Nothing Really Matters - Hugh Dennis, Ria Lina, Harry Cliff and Yvette Fuentes

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The concept of nothingness

2:08Hello, I'm Adam Rutherford. And I'm Jessica Fosterkew. And this is The Infinite Monkey Cage. Adam, we've got nothing to talk about today. Okay, this is going to be a short program. Could you just look at that line in the script? Could you give it another go with slightly different intonation? Adam, we have got nothing to talk about today. That's right, we're talking about nothing. We're talking about the concept of nothing, the science of nothingness. Does nothingness even truly exist?

2:41Am I having some kind of existential crisis already? We have some guests here to discuss how nothing really matters to physicists. And some comedians. Friends, please welcome Aparo. They are. Hi, I'm Ria Lino. I'm a scientist and a comedian. They don't always go well together. But here they do. So thank you for having me. Ria, have you had any thoughts about whether you would harness any of the properties of nothingness into a superpower?

3:14I think about this a lot. I think that if we could turn the nothingness into a superpower, I would take it and I would turn what is actually the nothingness of pretending that you have a lot of money. But in fact, it's all invested in tech companies that may or may not be worth anything and calling yourself the richest man in the world. And I would turn it into what it actually is, which is nothing. Hi, I'm Harry Cliff.

3:46I'm a particle physicist at the University of Cambridge. Snazzy. I'm so glad I went first. Any thoughts on the superpowers or? Yeah, I think I would use nothingness as power to expand space because I live in quite a small two bedroom flat and we now have an 18 month old and I'm having to move my office to turn into her bedroom. So if we can make it a bit bigger, that would be great. Brilliant. I'm Yvette Fuentes. I'm a professor of theoretical physics at the University of Southampton and a fellow of Keeble College in Oxford.

4:21And I did think about what superpower would I have if I harnessed some property of nothing. And I thought I would love to appear and disappear, but in a fun quantum bubbly way. What is the fun bubbly way of thinking about quantum physics? Well, first of all, you need to be in couples. Well, that depends if you have mass or not, but we have mass, right? So then we need to be in a couple.

4:52So that's why I brought my husband because we like to appear and disappear as pairs. And then it's kind of fun because we can choose if we want to be electrons. Then he has to be a positron. And we have an interesting marriage.

5:07That's such a great way of keeping it fresh.

5:12Wow. I thought I knew all the kinks. Hugh. I'm Hugh Dennis, and this isn't quite the programme I was expecting.

5:20And that is our panel.

5:26What is your feeling about absolutely nothing, Hugh? If an empty box really has nothing in it, what's really inside? If an empty box has got nothing in it, what's really in the box? Yeah. Well, I don't know what should be in the box, and that is the iPhone that the delivery driver has stolen.

5:44But I just think I'm interested in the whole concept of nothingness. But to me, it already seems like a sort of, dare I say it, one of those sort of strange philosophical questions that probably has got an easy answer. It's like, you know, if a tree falls over in the wood and no one hears it, has it made a sound? To which, for me, the answer has always been, yes. Clearly, it has made a sound. And if the tree hasn't made a sound, the badger who said it's fallen on has definitely made a sound. Look, I'm going to pass this straight to Harry.

6:18He just said it's an easy question to answer.

What is nothing in physics

6:21Harry, what is nothingness? We have no idea, actually, is the answer. I mean, it's a great topic. Because actually, nothingness is at the center of most of the biggest mysteries in physics and cosmology today. So understanding nothing is absolutely crucial to figuring out why the universe is as it is and how it began. And it's actually what we've studied. I work at the Large Hadron Collider at CERN. And basically, what that machine does, in some sense, is it studies nothing in very, very high detail.

6:52So we're exploring the vacuum to try to answer questions like, how did matter come into existence? Why is the universe expanding? How did it begin? I don't know why you built such an expensive machine. You could have just studied the space between my ex-husband's ears. Ria, is that what you imagine when I say, think of nothing? How do you visualize it? Pretty much. Yeah. My marriage. Yeah. Well, but you know what? To be fair to both of us, neither of us ever thought to roleplay as positrons.

