 So the last of this series is a piece of the fitness cafe that we have here at St. Mary's. Today will be my colleague, Ali, who is one of my lecturers at the Pride Peace and Degree we have here at St. Mary's. And Ali is a cosmologist and we will be talking about testing gravity in the solar system. So any of you, Ali? I'm on the outside, sitting inside for a few moments at least. So what I'd like to talk about today is gravity. So it's a simple to monitor all these kind of very big ideas and ways in which we can test it, ways in which things like dark matter and dark energy and all these kinds of buzzwords and things like that. And then you have some new ideas that can come up as well. And here we go from there. So question number one is what's gravity? What's gravity? Again, idea of what is gravity? What do you call it? An attraction, maybe. Massive objects appear to have this kind of gravity. Gravity is a fundamental force of nature. And it appears that when we have massive objects, they attract. This force, this attraction is weaker as the objects get further away. So the question is, gravity is one of the forces of nature. Has it? Does it include any of the others? So snow and the other forces include the electromagnetic. So everything that we see around us is caused by the electromagnetic force. This is called the Delight for Electricity for Magnetism. There's many types of radiation. X-rays, gamma rays are all manifestations of electromagnetic. They're indifferent to gravity. There's also the nuclear force. This is a nuclear-strong force. The force of the nuclear is stuck together. It's got something like protons. Protons have this positive charge. They want to repel what charges them together. They want to keep them stuck together. Otherwise, all the atoms that we have will disintegrate. And you might think, well, what about gravity? So gravity does stick things together. And in fact, gravity's quite weak. And the thing that we need to keep gravity together is the nuclear-strong force. The nuclear-strong force is much bigger than the electromagnetic force. There's also a weak nuclear force. That's responsible for things like radioactive decalves. Gravity is, in fact, the weakest of all of these fundamental forces. And in physics, we have a restriction for the electromagnetic force. And in fact, right down, pretty much it's in the same mathematics. You've got them all together. It's one thing. Gravity is weird. And we've had them today to work out a way to write it down. So gravity not only likes to sit down on its own, but it also appears to have its own weirdities. There's some deeper questions, really. Where does gravity originate from? Why is gravity weird on this? What behavior is there on the universe? What about the universe? Everything exists. All of the gravity needs to be added to everything in the universe. What is the effect of that gravitational force on everything? Everything, as ever existed and will ever exist, is going to have at some point another gravity effect on it. So what's that? What's the effect of that, then? So we're going to discuss some of those things this afternoon. So what are the good scientists from there? If you come up with an idea, we can't just say we've come up with a good idea about it. We have to test it. We can't just come up with these ideas and observations and say, this is the perfect thing. We have to come up with a way in which to test something. So what we can do is we can use the equations and select something that we call a physically relevant situation. In our example, I'm going to show you a big planetary orbit. There's something that we know is there. We model it mathematically, we write down the equations, we solve them, we calculate them. That number, that calculation done. We go away and measure it. Let's see if the matches will be observed by just that number. So for instance, it could be what's the length of the year on Earth, what's the length of the year on Mars, something like that. It's a very easy calculation to do. We can go away and we can measure it. We can go away and we can calculate it in two months. But if they do, we can be happy. And I figured gravity was doing well. If they don't, throw it in the bin and try again. So for instance, if we consider the planetary orbit, we can consider some of the planetary's point masses. Now you might have some weird, all this enormous mass as just a point, but we think three things is quite mathematical all the time. It's idea of centric mass. And we know the objects on Earth, whether it's our stable or our stable, the centric mass of the bin or outside the base in which it stands. If I lean over too much, the centric mass of the engine goes vertically, the centric mass is vertically further out of where my feet are all over on my stable. So the idea of centric mass is a very intuitive one. We can do that for whole planets, for whole galaxies, for whole clusters of galaxies. We can treat them as just points in space for a certain amount. So we model the planets and the sun's point masses at the centre of them. And then we go away and we want to investigate the forces of the orbit. So we start here at this point in the year. We go around one year, two years, and we're doing it for billions of years. So the orbit of the orbit around the sun is the same. And we need an expression to help us calculate this. So we're going to use a Newton's theory of gravity. So Newton wrote down this theory of gravity and we get two masses. So one mass is big and one mass is small. It's going to be an equally sized gravitational field pulling them one to the other. And it depends on the distance squared. Because the distance gets bigger and the force gets bigger. Newton came up with this idea one day. It's happening in the field, thinking about apple schooling. So we observe freezes. We try to take a particular orbit freezes or cement it here on Mars. Then we go away and observe the motion of Mars and then I'll describe it to the one complete loop of the measurement. That here we go away and we calculate it with that. We'll see that they match. And they match very well for Newton's theory of gravity. So Newton's theory of gravity seems to be doing a lot of things for us. Mathematically it seems quite simple. You can get answers out of it. That's important. But also physically it seems quite useful. It seems to match with Newton's theory of gravity. So Newton's gravity is doing really well. Another thing