Solving the Universes Big Questions

- Welcome to today's Texas science festival session. I'm so excited to be here today and special thank you to Marielle, and Erin, and Christine, and Monica for working so hard on the back end of this. This session is, Solving the University's Big Questions with Karl Gebhardt and Katherine Freese. As reminder, this session is being recorded, just to let you know that as well, to be aware of that because your questions that you submit will be asked later on in the session. And we're so glad that you could join this session. I'm Rebecca McInroy with KUT radio. Also note to all the participants, you will be muted and without video for the duration of the webinar because this is one of our science sparks events. Each speaker will talk for about 10 minutes and then we'll move on to the Q&A. So they have these fantastic presentations ready to go. And after the presentations we'll move on to the Q&A. Another speaker will have presentation, another Q&A, and then we'll wrap up. So let's see, please use the Q&A feature by hovering over the bottom center of your screen at any time you submit question that you would like one of our speakers to answer we also have pre-submitted questions you provided and we'll do our best to get to all of them. would now with no further ado, like to introduce our first speaker. Karl Gebhardt holds the Isabel McCutcheon Harte Centennial Chair in Astronomy and the Herman and Joan Suit professorship in astrophysics at UT. He is one of the architects of the Hobby-Eberly Telescope Dark Energy Experiment that seeks to understand dark energy. Welcome Karl. will let you take it away. - Excellent. So thank you, Rebecca. and thanks to the organizers for doing this and thanks to all of you for showing up with this. have lot of fun stuff to talk about, and wanna jump right in. I've been working on this project for 20 years now, trying to understand how the universe evolves. The past say two or three years, we've been getting data and now it's pouring in and wanna show you some of the first results. And first, what wanna do, is put it all in context. So what I'm gonna do, wanna start on my whiteboard here and then I'm gonna switch to some presentation material. So just to give you the full-on big picture, what want you to do... So as researcher, what we're tryna do in astronomy and physics and astrophysics, is to understand where the universe came from, i.e, understand the big bang model. Is the big bang model the correct model? Are there small modifications or major modifications that we need to make? How does gravity work? It is remarkable that there are still fundamental concepts of gravity that we don't understand yet. What are the basic components of the universe? So let me explain how we do this. So imagine you as the researcher, as the astronomer, and I'm gonna have you down on the bottom of the whiteboard here, and you're looking out into the universe. You looked that way and you look this way. So I'm gonna put one dot down here at the bottom, so this is you. Let's put you down here. You're happy because you're looking out in the universe. And you look this way, and you look that way. We're going out as far as we can go. So we are looking out. There is an edge to the observable universe. There is definition. You can only look so far and you get to line, which is the observable universe. This is the length of time that light can travel since the universe began. 'Cause light has finite speed, you can only see so far. So there was limit for how far we can see. I'll come back to that in moment. So as you look out, you see galaxy here, nice spiral galaxy. There's another one here. You're looking farther out, you're going. There's more galaxies, more galaxies. And everywhere you look, you're seeing these galaxies. They're all throughout the universe. What is special about this? And this is how we tie it in to models of the universe, is that as you're looking out, you're looking at objects that are farther away. So these things, this line is representing distance from where you are. Now, what's also special about the universe, as already said this, is that light travels at finite speed. think all of this is relatively known and you probably understand this. But that means this object here, the light that left this object left long time ago than the light that left this object. So we see these objects out here as young as along. So this is, in terms of the universe, young in terms of the universe, old in terms of the universe. And so this is long time ago. So there's time axis in here as well. So we have what we call look back time. That is what we actually need. And I'm gonna show you some plots just like this. So what we do is we look at the galaxies here. We look at the galaxies here. We tried to see how they're arranged in space. We make map. We make map in the very early universe. We make map in the very nearby universe. And then we understand then from that map, we can understand the properties of the universe. For example, if the universe is expanding and we know it is, what's gonna happen is that the separation of the galaxies, how dense they are here, will change compared to here because the universe is expanding. On top of that, is this beautiful thing called gravity. That is if you had two galaxies that were really close together early on in the universe, as they evolved over time, the universe may be expanding but they may be close enough that they come together. So what you end up with, is groups of galaxies nearby because gravity works. So the two things that we get, the two major things that we get from this map, and I'll show you the map in moment that we've measured with our experiment, the two major things you get is how