Yet people actually have no idea what it really is. So recently there has been a very precise map of the dark matter in the universe and to talk about this. Today, we’ve got eleanor. She is a recent nyu graduate and she’s going to tell us a little bit about these new results, so hi eleanor hi hi. Everyone um hi um, so today i just want to discuss with you guys a little bit this uh kind of a big result and um, and for scientists for astronomers and astrophysicists and we’re also going to discuss a little bit dark matter and the dark energy survey Which is the project that has led to uh this huge thing, which is the release of the best ever the dark matter map? This is uh just one of the articles that we’re talking about this kind of huge discovery which happened in may uh, but just to begin with what is dark matter. How is dark matter even studied um, what is a dark metal map, and why do we care? Why does it matter so um ordinary matter makes up only five percent of the universe, meaning that everything we see with our naked eyes, it’s only five percent of what the universe is really made up of and it’s a little like mind blowing, i think um, then There’S dark energy, which accounts for about 70 percent um of the universe and dark energy, consists uh, i mean it’s what cosmologists hypothesize drive the accelerating expansion of the universe by counting interacting the force of gravity um and the last 25 is dark matter whose gravitational influence Finds galaxies together and we’re gon na just see this um a little bit better in a minute.

Why is it called dark matter? Because we can’t see it at all? It doesn’t emit reflect or absorb light or any other type of electromagnetic radiation, such as x rays or radio waves, which are widely used, uh in astronomy and astrophysics to study, stars, uh, stress formations, um, the universe in general, galaxies and so on so forth, but x Rays and radio waves are of no use when it comes to study dark matter. However, scientists have been able to infer dark matter’s presence and to study dark matter. So how did they do it bottom line? They studied the effects of dark matter on its surroundings, but how exactly um so today, i’m, just gon na briefly talk about three ways: um in which um, astronomers and services were able to get observational evidence for a dark matter. But there are many more i’m just going to mention three today, so the first one uh is through galaxy rotation through the study of galaxy rotation curves. So what is a rotation curve in the first place? A rotation curve is a plot of the orbital speeds of visible stars and gas um in in the galaxy versus their radial distance from the galaxy center. And so, if we look at a picture here of a spiral galaxy um, we know that the um the arms, the spiral arms rotates around the galactic center and um. We see we can even see from this the picture so by our naked eyes that the luminous mass density of a spiral galaxy seems to decrease and we go from as we go from the center to the arms to the outer edges.

And so, if luminous mass were all the matter that we should take into account, then we could model um a spiral galaxy as a model in which we have a mass at the center and little test masses orbiting around them and so just like, for example, our Solar system, we would expect the uh rotational velocity to decrease as we move away from the center uh, but the results shown that this is not the case, because what is being observed is rather a flat curve of the radial of this radial velocity uh. In relation to the distance from the center, meaning that there’s definitely matter there that we’re, not accounting for uh, they were not taking into account when we um model the spiral galaxy in this way, and so this was one of the very first um ways in which Uh astronomers were able to get observational evidence because uh the observations were not matching. The theory uh then there’s another way, uh, which is by by the study of galaxy clusters uh, which are actually crucial when it comes to study, dark matter um because their masses, so the mass of the galaxy cluster can be estimated in multiple independent ways, and this Means that in general you can carry out two different calculations of the of the mass of the like different calculations of the of the mass of the cluster and then at the end. You can compare the results and you can account for um any any difference, and at that point you can reason what the difference can be.

Um can be there and why uh there’s a difference in the first place. So two of the main ways in which uh the mass of the galaxy cluster can be calculated is one uh from the scatter in radial velocities um of the galaxies within a cluster and two um from the x rays that are emitted by the hot gas. In the clusters so um in the galaxy in a galaxy cluster um, we can derive the gravitational mass by measuring the orbital motions of the member of the cluster. So initially we can assume um for all the galaxies in a cluster to be uh roughly. At the same distance for us, and so any small um uh spread in the red shift so in there actually, in their actual distance from us, can be interpreted as um as orbital motion around the center of the cluster. And so when astronomers um. Think of a galaxy cluster in this way so model a cluster. In this way, then, they actually use this model to calculate the gravitational mass of the cluster, so the um, the phosphorous keeping them together and then this gravitational mass um is then compared uh with the luminous mass that you get from the calculation of the x rays. Emission from the hot gas so and then any any difference in this too um can be accounted for dark matter, or i mean in this way they were able to uh get a sense of that that something was there like.

