Prof. Michael Strauss, Chair of the Department of Astrophysical Sciences at Princeton University.

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Please send up to info at scientific sense dot. com. and. I can be reached at Gil at eappen Dot Info. My guest today is Mike Straws. Who is the chair of the Department of Fast Physical Sciences at Princeton University he uses large scale imaging and spectroscopy surveys of the sky to map the universe but the particular focus on studying the large scale distribution of galaxies to address questions in cosmology and galaxy properties in evolution. He's also particularly interested in quasars powered by supermassive black holes in the centers of galaxies. Welcome Michael. I'm very happy to be here. Thank you so much. Thanks for doing this so I want to start with. One of one of the papers a little bit older papers talking about costs logical parameters from SDS W map. So, you say the measure cost logical parameters using the three dimensional power spectrum from over two hundred, thousand galaxy in the slow in digital sky survey SDS says in combination with Wilkinson Microwave and isotope. He prob- W map and other data. So esky says is something from the ground and w map is something from from a I against that is correct. That is correct. And both of these. Have Produce Lot of data SPF started sometime in two thousand, two, thousand trend. Had A long tenure, twenty years with multiple upgrades to it. Ended W map sort of overlap with it between two thousand and two, thousand ten or so before Branca's satellite, kick them right after that. So we have. Two sets of data and and really kind of combining these two data. Looking at. Some of the. That are being more accepted nowadays. So talk a bit about the type of data that we got and. You know what hypotheses we could create some that. Okay. So perhaps, I can just say in general terms what the what the scientific program there is and what are. Just to try to explain how W MAPPING SDSS connected. So what s Tsn let's start with SDSS. So what SDSS? Was designed to do and did was to measure the distances and therefore well to measure what are called Red Shifts. which is a shift in the spectrum of a of a galaxy caused by the expansion of the universe. By measuring these shifts, which is straightforward. If you can measure the spectrum of of the galaxy, you can determine how far away that galaxy is and so one needs to remember that in when one looks at an astronomical image or looks at the sky in general, you're seeing everything as a as it appears in two dimensions. It's all in projection in you. Okay and if you see a star or galaxy or anything asteroid, you don't know. At first glance, which is relatively nearby, which is far away. So to get that third dimension, when needs when needs to measure? The Red Shifts and what the digital sky survey was do that on a larger scale than really had ever been done before? At the time we wrote that paper Rose Two hundred thousand galaxies that number has now. Now is is several million galaxies. And this is. This article. Yes. Yes. This is this is visible light. Light that that you're an I an hour and and my eyes can see although of course, with a large telescope, you going much much fainter than than than our is would be sensitive to So the distribution of galaxies is is, is there not just randomly sprinkled out there they formed in a large structures we call prefer to clusters of galaxies in which you know several thousand galaxies may be altogether in a relatively small volume of space large filaments of galaxies, enormous empty regions, which we call voids, which indeed have almost galaxies in them at all. And as astronomers I became aware of the fact that the galaxy distribution was so were so rich that there's so much structure. The obvious question is, why is that? What was the physical process that's that's going on? So the higher, the higher the redshift. The further away the galaxy. That is correct. And and what do you mean by Red Shifter's the light the Baid Length off the light has shifted to the. Longer wavelength. That is exactly right. So. When you measure the spectrum, which is the intensity of the light coming from a galaxy as a function of wavelength you see that spectrum has different features which turned out to be. In. The context of what we're talking about is usually due to A. By a specific elements in the atmosphere. So the stars that make up that galaxy and those features are shifted to longer wavelengths just as you said. By the expansion of the universe and it's it's not necessarily a subtle effect. Galaxies can have their You say of Galaxy has a redshift of one that means it's been shifted by one hundred percent relative to what it would be if the if there was expansion, the universe that is and and so so this is something that we can indeed measure directly a again just as you said, gibs a direct measurement of how far away that galaxies. Civility, they'll look different optically The galaxies at high redshift, for example, look different from the galaxies alot rich of. So in that in that context, what you're let me just rephrase that question you're asking the question. So let's back up slightly. Remember that if it's a very distant galaxy, I said Richard of one, for example, such a galaxy that. That light has been travelling to us for about seven billion years rough. It's it's not quite the same thing as saying that the galaxy seven billion light years away. But because of the finite speed of light, we're seeing that galaxy note as it is today but as it was in the past and so another way to ask you a question is have galaxies changed in their properties through cosmic time. And, of course, the context of that is remembering that universe's only. Put that in big air quotes only fourteen billion years old since the time of the Big Bang, which means that redshift one we're looking back at to. Roughly half. The. Current Age of the universe Okay. So you know you