The Infinite Monkey Cage - Jo Brand's Quantum World

Episode Date: December 13, 2023

Brian Cox and Robin Ince are subject to a non-hostile takeover by comedian and non-physicist Jo Brand, as she challenges the panel to help her understand the almost unbelievable world of cheeky particles who may or may not be in several places at once. To help Jo get to grips with the bizarre and strange world of our quantum universe, Brian and Robin are joined by theoretical physicist Prof Ben Allanach from the University of Cambridge and cosmologist Prof Fay Dowker from Imperial College London, who introduce Jo to the weird and wonderful ways of quantum theory, dead and alive cats and multiverses. Executive Producer: Alexandra Feachem.

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. BBC Sounds, music, radio, podcasts. Hello, I'm Brian Cox. I'm Robin Ince. And I'm Joe Brand. And this is my hostile takeover of the infinite monkey cage. Actually, it wasn't very hostile because Brian and Robin were very easily overpowered. We were. This show is going to be a takeover of the infinite monkey cage actually it wasn't very hostile because brian and robin were

very easily overpowered we were this show is going to be a little different because usually on monkey cage we we sit down together and we say we'd like to do a show about something that's interesting and we have lots of fun inviting guests but this time we've decided that we're going to do something different it was actually quite frightening it's one of the rarest moments of anything where i actually saw the physicist brian cox showing empathy to a guest because it's not generally something that he's been programmed to do so it was one of the strangest things to him suddenly just leaning forward and going but what would you like to talk about and i've never seen that you even met their eye without flinching and uh and uh joe so i thought oh thank heavens we're going to escape

from physics because brian always goes physics got any physics got any physics black holes physics physics physics and so we're oh what's joe going to come up with joe brown's going to come up with and joe said quantum mechanics which feels to me like a payola scam in the making to be quite honest so joe why what why did you choose that subject well i i have the absolute minimum amount of knowledge i think it's very interesting because to me it's not like science at all it's kind of like thinking something up and then just saying what about that and people going oh yes you might be right um that's theoretical physics yeah don't tell anyone we've been and i have to say uh um i i've tried who's read a brief history of time

three four quite a few i think the question though you change that you go who's started a brief history of time well i've done that about 14 times not brief enough in my opinion that brief history of time because like a page would have been good but it's not is it so um i kind of just want to i want to learn if quantum mechanics is what i really think it is it probably isn't so this is the first time we've done this on the show. So this genuinely was Joe getting in touch and saying, I want to understand quantum mechanics. Can we do an infinite monkey cage about it? To answer Joe's questions,

we have two of the world's greatest experts on quantum mechanics, past, present and future. And they are... I'm Ben Allen-Nack. I'm Professor of Theoretical Physics at the University of Cambridge. And what's baffling me is why the particles have a strange pattern of masses. I'm Faye Dauker.

I'm a professor of theoretical physics at Imperial College London. I work on quantum gravity, which is a theory that doesn't exist, but I'm trying to find one. And the scientific idea that baffles me is the block universe, which is the idea that the future already exists, the future has already happened, because it baffles me because if the future's already happened, then we're all dead.

Is it any clearer? Yeah, I think that'll do me, actually. No, I'm just getting started. That was fascinating. And this is our panel. Joe, let's start off with, so what do you know or believe you know so far about the idea of quantum mechanics and quantum physics? Well, I believe that quantum mechanics is a branch of physics that deals with the behaviour of matter and light on a subatomic and atomic level. And I read that in Women's Weekly, everyone. an atomic level.