much the universe expands over time because we're looking back in time and how gravity works. And this is one of the fundamental properties of what we're trying to get in our experiment. So let me switch here to some presentation material. And let me just walk you through the experiment that we're doing and how we're gonna try to solve what gravity is and how the universe expands. So this is the Hobby-Eberly Telescope Dark Energy Experiment. It's an idea. It was hallway conversation had 20 years ago in 2002, So 19 years ago. Yeah, can subtract. And we wanted to understand how the universe was expanding. We got together large group of people. It's mainly Texas project. It's Texas... We came up with it, Texas led and Texas, we have put up about 90% of the funding and we're using our telescope out in West Texas, the Hobby-Eberly telescope. One of the biggest telescopes in the world, fantastic telescope. We're taking one of the largest telescopes in the world. We built one of the biggest instruments in terms of taking information for how fast the galaxies are moving by factor of 100 on the planet. So we built the biggest instrument. We're doing one of the largest surveys in terms of time in terms of the data collection. And we're using the Texas advanced computing center which is one of the most powerful computers in the world. Those four things combined to make this kind of crazy survey. So let me walk through little bit of it. Here's the cartoon picture of what we think is in the universe. And can't stress enough how much about cartoon this is, it really is cartoon. What you have is you have time is running along this diagram here at an angle. The average size, so the average distance between galaxies is represented by the size of this comb. Down here you have the big bang, time equal to zero. All matter and energy is compressed to the small point. Very early on, you have this crazy concept called inflation that we don't quite understand yet, and the universe expands out. And then it expands, it's just going along with its initial expansion and expanding out. This is where the math comes in, and I'll show that in moment, that as it expands, there is material in the universe, galaxies, for example and gas. The galaxies can pull on each other even though the galaxies are expanding away from each other because of the initial expansion. This galaxy over here is pulling out this galaxy here and that expansion rate slows down over time. If you had enough mass it could go slow enough that it could actually stop and it could change to deceleration and go negative and the universe could come back together. That's not what we have. When we measured it, it looks like that. In fact, you can see here the expansion rate is going slower, slower, and slower and then it takes off. This is where we are. We are right around the time when the universe begins to take off. We divide the components of the universe into dark energy, I'll explain what that is in moment, dark matter, which you're gonna hear later from Dr. Freese, and atom. This is the stuff that we are made of. And this is the essential problem here. Then we just really quickly go over the history of dark energy and I'll explain what it actually mean by that. It was proposed by Einstein in 1919. He's rarely wrong but this is case where he thought he was wrong, but he might be right. 1929, Hubble discovered that the universe that Einstein used to come up with this idea was significantly larger and it was expanding. Einstein retracted his idea that he needed for that expansion. And it went away, he calls it the big blunder. About 80 years later, two teams, which got the Nobel prize later, discover there's this need for this extra acceleration, that is, the universe is not decelerating, it's in fact accelerating. Today, the theorists have drawn blank as to what that is. And so what dark energy is, what I've always had said, is that may not dark, it may not be energy. What dark energy is, it's the phrase that we use to represent our ignorance for how the universe is expanding. You could call it the ignorance term and it would be just as valid as call it dark energy. This is the equation that governs it. only put it down here because, in terms of what we're trying to do, it's relatively simple. won't go through the terms, but on the left over here is what we measure, the expansion rate. That's what we wanna do. And that's what we're gonna do with ethics. And on the right, is the theory. So on the right is the theory, on left is the observation, we measure the observations, we compare it to theory, modify the theory, take new observations, on and on. That's how it works. So let me bring in what we're doing.. So what HETDEX is, it's making this massive map of the universe. From that map then, we'll be able to turn that back in with this diagram that drew earlier for how the universe is expanding. And let me explain how we do it 'cause it's really kind of interesting. We are looking right in the Big Dipper. It's one of the only constellations that everyone knows. It's the one that know. don't know the constellations that well but do know the Big Dipper. We always make joke. We're gonna try to figure out what's inside the Big Dipper. So this is the region that we're gonna observe. We are gonna tile the sky with observation, observation, over and over again and completely cover the Big Dipper. If blew up little region here for what we observe, you'll see these little shapes here, that's the focal plane of the telescope. And what we do is each little shot here, expands into this image here. This image here is the focal plane at the telescope. And we take that focal plane and we just do snapshot of the sky of 15 minutes here, and then here, and then here, and