might imagined galaxies must have gotten started somehow and they presumably have evolved and changed over over billions of years. So the typical galaxy might see at at redshift one when the universes half of its present age will be different than than the galaxy today. So STF. Says, sorta provides a three dimensional view because using redshift can determine. They might be right. So so I've seen some sort of movies. T dementia movies that based on this. I don't know exactly which movies you've seen so I can't exactly come but but yes there are there are movies out there that you might have seen that indeed have are based on the data over sort of fly through of the distribution of galaxies, and you can see those clusters in this filaments and voids that I was making reference to before okay and and now w map data how how's that so So in a sense of what we learn about from the galaxy data is the distribution of galaxies today and then going back somewhat in cosmic history w mathis measuring. Different phase in the universe's solution, and in particular, the universe started a in hot big bang of roughly fourteen billion years ago and has been expanding ever since it's it was hot and one of the things that hot things do in general in physics anything that's hot glows gives off light. And so if the early universe was hot as people had hypothesize, then then all that all that heat should have there should be some radiation some light. Emitted from that and that was discovered that. That concept was confirmed dramatically nineteen sixty five. By serendipitous discovery by. Robert Wilson of what we now call the cosmic microwave background. Cosmic. Background. Radiation. So that is light as it were leftover from the Big Bang is a poetic way of saying. W MAP W map stamps for Wilkinson microwave and I saw probe. So microwave is the same microbes that was talking about the cosmic microwave background. Controversy is trying to measure whether there's any structure whatsoever. In the in I'm going to UC ABBREVIATION CNBC cosmic microwave background. You can ask the question the the universe is very structured. We see these clusters, these filaments, and voids. which stretch over distances of millions, where you tens of millions of light of light years. While when you measure the cosmic microwave background, you see it's incredibly smooth. And so one of the fundamental questions becomes how did an and again that is what you were seeing. There is crudely speaking the leftover light from the Big Bang it's it is a measure of what the what the universe looked like as it were at turns out. When you go through the details, it's your measuring at a time about four hundred, thousand years after the Big Bang. Go, into digression where that comes from. But in any case, you're seeing the light from four hundred thousand years after the Big Bang and the present day is is fourteen billion years later, it's quite a bit later. So the universe seemed to have been incredibly smooth back then and yet it's very structured today. So one of the fundamental questions becomes. How do we get from from there to hear are from then to now, I guess is a better way to say. And So our present understanding of that is that. That imagine you have a region of space where slightly more dense a little bit more masses associated with this region space than any other because it has a bit more mass, it has been gravitational pull and material will material meaning guests. We're not. We haven't made any stars yet Galaxies might start falling towards that and therefore increase the density a little bit more and that. So W map a Saddam new map created that CSM be. I, know that. So the plan our data since they. Just. Just improved that. That's right. Yes. What yet? So just to finish the logical. Thread we infer from the fact that the universe is very structured today that there must have been some structure at very subtle level in the cosmic microwave background, and that's what w map mission, the microwave anisotropic pro the. means the deviations from perfect smoothness. which w measured quite well, and as you said, the planck satellite of the European Space Agency just did that much better Really. Small right the different. Few Michael Kits, diff- difference of one part in one hundred thousand. So, yes. The the effective temperature the cosmic background is two point, seventy degrees Kelvin and the typical fluctuations are one part in one hundred thousand that. Yeah. So you're right it it becomes micro Kelvin. Tens of Micra Kelvin this is what's what's being measured but the amazing story is and that's and that comes back to the paper that that that you quoted is that you can put together. The measurements of the fluctuation scene in the early universe when the cosmic microwave background and the measurements of the structure from the galaxy distribution today and try to put together a single coherent picture about how the one might have evolved into the other when a statistically. With, things like the power spectrum which is. Some jargon we could we could go into. But it we can't. We now have a fairly complete understanding. Of. What the universe was like a four, four, hundred, thousand after the Big Bang and how it formed into the structures we see today and that was really the point of the paper but me just answer excite once you get me started I don't shut up. What in order to to make that connection, there are some. free parameters that you need to know about and those parameters end up being quantities like just how much dark matter is there in the universe how much dark energy which we may find ourselves. Coming back to talk about, is there in the universe, what is the expansion rate of the universe? There's a about five or six such numbers. Some of them are a little bit more a little bit more technical than those as well and those unique. To include those to to get a full picture and But the amazing story is that it really does fit together with five or six