 Welcome to Think Tech on OC16, Hawaii's weekly newscast on things that matter to tech and to Hawaii. I'm Keisha King. And I'm Cynthia Sinclair. In our show this time, we'll attend a talk by Professor Sven Vossen of the Department of Physics and Astronomy at UH Manoa. Sven presented his talk at the September Science Cafe. It was about dark matter in the universe, what it is, and how we can learn more about it. He took his PhD in physics at Princeton, then worked at the Large Hadron Collider and CERN in Europe. He came to UH in 2010. He also does experiments at the Bell II particle accelerator in Japan. Dark matter is exciting because it constitutes the majority of all mass in the universe. Learning about it links cosmology with elementary particle physics. This necessarily involves the study of the universe as a whole. Dark matter consists of the elementary particles that were produced in the early development of the universe. Sven gave us what he called a gentle introduction to particle physics and dark matter. He told us how experiments to test the particle dark matter hypothesis can be done. He also introduced us to his pet project, the development of a directional dark matter detector. Dark matter ties together so the largest thing started in nature. The universe as a whole, galaxies, and the expansion history of the universe, which is illustrated on the left. Here you can see a picture of our local home in the universe, the Milky Way Galaxy. We think it's surrounded by halo of dark matter particle. Some mysterious massive cloud that we have to probe exactly what it is. Dark matter is also connected to the study of the smallest constituents of nature. That's the domain of particle physics. So dark matter is especially interesting because it connects these to the studies of the largest and the smallest things in nature. What is the goal of all ever doing of particle physics? So the goal is kind of to understand everything, but more specifically what are the fundamental constituents of matter? What is everything made of? What are the smallest building blocks if you zoom in and in in nature or does it never stop? What are the forces that sort of govern how those things move? What's the proper mathematical framework? What are the right equations to describe those things? On a larger scale, what's the composition of the universe of a whole, you know, where does the universe come from, how does it evolve at the time? Before I can get to what I really want to talk about dark matter, I have to talk about what's matter that's not dark, okay? Ordinary matter. I call it ordinary matter. The ordinary matter is all you've ever come into contact with and probably ever will. Ordinary matter consists of atoms. All atoms consist only of three elementary particles. Any atom will kind of look like this, a big cloud of electrons on the outside and then a nucleus on the inside. The size is sort of a tenth of a billionth of a meter in size. So that's pretty small. Much smaller than that is the nucleus on the inside. Inside the nucleus, you've probably learned in high school on neutrons and protons. But today I understand even those are made up of other particles called quarks. There's only two types of those. It's actually very simple. Let me zoom in. This is a neutron made up of two down quarks and an up quark. Here's a proton made up of two up quarks and a down quark. So all the atoms, all the particles ultimately made out of up quarks, down quarks and electrons. So three particles are kind of needed to explain everything you come to contact with. And in addition, there's a fourth particle for the electron neutrino that can be produced in radioactive decays. And so what do we do with that? Well, as physicists, we really like to organize things, okay? That's one thing we really like to do. The first thing I'm going to do is I'm going to take those four particles and put them in a table. So here are the two quarks, the up quark and the down quark. Here's that electron on the outside of the atom and here's the electron neutrino. And so that's good. This can kind of explain most of everything you come to contact with. But it turns out, there's two copies of this in nature. Using higher energies, and that means either we look at cosmic rays coming in from space or we collide things with man-made particle accelerators. We found that there's two more copies of all of this. And you know, those copies aren't really good for anything. So in addition to these particles that I just talked about that make up everything you know, well, those are the first generation particles. There's two more generations of matter. And these are exactly equal to the first generation particles, but they have higher mass and they're unstable. So in the laboratory, I can take two electrons and collide them together and I can create all these other particles if I have enough energy. So today in nature, only the first generation is present. In the lab, we can make all three generations. And in the early universe, it was kind of like in the laboratory today. Energy is so much higher, the universe was hot. When it was young, all these particles were around in the early universe. But only the first generation were stable, so only they are around today. We've also come to understand forces better and also forces seem to ultimately be explained by elementary particles. And to illustrate that, we have this picture here. There are these two women in boats that throwing this ball back and forth. This basically shows that these two women are going to be repelled from each other by throwing this ball back and forth. And analogous to that, you understand today that when you have two charged particles, like two protons inside the atom, they have a positive charge. You might have remember from your physics or chemistry class, equal charges, they were held. The Coulomb's law, there's a force between them. Today, we understand that force is being due to a photon being exchanged back and forth between those two protons. So the photon is said to be the force carrier particle for the electric force. That's the electric force, but there's more forces in nature. So we found out that there's actually four forces in nature. So the one I just talked about was the electromagnetic interaction corresponding