And I read that in Women's Weekly, everyone. I would love it if Take a Break had more things. My quantum physicist husband has been having affairs in other universes. Ben, would you like to point out why Women's Weekly is incorrect? I think it's a bang on the money. It's about how matter behaves on very tiny distance scales and how it interacts. It describes other forces too, all forces as far as we know, apart from gravity, importantly. So as Brian knows, the standard model of particle physics has three forces in it, and they're all described by quantum theory very well. But the weird thing about quantum theory is that it's

inherently probabilistic. And this is a property of the particles themselves and that you can there's the heisenberg uncertainty principle which tells you you can't know where a particle is and how fast it's going at the same time there's there's like a fuzziness in its definition and there's some probabilities that you can describe if you get the theory right, but you can't squeeze it and, you know, measure it completely accurately because it's kind of fuzzy in a weird quantum probability way. And it's modern day magic. I mean, it's totally divorced from all our experience. And yet the experiments time and time again tell you,

you know, this is how the way that things work. why does that matter phase so so before quantum mechanics uh we have newtonian physics and everything appears to be completely predictable in principle why does it bother us that we then have a theory from the 1920s onwards i suppose which is probabilistic what does that mean it bothers some people and it doesn't bother others i mean famously einstein was said that he was disturbed by the lack of predictability of the theory the strangest thing about quantum mechanics i mean there are many strange things about quantum mechanics that's one of them but there are other ones which exhibit what is so different from our everyday expectations of how things behave. And the experiment that portrays that, which is called the double slit experiment, and in the double slit experiment, the way that a quantum particle behaves is so odd.

It's not just that you can't predict what it's going to do, but that if you allow it different possibilities then it's it does things that it was able to do before but now can't do so the double slit experiment has the following setup so there's a metal plate with two holes in it and you shoot electrons at this metal plate and the electrons go through the plate they travel through the experiment and they land on a screen so it causes a little flash of light when the electron reaches the screen and you can do the following thing you can block one of the slits and allow the electron to go through just one of the slits and there will be a pattern and you do this many many times so

you send many many electrons through and you don't know where the electron is going to hit this this scintillating screen where the flashes of light will be there's just some probability that it'll hit it in certain places and over time the electrons that hit the screen build up this pattern and it's roughly uniform pattern on the screen so they could be here they could be here they could be here and it's a roughly uniform pattern but now you open the other hole the other pattern on the screen. So they could be here, they could be here, they could be here and it's a roughly uniform pattern. But now you open the other hole, the other slit in the screen and you let the electrons go through again one by one and now there are parts of the screen that the electrons cannot reach

that they were able to reach before. Are they tired? They've had enough. you need a rest so it what's happened is that you've given the electrons different ways to go different paths different histories that it could take and just the possibility of doing different things means it changes the behavior of the outcome but is that totally random because it sort of implies that the outcome. But is that totally random? Because it sort of implies that the electrons have some sort of agency, doesn't it? It's like, today I'm going to go to that side of the screen.

Or is it just completely random? It's random in the sense that you don't know where they'll end up on the screen, but you can predict the pattern. Each electron behaves randomly, but the pattern is perfectly predictable and scientific. But the peculiar thing is that the particle cannot reach parts of the screen that it could reach when there was only one way for it to go. Why is that, Brian?

Well, I mean, I think that it's worth appreciating. It's a beautiful way of describing it. As Faye said, you've got a possibility that's open to something. It's just a particle in the standard picture. It's a piece of grain, a sand, right? You think of it like that. And it goes through a little slit and it goes through a screen. And then you open another way that it can get there

and suddenly it can't go where it went before that's tremendously strange i mean richard feynman's description was to picture it as going always and if you say it takes every possible path it can in some sense simultaneously then you can explain what's happening but that's weird isn't it you've got a particle that's doing everything it possibly can. It's like me saying to you, we'll go to Portsmouth. Oh, let's do that. He will. He always does a first date in Portsmouth.

In some sense, we take every possible path on our way to Portsmouth. It's only about two, actually. Yeah, the A3 or three in the A... Yeah, yeah. All right. Am I allowed to ask why or is that not yeah why does that happen then we don't know this let's just find out now just throw it out for a straw poll who currently now still thinks that

physics is a unitary pursuit and uh who's beginning to change their mind we've got work to do We've got a lot of work to do on this one, I think. But if we summarise, though, maybe... How can you summarise what's just happened? Well, because as Faye said, it goes to the central weirdness of quantum mechanics, doesn't it? That you've got this picture of a... If you want to think of a particle, then you think of it as going all possible routes that it can.