numbers. We can actually describe in a statistical way both the. CW mappin what's seen an SDSS out to really exquisite precision? So. So they're they're accepted theory today as lambda. and. And so in the paper, the parameters sort of fundamental tram-users like our hobbled constant and on. So we got all of that by SPSS and W. Map. And when the plan came in. Those. Things just with. Or? The I answered yes. Of course people. Look very very carefully to see what one of the questions is just told the story that there's this. Beautiful. Concordance. As it were between when season the cosmic microwave background and in the large-scale distribution of galaxies and. At. First scientists are always delighted when they they have a simple picture that describes everything and they work on that the air bars get smaller and smaller and they measured things ever better and everyone's happy and then some people say you know This is fun but it should be interesting to find something you and art of part of the motivation for finding something news I've already made reference to dark matter I've already made reference to dark energy Those are labels that we give to concepts that are required in the equations, and we can talk about each of those in turn, but if you really want ask The question. What what what are these things? Physically, you'd like to have more than G it all fits together beautifully, which is not yet a full explanation to okay. What is the dark matter made of what does this dark energy thing that you're talking and so astronomers have been very eager to to find chinks in the armor to find flaws in the logic or disconnect disconnects that where things don't fit. The Kazak could be pointing towards something fundamentally new and and we're we're we're never satisfied. We're never satisfied. Oh, we have a model that where we know how much dark energy there isn't much dark matter is and it all fits together and we're all happy but then. They're still basic on answer questions that the way to address the might be to to to find some some some aspects in which things don't quite fit together. Now. So the the littler understand about this Michael. So there is a general consensus that the overall proportions about seventy percent dark energy twenty, five dollars, Matt to incite percents matter that see. There's dental consensus around dead but we really don't know what you mean. Blind's. DETROIT, will dark matter of we understand better than dark energy. and. I can expand on that statement but But no, we don't if Y-. The basic question of what either of those things actually. Are. We we do not have an answer to that yet. Yeah this look dark matter a bit because I know that is one of the One of the objectives, of L., S. T. that your next and so maybe it's it's good to set the context around dark matter I know that a lot of candidates. Rims, Nino's primordial. Black, holes and so on and so. So what does our sort of current expectation that well so? One such candidates sort of everyone's favourite is that in the early universe? Our modern understanding the big bang is that various particles were created out of the the very hot the one can. Using our understanding a physics. We understand that with an high enough temperatures when can make all kinds of particles and that's where the protons, neutrons, electrons, and neutrinos and everything else came from an and maybe there was something else which is a hypothetical new particle that makes up the dark matter. And when when goes through those ideas and tries to imagine what that hypothetical particle might be there's a there's one particular strong theoretical candidate that comes out that's called a window weakly interacting massive particle, which is. It's a clever acronym but. Describes what it is weakly interacting the technical term about the kind of interactions it it has with itself with other particles. Yeah. But if if dark matter is made of wimps, we should we should there should be Williamson are streaming through us right now because there's sort of dark matter everywhere and it's weakly interacting, which is not means that it interacts at least a little bit and so. Based on that hope. People have developed. This is not my work at all people have developed very sophisticated laboratory experiments to try to detect this this stuff and have done have done. They've become in a sense of victims of their own success, which is to say that they. They sensitivities of these are getting so great that the WIMP and they haven't found anything yet that the WIMP the wimp model is starting to look. Like may not work after all and people are getting a little nervous about that it gets. Cleanest and best story of what the dark matter might be mid of and it's not working at the moment which is really really. Exciting a little scary. It says that we've maybe we're barking under some sort of wrong tree. Yea as an engineer, Michael and engineering long time ago but my intuition would have the. No of course, the theorists are infinitely Creative and are constantly coming up with new ideas. There's a whole. There's a whole story why the WIMPS are particularly compelling. But again, if it doesn't agree with what's what's experimentally Seen then then. It becomes, of course, quite a bit less compelling. And other candidates, neutrinos right at the masses of neutrinos and there's something something else that came out as hasty ascend wbz. So Astronomer, physicists have long. When when people I realized that neutrinos existed the simplest hypothesis was that there was no mass associated with these at all they were they traveled at the speed of light just like photons particles of light. But as people thought about a further, they realize there's no a party reason that they have to be massless maybe they do have some s and then. And again, the they should be created enormous numbers in the Big Bang, and then you try to ask whether they might have might there might be enough of them to create