Humans have always been innately curious with the world of random, those boundaries, those frontiers of knowledge. Look at where we are. We're in an institution that is finding on the principle of discovery and the simple truth that it is good to discover, that it is good to question and learn and to perspective the boundaries of the map. And that's what we're doing. In the Dark Matters sector we're trying to map out the universe and now we've just realized that beyond the shoreline exists this whole new world out there and we have to, I mean how could you not want to explore it? I'm going to speak about the incredible realization that science has made, that the universe that we see around us is just a quite literal tip of the iceberg that there exists a new dark side of our universe outweighing everything we can see five times over. It's when you get to answer such a fundamental question as to the nature of dark matter, something that I think we can see five times over, you have to want to know more. At least for me it is a deeply curiousity driven. I'm not going to say obsession but it's ten years now. We'll see how many more years before we discover the dark matter. If we look at on the scales between the stars we see these clouds of gas and dust. If you zoom out you realize that these stars and clouds of gas are actually distributed in discrete objects that we call galaxies. And then when you look out into the universe and you pick your favorite blank patch of sky, a patch of sky no larger than your thumbnail, hell light stretched. And then you point the Hubble Space Telescope at that patch. Behind your thumbnail lies six thousand individual galaxies, the majority of which are as large as this one above, if not larger. In other words there's a lot of stuff and yet I'm trying to argue that this, all of this, is an accounting error on the mass budget of the universe. When you form these simulations the gas is the yellow, the blue is the dark matter. Essentially there are clumps of dark matter that begin to collapse, they drag the gas inside this forming halo of dark matter, this giant cloud. And indeed that's the missing ingredient in the simulations. You need the dark matter to accelerate the formation of the galaxies, the formation of everything we can see. Thanks to the simulations you can get a very detailed prediction of the distribution of the dark matter. You can understand that it's clumps within clumps within clumps of ever more concentrated accumulations of the dark matter. You'll have streams or tendril like structures. I don't know what people did before then, quite frankly, it was, would have been immensely difficult to have pictured the dark matter, except for the fact that we have the analogous case where we look into the air, we see nothing, yet we see the trees move. So we can get a picture of the wind and understand that. And in fact the analogy is even more apt, a century and a half ago, but there are buds we didn't have the atomic theory, we didn't actually know what the air was made of, but we were very sure it was real in there because we could see as effects of the wind through the wind or the things that we could see. And in that same way we know that dark matter is there, even though we don't know what it is made of, because we see the motion of the visible stars and the gas in this well, pooled by the gravity of the unseen partner. Just as in our atomic, our barionic universe, we have particles and we have anti-particle, we have anti-matter. And you bring a matter and anti-matter together and they will annihilate and give an incredible amount of energy out in that typically gamma radiation, very, very energetic light. Well, there was a theory that the dark matter could be its own anti-particle. That prediction was made, I should say, maps for this in simulated universes. This is the dark matter, this is the core of a galaxy like our own Milky Way. Fantastic amounts of little substructures, dark matter, blogs essentially lie around the galaxy, each of which could be making gamma radiation annihilating when it meets itself. This is the Milky Way, Cinegeon, and right in the heart of our Milky Way with a density of the dark matter will be most concentrated. We see that peak. So we got excited. We thought that's it, we've nailed it. Astronomy has been particle physics to it, we have find the missing particle. No, turns out at the center of the Milky Way is a black hole. There's a lot of dead reminence stars called pulsars and they thread a lot of gamma radiation. And basically, we're kind of just seeing we suspect pulsars. The problem is, so far, at least from the simulation point of view, when we run the simulations with a self-interacting dark matter, it changes the way the visible behaves, the stars, the gas, that form the galaxies. And it's not clear to me that we need it. By that I mean, we're so still uncertain about how stars form and interact with the galaxies that there's enough wheel room there to bring the simulated predictions and the observations to alignment. But the more we learn about the visible sector and the larger the discrepancy remains between what we're predicting, what we're seeing through, say, Hubble, for example, then the demand for more complexity of the dark matter model increases. And I just have to hope that's where you go because it would be so much more fun if it was self-interacting. If I had a whole whole behavior ecology almost to it that we were just blind to because we just can't see dark matter. So in this little animation, we have our slowly spiraling Milky Way. The cloud of dark matter is just mining its own business essentially. And then we zoom in, this is our sun's motion through the dark matter of the Milky Way. So for half the year, the motion of the Earth is in the same direction as sun for half a year, it's in the opposite direction. So in other words, this wind of dark matter is faster for half the year and then slower the next half. And indeed, you've all successfully found at least, well, two of you have find it because in that time, this dark matter wind has rushed through you and will have collided with the atom of two I suspect of us in this room by this point after this length of time, knocking that atom flying. We don't make for very good dark matter textures where you're building a better one. And it is a sodium iodide crystal, essentially rock salt, doked in phallium such that when the dark matter collides, you get a flash of light in the visible. You put some very sensitive cameras either side, which is called PMTs on this crystal and you are waiting in your vessel for the dark matter that flies through us at this rate to glow. And essentially, you would expect to see this thing glowing more often when we move with the direction of the sun and then less when we are against it because of the headwind effect. And that is the principle of Sabre. Now the question of course is then where do you build such an experiment? Well, this detector is not only sensitive to dark matter, it's sensitive to anything that will collide with it, including the radiation from space, which we call cosmic rays. In our case, we went to Stole, so that's the gold mine in Stole and at 1024 meters depth, we are currently excavating the underground laboratory and the detector will be placed in there next year. This is all led by Professor Elizabeth Barbario from University of Melbourne and it is her story to tell. This project is called Sabre and they're in the darkness for the next three years. Sabre will sit and wait for the collision of a ghost-like particle at the bottom of a gold mine that will cause the crystal inside to glow. And if that doesn't sound the coolest experiment you've ever heard, I've failed tonight. We have never known so little about our universe. Science is not done, it's not something that's all written up in the textbooks and you have to memorize. We don't know what the dark matter is, we don't know what the dark energy is, we are blind as to what happens on scale smaller than quarks in the center of the nucleons in the center of the atom. We only recently were able to hear aggravitational waves and they revealed a whole population of black holes we never knew existed. There is so much we don't understand and it should be thrilling that science is not done and that if you are thinking about a career in science you don't even have the whole world to choose from, you have more than that. In the last few decades that's all they had to play with. Now you get an entire dark universe.