Jo Brand's Quantum World

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Hello, I'm Brian Cox.

I'm Robin Ace.

And I'm Joe Brandt.

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 little different because usually on Monkey Cage, 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 or ever 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 have 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

Joe, so I thought, oh, thank heavens, we're going to escape from physics because Brian always goes, physics, we've got to do physics, we've got to do physics, black holes, physics, physics, physics.

And so I went, 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?

Why did you choose that subject?

Well, 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.

That's theoretical physics.

Don't tell anyone.

We've been talking about that.

And I have to say,

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 I kind of just 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 Alanak, 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 Fay Dauke.

I'm 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 what baffles 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 Woman'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.

But Ben, would you like to point out why Woman's Weekly is incorrect?

I think it's 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 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 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.

But why does that matter phase?

So

before quantum mechanics,

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 nineteen twenties 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 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 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's going to hit 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 a 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 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.

So,

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 behaviour of the outcome.

But is that

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 of sand, right?

You think of it like that.

And it goes through a screen, a little slit, and it goes to 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 happened.

But that's weird.

Because there's everything it possibly can.

It's like me saying to you, we'll go to Portsmouth.

Oh, that's a good idea.

He always does.

states, in Portsmouth,

I think.

In some sense, we take every possible path on our way to Portsmouth.

Sibyl does any of that, actually.

There's three

or three and the A.

Yeah, yeah.

But it does.

Am I allowed to ask why, or is that not?

Yeah.

Why does that happen then?

We don't know.

We don't know.

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 who's willing to change their mind?

We've got work to do.

We've got a lot of work to do.

But if we summarise there, maybe we could say if we summarise this little bit.

Summarise what's just happening.

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.

Anyway, or Portsmouth, on its way to the screen.

You've got to take account of every every possible route, haven't you?

Which is worth underlining.

That's a a picture of reality that's odd.

But

is it true, because I'm sure I read it somewhere, that like by the very act of observing something,

you change it, or it changes its behaviour, or?

Yeah, absolutely.

So

before you observe the electrons in the double slits, you don't know which path, you know, 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 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 completely different.

And that's because our experience is on this larger classical world where these rules don't seem to apply to us.

So we've got no experience of them.

The reason I said earlier that the Woman's Weekly, what was it that you where did you get that from?

Women's Weekly.

The reason I introduced it and said 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 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 Schrödinger'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 Schrödinger'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 is the this seems to me to be before we just move on to that, I don't know if you have the same problem which I would have, which is

all these things that have been 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 kinds of ideas within it.

But when we get to this idea of the behavior of particles, actually,

we don't have the right language to describe it.

Yeah, so I'm going to describe a cat.

So, the showing is cats, a thought experiment.

No one's 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, that 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 a quantum state.

So before you observe it, indeed,

it should be in a quantum state of being, you know, half probability dead, but not just like, 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 Schrödinger 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?

I don't know.

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?

They're very, you know, that's what I'm just wondering.

You know,

if we've put a cat in there, it's looking as well.

I kind of feel that the RSPCA should be the act.

So, yeah, 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.

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's breaking a white coat with a clipboard, right?

But you were saying, like, the slit could be the observer.

Did you say that earlier on?

If you had an extra measurement device on the slit that was.

Oh, I see.

But it doesn't need to be a human, but it can be a human.

No, can it not be?

I mean, personally, I don't think it.

I I mean, phase 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 and with those big systems that there's a collapse.

And so you would call a big system like a cat.

You know, 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?

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Hi, I'm Morgan Sung, host of Close All Tabs from KQED, where every week we reveal how the online world collides with everyday life.

There was the six-foot cartoon otter who came out from behind a curtain.

It actually really matters that driverless cars are going to mess up in ways that humans wouldn't.

Should I be telling this thing all about my love life?

I think we will see a Twitch streamer president maybe within our lifetimes.

You can find Close All Tabs wherever you listen to podcasts.

I mean, I don't know if you have this, Joe.

There is a point when I listen, and I know that, 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

no

expert, hooray!

In the sense that

there is no consensus, there's no scientific consensus on on the picture that you should have of what is going on in a quantum system.

There are different interpretations, people favor them one over the other, but we cannot tell you what is going on 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 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,

it then becomes silent.

I mean, are there, 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 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

ways of looking at stuff and are happy to go ahead with that.

Because to most people, science is about facts and about proving them, isn't it?