7:24There you go. I missed on that one. I don't think anyone's ever thought of that apart from Yvette. Yvette, what do you think is the difference between an everyday person's perception of what nothing means, which you've slightly alluded to in your weird bedroom games, but what it means to a physicist? Well, yes, I agree. This is a very important question in physics, but it's actually been a very important question for humanity from ancient times. And back in the day when, you know, the Greeks were asking this kind of questions, science

7:58and philosophy were not separable. So I would like to start back in ancient times and talk about, for example, Paramedes, who thought about what is nothing. And he is famous for saying what is, is, and what's not, is not. I thought you would like that one. Yeah. Sounds to make perfect sense. You've really got this sorted to you, haven't you? I've got no problem with nothingness.

8:29No problem with it. Hugh, do you have anything that you've, what do you visualise if you think of nothingness? Like, well, if I'm perfectly honest, I think probably like an awful lot of people, nothingness absolutely terrifies me, really. Because I think most people, don't they, they fill, they fill space with something. The idea that there is nothing is odd and very scary, I think. So psychologically uncomfortable for, for humans, is that? Why don't we try to imagine it? Do you guys want to play like a game with me and think about nothing?

9:02I'll be a positron. Okay, so close your eyes and think about the universe as big as it is. And now think about the universe without matter.

9:19Okay, so get a feel of that. Now think about the universe without light, without any other fields. What is still there? Space and time. Now think about the universe without...

9:39Oh, this is deeply uncomfortable.

9:46Emptiness makes us uncomfortable, right? That's something very interesting, because as physicists, we want something to be empty, so we built a vacuum, for example. But then we don't really want it to be empty, and we find something in it. I don't know, Hugh and Ria, if you would agree. I think comedians find it particularly repulsive to be met with a wall of nothing, audibly. That is like, unless you're going to use it, there are some comedians, I guess,

10:17who work with the gaps between things incredibly well. So this is what leads me to believe there may or may not be a God, because you're right. As a new comedian, you're scared of silence. When there's nothing happening, you're like, I'm dying, I'm failing, everyone's judging me. But then as you get more skilled as a comedian, you control that silence. You know what's coming. You know that you're going to break that silence with a fantastic joke or a cliffhanger. And it makes you feel like God. So I get it. I get why God went, I'm bored. Let's big bang this.

10:48I'm controlling this nothing. You say the universe was created just out of boredom. Out of the awkwardness of the nothing. And you went, yeah, too awkward. I'll do the universe. Yeah, exactly. In two seconds, no one could handle it. And somebody created a world. My dad was a bishop, right? So he was very, you know, sort of a theological man. But I used to occasionally try jokes about God on him. My favorite one was always, you know, whatever you think about creation, God is definitely a builder. He's definitely a builder. He tells us he's coming back, but he gives us no indication of when that will be.

11:28It's more than snags as well, isn't it? Yeah, it's more than snagging. Yeah, yeah. Okay, so Yvette's mentioned about, you know, when we first started thinking about this in the Western tradition. Harry, what was it that the Greeks and the ancient classicists, how were they conceiving of nothingness? Well, I think Democritus said he was the guy that came out with the idea of an atom. If you take matter and you cut it and you cut it, eventually you'll get to something that you can't cut anymore, a smallest thing. And he said the universe is atoms and the void. So it's stuff and the absence of stuff, and that's what the universe is made from.

12:01But other people disagreed with that. I think Aristotle said there was no such thing as nothing. The first sort of scientific ideas really come with people like Robert Boyle, where they start to pump air out of glass containers and they discover that candles go out. Or that if you ring a bell in a vacuum, you can't hear it. And so people start to understand, okay, there is actually a sort of a physical thing that we call a vacuum. But what we now know, actually, in some sense, the Democritus is wrong.

Empty space and quantum fields

12:26Actually, I mean, maybe this undermines the whole show, but there isn't any such thing as nothing. You can't actually have nothingness. Imagine you go to some distant part of the universe where there's, you know, more or less empty space and you build a box. And you suck out all the stray atoms and particles. You remove all the photons, all the light, everything. What's in that box is not nothing. In fact, it's really, really busy. Essentially, what physics tells us is that even empty space is seething and there's stuff going on there all the time, which you cannot stop. Okay, hold on. Is it seething like it's really angry or do you mean it's teeming, like it's busy?

