 There's me in past days before I had the beard. I think it might make me look younger, I'm not sure. So I'd like to talk to you this evening about physics. I'm going to talk to you about two aspects of physics. The physics of the very big and the physics of the very small. And there's two reasons I'd like to talk to you about these two areas of physics. Firstly, they're in of themselves interesting and lead to some really weird behaviors in the universe and our simple brains find it very, very hard to comprehend. And secondly, I'd like you to go away with the idea and the knowledge that between these two theories of the big and the small, there's an enormous gap in physics and we don't have one model that shows us how the entire world works. Now, physics is just an application of mathematics and physicists love to write everything down like this and use everything to mathematics, which is just the way that these sorts of people think. But when we take these equations a little bit further, we end up in some of the weirdness of the world. Now, when I stood up, you were kind enough to give me a round of applause, which I thought was very generous because you got no idea who I am and if I'm going to be any good and manage to explain these concepts to you. But I'd like you to think through in your head why, when you clap, there's a noise. So we think, if we're an acoustic engineer, we think, oh, there's vibrations in the air that go through to the ear. If we're a neuroscientist or a biologist, we think, well, these vibrations in the ear start to vibrate the ear drums on our ears and through the little bones and into the cochlear and into our brains, blah, blah, blah. If we're a physicist, we might think, well, hang on a minute, why were my two hands stopped? Why didn't my hands pass through each other? Why does my bottle of water stand there and not fall through? And we think to ourselves, I know the answer to that. I know it's because these things are solids, yeah? But actually, that's a contrary, that's a circular argument because the fact that they're solids is the reason they don't fall through each other. That's our definition. If we think back to our high school physics, everything in the world is made of atoms. Can someone tell me the constituents of an atom orbiting around the outside? We have electrons. Thank you very much, sir. Someone paid attention in physics at school. And right in the middle, we have a nucleus. Thank you very much. Made up of protons and neutrons. Now, we know from some work done by Ernest Rutherford that the nucleus is really small compared to the size of the atom. And in fact, if I take an atom and blow it up to the size of Munich, then the nucleus will be the size of a football. So the nucleus is really, really tiny compared to the rest of it. So there's a whole lot of free space. So the theories around in the early 1920s were that the electrons on the outside were appelling each other like two magnets and they couldn't go through each other. But when you start to do the maths behind that, you realize this isn't true. There's something else stopping them going through each other. And this is called the Pauli Exclusion Principle. Now, Pauli was one of these scientists. Now, this is from the 1920s in Copenhagen. It's an amazing picture. It's one of my favorite pictures. Unfortunately, you can see the misogyny around in the time. There's only one female amongst all of these people, Mary Curie. But these are some absolutely amazing scientists in the time they were trying to understand these problems in physics. They were also trying to understand something called the ultraviolet crisis. The ultraviolet crisis said that if I look at the way that this light bulb over here works and I apply my model of physics today, I should be getting so much ultraviolet light off this light bulb here that I should be getting sunburn stood here. I've also realized that when I'm doing this talk, I'm not here at that light, so I can't see you guys anymore. These models weren't working. There was something broken in the models. Einstein at the time, the most recognizable guy, sat here in the middle, was working on something called the photoelectric effect. And all of these people thought, well, there's another way that the world works. And Planck came up, Planck's here. Planck came up with this, sorry, Pauli is there, Pauli is there, Pauli is there. Pauli came up with this theory of the fact that things can't go through each other. And then Planck came up with a theory that everything's in quantum. Now, Edwin Schrodinger one day was out for a walk and Edwin Schrodinger could use these things much better than I can. And Edwin Schrodinger came up with this equation. Now, he was out for a walk with his girlfriend along a romantic pier somewhere and he was thinking through the mathematics behind quantum mechanics and what possible formula you could have behind it. He was not a very romantic guy and I should also add that at the time he was walking down the pier with his girlfriend thinking about quantum mechanics, but his wife had no idea where he was. But he came up with this equation. I'm not going to try and explain this equation to you because it's horribly complicated to try and apply any of these things. It's what we call a differential equation which means its answer is not a number, it's not a number 42. The answer to this equation is another and probably far more complicated equation. One number I'm going to point out to you is this number here. Does anyone know what this stands for? Imaginary number, exactly. With this work, we have to add in imaginary numbers. Now, they're called imaginary numbers because they don't exist. It's the square root of minus one and clearly minus one has no square root because you can't multiply two numbers together to get minus one because two minus is to make a positive. But mathematicians at the time, sorry, mathematicians before had thought this through and imagined what would happen if we were able to do that and give this a number and would this work and would this be useful and yes, this then became an incredibly useful tool that we were able to apply here. That gave us some more problems because when we start to apply this equation to the real world, we get these two weird problems. This you may have heard of is the famous dual slit experiment. This is where you shine a light through two slits and they give you interference patterns behind them. So as the light comes through, it gives me dark and light fringes of light and I know this works and I can do this experiment in the bath. If you sit in the bath and you make a couple of slits with some little rubber ducks in the bath and you're going to need something in the bath that vibrates so you probably