And that involves, I suppose, in principle, going via the Andromeda galaxy, right? In principle. Or Portsmouth. think of it as going all possible routes that it can and that involves i suppose in principle going via the andromeda galaxy right in principle or portsmouth anywhere or portsmouth on its way to the screen you've got that you've got to take account of every possible route haven't you which is it's worth underlining that's a picture of reality that's odd but is it is it is it true i'm sure i read it somewhere that like that by the very act of observing something, you change it or it changes its behaviour? Yeah, absolutely.

So before you observe the electrons in the double slit, you don't know which path. It's gone through both paths in some sense, right, through both slits. But when you observe it with a you measure which slit it's gone through then it's it's like oh it's the right hand slit it's definitely gone through that slit and there's a difference between those two systems before and after and it's very counterintuitive right it's uh completely and that's because our experience is on this larger classical world where these rules don't seem to apply to us you know so we have got

no experience of them the reason i said earlier that there was it women's weekly what was it women's weekly the the reason i i introduced it and said it it might be wrong is because well i said it was definitively wrong actually but the reason was that it said that this only applies to little things and i think when when you have the picture that well it's electrons or something but our world this thing that we perceive, it doesn't behave like that at all. Everybody knows which route everything takes if you throw a tennis ball and so on.

But you get a real feel for how strange that theory is if you just believe it, take it at face value, if you transfer that to big things. And the famous example would be Schrodinger's cat. So could you discuss how strange this gets if you apply the theory and there's no reason why we shouldn't or maybe you think we can discuss that but if you apply the theory to something like a cat or a human can i just check so joe you know about schrodinger's cat and that idea that there's a cat in a box and it's both dead and alive until observed.

Yeah, I do know about it, but I just think it's not both dead and alive. It's just when the lid's on, you can't see it, so you don't know what it is. See, which I think, again, this seems to me to be, before we just move on, I don't know if you have the same problem which I would have, which is all these things that are being talked about we have this kind of picture theory in our brain and so most of the things that we talk about especially if we talk about biology for instance you're normally able to picture most of the different kind of ideas within it but when we get to this idea of the behavior of particles actually don't you think we don't have

the right language yeah describe it yeah so i think i describe a cat so the showing is cats a thought experiment has actually done this, thankfully. But you put a radioactively decaying source, like an atom, in a box. And if the radiation comes out, which it only happens randomly, it's a quantum process, radioactive decay. We know that. So it comes out at random time. Then it would hit a poison vial and kill the cat.

So whether the poison vial has been hit or not is decided by quantum physics. And so whether the cat is dead or alive is defined by the quantum state. So before you observe it, indeed, it should be in a quantum state of being half probability dead, but not just half dead not just half dead, but I mean like completely dead with half a probability or completely alive with half probability. And then when you open it, you collapse the wave function, it's called, into one of the different states. So you find out whether it's dead or alive. And if you put the lid back on and then have a look again, of course, if it's dead initially, it will stay dead. But I think Schrodinger was teasing at the difficulty with it

because the cat is a macroscopic object, it's a big object. Big objects, as far as our experience tells us, don't live by these quantum laws. And yet here's a system you could set up where it should live by a quantum law. So what's going on? But is the cat the observer, though? Wouldn't also the cat be the observer?

Because they are. They look around a lot don't they're very you know that's what i'm just wondering you know what if we put a cat in there it's looking as well i kind of feel that the rspca should be the so yeah this this is the textbook version of quantum mechanics that we teach our students. We do teach them that you apply quantum mechanics to a quantum system, and it's in a quantum state, which might be in this so-called superposition of two different states. It's in that superposition until you make a measurement, and then the act of measuring changes the system and collapses the quantum system into, say, one or other of these states. What the textbook theory of quantum mechanics does not tell us is what qualifies anyone or anything or any other system to be the observer.