12:59Well, okay. Or is it just angry and it's nothingness? It's not angry. It's sort of jittering. It's sort of like excited. It's not too much coffee. It's not perimenopause. Are these all the fields? So you suck out all the mass and you're left with all the fields? Yeah, exactly. So like in particle physics, what we actually think of as being the basic building blocks of the universe are not particles, but these things called fields. Yeah, hold on. Hold on. Sorry. Whoa, whoa, whoa. He started with the box at the edge of the universe. I feel like we need to break this down. Okay. Yeah, the audience are ready for this, but I'm not. Can I just quickly come back to, if you ring a bell in a vacuum, it doesn't dong, doesn't that sort of counter Hugh's thing about the tree falling on the, was it beaver?

13:40Badger.

13:42What is happening here? If a tree falls on a badger and no one's there to witness it and it happens in a vacuum, then did it still make a crashing noise? Yeah, but the noise was never transmitted, presumably. Right. Isn't it? So if a badger rings a bell in a box.

14:03I mean, this is not the program I thought it was going to be. Wait, is the gravity field in the box? Do we have a cat in the box as well? There's a cat in the box with the badger or the beaver? Because that might make a difference. And if you ring the bell, you can't hear it, but the cat salivates.

14:19Isn't that a dog? I don't care. So there's a dog there? Hang on. I'll tell you what there is in there. A positron. That's what's in there. Right, you hold that down. Harry, there's a box in space. Yes? Yeah. And let's start with matter. Matter is made of atoms. Yeah. And it's stuff. Yeah. Right? So using a vacuum, using a hoover, you suck out all of the atoms from the box. Yeah. And now there's nothing in it. Now there's nothing in it, in principle. Well, actually, I mean, it's even a question of whether you could even really do this in

14:52practice. Because if you build a box, the box is made of something. Yeah. And the surface of that box will give off radiation because it's warm. So like every body, like if you have an infrared camera in the dark and you look at some hot body, it's giving off infrared light, for example. So unless you'd have to cool the box down to absolute zero so that it was no longer giving off any kind of electromagnetic radiation. So then there's no light in the box either. But then you've got another problem, which is the universe is full of these things called neutrinos, these ghostly particles that zip through space. They're produced in the sun and in the stars.

15:24And they go through everything. They'll go through solid containers. So they would still be zipping through your box. And there's not really very much you can do to stop them unless you make the box light years thick made of lead. Light years thick. Yeah. What's that in distance terms? A lot. A long way. So your box is made of lead and it's millions of miles thick. Yeah. And it's absolute zero, minus 273 degrees Celsius. Yeah. And then it would theoretically be neutrino resistant.

15:55As close as you could get. Yeah. How much filling is there if the casing is that massive? Well, yeah, that's a good question. I mean, it's going to be expensive box for sure. Rears hands up, which is so polite. I'm sorry. Let's just go back to the box, right? Let's make it out of... Why are we making it out of lead? That's poisonous. Something dense. Something dense. Okay, fine. Lead. Lead. What else is in the box once we are in that one point in time where there are no neutrinos? What's left in the box then are the fields. So, yeah. Okay. Well, I am going to need...

16:27Right. Yvette and Hugh, say your things. Can we talk about badgers? I would be much more comfortable with that. I still want to talk about cats in boxes. Okay. So, I will continue the story, but I'll put the cat on the box. Because when you get rid of everything and you're left with fields, let's talk about the electromagnetic field, basically light. Well, one of the things we found last century is that light behaves quantum mechanically.

17:00So, should we go there? Well, yeah. So, wait. Light is made of photons, right? And photons are stuff. Yes. So, there's stuff. If there's light, if there's electromagnetism inside the box, there's stuff in the box. It's not empty. Yes, there's stuff in the box. But quantum mechanics, which is the physics that describes what's very, very small, although that is now debatable with new experiments, but let's not go there. It's very different to the physics that we see with our eyes, which is Newtonian physics. Now, the physics you learn in high school, I have a ball and I throw it, it bounces back