that you'll find the planets do is in fact they don't have circular orbits. They have elliptical orbits. So an ellipse is just a squashed circle. Instead of having one centre ellipters have two points for them. One of the points is called up. And the other one is the point is the perihelion. And the point that's first away is that you're going to get a point where you're going to get a point that's first away is the perihelion. And that's the point that's first away is the perihelion. That's you're going to get a point where you're going to get a point where you're going to get a point where you're going to get a point that could be any planet. The Earth, the new, sort of the Earth, the Mars, being the students of Saturn's object. Some of them are quite close to being circular. Some of them are much more squashed. And the reason for that is that when the solar system formed about 5 billion years ago there are particular emotions are locked pretty much in that configuration. The doors are safe. Now what's interesting is that the, always a mercury is a particular term. Mercury is really a case in the cell system. What? Mercury moves around the wrong way. So one of the planets moving around is, we consider from the top, let's imagine that they're all moving around the clock. What? Mercury moves around the clock. Again, the weird reading is the formation of the cell system. Mercury moves around the wrong way. The second thing is that there's very little moves. So the orbit isn't just sitting in a little bit flat, it's actually moving around like this. We call that procession. So it tries to stay in orbit, but it stays in orbit slightly changes the iron element which makes a little bit of a difference to the rest of the planets. So all of the other planets are supposed to move much stick to that plane at 2 degrees. So this procession occurs, and you can model this procession with the map that it feels well. You can use Newton's laws to explain what's going on. You can calculate what that procession is, and you can measure it, and people are able to do this. And the measurement that we got in 1850 on the telescope in the map is this. We've got this sound that we have in the Newtonian dimension, 530 up, and we look at the dimension of 574. It's moving around. So Newton is moving around, and we've been teaching scores in the 90s for hundreds of years. Well, not quite, but there is something that we say about the telescope. So this confused a little bit before a long time. So for a while people thought that there must be another planet hidden in the cell system that was dragging on the, we haven't taken it into account in the calculations. We call this a mystery planet, planet X. And, well, basically to this in that, because in 1859, observation techniques had hit one that great, and we just haven't observed it yet for a long time. And there are various papers in the Allens of the World Society for that time, very rapidly in general, suggesting what are the properties and the movements of this planet X. I know that planet X isn't there now. You've never seen one. So there might be something useful out there. How do we explain why Newton's theory around time? So that kind of sat around is a problem, but people are like, well, the rest of Newton's theories seem to work quite well. So let's just imagine that, you know, we can put that to one side for a moment. And then, this is our time. This is our final time, I'm sure you will know. And in 1905, it gave us a special theory of relativity. And in 1915, 100 years ago, he gave us a general theory of relativity. And one of the things that a general theory of relativity does, is it tries to explain gravity. It tries to explain gravity in a completely different way. What's interesting is if you make the calculation of Einstein's theory of gravity, suddenly you get a much better fit to observation than Newton did here. So here, Einstein's theory of gravity, this is theory of gravity, is an assembler of atoms. Why don't we just use Einstein's theory to talk about that sort of time? Because we use this theory clearly, isn't it? And the short answer is Hawkins' razor. In other words, Newton's theory works very, very well for most cases. In fact, we can send man to the moon using a meter-plot. When NASA was working out how much rocket fuel it needed to each stay with the sat and fly rocket, to send man to the moon, and in each stage of the lunar land, when you turn round in the morning and wake up, all it did is it had a computer using meter-plots to calculate the amount of fuel within the moon. It didn't need a complicated mathematics for Einstein's theory. We should only really reach for Einstein's theory when we need to. In situators where Newton's theory is not important at all, because Einstein's theory is hard. It's much harder than mathematics. So for instance, lots. We imagine that light is just this massless thing that travels through the universe. But things with their mass, that means Newton can then have no gravitational pull. Einstein differs. I don't think that's even true. In fact, you can measure how much light is affected by stars, by the gravity of the stars. So you need Einstein's theory for that. Newton's theory of the world. Black holes. The amount of gravity of black holes is so strong that light can't escape them. Newton's theory has nothing to do with that. And in the beginning of the universe, Newton, if you're just to speak about cosmology, in the beginning of the universe properly, you need to think about the full-complete catching of the quantum effects and the relativistic cosmic effects in Newton's theory, that's it. And in fact, we can make some assumptions. And this is an expression for Einstein's theory that's complicated. But under a series of certain assumptions, we can basically make it tell you that Newton's theory. We know how to do that very, very well. So as long as we know that we're moving with those assumptions, we're fine. Those assumptions have to plug. And those will not even be a weak field, a very weak gravitational field. And things that vary in time, then we're fine. We can always use these theories. Otherwise, we've got to go to the complicated Einstein theory. And that's why we didn't have answers to his question until the beginning of the 20th century, 100 years ago. Even though 150 years ago, we're ready to observe this. Now, Einstein's picture of what gravity was doing, if it had a lot of Newton's, Newton's