It just leaves all of that completely open. The concept of measurement is really central to the theory. The concept of observer is really central to the theory. Everything hangs on it. But the theory is utterly silent about what that is. So it just leaves you up to your own good taste and intuition to make this division between the quantum system that we describe using quantum mechanics and quantum states and superpositions and wave particle duality and the rest that is us with

our lab equipment and whatever so you can if you want consider the cat to be an observer but nothing tells you that that's right or wrong that's the weird thing it's really completely missing that crucial ingredient but then again doesn't that give you such a multitude of choices that you could choose the cat to be the observer i mean to me an observer of breaking a white coat with a clipboard right but you were saying like the slit could be the observe did you say that earlier on if you had an extra measurement device on the slip that was oh i see but it doesn't need to be a human but it can be a human no i mean personally i don't think it you're i mean face i completely agree that the observer isn't defined but it seems to me it seems to be

when you've got large organized systems of quantum systems that are all piled on top of each other. For example, lab equipment is macroscopic. It's not a tiny thing. It seems to be when they interact with those big systems that there's a collapse. And so you would call a big system like a cat. Perhaps that would be an observer in that case. I love the idea of calling a cat a big system. The idea of going into a pet

shop. What size of system would you like? 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 for the small coffee all day long. Taxes extra at participating Wendy's until May 5th. Terms and conditions apply. Fading 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. I mean, I don't know if you have this, Jo. There is a point when I listen, and I know, you know, I've read books on this, but there is, again, that kind of thinking of cats, that moment where your brain goes into the Homer Simpson kind of meow, meow, meow, meow, meow, meow, meow.

Because you're trying to create so many pictures and you can't come up with... And that, I think, is where you feel that kind of moment where the floor underneath you is beginning to disappear. Absolutely. I mean, I'm kind of slightly feeling like I've been given drugs at the moment because I can't quite grasp... Well, I grasp it for a second and then it just

goes away and i'm not sure i've even understood it really that's the right feeling though there is in the sense that in the sense that our current there is no consensus there's no scientific consensus on the picture that you should have of what is going on in a quantum system there are different interpretations people favor them over one over the other but we cannot tell you what is going on in inside the box so you say here's my quantum system it's in this box there's no description of what that system is doing in the box. We don't have that. That's the exciting and wonderful thing. That's the thing I enthuse my students about.

I say, I'm going to teach you this thing, but there's something missing from it, which is you have to take on board that there's this fundamental concept of measurement, of observation, which is crucial to the theory because it's useless without it because the theory only gives you predictions for results of observations and measurements so it's absolutely crucial but theory doesn't tell you what it is and if you want to apply it to the whole universe

that it then becomes silent i mean are that what would you say is the percentage of sort of traditional scientists who just feel they need to lie down after they hear something like what you said and and people who can kind of be i don't know sort of loose enough to sort of take on board that there's all these competing um ways of of looking at stuff and are happy to go ahead with that because for most people science is about facts and about proving them isn't it but it sounds to me like you can't really really you you've got a missing gray area where you can't prove anything because is it because you don't know enough or is it because you don't think it's ever going to be you know it's difficult to find experiments that can discriminate between one

interpretation and another one for example many worlds quantum mechanics which is quite an extreme interpretation but the philosophy is important and the metaphysics of you know what really does it mean i think it's fascinating and it fascinates all of us probably we don't know the answers could you just um you mentioned the many worlds interpretation. Before we move on to the hard stuff, so that's the foundational stuff, we're going to move on to quantum gravity. You will all receive a certificate at the end of this show. The many worlds interpretation.