17:33and it will fall exactly here. That's like the physics that we use in high school. But we learned last century that there is a more fundamental theory of physics, which is called quantum mechanics, which is, in a way, related to cats and boxes. Well, you're going to explain that. And I'm going to explain that, yes. So, quantum mechanics is a very strange theory because we can calculate mathematically. So, we have a mathematical formalism and we can calculate what's going to happen, make

18:07predictions very well. We actually invented the laser thanks to quantum mechanics. But what's really fun about the theory, or at least that's how I find it, is that we don't understand what the theory is at all. Coming back to nothingness. We don't understand why, what is the wave function. Maybe you've heard about that. But the wave function can say that a particle is, let's say, here and there at the same time. And we really don't know physically what that exactly means, but we use it to build lasers

18:41and to do another, like, build quantum computers and things like that so we can use it. But one of the things that quantum mechanics also predicts is that the vacuum, the ground state of fields is not empty, but it's full of particles. But when you talk about fields, what are the fields made of? Yeah, because I'm thinking Yorkshire Dales, Brecon Beacons, and I don't think that's what

19:11we're rolling with here. Well, for example, yes, the electromagnetic field, like you said correctly, is made out of photons. Which is stuff. Which is... It's not matter. It doesn't have a mass. It doesn't have a mass. But it is a thing. But it has energy. Right. But does that mean it exists as a thing? I mean, I don't even know. I'm a biologist. None of this... You're just making this up. Hugh's been talking about badgers and beavers. I want to hear about the cat. Yes, because we haven't connected to the cat yet, but we can do that later if you want.

19:42OK. Well, I want to understand a little bit better, like, we've talked about a vacuum, and I think I understand that. So you've sucked all the air out. Is the vacuum perfect?

The Large Hadron Collider vacuum

19:52A good example of the biggest sort of very high vacuum that we have on Earth. One example is in the Large Hadron Collider itself. You've got these pipes that carry these particles that we accelerate to very high speeds, and you don't want them to bump into things. So you remove all of the air as much as possible. Now, there is still going to be a few atoms drifting about in that pipe, but that is very, very close to a perfect vacuum, at least as good as we can do on Earth without going to outer space and having light years worth of lead. So that's probably practically what we can achieve, but it's not actually a vacuum because

20:22there's still going to be stuff in there. And once you've done all that, so you've got rid of everything, how do you observe it? Well, then you put something in and you crash it into each other. So you never get to absolute, because you can't... It turns out there's a camera in there all along, made out of loads of other things. But I suppose the point is, even if you could make a perfect vacuum, let's just ignore the practicalities for a second and imagine you could get rid of everything. The point is that even what is left in there is not nothing.

20:53It's still really busy. And this comes down to sort of what the universe is actually really made of. And we talk about particles making up atoms and atoms making up us. But really, particles aren't fundamental. They're made of something else. They're made of what we call these fields. So the atoms in our bodies, we contain these particles called electrons. Now, you can make electrons. You can create an electron and a positron, as we've discussed already. And that is because, essentially, the electron is made out of this fluid-like thing called the electron field that fills the entire universe. And if you make it wobble, it's a bit like putting a wave through water, that ripple appears

21:27as a particle. So even if you get rid of all the particles, that's like having your kind of ocean completely still with no waves. But the ocean is still there. And those fields are there in space. And you cannot get rid of them. So an electron, which we're saying has mass, is actually a ripple? In a field. In a field. Yeah. The smallest possible ripple you're allowed to have in the field. But the fields must be made of something, right? No. They are a thing. No. No. No. I'm not accepting that. Look, everyone thought that atoms, atoms are called atoms because it means they're uncuttable.

22:00People used to think that atoms were indivisible. And then Rutherford, not my grandfather, showed that they're made of stuff, which is positrons and electrons, right? And then quantum people came up and said, well, actually, they're made of other stuff, which are like quarks and gluons and muons and things. It's just making stuff up. They're made of something. And then you get to the end of it and you say it's just fields. And then you say that fields, in 10 years' time or 50 years' time or 100 years' time, someone's going to say, actually, fields are made of something. Yvette, have you got a way that might help us visualize these fields?

22:32Well, let me think about maybe taking a step back. I'm ready for that. And talking about something we can imagine back from high school, maybe. Yes, please. So let's think about having a pendulum. So with a pendulum, you pull on it. And by doing that, because we have gravity acting on it, we're giving it some energy. And the pendulum will start oscillating. And then depending on how far we pull on it, then it will oscillate faster or slower.

