The Big Bang with Harry Hill, Phil Wang and Professor Chris Lintott

Added: 2026-05-05

[00:00:00]It's time for our theme of the week.

[00:00:07]The Big Bang.

[00:00:10]The Big Bang and we're joined by Chris Lintott who is Professor of Astrophysics at the Department of Physics at Oxford University. Does it get any better than that? It's a good title, isn't it?

[00:00:19]Congratulations.

[00:00:20]>> Thank thank you very much. My mother's very proud. I bet she is, yeah. Yeah, imagine how my mum feels.

[00:00:26]Yeah, used to be a doctor.

[00:00:28]Uh do you know Phil Plait? Uh we've never met, but hi, nice to see you. Big fan. Actually Big fan of physics. Of physics in general. Big science, yeah, big science.

[00:00:37]Good. Phil was at Cambridge, your arch enemy.

[00:00:41]And he did engineering. I did engineering, yeah. I was there, too. At Cambridge? Yeah, yeah, yeah. When? Uh 1990 to 2003. Oh.

[00:00:51]>> Oh, I was 2008 to 12.

[00:00:52]>> Okay, you're younger. Good. All right, this is not never going to make the podcast.

[00:00:55]>> When you talk about Oh, it is. I'm [laughter] going to insist that it is.

[00:00:58]>> Yeah, yeah. Getting to know you.

[00:01:00]Um so And now imagine there is some overlap between engineering and Yeah, we need engineers. They do useful things, but also all I get letters with crazy theories of the universe. So people who think they've solved everything and it's almost always retired engineers. Really?

[00:01:17]>> Who just think the universe should be simple and they've worked it out and if only I would listen to them or read 200 pages of handwritten notes.

[00:01:23]>> unified theory >> That's right. Yeah, yeah, yeah, yeah, it's often involving, you know, if you take the orbit of Mercury and divide by the mass of Jupiter, you get a number that's kind of similar to the strength of an atomic uh pull in a nucleus and so on. Oh, you've got my letter, then.

[00:01:37]>> Yes, yes, yes. The [laughter] pictures The pictures were lovely, Harry.

[00:01:41]Well, there is a certain kind of logic to it being simple, isn't there? Yeah, we I mean, some ways people would say the universe is simpler than it should be. Like there's no guarantee that we should live in a universe that we can understand. And yet we we've got somewhere in trying to understand it.

[00:01:55]But it's got this crazy thing at the start, which is our theme, which is this idea that it started in what we seem to call the Big Bang, which we don't understand. Oh, you don't understand >> Well, not the very moment. If the Big Bang is this moment at the beginning where everything started, that's also the place where physics breaks. So we can go right back to just after the Big Bang and I can tell you sensible things about the universe. But that moment of the clock starting, time equals zero, uh there's some you can make some stuff up. You can have some fun thinking about what physics might be there, but we basically don't know what happened. It's impossible to imagine what that could be before anything. Yes, and I think you could people like me occasionally make a good living out of pretending that we know what that is like. We can stand there and go, "Imagine a time before time." Or imagine that the whole universe was infinitesimally small and that sounds like I know what I'm talking about. But basically none of those words mean anything. What we do know is just after that the everything was crammed close together, the universe was very hot and dense and it's been expanding ever since. So the Big Bang theory, the idea that there's this expansion, we do understand. Okay, so you so you can answer the question, my first question, what is the Big Bang? Yeah, it's this idea that the universe was in this hot, dense state and expanded outwards ever since.

[00:03:13]>> So everything was in one Pretty close to one place, one dot, A dot even. Yeah, yeah, yeah. What I've always wondered is you know how the the universe is still expanding, everything is still hurtling away from each other. Are you able to draw lines?

[00:03:27]Is that how you do you actually know where the Big Bang was? Well, if you try to do that, it looks like we're at the middle of it because everything is expanding away from us. So there's a brief moment where you go, "Oh, we must be very important. We live at the center of the universe." But you'd get the same answer wherever you were. Surely you wouldn't though because no, this is a very good theory. I'm surprised no one has actually come up with that.

[00:03:46]>> Retired engineer, you see. What theory?

[00:03:48]>> Retired engineer. About drawing all the lines. You just draw lines.

[00:03:51]You get >> [laughter] >> You just draw the lines.