then here, and we make this giant map of the Big Dipper. If blow up one of these little boxes here, what you get is what's called an integral field unit. What is looking at are optical fibers. If blow up one of those regions there, you can see the individual optical fiber. All an optical fiber is, is piece of glass that's turned into rod. You can put the glass in your focal plane and then you run that, you make that piece down into your telescope, and then you end up with an emission line. What this is, what you're looking at, is transition, specific transition of hydrogen that happened in the galaxy 10 billion years ago, far, far away where it measured lot of hydrogen gas. This is cause it started forming and we now, we can get how fast it's moving because we know the wavelength of that gas. We know where it is and the sky, cause we can trace it back. This is the three-dimensional map that we have. We have the location on the sky. Then we have how far away it is and then we can get the expansion rate. So here's how it works. These are many lines that we get. We're gonna have about 10 million of these lines. And we are writing code furiously to try to find them all. But there is an issue that we get confused by some lines that are real and some lines that are false. But this is the example of... I'm not gonna show you 10 million of these. So here is the map that I'm very excited about. took that map. This is the same plot showed before. Now here's that angle we are looking out on the sky. You are down in the middle here. plot this in terms of distance. This is megaparsecs. We can convert that to kilometers, 3.1 by 10 and 19. And you're looking out in the universe. This is the data. So this is the distance and this is where they are in the stock. And what you see, and when made this, just kind of like stared at it for days, weeks, months, think made this back in December and I'm still staring at it, is you see the clustering. This is gravity working. This is what kind of blew me up. We've seen this before, but hadn't seen it in my data. And when we got the data, said, it actually worked." It's $42 million experiment and boom, there it is. And so here's the data. Here's this simulation. And so what we do is, we look at how clunky it is here, to how clumpy it is in the simulation. And then we can tune how much the universe expands and how much gravity works. If you look in the distant universe, so here's that same picture, this little one here is the one just showed you. But now we have data that's very far away. If flip back and forth, you can see lots of structure here but you don't see any structure in the distant universe. And also when first made this, said "Why don't see structure?" And was little bit concerned that we have problem here. And it took me like few minutes and said, 'cause gravity hasn't turned on yet really." This is how the galaxies are originally distributed and it hasn't really turned on. So you don't see much structure here and you do see structure here, that it was the experiment that we're gonna try to make. No one has seen this before, this is the first map. And now we're trying to turn that into real data in terms of our constraint. So problem, however though, is that we have problem trying to discriminate these galaxies that are far away from the nearby galaxies. We don't want to impart the nearby galaxies onto the distant ones, and the distance from the nearby. And it's really, really hard to do it with the machine code. We've been trying and I'm working hard on that, but we are trying to use visual classification. So this is where we trained whole bunch of undergrads and how it works now is what we're doing, and I'll show you this in moment, is galaxy pops up on your cell phone and you swipe left, if it's distant or swipe right if it's nearby. We call this AstroTinder. And how it works is this image pops up. It has been tremendously powerful. If you go, and really encourage you to do this, it's kind of addictive because as soon as you swipe, another thing pops up and you have to like categorize that one. Again, we have about 10 million of these sources we wanna go to. Our group is not that big, we only have like 20, 30 astronomers that are working on this. And so we need to train citizens. So please sign up. We're using the Zooniverse site and it's called the Dark Energy Explorer. So this is what we need you for. wanna end with curving here. This is the same graph showed before. Now I'm gonna put it in context with the whole universe here, that is, here's the observable universe. This is where the nearby galaxies are in HETDEX. This is where the distant galaxies are in HETDEX. And when made this, and these are the other experiments that are out there. There's one called DESI that's gonna fill in the gap here. Beyond HETDEX, no experiments out there. We are the most distant by far, and there's nothing in long timeframe until we get to the edge of the observable universe. Just appreciate this plot. What we're doing, is we're effectively halfway out right now in the observable universe. And when first made this, kinda got nervous. One of the reasons want into astronomy, is because love the idea of the insignificant trying, cause we're completely insignificant our existence, trying to understand the formation of the universe as whole. And then you wanna map the universe. But when look at this, say we're halfway out in the observable universe. Not that long in the future, we are gonna map out the whole thing. Not quite in my lifetime, but humans will. For me, this made me little anxious because universe just got little smaller. So let me end with that and just say where we are. So this is the first map we seen in the distant universe. We really do need help to