one simply said, object A, object B, they're pulling each other mutually. And how distance between them and other forces. Now, he used that idea because all those other forces are electromagnetic and nuclear forces. We won't have the same idea. Objects, mutually pulling each other with this force. Einstein said that gravity is not one. Now, I'm actually going to develop geometry. Your classic picture, this picture, she's rubbed a tablecloth. It's nice and flat. It's massive. And it bends. And everything that needs to travel along, it's curved. It bends. Light rays, the motion of planets and moons of stars. So for everything, this is the Earth. The moon is just sitting around this mass because of the geometry. It's not necessarily the moon or the other moon. It doesn't have to be imagined because it's straight, it's only the other moon. It's just a facet to do it. So this gives us an idea of actually how to treat gravity, not necessarily as thought as a geometry. And then all we can see is that if we get right to the, before we are on the moon, and we're looking at light from distance, but what can actually happen is if there are other objects behind this distance, what you're trying to do is you're going to go around, you're not going to get that, a quick gravitational lens. And our expectation is that we're going to go straight up. So if you've got two objects like this, a star that way, you're going to go to the east, around the star. It's not going to look like it bends around, but then travels straight to the Earth. And this is another clear indication of how it's going to be. So there is a prediction of how close they are, and we can see these things in this case. News is there, it doesn't know anything about, it doesn't know anything about how light and gravity interact. So using GR, we can attempt to, for instance, model the behavior of galaxies. This is the spiral of galaxies. And we want to basically think about the motion, the speed at which the galaxy moves, the luminosity of the light, how far up the light is going to be. And the size of the galaxy. So those things should be related. All maxim is right to galaxy means bit of opposite. All relative in and out. But we still have some issues. What we expect to see is, as we move away from the center of the galaxy, different bits of the spiral of galaxies, which will just slow down. And they don't. This is what we expect. A flat galaxy rotation. And this is worrying because, again, this is now Einstein's theory, and we can't get a prediction that matches observation. So again, it's in this group. Some of you are not quite matching the theory that we did. So there are a few other things that can happen. There appears to be a relationship between the massive things and the rotational velocity. The problem is that in our current theories, this is the line that we expect. So if we just take GR on its own, when it starts a really great period, it's interacting with all the surfaces that we look for galaxies, it doesn't actually match our circle. There's something more in play. Maybe Einstein didn't think about everything. So how do we solve these kinds of things? Well, one idea is to introduce people to darkness. So everything that I saw in this picture is luminous matter. I look at the amount of light that I get out of this, and the amount of light that I get out of there. I can infer how much matter there is in the galaxy. It's a luminous matter. And then what I can do is I can... from the speed at which things are rotating, I can figure out both size and velocity. What if there's more matter that I can't see? If there's more matter that I can't see, then the galaxies are moving as fast as they can. It's a luminous matter, which means they're in a gravitational system moving faster. If there's less matter, and I can't see the light, then it's just slow down. So maybe there is a sort of dark matter that can explain what's going on. This is really good, actually. If you put dark matter into your models, it explains everything you see in the galaxy. It explains everything that we see in the run, the simulation of the early universe. There isn't enough matter in the early universe, but the gravity of the universe expands, and there's nothing to place at the top together. We wouldn't have what we call the seeds of large-scale structure. We wouldn't have galaxies, but the beginning of galaxies. We wouldn't be if there wasn't enough matter in the early universe. We would be looking at just one part. There had to be some more matter to make sure that we can come together. The problem with dark matter is that no one has seen it yet. We keep looking for it. We keep looking for it on top of the International Space Station. We keep looking for it in the Large Hadron Club for years. We keep looking for it for 50, 60 years down the bottom of Mines in New Yorkshire. Can't believe it. Now, you can argue, well, okay, it's quite hard to say, I'm sure it's going to get better and better and better, but even the people who have been hunting for it for decades are starting to wonder, hmm, is it really there? You've found the matter in some instance, and you didn't think about something in a convenient way, and then you didn't think about the consequences later. That might be the case. So are there any other ideas? Another idea is to basically take the dynamics that we have and modify them to modify the thing. We do it at the scales at which galaxies are found. So on the scale of the solar system, on the Earth, the gravity seems to be very, very bad, but on the Galaxy scale, general relativity seems to be very, very bad. So at this scale, the temperature of the wind is 10 meters per second. It's weird. Maybe we need to think about having a gravity period isn't quite that, you know, that's it. Now, the gravity of the Earth is 10 meters per second. So we're looking for a number that is almost a billion, billion times, sorry, a million, million times smaller than the acceleration time. There we go. Now, it's over. This is quite easy. In the last about 10 years, we've worked out a nice place to make this a period in a very coherent way. We can write properly down the theory that we can get numbers out of and then calculate as they matter. You have to put in a lot of numbers by hand. You have to say, I go away and I look at Galaxy, from those observations, I get numbers. I can put those numbers in my match, but I know in your way of getting the numbers out straight