23:06And any energy is allowed. So that's a classical pendulum. But now, if you quantize the pendulum, what quantum mechanics would say is that not all the energies are allowed. And in particular, in a classical pendulum, you could say, well, let's not give it any energy. So the pendulum would not move. Right? It would just stay still. You'll not know this if you're listening on the radio, but she's done quite a funny finger gesture. Just a dangling pendulum. So what happens, classically, you can have a pendulum without any energy.

23:41But quantum mechanically, in particular, the lowest energy has some energy. So it can't be zero. So you have like a little oscillation. So that would be the ground state energy or the vacuum energy of that oscillator. But the interesting thing about fields is that you can describe a field, mathematically, as an infinite number of oscillators. So maybe we can go back and think about the ocean. So a field that would be like the ocean, you could think about it as made as an infinite number of different oscillators.

24:19Okay. So each one of them with a different frequency, and each one of them has this vacuum energy or ground state energy. Do you know, through this whole thing, I'm just thinking Isaac Newton had it really easy, didn't he?

24:34All he did was sit under an apple tree. That was literally... Under an oscillating apple tree, because it hit him, didn't it? With neutrinos absolutely dripping down through it. I think this is going to be a tempting fate here. How do you know that?

24:52How do you demonstrate what you've just described, very eloquently? Because it sounds very mathematical and theoretical. Yes, because we can do experiments and measure it. So let me talk about the Casimir effect. So in the Casimir effect, think about having two mirrors. So you make a box, but out of these like mirrors. And then you have your electromagnetic field inside. So you have your light. And then you start doing the process that Harry described, that you start taking these photons out.

25:27How for now doesn't matter. Just imagine we do that until we take them all out. I think it matters. So then you'll have this vacuum energy, right? And when you have this vacuum energy, that's when you get these creations of pairs. Like, you know, my husband and I have this going on. So that's when you get that situation. So you need to be very quiet. So, Rina, you know that that's maybe like a little couple's advice, is that you need to be very quiet.

25:58And then you can get the positron-electron dance going on. But anyway, we can leave that for... Wait, so to clarify, the reason I got divorced is because my husband and I did not have two mirrors facing each other.

26:10Okay, yeah. Fair enough. Can I just clarify? Harry told us that the photons were the result of rippling the field. So if we've taken out the photons, surely we've taken out the field. But you're saying that we've taken out the photons but left in an electromagnetic field, therefore equals infinite energy. Does anyone else feel like they don't even need to try ketamine now?

26:37That's great. Wait, I think you're the only one who didn't take it before we started the show. I think that does feel a bit like that's what's happened. So remember that the field is like the ocean. Yes. And that it's made of many, an infinite number of harmonic oscillators with different frequencies. By taking all the photons basically means like you try to bring the ocean to its steady state, as steady as you can get it. But what you find is that the lowest energy is not zero.

27:10There is energy in there and it's actually infinite. So now what we have is we have these two plates and there's an infinite energy inside those plates. And it gets even crazier because outside the plates, it's also infinite, but infinites are not the same. They're different times.

Vacuum energy and the universe

27:33Wait, wait, wait, wait, can I just, I have a problem with, you do everything, but I have an issue with infinite energy. Surely the universe has finite energy, doesn't it? No. It doesn't. Mm-mm. Why is my car so expensive to fill up? Maybe one thing to say. So this idea that the empty space has infinite energy, I mean, it's actually, theoretically, that's what theory says. But we know that's not true. Because if it were true, the universe would be ripped to pieces in an instant.

28:06And there is this huge problem. Which is a problem. Which would be bad. Right. It would be bad. Yeah, I don't want that. There's this thing in cosmology, which is known as the worst prediction in science, which is where particle physicists and quantum physicists, like Yvette and I, do calculations and they work out that the vacuum has this apocalyptic amount of energy in it. And then you can actually measure how much energy is in the vacuum by looking at the expansion of the universe. Because this vacuum energy actually has a kind of anti-gravitational effect on the universe. And it makes space itself expand at an accelerating rate.