to to explain the doctor and to make a long story short neutrinos don't work for two reasons. First of all, we now know we we I mean we we do know. Now. With confidence neutrinos have mass. We don't know how much it is, but we know it's very small and with those limits on what the mess might be and then and the numbers we have a pretty good estimate of how many neutrinos that there should be. There's simply not enough to to make up the dark matter. That's that's the simplest way. To explain why why neutrinos end up not working after all Another it's another disappointment in with regard. The. Other fundamental parameter is the Hubble Yes. Hubble. Constant. And You got fair amount of precision around that does STF says in w map, and then I understand that there was another measurement from the Supernova that seem to sort of divide. So this is this is very much observe I was saying earlier that there's great excitement or there's great eagerness in the scientific community to find chinks in the armor to find discrepancies and what you're referring to exactly that so. As as Your listeners may know the Hubble constant measures the expansion rate of the universe, and there's a whole variety of different ways to do this, and the stormers have been trying to do this since the time of Hubble himself back. In the Nineteen Nineteen Thirties And now the measurements have gotten astonishingly precise and one way to to its expansion rate of the universe. It's a measure of how fast the galaxy is moving away relative to its distance. So That sounds straightforward. You measured the distance you measure how fast it's moving away from the redshift you're done. So that's one one. Approach and Many different variants on that particular theme. But crudely speaking the number that comes out and funny astronomer units is about seventy two or seventy three. When the the other way to do it is to measure measure the detailed fluctuations in the cosmic microwave background from I still being map, and now you mentioned the the planck satellite which has made more precise measurements, and that gives you slightly more indirectly a measure of expansion rate of the universe and when you go through that in the same funny units, the number comes out to be seven. So sixty seven versus seventy, three ish, and then everyone just starts arguing and so is someone made mistakes mistake or systematic error. What happens if we use other measurement that gets a seventy one instead of seventy three. At the moment, it looks like real discrepancy which has gotten people all excited again because it says, this is you know we were getting a little bored by just how beautifully everything was putting together. We need we need something to give us a new handle on something we we really wanted to discover something fundamentally new rather than. Just just see it off it beautifully with A. Couple of weeks ago Mike Somebody has said he used to be. One. Hundred. Seventy five sorta work now, we are really worried about. Seventy three dollars go. Yeah. When I was a graduate student, I'm not old enough. I can say that when I was a graduate student indeed. Versus hundred. Were the values over which people battled and but with enormous uncertainties and and now. Now, these two quite different ways of measuring are getting. What seemed to be statistically significant differences in again where whether so of course, again, the theorists are having a field day and inventing. All kinds of interesting mechanisms by which you could get this discrepancy new new kinds of physics than that might possibly explain, right So that brings us to. In Utah Roy that's being built. The Large Synopsis Stop You right there and say it has changed its name. The paper I gave you. Just, published just before the name change. So by by Congressional decree actually the US Congress. This was renamed to the Virus Ruben Observatory. Legacy survey of space in time. because. Large synoptic survey telescope. No one knew what snap Dick Meant and anyway there's a variety of problems with that ole title but So various see Ruben As you probably know she was breaking astronomer just passed away. Five years ago something like that who? Many wonderful things in astronomy. But one of them is that she really she looked at the rotations what's called the rotation curves of galaxies, the way galaxy rotation and came up with the most solid evidence Today that galaxies are are dominated by dark matter the most most of the mass of galaxies in the form of dark matter and so the So this. Observatory Yep. This something is being is being built in Chile frustratingly like so many other aspects of our lives, the construction actually temporarily halted because of of covid nineteen. but but. things are improving the health situation. She lays improving him I. I just heard and things should start up again soon. So I don't know the geog. Michael I know that other things that other things being bitten Julius. Further further north yes. Chile. Is is well first of all. One of the most beautiful countries in the world is one of my favorite places took to go. It's completely north-south country. It's a very, very long and skinny. Any country in. The two thousand can't remember if it's two thousand kilometers of two thousand miles long. Should know that But You know on on. On the western side of course is the Pacific Ocean. These side is defined by the Andes Mountains and. And the northern parts of Chile are are dry. Extraordinarily, dry northern parts of the Tacoma desert where you mentioned the Simon's observatory, for example, So that combination of mountainous close to ocean in very very dry conditions makes it really one of the best places in the world to do astronomy and so many of the next generation large or current and next generation large facilities telescopic facilities are being built. In Chile. and. Southern, fit. So. When you're an astronomer and you working from the Earth as you as you question hints, you can you