[00:03:56]I thought I was being so smart. Uh think of it as stretching, right? So don't think about the universe Don't think even though we call it the Big Bang, don't think of it as an explosion. Think about it as space stretching. And so if you stretch space in every direction, then everything is getting further away from everything else.

[00:04:13]Hang on, hang on. I haven't got that.

[00:04:15]Well, try People sometimes think about this like if you have I'm sure you do this on a on the weekend. If you're baking a nice loaf of raisin bread. This is a terrible analogy, but let's imagine that's what you're doing. When you put it in the oven it expands, the bread expands and the raisins get further apart from each other. And if you were sitting on one of those raisins, you'd see all the other raisins rushing away from you and you'd think you were the most important raisin.

[00:04:39]>> Raisin. Or like if you have a big rubber band and you have a little dot there and you stretch it all, that dot only moves about that much.

[00:04:44]>> That's right, yeah. I get it, I get it, I get it. And so we can measure how much how fast space is stretching and it's not How fast is it?

[00:04:51]>> that so if you take a megaparsec, which is what, about 3 million light years, so a lot, then every kilometers every second all of that space gets 70 kilometers longer. So it's not very much compared to millions of light years. And that's why, you know, it's not that the Earth's expanding, you're not expanding, I'm not expanding because of the expansion of space. But if you take the whole universe, it becomes this thing that dominates. Phil looks like he's going to be sick.

[00:05:20]>> [laughter] >> So say say billion too much. It's a lot of information, isn't it? Yeah, it is.

[00:05:26]It's the idea that everything is moving really fast right now and that are we are we going to like lose are we going to get too far from each other that you know, we're not held together by gravity anymore? Well, we're not. The universe isn't held together by gravity. When people started When we saw, it's about 100 years ago people started to realize that space was expanding. What they thought would be happening was that gravity would pull everything back together. And so you'd have this phase where the universe expands And then goes back, yeah.

[00:05:53]>> goes backwards and then ends up in the opposite of a Big Bang, which is called in in the papers. People call it a Big Crunch. But they also call it There's a group of people who call it the Gnagnib, which is Big Bang backwards.

[00:06:05]>> Which is very nice. This is what we expect from our nerds.

[00:06:07]>> Yes, you get Big Bang, Gnagnib. And then [laughter] then you can cheat cuz then you can just have it rebound. And then you have this nice bouncy universe, which gets you out of having to explain how it starts in the in the first place.

[00:06:18]>> Now, Chris, you said we only worked it out about When was it? We About 100 years ago we started to realize And and you know, what was it that we discovered that So it was looking at galaxies. So we live in a galaxy, we live in the Milky Way with billions of stars and we realized about 100 years ago this year that there were other galaxies. So the universe is speckled with these things.

[00:06:39]And then they worked out that they were moving away from us and the further away they were, the faster they were moving away from us. So that's this stretching effect produces this. And then the thing that really sealed it was in the '60s when they discovered that there's this faint light that fills the universe called the microwave background. Was discovered by people um who were trying to work out how to communicate with radio over long distances. Uh they built this this telescope. Um they had problems with pigeons cuz pigeon poo emits radio waves, so they had to keep cleaning out the the telescope of pigeon poo. Radio waves? Yeah, yeah. And if you tune in Yeah, if you choose the right frequency Pigeon FM. Yep, exactly. Maybe they're communicating with each other.

[00:07:21]Once you pigeon hits Slow down a bit. [laughter] What What is Pigeon hits all day long.

[00:07:26]Yeah.

[00:07:28]Yeah, proof proof. Um You know this one, guys? What What What is it So why does it emit radio waves? Uh that's a biology question, so you'd need a different guest I'm so sorry. Yeah. Is it like radio >> [laughter] >> Is it like radioactivity? I don't know.

[00:07:44]It's They describe it in the paper. So the people who are looking for this stuff describe it as the telescope being coated in a white dielectric substance, which they had to clean. Do you imagine you've gone to actually these engineers Yeah, yeah. But also you've gone to university, you've become an engineer, you work at Bell Labs on the most cutting-edge radio technology there is.

[00:08:01]And what you're actually doing with your time is scraping away pigeon poo with a toothbrush from your instrument. That's what I call my autobiographies.