to charge and electricity. Drawing nuclear force holds together the particles inside the nucleus of atoms. The weak nuclear force governs reactive decay and then there's gravity. And just like I put the matter particles in the box, I can put these force particles in the box. Here they are. There's four of them and for each force in nature, there's sort of a force carrier particle that can explain the force. So the photon is the only one I'm going to talk about in this talk. The photon has to do with light. It's the particle that makes up light, basically. Today we understand light is being made up of quantized little particles called photons. The other forces too have force carrier particles, which I won't talk about except on this slide. So the strong nuclear force corresponds to glue on exchange. The weak nuclear force has two force carriers, shown here the Z and the W boson. And these particles have been detected in nature. We think that gravity has a force carrier particle called the graviton, but it has not been detected directly. With this new understanding now, what happens when you see something? How does it work at the elementary particle level? So what happens when you see, let's say, the light up there or the sun? What's actually happening at a detail level? So the light emits photon, photon comes here and hits my eye. Okay, what if you see other people? What's happening? Okay, I see reflection people saying, yeah, the photon hits the other people, it's reflected. What happens if you see yourself in the mirror? Okay, bouncing off of you, bouncing in the mirror, bouncing back to your eye. Okay, I have to think about that for a second. What if you see a very dark object? Like this thing here is much darker than maybe my hand here. So how come you can still see it? Why is it darker? It still reflects, but not so much. It absorbs maybe a little bit of the light. You know, absorbs maybe some of the light frequencies, some of the photons. Okay, so dark thing maybe blocks light, it absorbs light. Okay, and so I'm going to work my way up to dark, because we're going to talk about dark matter. And you see, dark matter is different than a normal dark object. So this is the modern picture. On the left, we have what happens when I see, here's an electron in my eye. And we think of that now as a particle of light, a photon coming in and being absorbed by an electron in my eye. When a lamp emits some light, you know, there's an electron that has high energy, it emits a photon and then the electron goes on. This is sort of called a space-time diagram. That's not really important, but we now think of all processes as sort of simple diagrams like that. Putting everything together, three generations of matter particles. One makes up everything we know about. There's two more we can make in nature. There's force-care particles for each force of nature. Okay, and so this is, you know, there's a theoretical framework that is highly mathematical that describes, you know, how all of these particles move under these forces. It's called the standard model of particle physics. And people came up with it in the 70s. It took a long time to get there. And this model also predicted a new particle, the Higgs boson. This was required so that the equations could be solved at high energies, you know, describing things that move fast. What do we mean by theory and physics? I want to say if theory and physics is different than if you have sort of a theory, just an idea. You know, these theories, I would say, they're the crowning intellectual achievements of humanity. You know, the standard model predicts basically the structure of all atoms, the shape of the electronic orbitals. In principle, you can't get all the chemistry from it. And the standard model is the most precise, quantitative physical theory that's ever been constructed by mankind. And it's tested to one part per trillion. You know, all the particles that make a matter, all the particles that make up forces, we have an amazing, accurately theoretical framework. So it seems kind of like we're done, right? So now we're going to take a step back and think about, that's all I like to put things into boxes. So now I'm going to think about the theories that have been developed over time in physics and see where we're at. And so we're going to start with the first theory of physics that you probably learned about in school, Newton, okay. So that was part of classical mechanics. So that's at the origin point in my little graph here. And so Newton, he was also the guy with the apples. He also came up with Newtonian mechanical gravity. So I'm starting here with a theory that only has forces and no special effects. And then I'm adding gravity here, going up along the z-axis here, the vertical axis. So now I want to have a theory that can also work in sort of other special circumstances. For instance, when theories move very fast, I need a slightly different version of Newtonian mechanics then. I need relativity and Einstein came up with that in 1905. So that's quite a bit later. He added a theory that can work here when you turn on relativistic effects when things move fast. He wasn't happy with that. Einstein also was thinking about gravity. So he wanted to combine his theory of gravity. So I wanted to basically take gravity up here and combine it relatively here. And he did that. It took him another 10 years, okay. You know, one of the smartest people I've ever lived. In another 10 years of work, he came up with general relativity that basically described gravity as the curvature of a space-time. So that's a very deep concept instead of another big achievement of theoretical physics. But it turns out that wasn't enough to describe all of nature because when we probed into subatomic physics, we didn't add another theory. We needed a theory that could explain creation and annihilation of particles, how new particles get created in our particle accelerators. And so for that, we needed the theory of quantum mechanics, which you might have heard about. And so the quantum regime is on my horizontal axis here, going towards the right over here. 1925, it came out of the quantum mechanics. At particle accelerators, actually things are both very small, they're subatomic, and they move very fast in relativity. So