The two questions were actually matching, and so something was there and then another way in which they’re able to get a sense of the presence of dark matter was through gravitational lensing, which is the phenomenon through which uh you have a source that is emitting light and You’Re of the observer and then light is then is being bended um from the mass that is between you and the source that is emitting the light um. So scientists found dark matter by looking at the light that was coming from distant galaxies, because often that light was seen to be distorted or bent more than what the foreground matter could account for so they knew the mass that was between them and the source. There was a meeting lying so between them and the galaxy uh, but they actually noticed um the light to be way more distorted than it should have been, and so this was a hint of some more matter that was there that they couldn’t see, but that was There – and there was bending light, and so here you can see it from the image like this is what gravitational lensing look like. You see all this bending of light that they see uh, but again this is the um. I i just wanted to mention these three ways, but there are many different other ways in which um they were able to get uh to infer dark, matter’s presence. So i i also want to mention a little bit um the dark energy survey, which is um the project that has led to the discovery of this new dark matter, map uh.

So the dark energy survey is a collaboration of more than 400 scientists from 25 institutions. In seven countries – and it was um created to tackle big questions like what is our universe made of um? How is matter distributed what’s the role of dark energy and dark matter uh in our universe? What role do they play um and uh for the dark matter? Map uh, they use artificial intelligence to analyze images of 226 millions of galaxies in the southern sky um in the the project. The survey lasted six years um during which uh they surveyed five thousand square degrees of sky, which is almost one eighth of the entire sky and they catalog the hundreds of millions of objects, uh especially galaxies, and to do this um, they used the um giant, uh Dark energy camera to acquire the photographs that they used to create the map uh. This camera is located um at the victor blanco telescope, dom in chile, and it is one of the most powerful digital cameras in the world and so the results. So the map the results in new map was announced on may 27 um and the map drew on data from the project’s first three years, um, which indeed are 226 million galaxy, observed um over 345 nights and the so the team said that this let them create The largest and most precise maps yet of the distribution of galaxy in the universe because they first saw with the camera they were applying.

They were actually acquiring uh the the location in the the position of multiple objects and galaxies, and then they were taking those photos and then, after that, they were um using artificial intelligence to locate dark matter in those within those objects. Setting in that actually part of the sky and, of course also the generic matter map, they also um, were able to to create the new dark matter map that you see here in purple, um in the context of the south southern hemisphere, sky um. So this is a um close up to the map here, um, which depicts all the dark matter that was detected in the foreground of those galaxies. There have been already lots of papers published and then did the the the the and the results have been analyzed and some conclusion and has been have been drawn. So let’s just look at two of the main implications of of these results. Um so far, so the first one is that by looking and studying this map, scientists were able to confirm some of the predictions of what astronomers call the standard cosmological cosmological model, which is the simplest model that we have so far. That explains what’s what’s observed in our universe. Um, specifically something that it’s in in this model is the web like structure of our universe, and this has been observed also in this map, meaning that dark matter seems to um confirm this web like structure of um of matter.