[00:08:08]>> [laughter] >> Um Anyway, they discovered this background light and that's the the echo of the Big Bang. It's the leftover light from this time when the universe was hot and it it surrounds us. If you've got an old telly um with an aerial and things like that. Or if you can imagine having such a thing. Um when you have the static in the telly, 5% of that static is from the Big Bang.

[00:08:31]It's this leftover radiation. Amazing.

[00:08:33]Detected with a telly. Mm. But not now we've gone digital. As in the noise.

[00:08:37]>> Yeah, yeah, the black and white, yeah.

[00:08:39]Um And so when did when did it happen, this Big Bang? So we think the universe is 13.8 billion years ago years old. So 13.8 billion years and the solar system's about 5 billion years. So we came along about 2/3 of the way through the history of the universe or the Earth came along then. Was it loud?

[00:09:01]There were sounds? Were there were sounds? Yeah, so so because it's hot and dense, sound waves can travel in space.

[00:09:06]So in the first 300,000 years of the universe's history, you could scream in space. But was the Big Bang itself a noise?

[00:09:15]>> see.

[00:09:15]>> Oh, I see. Yeah. Um I don't think so. We don't see Trying to answer the >> Cuz it's not an explosion, you see. It's not an explosion. It's just this Yeah.

[00:09:24]It's a sudden It's the Yeah. But it's interesting you say that because it was you could hear sound because it was dense enough for a sound to travel. And this microwave background light, we see the imprint of those sound waves. So those sound waves produced the structure we see today. So we're sort of leftover echoes of the Big Bang.

[00:09:44]Fascinating.

[00:09:46]Will it happen again? No, we of course it won't. That's a good question. No, we don't know. I like don't know, but the universe is expanding. It's actually speeding up, which is confusing. We don't understand why it's speeding up.

[00:09:57]And so people have said maybe in the far future it would bud off new universes.

[00:10:01]So each universe produces more big bangs. So So maybe it's not a stupid question.

[00:10:05]>> Like a tearaway sharing loaf. Yeah, that's right. Yeah, yeah, yeah. But But expanding with raisins.

[00:10:11]Yeah, yeah, right.

[00:10:12]>> are important. So yeah, the tearaway sharing loaf model of the universe. As opposed to a traybake, which is very neatly cut. Yeah, and flatter. So we can rule that out. I think we could rule out traybake.

[00:10:26]What is the significance of the Big Bang, I suppose? I mean, it's nice to know this stuff, but does it have any practical Well, all of this stuff in the universe was created in those hot dense conditions. So when you look at the sun, the hydrogen and the helium in the sun were made in the Big Bang. All the stuff we're made of was added later. But But also the structure of the universe. So So everything we see around us was set from that that that very beginning. The weird thing is that we got a universe where interesting things happen. If you think you could randomly select any set of rules of physics, you're going to get a very boring universe most of the time.

[00:11:03]And yet here we are in this one.

[00:11:04]>> Yeah, could that be an argument for for for somebody up there? Maybe. Yeah, I mean, you could put God at the beginning if you want. Is God like is like that? Yeah.

[00:11:16]Compressing it all. And then giving up.

[00:11:19]Isn't that just an argument for [snorts] chaos? Uh And what's the thermodynamic Oh, for creating entropy.

[00:11:27]>> Entropy.

[00:11:27]>> Well, entropy is a problem. So we'll do with God then entropy. So you can have God at the beginning, but that feels to a physicist that feels like cheating. Uh like that's that's the same as me going, "Oh yes, it was created by I don't know, Brian. Brian created the Big Bang." And And then we go >> Good for Brian. Yeah, got to got to be a Brian. Uh entropy Yeah, so there's also the sense Also do you have a job? Yeah. Well, there's lots of universe to study afterwards.

[00:11:52]It'd be nice to know the beginning was nailed down, to be honest. It's a bit upsetting that we don't know. [laughter] It literally the first question you asked and my answer is I don't know, which isn't very good [laughter] after the introduction. Uh but yeah, the entropy, the sense that the universe um devolves into chaos over time. So one of the things we don't understand about the Big Bang is why it set us up so that stuff could happen. It could have produced a universe that was just chaotic from the beginning. It was just a mess of particles. Well, it could have done, I suppose. I mean, this it might have been that several and just the one we know. Yeah, and then people argue that okay, so we're living in this one, so it's not surprising it's one that produced life. But I don't know. Again, it feels like cheating.