away. And that's true. Because our expectation of visit is that we can put in everything we need beforehand and then have it. It's a bit messy to find work hand numbers from the experiment and then use that to fix it. Say, ah-ha, we knew the answer a lot. Yeah. To find you is a problem for us. Now, these ideas of dark matter, also dark energy, so dark matter is, as I was saying, this idea that you have all of this matter that sits around in the universe, but you can't see it. Also, there's going to be a dark energy that's in serious force that is explaining why the universe is so important. The ultimate big matter in the universe was initially expanding, but in fact, in physical expansion, it's actually speeding up. It's not slowing down, it's speeding up. So, in the term that it's expanded and then the graph is pulling it back, it's actually speeding up. It was something you believe as an image of dark energy. Dark energy won the Nobel Prize in the year, so in 2013, signed for everything, this measurement, this is a picture of the night sky and this temperature fluctuates so if you look up in the sky, it's sensitive enough to the moment that you can detect about 3 degrees of heat. Now, 3 degrees of heat, so the cause of it might go away back. So, left over heat from the big bang, so the temperature of the big bang, a few seconds after this is about 10 to an hour of 10 degrees Celsius. So that's 1 put up by 10 zeros. And then the universe expanded and it cooled down. The energy density dropped, dramatically. Nearly 14 billion years later, that heat is now 3 degrees. But in fact, it's at 3 degrees and it's slightly hotter in some places and it's slightly colder sometimes. So this is basically telling us where the hotspots from the cold spots are 100,000 of a degree big. And they're really tiny fluctuations so at least we're really sensitive to the amount of saturation that you measure these things at the moment. Then you can't see. So the earliest satellite that went to measure this in 2019, which is one picture, a series of satellites produced a picture in 2003 and these produced the best picture we've got so far in 2013. And you can't easily go much better in this picture. We're basically the limits of technology because in order to use measurement or something coupled, you have to be coupled and you want to easily detect what's going on. So they have to fill their satellite in space to something colder than this to measure the deviation time. So from that picture, we were able to get with the power spectrum. So the power spectrum tells us as we go along in the sky, just 0.1 degree, 1 degree, 90 degrees across the sky, how's the temperature change? And the red points are the data points of the data from the map of the spectrum. The green line here, the green line should be. And what's interesting is that the theory, the red point, pretty much match much better than the silver and silver states. They're pretty much match at the same time. So you make a measurement and you make another measurement and you make another measurement and you see what's the range of the range. They're all really close to getting the arrows. They're all a bit in space. They're out of the arrow, I would say. It looks so like as we keep going along here, there are normal arrows. It's not the renown arrows, it's just a really, really small, a small point to make them work. So what this picture does is it assumes dark matter, assumes dark energy, assumes visible matter, assumes general relativity. And we seem to get a pretty good fit, the best ever fit, we've got into the theory of this emotion. And what we have to put into your theory is that you can get a universe that's made up of about 5% of all the energy matter. So 95% of the universe has made up all the weirdest things in the world. About 26% of dark matter and about 68% of dark energy. So most of the universe has made up of energy. We know nothing about it. We know zero. We know that it falls into the accelerated The dark matter is a thing that made me think of a better idea that we know what it can't be because we've been looking for it and we know what it can be. All of the places that we haven't found may only be part of it, but there are so many possibilities so we don't really have fraction of what the universe is. And so these are the two cornerstones of the universe. The theory of gravity was the idea that the universe was being predicted by dark energy and dark matter And what they know how to do is to take these assumptions we can draw together a series of observations as soon as the predictions seem to match observations so we can basically keep going back in the past. We can always say how energy matters are distributed in the universe. That matter and the temperature tells us what the universe was doing. The universe was about 330,000 years old. The universe is 14 billion years old. So we can go back nearly 14 billion years to what the universe was doing then. If this temperature matters, what the matter, the energy was doing then. As I've explained to you, there are some issues, there are some issues in the general world. There are some issues that don't matter. If we want to first match the galaxies, we have to put dark matter in them and then we don't understand what that matter is. If we want to first match the cosmology, we have to put dark energy in them. So how hard do you have to work if you're up to the next generation? To actually say, yes, I'm happy with this. So far, all of my observations match my directions and I'm very clear about what's happening in the universe. So how does the universe come up with the galaxies? The magic is a way to explain where that flat rotation curve comes from without dark matter. And basically, what it says is that if you take the user-sector law, the user-sector law is ever to come. That's what I'm talking about. The F here is the gravitational law that we took into account. And the A is something called the rotation velocity. So if you know the velocity across what's in the unique ground, and it's the size of all the things that are moving in, you know the acceleration. It goes to least variable. And the gravitational force goes to a constant, very small number. It's the size of the two masses, the right and the fire, the size of the all the speeds. Now, the idea is to reform this law which is held quite... and change it before we get to this explanation. Now, you might think, well, why? If we can use it