are distorted.

So, in fact, all galaxies in the universe have been distorted very, very slightly by the curved space-etime, by this gravitational lensing effect. So by looking at the shapes of distant galaxies, we can reconstruct the distribution of mass in the universe, make a map of the dark matter in the universe using gravitational lensing. So without general relativity, would we be looking up at the sky and going, that galaxy should not be there, and there would be a confusion if, I'll clumsily say, the geography of the sky would be somehow confused,

because without general relativity, we wouldn't... That's right, yeah. Yeah, so it's basically, you can do some calculations without general relativity, which are wrong by a factor of two, so you'd actually get the wrong impression about what was out there in the universe if you didn't use general relativity. In terms of during Einstein's lifetime what were the most important observations

that were made? We had Arthur Eddington in 1919 that was that was the big moment in terms of front page splashes etc. What else after that? Well just a few years after Einstein published these equations in 1915 we discovered that the universe was expanding so Hubble and collaborators found that the distant galaxies were all moving away from us. And that was then, you know, became a solution of Einstein's equations, an expanding universe. The 1930s, we discovered dark matter,

the first evidence for dark matter, which again has to be folded in as a component of sort of mass energy in his equations. And then in the, actually in the 1940s, there was the first suggestions that there might be a Big Bang, a remnant radiation from the Big Bang was predicted, but it wasn't until the 1960s that that actually was detected. So there were a series of things

that actually all fitted into that framework. You know, it was a remarkable sort of result, I think. General relativity is a 100-year-old theory. It's still at the frontier of modern physics today. Will it remain so, you think, for the foreseeable future? It's certainly at the frontier today. In fact, you know, as we stand here at Jodrell Bank, basically 24 hours a day, that telescope is doing observations

that rely on Einstein's's theory general theory of relativity published 100 years ago and that's that's still the framework in which we interpret these observations and it still works for us and we'll use it as long as it continues to work for us yeah absolutely i mean general relativity underpins all of our forecasts and expectations about what we see when we look at cosmological observations of the universe. And so when we make those observations, we're actually testing general relativity by seeing if it fits the observations or not. And there's certainly a lot of people in cosmology today

who are wondering whether we'll still get observations which fit this theory. It's interesting you use the... Tim used the word framework. So it's not just a theory that makes predictions that we test. It's the theory that we use to interpret pretty much every observation that we make in modern astronomy. If we were looking up in the sky, if we had our radio eyes looking up in the sky now, looking straight through these clouds, which is handy from England, out into the universe, we see these points of light, scattered radio waves, scattered around the sky. They are generated by

supermassive black holes in the distant universe that's where that energy is coming from that we see that was the very first solution of einstein's field equations by carl schwarzschild just a year after einstein published those equations and there we are they're still there in the sky above us and we're observing them with this telescope now so it's really basic isn't it you wouldn't understand the radio sky without that theory. You'd look at it and say, I don't know what's happening in that sky. Yeah, and we found those things first in the 1940s, and it wasn't until the end of the 1960s

that it was realised that the black holes were the energy source. But the black holes themselves had been predicted by Einstein's equations decades before. Do you think Einstein would have been surprised to see that his theory lasted 100 years and survived such precision tests? Or do you think he would have, the stories are that he thought that it was so beautiful that it couldn't possibly fail any experimental tests. Maybe that's overselling it a bit. But do you think he'd have been surprised and delighted? Yes, I think it's amazing that Einstein's general relativity

still fits all the data today. And one of the really interesting things that's happened over the years is that it seems like we only understand only 5% of what the universe is made of. There seems to be weird dark matter, weird stuff we call dark energy, which seems to make up the majority of the contents of the universe. So then we're looking at these observations and we're trying to understand, well, how can we tally all of that together? And since we don't really know what any of this, most of the universe is, then you have to ask the

question, well, maybe there's something wrong with the fundamental theory that we've got to describe the universe. You know, in a sense, we would love to prove Einstein wrong because that would be a great step forward in our understanding of physics. But in fact, we're just continually proving him ever more right, I think, at the moment. I've got loads of emails in my inbox of people who've proved Einstein wrong. Surely one of them will be right. So for the purposes of this programme,

and in fact for the purposes of physics at large, we can take it that Einstein remains right? Well, we can certainly for the purposes of my inbox. But actually, we've talked to the observational astronomers there. It's worth talking to a theorist, a modeller of universes, to see where the boundaries of general relativity might lie. So we went back to Durham to talk to Professor Carlos Frank might lie. So we went back to Durham to talk to Professor Carlos Frank. Why don't we go back to Durham? Why don't we just do it the

first time we went to Durham? This has been very poorly thought out. Yeah, I mean, today, actually, it's paradoxical that the universe, we know a lot more about the universe than we know about Robin Ince or about a human being. Even though the universe is very big and seemingly very complex, it is the application of Einstein's theory that simplifies it and makes it in fact a very, very simple object to study, far simpler than a human being, let alone a human mind. And so it is thanks to Einstein that we conceive, at least us cosmologists of the universe, as a simple system. And we're actually lucky that we are physicists and not biologists because we deal with a system

that is easy to understand and we can calculate things and we can make predictions, which is what physics is all about. Whereas poor biological colleagues, they have a really hard time. They're studying something far more complex and they haven't had the range time

to simplify the system. So all we know about cosmology today is possible thanks to the genius of this one man. I just wanted to ask what the cutting edge of research into general relativity itself is today. Right. So general relativity is part and parcel of our...