[00:12:32]Um you've invented the anthropic principle there. That's what that's called, this idea. Yeah, this idea.

[00:12:37]Harry Harry's anthropic principle. This idea that the universe is the way it is because we happen to exist in it. But it still feels like cheating. What I want is somebody to write down an equation that will tell me why the Big Bang had to produce a universe like this and ideally what happened before it. Cuz I could have been a history of the universe before the Big Bang that we don't understand. How can you How can you have a history with no time?

[00:13:01]Well, time doesn't have to start in the Big Bang. Our time started then, but maybe there was some other Yeah, maybe there was a universe that collapsed to start our Big Bang or maybe we were We We don't This is going to blow your mind. We don't have to be the first bit of sharing loaf.

[00:13:16]Our universe could have been one of the pieces that's been ripped off. Yeah, exactly. And so you've got this time that exists in the pre-loaf stage. God damn.

[00:13:25]>> [laughter] >> There's a proving universe. Yes. Yeah.

[00:13:28]Yeah, we're going to have to write paper after this. I think this is this definitely a new theory coming here.

[00:13:33]I actually feel like crying. Really?

[00:13:35][laughter] In a In a good way?

[00:13:37]>> What um have you seen the film Interstellar? I have. Yeah.

[00:13:41]>> Do you understand that? Bits of it. You know what annoys me about Interstellar?

[00:13:44]They're going on this journey to a black hole, to save humanity. And there's the It's got one of the great training montages of all time. There's like 10 minutes of film time of them like driving through cornfields and doing weights and and arguing. And then they get into space and then one of them goes, "So what is a black hole?" And you just [laughter] think that surely that's day one of training if you're going on a black hole. I think that was for us, really, wasn't it?

[00:14:07]>> [laughter] >> For the viewers.

[00:14:09]When you When you watch a sci-fi movie as a physicist, is it entertaining [clears throat] or annoying? I like it as long as they don't explain the science. So you know, there's Danny Boyle's Sunshine, right? Where they're like, "The sun is turning off and we have to launch a bomb to fix it." I'm like, "Great, got it. Good." And then they go, "The bomb is made of dark matter." And I was like, "No, stop it.

[00:14:28]Stop saying things." I was happy with the magic bomb. That's fine.

[00:14:33]They're always trying to overexplain things, aren't they?

[00:14:35]It's a bit like when you when we watch films with comedians in. Don't you find that?

[00:14:39]>> It never is never realistic at all. I have to turn off every single time. You mean the drinking, the arguing?

[00:14:45]>> [laughter] >> None of that's real? The crying. It's not enough.

[00:14:50]So while we've got you here, Chris, what should we be looking forward to in the night sky? I know you you're the co-host of The Sky at Night with Maggie Aderin-Pocock. Yeah, exactly. Um next year um is all about asteroids. So a few years ago we decided as a species to uh attack uh an asteroid called Dimorphos.

[00:15:12]We smacked into it with something the size of a washing machine uh to try and deflect it as a a dress rehearsal for what we'd do if we saw an asteroid coming towards us. And um we're sending a European probe called Hera that gets there next year to see what crater we left. So that will be quite exciting.

[00:15:27]We'll We'll find out whether we can save the world if we see an asteroid coming towards us. And then there's a new telescope. We've got the Vera Rubin Observatory that it it's this It's got this Well, it's a billion-dollar project. It's got the world's largest camera and it's going to scan the whole sky every 3 nights starting in January.

[00:15:44]And the images are going to be spectacular. So you're going to see lots of basically really cool space pictures coming from this observatory we've been working on. Where's the observatory?

[00:15:51]>> It's in Chile, in the Atacama Desert.

[00:15:53]>> Chile, oh. Because it last rained there in 1923. What?

[00:15:58]>> [laughter] >> So it's a good place to put a telescope.

[00:16:00]Oh my gosh. Imagine it rains the first day you start.

[00:16:03]>> Yeah, yeah, yeah, yeah. That's That's my [laughter] kind of luck, actually.

[00:16:07]Well, this is fantastic, Chris. It sounds like it's a really exciting time to be an astronomer.

[00:16:12]>> It's fun. We've got new toys and the universe keeps expanding, so there's more to see. Fantastic. Thanks so much.

[00:16:17]Uh that was our theme, The Big Bang, with our friend Chris Lintott.