But it sounds to me like you can't re really,

you've got a missing grey 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,

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, even though we don't know the answers.

Could you just, you mentioned the many worlds interpretation before we move on to the hard stuff?

So that's the foundational stuff, but I'm 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?

Schrodinger's cat, okay, alive and dead.

Then, when you make the measurement into alive or dead, the universe splits into two universes.

In one of them, 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

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

gubbins.

This is what I'm wanting to check, though.

I mean, hands up, who's following it so far?

Yeah, so the vast majority of them.

And hands up, who's kind of 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 understanding of all this, and if I'm just holding you all back by going,

I don't think 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 thought

Stevie Smith, are they waving or drowning?

I really don't know for sure.

But I think that 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 the but you know, but 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 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 have to surrender early on.

Would you say, Faye?

Quantum mechanics is amazing because it's our most successful physical theory.

There's no limit 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 and all 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

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 do not know.

We as human beings have not yet figured out what is going on in a quantum system.

Do you fade?

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 filled in because it seems to me 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 slightly different from some questions that people struggle with 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 conceptual, it's a conceptual struggle.

We have to create the right concepts, and we don't know what they are, but it's that conceptual struggle which has always taken place within science and within physics.

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.

Faye, can we talk about your field?

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 research is?

We can define gravity first, because that's the thing.

We can define gravity first.

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 and the earth, between the earth and the moon, between the sun and the earth, between any two bodies,

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 Joe, so I'm over here and Joe is over there, so we're distant from each other.

If I want to influence 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 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.

Not necessarily, but.

There's a big question, which is

why.

So,

I mean, Faye works 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 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 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 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 could measure the curvature in space-time absolutely precisely at 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 wave looking at things, or the force in the Newtonian wave 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 should be a quantum theory of gravity, right?

Yeah, Joe?

Yeah.

But

why does it matter?

So,

let's talk about what a quantum theory of gravity might look like.

So, for example, I know, Ben, you work on string theory, which is a.

Oh, we're not going to go there, Arthur.

Well, it is

a attempt to build a quantum theory of gravity, right?

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, okay, 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 strings.

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 strings, it kind of spreads the infinity out in a sort of weird way.

In a mathematical way,

and

it makes the theory make sense.

So 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.

10 extra dimensions, and how big are they?

The little stuff?

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 six and you need to kind of hide them somewhere.

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 t 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 ri 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

get anywhere with that

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 gravity.

And I hope I may well be wrong in this, I very often am.

But the fact that one of the big issues is getting to the beginning of the universe.

That you can't manage to get these two different ideas, quantum mechanics and gravity, to work together.

So we can get back to what is it, 10 to the minus 37 now, or 10 to the minus 38 of a second.

That's how that

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 word, it's 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 answer these most fundamental questions about the origin of the universe.

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, oh yeah, but what about this?

And everything is overturned.

And then you sort of need to start re-examining it again.

That's when the big, 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 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, it 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, as 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 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 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's like, well, no, yeah, that is scary.

It was Fred Hoyle who termed the phrase.

He didn't like the theory of the expanding universe, and he framed it, he was using it as a pejorative term in a radio interview, actually.

Oh, and it got adopted.

And then everyone,

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 at it, and then went, oh, yeah, cheers, thanks for it.

It was the same with Black Hole, wasn't it?

The same thing.

That was, was that John Wheeler?

My daughter actually asked

Chat GPT 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 gonna use that and pretend it wasn't chat GPT

with 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.

That's all right.

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?

One of the worst forms of entropy.

What else have you got there, Brad?

Related actually.

Given the relativistic effects of time dilation on a moving body, how fast does a lattice have to travel to outlast Rishi Sanak'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 say I'm quite proud of it when I was a student?

And

because I had a candle alight and the bed caught fire.

But you know what it's like when you're a bit drunk, you just go, well, 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?

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 Fadauka, Professor Ben Elenak, and Dr.

Doctor Doctor, Dr.

Doctor, Doctor, Doctor, Doctor, Dr.

Joe Brown.

Thank

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 likes 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 that's his favourite.

I feel like I just sat next to Judy Denver.

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 the partnership with the 67-year-old Sky at Night.

So, hopefully, we'll see you then.

Bye-bye.

In the infinite monkey cage.

Without your trousers.

In the infinite monkey cage.

Feeling that 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 Clemen, 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've got him.

Obviously, it was 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.

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