to explain what's going on with this rotation, that was invented in the form of matter that we haven't been able to see. Namely, atomism. And then we go into all the other consequences. What we do is we add an extra term into this unit in second law. And what that extra term does is it gives you exactly the behavior you need in matter. So it gives you the Newtonian behavior when you want it. So you'll get that acceleration much bigger in the gap. And constant. The V goes to constant is a flat rotation. So what I did was add an extra term into my law of physics. And I can explain it to everyone. Without a swing, we are massive. Without a swing, anything. Then you say, OK. So I've worked out how to fix rotation. So I'm going to test this in a different range. You'll have to see how I can make this work in other regions as well. But the problem is that we need to test it in low-acceleration environment. Because any law of potential acceleration is 10 to the minus 10. As I said earlier, the acceleration is 10 meters to the minus 10. So we can't test this in the environment. Now, that sounds like a problem. But it's OK. We're used to not testing everything on Earth. We have to find somewhere that isn't a galaxy but some millions of light years ahead to test these areas of gravity. Now, it turns out that you can find just such a point in the services. So if you pick two masses at the side of the Earth, the gravitational masses are trapped. Right? For all of the, let's say, well, the international space ocean, we always need to have the international currents. OK? We can mention it falling to the Earth. But what errors are often had to do is to push it back into the Earth. So the Earth is a trap for the sun and a trap to it. But it must definitely be a point in between where the two attractions can't stand. OK? And in fact, if you write down the theory of gravity and the sun and the theory of gravity on the Earth, you'll see that one is the minus sign and one is the plus sign, minus the plus and sub point and I've got to equal zero. And so there is a point, somewhere between the Earth and the sun, where the acceleration is zero. Now, if the acceleration is zero there, close to it, it must be small. It must be around this tending point. So we want to go there. And those points are for several points. That's the mathematical term for that point. And several points are really easy to picture. They're print. They're just print. That's all there is. You ever go in the evening and you see one? And you see, you only see print. So there you go. What it has, it has a minimum one direction, a maximum one angle. So if you're people, the Earth would say for him, the sun to appear, fall down towards the Earth, fall down towards the sun. It's a very unstable book, one way, a very stable book. And so these seven points are very good if you want to test these ideas. Speaking of that. So it turns out that in this weird theory, the force is going to go towards the square root of the distance between around the subtle point. Now that's interesting if you want to test forces. But another point that we need to take is the circle of tidal stresses. Tidal stresses are what cause the tide to move. When the moon is in a particular position in the sky, it pulls on the tide. It pulls on the tide so that they get stretched as they come in and out. So it's just scorched. And the distribution of that so the variation of the force of the distance moved to the point of tidal stress. The stress is just some force that we put on top of it. And we use the principle that's taken the last pattern of stretching and the stress of attention. But that doesn't necessarily need to change straightforwardly. It can change in different ways in different directions. Now the tidal stresses for this force basically go like one over the distance. The thing is, what that means is that we get to the sound and the tidal stress is just some force. One over zero is even. So this isn't one of those with the regular Newton or Einstein gravitational force. It's what happens with the fixed gravitational force. So scientists are interested in using this as a way to measure whether we have this region and this goes. So this is the sector. Around the southern point there must be some weird region where the weird theory applies. If the weird theory applies we can make weird observations. There's a weird observation and they're different to the Einstein's theory. I'm not sure. How do we do it? This is a picture of the laser in the front of space. This is a space mission that was proposed by the European Space Agency. And what it's looking for is a reference in space time. So we're used to having a point and it's dark so we can all get ripples and glutes. It turns out that from Einstein's theory the one key observation we haven't made yet is that there should be ripples in space time. In that flux so you take the table that we're going to talk to and imagine now that the laser is set up and then you ripples in the table. We should be able to measure that very, very weak. And one of the grand issues was to put that three of these things in space and the other things in the middle of it three of these things in space and then measure if the ripples of space have come along how that changes in room so it can be about 300 kilometres long. And you can measure the radiation on these lasers and you might be able to stop these ripples and so forth. But what's interesting is that these are very sensitive gravitational instruments and so if they're incidental we might be able to use them to test these other ripples. And this is the mission in question this is the least part one. This is the test mission and the big mission. We're not going to launch a big mission straight away. We didn't send a product one to the moon because it was one to ten and had to go into Earth orbit then they had to go around the moon then they had to go around the moon in the map and then they had to go around the moon. So you don't be sensitive in a straight way you have to test the instruments. You're going to spend 100 billion euros just to increase the price agency. Building a machine you've got to test the instruments in the world so you build this little ten across a few billion euros. And what it's mentioned is just testing one of those lasers so you have two masses that can be there are three floating in space there's a gravitational force of one of the between them you've said a laser being