It's one of those, isn't it? One minute, without hesitation, deviation or repetition. Can you explain the many worlds interpretation of quantum mechanics? Schrödinger's cat, okay, alive and dead dead then when you make the measurement into alive or dead the universe splits into two universes in one of them uh the cat's alive and in the other one it's dead okay so every quantum measurement every quantum interaction that's measured splits the universe up and there's one possibility in each but there are many many universes and they're always multiply um you know making babies and if you don't feel like you're on drugs now then there's something wrong with you oh that's a good thing can i just ask the audience you're

obviously kind of interested in science and all the general they were gubbins this is what i'm wanting to check though i mean hands up who's following it so far yeah so like the vast majority of them and hands up who's who's kind of not not following it at all and wants to go home no not me no i do find it interesting but i'm just interested in what your kind of level of of understanding of of all this and and if i'm just holding you all back by going it is really counterintuitive i mean what i loved was there was someone when you asked that and they didn't just put their hand up they started waving and i immediately oh sorry stevie smith are they waving or drowning i really don't't know for sure. But I think the idea that someone can grasp it in half an hour or, you know, the ramifications and all...

I think that's an important thing, isn't it? That sometimes you get books that come out which kind of say, we're going to explain everything about... I don't just mean yours, Brian. But, you know, they're going to explain everything. And you're not going to grasp it in one radio show. You're not going to grasp it in one radio show. You're not going to grasp it in one book because even what you're grasping is perhaps not solid enough to...

You know, it is gradual, isn't it? That every now and again, like you were saying, Joe, you get this little moment where you think, oh, I think I understand it. And then some days it lasts long enough that you think, oh, now I can explain it to my friends. And then you find out that your head kind of understands it but your mouth doesn't you know and there's all of these different levels of it so i think it's important for people not to sometimes feel that they they

have to surrender early on would you say faith quantum mechanics is amazing because it's our most successful physical theory there's no limit to to what we can apply quantum mechanics to that we know of. And it explains things from the abundances of the light elements that are produced in the very early universe, to the results of the Large Hadron Collider, to the properties of the semiconductor materials that underpin modern technology in all our phones and computers. that underpin modern technology in all our phones and computers. So you can't overstate just how successful it is as a scientific theory. And yet, and that's the amazing thing, that and yet there is no consensus about how to understand what it is telling us about the nature of reality. You have both those things going on at the same time. So it's stupendously exciting because there's truth there. There has to be because it's so successful. It lets us do so

many things. And yet there's this gap, there's this empty space where a picture of the quantum world should be. And we cannot give it to you we we do not know we we we as human beings have not yet figured out what is going on in a quantum system you do you think someone knows and they're going to come along like einstein did and go i know and then and then suddenly it's it's filled in because it seems to me like like a quantum jump or a quantum leap is about in many ways just making a completely illogical connection say between two things correct me if i'm wrong but is it something like that yes i think we will know there will be progress because it's such an intensely interesting question and lots of people

are thinking about it and it's a it's slightly different from some questions that people struggle with in in physics and science which are all to do with let's put this equation on a big enough computer so we can solve it because it's it's conceptual it's a conceptual struggle you have to we have to create the right concepts and we we don't know what they are but it's that conceptual struggle which has always taken place within science and within physics and i have complete confidence that we will eventually know the answer to the question can i just say i think it's going to be you i do can we talk about your field so so one of the ways we're trying to make progress is

quantum gravity which i'd like to talk about now which is really applying quantum mechanics i suppose to the universe as a whole so could you outline what that project that gravity first because that's the thing we can can define gravity first. So, Joe, what is gravity to you? It's a force. Brilliant. Faye, would you like to add anything? How long have you got, Faye? So, Joe's describing our understanding of gravity that we learned from Newton,

Newton's theory of universal gravitation. So, in that theory, gravity is a force. It's a force between every two bodies in the universe so between any two of us between any one of us on the earth between the earth and the moon between the sun and the earth between any two bodies there's this there's this universal force. And the theory tells us exactly what the strength of that force is. And we can do fantastically precise calculations about celestial mechanics, the motion of the planets, checks out almost exactly right. There's a slight discrepancy in the predictions of Newtonian theory

for the orbits of the planets. And that was a puzzle for a long time. And another puzzle about the Newtonian theory is that you can't feel this force. So according to the theory, there's this force of gravity that the Earth is exerting on you right now, pulling you towards the centre of the earth. But if you think about your bodily sensations right now, you'll find, if you pay close enough attention, that you can feel a force, which is the force of your chair pushing up on your bum. But you cannot feel any force pulling you down. So this Newtonian force that the Newtonian theory says is there, you can't feel it.