28:38And so in the late 90s, some astronomers discovered that if you look at very distant galaxies, they are moving away from us and they're getting faster and faster with time, which is the opposite of what we expected. Because we expected that gravity would sort of slow the Big Bang down and stuff would start coming back together, perhaps, eventually. But instead, it's getting faster. And this tells us that there is energy in the vacuum. And this energy is driving this acceleration of the universe. And you can use, okay, how fast is the universe accelerating? You can use that to work out how much energy there is in the vacuum. And you get a number that is 10 to the power of 120.

29:11So that's one with 120 zeros after it times smaller than what quantum mechanics tells us it should be. But, Harry, we're not sure about all of these things, right? They're just like, let's be fair. I'm glad you said that, Harry. Let's be fair. Let's be fair. We're not sure about all these things because we have, like, dark matter and dark energy, which we don't know what they are. And so these are, like, our understandings so far. But I think these are not subtle questions. No, no, of course. This is all stuff we don't really understand.

29:41But the point is, like, what quantum mechanics tells us completely clashes with what astronomy tells us about them. But this is based on an observation. This is a real observation of the real universe. What you see is this accelerating expansion. And then you think, OK, well, what can give you this? And one of the things that can give you it is not the only thing. But one of the explanations is vacuum energy. But the vacuum energy you would assume from the acceleration of the universe is tiny. It's like a very, very small number. Whereas quantum mechanics says it's a gigantic number. And the vacuum energy is made of what? Well, it's made of these little quantum fluctuations that Yvette's been talking about in these fields.

30:15We know about 17 fields. Now he's blaming me for everything. So we know of 17 particles in the universe that make up everything, including, like, quarks, electrons, the Higgs boson. There is a field for each of them. Each particle is a ripple in its own field. So in a bit of empty space, we know there are at least 17 fields. And you can take all the quantum fluctuations in all those fields, add them up, and you get this gigantic number. And then you look at astronomy and you say, that tells us it's a very, very small number. And we just don't know what's going on with that. It's the same question I asked earlier.

30:45How do you know that? The 17 particles, these are things like the Higgs boson, things found through the Large Hadron Collider. Exactly. So when I said the LHC study is a vacuum, I mean, literally, what we're really doing is hitting nothing. We're hitting empty space really hard, and we're making it wobble. And we're seeing what comes out. I've tried that and you fall over. How on earth do you smash nothing and learn something? These fields are there in the vacuum, right? So if you put two very, very fast things and you make them smack into each other, they will make those fields wobble and vibrate.

31:20And the most recent thing we discovered it can do is wobble in this particular way that comes up as this Higgs boson particle. And maybe there are others. Maybe there are dark matter particles that we can make come out of this vacuum. But we don't know yet. And that's why we keep doing the experiments. But will any of this work lower my energy bills? And if not... I think I have a way to bring this, like, more down to earth. I'm following it fine. I'm doing physics A-level.

31:53Yeah, but it was easy back then. There were no Higgs boson fields. There was, like, one field. And it was the one Newton was in. It's the most ridiculously complicated subject, isn't it? I did geography at university. Absolutely fine.

32:10How are you at colouring in maps? Oh, come on. I know. I'm sorry. I am sorry. I'm sorry. Yvette, bring it back down to earth. Bring us back down to earth. Yes. So we were... It's similar to what Harry was saying, but with an experiment that we can actually do in the lab in Earth. So back to the mirrors. And I was talking about these vacuum energies, like empty ground state energies inside the mirrors and outside. And then you can calculate, like I was saying, not all infinites are the same. And what a consequence of that is that you can calculate and you can find that due to the

32:44vacuum between the plates, there is a force and that force is called the Casimir effect. And we've measured it. We found that that force is real. And not only that, but geckos have... What do you call the things that... Now we're back into my kind of stuff. Like suction pads, aren't they? They stick to things with an electrostatic force. Because they, using the Casimir effect, they can stick to the walls and walk using this force.

33:15So we know that it's a real thing. Geckos walk with the vacuum energy. I never heard that. That's amazing. You never heard that? It's Casimir effect. Oh, wow. So hang on, if geckos always got a mirror in front and behind? Yes. And they're in a box with a badger, a dog... And a cat. A cat, you and your husband. A Dyson and a leaf blower.