around and one laser being around but if they match and you get a picture that says they match that's fine if one gets a move from there to the other one the laser that you get the laser doesn't match and you can see that very very easily so you can test the gravitational theory with a lot of tests very very nice test So this is what we expect to get this is the iron star this is the weird thing so this is you get closer they're very different and they're very very different so it's not that you would expect not just that you expect something different it's so different you can't miss it now that's really important because if you have an instrument that really senses that effect it's dotted points and your signal is very strong you want to hope you can see it now the problem is if you're going to measure something with a meter ruler and it's sensitive to ten centimeters that's not correct it's sensitive and the science that we often speak about is we use statistics to work out how likely the result is so how likely is it that it's actually a result how likely is it that something happened by a few just by random I'll tell you if I pick up a coin ten times and I get six heads and four heads is it reasonable to assume that the coin is fair or not probably not ten isn't many trucks unless they're hundreds and that if I pick up a thousand it's still getting as one side and 40% is the other then you can start to argue that there's a chance that the coin is not fair so we get this idea that there's normal probability distribution so a normal probability distribution basically maps all kinds of different things if you take in a population their heights their lengths even their shoe sizes they're all mapped by a probability distribution most people sit around the center some people are short so although there are all people in society for instance we're replacing professional basketball and there are a lot in our short people but there are a lot that we're not necessarily in America we're just out of touch and we get this idea of a signal a signal is looking for the standard deviation and then one signal around me or the chart is something to be fluent about that it's just under 30% and we go to this 2 sigma recovering more of the population chances of what's left is 5 signals the gold standard of this is 5 signals when we were looking for the Higgs boson you've already heard of the Higgs boson a couple of years ago we were all waiting until they collected enough measurements to hit that 5 signal to say that chance of a flute was 1 in 3.5 million so the chance of this being brought is 1 in 3.499191 enormously large chance of something in this experiment one expires in 1588 and that's great because it tells you either that your theory is right and you're going to see something or you don't see something it tells you your theory is wrong beyond belief so it's a double-edged sword even you see something and you can say okay our standard wasn't quite right I'm going to collect my own words or you can say that's the drawing board these theories are so wrong don't even talk about them now what's interesting is in fact 28 signal is in this map the people think we can actually get close but this is saying your foot the noob it's actually the instrument it's probably down in the and what if you can get very close to the sound we can get very close to that point in space so this is 50 signal 60 signal down here and now they think that's slightly different now this is a nice test but also it's a nice test because it's direct so you go to a point in space and you measure you don't want to do astrophysics astrophysics is messy astrophysics is messy and you just see like this you can take the you can learn and measure the data what are the different accelerations there from galaxies so dwarf galaxies is a small one gas is so I'm just going to just explain this spiral is basically and they're a bit wheeling next then you can get groups of galaxies and then you go and you say what's the accelerations there because you remember 10 to the minus 10 was the galactic accelerations there and lots of galaxies are these spirals they're pretty much around but lots of these are not actually being and some of these are not so if you're going to do everything astrophysics you're going to be in trouble it's nice to have a nice direct test which is what this test around us is cancellation the final thing I want to say is that when you test gravity with boundary so we know that the orbits in the solar system are not they're nice and elliptical as general as it is we know that galaxies are doing something if you look at the dark matter over there but actually there's a very big region when you think about accelerations that isn't tested and that's interesting because this test will test us in a minute so scientists have been waiting to test everything from the very beginning very soon and it looks like there's an opportunity to do that so the last thing I want to say is that it appears that we have many ingredients for our theories and we appear to have some idea of what may be the universe is now even though we don't necessarily well understand so hopefully you'll see that there's quite a lot about the gravity in the universe we do understand we can measure a lot now although this is precision science but there's still quite a lot to be figured out every time I go and speak to students so that could be you who changes our understanding of the whole universe because so far there are lots of big questions that we haven't answered thank you for listening we'll pass it on to you Thank you Alicore for the testing to you Do you have any questions for Alicore? Do you have any questions for Alicore? Do you have any questions for Alicore? Do you have any questions for you? Do you have any questions for anything Yes Johnny What about I don't know I don't understand what you're saying but maybe does anybody else know what I am doing? I'm doing basically understanding is if needed there's a solution and that needs to be worked Yeah there's no question about the person who's coming here So in the history of science and fire, that's quite common. People come up with ideas to fill in the gap, and then they say, OK, well, why assume that? One, what else is it involved in? Two, where else? How can it come? So when they did that with the dark matter for the galaxy, and then they said, OK, if there's this dark matter hanging around the galaxy, how