It's a tool of the trade for us today. However, one of the things that has people very puzzled is one of the most dramatic discoveries in science of the last 15 years, and that is that our universe is going to be berserk. So our universe is not behaving as Einstein thought it would, and as you might expect any reasonable universe to behave, a universe has gone into a phase in which it's expanding at an ever-accelerating rate. So the expansion is getting worse and worse and worse and worse. Now, that is exactly not what you would expect because if all the universe was matter, mass, mass produces gravity.

As the Americans like to say, gravity sucks, meaning that gravity pulls. So gravity would start to slow down the expansion of the universe because it's attracting matter onto itself. And yet, astronomers discovered about 15 years ago that the opposite is happening. Our universe is accelerating in its expansion. The expansion is getting faster and faster and faster. Why is it doing this? What's got into our universe? And we really don't know. And one sign of when scientists don't know what they're talking about is they come up with a very elegant label for what they're doing. So we call this dark energy. Isn't

that beautiful? Suggestive dark energy. But to me, it suggests we have no clue what we're doing. And that's exactly what is happening. Now, there are two explanations. I don't know which one is more distasteful than the other for the dark energy. One of them is that Mr. Einstein was almost right but not quite right, and that the Einstein equations need to be modified. And we say that, we shiver, we shake before we say something like that, because Einstein's equations are so beautiful, so well tested,

that if you want to tamper with them, you better do it in a very careful way. And that's what many people are doing now, and under the label of modified gravity, trying to modify Einstein's equations subtly, subtly. You cannot do it in a very impertinent way because he'll come to haunt you because, as I said, relativity is tested. But one way to understand dark energy

is that there's more to gravity than Einstein. So that's one. The other explanation for this accelerated expansion of the universe is even more distasteful. It has to do with the multiverse. So this explanation is that in fact there's not just one universe, but there's a multitude of universes.

Now, in this view of the multiverse, there are many, many instances of the universe. Some have general relativity, others don't. Some have general relativity, others don't. Some have dark energies and others don't. But in this vision, you could imagine that relativity wouldn't really necessarily apply in all these parts of the multiverse. And I feel very sorry for, well, there wouldn't be any beings, but if there were beings in the universe without general relativity, they would really be missing out on something great. So for all of the talk over the last two shows,

we still have one big stumbling block, don't we? Which is the idea of bringing together Einstein and quantum mechanics. Yeah, ultimately the problem might be a theoretical one in that we have two superb theoretical structures that describe the universe on the very large scales, that's general relativity, and the universe on the very smallest scales. And in fact, the rest of the universe, which is quantum theory. Here's Sean Carroll, science advisor on Thor.

I think there's no question we need a better theory of gravity. As wonderful as general relativity is, it's my favorite single theory, it doesn't play well with quantum mechanics. And quantum mechanics is sort of more important than general relativity in some sense. General relativity, even though it changed our notions of what space and time were, it still spoke the language of classical Newtonian mechanics. There's stuff, which is the curvature of space-time. It evolves. You can observe it perfectly. It's deterministic and so forth.

And we know that the world is fundamentally quantum mechanical. And that plays along with the fact that general relativity makes predictions we don't think can be right. General relativity predicts that the curvature of space-time becomes infinitely big at certain places like the Big Bang. So we need a better theory if we're going to actually understand what happened at the Big Bang. So we need a better theory if we're going to actually understand what happened at the Big Bang. We needed a theory that at the very least includes quantum gravity and might end up looking completely different. Whether it will be as beautiful as general relativity is not my job to say. I have a feeling that the correct theory of the world will be beautiful, but our job as physicists is just to find the theory and then we'll decide afterwards whether it's beautiful or not.

Will the idea of space-time and the geometry, this stuff, the fabric of the universe, will that survive, do you think, in any form? Or is it some kind of emergent property and there'll be a deeper explanation for it? My own guess is that space-time is definitely emergent. In fact, I think that space has almost no hope of surviving to be a fundamental part of our universe. And this is one of the things I'm doing research on myself right now. How does space, the very idea of space, emerge from a more fundamental quantum description?

Time has a chance of surviving. That's kind of an open question. There's sort of different versions of quantum mechanics, and some of them time plays a fundamental role, and others time itself is emergent. So we have to, you know, take Einstein's example seriously, not in promoting space time, but in being open and willing to go where the theory wants us to follow it, rather than deciding ahead of time what the answer's going to be. Well, that's worrying, isn't it? No space and no time. Where am I going to live? Typical comedian. Self-centred.

The universe doesn't care about you, you know. It's not about giving you a home. That's not what the universe is there for. A home for comedy. That's probably a BBC channel. Yeah. So where does this take us, then? Well, we have a theory, 100 years after it was first published that has passed every experimental test that's been thrown at it and yet that we think cannot be the whole story.

So it's an intriguing position for physics to be in at the turn of the 21st century. That's what I love about science. It always ends with to be continued. It does. And Carlos Frank has got an extremely worrying theory about how it might continue. There must be something bigger than relativity.

What shape it will take, whether it would be a marriage with quantum physics, whether it would be a stroke of genius by a new Einstein, we can only speculate because we haven't got the answer. So I'm hoping there will be, you know, Robin Einstein or somebody who will come along. No one will be more surprised than me if Robin Einstein comes along and solves the problem.

I would prefer to play a Einstein movie. Well, in this universe, but in another universe, I'm really clever, apparently. That's why I always read about the multiverse, the hope of someone better than me. You'll have a thing now on the train back from Durham, you'll have my big London ring you up and go, I've got it! Well, fancy that.

In the infinite monkey cage, that naughty monkey in the infinite monkey cage, without your trousers in the infinite monkey cage. Turned out nice again. In the infinite monkey cage. Till now, nice again. 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. 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. you