can't see the entire sky. There's parts of this guy there hidden beneath your feet and will be no matter no matter how the earth turns So. When when S. T. The Ruben Observatory when we were first having the discussions of where to build it. That was one of the questions that she would be more important in the Northern Hemisphere, the Southern Hemisphere, and after much discussion we decided that what we need to do is find the best site in terms of its weather. How many clear nights it has an others, such things, and that was more important than than agonizing over whether the northern half of the sky. This other never this guy was was was more fundamentally interesting. You can make strong arguments in both directions. So. So what it will do it it it it takes pictures. That's all it does. It takes pictures. It does we're talking about spectrum before. That's not something that the. Rhythms of a toy will do but what it will do is it will be. of a particularly large telescope. So when people talk about the size of the of telescope the things that care about. Collecting area, how large the mirror the primary mirrors and that mirrors about eight and a half meters across a point four meters I think is the official number. and the other aspect of it is that you want to be able to take a picture of large swath of skype. At, once the what's called the field of view of the telescope and Ellison t the Victory will have the largest combination of. Of Primary Mirror size and field of view of of any telescope in the world by by. By large factor. So it's particularly well suited for the mapping. Of just taking pictures of everything that's there the large. The large size of the primary mirror means it's tremendously sensitive to very faint objects large field of view to get a lot of objects at once. Her. Engineering. Challenge obviously eight point four meters. Ya. Indict. The Primary Mirror. And a camera. That's right. That's right. And so so the the project style goodness. I I heard of the first inklings. The project that I heard of was the late nineteen ninety s Tony. Tyson. who was at the time at Bell Labs here, New Jersey. It's now at UC University of California. Davis. was was starting to think think about this. And but it really started taking off becoming serious project in the in the two thousands and it was formally approved. By the National Science Foundation saying, yes were we're going to put money into this in two thousand fourteen? And it's also says if you could describe a little bit sort of the operations and. As you said, three point two Giga pixels, which means that every time you take a picture. which we will do every thirty seconds. For fourteen years straight or at least when the sun is down for ten years straight. We will have a picture of with three point, two Giga pixels that's covering. An area. Remember these numbers Approaching Forty Times the area of the full moon. And if I? Did the arithmetic in my head correctly and and so what what one can do with that is is you can take pictures of the sky and we all love looking at astronaut Michael Pictures but we can take pictures of the sky and then we can do it again and then we can do it again and we do it again. So why do you? Keep on doing they say I've got a picture what what more detail the first thing that you do is you had the interest together and so you get an effective exposure time that will be that will be much longer and you can see see very much much fainter stars, galaxies but the other thing that you then become sensitive to is everything that's changing you can. So we're used to thinking of the the skies, the heavens as being static as changing on timescales much longer than any human lifetime. But that is the story is far more interesting than that. First of all the things that move stars can be seen to be moving across the sky very slowly. But if you measure carefully enough over long period of time, you can measure that you can measure asteroids within our own solar system and the Reuven Observatory will discover I. Don't remember the number but millions millions of of asteroids over over its lifetime and. That's important. Dot Dinosaur. Well. This is an interesting question I. Mean we one of the scientific motivation to ask the question? Is there an asteroid with our name on one that's going to collide with the earth and the way you find out is by cataloging as as? As many Astra's as you can find them figuring out there bitten and asking the question. Whether anyone has any any of the most likely to collide with us So that is certainly one of the things Yup then you take. So, then you take the pictures micro so Different. That you're using. So yes, by combining the different filters, you basically can make a color color picture and their. their six filters ranging a over. This is a visible light telescopes ranges from the bluest shortest wavelengths light that that the Earth's atmosphere transmits below which the ozone layer cut you off and goes to the longest wavelengths that the kind of detectors that were using. use if you it's what astronomers call the. Optical range beyond which the technology for the detectors at the change So we we are we we will take images in six different filters, and with that, you can not just make pretty color pictures of course, which we will do, but also measure very precisely. The relative brightness in the different filters gives you till about the the physical nature of the objects that we're looking at the stars, the galaxies, the asteroids, and everything else. Is just bouncing around the sky Indeed one of the things that the telescope has been designed to do is is move very quickly for exactly that reason, you don't want to spend all your time sloughing. That's the jargon that we use from one region the sky to another you you'd like to spend as much time actually taking exposures and as little as time is. Going in transition from one to the other because that's sort of wasted time as it were so