go through these sources, we're doing that now. And then what we do is we take that input that we get from the citizen science campaign, turn that into machine learning algorithms, and then we go back and forth. That's the big picture. Our data taking is gonna go for another two years. We probably have result in our analysis right now. We're just on the edge of pushing that computer stroke, just hitting that button just so we can see what the expansion rate is doing, but we're working through little bit about the kinks. So that's where we are right now. Thanks for listening. - I'm blown away. And yet again, I'm blown away. So we have bunch of incredible questions to ask. First of all, Valentino asks, what do you think happened before the big bang? What was the catalyst for the big thing? - There's lots of theories out there. There's multitude of theories on what happens before the big bang. And what do as scientist, I'm not gonna talk about them, because for me as scientist what is important as an observer, is if it can't be proven, if can't get observational data and put constraint on it, that doesn't mean it's not interesting, but turned it more into like philosophy, really interesting philosophy. read it, study it, try to do calculations. I'm not theorist, but still try anyway. But am not gonna conjecture because it's been... dark energy is already such mystery right now. I'm gonna focus on and something can go after and say something about. So, I'm sorry, Valentino. I'm not gonna comment on that 'cause it's outside of my regime as well. But thanks for the question. - love that. So David has question here. David says, what can human eyes do using AstroTinder, which is phenomenal name by the way, that you're struggling to automate with software. - So that's perfect. So we give few examples on the Zooniverse site, on the AstroTinder site. My dean gets mad at me if call it AstroTinder site. One big problem is, if you have nearby galaxy and you have an emission line from very distant galaxy, sometimes just because of projection effects you can get an object nearby and one very far away, it looks like this object is associated to that object. The human eye is really good at distinguishing that, no, it's distant, whereas the computer code is really hard to do that. And believe me, this is what do. do computer programming, and am struggling to understand that distinction. And it gives some really nice examples that says, here's clean case of nearby, here's clean case at distance. Here's one where we're confused. And one thing that we do, is each galaxy that is swiped. We do it about 15, 20 times. We look at the distribution of swipes. If we have one that is like equal distance and equal nearby from the 20 or so people, those are the ones that we go in and take look at. So we're using big group to help us sift through all the easier ones and then we're left with the hard ones. And if you take look at the site, that's all explained. - So we have one last question and then we're gonna have to follow up and do viewers views on this. 'Cause have so many questions that wanna explore but we don't have time to go into today. So this is the last question and it's from Dan. Dan asks, how does one become dark energy explorer? What is required? - So all you need is cell phone. So if you have smartphone, you'd go to Zooniverse, sign in so we can track your username. There's button in the Zooniverse site that says dark energy explorer, hit that and you can get categorizing within like about minute or two. do it all the time when I'm bored. Someday we're all gonna stand in line again. got COVID shot. stood in line. don't know how many categorize just standing in line for the COVID shot. It's really is difference. - This is so fantastic. So Karl, thank you so much. This was really wonderful. And there's so much to think about and I'm excited to follow up hopefully soon. - Thank you. - Take care. - Thank you, Rebecca. - We have another presenter. Our next speaker is Katherine Freese. She holds the Jeff and Gail Kodosky Endowed Chair in Physics at UT. Hello, Katie. And she was recently elected... - Hi Rebecca. - To the National Academy of sciences and she is one of the first to propose ways to discover dark matter. So Katherine, it is all yours. - So let me get into presentation mode. There we go. So want to start by reflecting upon humans from antiquity. So people have always wondered, where did we come from? Where are we going? What is out there? And there were creation myths for every culture. And then about 100 years ago, starting with the brilliant work of Albert Einstein, we have our own creation myth. It's called the Hot Big Bang. But the difference is, that we nailed it. It's right. The observational evidence is there. It's really unbelievable in human history, the amount we've learned about the cosmos in the past century is just mind boggling. always like to reflect on that and appreciate that get to work in this exciting field. So it all started with Einstein's relativity in 1915. And soon after he wrote down his equations. Other people applied these ideas to the universe as whole and realized that there's three possibilities for the universe. It could be expanding, it could be contracting, or it could be static. Einstein actually liked the idea of static universe. That's lot more there's lot of symmetry, things unchanging in time, but the truth is, it's not, it's expanding. And that was discovered in 1929. Edwin Hubble looked at distant galaxies and saw that in fact, they are moving apart from one another. So everywhere you are, you see the universe expanding away from you. But as Karl said obviously we have nearby galaxies that are we're merging with right now. So gravity wins on small scales in