So this also is well for dark matter, but this has been revealed in past studies for in terms of the web like structure of regular matter, but it it was expected to be to be this way. So, according to the model um, it was expected that the distribution of matter will be um a web like structure, but another kind of like even a bit more interesting implication of this result. Is this one, the second implication because by studying these maps um, so this new map scientists found hints that the universe might be a few percent smoother than expected. In essence, um. It is more spread out than the current best theories predict, and so what they, what they were able to infer from this map is that uh, dark energy seems to be um more uniformly distributed than what what they were expecting so, and this is not aligned with Um the predictions of iceland generativity, which actually suggests that dark matter should be more clumpy and less uniformly distributed um, and so this is kind of a big deal because um. So i was looking at some of the videos of some of the authors of the project. Discussing being this, and they were, of course, like kind of more excited about the second implication rather than the first one because um they are already discussing. That i mean, though the evidence is by no means. Definitely they might be so someone said that perhaps we’re beginning to see into new physics and one of the main authors, um neil jeffrey uh, said that this would correspond to possibly changing the loss of gravity as described by answer because so far the second implication of These results seems to go against uh ice and general dvd and so um in this few videos that i was watching.

They were just very excited to carry on the work and to see what this would lead us uh. It was it’s kind of exciting for someone who’s in the field, working uh on dark matter and dark energy uh, so wow wow um. I i think it’s um, mind blowing there’s, so much that we don’t know yet, but also as i mentioned earlier. So this map was doing on data from the first three years of the survey. There are three more years of data that haven’t been analyzed yet, and so i think this makes it even more exciting for what is to come. Okay, great. Thank you. Thank you. Thank you. Eleanor questions, um shout out Music. Keep it up. Looking at this thing, uh looking at map, it looks like it has a boundary, the the whitish aura or something like you know, enveloping the purple black thing. Is that part of what is it exactly? Let me not speak like it’s a milky way, isn’t it. I guess it’s a smoothie way, it’s a milky way to make your way. Okay, maybe this is uh. You know, i’m, not sure. If you can answer this, but you know, is ai the best way to do this, and – and why is ai the best way to to to work this out? You know can’t, you work it out with some actual equations, yeah yeah. Sorry, i i thought i thought you would know that don’t be illustrated from what we know on this project.

They just had like tons of pictures of the sky to analyze. So would you suggest another way? Well, i mean i don’t know information, just like everything is being done by a.i now um. Is it a good idea? That’S, i don’t mean like the machines are taking over. I just i just mean, like you know, it seems like the go to thing for everybody in science. Now um did you use ai in your project? No, no. She was biologically intelligent. I have to say i prefer to do like some of the photometry, my stuff, like with the project that i had. I didn’t have to to use like to do like large, computation it wasn’t computational based. It was observation based so uh. I prefer it that way. For now at least, it was for my thesis, my cops but we’ll see. Maybe the point is: is that there’s so much data that somehow that’s more efficient? And then you uh, you train it first using certain models and then you use a i because you can’t you don’t, want to you know, expand the computational cost, maybe it’s something like that. Does that sound plausible? How would i know i don’t know you’re uh you’re you’re, ai guy yeah, maybe yeah. Maybe i like i like adobe illustrator, but actually this is one of the places where we should be testing our quantum computational resources. Quantum ai yeah to train wait. Dark amount of map well it’s got a lot of buzzwords in it.

I like it, but we don’t have a single qubit in this room. I have a question but i’m, not sure if you can answer that does dark matter do anything. Apart from having mass, i don’t know, but it has mass, and so it bends for like space time same as regular matter, not sure if anyone knows yeah, you don’t even know what it is. So one kilogram of dark matter is same as one kilogram of anything. Really yeah: okay, all right pay more attention, abuba. What is best way to start to study dark matter? Can you recommend like a textbook? No, i hate textbooks something online in recent textbooks, sucks i’m, not sure if nasa, you know that so on nasa’s website there’s a lot of stimulation like as i saw one for exoplanets like 3d simulation. I don’t know if they have a mapping of this, but, as tim was saying earlier, really we know nothing on their candidian, dark and dark matter. So i i’m not even sure if they have something online like a 3d simulation or anything um, something that can be mapped. This is probably the the the best map so far. Okay, so thank you very much. Eleanor who’s very interesting yeah, so um we’ll leave it there, and so, if you liked this video, then please consider subscribing to our channel, and we will see you next time, bye.

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