telescope. Yeah. Go ahead. Making. Goods. Making mystically. It's all robotics, right so it is basically the on. Well. So you have to, of course, program that robot rather carefully. So indeed, there's a great deal of discussion which. About sort of two levels of of questions. One is the one that you hint hit into that. You know the the night the sun has just gone down. Let's the telescope and start exposing and you definitely you definitely have programmed in. Here's the program for tonight, we're going to observe this field and then go slow over to this field and this one and It's thirty seconds of Papas is this is the is the standard Operations that were planning to and so yes, there is an algorithm that says, okay. Let's try to cover the sky this way through the night There's a broader an interesting conversation about. Okay. You have six different filter filters for every exposure. You have to decide which one you have this idea in the back of your mind that you want to see things change but you also have this idea that you'd really like to measure the sky with as much sensitivity as possible and. And you know the asteroids are moving quickly and the stars moving slowly and maybe a Supernova will explode and you'd like to be sensitive to that. How do you design your? Survey to maximize your ability to do all that science we went through an exercise. Now over ten years ago where we tried to tabulate or basically wrote a book. Listing all the signs that could be done, and basically every paragraph of this book was a PhD thesis or Chris Potential PhD thesis and the book was six hundred pages long and and that was civil ten years ago if we were to do it again of probably end up being twice as long. So that is there's a huge range of different science that can be done. I mentioned the asteroids large-scale structure of the universe that we talked about before the most distant galaxies and quasars and everything in between, and we find ourselves wanting wanting to do the science. We wanted to have it all again, we're astronomers are tend to be very greedy and and and say you know and so much discussion of well with the optimized the survey to make this science. Particularly Powerful, are we gonNA second be at the expense of our asteroid science or something else like that, and so coming up with that balances? Subject of much discussion that we're having a lot a lot of fun. It's Optimization problem by. Short. One. Is You GotTa let me make a statement can cut me. One issue with being prescriptive though is that the bringing of status biases that's Right. So Lupino astronomers were used are used to this challenge you know. A colleague of mine has a Mug that says something like I unconscious. Of the unexpected or something like that and so you know part of the spirit of this is that Well, first of all, we can allow ourselves flexibility to to change our mind about how we're gonna how we carry out the observations if if if we see compelling reasons to do so but you know what astronomers do they take these series picture these series of pictures and we keep everything. you may contrast that with particle physicist who have enormous accelerators where they bang protons together and it turns out that there's so much information that comes out of this collision they have no choice but to throw away ninety, nine, point, nine, nine. Nine. percent of the data before. Simply cannot. Possibly keep up with. So they have snuck, it has built into the hardware filters to just look for the things that they're looking for, and so when astronomer here is that they shut her because they know we are so ignorant about what's out there in the universe that we don't want to throw in throat anything a priori and sort of keep everything. going. Of Keep every bit of data that we can. Yeah. So these Yeah, these numbers have quite quite striking. So it says that I don't know if I got this right thirty, two, trillion wage detrimental in about. Numbers of starts this right? So you're talking about something like he's. Only twenty, two, twenty terabytes two. Thousand. Twenty therapy you. At least the first incarnation of the Sloan Digital Sky Survey was a few tens of terabytes. We illnesses table basically get that quantity of data. Every night. In the Ruben Observatory. So so yes, and the end of the survey you keep that for ten years at adds up pretty quickly and at the end of the survey, the numbers are tens of Peta Bites close to one hundred terabytes So. Yep. So is it coming back to the yes? Yes. Yes. So as we just said the telescopes, the Chilean Andes but yes, we'll be we'll be piped in real time through a network that goes through for Brazil and then into. floor the. Than into. into the United States and. So yes, the the majority of the processing will actually happen physically you might states. That's right. Okay and so so so what do you hope to find here Michael Assuming that the expression goes yo you get consevative what are the? What are the specific areas that that you believe will will one of the questions is the one that we were talking about before namely this. Dark. Matter Dark Energy Question certainly one one of them in one of the key themes that the Ruben Observatory is really designed. To address and. One of the ways it does that is to. You know we talk about dark matter of one of the problems with dark matter is by it's by by definition by by its very name it is not something that we can see directly and so you say, how can we learn about dark matter by taking pictures well turns out as unsigned. Showed that matter can bend light. So if you have dark matter clumpy dark matter dark matter gravitates pulls together gravitationally it will be imagine a clump of matter in the galaxy beyond that clump somewhere the that the light from that Galaxy, we'll get bent and therefore distorted by that lump of dark matter and and this is an effect that that's that's measurable. The shapes of galaxies are systematically distorted by the