the attractive sense but on the large, universe is expanding. So that's the basic concept of the Hot Big Bang. It started 14 billion years ago as primordial soup of hot quirks, leptons, gauge bosons, various particles. And they were really tightly packed together, condensed. And as the time goes on the universe expands and cools off. So this Hot Big Bang picture, while it is incomplete, there's lot more we have to do, is correct. And so the universe has been cooling and expanding from the beginning. And this is always fun picture to show. We call this the raisin bread model of the universe. So the raisins in this loaf of raisin bread are meant to... You can think of them as the galaxies. And as time goes on, if you put this dough in the oven, the loaf rises. So they tear up, never done. And so you can think of the raisins as moving apart from one another not because they're running or have any physical action but simply because they're sitting there and being pulled apart from one another. And that's what's going on with the galaxies in the universe as well. But he difference is that the raising bread has central point but the universe does not. So there's no special point in the universe. We are not special point. Nowhere else is either as well. And it's also fun to think about looking backwards in time. So if we do go backwards in time, then of course everything contracts closer and closer together. So everything in this room can certainly contract to point. But what if the universe is infinite, which is beyond the observable part of the universe there is stuff out there that we just can't see because it would have taken longer than the age of the universe for the light to get to us. So what if the universe is infinite? Well then as you contract backwards in time that infinite the universe, it's still infinite. So what happens when we talk about the Big Bang is that... wish these slides will stop jumping, is that if you do this contraction eventually the density becomes so high. Everything's packed together so tightly that our laws of physics fail. We don't know what to do. The theory fails. You would need theory of quantum mechanics with gravity called quantum gravity. And we don't really have that string theory. And so that is really what's meant by the Big Bang. It's this time where our calculations fail. And the other thing always like to point out about the Big Bang is it's not physical point. It's point in time, not point in space. So it happens everywhere at once. It's not an explosion either, but if you want to think of an explosion please, put one everywhere universe at the same time. So that leads me one of the big unanswered questions. Yeah, sure, we understand the evolution of the universe, but we don't what the universe has made off. It's bizarre situation. Here we are in precision cosmology, but if we take everything from our daily experience, our bodies, the chairs we sit in, the walls of the room, the cocktails, the earth, the sun everything that we know about, all of us made of atoms and all of that adds up to only 5% of the universe. This is the same slide that Karl show. So ordinary stuff that we know in our daily lives is only 5%, leaving us with 25% roughly dark matter and the dark energy that Karl talked about. So what I'm gonna talk about is... And, here's book wrote for the public. So please have look, you can get it on Amazon for $10. "The Cosmic Cocktail" and here are the contents of the cosmic cocktail. always like to point out, it's only millionth of ounce supermassive black holes. So black holes and dark matter are not the same thing. But in this mix, in this 10 ounce drink, you have almost three ounces of dark matter and seven ounces of dark energy. And please make it shaken, not stirred in the early universe, everything's bumping into each other. So this dark matter problem is 80 years old. It takes back to... guess, 90 years old. What am saying? It dates back to the 1930s. So here's Fritz Zwicky who was looking at cluster of galaxies and saw that the galaxies that were moving around the center were moving too rapidly. So the bright things that he saw, the bright galaxies, they should be responsible for the motions of the outer galaxies, but it didn't add up. So he thought, well, let's add in some extra material to provide the gravitational pull to speed up these galaxies that are far out from the center. And then the name "Dunklwe Materie" into existence, where that is the German for dark matter. He was Swiss scientist. And "Dunkle" just means dark. It doesn't shine. It's not stars. And have to tell story about him. He was quite fellow. In his book he called his colleagues, spherical bastards because they're bastards no matter what direction you look at them from. So love that story about him. So there is lot of debate. Is there dark matter or not? And then it was really Vera Rubin in the 1970s who nailed it. She found dark matter in every single galaxy she looked at. And that led to consensus in the scientific community that dark matter must exist. And that we have to go understand what it is. It's also behind me, the Milky Way. So here's picture of it. About the center there's supermassive black hole that weighs 4 million times as much as the sun. It's not yellow. It's just so you can see it. And it is responsible for the 2020 Nobel prize in physics. Half of it went to Andrea Ghez and Reinhardt Genzel for discovery of this supermassive black hole at the center of our galaxy weighing for million times as much as the sun. Then as you move out along these arms, it's like pinwheel. That's where the stars are including our sun, is along one of these spiral arms. So now we take this whole thing and put it on its side and we call that the disc of the