And that's kind of weird. It's a weird, puzzling thing. And Newton himself called his theory absurd. So he wrote a letter in which he says that this theory, my theory of gravity, is absurd. It's really not the kind of thing that anyone who has any sense can believe in. This is his own theory of gravity. Because it acts at a distance without any mechanism that creates it. So if I want to influence Jo, so I'm over here and Jo is over there,

so we're distant from each other. If I want to influence her her i have to do it via some physical mechanism you would think i'd have to you know throw a piece of paper at her or send sound waves from me to her or use a rope or some physical thing has to produce this influence of me on on joe but gravity is not like that the force of gravity acts without any mechanism at all and newton said well that's just absurd no one can believe that but it was immensely successful no one questioned it until einstein and einstein solved the problem of the absurdity of this force which acts at a distance with no mechanism, by saying, ah, there is no such force. There is no Newtonian force of gravitation between two objects in the universe.

It doesn't exist. The reason you don't feel it is because there is no such force. So your own experience accords with Einstein's view and doesn't accord with Newton's view. But of course that leaves you with a problem because now you have to explain why the planets orbit the sun, for example. There's no force between them, so why do the planets orbit the sun?

And Einstein answered that question by introducing to physics a new physical substance, a new thing, a new concept, and that concept is space-time. And that space-time is curved and bent and warped by the sun, and the planets interact with that space-time, that curved space-time, and that's what causes that interaction between space-time and matter and the planets.

That's what causes the planets to orbit the sun. So the concept of force melts away. There is no such concept anymore in general relativity. It's replaced by the concept of interaction. And there's a new kind of thing, a new kind of substance, which is space-time. See, I think that's the politest way I've ever heard someone say to you, anyway, Joe, no, you're wrong.

Well, I don't mind that at all, but I'm looking at Ben's face. Go on, Ben, say something that supports me. No, not necessarily, but... There's a big question, which is why... So, I mean, Faye works on on quantum gravity she's the expert on trying to find theories of quantum gravity but one question you might say is why do you want to why do you want to have quantum why do we expect there to be a theory that's both quantum and gravity and what's the problem right when you try and marry the two and um the problem is the theory

no longer makes any sense you try and make predictions for the probabilities of things to interact gravitationally and you get nonsense you get infinity and you know probabilities bigger than one don't make any sense if you imagine an electron and the gravitational force due to an electron okay or the gravitational field around an electron. If you could measure that field precisely, you can measure the curvature in space-time absolutely precisely in a couple of points, you could triangulate back and find exactly where that electron was, okay?

But the electron's fuzzy in a quantum sense. Like I said, it's got some fuzziness in its position. It's sort of spread out in position. And so you can't do that. There's a paradox there. So the field itself, the space and time itself in the Einsteinian way of looking at things or the force in the Newtonian way of looking at things

should be quantized or at least interact with the quantum system in a sort of fuzzy... It's got to be fuzzy as well. So that's why we think one of the reasons that you might think that there's a there should be a quantum theory of gravity right yeah joe yeah good but why why does it what why why does it matter so what would let's talk about what a quantum theory of gravity might look like so So, for example, I know, Ben, you work on string theory, which is a...

Oh, we're not going to go there, are we? Well, it is... It's an attempt to build a quantum theory of gravity. Absolutely, yeah. And I would... It might be the most successful attempt so far of building a quantum theory of gravity, actually. So instead of... OK, string theory is this.