distribution of dark matter that's out there, and we can measure that statistically in the the current surveys are now just starting to begin to do this and and Reuben Observatory is really designed to do this. On, on the large scale with with exquisite precision so this will give us a map now, not just where the galaxies were, which is kind of what we were talking about earlier. but where the dark matter is and how the dark matters distributed and that then gives you. Additional constraints on what the physical nature the dark matter is. It turns out the dark energy also turns out to be important. In all of this and it all becomes very exciting that way. So, is it is it because So so we can get some idea of the movement. In this in the context of a basically what we remember it was talking before about trying to put together a coherent picture. Of how the structure in the universe today is related to the what you see in the cosmic microwave background. What this will allow us to do is what we see what what we did with the Sloan digital sky surveys look at the distribution of galaxies, but I just said that. Galaxies represents most of the massive galaxies is a dark matter and you really want to know what the matters doing. The galaxies are almost an afterthought and it's the after thought that we can see which is what we've used but by measuring. The distribution of dark matter we can sort of measure more directly the quantity the thing that that at least in terms of the formation of structure in the universe the thing that. Counts more and. So this and and we can do this as a function of cosmic time. Because again we can We can look at different distances in the universe and that's referring to different different times in cosmic history. So we can ask the question. How did the dark matter? Clump together as a function of time and that gives. Has the potential to give us fundamental new insights? And so so we get. distributed. Brevity Nitro you actually use that term when I was describing this this spending applied but yes, this is gravitational lensing, which again is in effect. I. Predicted by Einstein it's a it's an outcome of his general theory of relativity. Famously for the change in the position of of stars during a solar eclipse but then. Seen in a in the context of galaxies only in the first scene in the late nineteen seventies and has become a growth industry in our field ever since. and. That will give you mentioned sort of getting inventory or the solar system. Planet. Yes. Important. Yeah. So people are excited about whether there might be another. Significantly. Massive planet like object I have to use my terms carefully. The Outer Solar System Beyond the orbit of Pluto. As as you know, Pluto, itself is the least massive of all. More less than any of the the planets that we usually refer to it, and and indeed there are several other objects seen in the outer solar system with comparable masses but there is indirect. Evidence. which I am eighty percent convinced by at this point. That there is there's a significantly more massive object quite a bit for the away. This is the planet nine that you are from which is which which made headlines. We haven't actually found it yet. There's this quite indirect evidence that it that it might exist out there Could. This couldn't Ruben Observatory find perhaps others are looking. It turns out knowing the sky is a big place in knowing where to look as this. Is Not easy. And if if it happens to be a place in its orbit that is incredibly of sufficiently far away it will be below the sensitivity of even the Rupin Observatory so there's no there's no guarantee of success whatsoever, but it would be truly setting discovery. There was some speculation. Mike. I don't know if this. I saw that was. That was A. Speculation I think is a fine word. I mean sure why not let of like. I'm not sure I have much until the. Together. But this is a good segue into quasars. And this is radio of great interest for you. So slightly seeing some pictures in the eighties that this doesn't train shed that come out of these these things. I. Remember maybe I'm I couldn't quite remember, but they used to be called quasars and then they used to call wizards long term I use. People use those to two terms to change a blade. The history is. Stanford quasi stellar object, which is which is referring to the fact that when they were first discovered. People remark that if you just take a picture of them, it just looks like a dot just like a star does in in a in an astronaut imaging and yet it wasn't a star. So dust quakers quasi stellar objects really and. Then it got shortened. To, quasars and that's the term that that I like. Y- Yes I. Think. It's easier. It's easier to say. So our current understanding is that well one of the. Well, let's back up just a little bit The Nobel Prize announced two weeks ago in physics was given to a Andrea says and reinhard. Gansel, for their observations of Stars in the vicinity of the very center of our own Milky Way? Proving. Beyond any doubt that that there is a as what we call a supermassive black hole four million times more massive than the Sun at the center of the Milky Way and So that the our own Milky Way Galaxy is not unique. In fact, as far as we can tell, Gal Galaxies essentially all galaxies, all massive galaxies sufficiently large galaxies have a supermassive black hole. In their center so Any questions come up and say, well. Where did that come from? How does it get? They're out to get started And one the next question to ask is it okay. If there's a supermassive black hole there what happens when something wanders too close to it. So black holes famously. Once, you cross the event horizon you're never escaping again. So black holes in practice can only grow in Mass you're. So, a QUASAR. QUASAR. Is A supermassive black hole in the center of a galaxy into which material is actively falling. It wants it falls all the way in it's gone. We don't see any. There's