we need to be over here. We need a theory that has both quantum mechanics and relativity in it. That's called quantum field theory over here. And that was developed in the 70s. And the final touches came from Feynman, Tomonaga, and Schwinger. So the question was, are we done? Well, you notice that this thing here is down in the vertical direction, it's still at the origin. It doesn't have gravity incorporated into it. So now we're in the situation where we have one theory over here that describes the universe as a whole and its evolution and gravity. And we have another theory down here that describes particle accelerators, creation of particles, and relativistic objects. What we wanna have is a theory that's up there. We wanna have a theory of everything. So we're definitely not finished from this perspective. We haven't found a theoretical framework that actually describes everything in one. But this is actually far from finished. Of course, in addition to looking inward into the smallest things, you can look outward into the universe as a whole, into the largest objects. And this is sort of cartoon of the universe that's quite useful. The vertical axis here illustrates space and the idea that the universe gets bigger with time. Horizontal axis is time. This horizontal axis, we now know that the universe is sort of 13.78 billion years old. You understand the universe to sort of 1% precision. It's not the same precision as in particle physics. We're talking about par patrillion, but it's starting to get accurate. And we now also have sort of a standard model of the universe, but it's at the 1% level. We know there was a big bang at the beginning. We think there was a period of very rapid expansion, called inflation. This slope here, this line here, tells you the speed at which the universe is expanding. And so this, you see, initially it's expanding fast. Then it's expanding roughly at a constant rate. And so what do we expect for the universe based on what you know? Well, the universe, it's kind of like an explosion a little bit. So explosion, things fly out. So that's what's happening here. Explosion in space with lots of stuff that also has a lot of gravity. You know, if there's too much gravity, eventually the stuff will slow down and go back together again, right? But if there's not enough stuff, it'll keep sort of going outward forever. So you would either expect the slope to become smaller or continue at the same rate. Or we'll actually look at the universe in the last seven billion years, the expansion rate has been accelerating. So yours actually started to expand more rapidly. So here's the problem, because none of the other stuff what it's told you about, if you thought about it at all, none of it can actually explain this feature that the expansion of the universe is speeding up. We don't know what's causing this, okay? So if you have a name for this, we call it dark energy, but that's a name. We don't really know what that is. Okay, we can also analyze what happened inside the universe with things that we can measure. We can see light from the early universe. This makes up some of the static on your TV. When you turn it on, that fuzzy picture you see, some of the signals created by the light, not too long after the Big Bang. We can look at the structures that's formed out here, ending up with galaxies in a home universe today, satellites that can observe these things. And what we basically learn if we analyze the universe is that all the standard model particles I told about, I said early on, they can explain everything you see. Yes, that's true in everyday life, but in the universe, they actually only can explain about 5% of the energy in the universe. And then about a quarter of the energy in the universe we call dark matter. So this is similar to regular matter in that it's gravitational. It doesn't lead to this increased rate of expansion, but we cannot see it in the same way as normal matter. And so now I talked about, how do we see things? We see things by them interacting with photons. That's a normal picture. So this is a new type of matter that doesn't interact with photon. Okay, so here's my question to you then. Is dark matter actually a good name for dark matter? I mean, that is the name, but is it appropriate? We said in a normal dark object, we call it dark because it doesn't really reflect light, right? But I'm telling you, dark matter is something that doesn't interact with photons at all. It's transparent matter, exactly. That's what I wanted you to say. Yeah, so dark matter is something, light will just pass through it. It doesn't emit light, so that sense it's dark. It's not like a glowing lamp, but it's not dark like a person who sort of, you know, wears a dark shirt and they absorb the light. It doesn't reflect off of them. If you're showing a light on dark matter, it will just go through the dark matter. That's more like transparent matter. But we can't see it. So here's an elaborate picture that took a lot of time to produce that shows, you know, regions, it shows two galaxy clusters that have collided out in the universe. And it shows two regions that are colored blue here where there is dark matter. And the way it can sense that it's there, it's by its gravitational effects on light. It still bends light as it propagates. Luckily, we have a theory called supersymmetry, which also predicts particles. Okay, so particles over here and particles over here. Take a normal particle and put a little wiggle over it. We call it a sparticle. Just like we have the top quark over here, the last matter particle to be discovered. We have the stop quark over here. We have the gluon over here and the gluino over here. Okay, so what's kind of amazing is that this theory roughly doubled the amount of particles, but some of them, the gray ones over here, the superpowers over the force carriers actually have the right properties to explain the dark matter. This theory, you know, was invented though before we really knew about dark matter. So it's not sort of a prediction in hindsight. So that's pretty powerful. It was invented for other reasons and it has something that could explain the dark matter in it. Doesn't mean it's right, but it's interesting. Supersymmetry is good for a bunch of other reasons too. So