Instead of imagining particles, which we think of as little dots, you can think of really tiny, sort of quantum vibrating loops of string. So they're extended objects, and that tames some of these problems with quantum gravity. If you have particles,

it turns out there are infinities in these scattering amplitudes, in these scattering probabilities. But if you have particles it turns out there are infinities in these in these scattering amplitudes in the in these scattering probabilities but if you if you have strings it kind of spreads the infinity out uh in a in a weird way in a mathematical way and it makes them um it makes the theory make sense so you can you can now calculate sensible probabilities of things interacting gravitationally within this string theory. There is a problem. You do need 10 extra dimensions, but we won't talk about that. So you need 10 extra dimensions, and how big are they, the little strings?

So, of course, we're only aware of three spatial dimensions and one time, right? So if you've got a 10-dimensional theory, you need need six and you need to kind of hide them somewhere so um so the idea is that every point in space has six other directions but they're like curled up in little circles on each other and so really to also really tiny so they wouldn't x they wouldn't affect conveniently so they wouldn't affect the experimental results that we've seen so far so basically that's just crowbarring something in to make it fit the yeah no you're right i mean you build the the initial idea was great um and uh but then people realized theoretically it fell apart unless it had these extra dimensions it was unstable and it wouldn't but if you have these extra dimensions then it worked and we don't know i mean it is so

that's kind of a crowbar to try and make the theory work. But the theory of quantum gravity is so difficult to, you know, get anywhere with that, you know, people entertain it, even though it's got these six extra dimensions. I've known, do you know what, of all the shows that we've done over 27 series,

this is the one that most needs at the end, if you've been affected by any of the issues that you've heard in this show but this is what we haven't really brought up i suppose is the quantum graph and i hope i may well be wrong in this i very often am but the the fact that one of the big issues is getting to the beginning of the universe that that you can't manage to get these two different ideas quantum mechanics and gravity to to work so we can get back to what? Is it 10 to the minus 37 now? 10 to the minus 38 of a second? That's how, in terms of the first moments of the universe,

but the next bit becomes currently impregnable because we can't get these two things to work together. Absolutely. So at the beginning of the universe, we believe there was a Big Bang. But what that really means, so that's just a placeholder name for a moment where physics breaks down. So we have lots of those little phrases, which just mean we don't know. And the Big Bang is just a phrase like that.

So at the Big Bang, physics as we know it cannot be used anymore. So we can't use Einstein's theory of general relativity. So quantum gravity would be the theory that would take over from general relativity at that moment, and we would be able to answer the question, what happened before the Big Bang, even if there was a beginning? All of these questions would become amenable to we would be able to address them

if we had this theory of quantum gravity. So it's exactly at that earliest time that we need a theory of quantum gravity to to answer the these most fundamental questions about the origin of the universe can i can i just say one thing as well how much how important do you think scientists themselves are in all this because you're going to hate me for this but when i was at brunel i did a course called the sociology of science and it was all about how different individual scientists had like a kind of a kind of impact on how science progressed so you know what happens in science is it's not the increasing amount of knowledge building and then suddenly ta-da there you are it is like a quantum jump so you're going down one road and then someone goes,

I don't know, but what about this? And everything is overturned. And then you sort of need to start re-examining it again. That's when the really big discoveries and changes of picture happen. So I think the difference is what's happening at the cutting edge of science. And things are uncertain, we don't really know. it's the difference is what's happening at the cutting edge of science and there you know things are uncertain we don't really know and there i think the scientists do on a short time scale it does matter what people think and there are fashions and things at that cutting edge

but eventually once you experiment is the grand arbiter and it tells you in the end it tells you okay these theories are wrong even though they were very popular they're just not right in nature and you know eventually things seem to bed in if i ask a philosophical question because really what we're talking about is we've talked in the last few minutes is a theory that aims to describe the origin of the universe so philosophically if we had such a theory what what would that mean do you think to you and in everyday life what would it mean if we fully understood how the universe began if indeed it began well i suppose it would explain everything that we don't understand wouldn't it that's well

that's what it should be doing but what what I don't understand about the Big Bang is like, who came up with that? I mean, it could have been anything really, couldn't it? It's just like, oh, there was a Big Bang. That's like something a three-year-old would go, oh, Big Bang! And then it was... Well, no, yeah, that is, yeah.