galaxy. And again, here's the sun which is about 25,000 light years from the center. But that is just the tip of the iceberg. In fact, an artist's rendition of our whole Milky Way would look like this. There are the spiral alarms, and there's this giant, we call it halo, made of dark matter. And that's what most of the galaxy made off. So of dark matter, although it's 90 years old, at this point, it's like jigsaw puzzle. There's so many different pieces that show that in fact, it's gotta be there. This is very interesting one where, this is called the Bullet Cluster. Here you have two clusters of galaxies that are in the process merging with each other. And so after the first collision, what happened? Well, the gas which is shown in pink is due to x-ray observations. So the gas got stuck during the collision. So is as though you and would bump into each other, well, we wouldn't get very far. So they have strong interactions, electromagnetic interactions, these gas particles and they get stuck. But on the other hand in blue, is shown additional material that behaves completely differently. And that is the dark matter. So there's the different behavior of the stuff that gets stuck versus the dark matter, that just kept going through the collision. This is really good evidence that there's two types of masses out out there. So another thing that's fun to think about is that without dark matter, we wouldn't exist. This is computer simulation of dark matter particles earlier in the universe being spread out almost uniformly but then they clumped together to make structure and then later on ordinary matter can fall in along with the dark matter. The whole process wouldn't happen, if you didn't have dark matter jumpstarting it. So we start out with these spread out pieces of dark matter and as time goes on, they clump together, clump together, clump together and here in the simulation is the universe today. And so you see these long filaments of structure with the galaxies and clusters at the nodes or intersections of these filaments. So the question that work on is, what is the dark matter? And there are many potential candidates. And certainly don't have time to talk about most of them. However, there are two that are particularly well-motivated, WIMPs and Axions. And the reason for that is that they have reason to exist which is not just dark matter, but they're already there in particle theories that are trying to solve problems with particle physics. So they basically kill two birds with one stone. The thing that I'm gonna talk about is the WIMPs. These are weakly interacting massive particles. That's what it stands for. And there are billions passing through your body every second. So of the four forces of nature, they don't have these two forces, stronger electromagnetic forces, and yes, they feel gravity. But then there are four fundamental forces and the one that's still left is the weak interactions which is responsible for radioactivity. So if you postulate that you have these particles and they they weigh about one to 10,000 times as much as the proton, then they make really good dark matter candidates because you ended up with exactly the right abundance of dark matter was simply this puzzle that they had weak interactions in the early universe. And you can calculate how many are left today and the answer comes out right. So there are many ways to look for these WIMPs but wanted just to mention some of them. And so one of them is at CERN in Geneva and here, yes you can go skiing back here. So this is 17 mile rang of protons being accelerated in opposing directions and where they collide there are detectors that look for signs of the production of dark matter particles. So this is Fabiola Gianotti. She now the director general of CERN in front of one of these giant, giant experiments. Look at this detector with this small person standing there. And here's Peter Higgs in front of the other one, the CMS detector. These two jobs detectors which did discover the Higgs boson which weighs 125 times as much as the sun. They're looking for dark matter. And as yet haven't found anything. So as said, protons, colliding produced particles. And then in the end you're hoping that you could discover in this case, super symmetric dark matter candidate. So nothing discovered yet. And that leads me to another way to look for WIMPs which is, underground direct detection laboratory experiments, which take advantage, said, there's billions passing through you every second, well, so let's go look for those. So there are these underground detectors containing nuclei that are bombarded all the time by WIMPs. And the WIMPs would deposit very small amount of energy. And the count rate is really low, one per count per kilogram of detector per day, and very small energy deposit. Very, very difficult calculations. And we were among the people who did the.. did the calculations of the scattering rates of these things and convinced people, let's build experiments. And that's been going on for 30 years now which dates me, but so is life, that's life. And so here we have this worldwide effort looking for these particles. And there is one here and outside of Italy, in the Grand Sasso tunnel. You have to go mile underground. And DAMA/LIBRA experiment has signal exactly as we predicted that the signal goes up and down with the time of year annual modulation, as your earth moves around the sun. So they're the only ones with signal, and what's gonna happen now is that there are new experiments made of the same material that are gonna be testing this within the next five years. So we'll know whether or not this discovery is there. So ask me in the question session, I'll tell you about our new idea for dark better detection