much is it? Then more or less the invisible appears invisible. What happens if we put it in into the early universe? So it turns out, right when we put it in, we need to put it in. So it seems to be needed in lots of different areas. So that's a strong indication that there's something playing. That's a strong idea that the negative is a product. The problem has come for dark matter, is that no one's been finding it, but keep looking, and you haven't managed to find it. And either it interacts very, very weakly, which is true, gravity is a very, very weak interaction. If I'm standing here, I don't necessarily feel that I'm pulling the soap and soap and putting it in me, whereas I'm going to get a fridge magnet and a different thing, and it can require gravity. So the problem is, is to find the dark matter in any other way, other than with gravity, it's quite hard. But you're right to say, well, we've been looking at it for a long time. Didn't we just fit in and put it in the mass? Yeah, it's a strong argument that it's right. And this is where this other idea that was to be modified has now become a bit more popular. In the 80s, it was kind of considered, well, that's an idea, and there are 100 ideas that are coming up. It's an idea that's kind of static, but it's almost at the same position as people say, OK, the moment is dark, and the dark energy is more worrying. Because, as I showed you in the pie chart, it appears that most of the universe is in the dark. And we have, I can't emphasise enough, no clue what it is. And worse than that, if you try and put together the quantum ideas of universe and the gravity ideas of universe, the quantum ideas predict an amount of dark energy that you can get. It's something that we would have tamed if a power of 100 is smaller than it should be. So that's 1, quite about 100 to the power of 100, OK? So to know it's astronomical, it could be wrong. But somehow, there's something that's making the universe acceptable, you know? And it's, it's, it's a thing. If the dark energy is even worse than feeling the mass, it's just like, you put it in because that, that's the only thing that appears to be, we have no clue. And there are more satellites that are coming in through it. So that was the mission that's going to be launched this year after the pie chart. There are three more that are going to be launched by the human space entity, by the end of 2018. All of them are looking for hints of what this could be, if they don't matter. Whether they'll find it or not, but it's something that's on scientists minds a lot. There's every other bit of genealogy that seems to match. To give up on it so, so easily is, is a lot of things to be shared. Any other questions? Any other questions that you have? So how, how do you, does anybody look at what's going on in the universe itself? Right, OK, so, it's a lit, have you seen? It, it, it boils down to what you mean by the universe itself. So it's a bit like we live in the universe and the universe is expanded. What's an expanded hint? A lot of people say, what's an expanded hint? Nothing, the universe is just expanded. What it appears is that, if I take, let's say I pick year one, two points in space, in year 10, they've moved apart, in year 20, they've moved apart. Because the space itself is moving further apart. The universe could be relevant. More than that, the universe doesn't have to be flat. It doesn't have to have an edge. We are limited by the fact that light takes a certain amount of time to reach us, light travels at a certain speed, it's 300 million meters per second. That's enough time, it's so quick and you can go around the earth, this comes to be a seven and a half times per second. But it still takes an amount of time. So there's a visible universe and then there's a whole universe. And we try to get hints of what a whole universe is like from the visible part. It could be completely different from that. Unlawfully, but it could be completely, we could just be like a bubble. The universe outside could actually be rotated. We might be able to get a hint of that from the edge of the visible universe, but because it's the universe itself, it's the everything and everything. It's easy to do this, but it could be rotated. What effect does that have? Not much, because it's the whole universe. If you were rotating inside the universe, if you were rotating, you have a reference to something that's static. If the whole universe is rotating, then you have more references to it. You don't notice the difference. I mean, I'm on the earth, and the earth is rotated right now. I don't really see it. I can measure it very carefully. I have a pendulum, and the pendulum will make a slight procession in this. I think I have a pendulum, and there's a scientific procession under the sea. It makes a slight deviation. But that's because we believe we're stationary and the earth is moving. And it's basically pulling on it slightly differently as it rotates. There's a whole universe to it. It's hanging out slightly differently. But if you have a pendulum and a wreck, you still have a pendulum that's going to go to the earth. So the universe is still time-consuming. It's going to go to the earth, the climate, it's going to start going to the earth. It's going to speed up the universe. Right, it's so much faster. Right, okay. It's getting a little bit more flexible. It's getting a little bit more dangerous. It's kicking the wreck. Yes, I think you're doing a little bit more of a good job at work. You're so good at this. And if you're playing, it's kicking the wreck. And it's doing it. You're so good at the work. That's it. Short, although... No, it's a good job. Although the issue of doing these experiments on earth is that there's gravity on the earth. Okay, but you have to worry about it. If you're on the universe, you don't have to worry about the gravity. So it's a bit like doing a tablecloth experiment, and you distort the tablecloth and you take a ping pong ball and we flip it. It goes around in circles, and eventually it goes to the bottom. That's because there's gravity on the earth when you do these experiments. If you did it in deep space, if you did it in deep space, you'd have to call that different. You do it in deep space, the tablecloth, that's different. So, you're a bit careful about analogies on earth, but I take your point. It's certainly a way... There is an effect, okay? It's called the lens theory effect. Rotating