It was Fred Hoyle who termed the phrase. He didn't like the theory of the expanding universe. And he was using it as a pejorative term in a radio interview actually oh and it got adopted and then oh i see that's a good name we'll use that so you're right it was someone going oh yeah well these are a big bang and was looking down and then oh yeah cheers thanks black hole wasn't it the same thing that was was that john wheeler... My daughter actually asked, what is it, it's ChatGPT, to ask to write five jokes in the style of me.

And one of them was apparently, I went into a shop and said, have you got something that will make me look thin? And the shop assistant said, try a black hole, that sucks everything in. So that's not a bad joke, is it? I'm going to use that and pretend it wasn't chat GP. It was me.

That's the joke you can take away with you. We asked our audience, what is the burning question you would like the Infinite Monkey Cage to answer, and why so? Oh, this is very good. Did Avon die in the final episode of Blake 7, right? I thought that was going to be from you as well, I know.

So the... Sorry, where does Robin get those magnificent manly cardigans? Yeah, yeah, they are manly, aren't they? And I'm wearing manly badges today as well. Joe, you've got some as well. Oh, yes. What force is acting on my husband's socks that

causes them to defy the laws of elastic, fall off his feet and disperse around the house. Oh, knitwear entropy, one of the worst forms of entropy. What else have you got there, Rob? Related, actually. Given the relativistic effects of time dilation on a moving body, how fast does a lattice have to travel

to outlast Rishi Sunak's premiership? Who really did start the fire why i've always suspected billy joel that's from kira thank you i burnt my flat down can i just sound quite proud of it when i was a student and um because i had a candle alight and the bed caught fire but you know when it's like when you're a student and because I had a candle alight and the bed caught fire. But you know when it's like when you're a bit drunk you just go, sort it out in the morning don't you? So eventually the whole thing went up. So I

started the fire. Well it's another one similar. What are these things that can only get better? And when will that happen according to the rules that govern the effects of the space-time continuum yeah i like this what's that bright light in the sky that seems to be getting closer i would like to know how worried i should be and that's from a concerned t-rex

thank you to our panel professor faydauka professor ben ellenack and dr dr dr dr I'm a concerned T-Rex. Thank you to our panel and Professor Faye Dyerka, Professor Ben Elenak, and Dr, Dr, Dr, Dr, Dr, Dr, Dr, Dr, Dr, Dr, Dr Joe Bram. Thank you. We're 14 years old now, and so, like a lot of teenagers, we don't think you understand us or our music and actually I say you don't understand us, you probably do understand me, it's just Brian you don't understand when he

talks about Lagrangian mechanics and you probably will understand his music because you like show tunes generally don't you, that is your favourite thing. Isn't it rich aren't we a pair you with your feet on the ground, me in the air.

Anyway, so that's his favourite. I feel like I just sat next to Judi Dench. I know. But anyway, so we might think that we know it all, but next week we are joining up with a show that really is a properly grown up show because next week we are doing a show which is

a partnership with the 67 year old Sky At Night. So, hopefully, we'll see you then. Bye-bye. APPLAUSE Monkey cage Without your trousers In the infinite Monkey cage Till now nice again Have you ever wondered Who you really are? It clicked in my mind suddenly

I was like Why have I never done this? I'm Jenny Kleeman A writer and journalist In my new series The Gift From BBC Radio 4 I've been uncovering

Extraordinary truths that emerge when people take at-home DNA tests. He said, what do you know? You don't even know that your father's black. So I'm like, Jeff, we got him. And he's like, what are you talking about? And I go, we got him. Obviously, it was a completely unintended consequence of a gift.

Join me as I investigate what happens when genealogy, technology and identity collide. Listen to The Gift on BBC Sounds. 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 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,

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