The Big Bang and inflation

33:33Talking about nothingness, is there any theory that there was nothing at all right at the start? We're talking about the universe as it is now, right? Yeah. So what happened before that? Or was there no before that? So the kind of accepted cosmological story is that you have the Big Bang. But before we call the Hot Big Bang, which is this kind of very, very hot, dense state where you have lots of particles being created, there's this period called inflation. We know all about that. Yeah. But it was a lot higher than 4%.

34:03It was this period in the very early universe where space was expanding exponentially quickly. So this very, very rapid expansion of space. And that was driven by, theorists think, a very, very, very high form of vacuum energy. So that was a time when the vacuum had way more energy in it than it does now. When that process ended, that vacuum energy converted into matter and light and particles, and that gave rise to the universe. So in some sense, in the kind of most popular cosmological theory, everything came out of the vacuum, this kind of energy of the vacuum.

34:35But then what's the vacuum energy made of? That means that there isn't, the Big Bang isn't the origin of everything. I mean, theorists have this thing called the inflaton, which is... You just make stuff up. Yeah.

34:46It sounds like a bouncy castle. Do you want to use different words for different things in physics, maybe? But also not make up words like inflaton. This sounds not like physics. This sounds like philosophy. OK, so the evidence for inflation that it happened is the fact that if you look over there, very, very far, and you look over there very, very far, so the opposite sides of the universe, and you measure the temperature and the density of matter as far back as we can see in time, so right back to about 380,000 years after the Big Bang, those two patches of sky look exactly the same.

35:19They're the same temperature, same density of matter, and you cannot explain that unless they were once in the same place, and then were kind of spread out in a very rapid expansion across the whole sky. So basically, the reason the universe, we think, looks the same in every direction is because at one point, it was a patch of vacuum, smaller than an atom, that then got stretched. Sorry, am I... Wormholes. Wormholes. Wormholes. OK, I mean, submit your paper to the archive and we can discuss it.

35:49We already know that space folds, so you're saying they must have started here and then gone, poof, with a force pushed apart. What if the universe was just folded that way and it unfolded? Sure. I mean, I'm not a cosmologist. Excuse me, I have to go write a paper. I'll go right back. There are some theories like that. For example, Roger Penrose has his cyclic conformal cosmology in which he doesn't think the Big Bang was in the way we understand it.

36:21He also doesn't think inflation was there. And he has a different way of understanding the universe in terms of what he calls eons. There are like periods of the universe with a, say, softer Big Bang. I don't know how one would explain that. But then you have more like a cyclic thing. And that's also interesting. And it brings out back to some things that you were mentioning, that also in ancient Greece and also the Hindus and in Buddhism, there were attempts to understand where the universe comes from.

36:55And, for example, in the Abrahamic religions where you have Christianity, Judaism, Islam, there's this idea that God, out of nothing, created the universe, whereas more like the Hindu tradition or Buddhism thought more about the universe is eternal and it has always been there. And, well, in physics, I guess the most accepted theory is the one of the Big Bang. But there has been people and very, you know, smart people, very talented people coming up with other models,

37:29which are more like a cyclic, like in Hindus. But will we ever know? Is it possible to know? Yeah, I mean, there are experiments that are going on where you look for gravitational waves, so ripples in space and time that come from inflation. So there are certain theories where if you look at the light from the Big Bang, this remnant light called the cosmic microwave background that is everywhere all around us, you look for these twisting patterns in that light, that could tell you whether this inflation process really, really happens.

38:01We have a lot of circumstantial evidence for it, the fact that everything looks the same in every direction, the fact that space is really, really flat. Maybe we don't want to get into what that means. How do you find your way around a universe that looks exactly the same in every direction? And it looks the same if you really zoom out. I use ways. Ways? Ways. Cosmological ways. Yeah. These three words. The universe isn't flat. You just bypass that by saying, let's pretend it's flat, and then just ignore the fact that it isn't, because it isn't. What do you mean it isn't? Well, it's not. It is flat.