we talked about there being four forces in nature. So that's today in the cold universe. If you heat up the universe and go back in time, if you would have higher energies corresponding to earlier in time, basically, we see that the electromagnetic force, for instance, and the weak nuclear force they basically become like one force. We've already probed the Large Hadron Collider. This is explained by the Higgs boson. With new theories, we can actually also unite those forces with a strong nuclear force at some higher energy called the grand unification scale that just means it's an energy where these two forces look like one. So our dream then is just to spill on this. Our idea is maybe some theories involving supersymmetry could be built that would take all the four forces so that they became one force in the beginning of the universe, basically at higher energies, but even incorporate gravity. So to summarize, we basically dream of having a deeper theory that combines the description of the universe as a whole like general relativity and the center model of particle physics. We want to unify all the forces in nature when I explain also why there's three generation. This is all kind of random, right? When I explain where does this picture come from? What are the, why are there these different masses for the particles? So Einstein's dream, you know, dream of physics then is to sort of unify everything into a simpler, deeper model. We even had predictions that the exact amount of dark matter could be explained by supersymmetry if the supersymmetric particles were light. You can calculate how much dark matter should it be, and it roughly comes out right. So we're very excited when the Large Hadron Collider turned on. We're hoping to see a lot of supersymmetric particles, but I can already tell you we didn't see a single one, okay? So we took a wrong turn there. How can we test this hypothesis? So our first hope was to, we would produce the dark matter particles with the particle accelerator. And the first try for that was the Large Hadron Collider. So particle accelerators, it's basically the idea that you collide beams of particles. Those particles move fast. They're first generation particles in the center model, like electrons or protons made out of up and down quarks. But when they collide, if you have enough energy, we have a relativity that energy turns into mass and you create second and third generation particles. Or new particles that maybe you didn't know about yet, like sparticles. This is how we found second and third generations. So this is how we could find sparticles. The detecting arc matter is very hard so it doesn't interact with light, right? You cannot see it directly. You can reuse this gravitational lensing to see where it's located, its gravitational effect, but that doesn't mean you're directly interacting with it. But we predict that there's a small chance that the dark matter come in and interact with the nuclear particles inside the center of the atom. And so this is what we want to detect. We want to see when we build a large container of stuff, have dark matter come in and kick individual atoms and see how they move. And we think we often need a ton of material and we're going to see one interaction per year. And we think this experiment has to run underground at the bottom of a mineshaft to be shielded from cosmic rays. So this is again one of those crazy experiments it's really hard to do. So people have started building these experiments for a few decades now and they started out small and they didn't see anything. And to make life harder, we don't really know the probability of the dark matter coming in. If you want to know more about the Department of Physics and Astronomy at UH Manoa, see phys.hawaii.edu. If you want to know more about Sven Bossen, see phys.hawaii.edu slash faculty. It's clearly in Hawaii's best interest to do and encourage scientific research in physics, astronomy, and dark matter. Yes, we do want to be a center for scientific research in the Pacific and the world. It's not only important to Sven and his colleagues, students, and the university, but to everyone in Hawaii, including our unborn generations of world-class scientists. And now let's check out our ThinkTech schedule of events going forward. ThinkTech broadcasts its talk shows live on the internet from 11 a.m. to 5 p.m. on weekdays. Then we broadcast our earlier shows all night long and on the weekends. If you missed a show or if you want to replay or share our shows, they're all archived on demand on ThinkTechHawaii.com and YouTube. And we post all our shows as podcasts on iTunes. Visit ThinkTechHawaii.com for our weekly calendar and livestream and YouTube links. Or better yet, sign up on our email list and get our daily email advisories. 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Thanks to our ThinkTech underwriters and grand tours, the Atherton Family Foundation, Carol Mun Lee and the Friends of ThinkTech, the Center for Microbial Oceanography Research and Education, Collateral Analytics, The Cook Foundation, Dwayne Kurisu, the Hawaii Community Foundation, the Hawaii Council of Associations of Abarbon Owners, Hawaii Energy, the Hawaii Energy Policy Forum, Hawaiian Electric Company, Integrated Security Technologies, Galen Ho of BAE Systems, Kamehameha Schools, MW Group, the Shidler Family Foundation, the Sydney Stern Memorial Trust, VOLO Foundation, Yuriko J. Sugimura. Thanks so much to you all. Okay, Cynthia, that wraps up this week's edition of ThinkTech. Remember, you can watch ThinkTech on Spectrum OC-16 several times every week. For additional times, check out oc16.tv. For lots more ThinkTech videos and for underwriting and sponsorship opportunities on ThinkTech, visit ThinkTechHawaii.com. Be a guest or a host, a producer or an intern, and help us reach and have an impact on Hawaii. Thanks so much for being a part of our ThinkTech family and for supporting our open discussion of tech, energy, diversification, and global awareness, and of course the ongoing search for innovation and scientific knowledge wherever we can find it. You can watch this show throughout the week and tune in next Sunday evening for our next important ThinkTech episode. I'm Keisha Key. And I'm Cynthia Sinclair. Aloha, everyone.