things and gravitating in general produces weird forces. But not nearly enough to cause this acceleration expansion for the universe, unfortunately. People will ration their brains for decades trying to find an explanation for this dark energy, using just relative energy. So, that's what I had to put in this tablecloth experiment. Any other questions? Any other thoughts? Any other random ideas? I have one, though. Do you say you got the market and dark energy? Now, what is the difference between the two? Oh, because the matter and the energy could be the same, but Icelanders and the matter and the energy are the same. So, dark energy... The same dark energy you can sit around in, like, atoms or lumps of matter, like, regular, visible matter. It's just that we don't know what the lumps are made of. Okay? So, there are... The other idea is that neutrinos, this fundamental problem of neutrinos, could be the dark matter. So, neutrinos are just these particles that get produced through the sun, and the sun undergoes a nuclear fusion. These neutrinos get produced, and they're streaming through us right now. They interact with us. We, very, very rarely interact with them. There are billions of neutrinos going through the water. So, for a long time, people thought, well, we have neutrinos in the dark matter. Okay? Or they are a matter that you feel gravitationally, objectively, that you have a central matter and you feel them, and you can't see them. They don't interact with that electromagnetic force. There's no interaction. So, it could just be that atoms are made of some weird stuff, weird, dark stuff that no one interacts with. The dark energy is really quite different. The dark energy is a bit like taking a balloon, okay, and blowing into the balloon with a constant pressure. Every point in the balloon is sort of something that starts moving away from you. But there's no sense in that energy. It's just everywhere. So, if you were like an analogy, let's say you were in the swimming pool, okay, and you're still in the middle of swimming, you're in the visible state. Suddenly, out of the swimming pool could be popping in and out of existence all this dark matter. These voids are popping in and out. But the dark energy could be, for instance, the current. So, they're very, very different things. The dark energy is everywhere all the time. And the dark matter is particular. You just can't see it. How can you then try to make it or to detect it if you can't see it? Well, well. So, if the dark matter is made of things in our current theories, things that don't interact, for instance, the Adrinos was that idea because they're not heavy. And there are other ideas for particles that don't interact with light, that do exist. They may even need to find a value that can reach new particle physics for properties of light. So, that's what they've been doing as a large hydropower. They've been trying to make weird particles be heavy enough to be dark matter that don't interact with light. But it hasn't gone very far. To protect the theoretical, it makes things that don't interact with light that haven't been there all the time. So, the dark energy is even worse. We have to infer the dark energy from other agents for instance. Supernetic. So, supernetic are stars that explode. And they give out animatic light. There are some supernetic stars that explode. There are certain stars that give out a certain amount of light that's fixed. So, if you know the fixed amount of light that's going to be scattered, the light is, and you have the right, it shouldn't even be perceivable because it's a standing brightness. Is that going to be a hundred-four-fold? Then you can work out of this moving away from the world. To begin with, so far, the only way we understand the major dark energy is through the observation of light. Not just planets, but all galaxies. All stars. Massive stars as well. The missions that are looking to be launched, what they want to do is look at old lights, so light from the very early night from the edgings observable, and see what the emotional characters look like there. Because if you can work out what they're like now, is the amount of dark energy constant? Can it go up? Can it go down? If it's been constant, then that can rule out certain kinds of dark energy. If it's not, and it's gotten bigger and bigger, then that means you need a different kind of light. Wait five or ten years, and then maybe it'll be able to come up with a new structure. There's a sort of suggestion that the future will actually be able to do to manage the system. So, would you say that the research now is important? Could it be critical? Or is that something that needs to be added to the story? So, the story is is that on the expected lifetime of humans on this planet before the sun explodes and kills the sun. With the sun at some point will run out of field, turn it to a red giant, and melt it. On that time scale, the effect that you're talking about isn't significant. These things happen in astronomical times, billions of years. We believe that we have a few tens of millions of habits of the life on the earth, if we haven't destroyed them. No, it's the answer to your question. Astronomical times because they really are astronomical. There are ideas to do what we call real-time cosmology, which is try and measure things, and then see if we can do it better and see how much they're changing. We haven't got sensitive enough instruments yet. Maybe in ten years' time we might. If these instruments that are on the earth now in space, there's a generational shift that's looking to me. The Hubble Space Telescope, for instance, has been up in space until 1990. It was a massively impressive use of the universe. We can't get as much of it as we want with the atmosphere. So once things get more moving to space, maybe we'll be able to say something, but at the minute we're still not quite sensitive enough to see in real times what's been these observations. Can you find any questions? In that case, thank you so much for attending. So this is the last of this series, and the physics class will start again in October. Sometime in October, we'll have to decide a new program. By the end, we'll have one physics class to talk every about three months or something, so four physics classes per year, and we'll start again in the future. Thank you so much for being with us. Hopefully you will enjoy it. I did personally. So thank you to Ali.