want to take a friend with you as well, you can actually see this effect inside the bath but that equation I just showed you said that that doesn't just apply to waves. This should apply to particles because all particles act as waves. So if I start to put a single atom through one of these slits, it starts to behave in this weird way. But if I put multiple atoms through, I can understand them interfering with each other like the waves do, but if I put a single atom through from here, it behaves in these slit waves the only way the maths work is if that has passed through both holes at the same time. So this atom has gone through both holes at the same time and added itself back up together to the other side. Now this is really hard for us to understand because our brains evolved on the 10 meter scale of living on a savannah somewhere. And this is just weird and mad. And if I send a single one through, it's acting the same way and that just doesn't make sense. And if you do the maths, you say that it's gone through both and we say the states are superimposed on each other. It's done both things at the same time and the universe doesn't decide whether it's gone through the left slit or the right slit or whatever it's done until it's looked at by an observer. And then Edwin Schrodinger, he of The Romance, came up with this model and he said, well, what about if I fire it through the slits and it doesn't know where it's going to land and if it appears in place A, a cat dies and if it appears in place B, the cat doesn't die. But I have this in a complete sealed box and you've told me that it doesn't decide which one it went through to open the box. Well, that means the cat, if the cat were going to be killed it went through the left hand hole, doesn't decide whether it's dead or alive until it's looked at by a human being. So the maths tells us that this cat is both dead and alive at the same time. That's clearly mad, but it is the way the world works. Now, this we don't need to go into too much detail on. This is the standard model of physics. It's on the at CERN. This is trying to say what are the particles that the universe is made up of? What are we made up of? We're made up of these things over here. These make the nucleus, the electrons, these things that fly out of the sun. On the right hand side we have the forces in the universe but there's no gravity on this chart. This clearly upset those people in the picture I showed you earlier. Einstein at the same time was working on two theories of relativity. First, the special theory of relativity which is looking now at very fast things, looking at the speed of light and saying the speed of light is constant in the universe. If you do the maths behind that in the equations from a guy called Ernest Maxwell, you come out with the fact that E equals MC squared. This is his first theory. This is the simpler one in that I can understand maybe 10% of it. His second theory, which was the general theory of relativity, explained to us in his world how gravity works. This equation looks like this. What this equation is telling us, and I don't understand this, what this equation is telling us is that gravity isn't a force like the other forces. It's actually a warping of space and time. The Earth warps the space and time around it. A satellite orbits around the Earth because as far as the satellite is concerned space-time is warped and it's going in a geodistic, a straight line, the shortest line between two points. But if I apply this equation to the rest of the universe, I start to get some other really, really weird things happening. Imagine I'm a polevolta. I know it's hard to imagine, I don't look very athletic. I've got a 10 meter long polevolta on my shoulder. I'm going to run this through a garage that I store my car. It's got a door at both ends, but it's only 10 meters long. I can only open one door at a time. The first door or the second door. Clearly, I can't run through this garage with my pole. It won't fit. This equation tells me that if I run fast enough through the garage, I can get the pole through. And the reason is that the faster I move, the shorter I become. So not only time changes, but space changes. Again, this is hard for us to understand. Now, I've tried to test this in the real world in Germany. Now, luckily, I had an able assistant. My partner is German and really knows how to get the best out of a hire car when going up the autobahn, basically a binary right foot. But no matter how fast we go with that car, we are nowhere near the speeds that we need to go out to understand this. So this model is very, very confusing for our very simple brains again. And this is just to do with the environment that we grew up in. This also tells me that if I were to throw my friend David into a black hole, sorry, David, we would see time in different ways because both speed and acceleration and gravity affects time and the perception of time. So from David's point of view, although he's slightly crossed with me, I've thrown him into a black hole. He's hurtling towards the black hole and he just sees himself getting closer and closer to the black hole until the gravity pulls him apart and then he dies his grishes. I don't see that because of the effect of gravity on time, on his time relative to my time, I see him getting closer and closer to the black hole but slowing down. So if he were talking to me, if he were closer to the black hole, he would go like this. He would never cross into the black hole. I would never be able to see him if I waited a million times a time in the universe. I would never see him. And what Einstein is telling us with this equation and these concepts is that there is no concept of now. Everybody's now is different. There's no universe or time across the universe. So we have these lovely, lovely two equations coming out from here. But we have a problem. When we look at the universe, we have this problem. Anyone know what this is a picture of? This is dark matter. We know that when we look at the universe, we know that there's more mass out there than we can see. So there's a problem with one of these two equations. One of these two equations is not telling us the way the world really works. We know there's dark matter out of there because if we look at a galaxy, so you know a galaxy, a big spiral arm galaxy, and it's spinning around on its axis, we know that in the center of this galaxy must be enough mass to keep all the stars in, not to spin out. But when we add up all the mass from the stars spinning around this center of this galaxy, there's not enough mass there. In fact, there's only 5% of the mass we'd expect to be there. So 95% of the mass is something that we can't see, can't detect, don't understand, and have