Measuring the shape of space

38:31So we can do experiments where you can measure the shape of space. Imagine you put, like, three spacecraft, and you fire laser beams between them in space so they meet, and you measure the angles between those laser beams. Sometimes if those angles add up to 180 degrees, it means that space is not curved. If it was curved, then it wouldn't add up. So you can kind of do this in a kind of cosmological way, and you can tell that the universe is flat. So the space is flat. It's not bent in any particular direction. But we know that light bends around large objects. Oh, yeah, yeah. There's gravitational lenses. I mean when you, like, zoom out. Like, locally, yeah, it's bent. Like, around the Earth, it's bent.

39:02Yeah. Well, like, take this table, for example. Like, on average, the table is flat. But if you go in detail, there's these little creases in it, and there's places where our mugs have been placed. So it's kind of curved locally, but on a kind of, you know, a big scale, it's flat. And the universe is like that. It's curved locally near stars and galaxies, but when you zoom out to cosmic scales, it's flat. At least as far as we can, from the measurements we can make at the moment, to the best of our knowledge. Is it flat and thick, or is it flat and thin?

39:32Like a bird. Is it like a pancake, or is it like a... Have we found the elephants yet, or the turtle?

39:43You're testing me now. That depends on the precision, right? Yeah. I want to say something about a really interesting experiment where you can see that, depending on your precision, things can look flat or not flat. So I work in the interface of quantum mechanics and general relativity, and I'm interested in how can you use quantum stuff to measure gravity and things like that. So my colleagues working in gravity, when I told them I wanted to use atoms and things like that to measure the curvature of space-time and things like that,

40:16they laugh at me because they said that basically space-time is flat, like you were saying, at very small scales. So we can see that space-time is not flat, let's say, at the scales of satellites and Earth. All our GPS makes corrections due to general relativity that tells us that space-time is curved. But people used to think that in small scales, let's say in this table, well, it's obvious that it's flat, but it's not. So there was a beautiful experiment by Dave Wineland in NIST

40:47where he took an atomic clock. So those are atoms that measure time very precisely. And he saw that in 33 centimetres, space-time was curved due to the Earth. Now the experiments have improved, and they can see that space-time is curved at the millimetre scales. So the better the precision in your measurements, then you might find that that's not true, right? Yeah, yeah. Also, have we got spaceships with laser beams? There is a plan to build one.

41:17It's called ELISA, and it's this gravitational wave experiment the European Space Agency, I think are still planning to launch, where you have three spacecraft flying in formation with, I think, distances of millions of miles between them. And they fire laser beams backwards and forwards to measure gravitational waves that, in principle, could let you study the very early universe. Are we all agreed that nothing exists or doesn't exist? No, I don't mean nothing exists as in nothing exists in the universe, that the concept of nothing,

41:48I don't know what the question is. Is wrong. I said, is there always something? I think based on this conversation, what we can agree is that physicists don't know everything. We don't know nothing. We don't know nothing. We don't know nothing, but we don't know everything. All right, well, look. And there's two types of infinite and there's a hot Big Bang and an ugly one. And fields exist, but they're made of something, but they still exist in nothing and they existed before the universe. I mean, we've absolutely nailed it. I also think, I was interested to hear the phrase,

42:20you know, I work in gravity. I like to think that I also work in gravity.

42:25I thought I might be too thick for this theme, but turns out my head wasn't empty at all, actually. It's full of fields. Yes, which are made of something or nothing they haven't decided yet.

Audience responses and signoff

42:34On this week's topic, we did ask our audience, when people ask you what you're up to and you say, nothing much, what are you really doing? I've got a wonderful answer from Liz that says, sometimes I sit and think and sometimes I just sit. When people ask you what you're up to and you say nothing much, what are you really doing? I'm worrying about the employability of English literature graduates. And that's from Lucy's dad. Sue says, cuddling my cat.

43:09I love him. He doesn't love me so much. I suffer the pain. We never did get to Yvette's cat, though, did we? We did. I mean, we discussed turtles, beavers, badgers. Elephants. And I was just thinking that, but maybe we should leave that for another time. Tantalising. Yes, if ever a show needed a part two. Okay, so that's it. Thank you to our brilliant audience. Without you, we'd be nothing. Or would we? And thank you to our panel, Yvette Fuentes, Harry Cliff, Ria Lina and Hugh Dennis.

43:41That's all for now. Goodbye. Goodbye. Till now, nice again.

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