nothing further to see but on the way in, it's not going to go straight in on a radio. Radio Straight in it's it's more likely tend up in orbit around that black hole, and if we're talking about gas moving in right under the extreme gravity of the black hole, that gas could be moving enormously fast and friction viscosity in what's called an accretion disk that forms around a black hole. Causes it to heat up and glow. So paradoxically, a black hole, which is by definition sort of let's that's the ultimate dark matter. There's nothing to see but in its vicinity things. Astonishingly brightly and indeed that's that is our current understanding of what the quiz. Is. So so I used to think that cases are. Sort of long ago. So you have to look back in time we'll to black holes. Once. So the other thing to say is that. When we're seeing a QUASAR as I said. It's the process of material falling into the black hole. So we're watching the black hole grow, which is to say, this is probably the mechanism by which the supermassive black hole in our own Milky Way. Grew. So our our own Milky Way was probably quasar sometime in the past. most galaxies today have. Black Holes That is the material is not actively falling into them right now and they're sort of just sitting there, and when has to work a little harder to to infer the presence But but you're right the majority of the quasars the time in the universe win win mid most most black holes. Gain, most of their mass and we're shining quasars was indeed. In. In in the what's sometimes called cosmic new when the universe was probably three or two to three to four billion years old impaired to the fourteen billion years old and so yes quasars in the nearby University of recent universe. Quite rare. But they're quite a bit more common. When we look at high riches. And so supply understand it's be Michael. So don't be know that there are massive black holes in most of the reasonably sized galaxy centers, but we don't see the will not be just some of the some of the nearby. Black holes do have jets but you were in in order to get the jets you need the material falling him okay. Yeah. So any any supermassive black hole if that appreciable amount of material. Yes. So there's two different. That is related things that we've just talked about one is that's the material falls in it goes in orbit around the black hole forms called an accretion discs. So the mental picture you WanNa have. This black ball that represents the black hole itself and a sort of a dinner plate around it or Frisbee. I'm trying to draw mental immature, which is the Christian does the jets come out are are are due to Strong magnetic fields that thread that Frisbee or accretion disk that I've talked about that comes out of perpendicular to your Frisbee there and whether that happens in every case or not is unclear in fact. Many quasars are shining very brightly and don't don't have any obvious sign of of jets. So it's it's not it's not a universal connection and probably quasars go through different phases in different parts of their life cycle if I can use that. That that term when they might have jets and other times, they may not and those are some of the questions fundamental questions we find ourselves at the. Department of Research. Yeah Yeah I remember. Like I mentioned I remember seeing the pictures and was by. These. Tens of millions. Hundreds of millions. That's that's really big. But. Even tens of it's quite clear if. You can actually have services incredible. So. In conclusion, do I want to return to in again? So you've been intimately involved. Two or three years again, Kovic have slowed things down like so many things in our lives at the official date has been October twenty twenty two to start a ten year survey of this project of of mapping the have heavens, and that will probably be delayed by some amount and there's much discussion about exactly how to how to do that But but yes. So. So if you look forward ten years, Michael What what what do you think? Let, me ask the Diffley us. So be so wonderful things about astronomy. Is. How bad we are at answering that question which is to say we've constantly been surprised. You could you. You can go through the mental exercise of going back ten years or twenty years and imagining asking. Yourself versions of that question and an each case he would be wildly wrong about what the most exciting things to happen are astronomy really is a field in which we we are. We are imaginations have been have been rather poor in in guessing at the most exciting things might be. So you know if you ask what? Have we done this ten years ago we would have. Only a handful of people would have imagined that we'd be finding colliding black holes with a lie go through gravitational waves, for example, and that that is just a you know one of the most exciting developments go go back thirty years ago known known was really T- talking seriously about black holes in the centers of gallons or the fact that planets existed and other stars or that the universe expansion is accelerating just to talk about some of some of the most exciting things that have happened in my astronomical lifetime. So. So you know I. I could tell some story about. Dark dark energy dark matter. But but you know I suspect ten years from now. We'll look back and say. Boy were we naive back there we'll just completely missed the point or this discovery. Field and and and is really have really. Rock the foundations and and again it's up to our imagination to come up with what that might be me. Yeah Yeah. I was thinking very pro. If Asteroid Caddick for. That would be very good. Excellent excellent yeah. enjoyed. Spending time. Thank you. But This is a scientific sense podcast providing unscripted conversations with leading academics and researchers on a variety of topics. If you lie to sponsor this podcast, please reach out to info at scientific sense dot, com.

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