absolutely no idea what it is. So if a physicist ever tells you they understand the universe, they're not a physicist. We don't even know what 95% of the universe is made of. This picture serves two purposes. There's another force out there called dark energy. And dark energy is something that is accelerating the galaxies away from each other. Because if we look at the galaxies and they all have gravitational attraction, they should all be sucking towards each other. So we'd expect there's a big bang to slow down and either stop or slow down and then crunch back in. It doesn't do either of those things. The universe continues to expand and there's something in there called dark energy. It's called dark energy because, guess what? We have no idea what it is. Einstein's equation originally had another term here which he called the universal constant. And he added it to this equation because he thought the universe must have some sort of force pushing it apart. He then decided later on in life, looking at the facts that were coming in at the time from the universe, that that was wrong and he removed it from his equation. He called it the biggest mistake of his life. Which isn't too bad for your life, is it? That is your biggest mistake. After he died, though, we then had to add that factor back into this equation. So Einstein was wrong twice, which is quite an achievement. So here we have this equation, Schrodinger, our romantic guy. Down here we have our equation of relativity and they're very big. And in the middle, we have the best picture I could find of fridge magnets. And the reason I put that in there is because we can't explain with all of these equations a fridge magnet. Because the fridge magnet's stickiness to the fridge is magnetic force is governed by this equation. The fact that if it's not stuck on a fridge, it drops to the floor is governed by this equation at the bottom. And we don't have a holistic equation or a holistic way to describe the behavior of that fridge magnet. If I look at my mobile phone, which is somewhere in one of my pockets, I know that I've had someone has had to use this equation to define the microelectronics in there. And here are so small and so compact that it needs quantum mechanics to be able to understand it. It needs this equation. Why? Not that my phone is going very fast even when it's in the car with my girlfriend. It's because it has a GPS receiver in it and the GPS satellites orbiting around the earth go at a speed. Fast enough that this equation at the bottom has a tiny effect on the clocks in there. And we have to apply these relativistic equations corrections to the satellites to enable the GPS on the phone to work. So without both of these, my world wouldn't work. And this is why really I think I've wasted my life in insurance. It's paid the bills, but it's not been that interesting. What I'd really love to have done was worked on the gap between these two equations. Thank you very much. Yeah, we have five minutes for a few questions. Anybody has questions? Questions? Oh, I'm scared now. Hey! Falling into the black hole. He's speaking later. I hope he doesn't. Yeah. Is there anything to know? There is no now in the universe. So we can see that even the experiments done from Einstein's field equations are needing very accurate clocks. So putting atomic clocks on an airplane and flying the airplane around the earth. Now, because it did two things. Because it went up, its gravity changed, which has one effect on time. And because it was accelerating, it had another effect. They're actually in different directions, depending on which around the earth it goes. And when it landed, the clock that was on the ground and the clock that was in the airplane were indeed different. So there is no relative absolute now that I can say. So I can say that something, to me, happened 130 million years ago. Maybe the two recently detected gravitational waves. I think they were 130 million years ago. But that's my 130 million years ago. For that star, it might look different. So there is no concept of single time in the universe. So space and time are considered one complete thing. And we exist on a plane of space and time. So there is no consistent now. Why do they want to write in mathematics? That's a very good question. Because it's the only way to explain the universe. I've tried to explain it a little bit by waving my hands. But you can't then do any calculations off the back of it. So in the same way as an engineer building a bridge, they would look at the equation, they look at the weight of the bridge and how much force is on each of the components inside it. They're going to use mathematics to solve it. From a physics point of view, it comes down to mathematics to be able to solve the equations to come out with the answer. Now it's a really good question. There is a better way to look at the universe. And maybe there is a better way to look at the universe that wouldn't give me this horrible gap with my fridge magnets. I don't know. It's a good question. But it's the way that all the physics is built on mathematics. Last question. Hi. Yeah. I can't remember the movie. It might have been when I fell asleep. What was the ending of the movie quickly? Oh no, because that was it. And then you appeared behind a bookcase. It made no sense to me at all. There were some bits in it which I think were to do with time dilation weren't there? Is that the film where they got near to black holes? They had time dilation effects and stuff like that. Was it in that film? Yeah, that bit made sense. But at the end of it, it just, to my mind, it turned into a weird fantasy of psychological thriller or something. Yeah, so it was kind of cool. And then it went, uh, Hollywood. I have a question. You said that the cat... you cannot know if the cat lives or not. Yes. But the cat knows that it's living or not. Okay, so there's two models there. So the cat is in both alive and dead at the same time. So the cat could be two cats. So there's the many worlds interpretation quantum mechanics which says that every time one of these quantum events happens, the universe splits. And there are two universes. One with the cat dead, one with the cat alive. And therefore we live in one of these two universes. This kind of makes a little bit more sense to us, but it means imagine how many universes that have to be out there that every tiny, not just a decision that we make, but every quantum event generates a new universe. It's just an unbelievably massive amount of, um, infinities. Secondly, what does it matter if the cat knows whether it's dead or alive because it can't pass on the information until you open the box? Okay. Okay, guys. Great. Thank you for your attention. Really appreciate it. Thank you.