using gold and DNA. But think should really hurry up. So I'm going to go ahead and mention indirect detection which is dark matter particles annihilating with each other give signals that you can look for including photons, gamma rays, very high energy photons. And there is also an interesting signal there. At the center of our galaxy there's an excess of gamma rays. And maybe that's from dark matter. So these are sort of the two signals of potential detection that we have. We have this DAMA and this gamma ray excess near the galactic center. I'm really out of time, but have to tell you about dark stars. This was our baby. This is me, Doug Spolyar and Paolo Gondolo. No, this movie is nothing to do with us, it predates us. But the idea is, that there could have been very early stars. The first stars to form in the history of the universe would be made of hydrogen and helium powered by dark matter annihilation, the same kind of WIMPs. And if that's true, then they could grow to be very large and there'll be seen. And then in the next, not in the Hubble Space Telescope, but the next one that's launching in few years, the James Webb Space Telescope that could eventually collapse to explain these supermassive black holes. So to conclude, I've talked about bunch of different ways to hunt for WIMPs in the next decade. And so in this pie chart, we can hope to get somewhere with the question of what is the dark matter of the universe. And was going to end with joke, but I'm so short on time that better stop. So will extend. It's great joke, so ask me. But want extend and, here. - knew you have to tell joke Katie. - do. Yeah, agree. So what do we know about dark energy? Well, we know what Karl told us. And he also said something that's absolutely correct which is as theorist, have no idea what dark energy is. You might as well call it gobbledygook, but we do know that matter's attractive whereas dark energy is somehow repulsive, it's causing this acceleration. So here we were at panel in New York at the world science festival, but the three women here, were talking about dark matter and the three men talking about dark energy. And said, the only thing we know about dark energy that is absolutely correct. So that's it. will stop sharing. And I'm sorry if went over. - It was fantastic. Thank you so much, Katie. And you're going to have to join Karl and had for viewers review. We were supposed to do one before and... - would love to. - We're gonna have to do it. So Cyrus asks, could our universe be just one among multiverse. - That is very good question. So that leads us beyond the observable universe. We have no way to probe out there, at least not now. And so if there are there things out there, that would take longer than the speed of light to get here. So we have no idea what's out there. So is it possible that very early on you had bunch of different places in different pockets of the universe that evolved independently. And we can think of those as multi-verse and they could even have very different properties from ours. They could have... If the strength of electromagnetism there is different by tiny, tiny amount, well then you wouldn't have nuclear, our nuclear would fall apart. So the properties of this other thing out there, it's certainly possible. And in string theory you have 10 to the 500 different possible universes. So yeah, that could be out there. But my problem, agree with Karl that at the moment this is philosophy cause we can't probe it. don't wanna go there, but yeah, we should think about it. It's fun. - So I'm glad Amanda asked this next question 'cause was very curious about this. What is the new detection using gold and DNA? - goody. get to tell you about that. Believe it or not, you can buy from company called Illumina, nanometers thin layer of gold with bunch of DNA strands hanging down. So nanometer thin means there's one atom in the thickness of the damn thing. And forget what they use that for, but the technology is there. The DNA is bound to the gold, but what we're going to do with it is, when WIMP comes along, it doesn't break DNA. It's good for us that it doesn't. But it would definitely knock the golden nucleus forward into these hanging strands of DNA and then the gold would break the DNA. And now the beautiful thing about DNA is you can control it completely. So in each of these strands, you know the order is the AGCT dot, dot, dot, the order of these bases. And so, when once it snaps off one of these DNA strands, you can reconstruct where the break happened. That means you can track where the gold went and extrapolating backwards. You can extract, where did the WIMP come from? And as soon as you have this directional sensitivity, well, we know that in one direction we expect lot more WIMPs than the other, so then we'll really know, yes, this has gotta be it. 'Cause there's 10 times as many coming from this direction as from that direction. So that'll be, and then we can learn lot. - Yeah, incredible. Just incredible. Well, cannot thank you enough. You, Katherine Freese and Karl Gebhardt. Thank you not only for joining us today, but for the incredible work that you continue to do, that is exciting and inspiring for all of us. have quick thing to say before we wrap up, and that is thank you to everyone for joining us for the Texas science festival talk, Solving the University's Big Questions. And please be sure to visit the sciencefest.utexas.edu to sign up for more sessions between now and March 26th and contact [email protected] if you have any follow ups from today's session. Thank you for your interest in Texas science. And thank you so much for joining us and for including me, Christine, it's been great pleasure. Have beautiful, beautiful afternoon. Bye.